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Sample records for surface band bending

  1. Complete surface plasmon-polariton band gap and gap-governed waveguiding, bending and splitting

    Science.gov (United States)

    Wu, Fengqin; Han, Dezhuan; Hu, Xinhua; Liu, Xiaohan; Zi, Jian

    2009-05-01

    We show theoretically that a complete band gap for surface plasmon-polaritons (SPPs) can exist in a flat metal surface coated with a two-dimensional periodic array of dielectric cylinders. Based on the SPP band gap, gap-governed SPP waveguides, bends and splitters at telecom wavelengths can be achieved by introducing line defects. Numerical simulations show that the proposed SPP waveguides have a very low loss, while SPP bends and splitters can bend and split guided SPPs efficiently. The proposed SPP waveguides, bends and splitters could thus be exploited to construct compact integrated optical circuits in the emerging field of plasmonics.

  2. Trigger of the Ubiquitous Surface Band Bending in 3D Topological Insulators

    Directory of Open Access Journals (Sweden)

    E. Frantzeskakis

    2017-11-01

    Full Text Available The main scientific activity in the field of topological insulators (TIs consists of determining their electronic structure by means of magnetotransport and electron spectroscopy with a view to devices based on topological transport. There is, however, a caveat in this approach. There are systematic experimental discrepancies on the electronic structure of the most pristine surfaces of TI single crystals as determined by Shubnikov–de Haas oscillations and by angle-resolved photoelectron spectroscopy (ARPES. We identify intense ultraviolet illumination—that is inherent to an ARPES experiment—as the source for these experimental differences. We explicitly show that illumination is the key parameter, or in other words, the trigger, for energetic shifts of electronic bands near the surface of a TI crystal. This finding revisits the common belief that surface decoration is the principal cause of surface band bending and explains why band bending is not a prime issue in illumination-free magnetotransport studies. Our study further clarifies the role of illumination on the electronic band structure of TIs by revealing its dual effect: downward band bending on very small time scales followed by band flattening at large time scales. Our results therefore allow us to present and predict the complete evolution of the band structure of TIs in a typical ARPES experiment. By virtue of our findings, we pinpoint two alternatives of how to approach flat-band conditions by means of photon-based techniques and we suggest a microscopic mechanism that can explain the underlying phenomena.

  3. Trigger of the Ubiquitous Surface Band Bending in 3D Topological Insulators

    Science.gov (United States)

    Frantzeskakis, E.; Ramankutty, S. V.; de Jong, N.; Huang, Y. K.; Pan, Y.; Tytarenko, A.; Radovic, M.; Plumb, N. C.; Shi, M.; Varykhalov, A.; de Visser, A.; van Heumen, E.; Golden, M. S.

    2017-10-01

    The main scientific activity in the field of topological insulators (TIs) consists of determining their electronic structure by means of magnetotransport and electron spectroscopy with a view to devices based on topological transport. There is, however, a caveat in this approach. There are systematic experimental discrepancies on the electronic structure of the most pristine surfaces of TI single crystals as determined by Shubnikov-de Haas oscillations and by angle-resolved photoelectron spectroscopy (ARPES). We identify intense ultraviolet illumination—that is inherent to an ARPES experiment—as the source for these experimental differences. We explicitly show that illumination is the key parameter, or in other words, the trigger, for energetic shifts of electronic bands near the surface of a TI crystal. This finding revisits the common belief that surface decoration is the principal cause of surface band bending and explains why band bending is not a prime issue in illumination-free magnetotransport studies. Our study further clarifies the role of illumination on the electronic band structure of TIs by revealing its dual effect: downward band bending on very small time scales followed by band flattening at large time scales. Our results therefore allow us to present and predict the complete evolution of the band structure of TIs in a typical ARPES experiment. By virtue of our findings, we pinpoint two alternatives of how to approach flat-band conditions by means of photon-based techniques and we suggest a microscopic mechanism that can explain the underlying phenomena.

  4. Orientation-dependent chemistry and band-bending of Ti on polar ZnO surfaces.

    Science.gov (United States)

    Borghetti, Patrizia; Mouchaal, Younes; Dai, Zongbei; Cabailh, Gregory; Chenot, Stéphane; Lazzari, Rémi; Jupille, Jacques

    2017-04-19

    Orientation-dependent reactivity and band-bending are evidenced upon Ti deposition (1-10 Å) on polar ZnO(0001)-Zn and ZnO(0001[combining macron])-O surfaces. At the onset of the Ti deposition, a downward band-bending was observed on ZnO(0001[combining macron])-O while no change occurred on ZnO(0001)-Zn. Combining this with the photoemission analysis of the Ti 2p core level and Zn L 3 (L 2 )M 45 M 45 Auger transition, it is established that the Ti/ZnO reaction is of the form Ti + 2ZnO → TiO 2 + 2Zn on ZnO(0001)-Zn and Ti + yZnO → TiZn x O y + (y - x)Zn on ZnO(0001[combining macron])-O. Consistently, upon annealing thicker Ti adlayers, the metallic zinc is removed to leave ZnO(0001)-Zn surfaces covered with a TiO 2 -like phase and ZnO(0001[combining macron])-O surfaces covered with a defined (Ti, Zn, O) compound. Finally, a difference in the activation temperature between the O-terminated (500 K) and Zn-terminated (700 K) surfaces is observed, which is tentatively explained by different electric fields in the space charge layer at ZnO surfaces.

  5. Electron band bending of polar, semipolar and non-polar GaN surfaces

    Czech Academy of Sciences Publication Activity Database

    Bartoš, Igor; Romanyuk, Olexandr; Houdková, Jana; Paskov, P.P.; Paskova, T.; Jiříček, Petr

    2016-01-01

    Roč. 119, č. 10 (2016), 1-7, č. článku 105303. ISSN 0021-8979 R&D Projects: GA ČR GA15-01687S Grant - others:AVČR(CZ) M100101201 Institutional support: RVO:68378271 Keywords : GaN * XPS * band bending Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.068, year: 2016

  6. Determination of the surface band bending in InxGa1−xN films by hard x-ray photoemission spectroscopy

    Directory of Open Access Journals (Sweden)

    Mickael Lozac'h, Shigenori Ueda, Shitao Liu, Hideki Yoshikawa, Sang Liwen, Xinqiang Wang, Bo Shen, Kazuaki Sakoda, Keisuke Kobayashi and Masatomo Sumiya

    2013-01-01

    Full Text Available Core-level and valence band spectra of InxGa1−xN films were measured using hard x-ray photoemission spectroscopy (HX-PES. Fine structure, caused by the coupling of the localized Ga 3d and In 4d with N 2s states, was experimentally observed in the films. Because of the large detection depth of HX-PES (~20 nm, the spectra contain both surface and bulk information due to the surface band bending. The InxGa1−xN films (x = 0–0.21 exhibited upward surface band bending, and the valence band maximum was shifted to lower binding energy when the mole fraction of InN was increased. On the other hand, downward surface band bending was confirmed for an InN film with low carrier density despite its n-type conduction. Although the Fermi level (EF near the surface of the InN film was detected inside the conduction band as reported previously, it can be concluded that EF in the bulk of the film must be located in the band gap below the conduction band minimum.

  7. Effects of surface treatment using aqua regia solution on the change of surface band bending of p-type GaN

    Science.gov (United States)

    Kim, Jong Kyu; Kim, Ki-Jeong; Kim, Bongsoo; Kim, Jae Nam; Kwak, Joon Seop; Park, Yong Jo; Lee, Jong-Lam

    2001-03-01

    Effects of surface treatment on the change of band bending at the surface of p-type GaN were studied using synchrotron radiation photoemission spectroscopy, and the results were used to interpret the reduction of contact resistivity by the surface treatment. The contact resistivity on p-type GaN decreased from (5.1±1.2)×10-1 to (9.3±3.5)×10-5Ω cm2 by the surface treatment using aqua regia prior to Pt deposition. Surface band bending was reduced by 0.58 eV and 0.87 eV after the surface treatments by HCl and aqua regia solutions, respectively. The atomic ratio of Ga/N decreased as the photoelectron detection angle was decreased, indicating that the surface oxide was mainly composed of Ga and O, GaOx, formed during high-temperature annealing for the generation of holes, and Ga vacancies, VGa, were produced below the GaOx layer. Consequently, the aqua regia treatment plays a role in removing GaOx formed on p-type GaN, leading to the shift of the Fermi level toward the energy levels of VGa located near the valence band edge. This causes the decrease of barrier height for the transport of holes, resulting in the good ohmic contacts to p-type GaN.

  8. Electron band bending and surface sensitivity: X-ray photoelectron spectroscopy of polar GaN surfaces

    Czech Academy of Sciences Publication Activity Database

    Bartoš, Igor; Romanyuk, Olexandr; Paskova, T.; Jiříček, Petr

    2017-01-01

    Roč. 664, Oct (2017), s. 241-245 ISSN 0039-6028 R&D Projects: GA ČR(CZ) GBP108/12/G108; GA MŠk LM2015088 Institutional support: RVO:68378271 Keywords : GaN * XPS * band banding Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 2.062, year: 2016

  9. Metal Ni-loaded g-C3N4 for enhanced photocatalytic H2 evolution activity: the change in surface band bending.

    Science.gov (United States)

    Bi, Lingling; Xu, Dandan; Zhang, Lijing; Lin, Yanhong; Wang, Dejun; Xie, Tengfeng

    2015-11-28

    A series of Ni@g-C3N4 composites were synthesized by a simple solvent thermal method using melamine and acetylacetone nickel as precursors. The results of X-ray diffraction, transmission electron microscopy and high resolution transmission electron microscopy indicate that Ni was successfully loaded on g-C3N4. And the Ni loaded greatly enhances the photocatalytic H2 evolution activity of g-C3N4 compared to the pure g-C3N4. In order to study the role of Ni, the surface photovoltage, the surface photocurrent and photoluminescence measurements were used to investigate the photogenerated charge properties of g-C3N4. What is more, Mott-Schottky plots and work function measurements confirmed the surface band bending change of g-C3N4 contacting with Ni. Those results demonstrate that Ni coating deepens surface band bending of g-C3N4, resulting in higher separation efficiency of photogenerated charge carriers, which is contributed to the enhanced photocatalytic H2 evolution activity.

  10. Effects of texture on shear band formation in plane strain tension/compression and bending

    DEFF Research Database (Denmark)

    Kuroda, M.; Tvergaard, Viggo

    2007-01-01

    model analysis. Third, shear band developments in plane strain pure bending of a sheet specimen with the typical textures are studied. Regions near the surfaces in a bent sheet specimen are approximately subjected to plane strain tension or compression. From this viewpoint, the bendability of a sheet......In this study, effects of typical texture components observed in rolled aluminum alloy sheets on shear band formation in plane strain tension/compression and bending are systematically studied. The material response is described by a generalized Taylor-type polycrystal model, in which each grain...... are obtained: i.e. the critical strain at the onset of shear banding and the corresponding orientation of shear band. Second, the shear band development in plane strain tension/compression is analyzed by the finite element method. Predictability of the finite element analysis is compared to that of the simple...

  11. Origin of bending in uncoated microcantilever - Surface topography?

    International Nuclear Information System (INIS)

    Lakshmoji, K.; Prabakar, K.; Tripura Sundari, S.; Jayapandian, J.; Tyagi, A. K.; Sundar, C. S.

    2014-01-01

    We provide direct experimental evidence to show that difference in surface topography on opposite sides of an uncoated microcantilever induces bending, upon exposure to water molecules. Examination on opposite sides of the microcantilever by atomic force microscopy reveals the presence of localized surface features on one side, which renders the induced stress non-uniform. Further, the root mean square inclination angle characterizing the surface topography shows a difference of 73° between the opposite sides. The absence of deflection in another uncoated microcantilever having similar surface topography confirms that in former microcantilever bending is indeed induced by differences in surface topography

  12. A wave-bending structure at Ka-band using 3D-printed metamaterial

    Science.gov (United States)

    Wu, Junqiang; Liang, Min; Xin, Hao

    2018-03-01

    Three-dimensional printing technologies enable metamaterials of complex structures with arbitrary inhomogeneity. In this work, a 90° wave-bending structure at the Ka-band (26.5-40 GHz) based on 3D-printed metamaterials is designed, fabricated, and measured. The wave-bending effect is realized through a spatial distribution of varied effective dielectric constants. Based on the effective medium theory, different effective dielectric constants are accomplished by special, 3D-printable unit cells, which allow different ratios of dielectric to air at the unit cell level. In contrast to traditional, metallic-structure-included metamaterial designs, the reported wave-bending structure here is all dielectric and implemented by the polymer-jetting technique, which features rapid, low-cost, and convenient prototyping. Both simulation and experiment results demonstrate the effectiveness of the wave-bending structure.

  13. Ultrathin 90-degree sharp bends for spoof surface plasmon polaritons

    DEFF Research Database (Denmark)

    Yang, Yihao; Chen, Hongsheng; Xiao, Sanshui

    2015-01-01

    surface plasmons around 90-degree sharp bends on ultrathin metallic films in the microwave regime. We demonstrate that by judiciously engineering the structure, the dispersion relation can be designed to reduce the scattering. Furthermore, the reflection can be suppressed by proper structural decoration...

  14. Single-mode optical fiber design with wide-band ultra low bending-loss for FTTH application.

    Science.gov (United States)

    Watekar, Pramod R; Ju, Seongmin; Han, Won-Taek

    2008-01-21

    We propose a new design of a single-mode optical fiber (SMF) which exhibits ultra low bend sensitivity over a wide communication band (1.3 microm to 1.65 microm). A five-cladding fiber structure has been proposed to minimize the bending loss, estimated to be as low as 4.4x10(-10) dB/turn for the bend radius of 10 mm.

  15. Raman study of band-bending at ZnSe/GaAs(001) interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bass, Utz; Frey, Alex; Mahapatra, Suddhasatta; Schumacher, Claus; Brunner, Karl; Geurts, Jean [Universitaet Wuerzburg, Physikalisches Institut, Experimentelle Physik III, Am Hubland, 97074 Wuerzburg (Germany)

    2011-07-01

    At heterovalent interfaces thermodynamically induced intermixing of the constituent materials with different numbers of valence electrons usually causes large variations in band offsets and local doping density, depending on the spatial arrangement of atoms at the interface. We varied the interface stoichiometry of n-doped ZnSe / GaAs (001) heterostructures by the predeposition of different amounts of Zn or Se on n-GaAs prior to n-ZnSe layer growth by MBE. The induced changes in band bending were optically analysed by Raman spectroscopy from coupled plasmon-LO-phonon modes and by Far-Infrared reflectance spectroscopy for calibration. We detect a depletion layer of about 50 nm at the heterointerface, which partially shifts from the GaAs into the ZnSe with Se predeposition. Together with data from electrical transport across the interface and capacitance-voltage profiling, our results are explained consistently by a 550 mV potential barrier in the conduction band at a Zn-rich n-ZnSe / n-GaAs interface, which is tuned down to about 70 mV by increasing Se predeposition. In addition, PL signatures for excitation above and below the ZnSe band gap are presented.

  16. Bending and splitting of spoof surface acoustic waves through structured rigid surface

    Science.gov (United States)

    Xie, Sujun; Ouyang, Shiliang; He, Zhaojian; Wang, Xiaoyun; Deng, Ke; Zhao, Heping

    2018-03-01

    In this paper, we demonstrated that a 90°-bended imaging of spoof surface acoustic waves with subwavelength resolution of 0.316λ can be realized by a 45° prism-shaped surface phononic crystal (SPC), which is composed of borehole arrays with square lattice in a rigid plate. Furthermore, by combining two identical prism-shaped phononic crystal to form an interface (to form a line-defect), the excited spoof surface acoustic waves can be split into bended and transmitted parts. The power ratio between the bended and transmitted surface waves can be tuned arbitrarily by adjusting the defect size. This acoustic system is believed to have potential applications in various multifunctional acoustic solutions integrated by different acoustical devices.

  17. Observation of band bending of metal/high-k Si capacitor with high energy x-ray photoemission spectroscopy and its application to interface dipole measurement

    Science.gov (United States)

    Kakushima, K.; Okamoto, K.; Tachi, K.; Song, J.; Sato, S.; Kawanago, T.; Tsutsui, K.; Sugii, N.; Ahmet, P.; Hattori, T.; Iwai, H.

    2008-11-01

    Band bendings of Si substrates have been observed using hard x-ray photoemission spectroscopy. With a capability of collecting photoelectrons generated as deep as 40 nm, the binding energy shift in a core level caused by the potential profile at the surface of the substrate results in a spectrum broadening. The broadening is found to be significant when heavily doped substrates are used owing to its steep potential profile. The surface potential of the substrate can be obtained by deconvolution of the spectrum. This method has been applied to observe the band bending profile of metal-oxide-semiconductor capacitors with high-k gate dielectrics. By comparing the band bending profiles of heavily-doped n+- and p+-Si substrates, the interface dipoles presented at interfaces can be estimated. In the case of W gated La2O3/La-silicate capacitor, an interface dipole to shift the potential of -0.45 V has been estimated at La-silicate/Si interface, which effectively reduces the apparent work function of W. On the other hand, an interface dipole of 0.03-0.07 V has been found to exist at Hf-silicate/SiO2 interface for W gated HfO2/Hf-silicate/SiO2 capacitor.

  18. Second-order infinitesimal bendings of surfaces of revolution with flattening at the poles

    International Nuclear Information System (INIS)

    Sabitov, I Kh

    2014-01-01

    We study infinitesimal bendings of surfaces of revolution with flattening at the poles. We begin by considering the minimal possible smoothness class C 1 both for surfaces and for deformation fields. Conditions are formulated for a given harmonic of a first-order infinitesimal bending to be extendable into a second order infinitesimal bending. We finish by stating a criterion for nonrigidity of second order for closed surfaces of revolution in the analytic class. We also give the first concrete example of such a nonrigid surface. Bibliography: 15 entries

  19. Electronic structure and band alignment of 9,10-phenanthrenequinone passivated silicon surfaces

    Science.gov (United States)

    Avasthi, Sushobhan; Qi, Yabing; Vertelov, Grigory K.; Schwartz, Jeffrey; Kahn, Antoine; Sturm, James C.

    2011-07-01

    In this work we demonstrate that the room-temperature deposition of the organic molecule 9,10-phenanthrenequinone (PQ) reduces the surface defect density of the silicon (100) surface by chemically bonding to the surface dangling bonds. Using various spectroscopic measurements we have investigated the electronic structure and band alignment properties of the PQ/Si interface. The band-bending at the PQ-passivated silicon surface is negligible for both n- and p-type substrates, demonstrating a low density of surface defects. Finally we show that PQ forms a semiconducting wide-bandgap type-I heterojunction with silicon.

  20. Surface roughness and the flexural and bend strength of zirconia after different surface treatments.

    Science.gov (United States)

    Hjerppe, Jenni; Närhi, Timo O; Vallittu, Pekka K; Lassila, Lippo V J

    2016-10-01

    Different surface treatments are commonly used during the fabrication of zirconia fixed dental prostheses. However, such treatments can affect the properties of the zirconia framework material. The purpose of this in vitro study was to determine the effect of different surface treatments on the surface roughness and flexural and bend strength of zirconia. Seventy-two zirconia disks (n=8) and 72 zirconia bars (n=8) were sintered and divided into 9 groups for different surface treatments: sintered control, airborne-particle abraded with 50-μm aluminum oxide, airborne-particle abraded with Rocatec soft (30 μm), airborne-particle abraded with Rocatec (105 μm), grinding dry with a micromotor, turbine grinding under water cooling, grinding with silicon carbide paper, diamond paste polishing, and steam cleaning. The biaxial flexural strength of the disks (diameter 19 mm, thickness 1.6 mm) and 3-point bend test of the bars (thickness 2 mm, height 2 mm, length 25 mm) were measured dry at room temperature. One-way ANOVA followed by the Tukey HSD test (α=.05) and Pearson correlation test were used for statistical analysis. Airborne-particle abrasion and silicon carbide paper grinding increased the flexural and bend strength of zirconia specimens (Pzirconia framework material. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  1. Surface band structures on Nb(001)

    International Nuclear Information System (INIS)

    Fang, B.; Lo, W.; Chien, T.; Leung, T.C.; Lue, C.Y.; Chan, C.T.; Ho, K.M.

    1994-01-01

    We report the joint studies of experimental and theoretical surface band structures of Nb(001). Angle-resolved photoelectron spectroscopy was used to determine surface-state dispersions along three high-symmetry axes bar Γ bar M, bar Γ bar X, and bar M bar X in the surface Brillouin zone. Ten surface bands have been identified. The experimental data are compared to self-consistent pseudopotential calculations for the 11-layer Nb(001) slabs that are either bulk terminated or fully relaxed (with a 12% contraction for the first interlayer spacing). The band calculations for a 12% surface-contracted slab are in better agreement with the experimental results than those for a bulk-terminated slab, except for a surface resonance near the Fermi level, which is related to the spin-orbit interaction. The charge profiles for all surface states or resonances have been calculated. Surface contraction effects on the charge-density distribution and the energy position of surface states and resonances will also be discussed

  2. Residual compressive surface stress increases the bending strength of dental zirconia.

    Science.gov (United States)

    Inokoshi, Masanao; Zhang, Fei; Vanmeensel, Kim; De Munck, Jan; Minakuchi, Shunsuke; Naert, Ignace; Vleugels, Jozef; Van Meerbeek, Bart

    2017-04-01

    To assess the influence of surface treatment and thermal annealing on the four-point bending strength of two ground dental zirconia grades. Fully-sintered zirconia specimens (4.0×3.0×45.0mm 3 ) of Y-TZP zirconia (LAVA Plus, 3M ESPE) and Y-TZP/Al 2 O 3 zirconia (ZirTough, Kuraray Noritake) were subjected to four surface treatments: (1) 'GROUND': all surfaces were ground with a diamond-coated grinding wheel on a grinding machine; (2) 'GROUND+HEAT': (1) followed by annealing at 1100°C for 30min; (3) 'GROUND+Al 2 O 3 SANDBLASTED': (1) followed by sandblasting using Al 2 O 3 ; (4) 'GROUND+CoJet SANDBLASTED': (1) followed by tribochemical silica (CoJet) sandblasting. Micro-Raman spectroscopy was used to assess the zirconia-phase composition and potentially induced residual stress. The four-point bending strength was measured using a universal material-testing machine. Weibull analysis revealed a substantially higher Weibull modulus and slightly higher characteristic strength for ZirTough (Kuraray Noritake) than for LAVA Plus (3M ESPE). For both zirconia grades, the 'GROUND' zirconia had the lowest Weibull modulus in combination with a high characteristic strength. Sandblasting hardly changed the bending strength but substantially increased the Weibull modulus of the ground zirconia, whereas a thermal treatment increased the Weibull modulus of both zirconia grades but resulted in a significantly lower bending strength. Micro-Raman analysis revealed a higher residual compressive surface stress that correlated with an increased bending strength. Residual compressive surface stress increased the bending strength of dental zirconia. Thermal annealing substantially reduced the bending strength but increased the consistency (reliability) of 'GROUND' zirconia. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  3. Stiffness Matrix of Thin-Walled Open Bar Subject to Bending, Bending Torsion and Shift of Cross Section Middle Surface

    Science.gov (United States)

    Panasenko, N. N.; Sinelschikov, A. V.

    2017-11-01

    One of the main stages in the analysis of complex 3D structures and engineering constructions made of thin-walled open bars using FEM is a stiffness matrix developing. Taking into account middle surface shear deformation caused by the work of tangential stresses in the formula to calculate a potential energy of thin-walled open bars, the authors obtain an important correction at calculation of the bar deformation and fundamental frequencies. The results of the analysis of the free end buckling of a cantilever H-bar under plane bending differ from exact solution by 0.53%. In the course of comparison of the obtained results with the cantilever bar buckling regardless the middle surface shear deformation, an increase made 16.6%. The stiffness matrix of a thin-walled open bar developed in the present work can be integrated into any software suite using FEM for the analysis of complex 3-D structures and engineering constructions with n-freedoms.

  4. Analysis of Surface Roughening in AA6111 Automotive Sheet Under Pure Bending

    Science.gov (United States)

    Shi, Y.; Zhao, P. Z.; Jin, H.; Wu, P. D.; Lloyd, D. J.

    2016-02-01

    The finite element method is used to numerically simulate the topographic development in an aluminum sheet, AA6111, under pure bending. The measured electron backscatter diffraction data are directly incorporated into the finite element model, and the constitutive response at an integration point is described by the single crystal plasticity theory. The effects of strain-rate sensitivity, work hardening, and imposed initial surface roughness on surface roughening are studied. It is found that the grains in top surface layers of the sheet play a big role in controlling the outer surface roughness due to the strain gradient across sheet thickness in bending, while the grain size and texture of the surface layers have a direct impact on finishing surface qualities.

  5. Interface dipole and band bending in the hybrid p -n heterojunction Mo S2/GaN (0001 )

    Science.gov (United States)

    Henck, Hugo; Ben Aziza, Zeineb; Zill, Olivia; Pierucci, Debora; Naylor, Carl H.; Silly, Mathieu G.; Gogneau, Noelle; Oehler, Fabrice; Collin, Stephane; Brault, Julien; Sirotti, Fausto; Bertran, François; Le Fèvre, Patrick; Berciaud, Stéphane; Johnson, A. T. Charlie; Lhuillier, Emmanuel; Rault, Julien E.; Ouerghi, Abdelkarim

    2017-09-01

    Hybrid heterostructures based on bulk GaN and two-dimensional (2D) materials offer novel paths toward nanoelectronic devices with engineered features. Here, we study the electronic properties of a mixed-dimensional heterostructure composed of intrinsic n -doped Mo S2 flakes transferred on p -doped GaN(0001) layers. Based on angle-resolved photoemission spectroscopy (ARPES) and high resolution x-ray photoemission spectroscopy (HR-XPS), we investigate the electronic structure modification induced by the interlayer interactions in Mo S2/GaN heterostructure. In particular, a shift of the valence band with respect to the Fermi level for Mo S2/GaN heterostructure is observed, which is the signature of a charge transfer from the 2D monolayer Mo S2 to GaN. The ARPES and HR-XPS revealed an interface dipole associated with local charge transfer from the GaN layer to the Mo S2 monolayer. Valence and conduction band offsets between Mo S2 and GaN are determined to be 0.77 and -0.51 eV , respectively. Based on the measured work functions and band bendings, we establish the formation of an interface dipole between GaN and Mo S2 of 0.2 eV.

  6. Surface crack growth subject to bending and biaxial tension-compression

    Directory of Open Access Journals (Sweden)

    V. Shlyannikov

    2016-01-01

    Full Text Available Fatigue surface crack growth and the in-plane and out-of-plane constraint effects are studied through experiments and computations for aluminium alloy D16T. Subjects for studies are cruciform specimens under different biaxial loading and bending central notched specimens with external semi-elliptical surface crack. Both the optical microscope measurements and the crack opening displacement (COD method are used to monitor and calculate both crack depth and crack length during the tests. The variation of crack growth rate and surface crack paths behaviour is studied under cyclic pure bending and biaxial tension-compression fatigue loading. This work is centered on the relations between crack size on the free surface of specimen considered configurations, COD and aspect ratio under different fatigue loading conditions. For the experimental surface crack paths in tested specimens the T-stress, the local triaxiality parameter h, the out-of-plane TZ factor and the governing parameter for the 3D-fields of the stresses and strains at the crack tip in the form of In-integral were calculated as a function of aspect ratio by finite element analysis to characterization of the constraint effects along semi-elliptical crack front. The plastic stress intensity factor approach is applied to the fatigue crack growth on the free surface of the tested bending and cruciform specimens as well as the deepest point of the semi-elliptical surface crack front. As result fatigue surface crack paths or crack front positions as a function of accumulated number of cycle of loading are obtained.

  7. Atomic scale images of acceptors in III-V semiconductors. Band bending, tunneling paths and wave functions

    Energy Technology Data Exchange (ETDEWEB)

    Loth, S.

    2007-10-26

    This thesis reports measurements of single dopant atoms in III-V semiconductors with low temperature Scanning Tunneling Microscopy (STM) and Scanning Tunneling Spectroscopy (STS). It investigates the anisotropic spatial distribution of acceptor induced tunneling processes at the {l_brace}110{r_brace} cleavage planes. Two different tunneling processes are identified: conventional imaging of the squared acceptor wave function and resonant tunneling at the charged acceptor. A thorough analysis of the tip induced space charge layers identifies characteristic bias windows for each tunnel process. The symmetry of the host crystal's band structure determines the spatial distribution of the tunneling paths for both processes. Symmetry reducing effects at the surface are responsible for a pronounced asymmetry of the acceptor contrasts along the principal [001] axis. Uniaxial strain fields due to surface relaxation and spin orbit interaction of the tip induced electric field are discussed on the basis of band structure calculations. High-resolution STS studies of acceptor atoms in an operating p-i-n diode confirm that an electric field indeed changes the acceptor contrasts. In conclusion, the anisotropic contrasts of acceptors are created by the host crystal's band structure and concomitant symmetry reduction effects at the surface. (orig.)

  8. Surface effects on static bending of nanowires based on non-local elasticity theory

    Directory of Open Access Journals (Sweden)

    Quan Wu

    2015-10-01

    Full Text Available The surface elasticity and non-local elasticity effects on the elastic behavior of statically bent nanowires are investigated in the present investigation. Explicit solutions are presented to evaluate the surface stress and non-local elasticity effects with various boundary conditions. Compared with the classical Euler beam, a nanowire with surface stress and/or non-local elasticity can be either stiffer or less stiff, depending on the boundary conditions. The concept of surface non-local elasticity was proposed and its physical interpretation discussed to explain the combined effect of surface elasticity and non-local elasticity. The effect of the nanowire size on its elastic bending behavior was investigated. The results obtained herein are helpful to characterize mechanical properties of nanowires and aid nanowire-based devices design.

  9. The (001) 3C SiC surface termination and band structure after common wet chemical etching procedures, stated by XPS, LEED, and HREELS

    Science.gov (United States)

    Tengeler, Sven; Kaiser, Bernhard; Ferro, Gabriel; Chaussende, Didier; Jaegermann, Wolfram

    2018-01-01

    The (001) surface of cubic silicon carbide (3C SiC) after cleaning, Ar sputtering and three different wet chemical etching procedures was thoroughly investigated via (angle resolved) XPS, HREELS, and LEED. While Ar sputtering was found to be unsuitable for surface preparation, all three employed wet chemical etching procedures (piranha/NH4F, piranha/HF, and RCA) provide a clean surface. HF as oxide removal agent tends to result in fluorine traces on the sample surface, despite thorough rinsing. All procedures yield a 1 × 1 Si-OH/C-H terminated surface. However, the XPS spectra reveal some differences in the resulting surface states. NH4F for oxide removal produces a flat band situation, whereas the other two procedures result in a slight downward (HF) or upward (RCA) band bending. Because the band bending is small, it can be concluded that the number of unsaturated surface defects is low.

  10. Effects of surface condition on the work function and valence-band position of ZnSnN2

    Science.gov (United States)

    Shing, Amanda M.; Tolstova, Yulia; Lewis, Nathan S.; Atwater, Harry A.

    2017-12-01

    ZnSnN2 is an emerging wide band gap earth-abundant semiconductor with potential applications in photonic devices such as solar cells, LEDs, and optical sensors. We report the characterization by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy of reactively radio-frequency sputtered II-IV-nitride ZnSnN2 thin films. For samples transferred in high vacuum, the ZnSnN2 surface work function was 4.0 ± 0.1 eV below the vacuum level, with a valence-band onset of 1.2 ± 0.1 eV below the Fermi level. The resulting band diagram indicates that the degenerate bulk Fermi level position in ZnSnN2 shifts to mid-gap at the surface due to band bending that results from equilibration with delocalized surface states within the gap. Brief (oxygen-evolution reaction.

  11. Nonpolar nitrous oxide dimer: Observation of combination bands of (14N2O)2 and (15N2O)2 involving the torsion and antigeared bending modes

    Science.gov (United States)

    Rezaei, M.; Michaelian, K. H.; Moazzen-Ahmadi, N.

    2012-03-01

    Spectra of the nonpolar nitrous oxide dimer in the region of the N2O ν1 fundamental band were observed in a supersonic slit-jet apparatus. The expansion gas was probed using radiation from a quantum cascade or a tunable diode laser, with both lasers employed in a rapid-scan signal averaging mode. Four bands were observed and analyzed: new combination bands involving the intermolecular conrotation of the monomers (Ag antigeared bend) for (14N2O)2 and (15N2O)2, the previously reported torsional combination band for (14N2O)2 with improved signal-to-noise ratio, and the same torsional combination band for (15N2O)2. The resulting frequencies for the intermolecular antigeared mode are 96.0926(1) and 95.4912(1) cm-1 for (14N2O)2 and (15N2O)2, respectively. This is the third of the four intermolecular frequencies which has now been measured experimentally, the others being the out-of-plane torsion and the geared bend modes. Our experimental results are in good agreement with two recent high level ab initio theoretical calculations.

  12. V-Band Wireless Surface Networks Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA GLENN RESEARCH CENTER in Topic O1.10 has identified the need to provide surface communications networks for human and robotic missions to explore the Moon and...

  13. On the bending and buckling behaviors of Mindlin nanoplates considering surface energies

    Science.gov (United States)

    Ansari, R.; Shahabodini, A.; Faghih Shojaei, M.; Mohammadi, V.; Gholami, R.

    2014-03-01

    Due to the high surface to volume ratio of the nanoscale domain, the surface stress effect is a major concern in the analysis of mechanical response of the nanomaterials and nanostructures. This paper is concerned with the applicability of a continuum model including the surface properties for describing the bending and buckling configuration of the nanoscale plates. The Gurtin-Murdoch surface theory of elasticity is first incorporated into Mindlin’s plate theory. Then, the principle of virtual work is applied to derive the size-dependent governing equations along with various boundary conditions. To solve the governing equations, the generalized differential quadrature (GDQ) method is employed. The critical uniaxial and biaxial buckling loads and the maximum deflection of the nanoplate due to a uniform transverse load are calculated in the presence and absence of the surface effects for various edge conditions. It is found that the significance of the surface effects on the response of the nanoplate relies on its size, type of edge support and selected surface constants.

  14. Band mapping of surface states vs. adsorbate coverage

    International Nuclear Information System (INIS)

    Rotenberg, E.; Kevan, S.D.; Denlinger, J.D.; Chung, Jin-Wook

    1997-01-01

    The theory of electron bands, which arises from basic quantum mechanical principles, has been the cornerstone of solid state physics for over 60 years. Simply put, an energy band is an electron state in a solid whose energy varies with its momentum (similar to, but with a more complicated dependence than, how a free electron's energy is proportional to its momentum squared). Much attention over the last 15 years has been given to the study of band structure of surfaces and interfaces, especially as the applications of these two-dimensional systems have become increasingly important to industry and science. The ultraESCA endstation at beamline 7.01 at the Advanced Light Source was developed for very high-energy - (∼50 meV) and angular - ( 12 photons/sec) makes the detailed study of the evolution of bands possible. The authors are interested in learning how, when one forms a chemical bond between a metal and an overlaying atom or molecule, the resulting charge transfer to or from the adsorbate affects the surface bands. In some cases of interest, intermediate coverages lead to different band structure than at the extremes of clean and saturated surfaces. Surfaces of tungsten are particularly interesting, as their atomic geometry has been shown to be exquisitely sensitive to both the surface vibrational and electronic properties. In this study, the authors looked at the surface bands of tungsten ((110) surface), as a function both of coverage and mass of overlaying atoms. The adsorbed atoms were hydrogen and the alkali atoms lithium and cesium

  15. Surface orientation effects on bending properties of surgical mesh are independent of tensile properties.

    Science.gov (United States)

    Simon, David D; Andrews, Sharon M; Robinson-Zeigler, Rebecca; Valdes, Thelma; Woods, Terry O

    2018-02-01

    Current mechanical testing of surgical mesh focuses primarily on tensile properties even though implanted devices are not subjected to pure tensile loads. Our objective was to determine the flexural (bending) properties of surgical mesh and determine if they correlate with mesh tensile properties. The flexural rigidity values of 11 different surgical mesh designs were determined along three textile directions (machine, cross-machine, and 45° to machine; n = 5 for each) using ASTM D1388-14 while tracking surface orientation. Tensile testing was also performed on the same specimens using ASTM D882-12. Linear regressions were performed to compare mesh flexural rigidity to mesh thickness, areal mass density, filament diameter, ultimate tensile strength, and maximum extension. Of 33 mesh specimen groups, 30 had significant differences in flexural rigidity values when comparing surface orientations (top and bottom). Flexural rigidity and mesh tensile properties also varied with textile direction (machine and cross-machine). There was no strong correlation between the flexural and tensile properties, with mesh thickness having the best overall correlation with flexural rigidity. Currently, surface orientation is not indicated on marketed surgical mesh, and a single mesh may behave differently depending on the direction of loading. The lack of correlation between flexural stiffness and tensile properties indicates the need to examine mesh bending stiffness to provide a more comprehensive understanding of surgical mesh mechanical behaviors. Further investigation is needed to determine if these flexural properties result in the surgical mesh behaving mechanically different depending on implantation direction. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 854-862, 2018. © 2017 Wiley Periodicals, Inc.

  16. Modelling of the bending behaviour of double floor systems for different contact surfaces

    Directory of Open Access Journals (Sweden)

    Attila PUSKAS

    2014-07-01

    Full Text Available In the practice of prefabricated concrete structures considerable surfaces of intermediate floors are constructed using double floor systems with prefabricated bottom layer and upper layer. This second layer is cast on site. The quality of the prefabricated concrete is often of superior class with respect to the monolithic layer. In the service state of the double floor system, important compressive stresses appear in the upper concrete layer. On the other hand, the bond quality between the concrete layers cast in successive stages raises questions especially in the case of hollow core floor units with no connecting reinforcement in-between. The paper presents results of the numerical models prepared for double floor elements having different thicknesses for the top and bottom layers, subjected to bending. Three situations have been studied: stepped top surface of the prefabricated slab with no connecting reinforcement, broom swept tracks on the prefabricated slab with no connecting reinforcement and broom swept tracks on the prefabricated slab with stirrups connecting the concrete layers. For each situation two different ratios of the thicknesses of the layers have been considered. The results are emphasizing the critical regions of the elements, the differences in crack development and in the behaviour resulting from surface preparation and use of connecting reinforcements.

  17. Surface Plasmon Resonance and Bending Loss-Based U-Shaped Plastic Optical Fiber Biosensors

    Directory of Open Access Journals (Sweden)

    Ariadny da S. Arcas

    2018-02-01

    Full Text Available Escherichia coli (E. coli is a large and diverse bacteria group that inhabits the intestinal tract of many mammals. Most E. coli strains are harmless, however some of them are pathogenic, meaning they can make one sick if ingested. By being in the feces of animals and humans, its presence in water and food is used as indicator of fecal contamination. The main method for this microorganism detection is the bacterial culture medium that is time-consuming and requires a laboratory with specialized personnel. Other sophisticated methods are still not fast enough because they require sending samples to a laboratory and with a high cost of analysis. In this paper, a gold-coated U-shaped plastic optical fiber (POF biosensor for E. coli bacteria detection is presented. The biosensor works by intensity modulation principle excited by monochromatic light where the power absorption is imposed by predominant effect of either bending loss or surface plasmon resonance (SPR, depending on the gold thickness. Bacterial selectivity is obtained by antibody immobilization on the fiber surface. The biosensor showed a detection limit of 1.5 × 103 colony-forming units (CFU/mL, demonstrating that the technology can be a portable, fast response and low-cost alternative to conventional methodologies for quality analysis of water and food.

  18. Size effects on electromechanical coupling fields of a bending piezoelectric nanoplate due to surface effects and flexoelectricity

    Science.gov (United States)

    Zhang, Zhengrong; Jiang, Liying

    2014-10-01

    Due to large surface to volume ratio and manifest strain gradients typically present in nanostructures, it is essential to incorporate both surface effects and flexoelectricity in studying the size-dependent electromechanical coupling behaviors of piezoelectric materials at the nano-scale. In the current work, a modified Kirchhoff plate model with the consideration of residual surface stress, surface elasticity, surface piezoelectricity, and flexoelectricity is developed to investigate the electroelastic responses and vibrational behaviors of a bending piezoelectric nanoplate (PNP). The governing equations and the corresponding boundary conditions accounting for both the surface effects and the flexoelectricity are derived by the variational principle. Ritz approximate solutions of the static bending and the free vibration indicate that these nano-scale features are more prominent for thinner plates with smaller thickness. The simulation results also reveal that the influence of the flexoelectricity and the surface effects upon the bending behaviors of the PNP depends on the applied electrical loading and the plate dimensions. Moreover, it is also observed that the frequency tuning of PNP-based nanoresonators by adjusting applied electrical load can be modified by both the flexoelectricity and the surface effects. The current work is expected to provide increased understanding on the theoretical basis for the design and applications of PNP-based nanodevices.

  19. Torsion-rotation structure and quasi-symmetric-rotor behaviour for the CH3SH asymmetric CH3-bending and C-H stretching bands of E parentage

    Science.gov (United States)

    Lees, R. M.; Xu, Li-Hong; Guislain, B. G.; Reid, E. M.; Twagirayezu, S.; Perry, D. S.; Dawadi, M. B.; Thapaliya, B. P.; Billinghurst, B. E.

    2018-01-01

    High-resolution Fourier transform spectra of the asymmetric methyl-bending and methyl-stretching bands of CH3SH have been recorded employing synchrotron radiation at the FIR beamline of the Canadian Light Source. Analysis of the torsion-rotation structure and relative intensities has revealed the novel feature that for both bend and stretch the in-plane and out-of-plane modes behave much like a Coriolis-coupled l-doublet pair originating from degenerate E modes of a symmetric top. As the axial angular momentum K increases, the energies of the coupled "l = ±1" modes diverge linearly, with effective Coriolis ζ constants typical for symmetric tops. For the methyl-stretching states, separated at K = 0 by only about 1 cm-1, the assigned sub-bands follow a symmetric top Δ(K - l) = 0 selection rule, with only ΔK = -1 transitions observed to the upper l = -1 in-plane A‧ component and only ΔK = +1 transitions to the lower l = +1 out-of-plane A″ component. The K = 0 separation of the CH3-bending states is larger at 9.1 cm-1 with the l-ordering reversed. Here, both ΔK = +1 and ΔK = -1 transitions are seen for each l-component but with a large difference in relative intensity. Term values for the excited state levels have been fitted to J(J + 1) power-series expansions to obtain substate origins. These have then been fitted to a Fourier model to characterize the torsion-K-rotation energy patterns. For both pairs of vibrational states, the torsional energies display the customary oscillatory behaviour as a function of K and have inverted torsional splittings relative to the ground state. The spectra show numerous perturbations, indicating local resonances with the underlying bath of high torsional levels and vibrational combination and overtone states. The overall structure of the two pairs of bands represents a new regime in which the vibrational energy separations, torsional splittings and shifts due to molecular asymmetry are all of the same order, creating a

  20. Oxygen effects on the interfacial electronic structure of titanyl phthalocyanine film: p-Type doping, band bending and Fermi level alignment

    International Nuclear Information System (INIS)

    Nishi, Toshio; Kanai, Kaname; Ouchi, Yukio; Willis, Martin R.; Seki, Kazuhiko

    2006-01-01

    The effect of oxygen doping on titanyl phthalocyanine (TiOPc) film was investigated by ultraviolet photoelectron spectroscopy (UPS). The electronic structure of the interface formed between TiOPc films deposited on highly oriented pyrolytic graphite (HOPG) was clearly different between the films prepared in ultrahigh vacuum (UHV) and under O 2 atmosphere (1.3 x 10 -2 Pa). The film deposited in UHV showed downward band bending characteristic of n-type semiconductor, possibly due to residual impurities working as unintentional n-type dopants. On the other hand, the film deposited under O 2 atmosphere showed upward band bending characteristic of p-type semiconductor. Such trends, including the conversion from n- to p-type, are in excellent correspondence with reported field effect transistor characteristics of TiOPc, and clearly demonstrates that bulk TiOPc film was p-doped with oxygen. In order to examine the Fermi level alignment between TiOPc film and the substrate, the energy of the highest occupied molecular orbital (HOMO) of TiOPc relative to the Fermi level of the conductive substrate was determined for various substrates. The alignment between the Fermi level of conductive substrate and Fermi level of TiOPc film at fixed energy in the bandgap was not observed for the TiOPc film prepared in UHV, possibly because of insufficient charge density in the TiOPc film. This situation was drastically changed when the TiOPc film exposed to O 2 , and clear alignment of the Fermi level fixed at 0.6 eV above the HOMO with the Fermi level of the conducting substrate was observed, probably by p-type doping effect of oxygen. These are the first direct and quantitative information about bulk oxygen doping from the viewpoint of the electronic structure. These results suggest that similar band bending with Fermi level alignment may be also achieved for other organic semiconductors under practical device conditions, and also call for caution at the comparison of experimental

  1. Trigger of the ubiquitous surface band bending in 3D topological insulators

    NARCIS (Netherlands)

    Frantzeskakis, E.; Ramankutty, S.V.; de Jong, N.; Huang, Y.K.; Pan, Y.; Tytarenko, A.; Radovic, M.; Plumb, N.C.; Shi, M.; Varykhalov, A.; de Visser, A.; van Heumen, E.; Golden, M.S.

    2017-01-01

    The main scientific activity in the field of topological insulators (TIs) consists of determining their electronic structure by means of magnetotransport and electron spectroscopy with a view to devices based on topological transport. There is, however, a caveat in this approach. There are

  2. Pass-band reconfigurable spoof surface plasmon polaritons

    Science.gov (United States)

    Zhang, Hao Chi; He, Pei Hang; Gao, Xinxin; Tang, Wen Xuan; Cui, Tie Jun

    2018-04-01

    In this paper, we introduce a new scheme to construct the band-pass tunable filter based on the band-pass reconfigurable spoof surface plasmon polaritons (SPPs), whose cut-off frequencies at both sides of the passband can be tuned through changing the direct current (DC) bias of varactors. Compared to traditional technology (e.g. microstrip filters), the spoof SPP structure can provide more tight field confinement and more significant field enhancement, which is extremely valuable for many system applications. In order to achieve this scheme, we proposed a specially designed SPP filter integrated with varactors and DC bias feeding structure to support the spoof SPP passband reconfiguration. Furthermore, the full-wave simulated result verifies the outstanding performance on both efficiency and reconfiguration, which has the potential to be widely used in advanced intelligent systems.

  3. Disorder enabled band structure engineering of a topological insulator surface

    International Nuclear Information System (INIS)

    Xu, Yishuai; Chiu, Janet; Miao, Lin; He, Haowei

    2017-01-01

    Three-dimensional topological insulators are bulk insulators with Z 2 topological electronic order that gives rise to conducting light-like surface states. These surface electrons are exceptionally resistant to localization by non-magnetic disorder, and have been adopted as the basis for a wide range of proposals to achieve new quasiparticle species and device functionality. Recent studies have yielded a surprise by showing that in spite of resisting localization, topological insulator surface electrons can be reshaped by defects into distinctive resonance states. Here we use numerical simulations and scanning tunnelling microscopy data to show that these resonance states have significance well beyond the localized regime usually associated with impurity bands. Lastly, at native densities in the model Bi 2 X 3 (X=Bi, Te) compounds, defect resonance states are predicted to generate a new quantum basis for an emergent electron gas that supports diffusive electrical transport.

  4. Investigations of the Band Structure and Morphology of Nanostructured Surfaces

    Science.gov (United States)

    Knox, Kevin R.

    2011-12-01

    In this dissertation, I examine the electronic structure of two very different types of two-dimensional systems: valence band electrons in single layer graphene and electronic states created at the vacuum interface of single crystal copper surfaces. The characteristics of both electronic systems depend intimately on the morphology of the surfaces they inhabit. Thus, in addition to discussing the respective band structures of these systems, a significant portion of this dissertation will be devoted to measurements of the surface morphology of these systems. Free-standing exfoliated monolayer graphene is an ultra-thin flexible membrane and, as such, is known to exhibit large out-of-plane deformation due to substrate and adsorbate interaction as well as thermal vibrations and, possibly, intrinsic buckling. Such crystal deformation is known to limit mobility and increase local chemical reactivity. Additionally, deformations present a measurement challenge to researchers wishing to determine the band structure by angle-resolved photoemission since they limit electron coherence in such measurements. In this dissertation, I present low energy electron microscopy and micro probe diffraction measurements, which are used to image and characterize corrugation in SiO2-supported and suspended exfoliated graphene at nanometer length scales. Diffraction line-shape analysis reveals quantitative differences in surface roughness on length scales below 20 nm which depend on film thickness and interaction with the substrate. Corrugation decreases with increasing film thickness, reflecting the increased stiffness of multilayer films. Specifically, single-layer graphene shows a markedly larger short range roughness than multilayer graphene. Due to the absence of interactions with the substrate, suspended graphene displays a smoother morphology and texture than supported graphene. A specific feature of suspended single-layer films is the dependence of corrugation on both adsorbate load

  5. Surface roughness of orthodontic band cements with different compositions

    Directory of Open Access Journals (Sweden)

    Françoise Hélène van de Sande

    2011-06-01

    Full Text Available OBJECTIVES: The present study evaluated comparatively the surface roughness of four orthodontic band cements after storage in various solutions. MATERIAL AND METHODS: Eight standardized cylinders were made from 4 materials: zinc phosphate cement (ZP, compomer (C, resin-modified glass ionomer cement (RMGIC and resin cement (RC. Specimens were stored for 24 h in deionized water and immersed in saline (pH 7.0 or 0.1 M lactic acid solution (pH 4.0 for 15 days. Surface roughness readings were taken with a profilometer (Surfcorder SE1200 before and after the storage period. Data were analyzed by two-way ANOVA and Tukey's test (comparison among cements and storage solutions or paired t-test (comparison before and after the storage period at 5% significance level. RESULTS: The values for average surface roughness were statistically different (pRMGIC>C>R (p0.05. Compared to the current threshold (0.2 µm related to biofilm accumulation, both RC and C remained below the threshold, even after acidic challenge by immersion in lactic acid solution. CONCLUSIONS: Storage time and immersion in lactic acid solution increased the surface roughness of the majority of the tested cements. RC presented the smoothest surface and it was not influenced by storage conditions.

  6. Direct observation of a surface resonance state and surface band inversion control in black phosphorus

    Science.gov (United States)

    Ehlen, N.; Sanna, A.; Senkovskiy, B. V.; Petaccia, L.; Fedorov, A. V.; Profeta, G.; Grüneis, A.

    2018-01-01

    We report a Cs-doping-induced band inversion and the direct observation of a surface resonance state with an elliptical Fermi surface in black phosphorus (BP) using angle-resolved photoemission spectroscopy. By selectively inducing a higher electron concentration (1.7 ×1014cm-2 ) in the topmost layer, the changes in the Coulomb potential are sufficiently large to cause surface band inversion between the parabolic valence band of BP and a parabolic surface state around the Γ point of the BP Brillouin zone. Tight-binding calculations reveal that band gap openings at the crossing points in the two high-symmetry directions of the Brillouin zone require out-of-plane hopping and breaking of the glide mirror symmetry. Ab initio calculations are in very good agreement with the experiment if a stacking fault on the BP surface is taken into account. The demonstrated level of control over the band structure suggests the potential application of few-layer phosphorene in topological field-effect transistors.

  7. Band bending and alignment at the spinel/perovskite γ−Al2O3/SrTiO3 heterointerface

    DEFF Research Database (Denmark)

    Schütz, P.; Pfaff, F.; Scheiderer, P.

    2015-01-01

    We present a comprehensive study of the band bending and alignment at the interface of γ -Al2O3/SrTiO3 heterostructures by hard x-ray photoelectron spectroscopy. Ourmeasurements find no signs for a potential gradient within the polar γ -Al2O3 film as predicted by the basic electronic reconstructi...

  8. Development of vehicle model test-bending of a simple structural surfaces model for automotive vehicle sedan

    Science.gov (United States)

    Nor, M. K. Mohd; Noordin, A.; Ruzali, M. F. S.; Hussen, M. H.; Mustapa@Othman, N.

    2017-04-01

    Simple Structural Surfaces (SSS) method is offered as a means of organizing the process for rationalizing the basic vehicle body structure load paths. The application of this simplified approach is highly beneficial in the development of modern passenger car structure design. In Malaysia, the SSS topic has been widely adopted and seems compulsory in various automotive programs related to automotive vehicle structures in many higher education institutions. However, there is no real physical model of SSS available to gain considerable insight and understanding into the function of each major subassembly in the whole vehicle structures. Based on this motivation, a real physical SSS of sedan model and the corresponding model vehicle tests of bending is proposed in this work. The proposed approach is relatively easy to understand as compared to Finite Element Method (FEM). The results prove that the proposed vehicle model test is useful to physically demonstrate the importance of providing continuous load path using the necessary structural components within the vehicle structures. It is clearly observed that the global bending stiffness reduce significantly when more panels are removed from the complete SSS model. The analysis shows the front parcel shelf is an important subassembly to sustain bending load.

  9. Surface Floating 2D Bands in Layered Nonsymmorphic Semimetals: ZrSiS and Related Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Topp, Andreas; Queiroz, Raquel; Grüneis, Andreas; Müchler, Lukas; Rost, Andreas W.; Varykhalov, Andrei; Marchenko, Dmitry; Krivenkov, Maxim; Rodolakis, Fanny; McChesney, Jessica L.; Lotsch, Bettina V.; Schoop, Leslie M.; Ast, Christian R.

    2017-12-01

    In this work, we present a model of the surface states of nonsymmorphic semimetals. These are derived from surface mass terms that lift the high degeneracy imposed in the band structure by the nonsymmorphic bulk symmetries. Reflecting the reduced symmetry at the surface, the bulk bands are strongly modified. This leads to the creation of two-dimensional floating bands, which are distinct from Shockley states, quantum well states or topologically protected surface states. We focus on the layered semimetal ZrSiS to clarify the origin of its surface states. We demonstrate an excellent agreement between DFT calculations and ARPES measurements and present an effective four-band model in which similar surface bands appear. Finally, we emphasize the role of the surface chemical potential by comparing the surface density of states in samples with and without potassium coating. Our findings can be extended to related compounds and generalized to other crystals with nonsymmorphic symmetries.

  10. Dose banding as an alternative to body surface area-based dosing of chemotherapeutic agents

    NARCIS (Netherlands)

    E. Chatelut (Etienne); M.L. White-Koning (M.); A.H.J. Mathijssen (Ron); F. Puisset (F.); S.D. Baker (Sharyn); A. Sparreboom (Alex)

    2012-01-01

    textabstractBackground: Dose banding is a recently suggested dosing method that uses predefined ranges (bands) of body surface area (BSA) to calculate each patients dose by using a single BSA-value per band. Thus, drugs with sufficient long-term stability can be prepared in advance. The main

  11. Large Rashba spin splitting of a metallic surface-state band on a semiconductor surface

    Science.gov (United States)

    Yaji, Koichiro; Ohtsubo, Yoshiyuki; Hatta, Shinichiro; Okuyama, Hiroshi; Miyamoto, Koji; Okuda, Taichi; Kimura, Akio; Namatame, Hirofumi; Taniguchi, Masaki; Aruga, Tetsuya

    2010-01-01

    The generation of spin-polarized electrons at room temperature is an essential step in developing semiconductor spintronic applications. To this end, we studied the electronic states of a Ge(111) surface, covered with a lead monolayer at a fractional coverage of 4/3, by angle-resolved photoelectron spectroscopy (ARPES), spin-resolved ARPES and first-principles electronic structure calculation. We demonstrate that a metallic surface-state band with a dominant Pb 6p character exhibits a large Rashba spin splitting of 200 meV and an effective mass of 0.028 me at the Fermi level. This finding provides a material basis for the novel field of spin transport/accumulation on semiconductor surfaces. Charge density analysis of the surface state indicated that large spin splitting was induced by asymmetric charge distribution in close proximity to the nuclei of Pb atoms. PMID:20975678

  12. Analysis of a bending test on a full-scale PWR hot leg elbow containing a surface crack

    Energy Technology Data Exchange (ETDEWEB)

    Delliou, P. le [Electricite de France, EDF, 77 - Moret-sur-Loing (France). Dept. MTC; Julisch, P.; Hippelein, K. [Stuttgart Univ. (Germany). Staatliche Materialpruefungsanstalt; Bezdikian, G. [Electricite de France, EDF, 92 - Paris la Defense (France). Direction Production Transport

    1998-11-01

    EDF, in co-operation with Framatome, has conducted a large research programme on the mechanical behaviour of thermally aged cast duplex stainless steel elbows, which are part of the main primary circuit of French PWR. One important task of this programme consisted of testing a full-scale PWR hot leg elbow. The elbow contained a semi-elliptical circumferential notch machined on the outer surface of the intrados as well as casting defects located on the flanks. To simulate the end-of-life condition of the component regarding material toughness, it had undergone a 2400 hours ageing heat treatment at 400 C. The test preparation and execution, as well as the material characterization programme, were committed to MPA. The test was conducted under constant internal pressure and in-plane bending (opening mode) at 200 C. For safety reasons, it took place on an open air-site: the Meppen military test ground. At the maximum applied moment (6000 kN.m), the notch did not initiate. This paper presents the experimental results and the fracture mechanics analysis of the test, based on finite element calculations. (orig.)

