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Sample records for high velocity oxygen-fuel

  1. Analysis of a High Velocity Oxygen-Fuel (HVOF) thermal spray torch. Part 1, Numerical formulation

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1994-01-01

    The fluid and particle dynamics of a High Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The spray nozzle is axisymmetric with powder injection on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. Choked flow conditions occur at the exit of the aircap and a supersonic, under-expanded jet develops externally. The CFD simulation assumes three injection streams (solid metal particles with argon as a carrier gas, premixed oxygen/fuel, and air) inside the aircap and solves the combusting two-phase flow until the external spray stream decays to sonic conditions. The numerical formulation solves the mass, momentum, and energy transfer for both the gas and particle phase and strongly couples each phase. The combustion process is modeled using approximate equilibrium chemistry with dissociation of the gas with a total of nine species. Melting and re-solidification of the metal panicles is modeled as a lumped-mass system. Turbulent flow is modeled by a two equation k-{epsilon} turbulence model, including compressibility effects on turbulent dissipation. A time iterative, implicit, finite volume numerical method is used to solve the partial differential equations. A companion paper [10] presents the results of the numerical simulation and gives a detailed discussion of the gas and panicle dynamics.

  2. Analysis of a High Velocity Oxygen-Fuel (HVOF) thermal spray torch. Part 2, Computational results

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1993-12-31

    The fluid dynamics inside and outside a High Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The spray nozzle is axisymmetric with powder injected on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap choked flow conditions occur at the exit of the aircap and a supersonic, under-expanded jet develops externally. The details of the CFD simulation are given in a companion paper. This paper describes the general gas dynamic features of HVOF spraying and then gives a detailed discussion of the computational predictions of the present analysis. The gas velocity, temperature, pressure and Mach number distributions are presented for various locations inside and outside the torch. Characteristics of the metal spray particle velocity, temperature, Mach number, trajectory, and phase state (solid or liquid) are also presented and discussed. Extensive numerical flow visualization is provided to show flow features such as mixing layers, shock waves, and expansion waves.

  3. Computational fluid dynamic analysis of a High-Velocity Oxygen-Fuel (HVOF) thermal spray torch

    SciTech Connect

    Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.

    1995-09-01

    The gas dynamics of a High-Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamics (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder feed. The injection nozzle is assumed to be axisymmetric with premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. The aircap, a cronically converging nozzle, achieves choked flow conditions at the exit and a supersonic, under-expanded jet develops externally. Finite difference equations for mass, momentum, and energy conservation are solved for the gas dynamics. The combustion process is modeled using a single-step and a 12-step quasi-global finite-rate chemistry model with dissociation of the gas and a total of nine species. Turbulent flow inside the aircap and in the free-jet decay is modeled using a two-equation k-{epsilon} model. An iterative, implicit, finite volume numerical method is used to solve the gas dynamic equations inside and outside the torch . The CFD results are compared with recent experimental measurements of pressure inside the HVOF aircap. Comparisons are made for two flow rates of premixed fuel and oxygen and air cooling. This paper presents the first published comparisons of CFD predictions and experimental measurements for HVOF tbermal spraying.

  4. Effect of Operating Parameters on a Dual-Stage High Velocity Oxygen Fuel Thermal Spray System

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed N.; Shamim, Tariq

    2014-08-01

    High velocity oxygen fuel (HVOF) thermal spray systems are being used to apply coatings to prevent surface degradation. The coatings of temperature sensitive materials such as titanium and copper, which have very low melting points, cannot be applied using a single-stage HVOF system. Therefore, a dual-stage HVOF system has been introduced and modeled computationally. The dual-spray system provides an easy control of particle oxidation by introducing a mixing chamber. In addition to the materials being sprayed, the thermal spray coating quality depends to a large extent on flow behavior of reacting gases and the particle dynamics. The present study investigates the influence of various operating parameters on the performance of a dual-stage thermal spray gun. The objective is to develop a predictive understanding of various parameters. The gas flow field and the free jet are modeled by considering the conservation of mass, momentum, and energy with the turbulence and the equilibrium combustion sub models. The particle phase is decoupled from the gas phase due to very low particle volume fractions. The results demonstrate the advantage of a dual-stage system over a single-stage system especially for the deposition of temperature sensitive materials.

  5. Characteristics of MCrAlY coatings sprayed by high velocity oxygen-fuel spraying system

    SciTech Connect

    Itoh, Y.; Saitoh, M.; Tamura, M.

    2000-01-01

    High velocity oxygen-fuel (HVOF) spraying system in open air has been established for producing the coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Fe, Ni and/or Co) coatings can be applied to provide resistance against oxidation and corrosion to the hot parts of gas turbines. Also, it is well known that the thicker coating can be sprayed in comparison with any other thermal spraying systems due to improved residual stresses. However, thermal and mechanical properties of HVOF coatings have not been clarified. Especially, the characteristics of residual stress, that are the most important property from the view point of production technique, have not been made clear. In this paper, the mechanical properties of HVOF sprayed MCrAlY coatings were measured in both the case of as-sprayed and heat-treated coatings in comparison with a vacuum plasma sprayed MCrAlY coatings. It was confirmed that the mechanical properties of HVOF sprayed MCrAlY coatings could be improved by a diffusion heat treatment to equate the vacuum plasma sprayed MCrAlY coatings. Also, the residual stress characteristics were analyzed using a deflection measurement technique and a X-ray technique. The residual stress of HVOF coating was reduced by the shot-peening effect comparable to that of a plasma spray system in open air. This phenomena could be explained by the reason that the HVOF sprayed MCrAlY coating was built up by poorly melted particles.

  6. Computational fluid dynamics analysis of a wire-feed, high-velocity oxygen-fuel (HVOF) thermal spray torch

    SciTech Connect

    Lopez, A.R.; Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.

    1996-09-01

    The fluid and particle dynamics of a High-Velocity Oxygen-Fuel Thermal Spray torch are analyzed using computational and experimental techniques. Three-dimensional Computational Fluid Dynamics (CFD) results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire (DJRW) torch. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Premixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled using a single-step finite-rate chemistry model with a total of 9 gas species which includes dissociation of combustion products. A continually-fed steel wire passes through the center of the nozzle and melting occurs at a conical tip near the exit of the aircap. Wire melting is simulated computationally by injecting liquid steel particles into the flow field near the tip of the wire. Experimental particle velocity measurements during wire feed were also taken using a Laser Two-Focus (L2F) velocimeter system. Flow fields inside and outside the aircap are presented and particle velocity predictions are compared with experimental measurements outside of the aircap.

  7. Manufacturing and Properties of High-Velocity Oxygen Fuel (HVOF)-Sprayed FeVCrC Coatings

    NASA Astrophysics Data System (ADS)

    Sassatelli, Paolo; Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo

    2016-09-01

    This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from "extreme" settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV0.3, exhibit wear rates of ≈2 × 10-6 mm3/(Nm) in ball-on-disk tests against sintered Al2O3 spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments.

  8. Computational analysis of a three-dimensional High-Velocity Oxygen-Fuel (HVOF) Thermal Spray torch

    SciTech Connect

    Hassan, B.; Lopez, A.R.; Oberkampf, W.L.

    1995-07-01

    An analysis of a High-Velocity Oxygen-Fuel Thermal Spray torch is presented using computational fluid dynamics (CFD). Three-dimensional CFD results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire torch, but wire feed is not simulated. To the authors` knowledge, these are the first published 3-D results of a thermal spray device. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Argon is injected through the center of the nozzle. Pre-mixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled assuming instantaneous chemistry. A standard, two-equation, K-{var_epsilon} turbulence model is employed for the turbulent flow field. An implicit, iterative, finite volume numerical technique is used to solve the coupled conservation of mass, momentum, and energy equations for the gas in a sequential manner. Flow fields inside and outside the aircap are presented and discussed.

  9. Manufacturing and Properties of High-Velocity Oxygen Fuel (HVOF)-Sprayed FeVCrC Coatings

    NASA Astrophysics Data System (ADS)

    Sassatelli, Paolo; Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo

    2016-10-01

    This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from "extreme" settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV0.3, exhibit wear rates of ≈2 × 10-6 mm3/(Nm) in ball-on-disk tests against sintered Al2O3 spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments.

  10. Friction and wear properties of high-velocity oxygen fuel sprayed WC-17Co coating under rotational fretting conditions

    NASA Astrophysics Data System (ADS)

    Luo, Jun; Cai, Zhenbing; Mo, Jiliang; Peng, Jinfang; Zhu, Minhao

    2016-05-01

    Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.

  11. Effect of the increase in the entrance convergent section length of the gun nozzle on the high-velocity oxygen fuel and cold spray process

    NASA Astrophysics Data System (ADS)

    Sakaki, K.; Shimizu, Y.

    2001-09-01

    Nozzle geometry, which influences combustion gas dynamics and, therefore, sprayed particle behavior, is one of the most important parameters in the high-velocity oxygen-fuel (HVOF) thermal spray process. The nozzle geometry is also important in the cold spray method. The gas flows in the entrance convergent section of the nozzle exhibit a relatively higher temperature and are subsonic; thus, this region is most suitable for heating spray particles. In this study, numerical simulation and experiments investigated the effect of the entrance geometry of the gun nozzle on the HVOF process. The process changes inside the nozzle, as obtained by numerical simulation studies, were related to the coating properties. An Al2O3-40 mass% TiO2 powder was used for the experimental studies. The change in entrance convergent section length (rather than barrel part length or total length) of the gun nozzle had a significant effect on the deposition efficiency, microstructure, and hardness. The deposition efficiency and hardness increased as this geometry increased. On the other hand, the calculated and measured particle velocity showed a slight decrease. This effect on the HVOF process will also be applied to the nozzle design for the cold spray method.

  12. Ultrasonic cavitation erosion of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating in NaCl solution.

    PubMed

    Hong, Sheng; Wu, Yuping; Zhang, Jianfeng; Zheng, Yugui; Qin, Yujiao; Lin, Jinran

    2015-09-01

    The high-velocity oxygen-fuel (HVOF) spraying process was used to prepare near-nanostructured WC-10Co-4Cr coating. The cavitation erosion behavior and mechanism of the coating in 3.5 wt.% NaCl solution were analyzed in detail. The results showed that the amorphous phase and WC grain were present in the coating. The cavitation erosion resistance of the coating was about 1.27 times that of the stainless steel 1Cr18Ni9Ti under the same testing conditions. The effects of erosion time on the microstructural evolution were discussed. It was revealed that cracks initiated at the edge of pre-existing pores and propagated along the carbide-binder interface, leading to the pull-out of carbide particle and the formation of pits and craters on the surface. The main failure mechanism of the coating was erosion of the binder phases, brittle detachment of hard phases and formation of pitting corrosion products. PMID:25617967

  13. Long-term carbide development in high-velocity oxygen fuel/high-velocity air fuel Cr3C2-NiCr coatings heat treated at 900 °C

    NASA Astrophysics Data System (ADS)

    Matthews, S.; Hyland, M.; James, B.

    2004-12-01

    During the deposition of Cr3C2-NiCr coatings, compositional degradation occurs, primarily through the dissolution of the carbide phase into the matrix. Exposure at an elevated temperature leads to transformations in the compositional distribution and microstructure. While these have been investigated in short-term trials, no systematic investigations of the long-term microstructural development have been presented for high-velocity sprayed coatings. In this work, high-velocity air fuel (HVAF) and high-velocity oxygen fuel (HVOF) coatings were treated at 900 °C for up to 60 days. Rapid refinement of the supersaturated matrix phase occurred, with the degree of matrix phase alloying continuing to decrease over the following 20 to 40 days. Carbide nucleation in the HVAF coatings occurred preferentially on the retained carbide grains, while that in the HVOF coatings developed in the regions of greatest carbide dissolution. This difference resulted in a variation in carbide morphologies. Preferential horizontal growth was evident in both coatings over the first 20 to 30 days of exposure, beyond which spheroidization of the microstructure occurred. After 30 days, the carbide morphology of both coatings was comparable, tending toward an expansive structure of coalesced carbide grains. The development of the carbide phase played a significant role in the microhardness variation of these coatings with time.

  14. Application of high velocity oxygen fuel flame (HVOF) spraying to fabrication of La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Lin; Li, Cheng-Xin; Li, Chang-Jiu; Yang, Guan-Jun; Liu, Meilin

    2016-01-01

    La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) is considered a promising electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to its high ionic conductivity and stability under fuel cell operating conditions. Here we report our findings in investigating the feasibility of using a high velocity oxygen fuel flame (HVOF) spraying process for cost-effective fabrication of dense LSGM electrolyte membranes. The flame and in-flight particle behavior were simulated numerically to optimize the microstructure and phase compositions of the LSGM deposits. The measured gas leakage rate of an LSGM deposit is ∼7 × 10-7 cm4gf-1 s-1. The single cell assembled with 50-55 μm HVOF-sprayed LSGM electrolyte shows open circuit voltage (OCV) of 1.08 V at 800 °C, suggesting that the as-sprayed LSGM deposit is dense enough for direct application as SOFC electrolyte. At 800 °C, the ionic conductivity of the sprayed LSGM deposit is ∼0.04 S cm-1, indicating that the HVOF spraying is a promising process for low-temperature fabrication of dense LSGM electrolyte membranes for IT-SOFCs.

  15. High performance methanol-oxygen fuel cell with hollow fiber electrode

    NASA Technical Reports Server (NTRS)

    Lawson, Daniel D. (Inventor); Ingham, John D. (Inventor)

    1983-01-01

    A methanol/air-oxygen fuel cell including an electrode formed by open-ended ion-exchange hollow fibers having a layer of catalyst deposited on the inner surface thereof and a first current collector in contact with the catalyst layer. A second current collector external of said fibers is provided which is immersed along with the hollow fiber electrode in an aqueous electrolyte body. Upon passage of air or oxygen through the hollow fiber electrode and introduction of methanol into the aqueous electrolyte, a steady current output is obtained. Two embodiments of the fuel cell are disclosed. In the first embodiment the second metal electrode is displaced away from the hollow fiber in the electrolyte body while in the second embodiment a spiral-wrap electrode is provided about the outer surface of the hollow fiber electrode.

  16. Properties of Aluminum Deposited by a High-Velocity Oxygen-Fueled Process

    SciTech Connect

    Chow, R; Decker, T A; Gansert, R V; Gansert, D; Lee, D

    2001-06-12

    Aluminum coatings deposited by a HVOF process have been demonstrated and relevant coating properties evaluated according to two deposition parameters, the spray distance and the oxygen-to-fuel flow ratio. The coating porosity, surface roughness, and microhardness are measured. The coating properties are fairly insensitive to spray distance, the distance between the nozzle and the workpiece, and fuel ratios, the oxygen-to-fuel flow. Increasing the fuel content does appear to improve the process productivity in terms of surface roughness. Minimization of nozzle loading is discussed.

  17. High Velocity Gas Gun

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  18. Health effects of oxygenated fuels.

    PubMed Central

    Costantini, M G

    1993-01-01

    The use of oxygenated fuels is anticipated to increase over the next decades. This paper reviews the toxicological and exposure information for methyl tertiary-butyl ether (MTBE), a fuel additive, and methanol, a replacement fuel, and discusses the possible health consequences of exposure of the general public to these compounds. For MTBE, the health effects information available is derived almost exclusively from rodent studies, and the exposure data are limited to a few measurements at some service stations. Based on these data, it appears unlikely that the normal population is at high risk of exposure to MTBE vapor. However, in the absence of health and pharmacokinetic data in humans or in nonhuman primates, this conclusion is not strongly supported. Similarly, there are a number of uncertainties to take into consideration in estimating human risk from the use of methanol as a fuel. Although methanol may be toxic to humans at concentrations that overwhelm certain enzymes involved in methanol metabolism, the data available provide little evidence to indicate that exposure to methanol vapors from the use of methanol as a motor vehicle fuel will result in adverse health effects. The uncertainties in this conclusion are based on the lack of information on dose-response relationship at reasonable, projected exposure levels and of studies examining end points of concern in sensitive species. In developing a quantitative risk assessment, more needs to be known about health effects in primates or humans and the range of exposure expected for the general public for both compounds. PMID:8020439

  19. High velocity acoustics

    NASA Astrophysics Data System (ADS)

    Legendre, R.

    1992-09-01

    Different types of aerodynamically generated noise of practical interest are examined using a novel, physically based, approach. A simple source model for turbulence noise is proposed. The prediction for turbulent mixing layer noise, produced by this model based on a simple monopole-type source mechanism, is that the radiated sound power varies as the eighth power of the relative velocity. The model is too simple to allow calculations to be carried further to the extent of determining the radiated sound power level, so that an empirical factor must still be considered, as in the case of Lighthill's formula.

  20. The characteristics of alumina scales formed on HVOF-sprayed MCrAlY coatings[High Velocity Oxygen Fuel

    SciTech Connect

    Toma, D.; Brandl, W.; Koester, U.

    2000-02-01

    HVOF MCrAlY (M = Ni, Co) coatings were isothermally oxidized in synthetic air between 850 and 1050 C for times up to 167 hr. During thermal spraying, aluminum and yttrium oxidized to form a fine oxide dispersion. The HVOF MCrAlY coatings exhibited a microstructure similar to ODS alloys. The fine dispersion consisted of Al{sub 2}O{sub 3} and aluminum-yttrium oxides. The oxidation experiments showed that the oxidation rate of HVOF coatings was two times slower than the oxidation rate of VPS MCrAlY coatings. The oxidation mechanism changed mainly in the transient-stage (no metastable modification of Al{sub 2}O{sub 3} formed) and it was assumed that the oxide dispersion hindered diffusion of various elements from the bulk material during oxidation. The formation of the fine oxide dispersion also influenced the adherence of the oxide scale. The microstructures of the transient oxide scales were examined by X-ray diffraction (XRD) scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

  1. The velocity distribution of cometary hydrogen - Evidence for high velocities?

    NASA Technical Reports Server (NTRS)

    Brown, Michael E.; Spinrad, Hyron

    1993-01-01

    The Hamilton Echelle spectrograph on the 3-m Shane telescope at Lick Observatory was used to obtain high-velocity and spatial resolution 2D spectra of H-alpha 6563-A emission in Comets Austin and Levy. The presence of the components expected from water dissociation and collisional thermalization in the inner coma is confirmed by the hydrogen velocity distribution. In Comet Austin, the potential high-velocity hydrogen includes velocities of up to about 40 km/s and is spatially symmetric with respect to the nucleus. In Comet Levy, the high-velocity hydrogen reaches velocities of up to 50 km/s and is situated exclusively on the sunward side of the nucleus. The two distinct signatures of high-velocity hydrogen imply two distinct sources.

  2. Dust in High Velocity Clouds

    NASA Astrophysics Data System (ADS)

    Wakker, B. P.

    The facilities available in Groningen to produce IRAS maps were used to make comparatively high-quality maps of two fields where a high-velocity cloud (HVC) is observed in the 21-cm line. The HVC's are not discernable in these maps although one would expect to see them if the relation between 100 micron emission and H I column density found by Boulanger, Baud & van Albada (1985) is used. The implications of this non-detection are discussed in this contribution.

  3. High velocity impact experiment (HVIE)

    SciTech Connect

    Toor, A.; Donich, T.; Carter, P.

    1998-02-01

    The HVIE space project was conceived as a way to measure the absolute EOS for approximately 10 materials at pressures up to {approximately}30 Mb with order-of-magnitude higher accuracy than obtainable in any comparable experiment conducted on earth. The experiment configuration is such that each of the 10 materials interacts with all of the others thereby producing one-hundred independent, simultaneous EOS experiments The materials will be selected to provide critical information to weapons designers, National Ignition Facility target designers and planetary and geophysical scientists. In addition, HVIE will provide important scientific information to other communities, including the Ballistic Missile Defense Organization and the lethality and vulnerability community. The basic HVIE concept is to place two probes in counter rotating, highly elliptical orbits and collide them at high velocity (20 km/s) at 100 km altitude above the earth. The low altitude of the experiment will provide quick debris strip-out of orbit due to atmospheric drag. The preliminary conceptual evaluation of the HVIE has found no show stoppers. The design has been very easy to keep within the lift capabilities of commonly available rides to low earth orbit including the space shuttle. The cost of approximately 69 million dollars for 100 EOS experiment that will yield the much needed high accuracy, absolute measurement data is a bargain!

  4. High velocity pulsed wire-arc spray

    NASA Technical Reports Server (NTRS)

    Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor); Kincaid, Russell W. (Inventor)

    1999-01-01

    Wire arc spraying using repetitively pulsed, high temperature gas jets, usually referred to as plasma jets, and generated by capillary discharges, substantially increases the velocity of atomized and entrained molten droplets. The quality of coatings produced is improved by increasing the velocity with which coating particles impact the coated surface. The effectiveness of wire-arc spraying is improved by replacing the usual atomizing air stream with a rapidly pulsed high velocity plasma jet. Pulsed power provides higher coating particle velocities leading to improved coatings. 50 micron aluminum droplets with velocities of 1500 m/s are produced. Pulsed plasma jet spraying provides the means to coat the insides of pipes, tubes, and engine block cylinders with very high velocity droplet impact.

  5. High velocity gas in external galaxies

    NASA Technical Reports Server (NTRS)

    Kamphuis, J.; Vanderhulst, J. M.; Sancisi, R.

    1990-01-01

    Two nearby, nearly face-on spiral galaxies, M 101 and NGC 6946, observed in the HI with the Westerbork Synthesis Radio Telescope (WSRT) as part of a program to search for high velocity gas in other galaxies, are used to illustrate the range of properties of high velocity gas in other galaxies found thusfar.

  6. Microstructural and Tribological Investigation of High-Velocity Suspension Flame Sprayed (HVSFS) Al2O3 Coatings

    NASA Astrophysics Data System (ADS)

    Bolelli, Giovanni; Rauch, Johannes; Cannillo, Valeria; Killinger, Andreas; Lusvarghi, Luca; Gadow, Rainer

    2009-03-01

    Al2O3 coatings were manufactured by the high-velocity suspension flame spraying (HVSFS) technique using a nanopowder suspension. Their structural and microstructural characteristics, micromechanical behavior, and tribological properties were studied and compared to conventional atmospheric plasma sprayed and high-velocity oxygen-fuel-sprayed Al2O3 coatings manufactured using commercially available feedstock. The HVSFS process enables near full melting of the nanopowder particles, resulting in very small and well flattened lamellae (thickness range 100 nm to 1 μm), almost free of transverse microcracking, with very few unmelted inclusions. Thus, porosity is much lower and pores are smaller than in conventional coatings. Moreover, few interlamellar or intralamellar cracks exist, resulting in reduced pore interconnectivity (evaluated by electrochemical impedance spectroscopy). Such strong interlamellar cohesion favors much better dry sliding wear resistance at room temperature and at 400 °C.

  7. 29 CFR 1910.253 - Oxygen-fuel gas welding and cutting.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) high having a fire-resistance rating of at least one-half hour. (iv) Where a liquid oxygen system is to... 29 Labor 5 2012-07-01 2012-07-01 false Oxygen-fuel gas welding and cutting. 1910.253 Section 1910..., DEPARTMENT OF LABOR OCCUPATIONAL SAFETY AND HEALTH STANDARDS Welding, Cutting and Brazing § 1910.253...

  8. 29 CFR 1910.253 - Oxygen-fuel gas welding and cutting.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) high having a fire-resistance rating of at least one-half hour. (iv) Where a liquid oxygen system is to... 29 Labor 5 2011-07-01 2011-07-01 false Oxygen-fuel gas welding and cutting. 1910.253 Section 1910..., DEPARTMENT OF LABOR OCCUPATIONAL SAFETY AND HEALTH STANDARDS Welding, Cutting and Brazing § 1910.253...

  9. Instrumented impact testing at high velocities

    SciTech Connect

    Delfosse, D.; Pageau, G.; Bennett, R.; Poursartip, A. Defence Research Establishment Valcartier, Courcelette )

    1993-01-01

    Impact loading of carbon fiber-reinforced plastic (CFRP) aircraft parts is a major concern. Birds or hailstones striking an aircraft generally have a low mass and a high velocity, whereas typically instrumented impact experiments are performed with a high mass and a low velocity. Our aim has been to build an instrumented impact facility with a low-mass projectile capable of simulating these impact events, since there is evidence that a low-velocity impact will not always result in the same amount or even type of damage as a high-velocity impact. This paper provides a detailed description of the instrumented low-mass impact facility at The University of British Columbia (UBC). A gas gun is used to accelerate the instrumented projectile to impact velocities as high as 50 m/s, corresponding to an energy level of 350 J. The contact force during the impact event is measured by an incorporated load cell. The necessary mathematical operations to determine the real load-displacement curves are outlined, and the results of some impact events at different velocities are shown. 23 refs.

  10. High velocity formability and factors affecting it

    NASA Astrophysics Data System (ADS)

    Dehra, Mala Seth

    High velocity forming methods successfully address problems faced in conventional forming techniques. They can be effectively used for forming metals with low formability like aluminum alloys and high strength steel. They can be instrumental is manufacturing of lighter vehicles with higher fuel efficiency. Electromagnetic forming (EMF) is an HVF method that is gaining wide acceptance due to its advantages and scope for commercialization. A number of experimental studies were carried out with EMF with the main goal of exploring fundamentals about material formability at high velocities, which can be used to establish practical design guidelines and to make models of high velocity formability. Thus the main factors that influence high velocity formability-inertia/size effects; changes in constitutive behavior; impact; and dynamic failure modes, were studied mainly with experiments. The role of changes in constitutive behavior in improving formability was studied from existing studies and new theoretical studies involving High velocity Forming Limit Diagram (FLD) and through solving an inverse problem of ring expansion. Tube free-expansion experiments were carried out to demonstrate enhanced metal formability even in the absence of die impact. To further establish the significance of inertia, electromagnetic ring free-expansion experiments with rings of different aspect ratios were carried out. A higher aspect ratio sample had better formability in terms of uniform and total elongation and also had fewer necks than a low aspect ratio (more slender) ring at the same velocity. The results clearly demonstrated the influence of sample aspect ratio (dimensions) and hence inertia on high velocity formability. Die impact experiments were carried out with tubes and rings to show the beneficial influence of die arrest of a moving sample. It was revealed that die impact in an appropriate range of velocities can significantly suppress failure and reduce the number of tears and

  11. Internal Detonation Velocity Measurements Inside High Explosives

    SciTech Connect

    Benterou, J; Bennett, C V; Cole, G; Hare, D E; May, C; Udd, E

    2009-01-16

    In order to fully calibrate hydrocodes and dynamic chemistry burn models, initiation models and detonation models of high explosives, the ability to continuously measure the detonation velocity within an explosive is required. Progress on an embedded velocity diagnostic using a 125 micron diameter optical fiber containing a chirped fiber Bragg grating is reported. As the chirped fiber Bragg grating is consumed by the moving detonation wave, the physical length of the unconsumed Bragg grating is monitored with a fast InGaAs photodiode. Experimental details of the associated equipment and data in the form of continuous detonation velocity records within PBX-9502 are presented. This small diameter fiber sensor has the potential to measure internal detonation velocities on the order of 10 mm/{micro}sec along path lengths tens of millimeters long.

  12. Thermally regenerative hydrogen/oxygen fuel cell power cycles

    NASA Technical Reports Server (NTRS)

    Morehouse, J. H.

    1986-01-01

    Two innovative thermodynamic power cycles are analytically examined for future engineering feasibility. The power cycles use a hydrogen-oxygen fuel cell for electrical energy production and use the thermal dissociation of water for regeneration of the hydrogen and oxygen. The TDS (thermal dissociation system) uses a thermal energy input at over 2000 K to thermally dissociate the water. The other cycle, the HTE (high temperature electrolyzer) system, dissociates the water using an electrolyzer operating at high temperature (1300 K) which receives its electrical energy from the fuel cell. The primary advantages of these cycles is that they are basically a no moving parts system, thus having the potential for long life and high reliability, and they have the potential for high thermal efficiency. Both cycles are shown to be classical heat engines with ideal efficiency close to Carnot cycle efficiency. The feasibility of constructing actual cycles is investigated by examining process irreversibilities and device efficiencies for the two types of cycles. The results show that while the processes and devices of the 2000 K TDS exceed current technology limits, the high temperature electrolyzer system appears to be a state-of-the-art technology development. The requirements for very high electrolyzer and fuel cell efficiencies are seen as determining the feasbility of the HTE system, and these high efficiency devices are currently being developed. It is concluded that a proof-of-concept HTE system experiment can and should be conducted.

  13. High Resolution Velocity Structure in Eastern Turkey

    SciTech Connect

    Pasyanos, M; Gok, R; Zor, E; Walter, W

    2004-09-03

    We investigate the crustal and upper mantle structure of eastern Turkey where the Anatolian, Arabian and Eurasian Plates meet and form a complex tectonic structure. The Bitlis suture is a continental collision zone between the Anatolian plateau and the Arabian plate. Broadband data available through the Eastern Turkey Seismic Experiment (ETSE) provided a unique opportunity for studying the high resolution velocity structure. Zor et al. found an average 46 km thick crust in Anatolian plateau using six-layered grid search inversion of the ETSE receiver functions. Receiver functions are sensitive to the velocity contrast of interfaces and the relative travel time of converted and reverberated waves between those interfaces. The interpretation of receiver function alone with many-layered parameterization may result in an apparent depth-velocity tradeoff. In order to improve previous velocity model, we employed the joint inversion method with many layered parameterization of Julia et al. (2000) to the ETSE receiver functions. In this technique, the receiver function and surface-wave observations are combined into a single algebraic equation and each data set is weighted by an estimate of the uncertainty in the observations. We consider azimuthal changes of receiver functions and have stacked them into different groups. We calculated the receiver functions using iterative time-domain deconvolution technique and surface wave group velocity dispersion curves between 10-100 sec. We are making surface wave dispersion measurements at the ETSE stations and have incorporated them into a regional group velocity model. Preliminary results indicate a strong trend in the long period group velocity in the northeast. This indicates slow upper mantle velocities in the region consistent with Pn, Sn and receiver function results. We started with both the 1-D model that is obtained with the 12 tones dam explosion shot data recorded by ETSE network and the existing receiver function

  14. Consideration of wear rates at high velocity

    NASA Astrophysics Data System (ADS)

    Hale, Chad S.

    The development of the research presented here is one in which high velocity relative sliding motion between two bodies in contact has been considered. Overall, the wear environment is truly three-dimensional. The attempt to characterize three-dimensional wear was not economically feasible because it must be analyzed at the micro-mechanical level to get results. Thus, an engineering approximation was carried out. This approximation was based on a metallographic study identifying the need to include viscoplasticity constitutive material models, coefficient of friction, relationships between the normal load and velocity, and the need to understand wave propagation. A sled test run at the Holloman High Speed Test Track (HHSTT) was considered for the determination of high velocity wear rates. In order to adequately characterize high velocity wear, it was necessary to formulate a numerical model that contained all of the physical events present. The experimental results of a VascoMax 300 maraging steel slipper sliding on an AISI 1080 steel rail during a January 2008 sled test mission were analyzed. During this rocket sled test, the slipper traveled 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s. This type of environment was never considered previously in terms of wear evaluation. Each of the features of the metallography were obtained through micro-mechanical experimental techniques. The byproduct of this analysis is that it is now possible to formulate a model that contains viscoplasticity, asperity collisions, temperature and frictional features. Based on the observations of the metallographic analysis, these necessary features have been included in the numerical model, which makes use of a time-dynamic program which follows the movement of a slipper during its experimental test run. The resulting velocity and pressure functions of time have been implemented in the explicit finite element code, ABAQUS. Two-dimensional, plane strain models

  15. High precision radial velocities with GIANO spectra

    NASA Astrophysics Data System (ADS)

    Carleo, I.; Sanna, N.; Gratton, R.; Benatti, S.; Bonavita, M.; Oliva, E.; Origlia, L.; Desidera, S.; Claudi, R.; Sissa, E.

    2016-06-01

    Radial velocities (RV) measured from near-infrared (NIR) spectra are a potentially excellent tool to search for extrasolar planets around cool or active stars. High resolution infrared (IR) spectrographs now available are reaching the high precision of visible instruments, with a constant improvement over time. GIANO is an infrared echelle spectrograph at the Telescopio Nazionale Galileo (TNG) and it is a powerful tool to provide high resolution spectra for accurate RV measurements of exoplanets and for chemical and dynamical studies of stellar or extragalactic objects. No other high spectral resolution IR instrument has GIANO's capability to cover the entire NIR wavelength range (0.95-2.45 μm) in a single exposure. In this paper we describe the ensemble of procedures that we have developed to measure high precision RVs on GIANO spectra acquired during the Science Verification (SV) run, using the telluric lines as wavelength reference. We used the Cross Correlation Function (CCF) method to determine the velocity for both the star and the telluric lines. For this purpose, we constructed two suitable digital masks that include about 2000 stellar lines, and a similar number of telluric lines. The method is applied to various targets with different spectral type, from K2V to M8 stars. We reached different precisions mainly depending on the H-magnitudes: for H ˜ 5 we obtain an rms scatter of ˜ 10 m s-1, while for H ˜ 9 the standard deviation increases to ˜ 50 ÷ 80 m s-1. The corresponding theoretical error expectations are ˜ 4 m s-1 and 30 m s-1, respectively. Finally we provide the RVs measured with our procedure for the targets observed during GIANO Science Verification.

  16. High velocity clouds in nearby disk galaxies

    NASA Technical Reports Server (NTRS)

    Schulman, Eric; Bregman, Joel N.; Roberts, Morton S.; Brinks, Elias

    1993-01-01

    Clouds of neutral hydrogen in our galaxy with the absolute value of v greater than 100 km/s cover approximately 10 percent of the sky to a limiting column density of 1 x 10(exp 18) cm(exp -2). These high velocity clouds (HVCs) may dominate the kinetic energy of neutral hydrogen in non-circular motion, and are an important though poorly understood component of galactic gas. It has been suggested that the HVCs can be reproduced by a combination of three phenomena: a galactic fountain driven by disk supernovae which would account for most of the HVCs, material tidally torn from the Magellanic Clouds, and an outer arm complex which is associated with the large scale structure of the warped galactic disk. We sought to detect HVCs in external galaxies in order to test the galactic fountain model.

  17. Quench propagation velocity for highly stabilized conductors

    SciTech Connect

    Mints, R.G. |; Ogitsu, T. |; Devred, A.

    1995-05-01

    Quench propagation velocity in conductors having a large amount of stabilizer outside the multifilamentary area is considered. It is shown that the current redistribution process between the multifilamentary area and the stabilizer can strongly effect the quench propagation. A criterion is derived determining the conditions under which the current redistribution process becomes significant, and a model of effective stabilizer area is suggested to describe its influence on the quench propagation velocity. As an illustration, the model is applied to calculate the adiabatic quench propagation velocity for a conductor geometry with a multifilamentary area embedded inside the stabilizer.

  18. Holographic photography of high velocity particles

    NASA Technical Reports Server (NTRS)

    Dyes, W. A.; Mc Cabe, B. J.; Ward, J. H.

    1970-01-01

    Fourier transform hologram camera increases the velocity range for holography by a factor of 10 to 1000. Two different optical systems, using a triangular arrangement of beam splitters and a mirror to illuminate the object from two directions, are investigated.

  19. On optical studies of high-velocity clouds

    NASA Technical Reports Server (NTRS)

    York, D. G.; Burks, G. S.; Gibney, T. B.

    1986-01-01

    Lists of distant objects that can be used to study physical conditions in, and distances of, 21 cm (Oort) high-velocity clouds are presented. Recent published observations are used to compile positions, velocities, and distances of the clouds.

  20. Organic carbonyl compounds in Albuquerque, New Mexico, air: A preliminary study of the effects of oxygenated fuel use

    SciTech Connect

    Popp, C.J.; Zhang, Lin; Gaffney, J.S.

    1993-06-01

    A suite of inorganic and organic species were analyzed for four 2--4 day time periods over a year in Albuquerque, New Mexico to determine baseline conditions for organic pollutants under the current air pollution control parameters. Concentrations of low molecular weight carbonyl compounds were relatively high compared with areas such as Los Angeles. Formio acid concentrations in air samples were significant even in winter. In addition, ratios of peroxypropionyl nitrate to peroxyacyetyl nitrate are higher than expected and may be related to the use of oxygenated fuels which are used to mitigate CO concentrations. The number of CO violations in Albuquerque has decreased steadily since 1982 and the downward trend has continued since 1989 when oxygenated fuel use was mandated. It is, therefore, difficult to correlate the drop in CO violations directly to the use of oxygenated fuels when such factors as fleet turnover, woodburning controls, emissions testing and meteorological conditions also may be playing significant roles. More detailed studies are needed to determine the specific relationship between the use of oxygenated fuels and the air quality in Albuquerque, New Mexico and similar urban areas in the western United States.

  1. High and low velocity detonation in a highly insensitive explosive

    NASA Astrophysics Data System (ADS)

    Sandusky, H. W.; Hayden, H. F.

    2014-05-01

    Low-velocity detonation (LVD) in a solid explosive from input shocks below the threshold for high-velocity detonation (HVD) had been previously reported for PBXN-109 in two gap tests with sample diameters of 36.5 and 73.0 mm. Similar phenomenon has now been observed for the highly insensitive PBXIH-140, whose critical diameter of ~100 mm required an even larger gap test with a sample diameter of 178 mm. When just exceeding the critical gap for HVD, LVD propagated at similar velocities as in PBXN-109 and would punch clean holes in a witness plate like HVD. For somewhat greater gaps, there was enough shock reaction to drive LVD at constant but reduced velocities as the input shock decreased to ~ ½ of critical. With a different formulation now exhibiting LVD, it may be more prevalent than previously realized. It is speculated to occur in various confinements when small percentages of easily detonable ingredients fail to initiate the remainder of less shock sensitive ingredients.

  2. Detailed chemical kinetic modeling of diesel combustion with oxygenated fuels

    SciTech Connect

    Pitz, W J; Curran, H J; Fisher, E; Glaude, P A; Marinov, N M; Westbrook, C K

    1999-10-28

    The influence of oxygenated hydrocarbons as additives to diesel fuels on ignition, NOx emissions and soot production has been examined using a detailed chemical kinetic reaction mechanism. N-heptane was used as a representative diesel fuel, and methanol, ethanol, dimethyl ether and dimethoxymethane were used as oxygenated fuel additives. It was found that addition of oxygenated hydrocarbons reduced NOx levels and reduced the production of soot precursors. When the overall oxygen content in the fuel reached approximately 25% by mass, production of soot precursors fell effectively to zero, in agreement with experimental studies. The kinetic factors responsible for these observations are discussed.

  3. High-velocity tails on the velocity distribution of solar wind ions

    SciTech Connect

    Ogilvie, K.W. ); Geiss, J. ); Gloeckler, G. ); Berdichevsky, D. ); Wilken, B. )

    1993-03-01

    Recent observations of the solar wind using the SWICS instrument on the Ulysses spacecraft have shown the presence of high-velocity [open quotes]tails[close quotes] on the velocity distribution of protons. Similar features have also been observed on the velocity distributions of helium and oxygen ions. Of the order of 1% of the solar wind density is involved in these tails, which are approximately exponential in shape and persist to V = V[sub B] + 10V[sub th] or beyond, where V[sub B] is the bulk velocity and V[sub th] the thermal velocity of the solar wind. This paper contains a preliminary description of the phenomenon. It is clear that it is ultimately connected with the passage of interplanetary shocks past the spacecraft and that particle acceleration at oblique shocks is involved. 21 refs., 6 figs., 2 tabs.

  4. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 5 2011-10-01 2011-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  5. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 5 2013-10-01 2013-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  6. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  7. Cryogenic Testing of High-Velocity Spoke Cavities

    SciTech Connect

    Hopper, Christopher S.; Delayen, Jean R.; Park, HyeKyoung

    2014-12-01

    Spoke-loaded cavities are being investigated for the high-velocity regime. The relative compactness at low-frequency makes them attractive for applications requiring, or benefiting from, 4 K operation. Additionally, the large velocity acceptance makes them good candidates for the acceleration of high-velocity protons and ions. Here we present the results of cryogenic testing of a 325 MHz, β0= 0.82 single-spoke cavity and a 500 MHz, β0 = 1 double-spoke cavity.

  8. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 5 2014-10-01 2014-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  9. 46 CFR 153.353 - High velocity vents.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 5 2012-10-01 2012-10-01 false High velocity vents. 153.353 Section 153.353 Shipping... Systems § 153.353 High velocity vents. The discharge point of a B/3 or 4m venting system must be located..., unimpeded jet; (b) The jet has a minimum exit velocity of 30 m/sec (approx. 98.4 ft/sec); and (c) The...

  10. Implications of high-velocity interstellar H I absorption features

    NASA Technical Reports Server (NTRS)

    Cowie, L.; York, D. G.; Laurent, C.; Vidal-Madjar, A.

    1979-01-01

    Contributions to the interstellar H I column density at high velocities from immediate postshock gas and from the cooling gas behind a shock are compared. The detection of high-velocity H I in L-epsilon and L-delta for Iota Ori is reported and interpreted as cooling gas behind a shock of 100 km/s velocity. The immediate postshock gas should be observable for shock velocities greater than 200 km/s and permits direct determination of the velocities of adiabatic shocks in the interstellar medium. It is pointed out that interstellar L-alpha and L-beta lines may not have purely Lorentzian profiles if high-velocity H I is a widespread phenomenon.

  11. Punch valve development testing: Low and high velocity test results

    SciTech Connect

    Replogle, W.C.; Brandon, S.L.

    1996-09-01

    This is a report on the use of quasi-static tests to predict fundamental parameters for punch valve development. This report summarizes the results from low and high velocity tests performed with 0.63 and 0.38 cm diameter plungers, 5 cm long penetrating aluminium and composite targets. The low velocity tests, 0.025 m/s, were performed to understand the effects and interactions of plunger diameter plunger tip shape, target material, and target support on penetration energy and plunger functionality. High velocity tests, 75 m/s, were compared to low velocity results.

