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Sample records for quantum wires

  1. Comparison of quantum confinement effects between quantum wires and dots

    SciTech Connect

    Li, Jingbo; Wang, Lin-Wang

    2004-03-30

    Dimensionality is an important factor to govern the electronic structures of semiconductor nanocrystals. The quantum confinement energies in one-dimensional quantum wires and zero-dimensional quantum dots are quite different. Using large-scale first-principles calculations, we systematically study the electronic structures of semiconductor (including group IV, III-V, and II-VI) surface-passivated quantum wires and dots. The band-gap energies of quantum wires and dots have the same scaling with diameter for a given material. The ratio of band-gap-increases between quantum wires and dots is material-dependent, and slightly deviates from 0.586 predicted by effective-mass approximation. Highly linear polarization of photoluminescence in quantum wires is found. The degree of polarization decreases with the increasing temperature and size.

  2. Unmodulated spin chains as universal quantum wires

    SciTech Connect

    Wojcik, Antoni; Kurzynski, Pawel; Grudka, Andrzej; Luczak, Tomasz; Gdala, Tomasz; Bednarska, Malgorzata

    2005-09-15

    We study a quantum state transfer between two qubits interacting with the ends of a quantum wire consisting of linearly arranged spins coupled by an excitation conserving, time-independent Hamiltonian. We show that, if we control the coupling between the source and the destination qubits and the ends of the wire, the evolution of the system can lead to an almost perfect transfer even in the case in which all nearest-neighbour couplings between the internal spins of the wire are equal.

  3. Transport in partially equilibrated inhomogeneous quantum wires.

    SciTech Connect

    Levchenko, A.; Micklitz, T.; Rech, J.; Matveev, K. A.; Materials Science Division; Freie Univ. Berlin; Centre de Physique Theorique

    2010-01-01

    We study transport properties of weakly interacting one-dimensional electron systems including on an equal footing thermal equilibration due to three-particle collisions and the effects of large-scale inhomogeneities. We show that equilibration in an inhomogeneous quantum wire is characterized by the competition of interaction processes which reduce the electrons total momentum and such which change the number of right- and left-moving electrons. We find that the combined effect of interactions and inhomogeneities can dramatically increase the resistance of the wire. In addition, we find that the interactions strongly affect the thermoelectric properties of inhomogeneous wires and calculate their thermal conductance, thermopower, and Peltier coefficient.

  4. Electrochemical Fabrication of Metallic Quantum Wires

    ERIC Educational Resources Information Center

    Tao, Nongjian

    2005-01-01

    The fabrication of metallic quantum wires using simple electrochemical techniques is described. The conductance of the system can be readily measured that allows one to constantly monitor the conductance during fabrication and use conductance quantization as a signature to guide the fabrication.

  5. Spectroscopic properties of colloidal indium phosphide quantum wires

    SciTech Connect

    Wang, Lin-Wang; Wang, Fudong; Yu, Heng; Li, Jingbo; Hang, Qingling; Zemlyanov, Dmitry; Gibbons, Patrick C.; Wang, Lin-Wang; Janes, David B.; Buhro, William E.

    2008-07-11

    Colloidal InP quantum wires are grown by the solution-liquid-solid (SLS) method, and passivated with the traditional quantum dots surfactants 1-hexadecylamine and tri-n-octylphosphine oxide. The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to other experimental results for InP quantum dots and wires, and to the predictions of theory. The photoluminescence behavior of the wires is also investigated. Efforts to enhance photoluminescence efficiencies through photochemical etching in the presence of HF result only in photochemical thinning or photo-oxidation, without a significant influence on quantum-wire photoluminescence. However, photo-oxidation produces residual dot and rod domains within the wires, which are luminescent. The results establish that the quantum-wire band gaps are weakly influenced by the nature of the surface passivation, and that colloidal quantum wires have intrinsically low photoluminescence efficiencies.

  6. In situ grown quantum-wire lasers

    NASA Astrophysics Data System (ADS)

    Coldren, L. A.; Gossard, A. C.; English, J. H.; Mui, D.; Corzine, S. W.

    1994-04-01

    This program concentrated on developing techniques to better understand and fabricate quantum-confined structures. The goal was to create the enabling technology for more efficient semiconductor lasers and integrated optoelectronic circuits. Over the contract period, significant advances occurred in the development of quantum-confined lasers, UHV in-situ processing technology, and the underlying theory for quantum-confined laser structures. The quantum-confined laser work included both quantum-wire laser and vertical-cavity laser development. This latter effort also required substantial improvements in the MBE growth technology. Much of this technology is now ready for transfer to industry. In fact, a number of joint projects with industry are underway, as a result of this program.

  7. Negative excess noise in gated quantum wires

    SciTech Connect

    Dolcini, F.; Trauzettel, B.; Safi, I.; Grabert, H.

    2009-04-23

    The electrical current noise of a quantum wire is expected to increase with increasing applied voltage. We show that this intuition can be wrong. Specifically, we consider a single channel quantum wire with impurities and with a capacitive coupling to a metallic gate, and find that its excess noise, defined as the change in the noise caused by the finite voltage, can be negative at zero temperature. This feature is present both for large (c>>c{sub q}) and small (c<quantum capacitance of the wire. In particular, for c>>c{sub q}, negativity of the excess noise can occur at finite frequency when the transmission coefficients are energy dependent, i.e. in the presence of Fabry-Perot resonances or band curvature. In the opposite regime c < or approx. c{sub q}, a non trivial voltage dependence of the noise arises even for energy independent transmission coefficients: at zero frequency the noise decreases with voltage as a power law when c

  8. Discrete versus continuous wires on quantum networks.

    PubMed

    Aharony, Amnon; Entin-Wohlman, Ora

    2009-03-26

    Mesoscopic systems and large molecules are often modeled by graphs of one-dimensional wires connected at vertices. In this paper, we discuss the solutions of the Schrödinger equation on such graphs, which have been named "quantum networks". Such solutions are needed for finding the energy spectrum of single electrons on such finite systems or for finding the transmission of electrons between leads which connect such systems to reservoirs. Specifically, we compare two common approaches. In the "continuum" approach, one solves the one-dimensional Schrödinger equation on each continuous wire and then uses the Neumann-Kirchoff-de Gennes matching conditions at the vertices. Alternatively, one replaces each wire by a finite number of "atoms" and then uses the tight binding model for the solution. Here, we show that these approaches cannot generally give the same results, except for special energies, unless the lattice constant of the tight binding model tends to zero. Even in the limit of the vanishing lattice constant, the two approaches coincide only if the tight binding parameters obey very special relations. The different consequences of the two approaches are then demonstrated via the example of a T-shaped scatterer. PMID:19673064

  9. Comparing conductance quantization in quantum wires and quantum Hall systems

    NASA Astrophysics Data System (ADS)

    Alekseev, Anton Yu.; Cheianov, Vadim V.; Fröhlich, Jürg

    1996-12-01

    We suggest a means to calculate the dc conductance of a one-dimensional electron system described by the Luttinger model. Our approach is based on the ideas of Landauer and Büttiker on transport in ballistic channels and on the methods of current algebra. We analyze in detail the way in which the system can be coupled to external reservoirs. This determines whether the conductance is renormalized or not. We provide a parallel treatment of a quantum wire and a fractional quantum Hall system on a cylinder with two widely separated edges. Although both systems are described by the same effective theory, the physical electrons are identified with different types of excitations, and hence the coupling to external reservoirs is different. As a consequence, the conductance in the wire is quantized in integer units of e2/h per spin orientation whereas the Hall conductance allows for fractional quantization.

  10. Quantum stability and magic lengths of metal atom wires

    NASA Astrophysics Data System (ADS)

    Cui, Ping; Choi, Jin-Ho; Lan, Haiping; Cho, Jun-Hyung; Niu, Qian; Yang, Jinlong; Zhang, Zhenyu

    2016-06-01

    Metal atom wires represent an important class of nanomaterials in the development of future electronic devices and other functional applications. Using first-principles calculations within density functional theory, we carry out a systematic study of the quantum stability of freestanding atom wires consisting of prototypical metal elements with s -, s p -, and s d -valence electrons. We explore how the quantum mechanically confined motion and local bonding of the valence electrons in these different wire systems can dictate their overall structural stability and find that the formation energy of essentially all the wires oscillates with respect to their length measured by the number n of atoms contained in the wires, establishing the existence of highly preferred (or magic) lengths. Furthermore, different wire classes exhibit distinctively different oscillatory characteristics and quantum stabilities. Alkali metal wires possessing an unpaired s valence electron per atom exhibit simple damped even-odd oscillations. In contrast, Al and Ga wires containing three s2p1 valence electrons per atom generally display much larger and undamped even-odd energy oscillations due to stronger local bonding of the p orbitals. Among the noble metals, the s -dominant Ag wires behave similarly to the linear alkali metal wires, while Au and Pt wires distinctly prefer to be structurally zigzagged due to strong relativistic effects. These findings are discussed in connection with existing experiments and should also be instrumental in future experimental realization of different metal atom wires in freestanding or supported environments with desirable functionalities.

  11. Nonequilibrium functional bosonization of quantum wire networks

    SciTech Connect

    Ngo Dinh, Stephane; Bagrets, Dmitry A.; Mirlin, Alexander D.

    2012-11-15

    We develop a general approach to nonequilibrium nanostructures formed by one-dimensional channels coupled by tunnel junctions and/or by impurity scattering. The formalism is based on nonequilibrium version of functional bosonization. A central role in this approach is played by the Keldysh action that has a form reminiscent of the theory of full counting statistics. To proceed with evaluation of physical observables, we assume the weak-tunneling regime and develop a real-time instanton method. A detailed exposition of the formalism is supplemented by two important applications: (i) tunneling into a biased Luttinger liquid with an impurity, and (ii) quantum Hall Fabry-Perot interferometry. - Highlights: Black-Right-Pointing-Pointer A nonequilibrium functional bosonization framework for quantum wire networks is developed Black-Right-Pointing-Pointer For the study of observables in the weak tunneling regime a real-time instanton method is elaborated. Black-Right-Pointing-Pointer We consider tunneling into a biased Luttinger liquid with an impurity. Black-Right-Pointing-Pointer We analyze electronic Fabry-Perot interferometers in the integer quantum Hall regime.

  12. Universal entanglement crossover of coupled quantum wires

    NASA Astrophysics Data System (ADS)

    Vasseur, Romain; Jacobsen, Jesper; Saleur, Hubert

    2014-03-01

    We consider the entanglement between two one-dimensional quantum wires (Luttinger Liquids) coupled by tunneling through a quantum impurity. The physics of the system involves a crossover between weak and strong coupling regimes characterized by an energy scale TB, and methods of conformal field theory therefore cannot be applied. The evolution of the entanglement in this crossover has led to many numerical studies, but has remained little understood, analytically or even qualitatively. This is, in part, due to the fact that the entanglement in this case is non-perturbative in the tunneling amplitude. We argue that the correct universal scaling form of the entanglement entropy S (for an arbitrary interval containing the impurity) is ∂S / ∂lnL = f(LTB) . In the special case where the coupling to the impurity can be refermionized, we show how the universal function f(LTB) can be obtained analytically using recent results on form factors of twist fields and a defect massless-scattering formalism. Our results are carefully checked against numerical simulations. This work was supported by the the French ANR (ANR Projet 2010 Blanc SIMI 4 : DIME), the US DOE (grant number DE-FG03-01ER45908), the Quantum Materials program of LBNL (RV) and the Institut Universitaire de France (JLJ).

  13. Electronic Conduction through Atomic Chains, Quantum Well and Quantum Wire

    NASA Astrophysics Data System (ADS)

    Sharma, A. C.

    2011-07-01

    Charge transport is dynamically and strongly linked with atomic structure, in nanostructures. We report our ab-initio calculations on electronic transport through atomic chains and the model calculations on electron-electron and electron-phonon scattering rates in presence of random impurity potential in a quantum well and in a quantum wire. We computed synthesis and ballistic transport through; (a) C and Si based atomic chains attached to metallic electrodes, (b) armchair (AC), zigzag (ZZ), mixed, rotated-AC and rotated-ZZ geometries of small molecules made of 2S, 6C & 4H atoms attaching to metallic electrodes, and (c) carbon atomic chain attached to graphene electrodes. Computed results show that synthesis of various atomic chains are practically possible and their transmission coefficients are nonzero for a wide energy range. The ab-initio calculations on electronic transport have been performed with the use of Landauer-type scattering formalism formulated in terms of Grben's functions in combination with ground-state DFT. The electron-electron and electron-phonon scattering rates have been calculated as function of excitation energy both at zero and finite temperatures for disordered 2D and 1D systems. Our model calculations suggest that electron scattering rates in a disordered system are mainly governed by effective dimensionality of a system, carrier concentration and dynamical screening effects.

  14. Interaction-induced backscattering in short quantum wires

    NASA Astrophysics Data System (ADS)

    Rieder, M.-T.; Micklitz, T.; Levchenko, A.; Matveev, K. A.

    2014-10-01

    We study interaction-induced backscattering in clean quantum wires with adiabatic contacts exposed to a voltage bias. Particle backscattering relaxes such systems to a fully equilibrated steady state only on length scales exponentially large in the ratio of bandwidth of excitations and temperature. Here we focus on shorter wires in which full equilibration is not accomplished. Signatures of relaxation then are due to backscattering of hole excitations close to the band bottom which perform a diffusive motion in momentum space while scattering from excitations at the Fermi level. This is reminiscent to the first passage problem of a Brownian particle and, regardless of the interaction strength, can be described by an inhomogeneous Fokker-Planck equation. From general solutions of the latter we calculate the hole backscattering rate for different wire lengths and discuss the resulting length dependence of interaction-induced correction to the conductance of a clean single channel quantum wire.

  15. IR photodetector based on rectangular quantum wire in magnetic field

    SciTech Connect

    Jha, Nandan

    2014-04-24

    In this paper we study rectangular quantum wire based IR detector with magnetic field applied along the wires. The energy spectrum of a particle in rectangular box shows level repulsions and crossings when external magnetic field is applied. Due to this complex level dynamics, we can tune the spacing between any two levels by varying the magnetic field. This method allows user to change the detector parameters according to his/her requirements. In this paper, we numerically calculate the energy sub-band levels of the square quantum wire in constant magnetic field along the wire and quantify the possible operating wavelength range that can be obtained by varying the magnetic field. We also calculate the photon absorption probability at different magnetic fields and give the efficiency for different wavelengths if the transition is assumed between two lowest levels.

  16. Time-Domain Simulation of Three Dimensional Quantum Wires.

    PubMed

    Sullivan, Dennis M; Mossman, Sean; Kuzyk, Mark G

    2016-01-01

    A method is presented to calculate the eigenenergies and eigenfunctions of quantum wires. This is a true three-dimensional method based on a direct implementation of the time-dependent Schrödinger equation. It makes no approximations to the Schrödinger equation other than the finite-difference approximation of the space and time derivatives. The accuracy of our method is tested by comparing it to analytical results in a cylindrical wire. PMID:27124603

  17. Time-Domain Simulation of Three Dimensional Quantum Wires

    PubMed Central

    Mossman, Sean; Kuzyk, Mark G.

    2016-01-01

    A method is presented to calculate the eigenenergies and eigenfunctions of quantum wires. This is a true three-dimensional method based on a direct implementation of the time-dependent Schrödinger equation. It makes no approximations to the Schrödinger equation other than the finite-difference approximation of the space and time derivatives. The accuracy of our method is tested by comparing it to analytical results in a cylindrical wire. PMID:27124603

  18. Multisublevel Magnetoquantum Conductance in Single and Coupled Double Quantum Wires

    SciTech Connect

    Lyo, Sungkwun Ken; Huang, Danhong

    2001-09-15

    We study the ballistic and diffusive magnetoquantum transport using a typical quantum point contact geometry for single and tunnel-coupled double wires that are wide (less than or similar to1 mum) in one perpendicular direction with densely populated sublevels and extremely confined in the other perpendicular (i.e., growth) direction. A general analytic solution to the Boltzmann equation is presented for multisublevel elastic scattering at low temperatures. The solution is employed to study interesting magnetic-field dependent behavior of the conductance such as a large enhancement and quantum oscillations of the conductance for various structures and field orientations. These phenomena originate from the following field-induced properties: magnetic confinement, displacement of the initial- and final-state wave functions for scattering, variation of the Fermi velocities, mass enhancement, depopulation of the sublevels and anticrossing (in double quantum wires). The magnetoconductance is strikingly different in long diffusive (or rough. dirty) wires from the quantized conductance in short ballistic (or clean) wires. Numerical results obtained for the rectangular confinement potentials in the growth direction are satisfactorily interpreted in terms of the analytic solutions based on harmonic confinement potentials. Some of the predicted features of the field-dependent diffusive and quantized conductances are consistent with recent data from GaAs/AlxGa1-xAs double quantum wires.

  19. Conductivity of quantum wires in uniform magnetic fields

    SciTech Connect

    Sinyavskii, E. P. Khamidullin, R. A.

    2006-11-15

    The features of the de conductivity of quantum wires in longitudinal and transverse magnetic fields are studied for degenerate and nondegenerate electron gas. The conductivity is calculated on the basis of the Kubo formalism with regard to the elastic scattering of charge carriers at long-wavelength lattice vibrations. The final theoretical results for the conductivity are compared to the experimental data. The suggested model of quantum wires allows, among other things, an interpretation of the nonmonotonic dependence of the transverse magnetoresistance on the magnetic field.

  20. The Quantum Socket: Wiring for Superconducting Qubits - Part 1

    NASA Astrophysics Data System (ADS)

    McConkey, T. G.; Bejanin, J. H.; Rinehart, J. R.; Bateman, J. D.; Earnest, C. T.; McRae, C. H.; Rohanizadegan, Y.; Shiri, D.; Mariantoni, M.; Penava, B.; Breul, P.; Royak, S.; Zapatka, M.; Fowler, A. G.

    Quantum systems with ten superconducting quantum bits (qubits) have been realized, making it possible to show basic quantum error correction (QEC) algorithms. However, a truly scalable architecture has not been developed yet. QEC requires a two-dimensional array of qubits, restricting any interconnection to external classical systems to the third axis. In this talk, we introduce an interconnect solution for solid-state qubits: The quantum socket. The quantum socket employs three-dimensional wires and makes it possible to connect classical electronics with quantum circuits more densely and accurately than methods based on wire bonding. The three-dimensional wires are based on spring-loaded pins engineered to insure compatibility with quantum computing applications. Extensive design work and machining was required, with focus on material quality to prevent magnetic impurities. Microwave simulations were undertaken to optimize the design, focusing on the interface between the micro-connector and an on-chip coplanar waveguide pad. Simulations revealed good performance from DC to 10 GHz and were later confirmed against experimental measurements.

  1. Lattice thermal conductance of quantum wires with disorder

    NASA Astrophysics Data System (ADS)

    Vyhmeister, Erik; Hershfield, Selman

    We model the lattice thermal conductance in long quantum wires connected to two large heat baths at different temperatures in the harmonic approximation. The thermal conductance is computed with the Landauer formula for phonons, where it is related to the sum over all transmission probabilities for phonons through the wire. The net transmission probability is computed using a recursive Green function technique, which allows one to study long wires efficiently. We consider several different kinds of disorder to reduce the lattice thermal conductivity: periodic rectangular holes of varying sizes and shapes, periodic triangular holes, and narrow bands, averaged over randomness to account for variance in manufacturing. Depending on the model, the thermal conductance was reduced by 80 percent or more from the perfectly ordered wire case. Funded by NSF grant DMR-1461019.

  2. Thermal Conductivity of Quantum Wires with Surface Roughness

    NASA Astrophysics Data System (ADS)

    Hershfield, Selman; Muttalib, Khandker

    Quantum wires have been shown to have greatly reduced thermal conductivity compared to bulk systems because of the increased role of surface scattering. The lattice thermal conductance and conductivity is calculated in the harmonic approximation for a long quantum wire placed between two heat baths using the Landauer formula for phonons and a recursive Green function technique to compute the transmission probabilities. The width of the wires is varied in the transverse direction so as to have a root mean square value σ and correlation length L. As observed experimentally, we find that the thermal conductance is decreased with increasing σ and increased as L increases. The full scaling of the thermal conductance as a function of σ, L, the width and the length of the sample is discussed. The simulations are also compared to approximate techniques such as modeling the surfaces as having diffusive scattering.

  3. Superradiance in a two-channel quantum wire

    SciTech Connect

    Tayebi, A.; Zelevinsky, V.

    2014-10-15

    A one-dimensional, two-channel quantum wire is studied in the effective non-Hermitian Hamiltonian framework. Analytical expressions are derived for the band structure of the isolated wire. Quantum states and transport properties of the wire coupled to two ideal leads at the edges are studied in detail. The width distribution of the quasistationary states varies as a function of the coupling strength to the environment. At weak coupling, all the eigenenergies uniformly acquire small widths. The picture changes entirely at strong coupling, a certain number of states (“super-radiant”) are greatly broadened, while the rest remain long-lived states, a pure quantum mechanical effect as a consequence of quantum interference. The transition between the two regimes greatly influences the transport properties of the system. The maximum transmission through the wire occurs at the super-radiance transition. We consider also a realistic situation with energy-dependent coupling to the continuum due to the existence of decay threshold where super-radiance still plays a significant role in transport properties of the system.

  4. Ballistic transport through coupled T-shaped quantum wires

    NASA Astrophysics Data System (ADS)

    Lin, Yuh-Kae; Lin, Kao-Chin; Chuu, Der-San

    2004-05-01

    The ballistic conductance of a coupled T-shaped semiconductor quantum wire (CTQW) is studied. Two types of CTQW are considered, one of which is a Π-shaped quantum wire ( ΠQW) which consists of two vertical arms on the same side of the horizontal arm and the other a Π-clone quantum wire ( ΠCQW) which consists of two vertical armes on the opposite sides of the horizontal arm. The mode matching method and Landauer-Buttiker theory are employed to study the energy dependence of the ballistic conductance. Most of transmission profiles of ΠQW and ΠCQW are found to be distinguishable for large separation d between the two vertical arms. The transmission probability manifests oscillatory behavior when d is increased. When a potential is applied to the connection region, it results in decoupling or coupling effects between the two T-shaped quantum wires according to whether it is positive or negative. When magnetic field is applied to CTQW, the transmission profiles are found to be affected prominently even if the electron passes through the field free region only.

  5. Quantum wire hybridized with a single-level impurity.

    PubMed

    Lerner, Igor V; Yudson, Vladimir I; Yurkevich, Igor V

    2008-06-27

    We have studied low-temperature properties of interacting electrons in a one-dimensional quantum wire (Luttinger liquid) side-hybridized with a single-level impurity. The hybridization induces a backscattering of electrons in the wire which strongly affects its low-energy properties. Using a one-loop renormalization group approach valid for a weak electron-electron interaction, we have calculated a transmission coefficient through the wire, T(epsilon), and a local density of states, nu(epsilon) at low energies epsilon. In particular, we have found that the antiresonance in T(epsilon) has a generalized Breit-Wigner shape with the effective width Gamma(epsilon) which diverges at the Fermi level. PMID:18643692

  6. Dissipation in a Quantum Wire: Fact and Fantasy

    NASA Astrophysics Data System (ADS)

    Das, Mukunda P.; Green, Frederick

    2008-10-01

    Where, and how, does energy dissipation of electrical energy take place in a ballistic wire? Fully two decades after the advent of the transmissive phenomenology of electrical conductance, this deceptively simple query remains unanswered. We revisit the quantum kinetic basis of dissipation and show its power to give a definitive answer to our query. Dissipation leaves a clear, quantitative trace in the non-equilibrium current noise of a quantum point contact; this signature has already been observed in the laboratory. We then highlight the current state of accepted understandings in the light of well-known yet seemingly contradictory measurements. The physics of mesoscopic transport rests not in coherent carrier transmission through a perfect and dissipationless metallic channel, but explicitly in their dissipative inelastic scattering at the wire's interfaces and adjacent macroscopic leads.

  7. A Model of Resonance Scattering on Curved Quantum Wires

    NASA Astrophysics Data System (ADS)

    Exner, Pavel

    A model of electron motion in a curved quantum wire of a finite length 2D attached to a pair of macroscopic electrodes is studied. Regarding the problem as a two-dimensional one, we model the electrodes as halfplanes and the quantum wire as a line segment joining them; it supports a potential which is a combination of a constant transversal-mode energy and an attractive curvature-induced term. We show that the bound states which may be present at an infinite quantum wire turn into resonances and that spectral concentration is valid as D .Translated AbstractEin Modell der Resonanzstreuung auf gekrümmten, dünnen DrähtenDas Modell einer Elektronenbewegung in einem gekrümmten, ultradünnen Draht der Länge 2D, der zwei makroskopische Elektroden verbindet, wird untersucht. Das Modell als zweidimensional betrachtend, nehmen wir die Elektroden als Halbebenen und den Draht als verbindendes Liniensegment. Das Potential ist eine Kombination aus konstanter Transversalmoden-energie und einem anziehenden, von der Krümmung hervorgerufenen Term. Wir zeigen, daß der gebundene Zustand, der im unendlich langen Draht auftreten kann, in Resonanzen übergeht, und die Spektraldichte für D gilt.

  8. Quasiclassical theory of disordered multi-channel Majorana quantum wires

    NASA Astrophysics Data System (ADS)

    Neven, Patrick; Bagrets, Dmitry; Altland, Alexander

    2013-05-01

    Multi-channel spin-orbit quantum wires, when subjected to a magnetic field and proximity coupled to an s-wave superconductor, may support Majorana states. We study what happens to these systems in the presence of disorder. Inspired by the widely established theoretical methods of mesoscopic superconductivity, we develop á la Eilenberger a quasiclassical approach to topological nanowires valid in the limit of strong spin-orbit coupling. We find that the ‘Majorana number’ {\\cal M} , distinguishing between the state with Majorana fermions (symmetry class B) and no Majorana fermions (class D), is given by the product of two Pfaffians of gapped quasiclassical Green's functions fixed by the right and left terminals connected to the wire. A numerical solution of the Eilenberger equations reveals that the class D disordered quantum wires are prone to the formation of the zero-energy anomaly (class D impurity spectral peak) in the local density of states that shares the key features of the Majorana peak. In this way, we confirm the robustness of our previous conclusions (Bagrets and Altland 2012 Phys. Rev. Lett. 109 227005) on a more restrictive system setup. Generally speaking, we find that the quasiclassical approach provides a highly efficient means to address disordered class D superconductors both in the presence and in the absence of topological structures.

  9. Localized end states in density modulated quantum wires and rings.

    PubMed

    Gangadharaiah, Suhas; Trifunovic, Luka; Loss, Daniel

    2012-03-30

    We study finite quantum wires and rings in the presence of a charge-density wave gap induced by a periodic modulation of the chemical potential. We show that the Tamm-Shockley bound states emerging at the ends of the wire are stable against weak disorder and interactions, for discrete open chains and for continuum systems. The low-energy physics can be mapped onto the Jackiw-Rebbi equations describing massive Dirac fermions and bound end states. We treat interactions via the continuum model and show that they increase the charge gap and further localize the end states. The electrons placed in the two localized states on the opposite ends of the wire can interact via exchange interactions and this setup can be used as a double quantum dot hosting spin qubits. The existence of these states could be experimentally detected through the presence of an unusual 4π Aharonov-Bohm periodicity in the spectrum and persistent current as a function of the external flux. PMID:22540720

  10. Individual single-wall carbon nanotubes as quantum wires

    NASA Astrophysics Data System (ADS)

    Tans, Sander J.; Devoret, Michel H.; Dai, Hongjie; Thess, Andreas; Smalley, Richard E.; Geerligs, L. J.; Dekker, Cees

    1997-04-01

    Carbon nanotubes have been regarded since their discovery1 as potential molecular quantum wires. In the case of multi-wall nanotubes, where many tubes are arranged in a coaxial fashion, the electrical properties of individual tubes have been shown to vary strongly from tube to tube2,3, and to be characterized by disorder and localization4. Single-wall nanotubes5,6 (SWNTs) have recently been obtained with high yields and structural uniformity7. Particular varieties of these highly symmetric structures have been predicted to be metallic, with electrical conduction occurring through only two electronic modes8-10. Because of the structural symmetry and stiffness of SWNTs, their molecular wavefunctions may extend over the entire tube. Here we report electrical transport measurements on individual single-wall nanotubes that confirm these theoretical predictions. We find that SWNTs indeed act as genuine quantum wires. Electrical conduction seems to occur through well separated, discrete electron states that are quantum-mechanically coherent over long distance, that is at least from contact to contact (140nm). Data in a magnetic field indicate shifting of these states due to the Zeeman effect.

  11. Polariton dispersion of a quantum wire superlattice system

    NASA Astrophysics Data System (ADS)

    Wilson, K. S. Joseph; Amalanathan, M.; Revathy, V.; Lenin, S. Maria

    2015-06-01

    Superlattices have drawn considerable attention in the recent years. In this work, the behaviour of polaritons in a quantum wire superlattice is analysed both at the brillouin zone edge and at centre of the brillouin zone using LiNbO3/ LiTaO3 as an example. The significance of the polariton modes in both the cases are analysed. New modes on the polaritonic gap, where the propagation of electromagnetic wave is forbidden, is obtained in the system as suggested by some recent literature. The effect on nonlinear interactions of phonon polaritons in LiNbO3/ LiTaO3 superlattices is also discussed.

  12. Polariton dispersion of a quantum wire superlattice system

    SciTech Connect

    Wilson, K. S. Joseph; Revathy, V.; Amalanathan, M.; Lenin, S. Maria

    2015-06-24

    Superlattices have drawn considerable attention in the recent years. In this work, the behaviour of polaritons in a quantum wire superlattice is analysed both at the brillouin zone edge and at centre of the brillouin zone using LiNbO3/ LiTaO3 as an example. The significance of the polariton modes in both the cases are analysed. New modes on the polaritonic gap, where the propagation of electromagnetic wave is forbidden, is obtained in the system as suggested by some recent literature. The effect on nonlinear interactions of phonon polaritons in LiNbO3/ LiTaO3 superlattices is also discussed.

  13. Constraints on conductances for Y-junctions of quantum wires

    NASA Astrophysics Data System (ADS)

    Aristov, D. N.

    2011-03-01

    We consider the Y-junction, connecting three quantum wires, in the scattering states formalism. In the absence of fermionic interaction we analyze the restrictions on the values of conductance matrix, imposed by the unitarity of scattering S matrix. Using the combination of numerical and analytical results, we describe the four-dimensional body of values of reduced conductance matrix. We show that this body touches the unit sphere at six points only, in accordance with Birkhoff-von Neumann theorem. It implies that the Abelian bosonization analysis for the vanishing interaction strength can be performed only in the vicinity of these six points.

  14. The Quantum Socket: Wiring for Superconducting Qubits - Part 3

    NASA Astrophysics Data System (ADS)

    Mariantoni, M.; Bejianin, J. H.; McConkey, T. G.; Rinehart, J. R.; Bateman, J. D.; Earnest, C. T.; McRae, C. H.; Rohanizadegan, Y.; Shiri, D.; Penava, B.; Breul, P.; Royak, S.; Zapatka, M.; Fowler, A. G.

    The implementation of a quantum computer requires quantum error correction codes, which allow to correct errors occurring on physical quantum bits (qubits). Ensemble of physical qubits will be grouped to form a logical qubit with a lower error rate. Reaching low error rates will necessitate a large number of physical qubits. Thus, a scalable qubit architecture must be developed. Superconducting qubits have been used to realize error correction. However, a truly scalable qubit architecture has yet to be demonstrated. A critical step towards scalability is the realization of a wiring method that allows to address qubits densely and accurately. A quantum socket that serves this purpose has been designed and tested at microwave frequencies. In this talk, we show results where the socket is used at millikelvin temperatures to measure an on-chip superconducting resonator. The control electronics is another fundamental element for scalability. We will present a proposal based on the quantum socket to interconnect a classical control hardware to a superconducting qubit hardware, where both are operated at millikelvin temperatures.

  15. Quantum Monte Carlo Studies of Interaction-Induced Localization in Quantum Dots and Wires

    NASA Astrophysics Data System (ADS)

    Devrim Güçlü, A.

    2009-03-01

    We investigate interaction-induced localization of electrons in both quantum dots and inhomogeneous quantum wires using variational and diffusion quantum Monte Carlo methods. Quantum dots and wires are highly tunable systems that enable the study of the physics of strongly correlated electrons. With decreasing electronic density, interactions become stronger and electrons are expected to localize at their classical positions, as in Wigner crystallization in an infinite 2D system. (1) Dots: We show that the addition energy shows a clear progression from features associated with shell structure to those caused by commensurability of a Wigner crystal. This cross-over is, then, a signature of localization; it occurs near rs˜20. For higher values of rs, the configuration symmetry of the quantum dot becomes fully consistent with the classical ground state. (2) Wires: We study an inhomogeneous quasi-one-dimensional system -- a wire with two regions, one at low density and the other high. We find that strong localization occurs in the low density quantum point contact region as the gate potential is increased. The nature of the transition from high to low density depends on the density gradient -- if it is steep, a barrier develops between the two regions, causing Coulomb blockade effects. We find no evidence for ferromagnetic spin polarization for the range of parameters studied. The picture emerging here is in good agreement with the experimental measurements of tunneling between two wires. Collaborators: C. J. Umrigar (Cornell), Hong Jiang (Fritz Haber Institut), Amit Ghosal (IISER Calcutta), and H. U. Baranger (Duke).

  16. Practicality of spin chain wiring in diamond quantum technologies.

    PubMed

    Ping, Yuting; Lovett, Brendon W; Benjamin, Simon C; Gauger, Erik M

    2013-03-01

    Coupled spin chains are promising candidates for wiring up qubits in solid-state quantum computing (QC). In particular, two nitrogen-vacancy centers in diamond can be connected by a chain of implanted nitrogen impurities; when driven by suitable global fields the chain can potentially enable quantum state transfer at room temperature. However, our detailed analysis of error effects suggests that foreseeable systems may fall far short of the fidelities required for QC. Fortunately the chain can function in the more modest role as a mediator of noisy entanglement, enabling QC provided that we use subsequent purification. For instance, a chain of 5 spins with interspin distances of 10 nm has finite entangling power as long as the T(2) time of the spins exceeds 0.55 ms. Moreover we show that repurposing the chain this way can remove the restriction to nearest-neighbor interactions, so eliminating the need for complicated dynamical decoupling sequences. PMID:23521240

  17. Electron transport in coupled double quantum wells and wires

    SciTech Connect

    Harff, N.E.; Simmons, J.A.; Lyo, S.K.

    1997-04-01

    Due to inter-quantum well tunneling, coupled double quantum wells (DQWs) contain an extra degree of electronic freedom in the growth direction, giving rise to new transport phenomena not found in single electron layers. This report describes work done on coupled DQWs subject to inplane magnetic fields B{sub {parallel}}, and is based on the lead author`s doctoral thesis, successfully defended at Oregon State University on March 4, 1997. First, the conductance of closely coupled DQWs in B{sub {parallel}} is studied. B{sub {parallel}}-induced distortions in the dispersion, the density of states, and the Fermi surface are described both theoretically and experimentally, with particular attention paid to the dispersion anticrossing and resulting partial energy gap. Measurements of giant distortions in the effective mass are found to agree with theoretical calculations. Second, the Landau level spectra of coupled DQWs in tilted magnetic fields is studied. The magnetoresistance oscillations show complex beating as Landau levels from the two Fermi surface components cross the Fermi level. A third set of oscillations resulting from magnetic breakdown is observed. A semiclassical calculation of the Landau level spectra is then performed, and shown to agree exceptionally well with the data. Finally, quantum wires and quantum point contacts formed in DQW structures are investigated. Anticrossings of the one-dimensional DQW dispersion curves are predicted to have interesting transport effects in these devices. Difficulties in sample fabrication have to date prevented experimental verification. However, recently developed techniques to overcome these difficulties are described.

  18. Quantum conductance of silicon-doped carbon wire nanojunctions

    PubMed Central

    2012-01-01

    Unknown quantum electronic conductance across nanojunctions made of silicon-doped carbon wires between carbon leads is investigated. This is done by an appropriate generalization of the phase field matching theory for the multi-scattering processes of electronic excitations at the nanojunction and the use of the tight-binding method. Our calculations of the electronic band structures for carbon, silicon, and diatomic silicon carbide are matched with the available corresponding density functional theory results to optimize the required tight-binding parameters. Silicon and carbon atoms are treated on the same footing by characterizing each with their corresponding orbitals. Several types of nanojunctions are analyzed to sample their behavior under different atomic configurations. We calculate for each nanojunction the individual contributions to the quantum conductance for the propagating σ, Π, and σ∗electron incidents from the carbon leads. The calculated results show a number of remarkable features, which include the influence of the ordered periodic configurations of silicon-carbon pairs and the suppression of quantum conductance due to minimum substitutional disorder and artificially organized symmetry on these nanojunctions. Our results also demonstrate that the phase field matching theory is an efficient tool to treat the quantum conductance of complex molecular nanojunctions. PMID:23130998

  19. Electronic Transport in Quantum Wires with Magnetic Quantum Dots in Series

    NASA Astrophysics Data System (ADS)

    Souma, S.; Lee, S. J.; Kim, N.; Kang, T. W.; Ihm, G.; Suzuki, A.

    2002-03-01

    Recent advances in nanofabrication allow microstructured magnetic potentials to be applied to ballistic electrons in high mobility two-dimensional electron gases (2DEG). Electronic transport in quantum wires with single magnetic quantum dot was studied by some of present authors [1], where the magnetic quantum dot is defined by two different magnetic fields B and B0 inside and outside the circular region, respectively. It was shown that the conductance properties depend strongly on whether B^* is parallel or antiparallel to B_0. In this work, we investigate the conductance of quantum wires with magnetic quantum dots in series. The each magnetic quantum dot is defined in the same way as the single dot case. Conductance is calculated numerically by applying the recursive Green's function method based on the lattice Hamiltonian. Our numerical results show the conductance modulation due to the presence of new types of quasi-bound states formed around multiple magnetic quantum dots. [1]H.-S. Sim, G. Ihm, N. Kim, and K. J. Chang, Phys. Rev. Lett 87, 146601 (2001)

  20. Nonlinear Conductance of Long Quantum Wires at a Conductance Plateau Transition: Where Does the Voltage Drop?

    NASA Astrophysics Data System (ADS)

    Micklitz, T.; Levchenko, A.; Rosch, A.

    2012-07-01

    We calculate the linear and nonlinear conductance of spinless fermions in clean, long quantum wires, where short-ranged interactions lead locally to equilibration. Close to the quantum phase transition, where the conductance jumps from zero to one conductance quantum, the conductance obtains a universal form governed by the ratios of temperature, bias voltage, and gate voltage. Asymptotic analytic results are compared to solutions of a Boltzmann equation which includes the effects of three-particle scattering. Surprisingly, we find that for long wires the voltage predominantly drops close to one end of the quantum wire due to a thermoelectric effect.

  1. Thermal conductance associated with six types of vibration modes in quantum wire modulated with quantum dot

    NASA Astrophysics Data System (ADS)

    Peng, Xiao-Fang; Wang, Xin-Jun; Chen, Li-Qun; Li, Jian-Bo; Zhou, Wu-Xing; Zhang, Gui; Chen, Ke-Qiu

    2014-06-01

    We study the ballistic phonon transport and thermal conductance of six low-lying vibration modes in quantum wire modulated with quantum dot at low temperatures. A comparative analysis is made among the six vibrational modes. The results show that the transmission rates of the six vibrational modes relative to reduced frequency display periodic or quasi-periodic oscillatory behavior. Among the four acoustic modes, the thermal conductance contributed by the torsional mode is the smallest, and the thermal conductances of other acoustic modes have adjacent values. It is also found that the thermal conductance of the optical mode increases from zero monotonously. Moreover, the total thermal conductance in concavity-shaped quantum structure is lower than that in convexity-shaped quantum structure. These thermal conductance values can be adjusted by changing the structural parameters of the quantum dot.

  2. Comparison studies of infrared photodetectors with a quantum-dot and a quantum-wire base

    NASA Astrophysics Data System (ADS)

    El Tokhy, M. S.; Mahmoud, I. I.; Konber, H. A.

    2011-12-01

    This paper mainly presents a theoretical analysis for the characteristics of quantum dot infrared photodetectors (QDIPs) and quantum wire infrared photodetectors (QRIPs). The paper introduces a unique mathematical model of solving Poisson's equations with the usage of Lambert W functions for infrared detectors' structures based on quantum effects. Even though QRIPs and QDIPs have been the subject of extensive researches and development during the past decade, it is still essential to implement theoretical models allowing to estimate the ultimate performance of those detectors such as photocurrent and its figure-of-merit detectivity vs. various parameter conditions such as applied voltage, number of quantum wire layers, quantum dot layers, lateral characteristic size, doping density, operation temperature, and structural parameters of the quantum dots (QDs), and quantum wires (QRs). A comparison is made between the computed results of the implemented models and fine agreements are observed. It is concluded from the obtained results that the total detectivity of QDIPs can be significantly lower than that in the QRIPs and main features of the QRIPs such as large gap between the induced photocurrent and dark current of QRIP which allows for overcoming the problems in the QDIPs. This confirms what is evaluated before in the literature. It is evident that by increasing the QD/QR absorption volume in QDIPs/QRIPs as well as by separating the dark current and photocurrents, the specific detectivity can be improved and consequently the devices can operate at higher temperatures. It is an interesting result and it may be benefit to the development of QDIP and QRIP for infrared sensing applications.

  3. Negative tunneling magneto-resistance in quantum wires with strong spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Han, Seungju; Serra, Llorenç; Choi, Mahn-Soo

    2015-06-01

    We consider a two-dimensional magnetic tunnel junction of the FM/I/QW(FM+SO)/I/N structure, where FM, I and QW(FM+SO) stand for a ferromagnet, an insulator and a quantum wire with both magnetic ordering and Rashba spin-orbit (SOC), respectively. The tunneling magneto-resistance (TMR) exhibits strong anisotropy and switches sign as the polarization direction varies relative to the quantum-wire axis, due to interplay among the one-dimensionality, the magnetic ordering, and the strong SOC of the quantum wire.

  4. Study of energy eigenvalues and density of states of carriers in a triangular quantum wire

    NASA Astrophysics Data System (ADS)

    Deyasi, Arpan; Bhattacharyya, S.; Das, N. R.

    2012-10-01

    Energy eigenvalues and density of states of carriers in a finite barrier triangular quantum wire embedded inside a rectangular quantum wire are numerically investigated using finite difference technique (FD-Q). Time-independent Schrödinger's equation is solved with appropriate boundary conditions for computation of lowest three eigenstates. The wire is made of lower bandgap GaAs material surrounded by wider bandgap AlxGa1-xAs, and the analysis is carried out by taking into consideration of the conduction band discontinuity and effective mass mismatch at the boundaries. The eigenvalues and the density of states are plotted as function of wire dimension and mole fraction (x). The results are also compared with those obtained using rectangular quantum wire.

  5. Externally controlled local magnetic field in a conducting mesoscopic ring coupled to a quantum wire

    SciTech Connect

    Maiti, Santanu K.

    2015-01-14

    In the present work, the possibility of regulating local magnetic field in a quantum ring is investigated theoretically. The ring is coupled to a quantum wire and subjected to an in-plane electric field. Under a finite bias voltage across the wire a net circulating current is established in the ring which produces a strong magnetic field at its centre. This magnetic field can be tuned externally in a wide range by regulating the in-plane electric field, and thus, our present system can be utilized to control magnetic field at a specific region. The feasibility of this quantum system in designing spin-based quantum devices is also analyzed.

  6. Quantum size effects in competing charge and spin orderings of dangling bond wires on Si(001)

    SciTech Connect

    Lee, Ji Young; Cho, Jun-Hyung; Zhang, Zhenyu

    2009-01-01

    Using spin-polarized density-functional theory calculations, we investigate the competition between charge and spin orderings in dangling-bond DB wires of increasing lengths fabricated on an H-terminated Si 001 surface. For wires containing less than ten DBs as studied in recent experiments, we find antiferromagnetic AF ordering to be energetically much more favorable than charge ordering. The energy preference of AF ordering shrinks in an oscillatory way as the wire length increases and preserves its sign even for DB wires of infinite length. The oscillatory behavior can be attributed to quantum size effects as the DB electrons fill discrete quantum levels. The predicted AF ordering is in startling contrast with the prevailing picture of charge ordering due to Jahn-Teller distortion or Peierls instability for wires of finite or infinite lengths, respectively.

  7. Correlating Electronic Transport to Atomic Structures in Self-Assembled Quantum Wires

    SciTech Connect

    Li, An-Ping; Qin, Shengyong; Kim, Tae Hwan; Ouyang, Wenjie; Zhang, Yanning; Weitering, Harm H; Shih, Chih-Kang; Baddorf, Arthur P; Wu, Ruiqian

    2012-01-01

    Quantum wires, as a smallest electronic conductor, are expected to be a fundamental component in all quantum architectures. The electronic conductance in quantum wires, however, is often dictated by structural instabilities and electron localization at the atomic scale. Here we report on the evolutions of electronic transport as a function of temperature and interwire coupling as the quantum wires of GdSi{sub 2} are self-assembled on Si(100) wire-by-wire. The correlation between structure, electronic properties, and electronic transport are examined by combining nanotransport measurements, scanning tunneling microscopy, and density functional theory calculations. A metal-insulator transition is revealed in isolated nanowires, while a robust metallic state is obtained in wire bundles at low temperature. The atomic defects lead to electron localizations in isolated nanowire, and interwire coupling stabilizes the structure and promotes the metallic states in wire bundles. This illustrates how the conductance nature of a one-dimensional system can be dramatically modified by the environmental change on the atomic scale.

  8. The quantum pinch effect in semiconducting quantum wires: A bird’s-eye view

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2016-01-01

    Those who measure success with culmination do not seem to be aware that life is a journey not a destination. This spirit is best reflected in the unceasing failures in efforts for solving the problem of controlled thermonuclear fusion for even the simplest pinches for over decades; and the nature keeps us challenging with examples. However, these efforts have permitted researchers the obtention of a dense plasma with a lifetime that, albeit short, is sufficient to study the physics of the pinch effect, to create methods of plasma diagnostics, and to develop a modern theory of plasma processes. Most importantly, they have impregnated the solid state plasmas, particularly the electron-hole plasmas in semiconductors, which do not suffer from the issues related with the confinement and which have demonstrated their potential not only for the fundamental physics but also for the device physics. Here, we report on a two-component, cylindrical, quasi-one-dimensional quantum plasma subjected to a radial confining harmonic potential and an applied magnetic field in the symmetric gauge. It is demonstrated that such a system, as can be realized in semiconducting quantum wires, offers an excellent medium for observing the quantum pinch effect at low temperatures. An exact analytical solution of the problem allows us to make significant observations: Surprisingly, in contrast to the classical pinch effect, the particle density as well as the current density display a determinable maximum before attaining a minimum at the surface of the quantum wire. The effect will persist as long as the equilibrium pair density is sustained. Therefore, the technological promise that emerges is the route to the precise electronic devices that will control the particle beams at the nanoscale.

  9. Magnetoresistance of One-Dimensional Subbands in Tunnel-Coupled Double Quantum Wires

    SciTech Connect

    Moon, J.S.; Blount, M.A.; Simmons, J.A.; Wendt, J.R.; Lyo, S.K.; Reno, J.L.

    1999-08-04

    The authors study the low-temperature in-plane magnetoresistance of tunnel-coupled quasi-one-dimensional quantum wires. The wires are defined by two pairs of mutually aligned split gates on opposite sides of a {le} 1 micron thick AlGaAs/GaAs double quantum well heterostructure, allowing independent control of the width of each quantum well. In the ballistic regime, when both wires are defined and the field is perpendicular to the current, a large resistance peak at {approximately}6 Tesla is observed with a strong gate voltage dependence. The data is consistent with a counting model whereby the number of subbands crossing the Fermi level changes with field due to the formation of an anticrossing in each pair of 1D subbands.

  10. Indium segregation during III–V quantum wire and quantum dot formation on patterned substrates

    SciTech Connect

    Moroni, Stefano T.; Dimastrodonato, Valeria; Chung, Tung-Hsun; Juska, Gediminas; Gocalinska, Agnieszka; Pelucchi, Emanuele; Vvedensky, Dimitri D.

    2015-04-28

    We report a model for metalorganic vapor-phase epitaxy on non-planar substrates, specifically V-grooves and pyramidal recesses, which we apply to the growth of InGaAs nanostructures. This model—based on a set of coupled reaction-diffusion equations, one for each facet in the system—accounts for the facet-dependence of all kinetic processes (e.g., precursor decomposition, adatom diffusion, and adatom lifetimes) and has been previously applied to account for the temperature-, concentration-, and temporal-dependence of AlGaAs nanostructures on GaAs (111)B surfaces with V-grooves and pyramidal recesses. In the present study, the growth of In{sub 0.12}Ga{sub 0.88}As quantum wires at the bottom of V-grooves is used to determine a set of optimized kinetic parameters. Based on these parameters, we have modeled the growth of In{sub 0.25}Ga{sub 0.75}As nanostructures formed in pyramidal site-controlled quantum-dot systems, successfully producing a qualitative explanation for the temperature-dependence of their optical properties, which have been reported in previous studies. Finally, we present scanning electron and cross-sectional atomic force microscopy images which show previously unreported facetting at the bottom of the pyramidal recesses that allow quantum dot formation.

