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Sample records for ni okeru edge

  1. El Niño/La Niña shelf edge flow and Australian western rock lobsters

    NASA Astrophysics Data System (ADS)

    Clarke, A. J.; Li, J.

    2004-06-01

    Due to the leak in the gappy western equatorial Pacific, sea level (SL) is highly correlated with El Niño all along the western Australian coast. According to standard theory, this coastal interannual (IA) signal should propagate westward as Rossby waves with large zonal scale. High-resolution satellite SL estimates show that along the shelf edge south of 23°S the IA SL signal does not have the expected large spatial scale as it decreases rapidly seaward from the shelf edge. The drop in IA SL amplitude coincides with the mean position of the Leeuwin Current (LC). Theory shows how a nearly meridional mean flow, as in the case of the LC, can induce this fall in IA signal amplitude. The associated IA shelf-edge flow tends to strengthen the LC during La Niña, weaken it during El Niño and may profoundly affect the recruitment of the western rock lobster.

  2. Magnetic circular x-ray dichroisms of Fe-Ni alloys at K edge.

    SciTech Connect

    Freeman, A. J.; Gofron, K. J.; Kimball, C. W.; Lee, P. L.; Montano, P. A.; Rao, F.; Wang, X.

    1997-04-03

    Magnetic Circular X-ray Dichroism (MCXD) studies at K edges of Fe-Ni alloys reveal changes of the MCXD signal with composition and crystal structure. We observe that the signal at the invar composition is of comparable strength as other compositions. Moreover, the edge position is strongly dependent on lattice constant. First principles calculations demonstrate that the shape and strength of the signal strongly depends on the crystal orientation, composition, and lattice constant. We find direct relation between the MCXD signal and the p DOS. We find that the MCXD at K edge probes the magnetism due to itinerant electrons.

  3. Local structure of ball-milled LaNi{sub 5} hydrogen storage material by Ni K-edge EXAFS

    SciTech Connect

    Joseph, B.; Iadecola, A.; Schiavo, B.; Cognigni, A.; Olivi, L.; D'Ali Staiti, G.; Saini, N.L.

    2010-07-15

    Local structure of the nanostructured LaNi{sub 5} hydrogen storage alloys, prepared by ball-milling, has been studied using Ni K-edge extended X-ray absorption fine structure spectroscopy. Results indicate that the ball-milling up to 100 h results in the production of nanoparticles characterized by large atomic disorder and slightly reduced unit-cell volume, compared to the bulk LaNi{sub 5}. High temperature annealing appears to help in partial recovery of atomic order in the ball-milled samples; however, long-time ball-milled samples retain large disorder even after the high temperature annealing. The results suggest that the large disorder and the reduced unit-cell volume might be causing a higher energy-barrier for the hydride-phase formation in the long time ball-milled LaNi{sub 5} powders. - Graphical Abstract: X-ray diffraction (XRD) pattern (left panel) and Fourier transforms of the Ni K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy (right panel) of bulk LaNi{sub 5} hydrogen storage material (structure model is given in the middle) together with the same after 100 h ball-milling. Milled samples show a remarkable reduction intensity and broadening of the XRD peaks. Substantial damping of the amplitude and a slight shrinkage of the profile are observed in the EXAFS spectrum. These results indicate that the ball-milling up to 100 h results in the production of nanoparticles characterized by slightly reduced unit-cell volume and substantial atomic disorder compared to the bulk LaNi5. High temperature annealing appears to help in partial recovery of atomic order in the ball-milled samples; however, long-time ball-milled samples retain the disorder even after the high temperature annealing. The results suggest that the large disorder and the reduced unit-cell volume might be causing a higher energy-barrier for the hydride-phase formation in the long-time ball-milled LaNi{sub 5} powders.

  4. Temperature and high-pressure dependent x-ray absorption of SmNiO3 at the Ni K and Sm L3 edges

    NASA Astrophysics Data System (ADS)

    Massa, Néstor E.; Ramos, Aline Y.; Tolentino, Helio C. N.; Sousa-Neto, Narcizo M.; Fonseca, Jairo, Jr.; Alonso, José Antonio

    2015-12-01

    We report on x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) measurements of SmNiO3 from 20 K to 600 K and up to 38 GPa at the Ni K and Sm L3 edges. A multiple component pre-Ni K edge tail is understood, originating from 1 s transitions to 3d-4p states while a post-edge shoulder increases distinctively smoothly, at about the insulator to metal phase transition (TIM), due to the reduction of electron-phonon interactions as the Ni 3d and O 2p band overlap triggers the metallic phase. This effect is concomitant with pressure-induced Ni-O-Ni angle increments toward more symmetric Ni3+ octahedra of the rhombohedral R¯3c space group. Room temperature pressure-dependent Ni white line peak energies have an abrupt ˜3.10 ± 0.04 GPa valence discontinuity from non-equivalent Ni3+δ + Ni3-δ charge disproportionate net unresolved absorber turning at ˜TIM into Ni3+ of the orthorhombic Pbnm metal oxide phase. At 20 K the overall white line response, still distinctive at TIM ˜8.1 ± 0.6 GPa is much smoother due to localization. Octahedral bond contraction up to 38 GPa and at 300 K and 20 K show breaks in its monotonic increase at the different structural changes. The Sm L3 edge does not show distinctive behaviors either at 300 K or 20 K up to about 35 GPa but the perovskite Sm cage, coordinated to eight oxygen atoms, undergoes strong uneven bond contractions at intermediate pressures where we found the coexistence of octahedral and rhombohedral superexchange angle distortions. We found that the white line pressure-dependent anomaly may be used as an accurate alternative for delineating pressure-temperature phase diagrams.

  5. Local disorder investigation in NiS(2-x)Se(x) using Raman and Ni K-edge x-ray absorption spectroscopies.

    PubMed

    Marini, C; Joseph, B; Caramazza, S; Capitani, F; Bendele, M; Mitrano, M; Chermisi, D; Mangialardo, S; Pal, B; Goyal, M; Iadecola, A; Mathon, O; Pascarelli, S; Sarma, D D; Postorino, P

    2014-11-12

    We report on Raman and Ni K-edge x-ray absorption investigations of a NiS(2-x)Se(x) (with x = 0.00, 0.50/0.55, 0.60, and 1.20) pyrite family. The Ni K-edge absorption edge shows a systematic shift going from an insulating phase (x = 0.00 and 0.50) to a metallic phase (x = 0.60 and 1.20). The near-edge absorption features show a clear evolution with Se doping. The extended x-ray absorption fine structure data reveal the evolution of the local structure with Se doping which mainly governs the local disorder. We also describe the decomposition of the NiS(2-x)Se(x) Raman spectra and investigate the weights of various phonon modes using Gaussian and Lorentzian profiles. The effectiveness of the fitting models in describing the data is evaluated by means of Bayes factor estimation. The Raman analysis clearly demonstrates the disorder effects due to Se alloying in describing the phonon spectra of NiS(2-x)Se(x) pyrites.

  6. Approximating the near-edge mass absorption coefficients for Ni using an ultra-thin bimetal foil

    SciTech Connect

    Alkire, Randall W.

    2016-11-01

    In an effort to improve the characteristics of a fluorescing metal-foil-based beam position monitor, a new bimetal ultra-thin (0.98/0.67 µm) Ti–Ni foil was introduced to replace an existing single-element ultra-thin 0.5 µm thick Cr foil. During characterization it was determined that absorption measurements on the bimetal foil could be used to fit the Ni mass absorption coefficients accurately in the vicinity of the NiKedge. Comparison with experimental results from the literature demonstrated that the fitting procedure produced coefficients with uncertainties of the order of ±1%. Once determined, these fit coefficients allowed the thickness of an independently mounted 8 µm thick Ni foil to be computed from absorption measurements instead of relying on a tool-based measurement of the foil thickness. Using the 8 µm thick foil, a continuous map of Ni mass absorption coefficients was produced at 1 eV resolution throughout the near-edge region. Lastly, this high-resolution map marks a significant improvement over the existing NIST XCOM or FFAST database mass absorption coefficients, which have estimated errors of 10–20% for the near-edge region.

  7. Ni K-Edge XANES Analyses of Residual Ni Catalyst in Carbon Nanofiber Using Full Multiple Scattering Theory

    SciTech Connect

    Ushiro, Mayuko; Ohminami, Kenryo; Nagamatsu, Shin-ichi; Fujikawa, Takashi; Asakura, Kiyotaka

    2007-02-02

    Residual Ni species after Ni removal treatment of carbon nanofibers have been investigated by use of XAFS analyses. Most of the Ni impurities are in Ni monomer which is located on defects in carbon nanofibers. The XAFS analyses combined with the multiple scattering theory give useful information on nano-structures of small amount species. Molecular orbital calculation also support the results from the XAFS analyses.

  8. Approximating the near-edge mass absorption coefficients for Ni using an ultra-thin bimetal foil

    DOE PAGES

    Alkire, Randall W.

    2016-11-01

    In an effort to improve the characteristics of a fluorescing metal-foil-based beam position monitor, a new bimetal ultra-thin (0.98/0.67 µm) Ti–Ni foil was introduced to replace an existing single-element ultra-thin 0.5 µm thick Cr foil. During characterization it was determined that absorption measurements on the bimetal foil could be used to fit the Ni mass absorption coefficients accurately in the vicinity of the NiKedge. Comparison with experimental results from the literature demonstrated that the fitting procedure produced coefficients with uncertainties of the order of ±1%. Once determined, these fit coefficients allowed the thickness of an independently mounted 8 µm thickmore » Ni foil to be computed from absorption measurements instead of relying on a tool-based measurement of the foil thickness. Using the 8 µm thick foil, a continuous map of Ni mass absorption coefficients was produced at 1 eV resolution throughout the near-edge region. Lastly, this high-resolution map marks a significant improvement over the existing NIST XCOM or FFAST database mass absorption coefficients, which have estimated errors of 10–20% for the near-edge region.« less

  9. Ni K-Edge XAS Suggests that Coordination of Ni II to the Unstructured Amyloidogenice Region of the Human Prion Protein Produces a Ni2 bis-u-hydroxo Dimer

    SciTech Connect

    Shearer,J.; Soh, P.

    2007-01-01

    Prion diseases are thought to be caused by the misfolding of the ubiquitous neuronal membrane prion protein (PrP) through an unknown mechanism that may involve Cu{sup II} coordination to the PrP. Previous work has utilized Ni{sup II} as a diamagnetic probe for Cu{sup II} coordination [C.E. Jones, M. Klewpatinond, S.R. Abdelraheim, D.R. Brown, J.H. Viles, J. Mol. Biol. 346 (2005) 1393-1407]. Herein we investigate Ni{sup II} coordination to the PrP fragment PrP(93-114) (AcN-GGTHSQWNKPSKPKTNMKHMAG) at pH = 10.0 by Ni K-edge X-ray absorption spectroscopy (XAS). We find that two equivalents of Ni{sup II} will coordinate to PrP(93-114) by UV/Vis titrations and mass spectrometry. Ni K-edge XAS data is consistent with Ni{sup II} ligated by five N/O based ligands (three N/O ligands at 2.01(2) {angstrom} and two at 1.855(2) {angstrom}). We were also able to locate a Ni-Ni vector at 3.1(1) {angstrom}, which suggests the two Ni{sup II} centers are contained in a bis-{mu}-hydroxo dimer. We therefore suggest that Ni{sup II} may not be a suitable diamagnetic mimic for Cu{sup II} coordination within the PrP since differential coordination modes for the two metals exist.

  10. Surface complexation of heavy metal cations on clay edges: insights from first principles molecular dynamics simulation of Ni(II)

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Liu, Xiandong; Lu, Xiancai; He, Mengjia; Jan Meijer, Evert; Wang, Rucheng

    2017-04-01

    Aiming at an atomistic mechanism of heavy metal cation complexing on clay surfaces, we carried out systematic first principles molecular dynamics (FPMD) simulations to investigate the structures, free energies and acidity constants of Ni(II) complexes formed on edge surfaces of 2:1 phyllosilicates. Three representative complexes were studied, including monodentate complex on the tbnd SiO site, bidentate complex on the tbnd Al(OH)2 site, and tetradentate complex on the octahedral vacancy where Ni(II) fits well into the lattice. The complexes structures were characterized in detail. Computed free energy values indicate that the tetradentate complex is significantly more stable than the other two. The calculated acidity constants indicate that the tetradentate complex can get deprotonated (pKa = 8.4) at the ambient conditions whereas the other two hardly deprotonate due to extremely high pKa values. By comparing with the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) model, the vacant site has been assigned to the strong site and the other two to the weak site, respectively. Thus a link has been built between atomistic simulations and macroscopic experiments and it is deduced that this should also apply to other heavy metal cations based on additional simulations of Co(II) and Cu(II) and previous simulations of Fe(II) and Cd(II)). This study forms a physical basis for understanding the transport and fixation of heavy metal elements in many geologic environments.

  11. X-ray Faraday effect at the L2,3 edges of Fe, Co, and Ni: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Kuneš, J.; Oppeneer, P. M.; Mertins, H.-Ch.; Schäfers, F.; Gaupp, A.; Gudat, W.; Novák, P.

    2001-11-01

    The x-ray Faraday effect at the L2,3 edges of the 3d ferromagnets Fe, Co, Ni and of Fe0.5Ni0.5 alloy is studied both theoretically and experimentally. We perform ab initio calculations of the x-ray Faraday effect on the basis of the local spin-density approximation and we adopt the linear-response formalism to describe the material's response to the incident light. Experimental x-ray Faraday rotation and ellipticity spectra are measured with linearly polarized soft-x-ray synchrotron radiation at BESSY, Berlin. The measured x-ray Faraday rotations are remarkably large, up to 2.8×105 deg/mm, which is more than one order of magnitude larger than those observed in the visible range. From the measured Faraday spectra we determine the intrinsic dichroic contributions to the dispersive and absorptive parts of the refractive index, and compare these to ab initio calculated counterparts. The theoretical dichroic spectra are in good qualitative agreement with the experimental data. The inclusion of the spin polarization of the core states leads to a small, yet non-negligible, improvement of the theoretical dichroic spectra. Our results illustrate that the many-particle x-ray excitation spectrum can be sufficiently well approximated by the Kohn-Sham single-particle spectrum. From the computed magneto-x-ray spectra we determine, using the sum rules, the orbital moments, which we compare to the exact orbital moments.

  12. Unique edge-sharing sulfate-transition metal coordination in Na{sub 2}M(SO{sub 4}){sub 2} (M=Ni and Co)

    SciTech Connect

    Fry, Allyson M.; Sweeney, Owen T.; Adam Phelan, W.; Drichko, Natalia; Siegler, Maxime A.; McQueen, Tyrel M.

    2015-02-15

    Two compounds, Na{sub 2}Ni(SO{sub 4}){sub 2} and Na{sub 2}Co(SO{sub 4}){sub 2}, were synthesized and their structure and properties were characterized. They adopt a structure that contains a bidentate coordination of sulfate to the transition metal center, which was determined via single crystal X-ray diffraction combined with model refinements to both laboratory X-ray and time-of-flight neutron powder diffraction data. The compounds were both found to crystallize in the C2/c space group with Z=24 and a unit cell of a=23.3461(3) Å, b=10.3004(1) Å, c=17.4115(2) Å, β=98.8659(9)°, and V=4136.99(8) Å{sup 3} for the cobalt analog and a=23.2253(1) Å, b=10.26155(6) Å, c=17.3353(1) Å, β=99.0376(5)°, and V=4080.20(5) Å{sup 3} for the nickel analog. Magnetization measurements show that the transition metal centers have negligible interactions with neighboring sites. Infrared and Raman spectroscopies were used to further probe the unique sulfate-transition metal coordination, and confirm the bidentate binding motif. The resulting pseudo-trigonal bipyramidal coordination produces vivid violet, Na{sub 2}Co(SO{sub 4}){sub 2}, and yellow, Na{sub 2}Ni(SO{sub 4}){sub 2}, colors that were probed by diffuse reflectance. - Graphical abstract: Two blue distorted transition metal octahedra (oxygen in red) bridged by two sulfate tetrahedra are shown here. Each bridging sulfate tetrahedra shares an edge with one octahedron and a corner with the other. All of the remaining corners of the octahedra are corner sharing with four tetrahedra forming a polyhedral network. - Highlights: • Structure of Na2Ni(SO4)2 and Na2Co(SO4)2 is determined. • Unique sulfate-transition metal binding observed in the new structure. • Combined diffraction and spectroscopic techniques were used. • Magnetization measurements show negligible interactions between sites.

  13. Low-temperature adsorption of H2S on Ni(001) studied by near-edge- and surface-extended-x-ray-absorption fine structure

    NASA Astrophysics Data System (ADS)

    McGrath, R.; MacDowell, A. A.; Hashizume, T.; Sette, F.; Citrin, P. H.

    1989-11-01

    The adsorption of H2S on Ni(001) has been studied with surface-extended x-ray-absorption fine structure and near-edge x-ray-absorption fine structure (NEXAFS) using the AT&T Bell Laboratories X15B beamline at the National Synchrotron Light Source. At 95 K and full saturation coverage, ~0.45 monolayer (ML) of S atoms in fourfold-hollow sites are produced, characteristic of room-temperature adsorption, accompanied by ~0.05 ML of oriented molecular H2S. Both these atomic and molecular chemisorbed species are buried under ~0.9 ML of disordered physisorbed H2S. No evidence for HS is found. Above 190 K the two molecular H2S phases desorb, leaving only dissociated S. These findings differ from previously reported interpretations of data obtained with high-resolution electron-energy-loss spectroscopy. They also exemplify the utility of NEXAFS for identifying and quantifying atomic and molecular surface species even when their difference involves only H and the two species coexist.

  14. Edge Bioinformatics

    SciTech Connect

    Lo, Chien-Chi

    2015-08-03

    Edge Bioinformatics is a developmental bioinformatics and data management platform which seeks to supply laboratories with bioinformatics pipelines for analyzing data associated with common samples case goals. Edge Bioinformatics enables sequencing as a solution and forward-deployed situations where human-resources, space, bandwidth, and time are limited. The Edge bioinformatics pipeline was designed based on following USE CASES and specific to illumina sequencing reads. 1. Assay performance adjudication (PCR): Analysis of an existing PCR assay in a genomic context, and automated design of a new assay to resolve conflicting results; 2. Clinical presentation with extreme symptoms: Characterization of a known pathogen or co-infection with a. Novel emerging disease outbreak or b. Environmental surveillance

  15. Edge Detection,

    DTIC Science & Technology

    1985-09-01

    PROJECT. T ASK0 Artificial Inteligence Laboratory AREA It WORK UNIT NUMBERS V 545 Technology Square ( Cambridge, HA 02139 I I* CONTOOL1LIN@4OFFICE NAME...ARD-A1t62 62 EDGE DETECTION(U) NASSACNUSETTS INST OF TECH CAMBRIDGE 1/1 ARTIFICIAL INTELLIGENCE LAB E C HILDRETH SEP 85 AI-M-8 N99SI4-8S-C-6595...used to carry out this analysis. cce~iO a N) ’.~" D LI’BL. P p ------------ Sj. t i MASSACHUSETTS INSTITUTE OF TECHNOLOGY i ARTIFICIAL INTELLIGENCE

  16. The Edge

    NASA Technical Reports Server (NTRS)

    2006-01-01

    6 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the edge (running diagonally from the lower left to the upper right) of a trough, which is part of a large pit crater complex in Noachis Terra. This type of trough forms through the collapse of surface materials into the subsurface, and often begins as a series of individual pit craters. Over time, continued collapse increases the diameter of individual pits until finally, adjacent pits merge to form a trough such as the one captured in this image. The deep shadowed area is caused in part by an overhang; layered rock beneath this overhang is less resistant to erosion, and thus has retreated tens of meters backward, beneath the overhang. A person could walk up inside this 'cave' formed by the overhanging layered material.

    Location near: 47.0oS, 355.7oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  17. Use of HERFD-XANES at the U L3- and M4-Edges To Determine the Uranium Valence State on [Ni(H2O)4]3[U(OH,H2O)(UO2)8O12(OH)3].

    PubMed

    Bès, René; Rivenet, Murielle; Solari, Pier-Lorenzo; Kvashnina, Kristina O; Scheinost, Andreas C; Martin, Philippe M

    2016-05-02

    We report and discuss here the unambiguous uranium valence state determination on the complex compound [Ni(H2O)4]3[U(OH,H2O)(UO2)8O12(OH)3] by using high-energy-resolution fluorescence detection-X-ray absorption near-edge structure spectroscopy (HERFD-XANES). The spectra at both U L3- and M4-edges confirm that all five nonequivalent U atoms are solely in the hexavalent form in this compound, as previously suggested by bond-valence-sum analysis and X-ray diffraction pattern refinement. Moreover, the presence of the preedge feature, due to the 2p3/2-5f quadrupole transition, has been observed in the U L3-edge HERFD-XANES spectrum, in agreement with theoretical and experimental observations of other uranium-based compounds. Recently, this feature has been proposed as a possible tool to determine the uranium oxidation state in a manner similar to that of 3d and 4d metals. Nevertheless, this feature is also very sensitive to the uranium local environment, as revealed by our theoretical calculations, and consequently could not be used to attribute without ambiguity the uranium valence state. In contrast, U M4-edge HERFD-XANES appears to be the most straightforward and reliable way to assess the uranium valence state in very complex materials such as [Ni(H2O)4]3[U(OH,H2O)(UO2)8O12(OH)3] or a mixture of compounds.

  18. Waves in Seagrass Systems: Review and Technical Recommendations

    DTIC Science & Technology

    2006-11-01

    T. Terawaki. 1998. Relationship between Zostera marina beds and bottom sediments, wave action offshore in Naruto , southern Japan (original title... Naruto chisaki ni okeru amamo-ba to teishitsu oyobi haro tono kankei). Fisheries Engineering (Japan)/Suisan Kogaku (Japan) 34:299-304. Dean, R. G

  19. Randomized SUSAN edge detector

    NASA Astrophysics Data System (ADS)

    Qu, Zhi-Guo; Wang, Ping; Gao, Ying-Hui; Wang, Peng

    2011-11-01

    A speed up technique for the SUSAN edge detector based on random sampling is proposed. Instead of sliding the mask pixel by pixel on an image as the SUSAN edge detector does, the proposed scheme places the mask randomly on pixels to find edges in the image; we hereby name it randomized SUSAN edge detector (R-SUSAN). Specifically, the R-SUSAN edge detector adopts three approaches in the framework of random sampling to accelerate a SUSAN edge detector: procedure integration of response computation and nonmaxima suppression, reduction of unnecessary processing for obvious nonedge pixels, and early termination. Experimental results demonstrate the effectiveness of the proposed method.

  20. Reviews Book: The 4% Universe: Dark Matter, Dark Energy and the Race to Discover the Rest of Reality Book: Quantitative Understanding of Biosystems: An Introduction to Biophysics Book: Edison's Electric Light: The Art of Invention Book: The Edge of Physics: Dispatches from the Frontiers of Cosmology Equipment: Voicebox Equipment: Tracker 4 Books: Hands-On Introduction to NI LabVIEW with Vernier, and Engineering Projects with NI LabVIEW and Vernier Places to Visit: Discovery Museum Book: Philosophy of Science: A Very Short Introduction Web Watch

    NASA Astrophysics Data System (ADS)

    2011-11-01

    WE RECOMMEND Quantitative Understanding of Biosystems: An Introduction to Biophysics Text applies physics to biology concepts Edison's Electric Light: The Art of Invention Edison's light still shines brightly The Edge of Physics: Dispatches from the Frontiers of Cosmology Anecdotes explore cosmology Voicebox Voicebox kit discovers the physics and evolution of speech Tracker 4 Free software tracks motion analysis Hands-On Introduction to NI LabVIEW with Vernier, and Engineering Projects with NI LabVIEW and Vernier Books support the LabVIEW software Discovery Museum Newcastle museum offers science enjoyment for all Philosophy of Science: A Very Short Introduction Philosophy opens up science questions WORTH A LOOK The 4% Universe: Dark Matter, Dark Energy and the Race to Discover the Rest of Reality Book researches the universe WEB WATCH Superconductivity websites are popular

  1. Electronic structure, magnetic and structural properties of Ni doped ZnO nanoparticles

    SciTech Connect

    Kumar, Shalendra; Vats, Prashant; Gautam, S.; Gupta, V.P.; Verma, K.D.; Chae, K.H.; Hashim, Mohd; Choi, H.K.

    2014-11-15

    Highlights: • XRD, and HR-TEM results show the single phase nature of Ni doped ZnO nanoparticles. • dc magnetization results indicate the RT-FM in Ni doped ZnO nanoparticles. • Ni L{sub 3,2} edge NEXAFS spectra infer that Ni ions are in +2 valence state. • O K edge NEXAFS spectra show that O vacancy increases with Ni doping in ZnO. - Abstract: We report structural, magnetic and electronic structural properties of Ni doped ZnO nanoparticles prepared by auto-combustion method. The prepared nanoparticles were characterized by using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and dc magnetization measurements. The XRD and HR-TEM results indicate that Ni doped ZnO nanoparticles have single phase nature with wurtzite lattice and exclude the presence of secondary phase. NEXAFS measurements performed at Ni L{sub 3,2}-edges indicates that Ni ions are in +2 valence state and exclude the presence of Ni metal clusters. O K-edge NEXAFS spectra indicate an increase in oxygen vacancies with Ni-doping, while Zn L{sub 3,2}-edge show the absence of Zn-vacancies. The magnetization measurements performed at room temperature shows that pure and Ni doped ZnO exhibits ferromagnetic behavior.

  2. The accumulation of Ni in serpentines and garnierites from the Falcondo Ni-laterite deposit (Dominican Republic) elucidated by means of μXAS

    NASA Astrophysics Data System (ADS)

    Roqué-Rosell, Josep; Villanova-de-Benavent, Cristina; Proenza, Joaquín A.

    2017-02-01

    Ni-bearing serpentines and garnierites (Ni-bearing Mg-phyllosilicates) are the main Ni ores in the Falcondo Ni-laterite deposit (Dominican Republic). In the present paper a set of garnierite samples and the associated Ni-bearing serpentines with characteristic mineral compositions and textures, from the saprolite horizon, were studied by EMPA, μXRF and μXAS. The ultimate goal is to elucidate, for the first time, the Fe speciation and the Ni local environment of saprolite ores from Ni-laterites of the Dominican Republic. The chemical composition of the minerals has been obtained by means of EMPA and the Ni, Fe and Cr elemental maps obtained by μXRF allowed distinguishing the saprolite fragments containing Ni-bearing serpentines and Fe oxyhydroxides from the garnierite veins. The Fe K-edge μXANES demonstrated that Fe in the Ni-poor primary serpentine is mostly in the Fe2+ form, whereas in the Ni-bearing serpentine constituting the bulk of the saprolite and in the Fe-bearing garnierite Type I Fe was in the form of Fe3+. In parallel, the local environment of Ni determined by means of Ni K-edge μEXAFS confirmed that in Ni-poor primary serpentines Ni formed a homogeneous Ni-Mg solid solution, in garnierites formed Ni-Ni clusters, and in Ni-bearing secondary serpentines Ni was found in Ni-Mg and Ni-Ni mixed sites. This paper explains the accumulation of Ni, the speciation of Fe in garnierites with various mineral compositions and in Ni-bearing serpentines from the saprolite horizon in Ni-laterite deposits.

  3. Damage buildup and edge dislocation mobility in equiatomic multicomponent alloys

    NASA Astrophysics Data System (ADS)

    Granberg, F.; Djurabekova, F.; Levo, E.; Nordlund, K.

    2017-02-01

    A new class of single phase metal alloys of equal atomic concentrations has shown very promising mechanical properties and good corrosion resistance. Moreover, a significant reduction in damage accumulation during prolonged irradiation has also been observed in these equiatomic multicomponent alloys. A comparison of elemental Ni with the two component NiFe- and the three component NiCoCr-alloy showed a substantial reduction in damage in both alloys, and an even larger difference was seen if only larger clusters were considered. One of the factors limiting the damage build-up in the alloys compared to the elemental material was seen to be dislocation mobility (Granberg et al., 2016). In this Article, we focus on a more thorough investigation of the mobility of edge dislocations in different cases of the Ni-, NiFe- and NiCoCr-samples. We find that even though the saturated amount of defects in the alloys is lower than in elemental Ni, the defect buildup in the early stages is faster in the alloys. We also find that the dislocation mobility in NiFe is lower than in Ni, at low stresses, and that the onset stress in NiFe is higher than in Ni. The same phenomenon was seen in comparison between NiFe and NiCoCr, since the three component alloy had lower dislocation mobility and higher onset stress. The dislocation velocity in elemental Ni plateaued out just under the forbidden velocity, whereas the alloys showed a more complex behaviour.

  4. Supersonic Leading Edge Receptivity

    NASA Technical Reports Server (NTRS)

    Maslov, Anatoly A.

    1998-01-01

    This paper describes experimental studies of leading edge boundary layer receptivity for imposed stream disturbances. Studies were conducted in the supersonic T-325 facility at ITAM and include data for both sharp and blunt leading edges. The data are in agreement with existing theory and should provide guidance for the development of more complete theories and numerical computations of this phenomena.

  5. Agile robotic edge finishing

    SciTech Connect

    Powell, M.

    1996-08-01

    Edge finishing processes have seemed like ideal candidates for automation. Most edge finishing processes are unpleasant, dangerous, tedious, expensive, not repeatable and labor intensive. Estimates place the cost of manual edge finishing processes at 12% of the total cost of fabricating precision parts. For small, high precision parts, the cost of hand finishing may be as high as 305 of the total part cost. Up to 50% of this cost could be saved through automation. This cost estimate includes the direct costs of edge finishing: the machining hours required and the 30% scrap and rework rate after manual finishing. Not included in these estimates are the indirect costs resulting from cumulative trauma disorders and retraining costs caused by the high turnover rate for finishing jobs.. Despite the apparent economic advantages, edge finishing has proven difficult to automate except in low precision and/or high volume production environments. Finishing automation systems have not been deployed successfully in Department of Energy defense programs (DOE/DP) production, A few systems have been attempted but have been subsequently abandoned for traditional edge finishing approaches: scraping, grinding, and filing the edges using modified dental tools and hand held power tools. Edge finishing automation has been an elusive but potentially lucrative production enhancement. The amount of time required for reconfiguring workcells for new parts, the time required to reprogram the workcells to finish new parts, and automation equipment to respond to fixturing errors and part tolerances are the most common reasons cited for eliminating automation as an option for DOE/DP edge finishing applications. Existing automated finishing systems have proven to be economically viable only where setup and reprogramming costs are a negligible fraction of overall production costs.

  6. Effect of interactions on edge property measurements in magnetic multilayers

    NASA Astrophysics Data System (ADS)

    McMichael, Robert; Zhu, Meng

    2010-03-01

    The edges of patterned thin films are important, especially in magnetic nanostructures. In previous work, it has been shown that the magnetic properties of film edges in Ni80Fe20 (Py) stripe arrays can be measured with a precision of a few percent using the ferromagnetic resonance (FMR) of localized edge modes. In this work, we extend this measurement technique to multilayer films, showing the effects of interactions between edge modes in the magnetic layers. We fabricate magnetic multilayer stripes consisting of 10 nm Py / x Cu / 20 nm Py, where x ranges from 1 nm to 20 nm, and we find that the edge saturation fields of both Py layers increase as the spacer is reduced, indicating enhanced magnetostatic interactions. An approximate analytical model based on the static dipolar interactions is used to simulate experimental and micromagnetic model data.

  7. The digital step edge

    NASA Technical Reports Server (NTRS)

    Haralick, R. M.

    1982-01-01

    The facet model was used to accomplish step edge detection. The essence of the facet model is that any analysis made on the basis of the pixel values in some neighborhood has its final authoritative interpretation relative to the underlying grey tone intensity surface of which the neighborhood pixel values are observed noisy samples. Pixels which are part of regions have simple grey tone intensity surfaces over their areas. Pixels which have an edge in them have complex grey tone intensity surfaces over their areas. Specially, an edge moves through a pixel only if there is some point in the pixel's area having a zero crossing of the second directional derivative taken in the direction of a non-zero gradient at the pixel's center. To determine whether or not a pixel should be marked as a step edge pixel, its underlying grey tone intensity surface was estimated on the basis of the pixels in its neighborhood.

  8. The Edge supersonic transport

    NASA Technical Reports Server (NTRS)

    Agosta, Roxana; Bilbija, Dushan; Deutsch, Marc; Gallant, David; Rose, Don; Shreve, Gene; Smario, David; Suffredini, Brian

    1992-01-01

    As intercontinental business and tourism volumes continue their rapid expansion, the need to reduce travel times becomes increasingly acute. The Edge Supersonic Transport Aircraft is designed to meet this demand by the year 2015. With a maximum range of 5750 nm, a payload of 294 passengers and a cruising speed of M = 2.4, The Edge will cut current international flight durations in half, while maintaining competitive first class, business class, and economy class comfort levels. Moreover, this transport will render a minimal impact upon the environment, and will meet all Federal Aviation Administration Part 36, Stage III noise requirements. The cornerstone of The Edge's superior flight performance is its aerodynamically efficient, dual-configuration design incorporating variable-geometry wingtips. This arrangement combines the benefits of a high aspect ratio wing at takeoff and low cruising speeds with the high performance of an arrow-wing in supersonic cruise. And while the structural weight concerns relating to swinging wingtips are substantial, The Edge looks to ever-advancing material technologies to further increase its viability. Heeding well the lessons of the past, The Edge design holds economic feasibility as its primary focus. Therefore, in addition to its inherently superior aerodynamic performance, The Edge uses a lightweight, largely windowless configuration, relying on a synthetic vision system for outside viewing by both pilot and passengers. Additionally, a fly-by-light flight control system is incorporated to address aircraft supersonic cruise instability. The Edge will be produced at an estimated volume of 400 aircraft and will be offered to airlines in 2015 at $167 million per transport (1992 dollars).

  9. High Speed Edge Detection

    NASA Technical Reports Server (NTRS)

    Prokop, Norman F (Inventor)

    2015-01-01

    Analog circuits for detecting edges in pixel arrays are disclosed. A comparator may be configured to receive an all pass signal and a low pass signal for a pixel intensity in an array of pixels. A latch may be configured to receive a counter signal and a latching signal from the comparator. The comparator may be configured to send the latching signal to the latch when the all pass signal is below the low pass signal minus an offset. The latch may be configured to hold a last negative edge location when the latching signal is received from the comparator.

  10. High Speed Edge Detection

    NASA Technical Reports Server (NTRS)

    Prokop, Norman F (Inventor)

    2016-01-01

    Analog circuits for detecting edges in pixel arrays are disclosed. A comparator may be configured to receive an all pass signal and a low pass signal for a pixel intensity in an array of pixels. A latch may be configured to receive a counter signal and a latching signal from the comparator. The comparator may be configured to send the latching signal to the latch when the all pass signal is below the low pass signal minus an offset. The latch may be configured to hold a last negative edge location when the latching signal is received from the comparator.

  11. Swords with Blunt Edges

    ERIC Educational Resources Information Center

    Popham, W. James

    2004-01-01

    Many U.S. educators now wonder whether they're teachers or targets. This mentality stems from the specter of their school being sanctioned for failing the state accountability tests mandated under No Child Left Behind (NCLB). According to this author, most of those tests are like blunt-edged swords: They function badly in two directions. While…

  12. The Inner Urban Edge

    ERIC Educational Resources Information Center

    Ferebee, Ann; Carpenter, Edward K.

    1974-01-01

    In this article, renewal of the inner urban edge is discussed. Norfolk (Virginia) is attempting to blur the difference between old and new neighbor hoods through zoning and architectural controls. Cincinnati (Ohio) is developing an environmentally sound hillside design. Reading (Pennsylvania) is utilizing old railyards for greenbelts of hiking and…

  13. Characterization of heterogeneous nickel sites in CO dehydrogenase from Clostridium thermoaceticum by nickel L-edge x-ray spectroscopy

    SciTech Connect

    Ralston, C.Y.; Kumar, M.; Ragsdale, S.W.

    1997-04-01

    L-edge x-ray absorption spectroscopy (XAS) is a useful spectroscopic technique for determining the electronic state of transition metals. For first row transition metals, the L-edge represents a transition from 2p core levels to 3d valence levels. Coulomb and exchange interactions between the core hole and 3d valence electrons make the L-edge sensitive to the number and configuration of 3d electrons, hence to the metal spin state and oxidation state. The authors have used L-edge XAS to characterize the Ni sites in the carbon monoxide dehydrogenase (CODH) enzyme from Clostridium thermoaceticum. This CODH catalyzes both CO oxidation and acetyl-CoA synthesis at two Ni and Fe containing centers, C and A, respectively. Since the enzyme exhibits complex EPR signals that never integrate to one spin per Ni, there is evidence for heterogeneity in the types of Ni present. The Ni L-edge protein spectra were recorded at ALS beamline 9.3.2. The photon energy resolutions used for protein samples and for Ni model compound spectra were 350 and 270 meV respectively. During data collection the sample chamber was maintained at less than 5{times}10{sup {minus}9} Torr using a helium cryopump. Model compound spectra were measured using total electron yield detection, while protein spectra were recorded using fluorescence detection with a windowless 13-element germanium detector, and were calibrated using the total electron yield spectrum of NiF{sub 2} or NiO. Each protein spectrum presented represents the sum of approximately 40 15-minute scans. The authors have found that by using L-edge XAS they are able to distinguish between different spin and oxidation states of Ni compounds. They have used this result to characterize the Ni containing CODH protein in various states. The L-edge spectra are consistent with other results showing that when CODH is reacted with CO, the metal centers undergo reduction.

  14. Superpixel edges for boundary detection

    SciTech Connect

    Moya, Mary M.; Koch, Mark W.

    2016-07-12

    Various embodiments presented herein relate to identifying one or more edges in a synthetic aperture radar (SAR) image comprising a plurality of superpixels. Superpixels sharing an edge (or boundary) can be identified and one or more properties of the shared superpixels can be compared to determine whether the superpixels form the same or two different features. Where the superpixels form the same feature the edge is identified as an internal edge. Where the superpixels form two different features, the edge is identified as an external edge. Based upon classification of the superpixels, the external edge can be further determined to form part of a roof, wall, etc. The superpixels can be formed from a speckle-reduced SAR image product formed from a registered stack of SAR images, which is further segmented into a plurality of superpixels. The edge identification process is applied to the SAR image comprising the superpixels and edges.

  15. Shape of patch edges affects edge permeability for meadow voles.

    PubMed

    Nams, Vilis O

    2012-09-01

    Human development typically fragments natural habitats into patches, affecting population and metapopulation dynamics via changes in animal behavior. Emigration from one habitat patch to another has a large effect on population and metapopulation dynamics. One factor that affects emigration is permeability of patch edges. This study looks at the effects of edge shape (convex, concave, and straight) on edge permeability for meadow voles (Microtus pennsylvanicus).. I tested five hypotheses for responses of animal movement to patch shape: (1) neutral edge response; (2) edge attraction; (3) edge avoidance; (4) time-minimizing, in which an animal attempts to minimize the time spent in inhospitable matrix, and thus travels as far as possible in the patch before crossing the edge; and (5) protection, in which an animal attempts to maximize protection while in the inhospitable matrix by keeping the patch close by. These hypotheses were tested by an experimental manipulation of meadow vole habitats. A strip was mowed with different edge shapes through an old field, and vole response was measured by tracking plates. Voles crossed edges at concave treatments twice as often compared to convex and straight shapes. Hypotheses (2) and (5) were supported. Although edge attraction causes a passive effect of a decrease in edge-crossing at concavities, this effect was eclipsed by the active effect of voles choosing to cross at concavities. The results can be generalized to edge tortuosity in general. Conservation biologists should consider edge shapes when exploring the effects of habitat fragmentation on animal populations.

  16. Edge detection by nonlinear dynamics

    SciTech Connect

    Wong, Yiu-fai

    1994-07-01

    We demonstrate how the formulation of a nonlinear scale-space filter can be used for edge detection and junction analysis. By casting edge-preserving filtering in terms of maximizing information content subject to an average cost function, the computed cost at each pixel location becomes a local measure of edgeness. This computation depends on a single scale parameter and the given image data. Unlike previous approaches which require careful tuning of the filter kernels for various types of edges, our scheme is general enough to be able to handle different edges, such as lines, step-edges, corners and junctions. Anisotropy in the data is handled automatically by the nonlinear dynamics.

  17. Edge turbulence in tokamaks

    NASA Astrophysics Data System (ADS)

    Nedospasov, A. V.

    1992-12-01

    Edge turbulence is of decisive importance for the distribution of particle and energy fluxes to the walls of tokamaks. Despite the availability of extensive experimental data on the turbulence properties, its nature still remains a subject for discussion. This paper contains a review of the most recent theoretical and experimental studies in the field, including mainly the studies to which Wootton (A.J. Wooton, J. Nucl. Mater. 176 & 177 (1990) 77) referred to most in his review at PSI-9 and those published later. The available theoretical models of edge turbulence with volume dissipation due to collisions fail to fully interpret the entire combination of experimental facts. In the scrape-off layer of a tokamak the dissipation prevails due to the flow of current through potential shifts near the surface of limiters of divertor plates. The different origins of turbulence at the edge and in the core plasma due to such dissipation are discussed in this paper. Recent data on the electron temperature fluctuations enabled one to evaluate the electric probe measurements of turbulent flows of particles and heat critically. The latest data on the suppression of turbulence in the case of L-H transitions are given. In doing so, the possibility of exciting current instabilities in biasing experiments (rather than only to the suppression of existing turbulence) is given some attention. Possible objectives of further studies are also discussed.

  18. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals

    NASA Astrophysics Data System (ADS)

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-01

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices.Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni

  19. Are shrubland birds edge specialists?

    PubMed

    Schlossberg, Scott; King, David I

    2008-09-01

    In studies of forest fragmentation, birds of scrubby, early-successional habitats are considered edge specialists. Because these birds are assumed to thrive in fragmented, edge-dominated areas, their landscape ecology has received little attention from ecologists. With populations of shrubland birds declining throughout the eastern United States, the question of whether or not these birds really prefer edge habitats has important conservation implications. We used a meta-analysis to test how edges affect the abundance of shrubland birds in early-successional habitats. We analyzed data for 17 species from seven studies that compared the abundances of birds in the interiors and edges of regenerating clearcuts surrounded by mature forest. The meta-analysis clearly showed that shrubland birds avoid edges. All 17 species tested had higher abundances in patch centers than along edges, and edge effects were significant for 8 of 17 species. The key implication of this result is that small or irregular patches, dominated by edge, are unlikely to provide suitable habitat for shrubland birds. Thus, management for these declining species should involve providing large patches and minimizing edges. These findings demonstrate the importance of testing widely accepted ecological classifications and the need to view landscape ecology from the perspective of non-forest wildlife.

  20. Edge remap for solids

    SciTech Connect

    Kamm, James R.; Love, Edward; Robinson, Allen C.; Young, Joseph G.; Ridzal, Denis

    2013-12-01

    We review the edge element formulation for describing the kinematics of hyperelastic solids. This approach is used to frame the problem of remapping the inverse deformation gradient for Arbitrary Lagrangian-Eulerian (ALE) simulations of solid dynamics. For hyperelastic materials, the stress state is completely determined by the deformation gradient, so remapping this quantity effectively updates the stress state of the material. A method, inspired by the constrained transport remap in electromagnetics, is reviewed, according to which the zero-curl constraint on the inverse deformation gradient is implicitly satisfied. Open issues related to the accuracy of this approach are identified. An optimization-based approach is implemented to enforce positivity of the determinant of the deformation gradient. The efficacy of this approach is illustrated with numerical examples.

  1. Edge phonons in black phosphorus

    PubMed Central

    Ribeiro, H. B.; Villegas, C. E. P.; Bahamon, D. A.; Muraca, D.; Castro Neto, A. H.; de Souza, E. A. T.; Rocha, A. R.; Pimenta, M. A.; de Matos, C. J. S.

    2016-01-01

    Black phosphorus has recently emerged as a new layered crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and behaviour of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Polarized Raman results show the appearance of new modes at the edges of the sample, and their spectra depend on the atomic structure of the edges (zigzag or armchair). Theoretical simulations confirm that the new modes are due to edge phonon states that are forbidden in the bulk, and originated from the lattice termination rearrangements. PMID:27412813

  2. Edge phonons in black phosphorus

    NASA Astrophysics Data System (ADS)

    Ribeiro, H. B.; Villegas, C. E. P.; Bahamon, D. A.; Muraca, D.; Castro Neto, A. H.; de Souza, E. A. T.; Rocha, A. R.; Pimenta, M. A.; de Matos, C. J. S.

    2016-07-01

    Black phosphorus has recently emerged as a new layered crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and behaviour of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Polarized Raman results show the appearance of new modes at the edges of the sample, and their spectra depend on the atomic structure of the edges (zigzag or armchair). Theoretical simulations confirm that the new modes are due to edge phonon states that are forbidden in the bulk, and originated from the lattice termination rearrangements.

  3. The Facilitator's Edge: Group Sessions for Edge-ucators.

    ERIC Educational Resources Information Center

    Handcock, Helen

    The Facilitator's Edge is a workshop series based on the life/work messages of The Edge magazine. The workshops are deigned to help educators, youth workers, and their career practitioners facilitate conscious career building. This manual consists of five group sessions, each focusing on a different career-building theme. "Megatrends and…

  4. Giant edge state splitting at atomically precise graphene zigzag edges

    PubMed Central

    Wang, Shiyong; Talirz, Leopold; Pignedoli, Carlo A.; Feng, Xinliang; Müllen, Klaus; Fasel, Roman; Ruffieux, Pascal

    2016-01-01

    Zigzag edges of graphene nanostructures host localized electronic states that are predicted to be spin-polarized. However, these edge states are highly susceptible to edge roughness and interaction with a supporting substrate, complicating the study of their intrinsic electronic and magnetic structure. Here, we focus on atomically precise graphene nanoribbons whose two short zigzag edges host exactly one localized electron each. Using the tip of a scanning tunnelling microscope, the graphene nanoribbons are transferred from the metallic growth substrate onto insulating islands of NaCl in order to decouple their electronic structure from the metal. The absence of charge transfer and hybridization with the substrate is confirmed by scanning tunnelling spectroscopy, which reveals a pair of occupied/unoccupied edge states. Their large energy splitting of 1.9 eV is in accordance with ab initio many-body perturbation theory calculations and reflects the dominant role of electron–electron interactions in these localized states. PMID:27181701

  5. Wing Leading Edge Debris Analysis

    NASA Technical Reports Server (NTRS)

    Shah, Sandeep; Jerman, Gregory

    2004-01-01

    This is a slide presentation showing the Left Wing Leading Edge (WLE) heat damage observations: Heavy "slag" deposits on select RCC panels. Eroded and knife-edged RCC rib sections. Excessive overheating and slumping of carrier panel tiles. Missing or molten attachment bolts but intact bushing. Deposit mainly on "inside" RCC panel. Deposit on some fractured RCC surface

  6. Rock Segmentation through Edge Regrouping

    NASA Technical Reports Server (NTRS)

    Burl, Michael

    2008-01-01

    Rockster is an algorithm that automatically identifies the locations and boundaries of rocks imaged by the rover hazard cameras (hazcams), navigation cameras (navcams), or panoramic cameras (pancams). The software uses edge detection and edge regrouping to identify closed contours that separate the rocks from the background.

  7. Improved Edge Performance in MRF

    NASA Technical Reports Server (NTRS)

    Shorey, Aric; Jones, Andrew; Durnas, Paul; Tricard, Marc

    2004-01-01

    The fabrication of large segmented optics requires a polishing process that can correct the figure of a surface to within a short distance from its edges-typically, a few millimeters. The work here is to develop QED's Magnetorheological Finishing (MRF) precision polishing process to minimize residual edge effects.

  8. The Robotic Edge Finishing Laboratory

    SciTech Connect

    Loucks, C.S.; Selleck, C.B.

    1990-08-01

    The Robotic Edge Finishing Laboratory at Sandia National Laboratories is developing four areas of technology required for automated deburring, chamfering, and blending of machined edges: (1) the automatic programming of robot trajectories and deburring processes using information derived from a CAD database, (2) the use of machine vision for locating the workpiece coupled with force control to ensure proper tool contact, (3) robotic deburring, blending, and machining of precision chamfered edges, and (4) in-process automated inspection of the formed edge. The Laboratory, its components, integration, and results from edge finishing experiments to date are described here. Also included is a discussion of the issues regarding implementation of the technology in a production environment. 24 refs., 17 figs.

  9. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals.

    PubMed

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-21

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices.

  10. Ni cycling in mangrove sediments from New Caledonia

    NASA Astrophysics Data System (ADS)

    Noel, V. S.; Morin, G.; Juillot, F.; Marchand, C.; Brest, J.; Bargar, J.; Munoz, M.; Ardo, S.; Brown, G. E.

    2014-12-01

    In New Caledonia, mangroves receive large inputs of lateritic materials eroded from massive ultramafic deposits enriched in Fe, Ni, Mn, Cr, and Co. Because of the major physicochemical gradients, especially redox gradients, that characterize these ecosystems, mineralogical transformations may influence the crystal-chemistry and bioavailability of Ni and its mobility towards a lagoon of over 20,000 km2. Bulk and spatially resolved chemical analyses by SEM-EDXS were coupled with Ni K-edge X-ray absorption fine structure (XAFS) spectroscopy analysis to characterize the vertical and lateral changes in Ni speciation across the intertidal zone of a mangrove forest in the Vavouto Bay (New Caledonia) where Ni concentrations range from 1000 to 5300 mg•kg-1. XAFS results indicate that phyllosilicates and goethite inherited from the eroded lateritic materials are the dominant Ni-bearing phases in the surface horizons of the mangrove sediments. They are fully preserved at depth in the dry and oxic salt flat area, located on the inland side of the coast. In contrast, beneath the vegetated Rhizophoras and Avicennias stands Ni-bearing goethites rapidly diminish with increasing depth in the anoxic horizons of the sediments, and pyrite and organic complexes become the dominant Ni-containing species. Moreover, Ni incorporation in pyrite is more developed in the sediments beneath the intermediate Avicennia stand than beneath the Rhizophora stand that is closest to the shore. Such lateral changes in Ni speciation may be related to reoxidation of Ni-bearing pyrites in the Rhizophora stand, which is subject to periodic alternation of reducing and oxidizing events due to tidal fluctuations. These major changes in Ni speciation could significantly influence Ni mobility across the interidal zone. Indeed, as estimated with respect to Ti concentration, which is taken as a geochemical invariant, Ni is found to be immobile in the salt flat, to accumulate beneath the Avicennia stand, and to

  11. Structural evolution of NiAg heterogeneous alloys upon annealing

    NASA Astrophysics Data System (ADS)

    Proux, O.; Mimault, J.; Revenant-Brizard, C.; Regnard, J. R.; Mevel, B.

    1999-01-01

    NiAg heterogeneous alloys were studied by x-ray diffraction and x-ray absorption spectroscopy at the Ni K-edge using a total electron yield detection. In the as-deposited 0953-8984/11/1/013/img8 alloys of 0.10 and 0.15 Ni atomic fraction, most of the Ni atoms are in substitutional sites in the Ag matrix. At higher Ni concentration, the Ni atoms outside the Ag-rich phase become numerous enough to group together in small clusters. An important disorder in the neighbourhood of Ni atoms is demonstrated. At low annealing temperature (up to 0953-8984/11/1/013/img9C), in 0953-8984/11/1/013/img10 and 0953-8984/11/1/013/img11, some Ni atoms are still present in substitutional sites in the Ag matrix and the small Ni particles are under strain. A very short-range order exists in this state. After a 0953-8984/11/1/013/img9C annealing, the Ni particles grow, and the Ag-rich phase remains in a steady structural state. After a higher annealing (0953-8984/11/1/013/img13C), the local Ni atomic environment becomes well ordered and typical of the pure Ni FCC phase. The Ag-rich crystallites are impoverished in Ni atoms and grow with elimination of defects. Ni grains are generally smaller than 1 nm for as-deposited alloys and reach several nanometres after a 0953-8984/11/1/013/img13C annealing for 10 min.

  12. [Hydrogen induced C-C, C-N, and C-S bond activities on Pi and Ni surfaces]: Summary

    SciTech Connect

    Gland, J.L.

    1994-12-31

    This document summarizes research applied to chemical bond activation studies. Topics summarized include: Carbon nitrogen bonds experimentation with aniline on Ni(111), Mi(100), and Pt(111) surfaces; carbon sulfur bonds experimentation with methanethiol, phenylthiol, and dimethyl disulfide on Pt(111) and Ni(111) surfaces; carbon-carbon bonds experimentation on Ni(100), Ni(111) and Pt(111) surfaces; and in-situ fluorescence yield near edge spectroscopy.

  13. Edge-on Galaxy

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Hubble Space Telescope has imaged an unusual edge-on galaxy, revealing remarkable details of its warped dusty disc and showing how colliding galaxies trigger the birth of new stars.

    The image, taken by Hubble's Wide Field and Planetary Camera 2 (WFPC2), is online at http://heritage.stsci.edu and http://www.jpl.nasa.gov/images/wfpc. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. During observations of the galaxy, the camera passed a milestone, taking its 100,000th image since shuttle astronauts installed it in Hubble in 1993.

    The dust and spiral arms of normal spiral galaxies, like our Milky Way, look flat when seen edge- on. The new image of the galaxy ESO 510-G13 shows an unusual twisted disc structure, first seen in ground-based photographs taken at the European Southern Observatory in Chile. ESO 510-G13 lies in the southern constellation Hydra, some 150 million light-years from Earth. Details of the galaxy's structure are visible because interstellar dust clouds that trace its disc are silhouetted from behind by light from the galaxy's bright, smooth central bulge.

    The strong warping of the disc indicates that ESO 510-G13 has recently collided with a nearby galaxy and is in the process of swallowing it. Gravitational forces distort galaxies as their stars, gas, and dust merge over millions of years. When the disturbances die out, ESO 510-G13 will be a single galaxy.

    The galaxy's outer regions, especially on the right side of the image, show dark dust and bright clouds of blue stars. This indicates that hot, young stars are forming in the twisted disc. Astronomers believe star formation may be triggered when galaxies collide and their interstellar clouds are compressed.

    The Hubble Heritage Team used WFPC2 to observe ESO 510-G13 in April 2001. Pictures obtained through blue, green, and red filters were combined to make this color-composite image, which emphasizes the contrast between the dusty

  14. Atomic structure relaxation in nanocrystalline NiO studied by EXAFS spectroscopy: Role of nickel vacancies

    NASA Astrophysics Data System (ADS)

    Anspoks, A.; Kalinko, A.; Kalendarev, R.; Kuzmin, A.

    2012-11-01

    Nanocrystalline NiO samples have been studied using the Ni K-edge extended x-ray absorption fine structure (EXAFS) spectroscopy and recently developed modeling technique, combining classical molecular dynamics with ab initio multiple-scattering EXAFS calculations (MD-EXAFS). Conventional analysis of the EXAFS signals from the first two coordination shells of nickel revealed that (i) the second shell average distance R(Ni-Ni2) expands in nanocrystalline NiO compared to microcrystalline NiO, in agreement with overall unit cell volume expansion observed by x-ray diffraction; (ii) on the contrary, the first shell average distance R(Ni-O1) in nanocrystalline NiO shrinks compared to microcrystalline NiO; (iii) the thermal contribution into the mean-square relative displacement σ2 is close in both microcrystalline and nanocrystalline NiO and can be described by the Debye model; (iv) the static disorder is additionally present in nanocrystalline NiO in both the first Ni-O1 and second Ni-Ni2 shells due to nanocrystal structure relaxation. Within the MD-EXAFS method, the force-field potential models have been developed for nanosized NiO using as a criterion the agreement between the experimental and theoretical EXAFS spectra. The best solutions have been obtained for the 3D cubic-shaped nanoparticle models with nonzero Ni vacancy concentration Cvac: Cvac≈0.4-1.2% for NiO nanoparticles having the cube size of L≈3.6-4.2 nm and Cvac≈1.6-2.0% for NiO thin film composed of cubic nanograins with a size of L≈1.3-2.1 nm. Thus our results show that the Ni vacancies in nanosized NiO play important role in its atomic structure relaxation along with the size reduction effect.

  15. Equilibrium shape of graphene domains on Ni(111)

    NASA Astrophysics Data System (ADS)

    Li, Meifang; Hannon, James B.; Tromp, Rudoff M.; Sun, Jiebing; Li, Junwen; Shenoy, Vivek B.; Chason, Eric

    2013-07-01

    We have determined the equilibrium shape of graphene domains grown on Ni(111) via carbon segregation at 925∘C. In situ, spatially resolved electron diffraction measurements were used to determine the crystallographic orientation of the edges of the graphene domains. In contrast to recent theoretical predictions of a nearly circular shape, we show that graphene domains, which nucleate with random shapes, all evolve toward a triangular equilibrium shape with “zigzag” edges. Only one of the two possible zigzag edge orientations is observed.

  16. Measurement of K Shell Photoelectric Cross Sections at a K Edge--A Laboratory Experiment

    ERIC Educational Resources Information Center

    Nayak, S. V.; Badiger, N. M.

    2007-01-01

    We describe in this paper a new method for measuring the K shell photoelectric cross sections of high-Z elemental targets at a K absorption edge. In this method the external bremsstrahlung (EB) photons produced in the Ni target foil by beta particles from a weak[superscript 90]Sr-[superscript 90]Y beta source are passed through an elemental target…

  17. Edge equilibrium code for tokamaks

    SciTech Connect

    Li, Xujing; Drozdov, Vladimir V.

    2014-01-15

    The edge equilibrium code (EEC) described in this paper is developed for simulations of the near edge plasma using the finite element method. It solves the Grad-Shafranov equation in toroidal coordinate and uses adaptive grids aligned with magnetic field lines. Hermite finite elements are chosen for the numerical scheme. A fast Newton scheme which is the same as implemented in the equilibrium and stability code (ESC) is applied here to adjust the grids.

  18. Edge instabilities of topological superconductors

    NASA Astrophysics Data System (ADS)

    Hofmann, Johannes S.; Assaad, Fakher F.; Schnyder, Andreas P.

    2016-05-01

    Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground-state degeneracy. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry-broken phases, which lift the ground-state degeneracy. We examine the instabilities of the flat-band edge states of dx y-wave superconductors by performing a mean-field analysis in the Majorana basis of the edge states. The leading instabilities are Majorana mass terms, which correspond to coherent superpositions of particle-particle and particle-hole channels in the fermionic language. We find that attractive interactions induce three different mass terms. One is a coherent superposition of imaginary s -wave pairing and current order, and another combines a charge-density-wave and finite-momentum singlet pairing. Repulsive interactions, on the other hand, lead to ferromagnetism together with spin-triplet pairing at the edge. Our quantum Monte Carlo simulations confirm these findings and demonstrate that these instabilities occur even in the presence of strong quantum fluctuations. We discuss the implications of our results for experiments on cuprate high-temperature superconductors.

  19. Quantifying covalent interactions with resonant inelastic soft X-ray scattering: Case study of Ni2+ aqua complex

    NASA Astrophysics Data System (ADS)

    Kunnus, K.; Josefsson, I.; Schreck, S.; Quevedo, W.; Miedema, P. S.; Techert, S.; de Groot, F. M. F.; Föhlisch, A.; Odelius, M.; Wernet, Ph.

    2017-02-01

    We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. We propose that 2p3d RIXS at the Ni L3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations.

  20. Quantifying covalent interactions with resonant inelastic soft X-ray scattering: Case study of Ni2+ aqua complex

    DOE PAGES

    Kunnus, K.; Josefsson, I.; Schreck, S.; ...

    2016-12-23

    We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. Here, we propose that 2p3d RIXS at the Ni L3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations.

  1. On the Edge: Haptic Discrimination of Edge Sharpness

    PubMed Central

    Skinner, Andy L.; Kent, Christopher; Rossiter, Jonathan M.; Benton, Christopher P.; Groen, Martin G. M.; Noyes, Jan M.