  12. Application of a velocity interferometer to high-speed phenomena

    NASA Astrophysics Data System (ADS)

    Prinse, Wim C.; Cheng, Lun K.; Verbeek, H. J.; Bruinsma, Anastasius J.; v. d. Steen, A. C.

    1997-05-01

    We have developed a Fabry-Perot Velocity Interferometer System (F-PVIS) to measure the velocity of materials, moving with very high speeds. The F-PVIS has e.g. been applied to measure the velocity of a flyer launched by an electric gun. This gun is capable of accelerating thin plastic flyers to very high velocities (up to 8 km/s). The velocity measuring system consists of a one Watt laser, a Fabry-Perot etalon with lenses, a rotating-mirror streak camera and fiber optics to optically connect the laser and the F-P etalon to the object to be measured. The total system very efficiently handles the available light, and is able to measure velocities in the range of 100 m/s to several km/s. Currently we are able to perform two kinds of velocity measurements: (1) The evolution of the velocity of the flyer during the acceleration process. This kind of measurement is performed to calibrate the velocity of the flyer as a function of the voltage on the capacitor bank of the electric gun and as a function of the thickness, diameter and specific mass of the flyer. (2) The time resolved particle velocity at the interface of a sample, subjected to a shock wave, and a transparent material like PMMA or quartz. From the interface velocity the pressure in the sample can be determined, both for inert, solid materials and for detonating substances. With a minor modification in the above mentioned set-up we can also measure the particle velocity in a ceramic powder. Recently we also succeeded in measuring the particle velocity of the tip of a multimode quartz fiber, inserted into an explosive sample. Interpretation of this measurement is still a problem.

  13. The sound velocity measurement in diacylglycerol oil under high pressure

    NASA Astrophysics Data System (ADS)

    Rostocki, A. J.; Malanowski, A.; Tarakowski, R.; Szlachta, K.; Kiełczyński, P.; Szalewski, M.; Balcerzak, A.; Ptasznik, S.

    2013-03-01

    In this article, the influence of high pressure on sound velocity at 293 K has been presented. The investigated diacylglycerol oil (DAG - [D82T18]AG) was composed of 82% DAGs and 18% triacylglycerols. The variation of sound velocity with hydrostatic pressure for DAG was evaluated up to 400 MPa. The phase transformation in DAG has been observed as a discontinuity of the dependence of sound velocity on pressure. The sound velocity during the phase transition has shown distinct increment. Also the volume changes have been measured. It has shown the rapid drop of the volume at the phase transformation pressure due to the possible crystallization of DAG oil.

  14. Dynamic Strengthening During High Velocity Shear Experiments with Siliceous Rocks

    NASA Astrophysics Data System (ADS)

    Liao, Z.; Chang, J. C.; Boneh, Y.; Chen, X.; Reches, Z.

    2011-12-01

    It is generally accepted that dynamic-weakening is essential for earthquake instability, and many experimental works have documented this weakening. Recent observations revealed also opposite trends of dynamic-strengthening in experiments (Reches & Lockner, 2010). We present here our experimental results of this dynamic-strengthening and discuss possible implications to earthquake behavior. We ran hundreds of experiments on experimental faults made of siliceous rock including granite, syenite, diorite, and quartzite. The experimental fault is comprised of two solid cylindrical blocks with a raised-ring contact of 7 cm diameter and 1 cm width. We recognized general, three regimes of strength-velocity relations: (I) Dynamic weakening (drop of 20-60% of static strength) as slip velocity increased from ~0.0003 m/s (lowest experimental velocity) to a critical velocity, Vc=0.008-0.16 m/s; (II) Abrupt transition to dynamic strengthening regime during which the fault strength almost regains its static strength; and (III) Quasi-constant strength with further possible drops as velocity approaches ~1 m/s. The critical velocity depends on the sample lithology: Vc is ~0.06 m/s for granite, ~0.008 m/s for syenite, ~0.01 m/s for diorite, and ~0.16 m/s for quartzite. The strengthening stage is associated with temperature increase, wear-rate increase, and the occurrence of intense, high frequency stick-slip events (Reches & Lockner, 2010). Sammis et al., (this meeting) attributed this strengthening to dehydration of the thin water layer that covers the gouge particles as the temperature increases. On the other hand, we note that tens of experiments with dolomite samples (non-siliceous), which were deformed under similar conditions, did not exhibit the velocity strengthening (unpublished). Based on the analyses by Andrews (2004, 2005), we speculate that velocity strengthening may bound the slip velocity. The numerical models of Andrews show that the slip velocity along a slip

  15. High Velocity Absorption during Eta Car B's Periastron Passage

    NASA Technical Reports Server (NTRS)

    Nielsen, Krister E.; Groh, J. H.; Hillier, J.; Gull, Theodore R.; Owocki, S. P.; Okazaki, A. T.; Damineli, A.; Teodoro, M.; Weigelt, G.; Hartman, H.

    2010-01-01

    Eta Car is one of the most luminous massive stars in the Galaxy, with repeated eruptions with a 5.5 year periodicity. These events are caused by the periastron passage of a massive companion in an eccentric orbit. We report the VLT/CRIRES detection of a strong high-velocity, (<1900 km/s) , broad absorption wing in He I at 10833 A during the 2009.0 periastron passage. Previous observations during the 2003.5 event have shown evidence of such high-velocity absorption in the He I 10833 transition, allowing us to conclude that the high-velocity gas is crossing the line-of-sight toward Eta Car over a time period of approximately 2 months. Our analysis of HST/STlS archival data with observations of high velocity absorption in the ultraviolet Si IV and C IV resonance lines, confirm the presence of a high-velocity material during the spectroscopic low state. The observations provide direct detection of high-velocity material flowing from the wind-wind collision zone around the binary system, and we discuss the implications of the presence of high-velocity gas in Eta Car during periastron

  16. Superconducting spoke cavities for high-velocity applications

    SciTech Connect

    Hopper, Christopher S.; Delayen, Jean R.

    2013-10-01

    To date, superconducting spoke cavities have been designed, developed, and tested for particle velocities up to {beta}{sub 0}~0.6, but there is a growing interest in possible applications of multispoke cavities for high-velocity applications. We have explored the design parameter space for low-frequency, high-velocity, double-spoke superconducting cavities in order to determine how each design parameter affects the electromagnetic properties, in particular the surface electromagnetic fields and the shunt impedance. We present detailed design for cavities operating at 325 and 352 MHz and optimized for {beta}{sub 0}~=0.82 and 1.

  17. Shockwave determination of the shear velocity at very high pressures.

    NASA Technical Reports Server (NTRS)

    Anderson, O. L.

    1972-01-01

    Description of a proposed shockwave experiment that may provide some understanding on the behavior of planet core materials in the presence of high temperatures and pressures. Shockwave experimentation is shown to offer promise of revealing some information on shear velocity behavior at high pressures, and its relevance to properties of planet interiors consists in that abrupt changes in shear velocities at boundary layers could be experimentally confirmed where abrupt changes in density are suspected from seismic interpretation.

  18. Response of polymer composites to high and low velocity impact

    NASA Technical Reports Server (NTRS)

    Hsieh, C. Y.; Mount, A.; Jang, B. Z.; Zee, R. H.

    1990-01-01

    The present investigation of fiber-reinforced polymer matrix composites' impact characteristics employed a drop tower for the low-velocity impact case and a novel, projectile instantaneous velocity-measuring sensor for high-velocity impact. Attention was given to the energy loss of projectiles in composites reinforced with polyethylene, kevlar, and graphite. Two distinct energy-loss mechanisms are noted, the first of which is due to the actual fracture process while the other is due to the generation of friction heat. The drop-tower impact-test results furnish the strain-rate dependence of the energy loss.

  19. Fluid shielding of high-velocity jet noise

    NASA Technical Reports Server (NTRS)

    Goodykoontz, J. H.

    1984-01-01

    Experimental noise data for a nozzle exhaust system incorporating a thermal acoustic shield (TAS) are presented to show the effect of changes in geometric and flow parameters on attenuation of high-velocity jet exhaust noise in the flyover plane. The results are presented for a 10.00-cm-diameter primary conical nozzle with a TAS configuration consisting of a 2.59- or 5.07-cm-wide annular gap. Shield-stream exhaust velocity was varied from 157 to 248 m/sec to investigate the effect of velocity ratio. The results showed that increasing the annular gap width increases attenuation of high-frequency noise when comparisons are made on the same ideal thrust basis. Varying the velocity ratio had a minor effect on the noise characteristics of the nozzles investigated.

  20. Methyl ester oxygenated fuels for diesel mining applications

    SciTech Connect

    McDonald, J.; Purcell, D.L.; McClure, B.T.

    1995-12-31

    The US. Bureau of Mines has completed a laboratory evaluation of exhaust emissions from a diesel engine using an oxygenated diesel fuel. The fuels tested were soy methyl esters in a neat (100%) form and low sulfur, petroleum number 2 diesel fuel (D2). The engine tested was a Caterpillar 3304, indirect injection, naturally aspirated, 75 kW, diesel engine that is typical of engines used in underground mining applications. The objective was to determine the extent to which oxygenated fuels, such as methyl esters, reduce diesel particulate matter (DPM), and their influence on upon gaseous emissions such as total hydrocarbons, CO, NO{sub x}, NO{sub 2}, formaldehyde, and other exhaust emissions. Heavy- and light-duty transient tests were used to simulate load cycles typical of mine applications. The soy methyl ester fuel produced greater amounts of volatile DPM (organic material) but much less nonvolatile DPM (carbon soot) for overall DPM reductions. A diesel oxidation catalyst (DOC) typical of the type commonly used in metal and nonmetal mines was tested with both fuels. The DOC further reduced the volatile and total DPM when used with the soy methyl esters, but increased the total DPM for D2 due to sulfate formation. The soy methyl ester fuel reduced CO and hydrocarbon, and NO, emissions. The DOC further reduced CO and hydrocarbon emissions.

  1. Cosolvent effects of oxygenated fuels on PAH solubility

    SciTech Connect

    Chen, C.S.; Delfino, J.J.

    1997-04-01

    Cosolvents have been recognized to have a significant impact on the redistribution and movement of hydrophobic organic compounds (HOCs) in the environment. The cosolvent effect of oxygenated compounds (methanol, ethanol, and methyl tert-butyl ether) on the solubility of polynuclear aromatic hydrocarbons (PAHs) was examined by laboratory experiments. Coal-tar-contaminated sediment was used to study the redistribution and facilitated solubilization of 18 PAH compounds in both sediment and aqueous phases caused by cosolvent effects when oxygenated fuel spills occur. A batch dilution experiment was designed to represent the dilution effect of the cosolvent in a simulated river system. The results indicate that PAH solubility increased essentially in a long-linear manner with an increased volume fraction of methanol and ethanol. Deviations from a log-linear relationship were observed for methyl tert-butyl ether due to its limited aqueous solubility, and the cosolvent effect was seen only at the simulated fuel spill site. A linear relationship between the cosolvency power and logarithm of octanol/water partition coefficient was observed.

  2. Detection of velocity in high temperature liquid metals

    NASA Technical Reports Server (NTRS)

    Mikrovas, A. C.; Argyropoulos, S. A.

    1993-01-01

    Various efforts have been made to measure velocity in liquid metals. All of these efforts, however, share the same inherent limitation, namely, not being operative at the high temperatures required by liquid metals and liquid slags in an industrial application. In this paper, the current methods used were reviewed, and a new technique was presented for the measurement of velocity in high temperature liquid metals. In using this technique there are two stages. Starting with the calibration stage and then moving to the actual measurement stage by making use of the data obtained from calibration stage. Calibration proceeds in the following manner. Metallic spheres moving with a specific velocity are immersed in liquid metal held under isothermal conditions and at specific temperature. Their melting times are determined very accurately with a novel technique. These measurements are repeated for different metal bath temperatures and for different velocities of metallic spheres. In this manner it is possible to calculate the correlation between velocity and melting times for each metal bath temperature. During the actual measurement stage, when the metal bath temperature is known and its velocity is unknown, the magnitude of the unknown liquid metal velocity can be derived as follows: metallic spheres are immersed into the moving liquid metal and their melting times are determined. Using the above mentioned correlations, it will be shown that the magnitude of the unknown velocity in liquid metal can be deduced. This new technique was applied to high temperature liquid aluminum and liquid steel and these results were presented. The potential applicability of this technique in other liquid metals and liquid slags will also be discussed.

  3. Orbital Transfer Vehicle Engine Technology High Velocity Ratio Diffusing Crossover

    NASA Technical Reports Server (NTRS)

    Lariviere, Brian W.

    1992-01-01

    High speed, high efficiency head rise multistage pumps require continuous passage diffusing crossovers to effectively convey the pumped fluid from the exit of one impeller to the inlet of the next impeller. On Rocketdyne's Orbital Transfer Vehicle (OTV), the MK49-F, a three stage high pressure liquid hydrogen turbopump, utilizes a 6.23 velocity ratio diffusing crossover. This velocity ratio approaches the diffusion limits for stable and efficient flow over the operating conditions required by the OTV system. The design of the high velocity ratio diffusing crossover was based on advanced analytical techniques anchored by previous tests of stationary two-dimensional diffusers with steady flow. To secure the design and the analytical techniques, tests were required with the unsteady whirling characteristics produced by an impeller. A tester was designed and fabricated using a 2.85 times scale model of the MK49-F turbopumps first stage, including the inducer, impeller, and the diffusing crossover. Water and air tests were completed to evaluate the large scale turbulence, non-uniform velocity, and non-steady velocity on the pump and crossover head and efficiency. Suction performance tests from 80 percent to 124 percent of design flow were completed in water to assess these pump characteristics. Pump and diffuser performance from the water and air tests were compared with the actual MK49-F test data in liquid hydrogen.

  4. Pierce Prize Lecture: High Velocity Clouds: Cosmological and Galactic Weather

    NASA Astrophysics Data System (ADS)

    Sembach, K.

    2001-12-01

    The Milky Way and its surrounding environs contain gas moving at high velocities with respect to the Sun. For the past half century, most of the information available for these high velocity clouds (HVCs) has come from H I 21cm surveys. Improvements in these surveys have recently led to the idea that some of the high velocity H I clouds may be located outside the Milky Way within the Local Group. Such a hypothesis is testable by various means, but the neutral gas content of the clouds tells only half of a much more complex story. In this talk I will present new information about the ionized gas within HVCs, their impact on the gaseous atmosphere of the Galaxy, and their relevance to the cosmic web of hot gas that may contain a significant fraction of the baryonic material in the low-redshift universe.

  5. Mixing between High Velocity Clouds and the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Gritton, Jeffrey A.; Shelton, Robin L.; Kwak, Kyujin

    2014-11-01

    In the Galactic halo, metal-bearing Galactic halo material mixes into high velocity clouds (HVCs) as they hydrodynamically interact. This interaction begins long before the clouds completely dissipate and long before they slow to the velocity of the Galactic material. In order to make quantitative estimates of the mixing efficiency and resulting metal enrichment of HVCs, we made detailed two- and three-dimensional simulations of cloud-interstellar medium interactions. Our simulations track the hydrodynamics and time-dependent ionization levels. They assume that the cloud originally has a warm temperature and extremely low metallicity while the surrounding medium has a high temperature, low density, and substantial metallicity, but our simulations can be generalized to other choices of initial metallicities. In our simulations, mixing between cloud and halo gas noticeably raises the metallicity of the high velocity material. We present plots of the mixing efficiency and metal enrichment as a function of time.

  6. Mixing between high velocity clouds and the galactic halo

    SciTech Connect

    Gritton, Jeffrey A.; Shelton, Robin L.; Kwak, Kyujin E-mail: rls@physast.uga.edu

    2014-11-01

    In the Galactic halo, metal-bearing Galactic halo material mixes into high velocity clouds (HVCs) as they hydrodynamically interact. This interaction begins long before the clouds completely dissipate and long before they slow to the velocity of the Galactic material. In order to make quantitative estimates of the mixing efficiency and resulting metal enrichment of HVCs, we made detailed two- and three-dimensional simulations of cloud-interstellar medium interactions. Our simulations track the hydrodynamics and time-dependent ionization levels. They assume that the cloud originally has a warm temperature and extremely low metallicity while the surrounding medium has a high temperature, low density, and substantial metallicity, but our simulations can be generalized to other choices of initial metallicities. In our simulations, mixing between cloud and halo gas noticeably raises the metallicity of the high velocity material. We present plots of the mixing efficiency and metal enrichment as a function of time.

  7. MAGNETIZED GAS IN THE SMITH HIGH VELOCITY CLOUD

    SciTech Connect

    Hill, Alex S.; McClure-Griffiths, Naomi M.; Mao, S. A.; Benjamin, Robert A.; Lockman, Felix J. E-mail: naomi.mcclure-griffiths@csiro.au E-mail: benjamir@uww.edu

    2013-11-01

    We report the first detection of magnetic fields associated with the Smith High Velocity Cloud. We use a catalog of Faraday rotation measures toward extragalactic radio sources behind the Smith Cloud, new H I observations from the Robert C. Byrd Green Bank Telescope, and a spectroscopic map of Hα from the Wisconsin H-Alpha Mapper Northern Sky Survey. There are enhancements in rotation measure (RM) of ≈100 rad m{sup –2} which are generally well correlated with decelerated Hα emission. We estimate a lower limit on the line-of-sight component of the field of ≈8 μG along a decelerated filament; this is a lower limit due to our assumptions about the geometry. No RM excess is evident in sightlines dominated by H I or Hα at the velocity of the Smith Cloud. The smooth Hα morphology of the emission at the Smith Cloud velocity suggests photoionization by the Galactic ionizing radiation field as the dominant ionization mechanism, while the filamentary morphology and high (≈1 Rayleigh) Hα intensity of the lower-velocity magnetized ionized gas suggests an ionization process associated with shocks due to interaction with the Galactic interstellar medium. The presence of the magnetic field may contribute to the survival of high velocity clouds like the Smith Cloud as they move from the Galactic halo to the disk. We expect these data to provide a test for magnetohydrodynamic simulations of infalling gas.

  8. A mechanism for high wall-rock velocities in rockbursts

    USGS Publications Warehouse

    McGarr, A.

    1997-01-01

    Considerable evidence has been reported for wall-rock velocities during rockbursts in deep gold mines that are substantially greater than ground velocities associated with the primary seismic events. Whereas varied evidence suggests that slip across a fault at the source of an event generates nearby particle velocities of, at most, several m/s, numerous observations, in nearby damaged tunnels, for instance, imply wall-rock velocities of the order of 10 m/s and greater. The common observation of slab buckling or breakouts in the sidewalls of damaged excavations suggests that slab flexure may be the mechanism for causing high rock ejection velocities. Following its formation, a sidewall slab buckles, causing the flexure to increase until the stress generated by flexure reaches the limit 5 that can be supported by the sidewall rock. I assume here that S is the uniaxial compressive strength. Once the flexural stress exceeds S, presumably due to the additional load imposed by a nearby seismic event, the slab fractures and unflexes violently. The peak wall-rock velocity v thereby generated is given by v=(3 + 1-??2/2)1 2 S/?????E for rock of density ??, Young's modulus E, and Poisson's ratio ??. Typical values of these rock properties for the deep gold mines of South Africa yield v= 26 m/s and for especially strong quartzites encountered in these same mines, v> 50m/s. Even though this slab buckling process leads to remarkably high ejection velocities and violent damage in excavations, the energy released during this failure is only a tiny fraction of that released in the primary seismic event, typically of magnitude 2 or greater.

  9. A High-Velocity Collision With Our Galaxy's Disk

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-08-01

    What caused the newly discovered supershell in the outskirts of our galaxy? A new study finds evidence that a high-velocity cloud may have smashed into the Milky Ways disk millions of years ago.Mysterious Gas ShellsA single velocity-channel map of the supershell GS040.2+00.670, with red contours marking the high-velocity cloud at its center. [Adapted from Park et al. 2016]The neutral hydrogen gas that fills interstellar space is organized into structures like filaments, loops, and shells. Supershells are enormous shells of hydrogen gas that can have radii of a thousand light-years or more; weve spotted about 20 of these in our own galaxy, and more in nearby dwarfs and spiral galaxies.How do these structures form? One theory is that they result from several supernovae explosions occurring in the same area. But the energy needed to create a supershell is more than 3 x 1052 erg, which corresponds to over 30 supernovae quite a lot to have exploding in the same region.Theres an interesting alternative scenario: the supershells might instead be caused by the impacts of high-velocity clouds that fall into the galactic disk.Velocity data for the compact high-velocity cloud CHVC040. The cloud is moving fast enough to create the supershell observed. [Adapted from Park et al. 2016]The Milky Ways Speeding CloudsHigh-velocity clouds are clouds of mostly hydrogen that speed through the Milky Way with radial velocities that are very different from the material in the galactic disk. The origins of these clouds are unknown, but its proposed that they come from outside the galaxy they might be fragments of a nearby, disrupting galaxy, or they might have originated from flows of accreting gas in the space in between galaxies.Though high-velocity clouds have long been on the list of things that might cause supershells, weve yet to find conclusive evidence of this. But that might have just changed, with a recent discovery by a team of scientists led by Geumsook Park (Seoul National

  10. Certain optimal parameters of high-velocity Venturi ejection tubes

    NASA Astrophysics Data System (ADS)

    Stark, S. B.; Reznichenko, I. G.; Pavlenko, Y. P.

    1984-11-01

    The influence of the geometrical characteristics of centrifugal nozzles in high velocity Venturi ejection tubes for atomizing liquid in gas cleaning plant is analyzed. An optimal value of the nozzle geometrical characteristic, which is a function of the degree of filling of the nozzle outlet opening by the liquid, is given, at which the throat length is independent of water pressure before the nozzle.

  11. High-Velocity Star Formation in the Large Magellanic Cloud.

    PubMed

    Graff; Gould

    2000-05-01

    Light-echo measurements show that SN 1987A is 425 pc behind the LMC disk. It is continuing to move away from the disk at 18 km s-1. Thus, it has been suggested that SN 1987A was ejected from the LMC disk. However, SN 1987A is a member of a star cluster, so this entire cluster would have to have been ejected from the disk. We show that the cluster was formed in the LMC disk, with a velocity perpendicular to the disk of about 50 km s-1. Such high-velocity formation of a star cluster is unusual, having no known counterpart in the Milky Way.

  12. Electric rail gun projectile acceleration to high velocity

    NASA Technical Reports Server (NTRS)

    Bauer, D. P.; Mccormick, T. J.; Barber, J. P.

    1982-01-01

    Electric rail accelerators are being investigated for application in electric propulsion systems. Several electric propulsion applications require that the rail accelerator be capable of launching projectiles at velocities above 10 km/s. An experimental program was conducted to develop rail accelerator technology for high velocity projectile launch. Several 6 mm bore, 3 m long rail accelerators were fabricated. Projectiles with a mass of 0.2 g were accelerated by plasmas, carrying currents up to 150 kA. Experimental design and results are described. Results indicate that the accelerator performed as predicted for a fraction of the total projectile acceleration. The disparity between predicted and measured results are discussed.

  13. INTERMEDIATE-VELOCITY MOLECULAR GAS AT HIGH NORTHERN GALACTIC LATITUDES

    SciTech Connect

    Magnani, Loris; Smith, Allison J.

    2010-10-20

    We surveyed the CO(1-0) transition in 16 regions at Galactic latitudes >45{sup 0} which contain compact dust cores less than half a degree in size with E(B - V) values {approx} 0.1 mag. We discovered three new intermediate-velocity molecular clouds and two high-latitude molecular clouds with more typical local standard of rest velocity ({approx}0 km s{sup -1}). The three intermediate-velocity molecular clouds (detected in CO emission in 11 lines of sight) nearly double the number of previously known, CO-emitting clouds. In order to detect the CO(1-0) line, N(H{sub 2}) values of at least 10{sup 19} cm{sup -2} are necessary, implying that the molecular/atomic fraction of these objects is significant and is in contrast to the primarily atomic lines of sight with log N(H{sub 2}) < 17.3 detected in absorption by FUSE. The three molecular clouds are projected on and likely associated with a previously known intermediate-velocity H I feature known as the Intermediate Velocity Spur that may extend to the Galactic halo.

  14. HST-FGS parallaxes of two high-velocity stars.

    NASA Astrophysics Data System (ADS)

    MacConnell, D. Jack; Osborn, Wayne H.; Miller, Richard J.

    1997-09-01

    Astrometric position measurements with the Hubble Space Telescope's Fine Guidance System have been used to measure the trigonometric parallaxes of two high-velocity stars, R50 = G166-37 and W624 = G16-25. In both cases, the parallaxes are small and confirm large velocities in the galactocentric rest frame. We derive pi_ {abs} = 5.2 +/- 0.7 mas and vrf = 467 kms for R50. The results for W624 are pi_ {abs} = 3.8 +/- 1.0 and vrf = 326 kms with an uncertainty of about 30%. Our results support a value for the galactic escape velocity at the solar distance of about 475 kms.

  15. Friction and Wear of Carbonate Rocks Under High Velocity Sliding

    NASA Astrophysics Data System (ADS)

    Boneh, Y.; Sagy, A.; Reches, Z.

    2012-12-01

    We experimentally investigated the relations between friction and wear-rate during steady-state, high-velocity slip along carbonate faults. Our observations demonstrate a systematic reduction of both friction coefficient and wear-rate with increase of both slip-velocity and normal stress. The experiments were conducted with a rotary shear apparatus on solid, ring-shaped rock samples that slipped for displacements up to tens of meters, with continuous monitoring of stresses, wear and temperature. We performed 107 experiments on experimental faults made of Kasota dolomite, Dover limestone and a fault made of rock-pair Kasota dolomite and Blue quartzite. The friction/wear analysis is focused on the steady-state stage under slip velocity range of 0.002 to 0.96 m/s, and normal stress from 0.25 to 6.9 MPa. The experiments reveal a combined effect of slip-velocity and normal stress on the wear-rate. Under relatively low velocities (V < 0.5 m/s for limestone and V < 0.12 m/s for dolomite-quartzite pair), the wear-rate is proportional to the normal stress, in agreement with Archard (1953) model. On the other hand, in the higher velocity range of V ~ 0.5 - 1 m/s, the wear-rate is not proportional to the normal stress and it reduces with increasing slip-velocity. Further, the velocity effect on the wear-rate becomes stronger with increasing normal stress approaching negligible wear production. The experiments indicate that the steady-state frictional strength of these carbonate samples is best correlated with the power-density (= shear stress * slip-velocity, MW/m2). The observed friction/power-density relation show three regimes: (1) high (μ ~ 0.9), quasi-constant friction coefficient under low power-density of < 0.05 MW/m2; (2) low (μ ~ 0.3), quasi-constant friction coefficient under high power-density > 0.4 MW/m2; and (3) transition zone of friction coefficient dropping from ~ 0.9 to ~ 0.3 for intermediated power density ranging 0.05 - 0.4 MW/m2. During experiments with

  16. High-speed velocity measurements on an EFI-system

    NASA Astrophysics Data System (ADS)

    Prinse, W. C.; van't Hof, P. G.; Cheng, L. K.; Scholtes, J. H. G.

    2007-01-01

    For the development of an Exploding Foil Initiator for Insensitive Munitions applications the following topics are of interest: the electrical circuit, the exploding foil, the velocity of the flyer, the driver explosive, the secondary flyer and the acceptor explosive. Several parameters of the EFI have influences on the velocity of the flyer. To investigate these parameters a Fabry-Perot Velocity Interferometer System (F-PVIS) has been used. The light to and from the flyer is transported by a multimode fibre terminated with a GRIN-lens. By this method the velocity of very tiny objects (0.1 mm), can be measured. The velocity of flyer can be recorded with nanosecond resolution, depending on the Fabry-Perot etalon and the streak camera. With this equipment the influence of the dimensions of the exploding foil and the flyer on the velocity and the acceleration of the flyer are investigated. Also the integrity of the flyer during flight can be analyzed. To characterize the explosive material, to be used as driver explosive in EFI's, the initiation behaviour of the explosive has been investigated by taking pictures of the explosion with a high speed framing and streak camera. From these pictures the initiation distance and the detonation behaviour of the explosive has been analyzed. Normally, the driver explosive initiates the acceptor explosive (booster) by direct contact. This booster explosive is embedded in the main charge of the munitions. The combination of initiator, booster explosive and main charge explosive is called the detonation train. In this research the possibility of initiation of the booster by an intermediate flyer is investigated. This secondary flyer can be made of different materials, like aluminium, steel and polyester with different sizes. With the aid of the F-PVIS the acceleration of the secondary flyer is investigated. This reveals the influence of the thickness and density of the flyer on the acceleration and final velocity. Under certain

  17. High Velocity Forming of Magnesium and Titanium Sheets

    SciTech Connect

    Revuelta, A.; Larkiola, J.; Korhonen, A. S.; Kanervo, K.

    2007-04-07

    Cold forming of magnesium and titanium is difficult due to their hexagonal crystal structure and limited number of available slip systems. However, high velocity deformation can be quite effective in increasing the forming limits. In this study, electromagnetic forming (EMF) of thin AZ31B-O magnesium and CP grade 1 titanium sheets were compared with normal deep drawing. Same dies were used in both forming processes. Finite element (FE) simulations were carried out to improve the EMF process parameters. Constitutive data was determined using Split Hopkinson Pressure Bar tests (SHPB). To study formability, sample sheets were electromagnetically launched to the female die, using a flat spiral electromagnetic coil and aluminum driver sheets. Deep drawing tests were made by a laboratory press-machine.Results show that high velocity forming processes increase the formability of Magnesium and Titanium sheets although process parameters have to be carefully tuned to obtain good results.

  18. Gouge initiation in high-velocity rocket sled testing

    SciTech Connect

    Tachau, R.D.M.; Trucano, T.G.; Yew, C.H.

    1994-07-01

    A model is presented which describes the formation of surface damage ``gouging`` on the rails that guide rocket sleds. An unbalanced sled can randomly cause a very shallow-angle, oblique impact between the sled shoe and the rail. This damage phenomenon has also been observed in high-velocity guns where the projectile is analogous to the moving sled shoe and the gun barrel is analogous to the stationary rail. At sufficiently high velocity, the oblique impact will produce a thin hot layer of soft material on the contact surfaces. Under the action of a normal moving load, the soft layer lends itself to an anti-symmetric deformation and the formation of a ``hump`` in front of the moving load. A gouge is formed when this hump is overrun by the sled shoe. The phenomenon is simulated numerically using the CTH strong shock physics code, and the results are in good agreement with experimental observation.

  19. High Velocity Forming of Magnesium and Titanium Sheets

    NASA Astrophysics Data System (ADS)

    Revuelta, A.; Larkiola, J.; Korhonen, A. S.; Kanervo, K.

    2007-04-01

    Cold forming of magnesium and titanium is difficult due to their hexagonal crystal structure and limited number of available slip systems. However, high velocity deformation can be quite effective in increasing the forming limits. In this study, electromagnetic forming (EMF) of thin AZ31B-O magnesium and CP grade 1 titanium sheets were compared with normal deep drawing. Same dies were used in both forming processes. Finite element (FE) simulations were carried out to improve the EMF process parameters. Constitutive data was determined using Split Hopkinson Pressure Bar tests (SHPB). To study formability, sample sheets were electromagnetically launched to the female die, using a flat spiral electromagnetic coil and aluminum driver sheets. Deep drawing tests were made by a laboratory press-machine. Results show that high velocity forming processes increase the formability of Magnesium and Titanium sheets although process parameters have to be carefully tuned to obtain good results.

  20. Gouge initiation in high-velocity rocket sled testing

    NASA Astrophysics Data System (ADS)

    Tachau, R. D. M.; Trucano, T. G.; Yew, C. H.

    1994-07-01

    A model is presented which describes the formation of surface damage 'gouging' on the rails that guide rocket sleds. An unbalanced sled can randomly cause a very shallow-angle, oblique impact between the sled shoe and the rail. This damage phenomenon has also been observed in high-velocity guns where the projectile is analogous to the moving sled shoe and the gun barrel is analogous to the stationary rail. At sufficiently high velocity, the oblique impact will produce a thin hot layer of soft material on the contact surfaces. Under the action of a normal moving load, the soft layer lends itself to an anti-symmetric deformation and the formation of a 'hump' in front of the moving load. A gouge is formed when this hump is overrun by the sled shoe. The phenomenon is simulated numerically using the CTH strong shock physics code, and the results are in good agreement with experimental observation.

  1. [Effects of oxygenated fuels on emissions and carbon composition of fine particles from diesel engine].

    PubMed

    Shi, Xiao-Yan; He, Ke-Bin; Zhang, Jie; Ge, Yun-Shan; Tan, Jian-Wei

    2009-06-15

    Acetal (1,1-diethoxyethane) is considered as an alternative to ethanol as bio-derived additive for diesel fuel, which is miscible in diesel fuel. Biodiesel can improve the oxygen content and flash point of the fuel blend of acetal and diesel fuel. Two oxygenated fuels were prepared: a blend of 10% acetal + 90% diesel fuel and 10% acetal + 10% biodiesel + 80% diesel fuel. The emissions of NO(x), HC and PM2.5 from oxygenated fuels were investigated on a diesel engine bench at five modes according to various loads at two steady speeds and compared with base diesel fuel. Additionally, the carbon compositions of PM2.5 were analyzed by DRI thermal/optical carbon analyzer. Oxygenated fuels have unconspicuous effect on NO(x) emission rate but HC emission rate is observed significantly increased at some modes. The emission rate of PM2.5 is decreased by using oxygenated fuels and it decreases with the increase of fuel oxygen content. The emission rates of TC (total carbon) and EC (elemental carbon) in PM2.5 are also decreased by oxygenated fuels. The emission rate of organic carbon (OC) is greatly decreased at modes of higher engine speed. The OC/EC ratios of PM2.5 from oxygenated fuels are higher than that from base diesel fuel at most modes. The carbon compositions fractions of PM2.5 from the three test fuels are similar, and OC1 and EC1 are contributed to the most fractions of OC and EC, respectively. Compared with base diesel fuel, oxygenated fuels decrease emission rate of PM2.5, and have more OC contribution to PM2.5 but have little effect on carbon composition fractions.

  2. Three-dimensional orientation of compact high velocity clouds

    NASA Astrophysics Data System (ADS)

    Heitsch, F.; Bartell, B.; Clark, S. E.; Peek, J. E. G.; Cheng, D.; Putman, M.

    2016-10-01

    We present a proof-of-concept study of a method to estimate the inclination angle of compact high velocity clouds (CHVCs), i.e. the angle between a CHVC's trajectory and the line of sight. The inclination angle is derived from the CHVC's morphology and kinematics. We calibrate the method with numerical simulations, and we apply it to a sample of CHVCs drawn from HIPASS (Putman et al.). Implications for CHVC distances are discussed.

  3. VELOCITY BUNCHING OF HIGH-BRIGHTNESS ELECTRON BEAMS

    SciTech Connect

    Anderson, S G; Musumeci, P; Rosenzweig, J B; Brown, W J; England, R J; Ferrario, M; Jacob, J S; Thompson, M C; Travish, G; Tremaine, A M; Yoder, R

    2004-10-15

    Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modern high brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS) experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly in ICS experiments

  4. Aerosol production by high-velocity molten-metal droplets

    SciTech Connect

    Rader, D J; Benson, D A

    1988-06-01

    This report presents the results of an experimental study of the aerosol produced by high-velocity molten-metal droplets. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. The primary droplets are produced by the heating and electromagnetic launch of metal wires; velocities approaching Mach 1 can be obtained at present. Size distributions obtained tungsten and zirconium droplets burning in air. Lognormal size distributions were observed in both cases with DMPS-equivalent mean diameters of about 0.4 ..mu..m and geometric standard deviations of about two. SEM and TEM analysis of aerosol samples collected by a point-to-plane electrostatic precipitator showed that the majority of these particles were web-like chain agglomerates. Tests performed in argon atmospheres produced several orders-of-magnitude less aerosol mass than in equivalent air tests, supporting the key role combustion plays in secondary aerosol generation. 26 refs., 14 figs., 2 tabs.

  5. Two high-velocity encounters of elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Balcells, Marc; Borne, Kirk D.; Hoessel, John G.

    1989-01-01

    This paper describes results obtained on a simulation of two high-velocity encounters of NGC 4782/4783 and NGC 2672/2673 binary elliptical galaxies which differ substantially in mass ratio (about 1 for the first pair, and about 10 for the second). CCD images and velocities obtained from digital spectra were used to constrain simulations of the galaxy collisions. The binary orbital elements, the orientation of the orbit in the sky, the time since pericenter, and the dynamical mass of the pair were derived. Results suggested that the dumb-bell galaxy NGC 4782/4783 is not a supermassive galaxy, as was claimed earlier on the basis of the high relative velocity and high central dispersion, but has a moderate mass to luminosity ratio M/L(B) of about 10. It was concluded that its trajectory changed from hyperbolic to elliptical as a result of energy lost during the collision. It was found that the NGC 2672/2673 also has a moderate M/L(B) of about 7.

  6. Experimental and numerical studies of high-velocity impact fragmentation

    SciTech Connect

    Kipp, M.E.; Grady, D.E.; Swegle, J.W.

    1993-08-01

    Developments are reported in both experimental and numerical capabilities for characterizing the debris spray produced in penetration events. We have performed a series of high-velocity experiments specifically designed to examine the fragmentation of the projectile during impact. High-strength, well-characterized steel spheres (6.35 mm diameter) were launched with a two-stage light-gas gun to velocities in the range of 3 to 5 km/s. Normal impact with PMMA plates, thicknesses of 0.6 to 11 mm, applied impulsive loads of various amplitudes and durations to the steel sphere. Multiple flash radiography diagnostics and recovery techniques were used to assess size, velocity, trajectory and statistics of the impact-induced fragment debris. Damage modes to the primary target plate (plastic) and to a secondary target plate (aluminum) were also evaluated. Dynamic fragmentation theories, based on energy-balance principles, were used to evaluate local material deformation and fracture state information from CTH, a three-dimensional Eulerian solid dynamics shock wave propagation code. The local fragment characterization of the material defines a weighted fragment size distribution, and the sum of these distributions provides a composite particle size distribution for the steel sphere. The calculated axial and radial velocity changes agree well with experimental data, and the calculated fragment sizes are in qualitative agreement with the radiographic data. A secondary effort involved the experimental and computational analyses of normal and oblique copper ball impacts on steel target plates. High-resolution radiography and witness plate diagnostics provided impact motion and statistical fragment size data. CTH simulations were performed to test computational models and numerical methods.

  7. Velocity field measurements on high-frequency, supersonic microactuators

    NASA Astrophysics Data System (ADS)

    Kreth, Phillip A.; Ali, Mohd Y.; Fernandez, Erik J.; Alvi, Farrukh S.

    2016-05-01

    The resonance-enhanced microjet actuator which was developed at the Advanced Aero-Propulsion Laboratory at Florida State University is a fluidic-based device that produces pulsed, supersonic microjets by utilizing a number of microscale, flow-acoustic resonance phenomena. The microactuator used in this study consists of an underexpanded source jet that flows into a cylindrical cavity with a single, 1-mm-diameter exhaust orifice through which an unsteady, supersonic jet issues at a resonant frequency of 7 kHz. The flowfields of a 1-mm underexpanded free jet and the microactuator are studied in detail using high-magnification, phase-locked flow visualizations (microschlieren) and two-component particle image velocimetry. These are the first direct measurements of the velocity fields produced by such actuators. Comparisons are made between the flow visualizations and the velocity field measurements. The results clearly show that the microactuator produces pulsed, supersonic jets with velocities exceeding 400 m/s for roughly 60 % of their cycles. With high unsteady momentum output, this type of microactuator has potential in a range of ow control applications.

  8. Ultrasonic Velocity and Texture of High RRR Niobium

    SciTech Connect

    S. R. Agnew; F. Zeng; G.R. Myneni

    2003-06-01

    Conventional assessments of the mechanical properties of rolled high RRR niobium plate material via tensile testing have revealed an unusually low apparent Young's moduli and yield strength in some annealed samples. These observations motivated a series of measurements of ultrasonic velocity, a dynamic assessment of the elastic moduli. In fact, the dynamic modulus is within the range of normal for all samples tested. However, there is a trend of increasing shear velocities for shear waves propagating through the sheet thickness and polarized in the sheet transverse direction. Careful analyses of the crystallographic texture using SEM-based electron backscattered diffraction (EBSD) have revealed a subtle, but systematic change in the texture, which can explain the trend. It is further important to note that the change in texture is not observable from surface measurements using x-ray diffraction, but requires sectioning of the samples. Thus, measurements of ultrasonic velocity represent a non-destructive evaluation tool which is extremely sensitive to subtle changes in the texture of high RRR niobium. Finally, there are material lot variations, which are currently attributed to the effects of impurities, such as Ta and H.

  9. Energy loss of heavy ions at high velocity

    NASA Astrophysics Data System (ADS)

    Andersen, J. U.; Ball, G. C.; Davies, J. A.; Davies, W. G.; Forster, J. S.; Geiger, J. S.; Geissel, H.; Ryabov, V. A.

    1994-05-01

    The slowing down of heavy ions by electronic stopping at high velocity is discussed. The ions are nearly fully stripped and have a well defined charge with relatively small fluctuations. Owing to the large charge of the ions, the classical Bohr formula applies instead of the Bethe formula, which is based on a quantum perturbation calculation. It is essential to include the Barkas effect in the description since it becomes quite large for heavy ions, especially in high-Z materials. In Lindhard's treatment [Nucl. Instr. and Meth. 132 (1976) l], the Barkas correction is viewed as an effect of dynamic screening of the ion potential in the initial phase of a collision with an electron, which reduces the relative velocity and therefore enhances the cross section. With inclusion of this enhancement factor for all impact parameters, as evaluated by Jackson and McCarthy for distant collisions [Phys. Rev. B 6 (1972) 4131], the description reproduces within a few percent measurements for 15 MeV/u Br on Si, Ni, and Au and for 10 MeV/u Kr on Al, Ni, and Au. The procedure is shown also to apply at lower velocities near the stopping maximum, albeit with less accuracy. The straggling in energy loss has been analyzed for a measurement on Si and it is well described by a combination of about equal contributions from fluctuations in the number of violent collisions with single electrons (Bohr straggling) and from fluctuations in ion charge state.

