Sample records for tass tunnel aespoe

  1. TDRSS Augmentation Service for Satellites (TASS)

    NASA Technical Reports Server (NTRS)

    Heckler, Gregory W.; Gramling, Cheryl; Valdez, Jennifer; Baldwin, Philip

    2016-01-01

    In 2015, NASA Goddard Space Flight Center (GSFC) reinvigorated the development of the TDRSS Augmentation Service for Satellites (TASS). TASS is a global, space-based, communications and navigation service for users of Global Navigation Satellite Systems (GNSS) and the Tracking and Data Relay Satellite System (TDRSS). TASS leverages the existing TDRSS to provide an S-band beacon radio navigation and messaging source to users at orbital altitudes 1400 km and below.

  2. Simulation of Benchmark Cases with the Terminal Area Simulation System (TASS)

    NASA Technical Reports Server (NTRS)

    Ahmad, Nash'at; Proctor, Fred

    2011-01-01

    The hydrodynamic core of the Terminal Area Simulation System (TASS) is evaluated against different benchmark cases. In the absence of closed form solutions for the equations governing atmospheric flows, the models are usually evaluated against idealized test cases. Over the years, various authors have suggested a suite of these idealized cases which have become standards for testing and evaluating the dynamics and thermodynamics of atmospheric flow models. In this paper, simulations of three such cases are described. In addition, the TASS model is evaluated against a test case that uses an exact solution of the Navier-Stokes equations. The TASS results are compared against previously reported simulations of these banchmark cases in the literature. It is demonstrated that the TASS model is highly accurate, stable and robust.

  3. Simulation of Benchmark Cases with the Terminal Area Simulation System (TASS)

    NASA Technical Reports Server (NTRS)

    Ahmad, Nashat N.; Proctor, Fred H.

    2011-01-01

    The hydrodynamic core of the Terminal Area Simulation System (TASS) is evaluated against different benchmark cases. In the absence of closed form solutions for the equations governing atmospheric flows, the models are usually evaluated against idealized test cases. Over the years, various authors have suggested a suite of these idealized cases which have become standards for testing and evaluating the dynamics and thermodynamics of atmospheric flow models. In this paper, simulations of three such cases are described. In addition, the TASS model is evaluated against a test case that uses an exact solution of the Navier-Stokes equations. The TASS results are compared against previously reported simulations of these benchmark cases in the literature. It is demonstrated that the TASS model is highly accurate, stable and robust.

  4. Advection of Microphysical Scalars in Terminal Area Simulation System (TASS)

    NASA Technical Reports Server (NTRS)

    Ahmad, Nashat N.; Proctor, Fred H.

    2011-01-01

    The Terminal Area Simulation System (TASS) is a large eddy scale atmospheric flow model with extensive turbulence and microphysics packages. It has been applied successfully in the past to a diverse set of problems ranging from prediction of severe convective events (Proctor et al. 2002), tracking storms and for simulating weapons effects such as the dispersion and fallout of fission debris (Bacon and Sarma 1991), etc. More recently, TASS has been used for predicting the transport and decay of wake vortices behind aircraft (Proctor 2009). An essential part of the TASS model is its comprehensive microphysics package, which relies on the accurate computation of microphysical scalar transport. This paper describes an evaluation of the Leonard scheme implemented in the TASS model for transporting microphysical scalars. The scheme is validated against benchmark cases with exact solutions and compared with two other schemes - a Monotone Upstream-centered Scheme for Conservation Laws (MUSCL)-type scheme after van Leer and LeVeque's high-resolution wave propagation method. Finally, a comparison between the schemes is made against an incident of severe tornadic super-cell convection near Del City, Oklahoma.

  5. The TASS Method for Scoring Production Work

    ERIC Educational Resources Information Center

    Orsborn, Karen J.

    1977-01-01

    Describes and recommends to typing teachers the Time and Speed Scoring (TASS) method for testing typewriting production and figuring production rates. This method measures speed and quality as two separate items, because proficiency in production typewriting should reflect the student's skill in typing both accurately and quickly. (MF)

  6. TASS Model Application for Testing the TDWAP Model

    NASA Technical Reports Server (NTRS)

    Switzer, George F.

    2009-01-01

    One of the operational modes of the Terminal Area Simulation System (TASS) model simulates the three-dimensional interaction of wake vortices within turbulent domains in the presence of thermal stratification. The model allows the investigation of turbulence and stratification on vortex transport and decay. The model simulations for this work all assumed fully-periodic boundary conditions to remove the effects from any surface interaction. During the Base Period of this contract, NWRA completed generation of these datasets but only presented analysis for the neutral stratification runs of that set (Task 3.4.1). Phase 1 work began with the analysis of the remaining stratification datasets, and in the analysis we discovered discrepancies with the vortex time to link predictions. This finding necessitated investigating the source of the anomaly, and we found a problem with the background turbulence. Using the most up to date version TASS with some important defect fixes, we regenerated a larger turbulence domain, and verified the vortex time to link with a few cases before proceeding to regenerate the entire 25 case set (Task 3.4.2). The effort of Phase 2 (Task 3.4.3) concentrated on analysis of several scenarios investigating the effects of closely spaced aircraft. The objective was to quantify the minimum aircraft separations necessary to avoid vortex interactions between neighboring aircraft. The results consist of spreadsheets of wake data and presentation figures prepared for NASA technical exchanges. For these formation cases, NASA carried out the actual TASS simulations and NWRA performed the analysis of the results by making animations, line plots, and other presentation figures. This report contains the description of the work performed during this final phase of the contract, the analysis procedures adopted, and sample plots of the results from the analysis performed.

  7. The Beginner's Guide to Wind Tunnels with TunnelSim and TunnelSys

    NASA Technical Reports Server (NTRS)

    Benson, Thomas J.; Galica, Carol A.; Vila, Anthony J.

    2010-01-01

    The Beginner's Guide to Wind Tunnels is a Web-based, on-line textbook that explains and demonstrates the history, physics, and mathematics involved with wind tunnels and wind tunnel testing. The Web site contains several interactive computer programs to demonstrate scientific principles. TunnelSim is an interactive, educational computer program that demonstrates basic wind tunnel design and operation. TunnelSim is a Java (Sun Microsystems Inc.) applet that solves the continuity and Bernoulli equations to determine the velocity and pressure throughout a tunnel design. TunnelSys is a group of Java applications that mimic wind tunnel testing techniques. Using TunnelSys, a team of students designs, tests, and post-processes the data for a virtual, low speed, and aircraft wing.

  8. Behaviour of tunnel lining material in road tunnel fire

    NASA Astrophysics Data System (ADS)

    Tomar, M.; Khurana, S.; Singh, R.

    2018-04-01

    The worldwide road tunnel linings are protected against possible fire scenarios to safeguard the structure and assist in occupant evacuation. There are various choices of active and passive protection available, passive protections includes calcium silicate boards, polypropylene fibers, vermiculite cement based sprays, and other intumescent materials. Tunnel fire is a complex phenomenon and researchers in the past has highlighted that there are various factors which affect the tunnel fires. The effect of passive protection techniques on tunnel fire is not well understood, especially for the insulation boards. It’s been understood from past research that for a heavy good vehicular (HGV) fire in the tunnel, the heat feedback effect is significant. Insulation boards may also affect the tunnel fires by altering the heat feedback effect in vehicular tunnels and hence this can affect the overall heat release rates and temperature profile inside a tunnel. This study focuses on studying the role of insulation boards in tunnel fires and evaluating its effect on overall heat release rate and tunnel temperatures.

  9. Giant tunneling magnetoresistance and tunneling spin polarization in magnetic tunnel junctions with MgO (100) tunnel barriers

    NASA Astrophysics Data System (ADS)

    Parkin, Stuart

    2006-03-01

    Recent advances in generating, manipulating and detecting spin-polarized electrons and electrical current make possible new classes of spin based sensor, memory and logic devices [1]. One key component of many such devices is the magnetic tunneling junction (MTJ) - a sandwich of thin layers of metallic ferromagnetic electrodes separated by a tunneling barrier, typically an oxide material only a few atoms thick. The magnitude of the tunneling current passing through the barrier can be adjusted by varying the relative magnetic orientation of the adjacent ferromagnetic layers. As a result, MTJs can be used to sense the magnitude of magnetic fields or to store information. The electronic structure of the ferromagnet together with that of the insulator determines the spin polarization of the current through an MTJ -- the ratio of 'up' to 'down' spin electrons. Using conventional amorphous alumina tunnel barriers tunneling spin polarization (TSP) values of up to ˜55% are found for conventional 3d ferromagnets, such as CoFe, but using highly textured crystalline MgO tunnel barriers TSP values of more than 90% can be achieved for otherwise the same ferromagnet [2]. Such TSP values rival those previously observed only with half-metallic ferromagnets. Corresponding giant values of tunneling magnetoresistance (TMR) are found, exceeding 350% at room temperature and nearly 600% at 3K. Perhaps surprisingly the MgO tunnel barrier can be quite rough: its thickness depends on the local crystalline texture of the barrier, which itself is influenced by structural defects in the underlayer. We show that the magnitude and the sign of the TMR is strongly influenced by defects in the tunnel barrier and by the detailed structure of the barrier/ferromagnet interfaces. The observation of Kondo-assisted tunneling phenomena will be discussed as well as the detailed dependence of TMR on chemical bonding at the interfaces [3]. [1] .S.S.P. Parkin, X. Jiang, C. Kaiser, et al., Proc. IEEE 91, 661

  10. Instantons re-examined: dynamical tunneling and resonant tunneling.

    PubMed

    Le Deunff, Jérémy; Mouchet, Amaury

    2010-04-01

    Starting from trace formulas for the tunneling splittings (or decay rates) analytically continued in the complex time domain, we obtain explicit semiclassical expansions in terms of complex trajectories that are selected with appropriate complex-time paths. We show how this instantonlike approach, which takes advantage of an incomplete Wick rotation, accurately reproduces tunneling effects not only in the usual double-well potential but also in situations where a pure Wick rotation is insufficient, for instance dynamical tunneling or resonant tunneling. Even though only one-dimensional autonomous Hamiltonian systems are quantitatively studied, we discuss the relevance of our method for multidimensional and/or chaotic tunneling.

  11. The Design of Wind Tunnels and Wind Tunnel Propellers

    NASA Technical Reports Server (NTRS)

    Warner, Edward P; Norton, F H; Hebbert, C M

    1919-01-01

    Report discusses the theory of energy losses in wind tunnels, the application of the Drzewiecki theory of propeller design to wind tunnel propellers, and the efficiency and steadiness of flow in model tunnels of various types.

  12. The self streamlining wind tunnel. [wind tunnel walls

    NASA Technical Reports Server (NTRS)

    Goodyer, M. J.

    1975-01-01

    A two dimensional test section in a low speed wind tunnel capable of producing flow conditions free from wall interference is presented. Flexible top and bottom walls, and rigid sidewalls from which models were mounted spanning the tunnel are shown. All walls were unperforated, and the flexible walls were positioned by screw jacks. To eliminate wall interference, the wind tunnel itself supplied the information required in the streamlining process, when run with the model present. Measurements taken at the flexible walls were used by the tunnels computer check wall contours. Suitable adjustments based on streamlining criteria were then suggested by the computer. The streamlining criterion adopted when generating infinite flowfield conditions was a matching of static pressures in the test section at a wall with pressures computed for an imaginary inviscid flowfield passing over the outside of the same wall. Aerodynamic data taken on a cylindrical model operating under high blockage conditions are presented to illustrate the operation of the tunnel in its various modes.

  13. Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Piquemal-Banci, M.; Galceran, R.; Bouzehouane, K.

    We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

  14. Tunnel and Station Cost Methodology : Mined Tunnels

    DOT National Transportation Integrated Search

    1983-01-01

    The main objective of this study was to develop a model for estimating the cost of subway station and tunnel construction. This report describes a cost estimating methodology for subway tunnels that can be used by planners, designers, owners, and gov...

  15. Spin-dependent tunneling effects in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Gao, Li

    2009-03-01

    It has long been known that current extracted from magnetic electrodes through ultra thin oxide tunnel barriers is spin polarized. This current gives rise to two important properties: tunneling magnetoresistance (TMR) when the tunnel barrier is sandwiched between two thin magnetic electrodes and, spin momentum transfer, which can be used to manipulate the magnetic state of the magnetic electrodes. In the first part of my talk I show how the structure of thin CoFe layers can be made amorphous by simply sandwiching them between two amorphous layers, one of them the tunnel barrier. No glass forming elements are needed. By slightly changing the thickness of these layers or by heating them above their glass transition temperature they become crystalline. Surprisingly, the TMR of the amorphous structure is significantly higher than of its crystalline counterpart. The tunneling anisotropic magnetoresistance, which has complex voltage dependence, is also discussed. In the second part of my talk I discuss the microwave emission spectrum from magnetic tunnel junctions induced by spin torque from spin polarized dc current passed through the device. We show that the spectrum is very sensitive to small variations in device structures, even in those devices which exhibit similarly high TMR (˜120%) and which have similar resistance-area products (˜4-10 φμm^2). We speculate that these variations are due to non-uniform spatial magnetic excitation arising from inhomogeneous current flow through the tunnel barrier. [In collaboration with Xin Jiang, M. Hayashi, Rai Moriya, Brian Hughes, Teya Topuria, Phil Rice, and Stuart S.P. Parkin

  16. View down tank tunnel (tunnel no. 2) showing pipes and ...

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

    View down tank tunnel (tunnel no. 2) showing pipes and walkway of metal grating, side tunnel to tank 3 is on the left - U.S. Naval Base, Pearl Harbor, Diesel Purification Plant, North Road near Pierce Street, Pearl City, Honolulu County, HI

  17. New drainage tunnel of the tunnel Višňové - design and excavation

    NASA Astrophysics Data System (ADS)

    Jurík, Igor; Grega, Ladislav; Valko, Jozef; Janega, Peter

    2017-09-01

    The actual pilot tunnel dated to the period of geological and hydrogeological survey, is designed as a part of the tunnel Višňové, which is located at the section of the D1 motorway Lietavská Lúčka - Višňové - Dubná Skala in Slovakia. Drainage tunnel will be used for the drainage of the main tunnel tubes, where the maximum inflow from the eastern portal is greater than 250 l.s-1. Overlapping of the initial pilot tunnel with the profile of the southern tunnel tube led to the demolition of the portal sections of the pilot tunnel during the excavation of main tunnel tubes. These sections were replaced by new drainage tunnels, with the lengths of 288.0 meters from west portal and 538.0 meters from eastern portal, to ensure access from both portals. The new drainage tunnel is excavated under the level of the two main tunnel tubes. Drainage pipes with a diameter of 250 mm will be installed from cleaning niches in the main tunnel tubes to the new drainage tunnel.

  18. Carpal Tunnel Syndrome

    MedlinePlus

    ... a passing cramp? It could be carpal tunnel syndrome. The carpal tunnel is a narrow passageway of ... three times more likely to have carpal tunnel syndrome than men. Early diagnosis and treatment are important ...

  19. Enhancing metal-insulator-insulator-metal tunnel diodes via defect enhanced direct tunneling

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alimardani, Nasir; Conley, John F., E-mail: jconley@eecs.oregonstate.edu

    Metal-insulator-insulator-metal tunnel diodes with dissimilar work function electrodes and nanolaminate Al{sub 2}O{sub 3}-Ta{sub 2}O{sub 5} bilayer tunnel barriers deposited by atomic layer deposition are investigated. This combination of high and low electron affinity insulators, each with different dominant conduction mechanisms (tunneling and Frenkel-Poole emission), results in improved low voltage asymmetry and non-linearity of current versus voltage behavior. These improvements are due to defect enhanced direct tunneling in which electrons transport across the Ta{sub 2}O{sub 5} via defect based conduction before tunneling directly through the Al{sub 2}O{sub 3}, effectively narrowing the tunnel barrier. Conduction through the device is dominated by tunneling,more » and operation is relatively insensitive to temperature.« less

  20. Tunneling spin polarization in planar tunnel junctions: measurements using NbN superconducting electrodes and evidence for Kondo-assisted tunneling

    NASA Astrophysics Data System (ADS)

    Yang, Hyunsoo

    2006-03-01

    The fundamental origin of tunneling magnetoresistance in magnetic tunnel junctions (MTJs) is the spin-polarized tunneling current, which can be measured directly using superconducting tunneling spectroscopy (STS). The STS technique was first developed by Meservey and Tedrow using aluminum superconducting electrodes. Al has been widely used because of its low spin orbit scattering. However, measurements must be made at low temperatures (<0.4 K) because of the low superconducting transition temperature of Al. Here, we demonstrate that superconducting electrodes formed from NbN can be used to measure tunneling spin polarization (TSP) at higher temperatures up to ˜1.2K. The tunneling magnetoresistance and polarization of the tunneling current in MTJs is highly sensitive to the detailed structure of the tunneling barrier. Using MgO tunnel barriers we find TSP values as high as 90% at 0.25K. The TMR is, however, depressed by insertion of ultra thin layers of both non-magnetic and magnetic metals in the middle of the MgO barrier. For ultra-thin, discontinuous magnetic layers of CoFe, we find evidence of Kondo assisted tunneling, from increased conductance at low temperatures (<50K) and bias voltage (<20 mV). Over the same temperature and bias voltage regimes the tunneling magnetoresistance is strongly depressed. We present other evidence of Kondo resonance including the logarithmic temperature dependence of the zero bias conductance peak. We infer the Kondo temperature from both the spectra width of this conductance peak as well as the temperature dependence of the TMR depression. The Kondo temperature is sensitive to the thickness of the inserted CoFe layer and decreases with increased CoFe thickness. * performed in collaboration with S-H. Yang, C. Kaiser, and S. Parkin.

  1. Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Parui, Subir, E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu; Ribeiro, Mário; Atxabal, Ainhoa

    The relevance for modern computation of non-volatile high-frequency memories makes ac-transport measurements of magnetic tunnel junctions (MTJs) crucial for exploring this regime. Here, we demonstrate a frequency-mediated effect in which the tunnel magnetoimpedance reverses its sign in a classical Co/Al{sub 2}O{sub 3}/NiFe MTJ, whereas we only observe a gradual decrease in the tunnel magnetophase. Such effects are explained by the capacitive coupling of a parallel resistor and capacitor in the equivalent circuit model of the MTJ. Furthermore, we report a positive tunnel magnetocapacitance effect, suggesting the presence of a spin-capacitance at the two ferromagnet/tunnel-barrier interfaces. Our results are important formore » understanding spin transport phenomena at the high frequency regime in which the spin-polarized charge accumulation due to spin-dependent penetration depth at the two interfaces plays a crucial role.« less

  2. Viscoelastic substance in prefilled syringe as an etiology of Toxic Anterior Segment Syndrome.

    PubMed

    Althomali, Talal Abdulrahman

    2016-09-01

    Toxic Anterior Segment Syndrome (TASS) is an acute postoperative inflammatory reaction in which a noninfectious substance enters the anterior segment and induces toxic damage to the intraocular tissues. To present etiologic investigation of two consecutive clusters of TASS. TASS outbreak and investigation: This paper presents two consecutive clusters of TASS in 15 of the 24 uneventful surgeries and the investigation carried out to find the etiology. After the occurrence of first cluster of TASS, sterilization-related etiology was explored; however, we did not find any lacunae in the sterilization and cleaning process in the operating theater (OT). Nevertheless, multiple changes in cleaning process were implemented. Still a second cluster of TASS was encountered in the following session of OT. Several other factors which include preservatives, hand gloves, intraocular lenses, medications/solutions, intraocular penetration of topically administered drugs, and viscoelastics were investigated as the possible etiology of the second consecutive cluster of TASS; however, most of them were ruled out. The newly introduced viscoelastic I-visc® 1.4% sodium hyaluronate (I medical, i-Medical Ophthalmic International GmbH, Heidelberg, Germany) was thought to be the most likely cause and was replaced with previously in use sodium hyaluronate 1.5% and lidocaine hydrochloride 1% (Visthesia, CZ, Germany) in the following session of OT. No further TASS incident was encountered after replacing the viscoelastic. Investigation revealed that 1.4% sodium hyaluronate in prefilled syringe (PFS) (I-visc® 1.4%) was the etiologic factor of two consecutive clusters of TASS. While TASS due to residual denatured ophthalamic viscosurgical devices (OVDs) is a common knowledge, current study brings out that even disposable viscoelastic material supplied in PFSs can be an etiology of TASS. It is important to recognize that contamination of OVDs with endotoxins can occur at the time of manufacturing

  3. Safety in tunnels : transport of dangerous goods through road tunnels : highlights

    DOT National Transportation Integrated Search

    2001-10-01

    A serious incident involving dangerous goods in a tunnel can be extremely costly in terms of loss of human lives, environmental degradation, tunnel damage and transport disruption. On the other hand, needlessly banning dangerous goods from tunnels ma...

  4. Toxic Anterior Segment Syndrome Outbreak after Cataract Surgery Triggered by Viscoelastic Substance.

    PubMed

    Altıntaş, AyşeGül Koçak; Ciritoğlu, Meryem Yaşar; BeyazyıldıZ, Özlem; Can, Çiğdem Ülkü; Polat, Sibel

    2017-01-01

    The purpose of this study is to present toxic anterior segment syndrome (TASS) outbreak at our clinic and discuss possible causes of TASS. Thirty-four eyes of 34 patients developed TASS in a consecutive 2 weeks period were included in this study. Both anterior segment and fundus examinations were performed before and after uncomplicated cataract surgery. During the follow-up period, clinical features and all possible causes were evaluated including perioperative products and processing such as sterilization technique of surgical instruments, irrigating solutions, drugs, viscoelastic substance (VES), and intraocular lens. Patients had corneal edema, anterior chamber reactions, and decreased vision. No patient had purulent secretion, chemosis, lid involvement, and pain. At first 2 postoperative days, patients treated as infectious endophthalmitis by topical and oral antibiotics and then TASS was suspected, and patients treated completely with topical steroids. Suspected cause for TASS was VES substance, 2% sodium hyaluronate which had newly been used as VES product in phacoemulsification surgery. No new case has occurred after stopped usage of this VES product. As far as we know, this is the largest report of TASS outbreak in the shortest period from the same clinic caused by VES. Suboptimal products of surgical materials can be the cause of TASS. Close monitoring of each surgical step and elimination of causative agent can prevent the outbreaks of TASS.

  5. Toxic anterior segment syndrome following penetrating keratoplasty.

    PubMed

    Maier, Philip; Birnbaum, Florian; Böhringer, Daniel; Reinhard, Thomas

    2008-12-01

    To describe an outbreak of toxic anterior segment syndrome (TASS) following penetrating keratoplasty (PK) and to examine its possible causes. Owing to a series of TASS following PK between June 6, 2007, and October 2, 2007, we reviewed the records of all patients who had undergone PK during that time. In addition to routine microbial tests on organ culture media, we looked for specific pathogens and endotoxins in all of the materials used for organ culture or PK. Furthermore, we analyzed all of the perioperative products and instrument processing. Of the 94 patients who underwent PK, we observed 24 cases of postoperative sterile keratitis. Causal research revealed that the accumulation of cleaning substances or heat-stable endotoxins on the surface of the routinely used guided trephine system was most likely responsible for the TASS. To our knowledge, this is the first report on TASS following PK. Suboptimal reprocessing of surgical instruments may be an important cause of TASS as in this series the TASS-like symptoms resolved after modified instrument-cleaning procedures. The standardization of protocols for processing reusable trephine systems might prevent outbreaks of TASS following PK.

  6. Magnetic tunnel junctions utilizing diamond-like carbon tunnel barriers

    NASA Astrophysics Data System (ADS)

    Cadieu, F. J.; Chen, Li; Li, Biao

    2002-05-01

    We have devised a method whereby thin particulate-free diamond-like carbon films can be made with good adhesion onto even room-temperature substrates. The method employs a filtered ionized carbon beam created by the vacuum impact of a high-energy, approximately 1 J per pulse, 248 nm excimer laser onto a carbon target. The resultant deposition beam can be steered and deflected by magnetic and electric fields to paint a specific substrate area. An important aspect of this deposition method is that the resultant films are particulate free and formed only as the result of atomic species impact. The vast majority of magnetic tunnel junctions utilizing thin metallic magnetic films have employed a thin oxidized layer of aluminum to form the tunnel barrier. This has presented reproducibility problems because the indicated optimal barrier thickness is only approximately 13 Å thick. Magnetic tunnel junctions utilizing Co and permalloy films made by evaporation and sputtering have been fabricated with an intervening diamond-like carbon tunnel barrier. The diamond-like carbon thickness profile has been tapered so that seven junctions with different barrier thickness can be formed at once. Magnetoresistive (MR) measurements made between successive permalloy strip ends include contributions from two junctions and from the permalloy and Co strips that act as current leads to the junctions. Magnetic tunnel junctions with thicker carbon barriers exhibit MR effects that are dominated by that of the permalloy strips. Since these tunnel barriers are formed without the need for oxygen, complete tunnel junctions can be formed with all high-vacuum processing.

  7. Influence of Short Distance Super-large Diameter Shield Tunneling on Existing Tunnels in Sea Areas

    NASA Astrophysics Data System (ADS)

    Li, Zhuolin; Liu, Dagang; Wang, Mingnian; Xiao, Shihui; Yuan, Jiawei

    2018-03-01

    In oder to find out the influence of large diameter shield tunneling on the existing tunnel under the condition of compound strata in the sea area, taking the Maliuzhou traffic tunnel as the research background, numerical simulation and field test were combined to get the regulation of the additional internal force and deformation of the existing tunnel caused by the shield tunneling. Analysis of the data showed that: the shield construction caused the secondary additional internal force; The moment of the vault was most affected by the tunnel excavation; The axial force of the arch bottom was most affected by the excavation of the tunnel. The deformation of arch waist near excavation tunnel was more affected by tunnel excavation than that of the other side. Combined with the construction experience, the influence of the tunnel close-distance construction on the existing tunnel was within the control range, which could ensure the normal construction.

  8. Probing individual tunneling fluctuators with coherently controlled tunneling systems

    NASA Astrophysics Data System (ADS)

    Meißner, Saskia M.; Seiler, Arnold; Lisenfeld, Jürgen; Ustinov, Alexey V.; Weiss, Georg

    2018-05-01

    Josephson junctions made from aluminum and its oxide are the most commonly used functional elements for superconducting circuits and qubits. It is generally known that the disordered thin film AlOx contains atomic tunneling systems. Coherent tunneling systems may couple strongly to a qubit via their electric dipole moment, giving rise to spectral level repulsion. In addition, slowly fluctuating tunneling systems are observable when they are located close to coherent ones and distort their potentials. This interaction causes telegraphic switching of the coherent tunneling systems' energy splitting. Here, we measure such switching induced by individual fluctuators on timescales from hours to minutes using a superconducting qubit as a detector. Moreover, we extend the range of measurable switching times to millisecond scales by employing a highly sensitive single-photon qubit swap spectroscopy and statistical analysis of the measured qubit states.

  9. Fabrication of magnetic tunnel junctions with a single-crystalline LiF tunnel barrier

    NASA Astrophysics Data System (ADS)

    Krishna Narayananellore, Sai; Doko, Naoki; Matsuo, Norihiro; Saito, Hidekazu; Yuasa, Shinji

    2018-04-01

    We fabricated Fe/LiF/Fe magnetic tunnel junctions (MTJs) by molecular beam epitaxy on a MgO(001) substrate, where LiF is an insulating tunnel barrier with the same crystal structure as MgO (rock-salt type). Crystallographical studies such as transmission electron microscopy and nanobeam electron diffraction observations revealed that the LiF tunnel barrier is single-crystalline and has a LiF(001)[100] ∥ bottom Fe(001)[110] crystal orientation, which is constructed in the same manner as MgO(001) on Fe(001). Also, the in-plane lattice mismatch between the LiF tunnel barrier and the Fe bottom electrode was estimated to be small (about 0.5%). Despite such advantages for the tunnel barrier of the MTJ, the observed tunnel magnetoresistance (MR) ratio was low (˜6% at 20 K) and showed a significant decrease with increasing temperature (˜1% at room temperature). The results imply that indirect tunneling and/or thermally excited carriers in the LiF tunnel barrier, in which the current basically is not spin-polarized, play a major role in electrical transport in the MTJ.

  10. Evaluation of the Space Shuttle Transatlantic Abort Landing Atmospheric Sounding System

    NASA Technical Reports Server (NTRS)

    Leahy, Frank B.

    2003-01-01

    A study was conducted to determine the quality of thermodynamic and wind data measured by or derived from the Transatlantic Abort Landing (TAL) Atmospheric Sounding System (TASS). The system has Global Positioning System (GPS) tracking capability and includes a helium-filled latex balloon that carries an instrument package (sonde) and various ground equipment that receives and processes the data from the sonde. TASS is used to provide vertical profiles of thermodynamic and low-resolution wind data in support of Shuttle abort landing operations at TAL sites. TASS uses GPS to determine height, wind speed, and wind direction. The TASS sonde has sensors that directly measure air temperature and relative humidity. These are then used to derive air pressure and density. Test flights were conducted where a TASS sonde and a reference sonde were attached to the same balloon and the two profiles were compared. The objective of the testing was to determine if TASS thermodynamic and wind data met Space Shuttle Program (SSP) accuracy requirements outlined in the Space Shuttle Launch and Landing Program Requirements Document (PRD).

  11. Recognition Tunneling

    PubMed Central

    Lindsay, Stuart; He, Jin; Sankey, Otto; Hapala, Prokop; Jelinek, Pavel; Zhang, Peiming; Chang, Shuai; Huang, Shuo

    2010-01-01

    Single molecules in a tunnel junction can now be interrogated reliably using chemically-functionalized electrodes. Monitoring stochastic bonding fluctuations between a ligand bound to one electrode and its target bound to a second electrode (“tethered molecule-pair” configuration) gives insight into the nature of the intermolecular bonding at a single molecule-pair level, and defines the requirements for reproducible tunneling data. Simulations show that there is an instability in the tunnel gap at large currents, and this results in a multiplicity of contacts with a corresponding spread in the measured currents. At small currents (i.e. large gaps) the gap is stable, and functionalizing a pair of electrodes with recognition reagents (the “free analyte” configuration) can generate a distinct tunneling signal when an analyte molecule is trapped in the gap. This opens up a new interface between chemistry and electronics with immediate implications for rapid sequencing of single DNA molecules. PMID:20522930

  12. Carpal Tunnel Syndrome

    PubMed Central

    Zimmerman, Gregory R.

    1994-01-01

    Carpal tunnel syndrome is a neuropathy resulting from compression of the median nerve as it passes through a narrow tunnel in the wrist on its way to the hand. The lack of precise objective and clinical tests, along with symptoms that are synonymous with other syndromes in the upper extremity, cause carpal tunnel syndrome to appear to be a rare entity in athletics. However, it should not be ruled out as a possible etiology of upper extremity paralysis in the athlete. More typically, carpal tunnel syndrome is the most common peripheral entrapment neuropathy encountered in industry. Treatment may include rest and/or splinting of the involved wrist, ice application, galvanic stimulation, or iontophoresis to reduce inflammation, and then transition to heat modalities and therapeutic exercises for developing flexibility, strength, and endurance. In addition, an ergonomic assessment should be conducted, resulting in modifications to accommodate the carpal tunnel syndrome patient. ImagesFig 3.Fig 4.Fig 5.Fig 6.Fig 7. PMID:16558255

  13. The Tunnels of Samos

    NASA Technical Reports Server (NTRS)

    Apostol, Tom M. (Editor)

    1995-01-01

    This 'Project Mathematics' series video from CalTech presents the tunnel of Samos, a famous underground aquaduct tunnel located near the capital of Pithagorion (named after the famed Greek mathematician, Pythagoras, who lived there), on one of the Greek islands. This tunnel was constructed around 600 BC by King Samos and was built under a nearby mountain. Through film footage and computer animation, the mathematical principles and concepts of why and how this aquaduct tunnel was built are explained.

  14. Interior of Tunnel No. 1356, Stick Pile Tunnel showing timber ...

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

    Interior of Tunnel No. 1356, Stick Pile Tunnel showing timber framing and missing posts, looking northeast. - Western Maryland Railway, Cumberland Extension, Pearre to North Branch, from WM milepost 125 to 160, Pearre, Washington County, MD

  15. View of entrance tunnel. Tunnel right to Control Center, left ...

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

    View of entrance tunnel. Tunnel right to Control Center, left to Antenna Silos - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

  16. Single Electron Tunneling

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ruggiero, Steven T.

    Financial support for this project has led to advances in the science of single-electron phenomena. Our group reported the first observation of the so-called ''Coulomb Staircase'', which was produced by tunneling into ultra-small metal particles. This work showed well-defined tunneling voltage steps of width e/C and height e/RC, demonstrating tunneling quantized on the single-electron level. This work was published in a now well-cited Physical Review Letter. Single-electron physics is now a major sub-field of condensed-matter physics, and fundamental work in the area continues to be conducted by tunneling in ultra-small metal particles. In addition, there are now single-electron transistors thatmore » add a controlling gate to modulate the charge on ultra-small photolithographically defined capacitive elements. Single-electron transistors are now at the heart of at least one experimental quantum-computer element, and single-electron transistor pumps may soon be used to define fundamental quantities such as the farad (capacitance) and the ampere (current). Novel computer technology based on single-electron quantum dots is also being developed. In related work, our group played the leading role in the explanation of experimental results observed during the initial phases of tunneling experiments with the high-temperature superconductors. When so-called ''multiple-gap'' tunneling was reported, the phenomenon was correctly identified by our group as single-electron tunneling in small grains in the material. The main focus throughout this project has been to explore single electron phenomena both in traditional tunneling formats of the type metal/insulator/particles/insulator/metal and using scanning tunneling microscopy to probe few-particle systems. This has been done under varying conditions of temperature, applied magnetic field, and with different materials systems. These have included metals, semi-metals, and superconductors. Amongst a number of results, we have

  17. Introduction to cryogenic wind tunnels

    NASA Technical Reports Server (NTRS)

    Goodyer, M. J.

    1985-01-01

    The background to the evolution of the cryogenic wind tunnel is outlined, with particular reference to the late 60's/early 70's when efforts were begun to re-equip with larger wind tunnels. The problems of providing full scale Reynolds numbers in transonic testing were proving particularly intractible, when the notion of satisfying the needs with the cryogenic tunnel was proposed, and then adopted. The principles and advantages of the cryogenic tunnel are outlined, along with guidance on the coolant needs when this is liquid nitrogen, and with a note on energy recovery. Operational features of the tunnels are introduced with reference to a small low speed tunnel. Finally the outstanding contributions are highlighted of the 0.3-Meter Transonic Cryogenic Tunnel (TCT) at NASA Langley Research Center, and its personnel, to the furtherance of knowledge and confidence in the concept.

  18. View of Water Storage Tank off entrance tunnel. Tunnel at ...

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

    View of Water Storage Tank off entrance tunnel. Tunnel at left of image to Launch Silos - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

  19. Predicition and Discovery of High Tunneling Magnetoresistance in Magnetic Tunnel Junctions with Crystalline Barriers

    NASA Astrophysics Data System (ADS)

    Butler, William

    2005-03-01

    Tunneling magnetoresistance in excess of 200% has recently been observed in magnetic tunnel junctions using bcc Fe or bcc CoFe electrodes with crystalline MgO tunnel barriers[1,2]. These results demonstrate that tunneling magnetoresistance depends on more than the ``electrode polarization''. This talk will describe the calculations that predicted high TMR in these and other systems[3,4,5]. These calculations helped us to understand certain principles that may lead to high TMR through coherent electron tunneling. They can be briefly summarized as follows: (1) If the symmetry of a Bloch state can be preserved as electrons cross the interfaces between the electrode and the tunnel barrier, this be used to advantage for spin filtering. (2) Evanescent states of different symmetries decay at different rates in the barrier. (3) Interfacial bonding can be very important in determining the probability that an electron can traverse the interface. (4) Electrons of disallowed symmetry cannot propagate in an electrode. Once these simple principles are understood, simple band codes can be used to screen and to develop heterostructures with the proper symmetries to obtain high TMR. [1] S. S. P. Parkin, C. Kaiser, A. Panchula, P. M. Rice, B. Hughes, M. Samant AND S.-H. Yang, ``Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers,'' Nature Materials, Advance Online Publication [2] S. Yuasa, T. Nagahama, A. Fukushima, Y. Suzuki, K. Ando, ``Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions,'' Nature Materials, Advance Online Publication [3] W. H. Butler, X.-G. Zhang, T. C. Schulthess, and J. M. MacLaren, ``Spin-dependent tunneling conductance of Fe | MgO | Fe sandwiches'' Phys. Rev. B 63, 054416 (2001) [4] J. Mathon, A. Umerski, ``Theory of tunneling magnetoresistance of an epitaxial Fe/MgO/Fe(001) junction,'' Phys. Rev. B 63, 220403(R) (2001). [5] X.-G. Zhang, and W. H. Butler, ``Large magnetoresistance in

  20. Influence of trap-assisted tunneling on trap-assisted tunneling current in double gate tunnel field-effect transistor

    NASA Astrophysics Data System (ADS)

    Zhi, Jiang; Yi-Qi, Zhuang; Cong, Li; Ping, Wang; Yu-Qi, Liu

    2016-02-01

    Trap-assisted tunneling (TAT) has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor (TFET). In this paper, we assess subthreshold performance of double gate TFET (DG-TFET) through a band-to-band tunneling (BTBT) model, including phonon-assisted scattering and acoustic surface phonons scattering. Interface state density profile (Dit) and the trap level are included in the simulation to analyze their effects on TAT current and the mechanism of gate leakage current. Project supported by the National Natural Science Foundation of China (Grant Nos. 61574109 and 61204092).

  1. Tunnelling in Dante's Inferno

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Furuuchi, Kazuyuki; Sperling, Marcus, E-mail: kazuyuki.furuuchi@manipal.edu, E-mail: marcus.sperling@univie.ac.at

    2017-05-01

    We study quantum tunnelling in Dante's Inferno model of large field inflation. Such a tunnelling process, which will terminate inflation, becomes problematic if the tunnelling rate is rapid compared to the Hubble time scale at the time of inflation. Consequently, we constrain the parameter space of Dante's Inferno model by demanding a suppressed tunnelling rate during inflation. The constraints are derived and explicit numerical bounds are provided for representative examples. Our considerations are at the level of an effective field theory; hence, the presented constraints have to hold regardless of any UV completion.

  2. Inelastic tunnel diodes

    NASA Technical Reports Server (NTRS)

    Anderson, L. M. (Inventor)

    1984-01-01

    Power is extracted from plasmons, photons, or other guided electromagnetic waves at infrared to midultraviolet frequencies by inelastic tunneling in metal-insulator-semiconductor-metal diodes. Inelastic tunneling produces power by absorbing plasmons to pump electrons to higher potential. Specifically, an electron from a semiconductor layer absorbs a plasmon and simultaneously tunnels across an insulator into metal layer which is at higher potential. The diode voltage determines the fraction of energy extracted from the plasmons; any excess is lost to heat.

  3. Study of tunneling transport in Si-based tunnel field-effect transistors with ON current enhancement utilizing isoelectronic trap

    NASA Astrophysics Data System (ADS)

    Mori, Takahiro; Morita, Yukinori; Miyata, Noriyuki; Migita, Shinji; Fukuda, Koichi; Mizubayashi, Wataru; Masahara, Meishoku; Yasuda, Tetsuji; Ota, Hiroyuki

    2015-02-01

    The temperature dependence of the tunneling transport characteristics of Si diodes with an isoelectronic impurity has been investigated in order to clarify the mechanism of the ON-current enhancement in Si-based tunnel field-effect transistors (TFETs) utilizing an isoelectronic trap (IET). The Al-N complex impurity was utilized for IET formation. We observed three types of tunneling current components in the diodes: indirect band-to-band tunneling (BTBT), trap-assisted tunneling (TAT), and thermally inactive tunneling. The indirect BTBT and TAT current components can be distinguished with the plot described in this paper. The thermally inactive tunneling current probably originated from tunneling consisting of two paths: tunneling between the valence band and the IET trap and tunneling between the IET trap and the conduction band. The probability of thermally inactive tunneling with the Al-N IET state is higher than the others. Utilization of the thermally inactive tunneling current has a significant effect in enhancing the driving current of Si-based TFETs.

  4. Bioactivity of Several Herbicides on the Nanogram Level Under Different Soil Moisture Conditions.

    PubMed

    Jung, S C; Kuk, Y I; Senseman, S A; Ahn, H G; Seong, C N; Lee, D J

    2015-01-01

    In this study, a double-tube centrifuge method was employed to determine the effects of soil moisture on the bioactivity of cafenstrole, pretilachlor, benfuresate, oxyfluorfen and simetryn. In general, the available herbicide concentration in soil solution (ACSS) showed little change as soil moisture increased for herbicides. The total available herbicide in soil solution (TASS) typically increased as soil moisture increased for all herbicides. The relationship between TASS and % growth rate based on dry weight showed strong linear relationships for both cafenstrole and pretilachlor, with r2 values of 0.95 and 0.84, respectively. Increasing TASS values were consistent with increasing herbicide water solubility, with the exception of the ionizable herbicide simetryn. Plant absorption and % growth rate exhibited a strong linear relationship with TASS. According to the results suggested that TASS was a better predictor of herbicidal bioactivity than ACSS for all herbicides under unsaturated soil moisture conditions.

  5. Cubital Tunnel Syndrome

    MedlinePlus

    ... Tunnel Syndrome Find a hand surgeon near you. Videos Cubital Tunnel Syndrome Close Popup Figures Figure 1 - ... or "in." Also, avoid using media types like "video," "article," and "picture." Tip 4: Your results can ...

  6. The aeolian wind tunnel

    NASA Technical Reports Server (NTRS)

    Iversen, J. D.

    1991-01-01

    The aeolian wind tunnel is a special case of a larger subset of the wind tunnel family which is designed to simulate the atmospheric surface layer winds to small scale (a member of this larger subset is usually called an atmospheric boundary layer wind tunnel or environmental wind tunnel). The atmospheric boundary layer wind tunnel is designed to simulate, as closely as possible, the mean velocity and turbulence that occur naturally in the atmospheric boundary layer (defined as the lowest portion of the atmosphere, of the order of 500 m, in which the winds are most greatly affected by surface roughness and topography). The aeolian wind tunnel is used for two purposes: to simulate the physics of the saltation process and to model at small scale the erosional and depositional processes associated with topographic surface features. For purposes of studying aeolian effects on the surface of Mars and Venus as well as on Earth, the aeolian wind tunnel continues to prove to be a useful tool for estimating wind speeds necessary to move small particles on the three planets as well as to determine the effects of topography on the evolution of aeolian features such as wind streaks and dune patterns.

  7. Heavy-Atom Tunneling Calculations in Thirteen Organic Reactions: Tunneling Contributions are Substantial, and Bell's Formula Closely Approximates Multidimensional Tunneling at ≥250 K.

    PubMed

    Doubleday, Charles; Armas, Randy; Walker, Dana; Cosgriff, Christopher V; Greer, Edyta M

    2017-10-09

    Multidimensional tunneling calculations are carried out for 13 reactions, to test the scope of heavy-atom tunneling in organic chemistry, and to check the accuracy of one-dimensional tunneling models. The reactions include pericyclic, cycloaromatization, radical cyclization and ring opening, and S N 2. When compared at the temperatures that give the same effective rate constant of 3×10 -5  s -1 , tunneling accounts for 25-95 % of the rate in 8 of the 13 reactions. Values of transmission coefficients predicted by Bell's formula, κ Bell  , agree well with multidimensional tunneling (canonical variational transition state theory with small curvature tunneling), κ SCT . Mean unsigned deviations of κ Bell vs. κ SCT are 0.08, 0.04, 0.02 at 250, 300 and 400 K. This suggests that κ Bell is a useful first choice for predicting transmission coefficients in heavy-atom tunnelling. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. TOPICAL REVIEW: Spin-dependent tunnelling in magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Tsymbal, Evgeny Y.; Mryasov, Oleg N.; LeClair, Patrick R.

    2003-02-01

    The phenomenon of electron tunnelling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunnelling (SDT) in magnetic tunnel junctions (MTJs) has recently aroused enormous interest and has developed in a vigorous field of research. The large tunnelling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible applications in non-volatile random-access memories and next-generation magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of SDT. In this review article we present an overview of this field of research. We discuss various factors that control the spin polarization and magnetoresistance in MTJs. Starting from early experiments on SDT and their interpretation, we consider thereafter recent experiments and models which highlight the role of the electronic structure of the ferromagnets, the insulating layer, and the ferromagnet/insulator interfaces. We also discuss the role of disorder in the barrier and in the ferromagnetic electrodes and their influence on TMR.

  9. Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope.

    PubMed

    Nazin, G V; Wu, S W; Ho, W

    2005-06-21

    The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends.

  10. View of entrance tunnel outside Portal elevator. Tunnel ahead to ...

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

    View of entrance tunnel outside Portal elevator. Tunnel ahead to Control Center, right to Launchers, left to Antenna Silos - Titan One Missile Complex 2A, .3 miles west of 129 Road and 1.5 miles north of County Line Road, Aurora, Adams County, CO

  11. Vacuum phonon tunneling.

    PubMed

    Altfeder, Igor; Voevodin, Andrey A; Roy, Ajit K

    2010-10-15

    Field-induced phonon tunneling, a previously unknown mechanism of interfacial thermal transport, has been revealed by ultrahigh vacuum inelastic scanning tunneling microscopy (STM). Using thermally broadened Fermi-Dirac distribution in the STM tip as in situ atomic-scale thermometer we found that thermal vibrations of the last tip atom are effectively transmitted to sample surface despite few angstroms wide vacuum gap. We show that phonon tunneling is driven by interfacial electric field and thermally vibrating image charges, and its rate is enhanced by surface electron-phonon interaction.

  12. New Tunneling Features in Polar III-Nitride Resonant Tunneling Diodes

    NASA Astrophysics Data System (ADS)

    Encomendero, Jimy; Faria, Faiza Afroz; Islam, S. M.; Protasenko, Vladimir; Rouvimov, Sergei; Sensale-Rodriguez, Berardi; Fay, Patrick; Jena, Debdeep; Xing, Huili Grace

    2017-10-01

    For the past two decades, repeatable resonant tunneling transport of electrons in III-nitride double barrier heterostructures has remained elusive at room temperature. In this work we theoretically and experimentally study III-nitride double-barrier resonant tunneling diodes (RTDs), the quantum transport characteristics of which exhibit new features that are unexplainable using existing semiconductor theory. The repeatable and robust resonant transport in our devices enables us to track the origin of these features to the broken inversion symmetry in the uniaxial crystal structure, which generates built-in spontaneous and piezoelectric polarization fields. Resonant tunneling transport enabled by the ground state as well as by the first excited state is demonstrated for the first time over a wide temperature window in planar III-nitride RTDs. An analytical transport model for polar resonant tunneling heterostructures is introduced for the first time, showing a good quantitative agreement with experimental data. From this model we realize that tunneling transport is an extremely sensitive measure of the built-in polarization fields. Since such electric fields play a crucial role in the design of electronic and photonic devices, but are difficult to measure, our work provides a completely new method to accurately determine their magnitude for the entire class of polar heterostructures.

  13. PREFACE: Time-resolved scanning tunnelling microscopy Time-resolved scanning tunnelling microscopy

    NASA Astrophysics Data System (ADS)

    Zandvliet, Harold J. W.; Lin, Nian

    2010-07-01

    Scanning tunnelling microscopy has revolutionized our ability to image, manipulate, and investigate solid surfaces on the length scale of individual atoms and molecules. The strength of this technique lies in its imaging capabilities, since for many scientists 'seeing is believing'. However, scanning tunnelling microscopy also suffers from a severe limitation, namely its poor time resolution. Recording a scanning tunnelling microscopy image typically requires a few tens of seconds for a conventional scanning tunnelling microscope to a fraction of a second for a specially designed fast scanning tunnelling microscope. Designing and building such a fast scanning tunnelling microscope is a formidable task in itself and therefore, only a limited number of these microscopes have been built [1]. There is, however, another alternative route to significantly enhance the time resolution of a scanning tunnelling microscope. In this alternative method, the tunnelling current is measured as a function of time with the feedback loop switched off. The time resolution is determined by the bandwidth of the IV converter rather than the cut-off frequency of the feedback electronics. Such an approach requires a stable microscope and goes, of course, at the expense of spatial information. In this issue, we have collected a set of papers that gives an impression of the current status of this rapidly emerging field [2]. One of the very first attempts to extract information from tunnel current fluctuations was reported by Tringides' group in the mid-1990s [3]. They showed that the collective diffusion coefficient can be extracted from the autocorrelation of the time-dependent tunnelling current fluctuations produced by atom motion in and out of the tunnelling junction. In general, current-time traces provide direct information on switching/conformation rates and distributions of residence times. In the case where these processes are thermally induced it is rather straightforward to map

  14. Interband Lateral Resonant Tunneling Transistor.

    DTIC Science & Technology

    1994-11-14

    INTERBAND LATERAL RESONANT TUNNELING TRANSISTOR 10 BACKGROUND OF THE INVENTION Field of the Invention This invention pertains to a tunneling transistor...and in 15 particular to an interband lateral resonant tunneling transistor. Description of Related Art Conventional semiconductor technologies are... interband lateral resonant tunneling transistor along the cross-section B-B of Figure 2c. Figure 4 is another preferred embodiment cross-sectional 20

  15. Where tunneling equipment is heading

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Singhal, R.K.

    1984-02-01

    A variety of equipment is being used for roadheading and tunneling in the mining industry. This includes hydraulic/rotary precussive drills for use in conventional drill and blast, drum-type continuous miners, roadheaders, mini-and midi-full facers for small size openings, soft rock shielded tunnel boring machines, and hard rock tunnel boring machines. The availability, performance, and specifications for tunneling equipment are discussed.

  16. Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

    PubMed Central

    Nazin, G. V.; Wu, S. W.; Ho, W.

    2005-01-01

    The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends. PMID:15956189

  17. Tunnel operations study.

    DOT National Transportation Integrated Search

    2013-12-01

    In June 2000, the State of Alaska Department of Transportation and Public Facilities completed construction of the Whittier Access Project by converting the existing 2.5- : mile Whittier Tunnel into the worlds only dual-use highway/rail tunnel wit...

  18. TDRSS Augmentation System for Satellites

    NASA Technical Reports Server (NTRS)

    Heckler, Gregory W.; Gramling, Cheryl; Valdez, Jennifer; Baldwin, Philip

    2016-01-01

    In 2015, NASA Goddard Space Flight Center (GSFC) reinvigorated the development of the TDRSS Augmentation Service for Satellites (TASS). TASS is a global, space-based, communications and navigation service for users of Global Navigation Satellite Systems(GNSS) and the Tracking and Data Relay Satellite System (TDRSS). TASS leverages the existing TDRSS to provide an S-band beacon radio navigation and messaging source to users at orbital altitudes 1400 km and below.

  19. Green Tunnel Construction Technology and Application

    NASA Astrophysics Data System (ADS)

    Zhang, J. L.; Shi, P. X.; Huang, J.; Li, H. G.; Zhou, X. Q.

    2018-05-01

    With the dramatic growth of urban tunnels in recent years, energy saving and environmental protection have received intensive attention in tunnel construction and operation. As reference to the concept of green buildings, this paper proposes the concept of green tunnels. Combining with the key issues of tunnel design, construction, operation and maintenance, the major aspects of green tunnels including prefabricated construction, noise control, ventilation & lighting energy saving, and digital intelligent maintenance are discussed and the future development of green tunnels is outlined with the economic and social benefits as indicators.

  20. Toxic anterior segment syndrome outbreak after vitrectomy and silicone oil injection.

    PubMed

    Moisseiev, Elad; Barak, Adiel

    2012-01-01

    To report a rare outbreak of toxic anterior segment syndrome (TASS) in 4 patients who underwent vitrectomy with silicone oil injection. Review of the medical charts of all patients who underwent surgery in the operating theater of our department during a 10-day period in May 2011. We report on 4 patients who developed TASS after vitrectomy with silicone oil injection. The clinical presentation was typical of TASS, and different from the anterior chamber reaction that may occur after silicone oil injection. All cases were treated effectively with topical steroids, and the outbreak stopped after the silicone oil batch was exchanged. We discuss the possible mechanisms for this unusual TASS outbreak, and suggest the silicone oil as its cause.

  1. Techniques For Mass Production Of Tunneling Electrodes

    NASA Technical Reports Server (NTRS)

    Kenny, Thomas W.; Podosek, Judith A.; Reynolds, Joseph K.; Rockstad, Howard K.; Vote, Erika C.; Kaiser, William J.

    1993-01-01

    Techniques for mass production of tunneling electrodes developed from silicon-micromachining, lithographic patterning, and related microfabrication processes. Tunneling electrodes named because electrons travel between them by quantum-mechanical tunneling; tunneling electrodes integral parts of tunneling transducer/sensors, which act in conjunction with feedback circuitry to stabilize tunneling currents by maintaining electrode separations of order of 10 Angstrom. Essential parts of scanning tunneling microscopes and related instruments, and used as force and position transducers in novel microscopic accelerometers and infrared detectors.

  2. Magnetic Fluxtube Tunneling

    NASA Technical Reports Server (NTRS)

    Dahlburg, Russell B.; Antiochos,, Spiro K.; Norton, D.

    1996-01-01

    We present numerical simulations of the collision and subsequent interaction of two initially orthogonal, twisted, force free field magnetic fluxtubes. The simulations were carried out using a new three dimensional explicit parallelized Fourier collocation algorithm for solving the viscoresistive equations of compressible magnetohydrodynamics. It is found that, under a wide range of conditions, the fluxtubes can 'tunnel' through each other. Two key conditions must be satisfied for tunneling to occur: the magnetic field must be highly twisted with a field line pitch much greater than 1, and the magnetic Lundquist number must be somewhat large, greater than or equal to 2880. This tunneling behavior has not been seen previously in studies of either vortex tube or magnetic fluxtube interactions. An examination of magnetic field lines shows that tunneling is due to a double reconnection mechanism. Initially orthogonal field lines reconnect at two specific locations, exchange interacting sections and 'pass' through each other. The implications of these results for solar and space plasmas are discussed.

  3. Orbital-resolved nonadiabatic tunneling ionization

    NASA Astrophysics Data System (ADS)

    Zhang, Qingbin; Basnayake, Gihan; Winney, Alexander; Lin, Yun Fei; Debrah, Duke; Lee, Suk Kyoung; Li, Wen

    2017-08-01

    In this theoretical work, we show that both the orbital helicity (p+ vs p-) and the adiabaticity of tunneling have a significant effect on the initial conditions of tunneling ionization. We developed a hybrid quantum (numerical solution of the time-dependent Schrödinger equation) and classical (back propagation of trajectories) approach to extract orbital-specific initial conditions of electrons at the tunneling exit. Clear physical insight connecting these initial conditions with the final momentum and deflection angles of electrons are presented. Moreover, the adiabaticity of tunneling ionization is characterized by comparing the initial conditions with those with a static field. Significant nonadiabatic tunneling is found to persist beyond a Keldysh parameter of less than 0.5.

  4. Within-Tunnel Variations in Pressure Data for Three Transonic Wind Tunnels

    NASA Technical Reports Server (NTRS)

    DeLoach, Richard

    2014-01-01

    This paper compares the results of pressure measurements made on the same test article with the same test matrix in three transonic wind tunnels. A comparison is presented of the unexplained variance associated with polar replicates acquired in each tunnel. The impact of a significance component of systematic (not random) unexplained variance is reviewed, and the results of analyses of variance are presented to assess the degree of significant systematic error in these representative wind tunnel tests. Total uncertainty estimates are reported for 140 samples of pressure data, quantifying the effects of within-polar random errors and between-polar systematic bias errors.

  5. Atomistic modeling trap-assisted tunneling in hole tunnel field effect transistors

    NASA Astrophysics Data System (ADS)

    Long, Pengyu; Huang, Jun Z.; Povolotskyi, Michael; Sarangapani, Prasad; Valencia-Zapata, Gustavo A.; Kubis, Tillmann; Rodwell, Mark J. W.; Klimeck, Gerhard

    2018-05-01

    Tunnel Field Effect Transistors (FETs) have the potential to achieve steep Subthreshold Swing (S.S.) below 60 mV/dec, but their S.S. could be limited by trap-assisted tunneling (TAT) due to interface traps. In this paper, the effect of trap energy and location on OFF-current (IOFF) of tunnel FETs is evaluated systematically using an atomistic trap level representation in a full quantum transport simulation. Trap energy levels close to band edges cause the highest leakage. Wave function penetration into the surrounding oxide increases the TAT current. To estimate the effects of multiple traps, we assume that the traps themselves do not interact with each other and as a whole do not modify the electrostatic potential dramatically. Within that model limitation, this numerical metrology study points to the critical importance of TAT in the IOFF in tunnel FETs. The model shows that for Dit higher than 1012/(cm2 eV) IO F F is critically increased with a degraded IO N/IO F F ratio of the tunnel FET. In order to have an IO N/IO F F ratio higher than 104, the acceptable Dit near Ev should be controlled to no larger than 1012/(cm2 eV) .

  6. The S-Tunnel for tunnelled dialysis catheter: an alternative approach to the prevention of displacement.

    PubMed

    Jenkins, Glyndwr W; Kelly, Michael; Anwar, Siddiq; Ahmed, Saeed S

    2015-01-01

    Vascular access has been described in the literature anywhere from the 'Achilles Heel' to the 'Cornerstone' of haemodialysis. Displacement of a central venous catheter is not an uncommon occurrence. We discuss an alternative method of placement for the tunnelled central venous catheter to prevent displacement in those patients with excess anterior chest wall soft tissue. A new surgical technique for placement of a tunnelled central venous catheter was developed in an attempt to reduce the number of displacements. This involved the creation of a second tunnel at a 90° angle to the original retrograde tunnelled path. The authors have currently placed five 'S-Line' tunnelled central venous catheters with no reports of displacement or line infection over a period of 18 months. The 'S-Line' offers a simple, straightforward and most importantly safe method to reduce the incidence of tunnelled right internal jugular central venous catheter displacement.

  7. Validation of a Compact Isokinetic Total Water Content Probe for Wind Tunnel Characterization at NASA Glenn Icing Research Tunnel and at NRC Ice Crystal Tunnel

    NASA Technical Reports Server (NTRS)

    Davison, Craig R.; Landreville, Charles; Ratvasky, Thomas P.

    2017-01-01

    A new compact isokinetic probe to measure total water content in a wind tunnel environment has been developed. The probe has been previously tested under altitude conditions. This paper presents a comprehensive validation of the probe under a range of liquid water conditions at sea level in the NASA Glenn Icing Research Tunnel and with ice crystals at sea level at the NRC wind tunnel. The compact isokinetic probe is compared to tunnel calibrations and other probes.

