Science.gov

Sample records for aligned biaxial tungsten

  1. Vertically aligned biaxially textured molybdenum thin films

    SciTech Connect

    Krishnan, Rahul; Riley, Michael; Lee, Sabrina; Lu, Toh-Ming

    2011-09-15

    Vertically aligned, biaxially textured molybdenum nanorods were deposited using dc magnetron sputtering with glancing flux incidence (alpha = 85 degrees with respect to the substrate normal) and a two-step substrate-rotation mode. These nanorods were identified with a body-centered cubic crystal structure. The formation of a vertically aligned biaxial texture with a [110] out-of-plane orientation was combined with a [-110] in-plane orientation. The kinetics of the growth process was found to be highly sensitive to an optimum rest time of 35 seconds for the two-step substrate rotation mode. At all other rest times, the nanorods possessed two separate biaxial textures each tilted toward one flux direction. While the in-plane texture for the vertical nanorods maintains maximum flux capture area, inclined Mo nanorods deposited at alpha = 85 degrees without substrate rotation display a [-1-1-4] in-plane texture that does not comply with the maximum flux capture area argument. Finally, an in situ capping film was deposited with normal flux incidence over the biaxially textured vertical nanorods resulting in a thin film over the porous nanorods. This capping film possessed the same biaxial texture as the nanorods and could serve as an effective substrate for the epitaxial growth of other functional materials.

  2. Biaxially aligned template films fabricated by inclined-substrate deposition for YBCO-coated conductor applications.

    SciTech Connect

    Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A.; Dorris, S. E.; Miller, D. J.; Balachandran, U.

    2002-08-12

    Inclined substrate deposition (ISD) has the potential for rapid production of high-quality biaxially textured buffer layers, which are important for YBCO-coated conductor applications. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 {angstrom}/sec. Columnar grains with a roof-tile surface structure were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are tilted at an angle from the substrate normal. A small {phi}-scan full-width at half maximum (FWHM) of {approx}9{sup o} was observed on MgO films deposited at an inclination angle of 55{sup o}. In-plane texture in the ISD MgO films developed in the first 0.5 {micro}m from the interface, then stabilized with further increases in film thickness. YBCO films deposited by pulsed laser deposition on ISD-MgO buffered Hastelloy C276 substrates were biaxially aligned with the c-axis parallel to the substrate normal. T{sub c} of 91 K with a sharp transition and transport J{sub c} of 5.5 x 10{sup 5} A/cm{sup 2} at 77 K in self-field were measured on a YBCO film that was 0.46-{micro}m thick, 4-mm wide, 10-mm long.

  3. Lattice Spin Simulations of Topological Defects in Biaxial Nematic Films with Homeotropic Surface Alignment

    NASA Astrophysics Data System (ADS)

    Preeti, Gouripeddi Sai; Zannoni, Claudio; Chiccoli, Cesare; Pasini, Paolo; Sastry, Vanka S. S.

    2013-05-01

    We present a detailed Monte Carlo study of the effects of biaxiality on the textures of nematic films with specific homeotropic boundary conditions. We have used the Straley generalized Hamiltonian for a wide range of biaxial parameters and the differences obtained in the polarized microscopy images are analyzed for the various cases.

  4. Biaxial shear of confined colloidal hard spheres: the structure and rheology of the vorticity-aligned string phase.

    PubMed

    Lin, Neil Y C; Cheng, Xiang; Cohen, Itai

    2014-03-28

    Using a novel biaxial confocal rheoscope, we investigate the flow of the shear induced vorticity aligned string phase [X. Cheng et al., Proc. Natl. Acad. Sci. U. S. A., 2011, 109, 63], which has a highly anisotropic microstructure. Using biaxial shear protocols we show that we have excellent control of the string phase anisotropic morphology. We choose a shear protocol that drives the system into the string phase. Subsequently, a biaxial force measurement device is used to determine the suspension rheology along both the flow and vorticity directions. We find no measurable dependence of the suspension stress response along the shear and vorticity directions due to the hydrodynamically induced string morphology. In particular, we find that the suspension's high frequency stress response is nearly identical along the two orthogonal directions. While we do observe an anisotropic stress response at lower shear frequencies associated with shear thinning, we show that this anisotropy is independent of the shear induced string structure. These results suggest that for the range of flows explored, Brownian and hydrodynamic contributions to the stress arising from the anisotropic suspension microstructure are sufficiently weak that they do not significantly contribute to the rheology. Collectively, this study presents a general and powerful approach for using biaxial confocal rheometry to elucidate the relationship between microstructure and rheology in complex fluids driven far-from-equilibrium.

  5. Tungsten

    SciTech Connect

    1996-08-01

    The name tungsten, derived from the Swedish words {open_quotes}tung{close_quotes} and {open_quotes}sten{close_quotes}, meaning heavy stone, was first applied to a tungsten-containing mineral in 1755. The mineral, itself, was subsequently identified by C.W. Scheele in 1781, and named scheelite. Metallic tungsten was first isolated from the mineral wolframite in 1783, and given the German name {open_quotes}wolfram,{close_quotes} which remains an alternative name for the element. Ultimately, the English word, tungsten, became the official name, while W remains the element`s chemical symbol. This article discusses the geology, exploitation, applications, and market overview of tungsten.

  6. Measurement of pair-production by high energy photons in an aligned tungsten crystal

    NASA Astrophysics Data System (ADS)

    Moore, R.; Parker, M. A.; Baurichter, A.; Kirsebom, K.; Medenwaldt, R.; Mikkelsen, U.; Møller, S. P.; Uggerhøj, E.; Worm, T.; Doble, N.; Elsener, K.; Ballestrero, S.; Sona, P.; Strakhovenko, V. M.; Biino, C.; Vilakazi, Z. Z.

    1996-10-01

    A new measurement has been made of the rate of pair-production in a 3.2 mm thick tungsten crystal, exposed to photons with energies in the range 10 to 150 GeV, for angles of incidence up to 10 mrad from the crystal axis. A strong enhancement of the pair-production rate is observed when the beam is aligned along the <100> crystal axis, as compared to a random orientation. This effect can be exploited in the NA48 CP-violation experiment by using a thin crystal rather than an amorphous material to convert photons, thus minimising the scattering of kaons in the converter.

  7. Large-area alignment of tungsten oxide nanowires over flat and patterned substrates for room-temperature gas sensing.

    PubMed

    Cheng, Wei; Ju, Yanrui; Payamyar, Payam; Primc, Darinka; Rao, Jingyi; Willa, Christoph; Koziej, Dorota; Niederberger, Markus

    2015-01-01

    Alignment of nanowires over a large area of flat and patterned substrates is a prerequisite to use their collective properties in devices such as gas sensors. In this work, uniform single-crystalline ultrathin W18 O49 nanowires with diameters less than 2 nm and aspect ratios larger than 100 have been synthesized, and, despite their flexibility, assembled into thin films with high orientational order over a macroscopic area by the Langmuir-Blodgett technique. Alignment of the tungsten oxide nanowires was also possible on top of sensor substrates equipped with electrodes. Such sensor devices were found to exhibit outstanding sensitivity to H2 at room temperature. PMID:25412600

  8. Preparation of bi-axially aligned YBa 2Cu 3O 7- δ film on CeO 2-buffered MgO by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Yamagiwa, K.; Hiei, H.; Takahashi, Y.; Kim, S. B.; Matsumoto, K.; Ikuta, H.; Mizutani, U.; Hirabayashi, I.

    2000-06-01

    We have succeeded in preparing in-plane aligned YBa 2Cu 3O 7- δ (Y123) film by chemical solution deposition (CSD) processing on CeO 2 (100)-buffered MgO (100) substrates. The CeO 2 buffer film was deposited on MgO (100) single crystalline substrate by pulsed laser deposition (PLD). For CSD coating, a homogeneous coating solution having a molar ratio of Y:Ba:Cu=1:2:3, was prepared by dissolving metal naphthenates in toluene. This solution was spin-coated both on the YSZ (100) and on the CeO 2-buffered MgO (100) single crystalline substrates. The precursor films were calcined at 425°C and fired at various temperatures under low oxygen partial pressure ( pO 2). All Y123 films showed strong (00 n) peaks, which correspond to c-axis orientation perpendicular to the substrates and their a/ b-axes were in-plane aligned. We confirmed that CeO 2 buffer is usable for CSD processing. While the Y123 films on the YSZ reacted with the substrate forming BaZrO 3 phase and did not show sufficient superconducting properties. The Tc,zero value of the Y123 film prepared on CeO 2-buffered MgO substrate was 91.5 K and Jc was 1.2×10 5 A/cm 2 at 77 K, 0 T.

  9. Epitaxial growth of biaxially oriented YBCO films on silver

    NASA Astrophysics Data System (ADS)

    Liu, Danmin; Zhou, Meiling; Wang, Xue; Suo, Hongli; Zuo, Tieyong; Schindl, Michael; Flükiger, René

    2001-09-01

    YBCO films were deposited on (100), (110) and (111) oriented silver single crystals and { 100} <100>, { 110} <211> and { 012} <100> biaxially textured Ag substrates by pulsed laser deposition. It is shown that the (100) and (110) orientated single crystals and the { 110} biaxially textured Ag tape are all suitable for the deposition of YBCO thin films with c-axis in-plane alignment. The Jc of YBCO film deposited on { 110} <211> biaxially textured Ag foil is 7×105A cm-2 at 77 K, 0 T. A scheme for the regular growth of YBCO on silver was put forward.

  10. High Tc YBCO superconductor deposited on biaxially textured Ni substrate

    DOEpatents

    Budai, John D.; Christen, David K.; Goyal, Amit; He, Qing; Kroeger, Donald M.; Lee, Dominic F.; List, III, Frederick A.; Norton, David P.; Paranthaman, Mariappan; Sales, Brian C.; Specht, Eliot D.

    1999-01-01

    A superconducting article includes a biaxially-textured Ni substrate, and epitaxial buffer layers of Pd (optional), CeO.sub.2 and YSZ, and a top layer of in-plane aligned, c-axis oriented YBCO having a critical current density (J.sub.c) in the range of at least 100,000 A/cm.sup.2 at 77 K.

  11. Biaxial Creep Specimen Fabrication

    SciTech Connect

    JL Bump; RF Luther

    2006-02-09

    This report documents the results of the weld development and abbreviated weld qualification efforts performed by Pacific Northwest National Laboratory (PNNL) for refractory metal and superalloy biaxial creep specimens. Biaxial creep specimens were to be assembled, electron beam welded, laser-seal welded, and pressurized at PNNL for both in-pile (JOYO reactor, O-arai, Japan) and out-of-pile creep testing. The objective of this test campaign was to evaluate the creep behavior of primary cladding and structural alloys under consideration for the Prometheus space reactor. PNNL successfully developed electron beam weld parameters for six of these materials prior to the termination of the Naval Reactors program effort to deliver a space reactor for Project Prometheus. These materials were FS-85, ASTAR-811C, T-111, Alloy 617, Haynes 230, and Nirnonic PE16. Early termination of the NR space program precluded the development of laser welding parameters for post-pressurization seal weldments.

  12. Fragmentation in Biaxial Tension

    SciTech Connect

    Campbell, G H; Archbold, G C; Hurricane, O A; Miller, P L

    2006-06-13

    We have carried out an experiment that places a ductile stainless steel in a state of biaxial tension at a high rate of strain. The loading of the ductile metal spherical cap is performed by the detonation of a high explosive layer with a conforming geometry to expand the metal radially outwards. Simulations of the loading and expansion of the metal predict strain rates that compare well with experimental observations. A high percentage of the HE loaded material was recovered through a soft capture process and characterization of the recovered fragments provided high quality data, including uniform strain prior to failure and fragment size. These data were used with a modified fragmentation model to determine a fragmentation energy.

  13. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    A three year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for non-proportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved undertanding were through several critical non-proportional loading experiments. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C.

  14. Elevated temperature biaxial fatigue

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1985-01-01

    A 3 year experimental program for studying elevated temperature biaxial fatigue of a nickel based alloy Hastelloy-X has been completed. A new high temperature fatigue test facility with unique capabilities has been developed. Effort was directed toward understanding multiaxial fatigue and correlating the experimental data to the existing theories of fatigue failure. The difficult task of predicting fatigue lives for nonproportional loading was used as an ultimate test for various life prediction methods being considered. The primary means of reaching improved understanding were through several critical nonproportional loading experiments. The direction of cracking observed on failed specimens was also recorded and used to guide the development of the theory. Cyclic deformation responses were permanently recorded digitally during each test. It was discovered that the cracking mode switched from primarily cracking on the maximum shear planes at room temperature to cracking on the maximum normal strain planes at 649 C. In contrast to some other metals, loading path in nonproportional loading had little effect on fatigue lives. Strain rate had a small effect on fatigue lives at 649 C. Of the various correlating parameters the modified plastic work and octahedral shear stress were the most successful.

  15. Transparency Film for Demonstration of Biaxial Optics.

    ERIC Educational Resources Information Center

    Camp, Paul R.

    1994-01-01

    Explains why transparency film demonstrates biaxial optical properties. Provides detailed descriptions of the procedure and equipment needed for large-scale optics demonstrations of the polarization interference pattern produced by biaxial crystals. (DDR)

  16. Process for ion-assisted laser deposition of biaxially textured layer on substrate

    DOEpatents

    Russo, Richard E.; Reade, Ronald P.; Garrison, Stephen M.; Berdahl, Paul

    1995-01-01

    A process for depositing a biaxially aligned intermediate layer over a non-single crystal substrate is disclosed which permits the subsequent deposition thereon of a biaxially oriented superconducting film. The process comprises depositing on a substrate by laser ablation a material capable of being biaxially oriented and also capable of inhibiting the migration of substrate materials through the intermediate layer into such a superconducting film, while simultaneously bombarding the substrate with an ion beam. In a preferred embodiment, the deposition is carried out in the same chamber used to subsequently deposit a superconducting film over the intermediate layer. In a further aspect of the invention, the deposition of the superconducting layer over the biaxially oriented intermediate layer is also carried out by laser ablation with optional additional bombardment of the coated substrate with an ion beam during the deposition of the superconducting film.

  17. Process for ion-assisted laser deposition of biaxially textured layer on substrate

    DOEpatents

    Russo, R.E.; Reade, R.P.; Garrison, S.M.; Berdahl, P.

    1995-07-11

    A process for depositing a biaxially aligned intermediate layer over a non-single crystal substrate is disclosed which permits the subsequent deposition thereon of a biaxially oriented superconducting film. The process comprises depositing on a substrate by laser ablation a material capable of being biaxially oriented and also capable of inhibiting the migration of substrate materials through the intermediate layer into such a superconducting film, while simultaneously bombarding the substrate with an ion beam. In a preferred embodiment, the deposition is carried out in the same chamber used to subsequently deposit a superconducting film over the intermediate layer. In a further aspect of the invention, the deposition of the superconducting layer over the biaxially oriented intermediate layer is also carried out by laser ablation with optional additional bombardment of the coated substrate with an ion beam during the deposition of the superconducting film. 8 figs.

  18. Analysis of Deformation Mechanisms Associated with Biaxially Oriented Polypropylene Films

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Hsu, Shaw Ling

    1998-03-01

    Biaxially oriented samples can be prepared either by simultaneous or sequential deformation along two orthogonal directions. Generally speaking the orientation achieved in the plane of the film is independent of the method. In this study, we demonstrate that for sequential deformation, the degree of orientation achieved in the two orthogonal directions is dependent on initial sample morphology and deformation parameters. The achievable orientation is strongly dependent on the degree of crystallinity and initial crystallite dimensions. Samples containing small crystallites can achieve significantly higher orientation in the transverse direction (restretching step). The ultimate morphology is dictated by the temperature at which second drawing occurs. At lower deformation temperature, rotation of stacked crystalline lamellae can be accomplished to form biaxially oriented films. At higher temperatures, the dominant mechanism is unfolding of crystalline chain segments followed by recrystallization into units aligned with the restretching direction. X-ray diffraction, polarized infrared and Raman spectroscopy, and calorimetric techniques were employed to analyze these structural transformations.

  19. "CLASPing" tungsten's effects on microtubules with "PINs".

    PubMed

    Adamakis, Ioannis Dimosthenis S; Panteris, Emmanuel; Eleftheriou, Eleftherios P

    2015-01-01

    Tungsten, supplied as sodium tungstate, inhibits root elongation in Arabidopsis thaliana, which has been attributed to a diminishing of PIN2 and PIN3 auxin efflux carriers. In this work, we sought to analyze the effect of tungsten on cortical microtubules and CLASP (Cytoplasmic Linker Associated Protein), which are also involved in the anisotropic cell expansion of root cells. Seedlings grown in a tungsten-free substrate for 4 d and then transplanted into a tungsten-containing substrate exhibited randomly oriented microtubules in a time-dependent manner. While tungsten had no effect on roots treated for 3 h, microtubule alignment was obviously affected in the transition and elongation zones after a 6, 12, 24, 48 h tungsten treatment, at prolonged tungsten administrations and in seedlings grown directly in the presence of tungsten. This change in microtubule orientation may be associated with the reduction of CLASP protein expression induced by tungsten, as evidenced in experiments with plants expressing the CLASP-GFP protein. A possible mechanism, by which the coordinated functions of CLASP, PIN2 and microtubules are affected, as revealed by inhibited root growth, is discussed. PMID:26313814

  20. Biaxially textured articles formed by plastic deformation

    DOEpatents

    Goyal, Amit

    2001-01-01

    A method of preparing a biaxially textured article comprises the steps of providing a metal preform, coating or laminating the preform with a metal layer, deforming the layer to a sufficient degree, and rapidly recrystallizing the layer to produce a biaxial texture. A superconducting epitaxial layer may then be deposited on the biaxial texture. In some embodiments the article further comprises buffer layers, electromagnetic devices or electro-optical devices.

  1. Biaxially oriented film on flexible polymeric substrate

    DOEpatents

    Finkikoglu, Alp T.; Matias, Vladimir

    2009-10-13

    A flexible polymer-based template having a biaxially oriented film grown on the surface of a polymeric substrate. The template having the biaxially oriented film can be used for further epitaxial growth of films of interest for applications such as photovoltaic cells, light emitting diodes, and the like. Methods of forming such a flexible template and providing the polymeric substrate with a biaxially oriented film deposited thereon are also described.

  2. Biaxial stress effects on hysteresis and MIVC

    NASA Astrophysics Data System (ADS)

    Sablik, M. J.; Kwun, H.; Burkhardt, G. L.

    1995-02-01

    Changes in the magnetic properties of a cruciform-shaped SAE-4130 steel specimen were measured under biaxial stress conditions. Compared to model predictions are the experimental remanence at various biaxial stresses and the magnetically induced velocity changes (MIVC) of ultrasonic shear and longitudinal waves propagated perpendicular to the stress plane.

  3. Buffer layers on biaxially textured metal substrates

    DOEpatents

    Shoup, Shara S.; Paranthamam, Mariappan; Beach, David B.; Kroeger, Donald M.; Goyal, Amit

    2001-01-01

    A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

  4. Biaxially Stretched Polycarbonate Film For Capacitors

    NASA Technical Reports Server (NTRS)

    Yen, Shaio-Ping S.; Lowry, Lynn E.; Bankston, Clyde P.

    1992-01-01

    Report describes experiments on effects of biaxial stretching on crystal structures, dielectric properties, and sellected thermal and mechanical properties of biaxially stretched polycarbonate films. Highest stretch ratios produce highest degree of crystallinity, with single crystalline phase and distribution of crystallites more nearly isotropic than uniaxially oriented film. Electrical properties at high temperatures improved.

  5. Biaxially corrugated flexible sheet material

    DOEpatents

    Schmertz, John C.

    1991-04-16

    A flexible biaxially corrugated sheet material is formed from a plurality of identical trapezium segments which are arranged in a plurality of long strips a single segment wide. Adjacent strips are mirror images of each other and connected along adjoining sides with the angles of the four corners of adjacent segments being alternately less than 360.degree. and greater than 360.degree. along the length of a strip such that the sheet material has an undulating configuration, and is inherently curved and cannot lie in a flat plane.

  6. Singular values, nematic disclinations, and emergent biaxiality.

    PubMed

    Čopar, Simon; Dennis, Mark R; Kamien, Randall D; Žumer, Slobodan

    2013-05-01

    Both uniaxial and biaxial nematic liquid crystals are defined by orientational ordering of their building blocks. While uniaxial nematics only orient the long molecular axis, biaxial order implies local order along three axes. As the natural degree of biaxiality and the associated frame that can be extracted from the tensorial description of the nematic order vanishes in the uniaxial phase, we extend the nematic director to a full biaxial frame by making use of a singular value decomposition of the gradient of the director field instead. The degrees of freedom are unveiled in the form of quasidefects and the similarities and differences between the uniaxial and biaxial phase are analyzed by applying the algebraic rules of the quaternion group to the uniaxial phase. PMID:23767474

  7. Search for microscopic and macroscopic biaxiality in the cybotactic nematic phase of new oxadiazole bent-core mesogens.

    PubMed

    Kim, Young-Ki; Cukrov, Greta; Vita, Francesco; Scharrer, Eric; Samulski, Edward T; Francescangeli, Oriano; Lavrentovich, Oleg D

    2016-06-01

    The possibility of biaxial orientational order in nematic liquid crystals is a subject of intense current interest. We explore the tendencies toward local and global biaxial ordering in the recently synthesized trimethylated oxadiazole-based bent-core mesogens with a pronounced asymmetric (bow-type) shape of molecules. The combination of x-ray diffraction and optical studies suggests that the biaxial order is expressed differently at the short- and long-range scales. Locally, at the scale of a few molecules, x-ray-diffraction data demonstrate biaxial packing. However, above the mesoscopic scale, the global orientational order in all three compounds is uniaxial, as evidenced by uniform homeotropic alignment of the nematic phase which is optically tested over the entire temperature range and by the observations of topological defects induced by individual and aggregated colloidal spheres in the nematic bulk. PMID:27415328

  8. Search for microscopic and macroscopic biaxiality in the cybotactic nematic phase of new oxadiazole bent-core mesogens

    NASA Astrophysics Data System (ADS)

    Kim, Young-Ki; Cukrov, Greta; Vita, Francesco; Scharrer, Eric; Samulski, Edward T.; Francescangeli, Oriano; Lavrentovich, Oleg D.

    2016-06-01

    The possibility of biaxial orientational order in nematic liquid crystals is a subject of intense current interest. We explore the tendencies toward local and global biaxial ordering in the recently synthesized trimethylated oxadiazole-based bent-core mesogens with a pronounced asymmetric (bow-type) shape of molecules. The combination of x-ray diffraction and optical studies suggests that the biaxial order is expressed differently at the short- and long-range scales. Locally, at the scale of a few molecules, x-ray-diffraction data demonstrate biaxial packing. However, above the mesoscopic scale, the global orientational order in all three compounds is uniaxial, as evidenced by uniform homeotropic alignment of the nematic phase which is optically tested over the entire temperature range and by the observations of topological defects induced by individual and aggregated colloidal spheres in the nematic bulk.

  9. Liquid crystal display modes in a nontilted bent-core biaxial smectic liquid crystal

    NASA Astrophysics Data System (ADS)

    Nagaraj, Mamatha; Panarin, Y. P.; Vij, J. K.; Keith, C.; Tschierske, C.

    2010-11-01

    Liquid crystal display (LCD) modes associated with the rotation of the secondary director in nontilted, biaxial smectic phase of an achiral bent-core compound are demonstrated. For LCDs, we find that at least four display modes are possible using SmAPA phase of the studied material, in which the minor directors in adjacent layers are aligned antiferroelectrically. The advantages of these modes include low driving field (1-2 V/μm), high contrast ratio 1000:1, relatively fast switching time of 0.5 ms and continuous gray scale. The molecular short axis or the polar axis in a negative dielectric, biaxial material is oriented by the in-plane electric field by a combination dielectric biaxiality and polarity at low electric fields and polarity at higher fields.

  10. Failure mechanisms in laminated carbon/carbon composites under biaxial compression

    SciTech Connect

    Grape, J.A.; Gupta, V.

    1995-07-01

    The failure mechanisms of 2D carbon/carbon (C/C) woven laminates have been determined under inplane biaxial compression loads, and the associated failure envelopes that account for the effect of matrix-type and loading directions were also obtained. The failure was in the form of micro-kinking of fiber bundles, interspersed with localized interply delaminations to form an overall shear fault. The shear fault was aligned with the major axis of loading except at above 75% of balanced biaxial compressive stress where failure occurred along both axes. Although the biaxial strength varied significantly with the ratio of in-plane principal stresses, R, there was no variation in the local failure mechanisms. Accordingly, it was found that the samples fail upon achieving a critical strain along the primary axis of loading.

  11. Biaxial ferromagnetic liquid crystal colloids.

    PubMed

    Liu, Qingkun; Ackerman, Paul J; Lubensky, Tom C; Smalyukh, Ivan I

    2016-09-20

    The design and practical realization of composite materials that combine fluidity and different forms of ordering at the mesoscopic scale are among the grand fundamental science challenges. These composites also hold a great potential for technological applications, ranging from information displays to metamaterials. Here we introduce a fluid with coexisting polar and biaxial ordering of organic molecular and magnetic colloidal building blocks exhibiting the lowest symmetry orientational order. Guided by interactions at different length scales, rod-like organic molecules of this fluid spontaneously orient along a direction dubbed "director," whereas magnetic colloidal nanoplates order with their dipole moments parallel to each other but pointing at an angle to the director, yielding macroscopic magnetization at no external fields. Facile magnetic switching of such fluids is consistent with predictions of a model based on competing actions of elastic and magnetic torques, enabling previously inaccessible control of light. PMID:27601668

  12. High-strain-rate, high-temperature biaxial testing of DOP-26 iridium

    SciTech Connect

    George, T.G.

    1988-05-01

    High-strain-rate biaxial punch tests were performed on DOP-26 (Ir-0.3 wt.% tungsten) iridium-alloy disc given annealing and aging heat treatments. Test temperatures ranged between 600 and 1440/degree/C, and punch velocity was held constant at 45 m/s. Three types of samples were evaluated: Z-batch old-process discs, B-batch old-process discs, and B-batch new-process discs. The results indicate that batch-to-batch variations in ductility are significant and that new-process iridium is slightly more ductile than old-process material. 12 refs., 43 figs., 26 tabs.

  13. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.

    2001-01-01

    A biaxially textured alloy article comprises Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacted and heat treated, then rapidly recrystallized to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

  14. Molecular field theory for biaxial smectic A liquid crystals.

    PubMed

    To, T B T; Sluckin, T J; Luckhurst, G R

    2013-10-01

    Thermotropic biaxial nematic phases seem to be rare, but biaxial smectic A phases less so. Here we use molecular field theory to study a simple two-parameter model, with one parameter promoting a biaxial phase and the second promoting smecticity. The theory combines the biaxial Maier-Saupe and McMillan models. We use alternatively the Sonnet-Virga-Durand (SVD) and geometric mean approximations (GMA) to characterize molecular biaxiality by a single parameter. For non-zero smecticity and biaxiality, the model always predicts a ground state biaxial smectic A phase. For a low degree of smectic order, the phase diagram is very rich, predicting uniaxial and biaxial nematic and smectic phases, with the addition of a variety of tricritical and tetracritical points. For higher degrees of smecticity, the region of stability of the biaxial nematic phase is restricted and eventually disappears, yielding to the biaxial smectic phase. Phase diagrams from the two alternative approximations for molecular biaxiality are similar, except inasmuch that SVD allows for a first-order isotropic-biaxial nematic transition, whereas GMA predicts a Landau point separating isotropic and biaxial nematic phases. We speculate that the rarity of thermotropic biaxial nematic phases is partly a consequence of the presence of stabler analogous smectic phases.

  15. Biaxial tension on polymer in thermoforming range

    NASA Astrophysics Data System (ADS)

    Becker, S.; Combeaud, C.; Fournier, F.; Rodriguez, J.; Billon, N.

    2010-06-01

    This paper presents an experimental characterization of mechanical properties of a polyethylene terephtalate (PET) resin classically used in stretch blow moulding process. We have applied on such a material a well established experimental protocol at CEMEF, including new and relevant biaxial tensile tests. The experimental set-up relative to biaxial tension will be presented and described in a first part of the paper. Furthermore, we will focus on the experimental DMTA preliminary tests which are required to estimate the resin sensibility to temperature and strain rate in linear viscoelasticity domain. Finally, we will be interested in the material large strain behaviour: biaxial tensile results are presented and discussed. Finally, such an experimental approach should allow a relevant modelling of polymer physics and mechanics; this point will not be discussed here because of a lack of time.

  16. Biaxial load effects in fracture mechanics

    NASA Technical Reports Server (NTRS)

    Liebowitz, H.; Lee, J. D.; Eftis, J.

    1977-01-01

    It is found that the standard expressions for elastic stress and displacement in the crack-tip region (i.e., the so-called singular solution) cannot be considered to be approximations that are acceptable in a completely general sense. This conclusion is best illustrated by the instance of a biaxially loaded infinite sheet with a flat horizontal central crack, where the effect of load applied parallel to the plane of the crack appears entirely in the second terms of the series representations for local stresses and displacements. An elastoplastic finite-element analysis of the same biaxially loaded finite specimen geometry shows that the global energy release rate, the J-integral, the plastic stress and strain intensity factors (in the sense of Hilton and Hutchinson), and the size of the crack border region plastic yield, all have pronounced biaxial load dependence.

  17. Strength of composite laminates under biaxial loads

    NASA Astrophysics Data System (ADS)

    Hinton, M. J.; Soden, P. D.; Kaddour, A. S.

    1996-05-01

    Five well known failure criteria and one simple progressive model have been used in conjunction with laminate theory, which allows for nonlinear lamina shear behaviour, to predict the initial and final failure strengths of filament wound composite tubes. The predictions have been compared with experimental leakage and fracture stresses for ±75°, ±55° and ±45° filament wound GRP tubes subjected to a wide range of biaxial stress systems including biaxial compression. In some cases the fracture strengths were a factor of 10 higher than the initial failure predictions. The simple progressive failure theory predictions gave the best agreement with the experimental results.

  18. Tungsten Filament Fire

    ERIC Educational Resources Information Center

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  19. Tungsten filament fire

    NASA Astrophysics Data System (ADS)

    Ruiz, Michael J.; Perkins, James

    2016-05-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent light bulb is being replaced by compact fluorescent and LED lamps.

  20. Electrodeposition of biaxially textured layers on a substrate

    SciTech Connect

    Bhattacharya, Raghu N; Phok, Sovannary; Spagnol, Priscila; Chaudhuri, Tapas

    2013-11-19

    Methods of producing one or more biaxially textured layer on a substrate, and articles produced by the methods, are disclosed. An exemplary method may comprise electrodepositing on the substrate a precursor material selected from the group consisting of rare earths, transition metals, actinide, lanthanides, and oxides thereof. An exemplary article (150) may comprise a biaxially textured base material (130), and at least one biaxially textured layer (110) selected from the group consisting of rare earths, transition metals, actinides, lanthanides, and oxides thereof. The at least one biaxially textured layer (110) is formed by electrodeposition on the biaxially textured base material (130).

  1. Biaxially textured metal substrate with palladium layer

    DOEpatents

    Robbins, William B [Maplewood, MN

    2002-12-31

    Described is an article comprising a biaxially textured metal substrate and a layer of palladium deposited on at least one major surface of the metal substrate; wherein the palladium layer has desired in-plane and out-of-plane crystallographic orientations, which allow subsequent layers that are applied on the article to also have the desired orientations.

  2. Instability of a Biaxial Nematic Liquid Crystal Formed by Homeotropic Anchoring on Surface Grooves

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi-Dong; Xuan, Li

    2011-10-01

    A method used to treat the elastic distortion of a uniaxial nematic liquid crystal induced by homogeneous anchoring on the surface grooves is generalized to biaxial nematic liquid crystals under the homeotropic anchoring condition. Employing some approximations for the elastic constants, we obtain an additional term in the elastic energy per unit area which depends on the angle between the minor director at infinity and the direction of the grooves, with a period of π/2. This leads to instability on the surface grooves so that two states with crossed minor directors are energetically indistinguishable. Our theoretical study explains why the homeotropic alignment method developed for uniaxial liquid crystals loses efficacy for biaxial nematics.

  3. Shear flow simulations of biaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Sarman, Sten

    1997-08-01

    We have calculated the viscosities of a biaxial nematic liquid crystal phase of a variant of the Gay-Berne fluid [J. G. Gay and B. J. Berne, J. Chem. Phys. 74, 3316 (1981)] by performing molecular dynamics simulations. The equations of motion have been augmented by a director constraint torque that fixes the orientation of the directors. This makes it possible to fix them at different angles relative to the stream lines in shear flow simulations. In equilibrium simulations the constraints generate a new ensemble. One finds that the Green-Kubo relations for the viscosities become linear combinations of time correlation function integrals in this ensemble whereas they are complicated rational functions in the conventional canonical ensemble. We have evaluated these Green-Kubo relations for all the shear viscosities and all the twist viscosities. We have also calculated the alignment angles, which are functions of the viscosity coefficients. We find that there are three real alignment angles but a linear stability analysis shows that only one of them corresponds to a stable director orientation. The Green-Kubo results have been cross checked by nonequilibrium shear flow simulations. The results from the different methods agree very well. Finally, we have evaluated the Miesowicz viscosities [D. Baalss, Z. Naturforsch. Teil A 45, 7 (1990)]. They vary by more than 2 orders of magnitude. The viscosity is consequently highly orientation dependent.

  4. Molecular dynamics of biaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Sarman, Sten

    1996-01-01

    We devise a constraint algorithm that makes the angular velocity of the director of a liquid crystal a constant of motion. When the angular velocity is set equal to zero, a director based coordinate system becomes an inertial frame. This is a great advantage because most thermodynamic properties and time correlation functions of a liquid crystal are best expressed relative to a director based coordinate system. One also prevents the director reorientation from interfering with the tails of the time correlation functions. When the angular velocity is forced to be zero the constraints do not do any work on the system. This makes it possible to prove that ensemble averages of phase functions and time correlation functions are unaffected by the director constraint torques. The constraint algorithm also facilitates generalization of nonequilibrium molecular dynamics algorithms to liquid crystal phases. In order to test the algorithm numerically we have simulated a biaxial nematic phase of a variant of the Gay-Berne fluid [J. G. Gay and B. J. Berne, J. Chem. Phys. 74, 3316 (1981)]. The director constraint algorithm works very well. We have calculated the velocity autocorrelation functions and the self diffusion coefficients. In a biaxial nematic liquid crystal there are three independent components of the self-diffusion tensor. They have been found to be finite and different thus proving that we really simulate a liquid rather than a solid and that the symmetry is biaxial. Simulation of biaxial liquid crystals requires fairly large systems. We have therefore developed an algorithm that we run on a parallel computer instead of an ordinary work station.

  5. Method for making biaxially textured articles by plastic deformation

    DOEpatents

    Goyal, Amit

    2002-01-01

    A method of preparing a biaxially textured article comprises the steps of providing a metal preform, coating or laminating the preform with a metal layer, deforming the layer to a sufficient degree, and rapidly recrystallizing the layer to produce a biaxial texture. A superconducting epitaxial layer may then be deposited on the biaxial texture. In some embodiments the article further comprises buffer layers, electromagnetic devices or electro-optical devices.

  6. Biaxial tension of fibrous tissue: using finite element methods to address experimental challenges arising from boundary conditions and anisotropy.

    PubMed

    Jacobs, Nathan T; Cortes, Daniel H; Vresilovic, Edward J; Elliott, Dawn M

    2013-02-01

    Planar biaxial tension remains a critical loading modality for fibrous soft tissue and is widely used to characterize tissue mechanical response, evaluate treatments, develop constitutive formulas, and obtain material properties for use in finite element studies. Although the application of tension on all edges of the test specimen represents the in situ environment, there remains a need to address the interpretation of experimental results. Unlike uniaxial tension, in biaxial tension the applied forces at the loading clamps do not transmit fully to the region of interest (ROI), which may lead to improper material characterization if not accounted for. In this study, we reviewed the tensile biaxial literature over the last ten years, noting experimental and analysis challenges. In response to these challenges, we used finite element simulations to quantify load transmission from the clamps to the ROI in biaxial tension and to formulate a correction factor that can be used to determine ROI stresses. Additionally, the impact of sample geometry, material anisotropy, and tissue orientation on the correction factor were determined. Large stress concentrations were evident in both square and cruciform geometries and for all levels of anisotropy. In general, stress concentrations were greater for the square geometry than the cruciform geometry. For both square and cruciform geometries, materials with fibers aligned parallel to the loading axes reduced stress concentrations compared to the isotropic tissue, resulting in more of the applied load being transferred to the ROI. In contrast, fiber-reinforced specimens oriented such that the fibers aligned at an angle to the loading axes produced very large stress concentrations across the clamps and shielding in the ROI. A correction factor technique was introduced that can be used to calculate the stresses in the ROI from the measured experimental loads at the clamps. Application of a correction factor to experimental biaxial

  7. Simple solutions of multilayered discs subjected to biaxial moment loading.

    SciTech Connect

    Hsueh, Chun-Hway; Kelly, J R

    2009-01-01

    The purpose of this study was to derive a simple closed-form solution for the stress distribution through the thickness of multilayered discs subjected to biaxial moment loading, such that it can be used readily to evaluate the biaxial strength of multilayered dental ceramics using biaxial flexure tests. Methods A simple analytical model was developed to derive the stress distribution through the thickness of multilayered discs subjected to biaxial moment loading. The accuracy of the solution was verified by comparing with previous rigorous analytical solutions and finite element results. The results obtained from Roark's formulas for bilayered discs were also included for comparison.

  8. Alignment Tool For Welding Sensor

    NASA Technical Reports Server (NTRS)

    Gilbert, Jeffrey L.; Steffins, Alfred P.

    1992-01-01

    Alignment tool enables accurate positioning of optoelectronic sensor measuring weld penetration. Designed for use on tungsten/inert-gas welding apparatus, used to adjust position of sensor so photodiode puts out maximum signal. Tangs of slotted cap bent slightly inward to provide spring force holding cap snugly on sensor mount. Tool installed and removed without aid of other tools. Length of pointer adjusted with set-screws. Used with variety of gas cup and electrode lengths.

  9. Role of Molecular Structure on X-ray Diffraction in Uniaxial and Biaxial Phases of Thermotropic Liquid Crystals

    SciTech Connect

    Acharya, Bharat R.; Kang, Shin-Woong; Prasad, Veena; Kumar, Satyendra

    2009-04-29

    X-ray diffraction is one of the most definitive methods to determine the structure of condensed matter phases, and it has been applied to unequivocally infer the structures of conventional calamitic and lyotropic liquid crystals. With the advent of bent-core and tetrapodic mesogens and the discovery of the biaxial nematic phase in them, the experimental results require more careful interpretation and analysis. Here, we present ab-initio calculations of X-ray diffraction patterns in the isotropic, uniaxial nematic, and biaxial nematic phases of bent-core mesogens. A simple Meier-Saupe-like molecular distribution function is employed to describe both aligned and unaligned mesophases. The distribution function is decomposed into two, polar and azimuthal, distribution functions to calculate the effect of the evolution of uniaxial and biaxial nematic orientational order. The calculations provide satisfactory semiquantitative interpretations of experimental results. The calculations presented here should provide a pathway to more refined and quantitative analysis of X-ray diffraction data from the biaxial nematic phase.

  10. Role of Molecular Structure on X-ray Diffraction in Thermotropic Uniaxial and Biaxial Nematic Liquid Crystal Phases

    SciTech Connect

    Acharya, Bharat R.; Kang, Shin-Woong; Prasad, Veena; Kumar, Satyendra

    2009-08-27

    X-ray diffraction is one of the most definitive methods to determine the structure of condensed matter phases, and it has been applied to unequivocally infer the structures of conventional calamitic and lyotropic liquid crystals. With the advent of bent-core and tetrapodic mesogens and the discovery of the biaxial nematic phase in them, the experimental results require more careful interpretation and analysis. Here, we present ab-initio calculations of X-ray diffraction patterns in the isotropic, uniaxial nematic, and biaxial nematic phases of bent-core mesogens. A simple Meier-Saupe-like molecular distribution function is employed to describe both aligned and unaligned mesophases. The distribution function is decomposed into two, polar and azimuthal, distribution functions to calculate the effect of the evolution of uniaxial and biaxial nematic orientational order. The calculations provide satisfactory semiquantitative interpretations of experimental results. The calculations presented here should provide a pathway to more refined and quantitative analysis of X-ray diffraction data from the biaxial nematic phase.

  11. Structures having enhanced biaxial texture and method of fabricating same

    DOEpatents

    Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

    1998-04-21

    A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

  12. Structures having enhanced biaxial texture and method of fabricating same

    DOEpatents

    Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

    1998-04-14

    A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

  13. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2004-09-14

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  14. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-05-10

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  15. Biaxially textured articles formed by power metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-26

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  16. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-07-29

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  17. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-26

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  18. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-01-25

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  19. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goval, Amit; Williams, Robert K.; Kroeger, Donald M.

    2005-06-07

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  20. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-05

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of ternary mixtures consisting of: Ni powder, Cu powder, and Al powder, Ni powder, Cr powder, and Al powder; Ni powder, W powder and Al powder; Ni powder, V powder, and Al powder; Ni powder, Mo powder, and Al powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  1. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-08-19

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  2. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2004-09-28

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  3. Alternative processing methods for tungsten-base composite materials

    SciTech Connect

    Ohriner, E.K.; Sikka, V.K.

    1995-12-31

    Tungsten composite materials contain large amounts of tungsten distributed in a continuous matrix phase. Current commercial materials include the tungsten-nickel-iron with cobalt replacing some or all of the iron, and also tungsten-copper materials. Typically, these are fabricated by liquid-phase sintering of blended powders. Liquid-phase sintering offers the advantages of low processing costs, established technology, and generally attractive mechanical properties. However, liquid-phase sintering is restricted to a very limited number of matrix alloying elements and a limited range of tungsten and alloying compositions. In the past few years, there has been interest in a wider range of matrix materials that offer the potential for superior composite properties. These must be processed by solid-state processes and at sufficiently low temperatures to avoid undesired reactions between the tungsten and the matrix phase. These processes, in order of decreasing process temperature requirements, include hot-isostatic pressing (HIPing), hot extrusion, and dynamic compaction. The HIPing and hot extrusion processes have also been used to improve mechanical properties of conventional liquid-phase-sintered materials. Results of laboratory-scale investigations of solid-state consolidation of a variety of matrix materials, including titanium, hafnium, nickel aluminide, and steels are reviewed. The potential advantages and disadvantages of each of the possible alternative consolidation processes are identified. Postconsolidation processing to control microstructure and macrostructure is discussed, including novel methods of controlling microstructure alignment.

  4. Alternative processing methods for tungsten-base composite materials

    SciTech Connect

    Ohriner, E.K.; Sikka, V.K.

    1996-06-01

    Tungsten composite materials contain large amounts of tungsten distributed in a continuous matrix phase. Current commercial materials include the tungsten-nickel-iron with cobalt replacing some or all of the iron, and also tungsten-copper materials. Typically, these are fabricated by liquid-phase sintering of blended powders. Liquid-phase sintering offers the advantages of low processing costs, established technology, and generally attractive mechanical properties. However, liquid-phase sintering is restricted to a very limited number of matrix alloying elements and a limited range of tungsten and alloying compositions. In the past few years, there has been interest in a wider range of matrix materials that offer the potential for superior composite properties. These must be processed by solid-state processes and at sufficiently low temperatures to avoid undesired reactions between the tungsten and the matrix phase. These processes, in order of decreasing process temperature requirements, include hot isostatic pressing (HEPing), hot extrusion, and dynamic compaction. The HIPing and hot extrusion processes have also been used to improve mechanical properties of conventional liquid-phase-sintered materials. The results of laboratory-scale investigations of solid-state consolidation of a variety of matrix materials, including titanium, hafnium, nickel aluminide, and steels are reviewed. The potential advantages and disadvantages of each of the possible alternative consolidation processes are identified. Post consolidation processing to control microstructure and macrostructure is discussed, including novel methods of controlling microstructure alignment.

  5. Micromagnetic model for biaxial stress effects on magnetic properties

    NASA Astrophysics Data System (ADS)

    Sablik, M. J.; Riley, L. A.; Burkhardt, G. L.; Kwun, H.; Cannell, P. Y.; Watts, K. T.; Langman, R. A.

    1994-04-01

    A micromagnetic formulation has been developed for modeling the effect of biaxial stress on magnetoelastic processes in polycrystalline steels. The formulation uses a modified version of the Kashiwaya model for the effect of biaxial stress on magnetic properties and combines it with the Schneider-Cannell-Watts model for magnetoelastic processes in steels. In particular, the model involves use of an effective stress equal to one of the deviatoric (i.e. distortional) normal stress components, depending on whether the field is parallel to a tensile or compressive axis or to the third axis perpendicular to the plane of biaxial stress. Computer results are compared to experimental results on the effects of biaxial stress on magnetic properties in mild steel and in SAE-4130 steel. Good qualitative agreement is found in almost all cases, in that in going from one biaxial stress case to the next, the same kinds of changes are seen magnetically.

  6. Tungsten diffusion in olivine

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Van Orman, J. A.

    2014-03-01

    Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

  7. High purity tungsten targets

    NASA Technical Reports Server (NTRS)

    1975-01-01

    High purity tungsten, which is used for targets in X-ray tubes was considered for space processing. The demand for X-ray tubes was calculated using the growth rates for dental and medical X-ray machines. It is concluded that the cost benefits are uncertain.

  8. Gas tungsten arc welder

    DOEpatents

    Christiansen, D.W.; Brown, W.F.

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  9. Biaxial mechanical characterization of bat wing skin.

    PubMed

    Skulborstad, A J; Swartz, S M; Goulbourne, N C

    2015-06-01

    The highly flexible and stretchable wing skin of bats, together with the skeletal structure and musculature, enables large changes in wing shape during flight. Such compliance distinguishes bat wings from those of all other flying animals. Although several studies have investigated the aerodynamics and kinematics of bats, few have examined the complex histology and mechanical response of the wing skin. This work presents the first biaxial characterization of the local deformation, mechanical properties, and fiber kinematics of bat wing skin. Analysis of these data has provided insight into the relationships among the structural morphology, mechanical properties, and functionality of wing skin. Large spatial variations in tissue deformation and non-negligible fiber strains in the cross-fiber direction for both chordwise and spanwise fibers indicate fibers should be modeled as two-dimensional elements. The macroscopic constitutive behavior was anisotropic and nonlinear, with very low spanwise and chordwise stiffness (hundreds of kilopascals) in the toe region of the stress-strain curve. The structural arrangement of the fibers and matrix facilitates a low energy mechanism for wing deployment and extension, and we fabricate examples of skins capturing this mechanism. We propose a comprehensive deformation map for the entire loading regime. The results of this work underscore the importance of biaxial field approaches for soft heterogeneous tissue, and provide a foundation for development of bio-inspired skins to probe the effects of the wing skin properties on aerodynamic performance. PMID:25895436

  10. Laminate articles on biaxially textured metal substrates

    DOEpatents

    Beach, David B.; Morrell, Jonathan S.; Paranthaman, Mariappan; Chirayil, Thomas; Specht, Eliot D.; Goyal, Amit

    2003-12-16

    A laminate article comprises a substrate and a biaxially textured (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer over the substrate, wherein 0biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

  11. Biaxial strain and variable stiffness in aponeuroses

    PubMed Central

    Azizi, Emanuel; Roberts, Thomas J

    2009-01-01

    The elastic structures of many muscles include both an extramuscular free tendon as well as a sheet-like aponeurosis. An important distinguishing feature of aponeuroses is that these tendinous structures function as the attachment and insertion surfaces of muscle fascicles and therefore surround a substantial portion of the muscle belly. As a result, aponeuroses must expand both parallel (longitudinal) and perpendicular (transverse) to a muscle's line of action when contracting muscles bulge to maintain a constant volume. In this study, we use biplanar high-speed fluoroscopy to track the strain patterns of the turkey lateral gastrocnemius aponeurosis during active and passive force production in situ. We find that the behaviour of the aponeurosis during passive force production is consistent with uniaxial loading, as aponeuroses stretch only in the longitudinal direction. By contrast, our results show that aponeuroses are stretched in both longitudinal and transverse directions during active force production and that transverse strains are on average 4 times greater than longitudinal strains. Biaxial loading of aponeuroses appears to effectively modulate longitudinal stiffness, as we find the measured stiffness in the longitudinal direction varies in proportion to transverse strain. We conclude that biaxial strain during active force production distinguishes aponeuroses from free tendons and may function to dynamically modulate stiffness along the axis of muscle force production. It is likely that consideration of strains measured only in the longitudinal direction result in an underestimation of aponeurosis stiffness as well as its capacity for elastic energy storage. PMID:19596897

  12. Chemical downstream etching of tungsten

    SciTech Connect

    Blain, M.G.; Jarecki, R.L.; Simonson, R.J.

    1998-07-01

    The downstream etching of tungsten and tungsten oxide has been investigated. Etching of chemical vapor deposited tungsten and e-beam deposited tungsten oxide samples was performed using atomic fluorine generated by a microwave discharge of argon and NF{sub 3}. Etching was found to be highly activated with activation energies approximated to be 6.0{plus_minus}0.5thinspkcal/mol and 5.4{plus_minus}0.4thinspkcal/mol for W and WO{sub 3}, respectively. In the case of F etching of tungsten, the addition of undischarged nitric oxide (NO) directly into the reaction chamber results in the competing effects of catalytic etch rate enhancement and the formation of a nearly stoichiometric WO{sub 3} passivating tungsten oxide film, which ultimately stops the etching process. For F etching of tungsten oxide, the introduction of downstream NO reduces the etch rate. {copyright} {ital 1998 American Vacuum Society.}

  13. A comparative study of deformation in carbon/carbon and carbon/polyimide laminates under bi-axial compression

    SciTech Connect

    Gupta, V.; Grape, J.A.

    1994-12-31

    The failure mechanisms of laminated 2-D carbon/carbon (C/C) and carbon/polyimide (C/P) composites have been determined under inplane biaxial compression loads, and the associated failure envelopes that account for the effect of matrix-type and loading directions, are also obtained. For the C/C laminates, the failure was in the form of micro-kinking of fiber-bundles, interspersed by localized interply delaminations to form the overall shear-fault. The shear fault was aligned with the major use of loading, except at above 75% of balanced biaxial stress, where failure occurred alone both axes. For the C/P laminates, however, the overall failure was primarily in the form of axial interply delaminations aligned with the principal axis of loading, with only secondary events of kinking in few bundles. Although the biaxial strength for both C/C and C/P samples varied significantly with the ratio of in-plane principal stresses, R, there was no variation in the local failure mechanisms. Accordingly, it was found that both materials fail upon achieving a maximum strain along the primary axis of loading.

  14. Biaxial Nematic Phase in Model Bent-Core Systems

    NASA Astrophysics Data System (ADS)

    Grzybowski, Piotr; Longa, Lech

    2011-07-01

    We determine the bifurcation phase diagrams with isotropic (I), uniaxial (NU) and biaxial (NB) nematic phases for model bent-core mesogens using Onsager-type theory. The molecules comprise two or three Gay-Berne interacting ellipsoids of uniaxial and biaxial shape and a transverse central dipole. The Landau point is found to turn into an I-NB line for the three-center model with a large dipole moment. For the biaxial ellipsoids, a line of Landau points is observed even in the absence of the dipoles.

  15. Reflection of electromagnetic waves at a biaxial-isotropic interface

    NASA Technical Reports Server (NTRS)

    Njoku, E. G.

    1983-01-01

    The reflection of electromagnetic waves at a plane boundary between isotropic and biaxial media has been investigated using the kDB approach. The general case has been considered in which the principal dielectric axes of the biaxial medium are oriented at an arbitrary angle to the normal of the plane boundary. In general, two characteristic waves propagate in the biaxial medium, leading to coupling of vertical and horizontal polarizations in the reflected waves. Some special cases are illustrated. The results have applications to problems in remote sensing and integrated optics.

  16. Conductive and robust nitride buffer layers on biaxially textured substrates

    DOEpatents

    Sankar, Sambasivan; Goyal, Amit; Barnett, Scott A.; Kim, Ilwon; Kroeger, Donald M.

    2004-08-31

    The present invention relates to epitaxial, electrically conducting and mechanically robust, cubic nitride buffer layers deposited epitaxially on biaxially textured substrates such as metal and alloys. The invention comprises of a biaxially textured substrate with epitaxial layers of nitrides. The invention also discloses a method to form such epitaxial layers using a high rate deposition method as well as without the use of forming gases. The invention further comprises epitaxial layers of oxides on the biaxially textured nitride layers. In some embodiments the article further comprises electromagnetic devices which may be super conducting properties.

  17. Conductive and robust nitride buffer layers on biaxially textured substrates

    DOEpatents

    Sankar, Sambasivan [Chicago, IL; Goyal, Amit [Knoxville, TN; Barnett, Scott A [Evanston, IL; Kim, Ilwon [Skokie, IL; Kroeger, Donald M [Knoxville, TN

    2009-03-31

    The present invention relates to epitaxial, electrically conducting and mechanically robust, cubic nitride buffer layers deposited epitaxially on biaxially textured substrates such as metals and alloys. The invention comprises of a biaxially textured substrate with epitaxial layers of nitrides. The invention also discloses a method to form such epitaxial layers using a high rate deposition method as well as without the use of forming gases. The invention further comprises epitaxial layers of oxides on the biaxially textured nitride layer. In some embodiments the article further comprises electromagnetic devices which may have superconducting properties.

  18. Biaxial and antiferroelectric structure of the orthogonal smectic phase of a bent-shaped molecule and helical structure in a chiral mixture system

    NASA Astrophysics Data System (ADS)

    Kang, Sungmin; Nguyen, Ha; Nakajima, Shunpei; Tokita, Masatoshi; Watanabe, Junji

    2013-05-01

    We examined the biaxial and antiferroelectric properties in the Smectic-APA (Sm-APA) phase of bent-shaped DC-S-8. The biaxiality, which results from the existence of a secondary director, was well established from birefringence observations in the homeotropically aligned Sm-APA. By entering into Sm-APA phase, the birefringence (Δn, difference between two refractive indices of short axes) continuously increased from 0 to 0.02 with decreasing temperature. The antiferroelectric switching and second harmonic generation (SHG) activity on the field-on state were also observed in the Sm-APA phase, and the evaluated spontaneous polarization (PS) value strongly depended on temperature. The temperature dependence of Δn and PS resembles each other and follows Haller's approximation, showing that the biaxiality is due to polar packing in which the molecules are preferentially packed with their bent direction arranged in the same direction, and that the phase transition of Sm-APA to Sm-A is second order. The biaxiality was further examined in chiral Sm-APA*. Doping with chiral components induced the helical twisting of the secondary director in the Sm-APA* phase, which was confirmed by observing the reflection of the circular dichroism (CD) bands in the homeotropically aligned cell. The helical pitch of Sm-APA* is tunable in the range of 300-700 nm wavelength with a variation in the chiral content of 5 to 10 weight (wt)%.

  19. Biaxially textured articles formed by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-10-21

    A strengthened, biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed, compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: Ni, Ag, Ag--Cu, Ag--Pd, Ni--Cu, Ni--V, Ni--Mo, Ni--Al, Ni--Cr--Al, Ni--W--Al, Ni--V--Al, Ni--Mo--Al, Ni--Cu--Al; and at least one fine metal oxide powder; the article having a grain size which is fine and homogeneous; and having a dominant cube oriented {100}<100> orientation texture; and further having a Curie temperature less than that of pure Ni.

  20. Biaxial stress relaxation in glassy polymers - Polymethylmethacrylate.

    NASA Technical Reports Server (NTRS)

    Sternstein, S. S.; Ho, T. C.

    1972-01-01

    Biaxial stress relaxation studies were performed on glassy polymethylmethacrylate in combined torsion-tension strain fields using a specially designed apparatus with exceptionally high stiffness and low cross talk between the torsional and tensile load measuring transducers. It was found that at low strain levels uniaxial tension relaxation is slower than pure torsion relaxation; tensile-component relaxation rates are unaffected by the level of torsional strain; torsional-component relaxation rates decrease as tensile strain is increased; uniaxial tension relaxation rates approach the pure torsion rates at higher strains (about 2%). A phenomenological treatment is presented which shows that relaxation rates can be coupled to the strain fields in which they are observed and yet be consistent with the concepts of linear viscoelasticity and the Boltzmann superposition integral.

  1. Helium bubble bursting in tungsten

    SciTech Connect

    Sefta, Faiza; Juslin, Niklas; Wirth, Brian D.

    2013-12-28

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz.