    2013-01-01

    The increasing ubiquity of haptic displays (e.g., smart phones and tablets) necessitates a better understanding of the perceptual capabilities of the human haptic system. Haptic displays will soon be capable of locally deforming to create simple 3D shapes. This study investigated the sensitivity of our haptic system to a fundamental component of shapes: edges. A novel set of eight high quality shape stimuli with test edges that varied in sharpness were fabricated in a 3D printer. In a two alternative, forced choice task, blindfolded participants were presented with two of these shapes side by side (one the reference, the other selected randomly from the remaining set of seven) and after actively exploring the test edge of each shape with the tip of their index finger, reported which shape had the sharper edge. We used a model selection approach to fit optimal psychometric functions to performance data, and from these obtained just noticeable differences and Weber fractions. In Experiment 1, participants performed the task with four different references. With sharpness defined as the angle at which one surface meets the horizontal plane, the four JNDs closely followed Weber’s Law, giving a Weber fraction of 0.11. Comparisons to previously reported Weber fractions from other haptic manipulations (e.g. amplitude of vibration) suggests we are sufficiently sensitive to changes in edge sharpness for this to be of potential utility in the design of future haptic displays. In Experiment 2, two groups of participants performed the task with a single reference but different exploration strategies; one was limited to a single touch, the other unconstrained and free to explore as they wished. As predicted, the JND in the free exploration condition was lower than that in the single touch condition, indicating exploration strategy affects sensitivity to edge sharpness. PMID:24023852

  2. Optical Characterization of Strong UV Luminescence Emitted from the Excitonic Edge of Nickel Oxide Nanotowers

    PubMed Central

    Ho, Ching-Hwa; Kuo, Yi-Ming; Chan, Ching-Hsiang; Ma, Yuan-Ron

    2015-01-01

    NiO had been claimed to have the potential for application in transparent conducting oxide, electrochromic device for light control, and nonvolatile memory device. However, the detailed study of excitonic transition and light-emission property of NiO has rarely been explored to date. In this work, we demonstrate strong exciton-complex emission of high-quality NiO nanotowers grown by hot-filament metal-oxide vapor deposition with photoluminescence as an evaluation tool. Fine and clear emission features coming from the excitonic edge of the NiO are obviously observed in the photoluminescence spectra. A main excitonic emission of ~3.25 eV at 300 K can be decomposed into free exciton, bound excitons, and donor-acceptor-pair irradiations at lowered temperatures down to 10 K. The band-edge excitonic structure for the NiO nanocrystals has been evaluated and analyzed by transmission and thermoreflectacne measurements herein. All the experimental results demonstrate the cubic NiO thin-film nanotower is an applicable direct-band-gap material appropriate for UV luminescence and transparent-conducting-oxide applications. PMID:26506907

  3. Image recovery from edge primitives

    NASA Technical Reports Server (NTRS)

    Alter-Gartenberg, Rachel; Huck, Friedrich O.; Narayanswamy, Ramkumar

    1990-01-01

    A method for extracting edge primitives from Mach-band patterns is presented together with a method for recovering image representations of features outlined by the edge boundaries. The accuracy, stability, and resolution of these representations are assessed. Since these representations are most commonly used in characterizing targets, this method of low-level processing offers new opportunities for computer vision and high data-compressing coding. Two bandpass filters are considered, the spatially invariant Laplacian of Gaussian filter and spatially variant intensity-dependent spatial (IDS) summation. It is shown that the recovery from the IDS bandpass data is particularly advantageous in applications for which robustness to local and temporal variations in illumination is important. It is concluded that the edge primitives extracted from bandpassed images can be an efficient way to store, transmit, and represent images.

  4. Edge Coloring, Polyhedra and Probability

    DTIC Science & Technology

    1998-11-01

    also \\dBi{v)-\\dB*{v)\\ < i<Jand|m Al(5J)- idef (SJ)| < | . t f ll t t \\8\\ {\\ | X ^ n(J follows from (a) and ±A < |B?| < 3A. D Preparing the marking...chromatic index of G and is denoted by x ’{G). We consider the edge coloring problem in the framework of the relationship between an integer program and its...linear programming relaxation. To do this we first formulate edge coloring as an integer program and let x *(G) be the optimum of the linear

  5. Role of Edges in Complex Network Epidemiology

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Jiang, Zhi-Hong; Wang, Hui; Xie, Fei; Chen, Chao

    2012-09-01

    In complex network epidemiology, diseases spread along contacting edges between individuals and different edges may play different roles in epidemic outbreaks. Quantifying the efficiency of edges is an important step towards arresting epidemics. In this paper, we study the efficiency of edges in general susceptible-infected-recovered models, and introduce the transmission capability to measure the efficiency of edges. Results show that deleting edges with the highest transmission capability will greatly decrease epidemics on scale-free networks. Basing on the message passing approach, we get exact mathematical solution on configuration model networks with edge deletion in the large size limit.

  6. Supporting interactive graph exploration using edge plucking

    NASA Astrophysics Data System (ADS)

    Wong, Nelson; Carpendale, Sheelagh

    2007-01-01

    Excessive edge density in graphs can cause serious readability issues, which in turn can make the graphs difficult to understand or even misleading. Recently, we introduced the idea of providing tools that offer interactive edge bending as a method by which edge congestion can be disambiguated. We extend this direction, presenting a new tool, Edge Plucking, which offers new interactive methods to clarify node-edge relationships. Edge Plucking expands the number of situations in which interactive graph exploration tools can be used to address edge congestion.

  7. Enhancement of the Hydrogen Evolution Reaction from Ni-MoS2 Hybrid Nanoclusters

    PubMed Central

    2016-01-01

    This report focuses on a novel strategy for the preparation of transition metal–MoS2 hybrid nanoclusters based on a one-step, dual-target magnetron sputtering, and gas condensation process demonstrated for Ni-MoS2. Aberration-corrected STEM images coupled with EDX analysis confirms the presence of Ni and MoS2 in the hybrid nanoclusters (average diameter = 5.0 nm, Mo:S ratio = 1:1.8 ± 0.1). The Ni-MoS2 nanoclusters display a 100 mV shift in the hydrogen evolution reaction (HER) onset potential and an almost 3-fold increase in exchange current density compared with the undoped MoS2 nanoclusters, the latter effect in agreement with reported DFT calculations. This activity is only reached after air exposure of the Ni-MoS2 hybrid nanoclusters, suggested by XPS measurements to originate from a Ni dopant atoms oxidation state conversion from metallic to 2+ characteristic of the NiO species active to the HER. Anodic stripping voltammetry (ASV) experiments on the Ni-MoS2 hybrid nanoclusters confirm the presence of Ni-doped edge sites and reveal distinctive electrochemical features associated with both doped Mo-edge and doped S-edge sites which correlate with both their thermodynamic stability and relative abundance. PMID:27818842

  8. Edge enhanced morphology for infrared image analysis

    NASA Astrophysics Data System (ADS)

    Bai, Xiangzhi; Liu, Haonan

    2017-01-01

    Edge information is one of the critical information for infrared images. Morphological operators have been widely used for infrared image analysis. However, the edge information in infrared image is weak and the morphological operators could not well utilize the edge information of infrared images. To strengthen the edge information in morphological operators, the edge enhanced morphology is proposed in this paper. Firstly, the edge enhanced dilation and erosion operators are given and analyzed. Secondly, the pseudo operators which are derived from the edge enhanced dilation and erosion operators are defined. Finally, the applications for infrared image analysis are shown to verify the effectiveness of the proposed edge enhanced morphological operators. The proposed edge enhanced morphological operators are useful for the applications related to edge features, which could be extended to wide area of applications.

  9. Shape-dependent canny edge detector

    NASA Astrophysics Data System (ADS)

    Panetta, Karen A.; Agaian, Sos S.; Nercessian, Shahan C.; Almunstashri, Ali A.

    2011-08-01

    Edges characterize the boundaries of objects in images and are informative structural cues for computer vision and target/object detection and recognition systems. The Canny edge detector is widely regarded as the edge detection standard. It is fairly adaptable to different environments, as its parametric nature attempts to tailor the detection of edges based on image-dependent characteristics or the particular requirements of a given implementation. Though it has been used in a myriad of image processing tasks, the Canny edge detector is still vulnerable to edge losses, localization errors, and noise sensitivity. These issues are largely due to the key tradeoff made in the scale and size of the edge detection filters used by the algorithm. Small-scaled filters are sensitive to edges but also to noise, whereas large-scaled filters are robust to noise but could filter out fine details. In this paper, novel edge detection kernel generalizations and a shape-dependent edge detector are introduced to alleviate these shortcomings. While most standard edge detection algorithms are based on convolving the input image with fixed size square kernels, this paper will illustrate the benefits of different filter sizes, and more importantly, different kernel shapes for edge detection. Moreover, new edge fusion methods are introduced to more effectively combine the individual edge responses. Existing edge detectors, including the Canny edge detector, can be obtained from the generalized edge detector by specifying corresponding parameters and kernel shapes. The proposed representations and edge detector have been qualitatively and quantitatively evaluated on several different types of image data. Computer simulations demonstrate that nonsquare kernel approaches can outperform square kernel approaches such as Canny, Sobel, Prewitt, Roberts, and others, providing better tradeoffs between noise rejection, accurate edge localization, and resolution. Where possible, Pratt's figure of

  10. Laplacian operator-based edge detectors.

    PubMed

    Wang, Xin

    2007-05-01

    Laplacian operator is a second derivative operator often used in edge detection. Compared with the first derivative-based edge detectors such as Sobel operator, the Laplacian operator may yield better results in edge localization. Unfortunately, the Laplacian operator is very sensitive to noise. In this paper, based on the Laplacian operator, a model is introduced for making some edge detectors. Also, the optimal threshold is introduced for obtaining a Maximum a Posteriori (MAP) estimate of edges.

  11. A scanning tunnelling microscopy study of C and N adsorption phases on the vicinal Ni(100) surfaces Ni(810) and Ni(911)

    NASA Astrophysics Data System (ADS)

    Driver, S. M.; Toomes, R. L.; Woodruff, D. P.

    2016-04-01

    The influence of N and C chemisorption on the morphology and local structure of nominal Ni(810) and Ni(911) surfaces, both vicinal to (100) but with [001] and [ 01 1 bar ] step directions, respectively, has been investigated using scanning tunnelling microscopy (STM) and low energy electron diffraction. Ni(911) undergoes substantial step bunching in the presence of both adsorbates, with the (911)/N surface showing (411) facets, whereas for Ni(810), multiple steps 2-4 layers high are more typical. STM atomic-scale images show the (2 × 2)pg 'clock' reconstruction on the (100) terraces of the (810) surfaces with both C and N, although a second c(2 × 2) structure, most readily reconciled with a 'rumpling' reconstruction, is also seen on Ni(810)/N. On Ni(911), the clock reconstruction is not seen on the (100) terraces with either adsorbate, and these images are typified by protrusions on a (1 × 1) mesh. This absence of clock reconstruction is attributed to the different constraints imposed on the lateral movements of the surface Ni atoms adjacent to the up-step edge of the terraces with a [ 01 1 bar ] step direction.

  12. The Problem of the Edge.

    ERIC Educational Resources Information Center

    Faatz, Judith A.

    1998-01-01

    Describes a field study in a local ecosystem which allows high school students to investigate the edge effect, where a meadow and a forest meet. Students measure soil moisture content, soil temperature, air temperature, relative humidity, wind intensity, and illumination level. Teachers can help students apply their findings to understand problems…

  13. Failure During Sheared Edge Stretching

    NASA Astrophysics Data System (ADS)

    Levy, B. S.; van Tyne, C. J.

    2008-12-01

    Failure during sheared edge stretching of sheet steels is a serious concern, especially in advanced high-strength steel (AHSS) grades. The shearing process produces a shear face and a zone of deformation behind the shear face, which is the shear-affected zone (SAZ). A failure during sheared edge stretching depends on prior deformation in the sheet, the shearing process, and the subsequent strain path in the SAZ during stretching. Data from laboratory hole expansion tests and hole extrusion tests for multiple lots of fourteen grades of steel were analyzed. The forming limit curve (FLC), regression equations, measurement uncertainty calculations, and difference calculations were used in the analyses. From these analyses, an assessment of the primary factors that contribute to the fracture during sheared edge stretching was made. It was found that the forming limit strain with consideration of strain path in the SAZ is a major factor that contributes to the failure of a sheared edge during stretching. Although metallurgical factors are important, they appear to play a somewhat lesser role.

  14. Ni cycling in mangrove sediments from New Caledonia

    NASA Astrophysics Data System (ADS)

    Noël, Vincent; Morin, Guillaume; Juillot, Farid; Marchand, Cyril; Brest, Jessica; Bargar, John R.; Muñoz, Manuel; Marakovic, Grégory; Ardo, Sandy; Brown, Gordon E.

    2015-11-01

    Covering more than 70% of tropical and subtropical coastlines, mangrove intertidal forests are well known to accumulate potentially toxic trace metals in their sediments, and thus are generally considered to play a protective role in marine and lagoon ecosystems. However, the chemical forms of these trace metals in mangrove sediments are still not well known, even though their molecular-level speciation controls their long-term behavior. Here we report the vertical and lateral changes in the chemical forms of nickel, which accumulates massively in mangrove sediments downstream from lateritized ultramafic deposits from New Caledonia, where one of nature's largest accumulations of nickel occurs. To accomplish this we used Ni K-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy data in combination with microscale chemical analyses using Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (SEM-EDXS). After Principal Component and Target Transform analyses (PCA-TT), the EXAFS data of the mangrove sediments were reliably least-squares fitted by linear combination of 3-components chosen from a large model compound spectral database including synthetic and natural Ni-bearing sulfides, clay minerals, oxyhydroxides, and organic complexes. Our results show that in the inland salt flat Ni is hosted in minerals inherited from the eroded lateritic materials, i.e. Ni-poor serpentine (44-58%), Ni-rich talc (20-31%), and Ni-goethite (18-24%). In contrast, in the hydromorphic sediments beneath the vegetated Avicennia and Rhizophora stands, a large fraction of Ni is partly redistributed into a neoformed smectite pool (20-69% of Ni-montmorillonite), and Ni speciation significantly changes with depth in the sediment. Indeed, Ni-rich talc (25-56%) and Ni-goethite (15-23%) disappear below ∼15 cm depth in the sediment and are replaced by Ni-sorbed pyrite (23-52%) in redox-active intermediate depth layers and by pyrite (34-55%) in the deepest

  15. Development of edge effects around experimental ecosystem hotspots is affected by edge density and matrix type

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ecological edge effects are sensitive to landscape context. In particular, edge effects can be altered by matrix type and by the presence of other nearby edges. We experimentally altered patch configurations in an African savanna to determine how edge density and matrix type influence edge effect de...

  16. Incoherent Ag islands growth on Ni(100)

    NASA Astrophysics Data System (ADS)

    Marie, J. B.; Braems, I.; Bellec, A.; Chacon, C.; Creuze, J.; Girard, Y.; Gueddani, S.; Lagoute, J.; Repain, V.; Rousset, S.

    2017-02-01

    Growth of two-dimensional superstructure and island morphologies of silver atoms evaporated on a nickel (100) surface are studied by scanning tunneling microscopy. Near-equilibrium islands form at moderate annealing temperature (lower than 500 K) and present two kinds of morphologies. While they share a common monolayer c(2×8) superstructure, two distinct populations of islands coexist: rounded islands grown on the surface and spindle-shaped islands grown inside the Ni surface. The latter present a clear saturation of their density with increasing coverage. These shapes are mostly dominated by boundary energies as confirmed by a simple two-dimensional Wulff model whose parameters are derived using molecular statics simulations. Further annealing to 700 K leads to long Ag strips decorating the Ni step edges.

  17. XANES spectral changes for discotic liquid crystals of bis[1,2-bis(3,4-dioctyloxyphenyl) ethanedione dioximato]Ni(II)

    NASA Astrophysics Data System (ADS)

    Yokomizo, Mitsutoshi; Kurisaki, Tsutomu; Yamaguchi, Toshio; Wakita, Hisanobu; Oka-Inagaki, Yoshio; Ohta, Kazuchika

    The one-dimensional stacking structures of a liquid crystal Ni complex- [1,2-bis(3,4-dialkoxyphenyl)ethanedione dioximato]Ni(II), [Ni{(C8O)4dpg}2],which shows thermochromism, (see Fig. 1) have been investigated over a temperature range from room temperature to 220°C by analyzing X-ray absorption near-edge structure (XANES) spectra together with a DV-X[alpha] molecular orbital calculation. The thermochromic character of the complex is discussed through the structural change with temperature in Ni--Ni and Ni to ligand atom interactions.

  18. Nature of Graphene Edges: A Review

    NASA Astrophysics Data System (ADS)

    Acik, Muge; Chabal, Yves J.

    2011-07-01

    Graphene edges determine the optical, magnetic, electrical, and electronic properties of graphene. In particular, termination, chemical functionalization and reconstruction of graphene edges leads to crucial changes in the properties of graphene, so control of the edges is critical to the development of applications in electronics, spintronics and optoelectronics. Up to date, significant advances in studying graphene edges have directed various smart ways of controlling the edge morphology. Though, it still remains as a major challenge since even minor deviations from the ideal shape of the edges significantly deteriorate the material properties. In this review, we discuss the fundamental edge configurations together with the role of various types of edge defects and their effects on graphene properties. Indeed, we highlight major demanding challenges to find the most suitable technique to characterize graphene edges for numerous device applications such as transistors, sensors, actuators, solar cells, light-emitting displays, and batteries in graphene technology.

  19. An x-ray absorption spectroscopy study of Ni-Mn-Ga shape memory alloys.

    PubMed

    Sathe, V G; Dubey, Aditi; Banik, Soma; Barman, S R; Olivi, L

    2013-01-30

    The austenite to martensite phase transition in Ni-Mn-Ga ferromagnetic shape memory alloys was studied by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy. The spectra at all the three elements', namely, Mn, Ga and Ni, K-edges in several Ni-Mn-Ga samples (with both Ni and Mn excess) were analyzed at room temperature and low temperatures. The EXAFS analysis suggested a displacement of Mn and Ga atoms in opposite direction with respect to the Ni atoms when the compound transforms from the austenite phase to the martensite phase. The first coordination distances around the Mn and Ga atoms remained undisturbed on transition, while the second and subsequent shells showed dramatic changes indicating the presence of a modulated structure. The Mn rich compounds showed the presence of antisite disorder of Mn and Ga. The XANES results showed remarkable changes in the unoccupied partial density of states corresponding to Mn and Ni, while the electronic structure of Ga remained unperturbed across the martensite transition. The post-edge features in the Mn K-edge XANES spectra changed from a double peak like structure to a flat peak like structure upon phase transition. The study establishes strong correlation between the crystal structure and the unoccupied electronic structure in these shape memory alloys.

  20. Black Phosphorus Transistors with Near Band Edge Contact Schottky Barrier

    NASA Astrophysics Data System (ADS)

    Ling, Zhi-Peng; Sakar, Soumya; Mathew, Sinu; Zhu, Jun-Tao; Gopinadhan, K.; Venkatesan, T.; Ang, Kah-Wee

    2015-12-01

    Black phosphorus (BP) is a new class of 2D material which holds promise for next generation transistor applications owing to its intrinsically superior carrier mobility properties. Among other issues, achieving good ohmic contacts with low source-drain parasitic resistance in BP field-effect transistors (FET) remains a challenge. For the first time, we report a new contact technology that employs the use of high work function nickel (Ni) and thermal anneal to produce a metal alloy that effectively reduces the contact Schottky barrier height (ΦB) in a BP FET. When annealed at 300 °C, the Ni electrode was found to react with the underlying BP crystal and resulted in the formation of nickel-phosphide (Ni2P) alloy. This serves to de-pin the metal Fermi level close to the valence band edge and realizes a record low hole ΦB of merely ~12 meV. The ΦB at the valence band has also been shown to be thickness-dependent, wherein increasing BP multi-layers results in a smaller ΦB due to bandgap energy shrinkage. The integration of hafnium-dioxide high-k gate dielectric additionally enables a significantly improved subthreshold swing (SS ~ 200 mV/dec), surpassing previously reported BP FETs with conventional SiO2 gate dielectric (SS > 1 V/dec).

  1. Black Phosphorus Transistors with Near Band Edge Contact Schottky Barrier

    PubMed Central

    Ling, Zhi-Peng; Sakar, Soumya; Mathew, Sinu; Zhu, Jun-Tao; Gopinadhan, K.; Venkatesan, T.; Ang, Kah-Wee

    2015-01-01

    Black phosphorus (BP) is a new class of 2D material which holds promise for next generation transistor applications owing to its intrinsically superior carrier mobility properties. Among other issues, achieving good ohmic contacts with low source-drain parasitic resistance in BP field-effect transistors (FET) remains a challenge. For the first time, we report a new contact technology that employs the use of high work function nickel (Ni) and thermal anneal to produce a metal alloy that effectively reduces the contact Schottky barrier height (ΦB) in a BP FET. When annealed at 300 °C, the Ni electrode was found to react with the underlying BP crystal and resulted in the formation of nickel-phosphide (Ni2P) alloy. This serves to de-pin the metal Fermi level close to the valence band edge and realizes a record low hole ΦB of merely ~12 meV. The ΦB at the valence band has also been shown to be thickness-dependent, wherein increasing BP multi-layers results in a smaller ΦB due to bandgap energy shrinkage. The integration of hafnium-dioxide high-k gate dielectric additionally enables a significantly improved subthreshold swing (SS ~ 200 mV/dec), surpassing previously reported BP FETs with conventional SiO2 gate dielectric (SS > 1 V/dec). PMID:26667402

  2. Quantifying edge significance on maintaining global connectivity

    PubMed Central

    Qian, Yuhua; Li, Yebin; Zhang, Min; Ma, Guoshuai; Lu, Furong

    2017-01-01

    Global connectivity is a quite important issue for networks. The failures of some key edges may lead to breakdown of the whole system. How to find them will provide a better understanding on system robustness. Based on topological information, we propose an approach named LE (link entropy) to quantify the edge significance on maintaining global connectivity. Then we compare the LE with the other six acknowledged indices on the edge significance: the edge betweenness centrality, degree product, bridgeness, diffusion importance, topological overlap and k-path edge centrality. Experimental results show that the LE approach outperforms in quantifying edge significance on maintaining global connectivity. PMID:28349923

  3. Saddle-node dynamics for edge detection

    SciTech Connect

    Wong, Y.F.

    1994-09-01

    The author demonstrates how the formulation of a nonlinear scale-space filter can be used for edge detection and junction analysis. By casting edge-preserving filtering in terms of maximizing information content subject to an average cost function, the computed cost at each pixel location becomes a local measure of edgeness. This computation depends on a single scale parameter and the given image data. Unlike previous approaches which require careful tuning of the filter kernels for various types of edges, this scheme is general enough to be able to handle different edges, such as lines, step edges, corners and junctions. Anisotropy in the data is handled automatically by the nonlinear dynamics.

  4. Goethite aging explains Ni depletion in upper units of ultramafic lateritic ores from New Caledonia

    NASA Astrophysics Data System (ADS)

    Dublet, Gabrielle; Juillot, Farid; Morin, Guillaume; Fritsch, Emmanuel; Fandeur, Dik; Brown, Gordon E.

    2015-07-01

    An upward loss of Ni is commonly reported in the oxide-rich unit of Ni-laterite deposits developed over ultramafic rocks in tropical regions, especially in freely drained and deeply weathered regoliths. Because goethite is the major mineral constituent of such oxide-rich units, this Ni loss has been linked to compositional changes in goethite. In the present study, we have investigated possible correlations between Ni contents in the bulk laterite, and the evolution of goethite in terms of composition and crystallinity, in two Ni-rich and one Ni-poor lateritic profiles from New Caledonia. Ni K-edge Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy indicates that goethite hosts the main fraction of Ni in the three profiles investigated. Asbolane/lithiophorite identified as accessory minerals by X-ray diffraction (XRD) have little effect on the vertical variations in bulk Ni content in spite of the fact that the Ni contents of these Mn-oxides can be significant at certain depths. The gradual decrease in Ni content from the bottom to the top of the three Ni lateritic profiles correlates with a decrease in the Ni content of goethite as determined by electron probe micro-analysis. In addition, XRD data show that these compositional trends are linked to an increase of the mean coherent domain size of goethite. These observations support the hypothesis that Ni is expelled from goethite as it ages through successive dissolution and recrystallization cycles during the lateritization process. Comparison of laterites having different degrees of weathering suggests that this aging process could also play a significant role in the regional variability of Ni content in Ni-laterite deposits.

  5. Feature Extraction Without Edge Detection

    DTIC Science & Technology

    1993-09-01

    feature? A.I. Memo 1356, MIT Artificial Intellegence Lab, April 1992. [65] W. A. Richards, B. Dawson, and D. Whittington. Encoding contour shape by...AD-A279 842 . " Technical Report 1434 --Feature Extraction Without Edge Detection Ronald D. Chane MIT Artificial .Intelligencc Laboratory ",, 𔃾•d...Chaney 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER Massachusetts Institute of Technology Artificial

  6. Etching Of Semiconductor Wafer Edges

    DOEpatents

    Kardauskas, Michael J.; Piwczyk, Bernhard P.

    2003-12-09

    A novel method of etching a plurality of semiconductor wafers is provided which comprises assembling said plurality of wafers in a stack, and subjecting said stack of wafers to dry etching using a relatively high density plasma which is produced at atmospheric pressure. The plasma is focused magnetically and said stack is rotated so as to expose successive edge portions of said wafers to said plasma.

  7. Retention and the competitive edge.

    PubMed

    Lemery, L D

    2000-01-01

    I believe that retaining effective, seasoned employees enhances an organization's ability to compete in the marketplace. Though these seasoned employees seem to be more explicitly expensive, a detailed analysis of the costs involved in hiring and orienting replacement personnel may prove this assumption false. In addition, seasoned employees' intimate job knowledge actually constitutes the organization's competitive edge. Therefore, retaining seasoned personnel seems to become an important, mission- and vision-imperative institutional objective.

  8. Topological edge states in pnictides

    NASA Astrophysics Data System (ADS)

    Youmans, Cody; Ghaemi, Pouyan; Kargarian, Mehdi

    In some members of the ferro-pnictides, non-trivial topology in the bulk band-structure is related to potentially observable gapless edge states. We study these states numerically and analytically for a range of parameters, with and without superconductivity and antiferromagnetic SDW ordering, and their relation to the symmetries and topologically non-trivial aspects of our model Hamiltonian. Support was provided by the Doctoral Student Research Grant program at the Graduate Center, CUNY.

  9. Geometric and electronic structures of the Ni(I) and methyl-Ni(III) intermediates of methyl-coenzyme M reductase.

    PubMed

    Sarangi, Ritimukta; Dey, Mishtu; Ragsdale, Stephen W

    2009-04-14

    Methyl-coenzyme M reductase (MCR) catalyzes the terminal step in the formation of biological methane from methyl-coenzyme M (Me-SCoM) and coenzyme B (CoBSH). The active site in MCR contains a Ni-F(430) cofactor, which can exist in different oxidation states. The catalytic mechanism of methane formation has remained elusive despite intense spectroscopic and theoretical investigations. On the basis of spectroscopic and crystallographic data, the first step of the mechanism is proposed to involve a nucleophilic attack of the Ni(I) active state (MCR(red1)) on Me-SCoM to form a Ni(III)-methyl intermediate, while computational studies indicate that the first step involves the attack of Ni(I) on the sulfur of Me-SCoM, forming a CH(3)(*) radical and a Ni(II)-thiolate species. In this study, a combination of Ni K-edge X-ray absorption spectroscopic (XAS) studies and density functional theory (DFT) calculations have been performed on the Ni(I) (MCR(red1)), Ni(II) (MCR(red1-silent)), and Ni(III)-methyl (MCR(Me)) states of MCR to elucidate the geometric and electronic structures of the different redox states. Ni K-edge EXAFS data are used to reveal a five-coordinate active site with an open upper axial coordination site in MCR(red1). Ni K-pre-edge and EXAFS data and time-dependent DFT calculations unambiguously demonstrate the presence of a long Ni-C bond ( approximately 2.04 A) in the Ni(III)-methyl state of MCR. The formation and stability of this species support mechanism I, and the Ni-C bond length suggests a homolytic cleavage of the Ni(III)-methyl bond in the subsequent catalytic step. The XAS data provide insight into the role of the unique F(430) cofactor in tuning the stability of the different redox states of MCR.

  10. Edge-driven microplate kinematics

    USGS Publications Warehouse

    Schouten, Hans; Klitgord, Kim D.; Gallo, David G.

    1993-01-01

    It is known from plate tectonic reconstructions that oceanic microplates undergo rapid rotation about a vertical axis and that the instantaneous rotation axes describing the microplate's motion relative to the bounding major plates are frequently located close to its margins with those plates, close to the tips of propagating rifts. We propose a class of edge-driven block models to illustrate how slip across the microplate margins, block rotation, and propagation of rifting may be related to the relative motion of the plates on either side. An important feature of these edge-driven models is that the instantaneous rotation axes are always located on the margins between block and two bounding plates. According to those models the pseudofaults or traces of disrupted seafloor resulting from the propagation of rifting between microplate and major plates may be used independently to approximately trace the continuous kinematic evolution of the microplate back in time. Pseudofault geometries and matching rotations of the Easter microplate show that for most of its 5 m.y. history, block rotation could be driven by the drag of the Nazca and Pacific plates on the microplate's edges rather than by a shear flow of mantle underneath.

  11. Fluorescence x-ray absorption fine structure studies of Fe-Ni-S and Fe-Ni-Si melts to 1600 K

    SciTech Connect

    Manghnani, M.H.; Hong, X.; Balogh, J.; Amulele, G.; Sekar, M.; Newville, M.

    2008-04-29

    We report Ni K-edge fluorescence x-ray absorption fine structure spectra (XAFS) for Fe{sub 0.75}Ni{sub 0.05}S{sub 0.20} and Fe{sub 0.75}Ni{sub 0.05}Si{sub 0.20} ternary alloys from room temperature up to 1600 K. A high-temperature furnace designed for these studies incorporates two x-ray transparent windows and enables both a vertical orientation of the molten sample and a wide opening angle, so that XAFS can be measured in the fluorescence mode with a detector at 90{sup o} with respect to the incident x-ray beam. An analysis of the Ni XAFS data for these two alloys indicates different local structural environments for Ni in Fe{sub 0.75}Ni{sub 0.05}S{sub 0.20} and Fe{sub 0.75}Ni{sub 0.05}Si{sub 0.20} melts, with more Ni-Si coordination than Ni-S coordination persisting from room temperature through melting. These results suggest that light elements such as S and Si may impact the structural and chemical properties of Fe-Ni alloys with a composition similar to the earth's core.

  12. Microwave synthesis and effect of CTAB on ferromagnetic properties of NiO, Co3O4 and NiCo2O4 nanostructures

    NASA Astrophysics Data System (ADS)

    Anandha Babu, G.; Ravi, G.; Hayakawa, Y.

    2015-04-01

    Cubic-structured NiO, Co3O4 and spinel-structured NiCo2O4 were synthesized via microwave route. The structural properties of NiO, Co3O4 and NiCo2O4 nanostructures were investigated by X-ray diffraction analysis, and it showed smaller crystallite size for NiO than Co3O4 and NiCo2O4 by using Williamson-Hall method. Flake-like and hexagonal plate-like morphologies were ascertained from HRSEM and TEM analyses. Optical properties of these materials were investigated by photoluminescence study, and it presents the band edge emission for all materials with supplementary emissions in visible region due to the presence of defects such as vacancy and interstitial. Raman and FTIR spectra provide the functional characteristics of NiO, Co3O4 and NiCo2O4 nanostructures. XPS measurement revealed the purity and composition of these nanostructures. Room temperature magnetic measurements were investigated using vibrating sample magnetometer. The low coercivity and remanent magnetization for NiO, Co3O4 and NiCo2O4 nanostructures confirmed that these nanoparticles exhibit a weak ferromagnetic behaviour.

  13. Quantifying covalent interactions with resonant inelastic soft X-ray scattering: Case study of Ni2+ aqua complex

    SciTech Connect

    Kunnus, K.; Josefsson, I.; Schreck, S.; Quevedo, W.; Miedema, P. S.; Techert, S.; de Groot, F. M. F.; Föhlisch, A.; Odelius, M.; Wernet, Ph.

    2016-12-23

    We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. Here, we propose that 2p3d RIXS at the Ni L3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations.

  14. Knife-edge seal for vacuum bagging

    NASA Technical Reports Server (NTRS)

    Rauschl, J. A.

    1980-01-01

    Cam actuated clamps pinch bagging material between long knife edge (mounted to clamps) and high temperature rubber cushion bonded to baseplate. No adhesive, tape, or sealing groove is needed to seal edge of bagging sheet against base plate.

  15. Hydrogen induced C-C, C-N, and C-S bond activation on Pt and Ni surfaces

    SciTech Connect

    Gland, J.L.

    1992-12-01

    The work has focussed on hydrogen induced bond activation in adsorbed organic molecules and intermediates containin C-S and C-N and C-C bonds on Ni(100), Ni(111), and Pt(111) surfaces. Fluorescence Yield Near Edge Spectroscopy (FYNES) above the carbon K edge was used for adsorbed organic reactants and in-situ kinetic studies of bond activation. Results indicate that the activation is enhanced on Ni relative to Pt. Methylthiolate and methylamine adsorbed on Pt(111) were studied.

  16. Hydrogen induced C-C, C-N, and C-S bond activation on Pt and Ni surfaces

    SciTech Connect

    Gland, J.L.

    1992-01-01

    The work has focussed on hydrogen induced bond activation in adsorbed organic molecules and intermediates containin C-S and C-N and C-C bonds on Ni(100), Ni(111), and Pt(111) surfaces. Fluorescence Yield Near Edge Spectroscopy (FYNES) above the carbon K edge was used for adsorbed organic reactants and in-situ kinetic studies of bond activation. Results indicate that the activation is enhanced on Ni relative to Pt. Methylthiolate and methylamine adsorbed on Pt(111) were studied.

  17. Edge and coupled core/edge transport modeling in tokamak

    SciTech Connect

    Pearlstein, L D; Casper, T A; Cohen, R H; LoDestro, L L; Mattor, N; Porter, G D; Rensink, M E; Rognlien, T D; Ryutov, D D; Scott, H A; Wan, A

    1998-10-14

    Recent advances in the theory and modelling of tokamak edge, scrape-off-layer and divertor plasmas are described. The effects of the poloidal ExB drift on inner/outer divertor-plate asymmetries within a 1D analysis are shown to be in good agreement with experimental observations; above a critical v ExB, the model predicts transitions to supersonic SOL flow at the inboard midplane. Two-dimensional simulations show the importance of ExB flow in the private-flux region and B-drift effects. A theory of rough plasma-facing surfaces is given, and interesting effects, some traveling back up the magnetic field-lines to the SOL plasma, are predicted. The parametric dependence of detached-plasma states in slab geometry has been explored; with sufficient pumping, the location of the ionization front can be controlled; otherwise only fronts at the plate or the X-point are stable. Studies with a more accurate Monte-Carlo neutrals model and a detailed non-LTE radiation-transport code indicate various effects are important for quantitative rnodelling. Long-lived oscillatory UEDGE solutions in both ITER and DIII-D are reported. Detailed simulations of the DIII-D core and edge are presented; impurity and plasma flow are shown to be well modelled with UEDGE, and the roles of impurity and neutral transport in the edge and SOL are discussed.

  18. Reduction of Free-Edge Stress Concentration

    DTIC Science & Technology

    1985-01-01

    oscillatory type of behavior near the free edge of the capped laminate before converging to zero further inside the laminate. The length of the edge effect is...Condition," J. Comp. Materials. Vol. 14 (1980), p. 2. 13. Altus, E., Rotem, A. and Shmueli, M., "Free Edge Effect in Angle- Ply Laminates - A New

  19. Understanding and preventing the edge effect.

    PubMed

    Cheneau, Edouard; Wolfram, Roswitha; Leborgne, Laurent; Waksman, Ron

    2003-02-01

    Edge stenosis, combining neointimal proliferation and negative remodeling, remains a serious limitation of vascular brachytherapy. This review comprehensively presents terminology, definitions, mechanisms, and treatment strategies to better understand the complexities of edge narrowing. The major contributors to this phenomenon are known; understanding the practical solutions will enable us to further minimize the problem of the edge effect.

  20. Densified edge seals for fuel cell components

    DOEpatents

    DeCasperis, Anthony J.; Roethlein, Richard J.; Breault, Richard D.

    1982-01-01

    A porous fuel cell component, such as an electrode substrate, has a densified edge which forms an improved gas seal during operation when soaked with electrolyte. The edges are made from the same composition as the rest of the component and are made by compressing an increased thickness of this material along the edges during the fabrication process.

  1. EXAFS and XANES investigation of (Li, Ni) codoped ZnO thin films grown by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Mino, Lorenzo; Gianolio, Diego; Bardelli, Fabrizio; Prestipino, Carmelo; Senthil Kumar, E.; Bellarmine, F.; Ramanjaneyulu, M.; Lamberti, Carlo; Ramachandra Rao, M. S.

    2013-09-01

    Ni doped, Li doped and (Li, Ni) codoped ZnO thin films were successfully grown using a pulsed laser deposition technique. Undoped and doped ZnO thin films were investigated using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge spectroscopy (XANES). Preliminary investigations on the Zn K-edge of the undoped and doped ZnO thin films revealed that doping has not influenced the average Zn-Zn bond length and Debye-Waller factor. This shows that both Ni and Li doping do not appreciably affect the average local environment of Zn. All the doped ZnO thin films exhibited more than 50% of substitutional Ni, with a maximum of 77% for 2% Ni and 2% Li doped ZnO thin film. The contribution of Ni metal to the EXAFS signal clearly reveals the presence of Ni clusters. The Ni-Ni distance in the Ni0 nanoclusters, which are formed in the film, is shorter with respect to the reference Ni metal foil and the Debye-Waller factor is higher. Both facts perfectly reflect what is expected for metal nanoparticles. At the highest doping concentration (5%), the presence of Li favors the growth of a secondary NiO phase. Indeed, 2% Ni and 5% Li doped ZnO thin film shows %Nisub = 75 ± 11, %Nimet = 10 ± 8, %NiO = 15 ± 8. XANES studies further confirm that the substitutional Ni is more than 50% in all the samples. These results explain the observed magnetic properties.

  2. Thermodynamic Modeling of Poorly Complexing Metals in Concentrated Electrolyte Solutions: An X-Ray Absorption and UV-Vis Spectroscopic Study of Ni(II) in the NiCl2-MgCl2-H2O System

    PubMed Central

    Zhang, Ning; Brugger, Joël; Etschmann, Barbara; Ngothai, Yung; Zeng, Dewen

    2015-01-01

    Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at RNi-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg-1 NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg-1 NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system. PMID:25885410

  3. Thermodynamic modeling of poorly complexing metals in concentrated electrolyte solutions: an X-ray absorption and UV-Vis spectroscopic study of Ni(II) in the NiCl2-MgCl2-H2O system.

    PubMed

    Zhang, Ning; Brugger, Joël; Etschmann, Barbara; Ngothai, Yung; Zeng, Dewen

    2015-01-01

    Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at RNi-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg(-1) NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg(-1) NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system.

  4. Results from the EDGES Survey

    NASA Astrophysics Data System (ADS)

    van Zee, Liese; EDGES Team

    2017-03-01

    Results are presented from a deep imaging survey with the Spitzer Space Telescope which was designed to identify and measure the faint stellar populations around nearby galaxies. The Extended Disk Galaxy Exploration Science (EDGES) Survey includes a sample of 92 nearby galaxies with a range of morphological types and environments. The observations include a field-of-view of at least 5 times the optical size and are deep enough to detect stellar mass surface densities of several hundredths of a solar mass per square parsec. The observations reveal extended stellar features, such as stellar disks and stellar streams, around many of the target galaxies, as expected from hierarchical galaxy formation scenarios.

  5. K-edge densitometer (KED)

    SciTech Connect

    Sprinkle, J.K.; Hansen, W.J.

    1993-02-11

    In 1979, a K-edge densitometer (KED) was installed by the Safeguards Assay group from Los Alamos National Laboratory in the PNC reprocessing plant at Tokai-mura, Japan. It uses an active nondestructive assay technique, KED, to measure the plutonium concentration of the product solution. The measurement uncertainty of an assay depends on the count time chosen, but can be 0.5% or better. The computer hardware and software were upgraded in 1992. This manual describes the operation of the instrument, with an emphasis on the user interface to the software.

  6. Continuum Gyrokinetic Edge New Technology

    SciTech Connect

    Dorr, M. R.; Hittinger, J. A.; Dorf, M.; Cohen, R.; Ghosh, D.; Lee, W.; Reynolds, C.

    2016-05-02

    COGENT is a simulation code that models the plasma evolution in the edge region of a tokamak fusion reactor, from the open field line scrape-off layer, across the separatrix, and into the core. The model is based on the 4D gyrokinetic closure of the kinetic equations for a plasma coupled to an electrostatic potential field. The background magnetic field is prescribed either analytically or generated from experimental data, and the grid is aligned with magnetic flux surfaces. Multiple collision operator options are provided, from Krook to fully nonlinear Fokker-Planck.

  7. Environmental Dataset Gateway (EDG) Search Widget

    EPA Pesticide Factsheets

    Use the Environmental Dataset Gateway (EDG) to find and access EPA's environmental resources. Many options are available for easily reusing EDG content in other other applications. This allows individuals to provide direct access to EPA's metadata outside the EDG interface. The EDG Search Widget makes it possible to search the EDG from another web page or application. The search widget can be included on your website by simply inserting one or two lines of code. Users can type a search term or lucene search query in the search field and retrieve a pop-up list of records that match that search.

  8. Environmental Dataset Gateway (EDG) REST Interface

    EPA Pesticide Factsheets

    Use the Environmental Dataset Gateway (EDG) to find and access EPA's environmental resources. Many options are available for easily reusing EDG content in other other applications. This allows individuals to provide direct access to EPA's metadata outside the EDG interface. The EDG REST Interface allows each users to query the catalog through a URL using REST syntax. Accessing individual metadata documents through their REST URLs, or groups of documents that match specific search criteria through a REST-formatted search URL, provides powerful functionality for searching, viewing, and sharing EDG records.

  9. Fractal-based image edge detection

    NASA Astrophysics Data System (ADS)

    Luo, Huiguo; Zhu, Yaoting; Zhu, Guang-Xi; Wan, Faguang; Zhang, Ping

    1993-08-01

    Image edge is an important feature of image. Usually, we use Laplacian or Sober operator to get an image edge. In this paper, we use fractal method to get the edge. After introducing Fractal Brownian Random (FBR) field, we give the definition of Discrete Fractal Brownian Increase Random (DFBIR) field and discuss its properties, then we apply the DFBIR field to detect the edge of an image. According to the parameters H and D of DFBIR, we give a measure M equals (alpha) H + (beta) D. From the M value of each pixel, we can detect the edge of image.

  10. Evaluating Edge Detection through Boundary Detection

    NASA Astrophysics Data System (ADS)

    Wang, Song; Ge, Feng; Liu, Tiecheng

    2006-12-01

    Edge detection has been widely used in computer vision and image processing. However, the performance evaluation of the edge-detection results is still a challenging problem. A major dilemma in edge-detection evaluation is the difficulty to balance the objectivity and generality: a general-purpose edge-detection evaluation independent of specific applications is usually not well defined, while an evaluation on a specific application has weak generality. Aiming at addressing this dilemma, this paper presents new evaluation methodology and a framework in which edge detection is evaluated through boundary detection, that is, the likelihood of retrieving the full object boundaries from this edge-detection output. Such a likelihood, we believe, reflects the performance of edge detection in many applications since boundary detection is the direct and natural goal of edge detection. In this framework, we use the newly developed ratio-contour algorithm to group the detected edges into closed boundaries. We also collect a large data set ([InlineEquation not available: see fulltext.]) of real images with unambiguous ground-truth boundaries for evaluation. Five edge detectors (Sobel, LoG, Canny, Rothwell, and Edison) are evaluated in this paper and we find that the current edge-detection performance still has scope for improvement by choosing appropriate detectors and detector parameters.

  11. A novel algorithm for the edge detection and edge enhancement of medical images.

    PubMed

    Crooks, I; Fallone, B G

    1993-01-01

    A novel algorithm, histogram shifting (HS) is presented, which performs edge detection or edge enhancement with the choice of two parameters. The histogram of a region surrounding each pixel is found and translated toward the origin, resulting in the new pixel value. Images from a variety of medical imaging modalities were processed with HS to perform detection and enhancement of edges. Comparison with results obtained from conventional edge detection (e.g., Sobel) and with conventional edge-enhancement algorithms is discussed. HS appears to perform the edge-detection operation without introducing "double-edge" effects often obtained with conventional edge-detection algorithms. HS also appears to perform edge enhancement without introducing extensive noise artifacts, which may be noticeable with many edge-enhancement algorithms.

  12. Measuring edge importance to improve immunization performance

    NASA Astrophysics Data System (ADS)

    Huang, He; Yan, Zhijun; Pan, Yaohui

    2014-12-01

    The edge heterogeneity has a remarkable influence on disease spreading, but it has seldom been considered in the disease-controlling policies. Based on the gravity model, we propose the edge importance index to describe the influence of edge heterogeneity on immunization strategies. Then the edge importance and contact weight are combined to calculate the infection rates on the I-S (Infected-Susceptible) edges in the complex network, and the difference of the infection rates on strong and weak ties is analyzed. Simulation results show that edge heterogeneity has a significant influence on the performance of immunization strategies, and better immunization efficiency is derived when the vaccination rate of the nodes in the weak I-S edges is increased.

  13. Reflections on the Knife Edge

    PubMed Central

    Murphy, John Patrick Michael

    2011-01-01

    Introduction The accompanying article, written by John Murphy, a retired lawyer and lifelong outdoorsman from his beloved Colorado Rockies, draws the striking parallel between his experiences as a mountain climber and as a patient with metastatic melanoma facing the hope and uncertainty of experimental therapy. Both are life-threatening circumstances, demanding courage and hope, and challenging our soul in a way almost unique to human experience. Both involve a conscious choice to move forward into dangerous and uncertain territory, and require a determination to look death (John's “Reaper”) in the eye. Many remarkable books and films have been written about such experiences. I recall in particular the 2003 documentary film Touching the Void, about the incredible survival of a mountaineer who returned from a perilous fall in Peru. I highly recommend it to the reader. Another is Laura Hillenbrand's Unbroken: A World War II Story of Survival, Resilience, and Redemption (Random House, 2010), about the survival of a prisoner of war, the celebrated miler Louis Zamperini. Again, unbridled courage and undeniable hope turned futility into future. John Murphy's reflections remind us of the daily heroism of our patients who are holding tight to the lifeline offered by clinical research. Good climbing, John. All of us are with you on that Knife Edge, waiting for our turn to ascend... and hoping to be as courageous as you were then on Capitol Peak and are again now on the Knife Edge of a clinical trial. For our turn will come. PMID:21349953

  14. Haptic Edge Detection Through Shear

    NASA Astrophysics Data System (ADS)

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-03-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.

  15. Haptic Edge Detection Through Shear

    PubMed Central

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-01-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals. PMID:27009331

  16. Direct Observation of Charge Order in Triangular Metallic AgNiO2 by Single-Crystal Resonant X-Ray Scattering

    NASA Astrophysics Data System (ADS)

    Pascut, G. L.; Coldea, R.; Radaelli, P. G.; Bombardi, A.; Beutier, G.; Mazin, I. I.; Johannes, M. D.; Jansen, M.

    2011-04-01

    We report resonant x-ray scattering measurements on a single crystal of the orbitally degenerate triangular metallic antiferromagnet 2H-AgNiO2 to probe the spontaneous transition to a triple-cell superstructure at temperatures below TS=365K. We observe a strong resonant enhancement of the supercell reflections through the Ni K edge. The empirically extracted K-edge shift between the crystallographically distinct Ni sites of 2.5(3) eV is much larger than the value expected from the shift in final states, and implies a core-level shift of ˜1eV, thus providing direct evidence for the onset of spontaneous honeycomb charge order in the triangular Ni layers. We also provide band-structure calculations that explain quantitatively the observed edge shifts in terms of changes in the Ni electronic energy levels due to charge order and hybridization with the surrounding oxygens.

  17. An analysis of the x-ray linear dichroism spectrum for NiO thin films grown on vicinal Ag(001)

    SciTech Connect

    Wu, Y.Z.; Zhao, Y.; Arenholz, E.; Young, A.T.; Sinkovic, B.; Qiu, Z.Q.

    2008-05-10

    Antiferromagnetic (AFM) NiO thin films are grown epitaxially on vicinal Ag(118) substrate and investigated by x-ray linear dichroism (XLD). We find that the NiO AFM spin exhibits an in-plane spin reorientation transition from parallel to perpendicular to the step edges with increasing the NiO film thickness. In addition to the conventional L{sub 2} adsorption edge, x-ray linear dichroism (XLD) effect at the Ni L{sub 3} adsorption edge is also measured and analyzed. The result identifies a small energy shift of the L{sub 3} peak. Temperature-dependent measurement confirms that the observed XLD effect in this system at the normal incidence of the x-rays originates entirely from the NiO magnetic ordering.

  18. Magnetic properties of Ni and Cu-Ni nanoparticles

    NASA Astrophysics Data System (ADS)

    Ganga, B. G.; Santhosh, P. N.; Thomas, P. John

    2012-06-01

    Ni and Cu-Ni nanoparticles were prepared by solution phase method and crystal phase was identified by XRD. SEM and EDX were used to analyze morphology and elemental composition of nanoparticles. Magnetic measurements indicate that Ni nanoparticles are superparamagnetic at room temperature and blocking temperature is around 103 K. Ferromagnetism is observed in the case of Cu-Ni nanoparticles with decrease in magnetization compared to Ni nanoparticles.

  19. [NiIII(OMe)]-mediated reductive activation of CO2 affording a Ni(κ1-OCO) complex

    DOE PAGES

    Chiou, Tzung -Wen; Tseng, Yen -Ming; Lu, Tsai -Te; ...

    2016-02-24

    Here, carbon dioxide is expected to be employed as an inexpensive and potential feedstock of C1 sources for the mass production of valuable chemicals and fuel. Versatile chemical transformations of CO2, i.e. insertion of CO2 producing bicarbonate/acetate/formate, cleavage of CO2 yielding μ-CO/μ-oxo transition-metal complexes, and electrocatalytic reduction of CO2 affording CO/HCOOH/CH3OH/CH4/C2H4/oxalate were well documented. Herein, we report a novel pathway for the reductive activation of CO2 by the [NiIII(OMe)(P(C6H3-3-SiMe3-2-S)3)]– complex, yielding the [NiIII(κ1-OCO˙–)(P(C6H3-3-SiMe3-2-S)3)]– complex. The formation of this unusual NiIII(κ1-OCO˙–) complex was characterized by single-crystal X-ray diffraction, EPR, IR, SQUID, Ni/S K-edge X-ray absorption spectroscopy, and Ni valence-to-core X-ray emissionmore » spectroscopy. The inertness of the analogous complexes [NiIII(SPh)], [NiII(CO)], and [NiII(N2H4)] toward CO2, in contrast, demonstrates that the ionic [NiIII(OMe)] core attracts the binding of weak σ-donor CO2 and triggers the subsequent reduction of CO2 by the nucleophilic [OMe]– in the immediate vicinity. This metal–ligand cooperative activation of CO2 may open a novel pathway promoting the subsequent incorporation of CO2 in the buildup of functionalized products.« less

  20. Three-dimensional phase field simulation of the morphology and growth kinetics of Ni4Ti3 precipitates in a NiTi alloy

    NASA Astrophysics Data System (ADS)

    Ke, C. B.; Cao, S.; Zhang, X. P.

    2014-07-01

    A three-dimensional phase field model is applied to study the morphology and growth kinetics of Ni4Ti3 precipitates, as well as the Ni concentration distribution feature, during the aging of a NiTi alloy. The model can reproduce well the multiple-variants morphology of Ni4Ti3 precipitates. The diameter-to-thickness ratio of lenticular Ni4Ti3 precipitates in the equilibrium shape is 4.2. Simulation results show that the Ni depletion region near the face of Ni4Ti3 precipitates is broader than that near the edge of the precipitates, and both the depletion level of Ni concentration and the length of the Ni depletion region adjacent to the precipitates increase with the aging time. The growth of the precipitate diameter and thickness can be described by the power-law fitting equation, with growth exponent m = 0.47 for the diameter and m = 0.46 for the thickness, which are in good agreement with those obtained in previous experimental and analytical studies.

  1. Coupled edge-core model of fusion reactor

    NASA Astrophysics Data System (ADS)

    Zagórski, R.; Kulinski, S.; Scholz, M.

    1997-10-01

    A model has been developed which is capable to describe in a self consistent way the plasma dynamics in the centre and edge region of a fusion reactor. The core plasma is treated in the frame of the 0D model in which an empirical scaling law for the energy confinement time is included. The model accounts for energy losses due to Bremsstrahlung and line radiation as well as alpha particle heating. A 1D analytical model for plasma and impurity transport outside the last close magnetic surface (LCMS) is applied. The model accounts for the strong gradients of the plasma parameters along the magnetic field lines in the divertor. The sputtering phenomena at the plate and radiating cooling by injected impurities are treated self consistently in the model. The model has been used to investigate operating regimes of the ignition experiment. Analysis have been performed for different first wall materials (C, Ni, Mo, W) for ITER like tokamak.

  2. Edge detection in microscopy images using curvelets

    PubMed Central

    Gebäck, Tobias; Koumoutsakos, Petros

    2009-01-01

    Background Despite significant progress in imaging technologies, the efficient detection of edges and elongated features in images of intracellular and multicellular structures acquired using light or electron microscopy is a challenging and time consuming task in many laboratories. Results We present a novel method, based on the discrete curvelet transform, to extract a directional field from the image that indicates the location and direction of the edges. This directional field is then processed using the non-maximal suppression and thresholding steps of the Canny algorithm to trace along the edges and mark them. Optionally, the edges may then be extended along the directions given by the curvelets to provide a more connected edge map. We compare our scheme to the Canny edge detector and an edge detector based on Gabor filters, and show that our scheme performs better in detecting larger, elongated structures possibly composed of several step or ridge edges. Conclusion The proposed curvelet based edge detection is a novel and competitive approach for imaging problems. We expect that the methodology and the accompanying software will facilitate and improve edge detection in images available using light or electron microscopy. PMID:19257905

  3. Enhanced optical absorption and photocatalytic activity of anatase TiO2 through (Si,Ni) codoping

    NASA Astrophysics Data System (ADS)

    Lin, Yanming; Jiang, Zhenyi; Zhu, Chaoyuan; Hu, Xiaoyun; Zhang, Xiaodong; Zhu, Haiyan; Fan, Jun

    2012-08-01

    The electronic and optical properties of (Si,Ni)-codoped anatase TiO2 are investigated using the density functional theory. The calculated results indicate that the synergistic effects of (Si,Ni) codoping can effectively extend the optical absorption edge, which can lead to higher visible-light photocatalytic activity than pure anatase TiO2. To verify the reliability of our calculated results, nanocrystalline (Si,Ni)-codoped TiO2 is synthesized by a sol-gel-solvothermal method, and experimental results also show that the (Si,Ni)-codoped sample exhibits better absorption performance and higher photocatalytic activities than pure TiO2.

  4. Polarity control of h-BN nanoribbon edges by strain and edge termination.

    PubMed

    Yamanaka, Ayaka; Okada, Susumu

    2017-03-29

    We studied the polarity of h-BN nano-flakes in terms of their edge geometries, edge hydrogen termination, and uniaxial strain by evaluating their electrostatic potential using density functional theory. Our calculations have shown that the polarity of the nanoribbons is sensitive to their edge shape, edge termination, and uniaxial tensile strain. Polarity inversion of the ribbons can be induced by controlling the hydrogen concentration at the edges and the uniaxial tensile strain. The polarity inversion indicates that h-BN nanoribbons can exhibit non-polar properties at a particular edge hydrogen concentration and tensile strain, even though the nanoribbons essentially have polarity at the edge. We also found that the edge angle affects the polarity of nanoribbons with hydrogenated edges.

  5. Coulomb edge effects in graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Jaskolski, W.; Ayuela, A.

    2014-10-01

    Coulomb effects in graphene nanoribbons with arbitrary edges are investigated with the use of a mean-field Hubbard model. It was recently shown that chiral ribbons with minimal edges, characterized by the translation vector (n,m), have a similar structure of bands localized around the Fermi energy as pure zigzag ribbons (n-m,0). Here we show that these flat bands in both ribbon cases differ in detail due to the perturbation induced by armchair edge nodes. For chiral ribbons the edge bands split at the zone boundary, where the corresponding bands of (n-m,0) zigzag ribbons are degenerate. Coulomb interactions enhance strongly this splitting and at the same time they bring spin into play. We modify each edge keeping global sublattice balance to find that spin degeneracy can be partially lifted. The breaking of spin-degeneracy depends on the asymmetry between the edges and in some cases leads to spin-polarized currents.

  6. Skeletal octahedral nanoframe with Cartesian coordinates via geometrically precise nanoscale phase segregation in a Pt@Ni core-shell nanocrystal.

    PubMed

    Oh, Aram; Baik, Hionsuck; Choi, Dong Shin; Cheon, Jae Yeong; Kim, Byeongyoon; Kim, Heejin; Kwon, Seong Jung; Joo, Sang Hoon; Jung, Yousung; Lee, Kwangyeol

    2015-03-24

    Catalytic properties of nanoparticles can be significantly enhanced by controlling nanoscale alloying and its structure. In this work, by using a facet-controlled Pt@Ni core-shell octahedron nanoparticle, we show that the nanoscale phase segregation can have directionality and be geometrically controlled to produce a Ni octahedron that is penetrated by Pt atoms along three orthogonal Cartesian axes and is coated by Pt atoms along its edges. This peculiar anisotropic diffusion of Pt core atoms along the ⟨100⟩ vertex, and then toward the ⟨110⟩ edges, is explained via the minimum strain energy for Ni-Ni pair interactions. The selective removal of the Ni-rich phase by etching then results in structurally fortified Pt-rich skeletal PtNi alloy framework nanostructures. Electrochemical evaluation of this hollow nanoframe suggests that the oxygen reduction reaction (ORR) activity is greatly improved compared to conventional Pt catalysts.

  7. [Artificial crowns influence upon edge parodontium status].

    PubMed

    Zhulev, E N; Serov, A B

    2010-01-01

    With the aim of prosthetic treatment efficacy increase study of edge parodontium tissue reaction upon different types of artificial crowns was done and methods of chronic localized parodontitis prevention were developed. Changes of the main gingival fluid characteristics (amount, acidity, interleukine-1beta concentration) and indicators of microcirculation in edge parodontium of the teeth under the artificial crowns influence were disclosed. There were developed methods of chronic localized parodontitis prevention produced by artificial crowns edge.

  8. Structural and magnetic properties of Ni/Mn codoped ZnO nanoparticles

    NASA Astrophysics Data System (ADS)

    Vijayaprasath, G.; Murugan, R.; Asaithambi, S.; Sakthivel, P.; Mahalingam, T.; Ravi, G.

    2016-05-01

    We report systematic studies of the magnetic properties of Ni and Mn co-doped ZnO nanoparticles prepared by co-precipitation method. Structural characterization reveals that Ni and Mn ions substituted into ZnO lattices without any secondary phases formation. Photoluminescence and Raman spectra shows that the Ni/Mn were doped into the ZnO lattice resulting slight shift in near-band-edge emission. Moreover, the novel Raman peak at 586 cm-1 indicates two kinds of cations via doping that could affect the local polarizability. Magnetic measurements of the nanoparticles exhibits ferromagnetic behavior at room-temperature.