  8. Submucosal tunneling techniques: current perspectives.

    PubMed

    Kobara, Hideki; Mori, Hirohito; Rafiq, Kazi; Fujihara, Shintaro; Nishiyama, Noriko; Ayaki, Maki; Yachida, Tatsuo; Matsunaga, Tae; Tani, Johji; Miyoshi, Hisaaki; Yoneyama, Hirohito; Morishita, Asahiro; Oryu, Makoto; Iwama, Hisakazu; Masaki, Tsutomu

    2014-01-01

    Advances in endoscopic submucosal dissection include a submucosal tunneling technique, involving the introduction of tunnels into the submucosa. These tunnels permit safer offset entry into the peritoneal cavity for natural orifice transluminal endoscopic surgery. Technical advantages include the visual identification of the layers of the gut, blood vessels, and subepithelial tumors. The creation of a mucosal flap that minimizes air and fluid leakage into the extraluminal cavity can enhance the safety and efficacy of surgery. This submucosal tunneling technique was adapted for esophageal myotomy, culminating in its application to patients with achalasia. This method, known as per oral endoscopic myotomy, has opened up the new discipline of submucosal endoscopic surgery. Other clinical applications of the submucosal tunneling technique include its use in the removal of gastrointestinal subepithelial tumors and endomicroscopy for the diagnosis of functional and motility disorders. This review suggests that the submucosal tunneling technique, involving a mucosal safety flap, can have potential values for future endoscopic developments.

  9. The comparison between limited open carpal tunnel release using direct vision and tunneling technique and standard open carpal tunnel release: a randomized controlled trial study.

    PubMed

    Suppaphol, Sorasak; Worathanarat, Patarawan; Kawinwongkovit, Viroj; Pittayawutwinit, Preecha

    2012-04-01

    To compare the operative outcome of carpal tunnel release between limited open carpal tunnel release using direct vision and tunneling technique (group A) with standard open carpal tunnel release (group B). Twenty-eight patients were enrolled in the present study. A single blind randomized control trial study was conducted to compare the postoperative results between group A and B. The study parameters were Levine's symptom severity and functional score, grip and pinch strength, and average two-point discrimination. The postoperative results between two groups were comparable with no statistical significance. Only grip strength at three months follow up was significantly greater in group A than in group B. The limited open carpal tunnel release in the present study is effective comparable to the standard open carpal tunnel release. The others advantage of this technique are better cosmesis and improvement in grip strength at the three months postoperative period.

  10. An analysis of combustion studies in shock expansion tunnels and reflected shock tunnels

    NASA Technical Reports Server (NTRS)

    Jachimowski, Casimir J.

    1992-01-01

    The effect of initial nonequilibrium dissociated air constituents on the combustion of hydrogen in high-speed flows for a simulated Mach 17 flight condition was investigated by analyzing the results of comparative combustion experiments performed in a reflected shock tunnel test gas and in a shock expansion tunnel test gas. The results were analyzed and interpreted with a one-dimensional quasi-three-stream combustor code that includes finite rate combustion chemistry. The results of this study indicate that the combustion process is kinetically controlled in the experiments in both tunnels and the presence of the nonequilibrium partially dissociated oxygen in the reflected shock tunnel enhances the combustion. Methods of compensating for the effect of dissociated oxygen are discussed.

  11. Does flexible tunnel drilling affect the femoral tunnel angle measurement after anterior cruciate ligament reconstruction?

    PubMed

    Muller, Bart; Hofbauer, Marcus; Atte, Akere; van Dijk, C Niek; Fu, Freddie H

    2015-12-01

    To quantify the mean difference in femoral tunnel angle (FTA) as measured on knee radiographs between rigid and flexible tunnel drilling after anatomic anterior cruciate ligament (ACL) reconstruction. Fifty consecutive patients that underwent primary anatomic ACL reconstruction with a single femoral tunnel drilled with a flexible reamer were included in this study. The control group was comprised of 50 patients all of who underwent primary anatomic ACL reconstruction with a single femoral tunnel drilled with a rigid reamer. All femoral tunnels were drilled through a medial portal to ensure anatomic tunnel placement. The FTA was determined from post-operative anterior-to-posterior (AP) radiographs by two independent observers. A 5° difference between the two mean FTA was considered clinically significant. The average FTA, when drilled with a rigid reamer, was 42.0° ± 7.2°. Drilling with a flexible reamer resulted in a mean FTA of 44.7° ± 7.0°. The mean difference of 2.7° was not statistically significant. The intraclass correlation coefficient for inter-tester reliability was 0.895. The FTA can be reliably determined from post-operative AP radiographs and provides a useful and reproducible metric for characterizing femoral tunnel position after both rigid and flexible femoral tunnel drilling. This has implications for post-operative evaluation and preoperative treatment planning for ACL revision surgery. IV.

  12. Charge Islands Through Tunneling

    NASA Technical Reports Server (NTRS)

    Robinson, Daryl C.

    2002-01-01

    It has been recently reported that the electrical charge in a semiconductive carbon nanotube is not evenly distributed, but rather it is divided into charge "islands." This paper links the aforementioned phenomenon to tunneling and provides further insight into the higher rate of tunneling processes, which makes tunneling devices attractive. This paper also provides a basis for calculating the charge profile over the length of the tube so that nanoscale devices' conductive properties may be fully exploited.

  13. Wind tunnel

    NASA Technical Reports Server (NTRS)

    Wilson, E. M. (Inventor)

    1969-01-01

    A supersonic wind wind tunnel is described for testing several air foils mounted in a row. A test section of a wind tunnel contains means for mounting air foil sections in a row, means for rotating each section about an axis so that the angle of attack of each section changes with the other sections, and means for rotating the row with respect to the air stream so that the row forms an oblique angle with the air stream.

  14. Wideband Feedback Circuit For Tunneling Sensor

    NASA Technical Reports Server (NTRS)

    Kaiser, William J.; Kenny, Thomas W.; Rockstad, Howard K.; Reynolds, Joseph K.

    1994-01-01

    Improved feedback circuit designed for use in controlling tunneling displacement transducer. Features include stability and nearly flat frequency response up to 50 kHz. Transducer could be that in scanning tunneling microscope, or any of micromachined electromechanical transducers described in "Micromachined Electron-Tunneling Infrared Detectors" (NPO-18413), "Micromachined Tunneling Accelerometer" (NPO-18513), and "Improved Electromechanical Infrared Sensor" (NPO-18560).

  15. Carpal tunnel and median nerve volume changes after tunnel release in patients with the carpal tunnel syndrome: a magnetic resonance imaging (MRI) study.

    PubMed

    Crnković, T; Trkulja, V; Bilić, R; Gašpar, D; Kolundžić, R

    2016-05-01

    Our aim was to study the dynamics of the post-surgical canal and nerve volumes and their relationships to objective [electromyoneurography (EMNG)] and subjective (pain) outcomes. Forty-seven patients with carpal tunnel syndrome (CTS) (median age 52, range 23-75 years) with a prominent narrowing of the median nerve within the canal (observed during carpal tunnel release) were evaluated clinically using EMNG and magnetic resonance imagining (MRI) before and at 90 and 180 days post-surgery. Canal and nerve volumes increased, EMNG findings improved and pain resolved during the follow-up. Increase in tunnel volume was independently associated with increased nerve volume. A greater post-surgical nerve volume was independently associated with a more prominent resolution of pain, but not with the extent of EMNG improvement, whereas EMNG improvement was not associated with pain resolution. Data confirm that MRI can detect even modest changes in the carpal tunnel and median nerve volume and that tunnel release results in tunnel and nerve-volume increases that are paralleled by EMNG and clinical improvements. Taken together, these observations suggest that MRI could be used to objectivise persistent post-surgical difficulties in CTS patients. Level of evidence 3 (follow-up study).

  16. Klein tunneling phenomenon with pair creation process

    NASA Astrophysics Data System (ADS)

    Wu, G. Z.; Zhou, C. T.; Fu, L. B.

    2018-01-01

    In this paper, we study the Klein tunneling phenomenon with electron-positron pair creation process. Pairs can be created from the vacuum by a supercritical single-well potential (for electrons). In the time region, the time-dependent growth pattern of the created pairs can be characterized by four distinct regimes which can be considered as four different statuses of the single well. We find that if positrons penetrate the single well by Klein tunneling in different statuses, the total number of the tunneling positrons will be different. If Klein tunneling begins at the initial stage of the first status i.e. when the sing well is empty, the tunneling process and the total number of tunneling positrons are similar to the traditional Klein tunneling case without considering the pair creation process. As the tunneling begins later, the total tunneling positron number increases. The number will finally settle to an asymptotic value when the tunneling begins later than the settling-down time t s of the single well which has been defined in this paper.

  17. Giant tunnelling electroresistance in metal/ferroelectric/semiconductor tunnel junctions by engineering the Schottky barrier

    NASA Astrophysics Data System (ADS)

    Xi, Zhongnan; Ruan, Jieji; Li, Chen; Zheng, Chunyan; Wen, Zheng; Dai, Jiyan; Li, Aidong; Wu, Di

    2017-05-01

    Recently, ferroelectric tunnel junctions have attracted much attention due to their potential applications in non-destructive readout non-volatile memories. Using a semiconductor electrode has been proven effective to enhance the tunnelling electroresistance in ferroelectric tunnel junctions. Here we report a systematic investigation on electroresistance of Pt/BaTiO3/Nb:SrTiO3 metal/ferroelectric/semiconductor tunnel junctions by engineering the Schottky barrier on Nb:SrTiO3 surface via varying BaTiO3 thickness and Nb doping concentration. The optimum ON/OFF ratio as great as 6.0 × 106, comparable to that of commercial Flash memories, is achieved in a device with 0.1 wt% Nb concentration and a 4-unit-cell-thick BaTiO3 barrier. With this thinnest BaTiO3 barrier, which shows a negligible resistance to the tunnelling current but is still ferroelectric, the device is reduced to a polarization-modulated metal/semiconductor Schottky junction that exhibits a more efficient control on the tunnelling resistance to produce the giant electroresistance observed. These results may facilitate the design of high performance non-volatile resistive memories.

  18. Giant tunnelling electroresistance in metal/ferroelectric/semiconductor tunnel junctions by engineering the Schottky barrier

    PubMed Central

    Xi, Zhongnan; Ruan, Jieji; Li, Chen; Zheng, Chunyan; Wen, Zheng; Dai, Jiyan; Li, Aidong; Wu, Di

    2017-01-01

    Recently, ferroelectric tunnel junctions have attracted much attention due to their potential applications in non-destructive readout non-volatile memories. Using a semiconductor electrode has been proven effective to enhance the tunnelling electroresistance in ferroelectric tunnel junctions. Here we report a systematic investigation on electroresistance of Pt/BaTiO3/Nb:SrTiO3 metal/ferroelectric/semiconductor tunnel junctions by engineering the Schottky barrier on Nb:SrTiO3 surface via varying BaTiO3 thickness and Nb doping concentration. The optimum ON/OFF ratio as great as 6.0 × 106, comparable to that of commercial Flash memories, is achieved in a device with 0.1 wt% Nb concentration and a 4-unit-cell-thick BaTiO3 barrier. With this thinnest BaTiO3 barrier, which shows a negligible resistance to the tunnelling current but is still ferroelectric, the device is reduced to a polarization-modulated metal/semiconductor Schottky junction that exhibits a more efficient control on the tunnelling resistance to produce the giant electroresistance observed. These results may facilitate the design of high performance non-volatile resistive memories. PMID:28513590

  19. Resonant torus-assisted tunneling.

    PubMed

    Yi, Chang-Hwan; Yu, Hyeon-Hye; Kim, Chil-Min

    2016-01-01

    We report a new type of dynamical tunneling, which is mediated by a resonant torus, i.e., a nonisolated periodic orbit. To elucidate the phenomenon, we take an open elliptic cavity and show that a pair of resonances localized on two classically disconnected tori tunnel through a resonant torus when they interact with each other. This so-called resonant torus-assisted tunneling is verified by using Husimi functions, corresponding actions, Husimi function distributions, and the standard deviations of the actions.

  20. Distributions of tunnel splittings in quantum tunneling of magnetization in the single-molecule magnet, manganese12-acetate

    NASA Astrophysics Data System (ADS)

    Mertes, Kevin Mathias

    I present the results of an experimental investigation of quantum tunneling of magnetization in the single molecule magnet, Mn12-acetate, for magnetic fields applied along the easy c-axis of the crystal. Magnetization measurements for temperatures below 2 Kelvin reveal new properties of the nature of tunneling in Mn12-acetate: an abrupt cross-over from thermally-assisted tunneling to pure ground state tunneling, strong suppression of ground state tunneling for temperatures corresponding to the thermally activated regime and the unexpected dependence of the tunnel splitting determined from the Landau-Zener-Stueckelberg formalism on the magnetic field sweep rate. It is shown that the measured data is inconsistent with a system of identical molecules. The data is shown to be consistent with the presence of a broad log-normal distribution of second order transverse anisotropy which drives the tunneling process. A general method of determining the distribution is developed.

  1. Submucosal Tunneling Endoscopic Resection (STER) and Other Novel Applications of Submucosal Tunneling in Humans.

    PubMed

    Liu, Bing-Rong; Song, Ji-Tao

    2016-04-01

    The submucosal tunneling technique was originally developed to provide safe access to the peritoneal cavity for natural orifice transluminal endoscopic surgery procedures. With this technique, the submucosal tunnel becomes the working space for partial myotomy and tumor resection. The submucosal space has come to represent the "third space" distinguished from gastrointestinal lumen (first space) and peritoneal cavity (second space). New applications continue to be developed and further clinical applications in the future are anticipated. This article summarizes the current applications of submucosal tunneling endoscopic resection for subepithelial tumors and describes other related uses of submucosal tunneling. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Effect of Blast-Induced Vibration from New Railway Tunnel on Existing Adjacent Railway Tunnel in Xinjiang, China

    NASA Astrophysics Data System (ADS)

    Liang, Qingguo; Li, Jie; Li, Dewu; Ou, Erfeng

    2013-01-01

    The vibrations of existing service tunnels induced by blast-excavation of adjacent tunnels have attracted much attention from both academics and engineers during recent decades in China. The blasting vibration velocity (BVV) is the most widely used controlling index for in situ monitoring and safety assessment of existing lining structures. Although numerous in situ tests and simulations had been carried out to investigate blast-induced vibrations of existing tunnels due to excavation of new tunnels (mostly by bench excavation method), research on the overall dynamical response of existing service tunnels in terms of not only BVV but also stress/strain seemed limited for new tunnels excavated by the full-section blasting method. In this paper, the impacts of blast-induced vibrations from a new tunnel on an existing railway tunnel in Xinjiang, China were comprehensively investigated by using laboratory tests, in situ monitoring and numerical simulations. The measured data from laboratory tests and in situ monitoring were used to determine the parameters needed for numerical simulations, and were compared with the calculated results. Based on the results from in situ monitoring and numerical simulations, which were consistent with each other, the original blasting design and corresponding parameters were adjusted to reduce the maximum BVV, which proved to be effective and safe. The effect of both the static stress before blasting vibrations and the dynamic stress induced by blasting on the total stresses in the existing tunnel lining is also discussed. The methods and related results presented could be applied in projects with similar ground and distance between old and new tunnels if the new tunnel is to be excavated by the full-section blasting method.

  3. Electrically tunable tunneling rectification magnetoresistance in magnetic tunneling junctions with asymmetric barriers.

    PubMed

    Wang, Jing; Huang, Qikun; Shi, Peng; Zhang, Kun; Tian, Yufeng; Yan, Shishen; Chen, Yanxue; Liu, Guolei; Kang, Shishou; Mei, Liangmo

    2017-10-26

    The development of multifunctional spintronic devices requires simultaneous control of multiple degrees of freedom of electrons, such as charge, spin and orbit, and especially a new physical functionality can be realized by combining two or more different physical mechanisms in one specific device. Here, we report the realization of novel tunneling rectification magnetoresistance (TRMR), where the charge-related rectification and spin-dependent tunneling magnetoresistance are integrated in Co/CoO-ZnO/Co magnetic tunneling junctions with asymmetric tunneling barriers. Moreover, by simultaneously applying direct current and alternating current to the devices, the TRMR has been remarkably tuned in the range from -300% to 2200% at low temperature. This proof-of-concept investigation provides an unexplored avenue towards electrical and magnetic control of charge and spin, which may apply to other heterojunctions to give rise to more fascinating emergent functionalities for future spintronics applications.

  4. Scanning tunneling microscope nanoetching method

    DOEpatents

    Li, Yun-Zhong; Reifenberger, Ronald G.; Andres, Ronald P.

    1990-01-01

    A method is described for forming uniform nanometer sized depressions on the surface of a conducting substrate. A tunneling tip is used to apply tunneling current density sufficient to vaporize a localized area of the substrate surface. The resulting depressions or craters in the substrate surface can be formed in information encoding patterns readable with a scanning tunneling microscope.

  5. Electromagnetics for Detecting Shallow Tunnels

    NASA Astrophysics Data System (ADS)

    Won, I.

    2006-05-01

    Detecting tunnels by geophysical means, even very shallow ones, has been difficult, to say the least. Despite heavy R&D funding from the military since the early 70s, geophysicists have not produced tools that are simple and practical enough to meet the military needs. The initial interest and R&D funding on the subject perhaps started with the Vietcong tunnels in the 60s. Tunnels in the Korean DMZ, first found in the mid 70s, sharply escalated the R&D spending. During the 90s, covert tunnels along the US-Mexico border have kept the topic alive but at a minimal funding level. Most recent interest appears to be in the terrorism-related shallow tunnels, more or less anywhere in the regions of conflict. Despite the longstanding effort in the geophysical community under heavy public funding, there is a dearth of success stories where geophysicists can actually claim to have found hitherto unknown tunnels. For instance, geophysics has not discovered a single tunnel in Vietnam or in Korea! All tunnels across the Korean DMZ were found from human intelligence. The same is true to all illicit tunnels found along the southwestern border. The tunnels under discussion are clandestine, which implies that the people who built them do not wish others to succeed in finding them. The place around the tunnel, therefore, may not be the friendliest venue for surveyors to linger around. The situation requires tools that are fast, little noticeable, and hardly intrusive. Many geophysical sensors that require ground contacts, such as geophones and electrodes that are connected by a myriad of cables, may not be ideal in this situation. On the other hand, a sensor that can be carried by vehicle without stopping, and is nothing obviously noticeable to bystanders, could be much more acceptable. Working at unfriendly environment also requires forgoing our usual practices where we collect data leisurely and make pretty maps later. To be useful, geophysical tools must be able to process

  6. Quantum temporal probabilities in tunneling systems

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Anastopoulos, Charis, E-mail: anastop@physics.upatras.gr; Savvidou, Ntina, E-mail: ksavvidou@physics.upatras.gr

    We study the temporal aspects of quantum tunneling as manifested in time-of-arrival experiments in which the detected particle tunnels through a potential barrier. In particular, we present a general method for constructing temporal probabilities in tunneling systems that (i) defines ‘classical’ time observables for quantum systems and (ii) applies to relativistic particles interacting through quantum fields. We show that the relevant probabilities are defined in terms of specific correlation functions of the quantum field associated with tunneling particles. We construct a probability distribution with respect to the time of particle detection that contains all information about the temporal aspects ofmore » the tunneling process. In specific cases, this probability distribution leads to the definition of a delay time that, for parity-symmetric potentials, reduces to the phase time of Bohm and Wigner. We apply our results to piecewise constant potentials, by deriving the appropriate junction conditions on the points of discontinuity. For the double square potential, in particular, we demonstrate the existence of (at least) two physically relevant time parameters, the delay time and a decay rate that describes the escape of particles trapped in the inter-barrier region. Finally, we propose a resolution to the paradox of apparent superluminal velocities for tunneling particles. We demonstrate that the idea of faster-than-light speeds in tunneling follows from an inadmissible use of classical reasoning in the description of quantum systems. -- Highlights: •Present a general methodology for deriving temporal probabilities in tunneling systems. •Treatment applies to relativistic particles interacting through quantum fields. •Derive a new expression for tunneling time. •Identify new time parameters relevant to tunneling. •Propose a resolution of the superluminality paradox in tunneling.« less

  7. Outbreak of toxic anterior segment syndrome following cataract surgery associated with impurities in autoclave steam moisture.

    PubMed

    Hellinger, Walter C; Hasan, Saiyid A; Bacalis, Laura P; Thornblom, Deborah M; Beckmann, Susan C; Blackmore, Carina; Forster, Terri S; Tirey, Jason F; Ross, Mary J; Nilson, Christian D; Mamalis, Nick; Crook, Julia E; Bendel, Rick E; Shetty, Rajesh; Stewart, Michael W; Bolling, James P; Edelhauser, Henry F

    2006-03-01

    Toxic anterior segment syndrome (TASS), a complication of cataract surgery, is a sterile inflammation of the anterior chamber of the eye. An outbreak of TASS was recognized at an outpatient surgical center and its affiliated hospital in December 2002. Medical records of patients who underwent cataract surgery during the outbreak were reviewed, and surgical team members who participated in the operations were interviewed. Potential causes of TASS were identified and eliminated. Feedwater from autoclave steam generators and steam condensates were analyzed by use of spectroscopy and ion chromatography. During the outbreak, 8 (38%) of 21 cataract operations were complicated by TASS, compared with 2 (0.07%) of 2,713 operations performed from January 1996 through November 2002. Results of an initial investigation suggested that cataract surgical equipment may have been contaminated by suboptimal equipment reprocessing or as a result of personnel changes. The frequency of TASS decreased (1 of 44 cataract operations) after reassignment of personnel and revision of equipment reprocessing procedures. Further investigation identified the presence of impurities (eg, sulfates, copper, zinc, nickel, and silica) in autoclave steam moisture, which was attributed to improper maintenance of the autoclave steam generator in the outpatient surgical center. When impurities in autoclave steam moisture were eliminated, no cases of TASS were observed after more than 1,000 cataract operations. Suboptimal reprocessing of cataract surgical equipment may evolve over time in busy, multidisciplinary surgical centers. Clinically significant contamination of surgical equipment may result from inappropriate maintenance of steam sterilization systems. Standardization of protocols for reprocessing of cataract surgical equipment may prevent outbreaks of TASS and may be of assistance during outbreak investigations.

  8. A Top Pilot Tunnel Preconditioning Method for the Prevention of Extremely Intense Rockbursts in Deep Tunnels Excavated by TBMs

    NASA Astrophysics Data System (ADS)

    Zhang, Chuanqing; Feng, Xiating; Zhou, Hui; Qiu, Shili; Wu, Wenping

    2012-05-01

    The headrace tunnels at the Jinping II Hydropower Station cross the Jinping Mountain with a maximum overburden depth of 2,525 m, where 80% of the strata along the tunnels consist of marble. A number of extremely intense rockbursts occurred during the excavation of the auxiliary tunnels and the drainage tunnel. In particular, a tunnel boring machine (TBM) was destroyed by an extremely intense rockburst in a 7.2-m-diameter drainage tunnel. Two of the four subsequent 12.4-m-diameter headrace tunnels will be excavated with larger size TBMs, where a high risk of extremely intense rockbursts exists. Herein, a top pilot tunnel preconditioning method is proposed to minimize this risk, in which a drilling and blasting method is first recommended for the top pilot tunnel excavation and support, and then the TBM excavation of the main tunnel is conducted. In order to evaluate the mechanical effectiveness of this method, numerical simulation analyses using the failure approaching index, energy release rate, and excess shear stress indices are carried out. Its construction feasibility is discussed as well. Moreover, a microseismic monitoring technique is used in the experimental tunnel section for the real-time monitoring of the microseismic activities of the rock mass in TBM excavation and for assessing the effect of the top pilot tunnel excavation in reducing the risk of rockbursts. This method is applied to two tunnel sections prone to extremely intense rockbursts and leads to a reduction in the risk of rockbursts in TBM excavation.

  9. Tunnel Detection Using Seismic Methods

    NASA Astrophysics Data System (ADS)

    Miller, R.; Park, C. B.; Xia, J.; Ivanov, J.; Steeples, D. W.; Ryden, N.; Ballard, R. F.; Llopis, J. L.; Anderson, T. S.; Moran, M. L.; Ketcham, S. A.

    2006-05-01

    Surface seismic methods have shown great promise for use in detecting clandestine tunnels in areas where unauthorized movement beneath secure boundaries have been or are a matter of concern for authorities. Unauthorized infiltration beneath national borders and into or out of secure facilities is possible at many sites by tunneling. Developments in acquisition, processing, and analysis techniques using multi-channel seismic imaging have opened the door to a vast number of near-surface applications including anomaly detection and delineation, specifically tunnels. Body waves have great potential based on modeling and very preliminary empirical studies trying to capitalize on diffracted energy. A primary limitation of all seismic energy is the natural attenuation of high-frequency energy by earth materials and the difficulty in transmitting a high- amplitude source pulse with a broad spectrum above 500 Hz into the earth. Surface waves have shown great potential since the development of multi-channel analysis methods (e.g., MASW). Both shear-wave velocity and backscatter energy from surface waves have been shown through modeling and empirical studies to have great promise in detecting the presence of anomalies, such as tunnels. Success in developing and evaluating various seismic approaches for detecting tunnels relies on investigations at known tunnel locations, in a variety of geologic settings, employing a wide range of seismic methods, and targeting a range of uniquely different tunnel geometries, characteristics, and host lithologies. Body-wave research at the Moffat tunnels in Winter Park, Colorado, provided well-defined diffraction-looking events that correlated with the subsurface location of the tunnel complex. Natural voids related to karst have been studied in Kansas, Oklahoma, Alabama, and Florida using shear-wave velocity imaging techniques based on the MASW approach. Manmade tunnels, culverts, and crawl spaces have been the target of multi-modal analysis

  10. Legal and Social Protection for Soviet Servicemen: A Reality of Mere Declaration?

    DTIC Science & Technology

    1991-04-05

    in JPRS-UMA-90-023, 15 October 1990, p. 43. 41 Oleg Moskovskiy, Newscast, TASS International Service, 24 December 1990, in FBIS-SOV-90-248, 26...in CDSP, 7 November 1990, p. 30. 67 S. Kuznetsov , "For Whom the Paratroopers Are Looking," Selskaya zhizn, 12 January 1991, p. 6, in FBIS-SOV-91-012... Oleg . Newscast. TASS International Service, 24 December 1990, in FBIS-SOV--90-248, 26 December 1990, p. 60. . Newscast. TASS, 29 January 1991, in

  11. Atomistic nature in band-to-band tunneling in two-dimensional silicon pn tunnel diodes

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tabe, Michiharu, E-mail: tabe.michiharu@shizuoka.ac.jp; Tan, Hoang Nhat; Mizuno, Takeshi

    We study low-temperature transport properties of two-dimensional (2D) Si tunnel diodes, or Si Esaki diodes, with a lateral layout. In ordinary Si Esaki diodes, interband tunneling current is severely limited because of the law of momentum conservation, while nanoscale Esaki diodes may behave differently due to the dopants in the narrow depletion region, by atomistic effects which release such current limitation. In thin-Si lateral highly doped pn diodes, we find clear signatures of interband tunneling between 2D-subbands involving phonon assistance. More importantly, the tunneling current is sharply enhanced in a narrow voltage range by resonance via a pair of amore » donor- and an acceptor-atom in the pn junction region. Such atomistic behavior is recognized as a general feature showing up only in nanoscale tunnel diodes. In particular, a donor-acceptor pair with deeper ground-state energies is likely to be responsible for such a sharply enhanced current peak, tunable by external biases.« less

  12. Long-range electron tunneling.

    PubMed

    Winkler, Jay R; Gray, Harry B

    2014-02-26

    Electrons have so little mass that in less than a second they can tunnel through potential energy barriers that are several electron-volts high and several nanometers wide. Electron tunneling is a critical functional element in a broad spectrum of applications, ranging from semiconductor diodes to the photosynthetic and respiratory charge transport chains. Prior to the 1970s, chemists generally believed that reactants had to collide in order to effect a transformation. Experimental demonstrations that electrons can transfer between reactants separated by several nanometers led to a revision of the chemical reaction paradigm. Experimental investigations of electron exchange between redox partners separated by molecular bridges have elucidated many fundamental properties of these reactions, particularly the variation of rate constants with distance. Theoretical work has provided critical insights into the superexchange mechanism of electronic coupling between distant redox centers. Kinetics measurements have shown that electrons can tunnel about 2.5 nm through proteins on biologically relevant time scales. Longer-distance biological charge flow requires multiple electron tunneling steps through chains of redox cofactors. The range of phenomena that depends on long-range electron tunneling continues to expand, providing new challenges for both theory and experiment.

  13. Quantum tunneling with friction

    NASA Astrophysics Data System (ADS)

    Tokieda, M.; Hagino, K.

    2017-05-01

    Using the phenomenological quantum friction models introduced by P. Caldirola [Nuovo Cimento 18, 393 (1941), 10.1007/BF02960144] and E. Kanai [Prog. Theor. Phys. 3, 440 (1948), 10.1143/ptp/3.4.440], M. D. Kostin [J. Chem. Phys. 57, 3589 (1972), 10.1063/1.1678812], and K. Albrecht [Phys. Lett. B 56, 127 (1975), 10.1016/0370-2693(75)90283-X], we study quantum tunneling of a one-dimensional potential in the presence of energy dissipation. To this end, we calculate the tunneling probability using a time-dependent wave-packet method. The friction reduces the tunneling probability. We show that the three models provide similar penetrabilities to each other, among which the Caldirola-Kanai model requires the least numerical effort. We also discuss the effect of energy dissipation on quantum tunneling in terms of barrier distributions.

  14. Electron-Tunneling Magnetometer

    NASA Technical Reports Server (NTRS)

    Kaiser, William J.; Kenny, Thomas W.; Waltman, Steven B.

    1993-01-01

    Electron-tunneling magnetometer is conceptual solid-state device operating at room temperature, yet offers sensitivity comparable to state-of-art magnetometers such as flux gates, search coils, and optically pumped magnetometers, with greatly reduced volume, power consumption, electronics requirements, and manufacturing cost. Micromachined from silicon wafer, and uses tunneling displacement transducer to detect magnetic forces on cantilever-supported current loop.

  15. Two-dimensional wind tunnel

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Information on the Japanese National Aerospace Laboratory two dimensional transonic wind tunnel, completed at the end of 1979 is presented. Its construction is discussed in detail, and the wind tunnel structure, operation, test results, and future plans are presented.

  16. Investigation of Corner Effect and Identification of Tunneling Regimes in L-Shaped Tunnel Field-Effect-Transistor.

    PubMed

    Najam, Faraz; Yu, Yun Seop

    2018-09-01

    Corner-effect existing in L-shaped tunnel field-effect-transistor (LTFET) was investigated using numerical simulations and band diagram analysis. It was found that the corner-effect is caused by the convergence of electric field in the sharp source corner present in an LTFET, thereby increasing the electric field in the sharp source corner region. It was found that in the corner-effect region tunneling starts early, as a function of applied bias, as compared to the rest of the channel not affected by corner-effect. Further, different tunneling regimes as a function of applied bias were identified in the LTFET including source to channel and channel to channel tunneling regimes. Presence of different tunneling regimes in LTFET was analytically justified with a set of equations developed to model source to channel, and channel to channel tunneling currents. Drain-current-gate-voltage (Ids-Vgs) characteristics obtained from the equations is in reasonable qualitative agreement with numerical simulation.

  17. Experimental Evidence for Quantum Tunneling Time

    NASA Astrophysics Data System (ADS)

    Camus, Nicolas; Yakaboylu, Enderalp; Fechner, Lutz; Klaiber, Michael; Laux, Martin; Mi, Yonghao; Hatsagortsyan, Karen Z.; Pfeifer, Thomas; Keitel, Christoph H.; Moshammer, Robert

    2017-07-01

    The first hundred attoseconds of the electron dynamics during strong field tunneling ionization are investigated. We quantify theoretically how the electron's classical trajectories in the continuum emerge from the tunneling process and test the results with those achieved in parallel from attoclock measurements. An especially high sensitivity on the tunneling barrier is accomplished here by comparing the momentum distributions of two atomic species of slightly deviating atomic potentials (argon and krypton) being ionized under absolutely identical conditions with near-infrared laser pulses (1300 nm). The agreement between experiment and theory provides clear evidence for a nonzero tunneling time delay and a nonvanishing longitudinal momentum of the electron at the "tunnel exit."

  18. Tunneling from the past horizon

    NASA Astrophysics Data System (ADS)

    Kang, Subeom; Yeom, Dong-han

    2018-04-01

    We investigate a tunneling and emission process of a thin-shell from a Schwarzschild black hole, where the shell was initially located beyond the Einstein-Rosen bridge and finally appears at the right side of the Penrose diagram. In order to obtain such a solution, we should assume that the areal radius of the black hole horizon increases after the tunneling. Hence, there is a parameter range such that the tunneling rate is exponentially enhanced, rather than suppressed. We may have two interpretations regarding this. First, such a tunneling process from the past horizon is improbable by physical reasons; second, such a tunneling is possible in principle, but in order to obtain a stable Einstein-Rosen bridge, one needs to restrict the parameter spaces. If such a process is allowed, this can be a nonperturbative contribution to Einstein-Rosen bridges as well as eternal black holes.

  19. Molecular series-tunneling junctions.

    PubMed

    Liao, Kung-Ching; Hsu, Liang-Yan; Bowers, Carleen M; Rabitz, Herschel; Whitesides, George M

    2015-05-13

    Charge transport through junctions consisting of insulating molecular units is a quantum phenomenon that cannot be described adequately by classical circuit laws. This paper explores tunneling current densities in self-assembled monolayer (SAM)-based junctions with the structure Ag(TS)/O2C-R1-R2-H//Ga2O3/EGaIn, where Ag(TS) is template-stripped silver and EGaIn is the eutectic alloy of gallium and indium; R1 and R2 refer to two classes of insulating molecular units-(CH2)n and (C6H4)m-that are connected in series and have different tunneling decay constants in the Simmons equation. These junctions can be analyzed as a form of series-tunneling junctions based on the observation that permuting the order of R1 and R2 in the junction does not alter the overall rate of charge transport. By using the Ag/O2C interface, this system decouples the highest occupied molecular orbital (HOMO, which is localized on the carboxylate group) from strong interactions with the R1 and R2 units. The differences in rates of tunneling are thus determined by the electronic structure of the groups R1 and R2; these differences are not influenced by the order of R1 and R2 in the SAM. In an electrical potential model that rationalizes this observation, R1 and R2 contribute independently to the height of the barrier. This model explicitly assumes that contributions to rates of tunneling from the Ag(TS)/O2C and H//Ga2O3 interfaces are constant across the series examined. The current density of these series-tunneling junctions can be described by J(V) = J0(V) exp(-β1d1 - β2d2), where J(V) is the current density (A/cm(2)) at applied voltage V and βi and di are the parameters describing the attenuation of the tunneling current through a rectangular tunneling barrier, with width d and a height related to the attenuation factor β.

  20. Automated Boundary Conditions for Wind Tunnel Simulations

    NASA Technical Reports Server (NTRS)

    Carlson, Jan-Renee

    2018-01-01

    Computational fluid dynamic (CFD) simulations of models tested in wind tunnels require a high level of fidelity and accuracy particularly for the purposes of CFD validation efforts. Considerable effort is required to ensure the proper characterization of both the physical geometry of the wind tunnel and recreating the correct flow conditions inside the wind tunnel. The typical trial-and-error effort used for determining the boundary condition values for a particular tunnel configuration are time and computer resource intensive. This paper describes a method for calculating and updating the back pressure boundary condition in wind tunnel simulations by using a proportional-integral-derivative controller. The controller methodology and equations are discussed, and simulations using the controller to set a tunnel Mach number in the NASA Langley 14- by 22-Foot Subsonic Tunnel are demonstrated.

  1. Horizontal Directionality of Ambient Sea Noise in the North Pacific Ocean

    DTIC Science & Technology

    1976-05-01

    Naval Undersea Center, NUC TN-988, TASS Test Bed Project Quick Look Report, TASS Self -Noise Operations, 12-16 March 1973 (U), by A. G. Fabula, April...November 1972 (C). 18. Naval Undersea Center, NUC TN-941, Quick Look Report, TASS Self -Noise Operations, 15-29 January 1973, Phase I (U), by A. G. Fabula...isolition "Modt-IS in an effort to reduce self -noisc conntaminition (!er. 1Wf. 1 5). At-ve* cxpi~rimcr~s were also ~ ,. condudctd with the NUC SPARIOMY

  2. Mars Surface Tunnel Element Concept

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A.; Jefferies, Sharon; Howe, A. Scott; Howard, Robert; Mary, Natalie; Watson, Judith; Lewis, Ruthan

    2016-01-01

    When the first human visitors on Mars prepare to return to Earth, they will have to comply with stringent planetary protection requirements. Apollo Program experience warns that opening an EVA hatch directly to the surface will bring dust into the ascent vehicle. To prevent inadvertent return of potential Martian contaminants to Earth, careful consideration must be given to the way in which crew ingress their Mars Ascent Vehicle (MAV). For architectures involving more than one surface element-such as an ascent vehicle and a pressurized rover or surface habitat-a retractable tunnel that eliminates extravehicular activity (EVA) ingress is an attractive solution. Beyond addressing the immediate MAV access issue, a reusable tunnel may be useful for other surface applications, such as rover to habitat transfer, once its primary mission is complete. A National Aeronautics and Space Administration (NASA) team is studying the optimal balance between surface tunnel functionality, mass, and stowed volume as part of the Evolvable Mars Campaign (EMC). The study team began by identifying the minimum set of functional requirements needed for the tunnel to perform its primary mission, as this would presumably be the simplest design, with the lowest mass and volume. This Minimum Functional Tunnel then becomes a baseline against which various tunnel design concepts and potential alternatives can be traded, and aids in assessing the mass penalty of increased functionality. Preliminary analysis indicates that the mass of a single-mission tunnel is about 237 kg, not including mass growth allowance.

  3. Tunneling into fuzzball states

    NASA Astrophysics Data System (ADS)

    Mathur, Samir D.

    2010-01-01

    String theory suggests that black hole microstates are quantum, horizon sized ‘fuzzballs', rather than smooth geometries with horizon. Radiation from fuzzballs can carry information and does not lead to information loss. But if we let a shell of matter collapse then it creates a horizon, and it seems that subsequent radiation will lead to information loss. We argue that the resolution to this problem is that the shell can tunnel to the fuzzball configurations. The amplitude for tunneling is small because we are relating two macroscopically different configurations, but the number of states that we can tunnel to, given through the Bekenstein entropy, is very large. These small and large numbers can cancel each other, making it possible for the shell to tunnel into fuzzball states before a significant amount of radiation has been emitted. This offers a way to resolve the information paradox.

  4. Disturbance of tunneling coherence by oxygen vacancy in epitaxial Fe/MgO/Fe magnetic tunnel junctions.

    PubMed

    Miao, G X; Park, Y J; Moodera, J S; Seibt, M; Eilers, G; Münzenberg, M

    2008-06-20

    Oxygen vacancies in the MgO barriers of epitaxial Fe/MgO/Fe magnetic tunnel junctions are observed to introduce symmetry-breaking scatterings and hence open up channels for noncoherent tunneling processes that follow the normal WKB approximation. The evanescent waves inside the MgO barrier thus experience two-step tunneling, the coherent followed by the noncoherent process, and lead to lower tunnel magnetoresistance, higher junction resistance, as well as increased bias and temperature dependence. The characteristic length of the symmetry scattering process is determined to be about 1.6 nm.

  5. Distribution of tunnelling times for quantum electron transport.

    PubMed

    Rudge, Samuel L; Kosov, Daniel S

    2016-03-28

    In electron transport, the tunnelling time is the time taken for an electron to tunnel out of a system after it has tunnelled in. We define the tunnelling time distribution for quantum processes in a dissipative environment and develop a practical approach for calculating it, where the environment is described by the general Markovian master equation. We illustrate the theory by using the rate equation to compute the tunnelling time distribution for electron transport through a molecular junction. The tunnelling time distribution is exponential, which indicates that Markovian quantum tunnelling is a Poissonian statistical process. The tunnelling time distribution is used not only to study the quantum statistics of tunnelling along the average electric current but also to analyse extreme quantum events where an electron jumps against the applied voltage bias. The average tunnelling time shows distinctly different temperature dependence for p- and n-type molecular junctions and therefore provides a sensitive tool to probe the alignment of molecular orbitals relative to the electrode Fermi energy.

  6. The Channel Tunnel

    NASA Technical Reports Server (NTRS)

    2006-01-01

    The Channel Tunnel is a 50.5 km-long rail tunnel beneath the English Channel at the Straits of Dover. It connects Dover, Kent in England with Calais, northern France. The undersea section of the tunnel is unsurpassed in length in the world. A proposal for a Channel tunnel was first put forward by a French engineer in 1802. In 1881, a first attempt was made at boring a tunnel from the English side; the work was halted after 800 m. Again in 1922, English workers started boring a tunnel, and advanced 120 m before it too was halted for political reasons. The most recent attempt was begun in 1987, and the tunnel was officially opened in 1994. At completion it was estimated that the project cost around $18 billion. It has been operating at a significant loss since its opening, despite trips by over 7 million passengers per year on the Eurostar train, and over 3 million vehicles per year.

    With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

    The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring

  7. 47 CFR 15.211 - Tunnel radio systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Tunnel radio systems. 15.211 Section 15.211... Tunnel radio systems. An intentional radiator utilized as part of a tunnel radio system may operate on... system (intentional radiator and all connecting wires) shall be contained solely within a tunnel, mine or...

  8. 47 CFR 15.211 - Tunnel radio systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 1 2014-10-01 2014-10-01 false Tunnel radio systems. 15.211 Section 15.211... Tunnel radio systems. An intentional radiator utilized as part of a tunnel radio system may operate on... system (intentional radiator and all connecting wires) shall be contained solely within a tunnel, mine or...

  9. 47 CFR 15.211 - Tunnel radio systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 1 2013-10-01 2013-10-01 false Tunnel radio systems. 15.211 Section 15.211... Tunnel radio systems. An intentional radiator utilized as part of a tunnel radio system may operate on... system (intentional radiator and all connecting wires) shall be contained solely within a tunnel, mine or...

  10. 47 CFR 15.211 - Tunnel radio systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Tunnel radio systems. 15.211 Section 15.211... Tunnel radio systems. An intentional radiator utilized as part of a tunnel radio system may operate on... system (intentional radiator and all connecting wires) shall be contained solely within a tunnel, mine or...

  11. 47 CFR 15.211 - Tunnel radio systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 1 2012-10-01 2012-10-01 false Tunnel radio systems. 15.211 Section 15.211... Tunnel radio systems. An intentional radiator utilized as part of a tunnel radio system may operate on... system (intentional radiator and all connecting wires) shall be contained solely within a tunnel, mine or...

  12. Experimental Evidence for Quantum Tunneling Time.

    PubMed

    Camus, Nicolas; Yakaboylu, Enderalp; Fechner, Lutz; Klaiber, Michael; Laux, Martin; Mi, Yonghao; Hatsagortsyan, Karen Z; Pfeifer, Thomas; Keitel, Christoph H; Moshammer, Robert

    2017-07-14

    The first hundred attoseconds of the electron dynamics during strong field tunneling ionization are investigated. We quantify theoretically how the electron's classical trajectories in the continuum emerge from the tunneling process and test the results with those achieved in parallel from attoclock measurements. An especially high sensitivity on the tunneling barrier is accomplished here by comparing the momentum distributions of two atomic species of slightly deviating atomic potentials (argon and krypton) being ionized under absolutely identical conditions with near-infrared laser pulses (1300 nm). The agreement between experiment and theory provides clear evidence for a nonzero tunneling time delay and a nonvanishing longitudinal momentum of the electron at the "tunnel exit."

  13. Phonon-Mediated Tunneling into Graphene

    NASA Astrophysics Data System (ADS)

    Wehling, T. O.; Grigorenko, I.; Lichtenstein, A. I.; Balatsky, A. V.

    2008-11-01

    Recent scanning tunneling spectroscopy experiments on graphene reported an unexpected gap of about ±60meV around the Fermi level [V. W. Brar , Appl. Phys. Lett.APPLAB0003-6951 91, 122102 (2007); 10.1063/1.2771084Y. Zhang , Nature Phys.NPAHAX1745-2481 4, 627 (2008)10.1038/nphys1022]. Here we give a theoretical investigation explaining the experimentally observed spectra and confirming the phonon-mediated tunneling as the reason for the gap: We study the real space properties of the wave functions involved in the tunneling process by means of ab initio theory and present a model for the electron-phonon interaction, which couples the graphene’s Dirac electrons with quasifree-electron states at the Brillouin zone center. The self-energy associated with this electron-phonon interaction is calculated, and its effects on tunneling into graphene are discussed. Good agreement of the tunneling density of states within our model and the experimental dI/dU spectra is found.

  14. Phonon mediated tunneling into graphene

    NASA Astrophysics Data System (ADS)

    Wehling, Tim; Grigorenko, Ilya; Lichtenstein, Alexander; Balatsky, Alexander

    2009-03-01

    Recent scanning tunneling spectroscopy experiments [V. W. Brar et al., Appl. Phys. Lett. 91, 122102 (2007); Y. Zhang et al., Nature Phys. 4, 627 (2008)] on graphene reported an unexpected gap of about ±60,eV around the Fermi level. Here, we give a theoretical investigation explaining the experimentally observed spectra and confirming the phonon mediated tunneling as the reason for the gap: We study the real space properties of the wave functions involved in the tunneling process by means of ab-initio theory and present a model for the electron-phonon interaction, which couples the graphene's Dirac electrons with quasi free electron states at the Brillouin zone center. The self-energy associated with this electron-phonon interaction is calculated and its effects on tunneling into graphene are discussed. In particular, good agreement of the tunneling density of states within our model and the experimental dI/dU spectra is found.

  15. Toxic anterior segment syndrome caused by autoclave reservoir wall biofilms and their residual toxins.

    PubMed

    Sorenson, Andrew L; Sorenson, Robert L; Evans, David J

    2016-11-01

    To identify etiology of toxic anterior segment syndrome (TASS) after uneventful phacoemulsification. EyeMD Laser and Surgery Center, Oakland, California. Retrospective case series. Patient charts with TASS were reviewed. Reservoirs of 2 autoclaves associated with these cases were cultured for bacterial contamination. Cultures were performed on 23 other autoclave reservoirs at surgery centers in the local area. The main outcome measures were the incidence of TASS and prevalence of bacterial biofilm contamination of autoclave reservoirs. From 2010 to 2013, 11 935 consecutive cataract surgeries were performed at 1 center by multiple surgeons with no reported TASS. Between January 1, 2014, and January 15, 2015, 10 cases of TASS occurred out of 3003 cataract surgeries; these patients' charts were reviewed. Cultures of 2 Statim autoclave reservoir walls grew Bacillus species, Williamsia species, Mycobacterium mucogenicum, and Candida parapsilosis. Scanning electron microscopy of reservoir wall sections showed prominent biofilm. The 2 autoclaves were replaced in January 2015. Subsequently, 2875 cataract surgeries were performed with no reported TASS (P < .001, χ 2 test). Eighteen of 23 additional regional autoclaves were also contaminated with bacterial biofilms. Toxic anterior segment syndrome was strongly associated with bacterial biofilm contamination of autoclave reservoirs. An etiological mechanism might involve transport of heat-stable bacterial cell antigens in the steam with deposition on surgical instrumentation. Data suggest widespread prevalence of bacterial biofilms on fluid-reservoir walls, despite adherence to manufacturer guidelines for cleaning and maintenance. Prevention or elimination of autoclave fluid-reservoir biofilms might reduce the risk for postoperative TASS. None of the authors has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  16. Strain-enhanced tunneling magnetoresistance in MgO magnetic tunnel junctions

    PubMed Central

    Loong, Li Ming; Qiu, Xuepeng; Neo, Zhi Peng; Deorani, Praveen; Wu, Yang; Bhatia, Charanjit S.; Saeys, Mark; Yang, Hyunsoo

    2014-01-01

    While the effects of lattice mismatch-induced strain, mechanical strain, as well as the intrinsic strain of thin films are sometimes detrimental, resulting in mechanical deformation and failure, strain can also be usefully harnessed for applications such as data storage, transistors, solar cells, and strain gauges, among other things. Here, we demonstrate that quantum transport across magnetic tunnel junctions (MTJs) can be significantly affected by the introduction of controllable mechanical strain, achieving an enhancement factor of ~2 in the experimental tunneling magnetoresistance (TMR) ratio. We further correlate this strain-enhanced TMR with coherent spin tunneling through the MgO barrier. Moreover, the strain-enhanced TMR is analyzed using non-equilibrium Green's function (NEGF) quantum transport calculations. Our results help elucidate the TMR mechanism at the atomic level and can provide a new way to enhance, as well as tune, the quantum properties in nanoscale materials and devices. PMID:25266219

  17. Homoepitaxial graphene tunnel barriers for spin transport

    NASA Astrophysics Data System (ADS)

    Friedman, Adam

    Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions (magnetic field, temperature, etc.) usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. We demonstrate successful tunneling, charge, and spin transport with a fluorinated graphene tunnel barrier on a graphene channel. We show that while spin transport stops short of room temperature, spin polarization efficiency values are the highest of any graphene spin devices. We also demonstrate that hydrogenation of graphene can also be used to create a tunnel barrier. We begin with a four-layer stack of graphene and hydrogenate the top few layers to decouple them from the graphene transport channel beneath. We demonstrate successful tunneling by measuring non-linear IV curves and a weakly temperature dependent zero-bias resistance. We demonstrate lateral transport of spin currents in non-local spin-valve structures and determine spin lifetimes with the non-local Hanle effect to be commensurate with previous studies. The measured spin polarization efficiencies for hydrogenated graphene are higher than most oxide tunnel barriers on graphene, but not as high as with fluorinated graphene tunnel barriers. However, here we show that spin transport persists up to room temperature. Our results for the hydrogenated graphene tunnel barriers are compared with fluorinated tunnel barriers and we discuss the

  18. Tunneling magnetoresistance and electroresistance in Fe/PbTiO{sub 3}/Fe multiferroic tunnel junctions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dai, Jian-Qing, E-mail: djqkust@sina.com

    We perform first-principles electronic structure and spin-dependent transport calculations for a Fe/PbTiO{sub 3}/Fe multiferroic tunnel junction with asymmetric TiO{sub 2}- and PbO-terminated interfaces. We demonstrate that the interfacial electronic reconstruction driven by the in situ screening of ferroelectric polarization, in conjunction with the intricate complex band structure of barrier, play a decisive role in controlling the spin-dependent tunneling. Reversal of ferroelectric polarization results in a transition from insulating to half-metal-like conducting state for the interfacial Pb 6p{sub z} orbitals, which acts as an atomic-scale spin-valve by releasing the tunneling current in antiparallel magnetization configuration as the ferroelectric polarization pointing tomore » the PbO-terminated interface. This effect produces large change in tunneling conductance. Our results open an attractive avenue in designing multiferroic tunnel junctions with excellent performance by exploiting the interfacial electronic reconstruction originated from the in situ screening of ferroelectric polarization.« less

  19. Scanning Tunneling Optical Resonance Microscopy

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila; Wilt, Dave; Raffaelle, Ryne; Gennett, Tom; Tin, Padetha; Lau, Janice; Castro, Stephanie; Jenkins, Philip; Scheiman, Dave

    2003-01-01

    Scanning tunneling optical resonance microscopy (STORM) is a method, now undergoing development, for measuring optoelectronic properties of materials and devices on the nanoscale by means of a combination of (1) traditional scanning tunneling microscopy (STM) with (2) tunable laser spectroscopy. In STORM, an STM tip probing a semiconductor is illuminated with modulated light at a wavelength in the visible-to-near-infrared range and the resulting photoenhancement of the tunneling current is measured as a function of the illuminating wavelength. The photoenhancement of tunneling current occurs when the laser photon energy is sufficient to excite charge carriers into the conduction band of the semiconductor. Figure 1 schematically depicts a proposed STORM apparatus. The light for illuminating the semiconductor specimen at the STM would be generated by a ring laser that would be tunable across the wavelength range of interest. The laser beam would be chopped by an achromatic liquid-crystal modulator. A polarization-maintaining optical fiber would couple the light to the tip/sample junction of a commercial STM. An STM can be operated in one of two modes: constant height or constant current. A STORM apparatus would be operated in the constant-current mode, in which the height of the tip relative to the specimen would be varied in order to keep the tunneling current constant. In this mode, a feedback control circuit adjusts the voltage applied to a piezoelectric actuator in the STM that adjusts the height of the STM tip to keep the tunneling current constant. The exponential relationship between the tunneling current and tip-to-sample distance makes it relatively easy to implement this mode of operation. The choice of method by which the photoenhanced portion of the tunneling current would be measured depends on choice of the frequency at which the input illumination would be modulated (chopped). If the frequency of modulation were low enough (typically < 10 Hz) that the

  20. New generation of free-piston shock tunnels

    NASA Technical Reports Server (NTRS)

    Morrison, W. R. B.; Stalker, R. J.; Duffin, J.

    1990-01-01

    Consideration is given to three free-piston driven hypersonic tunnels under construction that will greatly enhance existing test capabilities. The tunnel being built at Caltech will feature energy capabilities about 40 percent higher than those of the world's largest operational free-piston tunnel to date. The second tunnel under construction will allow full-size engine hardware at near-orbital speeds. The third facility is a high-performance expansion tube that will be capable of generating high enthalpy flows at speeds of up to 9 km/sec. It will provide flows with dissociation levels much lower than are attainable with a reflected shock tunnel, approaching actual flight conditions. A table shows the tunnels' characteristics.

  1. Geological Prediction Ahead of Tunnel Face in the Limestone Formation Tunnel using Multi-Modal Geophysical Surveys

    NASA Astrophysics Data System (ADS)

    Zaki, N. F. M.; Ismail, M. A. M.; Hazreek Zainal Abidin, Mohd; Madun, Aziman

    2018-04-01

    Tunnel construction in typical karst topography face the risk which unknown geological condition such as abundant rainwater, ground water and cavities. Construction of tunnel in karst limestone frequently lead to potentially over-break of rock formation and cause failure to affected area. Physical character of limestone which consists large cavity prone to sudden failure and become worsen due to misinterpretation of rock quality by engineer and geologists during analysis stage and improper method adopted in construction stage. Consideration for execution of laboratory and field testing in rock limestone should be well planned and arranged in tunnel construction project. Several tests including Ground Penetration Radar (GPR) and geological face mapping were studied in this research to investigate the performances of limestone rock in tunnel construction, measured in term of rock mass quality that used for risk assessment. The objective of this study is to focus on the prediction of geological condition ahead of tunnel face using short range method (GPR) and verified by geological face mapping method to determine the consistency of actual geological condition on site. Q-Value as the main indicator for rock mass classification was obtained from geological face mapping method. The scope of this study is covering for tunnelling construction along 756 meters in karst limestone area which located at Timah Tasoh Tunnel, Bukit Tebing Tinggi, Perlis. For this case study, 15% of GPR results was identified as inaccurate for rock mass classification in which certain chainage along this tunnel with 34 out of 224 data from GPR was identified as incompatible with actual face mapping.

  2. Tunneling Flight Time, Chemistry, and Special Relativity.

    PubMed

    Petersen, Jakob; Pollak, Eli

    2017-09-07

    Attosecond ionization experiments have not resolved the question "What is the tunneling time?". Different definitions of tunneling time lead to different results. Second, a zero tunneling time for a material particle suggests that the nonrelativistic theory includes speeds greater than the speed of light. Chemical reactions, occurring via tunneling, should then not be considered in terms of a nonrelativistic quantum theory calling into question quantum dynamics computations on tunneling reactions. To answer these questions, we define a new experimentally measurable paradigm, the tunneling flight time, and show that it vanishes for scattering through an Eckart or a square barrier, irrespective of barrier length or height, generalizing the Hartman effect. We explain why this result does not lead to experimental measurement of speeds greater than the speed of light. We show that this tunneling is an incoherent process by comparing a classical Wigner theory with exact quantum mechanical computations.

  3. Aeroelastic instability stoppers for wind tunnel models

    NASA Technical Reports Server (NTRS)

    Doggett, R. V., Jr.; Ricketts, R. H. (Inventor)

    1981-01-01

    A mechanism for diverting the flow in a wind tunnel from the wing of a tested model is described. The wing is mounted on the wall of a tunnel. A diverter plate is pivotally mounted on the tunnel wall ahead of the model. An actuator fixed to the tunnel is pivotably connected to the diverter plate, by plunger. When the model is about to become unstable during the test the actuator moves the diverter plate from the tunnel wall to divert maintaining stable model conditions. The diverter plate is then retracted to enable normal flow.

  4. Multisensor system for tunnel inspection

    NASA Astrophysics Data System (ADS)

    Idoux, Maurice

    2005-01-01

    The system is aimed at assisting inspection and monitoring of the degradation of tunnels in order to minimize maintenance and repair time. ATLAS 70 is a complete sensors/software package which enables thorough diagnosis of tunnel wall conditions. The data collected locally are stored on a computer hard disk for subsequent analysis in a remote location via elaborate dedicated software. The sensors and local computer are loaded onto a rail and/or road vehicle of specific design, i.e. with even travelling speed of 2 to 5 km/h. Originally, the system has been developed for the Paris Underground Company and has since been applied to rail and road tunnels, large town sewage systems, clean water underground aqueducts and electric cable tunnels.

  5. V/STOL wind-tunnel testing

    NASA Technical Reports Server (NTRS)

    Koenig, D. G.

    1984-01-01

    Factors influencing effective program planning for V/STOL wind-tunnel testing are discussed. The planning sequence itself, which includes a short checklist of considerations that could enhance the value of the tests, is also described. Each of the considerations, choice of wind tunnel, type of model installation, model development and test operations, is discussed, and examples of appropriate past and current V/STOL test programs are provided. A short survey of the moderate to large subsonic wind tunnels is followed by a review of several model installations, from two-dimensional to large-scale models of complete aircraft configurations. Model sizing, power simulation, and planning are treated, including three areas is test operations: data-acquisition systems, acoustic measurements in wind tunnels, and flow surveying.