  2. Biaxial Yield Surface Investigation of Polymer-Matrix Composites

    PubMed Central

    Ye, Junjie; Qiu, Yuanying; Zhai, Zhi; He, Zhengjia

    2013-01-01

    This article presents a numerical technique for computing the biaxial yield surface of polymer-matrix composites with a given microstructure. Generalized Method of Cells in combination with an Improved Bodner-Partom Viscoplastic model is used to compute the inelastic deformation. The validation of presented model is proved by a fiber Bragg gratings (FBGs) strain test system through uniaxial testing under two different strain rate conditions. On this basis, the manufacturing process thermal residual stress and strain rate effect on the biaxial yield surface of composites are considered. The results show that the effect of thermal residual stress on the biaxial yield response is closely dependent on loading conditions. Moreover, biaxial yield strength tends to increase with the increasing strain rate. PMID:23529150

  3. Mineral resource of the month: tungsten

    USGS Publications Warehouse

    Shedd, Kim B.

    2012-01-01

    The article offers information on tungsten. It says that tungsten is a metal found in chemical compounds such as in the scheelite and ore minerals wolframite. It states that tungsten has the highest melting point and it forms a compound as hard as diamond when combined with carbon. It states that tungsten can be used as a substitute for lead in fishing weights, ammunition, and hunting shot. Moreover, China started to export tungsten materials and products instead of tungsten raw materials.

  4. Interaction of tungsten with tungsten carbide in a copper melt

    NASA Astrophysics Data System (ADS)

    Bodrova, L. E.; Goida, E. Yu.; Pastukhov, E. A.; Marshuk, L. A.; Popova, E. A.

    2013-07-01

    The chemical interaction between tungsten and tungsten carbide in a copper melt with the formation of W2C at 1300°C is studied. It is shown that the mechanical activation of a composition consisting of copper melt + W and WC powders by low-temperature vibrations initiates not only the chemical interaction of its solid components but also their refinement.

  5. Generalized Jones matrix method for homogeneous biaxial samples.

    PubMed

    Ortega-Quijano, Noé; Fade, Julien; Alouini, Mehdi

    2015-08-10

    The generalized Jones matrix (GJM) is a recently introduced tool to describe linear transformations of three-dimensional light fields. Based on this framework, a specific method for obtaining the GJM of uniaxial anisotropic media was recently presented. However, the GJM of biaxial media had not been tackled so far, as the previous method made use of a simplified rotation matrix that lacks a degree of freedom in the three-dimensional rotation, thus being not suitable for calculating the GJM of biaxial media. In this work we propose a general method to derive the GJM of arbitrarily-oriented homogeneous biaxial media. It is based on the differential generalized Jones matrix (dGJM), which is the three-dimensional counterpart of the conventional differential Jones matrix. We show that the dGJM provides a simple and elegant way to describe uniaxial and biaxial media, with the capacity to model multiple simultaneous optical effects. The practical usefulness of this method is illustrated by the GJM modeling of the polarimetric properties of a negative uniaxial KDP crystal and a biaxial KTP crystal for any three-dimensional sample orientation. The results show that this method constitutes an advantageous and straightforward way to model biaxial media, which show a growing relevance for many interesting applications.

  6. TUNGSTEN BASE ALLOYS

    DOEpatents

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  7. Preparation of tungsten oxide

    DOEpatents

    Bulian, Christopher J.; Dye, Robert C.; Son, Steven F.; Jorgensen, Betty S.; Perry, W. Lee

    2009-09-22

    Tungsten trioxide hydrate (WO.sub.3.H.sub.2O) was prepared from a precursor solution of ammonium paratungstate in concentrated aqueous hydrochloric acid. The precursor solution was rapidly added to water, resulting in the crash precipitation of a yellow white powder identified as WO.sub.3.H.sub.2O nanosized platelets by x-ray diffraction and scanning electron microscopy. Annealing of the powder at 200.degree. C. provided cubic phase WO.sub.3 nanopowder, and at 400.degree. C. provided WO.sub.3 nanopowder as a mixture of monoclinic and orthorhombic phases.

  8. Domain walls and anchoring transitions mimicking nematic biaxiality in the oxadiazole bent-core liquid crystal C7.

    PubMed

    Kim, Young-Ki; Cukrov, Greta; Xiang, Jie; Shin, Sung-Tae; Lavrentovich, Oleg D

    2015-05-28

    We investigate the origin of "secondary disclinations" that were recently described as new evidence of a biaxial nematic phase in an oxadiazole bent-core thermotropic liquid crystal C7. Using an assortment of optical techniques such as polarizing optical microscopy, LC PolScope, and fluorescence confocal polarizing microscopy, we demonstrate that the secondary disclinations represent non-singular domain walls formed in a uniaxial nematic phase during the surface anchoring transition, in which surface orientation of the director changes from tangential (parallel to the bounding plates) to tilted. Each domain wall separates two regions with the director tilted in opposite azimuthal directions. At the centre of the wall, the director remains parallel to the bounding plates. The domain walls can be easily removed by applying a moderate electric field. The anchoring transition is explained by the balance of (a) the intrinsic perpendicular surface anchoring produced by the polyimide aligning layer and (b) tangential alignment caused by ionic impurities forming electric double layers. The model is supported by the fact that the temperature of the tangentially tilted anchoring transition decreases as the cell thickness increases and as the concentration of ionic species (added salt) increases. We also demonstrate that the surface alignment is strongly affected by thermal degradation of the samples. This study shows that C7 exhibits only a uniaxial nematic phase and demonstrates yet another mechanism (formation of "secondary disclinations") by which a uniaxial nematic phase can mimic a biaxial nematic behaviour. PMID:25820380

  9. Domain walls and anchoring transitions mimicking nematic biaxiality in the oxadiazole bent-core liquid crystal C7.

    PubMed

    Kim, Young-Ki; Cukrov, Greta; Xiang, Jie; Shin, Sung-Tae; Lavrentovich, Oleg D

    2015-05-28

    We investigate the origin of "secondary disclinations" that were recently described as new evidence of a biaxial nematic phase in an oxadiazole bent-core thermotropic liquid crystal C7. Using an assortment of optical techniques such as polarizing optical microscopy, LC PolScope, and fluorescence confocal polarizing microscopy, we demonstrate that the secondary disclinations represent non-singular domain walls formed in a uniaxial nematic phase during the surface anchoring transition, in which surface orientation of the director changes from tangential (parallel to the bounding plates) to tilted. Each domain wall separates two regions with the director tilted in opposite azimuthal directions. At the centre of the wall, the director remains parallel to the bounding plates. The domain walls can be easily removed by applying a moderate electric field. The anchoring transition is explained by the balance of (a) the intrinsic perpendicular surface anchoring produced by the polyimide aligning layer and (b) tangential alignment caused by ionic impurities forming electric double layers. The model is supported by the fact that the temperature of the tangentially tilted anchoring transition decreases as the cell thickness increases and as the concentration of ionic species (added salt) increases. We also demonstrate that the surface alignment is strongly affected by thermal degradation of the samples. This study shows that C7 exhibits only a uniaxial nematic phase and demonstrates yet another mechanism (formation of "secondary disclinations") by which a uniaxial nematic phase can mimic a biaxial nematic behaviour.

  10. Biaxial nematic phase stability and demixing behaviour in monolayers of rod-plate mixtures.

    PubMed

    Martínez-Ratón, Yuri; González-Pinto, Miguel; Velasco, Enrique

    2016-09-21

    We theoretically study the phase behaviour of monolayers of hard rod-plate mixtures using a fundamental-measure density functional in the restricted-orientation (Zwanzig) approximation. Particles can rotate in 3D but their centres of mass are constrained to be on a flat surface. In addition, we consider both species to be subject to an attractive potential proportional to the particle contact area on the surface and with adsorption strengths that depend on the species type. Particles have board-like shape, with sizes chosen using a symmetry criterion: same volume and same aspect ratio κ. Phase diagrams were calculated for κ = 10, 20 and 40 and different values of adsorption strengths. For small adsorption strengths the mixtures exhibit a second-order uniaxial nematic-biaxial nematic transition for molar fraction of rods 0 ≤x≲ 0.9. In the uniaxial nematic phase the particle axes of rods and plates are aligned perpendicular and parallel to the monolayer, respectively. At the transition, the orientational symmetry of the plate axes is broken, and they orient parallel to a director lying on the surface. For large and equal adsorption strengths the mixture demixes at low pressures into a uniaxial nematic phase, rich in plates, and a biaxial nematic phase, rich in rods. The demixing transition is located between two tricritical points. Also, at higher pressures and in the plate-rich part of the phase diagram, the system exhibits a strong first-order uniaxial nematic-biaxial nematic phase transition with a large density coexistence gap. When rod adsorption is considerably large while that of plates is small, the transition to the biaxial nematic phase is always of second order, and its region of stability in the phase diagram considerably widens. At very high pressures the mixture can effectively be identified as a two-dimensional mixture of squares and rectangles which again demixes above a certain critical point. We also studied the relative stability of uniform

  11. Biaxial nematic phase stability and demixing behaviour in monolayers of rod-plate mixtures.

    PubMed

    Martínez-Ratón, Yuri; González-Pinto, Miguel; Velasco, Enrique

    2016-09-21

    We theoretically study the phase behaviour of monolayers of hard rod-plate mixtures using a fundamental-measure density functional in the restricted-orientation (Zwanzig) approximation. Particles can rotate in 3D but their centres of mass are constrained to be on a flat surface. In addition, we consider both species to be subject to an attractive potential proportional to the particle contact area on the surface and with adsorption strengths that depend on the species type. Particles have board-like shape, with sizes chosen using a symmetry criterion: same volume and same aspect ratio κ. Phase diagrams were calculated for κ = 10, 20 and 40 and different values of adsorption strengths. For small adsorption strengths the mixtures exhibit a second-order uniaxial nematic-biaxial nematic transition for molar fraction of rods 0 ≤x≲ 0.9. In the uniaxial nematic phase the particle axes of rods and plates are aligned perpendicular and parallel to the monolayer, respectively. At the transition, the orientational symmetry of the plate axes is broken, and they orient parallel to a director lying on the surface. For large and equal adsorption strengths the mixture demixes at low pressures into a uniaxial nematic phase, rich in plates, and a biaxial nematic phase, rich in rods. The demixing transition is located between two tricritical points. Also, at higher pressures and in the plate-rich part of the phase diagram, the system exhibits a strong first-order uniaxial nematic-biaxial nematic phase transition with a large density coexistence gap. When rod adsorption is considerably large while that of plates is small, the transition to the biaxial nematic phase is always of second order, and its region of stability in the phase diagram considerably widens. At very high pressures the mixture can effectively be identified as a two-dimensional mixture of squares and rectangles which again demixes above a certain critical point. We also studied the relative stability of uniform

  12. Biaxial deformation in high purity aluminum

    SciTech Connect

    Livescu, V.; Bingert, J. F.; Liu, C.; Lovato, M. L.; Patterson, B. M.

    2015-09-25

    The convergence of multiple characterization tools has been applied to investigate the relationship of microstructure on damage evolution in high purity aluminum. The extremely coarse grain size of the disc-shaped sample provided a quasi-two dimensional structure from which the location of surface-measured features could be inferred. In particular, the role of pre-existing defects on damage growth was accessible due to the presence of casting porosity in the aluminum. Micro tomography, electron backscatter diffraction, and digital image correlation were applied to interrogate the sample in three dimensions. Recently micro-bulge testing apparatus was used to deform the pre-characterized disc of aluminum in biaxial tension, and related analysis techniques were applied to map local strain fields. Subsequent post-mortem characterization of the failed sample was performed to correlate structure to damaged regions. We determined that strain localization and associated damage was most strongly correlated with grain boundary intersections and plastic anisotropy gradients between grains. Pre-existing voids played less of an apparent role than was perhaps initially expected. Finally, these combined techniques provide insight to the mechanism of damage initiation, propagation, and failure, along with a test bed for predictive damage models incorporating anisotropic microstructural effects.

  13. Biaxial deformation in high purity aluminum

    DOE PAGES

    Livescu, V.; Bingert, J. F.; Liu, C.; Lovato, M. L.; Patterson, B. M.

    2015-09-25

    The convergence of multiple characterization tools has been applied to investigate the relationship of microstructure on damage evolution in high purity aluminum. The extremely coarse grain size of the disc-shaped sample provided a quasi-two dimensional structure from which the location of surface-measured features could be inferred. In particular, the role of pre-existing defects on damage growth was accessible due to the presence of casting porosity in the aluminum. Micro tomography, electron backscatter diffraction, and digital image correlation were applied to interrogate the sample in three dimensions. Recently micro-bulge testing apparatus was used to deform the pre-characterized disc of aluminum inmore » biaxial tension, and related analysis techniques were applied to map local strain fields. Subsequent post-mortem characterization of the failed sample was performed to correlate structure to damaged regions. We determined that strain localization and associated damage was most strongly correlated with grain boundary intersections and plastic anisotropy gradients between grains. Pre-existing voids played less of an apparent role than was perhaps initially expected. Finally, these combined techniques provide insight to the mechanism of damage initiation, propagation, and failure, along with a test bed for predictive damage models incorporating anisotropic microstructural effects.« less

  14. Graphene flakes under controlled biaxial deformation

    PubMed Central

    Androulidakis, Charalampos; Koukaras, Emmanuel N.; Parthenios, John; Kalosakas, George; Papagelis, Konstantinos; Galiotis, Costas

    2015-01-01

    Thin membranes, such as monolayer graphene of monoatomic thickness, are bound to exhibit lateral buckling under uniaxial tensile loading that impairs its mechanical behaviour. In this work, we have developed an experimental device to subject 2D materials to controlled equibiaxial strain on supported beams that can be flexed up or down to subject the material to either compression or tension, respectively. Using strain gauges in tandem with Raman spectroscopy measurements, we monitor the G and 2D phonon properties of graphene under biaxial strain and thus extract important information about the uptake of stress under these conditions. The experimental shift over strain for the G and 2D Raman peaks were found to be in the range of 62.3 ± 5 cm–1/%, and 148.2 ± 6 cm–1/%, respectively, for monolayer but also bilayer graphenes. The corresponding Grüneisen parameters for the G and 2D peaks were found to be between 1.97 ± 0.15 and 2.86 ± 0.12, respectively. These values agree reasonably well with those obtained from small-strain bubble-type experiments. The results presented are also backed up by classical and ab initio molecular dynamics simulations and excellent agreement of Γ-E2g shifts with strains and the Grüneisen parameter was observed. PMID:26666692

  15. Alignment validation

    SciTech Connect

    ALICE; ATLAS; CMS; LHCb; Golling, Tobias

    2008-09-06

    The four experiments, ALICE, ATLAS, CMS and LHCb are currently under constructionat CERN. They will study the products of proton-proton collisions at the Large Hadron Collider. All experiments are equipped with sophisticated tracking systems, unprecedented in size and complexity. Full exploitation of both the inner detector andthe muon system requires an accurate alignment of all detector elements. Alignmentinformation is deduced from dedicated hardware alignment systems and the reconstruction of charged particles. However, the system is degenerate which means the data is insufficient to constrain all alignment degrees of freedom, so the techniques are prone to converging on wrong geometries. This deficiency necessitates validation and monitoring of the alignment. An exhaustive discussion of means to validate is subject to this document, including examples and plans from all four LHC experiments, as well as other high energy experiments.

  16. Factors associated with biaxial texturing of Cu tapes for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Sung, T. H.; Han, S. C.; Han, Y. H.; Jeong, N. H.; Kim, C. J.; Jun, B. H.; Oh, S. S.; Kim, H. S.; Kim, T. H.; No, K. S.

    2007-10-01

    A biaxially textured Cu(2 0 0) tape was used as a substrate for YBCO coated conductors by cold rolling followed by recrystallization heat treatment. In this work, we studied the influence of annealing conditions and final tape thickness on the recrystallization process. Phi (ϕ) scan and omega (ω) scan XRD revealed that the best in-plane and out-of-plane alignment of the Cu tape (thickness 100 μm), measured in terms of full width half maximum (FWHM) values of 6.64° and 4.49°, were obtained by annealing at 800 °C for 30 min. The texture of CeO2 buffer layer thermally-evaporated on the Cu tape was also analyzed.

  17. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  18. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  19. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  20. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  1. 49 CFR 173.338 - Tungsten hexafluoride.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Tungsten hexafluoride. 173.338 Section 173.338... SHIPMENTS AND PACKAGINGS Gases; Preparation and Packaging § 173.338 Tungsten hexafluoride. (a) Tungsten... expansion test, must be condemned if removed from tungsten hexafluoride service....

  2. High strength uranium-tungsten alloy process

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1990-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  3. High strength uranium-tungsten alloys

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1991-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  4. METHOD OF MAKING TUNGSTEN FILAMENTS

    DOEpatents

    Frazer, J.W.

    1962-12-18

    A method of making tungsten filaments is described in which the tungsten is completely free of isotope impurities in the range of masses 234 to 245 for use in mass spectrometers. The filament comprises a tantalum core generally less than 1 mil in diameter having a coating of potassium-free tantalum-diffused tungsten molecularly bonded thereto. In the preferred process of manufacture a short, thin tantalum filament is first mounted between terminal posts mounted in insulated relation through a backing plate. The tungsten is most conveniently vapor plated onto the tantalum by a tungsten carbonyl vapor decomposition method having a critical step because of the tendency of the tantalum to volatilize at the temperature of operntion of the filament. The preferred recipe comprises volatilizing tantalum by resistance henting until the current drops by about 40%, cutting the voltage back to build up the tungsten, and then gradually building the temperature back up to balance the rate of tungsten deposition with the rate of tantalum volatilization. (AEC)

  5. Biaxial mechanics and inter-lamellar shearing of stem-cell seeded electrospun angle-ply laminates for annulus fibrosus tissue engineering.

    PubMed

    Driscoll, Tristan P; Nakasone, Ryan H; Szczesny, Spencer E; Elliott, Dawn M; Mauck, Robert L

    2013-06-01

    The annulus fibrosus (AF) of the intervertebral disk plays a critical role in vertebral load transmission that is heavily dependent on the microscale structure and composition of the tissue. With degeneration, both structure and composition are compromised, resulting in a loss of AF mechanical function. Numerous tissue engineering strategies have addressed the issue of AF degeneration, but few have focused on recapitulation of AF microstructure and function. One approach that allows for generation of engineered AF with appropriate (+/-)30° lamellar microstructure is the use of aligned electrospun scaffolds seeded with mesenchymal stem cells (MSCs) and assembled into angle-ply laminates (APL). Previous work indicates that opposing lamellar orientation is necessary for development of near native uniaxial tensile properties. However, most native AF tensile loads are applied biaxially, as the disk is subjected to multi-axial loads and is constrained by its attachments to the vertebral bodies. Thus, the objective of this study was to evaluate the biaxial mechanical response of engineered AF bilayers, and to determine the importance of opposing lamellar structure under this loading regime. Opposing bilayers, which replicate native AF structure, showed a significantly higher modulus in both testing directions compared to parallel bilayers, and reached ∼60% of native AF biaxial properties. Associated with this increase in biaxial properties, significantly less shear, and significantly higher stretch in the fiber direction, was observed. These results provide additional insight into native tissue structure-function relationships, as well as new benchmarks for engineering functional AF tissue constructs.

  6. RECOVERY OF URANIUM FROM TUNGSTEN

    DOEpatents

    Newnam, K.

    1959-02-01

    A method is presented for the rccovery of uranium which has adhered to tungsten parts in electromagnetic isotope separation apparatus. Such a tungsten article is dissolved electrolytically in 20% NaOH by using the tungsten article as the anode. The resulting solution, containing soluble sodium lungstate and an insoluble slime, is then filtered. The slime residue is ignited successively with sodium nitrate and sodium pyrosulfate and leashed, and the resulting filtrates are combined with the original filtrate. Uranium is then recovered from the combined flltrates by diuranate precipitation.

  7. Tungsten Toxicity in Plants

    PubMed Central

    Adamakis, Ioannis-Dimosthenis S.; Panteris, Emmanuel; Eleftheriou, Eleftherios P.

    2012-01-01

    Tungsten (W) is a rare heavy metal, widely used in a range of industrial, military and household applications due to its unique physical properties. These activities inevitably have accounted for local W accumulation at high concentrations, raising concerns about its effects for living organisms. In plants, W has primarily been used as an inhibitor of the molybdoenzymes, since it antagonizes molybdenum (Mo) for the Mo-cofactor (MoCo) of these enzymes. However, recent advances indicate that, beyond Mo-enzyme inhibition, W has toxic attributes similar with those of other heavy metals. These include hindering of seedling growth, reduction of root and shoot biomass, ultrastructural malformations of cell components, aberration of cell cycle, disruption of the cytoskeleton and deregulation of gene expression related with programmed cell death (PCD). In this article, the recent available information on W toxicity in plants and plant cells is reviewed, and the knowledge gaps and the most pertinent research directions are outlined. PMID:27137642

  8. Tungsten resources of Brazil

    USGS Publications Warehouse

    White, Max Gregg

    1974-01-01

    Brazilian tungsten production, 85 percent of which is exported, comes almost entirely from scheelite-bearing tactites in northeast Brazil, and has reached an annual rate of about 2,000 metric tons (2,200 short tons) of scheelite concentrate with 70 percent WO3. Scheelite ore reserves, located principally in the State of Rio Grande do Norte, are estimated to be as high as 8,300,000 tons (9,100,000 short tons) containing 0.7 percent WO3. Minor deposits (or those about which only minimal information is available) of wolframite, with which some cassiterite is associated, are located in Sao Paulo, Santa Catarina, and Rio Grande do Sul. Both the scheelite and the wolframite deposits are considered . to be late Precambrian A (620 to 900 m.y.) or early Cambrian in age.

  9. Servo-controlled biaxial test system

    SciTech Connect

    Thayer, W.L.

    1983-02-11

    A large test program requiring axial torsion tests was submitted to the Materials Test and Evaluation Section of the Engineering Sciences Division by the Chemistry Department. The objective of these tests was to provide insight with regard to the fundamental aspects of plastic deformation and hardening of nickel. Thes tests will also provide the constants necessary for a constitutive equation for use in weld modeling. The weld models will attempt to predict residual stresses in nickel welds. The test program consisted of approximately 70 specimens of high purity nickel to be tested in torsion over a large temperature range (RT - 900/sup 0/C) at a strain rate of about 1 x 10/sup -4/ in./in./sec to steady state at each temperature. After having attained steady state, the strain-rate-reversal (Bauschinger test) and incremental-changes-in-strain-rate tests (10/sup -4/ to 2 x 10/sup -3/ in./in./sec) at constant structure will be conducted. Additional tests such as transient backstress and yield surface distortion (using multi-axial stress states) will be carried out. This particular request required a biaxial test machine capable of more than 360/sup 0/ rotation in torsion. Temperature capabilities, atmosphere control, and a control system were also needed whereby the machine could be operated in torsion using strain control. Such a machine did not commercially exist so it was necessary to build one. The basic unit chosen was a 20K Servo-Electric Hydraulic Test Machine to which we added a simple anti-rotation fixture for the ram. This constituted the axial portion of the system.

  10. Biaxial mechanical modeling of the small intestine.

    PubMed

    Bellini, Chiara; Glass, Paul; Sitti, Metin; Di Martino, Elena S

    2011-11-01

    Capsule endoscopes are pill-size devices provided with a camera that capture images of the small intestine from inside the body after being ingested by a patient. The interaction between intestinal tissue and capsule endoscopes needs to be investigated to optimize capsule design while preventing tissue damage. To that purpose, a constitutive model that can reliably predict the mechanical response of the intestinal tissue under complex mechanical loading is required. This paper describes the development and numerical validation of a phenomenological constitutive model for the porcine duodenum, jejunum and ileum. Parameters characterizing the mechanical behavior of the material were estimated from planar biaxial test data, where intestinal tissue specimens were simultaneously loaded along the circumferential and longitudinal directions. Specimen-specific Fung constitutive models were able to accurately predict the planar stress-strain behavior of the tested samples under a wide range of loading conditions. To increase model generality, average anisotropic constitutive relationships were also generated for each tissue region by fitting average stress-strain curves to the Fung potential. Due to the observed variability in the direction of maximum stiffness, the average Fung models were less anisotropic than the specimen-specific models. Hence, average isotropic models in the Neo-Hookean and Mooney-Rivlin forms were attempted, but they could not adequately describe the degree of nonlinearity in the tissue. Values of the R2 for the nonlinear regressions were 0.17, 0.44 and 0.93 for the average Neo-Hookean, Mooney-Rivlin and Fung models, respectively. Average models were successfully implemented into FORTRAN routines and used to simulate capsule deployment with a finite element method analysis. PMID:22098873

  11. Field response and switching times in biaxial nematics

    NASA Astrophysics Data System (ADS)

    Berardi, Roberto; Muccioli, Luca; Zannoni, Claudio

    2008-01-01

    We study by means of virtual molecular dynamics computer experiments the response of a bulk biaxial nematic to an applied external field and, in particular, the relative speed of reorientation of the principal director axis and of the secondary one, typical of these new materials, upon a π /2 field switch. We perform the simulations setting up and integrating the equations of motion for biaxial Gay-Berne particles using quaternions and a suitable time reversible symplectic integrator. We find that switching of the secondary axis is up to an order of magnitude faster than that of the principal axis, and that under fields above a certain strength a reorganization of local domains, temporarily disrupting the nematic and biaxial ordering, rather than a collective concerted reorientation occurs.

  12. On the Biaxial Mechanical Response of Porcine Tricuspid Valve Leaflets.

    PubMed

    Amini Khoiy, Keyvan; Amini, Rouzbeh

    2016-10-01

    Located on the right side of the heart, the tricuspid valve (TV) prevents blood backflow from the right ventricle to the right atrium. Similar to other cardiac valves, quantification of TV biaxial mechanical properties is essential in developing accurate computational models. In the current study, for the first time, the biaxial stress-strain behavior of porcine TV was measured ex vivo under different loading protocols using biaxial tensile testing equipment. The results showed a highly nonlinear response including a compliant region followed by a rapid transition to a stiff region for all of the TV leaflets both in the circumferential and in the radial directions. Based on the data analysis, all three leaflets were found to be anisotropic, and they were stiffer in the circumferential direction in comparison to the radial direction. It was also concluded that the posterior leaflet was the most anisotropic leaflet. PMID:27538260

  13. Failure of composite plates under static biaxial planar loading

    NASA Technical Reports Server (NTRS)

    Waas, Anthony M.; Khamseh, Amir R.

    1992-01-01

    The project involved detailed investigations into the failure mechanisms in composite plates as a function of hole size (holes centrally located in the plates) under static loading. There were two phases to the project, the first dealing with uniaxial loads along the fiber direction, and the second dealing with coplanar biaxial loading. Results for the uniaxial tests have been reported and published previously, thus this report will place emphasis on the second phase of the project, namely the biaxial tests. The composite plates used in the biaxial loading experiments, as well as the uniaxial, were composed of a single ply unidirectional graphite/epoxy prepreg sandwiched between two layers of transparent thermoplastic. This setup enabled us to examine the failure initiation and propagation modes nondestructively, during the test. Currently, similar tests and analysis of results are in progress for graphite/epoxy cruciform shaped flat laminates. The results obtained from these tests will be available at a later time.

  14. Method of forming biaxially textured alloy substrates and devices thereon

    DOEpatents

    Goyal, Amit; Specht, Eliot D.; Kroeger, Donald M.; Paranthaman, Mariappan

    2000-01-01

    Specific alloys, in particular Ni-based alloys, that can be biaxially textured, with a well-developed, single component texture are disclosed. These alloys have a significantly reduced Curie point, which is very desirable from the point of view of superconductivity applications. The biaxially textured alloy substrates also possess greatly enhanced mechanical properties (yield strength, ultimate tensile strength) which are essential for most applications, in particular, superconductors. A method is disclosed for producing complex multicomponent alloys which have the ideal physical properties for specific applications, such as lattice parameter, degree of magnetism and mechanical strength, and which cannot be in textured form. In addition, a method for making ultra thin biaxially textured substrates with complex compositions is disclosed.

  15. Method of forming biaxially textured alloy substrates and devices thereon

    DOEpatents

    Goyal, Amit; Specht, Eliot D.; Kroeger, Donald M.; Paranthaman, Mariappan

    1999-01-01

    Specific alloys, in particular Ni-based alloys, that can be biaxially textured, with a well-developed, single component texture are disclosed. These alloys have a significantly reduced Curie point, which is very desirable from the point of view of superconductivity applications. The biaxially textured alloy substrates also possess greatly enhanced mechanical properties (yield strength, ultimate tensile strength) which are essential for most applications, in particular, superconductors. A method is disclosed for producing complex multicomponent alloys which have the ideal physical properties for specific applications, such as lattice parameter, degree of magnetism and mechanical strength, and which cannot be fabricated in textured form. In addition, a method for making ultra thin biaxially textured substrates with complex compositions is disclosed.

  16. Why Tungsten Instead of Wolfram?

    NASA Astrophysics Data System (ADS)

    Jensen, William B.

    2008-04-01

    In response to a reader query, the column traces the reason that American and British chemical literature use the name tungsten for element 74, while northern European literature uses the name wolfram.

  17. Heated die facilitates tungsten forming

    NASA Technical Reports Server (NTRS)

    Chattin, J. H.; Haystrick, J. E.; Laughlin, J. C.; Leidy, R. A.

    1966-01-01

    Tungsten forming in a press brake employs a bottom die assembly with a heating manifold between two water-cooled die sections. The manifold has hydrogen-oxygen burners spaced along its length for even heat during forming.

  18. Polycrystalline ferroelectric or multiferroic oxide articles on biaxially textured substrates and methods for making same

    DOEpatents

    Goyal, Amit; Shin, Junsoo

    2015-03-31

    A polycrystalline ferroelectric and/or multiferroic oxide article includes a substrate having a biaxially textured surface; at least one biaxially textured buffer layer supported by the substrate; and a biaxially textured ferroelectric or multiferroic oxide layer supported by the buffer layer. Methods for making polycrystalline ferroelectric and/or multiferroic oxide articles are also disclosed.

  19. Alignment of the diamond nitrogen vacancy center by strain engineering

    SciTech Connect

    Karin, Todd; Dunham, Scott; Fu, Kai-Mei

    2014-08-04

    The nitrogen vacancy (NV) center in diamond is a sensitive probe of magnetic field and a promising qubit candidate for quantum information processing. The performance of many NV-based devices improves by aligning the NV(s) parallel to a single crystallographic direction. Using ab initio theoretical techniques, we show that NV orientation can be controlled by high-temperature annealing in the presence of strain under currently accessible experimental conditions. We find that (89 ± 7)% of NVs align along the [111] crystallographic direction under 2% compressive biaxial strain (perpendicular to [111]) and an annealing temperature of 970 °C.

  20. Controlling biaxial strain in an inflated elastomeric membrane

    NASA Astrophysics Data System (ADS)

    Blaedel, K. L.; Radewan, C. H.; Feng, W. W.

    1985-11-01

    An apparatus for the study of the viscoelastic and aging mechanical behavior of polymers under biaxial loading is described in which the inflation of a plane circular membrane is used to obtain a biaxial state of stress. The properties of polymers are determined using a relaxation test, with deformations of the membrane remaining unchanged while the inflating pressure is being measured. The height of the deformed membrane is controlled by using a phototransistor and an infrared emitting diode. A schematic of the apparatus and a block diagram of the electronics used to regulate the height of the membrane are presented along with some test results.

  1. Method for forming biaxially textured articles by powder metallurgy

    DOEpatents

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2002-01-01

    A method of preparing a biaxially textured alloy article comprises the steps of preparing a mixture comprising Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacting the mixture, followed by heat treating and rapidly recrystallizing to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

  2. Growth and field emission of tungsten oxide nanotip arrays on ITO glass substrate

    NASA Astrophysics Data System (ADS)

    Huang, Kai; Pan, Qingtao; Yang, Feng; Ni, Shibi; He, Deyan

    2007-09-01

    High-density and uniformly aligned tungsten oxide nanotip arrays have been deposited by a conventional thermal evaporation on ITO glass substrates without any catalysts or additives. The temperature of substrate was 450-500 °C. It was shown that the tungsten oxide nanotips are single-crystal grown along [0 1 0] direction. For commercial applications, field emission of the tungsten oxide nanotip arrays was characterized in a poor vacuum at room temperature. The field emission behaviors are in agreement with Fowler-Nordheim theory. The turn-on field is 2.8 V μm -1 as d is 0.3 mm. The excellent field emission performances indicated that the tungsten oxide nanotip arrays grown by the present approach are a good candidate for application in vacuum microelectronic devices.

  3. Detection of an intermediate biaxial phase in the phase diagram of biaxial liquid crystals: Entropic sampling study

    NASA Astrophysics Data System (ADS)

    Kamala Latha, B.; Jose, Regina; Murthy, K. P. N.; Sastry, V. S. S.

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence NB-NB1-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases.

  4. Detection of an intermediate biaxial phase in the phase diagram of biaxial liquid crystals: entropic sampling study.

    PubMed

    Kamala Latha, B; Jose, Regina; Murthy, K P N; Sastry, V S S

    2014-05-01

    We investigate the phase sequence of biaxial liquid crystals, based on a general quadratic model Hamiltonian over the relevant parameter space, with a Monte Carlo simulation which constructs equilibrium ensembles of microstates, overcoming possible (free) energy barriers (combining entropic and frontier sampling techniques). The resulting phase diagram qualitatively differs from the universal phase diagram predicted earlier from mean-field theory (MFT), as well as the Monte Carlo simulations with the Metropolis algorithm. The direct isotropic-to-biaxial transition predicted by the MFT is replaced in certain regions of the space by the onset of an additional intermediate biaxial phase of very low order, leading to the sequence N(B)-N(B1)-I. This is due to inherent barriers to fluctuations of the components comprising the total energy, and may explain the difficulties in the experimental realization of these phases.

  5. Alignment fixture

    DOEpatents

    Bell, Grover C.; Gibson, O. Theodore

    1980-01-01

    A part alignment fixture is provided which may be used for precise variable lateral and tilt alignment relative to the fixture base of various shaped parts. The fixture may be used as a part holder for machining or inspection of parts or alignment of parts during assembly and the like. The fixture includes a precisely machined diameter disc-shaped hub adapted to receive the part to be aligned. The hub is nested in a guide plate which is adapted to carry two oppositely disposed pairs of positioning wedges so that the wedges may be reciprocatively positioned by means of respective micrometer screws. The sloping faces of the wedges contact the hub at respective quadrants of the hub periphery. The lateral position of the hub relative to the guide plate is adjusted by positioning the wedges with the associated micrometer screws. The tilt of the part is adjusted relative to a base plate, to which the guide plate is pivotally connected by means of a holding plate. Two pairs of oppositely disposed wedges are mounted for reciprocative lateral positioning by means of separate micrometer screws between flanges of the guide plate and the base plate. Once the wedges are positioned to achieve the proper tilt of the part or hub on which the part is mounted relative to the base plate, the fixture may be bolted to a machining, inspection, or assembly device.

  6. Curriculum Alignment.

    ERIC Educational Resources Information Center

    Crowell, Ronald; Tissot, Paula

    Curriculum alignment (CA) refers to the congruence of all the elements of a school's curriculum: curriculum goals; instructional program--what is taught and the materials used; and tests used to judge outcomes. CA can be a very powerful can be a very powerful factor in improving schools. Although further research is needed on CA, there is…

  7. Investigation of the interface characteristics of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions

    NASA Astrophysics Data System (ADS)

    Shi, Li-Bin; Liu, Xu-Yang; Dong, Hai-Kuan

    2016-09-01

    We investigate the interface behaviors of Y2O3/GaAs under biaxial strain, triaxial strain, and non-strain conditions. This study is performed by first principles calculations based on density functional theory (DFT). First of all, the biaxial strain is realized by changing the lattice constants in ab plane. Averaged electrostatic potential (AEP) is aligned by establishing Y2O3 and GaAs (110) surfaces. The band offsets of Y2O3/GaAs interface under biaxial strain are investigated by generalized gradient approximation and Heyd-Scuseria-Ernzerhof (HSE) functionals. The interface under biaxial strain is suitable for the design of metal oxide semiconductor (MOS) devices because the valence band offsets (VBO) and conduction band offsets (CBO) are larger than 1 eV. Second, the triaxial strain is applied to Y2O3/GaAs interface by synchronously changing the lattice constants in a, b, and c axis. The band gaps of Y2O3 and GaAs under triaxial strain are investigated by HSE functional. We compare the VBO and CBO under triaxial strain with those under biaxial strain. Third, in the absence of lattice strain, the formation energies, charge state switching levels, and migration barriers of native defects in Y2O3 are assessed. We investigate how they will affect the MOS device performance. It is found that VO+2 and Oi-2 play a very dangerous role in MOS devices. Finally, a direct tunneling leakage current model is established. The model is used to analyze current and voltage characteristics of the metal/Y2O3/GaAs.

  8. Gas-tungsten arc welding of aluminum alloys

    DOEpatents

    Frye, L.D.

    1982-03-25

    The present invention is directed to a gas-tungsten arc welding method for joining together structures formed of aluminum alloy with these structures disposed contiguously to a heat-damagable substrate of a metal dissimilar to the aluminum alloy. The method of the present invention is practiced by diamond machining the fay surfaces of the aluminum alloy structures to profice a mirror finish thereon having a surface roughness in the order of about one microinch. The fay surface are aligned and heated sufficiently by the tungsten electrode to fuse the aluminum alloy continguous to the fay surfaces to effect the weld joint. The heat input used to provide an oxide-free weld is significantly less than that required if the fay surfaces were prepared by using conventional chemical and mechanical practices.

  9. Gas-tungsten arc welding of aluminum alloys

    DOEpatents

    Frye, Lowell D.

    1984-01-01

    A gas-tungsten arc welding method for joining together structures formed of aluminum alloy with these structures disposed contiguously to a heat-damagable substrate of a metal dissimilar to the aluminum alloy. The method of the present invention is practiced by diamond machining the fay surfaces of the aluminum alloy structures to provide a mirror finish thereon having a surface roughness in the order of about one microinch. The fay surfaces are aligned and heated sufficiently by the tungsten electrode to fuse the aluminum alloy contiguous to the fay surfaces to effect the weld joint. The heat input used to provide an oxide-free weld is significantly less than that required if the fay surfaces were prepared by using conventional chemical and mechanical practices.

  10. Polarographic determination of tungsten in rocks

    USGS Publications Warehouse

    Reichen, L.E.

    1954-01-01

    This work was undertaken to develop a simpler and faster method than the classical gravimetric procedure for the determination of tungsten in rocks and ores. A new polarographic wave of tungsten is obtained in a supporting electrolyte of dilute hydrochloric acid containing tartrate ion. This permits the determination of tungsten both rapidly and accurately. No precipitation of the tungsten is necessary, and only the iron need be separated from the tungsten. The accuracy is within the limits of a polarographic procedure; comparison of polarographic and gravimetric results is given. The method reduces appreciably the amount of time ordinarily consumed in determination of tungsten.

  11. Process Of Bonding Copper And Tungsten

    DOEpatents

    Slattery, Kevin T.; Driemeyer, Daniel E.; Davis, John W.

    2000-07-18

    Process for bonding a copper substrate to a tungsten substrate by providing a thin metallic adhesion promoting film bonded to a tungsten substrate and a functionally graded material (FGM) interlayer bonding the thin metallic adhesion promoting film to the copper substrate. The FGM interlayer is formed by sintering a stack of individual copper and tungsten powder blend layers having progressively higher copper content/tungsten content, by volume, ratio values in successive powder blend layers in a lineal direction extending from the tungsten substrate towards the copper substrate. The resulting copper to tungsten joint well accommodates the difference in the coefficient of thermal expansion of the materials.

  12. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B.; Portavoce, A.; Grosjean, C.

    2014-01-07

    Two doses (10{sup 13} and 10{sup 15} cm{sup −2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960 °C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%–0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.

  13. Singular topology of optical absorption in biaxial crystals.

    PubMed

    Joly, Simon; Petit, Yannick; Boulanger, Benoît; Segonds, Patricia; Félix, Corinne; Ménaert, Bertrand; Aka, Gérard

    2009-10-26

    We show for the first time that biaxial crystals exhibit continua of directions of propagation where the absorption coefficient is the same for the two associated polarization modes. This statement is supported by both calculations and experimental data obtained in Nd:YCOB.

  14. The effects of biaxial loading on the fracture characteristics of several engineering materials

    NASA Technical Reports Server (NTRS)

    Jones, D. L.; Poulose, P. K.; Liebowitz, H.

    1986-01-01

    Using the George Washington University biaxial test system, a static fracture toughness study of two polymers (PMMA and PVC) and three aluminum alloys was performed for several variations in specimen geometry. Photoelastic experiments indicate that the applied load biaxiality has a very strong influence on the size and shape of the crack-tip stress field, and fracture toughness values for both polymers were seen to decrease with increasing load biaxiality. The load biaxiality was also found to have a strong influence on the crack growth direction in PMMA and a negligible influence on the PVC. The 7075-T6 aluminum toughness values increased with biaxiality, while intermediate peak toughness values were noted at a 0.5 biaxiality ratio for the more ductile 2024-T3 and 6061-T4 alloys. Fracture toughnesses at the highest biaxiality ratios were found to be equal to the uniaxial results.

  15. Biaxial order and a rotation of the minor director in the nematic phase of an organo-siloxane tetrapode by the electric field

    NASA Astrophysics Data System (ADS)

    Merkel, K.; Nagaraj, M.; Kocot, A.; Kohlmeier, A.; Mehl, G. H.; Vij, J. K.

    2012-03-01

    Biaxiality in the nematic phase for a liquid crystalline tetrapode made up of organo-siloxanes mesogens is investigated using polarized infrared spectroscopy. An ordering of the minor director for the homeotropically aligned sample is found to depend on the amplitude of the in-plane electric field. On increasing the in-plane electric field, the minor director, lying initially along the rubbing direction, rotates to the direction of the applied field. The scalar order parameters of the second rank tensor are found to depend significantly on the strength of the electric field. A most significant increase is found in the nematic order parameter and in the parameter that characterizes the phase biaxiality.

  16. A new direct process to prepare YBa 2Cu 3O 7- δ films on biaxially textured Ag{110}<211>

    NASA Astrophysics Data System (ADS)

    Wang, Rongping; Zhou, Yueliang; Pan, Shaohua; He, Meng; Chen, Zhenghao; Yang, Guozhen

    1999-12-01

    YBa 2Cu 3O 7- δ (YBCO) films were successfully prepared on biaxially textured Ag{110}<211> substrates by using pulsed laser deposition. X-ray diffraction results showed that the degree of preferential orientation of Ag{110}<211> substrates varied with increasing annealing temperature. With a thin template layer deposited at low temperature, YBCO film with c-axis orientation and in-plane biaxial alignment could be obtained at high deposition temperature. Scanning electron microscopy observation revealed that YBCO grains enlarged, but Ag grains on the surface of the YBCO films became smaller with increasing deposition temperature. At optimal deposition conditions, Ag atoms diffuse into the YBCO grain boundaries, and then fill in the weak-link regions in the YBCO film, resulting in the easier conduction. Jc value of 5×10 5 A/cm 2 was obtained at 77 K and zero magnetic field for the best YBCO film in our work.

  17. Uniaxial and biaxial mechanical properties of porcine linea alba.

    PubMed

    Cooney, Gerard M; Moerman, Kevin M; Takaza, Michael; Winter, Des C; Simms, Ciaran K

    2015-01-01

    Incisional hernia is a severe complication post-laparoscopic/laparotomy surgery that is commonly associated with the linea alba. However, the few studies on the mechanical properties of the linea alba in the literature appear contradictory, possible due to challenges with the physical dimensions of samples and variations in protocol. This study focuses on the tensile mechanical characterisation of the porcine linea alba, as determined by uniaxial and equi-load biaxial testing using image-based strain measurement methods. Results show that the linea alba demonstrated a non-linear elastic, anisotropic behaviour which is often observed in biological soft tissues. The transverse direction (parallel to fibres) was found to be approximately eight times stiffer than the longitudinal (cross-fibre) direction under both uniaxial and equi-load biaxial loading. The equi-load biaxial tensile tests revealed that contraction could occur in the transverse direction despite increasing load, probably due to the anisotropy of the tissue. Optical surface marker tracking and digital image correlation methods were found to greatly improve the accuracy of stretch measurement, resulting in a 75% change in the apparent stiffness compared to using strain derived from machine cross-head displacement. Additionally, a finite element model of the experiments using a combination of an Ogden and fibre exponential power law model for the linea alba was implemented to quantify the effect of clamping and tissue dimensions (which are suboptimal for tensile testing) on the results. The preliminary model results were used to apply a correction factor to the uniaxial experimental data prior to inverse optimisation to derive best fit material parameters for the fibre reinforced Ogden model. Application of the model to the equi-load biaxial case showed some differences compared to the experimental data, suggesting a more complex anisotropic model may be necessary to capture biaxial behaviour. These

  18. ALIGNING JIG

    DOEpatents

    Culver, J.S.; Tunnell, W.C.

    1958-08-01

    A jig or device is described for setting or aligning an opening in one member relative to another member or structure, with a predetermined offset, or it may be used for measuring the amount of offset with which the parts have previously been sct. This jig comprises two blocks rabbeted to each other, with means for securing thc upper block to the lower block. The upper block has fingers for contacting one of the members to be a1igmed, the lower block is designed to ride in grooves within the reference member, and calibration marks are provided to determine the amount of offset. This jig is specially designed to align the collimating slits of a mass spectrometer.

  19. Image alignment

    SciTech Connect

    Dowell, Larry Jonathan

    2014-04-22

    Disclosed is a method and device for aligning at least two digital images. An embodiment may use frequency-domain transforms of small tiles created from each image to identify substantially similar, "distinguishing" features within each of the images, and then align the images together based on the location of the distinguishing features. To accomplish this, an embodiment may create equal sized tile sub-images for each image. A "key" for each tile may be created by performing a frequency-domain transform calculation on each tile. A information-distance difference between each possible pair of tiles on each image may be calculated to identify distinguishing features. From analysis of the information-distance differences of the pairs of tiles, a subset of tiles with high discrimination metrics in relation to other tiles may be located for each image. The subset of distinguishing tiles for each image may then be compared to locate tiles with substantially similar keys and/or information-distance metrics to other tiles of other images. Once similar tiles are located for each image, the images may be aligned in relation to the identified similar tiles.

  20. Biaxial casting apparatus for isolating radioactive waste

    SciTech Connect

    Manchale, F. Jr.; Manchak, F. III.

    1992-10-20

    This patent describes apparatus for isolating hazardous radioactive waste for disposal. It comprises: a bifurcated centrifugal casting mold having at least two separable mold parts, the mold being supported for rotation about a first axis; means for supporting a completed monolith in the apparatus with the mold parts removed therefrom; powered drive means for rotating the mold and the monolith about the first axis; mold removal means aligned along a second axis substantially perpendicular to the first axis for removing the separate parts of the bifurcated casting mold from a monolith while leaving the monolith supported in the apparatus for rotation about the first axis; means for injecting a charge of radiation shielding material into a pre-formed shell placed in the mold; and means for heating the interior of the shell during rotation of the mold about the first axis.

  1. Composite biaxially textured substrates using ultrasonic consolidation

    DOEpatents

    Blue, Craig A; Goyal, Amit

    2013-04-23

    A method of forming a composite sheet includes disposing an untextured metal or alloy first sheet in contact with a second sheet in an aligned opposing position; bonding the first sheet to the second sheet by applying an oscillating ultrasonic force to at least one of the first sheet and the second sheet to form an untextured intermediate composite sheet; and annealing the untextured intermediate composite sheet at a temperature lower than a primary re-crystallization temperature of the second sheet and higher than a primary re-crystallization temperature of the first sheet to convert the untextured first sheet into a cube textured sheet, wherein the cube texture is characterized by a .phi.-scan having a FWHM of no more than 15.degree. in all directions, the second sheet remaining untextured, to form a composite sheet.

  2. Accurate pointing of tungsten welding electrodes

    NASA Technical Reports Server (NTRS)

    Ziegelmeier, P.

    1971-01-01

    Thoriated-tungsten is pointed accurately and quickly by using sodium nitrite. Point produced is smooth and no effort is necessary to hold the tungsten rod concentric. The chemically produced point can be used several times longer than ground points. This method reduces time and cost of preparing tungsten electrodes.

  3. Method of synthesizing tungsten nanoparticles

    DOEpatents

    Thoma, Steven G; Anderson, Travis M

    2013-02-12

    A method to synthesize tungsten nanoparticles has been developed that enables synthesis of nanometer-scale, monodisperse particles that can be stabilized only by tetrahydrofuran. The method can be used at room temperature, is scalable, and the product concentrated by standard means. Since no additives or stabilizing surfactants are required, this method is particularly well suited for producing tungsten nanoparticles for dispersion in polymers. If complete dispersion is achieved due to the size of the nanoparticles, then the optical properties of the polymer can be largely maintained.

  4. Tungsten silicide formation from sequentially sputtered tungsten and silicon films

    NASA Astrophysics Data System (ADS)

    Molarius, J. M.; Franssila, S.; Drozdy, G.; Saarilahti, J.

    1991-11-01

    As-deposited tungsten silicide films have typically high resistivity and require annealing to lower the resistivity to practical values. Rapid thermal annealing (RTA) has emerged as the main method because impurity diffusion in silicides is extremely fast. In this study we have explored the possibility of reducing the required thermal budget for tungsten silicide annealing by sputtering multilayer W /Si films. In addition to direct technological relevance, multilayer structures offer new insights into silicide formation. We propose a hypothesis "oxygen supply to interface ratio" for explaining why multilayer W /Si structures are beneficial for silicide formation. We have prevented the possible oxygen barrier formation at the W /Si interface by diminishing the oxygen supply by several means: substrate heating during deposition, multiple thin layers, a silicon capping layer and argon purging during RTA. Tetragonal WSi 2 is formed at 700°C and no silicon-rich phases are observed. Low-resistivity WSi 2 is produced by RTA at 1000°C, 120 s. Sheet resistance values around 3 ω/□ amends the use of tungsten silicide in practical polycide structures. The ultimate resistivity of our WSi 2, 30 μω · cm, is among the lowest reported for tungsten silicide, and it is achieved in a very straightforward fashion, using typical production equipment.

  5. Fabrication of tungsten wire needles

    SciTech Connect

    Roder, A.

    1983-02-01

    Fine point needles for field emissoin are conventionally produced by electrolytically or chemically etching tungsten wire. Points formed in this manner have a typical tip radius of about 0.5 microns and a cone angle of some 30 degrees. The construction of needle matrix detector chambers has created a need for tungsten needles whose specifications are: 20 mil tungsten wire, 1.5 inch total length, 3 mm-long taper (resulting in a cone angle of about 5 degrees), and 25 micron-radius point (similar to that found on sewing needles). In the process described here for producing such needles, tungsten wire, immersed in a NaOH solution and in the presence of an electrode, is connected first to an ac voltage and then to a dc supply, to form a taper and a point on the end of the wire immersed in the solution. The process parameters described here are for needles that will meet the above specifications. Possible variations will be discussed under each approprite heading.

  6. Mineral of the month: tungsten

    USGS Publications Warehouse

    Shedd, Kim B.

    2006-01-01

    Tungsten has the highest melting point of all metals, one of the highest densities and, when combined with carbon, is almost as hard as diamond. These and other properties make it useful in a wide variety of important commercial, industrial and military applications.

  7. Vacuum Gas Tungsten Arc Welding

    NASA Technical Reports Server (NTRS)

    Weeks, J. L.; Todd, D. T.; Wooten, J. R.

    1997-01-01

    A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

  8. Scaling rules for critical current density in anisotropic biaxial superconductors

    NASA Astrophysics Data System (ADS)

    Li, Yingxu; Kang, Guozheng; Gao, Yuanwen

    2016-06-01

    Recent researches highlight the additional anisotropic crystallographic axis within the superconducting plane of high temperature superconductors (HTS), demonstrating the superconducting anisotropy of HTS is better understood in the biaxial frame than the previous uniaxial coordinates within the superconducting layer. To quantitatively evaluate the anisotropy of flux pinning and critical current density in HTS, we extend the scaling rule for single-vortex collective pinning in uniaxial superconductors to account for flux-bundle collective pinning in biaxial superconductors. The scaling results show that in a system of random uncorrected point defects, the field dependence of the critical current density is described by a unified function with the scaled magnetic field of the isotropic superconductor. The obtained angular dependence of the critical current density depicts the main features of experimental observations, considering possible corrections due to the strong-pinning interaction.

  9. Design of a biaxial mechanical loading bioreactor for tissue engineering.

    PubMed

    Bilgen, Bahar; Chu, Danielle; Stefani, Robert; Aaron, Roy K

    2013-01-01

    We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0

  10. Design of a biaxial mechanical loading bioreactor for tissue engineering.

    PubMed

    Bilgen, Bahar; Chu, Danielle; Stefani, Robert; Aaron, Roy K

    2013-04-25

    We designed a loading device that is capable of applying uniaxial or biaxial mechanical strain to a tissue engineered biocomposites fabricated for transplantation. While the device primarily functions as a bioreactor that mimics the native mechanical strains, it is also outfitted with a load cell for providing force feedback or mechanical testing of the constructs. The device subjects engineered cartilage constructs to biaxial mechanical loading with great precision of loading dose (amplitude and frequency) and is compact enough to fit inside a standard tissue culture incubator. It loads samples directly in a tissue culture plate, and multiple plate sizes are compatible with the system. The device has been designed using components manufactured for precision-guided laser applications. Bi-axial loading is accomplished by two orthogonal stages. The stages have a 50 mm travel range and are driven independently by stepper motor actuators, controlled by a closed-loop stepper motor driver that features micro-stepping capabilities, enabling step sizes of less than 50 nm. A polysulfone loading platen is coupled to the bi-axial moving platform. Movements of the stages are controlled by Thor-labs Advanced Positioning Technology (APT) software. The stepper motor driver is used with the software to adjust load parameters of frequency and amplitude of both shear and compression independently and simultaneously. Positional feedback is provided by linear optical encoders that have a bidirectional repeatability of 0.1 μm and a resolution of 20 nm, translating to a positional accuracy of less than 3 μm over the full 50 mm of travel. These encoders provide the necessary position feedback to the drive electronics to ensure true nanopositioning capabilities. In order to provide the force feedback to detect contact and evaluate loading responses, a precision miniature load cell is positioned between the loading platen and the moving platform. The load cell has high accuracies of 0

  11. The yield behavior of polyethylene tubes subjected to biaxial loadings

    NASA Technical Reports Server (NTRS)

    Semeliss, M.; Wong, R.; Tuttle, M.

    1990-01-01

    High-density polyethylene is subjected to biaxial states of stress to examine the yield behavior of the semicrystalline thermoplastic under constant octahedral shear-stress rates. Combinations of internal pressures and axial loads are applied to thin-walled tubes of polyethylene, and the strain response in the axial and hoop directions are measured. The polyethylene specimens are found to be anisotropic, and the experimental measurements are compared to yield criteria that are applicable to isotropic and anisotropic materials.

  12. Anomalously temperature-independent birefringence in biaxial optical crystals

    SciTech Connect

    Grechin, Sergei G; Dmitriev, Valentin G; Dyakov, Vladimir A; Pryalkin, Vladimir I

    2000-01-31

    Temperature-independent birefringence in a biaxial crystal was predicted theoretically and observed experimentally for the first time. The width of the plot against temperature (the range corresponding to the temperature independence of the birefringence) at a fundamental radiation wavelength of 632.8 nm in a KTP crystal 5.9 mm long was more than 160{sup 0}C. (letters to the editor)

  13. Process development for cladding APT tungsten targets

    SciTech Connect

    Horner, M H; Barber, R; Dalder, E

    2000-11-27

    This report describes development of processes for cladding APT Target tungsten components with a thin layer (0.127-mm) of Alloy 718, Alloy 600 or 316L stainless steel alloy. The application requires that the cladding be thermally bonded to the tungsten in order to transfer heat generated in the tungsten volume to a surrounding coolant. High temperature diffusion bonding using the hot isostatic processing (HIP) technique was selected as the method for creating a metallurgical bond between pure tungsten tubes and rods and the cladding materials. Bonding studies using a uniaxially loaded vacuum hot press were conducted in preliminary experiments to determine acceptable time-temperature conditions for diffusion bonding. The results were successfully applied in cladding tungsten rods and tubes with these alloys. Temperatures 800-810 C were suitable for cladding tungsten with Alloy 600 and 316L stainless steel alloy, whereas tungsten was clad with Alloy 718 at 1020 C.

  14. Process Of Bonding Copper And Tungsten

    DOEpatents

    Slattery, Kevin T.; Driemeyer, Daniel E.