  11. Center-of-mass and internal motion of excitons in quantum wires

    NASA Astrophysics Data System (ADS)

    Glutsch, S.; Bechstedt, F.

    The properties of excitons, which are optically excited in single or coupled quantum wires, are studied within the effective-mass approximation. The two-particle wave functions and energies obey a Schrödinger equation with screened Coulomb interaction of electron and hole and their corresponding wire confinement potentials. This equation is approximately separated into an equation for the center-of-mass motion and another one more or less for the internal motion of the electron hole pairs. This allows a representation of absorption and luminescence spectra near a quantum-well exciton transition by a generalized Elliott formula.

  12. Silicon quantum wires on Ag(1 1 0): Fermi surface and quantum well states

    NASA Astrophysics Data System (ADS)

    Valbuena, M. A.; Avila, J.; Dávila, M. E.; Leandri, C.; Aufray, B.; Le Lay, G.; Asensio, M. C.

    2007-10-01

    One-dimensional Si quantum wires have been grown on silver single crystals upon deposition of ˜0.25 monolayer of Si on Ag(1 1 0) surfaces. Scanning tunneling microscopy (STM) clearly shows parallel 1D Si chains along the [-1 1 0] Ag crystallographic direction. Low Energy Electron Diffraction (LEED) confirms the massively parallel assembly of these selforganized Nanowires (NWs). We have characterized these nano-objects by measuring the dispersion of the NWs valence band at room temperature using Angle-Resolved PhotoEmission Spectroscopy (ARPES). Also, the Fermi Surface (FS) of the Ag(1 1 0) substrate has been mapped before and after the silicon deposition, trying to put in evidence the metallic or semiconductor character of the NWs silicon's states close to the Fermi level. Our results show the existence of well-defined quantum states associated to the silicon super-structure. Both LEED and ARUPS results confirm that the NWs have typical 1D features, however their metallic or semiconductor character could not be confirmed.

  13. Dielectric confinement influenced screened Coulomb potential for a semiconductor quantum wire

    NASA Astrophysics Data System (ADS)

    Aharonyan, K. H.; Margaryan, N. B.

    2016-01-01

    A formalism of the Thomas-Fermi method has been applied for studying the screening effect due to quasi-one-dimensional electron gas in a semiconductor cylindrical quantum wire embedded in the barrier environment. With taking into account of strongly low dielectric properties of the barrier material, an applicability of the quantum wire effective interaction potential of the confined charge carriers has been revealed. Both screened quasi- one-dimensional interaction potential and effective screening length analytical expressions are derived in the first time. It is shown that in the long wavelength moderate limit dielectric confinement effect enhances strength of the screening potential depending on the both radius of the wire and effective screening length, whereas in the long wavelength strong limit the screening potential solely is determined by barrier environment dielectric properties.

  14. Thermodynamical properties of triangular quantum wires: entropy, specific heat, and internal energy

    NASA Astrophysics Data System (ADS)

    Khordad, R.

    2016-07-01

    In the present work, thermodynamical properties of a GaAs quantum wire with equilateral triangle cross section are studied. First, the energy levels of the system are obtained by solving the Schrödinger equation. Second, the Tsallis formalism is applied to obtain entropy, internal energy, and specific heat of the system. We have found that the specific heat and entropy have certain physically meaningful values, which mean thermodynamic properties cannot take any continuous value, unlike classical thermodynamics in which they are considered as continuous quantities. Maximum of entropy increases with increasing the wire size. The specific heat is zero at special temperatures. Specific heat decreases with increasing temperature. There are several peaks in specific heat, and these are dependent on quantum wire size.

  15. Hole Transport and Spin Effects in Cleaved-Edge-Overgrowth Quantum Wires

    NASA Astrophysics Data System (ADS)

    Sulpizio, Joseph; Quay, Charis; de Picciotto, Rafi; West, K. W.; Pfeiffer, L. N.; Goldhaber-Gordon, David

    2009-03-01

    Transport measurements on ballistic GaAs electron wires have revealed a rich set of phenomena associated with one-dimensional (1D) quantum systems. Studies of transport in hole systems are a natural extension of these experiments due to the enhanced effective mass, g-factor, and spin-orbit coupling of holes over their electron counterparts. However, only recently has the creation of ballistic hole wire devices been possible due to breakthroughs in molecular beam epitaxy using the cleaved-edge-overgrowth (CEO) technique. We present measurements of hole transport in CEO GaAs quantum wires in magnetic field in a dilution refrigerator. Based on a simple model, we extract the g-factor for different field orientations, and also discuss evidence for observing spin-orbit coupling in a 1D system.

  16. Magnetoresistance of One-Dimensional Subbands in Tunnel-Coupled Double Quantum Wires

    SciTech Connect

    Blount, M.A.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1999-04-27

    We study the low-temperature in-plane magnetoresistance of tunnel-coupled quasi-one-dimensional quantum wires. The wires are defined by two pairs of mutually aligned split gates on opposite sides of a < 1 micron thick AlGaAs/GaAs double quantum well heterostructure, allowing independent control of their widths. In the ballistic regime, when both wires are defined and the field is perpendicular to the current, a large resistance peak at ~6 Tesla is observed with a strong gate voltage dependence. The data is consistent with a counting model whereby the number of subbands crossing the Fermi level changes with field due to the formation of an anticrossing in each pair of 1D subbands.

  17. Coulomb interaction effects on the Majorana states in quantum wires.

    PubMed

    Manolescu, A; Marinescu, D C; Stanescu, T D

    2014-04-30

    The stability of the Majorana modes in the presence of a repulsive interaction is studied in the standard semiconductor wire-metallic superconductor configuration. The effects of short-range Coulomb interaction, which is incorporated using a purely repulsive δ-function to model the strong screening effect due to the presence of the superconductor, are determined within a Hartree-Fock approximation of the effective Bogoliubov-De Gennes Hamiltonian that describes the low-energy physics of the wire. Through a numerical diagonalization procedure we obtain interaction corrections to the single particle eigenstates and calculate the extended topological phase diagram in terms of the chemical potential and the Zeeman energy. We find that, for a fixed Zeeman energy, the interaction shifts the phase boundaries to a higher chemical potential, whereas for a fixed chemical potential this shift can occur either at lower or higher Zeeman energies. These effects can be interpreted as a renormalization of the g-factor due to the interaction. The minimum Zeeman energy needed to realize Majorana fermions decreases with the increasing strength of the Coulomb repulsion. Furthermore, we find that in wires with multi-band occupancy this effect can be enhanced by increasing the chemical potential, i.e. by occupying higher energy bands. PMID:24722427

  18. Molecular Spintronics: Wiring Spin Coherence between Semiconductor Quantum Dots

    NASA Astrophysics Data System (ADS)

    Ouyang, Min

    2004-03-01

    Semiconductor quantum dots (QDs) are attractive candidates for scalable solid state implementations of quantum information processing based on electron spin states, where a crucial requirement for practical devices is to have efficient and tunable spin coupling between them. We focus on recent femtosecond time-resolved Faraday rotation studies of self-assembled multilayer spintronic devices based on colloidal quantum dots bridged by conjugated molecules (M. Ouyang et al., Science 301, 1074 (2003)). The data reveal the instantaneous transfer of spin coherence through conjugated molecular bridges spanning quantum dots of different size over a broad range of temperature. The room temperature spin transfer efficiency exceeds 20%, which approximately doubles the value measured at T=4.5K. A molecular π-orbital mediated spin coherence transfer mechanism is proposed to provide a qualitative insight into the experimental observations, suggesting a correlation between the stereochemistry of molecules and the transfer process. The results show that conjugated molecules can be used not only as physical links for the assembly of functional networks, but also as efficient channels for shuttling quantum information. This class of structures may be useful as two-spin quantum devices operating at ambient temperatures and may offer promising opportunities for future versatile molecule-based spintronic technologies.

  19. Preferential sites for InAsP/InP quantum wire nucleation using molecular dynamics

    NASA Astrophysics Data System (ADS)

    Nuñez-Moraleda, Bernardo; Pizarro, Joaquin; Guerrero, Elisa; Guerrero-Lebrero, Maria P.; Yáñez, Andres; Molina, Sergio Ignacio; Galindo, Pedro Luis

    2014-11-01

    In this paper, stress fields at the surface of the capping layer of self-assembled InAsP quantum wires grown on an InP (001) substrate have been determined from atomistic models using molecular dynamics and Stillinger-Weber potentials. To carry out these calculations, the quantum wire compositional distribution was extracted from previous works, where the As and P distributions were determined by electron energy loss spectroscopy and high-resolution aberration-corrected Z-contrast imaging. Preferential sites for the nucleation of wires on the surface of the capping layer were studied and compared with (i) previous simulations using finite element analysis to solve anisotropic elastic theory equations and (ii) experimentally measured locations of stacked wires. Preferential nucleation sites of stacked wires were determined by the maximum stress location at the MD model surface in good agreement with experimental results and those derived from finite element analysis. This indicates that MD simulations based on empirical potentials provide a suitable and flexible tool to study strain dependent atom processes.

  20. The geometry effect on energy transfer rate in a coupled-quantum-wires structure

    NASA Astrophysics Data System (ADS)

    Rafee, Vahdat

    2016-03-01

    The geometry effect on energy transfer rate in a coupled cylindrical quantum wires system is investigated. The corrected random phase approximation by the zero-temperature static Hubbard correction is employed to calculate dielectric function of the system. The geometry effect on energy transfer rate is studied for statically and dynamically screened electron-electron interaction. Both the linear and nonlinear regimes correspond respectively to weak and strong external field are considered. The calculations show that increasing wire radius increases energy transfer rate in both the static and dynamic screening approximations for electron-electron interactions. Moreover, the same trend is predicted by the calculations for both the linear and nonlinear regimes.

  1. Excitonic linewidth of organic quantum wires generated in reduced dimensionality matrices.

    PubMed

    Barisien, Thierry; Legrand, Laurent; Mu, Zhao; Hameau, Sophie

    2016-05-14

    Luminescent organic quantum wires are generated in diacetylene crystalline ultra-thin films grown on orientation-inducing surfaces obtained by poly-tetrafluoroethylene (teflon) deposition. The films are characterized by atomic force microscopy showing that quasi-two-dimensional surroundings are achieved. In this particular environment, pure dephasing processes still determine the wires' homogeneous emission widths, measured using micro-photoluminescence. Coherence times that are slightly shorter in the films also exhibit a distinctive temperature dependence. A model inspired by semiconductor physics for exciton-phonon coupling accounts for the observed behaviour and evidences the role of matrix dimensionality on the coherence properties. PMID:27108759

  2. InAs/InP single quantum wire formation and emission at 1.5 {mu}m

    SciTech Connect

    Alen, B.; Fuster, D.; Gonzalez, Y.; Gonzalez, L.; Martinez-Pastor, J.

    2006-12-04

    Isolated InAs/InP self-assembled quantum wires have been grown using in situ accumulated stress measurements to adjust the optimal InAs thickness. Atomic force microscopy imaging shows highly asymmetric nanostructures with average length exceeding more than ten times their width. High resolution optical investigation of as-grown samples reveals strong photoluminescence from individual quantum wires at 1.5 {mu}m. Additional sharp features are related to monolayer fluctuations of the two-dimensional InAs layer present during the early stages of the quantum wire self-assembling process.

  3. Electron interactions and lasing in high quality GaAs single quantum wires

    NASA Astrophysics Data System (ADS)

    Akiyama, Hidefumi

    2002-03-01

    Since the first observation of ground-state lasing in quantum wire lasers(W. Wegscheider, L. N Pfeiffer, M. M Dignam, A. Pinczuk, K. W West, S. L McCall, and R. Hull, Phys. Rev. Lett. 71), 4071 (1993)., questions about existence of band-gap renormalization and contribution of excitons to gain in lasing have been hotly argued but remain unsolved for about a decade. Here, we study these problems in highly-uniform T-shaped quantum wires (T-wires) of 14nm x 6nm cross-sectional size and lasers containing these T-wires, fabricated by the cleaved-edge overgrowth method with molecular-beam epitaxy and a recently developed annealing technique(M. Yoshita, H. Akiyama, L. N. Pfeiffer, and K. W. West, Jpn. J. Appl. Phys. 40), L252 (2001).. We studied PL of modulation-doped single T-wire structures with tunable 1-D electron density by electrical gating to study many-body electron interaction effects. It shows PL of 1-D neutral excitons and charged excitons at low densities, which evolves as the density increases to band-to-band optical recombination of single holes and an electron plasma with significant band-gap renormalization. In undoped twenty-T-wire samples, we found clear signatures of 1-D free excitons and 1-D continuum states in PLE spectra, and biexcitons in strongly pumped PL. We then studied twenty-T-wire lasers via optical pumping. Lasing by T-wires was observed up to about 100 K. Lasing energy was not at the free exciton energy, but at the low-energy tail of biexcitons. Therefore, origin of gain for lasing is attributed not to free excitons, but most probably to biexcitons. We finally realized a single-T-wire laser. In a laser bar of 500μm optical cavity with mirrors coated by gold, lasing was observed for 5-60 K via optical pumping. The threshold power was as low as 5 mW at 5 K, which is equivalent to 3 mA of current injection in generating electron-hole pairs in the device.

  4. Nuclear Quantum Effects in H(+) and OH(-) Diffusion along Confined Water Wires.

    PubMed

    Rossi, Mariana; Ceriotti, Michele; Manolopoulos, David E

    2016-08-01

    The diffusion of protons and hydroxide ions along water wires provides an efficient mechanism for charge transport that is exploited by biological membrane channels and shows promise for technological applications such as fuel cells. However, what is lacking for a better control and design of these systems is a thorough theoretical understanding of the diffusion process at the atomic scale. Here we focus on two aspects of this process that are often disregarded because of their high computational cost: the use of first-principles potential energy surfaces and the treatment of the nuclei as quantum particles. We consider proton and hydroxide ions in finite water wires using density functional theory augmented with an apolar cylindrical confining potential. We employ machine learning techniques to identify the charged species, thus obtaining an agnostic definition that takes explicitly into account the delocalization of the charge in the Grotthus-like mechanism. We include nuclear quantum effects (NQEs) through the thermostated ring polymer molecular dynamics method and model finite system size effects by considering Langevin dynamics on the potential of mean force of the charged species, allowing us to extract the same "universal" diffusion coefficient from simulations with different wire sizes. In the classical case, diffusion coefficients depend significantly on the potential energy surface, in particular on how dispersion forces modulate water-water distances. NQEs, however, make the diffusion less sensitive to the underlying potential and geometry of the wire. PMID:27440483

  5. Fermionic approach to junctions of multiple quantum wires attached to Tomonaga-Luttinger liquid leads

    NASA Astrophysics Data System (ADS)

    Shi, Zheng; Affleck, Ian

    2016-07-01

    Junctions of multiple one-dimensional quantum wires of interacting electrons have received considerable theoretical attention as a basic constituent of quantum circuits. While results have been obtained on these models using bosonization and density-matrix renormalization-group (DMRG) methods, another powerful technique is based on direct perturbation theory in the bulk interactions combined with the renormalization group. This technique has so far only been applied to the case in which finite-length interacting wires are attached to noninteracting Fermi liquid leads. We extend this method to cover the case of infinite-length interacting leads, obtaining results on two- and three-lead junctions in good agreement with previous bosonization and DMRG results.

  6. Spin-polarized current in Zeeman-split d-wave superconductor/quantum wire junctions

    NASA Astrophysics Data System (ADS)

    Emamipour, Hamidreza

    2016-06-01

    We study a thin-film quantum wire/unconventional superconductor junction in the presence of an intrinsic exchange field for a d-wave symmetry of the superconducting order parameter. A strongly spin-polarized current is generated due to an interplay between Zeeman splitting of bands and the nodal structure of the superconducting order parameter. We show that strongly spin-polarized current is achievable for both metallic and tunnel junctions. This is because of the presence of a quantum wire (one-dimensional metal) in our junction. While in two-dimensional junctions with both conventional [F. Giazotto, F. Taddei, Phys. Rev. B 77 (2008) 132501] and unconventional [J. Linder, T. Yokoyama, Y. Tanaka, A. Sudbo, Phys. Rev. B 78 (2008) 014516] pairing states, highly spin polarized current takes place just for a tunnel junction. Also, the obtained spin-polarized current is tunable in sign and magnitude in terms of exchange field and applied bias voltage.

  7. Hydrogenic donor impurity in parallel-triangular quantum wires: Hydrostatic pressure and applied electric field effects

    NASA Astrophysics Data System (ADS)

    Restrepo, R. L.; Giraldo, E.; Miranda, G. L.; Ospina, W.; Duque, C. A.

    2009-12-01

    The combined effects of the hydrostatic pressure and in-growth direction applied electric field on the binding energy of hydrogenic shallow-donor impurity states in parallel-coupled-GaAs- Ga1-xAlxAs-quantum-well wires are calculated using a variational procedure within the effective-mass and parabolic-band approximations. Results are obtained for several dimensions of the structure, shallow-donor impurity positions, hydrostatic pressure, and applied electric field. Our results suggest that external inputs such us hydrostatic pressure and in-growth direction electric field are two useful tools in order to modify the binding energy of a donor impurity in parallel-coupled-quantum-well wires.

  8. Suppression of Impurity Back Scattering in Double Quantum Wires: Theory Beyond the Born Approximation

    SciTech Connect

    Huang, Danhong; Lyo, S.K.

    1999-08-09

    The effect of higher-order corrections to the Born approximation is studied for the previously obtained giant conductance enhancement in tunnel-coupled double quantum wires in a parallel magnetic field. The relative correction is found to be significant and depends on various effects such as the magnetic field, electron and impurity densities, impurity positions, symmetric and asymmetric doping profiles, and center barrier thickness.

  9. Landauer-Type Transport Theory for Interacting Quantum Wires: Application to Carbon Nanotube Y Junctions

    NASA Astrophysics Data System (ADS)

    Chen, S.; Trauzettel, B.; Egger, R.

    2002-11-01

    We propose a Landauerlike theory for nonlinear transport in networks of one-dimensional interacting quantum wires (Luttinger liquids). A concrete example of current experimental focus is given by carbon nanotube Y junctions. Our theory has three basic ingredients that allow one to explicitly solve this transport problem: (i) radiative boundary conditions to describe the coupling to external leads, (ii) the Kirchhoff node rule describing charge conservation, and (iii) density matching conditions at every node.

  10. Landauer-type transport theory for interacting quantum wires: application to carbon nanotube y junctions.

    PubMed

    Chen, S; Trauzettel, B; Egger, R

    2002-11-25

    We propose a Landauerlike theory for nonlinear transport in networks of one-dimensional interacting quantum wires (Luttinger liquids). A concrete example of current experimental focus is given by carbon nanotube Y junctions. Our theory has three basic ingredients that allow one to explicitly solve this transport problem: (i) radiative boundary conditions to describe the coupling to external leads, (ii) the Kirchhoff node rule describing charge conservation, and (iii) density matching conditions at every node. PMID:12485088

  11. Comparison of inelastic and quasielastic scattering effects on nonlinear electron transport in quantum wires

    NASA Astrophysics Data System (ADS)

    Huang, Danhong; Gumbs, Godfrey

    2010-05-01

    When impurity and phonon scattering coexist, the Boltzmann equation has been solved accurately for nonlinear electron transport in a quantum wire. Based on the calculated nonequilibrium distribution of electrons in momentum space, the scattering effects on both the nondifferential (for a fixed dc field) and differential (for a fixed temperature) mobilities of electrons as functions of temperature and dc field have been demonstrated. The nondifferential mobility of electrons is switched from a linearly increasing function of temperature to a paraboliclike temperature dependence as the quantum wire is tuned from an impurity-dominated system to a phonon-dominated one, as described by Fang et al. [Phys. Rev. B 78, 205403 (2008)]. In addition, a maximum has been obtained in the dc field dependence of the differential mobility of electrons. The low-field differential mobility is dominated by the impurity scattering, whereas the high-field differential mobility is limited by the phonon scattering as described by Hauser et al. [Semicond. Sci. Technol. 9, 951 (1994)]. Once a quantum wire is dominated by quasielastic scattering, the peak of the momentum-space distribution function becomes sharpened and both tails of the equilibrium electron distribution centered at the Fermi edges are raised by the dc field after a redistribution of the electrons is fulfilled in a symmetric way in the low-field regime. If a quantum wire is dominated by inelastic scattering, on the other hand, the peak of the momentum-space distribution function is unchanged while both shoulders centered at the Fermi edges shift leftward correspondingly with increasing dc field through an asymmetric redistribution of the electrons even in low-field regime as described by Wirner et al. [Phys. Rev. Lett. 70, 2609 (1993)].

  12. Emergent Lorentz symmetry with vanishing velocity in a critical two-subband quantum wire.

    SciTech Connect

    Sitte, M.; Rosch, A.; Meyer, J. S.; Matveev, K. A.; Garst, M.; Materials Science Division; Univ. zu Koln; Ohio State Univ.

    2009-01-01

    We consider a quantum wire with two subbands of spin-polarized electrons in the presence of strong interactions. We focus on the quantum phase transition when the second subband starts to get filled as a function of gate voltage. Performing a one-loop renormalization group analysis of the effective Hamiltonian, we identify the critical fixed-point theory as a conformal field theory having an enhanced SU(2) symmetry and central charge 3/2. While the fixed point is Lorentz invariant, the effective 'speed of light' nevertheless vanishes at low energies due to marginally irrelevant operators leading to a diverging critical specific heat coefficient.

  13. Emergent Lorentz symmetry with vanishing velocity in a critical two-subband quantum wire.

    PubMed

    Sitte, M; Rosch, A; Meyer, J S; Matveev, K A; Garst, M

    2009-05-01

    We consider a quantum wire with two subbands of spin-polarized electrons in the presence of strong interactions. We focus on the quantum phase transition when the second subband starts to get filled as a function of gate voltage. Performing a one-loop renormalization group analysis of the effective Hamiltonian, we identify the critical fixed-point theory as a conformal field theory having an enhanced SU(2) symmetry and central charge 3/2. While the fixed point is Lorentz invariant, the effective "speed of light" nevertheless vanishes at low energies due to marginally irrelevant operators leading to a diverging critical specific heat coefficient. PMID:19518804

  14. Numerical Study of Spin-Dependent Transport Through a Magnetic Quantum Wire with Lattice Vacancy

    NASA Astrophysics Data System (ADS)

    Jafari, A.; Ghoranneviss, M.

    2016-03-01

    The impact of lattice vacancy on the spin dependent transport properties of a magnetic-quantum wire (MQW) has been investigated. A simple tight binding Hamiltonian to describe the model is used, where the quantum wire is attached to two semi-infinite one-dimensional non-magnetic electrodes. Based on the Landauer-Buttiker formalism all the calculations are performed numerically which describe two-terminal conductance. The results suggest that in presence of vacancy the transmission reduces and vacancy creates quasilocalized states around zero energy (E f = 0). In order to investigate spin-filtering effect of (MQW), the degree of polarization in the presence and absences of vacancy has been studied. Also it is found that the effect of vacancy decreases when the size of MQW increases. The results show that a magnetic quantum wire can be used as a spin filter. The application of the predicted results may be useful in designing molecular spin-polarized transistors in the future.

  15. Eigen function and corresponding eigen values of charge carriers in V-grooves quantum wires with variable width

    NASA Astrophysics Data System (ADS)

    Zaheri, Ali Hossein Mohammad

    2016-06-01

    In this work, we have calculated analytically the energy spectra of electrons and holes in V-grooves quantum wires. To modify wire structure, we have used the equations which suggested in the work of Inoshita et al. We introduce a new effective potential scheme which is applicable and matchable with actual interface geometry of this groove of ridge quantum wires. By applying this effective potential and considering a suitable transformed coordinate that allows the decoupling of the two-dimensional wave functions, we have calculated eigen values of the charge carriers in three states as well as the wave functions. We found that by increasing the curvature at the top of quantum wire (b) the energy eigen value decreases. Our results are in good agreement with the earlier investigations.

  16. Symmetry-induced quantum interference effects in metalloporphyrin wires.

    PubMed

    Ferradás, R; García-Suárez, V M; Ferrer, J

    2013-08-14

    We calculate the electronic and transport properties of a series of metalloporphyrin molecules sandwiched between gold electrodes using a combination of density functional theory and scattering theory. The impact of strong correlations at the central metallic atom is gauged by comparing our results obtained using conventional DFT and DFT + U approaches. The zero- and finite-bias transport properties may or may not show spin-filtering behavior, depending on the nature of the d state closest to the Fermi energy. The type of d state depends on the metallic atom and gives rise to interference effects that produce different Fano features. The inclusion of the U term opens a gap between the d states and changes the conductance and spin-filtering behavior qualitatively in some of the molecules. We explain the origin of the quantum interference effects found as due to the symmetry-dependent coupling between the d states and other molecular orbitals and propose the use of these systems as nanoscale chemical sensors. We also demonstrate that an adequate treatment of strong correlations is really necessary to correctly describe the transport properties of metalloporphyrins and similar molecular magnets. PMID:23838608

  17. Negative differential conductance in InAs wire based double quantum dot induced by a charged AFM tip

    SciTech Connect

    Zhukov, A. A.; Volk, Ch.; Winden, A.; Hardtdegen, H.; Schaepers, Th.

    2012-12-15

    We investigate the conductance of an InAs nanowire in the nonlinear regime in the case of low electron density where the wire is split into quantum dots connected in series. The negative differential conductance in the wire is initiated by means of a charged atomic force microscope tip adjusting the transparency of the tunneling barrier between two adjoining quantum dots. We confirm that the negative differential conductance arises due to the resonant tunneling between these two adjoining quantum dots. The influence of the transparency of the blocking barriers and the relative position of energy states in the adjoining dots on a decrease of the negative differential conductance is investigated in detail.

  18. Growth and fabrication of quantum wells, wires, and dots for optical applications

    NASA Astrophysics Data System (ADS)

    Gossard, Arthur C.; Petroff, Pierre M.; Coldren, Larry A.; Tsuchiya, Masahiro

    1990-05-01

    Although molecular beam and vapor phase epitaxial growth techniques can control layer thicknesses and uniformity at the atomic monolayer level of precision, control of quantum structure dimensions in lateral directions parallel to epitaxial layers is more difficult, with lithographic and focused beam techniques difficult to control below dimensions of order 100 nm. This is larger than the optimum maximum size for quantum wire and dot applications, which is of order 10 nm, as required for wire and dot devices to operate in their lowest quantum state/and not to be restricted to cryogenic temperature operation. An alternate, but challenging, means of defining small lateral dimensions is the use of the periodicity of atomic terrace steps on substrate crystals that are slightly misoriented with respect to principal crystal 1 For small misorientation of a crystal surface by a radians, the distance L5 between step edges is c/a, where c is the spacing between planes of substrate atoms. For a GaAs crystal misoriented two degrees from a (1 10) direction, L5 = 8 nm and thus is of the order of magnitude needed for quantum wire devices. Lateral periodicity of a quantum structure can be produced by growth of alternate half atomic layer coverage depositions in a step flow crystal growth mode. Structures showing this lateral periodicity have previously been grown both by molecular beam epitaxy and by metal-organic chemical vapor deposition.2'3 Deviations from a perfectly ordered lateral superlattice with layers perpendicular to the surface are important and are expected when the starting surface is not smooth with regular steps, when the crystal grows in an island growth mode, when there are kinks in the step edges, and when each pair of depositions deviates from an atomic monolayer total deposition. In recent work, we have measured surface smoothness and step regularity by in situ observations of the crystal growth surface by measurement of the widths of the specularly reflected

  19. Ultranarrow resonance in Coulomb drag between quantum wires at coinciding densities

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. P.; Gornyi, I. V.; Polyakov, D. G.

    2016-08-01

    We investigate the influence of the chemical potential mismatch Δ (different electron densities) on Coulomb drag between two parallel ballistic quantum wires. For pair collisions, the drag resistivity ρD(Δ ) shows a peculiar anomaly at Δ =0 with ρD being finite at Δ =0 and vanishing at any nonzero Δ . The "bodyless" resonance in ρD(Δ ) at zero Δ is only broadened by processes of multiparticle scattering. We analyze Coulomb drag for finite Δ in the presence of both two- and three-particle scattering within the kinetic equation framework, focusing on a Fokker-Planck picture of the interaction-induced diffusion in momentum space of the double-wire system. We describe the dependence of ρD on Δ for both weak and strong intrawire equilibration due to three-particle scattering.

  20. Voltage-induced conversion of helical to uniform nuclear spin polarization in a quantum wire

    NASA Astrophysics Data System (ADS)

    Kornich, Viktoriia; Stano, Peter; Zyuzin, Alexander A.; Loss, Daniel

    2015-05-01

    We study the effect of bias voltage on the nuclear spin polarization of a ballistic wire, which contains electrons and nuclei interacting via hyperfine interaction. In equilibrium, the localized nuclear spins are helically polarized due to the electron-mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Focusing here on nonequilibrium, we find that an applied bias voltage induces a uniform polarization, from both helically polarized and unpolarized spins available for spin flips. Once a macroscopic uniform polarization in the nuclei is established, the nuclear spin helix rotates with frequency proportional to the uniform polarization. The uniform nuclear spin polarization monotonically increases as a function of both voltage and temperature, reflecting a thermal activation behavior. Our predictions offer specific ways to test experimentally the presence of a nuclear spin helix polarization in semiconducting quantum wires.

  1. Interaction-induced corrections to conductance and thermopower in quantum wires.

    SciTech Connect

    Levchenko, A.; Ristivojevic, Z.; Micklitz, T.; Materials Science Division; Theorique de l'Ecole Normale Superieure; Freie Univ. Berlin

    2011-01-19

    We study transport properties of weakly interacting spinless electrons in one-dimensional single-channel quantum wires. The effects of interaction manifest as three-particle collisions due to the severe constraints imposed by the conservation laws on the two-body processes. We focus on short wires where the effects of equilibration on the distribution function can be neglected and the collision integral can be treated in perturbation theory. We find that interaction-induced corrections to conductance and thermopower rely on the scattering processes that change the number of right- and left-moving electrons. The latter requires transition at the bottom of the band which is exponentially suppressed at low temperatures. Our theory is based on the scattering approach that is beyond the Luttinger-liquid limit. We emphasize the crucial role of the exchange terms in the three-particle scattering amplitude that was not discussed in previous studies.

  2. Morphological evolution of InAs/InP quantum wires through aberration-corrected scanning transmission electron microscopy.

    PubMed

    Sales, D L; Varela, M; Pennycook, S J; Galindo, P L; González, L; González, Y; Fuster, D; Molina, S I

    2010-08-13

    Evolution of the size, shape and composition of self-assembled InAs/InP quantum wires through the Stranski-Krastanov transition has been determined by aberration-corrected Z-contrast imaging. High resolution compositional maps of the wires in the initial, intermediate and final formation stages are presented. (001) is the main facet at their very initial stage of formation, which is gradually reduced in favour of [114] or [118], ending with the formation of mature quantum wires with {114} facets. Significant changes in wire dimensions are measured when varying slightly the amount of InAs deposited. These results are used as input parameters to build three-dimensional models that allow calculation of the strain energy during the quantum wire formation process. The observed morphological evolution is explained in terms of the calculated elastic energy changes at the growth front. Regions of the wetting layer close to the nanostructure perimeters have higher strain energy, causing migration of As atoms towards the quantum wire terraces, where the structure is partially relaxed; the thickness of the wetting layer is reduced in these zones and the island height increases until the (001) facet is removed. PMID:20647625

  3. Bridging coupled wires and lattice Hamiltonian for two-component bosonic quantum Hall states

    NASA Astrophysics Data System (ADS)

    Fuji, Yohei; He, Yin-Chen; Bhattacharjee, Subhro; Pollmann, Frank

    2016-05-01

    We investigate a model of hard-core bosons with correlated hopping on the honeycomb lattice in an external magnetic field by means of a coupled-wire approach. It has been numerically shown that this model exhibits at half filling the bosonic integer quantum Hall (BIQH) state, which is a symmetry-protected topological phase protected by the U (1 ) particle conservation [Y.-C. He et al., Phys. Rev. Lett. 115, 116803 (2015), 10.1103/PhysRevLett.115.116803]. By combining the bosonization approach and a coupled-wire construction, we analytically confirm this finding and show that it even holds in the strongly anisotropic (quasi-one-dimensional) limit. We discuss the stability of the BIQH phase against tunnelings that break the separate particle conservations on different sublattices down to a global particle conservation. We further argue that a phase transition between two different BIQH phases is in a deconfined quantum critical point described by two copies of the (2 +1 ) -dimensional O (4 ) nonlinear sigma model with the topological θ term at θ =π . Finally, we predict a possible fractional quantum Hall state, the Halperin (221 ) state, at 1 /6 filling.

  4. Bias voltage dependence of the electron spin depolarization in quantum wires in the quantum Hall regime detected by the resistively detected NMR

    SciTech Connect

    Chida, K.; Yamauchi, Y.; Arakawa, T.; Kobayashi, K.; Ono, T.; Hashisaka, M.; Nakamura, S.; Machida, T.

    2013-12-04

    We performed the resistively-detected nuclear magnetic resonance (RDNMR) to study the electron spin polarization in the non-equilibrium quantum Hall regime. By measuring the Knight shift, we derive source-drain bias voltage dependence of the electron spin polarization in quantum wires. The electron spin polarization shows minimum value around the threshold voltage of the dynamic nuclear polarization.

  5. Non-Abelian topological spin liquids from arrays of quantum wires or spin chains

    NASA Astrophysics Data System (ADS)

    Huang, Po-Hao; Chen, Jyong-Hao; Gomes, Pedro R. S.; Neupert, Titus; Chamon, Claudio; Mudry, Christopher

    2016-05-01

    We construct two-dimensional non-Abelian topologically ordered states by strongly coupling arrays of one-dimensional quantum wires via interactions. In our scheme, all charge degrees of freedom are gapped, so the construction can use either quantum wires or quantum spin chains as building blocks, with the same end result. The construction gaps the degrees of freedom in the bulk, while leaving decoupled states at the edges that are described by conformal field theories (CFT) in (1 +1 ) -dimensional space and time. We consider both the cases where time-reversal symmetry (TRS) is present or absent. When TRS is absent, the edge states are chiral and stable. We prescribe, in particular, how to arrive at all the edge states described by the unitary CFT minimal models with central charges c <1 . These non-Abelian spin liquid states have vanishing quantum Hall conductivities, but nonzero thermal ones. When TRS is present, we describe scenarios where the bulk state can be a non-Abelian, nonchiral, and gapped quantum spin liquid, or a gapless one. In the former case, we find that the edge states are also gapped. The paper provides a brief review of non-Abelian bosonization and affine current algebras, with the purpose of being self-contained. To illustrate the methods in a warm-up exercise, we recover the tenfold way classification of two-dimensional noninteracting topological insulators using the Majorana representation that naturally arises within non-Abelian bosonization. Within this scheme, the classification reduces to counting the number of null singular values of a mass matrix, with gapless edge modes present when left and right null eigenvectors exist.

  6. Effects of spin-orbit interaction on the electronic structure of mono-layer quantum wires

    NASA Astrophysics Data System (ADS)

    Vaseghi, B.; Ghaffari, A.

    2016-07-01

    Simultaneous effects of spin-orbit interaction, external electric and magnetic fields and dimension on the electronic structure of a mono-layer quantum wire are investigated in this paper. Due to the direct effects of external electric field on the structure's symmetries and spin-orbit interaction, energy eigenvalues and functions of the system are calculated with axial or in-plane electric field. It is shown that spin-orbit interaction modifies energy eigenvalues and functions of the system with regard to external factors.

  7. Crystal-Phase Control by Solution-Solid-Solid Growth of II-VI Quantum Wires.

    PubMed

    Wang, Fudong; Buhro, William E

    2016-02-10

    A simple and potentially general means of eliminating the planar defects and phase alternations that typically accompany the growth of semiconductor nanowires by catalyzed methods is reported. Nearly phase-pure, defect-free wurtzite II-VI semiconductor quantum wires are grown from solid rather than liquid catalyst nanoparticles. The solid-catalyst nanoparticles are morphologically stable during growth, which minimizes the spontaneous fluctuations in nucleation barriers between zinc blende and wurtzite phases that are responsible for the defect formation and phase alternations. Growth of single-phase (in our cases the wurtzite phase) nanowires is thus favored. PMID:26731426

  8. Exploring semiconductor quantum dots and wires by high resolution electron microscopy

    SciTech Connect

    Molina Rubio, Sergio I; Galindo, Pedro; Gonzalez, Luisa; Ripalda, JM; Varela del Arco, Maria; Pennycook, Stephen J

    2010-01-01

    We review in this communication our contribution to the structural characterisation of semiconductor quantum dots and wires by high resolution electron microscopy, both in phase-contrast and Z-contrast modes. We show how these techniques contribute to predict the preferential sites of nucleation of these nanostructures, and also determine the compositional distribution in 1D and 0D nanostructures. The results presented here were produced in the framework of the European Network of Excellence entitled 'Self-Assembled semiconductor Nanostructures for new Devices in photonics and Electronics (SANDiE)'.

  9. Tuning Fano resonances by magnetic forces for electron transport through a quantum wire side coupled to a quantum ring

    NASA Astrophysics Data System (ADS)

    Szafran, B.; Poniedziałek, M. R.

    2010-08-01

    We consider electron transport in a quantum wire with a side-coupled quantum ring in a two-dimensional model that accounts for a finite width of the channels. We use the finite difference technique to solve the scattering problem as well as to determine the ring-localized states of the energy continuum. The backscattering probability exhibits Fano peaks for magnetic fields for which a ring-localized states appear at the Fermi level. We find that the width of the Fano resonances changes at high magnetic field. The width is increased (decreased) for resonant states with current circulation that produce the magnetic dipole moment that is parallel (antiparallel) to the external magnetic field. We indicate that the opposite behavior of Fano resonances due to localized states with clockwise and counterclockwise currents results from the magnetic forces which change the strength of their coupling to the channel and modify the lifetime of localized states.

  10. Dynamical properties of spin and subbands populations in 1D quantum wire

    NASA Astrophysics Data System (ADS)

    Vaseghi, B.; Khordad, R.; Golshan, M. M.

    2006-10-01

    In this paper we study the spin and subbands populations, as functions of time, for electrons in a quasi-1D quantum wire, with spin-orbit coupling (SOC), to which a perpendicular magnetic field is applied. The system is governed by the Hamiltonian which, in the strong magnetic field limit, resembles the Jaynes-Cummings model (JCM) in quantum optics (QO). Using a procedure similar to that in QO, we explicitly present the time-evolution operator, thereby calculating the spin states and subbands populations as functions of time. We show that the populations exhibit oscillations, depending on the interaction parameters, scale lengths and, particularly, the initial states of the system. Specifically, if the electrons are initially prepared in a maximal coherent superposition of spin states, the expectation values periodically collapse and revive. The collapse-revivals are most profound for the spin along the magnetic field and subbands populations.

  11. Confined acoustic and optical plasmons in double-layered quantum-wire arrays with strong tunneling

    NASA Astrophysics Data System (ADS)

    Dethlefsen, A. F.; Heyn, Ch.; Heitmann, D.; Schüller, C.

    2006-05-01

    We investigate electronic excitations in GaAs-AlxGa1-xAs double-layered quantum wire arrays with strong tunneling coupling by resonant inelastic light scattering. By applying an external electric field, we can change the one-dimensional (1D) electron density and the symmetry of the double quantum-well (DQW) structure at the same time. We identify confined optical 1D intersubband plasmons (COP) and confined acoustic 1D intersubband plasmons (CAP). Due to the tunneling coupling, the energies of the CAP exhibit a minimum for a symmetric DQW potential, whereas the energies of the COP are dominated by the total carrier density, and are nearly insensitive to the symmetry of the potential.

  12. Surface and interface phonon-polaritons in freestanding quantum well wire systems of polar ternary mixed crystals

    NASA Astrophysics Data System (ADS)

    Yan, C. L.; Bao, J.; Yan, Z. W.

    2016-03-01

    The surface and interface phonon-polaritons in freestanding rectangular quantum well wire systems consisting of polar ternary mixed crystals are investigated in the modified random-element-isodisplacement model and the Born-Huang approximation, based on the Maxwell's equations with the boundary conditions. The numerical results of the surface and interface phonon-polariton frequencies as functions of the wave-vector, geometric structure, and the composition of the ternary mixed crystals in GaAs/AlxGa1-xAs and ZnxCd1-xSe/ZnSe quantum well wire systems are obtained and discussed. It is shown that there are 10 and 8 branches of surface and interface phonon-polaritons in the two quantum well wire systems respectively. The effects of the "two-mode" and "one-mode" behaviors of the ternary mixed crystals on the surface and interface phonon-polariton modes are shown in the dispersion curves.

  13. Inelastic electron and Raman scattering from the collective excitations in quantum wires: Zero magnetic field

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2013-04-01

    The nanofabrication technology has taught us that an m-dimensional confining potential imposed upon an n-dimensional electron gas paves the way to a quasi-(n-m)-dimensional electron gas, with m ⩽ n and 1 ⩽ n, m ⩽ 3. This is the road to the (semiconducting) quasi-n dimensional electron gas systems we have been happily traversing on now for almost two decades. Achieving quasi-one dimensional electron gas (Q-1DEG) [or quantum wire(s) for more practical purposes] led us to some mixed moments in this journey: while the reduced phase space for the scattering led us believe in the route to the faster electron devices, the proximity to the 1D systems left us in the dilemma of describing it as a Fermi liquid or as a Luttinger liquid. No one had ever suspected the potential of the former, but it took quite a while for some to convince the others on the latter. A realistic Q-1DEG system at the low temperatures is best describable as a Fermi liquid rather than as a Luttinger liquid. In the language of condensed matter physics, a critical scrutiny of Q-1DEG systems has provided us with a host of exotic (electronic, optical, and transport) phenomena unseen in their higher- or lower-dimensional counterparts. This has motivated us to undertake a systematic investigation of the inelastic electron scattering (IES) and the inelastic light scattering (ILS) from the elementary electronic excitations in quantum wires. We begin with the Kubo's correlation functions to derive the generalized dielectric function, the inverse dielectric function, and the Dyson equation for the dynamic screened potential in the framework of Bohm-Pines' random-phase approximation. These fundamental tools then lead us to develop methodically the theory of IES and ILS for the Q-1DEG systems. As an application of the general formal results, which know no bounds regarding the subband occupancy, we compute the density of states, the Fermi energy, the full excitation spectrum [comprised of intrasubband and

  14. Magnetotransport in p-type Ge quantum well narrow wire arrays

    SciTech Connect

    Newton, P. J. Llandro, J.; Mansell, R.; Barnes, C. H. W.; Holmes, S. N.; Morrison, C.; Foronda, J.; Myronov, M.; Leadley, D. R.

    2015-04-27

    We report magnetotransport measurements of a SiGe heterostructure containing a 20 nm p-Ge quantum well with a mobility of 800 000 cm{sup 2} V{sup −1} s{sup −1}. By dry etching arrays of wires with widths between 1.0 μm and 3.0 μm, we were able to measure the lateral depletion thickness, built-in potential, and the phase coherence length of the quantum well. Fourier analysis does not show any Rashba related spin-splitting despite clearly defined Shubnikov-de Haas oscillations being observed up to a filling factor of ν = 22. Exchange-enhanced spin-splitting is observed for filling factors below ν = 9. An analysis of boundary scattering effects indicates lateral depletion of the hole gas by 0.5 ± 0.1 μm from the etched germanium surface. The built-in potential is found to be 0.25 ± 0.04 V, presenting an energy barrier for lateral transport greater than the hole confinement energy. A large phase coherence length of 3.5 ± 0.5 μm is obtained in these wires at 1.7 K.

  15. Electron motion induced by magnetic pulse in a bilayer quantum wire

    NASA Astrophysics Data System (ADS)

    Chwiej, T.

    2016-06-01

    We consider theoretical stimulation of electron motion in a quantum wire by means of ultrashort magnetic pulses of time duration between several and a few tens of picoseconds. In our considerations, an electron is confined in a nanowire which consists of two vertically stacked tunnel-coupled layers. If a magnetic pulse pierces this nanowire and its direction is parallel to the plane established by the layers, and additionally, it is perpendicular to the wire's axis, then the eigenstates of a single electron energy operator for vertical direction are hybridized by the off-diagonal terms of the full Hamiltonian. These terms depend linearly on the momentum operator, which means that such magnetically forced hybridization may induce electron motion in a nanowire. The classical counterpart of this quantum-mechanical picture is a situation in which the rotational electric field generated by a time-varying magnetic field pushes the charge densities localized in the upper and lower layers in opposite directions. We have found, however, that for an asymmetric vertical confinement in a bilayer nanowire, the major part of the single electron density starts to move in the direction of the local electric field in its layer forcing the minority part to move in this direction as well. It results in coherent motion of both densities in a particular direction. We analyze the dynamics of such motion in dependence on the time characteristics of a magnetic pulse and discuss potential applications of this effect in the construction of a magnetic valve.

  16. Generic framework for the secure Yuen 2000 quantum-encryption protocol employing the wire-tap channel approach

    SciTech Connect

    Mihaljevic, Miodrag J.

    2007-05-15

    It is shown that the security, against known-plaintext attacks, of the Yuen 2000 (Y00) quantum-encryption protocol can be considered via the wire-tap channel model assuming that the heterodyne measurement yields the sample for security evaluation. Employing the results reported on the wire-tap channel, a generic framework is proposed for developing secure Y00 instantiations. The proposed framework employs a dedicated encoding which together with inherent quantum noise at the attacker's side provides Y00 security.

  17. Electron-phonon interaction effect on the energy levels and diamagnetic susceptibility of quantum wires: Parallelogram and triangle cross section

    SciTech Connect

    Khordad, R. Bahramiyan, H.

    2014-03-28

    In this paper, optical phonon modes are studied within the framework of dielectric continuum approach for parallelogram and triangular quantum wires, including the derivation of the electron-phonon interaction Hamiltonian and a discussion on the effects of this interaction on the electronic energy levels. The polaronic energy shift is calculated for both ground-state and excited-state electron energy levels by applying the perturbative approach. The effects of the electron-phonon interaction on the expectation value of r{sup 2} and diamagnetic susceptibility for both quantum wires are discussed.

  18. Achieving effective terminal exciton delivery in quantum dot antenna-sensitized multistep DNA photonic wires.

    PubMed

    Spillmann, Christopher M; Ancona, Mario G; Buckhout-White, Susan; Algar, W Russ; Stewart, Michael H; Susumu, Kimihiro; Huston, Alan L; Goldman, Ellen R; Medintz, Igor L

    2013-08-27

    Assembling DNA-based photonic wires around semiconductor quantum dots (QDs) creates optically active hybrid architectures that exploit the unique properties of both components. DNA hybridization allows positioning of multiple, carefully arranged fluorophores that can engage in sequential energy transfer steps while the QDs provide a superior energy harvesting antenna capacity that drives a Förster resonance energy transfer (FRET) cascade through the structures. Although the first generation of these composites demonstrated four-sequential energy transfer steps across a distance >150 Å, the exciton transfer efficiency reaching the final, terminal dye was estimated to be only ~0.7% with no concomitant sensitized emission observed. Had the terminal Cy7 dye utilized in that construct provided a sensitized emission, we estimate that this would have equated to an overall end-to-end ET efficiency of ≤ 0.1%. In this report, we demonstrate that overall energy flow through a second generation hybrid architecture can be significantly improved by reengineering four key aspects of the composite structure: (1) making the initial DNA modification chemistry smaller and more facile to implement, (2) optimizing donor-acceptor dye pairings, (3) varying donor-acceptor dye spacing as a function of the Förster distance R0, and (4) increasing the number of DNA wires displayed around each central QD donor. These cumulative changes lead to a 2 orders of magnitude improvement in the exciton transfer efficiency to the final terminal dye in comparison to the first-generation construct. The overall end-to-end efficiency through the optimized, five-fluorophore/four-step cascaded energy transfer system now approaches 10%. The results are analyzed using Förster theory with various sources of randomness accounted for by averaging over ensembles of modeled constructs. Fits to the spectra suggest near-ideal behavior when the photonic wires have two sequential acceptor dyes (Cy3 and Cy3.5) and

  19. Synthesis of cadmium telluride quantum wires and the similarity of their band gaps to those of equidiameter cadmium telluride quantum dots

    SciTech Connect

    Wang, Lin-Wang; Sun, Jianwei; Wang, Lin-Wang; Buhro, William E.

    2008-07-11

    High-quality colloidal CdTe quantum wires having purposefully controlled diameters in the range of 5-11 nm are grown by the solution-liquid-solid (SLS) method, using Bi-nanoparticle catalysts, cadmium octadecylphosphonate and trioctylphosphine telluride as precursors, and a TOPO solvent. The wires adopt the wurtzite structure, and grow along the [002] direction (parallel to the c axis). The size dependence of the band gaps in the wires are determined from the absorption spectra, and compared to the experimental results for high-quality CdTe quantum dots. In contrast to the predictions of an effective-mass approximation, particle-in-a-box model, and previous experimental results from CdSe and InP dot-wire comparisons, the band gaps of CdTe dots and wires of like diameter are found to be experimentally indistinguishable. The present results are analyzed using density functional theory under the local-density approximation by implementing a charge-patching method. The higher-level theoretical analysis finds the general existence of a threshold diameter, above which dot and wire band gaps converge. The origin and magnitude of this threshold diameter is discussed.