  13. [Terahertz-band study on surface enhanced Raman scattering of nanoparticle].

    Science.gov (United States)

    Wu, Yu-Deng; Ren, Guang-Jun; Hao, Yun; Yao, Jian-Quan

    2013-05-01

    Study on surface-enhanced Raman scattering in the terahertz-band proved in that the terahertz-band Raman enhancement also exists. By studing principles of electromagnetic enhancement of surface-enhanced Raman scattering, using the finite difference time-domain method, the electromagnetic enhancement of surface enhanced Raman scattering of nano-particles irradiated by terahertz-wave was simulated, and the enhancement effect of terahertz waves was analyzed. Simulation experiments show that using finite-difference time-domain method could obtain effectively accurate simulation result of nano-particle scattering, proving that for terahertz waves, surface-enhanced effects on the surface of the nano-particle also exist. The results for surface enhanced Raman scattering extended from the visible and infrared to terahertz-band, and provide a basis for application of the combination of surface-enhanced Raman scattering and terahertz-wave.

  14. V-Band Wireless Surface Networks, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA GLENN RESEARCH CENTER in Topic O1.10 has identified the need to provide surface communications networks for human and robotic missions to explore the Moon and...

  15. Surface effect on band structure of flexural wave propagating in magneto-elastic phononic crystal nanobeam

    International Nuclear Information System (INIS)

    Zhang, Shunzu; Gao, Yuanwen

    2017-01-01

    A theoretical model is established to study the size-dependent performance of flexural wave propagation in magneto-elastic phononic crystal (PC) nanobeam with surface effect based on Euler–Bernoulli beam theory and Gurtin–Murdoch theory. Considering the magneto-mechanical coupling constitutive relation of magnetostrictive material, the influence of surface effect on band structure is calculated by the plane wave expansion method for PC nanobeam subjected to pre-stress and magnetic field loadings. Through the example of an epoxy/Terfenol-D PC nanobeam, it can be observed that the characteristics of flexural wave band structures are size-dependent, and remarkably affected by surface effect when the dimension of the PC beam reduces to the nanoscale. The edges and width of the band gap with surface effect are higher than those without surface effect, especially for high frequency region. And surface effect gradually reduces with the increasing of bulk layer-to-surface layer thickness ratio until the band gap descends to a constant for the conventional one in the absence of surface effect. The effects of surface elasticity and piezomagneticity on band gap are more prominent than the residual surface stress. In addition, a distinctly nonlinear variation of band gap appears under the combined effects of pre-stress and magnetic field. Moreover, with the varying of filling fraction, multi-peaks of the width of the band gap are obtained and discussed. These results could be helpful for the intelligent regulation of magneto-elastic PC nanobeam and the design of nanobeam-based devices. (paper)

  16. Surface effect on band structure of flexural wave propagating in magneto-elastic phononic crystal nanobeam

    Science.gov (United States)

    Zhang, Shunzu; Gao, Yuanwen

    2017-11-01

    A theoretical model is established to study the size-dependent performance of flexural wave propagation in magneto-elastic phononic crystal (PC) nanobeam with surface effect based on Euler-Bernoulli beam theory and Gurtin-Murdoch theory. Considering the magneto-mechanical coupling constitutive relation of magnetostrictive material, the influence of surface effect on band structure is calculated by the plane wave expansion method for PC nanobeam subjected to pre-stress and magnetic field loadings. Through the example of an epoxy/Terfenol-D PC nanobeam, it can be observed that the characteristics of flexural wave band structures are size-dependent, and remarkably affected by surface effect when the dimension of the PC beam reduces to the nanoscale. The edges and width of the band gap with surface effect are higher than those without surface effect, especially for high frequency region. And surface effect gradually reduces with the increasing of bulk layer-to-surface layer thickness ratio until the band gap descends to a constant for the conventional one in the absence of surface effect. The effects of surface elasticity and piezomagneticity on band gap are more prominent than the residual surface stress. In addition, a distinctly nonlinear variation of band gap appears under the combined effects of pre-stress and magnetic field. Moreover, with the varying of filling fraction, multi-peaks of the width of the band gap are obtained and discussed. These results could be helpful for the intelligent regulation of magneto-elastic PC nanobeam and the design of nanobeam-based devices.

  17. Mapping surface soil moisture with L-band radiometric measurements

    Science.gov (United States)

    Wang, James R.; Shiue, James C.; Schmugge, Thomas J.; Engman, Edwin T.

    1989-01-01

    A NASA C-130 airborne remote sensing aircraft was used to obtain four-beam pushbroom microwave radiometric measurements over two small Kansas tall-grass prairie region watersheds, during a dry-down period after heavy rainfall in May and June, 1987. While one of the watersheds had been burned 2 months before these measurements, the other had not been burned for over a year. Surface soil-moisture data were collected at the time of the aircraft measurements and correlated with the corresponding radiometric measurements, establishing a relationship for surface soil-moisture mapping. Radiometric sensitivity to soil moisture variation is higher in the burned than in the unburned watershed; surface soil moisture loss is also faster in the burned watershed.

  18. Recent Asteroid Disruptions in the WISE Dataset - Constraining Asteroid Surface Properties Using Solar System Dust Bands

    Science.gov (United States)

    Kehoe, A. E.; Shaw, C.; Kehoe, T. J. J.

    2017-12-01

    Zodiacal dust bands are a fine-structure feature of the mid-IR emission profile of the zodiacal cloud. The dust bands have been studied for many years dating back to the InfraRed Astronomical Satellite (IRAS) data of the 1980's. The recent discovery and modeling (Espy et al., 2009; 2010; Espy Kehoe et al., 2015) of a very young, still-forming dust band structure has shown that, in the early stages following an asteroid disruption, much information on the dust parameters of the original disruption is retained in the band. Partial dust bands allow a never-before-seen observational look at the size distribution and cross-sectional area of dust produced in an asteroidal disruption, before it has been lost or significantly altered by orbital and collisional decay. The study of these partial band structures reveals information on the way asteroids disrupt and allow us to reconstruct the surface properties of the parent asteroid, including the depth of the surface regolith and the size distribution of particles composing the regolith. Using the greatly increased sensitivity of the Wide-field Infrared Survey Explorer (WISE), we can now detect much fainter (and thus younger) dust bands. The WISE data also reveals much better longitudinal resolution of the bands, allowing a better constraint on the source and age of the disruption. We will present our newest results from the WISE dataset, including detection of faint partial dust bands, improved models of more prominent bands, and our constraints on the asteroid surface properties from modeling these structures.

  19. Production and testing of an s-band resonator with a Nb3Sn surface

    International Nuclear Information System (INIS)

    Peiniger, M.

    1983-01-01

    This report describes the preparation of a niobium s-band resonator with Nb3Sn surface using a special vapor phase deposition method. High-frequency superconductivity tests were performed on this resonator. Measurements of transition temperature, penetration depth, energy gap, and temperature dependence of surface conductivity of Nb3Sn, and resonator behaviour at high electrical field strengths are reported. (GSCH)

  20. Dual-band microstrip patch antenna based on metamaterial refractive surface

    Science.gov (United States)

    Salhi, Ridha; Labidi, Mondher; Boujemaa, Mohamed Ali; Choubani, Fethi

    2017-06-01

    In this paper, we present a new design of microstrip patch antenna based on metamaterial refractive surface (MRS). By optimizing the air gap between the MRS layer and the patch antenna to be 7 mm, the band width and the gain of the proposed antenna are significantly enhanced. The proposed prototype presents a dual band antenna. The center frequency for the first band is 2.44 GHz and the generated bandwidth is 25 MHz. The second band has a center frequency of 2.8 GHz and with a bandwidth of 50 MHz. The simulation results are analyzed and discussed in terms of return loss, gain and radiation pattern using electromagnetic simulator software. Finally, the designed dual band antenna is fabricated and different measurement results are performed and compared with simulation results in order to validate its performances. The proposed antenna supports WiBro (wireless broadband), ISM, WiFi, Bluetooth, WiMAX and radars services.

  1. Energy Bands and Fermi Surface for beta-MgMh and beta-MgTl

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt

    1977-01-01

    surfaces are found to be sp-like but there are narrow 5d bands far below—and wide 3d and 6d bands far above—the Fermi levels. For β′-MgHg the calculated angular variation of extremal cross sections of the Fermi surface agrees very well with de Haas-van Alphen data and thereby provide an interpretation......The energy bands of ordered β′-MgHg and β′-MgTl have been calculated by the relativistic linear-muffintin-orbital method. We show how the gross features of the energy bands may be estimated from Wigner-Seitz rules. The densities of states are calculated and the heat capacities derived. The Fermi...

  2. Surface properties in West Africa from spaceborne radars in C and Ku bands

    Science.gov (United States)

    Fatras, Christophe; Frappart, Frédéric; Mougin, Eric; Frison, Pierre-Louis; Faye, Gayane; Jarlan, Lionel

    2013-04-01

    We propose to compare the backscattering responses of land surfaces in West Africa for different radar spaceborne sensors: the nadir-looking radar altimeters and the side-looking radar scatterometers at different frequencies (Ku and C bands). The data used come from Envisat-RA2 measurements in Ku-band over the period 2003-2010 and the Jason-2 measurements in C band over mid-2008-2011 for radar altimetry, and from QuikSCAT - SeaWinds in Ku-band and Metop - ASCAT in C-band for radar scatterometry over the same time-spans. Along-track profiles and their temporal variations are analyzed and their behaviours are related to surfaces properties such as soil types, vegetation cover, and surface hydrology. Temporal variations of backscattering coefficients are extracted for main land covers along the bio-climatic transect (stone and sand deserts, saharo-sahelian, sahelian, and soudano-sahelian savannahs, tropical-seasonal and tropical forests) and compared to both rainfall estimates from TRMM and vegetation activity (NDVI) from MODIS. Range of variations of the backscattering signals are given for different surfaces and ecosystems along with delays between peaks of rainfall, backscattering responses of radar altimetry and scatterometry, and vegetation activity. The stability of the backscattering is also estimated over deserts and during the dry season over Sahelian environments. Finally, the complementarity of the different spaceborne sensors for continental surfaces monitoring is pointed out.

  3. Groundwater withdrawals 1976, 1990, and 2000--10 and land-surface-elevation changes 2000--10 in Harris, Galveston, Fort Bend, Montgomery, and Brazoria Counties, Texas

    Science.gov (United States)

    Kasmarek, Mark C.; Johnson, Michaela R.

    2013-01-01

    The study area comprising Harris County and parts of Galveston, Fort Bend, Montgomery, and Brazoria Counties in southeastern Texas forms part of one of the largest areas of land-surface-elevation change in the United States. Land-surface-elevation change in the study area primarily is caused by the withdrawal of groundwater. Groundwater withdrawn from the Chicot and Evangeline aquifers has been the primary source of water for municipal supply, industrial and commercial use, and irrigation in the study area. Groundwater withdrawals cause compaction of clay and silt layers abundant in the aquifers, which has in turn resulted in the widespread, substantial land-surface-elevation changes in the region with increased flooding. To estimate land-surface-elevation changes, the U.S. Geological Survey (USGS), in cooperation with the Harris-Galveston Subsidence District (HGSD), documented land-surface-elevation changes in the study area that occurred during 2000–10 and 2005–10 based on elevation data measured by 11 USGS borehole-extensometer sites, a National Geodetic Survey Continuously Operating Reference Station, and Global Positioning System Port-A-Measure (PAM) sites operated by the HGSD and the Fort Bend Subsidence District. Groundwater withdrawals in the study area also were documented for 1976, 1990, and 2000–10.

  4. The Impact of Surface Bending, A Complete Mineralogical Model and Movement of the Overriding Plate on Subduction Zones

    Science.gov (United States)

    Arredondo, Katrina Marie

    Modern observations of subduction zones provide only snapshots of a complex geologic system that can last tens of millions of years. Surface velocity measurements and seismic tomography images provide information on the possible forces acting on the plate and influencing slab shape and behavior. Modern subduction zones exhibit a wide range of behavior, from the rapidly rolling back Tonga subduction zone (where the trench is moving toward the subducting plate) to stationary trenches to trench advance (where the trench is moving toward the overriding plate). Slabs may also stagnate at 660 km while others directly penetrate into the lower mantle. Numerical models can combine observations and laboratory data to test and study possible forces that may explain the wide variety of behavior observed in modern subduction zones. Past numerical model studies have not studied the impact on subduction zone behavior from: composition-dependent phase transitions, a complete mineralogical model and movement of the overriding plate. Here we show that: 1) weakening of the subducting plate can be observed from the forebulge to the trench using highly detailed bathymetry and gravity measurement tracks parallel to the trench, 2) using a complete mineralogy model is important for accurate numerical models because incomplete approximations may overestimate slab stagnation and slab rollback, 3) in free subduction models, the complete mineralogy model creates a strong feedback loop between broad slab folds and trench velocities, and 4) the movement of the overriding plate is very important for slab rollback. Results presented in Chapter 1 indicate that the rheology in the numerical models should produce weakening in the slab as it bends into the trench, which is observed in the models of Chapter 2 and 3. Past published models can be analyzed in relation to Chapter 2 and 3 to determine if their conclusions are skewed by an overestimation of slab stagnation or trench rollback. The presented

  5. Parametric exponentially correlated surface emission model for L-band passive microwave soil moisture retrieval

    Science.gov (United States)

    Surface soil moisture is an important parameter in hydrology and climate investigations. Current and future satellite missions with L-band passive microwave radiometers can provide valuable information for monitoring the global soil moisture. A factor that can play a significant role in the modeling...

  6. Discrete impurity band from surface danging bonds in nitrogen and phosphorus doped SiC nanowires

    Science.gov (United States)

    Li, Yan-Jing; Li, Shu-Long; Gong, Pei; Li, Ya-Lin; Cao, Mao-Sheng; Fang, Xiao-Yong

    2018-04-01

    The electronic structure and optical properties of the nitrogen and phosphorus doped silicon carbide nanowires (SiCNWs) are investigated using first-principle calculations based on density functional theory. The results show doping can change the type of the band gap and improve the conductivity. However, the doped SiCNWs form a discrete impurity levels at the Fermi energy, and the dispersion degree decreases with the diameter increasing. In order to reveal the root of this phenomenon, we hydrogenated the doped SiCNWs, found that the surface dangling bonds were saturated, and the discrete impurity levels are degeneracy, which indicates that the discrete impurity band of the doped SiCNWs is derived from the dangling bonds. The surface passivation can degenerate the impurity levels. Therefore, both doping and surface passivation can better improve the photoelectric properties of the SiCNWs. The result can provide additional candidates in producing nano-optoelectronic devices.

  7. Orbital-angular-momentum based origin of Rashba-type surface band splitting.

    Science.gov (United States)

    Park, Seung Ryong; Kim, Choong H; Yu, Jaejun; Han, Jung Hoon; Kim, Changyoung

    2011-10-07

    We propose that the existence of local orbital angular momentum (OAM) on the surfaces of high-Z materials plays a crucial role in the formation of Rashba-type surface band splitting. Local OAM state in a Bloch wave function produces an asymmetric charge distribution (electric dipole). The surface-normal electric field then aligns the electric dipole and results in chiral OAM states and the relevant Rashba-type splitting. Therefore, the band splitting originates from electric dipole interaction, not from the relativistic Zeeman splitting as proposed in the original Rashba picture. The characteristic spin chiral structure of Rashba states is formed through the spin-orbit coupling and thus is a secondary effect to the chiral OAM. Results from first-principles calculations on a single Bi layer under an external electric field verify the key predictions of the new model.

  8. MODIS/Aqua Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Day V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS/Aqua Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Day (MYD21A1D.006). A new suite of MODIS Land Surface Temperature (LST) and...

  9. MODIS/Terra Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Night V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS/Terra Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Night (MOD21A1N.006). A new suite of MODIS Land Surface Temperature (LST) and...

  10. MODIS/Aqua Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Night V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS/Aqua Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Night (MYD21A1N.006). A new suite of MODIS Land Surface Temperature (LST) and...

  11. MODIS/Terra Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Day V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS/Terra Land Surface Temperature/3-Band Emissivity Daily L3 Global 1km SIN Grid Day (MOD21A1D.006). A new suite of MODIS Land Surface Temperature (LST) and...

  12. C-Band Airport Surface Communications System Standards Development, Phase I

    Science.gov (United States)

    Hall, Edward; Isaacs, James; Zelkin, Natalie; Henriksen. Steve

    2010-01-01

    This document is being provided as part of ITT's NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: "New ATM Requirements--Future Communications, C-Band and L-Band Communications Standard Development." The proposed future C-band (5091- to 5150-MHz) airport surface communication system, referred to as the Aeronautical Mobile Airport Communications System (AeroMACS), is anticipated to increase overall air-to-ground data communications systems capacity by using a new spectrum (i.e., not very high frequency (VHF)). Although some critical services could be supported, AeroMACS will also target noncritical services, such as weather advisory and aeronautical information services as part of an airborne System Wide Information Management (SWIM) program. AeroMACS is to be designed and implemented in a manner that will not disrupt other services operating in the C-band. This report defines the AeroMACS concepts of use, high-level system requirements, and architecture; the performance of supporting system analyses; the development of AeroMACS test and demonstration plans; and the establishment of an operational AeroMACS capability in support of C-band aeronautical data communications standards to be advanced in both international (International Civil Aviation Organization, ICAO) and national (RTCA) forums. This includes the development of system parameter profile recommendations for AeroMACS based on existing Institute of Electrical and Electronics Engineering (IEEE) 802.16e- 2009 standards

  13. Propagation of long-range surface plasmon polaritons in photonic band gap structures

    DEFF Research Database (Denmark)

    Boltasseva, Alexandra; Søndergaard, Thomas; Nikolajsen, Thomas

    2005-01-01

    We study the interaction of long-range surface plasmon polaritons (LR-SPPs), excited at telecommunication wavelengths, with photonic crystals (PCs) formed by periodic arrays of gold bumps that are arranged in a triangular lattice and placed symmetrically on both sides of a thin gold fil embedded...... in polymer. Radiation is delivered to and from the PC structures with the help of LR-SPP guides that consist of 8 mm wide and 15 nm thick gold stripes attached to wide film sections (of the same thickness) covered with bumps (diameter ~300 nm, height up to 150 nm on each side of the film). We investigate......, is rather weak, so that the photonic bandgap effect might be expected to take place only for some particular propagation directions. Preliminary experiments on LR-SPP bending and splitting at large angles are reported, and further research directions are discussed....

  14. Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

    Science.gov (United States)

    Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; McNichols, Brett W.; Miller, Elisa M.; Gu, Jing; Nozik, Arthur J.; Sellinger, Alan; Galli, Giulia; Beard, Matthew C.

    2017-05-01

    Band edge positions of semiconductors determine their functionality in many optoelectronic applications such as photovoltaics, photoelectrochemical cells and light emitting diodes. Here we show that band edge positions of lead sulfide (PbS) colloidal semiconductor nanocrystals, specifically quantum dots (QDs), can be tuned over 2.0 eV through surface chemistry modification. We achieved this remarkable control through the development of simple, robust and scalable solution-phase ligand exchange methods, which completely replace native ligands with functionalized cinnamate ligands, allowing for well-defined, highly tunable chemical systems. By combining experiments and ab initio simulations, we establish clear relationships between QD surface chemistry and the band edge positions of ligand/QD hybrid systems. We find that in addition to ligand dipole, inter-QD ligand shell inter-digitization contributes to the band edge shifts. We expect that our established relationships and principles can help guide future optimization of functional organic/inorganic hybrid nanostructures for diverse optoelectronic applications.

  15. Volume and surface photoemission from tungsten. I. Calculation of band structure and emission spectra

    DEFF Research Database (Denmark)

    Christensen, N. Egede; Feuerbacher, B.

    1974-01-01

    of photoemission spectra from W single crystals. The nondirect as well as the direct models for bulk photoemission processes are investigated. The emission from the three low-index surfaces (100), (110), and (111) exhibits strong dependence on direction and acceptance cone. According to the present band model...... there should essentially be no emission normal to the (110) face for photon energies between 9.4 and 10.6 eV. Experimental observation of emission in this gap, however, implies effects not included in the simple bulk models. In particular, effects arising from surface emission have been considered, i.......e., emission of those electrons which are excited in a single-step process from initial states near the surface to final states outside the crystal. The electrons that are emitted from the surface in directions perpendicular to the crystal planes carry information on the one-dimensional surface density...

  16. Surface plasmon polariton band gap structures: implications to integrated plasmonic circuits

    DEFF Research Database (Denmark)

    Bozhevolnyi, S. I.; Volkov, V. S.; Østergaard, John Erland

    2001-01-01

    Conventional photonic band gap (PBG) structures are composed of regions with periodic modulation of refractive index that do not allow the propagation of electromagnetic waves in a certain interval of wavelengths, i.e., that exhibit the PBG effect. The PBG effect is essentially an interference...... phenomenon related to strong multiple scattering of light in periodic media. The interest to the PBG structures has dramatically risen since the possibility of efficient waveguiding around a sharp corner of a line defect in the PBG structure has been pointed out. Given the perspective of integrating various...... PBG-based components within a few hundred micrometers, we realized that other two-dimensional waves, e.g., surface plasmon polaritons (SPPs), might be employed for the same purpose. The SPP band gap (SPPBG) has been observed for the textured silver surfaces by performing angular measurements...

  17. Structure-function relationships in human testis-determining factor SRY: an aromatic buttress underlies the specific DNA-bending surface of a high mobility group (HMG) box.

    Science.gov (United States)

    Racca, Joseph D; Chen, Yen-Shan; Maloy, James D; Wickramasinghe, Nalinda; Phillips, Nelson B; Weiss, Michael A

    2014-11-21

    Human testis determination is initiated by SRY, a Y-encoded architectural transcription factor. Mutations in SRY cause 46 XY gonadal dysgenesis with female somatic phenotype (Swyer syndrome) and confer a high risk of malignancy (gonadoblastoma). Such mutations cluster in the SRY high mobility group (HMG) box, a conserved motif of specific DNA binding and bending. To explore structure-function relationships, we constructed all possible substitutions at a site of clinical mutation (W70L). Our studies thus focused on a core aromatic residue (position 15 of the consensus HMG box) that is invariant among SRY-related HMG box transcription factors (the SOX family) and conserved as aromatic (Phe or Tyr) among other sequence-specific boxes. In a yeast one-hybrid system sensitive to specific SRY-DNA binding, the variant domains exhibited reduced (Phe and Tyr) or absent activity (the remaining 17 substitutions). Representative nonpolar variants with partial or absent activity (Tyr, Phe, Leu, and Ala in order of decreasing side-chain volume) were chosen for study in vitro and in mammalian cell culture. The clinical mutation (Leu) was found to markedly impair multiple biochemical and cellular activities as respectively probed through the following: (i) in vitro assays of specific DNA binding and protein stability, and (ii) cell culture-based assays of proteosomal degradation, nuclear import, enhancer DNA occupancy, and SRY-dependent transcriptional activation. Surprisingly, however, DNA bending is robust to this or the related Ala substitution that profoundly impairs box stability. Together, our findings demonstrate that the folding, trafficking, and gene-regulatory function of SRY requires an invariant aromatic "buttress" beneath its specific DNA-bending surface. © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

  18. Surface Plasmon-Induced Band Gap in the Photocurrent Response of Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Ribal Georges Sabat

    2010-01-01

    Full Text Available A 260 nm layer of organic bulk heterojunction blend of the polymer poly(3-hexylthiophene (P3HT and the fullerene [6,6]-phenyl C61-butyric (PCBM was spin-coated in between aluminum and gold electrodes, respectively, on top of a laser inscribed azo polymer surface-relief diffraction grating. Angle-dependent surface plasmons (SPs with a large band gap were observed in the normalized photocurrent by the P3HT-PCBM layer as a function of wavelength. The SP-induced photocurrents were also investigated as a function of the grating depth and spacing.

  19. Band Structure and Fermi Surface of Cu2Sb by the LMTO Method

    DEFF Research Database (Denmark)

    Jan, J. P.; Skriver, Hans Lomholt

    1977-01-01

    The linear muffin-tin orbital (LMTO) method of bandstructure calculation has been applied to the simple tetragonal compound Cu2Sb. The d bands of Cu lie substantially below the Fermi level, and the Fermi surface is a recognizable distortion of the free-electron model. The Fermi surface has sheets......-orbit splitting, and of another closed sheet. Earlier de Haas-van Alphen results are explained semiquantitatively by the model, which also accounts for open orbits seen in high-field magnetoresistance experiments....

  20. Backscattered EM-wave manipulation using low cost 1-bit reflective surface at W-band

    Science.gov (United States)

    Taher Al-Nuaimi, Mustafa K.; Hong, Wei; He, Yejun

    2018-04-01

    The design of low cost 1-bit reflective (non-absorptive) surfaces for manipulation of backscattered EM-waves and radar cross section (RCS) reduction at W-band is presented in this article. The presented surface is designed based on the reflection phase cancellation principle. The unit cell used to compose the proposed surface has an obelus (division symbol of short wire and two disks above and below) like shape printed on a grounded dielectric material. Using this unit cell, surfaces that can efficiently manipulate the backscattered RCS pattern by using the proposed obelus-shaped unit cell (as ‘0’ element) and its mirrored unit cell (as ‘1’ element) in one surface with a 180°  ±  35° reflection phase difference between their reflection phases are designed. The proposed surfaces can generate various kinds of backscattered RCS patterns, such as single, three, or four lobes or even a low-level (reduced RCS) diffused reflection pattern when those two unit cells are distributed randomly across the surface aperture. For experimental characterization purposes, a 50  ×  50 mm2 surface is fabricated and measured.

  1. Evidence of a green luminescence band related to surface flaws in high purity silica glass

    Energy Technology Data Exchange (ETDEWEB)

    Fournier, J.; Neauport, J.; Grua, P. [CEA, CESTA, F-33114 Le Barp (France); Fournier, J.; Fargin, E.; Jubera, V. [Univ Bordeaux, CNRS, ICMCB, F-33608 Pessac (France); Talaga, D. [Univ Bordeaux, CNRS, ISM, F-33405 Talence (France); Jouannigot, S. [Univ Bordeaux 1, LCTS, SAFRAN, CNRS, CEA, UMR 5801, Pessac (France)

    2010-07-01

    Using luminescence con-focal microscopy under 325 nm laser excitation, we explore the populations of defects existing in or at the vicinity of macroscopic surface flaws in fused silica. We report our luminescence results on two types of surface flaws: laser damage and indentation on fused silica polished surfaces. Luminescence cartographies are made to show the spatial distribution of each kind of defect. Three bands, centered at 1.89 eV, 2.75 eV and 2.25 eV are evidenced on laser damage and indentations. The band centered at 2.25 eV was not previously reported in photo luminescence experiments on indentations and pristine silica, for excitation wavelengths of 325 nm or larger. The luminescent objects, expected to be trapped in sub-surface micro-cracks, are possibly involved in the first step of the laser damage mechanism when fused silica is enlightened at 351 nm laser in nanosecond regime. (authors)

  2. [Analysis of the Muscle Fatigue Based on Band Spectrum Entropy of Multi-channel Surface Electromyography].

    Science.gov (United States)

    Liu, Jian; Zou, Renling; Zhang, Dongheng; Xu, Xiulin; Hu, Xiufang

    2016-06-01

    Exercise-induced muscle fatigue is a phenomenon that the maximum voluntary contraction force or power output of muscle is temporarily reduced due to muscular movement.If the fatigue is not treated properly,it will bring about a severe injury to the human body.With multi-channel collection of lower limb surface electromyography signals,this article analyzes the muscle fatigue by adoption of band spectrum entropy method which combined electromyographic signal spectral analysis and nonlinear dynamics.The experimental result indicated that with the increase of muscle fatigue,muscle signal spectrum began to move to low frequency,the energy concentrated,the system complexity came down,and the band spectrum entropy which reflected the complexity was also reduced.By monitoring the entropy,we can measure the degree of muscle fatigue,and provide an indicator to judge fatigue degree for the sports training and clinical rehabilitation training.

  3. Experimental verification of directional liquid surface wave emission at band edge frequencies

    International Nuclear Information System (INIS)

    Wang, Zhenyu; Zhang, Pei; Zhang, Yongqiang; Nie, Xiaofei

    2013-01-01

    Directional liquid surface wave emission at band edge frequencies is an interesting physical phenomenon and has already been studied in theoretical research. There has been no experimental validation of it to date, however. This paper has as its subject the experimental investigation of the emission effect when a point source is placed inside a finite square array of rigid cylinders standing vertically in liquid. Both the wave patterns and spatial intensities are obtained by experiment and compared with simulated results calculated by using the finite element method. We can see from this comparison that the two results correspond closely both at lower and upper band edge frequency. Obvious directional wave emission along a desired direction is observed in the source structures, confirming previous theoretical predictions. In the future, this method could serve as a directional liquid wave source in applications used in hydraulic and ocean engineering for the concentration of wave energy

  4. Fermi surface and band structure of BiPd from ARPES studies

    Science.gov (United States)

    Lohani, H.; Mishra, P.; Gupta, Anurag; Awana, V. P. S.; Sekhar, B. R.

    2017-03-01

    We present a detailed electronic structure study of the non-centrosymmetric superconductor BiPd based on our angle resolved photoemission spectroscopy (ARPES) measurements and Density Functional Theory (DFT) based calculations. We observe a high intensity distribution on the Fermi surface (FS) of this compound resulting from various electron and hole like bands which are present in the vicinity of the Fermi energy (Ef). The near Ef states are primarily composed of Bi-6p with a little admixture of Pd-4dx2-y2/zy orbitals. There are various spin-orbit split bands involved in the crossing of Ef making a complex FS. The FS mainly consists of multi sheets of three dimensions which disfavor the nesting between different sheets of the FS. Our comprehensive study elucidates that BiPd could be a s-wave multiband superconductor.

  5. ARPES on Na0.6CoO2: Fermi surface and unusual band dispersion.

    Science.gov (United States)

    Yang, H-B; Wang, S-C; Sekharan, A K P; Matsui, H; Souma, S; Sato, T; Takahashi, T; Takeuchi, T; Campuzano, J C; Jin, R; Sales, B C; Mandrus, D; Wang, Z; Ding, H

    2004-06-18

    The electronic structure of single crystals Na0.6CoO2, which are closely related to the superconducting Na0.3CoO2.yH(2)O (T(c) approximately 5 K), is studied by angle-resolved photoelectron spectroscopy. While the measured Fermi surface (FS) is consistent with the large FS enclosing the Gamma point from the band theory, the predicted small FS pockets near the K points are absent. In addition, the band dispersion is found to be highly renormalized, and anisotropic along the two principal axes (Gamma-K, Gamma-M). Our measurements also indicate that an extended flatband is formed slightly above E(F) along Gamma-K.

  6. Comprehensive nonlocal analysis of piezoelectric nanobeams with surface effects in bending, buckling and vibrations under magneto-electro-thermo-mechanical loading

    Science.gov (United States)

    Ebrahimi-Nejad, Salman; Boreiry, Mahya

    2018-03-01

    The bending, buckling and vibrational behavior of size-dependent piezoelectric nanobeams under thermo-magneto-mechano-electrical environment are investigated by performing a parametric study, in the presence of surface effects. The Gurtin-Murdoch surface elasticity and Eringen’s nonlocal elasticity theories are applied in the framework of Euler–Bernoulli beam theory to obtain a new non-classical size-dependent beam model for dynamic and static analyses of piezoelectric nanobeams. In order to satisfy the surface equilibrium equations, cubic variation of stress with beam thickness is assumed for the bulk stress component which is neglected in classical beam models. Results are obtained for clamped - simply-supported (C-S) and simply-supported - simply-supported (S-S) boundary conditions using a proposed analytical solution method. Numerical examples are presented to demonstrate the effects of length, surface effects, nonlocal parameter and environmental changes (temperature, magnetic field and external voltage) on deflection, critical buckling load and natural frequency for each boundary condition. Results of this study can serve as benchmarks for the design and analysis of nanostructures of magneto-electro-thermo-elastic materials.

  7. Fermi surface changes in dilute magnesium alloys: a pseudopotential band structure model

    International Nuclear Information System (INIS)

    Fung, W.K.

    1976-01-01

    The de Haas-van Alphen effect has been used to study the Fermi surface of pure magnesium and its dilute alloys containing lithium and indium. The quantum oscillations in magnetization were detected by means of a torque magnetometer in magnetic field up to 36 kilogauss and temperature range of 4.2 0 to 1.7 0 K. The results provide information on the effects of lithium and indium solutes on the Fermi surface of magnesium in changes of extremal cross sections and effective masses as well as the relaxation times associated with the orbits. The nonlocal pseudopotential model proposed by Kimball, Stark and Mueller has been fitted to the Fermi surface of magnesium and extended to include the dilute alloys, fitting all the observed de Haas-van Alphen frequencies with an accuracy of better than 1 percent. A modified rigid band interpretation including both Fermi energy and local band edge changes computed from the model, gives an overall satisfactory description of the observed frequency shifts. With the pseudo-wavefunctions provided by the nonlocal model, the relaxation times in terms of Dingle temperatures for several orbits have been predicted using Sorbello's multiple-plane-wave phase shift model. The calculation with phase shifts obtained from a model potential yields a greater anisotropy than has been observed experimentally, while a two-parameter phase shift model provides a good fit to the experimental results

  8. Metal-like Band Structures of Ultrathin Si {111} and {112} Surface Layers Revealed through Density Functional Theory Calculations.

    Science.gov (United States)

    Tan, Chih-Shan; Huang, Michael H

    2017-09-04

    Density functional theory calculations have been performed on Si (100), (110), (111), and (112) planes with tunable number of planes for evaluation of their band structures and density of states profiles. The purpose is to see whether silicon can exhibit facet-dependent properties derived from the presence of a thin surface layer having different band structures. No changes have been observed for single to multiple layers of Si (100) and (110) planes with a consistent band gap between the valence band and the conduction band. However, for 1, 2, 4, and 5 Si (111) and (112) planes, metal-like band structures were obtained with continuous density of states going from the valence band to the conduction band. For 3, 6, and more Si (111) planes, as well as 3 and 6 Si (112) planes, the same band structure as that seen for Si (100) and (110) planes has been obtained. Thus, beyond a layer thickness of five Si (111) planes at ≈1.6 nm, normal semiconductor behavior can be expected. The emergence of metal-like band structures for the Si (111) and (112) planes are related to variation in Si-Si bond length and bond distortion plus 3s and 3p orbital electron contributions in the band structure. This work predicts possession of facet-dependent electrical properties of silicon with consequences in FinFET transistor design. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Polarimetric Signatures from a Crop Covered Land Surface Measured by an L-band Polarimetric Radiometer

    DEFF Research Database (Denmark)

    Søbjærg, Sten Schmidl; Skou, Niels

    2003-01-01

    This paper describes preliminary results from field measurements of polarimetric azimuth signatures with the EMIRAD L-band polarimetric radiometer, performed over a land test site at the Institut National de la Recherche Agronomique in Avignon, France. Scans of 180 degrees in azimuth were carried...... out in order to identify an eventual dependence of the Stokes vector on the look-direction. Results indicate a clear signature, for bare soil as well as for the crop-covered surface, and variations of more than 10 K are observed....

  10. On the relationship between enamel band complexity and occlusal surface area in Equids (Mammalia, Perissodactyla

    Directory of Open Access Journals (Sweden)

    Nicholas A. Famoso

    2016-07-01

    Full Text Available Enamel patterns on the occlusal surfaces of equid teeth are asserted to have tribal-level differences. The most notable example compares the Equini and Hipparionini, where Equini have higher crowned teeth with less enamel-band complexity and less total occlusal enamel than Hipparionini. Whereas previous work has successfully quantified differences in enamel band shape by dividing the length of enamel band by the square root of the occlusal surface area (Occlusal Enamel Index, OEI, it was clear that OEI only partially removes the effect of body size. Because enamel band length scales allometrically, body size still has an influence on OEI, with larger individuals having relatively longer enamel bands than smaller individuals. Fractal dimensionality (D can be scaled to any level, so we have used it to quantify occlusal enamel complexity in a way that allows us to get at an accurate representation of the relationship between complexity and body size. To test the hypothesis of tribal-level complexity differences between Equini and Hipparionini, we digitally traced a sample of 98 teeth, one tooth per individual; 31 Hipparionini and 67 Equini. We restricted our sampling to the P3-M2 to reduce the effect of tooth position. After calculating the D of these teeth with the fractal box method which uses the number of boxes of various sizes to calculate the D of a line, we performed a t-test on the individual values of D for each specimen, comparing the means between the two tribes, and a phylogenetically informed generalized least squares regression (PGLS for each tribe with occlusal surface area as the independent variable and D as the dependent variable. The slopes of both PGLS analyses were compared using a t-test to determine if the same linear relationship existed between the two tribes. The t-test between tribes was significant (p < 0.0001, suggesting different D populations for each lineage. The PGLS for Hipparionini was a positive but not

  11. Relativistic Band Structure and Fermi Surface of PdTe2 by the LMTO Method

    DEFF Research Database (Denmark)

    Jan, J. P.; Skriver, Hans Lomholt

    1977-01-01

    The energy bands of the trigonal layer compound PdTe2 have been calculated, using the relativistic linear muffin-tin orbitals method. The bandstructure is separated into three distinct regions with low-lying Te 5s bands, conduction bands formed by Pd 4d and Te 5p states, and high-lying bands formed...

  12. Kinetic model for electric-field induced point defect redistribution near semiconductor surfaces

    Science.gov (United States)

    Gorai, Prashun; Seebauer, Edmund G.

    2014-07-01

    The spatial distribution of point defects near semiconductor surfaces affects the efficiency of devices. Near-surface band bending generates electric fields that influence the spatial redistribution of charged mobile defects that exchange infrequently with the lattice, as recently demonstrated for pile-up of isotopic oxygen near rutile TiO2 (110). The present work derives a mathematical model to describe such redistribution and establishes its temporal dependence on defect injection rate and band bending. The model shows that band bending of only a few meV induces significant redistribution, and that the direction of the electric field governs formation of either a valley or a pile-up.

  13. Kinetic model for electric-field induced point defect redistribution near semiconductor surfaces

    International Nuclear Information System (INIS)

    Gorai, Prashun; Seebauer, Edmund G.

    2014-01-01

    The spatial distribution of point defects near semiconductor surfaces affects the efficiency of devices. Near-surface band bending generates electric fields that influence the spatial redistribution of charged mobile defects that exchange infrequently with the lattice, as recently demonstrated for pile-up of isotopic oxygen near rutile TiO 2 (110). The present work derives a mathematical model to describe such redistribution and establishes its temporal dependence on defect injection rate and band bending. The model shows that band bending of only a few meV induces significant redistribution, and that the direction of the electric field governs formation of either a valley or a pile-up.

  14. Calculating the optical properties of defects and surfaces in wide band gap materials

    Science.gov (United States)

    Deák, Peter

    2018-04-01

    The optical properties of a material critically depend on its defects, and understanding that requires substantial and accurate input from theory. This paper describes recent developments in the electronic structure theory of defects in wide band gap materials, where the standard local or semi-local approximations of density functional theory fail. The success of the HSE06 screened hybrid functional is analyzed in case of Group-IV semiconductors and TiO2, and shown that it is the consequence of error compensation between semi-local and non-local exchange, resulting in a proper derivative discontinuity (reproduction of the band gap) and a total energy which is a linear function of the fractional occupation numbers (removing most of the electron self-interaction). This allows the calculation of electronic transitions with accuracy unseen before, as demonstrated on the single-photon emitter NV(-) center in diamond and on polaronic states in TiO2. Having a reliable tool for electronic structure calculations, theory can contribute to the understanding of complicated cases of light-matter interaction. Two examples are considered here: surface termination effects on the blinking and bleaching of the light-emission of the NV(-) center in diamond, and on the efficiency of photocatalytic water-splitting by TiO2. Finally, an outlook is presented for the application of hybrid functionals in other materials, as, e.g., ZnO, Ga2O3 or CuGaS2.

  15. CAROLS: A New Airborne L-Band Radiometer for Ocean Surface and Land Observations

    DEFF Research Database (Denmark)

    Zribi, Mehrez; Parde, Mickael; Boutin, Jacquline

    2011-01-01

    The "Cooperative Airborne Radiometer for Ocean and Land Studies" (CAROLS) L-Band radiometer was designed and built as a copy of the EMIRAD II radiometer constructed by the Technical University of Denmark team. It is a fully polarimetric and direct sampling correlation radiometer. It is installed ...... is conforming to specification and is a useful tool for Soil Moisture and Ocean Salinity (SMOS) satellite validation as well as for specific studies on surface soil moisture or ocean salinity.......The "Cooperative Airborne Radiometer for Ocean and Land Studies" (CAROLS) L-Band radiometer was designed and built as a copy of the EMIRAD II radiometer constructed by the Technical University of Denmark team. It is a fully polarimetric and direct sampling correlation radiometer. It is installed...... flights were carried out over South West France, the Valencia site and the Bay of Biscay (Atlantic Ocean) in 2007, 2008 and 2009, in coordination with in situ field campaigns. In order to validate the CAROLS data, various aircraft flight patterns and maneuvers were implemented, including straight...

  16. MODIS/Aqua Land Surface Temperature/3-Band Emissivity 8-Day L3 Global 1km SIN Grid V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS/Aqua Land Surface Temperature/3-Band Emissivity 8-Day L3 Global 1km SIN Grid (MYD21A2.006). A new suite of MODIS Land Surface Temperature (LST) and Emissivity...

  17. MODIS/Terra Land Surface Temperature/3-Band Emissivity 8-Day L3 Global 1km SIN Grid V006

    Data.gov (United States)

    National Aeronautics and Space Administration — MODIS/Terra Land Surface Temperature/3-Band Emissivity 8-Day L3 Global 1km SIN Grid (MOD21A2.006). A new suite of MODIS Land Surface Temperature (LST) and Emissivity...

  18. Utilization of surface Plasmon resonance band of silver nanoparticles for determination of critical micelle concentration of cationic surfactants

    Science.gov (United States)

    Salem, Jamil K.; El-Nahhal, Issa M.; Najri, Bassam A.; Hammad, Talaat M.

    2016-11-01

    We have utilized surface Plasmon resonance (SPR) band sensitivity to surfactant concentration to investigate the critical micelle concentration (cmc) of CTAB, HY and CPB. The process is based upon an in situ formation of silver nanoparticles (AgNPs) through the reduction of silver ions (Ag+) by diethylene triamine (DETA) at 25 °C. In the presence of cationic surfactants, Ag+ ions can be reduced to AgNPs in a few minutes, accompanied by changes in intensity and wavelength of the SPR band. The spectral shifts of SPR band and the change of color have been used to determine CMC values of cationic surfactants.

  19. Bend me, shape me

    CERN Document Server

    2002-01-01

    A Japanese team has found a way to bend and shape silicon substrates by growing a thin layer of diamond on top. The technique has been proposed as an alternative to mechanical bending, which is currently used to make reflective lenses for X-ray systems and particle physics systems (2 paragraphs).

  20. Impact of Surface Soil Moisture Variations on Radar Altimetry Echoes at Ku and Ka Bands in Semi-Arid Areas

    Directory of Open Access Journals (Sweden)

    Christophe Fatras

    2018-04-01

    Full Text Available Radar altimetry provides information on the topography of the Earth surface. It is commonly used for the monitoring not only sea surface height but also ice sheets topography and inland water levels. The radar altimetry backscattering coefficient, which depends on surface roughness and water content, can be related to surface properties such as surface soil moisture content. In this study, the influence of surface soil moisture on the radar altimetry echo and backscattering coefficient is analyzed over semi-arid areas. A semi-empirical model of the soil’s complex dielectric permittivity that takes into account that small-scale roughness and large-scale topography was developed to simulate the radar echoes. It was validated using waveforms acquired at Ku and Ka-bands by ENVISAT RA-2 and SARAL AltiKa respectively over several sites in Mali. Correlation coefficients ranging from 0.66 to 0.94 at Ku-band and from 0.27 to 0.96 at Ka-band were found. The increase in surface soil moisture from 0.02 to 0.4 (i.e., the typical range of variations in semi-arid areas increase the backscattering from 10 to 15 dB between the core of the dry and the maximum of the rainy seasons.

  1. Largely enhanced near band edge emission of ultrathin zinc oxide nanowire/gold nanoparticles composites by surface plasmon resonance

    Science.gov (United States)

    Li, Lei; Wang, Chenying; Han, Feng; Yang, Shuming; Jing, Weixuan; Jiang, Zhuangde

    2018-03-01

    Ultrathin zinc oxide nanowires with diameter less than 50 nm were synthesized by polyethyleneimine assisted solution method. Zinc oxide nanowire near band edge emission was enhanced obviously by gold nanoparticles coating, and a max 26 times enhancement was realized. The defects caused visible light emission was also quenched to noise level when gold was deposited more than 10 s. The large near band edge emission enhancement was caused by surface plasmon resonance mediated luminescent energy transfer, which absorbed the visible light energy and transferred to the near band edge emission. The large surface to volume ratio enhanced the coupling strength between gold nanoparticles and ultrathin zinc oxide nanowires. This research provide a method to improve the luminescent efficiency of zinc oxide nanowires.

  2. The Westerbork HI survey of spiral and irregular galaxies - II. R-band surface photometry of late-type dwarf galaxies

    NARCIS (Netherlands)

    Swaters, RA; Balcells, M

    R-band surface photometry is presented for 171 late-type dwarf and irregular galaxies. For a subsample of 46 galaxies B-band photometry is presented as well. We present surface brightness profiles as well as isophotal and photometric parameters including magnitudes, diameters and central surface

  3. Bending stresses in Facetted Glass Shells

    DEFF Research Database (Denmark)

    Bagger, Anne; Jönsson, Jeppe; Almegaard, Henrik

    2008-01-01

    A shell structure of glass combines a highly effective structural principle with a material of optimal permeability to light. A facetted shell structure has a piecewise plane geometry, and together the facets form an approximation to a curved surface. A distributed load on a plane-based facetted...... structure will locally cause bending moments in the loaded facets. The bending stresses are dependent on the stiffness of the joints. Approximate solutions are developed to estimate the magnitude of the bending stresses. A FE-model of a facetted glass shell structure is used to validate the expressions...

  4. Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

    Science.gov (United States)

    Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

    2018-01-01

    Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

  5. Bending induced electrical response variations in ultra-thin flexible chips and device modeling

    Science.gov (United States)

    Heidari, Hadi; Wacker, Nicoleta; Dahiya, Ravinder

    2017-09-01

    Electronics that conform to 3D surfaces are attracting wider attention from both academia and industry. The research in the field has, thus far, focused primarily on showcasing the efficacy of various materials and fabrication methods for electronic/sensing devices on flexible substrates. As the device response changes are bound to change with stresses induced by bending, the next step will be to develop the capacity to predict the response of flexible systems under various bending conditions. This paper comprehensively reviews the effects of bending on the response of devices on ultra-thin chips in terms of variations in electrical parameters such as mobility, threshold voltage, and device performance (static and dynamic). The discussion also includes variations in the device response due to crystal orientation, applied mechanics, band structure, and fabrication processes. Further, strategies for compensating or minimizing these bending-induced variations have been presented. Following the in-depth analysis, this paper proposes new mathematical relations to simulate and predict the device response under various bending conditions. These mathematical relations have also been used to develop new compact models that have been verified by comparing simulation results with the experimental values reported in the recent literature. These advances will enable next generation computer-aided-design tools to meet the future design needs in flexible electronics.

  6. Standard test methods for bend testing of material for ductility

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    1.1 These test methods cover bend testing for ductility of materials. Included in the procedures are four conditions of constraint on the bent portion of the specimen; a guided-bend test using a mandrel or plunger of defined dimensions to force the mid-length of the specimen between two supports separated by a defined space; a semi-guided bend test in which the specimen is bent, while in contact with a mandrel, through a specified angle or to a specified inside radius (r) of curvature, measured while under the bending force; a free-bend test in which the ends of the specimen are brought toward each other, but in which no transverse force is applied to the bend itself and there is no contact of the concave inside surface of the bend with other material; a bend and flatten test, in which a transverse force is applied to the bend such that the legs make contact with each other over the length of the specimen. 1.2 After bending, the convex surface of the bend is examined for evidence of a crack or surface irregu...

  7. Band-gap-confinement and image-state-recapture effects in the survival of anions scattered from metal surfaces

    International Nuclear Information System (INIS)

    Schmitz, Andrew; Shaw, John; Chakraborty, Himadri S.; Thumm, Uwe

    2010-01-01

    The resonant charge transfer process in the collision of hydrogen anions with metal surfaces is described within a single-active-electron wave-packet propagation method. The ion-survival probability is found to be strongly enhanced at two different surface-specific perpendicular velocities of the ion. It is shown that, while the low-velocity enhancement is induced from a dynamical confinement of the ion level inside the band gap, the high-velocity enhancement is due to electron recapture from transiently populated image states. Results are presented for Li(110), Cu(111), and Pd(111) surfaces.

  8. Design of LD in-band direct-pumping side surface polished micro-rod Nd:YVO4 laser

    International Nuclear Information System (INIS)

    Zhang Wen-Qi; Wang Fei; Liu Qiang; Gong Ma-Li

    2016-01-01

    To diminish the thermal load, two ways, that is, in-band direct pumping and micro-rod crystal, could be adopted at the same time. The efficiency of LD in-band direct-pumping side surface polished micro-rod Nd:YVO 4 laser is numerically analyzed. By optimizing parameters such as crystal length, laser mode radius, pump beam radius, doping concentration and crystal cross-section size, the overall efficiency can reach over 50%. It is found that with micro-rod crystal implemented in the laser oscillator, high overall efficiency LD in-band direct-pumping Nd:YVO 4 laser could be realized. High efficiency combined with low thermal load makes this laser an outstanding scheme for building high-power Nd:YVO 4 lasers. (paper)

  9. Band structure engineering of monolayer MoS₂ by surface ligand functionalization for enhanced photoelectrochemical hydrogen production activity.

    Science.gov (United States)

    Pan, Jing; Wang, Zilu; Chen, Qian; Hu, Jingguo; Wang, Jinlan

    2014-11-21

    To achieve photoelectrochemical (PEC) activity of MoS2 for hydrogen production through water splitting, the band edges of MoS2 should match with the hydrogen and oxygen production levels. Our first-principles calculations show that the band edges of monolayer MoS2 can be effectively tuned by surface ligand functionalization, resulting from the intrinsic dipole of the ligand itself and the induced dipole at the ligand/MoS2 interface. We further explore the influence of ligand coverage, ligand functionalization and the substrate on the band structure of MoS2. The hybrid C6H5CH2NH2/MoS2/graphene structures may be compelling candidates as they satisfy the stringent requirements of PEC water splitting.

  10. Energy band structure, fermi surfaces, magnetization densities, and properties of the rare-earths and actinides

    International Nuclear Information System (INIS)

    Freeman, A.J.

    1977-01-01

    Some aspects of the predictions of energy band theory for both the rare earths and actinides and their comparison with experiment are discussed. Recent developments in assessing eigenfunction behavior are emphasized. 5 figures

  11. Airborne Measurements of Rain and the Ocean Surface Backscatter Response at C- and Ku-band

    National Research Council Canada - National Science Library

    Fernandez, Daniel E; Chang, Paul S; Carswell, James R; Contreras, Robert F; Frasier, Stephen J

    2005-01-01

    ...) and the Simultaneous Frequency Microwave Radiometer (SFMR). IWRAP is a dual-band (C- and Ku), dual-polarized pencilbeam airborne radar that profiles the volume backscatter and Doppler velocity from rain and that also measures the ocean backscatter response...

  12. Plasmon Modulation Spectroscopy of Noble Metals to Reveal the Distribution of the Fermi Surface Electrons in the Conduction Band

    Directory of Open Access Journals (Sweden)

    Kentaro Takagi

    2017-12-01

    Full Text Available To directly access the dynamics of electron distribution near the Fermi-surface after plasmon excitation, pump-probe spectroscopy was performed by pumping plasmons on noble-metal films and probing the interband transition. Spectral change in the interband transitions is sensitive to the electron distribution near the Fermi-surface, because it involves the d valence-band to the conduction band transitions and should reflect the k-space distribution dynamics of electrons. For the continuous-wave pump and probe experiment, the plasmon modulation spectra are found to differ from both the current modulation and temperature difference spectra, possibly reflecting signatures of the plasmon wave function. For the femtosecond-pulse pump and probe experiment, the transient spectra agree well with the known spectra upon the excitation of the respective electrons resulting from plasmon relaxation, probably because the lifetime of plasmons is shorter than the pulse duration.

  13. Sea Surface Salinity and Wind Retrieval Algorithm Using Combined Passive-Active L-Band Microwave Data

    Science.gov (United States)

    Yueh, Simon H.; Chaubell, Mario J.

    2011-01-01

    Aquarius is a combined passive/active L-band microwave instrument developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, the global water cycle, and climate. The primary science objective of this mission is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean with a spatial resolution of 150 kilometers and a retrieval accuracy of 0.2 practical salinity units globally on a monthly basis. The measurement principle is based on the response of the L-band (1.413 gigahertz) sea surface brightness temperatures (T (sub B)) to sea surface salinity. To achieve the required 0.2 practical salinity units accuracy, the impact of sea surface roughness (e.g. wind-generated ripples and waves) along with several factors on the observed brightness temperature has to be corrected to better than a few tenths of a degree Kelvin. To the end, Aquarius includes a scatterometer to help correct for this surface roughness effect.

  14. Ka-band Doppler Scatterometer for Measurements of Ocean Vector Winds and Surface Currents

    Data.gov (United States)

    National Aeronautics and Space Administration — Ocean surface currents impact heat transport, surface momentum and gas fluxes, ocean productivity and marine biological communities. Ocean currents also have social...

  15. AVHRR Surface Temperature and Narrow-Band Albedo Comparison with Ground Measurements for the Greenland Ice Sheet

    Science.gov (United States)

    Haefliger, M.; Steffen, K.; Fowler, C.

    1993-01-01

    An ice-surface temperature retrieval algorithm for the Greenland ice sheet was developed using NOAA 11 thermal radiances from channels 4 and 5. Temperature, pressure and humidity profiles, cloud observations and skin temperatures from the Swiss Federal Institute of Technology (ETH) camp, located at the equilibrium line altitude at 49 deg17 min W, 69 deg 34 min N, were used in the LOWTRAN 7 model. Through a statistical analysis of daily clear sky profiles, the coefficients that correct for the atmospheric effects were determined for the ETH-Camp field season (May to August). Surface temperatures retrieved by this method were then compared against the in situ observations with a maximum difference of 0.6 K. The NOAA 11 narrow-band planetary albedo values for channels 1 and 2 were calculated using pre-launch calibration coefficients. Scattering and absorption by the atmosphere were modelled with LOWTRAN 7. Then, narrow-band albedo values for the AVHRR visible and near infrared channels were compared with in situ high resolution spectral reflectance measurements. In the visible band (580-680 nm), AVHRR-derived narrow-band albedo and the in situ measurements corrected with radiative transfer model LOWTRAN 7 showed a difference of less than 2%. For the near infrared channel (725-1100 nm) the difference between the measured and modelled narrow-band albedo was 14%. These discrepancies could be either the result of inaccurate aerosol scattering modelling (lack of the in situ observation), or the result of sensor drift due to degradation.

  16. Effects of surface roughness on sea ice freeboard retrieval with an Airborne Ku-Band SAR radar altimeter

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    2010-01-01

    Results from two years of the CryoSat Validation Experiment (CryoVEx) over sea ice in the western Arctic Ocean are presented. The estimation of freeboard, the height of sea ice floating above the water level, is one the main goals of the CryoSat-2 mission of the European Space Agency (ESA) in order...... to investigate sea ice volume changes on an Arctic wide scale. Freeboard retrieval requires precise radar range measurements to the ice surface, therefore we investigate the penetration of the Ku-Band radar waves into the overlying snow cover as well as the effects of sub-footprint-scale surface roughness using...

  17. An Improved Single-Channel Method to Retrieve Land Surface Temperature from the Landsat-8 Thermal Band

    Directory of Open Access Journals (Sweden)

    Jordi Cristóbal

    2018-03-01

    Full Text Available Land surface temperature (LST is one of the sources of input data for modeling land surface processes. The Landsat satellite series is the only operational mission with more than 30 years of archived thermal infrared imagery from which we can retrieve LST. Unfortunately, stray light artifacts were observed in Landsat-8 TIRS data, mostly affecting Band 11, currently making the split-window technique impractical for retrieving surface temperature without requiring atmospheric data. In this study, a single-channel methodology to retrieve surface temperature from Landsat TM and ETM+ was improved to retrieve LST from Landsat-8 TIRS Band 10 using near-surface air temperature (Ta and integrated atmospheric column water vapor (w as input data. This improved methodology was parameterized and successfully evaluated with simulated data from a global and robust radiosonde database and validated with in situ data from four flux tower sites under different types of vegetation and snow cover in 44 Landsat-8 scenes. Evaluation results using simulated data showed that the inclusion of Ta together with w within a single-channel scheme improves LST retrieval, yielding lower errors and less bias than models based only on w. The new proposed LST retrieval model, developed with both w and Ta, yielded overall errors on the order of 1 K and a bias of −0.5 K validated against in situ data, providing a better performance than other models parameterized using w and Ta or only w models that yielded higher error and bias.