    1999-11-23

    Process for bonding a copper substrate to a tungsten substrate by providing a thin metallic adhesion promoting film bonded to a tungsten substrate and a functionally graded material (FGM) interlayer bonding the thin metallic adhesion promoting film to the copper substrate. The FGM interlayer is formed by thermal plasma spraying mixtures of copper powder and tungsten powder in a varied blending ratio such that the blending ratio of the copper powder and the tungsten powder that is fed to a plasma torch is intermittently adjusted to provide progressively higher copper content/tungsten content, by volume, ratio values in the interlayer in a lineal direction extending from the tungsten substrate towards the copper substrate. The resulting copper to tungsten joint well accommodates the difference in the coefficient of thermal expansion of the materials.

  15. Twist-bend nematic phases of bent-shaped biaxial molecules.

    PubMed

    Tomczyk, Wojciech; Pająk, Grzegorz; Longa, Lech

    2016-09-28

    How can a change in molecular structure affect the relative stability and structural properties of the twist-bend nematic phase (NTB)? Here we extend the mean-field model(1) (C. Greco, G. R. Luckhurst and A. Ferrarini, Soft Matter, 2014, 10, 9318) for bent-shaped achiral molecules, to study the influence of arm molecular biaxiality and the value of the molecule's bend angle on the relative stability of NTB. In particular we show that by controlling the biaxiality of the molecule's arms, up to four ordered phases can become stable. They involve local uniaxial and biaxial variants of NTB, together with uniaxial and biaxial nematic phases. However, a V-shaped molecule shows a stronger ability to form stable NTB than a biaxial nematic phase, where the latter phase appears in the phase diagram only for bend angles greater than 140° and for large biaxiality of the two arms. PMID:27604824

  16. Design of Bioprosthetic Aortic Valves using biaxial test data.

    PubMed

    Dabiri, Y; Paulson, K; Tyberg, J; Ronsky, J; Ali, I; Di Martino, E; Narine, K

    2015-01-01

    Bioprosthetic Aortic Valves (BAVs) do not have the serious limitations of mechanical aortic valves in terms of thrombosis. However, the lifetime of BAVs is too short, often requiring repeated surgeries. The lifetime of BAVs might be improved by using computer simulations of the structural behavior of the leaflets. The goal of this study was to develop a numerical model applicable to the optimization of durability of BAVs. The constitutive equations were derived using biaxial tensile tests. Using a Fung model, stress and strain data were computed from biaxial test data. SolidWorks was used to develop the geometry of the leaflets, and ABAQUS finite element software package was used for finite element calculations. Results showed the model is consistent with experimental observations. Reaction forces computed by the model corresponded with experimental measurements when the biaxial test was simulated. As well, the location of maximum stresses corresponded to the locations of frequent tearing of BAV leaflets. Results suggest that BAV design can be optimized with respect to durability. PMID:26737002

  17. Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique

    PubMed Central

    2015-01-01

    Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU) or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13):135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode). The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d.) resonance frequency of the samples was 465.1 (± 1.5) kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power) of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field. PMID:26418550

  18. Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique.

    PubMed

    Pichardo, Samuel; Silva, Rafael R C; Rubel, Oleg; Curiel, Laura

    2015-01-01

    Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU) or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13):135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode). The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d.) resonance frequency of the samples was 465.1 (± 1.5) kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power) of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field.

  19. Design of Bioprosthetic Aortic Valves using biaxial test data.

    PubMed

    Dabiri, Y; Paulson, K; Tyberg, J; Ronsky, J; Ali, I; Di Martino, E; Narine, K

    2015-01-01

    Bioprosthetic Aortic Valves (BAVs) do not have the serious limitations of mechanical aortic valves in terms of thrombosis. However, the lifetime of BAVs is too short, often requiring repeated surgeries. The lifetime of BAVs might be improved by using computer simulations of the structural behavior of the leaflets. The goal of this study was to develop a numerical model applicable to the optimization of durability of BAVs. The constitutive equations were derived using biaxial tensile tests. Using a Fung model, stress and strain data were computed from biaxial test data. SolidWorks was used to develop the geometry of the leaflets, and ABAQUS finite element software package was used for finite element calculations. Results showed the model is consistent with experimental observations. Reaction forces computed by the model corresponded with experimental measurements when the biaxial test was simulated. As well, the location of maximum stresses corresponded to the locations of frequent tearing of BAV leaflets. Results suggest that BAV design can be optimized with respect to durability.

  20. Measured Biaxial Residual Stress Maps in a Stainless Steel Weld

    DOE PAGES

    Olson, Mitchell D.; Hill, Michael R.; Patel, Vipul I.; Muransky, Ondrej; Sisneros, Thomas A.

    2015-09-16

    Here, this paper describes a sequence of residual stress measurements made to determine a two-dimensional map of biaxial residual stress in a stainless steel weld. A long stainless steel (316L) plate with an eight-pass groove weld (308L filler) was used. The biaxial stress measurements follow a recently developed approach, comprising a combination of contour method and slitting measurements, with a computation to determine the effects of out-of-plane stress on a thin slice. The measured longitudinal stress is highly tensile in the weld- and heat-affected zone, with a maximum around 450 MPa, and compressive stress toward the transverse edges around ₋250more » MPa. The total transverse stress has a banded profile in the weld with highly tensile stress at the bottom of the plate (y = 0) of 400 MPa, rapidly changing to compressive stress (at y = 5 mm) of ₋200 MPa, then tensile stress at the weld root (y = 17 mm) and in the weld around 200 MPa, followed by compressive stress at the top of the weld at around ₋150 MPa. Finally, the results of the biaxial map compare well with the results of neutron diffraction measurements and output from a computational weld simulation.« less

  1. Measured Biaxial Residual Stress Maps in a Stainless Steel Weld

    SciTech Connect

    Olson, Mitchell D.; Hill, Michael R.; Patel, Vipul I.; Muransky, Ondrej; Sisneros, Thomas A.

    2015-09-16

    Here, this paper describes a sequence of residual stress measurements made to determine a two-dimensional map of biaxial residual stress in a stainless steel weld. A long stainless steel (316L) plate with an eight-pass groove weld (308L filler) was used. The biaxial stress measurements follow a recently developed approach, comprising a combination of contour method and slitting measurements, with a computation to determine the effects of out-of-plane stress on a thin slice. The measured longitudinal stress is highly tensile in the weld- and heat-affected zone, with a maximum around 450 MPa, and compressive stress toward the transverse edges around ₋250 MPa. The total transverse stress has a banded profile in the weld with highly tensile stress at the bottom of the plate (y = 0) of 400 MPa, rapidly changing to compressive stress (at y = 5 mm) of ₋200 MPa, then tensile stress at the weld root (y = 17 mm) and in the weld around 200 MPa, followed by compressive stress at the top of the weld at around ₋150 MPa. Finally, the results of the biaxial map compare well with the results of neutron diffraction measurements and output from a computational weld simulation.

  2. Fatigue flaw growth behavior in stiffened and unstiffened panels loaded in biaxial tension

    NASA Technical Reports Server (NTRS)

    Beck, E. J.

    1973-01-01

    The effect was investigated of biaxial loading on the flaw growth rate of 2219-T87 aluminum alloy that would be typical of Space Shuttle cryogenic tankage design. The stress distribution and stress concentration factors for several integrally stiffened panels under various loading conditions were obtained. The flaw growth behavior of both stiffened and unstiffened panels under biaxial loading conditions was determined. The effect of a complex stress state was studied by introducing flaws in fillet areas of biaxially loaded stiffened panels.

  3. Global alignment: Finding rearrangements during alignment

    SciTech Connect

    Brudno, Michael; Malde, Sanket; Poliakov, Alexander; Do, Chuong B.; Couronne, Olivier; Dubchak, Inna; Batzoglou, Serafim

    2003-01-06

    Motivation: To compare entire genomes from different species, biologists increasingly need alignment methods that are efficient enough to handle long sequences, and accurate enough to correctly align the conserved biological features between distant species. The two main classes of pairwise alignments are global alignment, where one string is transformed into the other, and local alignment, where all locations of similarity between the two strings are returned. Global alignments are less prone to demonstrating false homology as each letter of one sequence is constrained to being aligned to only one letter of the other. Local alignments, on the other hand, can cope with rearrangements between non-syntenic, orthologous sequences by identifying similar regions in sequences; this, however, comes at the expense of a higher false positive rate due to the inability of local aligners to take into account overall conservation maps.

  4. Mechanism of crystal alignment of CaO-stabilized ZrO2 through a mismatched interface of {110} <001> textured iron tape

    NASA Astrophysics Data System (ADS)

    Ichinose, Ataru; Watanabe, Ken; Naka, Junpei; Uchima, Takayuki; Horii, Shigeru; Doi, Toshiya

    2015-08-01

    To reduce the material cost in REBa2Cu3Oy-coated (RE: rare-earth elements) conductors, we attempted to exchange the high-cost metal substrate with iron. The biaxially textured iron was generally {110} <001>. Although this texture was unsuitable for buffer layer growth with a cubic structure because Fe(110) is a rectangle, (001)-oriented and biaxially aligned calcia-stabilized zirconia (CSZ) was the first to be successfully fabricated on iron tape. We found that the anisotropic deformation of CSZ is due to the rectangular shape of Fe(110). Furthermore, this deformation, as well as the easy formation of a CSZ(111) facet, was important in the formation of biaxially aligned CSZ.

  5. The role of biaxial stresses in discriminating between meaningful and illusory composite failure theories

    NASA Technical Reports Server (NTRS)

    Hart-Smith, L. J.

    1992-01-01

    The irrelevance of most composite failure criteria to conventional fiber-polymer composites is claimed to have remained undetected primarily because the experiments that can either validate or disprove them are difficult to perform. Uniaxial tests are considered inherently incapable of validating or refuting any composite failure theory because so much of the total load is carried by the fibers aligned in the direction of the load. The Ten-Percent Rule, a simple rule-of-mixtures analysis method, is said to work well only because of this phenomenon. It is stated that failure criteria can be verified for fibrous composites only by biaxial tests, with orthogonal in-plane stresses of the same as well as different signs, because these particular states of combined stress reveal substantial differences between the predictions of laminate strength made by various theories. Three scientifically plausible failure models for fibrous composites are compared, and it is shown that only the in-plane shear test (orthogonal tension and compression) is capable of distinguishing between them. This is because most theories are 'calibrated' against the measured uniaxial tension and compression tests and any cross-plied laminate tests dominated by those same states of stress must inevitably 'confirm' the theory.

  6. Tin-tungsten mineralizing processes in tungsten vein deposits: Panasqueira, Portugal

    NASA Astrophysics Data System (ADS)

    Lecumberri-Sanchez, P.; Pinto, F.; Vieira, R.; Wälle, M.; Heinrich, C. A.

    2015-12-01

    Tungsten has a high heat resistance, density and hardness, which makes it widely applied in industry (e.g. steel, tungsten carbides). Tungsten deposits are typically magmatic-hydrothermal systems. Despite the economic significance of tungsten, there are no modern quantitative analytical studies of the fluids responsible for the formation of its highest-grade deposit type (tungsten vein deposits). Panasqueira (Portugal) is a tungsten vein deposit, one of the leading tungsten producers in Europe and one of the best geologically characterized tungsten vein deposits. In this study, compositions of the mineralizing fluids at Panasqueira have been determined through combination of detailed petrography, microthermometric measurements and LA-ICPMS analyses, and geochemical modeling has been used to determine the processes that lead to tungsten mineralization. We characterized the fluids related to the various mineralizing stages in the system: the oxide stage (tin and tungsten mineralization), the sulfide stage (chalcopyrite and sphalerite mineralization) and the carbonate stage. Thus, our results provide information on the properties of fluids related with specific paragenetic stages. Furthermore we used those fluid compositions in combination with host rock mineralogy and chemistry to evaluate which are the controlling factors in the mineralizing process. This study provides the first quantitative analytical data on fluid composition for tungsten vein deposits and evaluates the controlling mineralization processes helping to determine the mechanisms of formation of the Panasqueira tin-tungsten deposit and providing additional geochemical constraints on the local distribution of mineralization.

  7. Field-Induced Rheology in Uniaxial and Biaxial Fields

    SciTech Connect

    MARTIN, JAMES E.

    1999-10-22

    Steady and oscillatory shear 3-D simulations of electro- and magnetorheology in uniaxial and biaxial fields are presented, and compared to the predictions of the chain model. These large scale simulations are three dimensional, and include the effect of Brownian motion. In the absence of thermal fluctuations, the expected shear thinning viscosity is observed in steady shear, and a striped phase is seen to rapidly form in a uniaxial field, with a shear slip zone in each sheet. However, as the influence of Brownian motion increases, the fluid stress decreases, especially at lower Mason numbers, and the striped phase eventually disappears, even when the fluid stress is still high. In a biaxial field, an opposite trend is seen, where Brownian motion decreases the stress most significantly at higher Mason numbers. to account for the uniaxial steady shear data they propose a microscopic chain model of the role played by thermal fluctuations on the rheology of ER and MR fluids that delineates the regimes where an applied field can impact the fluid viscosity, and gives an analytical prediction for the thermal effect. In oscillatory shear, a striped phase again appears in uniaxial field, at strain amplitudes greater than {approx} 0.15, and the presence of a shear slip zone creates strong stress nonlinearities at low strain amplitudes. In a biaxial field, a shear slip zone is not created, and so the stress nonlinearities develop only at expected strain amplitudes. The nonlinear dynamics of these systems is shown to be in good agreement with the Kinetic Chain Model.

  8. Biaxial shear/tension failure criteria of spectra single fibers

    NASA Astrophysics Data System (ADS)

    Sun, Jianzhuo

    An experimental study was conducted to develop the biaxial failure surface criteria of single Spectra 130d and 100d filaments in a torsion-tension environment. The cross-sectional profiles of single Spectra fibers were investigated using scanning electron microscopy and X-ray computed tomography. A pin-gripping method to fix the ends of a polyethylene single fiber was developed. Effects of pin diameter on failure stress for both Spectra 130d and 100d were characterized. It was found that the perturbed stress field effect can be neglected when the pin diameter is larger than 0.8 mm. Additionally, the effect of the sample's gage length on fiber tensile strength was investigated. The gage length of 5.5 mm was determined as an appropriate length for single fiber samples under stress-wave loading. A twisting apparatus was built for a single fiber to achieve specific degrees of shear strains. Quasi-static experiments were conducted using an MTS servo-hydraulic system to apply tensile loads on pre-twisted Spectra fibers. A tension Kolsky bar was employed to study the biaxial shear/tensile behavior of Spectra fibers at high strain rates. A decreasing trend of tensile strength, with increasing torsional strain, for Spectra fibers was observed. Furthermore, a torsional pendulum apparatus was developed to determine the torsional shear stresses in fibers at various levels of axial loading. The relationship between apparent shear stress and axial stress was discovered. Finally, a biaxial shear/tension failure criterion envelope of each of the Spectra fibers was established. Scanning electron microscopy images revealed the specific feature on the surface of twisted fibers and fracture surface of failure fibers.

  9. Lightweight, Low-CTE Tubes Made From Biaxially Oriented LCPs

    NASA Technical Reports Server (NTRS)

    Rubin, Leslie; Federico, Frank; Formato, Richard; Larouco, John; Slager, William

    2004-01-01

    Tubes made from biaxially oriented liquid-crystal polymers (LCPs) have been developed for use as penetrations on cryogenic tanks. ( Penetrations in this context denotes feed lines, vent lines, and sensor tubes, all of which contribute to the undesired conduction of heat into the tanks.) In comparison with corresponding prior cryogenic-tank penetrations made from stainless steels and nickel alloys, the LCP penetrations offer advantages of less weight and less thermal conduction. An additional major advantage of LCP components is that one can tailor their coefficients of thermal expansion (CTEs). The estimated cost of continuous production of LCP tubes of typical sizes is about $1.27/ft ($4.17/m) [based on 1998 prices]. LCP tubes that are compatible with liquid oxygen and that feature tailored biaxial molecular orientation and quasi-isotropic properties (including quasi-isotropic CTE) have been fabricated by a combination of proprietary and patented techniques that involve the use of counterrotating dies (CRDs). Tailoring of the angle of molecular orientation is what makes it possible to tailor the CTE over a wide range to match the CTEs of adjacent penetrations of other tank components; this, in turn, makes it possible to minimize differential-thermal expansion stresses that arise during thermal cycling. The fabrication of biaxially oriented LCP tubes by use of CRDs is not new in itself. The novelty of the present development lies in tailoring the orientations and thus the CTEs and other mechanical properties of the LCPs for the intended cryogenic applications and in modifications of the CRDs for this purpose. The LCP tubes and the 304-stainless-steel tubes that the LCP tubes were intended to supplant were tested with respect to burst strength, permeability, thermal conductivity, and CTE.

  10. Sol-gel deposition of buffer layers on biaxially textured metal substances

    DOEpatents

    Shoup, Shara S.; Paranthamam, Mariappan; Beach, David B.; Kroeger, Donald M.; Goyal, Amit

    2000-01-01

    A method is disclosed for forming a biaxially textured buffer layer on a biaxially oriented metal substrate by using a sol-gel coating technique followed by pyrolyzing/annealing in a reducing atmosphere. This method is advantageous for providing substrates for depositing electronically active materials thereon.

  11. Lattice model for biaxial and uniaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Sauerwein, Ricardo A.; de Oliveira, Mário J.

    2016-05-01

    We use a lattice gas model to describe the phase transitions in nematic liquid crystals. The phase diagram displays, in addition to the isotropic phase, the two uniaxial nematics, the rod-like and discotic nematics, and the biaxial nematic. Each site of the lattice has a constituent unit that takes only six orientations and is understood as being a parallelepiped brick with the three axes distinct. The possible orientations of a brick are those in which its axes are parallel to the axes of a Cartesian reference frame. The analysis of the model is performed by the use of a mean-field approximation and a Landau expansion of the free energy.

  12. The influence of uniaxial prestrain on biaxial r-values in 7075-O aluminium alloy

    SciTech Connect

    Anderson, N.; Brown, D.; McMurray, R. J.; Leacock, A. G.

    2011-05-04

    Biaxial test methods have been used to determine, not only yield behaviour under biaxial conditions, but also the strain response. This paper examines the influence of uniaxial prestrain upon the biaxial r-value by extending the disc compression test procedure proposed by Barlat et al. The extension involved the use of digital image measurements of in-plane strains. The material examined was a 7075-O condition aluminium alloy. The results of the experimental programme indicated that the biaxial r-value is unaffected by uniaxial prestrain. When using the disc compression test, the mode of deformation and therefore the biaxial r-value were found to be very sensitive to the prevailing friction conditions.

  13. Implementation of a Biaxial Resonant Fatigue Test Method on a Large Wind Turbine Blade

    SciTech Connect

    Snowberg, D.; Dana, S.; Hughes, S.; Berling, P.

    2014-09-01

    A biaxial resonant test method was utilized to simultaneously fatigue test a wind turbine blade in the flap and edge (lead-lag) direction. Biaxial resonant blade fatigue testing is an accelerated life test method utilizing oscillating masses on the blade; each mass is independently oscillated at the respective flap and edge blade resonant frequency. The flap and edge resonant frequency were not controlled, nor were they constant for this demonstrated test method. This biaxial resonant test method presented surmountable challenges in test setup simulation, control and data processing. Biaxial resonant testing has the potential to complete test projects faster than single-axis testing. The load modulation during a biaxial resonant test may necessitate periodic load application above targets or higher applied test cycles.

  14. Micromagnetic model for the influence of biaxial stress on hysteretic magnetic properties

    NASA Astrophysics Data System (ADS)

    Sablik, M. J.; Riley, L. A.; Burkhardt, G. L.; Kwun, H.; Cannell, P. Y.; Watts, K. T.; Langman, R. A.

    1994-05-01

    A micromagnetic formulation has been developed for modeling the effect of biaxial stress on magnetoelastic processes in polycrystalline steels. In particular, the formulation employs the Schneider-Cannell-Watts model and involves substitution of an effective stress equal to one of the deviatoric (i.e., distortional) normal stress components, depending on whether the field is parallel to a tensile or compressive axis or to the third axis perpendicular to the plane of biaxial stress. Computer results are compared to experimental results on the effects of biaxial stress on magnetic properties in mild steel and in SAE-4130 steel. Good qualitative agreement is found in almost all cases, in that in going from one biaxial stress case to the next, the same kinds of changes are seen magnetically. It is also shown from the model and the data that a method can be formulated to nondestructively determine the difference in biaxial stresses.

  15. Micromagnetic model for the influence of biaxial stress on hysteretic magnetic properties

    SciTech Connect

    Sablik, M.J.; Riley, L.A.; Burkhardt, G.L.; Kwun, H. ); Cannell, P.Y.; Watts, K.T. ); Langman, R.A. )

    1994-05-15

    A micromagnetic formulation has been developed for modeling the effect of biaxial stress on magnetoelastic processes in polycrystalline steels. In particular, the formulation employs the Schneider--Cannell--Watts model and involves substitution of an effective stress equal to one of the deviatoric (i.e., distortional) normal stress components, depending on whether the field is parallel to a tensile or compressive axis or to the third axis perpendicular to the plane of biaxial stress. Computer results are compared to experimental results on the effects of biaxial stress on magnetic properties in mild steel and in SAE-4130 steel. Good qualitative agreement is found in almost all cases, in that in going from one biaxial stress case to the next, the same kinds of changes are seen magnetically. It is also shown from the model and the data that a method can be formulated to nondestructively determine the difference in biaxial stresses.

  16. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  17. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  18. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  19. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  20. 40 CFR 421.100 - Applicability: Description of the primary tungsten subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... primary tungsten subcategory. 421.100 Section 421.100 Protection of Environment ENVIRONMENTAL PROTECTION... CATEGORY Primary Tungsten Subcategory § 421.100 Applicability: Description of the primary tungsten... tungsten at primary tungsten facilities....

  1. T-1018 UCLA Spacordion Tungsten Powder Calorimeter

    SciTech Connect

    Trentalange, Stephen; Tsai, Oleg; Igo, George; Huang, Huan; Pan, Yu Xi; Dunkelberger, Jay; Xu, Wen Qin; Soha, Aria; Heppelmann, Steven; Gagliardi, Carl; /Texas A-M

    2011-11-16

    The present experiments at the BNL-RHIC facility are evolving towards physics goals which require the detection of medium energy electromagnetic particles (photons, electrons, neutral pions, eta mesons, etc.), especially at forward angles. New detectors will place increasing demands on energy resolution, hadron rejection and two-photon resolution and will require large area, high performance electromagnetic calorimeters in a variety of geometries. In the immediate future, either RHIC or JLAB will propose a facility upgrade (Electron-Ion Collider, or EIC) with physics goals such as electron-heavy ion collisions (or p-A collisions) with a wide range of calorimeter requirements. An R and D program based at Brookhaven National Laboratory has awarded the group funding of approximately $110,000 to develop new types of calorimeters for EIC experiments. The UCLA group is developing a method to manufacture very flexible and cost-effective, yet high quality calorimeters based on scintillating fibers and tungsten powder. The design and features of the calorimeter can be briefly stated as follows: an arbitrarily large number of small diameter fibers (< 0.5 mm) are assembled as a matrix and held rigidly in place by a set of precision screens inside an empty container. The container is then back-filled with tungsten powder, compacted on a vibrating table and infused with epoxy under vacuum. The container is then removed. The resulting sub-modules are extremely uniform and achieve roughly the density of pure Lead. The sub-modules are stacked together to achieve a final detector of the desired shape. There is no dead space between sub-modules and the fibers can be in an accordion geometry bent to prevent 'channeling' of the particles due to accidental alignment of their track with the module axis. This technology has the advantage of being modular and inexpensive to the point where the construction work may be divided among groups the size of typical university physics departments

  2. Competition between capillarity, layering and biaxiality in a confined liquid crystal.

    PubMed

    Varga, S; Martinez-Ratón, Y; Velasco, E

    2010-05-01

    The effect of confinement on the phase behaviour and structure of fluids made of biaxial hard particles (cuboids) is examined theoretically by means of Onsager second-order virial theory in the limit where the long particle axes are frozen in a mutually parallel configuration. Confinement is induced by two parallel planar hard walls (slit-pore geometry), with particle long axes perpendicular to the walls (perfect homeotropic anchoring). In bulk, a continuous nematic-to-smectic transition takes place, while shape anisotropy in the (rectangular) particle cross-section induces biaxial ordering. As a consequence, four bulk phases, uniaxial and biaxial nematic and smectic phases, can be stabilised as the cross-sectional aspect ratio is varied. On confining the fluid, the nematic-to-smectic transition is suppressed, and either uniaxial or biaxial phases, separated by a continuous transition, can be present. Smectic ordering develops continuously from the walls for increasing particle concentration (in agreement with the supression of nematic-smectic second-order transition at confinement), but first-order layering transitions, involving structures with n and n + 1 layers, arise in the confined fluid at high concentration. Competition between layering and uniaxial-biaxial ordering leads to three different types of layering transitions, at which the two coexisting structures can be both uniaxial, one uniaxial and another biaxial, or both biaxial. Also, the interplay between molecular biaxiality and wall interactions is very subtle: while the hard wall disfavours the formation of the biaxial phase, biaxiality is against the layering transitions, as we have shown by comparing the confined phase behaviour of cylinders and cuboids. The predictive power of Onsager theory is checked and confirmed by performing some calculations based on fundamental-measure theory. PMID:20521078

  3. The dynamics of interacting folds under biaxial compressive stresses.

    PubMed

    Shin, Hyunjae; Dixit, Atray C; Stone, Howard A; Abkarian, Manouk; Kim, Pilnam

    2016-04-21

    The gradual in-plane compression of a solid film bonded to a soft substrate can lead to surface wrinkling and even to the formation of a network of folds for sufficiently high strain. An understanding of how these folds initiate, propagate, and interact with each other is still lacking. In a previous study, we developed an experimental system to observe the wrinkle-to-fold transition of layered elastic materials under biaxial compressive stresses. Here we focus on the dynamic interaction of a pair of propagating folds under biaxial compression. We find experimentally that their behavior is mediated through their tips and depends on the separation of the tips and their angle of interception. When the angle is lower than 45°, the two folds either form a unique fold by the coalescence of their tips when close enough, or bend their trajectories to intersect each other and form a lenticular region in analogy with cracks. When the angle is higher then 45°, the folds simply intersect and form a T-like junction. We rationalize this behavior by conducting numerical simulations to visualize the stress field around the two tips and find that the initial geometric position of the tips primarily determines the final state of the folds. PMID:27021924

  4. Method of depositing buffer layers on biaxially textured metal substrates

    DOEpatents

    Beach, David B.; Morrell, Jonathan S.; Paranthaman, Mariappan; Chirayil, Thomas; Specht, Eliot D.; Goyal, Amit

    2002-08-27

    A laminate article comprises a substrate and a biaxially textured (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer over the substrate, wherein 0biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

  5. Dynamic biaxial tissue properties of the human cadaver aorta.

    PubMed

    Shah, Chirag S; Hardy, Warren N; Mason, Matthew J; Yang, King H; Van Ee, Chris A; Morgan, Richard; Digges, Kennerly

    2006-11-01

    This study focuses on the biaxial mechanical properties of planar aorta tissue at strain rates likely to be experienced during automotive crashes. It also examines the structural response of the whole aorta to longitudinal tension. Twenty-six tissue-level tests were conducted using twelve thoracic aortas harvested from human cadavers. Cruciate samples were excised from the ascending, peri-isthmic, and descending regions. The samples were subjected to equibiaxial stretch at two nominal speed levels using a new biaxial tissue-testing device. Inertia-compensated loads were measured to facilitate calculation of true stress. High-speed videography and regional correlation analysis were used to track ink dots marked on the center of each sample to obtain strain. In a series of component-level tests, the response of the intact thoracic aorta to longitudinal stretch was obtained using seven aorta specimens. The aorta fails within the peri-isthmic region. The aorta fails in the transverse direction, and the intima fails before the media or adventitia. The aorta tissue exhibits nonlinear behavior. The aorta as complete structure can transect completely from 92 N axial load and 0.221 axial strain. Complete transection can be accompanied by intimal tears. These results have application to finite element modeling and the better understanding of traumatic rupture of the aorta. PMID:17311166

  6. Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning

    NASA Astrophysics Data System (ADS)

    Hofmann, U.; Aikio, M.; Janes, J.; Senger, F.; Stenchly, V.; Weiss, M.; Quenzer, H.-J.; Wagner, B.; Benecke, W.

    2013-03-01

    Low-cost automotive laser scanners for environment perception are needed to enable the integration of advanced driver assistant systems (ADAS) into all automotive vehicle segments, a key to reducing the number of traffic accidents on roads. An omnidirectional 360 degree laser scanning concept has been developed based on combination of an omnidirectional lens and a biaxial large aperture MEMS mirror. This omnidirectional scanning concept is the core of a small sized low-cost time-of-flight based range sensor development. This paper describes concept, design, fabrication and first measurement results of a resonant biaxial 7mm gimbal-less MEMS mirror that is electrostatically actuated by stacked vertical comb drives. Identical frequencies of the two resonant axes are necessary to enable the required circle scanning capability. A tripod suspension was chosen since it allows minimizing the frequency splitting of the two resonant axes. Low mirror curvature is achieved by a thickness of the mirror of more than 500 μm. Hermetic wafer level vacuum packaging of such large mirrors based on multiple wafer bonding has been developed to enable to achieve a large mechanical tilt angle of +/- 6.5 degrees in each axis. The 7mm-MEMS mirror demonstrates large angle circular scanning at 1.5kHz.

  7. Seed growth of tungsten diselenide nanotubes from tungsten oxides.

    PubMed

    Kim, Hyun; Yun, Seok Joon; Park, Jin Cheol; Park, Min Ho; Park, Ji-Hoon; Kim, Ki Kang; Lee, Young Hee

    2015-05-13

    We report growth of tungsten diselenide (WSe2) nanotubes by chemical vapor deposition with a two-zone furnace. WO3 nanowires were first grown by annealing tungsten thin films under argon ambient. WSe2 nanotubes were then grown at the tips of WO3 nanowires through selenization via two steps: (i) formation of tubular WSe2 structures on the outside of WO3 nanowires, resulting in core (WO3)-shell (WSe2) and (ii) growth of WSe2 nanotubes at the tips of WO3 nanowires. The observed seed growth is markedly different from existing substitutional growth of WSe2 nanotubes, where oxygen atoms are replaced by selenium atoms in WO3 nanowires to form WSe2 nanotubes. Another advantage of our growth is that WSe2 film was grown by simply supplying hydrogen gas, where the native oxides were reduced to thin film instead of forming oxide nanowires. Our findings will contribute to engineer other transition metal dichacogenide growth such as MoS2, WS2, and MoSe2. PMID:25581340

  8. Novel properties of Tungsten ditelluride

    NASA Astrophysics Data System (ADS)

    Liu, Huimei; National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Cent Collaboration

    Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 Tesla. By using density functional theory calculations, we qualitatively reproduced the observed spin texture. Since the spin texture would forbid back scatterings that are directly involved in the resistivity, we suggest that the SOC and the related spin and orbital angular momentum textures may play an important role in the anomalously large magnetoresistance of WTe2. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we also boost the electronic properties by applying a high pressure, and introduce superconductivity successfully.

  9. Mirrorlike pulsed laser deposited tungsten thin film

    SciTech Connect

    Mostako, A. T. T.; Khare, Alika; Rao, C. V. S.

    2011-01-15

    Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10{sup -5} Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness {approx}782 nm.

  10. Mirrorlike pulsed laser deposited tungsten thin film.

    PubMed

    Mostako, A T T; Rao, C V S; Khare, Alika

    2011-01-01

    Mirrorlike tungsten thin films on stainless steel substrate deposited via pulsed laser deposition technique in vacuum (10(-5) Torr) is reported, which may find direct application as first mirror in fusion devices. The crystal structure of tungsten film is analyzed using x-ray diffraction pattern, surface morphology of the tungsten films is studied with scanning electron microscope and atomic force microscope. The film composition is identified using energy dispersive x-ray. The specular and diffuse reflectivities with respect to stainless steel substrate of the tungsten films are recorded with FTIR spectra. The thickness and the optical quality of pulsed laser deposition deposited films are tested via interferometric technique. The reflectivity is approaching about that of the bulk for the tungsten film of thickness ∼782 nm. PMID:21280810

  11. Strengthening mechanisms of tungsten powder reinforced uranium

    SciTech Connect

    Lewis, M.A.K.; Hill, M.A.; Rollett, A.D.; Dunn, P.S.; Mortensen, A.; Massachusetts Inst. of Tech., Cambridge, MA )

    1989-01-01

    Tungsten powder reinforced uranium exhibits a three-fold increase in yield strength due to precipitation hardening. The tungsten-rich interphase precipitates form at moving phase boundaries during slow cooling. Further increases in yield strength, attained with increasing tungsten content, are due to composite strengthening; this is verified by increasing elastic modulus with increasing tungsten content. Age hardening behavior is observed, with strengthening occurring at aging temperatures low in the alpha phase. Aging higher in alpha gives initial strengthening followed by rapid overaging. Beta phase aging results in a very soft structure with precipitates visible optically. Wrought material exhibits significant strain hardening as well as composite strengthening due to elongation of the tungsten particles. 7 refs., 15 figs., 4 tabs.

  12. Strengthening mechanisms of tungsten powder reinforced uranium

    SciTech Connect

    Krawizcki, M.A.

    1990-04-01

    Tungsten powder reinforced uranium composites exhibit a three-fold increase in yield strength due to precipitation hardening. The tungsten-rich interphase precipitates form at the moving beta to alpha phase boundary during slow cooling. Further increases in yield strength, attained with increasing tungsten content, are due to composite strengthening. The composite strengthening is verified by increasing elastic modulus with increasing tungsten content. Age hardening behavior is observed, with strengthening occurring at aging temperatures low, in the alpha phase. Temperatures higher in alpha give initial strengthening followed by rapid overaging. Beta phase aging temperatures result in a very soft structure with interphase precipitates observable optically. Wrought material exhibits significant strain hardening as well as composite strengthening due to elongation of the tungsten particles. 36 refs., 36 figs., 10 tabs.

  13. Powder-in-tube and thick-film methods of fabricating high temperature superconductors having enhanced biaxial texture

    DOEpatents

    Goyal, Amit; Kroeger, Donald M.

    2003-11-11

    A method for forming an electronically active biaxially textured article includes the steps of providing a substrate having a single crystal metal or metal alloy surface, deforming the substrate to form an elongated substrate surface having biaxial texture and depositing an epitaxial electronically active layer on the biaxially textured surface. The method can include at least one annealing step after the deforming step to produce the biaxially textured substrate surface. The invention can be used to form improved biaxially textured articles, such as superconducting wire and tape articles having improved J.sub.c values.

  14. Development of tungsten fibre-reinforced tungsten composites towards their use in DEMO—potassium doped tungsten wire

    NASA Astrophysics Data System (ADS)

    Riesch, J.; Han, Y.; Almanstötter, J.; Coenen, J. W.; Höschen, T.; Jasper, B.; Zhao, P.; Linsmeier, Ch; Neu, R.

    2016-02-01

    For the next step fusion reactor the use of tungsten is inevitable to suppress erosion and allow operation at elevated temperature and high heat loads. Tungsten fibre-reinforced composites overcome the intrinsic brittleness of tungsten and its susceptibility to operation embrittlement and thus allow its use as a structural as well as an armour material. That this concept works in principle has been shown in recent years. In this contribution we present a development approach towards its use in a future fusion reactor. A multilayer approach is needed addressing all composite constituents and manufacturing steps. A huge potential lies in the optimization of the tungsten wire used as fibre. We discuss this aspect and present studies on potassium doped tungsten wire in detail. This wire, utilized in the illumination industry, could be a replacement for the so far used pure tungsten wire due to its superior high temperature properties. In tensile tests the wire showed high strength and ductility up to an annealing temperature of 2200 K. The results show that the use of doped tungsten wire could increase the allowed fabrication temperature and the overall working temperature of the composite itself.

  15. Recent Advances in Modeling Stress Distributions in Multilayers Subjected to Biaxial Flexure Tests

    SciTech Connect

    Hsueh, Chun-Hway; Luttrell, Claire Roberta

    2007-01-01

    Although biaxial flexure tests have been used extensively to measure the strength of brittle materials, the tests and analyses have been limited to materials of uniform properties. Despite the increasing applications of multilayered structures, characterization of their strengths using biaxial flexure tests has been difficult because the analytical description of the strength-fracture load relation for multilayers subjected to biaxial flexure tests is unavailable. The newly derived closed-form solutions for the elastic stress distributions in multilayered discs subjected to ring-on-ring tests are summarized here. These solutions are obtained by (i) finding the correlation between monolayered and multilayered discs subjected to biaxial bending moment and (ii) conversion from the existing solutions for monolayers. Using this methodology, the closed-form solutions for multilayers subjected to other biaxial flexure tests can also be obtained. Finite element results for ring-on-rings tests performed on (i) porcelain/zirconia bilayered discs and (ii) solid oxide fuel cells trilayered discs are also presented to validate the closed-form solutions. The closed-form solutions hence provide a basis for evaluating biaxial strength of multilayers using biaxial flexure tests.

  16. Design and Use of a Novel Bioreactor for Regeneration of Biaxially Stretched Tissue-Engineered Vessels.

    PubMed

    Huang, Angela Hai; Lee, Yong-Ung; Calle, Elizabeth A; Boyle, Michael; Starcher, Barry C; Humphrey, Jay D; Niklason, Laura E

    2015-08-01

    Conventional bioreactors are used to enhance extracellular matrix (ECM) production and mechanical strength of tissue-engineered vessels (TEVs) by applying circumferential strain, which is uniaxial stretching. However, the resulting TEVs still suffer from inadequate mechanical properties, where rupture strengths and compliance values are still very different from native arteries. The biomechanical milieu of native arteries consists of both circumferential and axial loading. Therefore, to better simulate the physiological stresses acting on native arteries, we built a novel bioreactor system to enable biaxial stretching of engineered arteries during culture. This new bioreactor system allows for independent control of circumferential and axial stretching parameters, such as displacement and beat rate. The assembly and setup processes for this biaxial bioreactor system are reliable with a success rate greater than 75% for completion of long-term sterile culture. This bioreactor also supports side-by-side assessments of TEVs that are cultured under three types of mechanical conditions (static, uniaxial, and biaxial), all within the same biochemical environment. Using this bioreactor, we examined the impact of biaxial stretching on arterial wall remodeling of TEVs. Biaxial TEVs developed the greatest wall thickness compared with static and uniaxial TEVs. Unlike uniaxial loading, biaxial loading led to undulated collagen fibers that are commonly found in native arteries. More importantly, the biaxial TEVs developed the most mature elastin in the ECM, both qualitatively and quantitatively. The presence of mature extracellular elastin along with the undulated collagen fibers may contribute to the observed vascular compliance in the biaxial TEVs. The current work shows that biaxial stretching is a novel and promising means to improve TEV generation. Furthermore, this novel system allows us to optimize biomechanical conditioning by unraveling the interrelationships among the

  17. Design and Use of a Novel Bioreactor for Regeneration of Biaxially Stretched Tissue-Engineered Vessels

    PubMed Central

    Huang, Angela Hai; Lee, Yong-Ung; Calle, Elizabeth A.; Boyle, Michael; Starcher, Barry C.; Humphrey, Jay D.

    2015-01-01

    Conventional bioreactors are used to enhance extracellular matrix (ECM) production and mechanical strength of tissue-engineered vessels (TEVs) by applying circumferential strain, which is uniaxial stretching. However, the resulting TEVs still suffer from inadequate mechanical properties, where rupture strengths and compliance values are still very different from native arteries. The biomechanical milieu of native arteries consists of both circumferential and axial loading. Therefore, to better simulate the physiological stresses acting on native arteries, we built a novel bioreactor system to enable biaxial stretching of engineered arteries during culture. This new bioreactor system allows for independent control of circumferential and axial stretching parameters, such as displacement and beat rate. The assembly and setup processes for this biaxial bioreactor system are reliable with a success rate greater than 75% for completion of long-term sterile culture. This bioreactor also supports side-by-side assessments of TEVs that are cultured under three types of mechanical conditions (static, uniaxial, and biaxial), all within the same biochemical environment. Using this bioreactor, we examined the impact of biaxial stretching on arterial wall remodeling of TEVs. Biaxial TEVs developed the greatest wall thickness compared with static and uniaxial TEVs. Unlike uniaxial loading, biaxial loading led to undulated collagen fibers that are commonly found in native arteries. More importantly, the biaxial TEVs developed the most mature elastin in the ECM, both qualitatively and quantitatively. The presence of mature extracellular elastin along with the undulated collagen fibers may contribute to the observed vascular compliance in the biaxial TEVs. The current work shows that biaxial stretching is a novel and promising means to improve TEV generation. Furthermore, this novel system allows us to optimize biomechanical conditioning by unraveling the interrelationships among the

  18. Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils.

    PubMed

    Ishii, T; Shi, L; Huang, R; Tsujino, N; Druzhbin, D; Myhill, R; Li, Y; Wang, L; Yamamoto, T; Miyajima, N; Kawazoe, T; Nishiyama, N; Higo, Y; Tange, Y; Katsura, T

    2016-02-01

    We have generated over 40 GPa pressures, namely, 43 and 44 GPa, at ambient temperature and 2000 K, respectively, using Kawai-type multi-anvil presses (KMAP) with tungsten carbide anvils for the first time. These high-pressure generations were achieved by combining the following pressure-generation techniques: (1) precisely aligned guide block systems, (2) high hardness of tungsten carbide, (3) tapering of second-stage anvil faces, (4) materials with high bulk modulus in a high-pressure cell, and (5) high heating efficiency.

  19. Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils.

    PubMed

    Ishii, T; Shi, L; Huang, R; Tsujino, N; Druzhbin, D; Myhill, R; Li, Y; Wang, L; Yamamoto, T; Miyajima, N; Kawazoe, T; Nishiyama, N; Higo, Y; Tange, Y; Katsura, T

    2016-02-01

    We have generated over 40 GPa pressures, namely, 43 and 44 GPa, at ambient temperature and 2000 K, respectively, using Kawai-type multi-anvil presses (KMAP) with tungsten carbide anvils for the first time. These high-pressure generations were achieved by combining the following pressure-generation techniques: (1) precisely aligned guide block systems, (2) high hardness of tungsten carbide, (3) tapering of second-stage anvil faces, (4) materials with high bulk modulus in a high-pressure cell, and (5) high heating efficiency. PMID:26931871

  20. Numerical and experimental study of cruciform specimens subjected to biaxial tensile test

    NASA Astrophysics Data System (ADS)

    Andrusca, L.; Goanta, V.; Barsanescu, P. D.; Steigmann, R.

    2016-08-01

    Multiaxial stress states are very common in engineering applications. To obtain a plane stress state in a material are used different experimental procedures. Biaxial tensile tests of cruciform specimens represent one of the most versatile techniques with accurate results for a wide range of materials. Specimen geometry and size must be adapted to biaxial experiments that use devices attached to universal testing machine. Biaxial tensile tests are performed using cruciform specimens optimized by a numerical study through finite element analysis and a custom built attachable device developed. The results obtained show that the method proposed in this paper can be used with good results to characterize the behaviour of ductile materials.

  1. Thermotropic Uniaxial and Biaxial Nematic and Smectic Phases in Bent-Core Mesogens

    SciTech Connect

    Prasad, Venna; Kang, Shin-Woong; Suresh, K.A.; Joshi, Leela; Wang, Qingbing; Kumar, Satyendra

    2010-07-20

    Two azo substituted achiral bent-core mesogens have been synthesized. Optical polarizing microscopy and synchrotron X-ray scattering studies of both compounds reveal the existence of the thermotropic uniaxial and biaxial nematic and three smectic phases at different temperatures in these single component small molecule systems. The transition from the uniaxial to biaxial nematic phase is confirmed to be second order. The transitions from the biaxial nematic to the underlying smectic phase and between the smectic phases have barely discernible heat capacity signatures and thus are also second order.

  2. Environmental fate of tungsten from military use.

    PubMed

    Clausen, Jay L; Korte, Nic

    2009-04-01

    This manuscript describes the distribution, fate and transport of tungsten used in training rounds at three small arms ranges at Camp Edwards on the Massachusetts Military Reservation (MMR), USA. Practice with tungsten/nylon rounds began in 2000 subsequent to a 1997 US Environmental Protection Agency ban on training with lead. Training with the tungsten rounds was halted in 2005 because of concerns regarding tungsten's environmental mobility and potential toxicity. This study, therefore, examines how tungsten partitions in the environment when fired on a small arms training range. Soil sampling revealed surface soil concentrations, highest at the berm face, up to 2080 mg/kg. Concentrations decreased rapidly with depth--at least by an order of magnitude by 25 cm. Nonetheless, tungsten concentrations remained above background to at least 150 cm. Pore-water samples from lysimeters installed in berm areas revealed a range of concentrations (<1-400 mg/L) elevated with respect to background although there was no discernable trend with depth. Groundwater monitoring well samples collected approximately 30 m below ground surface showed tungsten (0.001-0.56 mg/L) attributable to range use.

  3. Environmental fate of tungsten from military use.

    PubMed

    Clausen, Jay L; Korte, Nic

    2009-04-01

    This manuscript describes the distribution, fate and transport of tungsten used in training rounds at three small arms ranges at Camp Edwards on the Massachusetts Military Reservation (MMR), USA. Practice with tungsten/nylon rounds began in 2000 subsequent to a 1997 US Environmental Protection Agency ban on training with lead. Training with the tungsten rounds was halted in 2005 because of concerns regarding tungsten's environmental mobility and potential toxicity. This study, therefore, examines how tungsten partitions in the environment when fired on a small arms training range. Soil sampling revealed surface soil concentrations, highest at the berm face, up to 2080 mg/kg. Concentrations decreased rapidly with depth--at least by an order of magnitude by 25 cm. Nonetheless, tungsten concentrations remained above background to at least 150 cm. Pore-water samples from lysimeters installed in berm areas revealed a range of concentrations (<1-400 mg/L) elevated with respect to background although there was no discernable trend with depth. Groundwater monitoring well samples collected approximately 30 m below ground surface showed tungsten (0.001-0.56 mg/L) attributable to range use. PMID:19217645

  4. Biaxial mechanical properties of the human thoracic and abdominal aorta, common carotid, subclavian, renal and common iliac arteries.

    PubMed

    Kamenskiy, Alexey V; Dzenis, Yuris A; Kazmi, Syed A Jaffar; Pemberton, Mark A; Pipinos, Iraklis I; Phillips, Nick Y; Herber, Kyle; Woodford, Thomas; Bowen, Robert E; Lomneth, Carol S; MacTaggart, Jason N

    2014-11-01

    The biomechanics of large- and medium-sized arteries influence the pathophysiology of arterial disease and the response to therapeutic interventions. However, a comprehensive comparative analysis of human arterial biaxial mechanical properties has not yet been reported. Planar biaxial extension was used to establish the passive mechanical properties of human thoracic (TA, [Formula: see text]) and abdominal (AA, [Formula: see text]) aorta, common carotid (CCA, [Formula: see text]), subclavian (SA, [Formula: see text]), renal (RA, [Formula: see text]) and common iliac (CIA, [Formula: see text]) arteries from 11 deceased subjects ([Formula: see text] years old). Histological evaluation determined the structure of each specimen. Experimental data were used to determine constitutive parameters for a structurally motivated nonlinear anisotropic constitutive model. All arteries demonstrated appreciable anisotropy and large nonlinear deformations. Most CCA, SA, TA, AA and CIA specimens were stiffer longitudinally, while most RAs were stiffer circumferentially. A switch in anisotropy was occasionally demonstrated for all arteries. The CCA was the most compliant, least anisotropic and least frequently diseased of all arteries, while the CIA and AA were the stiffest and the most diseased. The severity of atherosclerosis correlated with age, but was not affected by laterality. Elastin fibers in the aorta, SA and CCA were uniformly and mostly circumferentially distributed throughout the media, while in the RA and CIA, elastin was primarily axially aligned and concentrated in the external elastic lamina. Constitutive modeling provided good fits to the experimental data for most arteries. Biomechanical and architectural features of major arteries differ depending on location and functional environment. A better understanding of localized arterial mechanical properties may support the development of site-specific treatment modalities for arterial disease.

  5. Electromagnetic biaxial vector scanner using radial magnetic field.

    PubMed

    Han, Aleum; Cho, Ah Ran; Ju, Suna; Ahn, Si-Hong; Bu, Jong-Uk; Ji, Chang-Hyeon

    2016-07-11

    We present an electromagnetic biaxial vector-graphic scanning micromirror. In contrast to conventional electromagnetic actuators using linear magnetic field, proposed device utilizes a radial magnetic field and uniquely designed current paths to enable the 2 degree-of-freedom scanning motion. As the radial field is generated by concentrically assembled magnets placed under the scanner die, large driving torque can be generated without the aid of hermetic packaging and relatively small device volume can be achieved. Mechanical half scan angle of 6.43° and 4.20° have been achieved at DC current of 250mA and 350mA for horizontal and vertical scans, respectively. Forced actuation along both scan axes has been realized by feedback control. PMID:27410851

  6. Conductive layer for biaxially oriented semiconductor film growth

    DOEpatents

    Findikoglu, Alp T.; Matias, Vladimir

    2007-10-30

    A conductive layer for biaxially oriented semiconductor film growth and a thin film semiconductor structure such as, for example, a photodetector, a photovoltaic cell, or a light emitting diode (LED) that includes a crystallographically oriented semiconducting film disposed on the conductive layer. The thin film semiconductor structure includes: a substrate; a first electrode deposited on the substrate; and a semiconducting layer epitaxially deposited on the first electrode. The first electrode includes a template layer deposited on the substrate and a buffer layer epitaxially deposited on the template layer. The template layer includes a first metal nitride that is electrically conductive and has a rock salt crystal structure, and the buffer layer includes a second metal nitride that is electrically conductive. The semiconducting layer is epitaxially deposited on the buffer layer. A method of making such a thin film semiconductor structure is also described.

  7. Magnetic properties of biaxially oriented Ni-V substrates

    SciTech Connect

    Bettinelli, D.; Petrisor, T.; Gambardella, U.; Boffa, V.; Ceresara, S.; Nistor, L.; Pop, V.; Scardi, P.

    1999-04-20

    The paper presents the structural and magnetic properties of a new non-magnetic biaxially textured substrate based on Ni{sub 100{minus}x}V{sub x} solid-solution for YBa{sub 2}Cu{sub 3}O{sub 7{minus}y} tape fabrication. The effective atomic magnetic moment monotonously decreases with the vanadium concentration, causing a corresponding decrease of Curie temperature. The Curie temperature reaches the zero value at about 11.5% of vanadium. The texturing studies revealed that (100)[-001] cube texture can be easily developed up to x = 11 at.%, by a cold rolling process followed by a recrystallization thermal treatment. The X-ray {omega} and {phi} scans have demonstrated that the samples have a good out-of-plane and in-plane texture for the whole solubility range, with FWHM of 7{degree} and 11{degree}, respectively. The correlation between the magnetic and structural anisotropy was also studied.

  8. Biaxial Compressive Strain Engineering in Graphene/Boron Nitride Heterostructures

    PubMed Central

    Pan, Wei; Xiao, Jianliang; Zhu, Junwei; Yu, Chenxi; Zhang, Gang; Ni, Zhenhua; Watanabe, K.; Taniguchi, T.; Shi, Yi; Wang, Xinran

    2012-01-01

    Strain engineered graphene has been predicted to show many interesting physics and device applications. Here we study biaxial compressive strain in graphene/hexagonal boron nitride heterostructures after thermal cycling to high temperatures likely due to their thermal expansion coefficient mismatch. The appearance of sub-micron self-supporting bubbles indicates that the strain is spatially inhomogeneous. Finite element modeling suggests that the strain is concentrated on the edges with regular nano-scale wrinkles, which could be a playground for strain engineering in graphene. Raman spectroscopy and mapping is employed to quantitatively probe the magnitude and distribution of strain. From the temperature-dependent shifts of Raman G and 2D peaks, we estimate the TEC of graphene from room temperature to above 1000K for the first time. PMID:23189242

  9. A resonant biaxial Helmholtz coil employing a fractal capacitor bank

    NASA Astrophysics Data System (ADS)

    Martin, James E.

    2013-09-01

    The design and construction of a series resonant biaxial Helmholtz coil for the production of magnetic fields as large as 500 G in the range of 100-2500 Hz is described. Important aspects of ac coil design are discussed, including: minimizing power losses due to the expected Joule heating, self-induced eddy currents, and skin resistance; controlling the stray capacitance; maximizing field homogeneity; and keeping peak voltages at acceptable levels. The design and construction of a computer-controlled, optically isolated fractal capacitor bank is then treated, and various aspects of capacitor selection and characterization were discussed. The system performance is demonstrated, including stability and the possibility of field component dephasing with typical magnetic samples.

  10. A resonant biaxial Helmholtz coil employing a fractal capacitor bank.

    PubMed

    Martin, James E

    2013-09-01

    The design and construction of a series resonant biaxial Helmholtz coil for the production of magnetic fields as large as 500 G in the range of 100-2500 Hz is described. Important aspects of ac coil design are discussed, including: minimizing power losses due to the expected Joule heating, self-induced eddy currents, and skin resistance; controlling the stray capacitance; maximizing field homogeneity; and keeping peak voltages at acceptable levels. The design and construction of a computer-controlled, optically isolated fractal capacitor bank is then treated, and various aspects of capacitor selection and characterization were discussed. The system performance is demonstrated, including stability and the possibility of field component dephasing with typical magnetic samples. PMID:24089847

  11. Failure analysis of composite laminates including biaxial compression

    NASA Technical Reports Server (NTRS)

    Tennyson, R. C.; Elliott, W. G.

    1983-01-01

    This report describes a continued effort on the development and application of the tensor polynomial failure criterion for composite laminate analysis. In particular, emphasis is given to the design, construction and testing of a cross-beam laminate configuration to obtain "pure' biaxial compression failure. The purpose of this test case was to provide to permit "closure' of the cubic form of the failure surface in the 1-2 compression-compression quadrant. This resulted in a revised set of interaction strength parameters and the construction of a failure surface which can be used with confidence for strength predictions, assuming a plane stress state exists. Furthermore, the problem of complex conjugate roots which can occur in some failure regions is addressed and an "engineering' interpretation is provided. Results are presented illustrating this behavior and the methodology for overcoming this problem is discussed.

  12. Biaxial flexing of a fiber reinforced aluminum composite

    SciTech Connect

    Tsangarakis, N.; Pepi, M.S. )

    1990-07-01

    A disk specimen of silicon carbide continuous fiber reinforced aluminum is used to study the response of the composite to biaxial tensile flexure. The maximum surface principal tensile strain is constant within a radius of 6.1 mm from the center of the disk. The strain is found to be sensitive to the damage introduced in the composite during flexing. Fiber breakage under monotonic loading is initiated within a fiber tensile strain 0.0038-0.0083. Under cyclic loading and for principal surface strain ranges exceeding 0.0035 the dominant damage mechanism leading to failure is fiber breakage. At smaller surface strain ranges, slip bands and cracks formed in the matrix. The limiting value of the cyclic fiber strain range for a life of one million cycles is 0.00132. This strain is 15 percent of the composite failure strain under uniaxial monotonic loading and 50 percent of the maximum strain in uniaxial tensile fatigue. 27 refs.

  13. Biaxially textured copper and copper iron alloy substrates for use in YBa2Cu3O7-x coated conductors

    NASA Astrophysics Data System (ADS)

    Varanasi, Chakrapani V.; Barnes, Paul N.; Yust, Nicholas A.

    2006-01-01

    Copper and Cu-Fe (Fe ~2.35 wt%) alloy substrates were thermo-mechanically processed and the biaxial texture development, magnetic properties, yield strength, and electrical resistivity were studied and compared to determine their suitability as substrates for high-temperature superconducting coated conductor applications. Average full width half maximum (FWHM) of 5.5° in Phi scans (in-plane alignment), and 6.6° in omega scans (out-of-plane alignment) was obtained in copper samples. Cu-Fe samples showed 5.9° FWHM in Phi scans and 5.9° in omega scans. Even with the presence of 2.35% Fe in the Cu-alloy, the saturation magnetization (Msat) value was found to be 4.27 emu g-1 at 5 K, which is less than in Ni samples by an order of magnitude and comparable to that of Ni-9 at.% W substrates. The yield strength of the annealed Cu-Fe alloy substrate was found to be at least two times higher than that of similarly annealed copper substrates. The electrical resistivity of Cu-Fe alloy was found to be an order of magnitude higher than that of pure copper at 77 K.

  14. Single crystal tungsten kinetic energy penetrators

    SciTech Connect

    Cline, C.F.; Gogolewski, R.P.