  9. Skyrmions at the Edge: Confinement Effects in Fe /Ir (111 )

    NASA Astrophysics Data System (ADS)

    Hagemeister, Julian; Iaia, Davide; Vedmedenko, Elena Y.; von Bergmann, Kirsten; Kubetzka, André; Wiesendanger, Roland

    2016-11-01

    We have employed spin-polarized scanning tunneling microscopy and Monte Carlo simulations to investigate the effect of lateral confinement onto the nano-Skyrmion lattice in Fe /Ir (111 ) . We find a strong coupling of one diagonal of the square magnetic unit cell to the close-packed edges of Fe nanostructures. In triangular islands this coupling in combination with the mismatching symmetries of the islands and of the square nano-Skyrmion lattice leads to frustration and triple-domain states. In direct vicinity to ferromagnetic NiFe islands, the surrounding Skyrmion lattice forms additional domains. In this case a side of the square magnetic unit cell prefers a parallel orientation to the ferromagnetic edge. These experimental findings can be reproduced and explained by Monte Carlo simulations. Here, the single-domain state of a triangular island is lower in energy, but nevertheless multidomain states occur due to the combined effect of entropy and an intrinsic domain wall pinning arising from the skyrmionic character of the spin texture.

  10. Modelling of edge localised modes and edge localised mode control

    SciTech Connect

    Huijsmans, G. T. A.; Loarte, A.; Chang, C. S.; Ferraro, N.; Sugiyama, L.; Waelbroeck, F.; Xu, X. Q.; Futatani, S.

    2015-02-15

    Edge Localised Modes (ELMs) in ITER Q = 10 H-mode plasmas are likely to lead to large transient heat loads to the divertor. To avoid an ELM induced reduction of the divertor lifetime, the large ELM energy losses need to be controlled. In ITER, ELM control is foreseen using magnetic field perturbations created by in-vessel coils and the injection of small D2 pellets. ITER plasmas are characterised by low collisionality at a high density (high fraction of the Greenwald density limit). These parameters cannot simultaneously be achieved in current experiments. Therefore, the extrapolation of the ELM properties and the requirements for ELM control in ITER relies on the development of validated physics models and numerical simulations. In this paper, we describe the modelling of ELMs and ELM control methods in ITER. The aim of this paper is not a complete review on the subject of ELM and ELM control modelling but rather to describe the current status and discuss open issues.

  11. An edge index for topological insulators

    NASA Astrophysics Data System (ADS)

    Prodan, Emil

    2009-03-01

    Topological insulators display dissipationless currents flowing at the edges of the samples. These currents are associated to chiral edge modes, whose existence is intrinsically linked to the topology of the electronic states of the bulk. The edge modes can be easily investigated when the edges are smooth and have a periodicity, but as soon as the periodicity is absent, the problem becomes un-traceable by purely theoretical means. In my talk I will exemplify the use of non-commutative calculus to explore the properties, especially the stability of the edge modes. For example, using such techniques one can give a fairly elementary proof that the edge modes in Chern insulators survive even for a rough (random) edge. Similarly, for the Spin-Hall effect, one can define an observable and its associated current whose conductance remains quantized during various deformations of the Hamiltonian system. It turns out that in all cases, the edge conductance is given by the index of a Fredholm operator, which provides a new topological invariant linked directly to the edge rather than the bulk.

  12. Moveable Leading Edge Device for a Wing

    NASA Technical Reports Server (NTRS)

    Pitt, Dale M. (Inventor); Eckstein, Nicholas Stephen (Inventor)

    2013-01-01

    A method and apparatus for managing a flight control surface system. A leading edge section on a wing of an aircraft is extended into a deployed position. A deformable section connects the leading edge section to a trailing section. The deformable section changes from a deformed shape to an original shape when the leading edge section is moved into the deployed position. The leading edge section on the wing is moved from the deployed position to an undeployed position. The deformable section changes to the deformed shape inside of the wing.

  13. Edge Segment-Based Automatic Video Surveillance

    NASA Astrophysics Data System (ADS)

    Hossain, M. Julius; Dewan, M. Ali Akber; Chae, Oksam

    2007-12-01

    This paper presents a moving-object segmentation algorithm using edge information as segment. The proposed method is developed to address challenges due to variations in ambient lighting and background contents. We investigated the suitability of the proposed algorithm in comparison with the traditional-intensity-based as well as edge-pixel-based detection methods. In our method, edges are extracted from video frames and are represented as segments using an efficiently designed edge class. This representation helps to obtain the geometric information of edge in the case of edge matching and moving-object segmentation; and facilitates incorporating knowledge into edge segment during background modeling and motion tracking. An efficient approach for background initialization and robust method of edge matching is presented, to effectively reduce the risk of false alarm due to illumination change and camera motion while maintaining the high sensitivity to the presence of moving object. Detected moving edges are utilized along with watershed algorithm for extracting video object plane (VOP) with more accurate boundary. Experiment results with real image sequence reflect that the proposed method is suitable for automated video surveillance applications in various monitoring systems.

  14. Study on edge extracting in noise image

    NASA Astrophysics Data System (ADS)

    Feng, Gui; Lin, Qiwei; Fu, QingQing

    2008-03-01

    In order to reduce the influence of noise on edge extracting and improve the precision of edge localization on the image, after analyzed the principle, strong points and short points of some traditional edge detecting methods, an effective algorithm for edge extracting in noise image was proposed in this paper. Adopting thought of traditional multi-directional and multistage combinational filtering, an image detail-preserving adaptive filter is designed to remove noise, and then extract the edge in the image. On the basis of the classical Sobel operator, we introduced an algorithm with resisting noise, good real-time and locating accurate edge. The algorithm can distinguish real edge from noise in terms of the theory of successive and smooth edge and random noise. The algorithm was accomplished under visual C++ 6.0 environment and tested by several standard images. The experimental result prove that the presented method is feasible and effective when the salt-pepper pollution of image is smaller than 15%, furthermore the method can extract edges with high location precision and good continuity accurately and effectively, at the same time, it has high processing speed.

  15. Edge mode spectroscopy and imaging for film edge properties in magnetic nanostructures

    NASA Astrophysics Data System (ADS)

    McMichael, Robert

    2014-03-01

    Lithography is an act of violence. Often, films are almost entirely obliterated by patterning, leaving only nanostructures behind with film edges that have borne the brunt of the damage, edges that carry with them the scars of energetic ion bombardment, reactive ions, liftoff and exposure to ambient conditions. In this talk, I will present a variation on ferromagnetic resonance force microscopy that can provide insight into the magnetic properties of film edges in magnetic nanostructures. The method relies on the non-uniformity of the magnetic field in patterned-film nanostructures that are magnetized in-plane, specifically, the low-field regions that form near where the magnetization is directed normal to the edge. In these regions, localized precession forms as trapped spin wave modes, and the resonance condition of these modes serves as an indicator of the edge properties. I will present modeling and measurements on a 500 nm diameter, 25 nm thick Permalloy disk to illustrate the method. Micromagnetic modeling of this disk predicts a main mode that is nearly uniform across the sample and three localized edge modes with higher resonance fields. The spectra measured with various tip positions and mode imaging are consistent with the modeling results. In addition to a strong center mode, three distinct edge modes are observed when the tip is near the disk edge. For a symmetric disk, the modeling predicts that the edge mode resonances are identical on the two opposite edges. However, the measured edge mode resonances on opposite edges of the disk are detected at different resonance fields, suggesting inhomogeneity of the edge properties. By rotating the applied field, we control the position of the localized edge mode along the edge of the disk and confirm that the edge mode resonance field has a strong angular dependence, showing that edge mode properties can vary significantly in a nominally circular disk.

  16. Efficient edge-guided full-waveform inversion by Canny edge detection and bilateral filtering algorithms

    NASA Astrophysics Data System (ADS)

    Xiang, Shiming; Zhang, Haijiang

    2016-11-01

    It is known full-waveform inversion (FWI) is generally ill-conditioned and various strategies including pre-conditioning and regularizing the inversion system have been proposed to obtain a reliable estimation of the velocity model. Here, we propose a new edge-guided strategy for FWI in frequency domain to efficiently and reliably estimate velocity models with structures of the size similar to the seismic wavelength. The edges of the velocity model at the current iteration are first detected by the Canny edge detection algorithm that is widely used in image processing. Then, the detected edges are used for guiding the calculation of FWI gradient as well as enforcing edge-preserving total variation (TV) regularization for next iteration of FWI. Bilateral filtering is further applied to remove noise but keep edges of the FWI gradient. The proposed edge-guided FWI in the frequency domain with edge-guided TV regularization and bilateral filtering is designed to preserve model edges that are recovered from previous iterations as well as from lower frequency waveforms when FWI is conducted from lower to higher frequencies. The new FWI method is validated using the complex Marmousi model that contains several steeply dipping fault zones and hundreds of horizons. Compared to FWI without edge guidance, our proposed edge-guided FWI recovers velocity model anomalies and edges much better. Unlike previous image-guided FWI or edge-guided TV regularization strategies, our method does not require migrating seismic data, thus is more efficient for real applications.

  17. Saturn's Rings Edge-on

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.

    For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.

    The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.

    This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).

    Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science

  18. XAFS and crystallographic studies of Ni(II) porphyrins in single crystals and in solution

    SciTech Connect

    Renner, M.W.; Furenlid, L.R.; Barkigia, K.M.; Fajer, J.

    1996-09-01

    Abstract. Nickel porphyrins serve as models for the active sites of several biological processes. Crystallographic and EXAFS results for a Ni meso-tetrapropyl porphyrin (NiTPrP) yield different Ni-N distances in solution and in the solid state. The Ni-N distances determined by single crystal polarized XAS and X-ray diffraction agree well. Polarized XANES experiments further establish that the pre-edge feature observed in square planar Ni(II) complexes is a ls-4pz transition. The single crystal and solution EXAFS results demonstrate that conformational variations of the porphyrin macrocycle can readily be imposed by environmental and/or packing forces and can thereby modulate the chemical and physical properties of porphyrinic chromophores and prosthetic groups.

  19. Beyond the Kuiper Belt Edge

    NASA Astrophysics Data System (ADS)

    Sheppard, Scott

    2012-06-01

    Of the thousands of known objects beyond Neptune, only one has a perihelion significantly beyond 50 AU, Sedna at 75 AU. Kuiper Belt surveys to date have not been optimized to survey beyond the Kuiper Belt edge at 50 AU. Most of these surveys either did not go faint enough, did not have the required long cadence to detect very slow moving objects or covered too small of an area of sky. The dynamical and physical properties of objects in this region offer key constraints on the formation and evolution of our solar system. In order to probe the Sedna like population of objects with moderate radii (100 km) we propose a deep wide-field outer solar system survey. This survey will allow us to determine if the objects beyond 50 AU are fainter than expected, if there is truly a dearth of objects, or if the Kuiper Belt continues again after some sizable gap possibly caused by a planet sized object. We will be able to examine the origin of Sedna and determine if this eccentric, distant body is unique (as once believed for Pluto) or just the first of a new class of object in the outer Solar System. We will also explore the Neptune Trojans and scattered disk populations through the survey.

  20. Beyond the Kuiper Belt Edge

    NASA Astrophysics Data System (ADS)

    Sheppard, Scott

    2011-01-01

    Of the thousands of known objects beyond Neptune, only one has a perihelion significantly beyond 50 AU, Sedna at 75 AU. Kuiper Belt surveys to date have not been optimized to survey beyond the Kuiper Belt edge at 50 AU. Most of these surveys either did not go faint enough, did not have the required long cadence to detect very slow moving objects or covered too small of an area of sky. The dynamical and physical properties of objects in this region offer key constraints on the formation and evolution of our solar system. In order to probe the Sedna like population of objects with moderate radii (100 km) we propose a deep wide-field outer solar system survey. This survey will allow us to determine if the objects beyond 50 AU are fainter than expected, if there is truly a dearth of objects, or if the Kuiper Belt continues again after some sizable gap possibly caused by a planet sized object. We will be able to examine the origin of Sedna and determine if this eccentric, distant body is unique (as once believed for Pluto) or just the first of a new class of object in the outer Solar System. We will also explore the Neptune Trojans and scattered disk populations through the survey.

  1. Beyond the Kuiper Belt Edge

    NASA Astrophysics Data System (ADS)

    Sheppard, Scott; Trujillo, Chad

    2012-02-01

    Of the thousands of known objects beyond Neptune, only one has a perihelion significantly beyond 50 AU, Sedna at 75 AU. Kuiper Belt surveys to date have not been optimized to survey beyond the Kuiper Belt edge at 50 AU. Most of these surveys either did not go faint enough, did not have the required long cadence to detect very slow moving objects or covered too small of an area of sky. The dynamical and physical properties of objects in this region offer key constraints on the formation and evolution of our solar system. In order to probe the Sedna like population of objects with moderate radii (100 km) we propose a medium wide-field outer solar system survey. This survey will allow us to determine if the objects beyond 50 AU are fainter than expected, if there is truly a dearth of objects, or if the Kuiper Belt continues again after some sizable gap possibly caused by a planet sized object. We will be able to examine the origin of Sedna and determine if this eccentric, distant body is unique (as once believed for Pluto) or just the first of a new class of object in the outer Solar System.

  2. Gyrokinetic Models for Edge Plasmas*

    NASA Astrophysics Data System (ADS)

    Dimits, Andris

    2010-11-01

    The use of gyrokinetic equations for the simulation of magnetic fusion edge and scrapeoff-layer plasmas requires that the equations be valid for large relative perturbation amplitudes and, possibly, large flows. The Hamiltonian gyrokinetic theory has therefore been extended to two new orderings [1,2] that are more general than the standard ones in that they allow for potential perturbations or ExB flows of order the thermal levels. These theories both generalize and show that additional terms should have been present some related prior work. Here, full (low-β) electromagnetic toroidal equation sets are presented, and he energy conservation relations are derived using Noether's theorem in a Lagrangian variational approach. Useful subsidiary and reduced orderings are also considered that result in considerable simplification, and methods for the numerical implementation of the new terms in the equations will also be discussed. *This work was performed for US DOE by LLNL under Contract DE-AC52-07NA27344 and is part of the ESL. [4pt] [1] A.M. Dimits et al., Phys. Fluids B4, 274 (1992). [0pt] [2] A.M. Dimits, Phys. Plasmas 17, 055901 (2010).

  3. Comparing object recognition from binary and bipolar edge features

    PubMed Central

    Jung, Jae-Hyun; Pu, Tian; Peli, Eli

    2017-01-01

    Edges derived from abrupt luminance changes in images carry essential information for object recognition. Typical binary edge images (black edges on white background or white edges on black background) have been used to represent features (edges and cusps) in scenes. However, the polarity of cusps and edges may contain important depth information (depth from shading) which is lost in the binary edge representation. This depth information may be restored, to some degree, using bipolar edges. We compared recognition rates of 16 binary edge images, or bipolar features, by 26 subjects. Object recognition rates were higher with bipolar edges and the improvement was significant in scenes with complex backgrounds.

  4. Theoretical Insights into the Effects of Oxidation and Mo-Doping on the Structure and Stability of Pt-Ni Nanoparticles.

    PubMed

    Cao, Liang; Mueller, Tim

    2016-12-14

    Pt-Ni nanoparticles are promising catalysts for the oxygen reduction reaction but they suffer from Ni dissolution in oxidizing conditions. It has recently been shown that it is possible to stabilize octahedral Pt-Ni nanoparticles by doping them with a small amount of Mo. Using ab initio calculations and a quaternary cluster expansion, we provide atomic-scale explanations for the enhanced stability of Mo-doped Pt-Ni nanoparticles. We predict that for Mo-doped Pt3Ni nanoparticles with only a small amount of Mo doping (around 1.6% mole fraction) the equilibrium concentration of Ni atoms on the particle surface is greatly reduced, limiting the rate at which Ni atoms dissolve from the particles. Mo doping also increases Pt/Ni vacancy formation energies in the surface layer, which further stabilizes the nanoparticles against Ni dissolution and helps preserve the nanoparticle shape. Our calculations also reveal insights into the shape evolution of Pt-Ni nanoparticles: the preferential oxidation of edges can make (111) face sites more vulnerable to dissolution than edge sites, which may contribute to the observed formation of Pt-Ni nanoframes and nanoparticles with concave surfaces.

  5. Eliminating Unbonded Edges In Explosive Bonding

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.; Kushnick, Anne C.

    1991-01-01

    Explosive-bonding technique elminates sharp unbonded notch normally occurring between flyer plate and baseplate. Makes it possible to simply break away unbonded outer extremity of flyer plate; no longer necessary to grind away unbonded edge to prevent collection of corrosive contaminants in edge voids. Method not limited to flat surfaces.

  6. How Forest Inhomogeneities Affect the Edge Flow

    NASA Astrophysics Data System (ADS)

    Boudreault, Louis-Étienne; Dupont, Sylvain; Bechmann, Andreas; Dellwik, Ebba

    2017-03-01

    Most of our knowledge on forest-edge flows comes from numerical and wind-tunnel experiments where canopies are horizontally homogeneous. To investigate the impact of tree-scale heterogeneities ({>}1 m) on the edge-flow dynamics, the flow in an inhomogeneous forest edge on Falster island in Denmark is investigated using large-eddy simulation. The three-dimensional forest structure is prescribed in the model using high resolution helicopter-based lidar scans. After evaluating the simulation against wind measurements upwind and downwind of the forest leading edge, the flow dynamics are compared between the scanned forest and an equivalent homogeneous forest. The simulations reveal that forest inhomogeneities facilitate flow penetration into the canopy from the edge, inducing important dispersive fluxes in the edge region as a consequence of the flow spatial variability. Further downstream from the edge, the forest inhomogeneities accentuate the canopy-top turbulence and the skewness of the wind-velocity components while the momentum flux remains unchanged. This leads to a lower efficiency in the turbulent transport of momentum within the canopy. Dispersive fluxes are only significant in the upper canopy. Above the canopy, the mean flow is less affected by the forest inhomogeneities. The inhomogeneities induce an increase in the mean wind speed that was found to be equivalent to a decrease in the aerodynamic height of the canopy. Overall, these results highlight the importance of forest inhomogeneities when looking at canopy-atmosphere exchanges in forest-edge regions.

  7. Annotated Bibliography of EDGE2D Use

    SciTech Connect

    J.D. Strachan and G. Corrigan

    2005-06-24

    This annotated bibliography is intended to help EDGE2D users, and particularly new users, find existing published literature that has used EDGE2D. Our idea is that a person can find existing studies which may relate to his intended use, as well as gain ideas about other possible applications by scanning the attached tables.

  8. How Forest Inhomogeneities Affect the Edge Flow

    NASA Astrophysics Data System (ADS)

    Boudreault, Louis-Étienne; Dupont, Sylvain; Bechmann, Andreas; Dellwik, Ebba

    2016-09-01

    Most of our knowledge on forest-edge flows comes from numerical and wind-tunnel experiments where canopies are horizontally homogeneous. To investigate the impact of tree-scale heterogeneities ({>}1 m) on the edge-flow dynamics, the flow in an inhomogeneous forest edge on Falster island in Denmark is investigated using large-eddy simulation. The three-dimensional forest structure is prescribed in the model using high resolution helicopter-based lidar scans. After evaluating the simulation against wind measurements upwind and downwind of the forest leading edge, the flow dynamics are compared between the scanned forest and an equivalent homogeneous forest. The simulations reveal that forest inhomogeneities facilitate flow penetration into the canopy from the edge, inducing important dispersive fluxes in the edge region as a consequence of the flow spatial variability. Further downstream from the edge, the forest inhomogeneities accentuate the canopy-top turbulence and the skewness of the wind-velocity components while the momentum flux remains unchanged. This leads to a lower efficiency in the turbulent transport of momentum within the canopy. Dispersive fluxes are only significant in the upper canopy. Above the canopy, the mean flow is less affected by the forest inhomogeneities. The inhomogeneities induce an increase in the mean wind speed that was found to be equivalent to a decrease in the aerodynamic height of the canopy. Overall, these results highlight the importance of forest inhomogeneities when looking at canopy-atmosphere exchanges in forest-edge regions.

  9. [Gap edge effect of Castanopsis kawakamii community].

    PubMed

    Liu, Jinfu; Hong, Wei; Li, Junqing; Lin, Rongfu

    2003-09-01

    This paper reported the characters of gap edge effect of Castanopsis kawakamii community in Sanming, Fujian Province. The species diversity, ecological dominance, and edge effect strength of 38 forest gaps with different development stages in different stands of Castanopsis kawakamii community were measured, and Shannon-Wiener index, Simpson index, and index of edge effect strength were calculated. The results showed that the index of the gap edge effect of Castanopsis kawakamii community was about 0.7-1.3 (according to the species diversity index) and 0.3-1.8 (according to the ecological dominance index). The gap edge effect had the trend of increasing the species diversity of forest communities. The index of gap effect was affected by the size and development stage of the gap and the related forest type. The study provided a theoretical basis for the maintenance of species diversity and the forest management in Castanopsis kawakamii community.

  10. Edge plasmons in monolayer black phosphorus

    NASA Astrophysics Data System (ADS)

    Bao, Zhi-Wei; Wu, Hong-Wei; Zhou, Yu

    2016-12-01

    In this paper, we numerically investigate the edge plasmons in monolayer black phosphorus. It is found that the complex effective indexes of these modes depend on the molecular configuration of the edge. We have calculated the ratio of the real over the imaginary part of the mode effective index, and the results indicate that such edge modes indeed possess outstanding propagation performances in the mid-infrared. In the case of black phosphorus nanoribbon, it seems that only the anti-symmetric modes have low losses, and may be of use in applications. Compared with those at the edge of monolayer black phosphorus, the propagation performances can be further enhanced due to the mode coupling between the two edges. In the end, the effects of substrates are discussed. Our study shows that monolayer black phosphorus may be regarded as a promising candidate for plasmonic applications in the mid-infrared.

  11. Sensitivity Analysis of Automated Ice Edge Detection

    NASA Astrophysics Data System (ADS)

    Moen, Mari-Ann N.; Isaksem, Hugo; Debien, Annekatrien

    2016-08-01

    The importance of highly detailed and time sensitive ice charts has increased with the increasing interest in the Arctic for oil and gas, tourism, and shipping. Manual ice charts are prepared by national ice services of several Arctic countries. Methods are also being developed to automate this task. Kongsberg Satellite Services uses a method that detects ice edges within 15 minutes after image acquisition. This paper describes a sensitivity analysis of the ice edge, assessing to which ice concentration class from the manual ice charts it can be compared to. The ice edge is derived using the Ice Tracking from SAR Images (ITSARI) algorithm. RADARSAT-2 images of February 2011 are used, both for the manual ice charts and the automatic ice edges. The results show that the KSAT ice edge lies within ice concentration classes with very low ice concentration or open water.

  12. Edge effects on water droplet condensation

    NASA Astrophysics Data System (ADS)

    Medici, Marie-Gabrielle; Mongruel, Anne; Royon, Laurent; Beysens, Daniel

    2014-12-01

    In this study we investigate the effect of geometrical or thermal discontinuities on the growth of water droplets condensing on a cooled substrate. Edges, corners, and cooled and noncooled boundaries can have a strong effect on the vapor concentration profile and mass diffusion around the drops. In comparison to growth in a pattern where droplets have to compete to catch vapor, which results in a linear water concentration profile directed perpendicularly to the substrate, droplets near discontinuities can get more vapor (outer edges, corners), resulting in faster growth or less vapor (inner edges), giving lower growth. When the cooling heat flux limits growth instead of mass diffusion (substrate with low thermal conductivity, strong heat exchange with air), edge effects can be canceled. In certain cases, growth enhancement can reach nearly 500% on edges or corners.

  13. Living on the edge: roads and edge effects on small mammal populations.

    PubMed

    Fuentes-Montemayor, Elisa; Cuarón, Alfredo D; Vázquez-Domínguez, Ella; Benítez-Malvido, Julieta; Valenzuela-Galván, David; Andresen, Ellen

    2009-07-01

    1. Roads may affect wildlife populations through habitat loss and disturbances, as they create an abrupt linear edge, increasing the proportion of edge exposed to a different habitat. Three types of edge effects have been recognized: abiotic, direct biotic, and indirect biotic. 2. We explored the direct biotic edge effects of 3- to 4-m wide roads, and also a previously unrecognized type of edge effect: social. We live-trapped two threatened endemic rodents from Cozumel Island (Oryzomys couesi cozumelae and Reithrodontomys spectabilis) in 16 plots delimited by roads on two sides, to compare edge effects between two adjacent edges (corners), single-edge and interior forest, on life history and social variables. 3. No significant edge effects were observed on the life-history variables, with the exception of differences in body condition between males and females of O. c. cozumelae near edges. Both species showed significant and contrasting effects on their social variables. 4. O. c. cozumelae was distributed according to its age and sex: the proportion of adults and males was higher in interior than near edges, while juveniles and females were more abundant near edges. More nonreproductive females were present in corners than in single-edge and interior, while the opposite distribution was observed for nonreproductive males. 5. The distribution of R. spectabilis was related to its age and reproductive condition, but not to its sex. The proportion of adults was significantly higher in corners, while juveniles were only caught in single-edge and interior quadrants. The proportion of reproductive individuals was higher in edge than interior quadrants, while reproductive females were only present in edge quadrants. 6. We found significant differences between the quadrants with the greatest edge exposure in comparison with other quadrants. The social edge effects we identified complement the typology of edge effects recognized in ecological literature. Our study provides

  14. Large Lewis No. Edge-Flame Instabilities

    NASA Technical Reports Server (NTRS)

    Buckmaster, J.

    2001-01-01

    Edge-flames play an important role in a number of microgravity investigations, and in the general study of flames. Examples include the candle-flame experiments carried out on board both the Space Shuttle and the Mir Space Station; the flame-spread-over-liquid work carried out by H. Ross and W. Sirignano amongst others and lifted turbulent diffusion flames. In all of these configurations a local two-dimensional flame structure can be identified which looks like a flame-sheet with an edge, and these structures exhibit dynamical behavior which characterizes them and distinguishes them from ad hoc 2D flame structures. Edge-flames can exist in both a non-premixed context (edges of diffusion flames) and in a premixed context (edges of deflagrations), but the work reported here deals with the edges of diffusion flames. It is particularly relevant, we believe, to oscillations that have been seen in both the candle-flame context, and the flame-spread-over-liquid context. These oscillations are periodic edge-oscillations (in an appropriate reference frame), sans oscillation of the trailing diffusion flame. It is shown that if the Lewis number of the fuel is sufficiently large (the Lewis number of the oxidizer is taken to be 1), and the Damkohler number is sufficiently small, oscillating-edge solutions can be found. Oscillations are encouraged by an on-edge convective flow and the insertion of a cold probe, discouraged by an off-edge convective flow. In the present work, the nature of these oscillations is examined in more depth, using a variety of numerical strategies.

  15. Ni-Co laterite deposits

    USGS Publications Warehouse

    Marsh, Erin E.; Anderson, Eric D.

    2011-01-01

    Nickel-cobalt (Ni-Co) laterite deposits are an important source of nickel (Ni). Currently, there is a decline in magmatic Ni-bearing sulfide lode deposit resources. New efforts to develop an alternative source of Ni, particularly with improved metallurgy processes, make the Ni-Co laterites an important exploration target in anticipation of the future demand for Ni. This deposit model provides a general description of the geology and mineralogy of Ni-Co laterite deposits, and contains discussion of the influences of climate, geomorphology (relief), drainage, tectonism, structure, and protolith on the development of favorable weathering profiles. This model of Ni-Co laterite deposits represents part of the U.S. Geological Survey Mineral Resources Program's effort to update the existing models to be used for an upcoming national mineral resource assessment.

  16. Manipulating the edge of instability

    PubMed Central

    Venkadesan, Madhusudhan; Guckenheimer, John; Valero-Cuevas, Francisco J.

    2009-01-01

    We investigate the integration of visual and tactile sensory input for dynamic manipulation. Our experimental data and computational modeling reveal that time-delays are as critical to task-optimal multisensory integration as sensorimotor noise. Our focus is a dynamic manipulation task “at the edge of instability.” Mathematical bifurcation theory predicts that this system will exhibit well-classified low-dimensional dynamics in this regime. The task was using the thumbpad to compress a slender spring prone to buckling as far as possible, just shy of slipping. As expected from bifurcation theory, principal components analysis gives a projection of the data onto a low dimensional subspace that captures 91-97% of its variance. In this subspace, we formulate a low-order model for the brain+hand+spring dynamics based on known mechanical and neurophysiological properties of the system. By systematically occluding vision and anesthetically blocking thumbpad sensation in 12 consenting subjects, we found that vision contributed to dynamic manipulation only when thumbpad sensation was absent. The reduced ability of the model system to compress the spring with absent sensory channels closely resembled the experimental results. Moreover, we found that the model reproduced the contextual usefulness of vision only if we took account of time-delays. Our results shed light on critical features of dynamic manipulation distinct from those of static pinch, as well as the mechanism likely responsible for loss of manual dexterity and increased reliance on vision when age or neuromuscular disease increase noisiness and/or time-delays during sensorimotor integration. PMID:17400231

  17. Characterization of Ni-rich hexagonal birnessite and its geochemical effects on aqueous Pb2+/Zn2+ and As(III)

    NASA Astrophysics Data System (ADS)

    Yin, Hui; Tan, Wenfeng; Zheng, Lirong; Cui, Haojie; Qiu, Guohong; Liu, Fan; Feng, Xionghan

    2012-09-01

    Hexagonal birnessite is the most ubiquitous manganese oxide in geological environments. It is often highly enriched in trace metal ions such as Ni and plays an important role in metal(loids) geochemistry. Nanostructured birnessites containing different amounts of Ni were synthesized by addition of Ni2+ to initial reactants. Powder X-ray diffraction (XRD), element analysis, field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), X-ray absorption spectroscopy (XAS) and isothermal adsorption and oxidation of metal(loids) were carried out to investigate the effects of Ni doping on the substructure and physicochemical properties of birnessite, and Ni crystal chemistry in birnessite. These Ni-rich birnessites have Ni contents as high as 2.99% (Ni5) and 6.08% (Ni10) in weight. EXAFS results show that Ni5 has 23.7% of the total Ni (0.71 wt.%) and Ni10 has 34.5% of the total Ni (2.10 wt.%) in Mn octahedral layer with the remaining Ni located at vacancies and edge sites. The Ni-rich birnessites have weaker crystallinity and thermal stability, fewer layers stacked along the c axis, ˜1.5-2.7 times larger surfaces areas, and a higher Mn average oxidation numbers (AONs) compared to the birnessite without Ni. Additionally, the doping of Ni during birnessite crystallization enhances the formation of vacancies in the layer; however, adsorption capacities for Pb2+ and Zn2+ by these Ni-rich birnessites are reduced, mainly because of vacancies and edge sites occupation by a large amount of Ni. The Ni-rich birnessites exhibit much higher oxidation capability and can completely oxidize As(III) in solution at rapid initial reaction rates under the experimental condition. The results indicate that incorporation of Ni into the natural birnessite in ferromanganese nodules may be achieved both by direct coprecipitation with Mn to build the layers and migration over time from adsorbed Ni on the surface into the layer

  18. Elastically Deformable Side-Edge Link for Trailing-Edge Flap Aeroacoustic Noise Reduction

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R. (Inventor); Lockard, David P. (Inventor); Moore, James B. (Inventor); Su, Ji (Inventor); Turner, Travis L. (Inventor); Lin, John C. (Inventor); Taminger, Karen M. (Inventor); Kahng, Seun K. (Inventor); Verden, Scott A. (Inventor)

    2014-01-01

    A system is provided for reducing aeroacoustic noise generated by an aircraft having wings equipped with trailing-edge flaps. The system includes a plurality of elastically deformable structures. Each structure is coupled to and along one of the side edges of one of the trailing-edge flaps, and is coupled to a portion of one of the wings that is adjacent to the one of the side edges. The structures elastically deform when the trailing-edge flaps are deployed away from the wings.

  19. Soft X-ray absorption spectroscopy and resonant inelastic X-ray scattering spectroscopy below 100 eV: probing first-row transition-metal M-edges in chemical complexes.

    PubMed

    Wang, Hongxin; Young, Anthony T; Guo, Jinghua; Cramer, Stephen P; Friedrich, Stephan; Braun, Artur; Gu, Weiwei

    2013-07-01

    X-ray absorption and scattering spectroscopies involving the 3d transition-metal K- and L-edges have a long history in studying inorganic and bioinorganic molecules. However, there have been very few studies using the M-edges, which are below 100 eV. Synchrotron-based X-ray sources can have higher energy resolution at M-edges. M-edge X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) could therefore provide complementary information to K- and L-edge spectroscopies. In this study, M2,3-edge XAS on several Co, Ni and Cu complexes are measured and their spectral information, such as chemical shifts and covalency effects, are analyzed and discussed. In addition, M2,3-edge RIXS on NiO, NiF2 and two other covalent complexes have been performed and different d-d transition patterns have been observed. Although still preliminary, this work on 3d metal complexes demonstrates the potential to use M-edge XAS and RIXS on more complicated 3d metal complexes in the future. The potential for using high-sensitivity and high-resolution superconducting tunnel junction X-ray detectors below 100 eV is also illustrated and discussed.

  20. In situ spectroscopic characterization of Ni1-xZnx/ZnO catalysts and their selectivity for acetylene semihydrogenation in excess ethylene

    SciTech Connect

    Spanjers, Charles S.; Sim, Richard S.; Sturgis, Nicholas P.; Kabius, Bernd; Rioux, Robert M.

    2015-10-30

    The structures of ZnO-supported Ni catalysts were explored with in situ X-ray absorption spectroscopy, temperature-programmed reduction, X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy, and electron energy loss spectroscopy. Calcination of nickel nitrate on a nanoparticulate ZnO support at 450 °C results in the formation of Zn-doped NiO (ca. N₀̣̣₈₅ Zn₀̣̣₁₅O) nanoparticles with the rock salt crystal structure. Subsequent in situ reduction monitored by X-ray absorption near-edge structure (XANES) at the Ni K edge reveals a direct transformation of the Zn-doped NiO nanoparticles to a face-centered cubic alloy, Ni1-xZnx, at ~400 °C with x increasing with increasing temperature. Both in situ XANES and ex situ HRTEM provide evidence for intermetallic β₁-NiZn formation at ~550 °C. In comparison to a Ni/SiO₂ catalyst, Ni/ZnO necessitates a higher temperature for the reduction of NiII to Ni⁰, which highlights the strong interaction between Ni and the ZnO support. The catalytic activity for acetylene removal from an ethylene feed stream is decreased by a factor of 20 on Ni/ZnO in comparison to Ni/SiO₂. The decrease in catalytic activity of Ni/ZnO is accompanied by a reduced absolute selectivity to ethylene. H–D exchange measurements demonstrate a reduced ability of Ni/ZnO to dissociate hydrogen in comparison to Ni/SiO₂.These results of the catalytic experiments suggest that the catalytic properties are controlled, in part, by the zinc oxide support and stress the importance of reporting absolute ethylene selectivity for the catalytic semihydrogenation of acetylene in excess ethylene.

  1. The oxidation of Ni-rich Ni-Al intermetallics

    NASA Technical Reports Server (NTRS)

    Doychak, Joseph; Smialek, James L.; Barrett, Charles A.

    1988-01-01

    The oxidation of Ni-Al intermetallic alloys in the beta-NiAl phase field and in the two phase beta-NiAl/gamma'-Ni3Al phase field has been studied between 1000 and 1400 C. The stoichiometric beta-NiAl alloy doped with Zr was superior to other alloy compositions under cyclic and isothermal oxidation. The isothermal growth rates did not increase monotonically as the alloy Al content was decreased. The characteristically ridged alpha-Al2O3 scale morphology, consisting of cells of thin, textured oxide with thick growth ridges at cell boundaries, forms on oxidized beta-NiAl alloys. The correlation of scale features with isothermal growth rates indicates a predominant grain boundary diffusion growth mechanism. The 1200 C cyclic oxidation resistance decreases near the lower end of the beta-NiAl phase field.

  2. Comparative Study of Edge Detectors in case of Echocardiographic Images

    NASA Astrophysics Data System (ADS)

    Saini, Kalpana; Dewal, M. L.; Rohit, Manoj Kumar

    2010-11-01

    In this paper we compare different edge detectors based on peak signal to noise ratio on Echocardiographic images. Edge detection is a critical element in image processing, since edges contain a major function of image information. The function of edge detection is to identify the boundaries of homogeneous regions in an image based on properties such as intensity and texture.We have taken Perwitt edge detector, Robarts edge detector, LoG edge detector, Canny edge detector, and Sobel edge detector for this comparison and study.

  3. Image Edge Extraction via Fuzzy Reasoning

    NASA Technical Reports Server (NTRS)

    Dominquez, Jesus A. (Inventor); Klinko, Steve (Inventor)

    2008-01-01

    A computer-based technique for detecting edges in gray level digital images employs fuzzy reasoning to analyze whether each pixel in an image is likely on an edge. The image is analyzed on a pixel-by-pixel basis by analyzing gradient levels of pixels in a square window surrounding the pixel being analyzed. An edge path passing through the pixel having the greatest intensity gradient is used as input to a fuzzy membership function, which employs fuzzy singletons and inference rules to assigns a new gray level value to the pixel that is related to the pixel's edginess degree.

  4. Electrostatic analysis of the tokamak edge plasma

    SciTech Connect

    Motley, R.W.

    1981-07-01

    The intrusion of an equipotential poloidal limiter into the edge plasma of a circular tokamak discharge distorts the axisymmetry in two ways: (1) it (partially) shorts out the top-to-bottom Pfirsch-Schlueter driving potentials, and (2) it creates zones of back current flow into the limiter. The resulting boundary mismatch between the outer layers and the inner axisymmetric Pfirsch-Schlueter layer provides free energy to drive the edge plasma unstable. Special limiters are proposed to symmetrize the edge plasma and thereby reduce the electrical and MHD activity in the boundary layer.

  5. An edge preserving differential image coding scheme

    NASA Technical Reports Server (NTRS)

    Rost, Martin C.; Sayood, Khalid

    1992-01-01

    Differential encoding techniques are fast and easy to implement. However, a major problem with the use of differential encoding for images is the rapid edge degradation encountered when using such systems. This makes differential encoding techniques of limited utility, especially when coding medical or scientific images, where edge preservation is of utmost importance. A simple, easy to implement differential image coding system with excellent edge preservation properties is presented. The coding system can be used over variable rate channels, which makes it especially attractive for use in the packet network environment.

  6. An optimal scale for edge detection

    NASA Astrophysics Data System (ADS)

    Geiger, Davi; Poggio, Tomaso

    1988-09-01

    Many problems in early vision are ill posed. Edge detection is a typical example. This paper applies regularization techniques to the problem of edge detection. The authors derive an optimal filter for edge detection with a size controlled by the regularization parameter lambda and compare it to the Gaussian filter. A formula relating the signal-to-noise ratio to the parameter lambda is derived from regularization analysis for the case of small values of lambda. Also discussed is the method of Generalized Cross Validation for obtaining the optimal filter scale. Finally, the authors use their framework to explain two perceptual phenomena: coarsely quantized images becoming recognizable by either blurring or adding noise.

  7. Cavitation on hydrofoils with sinusoidal leading edge

    NASA Astrophysics Data System (ADS)

    Johari, H.

    2015-12-01

    Cavitation characteristics of hydrofoils with sinusoidal leading edge were examined experimentally at a Reynolds number of 7.2 × 105. The hydrofoils had an underlying NACA 634-021 profile and an aspect ratio of 4.3. The sinusoidal leading edge geometries included three amplitudes of 2.5%, 5%, and 12% and two wavelengths of 25% and 50% of the mean chord length. Results revealed that cavitation on the leading edge-modified hydrofoils existed in pockets behind the troughs whereas the baseline hydrofoil produced cavitation along its entire span. Moreover, cavitation on the modified hydrofoils appeared at consistently lower angles of attack than on the baseline hydrofoil.

  8. Edge current in a small chiral superconductor

    NASA Astrophysics Data System (ADS)

    Suzuki, Shu-Ichiro; Asano, Yasuhiro

    2016-10-01

    We discuss a theoretical description of the edge current in a chiral superconductor. On the basis of the quasiclassical Green function formalism, we derive a useful expression of the chiral edge current which enable us to understand how Cooper pairs contribute to the electric current. We will show that the chiral edge current is carried by the combinations of two Cooper pairs belonging to different pairing symmetries. One Cooper pair belongs to the usual even-frequency pairing symmetry class. However, the other belongs to the odd-frequency symmetry class.

  9. Bulk Migration of Ni/NiO in Ni-YSZ during Reducing Conditions

    SciTech Connect

    Saraf, Laxmikant V.; Baer, Donald R.; Lea, Alan S.; Zhu, Zihua; Strohm, James J.; Sitzman, S. D.; King, David L.

    2010-02-09

    Understanding the migration of Ni/NiO in Ni-YSZ can potentially help to design a better solid oxide fuel cell (SOFC) anode. We have observed that extensive hydrogen reduction and methane steam reforming of Ni-YSZ caused bulk migration of Ni/NiO to at least ~ 5 µm deeper from the Ni-YSZ surface. No significant bulk migration effects were detected after simple thermal treatments in non-reducing/non-reforming environment. Surface analysis of a single zirconia grain in the first 10-20 nm region from annealed, hydrogen reduced and methane steam reformed Ni-YSZ shows Ni-enriched surface supporting earlier claims of Ni exsolution. 3D-EBSD analysis of thermally treated sample before exposing it to reducing and reforming environment indicated mixed NiO/YSZ phase with some porosity and random grain orientation. The surface analysis and mapping were carried out using ToF-SIMS and AES whereas EDS maps on FIB sliced areas on Ni-YSZ were utilized for the bulk analysis. The results provide additional information related to complex reactions occurring in SOFC during internal reforming conditions.

  10. In-situ observation of graphene growth on Ni(111)

    NASA Astrophysics Data System (ADS)

    Odahara, Genki; Otani, Shigeki; Oshima, Chuhei; Suzuki, Masahiko; Yasue, Tsuneo; Koshikawa, Takanori

    2011-06-01

    Graphene growth of mono-, bi- and tri-layers on Ni(111) through surface segregation was observed in situ by low energy electron microscopy. The carbon segregation was controlled by adjusting substrate temperature from 1200 K to 1050 K. After the completion of the first layer at 1125 K, the second layer grew at the interface between the first-layer and the substrate at 1050 K. The third layer also started to grow at the same temperature, 1050 K. All the layers exhibited a 1 × 1 atomic structure. The edges of the first-layer islands were straight lines, reflecting the hexagonal atomic structure. On the other hand, the shapes of the second-layer islands were dendritic. The edges of the third-layer islands were again straight lines similar to those of the first-layer islands. The phenomena presumably originate from the changes of interfacial-bond strength of the graphene to Ni substrate depending on the graphene thickness. No nucleation site of graphene layers was directly observed. All the layers expanded out of the field of view and covered the surface. The number of nucleation sites is extremely small on Ni(111) surface. This finding might open the way to grow the high quality, single-domain graphene crystals.

  11. Edge enhancement improves disruptive camouflage by emphasising false edges and creating pictorial relief

    PubMed Central

    Egan, John; Sharman, Rebecca J.; Scott-Brown, Kenneth C.; Lovell, Paul George

    2016-01-01

    Disruptive colouration is a visual camouflage composed of false edges and boundaries. Many disruptively camouflaged animals feature enhanced edges; light patches are surrounded by a lighter outline and/or a dark patches are surrounded by a darker outline. This camouflage is particularly common in amphibians, reptiles and lepidopterans. We explored the role that this pattern has in creating effective camouflage. In a visual search task utilising an ultra-large display area mimicking search tasks that might be found in nature, edge enhanced disruptive camouflage increases crypsis, even on substrates that do not provide an obvious visual match. Specifically, edge enhanced camouflage is effective on backgrounds both with and without shadows; i.e. this is not solely due to background matching of the dark edge enhancement element with the shadows. Furthermore, when the dark component of the edge enhancement is omitted the camouflage still provided better crypsis than control patterns without edge enhancement. This kind of edge enhancement improved camouflage on all background types. Lastly, we show that edge enhancement can create a perception of multiple surfaces. We conclude that edge enhancement increases the effectiveness of disruptive camouflage through mechanisms that may include the improved disruption of the object outline by implying pictorial relief. PMID:27922058

  12. Edge enhancement improves disruptive camouflage by emphasising false edges and creating pictorial relief.

    PubMed

    Egan, John; Sharman, Rebecca J; Scott-Brown, Kenneth C; Lovell, Paul George

    2016-12-06

    Disruptive colouration is a visual camouflage composed of false edges and boundaries. Many disruptively camouflaged animals feature enhanced edges; light patches are surrounded by a lighter outline and/or a dark patches are surrounded by a darker outline. This camouflage is particularly common in amphibians, reptiles and lepidopterans. We explored the role that this pattern has in creating effective camouflage. In a visual search task utilising an ultra-large display area mimicking search tasks that might be found in nature, edge enhanced disruptive camouflage increases crypsis, even on substrates that do not provide an obvious visual match. Specifically, edge enhanced camouflage is effective on backgrounds both with and without shadows; i.e. this is not solely due to background matching of the dark edge enhancement element with the shadows. Furthermore, when the dark component of the edge enhancement is omitted the camouflage still provided better crypsis than control patterns without edge enhancement. This kind of edge enhancement improved camouflage on all background types. Lastly, we show that edge enhancement can create a perception of multiple surfaces. We conclude that edge enhancement increases the effectiveness of disruptive camouflage through mechanisms that may include the improved disruption of the object outline by implying pictorial relief.

  13. An X-ray absorption spectroscopy investigation of the local atomic structure in Cu-Ni-Si alloy after severe plastic deformation and ageing

    NASA Astrophysics Data System (ADS)

    Azzeddine, H.; Harfouche, M.; Hennet, L.; Thiaudiere, D.; Kawasaki, M.; Bradai, D.; Langdon, T. G.

    2015-08-01

    The local atomic structure of Cu-Ni-Si alloy after severe plastic deformation (SPD) processing and the decomposition of supersaturated solid solution upon annealing were investigated by means of X-ray absorption spectroscopy. The coordination number and interatomic distances were obtained by analyzing experimental extend X-ray absorption fine structure data collected at the Ni K-edge. Results indicate that the environment of Ni atoms in Cu-Ni-Si alloy is strongly influenced by the deformation process. Moreover, ageing at 973 K affects strongly the atomic structure around the Ni atoms in Cu-Ni-Si deformed by equal channel angular pressing and high pressure torsion. This influence is discussed in terms of changes and decomposition features of the Cu-Ni-Si solid solution.

  14. Edge effect in fluid jet polishing.

    PubMed

    Guo, Peiji; Fang, Hui; Yu, Jingchi

    2006-09-10

    The edge effect is one of the most important subjects in optical manufacturing. The removal function at different positions of the sample in the process of fluid jet polishing (FJP) is investigated in the experiments. Furthermore, by using finite-element analysis (FEA), the distributions for velocity and pressure of slurry jets are simulated. Experimental results demonstrate that the removal function has a ring-shaped profile, except for a little change in the size at the operated area even if the nozzle extends beyond the edge of the sample. FEA simulations reveal a similar distribution of velocity with a cavity resulting in the ring-shaped profile of material removal at different impact positions. To a certain extent, therefore, the removal function at the edge of the surface of the sample appears similar to that inside of it, so that the classical edge effect can be neglected in FJP.

  15. Edge reconstruction-mediated graphene fracture

    NASA Astrophysics Data System (ADS)

    Zhang, Ziang; Kutana, Alex; Yakobson, Boris I.

    2015-01-01

    Creation of free edges in graphene during mechanical fracture is a process that is important from both fundamental and technological points of view. Here we derive an analytical expression for the energy of a free-standing reconstructed chiral graphene edge, with chiral angle varying from 0° to 30°, and test it by first-principles computations. We then study the thermodynamics and kinetics of fracture and show that during graphene fracture under uniaxial load it is possible to obtain fully reconstructed zigzag edges through sequential reconstructions at the crack tip. The preferable condition for this process is high temperature (T ~ 1000 K) and low (quasi-static) mechanical load (KI ~ 5.0 eV Å-5/2). Edge configurations of graphene nanoribbons may be tuned according to these guidelines.

  16. Miniature Trailing Edge Effector for Aerodynamic Control

    NASA Technical Reports Server (NTRS)

    Lee, Hak-Tae (Inventor); Bieniawski, Stefan R. (Inventor); Kroo, Ilan M. (Inventor)

    2008-01-01

    Improved miniature trailing edge effectors for aerodynamic control are provided. Three types of devices having aerodynamic housings integrated to the trailing edge of an aerodynamic shape are presented, which vary in details of how the control surface can move. A bucket type device has a control surface which is the back part of a C-shaped member having two arms connected by the back section. The C-shaped section is attached to a housing at the ends of the arms, and is rotatable about an axis parallel to the wing trailing edge to provide up, down and neutral states. A flip-up type device has a control surface which rotates about an axis parallel to the wing trailing edge to provide up, down, neutral and brake states. A rotating type device has a control surface which rotates about an axis parallel to the chord line to provide up, down and neutral states.

  17. Edge energies and shapes of nanoprecipitates.

    SciTech Connect

    Hamilton, John C.

    2006-01-01

    In this report we present a model to explain the size-dependent shapes of lead nano-precipitates in aluminum. Size-dependent shape transitions, frequently observed at nanolength scales, are commonly attributed to edge energy effects. This report resolves an ambiguity in the definition and calculation of edge energies and presents an atomistic calculation of edge energies for free clusters. We also present a theory for size-dependent shapes of Pb nanoprecipitates in Al, introducing the concept of ''magic-shapes'' defined as precipitate shapes having near zero elastic strains when inserted into similarly shaped voids in the Al matrix. An algorithm for constructing a complete set of magic-shapes is presented. The experimental observations are explained by elastic strain energies and interfacial energies; edge energies play a negligible role. We replicate the experimental observations by selecting precipitates having magic-shapes and interfacial energies less than a cutoff value.

  18. Folded membrane dialyzer with mechanically sealed edges

    DOEpatents

    Markley, Finley W.

    1976-01-01

    A semipermeable membrane is folded in accordion fashion to form a stack of pleats and the edges are sealed so as to isolate the opposite surfaces of the membrane. The stack is contained within a case that provides ports for flow of blood in contact with one surface of the membrane through channels formed by the pleats and also provides ports for flow of a dialysate through channels formed by the pleats in contact with the other surface of the membrane. The serpentine side edges of the membrane are sealed by a solidified plastic material, whereas effective mechanical means are provided to seal the end edges of the folded membrane. The mechanical means include a clamping strip which biases case sealing flanges into a sealed relationship with end portions of the membrane near the end edges, which portions extend from the stack and between the sealing flanges.

  19. Leading edge protection for composite blades

    NASA Technical Reports Server (NTRS)

    Brantley, J. W.; Irwin, T. P. (Inventor)

    1977-01-01

    A laminated filament composite structure, such as an airfoil for use in an environment in which it is subjected to both foreign object impact and bending is provided with improved leading edge protection. At least one fine wire mesh layer is partially bonded within the composite structure along its neutral bending axis. A portion of the wire mesh layer extends beyond the neutral bending axis and partially around the leading edge where it is bonded to the outer periphery of the primary composite structure. The wire mesh is clad with a metal such as nickel to provide an improved leading edge protective device which is firmly anchored within the composite structure. Also described is a novel method of constructing a composite airfoil so as to further minimize the possibility of losing the leading edge protective device due to delamination caused by impact and bending.

  20. Multi-dimensional edge detection operators

    NASA Astrophysics Data System (ADS)

    Youn, Sungwook; Lee, Chulhee

    2014-05-01

    In remote sensing, modern sensors produce multi-dimensional images. For example, hyperspectral images contain hundreds of spectral images. In many image processing applications, segmentation is an important step. Traditionally, most image segmentation and edge detection methods have been developed for one-dimensional images. For multidimensional images, the output images of spectral band images are typically combined under certain rules or using decision fusions. In this paper, we proposed a new edge detection algorithm for multi-dimensional images using secondorder statistics. First, we reduce the dimension of input images using the principal component analysis. Then we applied multi-dimensional edge detection operators that utilize second-order statistics. Experimental results show promising results compared to conventional one-dimensional edge detectors such as Sobel filter.

  1. The edge extraction of agricultural crop leaf

    NASA Astrophysics Data System (ADS)

    Wang, Beilei; Cao, Ying; Xiao, Huiming; Jiang, Huiyan; Liu, Hongjuan

    2009-07-01

    In agricultural engineering, to ensure rational use of pesticide and improvement of crop production, computer image recognition technology is currently applied to help farmers to identify the degree of crop diseases. Considering the importance of feature extraction in this field, in this paper, we first present and discuss several widely used edge operator, including Sobel, Prewitt, Roberts, Canny and LoG. Furthermore, an experiment is conducted to compare performance and accuracy of five operators by applying them to a leaf image taken from agricultural crop for edge detection. The results of experiment show that, in practice, LoG edge operator is relatively a better choice and performs well for edge detection of agricultural crop leaf image.

  2. Thermoelectric properties of high power factor sulfide NiSbS and Co substitution system Ni1- x Co x SbS

    NASA Astrophysics Data System (ADS)

    Miyata, Masanobu; Ozaki, Taisuke; Nishino, Shunsuke; Koyano, Mikio

    2017-02-01

    This paper describes experimental and theoretical investigations of electronic and thermoelectric (TE) properties of high power factor sulfide Ni1- x Co x SbS (x = 0, 0.10, 0.20, and 0.40). For NiSbS, even in the metallic behavior, the power factor PF of NiSbS is 1.9 mW·K-2·m-1 at 300 K, which exceeds the high performance TE sulfide materials as tetrahedrites or colusites. For the Ni1- x Co x SbS system, the residual electrical resistivity ρresidual increases. However, the thermopower S decreases in comparison with NiSbS. For density functional theory (DFT) calculations, the chemical potential μ for NiSbS is located at the edge of the pseudo-gap in the electronic density of states (DOS). Electronic structure μ is located at the peak of PF, as understood by the large transmission R(E) and ∂R(E)/∂E at Fermi energy E F for NiSbS. For Co-substitution, μ shifts to the valley of PF from the peak, indicating the importance of electron filling control for TE properties.

  3. Edge-Enabled Tactical Systems (Poster)

    DTIC Science & Technology

    2014-10-23

    Engineering Institute Contact: Grace Lewis glewis@sei.cmu.edu Current Capabilities Group Autonomy for Mobile Systems (GAMS) Portable middleware...distributed algorithms and tools to support warfighter-directed groups of autonomous sensors and robotic systems. The focus for FY14 was on area coverage...objects. Information Superiority to the Edge (ISE) Mobile application prototype that supports small edge units of soldiers or first responders by (1

  4. Applications of Hydrofoils with Leading Edge Protuberances

    DTIC Science & Technology

    2012-03-30

    APPLICATIONS OF HYDROFOILS WITH LEADING EDGE PROTUBERANCES Final Technical Report for Office of Naval Research contract...To) 03/30/2012 Final Technical Report 01-08-2008 to 31-12-2011 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Applications of Hydrofoils with Leading...AVAILABILITY STATEMENT Approved for public release; distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT The leading edge modified hydrofoils

  5. Commercial Technology at the Tactical Edge

    DTIC Science & Technology

    2013-06-01

    18th ICCRTS “C2 in Underdeveloped, Degraded and Denied Operational Environments” Commercial Technology at the Tactical Edge Topics: (7...Architectures, Technologies , and Tools (8): Networks and Networking Jonathan R. Agre Institute for Defense Analyses 4850 Mark Center Drive...4. TITLE AND SUBTITLE Commercial Technology at the Tactical Edge 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d

  6. Edge Equilibrium Code (EEC) For Tokamaks

    SciTech Connect

    Li, Xujling

    2014-02-24

    The edge equilibrium code (EEC) described in this paper is developed for simulations of the near edge plasma using the finite element method. It solves the Grad-Shafranov equation in toroidal coordinate and uses adaptive grids aligned with magnetic field lines. Hermite finite elements are chosen for the numerical scheme. A fast Newton scheme which is the same as implemented in the equilibrium and stability code (ESC) is applied here to adjust the grids

  7. Edge covers and independence: Algebraic approach

    NASA Astrophysics Data System (ADS)

    Kalinina, E. A.; Khitrov, G. M.; Pogozhev, S. V.

    2016-06-01

    In this paper, linear algebra methods are applied to solve some problems of graph theory. For ordinary connected graphs, edge coverings and independent sets are considered. Some results concerning minimum edge covers and maximum matchings are proved with the help of linear algebraic approach. The problem of finding a maximum matching of a graph is fundamental both practically and theoretically, and has numerous applications, e.g., in computational chemistry and mathematical chemistry.

  8. Interaction of gusts with forest edges

    NASA Astrophysics Data System (ADS)

    Ruck, Bodo; Tischmacher, Michael

    2012-05-01

    Experimental investigations in an atmospheric boundary layer wind tunnel were carried out in order to study the interaction of gusts with forest edges. Summarizing the state of knowledge in the field of forest damages generated by extreme storms, there is a strong indication that in many cases, windthrow of trees starts near the forest edge from where it spreads into the stand. The high-transient interaction between gusts and (porous) forest edges produce unsteady flow phenomena not known so far. From a fluid mechanical point of view, the flow type resembles a forward-facing porous step flow, which is significantly influenced by the characteristics of the oncoming atmospheric boundary layer flow and the shape and `porous properties' of the forest edge. The paper reports systematic investigations on the interaction of artificially generated gusts and forest edge models in an atmospheric boundary layer wind tunnel. The experimental investigations were carried out with a laser-based time-resolved PIV-system and high speed photography. Different flow phenomena like gust streching, vortex formation, Kelvin-Helmholtz instabilities or wake production of turbulence could be measured or visualized contributing to the understanding of the complex flow perfomance over the forest edge.

  9. Edge detecting new physics the Voronoi way

    NASA Astrophysics Data System (ADS)

    Debnath, Dipsikha; Gainer, James S.; Kim, Doojin; Matchev, Konstantin T.

    2016-05-01

    Edge detection is an important tool in the search for and exploration of physics beyond the standard model. Ideally one would be able to perform edge detection in a relatively model-independent way, however most analyses rely on more detailed properties (i.e. “shapes” or likelihood distributions) of the variable(s) of interest. We therefore present a sketch of how edge detection can be accomplished using Voronoi tessellations, focusing on the case of two-dimensional distributions for simplicity. After deriving some useful properties of the Voronoi tessellations of simplified distributions containing edges, we propose several algorithms for tagging the Voronoi cells in the vicinity of kinematic edges in real data and show that the efficiency of our methods is improved by the addition of a few Voronoi relaxation steps via Lloyd's method. Our results suggest specifically that Voronoi-based methods should be useful for relatively model-independent edge detection, and, more generally, that the wider adaptation of Voronoi tessellations may be useful in collider physics.

  10. Aircraft wing trailing-edge noise

    NASA Technical Reports Server (NTRS)

    Underwood, R. L.; Hodgson, T. H.

    1981-01-01

    The mechanism and sound pressure level of the trailing-edge noise for two-dimensional turbulent boundary layer flow was examined. Experiment is compared with current theory. A NACA 0012 airfoil of 0.61 m chord and 0.46 m span was immersed in the laminar flow of a low turbulence open jet. A 2.54 cm width roughness strip was placed at 15 percent chord from the leading edge on both sides of the airfoil as a boundary layer trip so that two separate but statistically equivalent turbulent boundary layers were formed. Tests were performed with several trailing-edge geometries with the upstream velocity U sub infinity ranging from a value of 30.9 m/s up to 73.4 m/s. Properties of the boundary layer for the airfoil and pressure fluctuations in the vicinity of the trailing-edge were examined. A scattered pressure field due to the presence of the trailing-edge was observed and is suggested as a possible sound producing mechanism for the trailing-edge noise.

  11. Nondiffusive plasma transport at tokamak edge

    NASA Astrophysics Data System (ADS)

    Krasheninnikov, S. I.