  20. Synthesis and characterization of lead selenide nanocrystal quantum dots and wires.

    PubMed

    Seo, Weonsik; Yun, Ju-Hyung; Park, Yun Chang; Han, Chang-Soo; Lee, Jihye; Jeong, Sohee

    2011-05-01

    Lead chalcogenide nanocrystalline materials offer possibilities of improving the efficiency of various optoelectric/thermoelectric applications, especially in solar cells, by generating more carriers with incoming photons, or by extending the bandgap toward the infra-red region. In this work, we suggest the synthetic approach of creating extended PbSe structures which shows better performances when incorporated into an electric device. Firstly, we synthesized monodisperse cubic-structured single-crystalline lead selenide nanocrystal quantum dots using lead acetate and oleic acid in non-coordinating solvent without additional surfactants. Also, single-crystal cubic PbSe nanowires were synthesized in a mixture of surfactants such as trioctylphosphine and phenyl ether. Morphologies of wires and dots were precisely controlled via reaction temperature and the surface ligands. Phenyl ether was found to facilitate the oriented attachment. Further, current-voltage characteristics of drop-casted 2D arrays of nanocrystalline materials were examined. PMID:21780455

  1. Dual fermionic variables and renormalization group approach to junctions of strongly interacting quantum wires

    NASA Astrophysics Data System (ADS)

    Giuliano, Domenico; Nava, Andrea

    2015-09-01

    Making a combined use of bosonization and fermionization techniques, we build nonlocal transformations between dual fermion operators, describing junctions of strongly interacting spinful one-dimensional quantum wires. Our approach allows for trading strongly interacting (in the original coordinates) fermionic Hamiltonians for weakly interacting (in the dual coordinates) ones. It enables us to generalize to the strongly interacting regime the fermionic renormalization group approach to weakly interacting junctions. As a result, on one hand, we are able to pertinently complement the information about the phase diagram of the junction obtained within the bosonization approach; on the other hand, we map out the full crossover of the conductance tensors between any two fixed points in the phase diagram connected by a renormalization group trajectory.

  2. Electron Raman scattering in semiconductor quantum well wire of cylindrical ring geometry

    NASA Astrophysics Data System (ADS)

    Re., Betancourt-Riera; Ri., Betancourt-Riera; M. Nieto Jalil, J.; Riera, R.

    2015-11-01

    We study the electron states and the differential cross section for an electron Raman scattering process in a semiconductor quantum well wire of cylindrical ring geometry. The electron Raman scattering developed here can be used to provide direct information about the electron band structures of these confinement systems. We assume that the system grows in a GaAs/Al0.35Ga0.65As matrix. The system is modeled by considering T = 0 K and also a single parabolic conduction band, which is split into a sub-band system due to the confinement. The emission spectra are discussed for different scattering configurations, and the selection rules for the processes are also studied. Singularities in the spectra are found and interpreted.

  3. Dirac electrons in graphene-based quantum wires and quantum dots

    NASA Astrophysics Data System (ADS)

    Peres, N. M. R.; Rodrigues, J. N. B.; Stauber, T.; Lopes dos Santos, J. M. B.

    2009-08-01

    In this paper we analyse the electronic properties of Dirac electrons in finite-size ribbons and in circular and hexagonal quantum dots. We show that due to the formation of sub-bands in the ribbons it is possible to spatially localize some of the electronic modes using a p-n-p junction. We also show that scattering of confined Dirac electrons in a narrow channel by an infinitely massive wall induces mode mixing, giving a qualitative reason for the fact that an analytical solution to the spectrum of Dirac electrons confined in a square box has not yet been found. A first attempt to solve this problem is presented. We find that only the trivial case k = 0 has a solution that does not require the existence of evanescent modes. We also study the spectrum of quantum dots of graphene in a perpendicular magnetic field. This problem is studied in the Dirac approximation, and its solution requires a numerical method whose details are given. The formation of Landau levels in the dot is discussed. The inclusion of the Coulomb interaction among the electrons is considered at the self-consistent Hartree level, taking into account the interaction with an image charge density necessary to keep the back-gate electrode at zero potential. The effect of a radial confining potential is discussed. The density of states of circular and hexagonal quantum dots, described by the full tight-binding model, is studied using the Lanczos algorithm. This is necessary to access the detailed shape of the density of states close to the Dirac point when one studies large systems. Our study reveals that zero-energy edge states are also present in graphene quantum dots. Our results are relevant for experimental research in graphene nanostructures. The style of writing is pedagogical, in the hope that newcomers to the subject will find this paper a good starting point for their research.

  4. Role of excited states for the material gain and threshold current density in quantum wire intersubband laser structures

    NASA Astrophysics Data System (ADS)

    Herrle, Thomas; Haneder, Stephan; Wegscheider, Werner

    2006-05-01

    We calculated the material gain and the threshold current density for quantum wire intersubband laser structures. In quantum cascade laser devices with active regions of lower dimensionality a reduction of the nonradiative losses and consequently an increase in the material gain and a reduction of the threshold current density is predicted. In our calculations of the material gain and the threshold current density for a realistic quantum wire intersubband laser structure fabricated by the cleaved edge overgrowth (CEO) technique, however, it turns out that excited states formed in those structures even reduce the material gain compared to conventional quantum well cascade lasers. The threshold current density also turns out to be increased due to the reduced material gain on the one hand and due to a small optical confinement factor in such structures on the other hand. The main consequence for the design of such quantum wire laser structures is to avoid the formation of excited states to be able to benefit from the reduction of the dimensionality of the electron system in terms of reduced nonradiative losses.

  5. (In,Ga)As sidewall quantum wires on shallow-patterned InP (311)A

    SciTech Connect

    Zhou, D.; Noetzel, R.; Gong, Q.; Offermans, P.; Koenraad, P.M.; Veldhoven, P.J. van; Otten, F.W.M. van; Eijkemans, T.J.; Wolter, J.H.

    2005-03-15

    (In,Ga)As sidewall quantum wires (QWires) are realized by chemical beam epitaxy along [01-1] mesa stripes on shallow-patterned InP (311)A substrates. The QWires exhibit strong lateral carrier confinement due to larger thickness and In composition compared to the adjacent quantum wells, as determined by cross-sectional scanning-tunneling microscopy and microphotoluminescence (micro-PL) spectroscopy. The PL of the (In,Ga)As QWires with InP and quaternary (Ga,In)(As,P) barriers reveals narrow linewidth, high efficiency, and large lateral carrier confinement energies of 60-70 meV. The QWires are stacked in growth direction with identical PL peak emission energy. The PL emission energy is not only controlled by the (In,Ga)As layer thickness but also by the patterned mesa height. Stacked (In,Ga)As QWires with quaternary barriers exhibit room temperature PL emission at 1.55 {mu}m in the technologically important wavelength region for telecommunication applications.

  6. Self-assembled GaN quantum wires on GaN/AlN nanowire templates.

    PubMed

    Arbiol, Jordi; Magen, Cesar; Becker, Pascal; Jacopin, Gwénolé; Chernikov, Alexey; Schäfer, Sören; Furtmayr, Florian; Tchernycheva, Maria; Rigutti, Lorenzo; Teubert, Jörg; Chatterjee, Sangam; Morante, Joan R; Eickhoff, Martin

    2012-12-01

    We present a novel approach for self-assembled growth of GaN quantum wires (QWRs) exhibiting strong confinement in two spatial dimensions. The GaN QWRs are formed by selective nucleation on {112[combining macron]0} (a-plane) facets formed at the six intersections of {11[combining macron]00} (m-plane) sidewalls of AlN/GaN nanowires used as a template. Based on microscopy observations we have developed a 3D model explaining the growth mechanism of QWRs. We show that the QWR formation is governed by self-limited pseudomorphic growth on the side facets of the nanowires (NWs). Quantum confinement in the QWRs is confirmed by the observation of narrow photoluminescence lines originating from individual QWRs with emission energies up to 4.4 eV. Time-resolved photoluminescence studies reveal a short decay time (~120 ps) of the QWR emission. Capping of the QWRs with AlN allows enhancement of the photoluminescence, which is blue-shifted due to compressive strain. The emission energies from single QWRs are modelled assuming a triangular cross-section resulting from self-limited growth on a-plane facets. Comparison with the experimental results yields an average QWR diameter of about 2.7 nm in agreement with structural characterization. The presented results open a new route towards controlled realization of one-dimensional semiconductor quantum structures with a high potential both for fundamental studies and for applications in electronics and in UV light generation. PMID:23100169

  7. Crystal-phase quantum dots in GaN quantum wires

    NASA Astrophysics Data System (ADS)

    Corfdir, Pierre; Hauswald, Christian; Marquardt, Oliver; Flissikowski, Timur; Zettler, Johannes K.; Fernández-Garrido, Sergio; Geelhaar, Lutz; Grahn, Holger T.; Brandt, Oliver

    2016-03-01

    We study the nature of excitons bound to I1 basal plane stacking faults in ensembles of ultrathin GaN nanowires by continuous-wave and time-resolved photoluminescence spectroscopy. These ultrathin nanowires, obtained by the thermal decomposition of spontaneously formed GaN nanowire ensembles, are tapered and have tip diameters down to 6 nm. With decreasing nanowire diameter, we observe a strong blueshift of the transition originating from the radiative decay of stacking fault-bound excitons. Moreover, the radiative lifetime of this transition in the ultrathin nanowires is independent of temperature up to 60 K and significantly longer than that of the corresponding transition in as-grown nanowires. These findings reveal a zero-dimensional character of the confined exciton state and thus demonstrate that I1 stacking faults in ultrathin nanowires act as genuine quantum dots.

  8. Tuning directional dependent metal–insulator transitions in quasi-1D quantum wires with spin–orbit density wave instability

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy

    2016-07-01

    We study directional dependent band gap evolutions and metal–insulator transitions (MITs) in model quantum wire systems within the spin–orbit density wave (SODW) model. The evolution of MIT is studied as a function of varying anisotropy between the intra-wire hopping ({{t}\\parallel} ) and inter-wire hopping ({{t}\\bot} ) with Rashba spin–orbit coupling. We find that as long as the anisotropy ratio (β ={{t}\\bot}/{{t}\\parallel} ) remains below 0.5, and the Fermi surface nesting is tuned to {{\\mathbf{Q}}1}=≤ft(π,0\\right) , an exotic SODW induced MIT easily develops, with its critical interaction strength increasing with increasing anisotropy. As β \\to 1 (2D system), the nesting vector switches to {{\\mathbf{Q}}2}=≤ft(π,π \\right) , making this state again suitable for an isotropic MIT. Finally, we discuss various physical consequences and possible applications of the directional dependent MIT.

  9. Tuning directional dependent metal-insulator transitions in quasi-1D quantum wires with spin-orbit density wave instability.

    PubMed

    Das, Tanmoy

    2016-07-27

    We study directional dependent band gap evolutions and metal-insulator transitions (MITs) in model quantum wire systems within the spin-orbit density wave (SODW) model. The evolution of MIT is studied as a function of varying anisotropy between the intra-wire hopping ([Formula: see text]) and inter-wire hopping ([Formula: see text]) with Rashba spin-orbit coupling. We find that as long as the anisotropy ratio ([Formula: see text]) remains below 0.5, and the Fermi surface nesting is tuned to [Formula: see text], an exotic SODW induced MIT easily develops, with its critical interaction strength increasing with increasing anisotropy. As [Formula: see text] (2D system), the nesting vector switches to [Formula: see text], making this state again suitable for an isotropic MIT. Finally, we discuss various physical consequences and possible applications of the directional dependent MIT. PMID:27248294

  10. Functionality of bismuth sulfide quantum dots/wires-glass nanocomposite as an optical current sensor with enhanced Verdet constant

    NASA Astrophysics Data System (ADS)

    Panmand, Rajendra P.; Kumar, Ganapathy; Mahajan, Satish M.; Kulkarni, Milind V.; Amalnerkar, D. P.; Kale, Bharat B.; Gosavi, Suresh. W.

    2011-02-01

    We report optical studies with magneto-optic properties of Bi2S3 quantum dot/wires-glass nanocomposite. The size of the Q-dot was observed to be in the range 3-15 nm along with 11 nm Q-wires. Optical study clearly demonstrated the size quantization effect with drastic band gap variation with size. Faraday rotation tests on the glass nanocomposites show variation in Verdet constant with Q-dot size. Bi2S3 Q-dot/wires glass nanocomposite demonstrated 190 times enhanced Verdet constant compared to the host glass. Prima facie observations exemplify the significant enhancement in Verdet constant of Q-dot glass nanocomposites and will have potential application in magneto-optical devices.

  11. Optical gain for the interband optical transition in InAsP/InP quantum well wire in the influence of laser field intensity

    NASA Astrophysics Data System (ADS)

    Saravanan, S.; Peter, A. John

    2016-05-01

    Intense high frequency laser field induced electronic and optical properties of heavy hole exciton in the InAs0.8P0.2/InP quantum wire is studied taking into account the geometrical confinement effect. Laser field related exciton binding energies and the optical band gap in the InAs0.8P0.2/InP quantum well wire are investigated. The optical gain, for the interband optical transition, as a function of photon energy, in the InAs0.8P0.2/InP quantum wire, is obtained in the presence of intense laser field. The compact density matrix method is employed to obtain the optical gain. The obtained optical gain in group III-V narrow quantum wire can be applied for achieving the preferred telecommunication wavelength.

  12. One-dimensional electronic systems in ultra-fine mesa etched InGaAs-InAlAs-InP quantum wires

    NASA Astrophysics Data System (ADS)

    Kern, K.; Demel, T.; Heitmann, D.; Grambow, P.; Ploog, K.; Razeghi, M.

    1990-04-01

    Quantum wire structures have been prepared by deep mesa etching of modulation doped InGaAs-InAlAs-InP heterostructures. In very narrow wires (width t ≈ 300 nm) it was possible to realize one-dimensional electronic systems (IDES) with quantum confined energy levels. The separation of the ID subbands was, as determined from magnetic depopulation, about 2.5 meV.

  13. Rashba-Zeeman-effect-induced spin filtering energy windows in a quantum wire

    SciTech Connect

    Xiao, Xianbo Nie, Wenjie; Chen, Zhaoxia; Zhou, Guanghui; Li, Fei

    2014-06-14

    We perform a numerical study on the spin-resolved transport in a quantum wire (QW) under the modulation of both Rashba spin-orbit coupling (SOC) and a perpendicular magnetic field by using the developed Usuki transfer-matrix method in combination with the Landauer-Büttiker formalism. Wide spin filtering energy windows can be achieved in this system for unpolarized spin injection. In addition, both the width of energy window and the magnitude of spin conductance within these energy windows can be tuned by varying Rashba SOC strength, which can be apprehended by analyzing the energy dispersions and spin-polarized density distributions inside the QW, respectively. Further study also demonstrates that these Rashba-SOC-controlled spin filtering energy windows show a strong robustness against disorders. These findings may not only benefit to further understand the spin-dependent transport properties of a QW in the presence of external fields but also provide a theoretical instruction to design a spin filter device.

  14. Magnetic memory of a single-molecule quantum magnet wired to a gold surface

    NASA Astrophysics Data System (ADS)

    Mannini, Matteo; Pineider, Francesco; Sainctavit, Philippe; Danieli, Chiara; Otero, Edwige; Sciancalepore, Corrado; Talarico, Anna Maria; Arrio, Marie-Anne; Cornia, Andrea; Gatteschi, Dante; Sessoli, Roberta

    2009-03-01

    In the field of molecular spintronics, the use of magnetic molecules for information technology is a main target and the observation of magnetic hysteresis on individual molecules organized on surfaces is a necessary step to develop molecular memory arrays. Although simple paramagnetic molecules can show surface-induced magnetic ordering and hysteresis when deposited on ferromagnetic surfaces, information storage at the molecular level requires molecules exhibiting an intrinsic remnant magnetization, like the so-called single-molecule magnets (SMMs). These have been intensively investigated for their rich quantum behaviour but no magnetic hysteresis has been so far reported for monolayers of SMMs on various non-magnetic substrates, most probably owing to the chemical instability of clusters on surfaces. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism synchrotron-based techniques, pushed to the limits in sensitivity and operated at sub-kelvin temperatures, we have now found that robust, tailor-made Fe4 complexes retain magnetic hysteresis at gold surfaces. Our results demonstrate that isolated SMMs can be used for storing information. The road is now open to address individual molecules wired to a conducting surface in their blocked magnetization state, thereby enabling investigation of the elementary interactions between electron transport and magnetism degrees of freedom at the molecular scale.

  15. Inelastic electron and Raman scattering from the collective excitations in quantum wires

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir

    2014-03-01

    The nanofabrication technology has taught us that an m-dimensional confining potential imposed upon an n-dimensional electron gas paves the way to a quasi-(n- m)-dimensional electron gas, with m <= n and 1 <= n , m <= 3 . This is the road to the (semiconducting) quasi- n dimensional electron gas systems we have been happily traversing on now for almost two decades. Achieving quasi-one dimensional electron gas (Q-1DEG) led us to some mixed moments in this journey: while the reduced phase space for the scattering led us believe in the route to the faster electron devices, the proximity to the 1D systems left us in the dilemma of describing it as a Fermi liquid or as a Luttinger liquid. No one had ever suspected the potential of the former, but it took quite a while for some to convince the others on the latter. A realistic Q-1DEG system at the low temperatures is best describable as a Fermi liquid rather than as a Luttinger liquid. This has motivated us to employ the Bohm-Pines' full RPA to develop a systematic methodology for the inelastic electron and light scattering from the collective (plasmon) excitations in Q-1DEG [or quantum wires]. We will discuss in detail the results published in AIP Advances 3, 042103 (2013).

  16. Magnetic memory of a single-molecule quantum magnet wired to a gold surface.

    PubMed

    Mannini, Matteo; Pineider, Francesco; Sainctavit, Philippe; Danieli, Chiara; Otero, Edwige; Sciancalepore, Corrado; Talarico, Anna Maria; Arrio, Marie-Anne; Cornia, Andrea; Gatteschi, Dante; Sessoli, Roberta

    2009-03-01

    In the field of molecular spintronics, the use of magnetic molecules for information technology is a main target and the observation of magnetic hysteresis on individual molecules organized on surfaces is a necessary step to develop molecular memory arrays. Although simple paramagnetic molecules can show surface-induced magnetic ordering and hysteresis when deposited on ferromagnetic surfaces, information storage at the molecular level requires molecules exhibiting an intrinsic remnant magnetization, like the so-called single-molecule magnets (SMMs). These have been intensively investigated for their rich quantum behaviour but no magnetic hysteresis has been so far reported for monolayers of SMMs on various non-magnetic substrates, most probably owing to the chemical instability of clusters on surfaces. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism synchrotron-based techniques, pushed to the limits in sensitivity and operated at sub-kelvin temperatures, we have now found that robust, tailor-made Fe(4) complexes retain magnetic hysteresis at gold surfaces. Our results demonstrate that isolated SMMs can be used for storing information. The road is now open to address individual molecules wired to a conducting surface in their blocked magnetization state, thereby enabling investigation of the elementary interactions between electron transport and magnetism degrees of freedom at the molecular scale. PMID:19182788

  17. Why a Magnetized Quantum Wire can Act as AN Optical Amplifier

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir

    We discuss the fundamental issues associated with the magnetoplasmon excitations in a semiconducting quantum wire characterized by a harmonic confining potential and subjected to an applied (perpendicular) magnetic field. The problem involves two length scales: l0 =√{ ℏ /m*ω0 } and lc =√{ ℏ /m*ωc } , which characterize the strengths of the confinement and the magnetic field (B). Essentially, we focus on the device aspects of the intersubband collective (magnetoroton) excitation, which observes a negative group velocity between maxon and roton. Existence of the negative group velocity is a clear manifestation of a medium with population inversion brought about due to a metastable state caused by the magnetic field that satisfies the condition B >Bth ; Bth being the threshold value below which the magnetoroton does not exist. A medium with an inverted population has the remarkable ability of amplifying a small optical signal of definite wavelength. An extensive scrutiny of the gain coefficient suggests an interesting and important application: the electronic device designed on the basis of such magnetoroton modes can act as an optical amplifier1.

  18. Kinetics of spin relaxation in quantum wires and channels: Boundary spin echo and formation of a persistent spin helix

    SciTech Connect

    Slipko, Valeriy A.; Pershin, Yuriy V.

    2011-10-15

    In this paper we use a spin kinetic equation to study spin-polarization dynamics in one-dimensional (1D) wires and 2D channels. The spin kinetic equation is valid in both diffusive and ballistic spin transport regimes and therefore is more general than the usual spin drift-diffusion equations. In particular, we demonstrate that in infinite 1D wires with Rashba spin-orbit interaction the exponential spin-relaxation decay can be modulated by an oscillating function. In the case of spin relaxation in finite length 1D wires, it is shown that an initially homogeneous spin polarization spontaneously transforms into a persistent spin helix. We find that a propagating spin-polarization profile reflects from a system boundary and returns back to its initial position similarly to the reflectance of sound waves from an obstacle. The Green's function of the spin kinetic equation is derived for both finite and infinite 1D systems. Moreover, we demonstrate explicitly that the spin relaxation in specifically oriented 2D channels with Rashba and Dresselhaus spin-orbit interactions of equal strength occurs similarly to that in 1D wires of finite length. Finally, a simple transformation mapping 1D spin kinetic equation into the Klein-Gordon equation with an imaginary mass is found thus establishing an interesting connection between semiconductor spintronics and relativistic quantum mechanics.

  19. Optical properties of stacked InGaAs sidewall quantum wires in InGaAsP/InP

    SciTech Connect

    Zhou, D.; Noetzel, R.; Otten, F.W.M. van; Eijkemans, T.J.; Wolter, J.H.

    2006-05-15

    We report on the optical properties of threefold stacked InGaAs sidewall quantum wires (QWires) with quaternary InGaAsP barriers grown on shallow-patterned InP (311)A substrates by chemical beam epitaxy. Temperature dependent photoluminescence (PL) reveals efficient carrier transfer from the adjacent quantum wells (QWells) into the QWires at low temperature, thermally activated repopulation of the QWells at higher temperature, and negligible localization of carriers along the QWires. Strong broadening of power dependent PL indicates enhanced state filling in the QWires compared to that in the QWells. Clear linear polarization of the PL from the QWires confirms the lateral quantum confinement of carriers. These results demonstrate excellent optical quality of the sidewall QWire structures with room temperature PL peak wavelength at 1.55 {mu}m for applications in fiber-based optical telecommunication systems.

  20. Self-ordering of quasi-quantum wire in InAlAs/AlGaAs multilayer nanostructure and its optical anisotropy

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Li, G. H.; Zhang, W.; Zhu, Z. M.; Han, H. X.; Wang, Z. P.; Zhou, W.; Wang, Z. G.

    2000-02-01

    Self-ordering of quasi-quantum wires in multilayer InAlAs/AlGaAs nanostructures grown by molecular beam epitaxy is identified. The chain-like structures along the [ 1 1¯ 0 ] direction formed by coalescence of quantum dots were observed. The photoluminescence of the nanostructures is partially polarized along the [1 1¯ 0] direction. The polarization ratio depends on the wavelength and the maximum polarization is on the lower energy side. The maximum polarization increases from 0.32 at 10 K to 0.53 at 100 K, and the energy position of maximum polarization moves near to PL peak with increasing temperature. They are all related to the existence of isolated islands and quasi-quantum wires in our sample. This result provides a novel approach to produce narrow quantum wires.

  1. Rashba spin-orbit coupling effects on the optical properties of double quantum wire under magnetic field

    NASA Astrophysics Data System (ADS)

    Karaaslan, Y.; Gisi, B.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.

    2016-05-01

    We investigate the effects of Rashba spin-orbit interaction on the optical absorption coefficients and refractive index changes associated with transitions between the first two lower-lying electronic levels in double quantum wire. The wire system represented by a symmetric, double quartic-well confinement potential is subjected to a perpendicular magnetic field. The analytical expressions of the linear and third-order nonlinear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism and iterative scheme. Optical properties are investigated as a function of structural parameter, magnetic field, Rashba spin-orbit interaction and photon energies. Numerical results reveal that competing effects between spin-orbit interaction and magnetic field modify strongly the optical properties and can be altered by these parameters.

  2. Zeeman effects on the tunneling spectra of a ferromagnetic d-wave superconductor in contact with a quantum wire

    NASA Astrophysics Data System (ADS)

    Emamipour, Hamidreza; Mehrabzad, Narges

    2016-07-01

    We study tunneling conductance in a quantum wire-insulator-ferromagnetic d-wave superconductor junction. The results show that exchange field of superconductor has a strong impact on tunneling spectra depending on the junction parameters. We have found a gap like structure in the tunneling limit when we have an interface normal to the (100) axis of superconductor. In the case of (110) axis of superconductor, there is not any zero- bias conductance peaks in tunneling spectra. For a metallic junction the dips disappear.

  3. Spin texturing in quantum wires with Rashba and Dresselhaus spin-orbit interactions and in-plane magnetic field

    NASA Astrophysics Data System (ADS)

    B, Gisi; S, Sakiroglu; İ, Sokmen

    2016-01-01

    In this work, we investigate the effects of interplay of spin-orbit interaction and in-plane magnetic fields on the electronic structure and spin texturing of parabolically confined quantum wire. Numerical results reveal that the competing effects between Rashba and Dresselhaus spin-orbit interactions and the external magnetic field lead to a complicated energy spectrum. We find that the spin texturing owing to the coupling between subbands can be modified by the strength of spin-orbit couplings as well as the magnitude and the orientation angle of the external magnetic field.

  4. NMR response of nuclear-spin helix in quantum wires with hyperfine and spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Stano, Peter; Loss, Daniel

    2014-11-01

    We calculate the nuclear magnetic resonance (NMR) response of a quantum wire where at low temperature a self-sustained electron-nuclear spin order is created. Our model includes the electron mediated Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange, electron spin-orbit interactions, nuclear dipolar interactions, and the static and oscillating NMR fields, all of which play an essential role. The paramagnet to helimagnet transition in the nuclear system is reflected in an unusual response: it absorbs at a frequency given by the internal RKKY exchange field, rather than the external static field, whereas the latter leads to a splitting of the resonance peak.

  5. A finite-difference technique for computation of electron states in core-shell quantum wires of different configurations

    NASA Astrophysics Data System (ADS)

    Deyasi, Arpan; Bhattacharyya, S.; Das, N. R.

    2014-06-01

    In this paper, electron energies in core-shell quantum wires (CSQW) of rectangular, triangular, T-shaped, H-shaped and circular geometries are numerically computed by solving a time-independent Schrödinger equation using the finite difference technique. Computation is performed for both normal and inverted structures of CSQW, taking into account Kane-type nonparabolicity, conduction band discontinuity, and effective mass mismatch at the hetero-interface. Sparse, structured Hamiltonian matrices are produced for the calculation of energy eigenvalues and intersubband transition energies. Comparative study reveals that for a given core width of normal CSQW, the eigenenergy is the highest for the triangular geometry and the lowest for the rectangular geometry. For inverted CSQW, the ground-state energy of the triangular wire decreases with increasing core width, unlike other geometries. Studies on the intersubband transition energy show that for triangular and H-shaped inverted CSQW, it varies in a direction opposite to that of other inverted structures. Suitable tailoring of wire dimensions indicates the possibility of tuning the transition energy for photonic applications.

  6. M-plane core-shell InGaN/GaN multiple-quantum-wells on GaN wires for electroluminescent devices.

    PubMed

    Koester, Robert; Hwang, Jun-Seok; Salomon, Damien; Chen, Xiaojun; Bougerol, Catherine; Barnes, Jean-Paul; Dang, Daniel Le Si; Rigutti, Lorenzo; de Luna Bugallo, Andres; Jacopin, Gwénolé; Tchernycheva, Maria; Durand, Christophe; Eymery, Joël

    2011-11-01

    Nonpolar InGaN/GaN multiple quantum wells (MQWs) grown on the {11-00} sidewalls of c-axis GaN wires have been grown by organometallic vapor phase epitaxy on c-sapphire substrates. The structural properties of single wires are studied in detail by scanning transmission electron microscopy and in a more original way by secondary ion mass spectroscopy to quantify defects, thickness (1-8 nm) and In-composition in the wells (∼16%). The core-shell MQW light emission characteristics (390-420 nm at 5 K) were investigated by cathodo- and photoluminescence demonstrating the absence of the quantum Stark effect as expected due to the nonpolar orientation. Finally, these radial nonpolar quantum wells were used in room-temperature single-wire electroluminescent devices emitting at 392 nm by exploiting sidewall emission. PMID:21967509

  7. Majorana modes and Kondo effect in a quantum dot attached to a topological superconducting wire (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Vernek, Edson; Ruiz-Tijerina, David; da Silva, Luis D.; Egues, José Carlos

    2015-09-01

    Quantum dot attached to topological wires has become an interesting setup to study Majorana bound state in condensed matter[1]. One of the major advantage of using a quantum dot for this purpose is that it provides a suitable manner to study the interplay between Majorana bound states and the Kondo effect. Recently we have shown that a non-interacting quantum dot side-connected to a 1D topological superconductor and to metallic normal leads can sustain a Majorana mode even when the dot is empty. This is due to the Majorana bound state of the wire leaking into the quantum dot. Now we investigate the system for the case in which the quantum dot is interacting[3]. We explore the signatures of a Majorana zero-mode leaking into the quantum dot, using a recursive Green's function approach. We then study the Kondo regime using numerical renormalization group calculations. In this regime, we show that a "0.5" contribution to the conductance appears in system due to the presence of the Majorana mode, and that it persists for a wide range of the dot parameters. In the particle-hole symmetric point, in which the Kondo effect is more robust, the total conductance reaches 3e^2/2h, clearly indicating the coexistence of a Majorana mode and the Kondo resonance in the dot. However, the Kondo effect is suppressed by a gate voltage that detunes the dot from its particle-hole symmetric point as well as by a Zeeman field. The Majorana mode, on the other hand, is almost insensitive to both of them. We show that the zero-bias conductance as a function of the magnetic field follows a well-known universal curve. This can be observed experimentally, and we propose that this universality followed by a persistent conductance of 0.5,e^2/h are evidence for the presence of Majorana-Kondo physics. This work is supported by the Brazilians agencies FAPESP, CNPq and FAPEMIG. [1] A. Y. Kitaev, Ann.Phys. {bf 303}, 2 (2003). [2] E. Vernek, P.H. Penteado, A. C. Seridonio, J. C. Egues, Phys. Rev. B {bf

  8. Growing InGaAs quasi-quantum wires inside semi-rhombic shaped planar InP nanowires on exact (001) silicon

    NASA Astrophysics Data System (ADS)

    Han, Yu; Li, Qiang; Chang, Shih-Pang; Hsu, Wen-Da; Lau, Kei May

    2016-06-01

    We report InGaAs quasi-quantum wires embedded in planar InP nanowires grown on (001) silicon emitting in the 1550 nm communication band. An array of highly ordered InP nanowire with semi-rhombic cross-section was obtained in pre-defined silicon V-grooves through selective-area hetero-epitaxy. The 8% lattice mismatch between InP and Si was accommodated by an ultra-thin stacking disordered InP/GaAs nucleation layer. X-ray diffraction and transmission electron microscope characterizations suggest excellent crystalline quality of the nanowires. By exploiting the morphological evolution of the InP and a self-limiting growth process in the V-grooves, we grew embedded InGaAs quantum-wells and quasi-quantum-wires with tunable shape and position. Room temperature analysis reveals substantially improved photoluminescence in the quasi-quantum wires as compared to the quantum-well reference, due to the reduced intrusion defects and enhanced quantum confinement. These results show great promise for integration of III-V based long wavelength nanowire lasers on the well-established (001) Si platform.

  9. Band structure of a three-dimensional topological insulator quantum wire in the presence of a magnetic field

    NASA Astrophysics Data System (ADS)

    Liu, Zhe; Jiang, Liwei; Zheng, Yisong

    2016-07-01

    By means of a numerical diagonalization approach, we calculate the electronic structure of a three-dimensional topological insulator (3DTI) quantum wire (QW) in the presence of a magnetic field. The QW can be viewed as a 3DTI film with lateral surfaces, when its rectangular cross section has a large aspect ratio. Our calculation indicates that nonchiral edge states emerge because of the confined states at the lateral surfaces. These states completely cover the valence band region among the Landau levels, which reasonably account for the absence of the ν <-1 quantum Hall effect in the relevant experimental works. In an ultrathin 3DTI film, inversion between the electron-type and hole-type bands occurs, which leads to the so-called pseudo-spin Hall effect. In a 3DTI QW with a square cross section, a tilting magnetic field can establish well-defined Landau levels in all four surfaces. In such a case, the quantum Hall edge states are localized at the square corners, characterized by the linearly crossing one-dimensional band profile. And they can be shifted between the adjacent corners by simply rotating the magnetic field.

  10. Band structure of a three-dimensional topological insulator quantum wire in the presence of a magnetic field.

    PubMed

    Liu, Zhe; Jiang, Liwei; Zheng, Yisong

    2016-07-13

    By means of a numerical diagonalization approach, we calculate the electronic structure of a three-dimensional topological insulator (3DTI) quantum wire (QW) in the presence of a magnetic field. The QW can be viewed as a 3DTI film with lateral surfaces, when its rectangular cross section has a large aspect ratio. Our calculation indicates that nonchiral edge states emerge because of the confined states at the lateral surfaces. These states completely cover the valence band region among the Landau levels, which reasonably account for the absence of the [Formula: see text] quantum Hall effect in the relevant experimental works. In an ultrathin 3DTI film, inversion between the electron-type and hole-type bands occurs, which leads to the so-called pseudo-spin Hall effect. In a 3DTI QW with a square cross section, a tilting magnetic field can establish well-defined Landau levels in all four surfaces. In such a case, the quantum Hall edge states are localized at the square corners, characterized by the linearly crossing one-dimensional band profile. And they can be shifted between the adjacent corners by simply rotating the magnetic field. PMID:27195483

  11. Dependence of the Hall Coefficient on a length of rectangular quantum wires with infinitely high potential under the influence of a Laser Radiation

    NASA Astrophysics Data System (ADS)

    Thu Huong, Nguyen; Quang Bau, Nguyen; Hung, Le Thai; Hung, Dao Manh

    2016-06-01

    The Hall coefficient (HC) of a strong electromagnetic wave (EMW) caused by confined electrons in a rectangular quantum wire (RQW) is theoretically studied by using the quantum kinetic equation for electrons. The problem is considered in the case of electrons - acoustic phonons scattering. Wave function and energy spectrum in a RQW are different from those in a cylindrical quantum wire (CQW) or two dimensional systems (2D). Therefore analytical expressions for the HC in a RQW is obtained, different from CQW or 2D. Numerical calculations are carried out with a specific GaAs/GaAsAl RQW to show clearly the dependence of HC on a length Lx (Ly) RQW with different low temperature values. We can see that the length Lx (Ly) increases in value within the domain that HC increases. The HC reaches a peak before slightly decreases when the length Lx (Ly) continues going up. However, the HC depends on the radius and the length of CQW and wire size of RQW Lx and Ly at different values of temperatures; this is the fundamental difference between CQW and RQW. If the length Lx (Ly) continues to increase, the HC remains constant. It means that HC is no longer dependent on the length of quantum wires (This behavior is similar to the case of the independence of the HC on the length in bulk semiconductor).

  12. Quantum theory of the effect of grain boundaries on the electrical conductivity of thin films and wires

    NASA Astrophysics Data System (ADS)

    Moraga, Luis; Henriquez, Ricardo; Solis, Basilio

    2015-08-01

    We calculate the electrical conductivity of a metallic sample under the effects of distributed impurities and a random distribution of grain boundaries by means of a quantum mechanical procedure based on Kubo formula. Grain boundaries are represented either by a one-dimensional regular array of Dirac delta potentials (Mayadas and Shatzkes model) or by its three-dimensional extension (Szczyrbowski and Schmalzbauer model). We give formulas expressing the conductivity of bulk samples, thin films and thin wires of rectangular cross-sections in the case when the samples are bounded by perfectly flat surfaces. We find that, even in the absence of surface roughness, the conductivity in thin samples is reduced from its bulk value. If there are too many grain boundaries per unit length, or their scattering strength is high enough, there is a critical value Rc of the reflectivity R of an individual boundary such that the electrical conductivity vanishes for R >Rc. Also, the conductivity of thin wires shows a stepwise dependence on R. The effect of weak random variations in the strength or separation of the grain boundaries is computed by means of the method of correlation length. Finally, the resistivity of nanometric polycrystalline tungsten films reported in Choi et al. J. Appl. Phys. (2014) 115 104308 is tentatively analyzed by means of the present formalism.

  13. The quantum-mechanical basis of an extended Landau-Lifshitz-Gilbert equation for a current-carrying ferromagnetic wire.

    PubMed

    Edwards, D M; Wessely, O

    2009-04-01

    An extended Landau-Lifshitz-Gilbert (LLG) equation is introduced to describe the dynamics of inhomogeneous magnetization in a current-carrying wire. The coefficients of all the terms in this equation are calculated quantum-mechanically for a simple model which includes impurity scattering. This is done by comparing the energies and lifetimes of a spin wave calculated from the LLG equation and from the explicit model. Two terms are of particular importance since they describe non-adiabatic spin-transfer torque and damping processes which do not rely on spin-orbit coupling. It is shown that these terms may have a significant influence on the velocity of a current-driven domain wall and they become dominant in the case of a narrow wall. PMID:21825349

  14. The quantum-mechanical basis of an extended Landau-Lifshitz-Gilbert equation for a current-carrying ferromagnetic wire

    NASA Astrophysics Data System (ADS)

    Edwards, D. M.; Wessely, O.

    2009-04-01

    An extended Landau-Lifshitz-Gilbert (LLG) equation is introduced to describe the dynamics of inhomogeneous magnetization in a current-carrying wire. The coefficients of all the terms in this equation are calculated quantum-mechanically for a simple model which includes impurity scattering. This is done by comparing the energies and lifetimes of a spin wave calculated from the LLG equation and from the explicit model. Two terms are of particular importance since they describe non-adiabatic spin-transfer torque and damping processes which do not rely on spin-orbit coupling. It is shown that these terms may have a significant influence on the velocity of a current-driven domain wall and they become dominant in the case of a narrow wall.

  15. Characterisation of multi-layer InAs/InP quantum wires by surface photovoltage and photoluminescence spectroscopies

    NASA Astrophysics Data System (ADS)

    Ivanov, Ts; Donchev, V.; Angelova, T.; Cros, A.; Cantarero, A.; Shtinkov, N.; Borissov, K.; Fuster, D.; González, Y.; González, L.

    2010-11-01

    The optical properties of multi-layer InAs/InP quantum wires (QWRs) with two different spacer thicknesses have been investigated by means of room temperature surface photovoltage (SPV) and photoluminescence (PL) spectroscopies, combined with empirical tight binding electronic structure calculations and structural data. The SPV and PL spectra reveal several features, which energy positions are in good agreement. They have been ascribed to excitonic transitions, which take place in the QWR families with heights differing by an integer number of monolayers. Comparing the experimental results with the theoretical ones, we have estimated the QWR family heights and the average atomic concentration of phosphorus in the QWRs. From the simultaneous analysis of the SPV amplitude and phase spectra, based on our vector model for SPV signal representation, a deeper understanding of the SPV results and of the mechanisms of carrier separation in the sample is obtained.

  16. Wurtzite GaAs Quantum Wires: One-Dimensional Subband Formation.

    PubMed

    Vainorius, Neimantas; Lehmann, Sebastian; Gustafsson, Anders; Samuelson, Lars; Dick, Kimberly A; Pistol, Mats-Erik

    2016-04-13

    It is of contemporary interest to fabricate nanowires having quantum confinement and one-dimensional subband formation. This is due to a host of applications, for example, in optical devices, and in quantum optics. We have here fabricated and optically investigated narrow, down to 10 nm diameter, wurtzite GaAs nanowires which show strong quantum confinement and the formation of one-dimensional subbands. The fabrication was bottom up and in one step using the vapor-liquid-solid growth mechanism. Combining photoluminescence excitation spectroscopy with transmission electron microscopy on the same individual nanowires, we were able to extract the effective masses of the electrons in the two lowest conduction bands as well as the effective masses of the holes in the two highest valence bands. Our results, combined with earlier demonstrations of thin crystal phase nanodots in GaAs, set the stage for the fabrication of crystal phase quantum dots having full three-dimensional confinement. PMID:27004550

  17. Quantum wire and magnetic control of a spin qubit in the Landau–Zener–Stückelberg interferometry transition

    NASA Astrophysics Data System (ADS)

    Danga, J. E.; Kenfack, S. C.; Fai, L. C.

    2016-05-01

    Landau–Zener–Stückelberg interferometry is extensively investigated in a 3D heterostructure magnetic quantum wire. Local magnetic fields are used to coherently manipulate and control a qubit’s quantum state. For our numerical calculations, a parabolic confinement is assumed. Energy eigenvalues, non-adiabatic and adiabatic transition probabilities are calculated from the diabatic and adiabatic bases for two-level systems. Here, we show that the spatial crossing between interspin levels becomes a spatial anticrossing if the two spin states are coupled by external fields, and that consequently, due to the spin dependence of the harmonic confinement, it will undergo Landau–Zener–Stückelberg interference. It is shown that the system undergoes nonadiabatic Landau–Zener dynamics for a strong confinement in a strong external field, whereas a weak external field induces adiabatic Landau–Zener transition dynamics. Our system allows the coupling strength between the level states at the anti(crossing) point to be modulated. This system allows one to tune the wire’s parabolic confinement potential using experimentally accessible parameters.

  18. On Improving Accuracy of Finite-Element Solutions of the Effective-Mass Schrödinger Equation for Interdiffused Quantum Wells and Quantum Wires

    NASA Astrophysics Data System (ADS)

    Topalović, D. B.; Arsoski, V. V.; Pavlović, S.; Čukarić, N. A.; Tadić, M. Ž.; Peeters, F. M.

    2016-01-01

    We use the Galerkin approach and the finite-element method to numerically solve the effective-mass Schrödinger equation. The accuracy of the solution is explored as it varies with the range of the numerical domain. The model potentials are those of interdiffused semiconductor quantum wells and axially symmetric quantum wires. Also, the model of a linear harmonic oscillator is considered for comparison reasons. It is demonstrated that the absolute error of the electron ground state energy level exhibits a minimum at a certain domain range, which is thus considered to be optimal. This range is found to depend on the number of mesh nodes N approximately as α0 logeα1(α2N), where the values of the constants α0, α1, and α2 are determined by fitting the numerical data. And the optimal range is found to be a weak function of the diffusion length. Moreover, it was demonstrated that a domain range adaptation to the optimal value leads to substantial improvement of accuracy of the solution of the Schrödinger equation. Supported by the Ministry of Education, Science, and Technological Development of Serbia and the Flemish fund for Scientific Research (FWO Vlaanderen)

  19. Optical properties of double quantum wires under the combined effect of spin-orbit interaction and in-plane magnetic field

    NASA Astrophysics Data System (ADS)

    Sakiroglu, S.; Gisi, B.; Karaaslan, Y.; Kasapoglu, E.; Sari, H.; Sokmen, I.

    2016-07-01

    In this work, we investigate the intersubband optical absorption coefficients and refractive index changes for transitions between the lower-lying electronic levels of double quantum wires formed by a symmetric, double quartic-well potential. The system is subjected to an external in-plane magnetic field and Rashba and Dresselhaus spin-orbit couplings are taken into account. The analytical expressions of the linear and nonlinear absorption coefficients and refractive index changes are obtained by using the compact density-matrix approach and iterative method. The dependence of the optical characteristics on the magnetic field, spin-orbit interactions, quantum wire radius, structural parameter and photon energies has been examined. Numerical results exhibit that the optical properties are considerably sensitive to the strength and orientation of magnetic field as well as to the spin-orbit couplings and thus can be controlled by these parameters.

  20. Quantum Wire Fabrication by E-Beam Elithography Using High-Resolution and High-Sensitivity E-Beam Resist ZEP-520

    NASA Astrophysics Data System (ADS)

    Nishida, Toshio; Notomi, Masaya; Iga, Ryuzo; Tamamura, Toshiaki

    1992-12-01

    We have evaluated the resolution of the positive electron-beam (E-beam) resist ZEP-520 using finely focused E-beam exposure for the application of quantum wire fabrication in a large area. Compared with the poly-methylmethacrylate (PMMA) resist conventionally used for nanofabrication, ZEP resist shows almost the same resolution under sensitivity improvement of one order of magnitude, and the throughput is increased by a factor of more than 100 by introducing a highly bright Zr/O/W thermal field emitter as an E-beam source. Other excellent performance characteristics, such as high dry-etching durability and process stability, allow us to apply ZEP resist for larger-area, high-density quantum wire fabrication. By both wet chemical etching and dry-etching combined with CBE selective growth, InGaAs nanostructures as small as 15 nm can be obtained with a pitch of 70 nm over several hundred μm squares.

  1. Localized states in a semiconductor quantum ring with a tangent wire

    SciTech Connect

    Yang, F.; Wu, M. W.

    2014-08-28

    We extend a special kind of localized state trapped at the intersection due to the geometric confinement, first proposed in a three-terminal-opening T-shaped structure [L. A. Openov, Europhys. Lett. 55, 539 (2001)], into a ring geometry with a tangent connection to the wire. In this ring geometry, there exists one localized state trapped at the intersection with energy lying inside the lowest subband. We systematically study this localized state and the resulting Fano-type interference due to the coupling between this localized state and the continuum ones. It is found that the increase of inner radius of the ring weakens the coupling to the continuum ones and the asymmetric Fano dip fades away. A wide energy gap in transmission appears due to the interplay of two types of antiresonances: the Fano-type antiresonance and the structure antiresonance. The size of this antiresonance gap can be modulated by adjusting the magnetic flux. Moreover, a large transmission amplitude can be obtained in the same gap area. The strong robustness of the antiresonance gap is demonstrated and shows the feasibility of the proposed geometry for a real application.

  2. Nature of the many-body excitations in a quantum wire: Theory and experiment

    NASA Astrophysics Data System (ADS)

    Tsyplyatyev, O.; Schofield, A. J.; Jin, Y.; Moreno, M.; Tan, W. K.; Anirban, A. S.; Ford, C. J. B.; Griffiths, J. P.; Farrer, I.; Jones, G. A. C.; Ritchie, D. A.

    2016-02-01

    The natural excitations of an interacting one-dimensional system at low energy are the hydrodynamic modes of a Luttinger liquid, protected by the Lorentz invariance of the linear dispersion. We show that beyond low energies, where the quadratic dispersion reduces the symmetry to Galilean, the main character of the many-body excitations changes into a hierarchy: calculations of dynamic correlation functions for fermions (without spin) show that the spectral weights of the excitations are proportional to powers of R2/L2 , where R is a length-scale related to interactions and L is the system length. Thus only small numbers of excitations carry the principal spectral power in representative regions on the energy-momentum planes. We have analyzed the spectral function in detail and have shown that the first-level (strongest) excitations form a mode with parabolic dispersion, like that of a renormalized single particle. The second-level excitations produce a singular power-law line shape to the first-level mode and multiple power laws at the spectral edge. We have illustrated a crossover to a Luttinger liquid at low energy by calculating the local density of states through all energy scales: from linear to nonlinear, and to above the chemical potential energies. In order to test this model, we have carried out experiments to measure the momentum-resolved tunneling of electrons (fermions with spin) from/to a wire formed within a GaAs heterostructure. We observe a well-resolved spin-charge separation at low energy with appreciable interaction strength and only a parabolic dispersion of the first-level mode at higher energies. We find a structure resembling the second-level excitations, which dies away rapidly at high momentum in line with the theoretical predictions here.

  3. Self-aligned silicon quantum wires on Ag(1 1 0)

    NASA Astrophysics Data System (ADS)

    Leandri, C.; Lay, G. Le; Aufray, B.; Girardeaux, C.; Avila, J.; Dávila, M. E.; Asensio, M. C.; Ottaviani, C.; Cricenti, A.

    2005-01-01

    Upon deposition of silicon onto the (1 1 0) surface of a silver crystal we have grown massively parallel one-dimensional Si nanowires. They are imaged in scanning tunnelling microscopy as straight, high aspect ratio, nanostructures, all with the same characteristic width of 16 Å, perfectly aligned along the atomic troughs of the bare surface. Low energy electron diffraction confirms the massively parallel assembly of these self-organized nanowires. Photoemission reveals striking quantized states dispersing only along the length of the nanowires, and extremely sharp, two-components, Si 2p core levels. This demonstrates that in the large ensemble each individual nanowire is a well-defined quantum object comprising only two distinct silicon atomic environments. We suggest that this self-assembled array of highly perfect Si nanowires provides a simple, atomically precise, novel template that may impact a wide range of applications.