    1992-05-01

    We have explored the terminal ballistic performance of single crystal tungsten as a kinetic energy penetrator. Scientific speculation as to the anticipated penetration performance and nature of the interaction between such a kinetic energy penetrator and semi-infinite and spaced metallic targets has led us to perform laboratory scale experiments and metallographic examinations of post-impact penetrator materials. The single tungsten crystals were ground into kinetic energy penetrators with the [l angle]111[r angle] and [l angle]100[r angle] crystal direction being coincident with the axis of symmetry of the penetrators. The crystals were electro-polished to their final diameter. We, compared the terminal performance at current ordnance speeds of [l angle]111[r angle] single crystal tungsten to 90W-10 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against a spaced steel (triple) target at sixty-five degrees obliquity. We also compared the terminal performance of [l angle]100[r angle] and [l angle]111[r angle] single crystal tungsten with 90W-10 and 98W02 (NiFe) cemented tungsten and textured pure tungsten in laboratory scale ballistic experiments against monolithic 4340 alloy steel (HRC = 36) at normal impact. We radiographed the penetrators during the interactions with the targets, we recovered portions of the penetrators after the ballistic experiments, and we conducted metallographic examinations of penetrator remnants. From the radiographic records and the metallographic examinations, we drew conclusions pertaining to insights into the terminal interactions of the penetrators with the targets and suggestions as to improved compositions of the cemented tungsten penetrators.

  15. Reliability analysis of structural ceramics subjected to biaxial flexure

    SciTech Connect

    Chao, Luen-Yuan.

    1993-01-01

    Two weakest-link fracture statistics formulations for multiaxial loading, Batdorf's flaw density and orientation distribution approach and Evans' elemental strength approach, were compared for identical fracture criteria and flaw-size distribution function. Despite some fundamental differences in the methodology used in calculating fracture probabilities for multiaxial loading, the two approaches gave identical predictions. A recent contradictory conclusion reported in the literature is shown to be incorrect. Fracture stresses of a sintered alumina and silicon nitride were assessed in qualified uniaxial (three-point and four-point) and biaxial (uniform-pressure-on-disk) flexure tests in inert conditions. The size and stress-state effects on the inert fracture stress of alumina were explained by a reliability analysis based on randomly oriented surface flaws and a mixed-mode fracture criterion. Fracture stresses of silicon nitride were in accord with a reliability analysis based on volume flaws with preferred orientation (crack plane normal to the maximum principal stress) and a normal stress fracture criterion. The preferred orientation of the flaws in silicon nitride resulted from stress-induced nucleation of cracks around pores. Alumina ceramic was also tested in deionized water at a low stressing rate (1 MPa/s). The decreased fracture stresses measured in both uniaxial and biaxial flexure tests in water as compared to the inert fracture stresses were consistent with subcritical crack growth behavior inferred from dynamic fatigue tests in water. The analysis of the size and stress-state effects on and time-dependent degradation of fracture stresses included consideration of the statistical uncertainties (90 percent confidence intervals) of the estimated Weibull (Weibull modulus, m, and characteristic strength, sigma[sub theta]) and slow-crack-growth (stress-intensity exponent, N, and critical crack growth rate, V[sub C]) parameters.

  16. Fabrication and properties of tungsten heavy metal alloys containing 30% to 90% tungsten

    SciTech Connect

    Gurwell, W.E.; Nelson, R.G.; Dudder, G.B.; Davis, N.C.

    1984-09-01

    In 1983, Pacific Northwest Laboratory conducted a survey of tungsten heavy metal alloys having lower-than-normal (<90%) tungsten content. The purpose of the work was to develop tougher, more impact-resistant high-density alloys for applications benefitting from improved mechanical properties. Tungsten heavy metal alloys of 30 to 90% tungsten content were fabricated and their mechanical properties measured. Although ultimate strength was essentially independent of tungsten content, lower tungsten-content alloys had lower yield stress, hardness, and density, and decidedly higher elongations and impact energies. Cold work was effective in raising strength and hardness but detrimental to elongation and impact energies. Precipitation hardening and strain aging raised hardness effectively but had less influence on other mechanical properties. 34 figures, 7 tables.

  17. Tungsten Ditelluride: a layered semimetal

    NASA Astrophysics Data System (ADS)

    Lee, Chia-Hui; Silva, Eduardo Cruz; Calderin, Lazaro; Nguyen, Minh An T.; Hollander, Matthew J.; Bersch, Brian; Mallouk, Thomas E.; Robinson, Joshua A.

    2015-06-01

    Tungsten ditelluride (WTe2) is a transition metal dichalcogenide (TMD) with physical and electronic properties that make it attractive for a variety of electronic applications. Although WTe2 has been studied for decades, its structure and electronic properties have only recently been correctly described. We experimentally and theoretically investigate the structure, dynamics and electronic properties of WTe2, and verify that WTe2 has its minimum energy configuration in a distorted 1T structure (Td structure), which results in metallic-like transport. Our findings unambiguously confirm the metallic nature of WTe2, introduce new information about the Raman modes of Td-WTe2, and demonstrate that Td-WTe2 is readily oxidized via environmental exposure. Finally, these findings confirm that, in its thermodynamically favored Td form, the utilization of WTe2 in electronic device architectures such as field effect transistors may need to be reevaluated.

  18. Tungsten wire for incandescent lamps

    SciTech Connect

    Walter, J.L.; Briant, C.L. )

    1990-09-01

    Tungsten wire for incandescent lamp filaments must operate at high temperatures and for long times. To meet these requirements, the grain morphology of the wire must be controlled to reduce the propensity for grain boundary sliding. The morphology is a function of the distribution of very small pockets of potassium in the wire and the mechanical processing from ingot to wire. The behavior of the filament is directly related to the grain morphology. This paper describes the mechanism by which the potassium is incorporated into and distributed in the ingot. The elongation and spheroidization of the bubbles during hot rolling and swaging is also examined and related to the grain morphology of wire. Some indications of the relationship between grain morphology and filament behavior are also given.

  19. Dielectronic recombination of tungsten ions

    NASA Astrophysics Data System (ADS)

    Li, Bowen; O'Sullivan, Gerry; Dong, Chenzhong; Chen, Ximeng

    2016-08-01

    Ab initio calculations of dielectronic recombination rate coefficients of Ne-, Pd- and Ag-like tungsten have been performed. Energy levels, radiative transition probabilities and autoionization rates were calculated using the Flexible Atomic Code. The contributions from different channels to the total rate coefficients are discussed. The present calculated rate coefficients are compared with other calculations where available. Excellent agreement has been found for Ne-like W while a large discrepancy was found for Pd-like W, which implies that more ab initio calculations and experimental measurements are badly needed. Further calculations demonstrated that the influence of configuration interaction is small while nonresonant radiative stabilizing (NRS) contribution to doubly excited non-autoionizing states are vital. The data obtained are expected to be useful for modeling plasmas for fusion applications, especially for the ITER community, which makes experimental verification even more essential.

  20. High strength and density tungsten-uranium alloys

    DOEpatents

    Sheinberg, Haskell

    1993-01-01

    Alloys of tungsten and uranium and a method for making the alloys. The amount of tungsten present in the alloys is from about 55 vol % to about 85 vol %. A porous preform is made by sintering consolidated tungsten powder. The preform is impregnated with molten uranium such that (1) uranium fills the pores of the preform to form uranium in a tungsten matrix or (2) uranium dissolves portions of the preform to form a continuous uranium phase containing tungsten particles.

  1. Maier-Saupe model for a mixture of uniaxial and biaxial molecules

    NASA Astrophysics Data System (ADS)

    Nascimento, E. S.; Henriques, E. F.; Vieira, A. P.; Salinas, S. R.

    2015-12-01

    We introduce shape variations in a liquid-crystalline system by considering an elementary Maier-Saupe lattice model for a mixture of uniaxial and biaxial molecules. Shape variables are treated in the annealed (thermalized) limit. We analyze the thermodynamic properties of this system in terms of temperature T , concentration c of intrinsically biaxial molecules, and a parameter Δ associated with the degree of biaxiality of the molecules. At the mean-field level, we use standard techniques of statistical mechanics to draw global phase diagrams, which are shown to display a rich structure, including uniaxial and biaxial nematic phases, a reentrant ordered region, and many distinct multicritical points. Also, we use the formalism to write an expansion of the free energy in order to make contact with the Landau-de Gennes theory of nematic phase transitions.

  2. Method of deforming a biaxially textured buffer layer on a textured metallic substrate and articles therefrom

    DOEpatents

    Lee, Dominic F.; Kroeger, Donald M.; Goyal, Amit

    2000-01-01

    The present invention provides methods and biaxially textured articles having a deformed epitaxial layer formed therefrom for use with high temperature superconductors, photovoltaic, ferroelectric, or optical devices. A buffer layer is epitaxially deposited onto biaxially-textured substrates and then mechanically deformed. The deformation process minimizes or eliminates grooves, or other irregularities, formed on the buffer layer while maintaining the biaxial texture of the buffer layer. Advantageously, the biaxial texture of the buffer layer is not altered during subsequent heat treatments of the deformed buffer. The present invention provides mechanical densification procedures which can be incorporated into the processing of superconducting films through the powder deposit or precursor approaches without incurring unfavorable high-angle grain boundaries.

  3. Dispersion of the temperature-noncritical frequency conversion and birefringence in biaxial optical crystals

    SciTech Connect

    Grechin, Sergei G; Dmitriev, Valentin G; Dyakov, Vladimir A; Pryalkin, Vladimir I

    2004-05-31

    Dispersion of the temperature-noncritical frequency conversion (phase matching) and birefringence in biaxial crystals is considered. The possibility of simultaneous realisation of these processes during SHG in a KTP crystal is discussed. (nonlinear optical phenomena)

  4. Maier-Saupe model for a mixture of uniaxial and biaxial molecules.

    PubMed

    Nascimento, E S; Henriques, E F; Vieira, A P; Salinas, S R

    2015-12-01

    We introduce shape variations in a liquid-crystalline system by considering an elementary Maier-Saupe lattice model for a mixture of uniaxial and biaxial molecules. Shape variables are treated in the annealed (thermalized) limit. We analyze the thermodynamic properties of this system in terms of temperature T, concentration c of intrinsically biaxial molecules, and a parameter Δ associated with the degree of biaxiality of the molecules. At the mean-field level, we use standard techniques of statistical mechanics to draw global phase diagrams, which are shown to display a rich structure, including uniaxial and biaxial nematic phases, a reentrant ordered region, and many distinct multicritical points. Also, we use the formalism to write an expansion of the free energy in order to make contact with the Landau-de Gennes theory of nematic phase transitions. PMID:26764707

  5. Suspended germanium cross-shaped microstructures for enhancing biaxial tensile strain

    NASA Astrophysics Data System (ADS)

    Ishida, Satomi; Kako, Satoshi; Oda, Katsuya; Ido, Tatemi; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2016-04-01

    We fabricate a suspended germanium cross-shaped microstructure to biaxially enhance residual tensile strain using a germanium epilayer directly grown on a silicon-on-insulator substrate. Such a suspended germanium system with enhanced biaxial tensile strain will be a promising platform for incorporating optical cavities toward the realization of germanium lasers. We demonstrate systematic control over biaxial tensile strain and photoluminescence peaks by changing structural geometry. The photoluminescence peaks corresponding to the direct recombination between the conduction Γ valley and two strain-induced separated valence bands have been clearly assigned. A maximum biaxial strain of 0.8% has been achieved, which is almost half of that required to transform germanium into a direct band-gap semiconductor.

  6. MAVID multiple alignment server.

    PubMed

    Bray, Nicolas; Pachter, Lior

    2003-07-01

    MAVID is a multiple alignment program suitable for many large genomic regions. The MAVID web server allows biomedical researchers to quickly obtain multiple alignments for genomic sequences and to subsequently analyse the alignments for conserved regions. MAVID has been successfully used for the alignment of closely related species such as primates and also for the alignment of more distant organisms such as human and fugu. The server is fast, capable of aligning hundreds of kilobases in less than a minute. The multiple alignment is used to build a phylogenetic tree for the sequences, which is subsequently used as a basis for identifying conserved regions in the alignment. The server can be accessed at http://baboon.math.berkeley.edu/mavid/.

  7. Nearest Alignment Space Termination

    2006-07-13

    Near Alignment Space Termination (NAST) is the Greengenes algorithm that matches up submitted sequences with the Greengenes database to look for similarities and align the submitted sequences based on those similarities.

  8. Biaxial Testing of 2219-T87 Aluminum Alloy Using Cruciform Specimens

    NASA Technical Reports Server (NTRS)

    Dawicke, D. S.; Pollock, W. D.

    1997-01-01

    A cruciform biaxial test specimen was designed and seven biaxial tensile tests were conducted on 2219-T87 aluminum alloy. An elastic-plastic finite element analysis was used to simulate each tests and predict the yield stresses. The elastic-plastic finite analysis accurately simulated the measured load-strain behavior for each test. The yield stresses predicted by the finite element analyses indicated that the yield behavior of the 2219-T87 aluminum alloy agrees with the von Mises yield criterion.

  9. Biaxial loading effects on fracture toughness of reactor pressure vessel steel

    SciTech Connect

    McAfee, W.J.; Bass, B.R.; Bryson, J.W. Jr.; Pennell, W.E.

    1995-03-01

    The preliminary phases of a program to develop and evaluate fracture methodologies for assessing crack-tip constraint effects on fracture toughness of reactor pressure vessel (RPV) steels have been completed by the Heavy-Section Steel Technology (HSST) Program. Objectives were to investigate effect of biaxial loading on fracture toughness, quantify this effect through existing stress-based, dual-parameter, fracture-toughness correlations, or propose and verify alternate correlations. A cruciform beam specimen with 2-D, shallow, through-thickness flaw and a special loading fixture was designed and fabricated. Tests were performed using biaxial loading ratios of 0:1 (uniaxial), 0.6:1, and 1:1 (equi-biaxial). Critical fracture-toughness values were calculated for each test. Biaxial loading of 0.6:1 resulted in a reduction in the lower bound fracture toughness of {approximately}12% as compared to that from the uniaxial tests. The biaxial loading of 1:1 yielded two subsets of toughness values; one agreed well with the uniaxial data, while one was reduced by {approximately}43% when compared to the uniaxial data. Results were evaluated using J-Q theory and Dodds-Anderson (D-A) micromechanical scaling model. The D-A model predicted no biaxial effect, while the J-Q method gave inconclusive results. When applied to the 1:1 biaxial data, these constraint methodologies failed to predict the observed reduction in fracture toughness obtained in one experiment. A strain-based constraint methodology that considers the relationship between applied biaxial load, the plastic zone width in the crack plane, and fracture toughness was formulated and applied successfully to the data. Evaluation of this dual-parameter strain-based model led to the conclusion that it has the capability of representing fracture behavior of RPV steels in the transition region, including the effects of out-of-plane loading on fracture toughness. This report is designated as HSST Report No. 150.

  10. A biaxial method for inplane shear testing. [shear strain in composite materials

    NASA Technical Reports Server (NTRS)

    Bush, H. G.; Weller, T.

    1978-01-01

    A biaxial method for performing inplane shear tests of materials using a shear frame is described. Aluminum plate and sandwich specimens were used to characterize the uniformity of shear strain imparted by the biaxial method of loading as opposed to the uniaxial method. The inplane stiffening effect of aluminum honeycomb core was determined. Test results for (+ or - 45) graphite-epoxy laminate are presented. Some theoretical considerations of subjecting an anisotropic material to a uniform shear deformation are discussed.

  11. International strategic mineral issues summary report: tungsten

    USGS Publications Warehouse

    Werner, Antony B.T.; Sinclair, W. David; Amey, Earle B.

    1998-01-01

    In 1995, China and the former Soviet Union accounted for over three-fourths of the world's mine production of tungsten. China alone produced about two-thirds of world output. Given its vast resources, China will likely maintain its prominent role in world tungsten supply. By the year 2020, changes in supply patterns are likely to result from declining output from individual deposits in Australia, Austria, and Portugal and the opening of new mines in Canada, China, and the United Kingdom.

  12. Phase diagram of the uniaxial and biaxial soft-core Gay-Berne model

    NASA Astrophysics Data System (ADS)

    Berardi, Roberto; Lintuvuori, Juho S.; Wilson, Mark R.; Zannoni, Claudio

    2011-10-01

    Classical molecular dynamics simulations have been used to explore the phase diagrams for a family of attractive-repulsive soft-core Gay-Berne models [R. Berardi, C. Zannoni, J. S. Lintuvuori, and M. R. Wilson, J. Chem. Phys. 131, 174107 (2009)] and determine the effect of particle softness, i.e., of a moderately repulsive short-range interaction, on the order parameters and phase behaviour of model systems of uniaxial and biaxial ellipsoidal particles. We have found that isotropic, uniaxial, and biaxial nematic and smectic phases are obtained for the model. Extensive calculations of the nematic region of the phase diagram show that endowing mesogenic particles with such soft repulsive interactions affect the stability range of the nematic phases, and in the case of phase biaxiality it also shifts it to lower temperatures. For colloidal particles, stabilised by surface functionalisation, (e.g., with polymer chains), we suggest that it should be possible to tune liquid crystal behaviour to increase the range of stability of uniaxial and biaxial phases (by varying solvent quality). We calculate second virial coefficients and show that they are a useful means of characterising the change in effective softness for such systems. For thermotropic liquid crystals, the introduction of softness in the interactions between mesogens with overall biaxial shape (e.g., through appropriate conformational flexibility) could provide a pathway for the actual chemical synthesis of stable room-temperature biaxial nematics.

  13. Investigation of the Leak Response of a Carbon-Fiber Laminate Loaded in Biaxial Tension

    NASA Technical Reports Server (NTRS)

    Jackson, Wade C.; Ratcliffe, James G.

    2013-01-01

    Designers of pressurized structures have been reluctant to use composite materials because of concerns over leakage. Biaxial stress states are expected to be the worst-case loading condition for allowing leakage to occur through microcracks. To investigate the leakage behavior under in-plane biaxial loading, a cruciform composite specimen was designed that would have a relatively large test section with a uniform 1:1 biaxial loading ratio. A 7.6-cm-square test section was desired for future investigations of the leakage response as a result of impact damage. Many iterations of the cruciform specimen were evaluated using finite element analysis to reduce stress concentrations and maximize the size of the uniform biaxial strain field. The final design allowed the specimen to go to relatively high biaxial strain levels without incurring damage away from the test section. The specimen was designed and manufactured using carbon/epoxy fabric with a four-ply-thick, quasi-isotropic, central test section. Initial validation and testing were performed on a specimen without impact damage. The specimen was tested to maximum biaxial strains of approximately 4500micro epsilon without apparent damage. A leak measurement system containing a pressurized cavity was clamped to the test section and used to measure the flow rate through the specimen. The leakage behavior of the specimen was investigated for pressure differences up to 172 kPa

  14. Tungsten targets the tumor microenvironment to enhance breast cancer metastasis.

    PubMed

    Bolt, Alicia M; Sabourin, Valérie; Molina, Manuel Flores; Police, Alice M; Negro Silva, Luis Fernando; Plourde, Dany; Lemaire, Maryse; Ursini-Siegel, Josie; Mann, Koren K

    2015-01-01

    The number of individuals exposed to high levels of tungsten is increasing, yet there is limited knowledge of the potential human health risks. Recently, a cohort of breast cancer patients was left with tungsten in their breasts following testing of a tungsten-based shield during intraoperative radiotherapy. While monitoring tungsten levels in the blood and urine of these patients, we utilized the 66Cl4 cell model, in vitro and in mice to study the effects of tungsten exposure on mammary tumor growth and metastasis. We still detect tungsten in the urine of patients' years after surgery (mean urinary tungsten concentration at least 20 months post-surgery = 1.76 ng/ml), even in those who have opted for mastectomy, indicating that tungsten does not remain in the breast. In addition, standard chelation therapy was ineffective at mobilizing tungsten. In the mouse model, tungsten slightly delayed primary tumor growth, but significantly enhanced lung metastasis. In vitro, tungsten did not enhance 66Cl4 proliferation or invasion, suggesting that tungsten was not directly acting on 66Cl4 primary tumor cells to enhance invasion. In contrast, tungsten changed the tumor microenvironment, enhancing parameters known to be important for cell invasion and metastasis including activated fibroblasts, matrix metalloproteinases, and myeloid-derived suppressor cells. We show, for the first time, that tungsten enhances metastasis in an animal model of breast cancer by targeting the microenvironment. Importantly, all these tumor microenvironmental changes are associated with a poor prognosis in humans. PMID:25324207

  15. Tungsten Targets the Tumor Microenvironment to Enhance Breast Cancer Metastasis

    PubMed Central

    Bolt, Alicia M.; Sabourin, Valérie; Molina, Manuel Flores; Police, Alice M.; Negro Silva, Luis Fernando; Plourde, Dany; Lemaire, Maryse; Ursini-Siegel, Josie; Mann, Koren K.

    2015-01-01

    The number of individuals exposed to high levels of tungsten is increasing, yet there is limited knowledge of the potential human health risks. Recently, a cohort of breast cancer patients was left with tungsten in their breasts following testing of a tungsten-based shield during intraoperative radiotherapy. While monitoring tungsten levels in the blood and urine of these patients, we utilized the 66Cl4 cell model, in vitro and in mice to study the effects of tungsten exposure on mammary tumor growth and metastasis. We still detect tungsten in the urine of patients’ years after surgery (mean urinary tungsten concentration at least 20 months post-surgery = 1.76 ng/ml), even in those who have opted for mastectomy, indicating that tungsten does not remain in the breast. In addition, standard chelation therapy was ineffective at mobilizing tungsten. In the mouse model, tungsten slightly delayed primary tumor growth, but significantly enhanced lung metastasis. In vitro, tungsten did not enhance 66Cl4 proliferation or invasion, suggesting that tungsten was not directly acting on 66Cl4 primary tumor cells to enhance invasion. In contrast, tungsten changed the tumor microenvironment, enhancing parameters known to be important for cell invasion and metastasis including activated fibroblasts, matrix metalloproteinases, and myeloid-derived suppressor cells. We show, for the first time, that tungsten enhances metastasis in an animal model of breast cancer by targeting the microenvironment. Importantly, all these tumor microenvironmental changes are associated with a poor prognosis in humans. PMID:25324207

  16. Tungsten targets the tumor microenvironment to enhance breast cancer metastasis.

    PubMed

    Bolt, Alicia M; Sabourin, Valérie; Molina, Manuel Flores; Police, Alice M; Negro Silva, Luis Fernando; Plourde, Dany; Lemaire, Maryse; Ursini-Siegel, Josie; Mann, Koren K

    2015-01-01

    The number of individuals exposed to high levels of tungsten is increasing, yet there is limited knowledge of the potential human health risks. Recently, a cohort of breast cancer patients was left with tungsten in their breasts following testing of a tungsten-based shield during intraoperative radiotherapy. While monitoring tungsten levels in the blood and urine of these patients, we utilized the 66Cl4 cell model, in vitro and in mice to study the effects of tungsten exposure on mammary tumor growth and metastasis. We still detect tungsten in the urine of patients' years after surgery (mean urinary tungsten concentration at least 20 months post-surgery = 1.76 ng/ml), even in those who have opted for mastectomy, indicating that tungsten does not remain in the breast. In addition, standard chelation therapy was ineffective at mobilizing tungsten. In the mouse model, tungsten slightly delayed primary tumor growth, but significantly enhanced lung metastasis. In vitro, tungsten did not enhance 66Cl4 proliferation or invasion, suggesting that tungsten was not directly acting on 66Cl4 primary tumor cells to enhance invasion. In contrast, tungsten changed the tumor microenvironment, enhancing parameters known to be important for cell invasion and metastasis including activated fibroblasts, matrix metalloproteinases, and myeloid-derived suppressor cells. We show, for the first time, that tungsten enhances metastasis in an animal model of breast cancer by targeting the microenvironment. Importantly, all these tumor microenvironmental changes are associated with a poor prognosis in humans.

  17. Endothelial cell alignment as a result of anisotropic strain and flow induced shear stress combinations

    PubMed Central

    Sinha, Ravi; Le Gac, Séverine; Verdonschot, Nico; van den Berg, Albert; Koopman, Bart; Rouwkema, Jeroen

    2016-01-01

    Endothelial cells (ECs) are continuously exposed in vivo to cyclic strain and shear stress from pulsatile blood flow. When these stimuli are applied in vitro, ECs adopt an appearance resembling their in vivo state, most apparent in their alignment (perpendicular to uniaxial strain and along the flow). Uniaxial strain and flow perpendicular to the strain, used in most in vitro studies, only represent the in vivo conditions in straight parts of vessels. The conditions present over large fractions of the vasculature can be better represented by anisotropic biaxial strains at various orientations to flow. To emulate these biological complexities in vitro, we have developed a medium-throughput device to screen for the effects on cells of variously oriented anisotropic biaxial strains and flow combinations. Upon the application of only strains for 24 h, ECs (HUVECs) aligned perpendicular to the maximum principal strain and the alignment was stronger for a higher maximum:minimum principal strain ratio. A 0.55 Pa shear stress, when applied alone or with strain for 24 h, caused cells to align along the flow. Studying EC response to such combined physiological mechanical stimuli was not possible with existing platforms and to our best knowledge, has not been reported before. PMID:27404382

  18. Electronic and optical properties of silicene under uni-axial and bi-axial mechanical strains: A first principle study

    NASA Astrophysics Data System (ADS)

    Mohan, Brij; Kumar, Ashok; Ahluwalia, P. K.

    2014-07-01

    The uni-axial and bi-axial mechanical strain mediated electronic band structures and dielectric properties of silicene have been investigated. It is found that on applying uni- and bi-axial strains, the band gap opens for smaller strain in silicene. However, on further increase of strain beyond 8% silicene changed into metal. The ultimate tensile strength estimated is 3.4 GPa. Imaginary part of dielectric function shows that the inter-band transitions are red-shifted for uni- and bi-axial tensile strains and are blue shifted for uni- and bi-axial compressive strains. Electron energy loss (EEL) function shows that the π+σ plasmon energies are red-shifted for uni- and bi-axial strains and blue-shifted for compressive strains. The π plasmons disappears for tensile and asymmetric strains. Bi-axial asymmetric strain is found to have no influence on inter-band transitions and π+σ plasmon energies.

  19. Girder Alignment Plan

    SciTech Connect

    Wolf, Zackary; Ruland, Robert; LeCocq, Catherine; Lundahl, Eric; Levashov, Yurii; Reese, Ed; Rago, Carl; Poling, Ben; Schafer, Donald; Nuhn, Heinz-Dieter; Wienands, Uli; /SLAC

    2010-11-18

    The girders for the LCLS undulator system contain components which must be aligned with high accuracy relative to each other. The alignment is one of the last steps before the girders go into the tunnel, so the alignment must be done efficiently, on a tight schedule. This note documents the alignment plan which includes efficiency and high accuracy. The motivation for girder alignment involves the following considerations. Using beam based alignment, the girder position will be adjusted until the beam goes through the center of the quadrupole and beam finder wire. For the machine to work properly, the undulator axis must be on this line and the center of the undulator beam pipe must be on this line. The physics reasons for the undulator axis and undulator beam pipe axis to be centered on the beam are different, but the alignment tolerance for both are similar. In addition, the beam position monitor must be centered on the beam to preserve its calibration. Thus, the undulator, undulator beam pipe, quadrupole, beam finder wire, and beam position monitor axes must all be aligned to a common line. All relative alignments are equally important, not just, for example, between quadrupole and undulator. We begin by making the common axis the nominal beam axis in the girder coordinate system. All components will be initially aligned to this axis. A more accurate alignment will then position the components relative to each other, without incorporating the girder itself.

  20. Interstellar Dust Grain Alignment

    NASA Astrophysics Data System (ADS)

    Andersson, B.-G.; Lazarian, A.; Vaillancourt, John E.

    2015-08-01

    Interstellar polarization at optical-to-infrared wavelengths is known to arise from asymmetric dust grains aligned with the magnetic field. This effect provides a potentially powerful probe of magnetic field structure and strength if the details of the grain alignment can be reliably understood. Theory and observations have recently converged on a quantitative, predictive description of interstellar grain alignment based on radiative processes. The development of a general, analytical model for this radiative alignment torque (RAT) theory has allowed specific, testable predictions for realistic interstellar conditions. We outline the theoretical and observational arguments in favor of RAT alignment, as well as reasons the "classical" paramagnetic alignment mechanism is unlikely to work, except possibly for the very smallest grains. With further detailed characterization of the RAT mechanism, grain alignment and polarimetry promise to not only better constrain the interstellar magnetic field but also provide new information on the dust characteristics.

  1. Effect of light sources and curing mode techniques on sorption, solubility and biaxial flexural strength of a composite resin

    PubMed Central

    CARVALHO, Andreia Assis; MOREIRA, Francine do Couto Lima; FONSECA, Rodrigo Borges; SOARES, Carlos José; FRANCO, Eduardo Batista; de SOUZA, João Batista; LOPES, Lawrence Gonzaga

    2012-01-01

    Adequate polymerization plays an important role on the longevity of the composite resin restorations. Objectives The aim of this study was to evaluate the effect of light-curing units, curing mode techniques and storage media on sorption, solubility and biaxial flexural strength (BFS) of a composite resin. Material and Methods Two hundred and forty specimens were made of one composite resin (Esthet-X) in a stainless steel mold (2 mm x 8 mm Ø), and divided into 24 groups (n=10) established according to the 4 study factors: light-curing units: quartz tungsten halogen (QTH) lamp and light-emitting diodes (LED); energy densities: 16 J/cm2 and 20 J/cm2; curing modes: conventional (CM) and pulse-delay (PD); and permeants: deionized water and 75% ethanol for 28 days. Sorption and solubility tests were performed according to ISO 4049:2000 specifications. All specimens were then tested for BFS according to ASTM F394-78 specification. Data were analyzed by three-way ANOVA followed by Tukey, Kruskal-Wallis and Mann-Whitney tests (α=0.05). Results In general, no significant differences were found regarding sorption, solubility or BFS means for the light-curing units and curing modes (p>0.05). Only LED unit using 16 J/cm2 and PD using 10 s produced higher sorption and solubility values than QTH. Otherwise, using CM (16 J/cm2), LED produced lower values of BFS than QTH (p<0.05). 75% ethanol permeant produced higher values of sorption and solubility and lower values of BFS than water (p<0.05). Conclusion Ethanol storage media produced more damage on composite resin than water. In general the LED and QTH curing units using 16 and 20 J/cm2 by CM and PD curing modes produced no influence on the sorption, solubility or BFS of the tested resin. PMID:22666845

  2. Macroscopic biaxiality and electric-field-induced rotation of the minor director in the nematic phase of a bent-core liquid crystal

    NASA Astrophysics Data System (ADS)

    Nagaraj, Mamatha; Merkel, K.; Vij, J. K.; Kocot, A.

    2010-09-01

    Biaxiality in the nematic phase has been investigated for the bent-core liquid-crystal para-heptylbenzoate diester, using polarised IR spectroscopy. Anisotropic fluctuations of the nematic director are discussed in terms of the self-assembly of the chiral conformers. The ordering of the minor director for the homeotropicaly aligned sample is found to depend on the rubbing of the substrates of the cell and the amplitude of in-plane electric field. On increasing the in-plane electric field, the rotation of the minor director in the plane of the substrate is observed with an angle of approximately 45°, where initially the minor director is shown to lie along the rubbing direction. It is also shown that on the average the long axis of the molecules is normal to the substrate with surface treatment, with and without rubbing. The electric in-plane field combined with rubbing is shown to induce biaxial order in the nematic phase of a material with negative dielectic anisotropy for the first time.

  3. Surface roughness of MgO thin film and its critical thickness for optimal biaxial texturing by ion-beam-assisted deposition

    SciTech Connect

    Miyata, S.; Ibi, A.; Izumi, T.; Shiohara, Y.

    2011-06-01

    We investigated the deposition time dependences of the in-plane grain alignment ({Delta}{phi}) and the surface roughness (w) of biaxially textured MgO thin films fabricated by ion-beam-assisted deposition (IBAD) and found a strong correlation between them. The time evolution of the surface roughness of IBAD-MgO showed an abrupt increase at the same time corresponding to the beginning of the deterioration in {Delta}{phi}. The roughness versus thickness profiles obtained under different deposition conditions with different assisting ion-beam currents collapsed to a single curve, even though the deposition rates were significantly different in each condition. This implies that the abrupt increase in roughness occurred at the same thickness--of about 4 nm--irrespective of the deposition rate. The result also indicated that the {Delta}{phi} deterioration began with the same thickness of about 4 nm. This ''critical'' thickness of about 4 nm might be related to the completion of the crystallization of the film. Further, deposition beyond the critical thickness, therefore, became merely a homoepitaxial deposition under the ''IBAD'' condition, which was far from optimal because of the ion bombardment and low temperature (no-heating), and thus {Delta}{phi} deteriorated. Based on these considerations, we propose an approach to attain a sharp texture in a IBAD-MgO-based biaxial substrate; moreover, we demonstrated this approach using a two-step deposition process.

  4. General expressions for the refractive indices of absorbing biaxial media as a function of the angle of incidence.

    PubMed

    Alberdi, C; Diñeiro, J M; Hernández, B; Sáenz, C

    2015-02-01

    In this work we obtain general expressions for the complex refractive indices of refracted waves as a function of the angle of incidence in the case of an electromagnetic wave propagating in a transparent isotropic medium that reaches an interface with a biaxial absorbing medium. The biaxial absorbing medium is only required to have a diagonalizable complex dielectric tensor. Obtained expressions can be applied to any orientation of the principal axes and can be specialized for isotropic, uniaxial or biaxial, or transparent or absorbing media. By using these expressions we have also obtained the surface of indices and the surface of absorption coefficients for an example of a biaxial absorbing medium.

  5. Inelastic response of metal matrix composites under biaxial loading

    NASA Technical Reports Server (NTRS)

    Lissenden, C. J.; Mirzadeh, F.; Pindera, M.-J.; Herakovich, C. T.

    1991-01-01

    Theoretical predictions and experimental results were obtained for inelastic response of unidirectional and angle ply composite tubes subjected to axial and torsional loading. The composite material consist of silicon carbide fibers in a titanium alloy matrix. This material is known to be susceptible to fiber matrix interfacial damage. A method to distinguish between matrix yielding and fiber matrix interfacial damage is suggested. Biaxial tests were conducted on the two different layup configurations using an MTS Axial/Torsional load frame with a PC based data acquisition system. The experimentally determined elastic moduli of the SiC/Ti system are compared with those predicted by a micromechanics model. The test results indicate that fiber matrix interfacial damage occurs at relatively low load levels and is a local phenomenon. The micromechanics model used is the method of cells originally proposed by Aboudi. Finite element models using the ABACUS finite element program were used to study end effects and fixture specimen interactions. The results to date have shown good correlation between theory and experiment for response prior to damage initiation.

  6. Automatic biaxial sun tracking mechanism for sun ray utilization devices

    SciTech Connect

    Hansen, P.A.

    1981-08-25

    The instant invention is an automatic biaxial sun tracking mechanism for use with sun ray utilization devices. Said devices are mounted on said invention, said devices forming no specific part of said invention. The invention is comprised of four principal parts: (1) a mount structure for positioning and supporting said sun ray utilization devices, (2) a polar shaft, (3) a declination crankshaft, and (4) suitable connecting members. Operation of the invention is as follows: the daily axis of said polar shaft is oriented parallel to the earth's polar axis. Said connecting members hold in a mutually perpendicular arrangement the daily axis of said polar shaft, the seasonal axis of a pivot pin for said mount structure, and the main journal axis of said declination crankshaft. Said connecting members with attached parts have suitable means to rotate about said daily axis one revolution per day. Said crankshaft has suitable means to rotate about said main journal axis one revolution per year. A suitable linkage, which simultaneously engages said crankshaft and said mount structure, serves to translate the rotary motion of said crankshaft into alternating pivotal motion of said mount structure. Modifications to the basic direct tracking form of the invention may be made for indirect tracking, heavy duty crankshaft and associated parts, and corrective compensation for a variety of rotational means.

  7. Viscoelasticity of brain corpus callosum in biaxial tension

    NASA Astrophysics Data System (ADS)

    Labus, Kevin M.; Puttlitz, Christian M.

    2016-11-01

    Computational models of the brain rely on accurate constitutive relationships to model the viscoelastic behavior of brain tissue. Current viscoelastic models have been derived from experiments conducted in a single direction at a time and therefore lack information on the effects of multiaxial loading. It is also unclear if the time-dependent behavior of brain tissue is dependent on either strain magnitude or the direction of loading when subjected to tensile stresses. Therefore, biaxial stress relaxation and cyclic experiments were conducted on corpus callosum tissue isolated from fresh ovine brains. Results demonstrated the relaxation behavior to be independent of strain magnitude, and a quasi-linear viscoelastic (QLV) model was able to accurately fit the experimental data. Also, an isotropic reduced relaxation tensor was sufficient to model the stress-relaxation in both the axonal and transverse directions. The QLV model was fitted to the averaged stress relaxation tests at five strain magnitudes while using the measured strain history from the experiments. The resulting model was able to accurately predict the stresses from cyclic tests at two strain magnitudes. In addition to deriving a constitutive model from the averaged experimental data, each specimen was fitted separately and the resulting distributions of the model parameters were reported and used in a probabilistic analysis to determine the probability distribution of model predictions and the sensitivity of the model to the variance of the parameters. These results can be used to improve the viscoelastic constitutive models used in computational studies of the brain.

  8. Atomic force microscopy study of biaxially oriented polypropylene films

    NASA Astrophysics Data System (ADS)

    Nie, H.-Y.; Walzak, M. J.; McIntyre, N. S.

    2004-08-01

    Atomic force microscopy (AFM) uses a very sharp pointed mechanical probe to collect real-space morphological information of solid surfaces. AFM was used in this study to image the surface morphology of a biaxially oriented polypropylene film. The polymer film is characterized by a nanometer-scale, fiberlike network structure, which reflects the drawing process used during the fabrication of the film. AFM was used to study polymer-surface treatment to improve wettability by exposing the polymer to ozone with or without ultraviolet (UV) irradiation. Surface-morphology changes observed by AFM are the result of the surface oxidation induced by the treatment. Due to the topographic features of the polymer film, the fiberlike structure has been used to check the performance of the AFM tip. An AFM image is a mixture of the surface morphology and the shape of the AFM tip. Therefore, it is important to check the performance of a tip to ensure that the AFM image collected reflects the true surface features of the sample, rather than contamination on the AFM tip.

  9. Evaporites and strata-bound tungsten mineralization

    SciTech Connect

    Ririe, G.T. )

    1989-02-01

    Discoidal gypsum crystal cavities occur in quartzites that host varying amounts of strata-bound scheelite mineralization near Halls Creek in Western Australia. The host quartzites have been regionally metamorphosed to greenschist facies and are contained within a Middle Proterozoic sequence that includes pelites, mafic and felsic volcanics, and volcaniclastic rocks. Textural, fluid inclusion, and oxygen isotope data indicate that scheelite was present in the host quartzites prior to regional metamorphism. The presence of crystal cavities after gypsum in the quartzites implies an evaporitic origin for this sequence. The continental-sabkha playa basins of the Mojave Desert, California, are suggested to be possible modern analogs-e.g., Searles Lake, where the tungsten content is up to 70 ppm WO{sub 3} in brines and 118 ppm in muds, and exceeds the amount of tungsten in all known deposits in the United States. Metamorphism of a continental evaporitic sequence containing tungsten could produce an assemblage of rocks very similar to those reported from several stratabound tungsten deposits. Some of these, such as at Halls Creek, may be related to original accumulations of tungsten in nonmarine evaporitic environments.

  10. Surface morphologies of He-implanted tungsten

    NASA Astrophysics Data System (ADS)

    Bannister, M. E.; Meyer, F. W.; Hijazi, H.; Unocic, K. A.; Garrison, L. M.; Parish, C. M.

    2016-09-01

    Surface morphologies of tungsten surfaces, both polycrystalline and single-crystal [1 1 0], were investigated using SEM and FIB/SEM techniques after implantations at elevated surfaces temperatures (1200-1300 K) using well-characterized, mono-energetic He ion beams with a wide range of ion energies (218 eV-250 keV). Nanofuzz was observed on polycrystalline tungsten (PCW) following implantation of 100-keV He ions at a flux threshold of 0.9 × 1016 cm-2 s-1, but not following 200-keV implantations with similar fluxes. No nanofuzz formation was observed on single-crystal [1 1 0] tungsten (SCW), despite fluxes exceeding those demonstrated previously to produce nanofuzz on polycrystalline tungsten. Pre-damaging the single-crystal tungsten with implanted C impurity interstitials did not significantly affect the surface morphologies resulting from the high-flux He ion implantations. The main factor leading to the different observed surface structures for the pristine and C-implanted single-crystal W samples appeared to be the peak He ion flux characterizing the different exposures. It was speculated that nanofuzz formation was not observed for any SCW target exposures because of increased incubation fluences required for such targets.

  11. Horizontal carbon nanotube alignment.

    PubMed

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies. PMID:27546174

  12. Horizontal carbon nanotube alignment.

    PubMed

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies.

  13. Orthodontics and Aligners

    MedlinePlus

    ... Repairing Chipped Teeth Teeth Whitening Tooth-Colored Fillings Orthodontics and Aligners Straighten teeth for a healthier smile. Orthodontics When consumers think about orthodontics, braces are the ...

  14. Tidal alignment of galaxies

    NASA Astrophysics Data System (ADS)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  15. Alignability of Optical Interconnects

    NASA Astrophysics Data System (ADS)

    Beech, Russell Scott

    With the continuing drive towards higher speed, density, and functionality in electronics, electrical interconnects become inadequate. Due to optics' high speed and bandwidth, freedom from capacitive loading effects, and freedom from crosstalk, optical interconnects can meet more stringent interconnect requirements. But, an optical interconnect requires additional components, such as an optical source and detector, lenses, holographic elements, etc. Fabrication and assembly of an optical interconnect requires precise alignment of these components. The successful development and deployment of optical interconnects depend on how easily the interconnect components can be aligned and/or how tolerant the interconnect is to misalignments. In this thesis, a method of quantitatively specifying the relative difficulty of properly aligning an optical interconnect is described. Ways of using this theory of alignment to obtain design and packaging guidelines for optical interconnects are examined. The measure of the ease with which an optical interconnect can be aligned, called the alignability, uses the efficiency of power transfer as a measure of alignment quality. The alignability is related to interconnect package design through the overall cost measure, which depends upon various physical parameters of the interconnect, such as the cost of the components and the time required for fabrication and alignment. Through a mutual dependence on detector size, the relationship between an interconnect's alignability and its bandwidth, signal-to-noise ratio, and bit-error -rate is examined. The results indicate that a range of device sizes exists for which given performance threshold values are satisfied. Next, the alignability of integrated planar-optic backplanes is analyzed in detail. The resulting data show that the alignability can be optimized by varying the substrate thickness or the angle of reflection. By including the effects of crosstalk, in a multi-channel backplane, the

  16. Electroanalytical determination of tungsten and molybdenum in proteins.

    PubMed

    Hagedoorn, P L; van't Slot, P; van Leeuwen, H P; Hagen, W R

    2001-10-01

    Recent crystal structure determinations accelerated the progress in the biochemistry of tungsten-containing enzymes. In order to characterize these enzymes, a sensitive determination of this metal in protein-containing samples is necessary. An electroanalytical tungsten determination has successfully been adapted to determine the tungsten and molybdenum content in enzymes. The tungsten and molybdenum content can be measured simultaneously from 1 to 10 microg of purified protein with little or no sample handling. More crude protein samples require precipitation of interfering surface active material with 10% perchloric acid. This method affords the isolation of novel molybdenum- and tungsten-containing proteins via molybdenum and tungsten monitoring of column fractions, without using radioactive isotopes. A screening of soluble proteins from Pyrococcus furiosus for tungsten, using anion-exchange column chromatography to separate the proteins, has been performed. The three known tungsten-containing enzymes from P. furiosus were recovered with this screening.

  17. Some Tungsten Oxidation-Reduction Chemistry: A Paint Pot Titration.

    ERIC Educational Resources Information Center

    Pickering, Miles; Monts, David L.

    1982-01-01

    Reports an oxidation-reduction experiment using tungsten, somewhat analogous to the classical student experiment involving oxidation-reduction of vanadium. Includes experimental procedures, results, and toxicity/cost of tungsten compounds. (Author/JN)

  18. Growth of tungsten oxide on carbon nanowalls templates

    SciTech Connect

    Wang, Hua; Su, Yan; Chen, Shuo; Quan, Xie

    2013-03-15

    Highlights: ► Tungsten oxide deposited on carbon nanowalls by hot filament chemical vapor deposition technique. ► This composite has two-dimensional uniform morphology with a crystalline structure of monoclinic tungsten trioxide. ► Surface photoelectric voltage measurements show that this product has photoresponse properties. - Abstract: In the present work we present a simple approach for coupling tungsten oxide with carbon nanowalls. The two-dimensional carbon nanowalls with open boundaries were grown using plasma enhanced hot filament chemical vapor deposition, and the subsequent tungsten oxide growth was performed in the same equipment by direct heating of a tungsten filament. The tungsten oxide coating is found to have uniform morphology with a crystalline structure of monoclinic tungsten trioxide. Surface photoelectric voltage measurements show that this product has photoresponse properties. The method of synthesis described here provides an operable route to the production of two-dimensional tungsten oxide nanocomposites.

  19. Biaxial order parameter in the homologous series of orthogonal bent-core smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    Sreenilayam, S.; Panarin, Y. P.; Vij, J. K.; Osipov, M.; Lehmann, A.; Tschierske, C.

    2013-07-01

    The fundamental parameter of the uniaxial liquid crystalline state that governs nearly all of its physical properties is the primary orientational order parameter (S) for the long axes of molecules with respect to the director. The biaxial liquid crystals (LCs) possess biaxial order parameters depending on the phase symmetry of the system. In this paper we show that in the first approximation a biaxial orthogonal smectic phase can be described by two primary order parameters: S for the long axes and C for the ordering of the short axes of molecules. The temperature dependencies of S and C are obtained by the Haller's extrapolation technique through measurements of the optical birefringence and biaxiality on a nontilted polar antiferroelectric (Sm-APA) phase of a homologous series of LCs built from the bent-core achiral molecules. For such a biaxial smectic phase both S and C, particularly the temperature dependency of the latter, are being experimentally determined. Results show that S in the orthogonal smectic phase composed of bent cores is higher than in Sm-A calamatic LCs and C is also significantly large.

  20. Element 74, the Wolfram Versus Tungsten Controversy

    SciTech Connect

    Holden,N.E.

    2008-08-11

    Two and a quarter centuries ago, a heavy mineral ore was found which was thought to contain a new chemical element called heavy stone (or tungsten in Swedish). A few years later, the metal was separated from its oxide and the new element (Z=74) was called wolfram. Over the years since that time, both the names wolfram and tungsten were attached to this element in various countries. Sixty years ago, IUPAC chose wolfram as the official name for the element. A few years later, under pressure from the press in the USA, the alternative name tungsten was also allowed by IUPAC. Now the original, official name 'wolfram' has been deleted by IUPAC as one of the two alternate names for the element. The history of this controversy is described here.

  1. Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression.

    PubMed

    Sirry, Mazin S; Butler, J Ryan; Patnaik, Sourav S; Brazile, Bryn; Bertucci, Robbin; Claude, Andrew; McLaughlin, Ron; Davies, Neil H; Liao, Jun; Franz, Thomas

    2016-10-01

    Understanding the passive mechanical properties of infarcted tissue at different healing stages is essential to explore the emerging biomaterial injection-based therapy for myocardial infarction (MI). Although rats have been widely used as animal models in such investigations, the data in literature that quantify the passive mechanical properties of rat heart infarcts is very limited. MI was induced in rats and hearts were harvested immediately (0 day), 7, 14 and 28 days after infarction onset. Left ventricle anterioapical samples were cut and underwent equibiaxial and non equibiaxial tension followed by uniaxial compression mechanical tests. Histological analysis was conducted to confirm MI and to quantify the size of the induced infarcts. Infarcts maintained anisotropy and the nonlinear biaxial and compressive mechanical behaviour throughout the healing phases with the circumferential direction being stiffer than the longitudinal direction. Mechanical coupling was observed between the two axes in all infarct groups. The 0, 7, 14 and 28 days infarcts showed 438, 693, 1048 and 1218kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p=0.0060, 0.0293, and 0.0268 for 0, 7 and 14 days groups). Collagen fibres were found to align in a preferred direction for all infarct groups supporting the observed mechanical anisotropy. The presented data are useful for developing material models for healing infarcts and for setting a baseline for future assessment of emerging mechanical-based MI therapies.

  2. Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression.

    PubMed

    Sirry, Mazin S; Butler, J Ryan; Patnaik, Sourav S; Brazile, Bryn; Bertucci, Robbin; Claude, Andrew; McLaughlin, Ron; Davies, Neil H; Liao, Jun; Franz, Thomas

    2016-10-01

    Understanding the passive mechanical properties of infarcted tissue at different healing stages is essential to explore the emerging biomaterial injection-based therapy for myocardial infarction (MI). Although rats have been widely used as animal models in such investigations, the data in literature that quantify the passive mechanical properties of rat heart infarcts is very limited. MI was induced in rats and hearts were harvested immediately (0 day), 7, 14 and 28 days after infarction onset. Left ventricle anterioapical samples were cut and underwent equibiaxial and non equibiaxial tension followed by uniaxial compression mechanical tests. Histological analysis was conducted to confirm MI and to quantify the size of the induced infarcts. Infarcts maintained anisotropy and the nonlinear biaxial and compressive mechanical behaviour throughout the healing phases with the circumferential direction being stiffer than the longitudinal direction. Mechanical coupling was observed between the two axes in all infarct groups. The 0, 7, 14 and 28 days infarcts showed 438, 693, 1048 and 1218kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p=0.0060, 0.0293, and 0.0268 for 0, 7 and 14 days groups). Collagen fibres were found to align in a preferred direction for all infarct groups supporting the observed mechanical anisotropy. The presented data are useful for developing material models for healing infarcts and for setting a baseline for future assessment of emerging mechanical-based MI therapies. PMID:27434651

  3. 40 CFR 721.10168 - Cesium tungsten oxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  4. 40 CFR 721.10168 - Cesium tungsten oxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  5. 40 CFR 721.10168 - Cesium tungsten oxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  6. 40 CFR 721.10168 - Cesium tungsten oxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  7. 40 CFR 721.10168 - Cesium tungsten oxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Cesium tungsten oxide. 721.10168... Substances § 721.10168 Cesium tungsten oxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as cesium tungsten oxide (PMN P-08-275; CAS No....

  8. Ultra-broad band absorber made by tungsten and aluminium

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhao, Ding; Li, Qiang; Qiu, Min

    2016-01-01

    A broadband absorber comprising tungsten cubic arrays, a alumina layer and a tungsten film, is numerically and experimentally investigated, which exhibits near-unity absorption of visible and near-infrared light from 400 nm to 1150 nm. Benefiting from high melting points of tungsten and alumina, this device has great application potential in solar cells and thermal emission.

  9. Raman scattering from rapid thermally annealed tungsten silicide

    NASA Technical Reports Server (NTRS)

    Kumar, Sandeep; Dasgupta, Samhita; Jackson, Howard E.; Boyd, Joseph T.

    1987-01-01

    Raman scattering as a technique for studying the formation of tungsten silicide is presented. The tungsten silicide films have been formed by rapid thermal annealing of thin tungsten films sputter deposited on silicon substrates. The Raman data are interpreted by using data from resistivity measurements, Auger and Rutherford backscattering measurements, and scanning electron microscopy.

  10. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    NASA Astrophysics Data System (ADS)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  11. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry

    NASA Astrophysics Data System (ADS)

    Aho, Johnathon M.; Qiang, Bo; Wigle, Dennis A.; Tschumperlin, Daniel J.; Urban, Matthew W.

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal–submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa–submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered

  12. Biaxial flexural strength of bilayered zirconia using various veneering ceramics

    PubMed Central

    Chantranikul, Natravee

    2015-01-01

    PURPOSE The aim of this study was to evaluate the biaxial flexural strength (BFS) of one zirconia-based ceramic used with various veneering ceramics. MATERIALS AND METHODS Zirconia core material (Katana) and five veneering ceramics (Cerabien ZR; CZR, Lava Ceram; LV, Cercon Ceram Kiss; CC, IPS e.max Ceram; EM and VITA VM9; VT) were selected. Using the powder/liquid layering technique, bilayered disk specimens (diameter: 12.50 mm, thickness: 1.50 mm) were prepared to follow ISO standard 6872:2008 into five groups according to veneering ceramics as follows; Katana zirconia veneering with CZR (K/CZR), Katana zirconia veneering with LV (K/LV), Katana zirconia veneering with CC (K/CC), Katana zirconia veneering with EM (K/EM) and Katana zirconia veneering with VT (K/VT). After 20,000 thermocycling, load tests were conducted using a universal testing machine (Instron). The BFS were calculated and analyzed with one-way ANOVA and Tukey HSD (α=0.05). The Weibull analysis was performed for reliability of strength. The mode of fracture and fractured surface were observed by SEM. RESULTS It showed that K/CC had significantly the highest BFS, followed by K/LV. BFS of K/CZR, K/EM and K/VT were not significantly different from each other, but were significantly lower than the other two groups. Weibull distribution reported the same trend of reliability as the BFS results. CONCLUSION From the result of this study, the BFS of the bilayered zirconia/veneer composite did not only depend on the Young's modulus value of the materials. Further studies regarding interfacial strength and sintering factors are necessary to achieve the optimal strength. PMID:26576251

  13. Tuning magnetism by biaxial strain in native ZnO.

    PubMed

    Peng, Chengxiao; Wang, Yuanxu; Cheng, Zhenxiang; Zhang, Guangbiao; Wang, Chao; Yang, Gui

    2015-07-01

    Magnetic ZnO, one of the most important diluted magnetic semiconductors (DMS), has attracted great scientific interest because of its possible technological applications in optomagnetic devices. Magnetism in this material is usually delicately tuned by the doping level, dislocations, and local structures. The rational control of magnetism in ZnO is a highly attractive approach for practical applications. Here, the tuning effect of biaxial strain on the d(0) magnetism of native imperfect ZnO is demonstrated through first-principles calculations. Our calculation results show that strain conditions have little effect on the defect formation energy of Zn and O vacancies in ZnO, but they do affect the magnetism significantly. For a cation vacancy, increasing the compressive strain will obviously decrease its magnetic moment, while tensile strain cannot change the moment, which remains constant at 2 μB. For a singly charged anion vacancy, however, the dependence of the magnetic moment on strain is opposite to that of the Zn vacancy. Furthermore, the ferromagnetic state is always present, irrespective of the strain type, for ZnO with two zinc vacancies, 2VZns. A large tensile strain is favorable for improving the Curie temperature and realizing room temperature ferromagnetism for ZnO-based native semiconductors. For ZnO with two singly charged oxygen vacancies, 2Vs, no ferromagnetic ordering can be observed. Our work points the way to the rational design of materials beyond ZnO with novel non-intrinsic functionality by simply tuning the strain in a thin film form.

  14. Modeling of biaxial gimbal-less MEMS scanning mirrors

    NASA Astrophysics Data System (ADS)

    von Wantoch, Thomas; Gu-Stoppel, Shanshan; Senger, Frank; Mallas, Christian; Hofmann, Ulrich; Meurer, Thomas; Benecke, Wolfgang

    2016-03-01

    One- and two-dimensional MEMS scanning mirrors for resonant or quasi-stationary beam deflection are primarily known as tiny micromirror devices with aperture sizes up to a few Millimeters and usually address low power applications in high volume markets, e.g. laser beam scanning pico-projectors or gesture recognition systems. In contrast, recently reported vacuum packaged MEMS scanners feature mirror diameters up to 20 mm and integrated high-reflectivity dielectric coatings. These mirrors enable MEMS based scanning for applications that require large apertures due to optical constraints like 3D sensing or microscopy as well as for high power laser applications like laser phosphor displays, automotive lighting and displays, 3D printing and general laser material processing. This work presents modelling, control design and experimental characterization of gimbal-less MEMS mirrors with large aperture size. As an example a resonant biaxial Quadpod scanner with 7 mm mirror diameter and four integrated PZT (lead zirconate titanate) actuators is analyzed. The finite element method (FEM) model developed and computed in COMSOL Multiphysics is used for calculating the eigenmodes of the mirror as well as for extracting a high order (n < 10000) state space representation of the mirror dynamics with actuation voltages as system inputs and scanner displacement as system output. By applying model order reduction techniques using MATLABR a compact state space system approximation of order n = 6 is computed. Based on this reduced order model feedforward control inputs for different, properly chosen scanner displacement trajectories are derived and tested using the original FEM model as well as the micromirror.