  6. Computational Multiqubit Tunnelling in Programmable Quantum Annealers

    DTIC Science & Technology

    2016-08-25

    ARTICLE Received 3 Jun 2015 | Accepted 26 Nov 2015 | Published 7 Jan 2016 Computational multiqubit tunnelling in programmable quantum annealers...state itself. Quantum tunnelling has been hypothesized as an advantageous physical resource for optimization in quantum annealing. However, computational ...qubit tunnelling plays a computational role in a currently available programmable quantum annealer. We devise a probe for tunnelling, a computational

  7. Resonance tunneling electron-vibrational spectroscopy of polyoxometalates.

    PubMed

    Dalidchik, F I; Kovalevskii, S A; Balashov, E M

    2017-05-21

    The tunneling spectra of the ordered monolayer films of decamolybdodicobaltate (DMDC) compounds deposited from aqueous solutions on HOPG were measured by scanning tunnel microscopy in air. The DMDC spectra, as well as the tunneling spectra of other polyoxometalates (POMs), exhibit well-defined negative differential resistances (NDRs). The mechanism of formation of these spectral features was established from the collection of revealed NDR dependences on the external varying parameters and found to be common to all systems exhibiting Wannier-Stark localization. A model of biresonance tunneling was developed to provide an explanation for the totality of experimental data, both the literature and original, on the tunneling POM probing. A variant of the tunneling electron-vibrational POM spectroscopy was proposed allowing the determination of the three basic energy parameters-energy gaps between the occupied and unoccupied states, frequencies of the vibrational transitions accompanying biresonance electron-tunneling processes, and electron-vibrational interaction constants on the monomolecular level.

  8. Resonance tunneling electron-vibrational spectroscopy of polyoxometalates

    PubMed Central

    Dalidchik, F. I.; Kovalevskii, S. A.

    2017-01-01

    The tunneling spectra of the ordered monolayer films of decamolybdodicobaltate (DMDC) compounds deposited from aqueous solutions on HOPG were measured by scanning tunnel microscopy in air. The DMDC spectra, as well as the tunneling spectra of other polyoxometalates (POMs), exhibit well-defined negative differential resistances (NDRs). The mechanism of formation of these spectral features was established from the collection of revealed NDR dependences on the external varying parameters and found to be common to all systems exhibiting Wannier–Stark localization. A model of biresonance tunneling was developed to provide an explanation for the totality of experimental data, both the literature and original, on the tunneling POM probing. A variant of the tunneling electron-vibrational POM spectroscopy was proposed allowing the determination of the three basic energy parameters—energy gaps between the occupied and unoccupied states, frequencies of the vibrational transitions accompanying biresonance electron-tunneling processes, and electron-vibrational interaction constants on the monomolecular level. PMID:28527451

  9. Subselenean tunneler melting head design: A preliminary study

    NASA Technical Reports Server (NTRS)

    Engblom, Bill; Graham, Eric; Perera, Jeevan; Strahan, Alan; Ro, Ted

    1988-01-01

    The placement of base facilities in subsurface tunnels created as a result of subsurface mining is described as an alternative to the establishing of a base on the lunar surface. Placement of the base facilities and operations in subselenean tunnels will allow personnel to live and work free from the problem of radiation and temperature variations. A conceptual design for a tunneling device applicable to such a lunar base application was performed to assess the feasibility of the concept. A tunneler was designed which would melt through the lunar material leaving behind glass lined tunnels for later development. The tunneler uses a nuclear generator which supplies the energy to thermally melt the regolith about the cone shaped head. Melted regolith is exacavated through intakes in the head and transferred to a truck which hauls it to the surface. The tunnel walls are solidified to provide support lining by using an active cooling system about the mid section of the tunneler. Also addressed is the rationale for a subselenean tunneler and the tunneler configuration and subsystems, as well as the reasoning behind the resulting design.

  10. Quantum electron tunneling in respiratory complex I.

    PubMed

    Hayashi, Tomoyuki; Stuchebrukhov, Alexei A

    2011-05-12

    We have simulated the atomistic details of electronic wiring of all Fe/S clusters in complex I, a key enzyme in the respiratory electron transport chain. The tunneling current theory of many-electron systems is applied to the broken-symmetry (BS) states of the protein at the ZINDO level. While the one-electron tunneling approximation is found to hold in electron tunneling between the antiferromagnetic binuclear and tetranuclear Fe/S clusters without major orbital or spin rearrangement of the core electrons, induced polarization of the core electrons contributes significantly to decrease the electron transfer rates to 19-56 %. Calculated tunneling energy is about 3 eV higher than Fermi level in the band gap of the protein, which supports that the mechanism of electron transfer is quantum mechanical tunneling, as in the rest of the electron transport chain. Resulting electron tunneling pathways consist of up to three key contributing protein residues between neighboring Fe/S clusters. A signature of the wave properties of electrons is observed as distinct quantum interferences when multiple tunneling pathways exist. In N6a-N6b, electron tunnels along different pathways depending on the involved BS states, suggesting possible fluctuations of the tunneling pathways driven by the local protein environment. The calculated distance dependence of the electron transfer rates with internal water molecules included is in good agreement with a reported phenomenological relation.

  11. A 2D analytical cylindrical gate tunnel FET (CG-TFET) model: impact of shortest tunneling distance

    NASA Astrophysics Data System (ADS)

    Dash, S.; Mishra, G. P.

    2015-09-01

    A 2D analytical tunnel field-effect transistor (FET) potential model with cylindrical gate (CG-TFET) based on the solution of Laplace’s equation is proposed. The band-to-band tunneling (BTBT) current is derived by the help of lateral electric field and the shortest tunneling distance. However, the analysis is extended to obtain the subthreshold swing (SS) and transfer characteristics of the device. The dependency of drain current, SS and transconductance on gate voltage and shortest tunneling distance is discussed. Also, the effect of scaling the gate oxide thickness and the cylindrical body diameter on the electrical parameters of the device is analyzed.

  12. Cryogenic wind tunnels: Unique capabilities for the aerodynamicist

    NASA Technical Reports Server (NTRS)

    Hall, R. M.

    1976-01-01

    The cryogenic wind-tunnel concept as a practical means for improving ground simulation of transonic flight conditions. The Langley 1/3-meter transonic cryogenic tunnel is operational, and the design of a cryogenic National Transonic Facility is undertaken. A review of some of the unique capabilities of cryogenic wind tunnels is presented. In particular, the advantages of having independent control of tunnel Mach number, total pressure, and total temperature are highlighted. This separate control over the three tunnel parameters will open new frontiers in Mach number, Reynolds number, aeroelastic, and model-tunnel interaction studies.

  13. Stress changes ahead of an advancing tunnel

    USGS Publications Warehouse

    Abel, J.F.; Lee, F.T.

    1973-01-01

    Instrumentation placed ahead of three model tunnels in the laboratory and ahead of a crosscut driven in a metamorphic rock mass detected stress changes several tunnel diameters ahead of the tunnel face. Stress changes were detected 4 diameters ahead of a model tunnel drilled into nearly elastic acrylic, 2??50 diameters ahead of a model tunnel drilled into concrete, and 2 diameters ahead of a model tunnel drilled into Silver Plume Granite. Stress changes were detected 7??50 diameters ahead of a crosscut driven in jointed, closely foliated gneisses and gneissic granites in an experimental mine at Idaho Springs, Colorado. These results contrast markedly with a theoretical elastic estimate of the onset of detectable stress changes at 1 tunnel diameter ahead of the tunnel face. A small compressive stress concentration was detected 2 diameters ahead of the model tunnel in acrylic, 1.25 diameters ahead of the model tunnel in concrete, and 1 diameter ahead of the model tunnel in granite. A similar stress peak was detected about 6 diameters ahead of the crosscut. No such stress peak is predicted from elastic theory. The 3-dimensional in situ stress determined in the field demonstrate that geologic structure controls stress orientations in the metamorphic rock mass. Two of the computed principal stresses are parallel to the foliation and the other principal stress is normal to it. The principal stress orientations vary approximately as the foliation attitude varies. The average horizontal stress components and the average vertical stress component are three times and twice as large, respectively, as those predicted from the overburden load. An understanding of the measured stress field appears to require the application of either tectonic or residual stress components, or both. Laboratory studies indicate the presence of proportionately large residual stresses. Mining may have triggered the release of strain energy, which is controlled by geologic structure. ?? 1973.

  14. Advancing Test Capabilities at NASA Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Bell, James

    2015-01-01

    NASA maintains twelve major wind tunnels at three field centers capable of providing flows at 0.1 M 10 and unit Reynolds numbers up to 45106m. The maintenance and enhancement of these facilities is handled through a unified management structure under NASAs Aeronautics and Evaluation and Test Capability (AETC) project. The AETC facilities are; the 11x11 transonic and 9x7 supersonic wind tunnels at NASA Ames; the 10x10 and 8x6 supersonic wind tunnels, 9x15 low speed tunnel, Icing Research Tunnel, and Propulsion Simulator Laboratory, all at NASA Glenn; and the National Transonic Facility, Transonic Dynamics Tunnel, LAL aerothermodynamics laboratory, 8 High Temperature Tunnel, and 14x22 low speed tunnel, all at NASA Langley. This presentation describes the primary AETC facilities and their current capabilities, as well as improvements which are planned over the next five years. These improvements fall into three categories. The first are operations and maintenance improvements designed to increase the efficiency and reliability of the wind tunnels. These include new (possibly composite) fan blades at several facilities, new temperature control systems, and new and much more capable facility data systems. The second category of improvements are facility capability advancements. These include significant improvements to optical access in wind tunnel test sections at Ames, improvements to test section acoustics at Glenn and Langley, the development of a Supercooled Large Droplet capability for icing research, and the development of an icing capability for large engine testing. The final category of improvements consists of test technology enhancements which provide value across multiple facilities. These include projects to increase balance accuracy, provide NIST-traceable calibration characterization for wind tunnels, and to advance optical instruments for Computational Fluid Dynamics (CFD) validation. Taken as a whole, these individual projects provide significant

  15. All NbN tunnel junction fabrication

    NASA Technical Reports Server (NTRS)

    Leduc, H. G.; Khanna, S. K.; Stern, J. A.

    1987-01-01

    The development of SIS tunnel junctions based on NbN for mixer applications in the submillimeter range is reported. The unique technological challenges inherent in the development of all refractory-compound superconductor-based tunnel junctions are highlighted. Current deposition and fabrication techniques are discussed, and the current status of all-NbN tunnel junctions is reported.

  16. Tunneling induced absorption with competing Nonlinearities

    PubMed Central

    Peng, Yandong; Yang, Aihong; Xu, Yan; Wang, Peng; Yu, Yang; Guo, Hongju; Ren, Tingqi

    2016-01-01

    We investigate tunneling induced nonlinear absorption phenomena in a coupled quantum-dot system. Resonant tunneling causes constructive interference in the nonlinear absorption that leads to an increase of more than an order of magnitude over the maximum absorption in a coupled quantum dot system without tunneling. Resonant tunneling also leads to a narrowing of the linewidth of the absorption peak to a sublinewidth level. Analytical expressions show that the enhanced nonlinear absorption is largely due to the fifth-order nonlinear term. Competition between third- and fifth-order nonlinearities leads to an anomalous dispersion of the total susceptibility. PMID:27958303

  17. Tunneling induced absorption with competing Nonlinearities.

    PubMed

    Peng, Yandong; Yang, Aihong; Xu, Yan; Wang, Peng; Yu, Yang; Guo, Hongju; Ren, Tingqi

    2016-12-13

    We investigate tunneling induced nonlinear absorption phenomena in a coupled quantum-dot system. Resonant tunneling causes constructive interference in the nonlinear absorption that leads to an increase of more than an order of magnitude over the maximum absorption in a coupled quantum dot system without tunneling. Resonant tunneling also leads to a narrowing of the linewidth of the absorption peak to a sublinewidth level. Analytical expressions show that the enhanced nonlinear absorption is largely due to the fifth-order nonlinear term. Competition between third- and fifth-order nonlinearities leads to an anomalous dispersion of the total susceptibility.

  18. Mechanical Tunneling in Solid Rock

    DOT National Transportation Integrated Search

    1979-12-01

    This report introduces the principles of mchanized tunneling and provides detailed guidelines for practical application. The subject is introduced with a detailed review of technical aspects and terms relating to mchanized tunneling. It discusses the...

  19. FHWA road tunnel design guidelines

    DOT National Transportation Integrated Search

    2004-07-01

    This document provides technical criteria and guidance for the planning and design of road tunnels. Specific areas covered include planning, studies and investigations, design, and design of construction, of tunnels and shafts. Performance concepts a...

  20. Cumberland Gap Tunnel pavement problems.

    DOT National Transportation Integrated Search

    2005-10-01

    Ground penetrating radar was used to verify voids beneath the concrete roadway located at the Cumberland Gap Tunnel, in Middelsboro, KY. Preliminary results indicate that several void areas reside beneath the north and southbound tunnel.

  1. [Tunnel neuropathies].

    PubMed

    Averochkin, A I; Shtul'man, D R

    1991-01-01

    Analysis is made of 261 patients operated on for tunnel neuropathies. Of these, there were 152 men and 109 women aged 15 to 82 years, the mean age being 46 years. Among 22 patterns of neuropathy, there dominated compression of the ulnar nerve in the cubital canal (104 patients) and compression of the median nerve in the carpal canal (76 patients) accounting for 69% of all the cases. 76 patients had two and more tunnel syndromes; double operative interventions were made in 23 patients. 58 patients (22.2%) recovered, 163 (62.75%) improved, no changes were recorded in 40 (15.3%) patients. There were no deteriorations.

  2. Dry wind tunnel system

    NASA Technical Reports Server (NTRS)

    Chen, Ping-Chih (Inventor)

    2013-01-01

    This invention is a ground flutter testing system without a wind tunnel, called Dry Wind Tunnel (DWT) System. The DWT system consists of a Ground Vibration Test (GVT) hardware system, a multiple input multiple output (MIMO) force controller software, and a real-time unsteady aerodynamic force generation software, that is developed from an aerodynamic reduced order model (ROM). The ground flutter test using the DWT System operates on a real structural model, therefore no scaled-down structural model, which is required by the conventional wind tunnel flutter test, is involved. Furthermore, the impact of the structural nonlinearities on the aeroelastic stability can be included automatically. Moreover, the aeroservoelastic characteristics of the aircraft can be easily measured by simply including the flight control system in-the-loop. In addition, the unsteady aerodynamics generated computationally is interference-free from the wind tunnel walls. Finally, the DWT System can be conveniently and inexpensively carried out as a post GVT test with the same hardware, only with some possible rearrangement of the shakers and the inclusion of additional sensors.

  3. Tunneling anisotropic magnetoresistance driven by magnetic phase transition.

    PubMed

    Chen, X Z; Feng, J F; Wang, Z C; Zhang, J; Zhong, X Y; Song, C; Jin, L; Zhang, B; Li, F; Jiang, M; Tan, Y Z; Zhou, X J; Shi, G Y; Zhou, X F; Han, X D; Mao, S C; Chen, Y H; Han, X F; Pan, F

    2017-09-06

    The independent control of two magnetic electrodes and spin-coherent transport in magnetic tunnel junctions are strictly required for tunneling magnetoresistance, while junctions with only one ferromagnetic electrode exhibit tunneling anisotropic magnetoresistance dependent on the anisotropic density of states with no room temperature performance so far. Here, we report an alternative approach to obtaining tunneling anisotropic magnetoresistance in α'-FeRh-based junctions driven by the magnetic phase transition of α'-FeRh and resultantly large variation of the density of states in the vicinity of MgO tunneling barrier, referred to as phase transition tunneling anisotropic magnetoresistance. The junctions with only one α'-FeRh magnetic electrode show a magnetoresistance ratio up to 20% at room temperature. Both the polarity and magnitude of the phase transition tunneling anisotropic magnetoresistance can be modulated by interfacial engineering at the α'-FeRh/MgO interface. Besides the fundamental significance, our finding might add a different dimension to magnetic random access memory and antiferromagnet spintronics.Tunneling anisotropic magnetoresistance is promising for next generation memory devices but limited by the low efficiency and functioning temperature. Here the authors achieved 20% tunneling anisotropic magnetoresistance at room temperature in magnetic tunnel junctions with one α'-FeRh magnetic electrode.

  4. Early Testing in the Icing Research Tunnel

    NASA Image and Video Library

    1944-09-21

    National Advisory Committee for Aeronautics (NACA) design engineers added the Icing Research Tunnel to the new Aircraft Engine Research Laboratory’s original layout to take advantage of the massive refrigeration system being constructed for the Altitude Wind Tunnel. The Icing Research Tunnel was built to study the formation of ice on aircraft surfaces and methods of preventing or eradicating that ice. Ice buildup adds extra weight, effects aerodynamics, and sometimes blocks airflow through engines. The Icing Research Tunnel is a closed-loop atmospheric wind tunnel with a 6- by 9-foot test section. The tunnel can produce speeds up to 300 miles per hour and temperatures from about 30 to –45⁰ F. Initially the tunnel used a spray bar system to introduce moisture into the airstream. NACA engineers struggled for nearly 10 years to perfect the spray system. The Icing Research Tunnel began testing in June of 1944. Initial testing, seen in this photograph, studied ice accumulation on propellers of a military aircraft. NACA reserach also produced a protected air scoop for the C–46 transport aircraft. A large number of C–46 aircraft were lost due to icing while flying supply runs over the Himalayas during World War II.

  5. Navigation Architecture for a Space Mobile Network

    NASA Technical Reports Server (NTRS)

    Valdez, Jennifer E.; Ashman, Benjamin; Gramling, Cheryl; Heckler, Gregory W.; Carpenter, Russell

    2016-01-01

    The Tracking and Data Relay Satellite System (TDRSS) Augmentation Service for Satellites (TASS) is a proposed beacon service to provide a global, space based GPS augmentation service based on the NASA Global Differential GPS (GDGPS) System. The TASS signal will be tied to the GPS time system and usable as an additional ranging and Doppler radiometric source. Additionally, it will provide data vital to autonomous navigation in the near Earth regime, including space weather information, TDRS ephemerides, Earth Orientation Parameters (EOP), and forward commanding capability. TASS benefits include enhancing situational awareness, enabling increased autonomy, and providing near real-time command access for user platforms. As NASA Headquarters' Space Communication and Navigation Office (SCaN) begins to move away from a centralized network architecture and towards a Space Mobile Network (SMN) that allows for user initiated services, autonomous navigation will be a key part of such a system. This paper explores how a TASS beacon service enables the Space Mobile Networking paradigm, what a typical user platform would require, and provides an in-depth analysis of several navigation scenarios and operations concepts. This paper provides an overview of the TASS beacon and its role within the SMN and user community. Supporting navigation analysis is presented for two user mission scenarios: an Earth observing spacecraft in low earth orbit (LEO), and a highly elliptical spacecraft in a lunar resonance orbit. These diverse flight scenarios indicate the breadth of applicability of the TASS beacon for upcoming users within the current network architecture and in the SMN.

  6. Light intensity distribution optimization for tunnel lamps in different zones of a long tunnel.

    PubMed

    Lai, Wei; Liu, Xianming; Chen, Weimin; Lei, Xiaohua; Cheng, Xingfu

    2014-09-22

    The light distributions in different tunnel zones have different requirements in order to meet the driver's visual system. In this paper, the light intensity distributions of tunnel lamps in different zones of a long tunnel are optimized separately. A common nonlinear optimization approach is proposed to minimize the consuming power as well as satisfy the luminance and glare requirements both on the road surface and on the wall set by International Commission on Illumination (CIE). Compared with that of the reported linear optimization method, the optimization model can save energy from 11% to 57.6% under the same installation conditions.

  7. Development of an Extruded Tunnel Lining System

    DOT National Transportation Integrated Search

    1983-12-01

    The objective of this report was to design, develop, fabricate, test and demonstrate a system for placing a continuously extruded tunnel liner. The Extruded Tunnel Lining System (ETLS) is a process for continuous slipforming of a concrete tunnel lini...

  8. The anisotropic tunneling behavior of spin transport in graphene-based magnetic tunneling junction

    NASA Astrophysics Data System (ADS)

    Pan, Mengchun; Li, Peisen; Qiu, Weicheng; Zhao, Jianqiang; Peng, Junping; Hu, Jiafei; Hu, Jinghua; Tian, Wugang; Hu, Yueguo; Chen, Dixiang; Wu, Xuezhong; Xu, Zhongjie; Yuan, Xuefeng

    2018-05-01

    Due to the theoretical prediction of large tunneling magnetoresistance (TMR), graphene-based magnetic tunneling junction (MTJ) has become an important branch of high-performance spintronics device. In this paper, the non-collinear spin filtering and transport properties of MTJ with the Ni/tri-layer graphene/Ni structure were studied in detail by utilizing the non-equilibrium Green's formalism combined with spin polarized density functional theory. The band structure of Ni-C bonding interface shows that Ni-C atomic hybridization facilitates the electronic structure consistency of graphene and nickel, which results in a perfect spin filtering effect for tri-layer graphene-based MTJ. Furthermore, our theoretical results show that the value of tunneling resistance changes with the relative magnetization angle of two ferromagnetic layers, displaying the anisotropic tunneling behavior of graphene-based MTJ. This originates from the resonant conduction states which are strongly adjusted by the relative magnetization angles. In addition, the perfect spin filtering effect is demonstrated by fitting the anisotropic conductance with the Julliere's model. Our work may serve as guidance for researches and applications of graphene-based spintronics device.

  9. Improved multidimensional semiclassical tunneling theory.

    PubMed

    Wagner, Albert F

    2013-12-12

    We show that the analytic multidimensional semiclassical tunneling formula of Miller et al. [Miller, W. H.; Hernandez, R.; Handy, N. C.; Jayatilaka, D.; Willets, A. Chem. Phys. Lett. 1990, 172, 62] is qualitatively incorrect for deep tunneling at energies well below the top of the barrier. The origin of this deficiency is that the formula uses an effective barrier weakly related to the true energetics but correctly adjusted to reproduce the harmonic description and anharmonic corrections of the reaction path at the saddle point as determined by second order vibrational perturbation theory. We present an analytic improved semiclassical formula that correctly includes energetic information and allows a qualitatively correct representation of deep tunneling. This is done by constructing a three segment composite Eckart potential that is continuous everywhere in both value and derivative. This composite potential has an analytic barrier penetration integral from which the semiclassical action can be derived and then used to define the semiclassical tunneling probability. The middle segment of the composite potential by itself is superior to the original formula of Miller et al. because it incorporates the asymmetry of the reaction barrier produced by the known reaction exoergicity. Comparison of the semiclassical and exact quantum tunneling probability for the pure Eckart potential suggests a simple threshold multiplicative factor to the improved formula to account for quantum effects very near threshold not represented by semiclassical theory. The deep tunneling limitations of the original formula are echoed in semiclassical high-energy descriptions of bound vibrational states perpendicular to the reaction path at the saddle point. However, typically ab initio energetic information is not available to correct it. The Supporting Information contains a Fortran code, test input, and test output that implements the improved semiclassical tunneling formula.

  10. Electron tunneling in proteins program.

    PubMed

    Hagras, Muhammad A; Stuchebrukhov, Alexei A

    2016-06-05

    We developed a unique integrated software package (called Electron Tunneling in Proteins Program or ETP) which provides an environment with different capabilities such as tunneling current calculation, semi-empirical quantum mechanical calculation, and molecular modeling simulation for calculation and analysis of electron transfer reactions in proteins. ETP program is developed as a cross-platform client-server program in which all the different calculations are conducted at the server side while only the client terminal displays the resulting calculation outputs in the different supported representations. ETP program is integrated with a set of well-known computational software packages including Gaussian, BALLVIEW, Dowser, pKip, and APBS. In addition, ETP program supports various visualization methods for the tunneling calculation results that assist in a more comprehensive understanding of the tunneling process. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  11. Tunneling Anomalous and Spin Hall Effects.

    PubMed

    Matos-Abiague, A; Fabian, J

    2015-07-31

    We predict, theoretically, the existence of the anomalous Hall effect when a tunneling current flows through a tunnel junction in which only one of the electrodes is magnetic. The interfacial spin-orbit coupling present in the barrier region induces a spin-dependent momentum filtering in the directions perpendicular to the tunneling current, resulting in a skew tunneling even in the absence of impurities. This produces an anomalous Hall conductance and spin Hall currents in the nonmagnetic electrode when a bias voltage is applied across the tunneling heterojunction. If the barrier is composed of a noncentrosymmetric material, the anomalous Hall conductance and spin Hall currents become anisotropic with respect to both the magnetization and crystallographic directions, allowing us to separate this interfacial phenomenon from the bulk anomalous and spin Hall contributions. The proposed effect should be useful for proving and quantifying the interfacial spin-orbit fields in metallic and metal-semiconductor systems.

  12. Survey Of Wind Tunnels At Langley Research Center

    NASA Technical Reports Server (NTRS)

    Bower, Robert E.

    1989-01-01

    Report presented at AIAA 14th Aerodynamic Testing Conference on current capabilities and planned improvements at NASA Langley Research Center's major wind tunnels. Focuses on 14 major tunnels, 8 unique in world, 3 unique in country. Covers Langley Spin Tunnel. Includes new National Transonic Facility (NTF). Also surveys Langley Unitary Plan Wind Tunnel (UPWT). Addresses resurgence of inexpensive simple-to-operate research tunnels. Predicts no shortage of tools for aerospace researcher and engineer in next decade or two.

  13. 75 FR 42643 - National Tunnel Inspection Standards

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-22

    ... inspectors; inspection frequencies; and a National Tunnel Inventory (NTI). DATES: Comments must be received... elements and specify an appropriate inspection frequency. Additionally, the DOT Inspector General (IG), in... with respect to how frequently tunnels are inspected. The frequency of tunnel inspections varies from...

  14. Railway tunnels in Europe and North America

    DOT National Transportation Integrated Search

    2002-05-01

    This list of railway tunnels (longer than 1, 000 m) was compiled by the secretariat from various national and international sources. The list is intended to serve as a reference inventory for a long railway tunnels in Europe and North America. Tunnel...

  15. Vehicle fires and fire safety in tunnels

    DOT National Transportation Integrated Search

    2002-09-20

    Tunnels present what is arguably the most hazardous environment, from the point of view of fire safety, that members of the public ever experience. The fire safety design of tunnels is carried out by tunnel engineers on the basis of a potential fire ...

  16. Materials Handling for Urban Tunneling in Rock

    DOT National Transportation Integrated Search

    1979-01-01

    An examination of prior forecasts of tunnel construction provides an estimate of 2.4 million feet of rock tunnel to be constructed during the 1976-2000 period. Tunnel projects for the near term (1980+) and far term (1990+) periods are defined for stu...

  17. Carpal Tunnel Syndrome (For Kids)

    MedlinePlus

    ... First Aid & Safety Doctors & Hospitals Videos Recipes for Kids Kids site Sitio para niños How the Body Works ... Search English Español Carpal Tunnel Syndrome KidsHealth / For Kids / Carpal Tunnel Syndrome What's in this article? Where ...

  18. Ivar Giaever, Tunneling, and Superconductors

    Science.gov Websites

    ... Interview with Ivar Giaever (video) Ivar Giaever - Science Video Interview: Tunneling in Semiconductors and Superconductors (video) How Quantum Tunneling Works (video) Top Some links on this page may take you to non

  19. Improved Design of Tunnel Supports : Volume 1 : Simplified Analysis for Ground-Structure Interaction in Tunneling

    DOT National Transportation Integrated Search

    1980-06-01

    The purpose of this report is to provide the tunneling profession with improved practical tools in the technical or design area, which provide more accurate representations of the ground-structure interaction in tunneling. The design methods range fr...

  20. Scale Model Icing Research Tunnel

    NASA Technical Reports Server (NTRS)

    Canacci, Victor A.

    1997-01-01

    NASA Lewis Research Center's Icing Research Tunnel (IRT) is the world's largest refrigerated wind tunnel and one of only three icing wind tunnel facilities in the United States. The IRT was constructed in the 1940's and has been operated continually since it was built. In this facility, natural icing conditions are duplicated to test the effects of inflight icing on actual aircraft components as well as on models of airplanes and helicopters. IRT tests have been used successfully to reduce flight test hours for the certification of ice-detection instrumentation and ice protection systems. To ensure that the IRT will remain the world's premier icing facility well into the next century, Lewis is making some renovations and is planning others. These improvements include modernizing the control room, replacing the fan blades with new ones to increase the test section maximum velocity to 430 mph, installing new spray bars to increase the size and uniformity of the artificial icing cloud, and replacing the facility heat exchanger. Most of the improvements will have a first-order effect on the IRT's airflow quality. To help us understand these effects and evaluate potential improvements to the flow characteristics of the IRT, we built a modular 1/10th-scale aerodynamic model of the facility. This closed-loop scale-model pilot tunnel was fabricated onsite in the various shops of Lewis' Fabrication Support Division. The tunnel's rectangular sections are composed of acrylic walls supported by an aluminum angle framework. Its turning vanes are made of tubing machined to the contour of the IRT turning vanes. The fan leg of the tunnel, which transitions from rectangular to circular and back to rectangular cross sections, is fabricated of fiberglass sections. The contraction section of the tunnel is constructed from sheet aluminum. A 12-bladed aluminum fan is coupled to a turbine powered by high-pressure air capable of driving the maximum test section velocity to 550 ft

  1. Rudolf Hermann, wind tunnels and aerodynamics

    NASA Astrophysics Data System (ADS)

    Lundquist, Charles A.; Coleman, Anne M.

    2008-04-01

    Rudolf Hermann was born on December 15, 1904 in Leipzig, Germany. He studied at the University of Leipzig and at the Aachen Institute of Technology. His involvement with wind tunnels began in 1934 when Professor Carl Wieselsberger engaged him to work at Aachen on the development of a supersonic wind tunnel. On January 6, 1936, Dr. Wernher von Braun visited Dr. Hermann to arrange for use of the Aachen supersonic wind tunnel for Army problems. On April 1, 1937, Dr. Hermann became Director of the Supersonic Wind Tunnel at the Army installation at Peenemunde. Results from the Aachen and Peenemunde wind tunnels were crucial in achieving aerodynamic stability for the A-4 rocket, later designated as the V-2. Plans to build a Mach 10 'hypersonic' wind tunnel facility at Kochel were accelerated after the Allied air raid on Peenemunde on August 17, 1943. Dr. Hermann was director of the new facility. Ignoring destruction orders from Hitler as WWII approached an end in Europe, Dr. Hermann and his associates hid documents and preserved wind tunnel components that were acquired by the advancing American forces. Dr. Hermann became a consultant to the Air Force at its Wright Field in November 1945. In 1951, he was named professor of Aeronautical Engineering at the University of Minnesota. In 1962, Dr. Hermann became the first Director of the Research Institute at the University of Alabama in Huntsville (UAH), a position he held until he retired in 1970.

  2. Franck-Condon fingerprinting of vibration-tunneling spectra.

    PubMed

    Berrios, Eduardo; Sundaradevan, Praveen; Gruebele, Martin

    2013-08-15

    We introduce Franck-Condon fingerprinting as a method for assigning complex vibration-tunneling spectra. The B̃ state of thiophosgene (SCCl2) serves as our prototype. Despite several attempts, assignment of its excitation spectrum has proved difficult because of near-degenerate vibrational frequencies, Fermi resonance between the C-Cl stretching mode and the Cl-C-Cl bending mode, and large tunneling splittings due to the out-of-plane umbrella mode. Hence, the spectrum has never been fitted to an effective Hamiltonian. Our assignment approach replaces precise frequency information with intensity information, eliminating the need for double resonance spectroscopy or combination differences, neither of which have yielded a full assignment thus far. The dispersed fluorescence spectrum of each unknown vibration-tunneling state images its character onto known vibrational progressions in the ground state. By using this Franck-Condon fingerprint, we were able to determine the predominant character of several vibration-tunneling states and assign them; in other cases, the fingerprinting revealed that the states are strongly mixed and cannot be characterized with a simple normal mode assignment. The assigned transitions from vibration-tunneling wave functions that were not too strongly mixed could be fitted within measurement uncertainty by an effective vibration-tunneling Hamiltonian. A fit of all observed vibration-tunneling states will require a full resonance-tunneling Hamiltonian.

  3. Homoepitaxial graphene tunnel barriers for spin transport

    NASA Astrophysics Data System (ADS)

    Friedman, Adam L.; van't Erve, Olaf M. J.; Robinson, Jeremy T.; Whitener, Keith E.; Jonker, Berend T.

    2016-05-01

    Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate that hydrogenation or fluorination of graphene can be used to create a tunnel barrier. We demonstrate successful tunneling by measuring non-linear IV curves and a weakly temperature dependent zero-bias resistance. We demonstrate lateral transport of spin currents in non-local spin-valve structures, and determine spin lifetimes with the non-local Hanle effect. We compare the results for hydrogenated and fluorinated tunnel and we discuss the possibility that ferromagnetic moments in the hydrogenated graphene tunnel barrier affect the spin transport of our devices.

  4. Comparison of emission factors for road traffic from a tunnel study (Gubrist tunnel, Switzerland) and from emission modeling

    NASA Astrophysics Data System (ADS)

    John, Christian; Friedrich, Rainer; Staehelin, Johannes; Schläpfer, Kurt; Stahel, Werner A.

    The emission factors of NO x, VOC and CO of a road tunnel study performed in September 1993 in the Gubrist tunnel, close to Zürich (Switzerland) are compared with results of emission calculations based on recent results of dynamometric test measurements. The emission calculations are carried out with a traffic emission model taking into account the detailed composition of the vehicle fleet in the tunnel, the average speed and the gradient of the road and the special aerodynamics in a tunnel. With the exception of NO x emission factors for heavy duty vehicles no evidence for a discrepancy between the results of the tunnel study and the emission modeling was found. The measured emission factors of individual hydrocarbons of light duty vehicles were in good agreement with the expectations for most components.

  5. Improved Design of Tunnel Supports : Volume 5 : Empirical Methods in Rock Tunneling -- Review and Recommendations

    DOT National Transportation Integrated Search

    1980-06-01

    Volume 5 evaluates empirical methods in tunneling. Empirical methods that avoid the use of an explicit model by relating ground conditions to observed prototype behavior have played a major role in tunnel design. The main objective of this volume is ...

  6. Scanning tunneling microscopy, orbital-mediated tunneling spectroscopy, and ultraviolet photoelectron spectroscopy of metal(II) tetraphenylporphyrins deposited from vapor.

    PubMed

    Scudiero, L; Barlow, D E; Mazur, U; Hipps, K W

    2001-05-02

    Thin films of vapor-deposited Ni(II) and Co(II) complexes of tetraphenylporphyrin (NiTPP and CoTPP) were studied supported on gold and embedded in Al-Al(2)O(3)-MTPP-Pb tunnel diodes, where M = Ni or Co. Thin films deposited onto polycrystalline gold were analyzed by ultraviolet photoelectron spectroscopy (UPS) using He I radiation. Scanning tunneling microscopy (STM) and orbital-mediated tunneling spectroscopy (STM-OMTS) were performed on submonolayer films of CoTPP and NiTPP supported on Au(111). Inelastic electron tunneling spectroscopy (IETS) and OMTS were measured in conventional tunnel diode structures. The highest occupied pi molecular orbital of the porphyrin ring was seen in both STM-OMTS and UPS at about 6.4 eV below the vacuum level. The lowest unoccupied pi molecular orbital of the porphyrin ring was observed by STM-OMTS and by IETS-OMTS to be located near 3.4 eV below the vacuum level. The OMTS spectra of CoTPP had a band near 5.2 eV (below the vacuum level) that was attributed to transient oxidation of the central Co(II) ion. That is, it is due to electron OMT via the half-filled d(z)(2) orbital present in Co(II) of CoTPP. The NiTPP OMTS spectra show no such band, consistent with the known difficulty of oxidation of the Ni(II) ion. The STM-based OMTS allowed these two porphyrin complexes to be easily distinguished. The present work is the first report of the observation of STM-OMTS, tunnel junction OMTS, and UPS of the same compounds. Scanning tunneling microscope-based orbital-mediated tunneling provides more information than UPS or tunnel junction-based OMTS and does so with molecular-scale resolution.

  7. Quantum Electron Tunneling in Respiratory Complex I1

    PubMed Central

    Hayashi, Tomoyuki; Stuchebrukhov, Alexei A.

    2014-01-01

    We have simulated the atomistic details of electronic wiring of all Fe/S clusters in complex I, a key enzyme in the respiratory electron transport chain. The tunneling current theory of many-electron systems is applied to the broken-symmetry (BS) states of the protein at the ZINDO level. One-electron tunneling approximation is found to hold in electron tunneling between the anti-ferromagnetic binuclear and tetranuclear Fe/S clusters with moderate induced polarization of the core electrons. Calculated tunneling energy is about 3 eV higher than Fermi level in the band gap of the protein, which supports that the mechanism of electron transfer is quantum mechanical tunneling, as in the rest of electron transport chain. Resulting electron tunneling pathways consist of up to three key contributing protein residues between neighboring Fe/S clusters. A distinct signature of the wave properties of electrons is observed as quantum interferences when multiple tunneling pathways exist. In N6a-N6b, electron tunnels along different pathways depending on the involved BS states, suggesting possible fluctuations of the tunneling pathways driven by the local protein environment. The calculated distance dependence of the electron transfer rates with internal water molecules included are in good agreement with a reported phenomenological relation. PMID:21495666

  8. Wind Tunnel Complex at the Aircraft Engine Research Laboratory

    NASA Image and Video Library

    1945-09-21

    This aerial photograph shows the entire original wind tunnel complex at the National Advisory Committee for Aeronautics (NACA) Aircraft Engine Research Laboratory. The large Altitude Wind Tunnel (AWT) at the center of the photograph dominates the area. The Icing Research Tunnel to the right was incorporated into the lab’s design to take advantage of the AWT’s powerful infrastructure. The laboratory’s first supersonic wind tunnel was added to this complex just prior to this September 1945 photograph. The AWT was the nation’s only wind tunnel capable of studying full-scale engines in simulated flight conditions. The AWT’s test section and control room were within the two-story building near the top of the photograph. The exhauster equipment used to thin the airflow and the drive motor for the fan were in the building to the right of the tunnel. The unique refrigeration equipment was housed in the structure to the left of the tunnel. The Icing Research Tunnel was an atmospheric tunnel that used the AWT’s refrigeration equipment to simulate freezing rain inside its test section. A spray bar system inside the tunnel was originally used to create the droplets. The 18- by 18-inch supersonic wind tunnel was built in the summer of 1945 to take advantage of the AWT’s powerful exhaust system. It was the lab’s first supersonic tunnel and could reach Mach 1.91. Eventually the building would house three small supersonic tunnels, referred to as the “stack tunnels” because of the vertical alignment. The two other tunnels were added to this structure in 1949 and 1951.

  9. Development of the safety control framework for shield tunneling in close proximity to the operational subway tunnels: case studies in mainland China.

    PubMed

    Li, Xinggao; Yuan, Dajun

    2016-01-01

    China's largest cities like Beijing and Shanghai have seen a sharp increase in subway network development as a result of the rapid urbanization in the last decade. The cities are still expanding their subway networks now, and many shield tunnels are being or will be constructed in close proximity to the existing operational subway tunnels. The execution plans for the new nearby shield tunnel construction calls for the development of a safety control framework-a set of control standards and best practices to help organizations manage the risks involved. Typical case studies and relevant key technical parameters are presented with a view to presenting the resulting safety control framework. The framework, created through collaboration among the relevant parties, addresses and manages the risks in a systematic way based on actual conditions of each tunnel crossing construction. The framework consists of six parts: (1) inspecting the operational subway tunnels; (2) deciding allowed movements of the existing tunnels and tracks; (3) simulating effects of the shield tunneling on the existing tunnels; (4) doing preparation work; (5) monitoring design and information management; and (6) measures and activation mechanism of the countermeasures. The six components are explained and demonstrated in detail. In the end, discussions made involve construction and post-construction settlement of the operational tunnel, application of the remedial grouting to rectify excessive settlements of the operational tunnel, and use of the innovative tool of the optical fiber measurement for tunnel movement monitoring. It is concluded that the construction movement of the tunnel can be controlled within 15 mm when the shield machine is <7 m in excavation diameter. The post-construction settlement of the tunnel buried in the very soft ground is much greater than its construction settlement, and last several years until reaching a final stable state. Two cases are outlined to demonstrate the

  10. Aeroacoustic research in wind tunnels: A status report

    NASA Technical Reports Server (NTRS)

    Bender, J.; Arndt, R. E. A.

    1973-01-01

    The increasing attention given to aerodynamically generated noise brings into focus the need for quality experimental research in this area. To meet this need several specialized anechoic wind tunnels have been constructed. In many cases, however, budgetary constraints and the like make it desirable to use conventional wind tunnels for this work. Three basic problems are inherent in conventional facilities: (1) high background noise, (2) strong frequency dependent reverberation effects, and (3) unique instrumentation problems. The known acoustic characteristics of several conventional wind tunnels are evaluated and data obtained in a smaller 4- x 5-foot wind tunnel which is convertible from a closed jet to an open jet mode are presented. The data from these tunnels serve as a guideline for proposed modifications to a 7- x 10-foot wind tunnel. Consideration is given to acoustic treatment in several different portions of the wind tunnel.

  11. Resonant tunneling in frustrated total internal reflection.

    PubMed

    Longhi, Stefano

    2005-10-15

    Anomalous light transmission and resonant tunneling in frustrated total internal reflection (FTIR) are theoretically predicted to occur at periodically curved interfaces. For a low-contrast index and for grazing incidence, it is shown that FTIR resonant tunneling provides an optical realization of field-induced barrier transparency in quantum tunneling.

  12. National Wind Tunnel Complex (NWTC)

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The National Wind Tunnel Complex (NWTC) Final Report summarizes the work carried out by a unique Government/Industry partnership during the period of June 1994 through May 1996. The objective of this partnership was to plan, design, build and activate 'world class' wind tunnel facilities for the development of future-generation commercial and military aircraft. The basis of this effort was a set of performance goals defined by the National Facilities Study (NFS) Task Group on Aeronautical Research and Development Facilities which established two critical measures of improved wind tunnel performance; namely, higher Reynolds number capability and greater productivity. Initial activities focused upon two high-performance tunnels (low-speed and transonic). This effort was later descoped to a single multipurpose tunnel. Beginning in June 1994, the NWTC Project Office defined specific performance requirements, planned site evaluation activities, performed a series of technical/cost trade studies, and completed preliminary engineering to support a proposed conceptual design. Due to budget uncertainties within the Federal government, the NWTC project office was directed to conduct an orderly closure following the Systems Design Review in March 1996. This report provides a top-level status of the project at that time. Additional details of all work performed have been archived and are available for future reference.

  13. Sonographically guided percutaneous needle release of the carpal tunnel for treatment of carpal tunnel syndrome: preliminary report.

    PubMed

    McShane, John M; Slaff, Samantha; Gold, Judith E; Nazarian, Levon N

    2012-09-01

    The purpose of this study was to evaluate the effectiveness of a novel treatment procedure, sonographically guided percutaneous needle release of the carpal tunnel, for individuals with carpal tunnel syndrome. Seventeen patients (89% female; mean age, 62 years; SD, 13.6 years) with a clinical diagnosis of carpal tunnel syndrome who had undergone a sonographically guided percutaneous needle release of the carpal tunnel at least 6 months before follow-up evaluation were retrospectively reviewed. At the follow-up evaluation, to ascertain previous and current symptoms as well as functional impairment, the patients filled out a hand diagram and a questionnaire. In addition, medical records were reviewed, and patients were queried regarding complications such as infection or nerve damage. Median nerve sonographic measurements and a physical evaluation were performed on a subset of 13 patients who came to the office for evaluation. Postprocedure sonography showed that patients had a significantly smaller (P = .03) cross-sectional area of the median nerve compared to pretreatment values. In addition, patients had significantly fewer symptoms (P < .0001), less functional impairment (P = .0002), and an improved hand diagram score (P < .0001). Postprocedure patients had grip strength that was 12 lb below average (≈1 SD below) compared to grip strength norms. However, most patients (84.6%) had negative clinical diagnostic test results for carpal tunnel syndrome, and 86% said they were satisfied with the procedure. There were no procedure-related infections or nerve injuries. Of the patients with carpal tunnel syndrome who agreed to participate in this study, most had favorable symptomatic and functional outcomes. Sonographically guided percutaneous needle release of the carpal tunnel may be an alternative option to traditional surgical treatment of carpal tunnel syndrome.

  14. Trap-assisted tunneling in Si-InAs nanowire heterojunction tunnel diodes.

    PubMed

    Bessire, Cedric D; Björk, Mikael T; Schmid, Heinz; Schenk, Andreas; Reuter, Kathleen B; Riel, Heike

    2011-10-12

    We report on the electrical characterization of one-sided p(+)-si/n-InAs nanowire heterojunction tunnel diodes to provide insight into the tunnel process occurring in this highly lattice mismatched material system. The lattice mismatch gives rise to dislocations at the interface as confirmed by electron microscopy. Despite this, a negative differential resistance with peak-to-valley current ratios of up to 2.4 at room temperature and with large current densities is observed, attesting to the very abrupt and high-quality interface. The presence of dislocations and other defects that increase the excess current is evident in the first and second derivative of the I-V characteristics as distinct peaks arising from trap-and phonon-assisted tunneling via the corresponding defect levels. We observe this assisted tunneling mainly in the forward direction and at low reverse bias but not at higher reverse biases because the band-to-band generation rates are peaked in the InAs, which is also confirmed by modeling. This indicates that most of the peaks are due to dislocations and defects in the immediate vicinity of the interface. Finally, we also demonstrate that these devices are very sensitive to electrical stress, in particular at room temperature, because of the extremely high electrical fields obtained at the abrupt junction even at low bias. The electrical stress induces additional defect levels in the band gap, which reduce the peak-to-valley current ratios.

  15. Overview of the 1989 Wind Tunnel Calibration Workshop

    NASA Technical Reports Server (NTRS)

    Henderson, Arthur, Jr.; Mckinney, L. Wayne

    1993-01-01

    An overview of the 1989 Wind Tunnel Calibration Workshop held at NASA LaRC in Hampton, VA on 19-20 Apr. 1989 is presented. The purpose of the Workshop was to explore wind tunnel calibration requirements as they relate to test quality and data accuracy, with the ultimate goal of developing wind tunnel calibration requirements for the major NASA wind tunnels at ARC, LaRC, and LeRC. The two sessions addressed the following topics: (1) what constitutes a properly calibrated wind tunnel; and (2) the status of calibration of NASA's major wind tunnels. The most significant contributions to the stated goals are highlighted, and the consensus of the Workshop's conclusions and recommendations regarding formulation and implementation of that goal are presented.

  16. The Langley Wind Tunnel Enterprise

    NASA Technical Reports Server (NTRS)

    Paulson, John W., Jr.; Kumar, Ajay; Kegelman, Jerome T.

    1998-01-01

    After 4 years of existence, the Langley WTE is alive and growing. Significant improvements in the operation of wind tunnels have been demonstrated and substantial further improvements are expected when we are able to truly address and integrate all the processes affecting the wind tunnel testing cycle.

  17. Micromachined electron tunneling infrared sensors

    NASA Technical Reports Server (NTRS)

    Kenny, T. W.; Kaiser, W. J.; Podosek, J. A.; Rockstad, H. K.; Reynolds, J. K.

    1993-01-01

    The development of an improved Golay cell is reported. This new sensor is constructed entirely from micromachined silicon components. A silicon oxynitride (SiO(x)N(y)) membrane is deflected by the thermal expansion of a small volume of trapped gas. To detect the motion of the membrane, an electron tunneling transducer is used. This sensor detects electrons which tunnel through the classically forbidden barrier between a tip and a surface; the electron current is exponentially dependent on the separation between the tip and the surface. The sensitivity of tunneling transducers constructed was typically better than 10(exp -3) A/square root of Hz. Through use of the electron tunneling transducer, the scaling laws which have prevented the miniaturization of the Golay cell are avoided. This detector potentially offers low cost fabrication, compatibility with silicon readout electronics, and operation without cooling. Most importantly, this detector may offer better sensitivity than any other uncooled infrared sensor, with the exception of the original Golay cell.

  18. Tunneling Plasmonics in Bilayer Graphene.

    PubMed

    Fei, Z; Iwinski, E G; Ni, G X; Zhang, L M; Bao, W; Rodin, A S; Lee, Y; Wagner, M; Liu, M K; Dai, S; Goldflam, M D; Thiemens, M; Keilmann, F; Lau, C N; Castro-Neto, A H; Fogler, M M; Basov, D N

    2015-08-12

    We report experimental signatures of plasmonic effects due to electron tunneling between adjacent graphene layers. At subnanometer separation, such layers can form either a strongly coupled bilayer graphene with a Bernal stacking or a weakly coupled double-layer graphene with a random stacking order. Effects due to interlayer tunneling dominate in the former case but are negligible in the latter. We found through infrared nanoimaging that bilayer graphene supports plasmons with a higher degree of confinement compared to single- and double-layer graphene, a direct consequence of interlayer tunneling. Moreover, we were able to shut off plasmons in bilayer graphene through gating within a wide voltage range. Theoretical modeling indicates that such a plasmon-off region is directly linked to a gapped insulating state of bilayer graphene, yet another implication of interlayer tunneling. Our work uncovers essential plasmonic properties in bilayer graphene and suggests a possibility to achieve novel plasmonic functionalities in graphene few-layers.

  19. Taking advantage of ground data systems attributes to achieve quality results in testing software

    NASA Technical Reports Server (NTRS)

    Sigman, Clayton B.; Koslosky, John T.; Hageman, Barbara H.

    1994-01-01

    During the software development life cycle process, basic testing starts with the development team. At the end of the development process, an acceptance test is performed for the user to ensure that the deliverable is acceptable. Ideally, the delivery is an operational product with zero defects. However, the goal of zero defects is normally not achieved but is successful to various degrees. With the emphasis on building low cost ground support systems while maintaining a quality product, a key element in the test process is simulator capability. This paper reviews the Transportable Payload Operations Control Center (TPOCC) Advanced Spacecraft Simulator (TASS) test tool that is used in the acceptance test process for unmanned satellite operations control centers. The TASS is designed to support the development, test and operational environments of the Goddard Space Flight Center (GSFC) operations control centers. The TASS uses the same basic architecture as the operations control center. This architecture is characterized by its use of distributed processing, industry standards, commercial off-the-shelf (COTS) hardware and software components, and reusable software. The TASS uses much of the same TPOCC architecture and reusable software that the operations control center developer uses. The TASS also makes use of reusable simulator software in the mission specific versions of the TASS. Very little new software needs to be developed, mainly mission specific telemetry communication and command processing software. By taking advantage of the ground data system attributes, successful software reuse for operational systems provides the opportunity to extend the reuse concept into the test area. Consistency in test approach is a major step in achieving quality results.

  20. Experimental Evidence for Wigner’s Tunneling Time

    NASA Astrophysics Data System (ADS)

    Camus, N.; Yakaboylu, E.; Fechner, L.; Klaiber, M.; Laux, M.; Mi, Y.; Hatsagortsyan, K. Z.; Pfeifer, T.; Keitel, C. H.; Moshammer, R.

    2018-04-01

    Tunneling of a particle through a barrier is one of the counter-intuitive properties of quantum mechanical motion. Thanks to advances in the generation of strong laser fields, new opportunities to dynamically investigate this process have been developed. In the so-called attoclock measurements the electron’s properties after tunneling are mapped on its emission direction. We investigate the tunneling dynamics and achieve a high sensitivity thanks to two refinements of the attoclock principle. Using near-IR wavelength we place firmly the ionization process in the tunneling regime. Furthermore, we compare the electron momentum distributions of two atomic species of slightly different atomic potentials (argon and krypton) being ionized under absolutely identical conditions. Experimentally, using a reaction microscope, we succeed in measuring the 3D electron momentum distributions for both targets simultaneously. Theoretically, the time resolved description of tunneling in strong-field ionization is studied using the leading quantum-mechanical Wigner treatment. A detailed analysis of the most probable photoelectron emission for Ar and Kr allows testing the theoretical models and a sensitive check of the electron initial conditions at the tunnel exit. The agreement between experiment and theory provides a clear evidence for a non-zero tunneling time delay and a non-vanishing longitudinal momentum at this point.

  1. Review of Aeronautical Wind Tunnel Facilities

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The nation's aeronautical wind tunnel facilities constitute a valuable technological resource and make a significant contribution to the global supremacy of U.S. aircraft, both civil and military. At the request of NASA, the National Research Council's Aeronautics and Space Engineering Board organized a commitee to review the state of repair, adequacy, and future needs of major aeronautical wind tunnel facilities in meeting national goals. The comittee identified three main areas where actions are needed to sustain the capability of NASA's aeronautical wind tunnel facilities to support the national aeronautical research and development activities: tunnel maintenance and upgrading, productivity enhancement, and accommodation of new requirements (particularly in hypersonics). Each of these areas are addressed and the committee recommendations for appropriate actions presented.

  2. High-temperature tunneling electroresistance in metal/ferroelectric/semiconductor tunnel junctions

    NASA Astrophysics Data System (ADS)

    Xi, Zhongnan; Jin, Qiao; Zheng, Chunyan; Zhang, Yongcheng; Lu, Chaojing; Li, Qiang; Li, Shandong; Dai, Jiyan; Wen, Zheng

    2017-09-01

    Recently, ferroelectric tunnel junctions (FTJs) have attracted great attention due to promising applications in non-volatile memories. In this study, we report high-temperature tunneling electroresistance (TER) of metal/ferroelectric/semiconductor FTJs. Hysteretic resistance-voltage loops are observed in the Pt/BaTiO3/Nb:SrTiO3 tunnel junction from 300 to 513 K due to the modulation of interfacial Schottky barrier by polarization switching in the 4 u.c.-thick BaTiO3 barrier via a ferroelectric field effect. The Pt/BaTiO3/Nb:SrTiO3 device exhibits a giant ROFF/RON resistance ratio of ˜3 × 105 at 383 K and maintains bipolar resistance switching up to 513 K, suggesting excellent thermal endurance of the FTJs. The temperature-dependent TER behaviors are discussed in terms of the decrease of polarization in the BaTiO3 barrier, and the associated junction barrier profiles are deduced by transport and capacitance analyses. In addition, by extrapolating the retention time at elevated temperature in an Arrhenius-type relation, activation energy of ˜0.93 eV and room-temperature retention time of ˜70 years can be extracted.

  3. Femoral tunnel enlargement after anatomic ACL reconstruction: a biological problem?

    PubMed

    Silva, Alcindo; Sampaio, Ricardo; Pinto, Elisabete

    2010-09-01

    Tunnel enlargement after anterior cruciate ligament (ACL) reconstruction may compromise revision surgery. The cause of this tunnel enlargement is not yet fully understood, but it is thought to be multifactorial, with biomechanical and biological factors playing a role. Tunnel enlargement has been described particularly in patients who underwent ACL reconstruction with hamstring tendons with extracortical fixation devices. The purpose of our study was to evaluate prospectively with magnetic resonance imaging (MRI) the changes in femoral tunnel diameter following arthroscopic anatomic ACL reconstruction with hamstring tendons. At 3-month post-op, all tunnels had enlarged compared to the diameter of the drill and most tunnels enlarged more in the midsection than at the aperture. In the posterolateral tunnels, the entrance increased 16% in diameter and the middle of the tunnel increased 30% in diameter. In the anteromedial femoral tunnels, the tunnels enlarged 14% at the aperture and 35% in the midsection. All femoral tunnels enlarged and most of them enlarged in a fusiform manner. The biological factors explain better our findings than the mechanical theory, although mechanical factors may play a role and the cortical bone at the entrance of the tunnel may modify the way tunnels respond to mechanical stress.

  4. Laser-assisted electron tunneling in a STM junction

    NASA Astrophysics Data System (ADS)

    Chang, Shunhua Thomas

    2000-10-01

    Since its introduction in 1981, the Nobel prize-winning scanning tunneling microscope (STM) has been developed into a powerful yet conceptually simple instrument, replacing traditional scanning and transmission electron microscopes (SEM/TEM) in many of the microscopic surface phenomenon studies. The strength of the STM stems from the sensitive tunneling current-potential barrier width relationship of the electron tunneling process, and has been used to re-examine the frequency-mixing and harmonic generation properties of an non-linear metal- oxide-metal (MOM) tunneling junction. In this research, electron-tunneling events under polarized laser radiation at 514.5-nm argon and 10.6-μm carbon dioxide laser wavelengths were investigated. The objective is to understand the underlying interactive mechanisms between the tunneling junction and the external laser excitation. A commercial scanning tunneling microscope head and controller were incorporated into the experimental setup. Operation characteristics and the electrical properties of the STM junction were determined. Tunneling current and distance responses with respect to different laser polarization, modulation frequency, incident power, and tunneling distance were also conducted. From the experimental results it is shown that thermal expansion effect was the dominant source of response for laser modulation frequency up to about 100 kHz, in quantitative agreement with theoretical calculations. Different laser polarizations as the experiments demonstrated did not contribute significantly to the STM response in the investigated frequency range. The electric field induced by the laser beam was calculated to be one to two order of magnitudes lower than the field required to initiate field emission where the tunneling junction I- V curve is most non-linear. Also, the electrical coupling of the incident laser at the STM junction was determined to be non-critical at visible laser wavelength, and the reflected laser

  5. Radiometric dating of the Siloam Tunnel, Jerusalem.

    PubMed

    Frumkin, Amos; Shimron, Aryeh; Rosenbaum, Jeff

    2003-09-11

    The historical credibility of texts from the Bible is often debated when compared with Iron Age archaeological finds (refs. 1, 2 and references therein). Modern scientific methods may, in principle, be used to independently date structures that seem to be mentioned in the biblical text, to evaluate its historical authenticity. In reality, however, this approach is extremely difficult because of poor archaeological preservation, uncertainty in identification, scarcity of datable materials, and restricted scientific access into well-identified worship sites. Because of these problems, no well-identified Biblical structure has been radiometrically dated until now. Here we report radiocarbon and U-Th dating of the Siloam Tunnel, proving its Iron Age II date; we conclude that the Biblical text presents an accurate historic record of the Siloam Tunnel's construction. Being one of the longest ancient water tunnels lacking intermediate shafts, dating the Siloam Tunnel is a key to determining where and when this technological breakthrough took place. Siloam Tunnel dating also refutes a claim that the tunnel was constructed in the second century bc.

  6. A combustion driven shock tunnel to complement the free piston shock tunnel T5 at GALCIT

    NASA Technical Reports Server (NTRS)

    Belanger, Jacques; Hornung, Hans G.

    1992-01-01

    A combustion driven shock tunnel was designed and built at GALCIT to supply the hypersonic facility T5 with 'hot' hydrogen for mixing and combustion experiments. This system was chosen over other options for better flexibility and for safety reasons. The shock tunnel is described and the overall efficiency of the system is discussed. The biggest challenge in the design was to synchronize the combustion driven shock tunnel with T5. To do so, the main diaphragm of the combustion driven shock tunnel is locally melted by an electrical discharge. This local melting is rapidly followed by the complete collapse of the diaphragm in a very repeatable way. A first set of experiments on supersonic hydrogen transverse jets over a flat plate have just been completed with the system and some of the preliminary results are presented.

  7. Videogrammetric Model Deformation Measurement Technique for Wind Tunnel Applications

    NASA Technical Reports Server (NTRS)

    Barrows, Danny A.