  18. C-Band Airport Surface Communications System Engineering-Initial High-Level Safety Risk Assessment and Mitigation

    Science.gov (United States)

    Zelkin, Natalie; Henriksen, Stephen

    2011-01-01

    This document is being provided as part of ITT's NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract: "New ATM Requirements--Future Communications, C-Band and L-Band Communications Standard Development." ITT has completed a safety hazard analysis providing a preliminary safety assessment for the proposed C-band (5091- to 5150-MHz) airport surface communication system. The assessment was performed following the guidelines outlined in the Federal Aviation Administration Safety Risk Management Guidance for System Acquisitions document. The safety analysis did not identify any hazards with an unacceptable risk, though a number of hazards with a medium risk were documented. This effort represents an initial high-level safety hazard analysis and notes the triggers for risk reassessment. A detailed safety hazards analysis is recommended as a follow-on activity to assess particular components of the C-band communication system after the profile is finalized and system rollout timing is determined. A security risk assessment has been performed by NASA as a parallel activity. While safety analysis is concerned with a prevention of accidental errors and failures, the security threat analysis focuses on deliberate attacks. Both processes identify the events that affect operation of the system; and from a safety perspective the security threats may present safety risks.

  19. Membrane bending by protein-protein crowding.

    Science.gov (United States)

    Stachowiak, Jeanne C; Schmid, Eva M; Ryan, Christopher J; Ann, Hyoung Sook; Sasaki, Darryl Y; Sherman, Michael B; Geissler, Phillip L; Fletcher, Daniel A; Hayden, Carl C

    2012-09-01

    Curved membranes are an essential feature of dynamic cellular structures, including endocytic pits, filopodia protrusions and most organelles. It has been proposed that specialized proteins induce curvature by binding to membranes through two primary mechanisms: membrane scaffolding by curved proteins or complexes; and insertion of wedge-like amphipathic helices into the membrane. Recent computational studies have raised questions about the efficiency of the helix-insertion mechanism, predicting that proteins must cover nearly 100% of the membrane surface to generate high curvature, an improbable physiological situation. Thus, at present, we lack a sufficient physical explanation of how protein attachment bends membranes efficiently. On the basis of studies of epsin1 and AP180, proteins involved in clathrin-mediated endocytosis, we propose a third general mechanism for bending fluid cellular membranes: protein-protein crowding. By correlating membrane tubulation with measurements of protein densities on membrane surfaces, we demonstrate that lateral pressure generated by collisions between bound proteins drives bending. Whether proteins attach by inserting a helix or by binding lipid heads with an engineered tag, protein coverage above ~20% is sufficient to bend membranes. Consistent with this crowding mechanism, we find that even proteins unrelated to membrane curvature, such as green fluorescent protein (GFP), can bend membranes when sufficiently concentrated. These findings demonstrate a highly efficient mechanism by which the crowded protein environment on the surface of cellular membranes can contribute to membrane shape change.

  20. Homogeneity of Surface Sites in Supported Single-Site Metal Catalysts: Assessment with Band Widths of Metal Carbonyl Infrared Spectra.

    Science.gov (United States)

    Hoffman, Adam S; Fang, Chia-Yu; Gates, Bruce C

    2016-10-06

    Determining and controlling the uniformity of isolated metal sites on surfaces of supports are central goals in investigations of single-site catalysts because well-defined species provide opportunities for fundamental understanding of the surface sites. CO is a useful probe of surface metal sites, often reacting with them to form metal carbonyls, the infrared spectra of which provide insights into the nature of the sites and the metal-support interface. Metals bonded to various support surface sites give broad bands in the spectra, and when narrow bands are observed, they indicate a high degree of uniformity of the metal sites. Much recent work on single-site catalysts has been done with supports that are inherently nonuniform, giving supported metal species that are therefore nonuniform. Herein we summarize values of ν CO data characterizing supported iridium gem-dicarbonyls, showing that the most nearly uniform of them are those supported on zeolites and the least uniform are those supported on metal oxides. Guided by ν CO data of supported iridium gem-dicarbonyls, we have determined new, general synthesis methods to maximize the degree of uniformity of iridium species on zeolites and on MgO. We report results for a zeolite HY-supported iridium gem-dicarbonyl with full width at half-maximum values of only 4.6 and 5.2 cm -1 characterizing the symmetric and asymmetric CO stretches and implying that this is the most nearly uniform supported single-site metal catalyst.

  1. Plate girders under bending

    NARCIS (Netherlands)

    Abspoel, R.; Dubina, D.; Ungureanu, V.

    2016-01-01

    In a material economy driven plate girder design, the lever arm between the flanges will increase. This leads to higher stiffness and bending moment resistance, but also to an in-crease of the web slenderness. This means that high strength steels can be used leading to a large reduction of the steel

  2. DNA Bending elasticity

    Science.gov (United States)

    Sivak, David Alexander

    DNA bending elasticity on length scales of tens of basepairs is of critical importance in numerous biological contexts. Even the simplest models of DNA bending admit of few simple analytic results, thus there is a need for numerical methods to calculate experimental observables, such as distance distributions, forces, FRET efficiencies, and timescales of particular large-scale motions. We have implemented and helped develop a coarse-grained representation of DNA and various other covalently-linked groups that allows simple calculation of such observables for varied experimental systems. The simple freely-jointed chain (FJC) model and extremely coarse resolution proved useful in understanding DNA threading through nanopores, identifying steric occlusion by other parts of the chain as a prime culprit for slower capture as distance to the pore decreased. Enhanced sampling techniques of a finer resolution discrete wormlike chain (WLC) model permitted calculation of cyclization rates for small chains and identified the ramifications of a thermodynamically-sound treatment of thermal melts. Adding treatment of double-stranded DNA's helical nature and single-stranded DNA provided a model system that helped demonstrate the importance of statistical fluctuations in even highly-stressed DNA mini-loops, and allowed us to verify that even these constructs show no evidence of excitation-induced softening. Additional incorporation of salt-sensitivity to the model allowed us to calculate forces and FRET efficiencies for such mini-loops and their uncircularized precursors, thereby furthering the understanding of the nature of IHF binding and bending of its recognition sequence. Adding large volume-excluding spheres linked to the ends of the dsDNA permits calculation of distance distributions and thus small-angle X-ray scattering, whereby we demonstrated the validity of the WLC in describing bending fluctuations in DNA chains as short as 42 bp. We also make important connections

  3. Band structure and fermi surface of an extremely overdoped iron-based superconductor KFe2As2.

    Science.gov (United States)

    Sato, T; Nakayama, K; Sekiba, Y; Richard, P; Xu, Y-M; Souma, S; Takahashi, T; Chen, G F; Luo, J L; Wang, N L; Ding, H

    2009-07-24

    We have performed high-resolution angle-resolved photoemission spectroscopy on heavily overdoped KFe_{2}As_{2} (transition temperature T_{c} = 3 K). We observed several renormalized bands near the Fermi level with a renormalization factor of 2-4. While the Fermi surface around the Brillouin-zone center is qualitatively similar to that of optimally doped Ba_{1-x}K_{x}Fe_{2}As_{2} (x = 0.4; T_{c} = 37 K), the Fermi surface topology around the zone corner (M point) is markedly different: the two electron Fermi surface pockets are completely absent due to an excess of hole doping. This result indicates that the electronic states around the M point play an important role in the high-T_{c} superconductivity of Ba_{1-x}K_{x}Fe_{2}As_{2} and suggests that the interband scattering via the antiferromagnetic wave vector essentially controls the T_{c} value in the overdoped region.

  4. Spin-polarized quasi-one-dimensional state with finite band gap on the Bi/InSb(001) surface

    Science.gov (United States)

    Kishi, J.; Ohtsubo, Y.; Nakamura, T.; Yaji, K.; Harasawa, A.; Komori, F.; Shin, S.; Rault, J. E.; Le Fèvre, P.; Bertran, F.; Taleb-Ibrahimi, A.; Nurmamat, M.; Yamane, H.; Ideta, S.; Tanaka, K.; Kimura, S.

    2017-11-01

    One-dimensional (1D) electronic states were discovered on the 1D surface atomic structure of Bi fabricated on semiconductor InSb(001) substrates by angle-resolved photoelectron spectroscopy (ARPES). The 1D state showed steep, Dirac-cone-like dispersion along the 1D atomic structure with a finite direct band gap opening as large as 150 meV. Moreover, spin-resolved ARPES revealed the spin polarization of the 1D unoccupied states as well as that of the occupied states, the orientation of which inverted depending on the wave-vector direction parallel to the 1D array on the surface. These results reveal that a spin-polarized quasi-1D carrier was realized on the surface of 1D Bi with highly efficient backscattering suppression, showing promise for use in future spintronics and energy-saving devices.

  5. Revisiting magnetism of capped Au and ZnO nanoparticles: Surface band structure and atomic orbital with giant magnetic moment

    Energy Technology Data Exchange (ETDEWEB)

    Hernando, Antonio; Crespo, Patricia [Instituto de Magnetismo Aplicado, UCM-CSIC-ADIF, Las Rozas. P.O. Box 155, 28230 Madrid (Spain); Dept. Fisica de Materiales, Universidad Complutense, Madrid (Spain); Garcia, Miguel Angel [Instituto de Ceramica y Vidrio, CSIC, C/ Kelsen, 5, Madrid 28049 (Spain); Coey, Michael [Trinity College Dublin, Dublin (Ireland); Ayuela, Andres; Echenique, Pedro Miguel [Centro de Fisica de Materiales, CFM-MPC CSIC-UPV/EHU, Donostia International Physics Center (DIPC), 20018 San Sebastian (Spain); Departamento de Fisica de Materiales, Fac. de Quimicas, Universidad del Pais Vasco UPV-EHU, 20018 San Sebastian (Spain)

    2011-10-15

    In this article we review the exotic magnetism of nanoparticles (NPs) formed by substances that are not magnetic in bulk as described with generality in Section 1. In particular, the intrinsic character of the magnetism observed on capped Au and ZnO NPs is analysed. X-ray magnetic circular dichroism (XMCD) analysis has shown that the magnetic moments are intrinsic and lie in the Au and Zn atoms, respectively, as analysed in Section 2, where the general theoretical ideas are also revisited. Since impurity atoms bonded to the surface act as donor or acceptor of electrons that occupy the surface states, the anomalous magnetic response is analysed in terms of the surface band in Section 3. Finally, Section 4 summarizes our last theoretical proposal. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Influence from Polarized Galactic Background Noise on L-band Measurements of the Sea Surface Salinity

    DEFF Research Database (Denmark)

    Søbjærg, Sten Schmidl; Skou, Niels

    2004-01-01

    The polarimetric EMIRAD radiometer, based on novel digital down conversion and detection techniques, has been installed on a C-130 aircraft from the Royal Danish. Air Force during the L-band Ocean Salinity Airborne Campaign (LOSAC) in 2001 and 2003. Full 360° circle flight patterns around the same...... target area as well as clover leaf patterns have been measured, and both provide an azimuth signature of the ocean at a constant incidence angle. The resulting azimuth signatures show significant variations in all the three first Stokes parameters, and a correlation is found between the downwelling...

  7. The Impact of the Spectral Band Number and Width on the Oil Pollution Diagnostics on Earth Surface by Laser Fluorescence Method

    Directory of Open Access Journals (Sweden)

    Yu. V. Fedotov

    2017-01-01

    Full Text Available Using the remote sensing methods is the most promising for day-to-day control of oil pollution. The laser-induced fluorescence method provides efficient detection and classification of oil pollutions. To monitor oil pollutions on the earth surface is more complicated than on the water one because of lower fluorescence intensity and interfering fluorescence of natural objects available on the earth surface.Properties of oil pollution classifiers depend largely on the number and positions of spectral bands of fluorescence registration. Reducing the number of spectral bands allows us to diminish computation complexity and cost of equipment. In some cases the reduction increases classification accuracy. The number of spectral bands can be reduced through increasing their width.The paper presents mathematical modeling of oil pollution detection and classification. The experimentally obtained fluorescence spectra of oil pollutions on different substrates were used as input data. The k-nearest neighbors algorithm was used to detect and classify oil pollutions. Cross validation was applied in mathematical modeling.The mathematical modeling results have shown that for oil pollutions detection using over 8 spectral bands (band width less than 50 nm a classification error rate does not depend on the further increasing number of the spectral bands.As to the type classification of oil pollutions (4 classes, an increasing width of the spectral bands up to 60 nm (the number of spectral bands reduced up 7 does not lead to a significantly decreasing overall classification accuracy.In the case of the sort classification of oil pollutions (8 classes a local maximum of the overall accuracy has been observed at 25-30 nm width of the spectral band (14-16 spectral bands. The spectral resolution improvement (increasing the number of bands does give an essentially increasing accuracy.The paper has shown that to detect and classify oil pollutions on the earth surface

  8. Bomb-test 90Sr in Pacific and Indian Ocean surface water as recorded by banded corals

    International Nuclear Information System (INIS)

    Toggweiler, J.R.; Trumbore, S.

    1985-01-01

    We report here measurements of bomb-test 90 Sr activity in the CaCO 3 skeletons of banded head forming corals collected from nine locations in the tropical Pacific and Indian Oceans. Density variations in skeletal carbonate demarcate annual growth bands and allow one to section individual years. Measurements of 90 Sr activity in the annual bands reconstruct the activity of the water in which the coral grew. Our oldest records date to the early years of the nuclear era and record not only fallout deposition from the major U.S. and Soviet tests of 1958-1962, but also the huge, and largely unappreciated, localized inputs from the U.S. tests at Eniwetok and Bikini atolls during 1952-1958. In the 1960's the 90 Sr activity in Indian Ocean surface water was twice as high as activity levels in the South Pacific at comparable latitudes. We suggest that substantial amounts of northern hemisphere fallout moved west and south into the Indian Ocean via passages through the Indonesian archipelago. Equatorial Pacific 90 Sr levels have remained relatively constant from the mid 1960's through the end of 1970's in spite of 90 Sr decay, reflecting a large-scale transfer of water between the temperate and tropical North Pacific. Activity levels at Fanning Is. (4 0 N, 160 0 W) appear to vary in conjunction with the 3-4 year El Nino cycle. (orig.)

  9. Localized bending fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2012-01-01

    In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement...... of the strain distribution in the strand and helps in identifying potential failure mechanisms along the strand and at the wedge location. Initial analysis of the deformations shows that the bending fatigue behavior of the monostrand may be controlled either by local bending deformations or by relative...... displacement (opening/closing and sliding) of the helically wound wires. Moreover, the results are a step towards understanding the bending fatigue damage mechanisms of monostrand cables....

  10. A Novel Low-cost, Ka-band, High Altitude, Multi-Baseline Unmanned Aerial Vehicle Sensor for Surface Water Ocean Topography, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal presents the Ka-band SWOT Phenomenology Airborne Radar (KaSPAR) to support the surface water ocean topography (SWOT) mission for science and algorithm...

  11. AA, bending magnet, BLG

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    The very particular lattice of the AA required 2 types of dipole (bending magnets; BLG, long and narrow; BST, short and wide). The BLG had a steel length of 4.70 m, a good field width of 0.24 m, and a weight of about 70 t. Jean-Claude Brunet inspects the lower half of a BLG. For the BST magnets see 7811105 and 8006036.

  12. SIMULATION OF THE Ku-BAND RADAR ALTIMETER SEA ICE EFFECTIVE SCATTERING SURFACE

    DEFF Research Database (Denmark)

    Tonboe, Rasmus; Andersen, Søren; Pedersen, Leif Toudal

    2006-01-01

    A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model...... is initialised with in situ data collected during the May 2004 GreenIce ice camp in the Lincoln Sea (73ºW; 85ºN). Our results show that the snow cover is important for the effective scattering surface depth in sea ice and thus for the range measurement, ice freeboard and ice thickness estimation....

  13. Adsorption of Ti on LiAlH4 surfaces studied by band structure calculations

    International Nuclear Information System (INIS)

    Loevvik, O.M.

    2004-01-01

    LiAlH 4 is a potential light-weight hydrogen storage material if hydrogenation can be made reversible. In NaAlH 4 this may be done by adding small amounts of Ti, but the same effect has not yet been observed in LiAlH 4 . To understand these mechanisms, detailed studies of the materials with and without the additive are necessary. In this study, two-dimensional slabs representing the open (0 1 0) and densely packed (1 0 1) surfaces of LiAlH 4 have been used to model adsorption of titanium atoms on those surfaces. The results show that the Ti atom tends to move below the surface towards interstitial sites rather than binding to a Li ion or AlH 4 complex at the surface

  14. An Algorithm for Surface Current Retrieval from X-band Marine Radar Images

    Directory of Open Access Journals (Sweden)

    Chengxi Shen

    2015-06-01

    Full Text Available In this paper, a novel current inversion algorithm from X-band marine radar images is proposed. The routine, for which deep water is assumed, begins with 3-D FFT of the radar image sequence, followed by the extraction of the dispersion shell from the 3-D image spectrum. Next, the dispersion shell is converted to a polar current shell (PCS using a polar coordinate transformation. After removing outliers along each radial direction of the PCS, a robust sinusoidal curve fitting is applied to the data points along each circumferential direction of the PCS. The angle corresponding to the maximum of the estimated sinusoid function is determined to be the current direction, and the amplitude of this sinusoidal function is the current speed. For validation, the algorithm is tested against both simulated radar images and field data collected by a vertically-polarized X-band system and ground-truthed with measurements from an acoustic Doppler current profiler (ADCP. From the field data, it is observed that when the current speed is less than 0.5 m/s, the root mean square differences between the radar-derived and the ADCP-measured current speed and direction are 7.3 cm/s and 32.7°, respectively. The results indicate that the proposed procedure, unlike most existing current inversion schemes, is not susceptible to high current speeds and circumvents the need to consider aliasing. Meanwhile, the relatively low computational cost makes it an excellent choice in practical marine applications.

  15. Surface Clutter Suppression Techniques Applied to P-band Multi-Channel SAR Ice Sounder Data from East Antarctica

    DEFF Research Database (Denmark)

    Lin, Chung-Chi; Bekaert, David; Gebert, Nicolas

    Radar ice sounding allows for the retrieval of ice depth and provides information on ba-sal topography, basal conditions, flow, and layering. In the prospect of a possible future satellite ice sounding mission, surface clutters are expected to severely hamper measurement of radar ech-oes from...... the depth due to the unfavourable observation geometry. Synthetic aperture radar (SAR) processing enables to attenuate surface clutters in the forward and backward directions, but not in the across-track directions. Thus, additional across-track clutter cancellation is a crucial step for extracting weaker...... subsurface radar echoes. ESA’s P-band POLarimetric Airborne Radar Ice Sounder (POLARIS), recently upgraded with a larger antenna of 4 m length, enables simultaneous reception of up to 4 sub-aperture channels in across-track. Laboratory of Electromagnetics and Acoustics of Swiss Fed. Institute of Tech...

  16. An ultrathin wide-band planar metamaterial absorber based on a fractal frequency selective surface and resistive film

    International Nuclear Information System (INIS)

    Fan Yue-Nong; Cheng Yong-Zhi; Nie Yan; Wang Xian; Gong Rong-Zhou

    2013-01-01

    We propose an ultrathin wide-band metamaterial absorber (MA) based on a Minkowski (MIK) fractal frequency selective surface and resistive film. This absorber consists of a periodic arrangement of dielectric substrates sandwiched with an MIK fractal loop structure electric resonator and a resistive film. The finite element method is used to simulate and analyze the absorption of the MA. Compared with the MA-backed copper film, the designed MA-backed resistive film exhibits an absorption of 90% at a frequency region of 2 GHz–20 GHz. The power loss density distribution of the MA is further illustrated to explain the mechanism of the proposed MA. Simulated absorptions at different incidence cases indicate that this absorber is polarization-insensitive and wide-angled. Finally, further simulated results indicate that the surface resistance of the resistive film and the dielectric constant of the substrate can affect the absorbing property of the MA. This absorber may be used in many military fields

  17. Tubular lining material for pipelines having bends

    Energy Technology Data Exchange (ETDEWEB)

    Moringa, A.; Sakaguchi, Y.; Hyodo, M.; Yagi, I.

    1987-03-24

    A tubular lining material for pipelines having bends or curved portions comprises a tubular textile jacket made of warps and wefts woven in a tubular form overlaid with a coating of a flexible synthetic resin. It is applicable onto the inner surface of a pipeline having bends or curved portions in such manner that the tubular lining material with a binder onto the inner surface thereof is inserted into the pipeline and allowed to advance within the pipeline, with or without the aid of a leading rope-like elongated element, while turning the tubular lining material inside out under fluid pressure. In this manner the tubular lining material is applied onto the inner surface of the pipeline with the binder being interposed between the pipeline and the tubular lining material. The lining material is characterized in that a part of all of the warps are comprised of an elastic yarn around which, over the full length thereof, a synthetic fiber yarn or yarns have been left-and/or right-handedly coiled. This tubular lining material is particularly suitable for lining a pipeline having an inner diameter of 25-200 mm and a plurality of bends, such as gas service pipelines or house pipelines, without occurrence of wrinkles in the lining material in a bend.

  18. Ocean Surface Emissivity at L-band (1.4 GHz): The Dependence on Salinity and Roughness

    Science.gov (United States)

    LeVine, D. M.; Lang, R.; Wentz, F.; Messiner, T.

    2012-01-01

    A characterization of the emissivity of sea water at L-band is important for the remote sensing of sea surface salinity. Measurements of salinity are currently being made in the radio astronomy band at 1.413 GHz by ESA's Soil Moisture and Ocean Salinity (SMOS) mission and NASA's Aquarius instrument aboard the Aquarius/SAC-D observatory. The goal of both missions is accuracy on the order of 0.1 psu. This requires accurate knowledge of the dielectric constant of sea water as a function of salinity and temperature and also the effect of waves (roughness). The former determines the emissivity of an ideal (i.e. flat) surface and the later is the major source of error from predictions based on a flat surface. These two aspects of the problem of characterizing the emissivity are being addressed in the context of the Aquarius mission. First, laboratory measurements are being made of the dielectric constant of sea water. This is being done at the George Washington University using a resonant cavity. In this technique, sea water of known salinity and temperature is fed into the cavity along its axis through a narrow tube. The sea water changes the resonant frequency and Q of the cavity which, if the sample is small enough, can be related to the dielectric constant of the sample. An extensive set of measurements have been conducted at 1.413 GHz to develop a model for the real and imaginary part of the dielectric constant as a function of salinity and temperature. The results are compared to the predictions of models based on parameterization of the Debye resonance of the water molecule. The models and measurements are close; however, the differences are significant for remote sensing of salinity. This is especially true at low temperatures where the sensitivity to salinity is lowest.

  19. Band Structure and Fermi-Surface Properties of Ordered beta-Brass

    DEFF Research Database (Denmark)

    Skriver, Hans Lomholt; Christensen, N. E.

    1973-01-01

    , but that their position relative to the Fermi level is correct. The derived Fermi-surface model allows a detailed interpretation of the de Hass-van Alphen (dHvA) data. The present model has no open orbit along for B→∥ 〈110〉. This agrees with dHvA as well as magnetoresistance measurements. Four new extremal cross sections...

  20. Broad Band Data and Noise Observed with Surface Station and Borehole Station

    Science.gov (United States)

    Tunc, Suleyman; Ozel, Oguz; Safa Arslan, Mehmet; Behiye Akşahin, Bengi; Hatipoglu, Mustafa; Cagin Yalcintepe, Ragip; Ada, Samim; Meral Ozel, Nurcan

    2016-04-01

    Marmara region tectonically is very active and many destructive earthquakes happened in the past. North Anatolian Fault Zone crosses the Marmara region and it has three branches. The northern branch passes through Marmara Sea and expected future large earthquake will happen along this fault zone. There is a gap in seismic network in the Marmara region at offshore and onshore areas. We have started broadband borehole seismographic observations to obtain the detailed information about fault geometry and its stick-slip behavior beneath the western Marmara Sea, as a part of the MARsite collaborative Project, namely "New Directions in Seismic Hazard Assessment through Focused Earth Observation in the Marmara Supersite-MARsite". The target area western Marmara of Turkey. In the beginning of the project, we installed eight Broadband surface station around Marmara Sea in April 2014. Then, we added broadband sensor and broadband surface sensor at the same location in November 2014. In this study, we developed a Matlab application to calculate Power Spectral Density against the New Low Noise Model (NLNM) and New High Noise Model (NHNM) determined for one-hour segments of the data. Also we compared ambient noise of broadband borehole sensor and surface broadband sensor.

  1. Observation of Dirac-like energy band and ring-torus Fermi surface associated with the nodal line in topological insulator CaAgAs

    Science.gov (United States)

    Takane, Daichi; Nakayama, Kosuke; Souma, Seigo; Wada, Taichi; Okamoto, Yoshihiko; Takenaka, Koshi; Yamakawa, Youichi; Yamakage, Ai; Mitsuhashi, Taichi; Horiba, Koji; Kumigashira, Hiroshi; Takahashi, Takashi; Sato, Takafumi

    2018-01-01

    One of key challenges in current material research is to search for new topological materials with inverted bulk-band structure. In topological insulators, the band inversion caused by strong spin-orbit coupling leads to opening of a band gap in the entire Brillouin zone, whereas an additional crystal symmetry such as point-group and nonsymmorphic symmetries sometimes prohibits the gap opening at/on specific points or line in momentum space, giving rise to topological semimetals. Despite many theoretical predictions of topological insulators/semimetals associated with such crystal symmetries, the experimental realization is still relatively scarce. Here, using angle-resolved photoemission spectroscopy with bulk-sensitive soft-x-ray photons, we experimentally demonstrate that hexagonal pnictide CaAgAs belongs to a new family of topological insulators characterized by the inverted band structure and the mirror reflection symmetry of crystal. We have established the bulk valence-band structure in three-dimensional Brillouin zone, and observed the Dirac-like energy band and ring-torus Fermi surface associated with the line node, where bulk valence and conducting bands cross on a line in the momentum space under negligible spin-orbit coupling. Intriguingly, we found that no other bands cross the Fermi level and therefore the low-energy excitations are solely characterized by the Dirac-like band. CaAgAs provides an excellent platform to study the interplay among low-energy electron dynamics, crystal symmetry, and exotic topological properties.

  2. A theory for narrow-banded radio bursts at Uranus - MHD surface waves as an energy driver

    Science.gov (United States)

    Farrell, W. M.; Curtis, S. A.; Desch, M. D.; Lepping, R. P.

    1992-01-01

    A possible scenario for the generation of the narrow-banded radio bursts detected at Uranus by the Voyager 2 planetary radio astronomy experiment is described. In order to account for the emission burstiness which occurs on time scales of hundreds of milliseconds, it is proposed that ULF magnetic surface turbulence generated at the frontside magnetopause propagates down the open/closed field line boundary and mode-converts to kinetic Alfven waves (KAW) deep within the polar cusp. The oscillating KAW potentials then drive a transient electron stream that creates the bursty radio emission. To substantiate these ideas, Voyager 2 magnetometer measurements of enhanced ULF magnetic activity at the frontside magnetopause are shown. It is demonstrated analytically that such magnetic turbulence should mode-convert deep in the cusp at a radial distance of 3 RU.

  3. The Glacier and Land Ice Surface Topography Interferometer (GLISTIN): A Novel Ka-band Digitally Beamformed Interferometer

    Science.gov (United States)

    Moller, Delwyn K.; Heavey, Brandon; Hodges, Richard; Rengarajan, Sembiam; Rignot, Eric; Rogez, Francois; Sadowy, Gregory; Simard, Marc; Zawadzki, Mark

    2006-01-01

    The estimation of the mass balance of ice sheets and glaciers on Earth is a problem of considerable scientific and societal importance. A key measurement to understanding, monitoring and forecasting these changes is ice-surface topography, both for ice-sheet and glacial regions. As such NASA identified 'ice topographic mapping instruments capable of providing precise elevation and detailed imagery data for measurements on glacial scales for detailed monitoring of ice sheet, and glacier changes' as a science priority for the most recent Instrument Incubator Program (IIP) opportunities. Funded under this opportunity is the technological development for a Ka-Band (35GHz) single-pass digitally beamformed interferometric synthetic aperture radar (InSAR). Unique to this concept is the ability to map a significant swath impervious of cloud cover with measurement accuracies comparable to laser altimeters but with variable resolution as appropriate to the differing scales-of-interest over ice-sheets and glaciers.

  4. Influence of leaching on surface composition, microstructure, and valence band of single grain icosahedral Al-Cu-Fe quasicrystal

    International Nuclear Information System (INIS)

    Lowe, M.; McGrath, R.; Sharma, H. R.; Yadav, T. P.; Fournée, V.; Ledieu, J.

    2015-01-01

    The use of quasicrystals as precursors to catalysts for the steam reforming of methanol is potentially one of the most important applications of these new materials. To develop application as a technology requires a detailed understanding of the microscopic behavior of the catalyst. Here, we report the effect of leaching treatments on the surface microstructure, chemical composition, and valence band of the icosahedral (i-) Al-Cu-Fe quasicrystal in an attempt to prepare a model catalyst. The high symmetry fivefold surface of a single grain i-Al-Cu-Fe quasicrystal was leached with NaOH solution for varying times, and the resulting surface was characterized by x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The leaching treatments preferentially remove Al producing a capping layer consisting of Fe and Cu oxides. The subsurface layer contains elemental Fe and Cu in addition to the oxides. The quasicrystalline bulk structure beneath remains unchanged. The subsurface gradually becomes Fe 3 O 4 rich with increasing leaching time. The surface after leaching exhibits micron sized dodecahedral cavities due to preferential leaching along the fivefold axis. Nanoparticles of the transition metals and their oxides are precipitated on the surface after leaching. The size of the nanoparticles is estimated by high resolution transmission microscopy to be 5-20 nm, which is in agreement with the AFM results. Selected area electron diffraction (SAED) confirms the crystalline nature of the nanoparticles. SAED further reveals the formation of an interface between the high atomic density lattice planes of nanoparticles and the quasicrystal. These results provide an important insight into the preparation of model catalysts of nanoparticles for steam reforming of methanol

  5. Influence of leaching on surface composition, microstructure, and valence band of single grain icosahedral Al-Cu-Fe quasicrystal

    Science.gov (United States)

    Lowe, M.; Yadav, T. P.; Fournée, V.; Ledieu, J.; McGrath, R.; Sharma, H. R.

    2015-03-01

    The use of quasicrystals as precursors to catalysts for the steam reforming of methanol is potentially one of the most important applications of these new materials. To develop application as a technology requires a detailed understanding of the microscopic behavior of the catalyst. Here, we report the effect of leaching treatments on the surface microstructure, chemical composition, and valence band of the icosahedral (i-) Al-Cu-Fe quasicrystal in an attempt to prepare a model catalyst. The high symmetry fivefold surface of a single grain i-Al-Cu-Fe quasicrystal was leached with NaOH solution for varying times, and the resulting surface was characterized by x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The leaching treatments preferentially remove Al producing a capping layer consisting of Fe and Cu oxides. The subsurface layer contains elemental Fe and Cu in addition to the oxides. The quasicrystalline bulk structure beneath remains unchanged. The subsurface gradually becomes Fe3O4 rich with increasing leaching time. The surface after leaching exhibits micron sized dodecahedral cavities due to preferential leaching along the fivefold axis. Nanoparticles of the transition metals and their oxides are precipitated on the surface after leaching. The size of the nanoparticles is estimated by high resolution transmission microscopy to be 5-20 nm, which is in agreement with the AFM results. Selected area electron diffraction (SAED) confirms the crystalline nature of the nanoparticles. SAED further reveals the formation of an interface between the high atomic density lattice planes of nanoparticles and the quasicrystal. These results provide an important insight into the preparation of model catalysts of nanoparticles for steam reforming of methanol.

  6. Influence of leaching on surface composition, microstructure, and valence band of single grain icosahedral Al-Cu-Fe quasicrystal

    Energy Technology Data Exchange (ETDEWEB)

    Lowe, M.; McGrath, R.; Sharma, H. R. [Surface Science Research Centre and The Department of Physics, The University of Liverpool, Liverpool L69 3BX (United Kingdom); Yadav, T. P. [Hydrogen Energy Centre, Department of Physics, Banaras Hindu University, Varanasi 221005 (India); Fournée, V.; Ledieu, J. [Institut Jean Lamour (UMR7198 CNRS-Université de Lorraine), Parc de Saurupt, 54011 Nancy Cedex (France)

    2015-03-07

    The use of quasicrystals as precursors to catalysts for the steam reforming of methanol is potentially one of the most important applications of these new materials. To develop application as a technology requires a detailed understanding of the microscopic behavior of the catalyst. Here, we report the effect of leaching treatments on the surface microstructure, chemical composition, and valence band of the icosahedral (i-) Al-Cu-Fe quasicrystal in an attempt to prepare a model catalyst. The high symmetry fivefold surface of a single grain i-Al-Cu-Fe quasicrystal was leached with NaOH solution for varying times, and the resulting surface was characterized by x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The leaching treatments preferentially remove Al producing a capping layer consisting of Fe and Cu oxides. The subsurface layer contains elemental Fe and Cu in addition to the oxides. The quasicrystalline bulk structure beneath remains unchanged. The subsurface gradually becomes Fe{sub 3}O{sub 4} rich with increasing leaching time. The surface after leaching exhibits micron sized dodecahedral cavities due to preferential leaching along the fivefold axis. Nanoparticles of the transition metals and their oxides are precipitated on the surface after leaching. The size of the nanoparticles is estimated by high resolution transmission microscopy to be 5-20 nm, which is in agreement with the AFM results. Selected area electron diffraction (SAED) confirms the crystalline nature of the nanoparticles. SAED further reveals the formation of an interface between the high atomic density lattice planes of nanoparticles and the quasicrystal. These results provide an important insight into the preparation of model catalysts of nanoparticles for steam reforming of methanol.

  7. Can Thermal Bending Fracture Ice Shelves?

    Science.gov (United States)

    MacAyeal, D. R.; Sergienko, O. V.; Banwell, A. F.; Willis, I.; Macdonald, G. J.; Lin, J.

    2017-12-01

    Visco-elastic plates will bend if the temperature on one side is cooled. If the plate is constrained to float, as for sea ice floes, this bending will lead to tensile stresses that can fracture the ice. The hydroacoustic regime below sea ice displays increased fracture-sourced noise when air temperatures above the ice cools with the diurnal cycle. The McMurdo Ice Shelf, Antarctica, also displays a massive increase in seismicity during the cooling phase of the diurnal cycle, and this motivates the question: Can surface cooling (or other forcing with thermal consequences) drive through-thickness fracture leading to iceberg calving? Past study of this question for sea ice gives an upper limit of ice-plate thickness (order meters) for which diurnal-scale thermal bending fracture can occur; but could cooling with longer time scales induce fracture of thicker ice plates? Given the seismic evidence of thermal bending fracture on the McMurdo Ice Shelf, the authors examine this question further.

  8. Influence of the Electron-Electron Interaction in the Surface Valence Band on Low Energy Ion Scattering

    Science.gov (United States)

    Fomin, Vladimir M.; Devreese, Jozef T.

    1996-03-01

    The influence of the electron-electron interaction in the surface valence band on the low-energy ion scattering (LEIS) is investigated in the framework of the modified Muda---Newns approach. With this aim the Anderson-type electron-electron interaction term is taken into account in the Hamiltonian of the system and a resulting nonlinear set of equations of motion for the occupation number matrix is solved for various values of the effective electron-electron coupling constant U. It is demonstrated that for increasing U the steady-state value of the atomic level occupation number after the scattering increases. As a result, the ion survival probability is found, e. g., for the scattering of ^4He^+ ions from Cu to be a decreasing function of U. These results allow a consistent interpretation of the recent experimental data on low-energy He^+ ion scattering from metals. The work is supported by the C.E.C. Human Capital and Mobility Project "Quantification of Surface Analysis by Low Energy Ion Scattering". Also at the Technical University of Eindhoven, The Netherlands.

  9. Surface/Interface Carrier-Transport Modulation for Constructing Photon-Alternative Ultraviolet Detectors Based on Self-Bending-Assembled ZnO Nanowires.

    Science.gov (United States)

    Guo, Zhen; Zhou, Lianqun; Tang, Yuguo; Li, Lin; Zhang, Zhiqi; Yang, Hongbo; Ma, Hanbin; Nathan, Arokia; Zhao, Dongxu

    2017-09-13

    Surface/interface charge-carrier generation, diffusion, and recombination/transport modulation are especially important in the construction of photodetectors with high efficiency in the field of nanoscience. In the paper, a kind of ultraviolet (UV) detector is designed based on ZnO nanostructures considering photon-trapping, surface plasmonic resonance (SPR), piezophototronic effects, interface carrier-trapping/transport control, and collection. Through carefully optimized surface/interface carrier-transport modulation, a designed device with detectivity as high as 1.69 × 10 16 /1.71 × 10 16 cm·Hz 1/2 /W irradiating with 380 nm photons under ultralow bias of 0.2 V is realized by alternating nanoparticle/nanowire active layers, respectively, and the designed UV photodetectors show fast and slow recovery processes of 0.27 and 4.52 ms, respectively, which well-satisfy practical needs. Further, it is observed that UV photodetection could be performed within an alternative response by varying correlated key parameters, through efficient surface/interface carrier-transport modulation, spectrally resolved photoresponse of the detector revealing controlled detection in the UV region based on the ZnO nanomaterial, photodetection allowed or limited by varying the active layers, irradiation distance from one of the electrodes, standing states, or electric field. The detailed carrier generation, diffusion, and recombination/transport processes are well illustrated to explain charge-carrier dynamics contributing to the photoresponse behavior.

  10. BENDING BEHAVIOUR OF MAGNETIC COTTON YARNS

    Directory of Open Access Journals (Sweden)

    LUPU Iuliana G.

    2017-05-01

    Full Text Available Magnetic yarns are composite yarns, i.e. they combine elements of various natures and properties, with proven potential for electromagnetic interference (EMI shielding. In this paper, different mixtures of hard and soft magnetic powder were chosen to cover materials made of cotton yarn. The physical properties and bending behavior of the produced composite yarns were investigated in order to evaluate the yarns for further textile processing.The cotton yarn used as base material was covered with hard (barium hexaferrite BaFe12O19 and soft (Black Toner magnetic particles. An in-house developed laboratory equipment has been used to cover the twist cotton yarns with seven mixtures having different amounts of magnetic powder (30% – 50%. The bending behavior of the coated yarns was evaluated based on the average width of cracks which appeared on the yarn surface after repeated flexural tests. The obtained results revealed that usage of a polyurethane adhesive in the coating solution prevents crack formation on the surface of hard magnetic yarns after flexural tests. At the same time, the higher the mass percentage of hard magnetic powder in the mixture, the higher was the cracks’ width. The soft magnetic yarns are more flexible and a smaller crack width is observed on their surface. Both the coating solution composition and the powder diameter are expected to influence the bending behavior of coated yarns.

  11. Calculation and fitting of potential energy and dipole moment surfaces for the water molecule: Fully ab initio determination of vibrational transition energies and band intensities

    International Nuclear Information System (INIS)

    Kedziora, G.S.; Shavitt, I.

    1997-01-01

    Potential energy and dipole moment surfaces for the water molecule have been generated by multireference singles-and-doubles configuration interaction calculations using a large basis set of the averaged-atomic-natural-orbital type and a six-orbital-six-electron complete-active-space reference space. The surfaces are suitable for modeling vibrational transitions up to about 11000cm -1 above the ground state. A truncated singular-value decomposition method has been used to fit the surfaces. This fitting method is numerically stable and is a useful tool for examining the effectiveness of various fitting function forms in reproducing the calculated surface points and in extrapolating beyond these points. The fitted surfaces have been used for variational calculations of the 30 lowest band origins and the corresponding band intensities for transitions from the ground vibrational state. With a few exceptions, the results compare well with other calculations and with experimental data. copyright 1997 American Institute of Physics

  12. Ocean Surface Emissivity at L-band (1.4 GHz): The Dependence on Salinity and Roughness

    Science.gov (United States)

    Le Vine, D. M.; Lang, R. H.; Wentz, F. J.; Meissner, T.

    2012-12-01

    A characterization of the emissivity of sea water at L-band is important for the remote sensing of sea surface salinity. Measurements of salinity are currently being made in the radio astronomy band at 1.413 GHz by ESA's Soil Moisture and Ocean Salinity (SMOS) mission and NASA's Aquarius instrument aboard the Aquarius/SAC-D observatory. The goal of both missions is accuracy on the order of 0.2 psu. This requires accurate knowledge of the dielectric constant of sea water as a function of salinity and temperature and also the effect of waves (roughness). The former determines the emissivity of an ideal (i.e. flat) surface and the later is the major source of error from predictions based on a flat surface. These two aspects of the problem of characterizing the emissivity are being addressed in the context of the Aquarius mission. First, laboratory measurements are being made of the dielectric constant of sea water. This is being done at the George Washington University using a resonant cavity. In this technique, sea water of known salinity and temperature is fed into the cavity along its axis through a narrow tube. The sea water changes the resonant frequency and Q of the cavity which, if the sample is small enough, can be related to the dielectric constant of the sample. An extensive set of measurements have been conducted at 1.413 GHz to develop a model for the real and imaginary part of the dielectric constant as a function of salinity and temperature. The results are compared to the predictions of models based on parameterization of the Debye resonance of the water molecule. The models and measurements are close; however, the differences are significant for remote sensing of salinity. This is especially true at low temperatures where the sensitivity to salinity is lowest. Second, observations from Aquarius are being used to develop a model for the effect of wind-driven roughness (waves) on the emissivity in the open ocean. This is done by comparing the measured

  13. Monitoring Composites under Bending Tests with Infrared Thermography

    Directory of Open Access Journals (Sweden)

    Carosena Meola

    2012-01-01

    Full Text Available The attention of the present paper is focused on the use of an infrared imaging device to monitor the thermal response of composite materials under cyclic bending. Three types of composites are considered including an epoxy matrix reinforced with either carbon fibres (CFRP or glass fibres (GFRP and a hybrid composite involving glass fibres and aluminium layers (FRML. The specimen surface, under bending, displays temperature variations pursuing the load variations with cooling down under tension and warming up under compression; such temperature variations are in agreement with the bending moment. It has been observed that the amplitude of temperature variations over the specimen surface depends on the material characteristics. In particular, the presence of a defect inside the material affects the temperature distribution with deviation from the usual bending moment trend.

  14. Sheet Bending using Soft Tools

    Science.gov (United States)

    Sinke, J.

    2011-05-01

    Sheet bending is usually performed by air bending and V-die bending processes. Both processes apply rigid tools. These solid tools facilitate the generation of software for the numerical control of those processes. When the lower rigid die is replaced with a soft or rubber tool, the numerical control becomes much more difficult, since the soft tool deforms too. Compared to other bending processes the rubber backed bending process has some distinct advantages, like large radius-to-thickness ratios, applicability to materials with topcoats, well defined radii, and the feasibility of forming details (ridges, beads). These advantages may give the process exclusive benefits over conventional bending processes, not only for industries related to mechanical engineering and sheet metal forming, but also for other disciplines like Architecture and Industrial Design The largest disadvantage is that also the soft (rubber) tool deforms. Although the tool deformation is elastic and recovers after each process cycle, the applied force during bending is related to the deformation of the metal sheet and the deformation of the rubber. The deformation of the rubber interacts with the process but also with sheet parameters. This makes the numerical control of the process much more complicated. This paper presents a model for the bending of sheet materials using a rubber lower die. This model can be implemented in software in order to control the bending process numerically. The model itself is based on numerical and experimental research. In this research a number of variables related to the tooling and the material have been evaluated. The numerical part of the research was used to investigate the influence of the features of the soft lower tool, like the hardness and dimensions, and the influence of the sheet thickness, which also interacts with the soft tool deformation. The experimental research was focused on the relation between the machine control parameters and the most

  15. Localized bending fatigue behavior of high-strength steel monostrands

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2012-01-01

    In this paper, the localized bending fatigue behavior of pretensioned high strength steel monostrands is investigated. Furthermore, a new methodology using an optical photogrammetry system, which can quantify surface deformations on the strand is presented. The system allows measurement of the st...... displacement (opening/closing and sliding) of the helically wound wires. Moreover, the results are a step towards understanding the bending fatigue damage mechanisms of monostrand cables....

  16. Observation of an electron band above the Fermi level in FeTe0.55Se0.45 from in-situ surface doping

    International Nuclear Information System (INIS)

    Zhang, P.; Ma, J.; Qian, T.; Richard, P.; Ding, H.; Xu, N.; Xu, Y.-M.; Fedorov, A. V.; Denlinger, J. D.; Gu, G. D.

    2014-01-01

    We used in-situ potassium (K) evaporation to dope the surface of the iron-based superconductor FeTe 0.55 Se 0.45 . The systematic study of the bands near the Fermi level confirms that electrons are doped into the system, allowing us to tune the Fermi level of this material and to access otherwise unoccupied electronic states. In particular, we observe an electron band located above the Fermi level before doping that shares similarities with a small three-dimensional pocket observed in the cousin, heavily electron-doped KFe 2−x Se 2 compound.

  17. Maximizing band gaps in plate structures

    DEFF Research Database (Denmark)

    Halkjær, Søren; Sigmund, Ole; Jensen, Jakob Søndergaard

    2006-01-01

    Band gaps, i.e., frequency ranges in which waves cannot propagate, can be found in elastic structures for which there is a certain periodic modulation of the material properties or structure. In this paper, we maximize the band gap size for bending waves in a Mindlin plate. We analyze an infinite...

  18. Model-based surface soil moisture (SSM) retrieval algorithm using multi-temporal RISAT-1 C-band SAR data

    Science.gov (United States)

    Pandey, Dharmendra K.; Maity, Saroj; Bhattacharya, Bimal; Misra, Arundhati

    2016-05-01

    Accurate measurement of surface soil moisture of bare and vegetation covered soil over agricultural field and monitoring the changes in surface soil moisture is vital for estimation for managing and mitigating risk to agricultural crop, which requires information and knowledge to assess risk potential and implement risk reduction strategies and deliver essential responses. The empirical and semi-empirical model-based soil moisture inversion approach developed in the past are either sensor or region specific, vegetation type specific or have limited validity range, and have limited scope to explain physical scattering processes. Hence, there is need for more robust, physical polarimetric radar backscatter model-based retrieval methods, which are sensor and location independent and have wide range of validity over soil properties. In the present study, Integral Equation Model (IEM) and Vector Radiative Transfer (VRT) model were used to simulate averaged backscatter coefficients in various soil moisture (dry, moist and wet soil), soil roughness (smooth to very rough) and crop conditions (low to high vegetation water contents) over selected regions of Gujarat state of India and the results were compared with multi-temporal Radar Imaging Satellite-1 (RISAT-1) C-band Synthetic Aperture Radar (SAR) data in σ°HH and σ°HV polarizations, in sync with on field measured soil and crop conditions. High correlations were observed between RISAT-1 HH and HV with model simulated σ°HH & σ°HV based on field measured soil with the coefficient of determination R2 varying from 0.84 to 0.77 and RMSE varying from 0.94 dB to 2.1 dB for bare soil. Whereas in case of winter wheat crop, coefficient of determination R2 varying from 0.84 to 0.79 and RMSE varying from 0.87 dB to 1.34 dB, corresponding to with vegetation water content values up to 3.4 kg/m2. Artificial Neural Network (ANN) methods were adopted for model-based soil moisture inversion. The training datasets for the NNs were

  19. Forming and Bending of Metal Foams

    Science.gov (United States)

    Nebosky, Paul; Tyszka, Daniel; Niebur, Glen; Schmid, Steven

    2004-06-01

    This study examines the formability of a porous tantalum foam, known as trabecular metal (TM). Used as a bone ingrowth surface on orthopedic implants, TM is desirable due to its combination of high strength, low relative density, and excellent osteoconductive properties. This research aims to develop bend and stretch forming as a cost-effective alternative to net machining and EDM for manufacturing thin parts made of TM. Experimentally, bending about a single axis using a wiping die was studied by observing cracking and measuring springback. It was found that die radius and clearance strongly affect the springback properties of TM, while punch speed, embossings, die radius and clearance all influence cracking. Depending on the various combinations of die radius and clearance, springback factor ranged from .70-.91. To examine the affect of the foam microstructure, bending also was examined numerically using a horizontal hexagonal mesh. As the hexagonal cells were elongated along the sheet length, elastic springback decreased. This can be explained by the earlier onset of plastic hinging occurring at the vertices of the cells. While the numerical results matched the experimental results for the case of zero clearance, differences at higher clearances arose due to an imprecise characterization of the post-yield properties of tantalum. By changing the material properties of the struts, the models can be modified for use with other open-cell metallic foams.

  20. EFFECT OF CHANNEL BENDS ON TRANSVERSE MIXING

    African Journals Online (AJOL)

    user

    2017-06-05

    Jun 5, 2017 ... dy, where d is the flow depth, was found to vary laterally in all cross-sections. As the spiral motion due to the second bend develops it displaces the residual spiral motion from the first bend towards the outer bend causing it to decay completely around the middle of this bend. Transverse Tracer Distribution.

  1. Inferring Land Surface Model Parameters for the Assimilation of Satellite-Based L-Band Brightness Temperature Observations into a Soil Moisture Analysis System

    Science.gov (United States)

    Reichle, Rolf H.; De Lannoy, Gabrielle J. M.

    2012-01-01

    The Soil Moisture and Ocean Salinity (SMOS) satellite mission provides global measurements of L-band brightness temperatures at horizontal and vertical polarization and a variety of incidence angles that are sensitive to moisture and temperature conditions in the top few centimeters of the soil. These L-band observations can therefore be assimilated into a land surface model to obtain surface and root zone soil moisture estimates. As part of the observation operator, such an assimilation system requires a radiative transfer model (RTM) that converts geophysical fields (including soil moisture and soil temperature) into modeled L-band brightness temperatures. At the global scale, the RTM parameters and the climatological soil moisture conditions are still poorly known. Using look-up tables from the literature to estimate the RTM parameters usually results in modeled L-band brightness temperatures that are strongly biased against the SMOS observations, with biases varying regionally and seasonally. Such biases must be addressed within the land data assimilation system. In this presentation, the estimation of the RTM parameters is discussed for the NASA GEOS-5 land data assimilation system, which is based on the ensemble Kalman filter (EnKF) and the Catchment land surface model. In the GEOS-5 land data assimilation system, soil moisture and brightness temperature biases are addressed in three stages. First, the global soil properties and soil hydraulic parameters that are used in the Catchment model were revised to minimize the bias in the modeled soil moisture, as verified against available in situ soil moisture measurements. Second, key parameters of the "tau-omega" RTM were calibrated prior to data assimilation using an objective function that minimizes the climatological differences between the modeled L-band brightness temperatures and the corresponding SMOS observations. Calibrated parameters include soil roughness parameters, vegetation structure parameters

  2. Secondary turbulent flow in an infinte bend

    DEFF Research Database (Denmark)

    Christensen, H. Bo; Gislason, Kjartan; Fredsøe, Jørgen

    1999-01-01

    The flow in an infinite circular bend is inverstigated in both the laminar and fully turbulent flow case, by use of laminar flow solver, a k-e turbulence model, and a fully Reynolds stress turbulence model. The topic of the analysis is to investigate whether a counter-rotating secondary flow cell...... is formed near the surface at the outer bank. This cell might help to stabilise the bank and hereby be an important factor for the morphology in a meandering river. In the laminar runs stability criterion related to a Dean number was estabilshed. In the simulations with the k-e model and the Reynolds stress...

  3. Bending characteristics of resin concretes

    Directory of Open Access Journals (Sweden)

    Ribeiro Maria Cristina Santos

    2003-01-01

    Full Text Available In this research work the influence of composition and curing conditions in bending strength of polyester and epoxy concrete is analyzed. Various mixtures of resin and aggregates were considered in view of an optimal combination. The Taguchi methodology was applied in order to reduce the number of tests, and in order to evaluate the influence of various parameters in concrete properties. This methodology is very useful for the planning of experiments. Test results, analyzed by this methodology, shown that the most significant factors affecting bending strength properties of resin concretes are the type of resin, resin content and charge content. An optimal formulation leading to a maximum bending strength was achieved in terms of material parameters.

  4. A field experiment on microwave forest radiometry: L-band signal behaviour for varying conditions of surface wetness

    DEFF Research Database (Denmark)

    Grant, J. P.; Wigneron, J. P.; Van de Grind, A. A.

    2007-01-01

    France, using a multi-angle L-band (1.4 GHz) radiometer to measure from above the forest at horizontal polarization. At the same time, ground measurements were taken of soil and litter moisture content, while precipitation was also permanently monitored. This experiment was done in the context...... of the upcoming SMOS mission in order to improve our understanding of the behaviour of the L-band signal from forested areas for different wetness conditions and viewing angles. This is especially relevant for solving the problem of heterogeneity since a large fraction of SMOS pixels (~30x30 km²) is partially...... covered by forest. This paper describes the objectives and the overall set-up of the Bray-2004 experiment and shows some first results. The greater part of the horizontally polarized L-band signal is found to be dominated by the influence of physical temperature. Variations in soil and/or litter moisture...

  5. Isomer-Specific IR Spectroscopy of BENZENE-(WATER)N Clusters with N=1-8: New Insights from the Water Bend Fundamentals and Isotopically Substituted Clusters

    Science.gov (United States)

    Kusaka, Ryoji; Walsh, Patrick S.; Zwier, Timothy S.

    2014-06-01

    This talk will focus on the isomer-specific IR spectra of benzene-(water)n (BWn) clusters with n = 1-8, returning to a topic studied by our group some 20 years ago, but now with higher resolution (OH stretch region), with inclusion of data from isotopically substituted clusters, and with extension into the HOH bending mode region. Spectra are recorded using resonant ion-dip infrared spectroscopy, an IR-UV double resonance method. Isomer-specific IR spectra in the regions of OH, OD stretches and HOH, HOD bend of benzene-H_2O, -D_2O, -HOD, -(H_2O)_2, -(D_2O)_2, -HOD-DOD were recorded in order to investigate in greater detail the intermolecular potential energy surface between water and benzene. These spectra show strong combination bands in addition to the OH/OD stretch fundamentals arising from large-amplitude "tumbling" and tunneling along internal rotation and torsion coordinates of water(s) on the surface of benzene. Interestingly, the number of extra bands and spectral patterns change dramatically depending on cluster size, the kind of deuterated isomer, and the spectral region probed. In larger clusters with n=3-8, the water HOH bending region is explored for the first time. The prominent bending mode transitions in BW1-8 are spread over a relatively small range (1610-1660 wn), and shift with cluster size in a way that reflects the known structural changes that accompany the increase in size. By comparison of experiment with calculation, it is possible to assign the experimentally observed 1614 wn transition of BW1 and 1615 wn of BW2 bands to the π-bound water molecule. The 1620-1660 wn bands of BW3-8 are due to water molecules that can be categorized as single-acceptor, single-donor (AD) hydrogen-bonded waters. In the case of single-acceptor, double-donor (ADD) water molecules, which are expected to be seen from BW6,a they show higher-frequency bending vibrations and weaker IR intensity, which would correspond to very weakly observed bands in 1660-1750 wn for

  6. Fracture mechanics analysis for a mooring system subjected to tension and out-of-plane bending

    Science.gov (United States)

    Xue, X.; Chen, N.-Z.

    2017-12-01

    A fracture mechanics analysis for the mooring system of a semi-submersible accounting for out-of-plane bending (OPB) is presented in this paper. Stress ranges acting on the mooring chain links are calculated based on tension and OPB of mooring chain links induced by motions of wave frequency (WF) and low frequency (LF). The narrow-banded method is used for predicting the combined mooring loading process. Initial cracks are assumed to propagate from surfaces of chain links and stress intensity factors are then calculated in terms of stress ranges determined by a finite element analysis. The influence of the OPB on the remaining service life of mooring chain links is investigated and the results show that the remaining service life of mooring chain links connecting to fairleads is significantly reduced due to the OPB effects.