  4. Bloch Oscillations and Saturation to a Steady-State Current of an Electron Gas in a Modulated Quantum-Wire Superlattice in a High Electric Field

    NASA Astrophysics Data System (ADS)

    Lyo, S. K.; Huang, D.; Pan, W.

    2008-03-01

    We present rigorous theoretical results for the time-dependent and steady-state nonlinear DC current of an electron gas in a periodically modulated one-dimensional semiconductor quantum wire in a high electric field. The theoretical model considers electron-phonon and impurity scattering microscopically in the degenerate and the nondegenerate regime in a tight-binding model. The time-dependent oscillatory and saturation (i.e., steady-state) currents are studied as a function of the field, the radius of the wire, the elastic scattering rate, the lattice period, and the temperature. The radius controls the inelastic scattering rate. The distinctive roles of elastic and inelastic scattering for the current are contrasted and examined. Finally, we compare the results with those from an exact analytic formalism based on a relaxation-time model.

  5. Spin-orbit coupling in GaxIn1-xAs/InP two-dimensional electron gases and quantum wire structures

    NASA Astrophysics Data System (ADS)

    Schäpers, Th; Guzenko, V. A.; Bringer, A.; Akabori, M.; Hagedorn, M.; Hardtdegen, H.

    2009-06-01

    In this work, the effect of spin-orbit coupling in two-dimensional electron gases and quantum wire structures is discussed. First, the theoretical framework is introduced including spin-orbit coupling due to structural inversion asymmetry, the so-called Rashba effect, as well as the Dresselhaus term. The latter originates from bulk inversion asymmetry. With regard to wire structures, special attention is devoted to the influence of the particular shape of the confinement potential on the energy spectrum. As a model system GaxIn1-xAs/InP heterostructures are chosen, where different thicknesses of the strained Ga0.23In0.77As channel layer were introduced, in order to adjust the strength of the spin-orbit coupling. Hall bar structures as well as sets of identical wires with different widths were prepared. In two-dimensional electron gases, the strength of the spin-orbit coupling was extracted by analyzing the characteristic beating pattern in the Shubnikov-de Haas oscillations. In addition, the weak antilocalization was utilized to obtain information on the spin-orbit coupling. It is shown that for decreasing width of the strained layer the Rashba effect, which dominates in our layer systems, is increased. This behavior is attributed to the larger interface contribution if the electron wavefunction is strongly confined. The measurements on the wire structures revealed a transition from weak antilocalization to weak localization if the wire width is decreased. This effect is attributed to an enhanced spin diffusion length for strongly confined systems.

  6. Circular photogalvanic effect induced by near-infrared radiation in InAs quantum wires patterned quasi-two-dimensional electron system

    NASA Astrophysics Data System (ADS)

    Jiang, Chongyun; Chen, Yonghai; Ma, Hui; Yu, Jinling; Liu, Yu

    2011-06-01

    In this letter we investigated the InAs/InAlAs quantum wires (QWRs) superlattice by optically exciting the structure with near-infrared radiation. By varying the helicity of the radiation at room temperature we observed the circular photogalvanic effect related to the C2v symmetry of the structure, which could be attributed to the formation of a quasi-two-dimensional system underlying in the vicinity of the QWRs pattern. The ratio of Rashba and Dresselhaus terms shows an evolution of the spin-orbit interaction in quasi-two-dimensional structure with the QWR layer deposition thickness.

  7. Circular photogalvanic effect induced by near-infrared radiation in InAs quantum wires patterned quasi-two-dimensional electron system

    SciTech Connect

    Jiang Chongyun; Chen Yonghai; Ma Hui; Yu Jinling; Liu Yu

    2011-06-06

    In this letter we investigated the InAs/InAlAs quantum wires (QWRs) superlattice by optically exciting the structure with near-infrared radiation. By varying the helicity of the radiation at room temperature we observed the circular photogalvanic effect related to the C{sub 2v} symmetry of the structure, which could be attributed to the formation of a quasi-two-dimensional system underlying in the vicinity of the QWRs pattern. The ratio of Rashba and Dresselhaus terms shows an evolution of the spin-orbit interaction in quasi-two-dimensional structure with the QWR layer deposition thickness.

  8. High characteristic temperature ( To=322 K near room temperature) of V-grooved AlGaAs-GaAs quantum wire diode lasers

    NASA Astrophysics Data System (ADS)

    Kim, T. G.; Ogura, M.

    2000-01-01

    High characteristic temperature ( To=˜322 K) is demonstrated near room-temperature with V-grooved, AlGaAs-GaAs multiple quantum wire (QWR) lasers grown by flow rate modulation epitaxy. The wavelength tuning rate of temperature Δλ/Δ T measured for 300 μm long uncoated lasers is ˜0.19 nm/°C and that of injection current Δ λ/Δ I is extremely small, in between 0.02 and 0.03 nm/mA in the temperature range 10 to 70°C.

  9. Basic Wiring.

    ERIC Educational Resources Information Center

    Kaltwasser, Stan; And Others

    This module is the first in a series of three wiring publications; it serves as the foundation for students enrolled in a wiring program. It is a prerequisite to either "Residential Wiring" or "Commercial and Industrial Wiring." The module contains 16 instructional units that cover the following topics: occupational introduction; general safety;…

  10. Influence of composition and substrate miscut on the evolution of (105)-terminated in-plane Si{sub 1−x}Ge{sub x} quantum wires on Si(001)

    SciTech Connect

    Watzinger, H.; Glaser, M.; Zhang, J. J.; Daruka, I.; Schäffler, F.

    2014-07-01

    Isolated in-plane wires on Si(001) are promising nanostructures for quantum transport applications. They can be fabricated in a catalyst-free process by thermal annealing of self-organized Si{sub 1−x}Ge{sub x} hut clusters. Here, we report on the influence of composition and small substrate miscuts on the unilateral wire growth during annealing at 570 °C. The addition of up to 20% of Si mainly affects the growth kinetics in the presence of energetically favorable sinks for diffusing Ge atoms, but does not significantly change the wire base width. For the investigated substrate miscuts of <0.12°, we find geometry-induced wire tapering, but no strong influence on the wire lengths. Miscuts <0.02° lead to almost perfect quantum wires terminated by virtually step-free (105) and (001) facets over lengths of several 100 nm. Generally, the investigated Si{sub 1−x}Ge{sub x} wires are metastable: Annealing at ≥600 °C under otherwise identical conditions leads to the well-known coexistence of Si{sub 1−x}Ge{sub x} pyramids and domes.

  11. Donor impurity states and related terahertz range nonlinear optical response in GaN cylindrical quantum wires: Effects of external electric and magnetic fields

    SciTech Connect

    Correa, J. D.; Mora-Ramos, M. E.; Duque, C. A.

    2014-06-07

    We report a study on the optical absorption coefficient associated to hydrogenic impurity interstate transitions in zinc-blende GaN quantum wires of cylindrical shape taking into account the effects of externally applied static electric and magnetic fields. The electron states emerge within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement and external field effects. The nonlinear optical absorption is calculated using a recently derived expression for the dielectric susceptibility, obtained via a nonperturbative solution of the density-matrix Bloch equation. Our results show that this treatment eliminates not only the intensity-dependent bleaching effect but also the change in sign of the nonlinear contribution due to the combined effect of asymmetric impurity location and the applied electric field.

  12. Doping-induced stability in vanadium-doped ZnO quantum well wires (QWW): Combination of DFT calculations within experimental measurements

    NASA Astrophysics Data System (ADS)

    Yumak, A.; Goumri-Said, Souraya; Khan, Wilayat; Boubaker, Karem; Petkova, P.

    2016-07-01

    ZnO quantum well wires (QWW) have grown on glass substrates by an inexpensive, simplified and enhanced spray pyrolysis technique then doped by Vanadium. The effects of V-doping on the structural, morphological and optical properties of the QWW were investigated experimentally and theoretically. The accuracy of control can be achieved on functional performance by adjusting vanadium doping extent. The incorporation of Vanadium in ZnO-QWW induced the formation of band tailing in states. The interactions with phonons and the presence of a tail absorption profile are following the empirical Urbach law. The electronic structure using density functional theory have shown the changes induced by vanadium doping in ZnO-QWW, where the phonon band structure and density of states were reported. The DFT results showed a good agreement with the lattice compatibility theory as well as with the experimental results.

  13. Self-assembled InAs quantum wire lasers on (001)InP at 1.6 {mu}m

    SciTech Connect

    Suarez, F.; Fuster, D.; Gonzalez, L.; Gonzalez, Y.; Garcia, J. M.; Dotor, M. L.

    2006-08-28

    In this work, the authors present results on the growth by atomic layer molecular beam epitaxy and characterization of lasers with one and three stacked layers of InAs quantum wires (QWRs) as active zone and aluminum-free waveguides on (001) InP substrates. The separated confinement heterostructure consists of n-p InP claddings and a waveguide formed by short period superlattices of (InP){sub 5}/(GaInAs){sub 4} lattice matched to the InP substrate. The optimum growth conditions (substrate temperature and As and P pressures) have been determined to obtain waveguides with a flat surface in order to get a uniform QWR distribution. Lasing emission is observed at a wavelength of {approx}1.66 {mu}m up to 270 K from 15x3000 {mu}m{sup 2} devices, with a threshold current density at that temperature of 2 kA/cm{sup 2}.

  14. Donor impurity states and related terahertz range nonlinear optical response in GaN cylindrical quantum wires: Effects of external electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Correa, J. D.; Mora-Ramos, M. E.; Duque, C. A.

    2014-06-01

    We report a study on the optical absorption coefficient associated to hydrogenic impurity interstate transitions in zinc-blende GaN quantum wires of cylindrical shape taking into account the effects of externally applied static electric and magnetic fields. The electron states emerge within the effective mass approximation, via the exact diagonalization of the donor-impurity Hamiltonian with parabolic confinement and external field effects. The nonlinear optical absorption is calculated using a recently derived expression for the dielectric susceptibility, obtained via a nonperturbative solution of the density-matrix Bloch equation. Our results show that this treatment eliminates not only the intensity-dependent bleaching effect but also the change in sign of the nonlinear contribution due to the combined effect of asymmetric impurity location and the applied electric field.

  15. Residential Wiring.

    ERIC Educational Resources Information Center

    Taylor, Mark

    The second in a series of three curriculum packages on wiring, these materials for a five-unit course were developed to prepare postsecondary students for entry-level employment in the residential wiring trade. The five units are: (1) blueprint reading and load calculations; (2) rough-in; (3) service; (4) trim out and troubleshooting; and (5) load…

  16. Wire chamber

    DOEpatents

    Atac, Muzaffer

    1989-01-01

    A wire chamber or proportional counter device, such as Geiger-Mueller tube or drift chamber, improved with a gas mixture providing a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor.

  17. Wire Wise.

    ERIC Educational Resources Information Center

    Swanquist, Barry

    1998-01-01

    Discusses how today's technology is encouraging schools to invest in furnishings that are adaptable to computer use and telecommunications access. Explores issues concerning modularity, wiring management, ergonomics, durability, price, and aesthetics. (GR)

  18. No Wires.

    ERIC Educational Resources Information Center

    DeLoughry, Thomas J.

    1995-01-01

    The University of California at Santa Cruz has completed a successful test of a wireless computer network that would enable students and professors to get on line from anywhere on campus. The network, linked by radio waves, could save millions of dollars in campus wiring costs and would better meet student and faculty information needs. (MSE)

  19. Precision wire feeder for small diameter wire

    DOEpatents

    Brandon, E.D.; Hooper, F.M.; Reichenbach, M.L.

    1992-08-11

    A device for feeding small diameter wire having a diameter less than 0.04 mm (16 mil) to a welding station includes a driving wheel for controllably applying a non-deforming driving force to the wire to move the free end of the wire towards the welding station; and a tension device such as a torque motor for constantly applying a reverse force to the wire in opposition to the driving force to keep the wire taut. 1 figure.

  20. Precision wire feeder for small diameter wire

    DOEpatents

    Brandon, Eldon D.; Hooper, Frederick M.; Reichenbach, Marvin L.

    1992-01-01

    A device for feeding small diameter wire having a diameter less than 0.04 mm (16 mil) to a welding station includes a driving wheel for controllably applying a non-deforming driving force to the wire to move the free end of the wire towards the welding station; and a tension device such as a torque motor for constantly applying a reverse force to the wire in opposition to the driving force to keep the wire taut.

  1. Nonuniversal metallic behavior of superconducting wires

    SciTech Connect

    Renn, S.R.; Duan, J.

    1996-04-01

    We calculate the low temperature resistance of a narrow superconducting wire associated with quantum mechanical phase slippage. Particular attention is payed to the effects of Coulomb interactions. Using a renormalization group approach, we obtain the temperature dependent resistance. The results show that, near the superconductor-insulator transition, the wire displays quasimetallic behavior characterized by a small but finite low temperature resistance. {copyright} {ital 1996 The American Physical Society.}

  2. Windows: Life after Wire.

    ERIC Educational Resources Information Center

    Razwick, Jerry

    2003-01-01

    Although wired glass is extremely common in school buildings, the International Building Code adopted new standards that eliminate the use of traditional wired glass in K-12 schools, daycare centers, and athletic facilities. Wired glass breaks easily, and the wires can cause significant injuries by forming dangerous snags when the glass breaks.…

  3. Stretched Wire Mechanics

    SciTech Connect

    Bowden, Gordon; /SLAC

    2005-09-06

    Stretched wires are beginning to play an important role in the alignment of accelerators and synchrotron light sources. Stretched wires are proposed for the alignment of the 130 meter long LCLS undulator. Wire position technology has reached sub-micron resolution yet analyses of perturbations to wire straightness are hard to find. This paper considers possible deviations of stretched wire from the simple 2-dimensional catenary form.

  4. Concealed wire tracing apparatus

    DOEpatents

    Kronberg, James W.

    1994-01-01

    An apparatus and method that combines a signal generator and a passive signal receiver to detect and record the path of partially or completely concealed electrical wiring without disturbing the concealing surface. The signal generator applies a series of electrical pulses to the selected wiring of interest. The applied pulses create a magnetic field about the wiring that can be detected by a coil contained within the signal receiver. An audible output connected to the receiver and driven by the coil reflects the receivers position with respect to the wiring. The receivers audible signal is strongest when the receiver is directly above the wiring and the long axis of the receivers coil is parallel to the wiring. A marking means is mounted on the receiver to mark the location of the wiring as the receiver is directed over the wiring's concealing surface. Numerous marks made on various locations of the concealing surface will trace the path of the wiring of interest.

  5. Wire Test Grip Fixture

    NASA Technical Reports Server (NTRS)

    Burke, Christopher S.

    2011-01-01

    Wire-testing issues, such as the gripping strains imposed on the wire, play a critical role in obtaining clean data. In a standard test frame fitted with flat wedge grips, the gripping action alone creates stresses on the wire specimen that cause the wire to fail at the grip location. A new test frame, which is outfitted with a vacuum chamber, negated the use of any conventional commercially available wire test fixtures, as only 7 in. (17.8 cm) existed between the grip faces. An innovative grip fixture was designed to test thin gauge wire for a variety of applications in an existing Instron test frame outfitted with a vacuum chamber.

  6. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: 3.7 amps per wire, bundle of 15 or more wires, 70 C environment, and vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  7. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire; (2) bundle of 15 or more wires; (3) 70 C environment: and (4) vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  8. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1999-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 degree C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire (2) bundle of 15 or more wires (3) 70 C environment (4) vacuum of 10(exp -5) torr or less To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  9. Laser Wire Stripper

    NASA Technical Reports Server (NTRS)

    1983-01-01

    NASA-developed space shuttle technology is used in a laser wire stripper designed by Raytheon Company. Laser beams cut through insulation on a wire without damaging conductive metal, because laser radiation that melts plastic insulation is reflected by the metal. The laser process is fast, clean, precise and repeatable. It eliminates quality control problems and the expense of rejected wiring.

  10. Magnetism and spin-polarized transport in carbon atomic wires

    NASA Astrophysics Data System (ADS)

    Li, Z. Y.; Sheng, W.; Ning, Z. Y.; Zhang, Z. H.; Yang, Z. Q.; Guo, H.

    2009-09-01

    We report ab initio calculations of magnetic and spin-polarized quantum transport properties of pure and nitrogen-doped carbon atomic wires. For finite-sized wires with even number of carbon atoms, total magnetic moment of 2μB is found. On the other hand, wires with odd number atoms have no net magnetic moment. Doped with one or two nitrogen atom(s), the carbon atomic wires exhibit a spin-density-wave-like state. The magnetic properties can be rationalized through bonding patterns and unpaired states. When the wire is sandwiched between Au electrodes to form a transport junction, perfect spin filtering effect can be induced by slightly straining the wire.

  11. Electronic properties of quasi one-dimensional quantum wire models under equal coupling strength superpositions of Rashba and Dresselhaus spin-orbit interactions in the presence of an in-plane magnetic field

    SciTech Connect

    Papp, E.; Micu, C.; Racolta, D.

    2013-11-13

    In this paper one deals with the theoretical derivation of energy bands and of related wavefunctions characterizing quasi 1D semiconductor heterostructures, such as InAs quantum wire models. Such models get characterized this time by equal coupling strength superpositions of Rashba and Dresselhaus spin-orbit interactions of dimensionless magnitude a under the influence of in-plane magnetic fields of magnitude B. We found that the orientations of the field can be selected by virtue of symmetry requirements. For this purpose one resorts to spin conservations, but alternative conditions providing sensible simplifications of the energy-band formula can be reasonably accounted for. Besides the wavenumber k relying on the 1D electron, one deals with the spin-like s=±1 factors in the front of the square root term of the energy. Having obtained the spinorial wavefunction, opens the way to the derivation of spin precession effects. For this purpose one resorts to the projections of the wavenumber operator on complementary spin states. Such projections are responsible for related displacements proceeding along the Ox-axis. This results in a 2D rotation matrix providing both the precession angle as well as the precession axis.

  12. Electronic properties of quasi one-dimensional quantum wire models under equal coupling strength superpositions of Rashba and Dresselhaus spin-orbit interactions in the presence of an in-plane magnetic field

    NASA Astrophysics Data System (ADS)

    Papp, E.; Micu, C.; Racolta, D.

    2013-11-01

    In this paper one deals with the theoretical derivation of energy bands and of related wavefunctions characterizing quasi 1D semiconductor heterostructures, such as InAs quantum wire models. Such models get characterized this time by equal coupling strength superpositions of Rashba and Dresselhaus spin-orbit interactions of dimensionless magnitude a under the influence of in-plane magnetic fields of magnitude B. We found that the orientations of the field can be selected by virtue of symmetry requirements. For this purpose one resorts to spin conservations, but alternative conditions providing sensible simplifications of the energy-band formula can be reasonably accounted for. Besides the wavenumber k relying on the 1D electron, one deals with the spin-like s=±1 factors in the front of the square root term of the energy. Having obtained the spinorial wavefunction, opens the way to the derivation of spin precession effects. For this purpose one resorts to the projections of the wavenumber operator on complementary spin states. Such projections are responsible for related displacements proceeding along the Ox-axis. This results in a 2D rotation matrix providing both the precession angle as well as the precession axis.

  13. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 77.1802 Section 77.1802... Wires and Trolley Feeder Wires § 77.1802 Insulation of trolley wires, trolley feeder wires and...

  14. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 75.1003 Section 75.1003... Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires...

  15. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 75.1003 Section 75.1003... Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires...

  16. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 77.1802 Section 77.1802... Wires and Trolley Feeder Wires § 77.1802 Insulation of trolley wires, trolley feeder wires and...

  17. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 77.1802 Section 77.1802... Wires and Trolley Feeder Wires § 77.1802 Insulation of trolley wires, trolley feeder wires and...

  18. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 75.1003 Section 75.1003... Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires...

  19. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 75.1003 Section 75.1003... Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires...

  20. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 77.1802 Section 77.1802... Wires and Trolley Feeder Wires § 77.1802 Insulation of trolley wires, trolley feeder wires and...

  1. 30 CFR 77.1802 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 77.1802 Section 77.1802... Wires and Trolley Feeder Wires § 77.1802 Insulation of trolley wires, trolley feeder wires and...

  2. 30 CFR 75.1003 - Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires and trolley feeder wires. 75.1003 Section 75.1003... Insulation of trolley wires, trolley feeder wires and bare signal wires; guarding of trolley wires...

  3. Thin wire pointing method

    NASA Technical Reports Server (NTRS)

    Green, G.; Mattauch, R. J. (Inventor)

    1983-01-01

    A method is described for forming sharp tips on thin wires, in particular phosphor bronze wires of diameters such as one-thousandth inch used to contact micron size Schottky barrier diodes, which enables close control of tip shape and which avoids the use of highly toxic solutions. The method includes dipping an end of a phosphor bronze wire into a dilute solution of sulfamic acid and applying a current through the wire to electrochemically etch it. The humidity in the room is controlled to a level of less than 50%, and the voltage applied between the wire and another electrode in the solutions is a half wave rectified voltage. The current through the wire is monitored, and the process is stopped when the current falls to a predetermined low level.

  4. Sintered wire annode

    DOEpatents

    Falce, Louis R.; Ives, R. Lawrence

    2007-12-25

    A plurality of high atomic number wires are sintered together to form a porous rod that is parted into porous disks which will be used as x-ray targets. A thermally conductive material is introduced into the pores of the rod, and when a stream of electrons impinges on the sintered wire target and generates x-rays, the heat generated by the impinging x-rays is removed by the thermally conductive material interspersed in the pores of the wires.

  5. Zinc wired rebar

    SciTech Connect

    Zhang, X.G.; Hwang, J.

    1997-02-01

    A novel method for corrosion protection of rebar in concrete is reported wherein it is galvanically protected by attaching a zinc wire along its length. The self-corrosion and galvanic-corrosion loss of the zinc wire is dependent on the water/cement ratio, the size of the cathode, and the concrete cover thickness. The wire acts as a sacrificial anode when the rebar embedded in concrete is exposed to corrosive environments.

  6. Concealed wire tracing apparatus

    DOEpatents

    Kronberg, J.W.

    1994-05-31

    An apparatus and method that combines a signal generator and a passive signal receiver to detect and record the path of partially or completely concealed electrical wiring without disturbing the concealing surface is disclosed. The signal generator applies a series of electrical pulses to the selected wiring of interest. The applied pulses create a magnetic field about the wiring that can be detected by a coil contained within the signal receiver. An audible output connected to the receiver and driven by the coil reflects the receivers position with respect to the wiring. The receivers audible signal is strongest when the receiver is directly above the wiring and the long axis of the receivers coil is parallel to the wiring. A marking means is mounted on the receiver to mark the location of the wiring as the receiver is directed over the wiring's concealing surface. Numerous marks made on various locations of the concealing surface will trace the path of the wiring of interest. 4 figs.

  7. Weld Wire Investigation Summary

    SciTech Connect

    Cunningham, M.A.

    1999-03-22

    After GTA welding reservoir A production/process prove-in assemblies, X-ray examination detected a lack of sidewall fusion. After examining several possible causes, it was determined that the weld wire filler metal was responsible, particularly the wire cleaning process. The final conclusion was that the filler wire must be abrasively cleaned in a particular manner to perform as required. The abrasive process was incorporated into the wire material specification, ensuring consistency for all reservoir GTA welding at AlliedSignal Federal Manufacturing and Technologies (FM and T).

  8. Wire-inhomogeneity detector

    DOEpatents

    Gibson, G.H.; Smits, R.G.; Eberhard, P.H.

    1982-08-31

    A device for uncovering imperfections in electrical conducting wire, particularly superconducting wire, by detecting variations in eddy currents. Eddy currents effect the magnetic field in a gap of an inductor, contained in a modified commercial ferrite core, through which the wire being tested is passed. A small increase or decrease in the amount of conductive material, such as copper, in a fixed cross section of wire will unbalance a bridge used to measure the impedance of the inductor, tripping a detector and sounding an alarm.

  9. Quantum phase slip noise

    NASA Astrophysics Data System (ADS)

    Semenov, Andrew G.; Zaikin, Andrei D.

    2016-07-01

    Quantum phase slips (QPSs) generate voltage fluctuations in superconducting nanowires. Employing the Keldysh technique and making use of the phase-charge duality arguments, we develop a theory of QPS-induced voltage noise in such nanowires. We demonstrate that quantum tunneling of the magnetic flux quanta across the wire yields quantum shot noise which obeys Poisson statistics and is characterized by a power-law dependence of its spectrum SΩ on the external bias. In long wires, SΩ decreases with increasing frequency Ω and vanishes beyond a threshold value of Ω at T →0 . The quantum coherent nature of QPS noise yields nonmonotonous dependence of SΩ on T at small Ω .

  10. 1998 wire development workshop proceedings

    SciTech Connect

    1998-04-01

    This report consists of vugraphs of the presentations at the conference. The conference was divided into the following sessions: (1) First Generation Wire Development: Status and Issues; (2) First Generation Wire in Pre-Commercial Prototypes; (3) Second Generation Wire Development: Private Sector Progress and Issues; (4) Second Generation Wire Development: Federal Laboratories; and (5) Fundamental Research Issues for HTS Wire Development.

  11. VIEW SOUTHEASTBUILDING 4 NO. 1 WIRE MILL (1871) WIRE DRAWING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW SOUTHEAST-BUILDING 4 NO. 1 WIRE MILL (1871) WIRE DRAWING MACHINE - John A. Roebling's Sons Company & American Steel & Wire Company, South Broad, Clark, Elmer, Mott & Hudson Streets, Trenton, Mercer County, NJ

  12. Wire Array Photovoltaics

    NASA Astrophysics Data System (ADS)

    Turner-Evans, Dan

    Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use 100 times less material than conventional Si cells. The wires can be embedded in a transparent, flexible polymer to create a free-standing array that can be rolled up for easy installation in a variety of form factors. Furthermore, by incorporating multijunctions into the wire morphology, higher efficiencies can be achieved while taking advantage of the unique defect relaxation pathways afforded by the 3D wire geometry. The work in this thesis shepherded Si wires from undoped arrays to flexible, functional large area devices and laid the groundwork for multijunction wire array cells. Fabrication techniques were developed to turn intrinsic Si wires into full p-n junctions and the wires were passivated with a-Si:H and a-SiNx:H. Single wire devices yielded open circuit voltages of 600 mV and efficiencies of 9%. The arrays were then embedded in a polymer and contacted with a transparent, flexible, Ni nanoparticle and Ag nanowire top contact. The contact connected >99% of the wires in parallel and yielded flexible, substrate free solar cells featuring hundreds of thousands of wires. Building on the success of the Si wire arrays, GaP was epitaxially grown on the material to create heterostructures for photoelectrochemistry. These cells were limited by low absorption in the GaP due to its indirect bandgap, and poor current collection due to a diffusion length of only 80 nm. However, GaAsP on SiGe offers a superior combination of materials, and wire architectures based on these semiconductors were investigated for multijunction

  13. Commercial and Industrial Wiring.

    ERIC Educational Resources Information Center

    Kaltwasser, Stan; Flowers, Gary

    This module is the third in a series of three wiring publications, includes additional technical knowledge and applications required for job entry in the commercial and industrial wiring trade. The module contains 15 instructional units that cover the following topics: blueprint reading and load calculations; tools and equipment; service;…

  14. 2016 MOST WIRED.

    PubMed

    Barr, Paul; Butcher, Lola; Hoppszallern, Suzanna

    2016-07-01

    This year's IT survey shows that hospitals are aggressively fighting cyber crime and looking for ways to use data to help in the transition to value-based care. Find out who made the 2016 lists of Most Wired, Most Advanced, Most Improved and Most Wired-Small and Rural. PMID:27526506

  15. The exploding wire phenomenon

    NASA Astrophysics Data System (ADS)

    Aspden, H.

    1985-02-01

    Graneau's recent interpretation of the exploding wire phenomenon as an electrodynamic effect verifying Ampère's classical formulation is questioned. Instead, it is shown that the rupturing force arising from the imbalance of the self-induced electromotive force and the ohmic potential during an explosive current surge will account for the wire breaking into several segments, as is observed.

  16. Water Desalination with Wires.

    PubMed

    Porada, S; Sales, B B; Hamelers, H V M; Biesheuvel, P M

    2012-06-21

    We show the significant potential of water desalination using a novel capacitive wire-based technology in which anode/cathode wire pairs are constructed from coating a thin porous carbon electrode layer on top of electrically conducting rods (or wires). By alternately dipping an array of electrode pairs in freshwater with and in brine without an applied cell voltage, we create an ion adsorption/desorption cycle. We show experimentally how in six subsequent cycles we can reduce the salinity of 20 mM feed (brackish) water by a factor of 3, while application of a cation exchange membrane on the cathode wires makes the desalination factor increase to 4. Theoretical modeling rationalizes the experimental findings, and predicts that system performance can be significantly enhanced by material modifications. To treat large volumes of water, multiple stacks of wire pairs can be used simultaneously in a "merry-go-round" operational mode. PMID:26285717

  17. International space station wire program

    NASA Technical Reports Server (NTRS)

    May, Todd

    1995-01-01

    Hardware provider wire systems and current wire insulation issues for the International Space Station (ISS) program are discussed in this viewgraph presentation. Wire insulation issues include silicone wire contamination, Tefzel cold temperature flexibility, and Russian polyimide wire insulation. ISS is a complex program with hardware developed and managed by many countries and hundreds of contractors. Most of the obvious wire insulation issues are known by contractors and have been precluded by proper selection.

  18. Majorana fermions in noisy Kitaev wires

    NASA Astrophysics Data System (ADS)

    Hu, Ying; Cai, Zi; Baranov, Mikhail A.; Zoller, Peter

    2015-10-01

    Robustness of edge states and non-Abelian excitations of topological states of matter promises quantum memory and quantum processing, which are naturally immune to microscopic imperfections such as static disorder. However, topological properties will not in general protect quantum systems from time-dependent disorder or noise. Here we take the example of a network of Kitaev wires with Majorana edge modes storing qubits to investigate the effects of classical noise in the crossover from the quasistatic to the fast fluctuation regime. We present detailed results for the Majorana edge correlations, and fidelity of braiding operations for both global and local noise sources preserving parity symmetry, such as random chemical potentials and phase fluctuations. While in general noise will induce heating and dephasing, we identify examples of long-lived quantum correlations in the presence of fast noise due to motional narrowing, where external noise drives the system rapidly between the topological and nontopological phases.

  19. Next Generation Wiring

    NASA Technical Reports Server (NTRS)

    Medelius, Petro; Jolley, Scott; Fitzpatrick, Lilliana; Vinje, Rubiela; Williams, Martha; Clayton, LaNetra; Roberson, Luke; Smith, Trent; Santiago-Maldonado, Edgardo

    2007-01-01

    Wiring is a major operational component on aerospace hardware that accounts for substantial weight and volumetric space. Over time wire insulation can age and fail, often leading to catastrophic events such as system failure or fire. The next generation of wiring must be reliable and sustainable over long periods of time. These features will be achieved by the development of a wire insulation capable of autonomous self-healing that mitigates failure before it reaches a catastrophic level. In order to develop a self-healing insulation material, three steps must occur. First, methods of bonding similar materials must be developed that are capable of being initiated autonomously. This process will lead to the development of a manual repair system for polyimide wire insulation. Second, ways to initiate these bonding methods that lead to materials that are similar to the primary insulation must be developed. Finally, steps one and two must be integrated to produce a material that has no residues from the process that degrades the insulating properties of the final repaired insulation. The self-healing technology, teamed with the ability to identify and locate damage, will greatly improve reliability and safety of electrical wiring of critical systems. This paper will address these topics, discuss the results of preliminary testing, and remaining development issues related to self-healing wire insulation.

  20. Orbiter Kapton wire operational requirements and experience

    NASA Technical Reports Server (NTRS)

    Peterson, R. V.

    1994-01-01

    The agenda of this presentation includes the Orbiter wire selection requirements, the Orbiter wire usage, fabrication and test requirements, typical wiring installations, Kapton wire experience, NASA Kapton wire testing, summary, and backup data.

  1. Nanowire terahertz quantum cascade lasers

    SciTech Connect

    Grange, Thomas

    2014-10-06

    Quantum cascade lasers made of nanowire axial heterostructures are proposed. The dissipative quantum dynamics of their carriers is theoretically investigated using non-equilibrium Green functions. Their transport and gain properties are calculated for varying nanowire thickness, from the classical-wire regime to the quantum-wire regime. Our calculation shows that the lateral quantum confinement provided by the nanowires allows an increase of the maximum operation temperature and a strong reduction of the current density threshold compared to conventional terahertz quantum cascade lasers.

  2. Dual wire weld feed proportioner

    NASA Technical Reports Server (NTRS)

    Nugent, R. E.

    1968-01-01

    Dual feed mechanism enables proportioning of two different weld feed wires during automated TIG welding to produce a weld alloy deposit of the desired composition. The wires are fed into the weld simultaneously. The relative feed rates of the wires and the wire diameters determine the weld deposit composition.

  3. Splicing Wires Permanently With Explosives

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.; Kushnick, Anne C.

    1990-01-01

    Explosive joining process developed to splice wires by enclosing and metallurgically bonding wires within copper sheets. Joints exhibit many desirable characteristics, 100-percent conductivity and strength, no heat-induced annealing, no susceptibility to corrosion in contacts between dissimilar metals, and stability at high temperature. Used to join wires to terminals, as well as to splice wires. Applicable to telecommunications industry, in which millions of small wires spliced annually.

  4. Wire brush fastening device

    SciTech Connect

    Meigs, R.A.

    1993-08-31

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.

  5. Wire brush fastening device

    DOEpatents

    Meigs, Richard A.

    1995-01-01

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus.

  6. Wire brush fastening device

    DOEpatents

    Meigs, R.A.

    1995-09-19

    A fastening device is provided which is a variation on the conventional nut and bolt. The bolt has a longitudinal axis and threading helically affixed thereon along the longitudinal axis. A nut having a bore extending therethrough is provided. The bore of the nut has a greater diameter than the diameter of the bolt so the bolt can extend through the bore. An array of wire bristles are affixed within the bore so as to form a brush. The wire bristles extend inwardly from the bore and are constructed and arranged of the correct size, length and stiffness to guide the bolt within the bore and to restrain the bolt within the bore as required. A variety of applications of the wire brush nut are disclosed, including a bolt capture device and a test rig apparatus. 13 figs.

  7. Dielectric coated wire antennas

    NASA Technical Reports Server (NTRS)

    Richmond, J. H.; Newman, E. H.

    1976-01-01

    An electrically thin dielectric insulating shell on an antenna composed of electrically thin circular cylindrical wires is examined. A moment method solution is obtained, and the insulating shell is modeled by equivalent volume polarization currents. These polarization currents are related in a simple manner to the surface charge density on the wire antenna. In this way the insulating shell causes no new unknowns to be introduced, and the size of the impedance matrix is the same as for the uninsulated wires. The insulation is accounted for entirely through a modification of the symmetric impedance matrix. This modification influences the current distribution, impedance, efficiency, field patterns, and scattering properties. The theory is compared with measurement for dielectric coated antennas in air.

  8. 2. TYPICAL OVERHEAD WIRE CONSTRUCTION CURVE GUY WIRE ARRANGEMENT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. TYPICAL OVERHEAD WIRE CONSTRUCTION - CURVE GUY WIRE ARRANGEMENT (ABANDONED WEST LEG OF WYE AT SIXTH AVENUE AND PINE STREET) - Yakima Valley Transportation Company Interurban Railroad, Trackage, Yakima, Yakima County, WA

  9. Flying wires at Fermilab

    SciTech Connect

    Gannon, J.; Crawford, C.; Finley, D.; Flora, R.; Groves, T.; MacPherson, M.

    1989-03-01

    Transverse beam profile measurement systems called ''Flying Wires'' have been installed and made operational in the Fermilab Main Ring and Tevatron accelerators. These devices are used routinely to measure the emittance of both protons and antiprotons throughout the fill process, and for emittance growth measurements during stores. In the Tevatron, the individual transverse profiles of six proton and six antiproton bunches are obtained simultaneously, with a single pass of the wire through the beam. Essential features of the hardware, software, and system operation are explained in the rest of the paper. 3 refs., 4 figs.

  10. Wiring for space applications program

    NASA Technical Reports Server (NTRS)

    Hammoud, Ahmad

    1994-01-01

    The insulation testing and analysis consists of: identifying and prioritizing NASA wiring requirements; selecting candidate wiring constructions; developing test matrix and formulating test program; managing, coordinating, and conducting tests; and analyzing and documenting data, establishing guidelines and recommendations.

  11. NewsWire, 2002.

    ERIC Educational Resources Information Center

    Byrom, Elizabeth, Ed.; Bingham, Margaret, Ed.; Bowman, Gloria, Ed.; Shoemaker, Dan, Ed.

    2002-01-01

    This document presents the 3 2002 issues of the newsletter "NewsWire," (volume 5). Issue Number One focuses on collaborative Web projects. This issue begins with descriptions of four individual projects: "iEARN"; "Operation RubyThroat"; "Follow the Polar Huskies!"; and "Log in Your Animal Roadkill!" Features that follow include: "Bringing the…

  12. Basic Wiring. Second Edition.

    ERIC Educational Resources Information Center

    Kaltwasser, Stan; And Others

    This guide is designed to assist teachers conducting a foundation course to prepare students for additional courses of training for entry-level employment in either the residential or commercial and industrial wiring trades. Included in the guide are 17 instructional units and the following sections of information for teachers: guidelines in using…

  13. Improved wire chamber

    DOEpatents

    Atac, M.

    1987-05-12

    An improved gas mixture for use with proportional counter devices, such as Geiger-Mueller tubes and drift chambers. The improved gas mixture provides a stable drift velocity while eliminating wire aging caused by prior art gas mixtures. The new gas mixture is comprised of equal parts argon and ethane gas and having approximately 0.25% isopropyl alcohol vapor. 2 figs.

  14. Caroviologens: Towards molecular wires

    NASA Astrophysics Data System (ADS)

    Blanchard-Desce, M.; Arrhenius, T. S.; Dvolaïtzky, M.; Kugimiya, S.-I.; Lazrak, T.; Lehn, J.-M.

    1992-07-01

    Bispyridinium conjugated polyenes of different lengths and charges have been synthesized. Since they combine the features of carotenoids and of viologens, they have been termed caroviologens. Such molecules, possessing an extended conjugated chain fitted with polar electroactive endgroups, and having a length sufficient to span a lipid membrane could function as transmembrane electron channels, i.e., as molecular wires.

  15. A World without Wires

    ERIC Educational Resources Information Center

    Panettieri, Joseph C.

    2006-01-01

    The wireless bandwagon is rolling across Mississippi, picking up a fresh load of converts and turning calamity into opportunity. Traditional wired school networks, many of which unraveled during Hurricane Katrina, are giving way to advanced wireless mesh networks that frequently include voice-over-IP (VoIP) capabilities. Vendor funding is helping…

  16. Residential Wiring. Second Edition.

    ERIC Educational Resources Information Center

    Taylor, Mark; And Others

    This guide is designed to assist teachers conducting a course to prepare students for entry-level employment in the residential wiring trade. Included in the guide are six instructional units and the following sections of information for teachers: guidelines in using the unit components; academic and workplace skills classifications and…

  17. Easily-wired toggle switch

    NASA Technical Reports Server (NTRS)

    Dean, W. T.; Stringer, E. J.

    1979-01-01

    Crimp-type connectors reduce assembly and disassembly time. With design, no switch preparation is necessary and socket contracts are crimped to wires inserted in module attached to back of toggle switch engaging pins inside module to make electrical connections. Wires are easily removed with standard detachment tool. Design can accommodate wires of any gage and as many terminals can be placed on switch as wire gage and switch dimensions will allow.

  18. Wire EDM for Refractory Materials

    NASA Technical Reports Server (NTRS)

    Zellars, G. R.; Harris, F. E.; Lowell, C. E.; Pollman, W. M.; Rys, V. J.; Wills, R. J.

    1982-01-01

    In an attempt to reduce fabrication time and costs, Wire Electrical Discharge Machine (Wire EDM) method was investigated as tool for fabricating matched blade roots and disk slots. Eight high-strength nickel-base superalloys were used. Computer-controlled Wire EDM technique provided high quality surfaces with excellent dimensional tolerances. Wire EDM method offers potential for substantial reductions in fabrication costs for "hard to machine" alloys and electrically conductive materials in specific high-precision applications.

  19. 1997 wire development workshop: Proceedings

    SciTech Connect

    1997-04-01

    This conference is divided into the following sections: (1) First Generation Wires I; (2) First Generation Wires II; (3) Coated conductors I; and (4) Coated conductors II. Applications of the superconducting wires include fault current limiters, superconducting motors, transformers, and power transmission lines.

  20. Production of hot-wires

    NASA Astrophysics Data System (ADS)

    Dickinson, S. C.

    1983-04-01

    Several methods for producing hot-wire probes are described. Discussion includes the manufacture of probe bodies, soldering plated wires to the prongs etching Walaston type wires, and finishing the probe. This report is written as an instruction manual for researchers who desire to produce or repair their own sensors.

  1. Silver-sheathed multifilament wires

    NASA Astrophysics Data System (ADS)

    Wu, C. T.; Goretta, K. C.; Shi, D.; Lanagan, M. T.; Poeppel, R. B.

    1991-01-01

    The process for manufacturing Ag-sheathed multifilament superconducting wires was investigated. Bi2Sr(1.7)CaCu2O(x), Pb-doped Bi2Sr2Ca2Cu3O(x), or YBa2Cu3O(x) powders were packed into Ag tubes and swaged into long wires. Pieces were cut from each wire, packed into a second Ag tube and swaged or rolled into multifilament wires. Each wire was then sintered to produce a superconductor. Processing considerations included the sheath workability, effects of compacting and residual stresses, and heat treatment schedules. The superconducting properties of the Bi-based wires were superior to those of the YBa2Cu3O(x) wires at 4.2 K, but not at 77 K.

  2. From wires to cosmology

    NASA Astrophysics Data System (ADS)

    Amin, Mustafa A.; Baumann, Daniel

    2016-02-01

    We provide a statistical framework for characterizing stochastic particle production in the early universe via a precise correspondence to current conduction in wires with impurities. Our approach is particularly useful when the microphysics is uncertain and the dynamics are complex, but only coarse-grained information is of interest. We study scenarios with multiple interacting fields and derive the evolution of the particle occupation numbers from a Fokker-Planck equation. At late times, the typical occupation numbers grow exponentially which is the analog of Anderson localization for disordered wires. Some statistical features of the occupation numbers show hints of universality in the limit of a large number of interactions and/or a large number of fields. For test cases, excellent agreement is found between our analytic results and numerical simulations.

  3. Dental Arch Wire

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Straightening teeth is an arduous process requiring months, often years, of applying corrective pressure by means of arch wires-better known as brace-which may have to be changed several times in the course of treatment. A new method has been developed by Dr. George Andreasen, orthodontist and dental scientist at the University of Iowa. The key is a new type of arch wire material, called Nitinol, with exceptional elasticity which helps reduce the required number of brace changes. An alloy of nickel and titanium, Nitinol was originally developed for aerospace applications by the Naval Ordnance Laboratory, now the Naval Surface Weapons Laboratory, White Oaks, Maryland. NASA subsequently conducted additional research on the properties of Nitinol and on procedures for processing the metal.

  4. Wire insulation defect detector

    NASA Technical Reports Server (NTRS)

    Greulich, Owen R. (Inventor)

    2004-01-01

    Wiring defects are located by detecting a reflected signal that is developed when an arc occurs through the defect to a nearby ground. The time between the generation of the signal and the return of the reflected signal provides an indication of the distance of the arc (and therefore the defect) from the signal source. To ensure arcing, a signal is repeated at gradually increasing voltages while the wire being tested and a nearby ground are immersed in a conductive medium. In order to ensure that the arcing occurs at an identifiable time, the signal whose reflection is to be detected is always made to reach the highest potential yet seen by the system.

  5. Wiring for aerospace applications

    NASA Technical Reports Server (NTRS)

    Christian, J. L., Jr.; Dickman, J. E.; Bercaw, R. W.; Myers, I. T.; Hammoud, A. N.; Stavnes, M.; Evans, J.

    1992-01-01

    In this paper, the authors summarize the current state of knowledge of arc propagation in aerospace power wiring and efforts by the National Aeronautics and Space Administration (NASA) towards the understanding of the arc tracking phenomena in space environments. Recommendations will be made for additional testing. A database of the performance of commonly used insulating materials will be developed to support the design of advanced high power missions, such as Space Station Freedom and Lunar/Mars Exploration.

  6. Plated wire memory subsystem

    NASA Technical Reports Server (NTRS)

    Reynolds, L.; Tweed, H.

    1972-01-01

    The work performed entailed the design, development, construction and testing of a 4000 word by 18 bit random access, NDRO plated wire memory for use in conjunction with a spacecraft imput/output unit and central processing unit. The primary design parameters, in order of importance, were high reliability, low power, volume and weight. A single memory unit, referred to as a qualification model, was delivered.

  7. Dual wire welding torch and method

    DOEpatents

    Diez, Fernando Martinez; Stump, Kevin S.; Ludewig, Howard W.; Kilty, Alan L.; Robinson, Matthew M.; Egland, Keith M.

    2009-04-28

    A welding torch includes a nozzle with a first welding wire guide configured to orient a first welding wire in a first welding wire orientation, and a second welding wire guide configured to orient a second welding wire in a second welding wire orientation that is non-coplanar and divergent with respect to the first welding wire orientation. A method of welding includes moving a welding torch with respect to a workpiece joint to be welded. During moving the welding torch, a first welding wire is fed through a first welding wire guide defining a first welding wire orientation and a second welding wire is fed through a second welding wire guide defining a second welding wire orientation that is divergent and non-coplanar with respect to the first welding wire orientation.

  8. Unpacking of a Crumpled Wire from Two-Dimensional Cavities

    PubMed Central

    Sobral, Thiago A.; Gomes, Marcelo A. F.; Machado, Núbia R.; Brito, Valdemiro P.

    2015-01-01

    The physics of tightly packed structures of a wire and other threadlike materials confined in cavities has been explored in recent years in connection with crumpled systems and a number of topics ranging from applications to DNA packing in viral capsids and surgical interventions with catheter to analogies with the electron gas at finite temperature and with theories of two-dimensional quantum gravity. When a long piece of wire is injected into two-dimensional cavities, it bends and originates in the jammed limit a series of closed structures that we call loops. In this work we study the extraction of a crumpled tightly packed wire from a circular cavity aiming to remove loops individually. The size of each removed loop, the maximum value of the force needed to unpack each loop, and the total length of the extracted wire were measured and related to an exponential growth and a mean field model consistent with the literature of crumpled wires. Scaling laws for this process are reported and the relationship between the processes of packing and unpacking of wire is commented upon. PMID:26047315

  9. Unpacking of a Crumpled Wire from Two-Dimensional Cavities.

    PubMed

    Sobral, Thiago A; Gomes, Marcelo A F; Machado, Núbia R; Brito, Valdemiro P

    2015-01-01

    The physics of tightly packed structures of a wire and other threadlike materials confined in cavities has been explored in recent years in connection with crumpled systems and a number of topics ranging from applications to DNA packing in viral capsids and surgical interventions with catheter to analogies with the electron gas at finite temperature and with theories of two-dimensional quantum gravity. When a long piece of wire is injected into two-dimensional cavities, it bends and originates in the jammed limit a series of closed structures that we call loops. In this work we study the extraction of a crumpled tightly packed wire from a circular cavity aiming to remove loops individually. The size of each removed loop, the maximum value of the force needed to unpack each loop, and the total length of the extracted wire were measured and related to an exponential growth and a mean field model consistent with the literature of crumpled wires. Scaling laws for this process are reported and the relationship between the processes of packing and unpacking of wire is commented upon. PMID:26047315

  10. Wire detecting apparatus and method

    SciTech Connect

    Kronberg, J.W.

    1991-12-31

    This invention is comprised of an apparatus and method that combines a signal generator and a passive signal receiver to detect and record the path of partially or completely concealed electrical wiring without disturbing the concealing surface. The signal generator applies a series of electrical pulses to the selected wiring of interest. The applied pulses create a magnetic field about the wiring that can be detected by a coil contained within the signal receiver. An audible output connected to the receiver and driven by the coil reflects the receiver`s position with respect to the wiring. The receiver`s audible signal is strongest when the receiver is directly above the wiring and the long axis of the receiver`s coil is parallel to the wiring. A marking means is mounted on the receiver to mark the location of the wiring as the receiver is directed over the wiring`s concealing surface. Numerous marks made on various locations of the concealing surface will trace the path of the wiring of interest.