  10. The distance to the high velocity clouds of neutral hydrogen

    NASA Technical Reports Server (NTRS)

    Bregman, Joel N.

    1992-01-01

    The goal of this project was to determine the distance to high velocity gas clouds. These clouds are believed to lie in the halo of the galaxy, but this is a matter of controversy. The technique was used to look for the effect of absorption by these clouds against the light of stars at various distances along the line of sight to these clouds. This was done in the ultraviolet using the International Ultraviolet Explorer. Absorption at the velocity of the clouds was not found in any of the stars, which have kiloparsec distances. It was concluded that the vertical distance to these clouds is at least 1.5 kpc, putting them firmly in the halo of the galaxy.

  11. Low and high velocity impact response of thick hybrid composites

    NASA Technical Reports Server (NTRS)

    Hiel, Clement; Ishai, Ori

    1993-01-01

    The effects of low and high velocity impact on thick hybrid composites (THC's) were experimentally compared. Test Beams consisted of CFRP skins which were bonded onto an interleaved syntactic foam core and cured at 177 C (350 F). The impactor tip for both cases was a 16 mm (0.625 inch) steel hemisphere. In spite of the order of magnitude difference in velocity ranges and impactor weights, similar relationships between impact energy, damage size, and residual strength were found. The dependence of the skin compressive strength on damage size agree well with analytical open hole models for composite laminates and may enable the prediction of ultimate performance for the damaged composite, based on visual inspection.

  12. Vortex shedding flowmeters for liquids at high flow velocities

    NASA Technical Reports Server (NTRS)

    Siegwarth, J. D.

    1985-01-01

    A number of vortex shedding flowmeter designs for flow measurements in liquid oxygen ducts on the space shuttle main engines have been tested in a high head water flow test facility. The results have shown that a vortex shedding element or vane spanning the duct can give a linear response to an average flow velocity of 46 m/s (150 ft/s) in a 1 1/2 inch nominal (41 mm actual) diameter duct while a vane partially spanning the duct can give a linear response to velocities exceeding 55 m/s (180 ft/s). The maximum pressure drops across the flow sensing elements extrapolate to less than 0.7 MPa (100 psi) at 56 m/s (184 ft/s) for liquid oxygen. The test results indicate that the vanes probably cannot be scaled up with pipe size, at least not linearly.

  13. Analysis of high velocity impact on hybrid composite fan blades

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    This paper describes recent developments in the analysis of high velocity impact of composite blades using a computerized capability which consists of coupling a composites mechanics code with the direct-time integration features of NASTRAN. The application of the capability to determine the linear dynamic response of an intraply hybrid composite aircraft engine fan blade is described in detail. The predicted results agree with measured data. The results also show that the impact stresses reach sufficiently high magnitudes to cause failures in the impact region at early times of the impact event.

  14. Analysis of high velocity impact on hybrid composite fan blades

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Sinclair, J. H.

    1979-01-01

    Recent developments in the analysis of high velocity impact of composite blades are described, using a computerized capability which consists of coupling a composites mechanics code with the direct-time integration features of NASTRAN. The application of the capability to determine the linear dynamic response of an interply hybrid composite aircraft engine fan blade is described in detail. The results also show that the impact stresses reach sufficiently high magnitudes to cause failures in the impact region at early times of the impact event.

  15. High-velocity pulsars in the galactic halo

    SciTech Connect

    Eichler, D. ); Silk, J. )

    1992-08-14

    A common origin is proposed for high-velocity pulsars and for gamma-ray bursters. This source is a subdominant population of neutron stars that are in a spatially extended halo around our galaxy. Theoretical speculations and especially recent observations suggest the possible existence of a halo population of neutron stars. Specifically, recent reports of diskward-moving, high-latitude pulsars and of a nearly isotropic distribution of gamma-ray bursters motivate the authors to propose a source of neutron stars in the halo. They suggest that neutron stars could form by mergers of white dwarfs.

  16. High-Velocity Clouds and Superbubbles in Nearby Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Schulman, Eric

    1996-05-01

    The galactic fountain model predicts that energetic stellar winds and supernovae in OB associations produce superbubbles containing hot gas that breaks out of the Galactic disk, cools radiatively as it rises upward, and recombines and returns to the disk ballistically. The hot (T ~ 10^6 K) gas can be observed with X-ray telescopes, while the cool returning neutral hydrogen (H I) is detectable as 21 cm emission from high-velocity clouds (HVCs). In the Milky Way Galaxy, a combination of infalling material tidally torn from the Magellanic Clouds and a galactic fountain can explain the high-velocity clouds that cover about 10% of the sky down to a column density of 2 to 3 X 10^18 cm^-2. Sensitive H I observations of nearby disk galaxies were performed with the Arecibo 305 m radio telescope to search for and measure the mass of HVCs in other galaxies. Ten of 14 galaxies have high-velocity wings that can be modeled as arising from a component of galactic gas with a velocity dispersion of 30 or 50 km s^-1. The HVC mass for the 10 galaxies ranges from 6 X 10^7 solar mass to 4 X 10^9 solar mass, which corresponds to 4 to 14% of the total H I in the galaxies. This is the first survey to search for HVCs in more than a few galaxies, and the results imply that Galactic HVCs are a disk-wide phenomenon with a characteristic distance of 10 to 20 kpc, containing a substantial fraction (~10%) of the neutral hydrogen in the Galaxy and much of the random kinetic energy in neutral gas. 21 cm synthesis imaging of UGC 12732 and NGC 5668, performed with the Very Large Array, confirmed the Arecibo results that the former does not have high-velocity gas while the latter does. Two components of high-velocity gas are present in NGC~5668; one may be from an accretion event, while the other is visible due to the increased H I velocity dispersion throughout the optical disk and may be galactic fountain gas. Neither of these components are visible in the observations of UGC 12732, and this galaxy

  17. Controlling Btu input with high-velocity burners

    SciTech Connect

    Lukacs, J.J.

    1995-09-01

    StepFire{trademark} (sometimes called pulse fire) controls heat input through a burner by rapidly cycling from high fire to low fire (or from high fire to off) to control the temperature of either an entire kiln or a zone within a kiln. In the StepFire process, each burner, rather than an entire zone of burners, is controlled. The StepFire process provides a better approach to temperature control: high-velocity burners improve temperature distribution across the load, whether the burners are fired vertically downward or horizontally; reentrainment effect of the burners breaks up crown drift and allows dissipation of energy into the product; high-velocity burners generate less NO{sub x} and co than injector-type burners; high-velocity burners put most of the combustion air through the burners and do not have to rely on the mass flow of air from the cooling zone to complete combustion and provide uniformity; individual cycling of the burners does not radically change the total input of gases to the furnace, thereby allowing pressure control; because burners are cycled individually, the entire zone of the furnace does not go from a heating to a cooling mode, but continues at an input rate to maintain uniformity of energy input through the stepping process. StepFire use on all types of kilns results in improved product properties and quality, reduced fuel use, increased production, fewer rejects and reduction of NO{sub x} and CO emissions. Because the burners operate under their optimum conditions during most of the firing cycles, NO{sub x} formation is reduced, and the quenching effect of the flame by excess air is not present, reducing the generation of CO.

  18. Production of high density molecular beams with wide velocity scanning.

    PubMed

    Sheffield, L S; Woo, S O; Rathnayaka, K D D; Lyuksyutov, I F; Herschbach, D R

    2016-06-01

    We describe modifications of a pulsed rotating supersonic beam source that improve performance, particularly increasing the beam density and sharpening the pulse profiles. As well as providing the familiar virtues of a supersonic molecular beam (high intensity, narrowed velocity distribution, and drastic cooling of rotation and vibration), the rotating source enables scanning the translational velocity over a wide range. Thereby, beams of any atom or molecule available as a gas can be slowed or speeded. Using Xe beams in the slowing mode, we have obtained lab speeds down to about 40 ± 5 m/s with density near 10(11) cm(-3) and in the speeding mode lab speeds up to about 660 m/s and density near 10(14) cm(-3). We discuss some congenial applications. Providing low lab speeds can markedly enhance experiments using electric or magnetic fields to deflect, steer, or further slow polar or paramagnetic molecules. The capability to scan molecular speeds facilitates merging velocities with a codirectional partner beam, enabling study of collisions at very low relative kinetic energies, without requiring either beam to be slow. PMID:27370474

  19. Production of high density molecular beams with wide velocity scanning

    NASA Astrophysics Data System (ADS)

    Sheffield, L. S.; Woo, S. O.; Rathnayaka, K. D. D.; Lyuksyutov, I. F.; Herschbach, D. R.

    2016-06-01

    We describe modifications of a pulsed rotating supersonic beam source that improve performance, particularly increasing the beam density and sharpening the pulse profiles. As well as providing the familiar virtues of a supersonic molecular beam (high intensity, narrowed velocity distribution, and drastic cooling of rotation and vibration), the rotating source enables scanning the translational velocity over a wide range. Thereby, beams of any atom or molecule available as a gas can be slowed or speeded. Using Xe beams in the slowing mode, we have obtained lab speeds down to about 40 ± 5 m/s with density near 1011 cm-3 and in the speeding mode lab speeds up to about 660 m/s and density near 1014 cm-3. We discuss some congenial applications. Providing low lab speeds can markedly enhance experiments using electric or magnetic fields to deflect, steer, or further slow polar or paramagnetic molecules. The capability to scan molecular speeds facilitates merging velocities with a codirectional partner beam, enabling study of collisions at very low relative kinetic energies, without requiring either beam to be slow.

  20. Resonant Orbits and the High Velocity Peaks toward the Bulge

    NASA Astrophysics Data System (ADS)

    Molloy, Matthew; Smith, Martin C.; Evans, N. Wyn; Shen, Juntai

    2015-10-01

    We extract the resonant orbits from an N-body bar that is a good representation of the Milky Way, using the method recently introduced by Molloy et al. By decomposing the bar into its constituent orbit families, we show that they are intimately connected to the boxy-peanut shape of the density. We highlight the imprint due solely to resonant orbits on the kinematic landscape toward the Galactic center. The resonant orbits are shown to have distinct kinematic features and may be used to explain the cold velocity peak seen in the Apache Point Observatory Galactic Evolution Experiment commissioning data. We show that high velocity peaks are a natural consequence of the motions of stars in the 2:1 orbit family and that stars on other higher order resonances can contribute to the peaks. The locations of the peaks vary with bar angle and, with the tacit assumption that the observed peaks are due to the 2:1 family, we find that the locations of the high velocity peaks correspond to bar angles in the range {10}\\circ ≲ {θ }{bar}≲ 25^\\circ . However, some important questions about the nature of the peaks remain, such as their apparent absence in other surveys of the Bulge and the deviations from symmetry between equivalent fields in the north and south. We show that the absence of a peak in surveys at higher latitudes is likely due to the combination of a less prominent peak and a lower number density of bar supporting orbits at these latitudes.

  1. High Velocity Impact Response of Composite Lattice Core Sandwich Structures

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Zhang, Guoqi; Wang, Shixun; Ma, Li; Wu, Linzhi

    2014-04-01

    In this research, carbon fiber reinforced polymer (CFRP) composite sandwich structures with pyramidal lattice core subjected to high velocity impact ranging from 180 to 2,000 m/s have been investigated by experimental and numerical methods. Experiments using a two-stage light gas gun are conducted to investigate the impact process and to validate the finite element (FE) model. The energy absorption efficiency (EAE) in carbon fiber composite sandwich panels is compared with that of 304 stainless-steel and aluminum alloy lattice core sandwich structures. In a specific impact energy range, energy absorption efficiency in carbon fiber composite sandwich panels is higher than that of 304 stainless-steel sandwich panels and aluminum alloy sandwich panels owing to the big density of metal materials. Therefore, in addition to the multi-functional applications, carbon fiber composite sandwich panels have a potential advantage to substitute the metal sandwich panels as high velocity impact resistance structures under a specific impact energy range.

  2. High-velocity streams of dust originating from Saturn.

    PubMed

    Kempf, Sascha; Srama, Ralf; Horányi, Mihaly; Burton, Marcia; Helfert, Stefan; Moragas-Klostermeyer, Georg; Roy, Mou; Grün, Eberhard

    2005-01-20

    High-velocity submicrometre-sized dust particles expelled from the jovian system have been identified by dust detectors on board several spacecraft. On the basis of periodicities in the dust impact rate, Jupiter's moon Io was found to be the dominant source of the streams. The grains become positively charged within the plasma environment of Jupiter's magnetosphere, and gain energy from its co-rotational electric field. Outside the magnetosphere, the dynamics of the grains are governed by the interaction with the interplanetary magnetic field that eventually forms the streams. A similar process was suggested for Saturn. Here we report the discovery by the Cassini spacecraft of bursts of high-velocity dust particles (> or = 100 km s(-1)) within approximately 70 million kilometres of Saturn. Most of the particles detected at large distances appear to originate from the outskirts of Saturn's outermost main ring. All bursts of dust impacts detected within 150 Saturn radii are characterized by impact directions markedly different from those measured between the bursts, and they clearly coincide with the spacecraft's traversals through streams of compressed solar wind.

  3. High-velocity streams of dust originating from Saturn.

    PubMed

    Kempf, Sascha; Srama, Ralf; Horányi, Mihaly; Burton, Marcia; Helfert, Stefan; Moragas-Klostermeyer, Georg; Roy, Mou; Grün, Eberhard

    2005-01-20

    High-velocity submicrometre-sized dust particles expelled from the jovian system have been identified by dust detectors on board several spacecraft. On the basis of periodicities in the dust impact rate, Jupiter's moon Io was found to be the dominant source of the streams. The grains become positively charged within the plasma environment of Jupiter's magnetosphere, and gain energy from its co-rotational electric field. Outside the magnetosphere, the dynamics of the grains are governed by the interaction with the interplanetary magnetic field that eventually forms the streams. A similar process was suggested for Saturn. Here we report the discovery by the Cassini spacecraft of bursts of high-velocity dust particles (> or = 100 km s(-1)) within approximately 70 million kilometres of Saturn. Most of the particles detected at large distances appear to originate from the outskirts of Saturn's outermost main ring. All bursts of dust impacts detected within 150 Saturn radii are characterized by impact directions markedly different from those measured between the bursts, and they clearly coincide with the spacecraft's traversals through streams of compressed solar wind. PMID:15662418

  4. High velocity collisions - probing the edge of planetesimal growth

    NASA Astrophysics Data System (ADS)

    Teiser, J.; Wurm, G.

    2008-09-01

    field damage around the direct impact site. This near field damage can range from a thin circular trench around the sticking projectile material to a crater which also includes the impact site as material loss. Figure 1 gives an example for a collision with near field damage leading to mass loss. The balance between these two processes determines the mass balance of a collision. (3) When the impact energies are too high a large area of the target surface can be eroded away. This far field damage depends on the target size and thus is not important for realistic conditions. Due to the size dependance of the balance between near and far field damage small projectiles can lead to a net growth even with high velocities. Conclusions Based on experimental results we present a growth model which can be a solution to the question how planetesimal growth is possible once dust aggregates are compact and velocities tend to be destructive. Projectiles of a few mm in size hit a larger aggregate with a size of ~30 cm and leave a crater in the target surface which leads to a slight mass loss. In this colision the projectiles fragment into smaller pieces whereas the target mass hardly changes. In processes of this kind a large amount of sub-mm particles is formed which can lead to a mass gain in a following collisions. Although fragmentation plays a significant role in the high velocity range planetesimal growth via mutual collisions is possible. References [1] Blum, J. and Wurm, G. (2008) ARAA, in press. [2] Dominik, C. and Tielens, A. G. G. M. (1997) ApJ,480, 647-673. [3] Weidenschilling, S. J. and Cuzzi, J. N. (1993) in Levy, E. H. and Lunine, J. I., Protostars and Planets III, 1031-1060. [4] Blum, J. and Münch, (1993) Icarus, 106, 98-116. [5] Wurm, G. et al. (2005) Icarus, 178, 253-263.

  5. A model for ductile metal friction at high velocities

    NASA Astrophysics Data System (ADS)

    Hammerberg, J. E.; Ravelo, R. J.; Germann, T. C.

    We describe a meso-macro scale model for the frictional force at ductile metal interfaces for high velocities and large compressions. The model incorporates the micro-mesoscopic growth and refinement of material microstructure in a highly strained region at the sliding interface and incorporates both rate dependent plasticity and thermal conduction. The model compares favorably with recent large scale (1.8 billion atom) simulations to 50 ns of 3-dimensional polycrystalline 13-50 nm grain size Al-Al interfaces at pressures of 15 GPa using the SPaSM NonEquilibrium Molecular Dynamics (NEMD) simulation code. This work was performed under the auspices of the U.S. Dept. of Energy under Contract DE-AC52-06NA25396. The support of the LANL ASC-PEM program is gratefully acknowledged.

  6. Lyman-Alpha Observations of High Radial Velocity Stars

    NASA Astrophysics Data System (ADS)

    Bookbinder, Jay

    1990-12-01

    H I LYMAN -ALPHA (LY-A) IS ONE OF THE MOST IMPORTANT LINES EMITTED BY PLASMA IN THE TEMPERATURE RANGE OF 7000 TO 10 TO THE FIFTH POWER K IN LATE-TYPE STARS. IT IS A MAJOR COMPONENT OF THE TOTAL RADIATIVE LOSS RATE, AND IT PLAYS A CRUCIAL ROLE IN DETERMINING THE ATMOSPHERIC STRUCTURE AND IN FLUORESCING OTHER UV LINES. YET IT IS ALSO THE LEAST STUDIED MAJOR LINE IN THE FAR UV, BECAUSE MOST OF THE LINE FLUX IS ABSORBED BY THE ISM ALONG THE LINE OF SIGHT AND BECAUSE IT IS STRONGLY COMTAMINATED BY THE GEOCORONAL BACKGROUND. A KNOWLEDGE OF THE Ly-A PROFILE IS ALSO IMPORTANT FOR STUDIES OF DEUTERIUM IN THE INTERSTELLAR MEDIUM. BY OBSERVING HIGH RADIAL VELOCITY STARS WE WILL OBTAIN FOR THE FIRST TIME HIGH RESOLUTION SPECTRA OF THE CORE OF A STELLAR H I LYMAN-A EMISSION LINE PROFILE.

  7. Compressional velocity measurements for a highly fractured lunar anorthosite

    NASA Technical Reports Server (NTRS)

    Sondergeld, C. H.; Granryd, L. A.; Spetzler, H. A.

    1979-01-01

    The compressional wave (V sub p) velocities in three mutually perpendicular directions have been measured in lunar sample 60025,174, lunar anorthosite. V sub p measurements were made at ambient temperature and pressure and a new technique was developed to measure the velocities because of the tremendous acoustic wave attenuation of the lunar sample. The measured velocities were all less than 1 km/sec and displayed up to a 21% departure from the mean value of the three directions. The velocities agree with seismic wave velocities determined for the lunar surface at the collection site.

  8. Robustness of waves with a high phase velocity

    NASA Astrophysics Data System (ADS)

    Tajima, T.; Necas, A.

    2016-03-01

    Norman Rostoker pioneered research of (1) plasma-driven accelerators and (2) beam-driven fusion reactors. The collective acceleration, coined by Veksler, advocates to drive above-ionization plasma waves by an electron beam to accelerate ions. The research on this, among others, by the Rostoker group incubated the idea that eventually led to the birth of the laser wakefield acceleration (LWFA), by which a large and robust accelerating collective fields may be generated in plasma in which plasma remains robust and undisrupted. Besides the emergence of LWFA, the Rostoker research spawned our lessons learned on the importance of adiabatic acceleration of ions in collective accelerators, including the recent rebirth in laser-driven ion acceleration efforts in a smooth adiabatic fashion by a variety of ingenious methods. Following Rostoker's research in (2), the beam-driven Field Reversed Configuration (FRC) has accomplished breakthroughs in recent years. The beam-driven kinetic plasma instabilities have been found to drive the reactivity of deuteron-deuteron fusion beyond the thermonuclear yield in C-2U plasma that Rostoker started. This remarkable result in FRCs as well as the above mentioned LWFA may be understood with the aid of the newly introduced idea of the "robustness hypothesis of waves with a high phase velocity". It posits that when the wave driven by a particle beam (or laser pulse) has a high phase velocity, its amplitude is high without disrupting the supporting bulk plasma. This hypothesis may guide us into more robust and efficient fusion reactors and more compact accelerators.

  9. SPE (tm) regenerative hydrogen/oxygen fuel cells for extraterrestrial surface and microgravity applications

    NASA Technical Reports Server (NTRS)

    Mcelroy, J. F.

    1990-01-01

    Viewgraphs on SPE regenerative hydrogen/oxygen fuel cells for extraterrestrial surface and microgravity applications are presented. Topics covered include: hydrogen-oxygen regenerative fuel cell energy storage system; electrochemical cell reactions; SPE cell voltage stability; passive water removal SPE fuel cell; fuel cell performance; SPE water electrolyzers; hydrophobic oxygen phase separator; hydrophilic/electrochemical hydrogen phase separator; and unitized regenerative fuel cell.

  10. Effects of using oxygenated fuels on carbon monoxide, formaldehyde and acetaldehyde concentrations in Denver

    SciTech Connect

    Anderson, L.G.; Lanning, J.A.; Wilkes, E.; Jones, R.H.; Wolfe, P.

    1997-12-31

    Oxygenated fuels have been used during the winters in Denver since January 1988, in an attempt to reduce the atmospheric concentration of carbon monoxide. The authors began monitoring ambient concentrations of formaldehyde and acetaldehyde in Denver in December 1987 and have continued that monitoring every winter since. They now have nine seasons of ambient carbonyl data that coincide with oxygenated fuels usage. The authors will present results of the continuing analyses of atmospheric concentration data for CO collected in the Denver area, to determine the effectiveness of the program for reducing ambient CO. The program has been found to have near zero effect at the downtown Denver site, and 5%--12% reductions at several other sites. The formaldehyde and acetaldehyde concentration data will be analyzed to determine the effects of changing oxygenate concentration and composition on carbonyl concentrations. No significant effects have been found on either the concentrations of formaldehyde or acetaldehyde. The authors have also begun analyses of Colorado mandated IM240 emissions test data for CO and NO{sub x} for tests done during an oxygenated fuels period (January, February, November and December 1995) and a nonoxygenated fuels period (April through September 1995). A preliminary analysis of data for more than 100,000 vehicles suggests that oxygenated fuels lead to a reduction of CO emissions of about 13.4% and an increase of NO{sub x} emissions of about 14.6%, as a test fleet weighted average.

  11. 29 CFR 1910.253 - Oxygen-fuel gas welding and cutting.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... accordance with the regulations of the U.S. Department of Transportation, 49 CFR parts 171-179. (ii... 29 Labor 5 2014-07-01 2014-07-01 false Oxygen-fuel gas welding and cutting. 1910.253 Section 1910..., DEPARTMENT OF LABOR OCCUPATIONAL SAFETY AND HEALTH STANDARDS Welding, Cutting and Brazing § 1910.253...

  12. 29 CFR 1910.253 - Oxygen-fuel gas welding and cutting.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... accordance with the regulations of the U.S. Department of Transportation, 49 CFR parts 171-179. (ii... 29 Labor 5 2013-07-01 2013-07-01 false Oxygen-fuel gas welding and cutting. 1910.253 Section 1910..., DEPARTMENT OF LABOR OCCUPATIONAL SAFETY AND HEALTH STANDARDS Welding, Cutting and Brazing § 1910.253...

  13. Methods of Measurement of High Air Velocities by the Hot-wire Method

    NASA Technical Reports Server (NTRS)

    Weske, John R.

    1943-01-01

    Investigations of strengths of hot wires at high velocities were conducted with platinum, nickel, and tungsten at approximately 200 Degrees Celcius hot-wire temperature. The results appear to disqualify platinum for velocities approaching the sonic range; whereas nickel withstands sound velocity, and tungsten may be used for supersonic velocities under standard atmospheric conditions. Hot wires must be supported by rigid prolongs at high velocities to avoid wire breakage. Resting current measurements for constant temperature show agreement with King's relation.

  14. The acceleration of high-velocity clouds in supernova remnants

    NASA Technical Reports Server (NTRS)

    Mckee, C. F.; Cowie, L. L.; Ostriker, J. P.

    1978-01-01

    Interstellar clouds passed by blast waves emanating from supernova explosions will be accelerated by the ram pressure of the expanding interior shocked gas. We present numerical and analytical solutions for cloud acceleration in this environment, comparing the results with recent observations of faint, high-velocity (greater than 100 km/sec) filaments observed in Cygnus and Vela. Photons from the conductive interface between the clouds and the surrounding medium can provide the ionizing flux necessary for observable optical emission. Several predictions are made, the most important of which is that fast clouds of neutral hydrogen with column densities of about 10 quintillion per sq cm should be observable in 21 cm studies of SNRs.

  15. Deployable Emergency Shutoff Device Blocks High-Velocity Fluid Flows

    NASA Technical Reports Server (NTRS)

    Nabors, Sammy A.

    2015-01-01

    NASA's Marshall Space Flight Center has developed a device and method for blocking the flow of fluid from an open pipe. Motivated by the sea-bed oil-drilling catastrophe in the Gulf of Mexico in 2010, NASA innovators designed the device to plug, control, and meter the flow of gases and liquids. Anchored with friction fittings, spikes, or explosively activated fasteners, the device is well-suited for harsh environments and high fluid velocities and pressures. With the addition of instrumentation, it can also be used as a variable area flow metering valve that can be set based upon flow conditions. With robotic additions, this patent-pending innovation can be configured to crawl into a pipe then anchor and activate itself to block or control fluid flow.

  16. Solar wind collimation of the Jupiter high velocity dust streams

    NASA Astrophysics Data System (ADS)

    Flandes, A.; Krueger, H.

    2006-12-01

    The dust bursts discovered by the Ulysses dust sensor when approaching Jupiter in 1992 were later confirmed as collimated streams of high velocity (~200 km/s) charged (~5V) dust grains escaping from Jupiter and dominated by the interplanetary Magnetic field (IMF). With Cassini, a similar phenomenon was observed in Saturn. It was demonstrated that the Jovian dust streams are closely related to the solar wind compressed regions, either Corotating interaction regions (CIRs) or Coronal mass ejections (CMEs) ¨Cto a minor extent-. Actually the dust streams seem ultimately to be generated by such events. This can be explained considering that dust grains are accelerated as they gain substantial energy while compressed at the forward and reverse shocks that bound or precede these solar wind regions.

  17. Characterization of high velocity oxy-fuel combustion sprayed hydroxyapatite.

    PubMed

    Haman, J D; Lucas, L C; Crawmer, D

    1995-02-01

    Bioceramic coatings, created by the high velocity oxy-fuel combustion spraying of hydroxyapatite (HA) powders onto commercially pure titanium, were characterized in order to determine whether this relatively new coating process can be successfully applied to bioceramic coatings of orthopaedic and dental implants. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to characterize both the HA starting powders and coatings. A 12 wk immersion test was conducted and the resulting changes in the coatings were also characterized. Calcium ion release during dissolution was measured with flame atomic absorption during the first 6 weeks of the immersion study. A comparison of powder and coating X-ray diffraction patterns and lattice parameters revealed an HA-type coating with some loss in crystallinity. Fourier transform infrared results showed a partial loss of the OH- group during spraying, however the phosphate groups were still present. Scanning electron microscopy analysis showed a lamellar structure with very close coating-to-substrate apposition. The coatings experienced a loss of calcium during the immersion study, with the greatest release in calcium occurring during the first 6 days of the study. No significant structural or chemical changes were observed during the 12 wk immersion study. These results indicate that the high velocity oxy-fuel process can produce an HA-type coating; however, the process needs further optimization, specifically in the areas of coating-to-substrate bond strength and minimization of phases present other than HA, before it would be recommended for commercial use.

  18. Probability density distribution of velocity differences at high Reynolds numbers

    NASA Technical Reports Server (NTRS)

    Praskovsky, Alexander A.

    1993-01-01

    Recent understanding of fine-scale turbulence structure in high Reynolds number flows is mostly based on Kolmogorov's original and revised models. The main finding of these models is that intrinsic characteristics of fine-scale fluctuations are universal ones at high Reynolds numbers, i.e., the functional behavior of any small-scale parameter is the same in all flows if the Reynolds number is high enough. The only large-scale quantity that directly affects small-scale fluctuations is the energy flux through a cascade. In dynamical equilibrium between large- and small-scale motions, this flux is equal to the mean rate of energy dissipation epsilon. The pdd of velocity difference is a very important characteristic for both the basic understanding of fully developed turbulence and engineering problems. Hence, it is important to test the findings: (1) the functional behavior of the tails of the probability density distribution (pdd) represented by P(delta(u)) is proportional to exp(-b(r) absolute value of delta(u)/sigma(sub delta(u))) and (2) the logarithmic decrement b(r) scales as b(r) is proportional to r(sup 0.15) when separation r lies in the inertial subrange in high Reynolds number laboratory shear flows.

  19. High velocity vortex channeling in vicinal YBCO thin films.

    PubMed

    Puica, I; Lang, W; Durrell, J H

    2012-09-01

    We report on electrical transport measurements at high current densities on optimally doped YBa2Cu3O7-δ thin films grown on vicinal SrTiO3 substrates. Data were collected by using a pulsed-current technique in a four-probe arrangement, allowing to extend the current-voltage characteristics to high supercritical current densities (up to 24 MA cm(-2)) and high electric fields (more than 20 V/cm), in the superconducting state at temperatures between 30 and 80 K. The electric measurements were performed on tracks perpendicular to the vicinal step direction, such that the current crossed between ab planes, under magnetic field rotated in the plane defined by the crystallographic c axis and the current density. At magnetic field orientation parallel to the cuprate layers, evidence for the sliding motion along the ab planes (vortex channeling) was found. The signature of vortex channeling appeared to get enhanced with increasing electric field, due to the peculiar depinning features in the kinked vortex range. They give rise to a current-voltage characteristics steeper than in the more off-plane rectilinear vortex orientations, in the electric field range below approximately 1 V/cm. Roughly above this value, the high vortex channeling velocities (up to 8.6 km/s) could be ascribed to the flux flow, although the signature of ohmic transport appeared to be altered by unavoidable macroscopic self-heating and hot-electron-like effects.

  20. Fault gouge rheology under confined, high-velocity conditions

    NASA Astrophysics Data System (ADS)

    Reches, Z.; Madden, A. S.; Chen, X.

    2012-12-01

    We recently developed the experimental capability to investigate the shear properties of fine-grain gouge under confined conditions and high-velocity. The experimental system includes a rotary apparatus that can apply large displacements of tens of meters, slip velocity of 0.001- 2.0 m/s, and normal stress of 35 MPa (Reches and Lockner, 2010). The key new component is a Confined ROtary Cell (CROC) that can shear a gouge layer either dry or under pore-pressure. The pore pressure is controlled by two syringe pumps. CROC includes a ring-shape gouge chamber of 62.5 mm inner diameter, 81.25 mm outer diameter, and up to 3 mm thick gouge sample. The lower, rotating part of CROC contains the sample chamber, and the upper, stationary part includes the loading, hollow cylinder and setting for temperature, and dilation measurements, and pore-pressure control. Each side of the gouge chamber has two pairs of industrial, spring-energized, self-lubricating, teflon-graphite seals, built for particle media and can work at temperature up to 250 ded C. The space between each of the two sets of seals is pressurized by nitrogen. This design generates 'zero-differential pressure' on the inner seal (which is in contact with the gouge powder), and prevents gouge leaks. For the preliminary dry experiments, we used ~2.0 mm thick layers of room-dry kaolinite powder. Total displacements were on the order of meters and normal stress up to 4 MPa. The initial shear was accommodated by multiple internal slip surfaces within the kaolinite layer accommodated as oriented Riedel shear structures. Later, the shear was localized within a thin, plate-parallel Y-surface. The kaolinite layer was compacted at a quasi-asymptotic rate, and displayed a steady-state friction coefficient of ~ 0.5 with no clear dependence on slip velocity up to 0.15 m/s. Further experiments with loose quartz sand (grain size ~ 125 micron) included both dry runs and pore-pressure (distilled water) controlled runs. The sand was

  1. Entrainment in High-Velocity, High Temperature Plasma Jets Part I: Experimental Results

    SciTech Connect

    Fincke, J.R.; Crawford, D.M.; Snyder, S.C.; Swank, W.D.; Haggard, D.C.; Williamson, R.L.

    2002-03-27

    The development of a high-velocity, high-temperature argon plasma jet issuing into air has been investigated. In particular the entrainment of the surrounding air, its effect on the temperature and velocity profiles and the subsequent mixing and dissociation of oxygen has been examined in detail. The total concentration of oxygen and the velocity and temperature profiles in the jet were obtained from an enthalpy probe. High-resolution Thomson scattering provided an independent measure of plasma velocity and temperature, validating enthalpy probe measurements and providing non-intrusive measurements near the nozzle exit. The concentration of atomic oxygen was obtained from two-photon Laser Induced Fluorescence (LIF). Molecular oxygen concentration and temperature was obtained from Coherent Anti-Stokes Raman Spectroscopy (CARS). It was found that both the incompleteness of mixing at the molecular scale and the rate of oxygen dissociation and recombination effects jet behavior.

  2. High-density aerogels with ultralow sound velocity: Microstructure is a key parameter determining the sound velocity

    NASA Astrophysics Data System (ADS)

    Du, Ai; Zhou, Bin; Shen, Yang; Yu, Qiujie; Shen, Jun

    2014-03-01

    Aerogels are more and more regarded as a new state of matter nowadays because of its diverse chemical compositions and unique properties which could fill the gap between condensed matter and gas-state matter. Among the properties, the ultralow sound velocity in the aerogels (lower than that in the air) is of great interests. J. Fricke's group studied many kinds of aerogels with different compositions and found that the sound velocity was mainly influenced by the density. Thus they obtained the lowest sound velocity result (~ 100 m/s) in a low-density silica aerogel medium (~ 0.05 g.cm-3) . Here we studied the acoustical properties of the aerogels with the similar high density (about 1.3 g.cm-3) but different skeleton structure (nano-, micro- or nano-/micro- structured) by adjusting the phase separation mode. The sound velocities of all the aerogels are below 300 m.s-1, among which micro-/nano- structured aerogel exhibits lowest longitudinal wave velocity (below 80 m.s-1) . Further structural studies indicated that the hierarchical arrangement of microstructure is the key parameter determining the sound velocity besides the density. This work was supported by the National Natural Science Foundation of China (51102184, 51172163), National High-tech R&D Program of China (863 Program, 2013AA031801) and National Science and Technology Support Program (2013BAJ01B01).

  3. Numerical Investigation of High Velocity Suspension Flame Spraying

    NASA Astrophysics Data System (ADS)

    Taleby, M.; Hossainpour, S.

    2012-12-01

    High-velocity suspension flame spraying (HVSFS) has recently developed as a possible alternative to conventional HVOF-spraying employing liquid suspensions instead of dry powder feedstock enables the use of nanoparticles. From the fluid dynamics point of view, the HVSFS system is complex and involves three-phase (gas, liquid and solid particles) turbulent flow, heat transfer, evaporation of the suspension solvent, chemical reactions of main fuel (propane) and suspension solvent (ethanol) and supersonic/subsonic flow transitions. Computational fluid dynamic techniques were carried out to solve the mass, momentum, and energy conservation equations. The realizable k-ɛ turbulence model was used to account for the effect of turbulence. The HVSFS process involves two combustion reactions. A primary combustion process is the premixed oxygen-propane reaction and secondary process is the non-premixed oxygen-gaseous ethanol reaction. For each reaction, one step global reaction, which takes dissociations and intermediate reactions into account, was derived from the equilibrium chemistry code developed by Gordon and McBride and eddy dissipation model was used to calculate the rate of reactions based on the transport equations for all species (10 species) mass fractions. Droplets were tracked in the continuum in a Lagrangian approach. In this paper, flow field inside and outside the gun simulated to provide clear and complete insight about the HVSFS processes. Moreover, the effect of some operative parameters (oxy-fuel flow rate, ethanol flow rate, droplets injection velocity and droplets size) on the gas flow field along the centerline and droplets evaporation behavior was discussed.

  4. High velocity properties of the dynamic frictional force between ductile metals

    SciTech Connect

    Hammerberg, James Edward; Hollan, Brad L; Germann, Timothy C; Ravelo, Ramon J

    2010-01-01

    The high velocity properties of the tangential frictional force between ductile metal interfaces seen in large-scale NonEquilibrium Molecular Dynamics (NEMD) simulations are characterized by interesting scaling behavior. In many cases a power law decrease in the frictional force with increasing velocity is observed at high velocities. We discuss the velocity dependence of the high velocity branch of the tangential force in terms of structural transformation and ultimate transition, at the highest velocities, to confined fluid behavior characterized by a critical strain rate. The particular case of an Al/Al interface is discussed.

  5. Increased ductility in high velocity electromagnetic ring expansion

    NASA Astrophysics Data System (ADS)

    Altynova, Marina; Hu, Xiaoyu; Daehn, Glenn S.

    1996-07-01

    Thin rings have been rapidly expanded using large, transient magnetic fields to study the effect of deformation velocity on strains to failure of ductile metals. A classical electrodynamics analysis similar to one developed previously by Gourdin was employed to estimate sample velocities. Within expansion velocities studied (50 to 300 m/s), the experimental results show that ductility of Al 6061 and OFHC Cu increases monotonically with increasing velocity. In each case, sample strain at failure is almost twice as great at 300 m/s as in the static condition. Comparison to a one-dimensional rigid-viscoplastic dynamic finite element method analysis suggests that inertial effects are mainly responsible for enhanced ductility over a wide range of velocity.

  6. Photonic systems for high precision radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Halverson, Samuel

    2016-01-01

    I will discuss new instrumentation and techniques designed to maximize the Doppler radial velocity (RV) measurement precision of next generation exoplanet discovery instruments. These systems include a novel wavelength calibration device based on an all-fiber fabry-perot interferometer, a compact and efficient optical fiber image scrambler based on a single high-index ball lens, and a unique optical fiber mode mixer. These systems have been developed specifically to overcome three technological hurdles that have classically hindered high precision RV measurements in both the optical and near-infrared (NIR), namely: lack of available wavelength calibration sources, inadequate decoupling of the spectrograph from variable telescope illumination, and speckle-induced noise due to mode interference in optical fibers. The instrumentation presented here will be applied to the Habitable-zone Planet Finder, a NIR RV instrument designed to detect rocky planets orbiting in the habitable zones of nearby M-dwarfs, and represents a critical technological step towards the detection of potentially habitable Earth-like planets. While primarily focused in the NIR, many of these systems will be adapted to future optical RV instruments as well, such as NASA's new Extreme Precision Doppler Spectrometer for the WIYN telescope.

  7. Fault strength evolution during high velocity friction experiments with slip-pulse and constant-velocity loading

    NASA Astrophysics Data System (ADS)

    Liao, Z.; Chang, J. C.; Reches, Z.

    2014-12-01

    Seismic analyses show that slip during large earthquakes evolves in a slip-pulse mode that is characterized by abrupt, intense acceleration followed by moderate deceleration. We experimentally analyze the friction evolution under slip-pulse proxy of a large earthquake, and compare it with the evolution at loading modes of constant-velocity and changing-velocity. We present a series of 42 experiments conducted on granite samples sheared in a high-velocity rotary apparatus. The experiments were conducted on room-dry, solid granite samples at slip-velocities of 0.0006-1 m/s, and normal stress of 1-11.5 MPa. The constitutive relations are presented with respect to mechanical power-density: PD= [shear stress * slip velocity], with units of power per area (MW/m^2). The experimental constitutive relations strongly depend on the loading mode. Constant velocity mode displays initial weakening with increasing PD that is followed by strengthening for PD = 0.02-0.5 MW/m^2, and abrupt weakening at PD > 0.5 MW/m^2. Changing-velocity modes display gentle strengthening for PD < 0.2 MW/m^2 that is followed by abrupt weakening as PD reaches 0.7-0.8 MW/m^2. Beyond this level of power-density, the two loading modes diverge: in changing-velocity of quake-mode the experimental fault continues to weaken with friction coefficient approaching 0.2, whereas in changing-velocity of ramp-mode the fault strengthens with friction coefficient approaching 1.0. The analysis demonstrates that (1) the strength evolution and constitutive parameters of the granite fault strongly depend on the loading mode, and (2) the slip-pulse mode is energy efficient relatively to the constant-velocity mode as manifested by faster, more intense weakening and 50-90% lower energy dissipation. The results suggest that the frictional strength determined in slip-pulse experiments, is more relevant to simulations of earthquake rupture than frictional strength determined in constant-velocity experiments.Figure 1. Friction

  8. New electrocatalysts for hydrogen-oxygen fuel cells

    NASA Technical Reports Server (NTRS)

    Cattabriga, R. A.; Giner, J.; Parry, J.; Swette, L. L.

    1970-01-01

    Platinum-silver, palladium-gold, and platinum-gold alloys serve as oxygen reduction catalysts in high-current-density cells. Catalysts were tested on polytetrafluoroethylene-bonded cathodes and a hydrogen anode at an operating cell temperature of 80 degrees C.

  9. High velocity Herbig-Haro objects near CEP A

    NASA Astrophysics Data System (ADS)

    Lenzen, R.