  7. Effect of band alignment on photoluminescence and carrier escape from InP surface quantum dots grown by metalorganic chemical vapor deposition on Si

    Energy Technology Data Exchange (ETDEWEB)

    Halder, Nripendra N. [Advanced Technology Development Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Biswas, Pranab; Banerji, P., E-mail: pallab@matsc.iitkgp.ernet.in [Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302 (India); Dhabal Das, Tushar; Das, Sanat Kr.; Chattopadhyay, S. [Department of Electronic Science, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Biswas, D. [Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721 302 (India)

    2014-01-28

    A detailed analysis of photoluminescence (PL) from InP quantum dots (QDs) grown on Si has been carried out to understand the effect of substrate/host material in the luminescence and carrier escape process from the surface quantum dots. Such studies are required for the development of monolithically integrated next generation III-V QD based optoelectronics with fully developed Si microelectronics. The samples were grown by atmospheric pressure metalorganic chemical vapor deposition technique, and the PL measurements were made in the temperature range 10–80 K. The distribution of the dot diameter as well as the dot height has been investigated from atomic force microscopy. The origin of the photoluminescence has been explained theoretically. The band alignment of InP/Si heterostructure has been determined, and it is found be type II in nature. The positions of the conduction band minimum of Si and the 1st excited state in the conduction band of InP QDs have been estimated to understand the carrier escape phenomenon. A blue shift with a temperature co-efficient of 0.19 meV/K of the PL emission peak has been found as a result of competitive effect of different physical processes like quantum confinement, strain, and surface states. The corresponding effect of blue shift by quantum confinement and strain as well as the red shift by the surface states in the PL peaks has been studied. The origin of the luminescence in this heterojunction is found to be due to the recombination of free excitons, bound excitons, and a transition from the 1st electron excited state in the conduction band (e{sub 1}) to the heavy hole band (hh{sub 1}). Monotonic decrease in the PL intensity due to increase of thermally escaped carriers with temperature has been observed. The change in barrier height by the photogenerated electric-field enhanced the capture of the carriers by the surface states rather than their accumulation in the QD excited state. From an analysis of the dependence of

  8. CdS and Cd-Free Buffer Layers on Solution Phase Grown Cu2ZnSn(SxSe1- x)4 :Band Alignments and Electronic Structure Determined with Femtosecond Ultraviolet Photoemission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Richard; Barkhouse, Aaron; Wang, Wei; Yu, Luo; Shao, Xiaoyan; Mitzi, David; Hiroi, Homare; Sugimoto, Hiroki

    2013-12-02

    The heterojunctions formed between solution phase grown Cu2ZnSn(SxSe1- x)4(CZTS,Se) and a number of important buffer materials including CdS, ZnS, ZnO, and In2S3, were studied using femtosecond ultraviolet photoemission spectroscopy (fs-UPS) and photovoltage spectroscopy. With this approach we extract the magnitude and direction of the CZTS,Se band bending, locate the Fermi level within the band gaps of absorber and buffer and measure the absorber/buffer band offsets under flatband conditions. We will also discuss two-color pump/probe experiments in which the band bending in the buffer layer can be independently determined. Finally, studies of the bare CZTS,Se surface will be discussed including our observation of mid-gap Fermi level pinning and its relation to Voc limitations and bulk defects.

  9. Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

    Science.gov (United States)

    Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem

    2012-01-01

    Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

  10. Characterization of the Fermi surface of BEDT-TTF4[Hg2Cl6].PhCl by electronic band structure calculations

    International Nuclear Information System (INIS)

    Veiros, L.F.; Canadell, E.

    1994-01-01

    Tight-binding band structure calculations for the room temperature structure of BEDT-TTF 4 [Hg 2 Cl 6 ]-PhCl show the existence of closed electron and hole Fermi surfaces, in agreement with the 2D metallic conductivity of this salt. It is shown that these closed Fermi surfaces result from the hybridization of two hidden 1D Fermi surfaces. However, our study also shows that a transition associated with either a usual or a hidden nesting type mechanism is unlikely. This explains why this salt retains its metallic properties without any resistivity anomaly down to 1.3 K. Our study suggests that BEDT-TTF 4 [Hg 2 Cl 6 ]-PhCl is somewhat anisotropic 2D semimetal and should exhibit Shubnikov-de Haas oscillations corresponding to a cross-sectional area of approximately 13% of the first Brillouin zone. (orig.)

  11. Existence, character, and origin of surface-related bands in the high temperature iron pnictide superconductor BaFe(2-x)Co(x)As2.

    Science.gov (United States)

    van Heumen, Erik; Vuorinen, Johannes; Koepernik, Klaus; Massee, Freek; Huang, Yingkai; Shi, Ming; Klei, Jesse; Goedkoop, Jeroen; Lindroos, Matti; van den Brink, Jeroen; Golden, Mark S

    2011-01-14

    Low energy electron diffraction (LEED) experiments, LEED simulations, and finite slab density functional calculations are combined to study the cleavage surface of Co doped BaFe(2-x)Co(x)As2 (x = 0.1,0.17). We demonstrate that the energy dependence of the LEED data can only be understood from a terminating 1/2 Ba layer accompanied by distortions of the underlying As-Fe2-As block. As a result, surface-related Fe 3d states are present in the electronic structure, which we identify in angle resolved photoemission spectroscopy (ARPES) experiments. The close proximity of the surface-related states to the bulk bands inevitably leads to broadening of the ARPES signals, which excludes the use of the BaFe(2-x)Co(x)As2 system for accurate determination of self-energies using ARPES.

  12. Bending loss of terahertz pipe waveguides.

    Science.gov (United States)

    Lu, Jen-Tang; Hsueh, Yu-Chun; Huang, Yu-Ru; Hwang, Yuh-Jing; Sun, Chi-Kuang

    2010-12-06

    We present an experimental study on the bending loss of terahertz (THz) pipe waveguide. Bending loss of pipe waveguides is investigated for various frequencies, polarizations, core diameters, cladding thicknesses, and cladding materials. Our results indicate that the pipe waveguides with lower guiding loss suffer lower bending loss due to stronger mode confinement. The unexpected low bending loss in the investigated simple leaky waveguide structure promises variety of flexible applications.

  13. Nodular cast iron fatigue lifetime in cyclic plane bending

    Directory of Open Access Journals (Sweden)

    Marian Kokavec

    2012-05-01

    Full Text Available The fatigue behavior of a component is strongly dependent on the material and its surface condition. Therefore, the manner in which the surface is prepared during component manufacturing (surface roughness, residual stresses etc. has a decisive role in dictating the initiation time for fatigue cracks. The fatigue behavior of the same material, a nodular cast iron, with three different surface conditions (fine ground, sand blast and as-cast has been investigated under cyclic plane bending. The results show differences in fatigue strength, which are associated with the surface conditions. The characteristics of the surface layers of the different test specimens were examined by metallography.

  14. Sediment transport in an active erodible channel bend of ...

    Indian Academy of Sciences (India)

    and sediment transport modelling in a curved channel (Chang 1988). ... spiral motion of the flow directed normal to the main flow and the super-elevation of the water surface. The secondary current, which develops upon entering a channel bend, will eventually ... from flume studies and calibrated using the river data.

  15. Soil hydraulic parameters and surface soil moisture of a tilled bare soil plot inversely derived from l-band brightness temperatures

    KAUST Repository

    Dimitrov, Marin

    2014-01-01

    We coupled a radiative transfer model and a soil hydrologic model (HYDRUS 1D) with an optimization routine to derive soil hydraulic parameters, surface roughness, and soil moisture of a tilled bare soil plot using measured brightness temperatures at 1.4 GHz (L-band), rainfall, and potential soil evaporation. The robustness of the approach was evaluated using five 28-d data sets representing different meteorological conditions. We considered two soil hydraulic property models: the unimodal Mualem-van Genuchten and the bimodal model of Durner. Microwave radiative transfer was modeled by three different approaches: the Fresnel equation with depth-averaged dielectric permittivity of either 2-or 5-cm-thick surface layers and a coherent radiative transfer model (CRTM) that accounts for vertical gradients in dielectric permittivity. Brightness temperatures simulated by the CRTM and the 2-cm-layer Fresnel model fitted well to the measured ones. L-band brightness temperatures are therefore related to the dielectric permittivity and soil moisture in a 2-cm-thick surface layer. The surface roughness parameter that was derived from brightness temperatures using inverse modeling was similar to direct estimates from laser profiler measurements. The laboratory-derived water retention curve was bimodal and could be retrieved consistently for the different periods from brightness temperatures using inverse modeling. A unimodal soil hydraulic property function underestimated the hydraulic conductivity near saturation. Surface soil moisture contents simulated using retrieved soil hydraulic parameters were compared with in situ measurements. Depth-specific calibration relations were essential to derive soil moisture from near-surface installed sensors. © Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA.

  16. Analysis of Bending Waves in Phononic Crystal Beams with Defects

    Directory of Open Access Journals (Sweden)

    Yongqiang Guo

    2018-01-01

    Full Text Available Existing investigations on imperfect phononic crystal beams mainly concern periodic multi-span beams carrying either one or two channel waves with random or deterministic disorder in span-length. This paper studies the two channel bending waves in phononic crystal beams consisting of many phases of materials with defects introduced as one structural segment having different cross-sectional dimensions or material parameters. The method of reverberation-ray matrix (MRRM based on the Timoshenko beam theory, which can conduct high-frequency analysis, is extended for the theoretical analysis of dispersion and transmission of bending waves. The supercell technique and the Floquet–Bloch theorem are adopted for modeling the dispersion characteristics, and the whole finite structural model is used to calculate the transmission spectra. Experimental measurements and numerical calculations are provided to validate the displacement transmission obtained by the proposed MRRM, with the effect of damping on transmission spectra being concerned. The high-frequency calculation applicability of the proposed MRRM is also confirmed by comparing the present results with the corresponding ones either using the transfer matrix method (TMM or MRRM based on Euler—Bernoulli beam theory. The influences of defect size, defect form, and unit-cell number on the transmission spectra and the band structures are discussed. The drawn conclusions may be useful for designing or evaluating the defected phononic crystal beams in bending wave control. In addition, our conclusions are especially potential for identifying the defect location through bending wave signals.

  17. MIT miniaturized disk bend test

    International Nuclear Information System (INIS)

    Harling, O.K.; Lee, M.; Sohn, D.S.; Kohse, G.; Lau, C.W.

    1983-01-01

    A miniaturized disk bend test (MDBT) using transmission electron microscopy specimens for the determination of various mechanical properties is being developed at MIT. Recent progress in obtaining strengths and ductilities of highly irradiated metal alloys is reviewed. Other mechanical properties can also be obtained using the MDBT approach. Progress in fatigue testing and in determination of the ductile-to-brittle transition temperature is reviewed briefly. 11 figures

  18. Monitoring static shape memory polymers using a fiber Bragg grating as a vector-bending sensor

    Science.gov (United States)

    Li, Peng; Yan, Zhijun; Zhou, Kaiming; Zhang, Lin; Leng, Jinsong

    2013-01-01

    We propose and demonstrate a technique for monitoring the recovery deformation of the shape-memory polymers (SMP) using a surface-attached fiber Bragg grating (FBG) as a vector-bending sensor. The proposed sensing scheme could monitor the pure bending deformation for the SMP sample. When the SMP sample undergoes concave or convex bending, the resonance wavelength of the FBG will have red-shift or blue-shift according to the tensile or compressive stress gradient along the FBG. As the results show, the bending sensitivity is around 4.07 nm/cm-1. The experimental results clearly indicate that the deformation of such an SMP sample can be effectively monitored by the attached FBG not just for the bending curvature but also the bending direction.

  19. Finite element analysis of bending performance on polyurethane composite panel

    Science.gov (United States)

    Jia, Minli; Li, Hongqiao; Wang, Xiaoming

    2017-09-01

    The finite element analysis model of polyurethane composite panel (simply named PCP) is established by using ABAQUS software. In view of the PCPs made of different thickness of surface board, their bending performance is carried out on finite element analysis, and the load-deflection curves which come from it are compared with the experimental results. The results show that the values between finite element analysis and experiment agree well with each other. It can be deduced that the established finite element model is fit to simulate the bending test of PCPs. The simulation not only has certain reference significance to the optimal design for the bending performance of PCPs, but also to the choice of PCPs in the practical project.

  20. C-Band Airport Surface Communications System Standards Development. Phase II Final Report. Volume 2: Test Bed Performance Evaluation and Final AeroMACS Recommendations

    Science.gov (United States)

    Hall, Edward; Magner, James

    2011-01-01

    This report is provided as part of ITT s NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: New ATM Requirements-Future Communications, C-Band and L-Band Communications Standard Development and was based on direction provided by FAA project-level agreements for New ATM Requirements-Future Communications. Task 7 included two subtasks. Subtask 7-1 addressed C-band (5091- to 5150-MHz) airport surface data communications standards development, systems engineering, test bed and prototype development, and tests and demonstrations to establish operational capability for the Aeronautical Mobile Airport Communications System (AeroMACS). Subtask 7-2 focused on systems engineering and development support of the L-band digital aeronautical communications system (L-DACS). Subtask 7-1 consisted of two phases. Phase I included development of AeroMACS concepts of use, requirements, architecture, and initial high-level safety risk assessment. Phase II builds on Phase I results and is presented in two volumes. Volume I is devoted to concepts of use, system requirements, and architecture, including AeroMACS design considerations. Volume II (this document) describes an AeroMACS prototype evaluation and presents final AeroMACS recommendations. This report also describes airport categorization and channelization methodologies. The purposes of the airport categorization task were (1) to facilitate initial AeroMACS architecture designs and enable budgetary projections by creating a set of airport categories based on common airport characteristics and design objectives, and (2) to offer high-level guidance to potential AeroMACS technology and policy development sponsors and service providers. A channelization plan methodology was developed because a common global methodology is needed to assure seamless interoperability among diverse AeroMACS services potentially supplied by multiple service providers.

  1. C-Band Airport Surface Communications System Standards Development. Phase II Final Report. Volume 1: Concepts of Use, Initial System Requirements, Architecture, and AeroMACS Design Considerations

    Science.gov (United States)

    Hall, Edward; Isaacs, James; Henriksen, Steve; Zelkin, Natalie

    2011-01-01

    This report is provided as part of ITT s NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: New ATM Requirements-Future Communications, C-Band and L-Band Communications Standard Development and was based on direction provided by FAA project-level agreements for New ATM Requirements-Future Communications. Task 7 included two subtasks. Subtask 7-1 addressed C-band (5091- to 5150-MHz) airport surface data communications standards development, systems engineering, test bed and prototype development, and tests and demonstrations to establish operational capability for the Aeronautical Mobile Airport Communications System (AeroMACS). Subtask 7-2 focused on systems engineering and development support of the L-band digital aeronautical communications system (L-DACS). Subtask 7-1 consisted of two phases. Phase I included development of AeroMACS concepts of use, requirements, architecture, and initial high-level safety risk assessment. Phase II builds on Phase I results and is presented in two volumes. Volume I (this document) is devoted to concepts of use, system requirements, and architecture, including AeroMACS design considerations. Volume II describes an AeroMACS prototype evaluation and presents final AeroMACS recommendations. This report also describes airport categorization and channelization methodologies. The purposes of the airport categorization task were (1) to facilitate initial AeroMACS architecture designs and enable budgetary projections by creating a set of airport categories based on common airport characteristics and design objectives, and (2) to offer high-level guidance to potential AeroMACS technology and policy development sponsors and service providers. A channelization plan methodology was developed because a common global methodology is needed to assure seamless interoperability among diverse AeroMACS services potentially supplied by multiple service providers.

  2. Multichannel surface clutter suppression: East Antarctica P-band SAR ice sounding in the presence of grating lobes

    DEFF Research Database (Denmark)

    Bekaert, David; Gebert, Nicolas; Lin, Chung-Chi

    2014-01-01

    Ice sounding with radar is a well-established technique for the retrieval of ice depth, and provides information on ice structures and layering. Airborne radar ice sounders suffer from off-nadir surface clutter that masks the signal from bedrock and ice layers with unwanted but simultaneously...... received surface reflections. This is of importance for future satellite ice-sounding missions, as the spaceborne geometry leads to strong surface clutter even for deep subsurface returns. This paper presents analysis and comparison of different clutter-suppression techniques applied to data acquired...... of the receive channels were used to suppress the surface 'clutter'. However, with a channel spacing of 1.4 times the wavelength, the grating lobe imposes a limitation to the off-nadir angular range in which clutter can be effectively attenuated. Results of ice sounding over Jutulstraumen glacier are described...

  3. X-Band high range resolution radar measurements of sea surface forward scatter at low grazing angles

    CSIR Research Space (South Africa)

    Smit, JC

    2008-05-01

    Full Text Available Radar measurements of a radar calibration sphere test target suspended in sea surface multipath propagation conditions are reported. Wideband measurements together with high range resolution (HRR) processing were employed to resolve the direct...

  4. Surface sensing behavior and band edge properties of AgAlS2: Experimental observations in optical, chemical, and thermoreflectance spectroscopy

    Directory of Open Access Journals (Sweden)

    Ching-Hwa Ho

    2012-06-01

    Full Text Available Optical examination of a chaocogenide compound AgAlS2 which can spontaneously transfer to a AgAlO2 oxide has been investigated by thermoreflectance (TR spectroscopy herein. The single crystals of AgAlS2 were grown by chemical vapor transport (CVT method using ICl3 as a transport agent sealed in evacuated quartz tubes. The as-grown AgAlS2 crystals essentially possess a transparent and white color in vacuum. The crystal surface of AgAlS2 becomes darkened and brownish when putting AgAlS2 into atmosphere for reacting with water vapor or hydrogen gas. Undergoing the chemical reaction process, oxygen deficient AgAlO2-2x with brownish and reddish-like color on surface of AgAlS2 forms. The transition energy of deficient AgAlO2-2x was evaluated by TR experiment. The value was determined to be ∼2.452 eV at 300 K. If the sample is kept dry and moved away from moisture, AgAlS2 crystal can stop forming more deficient AgAlO2-2x surface oxides. The experimental TR spectra for the surface-reacted sample show clearly two transition features at EW=2.452 eV for deficient AgAlO2-2x and EU=3.186 eV for AgAlS2, respectively. The EU transition belongs to direct band-edge exciton of AgAlS2. Alternatively, for surface-oxidation process of AgAlS2 lasting for a long time, a AgAlO2 crystal with yellowish color will eventually form. The TR measurements show mainly a ground-state band edge exciton of E OX 1 detected for AgAlO2. The energy was determined to be E OX 1=2.792 eV at 300 K. The valence-band electronic structure of AgAlS2 has been detailed characterized using polarized-thermoreflectance (PTR measurements in the temperature range between 30 and 340 K. Physical chemistry behaviors of AgAlS2 and AgAlO2 have been comprehensively studied via detailed analyses of PTR and TR spectra. Based on the experimental analyses, optical and chemical behaviors of the AgAlS2 crystals under atmosphere are realized. A possible optical-detecting scheme for using AgAlS2 as a humidity

  5. Band selection and disentanglement using maximally localized Wannier functions: the cases of Co impurities in bulk copper and the Cu(111) surface

    Energy Technology Data Exchange (ETDEWEB)

    Korytar, Richard; Pruneda, Miguel; Ordejon, Pablo; Lorente, Nicolas [Centre d' Investigacio en Nanociencia i Nanotecnologia (CSIC-ICN), Campus de la UAB, E-08193 Bellaterra (Spain); Junquera, Javier, E-mail: rkorytar@cin2.e [Departamento de Ciencias de la Tierra y Fisica de la Materia Condensada, Universidad de Cantabria, E-39005 Santander (Spain)

    2010-09-29

    We have adapted the maximally localized Wannier function approach of Souza et al (2002 Phys. Rev. B 65 035109) to the density functional theory based SIESTA code (Soler et al 2002 J. Phys.: Condens. Mater. 14 2745) and applied it to the study of Co substitutional impurities in bulk copper as well as to the Cu(111) surface. In the Co impurity case, we have reduced the problem to the Co d-electrons and the Cu sp-band, permitting us to obtain an Anderson-like Hamiltonian from well defined density functional parameters in a fully orthonormal basis set. In order to test the quality of the Wannier approach to surfaces, we have studied the electronic structure of the Cu(111) surface by again transforming the density functional problem into the Wannier representation. An excellent description of the Shockley surface state is attained, permitting us to be confident in the application of this method to future studies of magnetic adsorbates in the presence of an extended surface state.

  6. Design and characterization of a low cost CubeSat multi-band optical receiver to map water ice on the lunar surface for the Lunar Flashlight mission

    Science.gov (United States)

    Vinckier, Quentin; Crabtree, Karlton; Paine, Christopher G.; Hayne, Paul O.; Sellar, Glenn R.

    2017-08-01

    Lunar Flashlight is an innovative NASA CubeSat mission dedicated to mapping water ice in the permanently shadowed regions of the Moon, which may act as cold traps for volatiles. To this end, a multi-band reflectometer will be sent to orbit the Moon. This instrument consists of an optical receiver aligned with four lasers, each of which emits sequentially at a different wavelength in the near-infrared between 1 μm and 2 μm. The receiver measures the laser light reflected from the lunar surface; continuum/absorption band ratios are then analyzed to quantify water ice in the illuminated spot. Here, we present the current state of the optical receiver design. To optimize the optical signal-to-noise ratio, we have designed the receiver so as to maximize the laser signal collected, while minimizing the stray light reaching the detector from solarilluminated areas of the lunar surface outside the field-of-view, taking into account the complex lunar topography. Characterization plans are also discussed. This highly mass- and volume-constrained mission will demonstrate several firsts, including being one of the first CubeSats performing science measurements beyond low Earth orbit.

  7. Bending and stretching of plates

    CERN Document Server

    Mansfield, E H; Hemp, W S

    1964-01-01

    The Bending and Stretching of Plates deals with elastic plate theory, particularly on small- and large-deflexion theory. Small-deflexion theory concerns derivation of basic equations, rectangular plates, plates of various shapes, plates whose boundaries are amenable to conformal transformation, plates with variable rigidity, and approximate methods. Large-deflexion theory includes general equations and some exact solutions, approximate methods in large-deflexion theory, asymptotic large-deflexion theories for very thin plates. Asymptotic theories covers membrane theory, tension field theory, a

  8. Theoretical investigation of the band alignment of graphene on a polar SrTi O3 (111) surface

    Science.gov (United States)

    Shin, Donghan; Demkov, Alexander A.

    2018-02-01

    Doping graphene layers presents a difficult practical and fundamental problem. We consider theoretically, the possibility of electrostatic doping of graphene by the intrinsic field of a polar substrate. By way of example, we perform density functional theory calculations for a graphene sheet placed on the (111)-oriented perovskite SrTi O3 surface. We find that the Fermi surface moves well below the Dirac point of graphene, resulting simultaneously in a fast conducting channel in graphene, and a slow (large-effective-mass) channel at the oxide surface. Additionally, electrostatic gating may open a way to explore peculiar states that, through the "no crossing," represent a hybrid carrier that exists simultaneously in both materials.

  9. Garment-Integrated Bend Sensor

    Directory of Open Access Journals (Sweden)

    Guido Gioberto

    2014-09-01

    Full Text Available Garment-integrated sensors equip clothes with a smart sensing capability, while preserving the comfort of the user. However, this benefit can be to the detriment of sensing accuracy due to the unpredictability of garment movement (which affects sensor positioning and textile folds (which can affect sensor orientation. However, sensors integrated directly into garments or fabric structures can also be used to detect the movement of the garment during wearing. Specifically, a textile bend sensor could be used to sense folds in the garment. We tested a garment-integrated stitched sensor for five types of folds, stitched on five different weights of un-stretchable denim fabric and analyzed the effects of fold complexity and fabric stiffness, under un-insulated and insulated conditions. Results show that insulation improves the linearity and repeatability of the sensor response, particularly for higher fold complexity. Stiffer fabrics show greater sensitivity, but less linearity. Sensor response amplitude is larger for more complex fold geometries. The utility of a linear bending response (insulated and a binary shorting response (un-insulated is discussed. Overall, the sensor exhibits excellent repeatability and accuracy, particularly for a fiber-based, textile-integrated sensor.

  10. Simulation and Analysis for Wide-band Scattering Characteristics of 2-D Linear and Nonlinear Sea Surfaces

    Directory of Open Access Journals (Sweden)

    Wang Jia-ning

    2015-06-01

    Full Text Available In this paper, the wideband backscattering fields of two-Dimensional (2-D linear and nonlinear sea surfaces are numerically simulated employing the Weighted Curvature Approximation (WCA method. A large number of Monte Carlo trials are performed to investigate the statistical characteristics of the rang-resolved sea clutter, especially for the sea spike phenomenon. Simulation results demonstrate that the long tail of the sea clutter intensity Probability Density Function (PDF tends to be more evident with finer radar resolution, higher wind speed, and when the radar sight changes from the crosswind direction to the upwind direction. Meanwhile, it is found that the nonlinear sea surfaces are more likely to have sea spikes. In addition, the Pareto distribution is demonstrated to describe the statistics of the sea clutter intensities better than the Kdistribution and Weibull distribution at low grazing angles.

  11. Electronic transitions and band offsets in C60:SubPc and C60:MgPc on MoO3 studied by modulated surface photovoltage spectroscopy

    International Nuclear Information System (INIS)

    Fengler, S.; Dittrich, Th.; Rusu, M.

    2015-01-01

    Electronic transitions at interfaces between MoO 3 layers and organic layers of C 60 , SubPc, MgPc, and nano-composite layers of SubPc:C 60 and MgPc:C 60 have been studied by modulated surface photovoltage (SPV) spectroscopy. For all systems, time dependent and modulated SPV signals pointed to dissociation of excitons at the MoO 3 /organic layer interfaces with a separation of holes towards MoO 3 . The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gaps (E HL ) of C 60 , SubPc, and MgPc and the effective E HL of SubPc:C 60 and MgPc:C 60 were measured. The offsets between the LUMO (ΔE L ) or HOMO (ΔE H ) bands were obtained with high precision and amounted to 0.33 or 0.73 eV for SubPc:C 60 , respectively, and to −0.33 or 0.67 eV for MgPc:C 60 , respectively. Exponential tails below E HL and most pronounced sub-bandgap transitions were characterized and ascribed to disorder and transitions from HOMO bands to unoccupied defect states

  12. Retrieving aerosol height from the oxygen A band: a fast forward operator and sensitivity study concerning spectral resolution, instrumental noise, and surface inhomogeneity

    Science.gov (United States)

    Hollstein, A.; Fischer, J.

    2014-05-01

    Hyperspectral radiance measurements in the oxygen A band are sensitive to the vertical distribution of atmospheric scatterers, which in principle allows the retrieval of aerosol height from future instruments like TROPOMI, OCO2, FLEX, and CarbonSat. Discussed in this paper is a fast and flexible forward operator for the simulation of hyperspectral radiances in the oxygen A band and, based on this scheme, a sensitivity study about the inversion quality of aerosol optical thickness, aerosol mean height, and aerosol type. The forward operator is based on a lookup table with efficient data compression based on principal component analysis. Linear interpolation and computation of partial derivatives is performed in the much smaller space of expansion coefficients rather than wavelength. Thus, this approach is computationally fast and, at the same time, memory efficient. The sensitivity study explores the impact of instrument design on the retrieval of aerosol optical thickness and aerosol height. Considered are signal to noise ratio, spectral resolution, and spectral sampling. Also taken into account are surface inhomogeneities and variations of the aerosol type.

  13. Two-phase jet impingement cooling for high heat flux wide band-gap devices using multi-scale porous surfaces

    International Nuclear Information System (INIS)

    Joshi, Shailesh N.; Dede, Ercan M.

    2017-01-01

    Highlights: • Jet impingement with phase change on multi-scale porous surfaces is investigated. • Porous coated flat, pin-fin, open tunnel, and closed tunnel structures are studied. • Boiling curve, heat transfer coefficient, and pressure drop metrics are reported. • Flow visualization shows vapor removal from the surface is a key aspect of design. • The porous coated pin-fin surface exhibits superior two-phase cooling performance. - Abstract: In the future, wide band-gap (WBG) devices such as silicon carbide and gallium nitride will be widely used in automotive power electronics due to performance advantages over silicon-based devices. The high heat fluxes dissipated by WBG devices pose extreme cooling challenges that demand the use of advanced thermal management technologies such as two-phase cooling. In this light, we describe the performance of a submerged two-phase jet impingement cooler in combination with porous coated heat spreaders and multi-jet orifices. The cooling performance of four different porous coated structures was evaluated using R-245fa as the coolant at sub-cooling of 5 K. The results show that the boiling performance of a pin-fin heat spreader is the highest followed by that for an open tunnel (OPT), closed tunnel (CLT), and flat heat spreader. Furthermore, the flat heat spreader demonstrated the lowest critical heat flux (CHF), while the pin-fin surface sustained a heat flux of 218 W/cm 2 without reaching CHF. The CHF values of the OPT and CLT surfaces were 202 W/cm 2 and 194 W/cm 2 , respectively. The pin-fin heat spreader has the highest two-phase heat transfer coefficient of 97,800 W/m 2 K, while the CLT surface has the lowest heat transfer coefficient of 69,300 W/m 2 K, both at a heat flux of 165 W/cm 2 . The variation of the pressure drop of all surfaces is similar for the entire range of heat fluxes tested. The flat heat spreader exhibited the least pressure drop, 1.73 kPa, while the CLT surface had the highest, 2.17 kPa at a

  14. Defect induced structural inhomogeneity, ultraviolet light emission and near-band-edge photoluminescence broadening in degenerate In2O3 nanowires

    Science.gov (United States)

    Mukherjee, Souvik; Sarkar, Ketaki; Wiederrecht, Gary P.; Schaller, Richard D.; Gosztola, David J.; Stroscio, Michael A.; Dutta, Mitra

    2018-04-01

    We demonstrate here defect induced changes on the morphology and surface properties of indium oxide (In2O3) nanowires and further study their effects on the near-band-edge (NBE) emission, thereby showing the significant influence of surface states on In2O3 nanostructure based device characteristics for potential optoelectronic applications. In2O3 nanowires with cubic crystal structure (c-In2O3) were synthesized via carbothermal reduction technique using a gold-catalyst-assisted vapor-liquid-solid method. Onset of strong optical absorption could be observed at energies greater than 3.5 eV consistent with highly n-type characteristics due to unintentional doping from oxygen vacancy ({V}{{O}}) defects as confirmed using Raman spectroscopy. A combination of high resolution transmission electron microscopy, x-ray photoelectron spectroscopy and valence band analysis on the nanowire morphology and stoichiometry reveals presence of high-density of {V}{{O}} defects on the surface of the nanowires. As a result, chemisorbed oxygen species can be observed leading to upward band bending at the surface which corresponds to a smaller valence band offset of 2.15 eV. Temperature dependent photoluminescence (PL) spectroscopy was used to study the nature of the defect states and the influence of the surface states on the electronic band structure and NBE emission has been discussed. Our data reveals significant broadening of the NBE PL peak consistent with impurity band broadening leading to band-tailing effect from heavy doping.

  15. Defect induced structural inhomogeneity, ultraviolet light emission and near-band-edge photoluminescence broadening in degenerate In 2 O 3 nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Souvik; Sarkar, Ketaki; Wiederrecht, Gary P.; Schaller, Richard D.; Gosztola, David J.; Stroscio, Michael A.; Dutta, Mitra

    2018-03-01

    We demonstrate here defect induced changes on the morphology and surface properties of indium oxide (In2O3) nanowires and further study their effects on the near-band-edge (NBE) emission, thereby showing the significant influence of surface states on In2O3 nanostructure based device characteristics for potential optoelectronic applications. In2O3 nanowires with cubic crystal structure (c-In2O3) were synthesized via carbothermal reduction technique using a gold-catalyst-assisted vapor–liquid–solid method. Onset of strong optical absorption could be observed at energies greater than 3.5 eV consistent with highly n-type characteristics due to unintentional doping from oxygen vacancy (VO) defects as confirmed using Raman spectroscopy. A combination of high resolution transmission electron microscopy, x-ray photoelectron spectroscopy and valence band analysis on the nanowire morphology and stoichiometry reveals presence of high-density of VO defects on the surface of the nanowires. As a result, chemisorbed oxygen species can be observed leading to upward band bending at the surface which corresponds to a smaller valence band offset of 2.15 eV. Temperature dependent photoluminescence (PL) spectroscopy was used to study the nature of the defect states and the influence of the surface states on the electronic band structure and NBE emission has been discussed. Our data reveals significant broadening of the NBE PL peak consistent with impurity band broadening leading to band-tailing effect from heavy doping.

  16. Sensitive spectrophotometric determination of ascorbic acid in drugs and foods using surface plasmon resonance band of silver nanoparticles

    Directory of Open Access Journals (Sweden)

    Kobra Zarei

    2015-12-01

    Full Text Available A simple and sensitive procedure was proposed for spectrophotometric determination of ascorbic acid. It was found that the reduction of Ag+ to silver nanoparticles (Ag-NPs by ascorbic acid in the presence of polyvinylpyrrolidone (PVP as a stabilizing agent produce very intense surface plasmon resonance peak of Ag-NPs. The plasmon absorbance of the Ag-NPs at λ = 440 nm allows the quantitative spectrophotometric detection of the ascorbic acid. The calibration curve was linear with concentration of ascorbic acid in the range of 0.5–60 μM. The detection limit was obtained as 0.08 μM. The influence of potential interfering substances on the determination of ascorbic acid was studied. The proposed method was successfully applied for the determination of ascorbic acid in some powdered drink mixtures, commercial orange juice, natural orange juice, vitamin C injection, effervescent tablet, and multivitamin tablet.

  17. KARIN: The Ka-Band Radar Interferometer for the Proposed Surface Water and Ocean Topography (SWOT) Mission

    Science.gov (United States)

    Esteban-Fernandez, Daniel; Peral, Eva; McWatters, Dalia; Pollard, Brian; Rodriguez, Ernesto; Hughes, Richard

    2013-01-01

    Over the last two decades, several nadir profiling radar altimeters have provided our first global look at the ocean basin-scale circulation and the ocean mesoscale at wavelengths longer than 100 km. Due to sampling limitations, nadir altimetry is unable to resolve the small wavelength ocean mesoscale and sub-mesoscale that are responsible for the vertical mixing of ocean heat and gases and the dissipation of kinetic energy from large to small scales. The proposed Surface Water and Ocean Topography (SWOT) mission would be a partnership between NASA, CNES (Centre National d'Etudes Spaciales) and the Canadian Space Agency, and would have as one of its main goals the measurement of ocean topography with kilometer-scale spatial resolution and centimeter scale accuracy. In this paper, we provide an overview of all ocean error sources that would contribute to the SWOT mission.

  18. Laser Micro Bending Process of Ti6Al4V Square Bar

    Directory of Open Access Journals (Sweden)

    Gang Chen

    2014-06-01

    Full Text Available Laser micro bending process of Ti6Al4V square bar are carried out using a 3D thermo-mechanical finite element analytical model (FEM. The transient temperature fields, displacement fields, stress fields and strain fields are obtained and analyzed. The results show that the bending angel during laser micro bending process is in good agreement with experimental measurements. The effects of process parameters on temperature and deformation are also investigated here. During the bending process the temperature increases with the increase of the laser power and the irradiation time. Radiation of the laser beam yields to a rapid temperature increase at the irradiated surface, which leads to the high temperature gradients between the irradiated surface and the unirradiated surface, which suggest that the mechanism of laser micro bending is the temperature gradient mechanism. The z displacement of forward direction and reverse direction increase when the laser power and irradiation time increase. Laser micro bending process can obtain the larger bending angles reverse to laser beam using higher laser power and shorter irradiation time.

  19. Flow structure and channel morphology at a natural confluent meander bend

    Science.gov (United States)

    Riley, James D.; Rhoads, Bruce L.

    2012-08-01

    Previous experimental, field, and modeling studies of confluence dynamics have focused mainly on junctions formed by straight channels. In contrast, natural rivers often meander and tributaries can enter meandering rivers on the outside of bends to form a junction planform known as a confluent meander bend. In this study, field measurements of three-dimensional velocity components and bed topography at a confluent meander bend reveal a complex hydrodynamic environment that responds to changes in momentum-flux ratio, while channel morphology remains relatively stable. Flow from the tributary deflects high-velocity flow and helical motion in the curving main river toward the inside of the bend, inducing bed scour and inhibiting point-bar development. The high junction angle forces the tributary flow to abruptly realign to the orientation of the downstream channel, initiating a counter-rotating helical cell over the outer portion of the bend. Two surface-convergent helical cells persist through the downstream channel, where the combined flows accelerate as the channel cross-sectional area is constricted by a bar along the downstream junction corner, precluding flow separation. Long-term stability of its planform suggests that this confluent meander bend represents a quasi-stable channel configuration. Overall, patterns of flow and channel morphology are quite different from typical patterns in most meander bends, but are generally consistent with a conceptual model of confluent meander bends derived from previous laboratory experiments and numerical modeling.

  20. Bending Fretting Fatigue Characteristics of 18CrNiMo7-6 Alloy Steel

    Directory of Open Access Journals (Sweden)

    SHEN Yan-tuan

    2017-07-01

    Full Text Available A series of bending fretting fatigue tests of 18CrNiMo7-6 alloy steel were carried out, the bending fretting fatigue S-N curve was built up, and an analysis was made on the test results. The results show that, the S-N curve of 18CrNiMo7-6 alloy steel presents a shape of "ε" curve, which is different from the medium carbon steel, and also different from the plain bending fatigue. With the increase of the bending fatigue stress, the fretting regime transforms from partial slip regime to mixed regime and slip regime. The wear mechanisms of fretting damage zones mainly are delaminated, abrasive wear and oxidative wear. In the mixed regime, the cracks are easy to initiate and propagate, and the cracks all originate from the subsurface of contact zone. Due to the different influence levels of the contact stress and bending fatigue stress, the initiation and propagation of the bending fretting fatigue cracks can be divided into three stages. Firstly, the cracks initiate from subsurface under the control of contact stress; then propagate to a larger angle direction under the joint control of contact stress and bending fatigue stress; lastly the cracks propagate vertically to contact surface until fracture failure under the control of bending fatigue stress.

  1. Discontinious Galerkin formulations for thin bending problems

    NARCIS (Netherlands)

    Nguyen, T.D.

    2008-01-01

    A structural thin bending problem is essentially associated with a fourth-order partial differential equation. Within the finite element framework, the numerical solution of thin bending problems demands the use of C^1 continuous shape functions. Elements using these functions are challenging and

  2. Bandwidth engineering of photonic crystal waveguide bends

    DEFF Research Database (Denmark)

    Borel, Peter Ingo; Frandsen, Lars Hagedorn; Harpøth, Anders

    2004-01-01

    An effective design principle has been applied to photonic crystal waveguide bends fabricated in silicon-on-insulator material using deep UV lithography resulting in a large increase in the low-loss bandwidth of the bends. Furthermore, it is experimentally demonstrated that the absolute bandwidth...... range can be adjusted in a post-fabrication thermal oxidation process....

  3. Bends and splitters in graphene nanoribbon waveguides

    DEFF Research Database (Denmark)

    Zhu, Xiaolong; Yan, Wei; Mortensen, N. Asger

    2013-01-01

    We investigate the performance of bends and splitters in graphene nanoribbon waveguides. Although the graphene waveguides are lossy themselves, we show that bends and splitters do not induce any additional loss provided that the nanoribbon width is sub-wavelength. We use transmission line theory...

  4. Anharmonic Bend-Stretch Coupling in Water

    NARCIS (Netherlands)

    Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S.; Cringus, Dan; Wiersma, Douwe A.; Corkum, Paul; Jonas, David M.; Miller, R.J. Dwayne.; Weiner, Andrew M.

    2006-01-01

    Following excitation of the H-O-H bending mode of water molecules in solution the stretching mode region is monitored over its entire width. The anharmonic coupling between the two modes results in a substantial change of the transient stretch absorption that decays with the bend depopulation time.

  5. Bandwidth engineering of photonic crystal waveguide bends

    DEFF Research Database (Denmark)

    Borel, Peter Ingo; Frandsen, Lars Hagedorn; Harpøth, Anders

    2004-01-01

    An effective design principle has been applied to photonic crystal waveguide bends fabricated in silicon-on-insulator material using deep UV lithography resulting in a large increase in the low-loss bandwidth of the bends. Furthermore, it is experimentally demonstrated that the absolute bandwidth...

  6. More on Estimation of Banded and Banded Toeplitz Covariance Matrices

    OpenAIRE

    Berntsson, Fredrik; Ohlson, Martin

    2017-01-01

    In this paper we consider two different linear covariance structures, e.g., banded and bended Toeplitz, and how to estimate them using different methods, e.g., by minimizing different norms. One way to estimate the parameters in a linear covariance structure is to use tapering, which has been shown to be the solution to a universal least squares problem. We know that tapering not always guarantee the positive definite constraints on the estimated covariance matrix and may not be a suitable me...

  7. New Observations of C-band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate From the Hurricane Imaging Radiometer (HIRAD)

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Buckley, C. D.; Biswas, S.; May, C.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; hide

    2012-01-01

    HIRAD flew on the WB-57 during NASA's GRIP (Genesis and Rapid Intensification Processes) campaign in August September of 2010. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eyewall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  8. In-plane and out-of-plane bending tests on carbon steel pipe bends

    International Nuclear Information System (INIS)

    Brouard, D.; Tremblais, A.; Vrillon, B.

    1979-01-01

    The objectives of these tests were to obtain experimental results on bends behaviour in elastic and plastic regime by in plane and out of plane bending. Results were used to improve the computer model, for large distorsion of bends, to be used in a simplified beam type computer code for piping calculations. Tests were made on type ANSI B 169 DN 5 bends in ASTM A 106 Grade B carbon steel. These tests made it possible to measure, for identical bends, in elastic regime, the flexibility factors and, in plastic regime, the total evolution in opening, in closing and out of plane. Flexibility factors of 180 0 bend without flanges are approximately the same in opening and in closing. The end effect due to flanges is not very significant, but it is important for 90 0 bends. In plastic regime, collapse loads or collapse moments of bends depends also of both the end effects and the angle bend. The end effects and the angle bend are more sensitive in opening than in closing. The interest of these tests is to procure some precise evolution curves of identical bends well characterized in geometry and metal strength, deflected in large distorsions. (orig./HP)

  9. Development of draw-bending testing method using digital image correlation system

    Science.gov (United States)

    Sekiguchi, Chiharu; Hakoyama, Tomoyuki; Kuwabara, Toshihiko; Fukiharu, Hiroshi

    2017-10-01

    A novel draw-bending testing method using a non-contact optical 3D deformation measuring system (ARAMIS®, GOM) was developed to investigate the deformation process of draw-bending. Furthermore, the accuracy of the fracture prediction based on a fracture criterion using the concept of forming limit stress was also investigated. The experimental apparatus is capable of applying draw-bending to a sheet specimen with a forming speed of 100 mm/s, which is comparable to those in real press forming operations. Specimens undergo bending-unbending under tension when passing over the die profile radius. The test materials is a 590MPa high-strength steel sheet. In order to evaluate the effect of the stress variation in the width direction of a specimen on the accuracy of the calculated draw-bending fracture stress σDB, the strain components on the upper surface of the specimen were measured using the ARAMIS® software. High-speed CMOS cameras were used to take synchronized images. The development of the strain field on the surface of the specimen was succssesfully measured. The σDB was calculated from the draw-bending force and the strain components at the moment immediately before fracture, and compared with the forming limit stress σPT measured for monotonic plane strain tension. It is concluded that the forming limit stress criterion is effective as a fracture criterion for the draw-bending of the test material.

  10. On the radiocarbon record in banded corals: exchange parameters and net transport of /sup 14/CO/sub 2/ between atmosphere and surface ocean

    Energy Technology Data Exchange (ETDEWEB)

    Druffel, E.M.; Suess, H.E.

    1983-02-20

    We have made radiocarbon measurements of banded hermatypic corals from Florida, Belize, and the Galapagos Islands. Interpretation is presented here of these previously reported results. These measurements represent the /sup 14/C//sup 12/C ratios in dissolved inorganic carbon (DIOC) in the surface ocean waters of the Gulf Stream and the Peru Current at the time of coral ring formation. A depletion in radiocarbon concentration was observed incoral rings that grew from A.D. 1900--1952. It was caused by dilution of existing /sup 14/C levels with dead CO/sub 2/ from fossil fuel burning (the Suess effect, or S/sub e/). A similar trend was observed in the distribution of bomb-produced /sup 14/C in corals that had grown during the years following A.D. 1952. The concentration of bomb-produced radiocarbon was much higher in corals from temperate regions (Florida, Belize, Hawaiian Islands) than in corals from tropical regions (Galapagos Islands and Canton Island). The apparent radiocarbon ages of the surface waters in temperate and tropical oceans during the preanthropogenic period range from about 280 to 520 years B.P. (-40 to -69%). At all investigated locations, it is likely that waters at subsurface depths have the same apparent radiocarbon age of about 670 years B.P. From the change of oceanic ..delta../sup 14/C in the surface during post-bomb times, the approximate annual rate of net input of /sup 14/CO/sub 2/ to the ocean waters is calculated to be about 8% of the prevailing /sup 14/C difference between atmosphere and ocean. From this input and from preanthropogenic ..delta../sup 14/C values found at each location, it can be seen that vertical mixing of water in the Peru Current is about 3 times greater than that in the Gulf Stream.

  11. The oroclinal bend in the South Island, New Zealand

    Science.gov (United States)

    Mortimer, N.

    2014-07-01

    Most of the South Island of New Zealand lies within an Eocene-Recent continental shear zone related to Pacific-Australia plate motion. Macroscopic finite strain in this shear zone has, in the past, been tracked through the deformation of the Dun Mountain Ophiolite Belt. This paper identifies additional sub-vertical basement strain markers including: Buller-Takaka Terrane boundary, Darran Suite and Jurassic volcanic belt within the Median Batholith, Taieri-Wakatipu-Goulter Synform axial trace, Esk Head Melange and bedding form surfaces within the Buller, Takaka and Torlesse terranes. An analysis of the oroclinal bend over the entire Zealandia continent shows that it is a composite feature involving pre- as well as post-Eocene bending of basement structures. Satisfactory paleogeographic reconstructions of Zealandia cannot be made without the use of substantial regional scale, non-rigid intracontinental deformation.

  12. Optimization of Beam Properties with Respect to Maximum Band-Gap

    DEFF Research Database (Denmark)

    Halkjær, Søren; Sigmund, Ole

    2004-01-01

    We study numerically the frequency band-gap phenomenon for bending waves in an infinite periodic beam. The outcome of the analysis is then subjected to an optimization problem in order to maximize these band-gaps. The band-gap maximization may be performed with respect to material parameters and ...

  13. The properties of photonic band gap and surface plasmon modes in the three-dimensional magnetized photonic crystals as the mixed polarized modes considered

    Science.gov (United States)

    Zhang, Hai-Feng; Liu, Shao-Bin; Jiang, Yu-Chi

    2015-04-01

    In this paper, the properties of photonic band gap (PBG) and surface plasmon modes in the three-dimensional (3D) magnetized plasma photonic crystals (MPPCs) with face-centered-cubic (fcc) lattices are theoretically investigated based on the plane wave expansion (PWE) method, in which the homogeneous magnetized plasma spheres are immersed in the homogeneous dielectric background, as the Voigt effects of magnetized plasma are considered (the incidence electromagnetic wave vector is perpendicular to the external magnetic field at any time). The dispersive properties of all of the EM modes are studied because the PBG is not only for the extraordinary and ordinary modes but also for the mixed polarized modes. The equations for PBGs also are theoretically deduced. The numerical results show that the PBG and a flatbands region can be observed. The effects of the dielectric constant of dielectric background, filling factor, plasma frequency and plasma cyclotron frequency (the external magnetic field) on the dispersive properties of all of the EM modes in such 3D MPPCs are investigated in detail, respectively. Theoretical simulations show that the PBG can be manipulated by the parameters as mentioned above. Compared to the conventional dielectric-air PCs with similar structure, the larger PBG can be obtained in such 3D MPPCs. It is also shown that the upper edge of flatbands region cannot be tuned by the filling factor and dielectric constant of dielectric background, but it can be manipulated by the plasma frequency and plasma cyclotron frequency.

  14. On the use of the post-closure methods uncertainty band to evaluate the performance of land surface models against eddy covariance flux data

    Science.gov (United States)

    Ingwersen, Joachim; Imukova, Kristina; Högy, Petra; Streck, Thilo

    2017-04-01

    The energy balance of eddy covariance (EC) flux data is normally not closed. Therefore, at least if used for modeling, EC flux data are usually post-closed, i.e. the measured turbulent fluxes are adjusted so as to close the energy balance. At the current state of knowledge, however, it is not clear how to partition the missing energy in the right way. Eddy flux data therefore contain some uncertainty due to the unknown nature of the energy balance gap, which should be considered in model evaluation and the interpretation of simulation results. We propose to construct the post-closure method uncertainty band (PUB), which essentially designates the differences between non-adjusted flux data and flux data adjusted with the three post-closure methods (Bowen ratio, latent heat flux (LE) and sensible heat flux (H) method). To demonstrate this approach, simulations with the NOAH-MP land surface model were evaluated based on EC measurements conducted at a winter wheat stand in Southwest Germany in 2011, and the performance of the Jarvis and Ball-Berry stomatal resistance scheme was compared. The width of the PUB of the LE was up to 110 W/m2 (21% of net radiation). Our study shows that it is crucial to account for the uncertainty of EC flux data originating from lacking energy balance closure. Working with only a single post-closing method might result in severe misinterpretations in model-data comparisons.

  15. Bending crystals. Solid state photomechanical properties of ...

    Indian Academy of Sciences (India)

    Unknown

    semiquinonate ligand, form as long thin needles that are observed to bend reversibly upon irradiation with NIR light. Crystallographic characterization reveals a stacked solid state lattice with planar molecules aligned with metal atoms atop one another.

  16. Big Bend National Park: Acoustical Monitoring 2010

    Science.gov (United States)

    2013-06-01

    During the summer of 2010 (September October 2010), the Volpe Center collected baseline acoustical data at Big Bend National Park (BIBE) at four sites deployed for approximately 30 days each. The baseline data collected during this period will he...

  17. Observations of C-Band Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate from the Hurricane Imaging Radiometer (HIRAD) during GRIP and HS3

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2013-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and at the time of this writing plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. This technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  18. Slice of a LEP bending magnet

    CERN Multimedia

    This is a slice of a LEP dipole bending magnet, made as a concrete and iron sandwich. The bending field needed in LEP is small (about 1000 Gauss), equivalent to two of the magnets people stick on fridge doors. Because it is very difficult to keep a low field steady, a high field was used in iron plates embedded in concrete. A CERN breakthrough in magnet design, LEP dipoles can be tuned easily and are cheaper than conventional magnets.

  19. Bending sound in graphene: Origin and manifestation

    International Nuclear Information System (INIS)

    Adamyan, V.M.; Bondarev, V.N.; Zavalniuk, V.V.

    2016-01-01

    Highlights: • The origin of sound-like dispersion of graphene bending mode is disclosed. • The speed of graphene bending sound is determined. • The renormalized graphene bending rigidity is derived. • The intrinsic corrugations of graphene are estimated. - Abstract: It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.

  20. Bending sound in graphene: Origin and manifestation

    Energy Technology Data Exchange (ETDEWEB)

    Adamyan, V.M., E-mail: vadamyan@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Bondarev, V.N., E-mail: bondvic@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Zavalniuk, V.V., E-mail: vzavalnyuk@onu.edu.ua [Department of Theoretical Physics, Odessa I.I. Mechnikov National University, 2 Dvoryanska St., Odessa 65026 (Ukraine); Department of Fundamental Sciences, Odessa Military Academy, 10 Fontanska Road, Odessa 65009 (Ukraine)

    2016-11-11

    Highlights: • The origin of sound-like dispersion of graphene bending mode is disclosed. • The speed of graphene bending sound is determined. • The renormalized graphene bending rigidity is derived. • The intrinsic corrugations of graphene are estimated. - Abstract: It is proved that the acoustic-type dispersion of bending mode in graphene is generated by the fluctuation interaction between in-plane and out-of-plane terms in the free energy arising with account of non-linear components in the graphene strain tensor. In doing so we use an original adiabatic approximation based on the alleged (confirmed a posteriori) significant difference of sound speeds for in-plane and bending modes. The explicit expression for the bending sound speed depending only on the graphene mass density, in-plane elastic constants and temperature is deduced as well as the characteristics of the microscopic corrugations of graphene. The obtained results are in good quantitative agreement with the data of real experiments and computer simulations.

  1. High temperature and low pressure chemical vapor deposition of silicon nitride on AlGaN: Band offsets and passivation studies

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, Pramod; Washiyama, Shun; Kaess, Felix; Hernandez-Balderrama, Luis H.; Haidet, Brian B.; Alden, Dorian; Franke, Alexander; Sarkar, Biplab; Kohn, Erhard; Collazo, Ramon; Sitar, Zlatko [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); Hayden Breckenridge, M. [Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States); REU, Physics Department at Wofford College, Spartanburg, South Carolina 29303 (United States)

    2016-04-14

    In this work, we employed X-ray photoelectron spectroscopy to determine the band offsets and interface Fermi level at the heterojunction formed by stoichiometric silicon nitride deposited on Al{sub x}Ga{sub 1-x}N (of varying Al composition “x”) via low pressure chemical vapor deposition. Silicon nitride is found to form a type II staggered band alignment with AlGaN for all Al compositions (0 ≤ x ≤ 1) and present an electron barrier into AlGaN even at higher Al compositions, where E{sub g}(AlGaN) > E{sub g}(Si{sub 3}N{sub 4}). Further, no band bending is observed in AlGaN for x ≤ 0.6 and a reduced band bending (by ∼1 eV in comparison to that at free surface) is observed for x > 0.6. The Fermi level in silicon nitride is found to be at 3 eV with respect to its valence band, which is likely due to silicon (≡Si{sup 0/−1}) dangling bonds. The presence of band bending for x > 0.6 is seen as a likely consequence of Fermi level alignment at Si{sub 3}N{sub 4}/AlGaN hetero-interface and not due to interface states. Photoelectron spectroscopy results are corroborated by current-voltage-temperature and capacitance-voltage measurements. A shift in the interface Fermi level (before band bending at equilibrium) from the conduction band in Si{sub 3}N{sub 4}/n-GaN to the valence band in Si{sub 3}N{sub 4}/p-GaN is observed, which strongly indicates a reduction in mid-gap interface states. Hence, stoichiometric silicon nitride is found to be a feasible passivation and dielectric insulation material for AlGaN at any composition.

  2. Surface effects in metal oxide-based nanodevices

    KAUST Repository

    Lien, Der Hsien

    2015-10-29

    As devices shrink to the nanoscale, surface-to-volume ratio increases and the surface-environment interaction becomes a major factor for affecting device performance. The variation of electronic properties, including the surface band bending, gas chemisorption or photodesorption, native surface defects, and surface roughness, is called "surface effects". Such effects are ambiguous because they can be either negative or beneficial effects, depending on the environmental conditions and device application. This review provides an introduction to the surface effects on different types of nanodevices, offering the solutions to respond to their benefits and negative effects and provides an outlook on further applications regarding the surface effect. This review is beneficial for designing nano-enabled photodetectors, harsh electronics, memories, sensors and transistors via surface engineering.

  3. Laser micro-bending for precise micro-fabrication of magnetic disk drive components

    Science.gov (United States)

    Matsushita, Naohisa

    2003-11-01

    Laser Micro-Bending technology attracts attention as one of the laser processing technology promising from now on. It has the feature that does not contact and does not have the spring back that fabrication in high accuracy can be performed. In our company, Laser Micro-Bending technology development is tackled about ten years before, and the laser bending fabrication technology of a sheet metal and ceramic material has so far been established. It has utilized as rapid prototyping of the sheet metal. But, by re-examination of laser oscillation control etc., it finds out that it is the excellent processing method for manufacture of the high precision mechanism parts for magnetic disk drives. This report explains the technology and machines of the roll and pitch adjustment of a magnetic head suspension, and flatting or crowning of the air bearing surface of a magnetic head slider by using Laser Micro-Bending technology.

  4. GROUND-BASED Paα NARROW-BAND IMAGING OF LOCAL LUMINOUS INFRARED GALAXIES. I. STAR FORMATION RATES AND SURFACE DENSITIES

    Energy Technology Data Exchange (ETDEWEB)

    Tateuchi, Ken; Konishi, Masahiro; Motohara, Kentaro; Takahashi, Hidenori; Kato, Natsuko Mitani; Kitagawa, Yutaro; Todo, Soya; Toshikawa, Koji; Sako, Shigeyuki; Uchimoto, Yuka K.; Ohsawa, Ryou; Asano, Kentaro; Kamizuka, Takafumi; Nakamura, Tomohiko; Okada, Kazushi [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Ita, Yoshifusa [Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Komugi, Shinya [Division of Liberal Arts, Kogakuin University, 2665-1, Hachioji, Tokyo 192-0015 (Japan); Koshida, Shintaro [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Manabe, Sho [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Nakashima, Asami, E-mail: tateuchi@ioa.s.u-tokyo.ac.jp [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); and others

    2015-03-15

    Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust produced by their active star formation, and it is difficult to measure their activity in optical wavelengths. We have carried out Paα narrow-band imaging observations of 38 nearby star forming galaxies including 33 LIRGs listed in the IRAS Revised Bright Galaxy Sample catalog with the Atacama Near InfraRed camera on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Paα fluxes, corrected for dust extinction using the Balmer decrement method (typically A{sub V} ∼ 4.3 mag), show a good correlation with those from the bolometric infrared luminosity of the IRAS data within a scatter of 0.27 dex. This suggests that the correction of dust extinction for the Paα flux is sufficient in our sample. We measure the physical sizes and surface densities of infrared luminosities (Σ{sub L(IR)}) and the SFR (Σ{sub SFR}) of star forming regions for individual galaxies, and we find that most of the galaxies follow a sequence of local ultra-luminous or luminous infrared galaxies (U/LIRGs) on the L(IR)-Σ{sub L(IR)} and SFR-Σ{sub SFR} plane. We confirm that a transition of the sequence from normal galaxies to U/LIRGs is seen at L(IR) = 8 × 10{sup 10} L {sub ☉}. Also, we find that there is a large scatter in physical size, different from normal galaxies or ULIRGs. Considering the fact that most U/LIRGs are merging or interacting galaxies, this scatter may be caused by strong external factors or differences in their merging stages.