  11. Manually Operated Welding Wire Feeder

    NASA Technical Reports Server (NTRS)

    Rybicki, Daniel J. (Inventor)

    2001-01-01

    A manual welding wire feeder apparatus comprising a bendable elongate metal frame with a feed roller mounted at the center thereof for rotation about an axis transverse to the longitudinal axis of the frame. The frame ends are turned up as tabs and each provided with openings in alignment with each other and the mid-width center of the roller surface. The tab openings are sized to accommodate welding wire and each extends to a side edge of the tab, both opening on the same side of the frame, whereby welding wire can be side-loaded onto the frame. On the side of the frame, opposite the roller a lock ring handle is attached tangentially and is rotatable about the attachment point and an axis perpendicular to the frame. The device is grasped in the hand normally used to hold the wire. A finger is placed through the loop ring and the frame positioned across the palm and lower fingers. The thumb is positioned atop the wire so it can be moved from the back of the frame across the roller, and towards the front. In doing so, the wire is advanced at a steady rate in axial alignment with the tab openings and roller. To accommodate different wire diameters the frame is bendable about its center in the plane of the frame axis and wire so as to keep the wire in sufficient tension against the roller and to keep the wire fixed when the frame is tilted and thumb pressure released.

  12. Wire Array Solar Cells: Fabrication and Photoelectrochemical Studies

    NASA Astrophysics Data System (ADS)

    Spurgeon, Joshua Michael

    /polymer composite films showed that their energy-conversion properties were comparable to those of an array attached to the growth substrate. High quantum efficiencies were observed relative to the packing density of the wires, particularly with illumination at high angles of incidence. The results indicate that an inexpensive, solid-state Si wire array solar cell is possible, and a plan is presented to develop one.

  13. Making Superconducting Welds between Superconducting Wires

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin I.; Eom, Byeong Ho

    2008-01-01

    A technique for making superconducting joints between wires made of dissimilar superconducting metals has been devised. The technique is especially suitable for fabrication of superconducting circuits needed to support persistent electric currents in electromagnets in diverse cryogenic applications. Examples of such electromagnets include those in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) systems and in superconducting quantum interference devices (SQUIDs). Sometimes, it is desirable to fabricate different parts of a persistent-current-supporting superconducting loop from different metals. For example, a sensory coil in a SQUID might be made of Pb, a Pb/Sn alloy, or a Cu wire plated with Pb/Sn, while the connections to the sensory coil might be made via Nb or Nb/Ti wires. Conventional wire-bonding techniques, including resistance spot welding and pressed contact, are not workable because of large differences between the hardnesses and melting temperatures of the different metals. The present technique is not subject to this limitation. The present technique involves the use (1) of a cheap, miniature, easy-to-operate, capacitor-discharging welding apparatus that has an Nb or Nb/Ti tip and operates with a continuous local flow of gaseous helium and (2) preparation of a joint in a special spark-discharge welding geometry. In a typical application, a piece of Nb foil about 25 m thick is rolled to form a tube, into which is inserted a wire that one seeks to weld to the tube (see figure). The tube can be slightly crimped for mechanical stability. Then a spark weld is made by use of the aforementioned apparatus with energy and time settings chosen to melt a small section of the niobium foil. The energy setting corresponds to the setting of a voltage to which the capacitor is charged. In an experiment, the technique was used to weld an Nb foil to a copper wire coated with a Pb/Sn soft solder, which is superconducting. The joint was evaluated as

  14. Metering Wheel-Wire Track Wire Boom Deployment Mechanism

    NASA Technical Reports Server (NTRS)

    Granoff, Mark S.

    2014-01-01

    The NASA MMS Spin Plane Double Probe (SDP) Deployer utilizes a helical path, rotating Metering Wheel and a spring loaded Wire "Holding" Track to pay out a "fixed end" 57 meter x 1.5 mm diameter Wire Boom stored between concentric storage cylinders. Unlike rotating spool type storage devices, the storage cylinders remain stationary, and the boom wire is uncoiled along the length of the cylinder via the rotation of the Metering Wheel. This uncoiling action avoids the need for slip-ring contacts since the ends of the wire can remain stationary. Conventional fixed electrical connectors (Micro-D type) are used to terminate to operational electronics.

  15. Review of wire chamber aging

    SciTech Connect

    Va'Vra, J.

    1986-02-01

    This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of variable tuning, the importance of purity of the wire chamber environment, as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16-17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25-28, 1986. 74 refs., 18 figs., 11 tabs.

  16. Neural wiring optimization.

    PubMed

    Cherniak, Christopher

    2012-01-01

    Combinatorial network optimization theory concerns minimization of connection costs among interconnected components in systems such as electronic circuits. As an organization principle, similar wiring minimization can be observed at various levels of nervous systems, invertebrate and vertebrate, including primate, from placement of the entire brain in the body down to the subcellular level of neuron arbor geometry. In some cases, the minimization appears either perfect, or as good as can be detected with current methods. One question such best-of-all-possible-brains results raise is, what is the map of such optimization, does it have a distinct neural domain? PMID:22230636

  17. Plated wire memory subsystem

    NASA Technical Reports Server (NTRS)

    Carpenter, K. H.

    1974-01-01

    The design, construction, and test history of a 4096 word by 18 bit random access NDRO Plated Wire Memory for use in conjunction with a spacecraft input/output and central processing unit is reported. A technical and functional description is given along with diagrams illustrating layout and systems operation. Test data is shown on the procedures and results of system level and memory stack testing, and hybrid circuit screening. A comparison of the most significant physical and performance characteristics of the memory unit versus the specified requirements is also included.

  18. Texture development in Galfenol wire

    NASA Astrophysics Data System (ADS)

    Boesenberg, A. J.; Restorff, J. B.; Wun-Fogle, M.; Sailsbury, H.; Summers, E.

    2013-05-01

    Galfenol (Fe-Ga alloy) wire fabrication provides a low cost alternative to directional solidification methods. This work evaluates the compositional dependence of the wire drawing suitability of Fe-Ga and characterizes the microstructural and magnetic properties of these wires. Wire has been produced with Ga contents between 10 at. % and 17 at. % to allow determination of the ductile to brittle transition (DTBT) in wire manufacture. Published results on chill cast bend specimens indicated that a DTBT occurs at roughly 15 at. % Ga. This DTBT was observed under tensile loading with a corresponding change in fracture behavior from transverse fracture to intergranular fracture. For improved magnetostrictive performance, higher Ga contents are desired, closer to the 17 at. % Ga evaluated in this work. Electron backscattered diffraction B-H loop and resonance measurements as a function of magnetic field (to determine modulus and coupling factor) are presented for as-drawn, furnace, and direct current (DC) annealed wire. Galfenol wire produced via traditional drawing methods is found to have a strong <110> (α) texture parallel to the drawing direction. As-drawn wire was observed to have a lower magnetic permeability and larger hysteresis than DC annealed wire. This is attributed to the presence of a large volume of crystalline defects; such as vacancies and dislocations.

  19. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  20. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  1. 49 CFR 234.241 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... underground wire. 234.241 Section 234.241 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION GRADE CROSSING SIGNAL SYSTEM SAFETY... of insulated wire; splice in underground wire. Insulated wire shall be protected from...

  2. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  3. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  4. 49 CFR 234.241 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... underground wire. 234.241 Section 234.241 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION GRADE CROSSING SIGNAL SYSTEM SAFETY... of insulated wire; splice in underground wire. Insulated wire shall be protected from...

  5. 49 CFR 236.74 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... underground wire. 236.74 Section 236.74 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RULES, STANDARDS, AND INSTRUCTIONS GOVERNING... wire; splice in underground wire. Insulated wire shall be protected from mechanical injury....

  6. Two-Wire to Four-Wire Audio Converter

    NASA Technical Reports Server (NTRS)

    Talley, G. L., Jr; Seale, B. L.

    1983-01-01

    Simple circuit provides interface between normally incompatible voicecommunication lines. Circuit maintains 40 dB of isolation between input and output halves of four-wire line permitting two-wire line to be connected. Balancing potentiometer, Rg, adjusts gain of IC2 to null feed through from input to output. Adjustment is done on workbench just after assembly.

  7. Grains and wires of d-wave superconductors

    NASA Astrophysics Data System (ADS)

    Nunner, Tamara S.; Hirschfeld, P. J.

    2006-01-01

    We investigate Andreev states in grains of d-wave superconductors and compare them with a previous analysis of d-wave quantum wires. For perfect nesting a zero-energy Andreev bound state exists for geometries containing an odd number of (110)-layers. Away from perfect nesting the Andreev resonance broadens and its resonance frequency becomes finite for small grains. With increasing system size the resonance frequency approaches zero at least when we assume a constant order parameter throughout the grain. This is contrary to (110)-wires, where the Andreev state occurs at zero energy for all wire widths. Multiple reflections from surfaces with different orientations give rise to interesting interference effects and modify the Andreev states near corners.

  8. Soft magnetic wires

    NASA Astrophysics Data System (ADS)

    Vázquez, M.

    2001-06-01

    An overview of the present state of the art on the preparation techniques, outstanding magnetic properties and applications of soft magnetic micro and nanowires is presented. Rapid solidification techniques (in-rotating-water quenching and drawing methods) to fabricate amorphous microwires with diameter in the range from 100 down to 1 μm are first described. Electrodeposition is also employed to prepare composite microtubes (magnetic coatings) and to fill porous membranes (diameter of the order of 0.1 μm). Magnetic behaviours of interest are related to the different hysteresis loops of samples: square-shaped loops typical of bistable behaviour, and nearly non-hysteretic loop with well-defined transverse anisotropy field. The role played by magnetic dipolar interactions in the magnetic behaviour of arrays of micro and nanowires is described. A particular analysis is done on the giant magnetoimpedance (GMI) effect in the radio and microwave frequency ranges exhibited by ultrasoft microwires. Finally, a few examples of applications are introduced for magnetostrictive and non-magnetostrictive wires, they are: “magnetoelastic pens”, micromotors; DC current-sensors based on GMI, and sharpened amorphous wire tips in spin polarised scanning tunneling microscopy.

  9. Improved superconducting magnet wire

    DOEpatents

    Schuller, I.K.; Ketterson, J.B.

    1983-08-16

    This invention is directed to a superconducting tape or wire composed of alternating layers of copper and a niobium-containing superconductor such as niobium of NbTi, Nb/sub 3/Sn or Nb/sub 3/Ge. In general, each layer of the niobium-containing superconductor has a thickness in the range of about 0.05 to 1.5 times its coherence length (which for Nb/sub 3/Si is 41 A) with each copper layer having a thickness in the range of about 170 to 600 A. With the use of very thin layers of the niobium composition having a thickness within the desired range, the critical field (H/sub c/) may be increased by factors of 2 to 4. Also, the thin layers of the superconductor permit the resulting tape or wire to exhibit suitable ductility for winding on a magnet core. These compositions are also characterized by relatively high values of critical temperature and therefore will exhibit a combination of useful properties as superconductors.

  10. Weakly coupled molecular photonic wires: synthesis and excited-state energy-transfer dynamics.

    PubMed

    Ambroise, Arounaguiry; Kirmaier, Christine; Wagner, Richard W; Loewe, Robert S; Bocian, David F; Holten, Dewey; Lindsey, Jonathan S

    2002-05-31

    Molecular photonic wires, which absorb light and undergo excited-state energy transfer, are of interest as biomimetic models for photosynthetic light-harvesting systems and as molecular devices with potential applications in materials chemistry. We describe the stepwise synthesis of four molecular photonic wires. Each wire consists of an input unit, transmission element, and output unit. The input unit consists of a boron-dipyrrin dye or a perylene-monoimide dye (linked either at the N-imide or the C9 position); the transmission element consists of one or three zinc porphyrins affording short or long wires, respectively; and the output unit consists of a free base (Fb) porphyrin. The components in the arrays are joined in a linear architecture via diarylethyne linkers (an ethynylphenyl linker is attached to the C9-linked perylene). The wires have been examined by static absorption, static fluorescence, and time-resolved absorption spectroscopy. Each wire (with the exception of the C9-linked perylene wire) exhibits a visible absorption spectrum that is the sum of the spectra of the component parts, indicating the relatively weak electronic coupling between the components. Excitation of each wire at the wavelength where the input unit absorbs preferentially (typically 480-520 nm) results in emission almost exclusively from the Fb porphyrin. The static emission and time-resolved data indicate that the overall rate constants and quantum efficiencies for end-to-end (i.e., input to output) energy transfer are as follows: perylene-(N-imide)-linked short wire, (33 ps)(-1) and >99%; perylene-(C9)-linked short wire, (26 ps)(-1) and >99%; boron-dipyrrin-based long wire, (190 ps)(-1) and 81%; perylene-(N-imide)-linked long wire, (175 ps)(-1) and 86%. Collectively, the studies provide valuable insight into the singlet-singlet excited-state energy-transfer properties in weakly coupled molecular photonic wires. PMID:12027698

  11. Focus on quantum efficiency

    NASA Astrophysics Data System (ADS)

    Buchleitner, Andreas; Burghardt, Irene; Cheng, Yuan-Chung; Scholes, Gregory D.; Schwarz, Ulrich T.; Weber-Bargioni, Alexander; Wellens, Thomas

    2014-10-01

    Technologies which convert light into energy, and vice versa, rely on complex, microscopic transport processes in the condensed phase, which obey the laws of quantum mechanics, but hitherto lack systematic analysis and modeling. Given our much improved understanding of multicomponent, disordered, highly structured, open quantum systems, this ‘focus on’ collection collects cutting-edge research on theoretical and experimental aspects of quantum transport in truly complex systems as defined, e.g., by the macromolecular functional complexes at the heart of photosynthesis, by organic quantum wires, or even photovoltaic devices. To what extent microscopic quantum coherence effects can (be made to) impact on macroscopic transport behavior is an equally challenging and controversial question, and this ‘focus on’ collection provides a setting for the present state of affairs, as well as for the ‘quantum opportunities’ on the horizon.

  12. The Current in a Wire

    ERIC Educational Resources Information Center

    Thompson, Keith

    2009-01-01

    This little problem arose because I was frustrated with the standard electromagnetism texts, which show the magnetic field due to a current-bearing wire outside the wire [proportional to] 1/r and inside [proportional to] r. However, they never point out that the moving electrons must be influenced by the magnetic field created by the other moving…

  13. Aircraft wiring program status report

    NASA Technical Reports Server (NTRS)

    Beach, Rex

    1995-01-01

    In this Naval Air Warfare Center (NAWC) Aircraft Division status report, the general and wire and cable component activities, the systems engineering activities, the aircraft wiring lead maintenance activities, the NAVAIR/NASA interface activities, and the Base Realignment and Closure (BRAC) Commission recommendations are presented.

  14. First Wire-Free Pacemaker Approved

    MedlinePlus

    ... Wire-Free Pacemaker Approved Treats irregular heartbeat without wired leads To use the sharing features on this ... said in a news release. In traditional pacemakers, wired leads may malfunction and require the device to ...

  15. Welding wire pressure sensor assembly

    NASA Technical Reports Server (NTRS)

    Morris, Timothy B. (Inventor); Milly, Peter F., Sr. (Inventor); White, J. Kevin (Inventor)

    1994-01-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  16. Welding wire pressure sensor assembly

    NASA Astrophysics Data System (ADS)

    Morris, Timothy B.; Milly, Peter F.; White, J. Kevin

    1993-05-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  17. Welding wire pressure sensor assembly

    NASA Astrophysics Data System (ADS)

    Morris, Timothy B.; Milly, Peter F., Sr.; White, J. Kevin

    1994-04-01

    The present invention relates to a device which is used to monitor the position of a filler wire relative to a base material being welded as the filler wire is added to a welding pool. The device is applicable to automated welding systems wherein nonconsumable electrode arc welding processes are utilized in conjunction with a filler wire which is added to a weld pool created by the electrode arc. The invention senses pressure deviations from a predetermined pressure between the filler wire and the base material, and provides electrical signals responsive to the deviations for actuating control mechanisms in an automatic welding apparatus so as to minimize the pressure deviation and to prevent disengagement of the contact between the filler wire and the base material.

  18. Apollo experience report: Electrical wiring subsystem

    NASA Technical Reports Server (NTRS)

    White, L. D.

    1975-01-01

    The general requirements of the electrical wiring subsystems and the problem areas and solutions that occurred during the major part of the Apollo Program are detailed in this report. The concepts and definitions of specific requirements for electrical wiring; wire-connecting devices; and wire-harness fabrication, checkout, and installation techniques are discussed. The design and development of electrical wiring and wire-connecting devices are described. Mission performance is discussed, and conclusions and recommendations for future programs are presented.

  19. Electrode carrying wire for GTAW welding

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E. (Inventor); Dyer, Gerald E. (Inventor)

    1990-01-01

    A welding torch for gas tungsten arc welding apparatus has a hollow tungsten electrode including a ceramic liner and forms the filler metal wire guide. The wire is fed through the tungsten electrode thereby reducing the size of the torch to eliminate clearance problems which exist with external wire guides. Since the wire is preheated from the tungsten more wire may be fed into the weld puddle, and the wire will not oxidize because it is always within the shielding gas.

  20. Internal wire guide for GTAW welding

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E. (Inventor); Dyer, Gerald E. (Inventor)

    1989-01-01

    A welding torch for gas tungsten arc welding apparatus has a filler metal wire guide positioned within the torch, and within the shielding gas nozzle. The wire guide is adjacent to the tungsten electrode and has a ceramic liner through which the wire is fed. This reduces the size of the torch and eliminates the outside clearance problems that exit with external wire guides. Additionally, since the wire is always within the shielding gas, oxidizing of the wire is eliminated.

  1. Sintered wire cathode

    DOEpatents

    Falce, Louis R.; Ives, R. Lawrence

    2009-06-09

    A porous cathode structure is fabricated from a plurality of wires which are placed in proximity to each other in elevated temperature and pressure for a sintering time. The sintering process produces the porous cathode structure which may be divided into a plurality of individual porous cathodes, one of which may be placed into a dispenser cathode support which includes a cavity for containing a work function reduction material such as BaO, CaO, and Al.sub.2O.sub.3. The work function reduction material migrates through the pores of the porous cathode from a work replenishment surface adjacent to the cavity of the dispenser cathode support to an emitting cathode surface, thereby providing a dispenser cathode which has a uniform work function and therefore a uniform electron emission.

  2. Mesoscopic mechanical resonators as quantum noninertial reference frames

    NASA Astrophysics Data System (ADS)

    Katz, B. N.; Blencowe, M. P.; Schwab, K. C.

    2015-10-01

    An atom attached to a micrometer-scale wire that is vibrating at a frequency ˜100 MHz and with displacement amplitude ˜1 nm experiences an acceleration magnitude ˜109ms -2 , approaching the surface gravity of a neutron star. As one application of such extreme noninertial forces in a mesoscopic setting, we consider a model two-path atom interferometer with one path consisting of the 100 MHz vibrating wire atom guide. The vibrating wire guide serves as a noninertial reference frame and induces an in principle measurable phase shift in the wave function of an atom traversing the wire frame. We furthermore consider the effect on the two-path atom wave interference when the vibrating wire is modeled as a quantum object, hence functioning as a quantum noninertial reference frame. We outline a possible realization of the vibrating wire, atom interferometer using a superfluid helium quantum interference setup.

  3. Infrared spectral marker bands characterizing a transient water wire inside a hydrophobic membrane protein.

    PubMed

    Wolf, Steffen; Freier, Erik; Cui, Qiang; Gerwert, Klaus

    2014-12-14

    Proton conduction along protein-bound "water wires" is an essential feature in membrane proteins. Here, we analyze in detail a transient water wire, which conducts protons via a hydrophobic barrier within a membrane protein to create a proton gradient. It is formed only for a millisecond out of three water molecules distributed at inactive positions in a polar environment in the ground state. The movement into a hydrophobic environment causes characteristic shifts of the water bands reflecting their different chemical properties. These band shifts are identified by time-resolved Fourier Transform Infrared difference spectroscopy and analyzed by biomolecular Quantum Mechanical/Molecular Mechanical simulations. A non-hydrogen bonded ("dangling") O-H stretching vibration band and a broad continuum absorbance caused by a combined vibration along the water wire are identified as characteristic marker bands of such water wires in a hydrophobic environment. The results provide a basic understanding of water wires in hydrophobic environments. PMID:25494795

  4. Infrared spectral marker bands characterizing a transient water wire inside a hydrophobic membrane protein

    NASA Astrophysics Data System (ADS)

    Wolf, Steffen; Freier, Erik; Cui, Qiang; Gerwert, Klaus

    2014-12-01

    Proton conduction along protein-bound "water wires" is an essential feature in membrane proteins. Here, we analyze in detail a transient water wire, which conducts protons via a hydrophobic barrier within a membrane protein to create a proton gradient. It is formed only for a millisecond out of three water molecules distributed at inactive positions in a polar environment in the ground state. The movement into a hydrophobic environment causes characteristic shifts of the water bands reflecting their different chemical properties. These band shifts are identified by time-resolved Fourier Transform Infrared difference spectroscopy and analyzed by biomolecular Quantum Mechanical/Molecular Mechanical simulations. A non-hydrogen bonded ("dangling") O-H stretching vibration band and a broad continuum absorbance caused by a combined vibration along the water wire are identified as characteristic marker bands of such water wires in a hydrophobic environment. The results provide a basic understanding of water wires in hydrophobic environments.

  5. Particle in a Moebius wire and half-integer orbital angular momentum

    SciTech Connect

    Miliordos, Evangelos

    2011-06-15

    Restricting one particle on the rim of a Moebius strip (Moebius wire), its wave functions are explicitly calculated through the nonrelativistic quantum theory. Demanding the wave function to be single valued, it is proven that in the case of a narrow strip the orbital angular momentum of the particle takes both integer and half-integer values of ({h_bar}/2{pi}). In addition, the energy values of two chiral Moebius wires are proven to be equal.

  6. Plasma chemistry in wire chambers

    SciTech Connect

    Wise, J.

    1990-05-01

    The phenomenology of wire chamber aging is discussed and fundamentals of proportional counters are presented. Free-radical polymerization and plasma polymerization are discussed. The chemistry of wire aging is reviewed. Similarities between wire chamber plasma (>1 atm dc-discharge) and low-pressure rf-discharge plasmas, which have been more widely studied, are suggested. Construction and use of a system to allow study of the plasma reactions occurring in wire chambers is reported. A proportional tube irradiated by an {sup 55}Fe source is used as a model wire chamber. Condensable species in the proportional tube effluent are concentrated in a cryotrap and analyzed by gas chromatography/mass spectrometry. Several different wire chamber gases (methane, argon/methane, ethane, argon/ethane, propane, argon/isobutane) are tested and their reaction products qualitatively identified. For all gases tested except those containing methane, use of hygroscopic filters to remove trace water and oxygen contaminants from the gas resulted in an increase in the average molecular weight of the products, consistent with results from low-pressure rf-discharge plasmas. It is suggested that because water and oxygen inhibit polymer growth in the gas phase that they may also reduce polymer deposition in proportional tubes and therefore retard wire aging processes. Mechanistic implications of the plasma reactions of hydrocarbons with oxygen are suggested. Unresolved issues in this work and proposals for further study are discussed.

  7. Fabrication of thermoelectric wire-matrix composites using electrodeposition

    NASA Astrophysics Data System (ADS)

    Behnke, Joseph Frederick

    Thermoelectric materials have potential applications in a wide range of heating and cooling systems. Thermoelectric coolers, for example, are small, lightweight, and silent. They have no moving parts or fluids. What hinders a broader use of thermoelectric materials is their inefficiency when compared to compressor based systems. Theoretical studies have shown that there is a possible enhancement in thermoelectric properties through quantum confinement of the material. Recent studies have attempted to show this enhancement through the fabrication of multilayers, quantum wires and coupled quantum dots. In this study, the fabrication of thermoelectric wire-matrix composites is attempted. Porous anodic aluminum oxide was chosen as the matrix material because of its high porosity, its uniform pore diameter, its low thermal conductivity, and its compatibility with current thermoelectric device structures. CoSb 3 was chosen as the wire material because of its potential to show an enhancement in thermoelectric properties above bulk values at diameters greater than other commonly used thermoelectric materials. Electrodeposition was chosen as the method of fabrication, as it best allowed for infiltration of wire material into the matrix. It was found, however, that cobalt and antimony could not be electrodeposited into the porous matrix from the same bath. Therefore a two bath, multilayer approach was used to fabricate wires, using a post anneal to form the CoSb3 phase. The formation of CoSb3 was demonstrated by depositing alternating layers of cobalt from a CoS0 47H2O bath and antimony from an Sb2O3 bath. Both baths were aqueous and contained a supporting electrolyte of citric acid and potassium citrate. Depositing the antimony layer for 22 times the duration of the cobalt deposition gave the correct stoichiometry in the multilayers. To form CoSb3, the multilayers were annealed in an antimony ambient at temperatures greater than 575°C. The post annealing was found to

  8. Silicon Vibrating Wires at Low Temperatures

    NASA Astrophysics Data System (ADS)

    Collin, Eddy; Filleau, Laure; Fournier, Thierry; Bunkov, Yuriy M.; Godfrin, Henri

    2008-03-01

    Nowadays microfabrication techniques originating from micro-electro nics enable to create mechanical objects of micron-size. The field of Micro-Electro-Mechanical devices (MEMs) is continuously expanding, with an amazingly broad range of applications at room temperature. Vibrating objects (torsional oscillators, vibrating wires) widely used at low temperatures to study quantum fluids, can be replaced advantageously by Silicon MEMs. In this letter we report on the study of Silicon vibrating wire devices. A goal-post structure covered with a metal layer is driven at resonance by the Laplace force acting on a current in a magnetic field, while the induced voltage arising from the cut magnetic flux allows to detect the motion. The characteristics of the resonance have been studied from 10 mK to 30 K, in vacuum and in 4He gas. In this article, we focus on the results obtained above 1.5 K, in vacuum and gas, and introduce some features observed at lower temperatures. The resonant properties can be quantitatively understood by means of simple models, from the linear regime to a highly non-linear response at strong drives. We demonstrate that the non-linearity is mostly due to the geometry of the vibrators. We also show that in our device the friction mechanisms originate in the metallic layers, and can be fully characterized. The interaction with 4He gas is fit to theory without adjustable parameters.

  9. Requirements for printed wiring boards

    NASA Technical Reports Server (NTRS)

    1984-01-01

    In order to maintain the high standards of the NASA printed wiring programs, this publication: prescribes NASA's requirements for assuring reliable rigid printed wiring boards; describes and incorporates basic considerations necessary to assure reliable rigid printed wiring boards; establishes the supplier's responsibility to train and certify personnel; provides for supplier documentation of the fabrication and inspection procedures to be used for NASA work, including supplier innovations and changes in technology; and provides visual workmanship standards to aid those responsible for determining quality conformance to the established requirements.

  10. Demonstrating Forces between Parallel Wires.

    ERIC Educational Resources Information Center

    Baker, Blane

    2000-01-01

    Describes a physics demonstration that dramatically illustrates the mutual repulsion (attraction) between parallel conductors using insulated copper wire, wooden dowels, a high direct current power supply, electrical tape, and an overhead projector. (WRM)

  11. Method of manufacturing superconductor wire

    SciTech Connect

    Motowidlo, Leszek

    2014-09-16

    A method for forming Nb.sub.3Sn superconducting wire is provided. The method employs a powder-in-tube process using a high-tin intermetallic compound, such as MnSn.sub.2, for producing the Nb.sub.3Sn. The use of a high-tin intermetallic compound enables the process to perform hot extrusion without melting the high-tin intermetallic compound. Alternatively, the method may entail drawing the wire without hot extrusion.

  12. Smart Wire Grid: Resisting Expectations

    SciTech Connect

    Ramsay, Stewart; Lowe, DeJim

    2014-03-03

    Smart Wire Grid's DSR technology (Discrete Series Reactor) can be quickly deployed on electrical transmission lines to create intelligent mesh networks capable of quickly rerouting electricity to get power where and when it's needed the most. With their recent ARPA-E funding, Smart Wire Grid has been able to move from prototype and field testing to building out a US manufacturing operation in just under a year.

  13. Smart Wire Grid: Resisting Expectations

    ScienceCinema

    Ramsay, Stewart; Lowe, DeJim

    2014-04-09

    Smart Wire Grid's DSR technology (Discrete Series Reactor) can be quickly deployed on electrical transmission lines to create intelligent mesh networks capable of quickly rerouting electricity to get power where and when it's needed the most. With their recent ARPA-E funding, Smart Wire Grid has been able to move from prototype and field testing to building out a US manufacturing operation in just under a year.

  14. 30 CFR 75.701-4 - Grounding wires; capacity of wires.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Grounding wires; capacity of wires. 75.701-4... SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Grounding § 75.701-4 Grounding wires; capacity of wires. Where grounding wires are used to ground metallic sheaths, armors, conduits,...

  15. 30 CFR 75.701-4 - Grounding wires; capacity of wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Grounding wires; capacity of wires. 75.701-4... SAFETY AND HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Grounding § 75.701-4 Grounding wires; capacity of wires. Where grounding wires are used to ground metallic sheaths, armors, conduits,...

  16. HTS Wire Development Workshop: Proceedings

    SciTech Connect

    Not Available

    1994-07-01

    The 1994 High-Temperature Superconducting Wire Development Workshop was held on February 16--17 at the St. Petersburg Hilton and Towers in St. Petersburg, Florida. The meeting was hosted by Florida Power Corporation and sponsored by the US Department of Energy`s Superconductivity Program for Electric Power Systems. The meeting focused on recent high-temperature superconducting wire development activities in the Department of Energy`s Superconductivity Systems program. The meeting opened with a general discussion on the needs and benefits of superconductivity from a utility perspective, the US global competitiveness position, and an outlook on the overall prospects of wire development. The meeting then focused on four important technology areas: Wire characterization: issues and needs; technology for overcoming barriers: weak links and flux pinning; manufacturing issues for long wire lengths; and physical properties of HTS coils. Following in-depth presentations, working groups were formed in each technology area to discuss the most important current research and development issues. The working groups identified research areas that have the potential for greatly enhancing the wire development effort. These areas are discussed in the summary reports from each of the working groups. This document is a compilation of the workshop proceedings including all general session presentations and summary reports from the working groups.

  17. 1 mil gold bond wire study.

    SciTech Connect

    Huff, Johnathon; McLean, Michael B.; Jenkins, Mark W.; Rutherford, Brian Milne

    2013-05-01

    In microcircuit fabrication, the diameter and length of a bond wire have been shown to both affect the current versus fusing time ratio of a bond wire as well as the gap length of the fused wire. This study investigated the impact of current level on the time-to-open and gap length of 1 mil by 60 mil gold bond wires. During the experiments, constant current was provided for a control set of bond wires for 250ms, 410ms and until the wire fused; non-destructively pull-tested wires for 250ms; and notched wires. The key findings were that as the current increases, the gap length increases and 73% of the bond wires will fuse at 1.8A, and 100% of the wires fuse at 1.9A within 60ms. Due to the limited scope of experiments and limited data analyzed, further investigation is encouraged to confirm these observations.

  18. Fabrication of Pd-Cr wire

    NASA Technical Reports Server (NTRS)

    Diamond, Sidney; Leach, Dennen M.

    1989-01-01

    Fabrication of Pd-13 percent Cr alloy wires is described. Melting, casting, swaging and annealing processes are discussed. Drawing to reach two diameters (0.003 inch and 0.00176 inch) of wire is described. Representative micrographs of the Pd-Cr alloy at selected stages during wire fabrication are included. The resistance of the wire was somewhat lower, by about 15 to 20 percent, than comparable wire of other alloys used for strain gages.

  19. Experimental Results for Space-Wire-D

    NASA Astrophysics Data System (ADS)

    Parkes, Steve; Gibson, David; Ferrer, Albert

    2015-09-01

    SpaceWire-D is a deterministic extension to SpaceWire that uses time-division multiplexing to schedule traffic within time-slots. It allows a single SpaceWire network to be used for both time-critical avionics control applications and asynchronous payload data-handling simultaneously using existing SpaceWire technology. In this paper we describe the services of SpaceWire-D and present experimental results for each service.

  20. Connecting to Thermocouples with Fewer Lead Wires

    NASA Technical Reports Server (NTRS)

    Goldsby, Jon C.

    2003-01-01

    A simple technique has been devised to reduce the number of lead wires needed to connect an array of thermocouples to the instruments (e.g., voltmeters) used to read their output voltages. Because thermocouple wires are usually made of expensive metal alloys, reducing the number of lead wires can effect a considerable reduction in the cost of such an array. Reducing the number of wires also reduces the number of terminals and the amount of space needed to accommodate the wires.

  1. Wire chambers revisited.

    PubMed

    Ott, R J

    1993-04-01

    Detectors used for radioisotope imaging have, historically, been based on scintillating crystal/photomultiplier combinations in various forms. From the rectilinear scanner through to modern gamma cameras and positron cameras, the basic technology has remained much the same. Efforts to overcome the limitations of this form of technology have foundered on the inability to reproduce the required sensitivity, spatial resolution and sensitive area at acceptable cost. Multiwire proportional chambers (MWPCs) have long been used as position-sensitive charged particle detectors in nuclear and high-energy physics. MWPCs are large-area gas-filled ionisation chambers in which large arrays of fine wires are used to measure the position of ionisation produced in the gas by the passage of charged particles. The important properties of MWPCs are high-spatial-resolution, large-area, high-count-rate performance at low cost. For research applications, detectors several metres square have been built and small-area detectors have a charged particle resolution of 0.4 mm at a count rate of several million per second. Modification is required to MWPCs for nuclear medicine imaging. As gamma rays or X-rays cannot be detected directly, they must be converted into photo- or Compton scatter electrons. Photon-electron conversion requires the use of high atomic number materials in the body of the chamber. Pressurised xenon is the most useful form of "gas only" photon-electron convertor and has been used successfully in a gamma camera for the detection of gamma rays at energies below 100 keV. This camera has been developed specifically for high-count-rate first-pass cardiac imaging. This high-pressure xenon gas MWPC is the key to a highly competitive system which can outperform scintillator-based systems. The count rate performance is close to a million counts per second and the intrinsic spatial resolution is better than the best scintillator-based camera. The MWPC camera produces quantitative

  2. Plasma arc torch with coaxial wire feed

    DOEpatents

    Hooper, Frederick M

    2002-01-01

    A plasma arc welding apparatus having a coaxial wire feed. The apparatus includes a plasma arc welding torch, a wire guide disposed coaxially inside of the plasma arc welding torch, and a hollow non-consumable electrode. The coaxial wire guide feeds non-electrified filler wire through the tip of the hollow non-consumable electrode during plasma arc welding. Non-electrified filler wires as small as 0.010 inches can be used. This invention allows precision control of the positioning and feeding of the filler wire during plasma arc welding. Since the non-electrified filler wire is fed coaxially through the center of the plasma arc torch's electrode and nozzle, the wire is automatically aimed at the optimum point in the weld zone. Therefore, there is no need for additional equipment to position and feed the filler wire from the side before or during welding.

  3. Californium Recovery from Palladium Wire

    SciTech Connect

    Burns, Jon D.

    2014-08-01

    The recovery of 252Cf from palladium-252Cf cermet wires was investigated to determine the feasibility of implementing it into the cermet wire production operation at Oak Ridge National Laboratory’s Radiochemical Engineering Development Center. The dissolution of Pd wire in 8 M HNO3 and trace amounts of HCl was studied at both ambient and elevated temperatures. These studies showed that it took days to dissolve the wire at ambient temperature and only 2 hours at 60°C. Adjusting the ratio of the volume of solvent to the mass of the wire segment showed little change in the kinetics of dissolution, which ranged from 0.176 mL/mg down to 0.019 mL/mg. A successful chromatographic separation of 153Gd, a surrogate for 252Cf, from Pd was demonstrated using AG 50x8 cation exchange resin with a bed volume of 0.5 mL and an internal diameter of 0.8 cm.

  4. Antenna coupled photonic wire lasers.

    PubMed

    Kao, Tsung-Yu; Cai, Xiaowei; Lee, Alan W M; Reno, John L; Hu, Qing

    2015-06-29

    Slope efficiency (SE) is an important performance metric for lasers. In conventional semiconductor lasers, SE can be optimized by careful designs of the facet (or the modulation for DFB lasers) dimension and surface. However, photonic wire lasers intrinsically suffer low SE due to their deep sub-wavelength emitting facets. Inspired by microwave engineering techniques, we show a novel method to extract power from wire lasers using monolithically integrated antennas. These integrated antennas significantly increase the effective radiation area, and consequently enhance the power extraction efficiency. When applied to wire lasers at THz frequency, we achieved the highest single-side slope efficiency (~450 mW/A) in pulsed mode for DFB lasers at 4 THz and a ~4x increase in output power at 3 THz compared with a similar structure without antennas. This work demonstrates the versatility of incorporating microwave engineering techniques into laser designs, enabling significant performance enhancements. PMID:26191717

  5. Measuring fermion parity correlations in 1D topological superconducting wires

    NASA Astrophysics Data System (ADS)

    Burnell, F. J.; Shnirman, Alexander; Oreg, Yuval

    2014-03-01

    Zero energy Majorana fermion states (Majoranas) can arise at the ends of a semiconducting wire in proximity with a superconductor. A first generation of experiments has detected a zero bias conductance peak in these systems that strongly suggests these Majoranas do exist; however, a definitive demonstration of the long-ranged entanglement that is crucial for potential applications in quantum computing has yet to be carried out. We will discuss a possible measurement scheme to detect this long-ranged entanglement in a wire system with two coupled pairs of Majoranas, by varying the coupling between one pair and measuring the effect this has on the state of the second pair. This work was supported by DFG, TAMU, ISF, EU FP7 Project SOLID, and ERC (FP7/2007-2013) 340210 grants, and the BMBF Project RUS 10/053 ``Topologische Materialien für Nanoelektronik.''

  6. Designing potentials by sculpturing wires

    SciTech Connect

    Della Pietra, Leonardo; Aigner, Simon; Groth, Soenke; Hagen, Christoph von; Schmiedmayer, Joerg; Bar-Joseph, Israel; Lezec, Henri J.

    2007-06-15

    Magnetic trapping potentials for atoms on atom chips are determined by the current flow in the chip wires. By modifying the shape of the conductor we can realize specialized current flow patterns and therefore microdesign the trapping potentials. We have demonstrated this by nano-machining an atom chip using the focused ion beam technique. We built a trap, a barrier, and using a Bose-Einstein Condensate as a probe we showed that by polishing the conductor edge the potential roughness on the selected wire can be reduced. Furthermore, we give different other designs and discuss the creation of a one-dimensional magnetic lattice on an atom chip.

  7. Wire Detection Algorithms for Navigation

    NASA Technical Reports Server (NTRS)

    Kasturi, Rangachar; Camps, Octavia I.

    2002-01-01

    In this research we addressed the problem of obstacle detection for low altitude rotorcraft flight. In particular, the problem of detecting thin wires in the presence of image clutter and noise was studied. Wires present a serious hazard to rotorcrafts. Since they are very thin, their detection early enough so that the pilot has enough time to take evasive action is difficult, as their images can be less than one or two pixels wide. Two approaches were explored for this purpose. The first approach involved a technique for sub-pixel edge detection and subsequent post processing, in order to reduce the false alarms. After reviewing the line detection literature, an algorithm for sub-pixel edge detection proposed by Steger was identified as having good potential to solve the considered task. The algorithm was tested using a set of images synthetically generated by combining real outdoor images with computer generated wire images. The performance of the algorithm was evaluated both, at the pixel and the wire levels. It was observed that the algorithm performs well, provided that the wires are not too thin (or distant) and that some post processing is performed to remove false alarms due to clutter. The second approach involved the use of an example-based learning scheme namely, Support Vector Machines. The purpose of this approach was to explore the feasibility of an example-based learning based approach for the task of detecting wires from their images. Support Vector Machines (SVMs) have emerged as a promising pattern classification tool and have been used in various applications. It was found that this approach is not suitable for very thin wires and of course, not suitable at all for sub-pixel thick wires. High dimensionality of the data as such does not present a major problem for SVMs. However it is desirable to have a large number of training examples especially for high dimensional data. The main difficulty in using SVMs (or any other example-based learning

  8. Infrared spectral marker bands characterizing a transient water wire inside a hydrophobic membrane protein

    SciTech Connect

    Wolf, Steffen; Gerwert, Klaus; Freier, Erik; Cui, Qiang

    2014-12-14

    Proton conduction along protein-bound “water wires” is an essential feature in membrane proteins. Here, we analyze in detail a transient water wire, which conducts protons via a hydrophobic barrier within a membrane protein to create a proton gradient. It is formed only for a millisecond out of three water molecules distributed at inactive positions in a polar environment in the ground state. The movement into a hydrophobic environment causes characteristic shifts of the water bands reflecting their different chemical properties. These band shifts are identified by time-resolved Fourier Transform Infrared difference spectroscopy and analyzed by biomolecular Quantum Mechanical/Molecular Mechanical simulations. A non-hydrogen bonded (“dangling”) O–H stretching vibration band and a broad continuum absorbance caused by a combined vibration along the water wire are identified as characteristic marker bands of such water wires in a hydrophobic environment. The results provide a basic understanding of water wires in hydrophobic environments.

  9. Anode wire aging tests with selected gases

    SciTech Connect

    Kadyk, J.; Wise, J.; Hess, D.; Williams, M. )

    1990-04-01

    As a continuation of earlier wire aging investigations, additional candidates for wire chamber gas and wire have been tested. These include the gases: argon/ethane, HRS gas, dimethyl ether, carbon dioxide/ethane, and carbon tetrafluoride/isobutane. Wires used were: gold- plated tungsten, Stablohm, Nicotin, and Stainless Steel. Measurements were made of the effects upon wire aging of impurities from plumbing materials or contamination from various types of oil. Attempts were made to induce wire aging by adding measured amounts of oxygen and halogen (methyl chloride) with negative results. In this paper, the possible role of electronegativity in the wire aging process is discussed, and measurements of electronegativity are made with several single carbon Freons, using both an electron capture detector and a wire chamber operating with dimethyl ether.

  10. Electrical wire insulation and electromagnetic coil

    DOEpatents

    Bich, George J.; Gupta, Tapan K.

    1984-01-01

    An electromagnetic coil for high temperature and high radiation application in which glass is used to insulate the electrical wire. A process for applying the insulation to the wire is disclosed which results in improved insulation properties.

  11. Quality control of microelectronic wire bonds

    NASA Technical Reports Server (NTRS)

    Thiel, R. A.; Schmidt, G. D.

    1975-01-01

    Report evaluates ultrasonic bonding of small-diameter aluminum wire joined to ceramic substrates metalized with thin-film and thick-film gold. Quick testing technique for nondestructive location of poor wire bonds is also presented.

  12. Put Your Cable Wiring to the Test.

    ERIC Educational Resources Information Center

    Day, C. William

    2001-01-01

    Discusses why schools and universities should use testing procedures in any wire bid specification for cable wiring and also know how experienced the installers are in testing and installing structured cabling systems. Key cabling terms are included. (GR)

  13. New insulation constructions for aerospace wiring applications

    NASA Technical Reports Server (NTRS)

    Slenski, George

    1994-01-01

    Outlined in this presentation is the background to insulation constructions for aerospace wiring applications, the Air Force wiring policy, the purpose and contract requirements of new insulation constructions, the test plan, and the test results.

  14. A manually set magnetic wire counter

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Magnetic storage wire counter design principles are given. Magnetic storage wire was coupled with two phase propagational driver in manual set counter shift register. Time delay between magnetic counter domain insertion and corresponding output pulse provides counting functions.

  15. Technique for stripping Teflon insulated wire

    NASA Technical Reports Server (NTRS)

    Babb, B. D.

    1967-01-01

    Cryogenic stripping of Teflon insulated wire leaves no residue and produces no physical damage. After the wire is immersed in liquid nitrogen, bent slightly, and returned to room temperature, the Teflon is removed by fingernails or flat-nosed pliers.

  16. Wire Capture Programs for Macintosh and IBM.

    ERIC Educational Resources Information Center

    Wiley, Gale

    1989-01-01

    Discusses wire capture programs (computer programs which gather and process wire services such as the Associated Press or United Press) for computer labs in journalism departments. Describes details of such programs for Macintosh, IBM, and IBM clones. (SR)

  17. Electrical Wire Insulation and Electromagnetic Coil

    SciTech Connect

    Bich, G. J.; Gupta, T. K.

    1984-01-31

    An electromagnetic coil for high temperature and high radiation application in which glass is used to insulate the electrical wire. A process for applying the insulation to the wire is disclosed which results in improved insulation properties.

  18. REACH. Residential Electrical Wiring Units.

    ERIC Educational Resources Information Center

    Ansley, Jimmy; Ennis, Mike

    As a part of the REACH (Refrigeration, Electro-Mechanical, Air-Conditioning, Heating) electromechanical cluster, this student manual contains individualized instructional units in the area of residential electrical wiring. The instructional units focus on grounded outlets, service entrance, and blueprint reading. Each unit follows a typical format…

  19. Flexible substrate for printed wiring

    NASA Technical Reports Server (NTRS)

    Asakura, M.; Yabe, K.; Tanaka, H.; Soda, A.

    1982-01-01

    A very flexible substrate for printed wiring is disclosed which is composed of a blend of phenoxy resin-polyisocyanate-brominated epoxy resin in which the equivalent ration of the functional groups is hydroxyl grouped: isocyanate group: epoxy group = 1:0.2 to 2:0.5 to 3. The product has outstanding solder resistance and is applied to metal without using adhesives.

  20. Health care's 100 most wired.

    PubMed

    Solovy, A; Serb, C

    1999-02-01

    They're wired all right, and America's 100 most techno-savvy hospitals and health systems share one more thing: a commitment to using technology to link with employees, patients, suppliers, and insurers. "We want to be a health care travel agency for our community," says one chief information officer. "And we see Internet technology as a key." PMID:10081454

  1. Regeneration: New Neurons Wire Up.

    PubMed

    Raymond, Pamela A

    2016-09-12

    Functional repair of damage in the nervous system requires re-establishment of precise patterns of synaptic connectivity. A new study shows that after selective ablation, zebrafish retinal neurons regenerate and reconstruct some, although not all, of their stereotypic wiring. PMID:27623258

  2. 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.

  3. Plated wire random access memories

    NASA Technical Reports Server (NTRS)

    Gouldin, L. D.

    1975-01-01

    A program was conducted to construct 4096-work by 18-bit random access, NDRO-plated wire memory units. The memory units were subjected to comprehensive functional and environmental tests at the end-item level to verify comformance with the specified requirements. A technical description of the unit is given, along with acceptance test data sheets.

  4. Wire-Wrap Chatter Detector

    NASA Technical Reports Server (NTRS)

    Fisch, G. Z.; Borden, T. J.

    1982-01-01

    Monitoring circuit responds to changes in resistance as little as 0.1 ohm. Has been used to detect defective wire-wrap connections during thermal and vibration tests. Defect is indicated to operator by light-emitting diode and by increase in count on a two-digit display.

  5. Ultrasonic Calibration Wire Test Phantom

    SciTech Connect

    Lehman, S K; Fisher, K A; Werve, M; Chambers, D H

    2004-09-24

    We designed and built a phantom consisting of vertical wires maintained under tension to be used as an ultrasonic test, calibration, and reconstruction object for the Lawrence Livermore National Laboratory annular array scanner. We provide a description of the phantom, present example data sets, preliminary reconstructions, example metadata, and MATLAB codes to read the data.

  6. Transport Through Carbon Nanotube Wires

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Kwak, Dochan (Technical Monitor)

    2001-01-01

    This viewgraph presentation deals with the use of carbon nanotubes as a transport system. Contact, defects, tubular bend, phonons, and mechanical deformations all contribute to reflection within the nanotube wire. Bragg reflection, however, is native to an ideal energy transport system. Transmission resistance depends primarily on the level of energy present. Finally, the details regarding coupling between carbon nanotubes and simple metals are presented.

  7. Novel Wiring Technologies for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Gibson, Tracy L.; Parrish, Lewis M.

    2014-01-01

    Because wire failure in aerospace vehicles could be catastrophic, smart wiring capabilities have been critical for NASA. Through the years, researchers at Kennedy Space Center (KSC) have developed technologies, expertise, and research facilities to meet this need. In addition to aerospace applications, NASA has applied its knowledge of smart wiring, including self-healing materials, to serve the aviation industry. This webinar will discuss the development efforts of several wiring technologies at KSC and provide insight into both current and future research objectives.

  8. Further Studies Of Hot-Wire Anemometry

    NASA Technical Reports Server (NTRS)

    Mckenzie, Robert; Logan, Pamela; Bershader, Daniel

    1990-01-01

    Report discusses factors affecting readings of hot-wire anemometer in turbulent supersonic boundary layer. Represents extension of work described in "Hot-Wire Anemometry Versus Laser-Induced Fluorescence" (ARC-11802). Presents theoretical analysis of responses of hot-wire probe to changes in flow; also compares measurements by hot-wire probe with measurements of same flows by laser-induced fluorescence (LIF).