    2006-01-01

    Videogrammetric measurement technique developments at NASA Langley were driven largely by the need to quantify model deformation at the National Transonic Facility (NTF). This paper summarizes recent wind tunnel applications and issues at the NTF and other NASA Langley facilities including the Transonic Dynamics Tunnel, 31-Inch Mach 10 Tunnel, 8-Ft high Temperature Tunnel, and the 20-Ft Vertical Spin Tunnel. In addition, several adaptations of wind tunnel techniques to non-wind tunnel applications are summarized. These applications include wing deformation measurements on vehicles in flight, determining aerodynamic loads based on optical elastic deformation measurements, measurements on ultra-lightweight and inflatable space structures, and the use of an object-to-image plane scaling technique to support NASA s Space Exploration program.

  8. JPRS Report, Proliferation Issues

    DTIC Science & Technology

    1992-03-03

    Moscow TASS in English 0856 GMT 1410 GMT 19 Feb 92 14 Feb 92 [Transmitted via KYODO] [By ITAR-TASS correspondent Sergey Kuznetsov ] [Text] Lieutenant...would be at variance with its pledges under the terms of nalist Oleg Andriyashkin, author of the information in the recent agreement on joint measures

  9. Design of Intelligent Power Supply System for Expressway Tunnel

    NASA Astrophysics Data System (ADS)

    Wang, Li; Li, Yutong; Lin, Zimian

    2018-01-01

    Tunnel lighting program is one of the key points of tunnel infrastructure construction. As tunnels tend to handle remote locations, power supply line construction generally has been having the distance, investment, high cost characteristics. To solve this problem, we propose a green, environmentally friendly, energy-efficient lighting system. This program uses the piston-wind which cars within tunnel produce as the power and combines with solar energy, physical lighting to achieve it, which solves the problem of difficult and high cost of highway tunnel section, and provides new ideas for the future construction of tunnel power supply.

  10. Characterization of Magnetic Tunnel Junctions by IETS and STS

    NASA Astrophysics Data System (ADS)

    Yang, Hyunsoo; Yang, See-Hun

    2005-03-01

    Inelastic electron tunneling spectroscopy (IETS) and superconducting tunneling spectroscopy (STS) have been employed to investigate spin-dependent tunneling in magnetic tunnel junctions (MTJs). MTJs were studied in which the ferromagnetic electrodes were formed from the 3d transition metals, Fe, Co and Ni and their alloys, and the tunnel barriers were formed from various nitrides and oxides including MgO. MTJs with MgO barriers exhibit more than 220% tunneling magnetoresistance (TMR) at room temperature[1]. IETS was used to measure the contributions of defects and impurities, as well as phonons and magnons, to the tunneling current. These processes give rise to conductance peaks at characteristic voltages according to their excitation energies. STS was used to measure the spin polarization of the tunneling current as well as to explore the role of spin-flip scattering in the tunneling process. The goal of this research is a more complete understanding of the mechanisms which gives rise to the bias voltage dependence of the TMR as well as indirect tunneling through states in the barrier. [1] S. S. P. Parkin, C. Kaiser, A. Panchula, P. Rice, B. Hughes, M. Samant, and S.-H. Yang, Nature Materials, vol. Published online: 31 October 2004, 2004.

  11. Proceedings - Workshop on Materials Handling for Tunnel Construction

    DOT National Transportation Integrated Search

    1977-08-01

    With the anticipated increases in tunnel construction in the next decade, greater demands will be made on transportation sytems to remove tunnel muck at rates consistent with tunnel excavation rates. This workshop discussed and noted that conventiona...

  12. Automatic control of cryogenic wind tunnels

    NASA Technical Reports Server (NTRS)

    Balakrishna, S.

    1989-01-01

    Inadequate Reynolds number similarity in testing of scaled models affects the quality of aerodynamic data from wind tunnels. This is due to scale effects of boundary-layer shock wave interaction which is likely to be severe at transonic speeds. The idea of operation of wind tunnels using test gas cooled to cryogenic temperatures has yielded a quantrum jump in the ability to realize full scale Reynolds number flow similarity in small transonic tunnels. In such tunnels, the basic flow control problem consists of obtaining and maintaining the desired test section flow parameters. Mach number, Reynolds number, and dynamic pressure are the three flow parameters that are usually required to be kept constant during the period of model aerodynamic data acquisition. The series of activity involved in modeling, control law development, mechanization of the control laws on a microcomputer, and the performance of a globally stable automatic control system for the 0.3-m Transonic Cryogenic Tunnel (TCT) are discussed. A lumped multi-variable nonlinear dynamic model of the cryogenic tunnel, generation of a set of linear control laws for small perturbation, and nonlinear control strategy for large set point changes including tunnel trajectory control are described. The details of mechanization of the control laws on a 16 bit microcomputer system, the software features, operator interface, the display and safety are discussed. The controller is shown to provide globally stable and reliable temperature control to + or - 0.2 K, pressure to + or - 0.07 psi and Mach number to + or - 0.002 of the set point value. This performance is obtained both during large set point commands as for a tunnel cooldown, and during aerodynamic data acquisition with intrusive activity like geometrical changes in the test section such as angle of attack changes, drag rake movements, wall adaptation and sidewall boundary-layer removal. Feasibility of the use of an automatic Reynolds number control mode with

  13. Tunneling with a hydrodynamic pilot-wave model

    NASA Astrophysics Data System (ADS)

    Nachbin, André; Milewski, Paul A.; Bush, John W. M.

    2017-03-01

    Eddi et al. [Phys. Rev Lett. 102, 240401 (2009), 10.1103/PhysRevLett.102.240401] presented experimental results demonstrating the unpredictable tunneling of a classical wave-particle association as may arise when a droplet walking across the surface of a vibrating fluid bath approaches a submerged barrier. We here present a theoretical model that captures the influence of bottom topography on this wave-particle association and so enables us to investigate its interaction with barriers. The coupled wave-droplet dynamics results in unpredictable tunneling events. As reported in the experiments by Eddi et al. and as is the case in quantum tunneling [Gamow, Nature (London) 122, 805 (1928), 10.1038/122805b0], the predicted tunneling probability decreases exponentially with increasing barrier width. In the parameter regimes examined, tunneling between two cavities suggests an underlying stationary ergodic process for the droplet's position.

  14. Bell P-39 in the Icing Research Tunnel

    NASA Image and Video Library

    1944-11-21

    A Bell P-39 Airacobra in the NACA Aircraft Engine Research Laboratory’s Icing Research Tunnel for a propeller deicing study. The tunnel, which began operation in June 1944, was built to study the formation of ice on aircraft surfaces and methods of preventing or eradicating that ice. Ice buildup adds extra weight to aircraft, effects aerodynamics, and sometimes blocks airflow through engines. NACA design engineers added the Icing Research Tunnel to the new AERL’s original layout to take advantage of the massive refrigeration system being constructed for the Altitude Wind Tunnel. The Icing Research Tunnel is a closed-loop atmospheric wind tunnel with a 6- by 9-foot test section. The tunnel can produce speeds up to 300 miles per hour and temperatures from about 30 to –45⁰ F. During World War II AERL researchers analyzed different ice protection systems for propeller, engine inlets, antennae, and wings in the icing tunnel. The P-39 was a vital low-altitude pursuit aircraft of the US during the war. NACA investigators investigated several methods of preventing ice buildup on the P-39’s propeller, including the use of internal and external electrical heaters, alcohol, and hot gases. They found that continual heating of the blades expended more energy than the aircraft could supply, so studies focused on intermittent heating. The results of the wind tunnel investigations were then compared to actual flight tests on aircraft.

  15. Fixed-Gap Tunnel Junction for Reading DNA Nucleotides

    PubMed Central

    2015-01-01

    Previous measurements of the electronic conductance of DNA nucleotides or amino acids have used tunnel junctions in which the gap is mechanically adjusted, such as scanning tunneling microscopes or mechanically controllable break junctions. Fixed-junction devices have, at best, detected the passage of whole DNA molecules without yielding chemical information. Here, we report on a layered tunnel junction in which the tunnel gap is defined by a dielectric layer, deposited by atomic layer deposition. Reactive ion etching is used to drill a hole through the layers so that the tunnel junction can be exposed to molecules in solution. When the metal electrodes are functionalized with recognition molecules that capture DNA nucleotides via hydrogen bonds, the identities of the individual nucleotides are revealed by characteristic features of the fluctuating tunnel current associated with single-molecule binding events. PMID:25380505

  16. GdN nanoisland-based GaN tunnel junctions.

    PubMed

    Krishnamoorthy, Sriram; Kent, Thomas F; Yang, Jing; Park, Pil Sung; Myers, Roberto C; Rajan, Siddharth

    2013-06-12

    Tunnel junctions could have a great impact on gallium nitride and aluminum nitride-based devices such as light-emitting diodes and lasers by overcoming critical challenges related to hole injection and p-contacts. This paper demonstrates the use of GdN nanoislands to enhance interband tunneling and hole injection into GaN p-n junctions by several orders of magnitude, resulting in low tunnel junction specific resistivity (1.3 × 10(-3) Ω-cm(2)) compared to the previous results in wide band gap semiconductors. Tunnel injection of holes was confirmed by low-temperature operation of GaN p-n junction with a tunneling contact layer, and strong electroluminescence down to 20 K. The low tunnel junction resistance combined with low optical absorption loss in GdN is very promising for incorporation in GaN-based light emitters.

  17. Concurrent myotomy and tunneling after establishment of a half tunnel instead of myotomy after establishment of a full tunnel: a more efficient method of peroral endoscopic myotomy.

    PubMed

    Philips, George M; Dacha, Sunil; Keilin, Steve A; Willingham, Field F; Cai, Qiang

    2016-04-01

    Peroral endoscopic myotomy (POEM) is a time-consuming and challenging procedure. Traditionally, the myotomy is done after the submucosal tunnel has been completed. Starting the myotomy earlier, after submucosal tunneling is half completed (concurrent myotomy and tunneling), may be more efficient. This study aims to assess if the method of concurrent myotomy and tunneling may decrease the procedural time and be efficacious. This is a retrospective case series of patients who underwent modified POEM (concurrent myotomy and tunneling) or traditional POEM at a tertiary care medical center. Modified POEM or traditional POEM was performed at the discretion of the endoscopist in patients presenting with achalasia. The total procedural duration, myotomy duration, myotomy length, and time per unit length of myotomy were recorded for both modified and traditional POEM. Modified POEM was performed in 6 patients whose mean age (± standard deviation [SD]) was 58 ± 13.3 years. Of these, 5 patients had type II achalasia and 1 patient had esophageal dysmotility. The mean Eckardt score (± SD) before the procedure was 8.8 ± 1.3. The modified technique was performed in 47 ± 8 minutes, with 6 ± 1 minutes required per centimeter of myotomy and 3 ± 1 minutes required per centimeter of submucosal space. The Eckardt score was 3 ± 1.1 at 1 month and 3 ± 2.5 at 3 months. The procedure time for modified POEM was significantly shorter than that for traditional POEM. Modified POEM with short submucosal tunneling may be more efficient than traditional POEM with long submucosal tunneling, and outcomes may be equivalent over short-term follow-up. Long-term data and randomized controlled studies are needed to compare the clinical efficacy of modified POEM with that of the traditional method.

  18. Quantum Tunnelling to the Origin and Evolution of Life

    PubMed Central

    Trixler, Frank

    2013-01-01

    Quantum tunnelling is a phenomenon which becomes relevant at the nanoscale and below. It is a paradox from the classical point of view as it enables elementary particles and atoms to permeate an energetic barrier without the need for sufficient energy to overcome it. Tunnelling might seem to be an exotic process only important for special physical effects and applications such as the Tunnel Diode, Scanning Tunnelling Microscopy (electron tunnelling) or Near-field Optical Microscopy operating in photon tunnelling mode. However, this review demonstrates that tunnelling can do far more, being of vital importance for life: physical and chemical processes which are crucial in theories about the origin and evolution of life can be traced directly back to the effects of quantum tunnelling. These processes include the chemical evolution in stellar interiors and within the cold interstellar medium, prebiotic chemistry in the atmosphere and subsurface of planetary bodies, planetary habitability via insolation and geothermal heat as well as the function of biomolecular nanomachines. This review shows that quantum tunnelling has many highly important implications to the field of molecular and biological evolution, prebiotic chemistry and astrobiology. PMID:24039543

  19. Physics and Technology of Resonant-Tunneling Devices

    DTIC Science & Technology

    1992-07-01

    Negative differential resistance, quantum-well inductance, suppressed shot noise, superlattice tunneling, Type-Il heterostructures, lattice...of these deviations is carried out in the accompanying manuscript of Appendix C. 3.1.3. Superlattice Resonant Tunneling In the 1970s, interest in...resonant-tunneling was driven by the desire to observe long-range coherent transport phenomena, such as Bloch oscillations in superlattice structures. In

  20. Insertion of a straight peritoneal catheter in an arcuate subcutaneous tunnel by a tunneler: long-term experience.

    PubMed

    Favazza, A; Petri, R; Montanaro, D; Boscutti, G; Bresadola, F; Mioni, G

    1995-01-01

    This study describes the results of the insertion of a straight Tenckhoff peritoneal catheter (PC) in an arcuate, caudally concave tunnel using a tunneler designed by the authors. It has a semicircular shape and a bending radius of 4.5 cm. A hospital renal unit. From June 1988 to February 1994, 112 straight Tenckhoff PCs, 62 with one deep cuff (single-cuff PC) and 50 with two cuffs (double-cuff PC), were inserted as first catheters in 112 patients (mean age 62 +/- 13 years), who underwent continuous ambulatory peritoneal dialysis (CAPD). The follow-up was 1099 months (mean 18 +/- 13 months) for single-cuff PCs and 1264 months (mean 25 +/- 15 months) for double-cuff PCs, respectively. After intraperitoneal placement of the PCs by median laparotomy, a 180 degrees arc bend tunnel, with both external and peritoneal exits directed downwards, was created by means of the tunneler. The rate of exit-site infection (ESI) was 0.27 episodes/year (epis/year). The probability of remaining ESI-free was 76%, 60%, and 55% at 1, 2, and 3 years. The rate of tunnel infection (TI) was 0.046 epis/year. The incidence of the double-cuff PC-related ESI and TI tended to be lower than the incidence observed with the single-cuff PC. Episodes of peritonitis were 60 (0.30 epis/year), where 6 were subsequent to ESI and/or TI. Two PCs were lost due to ESI, 3 due to TI, and 11 due to peritonitis. Drainage failure, due to displacement of the PC caused by straightening, involved 3 PCs; 2 were lost. PC survival was 92%, 82%, and 74% at 1, 2 and 3 years, respectively. By an easily used semicircular tunneler, the standard straight Tenckhoff PC can be stably positioned in an arcuate tunnel with both inner and outer exits directed downwards. This tunnel shape, as already suggested by some authors, appears to be an effective technical solution to reducing the PC-related complication rates.

  1. Band-to-band tunneling distance analysis in the heterogate electron–hole bilayer tunnel field-effect transistor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Padilla, J. L., E-mail: jose.padilladelatorre@epfl.ch; Departamento de Electrónica y Tecnología de los Computadores, Universidad de Granada, Avda. Fuentenueva s/n, 18071 Granada; Palomares, A.

    In this work, we analyze the behavior of the band-to-band tunneling distance between electron and hole subbands resulting from field-induced quantum confinement in the heterogate electron–hole bilayer tunnel field-effect transistor. We show that, analogously to the explicit formula for the tunneling distance that can be easily obtained in the semiclassical framework where the conduction and valence band edges are allowed states, an equivalent analytical expression can be derived in the presence of field-induced quantum confinement for describing the dependence of the tunneling distance on the body thickness and material properties of the channel. This explicit expression accounting for quantum confinementmore » holds valid provided that the potential wells for electrons and holes at the top and bottom of the channel can be approximated by triangular profiles. Analytical predictions are compared to simulation results showing very accurate agreement.« less

  2. Wind tunnel model and method

    NASA Technical Reports Server (NTRS)

    Jackson, C. M., Jr.; Summerfield, D. G. (Inventor)

    1974-01-01

    The design and development of a wind tunnel model equipped with pressure measuring devices are discussed. The pressure measuring orifices are integrally constructed in the wind tunnel model and do not contribute to distortions of the aerodynamic surface. The construction of a typical model is described and a drawing of the device is included.

  3. Ferroelectric tunneling element and memory applications which utilize the tunneling element

    DOEpatents

    Kalinin, Sergei V [Knoxville, TN; Christen, Hans M [Knoxville, TN; Baddorf, Arthur P [Knoxville, TN; Meunier, Vincent [Knoxville, TN; Lee, Ho Nyung [Oak Ridge, TN

    2010-07-20

    A tunneling element includes a thin film layer of ferroelectric material and a pair of dissimilar electrically-conductive layers disposed on opposite sides of the ferroelectric layer. Because of the dissimilarity in composition or construction between the electrically-conductive layers, the electron transport behavior of the electrically-conductive layers is polarization dependent when the tunneling element is below the Curie temperature of the layer of ferroelectric material. The element can be used as a basis of compact 1R type non-volatile random access memory (RAM). The advantages include extremely simple architecture, ultimate scalability and fast access times generic for all ferroelectric memories.

  4. The Ames 12-Foot Pressure Tunnel: Tunnel Empty Flow Calibration Results and Discussion

    NASA Technical Reports Server (NTRS)

    Zell, Peter T.; Banducci, David E. (Technical Monitor)

    1996-01-01

    An empty test section flow calibration of the refurbished NASA Ames 12-Foot Pressure Tunnel was recently completed. Distributions of total pressure, dynamic pressure, Mach number, flow angularity temperature, and turbulence are presented along with results obtained prior to facility demolition. Axial static pressure distributions along tunnel centerline are also compared. Test section model support geometric configurations will be presented along with a discussion of the issues involved with different model mounting schemes.

  5. Water-level, velocity, and dye measurements in the Chicago tunnels

    USGS Publications Warehouse

    Oberg, K.A.; Schmidt, A.R.; ,

    1993-01-01

    On April 13, 1992, a section of a 100-year-old underground freight tunnel in downtown Chicago, Illinois was breached where the tunnel crosses under the Chicago River, about 15 meters below land surface. The breach allowed water from the Chicago River to flow into the freight tunnels and into buildings connected to the tunnels. As a result, utility services to more than 100 buildings in downtown Chicago were lost, several hundred thousand workers were sent home, and the entire subway system and a major expressway in the Loop were shut down. The breach in the tunnel was sealed and the tunnel dewatered by the U.S. Army Corps of Engineers (Corps) and its contractors. The U.S. Geological Survey (USGS) assisted the Corps in their efforts to plug and dewater the freight tunnels and connected buildings. This assistance included the installation and operation of telemetered gages for monitoring water levels in the tunnel system and velocity measurements made in the vicinity of the tunnel breach. A fluorescent dye tracer was used to check for leaks in the plugs, which isolated the damaged portion of the Chicago freight tunnel from the remainder of the tunnel system.

  6. Methods for the fabrication of thermally stable magnetic tunnel junctions

    DOEpatents

    Chang, Y Austin [Middleton, WI; Yang, Jianhua J [Madison, WI; Ladwig, Peter F [Hutchinson, MN

    2009-08-25

    Magnetic tunnel junctions and method for making the magnetic tunnel junctions are provided. The magnetic tunnel junctions are characterized by a tunnel barrier oxide layer sandwiched between two ferromagnetic layers. The methods used to fabricate the magnetic tunnel junctions are capable of completely and selectively oxidizing a tunnel junction precursor material using an oxidizing gas containing a mixture of gases to provide a tunnel junction oxide without oxidizing the adjacent ferromagnetic materials. In some embodiments the gas mixture is a mixture of CO and CO.sub.2 or a mixture of H.sub.2 and H.sub.2O.

  7. Tunneling : the State of the Industry

    DOT National Transportation Integrated Search

    1976-05-01

    Tunneling is examined as an industry. The demand for its services, the makeup of the industry, some history and its problems and prospects, are analyzed. Industry participants are listed: owners, engineer firms, tunnel builders and specialized suppli...

  8. Nonoccupational Risk Factors for Carpal Tunnel Syndrome

    PubMed Central

    Solomon, Daniel H; Katz, Jeffrey N; Bohn, Rhonda; Mogun, Helen; Avorn, Jerry

    1999-01-01

    OBJECTIVE To examine the relation between selected nonoccupational risk factors and surgery for carpal tunnel syndrome. DESIGN Case-control study using an administrative database. PARTICIPANTS Enrollees of New Jersey Medicare or Medicaid programs during 1989 to 1991. MEASUREMENTS The outcome of interest was open or endoscopic carpal tunnel release. We examined the relation between carpal tunnel release and diabetes mellitus, thyroid disease, inflammatory arthritis, hemodialysis, pregnancy, use of corticosteroids, and hormone replacement therapy. MAIN RESULTS In multivariate models, inflammatory arthritis was strongly associated with carpal tunnel release (odds ratio [OR] 2.9; 95% confidence interval [CI] 2.2, 3.8). However, corticosteroid use also appeared to be associated with a greater likelihood of undergoing carpal tunnel release, even in the absence of inflammatory arthritis (OR 1.6; 95% CI 1.2, 2.1). Diabetes had a weak but significant association with carpal tunnel release (OR 1.4; 95% CI 1.2, 1.8), as did hypothyroidism (OR 1.7; 95% CI 1.1, 2.8), although patients with hyperthyroidism did not have any change in risk. Women who underwent carpal tunnel release were almost twice as likely to be users of estrogen replacement therapy as controls (OR 1.8; 95% CI 1.0, 3.2). CONCLUSIONS Although inflammatory arthritis is the most important nonoccupational risk factor for carpal tunnel release, these data substantiate the increase in risk associated with diabetes and untreated hypothyroidism. Further investigation in detailed clinical studies will be necessary to confirm whether changes in corticosteroid use and hormone replacement therapy offer additional means of risk reduction for this common condition. PMID:10337041

  9. Systems tunnel linear shaped charge lightning strike

    NASA Technical Reports Server (NTRS)

    Cook, M.

    1989-01-01

    Simulated lightning strike testing of the systems tunnel linear shaped charge (LSC) was performed at the Thiokol Lightning Test Complex in Wendover, Utah, on 23 Jun. 1989. The test article consisted of a 160-in. section of the LSC enclosed within a section of the systems tunnel. The systems tunnel was bonded to a section of a solid rocket motor case. All test article components were full scale. The systems tunnel cover of the test article was subjected to three discharges (each discharge was over a different grounding strap) from the high-current generator. The LSC did not detonate. All three grounding straps debonded and violently struck the LSC through the openings in the systems tunnel floor plates. The LSC copper surface was discolored around the areas of grounding strap impact, and arcing occurred at the LSC clamps and LSC ends. This test verified that the present flight configuration of the redesigned solid rocket motor systems tunnel, when subjected to simulated lightning strikes with peak current levels within 71 percent of the worst-case lightning strike condition of NSTS-07636, is adequate to prevent LSC ignition. It is therefore recommended that the design remain unchanged.

  10. Role of interface layers on Tunneling Magnetoresistance

    NASA Astrophysics Data System (ADS)

    Yang, See-Hun; Samant, Mahesh; Parkin, Stuart S. P.

    2002-03-01

    Thin non-magnetic metallic layers inserted at the interface between tunneling barriers and the ferromagnetic electrodes in magnetic tunnel junctions quenches the magnetoresistance (TMR) exhibited by some structures[1]. Studies have been carried out on exchange biased magnetic tunnel junction structures in which one of the ferromagnetic electrodes is pinned by coupling to IrMn or PtMn antiferromagnetic layers. For metallic aluminum interface layers thicknesses of just a few angstrom completely suppress the TMR although this characteristic thickness depends on the roughness of the tunneling barrier. A variety of structures will be discussed in which a number of interface layers have been introduced. In particular results for insertion of Cu, Ru and Cr layers on either side of the tunnel barrier will be presented. A number of techniques including XANES, XMCD and high resolution cross-section transmission electron microscopy have been used to study the structure and morphology of the interface layers and to correlate the structure of these layers with the magneto-transport properties of the tunneling junctions. [1] S.S.P. Parkin, US patent 5,764,567 issued by the United States Patent and Trademark Office, June 9, 1998.

  11. Calibration of transonic and supersonic wind tunnels

    NASA Technical Reports Server (NTRS)

    Reed, T. D.; Pope, T. C.; Cooksey, J. M.

    1977-01-01

    State-of-the art instrumentation and procedures for calibrating transonic (0.6 less than M less than 1.4) and supersonic (M less than or equal to 3.5) wind tunnels were reviewed and evaluated. Major emphasis was given to transonic tunnels. Continuous, blowdown and intermittent tunnels were considered. The required measurements of pressure, temperature, flow angularity, noise and humidity were discussed, and the effects of measurement uncertainties were summarized. A comprehensive review of instrumentation currently used to calibrate empty tunnel flow conditions was included. The recent results of relevant research are noted and recommendations for achieving improved data accuracy are made where appropriate. It is concluded, for general testing purposes, that satisfactory calibration measurements can be achieved in both transonic and supersonic tunnels. The goal of calibrating transonic tunnels to within 0.001 in centerline Mach number appears to be feasible with existing instrumentation, provided correct calibration procedures are carefully followed. A comparable accuracy can be achieved off-centerline with carefully designed, conventional probes, except near Mach 1. In the range 0.95 less than M less than 1.05, the laser Doppler velocimeter appears to offer the most promise for improved calibration accuracy off-centerline.

  12. III-V heterostructure tunnel field-effect transistor.

    PubMed

    Convertino, C; Zota, C B; Schmid, H; Ionescu, A M; Moselund, K E

    2018-07-04

    The tunnel field-effect transistor (TFET) is regarded as one of the most promising solid-state switches to overcome the power dissipation challenge in ultra-low power integrated circuits. TFETs take advantage of quantum mechanical tunneling hence exploit a different current control mechanism compared to standard MOSFETs. In this review, we describe state-of-the-art development of TFET both in terms of performances and of materials integration and we identify the main remaining technological challenges such as heterojunction defects and oxide/channel interface traps causing trap-assisted-tunneling (TAT). Mesa-structures, planar as well as vertical geometries are examined. Conductance slope analysis on InAs/GaSb nanowire tunnel diodes are reported, these two-terminal measurements can be relevant to investigate the tunneling behavior. A special focus is dedicated to III-V heterostructure TFET, as different groups have recently shown encouraging results achieving the predicted sub-thermionic low-voltage operation.

  13. III–V heterostructure tunnel field-effect transistor

    NASA Astrophysics Data System (ADS)

    Convertino, C.; Zota, C. B.; Schmid, H.; Ionescu, A. M.; Moselund, K. E.

    2018-07-01

    The tunnel field-effect transistor (TFET) is regarded as one of the most promising solid-state switches to overcome the power dissipation challenge in ultra-low power integrated circuits. TFETs take advantage of quantum mechanical tunneling hence exploit a different current control mechanism compared to standard MOSFETs. In this review, we describe state-of-the-art development of TFET both in terms of performances and of materials integration and we identify the main remaining technological challenges such as heterojunction defects and oxide/channel interface traps causing trap-assisted-tunneling (TAT). Mesa-structures, planar as well as vertical geometries are examined. Conductance slope analysis on InAs/GaSb nanowire tunnel diodes are reported, these two-terminal measurements can be relevant to investigate the tunneling behavior. A special focus is dedicated to III–V heterostructure TFET, as different groups have recently shown encouraging results achieving the predicted sub-thermionic low-voltage operation.

  14. Superpoissonian shot noise in organic magnetic tunnel junctions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cascales, Juan Pedro; Martinez, Isidoro; Aliev, Farkhad G., E-mail: farkhad.aliev@uam.es

    Organic molecules have recently revolutionized ways to create new spintronic devices. Despite intense studies, the statistics of tunneling electrons through organic barriers remains unclear. Here, we investigate conductance and shot noise in magnetic tunnel junctions with 3,4,9,10-perylene-teracarboxylic dianhydride (PTCDA) barriers a few nm thick. For junctions in the electron tunneling regime, with magnetoresistance ratios between 10% and 40%, we observe superpoissonian shot noise. The Fano factor exceeds in 1.5–2 times the maximum values reported for magnetic tunnel junctions with inorganic barriers, indicating spin dependent bunching in tunneling. We explain our main findings in terms of a model which includes tunnelingmore » through a two level (or multilevel) system, originated from interfacial bonds of the PTCDA molecules. Our results suggest that interfaces play an important role in the control of shot noise when electrons tunnel through organic barriers.« less

  15. Spin-dependent transport in antiferromagnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Merodio, P.; Kalitsov, A.; Béa, H.; Baltz, V.; Chshiev, M.

    2014-09-01

    We investigate the behaviour of spin transfer torque (STT) and tunnelling magnetoresistance (TMR) in epitaxial antiferromagnetic-based tunnel junctions using tight binding calculations in the framework of the Keldysh formalism. We find that the STT out-of-plane component exhibits a staggered spatial distribution similar to its in-plane component. This behaviour is specific to the use of a tunnel barrier and significantly differs from the out-of-plane torques reported in previous works using a metallic spacer. Additionally, we show that unlike conventional ferromagnetic-based tunnel junctions, the TMR can increase with applied bias and reach values comparable to typical magnetoresistances found for usual spin valves.

  16. Experience in design and construction of the Log tunnel

    NASA Astrophysics Data System (ADS)

    Jovičić, Vojkan; Goleš, Niko; Tori, Matija; Peternel, Miha; Vajović, Stanojle; Muhić, Elvir

    2017-09-01

    A twin highway Log tunnel is a part of a new motorway connection between Maribor and Zagreb, section Draženci-Gru\\vskovje, which is located towards the border crossing between Slovenia and Croatia. The tunnel is currently under construction, and only the excavation works have been completed during the writing of this paper. The terrain in the area of the Log tunnel is diverse, and the route of the highway in its vicinity is characterised by deep excavations, bridges or viaducts. The Log tunnel is approximately 250 m long, partly constructed as a gallery. The geological conditions are dominated by Miocene base rock, featuring layers of well-connected clastic rocks, which are covered by diluvium clays, silts, sands and gravels of different thicknesses. Due to the short length of the tunnel, the usual separation of the motorway route to the left and the right tunnel axes was not carried out. Thus, the tunnel was constructed with an intermediate pillar and was designed as a three-lane tunnel, including the stopping lane. The construction of the tunnel was carried out using the New Austrian tunnelling method (NATM), in which the central adit was excavated first and the intermediate pillar was constructed within it. The excavation of the main tubes followed and was divided into the top heading, bench and the invert, enabling the intermediate pillar to take the load off the top heading of both tubes. The secondary lining of the tunnel is currently under construction. The experience of the tunnel construction gathered so far is presented in the paper. The main emphasis is on the construction of the intermediate pillar, which had to take the significant and asymmetrical ground load.

  17. Understanding quantum tunneling using diffusion Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Inack, E. M.; Giudici, G.; Parolini, T.; Santoro, G.; Pilati, S.

    2018-03-01

    In simple ferromagnetic quantum Ising models characterized by an effective double-well energy landscape the characteristic tunneling time of path-integral Monte Carlo (PIMC) simulations has been shown to scale as the incoherent quantum-tunneling time, i.e., as 1 /Δ2 , where Δ is the tunneling gap. Since incoherent quantum tunneling is employed by quantum annealers (QAs) to solve optimization problems, this result suggests that there is no quantum advantage in using QAs with respect to quantum Monte Carlo (QMC) simulations. A counterexample is the recently introduced shamrock model (Andriyash and Amin, arXiv:1703.09277), where topological obstructions cause an exponential slowdown of the PIMC tunneling dynamics with respect to incoherent quantum tunneling, leaving open the possibility for potential quantum speedup, even for stoquastic models. In this work we investigate the tunneling time of projective QMC simulations based on the diffusion Monte Carlo (DMC) algorithm without guiding functions, showing that it scales as 1 /Δ , i.e., even more favorably than the incoherent quantum-tunneling time, both in a simple ferromagnetic system and in the more challenging shamrock model. However, a careful comparison between the DMC ground-state energies and the exact solution available for the transverse-field Ising chain indicates an exponential scaling of the computational cost required to keep a fixed relative error as the system size increases.

  18. Ac electronic tunneling at optical frequencies

    NASA Technical Reports Server (NTRS)

    Faris, S. M.; Fan, B.; Gustafson, T. K.

    1974-01-01

    Rectification characteristics of non-superconducting metal-barrier-metal junctions deduced from electronic tunneling have been observed experimentally for optical frequency irradiation of the junction. The results provide verification of optical frequency Fermi level modulation and electronic tunneling current modulation.

  19. Evanescent Modes and Tunnelling Instantaneously Act at a Distance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nimtz, Guenter; Stahlhofen, Alfons A.

    Photonic tunnelling experiments have shown that i) the Einstein energy relation is violated, ii) the tunnelling process is non-local, iii) the signal velocity is faster than light, i.e. superluminal, iv) the tunnelling signal is not observable, since photonic tunnelling is described by virtual photons, and v) according to the experimental results the signal velocity is infinite inside the barriers, implying that tunnelling instantaneously acts at a distance. We think these properties are not compatible with the claims of many text books on Special Relativity.

  20. High tunnels: protection for rather than from insect pests?

    PubMed

    Ingwell, Laura L; Thompson, Sarah L; Kaplan, Ian; Foster, Ricky E

    2017-12-01

    High tunnels are a season extension tool creating a hybrid of field and greenhouse growing conditions. High tunnels have recently increased in the USA and thus research on their management is lacking. One purported advantage of these structures is protection from common field pests, but evidence to support this claim is lacking. We compared insect pest populations in high tunnels with field production over two years for three crops: tomato, broccoli and cucumber. Greenhouse pests (e.g. aphids, whiteflies) were more prevalent in high tunnels, compared to field plots. Hornworms (tobacco (Manduca sexta L.) and tomato (M. quinquemaculata Haworth)), a common field pest on tomato, were also more abundant in high tunnels, requiring chemical control while field populations were low. The crucifer caterpillar complex (imported cabbageworm (Pieris rapae L.), diamondback moth (Plutella xylostella L.) and cabbage looper (Trichoplusia ni Hübner)) was also more abundant in high tunnels in 2010. Cucumber beetle (striped (Acalymma vittatum F.) and spotted (Diabrotica undecimpunctata Mannerheim)) densities were higher in high tunnels in 2010 and field plots in 2011. The common assumption that high tunnels offer protection from field pests was not supported. Instead, high tunnel growing conditions may facilitate higher pest populations. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  1. Effect of an Interfacial Layer on Electron Tunneling through Atomically Thin Al2O3 Tunnel Barriers.

    PubMed

    Wilt, Jamie; Sakidja, Ridwan; Goul, Ryan; Wu, Judy Z

    2017-10-25

    Electron tunneling through high-quality, atomically thin dielectric films can provide a critical enabling technology for future microelectronics, bringing enhanced quantum coherent transport, fast speed, small size, and high energy efficiency. A fundamental challenge is in controlling the interface between the dielectric and device electrodes. An interfacial layer (IL) will contain defects and introduce defects in the dielectric film grown atop, preventing electron tunneling through the formation of shorts. In this work, we present the first systematic investigation of the IL in Al 2 O 3 dielectric films of 1-6 Å's in thickness on an Al electrode. We integrated several advanced approaches: molecular dynamics to simulate IL formation, in situ high vacuum sputtering atomic layer deposition (ALD) to synthesize Al 2 O 3 on Al films, and in situ ultrahigh vacuum scanning tunneling spectroscopy to probe the electron tunneling through the Al 2 O 3 . The IL had a profound effect on electron tunneling. We observed a reduced tunnel barrier height and soft-type dielectric breakdown which indicate that defects are present in both the IL and in the Al 2 O 3 . The IL forms primarily due to exposure of the Al to trace O 2 and/or H 2 O during the pre-ALD heating step of fabrication. As the IL was systematically reduced, by controlling the pre-ALD sample heating, we observed an increase of the ALD Al 2 O 3 barrier height from 0.9 to 1.5 eV along with a transition from soft to hard dielectric breakdown. This work represents a key step toward the realization of high-quality, atomically thin dielectrics with electron tunneling for the next generation of microelectronics.

  2. Water Intrusion Problems in Transit Tunnels

    DOT National Transportation Integrated Search

    1986-05-01

    This report presents the findings of five case studies in which an in-depth analysis was made of tunnel water intrusion problems in transit tunnels. Water intrusion parameters of transit systems in Atlanta, Boston, Buffalo, New York and Washington, D...

  3. Electrochemistry at a Metal Nanoparticle on a Tunneling Film: A Steady-State Model of Current Densities at a Tunneling Ultramicroelectrode.

    PubMed

    Hill, Caleb M; Kim, Jiyeon; Bard, Allen J

    2015-09-09

    Here, a new methodology is proposed for treating electrochemical current densities in metal-insulator-metal nanoparticle (M-I-MNP) systems. The described model provides broad, practical insights about MNP-mediated electron transfer to redox species in solution, where electron transfer from the underlying electrode to a MNP via tunneling and heterogeneous electron transfer from the MNP to redox species in solution are treated as sequential steps. Tunneling is treated through an adaptation of the Simmons model of tunneling in metal-insulator-metal structures, and explicit equations are provided for tunneling currents, which demonstrate the effect of various experimental parameters, such as insulator thickness and MNP size. Overall, a general approach is demonstrated for determining experimental conditions where tunneling will have a measurable impact on the electrochemistry of M-I-MNP systems.

  4. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test Primary Partical Mean Size a (µm) Full Wind Tunnel Test 2 km/hr 24 km/hr Inlet...

  5. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test Primary Partical Mean Size a (µm) Full Wind Tunnel Test 2 km/hr 24 km/hr Inlet...

  6. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test Primary Partical Mean Size a (µm) Full Wind Tunnel Test 2 km/hr 24 km/hr Inlet...

  7. Evaluation of the Space Shuttle Transatlantic Abort Landing Atmospheric Sounding System

    NASA Technical Reports Server (NTRS)

    Leahy, Frank B.

    2004-01-01

    This paper describes a study that was conducted to determine the quality of thermodynamic and wind data measured by the Space Shuttle Transatlantic Abort Landing (TAL) Atmospheric Sounding System (TASS). The system has Global Positioning System (GPS) tracking capability and provides profiles of atmospheric parameters such as temperature, relative humidity, and wind in support of potential emergency Space Shuttle landings at TAL sites. Ten comparison flights between the Low-Resolution Flight Element (LRFE) of the Automated Meteorological Profiling System (AMPS) and TASS were conducted at the Eastern Test Range (ETR) in early 2002. Initial results indicated that wind, temperature, and relative humidity compared well. However, incorrect GPS settings in the TASS software were resulting in altitude differences of about 60 to 70 m (approximately 200 to 230 ft) and air pressure differences of approximately 4 hectoPascals (hPa). TASS software updates to correct altitude data were completed in early 2003. Subsequent testing showed that altitude and air pressure differences were generally less than 5 m and 1 hPa, respectively.

  8. Navigation Architecture For A Space Mobile Network

    NASA Technical Reports Server (NTRS)

    Valdez, Jennifer E.; Ashman, Benjamin; Gramling, Cheryl; Heckler, Gregory W.; Carpenter, Russell

    2016-01-01

    The Tracking and Data Relay Satellite System (TDRSS) Augmentation Service for Satellites (TASS) is a proposed beacon service to provide a global, space-based GPS augmentation service based on the NASA Global Differential GPS (GDGPS) System. The TASS signal will be tied to the GPS time system and usable as an additional ranging and Doppler radiometric source. Additionally, it will provide data vital to autonomous navigation in the near Earth regime, including space weather information, TDRS ephemerides, Earth Orientation Parameters (EOP), and forward commanding capability. TASS benefits include enhancing situational awareness, enabling increased autonomy, and providing near real-time command access for user platforms. As NASA Headquarters Space Communication and Navigation Office (SCaN) begins to move away from a centralized network architecture and towards a Space Mobile Network (SMN) that allows for user initiated services, autonomous navigation will be a key part of such a system. This paper explores how a TASS beacon service enables the Space Mobile Networking paradigm, what a typical user platform would require, and provides an in-depth analysis of several navigation scenarios and operations concepts.

  9. Statistical approach to tunneling time in attosecond experiments

    NASA Astrophysics Data System (ADS)

    Demir, Durmuş; Güner, Tuğrul

    2017-11-01

    Tunneling, transport of particles through classically forbidden regions, is a pure quantum phenomenon. It governs numerous phenomena ranging from single-molecule electronics to donor-acceptor transition reactions. The main problem is the absence of a universal method to compute tunneling time. This problem has been attacked in various ways in the literature. Here, in the present work, we show that a statistical approach to the problem, motivated by the imaginary nature of time in the forbidden regions, lead to a novel tunneling time formula which is real and subluminal (in contrast to various known time definitions implying superluminal tunneling). In addition to this, we show explicitly that the entropic time formula is in good agreement with the tunneling time measurements in laser-driven He ionization. Moreover, it sets an accurate range for long-range electron transfer reactions. The entropic time formula is general enough to extend to the photon and phonon tunneling phenomena.

  10. 1. West portal of Tunnel 26, contextual view to northeast ...

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

    1. West portal of Tunnel 26, contextual view to northeast from atop Tunnel 25 (HAER CA-201), with Tunnel 27 (HAER CA-203) visible in distance, 210mm lens. View is along new line, with original Central Pacific Transcontinental line crossing over the top above Tunnel 26. - Central Pacific Transcontinental Railroad, Tunnel No. 26, Milepost 133.29, Applegate, Placer County, CA

  11. Anatomical variations of the carpal tunnel structures

    PubMed Central

    Mitchell, Ryan; Chesney, Amy; Seal, Shane; McKnight, Leslie; Thoma, Achilleas

    2009-01-01

    There are many anatomical variations in and around the carpal tunnel that affect the nerves, tendons and arteries in this area. Awareness of these variations is important both during the clinical examination and during carpal tunnel release. The purpose of the present review is to highlight recognized anatomical variations within the carpal tunnel including variation in nerve anatomy, tendon anatomical variants, vascular anatomical variations and muscle anatomical variations. PMID:20808747

  12. General risks for tunnelling projects: An overview

    NASA Astrophysics Data System (ADS)

    Siang, Lee Yong; Ghazali, Farid E. Mohamed; Zainun, Noor Yasmin; Ali, Roslinda

    2017-10-01

    Tunnels are indispensable when installing new infrastructure as well as when enhancing the quality of existing urban living due to their unique characteristics and potential applications. Over the past few decades, there has been a significant increase in the building of tunnels, world-wide. Tunnelling projects are complex endeavors, and risk assessment for tunnelling projects is likewise a complex process. Risk events are often interrelated. Occurrence of a technical risk usually carries cost and schedule consequences. Schedule risks typically impact cost escalation and project overhead. One must carefully consider the likelihood of a risk's occurrence and its impact in the context of a specific set of project conditions and circumstances. A project's goals, organization, and environment impacts in the context of a specific set of project conditions and circumstances. Some projects are primarily schedule driven; other projects are primarily cost or quality driven. Whether a specific risk event is perceived fundamentally as a cost risk or a schedule risk is governed by the project-specific context. Many researchers have pointed out the significance of recognition and control of the complexity, and risks of tunnelling projects. Although all general information on a project such as estimated duration, estimated cost, and stakeholders can be obtained, it is still quite difficult to accurately understand, predict and control the overall situation and development trends of the project, leading to the risks of tunnelling projects. This paper reviews all the key risks for tunnelling projects from several case studies that have been carried out by other researchers. These risks have been identified and reviewed in this paper. As a result, the current risk management plan in tunnelling projects can be enhanced by including all these reviewed risks as key information.

  13. Transportation of Tunnel Muck by Pipeline

    DOT National Transportation Integrated Search

    1978-01-01

    The view reflected herein is that if the advancement of the technology of muck removal does not keep pace with advances in tunneling machine technology, muck removal can become the limiting constraint on the forward movement of the tunnel face, and h...

  14. Uncooled tunneling infrared sensor

    NASA Technical Reports Server (NTRS)

    Kenny, Thomas W. (Inventor); Kaiser, William J. (Inventor); Podosek, Judith A. (Inventor); Vote, Erika C. (Inventor); Muller, Richard E. (Inventor); Maker, Paul D. (Inventor)

    1995-01-01

    An uncooled infrared tunneling sensor in which the only moving part is a diaphragm which is deflected into contact with a micromachined silicon tip electrode prepared by a novel lithographic process. Similarly prepared deflection electrodes employ electrostatic force to control the deflection of a silicon nitride, flat diaphragm membrane. The diaphragm exhibits a high resonant frequency which reduces the sensor's sensitivity to vibration. A high bandwidth feedback circuit controls the tunneling current by adjusting the deflection voltage to maintain a constant deflection of the membrane. The resulting infrared sensor can be miniaturized to pixel dimensions smaller than 100 .mu.m. An alternative embodiment is implemented using a corrugated membrane to permit large deflection without complicated clamping and high deflection voltages. The alternative embodiment also employs a pinhole aperture in a membrane to accommodate environmental temperature variation and a sealed chamber to eliminate environmental contamination of the tunneling electrodes and undesireable accoustic coupling to the sensor.

  15. Resonant Tunneling Spin Pump

    NASA Technical Reports Server (NTRS)

    Ting, David Z.

    2007-01-01

    The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

  16. Relativistic features and time delay of laser-induced tunnel ionization

    NASA Astrophysics Data System (ADS)

    Yakaboylu, Enderalp; Klaiber, Michael; Bauke, Heiko; Hatsagortsyan, Karen Z.; Keitel, Christoph H.

    2013-12-01

    The electron dynamics in the classically forbidden region during relativistic tunnel ionization is investigated. The classical forbidden region in the relativistic regime is identified by defining a gauge-invariant total-energy operator. Introducing position-dependent energy levels inside the tunneling barrier, we demonstrate that the relativistic tunnel ionization can be well described by a one-dimensional intuitive picture. This picture predicts that, in contrast to the well-known nonrelativistic regime, the ionized electron wave packet arises with a momentum shift along the laser's propagation direction. This is compatible with results from a strong-field approximation calculation where the binding potential is assumed to be zero ranged. Further, the tunneling time delay, stemming from Wigner's definition, is investigated for model configurations of tunneling and compared with results obtained from the exact propagator. By adapting Wigner's time delay definition to the ionization process, the tunneling time is investigated in the deep-tunneling and in the near-threshold-tunneling regimes. It is shown that while in the deep-tunneling regime signatures of the tunneling time delay are not measurable at remote distance, they are detectable, however, in the latter regime.

  17. Tunneling time in space fractional quantum mechanics

    NASA Astrophysics Data System (ADS)

    Hasan, Mohammad; Mandal, Bhabani Prasad

    2018-02-01

    We calculate the time taken by a wave packet to travel through a classically forbidden region of space in space fractional quantum mechanics. We obtain the close form expression of tunneling time from a rectangular barrier by stationary phase method. We show that tunneling time depends upon the width b of the barrier for b → ∞ and therefore Hartman effect doesn't exist in space fractional quantum mechanics. Interestingly we found that the tunneling time monotonically reduces with increasing b. The tunneling time is smaller in space fractional quantum mechanics as compared to the case of standard quantum mechanics. We recover the Hartman effect of standard quantum mechanics as a special case of space fractional quantum mechanics.

  18. A small cable tunnel inspection robot design

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaolong; Guo, Xiaoxue; Huang, Jiangcheng; Xiao, Jie

    2017-04-01

    Modern city mainly rely on internal electricity cable tunnel, this can reduce the influence of high voltage over-head lines of urban city appearance and function. In order to reduce the dangers of cable tunnel artificial inspection and high labor intensity, we design a small caterpillar chassis in combination with two degrees of freedom robot with two degrees of freedom camera pan and tilt, used in the cable tunnel inspection work. Caterpillar chassis adopts simple return roller, damping structure. Mechanical arm with three parallel shafts, finish the up and down and rotated action. Two degrees of freedom camera pan and tilt are used to monitor cable tunnel with 360 °no dead angle. It looks simple, practical and efficient.

  19. Electronic structure of sputter deposited MgO(100) tunnel barriers in magnetic tunnel junction structures exhibiting giant tunneling magnetoresistance

    NASA Astrophysics Data System (ADS)

    Yang, See-Hun; Samant, Mahesh; Parkin, Stuart

    2007-03-01

    Giant tunneling magnetoresistance (TMR) in magnetic tunnel junctions formed with crystalline MgO tunnel barriers [1] have potential applications in a wide variety of spintronic devices. However, the relationship of the TMR to the detailed chemical and electronic structure of the MgO barrier and its interfaces with the ferromagnetic electrodes is not yet fully understood. We have carried out valence band photoemission spectroscopy and x-ray absorption spectroscopy to characterize the chemical state and electronic structure of sputter deposited, highly oriented, MgO (001) barriers and its interfaces with ferromagnetic electrodes. A large band gap of ˜7.5 eV is found even for ultrathin MgO layers. This is consistent with barrier heights found from fitting current versus voltage curves providing that very small effective electron masses are used. We discuss the role of thin Mg interface layers that we have used to reduce oxidation of the underlying ferromagnetic layer during the MgO layer formation [1]. [1] S. S. P. Parkin, C. Kaiser, A. Panchula, P. M. Rice, B. Hughes, M. Samant, S.-H. Yang, Nature Materials 3, 862 (2004).

  20. Insertion of tunneled hemodialysis catheters without fluoroscopy.

    PubMed

    Motta Elias, Rosilene; da Silva Makida, Sonia Cristina; Abensur, Hugo; Martins Castro, Manuel Carlos; Affonso Moysés, Rosa Maria; Pereira, Benedito Jorge; Bueno de Oliveira, Rodrigo; Luders, Cláudio; Romão, João Egidio

    2010-01-01

    The tunneled cuffed catheter (TCC) is used as a bridge access for hemodialysis. Few prospective studies have been designed to evaluate conversion from non-tunneled to TCC without the use of fluoroscopy when performed by nephrologists. We performed an observational prospective cohort in incident patients receiving hemodialysis through a non-tunneled right jugular vein catheter. 130 procedures were performed in 122 patients (51+/-18 years). The success rate was 100%. There was a total of 26,546 catheter days. Ninety-one of the 130 catheters were removed during the study period. Life table analysis revealed primary patency rates of 92%, 82%, and 68% at 30, 60, and 120 days, respectively. Infection requiring catheter removal occurred at a frequency of 0.09 per 100 catheter days. Catheter malfunction requiring intervention occurred at a rate of 0.03 per 100 catheter days. Hypertension and duration of existing non-tunneled catheter of less than 2 weeks were independently associated with better TCC survival. The conversion from non-tunneled to TCC performed by nephrologists and without fluoroscopy may be safe by using the internal right jugular vein. The ideal time to do this procedure is within less than 2 weeks of existing non-tunneled catheter.

  1. Turning Vanes inside the Altitude Wind Tunnel

    NASA Image and Video Library

    1944-02-21

    Men stand in front of turning vanes inside the Altitude Wind Tunnel (AWT) at the National Advisory Committee for Aeronautics (NACA) Aircraft Engine Research Laboratory. The AWT was the only wind tunnel capable of testing full-size aircraft engines in simulated altitude conditions. A large wooden drive fan, located on the other side of these vanes, created wind speeds up to 500 miles per hour. The drive shaft connected the fan to the induction motor located in an adjacent building. Turning vanes were located in each corner of the rectangular tunnel to straighten the airflow and direct it around the corners. This set of vanes was located in the 31-foot-diameter southeast corner of the tunnel. These elliptical panels consisted of 36 to 42 vertical vanes that were supported by three horizontal supports. The individual vanes were 2.5 feet long and half-moon shaped. The panel of vanes was affixed to the curved corner rings of the tunnel. Each set of turning vanes had a moveable vane in the middle of the lower level for personnel access. Each set of vanes took weeks to assemble before they were installed during the summer of 1943. This publicity photograph was taken just weeks after the tunnel became operational in February 1944.

  2. Nanowire Tunnel Field Effect Transistors: Prospects and Pitfalls

    NASA Astrophysics Data System (ADS)

    Sylvia, Somaia Sarwat

    The tunnel field effect transistor (TFET) has the potential to operate at lower voltages and lower power than the field effect transistor (FET). The TFET can circumvent the fundamental thermal limit of the inverse subthreshold slope (S) by exploiting interband tunneling of non-equilibrium "cold" carriers. The conduction mechanism in the TFET is governed by band-to-band tunneling which limits the drive current. TFETs built with III-V materials like InAs and InSb can produce enough tunneling current because of their small direct bandgap. Our simulation results show that although they require highly degenerate source doping to support the high electric fields in the tunnel region, the devices achieve minimum inverse subthreshold slopes of 30 mV/dec. In subthreshold, these devices experience both regimes of voltage-controlled tunneling and cold-carrier injection. Numerical results based on a discretized 8-band k.p model are compared to analytical WKB theory. For both regular FETs and TFETs, direct channel tunneling dominates the leakage current when the physical gate length is reduced to 5 nm. Therefore, a survey of materials is performed to determine their ability to suppress the direct tunnel current through a 5 nm barrier. The tunneling effective mass gives the best indication of the relative size of the tunnel currents. Si gives the lowest overall tunnel current for both the conduction and valence band and, therefore, it is the optimum choice for suppressing tunnel current at the 5 nm scale. Our numerical simulation shows that the finite number, random placement, and discrete nature of the dopants in the source of an InAs nanowire (NW) TFET affect both the mean value and the variance of the drive current and the inverse subthreshold slope. The discrete doping model gives an average drive current and an inverse subthreshold slope that are less than those predicted from the homogeneous doping model. The doping density required to achieve a target drive current is

  3. 1. West portal of Tunnel 34, contextual view to northeast ...

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

    1. West portal of Tunnel 34, contextual view to northeast from inside east end of Tunnel 33 (Cape Horn Tunnel), 135mm lens with electronic flash fill. - Central Pacific Transcontinental Railroad, Tunnel No. 34, Milepost 145.4, Colfax, Placer County, CA

  4. Evaluation of tunnel seismic prediction (TSP) result using the Japanese highway rock mass classification system for Pahang-Selangor Raw Water Transfer Tunnel

    NASA Astrophysics Data System (ADS)

    Von, W. C.; Ismail, M. A. M.

    2017-10-01

    The knowing of geological profile ahead of tunnel face is significant to minimize the risk in tunnel excavation work and cost control in preventative measure. Due to mountainous area, site investigation with vertical boring is not recommended to obtain the geological profile for Pahang-Selangor Raw Water Transfer project. Hence, tunnel seismic prediction (TSP) method is adopted to predict the geological profile ahead of tunnel face. In order to evaluate the TSP results, IBM SPSS Statistic 22 is used to run artificial neural network (ANN) analysis to back calculate the predicted Rock Grade Points (JH) from actual Rock Grade Points (JH) using Vp, Vs and Vp/Vs from TSP. The results show good correlation between predicted Rock Grade points and actual Rock Grade Points (JH). In other words, TSP can provide geological profile prediction ahead of tunnel face significantly while allowing continuously TBM excavation works. Identifying weak zones or faults ahead of tunnel face is crucial for preventative measures to be carried out in advance for a safer tunnel excavation works.

  5. Quantum Calculations of Electron Tunneling in Respiratory Complex III.

    PubMed

    Hagras, Muhammad A; Hayashi, Tomoyuki; Stuchebrukhov, Alexei A

    2015-11-19

    The most detailed and comprehensive to date study of electron transfer reactions in the respiratory complex III of aerobic cells, also known as bc1 complex, is reported. In the framework of the tunneling current theory, electron tunneling rates and atomistic tunneling pathways between different redox centers were investigated for all electron transfer reactions comprising different stages of the proton-motive Q-cycle. The calculations reveal that complex III is a smart nanomachine, which under certain conditions undergoes conformational changes gating electron transfer, or channeling electrons to specific pathways. One-electron tunneling approximation was adopted in the tunneling calculations, which were performed using hybrid Broken-Symmetry (BS) unrestricted DFT/ZINDO levels of theory. The tunneling orbitals were determined using an exact biorthogonalization scheme that uniquely separates pairs of tunneling orbitals with small overlaps out of the remaining Franck-Condon orbitals with significant overlap. Electron transfer rates in different redox pairs show exponential distance dependence, in agreement with the reported experimental data; some reactions involve coupled proton transfer. Proper treatment of a concerted two-electron bifurcated tunneling reaction at the Q(o) site is given.

  6. Monitoring of Deformation in Ground Before and After Tunnel Excavation

    NASA Astrophysics Data System (ADS)

    Eren, Mehmet; Hilmi Erkoç, Muharrem

    2017-04-01

    As population increase in metropolitan city, we need transportation and transmission tunnel. In this context, the engineers and administors attach impotance to building and planning underground-tunnel. Moreover, we must at regular intervals monitoring to deformation in underground-tunnel for quality and safety. Firstly, a deformation monitoring network is designed as perpendicular to the tunnel main axis. Secondly, the prescribed number of deformation measurements must be made. Finally, the deformation analysis is evaluated and its results is interpreted. This study investigates how deformation in monitoring network during and after tunnel excavate change.For this purpose, a deformation monitoring network of 18 object point and 4 reference point was established. Object points networks was designed steeply to the tunnel main axis as 3 cross section. Each cross section consisted of 3 point left, 2 point right and 1 point at the flowing line. Initial conditional measurement was made before tunnel excavation. Then the deformation measurement was made 5 period (1 period measured after tunnel excavate). All data sets were adjusted according to free adjustment method. The results from the investigation considering the tunnel line, a symmetrical subsidence was observed. The following day of tunnel excavation, we were observed %68 per of the total deformation. At the end of the last period measurements, %99 per of the total deformation was detected. Keywords: Tunnel, Deformation, Subsidence, Excavation

  7. Aeronautical Wind Tunnels, Europe and Asia

    DTIC Science & Technology

    2006-02-01

    User Fees Contact Information Dr. Surjatin Wiriadidjaja, UPT-LAGG, BPP Teknologi, Puspiptek, Serpong, Tangerang 15310, Indonesia. Tel: (62) 21 756...of the tunnel, FFA T1500 Transonic Wind Tunnel Circuit (Sweden) manufactured by The Swedish Defense Research Agency (FOI). 2.4 m Transonic Wind

  8. Altitude Wind Tunnel Control Room

    NASA Image and Video Library

    1945-05-21

    Researchers at the National Advisory Committee for Aeronautics (NACA) Aircraft Engine Research Laboratory monitor a ramjet's performance in the Altitude Wind Tunnel from the control room. The soundproof control room was just a few feet from the tunnel’s 20-foot-diameter test section. In the control room, the operators could control all aspects of the tunnel’s operation, including the air density, temperature, and speed. They also operated the engine or test article in the test section by controlling the angle-of-attack, speed, power, and other parameters. The men in this photograph are monitoring the engine’s thrust and lift. A NACA-designed 20-inch-diameter ramjet was installed in the tunnel in May 1945. Thrust figures from these runs were compared with drag data from tests of scale models in small supersonic tunnels to verify the ramjet’s feasibility. The tunnel was used to analyze the ramjet’s overall performance up to altitudes of 47,000 feet and speeds to Mach 1.84. The researchers found that an increase in altitude caused a reduction in the engine’s horsepower and identified optimal flameholder configurations.