  5. The effect of voluntary lateral trunk bending on balance recovery following multi-directional stance perturbations.

    Science.gov (United States)

    Küng, U M; Horlings, C G C; Honegger, F; Allum, J H J

    2010-05-01

    Stabilising shifts of the centre of mass (COM) are observed during balance recovery when subjects simultaneously execute voluntary unilateral knee flexion or unilateral arm raising. Here, we examined whether voluntary lateral trunk bending provided more beneficial stabilising effects, and how motor programs of balance corrections are combined with those of the focal voluntary action. The upright balance of 24 healthy young subjects (19-33 years of age) was perturbed using multi-directional rotations of the support-surface. The perturbations consisted of combined pitch and roll rotations (7.5 degrees and 60 degrees/s) presented randomly in six different directions. Three conditions were tested: perturbation of stance only (PO); combined balance perturbation and cued uphill bending of the trunk (CONT); and combined perturbation and cued downhill bending of the trunk (IPS). For comparison, subjects were required to perform trunk bending alone (TO). Outcome measures were biomechanical responses and surface EMG activity of several muscles. Calculated predicted outcomes (PO + TO) were compared with combined measures (CONT or IPS). CONT trunk bending uphill showed two phases of benefit in balance recovery for laterally but, in contrast to voluntary knee bending, not for posterior directed components of the perturbations. IPS trunk bending had negative effects on balance. Early balance correcting muscle responses were marginally greater than PO responses. Prominent secondary balance correcting responses, having a similar timing as voluntary responses observed under TO conditions, were seen under CONT only in trunk muscles. These, and later stabilising, responses had amplitudes as expected from PO + TO conditions being significantly greater than PO responses. The ability with which different muscle synergies for balance corrections and voluntary trunk bending were integrated into one indicates a flexible adjustment of the CNS programs to the demands of both tasks.

  6. The Charge Transport Properties of a HWCVD a-Si:H Thin Film under Bending Pressure

    Directory of Open Access Journals (Sweden)

    M. Boshta

    2008-01-01

    Full Text Available The transient thermoelectric effects (TTEs method is used to measure the ambipolar space charge built up in a low-pressure hot wire chemical vapor deposition (HWCVD technique a-Si:H layer deposited on a glass substrate. The stage 2 TTE-transients yield the trap state density difference with and without bending pressure up to 9 bars. The a-Si:H sample shows a reduction of the negative storage peaks at 0.045 eV and 0.026 eV with increasing pressure, while the positive (hole trap peak and the zero crossing practically do not change with the pressure. At the maximum bending pressure, the negative peaks are almost zero and shifted into the band gap or toward the conduction band. Our result shows that it is necessary to produce and mount hydrogenated thin film solar cell stress-free.

  7. Slice through an LHC bending magnet

    CERN Multimedia

    Slice through an LHC superconducting dipole (bending) magnet. The slice includes a cut through the magnet wiring (niobium titanium), the beampipe and the steel magnet yokes. Particle beams in the Large Hadron Collider (LHC) have the same energy as a high-speed train, squeezed ready for collision into a space narrower than a human hair. Huge forces are needed to control them. Dipole magnets (2 poles) are used to bend the paths of the protons around the 27 km ring. Quadrupole magnets (4 poles) focus the proton beams and squeeze them so that more particles collide when the beams’ paths cross. There are 1232 15m long dipole magnets in the LHC.

  8. Robotic Arm Comprising Two Bending Segments

    Science.gov (United States)

    Mehling, Joshua S.; Difler, Myron A.; Ambrose, Robert O.; Chu, Mars W.; Valvo, Michael C.

    2010-01-01

    The figure shows several aspects of an experimental robotic manipulator that includes a housing from which protrudes a tendril- or tentacle-like arm 1 cm thick and 1 m long. The arm consists of two collinear segments, each of which can be bent independently of the other, and the two segments can be bent simultaneously in different planes. The arm can be retracted to a minimum length or extended by any desired amount up to its full length. The arm can also be made to rotate about its own longitudinal axis. Some prior experimental robotic manipulators include single-segment bendable arms. Those arms are thicker and shorter than the present one. The present robotic manipulator serves as a prototype of future manipulators that, by virtue of the slenderness and multiple- bending capability of their arms, are expected to have sufficient dexterity for operation within spaces that would otherwise be inaccessible. Such manipulators could be especially well suited as means of minimally invasive inspection during construction and maintenance activities. Each of the two collinear bending arm segments is further subdivided into a series of collinear extension- and compression-type helical springs joined by threaded links. The extension springs occupy the majority of the length of the arm and engage passively in bending. The compression springs are used for actively controlled bending. Bending is effected by means of pairs of antagonistic tendons in the form of spectra gel spun polymer lines that are attached at specific threaded links and run the entire length of the arm inside the spring helix from the attachment links to motor-driven pulleys inside the housing. Two pairs of tendons, mounted in orthogonal planes that intersect along the longitudinal axis, are used to effect bending of each segment. The tendons for actuating the distal bending segment are in planes offset by an angle of 45 from those of the proximal bending segment: This configuration makes it possible to

  9. Minimal Bending Energies of Bilayer Polyhedra

    Science.gov (United States)

    Haselwandter, Christoph A.; Phillips, Rob

    2011-01-01

    Motivated by recent experiments on bilayer polyhedra composed of amphiphilic molecules, we study the elastic bending energies of bilayer vesicles forming polyhedral shapes. Allowing for segregation of excess amphiphiles along the ridges of polyhedra, we find that bilayer polyhedra can indeed have lower bending energies than spherical bilayer vesicles. However, our analysis also implies that, contrary to what has been suggested on the basis of experiments, the snub dodecahedron, rather than the icosahedron, generally represents the energetically favorable shape of bilayer polyhedra. PMID:21231425

  10. Surface potential domains on lamellar P3OT structures

    International Nuclear Information System (INIS)

    Perez-GarcIa, B; Abad, J; Urbina, A; Colchero, J; Palacios-Lidon, E

    2008-01-01

    In this work the electrostatic properties of poly(3-octylthiophene) thin films have been studied on a nanometer scale by means of electrostatic force microscopy and Kelvin probe microscopy (KPM). The KPM images reveal that different surface contact potential domains coexist on the polymer surface. This result, together with additional capacitance measurements, indicates that the potential domains are related to the existence of dipoles due to different molecular arrangements. Finally, capacitance measurements as a function of the tip-sample bias voltage show that in all regions large band bending effects take place

  11. Surface potential domains on lamellar P3OT structures

    Energy Technology Data Exchange (ETDEWEB)

    Perez-GarcIa, B [Departamento Fisica, Facultad de Quimica (Campus Espinardo), Universidad de Murcia, E-30100 Murcia (Spain); Abad, J [Departamento Fisica, Facultad de Quimica (Campus Espinardo), Universidad de Murcia, E-30100 Murcia (Spain); Urbina, A [Departamento Electronica, TecnologIa de Computadoras y Proyectos, Universidad Politecnica de Cartagena, E-30202 Cartagena (Spain); Colchero, J [Departamento Fisica, Facultad de Quimica (Campus Espinardo), Universidad de Murcia, E-30100 Murcia (Spain); Palacios-Lidon, E [Departamento Fisica, Facultad de Quimica (Campus Espinardo), Universidad de Murcia, E-30100 Murcia (Spain)

    2008-02-13

    In this work the electrostatic properties of poly(3-octylthiophene) thin films have been studied on a nanometer scale by means of electrostatic force microscopy and Kelvin probe microscopy (KPM). The KPM images reveal that different surface contact potential domains coexist on the polymer surface. This result, together with additional capacitance measurements, indicates that the potential domains are related to the existence of dipoles due to different molecular arrangements. Finally, capacitance measurements as a function of the tip-sample bias voltage show that in all regions large band bending effects take place.

  12. Bending Fatigue of Carburized Steel at Very Long Lives

    Science.gov (United States)

    Nelson, D. V.; Long, Z.

    2016-01-01

    The bending fatigue behavior of two carburized steels is investigated for lives between approximately 105 and 108 cycles. Cracks are observed to start at sub-surface inclusions and develop features on fracture surfaces resembling "fish eyes" in appearance. This type of sub-surface cracking tends to govern fatigue strength at long lives. Previous studies of "fish eye" fatigue in carburized steel have been relatively few and have mainly considered failures originating at depths beneath a carburized case, where compressive residual stresses are minimal and hardness values approach those in the core. This study provides fatigue data for cracks originating within cases at various depths where compressive residual stresses are substantial and hardness is much higher than in the core. Fatigue strength is predicted by a simple model, accounting for the influence of residual stresses and hardness values at the different depths at which cracks started. Predictions of fatigue strength are compared with data generated in this study.

  13. fMRI-compatible registration of jaw movements using a fiber-optic bend sensor

    Directory of Open Access Journals (Sweden)

    Peter Sörös

    2010-03-01

    Full Text Available A functional magnetic resonance imaging (fMRI-compatible fiber-optic bend sensor was investigated to assess whether the device could be used effectively to monitor opening and closing of the jaw during an fMRI experiment at 3 T. In contrast to surface electromyography, a bend sensor fixed to the chin of the participant is fast and easy to use and is not affected by strong electromagnetic fields. Bend sensor recordings are characterized by high validity (compared with concurrent video recordings of mouth opening and high reliability (comparing 2 independent measurements. The results of this study indicate that a bend sensor is able to record the opening and closing of the jaw associated with different overt speech conditions (producing the utterances /a/, /pa/, /pataka/ and the opening of the mouth without speech production. Data post-processing such as filtering was not necessary. There are several potential applications for bend sensor recordings of speech-related jaw movements. First, bend sensor recordings are a valuable tool to assess behavioral performance, such as response latencies, accuracies, and completion times, which is particularly important in children, seniors, or patients with various neurological or psychiatric conditions. Second, the timing information provided by bend sensor data may improve the predicted hemodynamic response that is used for fMRI analysis based on the general linear model (GLM. Third, bend sensor recordings may be included in GLM analyses not for statistical contrast purposes, but as a covariate of no interest, accounting for part of the data variance to model fMRI artifacts due to motion outside the field of view.

  14. Fabrication and Testing of Pyramidal X- Band Standard Horn Antenna

    OpenAIRE

    Hasan F. Khazaal; Haider Th. Salim Alrikabi; Anwar N. Mohammed Ali; Kadhim A. Neamah; Ali S. Shanan

    2017-01-01

    Standard horn antennas are an important device to evaluate many types of antennas, since they are used as a reference to any type of antennas within the microwave frequency bands. In this project the fabrication process and tests of standard horn antenna operating at X-band frequencies have been proposed. The fabricated antenna passed through multi stages of processing of its parts until assembling the final product. These stages are (milling, bending, fitting and welding). The assembled ante...

  15. Head movements while steering around bends

    NARCIS (Netherlands)

    Erp, J.B.F. van; Oving, A.B.

    2012-01-01

    In this study, the determinants of head motions (rotations) when driving around bends were investigated when drivers viewed the scene through a head-mounted display. The scene camera was either fixed or coupled to head motions along 2 or 3 axes of rotation. Eight participants drove around a

  16. Demonstration model of LEP bending magnet

    CERN Multimedia

    CERN PhotoLab

    1981-01-01

    To save iron and raise the flux density, the LEP bending magnet laminations were separated by spacers and the space between the laminations was filled with concrete. This is a demonstration model, part of it with the spaced laminations only, the other part filled with concrete.

  17. Design of a hydraulic bending machine

    Science.gov (United States)

    Steven G. Hankel; Marshall Begel

    2004-01-01

    To keep pace with customer demands while phasing out old and unserviceable test equipment, the staff of the Engineering Mechanics Laboratory (EML) at the USDA Forest Service, Forest Products Laboratory, designed and assembled a hydraulic bending test machine. The EML built this machine to test dimension lumber, nominal 2 in. thick and up to 12 in. deep, at spans up to...

  18. ANALYTICAL BENDING SOLUTION OF ALL CLAMPED ISOTROPIC ...

    African Journals Online (AJOL)

    The analytical bending solution of all clamped rectangular plate on Winkler foundation using characteristic orthogonal polynomials (COPs) was studied. This was achieved by partially integrating the governing differential equation of rectangular plate on elastic foundation four times with respect to its independents x and y ...

  19. Fractional behaviour at cyclic stretch-bending

    NARCIS (Netherlands)

    Emmens, W.C.; van den Boogaard, Antonius H.; Kazantzis, A.V.; de Hosson, J.Th.M.; Kolleck, R

    2010-01-01

    The fractional behaviour at cyclic stretch-bending has been studied by performing tensile tests at long specimens that are cyclically bent at the same time, on mild steel, dual-phase steel, stainless steel, aluminium and brass. Several types of fracture are observed, these are discussed, as are the

  20. Bending rate damping in elastic systems

    Science.gov (United States)

    Banks, H. T.; Wang, Y.; Fabiano, R. H.

    1989-01-01

    Preliminary results of an investigation of the bending rate damping model for elastic structures are presented. A model for which the internal damping term is physically plausible and which can accomodate cantilevered boundary conditions is discussed. The model formulation and mathematical foundations are given, and numerical results are discussed.

  1. Challenging the limits for beam bending designs

    DEFF Research Database (Denmark)

    Goltermann, Per

    2017-01-01

    The traditional design limits of beams in bending have been challenged by testing from very under-reinforced design to over-reinforced and strengthened over-reinforced designs in order to investigate if the current limits could be abolished. The ductility of normally reinforced beam depends...

  2. Experimental and Numerical Investigations of Applying Tip-bottomed Tool for Bending Advanced Ultra-high Strength Steel Sheet

    Science.gov (United States)

    Mitsomwang, Pusit; Borrisutthekul, Rattana; Klaiw-awoot, Ken; Pattalung, Aran

    2017-09-01

    This research was carried out aiming to investigate the application of a tip-bottomed tool for bending an advanced ultra-high strength steel sheet. The V-die bending experiment of a dual phase steel (DP980) sheet which had a thickness of 1.6 mm was executed using a conventional bending and a tip-bottomed punches. Experimental results revealed that the springback of the bent worksheet in the case of the tip-bottomed punch was less than that of the conventional punch case. To further discuss bending characteristics, a finite element (FE) model was developed and used to simulate the bending of the worksheet. From the FE analysis, it was found that the application of the tip-bottomed punch contributed the plastic deformation to occur at the bending region. Consequently, the springback of the worksheet reduced. In addition, the width of the punch tip was found to affect the deformation at the bending region and determined the springback of the bent worksheet. Moreover, the use of the tip-bottomed punch resulted in the apparent increase of the surface hardness of the bent worksheet, compared to the bending with the conventional punch.

  3. Research on stratified evolution of composite materials under four-point bending loading

    Science.gov (United States)

    Hao, M. J.; You, Q. J.; Zheng, J. C.; Yue, Z.; Xie, Z. P.

    2017-12-01

    In order to explore the effect of stratified evolution and delamination on the load capacity and service life of the composite materials under the four-point bending loading, the artificial tectonic defects of the different positions were set up. The four-point bending test was carried out, and the whole process was recorded by acoustic emission, and the damage degree of the composite layer was judged by the impact accumulation of the specimen - time-amplitude history chart, load-time-relative energy history chart, acoustic emission impact signal positioning map. The results show that the stratified defects near the surface of the specimen accelerate the process of material failure and expansion. The location of the delamination defects changes the bending performance of the composites to a great extent. The closer the stratification defects are to the surface of the specimen, the greater the damage, the worse the service capacity of the specimen.

  4. Symmetric bends how to join two lengths of cord

    CERN Document Server

    Miles, Roger E

    1995-01-01

    A bend is a knot securely joining together two lengths of cord (or string or rope), thereby yielding a single longer length. There are many possible different bends, and a natural question that has probably occurred to many is: "Is there a 'best' bend and, if so, what is it?"Most of the well-known bends happen to be symmetric - that is, the two constituent cords within the bend have the same geometric shape and size, and interrelationship with the other. Such 'symmetric bends' have great beauty, especially when the two cords bear different colours. Moreover, they have the practical advantage o

  5. Dust deposition in ventilation and air-conditioning duct bend flows

    International Nuclear Information System (INIS)

    Gao Ran; Li Angui

    2012-01-01

    Highlights: ► We study particle deposition on the four inner surface of the duct bend. ► We analyse the effect of five ways of placements of the bend on particle deposition. ► Gravity and inertia force enhance the deposition as relaxation time rises. ► Deposition coefficient increases as air velocity or particle diameter increases. - Abstract: Particles carried by airflows in ventilation and air-conditioning systems have adverse effects on the quality of air in buildings and hence the health of building occupants. Gaining insight on particle deposition onto ventilation and air-conditioning duct bends is important for controlling pollutant dispersion. Based on the Reynolds stress transport model (RSM), this paper has taken into account the effects of drag, lift force, gravity, inertia force, turbulent diffusions, particle size and air velocity on the dimensionless deposition velocity of particles in smooth duct bends using fully developed velocity profiles. At two different air velocities of 3.0 m/s and 7.0 m/s, the aforementioned effects were predicted by Reynolds-averaged Navier–Stokes (RANS)-Lagrangian simulation on square shaped duct bends with different ways of placement. Preliminary results suggest that gravity and inertia force enhance the dimensionless deposition as dimensionless relaxation time rises. Change tendency of the dimensionless particle deposition velocity on different surfaces of bend duct agrees well with previous studies. As air velocity and particle diameter increase, a significant increase of particle deposition coefficient in the duct bends is observed. Particle deposition to intrados can be intensified by the combined action of gravity and inertia force in different direction.

  6. Band Structure of Topological Insulator BiSbTe1.25Se1.75.

    Science.gov (United States)

    Lohani, H; Mishra, P; Banerjee, A; Majhi, K; Ganesan, R; Manju, U; Topwal, D; Kumar, P S Anil; Sekhar, B R

    2017-07-04

    We present our angle resolved photoelectron spectroscopy (ARPES) and density functional theory results on quaternary topological insulator (TI) BiSbTe 1.25 Se 1.75 (BSTS) confirming the non-trivial topology of the surface state bands (SSBs) in this compound. We find that the SSBs, which are are sensitive to the atomic composition of the terminating surface have a partial 3D character. Our detailed study of the band bending (BB) effects shows that in BSTS the Dirac point (DP) shifts by more than two times compared to that in Bi 2 Se 3 to reach the saturation. The stronger BB in BSTS could be due to the difference in screening of the surface charges. From momentum density curves (MDCs) of the ARPES data we obtained an energy dispersion relation showing the warping strength of the Fermi surface in BSTS to be intermediate between those found in Bi 2 Se 3 and Bi 2 Te 3 and also to be tunable by controlling the ratio of chalcogen/pnictogen atoms. Our experiments also reveal that the nature of the BB effects are highly sensitive to the exposure of the fresh surface to various gas species. These findings have important implications in the tuning of DP in TIs for technological applications.

  7. Mixed lipid bilayers with locally varying spontaneous curvature and bending.

    Science.gov (United States)

    Gueguen, Guillaume; Destainville, Nicolas; Manghi, Manoel

    2014-08-01

    A model of lipid bilayers made of a mixture of two lipids with different average compositions on both leaflets, is developed. A Landau Hamiltonian describing the lipid-lipid interactions on each leaflet, with two lipidic fields ψ 1 and ψ 2, is coupled to a Helfrich one, accounting for the membrane elasticity, via both a local spontaneous curvature, which varies as C 0 + C 1(ψ 1 - ψ 2/2), and a bending modulus equal to κ 0 + κ 1(ψ 1 + ψ 2)/2. This model allows us to define curved patches as membrane domains where the asymmetry in composition, ψ 1 - ψ 2, is large, and thick and stiff patches where ψ 1 + ψ 2 is large. These thick patches are good candidates for being lipidic rafts, as observed in cell membranes, which are composed primarily of saturated lipids forming a liquid-ordered domain and are known to be thick and flat nano-domains. The lipid-lipid structure factors and correlation functions are computed for globally spherical membranes and planar ones and for a whole set of parameters including the surface tension and the coupling in the two leaflet compositions. Phase diagrams are established, within a Gaussian approximation, showing the occurrence of two types of Structure Disordered phases, with correlations between either curved or thick patches, and an Ordered phase, corresponding to the divergence of the structure factor at a finite wave vector. The varying bending modulus plays a central role for curved membranes, where the driving force κ 1 C 0 (2) is balanced by the line tension, to form raft domains of size ranging from 10 to 100 nm. For planar membranes, raft domains emerge via the cross-correlation with curved domains. A global picture emerges from curvature-induced mechanisms, described in the literature for planar membranes, to coupled curvature- and bending-induced mechanisms in curved membranes forming a closed vesicle.

  8. Interaction of low-frequency axisymmetric ultrasonic guided waves with bends in pipes of arbitrary bend angle and general bend radius.

    Science.gov (United States)

    Verma, Bhupesh; Mishra, Tarun Kumar; Balasubramaniam, Krishnan; Rajagopal, Prabhu

    2014-03-01

    The use of ultrasonic guided waves for the inspection of pipes with elbow and U-type bends has received much attention in recent years, but studies for more general bend angles which may also occur commonly, for example in cross-country pipes, are limited. Here, we address this topic considering a general bend angle φ, a more general mean bend radius R in terms of the wavelength of the mode studied and pipe thickness b. We use 3D Finite Element (FE) simulation to understand the propagation of fundamental axisymmetric L(0,2) mode across bends of different angles φ. The effect of the ratio of the mean bend radius to the wavelength of the mode studied, on the transmission and reflection of incident wave is also considered. The studies show that as the bend angle is reduced, a progressively larger extent of mode-conversion affects the transmission and velocity characteristics of the L(0,2) mode. However the overall message on the potential of guided waves for inspection and monitoring of bent pipes remains positive, as bends seem to impact mode transmission only to the extent of 20% even at low bend angles. The conclusions seem to be valid for different typical pipe thicknesses b and bend radii. The modeling approach is validated by experiments and discussed in light of physics of guided waves. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Holey fibers for low bend loss

    Science.gov (United States)

    Nakajima, Kazuhide; Saito, Kotaro; Yamada, Yusuke; Kurokawa, Kenji; Shimizu, Tomoya; Fukai, Chisato; Matsui, Takashi

    2013-12-01

    Bending-loss insensitive fiber (BIF) has proved an essential medium for constructing the current fiber to the home (FTTH) network. By contrast, the progress that has been made on holey fiber (HF) technologies provides us with novel possibilities including non-telecom applications. In this paper, we review recent progress on hole-assisted type BIF. A simple design consideration is overviewed. We then describe some of the properties of HAF including its mechanical reliability. Finally, we introduce some applications of HAF including to high power transmission. We show that HAF with a low bending loss has the potential for use in various future optical technologies as well as in the optical communication network.

  10. Parallel monostrand stay cable bending fatigue

    DEFF Research Database (Denmark)

    Winkler, Jan Pawel

    This dissertation investigates the bending fatigue response of high-strength steel monostrands and multistrand stay cables to cyclic transverse deformations. Increasing bridge stock numbers and a push for longer cable-supported span lengths have led to an increased number of reported incidents...... deformations is the highest at the neutral axis of the monostrand. Moreover, the results indicate that the midspan and the anchorage of the monostrand are the two locations where the combination of tensile strains and the interwire movement is the most unfavorable. It was also shown that, in the absence...... in significant insight in the flexural behavior of a multistrand assembly in critical locations with respect to bending fatigue, i.e. guide deviator and exit of the socket. The thesis ends with an example of how the outcome of the research work can be used in the estimation of the life-cycle performance...

  11. Combined bending-torsion fatigue reliability. III

    Science.gov (United States)

    Kececioglu, D.; Chester, L. B.; Nolf, C. F., Jr.

    1975-01-01

    Results generated by three, unique fatigue reliability research machines which can apply reversed bending loads combined with steady torque are presented. AISI 4340 steel, grooved specimens with a stress concentration factor of 1.42 and 2.34, and Rockwell C hardness of 35/40 were subjected to various combinations of these loads and cycled to failure. The generated cycles-to-failure and stress-to-failure data are statistically analyzed to develop distributional S-N and Goodman diagrams. Various failure theories are investigated to determine which one represents the data best. The effects of the groove, and of the various combined bending-torsion loads, on the S-N and Goodman diagrams are determined. Two design applications are presented which illustrate the direct useability and value of the distributional failure governing strength and cycles-to-failure data in designing for specified levels of reliability and in predicting the reliability of given designs.

  12. Alternating bending-steady torque fatigue reliability

    Science.gov (United States)

    Kececioglu, D.; Chester, L. B.; Dodge, T. M.

    1974-01-01

    Results generated by three unique fatigue reliability research machines which can apply alternating-bending loads combined with steady torque are presented. Six-inch long, AISI steel, grooved specimens with a stress concentration factor of 1.42 and Rockwell C 35/40 hardness were subjected to various combinations of these loads and cycled to failure. The generated cycles-to-failure and staircase-testing data are statistically analyzed to develop distributional S-N and Goodman diagrams. Various failure theories are investigated to determine which one best represents the data. The effect of the groove and of the various combined bending-torsion loads on the finite and endurance life strength of such components, as well as on the Goodman diagram, are determined. Design applications are presented.

  13. Torsion and transverse bending of cantilever plates

    Science.gov (United States)

    Reissner, Eric; Stein, Manuel

    1951-01-01

    The problem of combined bending and torsion of cantilever plates of variable thickness, such as might be considered for solid thin high-speed airplane or missile wings, is considered in this paper. The deflections of the plate are assumed to vary linearly across the chord; minimization of the potential energy by means of the calculus of variations then leads to two ordinary linear differential equations for the bending deflections and the twist of the plate. Because the cantilever is analyzed as a plate rather than as a beam, the effect of constraint against axial warping in torsion is inherently included. The application of this method to specific problems involving static deflection, vibration, and buckling of cantilever plates is presented. In the static-deflection problems, taper and sweep are considered.

  14. Effect of confinements: Bending in Paramecium

    Science.gov (United States)

    Eddins, Aja; Yang, Sung; Spoon, Corrie; Jung, Sunghwan

    2012-02-01

    Paramecium is a unicellular eukaryote which by coordinated beating of cilia, generates metachronal waves which causes it to execute a helical trajectory. We investigate the swimming parameters of the organism in rectangular PDMS channels and try to quantify its behavior. Surprisingly a swimming Paramecium in certain width of channels executes a bend of its flexible body (and changes its direction of swimming) by generating forces using the cilia. Considering a simple model of beam constrained between two walls, we predict the bent shapes of the organism and the forces it exerts on the walls. Finally we try to explain how bending (by sensing) can occur in channels by conducting experiments in thin film of fluid and drawing analogy to swimming behavior observed in different cases.

  15. Nuclear fuels accounting interface: River Bend experience

    International Nuclear Information System (INIS)

    Barry, J.E.

    1986-01-01

    This presentation describes nuclear fuel accounting activities from the perspective of nuclear fuels management and its interfaces. Generally, Nuclear Fuels-River Bend Nuclear Group (RBNG) is involved on a day-by-day basis with nuclear fuel materials accounting in carrying out is procurement, contract administration, processing, and inventory management duties, including those associated with its special nuclear materials (SNM)-isotopics accountability oversight responsibilities as the Central Accountability Office for the River Bend Station. As much as possible, these duties are carried out in an integrated, interdependent manner. From these primary functions devolve Nuclear Fuels interfacing activities with fuel cost and tax accounting. Noting that nuclear fuel tax accounting support is of both an esoteric and intermittent nature, Nuclear Fuels-RBNG support of developments and applications associated with nuclear fuel cost accounting is stressed in this presentation

  16. BENDING BEHAVIOUR OF MAGNETIC COTTON YARNS

    OpenAIRE

    LUPU Iuliana G.; GROSU Marian C; CRAMARIUC Bogdan; CRAMARIUC Oana

    2017-01-01

    Magnetic yarns are composite yarns, i.e. they combine elements of various natures and properties, with proven potential for electromagnetic interference (EMI) shielding. In this paper, different mixtures of hard and soft magnetic powder were chosen to cover materials made of cotton yarn. The physical properties and bending behavior of the produced composite yarns were investigated in order to evaluate the yarns for further textile processing.The cotton yarn used as base material was covered w...

  17. Clinical bending of nickel titanium wires

    OpenAIRE

    Stephen Chain; Priyank Seth; Namrata Rastogi; Kenneth Tan; Mayank Gupta; Richa Singh

    2015-01-01

    Since the evolution and the involvement of Nickel Titanium wires in the field of Orthodontics. The treatment plan has evolved with the use of low force Nickel Titanium wires. Because of their high springback, low stiffness, they are the key initial wires in leveling and alignment but have poor formability. Since poor formability limits its ability to create variable arch forms thus; limits the form of treatment. We have devised a method to bend the Nickel Titanium wires to help in our invento...

  18. AA, assembly of wide bending magnet

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    The very particular lattice of the AA required 2 types of dipoles (bending magnets; BST, short and wide; BLG, long and narrow). The wide ones had a steel length of 2.71 m, a "good field" width of 0.564 m, and a weight of about 75 t. Here we see the copper coils being hoisted onto the lower half of a BST. See also 7811105, 8006050. For a BLG, see 8001044.

  19. Superconducting beam bending magnets at CERN

    CERN Multimedia

    CERN PhotoLab

    1977-01-01

    The photo shows Gerhard Kesseler with the cyogenic vessels for one of the 10.8 Tesla-metre beam bending magnets. The magnet itself (not visible) is sitting inside the superinsukated helium vessel (white). The next larger shell and the biggest tubular structure (with the largest part behind the person) is the insulation vacuum tank. See CERN Courier 1970 pp. 228-229 CERN Courier 1973 pp. 144-145 Yellow Report CERN 78-03, 1978

  20. Hydrodynamic processes in sharp meander bends and their morphological implications

    NARCIS (Netherlands)

    Blanckaert, K.

    2011-01-01

    The migration rate of sharp meander bends exhibits large variance and indicates that some sharply curved bends tend to stabilize. These observations remain unexplained. This paper examines three hydrodynamic processes in sharp bends with fixed banks and discusses their morphological implications:

  1. Characterization and study of photonic crystal fibres with bends

    International Nuclear Information System (INIS)

    Belhadj, W.; AbdelMalek, F.; Bouchriha, H.

    2006-01-01

    Analysis of a photonic crystal fibre (PRCF) with bends is presented. Using the versatile finite difference time domain method, the modal characteristics of the PCFs are found. Possibilities of employing PCFs with bends in sensing are discussed. It is found that a large evanescent field is present when the bend angle exceeds 45 o

  2. Fuzzy set theory applied to bend sequencing for sheet metal

    NARCIS (Netherlands)

    Ong, S.K.; de Vin, L.J.; de Vin, L.J.; Nee, A.Y.C.; Kals, H.J.J.

    1997-01-01

    Brake forming is widely applied in the high variety and small batch part manufacturing of sheet metal components, for the bending of straight bending lines. Currently, the planning of the bending sequences is a task that has to be performed manually, involving many heuristic criteria. However,

  3. Effects of laser bending on the microstructural constituents

    CSIR Research Space (South Africa)

    Tshabalala, L

    2012-01-01

    Full Text Available This article will illustrate the correlation between microstructural and microhardness changes in high-strength-low-alloy steel that occur as a result of laser-bending. Laser bending is a process of bending metal shapes using the laser beam...

  4. Low-loss adiabatic bend using minimised chip area.

    NARCIS (Netherlands)

    Roeloffzen, C.G.H.; de Ridder, R.M.; Driessen, A.; Leijtens, X.J.M.; Besten, J.H.

    2000-01-01

    For the increasing complexity of integrated optical structures, there is a need of bends, which occupy a chip area as small as possible. The best results with respect to loss can be obtained by adiabatic bends with decreasing radius and variable waveguide width. Detailed simulations using 2D bend

  5. HYBASE : HYperspectral BAnd SElection

    NARCIS (Netherlands)

    Schwering, P.B.W.; Bekman, H.H.P.T.; Seijen, H.H. van

    2009-01-01

    Band selection is essential in the design of multispectral sensor systems. This paper describes the TNO hyperspectral band selection tool HYBASE. It calculates the optimum band positions given the number of bands and the width of the spectral bands. HYBASE is used to assess the minimum number of

  6. First multi-bend achromat lattice consideration

    Energy Technology Data Exchange (ETDEWEB)

    Einfeld, Dieter, E-mail: dieter.einfeld@maxlab.lu.se [Lund University, PO Box 118, Lund SE-221 00 (Sweden); Plesko, Mark [COSYLAB, Teslova ulica 30, Ljubljana SI-1000 (Slovakia); Schaper, Joachim [HAWK University of Applied Sciences and Arts, Hohnsen 4, D-31134 Hildesheim (Germany)

    2014-08-27

    The first proposed lattice for a ‘diffraction-limited light source’ is reported. This approach has now more or less been used for the MAX IV project. By the beginning of 1990, three third-generation synchrotron light sources had been successfully commissioned in Grenoble, Berkeley and Trieste (ESRF, ALS and ELETTRA). Each of these new machines reached their target specifications without any significant problems. In parallel, already at that time discussions were underway regarding the next generation, the ‘diffraction-limited light source (DLSR)’, which featured sub-nm rad electron beam emittance, photon beam brilliance exceeding 10{sup 22} and the potential to emit coherent radiation. Also, at about that time, a first design for a 3 GeV DLSR was developed, based on a modified multiple-bend achromat (MBA) design leading to a lattice with normalized emittance of ∊{sub x} = 0.5 nm rad. The novel feature of the MBA lattice was the use of seven vertically focusing bend magnets with different bending angles throughout the achromat cell to keep the radiation integrals and resulting beam emittance low. The baseline design called for a 400 m ring circumference with 12 straight sections of 6 m length. The dynamic aperture behaviour of the DLSR lattice was estimated to produce > 5 h beam lifetime at 100 mA stored beam current.

  7. Emittance growth of bunched beams in bends

    International Nuclear Information System (INIS)

    Carlsten, B.E.; Raubenheimer, T.O.

    1995-01-01

    Talman [Phys. Rev. Lett. 56, 1429 (1986)] has proposed a novel relativistic effect that occurs when a charged particle beam is bent in the magnetic field from an external dipole. The consequence of this effect is that the space-charge forces from the particles do not exhibit the usual inverse-square energy dependence and some part of them are, in fact, independent of energy. This led to speculation that this effect could introduce significant emittance growth for a bending electron beam. Subsequently, it was shown that this effect's influence on the beam's transverse motion is canceled for a dc beam by a potential depression within the beam (to first order in the beam radius divided by the bend radius). In this paper, we extend the analysis to include short bunch lengths (as compared to the beam pipe dimensions) and find that there is no longer the cancellation for forces both transverse to and in the direction of motion. We provide an estimate for the emittance growth as a function of bend angle, beam radius, and current, and for magnetic compression of an electron bunch

  8. Stepwise bending of DNA by a single TATA box binding protein

    DEFF Research Database (Denmark)

    Tolic-Nørrelykke, Simon F; Rasmussen, Mette B; Pavone, Francesco S

    2006-01-01

    The TATA-box binding protein (TBP) is required by all three eucaryotic RNA polymerases for the initiation of transcription from most promoters. TBP recognizes, binds to, and bends promoter sequences called "TATA-boxes" in the DNA. We present results from the study of individual Saccharomyces...... cerevisiae TBPs interacting with single DNA molecules containing a TATA-box. Using video microscopy, we observed the Brownian motion of the beads tethered by short surface-bound DNA. When TBP binds to and bends the DNA, the conformation of the DNA changes and the amplitude of Brownian motion of the tehtered...

  9. 77 FR 36012 - PPL Bell Bend, LLC; Bell Bend Nuclear Power Plant Combined License Application; Notice of Intent...

    Science.gov (United States)

    2012-06-15

    ... by relocating the power block footprint and other plant components. For purposes of developing the... COMMISSION PPL Bell Bend, LLC; Bell Bend Nuclear Power Plant Combined License Application; Notice of Intent... its Bell Bend Nuclear Power Plant (BBNPP) site, located west of the existing Susquehanna Steam...

  10. 78 FR 4465 - PPL Bell Bend, LLC; Combined License Application for Bell Bend Nuclear Power Plant; Exemption

    Science.gov (United States)

    2013-01-22

    ... License Application for Bell Bend Nuclear Power Plant; Exemption 1.0 Background PPL Bell Bend, LLC... Regulations (10 CFR), Subpart C of Part 52, ``Licenses, Certifications, and Approvals for Nuclear Power Plants.'' This reactor is to be identified as Bell Bend Nuclear Power Plant (BBNPP), in Salem County...

  11. 76 FR 81992 - PPL Bell Bend, LLC; Combined License Application for Bell Bend Nuclear Power Plant; Exemption

    Science.gov (United States)

    2011-12-29

    ... License Application for Bell Bend Nuclear Power Plant; Exemption 1.0 Background PPL Bell Bend, LLC... for Nuclear Power Plants.'' This reactor is to be identified as Bell Bend Nuclear Power Plant (BBNPP... based upon the U.S. EPR reference COL (RCOL) application for UniStar's Calvert Cliffs Nuclear Power...

  12. Recent developments in bend-insensitive and ultra-bend-insensitive fibers

    Science.gov (United States)

    Boivin, David; de Montmorillon, Louis-Anne; Provost, Lionel; Montaigne, Nelly; Gooijer, Frans; Aldea, Eugen; Jensma, Jaap; Sillard, Pierre

    2010-02-01

    Designed to overcome the limitations in case of extreme bending conditions, Bend- and Ultra-Bend-Insensitive Fibers (BIFs and UBIFs) appear as ideal solutions for use in FTTH networks and in components, pigtails or patch-cords for ever demanding applications such as military or sensing. Recently, however, questions have been raised concerning the Multi-Path-Interference (MPI) levels in these fibers. Indeed, they are potentially subject to interferences between the fundamental mode and the higher-order mode that is also bend resistant. This MPI is generated because of discrete discontinuities such as staples, bends and splices/connections that occur on distance scales that become comparable to the laser coherent length. In this paper, we will demonstrate the high MPI tolerance of all-solid single-trench-assisted BIFs and UBIFs. We will present the first comprehensive study combining theoretical and experimental points of view to quantify the impact of fusion splices on coherent MPI. To be complete, results for mechanical splices will also be reported. Finally, we will show how the single-trench- assisted concept combined with the versatile PCVD process allows to tightly control the distributions of fibers characteristics. Such controls are needed to massively produce BIFs and to meet the more stringent specifications of the UBIFs.

  13. A preliminary bending fatigue spectrum for steel monostrand cables

    DEFF Research Database (Denmark)

    Winkler, Jan; Fischer, Gregor; Georgakis, Christos T.

    2011-01-01

    service life expectancy. The presented preliminary bending fatigue spectrum of high-strength monostrands is currently unavailable in the published literature. The presented results provide relevant information on the bending mechanism and fatigue characteristics of monostrand steel cables in tension......This paper presents the results of the experimental study on the bending fatigue resistance of high-strength steel monostrand cables. From the conducted fatigue tests in the high-stress, low-cycle region, a preliminary bending fatigue spectrum is derived for the estimation of monostrand cable...... and flexure and show that localized cable bending has a pronounced influence on the fatigue resistance of cables under dynamic excitations....

  14. Permanent bending and alignment of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Borschel, Christian; Spindler, Susann; Oertel, Michael; Ronning, Carsten [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lerose, Damiana [MPI fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle/Saale (Germany); Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Bochmann, Arne [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Christiansen, Silke H. [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); MPI fuer die Physik des Lichts, Guenther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Nietzsche, Sandor [Zentrum fuer Elektronenmikroskopie, Friedrich-Schiller-Universitaet Jena, Ziegelmuehlenweg 1, 07743 Jena (Germany)

    2011-07-01

    Ion beams can be used to bend or re-align nanowires permanently, after they have been grown. We have irradiated ZnO nanowires with ions of different species and energy, achieving bending and alignment in various directions. We study the bending of single nanowires as well as the simultaneous alignment of large ensembles of ZnO nanowires in detail. Computer simulations show that the bending is initiated by ion beam induced damage. Dislocations are identified to relax stresses and make the bending and alignment permanent and resistant against annealing procedures.

  15. Permanent bending and alignment of ZnO nanowires.

    Science.gov (United States)

    Borschel, Christian; Spindler, Susann; Lerose, Damiana; Bochmann, Arne; Christiansen, Silke H; Nietzsche, Sandor; Oertel, Michael; Ronning, Carsten

    2011-05-06

    Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.

  16. Influence of flock coating on bending rigidity of woven fabrics

    Science.gov (United States)

    Ozdemir, O.; Kesimci, M. O.

    2017-10-01

    This work presents the preliminary results of our efforts that focused on the effect of the flock coating on the bending rigidity of woven fabrics. For this objective, a laboratory scale flocking unit is designed and flocked samples of controlled flock density are produced. Bending rigidity of the samples with different flock densities are measured on both flocked and unflocked sides. It is shown that the bending rigidity depends on both flock density and whether the side to be measured is flocked or not. Adhesive layer thickness on the bending rigidity is shown to be dramatic. And at higher basis weights, flock density gets less effective on bending rigidity.

  17. Tunable waveguide bends with graphene-based anisotropic metamaterials

    KAUST Repository

    Chen, Zhao-xian

    2016-01-15

    We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.

  18. A Novel Low-cost, Ka-band, High Altitude, Multi-Baseline Unmanned Aerial Vehicle Sensor for Surface Water Ocean Topography, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The NRC Decadal Survey recommended the Surface Water Ocean Topography (SWOT) satellite mission to address terrestrial fresh water hydrology and physical oceanography...

  19. Accounting for Fiber Bending Effects in Homogenization of Long Fiber Reinforced Composites

    DEFF Research Database (Denmark)

    Poulios, Konstantinos; Niordson, Christian Frithiof

    2015-01-01

    The present work deals with homogenized finite-element models of long fiber reinforced composite materials in the context of studying compressive failure modes such as the formation of kink bands and fiber micro-buckling. Compared to finite-element models with an explicit discretization...... are in good agreement. In cases where the fiber bending stiffness is significant,the homogenized finite-element model exhibits size-scale dependent material behavior, as predicted by the model with explicitly discretized individual fibers....... of the material micro-structure including individual fibers, homogenized models are computationally more efficient and hence more suitable for modeling of larger and complex structure. Nevertheless, the formulation of homogenized models is more complicated, especially if the bending stiffness of the reinforcing...

  20. Cricket antennae shorten when bending (Acheta domesticus L.).

    Science.gov (United States)

    Loudon, Catherine; Bustamante, Jorge; Kellogg, Derek W

    2014-01-01

    Insect antennae are important mechanosensory and chemosensory organs. Insect appendages, such as antennae, are encased in a cuticular exoskeleton and are thought to bend only between segments or subsegments where the cuticle is thinner, more flexible, or bent into a fold. There is a growing appreciation of the dominating influence of folds in the mechanical behavior of a structure, and the bending of cricket antennae was considered in this context. Antennae will bend or deflect in response to forces, and the resulting bending behavior will affect the sensory input of the antennae. In some cricket antennae, such as in those of Acheta domesticus, there are a large number (>100) of subsegments (flagellomeres) that vary in their length. We evaluated whether these antennae bend only at the joints between flagellomeres, which has always been assumed but not tested. In addition we questioned whether an antenna undergoes a length change as it bends, which would result from some patterns of joint deformation. Measurements using light microscopy and SEM were conducted on both male and female adult crickets (Acheta domesticus) with bending in four different directions: dorsal, ventral, medial, and lateral. Bending occurred only at the joints between flagellomeres, and antennae shortened a comparable amount during bending, regardless of sex or bending direction. The cuticular folds separating antennal flagellomeres are not very deep, and therefore as an antenna bends, the convex side (in tension) does not have a lot of slack cuticle to "unfold" and does not lengthen during bending. Simultaneously on the other side of the antenna, on the concave side in compression, there is an increasing overlap in the folded cuticle of the joints during bending. Antennal shortening during bending would prevent stretching of antennal nerves and may promote hemolymph exchange between the antenna and head.

  1. Cricket antennae shorten when bending (Acheta domesticus L.

    Directory of Open Access Journals (Sweden)

    Catherine eLoudon

    2014-06-01

    Full Text Available Insect antennae are important mechanosensory and chemosensory organs. Insect appendages, such as antennae, are encased in a cuticular exoskeleton and are thought to bend only between segments or subsegments where the cuticle is thinner, more flexible, or bent into a fold. There is a growing appreciation of the dominating influence of folds in the mechanical behavior of a structure, and the bending of cricket antennae was considered in this context. Antennae will bend or deflect in response to forces, and the resulting bending behavior will affect the sensory input of the antennae. In some cricket antennae, such as in those of Acheta domesticus, there are a large number (>100 of subsegments (flagellomeres that vary in their length. We evaluated whether these antennae bend only at the joints between flagellomeres, which has always been assumed but not tested. In addition we questioned whether an antenna undergoes a length change as it bends, which would result from some patterns of joint deformation. Measurements using light microscopy and SEM were conducted on both male and female adult crickets (Acheta domesticus with bending in four different directions: dorsal, ventral, medial and lateral. Bending occurred only at the joints between flagellomeres, and antennae shortened a comparable amount during bending, regardless of sex or bending direction. The cuticular folds separating antennal flagellomeres are not very deep, and therefore as an antenna bends, the convex side (in tension does not have a lot of slack cuticle to unfold and does not lengthen during bending. Simultaneously on the other side of the antenna, on the concave side in compression, there is an increasing overlap in the folded cuticle of the joints during bending. Antennal shortening during bending would prevent stretching of antennal nerves and may promote hemolymph exchange between the antenna and head.

  2. The effect of temperature on the secondary electron emission yield from single crystal and polycrystalline diamond surfaces

    International Nuclear Information System (INIS)

    Stacey, A.; Prawer, S.; Rubanov, S.; Ahkvlediani, R.; Michaelson, Sh.; Hoffman, A.

    2009-01-01

    The effect of temperature in the 293-473 K range, on the secondary electron emission (SEE) yield of single crystal and polycrystalline diamond film surfaces is reported. For the polycrystalline films the SEE yield was found to decay as function of electron irradiation dose while for the single crystal an increase occurs first, followed by a decrease. For both surfaces, the SEE yield increases significantly upon heating and obtained a nearly constant value with electron dose at 473 K. These effects are explained as due to the temperature dependence of the electron beam induced hydrogen desorption and surface band bending.

  3. Limit loads for pipe bends under combined pressure and in-plane bending based on finite element limit analysis

    International Nuclear Information System (INIS)

    Oh, Chang Sik; Kim, Yun Jae

    2006-01-01

    In the present paper, approximate plastic limit load solutions for pipe bends under combined internal pressure and bending are obtained from detailed three-dimensional (3-D) FE limit analyses based on elastic-perfectly plastic materials with the small geometry change option. The present FE results show that existing limit load solutions for pipe bends are lower bounds but can be very different from the present FE results in some cases, particularly for bending. Accordingly closed-form approximations are proposed for pipe bends under combined pressure and in-plane bending based on the present FE results. The proposed limit load solutions would be a basis of defective pipe bends and be useful to estimate non-linear fracture mechanics parameters based on the reference stress approach

  4. Extension versus Bending for Continuum Robots

    Directory of Open Access Journals (Sweden)

    George Grimes

    2008-11-01

    Full Text Available In this paper, we analyze the capabilities of a novel class of continuous-backbone ("continuum" robots. These robots are inspired by biological "trunks, and tentacles". However, the capabilities of established continuum robot designs, which feature controlled bending but not extension, fall short of those of their biological counterparts. In this paper, we argue that the addition of controlled extension provides dual and complementary functionality, and correspondingly enhanced performance, in continuum robots. We present an interval-based analysis to show how the inclusion of controllable extension significantly enhances the workspace and capabilities of continuum robots.

  5. Clinical bending of nickel titanium wires

    Directory of Open Access Journals (Sweden)

    Stephen Chain

    2015-01-01

    Full Text Available Since the evolution and the involvement of Nickel Titanium wires in the field of Orthodontics. The treatment plan has evolved with the use of low force Nickel Titanium wires. Because of their high springback, low stiffness, they are the key initial wires in leveling and alignment but have poor formability. Since poor formability limits its ability to create variable arch forms thus; limits the form of treatment. We have devised a method to bend the Nickel Titanium wires to help in our inventory but also customized the wire according to the treatment.

  6. Can human rights law bend mass surveillance?

    Directory of Open Access Journals (Sweden)

    Rikke Frank Joergensen

    2014-02-01

    Full Text Available There is an increasing gap between the right to privacy and contemporary surveillance schemes. As a concrete example, the US surveillance operation PRISM and its impact on European citizens’ right to privacy is discussed. This paper provides a brief introduction to PRISM, continues with an outline of the right to privacy as stipulated in the International Covenant on Civil and Political Rights (ICCPR, the European Convention on Human Rights and the EU Directive on Data Protection, and moves on to discuss whether international human rights law may be used to bend mass surveillance.

  7. Deducing material quality in cast and hot-forged steels by new bending test

    Science.gov (United States)

    Valberg, Henry; Langøy, Morten; Nedreberg, Mette; Helvig, Torgeir

    2017-10-01

    A special bend test has been developed and applied for the purpose of characterization and comparison of the material ductility in crankpin steel discs manufactured by casting, or casting subsequently followed by hot open-die forging (ODF) or closed-die forging (CDF). The bending test specimen consists of a small rectangular plate of material with a round hole cut out in the middle. The "eye-shape" specimens were cut out from various positions either near to the surface of, or from the interior of the discs. The test method revealed differences in ductility for the investigated materials, and for different depth positions inside the discs. The roughening of the specimen surface on the top-side of the specimen bend also varied dependent on the processing method for the material. Current results show that this test method is useful for evaluation of material quality in differently processed material. Experimental bend test results are presented for differently processed variants of the same material, i.e., crankpin discs either made by solely casting or casting subsequently followed by hot working either by ODF or CDF.

  8. Combination Bands of the Nonpolar OCS Dimer Involving Intermolecular Modes

    Science.gov (United States)

    Rezaei, M.; Oliaee, J. Norooz; Moazzen-Ahmadi, N.; McKellar, A. R. W.

    2012-06-01

    Spectra of the nonpolar carbonyl sulfide in the region of the OCS ν_1 fundamental band were observed in a supersonic slit-jet apparatus. The expansion gas was probed using radiation from a tunable diode laser employed in a rapid-scan signal averaging mode. Three bands centered at 2085.906, 2103.504, and 2114.979 cm-1 were observed and anlysed. The rotational assignment and fitting of the bands were made by fixing the lower state parameters to those for the ground state of nonpolar (OCS)_2, thus confirming that they were indeed combination bands of the of the most stable isomer of OCS dimer. The band centered at 2085.906 cm-1 is a combination of the forbidden A_g intramolecular mode plus the geared bend intermolecular mode and that centered at 2114.979 cm-1 is a combination of the allowed B_u intramolecular mode plus the intermolecular van der Waals stretch. The combination at 2103.504 cm-1 can be assigned as a band whose upper state involves four quanta of the intramolecular bend or the B_u intramolecular mode plus two quanta of the intermolecular torsional mode. Isotopic work is needed to conclusively identify the vibrational assignment of this band. Our experimental frequencies for the geared bend and van der Waals modes are in good agreement with a recent high level ab initio calculation by Brown et al. J. Brown, Xiao-Gang Wang, T. Carrington Jr. and Richard Dawes, Journal of Chemical Physics, submitted.

  9. Geophysical exploration to estimate the surface conductivity of residual argillaceous bands in the groundwater repositories of coastal sediments of EOLGA, Nigeria

    Directory of Open Access Journals (Sweden)

    N.J. George

    2017-06-01

    Full Text Available Electrical geophysical applications exploit a petrophysical relationship governing the electrical properties of rocks/sediments when field data are coupled with laboratory data. Given the robust analytical techniques of electrical method and the interrelationship with laboratory measurements, it seems natural to classify, and hence simplify, the spatially aggregated conductivity information on the basis of rock/sediment lithology. This provides a unique link between lithological sediment/rock parameters and the physical parameters controlling bulk conductivity. In this work vertical electrical sounding (VES technique employing Schlumberger configuration integrated with sediment and water analysis have been used to determine the conductivity of argillaceous bands of aquifer sands (fine- coarse sands in Eastern Obolo Local Government Area (EOLGA. The analysis of the data shows that the aquifer systems composing of fine sands, siltstones and coarse sand have bulk and pore-water resistivities ranging from 40.1–2049.4 Ω m (average = 995.18 Ω m to 2.7–256.9 Ω m (average = 91.2 Ω m respectively. These ranges respectively correspond to porosity and formation factor of (19.5–40.6%; average = 29.2% and (7.1–19.7%; average = 12.95%. Within the limit of experimental errors clearly specified in the work, the intrinsic (clay-free formation factor (Fi was estimated to be 16.34 while the intrinsic porosity and the conductivity of the pore-scale clay (σA were respectively estimated to be 20.4% and 3.2679 mS/m. Accounting for this conductivity magnitude of argillaceous bands from bulk conductivity (σb of aquifer sands makes the aquifer systems in the area to be consistent with Archie’s law that is valid only in clay-free sandy formation. The graphical deductions and contour distribution of parameters realised from data processing could be used to derive input parameters for contaminant migration modelling and to improve the

  10. Enhanced surface area, high Zn interstitial defects and band gap reduction in N-doped ZnO nanosheets coupled with BiVO{sub 4} leads to improved photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Sonal [Deen Dayal Upadhyaya College, Dwarka, University of Delhi, New Delhi 110078 (India); Sharma, Rishabh, E-mail: rishabh.rammstien@gmail.com [Thin Film Laboratory, Department of Physics, Indian Institute of Technology, New Delhi 110016 (India); Mehta, Bodh Raj [Thin Film Laboratory, Department of Physics, Indian Institute of Technology, New Delhi 110016 (India)

    2017-07-31

    Highlights: • In this study, we report novel nitrogen doped ZnO (nanosheet)/BiVO{sub 4} nanocomposite with enhanced visible light photocatalytic activity tested on methylene blue dye. • In a typical composite synthesis process, individual metal oxides synthesized by chemical route were mixed through ultrasonication followed by annealing at the temperature of 400 °C. • To understand mechanism of action we carried out XRD, TEM, UV–vis spectroscopy, XPS, BET & PL of the samples. • Enhancement in photocatalytic performance of the composite was due to increased light absorption due to band gap reduction and formation intermediate band. • Also, charge exchange as per Z-scheme at the hetrojunction between N-ZnO and BiVO{sub 4} resulted in reduced charge recombination rate which is further responsible for enhancement in photocatalytic activity. - Abstract: For the first time, a series of Nitrogen-doped-ZnO nanosheet coupled with BiVO{sub 4} (N-ZnO/BiVO{sub 4}) heterojunctioned photocatalysts have been synthesized. The new N-ZnO/BiVO{sub 4} material has been prepared via a simple and effective method of precipitation followed by high temperature annealing process. The photocatalytic activities of the N-ZnO/BiVO{sub 4} composites were evaluated for the degradation of methylene blue (MB) a common organic pollutant under visible-light irradiation. The results revealed that photocatalytic activity of the coupled system was directly influenced by the percentage amount of BiVO{sub 4} in N-ZnO which affected the available exposed surface area for photoreactions. 30% N-ZnO/BiVO{sub 4} system exhibited remarkable performance than 10%N-ZnO/BiVO{sub 4}, 50%N-ZnO/BiVO{sub 4}, and also to their pristine counterparts. The composite demonstrated the degradation efficiency of 90% in 90 min which is 1.76 times the efficiency of pure ZnO for same time duration. This pronounced photocatalytic effect is ascribed to the reduced band gap and lowered recombination rate of ZnO due to

  11. Existence, character and origin of surface-related bands in the high temperature iron pnictide superconductor BaFe2-xCoxAs2

    NARCIS (Netherlands)

    van Heumen, E.; Vuorinen, J.; Koepernik, K.; Massee, F.; Huang, Y.; Shi, M.; Klei, J.; Goedkoop, J.; Lindroos, M.; van den Brink, J.; Golden, M.S.