    1988-01-01

    The discovery of a new Herbig-Haro object 2 arcmin northeast of Cep A is reported. High proper motions for this object and of various H-alpha knots west of Cep A (in GGD 37), are deduced by comparing new H-alpha images with the Palomar sky survey. For a distance of 725 pc, tangential velocities of 110 to 250 km/s are derived which have their common origin near the compact H II regions 2 and 3 (Hughes, 1985). The resulting kinematic age is 1800 + or - 400 yr. A weak pointlike source (I = 20.6 mag) is detected at the position of the compact H II region 3a. No further source (I less than or equal to 23 mag) could be found in the region of radio continuum emission. However, an elongated feature of diffuse 1-micron emission is observed in line with the northern chain of compact radio knots, which is directed from the central source to the new Herbig-Hero object. It is concluded that a center of activity near the H2O maser positions is responsible for Cep A, drives the molecular outflow, and also excites the compact radio continuum knots and surrounding HH objects. The observed total luminosity and the 21-cm radio continuum data are consistent with a B0.5V star or three B1 V ZAMS stars.

  10. High-velocity Bipolar Molecular Emission from an AGN Torus

    NASA Astrophysics Data System (ADS)

    Gallimore, Jack F.; Elitzur, Moshe; Maiolino, Roberto; Marconi, Alessandro; O'Dea, Christopher P.; Lutz, Dieter; Baum, Stefi A.; Nikutta, Robert; Impellizzeri, C. M. V.; Davies, Richard; Kimball, Amy E.; Sani, Eleonora

    2016-09-01

    We have detected in ALMA observations CO J=6\\to 5 emission from the nucleus of the Seyfert galaxy NGC 1068. The low-velocity (up to ±70 km s-1 relative to systemic) CO emission resolves into a 12 × 7 pc structure, roughly aligned with the nuclear radio source. Higher-velocity emission (up to ±400 km s-1) is consistent with a bipolar outflow in a direction nearly perpendicular (≃80°) to the nuclear disk. The position-velocity diagram shows that in addition to the outflow, the velocity field may also contain rotation about the disk axis. These observations provide compelling evidence in support of the disk-wind scenario for the active galactic nucleus obscuring torus.

  11. Application on Oxygenated Fuel of Mono-Ether Group in AN Idi Diesel Engine

    NASA Astrophysics Data System (ADS)

    Kim, Hyung-Gon; Choi, Seung-Hun; Oh, Young-Taig

    Effect of oxygen components of fuels on exhaust emissions has been investigated by applying an indirect injection (IDI) diesel engine. This research analyzed variation and/or difference of the engine performance and exhaust emission characteristics of the IDI diesel engine by fueling the commercial diesel fuel and four different mixed ratios of oxygenated blended fuels. Effect of the exhaust gas recirculation (EGR) method was analyzed on the NOx emission characteristics. Ethylene glycol mono-n-butyl ether (EGBE) contains 27% of oxygen components in itself, and it is a kind of effective oxygenated fuel of mono-ether group. Smoke emission from the EGBE was reduced remarkably relative to the commercial diesel fuel. The EGBE can supply oxygen components sufficiently at higher diesel engine loads and speeds. It was found that a simultaneous reduction of the smoke and the NOx was achieved with the oxygenated fuel (10 vol-%) and the cooled EGR method (10%).

  12. New oxygen-fuel burner significantly improves electric arc furnace productivity with less energy consumption

    SciTech Connect

    Untz, J.; Knowles, D.

    1984-11-01

    This article describes a new system of electric arc steelmaking based on use of oxygen with newly designed burner for increased productivity and reduced energy consumption. The need for the oxygen-fuel burner has been recognized for years. Because of the shape of the flux lines of the arc between electrodes, some areas receive much more heat than others and consequently melt faster, leaving portions of the furnace charge unmelted for some time. Until these cold areas are melted into the bath, the arcing process must continue in a less efficient mode, delaying the completion of the process and therefore reducing productivity and using more energy. Steelmakers have been looking for a heat source to apply to these cold areas so that all material would melt at the same time. The oxygen-fuel burner was chosen because of its ability to deliver a directed flame at temperatures nearing 5000/sup 0/F.

  13. A coupled-physics model for the vanadium oxygen fuel cell

    NASA Astrophysics Data System (ADS)

    Wandschneider, F. T.; Küttinger, M.; Noack, J.; Fischer, P.; Pinkwart, K.; Tübke, J.; Nirschl, H.

    2014-08-01

    A stationary two-dimensional model for the vanadium oxygen fuel cell is developed. The model consists of a single cell with two membranes, set up as of two half-cells and an intermediate chamber. The transport and balance of mass, momentum and charge are linked to the electrochemical reaction kinetics of the vanadium species and oxygen. The kinetic model for the cathode half-cell is extended by an empirical logistic function to describe the transient behavior of the half-cell. Additionally, experiments are conducted on a single vanadium oxygen fuel cell with 40 cm2 active membrane area. The experimental results are used to validate the simulation data. The effects of constant current discharging, polarization behavior and different flow rates on the cathode overpotential are studied by means of this model.

  14. IMPACT OF OXYGENATED FUEL ON DIESEL ENGINE PERFORMANCE AND EMISSIONS

    SciTech Connect

    Boehman, Andre L.

    2000-08-20

    potential improvements in energy efficiency within the transportation section, particularly in sport utility vehicles and light-duty trucks, that can be provided by deployment of diesel engines in passenger cars and trucks is a strong incentive to develop cleaner burning diesel engines and cleaner burning fuels for diesel engines. Thus, serious consideration of oxygenated diesel fuels is of significant practical interest and value to society. In the present work, a diesel fuel reformulating agent, CETANERTM, has been examined in a popular light-medium duty turbodiesel engine over a range of blending ratios. This additive is a mixture of glycol ethers and can be produced from dimethyl ether, which itself can be manufactured from synthesis gas using Air Products' Liquid Phase Dimethyl Ether (LPDME TM) technology. CETANERTM is a liquid, has an oxygen content of 36 wt.%, has a cetane number over 100 and is highly miscible in diesel fuel. This combination of physical and chemical properties makes CETANERTM an attractive agent for oxygenating diesel fuel. The present study considered CETANERTM ratios from 0 to 40 wt.% in a California Air Resources Board (CARB) specification diesel fuel. Particulate matter emissions, gaseous emissions and in-cylinder pressure traces were monitored over the AVL 8-Mode engine test protocol [7]. This paper presents the results from these measurements and discusses the implications of using high cetane number oxygenates in diesel fuel reformulation.

  15. High-velocity bipolar mass flow in the planetary nebula NGC 2392

    SciTech Connect

    Gieseking, F.; Becker, I.; Solf, J.

    1985-08-01

    Detailed spectroscopic observations of a high-velocity component in the velocity field of the Eskimo nebula, NGC 2392, are presented. It is interpreted as a jetlike multiknot bipolar mass flow with a velocity of nearly 200 km/s and a small angle of collimation less than 10 deg. Electron density, mass, kinetic energy, and power are estimated. 19 references.

  16. Low inlet gas velocity high throughput biomass gasifier

    DOEpatents

    Feldmann, Herman F.; Paisley, Mark A.

    1989-01-01

    The present invention discloses a novel method of operating a gasifier for production of fuel gas from carbonaceous fuels. The process disclosed enables operating in an entrained mode using inlet gas velocities of less than 7 feet per second, feedstock throughputs exceeding 4000 lbs/ft.sup.2 -hr, and pressures below 100 psia.

  17. Treatment Protocol for High Velocity/High Energy Gunshot Injuries to the Face

    PubMed Central

    Peled, Micha; Leiser, Yoav; Emodi, Omri; Krausz, Amir

    2011-01-01

    Major causes of facial combat injuries include blasts, high-velocity/high-energy missiles, and low-velocity missiles. High-velocity bullets fired from assault rifles encompass special ballistic properties, creating a transient cavitation space with a small entrance wound and a much larger exit wound. There is no dispute regarding the fact that primary emergency treatment of ballistic injuries to the face commences in accordance with the current advanced trauma life support (ATLS) recommendations; the main areas in which disputes do exist concern the question of the timing, sequence, and modes of surgical treatment. The aim of the present study is to present the treatment outcome of high-velocity/high-energy gunshot injuries to the face, using a protocol based on the experience of a single level I trauma center. A group of 23 injured combat soldiers who sustained bullet and shrapnel injuries to the maxillofacial region during a 3-week regional military conflict were evaluated in this study. Nine patients met the inclusion criteria (high-velocity/high-energy injuries) and were included in the study. According to our protocol, upon arrival patients underwent endotracheal intubation and were hemodynamically stabilized in the shock-trauma unit and underwent total-body computed tomography with 3-D reconstruction of the head and neck and computed tomography angiography. All patients underwent maxillofacial surgery upon the day of arrival according to the protocol we present. In view of our treatment outcomes, results, and low complication rates, we conclude that strict adherence to a well-founded and structured treatment protocol based on clinical experience is mandatory in providing efficient, appropriate, and successful treatment to a relatively large group of patients who sustain various degrees of maxillofacial injuries during a short period of time. PMID:23449809

  18. Theoretical analysis of the ultrasonic Doppler flowmeter for measurements of high flow velocities

    NASA Astrophysics Data System (ADS)

    Tabin, Jozef

    1987-07-01

    A geometric approach is used to analyze the ultrasonic Doppler flowmeter for measurements of flow velocities that are high but yet much smaller than the ultrasound velocity. The approach is based on the calculation of the transit time difference between the ultrasonic waves that are reflected from a moving particle at its various positions. Beam divergence is taken into account, and each path of the ultrasonic wave propagation is approximated by two rectilinear components. It is shown that the Doppler frequency shift is influenced not only by the suspended particle velocity, but also by the mean flow velocity of the fluid. This influence is of second order in the flow velocity.

  19. High- and low-temperature-stable thermite composition for producing high-pressure, high-velocity gases

    DOEpatents

    Halcomb, Danny L.; Mohler, Jonathan H.

    1990-10-16

    A high- and low-temperature-stable thermite composition for producing high-pressure and high-velocity gases comprises an oxidizable metal, an oxidizing reagent, and a high-temperature-stable gas-producing additive selected from the group consisting of metal carbides and metal nitrides.

  20. Equal velocity rule in heavy hadron production at high energy

    SciTech Connect

    Kitazoe, T. ); Inazawa, H.; Morii, T. )

    1989-01-01

    In this paper a production mechanism of heavy particles in e{sup +}e{sup {minus}} annihilations is studied on a field theoretical basis using the bound state wave functions. The requirement that wave functions of hadrons overlap maximally with each other leads to the conclusion that the model predicts a 2-jet structure in a one-loop diagram and heavy hadrons in a jet have an equal velocity. Heavy particle production cross sections and their characteristic energy distributions are calculated for some typical reactions.

  1. Spectral analysis of a high-velocity meteor

    NASA Technical Reports Server (NTRS)

    Harvey, G. A.

    1977-01-01

    A spectrogram of a fast optical meteor was reduced and analyzed, and 60 features were identified in the spectrum. Air and ionized elements in this meteor radiate throughout the spectrum from 3000 A to 6800 A. A mass of 9 mg and an effective radiation temperature of approximately 5700 K were computed for the meteor. Weight ratios of Ca:Fe, and Mg:Fe, and Na:Fe were computed. A plasma particle velocity distribution for meteors was derived, and the average collision speed obtained from this distribution was compared with the relative collision speed of a Fe-N2 gas mixture at 5700 K.

  2. High-resolution observations of the spatial and velocity distribution of cometary hydrogen

    NASA Technical Reports Server (NTRS)

    Brown, Michael E.; Spinrad, Hyron

    1992-01-01

    We have obtained high velocity and spatial resolution long-slit H alpha spectra of comets Austin (1989c1) and Levy (1990c). Spectra of both comets clearly show the existence of a low velocity thermalized component of hydrogen gas. The amount of slow hydrogen is estimated for comet Austin. The Levy spectrum shows an unusual high-velocity spatially-confined blob of hydrogen emission of unknown origin.

  3. Properties of solid polymer electrolyte fluorocarbon film. [used in hydrogen/oxygen fuel cells

    NASA Technical Reports Server (NTRS)

    Alston, W. B.

    1973-01-01

    The ionic fluorocarbon film used as the solid polymer electrolyte in hydrogen/oxygen fuel cells was found to exhibit delamination failures. Polarized light microscopy of as-received film showed a lined region at the center of the film thickness. It is shown that these lines were not caused by incomplete saponification but probably resulted from the film extrusion process. The film lines could be removed by an annealing process. Chemical, physical, and tensile tests showed that annealing improved or sustained the water contents, spectral properties, thermo-oxidative stability, and tensile properties of the film. The resistivity of the film was significantly decreased by the annealing process.

  4. The influence of slip velocity and temperature on permeability during and after high-velocity fault slip

    NASA Astrophysics Data System (ADS)

    Tanikawa, W.; Mukoyoshi, H.; Tadai, O.; Hirose, T.; Lin, W.

    2011-12-01

    Fluid transport properties in fault zones play an important role in dynamic processes during large earthquakes. If the permeability in a fault zone is low, high pore-fluid pressures caused by thermal pressurization (Sibson, 1973) or shear-induced compaction (Blanpied et al., 1992) can lead to an apparent reduction of fault strength. Changes in porosity and permeability of fault rocks within a fault zone during earthquakes and the subsequent progressive recovery of these properties may have a large influence on earthquake recurrence (Sleep and Blanpied, 1992). A rotary shear apparatus was used to investigate changes of fluid transport properties in a fault zone by real-time measurement of gas flow rates during and after shearing of hollow sandstone and granite cylinders at various slip rates. Our apparatus measures permeability parallel to the slip plane in both the slip zone and wall rocks. In all cases, permeability decreased rapidly with an increase of friction, but recovered soon after slip, reaching a steady state within several tens of minutes. The rate of reduction of permeability increased with increasing slip velocity. Permeability did not recover to pre-slip levels after low-velocity tests but recovered to exceed them after high-velocity tests. Frictional heating of gases at the slip surface increased gas viscosity, which increased gas flow rate to produce an apparent permeability increase. The irreversible permeability changes of the low-velocity tests were caused by gouge formation due to wearing and smoothing of the slip surface. The increase of permeability after high-velocity tests was caused by mesoscale fracturing in response to rapid temperature rise. Changes of pore fluid viscosity contributed more to changes of flow rate than did permeability changes caused by shear deformation, although test results from different rocks and pore fluids might be different. References Blanpied, M.L., Lockner, D.A., Byerlee, J.D., 1992. An earthquake mechanism

  5. EFFECTS OF HIGH SEDIMENT CONCENTRATIONS ON VELOCITY AND SEDIMENT DISTRIBUTIONS.

    USGS Publications Warehouse

    McCutcheon, Steve C.; Bradley, Jeffrey B.; ,

    1984-01-01

    Several classifications are required to describe sediment-transporting flow. The flow may be turbulent or laminar, Newtonian or non-Newtonian, and may also have a uniform or nonuniform concentration profile. As sediment concentration or transport increases, the character of flow changes. Generally, fall velocity and effective fall diameter decrease. The viscosity of the mixture increases. The flow becomes non-Newtonian when particle interaction becomes dominant. In the lowest concentration ranges, flows are Newtonian, generally nonuniform by concentration, and almost exclusively turbulent. Mudflows are non-Newtonian and usually laminar flows of a nearly uniform concentration. In the interim ranges are found transitions to non-Newtonian and laminar flows and uniform concentration profiles.

  6. Mechanical factors associated with the development of high ball velocity during an instep soccer kick.

    PubMed

    De Witt, John K; Hinrichs, Richard N

    2012-09-01

    The purpose of this study was to determine whether joint velocities and segmental angular velocities are significantly correlated with ball velocity during an instep soccer kick. We developed a deterministic model that related ball velocity to kicking leg and pelvis motion from the initiation of downswing until impact. Three-dimensional videography was used to collect data from 16 experienced male soccer players (age = 24.8 +/- 5.5 years; height = 1.80 +/- 0.07m; mass = 76.73 +/- 8.31 kg) while kicking a stationary soccer ball into a goal 12 m away with their right foot with maximal effort. We found that impact velocities of the foot center of mass (CM), the impact velocity of the foot CM relative to the knee, peak velocity of the knee relative to the hip, and the peak angular thigh velocity were significantly correlated with ball velocity. These data suggest that linear and angular velocities at and prior to impact are critical to developing high ball velocity. Since events prior to impact are critical for kick success, coordination and summation of speeds throughout the kicking motion are important factors. Segmental coordination that occurs during a maximal effort kick is critical for completing a successful kick.

  7. ARE HIGH VELOCITY PEAKS IN THE MILKY WAY BULGE DUE TO THE BAR?

    SciTech Connect

    Li, Zhao-Yu; Shen, Juntai; Rich, R. Michael; Kunder, Andrea; Mao, Shude

    2014-04-10

    Recently the commissioning APOGEE observations of the Galactic bulge reported that a significant fraction of stars (∼10%) are in a cold (σ{sub V} ≈ 30 km s{sup –1}) high velocity peak (Galactocentric radial velocity ≈200 km s{sup –1}). These stars are speculated to reflect the stellar orbits in the Galactic bar. In this study, we use two N-body models of a Milky Way-like disk galaxy with different bar strengths to critically examine this possibility. The general trends of the Galactocentric radial velocity distribution in observations and simulations are similar, but neither our models nor the BRAVA data reveal a statistically significant cold high velocity peak. A Monte Carlo test further suggests that it is possible for a spurious high velocity peak to appear if there are only a limited number of stars observed. Thus, the reported cold high velocity peak, even if it is real, is unlikely due to stars on the bar-supporting orbits. Our models do predict an excess of stars with high radial velocity, but not in a distinct peak. In the distance-velocity diagram, the high velocity particles in different fields exist at a similar distance ∼8.5 ± 1 kpc away from the Sun. This result may be explained by geometric intersections between the line-of-sight and the particle orbits; high velocity stars naturally exist approximately at the tangent point, without constituting a distinct peak. We further demonstrate that even without the presence of a bar structure, particle motions in an axisymmetric disk can also exhibit an excess of high velocity stars.

  8. Corrosion behavior of some high-temperature alloys under high velocity burnt fuel

    SciTech Connect

    Agarwal, D.C.; Brill, U.; Ibas, O.

    1995-12-31

    In a laboratory burner rig facility developed by Krupp VDM, the corrosion behavior of three high-temperature alloys was investigated under high velocity burnt fuel. A hot gas stream of burnt natural gas hits a sample at an angle of 45{degree}. Gas velocities of up to 80 m/s are obtained, and can be continuously adjusted by varying the air volume. By changing the sample to burner nozzle distance, a temperature gradient from 1,000 C in the center to 880 C at the edges of the sample can be achieved. Corrosion behavior of the two Fe-base alloys 310 S and 800H, and the Ni-base alloy 602CA, was evaluated by means of optical microscopy and SEM/EDAX analysis. According to results obtained so far, the alumina-former, alloy 602CA, provides best performance under high velocity burnt fuel at 880--1,000 C, as well as under steady state cyclic oxidation testing in air.

  9. Hohlraum Designs for High Velocity Implosions on NIF

    SciTech Connect

    Meezan, N B; Hicks, D G; Callahan, D A; Olson, R E; Schneider, M S; Thomas, C A; Robey, H F; Celliers, P M; Kline, J K; Dixit, S N; Michel, P A; Jones, O S; Clark, D S; Ralph, J E; Doeppner, T; MacKinnon, A J; Haan, S W; Landen, O L; Glenzer, S H; Suter, L J; Edwards, M J; Macgowan, B J; Lindl, J D; Atherton, L J

    2011-10-19

    In this paper, we compare experimental shock and capsule trajectories to design calculations using the radiation-hydrodynamics code HYDRA. The measured trajectories from surrogate ignition targets are consistent with reducing the x-ray flux on the capsule by about 85%. A new method of extracting the radiation temperature as seen by the capsule from x-ray intensity and image data shows that about half of the apparent 15% flux deficit in the data with respect to the simulations can be explained by HYDRA overestimating the x-ray flux on the capsule. The National Ignition Campaign (NIC) point-design target is designed to reach a peak fuel-layer velocity of 370 km/s by ablating 90% of its plastic (CH) ablator. The 192-beam National Ignition Facility laser drives a gold hohlraum to a radiation temperature (T{sub RAD}) of 300 eV with a 20 ns-long, 420 TW, 1.3 MJ laser pulse. The hohlraum x-rays couple to the CH ablator in order to apply the required pressure to the outside of the capsule. In this paper, we compare experimental measurements of the hohlraum T{sub RAD} and the implosion trajectory with design calculations using the code hydra. The measured radial positions of the leading shock wave and the unablated shell are consistent with simulations in which the x-ray flux on the capsule is artificially reduced by 85%. We describe a new method of inferring the T{sub RAD} seen by the capsule from time-dependent x-ray intensity data and static x-ray images. This analysis shows that hydra overestimates the x-ray flux incident on the capsule by {approx}8%.

  10. X-ray scattering and spectroscopy studies on diesel soot from oxygenated fuel under various engine load conditions

    USGS Publications Warehouse

    Braun, Andreas; Shah, N.; Huggins, Frank E.; Kelly, K.E.; Sarofim, A.; Jacobsen, C.; Wirick, S.; Francis, H.; Ilavsky, J.; Thomas, G.E.; Huffman, G.P.

    2005-01-01

    Diesel soot from reference diesel fuel and oxygenated fuel under idle and load engine conditions was investigated with X-ray scattering and X-ray carbon K-edge absorption spectroscopy. Up to five characteristic size ranges were found. Idle soot was generally found to have larger primary particles and aggregates but smaller crystallites, than load soot. Load soot has a higher degree of crystallinity than idle soot. Adding oxygenates to diesel fuel enhanced differences in the characteristics of diesel soot, or even reversed them. Aromaticity of idle soot from oxygenated diesel fuel was significantly larger than from the corresponding load soot. Carbon near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was applied to gather information about the presence of relative amounts of carbon double bonds (CC, CO) and carbon single bonds (C-H, C-OH, COOH). Using scanning X-ray transmission microspectroscopy (STXM), the relative amounts of these carbon bond states were shown to vary spatially over distances approximately 50 to 100 nm. The results from the X-ray techniques are supported by thermo-gravimetry analysis and high-resolution transmission electron microscopy. ?? 2005 Elsevier Ltd. All rights reserved.

  11. APPARATUS FOR PRODUCING HIGH VELOCITY SHOCK WAVES IN GASES

    DOEpatents

    Scott, F.R.; Josephson, V.

    1960-02-01

    >A device for producing a high-energy ionized gas region comprises an evacuated tapered insulating vessel and a substantially hemispherical insulating cap hermetically affixed to the large end of the vessel, an annular electrode having a diameter equal to and supported in the interior wall of the vessel at the large end and having a conductive portion inside the vessel, a second electrode supported at the small end of the vessel, means connected to the vessel for introducing a selected gas therein, a source of high potential having two poles. means for connecting one pole of the high potential source to the annular electrode, and means for connecting the other pole of the potential source to the second electrode.

  12. Inflow velocities of cold flows streaming into massive galaxies at high redshifts

    NASA Astrophysics Data System (ADS)

    Goerdt, Tobias; Ceverino, Daniel

    2015-07-01

    We study the velocities of the accretion along streams from the cosmic web into massive galaxies at high redshift with the help of three different suites of AMR hydrodynamical cosmological simulations. The results are compared to free-fall velocities and to the sound speeds of the hot ambient medium. The sound speed of the hot ambient medium is calculated using two different methods to determine the medium's temperature. We find that the simulated cold stream velocities are in violent disagreement with the corresponding free-fall profiles. The sound speed is a better albeit not always correct description of the cold flows' velocity. Using these calculations as a first order approximation for the gas inflow velocities vinflow = 0.9 vvir is given. We conclude from the hydrodynamical simulations as our main result that the velocity profiles for the cold streams are constant with radius. These constant inflow velocities seem to have a `parabola-like' dependency on the host halo mass in units of the virial velocity that peaks at Mvir = 1012 M⊙ and we also propose that the best-fitting functional form for the dependency of the inflow velocity on the redshift is a square root power-law relation: v_inflow ∝ √{z + 1} v_vir.

  13. Unique charge distribution in surface loops confers high velocity on the fast motor protein Chara myosin.

    PubMed

    Ito, Kohji; Yamaguchi, Yukie; Yanase, Kenji; Ichikawa, Yousuke; Yamamoto, Keiichi

    2009-12-22

    Most myosins have a positively charged loop 2 with a cluster of lysine residues that bind to the negatively charged N-terminal segment of actin. However, the net charge of loop 2 of very fast Chara myosin is zero and there is no lysine cluster in it. In contrast, Chara myosin has a highly positively charged loop 3. To elucidate the role of these unique surface loops of Chara myosin in its high velocity and high actin-activated ATPase activity, we have undertaken mutational analysis using recombinant Chara myosin motor domain. It was found that net positive charge in loop 3 affected V(max) and K(app) of actin activated ATPase activity, while it affected the velocity only slightly. The net positive charge in loop 2 affected K(app) and the velocity, although it did not affect V(max). Our results suggested that Chara myosin has evolved to have highly positively charged loop 3 for its high ATPase activity and have less positively charged loop 2 for its high velocity. Since high positive charge in loop 3 and low positive charge in loop 2 seem to be one of the reasons for Chara myosin's high velocity, we manipulated charge contents in loops 2 and 3 of Dictyostelium myosin (class II). Removing positive charge from loop 2 and adding positive charge to loop 3 of Dictyostelium myosin made its velocity higher than that of the wild type, suggesting that the charge strategy in loops 2 and 3 is widely applicable.

  14. Sound velocities in liquid lead at high temperatures

    SciTech Connect

    Hixson, R.S.; Winkler, M.A.; Shaner, J.W.

    1985-01-01

    A dynamic technique, the isobaric expansion experiment (IEX) is used to reach high temperature and pressure states in liquid lead. A unique technique is described for making sound speed measurements once a final equilibrium end state is obtained. Data over an extended density range are presented. The sound speed in liquid lead over this range appears to vary linearly with density, and has no dependence on temperature within our experimental precision.

  15. Temperature Dependence of Sound Velocity in High-Strength Fiber-Reinforced Plastics

    NASA Astrophysics Data System (ADS)

    Nomura, Ryuji; Yoneyama, Keiichi; Ogasawara, Futoshi; Ueno, Masashi; Okuda, Yuichi; Yamanaka, Atsuhiko

    2003-08-01

    Longitudinal sound velocity in unidirectional hybrid composites or high-strength fiber-reinforced plastics (FRPs) was measured along the fiber axis over a wide temperature range (from 77 K to 420 K). We investigated two kinds of high-strength crystalline polymer fibers, polyethylene (Dyneema) and polybenzobisoxazole (Zylon), which are known to have negative thermal expansion coefficients and high thermal conductivities along the fiber axis. Both FRPs had very high sound velocities of about 9000 m/s at low temperatures and their temperature dependences were very strong. Sound velocity monotonically decreased with increasing temperature. The temperature dependence of sound velocity was much stronger in Dyneema-FRP than in Zylon-FRP.

  16. MAGNETIC METHOD FOR PRODUCING HIGH VELOCITY SHOCK WAVES IN GASES

    DOEpatents

    Josephson, V.

    1960-01-26

    A device is described for producing high-energy plasmas comprising a tapered shock tube of dielectric material and having a closed small end, an exceedingly low-inductance coll supported about and axially aligned with the small end of the tapered tube. an elongated multiturn coil supported upon the remninder of the exterior wall of the shock tube. a potential source and switch connected in series with the low-inductance coil, a potential source and switch connected in series with the elongated coil, means for hermetically sealing the large end of the tube, means for purging the tube of gases, and means for admitting a selected gas into the shock tube.

  17. Search for auroral belt E-parallel fields with high-velocity barium ion injections

    NASA Technical Reports Server (NTRS)

    Heppner, J. P.; Ledley, B. G.; Miller, M. L.; Marionni, P. A.; Pongratz, M. B.

    1989-01-01

    In April 1984, four high-velocity shaped-charge Ba(+) injections were conducted from two sounding rockets at 770-975 km over northern Alaska under conditions of active auroral and magnetic disturbance. Spatial ionization (brightness) profiles of high-velocity Ba(+) clouds from photometric scans following each release were found to be consistent with the 28-sec theoretical time constant for Ba photoionization determined by Carlsten (1975). These observations therefore revealed no evidence of anomalous fast ionization predicted by the Alfven critical velocity hypothesis.

  18. Variables Affecting Smooth Particle Hydrodynamics Simulation of High-Velocity Flyer Plate Impact Experiments

    SciTech Connect

    Somasundaram, Deepak S; Trabia, Mohamed; O'Toole, Brendan; Hixson, Robert S

    2014-01-23

    This paper describes our work to characterize the variables affecting the smoothed particle hydrodynamics (SPH) method in the LS-DYNA package for simulating high-velocity flyer plate impact experiments. LS-DYNA simulations are compared with one-dimensional experimental data of an oxygen-free high-conductivity (OFHC) copper flyer plate impacting another plate of the same material. The comparison is made by measuring the velocity of a point on the back surface of the impact plate using the velocity interferometer system for any reflector (VISAR) technique.

  19. CELFE/NASTRAN Code for the Analysis of Structures Subjected to High Velocity Impact

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.

    1978-01-01

    CELFE (Coupled Eulerian Lagrangian Finite Element)/NASTRAN Code three-dimensional finite element code has the capability for analyzing of structures subjected to high velocity impact. The local response is predicted by CELFE and, for large problems, the far-field impact response is predicted by NASTRAN. The coupling of the CELFE code with NASTRAN (CELFE/NASTRAN code) and the application of the code to selected three-dimensional high velocity impact problems are described.

  20. Effect of High Air Velocities on the Distribution and Penetration of a Fuel Spray

    NASA Technical Reports Server (NTRS)

    Rothrock, A M

    1931-01-01

    By means of the NACA Spray Photography Equipment high speed moving pictures were taken of the formation and development of fuel sprays from an automatic injection valve. The sprays were injected normal to and counter to air at velocities from 0 to 800 feet per second. The air was at atmosphere temperature and pressure. The results show that high air velocities are an effective means of mixing the fuel spray with the air during injection.

  1. High Velocity Videoculography to Determination of the Pupil Dynamics

    SciTech Connect

    Villamar, Luis A.; Suaste, E.

    2008-08-11

    The characterization and determination of the dynamics pupillary in normal subjects, we can help to more accurately determine the behavior of the pupil; the videoculography is a tool that allows us to study the eye and especially the pupil to 30 frames per second in traditional form with the videoculography at high speed allows us to discuss our case in the pupil at 928 frames per second, this speed can determine with greater accuracy and precision dynamics eye, analyzing the movement pupillary each 1 ms approximately. This work shows the results of the capture and escape pupillary through this methodology, the results more accurately taking the capture of images between 5 and 7 ms about using a pulse with duration of 200 ms stimulation.

  2. Moderate Velocity Ball Impact of a Mock High-Explosive

    SciTech Connect

    Furmanski, Jevan; Rae, Philip; Clements, Bradford E.

    2012-06-05

    Modeling of thermal and mechanical events in high-explosive materials is complicated by the composite nature of the material, which experiences viscoelastic and plastic deformations and sustains damage in the form of microcracks that can dominate its overall behavior. A mechanical event of interest is projectile interaction with the material, which leads to extreme local deformation and adiabatic heating, which can potentially lead to adverse outcomes in an energetic material. Simulations of such an event predicted large local temperature rises near the path of a spherical projectile, but these were experimentally unconfirmed and hence potentially non-physical. This work concerns the experimental verification of local temperatures both at the surface and in the wake of a spherical projectile penetrating a mock (unreactive) high-explosive at {approx}700 m/s. Fast response thermocouples were embedded radially in a mid-plane of a cylindrical target, which was bonded around the thermocouples with epoxy and recorded by an oscilloscope through a low-pass filter with a bandwidth of 500 Hz. A peak temperature rise of 70 K was measured both at the equator of the projectile and in its wake, in good agreement with the temperature predicted in the minimally distorted elements at those locations by a finite element model in ABAQUS employing the ViscoSCRAM constitutive model. Further work is needed to elucidate the extreme temperature rises in material undergoing crushing or fragmentation, which is difficult to predict with meshed finite element methods due to element distortion, and also challenging to quantify experimentally.

  3. High resolution Rayleigh wave phase velocity tomography in northern North China

    NASA Astrophysics Data System (ADS)

    Wang, Weilai; Wu, Jianping; Fang, Lihua

    2012-04-01

    This study presents the Rayleigh wave phase velocity tomographic results in northern North China. The data are from 190 broad-band and 10 very broad-band stations of the North China Seismic Array and 50 permanent stations nearby. All available teleseismic vertical component time-series are used to extract the phase velocity dispersion curves of the fundamental mode Rayleigh wave by interstation method. Tomographic maps are obtained at periods of 10, 15, 25 and 60 s with a grid spacing of 0.25°× 0.25°. The short-period phase velocity maps show good correlation with the geological and tectonic features. To be specific, lower velocities correspond to North China Basin and depression area whereas higher velocities are associated with Taihangshan and Yanshan uplifts. At 25 s, there are obvious low-velocity anomalies in Jizhong depression and Beijing-Tianjin-Tangshan region, indicating that ascendant low velocity channel may be formed beneath these areas and induce the velocity difference in the upper crust. The phase velocity map at 60 s reflects the upper-mantle information in the study area. High-velocity anomalies are observed at Yanshan blocks north to Zhangjiakou-Bohai seismic belt, suggesting that the materials are stable beneath these areas or the asthenosphere is at deeper location. Low-velocity anomalies are mainly south to the seismic belt, implying the asthenosphere is shallower and the materials are transformed by the open stretching rift trending NNE, resulting in many NNE-directed fault belts. These structural differences at depth may be controlled by the fault activity and strong tectonic movements.

  4. Ignition process evolution at high supersonic velocities in channel

    NASA Astrophysics Data System (ADS)

    Goldfeld, M. A.; Starov, A. V.; Timofeev, K. Yu.; Vinogradov, V. A.

    2009-06-01

    The results of experimental research of multi-injector combustors in the regime of the attached pipe are presented. As a source of high-enthalpy working gas (air), hot shot wind tunnel IT-302M of ITAM, the Siberian Branch of the Russian Academy of Sciences was used. Tests have been carried out at Mach numbers 3, 4 and 5, in a range of change of total temperature from 2000K up to 3000K and static pressure from 0.08MPa up to 0.23MPa. Injector section has been manufactured in two versions with a various relative height of wedge-shaped injectors with parallel fuel injection. Influence of conditions on the entrance of the combustion chamber on ignition and a stable combustion of hydrogen was investigated. Intensive combustion of hydrogen has been received only at Mach numbers 3 and 4. Advantage of injector section with the greater relative height of injectors is revealed. The mechanism of fuel ignition in the combustion chamber of the given configuration was investigated: two-step ignition process including “kindling” and intensive combustion over all channel volume.

  5. Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

    NASA Astrophysics Data System (ADS)

    M, Chabot; K, Béroff; T, Pino; G, Féraud; N, Dothi; Padellec A, Le; G, Martinet; S, Bouneau; Y, Carpentier

    2012-11-01

    We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn-*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

  6. High Velocity Impact Interaction of Metal Particles with Porous Heterogeneous Materials with an Inorganic Matrix

    NASA Astrophysics Data System (ADS)

    Glazunov, A. A.; Ishchenko, A. N.; Afanasyeva, S. A.; Belov, N. N.; Burkin, V. V.; Rogaev, K. S.; Tabachenko, A. N.; Khabibulin, M. V.; Yugov, N. T.

    2016-03-01

    A computational-experimental investigation of stress-strain state and fracture of a porous heterogeneous material with an inorganic matrix, used as a thermal barrier coating of flying vehicles, under conditions of a high-velocity impact by a spherical steel projectile imitating a meteorite particle is discussed. Ballistic tests are performed at the velocities about 2.5 km/s. Numerical modeling of the high-velocity impact is described within the framework of a porous elastoplastic model including fracture and different phase states of the materials. The calculations are performed using the Euler and Lagrange numerical techniques for the velocities up to 10 km/s in a complete-space problem statement.

  7. High-velocity OH/IR stars at the Galactic centre

    NASA Astrophysics Data System (ADS)

    van Langevelde, H. J.; Brown, A. G. A.; Lindqvist, M.; Habing, H. J.; de Zeeuw, P. T.

    1992-07-01

    We present the results of a small survey for OH/IR stars at high radial velocities in the Galactic center region performed with the VLA and the Nancay telescope. We have detected two new OH/IR stars, one at a peculiar velocity of -309 km/s, the other at -355 km/s. These two objects and one previously detected high-velocity OH/IR star (OH 0.3-0.2, Baud et al., 1975) stand out in the 1, v diagram of OH/IR stars at the Galactic center. Are these stars just on the extreme edge of the radial velocity distribution? Or are these objects no longer bound to the Galactic center? We discuss these possibilities, showing that these are most likely bulge stars on elongated orbits passing close to the Galactic center.

  8. Heat Transfer and Hydraulic Flow Resistance for Streams of High Velocity

    NASA Technical Reports Server (NTRS)

    Lelchuk, V. L.

    1943-01-01

    Problems of hydraulic flow resistance and heat transfer for streams with velocities comparable with acoustic have present great importance for various fields of technical science. Especially, they have great importance for the field of heat transfer in designing and constructing boilers.of the "Velox" type. In this article a description of experiments and their results as regards definition of the laws of heat transfer in differential form for high velocity air streams inside smooth tubes are given.

  9. Planar near-nozzle velocity measurements during a single high-pressure fuel injection

    NASA Astrophysics Data System (ADS)

    Schlüßler, Raimund; Gürtler, Johannes; Czarske, Jürgen; Fischer, Andreas

    2015-09-01

    In order to reduce the fuel consumption and exhaust emissions of modern Diesel engines, the high-pressure fuel injections have to be optimized. This requires continuous, time-resolved measurements of the fuel velocity distribution during multiple complete injection cycles, which can provide a deeper understanding of the injection process. However, fuel velocity measurements at high-pressure injection nozzles are a challenging task due to the high velocities of up to 300 m/s, the short injection durations in the range and the high fuel droplet density especially near the nozzle exit. In order to solve these challenges, a fast imaging Doppler global velocimeter with laser frequency modulation (2D-FM-DGV) incorporating a high-speed camera is presented. As a result, continuous planar velocity field measurements are performed with a measurement rate of 200 kHz in the near-nozzle region of a high-pressure Diesel injection. The injection system is operated under atmospheric surrounding conditions with injection pressures up to 1400 bar thereby reaching fuel velocities up to 380 m/s. The measurements over multiple entire injection cycles resolved the spatio-temporal fluctuations of the fuel velocity, which occur especially for low injection pressures. Furthermore, a sudden setback of the velocity at the beginning of the injection is identified for various injection pressures. In conclusion, the fast measurement system enables the investigation of the complete temporal behavior of single injection cycles or a series of it. Since this eliminates the necessity of phase-locked measurements, the proposed measurement approach provides new insights for the analysis of high-pressure injections regarding unsteady phenomena.

  10. Development of a high-velocity free-flight launcher : the Ames light-gas gun

    NASA Technical Reports Server (NTRS)

    Charters, A C; Denardo, B Pat; Rossow, Vernon J

    1955-01-01

    Recent interest in long-range missiles has stimulated a search for new experimental techniques which can reproduce in the laboratory the high temperatures and Mach numbers associated with the missiles' flight. One promising possibility lies in free-flight testing of laboratory models which are flown at the full velocity of the missile. In this type of test, temperatures are approximated and aerodynamic heating of the model is representative of that experienced by the missile in high-velocity flight. A prime requirement of the free-flight test technique is a device which had the capacity for launching models at the velocities desired. In response to thie need, a gun firing light models at velocities up to 15,000 feet per second has been developed at the Ames Aeronautical Laboratory. The design of this gun, the analysis of its performance, and the results of the initial firing trials are described in this paper. The firing trials showed that the measured velocities and pressures agreed well with the predicted values. Also, the erosion of the launch tube was very small for the eleven rounds fired. The performance of the gun suggests that it will prove to be a satisfactory launcher for high-velocity free-flight tests. However, it should be mentioned that only the gross performance has been evaluated so far, and, consequently, the operation of the gun must be investigated in further detail before its performance can be reliably predicted over its full operating range.

  11. High Precision UTDR Measurements by Sonic Velocity Compensation with Reference Transducer

    PubMed Central

    Stade, Sam; Kallioinen, Mari; Mänttäri, Mika; Tuuva, Tuure

    2014-01-01

    An ultrasonic sensor design with sonic velocity compensation is developed to improve the accuracy of distance measurement in membrane modules. High accuracy real-time distance measurements are needed in membrane fouling and compaction studies. The benefits of the sonic velocity compensation with a reference transducer are compared to the sonic velocity calculated with the measured temperature and pressure using the model by Belogol'skii, Sekoyan et al. In the experiments the temperature was changed from 25 to 60 °C at pressures of 0.1, 0.3 and 0.5 MPa. The set measurement distance was 17.8 mm. Distance measurements with sonic velocity compensation were over ten times more accurate than the ones calculated based on the model. Using the reference transducer measured sonic velocity, the standard deviations for the distance measurements varied from 0.6 to 2.0 μm, while using the calculated sonic velocity the standard deviations were 21–39 μm. In industrial liquors, not only the temperature and the pressure, which were studied in this paper, but also the properties of the filtered solution, such as solute concentration, density, viscosity, etc., may vary greatly, leading to inaccuracy in the use of the Belogol'skii, Sekoyan et al. model. Therefore, calibration of the sonic velocity with reference transducers is needed for accurate distance measurements. PMID:24991939

  12. Variation of wave velocity and porosity of sandstone after high temperature heating

    NASA Astrophysics Data System (ADS)

    Sun, Qiang; Zhang, ·Weiqiang; Su, Tianming; Zhu, Shuyun

    2016-05-01

    This paper reports the variations of mass, porosity, and wave velocity of sandstone after high temperature heating. The range of temperature to which the sandstone specimens have been exposed is 25-850°C, in a heating furnace. It has been shown that below 300°C, porosity and wave velocity change very little. Above 300°C, there is a rapid increase in porosity, but the wave velocity decreases significantly. The results of thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) and mercury intrusion porosimetry (MIP) suggest that a series of changes occurred between 400 and 600°C in sandstone could be responsible for the different patterns of variation in porosity and wave velocity.