  15. Nondestructive measurement of esophageal biaxial mechanical properties utilizing sonometry.

    PubMed

    Aho, Johnathon M; Qiang, Bo; Wigle, Dennis A; Tschumperlin, Daniel J; Urban, Matthew W

    2016-07-01

    Malignant esophageal pathology typically requires resection of the esophagus and reconstruction to restore foregut continuity. Reconstruction options are limited and morbid. The esophagus represents a useful target for tissue engineering strategies based on relative simplicity in comparison to other organs. The ideal tissue engineered conduit would have sufficient and ideally matched mechanical tolerances to native esophageal tissue. Current methods for mechanical testing of esophageal tissues both in vivo and ex vivo are typically destructive, alter tissue conformation, ignore anisotropy, or are not able to be performed in fluid media. The aim of this study was to investigate biomechanical properties of swine esophageal tissues through nondestructive testing utilizing sonometry ex vivo. This method allows for biomechanical determination of tissue properties, particularly longitudinal and circumferential moduli and strain energy functions. The relative contribution of mucosal-submucosal layers and muscular layers are compared to composite esophagi. Swine thoracic esophageal tissues (n  =  15) were tested by pressure loading using a continuous pressure pump system to generate stress. Preconditioning of tissue was performed by pressure loading with the pump system and pre-straining the tissue to in vivo length before data was recorded. Sonometry using piezocrystals was utilized to determine longitudinal and circumferential strain on five composite esophagi. Similarly, five mucosa-submucosal and five muscular layers from thoracic esophagi were tested independently. This work on esophageal tissues is consistent with reported uniaxial and biaxial mechanical testing and reported results using strain energy theory and also provides high resolution displacements, preserves native architectural structure and allows assessment of biomechanical properties in fluid media. This method may be of use to characterize mechanical properties of tissue engineered esophageal

  16. Equipment simulation of selective tungsten deposition

    SciTech Connect

    Werner, C.; Ulacia, J.I.; Hopfmann, C.; Flynn, P. )

    1992-02-01

    This paper presents the numerical modeling of a cold wall reactor for selective tungsten chemical vapor deposition. In a two dimensional simulation the mass and heat transfer equations were solved considering the five chemical species H{sub 2}, WF{sub 6}, HF, WF{sub x}, and SiF{sub y}. Detailed models for multicomponent diffusion and for the autocatalytic tungsten nucleation process were implemented. Model results are in good agreement with experimental findings. The simulations are used to study the impact of reactor design on selectivity.

  17. Hole-Aligning Tool

    NASA Technical Reports Server (NTRS)

    Collins, Frank A.; Saude, Frank; Sep, Martin J.

    1996-01-01

    Tool designed for use in aligning holes in plates or other structural members to be joined by bolt through holes. Holes aligned without exerting forces perpendicular to planes of holes. Tool features screw-driven-wedge design similar to (but simpler than) that of some automotive exhaust-pipe-expanding tools.

  18. Bandgap-customizable germanium using lithographically determined biaxial tensile strain for silicon-compatible optoelectronics.

    PubMed

    Sukhdeo, David S; Nam, Donguk; Kang, Ju-Hyung; Brongersma, Mark L; Saraswat, Krishna C

    2015-06-29

    Strain engineering has proven to be vital for germanium-based photonics, in particular light emission. However, applying a large permanent biaxial tensile strain to germanium has been a challenge. We present a simple, CMOS-compatible technique to conveniently induce a large, spatially homogenous strain in circular structures patterned within germanium nanomembranes. Our technique works by concentrating and amplifying a pre-existing small strain into a circular region. Biaxial tensile strains as large as 1.11% are observed by Raman spectroscopy and are further confirmed by photoluminescence measurements, which show enhanced and redshifted light emission from the strained germanium. Our technique allows the amount of biaxial strain to be customized lithographically, allowing the bandgaps of different germanium structures to be independently customized in a single mask process.

  19. Phase Shift of Polarized Light after Transmission through a Biaxial Anisotropic Thin Film

    NASA Astrophysics Data System (ADS)

    Hou, Yong-Qiang; Li, Xu; He, Kai; Qi, Hong-Ji; Yi, Kui; Shao, Jian-Da

    2013-01-01

    Based on the theoretical analysis of biaxial birefringent thin films with characteristic matrix method, we investigate the phase shift on transmission of a tilted columnar biaxial film at normal and oblique incidence over 300-1200 nm for s- and p-polarized waves. Compared with the simplified calculation method, the interference effects of the birefringent thin film are considered to yield more accurate results. The quarter wavelength phase shift calculated with the characteristic matrix method is consistent with that monitored with in situ measurement by two-angle ellipsometry, which validates our complied program for the calculation of the phase shift of the biaxial anisotropic thin film. Furthermore, the characteristic matrix method can be easily used to obtain continuous adjustable phase retardation at oblique incidence, whereas the simplified calculation method is valid for the case of normal incidence. A greater generality and superiority of the characteristic matrix method is presented.

  20. Biaxial texture development in aluminum nitride layers during off-axis sputter deposition

    SciTech Connect

    Deng Ruopeng; Muralt, Paul; Gall, Daniel

    2012-09-15

    Polycrystalline aluminum nitride (AlN) layers were deposited by pulsed-dc reactive magnetron sputtering from a variable deposition angle {alpha} = 0 Degree-Sign -84 Degree-Sign in 5 mTorr pure N{sub 2} at room temperature. X-ray diffraction pole figure analyses show that layers deposited from a normal angle ({alpha} = 0 Degree-Sign ) exhibit fiber texture, with a random in-plane grain orientation and the c-axis tilted by 42 Degree-Sign {+-} 2 Degree-Sign off the substrate normal, yielding wurtzite AlN grains with the {l_brace}1012{r_brace} plane approximately parallel ({+-}2 Degree-Sign ) to the substrate surface. However, as {alpha} is increased to 45 Degree-Sign , two preferred in-plane grain orientations emerge, with populations I and II having the c-axis tilted toward and away from the deposition flux, by 53 Degree-Sign {+-} 2 Degree-Sign and 47 Degree-Sign {+-} 1 Degree-Sign off the substrate normal, respectively. Increasing {alpha} further to 65 Degree-Sign and 84 Degree-Sign , results in the development of a single population II with a 43 Degree-Sign {+-} 1 Degree-Sign tilt. This developing biaxial texture is attributed to a competitive growth mode under conditions where the adatom mobility is sufficient to cause intergrain mass transport, but insufficient for the thermodynamically favored low energy {l_brace}0001{r_brace} planes to align parallel to the layer surface. Consequently, AlN nuclei are initially randomly oriented and form a kinetically determined crystal habit exposing {l_brace}0001{r_brace} and {l_brace}1120{r_brace} facets. The expected direction of its highest growth rate is 49 Degree-Sign {+-} 5 Degree-Sign tilted relative to the c-axis, in good agreement with the 42 Degree-Sign -53 Degree-Sign measured tilt. The in-plane preferred orientation for {alpha} > 0 Degree-Sign is well explained by the orientation dependence in the cross section of the asymmetric pyramidal nuclei to capture directional deposition flux. The observed tilt is ideal for

  1. Chemical Solution Based Epitaxial Oxide Filmes on Biaxially Textured Ni-W Substrates with Improved Out-of-Plane Texture for YBCO Coated Conductors

    SciTech Connect

    Bhuiyan, Md S; Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan

    2007-01-01

    Epitaxial films of rare-earth (RE) niobates (where the rare earth includes La, Ce, and Nd) and lanthanum tantalate with pyrochlore structures were grown directly on biaxially textured nickel-3 at.% tungsten (Ni-W) substrates using a chemical solution deposition (CSD) process. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis revealed the surface morphology of the films to be smooth and homogeneous. Detailed X-ray diffraction analysis showed that the films of pyrochlore RE niobate and La-tantalate are highly textured with cube-on-cube epitaxy. The overall texture quality of the films was investigated by measuring the full-width half-maximum (FWHM) of the (004) and (222) rocking curves. We observed a sharper texture for both lanthanum niobate (La{sub 3}NbO{sub 7}) and lanthanum tantalate (La{sub 3}TaO{sub 7}) films compared to the underlying Ni-W substrate, though they have a larger lattice misfit with the Ni-W substrates. These results were comparable to the texture improvement observed in vacuum-deposited Y{sub 2}O{sub 3} seed layers. Texture improvement in the seed layer is the key towards obtaining YBCO films with a higher critical current density. Hence, solution-deposited La{sub 3}NbO{sub 7} and La{sub 3}TaO{sub 7} films can be used as a seed layer towards developing all metalorganic-deposited (MOD) buffer/YBCO architectures.

  2. Biaxial Stretch Improves Elastic Fiber Maturation, Collagen Arrangement, and Mechanical Properties in Engineered Arteries.

    PubMed

    Huang, Angela H; Balestrini, Jenna L; Udelsman, Brooks V; Zhou, Kevin C; Zhao, Liping; Ferruzzi, Jacopo; Starcher, Barry C; Levene, Michael J; Humphrey, Jay D; Niklason, Laura E

    2016-06-01

    Tissue-engineered blood vessels (TEVs) are typically produced using the pulsatile, uniaxial circumferential stretch to mechanically condition and strengthen the arterial grafts. Despite improvements in the mechanical integrity of TEVs after uniaxial conditioning, these tissues fail to achieve critical properties of native arteries such as matrix content, collagen fiber orientation, and mechanical strength. As a result, uniaxially loaded TEVs can result in mechanical failure, thrombus, or stenosis on implantation. In planar tissue equivalents such as artificial skin, biaxial loading has been shown to improve matrix production and mechanical properties. To date however, multiaxial loading has not been examined as a means to improve mechanical and biochemical properties of TEVs during culture. Therefore, we developed a novel bioreactor that utilizes both circumferential and axial stretch that more closely simulates loading conditions in native arteries, and we examined the suture strength, matrix production, fiber orientation, and cell proliferation. After 3 months of biaxial loading, TEVs developed a formation of mature elastic fibers that consisted of elastin cores and microfibril sheaths. Furthermore, the distinctive features of collagen undulation and crimp in the biaxial TEVs were absent in both uniaxial and static TEVs. Relative to the uniaxially loaded TEVs, tissues that underwent biaxial loading remodeled and realigned collagen fibers toward a more physiologic, native-like organization. The biaxial TEVs also showed increased mechanical strength (suture retention load of 303 ± 14.53 g, with a wall thickness of 0.76 ± 0.028 mm) and increased compliance. The increase in compliance was due to combinatorial effects of mature elastic fibers, undulated collagen fibers, and collagen matrix orientation. In conclusion, biaxial stretching is a potential means to regenerate TEVs with improved matrix production, collagen organization, and mechanical

  3. Uniaxial and biaxial tensile stress-stretch response of human linea alba.

    PubMed

    Cooney, Gerard M; Lake, Spencer P; Thompson, Dominic M; Castile, Ryan M; Winter, Des C; Simms, Ciaran K

    2016-10-01

    There are few studies on the stress-stretch behaviour of human linea alba, yet understanding the mechanics of this tissue is important for developing better methods of abdominal wound closure. Published data focuses mainly on porcine linea alba and for human tissue there are conflicting results and no bi-axial data available. This variability is likely due to challenges with the physical dimensions of the tissue and differences in experimental methodology. This study focussed on the tensile mechanical characterisation of the human linea alba using uniaxial and equi-load biaxial testing performed using image-based strain measurement methods. Thirteen freshly frozen human cadaveric abdominal walls were obtained and used to prepare 7 samples in both the transverse and longitudinal directions for uniaxial testing, and 13 square samples for bi-axial testing. The results showed significant anisotropy and for the equi-load biaxial tests the deformation was heavily biased in the longitudinal direction. In comparison with similar tests on porcine tissue from a previous study, it was found that the response of porcine linea alba to uniaxial loading is similar to that of human linea alba, with no statistically significant differences observed. Under biaxial loading human and porcine linea showed no statistical significance in the difference between their means in the transverse direction. However, a significant difference was observed in the longitudinal direction, and further study of the respective tissue structures is needed to better understand this result. These results provide the first data on the biaxial tensile properties of human linea alba and can aid in an improved assessment of wound closure mechanics. PMID:27367944

  4. Aligned selenium microtubes array: Synthesis, growth mechanism and photoelectrical properties

    NASA Astrophysics Data System (ADS)

    Filippo, Emanuela; Manno, Daniela; Serra, Antonio

    2011-06-01

    Aligned selenium microtubes array vertically grown on a silicon substrate was synthesized in a tubular furnace under argon flow at an evaporation temperature of 300 °C. The microtubes were characterized by Raman spectroscopy, X-ray diffraction, UV-vis spectroscopy, scanning and transmission electron microscopy. The photoelectrical properties of the microtube array with light were investigated. It was found a stable relative increase of the conductivity by 180% when the sample was taken from the dark and exposed with tungsten light and a sharp on/off switching behavior. These results hold promise for the fabrication of microtubes-detector arrays.

  5. Scratch resistance anisotropy in biaxially oriented polypropylene and poly(ethylene terephthalate) films

    NASA Astrophysics Data System (ADS)

    Nie, H.-Y.; Walzak, M. J.; McIntyre, N. S.

    2006-12-01

    Using a diamond-tipped stylus, scratch tests were conducted on biaxially oriented polypropylene and poly(ethylene terephthalate) films in the two draw directions, i.e., the machine-direction (MD) and the transverse-direction (TD) along which the draw ratios are different. Atomic force microscopy study of those scratches revealed a significant anisotropy in the scratch resistance between the MD and TD for both of the polymer films. We confirmed that the scratch resistance of polymer strands is closely related to the draw ratios, which determine the mechanical strength and optical clarity of biaxially oriented polymer films.

  6. Redox potentials of tungsten and its alloying partners-fundamentals of tungsten determination by redox titration.

    PubMed

    Wünsch, G

    1980-08-01

    The fundamentals of tungsten determination by redox titration in hydrochloric acid medium are describe. Conditional redox potentials are given for W, Cr, V, Fe, Ti, Mo, Cu and Sn as a function of HCl concentration. The basic experimental conditions and the difference in conditional potentials required for consecutive titrations are discussed. Any mixture of tungsten with other metals can be analysed without separation if it does not contain both Cr and Ti or both Mo and V.

  7. Thermal cycling and high power density hydrogen ion beam irradiation of tungsten layers on tungsten substrate

    NASA Astrophysics Data System (ADS)

    Airapetov, A. A.; Begrambekov, L. B.; Gretskaya, I. Yu; Grunin, A. V.; Dyachenko, M. Yu; Puntakov, N. A.; Sadovskiy, Ya A.

    2016-09-01

    Tungsten layers with iron impurity were deposited on tungsten substrates modeling re-deposited layers in a fusion device. The samples were tested by thermocycling and hydrogen ion beam tests. Thermocycling revealed globule formation on the surface. The size of the globules depended on iron impurity content in the coating deposited. Pore formation was observed which in some cases lead to exfoliation of the coatings. Hydrogen ion irradiation lead to formation of blisters on the coating and finally its exfoliation.

  8. Spinarc gas tungsten arc torch holder

    NASA Technical Reports Server (NTRS)

    Brace, D. F.; Crockett, J. L.

    1970-01-01

    Semiautomatic welding torch enables operator to control arc length, torch angle, and spring tension when welding small diameter aluminum tubing. Tungsten is preset for the weld to make arc initiation easier and to eliminate searching for the joint through a dark welding lens.

  9. Joining of Tungsten Armor Using Functional Gradients

    SciTech Connect

    John Scott O'Dell

    2006-12-31

    The joining of low thermal expansion armor materials such as tungsten to high thermal expansion heat sink materials has been a major problem in plasma facing component (PFC) development. Conventional planar bonding techniques have been unable to withstand the high thermal induced stresses resulting from fabrication and high heat flux testing. During this investigation, innovative functional gradient joints produced using vacuum plasma spray forming techniques have been developed for joining tungsten armor to copper alloy heat sinks. A model was developed to select the optimum gradient architecture. Based on the modeling effort, a 2mm copper rich gradient was selected. Vacuum plasma pray parameters and procedures were then developed to produce the functional gradient joint. Using these techniques, dual cooling channel, medium scale mockups (32mm wide x 400mm length) were produced with vacuum plasma spray formed tungsten armor. The thickness of the tungsten armor was up to 5mm thick. No evidence of debonding at the interface between the heat sink and the vacuum plasma sprayed material was observed.

  10. Gas tungsten arc welder with electrode grinder

    DOEpatents

    Christiansen, David W.; Brown, William F.

    1984-01-01

    A welder for automated closure of fuel pins by a gas tungsten arc process in which a rotating length of cladding is positioned adjacent a welding electrode in a sealed enclosure. An independently movable axial grinder is provided in the enclosure for refurbishing the used electrode between welds.

  11. Aminobisphenolate supported tungsten disulphido and dithiolene complexes.

    PubMed

    Salojärvi, E; Peuronen, A; Sillanpää, R; Damlin, P; Kivelä, H; Lehtonen, A

    2015-05-28

    Dioxotungsten(vi) complexes with tetradentate amino bisphenolates were converted into the corresponding Cs-symmetric amino bisphenolate disulphido complexes by a reaction with either Lawesson's reagent or P2S5. Further reaction with diethyl acetylenedicarboxylate leads to the formation of diamagnetic tungsten(iv) dithiolene compounds. The syntheses, crystal structures, spectroscopic and electrochemical characterization of such disulphido and dithiolene complexes are presented.

  12. Detonation in tungsten-loaded HMX

    SciTech Connect

    Goldstein, S.; Mader, C.L.

    1985-01-01

    The detonation behavior of X-0233, a heavily tungsten-loaded HMX explosive, has been studied using failure diameter measurements, plate dents, and aquarium tests. A model with features resembling those of a weak detonation describe the experimental results. 7 refs., 10 figs.

  13. Gas-driven permeation of deuterium through tungsten and tungsten alloys

    DOE PAGES

    Buchenauer, Dean A.; Karnesky, Richard A.; Fang, Zhigang Zak; Ren, Chai; Oya, Yasuhisa; Otsuka, Teppei; Yamauchi, Yuji; Whaley, Josh A.

    2016-03-25

    Here, to address the transport and trapping of hydrogen isotopes, several permeation experiments are being pursued at both Sandia National Laboratories (deuterium gas-driven permeation) and Idaho National Laboratories (tritium gas- and plasma-driven tritium permeation). These experiments are in part a collaboration between the US and Japan to study the performance of tungsten at divertor relevant temperatures (PHENIX). Here we report on the development of a high temperature (≤1150 °C) gas-driven permeation cell and initial measurements of deuterium permeation in several types of tungsten: high purity tungsten foil, ITER-grade tungsten (grains oriented through the membrane), and dispersoid-strengthened ultra-fine grain (UFG) tungstenmore » being developed in the US. Experiments were performed at 500–1000 °C and 0.1–1.0 atm D2 pressure. Permeation through ITER-grade tungsten was similar to earlier W experiments by Frauenfelder (1968–69) and Zaharakov (1973). Data from the UFG alloy indicates marginally higher permeability (< 10×) at lower temperatures, but the permeability converges to that of the ITER tungsten at 1000 °C. The permeation cell uses only ceramic and graphite materials in the hot zone to reduce the possibility for oxidation of the sample membrane. Sealing pressure is applied externally, thereby allowing for elevation of the temperature for brittle membranes above the ductile-to-brittle transition temperature.« less

  14. Electrokinetic treatment of firing ranges containing tungsten-contaminated soils.

    PubMed

    Braida, Washington; Christodoulatos, Christos; Ogundipe, Adebayo; Dermatas, Dimitris; O'Connor, Gregory

    2007-11-19

    Tungsten-based alloys and composites are being used and new formulations are being considered for use in the manufacturing of different types of ammunition. The use of tungsten heavy alloys (WHA) in new munitions systems and tungsten composites in small caliber ammunition could potentially release substantial amounts of this element into the environment. Although tungsten is widely used in industrial and military applications, tungsten's potential environmental and health impacts have not been thoroughly addressed. This necessitates the research and development of remedial technologies to contain and/or remove tungsten from soils that may serve as a source for water contamination. The current work investigates the feasibility of using electrokinetics for the remediation of tungsten-contaminated soils in the presence of other heavy metals of concern such as Cu and Pb with aim to removing W from the soil while stabilizing in situ, Pb and Cu. PMID:17686582

  15. Precision alignment device

    DOEpatents

    Jones, Nelson E.

    1990-01-01

    Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam.

  16. Precision alignment device

    DOEpatents

    Jones, N.E.

    1988-03-10

    Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam. 5 figs.

  17. Galaxy Alignments: An Overview

    NASA Astrophysics Data System (ADS)

    Joachimi, Benjamin; Cacciato, Marcello; Kitching, Thomas D.; Leonard, Adrienne; Mandelbaum, Rachel; Schäfer, Björn Malte; Sifón, Cristóbal; Hoekstra, Henk; Kiessling, Alina; Kirk, Donnacha; Rassat, Anais

    2015-11-01

    The alignments between galaxies, their underlying matter structures, and the cosmic web constitute vital ingredients for a comprehensive understanding of gravity, the nature of matter, and structure formation in the Universe. We provide an overview on the state of the art in the study of these alignment processes and their observational signatures, aimed at a non-specialist audience. The development of the field over the past one hundred years is briefly reviewed. We also discuss the impact of galaxy alignments on measurements of weak gravitational lensing, and discuss avenues for making theoretical and observational progress over the coming decade.

  18. Radiative Grain Alignment

    NASA Astrophysics Data System (ADS)

    Andersson, B. G.

    2015-12-01

    Polarization due to aligned dust grains was discovered in the interstellar medium more than 60 years ago. A quantitative, observationally well tested theory of the phenomenon has finally emerged in the last decade, promising not only an improved understanding of interstellar magnetic fields, but new tools for studying the dust environments and grain characteristics. This Radiative Alignment Torque (RAT) theory also has many potential applications in solar system physics, including for comet dust characteristics. I will review the main aspects of the theory and the observational tests performed to date, as well as some of the new possibilities for using polarization as a tool to study dust and its environment, with RAT alignment.

  19. Hybrid vehicle motor alignment

    DOEpatents

    Levin, Michael Benjamin

    2001-07-03

    A rotor of an electric motor for a motor vehicle is aligned to an axis of rotation for a crankshaft of an internal combustion engine having an internal combustion engine and an electric motor. A locator is provided on the crankshaft, a piloting tool is located radially by the first locator to the crankshaft. A stator of the electric motor is aligned to a second locator provided on the piloting tool. The stator is secured to the engine block. The rotor is aligned to the crankshaft and secured thereto.

  20. Pairwise Sequence Alignment Library

    SciTech Connect

    Jeff Daily, PNNL

    2015-05-20

    Vector extensions, such as SSE, have been part of the x86 CPU since the 1990s, with applications in graphics, signal processing, and scientific applications. Although many algorithms and applications can naturally benefit from automatic vectorization techniques, there are still many that are difficult to vectorize due to their dependence on irregular data structures, dense branch operations, or data dependencies. Sequence alignment, one of the most widely used operations in bioinformatics workflows, has a computational footprint that features complex data dependencies. The trend of widening vector registers adversely affects the state-of-the-art sequence alignment algorithm based on striped data layouts. Therefore, a novel SIMD implementation of a parallel scan-based sequence alignment algorithm that can better exploit wider SIMD units was implemented as part of the Parallel Sequence Alignment Library (parasail). Parasail features: Reference implementations of all known vectorized sequence alignment approaches. Implementations of Smith Waterman (SW), semi-global (SG), and Needleman Wunsch (NW) sequence alignment algorithms. Implementations across all modern CPU instruction sets including AVX2 and KNC. Language interfaces for C/C++ and Python.

  1. Pairwise Sequence Alignment Library

    2015-05-20

    Vector extensions, such as SSE, have been part of the x86 CPU since the 1990s, with applications in graphics, signal processing, and scientific applications. Although many algorithms and applications can naturally benefit from automatic vectorization techniques, there are still many that are difficult to vectorize due to their dependence on irregular data structures, dense branch operations, or data dependencies. Sequence alignment, one of the most widely used operations in bioinformatics workflows, has a computational footprintmore » that features complex data dependencies. The trend of widening vector registers adversely affects the state-of-the-art sequence alignment algorithm based on striped data layouts. Therefore, a novel SIMD implementation of a parallel scan-based sequence alignment algorithm that can better exploit wider SIMD units was implemented as part of the Parallel Sequence Alignment Library (parasail). Parasail features: Reference implementations of all known vectorized sequence alignment approaches. Implementations of Smith Waterman (SW), semi-global (SG), and Needleman Wunsch (NW) sequence alignment algorithms. Implementations across all modern CPU instruction sets including AVX2 and KNC. Language interfaces for C/C++ and Python.« less

  2. Contact barrier application of selective CVD-tungsten in a bipolar device

    NASA Astrophysics Data System (ADS)

    Körner, H.; Bertagnolli, E.; Maier, I.

    1989-09-01

    A selective CVD-tungsten (SCVD-W) contact barrier of 200 nm thickness, deposited via hydrogen reduction of WF 6, has been integrated in a bipolar polysilicon self-aligned transistor instead of the proven PtSi/TiW barrier. In order to restrict the silicon consumption at the highly doped polysilicon electrodes as much as possible, a temperature-ramped deposition process has been evaluated which uses a thin tungsten layer, created at 25°C via silicon reduction, as in situ barrier for the further deposition. The integrity of the tungsten diffusion barrier in the poly Si/SCVD-W/AlSiCu metallization has been tested after different postannealing cycles at 450°C. SEM and TEM investigations reveal a relatively smooth tungsten/silicon interface with ≤ 30 nm vertical Si consumption. No clear evidence of wormhole formation could be detected. The input and transfer characteristics of the transistor employing the SCVD-W barrier show an almost ideal performance, evidencing the absence of any degradation effect. The forward current gain is found to be constant over nearly six decades of collector current variation. The emitter-base diode breakdown occurs at a reverse voltage of 6.5 V, which is in close agreement with the best values for the reference metallization. In addition, low contact resistances ( R c( n+)=0.78 Ω ; R c( p+)=3.85 Ω) to the highly doped 8 × 2 Ωm 2 poly-Si contacts are reported which are stable even after a 60 min post-annealing treatment.

  3. Surface damage and structure evolution of recrystallized tungsten exposed to ELM-like transient loads

    NASA Astrophysics Data System (ADS)

    Yuan, Y.; Du, J.; Wirtz, M.; Luo, G.-N.; Lu, G.-H.; Liu, W.

    2016-03-01

    Surface damage and structure evolution of the full tungsten ITER divertor under transient heat loads is a key concern for component lifetime and plasma operations. Recrystallization caused by transients and steady-state heat loads can lead to degradation of the material properties and is therefore one of the most serious issues for tungsten armor. In order to investigate the thermal response of the recrystallized tungsten under edge localized mode-like transient thermal loads, fully recrystallized tungsten samples with different average grain sizes are exposed to cyclic thermal shocks in the electron beam facility JUDITH 1. The results indicate that not only does the microstructure change due to recrystallization, but that the surface residual stress induced by mechanical polishing strongly influences the surface cracking behavior. The stress-free surface prepared by electro-polishing is shown to be more resistant to cracking than the mechanically polished one. The resulting surface roughness depends largely on the loading conditions instead of the recrystallized-grain size. As the base temperature increases from room temperature to 400 °C, surface roughening mainly due to the shear bands in each grain becomes more pronounced, and sub-grains (up to 3 μm) are simultaneously formed in the sub-surface. The directions of the shear bands exhibit strong grain-orientation dependence, and they are generally aligned with the traces of {1 1 2} twin habit planes. The results suggest that twinning deformation and dynamic recrystallization represent the predominant mechanism for surface roughening and related microstructure evolution.

  4. In situ biaxial rotation at low-temperatures in high magnetic fields

    SciTech Connect

    Selby, N. S.; Crawford, M.; Tracy, L.; Reno, J. L.; Pan, W.

    2014-09-15

    We report the design, construction, and characterization of a biaxial sample rotation stage for use in a cryogenic system for orientation-dependent studies of anisotropic electronic transport phenomena at low temperatures and high magnetic fields. Our apparatus allows for continuous rotation of a sample about two axes, both independently and simultaneously.

  5. Application of hysteresis modeling to magnetic techniques for monitoring biaxial stress

    SciTech Connect

    Sablik, M.J.; Burkhardt, G.L.; Kwun, H.

    1993-12-31

    A probe, consisting of two excitation coils and a detection coil wrapped around a core with a Hall probe between the pole pieces, has been used to measure indirectly the influence of biaxial stress on the magnetic properties of a ferromagnetic specimen, in this case annealed SAE-4130 steel. Properties measured indirectly included remanence, coercivity, and first, third and fifth harmonic amplitudes. The properties were extracted from the voltage measured across the detection coil and incorporate the magnetic influence of the soft iron core, but with the effect of air gap variation between pole piece and sample kept to a controlled range. Results were compared to a micromagnetic model for the effect of biaxial stress on hysteresis and on magnetic properties. The micromagnetic model is a modified version of a model previously employed by Schneider et al. The experimental remanence variation due to biaxial stress compared very well to the predictions of the model. Furthermore, the model predict,s and experiment bears out, that the remanence with the field along one stress axis minus the remanence with the field along the other stress axis falls in a straight-line band of values when plotted against the difference of the two stresses. This suggests a possible NDE technique for detecting differences in biaxial stresses at a given location in a steel specimen.

  6. Biaxial loading and shallow-flaw effects on crack-tip constraint and fracture-toughness

    SciTech Connect

    Pennell, W.E.; Bass, B.R.; Bryson, J.W.; McAfee, W.J.; Theiss, T.J.; Rao, M.C.

    1993-12-01

    Uniaxial tests of single-edged notched bend (SENB) specimens with both deep- and shallow-flaws have shown elevated fracture-toughness for the shallow flaws. The elevation in fracture-toughness for shallow flaws has been shown to be the result of reduced constraint at the crack-tip. Biaxial loading has the potential to increase constraint at the crack-tip and thereby reduce some of the shallow-flaw, fracture-toughness elevation. Biaxial fracture-toughness tests have shown that the shallow-flaw, fracture-toughness elevation is reduced but not eliminated by biaxial loading. Dual-parameter, fracture-toughness correlations have been proposed to reflect the effect of crack-tip constraint on fracture-toughness. Test results from the uniaxial and biaxial tests were analyzed using the dual-parameter technology. Discrepancies between analysis results and cleavage initiation site data from fractographic examinations indicate that the analysis models are in need of further refinement. Addition of a precleavage, ductile-tearing element to the analysis model has the potential to resolve the noted discrepancies.

  7. Biaxial loading and shallow-flaw effects on crack-tip constraint and fracture-toughness

    SciTech Connect

    Pennell, W.E.; Bass, B.R.; Bryson, J.W.; McAfee, W.J.; Theiss, T.J.; Rao, M.C.

    1994-04-01

    Uniaxial tests of single-edged notched bend (SENB) specimens with both deep- and shallow-flaws have shown elevated fracturetoughness for the shallow flaws. The elevation in fracture-toughness for shallow flaws has been shown to be the result of reduced constraint at the crack-tip. Biaxial loading has the potential to increase constraint at the crack-tip and thereby reduce some of the shallow-flaw, fracture-toughness elevation. Biaxial fracture-toughness tests have shown that the shallow-flaw, fracture-toughness elevation is reduced but not eliminated by biaxial loading. Dual-parameter, fracture-toughness correlations have been proposed to reflect the effect of crack-tip constraint on fracture-toughness. Test results from the uniaxial and biaxial tests were analyzed using the dual-parameter technology. Discrepancies between analysis results and cleavage initiation site data from fractographic examinations indicate that the analysis models are in need of further refinement. Addition of a precleavage, ductile-tearing element to the analysis model has the potential to resolve the noted discrepancies.

  8. Failure Investigation for QP Steel Sheets under uniaxial and Equal-Biaxial Tension Conditions

    NASA Astrophysics Data System (ADS)

    Zou, Danqing; Li, Shuhui; He, Ji; Cui, Ronggao

    2016-08-01

    The Quenching and Partitioning (QP) steel sheet is new generation material to induce phase transformation for plasticity in forming vehicle parts. The phase transformation is strongly stress state dependent behavior in experiments, which should affect the failure timing and limit strain in forming processes. In this paper, Nakajima test with QP980 and DP1000 steel sheets under equal-biaxial loading condition is performed for failure behavior. X-ray diffraction (XRD) is adopted to obtain the volume fraction of retained austenite (fA). Digital Image Correlation (DIC) is used to record the surface strain field and its evolution during equal-biaxial tension deformation. The same level Dual Phase (DP) steel is also employed for the purpose of comparison. The results show that phase transformation in QP steel gives small impact on failure strain under equal biaxial tension condition which is contradicted with our understanding. It suggests that failure behavior under uniaxial tension of QP980 is strongly phase transformation dependent. But it shows almost independent under equal biaxial tension condition.

  9. Cruciform specimen design for testing advanced aeropropulsion materials under cyclic in-plane biaxial loading

    NASA Astrophysics Data System (ADS)

    Abdul-Aziz, Ali; Krause, David

    2006-03-01

    Investigating material behavior under complex stress states is often done using in-plane biaxial loading approach. Utilizing such techniques requires using cruciform type specimens fabricated from plate material tested by gripping the specimen at four locations and loaded along two orthogonal axes. Servohydraulic systems are generally used in this application which is similar to those used for uniaxial testing. These kind of testing capabilities are currently being conducted at NASA Glenn Research Center via a new in-house testing facility. This is in support of the development of major components for the Stirling Radioisotope Generator (SRG). It is also used to assist in the generation of an analytical life prediction methodology [1] and to experimentally verify the flight-design component's life. Further, this work is intended to carry the immediate goal of developing a specimen design that is fully compatible with the in-plane biaxial testing systems installed at NASA Glenn Research Center [2]. Thus, details of the specimen design and its applicability to the ongoing experimental activities are being reported and discussed. Finite element analyses were carried out to optimize the geometry of specimen and to evaluate the stress response under biaxial loading conditions [3, 4]. The material of interest used in this research is nickel based superalloy. The data presented concluded that the specimen can be used to investigate the deformation behavior under general forms of biaxial loading. The provided measurement and observation are limited to 1-in [2.54 cm] diameter circular region at the specimen center.

  10. PDV Probe Alignment Technique

    SciTech Connect

    Whitworth, T L; May, C M; Strand, O T

    2007-10-26

    This alignment technique was developed while performing heterodyne velocimetry measurements at LLNL. There are a few minor items needed, such as a white card with aperture in center, visible alignment laser, IR back reflection meter, and a microscope to view the bridge surface. The work was performed on KCP flyers that were 6 and 8 mils wide. The probes used were Oz Optics manufactured with focal distances of 42mm and 26mm. Both probes provide a spot size of approximately 80?m at 1550nm. The 42mm probes were specified to provide an internal back reflection of -35 to -40dB, and the probe back reflections were measured to be -37dB and -33dB. The 26mm probes were specified as -30dB and both measured -30.5dB. The probe is initially aligned normal to the flyer/bridge surface. This provides a very high return signal, up to -2dB, due to the bridge reflectivity. A white card with a hole in the center as an aperture can be used to check the reflected beam position relative to the probe and launch beam, and the alignment laser spot centered on the bridge, see Figure 1 and Figure 2. The IR back reflection meter is used to measure the dB return from the probe and surface, and a white card or similar object is inserted between the probe and surface to block surface reflection. It may take several iterations between the visible alignment laser and the IR back reflection meter to complete this alignment procedure. Once aligned normal to the surface, the probe should be tilted to position the visible alignment beam as shown in Figure 3, and the flyer should be translated in the X and Y axis to reposition the alignment beam onto the flyer as shown in Figure 4. This tilting of the probe minimizes the amount of light from the bridge reflection into the fiber within the probe while maintaining the alignment as near normal to the flyer surface as possible. When the back reflection is measured after the tilt adjustment, the level should be about -3dB to -6dB higher than the probes

  11. Tungsten-induced carcinogenesis in human bronchial epithelial cells.

    PubMed

    Laulicht, Freda; Brocato, Jason; Cartularo, Laura; Vaughan, Joshua; Wu, Feng; Kluz, Thomas; Sun, Hong; Oksuz, Betul Akgol; Shen, Steven; Peana, Massimiliano; Medici, Serenella; Zoroddu, Maria Antonietta; Costa, Max

    2015-10-01

    Metals such as arsenic, cadmium, beryllium, and nickel are known human carcinogens; however, other transition metals, such as tungsten (W), remain relatively uninvestigated with regard to their potential carcinogenic activity. Tungsten production for industrial and military applications has almost doubled over the past decade and continues to increase. Here, for the first time, we demonstrate tungsten's ability to induce carcinogenic related endpoints including cell transformation, increased migration, xenograft growth in nude mice, and the activation of multiple cancer-related pathways in transformed clones as determined by RNA sequencing. Human bronchial epithelial cell line (Beas-2B) exposed to tungsten developed carcinogenic properties. In a soft agar assay, tungsten-treated cells formed more colonies than controls and the tungsten-transformed clones formed tumors in nude mice. RNA-sequencing data revealed that the tungsten-transformed clones altered the expression of many cancer-associated genes when compared to control clones. Genes involved in lung cancer, leukemia, and general cancer genes were deregulated by tungsten. Taken together, our data show the carcinogenic potential of tungsten. Further tests are needed, including in vivo and human studies, in order to validate tungsten as a carcinogen to humans. PMID:26164860

  12. Tungsten-induced carcinogenesis in human bronchial epithelial cells.

    PubMed

    Laulicht, Freda; Brocato, Jason; Cartularo, Laura; Vaughan, Joshua; Wu, Feng; Kluz, Thomas; Sun, Hong; Oksuz, Betul Akgol; Shen, Steven; Peana, Massimiliano; Medici, Serenella; Zoroddu, Maria Antonietta; Costa, Max

    2015-10-01

    Metals such as arsenic, cadmium, beryllium, and nickel are known human carcinogens; however, other transition metals, such as tungsten (W), remain relatively uninvestigated with regard to their potential carcinogenic activity. Tungsten production for industrial and military applications has almost doubled over the past decade and continues to increase. Here, for the first time, we demonstrate tungsten's ability to induce carcinogenic related endpoints including cell transformation, increased migration, xenograft growth in nude mice, and the activation of multiple cancer-related pathways in transformed clones as determined by RNA sequencing. Human bronchial epithelial cell line (Beas-2B) exposed to tungsten developed carcinogenic properties. In a soft agar assay, tungsten-treated cells formed more colonies than controls and the tungsten-transformed clones formed tumors in nude mice. RNA-sequencing data revealed that the tungsten-transformed clones altered the expression of many cancer-associated genes when compared to control clones. Genes involved in lung cancer, leukemia, and general cancer genes were deregulated by tungsten. Taken together, our data show the carcinogenic potential of tungsten. Further tests are needed, including in vivo and human studies, in order to validate tungsten as a carcinogen to humans.

  13. Curriculum Alignment Research Suggests that Alignment Can Improve Student Achievement

    ERIC Educational Resources Information Center

    Squires, David

    2012-01-01

    Curriculum alignment research has developed showing the relationship among three alignment categories: the taught curriculum, the tested curriculum and the written curriculum. Each pair (for example, the taught and the written curriculum) shows a positive impact for aligning those results. Following this, alignment results from the Third…

  14. A method for planar biaxial mechanical testing that includes in-plane shear.

    PubMed

    Sacks, M S

    1999-10-01

    A limitation in virtually all planar biaxial studies of soft tissues has been the inability to include the effects of in-plane shear. This is due to the inability of current mechanical testing devices to induce a state of in-plane shear, due to the added cost and complexity. In the current study, a straightforward method is presented for planar biaxial testing that induces a combined state of in-plane shear and normal strains. The method relies on rotation of the test specimen's material axes with respect to the device axes and on rotating carriages to allow the specimen to undergo in-plane shear freely. To demonstrate the method, five glutaraldehyde treated bovine pericardium specimens were prepared with their preferred fiber directions (defining the material axes) oriented at 45 deg to the device axes to induce a maximum shear state. The test protocol included a wide range of biaxial strain states, and the resulting biaxial data re-expressed in material axes coordinate system. The resulting biaxial data was then fit to the following strain energy function W: [equation: see text] where E'ij is the Green's strain tensor in the material axes coordinate system and c and Ai are constants. While W was able to fit the data very well, the constants A5 and A6 were found not to contribute significantly to the fit and were considered unnecessary to model the shear strain response. In conclusion, while not able to control the amount of shear strain independently or induce a state of pure shear, the method presented readily produces a state of simultaneous in-plane shear and normal strains. Further, the method is very general and can be applied to any anisotropic planar tissue that has identifiable material axes.

  15. Temperature dependence of the biaxial modulus, intrinsic stress and composition of plasma deposited silicon oxynitride films

    NASA Technical Reports Server (NTRS)

    Harding, David R.; Ogbuji, Linus U. T.; Freeman, Mathieu J.

    1995-01-01

    Silicon oxynitride films were deposited by plasma-enhanced chemical-vapor deposition. The elemental composition was varied between silicon nitride and silicon dioxide: SiO(0.3)N(1.0), SiO(0.7)N(1.6), SiO(0.7)N(1.1), and SiO(1.7)N(0.%). These films were annealed in air, at temperatures of 40-240 C above the deposition temperature (260 C), to determine the stability and behavior or each composition. the biaxial modulus, biaxial intrinsic stress, and elemental composition were measured at discrete intervals within the annealing cycle. Films deposited from primarily ammonia possessed considerable hydrogen (up to 38 at.%) and lost nitrogen and hydrogen at anneal temperatures (260-300 C) only marginally higher than the deposition temperature. As the initial oxygen content increased a different mechanism controlled the behavior or the film: The temperature threshold for change rose to approximately equal to 350 C and the loss of nitrogen was compensated by an equivalent rise in the oxygen content. The transformation from silicon oxynitride to silica was completed after 50 h at 400 C. The initial biaxial modulus of all compositions was 21-3- GPa and the intrinsic stress was -30 to 85 MPa. Increasing the oxygen content raised the temperature threshold where cracking first occurred; the two film compositions with the highest initial oxygen content did not crack, even at the highest temperature (450 C) investigated. At 450 C the biaxial modulus increased to approximately equal to 100 GPa and the intrinsic stress was approximately equal to 200 MPa. These increases could be correlated with the observed change in the film's composition. When nitrogen was replaced by oxygen, the induced stress remained lower than the biaxial strength of the material, but, when nitrogen and hydrogen were lost, stress-relieving microcracking occurred.

  16. Experimental and analytical comparison of constraint effects due to biaxial loading and shallow-flaws

    SciTech Connect

    Theiss, T.J.; Bass, B.R.; Bryson, J.W.

    1993-12-31

    A program to develop and evaluate fracture methodologies for the assessment of crack-tip constraint effects on fracture toughness of reactor pressure vessel (RPV) steels has been initiated in the Heavy-Section Steel Technology (HSST) Program. The focus of studies described herein is on the evaluation of a micromechanical scaling model based on critical stressed volumes for quantifying crack-tip constraint through applications to experimental data. Data were utilized from single-edge notch bend (SENB) specimens and HSST-developed cruciform beam specimens that were tested in HSST shallow-crack and biaxial testing programs. Shallow-crack effects and far-field tensile out-of-plane biaxial loading have been identified as constraint issues that influence both fracture toughness and the extent of the toughness scatter band. Results from applications indicate that the micromechanical scaling model can be used successfully to interpret experimental data from the shallow- and deep-crack SENB specimen tests. When applied to the uniaxially and biaxially loaded cruciform specimens, the two methodologies showed some promising features, but also raised several questions concerning the interpretation of constraint conditions in the specimen based on near-tip stress fields. Crack-tip constraint analyses of the shallow-crack cruciform specimen based on near-tip stress fields. Crack-tip constraint analyses of the shallow-crack cruciform specimen subjected to uniaxial or biaxial loading conditions are shown to represent a significant challenge for these methodologies. Unresolved issued identified from these analyses require resolution as part of a validation process for biaxial loading applications.

  17. Evaporation-Induced Self-Assembly of Ultrathin Tungsten Oxide Nanowires over a Large Scale for Ultraviolet Photodetector.

    PubMed

    Cheng, Wei; Niederberger, Markus

    2016-03-15

    Self-assembly of inorganic nanowires on a large scale directly on a substrate represents a great challenge. Starting from colloidally stable dispersions of ultrathin tungsten oxide nanowires, we successfully assemble the nanowires on a centimeter scale on flat or patterned substrates by a simple evaporation-induced self-assembly method. The capillary flow generated during the evaporation is responsible for the assembly of the nanowires. The concentration of the nanowire dispersion has a significant influence on the self-assembly behavior. Well-aligned tungsten oxide nanowire thin films are achieved when the concentration of the dispersion is in the range from 0.5 to 3.0 mg/mL. While at higher concentrations disordered nanowire thin films with cracks are formed, lower concentrations do not result in the formation of a continuous thin film. A macroscopic device based on the self-assembled tungsten oxide nanowires is fabricated, exhibiting good performance for UV light detection. Our results may pave the road for integrating aligned ultrathin semiconductor nanowires into macroscopic devices for optoelectronic applications. PMID:26900019

  18. Electric field induced biaxiality and the electro-optic effect in a bent-core nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Nagaraj, Mamatha; Panarin, Y. P.; Manna, U.; Vij, J. K.; Keith, C.; Tschierske, C.

    2010-01-01

    We report the observation of a biaxial nematic phase in a bent-core molecular system using polarizing microscopy, electro-optics, and dielectric spectroscopy, where we find that the biaxiality exists on a microscopic scale. An application of electric field induces a macroscopic biaxiality and in consequence gives rise to electro-optic switching. This electro-optic effect shows significant potential in applications for displays due to its fast high-contrast response. The observed electro-optic switching is explained in terms of the interaction of the ferroelectric clusters with the electric field.

  19. Bend ductility of tungsten heavy alloys

    SciTech Connect

    Gurwell, W.E.; Garnich, M.R.; Dudder, G.B.; Lavender, C.A.

    1992-11-01

    A bend ductility test is used to indicate the formability of tungsten heavy alloys sheet. The primary test bends a notchless Charpy impact specimen to a bend angle of approximately 100C. This can be augmented by a bend-completion test. Finite element modeling as well as strain-gaged bend specimens elucidate the strain distribution in the specimen as a function of material thickness and bend angle. The bend ductilities of 70%W, 807.W and 90%W alloys are characterized. As expected, decreasing thickness or tungsten content enhances bend ductility. Oxidation is not detrimental; therefore, controlled atmosphere is not required for cooling. The potentially detrimental effects of mechanical working (e.g., rolling, roller-leveling, grit blasting, and peening) and machining (e.g., cutting and sanding) are illustrated.

  20. Femtosecond fiber laser additive manufacturing of tungsten

    NASA Astrophysics Data System (ADS)

    Bai, Shuang; Liu, Jian; Yang, Pei; Zhai, Meiyu; Huang, Huan; Yang, Lih-Mei

    2016-04-01

    Additive manufacturing (AM) is promising to produce complex shaped components, including metals and alloys, to meet requirements from different industries such as aerospace, defense and biomedicines. Current laser AM uses CW lasers and very few publications have been reported for using pulsed lasers (esp. ultrafast lasers). In this paper, additive manufacturing of Tungsten materials is investigated by using femtosecond (fs) fiber lasers. Various processing conditions are studied, which leads to desired characteristics in terms of morphology, porosity, hardness, microstructural and mechanical properties of the processed components. Fully dense Tungsten part with refined grain and increased hardness was obtained and compared with parts made with different pulse widths and CW laser. The results are evidenced that the fs laser based AM provides more dimensions to modify mechanical properties with controlled heating, rapid melting and cooling rates compared with a CW or long pulsed laser. This can greatly benefit to the make of complicated structures and materials that could not be achieved before.

  1. Ultrasonic ranking of toughness of tungsten carbide

    NASA Technical Reports Server (NTRS)

    Vary, A.; Hull, D. R.

    1983-01-01

    The feasibility of using ultrasonic attenuation measurements to rank tungsten carbide alloys according to their fracture toughness was demonstrated. Six samples of cobalt-cemented tungsten carbide (WC-Co) were examined. These varied in cobalt content from approximately 2 to 16 weight percent. The toughness generally increased with increasing cobalt content. Toughness was first determined by the Palmqvist and short rod fracture toughness tests. Subsequently, ultrasonic attenuation measurements were correlated with both these mechanical test methods. It is shown that there is a strong increase in ultrasonic attenuation corresponding to increased toughness of the WC-Co alloys. A correlation between attenuation and toughness exists for a wide range of ultrasonic frequencies. However, the best correlation for the WC-Co alloys occurs when the attenuation coefficient measured in the vicinity of 100 megahertz is compared with toughness as determined by the Palmqvist technique.

  2. The tungsten divertor experiment at ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Neu, R.; Asmussen, K.; Krieger, K.; Thoma, A.; Bosch, H.-S.; Deschka, S.; Dux, R.; Engelhardt, W.; García-Rosales, C.; Gruber, O.; Herrmann, A.; Kallenbach, A.; Kaufmann, M.; Mertens, V.; Ryter, F.; Rohde, V.; Roth, J.; Sokoll, M.; Stäbler, A.; Suttrop, W.; Weinlich, M.; Zohm, H.; Alexander, M.; Becker, G.; Behler, K.; Behringer, K.; Behrisch, R.; Bergmann, A.; Bessenrodt-Weberpals, M.; Brambilla, M.; Brinkschulte, H.; Büchl, K.; Carlson, A.; Chodura, R.; Coster, D.; Cupido, L.; de Blank, H. J.; de Peña Hempel, S.; Drube, R.; Fahrbach, H.-U.; Feist, J.-H.; Feneberg, W.; Fiedler, S.; Franzen, P.; Fuchs, J. C.; Fußmann, G.; Gafert, J.; Gehre, O.; Gernhardt, J.; Haas, G.; Herppich, G.; Herrmann, W.; Hirsch, S.; Hoek, M.; Hoenen, F.; Hofmeister, F.; Hohenöcker, H.; Jacobi, D.; Junker, W.; Kardaun, O.; Kass, T.; Kollotzek, H.; Köppendörfer, W.; Kurzan, B.; Lackner, K.; Lang, P. T.; Lang, R. S.; Laux, M.; Lengyel, L. L.; Leuterer, F.; Manso, M. E.; Maraschek, M.; Mast, K.-F.; McCarthy, P.; Meisel, D.; Merkel, R.; Müller, H. W.; Münich, M.; Murmann, H.; Napiontek, B.; Neu, G.; Neuhauser, J.; Niethammer, M.; Noterdaeme, J.-M.; Pasch, E.; Pautasso, G.; Peeters, A. G.; Pereverzev, G.; Pitcher, C. S.; Poschenrieder, W.; Raupp, G.; Reinmüller, K.; Riedl, R.; Röhr, H.; Salzmann, H.; Sandmann, W.; Schilling, H.-B.; Schlögl, D.; Schneider, H.; Schneider, R.; Schneider, W.; Schramm, G.; Schweinzer, J.; Scott, B. D.; Seidel, U.; Serra, F.; Speth, E.; Silva, A.; Steuer, K.-H.; Stober, J.; Streibl, B.; Treutterer, W.; Troppmann, M.; Tsois, N.; Ulrich, M.; Varela, P.; Verbeek, H.; Verplancke, Ph; Vollmer, O.; Wedler, H.; Wenzel, U.; Wesner, F.; Wolf, R.; Wunderlich, R.; Zasche, D.; Zehetbauer, T.; Zehrfeld, H.-P.

    1996-12-01

    Tungsten-coated tiles, manufactured by plasma spray on graphite, were mounted in the divertor of the ASDEX Upgrade tokamak and cover almost 90% of the surface facing the plasma in the strike zone. Over 600 plasma discharges have been performed to date, around 300 of which were auxiliary heated with heating powers up to 10 MW. The production of tungsten in the divertor was monitored by a W I line at 400.8 nm. In the plasma centre an array of spectral lines at 5 nm emitted by ionization states around W XXX was measured. From the intensity of these lines the W content was derived. Under normal discharge conditions W-concentrations around 0741-3335/38/12A/013/img12 or even lower were found. The influence on the main plasma parameters was found to be negligible. The maximum concentrations observed decrease with increasing heating power. In several low power discharges accumulation of tungsten occurred and the temperature profile was flattened. The concentrations of the intrinsic impurities carbon and oxygen were comparable to the discharges with the graphite divertor. Furthermore, the density and the 0741-3335/38/12A/013/img13 limits remained unchanged and no negative influence on the energy confinement or on the H-mode threshold was found. Discharges with neon radiative cooling showed the same behaviour as in the graphite divertor case.

  3. Tungsten-uranium penetrator target interaction

    SciTech Connect

    Dunn, P S; Damkroger, B K

    1994-10-01

    Several studies performed in recent years have been directed at determining the penetration mechanism of long rod kinetic energy penetrators into Rolled Homogeneous Armor (RHA). Much of the work has centered on comparing U-0.75Ti and Tungsten Heavy Alloys (WHA), with the goal being to relate the superior ballistic performance of the uranium materials to a fundamental difference in penetration mechanisms. This has been found to be true, with the dominant mechanisms being adiabatic shear in U-0.75Ti and bulk deformation in WHA. Recent work has sought to achieve improvements in the ballistic performance of the tungsten materials via both mechanical property improvements and alloy modifications designed to bring about adiabatic shear. As an alternative, the authors propose the consideration of materials which utilize mechanisms other than bulk deformation and adiabatic shear to optimize ballistic performance. This paper will present the postmortem analysis of a uranium-20 vol% tungsten composite penetrator fired into RHA at 0{degrees} obliquity. The analysis shows that the penetration mechanism in this material is bulk heating and extensive co-melting of the target and penetrator at the penetration interface. The results of the analysis will then be compared to a similar analysis made of targets into which U-0.75Ti penetrators had been fired.

  4. Controlled nanostructuration of polycrystalline tungsten thin films

    SciTech Connect

    Girault, B.; Eyidi, D.; Goudeau, P.; Guerin, P.; Bourhis, E. Le; Renault, P.-O.; Sauvage, T.

    2013-05-07

    Nanostructured tungsten thin films have been obtained by ion beam sputtering technique stopping periodically the growing. The total thickness was maintained constant while nanostructure control was obtained using different stopping periods in order to induce film stratification. The effect of tungsten sublayers' thicknesses on film composition, residual stresses, and crystalline texture evolution has been established. Our study reveals that tungsten crystallizes in both stable {alpha}- and metastable {beta}-phases and that volume proportions evolve with deposited sublayers' thicknesses. {alpha}-W phase shows original fiber texture development with two major preferential crystallographic orientations, namely, {alpha}-W<110> and unexpectedly {alpha}-W<111> texture components. The partial pressure of oxygen and presence of carbon have been identified as critical parameters for the growth of metastable {beta}-W phase. Moreover, the texture development of {alpha}-W phase with two texture components is shown to be the result of a competition between crystallographic planes energy minimization and crystallographic orientation channeling effect maximization. Controlled grain size can be achieved for the {alpha}-W phase structure over 3 nm stratification step. Below, the {beta}-W phase structure becomes predominant.

  5. Measurement of thermophysical property of plasma forming tungsten nanofiber layer

    NASA Astrophysics Data System (ADS)

    Kajita, Shin; Yagi, Takashi; Kobayashi, Kenichi; Tokitani, Masayuki; Ohno, Noriyasu

    2016-05-01

    Thermophysical property of a nanostructured tungsten layer formed on a tungsten film was investigated. A 1-µm-thick tungsten film deposited on a quartz glass substrate was irradiated with a high density helium plasma at the surface temperature of 1500 K. The plasma irradiation led to the formation of highly porous fiberform-nanostructured tungsten layer with a thickness of 3.5 µm. Impulse heating was applied at the interface of the film/substrate, and transient heat diffusion was observed using a pulsed light heating thermoreflectance apparatus. The thermoreflectance signals clearly differed between the nanostructure existing and mechanically removed regions; the difference can be attributed to thermal effusivity of the nanostructured tungsten layer. The estimated thermal conductivity of the nanostructured tungsten decreases to ∼2% of that of bulk when the density of the nanostructure is assumed to be ∼6% of the bulk value.

  6. Optics Alignment Panel

    NASA Technical Reports Server (NTRS)

    Schroeder, Daniel J.

    1992-01-01

    The Optics Alignment Panel (OAP) was commissioned by the HST Science Working Group to determine the optimum alignment of the OTA optics. The goal was to find the position of the secondary mirror (SM) for which there is no coma or astigmatism in the camera images due to misaligned optics, either tilt or decenter. The despace position was reviewed of the SM and the optimum focus was sought. The results of these efforts are as follows: (1) the best estimate of the aligned position of the SM in the notation of HDOS is (DZ,DY,TZ,TY) = (+248 microns, +8 microns, +53 arcsec, -79 arcsec), and (2) the best focus, defined to be that despace which maximizes the fractional energy at 486 nm in a 0.1 arcsec radius of a stellar image, is 12.2 mm beyond paraxial focus. The data leading to these conclusions, and the estimated uncertainties in the final results, are presented.

  7. Barrel alignment fixture

    NASA Astrophysics Data System (ADS)

    Sheeley, J. D.