    2011-01-01

    Low energy electron diffraction (LEED) experiments, LEED simulations, and finite slab density functional calculations are combined to study the cleavage surface of Co doped BaFe2-xCoxAs2 (x=0.1,0.17). We demonstrate that the energy dependence of the LEED data can only be understood from a

  12. Bending Behavior of Porous Sintered Stainless Steel Fiber Honeycombs

    Science.gov (United States)

    Zou, Shuiping; Wan, Zhenping; Lu, Longsheng; Tang, Yong

    2017-02-01

    A novel porous honeycomb-type substrate has been developed using solid-state sintering stainless steel fibers. The porous sintered stainless steel fiber honeycombs (PSSSFH) are composed of a skeleton of sintered stainless steel fibers, three-dimensionally interconnected porous structures and multiple parallel microchannels. The bending behavior of the PSSSFH is investigated using three-point bending tests. Four stages, including an elastic stage, a yielding stage with a plateau, a hardening stage and a failure stage, are observed during the bending process of the PSSSFH. In the initial yielding stage, the bending forces increase slowly with displacement increasing, and then a yielding plateau follows, which is unique compared with other porous materials. Moreover, the structure parameters of the PSSSFH are varied to investigate the influence on the bending strength. It is determined that the multiple parallel microchannels can enhance the bending strength of porous stainless steel fiber sintered substrates (PSSFSS) and do not influence the variation trend of bending strength of PSSFSS with porosity increasing. The open ratio is conducive to increasing the bending strength, and the microchannel diameters ranging from 0.5 mm to 1.5 mm have little influence on the bending strength. In addition, both the increasing of sintering temperature and sintering time can strengthen the PSSSFH.

  13. Band structure of semiconductors

    CERN Document Server

    Tsidilkovski, I M

    2013-01-01

    Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio

  14. Design Study: ELENA Bending Magnet Prototype

    CERN Document Server

    Schoerling, D

    2013-01-01

    The ELENA bending magnet prototype shall prove that the proposed design meets the requirements set by the ELENA beam dynamics. The following points will be discussed in detail: (i) production process of a magnetic yoke diluted with stainless steel plates, (ii) the stability and repeatability of the field homogeneity of such a yoke over the full working range, (iii) choice of soft magnetic steel, (iv) hysteresis effects, (v) mechanical deformations, (vi) thermal insulation to intercept heat load from baking for activation of NEG coating in the vacuum chamber, (vii) end shim design. In order to verify these points the following measurements will be performed: (i) Hall probe scanning, (ii) integrated field homogeneity measurement (DC), (iii) integrated field homogeneity measurement (AC).

  15. Development of miniature bending fatigue specimens

    International Nuclear Information System (INIS)

    Rao, G.R.; Chin, B.A.; Rowcliffe, A.

    1991-01-01

    Two new miniaturized bending fatigue specimens have been designed and developed to aid in the scoping of materials for fusion first-wall and blanket structural applications. One of these is rectangular in shape with a gauge section 6.35 mm in length, while the other is cut from a 3 mm transmission electron microscopy (TEM) disk and has a gauge length of 1.5 mm. Test rules for unirradiated annealed type 316 stainless steel tested at room temperature, 550deg C and 650deg C are presented. A good correlation between miniature and standard subsize fatigue specimen results was obtained. The miniature specimen results show the same dependence of strain range on cycles to failure as the standard subsize specimens with the miniature-disk specimen results falling below all the other results. The results indicate that these specimens provide reliable data that can be used to scope fatigue properties for fusion applications. (orig.)

  16. Load tests with a pipe bend DN 425, applying slowly changing bending loads up to occurrence of leak

    International Nuclear Information System (INIS)

    Uhlmann, D.; Hunger, H.

    1990-01-01

    The experimental program deals with the formation of incipient cracks and subsequent crack growth of axially oriented cracks at a pipe bend with a nominal width of DN 425. The pipe bend consists of the ferritic material 20MnMoNi55. The numerical experiments by means of 3 D-FE analyses concentrate on determining the influence of the asymmetric crack depths at the two bend halves, and of the multiple crack fields, on the effective crack strain. (DG) [de

  17. Strength tests of thin-walled elliptic duralumin cylinders in pure bending and in combined pure bending and torsion

    Science.gov (United States)

    Lundquist, Eugene E; Stowell, Elbridge Z

    1942-01-01

    An analysis is presented of the results of tests made by the Massachusetts Institute of Technology and by the National Advisory Committee for Aeronautics on an investigation of the strength of thin-walled circular and elliptic cylinders in pure bending and in combined torsion and bending. In each of the loading conditions, the bending moments were applied in the plane of the major axis of the ellipse.

  18. Coupling between shear and bending in the analysis of beam problems: Planar case

    Science.gov (United States)

    Shabana, Ahmed A.; Patel, Mohil

    2018-04-01

    The interpretation of invariants, such as curvatures which uniquely define the bending and twist of space curves and surfaces, is fundamental in the formulation of the beam and plate elastic forces. Accurate representations of curve and surface invariants, which enter into the definition of the strain energy equations, is particularly important in the case of large displacement analysis. This paper discusses this important subject in view of the fact that shear and bending are independent modes of deformation and do not have kinematic coupling; this is despite the fact that kinetic coupling may exist. The paper shows, using simple examples, that shear without bending and bending without shear at an arbitrary point and along a certain direction are scenarios that higher-order finite elements (FE) can represent with a degree of accuracy that depends on the order of interpolation and/or mesh size. The FE representation of these two kinematically uncoupled modes of deformation is evaluated in order to examine the effect of the order of the polynomial interpolation on the accuracy of representing these two independent modes. It is also shown in this paper that not all the curvature vectors contribute to bending deformation. In view of the conclusions drawn from the analysis of simple beam problems, the material curvature used in several previous investigations is evaluated both analytically and numerically. The problems associated with the material curvature matrix, obtained using the rotation of the beam cross-section, and the fundamental differences between this material curvature matrix and the Serret-Frenet curvature matrix are discussed.

  19. Dynamics of folding: Impact of fault bend folds on earthquake cycles

    Science.gov (United States)

    Sathiakumar, S.; Barbot, S.; Hubbard, J.

    2017-12-01

    Earthquakes in subduction zones and subaerial convergent margins are some of the largest in the world. So far, forecasts of future earthquakes have primarily relied on assessing past earthquakes to look for seismic gaps and slip deficits. However, the roles of fault geometry and off-fault plasticity are typically overlooked. We use structural geology (fault-bend folding theory) to inform fault modeling in order to better understand how deformation is accommodated on the geological time scale and through the earthquake cycle. Fault bends in megathrusts, like those proposed for the Nepal Himalaya, will induce folding of the upper plate. This introduces changes in the slip rate on different fault segments, and therefore on the loading rate at the plate interface, profoundly affecting the pattern of earthquake cycles. We develop numerical simulations of slip evolution under rate-and-state friction and show that this effect introduces segmentation of the earthquake cycle. In crustal dynamics, it is challenging to describe the dynamics of fault-bend folds, because the deformation is accommodated by small amounts of slip parallel to bedding planes ("flexural slip"), localized on axial surface, i.e. folding axes pinned to fault bends. We use dislocation theory to describe the dynamics of folding along these axial surfaces, using analytic solutions that provide displacement and stress kernels to simulate the temporal evolution of folding and assess the effects of folding on earthquake cycles. Studies of the 2015 Gorkha earthquake, Nepal, have shown that fault geometry can affect earthquake segmentation. Here, we show that in addition to the fault geometry, the actual geology of the rocks in the hanging wall of the fault also affect critical parameters, including the loading rate on parts of the fault, based on fault-bend folding theory. Because loading velocity controls the recurrence time of earthquakes, these two effects together are likely to have a strong impact on the

  20. Fourier Transform Infrared spectrum of the OCD bending mode in methanol-D1

    Science.gov (United States)

    Mukhopadhyay, Indra

    2016-03-01

    The infrared (IR) spectra corresponding to OCD bending vibration of asymmetrically deuterated methanol species CH2DOH have been recorded with a Fourier Transform Spectrometer. The spectrum shows a typical structure of a parallel a-type band. This is expected because the bending vibration mainly executed parallel to the symmetry axis The Q-branch lines are grouped closely around 896 cm-1 and the P- and R-Branches show complex structure. Nonetheless it was possible to assign a-type P- and R-branch lines up to K value of 8 and J value up to about 20 in most cases. The Q-branch lines for higher K values can be followed to about J = 15, the presence of which confirmed the assignments. The observations suggest that in the OCD bend some energy levels are highly interacted by highly excited torsional state from the ground torsional state. A full catalogue is presented along with the effective molecular parameters. An intensity anomaly was also observed in the transitions. So far it has been possible to assign only transitions between e0 ← e0 states. Plausible explanations of intensity anomaly are presented. Lastly, a number of optically pumped far infrared (FIR) laser lines have been assigned either to exact or tentative quantum states. These assignments should prove valuable for production of new FIR laser lines.

  1. Effect of interlayer bonding strength and bending stiffness on 2-dimensional materials’ frictional properties at atomic-scale steps

    International Nuclear Information System (INIS)

    Lang, Haojie; Peng, Yitian; Zeng, Xingzhong

    2017-01-01

    Highlights: • Bending of uncovered step edge of 2-dimensional materials could be a common phenomenon during friction processes. • 2-dimensional materials with large interlayer bonding strength possess good frictional properties at step. • Increased bending stiffness of step edge could be the major reason that lateral force increased with step height. - Abstract: Atomic-scale steps generally presented in 2-dimensional materials have important influence on the overall nanotribological properties of surface. Frictional properties at atomic-scale steps of two types of 2-dimensional materials are studied using calibrated atomic force microscopy (AFM) tip sliding against the steps. The lateral force at uncovered step is larger than covered step due to the bending of step edge. The lateral force at monolayer uncovered step edge of h-BN is lower than graphene because h-BN possesses higher interlayer bonding strength than graphene and the bending of h-BN step edge is suppressed to some extent. The high uncovered step exhibits much larger lateral force than low uncovered step, which could be mainly induced by increased bending stiffness of step edge rather than increased step height. The results revealed that interlayer bonding strength and bending stiffness have great influence on the lateral force at atomic-scale steps. The studies can provide a further understanding of frictional properties at atomic scale steps and could be helpful for the applications of 2-dimensional materials as lubricant coating.

  2. Effect of interlayer bonding strength and bending stiffness on 2-dimensional materials’ frictional properties at atomic-scale steps

    Energy Technology Data Exchange (ETDEWEB)

    Lang, Haojie; Peng, Yitian, E-mail: yitianpeng@dhu.edu.cn; Zeng, Xingzhong

    2017-07-31

    Highlights: • Bending of uncovered step edge of 2-dimensional materials could be a common phenomenon during friction processes. • 2-dimensional materials with large interlayer bonding strength possess good frictional properties at step. • Increased bending stiffness of step edge could be the major reason that lateral force increased with step height. - Abstract: Atomic-scale steps generally presented in 2-dimensional materials have important influence on the overall nanotribological properties of surface. Frictional properties at atomic-scale steps of two types of 2-dimensional materials are studied using calibrated atomic force microscopy (AFM) tip sliding against the steps. The lateral force at uncovered step is larger than covered step due to the bending of step edge. The lateral force at monolayer uncovered step edge of h-BN is lower than graphene because h-BN possesses higher interlayer bonding strength than graphene and the bending of h-BN step edge is suppressed to some extent. The high uncovered step exhibits much larger lateral force than low uncovered step, which could be mainly induced by increased bending stiffness of step edge rather than increased step height. The results revealed that interlayer bonding strength and bending stiffness have great influence on the lateral force at atomic-scale steps. The studies can provide a further understanding of frictional properties at atomic scale steps and could be helpful for the applications of 2-dimensional materials as lubricant coating.

  3. Band profiles of Mott-insulator/band-insulator heterointerfaces revealed by photocurrent and electromodulation spectroscopies

    Science.gov (United States)

    Nakamura, Masao

    2011-03-01

    Heterointerfaces of Mott insulators provide a good laboratory to explore unprecedented electronic states induced by the strong electron correlation. Although a number of intriguing phenomena have been reported so far, their fundamental origins have not been fully addressed yet. This is partly because the interface band profile, which is one of the most basic knowledge to understand the interface electronic states, is still left to be unveiled. In this study, we have investigated in detail the interface band profiles of Mott insulators employing photocurrent and electromodulation spectroscopies as well as the conventional current-voltage and capacitance-voltage characterizations. We chose p -type (LaMn O3 and La 2 Cu O4) and n -type (SrMn O3 and Sm 2 Cu O4) as the Mott insulators and these are epitaxially connected to Nb doped SrTi O3 (electron-doped band insulator). The photocurrent action spectra for these heterojunctions showed negligibly-small band reconstruction as well as the existence of band bending and discontinuity in the Mott insulators, which are of no salient discrepancy with the rigid-band picture valid in the interface of conventional semiconductors~. However, the electromodulation spectra clearly indicate the band reconstruction in the Mott insulators~. The results mean that the rigid-band picture is valid in the low carrier-density regime even in Mott-insulator/band-insulator interfaces, but the intentional charge modulation leads the electron correlation effect in the Mott insulators. This work was done in collaboration with A. Sawa, J. Fujioka, M. Kawasaki and Y. Tokura. I acknowledge the support from Japan Society for the Promotion of Science (JSPS) through its ``Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program)''.

  4. On the accuracy of analyses for in-plane bending of smooth pipe bends with end constraints

    International Nuclear Information System (INIS)

    Thomson, G.; Spence, J.

    1985-01-01

    The accuracy of theoretical analyses for in-plane bending of smooth pipebends with end constraints is discussed and investigated with a view to explaining and reducing the differences between the major works. An earlier theory of the authors is improved to give more accurate answers for bends with rigid flanges. Flanged bends are then examined in some detail, quantifying for the first time the important influence of the flange rigidity on the bend flexibility and stresses. A summary of some finite element analyses is presented from which it is clear that further work is desirable. (orig.)

  5. Statistical mechanics of bend flexoelectricity and the twist-bend phase in bent-core liquid crystals.

    Science.gov (United States)

    Shamid, Shaikh M; Dhakal, Subas; Selinger, Jonathan V

    2013-05-01

    We develop a Landau theory for bend flexoelectricity in liquid crystals of bent-core molecules. In the nematic phase of the model, the bend flexoelectric coefficient increases as we reduce the temperature toward the nematic to polar phase transition. At this critical point, there is a second-order transition from high-temperature uniform nematic phase to low-temperature nonuniform polar phase composed of twist-bend or splay-bend deformations. To test the predictions of Landau theory, we perform Monte Carlo simulations to find the director and polarization configurations as functions of temperature, applied electric field, and interaction parameters.

  6. The effect of cracks on the limit load of pipe bends under in-plane bending

    International Nuclear Information System (INIS)

    Griffiths, J.E.

    1976-06-01

    The limit analysis of the in-plane bending of curved tubes had received attention previously, but the effect of defects in the tube has not been considered. A lower bound has been established which, with no defects present, is in agreement with previous theoretical work. The method of linear programming allows cracks to be introduced into analysis, and results have been obtained for various geometries of defect. The results show that the presence of cracks in the pipe bend can have a marked effect on the theoretical limit load: a part-through crack penetrating only half the wall thickness will reduce the limit moment by up to 10%. The worst possible case of a through-crack may reduce the limit load by 60%. (author)

  7. The effect of cracks on the limit load of pipe bends under in-plane bending

    International Nuclear Information System (INIS)

    Griffiths, J.E.

    1976-06-01

    The limit analysis of the in-plane bending of curved tubes had received attention previously, but the effect of defects in the tube has not been considered. A lower bound is established, which, with no defects present, is in agreement with previous theoretical work. The method of linear programming allows cracks to be introduced into the analysis. and results have been obtained for various geometries of defect. The results show that the presence of cracks in the pipe bend can have a marked effect on the theoretical limit load: a part-through crack penetrating only half the wall thickness will reduce the limit moment by up to 10%. The worst possible case of a through-crack may reduce the limit load by 60% (author)

  8. Theoretical solution for light transmission of a bended hollow light guide

    Energy Technology Data Exchange (ETDEWEB)

    Kocifaj, Miroslav; Darula, Stanislav; Kittler, Richard [ICA, Slovak Academy of Sciences, 9, Dubravska Road, 845 03 Bratislava (Slovakia); Kundracik, Frantisek [Department of Experimental Physics, FMPI, Comenius University, Mlynska dolina, 842 48 Bratislava (Slovakia)

    2010-08-15

    Hollow light guides with very high reflective inner surfaces are novel daylight systems that collect sunlight and skylight available on the roof of buildings transporting it into deep or windowless interiors in building cores. Thus the better utilization of daylight can result in energy savings and wellbeing in these enclosed indoor spaces. An analytical complex solution of a straight tube system was solved in the HOLIGILM method with a user-friendly tool available on the http://www.holigilm.info. An even more difficult light flow transport is to be determined in bended tubes usually placed on sloped roofs where a bend is necessary to adjust the vertical pass through the ceilings. This paper presents the theoretical derivation of the model with its graphical representation and coordinate system respecting backward ray-tracing bend distortions. To imagine the resulting illuminance on the horizontal plane element in the interior, the virtual ray (i.e. luminance in an elementary solid angle) has to pass the ceiling diffuser interface, the inner mirror like tube with a bend, through a roof cupola attachment to the element of the sky and sun light source. Due to this complexity and the lengthy derivation and explanations more practical applications will be published later in a separate contribution. (author)

  9. FEA Simulation of Free-Bending - a Preforming Step in the Hydroforming Process Chain

    Science.gov (United States)

    Beulich, N.; Craighero, P.; Volk, W.

    2017-09-01

    High-strength steel and aluminum alloys are essential for developing innovative, lightly-weighted space frame concepts. The intended design is built from car body parts with high geometrical complexity and reduced material-thickness. Over the past few years, many complex car body parts have been produced using hydroforming. To increase the accuracy of hydroforming in relation to prospective car concepts, the virtual manufacturing of forming becomes more important. As a part of process digitalization, it is necessary to develop a simulation model for the hydroforming process chain. The preforming of longitudinal welded tubes is therefore implemented by the use of three-dimensional free-bending. This technique is able to reproduce complex deflection curves in combination with innovative low-thickness material design for hydroforming processes. As a first step to the complete process simulation, the content of this paper deals with the development of a finite element simulation model for the free-bending process with 6 degrees of freedom. A mandrel built from spherical segments connected by a steel rope is located inside of the tube to prevent geometrical instability. Critical parameters for the result of the bending process are therefore evaluated and optimized. The simulation model is verified by surface measurements of a two-dimensional bending test.

  10. C-band Scatterometers and Their Applications

    OpenAIRE

    Naeimi, Vahid; Wagner, Wolfgang

    2010-01-01

    C-band scatterometers have demonstrated to be valuable sensors for large-scale observation of the Earth's surface in a variety of disciplines. High temporal sampling in all weather conditions, multi-viewing capability and availability of long-term measurements make the European C-band scatterometers excellent Earth observation tools. Scatterometer data are used to extract geophysical parameters such as wind speed and direction, surface soil moisture, seasonal dynamics of vegetation, spatial a...

  11. Technique for determination of elastic limit of micron band-thick amorphous

    International Nuclear Information System (INIS)

    Zakharov, E.K.; Pol'dyaeva, G.P.; Tret'yakov, B.N.

    1984-01-01

    A method is suggested to determine the elastic limit of micron-thick amorphous band under bending. The elastic limit is determined by bending an amorphous band sample around a series of cylindrical mandrels of gradually decreasing radius. Experimental data on measuring the elastic limit of some amorphous iron base alloys according to the suggested technique are presented. The elastic limit of amorphous alloys is shown to lie in the 3140-4110 MPa range depending on chemical composition, which is about 2-2.5 times higher as compared to high-strength crystal alloys

  12. Effects of phosphorus-doping on energy band-gap, structural, surface, and photocatalytic characteristics of emulsion-based sol-gel derived TiO{sub 2} nano-powder

    Energy Technology Data Exchange (ETDEWEB)

    Ganesh, Ibram, E-mail: ibramganesh@arci.res.in

    2017-08-31

    Highlights: • Reported a novel route to synthesize high specific surface area P-doped TiO{sub 2} nano-powder photocatalysts. • Established methylene blue dye-sensitization mechanism of TiO{sub 2} photocatalyst. • Established the effects of methylene blue adsorption on the surface, structural and photocatalytic activity of P-doped TiO{sub 2}. • Established true quantum efficiency determination method for TiO{sub 2} photocatalysis. - Abstract: Different amounts of phosphorus (P)-doped TiO{sub 2} (PDT) nano-powders (P = 0–10 wt.%) were synthesized by following a new emulsion-based sol-gel (EBSG) route and calcined at 400 °C–800 °C for 6 h. These calcined PDT powders were then thoroughly characterized by means of XRD, XPS, SEM, FT-IR, FT-Raman, DRS, BET surface area, zeta-potential, cyclic-voltammetry and photocatalytic evaluation using methylene blue (MB) as a model-pollutant and established the effects of phosphorous doping on structural, surface, band-gap energy, and photocatalytic characteristics of TiO{sub 2} nano-powder formed in EBSG route. The characterization results suggest that the EBSG derived TiO{sub 2} nano-powder after calcination at 400 °C for 6 h is in the form of anatase phase when it was doped with <8 wt.% P, and it is in the amorphous state when doped with >8 wt.% P. Furthermore, these EBSG derived PDT powders own high negative zeta-potentials, high specific surface areas (up to >250 m{sup 2}/g), and suitable band-gap energies (<3.34 eV). Surprisingly, these PDT powders exhibit very high MB adsorption (up to 50%) from its aqueous 0.01 mM, 0.02 mM and 0.03 mM solutions during 30 min stirring in the dark, whereas, the commercial Degussa P-25 TiO{sub 2} nano-powder shows no adsorption. Among various photocatalysts investigated in this study, the 1 wt.% P-doped TiO{sub 2} nano-powder formed in EBSG route exhibited the highest photocatalytic activity for MB degradation reaction.

  13. Effect of Bend Radius on Magnitude and Location of Erosion in S-Bend

    Directory of Open Access Journals (Sweden)

    Quamrul H. Mazumder

    2015-01-01

    Full Text Available Solid particle erosion is a mechanical process that removes material by the impact of solid particles entrained in the flow. Erosion is a leading cause of failure of oil and gas pipelines and fittings in fluid handling industries. Different approaches have been used to control or minimize damage caused by erosion in particulated gas-solid or liquid-solid flows. S-bend geometry is widely used in different fluid handling equipment that may be susceptible to erosion damage. The results of a computational fluid dynamic (CFD simulation of diluted gas-solid and liquid-solid flows in an S-bend are presented in this paper. In addition to particle impact velocity, the bend radius may have significant influence on the magnitude and the location of erosion. CFD analysis was performed at three different air velocities (15.24 m/s–45.72 m/s and three different water velocities (0.1 m/s–10 m/s with entrained solid particles. The particle sizes used in the analysis range between 50 and 300 microns. Maximum erosion was observed in water with 10 m/s, 250-micron particle size, and a ratio of 3.5. The location of maximum erosion was observed in water with 10 m/s, 300-micron particle size, and a ratio of 3.5. Comparison of CFD results with available literature data showed reasonable and good agreement.

  14. Surface preparation of FeS[sub 2] via electrochemical etching and interface formation with metals

    Energy Technology Data Exchange (ETDEWEB)

    Bronold, M. (Abt. Solare Energetik, Hahn-Meitner-Inst. Berlin (Germany)); Bueker, K. (Abt. Solare Energetik, Hahn-Meitner-Inst. Berlin (Germany)); Kubala, S. (Abt. Solare Energetik, Hahn-Meitner-Inst. Berlin (Germany)); Pettenkofer, C. (Abt. Solare Energetik, Hahn-Meitner-Inst. Berlin (Germany)); Tributsch, H. (Abt. Solare Energetik, Hahn-Meitner-Inst. Berlin (Germany))

    1993-01-16

    The effect of passing cathodic currents at potentials of hydrogen evolution through differently pretreated n-type pyrite (FeS[sub 2]) electrodes is studied by XPS. It is shown that hydrogen evolution results in an etching of the crystal via dissolution of FeS[sub 2]. Surfaces that are destroyed through sputtering or polishing are restored through this etching procedure. (100) and (111) surfaces behave similar to each other. When depositing gold onto the electrochemically etched surface in ultrahigh vacuum no change of the band bending of the clean surface (650 meV) is observed. An abrupt interface with FeS-like defects in the pyrite is formed. deposition of platinum yields a ternary Pt-Fe-S interlayer between pyrite and metallic Pt. The band bending is reduced by 200 meV during contact formation. Concerning the chemical composition and the electronic structure the etched surfaces behave nearly identical to clean (100) cleavage planes of pyrite. (orig.)

  15. Investigation of cutting-induced damage in CMC bend bars

    Directory of Open Access Journals (Sweden)

    Neubrand A.

    2015-01-01

    Full Text Available Ceramic matrix composites (“CMC” with a strong fibre-matrix interface can be made damage-tolerant by introducing a highly porous matrix. Such composites typically have only a low interlaminar shear strength, which can potentially promote damage when preparing specimens or components by cutting. In order to investigate the damage induced by different cutting methods, waterjet cutting with and without abrasives, laser-cutting, wire eroding and cutoff grinding were used to cut plates of two different CMCs with a matrix porosity up to 35 vol.-%. For each combination of cutting method and composite, the flexural and interlaminar shear strength of the resulting specimens was determined. Additionally, the integrity of the regions near the cut surfaces was investigated by high-resolution x-ray computer tomography. It could be shown that the geometrical quality of the cut is strongly affected by the cutting method employed. Laser cut and waterjet cut specimens showed damage and delaminations near the cut surface leading to a reduced interlaminar shear strength of short bend bars in extreme cases.

  16. 36 CFR 7.41 - Big Bend National Park.

    Science.gov (United States)

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Big Bend National Park. 7.41 Section 7.41 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.41 Big Bend National Park. (a) Fishing; closed waters...

  17. Kantorovich-Euler Lagrange-Galerkin's method for bending analysis ...

    African Journals Online (AJOL)

    The Euler-Lagrange differential equation is determined for this functional. The Galerkin method is then used to obtain the unknown function f(x). Bending moment curvature relations are used to find the bending moments and their extreme values. The results obtained agree remarkably well with literature. The effectiveness ...

  18. Turbulence characteristics in sharp open-channel bends

    NARCIS (Netherlands)

    Blanckaert, K.; De Vriend, H.J.

    2005-01-01

    In spite of its importance, little is known about the turbulence characteristics in open-channel bends. This paper reports on an experimental investigation of turbulence in one cross section of an open-channel bend. Typical flow features are a bicellular pattern of cross-stream circulation

  19. Anharmonic bend-stretch coupling in neat liquid water

    NARCIS (Netherlands)

    Lindner, Joerg; Cringus, Dan; Pshenichnikov, Maxim S.; Voehringer, Peter

    2007-01-01

    Femtosecond mid-IR spectroscopy is used to study the vibrational relaxation dynamics in neat liquid water. By exciting the bending vibration and probing the stretching mode, it is possible to reliably determine the bending and librational lifetimes of water. The anharmonic coupling between the

  20. Gender differences in variability patterns of forward bending

    DEFF Research Database (Denmark)

    Villumsen, Morten; Madeleine, Pascal; Jørgensen, Marie Birk

    2016-01-01

    The variability pattern is highly relevant in the analysis of occupational physical exposures. It is hypothesized that gender differences exist in the variability pattern of forward bending between work and leisure.......The variability pattern is highly relevant in the analysis of occupational physical exposures. It is hypothesized that gender differences exist in the variability pattern of forward bending between work and leisure....

  1. Pacific plate motion change caused the Hawaiian-Emperor Bend

    NARCIS (Netherlands)

    Torsvik, Trond H.; Doubrovine, Pavel V.; Steinberger, Bernhard; Gaina, Carmen; Spakman, Wim; Domeier, Mathew

    2017-01-01

    A conspicuous 60° bend of the Hawaiian-Emperor Chain in the north-western Pacific Ocean has variously been interpreted as the result of an abrupt Pacific plate motion change in the Eocene (∼47 Ma), a rapid southward drift of the Hawaiian hotspot before the formation of the bend, or a combination of

  2. Deposition of a fine powder in horizontal pipelines and bends

    NARCIS (Netherlands)

    Reuvekamp, RJ; Ray, MB; Hoffmann, AC

    The deposition of a very fine powder in a horizontal, lean-phase pneumatic conveying conduit containing a 90degrees bend has been studied experimentally. The total deposition and the deposition pattern were studied as a function of superficial gas velocity, solids loading and bend geometry: one

  3. Strength Tests on Paper Cylinder in Compression, Bending and Shear

    Science.gov (United States)

    Rhodes, Richard V; Lundquist, Eugene E

    1931-01-01

    Static tests on paper cylinders were conducted at the Langley Memorial Aeronautical Laboratory at Langley Field, Virginia, to obtain qualitative information in connection with a study of the strength of stressed-skin fuselages. The effects of radius-thickness ratio and bulkhead spacing were investigated with the cylinders in compression, bending, combined bending and shear, and torsion.

  4. Rule bending by morally disengaged detectives : an ethnographic study

    NARCIS (Netherlands)

    Loyens, Kim

    2014-01-01

    Rule bending is a well-known practice in policing worldwide, often linked to 'noble cause corruption'. This ethnographic study shows how police detectives sometimes consider to creatively bend rules when rule abidance would lead to other values being jeopardized. This paper illustrates that the

  5. Disk-bend ductility tests for irradiated materials

    International Nuclear Information System (INIS)

    Klueh, R.L.; Braski, D.N.

    1984-01-01

    We modified the HEDL disk-bend test machine and are using it to qualitatively screen alloys that are susceptible to embrittlement caused by irradiation. Tests designed to understand the disk-bend test in relation to a uniaxial test are discussed. Selected results of tests of neutron-irradiated material are also presented

  6. Effect of Channel Bends on Transverse Mixing | Engmann | Nigerian ...

    African Journals Online (AJOL)

    Velocity and tracer concentration measurements made in a meandering channel are used to discuss the effect of bends on the transverse mixing of a conservative tracer introduced into the flow. It is shown that bend induced spiral motion greatly enhance the mixing potential of meandering channel flows; The magnitude of ...

  7. A rotary ultrasonic motor using bending vibration transducers.

    Science.gov (United States)

    Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

    2010-10-01

    A rotary ultrasonic motor using bending vibration transducers is proposed. In each transducer, two orthogonal bending vibrations are superimposed and an elliptical trajectory is generated at the driving foot. Typical output of the prototype is a no-load speed of 58 rpm and maximum torque of 9·5 Nm under an exciting voltage of 200 V(rms).

  8. Effect of membrane and through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity

    International Nuclear Information System (INIS)

    Yoo, Yeon-Sik

    2003-11-01

    This study clarified the effect of a membrane and a through-wall bending stresses on fatigue crack growth behavior and coolant leakage velocity due to irregularity of crack surface. Each stress component relates to fatigue crack growth behavior directly in general and thus the wild-used K I solutions are anticipated to give good evaluation results on it. Meanwhile, it is necessary to notify that surface irregularity for coolant leakage assessment is made by stress history in nature. Surface irregularity is known to be largely classified into the following two aspects: surface roughness due to continuous crack opening and closure behavior and surface turnover due to cyclic bending stress dominance. Therefore, the deterministic parameters on resistance of coolant leakage by surface irregularity are considered to be not only stress history but crack opening behavior. (author)

  9. Ondes de surface transverses sur plaques piézoélectriques avec réseaux de bandes metalliques déposés sur les 2 faces

    Science.gov (United States)

    Ballandras, S.; Gavignet, E.; Bigler, E.

    1995-09-01

    A theoretical model has been implemented to study surface transverse waves propagating on piezoelectric plates of finite thickness with thin metal strip gratings on both sides. Calculations have been performed for AT-cuts of quartz of thickness varying from 140 to 120 μm. The spatial period of the gratings was fixed to 20 μm (acoustic wavelength equal to 40 μm). The dispersion curve relating the angular frequency to the wavenumber presents more than one stopband as found in the usual analyses on semi-infinite substrates. These multiple high-frequency stopbands allow to design and realize high stability resonators or highly sensitive sensors for gravimetry, accelerometer applications, etc. Un modèle théorique a été mis en œuvre pour l'étude des propriétés des ondes de surface transverses se propageant sur des plaques piézoélectriques d'épaisseur finie avec des réseaux de fines bandes métalliques déposés sur chaque face. Les calculs ont été effectués pour des plaques de quartz voisines de la coupe AT et d'épaisseur variant de 140 à 120 μm. La périodicité des réseaux en regard a été fixée à 20 μm (longueur d'onde acoustique 40 μm). La courbe de dispersion reliant la pulsation au nombre d'ondes présente plusieurs bandes d'arrêt incluant celle habituellement mise en évidence pour un substrat semi-infini. L'existence de ces multiples bandes d'arrêt haute fréquence ouvre de nouvelles perspectives pour la réalisation de résonateurs ultrastables ou de capteurs de très grande sensibilité gravimétrique, accélérométrique, etc.

  10. Mechanical properties of different esthetic and conventional orthodontic wires in bending tests : An in vitro study.

    Science.gov (United States)

    Alobeid, Ahmad; Dirk, Cornelius; Reimann, Susanne; El-Bialy, Tarek; Jäger, Andreas; Bourauel, Christoph

    2017-05-01

    The goal of this study was to determine the mechanical properties of different esthetic and conventional orthodontic wires in three-point and four-point bending tests, and in a biomechanical test employing three bracket systems. The behavior of round wires with a diameter of 0.46 mm (0.018″) were investigated: uncoated nickel titanium (NiTi) wires, surface modified NiTi wires; FLI ® Orthonol Wire ® and glass fiber reinforced plastic wires. The biomechanical bending test was performed using the following bracket types: metal brackets (Discovery ® , Dentaurum), ceramic brackets (Fascination ® , Dentaurum), and plastic brackets (Elegance ® , Dentaurum). All bending tests were performed in the orthodontic measurement and simulation system (OMSS) at a temperature of 37 °C. The classical three-point bending test was performed according to an ISO standard (DIN EN ISO 15841:2007) using the appropriate thrust die and supports with a predefined span of 10 mm. In the other tests the supports or interbracket distances were chosen such that the free wire length was also 10 mm (5 mm between adjacent brackets). All wires were loaded centrally to a maximum of 3.1 and 3.3 mm in the biomechanical test, respectively. The force was measured upon unloading with a loading velocity of 1 mm/min. Each specimen was loaded twice and a total of 10 specimens tested for each product. Weighted means and the error of the weighted mean were calculated for each product. Fiber reinforced wires displayed lowest forces in three-point bending with values of 0.4 N at a displacement of 1 mm and 0.7 N at a 2 mm displacement. In four-point bending the forces were 0.9 N and 1.4 N, respectively, at the same displacements. Almost all of the translucent wires showed fracture upon bending at displacements greater than 3 mm, independent of the bending test and bracket type. The different investigated NiTi wires, surface modified or conventional, only showed minor variation, e.g., 2.2 N for

  11. A bend thickness sensitivity study of Candu feeder piping

    International Nuclear Information System (INIS)

    Li, M.; Aggarwal, M.L.; Meysner, A.; Micelotta, C.

    2005-01-01

    In CANDU reactors, feeder bends close to the connection at the fuel channel may be subjected to the highest Flow Accelerated Corrosion (FAC) and stresses. Feeder pipe stress analysis is crucial in the life extension of aging CANDU plants. Typical feeder pipes are interconnected by upper link plates and spacers. It is well known that the stresses at the bends are sensitive to the local bend thicknesses. It is also known from the authors' study (Li and et al, 2005) that feeder inter linkage effect is significant and cannot be ignored. The field measurement of feeder bend thickness is difficult and may be subjected to uncertainty in accuracy. Hence, it is desirable to know how the stress on a subject feeder could be affected by the bend thickness variation of the neighboring feeders. This effect cannot be evaluated by the traditional 'single' feeder model approach. In this paper, the 'row' and 'combined' models developed in the previous study (Li and et al, 2005), which include the feeder interactions, are used to investigate the sensitivity of bend thickness. A series of random thickness bounded by maximum and minimum measured values were applied to feeders in the model. The results show that an individual feeder is not sensitive to the bend thickness variation of the remaining feeders in the model, but depends primarily on its own bend thickness. The highest stress at a feeder always occurs when the feeder has the smallest possible bend thickness. A minimum acceptable bend thickness for individual feeders can be computed by an iterative computing process. The dependency of field thickness measurement and the amount of required analysis work can be greatly reduced. (authors)

  12. Compact Penta-Band Dual ZOR Antenna for Mobile Applications

    Directory of Open Access Journals (Sweden)

    Jae-Gon Lee

    2016-01-01

    Full Text Available A compact penta-band dual zeroth order resonator (ZOR antenna with band-stop filter is proposed for mobile applications. The ZOR antenna is designed with modified mushroom-like structures extended on nonground region to obtain good efficiency and broad bandwidth. This modified mushroom-like structure is confirmed as double negative (DNG transmission line by full wave simulated dispersion relation. Moreover, a bended patch and a band-stop filter (BSF are employed to increase efficiency and bandwidth, respectively. The length of each antenna is about λ0/10 at the resonant frequencies of 900 MHz and 1800 MHz, respectively. The overall dimension of the antenna is 54.4 mm (length × 4 mm (width × 5 mm (height. The total efficiencies in low and high bands are measured more than 40% and 70%, respectively.

  13. 75 FR 71666 - Bend/Ft. Rock Ranger District; Deschutes National Forest; Deschutes County, OR; West Bend...

    Science.gov (United States)

    2010-11-24

    ...; Deschutes County, OR; West Bend Vegetation Management Project EIS AGENCY: Forest Service, USDA. ACTION... INFORMATION: Background. Forested vegetation within the West Bend project area is outside of the Historic... they have the potential to remove important habitat structure, particularly large trees that are...

  14. Piezoelectric Pre-Stressed Bending Mechanism for Impact-Driven Energy Harvester

    Science.gov (United States)

    Abdal, A. M.; Leong, K. S.

    2017-06-01

    This paper experimentally demonstrates and evaluates a piezoelectric power generator bending mechanism based on pre-stressed condition whereby the piezoelectric transducer being bended and remained in the stressed condition before applying a force on the piezoelectric bending structure, which increase the stress on the piezoelectric surface and hence increase the generated electrical charges. An impact force is being exerted onto bending the piezoelectric beam and hence generating electrical power across an external resistive load. The proposed bending mechanism prototype has been manufactured by employing 3D printer technology in order to conduct the evaluation. A free fall test has been conducted as the evaluation method with varying force using a series of different masses and different fall heights. A rectangular piezoelectric harvester beam with the size of 32mm in width, 70mm in length, and 0.55mm in thickness is used to demonstrate the experiment. It can be seen from the experiment that the instantaneous peak to peak AC volt output measured at open-circuit is increasing and saturated at about of 70V when an impact force of about 80N is being applied. It is also found that a maximum power of about 53mW is generated at an impact force of 50N when it is connected to an external resistive load of 0.7KΩ. The reported mechanism is a promising candidate in the application of energy harvesting for powering various wireless sensor nodes (WSN) which is the core of Internet of Things (IoT).

  15. Generation of a bending angle radio occultation climatology (BAROCLIM) and its use in radio occultation retrievals

    Science.gov (United States)

    Scherllin-Pirscher, B.; Syndergaard, S.; Foelsche, U.; Lauritsen, K. B.

    2015-01-01

    In this paper, we introduce a bending angle radio occultation climatology (BAROCLIM) based on Formosat-3/COSMIC (F3C) data. This climatology represents the monthly-mean atmospheric state from 2006 to 2012. Bending angles from radio occultation (RO) measurements are obtained from the accumulation of the change in the raypath direction of Global Positioning System (GPS) signals. Best quality of these near-vertical profiles is found from the middle troposphere up to the mesosphere. Beside RO bending angles we also use data from the Mass Spectrometer and Incoherent Scatter Radar (MSIS) model (modified for RO purposes) to expand BAROCLIM in a spectral model, which (theoretically) reaches from the surface up to infinity. Due to the very high quality of BAROCLIM up to the mesosphere, it can be used to detect deficiencies in current state-of-the-art analysis and reanalysis products from numerical weather prediction (NWP) centers. For bending angles derived from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis fields from 2006 to 2012, e.g., we find a positive bias of 0.5 to 1% at 40 km, which increases to more than 2% at 50 km. BAROCLIM can also be used as a priori information in RO profile retrievals. In contrast to other a priori information (i.e., MSIS) we find that the use of BAROCLIM better preserves the mean of raw RO measurements. Global statistics of statistically optimized bending angle and refractivity profiles also confirm that BAROCLIM outperforms MSIS. These results clearly demonstrate the utility of BAROCLIM.

  16. Bending fluidic actuator for smart structures

    Science.gov (United States)

    Che-Ming Chang, Benjamin; Berring, John; Venkataram, Manu; Menon, Carlo; Parameswaran, M.

    2011-03-01

    This paper presents a novel silicone-based, millimeter-scale, bending fluidic actuator (BFA). Its unique parallel micro-channel design enables, for the first time, operation at low working pressure while at the same time having a very limited thickness expansion during pressurization. It also enables the actuator to have the highest ratios of angular displacement over length and torque over volume among previously proposed BFAs. In this work, this parallel micro-channel design is implemented by embedding the BFA with an innovative single winding conduit, which yields a simple, single-component configuration suitable for low-cost production and reliable performance. The BFA design can be easily scaled down to smaller dimensions and can be adapted to applications in restricted space, particularly minimally invasive surgery. In this work, the actuator is manufactured in TC-silicone through poly(methyl methacrylate) molds obtained by using laser cutting technology. Repeated angular displacement measurements on multiple prototypes having different stiffness are carried out. The experimental results are compared with an analytical model, which accurately predicts the performance of the device.

  17. Oxides Surfaces and Novel Electronic Properties

    Science.gov (United States)

    Koirala, Pratik

    The scope of this thesis extends to the study of surface structures and electronic properties in a number of complex oxides. The c(6x2) surface reconstruction on SrTiO3 (001) was solved using a combination of plan view transmission electron microscopy imaging, atomic resolution secondary electron imaging, and density functional theory calculations. This work provided fundamental insights on the effects of dielectric screening in secondary electron generation. A thorough analysis on the limitation and functionality of transmission plan view imaging showed that the kinematical approximations used in the separation of top and bottom surfaces is only valid in thin samples (˜5 nm or less for SrTiO3). The presence of an inversion center in the surface structure also made separation of the top and bottom surfaces more robust. Surface studies of two other oxides, KTaO3 and NdGaO3, provided understanding on the mechanism of surface heterogeneity and segregation. In the case of KTaO3, selective ion sputtering and the loss of K resulted in large stoichiometric variations at the surface. Annealing of such samples led to the formation of a potassium deficient tetragonal phase (K 6Ta10.8O30) on the surface. A similar phenomenon was also observed in NdGaO3. Exploratory surface studies of the rare earth scandates (ReScO3 , Re = Gd, Tb, Dy) led to the observation of large flexoelectric bending inside an electron microscope. Thin rods of these scandates bent by up to 90 degree under a focused electron beam; the bending was fully reversible. Ex-situ measurements of flexoelectric coe cient performed by an- other graduate student, Christopher Mizzi, confirmed that the scandates have a large flexocoupling voltage (˜42 V). Electronic structure of the lanthanide scandates was studied using temperature depen- dent X-ray photoelectron spectroscopy and hybrid density functional theory calculations. The amount of charging under X-ray illumination was greatly reduced with increasing

  18. Effects of tanalith-e impregnation substance on bending strengths and modulus of elasticity in bending of some wood types

    Directory of Open Access Journals (Sweden)

    Hakan Keskin

    2016-04-01

    Full Text Available The aim of this study was to investigate the effects of impregnation with Tanalith-E on the bending strengths and modulus of elasticity in bending of some wood types. The test samples prepared from beech, oak, walnut, poplar, ash and pine wood materials - that are of common use in the forest products industry of TURKEY - according to TS 345, were treated with according to ASTM D 1413-76 substantially. Un-impregnated samples according to impregnated wood materials, the bending strengths in beech to 6.83%, 5.12% in ash, 5.93% in pine, the elasticity module values to 7.15% in oak and ash, at a rate of 6.58% in the higher were found. The highest values of bending strengths and modulus of elasticity in bending were obtained in beech and ash woods impregnated with Tanalith-E, whereas the lowest values were obtained in the poplar wood.

  19. Weyl nodal surfaces

    Science.gov (United States)

    Türker, Oǧuz; Moroz, Sergej

    2018-02-01

    We consider three-dimensional fermionic band theories that exhibit Weyl nodal surfaces defined as two-band degeneracies that form closed surfaces in the Brillouin zone. We demonstrate that topology ensures robustness of these objects under small perturbations of a Hamiltonian. This topological robustness is illustrated in several four-band models that exhibit nodal surfaces protected by unitary or antiunitary symmetries. Surface states and Nielsen-Ninomiya doubling of nodal surfaces are also investigated.

  20. Line Mixing in Parallel and Perpendicular Bands of CO2: A Further Test of the Refined Robert-Bonamy Formalism

    Science.gov (United States)

    Boulet, C.; Ma, Qiancheng; Tipping, R. H.

    2015-01-01

    Starting from the refined Robert-Bonamy formalism [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)], we propose here an extension of line mixing studies to infrared absorptions of linear polyatomic molecules having stretching and bending modes. The present formalism does not neglect the internal degrees of freedom of the perturbing molecules, contrary to the energy corrected sudden (ECS) modeling, and enables one to calculate the whole relaxation matrix starting from the potential energy surface. Meanwhile, similar to the ECS modeling, the present formalism properly accounts for roles played by all the internal angular momenta in the coupling process, including the vibrational angular momentum. The formalism has been applied to the important case of CO2 broadened by N2. Applications to two kinds of vibrational bands (sigma yields sigma and sigma yields pi) have shown that the present results are in good agreement with both experimental data and results derived from the ECS model.

  1. Behavior of sandwich panels subjected to bending fatigue, axial compression loading and in-plane bending

    Science.gov (United States)

    Mathieson, Haley Aaron

    This thesis investigates experimentally and analytically the structural performance of sandwich panels composed of glass fibre reinforced polymer (GFRP) skins and a soft polyurethane foam core, with or without thin GFRP ribs connecting skins. The study includes three main components: (a) out-of-plane bending fatigue, (b) axial compression loading, and (c) in-plane bending of sandwich beams. Fatigue studies included 28 specimens and looked into establishing service life (S-N) curves of sandwich panels without ribs, governed by soft core shear failure and also ribbed panels governed by failure at the rib-skin junction. Additionally, the study compared fatigue life curves of sandwich panels loaded under fully reversed bending conditions (R=-1) with panels cyclically loaded in one direction only (R=0) and established the stiffness degradation characteristics throughout their fatigue life. Mathematical models expressing fatigue life and stiffness degradation curves were calibrated and expanded forms for various loading ratios were developed. Approximate fatigue thresholds of 37% and 23% were determined for non-ribbed panels loaded at R=0 and -1, respectively. Digital imaging techniques showed significant shear contribution significantly (90%) to deflections if no ribs used. Axial loading work included 51 specimens and examined the behavior of panels of various lengths (slenderness ratios), skin thicknesses, and also panels of similar length with various rib configurations. Observed failure modes governing were global buckling, skin wrinkling or skin crushing. In-plane bending involved testing 18 sandwich beams of various shear span-to-depth ratios and skin thicknesses, which failed by skin wrinkling at the compression side. The analytical modeling components of axially loaded panels include; a simple design-oriented analytical failure model and a robust non-linear model capable of predicting the full load-displacement response of axially loaded slender sandwich panels

  2. Residual stresses in U-bending deformations and expansion joints of heat exchanger tubes

    International Nuclear Information System (INIS)

    Kim, Woo Gon; Kim, Sun Jae; Jang, Jin Sung; Kuk, Ii Hiun; Bae, Kang Gug; Kim, Sung Chung

    2000-01-01

    Residual stress induced in U-bending and tube-to-tubesheet joint processes of PWR's rew-1 heat exchanger tube was measured by X-ray method and Hole-Drilling Method(HDM). Compressive residual stresses(-) at the extrados surface were induced in U-bending, and its maximum value reached -319MPa in axial direction at the position of ψ=0 deg. Tensile residual stresses (+) of 0σ zz =45 MPa and σ θθ =25MPa were introduced in the intrados surface at the position of ψ=0 deg. Maximum tensile residual stress of 170 MPa was measured at the flank side at the position of ψ=90 deg, i.e., at apex region. It was observed that higher stress gradient was generated at the irregular transition regions (ITR). The trend of residual stress induced by U-bending process of the tubes was found to be related with the change of ovality. The residual stress induced by the explosive joint method was found to be lower than that by the mechanical roll method. The gradient of residual stress along the expanded tube was highest at the transition region (TR), and the residual stress in circumferential direction was found to be higher than the residual stress in axial direction

  3. Creep relaxation of fuel pin bending and ovalling stresses

    International Nuclear Information System (INIS)

    Chan, D.P.; Jackson, R.J.

    1979-06-01

    Analytical methods for calculating fuel pin cladding bending and ovalling stresses due to pin bundle-duct mechanical interaction taking into account nonlinear creep are presented. Calculated results are in close agreement with finite element results by MARC-CDC program. The methods are used to investigate the effect of creep on the FTR fuel cladding bending and ovalling stresses. It is concluded that the cladding of 316 SS 20% CW and reference design has high creep rates in the FTR core region to keep the bending and ovalling stresses to low levels

  4. Investigation of ion induced bending mechanism for nanostructures

    Science.gov (United States)

    Rajput, Nitul S.; Tong, Zhen; Luo, Xichun

    2015-01-01

    Ion induced bending is a promising controlled technique for manipulating nanoscale structures. However, the underlying mechanism of the process is not well understood. In this letter, we report a detailed study of the bending mechanism of Si nanowires (NWs) under Ga+ irradiation. The microstructural changes in the NW due to ion beam irradiation are studied and molecular dynamics simulations are used to explore the ion-NW interaction processes. The simulation results are compared with the microstructural studies of the NW. The investigations inform a generic understanding of the bending process in crystalline materials, which we suggest to be feasible as a versatile manipulation and integration technique in nanotechnology.

  5. S-bend erosion in particulated multiphase flow with air and sand

    Directory of Open Access Journals (Sweden)

    Quamrul H Mazumder

    2016-09-01

    Full Text Available Solid particle erosion is a micro-mechanical process that removes material from a surface by repeated impact of entrained particles in the flow. Erosion is a leading cause of failure in fluid handling equipment such as pumps, pipes, valves, and fittings. The S-bend geometry is used to redirect flows in automotive, chemical processing, oil, gas, and food handling industries. An investigation was conducted using both computational fluid dynamics analysis and experimental methods to identify the location of maximum erosion. Three S-bend geometries with 12.7 mm inside diameter, r/D ratio of 1.5, three different air velocities and six different particle sizes were used in the current study. The experimental test section was of 12.7 mm inside diameter, r/D ratio of 1.5, and used 150 and 300 µm particle sizes.

  6. Bending, Vibration and Buckling of Laminated Composite Plates Using a Simple Four Variable Plate Theory

    Directory of Open Access Journals (Sweden)

    Atteshamuddin S. Sayyad

    Full Text Available Abstract In the present study, a simple trigonometric shear deformation theory is applied for the bending, buckling and free vibration of cross-ply laminated composite plates. The theory involves four unknown variables which are five in first order shear deformation theory or any other higher order theories. The in-plane displacement field uses sinusoidal function in terms of thickness co-ordinate to include the shear deformation effect. The transverse displacement includes bending and shear components. The present theory satisfies the zero shear stress conditions at top and bottom surfaces of plates without using shear correction factor. Equations of motion associated with the present theory are obtained using the dynamic version of virtual work principle. A closed form solution is obtained using double trigonometric series suggested by Navier. The displacements, stresses, critical buckling loads and natural frequencies obtained using present theory are compared with previously published results and found to agree well with those.

  7. Effect of torsion moment on failure bending moment for circumferentially cracked pipe

    International Nuclear Information System (INIS)

    Li, Yinsheng; Hasegawa, Kunio; Ida, Wataru; Hoang, Phuong H.; Bezensek, Bostjan

    2010-01-01

    When a crack is detected in a stainless steel pipe during in-service inspection, the limit load criterion given in the codes such as JSME Rules on Fitness-for-Service for Nuclear Power Plants or ASME Boiler and Pressure Vessel Code Section XI can be applied to evaluate the integrity of the pipe. However, in the current codes, the limit load criterion is only provided considering pressure and bending moment. The torsion moment is not considered, although torsion moment does exist in the nuclear power piping system. In this paper, finite element analyses are carried out for stainless steel pipe containing a circumferential surface crack under the combination of bending moment and torsion moment, considering different pipe dimensions and flaw sizes. Based upon the analysis results, a plastic collapse estimation method is proposed considering the existence of the torsion moment and its magnitude, and this method make it possible to evaluate the integrity of the pipe for general loading conditions. (author)

  8. Downhole instrument including a flexible probe which can travel freely around bends in a borehole

    International Nuclear Information System (INIS)

    Dickinson III, B. W. O.

    1985-01-01

    Bore hole instrument and methods of manufacturing and using the same. The instrument includes an elongated flexible probe which is inserted into a bore hole and can travel freely around bends of relatively short radius in the hole. The probe includes a plurality of sensors, explosive charges or the like which are spaced apart and embedded in a flexible body comprising a mass of cushioning material, with a flexible outer casing of fabric having a high tensile strength. The probe is driven into a bore hole in piston-like fashion, and the flexible body enables the probe to travel freely around bends of relatively short radius. Instrumentation for processing signals from the probe is located at the surface of the earth, and a flexible cable interconnects the instrumentation with the probe

  9. Wide Band to ''Double Band'' upgrade

    International Nuclear Information System (INIS)

    Kasper, P.; Currier, R.; Garbincius, P.; Butler, J.

    1988-06-01

    The Wide Band beam currently uses electrons obtained from secondary photon conversions to produce the photon beam incident on the experimental targets. By transporting the positrons produced in these conversions as well as the electrons it is possible to almost double the number of photons delivered to the experiments per primary beam proton. 11 figs

  10. Complex layered materials and periodic electromagnetic band-gap structures: Concepts, characterizations, and applications

    Science.gov (United States)

    Mosallaei, Hossein

    The main objective of this dissertation is to characterize and create insight into the electromagnetic performances of two classes of composite structures, namely, complex multi-layered media and periodic Electromagnetic Band-Gap (EBG) structures. The advanced and diversified computational techniques are applied to obtain their unique propagation characteristics and integrate the results into some novel applications. In the first part of this dissertation, the vector wave solution of Maxwell's equations is integrated with the Genetic Algorithm (GA) optimization method to provide a powerful technique for characterizing multi-layered materials, and obtaining their optimal designs. The developed method is successfully applied to determine the optimal composite coatings for Radar Cross Section (RCS) reduction of canonical structures. Both monostatic and bistatic scatterings are explored. A GA with hybrid planar/curved surface implementation is also introduced to efficiently obtain the optimal absorbing materials for curved structures. Furthermore, design optimization of the non-uniform Luneburg and 2-shell spherical lens antennas utilizing modal solution/GA-adaptive-cost function is presented. The lens antennas are effectively optimized for both high gain and suppressed grating lobes. The second part demonstrates the development of an advanced computational engine, which accurately computes the broadband characteristics of challenging periodic electromagnetic band-gap structures. This method utilizes the Finite Difference Time Domain (FDTD) technique with Periodic Boundary Condition/Perfectly Matched Layer (PBC/PML), which is efficiently integrated with the Prony scheme. The computational technique is successfully applied to characterize and present the unique propagation performances of different classes of periodic structures such as Frequency Selective Surfaces (FSS), Photonic Band-Gap (PBG) materials, and Left-Handed (LH) composite media. The results are

  11. Spectral band selection for classification of soil organic matter content

    Science.gov (United States)

    Henderson, Tracey L.; Szilagyi, Andrea; Baumgardner, Marion F.; Chen, Chih-Chien Thomas; Landgrebe, David A.

    1989-01-01

    This paper describes the spectral-band-selection (SBS) algorithm of Chen and Landgrebe (1987, 1988, and 1989) and uses the algorithm to classify the organic matter content in the earth's surface soil. The effectiveness of the algorithm was evaluated comparing the results of classification of the soil organic matter using SBS bands with those obtained using Landsat MSS bands and TM bands, showing that the algorithm was successful in finding important spectral bands for classification of organic matter content. Using the calculated bands, the probabilities of correct classification for climate-stratified data were found to range from 0.910 to 0.980.

  12. Advantages of customer/supplier involvement in the upgrade of River Bend`s IST program

    Energy Technology Data Exchange (ETDEWEB)

    Womack, R.L.; Addison, J.A.

    1996-12-01

    At River Bend Station, IST testing had problems. Operations could not perform the test with the required repeatability; engineering could not reliably trend test data to detect degradation; licensing was heavily burdened with regulatory concerns; and maintenance could not do preventative maintenance because of poor prediction of system health status. Using Energy`s Total Quality principles, it was determined that the causes were: lack of ownership, inadequate test equipment usage, lack of adequate procedures, and lack of program maintenance. After identifying the customers and suppliers of the IST program data, Energy management put together an upgrade team to address these concerns. These customers and suppliers made up the IST upgrade team. The team`s mission was to supply River Bend with a reliable, functional, industry correct and user friendly IST program. The IST program in place went through a verification process that identified and corrected over 400 individual program discrepancies. Over 200 components were identified for improved testing methods. An IST basis document was developed. The operations department was trained on ASME Section XI testing. All IST tests have been simplified and shortened, due to heavy involvement by operations in the procedure development process. This significantly reduced testing time, resulting in lower cost, less dose and greater system availability.