    2000-10-01

    Recent findings show that cross field edge plasma transport at tokamak edge does not necessarily obey a simple diffusive law [1], the only type of a transport model applied so far in the macroscopic modeling of edge plasma transport. Cross field edge transport is more likely due to plasma filamentation with a ballistic motion of the filaments towards the first wall. Moreover, it so fast that plasma recycles on the main chamber first wall rather than to flow into divertor as conventional picture of edge plasma fluxes suggests. Crudely speaking particle recycling wise diverted tokamak operates in a limiter regime due to fast anomalous non-diffusive cross field plasma transport. Obviously that this newly found feature of edge plasma anomalous transport can significantly alter a design of any future reactor relevant tokamaks. Here we present a simple model describing the motion of the filaments in the scrape off layer and discuss it implications for experimental observations. [1] M. Umansky, S. I. Krasheninnikov, B. LaBombard, B. Lipschultz, and J. L. Terry, Phys. Plasmas 6 (1999) 2791; M. Umansky, S. I. Krasheninnikov, B. LaBombard and J. L. Terry, Phys. Plasmas 5 (1998) 3373.

  12. Edge effects on water droplet condensation

    NASA Astrophysics Data System (ADS)

    Royon, Laurent; Montgruel, Anne; Medici, Marie Gabrielle; Beysens, Daniel

    2014-11-01

    The effect of geometrical or thermal discontinuities on the growth of water droplets condensing on a cooled substrate is investigated. Edges, corners, cooled/non cooled boundaries can have a strong effect on the vapor concentration profile and mass diffusion around the drops. In comparison to growth in a pattern where droplets have to compete to catch vapor, which results in a linear water concentration profile directed perpendicular to the substrate, droplets near discontinuities can get more vapor (outer edges, corners), resulting in faster growth or less vapor (inner edges), giving lower growth. When the cooling heat flux limits growth instead of mass diffusion (substrate with low thermal conductivity, strong heat exchange with air), edges effects can be canceled. In certain cases, the growth enhancement can reach nearly 500% on edges or corners which, on an inclined substrate, make droplets near the edges detach sooner than in the middle of the substrate. This effect is frequently observed with dew condensing on windows or car windshields. Such droplets, acting as wipers, can thus appreciably increase dew collection on a substrate.

  13. Iron speciation in human cancer cells by K-edge total reflection X-ray fluorescence-X-ray absorption near edge structure analysis

    NASA Astrophysics Data System (ADS)

    Polgári, Zs.; Meirer, F.; Sasamori, S.; Ingerle, D.; Pepponi, G.; Streli, C.; Rickers, K.; Réti, A.; Budai, B.; Szoboszlai, N.; Záray, G.

    2011-03-01

    X-ray absorption near edge structure (XANES) analysis in combination with synchrotron radiation induced total reflection X-ray fluorescence (SR-TXRF) acquisition was used to determine the oxidation state of Fe in human cancer cells and simultaneously their elemental composition by applying a simple sample preparation procedure consisting of pipetting the cell suspension onto the quartz reflectors. XANES spectra of several inorganic and organic iron compounds were recorded and compared to that of different cell lines. The XANES spectra of cells, independently from the phase of cell growth and cell type were very similar to that of ferritin, the main Fe store within the cell. The spectra obtained after CoCl 2 or NiCl 2 treatment, which could mimic a hypoxic state of cells, did not differ noticeably from that of the ferritin standard. After 5-fluorouracil administration, which could also induce an oxidative-stress in cells, the absorption edge position was shifted toward higher energies representing a higher oxidation state of Fe. Intense treatment with antimycin A, which inhibits electron transfer in the respiratory chain, resulted in minor changes in the spectrum, resembling rather the N-donor Fe-α,α'-dipyridyl complex at the oxidation energy of Fe(III), than ferritin. The incorporation of Co and Ni in the cells was followed by SR-TXRF measurements.

  14. Investigation of Ni@CoO core-shell nanoparticle films synthesized by sequential layer deposition

    NASA Astrophysics Data System (ADS)

    Spadaro, M. C.; Luches, P.; Benedetti, F.; Valeri, S.; Turchini, S.; Bertoni, G.; Ferretti, A. M.; Capetti, E.; Ponti, A.; D'Addato, S.

    2017-02-01

    Films of Ni@CoO core-shell nanoparticles (NP Ni core size d ≈ 11 nm) have been grown on Si/SiOx and lacey carbon supports, by a sequential layer deposition method: a first layer of CoO was evaporated on the substrate, followed by the deposition of a layer of pre-formed, mass-selected Ni NPs, and finally an overlayer of CoO was added. The Ni NPs were formed by a magnetron gas aggregation source, and mass selected with a quadrupole mass filter. The morphology of the films was investigated with Scanning Electron Microscopy and Scanning Transmission Electron Microscopy. The Ni NP cores have a shape compatible with McKay icosahedron, caused by multitwinning occurring during their growth in the source, and the Ni NP layer shows the typical random paving growth mode. After the deposition of the CoO overlayer, CoO islands are observed, gradually extending and tending to merge with each other, with the formation of shells that enclose the Ni NP cores. In situ X-ray Photoelectron Spectroscopy showed that a few Ni atomic layers localized at the core-shell interface are oxidized, hinting at the possibility of creating an intermediate NiO shell between Ni and CoO, depending on the deposition conditions. Finally, X-ray Magnetic Circular Dichroism at the Ni L2,3 absorption edge showed the presence of magnetization at room temperature even at remanence, revealing the possibility of magnetic stabilization of the NP film.

  15. Losing your edge: climate change and the conservation value of range-edge populations.

    PubMed

    Rehm, Evan M; Olivas, Paulo; Stroud, James; Feeley, Kenneth J

    2015-10-01

    Populations occurring at species' range edges can be locally adapted to unique environmental conditions. From a species' perspective, range-edge environments generally have higher severity and frequency of extreme climatic events relative to the range core. Under future climates, extreme climatic events are predicted to become increasingly important in defining species' distributions. Therefore, range-edge genotypes that are better adapted to extreme climates relative to core populations may be essential to species' persistence during periods of rapid climate change. We use relatively simple conceptual models to highlight the importance of locally adapted range-edge populations (leading and trailing edges) for determining the ability of species to persist under future climates. Using trees as an example, we show how locally adapted populations at species' range edges may expand under future climate change and become more common relative to range-core populations. We also highlight how large-scale habitat destruction occurring in some geographic areas where many species range edge converge, such as biome boundaries and ecotones (e.g., the arc of deforestation along the rainforest-cerrado ecotone in the southern Amazonia), can have major implications for global biodiversity. As climate changes, range-edge populations will play key roles in helping species to maintain or expand their geographic distributions. The loss of these locally adapted range-edge populations through anthropogenic disturbance is therefore hypothesized to reduce the ability of species to persist in the face of rapid future climate change.

  16. Three Dimensional Mapping of Nicle Oxidation States Using Full Field Xray Absorption Near Edge Structure Nanotomography

    SciTech Connect

    Nelson, G.J.; Chu, Y.; Harris, W.M.; Izzo, J.R.; Grew, K.N., Chiu, W.K.S.; Yi, J.; Andrews, J.C.; Liu, Y., Pierro, P.

    2011-04-28

    The reduction-oxidation cycling of the nickel-based oxides in composite solid oxide fuel cells and battery electrodes is directly related to cell performance. A greater understanding of nickel redox mechanisms at the microstructural level can be achieved in part using transmission x-ray microscopy (TXM) to explore material oxidation states. X-ray nanotomography combined with x-ray absorption near edge structure (XANES) spectroscopy has been applied to study samples containing distinct regions of nickel and nickel oxide (NiO) compositions. Digitally processed images obtained using TXM demonstrate the three-dimensional chemical mapping and microstructural distribution capabilities of full-field XANES nanotomography.

  17. Tunable magnetic states on the zigzag edges of hydrogenated and halogenated group-IV nanoribbons

    NASA Astrophysics Data System (ADS)

    Wang, Tzu-Cheng; Hsu, Chia-Hsiu; Huang, Zhi-Quan; Chuang, Feng-Chuan; Su, Wan-Sheng; Guo, Guang-Yu

    2016-12-01

    The magnetic and electronic properties of hydrogenated and halogenated group-IV zigzag nanoribbons (ZNRs) are investigated by first-principles density functional calculations. Fascinatingly, we find that all the ZNRs have magnetic edges with a rich variety of electronic and magnetic properties tunable by selecting the parent and passivating elements as well as controlling the magnetization direction and external strain. In particular, the electric property of the edge band structure can be tuned from the conducting to insulating with a band gap up to 0.7 eV. The last controllability would allow us to develop magnetic on-off nano-switches. Furthermore, ZNRs such as SiI, Ge, GeI and SnH, have fully spin-polarized metallic edge states and thus are promising materials for spintronics. The calculated magnetocrystalline anisotropy energy can be as large as ~9 meV/edge-site, being 2×103 time greater than that of bulk Ni and Fe (~5 μeV/atom), and thus has great potential for high density magneto-electric data-storage devices. Finally, the calculated exchange coupling strength and thus magnetic transition temperature increases as the applied strain goes from ‑5% to 5%. Our findings thus show that these ZNRs would have exciting applications in next-generation electronic and spintronic nano-devices.

  18. Tunable magnetic states on the zigzag edges of hydrogenated and halogenated group-IV nanoribbons

    PubMed Central

    Wang, Tzu-Cheng; Hsu, Chia-Hsiu; Huang, Zhi-Quan; Chuang, Feng-Chuan; Su, Wan-Sheng; Guo, Guang-Yu

    2016-01-01

    The magnetic and electronic properties of hydrogenated and halogenated group-IV zigzag nanoribbons (ZNRs) are investigated by first-principles density functional calculations. Fascinatingly, we find that all the ZNRs have magnetic edges with a rich variety of electronic and magnetic properties tunable by selecting the parent and passivating elements as well as controlling the magnetization direction and external strain. In particular, the electric property of the edge band structure can be tuned from the conducting to insulating with a band gap up to 0.7 eV. The last controllability would allow us to develop magnetic on-off nano-switches. Furthermore, ZNRs such as SiI, Ge, GeI and SnH, have fully spin-polarized metallic edge states and thus are promising materials for spintronics. The calculated magnetocrystalline anisotropy energy can be as large as ~9 meV/edge-site, being 2×103 time greater than that of bulk Ni and Fe (~5 μeV/atom), and thus has great potential for high density magneto-electric data-storage devices. Finally, the calculated exchange coupling strength and thus magnetic transition temperature increases as the applied strain goes from −5% to 5%. Our findings thus show that these ZNRs would have exciting applications in next-generation electronic and spintronic nano-devices. PMID:27982055

  19. Surface energy driven crystallization of amorphous Ni{sub 69}Cr{sub 14}P{sub 17} alloy

    SciTech Connect

    Schumacher, G.; Wanderka, N.; Wahi, R.P.

    1994-11-01

    Amorphous Ni{sub 69}Cr{sub l4}P{sub l7} specimens thinned for transmission electron microscopy have been studied in situ during thermal treatment. In the thinnest regions of the specimens (thickness d < 50 nm), a metastable hexagonal (Ni,Cr){sub 3}P phase nucleates at the perforation edge with the c-axis perpendicular to the specimen surface. The crystal width of this phase grows linearly with time. Above 530{degrees}C the hexagonal phase transforms into a stable b.c.t. (Ni,Cr){sub 3}P phase. It is concluded that the surface and grain boundary energies dominate nucleation and growth.

  20. Tensile Creep of Polycrystalline Near-Stoichiometric NiAl

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2002-01-01

    Long term tensile creep studies were conducted on binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms. Inverse and normal primary creep curves were observed depending on stress and temperature. It was concluded that the creep of NiAl is limited by dislocation mobility. The stress exponent for creep, n, increased from 5.5 at 1200 K to 13.9 at 700 K. The true activation energy for creep, Qc, was constant and equal to about 400 kJ per mole between 20 and 50 MPa but decreased to a constant value of 250 kJ per mole between 50 and 110 MPa. The activation energy was observed to be stress dependent above 110 MPa. The tensile creep results reported in this investigation were compared with compression creep data reported in the literature. A detailed discussion of the probable dislocation creep mechanisms governing compressive and tensile creep of NiAl is presented. It is concluded that the non-conservative motion of jogs on screw dislocations influenced the nature of the primary creep curves, where the climb of these jogs involves either the next nearest neighbor or the six-jump cycle vacancy diffusion mechanism. The probable nature of the atom vacancy exchange that occur within the core of an edge dislocation undergoing climb in NiAl are schematically examined.

  1. Edge location to subpixel values in digital imagery.

    PubMed

    Tabatabai, A J; Mitchell, O R

    1984-02-01

    A new method for locating edges in digital data to subpixel values and which is invariant to additive and multiplicative changes in the data is presented. For one-dimensional edge patterns an ideal edge is fit to the data by matching moments. It is shown that the edge location is related to the so-called ``Christoffel numbers.'' Also presented is the study of the effect of additive noise on edge location. The method is extended to include two-dimensional edge patterns where a line equation is derived to locate an edge. This in turn is compared with the standard Hueckel edge operator. An application of the new edge operator as an edge detector is also provided and is compared with Sobel and Hueckel edge detectors in presence and absence of noise.

  2. Partnership for Edge Physics Simulation (EPSI)

    SciTech Connect

    Schroder, Peter

    2015-02-11

    We propose to develop advanced simulation codes, based upon an extreme parallelism, first principles kinetic approach, to address the challenges associated with the edge region of magnetically confined plasmas. This work is relevant to both existing magnetic fusion facilities and essential for next-generation burning plasma experiments, such as ITER where success is critically dependent upon H-mode operation achieving an edge pedestal of sufficient height for good core plasma performance without producing deleterious large scale edge localized instabilities. The plasma edge presents a well-known set of multi-physics, multi-scale problems involving complex 3D magnetic geometry. Perhaps the greatest computational challenge is the lack of scale separation – temporal scales for drift waves, Alfven waves, ELM dynamics for example have strong overlap. Similar overlap occurs on the spatial scales for the ion poloidal gyro-radius, drift wave and pedestal width. The traditional approach of separating fusion problems into weakly interacting spatial or temporal domains clearly breaks down in the edge. A full kinetic model (full-f model) must be solved to understand and predict the edge physics including non-equilibrium thermodynamic issues arising from the magnetic topology (the open field lines producing a spatially sensitive velocity hole), plasma wall interactions, neutral and atomic physics. The plan here is to model these phenomena within a comprehensive first principles set of equations without the need for the insurmountable multiple-codes coupling issues by building on the XGC1 code developed under the SciDAC Proto-FSP Center for Plasma Edge Simulation (CPES). This proposal includes the critical participants in the XGC1 development. We propose enhancing the capability of XGC1 by including all the important turbulence physics contained in kinetic ion and electron electromagnetic dynamics, by extending the PIC technology to incorporate several positive features found

  3. Flap Edge Aeroacoustic Measurements and Predictions

    NASA Technical Reports Server (NTRS)

    Brooks, Thomas F.; Humphreys, William M., Jr.

    2000-01-01

    An aeroacoustic model test has been conducted to investigate the mechanisms of sound generation on high-lift wing configurations. This paper presents an analysis of flap side-edge noise, which is often the most dominant source. A model of a main element wing section with a half-span flap was tested at low speeds of up to a Mach number of 0.17, corresponding to a wing chord Reynolds number of approximately 1.7 million. Results are presented for flat (or blunt), flanged, and round flap-edge geometries, with and without boundary-layer tripping, deployed at both moderate and high flap angles. The acoustic database is obtained from a Small Aperture Directional Array (SADA) of microphones, which was constructed to electronically steer to different regions of the model and to obtain farfield noise spectra and directivity from these regions. The basic flap-edge aerodynamics is established by static surface pressure data, as well as by Computational Fluid Dynamics (CFD) calculations and simplified edge flow analyses. Distributions of unsteady pressure sensors over the flap allow the noise source regions to be defined and quantified via cross-spectral diagnostics using the SADA output. It is found that shear layer instability and related pressure scatter is the primary noise mechanism. For the flat edge flap, two noise prediction methods based on unsteady-surface-pressure measurements are evaluated and compared to measured noise. One is a new causality spectral approach developed here. The other is a new application of an edge-noise scatter prediction method. The good comparisons for both approaches suggest that much of the physics is captured by the prediction models. Areas of disagreement appear to reveal when the assumed edge noise mechanism does not fully define, the noise production. For the different edge conditions, extensive spectra and directivity are presented. Significantly, for each edge configuration, the spectra for different flow speeds, flap angles, and

  4. Fe, Ni and Zn speciation, in airborne particulate matter

    NASA Astrophysics Data System (ADS)

    Thiodjio Sendja, Bridinette; Aquilanti, Giuliana; Vassura, Ivano; Giorgetti, Marco

    2016-05-01

    The study of elemental speciation in atmospheric particulate matter is important for the assessment of the source of the particle as well for the evaluation of its toxicity. XANES data at Fe, Ni, and Zn K-edges are recorded on a sample of urban dust (from the Rimini area of Emilia Romagna region, Italy) deposited on a filter and on the NIST standard reference material 1648. Using linear combination fitting we give an indication of the chemical species of the three metals present in the samples.

  5. Dissecting new physics models through kinematic edges

    NASA Astrophysics Data System (ADS)

    Iyer, Abhishek M.; Maitra, Ushoshi

    2017-02-01

    Kinematic edges in the invariant mass distributions of different final state particles are typically a signal of new physics. In this work we propose a scenario wherein these edges could be utilized in discriminating between different classes of models. To this effect, we consider the resonant production of a heavy Higgs like resonance (H1) as a case study. Such states are a characteristic feature of many new physics scenarios beyond the standard model (SM). In the event of a discovery, it is essential to identify the true nature of the underlying theory. In this work we propose a channel, H1→t2t , where t2 is a vectorlike gauge singlet top-partner that decays into W b , Z t , h t . Invariant mass distributions constructed out of these final states are characterized by the presence of kinematic edges, which are unique to the topology under consideration. Further, since all the final state particles are SM states, the position in the edges of these invariant mass distributions can be used to exclusively determine the masses of the resonances. Observation of these features are meant to serve as a trigger, thereby mandating a more detailed analysis in a particular direction of parameter space. The absence of these edge like features, in the specific invariant mass distributions considered here, in minimal versions of supersymmetric models (MSSM) also serves as a harbinger of such non-MSSM-like scenarios.

  6. Trailing edge modifications for flatback airfoils.

    SciTech Connect

    Kahn, Daniel L.; van Dam, C.P.; Berg, Dale E.

    2008-03-01

    The adoption of blunt trailing edge airfoils (also called flatback airfoils) for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of thick airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. These airfoils do have the disadvantage of generating high levels of drag as a result of the low-pressure steady or periodic flow in the near-wake of the blunt trailing edge. Although for rotors, the drag penalty appears secondary to the lift enhancement produced by the blunt trailing edge, high drag levels are of concern in terms of the negative effect on the torque and power generated by the rotor. Hence, devices are sought that mitigate the drag of these airfoils. This report summarizes the literature on bluff body vortex shedding and bluff body drag reduction devices and proposes four devices for further study in the wind tunnel.

  7. Leading-edge effects in bypass transition

    NASA Astrophysics Data System (ADS)

    Nagarajan, S.; Lele, S. K.; Ferziger, J. H.

    The effect of a blunt leading edge on bypass transition is studied by numerical simulation. A mixed direct and large-eddy simulation of a flat plate with a super-ellipse leading edge is carried out at various conditions. Onset and completion of transition is seen to move upstream with increasing bluntness. For sharper leading edges, at lower levels of turbulence, transition usually occurs through instabilities on low-speed streaks as observed by Jacobs & Durbin (2001) and Brandt et al. (2004) whereas increasing either the turbulence intensity or the leading-edge bluntness brings into play another mechanism. Free-stream vortices are amplified at the leading edge because of stretching. In the case of particularly strong vortices, this interaction induces a localized streamwise vortical disturbance in the boundary layer which then grows as it convects downstream and eventually breaks down to form a turbulent spot. These disturbances, which are localized and hence wavepacket-like, move at speeds in the range 0.55 U_{infty} 0.65 U_{infty} and occur in the lower portion of the boundary layer. Simulations conducted with isolated vortices confirm such a response of the boundary layer.

  8. Numerical simulation of the edge tone phenomenon

    NASA Technical Reports Server (NTRS)

    Dougherty, N. S.; Liu, B. L.; Ofarrell, J. M.

    1994-01-01

    Time accurate Navier-Stokes computations were performed to study a class 2 (acoustic) whistle, the edge tone, and to gain knowledge of the vortex-acoustic coupling mechanisms driving production of these tones. Results were obtained by solving the full Navier-Stokes equations for laminar compressible air flow of a two dimensional jet issuing from a slit interacting with a wedge. Cases considered were determined by varying the distance from the slit to the wedge. Flow speed was kept constant at 1,750 cm/s as was the slit thickness of 0.1 cm, corresponding to conditions in the experiments of Brown. The analytical computations revealed edge tones to be present in four harmonic stages of jet flow instability over the wedge as the jet length was varied from 0.3 to 1.6 cm. Excellent agreement was obtained in all four edge tone stage cases between the present computational results and the experimentally obtained frequencies and flow visualization results of Brown. Specific edge tone generation phenomena and further confirmation of certain theories and empirical formulas concerning these phenomena were brought to light in this analytical simulation of edge tones.

  9. El Niño physics and El Niño predictability.

    PubMed

    Clarke, Allan J

    2014-01-01

    Much of the year-to-year climate variability on the Earth is associated with El Niño and the Southern Oscillation (ENSO). This variability is generated primarily by a coupled ocean-atmosphere instability near the eastern edge of the western equatorial Pacific warm pool. Here, I discuss the physics of this variability, including its phase locking to the seasonal cycle. ENSO growth typically occurs from April/May to November, and by July the perturbation is usually strong enough that it persists to the beginning of the following year, when ENSO events usually end. Consequently, predicting ENSO is easy from July to February but is more challenging across the April/May transition to the next event. I discuss precursors of this transition and recent results from dynamical and statistical models used for ENSO forecasting.

  10. X-ray absorption fine structure (XAFS) analyses of Ni species trapped in graphene sheet of carbon nanofibers

    SciTech Connect

    Ushiro, Mayuko; Uno, Kanae; Fujikawa, Takashi; Sato, Yoshinori; Tohji, Kazuyuki; Watari, Fumio; Chun, W.-J.; Koike, Yuichiro; Asakura, Kiyotaka

    2006-04-01

    Metal impurities in the carbon nanotubes and carbon nanofibers play an important role in understanding their physical and chemical properties. We apply the Ni K-edge x-ray absorption fine structure analyses to the local electronic and geometric structures around embedded Ni impurities used as catalysts in a carbon nanofiber in combination with multiple scattering analyses. We find almost Ni catalysts as metal particles are removed by the purification treatment. Even after the purification, residual 100 ppm Ni species are still absorbed; most of them are in monomer structure with Ni-C bond length 1.83 A, and each of them is substituted for a carbon atom in a graphene sheet.

  11. Water-Gas Shift and CO Methanation Reactions over Ni-CeO2(111) Catalysts

    SciTech Connect

    Senanayake, Sanjaya D; Evans, Jaime; Agnoli, Stefano; Barrio, Laura; Chen, Tsung-Liang; Hrbek, Jan; Radriguez, Jose

    2011-01-01

    X-ray and ultraviolet photoelectron spectroscopies were used to study the interaction of Ni atoms with CeO2(111) surfaces. Upon adsorption on CeO2(111) at 300 K, nickel remains in a metallic state. Heating to elevated temperatures (500 800 K) leads to partial reduction of the ceria substrate with the formation of Ni2? species that exists as NiO and/or Ce1-xNixO2-y. Interactions of nickel with the oxide substrate significantly reduce the density of occupied Ni 3d states near the Fermi level. The results of core-level photoemission and near-edge X-ray absorption fine structure point to weakly bound CO species on CeO2(111) which are clearly distinguishable from the formation of chemisorbed carbonates. In the presence of Ni, a stronger interaction is observed with chemisorption of CO on the admetal. When the Ni is in contact with Ce?3 cations, CO dissociates on the surface at 300 K forming NiCx compounds that may be involved in the formation of CH4 at higher temperatures. At medium and large Ni coverages ([0.3 ML), the Ni/CeO2(111) surfaces are able to catalyze the production of methane from CO and H2, with an activity slightly higher than that of Ni(100) or Ni(111). On the other hand, at small coverages of Ni (\\0.3 ML), the Ni/CeO2(111) surfaces exhibit a very low activity for CO methanation but are very good catalysts for the water gas shift reaction.

  12. Imaging Chemical Aggregation of Ni/NiO Particles from Reduced NiO-YSZ

    SciTech Connect

    Saraf, Laxmikant V.

    2011-07-20

    Energy dispersive X-ray spectroscopy (EDS) mapping of nickel oxide yttria-stabilized zirconia (NiO-YSZ) was carried out after various hydrogen reducing and methane steam reforming conditions. Nickel aggregation was visualized after methane steam reforming by correlating Ni K{sub {alpha}} map with scanning transmission electron microscopy (STEM) images. From the reduced O K{sub {alpha}} intensities in the Ni K{sub {alpha}} dominated regions after methane steam reforming, NiO reduction in to Ni can be interpreted. From correlation between Zr K{sub {alpha}} and O K{sub {alpha}} maps, high stability of YSZ was also realized. Examples of NiO-YSZ overlapped particles are considered to discuss chemical imaging of a single particle.

  13. A synthetic genetic edge detection program.

    PubMed

    Tabor, Jeffrey J; Salis, Howard M; Simpson, Zachary Booth; Chevalier, Aaron A; Levskaya, Anselm; Marcotte, Edward M; Voigt, Christopher A; Ellington, Andrew D

    2009-06-26

    Edge detection is a signal processing algorithm common in artificial intelligence and image recognition programs. We have constructed a genetically encoded edge detection algorithm that programs an isogenic community of E. coli to sense an image of light, communicate to identify the light-dark edges, and visually present the result of the computation. The algorithm is implemented using multiple genetic circuits. An engineered light sensor enables cells to distinguish between light and dark regions. In the dark, cells produce a diffusible chemical signal that diffuses into light regions. Genetic logic gates are used so that only cells that sense light and the diffusible signal produce a positive output. A mathematical model constructed from first principles and parameterized with experimental measurements of the component circuits predicts the performance of the complete program. Quantitatively accurate models will facilitate the engineering of more complex biological behaviors and inform bottom-up studies of natural genetic regulatory networks.

  14. Acoustic metamaterial for subwavelength edge detection.

    PubMed

    Molerón, Miguel; Daraio, Chiara

    2015-08-25

    Metamaterials have demonstrated the possibility to produce super-resolved images by restoring propagative and evanescent waves. However, for efficient information transfer, for example, in compressed sensing, it is often desirable to visualize only the fast spatial variations of the wave field (carried by evanescent waves), as the one created by edges or small details. Image processing edge detection algorithms perform such operation, but they add time and complexity to the imaging process. Here we present an acoustic metamaterial that transmits only components of the acoustic field that are approximately equal to or smaller than the operating wavelength. The metamaterial converts evanescent waves into propagative waves exciting trapped resonances, and it uses periodicity to attenuate the propagative components. This approach achieves resolutions ∼5 times smaller than the operating wavelength and makes it possible to visualize independently edges aligned along different directions.

  15. Grain edge detection of diamond grinding wheel

    NASA Astrophysics Data System (ADS)

    Zhou, Lijun; Cui, Changcai; Huang, Chunqi; Huang, Hui; Ye, Ruifang

    2013-01-01

    The topograpgy characterization of grinding wheel grain is indispensable for precision grinding, it depends on accurate edge detecting and recognition of abrasive grains from wheel bond to a large extent. Due to different reflective characteristics arising among different materials, difference between maximum and minimum intensity (Δ ) of diamond is larger than that of bond. This paper uses a new method for grain edge detection of resin-bonded diamond grinding wheel that combines the improved Canny operator in Method of Maximum Classes Square Error (called as OTSU) with ΔI obtained by the white light interferometry (WLI). The experimental results show that the method based on improved Canny operator can effectively detect the edge of diamond grain.

  16. Edge effects in composites by moire interferometry

    NASA Technical Reports Server (NTRS)

    Czarnek, R.; Post, D.; Herakovich, C.

    1983-01-01

    The very high sensitivity of moire interferometry has permitted the present edge effect experiments to be conducted at a low average stress and strain level, assuring linear and elastic behavior in the composite material samples tested. Sensitivity corresponding to 2450 line/mm moire was achieved with a 0.408 micron/fringe. Simultaneous observations of the specimen face and edge displacement fields showed good fringe definition despite the 1-mm thickness of the specimens and the high gradients, and it is noted that the use of a carrier pattern and optical filtering was effective in even these conditions. Edge effects and dramatic displacement gradients were confirmed in angle-ply composite laminates.

  17. Preparation of edge states by shaking boundaries

    NASA Astrophysics Data System (ADS)

    Shi, Z. C.; Hou, S. C.; Wang, L. C.; Yi, X. X.

    2016-10-01

    Preparing topological states of quantum matter, such as edge states, is one of the most important directions in condensed matter physics. In this work, we present a proposal to prepare edge states in Aubry-André-Harper (AAH) model with open boundaries, which takes advantage of Lyapunov control to design operations. We show that edge states can be obtained with almost arbitrary initial states. A numerical optimalization for the control is performed and the dependence of control process on the system size is discussed. The merit of this proposal is that the shaking exerts only on the boundaries of the model. As a by-product, a topological entangled state is achieved by elaborately designing the shaking scheme.

  18. Black phosphorus edges: a polarized Raman study

    NASA Astrophysics Data System (ADS)

    Ribeiro, H.; Villegas, C.; Bahamon, D.; Castro Neto, A.; de Souza, E.; Rocha, A.; Pimenta, M.; de Matos, C.

    Black phosphorus (BP) has been recently exfoliated down to few-layer thicknesses revealing numerous interesting features such as a tunable direct bandgap. Ever since, demonstrations of BP electronic devices have bloomed, as well as studies of the electric, optical, mechanical and thermal properties of its bulk and few-layer forms. However, the edges of BP crystals have, so far, been poorly characterized, even though the terminations of layered crystals are known to possess a range of interesting properties. In this work, the edges of exfoliated BP flakes are characterized by polarized confocal Raman spectroscopy. We will present experimental Raman spectra at zigzag and armchair edges, as well as density functional theory calculations that explain the peculiarities of the experimental data. Fapesp, INCT/Nanocarbono, Fapemig, CNPq, MackPesquisa, Grid-Unesp, CENAPAD-SP, and NRF.

  19. Diagnosing Topological Edge States via Entanglement Monogamy

    NASA Astrophysics Data System (ADS)

    Meichanetzidis, K.; Eisert, J.; Cirio, M.; Lahtinen, V.; Pachos, J. K.

    2016-04-01

    Topological phases of matter possess intricate correlation patterns typically probed by entanglement entropies or entanglement spectra. In this Letter, we propose an alternative approach to assessing topologically induced edge states in free and interacting fermionic systems. We do so by focussing on the fermionic covariance matrix. This matrix is often tractable either analytically or numerically, and it precisely captures the relevant correlations of the system. By invoking the concept of monogamy of entanglement, we show that highly entangled states supported across a system bipartition are largely disentangled from the rest of the system, thus, usually appearing as gapless edge states. We then define an entanglement qualifier that identifies the presence of topological edge states based purely on correlations present in the ground states. We demonstrate the versatility of this qualifier by applying it to various free and interacting fermionic topological systems.

  20. Contrast edge colors under different natural illuminations.

    PubMed

    Nieves, Juan Luis; Nascimento, Sérgio M C; Romero, Javier

    2012-02-01

    Essential to sensory processing in the human visual system is natural illumination, which can vary considerably not only across space but also along the day depending on the atmospheric conditions and the sun's position in the sky. In this work, edges derived from the three postreceptoral Luminance, Red-Green, and Blue-Yellow signals were computed from hyperspectral images of natural scenes rendered with daylights of Correlated Color Temperatures (CCTs) from 2735 to 25,889 K; for low CCT, the same analysis was performed using Planckian illuminants up to 800 K. It was found that average luminance and chromatic edge contrasts were maximal for low correlated color temperatures and almost constants above 10,000 K. The magnitude of these contrast changes was, however, only about 2% across the tested daylights. Results suggest that the postreceptoral opponent and nonopponent color vision mechanisms produce almost constant responses for color edge detection under natural illumination.

  1. Acoustic metamaterial for subwavelength edge detection

    PubMed Central

    Molerón, Miguel; Daraio, Chiara

    2015-01-01

    Metamaterials have demonstrated the possibility to produce super-resolved images by restoring propagative and evanescent waves. However, for efficient information transfer, for example, in compressed sensing, it is often desirable to visualize only the fast spatial variations of the wave field (carried by evanescent waves), as the one created by edges or small details. Image processing edge detection algorithms perform such operation, but they add time and complexity to the imaging process. Here we present an acoustic metamaterial that transmits only components of the acoustic field that are approximately equal to or smaller than the operating wavelength. The metamaterial converts evanescent waves into propagative waves exciting trapped resonances, and it uses periodicity to attenuate the propagative components. This approach achieves resolutions ∼5 times smaller than the operating wavelength and makes it possible to visualize independently edges aligned along different directions. PMID:26304739

  2. Controllable edge feature sharpening for dental applications.

    PubMed

    Fan, Ran; Jin, Xiaogang

    2014-01-01

    This paper presents a new approach to sharpen blurred edge features in scanned tooth preparation surfaces generated by structured-light scanners. It aims to efficiently enhance the edge features so that the embedded feature lines can be easily identified in dental CAD systems, and to avoid unnatural oversharpening geometry. We first separate the feature regions using graph-cut segmentation, which does not require a user-defined threshold. Then, we filter the face normal vectors to propagate the geometry from the smooth region to the feature region. In order to control the degree of the sharpness, we propose a feature distance measure which is based on normal tensor voting. Finally, the vertex positions are updated according to the modified face normal vectors. We have applied the approach to scanned tooth preparation models. The results show that the blurred edge features are enhanced without unnatural oversharpening geometry.

  3. A Synthetic Genetic Edge Detection Program

    PubMed Central

    Tabor, Jeffrey J.; Salis, Howard; Simpson, Zachary B.; Chevalier, Aaron A.; Levskaya, Anselm; Marcotte, Edward M.; Voigt, Christopher A.; Ellington, Andrew D.

    2009-01-01

    Summary Edge detection is a signal processing algorithm common in artificial intelligence and image recognition programs. We have constructed a genetically encoded edge detection algorithm that programs an isogenic community of E.coli to sense an image of light, communicate to identify the light-dark edges, and visually present the result of the computation. The algorithm is implemented using multiple genetic circuits. An engineered light sensor enables cells to distinguish between light and dark regions. In the dark, cells produce a diffusible chemical signal that diffuses into light regions. Genetic logic gates are used so that only cells that sense light and the diffusible signal produce a positive output. A mathematical model constructed from first principles and parameterized with experimental measurements of the component circuits predicts the performance of the complete program. Quantitatively accurate models will facilitate the engineering of more complex biological behaviors and inform bottom-up studies of natural genetic regulatory networks. PMID:19563759

  4. SALT segmented primary mirror: inductive edge sensors

    NASA Astrophysics Data System (ADS)

    Gajjar, Hitesh; Menzies, John; Buckley, David; Neel, Christian; Parbaud, Philippe; Royet, Stéphane

    2014-07-01

    The development of an inductive edge sensor is in process for the control of the Southern African Large Telescope's (SALT)1 segmented mirror primary. The original capacitive edge sensing system was not capable of maintaining the figure of the primary mirror due to excessive noise and a severe sensitivity to humidity despite exhaustive attempts at characterisation1. The prototype of the inductive edge sensor has progressed to a mature industrialised version that is in the process of being installed and commissioned on SALT. The performance of the sensor in response to temperature and RH is very good with a maximum error of 10nm typical after temperature compensation. The noise and control characteristics of the array have been simulated in order to establish the maximum cumulative error and error rate tolerable for the SALT specific case. It has been established through simulation that over the expected 5 day alignment cycle, a maximum cumulative error of 30nm can be tolerated.

  5. Floquet edge states in germanene nanoribbons

    PubMed Central

    Tahir, M.; Zhang, Q. Y.; Schwingenschlögl, U.

    2016-01-01

    We theoretically demonstrate versatile electronic properties of germanene monolayers under circularly, linearly, and elliptically polarized light. We show for the high frequency regime that the edge states can be controlled by tuning the amplitude of the light and by applying a static electric field. For circularly polarized light the band gap in one valley is reduced and in the other enhanced, enabling single valley edge states. For linearly polarized light spin-split states are found for both valleys, being connected by time reversal symmetry. The effects of elliptically polarized light are similar to those of circularly polarized light. The transport properties of zigzag nanoribbons in the presence of disorder confirm a nontrivial nature of the edge states under circularly and elliptically polarized light. PMID:27550632

  6. Predictability of the Arctic sea ice edge

    NASA Astrophysics Data System (ADS)

    Goessling, H. F.; Tietsche, S.; Day, J. J.; Hawkins, E.; Jung, T.

    2016-02-01

    Skillful sea ice forecasts from days to years ahead are becoming increasingly important for the operation and planning of human activities in the Arctic. Here we analyze the potential predictability of the Arctic sea ice edge in six climate models. We introduce the integrated ice-edge error (IIEE), a user-relevant verification metric defined as the area where the forecast and the "truth" disagree on the ice concentration being above or below 15%. The IIEE lends itself to decomposition into an absolute extent error, corresponding to the common sea ice extent error, and a misplacement error. We find that the often-neglected misplacement error makes up more than half of the climatological IIEE. In idealized forecast ensembles initialized on 1 July, the IIEE grows faster than the absolute extent error. This means that the Arctic sea ice edge is less predictable than sea ice extent, particularly in September, with implications for the potential skill of end-user relevant forecasts.

  7. Edge Detection in Landing Budgerigars (Melopsittacus undulatus)

    PubMed Central

    Bhagavatula, Partha; Claudianos, Charles; Ibbotson, Michael; Srinivasan, Mandyam

    2009-01-01

    Background While considerable scientific effort has been devoted to studying how birds navigate over long distances, relatively little is known about how targets are detected, obstacles are avoided and smooth landings are orchestrated. Here we examine how visual features in the environment, such as contrasting edges, determine where a bird will land. Methodology/Principal Findings Landing in budgerigars (Melopsittacus undulatus) was investigated by training them to fly from a perch to a feeder, and video-filming their landings. The feeder was placed on a grey disc that produced a contrasting edge against a uniformly blue background. We found that the birds tended to land primarily at the edge of the disc and walk to the feeder, even though the feeder was in the middle of the disc. This suggests that the birds were using the visual contrast at the boundary of the disc to target their landings. When the grey level of the disc was varied systematically, whilst keeping the blue background constant, there was one intermediate grey level at which the budgerigar's preference for the disc boundary disappeared. The budgerigars then landed randomly all over the test surface. Even though this disc is (for humans) clearly distinguishable from the blue background, it offers very little contrast against the background, in the red and green regions of the spectrum. Conclusions We conclude that budgerigars use visual edges to target and guide landings. Calculations of photoreceptor excitation reveal that edge detection in landing budgerigars is performed by a color-blind luminance channel that sums the signals from the red and green photoreceptors, or, alternatively, receives input from the red double-cones. This finding has close parallels to vision in honeybees and primates, where edge detection and motion perception are also largely color-blind. PMID:19809500

  8. Preparation of Ni doped ZnO thin films by SILAR and their characterization

    NASA Astrophysics Data System (ADS)

    Mondal, S.; Mitra, P.

    2013-02-01

    Pure and nickel (Ni) doped zinc oxide (NZO) thin films were deposited on glass substrates from ammonium zincate bath using successive ion layer adsorption and reaction (SILAR). Characterization techniques such as XRD, TEM, SEM and EDX were utilized to investigate the effect of Ni doping on the microstructure of Ni:ZnO thin films. Structural characterization by X-ray diffraction reveals the polycrystalline nature of the films. Particle size shows slightly decreasing trend with increasing nickel impurification. The average particle size for pure ZnO is 22.75 nm and it reduces to 20.51 nm for 10 % Ni doped ZnO. Incorporation of Ni was confirmed from elemental analysis using EDX. The value of fundamental absorption edge is 3.23 eV for pure ZnO and it decreases to 3.19 eV for 10 % Ni:ZnO. The activation energy barrier value to electrical conduction process increases from 0.261 eV for pure ZnO to 0.293 eV for 10 % Ni doped ZnO.

  9. Interfaces in La2NiO4- La2CuO4 superlattices

    NASA Astrophysics Data System (ADS)

    Smadici, S.; Lee, J. C. T.; Wang, S.; Abbamonte, P.; Logvenov, G.; Gozar, A.; Bozovic, I.

    2009-03-01

    Ni substitution on Cu sites in underdoped La2-xSrxCuO4 quickly restores Neel order. This was attributed to strong interaction between the Ni and doped holes. An open question was whether the additional Ni empty orbital or the different spin on Ni sites was at the origin of this strong interaction. We have addressed this problem with resonant soft x-ray scattering on a La2NiO4- La2CuO4 heterostructure. La2NiO4 and La2CuO4 have close lattice structures and electronic configurations. However, the x-ray scattering contrast between superlattice layers is greatly enhanced at soft x-ray resonant energies. Based on our measurements at the O K, La M, Cu L and Ni L edges a model of the charge, orbital and spin structures in these superlattices will be presented with a special emphasis on the interface region. This work was supported by Grants. DE-FG02- 06ER46285, DE-AC02-98CH10886, MA-509-MACA, DE-FG02-07ER46453 and DE-FG02-07ER46471.

  10. 16 CFR 1211.12 - Requirements for edge sensors.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Requirements for edge sensors. 1211.12... Requirements for edge sensors. (a) Normal operation test. (1) When installed on a representative door edge, an edge sensor shall actuate upon the application of a 15 pounds (66.7 N) or less force in the...

  11. Wing Leading Edge Concepts for Noise Reduction

    NASA Technical Reports Server (NTRS)

    Shmilovich, Arvin; Yadlin, Yoram; Pitera, David M.

    2010-01-01

    This study focuses on the development of wing leading edge concepts for noise reduction during high-lift operations, without compromising landing stall speeds, stall characteristics or cruise performance. High-lift geometries, which can be obtained by conventional mechanical systems or morphing structures have been considered. A systematic aerodynamic analysis procedure was used to arrive at several promising configurations. The aerodynamic design of new wing leading edge shapes is obtained from a robust Computational Fluid Dynamics procedure. Acoustic benefits are qualitatively established through the evaluation of the computed flow fields.

  12. Mechanisms and methods to resolve edge effect.

    PubMed

    Kuchulakanti, Pramod; Lew, Robert; Waksman, Ron

    2003-06-01

    Vascular brachytherapy (VBT) has established itself as a viable modality to treat in-stent restenosis (ISR). The problems associated with VBT have been understood well and remedied. Late thrombosis has been overcome to a great extent by prolonged antiplatelet therapy. Edge effect is another important limitation of VBT and is due to inadequate radiation coverage of the edges following VBT. It may be overcome by confining injury to the lesion segment and extending the radiation sources by a few millimeters from the injured segment.

  13. Active-edge planar radiation sensors

    PubMed Central

    Kenney, C.J.; Segal, J.D.; Westbrook, E.; Parker, Sherwood; Hasi, J.; Da Via, C.; Watts, S.; Morse, J.

    2007-01-01

    Many systems in medicine, biology, high-energy physics, and astrophysics require large area radiation sensors. In most of these applications, minimizing the amount of dead area or dead material is crucial. We have developed a new type of silicon radiation sensor in which the device is active to within a few microns of the mechanical edge. Their perimeter is made by a plasma etcher rather than a diamond saw. Their edges can be defined and also passivated by growing, in an intermediate step, a field oxide on the side surfaces. In this paper, the basic architecture and results from a synchrotron beam test are presented. PMID:18185839

  14. Airplane wing leading edge variable camber flap

    NASA Technical Reports Server (NTRS)

    Cole, J. B.

    1980-01-01

    The invention and design of an aerodynamic high lift device which provided a solution to an aircraft performance problem are described. The performance problem of converting a high speed cruise airfoil into a low speed aerodynamic shape that would provide landing and take-off characteristics superior to those available with contemporary high lift devices are addressed. The need for an improved wing leading edge device that would complement the high lift performance of a triple slotted trailing edge flap is examined. The mechanical and structural aspects of the variable camber flap are discussed and the aerodynamic performance aspects only as they relate to the invention and design of the device are presented.

  15. Near Field Trailing Edge Tone Noise Computation

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.

    2002-01-01

    Blunt trailing edges in a flow often generate tone noise due to wall-jet shear layer and vortex shedding. In this paper, the space-time conservation element (CE/SE) method is employed to numerically study the near-field noise of blunt trailing edges. Two typical cases, namely, flow past a circular cylinder (aeolian noise problem) and flow past a flat plate of finite thickness are considered. The computed frequencies compare well with experimental data. For the aeolian noise problem, comparisons with the results of other numerical approaches are also presented.

  16. Edge detection techniques for iris recognition system

    NASA Astrophysics Data System (ADS)

    Tania, U. T.; Motakabber, S. M. A.; Ibrahimy, M. I.

    2013-12-01

    Nowadays security and authentication are the major parts of our daily life. Iris is one of the most reliable organ or part of human body which can be used for identification and authentication purpose. To develop an iris authentication algorithm for personal identification, this paper examines two edge detection techniques for iris recognition system. Between the Sobel and the Canny edge detection techniques, the experimental result shows that the Canny's technique has better ability to detect points in a digital image where image gray level changes even at slow rate.

  17. Edge and Surface Plasmons in Graphene Nanoribbons.

    PubMed

    Fei, Z; Goldflam, M D; Wu, J-S; Dai, S; Wagner, M; McLeod, A S; Liu, M K; Post, K W; Zhu, S; Janssen, G C A M; Fogler, M M; Basov, D N

    2015-12-09

    We report on nano-infrared (IR) imaging studies of confined plasmon modes inside patterned graphene nanoribbons (GNRs) fabricated with high-quality chemical-vapor-deposited (CVD) graphene on Al2O3 substrates. The confined geometry of these ribbons leads to distinct mode patterns and strong field enhancement, both of which evolve systematically with the ribbon width. In addition, spectroscopic nanoimaging in the mid-infrared range 850-1450 cm(-1) allowed us to evaluate the effect of the substrate phonons on the plasmon damping. Furthermore, we observed edge plasmons: peculiar one-dimensional modes propagating strictly along the edges of our patterned graphene nanostructures.

  18. Edge and Surface Plasmons in Graphene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Fei, Z.; Goldflam, M. D.; Wu, J.-S.; Dai, S.; Wagner, M.; McLeod, A. S.; Liu, M. K.; Post, K. W.; Zhu, S.; Janssen, G. C. A. M.; Fogler, M. M.; Basov, D. N.

    2015-12-01

    We report on nano-infrared (IR) imaging studies of confined plasmon modes inside patterned graphene nanoribbons (GNRs) fabricated with high-quality chemical-vapor-deposited (CVD) graphene on Al2O3 substrates. The confined geometry of these ribbons leads to distinct mode patterns and strong field enhancement, both of which evolve systematically with the ribbon width. In addition, spectroscopic nano-imaging in mid-infrared 850-1450 cm-1 allowed us to evaluate the effect of the substrate phonons on the plasmon damping. Furthermore, we observed edge plasmons: peculiar one-dimensional modes propagating strictly along the edges of our patterned graphene nanostructures.

  19. Structural and magnetic properties of Ni78Fe22 thin films sandwiched between low-softening-point glasses and application in spin devices

    NASA Astrophysics Data System (ADS)

    Misawa, Takahiro; Mori, Sumito; Komine, Takashi; Fujioka, Masaya; Nishii, Junji; Kaiju, Hideo

    2016-12-01

    We investigate the structural and magnetic properties of Ni78Fe22 thin films sandwiched between low-softening-point (LSP) glasses, which can be used in spin quantum cross (SQC) devices utilizing stray magnetic fields generated from magnetic thin-film edges. We also calculate the stray magnetic field generated between the two edges of Ni78Fe22 thin-film electrodes in SQC devices and discuss the applicability to spin-filter devices. Using the established fabrication technique, we successfully demonstrate the formation of LSP-glass/Ni78Fe22/LSP-glass structures with smooth and clear interfaces. The coercivity of the Ni78Fe22 thin films is enhanced from 0.9 to 103 Oe by increasing the applied pressure from 0 to 1.0 MPa in the thermal pressing process. According to the random anisotropy model, the enhancement of the coercivity is attributed to the increase in the crystal grain size. The stray magnetic field is also uniformly generated from the Ni78Fe22 thin-film edge in the direction perpendicular to the cross section of the LSP-glass/Ni78Fe22/LSP-glass structures. Theoretical calculation reveals that a high stray field of approximately 5 kOe is generated when the distance between two edges of the Ni78Fe22 thin-film electrodes is less than 5 nm and the thickness of Ni78Fe22 is greater than 20 nm. These experimental and calculation results indicate that Ni78Fe22 thin films sandwiched between LSP glasses are useful as electrodes for SQC devices, serving as spin-filter devices.

  20. Real-time edge tracking using a tactile sensor

    NASA Technical Reports Server (NTRS)

    Berger, Alan D.; Volpe, Richard; Khosla, Pradeep K.

    1989-01-01

    Object recognition through the use of input from multiple sensors is an important aspect of an autonomous manipulation system. In tactile object recognition, it is necessary to determine the location and orientation of object edges and surfaces. A controller is proposed that utilizes a tactile sensor in the feedback loop of a manipulator to track along edges. In the control system, the data from the tactile sensor is first processed to find edges. The parameters of these edges are then used to generate a control signal to a hybrid controller. Theory is presented for tactile edge detection and an edge tracking controller. In addition, experimental verification of the edge tracking controller is presented.

  1. A new method of edge detection for object recognition

    USGS Publications Warehouse

    Maddox, Brian G.; Rhew, Benjamin

    2004-01-01

    Traditional edge detection systems function by returning every edge in an input image. This can result in a large amount of clutter and make certain vectorization algorithms less accurate. Accuracy problems can then have a large impact on automated object recognition systems that depend on edge information. A new method of directed edge detection can be used to limit the number of edges returned based on a particular feature. This results in a cleaner image that is easier for vectorization. Vectorized edges from this process could then feed an object recognition system where the edge data would also contain information as to what type of feature it bordered.

  2. Real time infrared video expansion based on edge

    NASA Astrophysics Data System (ADS)

    Wu, Yiliang; Hong, Jingxin; Chen, Huihuang

    2007-11-01

    This paper proposes an edge-directed interpolation algorithm for infrared images. At present, the resolution of infrared focus planar array (IFPA) is relatively low. Conventional linear interpolation schemes such as the pixels replacement, the bilinear interpolation and the bicubic interpolation result in blurred edges and zigzag pictures. The correlation of different edge direction was calculated at each pixel to be interpolated to detect the edge and the edge direction. There are 13 directions in two quadrants we have chosen. Most edge can be detected in this range. Pixels at the edge are interpolated along the edge. The non-edge pixels are bilinearly interpolated. Simulation results show that the proposed method effectively removed the zigzag and blur at the edge caused by conventional linear interpolation. And this method is easy to be carried out by hardware.

  3. Double side electroluminescence from p-NiO/n-ZnO nanowire heterojunctions

    SciTech Connect

    Wang, J.-Y.; Chen, Y.-T.; Chen, C.-T.; Chen, Y.-L.; Chen, Y.-F.; Lee, C.-Y.; Lin, C.-F.

    2009-09-28

    Double side light emission devices based on p-NiO/n-ZnO nanowire heterojunctions have been fabricated on indium tin oxide substrate by radio frequency magnetron sputtering combined with hydrothermal process. According to the energy band alignment, the detected broad visible and narrow ultraviolet electroluminescence arise from defect and band edge transitions in ZnO nanowires, respectively. The unique property of the double side emission is due to the nature of the large band gap of NiO film. It provides a good opportunity for the emission of a light emitting device with different colors on the top and back sides, simultaneously.

  4. Liquid-Crystal Light Valve Enhances Edges In Images

    NASA Technical Reports Server (NTRS)

    Chao, Tien-Hsin; Liu, Hua-Kuang

    1991-01-01

    Experiments show liquid-crystal light valve (LCLV) exhibits operating mode in which it enhances edges in images projected on it. Operates in edge-enhancing mode (or in combination of edge-enhancing and normal modes) by suitably adjusting bias voltage and frequency. Enhancement of edges one of most important preprocessing steps in optical pattern-recognition systems. Incorporated into image-processing system to enhance edges without introducing excessive optical noise.

  5. Nickel dispersion and enrichment at the bottom of the regolith: formation of pimelite target-like ores in rock block joints (Koniambo Ni deposit, New Caledonia)

    NASA Astrophysics Data System (ADS)

    Cathelineau, Michel; Quesnel, Benoît; Gautier, Pierre; Boulvais, Philippe; Couteau, Clément; Drouillet, Maxime

    2016-02-01

    In New Caledonian Ni deposits, the richest Ni silicate ores occur in fractures within the bedrock and saprolite, generally several tens of meters to hundred meters below the present-day surface. Fracture-related Ni silicate ore accounts for high Ni grades, at least a few weight percent above the average exploited grade (2.5 %). These Ni-rich veins are affected by active dissolution-precipitation processes at the level of the water table. Ni in solution is precipitated as silicates in thin layer cementing joints. This mineralization is characterized by chemical and mineralogical concentric zoning with an outer green rim around an inner white zone composed, from the edge to the centre of the block, (i) a highly oxidized and altered zone, (ii) a green pure Ni-rich pimelite zone, (iii) a zone (limited to a few centimetres) with a mixture of Ni-poor kerolite and Ni-rich pimelite and intermediate colours and (iv) a large white Mg-kerolite mineralization zone. This study proposes that the concentric zonation results from evapo-precipitation process related to alternate periods of hydration and drying, induced by water table movements. This extensive dispersion of Ni in concentrically zoned ores can partly explain the rather monotonous Ni grade of the bulk exploitation at the base of the regolith with values between 2 and 3 wt%.

  6. Tangential 2-D Edge Imaging for GPI and Edge/Impurity Modeling

    SciTech Connect

    Dr. Ricardo Maqueda; Dr. Fred M. Levinton

    2011-12-23

    Nova Photonics, Inc. has a collaborative effort at the National Spherical Torus Experiment (NSTX). This collaboration, based on fast imaging of visible phenomena, has provided key insights on edge turbulence, intermittency, and edge phenomena such as edge localized modes (ELMs) and multi-faceted axisymmetric radiation from the edge (MARFE). Studies have been performed in all these areas. The edge turbulence/intermittency studies make use of the Gas Puff Imaging diagnostic developed by the Principal Investigator (Ricardo Maqueda) together with colleagues from PPPL. This effort is part of the International Tokamak Physics Activity (ITPA) edge, scrape-off layer and divertor group joint activity (DSOL-15: Inter-machine comparison of blob characteristics). The edge turbulence/blob study has been extended from the current location near the midplane of the device to the lower divertor region of NSTX. The goal of this effort was to study turbulence born blobs in the vicinity of the X-point region and their circuit closure on divertor sheaths or high density regions in the divertor. In the area of ELMs and MARFEs we have studied and characterized the mode structure and evolution of the ELM types observed in NSTX, as well as the study of the observed interaction between MARFEs and ELMs. This interaction could have substantial implications for future devices where radiative divertor regions are required to maintain detachment from the divertor plasma facing components.

  7. The Edges of the Ocean: An Introduction.

    ERIC Educational Resources Information Center

    Burke, Kevin

    1979-01-01

    Introduces a series of related articles on the study of ocean/continent boundaries (margins) within the framework of plate tectonics. Topics discussed include: early attempts to interpret ocean/continent boundaries, Atlantic-type margins, Pacific-type margins, the edges of ancient oceans, and future challenges in the study of continental margins.…

  8. Hermetic Edge Seals for Photovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Nowlan, M. J.

    1986-01-01

    Corrosive atmospheric agents excluded to prolong cell life. Combination of two sealing techniques makes possible to protect solar cells from water vapor, oxygen, and other corrosive atmospheric constituents. Using three-step process, glass-to-metal hermetic seal formed around edge of solar-cell module. Elastomer seals used previously not as effective because they are permeable to water vapor and atmospheric gases.

  9. Strip edge cracking simulation in cold rolling

    NASA Astrophysics Data System (ADS)

    Hubert, C.; Dubar, L.; Dubar, M.; Dubois, A.

    2011-01-01

    This research work focuses on a specific defect which occurs during cold rolling of steel strips: edge-serration. Investigations on the industrial processes have led to the conclusion that this defect is the result of the edge-trimming and cold rolling sequences. The aim of this research work is to analyze the effect of the cutting process and the cold rolling on cracks occurrence, especially on strip edges. This study is performed using an experimental testing stand called Upsetting Rolling Test (URT). It allows to reproduce cold rolling contact parameters such as forward slip, reduction ratio and friction coefficients. Specimens sampled near trimmed industrial strip edges are deformed using the URT stand. Two sets of specimens with different stress states, obtained by annealing, are submitted to two reduction passes with extreme forward slips. Scanning electron microscopy observations added to 3D optical surface profiler topographies show that on one hand, forward slip has a major effect on cracks opening. On the other hand, cracks opening decreases according to high roll strip speed gradient. Concerning the heat-treated specimens, no crack appeared after all reduction passes, showing a large influence of the cutting process and consequently of the local stress state in the vicinity of the burnish and fracture regions.

  10. Edge currents in frustrated Josephson junction ladders

    NASA Astrophysics Data System (ADS)

    Marques, A. M.; Santos, F. D. R.; Dias, R. G.

    2016-09-01

    We present a numerical study of quasi-1D frustrated Josephson junction ladders with diagonal couplings and open boundary conditions, in the large capacitance limit. We derive a correspondence between the energy of this Josephson junction ladder and the expectation value of the Hamiltonian of an analogous tight-binding model, and show how the overall superconducting state of the chain is equivalent to the minimum energy state of the tight-binding model in the subspace of one-particle states with uniform density. To satisfy the constraint of uniform density, the superconducting state of the ladder is written as a linear combination of the allowed k-states of the tight-binding model with open boundaries. Above a critical value of the parameter t (ratio between the intra-rung and inter-rung Josephson couplings) the ladder spontaneously develops currents at the edges, which spread to the bulk as t is increased until complete coverage is reached. Above a certain value of t, which varies with ladder size (t = 1 for an infinite-sized ladder), the edge currents are destroyed. The value t = 1 corresponds, in the tight-binding model, to the opening of a gap between two bands. We argue that the disappearance of the edge currents with this gap opening is not coincidental, and that this points to a topological origin for these edge current states.

  11. Reading Edge. What Works Clearinghouse Intervention Report

    ERIC Educational Resources Information Center

    What Works Clearinghouse, 2012

    2012-01-01

    "Reading Edge" is a middle school literacy program that emphasizes cooperative learning, goal setting, feedback, classroom management techniques, and the use of metacognitive strategy, whereby students assess their own skills and learn to apply new ones. The program is a component of the "Success for All"[superscript 2]…

  12. The Cognitive Dimension--"Edge of Darkness."

    ERIC Educational Resources Information Center

    McGuigan, Jim

    This paper discusses the cognitive effect of a highly successful 1985 British television program, "Edge of Darkness," which was viewed by millions and received critical plaudits and the accolade of the industry itself. The program is shown to represent a significant television event for formal and cognitive reasons that can usefully be…

  13. Submillisecond Optical Knife-Edge Testing

    NASA Technical Reports Server (NTRS)

    Thurlow, P.

    1983-01-01

    Fast computer-controlled sampling of optical knife-edge response (KER) signal increases accuracy of optical system aberration measurement. Submicrosecond-response detectors in optical focal plane convert optical signals to electrical signals converted to digital data, sampled and feed into computer for storage and subsequent analysis. Optical data are virtually free of effects of index-of-refraction gradients.

  14. Superconducting Metallic Glass Transition-Edge-Sensors

    NASA Technical Reports Server (NTRS)

    Hays, Charles C. (Inventor)

    2013-01-01

    A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

  15. Zone edge effects with variable rate irrigation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Variable rate irrigation (VRI) systems may offer solutions to enhance water use efficiency by addressing variability within a field. However, the design of VRI systems should be considered to maximize application uniformity within sprinkler zones, while minimizing edge effects between such zones alo...

  16. New applications of Spectral Edge image fusion

    NASA Astrophysics Data System (ADS)

    Hayes, Alex E.; Montagna, Roberto; Finlayson, Graham D.