  9. A Seamless Ubiquitous Telehealthcare Tunnel

    PubMed Central

    Cheng, Po-Hsun; Lin, Bor-Shing; Yu, Chu; Hu, Shun-Hsiang; Chen, Sao-Jie

    2013-01-01

    Mobile handheld devices are rapidly using to implement healthcare services around the World. Fundamentally, these services utilize telemedicine technologies. A disconnection of a mobile telemedicine system usually results in an interruption, which is embarrassing, and reconnection is necessary during the communication session. In this study, the Stream Control Transmission Protocol (SCTP) is adopted to build a stable session tunnel to guarantee seamless switching among heterogeneous wireless communication standards, such as Wi-Fi and 3G. This arrangement means that the telemedicine devices will not be limited by a fixed wireless connection and can switch to a better wireless channel if necessary. The tunnel can transmit plain text, binary data, and video streams. According to the evaluation of the proposed software-based SCTP-Tunnel middleware shown, the performance is lower than anticipated and is slightly slower than a fixed connection. However, the transmission throughput is still acceptable for healthcare professionals in a healthcare enterprise or home care site. It is necessary to build more heterogeneous wireless protocols into the proposed tunnel-switching scheme to support all possible communication protocols. In addition, SCTP is another good choice for promoting communication in telemedicine and healthcare fields. PMID:23917812

  10. Videometric Applications in Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Burner, A. W.; Radeztsky, R. H.; Liu, Tian-Shu

    1997-01-01

    Videometric measurements in wind tunnels can be very challenging due to the limited optical access, model dynamics, optical path variability during testing, large range of temperature and pressure, hostile environment, and the requirements for high productivity and large amounts of data on a daily basis. Other complications for wind tunnel testing include the model support mechanism and stringent surface finish requirements for the models in order to maintain aerodynamic fidelity. For these reasons nontraditional photogrammetric techniques and procedures sometimes must be employed. In this paper several such applications are discussed for wind tunnels which include test conditions with Mach number from low speed to hypersonic, pressures from less than an atmosphere to nearly seven atmospheres, and temperatures from cryogenic to above room temperature. Several of the wind tunnel facilities are continuous flow while one is a short duration blowdown facility. Videometric techniques and calibration procedures developed to measure angle of attack, the change in wing twist and bending induced by aerodynamic load, and the effects of varying model injection rates are described. Some advantages and disadvantages of these techniques are given and comparisons are made with non-optical and more traditional video photogrammetric techniques.

  11. Concurrent myotomy and tunneling after establishment of a half tunnel instead of myotomy after establishment of a full tunnel: a more efficient method of peroral endoscopic myotomy

    PubMed Central

    Philips, George M.; Dacha, Sunil; Keilin, Steve A.; Willingham, Field F.; Cai, Qiang

    2016-01-01

    Background and study aims: Peroral endoscopic myotomy (POEM) is a time-consuming and challenging procedure. Traditionally, the myotomy is done after the submucosal tunnel has been completed. Starting the myotomy earlier, after submucosal tunneling is half completed (concurrent myotomy and tunneling), may be more efficient. This study aims to assess if the method of concurrent myotomy and tunneling may decrease the procedural time and be efficacious. Patients and methods: This is a retrospective case series of patients who underwent modified POEM (concurrent myotomy and tunneling) or traditional POEM at a tertiary care medical center. Modified POEM or traditional POEM was performed at the discretion of the endoscopist in patients presenting with achalasia. The total procedural duration, myotomy duration, myotomy length, and time per unit length of myotomy were recorded for both modified and traditional POEM. Results: Modified POEM was performed in 6 patients whose mean age (± standard deviation [SD]) was 58 ± 13.3 years. Of these, 5 patients had type II achalasia and 1 patient had esophageal dysmotility. The mean Eckardt score (± SD) before the procedure was 8.8 ± 1.3. The modified technique was performed in 47 ± 8 minutes, with 6 ± 1 minutes required per centimeter of myotomy and 3 ± 1 minutes required per centimeter of submucosal space. The Eckardt score was 3 ± 1.1 at 1 month and 3 ± 2.5 at 3 months. The procedure time for modified POEM was significantly shorter than that for traditional POEM. Conclusions: Modified POEM with short submucosal tunneling may be more efficient than traditional POEM with long submucosal tunneling, and outcomes may be equivalent over short-term follow-up. Long-term data and randomized controlled studies are needed to compare the clinical efficacy of modified POEM with that of the traditional method. PMID:27092318

  12. The Dornier Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Schlichting, H

    1938-01-01

    After completion of the required calibrations, the Dornier open-throat tunnel is now in operation. With an elliptic test section of 3 by 4 m (9.84 by 3.12 ft.), its length is 7 m (22.97 ft.), its maximum horsepower 800, and its maximum air speed 60 m/s (134.2 mph). As to local uniformity of velocity, static pressure as well as jet direction, and turbulence factor, this tunnel is on par with those of the good German and foreign research labs.

  13. Steep Turn On/Off Green Tunnel Transistors

    DTIC Science & Technology

    2010-12-17

    S. Cristoloveanu, D. Mariolle, D. Fraboulet, S. Deleonibus, “Lateral interband tunneling transistor in silicon-on-insulator," Applied Physics...concept of time dependant perturbation theory and Fermi’s Golden Rule (shown in Eq. (2.1) to calculate the transition rate of carriers tunneling into...E     (2.2) This equation shows that the functional form for the band-to-band tunneling rate has an exponential dependence on electric field

  14. Wind tunnel pressurization and recovery system

    NASA Technical Reports Server (NTRS)

    Pejack, Edwin R.; Meick, Joseph; Ahmad, Adnan; Lateh, Nordin; Sadeq, Omar

    1988-01-01

    The high density, low toxicity characteristics of refrigerant-12 (dichlorofluoromethane) make it an ideal gas for wind tunnel testing. Present limitations on R-12 emissions, set to slow the rate of ozone deterioration, pose a difficult problem in recovery and handling of large quantities of R-12. This preliminary design is a possible solution to the problem of R-12 handling in wind tunnel testing. The design incorporates cold temperature condensation with secondary purification of the R-12/air mixture by adsorption. Also discussed is the use of Freon-22 as a suitable refrigerant for the 12 foot wind tunnel.

  15. Intrinsic Tunneling in Phase Separated Manganites

    NASA Astrophysics Data System (ADS)

    Singh-Bhalla, G.; Selcuk, S.; Dhakal, T.; Biswas, A.; Hebard, A. F.

    2009-02-01

    We present evidence of direct electron tunneling across intrinsic insulating regions in submicrometer wide bridges of the phase-separated ferromagnet (La,Pr,Ca)MnO3. Upon cooling below the Curie temperature, a predominantly ferromagnetic supercooled state persists where tunneling across the intrinsic tunnel barriers (ITBs) results in metastable, temperature-independent, high-resistance plateaus over a large range of temperatures. Upon application of a magnetic field, our data reveal that the ITBs are extinguished resulting in sharp, colossal, low-field resistance drops. Our results compare well to theoretical predictions of magnetic domain walls coinciding with the intrinsic insulating phase.

  16. Airborne asbestos fibres monitoring in tunnel excavation.

    PubMed

    Gaggero, Laura; Sanguineti, Elisa; Yus González, Adrián; Militello, Gaia Maria; Scuderi, Alberto; Parisi, Giovanni

    2017-07-01

    Tunnelling across ophiolitic formation with Naturally Occurring Asbestos (NOA) can release fibres into the environment, exposing workers, and the population, if fibres spread outside the tunnel, leading to increased risk of developing asbestos-related disease. Therefore, a careful plan of environmental monitoring is carried out during Terzo Valico tunnel excavation. In the present study, data of 1571 samples of airborne dust, collected between 2014 and 2016 inside the tunnels, and analyzed by SEM-EDS for quantification of workers exposure, are discussed. In particular, the engineering and monitoring management of 100 m tunnelling excavation across a serpentinite lens (Cravasco adit), intercalated within calcschists, is reported. At this chrysotile occurrence, 84% of 128 analyzed samples (from the zone closer to the front rock) were above 2 ff/l. However, thanks to safety measures implemented and tunnel compartmentation in zones, the asbestos fibre concentration did not exceed the Italian standard of occupational exposure (100 ff/l) and 100% of samples collected in the outdoor square were below 1 ff/l. During excavation under normal working conditions, asbestos concentrations were below 2 ff/l in 97.4% of the 668 analyzed samples. Our results showed that air monitoring can objectively confirm the presence of asbestos minerals at a rock front in relative short time and provide information about the nature of the lithology at the front. The present dataset, the engineering measures described and the operative conclusions are liable to support the improvement of legislation on workers exposure to asbestos referred to the tunnelling sector, lacking at present. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Trajectories and traversal times in quantum tunneling

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Zhi Hong.

    1989-01-01

    The classical concepts of trajectories and traversal times applied to quantum tunneling are discussed. By using the Wentzel-Kramers-Brillouin approximation, it is found that in a forbidden region of a multidimensional space the wave function can be described by two sets of trajectories, or equivalently by two sets of wave fronts. The trajectories belonging to different sets are mutually orthogonal. An extended Huygens construction is proposed to determine these wave fronts and trajectories. In contrast to the classical results in the allowed region, these trajectories couple to each other. However, if the incident wave is normal to the turning surface, themore » trajectories are found to be independent and can be determined by Newton's equations of motion with inverted potential and energy. The multidimensional tunneling theory is then applied to the scanning tunneling microscope to calculate the current density distribution and to derive the expressions for the lateral resolution and the surface corrugation amplitude. The traversal time in quantum tunneling, i.e. tunneling time, is found to depend on model calculations and simulations. Computer simulation of a wave packet tunneling through a square barrier is performed. Several approaches, including the phase method, Larmor clock, and time-dependent barrier model, are investigated. For a square barrier, two characteristic times are found: One is equal to the barrier width divided by the magnitude of the imaginary velocity; the other is equal to the decay length divided by the incident velocity. It is believed that the tunneling time can only be defined operationally.« less

  18. Aeroservoelastic Wind-Tunnel Test of the SUGAR Truss Braced Wing Wind-Tunnel Model

    NASA Technical Reports Server (NTRS)

    Scott, Robert C.; Allen, Timothy J.; Funk, Christie J.; Castelluccio, Mark A.; Sexton, Bradley W.; Claggett, Scott; Dykman, John; Coulson, David A.; Bartels, Robert E.

    2015-01-01

    The Subsonic Ultra Green Aircraft Research (SUGAR) Truss-Braced Wing (TBW) aeroservoelastic (ASE) wind-tunnel test was conducted in the NASA Langley Transonic Dynamics Tunnel (TDT) and was completed in April, 2014. The primary goals of the test were to identify the open-loop flutter boundary and then demonstrate flutter suppression. A secondary goal was to demonstrate gust load alleviation (GLA). Open-loop flutter and limit cycle oscillation onset boundaries were identified for a range of Mach numbers and various angles of attack. Two sets of control laws were designed for the model and both sets of control laws were successful in suppressing flutter. Control laws optimized for GLA were not designed; however, the flutter suppression control laws were assessed using the TDT Airstream Oscillation System. This paper describes the experimental apparatus, procedures, and results of the TBW wind-tunnel test. Acquired system ID data used to generate ASE models is also discussed.2 study.

  19. Turbine endwall two-cylinder program. [wind tunnel and water tunnel investigation of three dimensional separation of fluid flow

    NASA Technical Reports Server (NTRS)

    Langston, L. S.

    1980-01-01

    Progress is reported in an effort to study the three dimensional separation of fluid flow around two isolated cylinders mounted on an endwall. The design and performance of a hydrogen bubble generator for water tunnel tests to determine bulk flow properties and to measure main stream velocity and boundary layer thickness are described. Although the water tunnel tests are behind schedule because of inlet distortion problems, tests are far enough along to indicate cylinder spacing, wall effects and low Reynolds number behavior, all of which impacted wind tunnel model design. The construction, assembly, and operation of the wind tunnel and the check out of its characteristics are described. An off-body potential flow program was adapted to calculate normal streams streamwise pressure gradients at the saddle point locations.

  20. Tunnel Junction Development Using Hydride Vapor Phase Epitaxy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ptak, Aaron J.; Simon, John D.; Schulte, Kevin L.

    We demonstrate for the first time III-V tunnel junctions grown using hydride vapor phase epitaxy (HVPE) with peak tunneling currents >8 A/cm 2, sufficient for operation of a multijunction device to several hundred suns of concentration. Multijunction solar cells rely on tunneling interconnects between subcells to enable series connection with minimal voltage loss, but tunnel junctions have never been shown using the HVPE growth method. HVPE has recently reemerged as a low-cost growth method for high-quality III-V materials and devices, including the growth of high-efficiency III-V solar cells. We previously showed single-junction GaAs solar cells with conversion efficiencies of ~24%more » with a path forward to equal or exceed the practical efficiency limits of crystalline Si. Moving to a multijunction device structure will allow for even higher efficiencies with minimal impact on cost, necessitating the development of tunnel interconnects. Here in this paper, we demonstrate the performance of both isolated HVPE-grown tunnel junctions, as well as single-junction GaAs solar cell structures with a tunnel junction incorporated into the contact region. We observe no degradation in device performance compared to a structure without the added junction.« less

  1. Tunnel Junction Development Using Hydride Vapor Phase Epitaxy

    DOE PAGES

    Ptak, Aaron J.; Simon, John D.; Schulte, Kevin L.; ...

    2017-10-18

    We demonstrate for the first time III-V tunnel junctions grown using hydride vapor phase epitaxy (HVPE) with peak tunneling currents >8 A/cm 2, sufficient for operation of a multijunction device to several hundred suns of concentration. Multijunction solar cells rely on tunneling interconnects between subcells to enable series connection with minimal voltage loss, but tunnel junctions have never been shown using the HVPE growth method. HVPE has recently reemerged as a low-cost growth method for high-quality III-V materials and devices, including the growth of high-efficiency III-V solar cells. We previously showed single-junction GaAs solar cells with conversion efficiencies of ~24%more » with a path forward to equal or exceed the practical efficiency limits of crystalline Si. Moving to a multijunction device structure will allow for even higher efficiencies with minimal impact on cost, necessitating the development of tunnel interconnects. Here in this paper, we demonstrate the performance of both isolated HVPE-grown tunnel junctions, as well as single-junction GaAs solar cell structures with a tunnel junction incorporated into the contact region. We observe no degradation in device performance compared to a structure without the added junction.« less

  2. Fabrication of magnetic tunnel junctions with epitaxial and textured ferromagnetic layers

    DOEpatents

    Chang, Y. Austin; Yang, Jianhua Joshua

    2008-11-11

    This invention relates to magnetic tunnel junctions and methods for making the magnetic tunnel junctions. The magnetic tunnel junctions include a tunnel barrier oxide layer sandwiched between two ferromagnetic layers both of which are epitaxial or textured with respect to the underlying substrate upon which the magnetic tunnel junctions are grown. The magnetic tunnel junctions provide improved magnetic properties, sharper interfaces and few defects.

  3. 30 CFR 77.213 - Draw-off tunnel escapeways.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Draw-off tunnel escapeways. 77.213 Section 77.213 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR COAL MINE SAFETY AND... Surface Installations § 77.213 Draw-off tunnel escapeways. When it is necessary for a tunnel to be closed...

  4. Self-contained instrument for measuring subterranean tunnel wall deflection

    DOEpatents

    Rasmussen, Donald Edgar; Hof, Jr., Peter John

    1978-01-01

    The deflection of a subterranean tunnel is measured with a rod-like, self-contained instrument that is adapted to be inserted into a radially extending bore of the tunnel adjacent an end of the tunnel where the tunnel is being dug. One end of the instrument is anchored at the end of the bore remote from the tunnel wall, while the other end of the intrument is anchored adjacent the end of the wall in proximity to the tunnel wall. The two ends of the instrument are linearly displaceable relative to each other; the displacement is measured by a transducer means mounted on the instrument. Included in the instrument is a data storage means including a paper tape recorder periodically responsive to a parallel binary signal indicative of the measured displacement.

  5. Tunneling contact IGZO TFTs with reduced saturation voltages

    NASA Astrophysics Data System (ADS)

    Wang, Longyan; Sun, Yin; Zhang, Xintong; Zhang, Lining; Zhang, Shengdong; Chan, Mansun

    2017-04-01

    We report a tunneling contact indium-gallium-zinc oxide (IGZO) thin film transistor (TFT) with a graphene interlayer technique in this paper. A Schottky junction is realized between a metal and IGZO with a graphene interlayer, leading to a quantum tunneling of the TFT transport in saturation regions. This tunneling contact enables a significant reduction in the saturation drain voltage Vdsat compared to that of the thermionic emission TFTs, which is usually equal to the gate voltage minus their threshold voltages. Measured temperature independences of the subthreshold swing confirm a transition from the thermionic emission to quantum tunneling transports depending on the gate bias voltages in the proposed device. The tunneling contact TFTs with the graphene interlayer have implications to reduce the power consumptions of certain applications such as the active matrix OLED display.

  6. Multistate outbreak of toxic anterior segment syndrome, 2005.

    PubMed

    Kutty, Preeta K; Forster, Terri S; Wood-Koob, Carol; Thayer, Nancy; Nelson, Robert B; Berke, Stanley J; Pontacolone, Lillian; Beardsley, Thomas L; Edelhauser, Henry F; Arduino, Matthew J; Mamalis, Nick; Srinivasan, Arjun

    2008-04-01

    To present the findings of an outbreak of toxic anterior segment syndrome (TASS). Six states, 7 ophthalmology surgical centers, United States. Cases were identified through electronic communication networks and via reports to a national TASS referral center. Information on the procedure, details of instrument reprocessing, and products used during cataract surgery were also collected. Medications used during the procedures were tested for endotoxin using a kinetic assay. The search identified 112 case patients (median age 74 years) from 7 centers from July 19, 2005, through November 28, 2005. Common presenting clinical features included blurred vision (60%), anterior segment inflammation (49%), and cell deposition (56%). Of the patients, 100 (89%) had been exposed to a single brand of balanced salt solution manufactured by Cytosol Laboratories and distributed by Advanced Medical Optics as AMO Endosol. Two patients continued to have residual symptoms. There were no reports of significant breaches in sterile technique or instrument reprocessing. Of 14 balanced salt solution lots, 5 (35%) had levels exceeding the endotoxin limit (0.5 EU/mL). Based on these findings, the balanced salt solution product was withdrawn, resulting in a termination of the outbreak. This is the first known report of an outbreak of TASS caused by intrinsic contamination of a product with endotoxin. Ophthalmologists and epidemiologists should be aware of TASS and its common causes. To facilitate investigations of adverse outcomes such as TASS, those performing cataract surgeries should document the type and lot numbers of products used intraoperatively.

  7. NACA Transonic Wind-tunnel Test Sections

    NASA Technical Reports Server (NTRS)

    Wright, Ray H; Ward, Vernon G

    1955-01-01

    Report presents an approximate subsonic theory for the solid-blockage interference in circular wind tunnels with walls slotted in the direction of flow. This theory indicated the possibility of obtaining zero blockage interference. Tests in a circular slotted tunnel based on the theory confirmed the theoretical predictions.

  8. Tunnelling from non-localised initial states

    NASA Technical Reports Server (NTRS)

    Bowcock, Peter; Gregory, Ruth

    1991-01-01

    An approach for calculating tunneling amplitudes from a nonlocalized initial state is presented. Generalizing the matching conditions and equations of motion to allow for complex momentum permits a description of tunneling in the presence of so-called classical motion. Possible applications of the method are presented.

  9. 49 CFR 177.810 - Vehicular tunnels.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... through any urban vehicular tunnel used for mass transportation. [Amdt. 177-52, 46 FR 5316, Jan. 19, 1981... 49 Transportation 2 2010-10-01 2010-10-01 false Vehicular tunnels. 177.810 Section 177.810 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY...

  10. Dielectric Sensors Based on Electromagnetic Energy Tunneling

    PubMed Central

    Siddiqui, Omar; Kashanianfard, Mani; Ramahi, Omar

    2015-01-01

    We show that metallic wires embedded in narrow waveguide bends and channels demonstrate resonance behavior at specific frequencies. The electromagnetic energy at these resonances tunnels through the narrow waveguide channels with almost no propagation losses. Under the tunneling behavior, high-intensity electromagnetic fields are produced in the vicinity of the metallic wires. These intense field resonances can be exploited to build highly sensitive dielectric sensors. The sensor operation is explained with the help of full-wave simulations. A practical setup consisting of a 3D waveguide bend is presented to experimentally observe the tunneling phenomenon. The tunneling frequency is predicted by determining the input impedance minima through a variational formula based on the Green function of a probe-excited parallel plate waveguide. PMID:25835188

  11. A century of wind tunnels since Eiffel

    NASA Astrophysics Data System (ADS)

    Chanetz, Bruno

    2017-08-01

    Fly higher, faster, preserve the life of test pilots and passengers, many challenges faced by man since the dawn of the twentieth century, with aviation pioneers. Contemporary of the first aerial exploits, wind tunnels, artificially recreating conditions encountered during the flight, have powerfully contributed to the progress of aeronautics. But the use of wind tunnels is not limited to aviation. The research for better performance, coupled with concern for energy saving, encourages manufacturers of ground vehicles to perform aerodynamic tests. Buildings and bridge structures are also concerned. This article deals principally with the wind tunnels built at ONERA during the last century. Somme wind tunnels outside ONERA, even outside France, are also evocated when their characteristics do not exist at ONERA.

  12. Band-to-band tunneling in Γ valley for Ge source lateral tunnel field effect transistor: Thickness scaling

    NASA Astrophysics Data System (ADS)

    Jain, Prateek; Rastogi, Priyank; Yadav, Chandan; Agarwal, Amit; Chauhan, Yogesh Singh

    2017-07-01

    The direct and indirect valleys in Germanium (Ge) are separated by a very small offset, which opens up the prospect of direct tunneling in the Γ valley of an extended Ge source tunnel field effect transistor (TFET). We explore the impact of thickness scaling of extended Ge source lateral TFET on the band to band tunneling (BTBT) current. The Ge source is extended inside the gate by 2 nm to confine the tunneling in Ge only. We observe that as the thickness is scaled, the band alignment at the Si/Ge heterojunction changes significantly, which results in an increase in Ge to Si BTBT current. Based on density functional calculations, we first obtain the band structure parameters (bandgap, effective masses, etc.) for the Ge and Si slabs of varying thickness, and these are then used to obtain the thickness dependent Kane's BTBT tunneling parameters. We find that electrostatics improves as the thickness is reduced in the ultra-thin Ge film ( ≤ 10 nm). The ON current degrades as we scale down in thickness; however, the subthreshold slope ( S S AVG ) improves remarkably with thickness scaling due to subsurface BTBT. We predict that 8 nm thin devices offer the best option for optimized ON current and S S AVG .

  13. Restoring proximal caries lesions conservatively with tunnel restorations

    PubMed Central

    Chu, Chun-Hung; Mei, May L; Cheung, Chloe; Nalliah, Romesh P

    2013-01-01

    The tunnel restoration has been suggested as a conservative alternative to the conventional box preparation for treating proximal caries. The main advantage of tunnel restoration over the conventional box or slot preparation includes being more conservative and increasing tooth integrity and strength by preserving the marginal ridge. However, tunnel restoration is technique-sensitive and can be particularly challenging for inexperienced restorative dentists. Recent advances in technology, such as the contemporary design of dental handpieces with advanced light-emitting diode (LED) and handheld comfort, offer operative dentists better vision, illumination, and maneuverability. The use of magnifying loupes also enhances the visibility of the preparation. The advent of digital radiographic imaging has improved dental imaging and reduced radiation. The new generation of restorative materials has improved mechanical properties. Tunnel restoration can be an option to restore proximal caries if the dentist performs proper case selection and pays attention to the details of the restorative procedures. This paper describes the clinical technique of tunnel restoration and reviews the studies of tunnel restorations. PMID:24019754

  14. Restoring proximal caries lesions conservatively with tunnel restorations.

    PubMed

    Chu, Chun-Hung; Mei, May L; Cheung, Chloe; Nalliah, Romesh P

    2013-07-30

    The tunnel restoration has been suggested as a conservative alternative to the conventional box preparation for treating proximal caries. The main advantage of tunnel restoration over the conventional box or slot preparation includes being more conservative and increasing tooth integrity and strength by preserving the marginal ridge. However, tunnel restoration is technique-sensitive and can be particularly challenging for inexperienced restorative dentists. Recent advances in technology, such as the contemporary design of dental handpieces with advanced light-emitting diode (LED) and handheld comfort, offer operative dentists better vision, illumination, and maneuverability. The use of magnifying loupes also enhances the visibility of the preparation. The advent of digital radiographic imaging has improved dental imaging and reduced radiation. The new generation of restorative materials has improved mechanical properties. Tunnel restoration can be an option to restore proximal caries if the dentist performs proper case selection and pays attention to the details of the restorative procedures. This paper describes the clinical technique of tunnel restoration and reviews the studies of tunnel restorations.

  15. 1. East portal of Tunnel 4, view to west with ...

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

    1. East portal of Tunnel 4, view to west with east portal of Tunnel 38 (HAER CA-211) visible in distance, 135mm lens with electronic flash fill. This tunnel was photographed to provide context, because even though somewhat enlarged, it illustrates the nature of the unlined hard rock tunnels typical of the original Central Pacific construction in 1868. - Central Pacific Transcontinental Railroad, Tunnel No. 4, Milepost 180.95, Cisco, Placer County, CA

  16. Resonant tunneling through S- and U-shaped graphene nanoribbons.

    PubMed

    Zhang, Z Z; Wu, Z H; Chang, Kai; Peeters, F M

    2009-10-14

    We theoretically investigate resonant tunneling through S- and U-shaped nanostructured graphene nanoribbons. A rich structure of resonant tunneling peaks is found emanating from different quasi-bound states in the middle region. The tunneling current can be turned on and off by varying the Fermi energy. Tunability of resonant tunneling is realized by changing the width of the left and/or right leads and without the use of any external gates.

  17. Silicon-based hot electron emitting substrate with double tunneling

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Zhan, Xinghua; Salcic, Zoran; Wong, Chee Cheong; Gao, Wei

    2017-07-01

    We propose a novel silicon structure, Hot Electron Emitting Substrate (HEES), which exhibits important effect of repeated tunneling at two different voltage ranges, which we refer to as double tunneling. In ambient atmosphere and room temperature, the I-V characteristic of HEES shows two current peaks during voltage sweep from 2 to 15 V. These two peaks are formed by the Fowler-Nordheim (FN) tunneling effect and tunneling diode mechanism, respectively.

  18. 1. West portal of Tunnel 27 in distance, contextual view ...

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

    1. West portal of Tunnel 27 in distance, contextual view to northeast looking past Tunnel 26 (HAER CA-202) from atop east portal of Tunnel 25 (HAER CA-201), 380mm lens. - Central Pacific Transcontinental Railroad, Tunnel No. 27, Milepost 133.9, Applegate, Placer County, CA

  19. The Design of Low-Turbulence Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Dryden, Hugh L; Abbott, Ira H

    1949-01-01

    Within the past 10 years there have been placed in operation in the United States four low-turbulence wind tunnels of moderate cross-sectional area and speed, one at the National Bureau of Standards, two at the NACA Langley Laboratory, and one at the NACA Ames Laboratory. This paper reviews briefly the state of knowledge and those features which make possible the attainment of low turbulence in wind tunnels. Specific applications to two wind tunnels are described.

  20. Extreme sub-threshold swing in tunnelling relays

    NASA Astrophysics Data System (ADS)

    AbdelGhany, M.; Szkopek, T.

    2014-01-01

    We propose and analyze the theory of the tunnelling relay, a nanoscale active device in which tunnelling current is modulated by electromechanical actuation of a suspended membrane above a fixed electrode. The tunnelling current is modulated exponentially with vacuum gap length, permitting an extreme sub-threshold swing of ˜10 mV/decade breaking the thermionic limit. The predicted performance suggests that a significant reduction in dynamic energy consumption over conventional field effect transistors is physically achievable.

  1. Effect of Wrist Posture on Carpal Tunnel Pressure while Typing

    PubMed Central

    Rempel, David M.; Keir, Peter J.; Bach, Joel M.

    2009-01-01

    Long weekly hours of keyboard use may lead to or aggravate carpal tunnel syndrome. The effects of typing on fluid pressure in the carpal tunnel, a possible mediator of carpal tunnel syndrome, are unknown. Twenty healthy subjects participated in a laboratory study to investigate the effects of typing at different wrist postures on carpal tunnel pressure of the right hand. Changes in wrist flexion/extension angle (p = 0.01) and radial/ulnar deviation angle (p = 0.03) independently altered carpal tunnel pressure; wrist deviations in extension or radial deviation were associated with an increase in pressure. The activity of typing independently elevated carpal tunnel pressure (p= 0.001) relative to the static hand held in the same posture. This information can guide the design and use of keyboards and workstations in order to minimize carpal tunnel pressure while typing. The findings may also be useful to clinicians and ergonomists in the management of patients with carpal tunnel syndrome who use a keyboard. PMID:18383144

  2. Substrate Tunnels in Enzymes: Structure-Function Relationships and Computational Methodology

    PubMed Central

    Kingsley, Laura J.; Lill, Markus A.

    2015-01-01

    In enzymes, the active site is the location where incoming substrates are chemically converted to products. In some enzymes, this site is deeply buried within the core of the protein and in order to access the active site, substrates must pass through the body of the protein via a tunnel. In many systems, these tunnels act as filters and have been found to influence both substrate specificity and catalytic mechanism. Identifying and understanding how these tunnels exert such control has been of growing interest over the past several years due to implications in fields such as protein engineering and drug design. This growing interest has spurred the development of several computational methods to identify and analyze tunnels and how ligands migrate through these tunnels. The goal of this review is to outline how tunnels influence substrate specificity and catalytic efficiency in enzymes with tunnels and to provide a brief summary of the computational tools used to identify and evaluate these tunnels. PMID:25663659

  3. Wind tunnel wall interference

    NASA Technical Reports Server (NTRS)

    Newman, Perry A.; Mineck, Raymond E.; Barnwell, Richard W.; Kemp, William B., Jr.

    1986-01-01

    About a decade ago, interest in alleviating wind tunnel wall interference was renewed by advances in computational aerodynamics, concepts of adaptive test section walls, and plans for high Reynolds number transonic test facilities. Selection of NASA Langley cryogenic concept for the National Transonic Facility (NTF) tended to focus the renewed wall interference efforts. A brief overview and current status of some Langley sponsored transonic wind tunnel wall interference research are presented. Included are continuing efforts in basic wall flow studies, wall interference assessment/correction procedures, and adaptive wall technology.

  4. Mechanical pre-cutting, a rediscovered tunneling technique

    NASA Astrophysics Data System (ADS)

    van Walsum, E.

    1991-04-01

    In 1950, the exact outlines of some circular tunnels, to be driven through chalk for the Corps of Engineers' Fort Randall Reservoir Project on the Missouri River at Pickstown, South Dakota, U.S.A., were pre-cut mechanically, i. e. prior to blasting the tunnel openings. No further applications of mechanical pre-cutting as a tunneling technique were made until the technique was rediscovered and further developed in France during the seventies. These further developments relate to the pre-cutting of harder rocks and the pre-cutting of cohesive and non-cohesive soils combined with the construction of a concrete pre-lining, i. e. a lining which is in place before the ground under it is excavated. Mechanical pre-cutting, as presently practiced, improves the quality and safety of tunneling and reduces surface settlement, noise and vibration. It is concluded that the technique is likely to be applied in the future in the construction of various types of underground structures whenever conventional tunneling is too risky or when environmental concerns are important.

  5. [Occupational carpal tunnel syndrome: 27 cases].

    PubMed

    Slimane, Neila Ben; Elleuch, Mohamed; Gharbi, Ezzedine; Babay, Habib; Hamdoun, Moncef

    2010-09-01

    Carpal tunnel syndrome is the most frequent of tunnel syndromes in the field of the professional sphere. It is related to repetitive movements of flexion-extension of the wrist and fingers or to a support on the heel of the hands. To determine the posts in a risk and to specify the modalities of guaranteed reimbursement of professional carpal tunnel syndrome. A retrospective and descriptive study of 27 medical files of employees indemnified for professional carpal tunnel syndrome registered in the medical control services of the social security office in charge of medical insurance of Tunis and Sousse during a period of 10 years (1995-2004). There were 24 women and 3 men with the average age of 40 years all occupying posts in a risk. Their average time of service is 15 years. Tow-thirds of them work in the clothing and textile industry. The attack is bilateral in 13 cases. Nightly acroparaesthesia rules the clinical rate (44.44% of cases). Motor disorders are noted in the quarter of cases. The electromyogram had confirmed diagnosis in all of cases. The previous state study put in evidence the antecedent of carpal tunnel syndrome in 5 cases and diabetes in one case. Twenty-one patients had profit of permanent partial incapacity with a rate varying from 3 to 25%. Five had got a transfer of working place and one stayed in the same post with a half-time work. The professional origin of carpal tunnel syndrome must be called up in front of an activity in a risk. The reparation is done according to picture 82 of occupational diseases.

  6. Wind Tunnel to Atmospheric Mapping for Static Aeroelastic Scaling

    NASA Technical Reports Server (NTRS)

    Heeg, Jennifer; Spain, Charles V.; Rivera, J. A.

    2004-01-01

    Wind tunnel to Atmospheric Mapping (WAM) is a methodology for scaling and testing a static aeroelastic wind tunnel model. The WAM procedure employs scaling laws to define a wind tunnel model and wind tunnel test points such that the static aeroelastic flight test data and wind tunnel data will be correlated throughout the test envelopes. This methodology extends the notion that a single test condition - combination of Mach number and dynamic pressure - can be matched by wind tunnel data. The primary requirements for affecting this extension are matching flight Mach numbers, maintaining a constant dynamic pressure scale factor and setting the dynamic pressure scale factor in accordance with the stiffness scale factor. The scaling is enabled by capabilities of the NASA Langley Transonic Dynamics Tunnel (TDT) and by relaxation of scaling requirements present in the dynamic problem that are not critical to the static aeroelastic problem. The methodology is exercised in two example scaling problems: an arbitrarily scaled wing and a practical application to the scaling of the Active Aeroelastic Wing flight vehicle for testing in the TDT.

  7. Highly doped layer for tunnel junctions in solar cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fetzer, Christopher M.

    A highly doped layer for interconnecting tunnel junctions in multijunction solar cells is presented. The highly doped layer is a delta doped layer in one or both layers of a tunnel diode junction used to connect two or more p-on-n or n-on-p solar cells in a multijunction solar cell. A delta doped layer is made by interrupting the epitaxial growth of one of the layers of the tunnel diode, depositing a delta dopant at a concentration substantially greater than the concentration used in growing the layer of the tunnel diode, and then continuing to epitaxially grow the remaining tunnel diode.

  8. ACL double-bundle reconstruction with one tibial tunnel provides equal stability compared to two tibial tunnels.

    PubMed

    Drews, Björn Holger; Seitz, Andreas Martin; Huth, Jochen; Bauer, Gerhard; Ignatius, Anita; Dürselen, Lutz

    2017-05-01

    The purpose of this study was to investigate whether an anterior cruciate ligament (ACL) double-bundle reconstruction with one tibial tunnel displays the same in vitro stability as a conventional double-bundle reconstruction with two tibial tunnels when using the same tensioning protocol. In 11 fresh-frozen cadaveric knees, ACL double-bundle reconstruction with one and two tibial tunnels was performed. The two grafts were tightened using 80 N in different flexion angles (anteromedial-bundle at 60° and posterolateral-bundle at 15°). Anterior tibial translation (134 N) and translation with combined rotatory and valgus loads (10 Nm valgus stress and 4 Nm internal tibial torque) were determined at 0°, 30°, 60° and 90° flexion. Measurements were taken in intact ACL, resected ACL, three-tunnel reconstruction and four-tunnel reconstruction. Additionally, the tension on the grafts was determined. Student's t test was performed for statistical analysis of the related samples. Significance was set at p < 0.017 according to Bonferroni correction. The two reconstructive techniques displayed no significant differences in comparison with the intact ACL in anterior tibial translation at 0°, 60° and 90° of flexion. The same results were obtained for the anterior tibial translation with a combined rotatory load at 60° and 90°. When directly comparing both reconstructive techniques, there were no significant differences for the anterior tibial translation and combined rotatory load at all flexion angles. The measured tension on grafts displayed similar load sharing between both bundles. Except at full extension, both grafts displayed a significantly different tension increase under anterior tibial translation for both techniques (p = 0.0086). Tightening both bundles in ACL double-bundle reconstruction with one or two tibial tunnels in different flexion angles achieved comparable restoration of stability, although there was different load sharing on the bundles

  9. Setup in the Icing Research Tunnel Test Section

    NASA Image and Video Library

    1969-02-21

    Technicians set up test hardware inside the test section of the Icing Research Tunnel at the National Aeronautics and Space Administration (NASA) Lewis Research Center. The Icing Research Tunnel was built in the early 1940s to study the formation of ice on aircraft surfaces and develop methods of preventing or eradicating that ice. Ice buildup is dangerous because it adds extra weight, effects aerodynamics, and sometimes blocks air flow through engines. The Icing Research Tunnel is a closed-loop atmospheric wind tunnel with a 6- by 9-foot test section. The tunnel can produce speeds up to 300 miles per hour and temperatures from 30 to -45 °F. NACA engineers struggled initially to perfect a spray bar system to introduce moisture into the airstream. The tunnel was shut down in the late 1950s as the center focused its energy exclusively on space. Industrial customers began using the tunnel sporadically, then steadily, in the 1960s. Boeing, Aerojet, Lockheed, Sikorsky, Beech and others ran tests during the 1960s. Boeing analyzed engine inlets for the CH-47 Chinook, CH-46 (Sea Knight) and CH-113. This photograph was taken during a series of 100 ice-phobic coatings for the Federal Aviation Administration. They found that many of the coatings reduced ice adhesion to the test sample, but they could not be used for aircraft applications.

  10. Object-Based Attention and Cognitive Tunneling

    ERIC Educational Resources Information Center

    Jarmasz, Jerzy; Herdman, Chris M.; Johannsdottir, Kamilla Run

    2005-01-01

    Simulator-based research has shown that pilots cognitively tunnel their attention on head-up displays (HUDs). Cognitive tunneling has been linked to object-based visual attention on the assumption that HUD symbology is perceptually grouped into an object that is perceived and attended separately from the external scene. The present research…

  11. Comparison of propeller cruise noise data taken in the NASA Lewis 8- by 6-foot wind tunnel with other tunnel and flight data

    NASA Technical Reports Server (NTRS)

    Dittmar, James H.

    1989-01-01

    The noise of advanced high speed propeller models measured in the NASA 8- by 6-foot wind tunnel has been compared with model propeller noise measured in another tunnel and with full-scale propeller noise measured in flight. Good agreement was obtained for the noise of a model counterrotation propeller tested in the 8- by 6-foot wind tunnel and in the acoustically treated test section of the Boeing Transonic Wind Tunnel. This good agreement indicates the relative validity of taking cruise noise data on a plate in the 8- by 6-foot wind tunnel compared with the free-field method in the Boeing tunnel. Good agreement was also obtained for both single rotation and counter-rotation model noise comparisons with full-scale propeller noise in flight. The good scale model to full-scale comparisons indicate both the validity of the 8- by 6-foot wind tunnel data and the ability to scale to full size. Boundary layer refraction on the plate provides a limitation to the measurement of forward arc noise in the 8- by 6-foot wind tunnel at the higher harmonics of the blade passing tone. The use of a validated boundary layer refraction model to adjust the data could remove this limitation.

  12. Comparison of propeller cruise noise data taken in the NASA Lewis 8- by 6-foot wind tunnel with other tunnel and flight data

    NASA Technical Reports Server (NTRS)

    Dittmar, James

    1989-01-01

    The noise of advanced high speed propeller models measured in the NASA 8- by 6-foot wind tunnel has been compared with model propeller noise measured in another tunnel and with full-scale propeller noise measured in flight. Good agreement was obtained for the noise of a model counterrotation propeller tested in the 8- by 6-foot wind tunnel and in the acoustically treated test section of the Boeing Transonic Wind Tunnel. This good agreement indicates the relative validity of taking cruise noise data on a plate in the 8- by 6-foot wind tunnel compared with the free-field method in the Boeing tunnel. Good agreement was also obtained for both single rotation and counter-rotation model noise comparisons with full-scale propeller noise in flight. The good scale model to full-scale comparisons indicate both the validity of the 8- by 6-foot wind tunnel data and the ability to scale to full size. Boundary layer refraction on the plate provides a limitation to the measurement of forward arc noise in the 8- by 6-foot wind tunnel at the higher harmonics of the blade passing tone. The sue of a validated boundary layer refraction model to adjust the data could remove this limitation.

  13. 1. West portal of Tunnel 23, contextual view to the ...

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

    1. West portal of Tunnel 23, contextual view to the west-northwest, 380mm lens. Tunnel 22 pierces the toe of Lookout Point. Note that the tracks have been realigned toward the Willamette River to bypass Tunnel 23. - Southern Pacific Railroad Natron Cutoff, Tunnel 23, Milepost 584.5, Westfir, Lane County, OR

  14. Instanton and noninstanton tunneling in periodically perturbed barriers: semiclassical and quantum interpretations.

    PubMed

    Takahashi, Kin'ya; Ikeda, Kensuke S

    2012-11-01

    In multidimensional barrier tunneling, there exist two different types of tunneling mechanisms, instanton-type tunneling and noninstanton tunneling. In this paper we investigate transitions between the two tunneling mechanisms from the semiclassical and quantum viewpoints taking two simple models: a periodically perturbed Eckart barrier for the semiclassical analysis and a periodically perturbed rectangular barrier for the quantum analysis. As a result, similar transitions are observed with change of the perturbation frequency ω for both systems, and we obtain a comprehensive scenario from both semiclassical and quantum viewpoints for them. In the middle range of ω, in which the plateau spectrum is observed, noninstanton tunneling dominates the tunneling process, and the tunneling amplitude takes the maximum value. Noninstanton tunneling explained by stable-unstable manifold guided tunneling (SUMGT) from the semiclassical viewpoint is interpreted as multiphoton-assisted tunneling from the quantum viewpoint. However, in the limit ω→0, instanton-type tunneling takes the place of noninstanton tunneling, and the tunneling amplitude converges on a constant value depending on the perturbation strength. The spectrum localized around the input energy is observed, and there is a scaling law with respect to the width of the spectrum envelope, i.e., the width ∝ℏω. In the limit ω→∞, the tunneling amplitude converges on that of the unperturbed system, i.e., the instanton of the unperturbed system.

  15. A tilting wind tunnel for fire behavior studies

    Treesearch

    David R. Weise

    1994-01-01

    The combined effects of wind velocity and slope on wildland fire behavior can be studied in the laboratory using a tilting wind tunnel. The tilting wind tunnel requires a commercially available fan to induce wind and can be positioned to simulate heading and backing fires spreading up and down slope. The tunnel is portable and can be disassembled for transport using a...

  16. Petrology and geochemistry of samples from bed-contact zones in Tunnel Bed 5, U12g-Tunnel, Nevada Test Site

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Connolly, J.R.; Keil, K.; Mansker, W.L.

    1984-10-01

    This report summarizes the detailed geologic characterization of samples of bed-contact zones and surrounding nonwelded bedded tuffs, both within Tunnel Bed 5, that are exposed in the G-Tunnel complex beneath Rainier Mesa on the Nevada Test Site (NTS). Original planning studies treated the bed-contact zones in Tunnel Bed 5 as simple planar surfaces of relatively high permeability. Detailed characterization, however, indicates that these zones have a finite thickness, are depositional in origin, vary considerably over short vertical and horizontal distances, and are internally complex. Fluid flow in a sequence of nonwelded zeolitized ash-flow or bedded tuffs and thin intervening reworkedmore » zones appears to be a porous-medium phenomenon, regardless of the presence of layering. There are no consistent differences in either bulk composition or detailed mineralogy between bedded tuffs and bed-contact zones in Tunnel Bed 5. Although the original bulk composition of Tunnel Bed 5 was probably peralkaline, extensive zeolitization has resulted in a present peraluminous bulk composition of both bedded tuffs and bed-contact zones. The major zeolite present, clinoptilolite, is intermediate (Ca:K:Na = 26:35:39) and effectively uniform in composition. This composition is similar to that of clinoptilolite from the tuffaceous beds of Calico Hills above the static water level in hole USW G-1, but somewhat different from that reported for zeolites from below the static water level in USW G-2. Tunnel Bed 5 also contains abundant hydrous manganese oxides. The similarity in composition of the clinoptilolites from Tunnel Bed 5 and those above the static water level at Yucca Mountain indicates that many of the results of nuclide-migration experiments in Tunnel Bed 5 would be transferrable to zeolitized nonwelded tuffs above the static water level at Yucca Mountain.« less

  17. 43 CFR 3832.42 - How do I locate a tunnel site?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... substantial post, board, or monument at the face of the tunnel, which is the point where the tunnel enters... height and width of the tunnel; and (4) The course and distance from the face or starting point to some... boundary lines of the tunnel at proper intervals as required under state law from the face of the tunnel...

  18. 43 CFR 3832.42 - How do I locate a tunnel site?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... substantial post, board, or monument at the face of the tunnel, which is the point where the tunnel enters... height and width of the tunnel; and (4) The course and distance from the face or starting point to some... boundary lines of the tunnel at proper intervals as required under state law from the face of the tunnel...

  19. Mars Surface Tunnel Element Concept

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A.; Mary, Natalie; Howe, A. Scott; Jeffries, Sharon

    2016-01-01

    How Mars surface crews get into their ascent vehicle has profound implications for Mars surface architecture. To meet planetary protection protocols, the architecture has get Intravehicular Activity (IVA)-suited crew into a Mars Ascent Vehicle (MAV) without having to step outside into the Mars environment. Pushing EVA suit don/doff and EVA operations to an element that remains on the surface also helps to minimize MAV cabin volume, which in turn can reduce MAV cabin mass. Because the MAV will require at least seven kilograms of propellant to ascend each kilogram of cabin mass, minimal MAV mass is desired. For architectures involving more than one surface element-such as an ascent vehicle and a pressurized rover or surface habitat-a retractable tunnel is an attractive solution. Beyond addressing the immediate MAV access issue, a reusable tunnel may be useful for other surface applications once its primary mission is complete. A National Aeronautics and Space Administration (NASA) team is studying the optimal balance between surface tunnel functionality, mass, and stowed volume as part of the Evolvable Mars Campaign (EMC). The "Minimum Functional Tunnel" is a conceptual design that performs a single function. Having established this baseline configuration, the next step is to trade design options, evaluate other applications, and explore alternative solutions.

  20. Management of Carpal Tunnel Syndrome.

    PubMed

    Mooar, Pekka A; Doherty, William J; Murray, Jayson N; Pezold, Ryan; Sevarino, Kaitlyn S

    2018-03-15

    The American Academy of Orthopaedic Surgeons (AAOS) has developed Appropriate Use Criteria (AUC) for Management of Carpal Tunnel Syndrome. Evidence-based information, in conjunction with the clinical expertise of physicians, was used to develop the criteria to improve patient care and obtain best outcomes while considering the subtleties and distinctions necessary in making clinical decisions. To provide the evidence foundation for this AUC, the AAOS Evidence-Based Medicine Unit provided the writing panel and voting panel with the 2016 AAOS Clinical Practice Guideline titled Management of Carpal Tunnel Syndrome Evidence-Based Clinical Practice Guideline. The Management of Carpal Tunnel Syndrome AUC clinical patient scenarios were derived from indications typical of patients with suspected carpal tunnel syndrome in clinical practice, as well as from current evidence-based clinical practice guidelines and supporting literature to identify the appropriateness of treatments. The 135 patient scenarios and 6 treatments were developed by the writing panel, a group of clinicians who are specialists in this AUC topic. Next, a separate, multidisciplinary, voting panel (made up of specialists and nonspecialists) rated the appropriateness of treatment of each patient scenario using a 9-point scale to designate a treatment as Appropriate (median rating, 7 to 9), May Be Appropriate (median rating, 4 to 6), or Rarely Appropriate (median rating, 1 to 3).

  1. Understanding Quantum Tunneling through Quantum Monte Carlo Simulations.

    PubMed

    Isakov, Sergei V; Mazzola, Guglielmo; Smelyanskiy, Vadim N; Jiang, Zhang; Boixo, Sergio; Neven, Hartmut; Troyer, Matthias

    2016-10-28

    The tunneling between the two ground states of an Ising ferromagnet is a typical example of many-body tunneling processes between two local minima, as they occur during quantum annealing. Performing quantum Monte Carlo (QMC) simulations we find that the QMC tunneling rate displays the same scaling with system size, as the rate of incoherent tunneling. The scaling in both cases is O(Δ^{2}), where Δ is the tunneling splitting (or equivalently the minimum spectral gap). An important consequence is that QMC simulations can be used to predict the performance of a quantum annealer for tunneling through a barrier. Furthermore, by using open instead of periodic boundary conditions in imaginary time, equivalent to a projector QMC algorithm, we obtain a quadratic speedup for QMC simulations, and achieve linear scaling in Δ. We provide a physical understanding of these results and their range of applicability based on an instanton picture.

  2. Enhancement of Spin-transfer torque switching via resonant tunneling

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chatterji, Niladri; Tulapurkar, Ashwin A.; Muralidharan, Bhaskaran

    We propose the use of resonant tunneling as a route to enhance the spin-transfer torque switching characteristics of magnetic tunnel junctions. The proposed device structure is a resonant tunneling magnetic tunnel junction based on a MgO-semiconductor heterostructure sandwiched between a fixed magnet and a free magnet. Using the non-equilibrium Green's function formalism coupled self consistently with the Landau-Lifshitz-Gilbert-Slonczewski equation, we demonstrate enhanced tunnel magneto-resistance characteristics as well as lower switching voltages in comparison with traditional trilayer devices. Two device designs based on MgO based heterostructures are presented, where the physics of resonant tunneling leads to an enhanced spin transfer torquemore » thereby reducing the critical switching voltage by up to 44%. It is envisioned that the proof-of-concept presented here may lead to practical device designs via rigorous materials and interface studies.« less

  3. Increased risk of obstructive pulmonary disease in tunnel workers.

    PubMed

    Ulvestad, B; Bakke, B; Melbostad, E; Fuglerud, P; Kongerud, J; Lund, M B

    2000-04-01

    Tunnel workers are exposed to gases and particles from blasting and diesel exhausts. The aim of this study was to assess the occurrence of respiratory symptoms and airflow limitation in tunnel workers and to relate these findings to years of exposure. Two hundred and twelve tunnel workers and a reference group of 205 other heavy construction workers participated in a cross sectional investigation. Exposure measurements were carried out to demonstrate the difference in exposure between the two occupational groups. Spirometric tests and a questionnaire on respiratory symptoms and smoking habits were applied. Atopy was determined by a multiple radioallergosorbent test (RAST). Radiological signs of silicosis were evaluated. Respiratory symptoms and lung function were studied in relation to years of exposure and adjusted for smoking habits and atopy. Compared with the reference subjects the tunnel workers had a significant decrease in forced vital capacity (FVC) % predicted and forced expiratory volume in one second (FEV(1)) % predicted when related to years of exposure. Adjusted FEV(1) decreased by 17 ml for each year of tunnel work exposure compared with 0.5 ml in outdoor heavy construction workers. The tunnel workers also reported significantly higher occurrence of respiratory symptoms. The prevalence of chronic obstructive pulmonary disease (COPD) was 14% in the tunnel workers compared with 8% in the reference subjects. Exposure to dust and gases from diesel exhaust, blasting, drilling and rock transport in tunnel work enhances the risk for accelerated decline in FEV(1), respiratory symptoms, and COPD in tunnel workers compared with other heavy construction workers.

  4. Scanning Tunneling Microscope For Use In Vacuum

    NASA Technical Reports Server (NTRS)

    Abel, Phillip B.

    1993-01-01

    Scanning tunneling microscope with subangstrom resolution developed to study surface structures. Although instrument used in air, designed especially for use in vacuum. Scanning head is assembly of small, mostly rigid components made of low-outgassing materials. Includes coarse-positioning mechanical-translation stage, on which specimen mounted by use of standard mounting stub. Tunneling tip mounted on piezoelectric fine-positioning tube. Application of suitable voltages to electrodes on piezoelectric tube controls scan of tunneling tip across surface of specimen. Electronic subsystem generates scanning voltages and collects data.

  5. Band-pass Fabry-Pèrot magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Sharma, Abhishek; Tulapurkar, Ashwin. A.; Muralidharan, Bhaskaran

    2018-05-01

    We propose a high-performance magnetic tunnel junction by making electronic analogs of optical phenomena such as anti-reflections and Fabry-Pèrot resonances. The devices we propose feature anti-reflection enabled superlattice heterostructures sandwiched between the fixed and the free ferromagnets of the magnetic tunnel junction structure. Our predictions are based on non-equilibrium Green's function spin transport formalism coupled self-consistently with the Landau-Lifshitz-Gilbert-Slonczewski equation. Owing to the physics of bandpass spin filtering in the bandpass Fabry-Pèrot magnetic tunnel junction device, we demonstrate an ultra-high boost in the tunnel magneto-resistance (≈5 × 104%) and nearly 1200% suppression of spin transfer torque switching bias in comparison to a traditional trilayer magnetic tunnel junction device. The proof of concepts presented here can lead to next-generation spintronic device design harvesting the rich physics of superlattice heterostructures and exploiting spintronic analogs of optical phenomena.

  6. Effects of static fingertip loading on carpal tunnel pressure

    NASA Technical Reports Server (NTRS)

    Rempel, D.; Keir, P. J.; Smutz, W. P.; Hargens, A.

    1997-01-01

    The purpose of this study was to explore the relationship between carpal tunnel pressure and fingertip force during a simple pressing task. Carpal tunnel pressure was measured in 15 healthy volunteers by means of a saline-filled catheter inserted percutaneously into the carpal tunnel of the nondominant hand. The subjects pressed on a load cell with the tip of the index finger and with 0, 6, 9, and 12 N of force. The task was repeated in 10 wrist postures: neutral; 10 and 20 degrees of ulnar deviation; 10 degrees of radial deviation; and 15, 30, and 45 degrees of both flexion and extension. Fingertip loading significantly increased carpal tunnel pressure for all wrist angles (p = 0.0001). Post hoc analyses identified significant increase (p < 0.05) in carpal tunnel pressure between unloaded (0 N) and all loaded conditions, as well as between the 6 and 12 N load conditions. This study demonstrates that the process whereby fingertip loading elevates carpal tunnel pressure is independent of wrist posture and that relatively small fingertip loads have a large effect on carpal tunnel pressure. It also reveals the response characteristics of carpal tunnel pressure to fingertip loading, which is one step in understanding the relationship between sustained grip and pinch activities and the aggravation or development of median neuropathy at the wrist.

  7. 4. East portal of Tunnel 22, view to the eastsoutheast, ...

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

    4. East portal of Tunnel 22, view to the east-southeast, 135mm lens with electronic flash fill. Note the depth of water within the tunnel, a sympton of the spring-laden slope above the tunnel that led to its eventual abandonment. - Southern Pacific Railroad Natron Cutoff, Tunnel 23, Milepost 584.5, Westfir, Lane County, OR

  8. Mitigation of wind tunnel wall interactions in subsonic cavity flows

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wagner, Justin L.; Casper, Katya Marie; Beresh, Steven J.

    In this study, the flow over an open aircraft bay is often represented in a wind tunnel with a cavity. In flight, this flow is unconfined, though in experiments, the cavity is surrounded by wind tunnel walls. If untreated, wind tunnel wall effects can lead to significant distortions of cavity acoustics in subsonic flows. To understand and mitigate these cavity–tunnel interactions, a parametric approach was taken for flow over an L/D = 7 cavity at Mach numbers 0.6–0.8. With solid tunnel walls, a dominant cavity tone was observed, likely due to an interaction with a tunnel duct mode. Furthermore, anmore » acoustic liner opposite the cavity decreased the amplitude of the dominant mode and its harmonics, a result observed by previous researchers. Acoustic dampeners were also placed in the tunnel sidewalls, which further decreased the dominant mode amplitudes and peak amplitudes associated with nonlinear interactions between cavity modes. This then indicates that cavity resonance can be altered by tunnel sidewalls and that spanwise coupling should be addressed when conducting subsonic cavity experiments. Though mechanisms for dominant modes and nonlinear interactions likely exist in unconfined cavity flows, these effects can be amplified by the wind tunnel walls.« less

  9. Mitigation of wind tunnel wall interactions in subsonic cavity flows

    DOE PAGES

    Wagner, Justin L.; Casper, Katya Marie; Beresh, Steven J.; ...

    2015-03-06

    In this study, the flow over an open aircraft bay is often represented in a wind tunnel with a cavity. In flight, this flow is unconfined, though in experiments, the cavity is surrounded by wind tunnel walls. If untreated, wind tunnel wall effects can lead to significant distortions of cavity acoustics in subsonic flows. To understand and mitigate these cavity–tunnel interactions, a parametric approach was taken for flow over an L/D = 7 cavity at Mach numbers 0.6–0.8. With solid tunnel walls, a dominant cavity tone was observed, likely due to an interaction with a tunnel duct mode. Furthermore, anmore » acoustic liner opposite the cavity decreased the amplitude of the dominant mode and its harmonics, a result observed by previous researchers. Acoustic dampeners were also placed in the tunnel sidewalls, which further decreased the dominant mode amplitudes and peak amplitudes associated with nonlinear interactions between cavity modes. This then indicates that cavity resonance can be altered by tunnel sidewalls and that spanwise coupling should be addressed when conducting subsonic cavity experiments. Though mechanisms for dominant modes and nonlinear interactions likely exist in unconfined cavity flows, these effects can be amplified by the wind tunnel walls.« less

  10. Rocket Plume Scaling for Orion Wind Tunnel Testing

    NASA Technical Reports Server (NTRS)

    Brauckmann, Gregory J.; Greathouse, James S.; White, Molly E.

    2011-01-01

    A wind tunnel test program was undertaken to assess the jet interaction effects caused by the various solid rocket motors used on the Orion Launch Abort Vehicle (LAV). These interactions of the external flowfield and the various rocket plumes can cause localized aerodynamic disturbances yielding significant and highly non-linear control amplifications and attenuations. This paper discusses the scaling methodologies used to model the flight plumes in the wind tunnel using cold air as the simulant gas. Comparisons of predicted flight, predicted wind tunnel, and measured wind tunnel forces-and-moments and plume flowfields are made to assess the effectiveness of the selected scaling methodologies.