  13. Isotropic band gaps and freeform waveguides observed in hyperuniform disordered photonic solids.

    Science.gov (United States)

    Man, Weining; Florescu, Marian; Williamson, Eric Paul; He, Yingquan; Hashemizad, Seyed Reza; Leung, Brian Y C; Liner, Devin Robert; Torquato, Salvatore; Chaikin, Paul M; Steinhardt, Paul J

    2013-10-01

    Recently, disordered photonic media and random textured surfaces have attracted increasing attention as strong light diffusers with broadband and wide-angle properties. We report the experimental realization of an isotropic complete photonic band gap (PBG) in a 2D disordered dielectric structure. This structure is designed by a constrained optimization method, which combines advantages of both isotropy due to disorder and controlled scattering properties due to low-density fluctuations (hyperuniformity) and uniform local topology. Our experiments use a modular design composed of Al2O3 walls and cylinders arranged in a hyperuniform disordered network. We observe a complete PBG in the microwave region, in good agreement with theoretical simulations, and show that the intrinsic isotropy of this unique class of PBG materials enables remarkable design freedom, including the realization of waveguides with arbitrary bending angles impossible in photonic crystals. This experimental verification of a complete PBG and realization of functional defects in this unique class of materials demonstrate their potential as building blocks for precise manipulation of photons in planar optical microcircuits and has implications for disordered acoustic and electronic band gap materials.

  14. Additive manufacturing and mechanical characterization of graded porosity scaffolds designed based on triply periodic minimal surface architectures.

    Science.gov (United States)

    Afshar, M; Anaraki, A Pourkamali; Montazerian, H; Kadkhodapour, J

    2016-09-01

    Since the advent of additive manufacturing techniques, triply periodic minimal surfaces have emerged as a novel tool for designing porous scaffolds. Whereas scaffolds are expected to provide multifunctional performance, spatially changing pore patterns have been a promising approach to integrate mechanical characteristics of different architectures into a unique scaffold. Smooth morphological variations are also frequently seen in nature particularly in bone and cartilage structures and can be inspiring for designing of artificial tissues. In this study, we carried out experimental and numerical procedures to uncover the mechanical properties and deformation mechanisms of linearly graded porosity scaffolds for two different mathematically defined pore structures. Among TPMS-based scaffolds, P and D surfaces were subjected to gradient modeling to explore the mechanical responses for stretching and bending dominated deformations, respectively. Moreover, the results were compared to their corresponding uniform porosity structures. Mechanical properties were found to be by far greater for the stretching dominated structure (P-Surface). For bending dominated architecture (D-Surface), although there was no global fracture for uniform structures, graded structure showed a brittle fracture at 0.08 strain. A layer by layer deformation mechanism for stretching dominated structure was observed. For bending dominated scaffolds, deformation was accompanied by development of 45° shearing bands. Finite element simulations were also performed and the results showed a good agreement with the experimental observations. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. In situ bend testing of niobium-reinforced alumina nanocomposites with and without single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Thomson, Katherine E.; Jiang Dongtao; Lemberg, Joseph A.; Koester, Kurt J.; Ritchie, Robert O.; Mukherjee, Amiya K.

    2008-01-01

    Alumina-based nanocomposites were fabricated and consolidated via spark plasma sintering. The effect of single-walled carbon nanotube (SWCNT) and niobium additions to nanocrystalline alumina was examined by in situ bend testing. The addition of 10 vol.% niobium to nanocrystalline alumina provided substantial improvement of fracture toughness (6.1 MPa m 1/2 )-almost three times that of nanocrystalline alumina. Observation of cracks emanating from Vickers indents, as well as bend specimen fracture surfaces, reveal the operation of ductile phase toughening in the Nb-Al 2 O 3 nanocomposites. Further addition of 5 vol.% SWCNTs to the 10 vol.%Nb-Al 2 O 3 revealed a more porous structure and less impressive fracture toughness-having an indentation and bend fracture toughness of 2.9 MPa m 1/2 and 3.3 MPa m 1/2 , respectively

  16. An analytical study on the bending of prismatic SMA beams

    International Nuclear Information System (INIS)

    Ostadrahimi, Alireza; Arghavani, Jamal; Poorasadion, Saeid

    2015-01-01

    In this study, an analytical solution is presented for pure bending of shape memory alloy (SMA) beams with symmetric cross section as well as symmetric behavior in tension and compression. To this end, a three-dimensional constitutive equation is reduced to one-dimensional form and employed to study the bending response of SMA beams at high (pseudo-elasticity) and low (shape memory effect) temperatures. An analytical expression for bending stress as well as polynomial approximation for shear stress and deflection are obtained. Derived equations for bending are employed to analyze an SMA beam with rectangular cross section and results are compared with those of the finite element method. The results of this work show good agreement when compared with experimental data and finite element results. Furthermore, the existence of several zero-stress fibers during unloading of SMA beams at low temperature is demonstrated. (paper)

  17. Effect of centrifugal transverse wakefield for microbunch in bend

    International Nuclear Information System (INIS)

    Stupakov, G.V.

    1999-01-01

    We calculate centrifugal force for a short bunch in vacuum moving in a circular orbit and estimate the emittance growth of the beam in a bend due to this force. copyright 1999 American Institute of Physics

  18. Computational Strategies for the Architectural Design of Bending Active Structures

    DEFF Research Database (Denmark)

    Tamke, Martin; Nicholas, Paul

    2013-01-01

    Active bending introduces a new level of integration into the design of architectural structures, and opens up new complexities for the architectural design process. In particular, the introduction of material variation reconfigures the design space. Through the precise specification...... of their stiffness, it is possible to control and pre-calibrate the bending behaviour of a composite element. This material capacity challenges architecture’s existing methods for design, specification and prediction. In this paper, we demonstrate how architects might connect the designed nature of composites...... with the design of bending-active structures, through computational strategies. We report three built structures that develop architecturally oriented design methods for bending-active systems using composite materials. These projects demonstrate the application and limits of the introduction of advanced...

  19. Magnetically Assisted Bilayer Composites for Soft Bending Actuators

    Science.gov (United States)

    Jang, Sung-Hwan; Na, Seon-Hong; Park, Yong-Lae

    2017-01-01

    This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics. PMID:28773007

  20. Magnetically Assisted Bilayer Composites for Soft Bending Actuators

    Directory of Open Access Journals (Sweden)

    Sung-Hwan Jang

    2017-06-01

    Full Text Available This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward one side of the structure. The nonhomogeneous distribution of the particles induces bending of the structure when inflated, as a result of asymmetric stiffness of the composite. The bilayer composites were then characterized with a scanning electron microscopy and thermogravimetric analysis. The bending performance and the axial expansion of the actuator were discussed for manipulation applications in soft robotics and bioengineering. The magnetically assisted manufacturing process for the soft bending actuator is a promising technique for various applications in soft robotics.

  1. Low Cycle Fatigue of Steel in Strain Controled Cyclic Bending

    Directory of Open Access Journals (Sweden)

    Kulesa Anna

    2016-03-01

    Full Text Available The paper presents a comparison of the fatigue life curves based on test of 15Mo3 steel under cyclic, pendulum bending and tension-compression. These studies were analyzed in terms of a large and small number of cycles where strain amplitude is dependent on the fatigue life. It has been shown that commonly used Manson-Coffin-Basquin model cannot be used for tests under cyclic bending due to the impossibility of separating elastic and plastic strains. For this purpose, some well-known models of Langer and Kandil and one new model of authors, where strain amplitude is dependent on the number of cycles, were proposed. Comparing the results of bending with tension-compression it was shown that for smaller strain amplitudes the fatigue life for both test methods were similar, for higher strain amplitudes fatigue life for bending tests was greater than for tension-compression.

  2. Computational Strategies for the Architectural Design of Bending Active Structures

    DEFF Research Database (Denmark)

    Tamke, Martin; Nicholas, Paul

    2013-01-01

    with the design of bending-active structures, through computational strategies. We report three built structures that develop architecturally oriented design methods for bending-active systems using composite materials. These projects demonstrate the application and limits of the introduction of advanced......Active bending introduces a new level of integration into the design of architectural structures, and opens up new complexities for the architectural design process. In particular, the introduction of material variation reconfigures the design space. Through the precise specification...... of their stiffness, it is possible to control and pre-calibrate the bending behaviour of a composite element. This material capacity challenges architecture’s existing methods for design, specification and prediction. In this paper, we demonstrate how architects might connect the designed nature of composites...

  3. Chikungunya means 'that which bends up', and describes the ...

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. CHIK virus was first isolated from patients during an epidemic in Tanzania in 1952-53. Chikungunya means 'that which bends up', and describes the symptoms caused by the severe joint pains.

  4. The relationship between torsional rigidity and bending strength ...

    African Journals Online (AJOL)

    torsional buckling resistance of bending members and when members are subjected to torsional loads. This study was based on a series of laboratory experiments on actual sized timber with the focus and emphasis on mechanical properties and ...

  5. When Blood Cells Bend: Understanding Sickle Cell Disease

    Science.gov (United States)

    ... Subscribe April 2012 Print this issue When Blood Cells Bend Understanding Sickle Cell Disease Send us your ... Diabetes? Sound Health Wise Choices Living with Sickle Cell Disease See a sickle cell disease expert regularly. ...

  6. Band - Weg interactie

    NARCIS (Netherlands)

    de Boer, Andries; ter Huerne, Henderikus L.; Noordermeer, Jacobus W.M.; Schipper, Dirk J.; prof.dr.ir. Molenaar, A.A.A.

    2008-01-01

    De huidige infrastructuur van wegen waarover men zich snel en comfortabel kan verplaatsen is niet meer weg te denken uit onze maatschappij. Twee “componenten” die hierbij een belangrijke rol spelen zijn het wegdek en de band. Het contact tussen band en wegdek is mede bepalend voor de veiligheid. De

  7. Photonic band structure computations.

    Science.gov (United States)

    Hermann, D; Frank, M; Busch, K; Wolfle, P

    2001-01-29

    We introduce a novel algorithm for band structure computations based on multigrid methods. In addition, we demonstrate how the results of these band structure calculations may be used to compute group velocities and effective photon masses. The results are of direct relevance to studies of pulse propagation in such materials.

  8. ZEBRAFISH CHROMOSOME-BANDING

    NARCIS (Netherlands)

    PIJNACKER, LP; FERWERDA, MA

    1995-01-01

    Banding techniques were carried out on metaphase chromosomes of zebrafish (Danio rerio) embryos. The karyotypes with the longest chromosomes consist of 12 metacentrics, 26 submetacentrics, and 12 subtelocentrics (2n = 50). All centromeres are C-band positive. Eight chromosomes have a pericentric

  9. Theory of bending waves with applications to disk galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Mark, J.W.K.

    1982-01-01

    A theory of bending waves is surveyed which provides an explanation for the required amplification of the warp in the Milky Way. It also provides for self-generated warps in isolated external galaxies. The shape of observed warps and partly their existence in isolated galaxies are indicative of substantial spheroidal components. The theory also provides a plausible explanation for the bending of the inner disk (<2 kpc) of the Milky Way.

  10. Calibration of combined bending-torsion fatigue reliability data reduction

    Science.gov (United States)

    Kececioglu, D.; Mcconnell, J. B.

    1969-01-01

    The combined bending-torsion fatigue reliability research machines are described. Three such machines are presently in operation. The calibration of these machines is presented in depth. Fatigue data generated with these machines for SAE 4340 steel grooved specimens subjected to reversed bending and steady torque loading are given. The data reduction procedure is presented. Finally, some comments are made about notch sensitivity and stress concentration as applied to combined fatigue.

  11. A cylindrical standing wave ultrasonic motor using bending vibration transducer.

    Science.gov (United States)

    Liu, Yingxiang; Chen, Weishan; Liu, Junkao; Shi, Shengjun

    2011-07-01

    A cylindrical standing wave ultrasonic motor using bending vibration transducer was proposed in this paper. The proposed stator contains a cylinder and a bending vibration transducer. The two combining sites between the cylinder and the transducer locate at the adjacent wave loops of bending vibration of the transducer and have a distance that equal to the half wave length of bending standing wave excited in the cylinder. Thus, the bending mode of the cylinder can be excited by the bending vibration of the transducer. Two circular cone type rotors are pressed in contact to the end rims of the teeth, and the preload between the rotors and stator is accomplished by a spring and nut system. The working principle of the proposed motor was analyzed. The motion trajectories of teeth were deduced. The stator was designed and analyzed with FEM. A prototype motor was fabricated and measured. Typical output of the prototype is no-load speed of 165rpm and maximum torque of 0.45Nm at an exciting voltage of 200V(rms). Copyright © 2010 Elsevier B.V. All rights reserved.

  12. Flexible deep-ultraviolet light-emitting diodes for significant improvement of quantum efficiencies by external bending

    Science.gov (United States)

    Shervin, Shahab; Oh, Seung Kyu; Park, Hyun Jung; Lee, Keon-Hwa; Asadirad, Mojtaba; Kim, Seung-Hwan; Kim, Jeomoh; Pouladi, Sara; Lee, Sung-Nam; Li, Xiaohang; Kwak, Joon Seop; Ryou, Jae-Hyun

    2018-03-01

    We report a new route to improve quantum efficiencies of AlGaN-based deep-ultraviolet light-emitting diodes (DUV LEDs) using mechanical flexibility of recently developed bendable thin-film structures. Numerical studies show that electronic band structures of AlGaN heterostructures and resulting optical and electrical characteristics of the devices can be significantly modified by external bending through active control of piezoelectric polarization. Internal quantum efficiency is enhanced higher than three times, when the DUV LEDs are moderately bent with concave curvatures. Furthermore, an efficiency droop at high injection currents is mitigated and turn-on voltage of diodes decreases with the same bending condition. The concept of bendable DUV LEDs with a controlled external strain can provide a new path for high-output-power and high-efficiency devices.

  13. Type number and rigidity of fibred surfaces

    International Nuclear Information System (INIS)

    Markov, P E

    2001-01-01

    Infinitesimal l-th order bendings, 1≤l≤∞, of higher-dimensional surfaces are considered in higher-dimensional flat spaces (for l=∞ an infinitesimal bending is assumed to be an analytic bending). In terms of the Allendoerfer type number, criteria are established for the (r,l)-rigidity (in the terminology of Sabitov) of such surfaces. In particular, an (r,l)-infinitesimal analogue is proved of the classical theorem of Allendoerfer on the unbendability of surfaces with type number ≥3 and the class of (r,l)-rigid fibred surfaces is distinguished

  14. Nonlinear Curvature Expressions for Combined Flapwise Bending, Chordwise Bending, Torsion and Extension of Twisted Rotor Blades

    Science.gov (United States)

    Kvaternik, R. G.; Kaza, K. R. V.

    1976-01-01

    The nonlinear curvature expressions for a twisted rotor blade or a beam undergoing transverse bending in two planes, torsion, and extension were developed. The curvature expressions were obtained using simple geometric considerations. The expressions were first developed in a general manner using the geometrical nonlinear theory of elasticity. These general nonlinear expressions were then systematically reduced to four levels of approximation by imposing various simplifying assumptions, and in each of these levels the second degree nonlinear expressions were given. The assumptions were carefully stated and their implications with respect to the nonlinear theory of elasticity as applied to beams were pointed out. The transformation matrices between the deformed and undeformed blade-fixed coordinates, which were needed in the development of the curvature expressions, were also given for three of the levels of approximation. The present curvature expressions and transformation matrices were compared with corresponding expressions existing in the literature.

  15. Early stages of Cs adsorption mechanism for GaAs nanowire surface

    Science.gov (United States)

    Diao, Yu; Liu, Lei; Xia, Sihao; Feng, Shu

    2018-03-01

    In this study, the adsorption mechanism of Cs adatoms on the (100) surface of GaAs nanowire with [0001] growth direction is investigated utilizing first principles method based on density function theory. The adsorption energy, work function, atomic structure and electronic property of clean surface and Cs-covered surfaces with different coverage are discussed. Results show that when only one Cs is adsorbed on the surface, the most favorable adsorption site is BGa-As. With increasing Cs coverage, work function gradually decreases and gets its minimum at 0.75 ML, then rises slightly when Cs coverage comes to 1 ML, indicating the existence of 'Cs-kill' phenomenon. According to further analysis, Cs activation process can effectively reduce the work function due to the formation of a downward band bending region and surface dipole moment directing from Cs adatom to the surface. As Cs coverage increases, the conduction band minimum and valence band maximum both shift towards lower energy side, contributed by the orbital hybridization between Cs-5s, Cs-5p states and Ga-4p, As-4s, As-4p states near Fermi level. The theoretical calculations and analysis in this study can improve the Cs activation technology for negative electron affinity optoelectronic devices based on GaAs nanowires, and also provide a reference for the further Cs/O or Cs/NF3 activation process.

  16. Mesh refinement study and experimental validation for stretch bending of sheet metals

    Science.gov (United States)

    Raupach, M.; Kreissl, S.; Vuaille, L.; Möller, T.; Friebe, H.; Volk, W.

    2017-09-01

    For sheet metal parts with small radii and large bending angles, the sheet metal forming simulation reaches their application limits. Alternatives are complex shell formulations and volume elements. For volume elements, the necessary number of elements over the thickness is important. Valid values are not available depending on discrete radii. Therefore in this work, a convergence study is performed using the example of an angular stretch bend test with a radius to thickness ratio of 1. For various states of mesh refinement, simulations are performed, various results are presented, analysed and discussed with regard to convergence behaviour to the necessary number of elements in thickness direction. Recommendations for suitable validation variables are derived. Based on the refinement study, a simulation model for an experimental validation is developed. The experiments are carried out in a sheet metal forming machine. Experimental angular stretch bend test with a punch radius of 1 mm are performed until failure and the strain distribution on the top side of the sheet is measured. Finally, simulation and experiments are compared based on the surface strain.

  17. Standard test method for guided bend test for ductility of welds

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2002-01-01

    1.1 This test method covers a guided bend test for the determination of soundness and ductility of welds in ferrous and nonferrous products. Defects, not shown by X rays, may appear in the surface of a specimen when it is subjected to progressive localized overstressing. This guided bend test has been developed primarily for plates and is not intended to be substituted for other methods of bend testing. 1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. Note 1—For additional information see Terminology E 6, and American Welding Society Standard D 1.1. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  18. The Role of Deep Mantle Flow in Shaping the Hawaiian-Emperor Bend

    Science.gov (United States)

    Hassan, R.; Müller, D.; Gurnis, M.; Williams, S.; Flament, N. E.

    2016-12-01

    Age-progressive volcanic hotspot tracks are typical surface expressions of plate tectonic movement on top of narrow plumes of hot material within Earth's mantle. Seismic imaging reveals that these plumes can be of deep origin, potentially rooted on thermochemical structures in the lower mantle. Although palaeomagnetic and radiometric age data suggest that mantle flow can advect plume conduits laterally, the flow dynamics underlying the formation of the sharp bend occurring only in the Hawaiian-Emperor hotspot track in the Pacific Ocean remains enigmatic. The north Pacific features long-lasting subduction systems, unlike those in the south Pacific. We present palaeogeographically-constrained numerical models of thermochemical convection demonstrating that flow in the deep lower mantle under the north Pacific was anomalously vigorous between 100 Ma and 50 Ma. These models show a sharp bend in the Hawaiian-Emperor hotspot track arising from the interplay of plume tilt and the lateral advection of plume sources. We show that the different trajectories of the Hawaiian and Louisville hotspot tracks arise from asymmetric deformation of thermochemical structures under the Pacific between 100 Ma and 50 Ma. This asymmetric deformation waned just before the Hawaiian-Emperor bend developed, owing to flow in the deepest lower mantle associated with slab descent in the north and south Pacific.

  19. Band parameters of phosphorene

    DEFF Research Database (Denmark)

    Lew Yan Voon, L. C.; Wang, J.; Zhang, Y.

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory...... are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene....

  20. Finite element bending behaviour of discretely delaminated ...

    African Journals Online (AJOL)

    user

    R can be obtained from partial derivatives of surface equation. ( , ). z f x y. = and yx ..... layered symmetric shells, cross ply shell shows less deflection values than the angle ply one. Table 4. .... to conclude regarding the relative behaviour of antisymmetric and symmetric stacking orders for delaminated shells. 4.1.3 Effect of ...

  1. How to determine the pressure of a methane-containing gas mixture by means of two weak Raman bands, v(3) and 2v(2)

    DEFF Research Database (Denmark)

    Hansen, Susanne Brunsgaard; Berg, Rolf W.; Stenby, Erling Halfdan

    2002-01-01

    , n3 (asymmetric C-H stretching) and 2n2 (overtone of the asymmetric C-H bending), is observed; the methane n3 band intensity is lowered relative to the methane 2n2 as the pressure is raised. The intensity ratios between these two bands, In3/I2n2, were determined and plotted as a function of pressure...

  2. Laparoscopic gastric banding

    Science.gov (United States)

    ... eat by making you feel full after eating small amounts of food. After surgery, your doctor can adjust the band ... You will feel full after eating just a small amount of food. The food in the small upper pouch will ...

  3. Decay of superdeformed bands

    International Nuclear Information System (INIS)

    Carpenter, M.P.; Khoo, T.L.; Lauritsen, T.

    1995-01-01

    One of the major challenges in the study of superdeformation is to directly connect the large number of superdeformed bands now known to the yrast states. In this way, excitation energies, spins and parities can be assigned to the levels in the second well which is essential to establish the collective and single-particle components of these bands. This paper will review some of the progress which has been made to understand the decay of superdeformed bands using the new arrays including the measurement of the total decay spectrum and the establishment of direct one-step decays from the superdeformed band to the yrast line in 194 Hg. 42 refs., 5 figs

  4. HYBASE - HYperspectral BAnd SElection tool

    NARCIS (Netherlands)

    Schwering, P.B.W.; Bekman, H.H.P.T.; Seijen, H.H. van

    2008-01-01

    Band selection is essential in the design of multispectral sensor systems. This paper describes the TNO hyperspectral band selection tool HYBASE. It calculates the optimum band positions given the number of bands and the width of the spectral bands. HYBASE is used to calculate the minimum number of

  5. Comparison of cyclic fatigue resistance and bending properties of two reciprocating nickel-titanium glide path files.

    Science.gov (United States)

    Özyürek, T; Uslu, G; Gündoğar, M; Yılmaz, K; Grande, N M; Plotino, G

    2018-02-25

    To compare the cyclic fatigue resistance and bending properties of R-Pilot and WaveOne Gold (WOG) Glider files, at intracanal temperature (35°C). Forty R-Pilot and 40 WOG Glider files were subjected to a cyclic fatigue resistance test (n = 20), calculating the time to fracture (TTF) in an artificial stainless steel canal. The length of the fractured file tips (FL) was also measured. The fracture surface of fragments was examined with a scanning electron microscope, and the cross-sectional area of the fractured surfaces was measured. Flexibility of the tested files (n = 20) was determined using 45° bending test. Data were analysed statistically using the Mann-Whitney U-test at 5% significance level. Time to fracture was significantly higher in the R-Pilot group compared to the WOG Glider (P < 0.05). There was no significant difference between groups for fracture length. The bending resistance of R-Pilot files was significantly greater than WOG Glider files (P < 0.05). A significant greater cyclic fatigue resistance was observed for R-Pilot files compared to WOG Glider instruments, although the bending resistance of WOG Glider files was lower. © 2018 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  6. Service water chemical cleaning at River Bend gets results

    International Nuclear Information System (INIS)

    Brice, T.O.; Glover, W.A.

    1994-01-01

    The largest known Service Water System (SWS) chemical cleaning ever performed at a nuclear plant was successfully completed at, River Bend Station. Corrosion product buildup was observed during system inspections in the first operating cycle and the first refueling outage in 1987. Under deposit corrosion was followed with microbiologically influenced corrosion (MIC) occurring as a later stage under deposits. The heavy corrosion caused blockage of heat exchanger tubes, fouling of valve seats, and general flow blockage throughout the system. Various options were evaluated for restoring the SWS back to an acceptable long term operating condition. The large scale chemical cleaning performed arrested the corrosion by removing the deposits down to the bare metal surfaces and leaving behind a protective passivation layer. After the cleaning, the open recirculating SWS was converted to a closed system. The implementation of a molybdate/nitrate water treatment program with a copper corrosion inhibitor maintained at a high pH (8.5--10.5) has significantly reduced corrosion rates in the closed system. This should extend the life of the SWS piping for the remaining life of the plant. Several field tests were conducted to qualify the process and demonstrate its ability to achieve acceptable cleaning results prior to being used on a larger scale. In the summer of 1992, temporary and permanent modifications were installed to divide the SWS into two separate cleaning loops for the system wide cleaning. The SWS chemical was successfully performed and completed on schedule during the fourth refueling outage. Post cleaning inspections at various locations throughout the Service Water System showed the process to be very effective at complete deposit removal

  7. Hurricane Spiral Bands.

    Science.gov (United States)

    Guinn, Thomas A.; Schubert, Wayne H.

    1993-10-01

    The spiral bands that occur in tropical cyclones can be conveniently divided into two classes-outer bands and inner bands. Evidence is presented here that the outer bands form as the result of nonlinear effects during the breakdown of the intertropical convergence zone (ITCZ) through barotropic instability. In this process a zonal strip of high potential vorticity (the ITCZ shear zone or monsoon trough) begins to distort in a varicose fashion, with the potential vorticity (PV) becoming pooled in local regions that are connected by filaments of high PV. As the pooled regions become more axisymmetric, the filaments become thinner and begin to wrap around the PV centers.It is argued that inner bands form in a different manner. As a tropical cyclone intensifies due to latent heat release, the PV field becomes nearly circular with the highest values of PV in the cyclone center. The radial gradient of PV provides a state on which PV waves (the generalization of Rossby waves) can propagate. The nonlinear breaking of PV waves then leads to an irreversible distortion of the PV contours and a downgradient flux of PV. The continuation of this proem tends to erode the high PV core of the tropical cyclone, to produce a surrounding surf zone, and hence to spread the PV horizontally. In a similar fashion, inner bands can also form by the merger of a vortex with a patch of relatively high PV air. As the merger proem occurs the patch of PV is quickly elongated and wrapped around the vortex. The resulting vortex is generally larger in horizontal extent and exhibits a spiral band of PV.When the formation of outer and inner bands is interpreted in the context of a normal-mode spectral model, they emerge as slow manifold phenomena; that is, they have both rotational and (balanced or slaved) gravitational mode aspects. In this sense, regarding them as simply gravity waves leads to an incomplete dynamical picture.

  8. Band-type microelectrodes for amperometric immunoassays

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ga-Yeon; Chang, Young Wook; Ko, Hyuk [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of); Kang, Min-Jung [Korea Institute of Science and Technology (KIST), Seoul (Korea, Republic of); Pyun, Jae-Chul, E-mail: jcpyun@yonsei.ac.kr [Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 120-749 (Korea, Republic of)

    2016-07-20

    A band-type microelectrode was made using a parylene-N film as a passivation layer. A circular-type, mm-scale electrode with the same diameter as the band-type microelectrode was also made with an electrode area that was 5000 times larger than the band-type microelectrode. By comparing the amperometric signals of 3,5,3′,5′-tetramethylbenzidine (TMB) samples at different optical density (OD) values, the band-type microelectrode was determined to be 9 times more sensitive than the circular-type electrode. The properties of the circular-type and the band-type electrodes (e.g., the shape of their cyclic voltammograms, the type of diffusion layer used, and the diffusion layer thickness per unit electrode area) were characterized according to their electrode area using the COMSOL Multiphysics software. From these simulations, the band-type electrode was estimated to have the conventional microelectrode properties, even when the electrode area was 100 times larger than a conventional circular-type electrode. These results show that both the geometry and the area of an electrode can influence the properties of the electrode. Finally, amperometric analysis based on a band-type electrode was applied to commercial ELISA kits to analyze human hepatitis B surface antigen (hHBsAg) and human immunodeficiency virus (HIV) antibodies. - Highlights: • A band-type microelectrode was made using a parylene-N film as a passivation layer. • The band-type microelectrode was 14-times more sensitive than circular-type electrode. • The influence of geometry on microelectrode properties was simulated using COMSOL. • The band-type electrode was applied to ELISA kits for hHBsAg and hHIV-antibodies.

  9. EDDY-360 rotating pancake probe inspection of small radius U-bends

    International Nuclear Information System (INIS)

    Glass, S.W.; Griffith, J.C.; Baumann, J.M.

    1988-01-01

    Conventional bobbin coil or 4 x 2 array pancake coil probes have not been able to detect or satisfactorily size primary side intergranular stress corrosion cracking in the small-radius U-bend regions of recirculating steam generators in pressurized water reactor systems. BandW has developed a rotating probe inspection system that improves inspection of these areas of the generator. The probe consists of a flexible neck connecting the small probe motor body with the head and sensing coil assembly. The probe is delivered to the tube through a snorkel connecting the probe driver with a remote manipulator. Test results demonstrate that the EDDY-360 probe does provide better sensitivity and sizing capability than conventional techniques

  10. Driven around the bend: Spatial evolution and controls on the orientation of helical bend flow in a natural submarine gravity current

    Science.gov (United States)

    Sumner, E.; Peakall, J.; Dorrell, R. M.; Parsons, D. R.; Darby, S. E.; Wynn, R. B.

    2014-12-01

    Submarine channel systems transport vast amounts of terrestrial sediment into the deep sea. Understanding the dynamics of the gravity currents that create these systems, and in particular, how these flows interact with and form bends, is fundamental to predicting system architecture and evolution. Bend flow is characterized by a helical structure and in rivers typically comprises inwardly directed near-bed flow and outwardly directed near-surface flow. Following a decade of debate, it is now accepted that helical flow in submarine channel bends can exhibit a variety of structures including being opposed to that observed in rivers. The new challenge is to understand what controls the orientation of helical flow cells within submarine flows and determines the conditions for reversal. We present data from the Black Sea showing, for the first time, the three-dimensional velocity and density structure of an active submarine gravity current. By calculating the forces acting on the flow, we evaluate what controls the orientation of helical flow cells. We demonstrate that radial pressure gradients caused by across-channel stratification of the flow are more important than centrifugal acceleration in controlling the orientation of helical flow. We also demonstrate that nonlocal acceleration of the flow due to topographic forcing and downstream advection of the cross-stream flow are significant terms in the momentum balance. These findings have major implications for conceptual and numerical models of submarine channel dynamics, because they show that three-dimensional models that incorporate across-channel flow stratification are required to accurately represent curvature-induced helical flow in such systems.

  11. Impact of Road Bends on Traffic Flow in a Single-Lane Traffic System

    Directory of Open Access Journals (Sweden)

    Zeng Junwei

    2014-01-01

    Full Text Available Taking the characteristics of road bends as a research object, this work proposes the cellular model (CA with road bends based on the NaSch model, with which the traffic flow is examined under different conditions, such as bend radius, bend arc length, and road friction coefficiency. The simulation results show that, with the increase of the bend radius, the peak flow will be continuously increased, and the fundamental diagram will become more similar to that of the classic NaSch model; the smaller the bend radius is, the easier it is for the occurrence of blockage; for different bend lengths, all the corresponding traffic flows show that the phenomenon of go-and-stop and the bends exert slight inhibitory effect on traffic flow; under the same bend radius, the inhibition effect of the bends on the traffic flow will be weakened with the increase of the friction coefficiency.

  12. Experiment research on ratcheting of pressurized pipe subjected reversed bending

    International Nuclear Information System (INIS)

    Gao Bingjun; Chen Xu; Chen Gang

    2005-01-01

    With a quasi-three point bending apparatus, ratcheting and ratcheting boundary were studied experimentally for pressurized low carbon 20 steel pipes under reversed bending on servo- electro-hydraulic axial-pressure testing system. It is found that ratcheting initiates firstly in hoop direction and that in axial direction follows with the increase of loading but less in magnitude. The circular cross section turns into ellipse as the ratcheting strain accumulates. Ratcheting strain rate grows with the increase of reversed bending load or internal pressure for both different specimen with different loading and same specimen with multi-step loading. In multi-step loading, ratcheting rate suffers from the ratcheting history, especially for that with ratcheting history at higher level loading. As different positions of the specimen endure different bending moment by the quasi-three point bending apparatus, ratcheting boundary is readily determined experimentally. By comparison with that determined by ASME, RCC-MR, it is shown both code are conservative. (authors)

  13. Investigation of span-chordwise bending anisotropy of honeybee forewings

    Directory of Open Access Journals (Sweden)

    JianGuo Ning

    2017-05-01

    Full Text Available In this study, the spanwise and chordwise bending stiffness EI of honeybee forewings were measured by a cantilevered bending test. The test results indicate that the spanwise EI of the forewing is two orders of magnitude larger than the chordwise EI. Three structural aspects result in this span-chordwise bending anisotropy: the distribution of resilin patches, the corrugation along the span and the leading edge vein of the venation. It was found that flexion lines formed by resilin patches revealed through fluorescence microscopy promoted the chordwise bending of the forewing during flapping flight. Furthermore, the corrugation of the wing and leading edge veins of the venation, revealed by micro-computed tomography, determines the relatively greater spanwise EI of the forewing. The span-chordwise anisotropy exerts positive structural and aerodynamic influences on the wing. In summary, this study potentially assists researchers in understanding the bending characteristics of insect wings and might be an important reference for the design and manufacture of bio-inspired wings for flapping micro aerial vehicles.

  14. Far-infrared high resolution synchrotron FTIR spectroscopy of the ν11 bending vibrational fundamental transition of dimethylsulfoxyde

    Science.gov (United States)

    Cuisset, Arnaud; Nanobashvili, Lia; Smirnova, Irina; Bocquet, Robin; Hindle, Francis; Mouret, Gaël; Pirali, Olivier; Roy, Pascale; Sadovskií, Dmitrií A.

    2010-05-01

    We report the first successful high resolution gas phase study of the 'parallel' band of DMSO at 380 cm -1 associated with the ν11 bending vibrational mode. The spectrum was recorded with a resolution of 0.0015 cm -1 using the AILES beamline of the SOLEIL synchrotron source, the IFS 125 FTIR spectrometer and a multipass cell providing an optical path of 150 m. The rotational constants and centrifugal corrections obtained from the analysis of the resolved rotational transitions reproduce the spectrum to the experimental accuracy.

  15. A SENSOR AND A METHOD FOR DETERMINING THE DIRECTION AND THE AMPLITUDE OF A BEND

    DEFF Research Database (Denmark)

    2000-01-01

    The present invention relates to an optical based bending sensor. In particular, the present invention relates to a fibre-based bending sensor for the determination of the direction and the amplitude of a bend. The present invention further relates to fibre-based bending sensors using long...... and the cladding modes. Thereby a relative splitting of transmission peaks in the spectrum of the LPG is induced, which is used to determine the bending amplitude and direction....

  16. Operation corrosion test of austenitic steel bends for supercritical coal boilers

    Directory of Open Access Journals (Sweden)

    Cizner J.

    2016-03-01

    Full Text Available Corrosion tests of both annealed and not annealed bends of HR3C and S304H steels in operation conditions of black and brown coal combustion boilers in EPRU and EDE. After a long-term exposure, the samples were assessed gravimetrically and metallographically. The comparison of annealed and unannealed states showed higher corrosion rates in the annealed state; corrosion of the sample surface did not essentially differ for compression and tensile parts of the beams. Detailed assessment of both steels is described in detail in this study.

  17. Fatigue crack growth in 2017A-T4 alloy subjected to proportional bending with torsion

    Directory of Open Access Journals (Sweden)

    D. Rozumek

    2017-10-01

    Full Text Available The paper presents the results of tests on the fatigue crack growth for a constant moment amplitude under combined bending with torsion in the aluminium alloy AW-2017A-T4. The tests were performed under different values of the load ratio R. Plane specimens with stress concentrators in form of the external one-sided sharp notch were tested. A non-uniform fatigue cracks growth on both lateral surfaces of specimens was observed during experimental tests. Fatigue cracks were developing in the specimens in two stages; quarter-elliptic edge cracks were observed at the beginning, then evolving into through cracks

  18. Experimental Study on Temperature Behavior of SC Structures under Pure Bending

    International Nuclear Information System (INIS)

    Ham, K. W.; Lee, K. J.; Park, D. S.; Jeon, J. H.

    2006-01-01

    SC(Steel plate Concrete) module method uses steel plate instead of reinforcing bar and mold in existing RC structure. Steel plate modules are fabricated in advance, installed and poured with concrete in construction field, so construction period is remarkably shortened by SC module technique. In case of existence of temperature gap between internal and external structure surface such as spent fuel storage pool, thermal stress is taken place and as a result of it, structural strength is deteriorated. In this study, we designed three test specimens and several tests with or without temperature heating were conducted to evaluate temperature behavior of SC structures under pure bending loading condition

  19. Bending analysis of a piezoelectric curved actuator with a generally graded property for the piezoelectric parameter

    International Nuclear Information System (INIS)

    Shi Zhifei; Zhang Taotao

    2008-01-01

    An analytical study on the bending behavior of a piezoelectric curved actuator with generally graded properties for the piezoelectric parameter g 31 is performed. The external electric potential is acting between the inner and outer surfaces of the actuator. A Taylor series expansion method is introduced and the exact solutions of the problem are obtained based on the theory of piezo-elasticity. The present analytical solutions are compared with the numerical results and good agreement is found. This work gives a sound background for the design and optimization of functionally graded piezoelectric curved actuators

  20. Effect of bend separation distance on the mass transfer in back-to-back pipe bends arranged in a 180° configuration

    Science.gov (United States)

    Chen, X.; Le, T.; Ewing, D.; Ching, C. Y.

    2016-12-01

    The mass transfer to turbulent flow through back-to-back pipe bends arranged in a 180° configuration with different lengths of pipe between the bends was measured using a dissolving gypsum test section in water. The measurements were performed for bends with a radius of curvature of 1.5 times the pipe diameter ( D) at a Reynolds numbers of 70,000 and Schmidt number of 1280. The maximum mass transfer in the bends decreased from approximately 1.8 times the mass transfer in the upstream pipe when there was no separation distance between the bends to 1.7 times when there was a 1 D or 5 D length of pipe between the bends. The location of the maximum mass transfer was on the inner sidewall downstream of the second bend when there was no separation distance between the bends. This location changed to the inner wall at the beginning of the second bend when there was a 1 D long pipe between the bends, and to the inner sidewall at the end of the first bend when there was a 5 D long pipe between the bends.

  1. Evaluation of River Bend Station Unit 1 Technical Specifications

    International Nuclear Information System (INIS)

    Baxter, D.E.; Bruske, S.J.

    1985-08-01

    This document was prepared for the Nuclear Regulatory Commission (NRC) to assist them in determining whether the River Bend Station Unit 1 Technical Specifications (T/S), which govern plant systems configurations and operations, are in conformance with the requirements of the Final Safety Analysis Report (FSAR) as amended, and the requirements of the Safety Evaluation Report (SER) as supplemented. A comparative audit of the FSAR as amended, and the SER as supplemented was performed with the River Bend T/S. Several discrepancies were identified and subsequently resolved through discussions with the cognizant NRC reviewer, NRC staff reviewers and/or utility representatives. The River Bend Station Unit 1 T/S, to the extent reviewed, are in conformance with the FSAR and SER

  2. Platonic scattering cancellation for bending waves in a thin plate

    KAUST Repository

    Farhat, Mohamed

    2014-04-10

    We propose an ultra-thin elastic cloak to control the scattering of bending waves in isotropic heterogeneous thin plates. The cloak design makes use of the scattering cancellation technique applied, for the first time, to the biharmonic operator describing the propagation of bending waves in thin plates. We first analyze scattering from hard and soft cylindrical objects in the quasistatic limit, then we prove that the scattering of bending waves from an object in the near and far-field regions can be suppressed significantly by covering it with a suitably designed coating. Beyond camouflaging, these findings may have potential applications in protection of buildings from earthquakes and isolating structures from vibrations in the motor vehicle industry.

  3. Differential quadrature method of nonlinear bending of functionally graded beam

    Science.gov (United States)

    Gangnian, Xu; Liansheng, Ma; Wang, Youzhi; Quan, Yuan; Weijie, You

    2018-02-01

    Using the third-order shear deflection beam theory (TBT), nonlinear bending of functionally graded (FG) beams composed with various amounts of ceramic and metal is analyzed utilizing the differential quadrature method (DQM). The properties of beam material are supposed to accord with the power law index along to thickness. First, according to the principle of stationary potential energy, the partial differential control formulae of the FG beams subjected to a distributed lateral force are derived. To obtain numerical results of the nonlinear bending, non-dimensional boundary conditions and control formulae are dispersed by applying the DQM. To verify the present solution, several examples are analyzed for nonlinear bending of homogeneous beams with various edges. A minute parametric research is in progress about the effect of the law index, transverse shear deformation, distributed lateral force and boundary conditions.

  4. Real-time resilient focusing through a bending multimode fiber.

    Science.gov (United States)

    Caravaca-Aguirre, Antonio M; Niv, Eyal; Conkey, Donald B; Piestun, Rafael

    2013-05-20

    Multimode optical fibers are attractive for biomedical and sensing applications because they possess a small cross section and can bend over small radii of curvature. However, mode phase-velocity dispersion and random mode coupling change with bending, temperature, and other perturbations, producing scrambling interference among propagating modes; hence preventing its use for focusing or imaging. To tackle this problem we introduce a system capable of re-focusing light through a multimode fiber in 37ms, one order of magnitude faster than demonstrated in previous reports. As a result, the focus spot can be maintained during significant bending of the fiber, opening numerous opportunities for endoscopic imaging and energy delivery applications. We measure the transmission matrix of the fiber by projecting binary-amplitude computer generated holograms using a digital micro-mirror device controlled by a field programmable gate array. The system shows two orders of magnitude enhancements of the focus spot relative to the background.

  5. System effects influencing the bending strength of timber beams

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager; Källsner, B.

    1998-01-01

    measurements of the strengths of a large number of shorttest pieces cut from the beams such that judgementally each test piece contains only a single defect cluster. The testpiece is spliced to stronger wood beam shafts in both ends. Due to the occurrence of a substantial number of splicefailures in the total...... test series of 197 tests a special maximum likelihood estimation procedure is applied to estimate theparameters. Assuming that the estimated parameters are applicable in the series system model for the full uncutbeams a theoretical bending strength distribution function is obtained in dependence......A stochastic model of hierarchical series system type for the bending strength of spruce beams isdefined from the anticipation that the bending failure takes place at a cross-section with a defect cluster formed by knots or grain irregularities. The parameters of the model are estimated from...

  6. Springback law study and application in incremental bending process

    Science.gov (United States)

    Zhang, Feifei; He, Kai; Dang, Xiaobing; Du, Ruxu

    2018-02-01

    One incremental bending process has been proposed for manufacturing the complex and thick ship-hull plates. The accuracy and efficiency for this novel process is mainly dependent on the loading path and thus the unavoidable springback behavior should be considered in the loading path determination. In this paper, firstly, the numerical simulation method is verified by the corresponding experiment, and then the springback law during the incremental bending process is investigated based on numerical simulation, and later the loading path based on the springback law and the minimum energy method is achieved for specific machining shape. Comparison between the designed curve based on springback law and the new simulation results verifies that the springback law obtained by numerical simulation is believable, so this study provides a new perspective for the further research on incremental bending process.

  7. Yield stress determination from miniaturized disk bend test data

    International Nuclear Information System (INIS)

    Sohn, D.S.; Kohse, G.; Harling, O.K.

    1985-04-01

    Methodology for testing 3.0 mm diameter by 0.25 mm thick disks by bending in a punch and die has been described previously. This paper describes the analysis of load/deflection data from such miniaturized disk bend tests (MDBT) using a finite element simulation. Good simulation has been achieved up to a point just beyond the predominantly elastic response, linear initial region. The load at which deviation from linearity begins has been found to correlate with yield stress, and yield stress has been successfully extracted from disk bend tests of a number of known materials. Although finite element codes capable of dealing with large strains and large rotations have been used, simulation of the entire load/deflection curve up to fracture of the specimen has not yet been achieved

  8. Experimentation and numerical modeling of forging induced bending (FIB) process

    Science.gov (United States)

    Naseem, S.; van den Boogaard, A. H.

    2016-10-01

    Accurate prediction of the final shape using numerical modeling has been a top priority in the field of sheet and bulk forming. Better shape prediction is the result of a better estimation of the physical stress and strain state. For experimental and numerical investigations of such estimations, simple benchmark processes are used. In this paper a benchmark process involving forging (flattening) of sheet metal between punch and die with negative clearance is proposed. The introduced material flow results in bending. Easy measurability of the angle of this bend makes this process suitable for validation purpose. Physical experiments are performed to characterize this bending angle due to flattening. Furthermore a numerical model is developed to capture this phenomenon. The main focus of this paper is the validation of the numerical model in terms of accurate prediction of the physical results.

  9. Photonic band gap materials

    Science.gov (United States)

    Cassagne, D.

    Photonic band gap materials Photonic band gap materials are periodic dielectric structures that control the propagation of electromagnetic waves. We describe the plane wave method, which allows to calculate the band structures of photonic crystals. By symmetry analysis and a perturbative approach, we predict the appearance of the low energy photonic band gaps of hexagonal structures. We propose new two-dimensional structures called graphite and boron nitride. Using a transfer matrix method, we calculate the transmission of the graphite structure and we show the crucial role of the coupling with external modes. We study the appearance of allowed modes in the photonic band gap by the introduction of localized defects in the periodicity. Finally, we discuss the properties of opals formed by self-organized silica microspheres, which are very promising for the fabrication of three-dimensional photonic crystals. Les matériaux à bandes interdites photoniques sont des structures diélectriques périodiques qui contrôlent la propagation des ondes électromagnétiques. Nous décrivons la méthode des ondes planes qui permet de calculer les structures de bandes des cristaux photoniques. Par une analyse de la symétrie et une approche perturbative, nous précisons les conditions d'existence des bandes interdites de basse énergie. Nous proposons de nouvelles structures bidimensionnelles appelées graphite et nitrure de bore. Grâce à une méthode de matrices de transfert, nous calculons la transmission de la structure graphite et nous mettons en évidence le rôle fondamental du couplage avec les modes extérieurs. Nous étudions l'apparition de modes permis dans la bande interdite grâce à l'introduction de défauts dans la périodicité. Enfin, nous discutons les propriétés des opales constituées de micro-billes de silice auto-organisées, qui sont très prometteuses pour la fabrication de cristaux photoniques tridimensionnels.

  10. Restrictive techniques: gastric banding

    Directory of Open Access Journals (Sweden)

    Katia Cristina da Cunha

    2006-03-01

    Full Text Available Surgery for the treatment of severe obesity has a definite role onthe therapeutic armamentarium all over the world. Initiated 40years ago, bariatric surgery has already a long way thanks tohundred of surgeons, who had constantly searched for the besttechnique for the adequate control of severe obesity. Among theimportant breakthroughs in obesity surgery there is theadjustable gastric band. It is a sylastic band, inflatable andadjustable, which is placed on the top of the stomach in order tocreate a 15-20 cc pouch, with an outlet of 1.3cm. The adjustablegastric band has also a subcutaneous reservoir through whichadjustments can be made, according to the patient evolution.The main feature of the adjustable gastric band is the fact thatis minimal invasive, reversible, adjustable and placedlaparoscopically. Then greatly diminishing the surgical traumato the severe obese patient. Belachew and Favretti’s techniqueof laparoscopic application of the adjustable gastric band isdescribed and the evolution of the technique during this years,as we has been practiced since 1998. The perioperative care ofthe patient is also described, as well as the follow-up and shortand long term controls.

  11. Influence of bending test configuration on cracking behavior of FRC

    DEFF Research Database (Denmark)

    Finazzi, Silvia; Paegle, Ieva; Fischer, Gregor

    2014-01-01

    This paper describes an investigation of the influence of the testing configuration for Fiber Reinforced Concrete in bending and aims at evaluating the influence of the test configuration details on the characterization of the material. Two different types of FRC, Steel Fiber Reinforced Concrete...... (SFRC) and Engineered Cementitious Composites (ECC), were tested and are described in this study. The materials were chosen so that one of them would be strain hardening (ECC) and the other tension softening (SFRC). Notched and un-notched three- and four-point bending tests were carried out to determine...

  12. Test Equal Bending by Gravity for Space and Time

    Science.gov (United States)

    Sweetser, Douglas

    2009-05-01

    For the simplest problem of gravity - a static, non-rotating, spherically symmetric source - the solution for spacetime bending around the Sun should be evenly split between time and space. That is true to first order in M/R, and confirmed by experiment. At second order, general relativity predicts different amounts of contribution from time and space without a physical justification. I show an exponential metric is consistent with light bending to first order, measurably different at second order. All terms to all orders show equal contributions from space and time. Beautiful minimalism is Nature's way.

  13. Flagella bending affects macroscopic properties of bacterial suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Potomkin, M.; Tournus, M.; Berlyand, L. V.; Aranson, I. S.

    2017-05-01

    To survive in harsh conditions, motile bacteria swim in complex environments and respond to the surrounding flow. Here, we develop a mathematical model describing how flagella bending affects macroscopic properties of bacterial suspensions. First, we show how the flagella bending contributes to the decrease in the effective viscosity observed in dilute suspension. Our results do not impose tumbling (random reorientation) as was previously done to explain the viscosity reduction. Second, we demonstrate how a bacterium escapes from wall entrapment due to the self-induced buckling of flagella. Our results shed light on the role of flexible bacterial flagella in interactions of bacteria with shear flow and walls or obstacles.

  14. Elastostatic bending of a bimaterial plate with a circular interface

    Science.gov (United States)

    Ogbonna, Nkem

    2015-08-01

    The elastostatic bending of an arbitrarily loaded bimaterial plate with a circular interface is analysed. It is shown that the deflections in the composite solid are directly related to the deflection in the corresponding homogeneous material by integral and differential operators. It is further shown that, by a simple transformation of elastic constants, the Airy stress function induced in the composite by a stretching singularity can be deduced from the deflection induced by a bending singularity. This result is significant for reduction of mathematical labour and for systematic construction of solutions for more complex structures with circular geometry.

  15. Bending Mechanical Behavior of Polyester Matrix Reinforced with Fique Fiber

    Science.gov (United States)

    Altoé, Giulio Rodrigues; Netto, Pedro Amoy; Barcelos, Mariana; Gomes, André; Margem, Frederico Muylaert; Monteiro, Sergio Neves

    Environmentally correct composites, made from natural fibers, are among the most investigated and applied today. In this paper, we investigate the mechanical behavior of polyester matrix composites reinforced with continuous fique fibers, through bending tensile tests. Specimens containing 0, 10, 20 and 30% in volume of fique fiber were aligned along the entire length of a mold to create plates of these composites, those plates were cut following the ASTM standard to obtained bending tests specimens. The test was conducted in a Instron Machine and the fractured specimens were analyzed by SEM, the results showed the increase in the materials tensile properties with the increase of fiber amount.

  16. [Effects of three types of veneering porcelain on bending strength of KAVO(TM) Y-TZP/porcelain bilayered structure].

    Science.gov (United States)

    Ma, Ting-ting; Yi, Yuan-fu; Shao, Long-quan; Tian, Jie-mo; Hou, Kang-lin; Zhang, Wei-wei; Wen, Ning; Deng, Bin

    2010-10-01

    To investigate the effect of three types of veneering porcelain on the bending strength of KAVO Y-TZP/porcelain layered structure. KAVO zirconia ceramics were used as the substructure. To form Y-TZP/porcelain bilayered structure, a leucite-based veneering porcelain was fired on the zirconia substructures by slip-casting technique with dentin washbake, and two nano-fluorapatite-based veneering porcelains were fired on the zirconia substructures by either slip-casting or pressed-on technique with or without liner coverage. The bending strength was tested according to ISO 6872 standard, and the veneered surfaces of the fracture samples were analyzed by scanning electron microscopy (SEM). For covering KAVO zirconia core material, the conventional veneering slurry-porcelain combined with liner or wash firing had significant higher bending strength than pressed-on porcelain. SEM showed that the main failure type at the interface was adhesive failure. Thin layer sintering using washbake program or liner on KAVO zirconia surface increases the surface wettability, and this procedure may be indispensable when veneering on the surface of dental zirconia.

  17. A system and a method comprising an array of bending elements for determining a condition

    DEFF Research Database (Denmark)

    2014-01-01

    direction, when exposed to a condition, which may be a temperature, a pressure, a pH, a humidity or a presence of a predetermined molecule. The elongated elements may have a first surface and a second surface having different degrees of contraction/extension when exposed to the condition, where the first......A system comprising a sensor element and a sensing system, a method of operating it, a sensor element and a method of providing it, where the sensor element has a substrate from which a plurality of elongate, bendable elements extend. The elongated elements are configured to bend, in the same...... surfaces all point in the same direction. The sensing system may relate on a large number of elongate elements positioned within a given area on the sensor element....

  18. Axial and coronal orientation of subaxial cervical zygapophysial joints and their effect on axial rotation and lateral bending.

    Science.gov (United States)

    Hsu, Wen-Hsing; Benzel, Edward C; Chen, Tzu-Yung; Chen, Yao-Liang

    2008-10-15

    Computerized tomography and image processing methodologies were used to analyze the axial and coronal orientation of cervical zygapophysial joints in asymptomatic adults. Surface motions of axial rotation and lateral bending were simulated. The study was designed to obtain the normal distribution and variation of facet orientation (FO) in axial and coronal planes to investigate factors affecting FO and to study the effects of FO on axial rotation and lateral bending. The FO of the subaxial cervical spine is usually evaluated in the sagittal plane. Cervical spine axial and coronal FO is usually considered to be horizontal. The literature reveals no statistical data for axial or coronal FO. Serial thin-sliced computed tomography scans of the cervical spine in asymptomatic adults were input into Image J, National Institutes of Health, image processing software. Bilateral zygapophysial joint angles from C2-C3 to C6-C7 were measured in the axial and coronal planes and collected from 100 subjects. The effect of gender, age, and correlation was analyzed. The surface motions of axial rotation and lateral bending were simulated in Abaqus CAE 6.5. Mathematical facet contact and range of motion were computed. The FO was widely distributed at each level. Gender had no significant association with FO. Age affected FO at most levels. Axial and coronal FO were significantly correlated. The zygapophysial joint of internally rotated/inverted FO contacted more perpendicularly to each other, and mathematical range of motion was smaller. The axial or coronal FO of the subaxial cervical spine was found with more variability. Age was significantly related to FO. Geometrically, internally rotated/inverted FO of axial rotation/lateral bending was morerestricted. The extent of axial rotation and lateral bending was correlated with each other.

  19. Involvement of membrane potential in alkaline band formation by internodal cells of Chara corallina.

    Science.gov (United States)

    Shimmen, Teruo; Wakabayashi, Akiko

    2008-10-01

    Internodal cells of Chara corallina form alkaline bands on their surface upon illumination via photosynthesis. In the present study, the effect of KCl on alkaline band formation was analyzed. When the extracellular KCl concentration was increased, alkaline band formation was extensively inhibited. Electrophysiological analysis unequivocally showed the need for inner negative membrane potential for alkaline band formation.

  20. Photoemission surface characterization of (0 0 1) In{sub 2}O{sub 3} thin film through the interactions with oxygen, water and carbon monoxide: Comparison with (1 1 1) orientation

    Energy Technology Data Exchange (ETDEWEB)

    Brinzari, V., E-mail: vbrinzari@mail.ru [State University of Moldova, str. Mateevich 60A, MD-2009 Chisinau, Republic of Moldova (Moldova, Republic of); Cho, B.K. [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Kamei, M. [National Institute for Material Science, Namiki, Tsukuba, Ibaraki (Japan); Korotcenkov, G., E-mail: ghkoro@yahoo.com [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of)

    2015-01-01

    Highlights: • SRPES of In{sub 2}O{sub 3}(0 0 1) thin film under heating activated gas exposures of O{sub 2}, H{sub 2}O, CO. • Changes in surface band bending and composition vs. these treatments. • Models of (0 0 1) surface terminations, compositions and zone diagrams. • Changes in VB spectra radically differ from the same ones for (1 1 1) film. • Adsorbed water species do not donate electrons into conduction band. - Abstract: Synchrotron radiation ultraviolet photoemission experiments at photon energies of 150 and 49 eV have been performed on (0 0 1) In{sub 2}O{sub 3} epitaxial layer with thickness of 120 nm grown by electron beam evaporation method. Valence band (VB) photoemission spectra have been monitored under separate oxygen, water and carbon monoxide exposures (100 L) at different sample temperatures within the range utilized for chemoresistive gas sensors operation (20–450 °C). Large changes in photoemission response within the whole VB were observed for all gases. Surface potential changes were identified as a shift of the valence band edge relative to the Fermi energy. It was found that the initial state of the In{sub 2}O{sub 3} surface after standard preparation procedure corresponded to highly reduced surface, close to “metallic” surface. Treatments in oxygen resulted in oxidation of the surface and regular upward band bending have been changing up to 0.27 eV. These two extreme states of the In{sub 2}O{sub 3} surface corresponded to the surface zone diagrams with accumulation layer and flat bands, respectively. Surface potential changes under water and carbon monoxide treatment have been irregular vs. temperature and small enough (<0.05 eV). However, the magnitudes of photoemission deviations under these treatments were large and comparable with intensity of an initial photoemission itself before the treatment (ΔI{sub ph} ∼ 10–40%). The obtained results have been compared with the ones previously received for (1 1 1) surface and

  1. Ultra wide band antennas

    CERN Document Server

    Begaud, Xavier

    2013-01-01

    Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recog

  2. Impedance-matching acoustic bend composed of perforated plates and side pipes

    Science.gov (United States)

    Yang, Yuzhen; Jia, Han; Lu, Wenjia; Sun, Zhaoyong; Yang, Jun

    2017-08-01

    In this article, we propose a design for an impedance-matching acoustic bend. The bending structure is composed of sub-wavelength unit cells containing perforated plates and side pipes that allow the mass density and the bulk modulus of each unit cell to be tuned simultaneously. The refractive index and the impedance of the acoustic bend can therefore be modulated simultaneously to guarantee both the bending effect and high acoustic transmission. The results of simulation of the sound pressure field distribution show that the bending effect of the proposed impedance-matching acoustic bend is very good. Transmission spectra are calculated for both the impedance-matching acoustic bend and an acoustic bend composed of the perforated plates alone for comparison. The results indicate that the impedance-matching acoustic bend successfully improves the impedance ratio while also obviously increasing the transmission.