  13. Measurement of High Frequency Perturbations to the Ion Velocity Distribution in the HELIX Helicon Plasma Source

    NASA Astrophysics Data System (ADS)

    Kline, J. L.; Boivin, R. F.; Franck, C.; Klinger, T.; Scime, E. E.

    2001-10-01

    Using lasers to measure plasma parameters has become more common in recent years. Lasers can provide information about plasma parameters without perturbing the plasma. The most common technique for ion parameter measurements is Laser Induced Fluorescence (LIF). LIF typically measures the ion velocity distribution and provides information about the ion temperatures and ion flows in the plasma. More recently, Skiff and Anderegg [1987] and Safarty et al. [1996] have shown that measurements of the perturbed ion velocity distribution can provide wave number information for waves propagating in a plasma due the non-local nature of the dielectric tensor. In the past two years, attempts have been made to measure the perturbed ion velocity distribution function at frequencies relevant to Helicon plasma sources. The objective of the measurements is to identify electrostatic oscillation associated to the slow wave or "Trivelpeice Gould modes" in helicon plasma sources. Past efforts to measure the perturbed ion velocity distribution function have been unsuccessful due to technical difficulties associated with measuring the cross correlation of the photon and reference signals. Using a high frequency SR544 Stanford Research lock-in amplifier, high frequency perturbations to the ion velocity distribution in a helicon source have been measured. Perturbed ion velocity distribution measurements, along with the related theory will be presented.

  14. Simultaneous measurement of density and sound velocity of liquid Fe-C at high pressure

    NASA Astrophysics Data System (ADS)

    Shimoyama, Y.; Terasaki, H. G.; Urakawa, S.; Kuwabara, S.; Takubo, Y.; Katayama, Y.

    2014-12-01

    Seismological and experimental studies show that the Earth's outer core is approximately 10% less dense than molten iron at the core pressure and temperature conditions, implying that some light elements exist in the core. The effect of light elements on density and bulk modulus of liquid iron is necessary for estimating of these core compositions. Sound velocity of liquid iron alloys is also important for identifying light elements in the core by comparison with observed seismic data. In this study, we have measured density and sound velocity of liquid Fe-C at SPring-8 beamline BL22XU using a DIA-type cubic anvil press (SMAP-I). Density was measured using X-ray absorption method (Katayama et al., 1993). We newly installed sound velocity measurement system using pulse-echo overlapping method (Higo et al., 2009) in this beamline. P-wave signals with a frequency of 35-37 MHz were generated and received by LiNbO3 transducer. Buffer rod and backing plated were adopted single-crystal sapphire. The sample length at high pressure and high temperature were measured from absorption contrast between sample and sapphire. We measured velocity and density of liquid Fe-C between 1.1-2.8 GPa and 1480-1740 K. Obtained density and velocity of Fe-C was found to increase with pressure. In contrast, the effect of temperature on density and velocity was negative. The relationship between these two properties will be discussed.

  15. Sound velocity of high-strength polymer with negative thermal expansion coefficient

    NASA Astrophysics Data System (ADS)

    Nomura, R.; Ueno, M.; Okuda, Y.; Burmistrov, S.; Yamanaka, A.

    2003-05-01

    Sound velocities of fiber reinforced plastics (FRPs) were measured along the fiber axis at temperatures between 360 and 77 K. We used two kinds of the high-strength crystalline polymer fibers, polyethylene (Dyneema) and polybenzobisoxazole (Zylon), which have negative thermal expansion coefficients. They also have high thermal conductivities and high resistances for flash over voltage, and are expected as new materials for coil bobbins or spacers at cryogenic temperatures. They have very large sound velocities of about 9000 (m/s) at 77 K, which are 4.5 times larger than that of the ordinary polyethylene fiber.

  16. Experimental verification of vapor deposition rate theory in high velocity burner rigs

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Santoro, Gilbert J.

    1985-01-01

    The main objective has been the experimental verification of the corrosive vapor deposition theory in high-temperature, high-velocity environments. Towards this end a Mach 0.3 burner-rig appartus was built to measure deposition rates from salt-seeded (mostly Na salts) combustion gases on the internally cooled cylindrical collector. Deposition experiments are underway.

  17. Temporary Network Development Capability in High Velocity Environments: A Dynamic Capability Study of Disaster Relief Organizations

    ERIC Educational Resources Information Center

    O'Brien, William Ross

    2010-01-01

    Organizations involved in crisis relief after a natural disaster face the multifaceted challenge of significantly changing needs of their various stakeholders, limited, ambiguous and even incorrect information, and highly compressed time limitations. Yet the performance of these organization in these high velocity environments is critical for the…

  18. Velocity Fields in H II Regions Using High Resolution Imaging Fabry-Perot Spectrometer

    NASA Astrophysics Data System (ADS)

    Seema, P.

    1996-05-01

    The thesis comprises of two parts: I. Instrumentation II. Observations, results and discussion. An imaging Fabry-Perot spectrometer (IFPS) is designed and constructed for the studies on kinematics of extended astronomical objects (Seema et al., 1992). IFPS comprises of a field aperture, collimating lens and a two dimensional imaging sensor called Imaging Photon Detector (IPD). It is the first time that IPD which uses a resistive anode for position determination is being used in the spectroscopic studies of astronomical objects. Observations were made on Orion and Trifid nebula covering a wide field of view using a 35cm Celestron-14 telescope (f/11 cassegrain) at Gurushikhar, Mt.Abu, India. Orion Nebula: Observations were made in [OIII] 5007A, line with a spectral resolution of 6 km/sec and spatial resolution of 4" covering a field of view of 10.5', to study (i) general velocity flow (ii) high velocity flow and (iii)random motions. Line profiles generated for about 2000 positions showed an asymmetric shape with (a)a narrow component 20 +- 3 km/sec and (b) a broad component 50 +- 3 km/sec. The two components could be interpreted in terms of the interaction of the ionized gas (from the trapezium stars) with the condensations present in the nebula, resulting in the secondary flows. The iso-velocity contour map generated for both the components showed velocity flow in agreement with the champagne flow model (Tenorio-Tagle 1982). A model emission line profile constructed assuming a champagne flow in [OIII] 5007A, line for a position 2' away from theta-1 C Ori showed a reasonably good agreement with the narrow component of the observed profile. Certain high velocity flow (~50 km/s) regions are observed to be superimposed on the main flow of the narrow component. These flows are either radiation pressure driven stellar winds or jets generated during the formation phase of Young stellar objects. The radial velocity was found to be low with no high velocity flow regions in

  19. Fault strength evolution during high velocity friction experiments with slip-pulse and constant-velocity loading

    NASA Astrophysics Data System (ADS)

    Liao, Zonghu; Chang, Jefferson C.; Reches, Ze'ev

    2014-11-01

    Seismic analyses show that slip during large earthquakes evolves in a slip-pulse mode that is characterized by abrupt, intense acceleration followed by moderate deceleration. We experimentally analyze the friction evolution under slip-pulse proxy of a large earthquake, and compare it with the evolution at loading modes of constant-velocity and changing-velocity. The experiments were conducted on room-dry, solid granite samples at slip-velocities of 0.0006-1 m/s, and normal stress of 1-11.5 MPa. The analysis demonstrates that (1) the strength evolution and constitutive parameters of the granite fault strongly depend on the loading mode, and (2) the slip-pulse mode is energy efficient relatively to the constant-velocity mode as manifested by faster, more intense weakening and 50-90% lower energy dissipation. The results suggest that the frictional strength determined in slip-pulse experiments, is more relevant to simulations of earthquake rupture than frictional strength determined in constant-velocity experiments. Further, for a finite amount of crustal elastic energy, the efficiency of slip-pulse would amplify earthquake instability.

  20. High-resolution CFD detects high-frequency velocity fluctuations in bifurcation, but not sidewall, aneurysms.

    PubMed

    Valen-Sendstad, Kristian; Mardal, Kent-André; Steinman, David A

    2013-01-18

    High-frequency flow fluctuations in intracranial aneurysms have previously been reported in vitro and in vivo. On the other hand, the vast majority of image-based computational fluid dynamics (CFD) studies of cerebral aneurysms report periodic, laminar flow. We have previously demonstrated that transitional flow, consistent with in vivo reports, can occur in a middle cerebral artery (MCA) bifurcation aneurysm when ultra-high-resolution direct numerical simulation methods are applied. The object of the present study was to investigate if such high-frequency flow fluctuations might be more widespread in adequately-resolved CFD models. A sample of N=12 anatomically realistic MCA aneurysms (five unruptured, seven ruptured), was digitally segmented from CT angiograms. Four were classified as sidewall aneurysms, the other eight as bifurcation aneurysms. Transient CFD simulations were carried out assuming a steady inflow velocity of 0.5m/s, corresponding to typical peak systolic conditions at the MCA. To allow for detection of clinically-reported high-frequency flow fluctuations and resulting flow structures, temporal and spatial resolutions of the CFD simulations were in the order of 0.1 ms and 0.1 mm, respectively. A transient flow response to the stationary inflow conditions was found in five of the 12 aneurysms, with energetic fluctuations up to 100 Hz, and in one case up to 900 Hz. Incidentally, all five were ruptured bifurcation aneurysms, whereas all four sidewall aneurysms, including one ruptured case, quickly reached a stable, steady state solution. Energetic, rapid fluctuations may be overlooked in CFD models of bifurcation aneurysms unless adequate temporal and spatial resolutions are used. Such fluctuations may be relevant to the mechanobiology of aneurysm rupture, and to a recently reported dichotomy between predictors of rupture likelihood for bifurcation vs. sidewall aneurysms.

  1. HIGH-VELOCITY CLOUDS IN THE GALACTIC ALL SKY SURVEY. I. CATALOG

    SciTech Connect

    Moss, V. A.; Kummerfeld, J. K.; McClure-Griffiths, N. M.; Murphy, T.; Pisano, D. J.; Curran, J. R.

    2013-11-01

    We present a catalog of high-velocity clouds (HVCs) from the Galactic All Sky Survey (GASS) of southern sky neutral hydrogen, which has 57 mK sensitivity and 1 km s{sup –1} velocity resolution and was obtained with the Parkes Telescope. Our catalog has been derived from the stray-radiation-corrected second release of GASS. We describe the data and our method of identifying HVCs and analyze the overall properties of the GASS population. We catalog a total of 1693 HVCs at declinations <0°, including 1111 positive velocity HVCs and 582 negative velocity HVCs. Our catalog also includes 295 anomalous velocity clouds (AVCs). The cloud line-widths of our HVC population have a median FWHM of ∼19 km s{sup –1}, which is lower than that found in previous surveys. The completeness of our catalog is above 95% based on comparison with the HIPASS catalog of HVCs upon which we improve by an order of magnitude in spectral resolution. We find 758 new HVCs and AVCs with no HIPASS counterpart. The GASS catalog will shed unprecedented light on the distribution and kinematic structure of southern sky HVCs, as well as delve further into the cloud populations that make up the anomalous velocity gas of the Milky Way.

  2. Jet Velocity Profile Effects on Spray Characteristics of Impinging Jets at High Reynolds and Weber Numbers

    NASA Astrophysics Data System (ADS)

    Rodrigues, Neil S.; Kulkarni, Varun; Sojka, Paul E.

    2014-11-01

    While like-on-like doublet impinging jet atomization has been extensively studied in the literature, there is poor agreement between experimentally observed spray characteristics and theoretical predictions (Ryan et al. 1995, Anderson et al. 2006). Recent works (Bremond and Villermaux 2006, Choo and Kang 2007) have introduced a non-uniform jet velocity profile, which lead to a deviation from the standard assumptions for the sheet velocity and the sheet thickness parameter. These works have assumed a parabolic profile to serve as another limit to the traditional uniform jet velocity profile assumption. Incorporating a non-uniform jet velocity profile results in the sheet velocity and the sheet thickness parameter depending on the sheet azimuthal angle. In this work, the 1/7th power-law turbulent velocity profile is assumed to provide a closer match to the flow behavior of jets at high Reynolds and Weber numbers, which correspond to the impact wave regime. Predictions for the maximum wavelength, sheet breakup length, ligament diameter, and drop diameter are compared with experimental observations. The results demonstrate better agreement between experimentally measured values and predictions, compared to previous models. U.S. Army Research Office under the Multi-University Research Initiative Grant Number W911NF-08-1-0171.

  3. Critical velocities for deflagration and detonation triggered by voids in a REBO high explosive

    SciTech Connect

    Herring, Stuart Davis; Germann, Timothy C; Jensen, Niels G

    2010-01-01

    The effects of circular voids on the shock sensitivity of a two-dimensional model high explosive crystal are considered. We simulate a piston impact using molecular dynamics simulations with a Reactive Empirical Bond Order (REBO) model potential for a sub-micron, sub-ns exothermic reaction in a diatomic molecular solid. The probability of initiating chemical reactions is found to rise more suddenly with increasing piston velocity for larger voids that collapse more deterministically. A void with radius as small as 10 nm reduces the minimum initiating velocity by a factor of 4. The transition at larger velocities to detonation is studied in a micron-long sample with a single void (and its periodic images). The reaction yield during the shock traversal increases rapidly with velocity, then becomes a prompt, reliable detonation. A void of radius 2.5 nm reduces the critical velocity by 10% from the perfect crystal. A Pop plot of the time-to-detonation at higher velocities shows a characteristic pressure dependence.

  4. Isolated Bacterial Spores at High-velocity Survive Surface Impacts in Vacuum

    NASA Astrophysics Data System (ADS)

    Austin, Daniel; Barney, Brandon

    We present experiments in which bacterial spores were found to survive being accelerated in vacuum to velocities in the range 30-120 m/s and impacted on a dense target. In these experiments, spores of Bacillus subtilis spores were charged using electrospray at atmospheric pressure, dried, and then introduced into high vacuum. Through choice of skimmers and beam tubes, different velocity ranges were achieved. An image-charge detector observed the charged spores, providing total charge and velocity. The spores then impacted a glass target within a collection vessel. After the experiment, the collection vessel contents were extracted and cultured. Several positive and negative controls were used, including the use of antibiotic-resistant spores and antibiotic-containing (rifampicin) agar for culturing. These impact velocities are of particular interest for possible transport of bacterial spores from Mars to Phobos, and may have implications for planetary protection in a Phobos sample return mission. In addition, bacteria may reach similar velocities during a spacecraft crash (e.g., within components, or from spacecraft to surface materials during impact, etc.), raising concerns about forward contamination. The velocities of interest to transport of life between planets (panspermia) are somewhat higher, but these results complement shock-based experiments and contribute to the general discussion of impact survivability of organisms.

  5. A Investigation of Gouge Initiation in High-Velocity Sliding Contact

    NASA Astrophysics Data System (ADS)

    Tachau, Robert David Mazur

    1991-02-01

    Surface damage has been observed on the rails of rocket sled tracks and on the barrels of high-velocity guns. The phenomenon is generally referred to as "gouging". Damage to a stationary surface (guider) is created from the oblique impact of a high-velocity object (slider) moving over its surface. The surface damage (gouge) is typically a shallow crater in the shape of a teardrop with the leading edge characterized by the wider end and a slightly raised lip. For rocket sleds, rail gouging occurs when the sled velocity is greater than 1.5 km/sec; while in guns, barrel gouging occurs when the velocity exceeds 4 km/sec. A model is developed to describe the phenomenon of gouging. An unbalanced slider randomly causes a shallow -angle, oblique impact between the slider and the guider. At sufficiently high velocity, the impact produces a thin, but very hot, layer of soft material at the contact surface. Under the action of a moving load, the soft layer lends itself to an antisymmetric deformation and a gouge is formed when this soft material is over-run by the slider. The model is simulated numerically with a hydrodynamic (CTH) code. The results of the simulations are in good agreement with the observed phenomena. Based on the simulated temperature and pressure profiles at the contact surface, design criteria for gouge mitigation are developed in this study.

  6. Effect of oxygenated fuels on physicochemical and toxicological characteristics of diesel particulate emissions.

    PubMed

    Zhang, Zhi-Hui; Balasubramanian, Rajasekhar

    2014-12-16

    A systematic study was conducted to make a comparative evaluation of the effects of blending five different oxygenates (diglyme (DGM), palm oil methyl ester (PME), dimethyl carbonate (DMC), diethyl adipate (DEA), and butanol (Bu)) with ultralow sulfur diesel (ULSD) at 2% and 4% oxygen levels on physicochemical and toxicological characteristics of particulate emissions from a nonroad diesel engine. All blended fuels led to an overall decrease in the particulate mass concentration and elemental carbon (EC) emissions, which was strongly associated with the oxygen content in fuels and the specific type of fuels used. In general, the proportion of particulate-bound organic carbon (OC) and water-soluble organic carbon (WSOC) increased while using oxygenated fuel blends. Compared to ULSD, all fuel blends showed different emission factors of particle-phase PAHs and n-alkanes, slight alterations in soot nanostructure, lower soot ignition temperature, and lower activation energy. The total counts of particles (≤ 560 nm diameter) emitted decreased gradually for ULSD blended with DMC, DEA, and Bu, while they increased significantly for other fuel blends. The in vitro toxicity of particulates significantly increased with ULSD blended with DMC and DEA, while it decreased when ULSD was blended with PME, DGM, and Bu. PMID:25383974

  7. Development and characterization of a 280 cm2 vanadium/oxygen fuel cell

    NASA Astrophysics Data System (ADS)

    Noack, Jens; Cremers, Carsten; Bayer, Domnik; Tübke, Jens; Pinkwart, Karsten

    2014-05-01

    A vanadium/oxygen fuel cell with an active area of 280 cm2 has been developed. The cell consisted of two membranes with two half-cells and an intermediate chamber. The maximum achieved power density was 23 mW cm-2 at 0.56 V with lambda air = 3 and a 1.6 M V2+ solution at room temperature. The average discharge power density was 19.6 mW cm-2 at a constant current density of 40 mA cm-2 with an average voltage efficiency of 33%. The fuel based energy density was 18.2% of the theoretical value with 11.8 Wh L-1. In comparison with a similarly constructed 50 cm2 cell, both achieved similar performance levels. An analysis using the half-cell potential profiles and by means of impedance spectroscopy revealed that, as for the 50 cm2 cell, the low rate of oxygen reduction reaction significantly affected the performance of the cell. Thus gives potential for the optimization of the cathode reaction and a reduction in the ohmic resistances potential for higher power densities.

  8. Study of the long-term operation of a vanadium/oxygen fuel cell

    NASA Astrophysics Data System (ADS)

    Noack, Jens; Cognard, Gwenn; Oral, Meryem; Küttinger, Michael; Roznyatovskaya, Nataliya; Pinkwart, Karsten; Tübke, Jens

    2016-09-01

    A vanadium/oxygen fuel cell (VOFC) with a geometrically active area of 51 cm2 and two membranes was discontinuously operated over a period of over 676 h with 47 successive tests at room temperature with a current density of 19.6 mA/cm2 in order to investigate signs of ageing. As well as measuring cell voltages, the test setup was also used to measure anode and redox potentials as well as cell and half-cell impedances. The performance data of the VOFC fluctuated widely over the course of the test period, due to different V2+ concentrations and instabilities of the starting solutions on the one hand and complex changes in cathode conditions on the other. The desired behaviour of the anode reactions was achieved primarily through improved methods for producing the V2+ solutions, and remained stable at the end of the experiments. The kinetics of the cathode reactions were temporarily increased by purging with 2 M H2SO4, however their performance decreased over time. The VOFC had symptoms of ageing by complex and overlaid changes in the cathode's triple phase boundary layer and in the special conditions between the two electrodes and membranes.

  9. The study on the heat transfer characteristics of oxygen fuel combustion boiler

    NASA Astrophysics Data System (ADS)

    Wu, Haibo; Liu, Zhaohui; Liao, Haiyan

    2016-10-01

    According to 350MW and 600MW boilers, under oxygen fuel condition, through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model, the temperature distribution, heat flux distribution and absorption heat distribution, etc. was obtained which compared with those under air condition. Through calculation, it is obtained that the primary and secondary flow mixed well, good tangentially fired combustion in furnace was formed, the temperature under air condition obviously higher than the temperature under O26 condition. The adiabatic flame temperature of wet cycle was slightly higher than that of dry cycle. The maximum heat load appeared on the waterwall around the burner area. The heat load gradually decreased along the furnace height up and down in burner area. The heat absorption capacity of the furnace under O26 was lower than that under the air condition. The heat absorption capacity of the platen heating surface under O26 was equal to that under air condition. And the heat absorbing capacity of waterwall under O26 was about7%~12% less than that under air condition.

  10. Estimation of pseudo-2D shear-velocity section by inversion of high frequency surface waves

    USGS Publications Warehouse

    Luo, Y.; Liu, J.; Xia, J.; Xu, Y.; Liu, Q.

    2006-01-01

    A scheme to generate pseudo-2D shear-velocity sections with high horizontal resolution and low field cost by inversion of high frequency surface waves is presented. It contains six steps. The key step is the joint method of crossed correlation and phase shift scanning. This joint method chooses only two traces to generate image of dispersion curve. For Rayleigh-wave dispersion is most important for estimation of near-surface shear-wave velocity, it can effectively obtain reliable images of dispersion curves with a couple of traces. The result of a synthetic example shows the feasibility of this scheme. ?? 2005 Society of Exploration Geophysicists.

  11. Experimental verification of corrosive vapor deposition rate theory in high velocity burner rigs

    NASA Technical Reports Server (NTRS)

    Gokoglu, S. A.; Santoro, G. J.

    1986-01-01

    The ability to predict deposition rates is required to facilitate modelling of high temperature corrosion by fused salt condensates in turbine engines. A corrosive salt vapor deposition theory based on multicomponent chemically frozen boundary layers (CFBL) has been successfully verified by high velocity burner rig experiments. The experiments involved internally air-impingement cooled, both rotating full and stationary segmented cylindrical collectors located in the crossflow of sodium-seeded combustion gases. Excellent agreement is found between the CFBL theory an the experimental measurements for both the absolute amounts of Na2SO4 deposition rates and the behavior of deposition rate with respect to collector temperature, mass flowrate (velocity) and Na concentration.

  12. Determination of minority-carrier lifetime and surface recombination velocity with high spacial resolution

    NASA Technical Reports Server (NTRS)

    Watanabe, M.; Actor, G.; Gatos, H. C.

    1977-01-01

    Quantitative analysis of the electron beam induced current in conjunction with high-resolution scanning makes it possible to evaluate the minority-carrier lifetime three dimensionally in the bulk and the surface recombination velocity two dimensionally, with a high spacial resolution. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two-dimensional mapping of the surface recombination velocity of phosphorus-diffused silicon diodes is presented as well as a three-dimensional mapping of the changes in the minority-carrier lifetime in ion-implanted silicon.

  13. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields

    DOEpatents

    Chaffin, R.J.; Dawson, L.R.; Fritz, I.J.; Osbourn, G.C.; Zipperian, T.E.

    1984-04-19

    In a field-effect transistor comprising a semiconductor having therein a source, a drain, a channel and a gate in operational relationship, there is provided an improvement wherein said semiconductor is a superlattice comprising alternating quantum well and barrier layers, the quantum well layers comprising a first direct gap semiconductor material which in bulk form has a certain bandgap and a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, the barrier layers comprising a second semiconductor material having a bandgap wider than that of said first semiconductor material, wherein the layer thicknesses of said quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice having a curve of electron velocity versus applied electric field which has a maximum electron velocity at a certain electric field, and wherein the thicknesses of said quantum well layers are selected to provide a superlattice curve of electron velocity versus applied electric field whereby, at applied electric fields higher than that at which the maximum electron velocity occurs in said first material when in bulk form, the electron velocities are higher in said superlattice than they are in said first semiconductor material in bulk form.

  14. Frictional strength of wet- and dry- talc gouge in high-velocity shear experiments

    NASA Astrophysics Data System (ADS)

    Chen, X.; Reches, Z.; Elwood Madden, A. S.

    2015-12-01

    The strength of the creeping segment of the San Andres fault may be controlled by the distinct weakness and stability of talc (Moore & Rymer, 2007). We analyze talc frictional strength at high slip-velocity of 0.002 - 0.66 m/s, long slip-distances of 0.01 m to 33 m, and normal stresses up to 4.1 MPa. This analysis bridges the gap between nucleation stage of low velocity/distance, and the frictional behavior during large earthquakes. We tested wet and dry samples of pure talc gouge in a confined rotary cell, and continuously monitored the slip-velocity, stresses, dilation and temperature. We run 29 experiments of single and stepped velocities to obtain 243 values of quasi-static frictional coefficients. Dry talc gouge showed distinct slip-strengthening: friction coefficient of µ ~0.4 at short slip-distances of D < 0.1 m, and it increased systematically to µ ~0.8 at slip-distances of D = 0.1- 1 m; at D > 1 m, the frictional strength saturated at µ= 0.8 - 1 level. Wet talc gouge (16-20% water) displayed low frictional strength of µ= 0.1-0.3, in agreement with published triaxial tests. The stepped-velocity runs revealed a consistent velocity-strengthening trend. For a velocity jump from V1 to V2, we used VD = (µ2 -µ1)/ln (V2/V1), and found that on average VD = 0.06 and 0.03 for dry and wet talc, respectively, and for slip distances shorter than 1 m. Microstructural analysis of post-shearing wet talc gouge revealed extreme slip localization to a principal-slip-zone of a few microns, and significant shear compaction of 10-30%. In contrast, dry talc gouge exhibited distributed shear in a wide zone and systematic shear dilation (10-50%). We propose slip along weak interlayer talc plates and thermal-pressurization as the possible weakening mechanisms for wet talc. The development of distributed secondary fault network along with substantial grain crushing is responsible for slip-strengthening in dry condition. Fig. 1. Friction maps of talc gouge as function of slip

  15. Analysis of group-velocity dispersion of high-frequency Rayleigh waves for near-surface applications

    USGS Publications Warehouse

    Luo, Y.; Xia, J.; Xu, Y.; Zeng, C.

    2011-01-01

    The Multichannel Analysis of Surface Waves (MASW) method is an efficient tool to obtain the vertical shear (S)-wave velocity profile using the dispersive characteristic of Rayleigh waves. Most MASW researchers mainly apply Rayleigh-wave phase-velocity dispersion for S-wave velocity estimation with a few exceptions applying Rayleigh-wave group-velocity dispersion. Herein, we first compare sensitivities of fundamental surface-wave phase velocities with group velocities with three four-layer models including a low-velocity layer or a high-velocity layer. Then synthetic data are simulated by a finite difference method. Images of group-velocity dispersive energy of the synthetic data are generated using the Multiple Filter Analysis (MFA) method. Finally we invert a high-frequency surface-wave group-velocity dispersion curve of a real-world example. Results demonstrate that (1) the sensitivities of group velocities are higher than those of phase velocities and usable frequency ranges are wider than that of phase velocities, which is very helpful in improving inversion stability because for a stable inversion system, small changes in phase velocities do not result in a large fluctuation in inverted S-wave velocities; (2) group-velocity dispersive energy can be measured using single-trace data if Rayleigh-wave fundamental-mode energy is dominant, which suggests that the number of shots required in data acquisition can be dramatically reduced and the horizontal resolution can be greatly improved using analysis of group-velocity dispersion; and (3) the suspension logging results of the real-world example demonstrate that inversion of group velocities generated by the MFA method can successfully estimate near-surface S-wave velocities. ?? 2011 Elsevier B.V.

  16. How pyroclastic flows attain high velocities- new insights from large-scale experiments

    NASA Astrophysics Data System (ADS)

    Breard, E.; Lube, G.; Jones, J.; Valentine, G. A.

    2015-12-01

    Explosive volcanic eruptions are most deadly when highly mobile pyroclastic density currents (PDCs) sweep down mountain flanks after eruption columns or lava domes collapse. An important goal in volcanic hazard assessment is to predict the velocity of PDCs in numerical hazard models. To date, this has only been partially successful for dilute PDCs, and major uncertainties remain with regard to the dynamics of PDCs that have coupled dense underflow and dilute ash-cloud regions. Interrogating these complex multiphase processes is only practical in the laboratory, but this introduces the problem of scale where it is difficult to minimise the boundary layer effects which, in small flows, can dominate behaviour. To bridge the gap, we synthesized large-scale PDCs by gravitational collapse of 1300 kg of a natural pyroclastic mixture and examined flow front velocity fields on inclined slopes. We show that, proximally, PDCs experience rapid expulsion of gas that entrains particles and yields a fast-moving turbulent and dilute cloud that becomes the flow head and moves at 200-250% of the impact velocity. Downstream, the turbulent cloud moves ahead of the underflow. We show that the velocity-dependent friction coefficient (which represents the major dissipative form of energy) directly relates to the kinematics of the underflow front. In experimental situations where the dilute flow front velocity exceeds at all times the underflow velocity, we propose a new analytical model to quantify the asymptotic waning of the flow front velocity with distance. Using measurements of the flow head geometry and density, we show that our model successfully predicts the flow front kinematics including a long-lasting period of deceleration. Importantly, the interplay between the turbulent flow front and the presence of an underflow leads to the formation of a wedge-shaped head characterized by unexpectedly high coefficients of entrainment of ambient air.

  17. Evidence for a high-velocity slab associated with the Hindu Kush seismic zone

    NASA Astrophysics Data System (ADS)

    Mellors, R. J.; Pavlis, G. L.; Hamburger, M. W.; Al-Shukri, H. J.; Lukk, A. A.

    1995-03-01

    We used teleseismic travel time residuals to determine lateral velocity variations of the crust and upper mantle in the Pamir-Hindu Kush region in Tadjikistan and Afghanistan. Data from 29 analog seismic stations in Tadjikistan and northern Afghanistan were used to determine travel time residuals for 210 teleseismic events ranging in distance from 28 deg to 87 deg and covering a broad range of azimuths. We inverted for velocity perturbations over a rectangular grid with a block size of 99 x 99 km. The model extended to a depth of 350 km with a 50-km-thick first layer and two 150-km-thick deeper layers. The results show a strong and well-resolved zone of high velocities in the upper mantle at depths greater than 200 km, coincident with the location of the Hindu Kush seismic zone. No clear velocity perturbations are associated with the Pamir seismic zone. Above 200 km little correlation is observed with the seismic zone, but indications of thicker crust under the Pamir and thinner crust under the Tadjik Depression are seen. The high velocities are most likely caused by the presence of oceanic lithosphere at depth.

  18. First high resolution P wave velocity structure beneath Tenerife Island, (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Garcia-Yeguas, Araceli; Ivan, Koulakov; Ibañez Jesus, M.; Valenti, Sallarès.

    2010-05-01

    3D velocity structure distribution has been imaged for first time using high resolution traveltime seismic tomography of the active volcano of Tenerife Island (Canary Islands, Spain). It is located in the Atlantic Ocean. In this island is situated the Teide stratovolcano (3718 m high) that is part of the Cañadas-Teide-Pico Viejo volcanic complex. Las Cañadas is a caldera system more than 20 kilometers wide where at least four distinct caldera processes have been identified. Evidence for many explosive eruptions in the volcanic complex has been found; the last noticeable explosive eruption (sub-plinean) occurred at Montaña Blanca around 2000 years ago. During the last 300 years, six effusive eruptions have been reported, the last of which took place at Chinyero Volcano on 18 November 1909. In January 2007, a seismic active experiment was carried out as part of the TOM-TEIDEVS project. About 6850 air gun shots were fired on the sea and recorded on a dense local seismic land network consisting of 150 independent (three component) seismic stations. The good quality of the recorded data allowed identifying P-wave arrivals up to offsets of 30-40 km obtaining more than 63000 traveltimes used in the tomographic inversion. The images have been obtained using ATOM-3D code (Koulakov, 2009). This code uses ray bending algorithms in the ray tracing for the forward modelling and in the inversion step it uses gradient methods. The velocity models show a very heterogeneous upper crust that is usual in similar volcanic environment. The tomographic images points out the no-existence of a magmatic chamber near to the surface and below Pico Teide. The ancient Las Cañadas caldera borders are clearly imaged featuring relatively high seismic velocity. Moreover, we have found a big low velocity anomaly in the northwest dorsal of the island. The last eruption took place in 1909 in this area. Furthermore, in the southeast another low velocity anomaly has been imaged. Several resolution

  19. MULTIPLE HIGH-VELOCITY SiO MASER FEATURES FROM THE HIGH-MASS PROTOSTAR W51 NORTH

    SciTech Connect

    Cho, Se-Hyung; Kim, Jaeheon; Byun, Do-Young E-mail: jhkim@kasi.re.kr

    2011-02-01

    We present the detection of multiple high-velocity silicon monoxide (SiO v = 1, 2, J = 1-0) maser features in the high-mass protostar W51 North which are distributed over an exceedingly large velocity range from 105 to 230 km s{sup -1}. The SiO v = 1, J = 1-0 maser emission shows 3-5 narrow components which span a velocity range from 154 to 230 km s{sup -1} according to observational epochs. The SiO v = 2, J = 1-0 maser also shows 3-5 narrow components that do not correspond to the SiO v = 1 maser and span a velocity range from 105 to 154 km s{sup -1}. The multiple maser components show significant changes on very short timescales (<1 month) from epoch to epoch. We suggest that the high-velocity SiO masers may be emanated from massive star-forming activity of the W51 North protostar as SiO maser jets and will be a good probe of the earliest evolutionary stages of high-mass star formation via an accretion model. Further high angular resolution observations will be required for confirmation.

  20. A Gravitational Double-scattering Mechanism for Generating High-velocity Objects during Halo Mergers

    NASA Astrophysics Data System (ADS)

    Samsing, Johan

    2015-02-01

    We present a dynamical model that describes how halo particles can receive a significant energy kick from the merger between their own host halo and a target halo. This could provide a possible explanation for some high-velocity objects, including extended systems like globular clusters (GCs). In the model we especially introduce a double-scattering mechanism, where a halo particle receives a significant part of its total energy kick by first undergoing a gravitational deflection by the target halo and subsequently by its original host halo. This generates an energy kick that is due to the relative velocity between the halos during the deflections. We derive analytically the total kick energy of the particle, which is composed of energy from the double-scattering mechanism and tidal fields, as a function of its position in its original host halo just before merger. In the case of a 1:10 merger, we find that the presented mechanisms can easily generate particles with a velocity approximately two times the virial velocity of the target halo. This motivates us to suggest that the high velocity of the recently discovered GC HVGC-1 can be explained by a head-on halo merger. Finally, we illustrate the orbital evolution of high-velocity particles outside the virial sphere of the target halo by solving the equation of motion in an expanding universe. We find a sweet spot around a scale factor of 0.3-0.5 for ejecting particles into large orbits, which can easily reach beyond approximately five virial radii.

  1. A GRAVITATIONAL DOUBLE-SCATTERING MECHANISM FOR GENERATING HIGH-VELOCITY OBJECTS DURING HALO MERGERS

    SciTech Connect

    Samsing, Johan

    2015-02-01

    We present a dynamical model that describes how halo particles can receive a significant energy kick from the merger between their own host halo and a target halo. This could provide a possible explanation for some high-velocity objects, including extended systems like globular clusters (GCs). In the model we especially introduce a double-scattering mechanism, where a halo particle receives a significant part of its total energy kick by first undergoing a gravitational deflection by the target halo and subsequently by its original host halo. This generates an energy kick that is due to the relative velocity between the halos during the deflections. We derive analytically the total kick energy of the particle, which is composed of energy from the double-scattering mechanism and tidal fields, as a function of its position in its original host halo just before merger. In the case of a 1:10 merger, we find that the presented mechanisms can easily generate particles with a velocity approximately two times the virial velocity of the target halo. This motivates us to suggest that the high velocity of the recently discovered GC HVGC-1 can be explained by a head-on halo merger. Finally, we illustrate the orbital evolution of high-velocity particles outside the virial sphere of the target halo by solving the equation of motion in an expanding universe. We find a sweet spot around a scale factor of 0.3-0.5 for ejecting particles into large orbits, which can easily reach beyond approximately five virial radii.

  2. High Velocity Oxidation and Hot Corrosion Resistance of Some ODS Alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Deadmore, D. L.

    1977-01-01

    Several oxide dispersion strengthened (ODS) alloys were tested for cyclic, high velocity, oxidation, and hot corrosion resistance. These results were compared to the resistance of an advanced, NiCrAl coated superalloy. An ODS FeCrAl were identified as having sufficient oxidation and hot corrosion resistance to allow potential use in an aircraft gas turbine without coating.

  3. Preservation of Cognitive Performance with Age during Exertional Heat Stress under Low and High Air Velocity

    PubMed Central

    Wright Beatty, Heather E.; Keillor, Jocelyn M.; Hardcastle, Stephen G.; Boulay, Pierre; Kenny, Glen P.

    2015-01-01

    Older adults may be at greater risk for occupational injuries given their reduced capacity to dissipate heat, leading to greater thermal strain and potentially cognitive decrements. Purpose. To examine the effects of age and increased air velocity, during exercise in humid heat, on information processing and attention. Methods. Nine young (24 ± 1 years) and 9 older (59 ± 1 years) males cycled 4 × 15 min (separated by 15 min rest) at a fixed rate of heat production (400 W) in humid heat (35°C, 60% relative humidity) under 0.5 (low) and 3.0 (high) m·s−1 air velocity wearing coveralls. At rest, immediately following exercise (end exercise), and after the final recovery, participants performed an abbreviated paced auditory serial addition task (PASAT, 2 sec pace). Results. PASAT numbers of correct responses at end exercise were similar for young (low = 49 ± 3; high = 51 ± 3) and older (low = 46 ± 5; high = 47 ± 4) males and across air velocity conditions, and when scored relative to age norms. Psychological sweating, or an increased sweat rate with the administration of the PASAT, was observed in both age groups in the high condition. Conclusion. No significant decrements in attention and speeded information processing were observed, with age or altered air velocity, following intermittent exercise in humid heat. PMID:25874223

  4. Ultraviolet Molecular Rayleigh Scattering Used to Measure Velocity in High-Speed Flow

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.

    1997-01-01

    Molecular Rayleigh scattering offers a means to measure gas flow parameters including density, temperature, and velocity. No seeding of the flow is necessary. The Rayleigh scattered power is proportional to the gas density, the spectral width is related to the gas temperature, and the shift in the frequency of the spectral peak is proportional to one component of the fluid velocity. Velocity measurements based on Rayleigh scattering are more suitable for high-speed flow, where the bulk fluid velocity is on the order of, or larger than, the molecular thermal velocities. Use of ultraviolet wavelengths for Rayleigh scattering diagnostics is attractive for two reasons. First, the Rayleigh scattering cross section is proportional to the inverse 4th power of the wavelength. And second, the reflectivity of metallic surfaces is generally less than it is at longer wavelengths. This is of particular interest in confined flow situations, such as in small wind tunnels and aircraft engine components, where the stray laser light scattered from the windows and internal surfaces in the test facility limits the application of Rayleigh scattering diagnostics. In this work at the NASA Lewis Research Center, molecular Rayleigh scattering of the 266-nm fourth harmonic of a pulsed, injection seeded Nd:YAG (neodymium:yttriumaluminum- garnet) laser was used to measure velocity in a supersonic free air jet with a 9.3- mm exit diameter. The frequency of the Rayleigh scattered light was analyzed with a planar mirror Fabry-Perot interferometer used in a static imaging mode, with the images recorded on a cooled, high-quantum-efficiency charge-coupled discharge (CCD) camera. In addition, some unshifted light from the same laser pulse was imaged through the interferometer to generate a reference. Data were obtained with single laser pulses at velocities up to Mach 1.3. The measured velocities were in good agreement with velocities calculated from isentropic flow relations. Our conclusion from

  5. Estimation of friction velocity from the wind-wave spectrum at extremely high wind speeds

    NASA Astrophysics Data System (ADS)

    Takagaki, N.; Komori, S.; Suzuki, N.

    2016-05-01

    The equilibrium range of wind-waves at normal and extremely high wind speeds was investigated experimentally using a high-speed wind-wave tank together with field measurements at normal wind speeds. Water level fluctuations at normal and extremely high wind speeds were measured with resistance-type wave gauges, and the wind-wave spectrum and significant phase velocity were calculated. The equilibrium range constant was estimated from the wind-wave spectrum and showed the strong relationship with inverse wave age at normal and extremely high wind speeds. Using the strong relation between the equilibrium range constant and inverse wave age, a new method for estimating the wind speed at 10-m height (U 10) and friction velocity (u*) was proposed. The results suggest that U 10 and u* can be estimated from wave measurements alone at extremely high wind speeds in oceans under tropical cyclones.

  6. Penetration of Liquid Jets into a High-velocity Air Stream

    NASA Technical Reports Server (NTRS)

    Chelko, Louis J

    1950-01-01

    Data are presented showing the penetration characteristics of liquid jets directed approximately perpendicular to a high-velocity air stream for jet-nozzle-throat diameters from 0.0135 to 0.0625 inch, air stream densities from 0.0805 to 0.1365 pound per cubic foot, liquid jet velocities from 168.1 to 229.0 feet per second and a liquid jet density of approximately 62 pounds per cubic foot. The data were analyzed and a correlation was developed that permitted the determination of the penetration length of the liquid jet for any operation condition within the range of variables investigated.

  7. Role of the leader in the rail gun channel at high launching velocities

    NASA Astrophysics Data System (ADS)

    Zagorskii, A. V.; Katsnel'Son, S. S.; Pravdin, S. S.; Fomichev, V. P.

    1992-08-01

    An analysis of the performance of a number of rail guns indicates that one of the factors limiting the launching velocity is the formation of a leader. In experiments, the leader is usually formed as a result of a plasma breakdown between the dielectric projectile and the channel walls. This can be prevented by various technical means. However, at high launching velocities (5 km/s and greater) a leader may form as a result of a breakdown in the ionized gas in the wake of a strong shock wave ahead of the projectile. Further research is needed to find ways of preventing the formation of a leader in the latter case.

  8. Alfven's critical ionization velocity observed in high power impulse magnetron sputtering discharges

    SciTech Connect

    Brenning, N.; Lundin, D.