  11. Use of 3D Printing for Custom Wind Tunnel Fabrication

    NASA Astrophysics Data System (ADS)

    Gagorik, Paul; Bates, Zachary; Issakhanian, Emin

    2016-11-01

    Small-scale wind tunnels for the most part are fairly simple to produce with standard building equipment. However, the intricate bell housing and inlet shape of an Eiffel type wind tunnel, as well as the transition from diffuser to fan in a rectangular tunnel can present design and construction obstacles. With the help of 3D printing, these shapes can be custom designed in CAD models and printed in the lab at very low cost. The undergraduate team at Loyola Marymount University has built a custom benchtop tunnel for gas turbine film cooling experiments. 3D printing is combined with conventional construction methods to build the tunnel. 3D printing is also used to build the custom tunnel floor and interchangeable experimental pieces for various experimental shapes. This simple and low-cost tunnel is a custom solution for specific engineering experiments for gas turbine technology research.

  12. Tunnel flexibility effect on the ground surface acceleration response

    NASA Astrophysics Data System (ADS)

    Baziar, Mohammad Hassan; Moghadam, Masoud Rabeti; Choo, Yun Wook; Kim, Dong-Soo

    2016-09-01

    Flexibility of underground structures relative to the surrounding medium, referred to as the flexibility ratio, is an important factor that influences their dynamic interaction. This study investigates the flexibility effect of a box-shaped subway tunnel, resting directly on bedrock, on the ground surface acceleration response using a numerical model verified against dynamic centrifuge test results. A comparison of the ground surface acceleration response for tunnel models with different flexibility ratios revealed that the tunnels with different flexibility ratios influence the acceleration response at the ground surface in different ways. Tunnels with lower flexibility ratios have higher acceleration responses at short periods, whereas tunnels with higher flexibility ratios have higher acceleration responses at longer periods. The effect of the flexibility ratio on ground surface acceleration is more prominent in the high range of frequencies. Furthermore, as the flexibility ratio of the tunnel system increases, the acceleration response moves away from the free field response and shifts towards the longer periods. Therefore, the flexibility ratio of the underground tunnels influences the peak ground acceleration (PGA) at the ground surface, and may need to be considered in the seismic zonation of urban areas.

  13. Tunneling anisotropic magnetoresistance in complex oxide tunnel junctions

    NASA Astrophysics Data System (ADS)

    Martínez, Benjamín; López-Mir, Laura; Galceran, Regina; Balcells, Lluis; Pomar, Alberto; Konstantinovic, Zorica; Sandiumenge, Felip; Frontera, Carlos; Advanced Characterization of Nanostructured Materials Team

    The magnetotransport properties of La2/3Sr1/3MnO3(LSMO)/LaAlO3(LAO)/ Pt tunneling junctions have been analyzed as a function of temperature and magnetic field. The junctions exhibit magnetoresistance (MR) values of about 37%, at H = 90 kOe at low temperature. However, the temperature dependence of MR indicates a clear distinct origin than that of conventional colossal MR. In addition, tunneling anisotropic MR (TAMR) values around 4% are found at low temperature and its angular dependence reflects the expected uniaxial anisotropy. The use of TAMR response could be an alternative of much easier technological implementation than conventional MTJs since only one magnetic electrode is required, thus opening the door to the implementation of more versatile devices. However, further studies are required in order to improve the strong temperature dependence at the present stage. Finantial support from Spanish Ministry of Economy and Competitiveness through the Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496), and projects MAT2012-33207 and MAT2015-71664-R is acknowledged.

  14. Heusler Alloyed Electrodes Integrated in Magnetic Tunnel-Junctions

    NASA Astrophysics Data System (ADS)

    Hütten, Andreas; Kämmerer, Sven; Schmalhorst, Jan; Reiss, Günter

    As a consequence of the growing theoretically predictions of 100% spin polarized half- and full-Heusler compounds over the past 6 years, Heusler alloys are among the most promising materials class for future magnetoelectronic and spintronic applications. We have integrated Co2MnSi as a representative of the full-Heusler compound family as one magnetic electrode into technological relevant magnetic tunnel junctions. The resulting tunnel magnetoresistance at 20 K was determined to be 95% corresponding to a Co2MnSi spin polarization of 66% in combination with an AlOx barrier thickness of 1.8 nm. For magnetic tunnel junctions prepared with an initially larger Al layer prior to oxidation the tunnel magnetoresistance at 20 K increases to about 108% associated with a Co2MnSi spin polarization of 72% clearly proving that Co2MnSi is already superior to 3d-based magnetic elements or their alloys. The corresponding room temperature values of the tunnel magnetoresistance are 33% and 41%, respectively. Structural and magnetic properties of the Co2MnSi AlOx - barrier interface have been studied with X-ray diffraction, electron and X-ray absorption spectroscopy and X-ray magnetic circular dichroism and it is shown that the ferromagnetic order of Mn and Co spins at this interface is only induced in optimally annealed Co2MnSi layer. The underlying atomic ordering mechanism responsible for achieving about its theoretical magnetic moment could be assigned to the elimination of Co-Si antisite defects whereas the reduction of Co-Mn antisite defects results in large tunnel magnetoresistance. The presence of a step like tunnel barrier which is already created during plasma oxidation while preparing the AlOx tunnel barrier has been identified as the current limitation to achieve larger tunnel magnetoresistance and hence larger spin polarization and is a direct consequence of the oxygen affinity of the Co2MnSi - Heusler elements Mn and Si.

  15. Reducing Mouse Anxiety during Handling: Effect of Experience with Handling Tunnels

    PubMed Central

    Gouveia, Kelly; Hurst, Jane L.

    2013-01-01

    Handling stress is a well-recognised source of variation in animal studies that can also compromise the welfare of research animals. To reduce background variation and maximise welfare, methods that minimise handling stress should be developed and used wherever possible. Recent evidence has shown that handling mice by a familiar tunnel that is present in their home cage can minimise anxiety compared with standard tail handling. As yet, it is unclear whether a tunnel is required in each home cage to improve response to handling. We investigated the influence of prior experience with home tunnels among two common strains of laboratory mice: ICR(CD-1) and C57BL/6. We compared willingness to approach the handler and anxiety in an elevated plus maze test among mice picked up by the tail, by a home cage tunnel or by an external tunnel shared between cages. Willingness to interact with the handler was much greater for mice handled by a tunnel, even when this was unfamiliar, compared to mice picked up by the tail. Once habituated to handling, C57BL/6 mice were most interactive towards a familiar home tunnel, whereas the ICR strain showed strong interaction with all tunnel handling regardless of any experience of a home cage tunnel. Mice handled by a home cage or external tunnel showed less anxiety in an elevated plus maze than those picked up by the tail. This study shows that using a tunnel for routine handling reduces anxiety among mice compared to tail handling regardless of prior familiarity with tunnels. However, as home cage tunnels can further improve response to handling in some mice, we recommend that mice are handled with a tunnel provided in their home cage where possible as a simple practical method to minimise handling stress. PMID:23840458

  16. Reducing mouse anxiety during handling: effect of experience with handling tunnels.

    PubMed

    Gouveia, Kelly; Hurst, Jane L

    2013-01-01

    Handling stress is a well-recognised source of variation in animal studies that can also compromise the welfare of research animals. To reduce background variation and maximise welfare, methods that minimise handling stress should be developed and used wherever possible. Recent evidence has shown that handling mice by a familiar tunnel that is present in their home cage can minimise anxiety compared with standard tail handling. As yet, it is unclear whether a tunnel is required in each home cage to improve response to handling. We investigated the influence of prior experience with home tunnels among two common strains of laboratory mice: ICR(CD-1) and C57BL/6. We compared willingness to approach the handler and anxiety in an elevated plus maze test among mice picked up by the tail, by a home cage tunnel or by an external tunnel shared between cages. Willingness to interact with the handler was much greater for mice handled by a tunnel, even when this was unfamiliar, compared to mice picked up by the tail. Once habituated to handling, C57BL/6 mice were most interactive towards a familiar home tunnel, whereas the ICR strain showed strong interaction with all tunnel handling regardless of any experience of a home cage tunnel. Mice handled by a home cage or external tunnel showed less anxiety in an elevated plus maze than those picked up by the tail. This study shows that using a tunnel for routine handling reduces anxiety among mice compared to tail handling regardless of prior familiarity with tunnels. However, as home cage tunnels can further improve response to handling in some mice, we recommend that mice are handled with a tunnel provided in their home cage where possible as a simple practical method to minimise handling stress.

  17. Fast Heavy-Atom Tunneling in Trifluoroacetyl Nitrene.

    PubMed

    Wu, Zhuang; Feng, Ruijuan; Li, Hongmin; Xu, Jian; Deng, Guohai; Abe, Manabu; Bégué, Didier; Liu, Kun; Zeng, Xiaoqing

    2017-12-04

    Chemical reactions involving quantum mechanical tunneling (QMT) increasingly attract the attention of scientists. In contrast to the hydrogen-tunneling as frequently observed in chemistry and biology, tunneling solely by heavy atoms is rare. Herein, we report heavy-atom tunneling in trifluoroacetyl nitrene, CF 3 C(O)N. The carbonyl nitrene CF 3 C(O)N in the triplet ground state was generated in cryogenic matrices by laser (193 or 266 nm) photolysis of CF 3 C(O)N 3 and characterized by IR and EPR spectroscopy. In contrast to the theoretically predicted activation barriers (>10 kcal mol -1 ), CF 3 C(O)N undergoes rapid rearrangement into CF 3 NCO with half-life times of less than 10 min and unprecedentedly large 14 N/ 15 N kinetic isotope effects (1.18-1.33) in solid Ar, Ne, and N 2 matrices even at 2.8 K. The tunneling disappearance of CF 3 C(O)N becomes much slower in the chemically active toluene and in 2-methyltetrahydrofuran at 5 K. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Analysis of different tunneling mechanisms of In{sub x}Ga{sub 1−x}As/AlGaAs tunnel junction light-emitting transistors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wu, Cheng-Han; Wu, Chao-Hsin, E-mail: chaohsinwu@ntu.edu.tw; Graduate Institute of Photonics and Optoelectronics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan

    The electrical and optical characteristics of tunnel junction light-emitting transistors (TJLETs) with different indium mole fractions (x = 5% and 2.5%) of the In{sub x}Ga{sub 1−x}As base-collector tunnel junctions have been investigated. Two electron tunneling mechanisms (photon-assisted or direct tunneling) provide additional currents to electrical output and resupply holes back to the base region, resulting in the upward slope of I-V curves and enhanced optical output under forward-active operation. The larger direct tunneling probability and stronger Franz-Keldysh absorption for 5% TJLET lead to higher collector current slope and less optical intensity enhancement when base-collector junction is under reverse-biased.

  19. Tarsal tunnel syndrome

    MedlinePlus

    Tibial nerve dysfunction; Neuropathy - posterior tibial nerve; Peripheral neuropathy - tibial nerve; Tibial nerve entrapment ... Tarsal tunnel syndrome is an unusual form of peripheral neuropathy . It occurs when there is damage to the ...

  20. Advanced Undergraduate Laboratory Experiment in Inelastic Electron Tunneling Spectroscopy.

    ERIC Educational Resources Information Center

    White, H. W.; Graves, R. J.

    1982-01-01

    An advanced undergraduate laboratory experiment in inelastic electron tunneling spectroscopy is described. Tunnel junctions were fabricated, the tunneling spectra of several molecules absorbed on the surface of aluminum oxide measured, and mode assignments made for several of the prominent peaks in spectra using results obtained from optical…

  1. Acoustic measurement study 40 by 80 foot subsonic wind tunnel

    NASA Technical Reports Server (NTRS)

    1974-01-01

    An acoustical study conducted during the period from September 1, 1973 to April 30, 1974 measured sound pressure levels and vibration amplitudes inside and outside of the subsonic tunnel and on the tunnel structure. A discussion of the technical aspects of the study, the field measurement and data reduction procedures, and results are presentd, and conclusions resulting from the study which bear upon near field and far field tunnel noise, upon the tunnel as an acoustical enclosure, and upon the sources of noise within the tunnel drive system are given.

  2. Carpal Tunnel Syndrome: Physical Therapy or Surgery?

    PubMed

    2017-03-01

    Carpal tunnel syndrome causes pain, numbness, and weakness in the wrist and hand. Nearly 50% of all work-related injuries are linked to carpal tunnel syndrome, and people with this injury are more likely to miss work because of it. Patients with carpal tunnel syndrome can be treated with physical therapy or surgery. Although surgery may be considered when the symptoms are severe, more than a third of patients do not return to work within 8 weeks after an operation. Based on the potential side effects and risks of surgery, patients often ask if they might try physical therapy first. An article in the March 2017 issue of JOSPT assesses the effectiveness of therapy and surgery to treat carpal tunnel syndrome. J Orthop Sports Phys Ther 2017;47(3):162. doi:10.2519/jospt.2017.0503.

  3. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 5 2011-07-01 2011-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test...

  4. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 5 2010-07-01 2010-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test...

  5. Structural Monitoring of Metro Infrastructure during Shield Tunneling Construction

    PubMed Central

    Ran, L.; Ye, X. W.; Ming, G.; Dong, X. B.

    2014-01-01

    Shield tunneling construction of metro infrastructure will continuously disturb the soils. The ground surface will be subjected to uplift or subsidence due to the deep excavation and the extrusion and consolidation of the soils. Implementation of the simultaneous monitoring with the shield tunnel construction will provide an effective reference in controlling the shield driving, while how to design and implement a safe, economic, and effective structural monitoring system for metro infrastructure is of great importance and necessity. This paper presents the general architecture of the shield construction of metro tunnels as well as the procedure of the artificial ground freezing construction of the metro-tunnel cross-passages. The design principles for metro infrastructure monitoring of the shield tunnel intervals in the Hangzhou Metro Line 1 are introduced. The detailed monitoring items and the specified alarming indices for construction monitoring of the shield tunneling are addressed, and the measured settlement variations at different monitoring locations are also presented. PMID:25032238

  6. Reactive tunnel junctions in electrically driven plasmonic nanorod metamaterials

    NASA Astrophysics Data System (ADS)

    Wang, Pan; Krasavin, Alexey V.; Nasir, Mazhar E.; Dickson, Wayne; Zayats, Anatoly V.

    2018-02-01

    Non-equilibrium hot carriers formed near the interfaces of semiconductors or metals play a crucial role in chemical catalysis and optoelectronic processes. In addition to optical illumination, an efficient way to generate hot carriers is by excitation with tunnelling electrons. Here, we show that the generation of hot electrons makes the nanoscale tunnel junctions highly reactive and facilitates strongly confined chemical reactions that can, in turn, modulate the tunnelling processes. We designed a device containing an array of electrically driven plasmonic nanorods with up to 1011 tunnel junctions per square centimetre, which demonstrates hot-electron activation of oxidation and reduction reactions in the junctions, induced by the presence of O2 and H2 molecules, respectively. The kinetics of the reactions can be monitored in situ following the radiative decay of tunnelling-induced surface plasmons. This electrically driven plasmonic nanorod metamaterial platform can be useful for the development of nanoscale chemical and optoelectronic devices based on electron tunnelling.

  7. Stonefish envenomation with acute carpal tunnel syndrome.

    PubMed

    Ling, Samuel K K; Cheng, S C; Yen, C H

    2009-12-01

    Stonefish envenomation is a common marine sting. Although stonefish injuries are commonly sustained during maritime activities, this local delicacy can also be considered a regional occupational hazard for chefs. The availability and consumption of stonefish in local restaurants has increased the risk of acute carpal tunnel syndrome after a stonefish injury. This case report describes acute carpal tunnel syndrome following stonefish envenomation. An excellent recovery was achieved after surgical decompression of the carpal tunnel syndrome. Standard management of stonefish injuries should therefore take into account the possibility that this orthopaedic emergency may complicate the injury.

  8. Wall Interference in Two-Dimensional Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Kemp, William B., Jr.

    1986-01-01

    Viscosity and tunnel-wall constraints introduced via boundary conditions. TWINTN4 computer program developed to implement method of posttest assessment of wall interference in two-dimensional wind tunnels. Offers two methods for combining sidewall boundary-layer effects with upper and lower wall interference. In sequential procedure, Sewall method used to define flow free of sidewall effects, then assessed for upper and lower wall effects. In unified procedure, wind-tunnel flow equations altered to incorporate effects from all four walls at once. Program written in FORTRAN IV for batch execution.

  9. Fast Laser Holographic Interferometry For Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Lee, George

    1989-01-01

    Proposed system makes holographic interferograms quickly in wind tunnels. Holograms reveal two-dimensional flows around airfoils and provide information on distributions of pressure, structures of wake and boundary layers, and density contours of flow fields. Holograms form quickly in thermoplastic plates in wind tunnel. Plates rigid and left in place so neither vibrations nor photgraphic-development process degrades accuracy of holograms. System processes and analyzes images quickly. Semiautomatic micro-computer-based desktop image-processing unit now undergoing development moves easily to wind tunnel, and its speed and memory adequate for flows about airfoils.

  10. Tunneling conductance of amine-linked alkyl chains.

    PubMed

    Prodan, Emil; Car, Roberto

    2008-06-01

    The tunneling transport theory developed in ref 9 (Phys. Rev. B 2007, 76, 115102) is applied to molecular devices made of alkyl chains linked to gold electrodes via amine groups. Using the analytic expression of the tunneling conductance derived in our previous work, we identify the key physical quantities that characterize the conductance of these devices. By investigating the transport characteristics of three devices, containing four, six, and eight methyl groups, we extract the dependence of the tunneling conductance on the chain's length, which is an exponential decay law in agreement with recent experimental data.

  11. Water tunnel flow visualization using a laser

    NASA Technical Reports Server (NTRS)

    Beckner, C.; Curry, R. E.

    1985-01-01

    Laser systems for flow visualization in water tunnels (similar to the vapor screen technique used in wind tunnels) can provide two-dimensional cross-sectional views of complex flow fields. This parametric study documents the practical application of the laser-enhanced visualization (LEV) technique to water tunnel testing. Aspects of the study include laser power levels, flow seeding (using flourescent dyes and embedded particulates), model preparation, and photographic techniques. The results of this study are discussed to provide potential users with basic information to aid in the design and setup of an LEV system.

  12. Tunneling-assisted transport of carriers through heterojunctions.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wampler, William R.; Myers, Samuel M.; Modine, Normand A.

    The formulation of carrier transport through heterojunctions by tunneling and thermionic emission is derived from first principles. The treatment of tunneling is discussed at three levels of approximation: numerical solution of the one-band envelope equation for an arbitrarily specified potential profile; the WKB approximation for an arbitrary potential; and, an analytic formulation assuming constant internal field. The effects of spatially varying carrier chemical potentials over tunneling distances are included. Illustrative computational results are presented. The described approach is used in exploratory physics models of irradiated heterojunction bipolar transistors within Sandia's QASPR program.

  13. Photon-assisted tunneling through a quantum dot

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kouwenhoven, L.P.; Jauhar, S.; McCormick, K.

    1994-07-15

    We study single-electron tunneling in a two-junction device in the presence of microwave radiation. We introduce a model for numerical simulations that extends the Tien-Gordon theory for photon-assisted tunneling to encompass correlated single-electron tunneling. We predict sharp current jumps which reflect the discrete photon energy [ital hf], and a zero-bias current whose sign changes when an electron is added to the central island of the device. Measurements on split-gate quantum dots show microwave-induced features that are in good agreement with the model.

  14. Tunnel Boring Machine Performance Study. Final Report

    DOT National Transportation Integrated Search

    1984-06-01

    Full face tunnel boring machine "TBM" performance during the excavation of 6 tunnels in sedimentary rock is considered in terms of utilization, penetration rates and cutter wear. The construction records are analyzed and the results are used to inves...

  15. Magnetic tunnel spin injectors for spintronics

    NASA Astrophysics Data System (ADS)

    Wang, Roger

    Research in spin-based electronics, or "spintronics", has a universal goal to develop applications for electron spin in a broad range of electronics and strives to produce low power nanoscale devices. Spin injection into semiconductors is an important initial step in the development of spintronic devices, with the goal to create a highly spin polarized population of electrons inside a semiconductor at room temperature for study, characterization, and manipulation. This dissertation investigates magnetic tunnel spin injectors that aim to meet the spin injection requirements needed for potential spintronic devices. Magnetism and spin are inherently related, and chapter 1 provides an introduction on magnetic tunneling and spintronics. Chapter 2 then describes the fabrication of the spin injector structures studied in this dissertation, and also illustrates the optical spin detection technique that correlates the measured electroluminescence polarization from quantum wells to the electron spin polarization inside the semiconductor. Chapter 3 reports the spin injection from the magnetic tunnel transistor (MTT) spin injector, which is capable of producing highly spin polarized tunneling currents by spin selective scattering in its multilayer structure. The MTT achieves ˜10% lower bound injected spin polarization in GaAs at 1.4 K. Chapter 4 reports the spin injection from CoFe-MgO(100) tunnel spin injectors, where spin dependent tunneling through MgO(100) produces highly spin polarized tunneling currents. These structures achieve lower bound spin polarizations exceeding 50% at 100 K and 30% in GaAs at 290 K. The CoFe-MgO spin injectors also demonstrate excellent thermal stability, maintaining high injection efficiencies even after exposure to temperatures of up to 400 C. Bias voltage and temperature dependent studies on these structures indicate a significant dependence of the electroluminescence polarization on the spin and carrier recombination lifetimes inside the

  16. Tunneling measurement of quantum spin oscillations

    NASA Astrophysics Data System (ADS)

    Bulaevskii, L. N.; Hruška, M.; Ortiz, G.

    2003-09-01

    We consider the problem of tunneling between two leads via a localized spin 1/2 or any other microscopic system (e.g., a quantum dot) which can be modeled by a two-level Hamiltonian. We assume that a constant magnetic field B0 acts on the spin, that electrons in the leads are in a voltage driven thermal equilibrium, and that the tunneling electrons are coupled to the spin through exchange and spin-orbit interactions. Using the nonequilibrium Keldysh formalism we find the dependence of the spin-spin and current-current correlation functions on the applied voltage between leads V, temperature T, B0, and on the degree and orientation mα of spin polarization of the electrons in the right (α=R) and left (α=L) leads. We show the following (a) The spin-spin correlation function exhibits a peak at the Larmor frequency, ωL, corresponding to the effective magnetic field B acting upon the spin as determined by B0 and the exchange field induced by tunneling of spin-polarized electrons. (b) If the mα’s are not parallel to B the second-order derivative of the average tunneling current I(V) with respect to V is proportional to the spectral density of the spin-spin correlation function, i.e., exhibits a peak at the voltage V=ħωL/e. (c) In the same situation when V>B the current-current correlation function exhibits a peak at the same frequency. (d) The signal-to-noise (shot-noise) ratio R for this peak reaches a maximum value of order unity, R⩽4, at large V when the spin is decoupled from the environment and the electrons in both leads are fully polarized in the direction perpendicular to B. (e) R≪1 if the electrons are weakly polarized, or if they are polarized in a direction close to B0, or if the spin interacts with the environment stronger than with the tunneling electrons. Our results of a full quantum-mechanical treatment of the tunneling-via-spin model when V≫B are in agreement with those previously obtained in the quasiclassical approach. We discuss also the

  17. Extruded Tunnel Lining System : Phase 1. Conceptual Design and Feasibility Testing.

    DOT National Transportation Integrated Search

    1979-09-01

    The Extruded Tunnel Lining System (ETLS) has been conceived as a means of continuously placing the final concrete tunnel lining directly behind a tunnel boring machine. The system will shorten the time required to excavate and line a tunnel section, ...

  18. A Description of the "Crow's Foot" Tunnel Concept

    NASA Technical Reports Server (NTRS)

    Parrish, Russell V.; Williams, Steven P.; Arthur, Jarvis J., III; Kramer, Lynda J.; Bailey, Randall E.; Prinzel, Lawrence J., III; Norman, R. Michael

    2006-01-01

    NASA Langley Research Center has actively pursued the development and the use of pictorial or three-dimensional perspective displays of tunnel-, pathway- or highway-in-the-sky concepts for presenting flight path information to pilots in all aircraft categories (e.g., transports, General Aviation, rotorcraft) since the late 1970s. Prominent among these efforts has been the development of the crow s foot tunnel concept. The crow's foot tunnel concept emerged as the consensus pathway concept from a series of interactive workshops that brought together government and industry display designers, test pilots, and airline pilots to iteratively design, debate, and fly various pathway concepts. Over years of use in many simulation and flight test activities at NASA and elsewhere, modifications have refined and adapted the tunnel concept for different applications and aircraft categories (i.e., conventional transports, High Speed Civil Transport, General Aviation). A description of those refinements follows the definition of the original tunnel concept.

  19. Intricate Conformational Tunneling in Carbonic Acid Monomethyl Ester.

    PubMed

    Linden, Michael M; Wagner, J Philipp; Bernhardt, Bastian; Bartlett, Marcus A; Allen, Wesley D; Schreiner, Peter R

    2018-04-05

    Disentangling internal and external effects is a key requirement for understanding conformational tunneling processes. Here we report the s- trans/ s- cis tunneling rotamerization of carbonic acid monomethyl ester (1) under matrix isolation conditions and make comparisons to its parent carbonic acid (3). The observed tunneling rate of 1 is temperature-independent in the 3-20 K range and accelerates when using argon instead of neon as the matrix material. The methyl group increases the effective half life (τ eff ) of the energetically disfavored s- trans-conformer from 3-5 h for 3 to 11-13 h for 1. Methyl group deuteration slows the rotamerization further (τ eff ≈ 35 h). CCSD(T)/cc-pVQZ//MP2/aug-cc-pVTZ computations of the tunneling probability suggest that the rate should be almost unaffected by methyl substitution or its deuteration. Thus the observed relative rates are puzzling, and they disagree with previous explanations involving fast vibrational relaxation after the tunneling event facilitated by the alkyl rotor.

  20. Carpal tunnel syndrome - an occupational hazard facing dentistry.

    PubMed

    Abichandani, Sagar; Shaikh, Saquib; Nadiger, Ramesh

    2013-10-01

    The authors wished to evaluate the comprehensive literature on carpal tunnel syndrome to discover work specific to carpal tunnel syndrome among dentists in order to determine whether there is any correlation with dentists having a higher prevalence of its occurrence. A review of dental literature involving carpal tunnel syndrome was undertaken. Details appearing in the literature before 1995 was reviewed in a comprehensive manner and the literature after 1995 were reviewed electronically. The prevalence of carpal tunnel syndrome is higher in dental professionals involved in various aspects of dental specialties. Abnormal postures, including muscle imbalances, muscle necrosis, trigger points, hypomobile joints, nerve compression and spinal disk herniation or degeneration may result in serious detrimental physiological changes in the body. These changes often result in pain, injury or possible neuroskeletal disorders. Dentists have an increased risk of carpal tunnel syndrome and precautions and care should be exercised to prevent detrimental irreversible changes occurring. © 2013 FDI World Dental Federation.

  1. Chaos-assisted tunneling in the presence of Anderson localization.

    PubMed

    Doggen, Elmer V H; Georgeot, Bertrand; Lemarié, Gabriel

    2017-10-01

    Tunneling between two classically disconnected regular regions can be strongly affected by the presence of a chaotic sea in between. This phenomenon, known as chaos-assisted tunneling, gives rise to large fluctuations of the tunneling rate. Here we study chaos-assisted tunneling in the presence of Anderson localization effects in the chaotic sea. Our results show that the standard tunneling rate distribution is strongly modified by localization, going from the Cauchy distribution in the ergodic regime to a log-normal distribution in the strongly localized case, for both a deterministic and a disordered model. We develop a single-parameter scaling description which accurately describes the numerical data. Several possible experimental implementations using cold atoms, photonic lattices, or microwave billiards are discussed.

  2. Enzyme dynamics and hydrogen tunnelling in a thermophilic alcohol dehydrogenase

    NASA Astrophysics Data System (ADS)

    Kohen, Amnon; Cannio, Raffaele; Bartolucci, Simonetta; Klinman, Judith P.; Klinman, Judith P.

    1999-06-01

    Biological catalysts (enzymes) speed up reactions by many orders of magnitude using fundamental physical processes to increase chemical reactivity. Hydrogen tunnelling has increasingly been found to contribute to enzyme reactions at room temperature. Tunnelling is the phenomenon by which a particle transfers through a reaction barrier as a result of its wave-like property. In reactions involving small molecules, the relative importance of tunnelling increases as the temperature is reduced. We have now investigated whether hydrogen tunnelling occurs at elevated temperatures in a biological system that functions physiologically under such conditions. Using a thermophilic alcohol dehydrogenase (ADH), we find that hydrogen tunnelling makes a significant contribution at 65°C this is analogous to previous findings with mesophilic ADH at 25°C ( ref. 5). Contrary to predictions for tunnelling through a rigid barrier, the tunnelling with the thermophilic ADH decreases at and below room temperature. These findings provide experimental evidence for a role of thermally excited enzyme fluctuations in modulating enzyme-catalysed bond cleavage.

  3. Increased risk of obstructive pulmonary disease in tunnel workers

    PubMed Central

    Ulvestad, B.; Bakke, B.; Melbostad, E.; Fuglerud, P.; Kongerud, J.; Lund, M. B.

    2000-01-01

    BACKGROUND—Tunnel workers are exposed to gases and particles from blasting and diesel exhausts. The aim of this study was to assess the occurrence of respiratory symptoms and airflow limitation in tunnel workers and to relate these findings to years of exposure.
METHODS—Two hundred and twelve tunnel workers and a reference group of 205 other heavy construction workers participated in a cross sectional investigation. Exposure measurements were carried out to demonstrate the difference in exposure between the two occupational groups. Spirometric tests and a questionnaire on respiratory symptoms and smoking habits were applied. Atopy was determined by a multiple radioallergosorbent test (RAST). Radiological signs of silicosis were evaluated. Respiratory symptoms and lung function were studied in relation to years of exposure and adjusted for smoking habits and atopy.
RESULTS—Compared with the reference subjects the tunnel workers had a significant decrease in forced vital capacity (FVC) % predicted and forced expiratory volume in one second (FEV1) % predicted when related to years of exposure. Adjusted FEV1 decreased by 17 ml for each year of tunnel work exposure compared with 0.5 ml in outdoor heavy construction workers. The tunnel workers also reported significantly higher occurrence of respiratory symptoms. The prevalence of chronic obstructive pulmonary disease (COPD) was 14% in the tunnel workers compared with 8% in the reference subjects.
CONCLUSION—Exposure to dust and gases from diesel exhaust, blasting, drilling and rock transport in tunnel work enhances the risk for accelerated decline in FEV1, respiratory symptoms, and COPD in tunnel workers compared with other heavy construction workers.

 PMID:10722766

  4. Assessment of electrical resistivity imaging for pre-tunneling geological characterization - A case study of the Qingdao R3 metro line tunnel

    NASA Astrophysics Data System (ADS)

    Li, Shucai; Xu, Shan; Nie, Lichao; Liu, Bin; Liu, Rentai; Zhang, Qingsong; Zhao, Yan; Liu, Quanwei; Wang, Houtong; Liu, Haidong; Guo, Qin

    2018-06-01

    Water inrush during tunneling is a significant problem in the underground infrastructure construction. Electrical resistivity imaging (ERI) is a technique that can detect and characterize a water body in an open fracture or fault by exploiting the resistivity contrast that exists between the water body and the surrounding materials. ERI is an efficient method for pre-tunneling geological characterization. In this study, a case study is presented in which tunnel-face and borehole ERI (TBERI) is performed by using the probe hole to detect a water body during tunnel construction. The construction site is a metro line site, situated in the city of Qingdao, China. Unlike the traditional cross-hole observation mode, TBERI only use a single borehole. The installation of injection electrodes inside the probe hole and the installation of measuring electrodes on the tunnel face is proposed as the observation mode. Furthermore, a numerical simulation is carried out before the real field experiment, and the simulation results show that the TBERI is capable of detecting a deeply buried water body. In addition, the water body in the field case is also identified by TBERI. The water body appears as a strongly conductive anomaly relative to the background materials. This study highlights the respective strengths and weaknesses of the TBERI for pre-tunneling geological characterization. This method is a relatively rapid means of investigating the studied area. This study clearly demonstrates the suitability of TBERI in a tunneling scenario.

  5. Wind tunnel interference factors for high-lift wings in closed wind tunnels. Ph.D. Thesis - Princeton Univ.

    NASA Technical Reports Server (NTRS)

    Joppa, R. G.

    1973-01-01

    A problem associated with the wind tunnel testing of very slow flying aircraft is the correction of observed pitching moments to free air conditions. The most significant effects of such corrections are to be found at moderate downwash angles typical of the landing approach. The wind tunnel walls induce interference velocities at the tail different from those induced at the wing, and these induced velocities also alter the trajectory of the trailing vortex system. The relocated vortex system induces different velocities at the tail from those experienced in free air. The effect of the relocated vortex and the walls is to cause important changes in the measured pitching moments in the wind tunnel.

  6. Counter tunnel exploration, mapping, and localization with an unmanned ground vehicle

    NASA Astrophysics Data System (ADS)

    Larson, Jacoby; Okorn, Brian; Pastore, Tracy; Hooper, David; Edwards, Jim

    2014-06-01

    Covert, cross-border tunnels are a security vulnerability that enables people and contraband to illegally enter the United States. All of these tunnels to-date have been constructed for the purpose of drug smuggling, but they may also be used to support terrorist activity. Past robotic tunnel exploration efforts have had limited success in aiding law enforcement to explore and map the suspect cross-border tunnels. These efforts have made use of adapted explosive ordnance disposal (EOD) or pipe inspection robotic systems that are not ideally suited to the cross-border tunnel environment. The Counter Tunnel project was sponsored by the Office of Secretary of Defense (OSD) Joint Ground Robotics Enterprise (JGRE) to develop a prototype robotic system for counter-tunnel operations, focusing on exploration, mapping, and characterization of tunnels. The purpose of this system is to provide a safe and effective solution for three-dimensional (3D) localization, mapping, and characterization of a tunnel environment. The system is composed of the robotic mobility platform, the mapping sensor payload, and the delivery apparatus. The system is able to deploy and retrieve the robotic mobility platform through a 20-cm-diameter borehole into the tunnel. This requirement posed many challenges in order to design and package the sensor and robotic system to fit through this narrow opening and be able to perform the mission. This paper provides a short description of a few aspects of the Counter Tunnel system such as mobility, perception, and localization, which were developed to meet the unique challenges required to access, explore, and map tunnel environments.

  7. 1. West portal of Tunnel 25, contextual view to northeast ...

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

    1. West portal of Tunnel 25, contextual view to northeast from Tunnel 24 (HAER CA-200), 135mm lens. - Central Pacific Transcontinental Railroad, Tunnel No. 25, Milepost 133.09, Applegate, Placer County, CA

  8. JPRS Report Science & Technology USSR: Earth Sciences.

    DTIC Science & Technology

    1987-07-09

    8217Ozone Hole’ Over the Antarctic (TASS, 23 Jan 87) 100 Polar Workers Establish Antarctic Base (TASS, 31 Dec 86) 101 Calculation of Production of...makes it possible to quickly turn the platforms from the drilling version into the production one. As compared with tradi- tional ones, they use...and Planning Institute of Ocean Geophysics, Yuzhmorgeologiya Production Association, Gelendzhik] [Abstract] A receiver has been developed for

  9. Cryogenic wind tunnels for high Reynolds number testing

    NASA Technical Reports Server (NTRS)

    Lawing, P. L.; Kilgore, R. A.; Mcguire, P. D.

    1986-01-01

    A compilation of lectures presented at various Universities over a span of several years is discussed. A central theme of these lectures has been to present the research facility in terms of the service it provides to, and its potential effect on, the entire community, rather than just the research community. This theme is preserved in this paper which deals with the cryogenic transonic wind tunnels at Langley Research Center. Transonic aerodynamics is a focus both because of its crucial role in determining the success of aeronautical systems and because cryogenic wind tunnels are especially applicable to the transonics problem. The paper also provides historical perspective and technical background for cryogenic tunnels, culminating in a brief review of cryogenic wind tunnel projects around the world. An appendix is included to provide up to date information on testing techniques that have been developed for the cryogenic tunnels at Langley Research Center. In order to be as inclusive and as current as possible, the appendix is less formal than the main body of the paper. It is anticipated that this paper will be of particular value to the technical layman who is inquisitive as to the value of, and need for, cryogneic tunnels.

  10. 2. West portal of Tunnel 23, view to the westnorthwest, ...

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

    2. West portal of Tunnel 23, view to the west-northwest, 135mm lens. Note the use of concrete face and wingwalls, with dressed stone voussoirs, wingwall coping, concrete parapet with stone belt course and coping, and rubble masonry slope protection flanking the portal. Built for the Oregon Eastern, this Southern Pacific Common Standard tunnel is contemporary with those built by different contractors for the California Northeastern at the south end of the Natron Cutoff (see Tunnel 17, HAER CA-218, and Tunnel 18, HAER CA-219). - Southern Pacific Railroad Natron Cutoff, Tunnel 23, Milepost 584.5, Westfir, Lane County, OR

  11. 2. West portal of Tunnel 22, view to the northwest, ...

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

    2. West portal of Tunnel 22, view to the northwest, 135mm lens. Note the use of concrete face and wingwalls, with dressed stone voussoirs, wingwall coping, concrete parapet with stone belt course and coping, and rubble masonry slope protection flanking the portal. Built for the Oregon Eastern, this Southern Pacific Common Standard tunnel is contemporary with those built by different contractors for the California Northeastern at the south end of the Natron Cutoff (see Tunnel 17, HAER CA-218, and Tunnel 18, HAER CA-219). - Southern Pacific Railroad Natron Cutoff, Tunnel 22, Milepost 581.85, Oakridge, Lane County, OR

  12. Improved Design of Beam Tunnel for 42 GHz Gyrotron

    NASA Astrophysics Data System (ADS)

    Singh, Udaybir; Kumar, Nitin; Purohit, L. P.; Sinha, A. K.

    2011-04-01

    In gyrotron, there is the chance of generation and excitation of unwanted RF modes (parasite oscillations). These modes may interact with electron beam and consequently degrade the beam quality. This paper presents the improved design of the beam tunnel to reduce the parasite oscillations and the effect of beam tunnel geometry on the electron beam parameters. The design optimization of the beam tunnel has been done with the help of 3-D simulation software CST-Microwave Studio and the effect of beam tunnel geometry on the electron beam parameters has been analyzed by EGUN code.

  13. Energy-gap spectroscopy of superconductors using a tunneling microscope

    NASA Technical Reports Server (NTRS)

    Le Duc, H. G.; Kaiser, W. J.; Stern, J. A.

    1987-01-01

    A unique scanning tunneling microscope (STM) system has been developed for spectroscopy of the superconducting energy gap. High-resolution control of tunnel current and voltage allows for measurement of superconducting properties at tunnel resistance levels 100-1000 greater than that achieved in prior work. The previously used STM methods for superconductor spectroscopy are compared to those developed for the work reported here. Superconducting energy-gap spectra are reported for three superconductors, Pb, PbBi, and NbN, over a range of tunnel resistance. The measured spectra are compared directly to theory.

  14. Modeling direct interband tunneling. I. Bulk semiconductors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pan, Andrew, E-mail: pandrew@ucla.edu; Chui, Chi On; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095

    Interband tunneling is frequently studied using the semiclassical Kane model, despite uncertainty about its validity. Revisiting the physical basis of this formula, we find that it neglects coupling to other bands and underestimates transverse tunneling. As a result, significant errors can arise at low and high fields for small and large gap materials, respectively. We derive a simple multiband tunneling model to correct these defects analytically without arbitrary parameters. Through extensive comparison with band structure and quantum transport calculations for bulk InGaAs, InAs, and InSb, we probe the accuracy of the Kane and multiband formulas and establish the superiority ofmore » the latter. We also show that the nonlocal average electric field should be used when applying either of these models to nonuniform potentials. Our findings are important for efficient analysis and simulation of bulk semiconductor devices involving tunneling.« less

  15. 4. East portal of Tunnel 25, view to southwest from ...

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

    4. East portal of Tunnel 25, view to southwest from west end of Tunnel 26 (HAER CA-202), 135mm lens. - Central Pacific Transcontinental Railroad, Tunnel No. 25, Milepost 133.09, Applegate, Placer County, CA

  16. Hydrodynamic optical soliton tunneling

    NASA Astrophysics Data System (ADS)

    Sprenger, P.; Hoefer, M. A.; El, G. A.

    2018-03-01

    A notion of hydrodynamic optical soliton tunneling is introduced in which a dark soliton is incident upon an evolving, broad potential barrier that arises from an appropriate variation of the input signal. The barriers considered include smooth rarefaction waves and highly oscillatory dispersive shock waves. Both the soliton and the barrier satisfy the same one-dimensional defocusing nonlinear Schrödinger (NLS) equation, which admits a convenient dispersive hydrodynamic interpretation. Under the scale separation assumption of nonlinear wave (Whitham) modulation theory, the highly nontrivial nonlinear interaction between the soliton and the evolving hydrodynamic barrier is described in terms of self-similar, simple wave solutions to an asymptotic reduction of the Whitham-NLS partial differential equations. One of the Riemann invariants of the reduced modulation system determines the characteristics of a soliton interacting with a mean flow that results in soliton tunneling or trapping. Another Riemann invariant yields the tunneled soliton's phase shift due to hydrodynamic interaction. Soliton interaction with hydrodynamic barriers gives rise to effects that include reversal of the soliton propagation direction and spontaneous soliton cavitation, which further suggest possible methods of dark soliton control in optical fibers.

  17. Hydrodynamic optical soliton tunneling.

    PubMed

    Sprenger, P; Hoefer, M A; El, G A

    2018-03-01

    A notion of hydrodynamic optical soliton tunneling is introduced in which a dark soliton is incident upon an evolving, broad potential barrier that arises from an appropriate variation of the input signal. The barriers considered include smooth rarefaction waves and highly oscillatory dispersive shock waves. Both the soliton and the barrier satisfy the same one-dimensional defocusing nonlinear Schrödinger (NLS) equation, which admits a convenient dispersive hydrodynamic interpretation. Under the scale separation assumption of nonlinear wave (Whitham) modulation theory, the highly nontrivial nonlinear interaction between the soliton and the evolving hydrodynamic barrier is described in terms of self-similar, simple wave solutions to an asymptotic reduction of the Whitham-NLS partial differential equations. One of the Riemann invariants of the reduced modulation system determines the characteristics of a soliton interacting with a mean flow that results in soliton tunneling or trapping. Another Riemann invariant yields the tunneled soliton's phase shift due to hydrodynamic interaction. Soliton interaction with hydrodynamic barriers gives rise to effects that include reversal of the soliton propagation direction and spontaneous soliton cavitation, which further suggest possible methods of dark soliton control in optical fibers.

  18. Advancement of Analysis Method for Electromagnetic Screening Effect of Mountain Tunnel

    NASA Astrophysics Data System (ADS)

    Okutani, Tamio; Nakamura, Nobuyuki; Terada, Natsuki; Fukuda, Mitsuyoshi; Tate, Yutaka; Inada, Satoshi; Itoh, Hidenori; Wakao, Shinji

    In this paper we report advancement of an analysis method for electromagnetic screening effect of mountain tunnel with a multiple conductor circuit model. On A.C. electrified railways it is a great issue to manage the influence of electromagnetic induction caused by feeding circuits. Tunnels are said to have a screening effect to reduce the electromagnetic induction because a large amount of steel is used in the tunnels. But recently the screening effect is less expected because New Austrian Tunneling Method (NATM), in which the amount of steel used is less than in conventional methods, is adopted as the standard tunneling method for constructing mountain tunnels. So we measured and analyzed the actual screening effect of mountain tunnels constructed with NATM. In the process of the analysis we have advanced a method to analyze the screening effect more precisely. In this method we can adequately model tunnel structure as a part of multiple conductor circuit.

  19. Micromachined Electron-Tunneling Infrared Detectors

    NASA Technical Reports Server (NTRS)

    Kenny, Thomas W.; Kaiser, William J.; Waltman, Stephen B.

    1993-01-01

    Pneumatic/thermal infrared detectors based partly on Golay-cell concept, but smaller and less fragile. Include containers filled with air or other gas trapped behind diaphragms. Infrared radiation heats sensors, causing gas to expand. Resulting deflections of diaphragms measured by displacement sensors based on principle of electron-tunneling transducers of scanning tunneling microscopes. Exceed sensitivity of all other miniature, uncooled infrared sensors presently available. Expected to include low consumption of power, broadband sensitivity, room-temperature operation, and invulnerability to ionizing radiation.

  20. Wooden Fan Blades in the Icing Research Tunnel

    NASA Image and Video Library

    1979-02-21

    The drive fan for the Icing Research Tunnel at the National Aeronautics and Space Administration (NASA) Lewis Research Center in Cleveland, Ohio. The Lewis Icing Research Program, which began during World War II, utilized both research aircraft and the icing tunnel throughout the 1940s and 1950s. The research program was cancelled in 1958 as Lewis focused on space. The tunnel continued to be used occasionally for industrial customers in the 1960s and early 1970s. Lewis’ icing research was formally reinstituted just months before this photograph in 1978. The Icing Research Tunnel’s original 4100-horsepower induction motor was coupled directly to the 24-foot-diameter fan. Neoprene boots protected the leading edges of the 12 spruce fan blades. The system generated air speeds up to 300 miles per hour through the tunnel’s 6- by 9-foot test section. A large tail faring extended from the center of the fan to uniformly guide the airflow down the tunnel. NASA Headquarters ordered modifications to the Icing Research Tunnel in 1985 after wooden fan blades in a wind tunnel at Langley Research Center failed. Despite the fact that the large hub, seen in the center of the fan, provided an extra layer of protection against blade failure, Headquarters ordered the installation of a new set of wooden blades. The blades were ordered but not installed. The tunnel technicians instead agreed to inspect the fan after each run. A new 5000-horsepower motor was installed in 1987, and the original fan blades were finally replaced in 1993.

  1. Technology and application of 3D tunnel information monitoring

    NASA Astrophysics Data System (ADS)

    Li, Changqing; Deng, Hongliang; Chen, Ge; Wang, Simiao; Guo, Yang; Wu, Shenglin

    2015-12-01

    It is very necessary that Implement information monitoring and dynamic construction because of Complex geological environment and lack of basic information in the process of tunnel construction. The monitoring results show that 3 d laser scanning technology and information management system has important theoretical significance and application value to ensure the safety of tunnel construction, rich construction theory and technology. It can be known in real time the deformation information and the construction information in near tunnel workplace and the whole tunnel section in real time. In the meantime, it can be known the deformation regularity in the tunnel excavation process and the early warning and forecasting in the form of graphic and data. In order to determine the reasonable time and provide basis for supporting parameters and lining.

  2. Tunneling-Electron-Induced Light Emission from Single Gold Nanoclusters.

    PubMed

    Yu, Arthur; Li, Shaowei; Czap, Gregory; Ho, W

    2016-09-14

    The coupling of tunneling electrons with the tip-nanocluster-substrate junction plasmon was investigated by monitoring light emission in a scanning tunneling microscope (STM). Gold atoms were evaporated onto the ∼5 Å thick Al2O3 thin film grown on the NiAl (110) surface where they formed nanoclusters 3-7 nm wide. Scanning tunneling spectroscopy (STS) of these nanoclusters revealed quantum-confined electronic states. Spatially resolved photon imaging showed localized emission hot spots. Size dependent study and light emission from nanocluster dimers further support the viewpoint that coupling of tunneling electrons to the junction plasmon is the main radiative mechanism. These results showed the potential of the STM to reveal the electronic and optical properties of nanoscale metallic systems in the confined geometry of the tunnel junction.

  3. View of Flume Tunnel #3 through Purple Mountain, showing flume ...

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

    View of Flume Tunnel #3 through Purple Mountain, showing flume entering into the tunnel. Looking south - Childs-Irving Hydroelectric Project, Childs System, Flume Tunnel No. 3, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

  4. Ultrafast demagnetization enhancement in CoFeB/MgO/CoFeB magnetic tunneling junction driven by spin tunneling current.

    PubMed

    He, Wei; Zhu, Tao; Zhang, Xiang-Qun; Yang, Hai-Tao; Cheng, Zhao-Hua

    2013-10-07

    The laser-induced ultrafast demagnetization of CoFeB/MgO/CoFeB magnetic tunneling junction is exploited by time-resolved magneto-optical Kerr effect (TRMOKE) for both the parallel state (P state) and the antiparallel state (AP state) of the magnetizations between two magnetic layers. It was observed that the demagnetization time is shorter and the magnitude of demagnetization is larger in the AP state than those in the P state. These behaviors are attributed to the ultrafast spin transfer between two CoFeB layers via the tunneling of hot electrons through the MgO barrier. Our observation indicates that ultrafast demagnetization can be engineered by the hot electrons tunneling current. It opens the door to manipulate the ultrafast spin current in magnetic tunneling junctions.

  5. Carpal Tunnel Exercises: Can They Relieve Symptoms?

    MedlinePlus

    ... relieve symptoms, such as pain and numbness. These exercises are most effective when combined with other treatments, such as behavior changes or wrist splints, for mild to moderate carpal tunnel syndrome. If your symptoms ... exercises — one type of carpal tunnel exercise — might help ...

  6. Polymer-mediated tunneling transport between carbon nanotubes in nanocomposites.

    PubMed

    Derosa, Pedro A; Michalak, Tyler

    2014-05-01

    Electron transport in nanocomposites has attracted a good deal of attention for some time now; furthermore, the ability to control its characteristics is a necessary step in the design of multifunctional materials. When conductive nanostructures (for example carbon nanotubes) are inserted in a non-conductive matrix, electron transport below the percolation threshold is dominated by tunneling and thus the conductive characteristics of the composite depends heavily on the characteristics of the tunneling currents between nanoinserts. A parameter-free approach to study tunneling transport between carbon nanotubes across a polymer matrix is presented. The calculation is done with a combination of Density Functional Theory and Green functions (an approach heavily used in molecular electronics) which is shown here to be effective in this non-resonant transport condition. The results show that the method can effectively capture the effect of a dielectric layer in tunneling transport. The current is found to exponentially decrease with the size of the gap for both vacuum and polymer, and that the polymer layer lowers the tunneling barrier enhancing tunneling conduction. For a polyacrylonitrile matrix, a four-fold decrease in the tunneling constant, compared to tunneling in vacuum, is observed, a result that is consistent with available information. The method is very versatile as any DFT functional (or any other quantum mechanics method) can be used and thus the most accurate method for each particular system can be chosen. Furthermore as more methods become available, the calculations can be revised and improved. This approach can be used to design functional materials for fine-tunning the tunneling transport, for instance, the effect of modifying the nanoinsert-matrix interface (for example, by adding functional groups to carbon nanotubes) can be captured and the comparative performance of each interface predicted by simulation.

  7. Wind tunnel testing of low-drag airfoils

    NASA Technical Reports Server (NTRS)

    Harvey, W. Donald; Mcghee, R. J.; Harris, C. D.

    1986-01-01

    Results are presented for the measured performance recently obtained on several airfoil concepts designed to achieve low drag by maintaining extensive regions of laminar flow without compromising high-lift performance. The wind tunnel results extend from subsonic to transonic speeds and include boundary-layer control through shaping and suction. The research was conducted in the NASA Langley 8-Ft Transonic Pressure Tunnel (TPT) and Low Turbulence Pressure Tunnel (LTPT) which have been developed for testing such low-drag airfoils. Emphasis is placed on identifying some of the major factors influencing the anticipated performance of low-drag airfoils.

  8. Probing semiconductor gap states with resonant tunneling.

    PubMed

    Loth, S; Wenderoth, M; Winking, L; Ulbrich, R G; Malzer, S; Döhler, G H

    2006-02-17

    Tunneling transport through the depletion layer under a GaAs {110} surface is studied with a low temperature scanning tunneling microscope (STM). The observed negative differential conductivity is due to a resonant enhancement of the tunneling probability through the depletion layer mediated by individual shallow acceptors. The STM experiment probes, for appropriate bias voltages, evanescent states in the GaAs band gap. Energetically and spatially resolved spectra show that the pronounced anisotropic contrast pattern of shallow acceptors occurs exclusively for this specific transport channel. Our findings suggest that the complex band structure causes the observed anisotropies connected with the zinc blende symmetry.

  9. 2. West portal of Tunnel 1, view to northeast, 135mm ...

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

    2. West portal of Tunnel 1, view to northeast, 135mm lens. Like the new tunnels built during this period, Tunnel 1 received a new concrete portal face with granite masonry voussoirs and coping. - Central Pacific Transcontinental Railroad, Tunnel No. 1, Milepost 164.34, Blue Canyon, Placer County, CA

  10. ``Phantom'' Modes in Ab Initio Tunneling Calculations: Implications for Theoretical Materials Optimization, Tunneling, and Transport

    NASA Astrophysics Data System (ADS)

    Barabash, Sergey V.; Pramanik, Dipankar

    2015-03-01

    Development of low-leakage dielectrics for semiconductor industry, together with many other areas of academic and industrial research, increasingly rely upon ab initio tunneling and transport calculations. Complex band structure (CBS) is a powerful formalism to establish the nature of tunneling modes, providing both a deeper understanding and a guided optimization of materials, with practical applications ranging from screening candidate dielectrics for lowest ``ultimate leakage'' to identifying charge-neutrality levels and Fermi level pinning. We demonstrate that CBS is prone to a particular type of spurious ``phantom'' solution, previously deemed true but irrelevant because of a very fast decay. We demonstrate that (i) in complex materials, phantom modes may exhibit very slow decay (appearing as leading tunneling terms implying qualitative and huge quantitative errors), (ii) the phantom modes are spurious, (iii) unlike the pseudopotential ``ghost'' states, phantoms are an apparently unavoidable artifact of large numerical basis sets, (iv) a presumed increase in computational accuracy increases the number of phantoms, effectively corrupting the CBS results despite the higher accuracy achieved in resolving the true CBS modes and the real band structure, and (v) the phantom modes cannot be easily separated from the true CBS modes. We discuss implications for direct transport calculations. The strategy for dealing with the phantom states is discussed in the context of optimizing high-quality high- κ dielectric materials for decreased tunneling leakage.

  11. Water tunnel flow visualization and wind tunnel data analysis of the F/A-18. [leading edge extension vortex effects

    NASA Technical Reports Server (NTRS)

    Erickson, G. E.

    1982-01-01

    Six degree of freedom studies were utilized to extract a band of yawing and rolling moment coefficients from the F/A-18 aircraft flight records. These were compared with 0.06 scale model data obtained in a 16T wind tunnel facility. The results, indicate the flight test yawing moment data exhibit an improvement over the wind tunnel data to near neutral stability and a significant reduction in lateral stability (again to anear neutral level). These data are consistent with the flight test results since the motion was characterized by a relatively slo departure. Flight tests repeated the slow yaw departure at M 0.3. Only 0.16 scale model wind tunnel data showed levels of lateral stability similar to the flight test results. Accordingly, geometric modifications were investigated on the 0.16 scale model in the 30x60 foot wind tunnel to improve high angle of attack lateral stability.

  12. Tunneling Spectra of a Quasifreestanding Graphene Monolayer

    NASA Astrophysics Data System (ADS)

    Li, Si-Yu; Bai, Ke-Ke; Zuo, Wei-Jie; Liu, Yi-Wen; Fu, Zhong-Qiu; Wang, Wen-Xiao; Zhang, Yu; Yin, Long-Jing; Qiao, Jia-Bin; He, Lin

    2018-05-01

    Considering the great success of scanning-tunneling-microscopy (STM) studies of graphene in the past ten years, it is quite surprising to notice that there is still a fundamental contradiction in the reported tunneling spectra of the quasifreestanding graphene monolayer. Many groups observed "V -shaped" spectra with linearly vanishing density of states at the Dirac point, whereas others reported spectra with a gap of ±60 meV pinned to the Fermi level in the quasifreestanding graphene monolayer. Here, we systematically study the two contradicting tunneling spectra of the quasifreestanding graphene monolayer on various substrates in the presence of different magnetic fields and demonstrate that both spectra are the "correct" spectra. However, the V -shaped spectrum exhibits only the contribution of the low-energy Dirac fermions, whereas the gapped spectrum is contributed by both the low-energy Dirac fermions and the high-energy nearly free-electron states due to the existence of the inelastic tunneling process. Our results indicate that interaction with substrates plays a vital role in affecting the spectra of graphene. We also show that it is possible to switch the tunneling spectra between the two distinct features at the nanoscale through voltage pulses applied to the STM tip.

  13. Tunnel Ventilation Control Using Reinforcement Learning Methodology

    NASA Astrophysics Data System (ADS)

    Chu, Baeksuk; Kim, Dongnam; Hong, Daehie; Park, Jooyoung; Chung, Jin Taek; Kim, Tae-Hyung

    The main purpose of tunnel ventilation system is to maintain CO pollutant concentration and VI (visibility index) under an adequate level to provide drivers with comfortable and safe driving environment. Moreover, it is necessary to minimize power consumption used to operate ventilation system. To achieve the objectives, the control algorithm used in this research is reinforcement learning (RL) method. RL is a goal-directed learning of a mapping from situations to actions without relying on exemplary supervision or complete models of the environment. The goal of RL is to maximize a reward which is an evaluative feedback from the environment. In the process of constructing the reward of the tunnel ventilation system, two objectives listed above are included, that is, maintaining an adequate level of pollutants and minimizing power consumption. RL algorithm based on actor-critic architecture and gradient-following algorithm is adopted to the tunnel ventilation system. The simulations results performed with real data collected from existing tunnel ventilation system and real experimental verification are provided in this paper. It is confirmed that with the suggested controller, the pollutant level inside the tunnel was well maintained under allowable limit and the performance of energy consumption was improved compared to conventional control scheme.

  14. Real-time simulator for helicopter rotor wind-tunnel operations

    NASA Technical Reports Server (NTRS)

    Talbot, P. D.; Peterson, R. L.; Graham, D. R.

    1986-01-01

    This paper describes the elements and operation of a simulator that is being used to train operators of the Rotor Test Apparatus (RTA) in the large-scale 40- by 80-Foot Wind Tunnel at Ames Research Center. The simulator, named TUTOR (for Tunnel Utilization Trainer with Operating Rotor) duplicates the controls of the rotor and its dynamic behavior, as well as the wind-tunnel controls. The simulation software uses a preexisting blade-element model of a four-bladed rotor with flapping and lead-lag degrees of freedom. Equations were developed for all hardware and controls of the RTA and of the wind tunnel that are normally required to perform a wind-tunnel test of a helicopter rotor. The simulator hardware consists of consoles designed to have the same appearance and functions as those in the control room of the 40- by 80-Foot Wind Tunnel, allowing input from three operators who normally establish the required operating conditions during a test run. Normal operating procedures can be practiced, as well as simulated emergencies such as rotor power failure.