  3. Faraday Rotation and L Band Oceanographic Measurements

    DEFF Research Database (Denmark)

    Skou, Niels

    2003-01-01

    Spaceborne radiometric measurements of the L band brightness temperature over the oceans make it possible to estimate sea surface salinity. However, Faraday rotation in the ionosphere disturbs the signals and must be corrected. Two different ways of assessing the disturbance directly from...

  4. Analytical approach to calculate bending, longitudinal and torsional local stiffness of an asymmetric circumferential crack with contact condition

    Science.gov (United States)

    Sharafi, Mojtaba Meidan; Nikravesh, Majid Yadavar; Safarpour, Pedram

    2017-09-01

    In this paper, bending, longitudinal and torsional stiffness of an eccentric circumferential crack is investigated with taking into account contact condition on the crack surfaces based on fracture mechanics. Although several researches have analyzed stress intensity factors of symmetric circumferential crack, the stiffness of an asymmetric circumferential crack in different directions (along and perpendicular to eccentricity) regarding contact condition has not been studied by an analytical method until now. In this paper we aim to describe behavior of eccentric circumferential crack under axial loading and establish a relation between axial force and the resulting displacement vector. The twisting angle of asymmetric circumferential crack due to torsional loading is also calculated and compared to twisting angle of a symmetric crack. In order to simulate the local bending stiffness in the contact condition, nonlinear governing equations of bending stiffness associated to cracked beam section is developed by dividing it to strip elements and utilizing stiffness equations related to noncontact condition. It is validated by 3D finite element (FE) nonlinear model. Results show a significant compatibility between presented analytical and 3D FE methods. Moreover results of simulations show that without taking into account contact condition, axial, torsional and bending stiffness of symmetric and asymmetric circumferential crack are equal and radius of un-cracked area is the only influential factor.

  5. Spontaneous bending of pre-stretched bilayers.

    Science.gov (United States)

    DeSimone, Antonio

    2018-01-01

    We discuss spontaneously bent configurations of pre-stretched bilayer sheets that can be obtained by tuning the pre-stretches in the two layers. The two-dimensional nonlinear plate model we use for this purpose is an adaptation of the one recently obtained for thin sheets of nematic elastomers, by means of a rigorous dimensional reduction argument based on the theory of Gamma-convergence (Agostiniani and DeSimone in Meccanica. doi:10.1007/s11012-017-0630-4, 2017, Math Mech Solids. doi:10.1177/1081286517699991, arXiv:1509.07003, 2017). We argue that pre-stretched bilayer sheets provide us with an interesting model system to study shape programming and morphing of surfaces in other, more complex systems, where spontaneous deformations are induced by swelling due to the absorption of a liquid, phase transformations, thermal or electro-magnetic stimuli. These include bio-mimetic structures inspired by biological systems from both the plant and the animal kingdoms.

  6. Secondary flow in sharp open-channel bends

    NARCIS (Netherlands)

    Blanckaert, K.; De Vriend, H.J.

    2004-01-01

    Secondary currents are a characteristic feature of flow in open-channel bends. Besides the classical helical motion (centre-region cell), a weaker and smaller counter-rotating circulation cell (outer-bank cell) is often observed near the outer bank, which is believed to play an important role in

  7. Bending It Like Beckham: How to Visually Fool the Goalkeeper

    NARCIS (Netherlands)

    Dessing, J.C.; Craig, C.M.

    2010-01-01

    Background: As bending free-kicks becomes the norm in modern day soccer, implications for goalkeepers have largely been ignored. Although it has been reported that poor sensitivity to visual acceleration makes it harder for expert goalkeepers to perceptually judge where the curved free-kicks will

  8. A Second Look at Brian Simon's "Bending the Rules"

    Science.gov (United States)

    Cox, Sue

    2016-01-01

    In this article the author revisits an important book: Brian Simon's "Bending the Rules: the Baker reform of education." Written by a key figure in the history of the journal FORUM as well as in the history of education, Simon's book documented the features of the Education Reform Bill of 1987 (the precursor to the Education Reform Act…

  9. Predicting bending stiffness of randomly oriented hybrid panels

    Science.gov (United States)

    Laura Moya; William T.Y. Tze; Jerrold E. Winandy

    2010-01-01

    This study was conducted to develop a simple model to predict the bending modulus of elasticity (MOE) of randomly oriented hybrid panels. The modeling process involved three modules: the behavior of a single layer was computed by applying micromechanics equations, layer properties were adjusted for densification effects, and the entire panel was modeled as a three-...

  10. Photoelastic stress analysis in mitred bend under internal pressure

    International Nuclear Information System (INIS)

    Sawa, Yoshiaki

    1987-01-01

    The stress analysis and stress relaxation in mitred bend subjected to internal pressure have been studied by means of the photoelastic stress freezing method. The experimental results show that stress concentration occurs in the wedge tip of the intersectional plane and it is considerably influenced by the bent angle. Then, the stress relaxation was obtained by planing the wedge tip. (author)

  11. Effect of entry bending moment on exit curvature in asymmetrical ...

    African Journals Online (AJOL)

    user

    increasing the reduction in thickness the average pressure is increased. Keywords: Asymmetrical Rolling; Modified Slab Method; Pressure Difference; Rolling Force; Bending Moment. 1. Introduction. In practice, rolling of plate and sheet asymmetry arises due to inequality in roll radii, roll velocity and interface friction. These.

  12. The Clinch Bend Regional Industrial Site and economic development opportunities

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-31

    This effort focuses initially on the Clinch Bend site. Other sites and developable tracts of land are identified with the assistance of communities in proximity to Oak Ridge, the State of Tennessee, and others, and compared with the projected site requirements for large industrial facilities.

  13. Bend-twist coupling potential of wind turbine blades

    DEFF Research Database (Denmark)

    Fedorov, Vladimir; Berggreen, Christian

    2014-01-01

    -twist coupling magnitude of up to 0.2 is feasible to achieve in the baseline blade structure made of glass-fiber reinforced plastics. Further, by substituting the glass-fibers with carbon-fibers the coupling effect can be increased to 0.4. Additionally, the effect of introduction of bend-twist coupling...

  14. High precision optical fiber alignment using tube laser bending

    NARCIS (Netherlands)

    Folkersma, Ger; Römer, Gerardus Richardus, Bernardus, Engelina; Brouwer, Dannis Michel; Herder, Justus Laurens

    2016-01-01

    In this paper, we present a method to align optical fibers within 0.2 μm of the optimal position, using tube laser bending and in situ measuring of the coupling efficiency. For near-UV wavelengths, passive alignment of the fibers with respect to the waveguides on photonic integrated circuit chips

  15. Asymptotic results for bifurcations in pure bending of rubber blocks

    OpenAIRE

    Coman, Ciprian; Destrade, Michel

    2008-01-01

    International audience; The bifurcation of an incompressible neo-Hookean thick block with a ratio of thickness to length {eta}, subject to pure bending, is considered. The two incremental equilibrium equations corresponding to a nonlinear pre-buckling state of strain are reduced to a fourth-order linear eigenproblem that displays a multiple turning point. It is found that for 0 {infty} dege...

  16. Steam bending qualities of eight timber species of Ghana | Ayarkwa ...

    African Journals Online (AJOL)

    Steam bending qualities of eight lesser used timber species of Ghana have been studied and compared with the quality of Mahogany (Khaya spp), a fast diminishing noble species, with the view to providing information for the furniture and glulam industries. Wood samples collected from three ecological forest zones of ...

  17. Flow resistance in a compound gravel-bed bend

    Indian Academy of Sciences (India)

    centrifugal force having a lateral momentum transfer. This force disappears after leaving a bend exit. Thus, the turbulent shear stress is the resistance that the flow has to overcome in transforming from a primary flow into a secondary flow pattern and vice versa. The increase in flow resistance in a meandering path can be ...

  18. Study of sharp bends in anisotropic potassium double tungstate waveguides

    NARCIS (Netherlands)

    Dubbink, T.; Sefünç, Mustafa; Pollnau, Markus; García Blanco, Sonia Maria

    Rare earth ion doped potassium double tungstate gain materials have recently shown a great promise for the development of waveguide amplifiers and lasers exhibiting excellent performance. To enable the use of this material in larger nanophotonic platforms, sharp bends are required. In this work we

  19. Reliability Analysis of Bending, Shear and Deflection Criteria of ...

    African Journals Online (AJOL)

    Reliability analysis of the safety levels of the criteria for bending, shear and deflection of singly reinforced, concrete slabs, have been evaluated over the practical range of thicknesses 100mm to 250mm. The First Order Reliability Method was employed in the evaluation procedure for continuous slabs of equal spans as a ...

  20. Adoption of improved rice varieties by farmers in Bende local ...

    African Journals Online (AJOL)

    The study investigated the adoption of improved rice varieties by farmers in Bende Local Government Area, Abia State, Nigeria. A multi-stage random sampling technique was used to select a total of 120 rice farmers. Descriptive statistics and tobit regression model were employed to analyze the data. Results showed that ...

  1. Bolted flanged connections subjected to longitudinal bending moments

    International Nuclear Information System (INIS)

    Blach, A.E.

    1992-01-01

    Flanges in piping systems and also pressure vessel flanges on tall columns are often subjected to longitudinal bending moments of considerable magnitude, be it from thermal expansion stresses in piping systems or from wind or seismic loadings on tall vertical pressure vessels. Except for the ASME Code, Section III, Subsections NB, NC, and ND, other pressure vessel and piping codes do not contain design ASME Nuclear Power Plant Code (Section III), an empirical formula is given, expressing a longitudinal bending moment in bolted flanged connections in terms of an equivalent internal pressure to be added to the design pressure of the flange. In this paper, an attempt is made to analyse the stresses on flanges and bolting due to external bending moments and to compare flange thicknesses thus obtained with thicknesses required using the equivalent design pressure specified in Subsections NB, NC, and ND. A design method is proposed, based on analysis and experimental work, which may be suitable for flange bending moment analysis when the rules of the Nuclear Power Plant Code are not mandatory. (orig.)

  2. Correlation between pipe bend geometry and allowable pressure in ...

    African Journals Online (AJOL)

    Determination of allowable pressure, which is one of the important criteria to evaluate the acceptability of pipe bends with shape irregularities, is complex as the analytical solution of the problem involves solution of complex differential equations. Artificial Neural Network (ANN) is used in this paper to determine the ...

  3. A Note on Stress Function Discontinuities in Plane Plastic Bending ...

    African Journals Online (AJOL)

    The variational and differential equation formulations of the stress function problem for combined plane bending and torsion of a fully plastic material are discussed. The nature of discontinuities to be expected as well as the actual degree of correspondence between the two formulations is determined. A modification of the ...

  4. Tidal bending of glaciers: a linear viscoelastic approach

    DEFF Research Database (Denmark)

    Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph

    2003-01-01

    In theoretical treatments of tidal bending of floating glaciers, the glacier is usually modelled as an elastic beam with uniform thickness, resting on an elastic foundation. With a few exceptions, values of the elastic (Young's) modulus E of ice derived from tidal deflection records of floating...

  5. Magnetically assisted bilayer composites for soft bending actuators

    NARCIS (Netherlands)

    Jang, S.H.; Na, Seon Hong; Park, Yong Lae

    2017-01-01

    This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically

  6. Bending strategies of convergently-evolved, articulated coralline algae.

    Science.gov (United States)

    Janot, Kyra G; Martone, Patrick T

    2018-03-05

    The evolution of uncalcified genicula in upright, calcified corallines has occurred at least three times independently, resulting in articulated corallines within Corallinoideae, Lithophylloideae, and Metagoniolithoideae. Genicula confer flexibility to otherwise rigid thalli, and the localization of bending at discrete intervals amplifies bending stress in genicular tissue. Genicular morphology must therefore be balanced between maintaining flexibility while mitigating or resisting stress. Genicula in the three articulated lineages differ in both cellular construction and development, which may result in different constraints on morphology. By studying the interaction between flexibility and morphological variation in multiple species, we investigate whether representatives of convergently evolving clades follow similar strategies to generate mechanically successful articulated fronds. By using computational models to explore different bending strategies, we show that there are multiple ways to generate flexibility in upright corallines but that not all morphological strategies are mechanically equivalent. Corallinoids have many joints, lithophylloids have pliant joints, and metagoniolithoids have longer joints - while these strategies can lead to comparable thallus flexibility, they also lead to different levels of stress amplification in bending. Moreover, genicula at greatest risk of stress amplification are typically the strongest, universally mitigating the trade-off between flexibility and stress reduction. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  7. Tidal bending of glaciers: a linear viscoelastic approach

    DEFF Research Database (Denmark)

    Reeh, Niels; Christensen, Erik Lintz; Mayer, Christoph

    2003-01-01

    glaciers are in the range 0.9-3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E approximate to 1 GPa adequately describes tidal bending of glaciers.In contrast, laboratory experiments with ice give E =93 GPa, i.e. 3-10 times higher than the glacier-derived values...

  8. Timoshenko-Wagner-Kappus Torsion Bending Theory and Wind ...

    Indian Academy of Sciences (India)

    Timoshenko-Wagner-Kappus Torsion Bending. Theory and Wind Tunnel Balance Design. S P Govinda Raju and K R Y Simha. S P Govinda Raju is a. Professor at the. Aero- space Engineering. Department, Indian. Institute of Science,. Bangalore. His interests are fluid mechanics, aircraft design, testing and analysis.

  9. BENDING OF REINFORCING BARS TESTING METHOD AND INFLUENCE ON STRUCTURES

    Directory of Open Access Journals (Sweden)

    Hari Warsianto

    2012-02-01

    Full Text Available Reinforcing bars in concrete elements functions as the component carrying tensile stresses after concretecracking. This is due to that fact that concrete exhibit very high compression strength combined with avery low tensile capacity. The tensile stressed are transferred to the bars by the bond between thereinforcement and the concrete.Bars are generally produced in strands 6 to 12 meter in length so that bending for transportation andhandling purposes becomes necessary. At the site bars are straightened, and then sometimes re-bent forassembling purposes. This process will result in a loading and re-loading of steel.The ASTM E-290 mandated that bars have to pass the bending test, whereas reinforcing steel bars arebend to almost 1800 to ensure material ductility. In the past five years the Construction and MaterialLaboratory, Diponegoro University has been questioned with the issue as to how far this bending andstraightening influences the quality and what the significance of testing is.This paper will evaluate theinfluence of bending and straightening and the testing procedure involved.

  10. Multiphase fluid structure interaction in bends and T-joints

    NARCIS (Netherlands)

    Cargnelutti, M.F.; Belfroid, S.P.C.; Schiferli, W.; Osch, M.M.E. van

    2010-01-01

    Air-water experiments were carried out in a horizontal 1" pipe system to measure the magnitude of the forces induced by the multiphase flow. Forces and accelerations were measured on a number of bends and T-joint configurations for a wide range of operating conditions. Five different configurations

  11. Sediment transport in an active erodible channel bend of ...

    Indian Academy of Sciences (India)

    Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood with ... Local variation of sediment transport is primarily controlled by active bank erosion, land spur and sand bar ..... of Water, Environment, Energy and Society (WEES)-2009, New Delhi, India, 1670–1676. Karmaker T, Dutta S ...

  12. Residual bending behaviour of sandwich composites after impact

    NARCIS (Netherlands)

    Baran, Ismet; Weijermars, Wouter

    2018-01-01

    This work investigates the residual mechanical behaviour of composite sandwich panels in bending after impact loading conditions. The sandwich panels were made of an epoxy/glass face sheet with three different core materials: styrene acrylonitrile foam, polyethylene terephthalate foam and Balsa

  13. Bi-2212/Ag tapes and laminates: effects of bending

    International Nuclear Information System (INIS)

    Ilyushechkin, A.Y.; Yamashita, T.; Williams, B.; Mackinnon, I.D.R.

    1999-01-01

    Superconducting Bi-2212 tapes and laminates are fabricated by a combination of dip-coating and partial melt processing. The heat treated tapes have critical current densities (J c ) up to 11 kA cm -2 . We investigate the degradation of critical current (I c ) during bending experiments for both single tapes and tapes with laminate structure. Although degradation of I c is observed in both forms, the characteristics of the degradation differ. It is determined that laminated tapes perform better than single tapes when critical current is measured against bending radius, and laminated tapes tolerate a higher strain for a given reduction in critical current. It is found that increasing the number of Bi-2212 layers increases the total I c of the laminated tape, but degradation of critical current is more pronounced during bending because of the increased total thickness of the laminate structure. It is also found that addition of silver to the Bi-2212 layers reduces critical current degradation during bending for both tapes and laminates. (author)

  14. A Novel Rotary Piezoelectric Motor Using First Bending Hybrid Transducers

    Directory of Open Access Journals (Sweden)

    Yingxiang Liu

    2015-08-01

    Full Text Available We report a novel rotary piezoelectric motor using bending transducers in this work. Three transducers are used to drive a disk-shaped rotor together by the elliptical movements of their driving tips; these motions are produced by the hybrid of two first bending vibration modes. The proposed piezoelectric transducer has a simple structure as it only contains an aluminum alloy beam and four pieces of PZT plates. Symmetrical structure is the only necessary condition in the design process as it will ensure the resonance frequencies of the two orthogonal first bending modes are equal. Transducers with first bending resonance frequency of about 53 kHz were fabricated and assembled into a rotary motor. The proposed motor exhibits good performance on speed and torque control. Under a working frequency of 53.2 kHz, the maximum no-load speed and the maximum torque of the prototype are tested to be 53.3 rpm and of 27 mN·m.

  15. Timoshenko–Wagner–Kappus Torsion Bending Theory and Wind ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 10. Timoshenko–Wagner–Kappus Torsion Bending Theory and Wind Tunnel Balance Design. S P Govinda Raju K R Y Simha. General Article Volume 7 Issue 10 October 2002 pp 54-58 ...

  16. Effect of entry bending moment on exit curvature in asymmetrical ...

    African Journals Online (AJOL)

    In addition, employing a bending moment at entry of the roll gap in a symmetrical rolling process causes pressure difference on the rolls and warping at the outlet, as happens in an asymmetrical rolling process. Similarly, increasing the roll diameter ratio increases the pressure differences, but the average pressure between ...

  17. Diagnosis of the Fracture and Fracture Energy of High-Ductility Steels in Instrumented Impact-Bending Tests

    Science.gov (United States)

    Farber, V. M.; Khotinov, V. A.; Morozova, A. N.; Lezhnin, N. V.; Martin, T.

    2015-09-01

    Fractures and their profiles are diagnosed by macro- and micro-fractographic analysis after impact bending tests of Charpy specimens of a high-ductility steel of strength class X80. The results of the analysis of fracture surfaces and fracture diagrams are used to determine the unit amount of energy expended on ductile fracture in various zones in terms of the average length of the ridges (bridges) in the microstructure.

  18. Bending and free vibration analysis of thick isotropic plates by using exponential shear deformation theory

    Directory of Open Access Journals (Sweden)

    Sayyad A. S.

    2012-06-01

    Full Text Available This paper presents a variationally consistent an exponential shear deformation theory for the bi-directional bending and free vibration analysis of thick plates. The theory presented herein is built upon the classical plate theory. In this displacement-based, refined shear deformation theory, an exponential functions are used in terms of thickness co-ordinate to include the effect of transverse shear deformation and rotary inertia. The number of unknown displacement variables in the proposed theory are same as that in first order shear deformation theory. The transverse shear stress can be obtained directly from the constitutive relations satisfying the shear stress free surface conditions on the top and bottom surfaces of the plate, hence the theory does not require shear correction factor. Governing equations and boundary conditions of the theory are obtained using the dynamic version of principle of virtual work. The simply supported thick isotropic square and rectangular plates are considered for the detailed numerical studies. Results of displacements, stresses and frequencies are compared with those of other refined theories and exact theory to show the efficiency of proposed theory. Results obtained by using proposed theory are found to be agree well with the exact elasticity results. The objective of the paper is to investigate the bending and dynamic response of thick isotropic square and rectangular plates using an exponential shear deformation theory.

  19. Band-notched spiral antenna

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Jae; Chang, John

    2018-03-13

    A band-notched spiral antenna having one or more spiral arms extending from a radially inner end to a radially outer end for transmitting or receiving electromagnetic radiation over a frequency range, and one or more resonance structures positioned adjacent one or more segments of the spiral arm associated with a notch frequency band or bands of the frequency range so as to resonate and suppress the transmission or reception of electromagnetic radiation over said notch frequency band or bands.

  20. Hybrid Method for Analyzing the Torsional Vibration of One-Dimensional Phononic-Band-Gap Shafts

    Science.gov (United States)

    Li, Lixia; Chen, Tianning; Wu, Jiuhui; Wang, Xiaopeng; Wang, Zhaofeng

    2012-05-01

    A hybrid method combining the transfer-matrix and lumped-mass methods is proposed to study the band gaps of torsional vibration in one-dimensional (1D) phononic band gap (PBG)-like shafts, which periodically arrange local resonant multilayer rings. The present method shows advantages over the transfer-matrix and lumped-mass methods for determining the inertia of rubber rings and fast convergence with less computational requirements. For light local resonators, the torsional band gaps, which were studied in three 1D PBG-like shafts by the hybrid method, agree well with those studied by the finite method. In addition, more precise evaluations of the starting frequency of the band gaps were carried out analytically. The methodology of the approach presented can also be employed to study the band gaps of bending and longitudinal waves.

  1. Semiconductor band alignment from first principles: a new nonequilibrium Green's function method applied to the CZTSe/CdS interface for photovoltaics

    DEFF Research Database (Denmark)

    Palsgaard, Mattias Lau Nøhr; Crovetto, Andrea; Gunst, Tue

    2016-01-01

    In this paper we present a method to obtain the band offset of semiconductor heterointerfaces from Density Functional Theory together with the nonequilibrium Green's function method. Band alignment and detailed properties of the interface between Cu2ZnSnSe4 and CdS are extracted directly from first...... principles simulations. The interface is important for photovoltaics applications where in particular the band offsets are important for efficiency. The band bending pose a problem for accurate atomistic simulations of band offsets due to its long range. Here we investigate two different methods for dealing...

  2. Effects of weak nonlinearity on the dispersion relation and frequency band-gaps of a periodic Bernoulli–Euler beam

    DEFF Research Database (Denmark)

    Sorokin, Vladislav S.; Thomsen, Jon Juel

    2016-01-01

    The paper deals with analytically predicting the effects of weak nonlinearity on the dispersion relation and frequency band-gaps of a periodic Bernoulli– Euler beam performing bending oscillations. Two cases are considered: (i) large transverse deflections, where nonlinear (true) curvature...

  3. Ligament rupture and unstable burst behaviors of axial flaws in steam generator U-bends

    International Nuclear Information System (INIS)

    Bahn, Chi Bum; Oh, Young-Jin; Majumdar, Saurin

    2015-01-01

    Highlights: • Ligament rupture and unstable burst pressure tests were conducted with U-bends. • In general, U-bends showed higher ligament rupture and burst pressures than straight tubes. • U-bend test data was bounded by 90% lower limit of the probabilistic models for straight tubes. • Prediction models for straight tubes could be conservatively applied to U-bends. - Abstract: Incidents of U-bend cracking in steam generator (SG) tubes have been reported, some of which have led to tube rupture. Experimental and analytical modeling efforts to determine the failure criteria of flawed SG U-bends are limited. To evaluate structural integrity of flawed U-bends, ligament rupture and unstable burst pressure tests were conducted on 57 and 152 mm bend radius U-bends with axial electrical discharge machining notches. In general, the ligament rupture and burst pressures of the U-bends were higher than those of straight tubes with similar notches. To quantitatively address the test data scatter issue, probabilistic models were introduced. All ligament rupture and burst pressures of U-bends were bounded by 90% lower limits of the probabilistic models for straight tubes. It was concluded that the prediction models for straight tubes could be applied to U-bends to conservatively evaluate the ligament rupture and burst pressures of U-bends with axial flaws.

  4. Investigation of chiral bands in {sup 106}Ag

    Energy Technology Data Exchange (ETDEWEB)

    Lieder, Evgenia [Themba LABS, Somerset West (South Africa); FhG, INT, Euskirchen (Germany); Lieder, Rainer; Bark, Rob; Lawrie, Elena; Lawrie, Kobus; Ntshangase, Sifiso; Mullins, Simon; Papka, Paul; Kheswa, Ntombi [Themba LABS, Somerset West (South Africa); Meng, Jie [PhS, PKU, Beijing (China); PhS, BUAA, Beijing (China); Qi, Bin [SDU, Weihai (China); Zhang, Shuangquan; Li, Zhipan [PhS, PKU, Beijing (China)

    2010-07-01

    Dipole bands in {sup 106}Ag have been studied with the {gamma}-detector array AFRODITE at iThemba LABS, South Africa. A {sup 96}Zr({sup 14}N,4n){sup 106}Ag reaction at a beam energy of 71 MeV has been used. The three previously known negative-parity bands in {sup 106}Ag have been extended. Bands 1 and 2 were proposed to be chiral partner bands. However, in view of the present results, bands 2 and 3 seem to be better candidates for chiral partner bands since their staggering parameters, B(M1)/B(E2) ratios, kinematic moments of inertia and quasiparticle alignments agree much better than those of bands 1 and 2. Triaxial relativistic mean field (RMF) and particle-rotor model (PRM) calculations support this interpretation. In the potential energy surface of {sup 106}Ag, obtained in RMF calculations, two minima have been found in the {beta}{sub 2}-{gamma} plane. Based on PRM calculations using the deformation parameters of the two minima and a {nu}h{sub 11/2} x {pi}g{sup -1}{sub 9/2} particle-hole configuration, bands 2 and 3 may represent partners with chiral vibration at {gamma}{approx}12degree. Band 1, located in the other minimum, may be a magnetic dipole band or the partner of a second pair of chiral bands.

  5. Effects of bending and heat on the ductility and fracture toughness of flange plate.

    Science.gov (United States)

    2012-05-01

    Bridge fabricators for the Texas Department of Transportation (TxDOT) have occasionally experienced the : formation of cracks in flange plate during bending operations, particularly when heat is applied. Bending the : flange plate is necessary for ce...

  6. Theoretical band alignment in an intermediate band chalcopyrite based material

    Science.gov (United States)

    Castellanos Águila, J. E.; Palacios, P.; Conesa, J. C.; Arriaga, J.; Wahnón, P.

    2017-12-01

    Band alignment is key to enhance the performance of heterojunction for chalcopyrite thin film solar cells. In this paper we report ab initio calculations of the electronic structures of CuGaS2:Cr with various Cr compositions, CuAlSe2 and ZnSe and the band alignment between their interfaces. We use density functional theory and the more accurate self-consistent GW scheme to obtain improved bulk band-gaps and band offsets. Band alignments of the interfacial region for CuGaS2:Cr/CuAlSe2 and CuGaS2:Cr/ZnSe systems were aligned with respect of an average electrostatic potential. Our results are in good agreement with experimental values for the bulk band-gaps. These theoretical band alignments show a characteristic staggered band alignment for the design of heterojunction devices in photovoltaic applications.

  7. Investigation of meso-failure behaviors of Jinping marble using SEM with bending loading system

    Directory of Open Access Journals (Sweden)

    Jianping Zuo

    2015-10-01

    Full Text Available In this study, the meso-failure mechanism and fracture surface of Jinping marble were investigated by means of scanning electron microscope (SEM with bending loading system and laser-scanner equipment. The Yantang and Baishan marbles specimens from Jinping II hydropower station were used. Test results show that the fracture toughness and mechanical behaviors of Yantang marble were basically higher than those of Baishan marble. This is mainly due to the fact that Baishan marble contains a large percentage of dolomite and minor mica. Crack propagation path and fracture morphology indicated that the direction of tensile stress has a significant effect on the mechanical behaviors and fracture toughness of Baishan marble. For Yantang and Baishan marbles, a large number of microcracks around the main crack tip were observed when the direction of tensile stress was parallel to the bedding plane. Conversely, few microcracks occurred when the direction of tensile stress was perpendicular to the bedding plane. The presence of a large number of microcracks at the main crack tip decreased the global fracture toughness of marble. The results of three-point bending tests showed that the average bearing capacity of intact marble is 3.4 times the notched marble, but the ductility property of the defective marble after peak load is better than that of the intact marble. Hence, large deformation may be generated before failure of intact marbles at Jinping II hydropower station. The fractal dimension of fracture surface was also calculated by the cube covering method. Observational result showed that the largest fractal dimension of Yantang marble is captured when the direction of tensile stress is parallel to the bedding plane. However, the fractal dimension of fracture surface of Yantang and Baishan marbles with tensile stress vertical to the bedding plane is relatively small. The fractal dimension can also be used to characterize the roughness of fracture

  8. A K/Ka band radiating element for Tx/Rx phased array

    KAUST Repository

    Sandhu, Ali Imran

    2017-01-20

    The paper presents a K/Ka band radiating element for TX/RX phased arrays. Dual band operations is obtained using a single radiating surface: a novel radiator is adopted and placed in a configuration in which dual band and single band elements are interleaved. The array elements are optimized to scan the beam in excess of 50° in both bands. A subarray with 49 Rx elements and 105 Tx elements was built and measured confirming the results obtained in simulations.

  9. Surface and Superconductivity

    Science.gov (United States)

    Gor'kov, L. P.

    2006-07-01

    Experiments reveal the existence of metallic bands at surfaces of metals and insulators. The bands can be doped externally. We review properties of surface superconductivity that may set up in such bands at low temperatures and various means of superconductivity defection. The fundamental difference as compared to the ordinary superconductivity in metals, besides its two-dimensionality lies in the absence of the center of space inversion. This results in mixing between the singlet and triplet channels of the Cooper pairing.

  10. Ferroelectric polarization effect on surface chemistry and photo-catalytic activity: A review

    Science.gov (United States)

    Khan, M. A.; Nadeem, M. A.; Idriss, H.

    2016-03-01

    The current efficiency of various photocatalytic processes is limited by the recombination of photogenerated electron-hole pairs in the photocatalyst as well as the back-reaction of intermediate species. This review concentrates on the use of ferroelectric polarization to mitigate electron-hole recombination and back-reactions and therefore improve photochemical reactivity. Ferroelectric materials are considered as wide band gap polarizable semiconductors. Depending on the surface polarization, different regions of the surface experience different extents of band bending and promote different carriers to move to spatially different locations. This can lead to some interesting interactions at the surface such as spatially selective adsorption and surface redox reactions. This introductory review covers the fundamental properties of ferroelectric materials, effect of an internal electric field/polarization on charge carrier separation, effect of the polarization on the surface photochemistry and reviews the work done on the use of these ferroelectric materials for photocatalytic applications such as dye degradation and water splitting. The manipulation of photogenerated charge carriers through an internal electric field/surface polarization is a promising strategy for the design of improved photocatalysts.

  11. Band alignment and interfacial chemical structure of the HfLaO/InGaZnO4 heterojunction investigated by x-ray photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Qian, Ling-Xuan; Wu, Ze-Han; Zhang, Yi-Yu; Liu, Xing-Zhao; Li, Yan-Rong; Liu, Yuan; Song, Jia-Qi

    2017-01-01

    Amorphous InGaZnO 4 thin film transistors (a-IGZO TFTs) with HfLaO gate dielectrics have been widely demonstrated to possess extremely excellent electrical characteristics, and thus show great potential for applications in various next-generation electronic products. Nevertheless, the in-depth understanding of HfLaO/IGZO interfacial features is still lacking, which makes further device optimization lack clear guidance. In this work, the band alignment and interfacial chemical structure of a sputtering-prepared HfLaO/IGZO heterojunction was investigated through x-ray photoelectron spectroscopy. The valence and conduction band offsets (Δ E v and Δ E c ) at the interface were determined to be 0.57 eV and 1.48 eV, respectively. The relatively large Δ E v is mainly attributed to the formation of the interfacial layer (IL) and thus the upward band bending from IGZO to the surface of HfLaO. Furthermore, it was found that the oxygen vacancies on the surface of IGZO were significantly suppressed upon the deposition of HfLaO, which not only explained the previously reported ultrahigh performance of a-IGZO/HfLaO TFTs to some extent, but also additionally validated the formation of the IL. Our findings have successfully revealed the importance of ILs in modifying the band alignment and interfacial trap states of HfLaO/IGZO heterojunctions, thus suggesting a potential route to further optimizing a-IGZO/HfLaO TFTs so as to satisfy the requirements of next-generation technologies. (paper)

  12. Respiratory monitoring system based on fiber optic macro bending

    Science.gov (United States)

    Purnamaningsih, Retno Wigajatri; Widyakinanti, Astari; Dhia, Arika; Gumelar, Muhammad Raditya; Widianto, Arif; Randy, Muhammad; Soedibyo, Harry

    2018-02-01

    We proposed a respiratory monitoring system for living activities in human body based on fiber optic macro-bending for laboratory scale. The respiration sensor consists of a single-mode optical fiber and operating on a wavelength at around 1550 nm. The fiber optic was integrated into an elastic fabric placed on the chest and stomach of the monitored human subject. Deformations of the flexible textile involving deformations of the fiber optic bending curvature, which was proportional to the chest and stomach expansion. The deformation of the fiber was detected using photodetector and processed using microcontroller PIC18F14K50. The results showed that this system able to display various respiration pattern and rate for sleeping, and after walking and running activities in real time.

  13. Coupled Torsional and Bending Vibrations of Actively Controlled Drillstrings

    Science.gov (United States)

    YIGIT, A. S.; CHRISTOFOROU, A. P.

    2000-06-01

    The dynamics of actively controlled drillstrings is studied. The equations of motion are derived using a lumped parameter model in which the coupling between torsional and bending vibrations is considered. The model also includes the dynamics of the rotary drive system which contains the rotary table, the gearbox and an armature controlled DC motor. The interactions between the drillstring and the borehole which are considered, include the impacts of collars with the borehole wall as well as bit rotation-dependent weight and torque on bit (WOB and TOB). Simulation results obtained by numerically solving the equations of motion are in close qualitative agreement with field and laboratory observations regarding stick-slip oscillations. A linear quadratic regulator (LQR) controller is designed based on a linearized model and is shown to be effective in eliminating this type of oscillations. It is also shown that for some operational parameters the control action may excite large bending vibrations due to coupling with the torsional motion.

  14. Unexpected decoupling of stretching and bending modes in protein gels.

    Science.gov (United States)

    Gibaud, Thomas; Zaccone, Alessio; Del Gado, Emanuela; Trappe, Véronique; Schurtenberger, Peter

    2013-02-01

    We show that gels formed by arrested spinodal decomposition of protein solutions exhibit elastic properties in two distinct frequency domains, both elastic moduli exhibiting a remarkably strong dependence on volume fraction. Considering the large difference between the protein size and the characteristic length of the network we model the gels as porous media and show that the high and low frequency elastic moduli can be respectively attributed to stretching and bending modes. The unexpected decoupling of the two modes in the frequency domain is attributed to the length scale involved: while stretching mainly relates to the relative displacement of two particles, bending involves the deformation of a strand with a thickness of the order of a thousand particle diameters.

  15. Ultrasonic Motor Using Bending Modes with Single Foot

    Directory of Open Access Journals (Sweden)

    Xiaohui Yang

    2013-01-01

    Full Text Available A new ultrasonic motor using bending modes with single foot is proposed in this study. Two groups of PZT elements are clamped between two horns and two ending caps, respectively, by bolts. Two horns are connected by the driving foot in the middle of the motor. Two orthogonal 3rd bending vibrations of the motor are superimposed and generate elliptical movement at the driving foot. The structure and working principle of the proposed motor are introduced. The structure parameters of the motor are obtained via the ANSYS software. A prototype is fabricated and tested using an impedance analyzer and a scanning laser Doppler vibrometer. The maximum mechanical output force and power of the prototype are measured to be 23 N and 2.9 W, respectively.

  16. Failure mechanism of PMI foam core sandwich beam in bending

    Directory of Open Access Journals (Sweden)

    Wang Bo

    2015-01-01

    Full Text Available Polymethacrylimide (PMI foams have been widely applied in aerospace engineering as the core material of sandwich structures. This paper proposes a modified model to predict the constitutive relation of PMI foams and compares it to existing testing data. The study is then applied to the investigation of the failure mechanism of PMI foam core sandwich beams in bending. Corresponding bending tests were carried out where a complex failure process was observed through a high-speed camera. Numerical model of the foregoing sandwich beam is developed, in which the maximum principal stress criteria is used to predict damage propagation in PMI foam core. Both results from tests and numerical simulation validate the reliability of the theoretical prediction of the failure of PMI foam core sandwich beam using the proposed modified model of PMI foams. This study provides a theoretic tool for the design of sandwich structures with PMI foam core.

  17. A plant-inspired robot with soft differential bending capabilities.

    Science.gov (United States)

    Sadeghi, A; Mondini, A; Del Dottore, E; Mattoli, V; Beccai, L; Taccola, S; Lucarotti, C; Totaro, M; Mazzolai, B

    2016-12-20

    We present the design and development of a plant-inspired robot, named Plantoid, with sensorized robotic roots. Natural roots have a multi-sensing capability and show a soft bending behaviour to follow or escape from various environmental parameters (i.e., tropisms). Analogously, we implement soft bending capabilities in our robotic roots by designing and integrating soft spring-based actuation (SSBA) systems using helical springs to transmit the motor power in a compliant manner. Each robotic tip integrates four different sensors, including customised flexible touch and innovative humidity sensors together with commercial gravity and temperature sensors. We show how the embedded sensing capabilities together with a root-inspired control algorithm lead to the implementation of tropic behaviours. Future applications for such plant-inspired technologies include soil monitoring and exploration, useful for agriculture and environmental fields.

  18. A Low Frequency FBG Accelerometer with Symmetrical Bended Spring Plates

    Directory of Open Access Journals (Sweden)

    Fufei Liu

    2017-01-01

    Full Text Available To meet the requirements for low-frequency vibration monitoring, a new type of FBG (fiber Bragg grating accelerometer with a bended spring plate is proposed. Two symmetrical bended spring plates are used as elastic elements, which drive the FBG to produce axial strains equal in magnitude but opposite in direction when exciting vibrations exist, leading to doubling the wavelength shift of the FBG. The mechanics model and a numerical method are presented in this paper, with which the influence of the structural parameters on the sensitivity and the eigenfrequency are discussed. The test results show that the sensitivity of the accelerometer is more than 1000 pm/g when the frequency is within the 0.7–20 Hz range.

  19. A thermo-viscoelastic approach for the characterization and modeling of the bending behavior of thermoplastic composites – Part II

    NARCIS (Netherlands)

    Ropers, Steffen; Sachs, Ulrich; Kardos, Marton; Osswald, Tim A.

    2017-01-01

    A proper description of the bending behavior is crucial to obtain accurate forming simulations, especially for continuous fiber-reinforced thermoplastic composites. These materials exhibit a highly temperature and bending-curvature dependent bending stiffness. These dependencies make the property

  20. L and P Band MMIC T/R Module Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This proposal is specifically written to address the need for improved L and P band T/R modules for use in active microwave surveillance of earth surface and...

  1. Effect of hexane treatment and uniaxial stretching on bending ...

    African Journals Online (AJOL)

    ... β31, defined as the bending piezoelectric stress constant, was calculated. After hexane treatment and uniaxial stretching of the PVDF film, the value of β31 was 5.75 mV/m and 8.00 mV/m for draw ratio of 1.5 and 2.5 was recorded. Fourier transform Infra-red (FTIR) spectrophotometry was used for structural investigations.

  2. Multi layer chromosome organization through DNA bending, bridging and extrusion

    OpenAIRE

    Gruber, S.

    2014-01-01

    All living cells have to master the extraordinarily extended and tangly nature of genomic DNA molecules in particular during cell division when sister chromosomes are resolved from one another and confined to opposite halves of a cell. Bacteria have evolved diverse sets of proteins, which collectively ensure the formation of compact and yet highly dynamic nucleoids. Some of these players act locally by changing the path of DNA through the bending of its double helical backbone. Other proteins...

  3. Concept for a self-correcting sheet metal bending operation

    OpenAIRE

    Damerow, U.; Tabakajew, D.; Borzykh, M.; Schaermann, W.; Homberg, W.; Trächtler, A.

    2014-01-01

    Geometrical deviations can appear in the production of plug contacts used in electrical connection technology and in fittings for the furniture industry. The reasons for this can be a variation in the properties of the semi-finished product, or wear phenomena on the forming machine itself or on the bending tools. When geometrical deviations appear, the process parameters normally have to be adjusted manually. Finding the most appropriate process parameters is currently done manually and is th...

  4. Suitability of sheet bending modelling techniques in CAPP applications

    OpenAIRE

    Streppel, A.H.; de Vin, L.J.; de Vin, L.J.; Brinkman, J.; Brinkman, J.; Kals, H.J.J.

    1993-01-01

    The use of CNC machine tools, together with decreasing lot sizes and stricter tolerance prescriptions, has led to changes in sheet-metal part manufacturing. In this paper, problems introduced by the difference between the actual material behaviour and the results obtained from analytical models and FEM simulations are discussed against the background of the required predictable accuracy in small-batch part manufacturing and FMS environments. The topics are limited to those relevant to bending...

  5. Magnetically Assisted Bilayer Composites for Soft Bending Actuators

    OpenAIRE

    Jang, Sung-Hwan; Na, Seon-Hong; Park, Yong-Lae

    2017-01-01

    This article presents a soft pneumatic bending actuator using a magnetically assisted bilayer composite composed of silicone polymer and ferromagnetic particles. Bilayer composites were fabricated by mixing ferromagnetic particles to a prepolymer state of silicone in a mold and asymmetrically distributed them by applying a strong non-uniform magnetic field to one side of the mold during the curing process. The biased magnetic field induces sedimentation of the ferromagnetic particles toward o...

  6. Orbital dynamics in a storage ring with electrostatic bending

    International Nuclear Information System (INIS)

    Mane, S.R.

    2008-01-01

    A storage ring where electrostatic fields contribute to the bending and focusing of the orbital motion has some novel features because, unlike a magnetostatic field, an electrostatic field can change the kinetic energy of the particles. I present analytical formulas to calculate the linear focusing gradient, dispersion, momentum compaction and natural chromaticity for a storage ring with a radial electrostatic field. I solve the formulas explicitly for a weak focusing model.

  7. The proteome of Populus nigra woody root: response to bending

    Science.gov (United States)

    Trupiano, Dalila; Rocco, Mariapina; Renzone, Giovanni; Scaloni, Andrea; Viscosi, Vincenzo; Chiatante, Donato; Scippa, Gabriella S.

    2012-01-01

    Background and Aims Morphological and biomechanical alterations occurring in woody roots of many plant species in response to mechanical stresses are well documented; however, little is known about the molecular mechanisms regulating these important alterations. The first forest tree genome to be decoded is that of Populus, thereby providing a tool with which to investigate the mechanisms controlling adaptation of woody roots to changing environments. The aim of this study was to use a proteomic approach to investigate the response of Populus nigra woody taproot to mechanical stress. Methods To simulate mechanical perturbations, the taproots of 30 one-year-old seedlings were bent to an angle of 90 ° using a steel net. A spatial and temporal two-dimensional proteome map of the taproot axis was obtained. We compared the events occurring in the above-bending, central bending and below-bending sectors of the taproot. Key Results The first poplar woody taproot proteome map is reported here; a total of 207 proteins were identified. Spatial and temporal proteomic analysis revealed that factors involved in plant defence, metabolism, reaction wood formation and lateral root development were differentially expressed in the various sectors of bent vs. control roots, seemingly in relation to the distribution of mechanical forces along the stressed woody taproots. A complex interplay among different signal transduction pathways involving reactive oxygen species appears to modulate these responses. Conclusions Poplar woody root uses different temporal and spatial mechanisms to respond to mechanical stress. Long-term bending treatment seem to reinforce the defence machinery, thereby enabling the taproot to better overcome winter and to be ready to resume growth earlier than controls. PMID:22437664

  8. PREDICTION OF BASALT FIBER REINFORCED CONCRETE PAVEMENT BENDING STRENGTH VALUES

    OpenAIRE

    Hidayet BAYRAKTAR; Ayhan SAMANDAR; Suat SARIDEMİR

    2017-01-01

    This paper proposes the potential of artificial neural network (ANN) system for estimating the bending strength values of the basalt fiber reinforced concrete pavements. Three main influential parameters; namely basalt fiber ratio, density and slump value of the fresh concrete were selected as input data. The model was trained, tested using 400 data sets which were the results of on-site experiment tests. ANN system results were also compared with the experimental test results. The research r...

  9. Wooden models of an AA quadrupole between bending magnets

    CERN Multimedia

    CERN PhotoLab

    1978-01-01

    At two points in the AA lattice, a quadrupole (QDN, defocusing, narrow) was tightly wedged between two bending magnets (BST, short, wide). This picture of wooden models lets one imagine the strong interaction between their magnetic fields. There was no way one could calculate with the necessary accuracy the magnetic effects and their consequences for the machine optics. The necessary corrections were made after measurements with a circulating beam, in a tedious iterative procedure, with corrrection coils and shims.

  10. Bending continuous structures with SMAs: a novel robotic fish design

    OpenAIRE

    Rossi, Claudio; Colorado Montaño, Julián; Coral Cuellar, William; Barrientos Cruz, Antonio

    2011-01-01

    In this paper, we describe our research on bio-inspired locomotion systems using deformable structures and smart materials, concretely shape memory alloys (SMAs). These types of materials allow us to explore the possibility of building motor-less and gear-less robots. A swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature o...

  11. Viscoelastic bending model for continuous fiber-reinforced thermoplastic composites in melt

    NARCIS (Netherlands)

    Sachs, U.; Akkerman, R.

    2017-01-01

    Bending of single plies or stacks of multiple plies is an essential deformation mechanism during thermoforming of thermoplastic composites. A reliable prediction of the forming process requires an accurate description of the bending behavior. To this end, a characterization method for the bending of

  12. Impact of bending speed and setup on flex cracks in multilayer ceramic capacitors

    DEFF Research Database (Denmark)

    Andersson, Caroline; Kristensen, Ole; Varescon, Elise

    2017-01-01

    A comparison of bending speed and experimental setups using 3-point or 4-point bending for introduction of flex cracks into multilayer ceramic capacitors (MLCCs) in a controlled manner is presented. The impact of bending speed and corresponding strain rates on the formed flex cracks detected by X...

  13. Femoral loading mechanics in the Virginia opossum, Didelphis virginiana: torsion and mediolateral bending in mammalian locomotion.

    Science.gov (United States)

    Gosnell, W Casey; Butcher, Michael T; Maie, Takashi; Blob, Richard W

    2011-10-15

    Studies of limb bone loading in terrestrial mammals have typically found anteroposterior bending to be the primary loading regime, with torsion contributing minimally. However, previous studies have focused on large, cursorial eutherian species in which the limbs are held essentially upright. Recent in vivo strain data from the Virginia opossum (Didelphis virginiana), a marsupial that uses a crouched rather than an upright limb posture, have indicated that its femur experiences appreciable torsion during locomotion as well as strong mediolateral bending. The elevated femoral torsion and strong mediolateral bending observed in D. virginiana might result from external forces such as a medial inclination of the ground reaction force (GRF), internal forces deriving from a crouched limb posture, or a combination of these factors. To evaluate the mechanism underlying the loading regime of opossum femora, we filmed D. virginiana running over a force platform, allowing us to measure the magnitude of the GRF and its three-dimensional orientation relative to the limb, facilitating estimates of limb bone stresses. This three-dimensional analysis also allows evaluations of muscular forces, particularly those of hip adductor muscles, in the appropriate anatomical plane to a greater degree than previous two-dimensional analyses. At peak GRF and stress magnitudes, the GRF is oriented nearly vertically, inducing a strong abductor moment at the hip that is countered by adductor muscles on the medial aspect of the femur that place this surface in compression and induce mediolateral bending, corroborating and explaining loading patterns that were identified in strain analyses. The crouched orientation of the femur during stance in opossums also contributes to levels of femoral torsion as high as those seen in many reptilian taxa. Femoral safety factors were as high as those of non-avian reptiles and greater than those of upright, cursorial mammals, primarily because the load

  14. Flow Instability and Secondary Vortex Evolution in 90 Degree Bend

    Science.gov (United States)

    Niu, Lin; Dou, Hua-Shu; Fluid Mechanics Research Team

    2013-11-01

    Three-dimensional incompressible Navier-Stokes equations are employed to simulate the laminar flow in a 90 degree bend with square cross-section. Then, the energy gradient theory is used to analyze the stability of the flow. The Reynolds number based on the channel width and the averaged velocity is 158, 394 and 790, respectively. It is found that at Re = 790, the value of the energy gradient function K increases as the fluid entering the curved section, causing flow instability and forming a pair of secondary vortices; then the secondary vortices gradually stabilizes and the value of K decreases. At the exit of the bend, the total pressure distribution in the cross-section presents serious distortion, which leads to a peak of K. As such, it promotes instability of the flow and causes a transition of two vortices to four vortices. With the flow ahead, the maximum of K in the cross section rises again, resulting in the transition of four vortices to eight vortices. While at low Re (Re = 158 and Re = 394), there is only one pair of vortices in the bend, which are stable, due to low value of K. This study shows that the occurrence of instability is closely related to the evolution of energy gradient function K. Graduate student in Fluid Mechanics.

  15. Adaptive process control for three-point bending

    Science.gov (United States)

    Schaller, T.; Raggenbass, A.; Reissner, J.

    1995-08-01

    The increasing level of competition in the sheet-metal working industry requires measures to reduce costs. There is considerable potential in the simplification of process procedures. Automated handling and the further processing of bent semifinished products require a high level of manufacturing precision in bending processes. However deviations in angles of several degrees from the desired values can arise as a result of material variations within one batch. An adaptive control system is developed in order to avoid expensive further manufacturing steps. This calculates the parameters required for the correction of the process control from variations in process values measured online. These adjustment values must be communicated to the bending machine and set during the ongoing forming process. For larger series of parts the coefficients of the correction matrix are also continuously improved, so that an optimum adaptive correction can be achieved for the current scatter in the material properties. The adaptive correction procedure is particularly effective in combination with the three-point bending technology. The highest levels of angular precision can already be achieved after a short independent optimization phase. However, the current spectrum of parts for a certain manufacturing task and a defined quality requirement should provide the basis for decisions concerning the economy of this process arrangement.

  16. A missing-bending-magnet scheme for PEP

    International Nuclear Information System (INIS)

    Liu, R.Z.; Winick, H.

    1988-01-01

    This article presents a missing-bending-magnet scheme for PEP as a modification that could be considered if PEP were available as a fully dedicated synchrotron radiation source. The scheme can be applied to one or more PEP sextants without changing the rest. By removing some bending magnets, rearranging the remaining magnets, and adding two quadrupoles, ten additional straight sections per sextant can be created, each 5 m or more in length, for insertion devices. Beam lines therefrom, plus possible beam lines from bending magnets would enter a continuous experimental hall instead of individual tunnels and halls for each beam line. This should result in construction cost savings and increased operations efficiency. The ideal beam orbit is unchanged at the two ends and the middle of the sextant. At the end of the curved part of the sextant the lattice functions match those of the long interaction region straight section in the low emittance configuration of PEP. The electron beam characteristics in the newly created straight sections are described, including the enlargement of the horizontal beam size due to the nonzero dispersion. Some disadvantages of the scheme are increased operations complexity due to the need for nine new quadrupole families, increased beam emittance (by 14.5% is one sextant is modified), and reduced dynamic aperture. However, the dynamic aperture is still about as large as the physical aperture and should be adequate for good beam lifetime and injection. (orig.)

  17. Curvature reduces bending strains in the quokka femur

    Directory of Open Access Journals (Sweden)

    Kyle McCabe

    2017-03-01

    Full Text Available This study explores how curvature in the quokka femur may help to reduce bending strain during locomotion. The quokka is a small wallaby, but the curvature of the femur and the muscles active during stance phase are similar to most quadrupedal mammals. Our hypothesis is that the action of hip extensor and ankle plantarflexor muscles during stance phase place cranial bending strains that act to reduce the caudal curvature of the femur. Knee extensors and biarticular muscles that span the femur longitudinally create caudal bending strains in the caudally curved (concave caudal side bone. These opposing strains can balance each other and result in less strain on the bone. We test this idea by comparing the performance of a normally curved finite element model of the quokka femur to a digitally straightened version of the same bone. The normally curved model is indeed less strained than the straightened version. To further examine the relationship between curvature and the strains in the femoral models, we also tested an extra-curved and a reverse-curved version with the same loads. There appears to be a linear relationship between the curvature and the strains experienced by the models. These results demonstrate that longitudinal curvature in bones may be a manipulable mechanism whereby bone can induce a strain gradient to oppose strains induced by habitual loading.

  18. Polarization sensitive beam bending using a spatially variant photonic crystal

    Science.gov (United States)

    Digaum, Jennefir L.; Pazos, Javier; Rumpf, Raymond; Chiles, Jeff; Fathpour, Sasan; Thomas, Jeremy N.; Kuebler, Stephen M.

    2015-02-01

    A spatially-variant photonic crystal (SVPC) that can control the spatial propagation of electromagnetic waves in three dimensions with high polarization sensitivity was fabricated and characterized. The geometric attributes of the SVPC lattice were spatially varied to make use of the directional phenomena of self-collimation to tightly bend an unguided beam coherently through a 90 degree angle. Both the lattice spacing and the fill factor of the SVPC were maintained to be nearly constant throughout the structure. A finite-difference frequency-domain computational method confirms that the SVPC can self-collimate and bend light without significant diffuse scatter caused by the bend. The SVPC was fabricated using multi-photon direct laser writing in the photo-polymer SU-8. Mid-infrared light having a vacuum wavelength of λ0 = 2.94 μm was used to experimentally characterize the SVPCs by scanning the sides of the structure with optical fibers and measuring the intensity of light emanating from each face. Results show that the SVPC is capable of directing power flow of one polarization through a 90-degree turn, confirming the self-collimating and polarization selective light-guiding properties of the structures.

  19. Flexoelectric effect on the electroelastic responses of bending piezoelectric nanobeams

    Science.gov (United States)

    Yan, Z.; Jiang, L. Y.

    2013-05-01

    Flexoelectricity, referring to a spontaneous electric polarization induced by strain gradient in dielectrics, presents a strong size dependency at the nanoscale. In the current work, the influence of the flexoelectric effect on the mechanical and electrical properties of bending piezoelectric nanobeams with different boundary conditions is investigated. Based on the extended linear piezoelectricity theory and the Euler beam model, analytical solutions of the electroelastic fields in the piezoelectric nanobeams subjected to both electrical and mechanical loads are obtained with the inclusion of the flexoelectric effect. Simulation results show that the flexoelectric effect on the elastic behavior of bending beams is sensitive to the beam boundary conditions and the applied electrical load. In addition, for a cantilever piezoelectric nanobeam, an axial relaxation strain is induced from the piezoelectric and flexoelectric effects, while these effects induce a resultant axial force in both the clamped-clamped and simply supported piezoelectric nanobeams. Results also indicate that the flexoelectric effect plays a significant role in the contact stiffness and electric polarization of piezoelectric beams when their thickness is at the nanoscale. It is found that the flexoelectric effect on the electroelastic responses of piezoelectric nanobeams is more pronounced for the beams with smaller thickness. These results are useful for understanding the fundamental mechanical and physical properties of bending piezoelectric nanobeams.

  20. Effect of steel fibres dosage in alkali-activated slag mortar on acoustic emission obtained during three-point bending tests

    Directory of Open Access Journals (Sweden)

    Topolář Libor

    2017-01-01

    Full Text Available The acoustic emission phenomenon is directly associated with nucleation of cracks in structural materials during loading. This paper analyses acoustic emission signals captured during three-point bending fracture tests of alkali-activated slag mortar specimens with different amount of steel fibres. Typical parameters of acoustic emission signals were identified for different mixtures to further describe the under-the-stress behaviour and failure development. The acoustic emission signals from crack growth were continuously monitored using acoustic emission sensors mounted on the specimen surface. Acoustic emission results are accompanied by selected mechanical fracture parameters determined via evaluation of load versus displacement diagrams recorded during three-point bending tests.