  9. Different mechanical properties in Seldinger guide wires

    PubMed Central

    Schummer, Wolfram

    2015-01-01

    Background and Aims: Most central venous catheters are placed using Seldinger guide wires. EN ISO 11070 is the guideline for testing guide wire flexing performance and tensile strength, and we can safely assume that guide wires in use meet these requirements. Unfortunately, EN ISO 11070 guidelines do not reflect the clinical requirements and we continue to see mechanical failures and their associated complications. Material and Methods: This in vitro study was performed in an accredited laboratory. With regard to flexing, we: (1) Established the minimum flexing performance needed to meet clinical requirements, (2) developed flexing performance tests which mimic clinical requirement, and (3) evaluated the mechanical properties of various guide wires relative to these requirements. With regard to tensile strength, we used the testing method prescribed in ISO 11070, but did not end the test at 5 Newton (N). We continued until the guide wire was damaged, or we reached maximum tractive force. We then did a wire-to-wire comparison. We examined two basic wire constructions, monofil and core and coil. Results: Tensile strength: All wires tested, except one, met EN ISO 11070 requirements for 5 N tensile strength. The mean of the wire types tested ranged from 15.06 N to 257.76 N. Flexing performance: None of the wires kinked. The monofil had no evidence of bending. Two core/coil wires displayed minor bending (angle 1.5°). All other wires displayed bending angles between 22.5° and 43.0°. Conclusion: We recommend that: (1) Clinicians use guide wires with high-end mechanical properties, (2) EN ISO 11070 incorporate our flexing test into their testing method, raise the flexing requirement to kink-proof, (3) and raise the tensile strength requirement to a minimum of 30 N, and (3) all manufacturers and suppliers be required to display mechanical properties of all guide wire, and guide wire kits sold. PMID:26702209

  10. NEMA wire and cable standards development programs

    NASA Technical Reports Server (NTRS)

    Baird, Robert W.

    1994-01-01

    The National Electrical Manufacturers Association (NEMA) is the nation's largest trade association for manufacturers of electrical equipment. Its member companies produce components, end-use equipment and systems for the generation, transmission, distribution, control and use of electricity. The wire and cable division is presented in 6 sections: building wire and cable, fabricated conductors, flexible cords, high performance wire and cable, magnet wire, and power and control cable. Participating companies are listed.

  11. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  12. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  13. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  14. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  15. 30 CFR 75.906 - Trailing cables for mobile equipment, ground wires, and ground check wires.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Trailing cables for mobile equipment, ground wires, and ground check wires. 75.906 Section 75.906 Mineral Resources MINE SAFETY AND HEALTH..., ground wires, and ground check wires. Trailing cables for mobile equipment shall contain one or...

  16. The effect of split gate dimensions on the electrostatic potential and 0.7 anomaly within one-dimensional quantum wires on a modulation doped GaAs/AlGaAs heterostructure

    NASA Astrophysics Data System (ADS)

    Smith, L. W.; Al-Taie, H.; Lesage, A. A. J.; Thomas, K. J.; Sfigakis, F.; See, P.; Griffiths, J. P.; Farrer, I.; Jones, G. A. C.; Ritchie, D. A.; Kelly, M. J.; Smith, C. G.

    We use a multiplexing scheme to measure the conductance properties of 95 split gates of 7 different gate dimensions fabricated on a GaAs/AlGaAs chip, in a single cool down. The number of devices for which conductance is accurately quantized reduces as the gate length increases. However, even the devices for which conductance is accurately quantized in units of 2e2 / h show no correlation between the length of electrostatic potential barrier in the channel and the gate length, using a saddle point model to estimate the barrier length. Further, the strength of coupling between the gates and the 1D channel does not increase with gate length beyond 0.7 μm. The background electrostatic profile appears as significant as the gate dimension in determining device behavior. We find a clear correlation between the curvature of the electrostatic barrier along the channel and the strength of the ``0.7 anomaly'' which identifies the electrostatic length of the channel as the principal factor governing the conductance of the 0.7 anomaly. Present address: Wisconsin Institute for Quantum Information, University of Wisconsin-Madison, Madison, WI.

  17. 49 CFR 236.838 - Wire, shunt.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Wire, shunt. 236.838 Section 236.838 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Wire, shunt. A wire forming part of a shunt circuit....

  18. 30 CFR 57.12047 - Guy wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Guy wires. 57.12047 Section 57.12047 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Electricity Surface and Underground § 57.12047 Guy wires. Guy wires of...

  19. Getting "Wired" for McLuhan's Cyberculture.

    ERIC Educational Resources Information Center

    McMurdo, George

    1995-01-01

    Examines the introduction of the computing magazine, "Wired", into the United Kingdom's (UK) market. Presents conversations with the founder and editorial staff of the UK edition, and discusses the accessibility of "Wired" via the World Wide Web. Describes 10 articles from United States "Wired" back-issues and presents critiques of a utopian…

  20. 49 CFR 393.28 - Wiring systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 5 2010-10-01 2010-10-01 false Wiring systems. 393.28 Section 393.28 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL MOTOR CARRIER SAFETY... NECESSARY FOR SAFE OPERATION Lamps, Reflective Devices, and Electrical Wiring § 393.28 Wiring...

  1. Home and School Technology: Wired versus Wireless.

    ERIC Educational Resources Information Center

    Van Horn, Royal

    2001-01-01

    Presents results of informal research on smart homes and appliances, structured home wiring, whole-house audio/video distribution, hybrid cable, and wireless networks. Computer network wiring is tricky to install unless all-in-one jacketed cable is used. Wireless phones help installers avoid pre-wiring problems in homes and schools. (MLH)

  2. Quantum Computation and Quantum Information

    NASA Astrophysics Data System (ADS)

    Nielsen, Michael A.; Chuang, Isaac L.

    2010-12-01

    Part I. Fundamental Concepts: 1. Introduction and overview; 2. Introduction to quantum mechanics; 3. Introduction to computer science; Part II. Quantum Computation: 4. Quantum circuits; 5. The quantum Fourier transform and its application; 6. Quantum search algorithms; 7. Quantum computers: physical realization; Part III. Quantum Information: 8. Quantum noise and quantum operations; 9. Distance measures for quantum information; 10. Quantum error-correction; 11. Entropy and information; 12. Quantum information theory; Appendices; References; Index.

  3. Quantum tunneling between bent semiconductor nanowires

    SciTech Connect

    Sousa, A. A.; Chaves, Andrey Farias, G. A.; Pereira, T. A. S.; Peeters, F. M.

    2015-11-07

    We theoretically investigate the electronic transport properties of two closely spaced L-shaped semiconductor quantum wires, for different configurations of the output channel widths as well as the distance between the wires. Within the effective-mass approximation, we solve the time-dependent Schrödinger equation using the split-operator technique that allows us to calculate the transmission probability, the total probability current, the conductance, and the wave function scattering between the energy subbands. We determine the maximum distance between the quantum wires below which a relevant non-zero transmission is still found. The transmission probability and the conductance show a strong dependence on the width of the output channel for small distances between the wires.

  4. Distribution of Transmission Eigenvalues in Disordered Wires with Symplectic Symmetry

    NASA Astrophysics Data System (ADS)

    Sakai, Hiroshi; Wakabayashi, Katsunori; Takane, Yositake

    2007-03-01

    We have numerically studied the electronic transport properties of quantum wires with symplectic symmetry based on the tight-binding model. The asymptotic behavior of the conductance crucially depends on the even-odd effect of the conducting channel, since one perfectly conducting channel exists only in the odd-channel system. The decay length of the conductance and the distribution of the largest transmission eigenvalues clearly show the even-odd difference. Our results are in excellent agreement with the random-matrix theory.

  5. Frequency response in short thermocouple wires

    NASA Technical Reports Server (NTRS)

    Forney, L. J.; Meeks, E. L.; Ma, J.; Fralick, G. C.

    1992-01-01

    Theoretical expressions are derived for the steady state frequency response of a thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for a nonuniform wire with unequal material properties and wire diameters across the junction. The amplitude ratio at low frequency omega approaches 0 agrees with the results of Scadron and Warshawsky (1952) for a steady state temperature distribution. Moreover, the frequency response for a nonuniform wire in the limit of infinite length l approaches infinity is shown to reduce to a simple expression that is analogous to the classic first order solution for a thermocouple wire with uniform properties. Theoretical expressions are also derived for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire and a two material wire with unequal material properties across the junction. For the case of a one material supported wire, an exact solution is derived which compares favorably with an approximate expression that only matches temperatures at the support junction. Moreover, for the case of a two material supported wire, an analytical expression is derived that closely correlates numerical results. Experimental measurements are made for the steady state frequency response of a supported thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a supported one material wire (type K) and a two material wire (type T) with unequal material properties across the junction. The data for the amplitude ratio and phase angle are correlated to within 10 pct. with the theoretical predictions of Forney and Fralick (1991). This is accomplished by choosing a natural frequency omega sub n for the wire data to correlate the first order response at large gas temperature frequencies. It is found that a large bead size, however, will increase the amplitude ratio at

  6. The nucleation mechanism of wire explosion

    NASA Astrophysics Data System (ADS)

    Tkachenko, S. I.; Vorob'ev, V. S.; Malyshenko, S. P.

    2004-02-01

    This study deals with the nucleation mechanism of electric explosion of wires allowing estimation of wire parameters at the start of the explosion for a wide range of experimental conditions. We analyse the dependence of the limit value of the energy deposited during the initial resistive phase of heating of the wire on the parameters of the wire and circuit as well as the size distribution of metal particles formed on electrical explosion of the wire. We discuss the correspondence of these results with previously published experimental data.

  7. Electromagnetic scattering by a straight thin wire

    NASA Technical Reports Server (NTRS)

    Shamansky, Harry T.; Dominek, Allen K.; Peters, Leon, Jr.

    1989-01-01

    The traveling-wave energy, which multiply diffracts on a straight thin wire, is represented as a sum of terms, each with a distinct physical meaning, that can be individually examined in the time domain. Expressions for each scattering mechanism on a straight thin wire are cast in the form of four basic electromagnetic wave concepts: diffraction, attachment, launch, and reflection. Using the basic mechanisms from P. Ya. Ufimtsev (1962), each of the scattering mechanisms is included into the total scattered field for the straight thin wire. Scattering as a function of angle and frequency is then compared to the moment-method solution. These analytic expressions are then extended to a lossy wire with a simple approximate modification using the propagation velocity on the wire as derived from the Sommerfeld wave on a straight lossy wire. Both the perfectly conducting and lossy wire solutions are compared to moment-method results, and excellent agreement is found. As is common with asymptotic solutions, when the electrical length of wire is smaller than 0.2 lambda the results lose accuracy. The expressions modified to approximate the scattering for the lossy thin wire yield excellent agreement even for lossy wires where the wire radius is on the order of skin depth.

  8. SpaceWire Data Handling Demonstration System

    NASA Astrophysics Data System (ADS)

    Mills, S.; Parkes, S. M.; O'Gribin, N.

    2007-08-01

    The SpaceWire standard was published in 2003 with the aim of providing a standard for onboard communications, defining the physical and data link layers of an interconnection, in order to improve reusability, reliability and to reduce the cost of mission development. The many benefits which it provides mean that it has already been used in a number of missions, both in Europe and throughout the world. Recent work by the SpaceWire community has included the development of higher level protocols for SpaceWire, such as the Remote Memory Access Protocol (RMAP) which can be used for many purposes, including the configuration of SpaceWire devices. Although SpaceWire has become very popular, the various ways in which it can be used are still being discovered, as are the most efficient ways to use it. At the same time, some in the space industry are not even aware of SpaceWire's existence. This paper describes the SpaceWire Data Handling Demonstration System that has been developed by the University of Dundee. This system simulates an onboard data handling network based on SpaceWire. It uses RMAP for all communication, and so demonstrates how SpaceWire and standardised higher level protocols can be used onboard a spacecraft. The system is not only a good advert for those who are unfamiliar with the benefits of SpaceWire, it is also a useful tool for those using SpaceWire to test ideas.

  9. Quantum cellular automata

    NASA Astrophysics Data System (ADS)

    Porod, Wolfgang; Lent, Craig S.; Bernstein, Gary H.

    1994-06-01

    The Notre Dame group has developed a new paradigm for ultra-dense and ultra-fast information processing in nanoelectronic systems. These Quantum Cellular Automata (QCA's) are the first concrete proposal for a technology based on arrays of coupled quantum dots. The basic building block of these cellular arrays is the Notre Dame Logic Cell, as it has been called in the literature. The phenomenon of Coulomb exclusion, which is a synergistic interplay of quantum confinement and Coulomb interaction, leads to a bistable behavior of each cell which makes possible their use in large-scale cellular arrays. The physical interaction between neighboring cells has been exploited to implement logic functions. New functionality may be achieved in this fashion, and the Notre Dame group invented a versatile majority logic gate. In a series of papers, the feasibility of QCA wires, wire crossing, inverters, and Boolean logic gates was demonstrated. A major finding is that all logic functions may be integrated in a hierarchial fashion which allows the design of complicated QCA structures. The most complicated system which was simulated to date is a one-bit full adder consisting of some 200 cells. In addition to exploring these new concepts, efforts are under way to physically realize such structures both in semiconductor and metal systems. Extensive modeling work of semiconductor quantum dot structures has helped identify optimum design parameters for QCA experimental implementations.

  10. NASA wiring for space applications program

    NASA Technical Reports Server (NTRS)

    Schulze, Norman

    1995-01-01

    An overview of the NASA Wiring for Space Applications Program and its relationship to NASA's space technology enterprise is given in viewgraph format. The mission of the space technology enterprise is to pioneer, with industry, the development and use of space technology to secure national economic competitiveness, promote industrial growth, and to support space missions. The objectives of the NASA Wiring for Space Applications Program is to improve the safety, performance, and reliability of wiring systems for space applications and to develop improved wiring technologies for NASA flight programs and commercial applications. Wiring system failures in space and commercial applications have shown the need for arc track resistant wiring constructions. A matrix of tests performed versus wiring constructions is presented. Preliminary data indicate the performance of the Tensolite and Filotex hybrid constructions are the best of the various candidates.

  11. Wire Crimp Connectors Verification using Ultrasonic Inspection

    NASA Technical Reports Server (NTRS)

    Cramer, K. Elliott; Perey, Daniel F.; Yost, William T.

    2007-01-01

    The development of a new ultrasonic measurement technique to quantitatively assess wire crimp connections is discussed. The amplitude change of a compressional ultrasonic wave propagating through the junction of a crimp connector and wire is shown to correlate with the results of a destructive pull test, which previously has been used to assess crimp wire junction quality. Various crimp junction pathologies (missing wire strands, incorrect wire gauge, incomplete wire insertion in connector) are ultrasonically tested, and their results are correlated with pull tests. Results show that the ultrasonic measurement technique consistently (as evidenced with pull-testing data) predicts good crimps when ultrasonic transmission is above a certain threshold amplitude level. A physics-based model, solved by finite element analysis, describes the compressional ultrasonic wave propagation through the junction during the crimping process. This model is in agreement within 6% of the ultrasonic measurements. A prototype instrument for applying the technique while wire crimps are installed is also presented.

  12. High Tc superconductors - Composite wire fabrication

    NASA Astrophysics Data System (ADS)

    Jin, S.; Sherwood, R. C.; van Dover, R. B.; Tiefel, T. H.; Johnson, D. W., Jr.

    1987-07-01

    The fabrication of fine-wire, composite superconductors consisting of a high-conductivity normal metal shell, such as Ag or Cu/Ni/Au, and a superconducting core of Ba2YCu3O oxide is described. The functions of the normal metal shell and the importance of using the proper diffusion barrier metals are discussed. A resistivity-temperature curve for the composite wire Ag/Ba2YCu3O7 is examined, and the compound inside the finished wire is analyzed using X-ray diffraction. It is observed that the zero-field critical current density of the wire at 77 K is about 175 A/sq cm and the superconducting core is continuous and retains phase composition after wire drawing and heat treatment. The supplying of oxygen to the core of the long wire during heat treatments is studied. The data reveal that it is possible to process ceramic superconductors into a desirable composite wire form.

  13. Enhanced absorption and carrier collection in Si wire arrays for photovoltaic applications

    SciTech Connect

    Kelzenberg, Michael D.; Boettcher, Shannon W.; Petykiewicz, Jan A.; Turner-Evans, Daniel B.; Putnam, Morgan C.; Warren, Emily L.; Spurgeon, Joshua M.; Briggs, Ryan M.; Lewis, Nathan S.; Atwater, Harry A.

    2010-02-14

    Si wire arrays are a promising architecture for solar-energy-harvesting applications, and may offer a mechanically flexible alternative to Si wafers for photovoltaics. To achieve competitive conversion efficiencies, the wires must absorb sunlight over a broad range of wavelengths and incidence angles, despite occupying only a modest fraction of the array’s volume. Here, we show that arrays having less than 5% areal fraction of wires can achieve up to 96% peak absorption, and that they can absorb up to 85% of day-integrated, above-bandgap direct sunlight. In fact, these arrays show enhanced near-infrared absorption, which allows their overall sunlight absorption to exceed the ray-optics light-trapping absorption limit18 for an equivalent volume of randomly textured planar Si, over a broad range of incidence angles. We furthermore demonstrate that the light absorbed by Si wire arrays can be collected with a peak external quantum efficiency of 0.89, and that they show broadband, near-unity internal quantum efficiency for carrier collection through a radial semiconductor/liquid junction at the surface of each wire. The observed absorption enhancement and collection efficiency enable a cell geometry that not only uses 1/100th the material of traditional wafer-based devices, but also may offer increased photovoltaic efficiency owing to an effective optical concentration of up to 20 times.

  14. Sintered wire cesium dispenser photocathode

    DOEpatents

    Montgomery, Eric J; Ives, R. Lawrence; Falce, Louis R

    2014-03-04

    A photoelectric cathode has a work function lowering material such as cesium placed into an enclosure which couples a thermal energy from a heater to the work function lowering material. The enclosure directs the work function lowering material in vapor form through a low diffusion layer, through a free space layer, and through a uniform porosity layer, one side of which also forms a photoelectric cathode surface. The low diffusion layer may be formed from sintered powdered metal, such as tungsten, and the uniform porosity layer may be formed from wires which are sintered together to form pores between the wires which are continuous from the a back surface to a front surface which is also the photoelectric surface.

  15. Parallel wire cable static load testing

    NASA Astrophysics Data System (ADS)

    Velasco Gil, Isabella C.

    This report is the result of two evaluations for the analysis of parallel wire cables. The purpose of the first assessment was to evaluate the stiffness and strength of parallel wire cables. For the methodology, three test setups were executed utilizing single wires, seven wire parallel cables, and 100 wire parallel cables as specimens. The parallel wire cables were connected with molted zinc to their sockets. The cables were manufactured by Wilolamb Construction. The results indicate that the single, seven, and 100 wire specimens had similar performance in yield stress, yield strain, modulus, and ultimate strain. However, the amount of strain decreased as the number of wires increased. Because the mechanical properties of the multi wires specimens had not significant difference, it is suggested that the zinc sockets had insignificant impact on their performance. Comparing these results to a previous test executed for parallel wire cables, there were significant differences on the ultimate capacity. It is assumed that the fabrication method of the cables were different. The second evaluation had two purposes. First, it was intended to compare the results of the single wire test from OSU to the single wire test results from Sherry Laboratories. From the analysis, it was found that the ultimate and yield loads were similar between both laboratories procedures, but their strength capacity and ultimate strain were different. It was observed that the Sherry Lab used a different method to compute the mechanical properties of the wire and that the measurement of the elongation was different to the procedures from OSU. Second, the secondary analysis was to evaluate if there is any significant difference between wires sanded at the mid-length of the specimen and wires that were not sanded. From this analysis it was observed that there was no difference between the sanded and non-sanded wires, which indicated that cross-section reduction should not be necessary for the

  16. Pin Wire Coating Trip Report

    SciTech Connect

    Spellman, G P

    2004-03-18

    A meeting to discuss the current pin wire coating problems was held at the Reynolds plant in Los Angeles on 2MAR04. The attendance list for Reynolds personnel is attached. there was an initial presentation which gave a brief history and the current status of pin wire coating at Reynolds. There was a presentation by Lori Primus on the requirements and issues for the coating. There was a presentation by Jim Smith of LANL on the chemistry and to some extent process development done to date. There was a long session covering what steps should be taken in the short term and, to a lesser extent, the long term. The coating currently being used is a blend of two polymers, polyethersulfone and polyparabanic acid (PPA) and some TiO2 filler. This system was accepted and put into production when the pin wire coating was outsourced to another company in 1974. When that company no longer was interested, the wire coating was brought in-house to Reynolds. At that time polyparabanic acid was actually a commercial product available from Exxon under the trade name Tradlon. However, it appears that the material used at Reynolds was synthesized locally. Also, it appears that a single large batch was synthesized in that time period and used up to 1997 when the supply ran out. The reason for the inclusion of TiO2 is not known although it does act as a rheological thickener. However, a more controlled thickening can be obtained with materials such as fumed silica. This material would have less likelihood of causing point imperfections in the coatings. Also, the mixing technique being used for all stages of the process is a relatively low shear ball mill process and the author recommends a high shear process such as a three roll paint mill, at least for the final mixing. Since solvent is added to the powder at Reynolds, it may be that they need to have the paint mill there.

  17. Reduced-Wiring Tactile Sensor

    NASA Technical Reports Server (NTRS)

    Ohm, Timothy R.

    1991-01-01

    Proposed tactile sensor on robot finger puts out multiplexed analog signals transmitted to control computer on fewer wires than needed to transmit equivalent digital signals. Analog output represents data on contact area of object being gripped, on position of object, and on direction and rate of slippage if any. Consists of chains of normally open switches and resistors on surface of finger. Each resistance double preceding resistance in each chain. Constant-current sources supply power to chains.

  18. Substrate effect on the band gap of semiconducting atomic wires

    NASA Astrophysics Data System (ADS)

    Simbeck, Adam J.; Nayak, Saroj K.

    2014-03-01

    The electronic structure of free-standing and supported semiconducting atomic wires is investigated using a combination of first-principles density functional theory (DFT) and many-body perturbation theory (MBPT). The band gaps predicted from DFT for SiH2 and GeH2 atomic wires are unaffected by the presence of the substrate, whereas the gaps calculated using MBPT under the GW approximation are reduced by about 1eV when the wires are supported. The reduction in the band gap is attributed to a change in the electronic correlation energy, which can be understood as a screened Coulomb interaction. These results highlight the importance of the role played by the substrate in manipulating the electronic and optical properties of quantum confined Si and Ge systems. Work supported by the Interconnect Focus Center (MARCO program), State of New York, NSF IGERT Program, Grant no. 0333314, NSF Petascale Simulations and Analysis (PetaApps) program, Grant No. 0749140, and computing resources of the CCNI at RPI.

  19. Low-energy theory of transport in Majorana wire junctions

    NASA Astrophysics Data System (ADS)

    Zazunov, A.; Egger, R.; Levy Yeyati, A.

    2016-07-01

    We formulate and apply a low-energy transport theory for hybrid quantum devices containing junctions of topological superconductor (TS) wires and conventional normal (N) or superconducting (S) leads. We model TS wires as spinless p -wave superconductors and derive their boundary Keldysh Green's function, capturing both the Majorana end state and continuum quasiparticle excitations in a unified manner. We also specify this Green's function for a finite-length TS wire. Junctions connecting different parts of the device are described by the standard tunneling Hamiltonian. Using this Hamiltonian approach, one also has the option to include many-body interactions in a systematic manner. For N-TS junctions, we provide the current-voltage (I -V ) characteristics at arbitrary junction transparency and give exact results for the shot-noise power and the excess current. For TS-TS junctions, analytical results for the thermal noise spectrum and for the I -V curve in the high-transparency low-bias regime are presented. For S-TS junctions, we compute the entire I -V curve and clarify the conditions for having a finite Josephson current.

  20. Investigation of Photovoltaic Properties of Single Core-Shell GaN/InGaN Wires.

    PubMed

    Messanvi, A; Zhang, H; Neplokh, V; Julien, F H; Bayle, F; Foldyna, M; Bougerol, C; Gautier, E; Babichev, A; Durand, C; Eymery, J; Tchernycheva, M

    2015-10-01

    We report the investigation of the photovoltaic properties of core-shell GaN/InGaN wires. The radial structure is grown on m-plane {11̅00} facets of self-assembled c̅-axis GaN wires elaborated by metal-organic vapor phase epitaxy (MOVPE) on sapphire substrates. The conversion efficiency of wires with radial shell composed of thick In0.1Ga0.9N layers and of 30× In0.18Ga0.82N/GaN quantum wells are compared. We also investigate the impact of the contact nature and layout on the carrier collection and photovoltaic performances. The contact optimization results in an improved conversion efficiency of 0.33% and a fill factor of 83% under 1 sun (AM1.5G) on single wires with a quantum well-based active region. Photocurrent spectroscopy demonstrates that the response ascribed to the absorption of InGaN/GaN quantum wells appears at wavelengths shorter than 440 nm. PMID:26378593

  1. Electronic conductance via atomic wires: a phase field matching theory approach

    NASA Astrophysics Data System (ADS)

    Szczęśniak, D.; Khater, A.

    2012-06-01

    A model is presented for the quantum transport of electrons, across finite atomic wire nanojunctions between electric leads, at zero bias limit. In order to derive the appropriate transmission and reflection spectra, familiar in the Landauer-Büttiker formalism, we develop the algebraic phase field matching theory (PFMT). In particular, we apply our model calculations to determine the electronic conductance for freely suspended monatomic linear sodium wires (MLNaW) between leads of the same element, and for the diatomic copper-cobalt wires (DLCuCoW) between copper leads on a Cu(111) substrate. Calculations for the MLNaW system confirm the correctness and functionality of our PFMT approach. We present novel transmission spectra for this system, and show that its transport properties exhibit the conductance oscillations for the odd- and even-number wires in agreement with previously reported first-principle results. The numerical calculations for the DLCuCoW wire nanojunctions are motivated by the stability of these systems at low temperatures. Our results for the transmission spectra yield for this system, at its Fermi energy, a monotonic exponential decay of the conductance with increasing wire length of the Cu-Co pairs. This is a cumulative effect which is discussed in detail in the present work, and may prove useful for applications in nanocircuits. Furthermore, our PFMT formalism can be considered as a compact and efficient tool for the study of the electronic quantum transport for a wide range of nanomaterial wire systems. It provides a trade-off in computational efficiency and predictive capability as compared to slower first-principle based methods, and has the potential to treat the conductance properties of more complex molecular nanojunctions.

  2. Method and apparatus for laying wire arrays

    DOEpatents

    Horowitz, Seymour M.; Nesbitt, Dale D.

    1986-01-01

    Wire arrays (11) having a continuous wire (12) which is formed into a predetermined pattern and adhered to a backing material or substrate (13) are fabricated by applying adhesive material (16a, 16b) along opposite edge portions (17, 18) of the substrate, positioning a row of winding spools (21) along each of the edge portions and repeatedly extending the wire between and around successive spools at the opposite edge portions. The wound wire is then traveled along each spool toward the substrate and into contact with the adhesive. The spools are then removed and a coating of hardenable material (54) is applied to secure the wound wire to the substrate. Tension in the wire is relieved prior to contact of the wire with the adhesive and a small amount of slack is introduced into the wire before the final coating step. Mechanism (32) is provided for lifting the spools away from the substrate without disturbing the wound wire. The method and apparatus enable manufacture of precisely configured wire arrays without complex or costly equipment and do not require structural alterations in the substrate for the purpose of accommodating to fabrication equipment.

  3. Analysis of Conical Wire Array Z-Pinch Stability with a Center Wire

    SciTech Connect

    Martinez, D.; Presura, R.; Wright, S.; Plechaty, C.; Neff, S.; Wanex, L.; Ampleford, D. J.

    2009-01-21

    Adding a center wire on the axis of a conical wire array produces conditions suitable for studying shear flow stabilization of the Z-pinch. The conical wire array produces and axial plasma flow while the center wire introduces a radial variation of the axial velocity. Experiments of this array configuration were preformed on the 1 MA Zebra Z-pinch generator and showed stabilization of the kink instability when a center wire was present. Comparison with equivalent cylindrical wire arrays indicates that the shear flow stabilization plays a role in the stabilization of the kink instability.

  4. Effect of low transverse magnetic field on the confinement strength in a quasi-1D wire

    SciTech Connect

    Kumar, Sanjeev; Thomas, K. J.; Smith, L. W.; Farrer, I.; Ritchie, D. A.; Jones, G. A. C.; Griffiths, J.; Pepper, M.

    2013-12-04

    Transport measurements in a quasi-one dimensional (1D) quantum wire are reported in the presence of low transverse magnetic field. Differential conductance shows weak quantised plateaus when the 2D electrons are squeezed electrostatically. Application of a small transverse magnetic field (0.2T) enhances the overall degree of quantisation due to the formation of magneto-electric subbands. The results show the role of magnetic field to fine tune the confinement strength in low density wires when interaction gives rise to double row formation.

  5. Thermal energy scavenger (rotating wire modules)

    SciTech Connect

    Hochstein, P.A.; Milton, H.W.; Pringle, W.L.

    1980-11-04

    A thermal energy scavenger assembly is is described including a plurality of temperature-sensitive wires made of material which exhibits shape memory due to a thermoelastic, martensitic phase transformation. The wires are placed in tension between fixed and movable plates which are, in turn, supported by a pair of wheels which are rotatably supported by a housing for rotation about a central axis. A pair of upper and lower cams are fixed to the housing and cam followers react with the respective cams. Each cam transmits forces through a pair of hydraulic pistons. One of the pistons is connected to a movable plate to which one end of the wires are connected whereby a stress is applied to the wires to strain the wires during a first phase and whereby the cam responds to the unstraining of the wires during a second phase. A housing defines fluid compartments through which hot and cold fluid passes and flows radially through the wires whereby the wires become unstrained and shorten in length when subjected to the hot fluid for causing a reaction between the cam followers and the cams to effect rotation of the wheels about the central axis of the assembly, which rotation of the wheels is extracted through beveled gearing. The wires are grouped into a plurality of independent modules with each module having a movable plate, a fixed plate and the associated hydraulic pistons and cam follower. The hydraulic pistons and cam follower of a module are disposed at ends of the wires opposite from the ends of the wires at which the same components of the next adjacent modules are disposed so that the cam followers of alternate modules react with one of the cams and the remaining cam followers of the remaining modules react with the other cam. There is also included stress limiting means in the form of coil springs associated with alternate ends of the wires for limiting the stress or strain in the wires.

  6. A Vibrating Wire System For Quadrupole Fiducialization

    SciTech Connect

    Wolf, Zachary

    2010-12-13

    A vibrating wire system is being developed to fiducialize the quadrupoles between undulator segments in the LCLS. This note provides a detailed analysis of the system. The LCLS will have quadrupoles between the undulator segments to keep the electron beam focused. If the quadrupoles are not centered on the beam axis, the beam will receive transverse kicks, causing it to deviate from the undulator axis. Beam based alignment will be used to move the quadrupoles onto a straight line, but an initial, conventional alignment must place the quadrupole centers on a straight line to 100 {micro}m. In the fiducialization step of the initial alignment, the position of the center of the quadrupole is measured relative to tooling balls on the outside of the quadrupole. The alignment crews then use the tooling balls to place the magnet in the tunnel. The required error on the location of the quadrupole center relative to the tooling balls must be less than 25 {micro}m. In this note, we analyze a system under construction for the quadrupole fiducialization. The system uses the vibrating wire technique to position a wire onto the quadrupole magnetic axis. The wire position is then related to tooling balls using wire position detectors. The tooling balls on the wire position detectors are finally related to tooling balls on the quadrupole to perform the fiducialization. The total 25 {micro}m fiducialization error must be divided between these three steps. The wire must be positioned onto the quadrupole magnetic axis to within 10 {micro}m, the wire position must be measured relative to tooling balls on the wire position detectors to within 15 {micro}m, and tooling balls on the wire position detectors must be related to tooling balls on the quadrupole to within 10 {micro}m. The techniques used in these three steps will be discussed. The note begins by discussing various quadrupole fiducialization techniques used in the past and discusses why the vibrating wire technique is our method

  7. Wire ablation dynamics model and its application to imploding wire arrays of different geometries.

    PubMed

    Esaulov, A A; Kantsyrev, V L; Safronova, A S; Velikovich, A L; Shrestha, I K; Williamson, K M; Osborne, G C

    2012-10-01

    The paper presents an extended description of the amplified wire ablation dynamics model (WADM), which accounts in a single simulation for the processes of wire ablation and implosion of a wire array load of arbitrary geometry and wire material composition. To investigate the role of wire ablation effects, the implosions of cylindrical and planar wire array loads at the university based generators Cobra (Cornell University) and Zebra (University of Nevada, Reno) have been analyzed. The analysis of the experimental data shows that the wire mass ablation rate can be described as a function of the current through the wire and some coefficient defined by the wire material properties. The aluminum wires were found to ablate with the highest rate, while the copper ablation is the slowest one. The lower wire ablation rate results in a higher inward velocity of the ablated plasma, a higher rate of the energy coupling with the ablated plasma, and a more significant delay of implosion for a heavy load due to the ablation effects, which manifest the most in a cylindrical array configuration and almost vanish in a single-planar array configuration. The WADM is an efficient tool suited for wire array load design and optimization in wide parameter ranges, including the loads with specific properties needed for the inertial confinement fusion research and laboratory astrophysics experiments. The data output from the WADM simulation can be used to simplify the radiation magnetohydrodynamics modeling of the wire array plasma. PMID:23214697

  8. Wire ablation dynamics model and its application to imploding wire arrays of different geometries

    NASA Astrophysics Data System (ADS)

    Esaulov, A. A.; Kantsyrev, V. L.; Safronova, A. S.; Velikovich, A. L.; Shrestha, I. K.; Williamson, K. M.; Osborne, G. C.

    2012-10-01

    The paper presents an extended description of the amplified wire ablation dynamics model (WADM), which accounts in a single simulation for the processes of wire ablation and implosion of a wire array load of arbitrary geometry and wire material composition. To investigate the role of wire ablation effects, the implosions of cylindrical and planar wire array loads at the university based generators Cobra (Cornell University) and Zebra (University of Nevada, Reno) have been analyzed. The analysis of the experimental data shows that the wire mass ablation rate can be described as a function of the current through the wire and some coefficient defined by the wire material properties. The aluminum wires were found to ablate with the highest rate, while the copper ablation is the slowest one. The lower wire ablation rate results in a higher inward velocity of the ablated plasma, a higher rate of the energy coupling with the ablated plasma, and a more significant delay of implosion for a heavy load due to the ablation effects, which manifest the most in a cylindrical array configuration and almost vanish in a single-planar array configuration. The WADM is an efficient tool suited for wire array load design and optimization in wide parameter ranges, including the loads with specific properties needed for the inertial confinement fusion research and laboratory astrophysics experiments. The data output from the WADM simulation can be used to simplify the radiation magnetohydrodynamics modeling of the wire array plasma.

  9. Tensile deformation of NiTi wires.

    PubMed

    Gall, Ken; Tyber, Jeff; Brice, Valerie; Frick, Carl P; Maier, Hans J; Morgan, Neil

    2005-12-15

    We examine the structure and properties of cold drawn Ti-50.1 at % Ni and Ti-50.9 at % Ni shape memory alloy wires. Wires with both compositions possess a strong <111> fiber texture in the wire drawing direction, a grain size on the order of micrometers, and a high dislocation density. The more Ni rich wires contain fine second phase precipitates, while the wires with lower Ni content are relatively free of precipitates. The wire stress-strain response depends strongly on composition through operant deformation mechanisms, and cannot be explained based solely on measured differences in the transformation temperatures. We provide fundamental connections between the material structure, deformation mechanisms, and resulting stress-strain responses. The results help clarify some inconsistencies and common misconceptions in the literature. Ramifications on materials selection and design for emerging biomedical applications of NiTi shape memory alloys are discussed. PMID:16138359

  10. Wire Whip Keeps Spray Nozzle Clean

    NASA Technical Reports Server (NTRS)

    Carroll, H. R.

    1982-01-01

    Air-turbine-driven wire whip is clamped near spray-gun mount. When spray gun is installed, wire whip is in position to remove foam buildup from nozzle face. Two lengths of wire 1 to 2 inches long and about 0.03 inch in thickness are used. Foam spray would be prevented from accumulating on nozzle face by increasing purge flow and cutting vortex-generating grooves inside cap and on nozzle flats.

  11. Space Shuttle Columbia Aging Wiring Failure Analysis

    NASA Technical Reports Server (NTRS)

    McDaniels, Steven J.

    2005-01-01

    A Space Shuttle Columbia main engine controller 14 AWG wire short circuited during the launch of STS-93. Post-flight examination divulged that the wire had electrically arced against the head of a nearby bolt. More extensive inspection revealed additional damage to the subject wire, and to other wires as well from the mid-body of Columbia. The shorted wire was to have been constructed from nickel-plated copper conductors surrounded by the polyimide insulation Kapton, top-coated with an aromatic polyimide resin. The wires were analyzed via scanning electron microscope (SEM), energy dispersive X-Ray spectroscopy (EDX), and electron spectroscopy for chemical analysis (ESCA); differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were performed on the polyimide. Exemplar testing under laboratory conditions was performed to replicate the mechanical damage characteristics evident on the failed wires. The exemplar testing included a step test, where, as the name implies, a person stepped on a simulated wire bundle that rested upon a bolt head. Likewise, a shear test that forced a bolt head and a torque tip against a wire was performed to attempt to damage the insulation and conductor. Additionally, a vibration test was performed to determine if a wire bundle would abrade when vibrated against the head of a bolt. Also, an abrasion test was undertaken to determine if the polyimide of the wire could be damaged by rubbing against convolex helical tubing. Finally, an impact test was performed to ascertain if the use of the tubing would protect the wire from the strike of a foreign object.

  12. Radiofrequency Wire Recanalization of Chronically Thrombosed TIPS.

    PubMed

    Majdalany, Bill S; Elliott, Eric D; Michaels, Anthony J; Hanje, A James; Saad, Wael E A

    2016-07-01

    Radiofrequency (RF) guide wires have been applied to cardiac interventions, recanalization of central venous thromboses, and to cross biliary occlusions. Herein, the use of a RF wire technique to revise chronically occluded transjugular intrahepatic portosystemic shunts (TIPS) is described. In both cases, conventional TIPS revision techniques failed to revise the chronically thrombosed TIPS. RF wire recanalization was successfully performed through each of the chronically thrombosed TIPS, demonstrating initial safety and feasibility in this application. PMID:26902703

  13. Nondestructive Evaluation of Aircraft and Spacecraft Wiring

    NASA Technical Reports Server (NTRS)

    White, John E.; Tucholski, Edward J.; Green, Robert E., Jr.

    2004-01-01

    Spacecraft, and especially aircraft, often fry well past their original design lives and, therefore, the need to develop nondestructive evaluation procedures for inspection of vital structures in these craft is extremely important. One of the more recent problems is the degradation of wiring and wiring insulation. The present paper describes several nondestructive characterization methods which afford the possibility to detect wiring and insulation degradation in-situ prior to major problems with the safety of aircraft and spacecraft.

  14. Wrapped Wire Detects Rupture Of Pressure Vessel

    NASA Technical Reports Server (NTRS)

    Hunt, James B.

    1990-01-01

    Simple, inexpensive technique helps protect against damage caused by continuing operation of equipment after rupture or burnout of pressure vessel. Wire wrapped over area on outside of vessel where breakthrough most likely. If wall breaks or burns, so does wire. Current passing through wire ceases, triggering cutoff mechanism stopping flow in vessel to prevent further damage. Applied in other situations in which pipes or vessels fail due to overpressure, overheating, or corrosion.

  15. Wire frame to MOVIE. BYU transfer program

    SciTech Connect

    Robbins, D.; Byers, L.D.; Benner, M.S.

    1982-12-01

    At SNLA, the primary computer-aided drafting tool is the Applicon Graphics System (AGS). The data base for mechanical parts on the AGS is a wire frame model. This report summarizes a method of adding surface information to the wire frame and passing this information up stream to MOVIE.BYU which is on a VAX computer and is used to produce shaded graphics pictures of the AGS wire frame model on a RAMTEK 9400 display terminal.

  16. Development of the Axial Instability in Low Wire Number Wire Array Z-Pinches

    SciTech Connect

    Knapp, P. F.; Bell, K. S.; Blesener, I. C.; Chalenski, D. A.; Douglass, J. D.; Greenly, J. B.; Martin, M. R.; McBride, R. D.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Kusse, B. R.; Hall, G. N.

    2009-01-21

    We are investigating the development of the axial instability, a modulation of the size of the coronal plasma that develops around each wire in wire-array Z-pinches. The modulation is a result of nonuniform ablation of material from the relatively cold wire core. It has long been known that the wavelength of this modulation is constant late in time and, since it is unique to different materials, it has come to be known as the fundamental mode. In these experiments we imaged individual wires with laser shadowgraphy early in time primarily in low wire number, large wire diameter aluminum arrays for ease of viewing. We Observe the development of this modulation from the time of initiation of coronal plasma, obtaining its dominant wavelength and amplitude growth as a function of time. We also studied the instability on coiled wires, which modify the wire ablation mechanism and completely suppress the fundamental mode[Hall2008]. time is discussed.

  17. 49 CFR 234.241 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... underground wire. 234.241 Section 234.241 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION GRADE CROSSING SAFETY, INCLUDING... Testing Maintenance Standards § 234.241 Protection of insulated wire; splice in underground...

  18. 49 CFR 234.241 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... underground wire. 234.241 Section 234.241 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION GRADE CROSSING SAFETY, INCLUDING... Testing Maintenance Standards § 234.241 Protection of insulated wire; splice in underground...

  19. 49 CFR 234.241 - Protection of insulated wire; splice in underground wire.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... underground wire. 234.241 Section 234.241 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION GRADE CROSSING SAFETY, INCLUDING... Testing Maintenance Standards § 234.241 Protection of insulated wire; splice in underground...

  20. Wired

    NASA Astrophysics Data System (ADS)

    Carlowicz, Michael

    Every American grade school and library ought to have free access to the Internet, and universities and institutions ought to have better access, according to the Clinton Administration.In an October 10 speech in Knoxville, Tennessee, President Clinton proposed that all of the nation's 100,000 public schools and 9,000 libraries receive a two-tiered E-rate (education rate) for access to Internet services. All schools and libraries should receive basic connections for free, as well as deep discounts on video conferencing and highspeed connections (with prices influenced by how much the school can afford to pay). The basic connections (and part of the cost of the more sophisticated connections) would be paid from a special federal fund that currently provides below-cost phone service to households in poor and rural areas. That fund is currently drawn from fees assessed on local and long-distance telephone providers; the Clinton Administration would have cable operators and cellular service providers contribute as well. Companies that provide Internet services would be paid at the best available commercial rate.

  1. Wired.

    ERIC Educational Resources Information Center

    Conklin, Aaron R.

    1998-01-01

    Discusses technology's impact on scoreboard design: the development of the light-emitting diode (LED) display. How the LED system works is explained, as are the advantages and disadvantages of LED compared with incandescent lamp boards. Final comments address deciding on materials for scoreboard casings. (GR)

  2. Superconducting-wire fabrication. Final report

    SciTech Connect

    Glad, W.E.; Chase, G.G.

    1990-05-01

    Experiments were done leading to the fabrication of high-temperature superconducting composite wire. Bulk superconductor was characterized by using optical microscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. The chemical compatibility of superconducting materials with a number of metal sheathing candidates was tested, with silver offering the best compatibility. Wire was fabricated by drawing 0.250-inch-diameter silver tubing packed with superconducting powder. Single core wires were drawn to 0.037-inch diameter. The best critical current performance (660 A/cm2) for leaded bismuth 2-2-2-3 material was achieved by flattening single-core wire before heat treatment.

  3. Effect of an Axial Wire on Conical Wire Array Z-Pinch Radiation

    SciTech Connect

    Presura, R.; Martinez, D.; Wright, S.; Plechaty, C.; Neff, S.; Wanex, L.; Ampleford, D. J.

    2009-01-21

    Adding a wire on the axis of wire arrays significantly affects the x-ray emission of the conical arrays, and much less that of the cylindrical ones. The radiation of the conical wire arrays increases with the thickness of the central wire, surpassing that of the equivalent cylindrical arrays. Significant energy is emitted early on, around the time of the conical shock formation, before the pinch stagnation.

  4. 47 CFR 76.804 - Disposition of home run wiring.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Disposition of home run wiring. 76.804 Section... MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cable Inside Wiring § 76.804 Disposition of home run wiring. (a) Building-by-building disposition of home run wiring. (1) Where an MVPD owns the home run wiring in an...

  5. 47 CFR 76.804 - Disposition of home run wiring.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Disposition of home run wiring. 76.804 Section... MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cable Inside Wiring § 76.804 Disposition of home run wiring. (a) Building-by-building disposition of home run wiring. (1) Where an MVPD owns the home run wiring in an...

  6. 47 CFR 76.804 - Disposition of home run wiring.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Disposition of home run wiring. 76.804 Section... MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Cable Inside Wiring § 76.804 Disposition of home run wiring. (a) Building-by-building disposition of home run wiring. (1) Where an MVPD owns the home run wiring in an...

  7. 46 CFR 129.340 - Cable and wiring.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Power Sources and Distribution Systems § 129.340 Cable and wiring. (a) If individual wires, rather than... tank, unless it supplies power to equipment in the tank; and (9) Have sheathing or wire insulation...) Cable and wire in power and lighting circuits must be #14 AWG or larger. Cable and wire in control...

  8. Processing A Printed Wiring Board By Single Bath Electrodeposition

    DOEpatents

    Meltzer, Michael P.; Steffani, Christopher P.; Gonfiotti, Ray A.

    2003-04-15

    A method of processing a printed wiring board by single bath electrodeposition. Initial processing steps are implemented on the printed wiring board. Copper is plated on the printed wiring board from a bath containing nickel and copper. Nickel is plated on the printed wiring board from the bath containing nickel and copper and final processing steps are implemented on the printed wiring board.

  9. Processing a printed wiring board by single bath electrodeposition

    DOEpatents

    Meltzer, Michael P.; Steffani, Christopher P.; Gonfiotti, Ray A.

    2010-12-07

    A method of processing a printed wiring board. Initial processing steps are implemented on the printed wiring board. Copper is plated on the printed wiring board from a bath containing nickel and copper. Nickel is plated on the printed wiring board from a bath containing nickel and copper and final processing steps are implemented on the printed wiring board.

  10. Effects of gapless bosonic fluctuations on Majorana fermions in an atomic wire coupled to a molecular reservoir

    NASA Astrophysics Data System (ADS)

    Hu, Ying; Baranov, Mikhail A.

    2015-11-01

    We discuss the effects of quantum and thermal fluctuations on the Majorana edge states in a topological atomic wire coupled to a superfluid molecular gas with gapless excitations. We find that the coupling between the Majorana edge states remains exponentially decaying with the length of the wire, even at finite temperatures smaller than the energy gap for bulk excitations in the wire. This exponential dependence is controlled solely by the localization length of the Majorana states. The fluctuations, on the other hand, provide the dominant contribution to the preexponential factor, which increases with temperature and the length of the wire. More important is that thermal fluctuations give rise to a decay of an initial correlation between Majorana edge states to its stationary value after some thermalization time. This stationary value is sensitive to the temperature and to the length of the wire and, although vanishing in the thermodynamic limit, can still be feasible in a mesoscopic system at sufficiently low temperatures. The thermalization time, on the other hand, is found to be much larger than the typical time scales in the wire and is sufficient for quantum operations with Majorana fermions before the temperature-induced decoherence sets in.

  11. Manifestations of quantum phase transitions in transport through nanosystems

    SciTech Connect

    Pustilnik, Michael

    2014-08-28

    The award led to several important new results in theory of interacting low-dimensional systems. The results are relevant for both traditional condensed matter systems, such as quantum wires and quantum spin chains, and for the relatively new field of ultra-cold atomic gases.

  12. Tuning a Tetrahertz Wire Laser

    NASA Technical Reports Server (NTRS)

    Qin, Qi; Williams, Benjamin S.; Kumar, Sushil; Reno, John L.; Hu, Qing

    2009-01-01

    Tunable terahertz lasers are desirable in applications in sensing and spectroscopy because many biochemical species have strong spectral fingerprints at terahertz frequencies. Conventionally, the frequency of a laser is tuned in a similar manner to a stringed musical instrument, in which pitch is varied by changing the length of the string (the longitudinal component of the wave vector) and/ or its tension (the refractive index). However, such methods are difficult to implement in terahertz semiconductor lasers because of their poor outcoupling efficiencies. Here, we demonstrate a novel tuning mechanism based on a unique 'wire laser' device for which the transverse dimension w is much much less than lambda. Placing a movable object close to the wire laser manipulates a large fraction of the waveguided mode propagating outside the cavity, thereby tuning its resonant frequency. Continuous single-mode redshift and blueshift tuning is demonstrated for the same device by using either a dielectric or metallic movable object. In combination, this enables a frequency tuning of approximately equal to 137 GHz (3.6%) from a single laser device at approximately equal to 3.8 THz.

  13. Improved Superconducting Wire for Wind Generators: Superconducting Wires for Direct-Drive Wind Generators

    SciTech Connect

    2012-01-01

    REACT Project: Brookhaven National Laboratory will develop a low-cost superconducting wire that could be used in high-power wind generators. Superconducting wire currently transports 600 times more electric current than a similarly sized copper wire, but is significantly more expensive. Brookhaven National Laboratory will develop a high-performance superconducting wire that can handle significantly more electrical current, and will demonstrate an advanced manufacturing process that has the potential to yield a several-fold reduction in wire costs while using a using negligible amount of rare earth material. This design has the potential to make a wind turbine generator lighter, more powerful, and more efficient, particularly for offshore applications.