    2016-05-01

    In this paper, we present new applications of the Spectral Edge image fusion method. The Spectral Edge image fusion algorithm creates a result which combines details from any number of multispectral input images with natural color information from a visible spectrum image. Spectral Edge image fusion is a derivative-based technique, which creates an output fused image with gradients which are an ideal combination of those of the multispectral input images and the input visible color image. This produces both maximum detail and natural colors. We present two new applications of Spectral Edge image fusion. Firstly, we fuse RGB-NIR information from a sensor with a modified Bayer pattern, which captures visible and near-infrared image information on a single CCD. We also present an example of RGB-thermal image fusion, using a thermal camera attached to a smartphone, which captures both visible and low-resolution thermal images. These new results may be useful for computational photography and surveillance applications.

  17. Social Justice as a Pedagogy of Edge

    ERIC Educational Resources Information Center

    Sonu, Debbie J.

    2010-01-01

    In this article, the author discusses social justice as a "pedagogy of edge." She argues that educators hold the privilege to begin reframing the dialogue on social justice as a relation of all subjects and to dredge from within the meanings drawn and practices made in honor of justice. This may require a shift away from social justice as a…

  18. The Cutting Edge, 1999-2000.

    ERIC Educational Resources Information Center

    Cutting Edge, 2000

    2000-01-01

    The Cutting Edge is a bimonthly newsletter of the Regional Center for Applied Technology and Training at Danville Community College (DCC) (Virginia) that provides the latest information on a wide range of issues including technology, business, employment trends, and new legislation. Articles from the first five issues discuss: (1) the July 2000…

  19. A neutral model of edge effects.

    PubMed

    Babak, Petro; He, Fangliang

    2009-02-01

    In this paper a spatially implicit neutral model for explaining the edge effects between habitats is proposed. To analyze this model we use two different approaches: a discrete approach that is based on the Master equation for a one step jump process and a continuous approach based on the approximation of the discrete jump process with the Kolmogorov-Fokker-Planck forward and backward equations. The discrete and continuous approaches are applied to analyze the species abundance distributions and the time to species extinction. Moreover, with the aid of the continuous approach a realistic classification of the behavior of species in local communities is developed. The species abundance dynamics at the edge between two distinct habitats is compared with those located in the homogeneous interior habitats using species abundance distributions and the first time to species extinction. We show that the structure of the links between local community and the metacommunity plays an important role on species persistence. Specifically, species at the edge between two distinct metacommunities have higher extinction rate than those in the interior habitats connected only to one metacommunity. Moreover, the same species might be persistent in the homogeneous interior habitat, but its probability of extinction from the edge local community could be very high.

  20. Acoustic streaming of a sharp edge.

    PubMed

    Ovchinnikov, Mikhail; Zhou, Jianbo; Yalamanchili, Satish

    2014-07-01

    Anomalous acoustic streaming is observed emanating from sharp edges of solid bodies that are vibrating in fluids. The streaming velocities can be orders of magnitude higher than expected from the Rayleigh streaming at similar amplitudes of vibration. Acoustic velocity of fluid relative to a solid body diverges at a sharp edge, giving rise to a localized time-independent body force acting on the fluid. This force results in a formation of a localized jet. Two-dimensional numerical simulations are performed to predict acoustic streaming for low amplitude vibration using two methods: (1) Steady-state solution utilizing perturbation theory and (2) direct transient solution of the Navier-Stokes equations. Both analyses agree with each other and correctly predict the streaming of a sharp-edged vibrating blade measured experimentally. The origin of the streaming can be attributed to the centrifugal force of the acoustic fluid flow around a sharp edge. The dependence of this acoustic streaming on frequency and velocity is examined using dimensional analysis. The dependence law is devised and confirmed by numerical simulations.

  1. Detection of edges using local geometry

    NASA Technical Reports Server (NTRS)

    Gualtieri, J. A.; Manohar, M.

    1989-01-01

    Researchers described a new representation, the local geometry, for early visual processing which is motivated by results from biological vision. This representation is richer than is often used in image processing. It extracts more of the local structure available at each pixel in the image by using receptive fields that can be continuously rotated and that go to third order spatial variation. Early visual processing algorithms such as edge detectors and ridge detectors can be written in terms of various local geometries and are computationally tractable. For example, Canny's edge detector has been implemented in terms of a local geometry of order two, and a ridge detector in terms of a local geometry of order three. The edge detector in local geometry was applied to synthetic and real images and it was shown using simple interpolation schemes that sufficient information is available to locate edges with sub-pixel accuracy (to a resolution increase of at least a factor of five). This is reasonable even for noisy images because the local geometry fits a smooth surface - the Taylor series - to the discrete image data. Only local processing was used in the implementation so it can readily be implemented on parallel mesh machines such as the MPP. Researchers expect that other early visual algorithms, such as region growing, inflection point detection, and segmentation can also be implemented in terms of the local geometry and will provide sufficiently rich and robust representations for subsequent visual processing.

  2. MHD edge instabilities in toroidal plasmas

    NASA Astrophysics Data System (ADS)

    Sugiyama, Linda

    2015-11-01

    Different types of MHD edge instabilities in different toroidal magnetically confined plasmas are compared. Large scale numerical simulations show that the nonlinear evolution of an unstable edge mode in a shaped plasma with a single X-point and a surrounding open field line region has a number of common features in the full resistive MHD model for strongly unstable and weaker instabilities. These include the relation of the nonlinear mode structure and dominant toroidal harmonics to the linear eigenmode spectrum, the effects of the mode on reducing the edge pressure or density gradient, the inward penetration of a ballooning-type perturbation into the plasma interior, and the potential to drive a coherent axisymmetric poloidal rotation of the outer part of the plasma, exhibited at different strengths. The results can be compared to experiment to estimate the usefulness and validity of the MHD model for predicting edge stability and instability properties. Work supported by the U.S. DOE OFES under Awards DE-SC-0007883, DE-FG02-04ER54802, and DE-SC-0008737. Some computation carried out at NERSC.

  3. The Cutting Edge: Workplace English. Instructional Guide.

    ERIC Educational Resources Information Center

    El Paso Community Coll., TX. Literacy Center.

    The instructional guide for the Cutting Edge workplace literacy program, a cooperative project of El Paso Community College (Texas) and Levi Strauss and Company, is an expanded version of one appendix the project handbook. It describes and provides an instructional model for the three-part, job-specific, video-based program of English as a Second…

  4. Strip edge cracking simulation in cold rolling

    SciTech Connect

    Hubert, C.; Dubar, L.; Dubar, M.; Dubois, A.

    2011-01-17

    This research work focuses on a specific defect which occurs during cold rolling of steel strips: edge-serration. Investigations on the industrial processes have led to the conclusion that this defect is the result of the edge-trimming and cold rolling sequences. The aim of this research work is to analyze the effect of the cutting process and the cold rolling on cracks occurrence, especially on strip edges.This study is performed using an experimental testing stand called Upsetting Rolling Test (URT). It allows to reproduce cold rolling contact parameters such as forward slip, reduction ratio and friction coefficients. Specimens sampled near trimmed industrial strip edges are deformed using the URT stand. Two sets of specimens with different stress states, obtained by annealing, are submitted to two reduction passes with extreme forward slips.Scanning electron microscopy observations added to 3D optical surface profiler topographies show that on one hand, forward slip has a major effect on cracks opening. On the other hand, cracks opening decreases according to high roll strip speed gradient. Concerning the heat-treated specimens, no crack appeared after all reduction passes, showing a large influence of the cutting process and consequently of the local stress state in the vicinity of the burnish and fracture regions.

  5. Students at the Edge of Space

    ERIC Educational Resources Information Center

    Kennon, Tillman; Roberts, Ed; Fuller, Teresa

    2008-01-01

    Space travel, even low Earth orbit, is probably several years away for most of us; however, students and teachers can research the edge of space by participating in the BalloonSat program. BalloonSat is an offshoot of the Space Grant Consortium's very successful RocketSat program. The Arkansas BalloonSat program consists of teacher-initiated…

  6. Atomic diffusion in liquid Ni, NiP, PdNiP, and PdNiCuP alloys

    SciTech Connect

    Chathoth, S. Mavila; Meyer, A.; Koza, M.M.; Juranyi, F.

    2004-11-22

    We investigated the self-diffusion of Ni in liquid Ni, Ni{sub 80}P{sub 20}, Pd{sub 40}Ni{sub 40}P{sub 20}, and Pd{sub 43}Ni{sub 10}Cu{sub 27}P{sub 20} at temperatures up to 1795 K with incoherent, quasielastic neutron scattering. Values of measured self-diffusion coefficients vary over the accessible temperature ranges as a function of composition only within 10%. Although mixing has a drastic effect on the liquidus temperature and the undercooling capabilities, a relation between these properties and the atomic diffusion in the liquid is not observed. Apparently, diffusive motion is governed by the packing fraction of the atoms, that is very similar in these dense liquids.

  7. Mapping Forest Edge Using Aerial Lidar

    NASA Astrophysics Data System (ADS)

    MacLean, M. G.

    2014-12-01

    Slightly more than 60% of Massachusetts is covered with forest and this land cover type is invaluable for the protection and maintenance of our natural resources and is a carbon sink for the state. However, Massachusetts is currently experiencing a decline in forested lands, primarily due to the expansion of human development (Thompson et al., 2011). Of particular concern is the loss of "core areas" or the areas within forests that are not influenced by other land cover types. These areas are of significant importance to native flora and fauna, since they generally are not subject to invasion by exotic species and are more resilient to the effects of climate change (Campbell et al., 2009). However, the expansion of development has reduced the amount of this core area, but the exact amount is still unknown. Current methods of estimating core area are not particularly precise, since edge, or the area of the forest that is most influenced by other land cover types, is quite variable and situation dependent. Therefore, the purpose of this study is to devise a new method for identifying areas that could qualify as "edge" within the Harvard Forest, in Petersham MA, using new remote sensing techniques. We sampled along eight transects perpendicular to the edge of an abandoned golf course within the Harvard Forest property. Vegetation inventories as well as Photosynthetically Active Radiation (PAR) at different heights within the canopy were used to determine edge depth. These measurements were then compared with small-footprint waveform aerial LiDAR datasets and imagery to model edge depths within Harvard Forest.

  8. Absorber topography dependence of phase edge effects

    NASA Astrophysics Data System (ADS)

    Shanker, Aamod; Sczyrba, Martin; Connolly, Brid; Waller, Laura; Neureuther, Andy

    2015-10-01

    Mask topography contributes to phase at the wafer plane, even for OMOG binary masks currently in use at the 22nm node in deep UV (193nm) lithography. Here, numerical experiments with rigorous FDTD simulation are used to study the impact of mask 3D effects on aerial imaging, by varying the height of the absorber stack and its sidewall angle. Using a thin mask boundary layer model to fit to rigorous simulations it is seen that increasing the absorber thickness, and hence the phase through the middle of a feature (bulk phase) monotonically changes the wafer-plane phase. Absorber height also influences best focus, revealed by an up/down shift in the Bossung plot (linewidth vs. defocus). Bossung plot tilt, however, responsible for process window variability at the wafer, is insensitive to changes in the absorber height (and hence also the bulk phase). It is seen to depend instead on EM edge diffraction from the thick mask edge (edge phase), but stays constant for variations in mask thickness within a 10% range. Both bulk phase and edge phase are also independent of sidewall angle fluctuation, which is seen to linearly affect the CD at the wafer, but does not alter wafer phase or the defocus process window. Notably, as mask topography varies, the effect of edge phase can be replicated by a thin mask model with 8nm wide boundary layers, irrespective of absorber height or sidewall angle. The conclusions are validated with measurements on phase shifting masks having different topographic parameters, confirming the strong dependence of phase variations at the wafer on bulk phase of the mask absorber.

  9. Comparison of benzene adsorption on Ni(111) and Ni(100)

    SciTech Connect

    Myers, A.K.; Schoofs, G.R.; Benziger, J.B.

    1987-04-23

    The adsorption of benzene on the Ni(100) and the Ni(111) crystal faces was compared in order to investigate the effect of crystallographic orientation on the interaction of benzene with nickel. Temperature programmed reaction (TPR) was used to characterize adsorption bond strengths and determine product distributions. Benzene was found to adsorb 44 kJ/mol less strongly on the Ni(111) plane than on the Ni(100) surface. Di-hydrogen evolution formed after decomposition of benzene was similar for both surfaces. Benzene chemisorption was modeled by using extended Hueckel theory (EHT), a semiempirical molecular orbital method. The calculations predict bonding of benzene over a threefold hollow site on Ni(111). Multicenter bonding of the benzene carbon atoms with the nickel atoms is indicated by the calculations. The binding strength of benzene is controlled by the degree of overlap of the carbon ..pi.. orbitals with the nickel atom orbitals. Benzene binds more strongly to the Ni(100) surface because the carbon ..pi.. orbitals can overlap with four nickel atoms on the fourfold hollow site, whereas on Ni(111) the carbon atoms are closely associated with only three nickel atoms on the threefold hollow site.

  10. Face the Edges: Catalytic Active Sites of Nanomaterials

    PubMed Central

    Ni, Bing

    2015-01-01

    Edges are special sites in nanomaterials. The atoms residing on the edges have different environments compared to those in other parts of a nanomaterial and, therefore, they may have different properties. Here, recent progress in nanomaterial fields is summarized from the viewpoint of the edges. Typically, edge sites in MoS2 or metals, other than surface atoms, can perform as active centers for catalytic reactions, so the method to enhance performance lies in the optimization of the edge structures. The edges of multicomponent interfaces present even more possibilities to enhance the activities of nanomaterials. Nanoframes and ultrathin nanowires have similarities to conventional edges of nanoparticles, the application of which as catalysts can help to reduce the use of costly materials. Looking beyond this, the edge structures of graphene are also essential for their properties. In short, the edge structure can influence many properties of materials. PMID:27980960

  11. Life on the edge: gastrointestinal parasites from the forest edge and interior primate groups.

    PubMed

    Chapman, Colin A; Speirs, Michaela L; Gillespie, Thomas R; Holland, Timothy; Austad, Kiersten M

    2006-04-01

    Humans are responsible for massive changes to primate habitats, and one unanticipated consequence of these alterations may be changes in host-parasite interactions. Edges are a ubiquitous aspect of human disturbance to forest landscapes. Here we examine how changes associated with the creation of edges in Kibale National Park, Uganda, alter the parasite community that is supported by two species of African colobines: the endangered red colobus (Piliocolobus tephrosceles) and the black-and-white colobus (Colobus guereza). An analysis of 822 fecal samples from edge and forest interior groups revealed no difference in the richness of parasite communities (i.e., the number of parasite species recovered from the host's fecal sample). However, for both species the proportion of individuals with multiple infections was greater in edge than forest interior groups. The prevalence of specific parasites also varied between edge and forest interior groups. Oesophagostomum sp., a potentially deleterious parasite, was 7.4 times more prevalent in red colobus on the edge than in those in the forest interior, and Entamoeba coli was four times more prevalent in red colobus on the edge than in animals from the forest interior. Environmental contamination with parasites (measured as parasite eggs/gm feces) by red colobus from the edge and forest interior differed in a similar fashion to prevalence for red colobus, but it did not differ for black-and-white colobus. For example, egg counts of Oesophagostomum sp. were 10 times higher in red colobus from the edge than in those from the interior. The less severe infections in the black-and-white colobus relative to the red colobus may reflect the fact that black-and-white colobus raid agricultural crops while red colobus do not. This nutritional gain may facilitate a more effective immune response to parasites by the black-and-white colobus. The fact that animals on the edge are likely not nutritionally stressed raises an intriguing

  12. Edge-effect interactions in fragmented and patchy landscapes.

    PubMed

    Porensky, Lauren M; Young, Truman P

    2013-06-01

    Ecological edges are increasingly recognized as drivers of landscape patterns and ecosystem processes. In fragmented and patchy landscapes (e.g., a fragmented forest or a savanna with scattered termite mounds), edges can become so numerous that their effects pervade the entire landscape. Results of recent studies in such landscapes show that edge effects can be altered by the presence or proximity of other nearby edges. We considered the theoretical significance of edge-effect interactions, illustrated various landscape configurations that support them and reviewed existing research on this topic. Results of studies from a variety of locations and ecosystem types show that edge-effect interactions can have significant consequences for ecosystems and conservation, including higher tree mortality rates in tropical rainforest fragments, reduced bird densities in grassland fragments, and bush encroachment and reduced wildlife densities in a tropical savanna. To clarify this underappreciated concept and synthesize existing work, we devised a conceptual framework for edge-effect interactions. We first worked to reduce terminological confusion by clarifying differences among terms such as edge intersection and edge interaction. For cases in which nearby edge effects interact, we proposed three possible forms of interaction: strengthening (presence of a second edge causes stronger edge effects), weakening (presence of a second edge causes weaker edge effects), and emergent (edge effects change completely in the presence of a second edge). By clarifying terms and concepts, this framework enables more precise descriptions of edge-effect interactions and facilitates comparisons of results among disparate study systems and response variables. A better understanding of edge-effect interactions will pave the way for more appropriate modeling, conservation, and management in complex landscapes.

  13. Search for Origin of Room Temperature Ferromagnetism Properties in Ni-Doped ZnO Nanostructure.

    PubMed

    Rana, Amit Kumar; Kumar, Yogendra; Rajput, Parasmani; Jha, Shambhu Nath; Bhattacharyya, Dibyendu; Shirage, Parasharam M

    2017-03-01

    The origin of room temperature (RT) ferromagnetism (FM) in Zn1-xNixO (0< x < 0.125) samples are systematically investigated through physical, optical, and magnetic properties of nanostructure, prepared by simple low-temperature wet chemical method. Reitveld refinement of X-ray diffraction pattern displays an increase in lattice parameters with strain relaxation and contraction in Zn/O occupancy ratio by means of Ni-doping. Similarly, scanning electron microscope demonstrates modification in the morphology from nanorods to nanoflakes with Ni doping, suggests incorporation of Ni ions in ZnO. More interestingly, XANES (X-ray absorption near edge spectroscopy) measurements confirm that Ni is being incorporated in ZnO as Ni(2+). EXAFS (extended X-ray absorption fine structure) analysis reveals that structural disorders near the Zn sites in the ZnO samples upsurges with increasing Ni concentration. Raman spectroscopy exhibits additional defect driven vibrational mode (at 275 cm(-1)), appeared only in Ni-doped samples and the shift with broadening in 580 cm(-1) peak, which manifests the presence of the oxygen vacancy (VO) related defects. Moreover, in photoluminescence (PL) spectra, we have observed a peak at 524 nm, indicating the presence of singly ionized VO(+), which may be activating bound magnetic polarons (BMPs) in dilute magnetic semiconductors (DMSs). Magnetization measurements indicate weak ferromagnetism at RT, which rises with increasing Ni concentration. It is therefore proposed that the effect of the Ni ions as well as the inherent exchange interactions arising from VO(+) assist to produce BMPs, which are accountable for the RT-FM in Zn1-xNixO (0< x < 0.125) system.

  14. Structural features of Ni-Cr-Si-B materials obtained by different technologies

    NASA Astrophysics Data System (ADS)

    Kornienko, E. E.; Nikulina, A. A.; Belousova, N. S.; Lazurenko, D. V.; Ivashutenko, A. S.; Kuz'min, V. I.

    2016-11-01

    This study considers the structural features of Ni-Cr-Si-B (Ni - base; 15.1 % Cr; 2 % Si; 2 % B; 0.4 % C) materials obtained by different methods. The self-fluxing coatings were deposited by plasma spraying on the tubes from low carbon steel. Bulk cylinder specimens of 20 mm diameter and 15 mm height were obtained by spark plasma sintering (SPS). The structure and phase composition of these materials were investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The major phases of coatings and sintered materials are γ-Ni, Ni3B, CrB and Cr7C3. We demonstrate that the particle unmelted in the process of plasma spraying or SPS consist of γ-Ni-NEB eutectic and also CrB and Cr7C3 inclusions. The prolonged exposure of powder to high temperatures as well as slow cooling rates by SPS provide for the growth of the structural components as compared to those of plasma coatings materials. High cooling rates at the plasma spraying by melted particles contribute to the formation of supersaturated solid solution of Cr, Si and Fe in γ-Ni. The structure of the melted particles in sintering material has gradient composition: the core constituted of Ni grains of 10 μm with γ-Ni-Ni3B eutectic on the edges. The results of the experiment demonstrate that the sintering material has a smaller microhardness in comparison with plasma coatings (650 and 850 MPa, respectively), but at the same time the material has higher density (porosity less than 1 %) than plasma coatings (porosity about 2.. .3 %).

  15. Edge-to-edge repair of tricuspid valve in a corrected transposition of the great vessels.

    PubMed

    Kotoulas, Christophoros; Jones, Robert Peter; Turkie, Wajdi; Hasan, Ragheb

    2008-01-01

    We describe the case of a 27-year-old Caucasian woman with corrected transposition of the great vessels, who presented with cardiac failure. She had severe regurgitation of the systemic tricuspid valve with a huge annulus that was not suitable for annuloplasty. She underwent a successful repair using the Alfieri edge-to-edge technique and was asymptomatic 15 months after surgery. Such a repair has not been reported in the past.

  16. Balancing the edge effects budget: bay scallop settlement and loss along a seagrass edge.

    PubMed

    Carroll, John M; Furman, Bradley T; Tettelbach, Stephen T; Peterson, Bradley J

    2012-07-01

    Edge effects are a dominant subject in landscape ecology literature, yet they are highly variable and poorly understood. Often, the literature suggests simple models for edge effects-positive (enhancement at the edge), negative (enhancement at the interior), or no effect (neutral)--on a variety of metrics, including abundance, diversity, and mortality. In the marine realm, much of this work has focused on fragmented seagrass habitats due to their importance for a variety of commercially important species. In this study, the settlement, recruitment, and survival of bay scallops was investigated across a variety of seagrass patch treatments. By simultaneously collecting settlers (those viable larvae available to settle and metamorphose) and recruits (those settlers that survive some period of time, in this case, 6 weeks) on the same collectors, we were able to demonstrate a "balance" between positive and negative edge effects, resulting in a net neutral effect. Scallop settlement was significantly enhanced along seagrass edges, regardless of patch type while survival was elevated within patch interiors. However, recruitment (the net result of settlement and post-settlement loss) did not vary significantly from edge to center, representing a neutral effect. Further, results suggest that post-settlement loss, most likely due to predation, appears to be the dominant mechanism structuring scallop abundance, not patterns in settlement. These data illustrate the complexity of edge effects, and suggest that the metric used to investigate the effect (be it abundance, survival, or other metrics) can often influence the magnitude and direction of the perceived effect. Traditionally, high predation along a habitat edge would have indicated an "ecological trap" for the species in question; however, this study demonstrates that, at the population level, an ecological trap may not exist.

  17. Synthesis and electrochemical behavior of nanostructured cauliflower-shape Co-Ni/Co-Ni oxides composites

    SciTech Connect

    Gupta, Vinay Kawaguchi, Toshikazu; Miura, Norio

    2009-01-08

    Nanostructured Co-Ni/Co-Ni oxides were electrochemically deposited onto stainless steel electrode by electrochemical method and characterized for their structural and supercapacitive properties. The SEM images indicated that the obtained Co-Ni/Co-Ni oxides had cauliflower-type nanostructure. The X-ray diffraction pattern showed the formation of Co{sub 3}O{sub 4}, NiO, Co and Ni. The EDX elemental mapping images indicated that Ni, Co and O are distributed uniformly. The deposited Co-Ni/Co-Ni oxides showed good supercapacitive characteristics with a specific capacitance of 331 F/g at 1 mA/cm{sup 2} current density in 1 M KOH electrolyte. A mechanism of the formation of cauliflower-shape Co-Ni/Co-Ni oxides was proposed. A variety of promising applications in the fields such as energy storage devices and sensors can be envisioned from Co-Ni/Co-Ni oxides.

  18. Multifractality in plasma edge electrostatic turbulence

    NASA Astrophysics Data System (ADS)

    Neto, C. Rodrigues; Guimarães-Filho, Z. O.; Caldas, I. L.; Nascimento, I. C.; Kuznetsov, Yu. K.

    2008-08-01

    Plasma edge turbulence in Tokamak Chauffage Alfvén Brésilien (TCABR) [R. M. O. Galvão et al., Plasma Phys. Contr. Fusion 43, 1181 (2001)] is investigated for multifractal properties of the fluctuating floating electrostatic potential measured by Langmuir probes. The multifractality in this signal is characterized by the full multifractal spectra determined by applying the wavelet transform modulus maxima. In this work, the dependence of the multifractal spectrum with the radial position is presented. The multifractality degree inside the plasma increases with the radial position reaching a maximum near the plasma edge and becoming almost constant in the scrape-off layer. Comparisons between these results with those obtained for random test time series with the same Hurst exponents and data length statistically confirm the reported multifractal behavior. Moreover, the persistence of these signals, characterized by their Hurst exponent, present radial profile similar to the deterministic component estimated from analysis based on dynamical recurrences.

  19. The red edge of plant leaf reflectance

    NASA Technical Reports Server (NTRS)

    Horler, D. N. H.; Dockray, M.; Barber, J.

    1983-01-01

    A detailed study of the red edge spectral feature of green vegetation based on laboratory reflectance spectrophotometry is presented. A parameter lambda is defined as the wavelength is defined as the wavelength of maximum slope and found to be dependent on chlorophyll concentration. Species, development stage, leaf layering, and leaf water content of vegetation also influences lambda. The maximum slope parameter is found to be independent of simulated ground area coverage. The results are interpreted in terms of Beer's Law and Kubelka-Munk theory. The chlorophyll concentration dependence of lambda seems to be explained in terms of a pure absorption effect, and it is suggested that the existence of two lambda components arises from leaf scattering properties. The results indicate that red edge measurements will be valuable for assessment of vegetative chlorophyll status and leaf area index independently of ground cover variations, and will be particularly suitable for early stress detection.

  20. Quantum nature of edge magnetism in graphene.

    PubMed

    Golor, Michael; Wessel, Stefan; Schmidt, Manuel J

    2014-01-31

    It is argued that the subtle crossover from decoherence-dominated classical magnetism to fluctuation-dominated quantum magnetism is experimentally accessible in graphene nanoribbons. We show that the width of a nanoribbon determines whether the edge magnetism is on the classical side, on the quantum side, or in between. In the classical regime, decoherence is dominant and leads to static spin polarizations at the ribbon edges, which are well described by mean-field theories. The quantum Zeno effect is identified as the basic mechanism which is responsible for the spin polarization and thereby enables the application of graphene in spintronics. On the quantum side, however, the spin polarization is destroyed by dynamical processes. The great tunability of graphene magnetism thus offers a viable route for the study of the quantum-classical crossover.

  1. Immune mechanism: a 'double-edged sword'.

    PubMed

    Musa, Mustaffa

    2013-05-01

    Immunology has now developed into an independent discipline in medicine which covers not only germ infection which is related to immunity solely but also covers a lot of non-infectious diseases such as autoimmune disease, allergies, and others. Therefore, "The Immune Mechanism: "A Double-Edged Sword" means that the immune mechanism (consisted of antibody mediated mechanism and T cell mediated mechanism), just like one edge playing the role of giving benefit (immunity) as it destroys the agent of infection, and another one can be detrimental as it will cause tissue/cell damages and then give rise to immune diseases (immunopathology). Now, the prevalence of these immune diseases is on the rise and has become a new challenge to our country towards developed country in 2020. Therefore, we have to make ample preparation (laboratory facilities/services, main power, and research) from now on in order to face the problems and challenges.

  2. Edge overload breakdown in evolving networks

    NASA Astrophysics Data System (ADS)

    Holme, Petter

    2002-09-01

    We investigate growing networks based on Barabási and Albert's algorithm for generating scale-free networks, but with edges sensitive to overload breakdown. The load is defined through edge betweenness centrality. We focus on the situation where the average number of connections per vertex is, like the number of vertices, linearly increasing in time. After an initial stage of growth, the network undergoes avalanching breakdowns to a fragmented state from which it never recovers. This breakdown is much less violent if the growth is by random rather than by preferential attachment (as defines the Barabási and Albert model). We briefly discuss the case where the average number of connections per vertex is constant. In this case no breakdown avalanches occur. Implications to the growth of real-world communication networks are discussed.

  3. Edges of Saturn's rings are fractal.

    PubMed

    Li, Jun; Ostoja-Starzewski, Martin

    2015-01-01

    The images recently sent by the Cassini spacecraft mission (on the NASA website http://saturn.jpl.nasa.gov/photos/halloffame/) show the complex and beautiful rings of Saturn. Over the past few decades, various conjectures were advanced that Saturn's rings are Cantor-like sets, although no convincing fractal analysis of actual images has ever appeared. Here we focus on four images sent by the Cassini spacecraft mission (slide #42 "Mapping Clumps in Saturn's Rings", slide #54 "Scattered Sunshine", slide #66 taken two weeks before the planet's Augus't 200'9 equinox, and slide #68 showing edge waves raised by Daphnis on the Keeler Gap) and one image from the Voyager 2' mission in 1981. Using three box-counting methods, we determine the fractal dimension of edges of rings seen here to be consistently about 1.63 ~ 1.78. This clarifies in what sense Saturn's rings are fractal.

  4. Submonolayer growth with decorated island edges

    NASA Astrophysics Data System (ADS)

    Kotrla, Miroslav; Krug, Joachim; Šmilauer, Pavel

    2000-05-01

    We study the dynamics of island nucleation in the presence of adsorbates using kinetic Monte Carlo simulations of a two-species growth model. Adatoms (A atoms) and impurities (B atoms) are codeposited, diffuse and aggregate subject to attractive AA and AB interactions. Activated exchange of adatoms with impurities is identified as the key process to maintain decoration of island edges by impurities during growth. While the presence of impurities strongly increases the island density, a change in the scaling of island density with flux, predicted by a rate equation theory for attachment-limited growth [D. Kandel, Phys. Rev. Lett. 78 (1997) 499], is not observed. We argue that, within the present model, even completely covered island edges do not provide efficient barriers to attachment.

  5. Edge physics considerations for IBW launch

    SciTech Connect

    Myra, J.R.; DIppolito, D.A.; Russell, D.A.; Rogers, J.H.

    1997-04-01

    Models for the edge interactions that occur in various regimes of IBW antenna operation have been developed. At high edge density, it is shown that rf sheath effects are important and give rise to significant power losses (anomalous loading). When the density at the antenna is low, the desired EPW-IBW mode transformation is sensitive to the density gradient scale length, and hence to ponderomotive effects. To treat the low density case, a second order equation describing mode transformation and reflection from the lower hybrid layer has been developed. Strong reflections are shown to occur when the density gradient is steep. Application of this model in the presence of self-consistent ponderomotive density modifications is the subject of a companion paper [1]. {copyright} {ital 1997 American Institute of Physics.}

  6. Absence of many-body mobility edges

    NASA Astrophysics Data System (ADS)

    De Roeck, Wojciech; Huveneers, Francois; Müller, Markus; Schiulaz, Mauro

    2016-01-01

    Localization transitions as a function of temperature require a many-body mobility edge in energy, separating localized from ergodic states. We argue that this scenario is inconsistent because local fluctuations into the ergodic phase within the supposedly localized phase can serve as mobile bubbles that induce global delocalization. Such fluctuations inevitably appear with a low but finite density anywhere in any typical state. We conclude that the only possibility for many-body localization to occur is lattice models that are localized at all energies. Building on a close analogy with a model of assisted two-particle hopping, where interactions induce delocalization, we argue why hot bubbles are mobile and do not localize upon diluting their energy. Numerical tests of our scenario show that previously reported mobility edges cannot be distinguished from finite-size effects.

  7. Domain Structures and Anisotropy in Exchange-coupled [Co/Pd]-NiFe and [Co/Ni]-NiFe Multilayers

    NASA Astrophysics Data System (ADS)

    Tryputen, Larysa; Chung, Sunjae; Mohseni, Majid; Nguyen, T. N. Anh; Åkerman, Johan; Guo, Feng; McMichael, Robert D.; Ross, Caroline A.

    2014-03-01

    Exchange-coupled multilayers [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe with strong perpendicular magnetic anisotropy have been proposed to use in spin-torque switching and oscillators devices with tilted fixed and free layer to improve their functional performance. We present an experimental study of the magnetization behavior of [Co/Pd]5-/NiFe and [Co/Ni]4-NiFe multilayers measured using magnetometry, magnetic force microscopy (MFM) and ferromagnetic resonance (FMR) as a function of the thickness of the top NiFe layer. We varied the thickness of the NiFe layer in [Co/Pd]5-NiFe (t), t = 0 - 80 nm and [Co/Ni]4-NiFe (t), t = 0.5 - 2.5 nm in order to study the interplay between perpendicular magnetization of the Co/Pd or Co/Ni multilayers and in-plane magnetization of the NiFe. Our magnetometry and FMR data suggest that the [Co/Ni]4/NiFe multilayer behaves like a homogeneous ferromagnetic film with anisotropy that reorients towards in-plane as the NiFe thickness increases, whereas the [Co/Pd]5/NiFe multilayer reveals more complex behavior in which the [Co/Pd] layer retains out-of-plane anisotropy while the magnetization of NiFe layer tilts in-plane with increasing thickness. MFM showed that domains with ~0.1 +/-m size were visible in [Co/Pd]-/NiFe with NiFe thickness of 20-80 nm. Multilayers were patterned into sub-100 nm dots using ion beam etching and their magnetization behavior are compared with unpatterned films.

  8. Hierarchical Ni-Mo-S nanosheets on carbon fiber cloth: A flexible electrode for efficient hydrogen generation in neutral electrolyte

    PubMed Central

    Miao, Jianwei; Xiao, Fang-Xing; Yang, Hong Bin; Khoo, Si Yun; Chen, Jiazang; Fan, Zhanxi; Hsu, Ying-Ya; Chen, Hao Ming; Zhang, Hua; Liu, Bin

    2015-01-01

    A unique functional electrode made of hierarchal Ni-Mo-S nanosheets with abundant exposed edges anchored on conductive and flexible carbon fiber cloth, referred to as Ni-Mo-S/C, has been developed through a facile biomolecule-assisted hydrothermal method. The incorporation of Ni atoms in Mo-S plays a crucial role in tuning its intrinsic catalytic property by creating substantial defect sites as well as modifying the morphology of Ni-Mo-S network at atomic scale, resulting in an impressive enhancement in the catalytic activity. The Ni-Mo-S/C electrode exhibits a large cathodic current and a low onset potential for hydrogen evolution reaction in neutral electrolyte (pH ~7), for example, current density of 10 mA/cm2 at a very small overpotential of 200 mV. Furthermore, the Ni-Mo-S/C electrode has excellent electrocatalytic stability over an extended period, much better than those of MoS2/C and Pt plate electrodes. Scanning and transmission electron microscopy, Raman spectroscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy were used to understand the formation process and electrocatalytic properties of Ni-Mo-S/C. The intuitive comparison test was designed to reveal the superior gas-evolving profile of Ni-Mo-S/C over that of MoS2/C, and a laboratory-scale hydrogen generator was further assembled to demonstrate its potential application in practical appliances. PMID:26601227

  9. Differentiator design and performance for edge sharpening

    USGS Publications Warehouse

    Pan, Jeng-Jong; Domingue, Julia O.

    1990-01-01

    A two-dimensional differentiator is useful for edge sharpening in digital image processing. In the design of a differentiator, differentiator coefficients that satisfy the specification of frequency response must be approximated. Four mathematical techniques - the minimax method, least-squares method, nonlinear programming, and linear programming - can be applied to solve the approximation problem. Results indicated that the differentiator derived from linear programming gives the highest resolution. -from Authors

  10. Permanent magnet edge-field quadrupole

    DOEpatents

    Tatchyn, Roman O.

    1997-01-01

    Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.

  11. Flow Control Over Sharp-Edged Wings

    DTIC Science & Technology

    2007-07-01

    each jet. A constant average mass flow of air was supplied to the jet using a closed-loop servo valve . Their data indicated that maximum lift...and screw angles of 90 and 45 degrees respectively. High-speed flow control valves were used to control the pulsed flow to each jet individually. The...leading edge contained three jet nozzles; however only two were used. The valve open-and-close cycle was manipulated using a computer function

  12. Rogue Edge Waves in the Ocean

    NASA Astrophysics Data System (ADS)

    Polukhina, Oxana; Kurkin, Andrey; Pelinovsky, Efim

    2010-05-01

    The investigation of anomalously large amplitude surface gravity waves on the sea surface (rogue or freak waves), which can appear suddenly and disappear in the same abrupt way, is very extensive in the recent years (see e.g., book [Kharif, Pelinovsky, Slunyaev 2009] and references there). However, any sudden displacements of water level or changes in flow velocities can also appear in the ocean wave motions of other types, including geophysical large-scale fields. The number of observations of such waves is still very small, they are even almost absent, but the investigations of such possible processes seem to be important for the applications. In the present paper the problem of rogue waves is discussed for edge waves in the coastal zone. Such waves belong to the class of topographically trapped waves, which are supposed to play dominant role in the dynamics of oceanic coastal zone. The amplitude of the waves reaches a maximum at the edge, and they are attenuated offshore. Direct visual observations of such waves are difficult, but such waves have been detected instrumentally in the nearshore wave field many times (see e.g. [Huntley and Bowen 1973; Bryan, Hows and Bowen 1998]). Edge waves are often considered as the major factor of the long-term evolution of coastal line, forming the rhythmic crescentic bars [Dolan and Ferm 1968; Bowen and Inman 1971; Guza and Inman 1975; Guza and Bowen 1981; Holman and Bowen 1982; Komar 1998]. In the present paper we summarize the results of the study of the nonlinear mechanisms of possible freak edge wave appearance: nonlinear dispersion enhancement and modulation instability.

  13. A collection of edge-based elements

    NASA Technical Reports Server (NTRS)

    Kempel, Leo C.; Volakis, John L.

    1992-01-01

    Edge-based elements have proved useful in solving electromagnetic problems since they are nondivergent. Previous authors have presented several two and three dimensional elements. Herein, we present four types of elements which are suitable for modeling several types of three dimensional geometries. Distorted brick and triangular prism elements are given in cartesian coordinates as well as the specialized cylindrical shell and pie-shaped prism elements which are suitable for problems best described in polar cylindrical coordinates.

  14. Resonant mode at the band edge

    NASA Astrophysics Data System (ADS)

    Castro-Garay, P.; Vargas Hernández, D.; Manzanares-Martinez, J.; Corella-Madueño, A.; Rosas-Burgos, A.; Tanori, Dra J.; Pellat, A.; Estrada, S.

    2016-09-01

    We have found the solution of the boundary value problem for reflectance and transmittance of normal circularly polarized light impinges on a cholesteric elastomer film with a twist defect. We have found a tunable resonant mode in the reflectance band for right and left circularly polarized light. When the values of chiral twist defect are increased in the cholesteric elastomer film, the resonant modes changes to shorter wavelength until the edge band is reached.

  15. On Bitstream Based Edge Detection Techniques

    DTIC Science & Technology

    2009-01-01

    IEEE Transactions on, vol. 38, no. 1, pp. xviii– iv, Feb 1992. [5] Rafael C. Gonzalez and Richard E. Woods, Digital Image Processing, Addison-Wesley...Carmona-Poyato, R. Medina- Carnicer, and F. J. Madrid- Cuevas , “Automatic genera- tion of consensus ground truth for the comparison of edge detection techniques,” Image Vision Comput., vol. 26, no. 4, pp. 496–511, 2008.

  16. Edge Detection Using a Complex Wavelet

    DTIC Science & Technology

    1993-12-01

    A complex wavelet of the form Psi(x, y) = C(x jy)exp(-p(x-sq+y-sq))) is used in the continuous wavelet transform to obtain edges from a digital image...and x and y are position variables. The square root of the sum of the squares of the real and imaginary parts of the wavelet transform are used to...radar images and the resulting images are shown. Continuous wavelet transform , Digital image.

  17. Rimmed and edge thickened Stodola shaped flywheel

    DOEpatents

    Kulkarni, S.V.; Stone, R.G.

    1983-10-11

    A flywheel is described that is useful for energy storage in a hybrid vehicle automotive power system or in some stationary applications. The flywheel has a body composed of essentially planar isotropic high strength material. The flywheel body is enclosed by a rim of circumferentially wound fiber embedded in resin. The rim promotes flywheel safety and survivability. The flywheel has a truncated and edge thickened Stodola shape designed to optimize system mass and energy storage capability. 6 figs.

  18. Permanent magnet edge-field quadrupole

    DOEpatents

    Tatchyn, R.O.

    1997-01-21

    Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis. 10 figs.

  19. Search for absorption edges in superexpansion bursts

    NASA Astrophysics Data System (ADS)

    in't Zand, Jean

    2013-09-01

    Our goal is to measure with the LETGS a series of bright type-I X-ray bursts with strong photospheric radius expansion ('superexpansion') to search for absorption edges due to the ashes of nuclear burning. We request a quick TOO, to be triggered by ISS-MAXI and Swift-BAT, with a total exposure time of 100 ks to obtain the detection of about 10 bursts.

  20. Solvotermal synthesis of NiO, Ni and NiS nanoparticles.

    PubMed

    Gutierrez, Angel; Perpiñán, M Felisa; Sánchez, Ana E; Torralba, M Carmen

    2013-01-01

    Nanoparticles of NiO, Ni or NiS have been obtained by solvothermal decomposition of different molecular precursors. The influence of several parameters, such as temperature, reaction time, solvent or capping agent used, in the nature and size of the obtained nanoparticle has been studied. The characterization by XRD and TEM techniques indicates that the nanoparticles of NiO exhibit average sizes of 3-8 nm, while those of Ni are in the 30-40 nm range. This difference in size has been attributed to the presence of molecules of the capping agent (n-octylamine or oleic acid) that surround the NiO nanoparticles but were not present in the nickel ones. The capping agent is, thus, preventing the aggregation of the smallest nanoparticles. The use of either a S-donor capping agent (4-mercaptopyridine) or a precursor having S-donor ligands (diethyldithiocarbamate) have led to the formation of NiS with average sizes around 35 nm. The magnetic properties of the nanoparticles have been studied, showing superparamagnetism and magnetic hysteresis below the blocking temperature, which, in time, is dependent of the particle size.

  1. Edge Diffraction Coefficients around Critical Rays

    NASA Astrophysics Data System (ADS)

    Fradkin, L.; Harmer, M.; Darmon, M.

    2014-04-01

    The classical GTD (Geometrical Theory of Diffraction) gives a recipe, based on high-frequency asymptotics, for calculating edge diffraction coefficients in the geometrical regions where only diffracted waves propagate. The Uniform GTD extends this recipe to transition zones between irradiated and silent regions, known as penumbra. For many industrial materials, e.g. steels, and frequencies utlized in industrial ultrasonic transducers, that is, around 5 MHz, asymptotics suggested for description of geometrical regions supporting the head waves or transition regions surrounding their boundaries, known as critical rays, prove unsatisfactory. We present a numerical extension of GTD, which is based on a regularized, variable step Simpson's method for evaluating the edge diffraction coefficients in the regions of interference between head waves, diffracted waves and/or reflected waves. In mathematical terms, these are the regions of coalescence of three critical points - a branch point, stationary point and/or pole, respectively. We show that away from the shadow boundaries, near the critical rays the GTD still produces correct values of the edge diffraction coefficients.

  2. Edge ratio and community structure in networks

    NASA Astrophysics Data System (ADS)

    Cafieri, Sonia; Hansen, Pierre; Liberti, Leo

    2010-02-01

    A hierarchical divisive algorithm is proposed for identifying communities in complex networks. To that effect, the definition of community in the weak sense of Radicchi [Proc. Natl. Acad. Sci. U.S.A. 101, 2658 (2004)] is extended into a criterion for a bipartition to be optimal: one seeks to maximize the minimum for both classes of the bipartition of the ratio of inner edges to cut edges. A mathematical program is used within a dichotomous search to do this in an optimal way for each bipartition. This includes an exact solution of the problem of detecting indivisible communities. The resulting hierarchical divisive algorithm is compared with exact modularity maximization on both artificial and real world data sets. For two problems of the former kind optimal solutions are found; for five problems of the latter kind the edge ratio algorithm always appears to be competitive. Moreover, it provides additional information in several cases, notably through the use of the dendrogram summarizing the resolution. Finally, both algorithms are compared on reduced versions of the data sets of Girvan and Newman [Proc. Natl. Acad. Sci. U.S.A. 99, 7821 (2002)] and of Lancichinetti [Phys. Rev. E 78, 046110 (2008)]. Results for these instances appear to be comparable.

  3. Canny edge-based deformable image registration

    NASA Astrophysics Data System (ADS)

    Kearney, Vasant; Huang, Yihui; Mao, Weihua; Yuan, Baohong; Tang, Liping

    2017-02-01

    This work focuses on developing a 2D Canny edge-based deformable image registration (Canny DIR) algorithm to register in vivo white light images taken at various time points. This method uses a sparse interpolation deformation algorithm to sparsely register regions of the image with strong edge information. A stability criterion is enforced which removes regions of edges that do not deform in a smooth uniform manner. Using a synthetic mouse surface ground truth model, the accuracy of the Canny DIR algorithm was evaluated under axial rotation in the presence of deformation. The accuracy was also tested using fluorescent dye injections, which were then used for gamma analysis to establish a second ground truth. The results indicate that the Canny DIR algorithm performs better than rigid registration, intensity corrected Demons, and distinctive features for all evaluation matrices and ground truth scenarios. In conclusion Canny DIR performs well in the presence of the unique lighting and shading variations associated with white-light-based image registration.

  4. Density Threshold for Edge Poloidal Flow Generation

    NASA Astrophysics Data System (ADS)

    Daniels, N.; Ware, A. S.; Newman, D. E.; Hidalgo, C.

    2004-11-01

    A numerical transport model is used to examine a density threshold for the onset of an edge poloidal velocity shear layer in toroidal devices. This work is motivated by recent experimental results from the TJ-II stellarator which indicate a critical density threshold for the development of an edge poloidal velocity shear layer [1]. Edge shear-flow layers are commonly observed in toroidal confinement devices, even in L-mode discharges. The numerical transport model has been used to examine internal transport barriers and front propagation of internal transport barriers [2]. The transport model couples together density, ion temperature, electron temperature, poloidal flow, toroidal flow, radial electric field, and a fluctuation envelope equation which includes a shear-suppression factor. In this work, we present results from a series of cases using parameters that are typical of TJ-II discharges. The dependence of the critical density threshold on flow damping and Reynolds stress drive is investigated. [1] C. Hidalgo, M. A. Pedrosa, L. Garcia, and A. Ware, "Direct experimental evidence of coupling between sheared flows development and increasing in level of turbulence in the TJ-II stellarator", submitted to Phys. Rev. E. [2] D. E. Newman, B. A. Carreras, D. Lopez-Bruna, P. H. Diamond, and V. B. Lebedev, Phys. Plasmas 5, 938 (1998).

  5. Large eddy simulation of trailing edge noise

    NASA Astrophysics Data System (ADS)

    Keller, Jacob; Nitzkorski, Zane; Mahesh, Krishnan

    2015-11-01

    Noise generation is an important engineering constraint to many marine vehicles. A significant portion of the noise comes from propellers and rotors, specifically due to flow interactions at the trailing edge. Large eddy simulation is used to investigate the noise produced by a turbulent 45 degree beveled trailing edge and a NACA 0012 airfoil. A porous surface Ffowcs-Williams and Hawkings acoustic analogy is combined with a dynamic endcapping method to compute the sound. This methodology allows for the impact of incident flow noise versus the total noise to be assessed. LES results for the 45 degree beveled trailing edge are compared to experiment at M = 0 . 1 and Rec = 1 . 9 e 6 . The effect of boundary layer thickness on sound production is investigated by computing using both the experimental boundary layer thickness and a thinner boundary layer. Direct numerical simulation results of the NACA 0012 are compared to available data at M = 0 . 4 and Rec = 5 . 0 e 4 for both the hydrodynamic field and the acoustic field. Sound intensities and directivities are investigated and compared. Finally, some of the physical mechanisms of far-field noise generation, common to the two configurations, are discussed. Supported by Office of Naval research.

  6. Resource distribution influences positive edge effects in a seagrass fish.

    PubMed

    Macreadie, Peter I; Hindell, Jeremy S; Keough, Michael J; Jenkins, Gregory P; Connolly, Rod M

    2010-07-01

    According to conceptual models, the distribution of resources plays a critical role in determining how organisms distribute themselves near habitat edges. These models are frequently used to achieve a mechanistic understanding of edge effects, but because they are based predominantly on correlative studies, there is need for a demonstration of causality, which is best done through experimentation. Using artificial seagrass habitat as an experimental system, we determined a likely mechanism underpinning edge effects in a seagrass fish. To test for edge effects, we measured fish abundance at edges (0-0.5 m) and interiors (0.5-1 m) of two patch configurations: continuous (single, continuous 9-m2 patches) and patchy (four discrete 1-m2 patches within a 9-m2 area). In continuous configurations, pipefish (Stigmatopora argus) were three times more abundant at edges than interiors (positive edge effect), but in patchy configurations there was no difference. The lack of edge effect in patchy configurations might be because patchy seagrass consisted entirely of edge habitat. We then used two approaches to test whether observed edge effects in continuous configurations were caused by increased availability of food at edges. First, we estimated the abundance of the major prey of pipefish, small crustaceans, across continuous seagrass configurations. Crustacean abundances were highest at seagrass edges, where they were 16% greater than in patch interiors. Second, we supplemented interiors of continuous treatment patches with live crustaceans, while control patches were supplemented with seawater. After five hours of supplementation, numbers of pipefish were similar between edges and interiors of treatment patches, while the strong edge effects were maintained in controls. This indicated that fish were moving from patch edges to interiors in response to food supplementation. These approaches strongly suggest that a numerically dominant fish species is more abundant at seagrass

  7. Emergent properties of patch shapes affect edge permeability to animals.

    PubMed

    Nams, Vilis O

    2011-01-01

    Animal travel between habitat patches affects populations, communities and ecosystems. There are three levels of organization of edge properties, and each of these can affect animals. At the lowest level are the different habitats on each side of an edge, then there is the edge itself, and finally, at the highest level of organization, is the geometry or structure of the edge. This study used computer simulations to (1) find out whether effects of edge shapes on animal behavior can arise as emergent properties solely due to reactions to edges in general, without the animals reacting to the shapes of the edges, and to (2) generate predictions to allow field and experimental studies to test mechanisms of edge shape response. Individual animals were modeled traveling inside a habitat patch that had different kinds of edge shapes (convex, concave and straight). When animals responded edges of patches, this created an emergent property of responding to the shape of the edge. The response was mostly to absolute width of the shapes, and not the narrowness of them. When animals were attracted to edges, then they tended to collect in convexities and disperse from concavities, and the opposite happened when animals avoided edges. Most of the responses occurred within a distance of 40% of the perceptual range from the tip of the shapes. Predictions were produced for directionality at various locations and combinations of treatments, to be used for testing edge behavior mechanisms. These results suggest that edge shapes tend to either concentrate or disperse animals, simply because the animals are either attracted to or avoid edges, with an effect as great as 3 times the normal density. Thus edge shape could affect processes like pollination, seed predation and dispersal and predator abundance.

  8. Local structural effects in Sr3NiRhO6 across magnetic transitions

    DOE PAGES

    Singh, Navneet; Khalid, S.; Bindu, R.

    2016-04-06

    Here, we investigate the temperature dependence of the structural parameters of quasi-one-dimensional Sr3NiRhO6 across the region of magnetic phase transitions using Ni K-edge and Sr K-edge x-ray absorption spectroscopy (XAS). The features in the x-ray absorption near-edge region are identified using multiple scattering calculations. The temperature-dependent extended x-ray absorption fine structure (EXAFS) studies show that the setting of the intra-chain super exchange interaction starts at ~200 K, which is well above the first transition temperature (45 K) revealed by magnetic susceptibility studies. The onset of the inter-chain super–super exchange interaction appears to be at ~125 K. Interestingly, the role playedmore » by direct exchange interaction between the Ni 3d and Rh 4d states in stabilising the magnetic interaction is less significant. The present results shed light on the generic features exhibited by isostructural compounds and may help in identifying the magnetic exchange pathways useful for understanding the unusual properties exhibited by such compounds.« less

  9. Electron energy loss spectroscopy of the L2,3 edge of phosphorus skutterudites and electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Sæterli, Ragnhild; Flage-Larsen, Espen; Prytz, Øystein; Taftø, Johan; Marthinsen, Knut; Holmestad, Randi

    2009-08-01

    In this study we report the results of experiments and theoretical calculations on the phosphorus L2,3 edges of the skutterudites CoP3 , LaFe4P12 , NiP3 , RhP3 , and IrP3 . Phosphorus s and d density of states above the Fermi level was studied by transmission electron energy loss spectroscopy while theoretical calculations were performed using both a real-space multiple-scattering procedure and density-functional theory. Generally, there are good agreements between both types of calculations and the experimental results. The near-edge structure of all the examined compounds shows the same overall features, including the metallic NiP3 and the metallic filled skutterudite LaFeP12 , and is well explained by comparison to phosphorus density of states. We also discuss the similarities to previously reported results on SiL2,3 edges and interpret the differences of the various skutterudites in terms of the electronegativities of the involved atom species.

  10. Eutectic superalloys by edge-defined, film-fed growth

    NASA Technical Reports Server (NTRS)

    Hurley, G. F.

    1975-01-01

    The feasibility of producing directionally solidified eutectic alloy composites by edge-defined, film-fed growth (EFG) was carried out. The three eutectic alloys which were investigated were gamma + delta, gamma/gamma prime + delta, and a Co-base TaC alloy containing Cr and Ni. Investigations into the compatibility and wettability of these metals with various carbides, borides, nitrides, and oxides disclosed that compounds with the largest (negative) heats of formation were most stable but poorest wetting. Nitrides and carbides had suitable stability and low contact angles but capillary rise was observed only with carbides. Oxides would not give capillary rise but would probably fulfill the other wetting requirements of EFG. Tantalum carbide was selected for most of the experimental portion of the program based on its exhibiting spontaneous capillary rise and satisfactory slow rate of degradation in the liquid metals. Samples of all three alloys were grown by EFG with the major experimental effort restricted to gamma + delta and gamma/gamma prime + delta alloys. In the standard, uncooled EFG apparatus, the thermal gradient was inferred from the growth speed and was 150 to 200 C/cm. This value may be compared to typical gradients of less than 100 C/cm normally achieved in a standard Bridgman-type apparatus. When a stream of helium was directed against the side of the bar during growth, the gradient was found to improve to about 250 C/cm. In comparison, a theoretical gradient of 700 C/cm should be possible under ideal conditions, without the use of chills. Methods for optimizing the gradient in EFG are discussed, and should allow attainment of close to the theoretical for a particular configuration.

  11. Urbanization impacts on mammals across urban-forest edges and a predictive model of edge effects.

    PubMed

    Villaseñor, Nélida R; Driscoll, Don A; Escobar, Martín A H; Gibbons, Philip; Lindenmayer, David B

    2014-01-01

    With accelerating rates of urbanization worldwide, a better understanding of ecological processes at the wildland-urban interface is critical to conserve biodiversity. We explored the effects of high and low-density housing developments on forest-dwelling mammals. Based on habitat characteristics, we expected a gradual decline in species abundance across forest-urban edges and an increased decline rate in higher contrast edges. We surveyed arboreal mammals in sites of high and low housing density along 600 m transects that spanned urban areas and areas turn on adjacent native forest. We also surveyed forest controls to test whether edge effects extended beyond our edge transects. We fitted models describing richness, total abundance and individual species abundance. Low-density housing developments provided suitable habitat for most arboreal mammals. In contrast, high-density housing developments had lower species richness, total abundance and individual species abundance, but supported the highest abundances of an urban adapter (Trichosurus vulpecula). We did not find the predicted gradual decline in species abundance. Of four species analysed, three exhibited no response to the proximity of urban boundaries, but spilled over into adjacent urban habitat to differing extents. One species (Petaurus australis) had an extended negative response to urban boundaries, suggesting that urban development has impacts beyond 300 m into adjacent forest. Our empirical work demonstrates that high-density housing developments have negative effects on both community and species level responses, except for one urban adapter. We developed a new predictive model of edge effects based on our results and the literature. To predict animal responses across edges, our framework integrates for first time: (1) habitat quality/preference, (2) species response with the proximity to the adjacent habitat, and (3) spillover extent/sensitivity to adjacent habitat boundaries. This framework will

  12. Ni-doped La0.5Sr0.5TiO3 nanofibers: Fabrication and intrinsic ferromagnetism

    NASA Astrophysics Data System (ADS)

    Ponhan, Wichaid; Amornkitbamrung, Vittaya; Maensiri, Santi

    2016-06-01

    We report room-temperature ferromagnetism in ˜104-133 nm nanofibers of La0.5Sr0.5Ti1- x Ni x O3 (0.02 ≤ x ≤ 0.05). As-spun nanofibers of La0.5Sr0.5Ti1- x Ni x O3 are fabricated by an electrospinning technique. Nanofibers of the as spun and calcined La0.5Sr0.5Ti1- x Ni x O3 samples are characterized using X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), X-ray absorption near edge structure (XANES) determination, and vibrating sample magnetometry (VSM). The results of XRD analysis and TEM together with selected electron diffraction (SEAD) analysis indicate that La0.5Sr0.5Ti1- x Ni x O3 nanofibers have a cubic perovskite structure with no secondary phase. The as-spun samples are paramagnetic, whereas the La0.5Sr0.5Ti1- x Ni x O3 samples are ferromagnetic having specific magnetizations of 0.098-0.484 emu/g at 10 kOe. The XPS spectra show that there are some oxygen vacancies in the nanofibers, which its may play an important role in inducing room-temperature ferromagnetism in La0.5Sr0.5Ti1- x Ni x O3 nanofibers. XANES spectra show that most of the Ni ions in La0.5Sr0.5Ti1- x Ni x O3 nanofibers are in the Ni2+ state mixed with some Ni metal. The finding of room temperature ferromagnetism in this nanofibrous structure of the La0.5Sr0.5Ti1- x Ni x O3 system is of interest in research on diluted magnetic oxides.

  13. Method for encapsulating the edge of a flexible sheet

    SciTech Connect

    Keenihan, James R; Clarey, Todd M

    2013-02-19

    The present invention is premised upon an inventive method of producing an over-molded edge portion on a flexible substrate, wherein the edge portion is void of open areas due to support devices in the mold cavity.

  14. Edge State and Intrinsic Hole Doping in Bilayer Phosphorene

    NASA Astrophysics Data System (ADS)

    Osada, Toshihito

    2015-01-01

    Using a simple LCAO model by Harrison, we have qualitatively studied the edge state of bilayer phosphorene, which is a unit structure of the layered crystal of black phosphorus. This model successfully reproduces the isolated edge state in the bulk gap in monolayer phosphorene. In bilayer phosphorene, however, it shows that edge states are almost buried in the valence band and there is no isolated midgap edge state at the zigzag edge. Since the buried edge state works as acceptor, holes are doped from the edge state into the bulk. This gives a possible explanation for p-type conduction in undoped black phosphorus. Under the vertical electric field, the intrinsic hole doping is reduced because a part of edge states move into the gap. These features of bilayer phosphorene might be better suited for device application.

  15. Research on reducing the edge effect in magnetorheological finishing.

    PubMed

    Hu, Hao; Dai, Yifan; Peng, Xiaoqiang; Wang, Jianmin

    2011-03-20

    The edge effect could not be avoided in most optical manufacturing methods based on the theory of computer controlled optical surfacing. The difference between the removal function at the workpiece edge and that inside it is also the primary cause for edge effect in magnetorheological finishing (MRF). The change of physical dimension and removal ratio of the removal function is investigated through experiments. The results demonstrate that the situation is different when MRF "spot" is at the leading edge or at the trailing edge. Two methods for reducing the edge effect are put into practice after analysis of the processing results. One is adopting a small removal function for dealing with the workpiece edge, and the other is utilizing the removal function compensation. The actual processing results show that these two ways are both effective on reducing the edge effect in MRF.