    2012-09-15

    Azimuthally rotating dense plasma structures, spokes, have recently been detected in several high power impulse magnetron sputtering (HiPIMS) devices used for thin film deposition and surface treatment, and are thought to be important for plasma buildup, energizing of electrons, as well as cross-B transport of charged particles. In this work, the drift velocities of these spokes are shown to be strongly correlated with the critical ionization velocity, CIV, proposed by Alfven. It is proposed as the most promising approach in combining the CIV and HiPIMS research fields is to focus on the role of spokes in the process of electron energization.

  9. High-precision measurement of satellite range and velocity using the EISCAT radar

    NASA Astrophysics Data System (ADS)

    Markkanen, J.; Nygrén, T.; Markkanen, M.; Voiculescu, M.; Aikio, A.

    2013-05-01

    This paper is a continuation of an earlier work by Nygrén et al. (2012), where the velocity of a hard target was determined from a set of echo pulses reflected by the target flying through the radar beam. Here the method is extended to include the determination of range at a high accuracy. The method is as follows. First, the flight time of the pulse from the transmitter to the target is determined at an accuracy essentially better than the accuracy given by the sampling interval. This method makes use of the fact that the receiver filtering creates slopes at the phase flips of the phase modulated echo pulse. A precise flight time is found by investigating the echo amplitude within this slope. A value of velocity is calculated from each echo pulse as explained in the earlier paper. Next, the ranges together with velocities from a single beam pass are combined to a measurement vector for a linear inversion problem. The solution of the inversion problem gives the time-dependent range and velocity from the time interval of satellite flight through the radar beam. The method is demonstrated using the EISCAT (European Incoherent Scatter) UHF radar and radio pulses reflected by a satellite. The achieved standard deviations of range are about 5-50 cm and those of velocity are about 3-25 mm s-1.

  10. Portable conduction velocity experiments using earthworms for the college and high school neuroscience teaching laboratory.

    PubMed

    Shannon, Kyle M; Gage, Gregory J; Jankovic, Aleksandra; Wilson, W Jeffrey; Marzullo, Timothy C

    2014-03-01

    The earthworm is ideal for studying action potential conduction velocity in a classroom setting, as its simple linear anatomy allows easy axon length measurements and the worm's sparse coding allows single action potentials to be easily identified. The earthworm has two giant fiber systems (lateral and medial) with different conduction velocities that can be easily measured by manipulating electrode placement and the tactile stimulus. Here, we present a portable and robust experimental setup that allows students to perform conduction velocity measurements within a 30-min to 1-h laboratory session. Our improvement over this well-known preparation is the combination of behaviorally relevant tactile stimuli (avoiding electrical stimulation) with the invention of minimal, low-cost, and portable equipment. We tested these experiments during workshops in both a high school and college classroom environment and found positive learning outcomes when we compared pre- and posttests taken by the students.

  11. Portable conduction velocity experiments using earthworms for the college and high school neuroscience teaching laboratory.

    PubMed

    Shannon, Kyle M; Gage, Gregory J; Jankovic, Aleksandra; Wilson, W Jeffrey; Marzullo, Timothy C

    2014-03-01

    The earthworm is ideal for studying action potential conduction velocity in a classroom setting, as its simple linear anatomy allows easy axon length measurements and the worm's sparse coding allows single action potentials to be easily identified. The earthworm has two giant fiber systems (lateral and medial) with different conduction velocities that can be easily measured by manipulating electrode placement and the tactile stimulus. Here, we present a portable and robust experimental setup that allows students to perform conduction velocity measurements within a 30-min to 1-h laboratory session. Our improvement over this well-known preparation is the combination of behaviorally relevant tactile stimuli (avoiding electrical stimulation) with the invention of minimal, low-cost, and portable equipment. We tested these experiments during workshops in both a high school and college classroom environment and found positive learning outcomes when we compared pre- and posttests taken by the students. PMID:24585472

  12. Rayleigh Scattering Diagnostic for Dynamic Measurement of Velocity Fluctuations in High Speed Jets

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Panda, Jayanta; Elam, Kristie A.

    2001-01-01

    A flow diagnostic technique based on the molecular Rayleigh scattering of laser light is used to obtain dynamic density and velocity data in a high speed flow. The technique is based on analyzing the Rayleigh scattered light with a Fabry-Perot interferometer used in the static, imaging mode. An analysis is presented that established a lower bound for measurement uncertainty of about 20 m/sec for individual velocity measurements obtained in a 100 microsecond time interval. Software and hardware interfaces were developed to allow computer control of all aspects of the experiment and data acquisition. The signals from three photomultiplier tubes were simultaneously recorded using photon counting at a 10 kHz sampling rate and 10 second recording periods. Density and velocity data, including distribution functions and power spectra, taken in a Mach 0.8 free jet, are presented.

  13. Velocity analysis using high-resolution semblance based on sparse hyperbolic Radon transform

    NASA Astrophysics Data System (ADS)

    Gong, Xiangbo; Wang, Shengchao; Zhang, Tianze

    2016-11-01

    Semblance measures the lateral coherency of the seismic events in a common mid-point gather, and it has been widely used for the normal-moveout-based velocity estimation. In this paper, we propose a new velocity analysis method by using high-resolution semblance based on sparse hyperbolic Radon transform (SHRT). Conventional semblance can be defined as the ratio of signal energy to total energy in the time gate. We replace the signal energy with the square of the sparse Radon panel and replace the total energy with the sparse Radon panel of the square data. Because of the sparsity-constrained inversion of SHRT, the new approach can produce higher resolution semblance spectra than the conventional semblance. We test this new semblance on synthetic and field data to demonstrate the improvements in velocity analysis.

  14. Group velocity locked vector dissipative solitons in a high repetition rate fiber laser.

    PubMed

    Luo, Yiyang; Li, Lei; Liu, Deming; Sun, Qizhen; Wu, Zhichao; Xu, Zhilin; Tang, Dingyuan; Fu, Songnian; Zhao, Luming

    2016-08-01

    Vectorial nature of dissipative solitons (DSs) with high repetition rate is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating group velocity locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same group velocity in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectrum, which can be considered as an auxiliary indicator of the group velocity locked vector DSs. Moreover, numerical simulations well confirm the experimental observations and further reveal the impact of the net cavity birefringence on the properties of the formed vector DSs. PMID:27505834

  15. Portable conduction velocity experiments using earthworms for the college and high school neuroscience teaching laboratory

    PubMed Central

    Shannon, Kyle M.; Gage, Gregory J.; Jankovic, Aleksandra; Wilson, W. Jeffrey

    2014-01-01

    The earthworm is ideal for studying action potential conduction velocity in a classroom setting, as its simple linear anatomy allows easy axon length measurements and the worm's sparse coding allows single action potentials to be easily identified. The earthworm has two giant fiber systems (lateral and medial) with different conduction velocities that can be easily measured by manipulating electrode placement and the tactile stimulus. Here, we present a portable and robust experimental setup that allows students to perform conduction velocity measurements within a 30-min to 1-h laboratory session. Our improvement over this well-known preparation is the combination of behaviorally relevant tactile stimuli (avoiding electrical stimulation) with the invention of minimal, low-cost, and portable equipment. We tested these experiments during workshops in both a high school and college classroom environment and found positive learning outcomes when we compared pre- and posttests taken by the students. PMID:24585472

  16. Relationship between the upper mantle high velocity seismic lid and the continental lithosphere

    NASA Astrophysics Data System (ADS)

    Priestley, Keith; Tilmann, Frederik

    2009-04-01

    The lithosphere-asthenosphere boundary corresponds to the base of the "rigid" plates - the depth at which heat transport changes from advection in the convecting deeper upper mantle to conduction in the shallow upper mantle. Although this boundary is a fundamental feature of the Earth, mapping it has been difficult because it does not correspond to a sharp change in temperature or composition. Various definitions of the lithosphere and asthenosphere are based on the analysis of different types of geophysical and geological observations. The depth to the lithosphere-asthenosphere boundary determined from these different observations often shows little agreement when they are applied to the same region because the geophysical and geological observations (i.e., seismic velocity, strain rate, electrical resistivity, chemical depletion, etc.) are proxies for the change in rheological properties rather than a direct measure of the rheological properties. In this paper, we focus on the seismic mapping of the upper mantle high velocity lid and low velocity zone and its relationship to the lithosphere and asthenosphere. We have two goals: (a) to examine the differences in how teleseismic body-wave travel-time tomography and surface-wave tomography image upper mantle seismic structure; and (b) to summarise how upper mantle seismic velocity structure can be related to the structure of the lithosphere and asthenosphere. Surface-wave tomography provides reasonably good depth resolution, especially when higher modes are included in the analysis, but lateral resolution is limited by the horizontal wavelength of the long-period surface waves used to constrain upper mantle velocity structure. Teleseismic body-wave tomography has poor depth resolution in the upper mantle, particularly when no strong lateral contrasts are present. If station terms are used, features with large lateral extent and gradual boundaries are attenuated in the tomographic image. Body-wave models are not

  17. High-resolution HI and CO observations of high-latitude intermediate-velocity clouds

    NASA Astrophysics Data System (ADS)

    Röhser, T.; Kerp, J.; Ben Bekhti, N.; Winkel, B.

    2016-08-01

    Context. Intermediate-velocity clouds (IVCs) are HI halo clouds that are likely related to a Galactic fountain process. In-falling IVCs are candidates for the re-accretion of matter onto the Milky Way. Aims: We study the evolution of IVCs at the disk-halo interface, focussing on the transition from atomic to molecular IVCs. We compare an atomic IVC to a molecular IVC and characterise their structural differences in order to investigate how molecular IVCs form high above the Galactic plane. Methods: With high-resolution HI observations of the Westerbork Synthesis Radio Telescope and 12CO(1 → 0) and 13CO(1 → 0) observations with the IRAM 30 m telescope, we analyse the small-scale structures within the two clouds. By correlating HI and far-infrared (FIR) dust continuum emission from the Planck satellite, the distribution of molecular hydrogen (H2) is estimated. We conduct a detailed comparison of the HI, FIR, and CO data and study variations of the XCO conversion factor. Results: The atomic IVC does not disclose detectable CO emission. The atomic small-scale structure, as revealed by the high-resolution HI data, shows low peak HI column densities and low HI fluxes as compared to the molecular IVC. The molecular IVC exhibits a rich molecular structure and most of the CO emission is observed at the eastern edge of the cloud. There is observational evidence that the molecular IVC is in a transient and, thus, non-equilibrium phase. The average XCO factor is close to the canonical value of the Milky Way disk. Conclusions: We propose that the two IVCs represent different states in a gradual transition from atomic to molecular clouds. The molecular IVC appears to be more condensed allowing the formation of H2 and CO in shielded regions all over the cloud. Ram pressure may accumulate gas and thus facilitate the formation of H2. We show evidence that the atomic IVC will evolve also into a molecular IVC in a few Myr. The reduced datacubes are only available at the CDS via

  18. Method and apparatus for optical Doppler tomographic imaging of fluid flow velocity in highly scattering media

    DOEpatents

    Nelson, John Stuart; Milner, Thomas Edward; Chen, Zhongping

    1999-01-01

    Optical Doppler tomography permits imaging of fluid flow velocity in highly scattering media. The tomography system combines Doppler velocimetry with high spatial resolution of partially coherent optical interferometry to measure fluid flow velocity at discrete spatial locations. Noninvasive in vivo imaging of blood flow dynamics and tissue structures with high spatial resolutions of the order of 2 to 10 microns is achieved in biological systems. The backscattered interference signals derived from the interferometer may be analyzed either through power spectrum determination to obtain the position and velocity of each particle in the fluid flow sample at each pixel, or the interference spectral density may be analyzed at each frequency in the spectrum to obtain the positions and velocities of the particles in a cross-section to which the interference spectral density corresponds. The realized resolutions of optical Doppler tomography allows noninvasive in vivo imaging of both blood microcirculation and tissue structure surrounding the vessel which has significance for biomedical research and clinical applications.

  19. Transport dynamics of a high-power-density matrix-type hydrogen-oxygen fuel cell

    NASA Technical Reports Server (NTRS)

    Prokopius, P. R.; Hagedorn, N. H.

    1974-01-01

    Experimental transport dynamics tests were made on a space power fuel cell of current design. Various operating transients were introduced and transport-related response data were recorded with fluidic humidity sensing instruments. Also, sampled data techniques were developed for measuring the cathode-side electrolyte concentration during transient operation.

  20. Hypersonic velocity measurement using Brillouin scattering technique. Application to water under high pressure and temperature.

    PubMed

    Decremps, Frederic; Datchi, Frederic; Polian, Alain

    2006-12-22

    This paper presents recent improvement on sound velocity measurements under extreme conditions, illustrated by the hypersonic sound velocity measurements of water up to 723 K and 9 GPa using Brillouin scattering technique. Because water at high pressure and high temperature is chemically very aggressive, these experiments have been carried out using a specific experimental set-up. The present data should be useful to better constrain the water equation of state at high density. This new development brings high-quality elastic data in a large pressure/temperature domain, which may afterwards benefit the understanding of many other fields as nonlinear acoustics, underwater sound, or physical acoustics from a more general point of view.

  1. The frequency and distribution of high-velocity gas in the Galaxy

    NASA Technical Reports Server (NTRS)

    Nichols, Joy S.

    1995-01-01

    The purpose of this study was to estimate the frequency and distribution of high-velocity gas in the Galaxy using UV absorption line measurements from archival high-dispersion IUE spectra and to identify particularly interesting regions for future study. Approximately 500 spectra have been examined. The study began with the creation of a database of all 0 and B stars with b less than or = to 30 deg observed with IUE at high dispersion over its 18-year lifetime. The original database of 2500 unique objects was reduced to 1200 objects which had optimal exposures available. The next task was to determine the distances of these stars so the high-velocity structures could be mapped in the Galaxy. Spectroscopic distances were calculated for each star for which photometry was available. The photometry was acquired for each star using the SIMBAD database. Preference was given to the ubvy system where available; otherwise the UBV system was used.

  2. High-Velocity Absorption Features in FUSE Spectra of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Vieira, G.

    2002-12-01

    Numerous broad (200 to 1000 km/sec) features in the FUSE spectrum (905-1187 A) of eta Carinae are identified as absorption by a forest of high-velocity narrow lines formed in the expanding circumstellar envelope. These features were previously thought to be P-Cygni lines arising in the wind of the central star. The features span a heliocentric velocity range of -140 to -580 km/sec and are seen prominently in low-ionization ground-state transitions (e.g. N I 1134-35, Fe II 1145-42, 1133, 1127-22, P II 1153, C I 1158) in addition to C III] 1176 A. The high-velocity components of the FUSE transitions have depths about 50% below the continuum. The identifications are consistent with the complex velocity structures seen in ground- and excited-state transitions of Mg I, Mg II, Fe II, V II, etc observed in STIS/E230H spectra (see accompanying posters by Gull, Vieira, and Danks). The origin of other broad features of similar width and depth in the FUSE spectrum, but without low-velocity ISM absorption, are unidentified. However, they are suspected of being absorption of singly-ionized iron-peak elements (e.g. Fe II, V II, Cr II) out of excited levels 1,000 to 20,000 cmE-1 above the ground state. The high-velocity features seen in Fe II 1145 are also present in Fe II 1608 (STIS/E140M), but are highly saturated in the latter. Since these transitions have nearly identical log (flambda) (1.998 vs. 2.080), the differences in the profiles are attributable to the different aperture sizes used (30x30 arcsec for FUSE, 0.2x0.2 arcsec for STIS/E140M). The high-velocity gas appears to be very patchy or has a small covering factor near the central star. Eta Carinae has been observed several times by FUSE over the past three years. The FUSE flux levels and spectral features in eta Car are essentially unchanged over the 2000 March to June 2002 period, establishing a baseline far-UV spectrum in advance of the predicted spectroscopic miniumum in 2003.

  3. High-Velocity Absorption Features in FUSE Spectra of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Vieira, G.

    2003-01-01

    Numerous broad (200 to 1000 km/sec) features in the FUSE spectrum (905-1187 A) of eta Carinae are identified as absorption by a forest of high-velocity narrow lines formed in the expanding circumstellar envelope. These features were previously thought to be P-Cygni lines arising in the wind of the central star. The features span a heliocentric velocity range of -140 to -580 km/sec and are seen prominently in low-ionization ground-state transitions (e.g. N I 1134-35, Fe II 1145-42, 1133, 1127- 22, P II 1153, C I 1158) in addition to C III] 1176 A. The high-velocity components of the FUSE transitions have depths about 50% below the continuum. The identifications are consistent with the complex velocity structures seen in ground- and excited-state transitions of Mg I, Mg 11, Fe II, V II, etc observed in STIS/E230H spectra. The origin of other broad features of similar width and depth in the FUSE spectrum, but without low-velocity ISM absorption, are unidentified. However, they are suspected of being absorption of singly-ionized iron-peak elements (e.g. Fe II, V II, Cr II) out of excited levels 1,000 to 20,000 cmE-l above the ground state. The high-velocity features seen in Fe II 1145 are also present in Fe II 1608 (STIS/E140M), but are highly saturated in the latter. Since these transitions have nearly identical log (flambda) (1.998 vs. 2.080), the differences in the profiles are attributable to the different aperture sizes used (30 x 30 arcsec for FUSE, 0.2 x 0.2 arcsec for STIS/E140M). The high-velocity gas appears to be very patchy or has a small covering factor near the central star. Eta Carinae has been observed several times by FUSE over the past three years. The FUSE flux levels and spectral features in eta Car are essentially unchanged over the 2000 March to June 2002 period, establishing a baseline far-UV spectrum in advance of the predicted spectroscopic minimum in 2003.

  4. The effects of varying resistance-training loads on intermediate- and high-velocity-specific adaptations.

    PubMed

    Jones, K; Bishop, P; Hunter, G; Fleisig, G

    2001-08-01

    The purpose of this study was to compare changes in velocity-specific adaptations in moderately resistance-trained athletes who trained with either low or high resistances. The study used tests of sport-specific skills across an intermediate- to high-velocity spectrum. Thirty NCAA Division I baseball players were randomly assigned to either a low-resistance (40-60% 1 repetition maximum [1RM]) training group or a high-resistance (70-90% 1RM) training group. Both of the training groups intended to maximallv accelerate each repetition during the concentric phase (IMCA). The 10 weeks of training consisted of 4 training sessions a week using basic core exercises. Peak force, velocity, and power were evaluated during set angle and depth jumps as well as weighted jumps using 30 and 50% 1RM. Squat 1RMs were also tested. Although no interactions for any of the jump tests were found, trends supported the hypothesis of velocity-specific training. Percentage gains suggest that the combined use of heavier training loads (70-90% 1RM) and IMCA tend to increase peak force in the lower-body leg and hip extensors. Trends also show that the combined use of lighter training loads (40-60% 1RM) and IMCA tend to increase peak power and peak velocity in the lower-body leg and hip extensors. The high-resistance group improved squats more than the low-resistance group (p < 0.05; +22.7 vs. + 16.1 kg). The results of this study support the use of a combination of heavier training loads and IMCA to increase 1RM strength in the lower bodies of resistance-trained athletes.

  5. Development of tunable high pressure CO2 laser for lidar measurements of pollutants and wind velocities

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Guerra, M.; Javan, A.

    1980-01-01

    The problem of laser energy extraction at a tunable monochromatic frequency from an energetic high pressure CO2 pulsed laser plasma, for application to remote sensing of atmospheric pollutants by Differential Absorption Lidar (DIAL) and of wind velocities by Doppler Lidar, was investigated. The energy extraction principle analyzed is based on transient injection locking (TIL) at a tunable frequency. Several critical experiments for high gain power amplification by TIL are presented.

  6. High Resolution Velocity Map Imaging Photoelectron Spectroscopy of the Beryllium Oxide Anion, BeO-

    NASA Astrophysics Data System (ADS)

    Dermer, Amanda Reed; Mascaritolo, Kyle; Heaven, Michael

    2016-06-01

    The photodetachment spectrum of BeO- has been studied using high resolution velocity map imaging photoelectron spectroscopy. The vibrational contours were imaged and compared with Franck-Condon simulations for the ground and excited states of the neutral. The electron affinity of BeO was measured for the first time, and anisotropies of several transitions were determined. Experimental findings are compared to high level ab initio calculations.

  7. Streptococcus mutans biofilm transient viscoelastic fluid behaviour during high-velocity microsprays.

    PubMed

    Fabbri, S; Johnston, D A; Rmaile, A; Gottenbos, B; De Jager, M; Aspiras, M; Starke, E M; Ward, M T; Stoodley, P

    2016-06-01

    Using high-speed imaging we assessed Streptococcus mutans biofilm-fluid interactions during exposure to a 60-ms microspray burst with a maximum exit velocity of 51m/s. S. mutans UA159 biofilms were grown for 72h on 10mm-length glass slides pre-conditioned with porcine gastric mucin. Biofilm stiffness was measured by performing uniaxial-compression tests. We developed an in-vitro interproximal model which allowed the parallel insertion of two biofilm-colonized slides separated by a distance of 1mm and enabled high-speed imaging of the removal process at the surface. S. mutans biofilms were exposed to either a water microspray or an air-only microburst. High-speed videos provided further insight into the mechanical behaviour of biofilms as complex liquids and into high-shear fluid-biofilm interaction. We documented biofilms extremely transient fluid behaviour when exposed to the high-velocity microsprays. The presence of time-dependent recoil and residual deformation confirmed the pivotal role of viscoelasticity in biofilm removal. The air-only microburst was effective enough to remove some of the biofilm but created a smaller clearance zone underlying the importance of water and the air-water interface of drops moving over the solid surface in the removal process. Confocal and COMSTAT analysis showed the high-velocity water microspray caused up to a 99.9% reduction in biofilm thickness, biomass and area coverage, within the impact area. PMID:26771168

  8. On projectile fragmentation at high-velocity perforation of a thin bumper

    NASA Astrophysics Data System (ADS)

    Myagkov, N. N.; Stepanov, V. V.

    2014-09-01

    By means of 3D numerical simulations, we study the statistical properties of the fragments cloud formed during high-velocity impact of a spherical projectile on a mesh bumper. We present a quantitative description of the projectile fragmentation, and study the nature of the transition from the damage to the fragmentation of the projectile when the impact velocity varies. A distinctive feature of the present work is that the calculations are carried out by smoothed particle hydrodynamics (SPH) method applied to the equations of mechanics of deformable solids (MDS). We describe the materials behavior by the Mie-Grüneisen equation of state and the Johnson-Cook model for the yield strength. The maximum principal stress spall model is used as the fracture model. It is shown that the simulation results of fragmentation based on the MDS equations by the SPH method are qualitatively consistent with the results obtained earlier on the basis of the molecular dynamics and discrete element models. It is found that the power-law distribution exponent does not depend on energy imparted to the projectile during the high-velocity impact. At the same time, our calculations show that the critical impact velocity, the power-law exponent and other critical exponents depend on the fracture criterion.

  9. HIGH-RESOLUTION SEISMIC VELOCITY AND ATTENUATION MODELS OF THE CAUCASUS-CASPIAN REGION

    SciTech Connect

    Mellors, R; Gok, R; Sandvol, E

    2007-07-10

    The southwest edge of Eurasia is a tectonically and structurally complex region that includes the Caspian and Black Sea basins, the Caucasus Mountains, and the high plateaus south of the Caucasus. Crustal and upper mantle velocities show great heterogeneity in this region and regional phases display variations in both amplitudes and travel time. Furthermore, due to a lack of quality data, the region has largely been unexplored in terms of the detailed lithospheric seismic structure. A unified high-resolution 3D velocity and attenuation model of the crust and upper mantle will be developed and calibrated. This model will use new data from 23 new broadband stations in the region analyzed with a comprehensive set of techniques. Velocity models of the crust and upper mantle will be developed using a joint inversion of receiver functions and surface waves. The surface wave modeling will use both event-based methods and ambient noise tomography. Regional phase (Pg, Pn, Sn, and Lg) Q model(s) will be constructed using the new data in combination with existing data sets. The results of the analysis (both attenuation and velocity modeling) will be validated using modeling of regional phases, calibration with selected events, and comparison with previous work. Preliminary analyses of receiver functions show considerable variability across the region. All results will be integrated into the KnowledgeBase.

  10. Study on the radiation property of high temperature gas relation with flight altitude and velocity

    NASA Astrophysics Data System (ADS)

    Meng, Weihua; Xu, Hang; Xiang, Jingbo; Song, Jiangtao

    2013-08-01

    While flying in the aerosphere at high speed, it will form shock wave around the noddle of flight vehicle. The radiation of hot air behind shock wave is a major factor responsible for the infrared signature of the vehicle, and has an important influence on the infrared detection system mounted in it. Calculating the infrared radiation of high temperature gas is significant for selecting an optimal detection band and improving detection capability of the IR system. In this paper, focused on the high-speed flight in typical altitude, the line-by-line method was adopted to calculate the radiation properties of high temperature gas around the noddle of the vehicle to study the relationship with the flight altitude and velocity. At first, based on the flight altitude, the related parameters of the flow, such as pressure, temperature and density, were calculated using the standard atmosphere model. Then, the parameters of the air which had passed through the shock wave were calculated according to the shock wave theory. At last, the line-by-line method had been used to calculate the radiant absorption coefficient of high temperature gas in different velocity and flight altitude. The results of calculation show that in the same velocity, the average absorption coefficient of high temperature gas is smaller while the higher flight altitude; in the same flight altitude, the coefficient is bigger while the higher velocity. And so, while flying in low altitude with high speed, the radiation of the hot air should be taken into consideration more carefully for infrared system design.

  11. Chemical reactions induced by high-velocity molecular impacts: challenges for closed-source mass spectrometry

    NASA Astrophysics Data System (ADS)

    Austin, Daniel

    2016-07-01

    Analysis of upper atmosphere composition using closed-source neutral mass spectrometers (e.g., Cassini INMS, MAVEN NGIMS) is subject to error due to chemical reactions caused by the high-velocity impacts of neutral molecules on the source surfaces. In addition to species traditionally considered "surface reactive" (e.g., O, N) it is likely that many or all impacting molecules are vibrationally excited to the point that chemical changes can occur. Dissociation, fragmentation, formation of radicals and ions, and other reactions likely obscure analysis of the native atmospheric composition, particularly of organic compounds. Existing techniques are not capable of recreating the relevant impact chemistry in the lab. We report on the development of a new capability allowing reactions of high-velocity neutrals impacting surfaces to be characterized directly. Molecules introduced into a vacuum chamber are impacted at several km/s by the surface of a high-speed rotor. These molecules subsequently impact multiple times on other surfaces within the vacuum chamber until they are thermalized, after which they are cryogenically collected and analyzed. Reaction pathways and thermodynamics for volatile compounds are then determined. We will present current results on this project, including data from low- and mid-range velocity experiments. This type of information is critical to clarify prior flight results and plan for future missions. Finally, we present a new type of inlet intended to significantly reduce fragmentation for impact velocities typical of a fly-by mission. Theoretical analysis indicates that this new inlet may reduce fragmentation by more than an order of magnitude for any encounter velocity.

  12. Supernova 2010ev: A reddened high velocity gradient type Ia supernova

    NASA Astrophysics Data System (ADS)

    Gutiérrez, Claudia P.; González-Gaitán, Santiago; Folatelli, Gastón; Pignata, Giuliano; Anderson, Joseph P.; Hamuy, Mario; Morrell, Nidia; Stritzinger, Maximilian; Taubenberger, Stefan; Bufano, Filomena; Olivares E., Felipe; Haislip, Joshua B.; Reichart, Daniel E.

    2016-05-01

    Aims: We present and study the spectroscopic and photometric evolution of the type Ia supernova (SN Ia) 2010ev. Methods: We obtain and analyze multiband optical light curves and optical/near-infrared spectroscopy at low and medium resolution spanning -7 days to +300 days from the B-band maximum. Results: A photometric analysis shows that SN 2010ev is a SN Ia of normal brightness with a light-curve shape of Δm15(B) = 1.12 ± 0.02 and a stretch s = 0.94 ± 0.01 suffering significant reddening. From photometric and spectroscopic analysis, we deduce a color excess of E(B - V) = 0.25 ± 0.05 and a reddening law of Rv = 1.54 ± 0.65. Spectroscopically, SN 2010ev belongs to the broad-line SN Ia group, showing stronger than average Si iiλ6355 absorption features. We also find that SN 2010ev is a high velocity gradient SN with v˙Si = 164 ± 7 km s-1 d-1. The photometric and spectral comparison with other supernovae shows that SN 2010ev has similar colors and velocities to SN 2002bo and SN 2002dj. The analysis of the nebular spectra indicates that the [Fe ii]λ7155 and [Ni ii]λ7378 lines are redshifted, as expected for a high velocity gradient supernova. All these common intrinsic and extrinsic properties of the high velocity gradient (HVG) group are different from the low velocity gradient (LVG) normal SN Ia population and suggest significant variety in SN Ia explosions. This paper includes data gathered with the Du Pont Telescope at Las Campanas Observatory, Chile; and the Gemini Observatory, Cerro Pachon, Chile (Gemini Program GS-2010A-Q-14). Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (ESO Programme 085.D-0577).

  13. Measuring densities of high-velocity metallic sprays using piezoelectric sensors

    SciTech Connect

    Lloyd, C. E.; Proud, W. G.

    2007-12-12

    Recent research efforts in large-scale hydrodynamic experiments have concentrated on the possibility of using piezoelectric sensors to study the evolution of ejecta. Ejecta are small (<100 m diameter) particulates that are ejected at high velocity (>1 km s{sup -1}) from a shocked surface. This paper investigates whether Dynasen PZT piezoelectric sensors are reliable and robust enough to measure accurate time-resolved stresses and densities in high-velocity metallic sprays. The sprays are assumed to have similar characteristics to ejecta sprays, and are generated by a gas gun and in a safe and reproducible manner. A complimentary diagnostic technique, utilising high-speed photography and fast x-radiography, measures the densities of the sprays independently, allowing the accuracy of the sensors to be assessed. The Dynasen sensors have been shown to perform relatively well in spray environments. Their accuracy can be improved by taking their mechanical impedance characteristics into account.

  14. Thin shell, high velocity inertial confinement fusion implosions on the national ignition facility.

    PubMed

    Ma, T; Hurricane, O A; Callahan, D A; Barrios, M A; Casey, D T; Dewald, E L; Dittrich, T R; Döppner, T; Haan, S W; Hinkel, D E; Berzak Hopkins, L F; Le Pape, S; MacPhee, A G; Pak, A; Park, H-S; Patel, P K; Remington, B A; Robey, H F; Salmonson, J D; Springer, P T; Tommasini, R; Benedetti, L R; Bionta, R; Bond, E; Bradley, D K; Caggiano, J; Celliers, P; Cerjan, C J; Church, J A; Dixit, S; Dylla-Spears, R; Edgell, D; Edwards, M J; Field, J; Fittinghoff, D N; Frenje, J A; Gatu Johnson, M; Grim, G; Guler, N; Hatarik, R; Herrmann, H W; Hsing, W W; Izumi, N; Jones, O S; Khan, S F; Kilkenny, J D; Knauer, J; Kohut, T; Kozioziemski, B; Kritcher, A; Kyrala, G; Landen, O L; MacGowan, B J; Mackinnon, A J; Meezan, N B; Merrill, F E; Moody, J D; Nagel, S R; Nikroo, A; Parham, T; Ralph, J E; Rosen, M D; Rygg, J R; Sater, J; Sayre, D; Schneider, M B; Shaughnessy, D; Spears, B K; Town, R P J; Volegov, P L; Wan, A; Widmann, K; Wilde, C H; Yeamans, C

    2015-04-10

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165  μm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Early results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating. PMID:25910132

  15. Thin Shell, High Velocity Inertial Confinement Fusion Implosions on the National Ignition Facility

    SciTech Connect

    Ma, T.; Hurricane, O. A.; Callahan, D. A.; Barrios, M. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Doppner, T.; Haan, S. W.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; MacPhee, A. G.; Pak, A.; Park, H. S.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J. D.; Springer, P. T.; Tommasini, R.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Celliers, P.; Cerjan, C. J.; Church, J. A.; Dixit, S.; Dylla-Spears, R.; Edgell, D.; Edwards, M. J.; Field, J.; Fittinghoff, D. N.; Frenje, J. A.; Gatu Johnson, M.; Grim, G.; Guler, N.; Hatarik, R.; Herrmann, H. W.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Khan, S. F.; Kilkenny, J. D.; Knauer, J.; Kohut, T.; Kozioziemski, B.; Kritcher, A.; Kyrala, G.; Landen, O. L.; MacGowan, B. J.; Mackinnon, A. J.; Meezan, N. B.; Merrill, F. E.; Moody, J. D.; Nagel, S. R.; Nikroo, A.; Parham, T.; Ralph, J. E.; Rosen, M. D.; Rygg, J. R.; Sater, J.; Sayre, D.; Schneider, M. B.; Shaughnessy, D.; Spears, B. K.; Town, R.P. J.; Volegov, P. L.; Wan, A.; Widmann, K.; Wilde, C. H.; Yeamans, C.

    2015-04-06

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165 μm in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Earlier results have shown good repeatability, with up to 1/2 the neutron yield coming from α-particle self-heating.

  16. Thin Shell, High Velocity Inertial Confinement Fusion Implosions on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Ma, T.; Hurricane, O. A.; Callahan, D. A.; Barrios, M. A.; Casey, D. T.; Dewald, E. L.; Dittrich, T. R.; Döppner, T.; Haan, S. W.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; MacPhee, A. G.; Pak, A.; Park, H.-S.; Patel, P. K.; Remington, B. A.; Robey, H. F.; Salmonson, J. D.; Springer, P. T.; Tommasini, R.; Benedetti, L. R.; Bionta, R.; Bond, E.; Bradley, D. K.; Caggiano, J.; Celliers, P.; Cerjan, C. J.; Church, J. A.; Dixit, S.; Dylla-Spears, R.; Edgell, D.; Edwards, M. J.; Field, J.; Fittinghoff, D. N.; Frenje, J. A.; Gatu Johnson, M.; Grim, G.; Guler, N.; Hatarik, R.; Herrmann, H. W.; Hsing, W. W.; Izumi, N.; Jones, O. S.; Khan, S. F.; Kilkenny, J. D.; Knauer, J.; Kohut, T.; Kozioziemski, B.; Kritcher, A.; Kyrala, G.; Landen, O. L.; MacGowan, B. J.; Mackinnon, A. J.; Meezan, N. B.; Merrill, F. E.; Moody, J. D.; Nagel, S. R.; Nikroo, A.; Parham, T.; Ralph, J. E.; Rosen, M. D.; Rygg, J. R.; Sater, J.; Sayre, D.; Schneider, M. B.; Shaughnessy, D.; Spears, B. K.; Town, R. P. J.; Volegov, P. L.; Wan, A.; Widmann, K.; Wilde, C. H.; Yeamans, C.

    2015-04-01

    Experiments have recently been conducted at the National Ignition Facility utilizing inertial confinement fusion capsule ablators that are 175 and 165 μ m in thickness, 10% and 15% thinner, respectively, than the nominal thickness capsule used throughout the high foot and most of the National Ignition Campaign. These three-shock, high-adiabat, high-foot implosions have demonstrated good performance, with higher velocity and better symmetry control at lower laser powers and energies than their nominal thickness ablator counterparts. Little to no hydrodynamic mix into the DT hot spot has been observed despite the higher velocities and reduced depth for possible instability feedthrough. Early results have shown good repeatability, with up to 1 /2 the neutron yield coming from α -particle self-heating.

  17. SPECTROSCOPIC OBSERVATIONS OF SN 2012fr: A LUMINOUS, NORMAL TYPE Ia SUPERNOVA WITH EARLY HIGH-VELOCITY FEATURES AND A LATE VELOCITY PLATEAU

    SciTech Connect

    Childress, M. J.; Scalzo, R. A.; Sim, S. A.; Tucker, B. E.; Yuan, F.; Schmidt, B. P.; Cenko, S. B.; Filippenko, A. V.; Silverman, J. M.; Contreras, C.; Hsiao, E. Y.; Phillips, M.; Morrell, N.; Jha, S. W.; McCully, C.; Anderson, J. P.; De Jaeger, T.; Forster, F.; Benetti, S.; Bufano, F.; and others

    2013-06-10

    We present 65 optical spectra of the Type Ia SN 2012fr, 33 of which were obtained before maximum light. At early times, SN 2012fr shows clear evidence of a high-velocity feature (HVF) in the Si II {lambda}6355 line that can be cleanly decoupled from the lower velocity ''photospheric'' component. This Si II {lambda}6355 HVF fades by phase -5; subsequently, the photospheric component exhibits a very narrow velocity width and remains at a nearly constant velocity of {approx}12,000 km s{sup -1} until at least five weeks after maximum brightness. The Ca II infrared triplet exhibits similar evidence for both a photospheric component at v Almost-Equal-To 12,000 km s{sup -1} with narrow line width and long velocity plateau, as well as an HVF beginning at v Almost-Equal-To 31,000 km s{sup -1} two weeks before maximum. SN 2012fr resides on the border between the ''shallow silicon'' and ''core-normal'' subclasses in the Branch et al. classification scheme, and on the border between normal and high-velocity Type Ia supernovae (SNe Ia) in the Wang et al. system. Though it is a clear member of the ''low velocity gradient'' group of SNe Ia and exhibits a very slow light-curve decline, it shows key dissimilarities with the overluminous SN 1991T or SN 1999aa subclasses of SNe Ia. SN 2012fr represents a well-observed SN Ia at the luminous end of the normal SN Ia distribution and a key transitional event between nominal spectroscopic subclasses of SNe Ia.

  18. Quasi-static and multi-site high velocity impact response of composite structures

    NASA Astrophysics Data System (ADS)

    Deka, Lakshya

    Understanding of low and high velocity transverse impact of laminated fiber reinforced composites is of interest in military, aerospace, marine and civilian structures. Recent advances in the field of numerical simulation provide a means of predicting the performance characteristics of layered materials for impact protection. The overall objective of this work is to investigate the behavior of laminated composites which include both thermoplastic and thermoset systems subjected to quasi-static, low and high velocity impact; both from an experimental and numerical modeling view point. To analyze this problem, a series of quasi-static, low and high velocity impact tests have been performed on laminated composite plates namely E-glass/polypropylene, S2-glass/epoxy and carbon/polyphenylene sulphide. To analyze the perforation mechanism, ballistic limit and damage evolution, an explicit three-dimensional finite element code LS-DYNA is used. Selecting proper material models and contact definition is one of the major criteria for obtaining accurate numerical simulation. Material model 162 (MAT 162), a progressive failure model based on modified Hashin's criteria and continuum damage mechanics (CDM) has been assigned to predict failure of the laminate. This approach is used because during transverse impact, a composite laminate undergoes progressive damage. The laminate and the projectile are meshed using brick elements with single integration points. The impact velocity ranges from 180 to 400 m s -1. This work focuses on three main aspects; (i) To obtain static and dynamic material properties to incorporate into the finite element model and predict the ballistic limit of a composite laminate based on the information from quasi-static punch shear test; (ii) To understand penetration, material erosion, ballistic limit and delamination mechanisms for single and multi-site high velocity (or ballistic) impact of composite laminates; (iii) To investigate the different failure

  19. High-resolution seismic tomography of compressional wave velocity structure at Newberry Volcano, Oregon Cascade Range

    SciTech Connect

    Achauer, U.; Evans, J.R.; Stauber, D.A.

    1988-09-10

    Compressional wave velocity structure is determined for the upper crust beneath Newberry Volcano, central Oregon, using a high-resolution active-source seismic-tomography method. Newberry Volcano is a bimodal shield volcano east of the axis of the Cascade Range. It is associated both with the Cascade Range and with northwest migrating silicic volcanism in southeast Oregon. High-frequency (approx.7 Hz) crustal phases, nominally Pg and a midcrustal reflected phase, travel upward through a target volume beneath Newberry Volcano to a dense array of 120 seismographs. This arrangement is limited by station spacing to 1- to 2-km resolution in the upper 5 to 6 km of the crust beneath the volcano's summit caldera. The experiment tests the hypothesis that Cascade Range volcanoes are underlain only by small magma chambers. A small low-velocity anomaly delineated abosut 3 km below the summit caldera supports this hypothesis for Newberry Volcano and is interpreted as a possible magma chamber of a few to a few tens of km/sup 3/ in volume. A ring-shaped high-velocity anomaly nearer the surface coincides with the inner mapped ring fractures of the caldera. It also coincides with a circular gravity high, and we interpret it as largely subsolidus silicic cone sheets. The presence of this anomaly and of silicic vents along the ring fractures suggests that the fractures are a likely eruption path between the small magma chamber and the surface.

  20. Real-time dynamics of high-velocity micro-particle impact

    NASA Astrophysics Data System (ADS)

    Veysset, David; Hsieh, Alex; Kooi, Steve; Maznev, Alex A.; Tang, Shengchang; Olsen, Bradley D.; Nelson, Keith A.

    High-velocity micro-particle impact is important for many areas of science and technology, from space exploration to the development of novel drug delivery platforms. We present real-time observations of supersonic micro-particle impacts using multi-frame imaging. In an all optical laser-induced projectile impact test, a monolayer of micro-particles is placed on a transparent substrate coated with a laser absorbing polymer layer. Ablation of a laser-irradiated polymer region accelerates the micro-particles into free space with speeds up to 1.0 km/s. The particles are monitored during the impact on the target with an ultrahigh-speed multi-frame camera that can record up to 16 images with time resolution as short as 3 ns. In particular, we investigated the high-velocity impact deformation response of poly(urethane urea) (PUU) elastomers to further the fundamental understanding of the molecular influence on dynamical behaviors of PUUs. We show the dynamic-stiffening response of the PUUs and demonstrate the significance of segmental dynamics in the response. We also present movies capturing individual particle impact and penetration in gels, and discuss the observed dynamics. The results will provide an impetus for modeling high-velocity microscale impact responses and high strain rate deformation in polymers, gels, and other materials.