  14. Growth of Quantum Wires on Step-Bunched Substrate

    SciTech Connect

    Liu, Feng

    2005-02-01

    This proposal initiates a combined theoretical and experimental multidisciplinary research effort to explore a novel approach for growing metallic and magnetic nanowires on step-bunched semiconductor and dielectric substrates, and to lay the groundwork for understanding the growth mechanisms and the electronic, electrical, and magnetic properties of metallic and magnetic nanowires. The research will focus on four topics: (1) fundamental studies of step bunching and self-organization in a strained thin film for creating step-bunched substrates. (2) Interaction between metal adatoms (Al,Cu, and Ni) and semiconductor (Si and SiGe) and dielectric (CaF2) surface steps. (3) growth and characterization of metallic and magnetic nanowires on step-bunched templates. (4) fabrication of superlattices of nanowires by growing multilayer films. We propose to attack these problems at both a microscopic and macroscopic level, using state-of-the-art theoretical and experimental techniques. Multiscale (electronic-atomic-continuum) theories will be applied to investigate growth mechanisms of nanowires: mesoscopic modeling and simulation of step flow growth of strained thin films, in particular, step bunching and self-organization will be carried out within the framework of continuum linear elastic theory; atomistic calculation of interaction between metal adatoms and semiconductor and dielectric surface steps will be done by large-scale computations using first-principles total-energy methods. In parallel, thin films and nanowires will be grown by molecular beam epitaxy (MBE), and the resultant structure and morphology will be characterized at the atomic level up to micrometer range, using a combination of different surface/interface probes, including scanning tunneling microscopy (STM, atomic resolution), atomic force microscopy (AFM, nanometer resolution), low-energy electron microscopy (LEEM, micrometer resolution), reflectance high-energy electron diffraction (RHEED), and x-ray diffraction. Finally, the electronic, electrical, and magnetic properties of the thin films and nanowires will be explored by both theory and experiment.

  15. Direct imaging of quantum wires nucleated at diatomic steps

    SciTech Connect

    Molina, S. I.; Varela, M.; Sales, D. L.; Ben, T.; Pizarro, J.; Galindo, P. L.; Fuster, D.; Gonzalez, Y.; Gonzalez, L.; Pennycook, S. J.

    2007-10-01

    Atomic steps at growth surfaces are important heterogeneous sources for nucleation of epitaxial nano-objects. In the presence of misfit strain, we show that the nucleation process takes place preferentially at the upper terrace of the step as a result of the local stress relaxation. Evidence for strain-induced nucleation comes from the direct observation by postgrowth, atomic resolution, Z-contrast imaging of an InAs-rich region in a nanowire located on the upper terrace surface of an interfacial diatomic step.

  16. 30 CFR 56.12047 - Guy wires.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Guy wires. 56.12047 Section 56.12047 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Electricity § 56.12047 Guy wires....

  17. 30 CFR 56.12047 - Guy wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Guy wires. 56.12047 Section 56.12047 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND NONMETAL MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Electricity § 56.12047 Guy wires....

  18. Lansce Wire Scanning Diagnostics Device Mechanical Design

    SciTech Connect

    Rodriguez Esparza, Sergio; Batygin, Yuri K.; Gilpatrick, John D.; Gruchalla, Michael E.; Maestas, Alfred J.; Pillai, Chandra; Raybun, Joseph L.; Sattler, F. D.; Sedillo, James Daniel; Smith, Brian G.

    2011-01-01

    The Accelerator Operations & Technology Division at Los Alamos National Laboratory operates a linear particle accelerator which utilizes 110 wire scanning diagnostics devices to gain position and intensity information of the proton beam. In the upcoming LANSCE improvements, 51 of these wire scanners are to be replaced with a new design, up-to-date technology and off-the-shelf components. This document outlines the requirements for the mechanical design of the LANSCE wire scanner and presents the recently developed linac wire scanner prototype. Additionally, this document presents the design modifications that have been implemented into the fabrication and assembly of this first linac wire scanner prototype. Also, this document will present the design for the second, third, and fourth wire scanner prototypes being developed. Prototypes 2 and 3 belong to a different section of the particle accelerator and therefore have slightly different design specifications. Prototype 4 is a modification of a previously used wire scanner in our facility. Lastly, the paper concludes with a plan for future work on the wire scanner development.

  19. LANSCE-R WIRE-SCANNER SYSTEM

    SciTech Connect

    Gruchalla, Michael E.

    2011-01-01

    The National Instruments cRIO platform is used for the new LANSCE-R wire-scanner systems. All wire-scanner electronics are integrated into a single BiRa BiRIO 4U cRIO chassis specifically designed for the cRIO crate and all interface electronics. The BiRIO chassis, actuator and LabVIEW VIs provide a complete wire-scanner system integrated with EPICS. The new wire-scanner chassis includes an 8-slot cRIO crate with Virtex-5 LX 110 FPGA and Power-PC real-time controller, the LANL-developed cRIO 2-axis wire-sensor analog interface module (AFE), NI9222 cRIO 4-channel 16-bit digitizer, cRIO resolver demodulator, cRIO event receiver, front-panel touch panel display, motor driver, and all necessary software, interface wiring, connectors and ancillary components. This wirescanner system provides a complete, turn-key, 2-axis wire-scanner system including 2-channel low-noise sensewire interface with variable DC wire bias and wireintegrity monitor, 16-bit signal digitizers, actuator motor drive and control, actuator position sensing, limit-switch interfaces, event receiver, LabVIEW and EPICS interface, and both remote operation and full stand-alone operation using the touch panel.

  20. Welding torch and wire feed manipulator

    NASA Technical Reports Server (NTRS)

    Williams, R. T.

    1967-01-01

    Welding torch and wire feed manipulator increase capability for performing automatic welding operations. The manipulator rotates on its horizontal axis to avoid obstacles as they approach the torch. The initial individual attitudes of the torch and wire guide are set with respect to the general configuration of the part.

  1. Superconducting wire with improved strain characteristics

    DOEpatents

    Luhman, Thomas; Klamut, Carl J.; Suenaga, Masaki; Welch, David

    1982-01-01

    A superconducting wire comprising a superconducting filament and a beryllium strengthened bronze matrix in which the addition of beryllium to the matrix permits a low volume matrix to exhibit reduced elastic deformation after heat treating which increases the compression of the superconducting filament on cooling and thereby improves the strain characteristics of the wire.

  2. Superconducting wire with improved strain characteristics

    DOEpatents

    Luhman, T.; Klamut, C.J.; Suenaga, M.; Welch, D.

    1979-12-19

    A superconducting wire comprising a superconducting filament and a beryllium strengthened bronze matrix in which the addition of beryllium to the matrix permits a low volume matrix to exhibit reduced elastic deformation after heat treating which increases the compression of the superconducting filament on cooling and thereby improve the strain characteristics of the wire.

  3. Superconducting wire with improved strain characteristics

    DOEpatents

    Luhman, Thomas; Klamut, Carl J.; Suenaga, Masaki; Welch, David

    1982-01-01

    A superconducting wire comprising a superconducting filament and a beryllium strengthened bronze matrix in which the addition of beryllium to the matrix permits a low volume matrix to exhibit reduced elastic deformation after heat treating which increases the compression of the superconducting filament on cooling and thereby improve the strain characteristics of the wire.

  4. Wire-Guide Manipulator For Automated Welding

    NASA Technical Reports Server (NTRS)

    Morris, Tim; White, Kevin; Gordon, Steve; Emerich, Dave; Richardson, Dave; Faulkner, Mike; Stafford, Dave; Mccutcheon, Kim; Neal, Ken; Milly, Pete

    1994-01-01

    Compact motor drive positions guide for welding filler wire. Drive part of automated wire feeder in partly or fully automated welding system. Drive unit contains three parallel subunits. Rotations of lead screws in three subunits coordinated to obtain desired motions in three degrees of freedom. Suitable for both variable-polarity plasma arc welding and gas/tungsten arc welding.

  5. Flywheel system using wire-wound rotor

    DOEpatents

    Chiao, Edward Young; Bender, Donald Arthur; Means, Andrew E.; Snyder, Philip K.

    2016-06-07

    A flywheel is described having a rotor constructed of wire wound onto a central form. The wire is prestressed, thus mitigating stresses that occur during operation. In another aspect, the flywheel incorporates a low-loss motor using electrically non-conducting permanent magnets.

  6. Glidden's Patent Application for Barbed Wire.

    ERIC Educational Resources Information Center

    Ray, Emily; Schamel, Wynell

    1997-01-01

    Describes a series of teaching activities to be used in conjunction with a reproduction of Joseph Glidden's patent for barbed wire fencing. These include document analysis, creative interpretation, and personal experience. Presents a brief history of the social and economic effects of the introduction of barbed wire to the West. (MJP)

  7. Microfabricated wire arrays for Z-pinch.

    SciTech Connect

    Spahn, Olga Blum; Rowen, Adam M.; Cich, Michael Joseph; Peake, Gregory Merwin; Arrington, Christian L.; Nash, Thomas J.; Klem, John Frederick; Romero, Dustin Heinz

    2008-10-01

    Microfabrication methods have been applied to the fabrication of wire arrays suitable for use in Z. Self-curling GaAs/AlGaAs supports were fabricated as an initial route to make small wire arrays (4mm diameter). A strain relief structure that could be integrated with the wire was designed to allow displacements of the anode/cathode connections in Z. Electroplated gold wire arrays with integrated anode/cathode bus connections were found to be sufficiently robust to allow direct handling. Platinum and copper plating processes were also investigated. A process to fabricate wire arrays on any substrate with wire thickness up to 35 microns was developed. Methods to handle and mount these arrays were developed. Fabrication of wire arrays of 20mm diameter was demonstrated, and the path to 40mm array fabrication is clear. With some final investment to show array mounting into Z hardware, the entire process to produce a microfabricated wire array will have been demonstrated.

  8. Add-On Shielding for Unshielded Wire

    NASA Technical Reports Server (NTRS)

    Koenig, J. C.; Billitti, J. W.; Tallon, J. M.

    1983-01-01

    Fabrication sequence used to produce compact shields slipped into place from free ends of wires already soldered into connectors at other ends. Single shields are formed into harnesses by connecting grounding jumpers. Technique is especially useful for small diameter wire attached to microminiature connectors.

  9. Twisted Pair Of Insulated Wires Senses Moisture

    NASA Technical Reports Server (NTRS)

    Laue, Eric G.; Stephens, James B.

    1989-01-01

    Sensitivity of electronic moisture sensor to low levels of moisture increased by new electrode configuration. Moisture-sensing circuit described in "Low-Cost Humidity Sensor" (NPO-16544). New twisted pair of wires takes place of flat-plate capacitor in circuit. Configuration allows for thermal expansion and contraction of polymer while maintaining nearly constant area of contact between polymer and wires.

  10. Wire ageing with the TEA photocathode

    SciTech Connect

    Va`vra, J.

    1996-06-01

    Recently several RICH protypes successfully tested a gaseous TEA photocathode. However, its wire ageing behavior is unknown. In principle, TEA is a more strongly bonded molecule than TMAE, and, as a result, one would expect better wire ageing behavior. This paper explores this question.

  11. SpaceWire Architectures: Present and Future

    NASA Technical Reports Server (NTRS)

    Rakow, Glen Parker

    2006-01-01

    A viewgraph presentation on current and future spacewire architectures is shown. The topics include: 1) Current Spacewire Architectures: Swift Data Flow; 2) Current SpaceWire Architectures : LRO Data Flow; 3) Current Spacewire Architectures: JWST Data Flow; 4) Current SpaceWire Architectures; 5) Traditional Systems; 6) Future Systems; 7) Advantages; and 8) System Engineer Toolkit.

  12. Long-Wearing Wire Guide For Welding Torch

    NASA Technical Reports Server (NTRS)

    Gutow, David A.; Burley, Richard K.; Gilbert, Jeffrey L.; Fogel, Irving

    1992-01-01

    Insert for wire-guide tube on tungsten/inert-gas welding apparatus extends life of guide tube and increases accuracy of weld. Hardened insert resists wear by sliding tungsten wire. Chamfer guides wire into insert.

  13. 47 CFR 76.804 - Disposition of home run wiring.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... wiring. The incumbent provider that has elected to abandon its home run wiring may remove its amplifiers... amplifiers or other active devices used in the wiring if an equivalent replacement can easily be...

  14. 47 CFR 76.804 - Disposition of home run wiring.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... wiring. The incumbent provider that has elected to abandon its home run wiring may remove its amplifiers... amplifiers or other active devices used in the wiring if an equivalent replacement can easily be...

  15. VIEW NORTHEASTLEFTBUILDING 9 NO 3 WIRE MILL (1876) RIGHTBUILDING 4 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW NORTHEAST-LEFT-BUILDING 9 NO 3 WIRE MILL (1876) RIGHT-BUILDING 4 NO 1 WIRE MILL (1871) - John A. Roebling's Sons Company & American Steel & Wire Company, South Broad, Clark, Elmer, Mott & Hudson Streets, Trenton, Mercer County, NJ

  16. VIEW WESTLEFTNO 1 WIRE MILL BUILDING 4 (1871) RIGHTNO 3 ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    VIEW WEST-LEFT-NO 1 WIRE MILL BUILDING 4 (1871) RIGHT-NO 3 WIRE MILL BUILDING 9 (1876) - John A. Roebling's Sons Company & American Steel & Wire Company, South Broad, Clark, Elmer, Mott & Hudson Streets, Trenton, Mercer County, NJ

  17. Wiring harnesses documented by punched-card technique

    NASA Technical Reports Server (NTRS)

    Hicks, W. W.; Kloezeman, W. G.

    1970-01-01

    Cards representing a connector are punched, sorted, and then used to printout wiring documentation for that connector. When wiring changes are made, new cards are punched and the wiring documentation is reprinted to reflect the latest configuration.

  18. Unusual Conductance in Cumulene Molecular Wires

    NASA Astrophysics Data System (ADS)

    Prasongkit, Jariyanee; Grigoriev, Anton; Wendin, Göran; Ahuja, Rajeev

    2009-03-01

    We report current-voltage curves and conductance of cumulene molecular wire suspended between Au(111) surfaces via thiolate bonds with full self-consistent ab initio calculation under external bias. The conductance of cumulene wires shows oscillatory behavior depending on the number of carbon atoms. Among all conjugated oligomers, we find that odd-number cumulene wires yield the highest conductance and present ballistic-like transport behavior. The reason has been traced to two factors: high density of state at the Fermi level, and the alignment of molecular orbital closed to Fermi level. Since the conductance depends weakly on applied bias, and the current voltage characteristic is linear under bias region -0.9 to 0.9 V, odd-number cumulene wire is a possible candidate as a near- perfect, ballistic one-dimensional molecular wire.

  19. Improved method of preparing composite superconducting wire

    DOEpatents

    Verhoeven, J.D.; Gibson, E.D.; Finnemore, D.K.; Ostenson, J.E.; Schmidt, F.A.; Owen, C.V.

    1979-10-17

    An improved method of preparing composite multifilament superconducting wire of Nb/sub 3/Sn in a copper matrix eliminates the necessity of coating the drawn wire with tin. A generalized cylindrical billet of an alloy of copper containing at least 15 weight percent niobium, present in the copper as discrete, randomly distributed and oriented dendritic-shaped particles, is provided with at least one longitudinal opening which is filled with tin to form a composite drawing rod. The drawing rod is then drawn to form a ductile composite multifilament wire containing a filament of tin. The ductile wire containing the tin can then be wound into magnet coils or other devices before heating to diffuse the tin through the wire to react with the niobium forming Nb/sub 3/Sn. Also described is an improved method for making large billets of the copper-niobium alloy by consumable-arc casting.

  20. Method of preparing composite superconducting wire

    DOEpatents

    Verhoeven, John D.; Gibson, Edwin D.; Finnemore, Douglas K.; Ostenson, Jerome E.; Schmidt, Frederick A.; Owen, Charles V.

    1985-08-06

    An improved method of preparing composite multifilament superconducting wire of Nb.sub.3 Sn in a copper matrix which eliminates the necessity of coating the drawn wire with tin. A generalized cylindrical billet of an alloy of copper containing at least 15 weight percent niobium, present in the copper as discrete, randomly distributed and oriented dendritic-shaped particles, is provided with at least one longitudinal opening which is filled with tin to form a composite drawing rod. The drawing rod is then drawn to form a ductile composite multifilament wire containing a filament of tin. The ductile wire containing the tin can then be wound into magnet coils or other devices before heating to diffuse the tin through the wire to react with the niobium forming Nb.sub.3 Sn. Also described is an improved method for making large billets of the copper-niobium alloy by consumable-arc casting.

  1. Realization of a Strained Atomic Wire Superlattice.

    PubMed

    Song, Inkyung; Goh, Jung Suk; Lee, Sung-Hoon; Jung, Sung Won; Shin, Jin Sung; Yamane, Hiroyuki; Kosugi, Nobuhiro; Yeom, Han Woong

    2015-11-24

    A superlattice of strained Au-Si atomic wires is successfully fabricated on a Si surface. Au atoms are known to incorporate into the stepped Si(111) surface to form a Au-Si atomic wire array with both one-dimensional (1D) metallic and antiferromagnetic atomic chains. At a reduced density of Au, we find a regular array of Au-Si wires in alternation with pristine Si nanoterraces. Pristine Si nanoterraces impose a strain on the neighboring Au-Si wires, which modifies both the band structure of metallic chains and the magnetic property of spin chains. This is an ultimate 1D version of a strained-layer superlattice of semiconductors, defining a direction toward the fine engineering of self-assembled atomic-scale wires. PMID:26446292

  2. Wire and Cable Cold Bending Test

    NASA Technical Reports Server (NTRS)

    Colozza, Anthony

    2010-01-01

    One of the factors in assessing the applicability of wire or cable on the lunar surface is its flexibility under extreme cold conditions. Existing wire specifications did not address their mechanical behavior under cold, cryogenic temperature conditions. Therefore tests were performed to provide this information. To assess this characteristic 35 different insulated wire and cable pieces were cold soaked in liquid nitrogen. The segments were then subjected to bending and the force was recorded. Any failure of the insulation or jacketing was also documented for each sample tested. The bending force tests were performed at room temperature to provide a comparison to the change in force needed to bend the samples due to the low temperature conditions. The results from the bending tests were plotted and showed how various types of insulated wire and cable responded to bending under cold conditions. These results were then used to estimate the torque needed to unroll the wire under these low temperature conditions.

  3. Wiring Damage Analyses for STS OV-103

    NASA Technical Reports Server (NTRS)

    Thomas, Walter, III

    2006-01-01

    This study investigated the Shuttle Program s belief that Space Transportation System (STS) wiring damage occurrences are random, that is, a constant occurrence rate. Using Problem Reporting and Corrective Action (PRACA)-derived data for STS Space Shuttle OV-103, wiring damage was observed to increase over the vehicle s life. Causal factors could include wiring physical deterioration, maintenance and inspection induced damage, and inspection process changes resulting in more damage events being reported. Induced damage effects cannot be resolved with existent data. Growth analysis (using Crow-AMSAA, or CA) resolved maintenance/inspection effects (e.g., heightened awareness) on all wire damages and indicated an overall increase since Challenger Return-to-Flight (RTF). An increasing failure or occurrence rate per flight cycle was seen for each wire damage mode; these (individual) rates were not affected by inspection process effects, within statistical error.

  4. The aging of wire chambers filled with dimethyl ether: wire and construction materials and freon impurities

    NASA Astrophysics Data System (ADS)

    Jibaly, Mohammed; Majewski, Stan; Chrusch, Peter; Wojcik, Randolph; Sauli, Fabio; Gaudaen, Jan

    1989-11-01

    This is a complete summary of our study of the aging of different types of wire chambers, with a variety of construction materials and wires, filled with dimethyl ether (DME) of varying degrees of purity. The resistive Nicotin and Stablohm wires were corroded by DME, producing fast aging. The moderately resistive stainless steel wires were able to withstand extended irradiation (up to 1 C/cm) in high-purity DME without any apparent damage; and gold-plated tungsten and molybdenum wires exhibited a comparable behavior. Many construction materials were tested and recommendations are thus reached as to what kinds of materials are safe in building DME-operated wire chambers. Among many different Freon and hydrocarbon impurities detected in DME by means of gas chromatography (GC), Freon-11 was found to be mostly responsible for the aging, even with noncorrosive stainless steel or gold-plated wires. The availability and feasibility of obtaining Freon-free DME is reported as well.

  5. Strain tolerant microfilamentary superconducting wire

    DOEpatents

    Finnemore, D.K.; Miller, T.A.; Ostenson, J.E.; Schwartzkopf, L.A.; Sanders, S.C.

    1993-02-23

    A strain tolerant microfilamentary wire capable of carrying superconducting currents is provided comprising a plurality of discontinuous filaments formed from a high temperature superconducting material. The discontinuous filaments have a length at least several orders of magnitude greater than the filament diameter and are sufficiently strong while in an amorphous state to withstand compaction. A normal metal is interposed between and binds the discontinuous filaments to form a normal metal matrix capable of withstanding heat treatment for converting the filaments to a superconducting state. The geometry of the filaments within the normal metal matrix provides substantial filament-to-filament overlap, and the normal metal is sufficiently thin to allow supercurrent transfer between the overlapped discontinuous filaments but is also sufficiently thick to provide strain relief to the filaments.

  6. 49 CFR 236.76 - Tagging of wires and interference of wires or tags with signal apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... with signal apparatus. 236.76 Section 236.76 Transportation Other Regulations Relating to... wires and interference of wires or tags with signal apparatus. Each wire shall be tagged or otherwise so... apparatus. Inspections and Tests; All Systems...

  7. 49 CFR 236.76 - Tagging of wires and interference of wires or tags with signal apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... with signal apparatus. 236.76 Section 236.76 Transportation Other Regulations Relating to... wires and interference of wires or tags with signal apparatus. Each wire shall be tagged or otherwise so... apparatus. Inspections and Tests; All Systems...

  8. 500 kV shield wires; Sectionalize or ground everywhere

    SciTech Connect

    Tuominen, M.W. )

    1992-01-01

    The primary purpose of shield wires on transmission lines in lightning protection. Development of fiber-optic shied wires added communications capabilities. Schemes for adapting fiber-optic shield wires to sectionalized shield wire designs remain untested. It is a present policy to segment and insulate 500 kV shield wires. Computer modeling and supportive field measurements have revealed a characteristic distribution of grounded tower voltage versus distance for long lines. The intent of this paper is to report these results plus predict the outcome of grounding shield wires on transmission lines already in place. Shield wires are often called overhead ground wires and abbreviated OHGW.

  9. In Situ Electrochemical Deposition of Microscopic Wires

    NASA Technical Reports Server (NTRS)

    Yun, Minhee; Myung, Nosang; Vasquez, Richard

    2005-01-01

    A method of fabrication of wires having micron and submicron dimensions is built around electrochemical deposition of the wires in their final positions between electrodes in integrated circuits or other devices in which the wires are to be used. Heretofore, nanowires have been fabricated by a variety of techniques characterized by low degrees of controllability and low throughput rates, and it has been necessary to align and electrically connect the wires in their final positions by use of sophisticated equipment in expensive and tedious post-growth assembly processes. The present method is more economical, offers higher yields, enables control of wire widths, and eliminates the need for post-growth assembly. The wires fabricated by this method could be used as simple electrical conductors or as transducers in sensors. Depending upon electrodeposition conditions and the compositions of the electroplating solutions in specific applications, the wires could be made of metals, alloys, metal oxides, semiconductors, or electrically conductive polymers. In this method, one uses fabrication processes that are standard in the semiconductor industry. These include cleaning, dry etching, low-pressure chemical vapor deposition, lithography, dielectric deposition, electron-beam lithography, and metallization processes as well as the electrochemical deposition process used to form the wires. In a typical case of fabrication of a circuit that includes electrodes between which microscopic wires are to be formed on a silicon substrate, the fabrication processes follow a standard sequence until just before the fabrication of the microscopic wires. Then, by use of a thermal SiO-deposition technique, the electrodes and the substrate surface areas in the gaps between them are covered with SiO. Next, the SiO is electron-beam patterned, then reactive-ion etched to form channels having specified widths (typically about 1 m or less) that define the widths of the wires to be formed. Drops

  10. Quantum well lasers

    SciTech Connect

    Zory, P.S. Jr.

    1993-01-01

    The semiconductor quantum well (QW) laser structure is rapidly becoming the preferred design in many applications because of its low threshold, design flexibility, and high reliability. The book begins with a brief, interesting foreword by C.H. Henry on the history of the QW laser concept and its early development. Following this introduction is a 79-page chapter by S.W. Corzine et al. on optical gain in III-V bulk and QW lasers. The next chapter on intraband relaxation and line broadening effects by M. Asada is an excellent expanded review of a topic introduced by Corzine. The remaining chapters describe multiple QW lasers, low-threshold QW laser, special aspects of AlGaAs and (short-wavelength) InGaAsP lasers, valence-band engineering, strained-layer QW lasers, AlGaInP QW lasers, and quantum wire lasers. These chapters are well written by recognized experts in the field.

  11. Development of a precision wire feeder for small-diameter wire

    SciTech Connect

    Brandon, E.D.

    1995-03-01

    At Sandia National Laboratories in Albuquerque, the author designed and fabricated a precision wire feeder to be used with high energy density (electron beam and laser beam) welding for weld joints where filler wire might be needed to fill a gap or to adjust the chemical composition so that a crack-free weld could be made. The wire feeder incorporates a 25,000 step-per-revolution motor to power a urethane-coated drive roll. A microprocessor-based controller provides precise control of the motor and allows both continuous and pulsed feeding of the wire. A unidirectional 0.75-in.-dia ball bearing is used to press the wire against the drive roll. A slight constant backward tension is maintained on the wire spool by a Bodine torque motor. A Teflon tube is used to guide the wire from the drive roll to the vicinity of the weld, where a hypodermic needle is used to aim the wire into the weld pool. The operation of the wire feeder was demonstrated by feeding a 10-mil-dia, Type 304 stainless steel wire into a variety of CO{sub 2} laser beam welds. The resulting welds are smooth and continuous, and the welds are considered to be completely satisfactory for a variety of applications.

  12. LANSCE wire scanning diagnostics device mechanical design

    SciTech Connect

    Rodriguez Esparza, Sergio

    2010-01-01

    The Los Alamos Neutron Science Center (LANSCE) is one of the major experimental science facilities at the Los Alamos National Laboratory (LANL). The core of LANSCE's work lies in the operation of a powerful linear accelerator, which accelerates protons up to 84% the speed oflight. These protons are used for a variety of purposes, including materials testing, weapons research and isotopes production. To assist in guiding the proton beam, a series of over one hundred wire scanners are used to measure the beam profile at various locations along the half-mile length of the particle accelerator. A wire scanner is an electro-mechanical device that moves a set of wires through a particle beam and measures the secondary emissions from the resulting beam-wire interaction to obtain beam intensity information. When supplemented with data from a position sensor, this information is used to determine the cross-sectional profile of the beam. This measurement allows beam operators to adjust parameters such as acceleration, beam steering, and focus to ensure that the beam reaches its destination as effectively as possible. Some of the current wire scanners are nearly forty years old and are becoming obsolete. The problem with current wire scanners comes in the difficulty of maintenance and reliability. The designs of these wire scanners vary making it difficult to keep spare parts that would work on all designs. Also many of the components are custom built or out-dated technology and are no longer in production.

  13. Wire Crimp Termination Verification Using Ultrasonic Inspection

    NASA Technical Reports Server (NTRS)

    Perey, Daniel F.; Cramer, K. Elliott; Yost, William T.

    2007-01-01

    The development of a new ultrasonic measurement technique to quantitatively assess wire crimp terminations is discussed. The amplitude change of a compressional ultrasonic wave propagating through the junction of a crimp termination and wire is shown to correlate with the results of a destructive pull test, which is a standard for assessing crimp wire junction quality. Various crimp junction pathologies such as undercrimping, missing wire strands, incomplete wire insertion, partial insulation removal, and incorrect wire gauge are ultrasonically tested, and their results are correlated with pull tests. Results show that the nondestructive ultrasonic measurement technique consistently (as evidenced with destructive testing) predicts good crimps when ultrasonic transmission is above a certain threshold amplitude level. A physics-based model, solved by finite element analysis, describes the compressional ultrasonic wave propagation through the junction during the crimping process. This model is in agreement within 6% of the ultrasonic measurements. A prototype instrument for applying this technique while wire crimps are installed is also presented. The instrument is based on a two-jaw type crimp tool suitable for butt-splice type connections. Finally, an approach for application to multipin indenter type crimps will be discussed.

  14. In-Situ Wire Damage Detection System

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Roberson, Luke; Tate, Lanetra; Smith, Trent; Gibson, Tracy; Medelius, Pedro; Jolley, Scott

    2012-01-01

    An In-Situ Wire Damage Detection System (ISWDDS) has been developed that is capable of detecting damage to a wire insulation, or a wire conductor, or to both. The system will allow for realtime, continuous monitoring of wiring health/integrity and reduce the number of false negatives and false positives while being smaller, lighter in weight, and more robust than current systems. The technology allows for improved safety and significant reduction in maintenance hours for aircraft, space vehicles, satellites, and other critical high-performance wiring systems for industries such as energy production and mining. The integrated ISWDDS is comprised of two main components: (1) a wire with an innermost core conductor, an inner insulation film, a conductive layer or inherently conductive polymer (ICP) covering the inner insulation film, an outermost insulation jacket; and (2) smart connectors and electronics capable of producing and detecting electronic signals, and a central processing unit (CPU) for data collection and analysis. The wire is constructed by applying the inner insulation films to the conductor, followed by the outer insulation jacket. The conductive layer or ICP is on the outer surface of the inner insulation film. One or more wires are connected to the CPU using the smart connectors, and up to 64 wires can be monitored in real-time. The ISWDDS uses time domain reflectometry for damage detection. A fast-risetime pulse is injected into either the core conductor or conductive layer and referenced against the other conductor, producing transmission line behavior. If either conductor is damaged, then the signal is reflected. By knowing the speed of propagation of the pulse, and the time it takes to reflect, one can calculate the distance to and location of the damage.

  15. Failure analysis of explanted sternal wires.

    PubMed

    Shih, Chun-Ming; Su, Yea-Yang; Lin, Shing-Jong; Shih, Chun-Che

    2005-05-01

    To classify and understand the mechanisms of surface damages and fracture mechanisms of sternal wires, explanted stainless steel sternal wires were collected from patients with sternal dehiscence following open-heart surgery. Surface alterations and fractured ends of sternal wires were examined and analyzed. Eighty fractured wires extracted from 25 patients from January 1999 to December 2003, with mean implantation interval of 55+/-149 days (range 5-729 days) after cardiac surgery, were studied by various techniques. The extracted wires were cleaned and the fibrotic tissues were removed. Irregularities and fractured ends were assayed by a scanning electron microscopy. After stereomicroscopy and documentation, the explants were cleaned with 1% sodium hypochlorite to remove the blood and tissues and was followed by cleaned with deionized water and alcohol. The explants were examined by stereomicroscopy, and irregularities on surface and fracture surfaces of sternal wires were assayed by scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and X-ray mapping. The explants with surrounding fibrotic tissue were stained and examined with stereomicroscopy and transmission electronic microscopy. Corrosion pits were found on the surface of explanted sternal wires. EDAX and X-ray mapping examinations revealed diminution of nickel concentration in the severely corroded pits on sternal wires. A feature of transgranular cracking was observed for stress corrosion cracking and striation character for typical corrosion fatigue was also identified. TEM examination of tissue showed the metallic particles in phagolysosomes of macrophages inside the surrounding sternal tissue. The synergic effect of hostile environment and the stress could be the precursors of failures for sternal wires. PMID:15576179

  16. Copper Wire Bonding Concerns and Best Practices

    NASA Astrophysics Data System (ADS)

    Chauhan, Preeti; Zhong, Z. W.; Pecht, Michael

    2013-08-01

    Copper wire bonding of microelectronic parts has developed as a means to cut the costs of using the more mature technology of gold wire bonding. However, with this new technology, changes in the bonding processes as well as bonding metallurgy can affect product reliability. This paper discusses the challenges associated with copper wire bonding and the solutions that the industry has been implementing. The paper also provides information to enable customers to conduct qualification and reliability tests on microelectronic packages to facilitate adoption in their target applications.

  17. Transient scattering from a thin arbitrary wire

    NASA Astrophysics Data System (ADS)

    Mohan, S. Ananda; Rao, Sadasiva M.

    1988-08-01

    The conjugate gradient (CG) method is applied to solve the problem of transient scattering from a thin arbitrary wire. The method is simple, efficient, and yields more accurate results than the marching-on-in-time procedure. Numerical examples for the case of a bent wire, a wire with discontinuous radii, and a circular loop are presented to highlight the advantages of this procedure. It is concluded that the occurrence of late-time oscillations may not be due to the accumulation of truncation of roundoff errors. These oscillations may be attributed to the insufficient sampling of the structure.

  18. Pulse speed on a plucked wire

    NASA Astrophysics Data System (ADS)

    Odekirk, Tristan; Slaton, William V.

    2012-04-01

    This paper serves to update an elegant experiment published in The Physics Teacher to measure the speed of a pulse on a taut metal wire. Unfortunately, commercially available units2 that serve the same purpose are priced outside the range of most high school or college physics teaching laboratories. Wakeland et al. show how an affordable adaptation of the traditional standing wave apparatus using taut metal wire and horseshoe magnets can be used to measure the speed of a pulse by using an oscilloscope to measure an induced voltage in the wire as the pulse transverses the middle of the magnets, which are a known distance apart.

  19. Wire-rope emplacement of diagnostics systems

    SciTech Connect

    Burden, W.L.

    1982-05-07

    The study reported here was initiated to determine if, with the Cable Downhole System (CDS) currently under development, there is an advantage to using continuous wire rope to lower the emplacement package to the bottom of the hole. A baseline design using two wire ropes as well as several alternatives are discussed in this report. It was concluded that the advantages of the wire-rope emplacement system do not justify the cost of converting to such a system, especially for LLNL's maximum emplacement package weights.

  20. Fabrication of FFTF fuel pin wire wrap

    SciTech Connect

    Epperson, E.M.

    1980-06-01

    Lateral spacing between FFTF fuel pins is required to provide a passageway for the sodium coolant to flow over each pin to remove heat generated by the fission process. This spacing is provided by wrapping each fuel pin with type 316 stainless steel wire. This wire has a 1.435mm (0.0565 in.) to 1.448mm (0.0570 in.) diameter, contains 17 +- 2% cold work and was fabricated and tested to exacting RDT Standards. About 500 kg (1100 lbs) or 39 Km (24 miles) of fuel pin wrap wire is used in each core loading. Fabrication procedures and quality assurance tests are described.

  1. Detectors Ensure Function, Safety of Aircraft Wiring

    NASA Technical Reports Server (NTRS)

    2013-01-01

    Pedro Medelius waited patiently in his lab at Kennedy Space Center. He had just received word that a colleague was bringing over a cable from a Space Shuttle solid rocket booster to test Medelius new invention. Medelius was calm until his colleague arrived, with about 30 other people. "Talk about testing under pressure," says Medelius. "There were people there from the Navy, the Air Force, and the Federal Aviation Administration." After the group s arrival, Medelius took a deep breath and connected his Standing Wave Reflectometer (SWR) to the cable. He wiggled the cable around, and the display showed a fault (a short or open circuit in wire) about an inch and a half inside the connector on the cable. His colleague questioned the results, because he had already checked that area on the cable. Medelius used the SWR to check again but got the same result. "That is when we took the cable apart and looked inside," Medelius says. "Lo and behold, that was exactly where the fault was." The impetus for Medelius new wire inspection technology came about in 1999 when one of the space shuttles lost power due to a fault somewhere in its more than 200 miles of electrical wiring. "The backup circuit was activated and prevented a major dysfunction, but nevertheless, there was a problem with the wiring," Medelius describes. Even though technicians used a device called a multimeter to measure the electrical current to find which wire had a fault, it could not pinpoint exactly where on the wire the fault was located. For that, technicians had to visually inspect the wire. "Sometimes they would have to remove the whole wire assembly and visually inspect every single wire. It was a very tedious operation because the wires are behind cabinets. They go all over the place in the shuttle," says Medelius. "NASA needed an instrument capable of telling them exactly where the faults were occurring." To meet NASA s needs for a highly precise device to inspect electrical power bundles, wires

  2. Colloidally deposited nanoparticle wires for biophysical detection

    NASA Astrophysics Data System (ADS)

    Shen, Sophie C.; Liu, Wen-Tao; Diao, Jia-Jie

    2015-12-01

    Among the techniques developed to prepare nanoparticle wires for multiple applications, the colloidal deposition method at interface has been regarded as cost-efficient and eco-friendly, and hence has attracted an increasing amount of research attention. In this report, the recent developments in preparing nanoparticle wires and integrated nanoparticle wire arrays using this technique have been reviewed. Furthermore, we have also discussed the application of these nanoparticle structures in detecting chemical and biological molecules. Project supported by the Fundamental Research Funds for the Central Universities through Xi’an Jiaotong University and the National Key Basic Research Program of China (Grant No. 2015CB856304).

  3. Filter line wiring designs in aircraft

    NASA Astrophysics Data System (ADS)

    Rowe, Richard M.

    1990-10-01

    The paper presents a harness design using a filter-line wire technology and appropriate termination methods to help meet high-energy radiated electromagnetic field (HERF) requirements for protection against the adverse effects of EMI on electrical and avionic systems. Filter-line interconnect harnessing systems discussed consist of high-performance wires and cables; when properly wired they suppress conducted and radiated EMI above 100 MHz. Filter-line termination devices include backshell adapters, braid splicers, and shield terminators providing 360-degree low-impedance terminations and enhancing maintainability of the system.

  4. Space Station Freedom secondary power wiring requirements

    NASA Technical Reports Server (NTRS)

    Sawyer, C. R.

    1994-01-01

    Secondary power is produced by DDCU's (direct current to direct current converter units) and routed to and through secondary power distribution assemblies (SPDA's) to loads or tertiary distribution assemblies. This presentation outlines requirements of Space Station Freedom (SSF) EEE (electrical, electronic, and electromechanical) parts wire and the approved electrical wire and cable. The SSF PDRD (Program Definition and Requirements Document) language problems and resolution are reviewed. The cable routing to and from the SPDA's is presented as diagrams and the wire recommendations and characteristics are given.

  5. Transport through single-channel atomic wires: Effects of connected sites on scattering phase and odd-even parity oscillations

    NASA Astrophysics Data System (ADS)

    Zhai, Feng; Xu, H. Q.

    2005-11-01

    Theoretical studies of scattering phase and odd-even parity oscillations of the conductance are presented for a finite atomic wire system, which is either connected with two single-channel leads or side-coupled to a single-channel perfect wire. The effects of connected sites on the scattering properties are examined. For a uniform atomic wire connected with two single-channel leads, it is found that when the number of atoms in the wire, n , and the two sequence numbers of the connected atomic sites, n1 and n2 (1⩽n1⩽n2⩽n) , satisfy the condition that (n+1)/gcd(n1,n+1-n2) is not an integer, the transmission coefficient, as a function of the incident electron energy, has zeros of second order. At these zeros the transmission phase is continuous. The zeros of the reflection coefficient, however, are always of first order, and the reflection phase has a lapse precisely by π at each of these zeros. For an atomic wire system side coupled to a perfect lead, the conclusions are reversed: the transmission zeros are always of first order, while the reflection zeros can be of high order. It is also shown that in this side-coupled configuration, both the transmission zeros and the reflection zeros are related to the generic properties of the isolated atomic wire system. The odd-even oscillations of the conductance have also been investigated for finite atomic wire systems in both configurations. It is found that the transmission of a finite atomic wire system depends not only on the parity of the number of atomic sites in the system, but also on the parity of the sequence numbers of the atomic sites through which the atomic wire system is connected with the leads. Finally, by taking a simple one-dimensional quantum wire system with several attached side branches as an example, we show that the transmission zeros of higher order can be found in a quantum system built from one-dimensional wires.

  6. Quantum correlation via quantum coherence

    NASA Astrophysics Data System (ADS)

    Yu, Chang-shui; Zhang, Yang; Zhao, Haiqing

    2014-06-01

    Quantum correlation includes quantum entanglement and quantum discord. Both entanglement and discord have a common necessary condition—quantum coherence or quantum superposition. In this paper, we attempt to give an alternative understanding of how quantum correlation is related to quantum coherence. We divide the coherence of a quantum state into several classes and find the complete coincidence between geometric (symmetric and asymmetric) quantum discords and some particular classes of quantum coherence. We propose a revised measure for total coherence and find that this measure can lead to a symmetric version of geometric quantum correlation, which is analytic for two qubits. In particular, this measure can also arrive at a monogamy equality on the distribution of quantum coherence. Finally, we also quantify a remaining type of quantum coherence and find that for two qubits, it is directly connected with quantum nonlocality.

  7. Chemically etched modulation in wire radius for wire array Z-pinch perturbation studies

    SciTech Connect

    Jones, B.; Deeney, C.; McKenney, J.L.; Garrity, J.E.; Lobley, D.K.; Martin, K.L.; Griego, A.E.; Ramacciotti, J.P.; Bland, S.N.; Lebedev, S.V.; Bott, S.C.; Ampleford, D.J.; Palmer, J.B.A.; Rapley, J.; Hall, G.

    2004-11-01

    A technique for manufacturing wires with imposed modulation in radius with axial wavelengths as short as 1 mm is presented. Extruded aluminum 5056 with 15 {mu}m diameter was masked and chemically etched to reduce the radius by {approx}20% in selected regions. Characterized by scanning electron microscopy, the modulation in radius is a step function with a {approx}10 {mu}m wide conical transition between thick and thin segments, with some pitting in etched regions. Techniques for mounting and aligning these wires in arrays for fast z-pinch experiments will be discussed. Axially mass-modulated wire arrays of this type will allow the study of seeded Rayleigh-Taylor instabilities in z pinches, corona formation, wire initiation with varying current density in the wire core, and correlation of perturbations between adjacent wires. This tool will support magnetohydrodynamics code validation in complex three-dimensional geometries, and perhaps x-ray pulse shaping.

  8. Quantum-size effects in the titanosilicate molecular sieve

    NASA Astrophysics Data System (ADS)

    Borello, Enzo; Lamberti, Carlo; Bordiga, Silvia; Zecchina, Adriano; Areán, Carlos Otero

    1997-10-01

    The recently synthesized Engelhard titanosilicate (ETS-10) represents a material which contains in the structure well defined atomic ⋯O-Ti-O-Ti-O⋯ quantum wires embedded in a highly insulating siliceous matrix. We report and discuss the UV-Vis spectrum of this material and compare the experimentally determined optical band gap with the results predicted by simple modeling of a titanium oxide semiconductor wire unidimensionally confined by an infinite potential barrier.

  9. Electrocatalytic monitoring of peptidic proton-wires.

    PubMed

    Dorčák, V; Kabeláč, M; Kroutil, O; Bednářová, K; Vacek, J

    2016-08-01

    The transfer of protons or proton donor/acceptor abilities is an important phenomenon in many biomolecular systems. One example is the recently proposed peptidic proton-wires (H-wires), but the ability of these His-containing peptides to transfer protons has only been studied at the theoretical level so far. Here, for the first time the proton transfer ability of peptidic H-wires is examined experimentally in an adsorbed state using an approach based on a label-free electrocatalytic reaction. The experimental findings are complemented by theoretical calculations at the ab initio level in a vacuum and in an implicit solvent. Experimental and theoretical results indicated Ala3(His-Ala2)6 to be a high proton-affinity peptidic H-wire model. The methodology presented here could be used for the further investigation of the proton-exchange chemistry of other biologically or technologically important macromolecules. PMID:27353221

  10. t matrix of metallic wire structures

    SciTech Connect

    Zhan, T. R. Chui, S. T.

    2014-04-14

    To study the electromagnetic resonance and scattering properties of complex structures of which metallic wire structures are constituents within multiple scattering theory, the t matrix of individual structures is needed. We have recently developed a rigorous and numerically efficient equivalent circuit theory in which retardation effects are taken into account for metallic wire structures. Here, we show how the t matrix can be calculated analytically within this theory. We illustrate our method with the example of split ring resonators. The density of states and cross sections for scattering and absorption are calculated, which are shown to be remarkably enhanced at resonant frequencies. The t matrix serves as the basic building block to evaluate the interaction of wire structures within the framework of multiple scattering theory. This will open the door to efficient design and optimization of assembly of wire structures.

  11. Printed wiring board system programmer's manual

    NASA Technical Reports Server (NTRS)

    Brinkerhoff, C. D.

    1973-01-01

    The printed wiring board system provides automated techniques for the design of printed circuit boards and hybrid circuit boards. The system consists of four programs: (1) the preprocessor program combines user supplied data and pre-defined library data to produce the detailed circuit description data; (2) the placement program assigns circuit components to specific areas of the board in a manner that optimizes the total interconnection length of the circuit; (3) the organizer program assigns pin interconnections to specific board levels and determines the optimal order in which the router program should attempt to layout the paths connecting the pins; and (4) the router program determines the wire paths which are to be used to connect each input pin pair on the circuit board. This document is intended to serve as a programmer's reference manual for the printed wiring board system. A detailed description of the internal logic and flow of the printed wiring board programs is included.

  12. Systems Analysis Teaching: The Kengor Wire Company

    ERIC Educational Resources Information Center

    Kennedy, W. J., Jr.; Derrick, L. R.

    1976-01-01

    Describes a group of systems analysis courses which utilizes a computer model of a company which makes house wire to provide a realistic representation of the complexities involved in industrial management. (CP)

  13. Autonomous Command Operation of the WIRE Spacecraft

    NASA Technical Reports Server (NTRS)

    Prior, Mike; Walyus, Keith; Saylor, Rick

    1999-01-01

    This paper presents the end-to-end design architecture for an autonomous commanding capability to be used on the Wide Field Infrared Explorer (WIRE) mission for the uplink of command loads during unattended station contacts. The WIRE mission is the fifth and final mission of NASA's Goddard Space Flight Center Small Explorer (SMEX) series to be launched in March of 1999. Its primary mission is the targeting of deep space fields using an ultra-cooled infrared telescope. Due to its mission design WIRE command loads are large (approximately 40 Kbytes per 24 hours) and must be performed daily. To reduce the cost of mission operations support that would be required in order to uplink command loads, the WIRE Flight Operations Team has implemented an autonomous command loading capability. This capability allows completely unattended operations over a typical two-day weekend period.

  14. Evaluation of Wiring Constructions for Space Applications

    NASA Technical Reports Server (NTRS)

    Hammoud, Ahmad N.; Stavnes, Mark W.; Dickman, John E.; Burkhardt, Linda A.; Woodford, Lynn M.; Ide, James R.; Muegge, ED

    1994-01-01

    A NASA Office of Safety and Mission Assurance (OS&MA) program to develop lightweight, reliable, and safe wiring insulations for aerospace applications is being performed by the NASA Lewis Research Center (LeRC). As part of this effort, a new wiring construction utilizing high strength PTFE (poly tetrafluoroethylene) as the insulation has been tested and compared with the existing military standard polyimide-based MIL-W-81381 wire construction. Electrical properties which were investigated included ac corona inception and extinction voltages (sea level and 60,000 feet), time/current to smoke, and wire fusing time. The two constructions were also characterized in terms of their mechanical properties of flexural strength, abrasion resistance (23 C and 150 C), and dynamic cut-through (23 C and 200 C). The results obtained in this testing effort are presented and discussed in this paper.

  15. 49 CFR 393.28 - Wiring systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    .... Electrical wiring shall be installed and maintained to conform to SAE J1292—Automobile, Truck, Truck-Tractor... conform to SAE J560. The reference to SAE J1292 shall not be construed to require circuit protection...

  16. 49 CFR 393.28 - Wiring systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    .... Electrical wiring shall be installed and maintained to conform to SAE J1292—Automobile, Truck, Truck-Tractor... conform to SAE J560. The reference to SAE J1292 shall not be construed to require circuit protection...

  17. 49 CFR 393.28 - Wiring systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    .... Electrical wiring shall be installed and maintained to conform to SAE J1292—Automobile, Truck, Truck-Tractor... conform to SAE J560. The reference to SAE J1292 shall not be construed to require circuit protection...

  18. 49 CFR 393.28 - Wiring systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    .... Electrical wiring shall be installed and maintained to conform to SAE J1292—Automobile, Truck, Truck-Tractor... conform to SAE J560. The reference to SAE J1292 shall not be construed to require circuit protection...

  19. Plasma etchback of multilayer printed wiring boards

    SciTech Connect

    Gentry, F.L.

    1980-06-01

    Removal of epoxy smear and glass fiber protrusions in multilayer printed wiring board holes was investigated. Gas plasma techniques, using a mixture of carbon tetrafluoride and oxygen, removed the eposies; however, the glass fibers were not affected.

  20. Improvements to Existing Jefferson Lab Wire Scanners

    SciTech Connect

    McCaughan, Michael D.; Tiefenback, Michael G.; Turner, Dennis L.

    2013-06-01

    This poster will detail the augmentation of selected existing CEBAF wire scanners with commercially available hardware, PMTs, and self created software in order to improve the scanners both in function and utility.