  15. NORTHERN END OF VIADUCT WHERE IT ENTERS BATTERY STREET TUNNEL. ...

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

    NORTHERN END OF VIADUCT WHERE IT ENTERS BATTERY STREET TUNNEL. LAKE UNION VISIBLE IN BACKGROUND. TUNNEL PROCEEDS IN CUT AND COVER FASHION DIRECTLY BENEATH BATTERY STREET. - Alaskan Way Viaduct and Battery Street Tunnel, Seattle, King County, WA

  16. Quantum Tunneling Affects Engine Performance.

    PubMed

    Som, Sibendu; Liu, Wei; Zhou, Dingyu D Y; Magnotti, Gina M; Sivaramakrishnan, Raghu; Longman, Douglas E; Skodje, Rex T; Davis, Michael J

    2013-06-20

    We study the role of individual reaction rates on engine performance, with an emphasis on the contribution of quantum tunneling. It is demonstrated that the effect of quantum tunneling corrections for the reaction HO2 + HO2 = H2O2 + O2 can have a noticeable impact on the performance of a high-fidelity model of a compression-ignition (e.g., diesel) engine, and that an accurate prediction of ignition delay time for the engine model requires an accurate estimation of the tunneling correction for this reaction. The three-dimensional model includes detailed descriptions of the chemistry of a surrogate for a biodiesel fuel, as well as all the features of the engine, such as the liquid fuel spray and turbulence. This study is part of a larger investigation of how the features of the dynamics and potential energy surfaces of key reactions, as well as their reaction rate uncertainties, affect engine performance, and results in these directions are also presented here.

  17. Design and Development of Low-Cost Water Tunnel for Educational Purpose

    NASA Astrophysics Data System (ADS)

    Zahari, M.; Dol, S. S.

    2015-04-01

    The hydrodynamic behaviour of immersed body is essential in fluid dynamics study. Water tunnel is an example of facility required to provide a controlled condition for fluid flow research. The operational principle of water tunnel is quite similar to the wind tunnel but with different working fluid and higher flow-pumping capacity. Flow visualization in wind tunnel is more difficult to conduct as turbulent flows in wind dissipate quickly whilst water tunnel is more suitable for such purpose due to higher fluid viscosity and wide variety of visualization techniques can be employed. The present work focusses on the design and development of open flow water tunnel for the purpose of studying vortex-induced vibration from turbulent vortex shedding phenomenon. The water tunnel is designed to provide a steady and uniform flow speed within the test section area. Construction details are discussed for development of low-cost water tunnel for quantitative and qualitative fluid flow measurements. The water tunnel can also be used for educational purpose such as fluid dynamics class activity to provide quick access to visualization medium for better understanding of various turbulence motion learnt in class.

  18. Tunnel Structured α-MnO 2 with Different Tunnel Cations (H + , K + , Ag + ) as Cathode Materials in Rechargeable Lithium Batteries: The Role of Tunnel Cation on Electrochemistry

    DOE PAGES

    Poyraz, Altug S.; Huang, Jianping; Cheng, Shaobo; ...

    2017-07-12

    α-MnO 2 type manganese dioxide is an interesting prospective cathode material for reversible lithium insertion owing to its cation accessible tunnels (0.46nm x 0.46nm), high voltage, and low cost. The tunneled structure is synthetically formed by the assistance of cations acting as structure directing agents where the cations may remain in the tunnel. The electrochemistry of this family of materials is strongly dependent on the morphological and physicochemical (i.e. surface area, crystallite size, and average manganese oxidation state) properties as well as tunnel occupancy. For this work, we prepared a set of materials Mn 8O 16·0.81H 2O, K 0.81Mn 8Omore » 16·0.78H 2O and Ag 1.33Mn 8O 16·0.95H 2O with similar nanorod morphology, crystallite size, surface area, and tunnel water content. This set of samples allowed us to investigate the role of tunnel cations in the electrochemistry of α-MnO 2 type manganese dioxide in a lithium based environment while minimizing the effects of the other parameters. The electrochemistry was evaluated using cyclic voltammetry, galvanostatic cycling, rate capability, and galvanostatic intermittent titration type testing. Mn 8O 16·0.81H 2O showed higher loaded voltages, improved capacity retention, and higher specific energy relative to K 0.81Mn 8O 16·0.78H 2O and Ag 1.33Mn 8O 16·0.95H 2O. After 100 cycles, Mn 8O 16·0.81H 2O delivered ~200% more capacity than Ag 1.33Mn 8O 16·0.95H 2O (64 vs. 129 mAh/g) and ~35% more capacity than K 0.81Mn 8O 16·0.78H 2O (85 vs. 129 mAh/g). Mn 8O 16·0.81H 2O also showed higher effective lithium diffusion coefficients (DLi+) and higher rate capability compared to K 0.81Mn 8O 16·0.78H 2O and Ag 1.33Mn 8O 16·0.95H 2O suggesting faster Li+ ion diffusion in the absence of large metal tunnel cations.« less

  19. Tunnel Structured α-MnO 2 with Different Tunnel Cations (H + , K + , Ag + ) as Cathode Materials in Rechargeable Lithium Batteries: The Role of Tunnel Cation on Electrochemistry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Poyraz, Altug S.; Huang, Jianping; Cheng, Shaobo

    α-MnO 2 type manganese dioxide is an interesting prospective cathode material for reversible lithium insertion owing to its cation accessible tunnels (0.46nm x 0.46nm), high voltage, and low cost. The tunneled structure is synthetically formed by the assistance of cations acting as structure directing agents where the cations may remain in the tunnel. The electrochemistry of this family of materials is strongly dependent on the morphological and physicochemical (i.e. surface area, crystallite size, and average manganese oxidation state) properties as well as tunnel occupancy. For this work, we prepared a set of materials Mn 8O 16·0.81H 2O, K 0.81Mn 8Omore » 16·0.78H 2O and Ag 1.33Mn 8O 16·0.95H 2O with similar nanorod morphology, crystallite size, surface area, and tunnel water content. This set of samples allowed us to investigate the role of tunnel cations in the electrochemistry of α-MnO 2 type manganese dioxide in a lithium based environment while minimizing the effects of the other parameters. The electrochemistry was evaluated using cyclic voltammetry, galvanostatic cycling, rate capability, and galvanostatic intermittent titration type testing. Mn 8O 16·0.81H 2O showed higher loaded voltages, improved capacity retention, and higher specific energy relative to K 0.81Mn 8O 16·0.78H 2O and Ag 1.33Mn 8O 16·0.95H 2O. After 100 cycles, Mn 8O 16·0.81H 2O delivered ~200% more capacity than Ag 1.33Mn 8O 16·0.95H 2O (64 vs. 129 mAh/g) and ~35% more capacity than K 0.81Mn 8O 16·0.78H 2O (85 vs. 129 mAh/g). Mn 8O 16·0.81H 2O also showed higher effective lithium diffusion coefficients (DLi+) and higher rate capability compared to K 0.81Mn 8O 16·0.78H 2O and Ag 1.33Mn 8O 16·0.95H 2O suggesting faster Li+ ion diffusion in the absence of large metal tunnel cations.« less

  20. 1. GENERAL VIEW OF ENTRANCE TO BLUE RIDGE TUNNEL (LEFT) ...

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

    1. GENERAL VIEW OF ENTRANCE TO BLUE RIDGE TUNNEL (LEFT) FROM SOUTHEAST. ORIGINAL BLUE RIDGE R.R. (CROZET) TUNNEL IS VISIBLE AT RIGHT. - Chesapeake & Ohio Railroad, Blue Ridge Tunnel, Highway 250 at Rockfish Gap, Afton, Nelson County, VA

  1. Planar Tunneling Spectroscopy of Graphene Nanodevices

    NASA Astrophysics Data System (ADS)

    Wang, Joel I.-Jan; Bretheau, Landry; Pisoni, Riccardo; Watanabe, Kenji; Taniguchi, Takashi; Jarillo-Herrero, Pablo

    2-D Van-der-Waals mesoscopic physics have seen a rapid development in the last 10 years, with new materials each year added to the toolbox. Stacking them like Lego enables the combination of their individual electronic properties. In particular, hexagonal boron nitride, which is an insulator, gives the possibility to perform planar (2-D to 2-D) tunneling spectroscopy within this type of heterostructures. Unlike standard transport measurements, tunneling spectroscopy enables to probe the electronic properties in the energy domain. Moreover, since planar tunneling probes a large area of the system, global quantum features such as quantum Hall effect, superconducting proximity effect or quantum confinement can be investigated. In this talk, we will present implementation of heterostructures consisting of graphene, hexagonal boron nitride, and graphite, fabricated for planar tunneling spectroscopy. In order to reveal the intrinsic properties of materials, the fabrication scheme aims at preserving the pristine nature of the 2-DEGS as well as minimizing the doping introduced by external probes. As a demonstration, measurements of these devices in normal states, high magnetic field environment, and induced superconducting state will be presented.

  2. Smart wing wind tunnel test results

    NASA Astrophysics Data System (ADS)

    Scherer, Lewis B.; Martin, Christopher A.; Appa, Kari; Kudva, Jayanth N.; West, Mark N.

    1997-05-01

    The use of smart materials technologies can provide unique capabilities in improving aircraft aerodynamic performance. Northrop Grumman built and tested a 16% scale semi-span wind tunnel model of the F/A-18 E/F for the on-going DARPA/WL Smart Materials and Structures-Smart Wing Program. Aerodynamic performance gains to be validated included increase in the lift to drag ratio, increased pitching moment (Cm), increased rolling moment (Cl) and improved pressure distribution. These performance gains were obtained using hingeless, contoured trailing edge control surfaces with embedded shape memory alloy (SMA) wires and spanwise wing twist via a SMA torque tube and are compared to a conventional wind tunnel model with hinged control surfaces. This paper presents an overview of the results from the first wind tunnel test performed at the NASA Langley's 16 ft Transonic Dynamic Tunnel. Among the benefits demonstrated are 8 - 12% increase in rolling moment due to wing twist, a 10 - 15% increase in rolling moment due to contoured aileron, and approximately 8% increase in lift due to contoured flap, and improved pressure distribution due to trailing edge control surface contouring.

  3. Quantum tunneling observed without its characteristic large kinetic isotope effects.

    PubMed

    Hama, Tetsuya; Ueta, Hirokazu; Kouchi, Akira; Watanabe, Naoki

    2015-06-16

    Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle's ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1-1.5) despite the large intrinsic H/D KIE of tunneling (≳ 100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system.

  4. Development of a Design Technology for Ground Support for Tunnels in Soil : Vol. II. Three Dimensional Finite Element Analysis of Advanced and Conventional Shield Tunneling

    DOT National Transportation Integrated Search

    1983-11-01

    The report presents design recommendations for concrete tunnel linings for transportation tunnels. The recommendations developed as a result of in-depth analysis and model testing of the behavior of concrete tunnel linings. The research addressed pro...

  5. Atomically Thin Al2O3 Films for Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Wilt, Jamie; Gong, Youpin; Gong, Ming; Su, Feifan; Xu, Huikai; Sakidja, Ridwan; Elliot, Alan; Lu, Rongtao; Zhao, Shiping; Han, Siyuan; Wu, Judy Z.

    2017-06-01

    Metal-insulator-metal tunnel junctions are common throughout the microelectronics industry. The industry standard AlOx tunnel barrier, formed through oxygen diffusion into an Al wetting layer, is plagued by internal defects and pinholes which prevent the realization of atomically thin barriers demanded for enhanced quantum coherence. In this work, we employ in situ scanning tunneling spectroscopy along with molecular-dynamics simulations to understand and control the growth of atomically thin Al2O3 tunnel barriers using atomic-layer deposition. We find that a carefully tuned initial H2O pulse hydroxylated the Al surface and enabled the creation of an atomically thin Al2O3 tunnel barrier with a high-quality M -I interface and a significantly enhanced barrier height compared to thermal AlOx . These properties, corroborated by fabricated Josephson junctions, show that atomic-layer deposition Al2O3 is a dense, leak-free tunnel barrier with a low defect density which can be a key component for the next generation of metal-insulator-metal tunnel junctions.

  6. Substrate tunnels in enzymes: structure-function relationships and computational methodology.

    PubMed

    Kingsley, Laura J; Lill, Markus A

    2015-04-01

    In enzymes, the active site is the location where incoming substrates are chemically converted to products. In some enzymes, this site is deeply buried within the core of the protein, and, in order to access the active site, substrates must pass through the body of the protein via a tunnel. In many systems, these tunnels act as filters and have been found to influence both substrate specificity and catalytic mechanism. Identifying and understanding how these tunnels exert such control has been of growing interest over the past several years because of implications in fields such as protein engineering and drug design. This growing interest has spurred the development of several computational methods to identify and analyze tunnels and how ligands migrate through these tunnels. The goal of this review is to outline how tunnels influence substrate specificity and catalytic efficiency in enzymes with buried active sites and to provide a brief summary of the computational tools used to identify and evaluate these tunnels. © 2015 Wiley Periodicals, Inc.

  7. Toward low-power electronics: tunneling phenomena in transition metal dichalcogenides.

    PubMed

    Das, Saptarshi; Prakash, Abhijith; Salazar, Ramon; Appenzeller, Joerg

    2014-02-25

    In this article, we explore, experimentally, the impact of band-to-band tunneling on the electronic transport of double-gated WSe2 field-effect transistors (FETs) and Schottky barrier tunneling of holes in back-gated MoS2 FETs. We show that by scaling the flake thickness and the thickness of the gate oxide, the tunneling current can be increased by several orders of magnitude. We also perform numerical calculations based on Landauer formalism and WKB approximation to explain our experimental findings. Based on our simple model, we discuss the impact of band gap and effective mass on the band-to-band tunneling current and evaluate the performance limits for a set of dichalcogenides in the context of tunneling transistors for low-power applications. Our findings suggest that WTe2 is an excellent choice for tunneling field-effect transistors.

  8. Homoepitaxial graphene tunnel barriers for spin transport (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Friedman, Adam L.

    2015-09-01

    Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions (magnetic field, temperature, etc.) usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate homoepitaxial tunnel barrier devices in which graphene serves as both the tunnel barrier and the high mobility transport channel. Beginning with multilayer graphene, we fluorinate or hydrogenate the top layer to decouple it from the bottom layer, so that it serves as a single monolayer tunnel barrier for both charge and spin injection into the lower graphene transport channel. We demonstrate successful tunneling by measuring non-linear IV curves, and a weakly temperature dependent zero bias resistance. We perform lateral transport of spin currents in non-local spin-valve structures and determine spin lifetimes with the non-local Hanle effect to be commensurate with previous studies (~200 ps). However, we also demonstrate the highest spin polarization efficiencies (~45%) yet measured in graphene-based spin devices [1]. [1] A.L. Friedman, et al., Homoepitaxial tunnel barriers with functionalized graphene-on-graphene for charge and spin transport, Nat. Comm. 5, 3161 (2014).

  9. Harmonic and reactive behavior of the quasiparticle tunnel current in SIS junctions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rashid, H., E-mail: hawal@chalmers.se; Desmaris, V.; Pavolotsky, A.

    In this paper, we show theoretically and experimentally that the reactive quasiparticle tunnel current of the superconductor tunnel junction could be directly measured at specific bias voltages for the higher harmonics of the quasiparticle tunnel current. We used the theory of quasiparticle tunneling to study the higher harmonics of the quasiparticle tunnel current in superconducting tunnel junction in the presence of rf irradiation. The impact of the reactive current on the harmonic behavior of the quasiparticle tunnel current was carefully studied by implementing a practical model with four parameters to model the dc I-V characteristics of the superconducting tunnel junction.more » The measured reactive current at the specific bias voltage is in good agreement with our theoretically calculated reactive current through the Kramers-Kronig transform. This study also shows that there is an excellent correspondence between the behavior of the predicted higher harmonics using the previously established theory of quasiparticle tunnel current in superconducting tunnel junctions by J.R. Tucker and M.J. Feldman and the measurements presented in this paper.« less

  10. The Denis-gruson Six-component Wind-tunnel Balance

    NASA Technical Reports Server (NTRS)

    1935-01-01

    The 6.C.1 balance is the first fully automatic balance assuring a continuous and simultaneous record of the aerodynamic characteristics of an airfoil in a wind tunnel. Because of the rapidity of the measurements a complete polar (six components) requires only about three minutes of wind, that is to say, of motive power, which is of interest for wind tunnels with high efficiency factors and may lead to the economical design of large size wind tunnels.

  11. Tunneling readout of hydrogen-bonding based recognition

    PubMed Central

    Chang, Shuai; He, Jin; Kibel, Ashley; Lee, Myeong; Sankey, Otto; Zhang, Peiming; Lindsay, Stuart

    2009-01-01

    Hydrogen bonding has a ubiquitous role in electron transport1,2 and in molecular recognition, with DNA base-pairing being the best known example.3 Scanning tunneling microscope (STM) images4 and measurements of the decay of tunnel-current as a molecular junction is pulled apart by the STM tip, 5 are sensitive to hydrogen-bonded interactions. Here we show that these tunnel-decay signals can be used to measure the strength of hydrogen bonding in DNA basepairs. Junctions that are held together by three hydrogen bonds per basepair (e.g., guanine-cytosine interactions) are stiffer than junctions held together by two hydrogen bonds per basepair (e.g., adenine-thymine interactions). Similar, but less-pronounced, effects are observed on the approach of the tunneling probe, implying that hydrogen-bond dependent attractive forces also have a role in determining the rise of current. These effects provide new mechanisms for making sensors that transduce a molecular recognition event into an electronic signal. PMID:19421214

  12. Resonant tunnelling in a quantum oxide superlattice

    DOE PAGES

    Choi, Woo Seok; Lee, Sang A.; You, Jeong Ho; ...

    2015-06-24

    Resonant tunneling is a quantum mechanical process that has long been attracting both scientific and technological attention owing to its intriguing underlying physics and unique applications for high-speed electronics. The materials system exhibiting resonant tunneling, however, has been largely limited to the conventional semiconductors, partially due to their excellent crystalline quality. Here we show that a deliberately designed transition metal oxide superlattice exhibits a resonant tunneling behaviour with a clear negative differential resistance. The tunneling occurred through an atomically thin, lanthanum δ- doped SrTiO 3 layer, and the negative differential resistance was realized on top of the bi-polar resistance switchingmore » typically observed for perovskite oxide junctions. This combined process resulted in an extremely large resistance ratio (~10 5) between the high and low resistance states. Lastly, the unprecedentedly large control found in atomically thin δ-doped oxide superlattices can open a door to novel oxide-based high-frequency logic devices.« less

  13. Tunneling of Two Interacting Fermions

    NASA Astrophysics Data System (ADS)

    Ishmukhamedov, Ilyas; Ishmukhamedov, Altay

    2018-04-01

    We consider two interacting atoms subject to a one-dimensional anharmonic trap and magnetic field gradient. This system has been recently investigated by the Heidelberg group in the experiment on two 6Li atoms. In the present paper the tunneling of two cold 6Li atoms, initially prepared in the center-of-mass and relative motion excited state, is explored and full time-dependent simulation of the tunneling dynamics is performed. The dynamics is analyzed for the interatomic coupling strength ranging from strong attraction to strong repulsion.

  14. 2. West portal of Tunnel 26, contextual view to northeast ...

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

    2. West portal of Tunnel 26, contextual view to northeast from track level, 135mm lens. Tunnel 27 (HAER CA-203) is visible in the distance. - Central Pacific Transcontinental Railroad, Tunnel No. 26, Milepost 133.29, Applegate, Placer County, CA

  15. Eastfacing portal of South Bergen Tunnel within Open Cut No. ...

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

    East-facing portal of South Bergen Tunnel within Open Cut No. 1 ( see HAER No. NJ-136-5. North Bergen Tunnel, for Open Cut No. 1 context), looking west - Delaware, Lackawanna & Western Railroad, South Bergen Tunnel, Jersey City, Hudson County, NJ

  16. Westfacing portal of South Bergen Tunnel within Open Cut No. ...

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

    West-facing portal of South Bergen Tunnel within Open Cut No. 1 ( see HAER No. NJ-136-5. North Bergen Tunnel, for Open Cut No. 1 context), looking east - Delaware, Lackawanna & Western Railroad, South Bergen Tunnel, Jersey City, Hudson County, NJ

  17. Report Tunneling Cost Reduction Study prepared for Fermilab

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Not Available

    1999-07-16

    Fermi National Accelerator Laboratories has a need to review the costs of constructing the very long tunnels which would be required for housing the equipment for the proposed Very Large Hadron Collider (VLHC) project. Current tunneling costs are high, and the identification of potential means of significantly reducing them, and thereby helping to keep overall project costs within an acceptable budget, has assumed great importance. Fermilab has contracted with The Robbins Company to provide an up-to-date appraisal of tunneling technology, and to review the potential for substantially improving currently the state-of-practice performance and construction costs in particular. The Robbins Companymore » was chosen for this task because of its long and successful experience in hard rock mechanical tunnel boring. In the past 40 years, Robbins has manufactured over 250 tunneling machines, the vast majority for hard rock applications. In addition to also supplying back-up equipment, Robbins has recently established a division dedicated to the manufacture of continuous conveying equipment for the efficient support of tunneling operations. The study extends beyond the tunnel boring machine (TBM) itself, and into the critical area of the logistics of the support of the machine as it advances, including manpower. It is restricted to proven methods using conventional technology, and its potential for incremental but meaningful improvement, rather than examining exotic and undeveloped means of rock excavation that have been proposed from time to time by the technical community. This is the first phase of what is expected to be a number of studies in increasing depth of technical detail, and as such has been restricted to the issues connected with the initial 34 kilometer circumference booster tunnel, and not the proposed 500 kilometer circumference tunnel housing the VLHC itself. The booster tunnel is entirely sited within low to medium strength limestone and dolomite

  18. Watching electrons tunnel

    NASA Astrophysics Data System (ADS)

    Moser, Simon

    2008-03-01

    To get insight to time resolved inner atomic or molecular processes, laser pulses of few femtoseconds or even attoseconds are needed. These short light pulse techniques ask for broad frequency spectra, control of dispersion and control of phase. Hence, linear optics fails and nonlinear optics in high electromagnetic fields is needed to satisfy the amount of control that is needed. One recent application of attosecond laser pulses is time resolved visualization of tunnel ionization in atoms applied to high electromagnetic fields. Here, Ne atom electrons are excited by an extreme ultraviolet attosecond laser pulse. After a while, a few cycles nearly infrared femtosecond laser pulse is applied to the atom causing tunnel ionization. The ion yield distribution can be measured as function of the delay time between excitation and ionization and so deliver insight to the time resolved mechanisms.

  19. 8- by 6-Foot Supersonic Wind Tunnel's Original Design

    NASA Image and Video Library

    1949-07-21

    Aerial view of the 8- by 6-Foot Supersonic Wind Tunnel in its original configuration at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory. The 8- by 6 was the laboratory’s first large supersonic wind tunnel. It was also the NACA’s most powerful supersonic tunnel, and its first facility capable of running an engine at supersonic speeds. The 8- by 6-foot tunnel has been used to study inlets and exit nozzles, fuel injectors, flameholders, exit nozzles, and controls on ramjet and turbojet propulsion systems. The 8- by 6 was originally an open-throat and non-return tunnel. This meant that the supersonic air flow was blown through the test section and out the other end into the atmosphere. In this photograph, the three drive motors in the structure at the left supplied power to the seven-stage axial-flow compressor in the light-colored structure. The air flow passed through flexible walls which were bent to create the desired speed. The test article was located in the 8- by 6-foot stainless steel test section located inside the steel pressure chamber at the center of this photograph. The tunnel dimensions were then gradually increased to slow the air flow before it exited into the atmosphere. The large two-story building in front of the tunnel was used as office space for the researchers.

  20. Autologous Fat Transfer in Secondary Carpal Tunnel Release

    PubMed Central

    Noszczyk, Bartłomiej H.

    2015-01-01

    Background: Carpal tunnel release is the gold standard for the treatment of median nerve compression disease. Recurrent or persistent symptoms do not occur in most patients, although a small number of them have indicated that such a postoperative condition indeed exists. Some patients undergo repeated treatments. In the majority of the cases, the disease is associated with scarring in the carpal tunnel or even reformation of the carpal ligament. The authors propose the usage of autologous fat grafting during secondary carpal tunnel release to inhibit the scarring process. Methods: Ten patients with recurrent or persistent symptoms underwent autologous fat grafting at the time of their repeated carpal tunnel release. Fat was harvested from the lower abdomen and grafted into the scarred transverse carpal ligament and surrounding tissues. Each patient underwent pre- and postoperative examinations and completed the carpal tunnel questionnaire (Boston) to evaluate their sensory and motor functions. The patients underwent 1 year of follow-up. Results: There were 2 main reasons for continued symptoms: a technical mistake resulting in incomplete release (IR) during the first operation and abundant scarring (ABS) in the operated area. The beneficial effects of the interventions were confirmed by a clinical study and by administering the carpal tunnel questionnaire to all patients (functional severity score decreased from 4.38 to 1.88 in IR and 3.62 to 1.48 in ABS group, sensory severity score from 3.26 to 1.7 in IR and 3.04 to 1.48 in ABS group; P < 0.05) after 12 months of follow-up. Conclusion: Our initial observations suggest the possible efficacy of adipose tissue in secondary carpal tunnel release. PMID:26090291

  1. 8. FIGUEROA STREET TUNNEL NO. 2, SOUTH PORTAL SEEN FROM ...

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

    8. FIGUEROA STREET TUNNEL NO. 2, SOUTH PORTAL SEEN FROM ABOVE NORTH PORTAL OF TUNNEL NO. 3. LOOKING 12°N. - Figueroa Street Tunnels, Mileposts 24.90, 25.14, 25.28, & 25.37 on Arroyo Seco Parkway, Los Angeles, Los Angeles County, CA

  2. 3. East portal of Tunnel 39, view to west with ...

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

    3. East portal of Tunnel 39, view to west with east portal of Tunnel 38 (HAER CA-211) visible in distance, 135mm lens with electronic flash fill. - Central Pacific Transcontinental Railroad, Tunnel No. 39, Milepost 180.95, Cisco, Placer County, CA

  3. Development of a 5-Component Balance for Water Tunnel Applications

    NASA Technical Reports Server (NTRS)

    Suarez, Carlos J.; Kramer, Brian R.; Smith, Brooke C.

    1999-01-01

    The principal objective of this research/development effort was to develop a multi-component strain gage balance to measure both static and dynamic forces and moments on models tested in flow visualization water tunnels. A balance was designed that allows measuring normal and side forces, and pitching, yawing and rolling moments (no axial force). The balance mounts internally in the model and is used in a manner typical of wind tunnel balances. The key differences between a water tunnel balance and a wind tunnel balance are the requirement for very high sensitivity since the loads are very low (typical normal force is 90 grams or 0.2 lbs), the need for water proofing the gage elements, and the small size required to fit into typical water tunnel models. The five-component balance was calibrated and demonstrated linearity in the responses of the primary components to applied loads, very low interactions between the sections and no hysteresis. Static experiments were conducted in the Eidetics water tunnel with delta wings and F/A-18 models. The data were compared to forces and moments from wind tunnel tests of the same or similar configurations. The comparison showed very good agreement, providing confidence that loads can be measured accurately in the water tunnel with a relatively simple multi-component internal balance. The success of the static experiments encouraged the use of the balance for dynamic experiments. Among the advantages of conducting dynamic tests in a water tunnel are less demanding motion and data acquisition rates than in a wind tunnel test (because of the low-speed flow) and the capability of performing flow visualization and force/moment (F/M) measurements simultaneously with relative simplicity. This capability of simultaneous flow visualization and for F/M measurements proved extremely useful to explain the results obtained during these dynamic tests. In general, the development of this balance should encourage the use of water tunnels for a

  4. SMART Rotor Development and Wind-Tunnel Test

    NASA Technical Reports Server (NTRS)

    Lau, Benton H.; Straub, Friedrich; Anand, V. R.; Birchette, Terry

    2009-01-01

    Boeing and a team from Air Force, NASA, Army, Massachusetts Institute of Technology, University of California at Los Angeles, and University of Maryland have successfully completed a wind-tunnel test of the smart material actuated rotor technology (SMART) rotor in the 40- by 80-foot wind-tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center, figure 1. The SMART rotor is a full-scale, five-bladed bearingless MD 900 helicopter rotor modified with a piezoelectric-actuated trailing-edge flap on each blade. The development effort included design, fabrication, and component testing of the rotor blades, the trailing-edge flaps, the piezoelectric actuators, the switching power amplifiers, the actuator control system, and the data/power system. Development of the smart rotor culminated in a whirl-tower hover test which demonstrated the functionality, robustness, and required authority of the active flap system. The eleven-week wind tunnel test program evaluated the forward flight characteristics of the active-flap rotor, gathered data to validate state-of-the-art codes for rotor noise analysis, and quantified the effects of open- and closed-loop active-flap control on rotor loads, noise, and performance. The test demonstrated on-blade smart material control of flaps on a full-scale rotor for the first time in a wind tunnel. The effectiveness and the reliability of the flap actuation system were successfully demonstrated in more than 60 hours of wind-tunnel testing. The data acquired and lessons learned will be instrumental in maturing this technology and transitioning it into production. The development effort, test hardware, wind-tunnel test program, and test results will be presented in the full paper.

  5. Ceramic and coating applications in the hostile environment of a high temperature hypersonic wind tunnel. [Langley 8-foot high temperature structures tunnel

    NASA Technical Reports Server (NTRS)

    Puster, R. L.; Karns, J. R.; Vasquez, P.; Kelliher, W. C.

    1981-01-01

    A Mach 7, blowdown wind tunnel was used to investigate aerothermal structural phenomena on large to full scale high speed vehicle components. The high energy test medium, which provided a true temperature simulation of hypersonic flow at 24 to 40 km altitude, was generated by the combustion of methane with air at high pressures. Since the wind tunnel, as well as the models, must be protected from thermally induced damage, ceramics and coatings were used extensively. Coatings were used both to protect various wind tunnel components and to improve the quality of the test stream. Planned modifications for the wind tunnel included more extensive use of ceramics in order to minimize the number of active cooling systems and thus minimize the inherent operational unreliability and cost that accompanies such systems. Use of nonintrusive data acquisition techniques, such as infrared radiometry, allowed more widespread use of ceramics for models to be tested in high energy wind tunnels.

  6. 1. East portal of Tunnel 3, view to west, 135mm ...

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

    1. East portal of Tunnel 3, view to west, 135mm lens. This tunnel was photographed to provide context, because even though somewhat enlarged, it illustrates the nature of the unlined hard rock tunnels typical of the original Central Pacific construction in 1868. - Central Pacific Transcontinental Railroad, Tunnel No. 3, Milepost 180.65, Cisco, Placer County, CA

  7. Drag Corrections in High-Speed Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Ludwieg, H.

    1947-01-01

    In the vicinity of a body in a wind tunnel the displacement effect of the wake, due to the finite dimensions of the stream, produces a pressure gradient which evokes a change of drag. In incompressible flow this change of drag is so small, in general, that one does not have to take it into account in wind-tunnel measurements; however, in compressible flow it beoomes considerably larger, so that a correction factor is necessary for measured values. Correction factors for a closed tunnel and an open jet with circular cross sections are calculated and compared with the drag - corrections already bown for high-speed tunnnels.

  8. Quasiparticle tunneling in the lowest Landau level

    NASA Astrophysics Data System (ADS)

    Hennel, Szymon; Scheidegger, Patrick; Kellermeier, Max; Hofmann, Andrea; Krähenmann, Tobias; Reichl, Christian; Wegscheider, Werner; Ihn, Thomas; Ensslin, Klaus

    2018-06-01

    We measure quasiparticle tunneling across a constriction in the first Landau level. In the limit of weak backscattering, the dependence of the tunneling conductance on temperature and dc-bias is in qualitative disagreement with existing theories. For stronger backscattering, data obtained in the ν =1 /3 state can be fitted to weak backscattering theory with the predicted effective fractional charge of e*=e /3 . The scaling parameter g is however not universal and depends strongly on the gate voltage applied to the constriction. At ν =4 /3 , a more complex picture emerges. We propose an interpretation in terms of selective tunneling between the multiple modes present at the edge.

  9. Construction of the 8- by 6-Foot Supersonic Wind Tunnel

    NASA Image and Video Library

    1948-06-21

    The 8- by 6-Foot Supersonic Wind Tunnel at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory was the nation’s largest supersonic facility when it began operation in April 1949. The emergence of new propulsion technologies such as turbojets, ramjets, and rockets during World War II forced the NACA and the aircraft industry to develop new research tools. In late 1945 the NACA began design work for new large supersonic wind tunnels at its three laboratories. The result was the 4- by 4-Foot Supersonic Wind Tunnel at Langley Memorial Aeronautical Laboratory, 6- by 6-foot supersonic wind tunnel at Ames Aeronautical Laboratory, and the largest facility, the 8- by 6-Foot Supersonic Wind Tunnel in Cleveland. The two former tunnels were to study aerodynamics, while the 8- by 6 facility was designed for supersonic propulsion. The 8- by 6-Foot Supersonic Wind Tunnel was used to study propulsion systems, including inlets and exit nozzles, combustion fuel injectors, flame holders, exit nozzles, and controls on ramjet and turbojet engines. Flexible sidewalls alter the tunnel’s nozzle shape to vary the Mach number during operation. A seven-stage axial compressor, driven by three electric motors that yield a total of 87,000 horsepower, generates air speeds from Mach 0.36 to 2.0. A section of the tunnel is seen being erected in this photograph.

  10. Quantum tunneling observed without its characteristic large kinetic isotope effects

    PubMed Central

    Hama, Tetsuya; Ueta, Hirokazu; Kouchi, Akira; Watanabe, Naoki

    2015-01-01

    Classical transition-state theory is fundamental to describing chemical kinetics; however, quantum tunneling is also important in explaining the unexpectedly large reaction efficiencies observed in many chemical systems. Tunneling is often indicated by anomalously large kinetic isotope effects (KIEs), because a particle’s ability to tunnel decreases significantly with its increasing mass. Here we experimentally demonstrate that cold hydrogen (H) and deuterium (D) atoms can add to solid benzene by tunneling; however, the observed H/D KIE was very small (1–1.5) despite the large intrinsic H/D KIE of tunneling (≳100). This strong reduction is due to the chemical kinetics being controlled not by tunneling but by the surface diffusion of the H/D atoms, a process not greatly affected by the isotope type. Because tunneling need not be accompanied by a large KIE in surface and interfacial chemical systems, it might be overlooked in other systems such as aerosols or enzymes. Our results suggest that surface tunneling reactions on interstellar dust may contribute to the deuteration of interstellar aromatic and aliphatic hydrocarbons, which could represent a major source of the deuterium enrichment observed in carbonaceous meteorites and interplanetary dust particles. These findings could improve our understanding of interstellar physicochemical processes, including those during the formation of the solar system. PMID:26034285

  11. Natural ventilation without air breathing in the top openings of highway tunnels

    NASA Astrophysics Data System (ADS)

    Jin, Sike; Jin, Jiali; Gong, Yanfeng

    2017-05-01

    A number of urban shallow-buried highway tunnels have been built in China. Despite much better internal air quality compared to the traditional tunnels, there is no sufficient theoretical ground or experimental support for the construction of such tunnels. Most researchers hold that natural ventilation in such tunnels depends on air breathing in the top openings, but some others are skeptical about this conclusion. By flow visualization technology on a tunnel experiment platform, we tested the characteristics of airflow in the top openings of highway tunnels. The results showed that air always flowed from outside to inside in all top openings above a continuous traffic stream, and the openings did not breathe at all. In addition, intake air in the top openings reached its maximum velocity at the tunnel entrance, and then gradually slowed down with tunnel depth increasing.

  12. Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions.

    PubMed

    Soni, Rohit; Petraru, Adrian; Meuffels, Paul; Vavra, Ondrej; Ziegler, Martin; Kim, Seong Keun; Jeong, Doo Seok; Pertsev, Nikolay A; Kohlstedt, Hermann

    2014-11-17

    Among recently discovered ferroelectricity-related phenomena, the tunnelling electroresistance (TER) effect in ferroelectric tunnel junctions (FTJs) has been attracting rapidly increasing attention owing to the emerging possibilities of non-volatile memory, logic and neuromorphic computing applications of these quantum nanostructures. Despite recent advances in experimental and theoretical studies of FTJs, many questions concerning their electrical behaviour still remain open. In particular, the role of ferroelectric/electrode interfaces and the separation of the ferroelectric-driven TER effect from electrochemical ('redox'-based) resistance-switching effects have to be clarified. Here we report the results of a comprehensive study of epitaxial junctions comprising BaTiO(3) barrier, La(0.7)Sr(0.3)MnO(3) bottom electrode and Au or Cu top electrodes. Our results demonstrate a giant electrode effect on the TER of these asymmetric FTJs. The revealed phenomena are attributed to the microscopic interfacial effect of ferroelectric origin, which is supported by the observation of redox-based resistance switching at much higher voltages.

  13. Ferroelectricity and tunneling electroresistance effect in asymmetric ferroelectric tunnel junctions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tao, L. L.; Wang, J., E-mail: jianwang@hku.hk

    2016-06-14

    We report the investigation on the ferroelectricity and tunneling electroresistance (TER) effect in PbTiO{sub 3} (PTO)-based ferroelectric tunnel junctions (FTJs) using first-principles calculations. For symmetric FTJs, we have calculated the average polarizations of PTO film and effective screening lengths of different metal electrodes for a number of FTJs, which is useful for experimental research. For asymmetric FTJs, significant asymmetric ferroelectric displacements in PTO film are observed, which is attributed to the intrinsic field generated by the two dissimilar electrodes. Moreover, by performing quantum transport calculations on those asymmetric FTJs, a sizable TER effect is observed. It is found that themore » asymmetry of ferroelectric displacements in PTO barrier, which is determined by the difference of work functions of the electrodes, controls the observed TER effect. Our results will help unravel the TER mechanism of asymmetric FTJs in most experiments and will be useful for the designing of FTJ-based devices.« less

  14. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, John F.; Zolper, John C.

    1997-01-01

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling.

  15. Semiconductor tunnel junction with enhancement layer

    DOEpatents

    Klem, J.F.; Zolper, J.C.

    1997-10-21

    The incorporation of a pseudomorphic GaAsSb layer in a runnel diode structure affords a new degree of freedom in designing runnel junctions for p-n junction device interconnects. Previously only doping levels could be varied to control the tunneling properties. This invention uses the valence band alignment band of the GaAsSb with respect to the surrounding materials to greatly relax the doping requirements for tunneling. 5 figs.

  16. Tunneling in axion monodromy

    DOE PAGES

    Brown, Jon; Cottrell, William; Shiu, Gary; ...

    2016-10-06

    The Coleman formula for vacuum decay and bubble nucleation has been used to estimate the tunneling rate in models of axion monodromy in recent literature. However, several of Coleman’s original assumptions do not hold for such models. Here we derive a new estimate with this in mind using a similar Euclidean procedure. We find that there are significant regions of parameter space for which the tunneling rate in axion monodromy is not well approximated by the Coleman formula. However, there is also a regime relevant to large field inflation in which both estimates parametrically agree. As a result, we alsomore » briefly comment on the applications of our results to the relaxion scenario.« less

  17. Three-dimensional scanning force/tunneling spectroscopy at room temperature.

    PubMed

    Sugimoto, Yoshiaki; Ueda, Keiichi; Abe, Masayuki; Morita, Seizo

    2012-02-29

    We simultaneously measured the force and tunneling current in three-dimensional (3D) space on the Si(111)-(7 × 7) surface using scanning force/tunneling microscopy at room temperature. The observables, the frequency shift and the time-averaged tunneling current were converted to the physical quantities of interest, i.e. the interaction force and the instantaneous tunneling current. Using the same tip, the local density of states (LDOS) was mapped on the same surface area at constant height by measuring the time-averaged tunneling current as a function of the bias voltage at every lateral position. LDOS images at negative sample voltages indicate that the tip apex is covered with Si atoms, which is consistent with the Si-Si covalent bonding mechanism for AFM imaging. A measurement technique for 3D force/current mapping and LDOS imaging on the equivalent surface area using the same tip was thus demonstrated.

  18. Charge Transport in 2D DNA Tunnel Junction Diodes.

    PubMed

    Yoon, Minho; Min, Sung-Wook; Dugasani, Sreekantha Reddy; Lee, Yong Uk; Oh, Min Suk; Anthopoulos, Thomas D; Park, Sung Ha; Im, Seongil

    2017-12-01

    Recently, deoxyribonucleic acid (DNA) is studied for electronics due to its intrinsic benefits such as its natural plenitude, biodegradability, biofunctionality, and low-cost. However, its applications are limited to passive components because of inherent insulating properties. In this report, a metal-insulator-metal tunnel diode with Au/DNA/NiO x junctions is presented. Through the self-aligning process of DNA molecules, a 2D DNA nanosheet is synthesized and used as a tunneling barrier, and semitransparent conducting oxide (NiO x ) is applied as a top electrode for resolving metal penetration issues. This molecular device successfully operates as a nonresonant tunneling diode, and temperature-variable current-voltage analysis proves that Fowler-Nordheim tunneling is a dominant conduction mechanism at the junctions. DNA-based tunneling devices appear to be promising prototypes for nanoelectronics using biomolecules. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. The design of an aerosol test tunnel for occupational hygiene investigations

    NASA Astrophysics Data System (ADS)

    Blackford, D. B.; Heighington, K.

    An aerosol test tunnel which provides large working sections is described and its performance evaluated. Air movement within the tunnel is achieved with a powerful D.C. motor and centrifugal fan. Test dusts are dispersed and injected into the tunnel by means of an aerosol generator. A unique divertor valve allows aerosol laden air to be either cleaned by a commercial pulse jet filtration unit or recycled around the tunnel to obtain a high aerosol concentration. The tunnel instrumentation is managed by a microcomputer which automatically controls the airspeed and aerosol concentration.

  20. NACA Engineer Examines Wind Tunnel Compressor Blades

    NASA Image and Video Library

    1955-09-21

    An engineer examines the main compressor for the 10- by 10-Foot Supersonic Wind Tunnel at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory. The engineers were preparing the new wind tunnel for its initial runs in early 1956. The 10- by 10 was the most powerful propulsion wind tunnel in the nation. The facility was part of Congress’ Unitary Plan Act which coordinated wind tunnel construction at the NACA, Air Force, industry, and universities. The 10- by 10 was the largest of the three NACA tunnels built under the act. The 20-foot diameter eight-stage axial flow compressor, seen in this photograph, could generate air flows up to Mach 2.5 through the test section. The stainless steel compressor had 584 blades ranging from 1.8 to 3.25 feet in length. This main compressor was complemented by a secondary axial flow compressor. Working in tandem the two could generate wind streams up to Mach 3.5. The Cleveland Chamber of Commerce presented NACA Lewis photographer Bill Bowles with a second place award for this photograph in their Business and Professional category. The photograph was published in October 1955 edition of its periodical, The Clevelander, which highlighted local professional photographers. Fellow Lewis photographer Gene Giczy won second place in another category for a photograph of Cleveland Municipal Airport.

  1. View of east entrance to Flume Tunnel #2. In foreground, ...

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

    View of east entrance to Flume Tunnel #2. In foreground, covered decking (covered by debris) protects the flume below it (not visible). The extreme top of the tunnel entrance is visible in the middle of the picture, just beyond the covered decking. This is typical of gravity tunnel entrances and the only photograph representing these features in the system. Looking south - Childs-Irving Hydroelectric Project, Childs System, Flume Tunnel No. 2, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

  2. Correlated sequential tunneling in Tomonaga-Luttinger liquid quantum dots

    NASA Astrophysics Data System (ADS)

    Thorwart, M.; Egger, R.; Grifoni, M.

    2005-02-01

    We investigate tunneling through a quantum dot formed by two strong impurites in a spinless Tomonaga-Luttinger liquid. Upon employing a Markovian master equation approach, we compute the linear conductance due to sequential tunneling processes. Besides the previously used lowest-order Golden Rule rates describing uncorrelated sequential tunneling (UST) processes, we systematically include higher-order correlated sequential tunneling (CST) diagrams within the standard Weisskopf-Wigner approximation. We provide estimates for the parameter regions where CST effects are shown to dominate over UST. Focusing mainly on the temperature dependence of the conductance maximum, we discuss the relation of our results to previous theoretical and experimental results.

  3. Contact area between femoral tunnel and interference screw in anatomic rectangular tunnel ACL reconstruction: a comparison of outside-in and trans-portal inside-out techniques.

    PubMed

    Hiramatsu, Kunihiko; Mae, Tatsuo; Tachibana, Yuta; Nakagawa, Shigeto; Shino, Konsei

    2018-02-01

    The purpose of this study was to compare the femoral tunnel length, the femoral graft bending angle at the femoral tunnel aperture, and the contact area between the femoral tunnel wall and an interference screw used for fixation in anatomic rectangular tunnel anterior cruciate ligament (ACL) reconstruction (ART ACLR). The study included 149 patients with primary ACL injury who underwent ART ACLR. Preoperatively, flexion angle of the index knee was checked under general anaesthesia. Those of less than 130° of passive flexion were assigned to the outside-in (OI) technique (78 patients), while the others to the trans-portal inside-out (TP) technique (71 patients). The patients underwent computed tomography with multiplanar reconstruction at 3-5 weeks post-operatively. Femoral tunnel length, graft bending angle, and contact ratio between the IFS and femoral tunnel were assessed. P < 0.05 was considered statistically significant. The femoral tunnel length in the OI technique was significantly longer than that in the TP technique (P < 0.001). The femoral graft bending angle in the OI technique was significantly more acute than that in the TP technique (P < 0.001). The contact ratio in the OI technique was significantly larger than that in the TP technique at every point in the femoral tunnel (P < 0.001). The OI technique resulted in a more acute femoral graft bending angle, longer mean femoral tunnel length, and larger contact ratio than the TP technique after ART ACLR. Retrospective comparative study, Level III.

  4. Criterions for condensation-free flow in supersonic tunnels

    NASA Technical Reports Server (NTRS)

    Burgess, Warren C; Seashore, Ferris L

    1949-01-01

    The results of an investigation of water-vapor condensation shocks in the air passing through supersonic tunnels are presented. Criterions for condensation-free flow are established by correlating experimental observations with the Volmer theory of nuclei formation. Experimental observations were made at Mach numbers up to 2.01. The criterions are presented in a form independent of tunnel-inlet stagnation pressure and are extended theoretically to a Mach number of 4.00. Preliminary evidence of the effect of tunnel size on the criterion is presented.

  5. 3. East portal of Tunnel 25, contextual view to southwest ...

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

    3. East portal of Tunnel 25, contextual view to southwest from atop Tunnel 26 (HAER CA-202), with the original Central Pacific Transcontinental line passing above the new line, 135mm lens. - Central Pacific Transcontinental Railroad, Tunnel No. 25, Milepost 133.09, Applegate, Placer County, CA

  6. View of Flume Tunnel #5 showing an example of concrete ...

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

    View of Flume Tunnel #5 showing an example of concrete flume covered with concrete slabs as it enters a tunnel under the road (FS 502). Looking southwest - Childs-Irving Hydroelectric Project, Childs System, Flume Tunnel No. 5, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

  7. Simulations of Resonant Intraband and Interband Tunneling Spin Filters

    NASA Technical Reports Server (NTRS)

    Ting, David; Cartoixa-Soler, Xavier; McGill, T. C.; Smith, Darryl L.; Schulman, Joel N.

    2001-01-01

    This viewgraph presentation reviews resonant intraband and interband tunneling spin filters It explores the possibility of building a zero-magnetic-field spin polarizer using nonmagnetic III-V semiconductor heterostructures. It reviews the extensive simulations of quantum transport in asymmetric InAs/GaSb/AlSb resonant tunneling structures with Rashba spin splitting and proposes a. new device concept: side-gated asymmetric Resonant Interband Tunneling Diode (a-RITD).

  8. Screens Would Protect Wind-Tunnel Fan Blades

    NASA Technical Reports Server (NTRS)

    Farmer, Moses G.

    1992-01-01

    Butterfly screen installed in wind tunnel between test section and fan blades to prevent debris from reaching fan blades if model structure fails. Protective screens deployed manually or automatically. Concept beneficial anywhere wind tunnels employed. Also useful in areas outside of aerospace industry, such as in airflow design of automobiles and other vehicles.

  9. Tunneling current in HfO2 and Hf0.5Zr0.5O2-based ferroelectric tunnel junction

    NASA Astrophysics Data System (ADS)

    Dong, Zhipeng; Cao, Xi; Wu, Tong; Guo, Jing

    2018-03-01

    Ferroelectric tunnel junctions (FTJs) have been intensively explored for future low power data storage and information processing applications. Among various ferroelectric (FE) materials studied, HfO2 and H0.5Zr0.5O2 (HZO) have the advantage of CMOS process compatibility. The validity of the simple effective mass approximation, for describing the tunneling process in these materials, is examined by computing the complex band structure from ab initio simulations. The results show that the simple effective mass approximation is insufficient to describe the tunneling current in HfO2 and HZO materials, and quantitative accurate descriptions of the complex band structures are indispensable for calculation of the tunneling current. A compact k . p Hamiltonian is parameterized to and validated by ab initio complex band structures, which provides a method for efficiently and accurately computing the tunneling current in HfO2 and HZO. The device characteristics of a metal/FE/metal structure and a metal/FE/semiconductor (M-F-S) structure are investigated by using the non-equilibrium Green's function formalism with the parameterized effective Hamiltonian. The result shows that the M-F-S structure offers a larger resistance window due to an extra barrier in the semiconductor region at off-state. A FTJ utilizing M-F-S structure is beneficial for memory design.

  10. Vision based tunnel inspection using non-rigid registration

    NASA Astrophysics Data System (ADS)

    Badshah, Amir; Ullah, Shan; Shahzad, Danish

    2015-04-01

    Growing numbers of long tunnels across the globe has increased the need for safety measurements and inspections of tunnels in these days. To avoid serious damages, tunnel inspection is highly recommended at regular intervals of time to find any deformations or cracks at the right time. While following the stringent safety and tunnel accessibility standards, conventional geodetic surveying using techniques of civil engineering and other manual and mechanical methods are time consuming and results in troublesome of routine life. An automatic tunnel inspection by image processing techniques using non rigid registration has been proposed. There are many other image processing methods used for image registration purposes. Most of the processes are operation of images in its spatial domain like finding edges and corners by Harris edge detection method. These methods are quite time consuming and fail for some or other reasons like for blurred or images with noise. Due to use of image features directly by these methods in the process, are known by the group, correlation by image features. The other method is featureless correlation, in which the images are converted into its frequency domain and then correlated with each other. The shift in spatial domain is the same as in frequency domain, but the processing is order faster than in spatial domain. In the proposed method modified normalized phase correlation has been used to find any shift between two images. As pre pre-processing the tunnel images i.e. reference and template are divided into small patches. All these relative patches are registered by the proposed modified normalized phase correlation. By the application of the proposed algorithm we get the pixel movement of the images. And then these pixels shifts are converted to measuring units like mm, cm etc. After the complete process if there is any shift in the tunnel at described points are located.

  11. Vibration-rotation-tunneling dynamics in small water clusters

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pugliano, Nick

    The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm -1 intermolecular vibration of the water dimer-d 4. Each of the VRT subbands originate from K a''=0 and terminate in either K a'=0 or 1. These data provide a complete characterization of the tunneling dynamics in themore » vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A' rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K a' quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a' symmetry, and the vibration is assigned as the v 12 acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D 2O-DOH isotopomer.« less

  12. Superconducting phonon spectroscopy using a low-temperature scanning tunneling microscope

    NASA Technical Reports Server (NTRS)

    Leduc, H. G.; Kaiser, W. J.; Hunt, B. D.; Bell, L. D.; Jaklevic, R. C.

    1989-01-01

    The low-temperature scanning tunneling microscope (STM) system described by LeDuc et al. (1987) was used to observe the phonon density of states effects in a superconductor. Using techniques based on those employed in macroscopic tunneling spectroscopy, electron tunneling current-voltage (I-V) spectra were measured for NbN and Pb, and dI/dV vs V spectra were measured using standard analog derivative techniques. I-V measurements on NbN and Pb samples under typical STM conditions showed no evidence for multiparticle tunneling effects.

  13. Chiral tunneling in gated inversion symmetric Weyl semimetal

    PubMed Central

    Bai, Chunxu; Yang, Yanling; Chang, Kai

    2016-01-01

    Based on the chirality-resolved transfer-matrix method, we evaluate the chiral transport tunneling through Weyl semimetal multi-barrier structures created by periodic gates. It is shown that, in sharp contrast to the cases of three dimensional normal semimetals, the tunneling coefficient as a function of incident angle shows a strong anisotropic behavior. Importantly, the tunneling coefficients display an interesting periodic oscillation as a function of the crystallographic angle of the structures. With the increasement of the barriers, the tunneling current shows a Fabry-Perot type interferences. For superlattice structures, the fancy miniband effect has been revealed. Our results show that the angular dependence of the first bandgap can be reduced into a Lorentz formula. The disorder suppresses the oscillation of the tunneling conductance, but would not affect its average amplitude. This is in sharp contrast to that in multi-barrier conventional semiconductor structures. Moreover, numerical results for the dependence of the angularly averaged conductance on the incident energy and the structure parameters are presented and contrasted with those in two dimensional relativistic materials. Our work suggests that the gated Weyl semimetal opens a possible new route to access to new type nanoelectronic device. PMID:26888491

  14. Chiral tunneling in gated inversion symmetric Weyl semimetal.

    PubMed

    Bai, Chunxu; Yang, Yanling; Chang, Kai

    2016-02-18

    Based on the chirality-resolved transfer-matrix method, we evaluate the chiral transport tunneling through Weyl semimetal multi-barrier structures created by periodic gates. It is shown that, in sharp contrast to the cases of three dimensional normal semimetals, the tunneling coefficient as a function of incident angle shows a strong anisotropic behavior. Importantly, the tunneling coefficients display an interesting periodic oscillation as a function of the crystallographic angle of the structures. With the increasement of the barriers, the tunneling current shows a Fabry-Perot type interferences. For superlattice structures, the fancy miniband effect has been revealed. Our results show that the angular dependence of the first bandgap can be reduced into a Lorentz formula. The disorder suppresses the oscillation of the tunneling conductance, but would not affect its average amplitude. This is in sharp contrast to that in multi-barrier conventional semiconductor structures. Moreover, numerical results for the dependence of the angularly averaged conductance on the incident energy and the structure parameters are presented and contrasted with those in two dimensional relativistic materials. Our work suggests that the gated Weyl semimetal opens a possible new route to access to new type nanoelectronic device.

  15. Aerodynamic performance of a low-speed wind tunnel.

    PubMed

    Frechen, F-B; Frey, M; Wett, M; Löser, C

    2004-01-01

    The determination of the odour mass flow emitted from a source is a very important step and forms the basis for all subsequent considerations and calculations. Wastewater treatment plants, as well as waste treatment facilities, consist of different kinds of odour sources. Unfortunately, most of the sources are passive sources, where no outward air flow-rate can be measured, but where odorants are obviously emitted. Thus, a type of sampling is required that allows to measure the emitted odour flow-rate (OFR). To achieve this, different methods are in use worldwide. Besides indirect methods, such as micrometeorological atmospheric dispersion models, which have not been used in Germany (in other countries due to different problems, direct methods are also used). Direct measurements include hood methods, commonly divided into static flux chambers, dynamic flux chambers and wind tunnels. The wind tunnel that we have been operating in principle since 1983 is different from all subsequent presented wind tunnels, in that we operate it at a considerably lower wind speed than the others. To describe the behaviour of this wind tunnel, measurement of the flow pattern in this low-speed tunnel are under way, and some initial results are presented here.

  16. Design of a Micro Cable Tunnel Inspection Robot

    NASA Astrophysics Data System (ADS)

    Song, Wei; Liu, Lei; Zhou, Xiaolong; Wang, Chengjiang

    2016-11-01

    As the ventilation system in cable tunnel is not perfect and the environment is closed, it is easy to accumulate toxic and harmful gas. It is a serious threat to the life safety of inspection staff. Therefore, a micro cable tunnel inspection robot is designed. The whole design plan mainly includes two parts: mechanical structure design and control system design. According to the functional requirements of the tunnel inspection robot, a wheel arm structure with crawler type is proposed. Some sensors are used to collect temperature, gas and image and transmit the information to the host computer in real time. The result shows the robot with crawler wheel arm structure has the advantages of small volume, quick action and high performance-price ratio. Besides, it has high obstacle crossing and avoidance ability and can adapt to a variety of complex cable tunnel environment.

  17. Virtual Processes and Quantum Tunnelling as Fictions

    ERIC Educational Resources Information Center

    Arthur, Richard T. W.

    2012-01-01

    In this paper it is argued that virtual processes are dispensable fictions. The argument proceeds by a comparison with the phenomenon of quantum tunnelling. Building on an analysis of Levy-Leblond and Balibar, it is argued that, although the phenomenon known as quantum tunnelling certainly occurs and is at the basis of many paradigmatic quantum…

  18. Autonomous Robotic Inspection in Tunnels

    NASA Astrophysics Data System (ADS)

    Protopapadakis, E.; Stentoumis, C.; Doulamis, N.; Doulamis, A.; Loupos, K.; Makantasis, K.; Kopsiaftis, G.; Amditis, A.

    2016-06-01

    In this paper, an automatic robotic inspector for tunnel assessment is presented. The proposed platform is able to autonomously navigate within the civil infrastructures, grab stereo images and process/analyse them, in order to identify defect types. At first, there is the crack detection via deep learning approaches. Then, a detailed 3D model of the cracked area is created, utilizing photogrammetric methods. Finally, a laser profiling of the tunnel's lining, for a narrow region close to detected crack is performed; allowing for the deduction of potential deformations. The robotic platform consists of an autonomous mobile vehicle; a crane arm, guided by the computer vision-based crack detector, carrying ultrasound sensors, the stereo cameras and the laser scanner. Visual inspection is based on convolutional neural networks, which support the creation of high-level discriminative features for complex non-linear pattern classification. Then, real-time 3D information is accurately calculated and the crack position and orientation is passed to the robotic platform. The entire system has been evaluated in railway and road tunnels, i.e. in Egnatia Highway and London underground infrastructure.

  19. Tunneling decay of false vortices

    NASA Astrophysics Data System (ADS)

    Lee, Bum-Hoon; Lee, Wonwoo; MacKenzie, Richard; Paranjape, M. B.; Yajnik, U. A.; Yeom, Dong-han

    2013-10-01

    We consider the decay of vortices trapped in the false vacuum of a theory of scalar electrodynamics in 2+1 dimensions. The potential is inspired by models with intermediate symmetry breaking to a metastable vacuum that completely breaks a U(1) symmetry, while in the true vacuum, the symmetry is unbroken. The false vacuum is unstable through the formation of true vacuum bubbles; however, the rate of decay can be extremely long. On the other hand, the false vacuum can contain metastable vortex solutions. These vortices contain the true vacuum inside in addition to a unit of magnetic flux and the appropriate topologically nontrivial false vacuum outside. We numerically establish the existence of vortex solutions which are classically stable; however, they can decay via tunneling. In general terms, they tunnel to a configuration which is a large, thin-walled vortex configuration that is now classically unstable to the expansion of its radius. We compute an estimate for the tunneling amplitude in the semiclassical approximation. We believe our analysis would be relevant to superconducting thin films or superfluids.