    1981-04-01

    Fabrication of slapper type detonator cables requires bonding of a thin barrel over a bridge. Location of the barrel hole with respect to the bridge is critical: the barrel hole must be centered over the bridge uniform spacing on each side. An alignment fixture which permits rapid adjustment of the barrel position with respect to the bridge is described. The barrel is manipulated by pincer-type fingers which are mounted on a small x-y table equipped with micrometer adjustments. Barrel positioning, performed under a binocular microscopy, is rapid and accurate. After alignment, the microscope is moved out of position and an infrared (IR) heat source is aimed at the barrel. A 5-second pulse of infrared heat flows the adhesive under the barrel and bonds it to the cable. Sapphire and Fotoform glass barrels were bonded successfully with the alignment fixture.

  8. Magnetically aligned supramolecular hydrogels.

    PubMed

    Wallace, Matthew; Cardoso, Andre Zamith; Frith, William J; Iggo, Jonathan A; Adams, Dave J

    2014-12-01

    The magnetic-field-induced alignment of the fibrillar structures present in an aqueous solution of a dipeptide gelator, and the subsequent retention of this alignment upon transformation to a hydrogel upon the addition of CaCl2 or upon a reduction in solution pH is reported. Utilising the switchable nature of the magnetic field coupled with the slow diffusion of CaCl2 , it is possible to precisely control the extent of anisotropy across a hydrogel, something that is generally very difficult to do using alternative methods. The approach is readily extended to other compounds that form viscous solutions at high pH. It is expected that this work will greatly expand the utility of such low-molecular-weight gelators (LMWG) in areas where alignment is key. PMID:25345918

  9. MUSE optical alignment procedure

    NASA Astrophysics Data System (ADS)

    Laurent, Florence; Renault, Edgard; Loupias, Magali; Kosmalski, Johan; Anwand, Heiko; Bacon, Roland; Boudon, Didier; Caillier, Patrick; Daguisé, Eric; Dubois, Jean-Pierre; Dupuy, Christophe; Kelz, Andreas; Lizon, Jean-Louis; Nicklas, Harald; Parès, Laurent; Remillieux, Alban; Seifert, Walter; Valentin, Hervé; Xu, Wenli

    2012-09-01

    MUSE (Multi Unit Spectroscopic Explorer) is a second generation VLT integral field spectrograph (1x1arcmin² Field of View) developed for the European Southern Observatory (ESO), operating in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently assembling and testing MUSE in the Integration Hall of the Observatoire de Lyon for the Preliminary Acceptance in Europe, scheduled for 2013. MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic instrument mechanical structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2011, all MUSE subsystems were integrated, aligned and tested independently in each institute. After validations, the systems were shipped to the P.I. institute at Lyon and were assembled in the Integration Hall This paper describes the end-to-end optical alignment procedure of the MUSE instrument. The design strategy, mixing an optical alignment by manufacturing (plug and play approach) and few adjustments on key components, is presented. We depict the alignment method for identifying the optical axis using several references located in pupil and image planes. All tools required to perform the global alignment between each subsystem are described. The success of this alignment approach is demonstrated by the good results for the MUSE image quality. MUSE commissioning at the VLT (Very Large Telescope) is planned for 2013.

  10. Toxicologic evaluation of tungsten: 28-day inhalation study of tungsten blue oxide in rats.

    PubMed

    Rajendran, Narayanan; Hu, Shu-Chieh; Sullivan, Dennis; Muzzio, Miguel; Detrisac, Carol J; Venezia, Carmen

    2012-12-01

    The toxicity and toxicokinetics of tungsten blue oxide (TBO) were examined. TBO is an intermediate in the production of tungsten powder, and has shown the potential to cause cellular damage in in vitro studies. However, in vivo evidence seems to indicate a lack of adverse effects. The present study was undertaken to address the dearth of longer-term inhalation toxicity studies of tungsten oxides by investigating the biological responses induced by TBO when administered via nose-only inhalation to rats at levels of 0.08, 0.325, and 0.65 mg TBO/L of air for 6 h/day for 28 consecutive days, followed by a 14-day recovery period. Inhaled TBO was absorbed systemically and blood levels of tungsten increased as inhaled concentration increased. Among the tissues analyzed for tungsten levels, lung, femur and kidney showed increased levels, with lung at least an order of magnitude greater than kidney or femur. By exposure day 14, tungsten concentration in tissues had reached steady-state. Increased lung weight was noted for both terminal and recovery animals and was attributed to deposition of TBO in the lungs, inducing a macrophage influx. Microscopic evaluation of tissues revealed a dose-related increase in alveolar pigmented macrophages, alveolar foreign material and individual alveolar foamy macrophages in lung. After a recovery period there was a slight reduction in the incidence and severity of histopathological findings. Based on the absence of other adverse effects, the increased lung weights and the microscopic findings were interpreted as nonadverse response to exposure and were not considered a specific reaction to TBO.

  11. Segment alignment control system

    NASA Technical Reports Server (NTRS)

    Aubrun, JEAN-N.; Lorell, Ken R.

    1988-01-01

    The segmented primary mirror for the LDR will require a special segment alignment control system to precisely control the orientation of each of the segments so that the resulting composite reflector behaves like a monolith. The W.M. Keck Ten Meter Telescope will utilize a primary mirror made up of 36 actively controlled segments. Thus the primary mirror and its segment alignment control system are directly analogous to the LDR. The problems of controlling the segments in the face of disturbances and control/structures interaction, as analyzed for the TMT, are virtually identical to those for the LDR. The two systems are briefly compared.

  12. PILOT optical alignment

    NASA Astrophysics Data System (ADS)

    Longval, Y.; Mot, B.; Ade, P.; André, Y.; Aumont, J.; Baustista, L.; Bernard, J.-Ph.; Bray, N.; de Bernardis, P.; Boulade, O.; Bousquet, F.; Bouzit, M.; Buttice, V.; Caillat, A.; Charra, M.; Chaigneau, M.; Crane, B.; Crussaire, J.-P.; Douchin, F.; Doumayrou, E.; Dubois, J.-P.; Engel, C.; Etcheto, P.; Gélot, P.; Griffin, M.; Foenard, G.; Grabarnik, S.; Hargrave, P..; Hughes, A.; Laureijs, R.; Lepennec, Y.; Leriche, B.; Maestre, S.; Maffei, B.; Martignac, J.; Marty, C.; Marty, W.; Masi, S.; Mirc, F.; Misawa, R.; Montel, J.; Montier, L.; Narbonne, J.; Nicot, J.-M.; Pajot, F.; Parot, G.; Pérot, E.; Pimentao, J.; Pisano, G.; Ponthieu, N.; Ristorcelli, I.; Rodriguez, L.; Roudil, G.; Salatino, M.; Savini, G.; Simonella, O.; Saccoccio, M.; Tapie, P.; Tauber, J.; Torre, J.-P.; Tucker, C.

    2016-07-01

    PILOT is a balloon-borne astronomy experiment designed to study the polarization of dust emission in the diffuse interstellar medium in our Galaxy at wavelengths 240 μm with an angular resolution about two arcminutes. Pilot optics is composed an off-axis Gregorian type telescope and a refractive re-imager system. All optical elements, except the primary mirror, are in a cryostat cooled to 3K. We combined the optical, 3D dimensional measurement methods and thermo-elastic modeling to perform the optical alignment. The talk describes the system analysis, the alignment procedure, and finally the performances obtained during the first flight in September 2015.

  13. Femtosecond laser-induced periodic surface structure formation on tungsten

    SciTech Connect

    Vorobyev, A. Y.; Guo Chunlei

    2008-09-15

    In this paper, we demonstrate the generation of periodic surface structures on a technologically important material, tungsten, at both 400 and 800 nm, despite that the table values of dielectric constants for tungsten at these two wavelengths suggest the absence of surface plasmons, a wave necessary for forming periodic structures on metals. Furthermore, we find that the structure periods formed on tungsten are significantly less than the laser wavelengths. We believe that the dielectric constants of tungsten change significantly due to intense laser pulse heating and surface structuring and roughening at nanometer scales, permitting surface plasmon excitation and periodic structure formation.

  14. Tungsten-induced carcinogenesis in human bronchial epithelial cells

    PubMed Central

    Laulicht, Freda; Brocato, Jason; Cartularo, Laura; Vaughan, Joshua; Wu, Feng; Kluz, Thomas; Sun, Hong; Oksuz, Betul Akgol; Shen, Steven; Paena, Massimilano; Medici, Serenella; Zoroddu, Maria Antonietta; Costa, Max

    2015-01-01

    Metals such as arsenic, cadmium, beryllium, and nickel are known human carcinogens; however, other transition metals, such as tungsten (W), remain relatively uninvestigated with regard to their potential carcinogenic activity. Tungsten production for industrial and military applications has almost doubled over the past decade and continues to increase. Here, for the first time, we demonstrate tungsten’s ability to induce carcinogenic related endpoints including cell transformation, increased migration, xenograft growth in nude mice, and the activation of multiple cancer related pathways in transformed clones as determined by RNA seq. Human bronchial epithelial cell line (Beas-2B) exposed to tungsten developed carcinogenic properties. In a soft agar assay, tungsten-treated cells formed more colonies than controls and the tungsten-transformed clones formed tumors in nude mice. RNA-sequencing data revealed that the tungsten-transformed clones altered the expression of many cancer-associated genes when compared to control clones. Genes involved in lung cancer, leukemia, and general cancer genes were deregulated by tungsten. Taken together, our data shows the carcinogenic potential of tungsten. Further tests are needed, including in vivo and human studies, in order to validate tungsten as a carcinogen to humans. PMID:26164860

  15. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... or tungsten carbide scrap raw materials. ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the...

  16. 40 CFR 421.310 - Applicability: Description of the secondary tungsten and cobalt subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... or tungsten carbide scrap raw materials. ... secondary tungsten and cobalt subcategory. 421.310 Section 421.310 Protection of Environment ENVIRONMENTAL... CATEGORY Secondary Tungsten and Cobalt Subcategory § 421.310 Applicability: Description of the...

  17. Molecular model of biaxial ordering in nematic liquid crystals composed of flat molecules with four mesogenic groups

    NASA Astrophysics Data System (ADS)

    Gorkunov, M. V.; Osipov, M. A.; Kocot, A.; Vij, J. K.

    2010-06-01

    Relative stability of uniaxial and biaxial nematic phases is analyzed in a model nematic liquid crystal composed of flat molecules of C2h symmetry with four mesogenic groups rigidly linked to the same center. The generalized effective quadrupole mean-field potential is proposed and its constants are evaluated numerically for the pair intermolecular potential based on Gay-Berne interaction between mesogenic groups. The dependencies of the constants on molecular shape parameters are systematically analyzed. Order parameters of the uniaxial and biaxial nematic phases are evaluated by direct minimization of the free energy at different temperatures. The corresponding phase diagrams are obtained enabling one to study the effects of molecular model parameters on the stability regions of uniaxial and biaxial phases. The results are used to clarify the nature of experimentally observed biaxial ordering in nematic liquid crystals composed of tetrapode molecules with the same symmetry.

  18. Effect of phase symmetry on the NMR spectrum of acetonitrile oriented in a uniaxial-biaxial-uniaxial phase

    NASA Astrophysics Data System (ADS)

    Deepak, H. S. Vinay; Yelamaggad, C. V.; Khetrapal, C. L.; Ramanathan, K. V.

    2016-09-01

    We report here the measurement of the Csbnd H and the Hsbnd H dipolar couplings of the methyl group of acetonitrile oriented in the biaxial liquid crystal potassium laurate/1-decanol/water system. These parameters show large variations when measured as a function of temperature. The variations follow the symmetry of the phase as the liquid crystal goes through the sequence of uniaxial - biaxial - uniaxial phases and show a close correspondence to the phase changes that occur in the liquid crystalline solvent coinciding with the onset of biaxiality. The Hsbnd Csbnd H bond angle calculated after incorporating vibrational corrections to the dipolar couplings is discussed in terms of contributions in the case of the biaxial liquid crystal arising from vibration-rotation interaction effects.

  19. Quantification of Shear Deformations and Corresponding Stresses in the Biaxially Tested Human Myocardium.

    PubMed

    Sommer, Gerhard; Haspinger, Daniel Ch; Andrä, Michaela; Sacherer, Michael; Viertler, Christian; Regitnig, Peter; Holzapfel, Gerhard A

    2015-10-01

    One goal of cardiac research is to perform numerical simulations to describe/reproduce the mechanoelectrical function of the human myocardium in health and disease. Such simulations are based on a complex combination of mathematical models describing the passive mechanical behavior of the myocardium and its electrophysiology, i.e., the activation of cardiac muscle cells. The problem in developing adequate constitutive models is the shortage of experimental data suitable for detailed parameter estimation in specific functional forms. A combination of shear and biaxial extension tests with different loading protocols on different specimen orientations is necessary to capture adequately the direction-dependent (orthotropic) response of the myocardium. In most experimental animal studies, where planar biaxial extension tests on the myocardium have been conducted, the generated shear stresses were neither considered nor discussed. Hence, in this study a method is presented which allows the quantification of shear deformations and related stresses. It demonstrates an approach for experimenters as to how the generation of these shear stresses can be minimized during mechanical testing. Experimental results on 14 passive human myocardial specimens, obtained from nine human hearts, show the efficiency of this newly developed method. Moreover, the influence of the clamping technique of the specimen, i.e., the load transmission between the testing device and the tissue, on the stress response is determined by testing an isotropic material (Latex). We identified that the force transmission between the testing device and the specimen by means of hooks and cords does not influence the performed experiments. We further showed that in-plane shear stresses definitely exist in biaxially tested human ventricular myocardium, but can be reduced to a minimum by preparing the specimens in an appropriate manner. Moreover, we showed whether shear stresses can be neglected when performing

  20. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    SciTech Connect

    Airapetov, A. A.; Begrambekov, L. B.; Buzhinskiy, O. I.; Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A.

    2015-12-15

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400–1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  1. Boron carbide coating deposition on tungsten and testing of tungsten layers and coating under intense plasma load

    NASA Astrophysics Data System (ADS)

    Airapetov, A. A.; Begrambekov, L. B.; Buzhinskiy, O. I.; Grunin, A. V.; Gordeev, A. A.; Zakharov, A. M.; Kalachev, A. M.; Sadovskiy, Ya. A.; Shigin, P. A.

    2015-12-01

    A device intended for boron carbide coating deposition and material testing under high heat loads is presented. A boron carbide coating 5 μm thick was deposited on the tungsten substrate. These samples were subjected to thermocycling loads in the temperature range of 400-1500°C. Tungsten layers deposited on tungsten substrates were tested in similar conditions. Results of the surface analysis are presented.

  2. Curriculum Alignment: Establishing Coherence

    ERIC Educational Resources Information Center

    Gagné, Philippe; Dumont, Laurence; Brunet, Sabine; Boucher, Geneviève

    2013-01-01

    In this paper, we present a step-by-step guide to implement a curricular alignment project, directed at professional development and student support, and developed in a higher education French as a second language department. We outline best practices and preliminary results from our experience and provide ways to adapt our experience to other…

  3. Optically Aligned Drill Press

    NASA Technical Reports Server (NTRS)

    Adderholdt, Bruce M.

    1994-01-01

    Precise drill press equipped with rotary-indexing microscope. Microscope and drill exchange places when turret rotated. Microscope axis first aligned over future hole, then rotated out of way so drill axis assumes its precise position. New procedure takes less time to locate drilling positions and produces more accurate results. Apparatus adapted to such other machine tools as milling and measuring machines.

  4. Aligning brains and minds

    PubMed Central

    Tong, Frank

    2012-01-01

    In this issue of Neuron, Haxby and colleagues describe a new method for aligning functional brain activity patterns across participants. Their study demonstrates that objects are similarly represented across different brains, allowing for reliable classification of one person’s brain activity based on another’s. PMID:22017984

  5. Aligned-or Not?

    ERIC Educational Resources Information Center

    Roseman, Jo Ellen; Koppal, Mary

    2015-01-01

    When state leaders and national partners in the development of the Next Generation Science Standards met to consider implementation strategies, states and school districts wanted to know which materials were aligned to the new standards. The answer from the developers was short but not sweet: You won't find much now, and it's going to…

  6. Fracture assessment of HSST Plate 14 shallow-flaw cruciform bend specimens tested under biaxial loading conditions

    SciTech Connect

    Bass, B.R.; McAfee, W.J.; Williams, P.T.; Pennell, W.E.

    1998-06-01

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow, surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a far-field, out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for an RPV material. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies, namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness; the conventional maximum principal stress criterion indicated no effect. A three-parameter Weibull model based on the hydrostatic stress criterion is shown to correlate the experimentally observed biaxial effect on cleavage fracture toughness by providing a scaling mechanism between uniaxial and biaxial loading states.

  7. Biaxial Fatigue Crack Growth Behavior in Aluminum Alloy 5083-H116 Under Ambient Laboratory and Saltwater Environments

    NASA Astrophysics Data System (ADS)

    Perel, V. Y.; Misak, H. E.; Mall, S.; Jain, V. K.

    2015-04-01

    Crack growth of aluminum alloy 5083 was investigated when subjected to the in-plane biaxial tension-tension fatigue with stress ratio of 0.5 under ambient laboratory and saltwater environments. Cruciform specimens with a center hole, containing a notch and precrack at 45° to the specimen's arms, were tested in a biaxial fatigue test machine. Two biaxiality ratios, λ = 1 and λ = 1.5, were studied. For λ = 1, crack propagated along a straight line collinearly with the precrack, while for λ = 1.5 case, the crack path was curved and non-collinear with the precrack. Uniaxial fatigue tests were also conducted. Crack growth rates were faster under the biaxiality fatigue in comparison to uniaxial fatigue at a given crack driving force (Δ K I or Δ G) in both environments. Further, an increase in biaxiality ratio increased the crack growth rate, i.e., faster for λ = 1.5 case than λ = 1 case. Both biaxial fatigue and saltwater environment showed detrimental effects on the fatigue crack growth resistance of 5083, and its combination is highly detrimental when compared to uniaxial fatigue.

  8. Preliminary assessment of the effects of biaxial loading on reactor pressure vessel structural-integrity-assessment technology

    SciTech Connect

    Pennell, W.E.; Bass, B.R.; Bryson, J.W.; Dickson, T.L.; McAfee, W.J.; Merkle, J.G.

    1996-04-01

    Effects of biaxial loading on shallow-flaw fracture toughness were studied to determine potential impact on structural integrity assessment of a reactor pressure vessel (RPV) under pressurized thermal shock (PTS) transient loading and pressure-temperature (PT) loading produced by reactor heatup and cooldown transients. Biaxial shallow-flaw fracture-toughness tests results were also used to determine the parameter controlling fracture in the transition temperature range, and to develop a related dual-parameter fracture-toughness correlation. Shallow-flaw and biaxial loading effects were found to reduce the conditional probability of crack initiation by a factor of nine when the shallow-flaw fracture-toughness K{sub Jc} data set, with biaxial-loading effects adjustments, was substituted in place of ASME Code K{sub Ic} data set in PTS analyses. Biaxial loading was found to reduce the shallow-flaw fracture toughness of RPV steel such that the lower-bound curve was located between ASME K{sub Ic} and K{sub IR} curves. This is relevant to future development of P-T curve analysis procedures. Fracture in shallow-flaw biaxial samples tested in the lower transition temperature range was shown to be strain controlled. A strain-based dual-parameter fracture-toughness correlation was developed and shown to be capable of predicting the effect of crack-tip constraint on fracture toughness for strain-controlled fracture.

  9. Evaluation of constraint methodologies applied to a shallow-flaw cruciform bend specimen tested under biaxial loading conditions

    SciTech Connect

    Bass, B.R.; McAfee, W.J.; Williams, P.T.; Pennell, W.E.

    1998-01-01

    A technology to determine shallow-flaw fracture toughness of reactor pressure vessel (RPV) steels is being developed for application to the safety assessment of RPVs containing postulated shallow surface flaws. Matrices of cruciform beam tests were developed to investigate and quantify the effects of temperature, biaxial loading, and specimen size on fracture initiation toughness of two-dimensional (constant depth), shallow surface flaws. The cruciform beam specimens were developed at Oak Ridge National Laboratory (ORNL) to introduce a prototypic, far-field. out-of-plane biaxial stress component in the test section that approximates the nonlinear stresses resulting from pressurized-thermal-shock or pressure-temperature loading of an RPV. Tests were conducted under biaxial load ratios ranging from uniaxial to equibiaxial. These tests demonstrated that biaxial loading can have a pronounced effect on shallow-flaw fracture toughness in the lower transition temperature region for RPV materials. The cruciform fracture toughness data were used to evaluate fracture methodologies for predicting the observed effects of biaxial loading on shallow-flaw fracture toughness. Initial emphasis was placed on assessment of stress-based methodologies. namely, the J-Q formulation, the Dodds-Anderson toughness scaling model, and the Weibull approach. Applications of these methodologies based on the hydrostatic stress fracture criterion indicated an effect of loading-biaxiality on fracture toughness, the conventional maximum principal stress criterion indicated no effect.

  10. Solid-state chemistry route for supported tungsten and tungsten carbide nanoparticles

    SciTech Connect

    Hugot, N.; Desforges, A.; Fontana, S.; Mareche, J.F.; Herold, C.; Albiniak, A.

    2012-10-15

    Nanoparticles of tungsten and tungsten carbide have been prepared using solid-state chemistry methods. After the vapor phase impregnation of a tungsten hexachloride precursor on a carbon support, a temperature-programmed reduction/carburization was performed. Several parameters were investigated and the evolution of obtained samples was followed by XRD and TEM. The optimization of the reaction parameters led to the preparation of W, W{sub 2}C and WC particles well dispersed on the support. WC phase however could not be obtained alone with less than 10 nm mean size. This could be explained by the carburization mechanism and the carbon diffusion on the support. - Graphical abstract: Bright field picture of carbon-supported WC nanoparticles dispersed on the surface of the sample 1223 K in 10% CH{sub 4}/90% H{sub 2}. Highlights: Black-Right-Pointing-Pointer We aimed at the preparation of supported nanoparticulate tungsten derivatives. Black-Right-Pointing-Pointer Several parameters were investigated. Black-Right-Pointing-Pointer The evolution of obtained samples was followed by XRD and TEM. Black-Right-Pointing-Pointer The optimal preparation led to W, W{sub 2}C and WC particles dispersed on the support.

  11. Lasing with conical diffraction feature in the KGd(WO4)2:Nd biaxial crystal

    NASA Astrophysics Data System (ADS)

    Brenier, Alain

    2016-09-01

    With an experimental set-up designed to record simultaneously the far-field and the near-field patterns, we got lasing with feature of conical diffraction in the biaxial Nd3+-doped KGd(WO4)2 crystal. The key-point is that the lasing direction is not single and is constituted by an angular distribution including the optical axis. Very slight changes of crystal orientation leads to crescent shape 1068-nm light distributions in the near-field. The beam launched towards the biaxial crystal is mainly linear polarized with its intensity in agreement with the Nd fluorescence angular distribution. A theoretical background is provided, including the monoclinic and triclinic symmetries and laser amplification including elliptical modes and cavity round trip.

  12. Tunable biaxial in-plane compressive strain in a Si nanomembrane transferred on a polyimide film

    SciTech Connect

    Kim, Munho; Mi, Hongyi; Cho, Minkyu; Seo, Jung-Hun; Ma, Zhenqiang; Zhou, Weidong; Gong, Shaoqin

    2015-05-25

    A method of creating tunable and programmable biaxial compressive strain in silicon nanomembranes (Si NMs) transferred onto a Kapton{sup ®} HN polyimide film has been demonstrated. The programmable biaxial compressive strain (up to 0.54%) was generated utilizing a unique thermal property exhibited by the Kapton HN film, namely, it shrinks from its original size when exposed to elevated temperatures. The correlation between the strain and the annealing temperature was carefully investigated using Raman spectroscopy and high resolution X-ray diffraction. It was found that various amounts of compressive strains can be obtained by controlling the thermal annealing temperatures. In addition, a numerical model was used to evaluate the strain distribution in the Si NM. This technique provides a viable approach to forming in-plane compressive strain in NMs and offers a practical platform for further studies in strain engineering.

  13. Tunable biaxial in-plane compressive strain in a Si nanomembrane transferred on a polyimide film

    NASA Astrophysics Data System (ADS)

    Kim, Munho; Mi, Hongyi; Cho, Minkyu; Seo, Jung-Hun; Zhou, Weidong; Gong, Shaoqin; Ma, Zhenqiang

    2015-05-01

    A method of creating tunable and programmable biaxial compressive strain in silicon nanomembranes (Si NMs) transferred onto a Kapton® HN polyimide film has been demonstrated. The programmable biaxial compressive strain (up to 0.54%) was generated utilizing a unique thermal property exhibited by the Kapton HN film, namely, it shrinks from its original size when exposed to elevated temperatures. The correlation between the strain and the annealing temperature was carefully investigated using Raman spectroscopy and high resolution X-ray diffraction. It was found that various amounts of compressive strains can be obtained by controlling the thermal annealing temperatures. In addition, a numerical model was used to evaluate the strain distribution in the Si NM. This technique provides a viable approach to forming in-plane compressive strain in NMs and offers a practical platform for further studies in strain engineering.

  14. Insertion Testing of Polyethylene Glycol Microneedle Array into Cultured Human Skin with Biaxial Tension

    NASA Astrophysics Data System (ADS)

    Takano, Naoki; Tachikawa, Hiroto; Miyano, Takaya; Nishiyabu, Kazuaki

    Aiming at the practical use of polyethylene glycol (PEG) microneedles for transdermal drug delivery system (DDS), a testing apparatus for their insertion into cultured human skin has been developed. To simulate the variety of conditions of human skin, biaxial tension can be applied to the cultured human skin. An adopted testing scheme to apply and control the biaxial tension is similar to the deep-draw forming technique. An attention was also paid to the short-time setup of small, thin and wet cultured skin. One dimensional array with four needles was inserted and influence of tension was discussed. It was found that tension, deflection of skin during insertion and original curvature of skin are the important parameters for microneedles array design.

  15. Computer simulation of crack propagation in ductile materials under biaxial dynamic loads

    SciTech Connect

    Chen, Y.M.

    1980-07-29

    The finite-difference computer program HEMP is used to simulate the crack-propagation phenomenon in two-dimensional ductile materials under truly dynamic biaxial loads. A comulative strain-damage criterion for the initiation of ductile fracture is used. To simulate crack propagation numerically, the method of equivalent free-surface boundary conditions and the method of artifical velocity are used in the computation. Centrally cracked rectangular aluminum bars subjected to constant-velocity biaxial loads at the edges are considered. Tensile and compressive loads in the direction of crack length are found, respectively, to increase and decrease directional instability in crack propagation, where the directional instability is characterized by branching or bifurcation.

  16. Mechanical properties of stanene under uniaxial and biaxial loading: A molecular dynamics study

    SciTech Connect

    Mojumder, Satyajit; Amin, Abdullah Al; Islam, Md Mahbubul

    2015-09-28

    Stanene, a graphene like two dimensional honeycomb structure of tin has attractive features in electronics application. In this study, we performed molecular dynamics simulations using modified embedded atom method potential to investigate mechanical properties of stanene. We studied the effect of temperature and strain rate on mechanical properties of α-stanene for both uniaxial and biaxial loading conditions. Our study suggests that with the increasing temperature, both the fracture strength and strain of the stanene decrease. Uniaxial loading in zigzag direction shows higher fracture strength and strain compared to the armchair direction, while no noticeable variation in the mechanical properties is observed for biaxial loading. We also found at a higher loading rate, material exhibits higher fracture strength and strain. These results will aid further investigation of stanene as a potential nano-electronics substitute.

  17. Biaxial load effects on the crack border elastic strain energy and strain energy rate

    NASA Technical Reports Server (NTRS)

    Eftis, J.; Subramonian, N.; Liebowitz, H.

    1977-01-01

    The validity of the singular solution (first term of a series representation) is investigated for the crack tip stress and displacement field in an infinite sheet with a flat line crack with biaxial loads applied to the outer boundaries. It is shown that if one retains the second contribution to the series approximations for stress and displacement in the calculation of the local elastic strain energy density and elastic strain energy rate in the crack border region, both these quantities have significant biaxial load dependency. The value of the J-integral does not depend on the presence of the second term of the series expansion for stress and displacement. Thus J(I) is insensitive to the presence of loads applied parallel to the plane of the crack.

  18. Exploiting design freedom in biaxial dielectrics to enable spatially overlapping optical instruments

    PubMed Central

    Akbarzadeh, Alireza; Qiu, Cheng-Wei; Danner, Aaron J.

    2013-01-01

    The optical behavior of gradient biaxial dielectrics has not been widely explored in the literature due to their complicated nature, but the extra degrees of freedom in the index tensor have the potential of yielding useful optical instruments which are otherwise unachievable. In this work, a design method is described in detail which allows one to combine the behavior of up to four totally independent isotropic optical instruments in an overlapping region of space. This is non-trivial because of the mixing of the index tensor elements in the Hamiltonians; previously known methods only handled uniaxial dielectrics (where only two independent isotropic optical functions could overlap). The biaxial method introduced also allows three-dimensional multi-faced Janus devices to be designed; these are worked out in an example of what is possible to design with the method. PMID:23792651

  19. Genuine effectively biaxial left-handed metamaterials due to extreme coupling.

    PubMed

    Menzel, Christoph; Alaee, Rasoul; Pshenay-Severin, Ekaterina; Helgert, Christian; Chipouline, Arkadi; Rockstuhl, Carsten; Pertsch, Thomas; Lederer, Falk

    2012-02-15

    Most left-handed metamaterials cannot be described by local effective permittivity or permeability tensors in the visible or near-infrared due to the mesoscopic size of the respective unit cells and the related strong spatial dispersion. We lift this problem and propose a metamaterial exhibiting artificial magnetism that does not suffer from this restriction. The artificial magnetism arises from the extreme coupling between both metallic films forming the unit cell. We show that its electromagnetic response can be properly described by biaxial local constitutive relations. A genuine biaxial left-handed fishnet metamaterial is suggested, which can be realized by atomic layer deposition to fabricate the nanoscaled spacing layers required for extreme coupling.

  20. Neutron diffraction investigation of an in-plane biaxial fatigued stainless steel sample of cruciform geometry

    NASA Astrophysics Data System (ADS)

    Taran, Yu V.; Balagurov, A. M.; Sheverev, S. G.; Schreiber, J.; Korsunsky, A. M.; Vorster, W. J. J.; Bomas, H.; Stoeberl, C.

    2008-03-01

    Fatigue and fracture under multiaxial stresses are among the most important current research topics aimed at ensuring improved reliability of industrial components. An ex situ in-plane biaxial low cycle fatigued sample of cruciform geometry from austenitic stainless steel AISI 321 H was investigated on the FSD stress-diffractometer at the IBR-2 pulsed nuclear reactor by using the neutron strain scanner and the uniaxial stress rig. The phase composition of fatigued material was determined and the residual macrostresses and phase microstresses were measured. To the best of our knowledge, no neutron diffraction investigations of materials subjected to biaxial loading have been previously carried out. The first results of the neutron diffraction experiment are presented and discussed.

  1. A generalized method for the analysis of planar biaxial mechanical data using tethered testing configurations.

    PubMed

    Zhang, Will; Feng, Yuan; Lee, Chung-Hao; Billiar, Kristen L; Sacks, Michael S

    2015-06-01

    Simulation of the mechanical behavior of soft tissues is critical for many physiological and medical device applications. Accurate mechanical test data is crucial for both obtaining the form and robust parameter determination of the constitutive model. For incompressible soft tissues that are either membranes or thin sections, planar biaxial mechanical testing configurations can provide much information about the anisotropic stress-strain behavior. However, the analysis of soft biological tissue planar biaxial mechanical test data can be complicated by in-plane shear, tissue heterogeneities, and inelastic changes in specimen geometry that commonly occur during testing. These inelastic effects, without appropriate corrections, alter the stress-traction mapping and violates equilibrium so that the stress tensor is incorrectly determined. To overcome these problems, we presented an analytical method to determine the Cauchy stress tensor from the experimentally derived tractions for tethered testing configurations. We accounted for the measured testing geometry and compensate for run-time inelastic effects by enforcing equilibrium using small rigid body rotations. To evaluate the effectiveness of our method, we simulated complete planar biaxial test configurations that incorporated actual device mechanisms, specimen geometry, and heterogeneous tissue fibrous structure using a finite element (FE) model. We determined that our method corrected the errors in the equilibrium of momentum and correctly estimated the Cauchy stress tensor. We also noted that since stress is applied primarily over a subregion bounded by the tethers, an adjustment to the effective specimen dimensions is required to correct the magnitude of the stresses. Simulations of various tether placements demonstrated that typical tether placements used in the current experimental setups will produce accurate stress tensor estimates. Overall, our method provides an improved and relatively straightforward

  2. Effect of Corneal Incision Enlargement on Surgically Induced Astigmatism in Biaxial Microincision Cataract Surgery

    PubMed Central

    Tetikoğlu, Mehmet; Yeter, Celal; Helvacıoğlu, Fırat; Aktaş, Serdar; Sağdık, Hacı Murat; Özcura, Fatih

    2016-01-01

    Objectives: To evaluate surgically induced astigmatism (SIA) in biaxial microincision cataract surgery with enlargement of one corneal incision during intraocular lens implantation (IOL). Materials and Methods: Data from 683 eyes with cataract that underwent biaxial microincision cataract surgery and IOL were retrospectively analyzed. The operated eyes were divided into 4 groups defined by final corneal incision length after IOL implantation. There were 83 eyes with 1.6 mm corneal incisions (group 1) and 200 eyes in each of the 2, 2.4, and 2.8 mm corneal incision groups (groups 2, 3 and 4, respectively). SIA was assessed using preoperative and postoperative keratometric values at one month. Results: The mean magnitude of SIA was 0.83±0.4 D in group 1, 0.93±0.5 D in group 2, 1.03±0.6 D in group 3 and 1.04±0.7 D in group 4. The SIA showed statistically significant differences between the four groups (p=0.05). Pairwise group comparisons revealed significant differences between groups 1 and 3 and groups 1 and 4 (p=0.005). Conclusion: Biaxial microincision cataract surgery with an incision size of 1.6 mm resulted in the least SIA. Enlargement of the corneal incision beyond 2.0 mm during IOL implantation led to significant increases in SIA. We believe that with the development and dissemination of IOLs which can be inserted through small corneal incisions, biaxial microincision cataract surgery will be the best choice to prevent SIA and increase visual acuity. PMID:27800270

  3. Mechanical characterisation of porcine rectus sheath under uniaxial and biaxial tension.

    PubMed

    Lyons, Mathew; Winter, Des C; Simms, Ciaran K

    2014-06-01

    Incisional hernia development is a significant complication after laparoscopic abdominal surgery. Intra-abdominal pressure (IAP) is known to initiate the extrusion of intestines through the abdominal wall, but there is limited data on the mechanics of IAP generation and the structural properties of rectus sheath. This paper presents an explanation of the mechanics of IAP development, a study of the uniaxial and biaxial tensile properties of porcine rectus sheath, and a simple computational investigation of the tissue. Analysis using Laplace׳s law showed a circumferential stress in the abdominal wall of approx. 1.1MPa due to an IAP of 11kPa, commonly seen during coughing. Uniaxial and biaxial tensile tests were conducted on samples of porcine rectus sheath to characterise the stress-stretch responses of the tissue. Under uniaxial tension, fibre direction samples failed on average at a stress of 4.5MPa at a stretch of 1.07 while cross-fibre samples failed at a stress of 1.6MPa under a stretch of 1.29. Under equi-biaxial tension, failure occurred at 1.6MPa with the fibre direction stretching to only 1.02 while the cross-fibre direction stretched to 1.13. Uniaxial and biaxial stress-stretch plots are presented allowing detailed modelling of the tissue either in silico or in a surrogate material. An FeBio computational model of the tissue is presented using a combination of an Ogden and an exponential power law model to represent the matrix and fibres respectively. The structural properties of porcine rectus sheath have been characterised and add to the small set of human data in the literature with which it may be possible to develop methods to reduce the incidence of incisional hernia development. PMID:24725440

  4. Flexural strength of dental composite restoratives: comparison of biaxial and three-point bending test.

    PubMed

    Chung, S M; Yap, A U J; Chandra, S P; Lim, C T

    2004-11-15

    This study compared two test methods used to evaluate the flexural strength of resin-based dental composites. The two test methods evaluated were the three-point bending test4 and the biaxial flexural test. Materials used in this investigation were from the same manufacturer (3M ESPE) and included microfill (A110), minifill (Z100 and Filtek Z250), polyacid modified (F2000), and flowable [Filtek Flowable (FF)] composites. Flexural strength was determined with the use of both test methods after 1 week of conditioning in water at 37 degrees C. Data were analyzed with the use of an ANOVA/Scheffe test and an independent-samples t test at significance level 0.05. Mean flexural strength (n = 7) ranged from 66.61 to 147.21 and 67.27 to 182.81 MPa for three-point bending and ball-on-three-ball biaxial test methods, respectively. In both test methods, Z100 was significantly stronger than all other composites evaluated. In the three-point bending test, flexural strength of Z250 was significantly higher than A110, F2000 and FF, and FF was significantly stronger than A110 and F2000. The biaxial test method arrived at the same conclusions except that there was no significant difference between Z250 and FF. Pearson's correlation revealed a significantly (p < 0.01) positive and good correlation (R2 = 0.72) in flexural strength between the two test methods. Although the biaxial test has the advantage of utilizing small specimens, the low reproducibility of this test method does not support the proposition that it is a more reliable test method when compared to the ISO three-point bending test. PMID:15386492

  5. Residual stresses in biaxially fatigued austenitic stainless steel sample of cruciform geometry

    NASA Astrophysics Data System (ADS)

    Taran, Yu V.; Balagurov, A. M.; Schreiber, J.; Evans, A.; Venter, A. M.

    2012-02-01

    A specifically designed cruciform-shaped austenitic stainless steel AISI 321 sample was subjected to ex-situ biaxial tension-compression cycling to establish ferromagnetic martensitic phase conversion under the action of plastic deformation. The time-of-flight neutron diffraction technique was employed for in-plane residual stress determination in this sample for both the austenitic and martensitic phases. The 2D data enabled determination of macro-, micro-, hydro- and deviatoric contributions to the total phase stresses.

  6. Residual stresses in biaxially fatigued austenitic stainless steel sample of cruciform geometry

    NASA Astrophysics Data System (ADS)

    Taran, Yu. V.; Balagurov, A. M.; Schreiber, J.; Evans, A.; Venter, A. M.

    2011-03-01

    A specifically designed cruciform-shaped austenitic stainless steel AISI 321 sample was subjected to ex-situ biaxial tension-compression cycling to establish ferromagnetic martensitic phase conversion under the action of plastic deformation. The time-of-flight neutron diffraction technique was employed for in-plane residual stress determination in this sample for both the austenitic and martensitic phases. The 2D data enabled determination of the macro-, micro-, hydro- and deviatoric contributions to the total phase stresses.

  7. MUSE alignment onto VLT

    NASA Astrophysics Data System (ADS)

    Laurent, Florence; Renault, Edgard; Boudon, Didier; Caillier, Patrick; Daguisé, Eric; Dupuy, Christophe; Jarno, Aurélien; Lizon, Jean-Louis; Migniau, Jean-Emmanuel; Nicklas, Harald; Piqueras, Laure

    2014-07-01

    MUSE (Multi Unit Spectroscopic Explorer) is a second generation Very Large Telescope (VLT) integral field spectrograph developed for the European Southern Observatory (ESO). It combines a 1' x 1' field of view sampled at 0.2 arcsec for its Wide Field Mode (WFM) and a 7.5"x7.5" field of view for its Narrow Field Mode (NFM). Both modes will operate with the improved spatial resolution provided by GALACSI (Ground Atmospheric Layer Adaptive Optics for Spectroscopic Imaging), that will use the VLT deformable secondary mirror and 4 Laser Guide Stars (LGS) foreseen in 2015. MUSE operates in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently commissioning MUSE in the Very Large Telescope for the Preliminary Acceptance in Chile, scheduled for September, 2014. MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile where that was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transported, fully aligned and without any optomechanical dismounting, onto VLT telescope where the first light was overcame the 7th of February, 2014. This paper describes the alignment procedure of the whole MUSE instrument with respect to the Very Large Telescope (VLT). It describes how 6 tons could be move with accuracy better than 0.025mm and less than 0.25 arcmin in order to reach alignment requirements. The success

  8. Xenon-Ion Drilling of Tungsten Films

    NASA Technical Reports Server (NTRS)

    Garner, C. E.

    1986-01-01

    High-velocity xenon ions used to drill holes of controlled size and distribution through tungsten layer that sheaths surface of controlled-porosity dispenser cathode of traveling wave-tube electron emitter. Controlled-porosity dispenser cathode employs barium/calcium/ aluminum oxide mixture that migrates through pores in cathode surface, thus coating it and reducing its work function. Rapid, precise drilling technique applied to films of other metals and used in other applications where micron-scale holes required. Method requires only few hours, as opposed to tens of hours by prior methods.

  9. Low temperature photoresponse of monolayer tungsten disulphide

    SciTech Connect

    Cao, Bingchen; Shen, Xiaonan; Shang, Jingzhi; Cong, Chunxiao; Yang, Weihuang; Eginligil, Mustafa E-mail: meginligil@ntu.edu.sg; Yu, Ting E-mail: meginligil@ntu.edu.sg

    2014-11-01

    High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD) method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup), while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  10. Tungsten fiber reinforced superalloys: A status review

    NASA Technical Reports Server (NTRS)

    Petrasek, D. W.; Signorelli, R. A.

    1981-01-01

    Improved performance of heat engines is largely dependent upon maximum cycle temperatures. Tungsten fiber reinforced superalloys (TFRS) are the first of a family of high temperature composites that offer the potential for significantly raising hot component operating temperatures and thus leading to improved heat engine performance. This status review of TFRS research emphasizes the promising property data developed to date, the status of TFRS composite airfoil fabrication technology, and the areas requiring more attention to assure their applicability to hot section components of aircraft gas turbine engines.

  11. Tungsten imido catalysts for selective ethylene dimerisation.

    PubMed

    Wright, Christopher M R; Turner, Zoë R; Buffet, Jean-Charles; O'Hare, Dermot

    2016-02-14

    A tungsten imido complex W(NDipp)Me3Cl (Dipp = 2,6-(i)Pr-C6H3) is active for the selective dimerisation of ethylene to yield 1-butene under mild conditions. Immobilisation and activation of W(NDipp)Cl4(THF) on layered double hydroxides, silica or polymethylaluminoxane yields active solid state catalysts for the selective dimerisation of ethylene. The polymethylaluminoxane-based catalyst displays a turnover frequency (4.0 molC2H4 molW(-1) h(-1)) almost 7 times that of the homogeneous catalyst.

  12. On the Use of Biaxial Properties in Modeling Annulus as a Holzapfel–Gasser–Ogden Material

    PubMed Central

    Momeni Shahraki, Narjes; Fatemi, Ali; Goel, Vijay K.; Agarwal, Anand

    2015-01-01

    Besides the biology, stresses and strains within the tissue greatly influence the location of damage initiation and mode of failure in an intervertebral disk. Finite element models of a functional spinal unit (FSU) that incorporate reasonably accurate geometry and appropriate material properties are suitable to investigate such issues. Different material models and techniques have been used to model the anisotropic annulus fibrosus, but the abilities of these models to predict damage initiation in the annulus and to explain clinically observed phenomena are unclear. In this study, a hyperelastic anisotropic material model for the annulus with two different sets of material constants, experimentally determined using uniaxial and biaxial loading conditions, were incorporated in a 3D finite element model of a ligamentous FSU. The purpose of the study was to highlight the biomechanical differences (e.g., intradiscal pressure, motion, forces, stresses, strains, etc.) due to the dissimilarity between the two sets of material properties (uniaxial and biaxial). Based on the analyses, the biaxial constants simulations resulted in better agreements with the in vitro and in vivo data, and thus are more suitable for future damage analysis and failure prediction of the annulus under complex multiaxial loading conditions. PMID:26090359

  13. Biaxial unloading and springback behavior of dual-phase DP590 steel using cruciform specimens

    NASA Astrophysics Data System (ADS)

    Korkolis, Yannis P.; Deng, Nengxiu; Kuwabara, Toshihiko

    2013-12-01

    The unloading behavior of a dual-phase steel (DP590) from a biaxial state of stress was probed using a newly-designed cruciform specimen. The specimen was designed to develop uniform and relatively large plastic strains (over 15% equivalent logarithmic plastic strain) in the gage section, before failure. Nine radial loading paths in the 1st quadrant of the plane stress space were probed. The experiments involved repeated loading and unloading up to failure. At every unloading, the initial response was found to agree with the linear, orthotropically elastic response of the undeformed material. This first linear response was followed by a second one, at a reduced slope. Beyond that, the recorded response was fully non-linear. The same sequence of events was observed during each reloading. The biaxial non-linear strain recovery components ɛxnl and ɛynl were measured to be on average approximately 11% of the elastic strains ɛxe and ɛye, respectively. This ratio was found to increase with plastic deformation. Subsequently, these biaxial experiments were used to calibrate the Yld2000-2D yield function.

  14. Effect of peroxide bleaching on the biaxial flexural strength and modulus of bovine dentin

    PubMed Central

    Carvalho, Adriana Oliveira; Ayres, Ana Paula Almeida; de Almeida, Letícia Cunha Amaral Gonzaga; Briso, André Luiz Fraga; Rueggeberg, Frederick Allen; Giannini, Marcelo

    2015-01-01

    Objective: This study evaluated the effects of carbamide peroxide and hydrogen peroxide on the biaxial flexural strength and flexural modulus of bovine dentin. Materials and Methods: Thirty coronal dentin disks (0.5 mm thick × 6.0 mm diameter) were prepared from bovine teeth. The disks were randomly divided into three groups (n=10): A control group (unbleached), a group bleached with 10% carbamide peroxide (8 h at 37°C), and a group bleached with 38% hydrogen peroxide (three 10 min applications at 37°C). The specimens were tested in a biaxial flexural apparatus held in a universal testing machine at 1.27 mm/min until failure occurred, and the biaxial mechanical properties were calculated. For each test parameter, the data were statistically analyzed by Fisher's PLSD test (predetermined α = 0.05). Results: The group bleached with 38% hydrogen peroxide demonstrated significantly lower flexural strength than the unbleached control group. Hydrogen peroxide treatment resulted in a significantly lower flexural modulus compared with the control group and with carbamide peroxide bleaching. Conclusion: Exposure of dentin to hydrogen peroxide significantly reduced both the flexural strength and the flexural modulus compared with the no-treatment control, whereas exposure to carbamide peroxide did not significantly affect either parameter. PMID:26038658

  15. Self-propelled Brownian spinning top: dynamics of a biaxial swimmer at low Reynolds numbers.

    PubMed

    Wittkowski, Raphael; Löwen, Hartmut

    2012-02-01

    Recently the Brownian dynamics of self-propelled (active) rodlike particles was explored to model the motion of colloidal microswimmers, catalytically driven nanorods, and bacteria. Here we generalize this description to biaxial particles with arbitrary shape and derive the corresponding Langevin equation for a self-propelled Brownian spinning top. The biaxial swimmer is exposed to a hydrodynamic Stokes friction force at low Reynolds numbers, to fluctuating random forces and torques as well as to an external and an internal (effective) force and torque. The latter quantities control its self-propulsion. Due to biaxiality and hydrodynamic translational-rotational coupling, the Langevin equation can only be solved numerically. In the special case of an orthotropic particle in the absence of external forces and torques, the noise-free (zero-temperature) trajectory is analytically found to be a circular helix. This trajectory is confirmed numerically to be more complex in the general case of an arbitrarily shaped particle under the influence of arbitrary forces and torques involving a transient irregular motion before ending up in a simple periodic motion. By contrast, if the external force vanishes, no transient regime is found, and the particle moves on a superhelical trajectory. For orthotropic particles, the noise-averaged trajectory is a generalized concho-spiral. We furthermore study the reduction of the model to two spatial dimensions and classify the noise-free trajectories completely finding circles, straight lines with and without transients, as well as cycloids and arbitrary periodic trajectories.

  16. Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2.

    PubMed

    Lloyd, David; Liu, Xinghui; Christopher, Jason W; Cantley, Lauren; Wadehra, Anubhav; Kim, Brian L; Goldberg, Bennett B; Swan, Anna K; Bunch, J Scott

    2016-09-14

    We demonstrate the continuous and reversible tuning of the optical band gap of suspended monolayer MoS2 membranes by as much as 500 meV by applying very large biaxial strains. By using chemical vapor deposition (CVD) to grow crystals that are highly impermeable to gas, we are able to apply a pressure difference across suspended membranes to induce biaxial strains. We observe the effect of strain on the energy and intensity of the peaks in the photoluminescence (PL) spectrum and find a linear tuning rate of the optical band gap of 99 meV/%. This method is then used to study the PL spectra of bilayer and trilayer devices under strain and to find the shift rates and Grüneisen parameters of two Raman modes in monolayer MoS2. Finally, we use this result to show that we can apply biaxial strains as large as 5.6% across micron-sized areas and report evidence for the strain tuning of higher level optical transitions.

  17. Biaxial Texture Evolution in MgO Films Fabricated Using Ion Beam-Assisted Deposition

    NASA Astrophysics Data System (ADS)

    Xue, Yan; Zhang, Ya-Hui; Zhao, Rui-Peng; Zhang, Fei; Lu, Yu-Ming; Cai, Chuan-Bing; Xiong, Jie; Tao, Bo-Wan

    2016-07-01

    The growth of multifunctional thin films on flexible substrates is important technologically, because flexible electronics require such a platform. In this study, we examined the evolution of biaxial texture in MgO films prepared using ion beam-assisted deposition (IBAD) on a Hastelloy substrate. Texture and microstructure developments were characterized through in situ reflection high-energy electron diffraction monitoring, x-ray diffraction, and atomic force microscopy, which demonstrated that biaxial texture was developed during the nucleation stage (~2.2 nm). The best biaxial texture was obtained with a thickness of approximately 12 nm. As MgO continued to grow, the influence of surface energy was reduced, and film growth was driven by the attempt to minimize volume free-energy density. Thus the MgO grains were subsequently rotated at the (002) direction toward the ion beam. In addition, an approach was developed for accelerating in-plane texture evolution by pre-depositing an amorphous MgO layer before IBAD.

  18. Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2.

    PubMed

    Lloyd, David; Liu, Xinghui; Christopher, Jason W; Cantley, Lauren; Wadehra, Anubhav; Kim, Brian L; Goldberg, Bennett B; Swan, Anna K; Bunch, J Scott

    2016-09-14

    We demonstrate the continuous and reversible tuning of the optical band gap of suspended monolayer MoS2 membranes by as much as 500 meV by applying very large biaxial strains. By using chemical vapor deposition (CVD) to grow crystals that are highly impermeable to gas, we are able to apply a pressure difference across suspended membranes to induce biaxial strains. We observe the effect of strain on the energy and intensity of the peaks in the photoluminescence (PL) spectrum and find a linear tuning rate of the optical band gap of 99 meV/%. This method is then used to study the PL spectra of bilayer and trilayer devices under strain and to find the shift rates and Grüneisen parameters of two Raman modes in monolayer MoS2. Finally, we use this result to show that we can apply biaxial strains as large as 5.6% across micron-sized areas and report evidence for the strain tuning of higher level optical transitions. PMID:27509768

  19. On the correct interpretation of measured force and calculation of material stress in biaxial tests.

    PubMed

    Nolan, D R; McGarry, J P

    2016-01-01

    Biaxial tests are commonly used to investigate the mechanical behaviour of soft biological tissues and polymers. In the current paper we uncover a fundamental problem associated with the calculation of material stress from measured force in standard biaxial tests. In addition to measured forces, localised unmeasured shear forces also occur at the clamps and the inability to quantify such forces has significant implications for the calculation of material stress from simplified force-equilibrium relationships. Unmeasured shear forces are shown to arise due to two distinct competing contributions: (1) negative shear force due to stretching of the orthogonal clamp, and (2) positive shear force as a result of material Poisson-effect. The clamp shear force is highly dependent on the specimen geometry and the clamp displacement ratio, as consequently, is the measured force-stress relationship. Additionally in this study we demonstrate that commonly accepted formulae for the estimation of material stress in the central region of a cruciform specimen are highly inaccurate. A reliable empirical correction factor for the general case of isotropic materials must be a function of specimen geometry and the biaxial clamp displacement ratio. Finally we demonstrate that a correction factor for the general case of non-linear anisotropic materials is not feasible and we suggest the use of inverse finite element analysis as a practical means of interpreting experimental data for such complex materials. PMID:26327453

  20. On the correct interpretation of measured force and calculation of material stress in biaxial tests.

    PubMed

    Nolan, D R; McGarry, J P

    2016-01-01

    Biaxial tests are commonly used to investigate the mechanical behaviour of soft biological tissues and polymers. In the current paper we uncover a fundamental problem associated with the calculation of material stress from measured force in standard biaxial tests. In addition to measured forces, localised unmeasured shear forces also occur at the clamps and the inability to quantify such forces has significant implications for the calculation of material stress from simplified force-equilibrium relationships. Unmeasured shear forces are shown to arise due to two distinct competing contributions: (1) negative shear force due to stretching of the orthogonal clamp, and (2) positive shear force as a result of material Poisson-effect. The clamp shear force is highly dependent on the specimen geometry and the clamp displacement ratio, as consequently, is the measured force-stress relationship. Additionally in this study we demonstrate that commonly accepted formulae for the estimation of material stress in the central region of a cruciform specimen are highly inaccurate. A reliable empirical correction factor for the general case of isotropic materials must be a function of specimen geometry and the biaxial clamp displacement ratio. Finally we demonstrate that a correction factor for the general case of non-linear anisotropic materials is not feasible and we suggest the use of inverse finite element analysis as a practical means of interpreting experimental data for such complex materials.

  1. Fabrication and reliable implementation of an ionic polymer-metal composite (IPMC) biaxial bending actuator

    NASA Astrophysics Data System (ADS)

    Lee, Gil-Yong; Choi, Jung-Oh; Kim, Myeungseon; Ahn, Sung-Hoon

    2011-10-01

    Ionic polymer-metal composites (IPMCs) are one of the most popular types of electro-active polymer actuator, due to their low electric driving potential, large deformation range, and light weight. IPMCs have been used as actuators or sensors in many areas of biomedical and robotic engineering. In this research, IPMCs were studied as a biaxial bending actuator capable of smart and flexible motion. We designed and fabricated this bending actuator and implemented it to have a reliable actuating motion using a systematic approach. The resulting device was bar shaped with a square cross section and had four insulated electrodes on its surface. By applying different voltages to these four electrodes, a biaxial bending motion can be induced. To construct this actuator, several fabrication processes were considered. We modified the Nafion stacking method, and established a complete sequence of actuator fabrication processes. Using these processes, we were able to fabricate an IPMC biaxial bending actuator with both high actuating force and high flexibility. Several experiments were conducted to investigate and verify the performance of the actuator. The IPMC actuator system was modeled from experimentally measured data, and using this actuator model, a closed-loop proportional integral (PI) controller was designed. Reference position tracking performances of open-loop and closed-loop systems were compared. Finally, circular motion tracking performances of the actuator tip were tested under different rotation frequencies and radii of a reference trajectory circle.

  2. Microstructure and tensile properties of tungsten at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Shen, Tielong; Dai, Yong; Lee, Yongjoong

    2016-01-01

    In order to support the development of the 5 MW spallation target for the European Spallation Source, the effect of fabrication process on microstructure, ductile-to-brittle transition temperature (DBTT), tensile and fracture behaviour of powder-metallurgy pure tungsten materials has been investigated. A hot-rolled (HR) tungsten piece of 12 mm thickness and a hot-forged (HF) piece of about 80 mm thickness were used to simulate the thin and thick blocks in the target. The two tungsten pieces were characterized with metallography analysis, hardness measurement and tensile testing. The HR piece exhibits an anisotropic grain structure with an average size of about 330 × 140 × 40 μm in rolling, long transverse and short transverse (thickness) directions. The HF piece possesses a bimodal grain structure with about 310 × 170 × 70 μm grain size in deformed part and about 25 μm sized grains remained from sintering process. Hardness (HV0.2) of the HR piece is slightly greater than that of the HF one. The ductility of the HR tungsten specimens is greater than that of the HF tungsten. For the HF tungsten piece, specimens with small grains in gauge section manifest lower ductility but higher strength. The DBTT evaluated from the tensile results is 250-300 °C for the HR tungsten and about 350 °C for the HF tungsten.