  1. Force-controlled lifting of molecular wires

    NASA Astrophysics Data System (ADS)

    Fournier, N.; Wagner, C.; Weiss, C.; Temirov, R.; Tautz, F. S.

    2011-07-01

    Lifting a single molecular wire off the surface with a combined frequency-modulated atomic force and tunneling microscope it is possible to monitor the evolution of both the wire configuration and the contacts simultaneously with the transport conductance experiment. In particular, critical points where individual bonds to the surface are broken and instabilities where the wire is prone to change its contact configuration can be identified in the force gradient and dissipation responses of the junction. This additional mechanical information can be used to unambiguously determine the conductance of a true molecular wire, that is, of a molecule that is contacted via a pointlike “crocodile clip” to each of the electrodes but is otherwise free.

  2. CADAT Printed-Wiring-Board Designer

    NASA Technical Reports Server (NTRS)

    Brinkerhoff, C. D.

    1982-01-01

    CADAT printed-wiring-board system (PWB) designs printed-circuit and hybrid-circuit boards. It is comprised of four programs: preprocessor, placement program, organizer program, and the router. Component placement and interconnection paths are optimized.

  3. Highly stretchable wrinkled gold thin film wires

    NASA Astrophysics Data System (ADS)

    Kim, Joshua; Park, Sun-Jun; Nguyen, Thao; Chu, Michael; Pegan, Jonathan D.; Khine, Michelle

    2016-02-01

    With the growing prominence of wearable electronic technology, there is a need to improve the mechanical reliability of electronics for more demanding applications. Conductive wires represent a vital component present in all electronics. Unlike traditional planar and rigid electronics, these new wearable electrical components must conform to curvilinear surfaces, stretch with the body, and remain unobtrusive and low profile. In this paper, the piezoresistive response of shrink induced wrinkled gold thin films under strain demonstrates robust conductive performance in excess of 200% strain. Importantly, the wrinkled metallic thin films displayed negligible change in resistance of up to 100% strain. The wrinkled metallic wires exhibited consistent performance after repetitive strain. Importantly, these wrinkled thin films are inexpensive to fabricate and are compatible with roll to roll manufacturing processes. We propose that these wrinkled metal thin film wires are an attractive alternative to conventional wires for wearable applications.

  4. Wiring test program insulation material related properties

    NASA Technical Reports Server (NTRS)

    Reher, Heinz-Josef

    1995-01-01

    This viewgraph presentation provides an overview of activities at DASA-RI concerning the testing of wires for manned spacecraft, including test facilities, arc-tracking tests, flammability tests, microgravity tests, and standardization, and outlines future activities.

  5. 49 CFR 236.57 - Shunt and fouling wires.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Shunt and fouling wires. 236.57 Section 236.57...: All Systems Track Circuits § 236.57 Shunt and fouling wires. (a) Except as provided in paragraph (b) of this section, shunt wires and fouling wires hereafter installed or replaced shall consist of...

  6. 21 CFR 870.1330 - Catheter guide wire.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Catheter guide wire. 870.1330 Section 870.1330...) MEDICAL DEVICES CARDIOVASCULAR DEVICES Cardiovascular Diagnostic Devices § 870.1330 Catheter guide wire. (a) Identification. A catheter guide wire is a coiled wire that is designed to fit inside...

  7. 30 CFR 57.12053 - Circuits powered from trolley wires.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Circuits powered from trolley wires. 57.12053... Electricity Surface and Underground § 57.12053 Circuits powered from trolley wires. Ground wires for lighting circuits powered from trolley wires shall be connected securely to the ground return circuit. Surface Only...

  8. Automatic reel controls filler wire in welding machines

    NASA Technical Reports Server (NTRS)

    Millett, A. V.

    1966-01-01

    Automatic reel on automatic welding equipment takes up slack in the reel-fed filler wire when welding operation is terminated. The reel maintains constant, adjustable tension on the wire during the welding operation and rewinds the wire from the wire feed unit when the welding is completed.

  9. 47 CFR 32.2321 - Customer premises wiring.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Customer premises wiring. 32.2321 Section 32... Customer premises wiring. (a) This account shall include all amounts transferred from the former Account 232, Station Connections, inside wiring subclass. (b) Embedded Customer Premises Wiring is...

  10. 30 CFR 77.701-3 - Grounding wires; capacity.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Grounding wires; capacity. 77.701-3 Section 77... MINES Grounding § 77.701-3 Grounding wires; capacity. Where grounding wires are used to ground metallic sheaths, armors, conduits, frames, casings, and other metallic enclosures, such grounding wires will...

  11. 30 CFR 77.701-3 - Grounding wires; capacity.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Grounding wires; capacity. 77.701-3 Section 77... MINES Grounding § 77.701-3 Grounding wires; capacity. Where grounding wires are used to ground metallic sheaths, armors, conduits, frames, casings, and other metallic enclosures, such grounding wires will...

  12. What's in the Walls: Copper, Fiber, or Coaxial Wiring?

    ERIC Educational Resources Information Center

    Weiss, Andrew M.

    1995-01-01

    Presents planning guidelines for wiring specifications for K-12 schools by reviewing advantages and disadvantages of using copper, fiber-optic, and coaxial wire. Addresses the future of network wiring and educational technology, and makes recommendations. A sidebar describes the physical appearance of different types of wire and a table compares…

  13. Quantum memory Quantum memory

    NASA Astrophysics Data System (ADS)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The

  14. Generation of shear flow in conical wire arrays with a center wire.

    SciTech Connect

    Wanex, L.; Neff, S.; Plechaty, C.; Ampleford, David J.; Wright, S.; Martinez, D.; Presura, R.

    2008-10-01

    At the Nevada Terawatt Facility we investigated the generation of a sheared plasma flow using conical wire arrays with an additional wire located on the axis of the pinch. The additional center wire generates axial current carrying plasma that serves as a target for the plasma accelerated from the outer wires, generating a sheared plasma flow which leads to the growth of the Kelvin-Helmholtz instability. These experiments were conducted on Zebra, a 2 TW pulse power device capable of delivering a 1 MA current in 100 ns. This paper will focus on the implosion dynamics that lead to shear flow and the development of the Kelvin Helmholtz instability.

  15. A Magnetic Sensor with Amorphous Wire

    PubMed Central

    He, Dongfeng; Shiwa, Mitsuharu

    2014-01-01

    Using a FeCoSiB amorphous wire and a coil wrapped around it, we have developed a sensitive magnetic sensor. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise spectrum of the sensor was about 30 pT/√Hz above 30 Hz. To show the sensitivity and the spatial resolution, the magnetic field of a thousand Japanese yen was scanned with the magnetic sensor. PMID:24940865

  16. 'Chrysanthemum petal' arrangements of silver nano wires.

    PubMed

    Cui, Hui-Wang; Jiu, Jin-Ting; Sugahara, Tohru; Nagao, Shijo; Suganuma, Katsuaki; Uchida, Hiroshi

    2014-12-01

    Highly ordered 'Chrysanthemum petal' arrangements of silver nano wires were fabricated in a biodegradable polymer of polyvinyl alcohol using a simple one-step blending method without any template. The degree of the arrangement increased with the decreasing content of polyvinyl alcohol. The mechanism for the formation of these 'Chrysanthemum petal' arrangements was discussed specifically. These 'Chrysanthemum petal' arrangements will be helpful to increase the electrical conductivity of silver nano wires films. PMID:25397618

  17. Energetic additive manufacturing process with feed wire

    SciTech Connect

    Harwell, Lane D.; Griffith, Michelle L.; Greene, Donald L.; Pressly, Gary A.

    2000-11-07

    A process for additive manufacture by energetic wire deposition is described. A source wire is fed into a energy beam generated melt-pool on a growth surface as the melt-pool moves over the growth surface. This process enables the rapid prototyping and manufacture of fully dense, near-net shape components, as well as cladding and welding processes. Alloys, graded materials, and other inhomogeneous materials can be grown using this process.

  18. Problems with aging wiring in Naval aircraft

    NASA Technical Reports Server (NTRS)

    Campbell, Frank J.

    1994-01-01

    The Navy is experiencing a severe aircraft electrical wiring maintenance problem as a result of the extensive use of an aromatic polyimide insulation that is deteriorating at a rate that was unexpected when this wire was initially selected. This problem has significantly affected readiness, reliability, and safety and has greatly increased the cost of ownership of Naval aircraft. Failures in wire harnesses have exhibited arcing and burning that will propagate drastically, to the interruption of many electrical circuits from a fault initiated by the failure of deteriorating wires. There is an urgent need for a capability to schedule aircraft rewiring in an orderly manner with a logically derived determination of which aircraft have aged to the point of absolute necessity. Excessive maintenance was demonstrated to result from the accelerated aging due to the parameters of moisture, temperature, and strain that exist in the Naval Aircraft environment. Laboratory studies have demonstrated that MIL-W-81381 wire insulation when aged at high humidities followed the classical Arrhenius thermal aging relationship. In an extension of the project a multifactor formula was developed that is now capable of predicting life under varying conditions of these service parameters. An automated test system has also been developed to analyze the degree of deterioration that has occurred in wires taken from an aircraft in order to obtain an assessment of remaining life. Since it is both physically and financially impossible to replace the wiring in all the Navy's aircraft at once, this system will permit expedient scheduling so that those aircraft that are most probable to have wiring failure problems can be overhauled first.

  19. Wrinkle-Free Hydroforming of Wire Mesh

    NASA Technical Reports Server (NTRS)

    Fadness, J.

    1986-01-01

    Plastic films lubricate workpiece so it deforms smoothly. Thin layers of plastic below top die and above bottom die ensure wire screen slides as shaped by hydroforming. Plastic layers are 0.0043 in. (0.11 m) thick. Preformed to contours of dies and final workpiece. New method of hydroforming fine-wire-mesh heat-shield screens eliminates wrinkles and marks. Prevents screen from being damaged and pores from becoming blocked.

  20. Endstates in multichannel spinless p-wave superconducting wires

    NASA Astrophysics Data System (ADS)

    Rieder, M.-T.; Kells, G.; Duckheim, M.; Meidan, D.; Brouwer, P. W.

    2012-09-01

    Multimode spinless p-wave superconducting wires with a width W much smaller than the superconducting coherence length ξ are known to have multiple low-energy subgap states localized near the wire's ends. Here we compare the typical energies of such endstates for various terminations of the wire: A superconducting wire coupled to a normal-metal stub, a weakly disordered superconductor wire and a wire with smooth confinement. Depending on the termination, we find that the energies of the subgap states can be higher or lower than for the case of a rectangular wire with hard-wall boundaries.

  1. Wiring photosystem I for direct solar hydrogen production.

    PubMed

    Lubner, Carolyn E; Grimme, Rebecca; Bryant, Donald A; Golbeck, John H

    2010-01-26

    The generation of H(2) by the use of solar energy is a promising way to supply humankind's energy needs while simultaneously mitigating environmental concerns that arise due to climate change. The challenge is to find a way to connect a photochemical module that harnesses the sun's energy to a catalytic module that generates H(2) with high quantum yields and rates. In this review, we describe a technology that employs a "molecular wire" to connect a terminal [4Fe-4S] cluster of Photosystem I directly to a catalyst, which can be either a Pt nanoparticle or the distal [4Fe-4S] cluster of an [FeFe]- or [NiFe]-hydrogenase enzyme. The keys to connecting these two moieties are surface-located cysteine residues, which serve as ligands to Fe-S clusters and which can be changed through site-specific mutagenesis to glycine residues, and the use of a molecular wire terminated in sulfhydryl groups to connect the two modules. The sulfhydryl groups at the end of the molecular wire form a direct chemical linkage to a suitable catalyst or can chemically rescue a [4Fe-4S] cluster, thereby generating a strong coordination bond. Specifically, the molecular wire can connect the F(B) iron-sulfur cluster of Photosystem I either to a Pt nanoparticle or, by using the same type of genetic modification, to the differentiated iron atom of the distal [4Fe-4S].(Cys)(3)(Gly) cluster of hydrogenase. When electrons are supplied by a sacrificial donor, this technology forms the cathode of a photochemical half-cell that evolves H(2) when illuminated. If such a device were connected to the anode of a photochemical half-cell that oxidizes water, an in vitro solar energy converter could be realized that generates only O(2) and H(2) in the light. A similar methodology can be used to connect Photosystem I to other redox proteins that have surface-located [4Fe-4S] clusters. The controlled light-driven production of strong reductants by such systems can be used to produce other biofuels or to provide

  2. Optical fiber sensors using vibration wires

    NASA Astrophysics Data System (ADS)

    Feng, Maria Q.; Suzuki, Hideyo

    1994-09-01

    Experimental research of new optical fiber sensors for monitoring civil infrastructure systems is presented. The proposed optical sensors employ a vibrating wire shoe tension can be modulated by external force, strain, or vibration and is translated into the change in the wire vibration frequency. The wire vibration frequency is detected by light sent to and reflected from the wire through an optical fiber cable. Compared to other existing optical fiber sensors which tend to suffer from the lack of reliability and robustness, the proposed sensors have two significant advantages: one is that the sensing head is a vibrating wire (rather than an optical fiber), which can sense a specific physical quantity without interference from miscellaneous effects; the other is that the wire vibration is a well understood physical phenomenon. In fact, with a high level of reliability, its frequency is optically measured and transmitted to recording and other devices through the optical fiber without attenuation or distortion. These advantages make the sensor system simple, reliable and robust, and hence more readily deployable in civil infrastructure applications.

  3. Needleless electrospinning with twisted wire spinneret

    NASA Astrophysics Data System (ADS)

    Holopainen, Jani; Penttinen, Toni; Santala, Eero; Ritala, Mikko

    2015-01-01

    A needleless electrospinning setup named ‘Needleless Twisted Wire Electrospinning’ was developed. The polymer solution is electrospun from the surface of a twisted wire set to a high voltage and collected on a cylindrical collector around the wire. Multiple Taylor cones are simultaneously self-formed on the downward flowing solution. The system is robust and simple with no moving parts aside from the syringe pump used to transport the solution to the top of the wire. The structure and process parameters of the setup and the results on the preparation of polyvinyl pyrrolidone (PVP), hydroxyapatite (HA) and bioglass fibers with the setup are presented. PVP fiber sheets with areas of 40 × 120 cm2 and masses up to 1.15 g were prepared. High production rates of 5.23 g h-1 and 1.40 g h-1 were achieved for PVP and HA respectively. The major limiting factor of the setup is drying of the polymer solution on the wire during the electrospinning process which will eventually force to interrupt the process for cleaning of the wire. Possible solutions to this problem and other ways to develop the setup are discussed. The presented system provides a simple way to increase the production rate and area of fiber sheet as compared with the conventional needle electrospinning.

  4. Wire-bond inspection in IC assembly

    NASA Astrophysics Data System (ADS)

    Rajeswari, Mandava; Rodd, Mike G.

    1996-02-01

    Wire-bonding in IC assembly process involves making a physical connection between the IC 'die' and the 'lead' by bonding wires between the two. Inspection of wire-bond quality is a' highly labor-intensive process and currently efforts are being made to automate it. This paper presents the results of a research conducted into developing a comprehensive automated wire- bond visual inspection system that is capable of performing final accept/reject inspection, providing on-line process feedback, and assisting in process validation. The proposed inspection system consists of the inspection of the bond on a bond pad, the bond on a lead and the inter-connecting wire between a bond pad and its corresponding lead. The algorithms are based on simple and easily extractable features that ensure achieving the desired accuracy and speed. A novel but simple illumination system is proposed to obtain the images of the inter- connecting wires. The proposed system is validated using several state-of-the-art IC samples. This work is sponsored by the Ministry of Science Technology and Environment, Malaysia and Intel Technology Pvt. Ltd., Malaysia.

  5. Thirteen Tesla magnet constructed with MJR wire

    SciTech Connect

    Siddall, M.; Efferson, K.; Mcdonald, W.

    1983-05-01

    The authors have constructed an insert booster superconducting magnet of 20 mm clear bore and outside diameter of 100 mm and height 130 mm, wound and reacted from the Teledyne patented foraminous layered foil (jelly roll) wire fabricated by low cost, non-rebundled reduction to wire. This magnet was placed inside the 101 mm bore of a NbTi wound solenoid which was operated at 8.5 Tesla. The total field achieved was 13.0 Tesla with no training quench observed; although training was initially observed when the magnet was first tested alone up to 4.6 Tesla at American Magnets, Inc. (AMI). The magnet winding techniques utilize Airco's fiberglass type wire insulation, an AMI proprietary cement, argon atmosphere 700/sup 0/C for 100 hour reaction, followed by a postreaction potting impregnation. The MJR wire lot used (M22) was short sample tested and the Ln (J /SUB c/ ) -vs-H line intersected the insert magnet operating curve at 13.5 Tesla. The wire lot used has a 34 volume % copper external sheath for quench protection. The wire was fabricated with 15.4 volume % niobium and bronze/niobium ratio of 3.0 with 13.% Sn bronze.

  6. Chemistry of radiation damage to wire chambers

    SciTech Connect

    Wise, J.

    1992-08-01

    Proportional counters are used to study aspects of radiation damage to wire chambers (wire aging). Principles of low-pressure, rf plasma chemistry are used to predict the plasma chemistry in electron avalanches (1 atm, dc). (1) Aging is studied in CF{sub 4}/iC{sub 4}H{sub 10} gas mixtures. Wire deposits are analyzed by Auger electron spectroscopy. An apparent cathode aging process resulting in loss of gain rather than in a self-sustained current is observed in CF{sub 4}-rich gases. A four-part model considering plasma polymerization of the hydrocarbon, etching of wire deposits by CF{sub 4}, acceleration of deposition processes in strongly etching environments, and reactivity of the wire surface is developed to understand anode wire aging in CF{sub 4}/iC{sub 4}H{sub 10} gases. Practical guidelines suggested by the model are discussed. (2) Data are presented to suggest that trace amounts of Freons do not affect aging rates in either dimethyl ether or Ar/C{sub 2}H{sub 6}. Apparent loss of gain is explained by attachment of primary electrons to a continuously increasing concentration of Freon 11 (CCl{sub 3}F) in the counter gas. An increase in the concentration of Freon 11 in dimethyl ether is caused by a distillation process in the gas supply bottle and is a natural consequence of the unequal volatilities of the two compounds.

  7. Si Wire-Array Solar Cells

    NASA Astrophysics Data System (ADS)

    Boettcher, Shannon

    2010-03-01

    Micron-scale Si wire arrays are three-dimensional photovoltaic absorbers that enable orthogonalization of light absorption and carrier collection and hence allow for the utilization of relatively impure Si in efficient solar cell designs. The wire arrays are grown by a vapor-liquid-solid-catalyzed process on a crystalline (111) Si wafer lithographically patterned with an array of metal catalyst particles. Following growth, such arrays can be embedded in polymethyldisiloxane (PDMS) and then peeled from the template growth substrate. The result is an unusual photovoltaic material: a flexible, bendable, wafer-thickness crystalline Si absorber. In this paper I will describe: 1. the growth of high-quality Si wires with controllable doping and the evaluation of their photovoltaic energy-conversion performance using a test electrolyte that forms a rectifying conformal semiconductor-liquid contact 2. the observation of enhanced absorption in wire arrays exceeding the conventional light trapping limits for planar Si cells of equivalent material thickness and 3. single-wire and large-area solid-state Si wire-array solar cell results obtained to date with directions for future cell designs based on optical and device physics. In collaboration with Michael Kelzenberg, Morgan Putnam, Joshua Spurgeon, Daniel Turner-Evans, Emily Warren, Nathan Lewis, and Harry Atwater, California Institute of Technology.

  8. Effect of a Wire on the Electromagnetic Field in an Accelerating Cavity in the Coaxial-Wire Method

    NASA Astrophysics Data System (ADS)

    Toyomasu, Takanori; Izawa, Masaaki; Kamiya, Yukihide

    1995-01-01

    A wire used in the coaxial-wire method to measure the characteristics of an accelerating cavity cannot be treated as a perturbator. Using a pill-box model, we analytically studied the electromagnetic field of a cavity with a wire. By this analysis, the effect of the wire on the resonance frequencies and Q-values of the cavity modes was clarified.

  9. 49 CFR 234.239 - Tagging of wires and interference of wires or tags with signal apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... with signal apparatus. 234.239 Section 234.239 Transportation Other Regulations Relating to... Tagging of wires and interference of wires or tags with signal apparatus. Each wire shall be tagged or... of the apparatus. This requirement applies to each wire at each terminal in all housings...

  10. 49 CFR 234.239 - Tagging of wires and interference of wires or tags with signal apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... with signal apparatus. 234.239 Section 234.239 Transportation Other Regulations Relating to... Tagging of wires and interference of wires or tags with signal apparatus. Each wire shall be tagged or... of the apparatus. This requirement applies to each wire at each terminal in all housings...

  11. Wiring design for the control of electromagnetic interference (EMI)

    NASA Technical Reports Server (NTRS)

    Kopasakis, George

    1995-01-01

    Wiring design is only one important aspect of EMI control. Other important areas for EMI are: circuit design, filtering, grounding, bonding, shielding, lighting, electrostatic discharge (ESD), transient suppression, and electromagnetic pulse (EMP). Topics covered include: wire magnetic field emissions at low frequencies; wire radiated magnetic field emissions at frequencies; wire design guidelines for EMI control; wire design guidelines for EMI control; high frequency emissions from cables; and pulse frequency spectra.

  12. Realizing Controllable Quantum States

    NASA Astrophysics Data System (ADS)

    Takayanagi, Hideaki; Nitta, Junsaku

    1. Entanglement in solid states. Orbital entanglement and violation of bell inequalities in mesoscopic conductors / M. Büttiker, P. Samuelsson and E. V. Sukhoruk. Teleportation of electron spins with normal and superconducting dots / O. Sauret, D. Feinberg and T. Martin. Entangled state analysis for one-dimensional quantum spin system: singularity at critical point / A. Kawaguchi and K. Shimizu. Detecting crossed Andreev reflection by cross-current correlations / G. Bignon et al. Current correlations and transmission probabilities for a Y-shaped diffusive conductor / S. K. Yip -- 2. Mesoscopic electronics. Quantum bistability, structural transformation, and spontaneous persistent currents in mesoscopic Aharonov-Bohm loops / I. O. Kulik. Many-body effects on tunneling of electrons in magnetic-field-induced quasi one-dimensional systems in quantum wells / T. Kubo and Y. Tokura. Electron transport in 2DEG narrow channel under gradient magnetic field / M. Hara et al. Transport properties of a quantum wire with a side-coupled quantum dot / M. Yamaguchi et al. Photoconductivity- and magneto-transport studies of single InAs quantum wires / A. Wirthmann et al. Thermoelectric transports in charge-density-wave systems / H. Yoshimoto and S. Kurihara -- 3. Mesoscopic superconductivity. Parity-restricted persistent currents in SNS nanorings / A. D. Zaikin and S. V. Sharov. Large energy dependence of current noise in superconductingh/normal metal junctions / F. Pistolesi and M. Houzet. Generation of photon number states and their superpositions using a superconducting qubit in a microcavity / Yu-Xi Liu, L. F. Wei and F. Nori. Andreev interferometry for pumped currents / F. Taddei, M. Governale and R. Fazio. Suppression of Cooper-pair breaking against high magnetic fields in carbon nanotubes / J. Haruyama et al. Impact of the transport supercurrent on the Josephson effect / S. N. Shevchenko. Josephson current through spin-polarized Luttinger liquid / N. Yokoshi and S. Kurihara

  13. STRS SpaceWire FPGA Module

    NASA Technical Reports Server (NTRS)

    Lux, James P.; Taylor, Gregory H.; Lang, Minh; Stern, Ryan A.

    2011-01-01

    An FPGA module leverages the previous work from Goddard Space Flight Center (GSFC) relating to NASA s Space Telecommunications Radio System (STRS) project. The STRS SpaceWire FPGA Module is written in the Verilog Register Transfer Level (RTL) language, and it encapsulates an unmodified GSFC core (which is written in VHDL). The module has the necessary inputs/outputs (I/Os) and parameters to integrate seamlessly with the SPARC I/O FPGA Interface module (also developed for the STRS operating environment, OE). Software running on the SPARC processor can access the configuration and status registers within the SpaceWire module. This allows software to control and monitor the SpaceWire functions, but it is also used to give software direct access to what is transmitted and received through the link. SpaceWire data characters can be sent/received through the software interface, as well as through the dedicated interface on the GSFC core. Similarly, SpaceWire time codes can be sent/received through the software interface or through a dedicated interface on the core. This innovation is designed for plug-and-play integration in the STRS OE. The SpaceWire module simplifies the interfaces to the GSFC core, and synchronizes all I/O to a single clock. An interrupt output (with optional masking) identifies time-sensitive events within the module. Test modes were added to allow internal loopback of the SpaceWire link and internal loopback of the client-side data interface.

  14. Studies of friction and wear characteristics of various wires for wire-brush skids

    NASA Technical Reports Server (NTRS)

    Dreher, R. C.

    1977-01-01

    The friction and wear characteristics of 22 types and sizes of wires for potential use in wire-brush skids were studied. These characteristics were determined by placing brushes made from candidate wires on a belt sander whose moving belt simulated landing roll-out distance. At the same time, the drag force and wear behavior were monitored. Data were obtained over distances up to 3048 m (10,000 ft) at preselected bearing pressures of 172 to 1034 kPa (25 to 150 psi). In general, the friction coefficient developed by the candidate wires was found to be independent of bearing pressure and ranged between 0.4 and 0.6 under the test conditions of this investigation. The friction coefficient was not degraded when the surface was wetted and appears to be independent of wire diameter except perhaps when wire size is relatively large compared with the surface asperities. Generally, the high friction demonstrated by the soft materials was accompanied by high wear rates; conversely, the hard materials provided greater wear resistance but offered lower friction. For all test wires, the wear was shown to increase with increasing bearing pressure, in general, for the same bearing pressure, wear increased with increasing wire diameter and decreased when the surface was wetted.

  15. Quantum simulation

    NASA Astrophysics Data System (ADS)

    Georgescu, I. M.; Ashhab, S.; Nori, Franco

    2014-01-01

    Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry, and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins, and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fast-growing field.

  16. Selected developments in laser wire stripping. [cutting insulation from aerospace-type wires and cables

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The operation of mechanical and thermal strippers and the early development of laser wire strippers are reviewed. NASA sponsored development of laser wire stripping for space shuttle includes bench-type strippers as well as an advanced portable hand-held stripper which incorporates a miniaturized carbon dioxide laser and a rotating optics unit with a gas-jet assist and debris exhaust. Drives and controls girdle the wire and slit the remaining slug without manual assistance. This unit can strip wire sizes 26 through 12 gage. A larger-capacity hand-held unit for wire sizes through 1/0 gage was built using a neodynium-doped yttrium aluminum garnet (Nd:YAG) laser. The hand-held units have a flexible umbilical cable to an accompanying cart that carries the power supply, gas supply, cooling unit, and the controls.

  17. Investigation of factors affecting the heater wire method of calibrating fine wire thermocouples

    NASA Technical Reports Server (NTRS)

    Keshock, E. G.

    1972-01-01

    An analytical investigation was made of a transient method of calibrating fine wire thermocouples. The system consisted of a 10 mil diameter standard thermocouple (Pt, Pt-13% Rh) and an 0.8 mil diameter chromel-alumel thermocouple attached to a 20 mil diameter electrically heated platinum wire. The calibration procedure consisted of electrically heating the wire to approximately 2500 F within about a seven-second period in an environment approximating atmospheric conditions at 120,000 feet. Rapid periodic readout of the standard and fine wire thermocouple signals permitted a comparison of the two temperature indications. An analysis was performed which indicated that the temperature distortion at the heater wire produced by the thermocouple junctions appears to be of negligible magnitude. Consequently, the calibration technique appears to be basically sound, although several practical changes which appear desirable are presented and discussed. Additional investigation is warranted to evaluate radiation effects and transient response characteristics.

  18. Preparation for Acceleration and Deceleration of Cold Rydberg Atoms in the Field of a Charged Wire

    NASA Astrophysics Data System (ADS)

    Goodsell, Anne; Nawarat, Poomirat; Harper, W. Colleen

    2015-05-01

    We are preparing for experiments using cold Rydberg atoms in linear Stark states. We cool and launch Rb atoms at 2-12 m/s toward a charged wire with a cylindrically-symmetric electric field. The cold cloud will be illuminated in mid-flight to promote atoms into the desired Rydberg state (e.g. n = 33-40). With a three-photon sequence we will access nf states and the nearby manifolds (parabolic quantum number 0 <=n1 <= (n -4)) with linear Stark shifts. This requires specific detuning of the the excitation laser, which allows us to selectively compare states that are strongly accelerated to states that are strongly decelerated. With the wire at +10 V, atoms launched at 10 m/s, and excitation near 750 μm from the wire, the displacement during the Rydberg lifetime (e.g. n = 35, τ = 30 μs) will be 200-300 μm farther for extreme attracted states (n1 = 0) than for extreme repelled states (n1 = 31). Detection will occur by spatially-dependent field ionization. Observations of atoms with zero angular momentum around the wire can be extended to atoms with nonzero angular momentum and also to study the dynamics of Rydberg atoms with a quadratic Stark shift, building on previous work with ground-state atoms. (Current address: Rensselaer Polytechnic Institute, Troy, NY).

  19. Reliable commercial HTS wire for power applications

    NASA Astrophysics Data System (ADS)

    Kellers, Jürgen; Masur, Lawrence J.

    2002-08-01

    The production of HTS wire for power applications is increasingly maturing into industrial dimensions. The most widely considered manufacturing method for this conductor is the BSCCO-2223-OPIT route, used internationally by many organizations, including American Superconductor. Significant advances in HTS wire technology have been made in the past years, with currently a guaranteed minimum critical current performance of 115 A at 77 K over commercial long length. For the HTS wire itself this is equivalent to an engineering current density of 13.5 kA/cm 2. During the past 18 months, American Superconductor increased its HTS wire manufacturing capacity in its Westborough operations from 250 to 500 km/year to meet the increased demand for development and demonstration purposes. While this level of quality and quantity is sufficient to demonstrate technical feasibility and reliability of prototype power applications, it cannot satisfy fully commercial requirements for economic viability. To address broader markets with a commercially viable product, a price level of $50/(kA m) is possible with BSCCO-2223-OPIT when manufactured in much larger quantities. Therefore, American Superconductor is currently siting a new facility dedicated solely to the manufacturing of BSCCO-OPIT-2223 wire in quantities of 10,000 km/year. Key initial applications for this wire are power transmission cables, industrial motors and electrical generators. This paper will report on the performance and reliability testing of BSCCO-2223 wires. We will discuss the electrical, bending, tensile, and fatigue testing results of wires manufactured for applications such as American Superconductor's 5000 hp ultra-compact motor. Due to their compactness, these motors will be less expensive to manufacture compared with conventional motors and will be more energy efficient. We will also review the stringent electrical, mechanical, and environmental testing developed jointly by American Superconductor and

  20. [A study of mechanical properties of orthodontic wires in tension].

    PubMed

    Konstantellos, B; Lagoudakis, M; Toutountzakis, N

    1990-12-01

    Orthodontic forces are applied to the teeth basically by means of different types of orthodontic wires. Knowledge of the mechanical properties of such wires are very helpful to the clinician in design and application of optimal force systems during orthodontic treatment. The basic mechanical properties were studied for 17 types of orthodontic wires (all rectangular and of the same size), in tension. Modulus of elasticity (E), yield strength (YS) and maximum elastic strain (Springback) (YS/E) were calculated for each type of wires. Stainless steel wires have demonstrated higher modulus of elasticity (and yield strength) in comparison with wires of nickel-titanium and beta titanium alloys. B-titanium wires showed higher modulus of elasticity than nickel-titanium ones. In addition stainless steel wires were found to have higher values for springback than cobalt-chromium ones and lower values (for the same variable) than nickel-titanium and B-titanium wires. PMID:2129597

  1. Vibration measurements of a wire scanner - Experimental setup and models

    NASA Astrophysics Data System (ADS)

    Herranz, Juan; Barjau, Ana; Dehning, Bernd

    2016-03-01

    In the next years the luminosity of the LHC will be significantly increased. This will require a much higher accuracy of beam profile measurement than actually achievable by the current wire scanner. The new performance demands a wire travelling speed up to 20 m s-1 and a position measurement accuracy of the order of 1 μm. The vibrations of the mechanical parts of the system and particularly the vibrations of the thin carbon wire have been identified as the major error sources of wire position uncertainty. Therefore the understanding of the wire vibrations has been given high priority for the design and operation of the new device. This article presents a new strategy to measure the wire vibrations based on the piezoresistive effect of the wire itself. An electronic readout system based on a Wheatstone bridge is used to measure the variation of the carbon wire resistance, which is directly proportional to the wire elongation caused by the oscillations.

  2. Frequency response of a thermocouple wire: Effects of axial conduction

    NASA Technical Reports Server (NTRS)

    Forney, L. J.; Fralick, G. C.

    1990-01-01

    Theoretical expressions are derived for the steady-state frequency response of a thermocouple wire. In particular, the effects of axial heat conduction are demonstrated for both a uniform thermocouple wire and a nonuniform wire with unequal material properties and wire diameters across the junction. For the case of a uniform wire, the amplitude ratio and phase angle compare favorably with the series solution of Scadron and Warshawsky (1952) except near the ends of the wire. For the case of a non-uniform wire, the amplitude ratio at low frequency omega yields 0 agrees with the results of Scadron and Warshawsky for a steady-state temperature distribution. Moreover, the frequency response for a non-uniform wire in the limit of infinite length l yields infinity is shown to reduce to a simple expression that is analogous to the classic first order solution for a thermocouple wire with uniform properties.

  3. Chinese NiTi wire--a new orthodontic alloy.

    PubMed

    Burstone, C J; Qin, B; Morton, J Y

    1985-06-01

    Chinese NiTi wire was studied by means of a bending test to determine wire stiffness, springback, and maximum bending moments. Chinese NiTi wire has an unusual deactivation curve (unlike steel and nitinol wires) in which relatively constant forces are produced over a long range of action. The characteristic flexural stiffness of NiTi wire is determined by the amount of activation. At large activations NiTi wires has a stiffness of only 7% that of a comparable stainless steel wire, and at small activations 28% of steel wire. For the same activation at large deflections, the forces produced are 36% that of a comparable nitinol wire. Chinese NiTi wire demonstrates phenomenal springback. It can be deflected 1.6 times as far as nitinol wire or 4.4 times as far as stainless steel wire without appreciable permanent deformation. NiTi wire is highly useful in clinical situations that require a low-stiffness wire with an extremely large springback. PMID:3890554

  4. Wire scanner software and firmware issues

    SciTech Connect

    Gilpatrick, John Doug

    2008-01-01

    The Los Alamos Neutron Science Center facility presently has 110 slow wire scanning profile measurement instruments located along its various beam lines. These wire scanners were developed and have been operating for at least 30 years. While the wire scanners solved many problems to operate and have served the facility well they have increasingly suffered from several problems or limitations, such as maintenance and reliability problems, antiquated components, slow data acquisition, and etc. In order to refurbish these devices, these wire scanners will be replaced with newer versions. The replacement will consist of a completely new beam line actuator, new cables, new electronics and brand new software and firmware. This note describes the functions and modes of operation that LabVIEW VI software on the real time controller and FPGA LabVIEW firmware will be required. It will be especially interesting to understand the overall architecture of these LabVIEW VIs. While this note will endeavor to describe all of the requirements and issues for the wire scanners, undoubtedly, there will be missing details that will be added as time progresses.

  5. Integrated Electrical Wire Insulation Repair System

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Jolley, Scott; Gibson, Tracy; Parks, Steven

    2013-01-01

    An integrated system tool will allow a technician to easily and quickly repair damaged high-performance electrical wire insulation in the field. Low-melt polyimides have been developed that can be processed into thin films that work well in the repair of damaged polyimide or fluoropolymer insulated electrical wiring. Such thin films can be used in wire insulation repairs by affixing a film of this low-melt polyimide to the damaged wire, and heating the film to effect melting, flow, and cure of the film. The resulting repair is robust, lightweight, and small in volume. The heating of this repair film is accomplished with the use of a common electrical soldering tool that has been modified with a special head or tip that can accommodate the size of wire being repaired. This repair method can furthermore be simplified for the repair technician by providing replaceable or disposable soldering tool heads that have repair film already "loaded" and ready for use. The soldering tool heating device can also be equipped with a battery power supply that will allow its use in areas where plug-in current is not available

  6. Impact of wire topology on channel routing

    SciTech Connect

    Blair, J.R.S.

    1986-01-01

    Channel routing is a method that has been widely used to overcome the inherent difficulties in the routing stage of automated VLSI chip and printed circuit board design. Almost all previous work on channel routing has restricted the wires to paths that are strictly monotonic (i.e., paths that do not backtrack in either the horizontal or vertical direction). The impact on single layer channel routing of wire topologies that provide considerably more wire routing flexibility than has previously been allowed is addressed here. A hierarchy of routing classes stemming from these generalized wire topologies is defined. It is shown that each of the routing classes is applicable to both the two row routing scenario (river routing) and the single row routing scenario. The routing classes are examined to see if the flexibility provided by the new wire types is useful for single row routing. Global routing under the channel routing scenario is briefly examined. In particular, a simplistic two layer global channel routing problem is shown to be NP-complete using two separate optimization criteria.

  7. Micro Wire-Drawing: Experiments And Modelling

    SciTech Connect

    Berti, G. A.; Monti, M.; Bietresato, M.; D'Angelo, L.

    2007-05-17

    In the paper, the authors propose to adopt the micro wire-drawing as a key for investigating models of micro forming processes. The reasons of this choice arose in the fact that this process can be considered a quasi-stationary process where tribological conditions at the interface between the material and the die can be assumed to be constant during the whole deformation. Two different materials have been investigated: i) a low-carbon steel and, ii) a nonferrous metal (copper). The micro hardness and tensile tests performed on each drawn wire show a thin hardened layer (more evident then in macro wires) on the external surface of the wire and hardening decreases rapidly from the surface layer to the center. For the copper wire this effect is reduced and traditional material constitutive model seems to be adequate to predict experimentation. For the low-carbon steel a modified constitutive material model has been proposed and implemented in a FE code giving a better agreement with the experiments.

  8. Quantum networks reveal quantum nonlocality.

    PubMed

    Cavalcanti, Daniel; Almeida, Mafalda L; Scarani, Valerio; Acín, Antonio

    2011-01-01

    The results of local measurements on some composite quantum systems cannot be reproduced classically. This impossibility, known as quantum nonlocality, represents a milestone in the foundations of quantum theory. Quantum nonlocality is also a valuable resource for information-processing tasks, for example, quantum communication, quantum key distribution, quantum state estimation or randomness extraction. Still, deciding whether a quantum state is nonlocal remains a challenging problem. Here, we introduce a novel approach to this question: we study the nonlocal properties of quantum states when distributed and measured in networks. We show, using our framework, how any one-way entanglement distillable state leads to nonlocal correlations and prove that quantum nonlocality is a non-additive resource, which can be activated. There exist states, local at the single-copy level, that become nonlocal when taking several copies of them. Our results imply that the nonlocality of quantum states strongly depends on the measurement context. PMID:21304513

  9. Distortions of the coulomb blockade conductance line in scanning gate measurements of inas nanowire based quantum dots

    SciTech Connect

    Zhukov, A. A.; Volk, Ch.; Winden, A.; Hardtdegen, H.; Schaepers, Th.

    2013-01-15

    We performed measurements at helium temperatures of the electronic transport in the linear regime in an InAs quantum wire in the presence of a charged tip of an atomic force microscope (AFM) at low electron concentration. We show that at certain concentration of electrons, only two closely placed quantum dots, both in the Coulomb blockade regime, govern conductance of the whole wire. Under this condition, two types of peculiarities-wobbling and splitting-arise in the behavior of the lines of the conductance peaks of Coulomb blockade. These peculiarities are measured in quantum-wire-based structures for the first time. We explain both peculiarities as an interplay of the conductance of two quantum dots present in the wire. Detailed modeling of wobbling behavior made in the framework of the orthodox theory of Coulomb blockade demonstrates good agreement with the obtained experimental data.

  10. Single and double valence configuration interactions for recovering the exponential decay law while tunneling through a molecular wire.

    PubMed

    Portais, Mathilde; Hliwa, Mohamed; Joachim, Christian

    2016-01-22

    The exponential decay of the electronic transmission through a molecular wire with its length is calculated using a configuration interaction elastic scattering quantum chemistry (CI-ESQC) theory [1, 2]. In the HOMO-LUMO gap and in a one-electron approximation, this decay is exponential since the scattering matrix comes from a product of spatial propagators along the wire. In a valence SD-CI (single and double-configurations interaction) description, such a product does not exist. An effective one was numerically obtained from the CI-ESQC scattering matrix. Fluctuations over the effective CI-exponential decay come from the truncation of the full CI basis set and also from many-body exchange-correlation effects along the molecular wire. PMID:26636919

  11. Single and double valence configuration interactions for recovering the exponential decay law while tunneling through a molecular wire

    NASA Astrophysics Data System (ADS)

    Portais, Mathilde; Hliwa, Mohamed; Joachim, Christian

    2016-01-01

    The exponential decay of the electronic transmission through a molecular wire with its length is calculated using a configuration interaction elastic scattering quantum chemistry (CI-ESQC) theory [1, 2]. In the HOMO-LUMO gap and in a one-electron approximation, this decay is exponential since the scattering matrix comes from a product of spatial propagators along the wire. In a valence SD-CI (single and double-configurations interaction) description, such a product does not exist. An effective one was numerically obtained from the CI-ESQC scattering matrix. Fluctuations over the effective CI-exponential decay come from the truncation of the full CI basis set and also from many-body exchange-correlation effects along the molecular wire.

  12. Rapid Real-Time SpaceWire Emulation

    NASA Astrophysics Data System (ADS)

    Mudie, Stephen; Parkes, Steve; Dunstan, Martin

    2015-09-01

    The SpaceWire Electronic Ground Support Equipment (EGSE) test and development unit from STAR-Dundee can be used to very rapidly emulate real-time behaviour of SpaceWire equipment. The behaviour of the equipment to emulate is described in a script using a SpaceWire specific scripting language. Once configured the SpaceWire EGSE unit operates independent of software. This paper describes three camera emulation scripts to demonstrate the rapid real-time SpaceWire emulation possible using the SpaceWire EGSE.

  13. Wire diameter dependence in the catalytic decomposition of H2

    NASA Astrophysics Data System (ADS)

    Umemoto, Hironobu

    2014-01-01

    Jansen et al. have demonstrated that the dissociaiton rate of H2 molecules on hot wire surfaces, normalized per unit surface area, depends on the wire diameter based on the electrical power consumption measurements [J. Appl. Phys. 66, 5749 (1989)]. Mathematical modeling calculations have also been presented to support their experimental results. In the present paper, it is shown that such a wire diameter dependence cannot be observed and that the H-atom density normalized by the wire surface area depends little on the wire diameter. Modeling calculations also show that the wire diameter dependence of the dissociation rate cannot be expected under typical decomposition conditions.

  14. Method of fabricating composite superconducting wire

    DOEpatents

    Strauss, Bruce P.; Reardon, Paul J.; Remsbottom, Robert H.

    1977-01-01

    An improvement in the method for preparing composite rods of superconducting alloy and normal metal from which multifilament composite superconducting wire is fabricated by bending longitudinally a strip of normal metal around a rod of superconductor alloy and welding the edges to form the composite rod. After the rods have preferably been provided with a hexagonal cross-sectional shape, a plurality of the rods are stacked into a normal metal extrusion can, sealed and worked to reduce the cross-sectional size and form multifilament wire. Diffusion barriers and high-electrical resistance barriers can easily be introduced into the wire by plating or otherwise coating the faces of the normal metal strip with appropriate materials.

  15. Amorphous wires in displacement sensing techniques

    NASA Astrophysics Data System (ADS)

    Hristoforou, E.; Niarchos, D.

    1992-10-01

    In this paper, a new displacement sensor is proposed which is based on the magnetostrictive delay line technique (MDL). Due to this technique, the displacement of a moving magnet at either the acoustic stress point of origin or the detecting coil can be sensed, due to the change of the peak value of the output voltage. This sensor uses the recently developed FeSiB and FeCoCrSiB amorphous wires. Reported results show a linear response for defined regions of displacement, and a monotonic one for the case of the 125 μm FeSiB wires. It is also shown that this sensor arrangement can be used for fabrication of displacement distribution integrated sensors. Finally, it is shown that use of amorphous wires makes the repeatability of the response of the sensor as accurate as 0.6% without using hardware or software calibration.

  16. Dispersion interaction between crossed conducting wires

    SciTech Connect

    Dobson, John F.; Gould, Timothy; Klich, Israel

    2009-07-15

    We compute the T=0 K Van der Waals (nonretarded Casimir) interaction energy E between two infinitely long, crossed conducting wires separated by a minimum distance D much greater than their radius. We find that, up to a logarithmic correction factor, E{proportional_to}-D{sup -1}|sin {theta}|{sup -1}f({theta}), where f({theta}) is a smooth bounded function of the angle {theta} between the wires. We recover a conventional result of the form E{proportional_to}-D{sup -4}|sin {theta}|{sup -1}g({theta}) when we include an electronic energy gap in our calculation. Our prediction of gap-dependent energetics may be observable experimentally for carbon nanotubes either via atomic force microscopy detection of the Van der Waals force or torque or indirectly via observation of mechanical oscillations. This shows that strictly parallel wires, as assumed in previous predictions, are not needed to see a unique effect of this type.

  17. Reusable Hot-Wire Cable Cutter

    NASA Technical Reports Server (NTRS)

    Pauken, Michael T.; Steinkraus, Joel M.

    2010-01-01

    During the early development stage of balloon deployment systems for missions, nichrome wire cable cutters were often used in place of pyro-actuated cutters. Typically, a nichrome wire is wrapped around a bundle of polymer cables with a low melting point and connected to a relay-actuated electric circuit. The heat from the nichrome reduces the strength of the cable bundle, which quickly breaks under a mechanical load and can thus be used as a release mechanism for a deployment system. However, the use of hand-made heated nichrome wire for cutters is not very reliable. Often, the wrapped nichrome wire does not cut through the cable because it either pulls away from its power source or does not stay in contact with the cable being cut. Because nichrome is not readily soldered to copper wire, unreliable mechanical crimps are often made to connect the nichrome to an electric circuit. A self-contained device that is reusable and reliable was developed to sever cables for device release or deployment. The nichrome wire in this new device is housed within an enclosure to prevent it from being damaged by handling. The electric power leads are internally connected within the unit to the nichrome wire using a screw terminal connection. A bayonet plug, a quick and secure method of connecting the cutter to the power source, is used to connect the cutter to the power leads similar to those used in pyro-cutter devices. A small ceramic tube [0.25-in. wide 0.5-in. long (.6.4-mm wide 13-mm long)] houses a spiraled nichrome wire that is heated when a cable release action is required. The wire is formed into a spiral coil by wrapping it around a mandrel. It is then laid inside the ceramic tube so that it fits closely to the inner surface of the tube. The ceramic tube provides some thermal and electrical insulation so that most of the heat generated by the wire is directed toward the cable bundle in the center of the spiral. The ceramic tube is cemented into an aluminum block, which

  18. Quantum ontologies

    SciTech Connect

    Stapp, H.P.

    1988-12-01

    Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988. 16 refs.

  19. Temperature effect on DNA molecular wires

    NASA Astrophysics Data System (ADS)

    Bui, Christopher Minh

    The demand of technology and information today has further pushed the fabrication process of nanotechnology, yet there are limits and obstacles set by the primary laws of physics. Therefore, researchers are pursuing alternative technologies. Deoxyribonucleic acids (DNA) molecular wire is one advantageous option due to its unique characteristics including self-assembly and naturally small; size. This thesis reports the temperature effect on the electrical properties of a double-stranded ?-DNA molecular wire. The data will help expand the DNA wire application and functionality. Thus, the data supports the charge hopping theory on DNA electrical conductivity. Diverse amount of literatures has demonstrated that DNA experiences a biochemical alteration when exposed under different temperature conditions. This change will also cause a change in the electrical properties. In this research, DNA will hang between two gold covered microelectrodes with a distance of 10 to 12 microns. The microelectrodes are fabricated through negative lithography techniques. Then, the samples were exposed to a numerous range of temperature from 25°C to 180°C and went through varying cycles of heating and cooling. The experimental results revealed that the DNA experienced a hysteresis like behavior where the impedance differed between the heating and cooling phase. The impedance of the DNA molecular wire increased when exposed to higher temperature. Furthermore, the impedance stops increasing after a certain amount of heat cycles before the DNA structure failed. The biology and thermodynamics of the DNA wire was analyzed due to the temperature hysteresis effect. The melting temperature and the bond dissociation temperature were evaluated to determine the cause of the impedance trends. The studies and analysis of the temperature effect provided certain insights towards the charge hopping transport mechanism. The thesis concludes with possible applications relating to the temperature effect of

  20. Quantum Computer Games: Quantum Minesweeper

    ERIC Educational Resources Information Center

    Gordon, Michal; Gordon, Goren

    2010-01-01

    The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…