  1. Experimental and analytical study of high velocity impact on Kevlar/Epoxy composite plates

    NASA Astrophysics Data System (ADS)

    Sikarwar, Rahul; Velmurugan, Raman; Madhu, Velmuri

    2012-12-01

    In the present study, impact behavior of Kevlar/Epoxy composite plates has been carried out experimentally by considering different thicknesses and lay-up sequences and compared with analytical results. The effect of thickness, lay-up sequence on energy absorbing capacity has been studied for high velocity impact. Four lay-up sequences and four thickness values have been considered. Initial velocities and residual velocities are measured experimentally to calculate the energy absorbing capacity of laminates. Residual velocity of projectile and energy absorbed by laminates are calculated analytically. The results obtained from analytical study are found to be in good agreement with experimental results. It is observed from the study that 0/90 lay-up sequence is most effective for impact resistance. Delamination area is maximum on the back side of the plate for all thickness values and lay-up sequences. The delamination area on the back is maximum for 0/90/45/-45 laminates compared to other lay-up sequences.

  2. Nonlinear free vibrations of centrifugally stiffened uniform beams at high angular velocity

    NASA Astrophysics Data System (ADS)

    Bekhoucha, F.; Rechak, S.; Duigou, L.; Cadou, J. M.

    2016-09-01

    In this paper, we study the bending nonlinear free vibrations of a centrifugally stiffened beam with uniform cross-section and constant angular velocity. The nonlinear intrinsic equations of motion used here are geometrically exact and specific to beams exhibiting large amplitude displacements and rotations associated with small strains. Based on the Timoshenko beam model, these equations are derived from Hamilton's principle, in which the warping is considered. All coupling terms are considered including Coriolis terms. The studied beams are isotropic with clamped-free boundary conditions. By combining the Galerkin method with the harmonic balance method, the equations of motion are converted into a quadratic function treated with a continuation method: the Asymptotic Numerical Method, where the generalized displacement vector is presented as a series expansion. While analysing the effect of the angular velocity, we determine the amplitude versus frequency variations which are plotted as backbone curves. Considering the first lagging and flapping modes, the changes in beam behaviour from hardening to softening are investigated and identified as a function of the angular velocity and the effect of shear. Particular attention is paid to high angular velocities for both Euler-Bernoulli and Timoshenko beams and the natural frequencies so obtained are compared with the results available in the literature.

  3. Higher velocity, high-foot implosions on the National Ignition Facility laser

    DOE PAGES

    Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.; Döppner, T.; Ma, T.; Park, H. -S.; Barrios Garcia, M. A.; Berzak Hopkins, L. F.; Casey, D. T.; Cerjan, C. J.; et al

    2015-05-15

    By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), andmore » the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1e15 neutrons, the total yield ~ v⁹˙⁴. This increase is considerably faster than the expected dependence for implosions without alpha heating ( ~v⁵˙⁹) and is additional evidence that these experiments have significant alpha heating.« less

  4. Higher velocity, high-foot implosions on the National Ignition Facility laser

    SciTech Connect

    Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.; Döppner, T.; Ma, T.; Park, H.-S.; Barrios Garcia, M. A.; Berzak Hopkins, L. F.; Casey, D. T.; Cerjan, C. J.; Dewald, E. L.; Dittrich, T. R.; Edwards, M. J.; Haan, S. W.; Hamza, A. V.; Kritcher, A. L.; Landen, O. L.; LePape, S.; MacPhee, A. G.; Milovich, J. L.; and others

    2015-05-15

    By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), and the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1 × 10{sup 15} neutrons, the total yield ∼ v{sup 9.4}. This increase is considerably faster than the expected dependence for implosions without alpha heating (∼v{sup 5.9}) and is additional evidence that these experiments have significant alpha heating.

  5. Higher velocity, high-foot implosions on the National Ignition Facility laser

    SciTech Connect

    Callahan, D. A.; Hurricane, O. A.; Hinkel, D. E.; Döppner, T.; Ma, T.; Park, H. -S.; Barrios Garcia, M. A.; Berzak Hopkins, L. F.; Casey, D. T.; Cerjan, C. J.; Dewald, E. L.; Dittrich, T. R.; Edwards, M. J.; Haan, S. W.; Hamza, A. V.; Kline, J. L.; Knauer, J. P.; Kritcher, A. L.; Landen, O. L.; LePape, S.; MacPhee, A. G.; Milovich, J. L.; Nikroo, A.; Pak, A. E.; Patel, P. K.; Rygg, J. R.; Ralph, J. E.; Salmonson, J. D.; Spears, B. K.; Springer, P. T.; Tommasini, R.; Benedetti, L. R.; Bionta, R. M.; Bond, E. J.; Bradley, D. K.; Caggiano, J. A.; Field, J. E.; Fittinghoff, D. N.; Frenje, J.; Gatu Johnson, M.; Grim, G. P.; Hatarik, R.; Merrill, F. E.; Nagel, S. R.; Izumi, N.; Khan, S. F.; Town, R. P. J.; Sayre, D. B.; Volegov, P.; Wilde, C. H.

    2015-05-15

    By increasing the velocity in “high foot” implosions [Dittrich et al., Phys. Rev. Lett. 112, 055002 (2014); Park et al., Phys. Rev. Lett. 112, 055001 (2014); Hurricane et al., Nature 506, 343 (2014); Hurricane et al., Phys. Plasmas 21, 056314 (2014)] on the National Ignition Facility laser, we have nearly doubled the neutron yield and the hotspot pressure as compared to the implosions reported upon last year. The implosion velocity has been increased using a combination of the laser (higher power and energy), the hohlraum (depleted uranium wall material with higher opacity and lower specific heat than gold hohlraums), and the capsule (thinner capsules with less mass). We find that the neutron yield from these experiments scales systematically with a velocity-like parameter of the square root of the laser energy divided by the ablator mass. By connecting this parameter with the inferred implosion velocity (v), we find that for shots with primary yield >1e15 neutrons, the total yield ~ v⁹˙⁴. This increase is considerably faster than the expected dependence for implosions without alpha heating ( ~v⁵˙⁹) and is additional evidence that these experiments have significant alpha heating.

  6. The detection of high-velocity outflows from M8E-IR

    NASA Technical Reports Server (NTRS)

    Mitchell, George F.; Allen, Mark; Beer, Reinhard; Dekany, Richard; Huntress, Wesley

    1988-01-01

    A high-resolution (0.059/cm) M band (4.6 micron) spectrum of the embedded young stellar object M8E-IR is presented and discussed. The spectrum shows strong absorption to large blueshifts in the rotational lines of the fundamental vibrational band, v = 1-0, of CO. The absorption is interpreted as being due to gas near to, and flowing from, the central object. The outflowing gas is warm (95-330 K) and consists of discrete velocity components with the very high velocities of 90, 130, 150, and 160 km/s. On the basis of a simple model, it is estimated that the observed outflows are less than 100 yr old.

  7. The Guitar nebula - A bow shock from a slow-spin, high-velocity neutron star

    NASA Technical Reports Server (NTRS)

    Cordes, James M.; Romani, Roger W.; Lundgren, Scott C.

    1993-01-01

    The discovery is reported of a prominent nebula produced by the motion of a high-velocity pulsar, PSR 2224 + 65, through partially neutral gas. The pulsar's transverse speed of over about 800 km/s makes it arguably the fastest known star in the Galaxy and guarantees that it will ultimately escape the Galactic potential well. A deep H-alpha image reveals a bright head and a giant limb-brightened 'body' whose variable width suggests that the ambient interstellar gas has density variations on length scales less than 0.1 pc. Thermalization of shock energy occurs at a rate of about 0.01 times the pulsar's spindown loss rate. These observations provide some insights into the likelihood of finding shocks around other pulsars and the use of nebulae to find high-velocity neutron stars either not acting as pulsars or with their radiation beamed away from the earth.

  8. Electrical method and apparatus for impelling the extruded ejection of high-velocity material jets

    DOEpatents

    Weingart, Richard C.

    1989-01-01

    A method and apparatus (10, 40) for producing high-velocity material jets provided. An electric current pulse generator (14, 42) is attached to an end of a coaxial two-conductor transmission line (16, 44) having an outer cylindrical conductor (18), an inner cylindrical conductor (20), and a solid plastic or ceramic insulator (21) therebetween. A coxial, thin-walled metal structure (22, 30) is conductively joined to the two conductors (18, 20) of the transmission line (16, 44). An electrical current pulse applies magnetic pressure to and possibly explosively vaporizes metal structure (22), thereby collapsing it and impelling the extruded ejection of a high-velocity material jet therefrom. The jet is comprised of the metal of the structure (22), together with the material that comprises any covering layers (32, 34) disposed on the structure. An electric current pulse generator of the explosively driven magnetic flux compression type or variety (42) may be advantageously used in the practice of this invention.

  9. Chronic symptoms after vestibular neuritis and the high velocity vestibulo-ocular reflex

    PubMed Central

    Patel, Mitesh; Arshad, Qadeer; Roberts, R Edward; Ahmad, Hena; Bronstein, Adolfo M.

    2015-01-01

    Hypothesis As the anterior and posterior semicircular canals are vital to the regulation of gaze stability, particularly during locomotion or vehicular travel, we tested whether the high velocity vestibulo-ocular reflex (VOR) of the three ipsilesional semicircular canals elicited by the modified Head Impulse Test would correlate with subjective dizziness or vertigo scores after vestibular neuritis (VN). Background Recovery following acute VN varies with around half reporting persistent symptoms long after the acute episode. However, an unanswered question is whether chronic symptoms are associated with impairment of the high velocity VOR of the anterior or posterior canals. Methods Twenty patients who had experienced an acute episode of VN at least three months earlier were included in this study. Participants were assessed with the video head impulse test (vHIT) of all six canals, bithermal caloric irrigation, the Dizziness Handicap Inventory (DHI) and the Vertigo Symptoms Scale short-form (VSS). Results Of these 20 patients, 12 felt that they had recovered from the initial episode whereas 8 did not and reported elevated DHI and VSS scores. However, we found no correlation between DHI or VSS scores and the ipsilesional single or combined vHIT gain, vHIT gain asymmetry or caloric paresis. The high velocity VOR was not different between patients who felt they had recovered and patients who felt they had not. Conclusions Our findings suggest that chronic symptoms of dizziness following VN are not associated with the high velocity VOR of the single or combined ipsilesional horizontal, anterior or posterior semicircular canals. PMID:26719963

  10. High-definition velocity-space tomography of fast-ion dynamics

    NASA Astrophysics Data System (ADS)

    Salewski, M.; Geiger, B.; Jacobsen, A. S.; Hansen, P. C.; Heidbrink, W. W.; Korsholm, S. B.; Leipold, F.; Madsen, J.; Moseev, D.; Nielsen, S. K.; Nocente, M.; Odstrčil, T.; Rasmussen, J.; Stagner, L.; Stejner, M.; Weiland, M.; the ASDEX Upgrade Team

    2016-10-01

    Velocity-space tomography of the fast-ion distribution function in a fusion plasma is usually a photon-starved tomography method due to limited optical access and signal-to-noise ratio of fast-ion D α (FIDA) spectroscopy as well as the strive for high-resolution images. In high-definition tomography, prior information makes up for this lack of data. We restrict the target velocity space through the measured absence of FIDA light, impose phase-space densities to be non-negative, and encode the known geometry of neutral beam injection (NBI) sources. We further use a numerical simulation as prior information to reconstruct where in velocity space the measurements and the simulation disagree. This alternative approach is demonstrated for four-view as well as for two-view FIDA measurements. The high-definition tomography tools allow us to study fast ions in sawtoothing plasmas and the formation of NBI peaks at full, half and one-third energy by time-resolved tomographic movies.

  11. Atomic collision experiments utilizing low-velocity, highly-charged ion beams

    SciTech Connect

    Johnson, B.M.; Jones, K.W.; Meron, M.

    1982-01-01

    Intense beams of highly-stripped ions are now routinely produced at low velocities using the Brookhaven dual MP-tandens in a unique four-stage accel/decel mode. This mode of operation combines three stages of acceleration, stripping at high energy, and one stage of deceleration to near-zero velocity. To date, experiments have used 10-100 nA beams of bare and few-electron heavy ions at energies as low as 0.2 MeV/amu, and upgrades of the facility should push the lower limit below 0.1 MeV/amu. Recent experiments, such as measurements of charge transfer and x-ray production for S/sup 6-16+/ on He and Ar at 6 to 20 MeV and P(b) measurements for MO x-rays produced in Cl/sup 16 +/ + Ar collisions at 20, 10, and 5 MeV have demonstrated the usefulness of highly-stripped, low-velocity projectiles. These experiments and a few possibilities for future experiments are discussed.

  12. Discovery of molecular hydrogen in a high-velocity cloud of the Galactic halo.

    PubMed

    Richter, P; de Boer, K S; Widmann, H; Kappelmann, N; Gringel, W; Grewing, M; Barnstedt, J

    1999-11-25

    The Milky Way's halo contains clouds of neutral hydrogen with high radial velocities which do not follow the general rotational motion of the Galaxy. Few distances to these high-velocity clouds are known, so even gross properties such as total mass are hard to determine. As a consequence, there is no generally accepted theory regarding their origin. One idea is that they result from gas that has cooled after being ejected from the Galaxy through fountain-like flows powered by supernovae; another is that they are composed of gas, poor in heavy elements, which is falling onto the disk of the Milky Way from intergalactic space. The presence of molecular hydrogen, whose formation generally requires the presence of dust (and therefore gas, enriched in heavy elements), could help to distinguish between these possibilities. Here we report the discovery of molecular hydrogen absorption in a high-velocity cloud along the line of sight to the Large Magellanic Cloud. We also derive for the same cloud an iron abundance which is half of the solar value. From these data, we conclude that gas in this cloud originated in the disk of the Milky Way.

  13. High-velocity frictional strength across the Tohoku-Oki megathrust determined from surface drilling torque

    NASA Astrophysics Data System (ADS)

    Ujiie, Kohtaro; Inoue, Tomoya; Ishiwata, Junya

    2016-03-01

    High-velocity frictional strength is one of the primary factors controlling earthquake faulting. The Japan Trench Fast Drilling Project drilled through the shallow plate boundary fault, where displacement was ~50 m during the 2011 Tohoku-Oki earthquake. To determine downhole frictional strength, we analyzed the surface drilling torque data acquired at rotation rates equivalent to seismic slip rates (0.8-1.3 m/s). The results show a clear contrast in high-velocity frictional strength across the plate boundary fault: the apparent friction coefficient of frontal prism sediments (hemipelagic mudstones) in the hanging wall is 0.1-0.3, while that of the underthrust sediments (mudstone, laminar pelagic claystone, and chert) in the footwall increases to 0.2-0.4. The apparent friction coefficient of the smectite-rich pelagic clay in the plate boundary fault is 0.08-0.19, which is consistent with that determined from high-velocity (1.1-1.3 m/s) friction experiments. This suggests that surface drilling torque is useful in obtaining downhole frictional strength.

  14. An Eulerian joint velocity-concentration PDF method for solute dispersion in highly heterogeneous porous media

    NASA Astrophysics Data System (ADS)

    Meyer, Daniel W.; Tchelepi, Hamdi A.; Jenny, Patrick

    2010-05-01

    In risk analysis applications involving heterogeneous formations, the knowledge of the solute concentration probability density function (PDF) at different spatial locations and times is crucial. We propose a new joint velocity-concentration PDF method applicable for highly heterogeneous porous media that accounts for advective transport, pore-scale dispersion and molecular diffusion. Unlike in low order approximation (LOA) methods that are valid for low conductivity variances ?Y 2 and where the one-point velocity PDF is typically assumed to be a Gaussian, the proposed joint PDF method honors the increasingly non-Gaussian velocity one-point PDF and the long-term velocity correlations that were reported in different Monte Carlo (MC) studies for ?Y 2 > 0.5 [e.g., Salandin, P. and V. Fiorotto, WRR, 1998. 34(5) and Trefry, M.G., F.P. Ruan, and D. McLaughlin, WRR, 2003. 39(3)]. Furthermore, the new joint PDF method does not involve any a-priori assumption about the shape of the resulting marginal concentration PDF. LOA methods that provide information on the concentration mean and variance [Fiori, A. and G. Dagan, Journal of Contaminant Hydrology, 2000. 45(1-2)] on the other hand are typically complemented by assuming that the concentration PDF has a β-PDF shape [Bellin, A. and D. Tonina, Journal of Contaminant Hydrology, 2007. 94(1-2)]. The Eulerian joint velocity-concentration PDF transport equation in our model is numerically solved with a computationally efficient particle method. The suggested joint PDF method is validated by comparison with MC data reported by Caroni and Fiorotto for Péclet numbers ranging from 10 to 104 and ?Y 2 = 1 and 2 [Caroni, E. and V. Fiorotto, Transport in Porous Media, 2005. 59(1)].

  15. High velocity anomaly beneath the Deccan volcanic province: Evidence from seismic tomography

    USGS Publications Warehouse

    Iyer, H.M.; Gaur, V.K.; Rai, S.S.; Ramesh, D.S.; Rao, C.V.R.; Srinagesh, D.; Suryaprakasam, K.

    1989-01-01

    Analysis of teleseismic P-wave residuals observed at 15 seismograph stations operated in the Deccan volcanic province (DVP) in west central India points to the existence of a large, deep anomalous region in the upper mantle where the velocity is a few per cent higher than in the surrounding region. The seismic stations were operated in three deployments together with a reference station on precambrian granite at Hyderabad and another common station at Poona. The first group of stations lay along a west-northwesterly profile from Hyderabad through Poona to Bhatsa. The second group roughly formed an L-shaped profile from Poona to Hyderabad through Dharwar and Hospet. The third group of stations lay along a northwesterly profile from Hyderabad to Dhule through Aurangabad and Latur. Relative residuals computed with respect to Hyderabad at all the stations showed two basic features: a large almost linear variation from approximately +1s for teleseisms from the north to-1s for those from the southeast at the western stations, and persistance of the pattern with diminishing magnitudes towards the east. Preliminary ray-plotting and three-dimensional inversion of the P-wave residual data delineate the presence of a 600 km long approximately N-S trending anomalous region of high velocity (1-4% contrast) from a depth of about 100 km in the upper mantle encompassing almost the whole width of the DVP. Inversion of P-wave relative residuals reveal the existence of two prominent features beneath the DVP. The first is a thick high velocity zone (1-4% faster) extending from a depth of about 100 km directly beneath most of the DVP. The second feature is a prominent low velocity region which coincides with the westernmost part of the DVP. A possible explanation for the observed coherent high velocity anomaly is that it forms the root of the lithosphere which coherently translates with the continents during plate motions, an architecture characteristic of precambrian shields. The low

  16. Velocity and pressure characteristics of a model SSME high pressure fuel turbopump

    NASA Technical Reports Server (NTRS)

    Tse, D. G-N.; Sabnis, J. S.; Mcdonald, H.

    1991-01-01

    Under the present effort an experiment rig has been constructed, an instrumentation package developed and a series of mean and rms velocity and pressure measurements made in a turbopump which modelled the first stage of the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump. The rig was designed so as to allow initial experiments with a single configuration consisting of a bell-mouth inlet, a flight impeller, a vaneless diffuser and a volute. Allowance was made for components such as inlet guide vanes, exit guide vanes, downstream pumps, etc. to be added in future experiments. This flexibility will provide a clear baseline set of experiments and allow evaluation in later experiments of the effect of adding specific components upon the pump performance properties. The rotational speed of the impeller was varied between 4260 and 7680 rpm which covered the range of scaled SSME rotation speeds when due allowance is made for the differing stagnation temperature, model to full scale. The results at the inlet obtained with rotational speeds of 4260, 6084 and 7680 rpm showed that the axial velocity at the bell-mouth inlet remained roughly constant at 2.2 of the bulk velocity at the exit of the turbopump near the center of the inlet, but it decreased rapidly with increasing radius at all three speeds. Reverse flow occurred at a radius greater than 0.9 R for all three speeds and the maximum negative velocity reduced from 1.3 of the bulk velocity at the exit of the turbopump at 4260 rpm to 0.35 at 7680 rpm, suggesting that operating at a speed closer to the design condition of 8700 rpm improved the inlet characteristics. The reverse flow caused positive prerotation at the impeller inlet which was negligibly small near the center but reached 0.7 of the impeller speed at the outer annulus. The results in the diffuser and the volute obtained at 7680 rpm show that the hub and shroud walls of the diffuser were characterized by regions of transient reverse flow with

  17. PTF 12gzk—A rapidly declining, high-velocity type Ic radio supernova

    SciTech Connect

    Horesh, Assaf; Kulkarni, Shrinivas R.; Corsi, Alessandra; Frail, Dale A.; Cenko, S. Bradley; Ben-Ami, Sagi; Gal-Yam, Avishay; Yaron, Ofer; Arcavi, Iair; Ofek, Eran O.; Kasliwal, Mansi M.

    2013-11-20

    Only a few cases of Type Ic supernovae (SNe) with high-velocity ejecta (≥0.2 c) have been discovered and studied. Here, we present our analysis of radio and X-ray observations of the Type Ic SN PTF 12gzk. The radio emission declined less than 10 days after explosion, suggesting SN ejecta expanding at high velocity (∼0.3 c). The radio data also indicate that the density of the circumstellar material (CSM) around the supernova is lower by a factor of ∼10 than the CSM around normal Type Ic SNe. PTF 12gzk may therefore be an intermediate event between a 'normal' SN Ic and a gamma-ray-burst-SN-like event. Our observations of this rapidly declining radio SN at a distance of 58 Mpc demonstrates the potential to detect many additional radio SNe, given the new capabilities of the Very Large Array (improved sensitivity and dynamic scheduling), which are currently missed, leading to a biased view of radio SNe Ic. Early optical discovery followed by rapid radio observations would provide a full description of the ejecta velocity distribution and CSM densities around stripped massive star explosions as well as strong clues about the nature of their progenitor stars.

  18. High-Resolution Hα Velocity Fields of Nearby Spiral Galaxies with the Southern African Large Telescope

    NASA Astrophysics Data System (ADS)

    Mitchell, Carl; Williams, Ted; Spekkens, Kristine; Lee-Waddell, Karen; Kuzio de Naray, Rachel; Sellwood, Jerry

    2016-01-01

    In an effort to test ΛCDM predictions of galaxy mass distributions, we have obtained spectrophotometric observations of several nearby spiral galaxies with the Southern African Large Telescope (SALT) Fabry-Pérot (FP) interferometer as part of the RSS Imaging spectroscopy Nearby Galaxy Survey. Utilizing the SALT FP's 8 arcmin field of view and 2 arcsec angular resolution, we have derived 2D velocity fields of the Hα emission line to high spatial resolution at large radii. We have modeled these velocity fields with the DiskFit software package and found them to be in good agreement with lower-resolution velocity fields of the HI 21 cm line for the same galaxies. Here we present our Hα kinematic map of the barred spiral galaxy NGC 578. At the distance to this galaxy (22 Mpc), our kinematic data has a spatial resolution of 185 pc and extends to galactocentric radii of 13 kpc. The high spatial resolution of this data allows us to resolve the inner rising part of the rotation curves, which is compromised by beam smearing in lower-resolution observations. We are using these Hα kinematic data, combined with HI 21 cm kinematics and broadband photometric observations, to place constraints on NGC 578's mass distribution.

  19. Episodic High-velocity Outflows from V899 Mon: A Constraint On The Outflow Mechanisms

    NASA Astrophysics Data System (ADS)

    Ninan, J. P.; Ojha, D. K.; Philip, N. S.

    2016-07-01

    We report the detection of large variations in the outflow wind velocity from a young eruptive star, V899 Mon, during its ongoing high accretion outburst phase. Such large variations in the outflow velocity (from -722 to -425 km s-1) have never been reported previously in this family of objects. Our continuous monitoring of this source shows that the multi-component, clumpy, and episodic high velocity outflows are stable in the timescale of a few days, and vary over the timescale of a few weeks to months. We detect significant decoupling in the instantaneous outflow strength to accretion rate. From the comparison of various possible outflow mechanisms in magnetospheric accretion of young stellar objects, we conclude magnetically driven polar winds to be the most consistent mechanism for the outflows seen in V899 Mon. The large scale fluctuations in outflow over the short period makes V899 Mon the most ideal source to constrain various magnetohydrodynamics simulations of magnetospheric accretion. Based on observations made with the Southern African Large Telescope (SALT).

  20. Ultrasound Velocity Measurements in High-Chromium Steel Under Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Lunev, Aleksey; Bochkareva, Anna; Barannikova, Svetlana; Zuev, Lev

    2016-04-01

    In the present study, the variation of the propagation velocity of ultrasound in the plastic deformation of corrosion-resistant high-chromium steel 40X13 with ferrite-carbide (delivery status), martensitic (quenched) and sorbitol (after high-temperature tempering) structures have beem studied/ It is found that each state shows its view of the loading curve. In the delivery state diagram loading is substantially parabolic throughout, while in the martensitic state contains only linear strain hardening step and in the sorbitol state the plastic flow curve is three-step. The velocity of ultrasonic surface waves (Rayleigh waves) was measured simultaneously with the registration of the loading curve in the investigated steel in tension. It is shown that the dependence of the velocity of ultrasound in active loading is determined by the law of plastic flow, that is, the staging of the corresponding diagram of loading. Structural state of the investigated steel is not only changing the type of the deformation curve under uniaxial tension, but also changes the nature of ultrasound speed of deformation.

  1. Electrical conductivity and velocity of highly ionized plasma flows - Theory and experiment.

    NASA Technical Reports Server (NTRS)

    Vendell, E. W.; Park, C.; Posch, R. E.

    1972-01-01

    Use of an immersible, three-coil, magnetic-induction probe, previously tested in a low-density supersonic argon jet, to measure electrical conductivity and velocity profiles of a highly ionized high-density nitrogen jet in the continuum flow regime where effects due to probe bow shocks and boundary layers might not be negligible. Measured centerline values of electrical conductivity and velocity were compared with predictions based on a theoretical analysis previously developed to study the gas as it expanded adiabatically and inviscidly from an equilibrium sonic state to the nozzle exit. The resulting numerical exit plane values for electron density and electron temperature were then substituted into the Spitzer-Haerm conductivity formula to compute a theoretical conductivity which agreed within 40% of the measured conductivity, while the calculated and experimental velocity values differed by as much as 50%. The lack of agreement was attributed to the possible use of invalid assumptions and boundary conditions in the computer analysis or to the unknown effects of shocks on the probe data.

  2. Electric and magnetic field measurements inside a high-velocity neutral beam undergoing ionization

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.; Swenson, C. M.; Brenning, N.; Baker, K.; Pfaff, R.

    1991-01-01

    Vector electric field measurements were made inside two ionizing, high-velocity streams of barium atoms in the earth's ionosphere, and a variety of electrical phenomena across the frequency spectrum are reported. A very large quasi-dc electric field was detected antiparallel to the beam velocity at a roughly 45 deg angle with the magnetic field B0. A very large component of E is found parallel to B0. The fluctuating electric fields are also quite large, of the same order of magnitude as the quasi-dc pulse. The wave energy maximizes at frequencies below the barium lower hybrid frequency and includes strong signatures of the oxygen cyclotron frequency. Measurements made on a subpayload separated across B0 by several hundred meters and along B0 by several km do not show the large pulse. Very large amplitude magnetic field fluctuations were observed in both bursts.

  3. The quest for TPa Hugoniot data: using the DEMG in high velocity pulsed power experiments

    SciTech Connect

    Peterson, Jeff H; Rousculp, Christopher L; Holtkamp, David B; Oro, David M; Griego, Jeffrey R; Atchison, Walter L; Reinovsky, Robert E

    2010-12-20

    ALT-3 is an experiment being designed in collaboration between Russian VNIIEF scientists and LANL that aims to conduct high velocity material experiments to measure shock velocities at pressures near 1 TPa. The DEMG (Disk Explosive Magnetic Generator) is used to drive >60MA currents to accelerate an aluminum liner to speeds in excess of 20 km/s. The 1-D model of the DEMG has been refined from a given current profile to a time-varying inductance. Various techniques are used to model the FOS (Foil Opening Switch) on the DEMG and a refined DEMG model is then used to drive a liner into various targets to determine the optimum design for the experiment and analyze the possible conditions and complications.

  4. Cavity dimensions for high velocity penetration events: A comparison of calculational results with data

    SciTech Connect

    Kmetyk, L.N.; Yarrington, P.

    1989-05-01

    Calculations were performed with the CTH and HULL finite difference wavecodes to evaluate computational capabilities for predicting depth and diameter of target cavities produced in high velocity penetration events. The calculations simulated selected tests in a set of armor penetration experiments conducted by the US Army Ballistic Research Laboratory and reported earlier in the literature. The tests and simulations involved penetration of semi-infinite targets by long rod projectiles over a range of impact velocities from 1.3 to 4.5 km/sec. Comparisons are made between the calculated and measured dimensions of the target cavities, and the sensitivity of the predicted results to target property variations is investigated. 9 refs., 18 figs., 3 tabs.

  5. LP 400-22, A Very Low Mass and High-Velocity White Dwarf

    NASA Technical Reports Server (NTRS)

    Kawka, Adela; Vennes, Stephane; Oswalt, Terry D.; Smith, J. Allyn; Silvestri, Nicole M.

    2006-01-01

    We report the identification of LP 400-22 (WD 2234+222) as a very low mass and high-velocity white dwarf. The ultraviolet GALEX and optical photometric colors and a spectral line analysis of LP 400-22 show this star to have an effective temperature of 11,080+/-140 K and a surface gravity of log g = 6.32 +/-0.08. Therefore, this is a helium-core white dwarf with a mass of 0.17 M,. The tangential velocity of this white dwarf is 414+/-43 km/s, making it one of the fastest moving white dwarfs known. We discuss probable evolutionary scenarios for this remarkable object.

  6. Effects of light illumination on electron velocity of AlGaN/GaN heterostructures under high electric field

    SciTech Connect

    Guo, Lei; Yang, Xuelin Cheng, Jianpeng; Sang, Ling; Xu, Fujun; Tang, Ning; Feng, Zhihong; Lv, Yuanjie; Wang, Xinqiang; Shen, B.; Ge, Weikun

    2014-12-15

    We have investigated the variation of electron velocity in AlGaN/GaN heterostructures depending on illuminating light intensity and wavelength. It is shown that the electron velocity at high electric field increases under above-band light illumination. This electron velocity enhancement is found to be related to the photo-generated cold holes which interact with hot electrons and thus accelerate the energy relaxation at high electric field. The results suggest an alternative way to improve the electron energy relaxation rate and hence the electron velocity in GaN based heterostructures.

  7. The Diversity of High- and Intermediate-Velocity Clouds: Complex C versus IV Arch

    NASA Astrophysics Data System (ADS)

    Richter, Philipp; Sembach, Kenneth R.; Wakker, Bart P.; Savage, Blair D.; Tripp, Todd M.; Murphy, Edward M.; Kalberla, Peter M. W.; Jenkins, Edward B.

    2001-09-01

    We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph (STIS) observations of interstellar ultraviolet absorption lines in the Galactic high-velocity cloud Complex C and the Intermediate-Velocity Arch (IV Arch) in the direction of the quasar PG 1259+593 (l=120.6d, b=+58.1d). Absorption lines from C II, N I, N II, O I, Al II, Si II, P II, S II, Ar I, Fe II, and Fe III are used to study the atomic abundances in these two halo clouds at VLSR~-130 km s-1 (Complex C) and -55 km s-1 (IV Arch). The O I/H I ratio provides the best measure of the overall metallicity in the diffuse interstellar medium because ionization effects do not alter the ratio, and oxygen is at most only lightly depleted from the gas into dust grains. For Complex C, we find an oxygen abundance of 0.093+0.125-0.047 times solar, consistent with the idea that Complex C represents the infall of low-metallicity gas onto the Milky Way. In contrast, the oxygen abundance in the IV Arch is 0.98+1.21-0.46 times solar, which indicates a Galactic origin. We report the detection of an intermediate-velocity absorption component at +60 km s-1 that is not seen in H I 21 cm emission. The clouds along the PG 1259+593 sight line have a variety of properties, proving that multiple processes are responsible for the creation and circulation of intermediate and high-velocity gas in the Milky Way halo. Partly based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  8. A beamforming method for plane wave Doppler imaging of high flow velocities

    NASA Astrophysics Data System (ADS)

    Mansour, Omar; Poepping, Tamie L.; Lacefield, James C.

    2016-04-01

    Plane wave imaging is desirable for its ability to achieve high frame rates, allowing the capture of fast dynamic events, and continuous Doppler data. In most implementations of plane-wave imaging, multiple low resolution image (LRI) frames from different plane wave tilt angles are compounded to form a single high resolution image (HRI) frame, thereby reducing the frame rate. Compounding is a low-pass mean filter that causes attenuation and aliasing to signals with high Doppler shifts. On the other hand, the lateral beam profile and hence the quality of the HRI frames is improved by increasing the number of compounded frames. Therefore, a tradeoff exists between the Doppler limits and beam profile. In this paper, we present a method that eliminates this tradeoff and produces high resolution images without the use of compounding. The method suppresses the off-focus (clutter) signal by spreading its spectrum, while keeping the spectrum of the in-focus signal intact. The spreading is achieved by using a random sequence of tilt angles, as opposed to a linear sweep. Experiments performed using a carotid vessel phantom with constant flow demonstrate that the spread-spectrum method more accurately measures the parabolic flow profile of the vessel and in particular outperforms conventional plane-wave Doppler at higher flow velocities. The spread-spectrum method is expected to be valuable for Doppler applications that require measurement of high velocities at high frame rates.

  9. Investigation of high velocity separator for particle removal in coal gasification plants. Phase II report

    SciTech Connect

    Linhardt, H.D.

    1980-01-15

    This report summarizes the results of Phase II of the High Velocity Particle Separator Program performed under Contract EF-77-C-01-2709. This high velocity wedge separator has the potential to reduce equipment size and cost of high temperature and pressurized particulate removal equipment for coal derived gases. Phase II has been directed toward testing and detailed conceptual design of an element suitable for a commercial scale high temperature, high pressure particle separator (HTPS). Concurrently, Phase IA has been conducted, which utilized the ambient analog method (AAM) for aerodynamic and collection performance investigation of each HTPS configuration prior and during hot testing. This report summarizes the results of Phase IA and II. The AAM effort established correlation of theoretical analysis and experiment for HTPS pressure drop, purge flow ratio and collection efficiency potential. Task I defined the initial test conditions to be the contract design point of 1800/sup 0/F and 350 psia. The 1800/sup 0/F, 350 psia testing represents the main high temperature testing with coal-derived particulates in the 2 to 10 micron range. Phase IA and Phase II have demonstrated efficient particle collection with acceptable pressure drop. In view of these encouraging results, it is reasonable to apply the developed technology toward future hot gas particulate cleanup requirements.

  10. High velocity continuous-flow reactor for the production of solar grade silicon

    NASA Technical Reports Server (NTRS)

    Woerner, L.

    1977-01-01

    The feasibility of a high volume, high velocity continuous reduction reactor as an economical means of producing solar grade silicon was tested. Bromosilanes and hydrogen were used as the feedstocks for the reactor along with preheated silicon particles which function both as nucleation and deposition sites. A complete reactor system was designed and fabricated. Initial preheating studies have shown the stability of tetrabromosilane to being heated as well as the ability to preheat hydrogen to the desired temperature range. Several test runs were made and some silicon was obtained from runs carried out at temperatures in excess of 1180 K.

  11. A scheme for tracking and pointing at small celestial bodies during high velocity encounters

    NASA Technical Reports Server (NTRS)

    Burdick, G. M.; Lin, H.-S.; Wong, E. C.

    1982-01-01

    A scheme has been developed and verified for closed-loop tracking and pointing space-borne science instruments at small celestial bodies, such as comets and asteroids, during high velocity encounters. To overcome ephemeris uncertainties for these bodies, the scheme involves sequential estimation of flyby model parameters. The design consists of a two-axis gimballed platform mounted on a three-axis stabilized spacecraft. A platform-mounted optical tracker provides closed-loop target measurements and precision micro-step actuators enable high-rate platform slewing. For comet missions which involve dust particle impact disturbances, a dual-mode attitude control scheme is presented for minimizing transient response time.

  12. Shells, holes, worms, high-velocity gas and the z-distribution of gas in galaxies.

    NASA Astrophysics Data System (ADS)

    Rand, R. J.

    The author gives an overview of the current observational understanding of vertically extended gas components in spiral galaxies and the various phenomena which come under such names as shells, holes, worms, and high-velocity gas. For the most part, the focus is on recent high-resolution interferometric studies. The author concentrates on cold gas, and briefly on warm ionized gas, in the Milky Way and a few nearby spirals. Along the way, it is seen how phenomena such as worms and shells may be related to the formation and maintenance of the vertically extended components.

  13. Meteorite Impact at the Bedout High, NW Australian Margin, and Seismic Velocities: is There a Connection?

    NASA Astrophysics Data System (ADS)

    Goncharov, A.; Kennard, J.; Becker, L.

    2004-12-01

    The Bedout High in the Roebuck Basin at the NW Australian Margin (NWAM) appears to be a good candidate for a massive impact structure associated with the global Permian/Triassic extinction event. On a regional and crustal scale, the NWAM is one of the best studied offshore areas of Australia: ocean-bottom seismograph (OBS) survey supplemented by deep reflection seismic studies in the region has enabled co-interpretation of conventional deep seismic reflection data and accurate seismic velocity models on several transects, including one across the Bedout High. The purpose of this research is to investigate if there is any manifestation of the meteorite impact on a crustal scale, and also on a finer scale of seismic velocity variation in the basement. The impact of the suggested magnitude may have significantly modified the crustal structure in the region. Depth conversion of reflection seismic data indicates that depth to basement at the top of the Bedout High is approximately 3.9 km, and that the High stands more than 4 km above the surrounding sedimentary basins. The basement and crust in the Roebuck Basin have a number of features that distinguish it from other basins at the NWAM. Rapid crustal thinning outboard of the Bedout High and the presence of a thick layer of magmatic underplating in the lower crust are among these features. The meteorite impact may have been one of the possible causes to have triggered upper mantle melting and generation of a voluminous layer of underplated material. On a finer scale, OBS-derived seismic velocity variation along the basement is speculatively interpreted to be consistent with impact-related effects. However, existing seismic and potential field data do not allow accurate estimates of the extent of the crust affected by the meteorite impact, and effects that it may have had on the subsequent rifting, thermal, sedimentation and hydrocarbon maturation regimes in the area. Further multidisciplinary research is necessary to

  14. Density and sound velocity of Fe-S liquids at high pressures

    NASA Astrophysics Data System (ADS)

    Jing, Z.; Sakamaki, T.; Yu, T.; Kono, Y.; Wang, Y.; Park, C.; Shen, G.

    2011-12-01

    Liquid iron is the dominant component in the Earth's outer core and possibly the cores (or outer cores) of other terrestrial planets like Moon, Mars, and Mercury. Seismological and geochemical observations suggest that light elements such as S, C, O, Si, H, etc may be present in the liquid cores. In order to constrain the abundances of light elements and understand their effects on the structure, dynamics, and evolution of planetary cores, it is crucial to determine the equation of state for Fe-light element alloying liquids under core conditions. However, density data on liquid Fe-light element alloys at core pressures are very limited and no sound velocity or bulk modulus data are available for these liquids at high pressures. This makes it difficult to extrapolate the equation of state to core pressures. As a result, density data on solid Fe alloys are often used in the literature to compare with seismological observations by making corrections for the volume of melting. In this study, we extend the density dataset for Fe-S liquids by measuring the density of liquid iron with 19wt% sulfur and 27wt% sulfur using the X-ray absorption technique in a DIA-type multianvil apparatus up to 7 GPa and 2173 K. Ion chambers and 2D X-ray radiographic images were used to measure intensities of the incident and transmitted monochromatic X-rays, with the photon energy optimized at 40 keV. The density was then determined from the Beer-Lambert law using the mass absorption coefficients. We have also developed techniques to directly measure the ultrasonic sound velocities in these liquids up to 5 GPa and 1773 K using a Paris-Edinburgh cell. The sound velocity was determined by measuring the travel time difference between the sample echo and the buffer rod echo using a waveform generator and a digital oscilloscope and by measuring the sample thickness using X-ray radiographic images. The combination of density and sound velocity data can provide tight constraints on the equation of

  15. [Estimates of velocity of the travelling wave in the high-range cochlea of the dolphin].

    PubMed

    Popov, V V; Supin, A Ia

    2014-07-01

    Auditory brainstem responses (ABR) to sound pulses of precisely defined spectrum band of 0.5 oct (from 11.2-16 to 90-128 kHz) were recorded in bottlenose dolphins Tursiops truncatus. At equal stimulus levels, ABR amplitude depended on the stimulus spectrum band: the higher the frequency, the higher the amplitude. ABR waveform little depended on the stimulus spectrum band, however ABR latency did depend: the higher the frequency, the shorter the latency. The latency difference between responses to the lowest-frequency (11.2-16 kHz) and the highest-frequency (90-129 kHz) stimuli was up to 0.3 ms. This latency difference was attributed to the time of the wave travelling along the basilar membrane. Therefore, the data were used to compute the travelling-wave velocity. The obtained estimates were: 38.2 oct/ms at the proximal (high-frequ- ency) end of the basilar membrane to 2.8 oct/ms at the distal (low-frequency) end. Comparison of the travelling-wave velocities in humans and dolphins shows that the travelling-wave velocity is linked to the characteristic frequency, not to the place in the cochlea.

  16. [Estimates of velocity of the travelling wave in the high-range cochlea of the dolphin].