  3. Calibration and Temperature Profile of a Tungsten Filament Lamp

    ERIC Educational Resources Information Center

    de Izarra, Charles; Gitton, Jean-Michel

    2010-01-01

    The goal of this work proposed for undergraduate students and teachers is the calibration of a tungsten filament lamp from electric measurements that are both simple and precise, allowing to determine the temperature of tungsten filament as a function of the current intensity. This calibration procedure was first applied to a conventional filament…

  4. Gas Tungsten Arc Welding. Welding Module 6. Instructor's Guide.

    ERIC Educational Resources Information Center

    Missouri Univ., Columbia. Instructional Materials Lab.

    This guide is intended to assist vocational educators in teaching a three-unit module in gas tungsten arc welding. The module has been designed to be totally integrated with Missouri's Vocational Instruction Management System. The basic principles involved in gas tungsten arc welding, supplies, and applications are covered. The materials included…

  5. Measurement of the Properties of Tungsten at High Temperatures

    NASA Technical Reports Server (NTRS)

    Margrave, J. L.

    1985-01-01

    The thermophysical properties of tungsten and other materials were measured using containerless techniques. Levitation of liquid silver, gallium and tungsten were studied. The studies of liquid aluminum are almost complete and are expected to derive new, reliable properties for liquid aluminum.

  6. Inflation by alignment

    SciTech Connect

    Burgess, C.P.; Roest, Diederik

    2015-06-08

    Pseudo-Goldstone bosons (pGBs) can provide technically natural inflatons, as has been comparatively well-explored in the simplest axion examples. Although inflationary success requires trans-Planckian decay constants, f≳M{sub p}, several mechanisms have been proposed to obtain this, relying on (mis-)alignments between potential and kinetic energies in multiple-field models. We extend these mechanisms to a broader class of inflationary models, including in particular the exponential potentials that arise for pGB potentials based on noncompact groups (and so which might apply to moduli in an extra-dimensional setting). The resulting potentials provide natural large-field inflationary models and can predict a larger primordial tensor signal than is true for simpler single-field versions of these models. In so doing we provide a unified treatment of several alignment mechanisms, showing how each emerges as a limit of the more general setup.

  7. Orbit IMU alignment: Error analysis

    NASA Technical Reports Server (NTRS)

    Corson, R. W.

    1980-01-01

    A comprehensive accuracy analysis of orbit inertial measurement unit (IMU) alignments using the shuttle star trackers was completed and the results are presented. Monte Carlo techniques were used in a computer simulation of the IMU alignment hardware and software systems to: (1) determine the expected Space Transportation System 1 Flight (STS-1) manual mode IMU alignment accuracy; (2) investigate the accuracy of alignments in later shuttle flights when the automatic mode of star acquisition may be used; and (3) verify that an analytical model previously used for estimating the alignment error is a valid model. The analysis results do not differ significantly from expectations. The standard deviation in the IMU alignment error for STS-1 alignments was determined to the 68 arc seconds per axis. This corresponds to a 99.7% probability that the magnitude of the total alignment error is less than 258 arc seconds.

  8. Nuclear reactor alignment plate configuration

    DOEpatents

    Altman, David A; Forsyth, David R; Smith, Richard E; Singleton, Norman R

    2014-01-28

    An alignment plate that is attached to a core barrel of a pressurized water reactor and fits within slots within a top plate of a lower core shroud and upper core plate to maintain lateral alignment of the reactor internals. The alignment plate is connected to the core barrel through two vertically-spaced dowel pins that extend from the outside surface of the core barrel through a reinforcement pad and into corresponding holes in the alignment plate. Additionally, threaded fasteners are inserted around the perimeter of the reinforcement pad and into the alignment plate to further secure the alignment plate to the core barrel. A fillet weld also is deposited around the perimeter of the reinforcement pad. To accomodate thermal growth between the alignment plate and the core barrel, a gap is left above, below and at both sides of one of the dowel pins in the alignment plate holes through with the dowel pins pass.

  9. Alignment reference device

    DOEpatents

    Patton, Gail Y.; Torgerson, Darrel D.

    1987-01-01

    An alignment reference device provides a collimated laser beam that minimizes angular deviations therein. A laser beam source outputs the beam into a single mode optical fiber. The output end of the optical fiber acts as a source of radiant energy and is positioned at the focal point of a lens system where the focal point is positioned within the lens. The output beam reflects off a mirror back to the lens that produces a collimated beam.

  10. Tungsten recycling in the United States in 2000

    USGS Publications Warehouse

    Shedd, Kim B.

    2011-01-01

    This report, which is one of a series of reports on metals recycling, defines and quantifies the flow of tungsten-bearing materials in the United States from imports and stock releases through consumption and disposition in 2000, with particular emphasis on the recycling of industrial scrap (new scrap) and used products (old scrap). Because of tungsten's many diverse uses, numerous types of scrap were available for recycling by a wide variety of processes. In 2000, an estimated 46 percent of U.S. tungsten supply was derived from scrap. The ratio of tungsten consumed from new scrap to that consumed from old scrap was estimated to be 20:80. Of all the tungsten in old scrap available for recycling, an estimated 66 percent was either consumed in the United States or exported to be recycled.

  11. Dynamic Alignment at SLS

    SciTech Connect

    Ruland, Robert E.

    2003-04-23

    The relative alignment of components in the storage ring of the Swiss Light Source (SLS) is guaranteed by mechanical means. The magnets are rigidly fixed to 48 girders by means of alignment rails with tolerances of less than {+-}15 {micro}m. The bending magnets, supported by 3 point ball bearings, overlap adjacent girders and thus establish virtual train links between the girders, located near the bending magnet centres. Keeping the distortion of the storage ring geometry within a tolerance of {+-}100 {micro}m in order to guarantee sufficient dynamic apertures, requires continuous monitoring and correction of the girder locations. Two monitoring systems for the horizontal and the vertical direction will be installed to measure displacements of the train link between girders, which are due to ground settings and temperature effects: The hydrostatic levelling system (HLS) gives an absolute vertical reference, while the horizontal positioning system (HPS), which employs low cost linear encoders with sub-micron resolution, measures relative horizontal movements. The girder mover system based on five DC motors per girder allows a dynamic realignment of the storage ring within a working window of more than {+-}1 mm for girder translations and {+-}1 mrad for rotations. We will describe both monitoring systems (HLS and HPS) as well as the applied correction scheme based on the girder movers. We also show simulations indicating that beam based girder alignment takes care of most of the static closed orbit correction.

  12. Alignment and alignment transition of bent core nematics

    NASA Astrophysics Data System (ADS)

    Elamain, Omaima; Hegde, Gurumurthy; Komitov, Lachezar

    2013-07-01

    We report on the alignment of nematics consisting of bimesogen bent core molecules of chlorine substituent of benzene derivative and their binary mixture with rod like nematics. It was found that the alignment layer made from polyimide material, which is usually used for promoting vertical (homeotropic) alignment of rod like nematics, promotes instead a planar alignment of the bent core nematic and its nematic mixtures. At higher concentration of the rod like nematic component in these mixtures, a temperature driven transition from vertical to planar alignment was found near the transition to isotropic phase.

  13. Polar cap arcs: Sun-aligned or cusp-aligned?

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Paxton, L. J.; Zhang, Qinghe; Xing, Zanyang

    2016-08-01

    Polar cap arcs are often called sun-aligned arcs. Satellite observations reveal that polar cap arcs join together at the cusp and are actually cusp aligned. Strong ionospheric plasma velocity shears, thus field aligned currents, were associated with polar arcs and they were likely caused by Kelvin-Helmholtz waves around the low-latitude magnetopause under a northward IMF Bz. The magnetic field lines around the magnetopause join together in the cusp region so are the field aligned currents and particle precipitation. This explains why polar arcs are cusp aligned.

  14. Corrosion and wear resistance of tungsten carbide-cobalt and tungsten carbide-cobalt-chromium thermal spray coatings

    SciTech Connect

    Quets, J.; Alford, J.R.

    1999-07-01

    Tungsten carbide thermal spray coatings provide wear surfaces to new and overhauled components for various industries. Their wear resistance is obtained by incorporating small tungsten carbide particles into a metal matrix. This presentation will show what parameters influence their corrosion resistance in the ASTM B-117 Salt Spray Corrosion Test,

  15. Time-dependent biaxial mechanical behavior of the aortic heart valve leaflet.

    PubMed

    Stella, John A; Liao, Jun; Sacks, Michael S

    2007-01-01

    Despite continued progress in the treatment of aortic valve (AV) disease, current treatments continue to be challenged to consistently restore AV function for extended durations. Improved approaches for AV repair and replacement rests upon our ability to more fully comprehend and simulate AV function. While the elastic behavior the AV leaflet (AVL) has been previously investigated, time-dependent behaviors under physiological biaxial loading states have yet to be quantified. In the current study, we performed strain rate, creep, and stress-relaxation experiments using porcine AVL under planar biaxial stretch and loaded to physiological levels (60 N/m equi-biaxial tension), with strain rates ranging from quasi-static to physiologic. The resulting stress-strain responses were found to be independent of strain rate, as was the observed low level of hysteresis ( approximately 17%). Stress relaxation and creep results indicated that while the AVL exhibited significant stress relaxation, it exhibited negligible creep over the 3h test duration. These results are all in accordance with our previous findings for the mitral valve anterior leaflet (MVAL) [Grashow, J.S., Sacks, M.S., Liao, J., Yoganathan, A.P., 2006a. Planar biaxial creep and stress relaxatin of the mitral valve anterior leaflet. Annals of Biomedical Engineering 34 (10), 1509-1518; Grashow, J.S., Yoganathan, A.P., Sacks, M.S., 2006b. Biaxial stress-stretch behavior of the mitral valve anterior leaflet at physiologic strain rates. Annals of Biomedical Engineering 34 (2), 315-325], and support our observations that valvular tissues are functionally anisotropic, quasi-elastic biological materials. These results appear to be unique to valvular tissues, and indicate an ability to withstand loading without time-dependent effects under physiologic loading conditions. Based on a recent study that suggested valvular collagen fibrils are not intrinsically viscoelastic [Liao, J., Yang, L., Grashow, J., Sacks, M.S., 2007

  16. Tungsten tetraboride, an inexpensive superhard material

    PubMed Central

    Mohammadi, Reza; Lech, Andrew T.; Xie, Miao; Weaver, Beth E.; Yeung, Michael T.; Tolbert, Sarah H.; Kaner, Richard B.

    2011-01-01

    Tungsten tetraboride (WB4) is an interesting candidate as a less expensive member of the growing group of superhard transition metal borides. WB4 was successfully synthesized by arc melting from the elements. Characterization using powder X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX) indicates that the as-synthesized material is phase pure. The zero-pressure bulk modulus, as measured by high-pressure X-ray diffraction for WB4, is 339 GPa. Mechanical testing using microindentation gives a Vickers hardness of 43.3 ± 2.9 GPa under an applied load of 0.49 N. Various ratios of rhenium were added to WB4 in an attempt to increase hardness. With the addition of 1 at.% Re, the Vickers hardness increased to approximately 50 GPa at 0.49 N. Powders of tungsten tetraboride with and without 1 at.% Re addition are thermally stable up to approximately 400 °C in air as measured by thermal gravimetric analysis. PMID:21690363

  17. Concentration dependent hydrogen diffusion in tungsten

    NASA Astrophysics Data System (ADS)

    Ahlgren, T.; Bukonte, L.

    2016-10-01

    The diffusion of hydrogen in tungsten is studied as a function of temperature, hydrogen concentration and pressure using Molecular Dynamics technique. A new analysis method to determine diffusion coefficients that accounts for the random oscillation of atoms around the equilibrium position is presented. The results indicate that the hydrogen migration barrier of 0.25 eV should be used instead of the presently recommended value of 0.39 eV. This conclusion is supported by both experiments and density functional theory calculations. Moreover, the migration volume at the saddle point for H in W is found to be positive: ΔVm ≈ 0.488 Å3, leading to a decrease in the diffusivity at high pressures. At high H concentrations, a dramatic reduction in the diffusion coefficient is observed, due to site blocking and the repulsive H-H interaction. The results of this study indicates that high flux hydrogen irradiation leads to much higher H concentrations in tungsten than expected.

  18. Fuzzy tungsten in a magnetron sputtering device

    NASA Astrophysics Data System (ADS)

    Petty, T. J.; Khan, A.; Heil, T.; Bradley, J. W.

    2016-11-01

    Helium ion induced tungsten nanostructure (tungsten fuzz) has been studied in a magnetron sputtering device. Three parameters were varied, the fluence from 3.4 × 1023-3.0 × 1024 m-2, the He ion energy from 25 to 70 eV, and the surface temperature from 900 to 1200 K. For each sample, SEM images were captured, and measurements of the fuzz layer thickness, surface roughness, reflectivity, and average structure widths are provided. A cross-over point from pre-fuzz to fully formed fuzz is found at 2.4 ± 0.4 × 1024 m-2, and a temperature of 1080 ± 60 K. No significant change was observed in the energy sweep. The fuzz is compared to low fluence fuzz created in the PISCES-A linear plasma device. Magnetron fuzz is less uniform than fuzz created by PISCES-A and with generally larger structure widths. The thicknesses of the magnetron samples follow the original Φ1/2 relation as opposed to the incubation fluence fit.

  19. Dynamic compaction of tungsten carbide powder.

    SciTech Connect

    Gluth, Jeffrey Weston; Hall, Clint Allen; Vogler, Tracy John; Grady, Dennis Edward

    2005-04-01

    The shock compaction behavior of a tungsten carbide powder was investigated using a new experimental design for gas-gun experiments. This design allows the Hugoniot properties to be measured with reasonably good accuracy despite the inherent difficulties involved with distended powders. The experiments also provide the first reshock state for the compacted powder. Experiments were conducted at impact velocities of 245, 500, and 711 m/s. A steady shock wave was observed for some of the sample thicknesses, but the remainder were attenuated due to release from the back of the impactor or the edge of the sample. The shock velocity for the powder was found to be quite low, and the propagating shock waves were seen to be very dispersive. The Hugoniot density for the 711 m/s experiment was close to ambient crystal density for tungsten carbide, indicating nearly complete compaction. When compared with quasi-static compaction results for the same material, the dynamic compaction data is seen to be significantly stiffer for the regime over which they overlap. Based on these initial results, recommendations are made for improving the experimental technique and for future work to improve our understanding of powder compaction.

  20. Vaccum Gas Tungsten Arc Welding, phase 1

    NASA Technical Reports Server (NTRS)

    Weeks, J. L.; Krotz, P. D.; Todd, D. T.; Liaw, Y. K.

    1995-01-01

    This two year program will investigate Vacuum Gas Tungsten Arc Welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. VGTAW appears to offer a significant improvement in weldability because of the clean environment and lower heat input needed. The overall objective of the program is to develop the VGTAW technology and implement it into a manufacturing environment that will result in lower cost, better quality and higher reliability aerospace components for the space shuttle and other NASA space systems. Phase 1 of this program was aimed at demonstrating the process's ability to weld normally difficult-to-weld materials. Phase 2 will focus on further evaluation, a hardware demonstration and a plan to implement VGTAW technology into a manufacturing environment. During Phase 1, the following tasks were performed: (1) Task 11000 Facility Modification - an existing vacuum chamber was modified and adapted to a GTAW power supply; (2) Task 12000 Materials Selection - four difficult-to-weld materials typically used in the construction of aerospace hardware were chosen for study; (3) Task 13000 VGTAW Experiments - welding experiments were conducted under vacuum using the hollow tungsten electrode and evaluation. As a result of this effort, two materials, NARloy Z and Incoloy 903, were downselected for further characterization in Phase 2; and (4) Task 13100 Aluminum-Lithium Weld Studies - this task was added to the original work statement to investigate the effects of vacuum welding and weld pool vibration on aluminum-lithium alloys.

  1. High temperature annealing of ion irradiated tungsten

    SciTech Connect

    Ferroni, Francesco; Yi, Xiaoou; Fitzgerald, Steven P.; Edmondson, Philip D.; Roberts, Steve G.

    2015-03-21

    In this study, transmission electron microscopy of high temperature annealing of pure tungsten irradiated by self-ions was conducted to elucidate microstructural and defect evolution in temperature ranges relevant to fusion reactor applications (500–1200°C). Bulk isochronal and isothermal annealing of ion irradiated pure tungsten (2 MeV W+ ions, 500°C, 1014 W+/cm2) with temperatures of 800, 950, 1100 and 1400°C, from 0.5 to 8 h, was followed by ex situ characterization of defect size, number density, Burgers vector and nature. Loops with diameters larger than 2–3 nm were considered for detailed analysis, among which all loops had View the MathML source and were predominantly of interstitial nature. In situ annealing experiments from 300 up to 1200°C were also carried out, including dynamic temperature ramp-ups. These confirmed an acceleration of loop loss above 900°C. At different temperatures within this range, dislocations exhibited behaviour such as initial isolated loop hopping followed by large-scale rearrangements into loop chains, coalescence and finally line–loop interactions and widespread absorption by free-surfaces at increasing temperatures. An activation energy for the annealing of dislocation length was obtained, finding Ea=1.34±0.2 eV for the 700–1100°C range.

  2. High temperature annealing of ion irradiated tungsten

    DOE PAGES

    Ferroni, Francesco; Yi, Xiaoou; Arakawa, Kazuto; Fitzgerald, Steven P.; Edmondson, Philip D.; Roberts, Steve G.

    2015-03-21

    In this study, transmission electron microscopy of high temperature annealing of pure tungsten irradiated by self-ions was conducted to elucidate microstructural and defect evolution in temperature ranges relevant to fusion reactor applications (500–1200°C). Bulk isochronal and isothermal annealing of ion irradiated pure tungsten (2 MeV W+ ions, 500°C, 1014 W+/cm2) with temperatures of 800, 950, 1100 and 1400°C, from 0.5 to 8 h, was followed by ex situ characterization of defect size, number density, Burgers vector and nature. Loops with diameters larger than 2–3 nm were considered for detailed analysis, among which all loops had View the MathML source andmore » were predominantly of interstitial nature. In situ annealing experiments from 300 up to 1200°C were also carried out, including dynamic temperature ramp-ups. These confirmed an acceleration of loop loss above 900°C. At different temperatures within this range, dislocations exhibited behaviour such as initial isolated loop hopping followed by large-scale rearrangements into loop chains, coalescence and finally line–loop interactions and widespread absorption by free-surfaces at increasing temperatures. An activation energy for the annealing of dislocation length was obtained, finding Ea=1.34±0.2 eV for the 700–1100°C range.« less

  3. Tungsten - Yttrium Based Nuclear Structural Materials

    NASA Astrophysics Data System (ADS)

    Ramana, Chintalapalle; Chessa, Jack; Martinenz, Gustavo

    2013-04-01

    The challenging problem currently facing the nuclear science community in this 21st century is design and development of novel structural materials, which will have an impact on the next-generation nuclear reactors. The materials available at present include reduced activation ferritic/martensitic steels, dispersion strengthened reduced activation ferritic steels, and vanadium- or tungsten-based alloys. These materials exhibit one or more specific problems, which are either intrinsic or caused by reactors. This work is focussed towards tungsten-yttrium (W-Y) based alloys and oxide ceramics, which can be utilized in nuclear applications. The goal is to derive a fundamental scientific understanding of W-Y-based materials. In collaboration with University of Califonia -- Davis, the project is designated to demonstrate the W-Y based alloys, ceramics and composites with enhanced physical, mechanical, thermo-chemical properties and higher radiation resistance. Efforts are focussed on understanding the microstructure, manipulating materials behavior under charged-particle and neutron irradiation, and create a knowledge database of defects, elemental diffusion/segregation, and defect trapping along grain boundaries and interfaces. Preliminary results will be discussed.

  4. Improving ASM stepper alignment accuracy by alignment signal intensity simulation

    NASA Astrophysics Data System (ADS)

    Li, Gerald; Pushpala, Sagar M.; Bradford, Bradley; Peng, Zezhong; Gottipati, Mohan

    1993-08-01

    As photolithography technology advances into submicron regime, the requirement for alignment accuracy also becomes much tighter. The alignment accuracy is a function of the strength of the alignment signal. Therefore, a detailed alignment signal intensity simulation for 0.8 micrometers EPROM poly-1 layer on ASM stepper was done based on the process of record in the fab to reduce misalignment and improve die yield. Oxide thickness variation did not have significant impact on the alignment signal intensity. However, poly-1 thickness was the most important parameter to affect optical alignments. The real alignment intensity data versus resist thickness on production wafers was collected and it showed good agreement with the simulated results. Similar results were obtained for ONO dielectric layer at a different fab.

  5. 40 CFR 440.60 - Applicability; description of the tungsten ore subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... tungsten ore subcategory. 440.60 Section 440.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Tungsten Ore Subcategory § 440.60 Applicability; description of the tungsten ore subcategory. The provisions of this subpart F are applicable to discharges from (a) mines that produce tungsten ore and...

  6. 40 CFR 440.60 - Applicability; description of the tungsten ore subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... tungsten ore subcategory. 440.60 Section 440.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Tungsten Ore Subcategory § 440.60 Applicability; description of the tungsten ore subcategory. The provisions of this subpart F are applicable to discharges from (a) mines that produce tungsten ore and...

  7. 40 CFR 440.60 - Applicability; description of the tungsten ore subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... tungsten ore subcategory. 440.60 Section 440.60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Tungsten Ore Subcategory § 440.60 Applicability; description of the tungsten ore subcategory. The provisions of this subpart F are applicable to discharges from (a) mines that produce tungsten ore and...

  8. AVID: A global alignment program.

    PubMed

    Bray, Nick; Dubchak, Inna; Pachter, Lior

    2003-01-01

    In this paper we describe a new global alignment method called AVID. The method is designed to be fast, memory efficient, and practical for sequence alignments of large genomic regions up to megabases long. We present numerous applications of the method, ranging from the comparison of assemblies to alignment of large syntenic genomic regions and whole genome human/mouse alignments. We have also performed a quantitative comparison of AVID with other popular alignment tools. To this end, we have established a format for the representation of alignments and methods for their comparison. These formats and methods should be useful for future studies. The tools we have developed for the alignment comparisons, as well as the AVID program, are publicly available. See Web Site References section for AVID Web address and Web addresses for other programs discussed in this paper. PMID:12529311

  9. Engineering cell alignment in vitro.

    PubMed

    Li, Yuhui; Huang, Guoyou; Zhang, Xiaohui; Wang, Lin; Du, Yanan; Lu, Tian Jian; Xu, Feng

    2014-01-01

    Cell alignment plays a critical role in various cell behaviors including cytoskeleton reorganization, membrane protein relocation, nucleus gene expression, and ECM remodeling. Cell alignment is also known to exert significant effects on tissue regeneration (e.g., neuron) and modulate mechanical properties of tissues including skeleton, cardiac muscle and tendon. Therefore, it is essential to engineer cell alignment in vitro for biomechanics, cell biology, tissue engineering and regenerative medicine applications. With advances in nano- and micro-scale technologies, a variety of approaches have been developed to engineer cell alignment in vitro, including mechanical loading, topographical patterning, and surface chemical treatment. In this review, we first present alignments of various cell types and their functionality in different tissues in vivo including muscle and nerve tissues. Then, we provide an overview of recent approaches for engineering cell alignment in vitro. Finally, concluding remarks and perspectives are addressed for future improvement of engineering cell alignment.

  10. AVID: A global alignment program.

    PubMed

    Bray, Nick; Dubchak, Inna; Pachter, Lior

    2003-01-01

    In this paper we describe a new global alignment method called AVID. The method is designed to be fast, memory efficient, and practical for sequence alignments of large genomic regions up to megabases long. We present numerous applications of the method, ranging from the comparison of assemblies to alignment of large syntenic genomic regions and whole genome human/mouse alignments. We have also performed a quantitative comparison of AVID with other popular alignment tools. To this end, we have established a format for the representation of alignments and methods for their comparison. These formats and methods should be useful for future studies. The tools we have developed for the alignment comparisons, as well as the AVID program, are publicly available. See Web Site References section for AVID Web address and Web addresses for other programs discussed in this paper.

  11. TSGC and JSC Alignment

    NASA Technical Reports Server (NTRS)

    Sanchez, Humberto

    2013-01-01

    NASA and the SGCs are, by design, intended to work closely together and have synergistic Vision, Mission, and Goals. The TSGC affiliates and JSC have been working together, but not always in a concise, coordinated, nor strategic manner. Today we have a couple of simple ideas to present about how TSGC and JSC have started to work together in a more concise, coordinated, and strategic manner, and how JSC and non-TSG Jurisdiction members have started to collaborate: Idea I: TSGC and JSC Technical Alignment Idea II: Concept of Clusters.

  12. CELT optics Alignment Procedure

    NASA Astrophysics Data System (ADS)

    Mast, Terry S.; Nelson, Jerry E.; Chanan, Gary A.; Noethe, Lothar

    2003-01-01

    The California Extremely Large Telescope (CELT) is a project to build a 30-meter diameter telescope for research in astronomy at visible and infrared wavelengths. The current optical design calls for a primary, secondary, and tertiary mirror with Ritchey-Chretién foci at two Nasmyth platforms. The primary mirror is a mosaic of 1080 actively-stabilized hexagonal segments. This paper summarizes a CELT report that describes a step-by-step procedure for aligning the many degrees of freedom of the CELT optics.

  13. Tungsten and tungsten-copper for coal-fired MHD power generation

    SciTech Connect

    Farrar, L.C. ); Shields, J.A. Jr. )

    1992-08-01

    This paper reports that magnetohydrodynamics (MHD) can improve the thermal efficiency and reduce levels of SO{sub x} and NO emissions of existing coal-fired power generation plants. Although the thermal and electrochemical environments for a coal-fired MHD channel challenge the materials used, platinum, tungsten, and tungsten-copper have been found to be suitable choices. Evaluations indicate these materials perform adequately as electrodes and other gas-side surfaces in the coal-fired MHD channel. Analysis of test elements has resulted in the identification of wear mechanisms. Testing of a prototypical coal-fired MHD channel incorporating these materials is under way and will be completed in 1993.

  14. Measurement of uptake and release of tritium by tungsten

    SciTech Connect

    Nakayama, M.; Torikai, Y.; Saito, M.; Penzhorn, R.D.; Isobe, K.; Yamanishi, T.; Kurishita, H.

    2015-03-15

    Tungsten is currently contemplated as plasma facing material for the divertor of future fusion machines. In this paper the uptake of tritium by tungsten and its release behavior have been investigated. Tungsten samples have been annealed at various temperatures and loaded at also different temperatures with deuterium containing 7.2 % tritium at a pressure of 1.2 kPa. A specific system was designed to assess the release of tritiated water and molecular tritium by the samples. Due to the rather low solubility of hydrogen isotopes in tungsten it is particularly important to be aware of the presence of hydrogen traps or thin oxide films. As shown in this work, traps or oxide films may affect the retention capability of tungsten and lead to significantly modified release properties. It became clear that there were capture sites that had different thermal stability and different capture intensity in tungsten after polishing, or oxide films that were grown on the surface of tungsten and had barrier effects.

  15. Tungsten Stable Isotope Compositions of Ferromanganese Crusts

    NASA Astrophysics Data System (ADS)

    Abraham, K.; Barling, J.; Hein, J. R.; Schauble, E. A.; Halliday, A. N.

    2014-12-01

    We report the first accurate and precise data for mass-dependent fractionation of tungsten (W) stable isotopes, using a double spike technique and MC-ICPMS. Results are expressed relative to the NIST 3136 W isotope standard as per mil deviations in 186W/184W (δ186W). Although heavy element mass-dependent fractionations are expected to be small, Tl and U both display significant low temperature isotopic fractionations. Theoretical calculations indicate that W nuclear volume isotopic effects should be smaller than mass-dependent fractionations at low temperatures. Hydrogenetic ferromanganese (Fe-Mn) crusts precipitate directly from seawater and have been used as paleoceanographic recorders of temporal changes in seawater chemistry. Crusts are strongly enriched in W and other metals, and are a promising medium for exploring W isotopic variability. Tungsten has a relatively long residence time in seawater of ~61,000 years, mainly as the tungstate ion (WO42-). Water depth profiles show conservative behaviour. During adsorption on Fe-Mn crusts, W species form inner-sphere complexes in the hexavalent (W6+) state. The major host phase is thought to be Mn oxides and the lighter W isotope is expected to be absorbed preferentially. Surface scrapings of 13 globally distributed hydrogenetic Fe-Mn crusts display δ186W from -0.08 to -0.22‰ (±0.03‰, 2sd). A trend toward lighter W isotope composition exists with increasing water depth (~1500 to ~5200m) and W concentration. One hydrothermal Mn-oxide sample is anomalously light and Mn nodules are both heavy and light relative to Fe-Mn crusts. Tungsten speciation depends on concentration, pH, and time in solution and is not well understood because of the extremely slow kinetics of the reactions. In addition, speciation of aqueous and/or adsorbed species might be sensitive to pressure, showing similar thermodynamic stability but different effective volumes. Thus, W stable isotopes might be used as a water-depth barometer in

  16. Solar sensor subsystems alignment check using solar scans for the Halogen Occultation Experiment

    NASA Technical Reports Server (NTRS)

    Jurczyk, S. G.; Moore, A. S.

    1989-01-01

    The alignment of a dual-axes sun sensor subsystem to a telescope having a multiple sensor subsystem is described. The sun sensor consists of two analog and one digital silicon detectors. The analog detectors are shadow mask type operating in the visible spectrum. The detectors are mounted for azimuth and elevation positioning of biaxial gimbals. The digital detector is a linear diode array that operates at a spectral position of 0.7 micron and is used for elevation positioning. The position signals correspond to relative angles between the sun sensor and the solar disk. These three detectors are aligned on an Invar structure which is mounted to a Cassegrain telescope. This telescope relays solar radiance to an eight channel detector subsystem operating in the infrared range from 2 to 10 microns. The test technique and results to check the boresight alignment of these two subsystems by scanning the solar disk will be reported. The boresight alignment for both the azimuth and elevation axes of the two detector subsystems is verified using this technique.

  17. Neutron irradiation effects on the microstructural development of tungsten and tungsten alloys

    NASA Astrophysics Data System (ADS)

    Hasegawa, Akira; Fukuda, Makoto; Yabuuchi, Kiyohiro; Nogami, Shuhei

    2016-04-01

    Data on the microstructural development of tungsten (W) and tungsten rhenium (Re) alloys were obtained after neutron irradiation at 400-800 °C in the Japan Materials Testing Reactor (JMTR), the experimental fast test reactor Joyo, and the High Flux Isotope Reactor (HFIR) for irradiation damage levels in the range of 0.09-1.54 displacement per atom (dpa). Microstructural observations showed that a small amount of Re (3-5%) in W-Re alloys is effective in suppressing void formation. In W-Re alloys with Re concentrations greater than 10%, acicular precipitates are the primary structural defects. In the HFIR-irradiated specimen, in which a large amount of Re was expected to be produced by the nuclear transmutation of W to Re because of the reactor's high thermal neutron flux, voids were not observed even in pure W. The synergistic effects of displacement damage and solid transmutation elements on microstructural development are discussed, and the microstructural development of tungsten materials utilized in fusion reactors is predicted.

  18. Density-functional studies of tungsten trioxide, tungsten bronzes, and related systems

    NASA Astrophysics Data System (ADS)

    Ingham, B.; Hendy, S. C.; Chong, S. V.; Tallon, J. L.

    2005-08-01

    Tungsten trioxide adopts a variety of structures which can be intercalated with charged species to alter the electronic properties, thus forming “tungsten bronzes.” Similar effects are observed upon removing oxygen from WO3 . We present a computational study of cubic and hexagonal alkali bronzes and examine the effects on cell size and band structure as the size of the intercalated ion is increased. With the exception of hydrogen (which is predicted to be unstable as an intercalate), the behavior of the bronzes are relatively consistent. NaWO3 is the most stable of the cubic systems, although in the hexagonal system the larger ions are more stable. The band structures are identical, with the intercalated atom donating its single electron to the tungsten 5d valence band. A study of fractional doping in the NaxWO3 system (0⩽x⩽1) showed a linear variation in cell parameter and a systematic shift in the Fermi level into the conduction band. In the oxygen-deficient WO3-x system the Fermi level undergoes a sudden jump into the conduction band at around x=0.2 . Lastly, three compounds of a layered WO4•α,ω -diaminoalkane hybrid series were studied and found to be insulating, with features in the band structure similar to those of the parent WO3 compound that relate well to experimental UV-visible spectroscopy results.

  19. Tensile behavior of tungsten and tungsten-alloy wires from 1300 to 1600 K

    NASA Technical Reports Server (NTRS)

    Hee, Man Yun

    1988-01-01

    The tensile behavior of a 200-micrometer-diameter tungsten lamp (218CS-W), tungsten + 1.0 atomic percent (a/o) thoria (ST300-W), and tungsten + 0.4 a/o hafnium carbide (WHfC) wires was determined over the temperature range 1300 t0 1600 K at strain rates of 3.3 X 10 to the -2 to 3.3 X 10 to the -5/sec. Although most tests were conducted on as-drawn materials, one series of tests was undertaken on ST300-W wires in four different conditions: as-drawn and vacuum-annealed at 1535 K for 1 hr, with and without electroplating. Whereas heat treatment had no effect on tensile properties, electropolishing significantly increased both the proportional limit and ductility, but not the ultimate tensile strength. Comparison of the behavior of the three alloys indicates that the HfC-dispersed material possesses superior tensile properties. Theoretical calculations indicate that the strength/ductility advantage of WHfC is due to the resistance to recrystallization imparted by the dispersoid.

  20. Electrode potentials of tungsten in fused alkali chlorides

    NASA Astrophysics Data System (ADS)

    Ivanov, A. B.; Volkovich, V. A.; Poskryakov, D. A.; Vasin, B. D.; Griffiths, T. R.

    2016-09-01

    Anodic dissolution of tungsten was studied at 823-1173 K in the melts based on NaCl-CsCl, NaCl-KCl-CsCl and LiCl-KCl-CsCl eutectic mixtures. The process results in the formation of W(IV) ions. Prolonged contact with silica results in oxidation W(IV) ions and decreasing tungsten concentration in the electrolyte due to formation of volatile higher oxidation state chloro- and oxychloro-species. Tungsten electrode potentials were measured in NaCl-CsCl and NaCl-KCl-CsCl based melts using potentiometry.

  1. Thermal expansion method for lining tantalum alloy tubing with tungsten

    NASA Technical Reports Server (NTRS)

    Watson, G. K.; Whittenberger, J. D.; Mattson, W. F.

    1973-01-01

    A differential-thermal expansion method was developed to line T-111 (tantalum - 8 percent tungsten - 2 percent hafnium) tubing with a tungsten diffusion barrier as part of a fuel element fabrication study for a space power nuclear reactor concept. This method uses a steel mandrel, which has a larger thermal expansion than T-111, to force the tungsten against the inside of the T-111 tube. Variables investigated include lining temperature, initial assembly gas size, and tube length. Linear integrity increased with increasing lining temperature and decreasing gap size. The method should have more general applicability where cylinders must be lined with a thin layer of a second material.

  2. Chemically assisted ion beam etching of polycrystalline and (100)tungsten

    NASA Technical Reports Server (NTRS)

    Garner, Charles

    1987-01-01

    A chemically assisted ion-beam etching technique is described which employs an ion beam from an electron-bombardment ion source and a directed flux of ClF3 neutrals. This technique enables the etching of tungsten foils and films in excess of 40 microns thick with good anisotropy and pattern definition over areas of 30 sq mm, and with a high degree of selectivity. (100) tungsten foils etched with this process exhibit preferred-orientation etching, while polycrystalline tungsten films exhibit high etch rates. This technique can be used to pattern the dispenser cathode surfaces serving as electron emitters in traveling-wave tubes to a controlled porosity.

  3. Reproductive effects and duckling survivability following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

    PubMed

    Mitchell, R R; Fitzgerald, S D; Aulerich, R J; Balander, R J; Powell, D C; Tempelmen, R J; Stevens, W; Bursia, S J

    2001-07-01

    Tungsten-iron and tungsten-polymer shot were given conditional approval for waterfowl hunting by the U.S. Fish and Wildlife Service based partly on the results of a 30-day acute toxicity trial utilizing mallards (Anas platyrhynchos). Final approval of the two tungsten-containing shot was contingent on the results of a 150-day study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult mallards. Reproductive data are presented in this paper. Sixteen male and 16 female adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). Reproductive performance was assessed during the last 90 days (day 61 to day 150) of the trial. There were no significant differences in egg production and fertility and hatchability of eggs from tungsten-iron- and tungsten-polymer-dosed ducks compared to control ducks. There was no evidence of differences in percent survivability and body weight of ducklings from tungsten-iron and tungsten-polymer mallards compared to ducklings from control ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards during the 150 day trial did not adversely affect reproduction or their offspring.

  4. Overcoming low-alignment signal contrast induced alignment failure by alignment signal enhancement

    NASA Astrophysics Data System (ADS)

    Lee, Byeong Soo; Kim, Young Ha; Hwang, Hyunwoo; Lee, Jeongjin; Kong, Jeong Heung; Kang, Young Seog; Paarhuis, Bart; Kok, Haico; de Graaf, Roelof; Weichselbaum, Stefan; Droste, Richard; Mason, Christopher; Aarts, Igor; de Boeij, Wim P.

    2016-03-01

    Overlay is one of the key factors which enables optical lithography extension to 1X node DRAM manufacturing. It is natural that accurate wafer alignment is a prerequisite for good device overlay. However, alignment failures or misalignments are commonly observed in a fab. There are many factors which could induce alignment problems. Low alignment signal contrast is one of the main issues. Alignment signal contrast can be degraded by opaque stack materials or by alignment mark degradation due to processes like CMP. This issue can be compounded by mark sub-segmentation from design rules in combination with double or quadruple spacer process. Alignment signal contrast can be improved by applying new material or process optimization, which sometimes lead to the addition of another process-step with higher costs. If we can amplify the signal components containing the position information and reduce other unwanted signal and background contributions then we can improve alignment performance without process change. In this paper we use ASML's new alignment sensor (as was introduced and released on the NXT:1980Di) and sample wafers with special stacks which can induce poor alignment signal to demonstrate alignment and overlay improvement.

  5. Ferromagnetism in exfoliated tungsten disulfide nanosheets

    PubMed Central

    2013-01-01

    Two-dimensional-layered transition metal dichalcogenides nanosheets have attracted tremendous attention for their promising applications in spintronics because the atomic-thick nanosheets can not only enhance the intrinsic properties of their bulk counterparts, but also give birth to new promising properties. In this paper, ultrathin tungsten disulfide (WS2) nanosheets were gotten by liquid exfoliation route from its bulk form using dimethylformamide (DMF). Compared to the antiferromagnetism bulk WS2, ultrathin WS2 nanosheets show intrinsic room-temperature ferromagnetism (FM) with the maximized saturation magnetization of 0.004 emu/g at 10 K, where the appearance of FM in the nanosheets is partly due to the presence of zigzag edges in the magnetic ground state at the grain boundaries. PMID:24134699

  6. A Study of Tungsten-Technetium Alloys

    NASA Technical Reports Server (NTRS)

    Maltz, J. W.

    1965-01-01

    Technetium is a sister element to rhenium and has many properties that are similar to rhenium. It is predicted that technetium will have about the same effects on tungsten as rhenium in regard to increase in workability, lowered ductile to brittle transition temperature, and improved ductility. The objectives of the current work are to recover technetium from fission product wastes at Hanford Atomic Products Operation and reduce to purified metal; prepare W-Tc alloys containing up to 50 atomic% Tc; fabricate the alloy ingots to sheet stock, assessing the effect of technetium on workability; and perform metallurgical and mechanical properties evaluation of the fabricated alloys. Previous reports have described the separation and purification of 800 g of technetium metal powder, melting of technetium and W-Tc alloys, and some initial observation of the alloy material.

  7. Tungsten-doped thin film materials

    DOEpatents

    Xiang, Xiao-Dong; Chang, Hauyee; Gao, Chen; Takeuchi, Ichiro; Schultz, Peter G.

    2003-12-09

    A dielectric thin film material for high frequency use, including use as a capacitor, and having a low dielectric loss factor is provided, the film comprising a composition of tungsten-doped barium strontium titanate of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3, where X is between about 0.5 and about 1.0. Also provided is a method for making a dielectric thin film of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3 and doped with W, where X is between about 0.5 and about 1.0, a substrate is provided, TiO.sub.2, the W dopant, Ba, and optionally Sr are deposited on the substrate, and the substrate containing TiO.sub.2, the W dopant, Ba, and optionally Sr is heated to form a low loss dielectric thin film.

  8. Thermomechanical processing of tungsten-copper composites

    SciTech Connect

    Ohriner, E.K.; Bryskin, B.

    1996-05-01

    A tungsten-40 wt% Cu composite was consolidated by liquid-phase sintering and further processed to full density by a number of deformation methods. Fully dense materials were obtained by hot extrusion or cold rolling of the W-Cu composite. Subsequent processing by cold rolling, cold swaging, or hot swaging did not produce large changes in the aspect ratio of the W particles. The materials develop high hardness with small grain sizes of 5 {mu}m or less. The work-hardening, recrystallization, and grain growth of the material are characterized, and the hardness and tensile properties are related to processing parameters. Wire with tensile strengths up to 1120 MPa were produced. Further improvements in properties are anticipated with optimized processing parameters.

  9. Pareto optimal pairwise sequence alignment.

    PubMed

    DeRonne, Kevin W; Karypis, George

    2013-01-01

    Sequence alignment using evolutionary profiles is a commonly employed tool when investigating a protein. Many profile-profile scoring functions have been developed for use in such alignments, but there has not yet been a comprehensive study of Pareto optimal pairwise alignments for combining multiple such functions. We show that the problem of generating Pareto optimal pairwise alignments has an optimal substructure property, and develop an efficient algorithm for generating Pareto optimal frontiers of pairwise alignments. All possible sets of two, three, and four profile scoring functions are used from a pool of 11 functions and applied to 588 pairs of proteins in the ce_ref data set. The performance of the best objective combinations on ce_ref is also evaluated on an independent set of 913 protein pairs extracted from the BAliBASE RV11 data set. Our dynamic-programming-based heuristic approach produces approximated Pareto optimal frontiers of pairwise alignments that contain comparable alignments to those on the exact frontier, but on average in less than 1/58th the time in the case of four objectives. Our results show that the Pareto frontiers contain alignments whose quality is better than the alignments obtained by single objectives. However, the task of identifying a single high-quality alignment among those in the Pareto frontier remains challenging.

  10. Regional and depth variability of porcine meniscal mechanical properties through biaxial testing.

    PubMed

    Kahlon, A; Hurtig, M B; Gordon, K D

    2015-01-01

    The menisci in the knee joint undergo complex loading in-vivo resulting in a multidirectional stress distribution. Extensive mechanical testing has been conducted to investigate the tissue properties of the knee meniscus, but the testing conditions do not replicate this complex loading regime. Biaxial testing involves loading tissue along two different directions simultaneously, which more accurately simulates physiologic loading conditions. The purpose of this study was to report mechanical properties of meniscal tissue resulting from biaxial testing, while simultaneously investigating regional variations in properties. Ten left, fresh porcine joints were obtained, and the medial and lateral menisci were harvested from each joint (twenty menisci total). Each menisci was divided into an anterior, middle and posterior region; and three slices (femoral, deep and tibial layers) were obtained from each region. Biaxial and constrained uniaxial testing was performed on each specimen, and Young's moduli were calculated from the resulting stress strain curves. Results illustrated significant differences in regional mechanical properties, with the medial anterior (Young's modulus (E)=11.14 ± 1.10 MPa), lateral anterior (E=11.54 ± 1.10 MPa) and lateral posterior (E=9.0 ± 1.2 MPa) regions exhibiting the highest properties compared to the medial central (E=5.0 ± 1.22 MPa), medial posterior (E=4.16 ± 1.13 MPa) and lateral central (E=5.6 ± 1.20 MPa) regions. Differences with depth were also significant on the lateral meniscus, with the femoral (E=12.7 ± 1.22 MPa) and tibial (E=8.6 ± 1.22 MPa) layers exhibiting the highest Young's moduli. This data may form the basis for future modeling of meniscal tissue, or may aid in the design of synthetic replacement alternatives.

  11. Theory of biaxial graded-index optical fiber. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Kawalko, Stephen F.

    1990-01-01

    A biaxial graded-index fiber with a homogeneous cladding is studied. Two methods, wave equation and matrix differential equation, of formulating the problem and their respective solutions are discussed. For the wave equation formulation of the problem it is shown that for the case of a diagonal permittivity tensor the longitudinal electric and magnetic fields satisfy a pair of coupled second-order differential equations. Also, a generalized dispersion relation is derived in terms of the solutions for the longitudinal electric and magnetic fields. For the case of a step-index fiber, either isotropic or uniaxial, these differential equations can be solved exactly in terms of Bessel functions. For the cases of an istropic graded-index and a uniaxial graded-index fiber, a solution using the Wentzel, Krammers and Brillouin (WKB) approximation technique is shown. Results for some particular permittivity profiles are presented. Also the WKB solutions is compared with the vector solution found by Kurtz and Streifer. For the matrix formulation it is shown that the tangential components of the electric and magnetic fields satisfy a system of four first-order differential equations which can be conveniently written in matrix form. For the special case of meridional modes, the system of equations splits into two systems of two equations. A general iterative technique, asymptotic partitioning of systems of equations, for solving systems of differential equations is presented. As a simple example, Bessel's differential equation is written in matrix form and is solved using this asymptotic technique. Low order solutions for particular examples of a biaxial and uniaxial graded-index fiber are presented. Finally numerical results obtained using the asymptotic technique are presented for particular examples of isotropic and uniaxial step-index fibers and isotropic, uniaxial and biaxial graded-index fibers.

  12. Biaxial loading and shallow-flaw effects on crack-tip constraint and fracture toughness

    SciTech Connect

    Bass, B.R.; Bryson, J.W.; Theiss, T.J.; Rao, M.C.

    1994-01-01

    A program to develop and evaluate fracture methodologies for the assessment of crack-tip constraint effects on fracture toughness of reactor pressure vessel (RPV) steels has been initiated in the Heavy-Section Steel Technology (HSST) Program. Crack-tip constraint is an issue that significantly impacts fracture mechanics technologies employed in safety assessment procedures for commercially licensed nuclear RPVs. The focus of studies described herein is on the evaluation of two stressed-based methodologies for quantifying crack-tip constraint (i.e., J-Q theory and a micromechanical scaling model based on critical stressed volumes) through applications to experimental and fractographic data. Data were utilized from single-edge notch bend (SENB) specimens and HSST-developed cruciform beam specimens that were tested in HSST shallow-crack and biaxial testing programs. Results from applications indicate that both the J-Q methodology and the micromechanical scaling model can be used successfully to interpret experimental data from the shallow- and deep-crack SENB specimen tests. When applied to the uniaxially and biaxially loaded cruciform specimens, the two methodologies showed some promising features, but also raised several questions concerning the interpretation of constraint conditions in the specimen based on near-tip stress fields. Fractographic data taken from the fracture surfaces of the SENB and cruciform specimens are used to assess the relevance of stress-based fracture characterizations to conditions at cleavage initiation sites. Unresolved issues identified from these analyses require resolution as part of a validation process for biaxial loading applications. This report is designated as HSST Report No. 142.

  13. TIME DEPENDENT BIAXIAL MECHANICAL BEHAVIOR OF THE AORTIC HEART VALVE LEAFLET

    PubMed Central

    Stella, John A.; Liao, Jun; Sacks, Michael S.

    2007-01-01

    Despite continued progress in the treatment of aortic valve (AV) disease, current treatments continue to be challenged to consistently restore AV function for extended durations. Improved approaches toward AV repair and replacement rests upon our ability to more fully comprehend and simulate AV function. While the elastic behavior the AV leaflet (AVL) has been previously investigated, time dependent behaviors under physiological biaxial loading states have yet to be quantified. In the current study, we performed strain rate, creep, and stress relaxation experiments using porcine AVL under planar biaxial stretch and loaded to physiological levels (60 N/m equi-biaxial tension), with strain rates ranging from quasi-static to physiologic. The resulting stress-strain responses were found to be independent of strain rate, as was the observed low level of hysteresis (∼17%). Stress relaxation and creep results indicated that while the AVL exhibited significant stress relaxation, it exhibited negligible creep over the three hour test duration. These results are all in accordance with our previous findings for the mitral valve anterior leaflet (MVAL) (Grashow et al., 2006, ABME vol. 34, pp. 315-25; Grashow et al., ABME, Vol. 34, pp. 1509-18, 2006), and support our observations that valvular tissues are functionally anisotropic, quasi-elastic biological materials. These results appear to be unique to valvular tissues, and indicate an ability to withstand loading without time-dependent effects under physiologic loading conditions. Based on a recent study that suggested valvular collagen fibrils are not intrinsically viscoelastic (Liao, et al., JBME, vol. 129, 2007), we speculate that the mechanisms underlying this quasi-elastic behavior may be attributed to supra-fibrillar structure unique to valvular tissue. These mechanisms are an important functional aspect of native valvular tissues, and are likely critical to improve our understanding of valvular disease and help guide

  14. Enhanced toughness and stable crack propagation in a novel tungsten fibre-reinforced tungsten composite produced by chemical vapour infiltration

    NASA Astrophysics Data System (ADS)

    Riesch, J.; Höschen, T.; Linsmeier, Ch; Wurster, S.; You, J.-H.

    2014-04-01

    Tungsten is a promising candidate for the plasma-facing components of a future fusion reactor, but its use is strongly restricted by its inherent brittleness. An innovative concept to overcome this problem is tungsten fibre-reinforced tungsten composite. In this paper we present the first mechanical test of such a composite material using a sample containing multiple fibres. The in situ fracture experiment was performed in a scanning electron microscope for close observation of the propagating crack. Stable crack propagation accompanied with rising load bearing capacity is observed. The fracture toughness is estimated using the test results and the surface observation.

  15. Band offsets for biaxially and uniaxially stressed silicon-germanium layers with arbitrary substrate and channel orientations

    NASA Astrophysics Data System (ADS)

    Eneman, Geert; Roussel, Philippe; Brunco, David Paul; Collaert, Nadine; Mocuta, Anda; Thean, Aaron

    2016-08-01

    The conduction and valence band offsets between a strained silicon-germanium layer and a silicon-germanium substrate are reported for arbitrary substrate and channel crystal orientations. The offsets are calculated both for the case of biaxial stress, corresponding approximately to the stress state of a thin strained channel in a planar field-effect transistor (FET), and for uniaxial stress, which is the approximate stress state for strained channels in a FinFET configuration. Significant orientation dependence is found for the conduction band offset, overall leading to the strongest electron quantum confinement in biaxial-tensile stressed channels on {100}-oriented substrates, and uniaxial-tensile stressed channels in the ⟨100⟩ and ⟨110⟩ directions. For biaxially stressed layers on {111} substrates, the conduction band offset is significantly smaller than for {100} or {110} directions. For the valence band offset, the dependence on crystal orientation is found to be small.

  16. Nova laser alignment control system

    SciTech Connect

    Van Arsdall, P.J.; Holloway, F.W.; McGuigan, D.L.; Shelton, R.T.

    1984-03-29

    Alignment of the Nova laser requires control of hundreds of optical components in the ten beam paths. Extensive application of computer technology makes daily alignment practical. The control system is designed in a manner which provides both centralized and local manual operator controls integrated with automatic closed loop alignment. Menudriven operator consoles using high resolution color graphics displays overlaid with transport touch panels allow laser personnel to interact efficiently with the computer system. Automatic alignment is accomplished by using image analysis techniques to determine beam references points from video images acquired along the laser chain. A major goal of the design is to contribute substantially to rapid experimental turnaround and consistent alignment results. This paper describes the computer-based control structure and the software methods developed for aligning this large laser system.

  17. Dust alignment in astrophysical environments

    NASA Astrophysics Data System (ADS)

    Lazarian, Alex; Thiem Hoang, Chi

    Dust is known to be aligned in interstellar medium and the arising polarization is extensively used to trace magnetic fields. What process aligns dust grains was one of the most long-standing problems of astrophysics in spite of the persistent efforts to solve it. For years the Davis-Greenstein paramagnetic alignment was the primary candidate for explaining grain alignment. However, the situation is different now and the most promising mechanism is associated with radiative torques (RATs) acting on irregular grains. I shall present the analytical theory of RAT alignment, discuss the observational tests that support this theory. I shall also discuss in what situations we expect to see the dominance of paramagnetic alignment.

  18. Nuclear reactor internals alignment configuration

    DOEpatents

    Gilmore, Charles B.; Singleton, Norman R.

    2009-11-10

    An alignment system that employs jacking block assemblies and alignment posts around the periphery of the top plate of a nuclear reactor lower internals core shroud to align an upper core plate with the lower internals and the core shroud with the core barrel. The distal ends of the alignment posts are chamfered and are closely received within notches machined in the upper core plate at spaced locations around the outer circumference of the upper core plate. The jacking block assemblies are used to center the core shroud in the core barrel and the alignment posts assure the proper orientation of the upper core plate. The alignment posts may alternately be formed in the upper core plate and the notches may be formed in top plate.

  19. Onorbit IMU alignment error budget

    NASA Technical Reports Server (NTRS)

    Corson, R. W.

    1980-01-01

    The Star Tracker, Crew Optical Alignment Sight (COAS), and Inertial Measurement Unit (IMU) from a complex navigation system with a multitude of error sources were combined. A complete list of the system errors is presented. The errors were combined in a rational way to yield an estimate of the IMU alignment accuracy for STS-1. The expected standard deviation in the IMU alignment error for STS-1 type alignments was determined to be 72 arc seconds per axis for star tracker alignments and 188 arc seconds per axis for COAS alignments. These estimates are based on current knowledge of the star tracker, COAS, IMU, and navigation base error specifications, and were partially verified by preliminary Monte Carlo analysis.

  20. Improving directivity of laser beams by employing the effect of conical refraction in biaxial crystals.

    PubMed

    Peet, V

    2010-09-13

    The far-field pattern of Gaussian beams transformed by conical refraction in biaxial crystal is analyzed. It is shown that one of the two outgoing beam components acquires, under certain conditions, a profile with a dominating central peak. The width of this peak can be made significantly smaller than the width of the parent diffraction-limited Gaussian beam at the same propagation distance. The formation of such structurally-stable sub-diffraction beam core improves the beam directivity. Another component is a charge-one optical vortex, that forms the annular shell of the beam and carries the rest of the beam power.

  1. Biaxially stretchable supercapacitors based on the buckled hybrid fiber electrode array

    NASA Astrophysics Data System (ADS)

    Zhang, Nan; Zhou, Weiya; Zhang, Qiang; Luan, Pingshan; Cai, Le; Yang, Feng; Zhang, Xiao; Fan, Qingxia; Zhou, Wenbin; Xiao, Zhuojian; Gu, Xiaogang; Chen, Huiliang; Li, Kewei; Xiao, Shiqi; Wang, Yanchun; Liu, Huaping; Xie, Sishen

    2015-07-01

    In order to meet the growing need for smart bionic devices and epidermal electronic systems, biaxial stretchability is essential for energy storage units. Based on porous single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) (SWCNT/PEDOT) hybrid fiber, we designed and fabricated a biaxially stretchable supercapacitor, which possesses a unique configuration of the parallel buckled hybrid fiber array. Owing to the reticulate SWCNT film and the improved fabrication technique, the hybrid fiber retained its porous architecture both outwardly and inwardly, manifesting a superior capacity of 215 F g-1. H3PO4-polyvinyl alcohol gel with an optimized component ratio was introduced as both binder and stretchable electrolyte, which contributed to the regularity and stability of the buckled fiber array. The buckled structure and the quasi one-dimensional character of the fibers endow the supercapacitor with 100% stretchability along all directions. In addition, the supercapacitor exhibited good transparency, as well as excellent electrochemical properties and stability after being stretched 5000 times.In order to meet the growing need for smart bionic devices and epidermal electronic systems, biaxial stretchability is essential for energy storage units. Based on porous single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) (SWCNT/PEDOT) hybrid fiber, we designed and fabricated a biaxially stretchable supercapacitor, which possesses a unique configuration of the parallel buckled hybrid fiber array. Owing to the reticulate SWCNT film and the improved fabrication technique, the hybrid fiber retained its porous architecture both outwardly and inwardly, manifesting a superior capacity of 215 F g-1. H3PO4-polyvinyl alcohol gel with an optimized component ratio was introduced as both binder and stretchable electrolyte, which contributed to the regularity and stability of the buckled fiber array. The buckled structure and the quasi one-dimensional character of the

  2. Transformation of vector beams with radial and azimuthal polarizations in biaxial crystals

    NASA Astrophysics Data System (ADS)

    Turpin, A.; Vargas, A.; Lizana, A.; Torres-Ruiz, F. A.; Estévez, I.; Moreno, I.; Campos, J.; Mompart, J.