  16. Investigation of Edge Effects in Thermoacoustic Couple Measurements

    DTIC Science & Technology

    1990-12-01

    22 Ill. RESULTS AND DISCUSSION -- 24 A. EDGE EFFECT ........................................................................................... 24...investigate the extent to which irregularities in the temperature difference extend into the plate interior. A. EDGE EFFECT We constructed a TAC (TAC#1) with

  17. Comparison of edges detected at different polarisations in MAESTRO data

    NASA Technical Reports Server (NTRS)

    Caves, Ronald G.; Harley, Peter J.; Quegan, Shaun

    1992-01-01

    Edge detection would appear to be a crucial tool for analyzing multi-polarized, multi-frequency, and multi-temporal Synthetic Aperture Radar (SAR) images. Edge structure provides a simple means for comparing different polarizations and frequencies, and for detecting changes over time. Due to the fact that edges and segments (homogeneous regions) are dual concepts, edge detection has an important role to play in identifying segments within which mean backscatter measurements for use in image classification can be made. As part of a general investigation into edge detection in SAR imagery, an initial investigation was carried out into the detectability and nature of edges in multi-polarized and multi-frequency SAR images. The contrast ratio (CR) operator was used to detect edges. This operator was previously shown to perform well at detecting edges in single-polarized and single-frequency SAR images.

  18. Universal edge bands induced by linearly polarized irradiation on phosphorene

    NASA Astrophysics Data System (ADS)

    Yang, Mou; Zhang, Wen-Lian; Cai, Zhi-Jun; Wang, Rui-Qiang; Bai, Yan-Kui

    2017-01-01

    Phosphorene (a monolayer of black phosphorus) is a large gap semiconductor with high mobility and has great application potential. Numerical calculations reveal that phosphorene is a topologically trivial material and can only host edge bands on specified edges such as the zigzag edge. A linearly polarized irradiation on the phosphorene lattice results in the dynamic gaps in the quasi-energy spectrum. We found that the irradiation polarized in the zigzag direction induces new edge bands within the dynamic gaps on any type of edge (zigzag, armchair, or other bearded edge). We proposed a new gauge independent quantity, δ +g, to account for the appearence of universal edge bands, where δ is the detune and g is the light induced valence-conduction band transition element. The number of edge bands in the dynamic gaps is reflected by the winding number of it.

  19. Spectral studies on sulfur poisoning of Pd/Mg6Ni by NEXAFS and XPS

    NASA Astrophysics Data System (ADS)

    Yagi, S.; Nambu, M.; Tsukada, C.; Ogawa, S.; Kutluk, G.; Namatame, H.; Taniguchi, M.

    2013-02-01

    We have studied on the hydrogen storage materials based on Mg-Ni alloy and fabricated the sample constructed with the Pd thin layer (TL) on Mg6Ni alloy substrate. The adsorption behavior of the dimethyl disulfide (DMS) molecules on the sample has been measured to reveal the sulfur poisoning of the Pd TL/Mg6Ni by means of XPS and Sulfur K-edge NEXAFS techniques. The chemisorbed DMS, methanethiolate (MT) and atomic S have been observed on the surface. Especially, it is clear that some atomic S has been oxidized by air and detected the adsorbate of the SO32- and SO42- species. During exposure to the atmosphere, most of the adsorbed DMS and MT adsorbates desorb from the Pd TL surface. We thus conclude the Pd TL might be able to prevent the hydrogen storage materials from the sulfur poisoning.

  20. Oxide/metal interface distance and epitaxial strain in the NiO/Ag(001) system.

    PubMed

    Lamberti, Carlo; Groppo, Elena; Prestipino, Carmelo; Casassa, Silvia; Ferrari, Anna Maria; Pisani, Cesare; Giovanardi, Chiara; Luches, Paola; Valeri, Sergio; Boscherini, Federico

    2003-07-25

    Geometric parameters of NiO films epitaxially grown on Ag(001) were determined using two independent experimental techniques and ab initio simulations. Primary beam diffraction modulated electron emission experiments determined that the NiO films grow with O on top of Ag and that the oxide/metal interface distance is d=2.3+/-0.1 A. Polarization-dependent x-ray absorption, at the Ni-K edge, determined the tetragonal strain (r( parallel )=2.046+/-0.009 A, r( perpendicular )=2.12+/-0.02 A) and d=2.37+/-0.05 A. Periodic slab model results agree with the experiments (d=2.40, r( parallel )=2.07, r( perpendicular )=2.10 A; the O-on-top configuration is the most stable).

  1. Oxide/Metal Interface Distance and Epitaxial Strain in the NiO/Ag(001) System

    NASA Astrophysics Data System (ADS)

    Lamberti, Carlo; Groppo, Elena; Prestipino, Carmelo; Casassa, Silvia; Ferrari, Anna; Pisani, Cesare; Giovanardi, Chiara; Luches, Paola; Valeri, Sergio; Boscherini, Federico

    2003-07-01

    Geometric parameters of NiO films epitaxially grown on Ag(001) were determined using two independent experimental techniques and abinitio simulations. Primary beam diffraction modulated electron emission experiments determined that the NiO films grow with O on top of Ag and that the oxide/metal interface distance is d=2.3±0.1 Å. Polarization-dependent x-ray absorption, at the Ni-K edge, determined the tetragonal strain (r∥=2.046±0.009 Å, r⊥=2.12±0.02 Å) and d=2.37±0.05 Å. Periodic slab model results agree with the experiments (d=2.40, r∥=2.07, r⊥=2.10 Å; the O-on-top configuration is the most stable).

  2. Interactions of Oxygen and Ethylene with Submonolayer Ag Films Supported on Ni(111)

    SciTech Connect

    Alamgir, F.M.; Senanayake, S.; Rettew, R.E.; Meyer, A.; Chen, T.-L.; Petersburg, C.; Flege, J.I.; Falta, J.

    2011-06-01

    We investigate the oxidation of, and the reaction of ethylene with, Ni(111) with and without sub-monolayer Ag adlayers as a function of temperature. The addition of Ag to Ni(111) is shown to enhance the activity towards the ethylene epoxidation reaction, and increase the temperature at which ethylene oxide is stable on the surface. We present a systematic study of the formation of chemisorbed oxygen on the Ag-Ni(111) surfaces and correlate the presence and absence of O{sup 1-} and O{sup 2-} surface species with the reactivity towards ethylene. By characterizing the samples with low-energy electron microscopy (LEEM) in combination with X-ray photoelectron spectroscopy (XPS), we have identified specific growth of silver on step-edge sites and successfully increased the temperature at which the produced ethylene oxide remains stable, a trait which is desirable for catalysis.

  3. Interactions of Oxygen and Ethylene with Submonolayer Ag Films Supported on Ni(111)

    SciTech Connect

    R Rettew; A Meyer; S Senanayake; T Chen; C Petersburg; J Flege; J Falta; F Alamgir

    2011-12-31

    We investigate the oxidation of, and the reaction of ethylene with, Ni(111) with and without sub-monolayer Ag adlayers as a function of temperature. The addition of Ag to Ni(111) is shown to enhance the activity towards the ethylene epoxidation reaction, and increase the temperature at which ethylene oxide is stable on the surface. We present a systematic study of the formation of chemisorbed oxygen on the Ag-Ni(111) surfaces and correlate the presence and absence of O{sup 1-} and O{sup 2-} surface species with the reactivity towards ethylene. By characterizing the samples with low-energy electron microscopy (LEEM) in combination with X-ray photoelectron spectroscopy (XPS), we have identified specific growth of silver on step-edge sites and successfully increased the temperature at which the produced ethylene oxide remains stable, a trait which is desirable for catalysis.

  4. Abnormal Intermetallic Compound Evolution in Ni/Sn/Ni and Ni/Sn-9Zn/Ni Micro Solder Joints Under Thermomigration

    NASA Astrophysics Data System (ADS)

    Zhao, N.; Deng, J. F.; Zhong, Y.; Huang, M. L.; Ma, H. T.

    2017-04-01

    Interfacial reactions in Ni/Sn/Ni and Ni/Sn-9Zn/Ni micro solder joints during thermomigration (TM) have been studied by reflowing solder joints on a hot plate. Asymmetrical growth and transformation of interfacial intermetallic compounds (IMCs) were clearly observed. The growth of the Ni3Sn4 IMC in the Ni/Sn/Ni solder joints was always fast at the cold end and relatively slow at the hot end. Only asymmetrical growth of the Ni5Zn21 IMC in the Ni/Sn-9Zn/Ni solder joints occurred at the beginning because Zn was the dominant TM species; however, asymmetrical transformation of the Ni5Zn21 IMC also occurred under the combined effect of Zn depletion and Ni dissolution and migration, resulting in formation of a thin τ-phase layer at the hot end and a thick τ-phase/Ni5Zn21/τ-phase sandwich structure at the cold end. TM of Ni and Zn atoms was identified towards the cold end, being responsible for the abnormal IMC evolution. Addition of Zn was found to slow the TM-induced IMC growth and Ni dissolution.

  5. Opposite effects of Cu and Pt atoms on graphene edges

    NASA Astrophysics Data System (ADS)

    Kano, Emi; Hashimoto, Ayako; Takeguchi, Masaki

    2017-02-01

    Metal atoms at graphene edges are important because they can modify the structure and properties of graphene; however, there are very few reports on their direct observation. We performed electron microscopy to investigate the stability and dynamics of Cu and Pt atoms at graphene edges. We found that Cu atoms mended graphene edges, while Pt atoms etched them, and these transformations were promoted by electron irradiation. Cu and Pt atoms formed different atomic configurations at graphene edges.

  6. Edge energies : atomistic calculations of a continuum quantity.

    SciTech Connect

    Hamilton, John C.

    2005-06-01

    Controlling the properties of self-assembled nanostructures requires controlling their shape. Size-dependent shape transitions, frequently observed at nanolength scales, are commonly attributed to edge energy effects. To rigorously test such theories against experiment, quantitative atomistic calculations of edge energies are essential, yet none exist. I describe a fundamental ambiguity in the atomistic definition of edge energies, propose a definition based on equimolar dividing surfaces, and present an atomistic calculation of edge energies for Pd clusters.

  7. Optical knife-edge technique for nanomechanical displacement detection

    SciTech Connect

    Karabacak, D.; Kouh, T.; Huang, C.C.; Ekinci, K.L.

    2006-05-08

    We describe an optical knife-edge technique for nanomechanical displacement detection. Here, one carefully focuses a laser spot on a moving edge and monitors the reflected power as the edge is displaced sideways. To demonstrate nanomechanical displacement detection using the knife-edge technique, we have measured in-plane resonances of nanometer scale doubly clamped beams. The obtained displacement sensitivity is in the {approx}1 pm/{radical}(Hz) range--in close agreement with a simple analytical model.

  8. Amount of Forest Edge at a 65 Hectare Scale

    EPA Pesticide Factsheets

    Forests provide economic and ecological value. High amounts of forest edge indicates a highly fragmented forest, which generally diminishes those economic and ecological values. EDGE65 is the percent of forest that is classified as edge using a 65 ha scale. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  9. Amount of Future Forest Edge at a 65 Hectare scale

    EPA Pesticide Factsheets

    Forests provide economic and ecological value. High amounts of forest edge indicates a highly fragmented forest, which generally diminishes those economic and ecological values. EDGE65 is the percent of forest that is classified as edge using a 65 ha scale. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  10. Amount of Forest Edge at a 2 Hectare Scale

    EPA Pesticide Factsheets

    Forests provide economic and ecological value. High amounts of forest edge indicates a highly fragmented forest, which generally diminishes those economic and ecological values. EDGE2 is the percent of forest that is classified as edge using a 2 ha scale. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  11. Amount of Future Forest Edge at a 2 Hectare Scale

    EPA Pesticide Factsheets

    Forests provide economic and ecological value. High amounts of forest edge indicates a highly fragmented forest, which generally diminishes those economic and ecological values. EDGE2 is the percent of forest that is classified as edge using a 2 ha scale. More information about these resources, including the variables used in this study, may be found here: https://edg.epa.gov/data/Public/ORD/NERL/ReVA/ReVA_Data.zip.

  12. Electrical properties and stoichiometry in La 2NiO 4

    NASA Astrophysics Data System (ADS)

    Sayer, M.; Odier, P.

    1987-03-01

    The electrical properties of La 2NiO 4 have been studied with respect to the stoichiometry of the material. The conductivity of reduced compositions has been measured between 20 and 1000 K and compared to that of the air-prepared ones. Nonstoichiometry is present in both cases and produces disorder leading to Anderson localization and to the definition of a mobility edge in the σx2- y2 itinerant band. Air-prepared compounds contain in addition a large number of Ni 3+ states which may overlap the itinerant σx2- y2 band. For reduced materials containing small amounts of Ni 3+, the electrical properties can be described below 200 K by a hopping conductivity at the Fermi level within a sharply peaked density of states. The results are well described within the frame of the Mott theory of variable range hopping. Above 200 K highly reduced materials exhibit direct excitation of holes from Ni 3+ states to the mobility edge in the itinerant band. Under conditions appropriate to air-prepared materials, the Fermi level is shifted toward the itinerant band and a major contribution to the conductivity arises from hopping at the Fermi level. At high temperature a progressive excitation of carriers from the localized states is anticipated with an eventual exhaustion region. This last assumption is corroborated with a shift of the conductivity maximum to higher temperature for increasingly reduced materials.

  13. Electron microscopy structure study of laser-clad TiC-Ni particle-reinforced coating

    SciTech Connect

    Ouyang, J.H.; Li, X.; Lei, T.C.

    2000-04-01

    The microstructure of a laser-clad TiC-Ni particle-reinforced coating on 1045 steel was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ion microprobe mass spectroscopy (IMMS). The microstructural constituents of the clad layers (CLs) were analyzed to be TiC particles, {gamma}-Ni primary dendrites, and interdendritic eutectics of {gamma}{sub E}-Ni plus M{sub 23}(CB){sub 6} and M{sub 6}(CB) carboborides. Three growth mechanisms of the original TiC particles were found: (1) stepped lateral growth at the edges, (2) radiated and cylindrically coupled growth at the edges, and (3) bridging growth of the clustered particles. Ordered and modulated structures were found in the original TiC particles. In addition to the original TiC particles, fine TiC particles precipitated from the liquid phase and {gamma}-Ni solid solution during laser cladding. The microstructures of the bonding zones (BZs) were intimately associated with laser processing parameters. The BZs of the clad coatings can be categorized into three types according to the combination of the CL with heat-affected zone (HAZ): (1) straight interface combination, (2) zigzag connection, and (3) combination by partial melting of prior austenitic grain boundaries of the substrate. The microstructural evolution of the CLs was discussed. The formation and phase transformation models of the BZs were proposed.

  14. Topological edge Mott insulating state in two dimensions at finite temperatures: Bulk and edge analysis

    NASA Astrophysics Data System (ADS)

    Yoshida, Tsuneya; Kawakami, Norio

    2016-08-01

    We study a bilayer Kane-Mele-Hubbard model with lattice distortion and interlayer spin exchange interaction under cylinder geometry. Our analysis based on real-space dynamical mean field theory with continuous-time quantum Monte Carlo demonstrates the emergence of a topological edge Mott insulating (TEMI) state which hosts gapless edge modes only in collective spin excitations. This is confirmed by the numerical calculations at finite temperatures for the spin-Hall conductivity and the single-particle excitation spectrum; the spin-Hall conductivity is almost quantized, σspinx y˜2 (e /2 π ) , predicting gapless edge modes carrying the spin current, while the helical edge modes in the single-particle spectrum are gapped out with respecting symmetry. It is clarified how the TEMI state evolves from the ordinary spin-Hall insulating state with increasing the Hubbard interaction at a given temperature and then undergoes a phase transition to a trivial Mott insulating state. With a bosonization approach at zero temperature, we further address which collective modes host gapless edge modes in the TEMI state.

  15. Measurement of 59Ni and 63Ni by accelerator mass spectrometry at CIAE

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoming; He, Ming; Ruan, Xiangdong; Xu, Yongning; Shen, Hongtao; Du, Liang; Xiao, Caijin; Dong, Kejun; Jiang, Shan; Yang, Xuran; Lan, Xiaoxi; Wu, Shaoyong; Zhao, Qingzhang; Cai, Li; Pang, Fangfang

    2015-10-01

    The long lived isotopes 59Ni and 63Ni can be used in many areas such as radioactive waste management, neutron dosimetry, cosmic radiation study, and so on. Based on the large accelerator and a big Q3D magnetic spectrometer, the measurement method for 59Ni and 63Ni is under development at the AMS facility at China Institute of Atomic Energy (CIAE). By using the ΔE-Q3D technique with the Q3D magnetic spectrometer, the isobaric interferences were greatly reduced in the measurements of 59Ni and 63Ni. A four anode gas ionization chamber was then used to further identify isobars. With these techniques, the abundance sensitivities of 59Ni and 63Ni measurements are determined as 59Ni/Ni = 1 × 10-13 and 63Ni/Ni = 2 × 10-12, respectively.

  16. Electrical upsetting of metal sheet forms weld edge

    NASA Technical Reports Server (NTRS)

    Scherba, E. S.

    1966-01-01

    Electric gathering of sheet stock edges forms metal sheets in the shape of gore sections with heavier edge areas that can be welded without loss of strength. The edges are gathered by progressive resistance heating and upsetting, and are formed automatically. This process avoids disturbance of the metals internal structure.

  17. 16 CFR 1211.12 - Requirements for edge sensors.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... of an edge sensor shall function as intended when subjected to: (i) Accelerated Aging Test of Gaskets... Requirements for edge sensors. (a) Normal operation test. (1) When installed on a representative door edge, an... direction perpendicular to the plane of the door. See figure 6. (2) With respect to the test of paragraph...

  18. 16 CFR 1211.12 - Requirements for edge sensors.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... of an edge sensor shall function as intended when subjected to: (i) Accelerated Aging Test of Gaskets... Requirements for edge sensors. (a) Normal operation test. (1) When installed on a representative door edge, an... direction perpendicular to the plane of the door. See figure 6. (2) With respect to the test of paragraph...

  19. 16 CFR 1211.12 - Requirements for edge sensors.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... of an edge sensor shall function as intended when subjected to: (i) Accelerated Aging Test of Gaskets... Requirements for edge sensors. (a) Normal operation test. (1) When installed on a representative door edge, an... direction perpendicular to the plane of the door. See figure 6. (2) With respect to the test of paragraph...

  20. 16 CFR 1211.12 - Requirements for edge sensors.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... of an edge sensor shall function as intended when subjected to: (i) Accelerated Aging Test of Gaskets... Requirements for edge sensors. (a) Normal operation test. (1) When installed on a representative door edge, an... direction perpendicular to the plane of the door. See figure 6. (2) With respect to the test of paragraph...

  1. Improved method of edge coating flat ribbon wire

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Method to coat the edges of flat ribbon wire is devised by using enamel with modified flow properties due to addition of 2 to 4 percent silicon. Conventional coating procedes several edge coatings to minimize oxidation and additional conventional coats are applied after edge coating to build up thickness.

  2. Uniform line integral representation of edge-diffracted fields.

    PubMed

    Umul, Yusuf Z

    2008-01-01

    A uniform line integral representation is derived for edge-diffracted fields by using the modified theory of physical optics and uniform asymptotic evaluation methods. The method is applied to the problem of diffraction of plane waves by a semi-infinite edge, which creates tip-diffracted fields with edge-diffracted waves. The uniform diffracted fields are plotted and examined numerically.

  3. Edge-based correlation image registration for multispectral imaging

    DOEpatents

    Nandy, Prabal

    2009-11-17

    Registration information for images of a common target obtained from a plurality of different spectral bands can be obtained by combining edge detection and phase correlation. The images are edge-filtered, and pairs of the edge-filtered images are then phase correlated to produce phase correlation images. The registration information can be determined based on these phase correlation images.

  4. Method of forming densified edge seals for fuel cell components

    DOEpatents

    DeCasperis, Anthony J.; Roethlein, Richard J.; Breault, Richard D.

    1981-01-01

    A porous fuel cell component, such as an electrode substrate, has a densified edge which forms an improved gas seal during operation when soaked with electrolyte. The edges are made from the same composition as the rest of the component and are made by compressing an increased thickness of this material along the edges during the fabrication process.

  5. Shashkov`s method retaining cell-edge unknowns

    SciTech Connect

    Roberts, R.M.

    1996-01-05

    Shashkov`s method for scalar cell-edge and cell-center variables is derived. Dot products for cell-edge vectors are computed for a corner of the cell. Next, the divergence and gradient are discretized. The diffusion equation is solved with cell-edge continuity and boundary conditions. A symmetric positive definite solution matrix is proven.

  6. Education Confronts Changing Demographics. The Challenge to Edge Cities.

    ERIC Educational Resources Information Center

    Tushnet, Naida C.

    This monograph introduces a conference addressing the educational issues of the edge cities of the urban Pacific Southwest. Edge cities on the outside of urban cores (edge cities) are currently facing many of the problems formerly experienced only in urban areas. Of the 30 fastest-growing cities of over 100,000 residents in the country, 19 are…

  7. Growth mode of carbide from C 2H 4 or CO on Ni( 1 1 1 )

    NASA Astrophysics Data System (ADS)

    Nakano, H.; Ogawa, J.; Nakamura, J.

    2002-08-01

    The growth of carbide on a Ni(1 1 1) surface by the decomposition of C 2H 4 and the Boudouard reaction (2CO g→C a+CO 2,g) was studied using scanning tunneling microscopy (STM), Auger electron spectroscopy and low energy electron diffraction. STM results showed that the carbide growth by the Boudouard reaction started at step edges on Ni(1 1 1), while for the C 2H 4 decomposition the carbide was formed preferentially at terrace sites with very low concentration of carbide at the step edge. The different behavior for the carbide growth was ascribed to the difference in the dissociation sites of CO and C 2H 4. As for the Boudouard reaction, CO was dissociated at the step edge and then carbon migrated into the bulk at a reaction temperature of 500 K. The carbon was then segregated at room temperature to the surface from the bulk to form a single domain of the ( 39× 39) R16.1° structure at the step edge. On the other hand, the C 2H 4 decomposition took place on the terrace leading to an isolated carbide unit or carbide short strings on the terrace.

  8. Orbital engineering near La2 NiO 4- La2 CuO 4 superlattice interfaces

    NASA Astrophysics Data System (ADS)

    Smadici, S.; Lee, J. C. T.; Morales, J.; Abbamonte, P.; Logvenov, G.; Gozar, A.; Bozovic, I.

    2011-03-01

    Orbital states of transition metal oxides present the opportunity of adjusting material properties to a specific purpose (orbital engineering). A comparison of the resonant soft x-ray reflectivity of La 2 Ni O4 - La 2 Cu O4 superlattices at Ni L and Cu L edges shows different spatial distributions of the occupation of Ni d x 2 -y 2 and d 3z 2 -r 2 orbitals in the LNO layers. This modulation of the Ni valence is possible through a pronounced modulation of the density of oxygen interstitial dopants within the structure which does not follow exactly the structure itself. This is the first observation of orbital engineering in a 214 oxide. This work was supported by Grants DE-FG02-06ER46285, DE-AC02-98CH10886, MA-509-MACA, DE-FG02-07ER46453 and DE-FG02-07ER46471.

  9. Accessing Ni(III)-thiolate versus Ni(II)-thiyl bonding in a family of Ni-N2S2 synthetic models of NiSOD.

    PubMed

    Broering, Ellen P; Dillon, Stephanie; Gale, Eric M; Steiner, Ramsey A; Telser, Joshua; Brunold, Thomas C; Harrop, Todd C

    2015-04-20

    Superoxide dismutase (SOD) catalyzes the disproportionation of superoxide (O2(• -)) into H2O2 and O2(g) by toggling through different oxidation states of a first-row transition metal ion at its active site. Ni-containing SODs (NiSODs) are a distinct class of this family of metalloenzymes due to the unusual coordination sphere that is comprised of mixed N/S-ligands from peptide-N and cysteine-S donor atoms. A central goal of our research is to understand the factors that govern reactive oxygen species (ROS) stability of the Ni-S(Cys) bond in NiSOD utilizing a synthetic model approach. In light of the reactivity of metal-coordinated thiolates to ROS, several hypotheses have been proffered and include the coordination of His1-Nδ to the Ni(II) and Ni(III) forms of NiSOD, as well as hydrogen bonding or full protonation of a coordinated S(Cys). In this work, we present NiSOD analogues of the general formula [Ni(N2S)(SR')](-), providing a variable location (SR' = aryl thiolate) in the N2S2 basal plane coordination sphere where we have introduced o-amino and/or electron-withdrawing groups to intercept an oxidized Ni species. The synthesis, structure, and properties of the NiSOD model complexes (Et4N)[Ni(nmp)(SPh-o-NH2)] (2), (Et4N)[Ni(nmp)(SPh-o-NH2-p-CF3)] (3), (Et4N)[Ni(nmp)(SPh-p-NH2)] (4), and (Et4N)[Ni(nmp)(SPh-p-CF3)] (5) (nmp(2-) = dianion of N-(2-mercaptoethyl)picolinamide) are reported. NiSOD model complexes with amino groups positioned ortho to the aryl-S in SR' (2 and 3) afford oxidized species (2(ox) and 3(ox)) that are best described as a resonance hybrid between Ni(III)-SR and Ni(II)-(•)SR based on ultraviolet-visible (UV-vis), magnetic circular dichroism (MCD), and electron paramagnetic resonance (EPR) spectroscopies, as well as density functional theory (DFT) calculations. The results presented here, demonstrating the high percentage of S(3p) character in the highest occupied molecular orbital (HOMO) of the four-coordinate reduced form of NiSOD (Ni

  10. Edge responses are different in edges under natural versus anthropogenic influence: a meta-analysis using ground beetles.

    PubMed

    Magura, Tibor; Lövei, Gábor L; Tóthmérész, Béla

    2017-02-01

    Most edges are anthropogenic in origin, but are distinguishable by their maintaining processes (natural vs. continued anthropogenic interventions: forestry, agriculture, urbanization). We hypothesized that the dissimilar edge histories will be reflected in the diversity and assemblage composition of inhabitants. Testing this "history-based edge effect" hypothesis, we evaluated published information on a common insect group, ground beetles (Coleoptera: Carabidae) in forest edges. A meta-analysis showed that the diversity-enhancing properties of edges significantly differed according to their history. Forest edges maintained by natural processes had significantly higher species richness than their interiors, while edges with continued anthropogenic influence did not. The filter function of edges was also essentially different depending on their history. For forest specialist species, edges maintained by natural processes were penetrable, allowing these species to move right through the edges, while edges still under anthropogenic interventions were impenetrable, preventing the dispersal of forest specialists out of the forest. For species inhabiting the surrounding matrix (open-habitat and generalist species), edges created by forestry activities were penetrable, and such species also invaded the forest interior. However, natural forest edges constituted a barrier and prevented the invasion of matrix species into the forest interior. Preserving and protecting all edges maintained by natural processes, and preventing anthropogenic changes to their structure, composition, and characteristics are key factors to sustain biodiversity in forests. Moreover, the increasing presence of anthropogenic edges in a landscape is to be avoided, as they contribute to the loss of biodiversity. Simultaneously, edges under continued anthropogenic disturbance should be restored by increasing habitat heterogeneity.

  11. Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

    PubMed

    Mani, Arjun; Benjamin, Colin

    2016-04-13

    On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible--the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.

  12. Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

    NASA Astrophysics Data System (ADS)

    Mani, Arjun; Benjamin, Colin

    2016-04-01

    On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible—the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.

  13. Kinetic effects in edge plasma: kinetic modeling for edge plasma and detached divertor

    NASA Astrophysics Data System (ADS)

    Takizuka, T.

    2017-03-01

    Detached divertor is considered a solution for the heat control in magnetic-confinement fusion reactors. Numerical simulations using the comprehensive divertor codes based on the plasma fluid modeling are indispensable for the design of the detached divertor in future reactors. Since the agreement in the results between detached-divertor experiments and simulations has been rather fair but not satisfactory, further improvement of the modeling is required. The kinetic effect is one of key issues for improving the modeling. Complete kinetic behaviors are able to be simulated by the kinetic modeling. In this paper at first, major kinetic effects in edge plasma and detached divertor are listed. One of the most powerful kinetic models, particle-in-cell (PIC) model, is described in detail. Several results of PIC simulations of edge-plasma kinetic natures are presented. Future works on PIC modeling and simulation for the deeper understanding of edge plasma and detached divertor are discussed.

  14. Climate Data Homogenization Using Edge Detection Algorithms

    NASA Astrophysics Data System (ADS)

    Hammann, A. C.; Rennermalm, A. K.

    2015-12-01

    The problem of climate data homogenization has predominantly been addressed by testing the likelihood of one or more breaks inserted into a given time series and modeling the mean to be stationary in between the breaks. We recast the same problem in a slightly different form: that of detecting step-like changes in noisy data, and observe that this problem has spawned a large number of approaches to its solution as the "edge detection" problem in image processing. With respect to climate data, we ask the question: How can we optimally separate step-like from smoothly-varying low-frequency signals? We study the hypothesis that the edge-detection approach makes better use of all information contained in the time series than the "traditional" approach (e.g. Caussinus and Mestre, 2004), which we base on several observations. 1) The traditional formulation of the problem reduces the available information from the outset to that contained in the test statistic. 2) The criterion of local steepness of the low-frequency variability, while at least hypothetically useful, is ignored. 3) The practice of using monthly data corresponds, mathematically, to applying a moving average filter (to reduce noise) and subsequent subsampling of the result; this subsampling reduces the amount of available information beyond what is necessary for noise reduction. Most importantly, the tradeoff between noise reduction (better with filters with wide support in the time domain) and localization of detected changes (better with filters with narrow support) is expressed in the well-known uncertainty principle and can be addressed optimally within a time-frequency framework. Unsurprisingly, a large number of edge-detection algorithms have been proposed that make use of wavelet decompositions and similar techniques. We are developing this framework in part to be applied to a particular set of climate data from Greenland; we will present results from this application as well as from tests with

  15. Edge ambipolar potential in toroidal fusion plasmas

    SciTech Connect

    Spizzo, G. Vianello, N.; Agostini, M.; Puiatti, M. E.; Scarin, P.; Spolaore, M.; Terranova, D.; White, R. B.; Abdullaev, S. S.; Schmitz, O.; Cavazzana, R.; Ciaccio, G.

    2014-05-15

    A series of issues with toroidally confined fusion plasmas are related to the generation of 3D flow patterns by means of edge magnetic islands, embedded in a chaotic field and interacting with the wall. These issues include the Greenwald limit in Tokamaks and reversed-field pinches, the collisionality window for ELM mitigation with the resonant magnetic perturbations (RMPs) in Tokamaks, and edge islands interacting with the bootstrap current in stellarators. Measurements of the 2D map of the edge electric field E{sup r}(r=a,θ,ϕ) in the RFX reversed-field pinch show that E{sup r} has the same helicity of the magnetic islands generated by a m/n perturbation: in fact, defining the helical angle u=mθ−nϕ+ωt, maps show a sinusoidal dependence as a function of u, E{sup r}=E{sup ~r}sin u. The associated E × B flow displays a huge convective cell with v(a)≠0 which, in RFX and near the Greenwald limit, determines a stagnation point for density and a reversal of the sign of E{sup r}. From a theoretical point of view, the question is how a perturbed toroidal flux of symmetry m/n gives rise to an ambipolar potential Φ=Φ{sup ~}sin u. On the basis of a model developed with the guiding center code ORBIT and applied to RFX and the TEXTOR tokamak, we will show that the presence of an m/n perturbation in any kind of device breaks the toroidal symmetry with a drift proportional to the gyroradius ρ, thus larger for ions (ρ{sub i} ≫ ρ{sub e}). Immediately, an ambipolar potential arises to balance the drifts, with the same symmetry as the original perturbation.

  16. Edge Simulation Laboratory Progress and Plans

    SciTech Connect

    Cohen, R

    2007-06-05

    The Edge Simulation Laboratory (ESL) is a project to develop a gyrokinetic code for MFE edge plasmas based on continuum (Eulerian) techniques. ESL is a base-program activity of OFES, with an allied algorithm research activity funded by the OASCR base math program. ESL OFES funds directly support about 0.8 FTE of career staff at LLNL, a postdoc and a small fraction of an FTE at GA, and a graduate student at UCSD. In addition the allied OASCR program funds about 1/2 FTE each in the computations directorates at LBNL and LLNL. OFES ESL funding for LLNL and UCSD began in fall 2005, while funding for GA and the math team began about a year ago. ESL's continuum approach is a complement to the PIC-based methods of the CPES Project, and was selected (1) because of concerns about noise issues associated with PIC in the high-density-contrast environment of the edge pedestal, (2) to be able to exploit advanced numerical methods developed for fluid codes, and (3) to build upon the successes of core continuum gyrokinetic codes such as GYRO, GS2 and GENE. The ESL project presently has three components: TEMPEST, a full-f, full-geometry (single-null divertor, or arbitrary-shape closed flux surfaces) code in E, {mu} (energy, magnetic-moment) coordinates; EGK, a simple-geometry rapid-prototype code, presently of; and the math component, which is developing and implementing algorithms for a next-generation code. Progress would be accelerated if we could find funding for a fourth, computer science, component, which would develop software infrastructure, provide user support, and address needs for data handing and analysis. We summarize the status and plans for the three funded activities.

  17. Compression and Tensile Creep of Binary NiAl

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.

    2005-01-01

    Compression creep and long term tensile creep studies were conducted on cast and extruded binary NiAl in the temperature range 700-1200 K with the objectives of characterizing and understanding the creep mechanisms. Inverse and normal primary creep curves were observed in both compression and tension creep depending on stress and temperature although an asymmetrical response was observed under these two stress states. It was concluded that the primary creep of NiAl is limited by dislocation mobility. The stress exponents, n, for compression and tensile creep were similar varying between about 5 and 14. However, there were significant differences in the stress dependence of the activation energies for compression and tensile creep. The true activation energy for tensile creep, Q(sub c), was constant and equal to about 400 kJ/mol between 20 and 50 MPa but decreased to a constant value of 250 kJ/mol between 50 and 110 MPa. The activation energy was observed to be inversely stress dependent above 110 MPa. In contrast, Q(sub c) = 300 kJ/mol for compression creep was constant between 25 and 70 MPa and inversely dependent on the true stress above 70 MPa. A detailed discussion of the probable dislocation creep mechanisms governing compressive and tensile creep of NiAl is presented. It is concluded that the non-conservative motion of jogs on screw dislocations influenced the nature of the primary creep curves, where the climb of these jogs involves either the next nearest neighbor or the six-jump cycle vacancy diffusion mechanism. The probable natures of the atom-vacancy exchange that occur within the core of an edge dislocation undergoing climb in NiAl are schematically examined.

  18. Hermetic edge sealing of photovoltaic modules

    NASA Technical Reports Server (NTRS)

    1983-01-01

    The edge sealing technique is accomplished by a combination of a chemical bond between glass and aluminum, formed by electrostatic bonding, and a metallurgical bond between aluminum and aluminum, formed by ultrasonic welding. Such a glass to metal seal promises to provide a low cost, long lifetime, highly effective hermetic seal which can protect module components from severe environments. Development of the sealing techniques and demonstration of their effectiveness by fabricating a small number of dummy modules, up to eight inches square in size, and testing them for hermeticity using helium leak testing methods are reviewed. Non-destructive test methods are investigated.

  19. Viscosity in the edge of tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Stacey, W. M.

    1993-05-01

    A fluid representation of viscosity has been incorporated into a set of fluid equations that are maximally ordered in the 'short radial gradient scale length' (srgsl) ordering that is appropriate for the edge of tokamak plasmas. The srgsl ordering raises viscous drifts and other viscous terms to leading order and fundamentally alters the character of the fluid equations. A leasing order viscous drift is identified. Viscous-driven radial particle and energy fluxes in the scrape-off layer and divertor channel are estimated to have an order unity effect in reducing radial peaking of energy fluxes transported along the field lines to divertor collector plates.

  20. Viscosity in the edge of tokamak plasmas

    SciTech Connect

    Stacey, W.M.

    1993-05-01

    A fluid representation of viscosity has been incorporated into a set of fluid equations that are maximally ordered in the ``short-radial-gradient-scale-length`` (srgsl) ordering that is appropriate for the edge of tokamak plasmas. The srgsl ordering raises viscous drifts and other viscous terms to leading order and fundamentally alters the character of the fluid equations. A leasing order viscous drift is identified. Viscous-driven radial particle and energy fluxes in the scrape-off layer and divertor channel are estimated to have an order unity effect in reducing radial peaking of energy fluxes transported along the field lines to divertor collector plates.

  1. The "edge effect" with patch test materials.

    PubMed

    Fyad, A; Masmoudi, M L; Lachapelle, J M

    1987-03-01

    A positive "edge effect", i.e., the accumulation on the skin of a chemical solution (such as fluorescein 0.01% in a 50/50 water-ethanol solution) at the periphery of the patch test sites has been demonstrated. It occurs with different test materials (Finn Chamber; Silver Patch Test; Patch Test Chamber). Practical implications are discussed: this observation could be important when discussing results of laboratory investigations. In clinical practice, it could explain the occurrence of "ring-shaped" positive allergic patch test reactions to chemicals used in solution, i.e., Kathon CG or hydrocortisone.

  2. Chiral Thermoelectrics with Quantum Hall Edge States

    NASA Astrophysics Data System (ADS)

    Sánchez, Rafael; Sothmann, Björn; Jordan, Andrew N.

    2015-04-01

    The thermoelectric properties of a three-terminal quantum Hall conductor are investigated. We identify a contribution to the thermoelectric response that relies on the chirality of the carrier motion rather than on spatial asymmetries. The Onsager matrix becomes maximally asymmetric with configurations where either the Seebeck or the Peltier coefficients are zero while the other one remains finite. Reversing the magnetic field direction exchanges these effects, which originate from the chiral nature of the quantum Hall edge states. The possibility to generate spin-polarized currents in quantum spin Hall samples is discussed.

  3. Large Format Transition Edge Sensor Microcalorimeter Arrays

    NASA Technical Reports Server (NTRS)

    Chervenak, J. A.; Adams, J. A.; Bandler, S. b.; Busch, S. E.; Eckart, M. E.; Ewin, A. E.; Finkbeiner, F. M.; Kilbourne, C. A.; Kelley, R. L.; Porst, J. P.; Porter, F. S.; Ray, C.; Sadleir, J. E.; Smith, S. J.; Wassell, E. J.

    2012-01-01

    We have produced a variety of superconducting transition edge sensor array designs for microcalorimetric detection of x-rays. Designs include kilopixel scale arrays of relatively small sensors (approximately 75 micron pitch) atop a thick metal heat sinking layer as well as arrays of membrane-isolated devices on 250 micron and up to 600 micron pitch. We discuss fabrication and performance of microstripline wiring at the small scales achieved to date. We also address fabrication issues with reduction of absorber contact area in small devices.

  4. Rimmed and edge thickened Stodola shaped flywheel

    DOEpatents

    Kulkarni, Satish V.; Stone, Richard G.

    1983-01-01

    A flywheel (10) is described that is useful for energy storage in a hybrid vehicle automotive power system or in some stationary applications. The flywheel (10) has a body (15) composed of essentially planar isotropic high strength material. The flywheel (10) body (15) is enclosed by a rim (50) of circumferentially wound fiber (2) embedded in resin (3). The rim (50) promotes flywheel (10) safety and survivability. The flywheel (10) has a truncated and edge thickened Stodola shape designed to optimize system mass and energy storage capability.

  5. Energy relaxation at quantum Hall edge

    NASA Astrophysics Data System (ADS)

    Levkivskyi, Ivan P.; Sukhorukov, Eugene V.

    2012-02-01

    In this work, we address the recent experiments [C. Altimiras , Nat. Phys.1745-247310.1038/nphys1429 6, 34 (2010); H. le Sueur , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.056803 105, 056803 (2010);C. Altimiras , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.226804 105, 226804 (2010)], where an electron distribution function at the quantum Hall (QH) edge at filling factor ν=2 has been measured with high precision. It has been reported that the energy of electrons injected into one of the two chiral edge channels with the help of a quantum point contact (QPC) is equally distributed between them, in agreement with earlier predictions, one being based on the Fermi gas approach [A. M. Lunde , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.81.041311 81, 041311(R) (2010)] and the other utilizing the Luttinger-liquid theory [P. Degiovanni , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.81.121302 81, 121302(R) (2010)]. We argue that the physics of the energy relaxation process at the QH edge may in fact be more rich, providing the possibility for discriminating between two physical pictures in experiment. Namely, using the recently proposed nonequilibrium bosonization technique [I. P. Levkivskyi , Phys. Rev. Lett., PRLTAO0031-900710.1103/PhysRevLett.103.036801 103, 036801 (2009)], we evaluate the electron distribution function and find that the initial “double-step” distribution created at a QPC evolves through several intermediate asymptotics before reaching eventual equilibrium state. At short distances, the distribution function is found to be asymmetric due to non-Gaussian current noise effects. At larger distances, where noise becomes Gaussian, the distribution function acquires symmetric Lorentzian shape. Importantly, in the regime of low QPC transparencies T, the width of the Lorentzian scales linearly with T, in contrast to the case of equilibrium Fermi distribution, the width of which scales as T. Therefore, we propose to do measurements at

  6. Nonlinear magnetohydrodynamics of edge localized mode precursors

    NASA Astrophysics Data System (ADS)

    Guo, Z. B.; Wang, Lu; Wang, X. G.

    2015-02-01

    A possible origin of edge-localized-mode (ELM) precursors based on nonlinear ideal peeling-ballooning mode is reported. Via nonlinear variational principle, a nonlinear evolution equation of the radial displacement is derived and solved, analytically. Besides an explosive growth in the initial nonlinear phase, it is found that the local displacement evolves into an oscillating state in the developed nonlinear phase. The nonlinear frequency of the ELM precursors scales as ωpr e˜x1 /3ξ̂ψ,i n 2 /3n , with x position in radial direction, ξ̂ ψ,i n strength of initial perturbation, and n toroidal mode number.

  7. Distributed Antenna-Coupled Transition Edge Sensors

    NASA Technical Reports Server (NTRS)

    Day, Peter K.; LeDuc, Henry G.; Lee, Richard A. M.; Dowell, C. Darren; Zmuidzinas, Jonas

    2006-01-01

    We describe progress toward realizing a new architecture for focal plane arrays for the Submillimeter and Far- Infrared (FIR) bands. This architecture is based on a detector design utilizing distributed hot{electron transition edge sensors (TES) coupled to slot antenna elements. Arrays utilizing this type of detector can be considerably easier to manufacture than membrane-isolated TES arrays, because the need for micro-machining is eliminated. We present background and rationale for this new array architecture and details of a new antenna design for an imaging polarimeter, which yields greater bandwidth than past designs. In addition, we describe a cryogenic facility for testing these arrays.

  8. Edge-on View of Saturn's Rings

    NASA Technical Reports Server (NTRS)

    1996-01-01

    TOP - This is a NASA Hubble Space Telescope snapshot of Saturn with its rings barely visible. Normally, astronomers see Saturn with its rings tilted. Earth was almost in the plane of Saturn's rings, thus the rings appear edge-on.

    In this view, Saturn's largest moon, Titan, is casting a shadow on Saturn. Titan's atmosphere is a dark brown haze. The other moons appear white because of their bright, icy surfaces. Four moons - from left to right, Mimas, Tethys, Janus, and Enceladus - are clustered around the edge of Saturn's rings on the right. Two other moons appear in front of the ring plane. Prometheus is on the right edge; Pandora, on the left. The rings also are casting a shadow on Saturn because the Sun was above the ring plane.

    BOTTOM - This photograph shows Saturn with its rings slightly tilted. The moon called Dione, on the lower right, is casting a long, thin shadow across the whole ring system due to the setting Sun on the ring plane. The moon on the upper left of Saturn is Tethys.

    Astronomers also are studying the unusual appearance of Saturn's rings. The bottom image displays a faint, narrow ring, the F-ring just outside the main ring, which normally is invisible from Earth. Close to the edge of Saturn's disk, the front section of rings seem brighter and more yellow than the back due to the additional lumination by yellowish Saturn.

    The color images were assembled from separate exposures taken August 6 (top) and November 17 (bottom), 1995 with the Wide Field Planetary Camera-2.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

    This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

  9. Chiral thermoelectrics with quantum Hall edge states.

    PubMed

    Sánchez, Rafael; Sothmann, Björn; Jordan, Andrew N

    2015-04-10

    The thermoelectric properties of a three-terminal quantum Hall conductor are investigated. We identify a contribution to the thermoelectric response that relies on the chirality of the carrier motion rather than on spatial asymmetries. The Onsager matrix becomes maximally asymmetric with configurations where either the Seebeck or the Peltier coefficients are zero while the other one remains finite. Reversing the magnetic field direction exchanges these effects, which originate from the chiral nature of the quantum Hall edge states. The possibility to generate spin-polarized currents in quantum spin Hall samples is discussed.

  10. Experimental investigation of leading-edge thrust at supersonic speeds

    NASA Technical Reports Server (NTRS)

    Wood, R. M.; Miller, D. S.

    1983-01-01

    Wings, designed for leading edge thrust at supersonic speeds, were investigated in the Unitary Plan Wind Tunnel at Mach numbers of 1.60, 1.80, 2.00, 2.16, and 2.36. Experimental data were obtained on a uncambered wing which had three interchangeable leading edges that varied from sharp to blunt. The leading edge thrust concept was evaluated. Results from the investigation showed that leading edge flow separation characteristics of all wings tested agree well with theoretical predictions. The experimental data showed that significant changes in wing leading edge bluntness did not affect the zero lift drag of the uncambered wings.

  11. Blind image deblurring with edge enhancing total variation regularization

    NASA Astrophysics Data System (ADS)

    Shi, Yu; Hong, Hanyu; Song, Jie; Hua, Xia

    2015-04-01

    Blind image deblurring is an important issue. In this paper, we focus on solving this issue by constrained regularization method. Motivated by the importance of edges to visual perception, the edge-enhancing indicator is introduced to constrain the total variation regularization, and the bilateral filter is used for edge-preserving smoothing. The proposed edge enhancing regularization method aims to smooth preferably within each region and preserve edges. Experiments on simulated and real motion blurred images show that the proposed method is competitive with recent state-of-the-art total variation methods.

  12. Three-dimensional edge extraction in optical scanning holography

    NASA Astrophysics Data System (ADS)

    Zong, Yonghong; Zhou, Changhe; Ma, Jianyong; Jia, Wei; Wang, Jin

    2016-10-01

    Edge extraction has found applications in various image processing fields, such as in pattern recognition. In this paper, a new method is proposed for edge extraction of three-dimensional objects in optical scanning holography (OSH). Isotropic and anisotropic edge extraction of 3D objects is simulated using spiral phase plates in OSH operating in an incoherent mode. We propose to use a delta function and a spiral phase plate as the pupil functions to realize isotropic and anisotropic edge extraction. Our computer simulations show the capability of extracting the edges of a given 3D object by spiral phase filtering in OSH.

  13. Edge Theories in Projected Entangled Pair State Models

    NASA Astrophysics Data System (ADS)

    Yang, S.; Lehman, L.; Poilblanc, D.; Van Acoleyen, K.; Verstraete, F.; Cirac, J. I.; Schuch, N.

    2014-01-01

    We analyze the low energy excitations of spin lattice systems in two dimensions at zero temperature within the framework of projected entangled pair state models. Perturbations in the bulk give rise to physical excitations located at the edge. We identify the corresponding degrees of freedom, give a procedure to derive the edge Hamiltonian, and illustrate that it can exhibit a rich phase diagram. For topological models, the edge Hamiltonian is constrained by the topological order in the bulk, which gives rise to one-dimensional edge models with unconventional properties; for instance, a topologically ordered bulk can protect a ferromagnetic Ising chain at the edge against spontaneous symmetry breaking.

  14. Electronic structure modulation of graphene edges by chemical functionalization

    NASA Astrophysics Data System (ADS)

    Taira, Remi; Yamanaka, Ayaka; Okada, Susumu

    2016-11-01

    Using the density functional theory with the effective screening medium method, we study the electronic properties of graphene nanoribbons with zigzag edges that are terminated by hydrogen and ketone, hydroxyl, carbonyl, and carboxyl functional groups. Our calculations showed that the work function and electronic structures of the edges of the nanoribbons are sensitive to the functional groups attached to the edges. The nearly free electron state emerges in the vacuum region outside the hydroxylated edges and crosses the Fermi level, indicating the possibility of negative electron affinity at the edges.

  15. Applications of Euler equations to sharp edge delta wings with leading edge vortices

    NASA Technical Reports Server (NTRS)

    Murman, Earll M.; Rizzi, Arthur

    1986-01-01

    Studies on the solution of discrete Euler equations past swept delta wing configurations with sharp leding edges are presented. Freestream Mach numbers range from zero to supersonic, although the Mach number normal to the leading edge is subsonic for all cases discussed. A few examples are given to show the application of the numerical methods to representative problems. The major dicussion is directed at the application of Computational Fluid Dynamics to the understanding of the fundamental fluid mechanic mechanisms of this class of flows.

  16. Wavelet Multiscale Edge Detection Using An ADALINE Neural Network To Match Up Edge Indicators

    DTIC Science & Technology

    2001-12-14

    the WMED is modified to use an ADALINE (ADAptive LInear NEuron) neural network that adapts to match up edge indicators across multiple wavelet levels...The ADALINE uses the least mean squared (LMS) learning rule to minimize the mean square error. The LMS algorithm is able to optimize the decision...boundaries of the network. This makes the boundaries more effective in the presence of noise. This paper will test the capability of the ADALINE to match up the edge indicators in noisy two-dimensional sidescan imagery.

  17. 3D Imaging of Nickel Oxidation States using Full Field X-ray Absorption Near Edge Structure Nanotomography

    SciTech Connect

    Nelson, George; Harris, William; Izzo, John; Grew, Kyle N.

    2012-01-20

    Reduction-oxidation (redox) cycling of the nickel electrocatalyst phase in the solid oxide fuel cell (SOFC) anode can lead to performance degradation and cell failure. A greater understanding of nickel redox mechanisms at the microstructural level is vital to future SOFC development. Transmission x-ray microscopy (TXM) provides several key techniques for exploring oxidation states within SOFC electrode microstructure. Specifically, x-ray nanotomography and x-ray absorption near edge structure (XANES) spectroscopy have been applied to study samples of varying nickel (Ni) and nickel oxide (NiO) compositions. The imaged samples are treated as mock SOFC anodes containing distinct regions of the materials in question. XANES spectra presented for the individual materials provide a basis for the further processing and analysis of mixed samples. Images of composite samples obtained are segmented, and the distinct nickel and nickel oxide phases are uniquely identified using full field XANES spectroscopy. Applications to SOFC analysis are discussed.

  18. Influence of edge on predator prey distribution and abundance

    NASA Astrophysics Data System (ADS)

    Ferguson, Steven H.

    2004-03-01

    I investigated the effect of spatial configuration on distribution and abundance of invertebrate trophic groups by counting soil arthropods under boxes (21 × 9.5 cm) arranged in six different patterns that varied in the amount of edge (137-305 cm). I predicted fewer individuals from the consumer trophic group (Collembola) in box groups with greater amount of edge. This prediction was based on the assumption that predators (mites, ants, spiders, centipedes) select edge during foraging and thereby reduce abundance of the less mobile consumer group under box patterns with greater edge. Consumer abundance (Collembola) was not correlated with amount of edge. Among the predator groups, mite, ant and centipede abundance related to the amount of edge of box groups. However, in contrast to predictions, abundance of these predators was negatively correlated with amount of edge in box patterns. All Collembola predators, with the exception of ants, were less clumped in distribution than Collembola. The results are inconsistent with the view that predators used box edges to predate the less mobile consumer trophic group. Alternative explanations for the spatial patterns other than predator-prey relations include (1) a negative relationship between edge and moisture, (2) a positive relationship between edge and detritus decomposition (i.e. mycelium as food for the consumer group), and (3) a negative relationship between edge and the interstices between adjacent boxes. Landscape patterns likely affect microclimate, food, and predator-prey relations and, therefore, future experimental designs need to control these factors individually to distinguish among alternative hypotheses.

  19. Microscale mineralogical characterization of As, Fe, and Ni in uranium mine tailings

    NASA Astrophysics Data System (ADS)

    Essilfie-Dughan, Joseph; Hendry, M. Jim; Warner, Jeff; Kotzer, Tom

    2012-11-01

    Uranium (U) ores can contain high concentrations of elements of concern (EOCs), such as arsenic (As) and nickel (Ni) present in sulfide and arsenide minerals. The U in these ores is often solubilized by adding H2SO4 to attain a pH ∼1 under oxic conditions. This process releases some EOCs from the primary minerals into solution. The barren raffinate (solution remaining after U extraction) is subsequently neutralized with Ca(OH)2 to a terminal pH of ∼10.5, resulting in a reduction in the aqueous concentrations of the EOCs. These neutralized raffinates are mixed with the non-reacted primary minerals and discharged as tailing into tailings management facilities (TMFs). To aid in the accurate characterization and quantification of the mineralogical controls on the concentrations of EOCs in the tailings porewater, their spatial distribution and speciation were studied at the micron scale in tailings samples collected from the Deilmann U Tailings Management Facility (DTMF), northern Saskatchewan, Canada. Backscattered electron images of the tailings samples generated using an electron microprobe show the presence of nodules (10-200 μm size) surrounded by bright rims. Wavelength dispersive spectrometric (WDS) and synchrotron-based micro-X-ray fluorescence (μ-XRF) elemental mapping show that the nodules are dominated by Ca and S (as gypsum) and the bright rims are dominated by Fe, As, and Ni. Micro-X-ray absorption near-edge structure (μ-XANES) spectra collected within and near the rims indicate that the Fe and Ni are present mainly in the +3 and +2 oxidation states, respectively; for As, the +5 oxidation state dominates but significant amounts of the +3 oxidation state are present in some areas. Linear combination fit analyses of the K-edges for the Fe, As, and Ni μ-XANES spectra to reference compounds suggest the Fe in the rims is present as ferrihydrite with As and Ni are adsorbed to it. Energy dispersive spectrometric (EDS) data indicate that isolated, highly

  20. Observed structures at the edges of Saturn's rings

    NASA Astrophysics Data System (ADS)

    Albers, N.; Sremcevic, M.; Esposito, L. W.

    2014-04-01

    The edges of Saturn's rings exhibit structure on a range of spatial and temporal scales. Aside from the known variability in edge location many edges feature clumping on orbital timescales. In cases like the B and A ring outer edges even larger, more persistent objects have been observed. Most of these features and the underlying physical processing creating them have been associated with moon-induced perturbations. In addition tomoon-associated structures like wakes and gaps at the Encke and Keeler gap due to the presence of Pan and Daphnis respectively, parts of ring material is found truncated from the edges downstream of the moon. These gaps are about a few km wide and located a few tens of km from the edge. Using primarily Cassini UVIS occultations we investigate spatial and temporal morphology of ring edges.

  1. Using new edges for anomaly detection in computer networks

    DOEpatents

    Neil, Joshua Charles

    2015-05-19

    Creation of new edges in a network may be used as an indication of a potential attack on the network. Historical data of a frequency with which nodes in a network create and receive new edges may be analyzed. Baseline models of behavior among the edges in the network may be established based on the analysis of the historical data. A new edge that deviates from a respective baseline model by more than a predetermined threshold during a time window may be detected. The new edge may be flagged as potentially anomalous when the deviation from the respective baseline model is detected. Probabilities for both new and existing edges may be obtained for all edges in a path or other subgraph. The probabilities may then be combined to obtain a score for the path or other subgraph. A threshold may be obtained by calculating an empirical distribution of the scores under historical conditions.

  2. Coaxial connector for use with printed circuit board edge connector

    DOEpatents

    Howard, Donald R.; MacGill, Robert A.

    1989-01-01

    A coaxial cable connector for interfacing with an edge connector for a printed circuit board whereby a coaxial cable can be interconnected with a printed circuit board through the edge connector. The coaxial connector includes a body having two leg portions extending from one side for receiving the edge connector therebetween, and a tubular portion extending from an opposing side for receiving a coaxial cable. A cavity within the body receives a lug of the edge connector and the center conductor of the coaxial cable. Adjacent lugs of the edge connector can be bend around the edge connector housing to function as spring-loaded contacts for receiving the coaxial connector. The lugs also function to facilitate shielding of the center conductor where fastened to the edge connector lug.

  3. Adaptively wavelet-based image denoising algorithm with edge preserving

    NASA Astrophysics Data System (ADS)

    Tan, Yihua; Tian, Jinwen; Liu, Jian

    2006-02-01

    A new wavelet-based image denoising algorithm, which exploits the edge information hidden in the corrupted image, is presented. Firstly, a canny-like edge detector identifies the edges in each subband. Secondly, multiplying the wavelet coefficients in neighboring scales is implemented to suppress the noise while magnifying the edge information, and the result is utilized to exclude the fake edges. The isolated edge pixel is also identified as noise. Unlike the thresholding method, after that we use local window filter in the wavelet domain to remove noise in which the variance estimation is elaborated to utilize the edge information. This method is adaptive to local image details, and can achieve better performance than the methods of state of the art.

  4. Visualization of a ferromagnetic metallic edge state in manganite strips.

    PubMed

    Du, Kai; Zhang, Kai; Dong, Shuai; Wei, Wengang; Shao, Jian; Niu, Jiebin; Chen, Jinjie; Zhu, Yinyan; Lin, Hanxuan; Yin, Xiaolu; Liou, Sy-Hwang; Yin, Lifeng; Shen, Jian

    2015-02-04

    Recently, broken symmetry effect induced edge states in two-dimensional electronic systems have attracted great attention. However, whether edge states may exist in strongly correlated oxides is not yet known. In this work, using perovskite manganites as prototype systems, we demonstrate that edge states do exist in strongly correlated oxides. Distinct appearance of ferromagnetic metallic phase is observed along the edge of manganite strips by magnetic force microscopy. The edge states have strong influence on the transport properties of the strips, leading to higher metal-insulator transition temperatures and lower resistivity in narrower strips. Model calculations show that the edge states are associated with the broken symmetry effect of the antiferromagnetic charge-ordered states in manganites. Besides providing a new understanding of the broken symmetry effect in complex oxides, our discoveries indicate that novel edge state physics may exist in strongly correlated oxides beyond the current two-dimensional electronic systems.

  5. Plasmons on the edge of MoS2 nanostructures

    NASA Astrophysics Data System (ADS)

    Andersen, Kirsten; Jacobsen, Karsten W.; Thygesen, Kristian S.

    2014-10-01

    Using ab initio calculations we predict the existence of one-dimensional (1D), atomically confined plasmons at the edges of a zigzag MoS2 nanoribbon. The strongest plasmon originates from a metallic edge state localized on the sulfur dimers decorating the Mo edge of the ribbon. A detailed analysis of the dielectric function reveals that the observed deviations from the ideal 1D plasmon behavior result from single-particle transitions between the metallic edge state and the valence and conduction bands of the MoS2 sheet. The Mo and S edges of the ribbon are clearly distinguishable in calculated spatially resolved electron energy loss spectrum owing to the different plasmonic properties of the two edges. The edge plasmons could potentially be utilized for tuning the photocatalytic activity of MoS2 nanoparticles.

  6. Significant Reduction in NiO Band Gap Upon Formation of LixNi1-xO alloys: Applications To Solar Energy Conversion

    SciTech Connect

    Alidoust, Nima; Toroker, Maytal Caspary; Keith, John A.; Carter, Emily A.

    2013-11-21

    Long-term sustainable solar energy conversion relies on identifying economical and versatile semiconductor materials with appropriate band structures for photovoltaic and photocatalytic applications (e.g., band gaps of ~1.5–2.0 eV). Nickel oxide (NiO) is an inexpensive yet highly promising candidate. Its charge-transfer character may lead to longer carrier lifetimes needed for higher efficiencies, and its conduction band edge is suitable for driving hydrogen evolution via water-splitting. However, NiO’s large band gap (~4 eV) severely limits its use in practical applications. Our first-principles quantum mechanics calculations show band gaps dramatically decrease to ~2.0 eV when NiO is alloyed with Li2O. In this paper, we show that LixNi1-xO alloys (with x=0.125 and 0.25) are p-type semiconductors, contain states with no impurity levels in the gap and maintain NiO’s desirable charge-transfer character. Lastly, we show that the alloys have potential for photoelectrochemical applications, with band edges well-placed for photocatalytic hydrogen production and CO2 reduction, as well as in tandem dye-sensitized solar cells as a photocathode.