  20. Thermal radiation scanning tunnelling microscopy

    NASA Astrophysics Data System (ADS)

    de Wilde, Yannick; Formanek, Florian; Carminati, Rémi; Gralak, Boris; Lemoine, Paul-Arthur; Joulain, Karl; Mulet, Jean-Philippe; Chen, Yong; Greffet, Jean-Jacques

    2006-12-01

    In standard near-field scanning optical microscopy (NSOM), a subwavelength probe acts as an optical `stethoscope' to map the near field produced at the sample surface by external illumination. This technique has been applied using visible, infrared, terahertz and gigahertz radiation to illuminate the sample, providing a resolution well beyond the diffraction limit. NSOM is well suited to study surface waves such as surface plasmons or surface-phonon polaritons. Using an aperture NSOM with visible laser illumination, a near-field interference pattern around a corral structure has been observed, whose features were similar to the scanning tunnelling microscope image of the electronic waves in a quantum corral. Here we describe an infrared NSOM that operates without any external illumination: it is a near-field analogue of a night-vision camera, making use of the thermal infrared evanescent fields emitted by the surface, and behaves as an optical scanning tunnelling microscope. We therefore term this instrument a `thermal radiation scanning tunnelling microscope' (TRSTM). We show the first TRSTM images of thermally excited surface plasmons, and demonstrate spatial coherence effects in near-field thermal emission.

  1. Sonographic diagnosis of carpal tunnel syndrome: a study in 200 hospital workers*

    PubMed Central

    Castro, Adham do Amaral e; Skare, Thelma Larocca; Nassif, Paulo Afonso Nunes; Sakuma, Alexandre Kaue; Barros, Wagner Haese

    2015-01-01

    Objective To describe the prevalence of carpal tunnel syndrome in a sample of 200 healthy hospital workers, establishing the respective epidemiological associations. Materials and Methods Two hundred individuals were submitted to wrist ultrasonography to measure the median nerve area. They were questioned and examined for epidemiological data, body mass index, carpal tunnel syndrome signs and symptoms, and submitted to the Boston carpal tunnel questionnaire (BCTQ) to evaluate the carpal tunnel syndrome severity. A median nerve area ≥ 9 mm2 was considered to be diagnostic of carpal tunnel syndrome. Results Carpal tunnel syndrome was diagnosed by ultrasonography in 34% of the sample. It was observed the association of carpal tunnel syndrome with age (p < 0.0001), paresthesia (p < 0.0001), Tinel’s test (p < 0.0001), Phalen’s test (p < 0.0001), BCTQ score (p < 0.0001), and years of formal education (p < 0.0001). Years of formal education was the only variable identified as an independent risk factor for carpal tunnel syndrome (95% CI = 1.03 to 1.24). Conclusion The prevalence of carpal tunnel syndrome in a population of hospital workers was of 34%. The number of years of formal education was the only independent risk factor for carpal tunnel syndrome. PMID:26543279

  2. Predictive formula for the length of tibial tunnel in anterior crucitate ligament reconstruction.

    PubMed

    Chernchujit, Bancha; Barthel, Thomas

    2009-12-01

    The anterior cruciate ligament (ACL) reconstruction using bone-patellar tendon bone graft is a common procedure in orthopedics. One challenging problem found is a graft-tunnel mismatch. Previous studies have reported the mathematic formula to predict the tibial angle length and angle to avoid graft-tunnel mismatch but these formulas have shown limited predictability. To propose a predictive formula for the length of tibial tunnel and to examine its predictability. Thirty six patients (26 males, 14 females) with ACL injury were included in this study. The preoperativemedial proximal tibial angle was measured. Intraoperatively, the tibial tunnel length and tibial entry point were measured. The postoperative coronal and saggital angle of tibial tunnel were measured from knee radiograph. The data were analysed by using trigonometry correlation and formulate the predictive formula of tibial tunnel length. We found that tibial tunnel length (T) has trigonometric correlation between the location of tibial tunnel entry point (w), coronal angle of tibial tunnel (b), saggital angle of tibial tunnel (a) and the medial proximal tibial slope (c) by using this formula T = Wcos(c)tan(b)/sin(a) This proposed predictive formula can well predict the length of the tibial tunnel at preoperative period to avoid graft-tunnel mismatch.

  3. Enhancement of capacitance benefit by drain offset structure in tunnel field-effect transistor circuit speed associated with tunneling probability increase

    NASA Astrophysics Data System (ADS)

    Asai, Hidehiro; Mori, Takahiro; Matsukawa, Takashi; Hattori, Junichi; Endo, Kazuhiko; Fukuda, Koichi

    2018-04-01

    The effect of a drain offset structure on the operation speed of a tunnel field-effect transistor (TFET) ring oscillator is investigated by technology computer-aided design (TCAD) simulation. We demonstrate that the reduction of gate-drain capacitance by the drain offset structure dramatically increases the operation speed of the ring oscillators. Interestingly, we find that this capacitance benefit to operation speed is enhanced by the increase in band-to-band tunneling probability. The “synergistic” speed enhancement by the drain offset structure and the tunneling rate increase will have promising application to the significant improvement of the operation speed of TFET circuits.

  4. Fermions tunnelling from the charged dilatonic black holes

    NASA Astrophysics Data System (ADS)

    Chen, De-You; Jiang, Qing-Quan; Zu, Xiao-Tao

    2008-10-01

    Kerner and Mann's recent work shows that for an uncharged and non-rotating black hole its Hawking temperature can be correctly derived by fermions tunnelling from its horizons. In this paper, our main work is to improve the analysis to deal with charged fermion tunnelling from the general dilatonic black holes, specifically including the charged, spherically symmetric dilatonic black hole, the rotating Einstein Maxwell dilaton axion (EMDA) black hole and the rotating Kaluza Klein (KK) black hole. As a result, the correct Hawking temperatures are well recovered by charged fermions tunnelling from these black holes.

  5. Ferroelectric tunnel junctions with multi-quantum well structures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ma, Zhijun; Zhang, Tianjin, E-mail: zhangtj@hubu.edu.cn; Hubei Collaborative Innovation Center for Advanced Organic Chemical Materials, Hubei University, Wuhan 430062

    Ferroelectric tunnel junctions (FTJs) with multi-quantum well structures are proposed and the tunneling electroresistance (TER) effect is investigated theoretically. Compared with conventional FTJs with monolayer ferroelectric barriers, FTJs with single-well structures provide TER ratio improvements of one order of magnitude, while FTJs with optimized multi-well structures can enhance this improvement by another order of magnitude. It is believed that the increased resonant tunneling strength combined with appropriate asymmetry in these FTJs contributes to the improvement. These studies may help to fabricate FTJs with large TER ratio experimentally and put them into practice.

  6. Spin injection in n-type resonant tunneling diodes.

    PubMed

    Orsi Gordo, Vanessa; Herval, Leonilson Ks; Galeti, Helder Va; Gobato, Yara Galvão; Brasil, Maria Jsp; Marques, Gilmar E; Henini, Mohamed; Airey, Robert J

    2012-10-25

    We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two emission lines attributed to neutral (X) and negatively charged excitons (X-). We have observed a voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to -88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the accumulation layers.

  7. Magnetization reversal mechanism of magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Liu, Cun-Ye; Li, Jian; Wang, Yue; Chen, Jian-Yong; Xu, Qing-Yu; Ni, Gang; Sang, Hai; Du, You-Wei

    2002-01-01

    Using the ion-beam-sputtering technique, we have fabricated Fe/Al2O3/Fe magnetic tunnelling junctions (MTJs). We have observed double-peaked shapes of curves, which have a level summit and a symmetrical feature, showing the magnetoresistance of the junction as a function of applied field. We have measured the tunnel conductance of MTJs which have insulating layers of different thicknesses. We have studied the dependence of the magnetoresistance of MTJs on tunnel conductance. The microstructures of hard- and soft-magnetic layers and interfaces of ferromagnets and insulators were probed. Analysing the influence of MJT microstructures, including those having clusters or/and granules in magnetic and non-magnetic films, a magnetization reversal mechanism (MRM) is proposed, which suggests that the MRM of tunnelling junctions may be explained by using a group-by-group reversal model of magnetic moments of the mesoscopical particles. We discuss the influence of MTJ microstructures, including those with clusters or/and granules in the ferromagnetic and non-magnetic films, on the MRM.

  8. Estimating Tunnel Strain in the Weak and Schistose Rock Mass Influenced by Stress Anisotropy: An Evaluation Based on Three Tunnel Cases from Nepal

    NASA Astrophysics Data System (ADS)

    Panthi, Krishna Kanta; Shrestha, Pawan Kumar

    2018-06-01

    Total plastic deformation in tunnels passing through weak and schistose rock mass consists of both time-independent and time-dependent deformations. The extent of this total deformation is heavily influenced by the rock mass deformability properties and in situ stress condition prevailing in the area. If in situ stress is not isotropic, the deformation magnitude is not only different along the longitudinal alignment but also along the periphery of the tunnel wall. This manuscript first evaluates the long-term plastic deformation records of three tunnel projects from the Nepal Himalaya and identifies interlink between the time-independent and time-dependent deformations using the convergence law proposed by Sulem et al. (Int J Rock Mech Min Sci Geomech 24(3):145-154, 1987a, Int J Rock Mech Min Sci Geomech 24(3):155-164, 1987b). Secondly, the manuscript attempts to establish a correlation between plastic deformations (tunnel strain) and rock mass deformable properties, support pressure and in situ stress conditions. Finally, patterns of time-independent and time-dependent plastic deformations are also evaluated and discussed. The long-term plastic deformation records of 24 tunnel sections representing four different rock types of three different headrace tunnel cases from Nepal Himalaya are extensively used in this endeavor. The authors believe that the proposed findings will be a step further in analysis of plastic deformations in tunnels passing through weak and schistose rock mass and along the anisotropic stress conditions.

  9. 30 CFR 77.212 - Draw-off tunnel ventilation fans; installation.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Draw-off tunnel ventilation fans; installation... UNDERGROUND COAL MINES Surface Installations § 77.212 Draw-off tunnel ventilation fans; installation. When fans are used to ventilate draw-off tunnels the fans shall be: (a) Installed on the surface; (b...

  10. Compartment Venting Analyses of Ares I First Stage Systems Tunnel

    NASA Technical Reports Server (NTRS)

    Wang, Qunzhen; Arner, Stephen

    2009-01-01

    Compartment venting analyses have been performed for the Ares I first stage systems tunnel using both the lumped parameter method and the three-dimensional (31)) transient computational fluid dynamics (CFD) approach. The main objective of venting analyses is to predict the magnitudes of differential pressures across the skin so the integrity of solid walls can be evaluated and properly designed. The lumped parameter method assumes the gas pressure and temperature inside the systems tunnel are spatially uniform, which is questionable since the tunnel is about 1,700 in. long and 4 in. wide. Therefore, 31) transient CFD simulations using the commercial CFD code FLUENT are performed in order to examine the gas pressure and temperature variations inside the tunnel. It was found that the uniform pressure and temperature assumptions inside the systems tunnel are valid during ascent. During reentry, the uniform pressure assumption is also reasonable but the uniform temperature assumption is not valid. Predicted pressure and temperature inside the systems tunnel using CFD are also compared with those from the lumped parameter method using the NASA code CHCHVENT. In general, the average pressure and temperature inside the systems tunnel from CFD are between the burst and crush results from CHCHVENT during both ascent and reentry. The skin differential pressure and pressure inside the systems tunnel relative to freestream pressure from CHCHVENT as well as velocity vectors and streamlines are also discussed in detail.

  11. Tunneling current spectroscopy of a nanostructure junction involving multiple energy levels.

    PubMed

    Kuo, David M-T; Chang, Yia-Chung

    2007-08-24

    A multilevel Anderson model is employed to simulate the system of a nanostructure tunnel junction with any number of one-particle energy levels. The tunneling current, including both shell-tunneling and shell-filling cases, is theoretically investigated via the nonequilibrium Green's function method. We obtain a closed form for the spectral function, which is used to analyze the complicated tunneling current spectra of a quantum dot or molecule embedded in a double-barrier junction. We also show that negative differential conductance can be observed in a quantum dot tunnel junction when the Coulomb interactions with neighboring quantum dots are taken into account.

  12. Detailed Uncertainty Analysis for Ares I Ascent Aerodynamics Wind Tunnel Database

    NASA Technical Reports Server (NTRS)

    Hemsch, Michael J.; Hanke, Jeremy L.; Walker, Eric L.; Houlden, Heather P.

    2008-01-01

    A detailed uncertainty analysis for the Ares I ascent aero 6-DOF wind tunnel database is described. While the database itself is determined using only the test results for the latest configuration, the data used for the uncertainty analysis comes from four tests on two different configurations at the Boeing Polysonic Wind Tunnel in St. Louis and the Unitary Plan Wind Tunnel at NASA Langley Research Center. Four major error sources are considered: (1) systematic errors from the balance calibration curve fits and model + balance installation, (2) run-to-run repeatability, (3) boundary-layer transition fixing, and (4) tunnel-to-tunnel reproducibility.

  13. Implementation of a Particle Image Velocimetry System for Wind Tunnel Flowfield Measurements

    DTIC Science & Technology

    2014-12-01

    Instrumentation Wind tunnel speed was measured by two pitot probes mounted on opposite tunnel walls upstream of the model and above the ground...board. The pitot probes were connected differentially to Scanivalve 1-psi transducers. A secondary measurement of wind tunnel speed was made with the...Manf. Model Range 1 Tunnel Vel (south pitot ) Transducer Scanivalve CR24D 1 psi 2 Tunnel Vel (north pitot ) Transducer Scanivalve CR24D 1 psi 3

  14. Topological view of quantum tunneling coherent destruction

    NASA Astrophysics Data System (ADS)

    Bernardini, Alex E.; Chinaglia, Mariana

    2017-08-01

    Quantum tunneling of the ground and first excited states in a quantum superposition driven by a novel analytical configuration of a double-well (DW) potential is investigated. Symmetric and asymmetric potentials are considered as to support quantum mechanical zero mode and first excited state analytical solutions. Reporting about a symmetry breaking that supports the quantum conversion of a zero-mode stable vacuum into an unstable tachyonic quantum state, two inequivalent topological scenarios are supposed to drive stable tunneling and coherent tunneling destruction respectively. A complete prospect of the Wigner function dynamics, vector field fluxes and the time dependence of stagnation points is obtained for the analytical potentials that support stable and tachyonic modes.

  15. Effect of annealing on the temperature dependence of inelastic tunneling contributions vis-à-vis tunneling magnetoresistance and barrier parameters in CoFe/MgO/NiFe magnetic tunnel junctions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bhusan Singh, Braj; Chaudhary, Sujeet, E-mail: sujeetc@physics.iitd.ac.in

    The effect of annealing on the changes in the inelastic tunneling contributions in tunneling conductance of ion beam sputtered CoFe/MgO/NiFe magnetic tunnel junctions (MTJs) is investigated. The inelastic contributions are evaluated using hopping conduction model of Glazman and Matveev in the temperature range of 25–300 K. The hopping through number of series of localized states present in the barrier due to structural defects increases from 9 (in as deposited MTJ) to 18 after annealing (at 200 °C/1 h); although no changes in the interface roughness of CoFe-MgO and MgO-NiFe interfaces are observed as revealed by the x-ray reflectance studies on planar MTJs. Themore » bias dependence of tunneling magnetoresistance (TMR) at 25 K is found to get improved after annealing as revealed by the value V{sub 1/2} (the bias value at which the TMR reaches to half of its value at nearly zero bias); which is 78 mV (in MTJ annealed at 200 °C/1 h) 2.5 times the value of 33 mV (in as deposited MTJ). At 25 K the inelastic tunneling spectra revealed the presence of zero bias anomaly and magnon excitations in the range of 10–15 mV. While the barrier height exhibited a strong temperature dependence with nearly 100% increase from the value at 300 K to 25 K, the temperature dependence of TMR becomes steep after annealing.« less

  16. Building information modelling review with potential applications in tunnel engineering of China.

    PubMed

    Zhou, Weihong; Qin, Haiyang; Qiu, Junling; Fan, Haobo; Lai, Jinxing; Wang, Ke; Wang, Lixin

    2017-08-01

    Building information modelling (BIM) can be applied to tunnel engineering to address a number of problems, including complex structure, extensive design, long construction cycle and increased security risks. To promote the development of tunnel engineering in China, this paper combines actual cases, including the Xingu mountain tunnel and the Shigu Mountain tunnel, to systematically analyse BIM applications in tunnel engineering in China. The results indicate that BIM technology in tunnel engineering is currently mainly applied during the design stage rather than during construction and operation stages. The application of BIM technology in tunnel engineering covers many problems, such as a lack of standards, incompatibility of different software, disorganized management, complex combination with GIS (Geographic Information System), low utilization rate and poor awareness. In this study, through summary of related research results and engineering cases, suggestions are introduced and an outlook for the BIM application in tunnel engineering in China is presented, which provides guidance for design optimization, construction standards and later operation maintenance.

  17. Building information modelling review with potential applications in tunnel engineering of China

    PubMed Central

    Zhou, Weihong; Qin, Haiyang; Fan, Haobo; Lai, Jinxing; Wang, Ke; Wang, Lixin

    2017-01-01

    Building information modelling (BIM) can be applied to tunnel engineering to address a number of problems, including complex structure, extensive design, long construction cycle and increased security risks. To promote the development of tunnel engineering in China, this paper combines actual cases, including the Xingu mountain tunnel and the Shigu Mountain tunnel, to systematically analyse BIM applications in tunnel engineering in China. The results indicate that BIM technology in tunnel engineering is currently mainly applied during the design stage rather than during construction and operation stages. The application of BIM technology in tunnel engineering covers many problems, such as a lack of standards, incompatibility of different software, disorganized management, complex combination with GIS (Geographic Information System), low utilization rate and poor awareness. In this study, through summary of related research results and engineering cases, suggestions are introduced and an outlook for the BIM application in tunnel engineering in China is presented, which provides guidance for design optimization, construction standards and later operation maintenance. PMID:28878970

  18. Building information modelling review with potential applications in tunnel engineering of China

    NASA Astrophysics Data System (ADS)

    Zhou, Weihong; Qin, Haiyang; Qiu, Junling; Fan, Haobo; Lai, Jinxing; Wang, Ke; Wang, Lixin

    2017-08-01

    Building information modelling (BIM) can be applied to tunnel engineering to address a number of problems, including complex structure, extensive design, long construction cycle and increased security risks. To promote the development of tunnel engineering in China, this paper combines actual cases, including the Xingu mountain tunnel and the Shigu Mountain tunnel, to systematically analyse BIM applications in tunnel engineering in China. The results indicate that BIM technology in tunnel engineering is currently mainly applied during the design stage rather than during construction and operation stages. The application of BIM technology in tunnel engineering covers many problems, such as a lack of standards, incompatibility of different software, disorganized management, complex combination with GIS (Geographic Information System), low utilization rate and poor awareness. In this study, through summary of related research results and engineering cases, suggestions are introduced and an outlook for the BIM application in tunnel engineering in China is presented, which provides guidance for design optimization, construction standards and later operation maintenance.

  19. Engineering and characterizing inverse tunneling magnetoresistance magnetic tunnel junctions with novel ferromagnetic electrodes

    NASA Astrophysics Data System (ADS)

    Xiang, Hua

    Magnetic tunnel junctions (MTJs) have attracted great interest for applications in read heads and nonvolatile magnetic random access memories. MTJs exhibit tunneling magnetoresistance (TMR), which is proportional to the spin polarization (SP) of ferromagnetic (FM) electrodes. This thesis describes the fabrication and characterization of inverse TMR MTJs with novel FM electrodes and tunnel barriers, including Fe3O4 and Fe4N electrodes and Ta2O5 tunnel barriers. Fe3O4 has been predicted to have perfect negative SP at the Fermi level, making it a promising FM electrode for inverse TMR MTJs. Two approaches were developed to grow epitaxial Fe3O 4 films on Si substrates, reactive sputtering and selective oxidation, and the physical properties were characterized. Epitaxial Fe3O 4 films with smooth surfaces were achieved using a TiN buffer and low temperature selective oxidation. Fe4N has also been predicted to have nearly perfect negative SP. Epitaxial Fe4N films were fabricated on Si substrates by reactive sputtering, and the magnetic properties and thermal stability were characterized. Fe4N is metastable with respect to decomposition into Fe and N 2. During room temperature air oxidation, an epitaxial Fe3O 4 layer formed on Fe4N surface, by incorporation of oxygen, decomposition of Fe4N, and release of N. We fabricated Fe4N/AlOx/Fe MTJs and found normal TMR for the as-prepared junction but inverse TMR with abnormal bias dependence after annealing. The TMR inversion is caused by an Fe3O4 layer at the Fe4N/AlO, interface. The abnormal bias dependence is caused by an imperfect Fe3O4/AlOx interface. Fe3O4 (or Fe4N)/Ta2O5/Fe MTJs show relatively low junction resistance and noisy TMR signals, due to the difficulty of preparing high quality Ta2O5 barriers. The effect of composition of bcc Co100-xFex electrodes on the TMR for AlOx-based MTJs has been studied. The TMR increases with x until it reaches a maximum of 66.7% at 28 at.% Fe, and then decreases. The reason for this TMR

  20. Petrology and geochemistry of the Tasse mantle xenoliths of the Canadian Cordillera: A record of Archean to Quaternary mantle growth, metasomatism, removal, and melting

    NASA Astrophysics Data System (ADS)

    Polat, Ali; Frei, Robert; Longstaffe, Fred J.; Thorkelson, Derek J.; Friedman, Eyal

    2018-07-01

    Mantle xenoliths hosted by the Quaternary Tasse alkaline basalts in the Canadian Cordillera, southeastern British Columbia, are mostly spinel lherzolite originating from subcontinental lithospheric mantle. The xenoliths contain abundant feldspar veins, melt pockets and spongy clinopyroxene, recording extensive alkaline metasomatism and partial melting. Feldspar occurs as veins and interstitial crystal in melt pockets. Melt pockets occur mainly at triple junctions, along grain boundaries, and consist mainly of olivine, cpx, opx and spinel surrounded by interstitial feldspar. The Nd, Sr and Pb isotopic compositions of the xenoliths indicate that their sources are characterized by variable mixtures of depleted MORB mantle and EM1 and EM2 mantle components. Large variations in εNd values (-8.2 to +9.6) and Nd depleted mantle model ages (TDM = 66 to 3380 Ma) are consistent with multiple sources and melt extraction events, and long-term (>3300 Ma) isolation of some source regions from the convecting mantle. Samples with Archean and Paleoproterozoic Nd model ages are interpreted as either have been derived from relict Laurentian mantle pieces beneath the Cordillera or have been eroded from the root of the Laurentian craton to the east and transported to the base of the Cordilleran lithosphere by edge-driven convection currents. The oxygen isotope compositions of the xenoliths (average δ18O = +5.1 ± 0.5‰) are similar to those of depleted mantle. The average δ18O values of olivine (+5.0 ± 0.2‰), opx (+5.9 ± 0.6‰), cpx (+6.0 ± 0.6‰) and spinel (+4.5 ± 0.2‰) are similar to mantle values. Large fractionations for olivine-opx, olivine-cpx and opx-cpx pairs, however, reflect disequilibrium stemming from metasomatism and partial melting. Whole-rock trace element, Nd, Sr, Pb and O isotope compositions of the xenoliths and host alkaline basalts indicate different mantle sources for these two suites of rocks. The xenoliths were derived from shallow lithospheric

  1. Tunnel and Station Cost Methodology Volume II: Stations

    DOT National Transportation Integrated Search

    1981-01-01

    The main objective of this study was to develop a model for estimating the cost of subway station and tunnel construction. This report describes a cost estimating methodology for subway tunnels that can be used by planners, designers, owners, and gov...

  2. 431 kA/cm2 peak tunneling current density in GaN/AlN resonant tunneling diodes

    NASA Astrophysics Data System (ADS)

    Growden, Tyler A.; Zhang, Weidong; Brown, Elliott R.; Storm, David F.; Hansen, Katurah; Fakhimi, Parastou; Meyer, David J.; Berger, Paul R.

    2018-01-01

    We report on the design and fabrication of high current density GaN/AlN double barrier resonant tunneling diodes grown via plasma assisted molecular-beam epitaxy on bulk GaN substrates. A quantum-transport solver was used to model and optimize designs with high levels of doping and ultra-thin AlN barriers. The devices displayed repeatable room temperature negative differential resistance with peak-to-valley current ratios ranging from 1.20 to 1.60. A maximum peak tunneling current density (Jp) of 431 kA/cm2 was observed. Cross-gap near-UV (370-385 nm) electroluminescence (EL) was observed above +6 V when holes, generated from a polarization induced Zener tunneling effect, recombine with electrons in the emitter region. Analysis of temperature dependent measurements, thermal resistance, and the measured EL spectra revealed the presence of severe self-heating effects.

  3. Electron tunneling through atomically flat and ultrathin hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Lee, Gwan-Hyoung; Yu, Young-Jun; Lee, Changgu; Dean, Cory; Shepard, Kenneth L.; Kim, Philip; Hone, James

    2011-12-01

    Electron tunneling through atomically flat and ultrathin hexagonal boron nitride (h-BN) on gold-coated mica was investigated using conductive atomic force microscopy. Low-bias direct tunneling was observed in mono-, bi-, and tri-layer h-BN. For all thicknesses, Fowler-Nordheim tunneling (FNT) occurred at high bias, showing an increase of breakdown voltage with thickness. Based on the FNT model, the barrier height for tunneling (3.07 eV) and dielectric strength (7.94 MV/cm) of h-BN are obtained; these values are comparable to those of SiO2.

  4. Nuclear fluxes during coherent tunnelling in asymmetric double well potentials

    NASA Astrophysics Data System (ADS)

    Liu, ChunMei; Manz, Jörn; Yang, Yonggang

    2015-08-01

    Previous results for nuclear fluxes during coherent tunnelling of molecules with symmetric double well potentials are extended to fluxes in asymmetric double well potentials. The theory is derived using the two-state approximation (TSA). The symmetric system serves as a reference. As an example, we consider the one-dimensional model of the tunnelling inversion of oriented ammonia, with semiclassical dipole coupling to an electric field. The tunnelling splitting increases with the dipole coupling by a factor f≥slant 1. The tunnelling time decreases by 1/f. The nuclear density appears as the sum of two parts: The tunnelling part decreases as {1/f}2 times the density of the symmetric reference, whereas the non-tunnelling part is the initial density times ≤ft({{1-1}/f}2\\right). Likewise, the nuclear flux decreases by 1/f, with essentially the same shape as for the symmetric reference, with maximum value at the potential barrier. Coherent nuclear tunnellings starting from the upper or lower wells of the asymmetric potential are equivalent. The results are universal, in the frame of the TSA, hence they allow straightforward extrapolations from one system to others. This is demonstrated by the prediction of isotope effects for five isotopomers of ammonia.

  5. JPRS Report, Environmental Issues

    DTIC Science & Technology

    1990-10-12

    IZVESTIYA 18 Sep] 33 UN Mission To Study Chernobyl Effects [TASS 19 Sep] 33 Rumors of’Crack’in Chernobyl Sarcophagus Rebutted [PRAVDA 18...Sep] 33 Russian Parliament Sets Up Chernobyl Committee [TASS 19 Sep] 34 Uranium Wastes Said Contaminating Kirovograd [Moscow TV 18 Sep] 35...following the Chernobyl disaster. The find- ings make it possible to reach conclusions about Cher- nobyl’s impact on the environment in those regions. The

  6. Enabling Advanced Wind-Tunnel Research Methods Using the NASA Langley 12-Foot Low Speed Tunnel

    NASA Technical Reports Server (NTRS)

    Busan, Ronald C.; Rothhaar, Paul M.; Croom, Mark A.; Murphy, Patrick C.; Grafton, Sue B.; O-Neal, Anthony W.

    2014-01-01

    Design of Experiment (DOE) testing methods were used to gather wind tunnel data characterizing the aerodynamic and propulsion forces and moments acting on a complex vehicle configuration with 10 motor-driven propellers, 9 control surfaces, a tilt wing, and a tilt tail. This paper describes the potential benefits and practical implications of using DOE methods for wind tunnel testing - with an emphasis on describing how it can affect model hardware, facility hardware, and software for control and data acquisition. With up to 23 independent variables (19 model and 2 tunnel) for some vehicle configurations, this recent test also provides an excellent example of using DOE methods to assess critical coupling effects in a reasonable timeframe for complex vehicle configurations. Results for an exploratory test using conventional angle of attack sweeps to assess aerodynamic hysteresis is summarized, and DOE results are presented for an exploratory test used to set the data sampling time for the overall test. DOE results are also shown for one production test characterizing normal force in the Cruise mode for the vehicle.

  7. 5. East portal of Tunnel 26, view to southwest, 135mm ...

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

    5. East portal of Tunnel 26, view to southwest, 135mm lens. Tunnel 25 (HAER CA-201) is visible in the distance. - Central Pacific Transcontinental Railroad, Tunnel No. 26, Milepost 133.29, Applegate, Placer County, CA

  8. Response of a Circular Tunnel Through Rock to a Harmonic Rayleigh Wave

    NASA Astrophysics Data System (ADS)

    Kung, Chien-Lun; Wang, Tai-Tien; Chen, Cheng-Hsun; Huang, Tsan-Hwei

    2018-02-01

    A factor that combines tunnel depth and incident wavelength has been numerically determined to dominate the seismic responses of a tunnel in rocks that are subjected to harmonic P- and S-waves. This study applies the dynamic finite element method to investigate the seismic response of shallow overburden tunnels. Seismically induced stress increments in the lining of a circular tunnel that is subjected to an incident harmonic R-wave are examined. The determination of R-wave considers the dominant frequency of acceleration history of the 1999 Chi-Chi earthquake measured near the site with damage to two case tunnels at specifically shallow depth. An analysis reveals that the normalized seismically induced axial, shear and flexural stress increments in the lining of a tunnel reach their respective peaks at the depth h/ λ = 0.15, where the ground motion that is generated by an incident of R-wave has its maximum. The tunnel radius has a stronger effect on seismically induced stress increments than does tunnel depth. A greater tunnel radius yields higher normalized seismically induced axial stress increments and lower normalized seismically induced shear and flexural stress increments. The inertia of the thin overburden layer above the tunnel impedes the propagation of the wave and affects the motion of the ground around the tunnel. With an extremely shallow overburden, such an effect can change the envelope of the normalized seismically induced stress increments from one with a symmetric four-petal pattern into one with a non-symmetric three-petal pattern. The simulated results may partially elucidate the spatial distributions of cracks that were observed in the lining of the case tunnels.

  9. Theory of electrically controlled resonant tunneling spin devices

    NASA Technical Reports Server (NTRS)

    Ting, David Z. -Y.; Cartoixa, Xavier

    2004-01-01

    We report device concepts that exploit spin-orbit coupling for creating spin polarized current sources using nonmagnetic semiconductor resonant tunneling heterostructures, without external magnetic fields. The resonant interband tunneling psin filter exploits large valence band spin-orbit interaction to provide strong spin selectivity.

  10. Armor rock habitat survey of Hampton Roads tunnel.

    DOT National Transportation Integrated Search

    1993-01-01

    The I-64 Hampton Roads Bridge-Tunnel spans the James River estuary and the lower Chesapeake Bay between the cities of Hampton and Norfolk. Two large wave-built spits, Willoughby Spit and Old Point Comfort, extend into the harbor beyond, the tunnels. ...

  11. The anatomy and histology of the bicipital tunnel of the shoulder.

    PubMed

    Taylor, Samuel A; Fabricant, Peter D; Bansal, Manjula; Khair, M Michael; McLawhorn, Alexander; DiCarlo, Edward F; Shorey, Mary; O'Brien, Stephen J

    2015-04-01

    The bicipital tunnel is the extra-articular, fibro-osseous structure that encloses the long head of the biceps tendon. Twelve cadaveric shoulder specimens underwent in situ casting of the bicipital tunnel with methyl methacrylate cement to demonstrate structural competence (n = 6) and en bloc harvest with gross and histologic evaluation (n = 6). The percentage of empty tunnel was calculated histologically by subtracting the proportion of cross-sectional area of the long head of the biceps tendon from that of the bicipital tunnel for each zone. Cement casting demonstrated that the bicipital tunnel was a closed space. Zone 1 extended from the articular margin to the distal margin of the subscapularis tendon. Zone 2 extended from the distal margin of the subscapularis tendon to the proximal margin of the pectoralis major tendon. Zone 3 was the subpectoral region. Zones 1 and 2 were both enclosed by a dense connective tissue sheath and demonstrated the presence of synovium. Zone 3 had significantly greater percentage of empty tunnel than zones 1 and 2 did (P < .01). The bicipital tunnel is a closed space with 3 distinct zones. Zones 1 and 2 have similar features, including the presence of synovium, but differ from zone 3. A significant bottleneck occurs between zone 2 and zone 3, most likely at the proximal margin of the pectoralis major tendon. The bicipital tunnel is a closed space where space-occupying lesions may produce a bicipital tunnel syndrome. Careful consideration should be given to surgical techniques that decompress both zones 1 and 2 of the bicipital tunnel. Copyright © 2015 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

  12. First principles studies of electron tunneling in proteins

    PubMed Central

    Hayashi, Tomoyuki; Stuchebrukhov, Alexei A.

    2014-01-01

    A first principles study of electronic tunneling along the chain of seven Fe/S clusters in respiratory complex I, a key enzyme in the respiratory electron transport chain, is described. The broken-symmetry states of the Fe/S metal clusters calculated at both DFT and semi-empirical ZINDO levels were utilized to examine both the extremely weak electronic couplings between Fe/S clusters and the tunneling pathways, which provide a detailed atomistic-level description of the charge transfer process in the protein. One-electron tunneling approximation was found to hold within a reasonable accuracy, with only a moderate induced polarization of the core electrons. The method is demonstrated to be able to calculate accurately the coupling matrix elements as small as 10−4 cm−1. A distinct signature of the wave properties of electrons is observed as quantum interferences of multiple tunneling pathways. PMID:25383312

  13. [Increased risk of chronic obstructive pulmonary disease among tunnel construction workers].

    PubMed

    Ulvestad, Bente; Lund, May Brit

    2003-08-28

    As tunnel workers are exposed to particles from drilling, blasting and diesel exhaust, we aimed to assess the occurrence of respiratory symptoms and lung function decline in underground construction workers and relate these findings to exposure. 212 tunnel workers and a reference group of 205 outdoor construction workers participated in a cross-sectional study. Respiratory symptoms and lung function were studied in relation to exposure. A subgroup of 29 non-smoking concrete workers who had been exposed to tunnel environment for one year, were examined by acoustic rhinometry, exhaled NO, spirometry and a questionnaire. Finally 122 tunnel workers were included in a prospective study in 1991 and re-examined in 1999. Among the tunnel workers the prevalence of chronic obstructive pulmonary disease (COPD) was 14% vs. 8% in the reference subjects. Compared to the reference subjects, the tunnel workers had a significant decrease in FEV1, related to years of exposure. Concrete workers from the tunnel site had significantly increased exhaled NO levels and nasal mucosal swelling compared to subjects who had performed similar tasks outdoors. The decrease in FEV1 was associated with cumulative exposure to respirable dust and quartz. Inhalation of construction-generated dust and gases enhances the risk of chronic obstructive pulmonary disease in tunnel workers.

  14. Phase Structure of Strong-Field Tunneling Wave Packets from Molecules.

    PubMed

    Liu, Ming-Ming; Li, Min; Wu, Chengyin; Gong, Qihuang; Staudte, André; Liu, Yunquan

    2016-04-22

    We study the phase structure of the tunneling wave packets from strong-field ionization of molecules and present a molecular quantum-trajectory Monte Carlo model to describe the laser-driven dynamics of photoelectron momentum distributions of molecules. Using our model, we reproduce and explain the alignment-dependent molecular frame photoelectron spectra of strong-field tunneling ionization of N_{2} reported by M. Meckel et al. [Nat. Phys. 10, 594 (2014)]. In addition to modeling the low-energy photoelectron angular distributions quantitatively, we extract the phase structure of strong-field molecular tunneling wave packets, shedding light on its physical origin. The initial phase of the tunneling wave packets at the tunnel exit depends on both the initial transverse momentum distribution and the molecular internuclear distance. We further show that the ionizing molecular orbital has a critical effect on the initial phase of the tunneling wave packets. The phase structure of the photoelectron wave packet is a key ingredient for modeling strong-field molecular photoelectron holography, high-harmonic generation, and molecular orbital imaging.

  15. Evaluation of TBM tunnels with respect to stability against spalling

    NASA Astrophysics Data System (ADS)

    Shaalan, Heyam; Ismail, Mohd Ashraf Mohd; Azit, Romziah

    2017-10-01

    As the depth of tunnels and underground construction increases, instability occurs in the form of rock bursting or spalling because of the induced stresses. Spalling may appear as a strong compressive stress causing crack growth behind the excavated surface and buckling of the thin rock slabs. In this paper, we describe how to reduce the rock spalling failure to increase the underground safety and the tunnel stability. Thus, a parametric study is implemented using 2-D Elasto-plastic finite elements stress analysis software to investigate the parameters that can minimize the extent and depth of the failure zone. The critical section of Pahang Selangor Raw Water Transfer Tunnel under high overburden is analyzed. The effect of the shotcrete lining thickness, tunnel size and the removal of fallouts or scaled v-notch on the failure zone depth is investigated. The results demonstrate that the shotcrete lining thickness has less influence on the failure depth, while a small tunnel diameter minimizes the failure depth. In addition, the stability of the tunnel improves by removing the loose rock mass.

  16. Efficient evaluation of atom tunneling combined with electronic structure calculations.

    PubMed

    Ásgeirsson, Vilhjálmur; Arnaldsson, Andri; Jónsson, Hannes

    2018-03-14

    Methodology for finding optimal tunneling paths and evaluating tunneling rates for atomic rearrangements is described. First, an optimal JWKB tunneling path for a system with fixed energy is obtained using a line integral extension of the nudged elastic band method. Then, a calculation of the dynamics along the path is used to determine the temperature at which it corresponds to an optimal Feynman path for thermally activated tunneling (instanton) and a harmonic approximation is used to estimate the transition rate. The method is illustrated with calculations for a modified two-dimensional Müller-Brown surface but is efficient enough to be used in combination with electronic structure calculations of the energy and atomic forces in systems containing many atoms. An example is presented where tunneling is the dominant mechanism well above room temperature as an H 3 BNH 3 molecule dissociates to form H 2 . Also, a solid-state example is presented where density functional theory calculations of H atom tunneling in a Ta crystal give close agreement with experimental measurements on hydrogen diffusion over a wide range in temperature.

  17. Wind tunnel technology for the development of future commercial aircraft

    NASA Technical Reports Server (NTRS)

    Szodruch, J.

    1986-01-01

    Requirements for new technologies in the area of civil aircraft design are mainly related to the high cost involved in the purchase of modern, fuel saving aircraft. A second important factor is the long term rise in the price of fuel. The demonstration of the benefits of new technologies, as far as these are related to aerodynamics, will,for the foreseeable future, still be based on wind tunnel measurements. Theoretical computation methods are very successfully used in design work, wing optimization, and an estimation of the Reynolds number effect. However, wind tunnel tests are still needed to verify the feasibility of the considered concepts. Along with other costs, the cost for the wind tunnel tests needed for the development of an aircraft is steadily increasing. The present investigation is concerned with the effect of numerical aerodynamics and civil aircraft technology on the development of wind tunnels. Attention is given to the requirements for the wind tunnel, investigative methods, measurement technology, models, and the relation between wind tunnel experiments and theoretical methods.

  18. Multiband corrections for the semi-classical simulation of interband tunneling in GaAs tunnel junctions

    NASA Astrophysics Data System (ADS)

    Louarn, K.; Claveau, Y.; Hapiuk, D.; Fontaine, C.; Arnoult, A.; Taliercio, T.; Licitra, C.; Piquemal, F.; Bounouh, A.; Cavassilas, N.; Almuneau, G.

    2017-09-01

    The aim of this study is to investigate the impact of multiband corrections on the current density in GaAs tunnel junctions (TJs) calculated with a refined yet simple semi-classical interband tunneling model (SCITM). The non-parabolicity of the considered bands and the spin-orbit effects are considered by using a recently revisited SCITM available in the literature. The model is confronted to experimental results from a series of molecular beam epitaxy grown GaAs TJs and to numerical results obtained with a full quantum model based on the non-equilibrium Green’s function formalism and a 6-band k.p Hamiltonian. We emphasize the importance of considering the non-parabolicity of the conduction band by two different measurements of the energy-dependent electron effective mass in N-doped GaAs. We also propose an innovative method to compute the non-uniform electric field in the TJ for the SCITM simulations, which is of prime importance for a successful operation of the model. We demonstrate that, when considering the multiband corrections and this new computation of the non-uniform electric field, the SCITM succeeds in predicting the electrical characteristics of GaAs TJs, and are also in agreement with the quantum model. Besides the fundamental study of the tunneling phenomenon in TJs, the main benefit of this SCITM is that it can be easily embedded into drift-diffusion software, which are the most widely-used simulation tools for electronic and opto-electronic devices such as multi-junction solar cells, tunnel field-effect transistors, or vertical-cavity surface-emitting lasers.

  19. Comparison of two ways of altering carpal tunnel pressure with ultrasound surface wave elastography.

    PubMed

    Cheng, Yu-Shiuan; Zhou, Boran; Kubo, Kazutoshi; An, Kai-Nan; Moran, Steven L; Amadio, Peter C; Zhang, Xiaoming; Zhao, Chunfeng

    2018-06-06

    Higher carpal tunnel pressure is related to the development of carpal tunnel syndrome. Currently, the measurement of carpal tunnel pressure is invasive and therefore, a noninvasive technique is needed. We previously demonstrated that speed of wave propagation through a tendon in the carpal tunnel measured by ultrasound elastography could be used as an indicator of carpal tunnel pressure in a cadaveric model, in which a balloon had to be inserted into the carpal tunnel to adjust the carpal tunnel pressure. However, the method for adjusting the carpal tunnel pressure in the cadaveric model is not applicable for the in vivo model. The objective of this study was to utilize a different technique to adjust carpal tunnel pressure via pressing the palm and to validate it with ultrasound surface wave elastography in a human cadaveric model. The outcome was also compared with a previous balloon insertion technique. Results showed that wave speed of intra-carpal tunnel tendon and the ratio of wave speed of intra-and outer-carpal tunnel tendons increased linearly with carpal tunnel pressure. Moreover, wave speed of intra carpal tunnel tendon via both ways of altering carpal tunnel pressure showed similar results with high correlation. Therefore, it was concluded that the technique of pressing the palm can be used to adjust carpal tunnel pressure, and pressure changes can be detected via ultrasound surface wave elastography in an ex vivo model. Future studies will utilize this technique in vivo to validate the usefulness of ultrasound surface wave elastography for measuring carpal tunnel pressure. Copyright © 2018 Elsevier Ltd. All rights reserved.

  20. 8. VIEW SOUTHWEST, INTERIOR VIEW, WIND TUNNEL 139 Naval ...

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

    8. VIEW SOUTHWEST, INTERIOR VIEW, WIND TUNNEL 139 - Naval Surface Warfare Center, Subsonic Wind Tunnel Building, Bounded by Clara Barton Parkway & McArthur Boulevard, Silver Spring, Montgomery County, MD

  1. Investigation of water droplet trajectories within the NASA icing research tunnel

    NASA Technical Reports Server (NTRS)

    Reehorst, Andrew; Ibrahim, Mounir

    1995-01-01

    Water droplet trajectories within the NASA Lewis Research Center's Icing Research Tunnel (IRT) were studied through computer analysis. Of interest was the influence of the wind tunnel contraction and wind tunnel model blockage on the water droplet trajectories. The computer analysis was carried out with a program package consisting of a three-dimensional potential panel code and a three-dimensional droplet trajectory code. The wind tunnel contraction was found to influence the droplet size distribution and liquid water content distribution across the test section from that at the inlet. The wind tunnel walls were found to have negligible influence upon the impingement of water droplets upon a wing model.

  2. In-vehicle nitrogen dioxide concentrations in road tunnels

    NASA Astrophysics Data System (ADS)

    Martin, Ashley N.; Boulter, Paul G.; Roddis, Damon; McDonough, Liza; Patterson, Michael; Rodriguez del Barco, Marina; Mattes, Andrew; Knibbs, Luke D.

    2016-11-01

    There is a lack of knowledge regarding in-vehicle concentrations of nitrogen dioxide (NO2) during transit through road tunnels in urban environments. Furthermore, previous studies have tended to involve a single vehicle and the range of in-vehicle NO2 concentrations that vehicle occupants may be exposed to is not well defined. This study describes simultaneous measurements of in-vehicle and outside-vehicle NO2 concentrations on a route through Sydney, Australia that included several major tunnels, minor tunnels and busy surface roads. Tests were conducted on nine passenger vehicles to assess how vehicle characteristics and ventilation settings affected in-vehicle NO2 concentrations and the in-vehicle-to-outside vehicle (I/O) concentration ratio. NO2 was measured directly using a cavity attenuated phase shift (CAPS) technique that gave a high temporal and spatial resolution. In the major tunnels, transit-average in-vehicle NO2 concentrations were lower than outside-vehicle concentrations for all vehicles with cabin air recirculation either on or off. However, markedly lower I/O ratios were obtained with recirculation on (0.08-0.36), suggesting that vehicle occupants can significantly lower their exposure to NO2 in tunnels by switching recirculation on. The highest mean I/O ratios for NO2 were measured in older vehicles (0.35-0.36), which is attributed to older vehicles having higher air exchange rates. The results from this study can be used to inform the design and operation of future road tunnels and modelling of personal exposure to NO2.

  3. 7. 'Tunnel No 14, Concrete Lining,' Southern Pacific Standard SingleTrack ...

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

    7. 'Tunnel No 14, Concrete Lining,' Southern Pacific Standard Single-Track Tunnel, ca. 1909. Under current numbering, this is now Tunnel 29 (HAER No. CA-205). - Central Pacific Transcontinental Railroad, Sacramento to Nevada state line, Sacramento, Sacramento County, CA

  4. The cryogenic wind tunnel for high Reynolds number testing. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Kilgore, R. A.

    1974-01-01

    Experiments performed at the NASA Langley Research Center in a cryogenic low-speed continuous-flow tunnel and in a cryogenic transonic continuous-flow pressure tunnel have demonstrated the predicted changes in Reynolds number, drive power, and fan speed with temperature, while operating with nitrogen as the test gas. The experiments have also demonstrated that cooling to cryogenic temperatures by spraying liquid nitrogen directly into the tunnel circuit is practical and that tunnel temperature can be controlled within very close limits. Whereas most types of wind tunnel could operate with advantage at cryogenic temperatures, the continuous-flow fan-driven tunnel is particularly well suited to take full advantage of operating at these temperatures. A continuous-flow fan-driven cryogenic tunnel to satisfy current requirements for test Reynolds number can be constructed and operated using existing techniques. Both capital and operating costs appear acceptable.

  5. 6. East portal of Tunnel 17, oblique view to westsouthwest, ...

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

    6. East portal of Tunnel 17, oblique view to west-southwest, 90mm lens. This view shows to advantage the stepped concrete wingwalls and fitted stone masonry coping protection flanking the portal, features typical of the Southern Pacific Common Standard tunnels of this period. - Southern Pacific Railroad Natron Cutoff, Tunnel No. 17, Milepost 408, Dorris, Siskiyou County, CA

  6. Westfacing portal of North Bergen Tunnel within Open Cut No. ...

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

    West-facing portal of North Bergen Tunnel within Open Cut No. 2 (see HAER No. NJ-137-7, South Bergen Tunnel, for Open Cut No. 2 context), looking east - Delaware, Lackawanna & Western Railroad, North Bergen Tunnel, Through Bergen Hill from Prospect Street at Ogden Avenue to John F. Kennedy Boulevard at Beacon Avenue, Jersey City, Hudson County, NJ

  7. Eastfacing portal of North Bergen Tunnel within Open Cut No. ...

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

    East-facing portal of North Bergen Tunnel within Open Cut No. 2 (see HAER No. NJ-137-7, South Bergen Tunnel, for Open Cut No. 2 context), looking west - Delaware, Lackawanna & Western Railroad, North Bergen Tunnel, Through Bergen Hill from Prospect Street at Ogden Avenue to John F. Kennedy Boulevard at Beacon Avenue, Jersey City, Hudson County, NJ

  8. 12. VIEW EAST, BUILDING 12 INTERIOR, WIND TUNNEL 157 ...

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

    12. VIEW EAST, BUILDING 12 INTERIOR, WIND TUNNEL 157 - Naval Surface Warfare Center, Transonic Wind Tunnel Building, Bounded by Clara Barton Parkway & McArthur Boulevard, Silver Spring, Montgomery County, MD

  9. 2. VIEW SOUTH OF WIND TUNNEL 157, NORTH ELEVATION ...

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

    2. VIEW SOUTH OF WIND TUNNEL 157, NORTH ELEVATION - Naval Surface Warfare Center, Transonic Wind Tunnel Building, Bounded by Clara Barton Parkway & McArthur Boulevard, Silver Spring, Montgomery County, MD

  10. Hawking radiation of Dirac particles via tunneling from a black plane

    NASA Astrophysics Data System (ADS)

    Li, Hui-Ling; Zhou, Teng-Jiao; Cai, Min

    2008-12-01

    Extending Kerner and Mann’s fermion tunneling, we investigate the Dirac particle’s tunneling radiation from a black plane in Anti-de Sitter space-time. The result shows that the tunneling probability is related to the change of Bekenstein-Hawking entropy.

  11. A Pediatric Near-Death Experience: Tunnel Variants.

    ERIC Educational Resources Information Center

    Serdahely, William J.

    1990-01-01

    Presents case study of boy who had near-death experience (NDE) due to nearly drowning when he was seven years old. Discusses case's variation of tunnel experience not before reported in either adult or pediatric NDE literature: while in the tunnel, the boy was comforted by two of his family's pets who had died prior to his accident. (Author/NB)

  12. Magnetic tunnel junction thermocouple for thermoelectric power harvesting

    NASA Astrophysics Data System (ADS)

    Böhnert, T.; Paz, E.; Ferreira, R.; Freitas, P. P.

    2018-05-01

    The thermoelectric power generated in magnetic tunnel junctions (MTJs) is determined as a function of the tunnel barrier thickness for a matched electric circuit. This study suggests that lower resistance area product and higher tunnel magnetoresistance will maximize the thermoelectric power output of the MTJ structures. Further, the thermoelectric behavior of a series of two MTJs, a MTJ thermocouple, is investigated as a function of its magnetic configurations. In an alternating magnetic configurations the thermovoltages cancel each other, while the magnetic contribution remains. A large array of MTJ thermocouples could amplify the magnetic thermovoltage signal significantly.

  13. Spin injection in n-type resonant tunneling diodes

    PubMed Central

    2012-01-01

    We have studied the polarized resolved photoluminescence of n-type GaAs/AlAs/GaAlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. Under resonant tunneling conditions, we have observed two emission lines attributed to neutral (X) and negatively charged excitons (X−). We have observed a voltage-controlled circular polarization degree from the quantum well emission for both lines, with values up to −88% at 15 T at low voltages which are ascribed to an efficient spin injection from the 2D gases formed at the accumulation layers. PMID:23098559

  14. Modeling direct interband tunneling. II. Lower-dimensional structures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pan, Andrew, E-mail: pandrew@ucla.edu; Chui, Chi On; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095

    We investigate the applicability of the two-band Hamiltonian and the widely used Kane analytical formula to interband tunneling along unconfined directions in nanostructures. Through comparisons with k·p and tight-binding calculations and quantum transport simulations, we find that the primary correction is the change in effective band gap. For both constant fields and realistic tunnel field-effect transistors, dimensionally consistent band gap scaling of the Kane formula allows analytical and numerical device simulations to approximate non-equilibrium Green's function current characteristics without arbitrary fitting. This allows efficient first-order calibration of semiclassical models for interband tunneling in nanodevices.

  15. Optical investigation of carrier tunneling in semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Emiliani, V.; Ceccherini, S.; Bogani, F.; Colocci, M.; Frova, A.; Shi, Song Stone

    1997-08-01

    The tunneling dynamics of excitons and free carriers in AlxGa1-xAs/GaAs asymmetric double quantum well and near-surface quantum well structures has been investigated by means of time-resolved optical techniques. The competing processes of carrier tunneling out of the quantum well and exciton formation and recombination inside the quantum well have been thoroughly studied in the range of the excitation densities relevant to device applications. A consistent picture capable of fully describing the carrier and exciton-tunneling mechanisms in both types of structures has been obtained and apparently contrasting results in the recent literature are clarified.

  16. Driver distraction in an unusual environment: Effects of text-messaging in tunnels.

    PubMed

    Rudin-Brown, Christina M; Young, Kristie L; Patten, Christopher; Lenné, Michael G; Ceci, Ruggero

    2013-01-01

    Text messaging while driving can be distracting and significantly increases the risk of being involved in a collision. Compared to freeway driving, driving in a tunnel environment introduces factors that may interact with driver attentional resources to exacerbate the effects of distraction on driving safety. With planning and design of the 18km Stockholm Bypass tunnel ongoing, and because of the potentially devastating consequences of crashes in long tunnels, it is critical to assess the effects of driver distraction in a tunnel environment. Twenty-four participants (25-50 years) drove in simulated highway and tunnel road environments while reading and writing text messages using their own mobile phones. As expected, compared to driving alone, text messaging was associated with decrements in driving performance and visual scanning behavior, and increases in subjective workload. Speeds were slower compared to baseline (no text-messaging) driving when participants performed the text-messaging tasks in the tunnel environment compared to the freeway, suggesting that drivers may have attempted to compensate more for the increased text-messaging-related workload when they were in the tunnel. On the other hand, increases in lane deviation associated with the most complex text-messaging task were more pronounced in the tunnel compared to on the freeway. Collectively, results imply that driver distraction in tunnels is associated with generally similar driving decrements as freeway driving; however, the potential consequences of these decrements in tunnels remain significantly more serious. Future research should attempt to elucidate the nature of any differential compensatory behavior in tunnel, compared to freeway, driving. In the meantime, drivers should be advised to refrain from text messaging, especially when driving in tunnels. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Large Swing Valve in the 10- by 10-Foot Supersonic Wind Tunnel

    NASA Image and Video Library

    1956-05-21

    A 24-foot diameter swing valve is seen in an open position inside the new 10- by 10-Foot Supersonic Wind Tunnel at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory. The 10- by 10 was the most powerful propulsion wind tunnel in the nation. After over three years of construction the tunnel was ready to conduct its first tests in early 1956. The 10- by 10-foot tunnel was part of Congress’ Unitary Plan Act which coordinated wind tunnel construction at the NACA, Air Force, industry, and universities. The 10- by 10 was the largest of the three NACA tunnels built under the act. This large swinging valve is critical to the operation of the facility. In one position the valve seals off the tunnel exhaust, making the tunnel a closed circuit, which is used for aerodynamic testing of models. In its other position, the valve acts as a seal across the tunnel and leaves the tunnel exhaust open. This arrangement is used when engines are fired. The air going through the tunnel is taken from the atmosphere and returned to the atmosphere after one pass through the tunnel. Engines up to five feet in diameter can be tested in the 10- by 10-foot test section. Air flows up to Mach 3.5 can be fed through the test section by a 250,000-horsepower axial-flow compressor fan. The incoming air must be dehumidified and cooled so that the proper conditions are present for the test. A large air dryer with 1,890 tons of activated alumina soaks up 1.5 tons of water per minute from the air flow. A cooling apparatus equivalent to 250,000 household air conditioners is used to cool the air.

  18. Smart tunnel: Docking mechanism

    NASA Technical Reports Server (NTRS)

    Schliesing, John A. (Inventor); Edenborough, Kevin L. (Inventor)

    1989-01-01

    A docking mechanism is presented for the docking of a space vehicle to a space station comprising a flexible tunnel frame structure which is deployable from the space station. The tunnel structure comprises a plurality of series connected frame sections, one end section of which is attached to the space station and the other end attached to a docking module of a configuration adapted for docking in the payload bay of the space vehicle. The docking module is provided with trunnions, adapted for latching engagement with latches installed in the vehicle payload bay and with hatch means connectable to a hatch of the crew cabin of the space vehicle. Each frame section comprises a pair of spaced ring members, interconnected by actuator-attenuator devices which are individually controllable by an automatic control means to impart relative movement of one ring member to the other in six degrees of freedom of motion. The control means includes computer logic responsive to sensor signals of range and attitude information, capture latch condition, structural loads, and actuator stroke for generating commands to the onboard flight control system and the individual actuator-attenuators to deploy the tunnel to effect a coupling with the space vehicle and space station after coupling. A tubular fluid-impervious liner, preferably fabric, is disposed through the frame sections of a size sufficient to accommodate the passage of personnel and cargo.

  19. 3. East portal of Tunnel 27, view to northeast from ...

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

    3. East portal of Tunnel 27, view to northeast from atop cut bank, 210mm lens. This view shows to good effect the original construction of the Harriman period tunnels, which were concreted fifty feet in from the portals with the balance being timber lined. In 1965 the east end of the tunnel collapsed, with the result that approximately 115 feet of the east end was 'daylighted' and the original east portal and concreted end were left in place, free-standing as seen here. - Central Pacific Transcontinental Railroad, Tunnel No. 27, Milepost 133.9, Applegate, Placer County, CA

  20. Posture and Loading in the Pathomechanics of Carpal Tunnel Syndrome: A Review.

    PubMed

    Vignais, Nicolas; Weresch, Justin; Keir, Peter J

    2016-01-01

    Carpal tunnel syndrome is a neuropathy of the median nerve at the wrist, and represents the most common peripheral neuropathy. It has long been an issue in the workplace because of healthcare costs and loss of productivity. The two main pathomechanisms of carpal tunnel syndrome include increased hydrostatic pressure within the carpal tunnel (carpal tunnel pressure) and contact stress (or impingement). As most cases of carpal tunnel syndrome in the workplace are labelled "idiopathic", a clear understanding of the physical parameters that may act as pathomechanisms is critical for its prevention. The aim of this review is to examine and quantify the influence of posture and loading factors on the increase of carpal tunnel pressure and median nerve contact stress. Forearm, wrist, and finger postures, as well as fingertip force have significant effects on carpal tunnel pressure. Contact stress on the median nerve is mainly a product of wrist posture and musculotendinous loading. Anatomical and musculoskeletal sources have been proposed to explain these effects. This critical review provides an improved understanding of pathomechanisms and etiology underlying carpal tunnel syndrome.