    2015-05-01

    We present both experimentally and theoretically the transformation of radially and azimuthally polarized vector beams when they propagate through a biaxial crystal and are transformed by the conical refraction phenomenon. We show that, at the focal plane, the transverse pattern is formed by a ring-like light structure with an azimuthal node, being this node found at diametrically opposite points of the ring for radial/azimuthal polarizations. We also prove that the state of polarization of the transformed beams is conical refraction-like, i.e. that every two diametrically opposite points of the light ring are linearly orthogonally polarized.

  3. Appraisal of formulas for stresses in bilayered dental ceramics subjected to biaxial moment loading

    SciTech Connect

    Hsueh, Chun-Hway; Thompson, G. A.

    2007-01-01

    Summary - Objectives: The purpose of this study was to compare three existing sets of formulas predicting stresses in a thin circular plate subjected to biaxial moment loading, such that limitations for each set of formulas could be understood. These formulas include American Society for Testing and Materials (ASTM) formulas for monolayered plates, Roark's formulas for bilayered plates, and Hsueh et al.'s formulas for multilayered plates. Methods: The three sets of formulas were summarized and appraised. Biaxial moment loading is generally achieved using biaxial flexure tests, and the plate is placed on a support ring and loaded in the central region. While both ASTM and Hsueh et al.'s formulas predict stresses through the thickness of the plate, Roark's formulas predict stresses only on the top and the bottom surfaces of the plate. Also, a simply supported plate at its edge is considered in Roark's formulas. We modified Roark's formulas to include the overhang region of the plate to more closely simulate the actual loading configuration. Then, the accuracy of formulas was examined by comparing with finite element results of monolayered and bilayered plates subjected to ring-on-ring loading. Results: Monolayer is a special case of bilayer, and both monolayer and bilayer are special cases of multilayer. For monolayered plates, ASTM and Hsueh et al.'s formulas are identical, and both are in excellent agreement with finite element results. For bilayered plates, Hsueh et al.'s formulas are in excellent agreement with finite element results. For both monolayered and bilayered plates, Roark's formulas deviate from finite element results while the modified Roark's formulas are accurate. Conclusions: Roark's formulas for evaluating the biaxial strength of bilayered dental ceramics will result in errors in predicted stresses which depend on the size of the overhang region of the plate in the actual loading configuration. Also, Roark's formulas are limited to predicting

  4. Collinear Acousto-Optical Transformation of Bessel Light Beams in Biaxial Gyrotropic Crystals

    NASA Astrophysics Data System (ADS)

    Belyi, V. N.; Kulak, G. V.; Krokh, G. V.; Shakin, O. V.

    2016-05-01

    The collinear acousto-optical transformation of Bessel light beams in biaxial gyrotropic crystals into two annular, internal conical refraction beams with orthogonal elliptical polarization is studied. It is found that the diffraction efficiency is maximal (~50-60%) for low ultrasound intensities and varies slightly with further increases in acoustic power. At high ultrasound intensities, the intensities of the transmitted and diffracted annular beams differ insignificantly. The possible use of this acousto-optical interaction for creating collinear tuneable narrow-band acousto-optical filters at low ultrasonic frequencies is demonstrated.

  5. Surface waves with simple exponential transverse decay at a biaxial bicrystalline interface.

    PubMed

    Nelatury, Sudarshan R; Polo, John A; Lakhtakia, Akhlesh

    2007-03-01

    The dispersion equation for surface waves--with simple transverse exponential decay at the interface of identical biaxial crystals with a relative twist about the axis normal to the interface and propagating along a bisector of the angle between the crystallographic configurations on either side of the interface--has several solutions of which only one is physical. The selected type of surface wave is possible only for a restricted range of the twist angle, which depends on the ratio of the maximum and the minimum of the principal refractive indexes and the angle between the optic ray axes.

  6. Polar properties of a hexagonally bonded GaN sheet under biaxial compression

    NASA Astrophysics Data System (ADS)

    Gao, Yanlin; Yayama, Tomoe; Okada, Susumu

    2016-09-01

    Using the density functional theory, we study the geometric and electronic structures of a GaN sheet possessing a honeycomb network. The sheet preserves the planar conformation under an equilibrium lattice constant of 3.2 Å, and has a semiconducting electronic structure with an indirect band gap of 2.28 eV. The biaxial compressive strain causes structural buckling, leading to polarization normal to the atomic layer. An external electric field normal to the layer also induces structural buckling with a height proportional to the field strength. The polarity of the buckled GaN sheet is tunable by attaching H atoms on Ga and N atoms.

  7. [Alignment of malpositioned canines].

    PubMed

    Wagner, L

    1991-03-01

    This article presents a system for aligning impacted canines. The base of this system is the lingual arch, a rigid reaction unit of four teeth, molars and premolars. From this base unit an impacted canine can be extruded, moved distally, jumped over the occlusion and derotated by segment arches, coil springs and elastic ligatures. The efficiency of this appliance is due to the elimination of undesired reactive forces, the safe moving of teeth, the possibility of an exact force application and the simple manipulation; also the esthetic inconvenience is minimal. All this results in a better prognosis and an essentially shorter treatment time. This appliance can be used in the upper and the lower jaw. Schematic drawings and clinical examples demonstrate this method.

  8. Polarographic determination of tungsten and molybdenum in sedimentary rocks

    SciTech Connect

    Vakhobova, R.U.; Lykova, F.P.; Milyavskii, Yu. S.; Rachinskaya, G.F.

    1985-12-01

    In order to determine microamounts of tungsten and molybdenum, one the most sensitive versions of polarography is used in this paper, called catalytic currents. In the development of a procedure for the determination of tungsten and molybdenum in geochemical items, the reduction of hydroxylamine (HA) is used, catalyzed by tungsten and molybdenum compounds in the presence of pyrocatechol, as on a background of dicarboxylic acids and hydroxy acids the HA reduction half-wave potentials, catalyzed by these elements, coincide. The investigations were conducted on a PPT-1 polarograph in the classical regime in a thermostatically controlled cell with a mercury dripping electrode and a saturated calomel comparison electrode. The authors develop a procedure for the simultaneous determination of n.10/sup -5/-n.10/sup -4/% of tungsten and molybdenum in sedimentary rocks.

  9. Tungsten-nickel-cobalt alloy and method of producing same

    DOEpatents

    Dickinson, James M.; Riley, Robert E.

    1977-03-15

    An improved tungsten alloy having a tungsten content of approximately 95 weight percent, a nickel content of about 3 weight percent, and the balance being cobalt of about 2 weight percent is described. A method for producing said tungsten-nickel-cobalt alloy is further described and comprises (a) coating the tungsten particles with a nickel-cobalt alloy, (b) pressing the coated particles into a compact shape, (c) heating said compact in hydrogen to a temperature in the range of 1400.degree. C and holding at this elevated temperature for a period of about 2 hours, (d) increasing this elevated temperature to about 1500.degree. C and holding for 1 hour at this temperature, (e) cooling to about 1200.degree. C and replacing the hydrogen atmosphere with an inert argon atmosphere while maintaining this elevated temperature for a period of about 1/2 hour, and (f) cooling the resulting alloy to room temperature in this argon atmosphere.

  10. Surface binding energies of beryllium/tungsten alloys

    NASA Astrophysics Data System (ADS)

    Gyoeroek, Michael; Kaiser, Alexander; Sukuba, Ivan; Urban, Jan; Hermansson, Kersti; Probst, Michael

    2016-04-01

    Binding energies of beryllium and tungsten atoms on surfaces of the alloys Be2W and Be12W were obtained from density functional theory calculations. Values of 4.08-5.63 eV for beryllium and 6.81-10.04 eV for tungsten were obtained. An analytical force field agrees for beryllium, but its tungsten surface atoms are too strongly bound. The surface binding energies of Be and W on Be12W surfaces is slightly smaller than on the pure Be and W surfaces, respectively. For higher tungsten content, i.e. for Be2W, the situation is more complicated. For some surfaces of this alloy the surface binding energies are enhanced while for others they are diminished, compared to the pure metal surfaces. The dependency of the cohesive energy on the mole fraction follows a linear relationship.

  11. Growth of tungsten oxide nanorods with carbon caps.

    PubMed

    Kichambare, Padmakar; Hii, King-Fu; Vallance, R Ryan; Sadanadan, B; Rao, Apparao M; Javed, Kazi; Menguc, M Pinar

    2006-02-01

    Hybrid nanostructures consisting of tungsten oxide nanorods with mushroom-shaped carbon caps were grown on electrochemically etched tungsten tips by thermal chemical vapor deposition with methane and argon. These nanorods grow along the radial direction and are very straight and smooth. Electron microscopy revealed a dominant diameter and length of approximately 50 nm and approximately 0.6 microm, respectively. High-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS) revealed the presence of crystalline monoclinic W18O49 in the nanorods, and the cap was entirely amorphous carbon. A plausible growth mechanism involves the reduction of tungsten oxide WO3, present on the tungsten surface, by methane at 900 degrees C. PMID:16573057

  12. Characterization of the impurities in tungsten/silicon-germanium contacts

    SciTech Connect

    Gregg, H.A. Sr.

    1986-03-26

    Secondary ion mass spectrometry and Auger electron spectrometry depth profiling were used to determine impurity distributions in sputter deposited tungsten films over N-type and P-type 80/20 silicon-germanium elements of thermoelectric devices. These analyses showed that silicon, oxygen, sodium, boron, and phosphorous were present as impurities in the tungsten film. All these impurities except oxygen and sodium came from the substrate. Oxygen was gettered by the tungsten films, while sodium was possibly the result of sample handling. Further, the results from this study indicate that an oxide build-up, primarily at the tungsten/silicon-germanium interface of the N-type materials, is the major contributor to contact resistance in thermoelectric devices.

  13. OBJECT KINETIC MONTE CARLO SIMULATIONS OF CASCADE ANNEALING IN TUNGSTEN

    SciTech Connect

    Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.

    2014-03-31

    The objective of this work is to study the annealing of primary cascade damage created by primary knock-on atoms (PKAs) of various energies, at various temperatures in bulk tungsten using the object kinetic Monte Carlo (OKMC) method.

  14. Tungsten Mobility During Alteration Processes: An Experimental Approach

    NASA Astrophysics Data System (ADS)

    Yin, N. H.; Fabre, S.; Quitté, G.

    2016-08-01

    Most chondrites show evidence of relatively low temperature alteration. Mass-dependent fractionation of non-traditional stable isotopes such as tungsten (W) are well suited to trace metal-silicate differentiation and alteration processes.

  15. Some observations on uranium carbide alloy/tungsten compatibility.

    NASA Technical Reports Server (NTRS)

    Phillips, W. M.

    1972-01-01

    Results of chemical compatibility tests between both pure tungsten and thoriated tungsten run at 1800 C for up to 3300 hours with uranium carbide alloys. Alloying with zirconium carbide appeared to widen the homogeneity range of uranium carbide, making additional carbon available for reaction with the tungsten. Reaction layers were formed both by vapor phase reaction and by physical contact, producing either or both UWC2 and W2C, depending upon the phases present in the starting fuel alloy. Formation of UWC2 results in slow growth of the reaction layer with time, while W2C reaction layers grow rapidly, allowing equilibrium to be reached in less than 2500 hours at 1800 C. Neither the presence of a thermal gradient nor the presence of thoria in the tungsten clad affect the reactions observed.

  16. A Compact Gas/Tungsten-Arc Welding Torch

    NASA Technical Reports Server (NTRS)

    Morgen, Gene E.

    1991-01-01

    Compact gas/tungsten-arc welding torch delivers 100-A current, yet used in confined spaces inaccessible to even smallest commercially available torch. Despite its extremely small size, torch contains all usual components and delivers high current.

  17. Refractory metals welded or brazed with tungsten inert gas equipment

    NASA Technical Reports Server (NTRS)

    Wisner, J. P.

    1965-01-01

    Appropriate brazing metals and temperatures facilitate the welding or brazing of base metals with tungsten inert gas equipment. The highest quality bond is obtained when TIG welding is performed in an inert atmosphere.

  18. Tungsten isotope ratio determinations by negative thermal ionization mass spectrometry

    NASA Astrophysics Data System (ADS)

    Völkening, Joachim; Köppe, Manfred; Heumann, Klaus G.

    1991-07-01

    A precise determination of the isotopic abundances of tungsten with natural isotopic composition is presented. WO-3 ions are generated by negative thermal ionization (NTI) in a double-filament ion source. La2O3 is used as a chemical substance to reduce the electron work function of the rhenium filament material. An ionization efficiency of 1% is obtained for sample loadings of 100 ng. The isotopic abundances are measured with relative standard deviations of 0.2% for the least abundant 180W isotope and 0.02-0.004% for the other tungsten isotopes. These improved isotopic data are used to recalculate the atomic weight of tungsten as 183.8417 ± 0.0001. The new NTI technique is an ideal tool for the application of isotope dilution mass spectrometry to analyse tungsten traces and for the measurement of isotopic shifts of this element in meteorites produced by the decay of 182Hf.

  19. Lunar Alignments - Identification and Analysis

    NASA Astrophysics Data System (ADS)

    González-García, A. César

    Lunar alignments are difficult to establish given the apparent lack of written accounts clearly pointing toward lunar alignments for individual temples. While some individual cases are reviewed and highlighted, the weight of the proof must fall on statistical sampling. Some definitions for the lunar alignments are provided in order to clarify the targets, and thus, some new tools are provided to try to test the lunar hypothesis in several cases, especially in megalithic astronomy.

  20. Ductile tungsten-nickel-alloy and method for manufacturing same

    DOEpatents

    Ludwig, Robert L.

    1978-01-01

    The tensile elongation of a tungsten-nickel-iron alloy containing essentially 95 weight percent reprocessed tungsten, 3.5 weight percent nickel, and 1.5 weight percent iron is increased from a value of less than about 1 percent up to about 23 percent by the addition of less than 0.5 weight percent of a reactive metal consisting of niobium and zirconium.

  1. Processing effects on the mechanical properties of tungsten heavy alloys

    NASA Technical Reports Server (NTRS)

    Kishi, Toshihito; German, R. M.

    1990-01-01

    Tungsten heavy alloys exhibit significant mechanical property sensitivities to the fabrication variables. These sensitivities are illustrated in this examination of vacuum sintering and the effects of composition, sintering temperature, and sintering time on the mechanical properties of tungsten heavy alloys. Measurements were conducted to assess the density, strength, hardness, and elongation dependencies. A detrimental aspect of vacuum sintering is matrix phase evaporation, although vacuum sintering does eliminate the need for postsintering heat treatments.

  2. Electrodeposited Biaxially Textured CeO2 and CeO2:Sm Buffer Layer for YBCO Superconductor Oxide Films

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Raghu; Phok, Sovannary; Spagnol, Priscila; Chaudhuri, Tapas

    2006-03-01

    Nonvacuum electrodeposition was used to prepare biaxially textured CeO2 and Sm-doped CeO2 coatings on Ni-W substrates. The samples were characterized by X-ray diffraction (including θ/2θ, pole figures, omega scans, and phi scans), atomic force microscopy (AFM), Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Full-width at half-maximum values of the ω scan and φ scan of the electrodeposited layers were better than those of the Ni-W base substrates, indicating improved biaxial texturing of the electrodeposited layers.

  3. Infarcted rat myocardium: Data from biaxial tensile and uniaxial compressive testing and analysis of collagen fibre orientation.

    PubMed

    Sirry, Mazin S; Butler, J Ryan; Patnaik, Sourav S; Brazile, Bryn; Bertucci, Robbin; Claude, Andrew; McLaughlin, Ron; Davies, Neil H; Liao, Jun; Franz, Thomas

    2016-09-01

    Myocardial infarction was experimentally induced in rat hearts and harvested immediately, 7, 14 and 28 days after the infarction induction. Anterior wall infarct samples underwent biaxial tensile and uniaxial compressive testing. Orientation of collagen fibres was analysed following mechanical testing. In this paper, we present the tensile and compressive stress-strain raw data, the calculated tensile and compressive moduli and the measured angles of collagen orientation. The presented data is associated with the research article titled "Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression" (Sirry et al., 2016) [1]. PMID:27579338

  4. Effects of the biaxial transverse crystal-field on the phase diagrams of a spin-1 nanowire

    NASA Astrophysics Data System (ADS)

    Magoussi, H.; Zaim, A.; Boughrara, M.; Kerouad, M.

    2016-09-01

    By using the effective field theory based on a probability distribution method, the phase diagrams and the magnetic properties of an Ising nanowire in the presence of the biaxial transverse crystal-field are investigated. The effects of the biaxial transverse crystal field, the interfacial coupling and the exchange interaction in the surface on the phase diagram, the magnetization and the internal energy are examined. Some characteristic phenomena are found such as the tricritical behavior, the critical end point and the re-entrant phenomenon.

  5. Irradiation effects in tungsten-copper laminate composite

    DOE PAGES

    Garrison, L. M.; Katoh, Yutai; Snead, Lance L.; Byun, Thak Sang; Reiser, Jens; Rieth, Michael

    2016-09-19

    Tungsten-copper laminate composite has shown promise as a structural plasma-facing component as compared to tungsten rod or plate. The present study evaluated the tungsten-copper composite after irradiation in the High Flux Isotope Reactor (HFIR) at temperatures of 410–780 °C and fast neutron fluences of 0.02–9.0 × 1025 n/m2, E > 0.1 MeV, 0.0039–1.76 displacements per atom (dpa) in tungsten. Tensile tests were performed on the composites, and the fracture surfaces were analyzed with scanning electron microscopy. Before irradiation, the tungsten layers had brittle cleavage failure, but the overall composite had 15.5% elongation at 22 °C. After only 0.0039 dpa thismore » was reduced to 7.7% elongation, and no ductility was observed after 0.2 dpa at all irradiation temperatures when tensile tested at 22 °C. In conclusion, tor elevated temperature tensile tests after irradiation, the composite only had ductile failure at temperatures where the tungsten was delaminating or ductile.« less

  6. Impact of Bi-Axial Shear on Atherogenic Gene Expression by Endothelial Cells.

    PubMed

    Chakraborty, Amlan; Chakraborty, Sutirtha; Jala, Venkatakrishna R; Thomas, Jonathan M; Sharp, M Keith; Berson, R Eric; Haribabu, Bodduluri

    2016-10-01

    This study demonstrated the effects of the directionality of oscillatory wall shear stress (WSS) on proliferation and proatherogenic gene expression (I-CAM, E-Selectin, and IL-6) in the presence of inflammatory mediators leukotriene B4 (LTB4) and bacterial lipopolysaccharide (LPS) from endothelial cells grown in an orbiting culture dish. Computational fluid dynamics (CFD) was applied to quantify the flow in the dish, while an analytical solution representing an extension of Stokes second problem was used for validation. Results indicated that WSS magnitude was relatively constant near the center of the dish and oscillated significantly (0-0.9 Pa) near the side walls. Experiments showed that LTB4 dominated the shear effects on cell proliferation and area. Addition of LPS didn't change proliferation, but significantly affected cell area. The expression of I-CAM1, E-Selectin and IL-6 were altered by directional oscillatory shear index (DOSI, a measure of the biaxiality of oscillatory shear), but not shear magnitude. The significance of DOSI was further reinforced by the strength of its interactions with other atherogenic factors. Hence, directionality of shear appears to be an important factor in regulating gene expression and provides a potential explanation of the propensity for increased vascular lesions in regions in the arteries with oscillating biaxial flow.

  7. Optical properties of phase shift on reflection and/or transmission through biaxial anisotropic thin films

    NASA Astrophysics Data System (ADS)

    Hou, Yongqiang; Qi, Hongji; Li, Xu; He, Kai; Fang, Ming; Yi, Kui; Shao, Jianda

    2013-07-01

    On the basis of theoretical analysis of biaxial birefringent thin films, this study investigates the optical properties of phase shift on reflection and/or transmission through slanted columnar TiO2 sculptured anisotropic thin film (ATF) deposited with glancing angle deposition (GLAD) technique via reactive electron-beam evaporation. The tilted nanocolumn microstructures of thin film induce the optical anisotropy. The optical constants dispersion equations of TiO2 ATF are determined from fitting the transmittance spectra for s- and p-polarized waves measured at normal and oblique incidence within 400-1200nm. With the extracted structure parameters, the phase shifts of polarized light are analyzed with the characteristic matrix and then measured with spectroscopic ellipsometry in the deposition plane. A reasonably good agreement between the theoretical studies and experimental measurements is obtained. In addition, the dependence of the phase shift on oblique incidence angle is also discussed. The results show a greater generality and superiority of the characteristic matrix method. Birefringence of the biaxial ATF performed a sophisticated phase modulation with varied incidence angles over a broad range to have a wide-angle phase shift.

  8. Fracture analysis of stiffened panels under biaxial loading with widespread cracking

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.

    1995-01-01

    An elastic-plastic finite-element analysis with a critical crack-tip opening angle (CTOA) fracture criterion was used to model stable crack growth and fracture of 2024-T3 aluminum alloy (bare and clad) panels for several thicknesses. The panels had either single or multiple-site damage (MSD) cracks subjected to uniaxial or biaxial loading. Analyses were also conducted on cracked stiffened panels with single or MSD cracks. The critical CTOA value for each thickness was determined by matching the failure load on a middle-crack tension specimen. Comparisons were made between the critical angles determined from the finite-element analyses and those measured with photographic methods. Predicted load-against-crack extension and failure loads for panels under biaxial loading, panels with MSD cracks, and panels with various numbers of stiffeners were compared with test data whenever possible. The predicted results agreed well with the test data even for large-scale plastic deformations. The analyses were also able to predict stable tearing behavior of a large lead crack in the presence of MSD cracks. The analyses were then used to study the influence of stiffeners on residual strength in the presence of widespread fatigue cracking. Small MSD cracks were found to greatly reduce the residual strength for large lead cracks even for stiffened panels.

  9. Specimen Designs for Testing Advanced Aeropropulsion Materials Under In-Plane Biaxial Loading

    NASA Technical Reports Server (NTRS)

    Ellis, John R.; Abul-Aziz, Ali

    2003-01-01

    A design study was undertaken to develop specimen designs for testing advanced aeropropulsion materials under in-plane biaxial loading. The focus of initial work was on developing a specimen design suitable for deformation and strength tests to be conducted under monotonic loading. The type of loading initially assumed in this study was the special case of equibiaxial, tensile loading. A specimen design was successfully developed after a lengthy design and optimization process with overall dimensions of 12 by 12 by 0.625 in., and a gage area of 3.875 by 3.875 by 0.080 in. Subsequently, the scope of the work was extended to include the development of a second design tailored for tests involving cyclic loading. A specimen design suitably tailored to meet these requirements was successfully developed with overall dimensions of 12 by 12 by 0.500 in. and a gage area of 2.375 by 2.375 by 0.050 in. Finally, an investigation was made to determine whether the specimen designs developed in this study for equibiaxial, tensile loading could be used without modification to investigate general forms of biaxial loading. For best results, it was concluded that specimen designs need to be optimized and tailored to meet the specific loading requirements of individual research programs.

  10. Method of depositing a protective layer over a biaxially textured alloy substrate and composition therefrom

    DOEpatents

    Goyal, Amit; Kroeger, Donald M.; Paranthaman, Mariappan; Lee, Dominic F.; Feenstra, Roeland; Norton, David P.

    2002-01-01

    A laminate article consists of a substrate and a biaxially textured protective layer over the substrate. The substrate can be biaxially textured and also have reduced magnetism over the magnetism of Ni. The substrate can be selected from the group consisting of nickel, copper, iron, aluminum, silver and alloys containing any of the foregoing. The protective layer can be selected from the group consisting of gold, silver, platinum, palladium, and nickel and alloys containing any of the foregoing. The protective layer is also non-oxidizable under conditions employed to deposit a desired, subsequent oxide buffer layer. Layers of YBCO, CeO.sub.2, YSZ, LaAlO.sub.3, SrTiO.sub.3, Y.sub.2 O.sub.3, RE.sub.2 O.sub.3, SrRuO.sub.3, LaNiO.sub.3 and La.sub.2 ZrO.sub.3 can be deposited over the protective layer. A method of forming the laminate article is also disclosed.

  11. Time-evolving collagen-like structural fibers in soft tissues: biaxial loading and spherical inflation

    NASA Astrophysics Data System (ADS)

    Topol, Heiko; Demirkoparan, Hasan; Pence, Thomas J.; Wineman, Alan

    2016-05-01

    This work considers a previously developed constitutive theory for the time dependent mechanical response of fibrous soft tissue resulting from the time dependent remodeling of a collagen fiber network that is embedded in a ground substance matrix. The matrix is taken to be an incompressible nonlinear elastic solid. The remodeling process consists of the continual dissolution of existing fibers and the creation of new fibers. Motivated by experimental reports on the enzyme degradation of collagen fibers, the remodeling is governed by first order chemical kinetics such that the dissolution rate is dependent upon the fiber stretch. The resulting time dependent mechanical response is sensitive to the natural configuration of the fibers when they are created, and different assumptions on the nature of the fiber's stress free state are considered here. The response under biaxial loading, a type of loading that has particular significance for the characterization of biological materials, is studied. The inflation of a spherical membrane is then analyzed in terms of the equal biaxial stretch that occurs in the membrane approximation. Different assumptions on the natural configuration of the fibers, combined with their time dependent dissolution and reforming, are shown to emulate alternative forms of creep and relaxation response. This formal similarity to viscoelastic phenomena occurs even though the underlying mechanisms are fundamentally different from the mechanism of macromolecular reconfiguration that one typically associates with viscoelastic response.

  12. Deposition of biaxially textured yttria-stabilized zirconia by ion-beam-assisted deposition.

    SciTech Connect

    Chudzik, M. P.

    1998-09-17

    Biaxially textured yttria (8 mol %)-stabilized zirconia (YSZ) thin films were deposited on randomly oriented Hastelloy C and Stainless Steel 304 at room temperature as a buffer layer for subsequent deposition of oriented YBa{sub 2}Cu{sub 3}O{sub x} films. The 0.16-1.3 {micro}m thick YSZ films were deposited by e-beam evaporation at rates of 1.2-3.2 {angstrom}/sec. Biaxially textured films were produced with an Ar/O{sub 2} ion beam directed at the substrate during film growth. X-ray diffraction was used to study in-plane and out-of-plane orientation as a function of ion-bombardment angle, film thickness, ion-to-atom flux ratio, and substrate material. In-plane and out-of-plane average-misorientation angles on these YSZ films that were deposited by ion-beam-assisted deposition were as low as 17 and 5.4{degree}, respectively, on as-received substrates.

  13. Dynamic buckling of columns by biaxial moments and uniform end torque

    NASA Astrophysics Data System (ADS)

    Leung, A. Y. T.

    2010-05-01

    A new concept of uniform torque is proposed for the dynamic torsional buckling analysis. A dynamic biaxial moments and torque buckling theory is presented for analysis in structural dynamics. Second-order effects of the axial force, biaxial moments and torque are considered. The consistent natural boundary moments and forces are derived to ensure the symmetry of the dynamic stiffness matrix in fulfilling the requirement of the reciprocal theorem and conservation of energy. The exact dynamic stiffness matrix is obtained using power series expansion. The derivatives of the analytical dynamic stiffness matrix with respect to different loading and geometric parameters are derived explicitly for sensitivity and continuation analyses. Generally distributed axial force can be analyzed without difficulty. It is pointed out that non-uniform sections may not be handled by power series due to the convergent problem. Global pictures for all kinds of linear dynamic buckling are given for the first time. The methodology is based on finite element formulation and therefore it can easily be extended to analyze structural frames.

  14. Practical approach in surface modification of biaxially oriented polypropylene films for gravure printability

    NASA Astrophysics Data System (ADS)

    Nuntapichedkul, Boonchai; Tantayanon, Supawan; Laohhasurayotin, Kritapas

    2014-09-01

    Biaxially oriented polypropylene (BOPP) film is one of the most popularly used materials for the gravure printing process in flexible packaging industry. The skin layers of BOPP film were associated with 3-6 weight % of propylene-ethylene copolymer. These films were completely biaxial-oriented by sequential stretching process after which the film surfaces were subjected to corona treatment integrated in the production line. The FT-IR results exhibited that polar functional groups as carbonyl molecules were established on the corona-treated BOPP film. The contact angles of these BOPP films were measured; the surface free energies (SFE) were then calculated. AFM topographical images also agreed well with the SFE which increased as the contents of propylene-ethylene copolymer increased. An approximated 20% increased SFE was obtained for the BOPP film that was associated with 6% propylene-ethylene copolymer. The printing quality on BOPP films was tested by light microscope which confirmed that the chromatic resolution of the printed images improved down to even more smaller groove sizes, 10 or 5 dot%. This improvement was also examined and found to correspond well with the interfacial tensions and work of adhesion between the inks and the modified BOPP films.

  15. Characterization of Biaxial and Triaxial Braids: Fiber Architecture and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Birkefeld, Karin; Röder, Mirko; von Reden, Tjark; Bulat, Martina; Drechsler, Klaus

    2012-06-01

    Biaxial and triaxial carbon fiber braids with off-axis braiding angles of 30°, 45° and 55° are characterized with respect to their fiber architecture. All braids are produced on a round mandrel with constant cross section. Detailed geometric information on the different braids, like roving dimensions, roving shapes and the degree of nesting is given. The findings from measurements in photomicrographs are used to construct meso-model yarn architectures at the unit cell level which are then analyzed with the WiseTex software (Lomov et al. Compos. Sci. Technol. 60:2083-2095, 2000). The results of the models' analysis with TexComp and comparison of mechanical properties with tests are consistent and essential for further steps in predictive modeling. Predictive modeling was also performed for biaxial braids based on the packing density in the material and parameters of the braiding process. The good conformance of the predictive models gives a validated starting point for development of braided structures concerning stiffness behavior. In addition, the information about the fiber architecture can be used for failure analysis on unit cell level.

  16. Application of magnetomechanical hysteresis modeling of magnetic techniques for monitoring neutron embrittlement and biaxial stress

    SciTech Connect

    Sablik, M.J.; Kwun, H.; Burkhardt, G.L.; Rollwitz, W.L.; Cadena, D.G.

    1993-01-31

    Objective of this project is to investigate experimentally and theoretically the effects of neutron embrittlement and biaxial stress on magnetic properties in steels, using various magnetic measurement techniques. If neutron embrittlement and biaxial stress can be measured via changes in magnetic properties, this should ultimately assist in safety monitoring of nuclear power plants and of gas and oil pipelines. This first-year report addresses the issue of using magnetic property changes to detect neutron embrittlement. The magnetic measurements were all done on irradiated specimens previously broken in two in a Charpy test to determine their embrittlement. The magnetic properties of the broken charpy specimens from D.C. Cook did not correlate well with fluence or embrittlement parameters, possible due to metallurgical reasons. correlation was better with Indian Point 2 specimens, with the nonlinear harmonic amplitudes showing the best correlation (R[sup 2][approximately]0.7). However, correlation was not good enough. It is recommended that tests be done on unbroken irradiated Charpy specimens, for which magnetic characterization data prior to irradiation is available, if possible.

  17. Critical points and symmetries of a free energy function for biaxial nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Chillingworth, D. R. J.

    2015-05-01

    We describe a general mean field model for the free energy function for a homogeneous medium of mutually interacting molecules, based on the formalism for a biaxial nematic liquid crystal set out by Katriel et al (1986) in an influential paper in Liquid Crystals 1 and subsequently called the KKLS formalism. The free energy is expressed as the sum of an entropy term and an interaction (Hamiltonian) term. Using the language of group representation theory we identify the order parameters as averaged components of a linear transformation, and characterize the full symmetry group of the entropy term in the liquid crystal context as a wreath product SO(3) ≀ Z2. The symmetry-breaking role of the Hamiltonian, pointed out by Katriel et al, is here made explicit in terms of centre manifold reduction at bifurcation from isotropy. We use tools and methods of equivariant singularity theory to reduce the bifurcation study to that of a D3-invariant function on R2, ubiquitous in liquid crystal theory, and to describe the ‘universal’ bifurcation geometry in terms of the superposition of a familiar swallowtail surface controlling uniaxial equilibria and another less familiar surface controlling biaxial equilibria. In principle this provides a template for all nematic liquid crystal phase transitions close to isotropy, although further work is needed to identify the absolute minima that are the critical points representing stable phases.

  18. Tungsten-molybdenum fractionation in estuarine environments

    NASA Astrophysics Data System (ADS)

    Mohajerin, T. Jade; Helz, George R.; Johannesson, Karen H.

    2016-03-01

    Dissolved tungsten (W) and molybdenum (Mo) concentrations were measured in surface waters and sediment pore waters of Terrebonne Bay, a shallow estuary in the Mississippi River delta, to investigate the biogeochemical processes that fractionate these Group 6 elements relative to one another during transit from weathering to sedimentary environments. Although many of the chemical properties of W and Mo are similar, the two elements behave autonomously, and the fractionation mechanisms are only partly understood. In sulfidic pore waters, dissolved Mo is depleted relative to river water-seawater mixtures, whereas dissolved W is >10-fold enriched. Reductive dissolution of poorly crystalline phases like ferrihydrite, which is a preferential host of W relative to Mo in grain coatings on river-borne particles, can explain the dissolved W enrichment. Dissolved W becomes increasingly enriched as H2S(aq) rises above about 60 μM due to transformation of WO42- to thiotungstates as well as to additional reductive dissolution of phases that host W. In contrast, as rising sulfide transforms MoO42- to thiomolybdates in pore waters, dissolved Mo is suppressed, probably owing to equilibration with an Fe-Mo-S phase. This putative phase appears to control the aqueous ion product, Q = [Fe2+][MoS42-]0.6 [H2S0]0.4/[H+]0.8, at a value of 10-7.78. Concentrations of dissolved W and Mo in pore waters bear no relation to concentrations in surface waters of the same salinity. In surface waters, dissolved Mo is nearly conserved in the estuarine mixing zone. Dissolved W appears also to be conserved except for several cases where W may have been enhanced by exchange with underlying, W-rich pore waters. With increasing salinity, the molar Mo/W ratio rises from about 10 to about 1000 in surface waters whereas it is mostly <10 in underlying pore waters and in highly sulfidic pore waters is mostly near 1. Differences in two chemical properties may account for this fractionation of Mo with respect to

  19. Lexical alignment in triadic communication.

    PubMed

    Foltz, Anouschka; Gaspers, Judith; Thiele, Kristina; Stenneken, Prisca; Cimiano, Philipp

    2015-01-01

    Lexical alignment refers to the adoption of one's interlocutor's lexical items. Accounts of the mechanisms underlying such lexical alignment differ (among other aspects) in the role assigned to addressee-centered behavior. In this study, we used a triadic communicative situation to test which factors may modulate the extent to which participants' lexical alignment reflects addressee-centered behavior. Pairs of naïve participants played a picture matching game and received information about the order in which pictures were to be matched from a voice over headphones. On critical trials, participants did or did not hear a name for the picture to be matched next over headphones. Importantly, when the voice over headphones provided a name, it did not match the name that the interlocutor had previously used to describe the object. Participants overwhelmingly used the word that the voice over headphones provided. This result points to non-addressee-centered behavior and is discussed in terms of disrupting alignment with the interlocutor as well as in terms of establishing alignment with the voice over headphones. In addition, the type of picture (line drawing vs. tangram shape) independently modulated lexical alignment, such that participants showed more lexical alignment to their interlocutor for (more ambiguous) tangram shapes compared to line drawings. Overall, the results point to a rather large role for non-addressee-centered behavior during lexical alignment.

  20. Drive alignment pays maintenance dividends

    SciTech Connect

    Fedder, R.

    2008-12-15

    Proper alignment of the motor and gear drive on conveying and processing equipment will result in longer bearing and coupling life, along with lower maintenance costs. Selecting an alignment free drive package instead of a traditional foot mounted drive and motor is a major advancement toward these goals. 4 photos.

  1. CATO: The Clone Alignment Tool.

    PubMed

    Henstock, Peter V; LaPan, Peter

    2016-01-01

    High-throughput cloning efforts produce large numbers of sequences that need to be aligned, edited, compared with reference sequences, and organized as files and selected clones. Different pieces of software are typically required to perform each of these tasks. We have designed a single piece of software, CATO, the Clone Alignment Tool, that allows a user to align, evaluate, edit, and select clone sequences based on comparisons to reference sequences. The input and output are designed to be compatible with standard data formats, and thus suitable for integration into a clone processing pipeline. CATO provides both sequence alignment and visualizations to facilitate the analysis of cloning experiments. The alignment algorithm matches each of the relevant candidate sequences against each reference sequence. The visualization portion displays three levels of matching: 1) a top-level summary of the top candidate sequences aligned to each reference sequence, 2) a focused alignment view with the nucleotides of matched sequences displayed against one reference sequence, and 3) a pair-wise alignment of a single reference and candidate sequence pair. Users can select the minimum matching criteria for valid clones, edit or swap reference sequences, and export the results to a summary file as part of the high-throughput cloning workflow.

  2. Transformation and Alignment in Similarity

    ERIC Educational Resources Information Center

    Hodgetts, Carl J.; Hahn, Ulrike; Chater, Nick

    2009-01-01

    This paper contrasts two structural accounts of psychological similarity: structural alignment (SA) and Representational Distortion (RD). SA proposes that similarity is determined by how readily the structures of two objects can be brought into alignment; RD measures similarity by the complexity of the transformation that "distorts" one…

  3. CATO: The Clone Alignment Tool.

    PubMed

    Henstock, Peter V; LaPan, Peter

    2016-01-01

    High-throughput cloning efforts produce large numbers of sequences that need to be aligned, edited, compared with reference sequences, and organized as files and selected clones. Different pieces of software are typically required to perform each of these tasks. We have designed a single piece of software, CATO, the Clone Alignment Tool, that allows a user to align, evaluate, edit, and select clone sequences based on comparisons to reference sequences. The input and output are designed to be compatible with standard data formats, and thus suitable for integration into a clone processing pipeline. CATO provides both sequence alignment and visualizations to facilitate the analysis of cloning experiments. The alignment algorithm matches each of the relevant candidate sequences against each reference sequence. The visualization portion displays three levels of matching: 1) a top-level summary of the top candidate sequences aligned to each reference sequence, 2) a focused alignment view with the nucleotides of matched sequences displayed against one reference sequence, and 3) a pair-wise alignment of a single reference and candidate sequence pair. Users can select the minimum matching criteria for valid clones, edit or swap reference sequences, and export the results to a summary file as part of the high-throughput cloning workflow. PMID:27459605

  4. CATO: The Clone Alignment Tool

    PubMed Central

    Henstock, Peter V.; LaPan, Peter

    2016-01-01

    High-throughput cloning efforts produce large numbers of sequences that need to be aligned, edited, compared with reference sequences, and organized as files and selected clones. Different pieces of software are typically required to perform each of these tasks. We have designed a single piece of software, CATO, the Clone Alignment Tool, that allows a user to align, evaluate, edit, and select clone sequences based on comparisons to reference sequences. The input and output are designed to be compatible with standard data formats, and thus suitable for integration into a clone processing pipeline. CATO provides both sequence alignment and visualizations to facilitate the analysis of cloning experiments. The alignment algorithm matches each of the relevant candidate sequences against each reference sequence. The visualization portion displays three levels of matching: 1) a top-level summary of the top candidate sequences aligned to each reference sequence, 2) a focused alignment view with the nucleotides of matched sequences displayed against one reference sequence, and 3) a pair-wise alignment of a single reference and candidate sequence pair. Users can select the minimum matching criteria for valid clones, edit or swap reference sequences, and export the results to a summary file as part of the high-throughput cloning workflow. PMID:27459605

  5. Lexical alignment in triadic communication

    PubMed Central

    Foltz, Anouschka; Gaspers, Judith; Thiele, Kristina; Stenneken, Prisca; Cimiano, Philipp

    2015-01-01

    Lexical alignment refers to the adoption of one’s interlocutor’s lexical items. Accounts of the mechanisms underlying such lexical alignment differ (among other aspects) in the role assigned to addressee-centered behavior. In this study, we used a triadic communicative situation to test which factors may modulate the extent to which participants’ lexical alignment reflects addressee-centered behavior. Pairs of naïve participants played a picture matching game and received information about the order in which pictures were to be matched from a voice over headphones. On critical trials, participants did or did not hear a name for the picture to be matched next over headphones. Importantly, when the voice over headphones provided a name, it did not match the name that the interlocutor had previously used to describe the object. Participants overwhelmingly used the word that the voice over headphones provided. This result points to non-addressee-centered behavior and is discussed in terms of disrupting alignment with the interlocutor as well as in terms of establishing alignment with the voice over headphones. In addition, the type of picture (line drawing vs. tangram shape) independently modulated lexical alignment, such that participants showed more lexical alignment to their interlocutor for (more ambiguous) tangram shapes compared to line drawings. Overall, the results point to a rather large role for non-addressee-centered behavior during lexical alignment. PMID:25762955

  6. Curriculum Alignment: Theory to Practice.

    ERIC Educational Resources Information Center

    Leitzel, Thomas C.; Vogler, Daniel E.

    Curriculum alignment is the conscious congruence of three educational elements: curriculum, instruction, and assessment. Alignment is rooted in the belief that instructional plans are established through outcomes-based content goals and the goal of assuring that delivery and assessment are congruent. Platform unity, based on the Principles of…

  7. Well-pump alignment system

    DOEpatents

    Drumheller, Douglas S.

    1998-01-01

    An improved well-pump for geothermal wells, an alignment system for a well-pump, and to a method for aligning a rotor and stator within a well-pump, wherein the well-pump has a whistle assembly formed at a bottom portion thereof, such that variations in the frequency of the whistle, indicating misalignment, may be monitored during pumping.

  8. Creep behavior of tungsten/niobium and tungsten/niobium-1 percent zirconium composites

    NASA Technical Reports Server (NTRS)

    Petrasek, D. W.; Titran, R. H.

    1988-01-01

    A study was conducted to determine the feasibility of using tungsten fiber reinforced niobium or niobium-1 percent zirconium matrix composites to meet the anticipated increased temperature and creep resistance requirements imposed by advanced space power systems. The results obtained on the short time tensile properties indicated that W/Nb composites showed significant improvements in high temperature strength and offer significant mass reductions for high temperature space power systems. The prime material requirement for space power systems applications is long time creep resistance. A study was conducted to determine the effect of high temperature exposure on the properties of these composites, with emphasis upon their creep behavior at elevated temperatures.

  9. Mechanistic, kinetic, and processing aspects of tungsten chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Stein, David

    This dissertation presents an investigation into tungsten chemical mechanical polishing (CMP). CMP is the industrially predominant unit operation that removes excess tungsten after non-selective chemical vapor deposition (CVD) during sub-micron integrated circuit (IC) manufacture. This work explores the CMP process from process engineering and fundamental mechanistic perspectives. The process engineering study optimized an existing CMP process to address issues of polish pad and wafer carrier life. Polish rates, post-CMP metrology of patterned wafers, electrical test data, and synergy with a thermal endpoint technique were used to determine the optimal process. The oxidation rate of tungsten during CMP is significantly lower than the removal rate under identical conditions. Tungsten polished without inhibition during cathodic potentiostatic control. Hertzian indenter model calculations preclude colloids of the size used in tungsten CMP slurries from indenting the tungsten surface. AFM surface topography maps and TEM images of post-CMP tungsten do not show evidence of plow marks or intergranular fracture. Polish rate is dependent on potassium iodate concentration; process temperature is not. The colloid species significantly affects the polish rate and process temperature. Process temperature is not a predictor of polish rate. A process energy balance indicates that the process temperature is predominantly due to shaft work, and that any heat of reaction evolved during the CMP process is negligible. Friction and adhesion between alumina and tungsten were studied using modified AFM techniques. Friction was constant with potassium iodate concentration, but varied with applied pressure. This corroborates the results from the energy balance. Adhesion between the alumina and the tungsten was proportional to the potassium iodate concentration. A heuristic mechanism, which captures the relationship between polish rate, pressure, velocity, and slurry chemistry, is presented

  10. Botulinum alignment for congenital esotropia.

    PubMed Central

    Ing, M R

    1992-01-01

    This is the first report of a group of patients with congenital esotropia examined for motor and sensory evidence of binocularity a minimum of 3 years after alignment by botulinum. Evidence for binocularity was clearly present in approximately one half of the patients. Lag time to satisfactory alignment was at least 1 month (average, 5 months) following the initial botulinum injection. The results must be considered preliminary. However, when these results are compared with those of patients with congenital esotropia aligned by incisional surgery by age 2 years and examined with the same testing devices by this same investigator, botulinum alignment appears to be less effective than surgical alignment in establishing evidence for binocularity (P < 0.005). PMID:1494828

  11. Space Mirror Alignment System

    NASA Technical Reports Server (NTRS)

    Jau, Bruno M.; McKinney, Colin; Smythe, Robert F.; Palmer, Dean L.

    2011-01-01

    An optical alignment mirror mechanism (AMM) has been developed with angular positioning accuracy of +/-0.2 arcsec. This requires the mirror s linear positioning actuators to have positioning resolutions of +/-112 nm to enable the mirror to meet the angular tip/tilt accuracy requirement. Demonstrated capabilities are 0.1 arc-sec angular mirror positioning accuracy, which translates into linear positioning resolutions at the actuator of 50 nm. The mechanism consists of a structure with sets of cross-directional flexures that enable the mirror s tip and tilt motion, a mirror with its kinematic mount, and two linear actuators. An actuator comprises a brushless DC motor, a linear ball screw, and a piezoelectric brake that holds the mirror s position while the unit is unpowered. An interferometric linear position sensor senses the actuator s position. The AMMs were developed for an Astrometric Beam Combiner (ABC) optical bench, which is part of an interferometer development. Custom electronics were also developed to accommodate the presence of multiple AMMs within the ABC and provide a compact, all-in-one solution to power and control the AMMs.

  12. Magnetic alignment and the Poisson alignment reference system

    NASA Astrophysics Data System (ADS)

    Griffith, L. V.; Schenz, R. F.; Sommargren, G. E.

    1990-08-01

    Three distinct metrological operations are necessary to align a free-electron laser (FEL): the magnetic axis must be located, a straight line reference (SLR) must be generated, and the magnetic axis must be related to the SLR. This article begins with a review of the motivation for developing an alignment system that will assure better than 100-μm accuracy in the alignment of the magnetic axis throughout an FEL. The 100-μm accuracy is an error circle about an ideal axis for 300 m or more. The article describes techniques for identifying the magnetic axes of solenoids, quadrupoles, and wiggler poles. Propagation of a laser beam is described to the extent of revealing sources of nonlinearity in the beam. Development of a straight-line reference based on the Poisson line, a diffraction effect, is described in detail. Spheres in a large-diameter laser beam create Poisson lines and thus provide a necessary mechanism for gauging between the magnetic axis and the SLR. Procedures for installing FEL components and calibrating alignment fiducials to the magnetic axes of the components are also described. The Poisson alignment reference system should be accurate to 25 μm over 300 m, which is believed to be a factor-of-4 improvement over earlier techniques. An error budget shows that only 25% of the total budgeted tolerance is used for the alignment reference system, so the remaining tolerances should fall within the allowable range for FEL alignment.

  13. Alignment technology for backside integration

    NASA Astrophysics Data System (ADS)

    Bauer, J.; Kulse, P.; Haak, U.; Old, G.; Scheuring, G.; Döbereiner, St.; Hillmann, F.; Brück, H.-J.; Kaynak, M.; Ehwald, K.-E.; Marschmeyer, St.; Birkholz, M.; Schulz, K.

    2011-03-01

    This paper presents a backside-to-frontside alignment technique for the backside processing of Si wafers. Integrated MEMS components like BiCMOS-embedded RF-MEMS switches require accurate (1-2μm) alignment. We demonstrate an alignment technique providing overlay values of less than 500 nm by using a backside alignment layer. The approach is enabled by a new non-contact wafer pre-alignment system of the Nikon Scanner S207D allowing precise loading (<5μm) of the wafer onto the exposure stage. Before starting the back-side MEMS process, the misalignment between frontside devices and backside alignment layer has to be measured. The alignment errors are applied as lithography overlay corrections to the backside MEMS process. For the specific application of deep Si etching (Bosch process), moreover, one has to consider the etch profile angle deviation across the wafer (tilting), which turned out in our experiments to amount up to 8 μm. During initial experiments with a Nikon i-line stepper NSR-2205 i- 11D the overlay has been corrected by the stepper offset parameters. These parameters have been obtained by summing up both the wafer and intra-field scaling errors caused by deep Si etching and backside-to-frontside alignment errors. Misalignments and tilting errors were all measured with a MueTec MT 3000 IR optical metrology system using overlay marks. The developed alignment technique is applied to BiCMOS-embedded MEMS devices, i.e. mm-wave RF switches and a viscosity sensor chip based on the IHP's high-speed SiGe technology. It turned out to be very promising for backside processed MEMS components with critical alignment requirements.

  14. Effect of reinforcement phase on the mechanical property of tungsten nanocomposite synthesized by spark plasma sintering

    SciTech Connect

    Lee, Jin -Kyu; Kim, Song -Yi; Ott, Ryan T.; Kim, Jin -Young; Eckert, Jürgen; Lee, Min -Ha

    2015-07-15

    Nanostructured tungsten composites were fabricated by spark plasma sintering of nanostructured composite powders. The composite powders, which were synthesized by mechanical milling of tungsten and Ni-based alloy powders, are comprised of alternating layers of tungsten and metallic glass several hundred nanometers in size. The mechanical behavior of the nanostructured W composite is similar to pure tungsten, however, in contrast to monolithic pure tungsten, some macroscopic compressive plasticity accompanies the enhanced maximum strength up to 2.4 GPa by introducing reinforcement. As a result, we have found that the mechanical properties of the composites strongly depend on the uniformity of the nano-grained tungsten matrix and reinforcement phase distribution.

  15. Development of tungsten-tantalum generator

    NASA Astrophysics Data System (ADS)

    Leblanc, A.; Babich, J.; Jhingran, S. G.

    The purpose of this project was to develop a useable tungsten (W)/tantalum (Ta) generator. Ta-178 is formed following the decay of its parent, W-178 (half-life: 21.7d) and has a half life of 9.3 minutes in turn yielding stable Hf-178. The decay of the parent isotope (W-178) occurs entirely by electron capture to the 9.3 minute Ta-178 state, without feeding the high spin Ta-178 isomer (half life 2.2 hours). In Ta-178 decay, 99.2% of the disintegrations proceed by electron capture and 0.18% by positron emission. Electron capture results in a 61.2% branch to the ground state of Hf-178 and 33.7% to the first excited state at 93 1KeV. The most prominent features of the radionuclide's energy spectrum are the hafnium characteristic radiation peaks with energies between 54.6 and 65.0 KeV. The radiation exposure dose of Ta-118 was calculated to be approximately one-twentieth that of Tc-99m on a per millicurie basis. A twenty-fold reduction in radiation exposure from Ta-178 compared with Tc-99m means that the usual administered dose can be increased three or four times, greatly increasing statistical accuracy while reducing radiation exposure by a factor of five.

  16. Tungsten Oxides for Photocatalysis, Electrochemistry, and Phototherapy.

    PubMed

    Huang, Zhen-Feng; Song, Jiajia; Pan, Lun; Zhang, Xiangwen; Wang, Li; Zou, Ji-Jun

    2015-09-23

    The conversion, storage, and utilization of renewable energy have all become more important than ever before as a response to ever-growing energy and environment concerns. The performance of energy-related technologies strongly relies on the structure and property of the material used. The earth-abundant family of tungsten oxides (WOx ≤3 ) receives considerable attention in photocatalysis, electrochemistry, and phototherapy due to their highly tunable structures and unique physicochemical properties. Great breakthroughs have been made in enhancing the optical absorption, charge separation, redox capability, and electrical conductivity of WOx ≤3 through control of the composition, crystal structure, morphology, and construction of composite structures with other materials, which significantly promotes the efficiency of processes and devices based on this material. Herein, the properties and synthesis of WOx ≤3 family are reviewed, and then their energy-related applications are highlighted, including solar-light-driven water splitting, CO2 reduction, and pollutant removal, electrochromism, supercapacitors, lithium batteries, solar and fuel cells, non-volatile memory devices, gas sensors, and cancer therapy, from the aspect of function-oriented structure design and control.

  17. The DAMPE silicon-tungsten tracker

    NASA Astrophysics Data System (ADS)

    Azzarello, P.; Ambrosi, G.; Asfandiyarov, R.; Bernardini, P.; Bertucci, B.; Bolognini, A.; Cadoux, F.; Caprai, M.; De Mitri, I.; Domenjoz, M.; Dong, Y.; Duranti, M.; Fan, R.; Fusco, P.; Gallo, V.; Gargano, F.; Gong, K.; Guo, D.; Husi, C.; Ionica, M.; La Marra, D.; Loparco, F.; Marsella, G.; Mazziotta, M. N.; Mesa, J.; Nardinocchi, A.; Nicola, L.; Pelleriti, G.; Peng, W.; Pohl, M.; Postolache, V.; Qiao, R.; Surdo, A.; Tykhonov, A.; Vitillo, S.; Wang, H.; Weber, M.; Wu, D.; Wu, X.; Zhang, F.

    2016-09-01

    The DArk Matter Particle Explorer (DAMPE) is a spaceborne astroparticle physics experiment, launched on 17 December 2015. DAMPE will identify possible dark matter signatures by detecting electrons and photons in the 5 GeV-10 TeV energy range. It will also measure the flux of nuclei up to 100 TeV, for the study of the high energy cosmic ray origin and propagation mechanisms. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon-tungsten tracker-converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is composed of six tracking planes of 2 orthogonal layers of single-sided micro-strip detectors, for a total detector surface of ca. 7 m2. The STK has been extensively tested for space qualification. Also, numerous beam tests at CERN have been done to study particle detection at silicon module level, and at full detector level. After description of the DAMPE payload and its scientific mission, we will describe the STK characteristics and assembly. We will then focus on some results of single ladder performance tests done with particle beams at CERN.

  18. Anthocyanins facilitate tungsten accumulation in Brassica

    SciTech Connect

    Hale, K.L.

    2002-11-01

    Accumulation of molybdenum in Brassica was recently found to be correlated with anthocyanin content, involving the formation of a blue complex. Here the role of anthocyanins in tungsten sequestration was investigated using three species of Brassica: B. rapa (cv. Fast plants), B. juncea (Indian mustard) and B. oleracea (red cabbage). Seedlings of B. rapa and B. juncea turned blue when supplied with colourless tungstate. The blue compound co-localized with anthocyanins in the peripheral cell layers, and the degree of blueness was correlated with anthocyanin content. The direct involvement of anthocyanins in the blue coloration was evident when purified anthocyanins showed a colour change from pink to blue in vitro upon addition of tungstate, over a wide pH range. Anthocyanin production was upregulated 3-fold by W in B. juncea, possibly reflecting a function for anthocyanins in W tolerance or sequestration. The presence of anthocyanins facilitated W accumulation in B. rapa: anthocyanin-containing seedlings accumulated 3-fold more W than an anthocyaninless mutant. There was no correlation between anthocyanin content and W tolerance under these conditions. The nature of the interaction between anthocyanins and tungstate was investigated. X-ray absorption spectroscopy showed no change in the local chemical environment of Wupon uptake of tungstate by the plant; HPLC analysis of purified anthocyanin with or without tungstate showed no peak shift after metal treatment.

  19. Rarefied gas flow through nanoscale tungsten channels.

    PubMed

    Ozhgibesov, M S; Leu, T S; Cheng, C H

    2013-05-01

    The aim of this work is to investigate argon flow behaviors through the channels with three types of boundary conditions. Current work deals with numerical simulations of rarefied gas flow through nano-channels using the Molecular Dynamics method. Taking into account that this method is very time consuming, we implemented all the simulations using CUDA capable graphic cards. We found that the well-known and relatively simple Maxwell model of boundary conditions is able to reproduce gas flow through a tungsten channel with irregularities and roughness, while it results in a significant error in the case of a smooth metal surface. We further found that the flow rate through a relatively short channel correlates nonlinearly with the channel's length. This finding is in contrast with the results available in extant literature. Our results are important for both numerical and theoretical analyses of rarefied gas flow in micro- and nano-systems where the choice of boundary conditions significantly influences flow. PMID:23528809

  20. Signal Analysis of Gas Tungsten Arc Welds

    NASA Technical Reports Server (NTRS)

    Eagar, T. W.

    1985-01-01

    Gas tungsten arc welding is a process in which the input parameters such as current, voltage and travel speed, can be easily controlled and/or monitored. However, weld quality is not solely a function of these parameters. An adaptive method of observing weld quality is desired to improve weld quality assurance. The use of dynamic electrical properties of the welding arc as a weld quality monitor was studied. The electrical properties of the arc are characterized by the current voltage transfer function. The hardware and software necessary to collect the data at a maximum rate of 45 kHz and to allow the off-line processing of this data are tested. The optimum input current waveform is determined. Bead-on-plate welds to observe such characteristics of the weld as the fundamental frequency of the puddle are studied. Future work is planned to observe changes of the arc response with changes in joint geometry, base metal chemistry, and shielding gas composition are discussed.