  7. Leading-edge vortices in insect flight

    NASA Astrophysics Data System (ADS)

    Ellington, Charles P.; van den Berg, Coen; Willmott, Alexander P.; Thomas, Adrian L. R.

    1996-12-01

    INSECTS cannot fly, according to the conventional laws of aerodynamics: during flapping flight, their wings produce more lift than during steady motion at the same velocities and angles of attack1-5. Measured instantaneous lift forces also show qualitative and quantitative disagreement with the forces predicted by conventional aerodynamic theories6-9. The importance of high-life aerodynamic mechanisms is now widely recognized but, except for the specialized fling mechanism used by some insect species1,10-13, the source of extra lift remains unknown. We have now visualized the airflow around the wings of the hawkmoth Manduca sexta and a 'hovering' large mechanical model-the flapper. An intense leading-edge vortex was found on the down-stroke, of sufficient strength to explain the high-lift forces. The vortex is created by dynamic stall, and not by the rotational lift mechanisms that have been postulated for insect flight14-16. The vortex spirals out towards the wingtip with a spanwise velocity comparable to the flapping velocity. The three-dimensional flow is similar to the conical leading-edge vortex found on delta wings, with the spanwise flow stabilizing the vortex.

  8. Bilayer Edges Catalyze Supported Lipid Bilayer Formation

    PubMed Central

    Weirich, Kimberly L.; Israelachvili, Jacob N.; Fygenson, D. Kuchnir

    2010-01-01

    Abstract Supported lipid bilayers (SLB) are important for the study of membrane-based phenomena and as coatings for biosensors. Nevertheless, there is a fundamental lack of understanding of the process by which they form from vesicles in solution. We report insights into the mechanism of SLB formation by vesicle adsorption using temperature-controlled time-resolved fluorescence microscopy at low vesicle concentrations. First, lipid accumulates on the surface at a constant rate up to ∼0.8 of SLB coverage. Then, as patches of SLB nucleate and spread, the rate of accumulation increases. At a coverage of ∼1.5 × SLB, excess vesicles desorb as SLB patches rapidly coalesce into a continuous SLB. Variable surface fluorescence immediately before SLB patch formation argues against the existence of a critical vesicle density necessary for rupture. The accelerating rate of accumulation and the widespread, abrupt loss of vesicles coincide with the emergence and disappearance of patch edges. We conclude that SLB edges enhance vesicle adhesion to the surface and induce vesicle rupture, thus playing a key role in the formation of continuous SLB. PMID:20085721

  9. Edge detection and texture classification by cuttlefish.

    PubMed

    Zylinski, Sarah; Osorio, Daniel; Shohet, Adam J

    2009-12-14

    Cephalopod mollusks including octopus and cuttlefish are adept at adaptive camouflage, varying their appearance to suit the surroundings. This behavior allows unique access into the vision of a non-human species because one can ask how these animals use spatial information to control their coloration pattern. There is particular interest in factors that affect the relative levels of expression of the Mottle and the Disruptive body patterns. Broadly speaking, the Mottle is displayed on continuous patterned surfaces whereas the Disruptive is used on discrete objects such as pebbles. Recent evidence from common cuttlefish, Sepia officinalis, suggests that multiple cues are relevant, including spatial scale, contrast, and depth. We analyze the body pattern responses of juvenile cuttlefish to a range of checkerboard stimuli. Our results suggest that the choice of camouflage pattern is consistent with a simple model of how cuttlefish classify visual textures, according to whether they are Uniform or patterned, and whether the pattern includes visual edges. In particular, cuttlefish appear to detect edges by sensing the relative spatial phases of two spatial frequency components (e.g., fundamental and the third harmonic Fourier component in a square wave). We discuss the relevance of these findings to vision and camouflage in aquatic environments.

  10. Edge reconstructions in fractional quantum Hall systems.

    NASA Astrophysics Data System (ADS)

    Joglekar, Yogesh; Nguyen, Hoang; Murthy, Ganpathy

    2003-03-01

    Two dimensional electron systems exhibiting fractional quantum Hall effects are characterized by a quantized Hall conductance and a dissipationless bulk. The transport in these systems occurs only at the edges where gapless excitations are possible [1]. We present a microscopic calculation of these egde-states at filling factors ν=1/3 and ν=2/5 using the Hamiltonian theory of the fractional quantum Hall effect [2]. We find that the quantum Hall egde undergoes a reconstruction as the confining potential, produced by the background charge density, softens [3,4]. Our results have implications to the tunneling experiments into the edge of a fractional quantum Hall system [5]. 1: X. G.Wen, Phys. Rev. Lett. 64, 2206 (1990). 2: R. Shankar and G. Murthy, Phys. Rev. Lett. 79, 4437 (1997). 3: C. de C. Chamon and X. G. Wen, Phys. Rev. B 49, 8227 (1994). 4: X. Wan, K. Yang, and E. H. Razayi, Phys. Rev. Lett. 88, 056802 (2002). 5: A.M.Chang et al., Phys. Rev. Lett. 86, 143 (2000).

  11. LES tests on airfoil trailing edge serration

    NASA Astrophysics Data System (ADS)

    Zhu, Wei Jun; Shen, Wen Zhong

    2016-09-01

    In the present study, a large number of acoustic simulations are carried out for a low noise airfoil with different Trailing Edge Serrations (TES). The Ffowcs Williams-Hawkings (FWH) acoustic analogy is used for noise prediction at trailing edge. The acoustic solver is running on the platform of our in-house incompressible flow solver EllipSys3D. The flow solution is first obtained from the Large Eddy Simulation (LES), the acoustic part is then carried out based on the instantaneous hydrodynamic pressure and velocity field. To obtain the time history data of sound pressure, the flow quantities are integrated around the airfoil surface through the FWH approach. For all the simulations, the chord based Reynolds number is around 1.5x106. In the test matrix, the effects from angle of attack, the TE flap angle, the length/width of the TES are investigated. Even though the airfoil under investigation is already optimized for low noise emission, most numerical simulations and wind tunnel experiments show that the noise level is further decreased by adding the TES device.

  12. Edge states in confined active fluids

    NASA Astrophysics Data System (ADS)

    Souslov, Anton; Vitelli, Vincenzo

    Recently, topologically protected edge modes have been proposed and realized in both mechanical and acoustic metamaterials. In one class of such metamaterials, Time-Reversal Symmetry is broken, and, to achieve this TRS breaking in mechanical and acoustic systems, an external energy input must be used. For example, motors provide a driving force that uses energy and, thus, explicitly break TRS. As a result, motors have been used as an essential component in the design of topological metamaterials. By contrast, we explore the design of topological metamaterials that use a class of far-from-equilibrium liquids, called polar active liquids, that spontaneously break TRS. We thus envision the confinement of a polar active liquid to a prescribed geometry in order to realize topological order with broken time-reversal symmetry. We address the design of the requisite geometries, for example a regular honeycomb lattice composed of annular channels, in which the active liquid may be confined. We also consider the physical character of the active liquid that, when introduced into the prescribed geometry, will spontaneously form the flow pattern of a metamaterial with topologically protected edge states. Finally, we comment on potential experimental realizations of such metamaterials.

  13. Extremotolerance in fungi: evolution on the edge.

    PubMed

    Gostincar, Cene; Grube, Martin; de Hoog, Sybren; Zalar, Polona; Gunde-Cimerman, Nina

    2010-01-01

    Our planet offers many opportunities for life on the edge: high and low temperatures, high salt concentrations, acidic and basic conditions and toxic environments, to name but a few extremes. Recent studies have revealed the diversity of fungi that can occur in stressful environments that are hostile to most eukaryotes. We review these studies here, with the additional purpose of proposing some mechanisms that would allow for the evolutionary adaptation of eukaryotic microbial life under extreme conditions. We focus, in particular, on life in ice and life at high salt concentrations, as there is a surprising similarity between the fungal populations in these two kinds of environments, both of which are characterized by low water activity. We propose steps of evolution of generalist species towards the development of specialists in extreme habitats. We argue that traits present in some fungal groups, such as asexuality, synthesis of melanin-like pigments and a flexible morphology, are preadaptations that facilitate persistence and eventual adaptation to conditions on the ecological edge, as well as biotope switches. These processes are important for understanding the evolution of extremophiles; moreover, they have implications for the emergence of novel fungal pathogens.

  14. Copper, nickel and zinc speciation in a biosolid-amended soil: pH adsorption edge, μ-XRF and μ-XANES investigations.

    PubMed

    Mamindy-Pajany, Yannick; Sayen, Stéphanie; Mosselmans, J Frederick W; Guillon, Emmanuel

    2014-07-01

    Metal solid phase speciation plays an important role in the control of the long-term stability of metals in biosolid-amended soils. The present work used pH-adsorption edge experiments and synchrotron-based spectroscopy techniques to understand the solid phase speciation of copper, nickel and zinc in a biosolid-amended soil. Comparison of metal adsorption edges on the biosolid-amended soil and the soil sample showed that Cu, Ni, and Zn can be retained by both soil and biosolid components such as amorphous iron phases, organic matter and clay minerals. These data are combined with microscopic results to obtain structural information about the surface complexes formed. Linear combination fitting of K-edge XANES spectra of metal hot-spots indicated consistent differences in metal speciation between metals. While organic matter plays a dominant role in Ni binding in the biosolid-amended soil, it was of lesser importance for Cu and Zn. This study suggests that even if the metals can be associated with soil components (clay minerals and organic matter), biosolid application will increase metals retention in the biosolid-amended soil by providing reactive organic matter and iron oxide fractions. Among the studied metals, the long-term mobility of Ni could be affected by organic matter degradation while Cu and Zn are strongly associated with iron oxides.

  15. Strong Enhancement of Near-Band-Edge Photoluminescence of ZnO Nanowires Decorated with Sputtered Metallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Purahmad, Mohsen; Stroscio, Michael A.; Dutta, Mitra

    2013-12-01

    The effect of the Ar plasma during metal deposition on the photoluminescence (PL) of metal-coated ZnO nanowires (NWs) has been investigated. Strong enhancement of near-band-edge emission (NBE) is observed for ZnO NWs coated with Al and Ni nanoparticles (NPs) by radiofrequency magnetron sputtering, while the samples coated with NPs by e-beam evaporation show quenching of the PL intensity. A model is proposed that satisfies the observed experimental results and assigns the strong enhancement of the NBE PL of ZnO NWs to excitons bound to structural defects in the surface layer of the ZnO NWs.

  16. Synthesis and Characterization of Pure Ni and Ni-Sn Intermetallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Yakymovych, A.; Ipser, H.

    2017-02-01

    The present research focused on the synthesis of Ni and Ni-Sn nanoparticles via a chemical reduction method using hydrazine hydrate. The syntheses were performed applying highly purified water or diethylene glycol as solvent. The produced nanoparticles were characterized by scanning electron microscopy and powder X-ray diffraction. The as-synthesized Ni-Sn nanoparticles with nominal starting ratios Ni:Sn = 3:1, 3:2, and 3:4 consisted of different amounts of pure Ni and a low-temperature Ni3Sn2 phase. It was found that all synthesized nanopowders had a spherical shape with the largest average size for pure Ni and decreasing size for particles containing Sn. X-ray diffraction showed that all synthesized nanoparticles contained Ni and a low-temperature Ni3Sn2 phase independent of the initial molar ratio; while Ni3Sn and Ni3Sn4 could not be detected.

  17. Photon Counting Using Edge-Detection Algorithm

    NASA Technical Reports Server (NTRS)

    Gin, Jonathan W.; Nguyen, Danh H.; Farr, William H.

    2010-01-01

    New applications such as high-datarate, photon-starved, free-space optical communications require photon counting at flux rates into gigaphoton-per-second regimes coupled with subnanosecond timing accuracy. Current single-photon detectors that are capable of handling such operating conditions are designed in an array format and produce output pulses that span multiple sample times. In order to discern one pulse from another and not to overcount the number of incoming photons, a detection algorithm must be applied to the sampled detector output pulses. As flux rates increase, the ability to implement such a detection algorithm becomes difficult within a digital processor that may reside within a field-programmable gate array (FPGA). Systems have been developed and implemented to both characterize gigahertz bandwidth single-photon detectors, as well as process photon count signals at rates into gigaphotons per second in order to implement communications links at SCPPM (serial concatenated pulse position modulation) encoded data rates exceeding 100 megabits per second with efficiencies greater than two bits per detected photon. A hardware edge-detection algorithm and corresponding signal combining and deserialization hardware were developed to meet these requirements at sample rates up to 10 GHz. The photon discriminator deserializer hardware board accepts four inputs, which allows for the ability to take inputs from a quadphoton counting detector, to support requirements for optical tracking with a reduced number of hardware components. The four inputs are hardware leading-edge detected independently. After leading-edge detection, the resultant samples are ORed together prior to deserialization. The deserialization is performed to reduce the rate at which data is passed to a digital signal processor, perhaps residing within an FPGA. The hardware implements four separate analog inputs that are connected through RF connectors. Each analog input is fed to a high-speed 1

  18. Ni{sub x}Cd{sub 1−x}O: Semiconducting alloys with extreme type III band offsets

    SciTech Connect

    Francis, Christopher A.; Detert, Douglas M.; Dubon, Oscar D.; Chen, Guibin; Yu, Kin M.; Walukiewicz, Wladek

    2015-01-12

    We have synthesized alloys of NiO and CdO that exhibit an extreme type III band offset and have studied the structural, electrical, and optical properties of Ni{sub x}Cd{sub 1−x}O over the entire composition range. The alloys are rocksalt structured and exhibit a monotonic shift of the (220) diffraction peak to higher 2θ angles with increasing Ni concentration. The electron mobility and electron concentration decrease with increasing x, and samples become insulating for Ni content x > 0.44. This decrease in n-type conductivity is consistent with the movement of the conduction band minimum from below to above the Fermi stabilization energy with increasing Ni content. The optical absorption edge of the alloys can be tuned continuously from CdO to NiO. The intrinsic gap of the alloys was calculated with the electrical and optical measurements and accounting for Burstein-Moss carrier filling and carrier-induced bandgap renormalization effects. We observe an uncommon composition dependence of the intrinsic bandgap on the alloy composition. The effect is tentatively attributed to an interaction between extended states of the conduction band and localized d-states of Ni.

  19. Preparation and property of duplex Ni-B-TiO2/Ni nano-composite coatings

    NASA Astrophysics Data System (ADS)

    Wang, Shu-Jen; Wang, Yuxin; Shu, Xin; Tay, Seeleng; Gao, Wei; Shakoor, R. A.; Kahraman, Ramazan

    2015-03-01

    The duplex Nickel-Boron-Titania/Nickel (Ni-B-TiO2/Ni) coatings were deposited on mild steel by using two baths with Ni as the inner layer. TiO2 nanoparticles were incorporated into the Ni-B coatings as the outer layer by using solid particle mixing method. The microstructure, morphology and corrosion resistance of the duplex Ni-B-TiO2/Ni nanocomposite coatings were systemically investigated. The results show that the duplex interface was uniform and the adhesion between two layers was very good. The microhardness of duplex Ni-B-TiO2/Ni coating was much higher than the Ni coating due to the outer layer of Ni-B-TiO2 coating. The corrosion resistance of the duplex Ni-B-TiO2/Ni coating was also significantly improved comparing with single Ni-B coating. The Ni-B-10 g/L TiO2/Ni coating was found to have the best corrosion resistance among these duplex coatings. This type of duplex Ni-B-TiO2/Ni coating, with high hardness and good corrosion resistance properties, should be able to find broad applications under adverse environmental conditions.

  20. Effect of site occupancy disorder on martensitic properties of Mn2NiIn type alloys: X-ray absorption fine structure study

    NASA Astrophysics Data System (ADS)

    Lobo, D. N.; Priolkar, K. R.; Koide, A.; Emura, S.

    2017-02-01

    We have carried out ab-initio calculations of the local structure of Mn and Ni in the Mn2Ni1.5In0.5 alloy with different site occupancies in order to understand the similarities in martensitic and magnetic properties of Mn2Ni1+xIn1-x and Ni2Mn1+xIn1-x alloys. Our results show that in Mn2Ni1+xIn1-x alloys, there is a strong possibility of Mn atoms occupying all the three X, Y, and Z sites of the X2YZ Heusler structure, while Ni atoms preferentially occupy the X sites. Such a site occupancy disorder of Mn atoms is in addition to a local structural disorder due to size differences between Mn and In atoms, which is also present in Ni2Mn1+xIn1-x alloys. Further, a comparison of the calculations with experimental x-ray absorption fine structure at the Mn and Ni K edges in Mn2-yNi1.6+yIn0.4 (-0.08 ≤ y ≤ 0.08) indicates a strong connection between martensitic transformation and occupancy of Z sites by Mn atoms.

  1. Directionally solidified lamellar eutectic superalloys by edge-defined, film-fed growth. [including tensile tests

    NASA Technical Reports Server (NTRS)

    Hurley, G. F.

    1975-01-01

    A program was performed to scale up the edge-defined, film-fed growth (EFG) method for the gamma/gamma prime-beta eutectic alloy of the nominal composition Ni-19.7 Cb - 6 Cr-2.5 Al. Procedures and problem areas are described. Flat bars approximately 12 x 1.7 x 200 mm were grown, mostly at speeds of 38 mm/hr, and tensile tests on these bars at 25 and 1000 C showed lower strength than expected. The feasibility of growing hollow airfoils was also demonstrated by growing bars over 200 mm long with a teardrop shaped cross-section, having a major dimension of 12 mm and a maximum width of 5 mm.

  2. Metal Structural Environment in ZnxNi1-xO Macroscale and Nanoscale Solid Solutions

    SciTech Connect

    Peck, Matthea A.; Langell, Marjorie A.

    2014-08-21

    The metal structural environments in macroscale and nanoscale ZnxNi1–xO solid solutions were examined using X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS). XRD demonstrates that solid solutions form for both macroscale (bulk) and nanoscale crystallites, and that the lattice parameter increases linearly as the amount of zinc increases, an indication of a homogeneous solid solution. XAS for both the bulk material and the nanoparticles reveals that the zinc atoms are incorporated into the rocksalt lattice and do not form zinc oxide clusters. The X-ray absorption near edge spectroscopy (XANES) of the Zn k-edge region in the solid solution is similar to the Ni k-edge region of NiO, and not the Zn k-edge region of ZnO. XPS confirms that solid solutions are formed; Auger parameters for zinc are consistent with a different geometry than the tetrahedral coordination of wurtzite ZnO. Nanoscaled solid solutions show evidence of a lattice contraction relative to macroscale solutions of the same concentration. While the contraction persists across the entire concentration range, the nanoparticle lattice parameter approaches the bulk ZnxNi1–xO value as the concentration of zinc increases to predict ZnO rocksalt lattice parameters that are in agreement with observed ZnO data.

  3. From Flashes to Edges to Objects: Recovery of Local Edge Fragments Initiates Spatiotemporal Boundary Formation

    PubMed Central

    Erlikhman, Gennady; Kellman, Philip J.

    2016-01-01

    Spatiotemporal boundary formation (SBF) is the perception of illusory boundaries, global form, and global motion from spatially and temporally sparse transformations of texture elements (Shipley and Kellman, 1993a, 1994; Erlikhman and Kellman, 2015). It has been theorized that the visual system uses positions and times of element transformations to extract local oriented edge fragments, which then connect by known interpolation processes to produce larger contours and shapes in SBF. To test this theory, we created a novel display consisting of a sawtooth arrangement of elements that disappeared and reappeared sequentially. Although apparent motion along the sawtooth would be expected, with appropriate spacing and timing, the resulting percept was of a larger, moving, illusory bar. This display approximates the minimal conditions for visual perception of an oriented edge fragment from spatiotemporal information and confirms that such events may be initiating conditions in SBF. Using converging objective and subjective methods, experiments showed that edge formation in these displays was subject to a temporal integration constraint of ~80 ms between element disappearances. The experiments provide clear support for models of SBF that begin with extraction of local edge fragments, and they identify minimal conditions required for this process. We conjecture that these results reveal a link between spatiotemporal object perception and basic visual filtering. Motion energy filters have usually been studied with orientation given spatially by luminance contrast. When orientation is not given in static frames, these same motion energy filters serve as spatiotemporal edge filters, yielding local orientation from discrete element transformations over time. As numerous filters of different characteristic orientations and scales may respond to any simple SBF stimulus, we discuss the aperture and ambiguity problems that accompany this conjecture and how they might be resolved

  4. Role of magnetic and orbital ordering at the metal-insulator transition in NdNiO{sub 3}

    SciTech Connect

    Scagnoli, V.; Staub, U.; Mulders, A. M.; Janousch, M.; Meijer, G. I.; Hammerl, G.; Tonnerre, J. M.; Stojic, N.

    2006-03-01

    Soft x-ray resonant scattering at the Ni L{sub 2,3} edges is used to test models of magnetic- and orbital-ordering below the metal-insulator transition in NdNiO{sub 3}. The large branching ratio of the L{sub 3} to L{sub 2} intensities of the (1/2 0 1/2) reflection and the observed azimuthal angle and polarization dependence originates from a noncollinear magnetic structure. The absence of an orbital signal and the noncollinear magnetic structure show that the nickelates are materials for which orbital ordering is absent at the metal-insulator transition.

  5. Dominating Role of Ni(0) on the Interface of Ni/NiO for Enhanced Hydrogen Evolution Reaction.

    PubMed

    Wang, Jing; Mao, Shanjun; Liu, Zeyan; Wei, Zhongzhe; Wang, Haiyan; Chen, Yiqing; Wang, Yong

    2017-03-01

    The research of a robust catalytic system based on single NiOx electrocatalyst for hydrogen evolution reaction (HER) remains a huge challenge. Particularly, the factors that dominate the catalytic properties of NiOx-based hybrids for HER have not been clearly demonstrated. Herein, a convenient protocol for the fabrication of NiOx@bamboo-like carbon nanotube hybrids (NiOx@BCNTs) is designed. The hybrids exhibit superb catalytic ability and considerable durability in alkaline solution. A benchmark HER current density of 10 mA cm(-2) has been achieved at an overpotential of ∼79 mV. In combination with the experimental results and density functional theory (DFT) calculations, this for the first time definitely validates that the inherent high Ni(0) ratio and the Ni(0) on the interface of Ni/NiO play a vital role in the outstanding catalytic performance. Especially, the Ni(0) on the interface of Ni/NiO performs superior activity for water splitting compared with that of bulk Ni(0). These conclusions provide guidance for the rational design of the future non-noble metallic catalysts.

  6. Reinterpreting the Sharp Edges of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Rimlinger, Thomas; Hamilton, Douglas P.; Hahn, Joseph M.

    2016-10-01

    Narrow ringlets are found throughout the Solar System and are typically 1-100 km wide. Angular momentum, L, is the key to understanding how narrow rings remain confined; L2 ∝ a(1 - e2) for semimajor axis a and eccentricity e. In a circular ring, L conservation demands that the ring quickly spread apart when some colliding particles lose energy while others gain it. By contrast, in an eccentric ring, energy loss and the associated decay of the average semi-major axes can be offset by a decrease in the average eccentricity. We argue that a ring's lifetime can be greatly extended if particles arrange themselves in this way (Borderies et al. 1984). The key difference of our model, however, is that rings need not be shepherded and can confine themselves provided they are sufficiently eccentric. Satellites merely extend the rings' lifespans by pumping up their eccentricities.This confinement mechanism can explain the existence and longevity of narrow ringlets in a variety of contexts. Saturn's Titan ringlet, which is quite circular, may nevertheless be able to confine itself indefinitely if its eccentricity decay is balanced by the increase from the resonance with Titan. Preliminary simulations presented by Rimlinger et al. at this year's DDA Conference have verified that this ring can self-confine even in the absence of any satellite; we update these findings with new results that include the effects of Titan. Furthermore, Mimas' resonance with the edge of the B ring may excite its higher order modes to similar effect. We update the findings of Hahn and Spitale (2013), who used artificial forces to confine the B ring's edge, and suggest that with a suitable viscosity and density, no such forces will be needed to keep the edge sharp. Finally, a ring that is "born" with a sufficiently high eccentricity may live for hundreds of millions or even billions of years in isolation if the rate of decay is slow enough. We present simulations exploring such a scenario.

  7. Objective evaluation of slanted edge charts

    NASA Astrophysics Data System (ADS)

    Hornung, Harvey (.

    2015-01-01

    Camera objective characterization methodologies are widely used in the digital camera industry. Most objective characterization systems rely on a chart with specific patterns, a software algorithm measures a degradation or difference between the captured image and the chart itself. The Spatial Frequency Response (SFR) method, which is part of the ISO 122331 standard, is now very commonly used in the imaging industry, it is a very convenient way to measure a camera Modulation transfer function (MTF). The SFR algorithm can measure frequencies beyond the Nyquist frequency thanks to super-resolution, so it does provide useful information on aliasing and can provide modulation for frequencies between half Nyquist and Nyquist on all color channels of a color sensor with a Bayer pattern. The measurement process relies on a chart that is simple to manufacture: a straight transition from a bright reflectance to a dark one (black and white for instance), while a sine chart requires handling precisely shades of gray which can also create all sort of issues with printers that rely on half-toning. However, no technology can create a perfect edge, so it is important to assess the quality of the chart and understand how it affects the accuracy of the measurement. In this article, I describe a protocol to characterize the MTF of a slanted edge chart, using a high-resolution flatbed scanner. The main idea is to use the RAW output of the scanner as a high-resolution micro-densitometer, since the signal is linear it is suitable to measure the chart MTF using the SFR algorithm. The scanner needs to be calibrated in sharpness: the scanner MTF is measured with a calibrated sine chart and inverted to compensate for the modulation loss from the scanner. Then the true chart MTF is computed. This article compares measured MTF from commercial charts and charts printed on printers, and also compares how of the contrast of the edge (using different shades of gray) can affect the chart MTF

  8. Edge effects on the electronic properties of phosphorene nanoribbons

    SciTech Connect

    Peng, Xihong; Copple, Andrew; Wei, Qun

    2014-10-14

    Two dimensional few-layer black phosphorus crystal structures have recently been fabricated and have demonstrated great potential in electronic applications. In this work, we employed first principles density functional theory calculations to study the edge and quantum confinement effects on the electronic properties of the phosphorene nanoribbons (PNR). Different edge functionalization groups, such as H, F, Cl, OH, O, S, and Se, in addition to a pristine case were studied for a series of ribbon widths up to 3.5 nm. It was found that the armchair-PNRs (APNRs) are semiconductors for all edge groups considered in this work. However, the zigzag-PNRs (ZPNRs) show either semiconductor or metallic behavior in dependence on their edge chemical species. Family 1 edges (i.e., H, F, Cl, OH) form saturated bonds with P atoms in the APNRs and ZPNRs, and the edge states keep far away from the band gap. However, Family 2 edges (pristine, O, S, Se) form weak unsaturated bonds with the p{sub z} orbital of the phosphorus atoms and bring edge states within the band gap of the ribbons. For the ZPNRs, the edge states of Family 2 are present around the Fermi level within the band gap, which close up the band gap of the ZPNRs. For the APNRs, these edge states are located at the bottom of the conduction band and result in a reduced band gap.

  9. An accurate fuzzy edge detection method using wavelet details subimages

    NASA Astrophysics Data System (ADS)

    Sedaghat, Nafiseh; Pourreza, Hamidreza

    2010-02-01

    Edge detection is a basic and important subject in computer vision and image processing. An edge detector is defined as a mathematical operator of small spatial extent that responds in some way to these discontinuities, usually classifying every image pixel as either belonging to an edge or not. Many researchers have been spent attempting to develop effective edge detection algorithms. Despite this extensive research, the task of finding the edges that correspond to true physical boundaries remains a difficult problem.Edge detection algorithms based on the application of human knowledge show their flexibility and suggest that the use of human knowledge is a reasonable alternative. In this paper we propose a fuzzy inference system with two inputs: gradient and wavelet details. First input is calculated by Sobel operator and the second is calculated by wavelet transform of input image and then reconstruction of image only with details subimages by inverse wavelet transform. There are many fuzzy edge detection methods, but none of them utilize wavelet transform as it is used in this paper. For evaluating our method, we detect edges of images with different brightness characteristics and compare results with canny edge detector. The results show the high performance of our method in finding true edges.

  10. The Effect of Nozzle Trailing Edge Thickness on Jet Noise

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda; Kinzie, Kevin; Haskin, Henry

    2004-01-01

    The effect of nozzle trailing edge thickness on broadband acoustic radiation and the production of tones is investigated for coannular nozzles. Experiments were performed for a core nozzle trailing edge thickness between 0.38 mm and 3.17 mm. The on-set of discrete tones was found to be predominantly affected by the velocity ratio, the ratio of the fan velocity to the core velocity, although some dependency on trailing edge thickness was also noted. For a core nozzle trailing edge thickness greater than or equal to 0.89 mm, tones were produced for velocity ratios between 0.91 and 1.61. For a constant nozzle trailing edge thickness, the frequency varied almost linearly with the core velocity. The Strouhal number based on the core velocity changed with nozzle trailing edge thickness and varied between 0.16 and 0.2 for the core nozzles used in the experiments. Increases in broadband noise with increasing trailing edge thickness were observed for tone producing and non-tone producing conditions. A variable thickness trailing edge (crenellated) nozzle resulted in no tonal production and a reduction of the broadband trailing edge noise relative to that of the corresponding constant thickness trailing edge.

  11. Hydrothermal Synthesis and Characterization of Ni-Al Montmorillonite-Like Phyllosilicates

    PubMed Central

    Reinholdt, Marc X.; Brendlé, Jocelyne; Tuilier, Marie-Hélène; Kaliaguine, Serge; Ambroise, Emmanuelle

    2013-01-01

    This work describes the first hydrothermal synthesis in fluoride medium of Ni-Al montmorillonite-like phyllosilicates, in which the only metallic elements in the octahedral sheet are Ni and Al. X-ray diffraction , chemical analysis, thermogravimetric and differential thermal analysis, scanning electron microscopy and transmission electron microscopy confirm that the synthesized samples are montmorillonite-like phyllosilicates having the expected chemical composition. The specific surface areas of the samples are relatively large (>100 m2 g−1) compared to naturally occurring montmorillonites. 29Si and 27Al nuclear magnetic resonance (NMR) indicate substitutions of Al for Si in the tetrahedral sheet. 19F NMR and Ni K-edge extended X-ray absorption fine structure (EXAFS) local probes highlight a clustering of the metal elements and of the vacancies in the octahedral sheet of the samples. These Ni-Al phyllosilicates exhibit a higher local order than in previously synthesized Zn-Al phyllosilicates. Unlike natural montmorillonites, where the distribution of transition metal cations ensures a charge equilibrium allowing a stability of the framework, synthetic montmorillonites entail clustering and instability of the lattice when the content of divalent element in the octahedral sheet exceeds ca. 20%. Synthesis of Ni-Al montmorillonite-like phyllosilicates, was successfully achieved for the first time. These new synthetic materials may find potential applications as catalysts or as materials with magnetic, optical or staining properties. PMID:28348321

  12. Enhancement of perpendicular magnetic anisotropy by compressive strain in alternately layered FeNi thin films.

    PubMed

    Sakamaki, M; Amemiya, K

    2014-04-23

    The effect of the lattice strain on magnetic anisotropy of alternately layered FeNi ultrathin films grown on a substrate, Cu(tCu = 0-70 ML)/Ni(48)Cu(52)(124 ML)/Cu(0 0 1) single crystal, is systematically studied by means of in situ x-ray magnetic circular dichroism (XMCD) and reflection high-energy electron diffraction (RHEED) analyses. To investigate the magnetic anisotropy of the FeNi layer itself, a non-magnetic substrate is adopted. From the RHEED analysis, the in-plane lattice constant, ain, of the substrate is found to shrink by 0.8% and 0.5% at tCu = 0 and 10 ML as compared to that of bulk Cu, respectively. Fe L-edge XMCD analysis is performed for n ML FeNi films grown on various ain, and perpendicular magnetic anisotropy (PMA) is observed at n = 3 and 5, whereas the film with n = 7 shows in-plane magnetic anisotropy. Moreover, it is found that PMA is enhanced with decreasing ain, in the case where a Cu spacer layer is inserted. We suppose that magnetic anisotropy in the FeNi films is mainly carried by Fe, and the delocalization of the in-plane orbitals near the Fermi level increases the perpendicular orbital magnetic moment, which leads to the enhancement of PMA.

  13. Comprehensive theoretical studies on the low-lying electronic states of NiF, NiCl, NiBr, and NiI.

    PubMed

    Zou, Wenli; Liu, Wenjian

    2006-04-21

    The low-lying electronic states of the nickel monohalides, i.e., NiF, NiCl, NiBr, and NiI, are investigated by using multireference second-order perturbation theory with relativistic effects taken into account. For the energetically lowest 11 lambda-S states and 26 omega states there into, the potential energy curves and corresponding spectroscopic constants (vertical and adiabatic excitation energies, equilibrium bond lengths, vibrational frequencies, and rotational constants) are reported. The calculated results are grossly in very good agreement with those solid experimental data. In particular, the ground state of NiI is shown to be different from those of NiF, NiCl, and NiBr, being in line with the recent experimental observation. Detailed analyses are provided on those states that either have not been assigned or have been incorrectly assigned by previous experiments.

  14. Study of edge detection task in dental panoramic radiographs.

    PubMed

    Gráfová, L; Kasparová, M; Kakawand, S; Procházka, A; Dostálová, T

    2013-01-01

    The purpose of this study is (1) to introduce a new approach for edge detection in orthopantograms (OPGs) and an improved automatic parameter selector for common edge detectors, (2) to present a comparison between our novel approach with common edge detectors and (3) to provide faster outputs without compromising quality. A new approach for edge detection based on statistical measures was introduced: (1) a set of N edge detection results is calculated from a given input image and a selected type of edge detector, (2) N correspondence maps are constructed from N edge detection results, (3) probabilities and average probabilities are computed, (4) an overall correspondence is evaluated for each correspondence map and (5) the correspondence map providing the best overall correspondence is taken as the result of edge detection procedure. A comparison with common edge detectors (the Roberts, Prewitt, Sobel, Laplacian of the Gaussian and Canny methods) with various parameter settings (304 combinations for each test image) was carried out. The methods were assessed objectively [edge mismatch error (EME), modified Hausdorff distance (MHD) and principal component analysis] and subjectively by experts in dentistry and based on time demands. The suitability of the new approach for edge detection in OPGs was confirmed by experts. The current conventional methods in edge detection in OPGs are inadequate (none of the tested methods reach an EME value or MHD value below 0.1). Our proposed approach for edge detection shows promising potential for its implementation in clinical dentistry. It enhances the accuracy of OPG interpretation and advances diagnosis and treatment planning.

  15. Quantum transport behavior of Ni-based dinuclear complexes in presence of zigzag graphene nanoribbon as electrode

    NASA Astrophysics Data System (ADS)

    Sarkar, Sunandan; Pramanik, Anup; Sarkar, Pranab

    2016-10-01

    Quantum transport properties of some Ni-based dinuclear complexes with different polydentate organic ligands have been studied by applying abinitio density functional theory along with nonequilibrium Green's function formulations. It is demonstrated that these materials are capable of showing multifunctional spin dependent properties by the influence of edge states of zigzag edged graphene nanoribbons. The current-voltage characteristics of these materials show spin dependent negative differential resistance behavior, spin filtering effect, and also voltage rectifying property. Proper tuning of these materials can alter these effects which may be utilized in various spintronic devices.

  16. Density functional theory study of the interfacial properties of Ni/Ni3Si eutectic alloy

    NASA Astrophysics Data System (ADS)

    Zhao, Yuhong; Wen, Zhiqin; Hou, Hua; Guo, Wei; Han, Peide

    2014-06-01

    In order to clarify the heterogeneous nucleation potential of α-Ni grains on Ni3Si particles in Ni-Ni3Si eutectic alloy, the work of adhesion (Wad), fracture toughness (G), interfacial energy (γi), and electronic structure of the index (0 0 1), (1 1 0) and (1 1 1) Ni/Ni3Si interfaces with two different cohesive manners are investigated using first-principles method based on density functional theory. Results indicate that the center site stacking sequence (OM) is preferable to continue the natural stacking sequence of bulk Ni and Ni3Si. Since OM stacking interfaces have larger Wad, G and γi than that of the top site stacking (OT) interfaces. The Ni/Ni3Si (1 1 0) interface with OM stacking has the best mechanical properties. Therefore, the formation of this interface can improve the stability, ductility and fracture toughness of Ni-Ni3Si eutectic alloy. The calculated interfacial energy of Ni/Ni3Si (0 0 1), (1 1 0) and (1 1 1) interfaces with OM stacking proves the excellent nucleation potency of Ni3Si particles for α-Ni phase from thermodynamic considerations. Besides, the electronic structure and chemical bonding of (1 1 0) interface with OM stacking are also discussed.

  17. A fast leading-edge pulse generator

    NASA Astrophysics Data System (ADS)

    Wang, R.

    1986-01-01

    The pulse generator consists of ECL semiconductor integrated circuits, high speed transistors and step restorer diodes, among others; its circuitry is simple. The leading edge of the output pulse is less than 100 ps, and the output impedance is 50 ohms. An ECL four-wire receiver connected as a closed loop circut is used in the oscillator section of the set. The pulse frequency varies as low as 10 Hz and as high as 100 MHz. The control of pulse with is based on the subtraction of two pulse widths. The output pulse width may be less than 10 ns and the maximum width may be as wide as an oscillator half cycle. The pulse amplitude is continuously adjustable from + or - 35 mV to + or - 5 V. The operating principle of the oscillator stage, a simplified logic diagram, waveforms at various points, a rectifier circuit in the first stage, positive pulse channel circuit, and an adjustable power source are shown.

  18. Observations on Leading-Edge Vortex Development

    NASA Astrophysics Data System (ADS)

    Glenn, Michael; Lang, Amy; Wahidi, Redha; Wilroy, Jacob

    2016-11-01

    Most of an insect's lift comes from the leading edge vortex (LEV) that they produce when flapping their wings. There are many variables that make a LEV either stronger or weaker such as: roughness from the scales on their wings, angle of attack (AoA) of wing, size of the wing, and speed of the wing during flapping motion. Experiments were conducted to study LEV development to gain a better understanding of butterfly flight and the importance of LEV formation. The variables emphasized in this particular experiment were the chord length Reynolds numbers. Two smooth plates of 4 inches and 7 inches were compared in this experiment with Re of 1500 and 3000. Matlab was used to track the LEV location and calculate the vorticity and circulation magnitudes. Differences in LEV vortex strength as a function of chord length will be presented. Funding was provided by NSF REU site Grant EEC 1358991 and CBET Grant 1628600.

  19. Wind turbine trailing edge aerodynamic brakes

    SciTech Connect

    Migliore, P G; Miller, L S; Quandt, G A

    1995-04-01

    Five trailing-edge devices were investigated to determine their potential as wind-turbine aerodynamic brakes, and for power modulation and load alleviation. Several promising configurations were identified. A new device, called the spoiler-flap, appears to be the best alternative. It is a simple device that is effective at all angles of attack. It is not structurally intrusive, and it has the potential for small actuating loads. It is shown that simultaneous achievement of a low lift/drag ratio and high drag is the determinant of device effectiveness, and that these attributes must persist up to an angle of attack of 45{degree}. It is also argued that aerodynamic brakes must be designed for a wind speed of at least 45 m/s (100 mph).

  20. Wing Leading Edge Joint Laminar Flow Tests

    NASA Technical Reports Server (NTRS)

    Drake, Aaron; Westphal, Russell V.; Zuniga, Fanny A.; Kennelly, Robert A., Jr.; Koga, Dennis J.

    1996-01-01

    An F-104G aircraft at NASA's Dryden Flight Research Center has been equipped with a specially designed and instrumented test fixture to simulate surface imperfections of the type likely to be present near the leading edge on the wings of some laminar flow aircraft. The simulated imperfections consisted of five combinations of spanwise steps and gaps of various sizes. The unswept fixture yielded a pressure distribution similar to that of some laminar flow airfoils. The experiment was conducted at cruise conditions typical for business-jets and light transports: Mach numbers were in the range 0.5-0.8, and unit Reynolds numbers were 1.5-2.5 million per foot. Skin friction measurements indicated that laminar flow was often maintained for some distance downstream of the surface imperfections. Further work is needed to more precisely define transition location and to extend the experiments to swept-wing conditions and a broader range of imperfection geometries.

  1. Edge Diffusion Flame Propagation and Stabilization Studied

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2004-01-01

    In most practical combustion systems or fires, fuel and air are initially unmixed, thus forming diffusion flames. As a result of flame-surface interactions, the diffusion flame often forms an edge, which may attach to burner walls, spread over condensed fuel surfaces, jump to another location through the fuel-air mixture formed, or extinguish by destabilization (blowoff). Flame holding in combustors is necessary to achieve design performance and safe operation of the system. Fires aboard spacecraft behave differently from those on Earth because of the absence of buoyancy in microgravity. This ongoing in-house flame-stability research at the NASA Glenn Research Center is important in spacecraft fire safety and Earth-bound combustion systems.

  2. Casimir force at a knife's edge

    SciTech Connect

    Graham, Noah; Shpunt, Alexander; Rahi, Sahand Jamal; Kardar, Mehran; Emig, Thorsten; Jaffe, Robert L.

    2010-03-15

    The Casimir force has been computed exactly for only a few simple geometries, such as infinite plates, cylinders, and spheres. We show that a parabolic cylinder, for which analytic solutions to the Helmholtz equation are available, is another case where such a calculation is possible. We compute the interaction energy of a parabolic cylinder and an infinite plate (both perfect mirrors), as a function of their separation and inclination, H and {theta}, and the cylinder's parabolic radius R. As H/R{yields}0, the proximity force approximation becomes exact. The opposite limit of R/H{yields}0 corresponds to a semi-infinite plate, where the effects of edge and inclination can be probed.

  3. Introduction to Solid Edge(TM)

    NASA Technical Reports Server (NTRS)

    Smith, John C.

    1997-01-01

    Solid Edge was conceived and developed to provide breakthrough levels of productivity for engineers and designers by providing tools focused on their daily work. This user-oriented approach led to a focus on five key areas: 1) assembly-focused design, 2) ease of use, 3) plug and play software, 4) superior part modeling, and 5) production drafting. Mechanical designers work primarily with assemblies of parts that together perform a useful function. The parts themselves are principally a consequence of the function of the assembly and the interrelationships between parts. Breakthroughs in productivity will come through a focus on making the design of assemblies easier, with enhanced part design a prerequisite to that. Enhancements already in development are part to part interaction, more assembly features applying to multiple parts, exploded assemblies, assembly playback, enhanced BOM, etc.

  4. Nonlinear magnetohydrodynamics of edge localized mode precursors

    SciTech Connect

    Guo, Z. B.; Wang, Lu; Wang, X. G.

    2015-02-15

    A possible origin of edge-localized-mode (ELM) precursors based on nonlinear ideal peeling-ballooning mode is reported. Via nonlinear variational principle, a nonlinear evolution equation of the radial displacement is derived and solved, analytically. Besides an explosive growth in the initial nonlinear phase, it is found that the local displacement evolves into an oscillating state in the developed nonlinear phase. The nonlinear frequency of the ELM precursors scales as ω{sub pre}∼x{sup 1/3}ξ{sup ^}{sub ψ,in}{sup 2/3}n, with x position in radial direction, ξ{sup ^}{sub ψ,in} strength of initial perturbation, and n toroidal mode number.

  5. Edge convection driven by externally applied potentials

    SciTech Connect

    D'Ippolito, D. A.; Myra, J. R.

    2000-08-01

    A theoretical model of convection in collisional tokamak edge and scrape-off-layer plasmas is described. In the linear theory, any mechanism for poloidal and toroidal symmetry breaking of the equilibrium will drive ExB flows; this result stems from the parallel thermal and pressure forces in Ohm's law. In the nonlinear theory, the quadratic coupling of the perturbations leads to quasilinear-type fluxes in the vorticity, density, and temperature equations. If the convection is strong enough, these fluxes lead to an ambipolarity constraint on the equilibrium electric field and to increased transport of particles and energy. The theory shows qualitative agreement with some tokamak experiments in which potential perturbations are externally driven by radio frequency antennas. (c) 2000 American Institute of Physics.

  6. Timing discriminator using leading-edge extrapolation

    DOEpatents

    Gottschalk, B.

    1981-07-30

    A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting is described. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

  7. Timing discriminator using leading-edge extrapolation

    DOEpatents

    Gottschalk, Bernard

    1983-01-01

    A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

  8. Chemical reactivity of Ni-Rh nanowires.

    PubMed

    Schoiswohl, J; Mittendorfer, F; Surnev, S; Ramsey, M G; Andersen, J N; Netzer, F P

    2006-09-22

    The properties of bimetallic Ni-Rh nanowires, fabricated by decorating the steps of vicinal Rh(111) surfaces by stripes of self-assembled Ni adatoms, have been probed by STM, photoemission, and ab initio density functional theory calculations. These Ni-Rh nanowires have specific electronic properties that lead to a significantly enhanced chemical reactivity towards oxygen. As a result, the Ni-Rh nanowires can be oxidized exclusively, generating novel quasi-one-dimensional oxide structures.

  9. Deprojecting Edge-on Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Pohlen, M.; Zaroubi, S.; Peletier, R. F.

    2007-05-01

    We present the results of a study of the intrinsic 3 dimensional distribution of stars in a pilot sample of ˜10 edge-on disk galaxies. The reconstruction of the 3D disk structure has been obtained through a direct deprojecting of the two-dimensional images subject to the assumption of axial symmetry. The deprojection method -- which utilises the so called Fourier slice theorem -- has been tested with a large set of artificial galaxy models seen under different inclinations (80 < i <= 90) with various stellar distributions (e.g. truncated, untruncated), and with different dust distributions (spatially and with varying optical depth). For this pilot sample we are able to recover all three main classes of disk shapes (untruncated, truncated, antitruncated) recently found for complete samples of intermediate to face-on galaxies (Erwin et al. 2005, Pohlen & Trujillo 2006). The parameters (scalelength and surface brightness) of the breaks in the radial light distribution (marking the truncations) are consistent with those of face-on galaxies. Consequently, we are now able to avoid some of the problems caused by the line-of-sight integration while fitting edge-on galaxies and show that the classification introduced for face-on galaxies is indeed consistent and independent of the geometry. For the first time we present deprojection of several slices, vertically extending and parallel to the major axis. This allows to measure the thick disk component, which appear as an increasing radial scalelength (i.e. h= h(z)). Furthermore, the deprojection allows the study of the vertical distribution of the outer disk, beyond the break region, where we measure a significant increase in scalelength with vertical distance from the major axis.

  10. On the similarity of the bonding in NiS and NiO

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.

    1985-01-01

    The bonding in NiS is found to be quite similar to that in NiO, having an ionic contribution arising from the donation of the Ni 4s electron to the S atom and a covalent component arising from bonds between the Ni 3d and the S 3p. The one-electron d bonds are found to be of equal strength for NiO and NiS, but the two-electron d bonds are weaker for NiS.

  11. Catalytic Partial Oxidation of CH4 over Ni-substituted Barium Hexaaluminate catalysts

    SciTech Connect

    T Gardner; J Spivey; A Campos; J Hissam; E Kugler; A Roy

    2011-12-31

    Ba{sub 0.75}Ni{sub y}Al{sub 12-y}O{sub 19-{delta}} (y = 0.2, 0.4, 0.6, 0.8 and 1.0) catalysts were tested for the partial oxidation of CH{sub 4} at temperatures between 200 and 900 C. Temperature programmed reaction results indicate that light-off for the partial oxidation reaction occurred between 665 and 687 C for all catalysts. Isothermal runs performed at 900 C on the catalysts showed stable reaction product concentrations, consistent with equilibrium. Post-reaction analysis of the used catalysts showed that there are two distinct zones in the catalyst bed. In a short leading edge of the bed, the apparently complete consumption of oxygen leads to a catalyst which XANES analysis shows is primarily Ni-substituted into the hexaaluminate phase. In the downstream portion of the bed, Ni is shown to be present as metallic Ni. This corresponds to a reaction sequence in which the oxidation of CH{sub 4} proceeds at the inlet until all oxygen is reacted, followed by the reaction of CO{sub 2} and H{sub 2}O with unreacted CH{sub 4}, and its derivatives, to produce the final syngas mixture. From the change in the unit-cell dimensions with Ni substitution, there is a clear indication that Ni{sup 2+}, which has a larger ionic radius than aluminum, substitutes for Al{sup 3+} in the hexaaluminate lattice in the synthesis process, and there is no restructuring of the bulk hexaaluminate phase after the Ni is removed from the lattice.

  12. Novel Electronic Behavior Driving NdNiO3 Metal-Insulator Transition

    NASA Astrophysics Data System (ADS)

    Upton, M. H.; Choi, Yongseong; Park, Hyowon; Liu, Jian; Meyers, D.; Chakhalian, J.; Middey, S.; Kim, Jong-Woo; Ryan, Philip J.

    2015-07-01

    We present evidence that the metal-insulator transition (MIT) in a tensile-strained NdNiO3 (NNO) film is facilitated by a redistribution of electronic density and that it neither requires Ni charge disproportionation nor a symmetry change [U. Staub et al., Phys. Rev. Lett. 88, 126402 (2002); R. Jaramillo et al., Nat. Phys. 10, 304 (2014)]. Given that epitaxial tensile strain in thin NNO films induces preferential occupancy of the eg dx2-y2 orbital we propose that the larger transfer integral of this orbital state with the O 2 p orbital state mediates a redistribution of electronic density from the Ni atom. A decrease in the Ni dx2-y2 orbital occupation is directly observed by resonant inelastic x-ray scattering below the MIT temperature. Furthermore, an increase in the Nd charge occupancy is measured by x-ray absorption at the Nd L3 edge. Both spin-orbit coupling and crystal field effects combine to break the degeneracy of the Nd 5 d states, shifting the energy of the Nd eg dx2-y2 orbit towards the Fermi level, allowing the A site to become an active acceptor during the MIT. This work identifies the relocation of electrons from the Ni 3 d to the Nd 5 d orbitals across the MIT. We propose that the insulating gap opens between the Ni 3 d and O 2 p states, resulting from Ni 3 d electron localization. The transition seems to be neither a purely Mott-Hubbard transition nor a simple charge transfer.

  13. Slope Edge Deformation and Permafrost Dynamics Along the Arctic Shelf Edge, Beaufort Sea, Canada

    NASA Astrophysics Data System (ADS)

    Paull, C. K.; Dallimore, S.; Caress, D. W.; Gwiazda, R.; Lundsten, E. M.; Anderson, K.; Riedel, M.; Melling, H.

    2015-12-01

    The shelf of the Canadian Beaufort Sea is underlain by relict offshore permafrost that formed in the long intervals of terrestrial exposure during glacial periods. At the shelf edge the permafrost thins rapidly and also warms. This area has a very distinct morphology that we attribute to both the formation and degradation of ice bearing permafrost. Positive relief features include circular to oval shaped topographic mounds, up to 10 m high and ~50 m in diameter which occur at a density of ~6 per km2. Intermixed are circular topographic depressions up to 20 m deep. This topography was investigated using an autonomous underwater vehicle that provides 1 m horizontal resolution bathymetry and chirp profiles, a remotely operated vehicle to document seafloor textures, and sediment cores to sample pore waters. A consistent down-core freshening at rates of 14 to 96 mM Cl- per meter was found in these pore waters near the shelf edge. Downward extrapolation of these trends indicates water with ≤335 mM Cl- should occur at 2.3 to 22.4 m sub-seafloor depths within this shelf edge deformation band. Pore water with 335 mM Cl- or less freezes at -1.4°C. As bottom water temperatures in this area are persistently (<-1.4°C) cold and ground ice was observed in some core samples, we interpret the volume changes associated with mound formation are in part due to pore water freezing. Thermal models (Taylor et al., 2014) predict brackish water along the shelf edge may be sourced in relict permafrost melting under the adjacent continental shelf. Buoyant brackish water is hypothesized to migrate along the base of the relict permafrost, to emerge at the shelf edge and then refreeze when it encounters the colder seafloor. Expansion generated by the formation of ice-bearing permafrost generates the positive relief mounds and ridges. The associated negative relief features may be related to permafrost dynamics also. Permafrost dynamics may have geohazard implications that are unique to the

  14. Edge Minority Heating Experiment in Alcator C-Mod

    SciTech Connect

    S.J. Zweben; J.L. Terry; P. Bonoli; R. Budny; C.S. Chang; C. Fiore; G. Schilling; S. Wukitch; J. Hughes; Y. Lin; R. Perkins; M. Porkolab; the Alcator C-Mod Team

    2005-03-25

    An attempt was made to control global plasma confinement in the Alcator C-Mod tokamak by applying ion cyclotron resonance heating (ICRH) power to the plasma edge in order to deliberately create a minority ion tail loss. In theory, an edge fast ion loss could modify the edge electric field and so stabilize the edge turbulence, which might then reduce the H-mode power threshold or improve the H-mode barrier. However, the experimental result was that edge minority heating resulted in no improvement in the edge plasma parameters or global stored energy, at least at power levels of radio-frequency power is less than or equal to 5.5 MW. A preliminary analysis of these results is presented and some ideas for improvement are discussed.

  15. Image segmentation on adaptive edge-preserving smoothing

    NASA Astrophysics Data System (ADS)

    He, Kun; Wang, Dan; Zheng, Xiuqing

    2016-09-01

    Nowadays, typical active contour models are widely applied in image segmentation. However, they perform badly on real images with inhomogeneous subregions. In order to overcome the drawback, this paper proposes an edge-preserving smoothing image segmentation algorithm. At first, this paper analyzes the edge-preserving smoothing conditions for image segmentation and constructs an edge-preserving smoothing model inspired by total variation. The proposed model has the ability to smooth inhomogeneous subregions and preserve edges. Then, a kind of clustering algorithm, which reasonably trades off edge-preserving and subregion-smoothing according to the local information, is employed to learn the edge-preserving parameter adaptively. At last, according to the confidence level of segmentation subregions, this paper constructs a smoothing convergence condition to avoid oversmoothing. Experiments indicate that the proposed algorithm has superior performance in precision, recall, and F-measure compared with other segmentation algorithms, and it is insensitive to noise and inhomogeneous-regions.

  16. Orbital Edge States in a Photonic Honeycomb Lattice

    NASA Astrophysics Data System (ADS)

    Milićević, M.; Ozawa, T.; Montambaux, G.; Carusotto, I.; Galopin, E.; Lemaître, A.; Le Gratiet, L.; Sagnes, I.; Bloch, J.; Amo, A.

    2017-03-01

    We experimentally reveal the emergence of edge states in a photonic lattice with orbital bands. We use a two-dimensional honeycomb lattice of coupled micropillars whose bulk spectrum shows four gapless bands arising from the coupling of p -like photonic orbitals. We observe zero-energy edge states whose topological origin is similar to that of conventional edge states in graphene. Additionally, we report novel dispersive edge states in zigzag and armchair edges. The observations are reproduced by tight-binding and analytical calculations, which we extend to bearded edges. Our work shows the potentiality of coupled micropillars in elucidating some of the electronic properties of emergent two-dimensional materials with orbital bands.

  17. Efficient method of image edge detection based on FSVM

    NASA Astrophysics Data System (ADS)

    Cai, Aiping; Xiong, Xiaomei

    2013-07-01

    For efficient object cover edge detection in digital images, this paper studied traditional methods and algorithm based on SVM. It analyzed Canny edge detection algorithm existed some pseudo-edge and poor anti-noise capability. In order to provide a reliable edge extraction method, propose a new detection algorithm based on FSVM. Which contains several steps: first, trains classify sample and gives the different membership function to different samples. Then, a new training sample is formed by increase the punishment some wrong sub-sample, and use the new FSVM classification model for train and test them. Finally the edges are extracted of the object image by using the model. Experimental result shows that good edge detection image will be obtained and adding noise experiments results show that this method has good anti-noise.

  18. Bacterial foraging based edge detection for cell image segmentation.

    PubMed

    Pan, Yongsheng; Zhou, Tao; Xia, Yong

    2015-01-01

    Edge detection is the most popular and common choices for cell image segmentation, in which local searching strategies are commonly used. In spite of their computational efficiency, traditional edge detectors, however, may either produce discontinued edges or rely heavily on initializations. In this paper, we propose a bacterial foraging based edge detection (BFED) algorithm for cell image segmentation. We model the gradients of intensities as the nutrient concentration and propel bacteria to forage along nutrient-rich locations via mimicking the behavior of Escherichia coli, including the chemotaxis, swarming, reproduction, elimination and dispersal. As a nature-inspired evolutionary technique, this algorithm can identify the desired edges and mark them as the tracks of bacteria. We have evaluated the proposed algorithm against the Canny, SUSAN, Verma's and an active contour model (ACM) based edge detectors on both synthetic and real cell images. Our results suggest that the BFED algorithm can identify boundaries more effectively and provide more accurate cell image segmentation.

  19. Loops and multiple edges in modularity maximization of networks

    NASA Astrophysics Data System (ADS)

    Cafieri, Sonia; Hansen, Pierre; Liberti, Leo

    2010-04-01

    The modularity maximization model proposed by Newman and Girvan for the identification of communities in networks works for general graphs possibly with loops and multiple edges. However, the applications usually correspond to simple graphs. These graphs are compared to a null model where the degree distribution is maintained but edges are placed at random. Therefore, in this null model there will be loops and possibly multiple edges. Sharp bounds on the expected number of loops, and their impact on the modularity, are derived. Then, building upon the work of Massen and Doye, but using algebra rather than simulation, we propose modified null models associated with graphs without loops but with multiple edges, graphs with loops but without multiple edges and graphs without loops nor multiple edges. We validate our models by using the exact algorithm for clique partitioning of Grötschel and Wakabayashi.

  20. Physical properties of rf magnetron sputter deposited NiO:WO3 thin films

    NASA Astrophysics Data System (ADS)

    Usha, K. S.; Sivakumar, R.; Sanjeeviraja, C.; Ichimura, M.

    2015-01-01

    The present study describes various physical properties of mixed nickel-tungsten oxide (NiO:WO3) (95:5) thin films prepared on glass substrate by rf magnetron sputtering due to the variation in rf power (100, 150, and 200 W). X-ray diffraction study shows that all the deposited films are amorphous in nature. The maximum transmittance of 97% in the infrared region was observed for the film deposited at 100 W rf power. A systematic reduction in the optical band gap is observed with increasing rf power, which is associated with the rf power induced effect leading to the production of localized states near the band edges of NiO:WO3. The Urbach energy (EU) value was found to increase with rf power, which may be due to the increased defects in the NiO matrix. From the optical study, we have evaluated various parameters such as refractive index, packing density, lattice dielectric constant, ratio between free carrier density and free carrier effective mass, plasma frequency, and dispersion energy parameters, etc. These results are discussed and correlated well with the light of possible mechanisms underlying the phenomena. The compositional purity of the film was confirmed by energy dispersive x-ray analysis (EDAX) and Auger electron spectroscopic (AES) measurements. The Raman spectra of NiO:WO3 films show two peaks corresponding to one-phonon LO mode at 560 cm-1 and two-phonon LO mode at 1100 cm-1 due to the vibrations of Ni-O bonds and a strong peak at 860 cm-1 corresponds to the stretching vibration of W-O pair in the WO6 group. The band edge emission at 369 nm was observed in photoluminescence spectra.

  1. [NiIII(OMe)]-mediated reductive activation of CO2 affording a Ni1-OCO) complex

    SciTech Connect

    Chiou, Tzung -Wen; Tseng, Yen -Ming; Lu, Tsai -Te; Weng, Tsu -Chien; Sokaras, Dimosthenes; Ho, Wei -Chieh; Kuo, Ting -Shen; Jang, Ling -Yun; Lee, Jyh -Fu; Liaw, Wen -Feng

    2016-02-24

    Here, carbon dioxide is expected to be employed as an inexpensive and potential feedstock of C1 sources for the mass production of valuable chemicals and fuel. Versatile chemical transformations of CO2, i.e. insertion of CO2 producing bicarbonate/acetate/formate, cleavage of CO2 yielding μ-CO/μ-oxo transition-metal complexes, and electrocatalytic reduction of CO2 affording CO/HCOOH/CH3OH/CH4/C2H4/oxalate were well documented. Herein, we report a novel pathway for the reductive activation of CO2 by the [NiIII(OMe)(P(C6H3-3-SiMe3-2-S)3)] complex, yielding the [NiIII1-OCO˙)(P(C6H3-3-SiMe3-2-S)3)] complex. The formation of this unusual NiIII1-OCO˙–) complex was characterized by single-crystal X-ray diffraction, EPR, IR, SQUID, Ni/S K-edge X-ray absorption spectroscopy, and Ni valence-to-core X-ray emission spectroscopy. The inertness of the analogous complexes [NiIII(SPh)], [NiII(CO)], and [NiII(N2H4)] toward CO2, in contrast, demonstrates that the ionic [NiIII(OMe)] core attracts the binding of weak σ-donor CO2 and triggers the subsequent reduction of CO2 by the nucleophilic [OMe] in the immediate vicinity. This metal–ligand cooperative activation of CO2 may open a novel pathway promoting the subsequent incorporation of CO2 in the buildup of functionalized products.

  2. Electrical and thermal transport in CeNi and LaNi

    NASA Astrophysics Data System (ADS)

    Rudajevová, Alexandra; Vasylyev, Denis; Musil, Ondřej

    2006-05-01

    We have measured the electrical resistivity and thermal conductivity of CeNi, LaNi and La 0.15Ce 0.85Ni in the temperature range 4-400 K simultaneously on the same specimen using the TTO option in PPMS (Quantum Design) facility. Anomalous behaviour of the resistivity and the Lorenz number for CeNi and La 0.15Ce 0.85Ni can be attributed to valence fluctuations.

  3. Integral edge seals for phosphoric acid fuel cells

    NASA Technical Reports Server (NTRS)

    Granata, Jr., Samuel J. (Inventor); Woodle, Boyd M. (Inventor); Dunyak, Thomas J. (Inventor)

    1992-01-01

    A phosphoric acid fuel cell having integral edge seals formed by an elastomer permeating an outer peripheral band contiguous with the outer peripheral edges of the cathode and anode assemblies and the matrix to form an integral edge seal which is reliable, easy to manufacture and has creep characteristics similar to the anode, cathode and matrix assemblies inboard of the seals to assure good electrical contact throughout the life of the fuel cell.

  4. Application technology of stacked film with highly controlled edge structure

    NASA Astrophysics Data System (ADS)

    Ichino, Katsunori; Tanouchi, Keiji; Iseki, Tomohiro; Ogata, Nobuhiro; Yamamoto, Taro; Yoshihara, Kosuke; Fujimoto, Akihiro

    2008-03-01

    On the device manufacturing, the film edge control around the wafer edge has been critical at the point of edge control of deposited film. So far, the film edge control is operated by the wafer edge exposure system and/or the edge beam remover. The immersion lithography which is applied to the device generation below 65 nm node requires more additional and severe items for film edge control. These typical requirements are position control of coating film and wafer bevel cleanness. For examples, top coat film is widely applied to the immersion lithography. But this topcoat film is easily peeled off, if top coat film edge should be directly located on the wafer substrate like Si wafer. Thus, the edge position of topcoat film must be controlled very carefully. And the particle or residues on the wafer bevel is thought to be one of the causes to generate immersion defect. Wafer bevel must be clean in order to reduce the immersion defect. Then we have developed novel application technology in order to solve these kinds of immersion defectivities. This new application technology is based on rinse solution technology and new hardware concept. This new application technology can control the edge position of coating film with high accuracy and can reduce the particle and residues. We show the edge position accuracy using our application technology and furthermore, the stability of edge position accuracy in case of multi-layered resist process. We also show the cleanness of the wafer bevel area at the same time. And we can achieve the immersion process with wide process latitude with innovative application technology.

  5. Neutron diffraction studies of the Na-ion battery electrode materials NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3

    NASA Astrophysics Data System (ADS)

    Yahia, H. Ben; Essehli, R.; Avdeev, M.; Park, J.-B.; Sun, Y.-K.; Al-Maadeed, M. A.; Belharouak, I.

    2016-06-01

    The new compounds NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 were synthesized by sol-gel method and their crystal structures were determined by using neutron powder diffraction data. These compounds were characterized by galvanometric cycling and cyclic voltammetry. NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 crystallize with a stuffed α-CrPO4-type structure. The structure consists of a 3D-framework made of octahedra and tetrahedra that are sharing corners and/or edges generating channels along [100] and [010], in which the sodium atoms are located. Of significance, in the structures of NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 a statistical disorder Ni2+/Cr3+ was observed on both the 8g and 4a atomic positions, whereas in NaCoCr2(PO4)3 the statistical disorder Co2+/Cr3+ was only observed on the 8g atomic position. When tested as negative electrode materials, NaCoCr2(PO4)3, NaNiCr2(PO4)3, and Na2Ni2Cr(PO4)3 delivered specific capacities of 352, 385, and 368 mA h g-1, respectively, which attests to the electrochemical activity of sodium in these compounds.

  6. Skyrmions at the Edge: Confinement Effects in Fe/Ir(111).

    PubMed

    Hagemeister, Julian; Iaia, Davide; Vedmedenko, Elena Y; von Bergmann, Kirsten; Kubetzka, André; Wiesendanger, Roland

    2016-11-11

    We have employed spin-polarized scanning tunneling microscopy and Monte Carlo simulations to investigate the effect of lateral confinement onto the nano-Skyrmion lattice in Fe/Ir(111). We find a strong coupling of one diagonal of the square magnetic unit cell to the close-packed edges of Fe nanostructures. In triangular islands this coupling in combination with the mismatching symmetries of the islands and of the square nano-Skyrmion lattice leads to frustration and triple-domain states. In direct vicinity to ferromagnetic NiFe islands, the surrounding Skyrmion lattice forms additional domains. In this case a side of the square magnetic unit cell prefers a parallel orientation to the ferromagnetic edge. These experimental findings can be reproduced and explained by Monte Carlo simulations. Here, the single-domain state of a triangular island is lower in energy, but nevertheless multidomain states occur due to the combined effect of entropy and an intrinsic domain wall pinning arising from the skyrmionic character of the spin texture.

  7. E2EDSM: An Edge-to-Edge Data Service Model for Mass Streaming Media Transmission

    NASA Astrophysics Data System (ADS)

    He, Junfeng; Wang, Hui; He, Ningwu; Sun, Zhigang; Gong, Zhenghu

    Existing distributed content delivery systems like P2P applications may provide significant benefits for content providers and end users. However, they just shifted the considerable cost and burden to Internet Service Providers (ISPs) and well-behaved end users. In P2P applications, the amount of data served by each ISP and payment of many costly transit links are increasing, but the corresponding service revenue from the peer-hosted data services provided doesn’t return. In this paper, we present a novel Edge-to-Edge Data Service Model (E2EDSM) which aims to avoid transferring redundant data over the costly core transit links as well as improving the transmission efficiency of mass streaming media. E2EDSM describes a new way for ISP to take part in the processing of content distribution and makes an effort to achieve a winwin goal. Experimental results based on simulation show that E2EDSM achieves better network performance.

  8. Laminar Flow Control Leading Edge Systems in Simulated Airline Service

    NASA Technical Reports Server (NTRS)

    Wagner, R. D.; Maddalon, D. V.; Fisher, D. F.

    1988-01-01

    Achieving laminar flow on the wings of a commercial transport involves difficult problems associated with the wing leading edge. The NASA Leading Edge Flight Test Program has made major progress toward the solution of these problems. The effectiveness and practicality of candidate laminar flow leading edge systems were proven under representative airline service conditions. This was accomplished in a series of simulated airline service flights by modifying a JetStar aircraft with laminar flow leading edge systems and operating it out of three commercial airports in the United States. The aircraft was operated as an airliner would under actual air traffic conditions, in bad weather, and in insect infested environments.

  9. Line Edge Detection and Characterization in SEM Images using Wavelets

    SciTech Connect

    Sun, W; Romagnoli, J A; Tringe, J W; L?tant, S E; Stroeve, P; Palazoglu, A

    2008-10-07

    Edge characterization has become increasingly important in nanotechnology due to the growing demand for precise nanoscale structure fabrication and assembly. Edge detection is often performed by thresholding the spatial information of a top-down image obtained by Scanning Electron Microscopy (SEM) or other surface characterization techniques. Results are highly dependent on an arbitrary threshold value, which makes it difficult to reveal the nature of the real surface and to compare results among images. In this paper, we present an alternative edge boundary detection technique based on the wavelet framework. Our results indicate that the method facilitates nano-scale edge detection and characterization, by providing a systematic threshold determination step.

  10. Testing the Topological Nature of the Fractional Quantum Hall Edge

    SciTech Connect

    Jolad, Shivakumar; Jain, Jainendra K.

    2009-03-20

    We carry out numerical diagonalization for much larger systems than before by restricting the fractional quantum Hall (FQH) edge excitations to a basis that is exact for a short-range interaction and very accurate for the Coulomb interaction. This enables us to perform substantial tests of the predicted universality of the edge physics. Our results suggest the possibility that the behavior of the FQH edge is intrinsically nonuniversal, even in the absence of edge reconstruction, and therefore may not bear a sharp and unique relation to the nature of the bulk FQH state.

  11. Edge magnetism of Heisenberg model on honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Huang, Wen-Min; Hikihara, Toshiya; Lee, Yen-Chen; Lin, Hsiu-Hau

    2017-03-01

    Edge magnetism in graphene sparks intense theoretical and experimental interests. In the previous study, we demonstrated the existence of collective excitations at the zigzag edge of the honeycomb lattice with long-ranged Néel order. By employing the Schwinger-boson approach, we show that the edge magnons remain robust even when the long-ranged order is destroyed by spin fluctuations. Furthermore, in the effective field-theory limit, the dynamics of the edge magnon is captured by the one-dimensional relativistic Klein-Gordon equation. It is intriguing that the boundary field theory for the edge magnon is tied up with its bulk counterpart. By performing density-matrix renormalization group calculations, we show that the robustness may be attributed to the closeness between the ground state and the Néel state. The existence of edge magnon is not limited to the honeycomb structure, as demonstrated in the rotated-square lattice with zigzag edges as well. The universal behavior indicates that the edge magnons may attribute to the uncompensated edges and can be detected in many two-dimensional materials.

  12. How visual edge features influence cuttlefish camouflage patterning.

    PubMed

    Chiao, Chuan-Chin; Ulmer, Kimberly M; Siemann, Liese A; Buresch, Kendra C; Chubb, Charles; Hanlon, Roger T

    2013-05-03

    Rapid adaptive camouflage is the primary defense of soft-bodied cuttlefish. Previous studies have shown that cuttlefish body patterns are strongly influenced by visual edges in the substrate. The aim of the present study was to examine how cuttlefish body patterning is differentially controlled by various aspects of edges, including contrast polarity, contrast strength, and the presence or absence of "line terminators" introduced into a pattern when continuous edges are fragmented. Spatially high- and low-pass filtered white or black disks, as well as isolated, continuous and fragmented edges varying in contrast, were used to assess activation of cuttlefish skin components. Although disks of both contrast polarities evoked relatively weak disruptive body patterns, black disks activated different skin components than white disks, and high-frequency information alone sufficed to drive the responses to white disks whereas high- and low-frequency information were both required to drive responses to black disks. Strikingly, high-contrast edge fragments evoked substantially stronger body pattern responses than low-contrast edge fragments, whereas the body pattern responses evoked by high-contrast continuous edges were no stronger than those produced by low-contrast edges. This suggests that line terminators vs. continuous edges influence expression of disruptive body pattern components via different mechanisms that are controlled by contrast in different ways.

  13. Edge effect on resistance scaling rules in graphene nanostructures.

    PubMed

    Xu, Guangyu; Torres, Carlos M; Tang, Jianshi; Bai, Jingwei; Song, Emil B; Huang, Yu; Duan, Xiangfeng; Zhang, Yuegang; Wang, Kang L

    2011-03-09

    We report an experimental investigation of the edge effect on the room-temperature transport in graphene nanoribbon and graphene sheet (both single-layer and bilayer). By measuring the resistance scaling behaviors at both low- and high-carrier densities, we show that the transport of single-layer nanoribbons lies in a strong localization regime, which can be attributed to an edge effect. We find that this edge effect can be weakened by enlarging the width, decreasing the carrier densities, or adding an extra layer. From graphene nanoribbon to graphene sheet, the data show a dimensional crossover of the transport regimes possibly due to the drastic change of the edge effect.

  14. Shock Reflection from Edges and from Slotted Walls

    DTIC Science & Technology

    1952-07-01

    Reference 1), the edge effect is restricted within the Mach cone which has an apex at the intersection point of the shock and the edge. Outside Mach cone...dimensional theory argument (Reference 2), one concludes that the edge effect results in a conical problem, ioe. all flow characteristics are constant along...zw = o and hence by irrotationality. o along OAo Thus the problem of finding u due to edge effect is to solve U - m(A.2) in the semi-circular region

  15. Two-dimensionally confined topological edge states in photonic crystals

    NASA Astrophysics Data System (ADS)

    Barik, Sabyasachi; Miyake, Hirokazu; DeGottardi, Wade; Waks, Edo; Hafezi, Mohammad

    2016-11-01

    We present an all-dielectric photonic crystal structure that supports two-dimensionally confined helical topological edge states. The topological properties of the system are controlled by the crystal parameters. An interface between two regions of differing band topologies gives rise to topological edge states confined in a dielectric slab that propagate around sharp corners without backscattering. Three-dimensional finite-difference time-domain calculations show these edges to be confined in the out-of-plane direction by total internal reflection. Such nanoscale photonic crystal architectures could enable strong interactions between photonic edge states and quantum emitters.

  16. Spiraling Edge: Fast Surface Reconstruction from Partially Organized Sample Points

    SciTech Connect

    Angel, Edward; Crossno, Patricia

    1999-07-12

    Many applications produce three-dimensional points that must be further processed to generate a surface. Surface reconstruction algorithms that start with a set of unorganized points are extremely time-consuming. Sometimes, however, points are generated such that there is additional information available to the reconstruction algorithm. We present Spiraling Edge, a specialized algorithm for surface reconstruction that is three orders of magnitude faster than algorithms for the general case. In addition to sample point locations, our algorithm starts with normal information and knowledge of each point's neighbors. Our algorithm produces a localized approximation to the surface by creating a star-shaped triangulation between a point and a subset of its nearest neighbors. This surface patch is extended by locally triangulating each of the points along the edge of the patch. As each edge point is triangulated, it is removed from the edge and new edge points along the patch's edge are inserted in its place. The updated edge spirals out over the surface until the edge encounters a surface boundary and stops growing in that direction, or until the edge reduces to a small hole that is filled by the final triangle.

  17. Edge magnetism of Heisenberg model on honeycomb lattice.

    PubMed

    Huang, Wen-Min; Hikihara, Toshiya; Lee, Yen-Chen; Lin, Hsiu-Hau

    2017-03-07

    Edge magnetism in graphene sparks intense theoretical and experimental interests. In the previous study, we demonstrated the existence of collective excitations at the zigzag edge of the honeycomb lattice with long-ranged Néel order. By employing the Schwinger-boson approach, we show that the edge magnons remain robust even when the long-ranged order is destroyed by spin fluctuations. Furthermore, in the effective field-theory limit, the dynamics of the edge magnon is captured by the one-dimensional relativistic Klein-Gordon equation. It is intriguing that the boundary field theory for the edge magnon is tied up with its bulk counterpart. By performing density-matrix renormalization group calculations, we show that the robustness may be attributed to the closeness between the ground state and the Néel state. The existence of edge magnon is not limited to the honeycomb structure, as demonstrated in the rotated-square lattice with zigzag edges as well. The universal behavior indicates that the edge magnons may attribute to the uncompensated edges and can be detected in many two-dimensional materials.

  18. Simulations of Edge Current Driven Kink Modes with BOUT + + code

    NASA Astrophysics Data System (ADS)

    Li, G. Q.; Xu, X. Q.; Snyder, P. B.; Turnbull, A. D.; Xia, T. Y.; Ma, C. H.; Xi, P. W.

    2013-10-01

    Edge kink modes (or peeling modes) play a key role in the ELMs. The edge kink modes are driven by peak edge current, which comes from the bootstrap current. We calculated sequences of equilibria with different edge current using CORSICA by keeping total current and pressure profile fixed. Based on these equilibria, with the 3-field BOUT + + code, we calculated the MHD instabilities driven by edge current. For linear low-n ideal MHD modes, BOUT + + results agree with GATO results. With the edge current increasing, the dominant modes are changed from high-n ballooning modes to low-n kink modes. The edge current provides also stabilizing effects on high-n ballooning modes. Furthermore, for edge current scan without keeping total current fixed, the increasing edge current can stabilize the high-n ballooning modes and cannot drive kink modes. The diamagnetic effect can stabilize the high-n ballooning modes, but has no effect on the low-n kink modes. Also, the nonlinear behavior of kink modes is analyzed. Work supported by China MOST grant 2013GB111000 and by China NSF grant 10975161. Also performed for USDOE by LLNL under DE-AC52-07NA27344.

  19. Development of X-43A Mach 10 Leading Edges

    NASA Technical Reports Server (NTRS)

    Ohlhorst, Craig W.; Glass, David E.; Bruce, Walter E., III; Lindell, Michael C.; Vaughn, Wallace L.; Dirling, R. B., Jr.; Hogenson, P. A.; Nichols, J. M.; Risner, N. W.; Thompson, D. R.

    2005-01-01

    The nose leading edge of the Hyper-X Mach 10 vehicle was orginally anticipated to reach temperatures near 4000 F at the leading-edge stagnation line. A SiC coated carbon/carbon (C/C) leading-edge material will not survive that extreme temperature for even a short duration single flight. To identify a suitable leading edge for the Mach 10 vehicle, arc-jet testing was performed on thirteen leading-edge segments fabricated from different material systems to evaluate their performance in a simulated flight environment. Hf, Zr, Si, and Ir based materials, in most cases as a coating on C/C, were included in the evaluation. Afterwards, MER, Tucson, AZ was selected as the supplier of the flight vehicle leading edges. The nose and the vertical and horizontal tail leading edges were fabricated out of a 3:1 biased high thermal conductivity C/C. The leading edges were coated with a three layer coating comprised of a SiC conversion of the top surface of the C/C, followed by a chemical vapor deposited layer of SiC, followed by a thin chemical vapor deposited layer of HfC. This paper will describe the fabrication of the Mach 10 C/C leading edges and the testing performed to validate performance.

  20. An Edge Rotation and Temperature Diagnostic on NSTX

    SciTech Connect

    T.M. Biewer; R.E. Bell; R. Feder; D.W. Johnson; R.W. Palladino

    2003-08-29

    A new diagnostic for the National Spherical Torus Experiment (NSTX) is described whose function is to measure ion rotation and temperature at the plasma edge. The diagnostic is sensitive to C III, C IV, and He II intrinsic emission, covering a radial region of 15 cm at the extreme edge of the outboard midplane. Thirteen chords are distributed between toroidal and poloidal views, allowing the toroidal and poloidal rotation and temperature of the plasma edge to be simultaneously measured with 10 ms resolution. Combined with the local pressure gradient and the EFIT code reconstructed magnetic field profile, the edge flow gives a measure of the local radial electric field.

  1. [Edge effect and its impacts on forest ecosystem: a review].

    PubMed

    Tian, Chao; Yang, Xin-bing; Liu, Yang

    2011-08-01

    Edge effect is an important concept in ecology and biological conservation, playing an important role in the study of ecological processes such as energy and material flow at ecosystem scale and landscape scale. This paper expatiated the connotation, features, quantitative evaluation (basis of quantitative analysis, strength, impact zone, and models, etc.), and applied aspects of edge effect, summarized the impacts of edge effect on forest ecosystem, analyzed the deficiencies in the study of edge effect, and prospected related research directions, aimed to provide references for forest and protected area management.

  2. Evidence for edge effects on multiple levels in tallgrass prairie

    USGS Publications Warehouse

    Winter, M.; Johnson, D.H.; Faaborg, J.

    2000-01-01

    We tested how edges affect nest survival and predator distribution in a native tallgrass prairie system in southwestern Missouri using artificial nests, natural nests of Dickcissels (Spiza americana) and Henslow's Sparrows (Ammodramus henslowii), and mammal track stations. Survival of artificial nests was lower within 30 m of forest edge. Nesting success of Dickcissels and Henslow's Sparrows was lower within 50 m to a shrubby edge than at greater distances, whereas fates of nests were not related to distances to roads, agricultural fields, or forests. Evidence from clay eggs placed in artificial nests indicated that mid-sized carnivores were the major predators within 30 m of forest edges. Furthermore, mid-sized carnivores visited track stations most frequently within 50 m of forest edges. Because proximity of woody habitat explained more variation in nest survival and mammal activity than did fragment size, it appears that edge effects were more pronounced than area effects. Edge effects appeared to be caused mainly by greater exposure of nests to midsized carnivores. We argue that, based on edge avoidance behavior, 'grassland-interior' species such as the Henslow's Sparrow respond to edge effects mainly by a decrease in density, whereas habitat generalists such as the Dickcissel are affected mainly by a decrease in nesting success.

  3. Understanding the edge effect in wetting: a thermodynamic approach.

    PubMed

    Fang, Guoping; Amirfazli, A

    2012-06-26

    Edge effect is known to hinder spreading of a sessile drop. However, the underlying thermodynamic mechanisms responsible for the edge effect still is not well-understood. In this study, a free energy model has been developed to investigate the energetic state of drops on a single pillar (from upright frustum to inverted frustum geometries). An analysis of drop free energy levels before and after crossing the edge allows us to understand the thermodynamic origin of the edge effect. In particular, four wetting cases for a drop on a single pillar with different edge angles have been determined by understanding the characteristics of FE plots. A wetting map describing the four wetting cases is given in terms of edge angle and intrinsic contact angle. The results show that the free energy barrier observed near the edge plays an important role in determining the drop states, i.e., (1) stable or metastable drop states at the pillar's edge, and (2) drop collapse by liquid spilling over the edge completely or staying at an intermediate sidewall position of the pillar. This thermodynamic model presents an energetic framework to describe the functioning of the so-called "re-entrant" structures. Results show good consistency with the literature and expand the current understanding of Gibbs' inequality condition.

  4. Edge magnetism of Heisenberg model on honeycomb lattice

    PubMed Central

    Huang, Wen-Min; Hikihara, Toshiya; Lee, Yen-Chen; Lin, Hsiu-Hau

    2017-01-01

    Edge magnetism in graphene sparks intense theoretical and experimental interests. In the previous study, we demonstrated the existence of collective excitations at the zigzag edge of the honeycomb lattice with long-ranged Néel order. By employing the Schwinger-boson approach, we show that the edge magnons remain robust even when the long-ranged order is destroyed by spin fluctuations. Furthermore, in the effective field-theory limit, the dynamics of the edge magnon is captured by the one-dimensional relativistic Klein-Gordon equation. It is intriguing that the boundary field theory for the edge magnon is tied up with its bulk counterpart. By performing density-matrix renormalization group calculations, we show that the robustness may be attributed to the closeness between the ground state and the Néel state. The existence of edge magnon is not limited to the honeycomb structure, as demonstrated in the rotated-square lattice with zigzag edges as well. The universal behavior indicates that the edge magnons may attribute to the uncompensated edges and can be detected in many two-dimensional materials. PMID:28266559

  5. Edge Plasma Boundary Layer Generated By Kink Modes in Tokamaks

    SciTech Connect

    L.E. Zakharov

    2010-11-22

    This paper describes the structure of the electric current generated by external kink modes at the plasma edge using the ideally conducting plasma model. It is found that the edge current layer is created by both wall touching and free boundary kink modes. Near marginal stability, the total edge current has a universal expression as a result of partial compensation of the δ-functional surface current by the bulk current at the edge. The resolution of an apparent paradox with the pressure balance across the plasma boundary in the presence of the surface currents is provided.

  6. Haptic Perception of Edge Sharpness in Real and Virtual Environments.

    PubMed

    Park, Jaeyoung; Provancher, William; Tan, Hong Z

    2016-09-21

    We investigate the accuracy with which the haptic sharpness perception of a virtual edge is matched to that of a real edge and the effect of the virtual surface stiffness on the match. The perceived sharpness of virtual edges was estimated in terms of the point of subjective equality (PSE) when participants matched the sharpness of virtual edges to that of real edges with a radius of 0.5, 2.5 and 12.5 mm over a virtual stiffness range of 0.6 to 3.0 N/mm. The perceived sharpness of a real and a virtual edge of the same radius was significantly different under all but one of the experimental conditions and there was a significant effect of virtual surface stiffness on the accuracy of the match. The results suggest that the latter is presumably due to a constant penetration force employed by the participants that influenced the penetration depth and perceived sharpness of virtual edges at different surface stiffness levels. Our findings provide quantitative relations for appropriately offsetting the radii of virtual edges in order to achieve the desired perceived sharpness of virtual edges.

  7. Exploring the graphene edges with coherent electron focusing

    NASA Astrophysics Data System (ADS)

    Rakyta, P.; Kormányos, A.; Cserti, J.; Koskinen, P.

    2010-03-01

    We study theoretically the coherent electron focusing in graphene nanoribbons. Using semiclassical and numerical tight-binding calculations we show that armchair edges give rise to equidistant peaks in the focusing spectrum. In the case of zigzag edges at low magnetic fields one can also observe focusing peaks but with increasing magnetic field a more complex interference structure emerges in the spectrum. This difference in the spectra can be observed even if the zigzag edge undergoes structural reconstruction. Therefore transverse electron focusing can help in the identification and characterization of the edge structure of graphene samples.

  8. Majorana edge modes in Kitaev model on honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Thakurathi, Manisha; Sengupta, Krishnendu; Sen, Diptiman

    2015-03-01

    We study the Majorana modes, both equilibrium and Floquet, which can appear at the edges of the Kitaev model on the honeycomb lattice. We first present the analytical solutions known for the equilibrium Majorana edge modes for both zigzag and armchair edges of a semi-infinite Kitaev model and chart the parameter regimes of the model in which they appear. We then examine how edge modes can be generated if the Kitaev coupling on the bonds perpendicular to the edge is varied periodically in time as periodic δ-function kicks. We derive a general condition for the appearance and disappearance of the Floquet edge modes as a function of the drive frequency for a generic d-dimensional integrable system. We confirm this general condition for the Kitaev model with a finite width by mapping it to a one-dimensional model. Our numerical and analytical study of this problem shows that Floquet Majorana modes can appear on some edges in the kicked system even when the corresponding equilibrium Hamiltonian has no Majorana mode solutions on those edges. We support our analytical studies by numerics for finite sized system which show that periodic kicks can generate modes at the edges and the corners of the lattice. We thank CSIR, India and DST, India for financial support.

  9. Kinetics of Ni Sorption in Soils: Roles of Soil Organic Matter and Ni Precipitation

    SciTech Connect

    Shi, Zhenqing; Peltier, Edward; Sparks, Donald L.

    2012-12-10

    The kinetics of Ni sorption to two Delaware agricultural soils were studied to quantitatively assess the relative importance of Ni adsorption on soil organic matter (SOM) and the formation of Ni layered double hydroxide (Ni-LDH) precipitates using both experimental studies and kinetic modeling. Batch sorption kinetic experiments were conducted with both soils at pH 6.0, 7.0, and 7.5 from 24 h up to 1 month. Time-resolved Ni speciation in soils was determined by X-ray absorption spectroscopy (XAS) during the kinetic experiments. A kinetics model was developed to describe Ni kinetic reactions under various reaction conditions and time scales, which integrated Ni adsorption on SOM with Ni-LDH precipitation in soils. The soil Ni speciation (adsorbed phases and Ni-LDH) calculated using the kinetics model was consistent with that obtained through XAS analysis during the sorption processes. Under our experimental conditions, both modeling and XAS results demonstrated that Ni adsorption on SOM was dominant in the short term and the formation of Ni-LDH precipitates accounted for the long-term Ni sequestration in soils, and, more interestingly, that the adsorbed Ni may slowly transfer to Ni-LDH phases with longer reaction times.

  10. Synthesis and catalytic performance of SiO2@Ni and hollow Ni microspheres

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Liu, Yanhua; Shi, Xueting; Yu, Zhengyang; Feng, Libang

    2016-11-01

    Nickel (Ni) catalyst has been widely used in catalytic reducing reactions such as catalytic hydrogenation of organic compounds and catalytic reduction of organic dyes. However, the catalytic efficiency of pure Ni is low. In order to improve the catalytic performance, Ni nanoparticle-loaded microspheres can be developed. In this study, we have prepared Ni nanoparticle-loaded microspheres (SiO2@Ni) and hollow Ni microspheres using two-step method. SiO2@Ni microspheres with raspberry-like morphology and core-shell structure are synthesized successfully using SiO2 microsphere as a template and Ni2+ ions are adsorbed onto SiO2 surfaces via electrostatic interaction and then reduced and deposited on surfaces of SiO2 microspheres. Next, the SiO2 cores are removed by NaOH etching and the hollow Ni microspheres are prepared. The NaOH etching time does no have much influence on the crystal structure, shape, and surface morphology of SiO2@Ni; however, it can change the phase composition evidently. The hollow Ni microspheres are obtained when the NaOH etching time reaches 10 h and above. The as-synthesized SiO2@Ni microspheres exhibit much higher catalytic performance than the hollow Ni microspheres and pure Ni nanoparticles in the catalytic reduction of methylene blue. Meanwhile, the SiO2@Ni catalyst has high stability and hence it can be recycled for reuse.

  11. Kinetics of Ni sorption in soils: roles of soil organic matter and Ni precipitation.

    PubMed

    Shi, Zhenqing; Peltier, Edward; Sparks, Donald L

    2012-02-21

    The kinetics of Ni sorption to two Delaware agricultural soils were studied to quantitatively assess the relative importance of Ni adsorption on soil organic matter (SOM) and the formation of Ni layered double hydroxide (Ni-LDH) precipitates using both experimental studies and kinetic modeling. Batch sorption kinetic experiments were conducted with both soils at pH 6.0, 7.0, and 7.5 from 24 h up to 1 month. Time-resolved Ni speciation in soils was determined by X-ray absorption spectroscopy (XAS) during the kinetic experiments. A kinetics model was developed to describe Ni kinetic reactions under various reaction conditions and time scales, which integrated Ni adsorption on SOM with Ni-LDH precipitation in soils. The soil Ni speciation (adsorbed phases and Ni-LDH) calculated using the kinetics model was consistent with that obtained through XAS analysis during the sorption processes. Under our experimental conditions, both modeling and XAS results demonstrated that Ni adsorption on SOM was dominant in the short term and the formation of Ni-LDH precipitates accounted for the long-term Ni sequestration in soils, and, more interestingly, that the adsorbed Ni may slowly transfer to Ni-LDH phases with longer reaction times.

  12. Edge contact dependent spin transport for n-type doping zigzag-graphene with asymmetric edge hydrogenation

    PubMed Central

    Deng, Xiaoqing; Zhang, Zhenhua; Tang, Guiping; Fan, Zhiqiang; Zhu, Huali; Yang, Changhu

    2014-01-01

    Spin transport features of the n-type doping zigzag graphene nanoribbons (ZGNRs) with an edge contact are investigated by first principle methods, where ZGNRs are C–H2 bonded at one edge while C–H bonded at the other to form an asymmetric edge hydrogenation. The results show that a perfect spin filtering effect (100%) in such ZGNR nanojunctions can be achieved in a very large bias region for the unchanged spin states regardless of bias polarities, and the nanojunction with a contact of two C–H2 bonded edges has larger spin polarized current than that with a contact of two C–H bonded edges. The transmission pathways and the projected density of states (PDOS) demonstrate that the edge of C-H2 bonds play a crucial role for the spin magnetism and spin-dependent transport properties. Moreover, the negative differential resistance (NDR) effect is also observed in the spin-polarized current. PMID:24509476

  13. Evolution of edge pedestal transport between edge-localized modes in DIII-D

    SciTech Connect

    Floyd, J.-P.; Stacey, W. M.; Mellard, S. C.; Groebner, R. J.

    2015-02-15

    Evolution of measured profiles of densities, temperatures, and velocities in the edge pedestal region between successive ELM (edge-localized mode) events are analyzed and interpreted in terms of the constraints imposed by particle, momentum and energy balance in order to gain insights regarding the underlying evolution of transport processes in the edge pedestal between ELMs in a series of DIII-D [J. Luxon, Nucl. Fusion 42, 614 (2002)] discharges. The data from successive inter-ELM periods during an otherwise steady-state phase of the discharges were combined into a composite inter-ELM period for the purpose of increasing the number of data points in the analysis. Variation of diffusive and non-diffusive (pinch) particle, momentum, and energy transport over the inter-ELM period are interpreted using the GTEDGE code for discharges with plasma currents from 0.5 to 1.5 MA and inter-ELM periods from 50 to 220 ms. Diffusive transport is dominant for ρ < 0.925, while non-diffusive and diffusive transport are very large and nearly balancing in the sharp gradient region 0.925 < ρ < 1.0. During the inter-ELM period, diffusive transport increases slightly more than non-diffusive transport, increasing total outward transport. Both diffusive and non-diffusive transport have a strong inverse correlation with plasma current.

  14. Oxidation-driven surface dynamics on NiAl(100)

    PubMed Central

    Qin, Hailang; Chen, Xidong; Li, Liang; Sutter, Peter W.; Zhou, Guangwen

    2015-01-01

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling up of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). By comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps. PMID:25548155

  15. Oxidation-driven surface dynamics on NiAl(100)

    DOE PAGES

    Qin, Hailang; Chen, Xidong; Li, Liang; ...

    2014-12-29

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling upmore » of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). As a result, by comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps, we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.« less

  16. Oxidation-driven surface dynamics on NiAl(100)

    NASA Astrophysics Data System (ADS)

    Qin, Hailang; Chen, Xidong; Li, Liang; Sutter, Peter W.; Zhou, Guangwen

    2015-01-01

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling up of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). By comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.

  17. Oxidation-driven surface dynamics on NiAl(100)

    SciTech Connect

    Qin, Hailang; Chen, Xidong; Li, Liang; Sutter, Peter W.; Zhou, Guangwen

    2014-12-29

    Atomic steps, a defect common to all crystal surfaces, can play an important role in many physical and chemical processes. However, attempts to predict surface dynamics under nonequilibrium conditions are usually frustrated by poor knowledge of the atomic processes of surface motion arising from mass transport from/to surface steps. Using low-energy electron microscopy that spatially and temporally resolves oxide film growth during the oxidation of NiAl(100) we demonstrate that surface steps are impermeable to oxide film growth. The advancement of the oxide occurs exclusively on the same terrace and requires the coordinated migration of surface steps. The resulting piling up of surface steps ahead of the oxide growth front progressively impedes the oxide growth. This process is reversed during oxide decomposition. The migration of the substrate steps is found to be a surface-step version of the well-known Hele-Shaw problem, governed by detachment (attachment) of Al atoms at step edges induced by the oxide growth (decomposition). As a result, by comparing with the oxidation of NiAl(110) that exhibits unimpeded oxide film growth over substrate steps, we suggest that whenever steps are the source of atoms used for oxide growth they limit the oxidation process; when atoms are supplied from the bulk, the oxidation rate is not limited by the motion of surface steps.

  18. Structural evaluation and nonlinear optical properties of Ni/NiO, Ni/NiCo2O4 and Co/Co3O4 nanocomposites

    NASA Astrophysics Data System (ADS)

    Rahulan, K. Mani; Padmanathan, N.; Philip, Reji; Balamurugan, S.; Kanakam, Charles C.

    2013-10-01

    Nanocomposites of Ni/NiO, Ni/NiCo2O4 and Co/Co3O4 have been synthesized by a chemical reduction technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) images confirm the mixed composite nature of the sample and uniform particle size of approximately 13 nm. Formation of Ni/NiCo3O4 solid solution or NiCo2O4 spinel phase in the mixed composite is confirmed by energy dispersive X-ray (EDX) spectrum. Magnetic hysteresis (M-H) curves of the nanocomposites show excellent ferromagnetic (FM) nature at room temperature. Nonlinear optical transmission of the nanocomposites is measured using the open aperture Z-scan technique employing 7 nanosecond laser pulses at 532 nm. Experimental results show that NiO/NiO-Co3O4/Co3O4 nanocomposites exhibit good optical limiting performance. From the measurements and numerical fitting of the data to theory, it is found that nonlinear absorption has contributions from excited state absorption and two-photon absorption. Optical limiting is enhanced in Co3O4 and Ni/NiCo2O4 in which the Co3O4 content has a larger volume ratio.

  19. Observing the in situ chiral modification of Ni nanoparticles using scanning transmission X-ray microspectroscopy

    NASA Astrophysics Data System (ADS)

    Watson, David J.; Acharya, Sushma; Nicklin, Richard E. J.; Held, Georg

    2014-11-01

    Enantioselective heterogeneous hydrogenation of Cdbnd O bonds is of great potential importance in the synthesis of chirally pure products for the pharmaceutical and fine chemical industries. One of the most widely studied examples of such a reaction is the hydrogenation of β-ketoesters and β-diketoesters over Ni-based catalysts in the presence of a chiral modifier. Here we use scanning transmission X-ray microscopy combined with near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) to investigate the adsorption of the chiral modifier, namely (R,R)-tartaric acid, onto individual nickel nanoparticles. The C K-edge spectra strongly suggest that tartaric acid deposited onto the nanoparticle surfaces from aqueous solutions undergoes a keto-enol tautomerisation. Furthermore, we are able to interrogate the Ni L2,3-edge resonances of individual metal nanoparticles which, combined with X-ray diffraction (XRD) patterns showed them to consist of a pure nickel phase rather than the more thermodynamically stable bulk nickel oxide. Importantly, there appears to be no "particle size effect" on the adsorption mode of the tartaric acid in the particle size range ~ 90-~ 300 nm.

  20. Wisps in the outer edge of the Keeler Gap

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.; Arnault, Ethan G.

    2015-11-01

    Superposed upon the relatively smooth outer edge of the Keeler Gap are a system of "wisps," which appear to be ring material protruding inward into the gap, usually with a sharp trailing edge and a smooth gradation back to the background edge location on the leading side (Porco et al. 2005, Science). The radial amplitude of wisps is usually 0.5 to 1 km, and their azimuthal extent is approximately a degree of longitude (~2400 km). Wisps are likely caused by an interplay between Daphnis (and perhaps other moons) and embedded moonlets within the ring, though the details remain unclear.Aside from the wisps, the Keeler Gap outer edge is the only one of the five sharp edges in the outer part of Saturn's A ring that is reasonably smooth in appearance (Tiscareno et al. 2005, DPS), with occultations indicating residuals less than 1 km upon a possibly non-zero eccentricity (R.G. French, personal communication, 2014). The other four (the inner and outer edges of the Encke Gap, the inner edge of the Keeler Gap, and the outer edge of the A ring itself) are characterized by wavy structure at moderate to high spatial frequencies, with amplitudes ranging from 2 to 30 km (Tiscareno et al. 2005, DPS).We will present a catalogue of wisp detections in Cassini images. We carry out repeated gaussian fits of the radial edge location in order to characterize edge structure and visually scan those fitted edges in order to detect wisps. With extensive coverage in longitude and in time, we will report on how wisps evolve and move, both within an orbit period and on longer timescales. We will also report on the frequency and interpretation of wisps that deviate from the standard morphology. We will discuss the implications of our results for the origin and nature of wisps, and for the larger picture of how masses interact within Saturn's rings.

  1. Structural, electronic structure, and band alignment properties at epitaxial NiO/Al2O3 heterojunction evaluated from synchrotron based X-ray techniques

    NASA Astrophysics Data System (ADS)

    Singh, S. D.; Nand, Mangla; Das, Arijeet; Ajimsha, R. S.; Upadhyay, Anuj; Kamparath, Rajiv; Shukla, D. K.; Mukherjee, C.; Misra, P.; Rai, S. K.; Sinha, A. K.; Jha, S. N.; Phase, D. M.; Ganguli, Tapas

    2016-04-01

    The valence band offset value of 2.3 ± 0.2 eV at epitaxial NiO/Al2O3 heterojunction is determined from photoelectron spectroscopy experiments. Pulsed laser deposited thin film of NiO on Al2O3 substrate is epitaxially grown along [111] direction with two domain structures, which are in-plane rotated by 60° with respect to each other. Observation of Pendellosung oscillations around Bragg peak confirms high interfacial and crystalline quality of NiO layer deposited on Al2O3 substrate. Surface related feature in Ni 2p3/2 core level spectra along with oxygen K-edge soft X-ray absorption spectroscopy results indicates that the initial growth of NiO on Al2O3 substrate is in the form of islands, which merge to form NiO layer for the larger coverage. The value of conduction band offset is also evaluated from the measured values of band gaps of NiO and Al2O3 layers. A type-I band alignment at NiO and Al2O3 heterojunction is also obtained. The determined values of band offsets can be useful in heterojunction based light emitting devices.

  2. California Niño/Niña.

    PubMed

    Yuan, Chaoxia; Yamagata, Toshio

    2014-04-25

    The present study shows the existence of intrinsic coastal air-sea coupled phenomenon in the coastal ocean off Baja California and California in boreal summer for the first time. It contributes significantly to the interannual sea surface temperature (SST) anomalies there. An initial decrease/increase in the equatorward alongshore surface winds weakens/strengthens the coastal upwelling and raises/lowers the coastal SSTs through oceanic mixed-layer processes. The resultant coastal warming/cooling, in turn, heats/cools the overlying atmosphere anomalously, decreases/increases the atmospheric pressure in the lower troposphere, generates an anomalous cross-shore pressure gradient, and thus reinforces or maintains the alongshore surface wind anomalies. The regional air-sea coupled phenomenon seems to be analogous to the well-known El Niño/Southern Oscillation (ENSO) in the tropical Pacific but with much smaller time and space scales, and may be referred to as California Niño/Niña in its intrinsic sense.

  3. Textbook Multigrid Efficiency for Leading Edge Stagnation

    NASA Technical Reports Server (NTRS)

    Diskin, Boris; Thomas, James L.; Mineck, Raymond E.

    2004-01-01

    A multigrid solver is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work which is a small (less than 10) multiple of the operation count in evaluating the discrete residuals. TME in solving the incompressible inviscid fluid equations is demonstrated for leading- edge stagnation flows. The contributions of this paper include (1) a special formulation of the boundary conditions near stagnation allowing convergence of the Newton iterations on coarse grids, (2) the boundary relaxation technique to facilitate relaxation and residual restriction near the boundaries, (3) a modified relaxation scheme to prevent initial error amplification, and (4) new general analysis techniques for multigrid solvers. Convergence of algebraic errors below the level of discretization errors is attained by a full multigrid (FMG) solver with one full approximation scheme (F.4S) cycle per grid. Asymptotic convergence rates of the F.4S cycles for the full system of flow equations are very fast, approaching those for scalar elliptic equations.

  4. Agile robotic edge finishing system research

    SciTech Connect

    Powell, M.A.

    1995-07-01

    This paper describes a new project undertaken by Sandia National Laboratories to develop an agile, automated, high-precision edge finishing system. The project has a two-year duration and was initiated in October, 1994. This project involves re-designing and adding additional capabilities to an existing finishing workcell at Sandia; and developing intelligent methods for automating process definition and for controlling finishing processes. The resulting system will serve as a prototype for systems that will be deployed into highly flexible automated production lines. The production systems will be used to produce a wide variety of products with limited production quantities and quick turnaround requirements. The prototype system is designed to allow programming, process definition, fixture re-configuration, and process verification to be performed off-line for new products. CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) models of the part will be used to assist with the automated process development and process control tasks. To achieve Sandia`s performance goals, the system will be employ advanced path planning, burr prediction expert systems, automated process definition, statistical process models in a process database, and a two-level control scheme using hybrid position-force control and fuzzy logic control. In this paper, we discuss the progress and the planned system development under this project.

  5. Textbook Multigrid Efficiency for Leading Edge Stagnation

    NASA Technical Reports Server (NTRS)

    Diskin, Boris; Thomas, James L.; Mineck, Raymond E.

    2004-01-01

    A multigrid solver is defined as having textbook multigrid efficiency (TME) if the solutions to the governing system of equations are attained in a computational work which is a small (less than 10) multiple of the operation count in evaluating the discrete residuals. TME in solving the incompressible inviscid fluid equations is demonstrated for leading-edge stagnation flows. The contributions of this paper include (1) a special formulation of the boundary conditions near stagnation allowing convergence of the Newton iterations on coarse grids, (2) the boundary relaxation technique to facilitate relaxation and residual restriction near the boundaries, (3) a modified relaxation scheme to prevent initial error amplification, and (4) new general analysis techniques for multigrid solvers. Convergence of algebraic errors below the level of discretization errors is attained by a full multigrid (FMG) solver with one full approximation scheme (FAS) cycle per grid. Asymptotic convergence rates of the FAS cycles for the full system of flow equations are very fast, approaching those for scalar elliptic equations.

  6. Continuum Edge Gyrokinetic Theory and Simulations

    SciTech Connect

    Xu, X Q; Xiong, Z; Dorr, M R; Hittinger, J A; Bodi, K; Candy, J; Cohen, B I; Cohen, R H; Colella, P; Kerbel, G D; Krasheninnikov, S; Nevins, W M; Qin, H; Rognlien, T D; Snyder, P B; Umansky, M V

    2007-01-09

    The following results are presented from the development and application of TEMPEST, a fully nonlinear (full-f) five dimensional (3d2v) gyrokinetic continuum edge-plasma code. (1) As a test of the interaction of collisions and parallel streaming, TEMPEST is compared with published analytic and numerical results for endloss of particles confined by combined electrostatic and magnetic wells. Good agreement is found over a wide range of collisionality, confining potential, and mirror ratio; and the required velocity space resolution is modest. (2) In a large-aspect-ratio circular geometry, excellent agreement is found for a neoclassical equilibrium with parallel ion flow in the banana regime with zero temperature gradient and radial electric field. (3) The four-dimensional (2d2v) version of the code produces the first self-consistent simulation results of collisionless damping of geodesic acoustic modes and zonal flow (Rosenbluth-Hinton residual) with Boltzmann electrons using a full-f code. The electric field is also found to agree with the standard neoclassical expression for steep density and ion temperature gradients in the banana regime. In divertor geometry, it is found that the endloss of particles and energy induces parallel flow stronger than the core neoclassical predictions in the SOL. (5) Our 5D gyrokinetic formulation yields a set of nonlinear electrostatic gyrokinetic equations that are for both neoclassical and turbulence simulations.

  7. Computational investigation of miniature trailing edge effectors

    NASA Astrophysics Data System (ADS)

    Lee, Hak-Tae

    Miniature trailing edge effectors (MiTEs) are small flaps (typically 1% to 5% chord) actuated with deflection angles of up to 90 degrees. The small size, combined with little required power and good control authority, enables the device to be used for high bandwidth control as well as conventional attitude control. However, some of the aerodynamic characteristics of these devices are complex and poorly understood. This research investigated the aerodynamics of MiTEs using incompressible Navier-Stokes flow solvers, INS2D and INS3D. To understand the flow structure and establish a parametric database, two dimensional steady-state computations were performed for MiTEs with various geometries and flow conditions. Time accurate computations were used to resolve the unsteady characteristics including transient response and vortex shedding phenomena. The frequency response was studied to fully identify the dynamics of MiTEs. Three dimensional computations show the change in control effectiveness with respect to the spanwise length of MiTEs as well as the spanwise lift distribution induced by these devices. Based on the CFD results, an approximate vortex panel model was developed for design purposes that reproduces the key characteristics of MiTEs. Two application areas for MiTEs were explored. Flutter suppression was demonstrated by combining a finite element structural model with the vortex panel model. The application of MiTEs to augment maximum lift and improve the post stall behavior of an airfoil was also investigated.

  8. Ultrasonic testing of plates containing edge cracks

    NASA Technical Reports Server (NTRS)

    Williams, J. H., Jr.; Karagulle, H.; Lee, S. S.

    1985-01-01

    The stress wave factor (SWF) signal is utilized for the nondestructive evaluation of plates containing perpendicular edge cracks. The effects of the existence lateral location and depth of the crack on the magnitude spectra of individual reflections in the SWF signal are studied. If the reflections in the SWF signal are not overlapped the short time Fourier analysis is applied. If the reflections are overlapped the short time homomorphic analysis (cepstrum analysis) is applied. Several reflections which have average resonant frequencies approximately at 0.9, 1.3, and 1.7 MHz are analyzed. It is observed that the magnitude ratios evaluated at average resonant frequencies decrease more with increasing d/h if the crack is located between the transducers, where h is plate thickness and d is crack depth. Moreover, for the plates, crack geometries, reflections, and frequencies considered, the average decibel drop depends mainly on the dimensionless parameter d/h and it is approximately -1 dB per 0.07 d/h. Changes in the average resonant frequencies of the magnitude spectra are also observed due to changes in the location of the crack.

  9. Mechanistic simulation of line-edge roughness

    NASA Astrophysics Data System (ADS)

    Biafore, John J.; Smith, Mark D.; Robertson, Stewart A.; Graves, Trey

    2007-03-01

    Physically-based photoresist models, such as those in PROLITH, have been very successful in describing photolithography from a continuum standpoint. These models allow engineers to accurately predict the final resist CD on the wafer and to analyze process robustness. However, as the critical dimension continues to shrink, yield-limiting phenomena are observed that are related to the molecular nature and reaction kinetics of photoresist materials. An example of these phenomena is line-edge roughness (LER). In this paper, the origin of LER is hypothesized to be caused by fluctuations occurring in the initial position of the reactants, fluctuations during the exposure process (shot noise) and fluctuations occurring during thermally-induced reaction-diffusion (post-exposure bake). We have developed a lattice-based mechanistic simulator to better understand the stochastic nature of reactant initial position, the exposure step, the importance of the discrete nature of the reactants, the coupling to the deprotection kinetics and the deep complexity evident in the diffusion-limited acid-quencher reaction.

  10. Spectral methods in edge-diffraction theories

    SciTech Connect

    Arnold, J.M. )

    1992-12-01

    Spectral methods for the construction of uniform asymptotic representations of the field diffracted by an aperture in a plane screen are reviewed. These are separated into contrasting approaches, roughly described as physical and geometrical. It is concluded that the geometrical methods provide a direct route to the construction of uniform representations that are formally identical to the equivalent-edge-current concept. Some interpretive and analytical difficulties that complicate the physical methods of obtaining uniform representations are analyzed. Spectral synthesis proceeds directly from the ray geometry and diffraction coefficients, without any intervening current representation, and the representation is uniform at shadow boundaries and caustics of the diffracted field. The physical theory of diffraction postulates currents on the diffracting screen that give rise to the diffracted field. The difficulties encountered in evaluating the current integrals are throughly examined, and it is concluded that the additional data provided by the physical theory of diffraction (diffraction coefficients off the Keller diffraction cone) are not actually required for obtaining uniform asymptotics at the leading order. A new diffraction representation that generalizes to arbitrary plane-convex apertures a formula given by Knott and Senior [Proc. IEEE 62, 1468 (1974)] for circular apertures is deduced. 34 refs., 1 fig.

  11. Hermetic edge sealing of photovoltaic modules

    NASA Technical Reports Server (NTRS)

    Nowlan, M. J.

    1983-01-01

    The feasibility of using an electrostatic bonding (ESB) and ultrasonic welding process to produce hermetic edge seals on terrestrial solar cell modules was investigated. The fabrication sequence is to attach an aluminum foil "gasket' to the perimeter of a glass sheet. A cell circuit is next encapsulated inside the gasket, and its aluminum foil back cover is seam welded ultrasonically to the gasket. An ESB process for sealing aluminum to glass was developed in an ambient air atmosphere, which eliminates the requirement for a vacuum or pressure vessel. An ultrasonic seam welding process was also developed which did not degrade the quality of the ESB seal. Good quality welds with minimal deformation were produced. The effectiveness of the above described sealing techniques was tested by constructing 400 sq cm (8 x 8 s64 sq in) sample modules, and then subjecting them to nondestructive fine and gross leak tests. The gross leak tests identified several different causes of leaks which were then eliminated by modifying the assembly process.

  12. Edge-localized-modes in tokamaks

    SciTech Connect

    Leonard, A. W.

    2014-09-15

    Edge-localized-modes (ELMs) are a ubiquitous feature of H-mode in tokamaks. When gradients in the H-mode transport barrier grow to exceed the MHD stability limit the ELM instability grows explosively, rapidly transporting energy and particles onto open field lines and material surfaces. Though ELMs provide additional particle and impurity transport through the H-mode transport barrier, enabling steady operation, the resulting heat flux transients to plasma facing surfaces project to large amplitude in future low collisionality burning plasma tokamaks. Measurements of the ELM heat flux deposition onto material surfaces in the divertor and main chamber indicate significant broadening compared to inter-ELM heat flux, with a timescale for energy deposition that is consistent with sonic ion flow and numerical simulation. Comprehensive ELM simulation is highlighting the important physics processes of ELM transport including parallel transport due to magnetic reconnection and turbulence resulting from collapse of the H-mode transport barrier. Encouraging prospects for ELM control and/or suppression in future tokamaks include intrinsic modes of ELM free operation, ELM triggering with frequent small pellet injection and the application of 3D magnetic fields.

  13. Synthesis and magnetic studies of Ni/NiO core/shell nanoparticles

    NASA Astrophysics Data System (ADS)

    Rinsha, C.; Anumol, C. N.; Chithra, M.; Sahu, B. N.; Sahoo, Subasa C.

    2015-06-01

    Ni/NiO core/shell nanoparticles were synthesized by chemical reduction method followed by oxidation by two different methods; (a) in air and (b) in microwave oven. Structural studies showed that the thickness of NiO shell on Ni core is less in air oxidized sample than the microwave oxidized samples which were supported by the magnetic studies. The samples prepared by air oxidation showed positive exchange biasing where as the samples prepared by microwave oxidation showed negative exchange biasing. Our study also showed that the thickness of the antiferromagnetic NiO is responsible for the different types of magnetic interactions at the interfaces between antiferromagnetic NiO and ferromagnetic Ni in Ni/NiO core/shell nanoparticles.

  14. Rationalization of Au concentration and distribution in AuNi@Pt core-shell nanoparticles for oxygen reduction reaction

    DOE PAGES

    An, Wei; Liu, Ping

    2015-09-18

    Improving the activity and stability of Pt-based core–shell nanocatalysts for proton exchange membrane fuel cells while lowering Pt loading has been one of the big challenges in electrocatalysis. Here, using density functional theory, we report the effect of adding Au as the third element to enhance the durability and activity of Ni@Pt core–shell nanoparticles (NPs) during the oxygen reduction reaction (ORR). Our results show that the durability and activity of a Ni@Pt NP can be finely tuned by controlling Au concentration and distribution. For a NiAu@Pt NP, the durability can be greatly promoted by thermodynamically favorable segregation of Au tomore » replace the Pt atoms at vertex, edge, and (100) facets on the shell, while still keeping the ORR activity on the active Pt(111) shell as high as that of Ni@Pt nanoparticles. Such behavior strongly depends on a direct interaction with the Ni interlayer. The results not only highlight the importance of interplay between surface strain on the shell and the interlayer–shell interaction in determining the durability and activity but also provide guidance on how to maximize the usage of Au to optimize the performance of core–shell (Pt) nanoparticles. As a result, such understanding has allowed us to discover a novel NiAu@Pt nanocatalyst for the ORR.« less

  15. Rationalization of Au concentration and distribution in AuNi@Pt core-shell nanoparticles for oxygen reduction reaction

    SciTech Connect

    An, Wei; Liu, Ping

    2015-09-18

    Improving the activity and stability of Pt-based core–shell nanocatalysts for proton exchange membrane fuel cells while lowering Pt loading has been one of the big challenges in electrocatalysis. Here, using density functional theory, we report the effect of adding Au as the third element to enhance the durability and activity of Ni@Pt core–shell nanoparticles (NPs) during the oxygen reduction reaction (ORR). Our results show that the durability and activity of a Ni@Pt NP can be finely tuned by controlling Au concentration and distribution. For a NiAu@Pt NP, the durability can be greatly promoted by thermodynamically favorable segregation of Au to replace the Pt atoms at vertex, edge, and (100) facets on the shell, while still keeping the ORR activity on the active Pt(111) shell as high as that of Ni@Pt nanoparticles. Such behavior strongly depends on a direct interaction with the Ni interlayer. The results not only highlight the importance of interplay between surface strain on the shell and the interlayer–shell interaction in determining the durability and activity but also provide guidance on how to maximize the usage of Au to optimize the performance of core–shell (Pt) nanoparticles. As a result, such understanding has allowed us to discover a novel NiAu@Pt nanocatalyst for the ORR.

  16. Synthesis of carbon nanofibers by CVD as a catalyst support material using atomically ordered Ni3C nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Meifeng; Li, Na; Shao, Wei; Zhou, Chungen

    2016-12-01

    Atomically ordered nickel carbide (Ni3C) nanoparticles in polygonal shapes were prepared through the reduction of nickelocene. A novel type of carbon nanofiber (CNF) with twisted conformation was synthesized successfully by catalytic chemical vapor deposition (CCVD) using the obtained Ni3C nanoparticles at a relatively low temperature of 350 °C, which is below the lower limit temperature of 400 °C for the growth of CNFs using metal catalysts. The growth mechanism of the twisted CNFs from Ni3C was freshly derived based on the detailed characterizations. Compared with the growth of CNFs from Ni, graphene layers nucleate at monoatomic step edges and grow in a layer-by-layer manner, while the rotation of the polygonal Ni3C nanoparticles fabricates the twisted conformation during the CNF growth. The electrochemical activity and performance of the twisted CNFs loaded with Pt as electrode catalysts for a polymer electrolyte membrane fuel cell (PEMFC) were measured to be better than those of straight CNFs grown from Ni nanoparticles at 500 °C, since the specific surface conformation helps to make the loaded Pt more homogeneous.

  17. Local structural effects in Sr3NiRhO6 across magnetic transitions

    SciTech Connect

    Singh, Navneet; Khalid, S.; Bindu, R.

    2016-04-06

    Here, we investigate the temperature dependence of the structural parameters of quasi-one-dimensional Sr3NiRhO6 across the region of magnetic phase transitions using Ni K-edge and Sr K-edge x-ray absorption spectroscopy (XAS). The features in the x-ray absorption near-edge region are identified using multiple scattering calculations. The temperature-dependent extended x-ray absorption fine structure (EXAFS) studies show that the setting of the intra-chain super exchange interaction starts at ~200 K, which is well above the first transition temperature (45 K) revealed by magnetic susceptibility studies. The onset of the inter-chain super–super exchange interaction appears to be at ~125 K. Interestingly, the role played by direct exchange interaction between the Ni 3d and Rh 4d states in stabilising the magnetic interaction is less significant. The present results shed light on the generic features exhibited by isostructural compounds and may help in identifying the magnetic exchange pathways useful for understanding the unusual properties exhibited by such compounds.

  18. 12 CFR 211.5 - Edge and agreement corporations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... notice. The Board shall publish in the Federal Register notice of any proposal to organize an Edge...) Factors considered by Board. The factors considered by the Board in acting on a proposal to organize an... inconsistent with the international and foreign business purposes for which Edge corporations are...

  19. 12 CFR 211.5 - Edge and agreement corporations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... notice. The Board shall publish in the Federal Register notice of any proposal to organize an Edge...) Factors considered by Board. The factors considered by the Board in acting on a proposal to organize an... inconsistent with the international and foreign business purposes for which Edge corporations are...

  20. 12 CFR 211.5 - Edge and agreement corporations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... notice. The Board shall publish in the Federal Register notice of any proposal to organize an Edge...) Factors considered by Board. The factors considered by the Board in acting on a proposal to organize an... inconsistent with the international and foreign business purposes for which Edge corporations are...