    PubMed

    Popov, V V; Supin, A Ia

    2014-07-01

    Auditory brainstem responses (ABR) to sound pulses of precisely defined spectrum band of 0.5 oct (from 11.2-16 to 90-128 kHz) were recorded in bottlenose dolphins Tursiops truncatus. At equal stimulus levels, ABR amplitude depended on the stimulus spectrum band: the higher the frequency, the higher the amplitude. ABR waveform little depended on the stimulus spectrum band, however ABR latency did depend: the higher the frequency, the shorter the latency. The latency difference between responses to the lowest-frequency (11.2-16 kHz) and the highest-frequency (90-129 kHz) stimuli was up to 0.3 ms. This latency difference was attributed to the time of the wave travelling along the basilar membrane. Therefore, the data were used to compute the travelling-wave velocity. The obtained estimates were: 38.2 oct/ms at the proximal (high-frequ- ency) end of the basilar membrane to 2.8 oct/ms at the distal (low-frequency) end. Comparison of the travelling-wave velocities in humans and dolphins shows that the travelling-wave velocity is linked to the characteristic frequency, not to the place in the cochlea. PMID:25669111

  17. A high stellar velocity dispersion for a compact massive galaxy at redshift z = 2.186.

    PubMed

    van Dokkum, Pieter G; Kriek, Mariska; Franx, Marijn

    2009-08-01

    Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the past ten billion years (10 Gyr). A key test of these results is a determination of the stellar kinematics of one of the compact galaxies: if the sizes of these objects are as extreme as has been claimed, their stars are expected to have much higher velocities than those in present-day galaxies of the same mass. Here we report a measurement of the stellar velocity dispersion of a massive compact galaxy at redshift z = 2.186, corresponding to a look-back time of 10.7 Gyr. The velocity dispersion is very high at km s(-1), consistent with the mass and compactness of the galaxy inferred from photometric data. This would indicate significant recent structural and dynamical evolution of massive galaxies over the past 10 Gyr. The uncertainty in the dispersion was determined from simulations that include the effects of noise and template mismatch. However, we cannot exclude the possibility that some subtle systematic effect may have influenced the analysis, given the low signal-to-noise ratio of our spectrum. PMID:19661911

  18. High velocity impingement of single droplets on a dry smooth surface

    NASA Astrophysics Data System (ADS)

    Faßmann, Benjamin W.; Bansmer, Stephan E.; Möller, Thorsten J.; Radespiel, Rolf; Hartmann, Michael

    2013-05-01

    The vertical impact of single, mono disperse water droplets on a dry smooth surface was studied experimentally by means of shadowgraphy. A glass substrate was mounted on a rotating wheel to obtain high impact velocities. The droplets were generated on demand. While the Ohnesorge number was kept constant, Weber number and Reynolds number were varied by adjusting the impact velocity. In all performed experiments, splashing was observed. The distinction of the different measurement series was done by the use of the Weber number. The different Weber numbers were, 3,500, 5,000 and 10,000. Phase-locked images were taken and the temporal evolution of the impact was reconstructed by means of the nondimensional impingement time. The outcome of the measurement was analysed by digital image processing to quantify the distribution of the diameter of the resulting secondary droplets in size and time as well as their velocity, and the total deposited mass fraction remaining on the surface after the impingement. In all cases, the greater part of the impinging primary droplet remained on the substrate.

  19. Analysis of particle behavior in High-Velocity Oxy-Fuel thermal spraying process

    NASA Astrophysics Data System (ADS)

    Katanoda, Hiroshi; Matsuo, Kazuyasu

    2003-08-01

    This paper analyzes the behavior of coating particle as well as the gas flow both of inside and outside the High-Velocity Oxy-Fuel (HVOF) thermal spraying gun by using quasi-one-dimensional analysis and numerical simulation. The HVOF gun in the present analysis is an axisymmetric convergent-divergent nozzle with the design Mach number of 2.0 followed by a straight passage called barrel. In the present analysis it is assumed that the influence of the particles injected in the gas flow is neglected, and the interaction between the particles is also neglected. The gas flow in the gun is assumed to be quasi-one-dimensional adiabatic flow. The velocity, temperature and density of gas in the jet discharged from the barrel exit are predicted by solving Navier-Stokes equations numerically. The particle equation of motion is numerically integrated using three-step Runge-Kutta method. The drag coefficient of the particle is calculated by linear interpolation of the experimental data obtained in the past. Particle mean temperature is calculated by using Ranz and Marchalls’ correlation for spherical particles. From the present analysis, the distributions of velocity and temperature of the coating particles flying inside and outside the HVOF gun are predicted.

  20. A high stellar velocity dispersion for a compact massive galaxy at redshift z = 2.186.

    PubMed

    van Dokkum, Pieter G; Kriek, Mariska; Franx, Marijn

    2009-08-01

    Recent studies have found that the oldest and most luminous galaxies in the early Universe are surprisingly compact, having stellar masses similar to present-day elliptical galaxies but much smaller sizes. This finding has attracted considerable attention, as it suggests that massive galaxies have grown in size by a factor of about five over the past ten billion years (10 Gyr). A key test of these results is a determination of the stellar kinematics of one of the compact galaxies: if the sizes of these objects are as extreme as has been claimed, their stars are expected to have much higher velocities than those in present-day galaxies of the same mass. Here we report a measurement of the stellar velocity dispersion of a massive compact galaxy at redshift z = 2.186, corresponding to a look-back time of 10.7 Gyr. The velocity dispersion is very high at km s(-1), consistent with the mass and compactness of the galaxy inferred from photometric data. This would indicate significant recent structural and dynamical evolution of massive galaxies over the past 10 Gyr. The uncertainty in the dispersion was determined from simulations that include the effects of noise and template mismatch. However, we cannot exclude the possibility that some subtle systematic effect may have influenced the analysis, given the low signal-to-noise ratio of our spectrum.

  1. HIGH-RESOLUTION SEISMIC VELOCITY AND ATTENUATION MODELS OF THE CAUCASUS-CASPIAN REGION

    SciTech Connect

    Mellors, R; Gok, R; Pasyanos, M; Skobeltsyn, G; Teoman, U; Godoladze, T; Sandvol, E

    2008-07-01

    The southwest edge of Eurasia is a tectonically and structurally complex region that includes the Caspian and Black Sea basins, the Caucasus Mountains, and the high plateaus south of the Caucasus. Using data from 25 broadband stations located in the region, new estimates of crustal and upper mantle thickness, velocity structure, and attenuation are being developed. Receiver functions have been determined for all stations. Depth to Moho is estimated using slant stacking of the receiver functions, forward modeling, and inversion. Moho depths along the Caspian and in the Kura Depression are in general poorly constrained using only receiver functions due to thick sedimentary basin sediments. The best fitting models suggest a low velocity upper crust with Moho depths ranging from 30 to 40 km. Crustal thicknesses increase in the Greater Caucasus with Moho depths of 40 to 50 km. Pronounced variations with azimuth of source are observed indicating 3D structural complexity and upper crustal velocities are higher than in the Kura Depression to the south. In the Lesser Caucasus, south and west of the Kura Depression, the crust is thicker (40 to 50 km) and upper crustal velocities are higher. Work is underway to refine these models with the event based surface wave dispersion and ambient noise correlation measurements from continuous data. Regional phase (Lg and Pg) attenuation models as well as blockage maps for Pn and Sn are being developed. Two methods are used to estimate Q: the two-station method to estimate inter-station Q and the reversed, two-station, two event method. The results are then inverted to create Lg and Pg Q maps. Initial results suggest substantial variations in both Pg and Lg Q in the region. A zone of higher Pg Q extends west from the Caspian between the Lesser and Greater Caucasus and a narrow area of higher Lg Q is observed.

  2. Characterization of High-Velocity Single Particle Impacts on Plasma-Sprayed Ceramic Coatings

    NASA Astrophysics Data System (ADS)

    Kiilakoski, Jarkko; Lindroos, Matti; Apostol, Marian; Koivuluoto, Heli; Kuokkala, Veli-Tapani; Vuoristo, Petri

    2016-08-01

    High-velocity impact wear can have a significant effect on the lifetime of thermally sprayed coatings in multiple applications, e.g., in the process and paper industries. Plasma-sprayed oxide coatings, such as Cr2O3- and TiO2-based coatings, are often used in these industries in wear and corrosion applications. An experimental impact study was performed on thermally sprayed ceramic coatings using the High-Velocity Particle Impactor (HVPI) at oblique angles to investigate the damage, failure, and deformation of the coated structures. The impact site was characterized by profilometry, optical microscopy, and scanning electron microscopy (SEM). Furthermore, the connection between the microstructural details and impact behavior was studied in order to reveal the damage and failure characteristics at a more comprehensive level. Differences in the fracture behavior were found between the thermally sprayed Cr2O3 and TiO2 coatings, and a concept of critical impact energy is presented here. The superior cohesion of the TiO2 coating inhibited interlamellar cracking while the Cr2O3 coating suffered greater damage at high impact energies. The HVPI experiment has proven to be able to produce valuable information about the deformation behavior of coatings under high strain rates and could be utilized further in the development of wear-resistant coatings.

  3. A novel platform to study magnetized high-velocity collisionless shocks

    NASA Astrophysics Data System (ADS)

    Higginson, D. P.; Korneev, Ph; Béard, J.; Chen, S. N.; d'Humières, E.; Pépin, H.; Pikuz, S.; Pollock, B.; Riquier, R.; Tikhonchuk, V.; Fuchs, J.

    2015-12-01

    An experimental platform to study the interaction of two colliding high-velocity (0.01-0.2 c; 0.05-20 MeV) proton plasmas in a high strength (20 T) magnetic field is introduced. This platform aims to study the collision of magnetized plasmas accelerated via the Target-Normal-Sheath-Acceleration mechanism and initially separated by distances of a few hundred microns. The plasmas are accelerated from solid targets positioned inside a few cubic millimeter cavity located within a Helmholtz coil that provides up to 20 T magnetic fields. Various parameters of the plasmas at their interaction location are estimated. These show an interaction that is highly non-collisional, and that becomes more and more dominated by the magnetic fields as time progresses (from 5 to 60 ps). Particle-in-cell simulations are used to reproduce the initial acceleration of the plasma both via simulations including the laser interaction and via simulations that start with preheated electrons (to save dramatically on computational expense). The benchmarking of such simulations with the experiment and with each other will be used to understand the physical interaction when a magnetic field is applied. Finally, the experimental density profile of the interacting plasmas is shown in the case without an applied magnetic magnetic field, so to show that without an applied field that the development of high-velocity shocks, as a result of particle-to-particle collisions, is not achievable in the configuration considered.

  4. DETECTION OF HIGH VELOCITY OUTFLOWS IN THE SEYFERT 1 GALAXY Mrk 590

    SciTech Connect

    Gupta, A.; Mathur, S.; Krongold, Y.

    2015-01-01

    We report on the detection of ultra-fast outflows in the Seyfert 1 galaxy Mrk 590. These outflows are identified through highly blueshifted absorption lines of O VIII and Ne IX in the medium energy grating spectrum and Si XIV and Mg XII in the high energy grating spectrum on board the Chandra X-ray observatory. Our best-fit photoionization model requires two absorber components at outflow velocities of 0.176c and 0.0738c and a third tentative component at 0.0867c. The components at 0.0738c and 0.0867c have high ionization parameters and high column densities, similar to other ultra-fast outflows detected at low resolution by Tombesi et al. We also found suggestive evidence for super-solar silicon in these components. These outflows carry sufficient mass and energy to provide effective feedback proposed by theoretical models. The component at 0.176c, on the other hand, has a low ionization parameter and low column density, similar to those detected by Gupta et al. in Ark 564. These absorbers occupy a different locus on the velocity versus ionization parameter plane and have opened up a new parameter space of active galactic nucleus (AGN) outflows. The presence of ultra-fast outflows in moderate luminosity AGNs poses a challenge to models of AGN outflows.

  5. Direct collapse black hole formation via high-velocity collisions of protogalaxies

    NASA Astrophysics Data System (ADS)

    Inayoshi, Kohei; Visbal, Eli; Kashiyama, Kazumi

    2015-10-01

    We propose high-velocity collisions of protogalaxies as a new pathway to form supermassive stars (SMSs) with masses of ˜105 M⊙ at high redshift (z > 10). When protogalaxies hosted by dark matter haloes with a virial temperature of ˜ 104 K collide with a relative velocity ≳ 200 km s-1, the gas is shock-heated to ˜106 K and subsequently cools isobarically via free-free emission and He+, He, and H line emission. Since the gas density ( ≳ 104 cm- 3) is high enough to destroy H2 molecules by collisional dissociation, the shocked gas never cools below ˜104 K. Once a gas cloud of ˜105 M⊙ reaches this temperature, it becomes gravitationally unstable and forms an SMS which will rapidly collapse into a supermassive black hole via general relativistic instability. We perform a simple analytic estimate of the number density of direct-collapse black holes (DCBHs) formed through this scenario (calibrated with cosmological N-body simulations) and find nDCBH ˜ 10- 9 Mpc- 3 (comoving) by z = 10. This could potentially explain the abundance of bright high-z quasars.

  6. Revisit of the relationship between the elastic properties and sound velocities at high pressures

    SciTech Connect

    Wang, Chenju; Yan, Xiaozhen; Xiang, Shikai Chen, Haiyan; Gu, Jianbing; Yu, Yin; Kuang, Xiaoyu

    2014-09-14

    The second-order elastic constants and stress-strain coefficients are defined, respectively, as the second derivatives of the total energy and the first derivative of the stress with respect to strain. Since the Lagrangian and infinitesimal strain are commonly used in the two definitions above, the second-order elastic constants and stress-strain coefficients are separated into two categories, respectively. In general, any of the four physical quantities is employed to characterize the elastic properties of materials without differentiation. Nevertheless, differences may exist among them at non-zero pressures, especially high pressures. Having explored the confusing issue systemically in the present work, we find that the four quantities are indeed different from each other at high pressures and these differences depend on the initial stress applied on materials. Moreover, the various relations between the four quantities depicting elastic properties of materials and high-pressure sound velocities are also derived from the elastic wave equations. As examples, we calculated the high-pressure sound velocities of cubic tantalum and hexagonal rhenium using these nexus. The excellent agreement of our results with available experimental data suggests the general applicability of the relations.

  7. A novel platform to study magnetized high-velocity collisionless shocks

    SciTech Connect

    Higginson, D. P.; Korneev, Ph; Béard, J.; Chen, S. N.; d'Humières, E.; Pépin, H.; Pikuz, S.; Pollock, B.; Riquier, R.; Tikhonchuk, V.; Fuchs, J.

    2014-12-13

    An experimental platform to study the interaction of two colliding high-velocity (0.01–0.2c; 0.05–20 MeV) proton plasmas in a high strength (20 T) magnetic field is introduced. This platform aims to study the collision of magnetized plasmas accelerated via the Target-Normal-Sheath-Acceleration mechanism and initially separated by distances of a few hundred microns. The plasmas are accelerated from solid targets positioned inside a few cubic millimeter cavity located within a Helmholtz coil that provides up to 20 T magnetic fields. Various parameters of the plasmas at their interaction location are estimated. These show an interaction that is highly non-collisional, and that becomes more and more dominated by the magnetic fields as time progresses (from 5 to 60 ps). Particle-in-cell simulations are used to reproduce the initial acceleration of the plasma both via simulations including the laser interaction and via simulations that start with preheated electrons (to save dramatically on computational expense). The benchmarking of such simulations with the experiment and with each other will be used to understand the physical interaction when a magnetic field is applied. In conclusion, the experimental density profile of the interacting plasmas is shown in the case without an applied magnetic magnetic field, so to show that without an applied field that the development of high-velocity shocks, as a result of particle-to-particle collisions, is not achievable in the configuration considered.

  8. The use of high velocity launchers for scientific and engineering studies

    SciTech Connect

    Asay, J.R.; Chhabildas, L.C.; Furnish, M.D.

    1991-01-01

    Shockwave techniques have been used for decades to study the dynamic states of matter in temperature and pressure regimes inaccessible by other methods. These techniques have been employed in a wide variety of scientific, military, and commercial applications. A principal scientific objective has been to determine high-pressure equations of state (EOS) to ultra-high pressures; pressures of tens of Mbar have been reported for several materials. Most recently, these methods have been used for studies of thermophysical properties under shock compression, including phase transition kinetics, and mechanical properties, such as the high-pressure yield strength. In this paper, a brief discussion of recent developments in high velocity launchers is given. Advances in techniques for subjecting materials to a wide range of loading conditions is presented, including selected illustrations of shockwave measurements to Mbar pressures. 54 refs.

  9. The first high-precision radial velocity search for extra-solar planets

    NASA Astrophysics Data System (ADS)

    Walker, Gordon A. H.

    2012-01-01

    some 30 years. The implication was that the planetary orbit might not be stable, and a Jovian planet surviving so close to a giant then seemed improbable. Later observations by others showed the stellar binary period was closer to 67 years, the primary was only a sub-giant and a weak, apparently synchronous chromospheric variation disappeared. Chromospheric activity was considered important because κ1 Cet, one of our program stars, showed a significant correlation of its radial velocity curve with chromospheric activity. ɛ Eri is a young, magnetically active star with spots making it a noisy target for radial velocities. While the signature of a highly elliptical orbit (e = 0.6) has persisted for more than three planetary orbits, some feel that even more extensive coverage is needed to confirm the identification despite an apparent complementary astrometric acceleration detected with the Hubble Space Telescope. We confined our initial analyses of the program stars to looking for circular orbits. In retrospect, it appears that some 10% of our sample did in fact have Jovian planetary companions in orbits with periods of years.

  10. Shear instability of plastically-deforming metals in high-velocity impact welding

    NASA Astrophysics Data System (ADS)

    Nassiri, Ali; Kinsey, Brad; Chini, Greg

    2016-10-01

    High-speed oblique impact of two metal plates results in the development of an intense shear region at their interface leading to interfacial profile distortion and interatomic bonding. If the relative velocity is sufficient, a distinct wavy morphology with a well-defined amplitude and wavelength is observed. Emergence of this morphology below the melting point of the metal plates is usually taken as evidence of a successful weld. Amongvarious proposed mechanisms, instability owing to large tangential velocity variations near the interface has received significant attention. With one exception, the few quantitative stability analyses of this proposed mechanism have treated an anti-symmetric/shear-layer base profile (i.e., a Kelvin-Helmholtz configuration) and employed an inviscid or Newtonian viscous fluid constitutive relation. The former stipulation implies the energy source for the instability is the presumed relative shearing motion of the two plates, while the latter is appropriate only if melting occurs locally near the interface. In this study, these restrictions, which are at odds with the conditions realized in high-velocity impact welding, are relaxed. A quantitative temporal linear stability analysis is performed to investigate whether the interfacial wave morphology could be the signature of a shear-driven high strain-rate instability of a perfectly plastic material undergoing a jet-like deformation near the interface. The resulting partial differential eigenvalue problem is solved numerically using a spectral collocation method in which customized boundary conditions near the interface are implemented to properly treat the singularity arising from the vanishing of the base flow strain-rate at the symmetry plane of the jet. The solution of the eigenvalue problem yields the wavelength and growth rate of the dominant wave-like disturbances along the interface and confirms that a shear instability of a plastically-deforming material is compatible with the

  11. High-velocity OH megamasers in IRAS 20100-4156: evidence for a supermassive black hole

    NASA Astrophysics Data System (ADS)

    Harvey-Smith, L.; Allison, J. R.; Green, J. A.; Bannister, K. W.; Chippendale, A.; Edwards, P. G.; Heywood, I.; Hotan, A. W.; Lenc, E.; Marvil, J.; McConnell, D.; Phillips, C. J.; Sault, R. J.; Serra, P.; Stevens, J.; Voronkov, M.; Whiting, M.

    2016-08-01

    We report the discovery of new, high-velocity narrow-line components of the OH megamaser in IRAS 20100-4156. Results from the Australian Square Kilometre Array Pathfinder (ASKAP)'s Boolardy Engineering Test Array (BETA) and the Australia Telescope Compact Array (ATCA) provide two independent measurements of the OH megamaser spectrum. We found evidence for OH megamaser clumps at -409 and -562 km s-1 (blue-shifted) from the systemic velocity of the galaxy, in addition to the lines previously known. The presence of such high velocities in the molecular emission from IRAS 20100-4156 could be explained by a ˜50 pc molecular ring enclosing a ˜3.8 billion solar mass black hole. We also discuss two alternatives, i.e. that the narrow-line masers are dynamically coupled to the wind driven by the active galactic nucleus or they are associated with two separate galactic nuclei. The comparison between the BETA and ATCA spectra provides another scientific verification of ASKAP's BETA. Our data, combined with previous measurements of the source enabled us to study the variability of the source over a 26 yr period. The flux density of the brightest OH maser components has reduced by more than a factor of 2 between 1988 and 2015, whereas a secondary narrow-line component has more than doubled in the same time. Plans for high-resolution very long baseline interferometry follow-up of this source are discussed, as are prospects for discovering new OH megamasers during the ASKAP early science programme.

  12. Petrophysical models of high velocity lower crust on the South Atlantic rifted margins: whence the asymmetry?

    NASA Astrophysics Data System (ADS)

    Trumbull, Robert B.; Franke, Dieter; Bauer, Klaus; Sobolev, Stephan V.

    2015-04-01

    Lower crustal bodies with high seismic velocity (Vp > 7km/s) underlie seaward-dipping reflector wedges on both margins of the South Atlantic, as on many other volcanic rifted margins worldwide. A comprehensive geophysical study of the South Atlantic margins by Becker et al. (Solid Earth, 5: 1011-1026, 2014) showed a strong asymmetry in the development of high-velocity lower crust (HVLC), with about 4 times larger volumes of HVLC on the African margin. That study also found interesting variations in the vertical position of HVLC relative to seaward-dipping reflectors which question a simple intrusive vs. extrusive relationship between these lower- and upper crustal features. The asymmetry of HVLC volumes on the conjugate margins is paradoxically exactly the opposite to that of surface lavas in the Paraná-Etendeka flood basalt province, which are much more voluminous on the South American margin. This contribution highlights the asymmetric features of magma distribution on the South Atlantic margins and explores their geodynamic significance. Petrophysical models of the HVLC are presented in the context of mantle melt generation, based on thickness-velocity (H-Vp) relations. These suggest that the greater volumes and average Vp values of HVLC on the African margin are due to active upwelling and high temperature, whereas passive upwelling under a thick lithospheric lid suppressed magma generation on the South American margin. The contrast in mantle upwelling rate and lithospheric thickness on the two margins predictably causes differential uplift, and this may help explain the greater accomodation space for surface lavas on the South American side although melt generation was strongest under the African margin.

  13. Acceleration to high velocities and heating by impact using Nike KrF laser

    SciTech Connect

    Karasik, Max; Weaver, J. L.; Velikovich, A. L.; Zalesak, S. T.; Bates, J. W.; Obenschain, S. P.; Schmitt, A. J.; Aglitskiy, Y.; Watari, T.; Arikawa, Y.; Sakaiya, T.; Murakami, M.; Azechi, H.; Oh, J.

    2010-05-15

    The Nike krypton fluoride laser [S. P. Obenschain, S. E. Bodner, D. Colombant, et al., Phys. Plasmas 3, 2098 (1996)] is used to accelerate planar plastic foils to velocities that for the first time reach 1000 km/s. Collision of the highly accelerated deuterated polystyrene foil with a stationary target produces approxGbar shock pressures and results in heating of the foil to thermonuclear temperatures. The impact conditions are diagnosed using DD fusion neutron yield, with approx10{sup 6} neutrons produced during the collision. Time-of-flight neutron detectors are used to measure the ion temperature upon impact, which reaches 2-3 keV.

  14. Aerosol formation from high-velocity uranium drops: Comparison of number and mass distributions. Final report

    SciTech Connect

    Rader, D.J.; Benson, D.A.

    1995-05-01

    This report presents the results of an experimental study of the aerosol produced by the combustion of high-velocity molten-uranium droplets produced by the simultaneous heating and electromagnetic launch of uranium wires. These tests are intended to simulate the reduction of high-velocity fragments into aerosol in high-explosive detonations or reactor accidents involving nuclear materials. As reported earlier, the resulting aerosol consists mainly of web-like chain agglomerates. A condensation nucleus counter was used to investigate the decay of the total particle concentration due to coagulation and losses. Number size distributions based on mobility equivalent diameter obtained soon after launch with a Differential Mobility Particle Sizer showed lognormal distributions with an initial count median diameter (CMD) of 0.3 {mu}m and a geometric standard deviation, {sigma}{sub g} of about 2; the CMD was found to increase and {sigma}{sub g} decrease with time due to coagulation. Mass size distributions based on aerodynamic diameter were obtained for the first time with a Microorifice Uniform Deposit Impactor, which showed lognormal distributions with mass median aerodynamic diameters of about 0.5 {mu}m and an aerodynamic geometric standard deviation of about 2. Approximate methods for converting between number and mass distributions and between mobility and aerodynamic equivalent diameters are presented.

  15. A SPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

    SciTech Connect

    Williams, Rik J.; Mathur, Smita; Poindexter, Shawn; Elvis, Martin; Nicastro, Fabrizio

    2012-04-15

    We employ three-band Spitzer-MIPS observations to search for cold dust emission in three neutral hydrogen compact high-velocity clouds (CHVCs) in the vicinity of the Milky Way. Far-infrared emission correlated with H I column density was previously reported in HVC Complex C, indicating that this object contains dust heated by the Galactic radiation field at its distance of {approx}10 kpc. Assuming published Spitzer, IRAS, and Planck, IR-H I correlations for Complex C, our Spitzer observations are of sufficient depth to directly detect 160 {mu}m dust emission in the CHVCs if it is present at the same level as in Complex C, but no emission is detected in any of the targets. For one of the targets (CHVC289) which has well-localized H I clumps, we therefore conclude that it is fundamentally different from Complex C, with either a lower dust-to-gas ratio or a greater distance from the Galactic disk (and consequently cooler dust temperature). Firm conclusions cannot be drawn for the other two Spitzer-observed CHVCs since their small-scale H I structures are not sufficiently well known; nonetheless, no extended dust emission is apparent despite their relatively high H I column densities. The lack of dust emission in CHVC289 suggests that at least some compact high-velocity clouds objects may exhibit very low dust-to-gas ratios and/or greater Galactocentric distances than large HVC complexes.

  16. Eulerian adaptive finite-difference method for high-velocity impact and penetration problems

    SciTech Connect

    Barton, Philip T.; Deiterding, Ralf; Meiron, Daniel I.; Pullin, Dale I

    2013-01-01

    Owing to the complex processes involved, faithful prediction of high-velocity impact events demands a simulation method delivering efficient calculations based on comprehensively formulated constitutive models. Such an approach is presented herein, employing a weighted essentially non-oscillatory (WENO) method within an adaptive mesh refinement (AMR) framework for the numerical solution of hyperbolic partial differential equations. Applied widely in computational fluid dynamics, these methods are well suited to the involved locally non-smooth finite deformations, circumventing any requirement for artificial viscosity functions for shock capturing. Application of the methods is facilitated through using a model of solid dynamics based upon hyper-elastic theory comprising kinematic evolution equations for the elastic distortion tensor. The model for finite inelastic deformations is phenomenologically equivalent to Maxwell s model of tangential stress relaxation. Closure relations tailored to the expected high-pressure states are proposed and calibrated for the materials of interest. Sharp interface resolution is achieved by employing level-set functions to track boundary motion, along with a ghost material method to capture the necessary internal boundary conditions for material interactions and stress-free surfaces. The approach is demonstrated for the simulation of high velocity impacts of steel projectiles on aluminium target plates in two and three dimensions.

  17. High-velocity intermittent running: effects of beta-alanine supplementation.

    PubMed

    Smith-Ryan, Abbie E; Fukuda, David H; Stout, Jeffrey R; Kendall, Kristina L

    2012-10-01

    The use of β-alanine in sport is widespread. However, the effects across all sport activities are inconclusive. The purpose of this study was to evaluate the effects of β-alanine supplementation on high-intensity running performance and critical velocity (CV) and anaerobic running capacity (ARC). Fifty recreationally trained men were randomly assigned, in a double-blind fashion, to a β-alanine group (BA, 2 × 800 mg tablets, 3 times daily; CarnoSyn; n = 26) or placebo group (PL, 2 × 800 mg maltodextrin tablets, 3 times daily; n = 24). A graded exercise test (GXT) was performed to establish peak velocity (PV). Three high-speed runs to exhaustion were performed at 110, 100, and 90% of PV, with 15 minutes of rest between bouts. The distances achieved were plotted over the time to exhaustion (TTE). Linear regression was used to determine the slope (CV) and y-intercept (ARC) of these relationships to assess aerobic and anaerobic performances, respectively. There were no significant treatment effects (p > 0.05) on CV or ARC for either men or women. Additionally, no TTE effects were evident for bouts at 90-110%PV lasting 1.95-5.06 minutes. There seems to be no ergogenic effect of β-alanine supplementation on CV, ARC, or high-intensity running lasting approximately 2-5 minutes in either men or women in the current study.

  18. Diffusion velocity correlation for nuclear graphite gasification at high temperature and low Reynolds numbers

    SciTech Connect

    El-Genk, M. S.; Tournier, J. M. P.

    2012-07-01

    The safety analysis of High-Temperature and Very High Temperature gas-cooled Reactors requires reliable estimates of nuclear graphite gasification as a function of temperature, among other parameters, in the unlikely event of an air ingress accident. Although the rates of the prevailing chemical reactions increase exponentially with temperature, graphite gasification at high temperatures is limited by the oxygen diffusion through the boundary layer. The effective diffusion velocity depends on the total flow rate and pressure of the bulk air-gas mixture. This paper develops a semi-empirical Sherwood number correlation for calculating the oxygen diffusion velocity. The correlation is based on a compiled database of the results of convective heat transfer experiments with wires and cylinders of different diameters in air, water and paraffin oil at 0.006 {<=} Re {<=} 1,604 and 0.068 {<=} Sc {<=} 35.2, and of mass transfer experiments at 4.8 {<=} Re {<=} 77 and 1,300 {<=} Sc {<=} 2,000. The developed correlation is within {+-} 8% of the compiled database of 567 data points and consistent with reported gasification rate measurements at higher temperatures in experiments using different size specimens of nuclear graphite grades of NBG-18 and NB-25, IG-11, IG-110 and IG-430 in atmospheric air at 0.08 {<=} Re {<=} 30. Unlike the Graetz solution that gives a constant Sh of 3.66 at Re {<=} 1.0, the present correlation shows Sh decreases monotonically to much lower values with decreasing Re. (authors)

  19. Iron containing vitamins and dietary supplements: control of the iron state using Mössbauer spectroscopy with high velocity resolution

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Semionkin, V. A.; Milder, O. B.; Novikov, E. G.

    2009-04-01

    Control of the iron state in iron containing vitamins and dietary supplements using Mössbauer spectroscopy with high velocity resolution was done. An improvement of velocity resolution appeared to be useful in determination of impurities and analysis of the main components in iron containing pharmaceuticals with better quality.

  20. SCEC CVM-Toolkit (CVM-T) -- High Performance Meshing Tools for SCEC Community Velocity Models

    NASA Astrophysics Data System (ADS)

    Small, P.; Maechling, P. J.; Ely, G. P.; Olsen, K. B.; Withers, K.; Graves, R. W.; Jordan, T. H.; Plesch, A.; Shaw, J. H.

    2010-12-01

    The SCEC Community Velocity Model Toolkit (CVM-T) enables earthquake modelers to quickly build, visualize, and validate large-scale 3D velocity meshes using SCEC CVM-H or CVM-4. CVM-T is comprised of three main components: (1) a current SCEC community velocity model for Southern California, (2) tools for extracting meshes from this model and visualizing them, and (3) an automated test framework for evaluating new releases of CVMs using SCEC’s AWP-ODC forward wave propagation software and one, or more, ground motion goodness of fit (GoF) algorithms. CVM-T is designed to help SCEC modelers build large-scale velocity meshes by extracting material properties from the most current version of Community Velocity Model H (CVM-H) and to provide a consistent interface as new CVM-H versions are developed. The CVM-T software provides a highly-scalable interface to CVM-H 6.2 (and later) voxets. Along with an improved interface to CVM-H material properties, the CVM-T software adds a geotechnical layer (GTL) to CVM-H 6.2+ based on Ely’s Vs30-derived GTL. The initial release of CVM-T also extends the coverage region for CVM-H 6.2 with a Hadley-Kanamori 1D background. Smoothing is performed within the transition boundary between the core model and the 1D background. The user interface now includes a C API that allows applications to query the model either by elevation or depth. The Extraction and Visualization Tools (EVT) include a parallelized 3D mesh generator which can quickly generate meshes (consisting of Vp, Vs, and density) from either CVM-H or CVM-4 with over 100 billion points. Python plotting scripts can be employed to plot horizontal or profile slices from existing meshes or directly from either CVM. The Automated Test Framework (ATF) is a system for quantitatively evaluating new versions of CVM-H and ensuring that the model improves against prior versions. The ATF employs the CruiseControl build and test framework to run an AWP-ODC simulation for the 2008 Chino

  1. Earthquake Energy Dissipation in Light of High-Velocity, Slip-Pulse Shear Experiments

    NASA Astrophysics Data System (ADS)

    Reches, Z.; Liao, Z.; Chang, J. C.

    2014-12-01

    We investigated the energy dissipation during earthquakes by analysis of high-velocity shear experiments conducted on room-dry, solid samples of granite, tonalite, and dolomite sheared at slip-velocity of 0.0006-1m/s, and normal stress of 1-11.5MPa. The experimental fault were loaded in one of three modes: (1) Slip-pulse of abrupt, intense acceleration followed by moderate deceleration; (2) Impact by a spinning, heavy flywheel (225 kg); and (3) Constant velocity loading. We refer to energy dissipation in terms of power-density (PD=shear stress*slip-velocity; units of MW/m^2), and Coulomb-energy-density (CED= mechanical energy/normal stress; units of m). We present two aspects: Relative energy dissipation of the above loading modes, and relative energy dissipation between impact experiments and moderate earthquakes. For the first aspect, we used: (i) the lowest friction coefficient of the dynamic weakening; (ii) the work dissipated before reaching the lowest friction; and (iii) the cumulative mechanical work during the complete run. The results show that the slip-pulse/impact modes are energy efficient relatively to the constant-velocity mode as manifested by faster, more intense weakening and 50-90% lower energy dissipation. Thus, for a finite amount of pre-seismic crustal energy, the efficiency of slip-pulse would amplify earthquake instability. For the second aspect, we compare the experimental CED of the impact experiments to the reported breakdown energy (EG) of moderate earthquakes, Mw = 5.6 to 7.2 (Chang et al., 2012). In is commonly assumed that the seismic EG is a small fraction of the total earthquake energy, and as expected in 9 out of 11 examined earthquakes, EG was 0.005 to 0.07 of the experimental CED. We thus speculate that the experimental relation of Coulomb-energy-density to total slip distance, D, CED = 0.605 × D^0.933, is a reasonable estimate of total earthquake energy, a quantity that cannot be determined from seismic data.

  2. A HIGH-METALLICITY, HIGH-VELOCITY CLOUD ALONG THE Mrk 421 SIGHT LINE: A TRACER OF COMPLEX M?

    SciTech Connect

    Yao Yangsen; Shull, J. Michael; Danforth, Charles W. E-mail: michael.shull@colorado.edu

    2011-02-10

    We present a new measurement, 0.85-3.5 Z{sub sun}, of the metallicity of high-velocity cloud (HVC) Complex M by analyzing ultraviolet spectroscopic observations of the blazar Mrk 421 taken with the Cosmic Origins Spectrograph on the Hubble Space Telescope and the Far-Ultraviolet Spectroscopic Explorer. Although an HVC at V{sub LSR} = -131 km s{sup -1} is not visible in 21 cm emission (log N{sub H{sub I}} < 18.38; 3{sigma}), it is detected in ultraviolet absorption lines of C II, N I, O I, O VI, Si II, Si III, Si IV, Fe II, and H I. By referencing velocities to the intermediate-velocity cloud at -60 km s{sup -1} and jointly analyzing H I absorption from high-order H I Lyman lines, we measure log N{sub H{sub I}} = 16.84{sup +0.34}{sub -0.13} (1{sigma}) in the HVC. Comparing H I and O I, we find an HVC metallicity [O/H] =0.32{sup +0.22}{sub -0.39}. Because the sight line passes {approx}4{sup 0} from the HVCs in Complex M, the detected HVC may represent the highest velocity component of the Complex, and our measurements provide a lower limit to its metallicity. The high, possibly super-solar metallicity, together with the low distance, z < 3.5 kpc, above the Galactic plane suggests that Complex M is condensed returning gas from a Galactic fountain.

  3. Formation and transformation of amino acids and amino acid precursors by high-velocity impacts

    NASA Astrophysics Data System (ADS)

    Kaneko, T.; Kobayashi, K.; Yamori, A.

    A wide variety of organic compounds have been found in extraterrestrial bodies such as comets and carbonaceous chondrites. It is plausible that these extraterrestrial bodies carried organic compounds such as amino acids or their precursors to the early Earth. It is claimed, however, that these extraterrestrial organics were destroyed during impacts to the Earth. We therefore examined possible transformation of amino acids and their precursors during high-velocity impacts by using a rail gun "HYPAC" in ISAS. Starting materials used in the impact experiments were (i) aqueous solution of glycine (10 mM or 1.0 M), and (ii) a mixture of ammonia, methanol and water. The target materials were sealed in stainless steel capsules, and shocked by impact with a polycarbonate projectile accelerated with "HYPAC" to the velocities of 2.5 - 7.0 km/s. A part of the products was acid-hydrolyzed. Both hydrolyzed an unhydrolyzed products were analyzed by mass spectrometry, high performance liquid chromatography and capillary electrophoresis and chromatography. When an aqueous solution containing ammonia, methanol and water was shocked by impact at the velocity of 6.4 km/s, a number of amino acids (e.g., serine and glycine) were detected after hydrolysis. The present results suggest that amino acid precursors could be formed during cometary impacts. When glycine solution was used as a starting material, about 40 % of glycine was recovered even after 6 km/s impact. Methylamine and ammonia, which are known as pyrolytic products of glycine, were detected, besides them, diketopiperazine and an unidentified product whose molecular weight was 134, were detected, while no glycine peptides were identified in them. It was shown that the impact processes resulted in the formation of amino acid condensates. Thermal stability of glycine precursor is comparable with glycine. The present results suggest that organic material could survive and/or formed during an impact process. Most of organic

  4. High Velocity Frictional Properties of a Clay-Bearing Fault Gouge and Implications for Earthquake Mechanics

    NASA Astrophysics Data System (ADS)

    Brunet, F.; Brantut, N.; Schubnel, A.; Rouzaud, J.; Shimamoto, T.

    2008-12-01

    Frictional properties of natural kaolinite-bearing gouge samples from the Median Tectonic Line (SW Japan) have been studied using a high-velocity rotary shear apparatus. For a slip velocity of 1~m.s-1 and normal stresses from 0.3 to 1.3~MPa, a dramatic slip-weakening behavior was observed. X-ray diffraction analysis of deformed samples and additional high-velocity friction experiments on pure kaolinite indicate kaolinite dehydration during slip. The critical slip-weakening distance Dc is of the order of 1~m to 10~m. These values are extrapolated to higher normal stresses, assuming that Dc is a thermal parameter. The calculation shows that dimensionally, Dc ∝ 1/σn2, where σn is the normal stress applied on the fault. The inferred Dc values range from a few centimeters at 10~MPa normal stress to a few hundreds of microns at 100~MPa normal stress. Microscopic observations show partial amorphization and dramatic grain size reduction (down to the nanometer scale) localized in a narrow zone of about 1 to 10~μm thickness. Fracture energy Gc is calculated and compared to surface energy due to grain size reduction, and energies of chemical reactions, showing that most of the fracture energy is converted into heat. The geophysical consequences of thermal dehydration of bonded water during seismic slip are then commented in the light of mineralogical and poro-mechanical data of several fault zones, which tend to show that this phenomenon has to be taken into account in most of sub-surface faults, and in hydrous rocks of subducted oceanic crust.

  5. Chemical abundances in a high-velocity RR Lyrae star near the bulge

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Rich, R. M.; Koch, A.; Xu, S.; Kunder, A.; Ludwig, H.-G.

    2016-05-01

    Low-mass variable high-velocity stars are interesting study cases for many aspects of Galactic structure and evolution. Until recently, the only known high- or hyper-velocity stars were young stars thought to originate from the Galactic center. Wide-area surveys such as APOGEE and BRAVA have found several low-mass stars in the bulge with Galactic rest-frame velocities higher than 350 km s-1. In this study we present the first abundance analysis of a low-mass RR Lyrae star that is located close to the Galactic bulge, with a space motion of ~-400 km s-1. Using medium-resolution spectra, we derived abundances (including upper limits) of 11 elements. These allowed us to chemically tag the star and discuss its origin, although our derived abundances and metallicity, at [Fe/H] =-0.9 dex, do not point toward one unambiguous answer. Based on the chemical tagging, we cannot exclude that it originated in the bulge. However, its retrograde orbit and the derived abundances combined suggest that the star was accelerated from the outskirts of the inner (or even outer) halo during many-body interactions. Other possible origins include the bulge itself, or the star might have been stripped from a stellar cluster or the Sagittarius dwarf galaxy when it merged with the Milky Way. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  6. High-velocity Interstellar Bullets in IRAS 05506+2414: A Very Young Protostar

    NASA Technical Reports Server (NTRS)

    Sahai, Raghvendra; Claussen, Mark; Sanchez Contreras, Carmen; Morris, Mark; Sarkar, Geetanjali

    2008-01-01

    We have made a serendipitous discovery of an enigmatic outflow source, IRAS 05506+2414 (hereafter IRAS 05506), as part of a multiwavelength survey of pre-planetary nebulae (PPNs). The HST optical and near-infrared images show a bright compact central source with a jet-like extension, and a fan-like spray of high-velocity (with radial velocities up to 350 km/s) elongated knots which appear to emanate from it. These structures are possibly analogous to the near-IR bullets'' seen in the Orion Nebula. Interferometric observations at 2.6 mm show the presence of a continuum source and a high-velocity CO outflow, which is aligned with the optical jet structure. IRAS 05506 is most likely not a PPN. We find extended NH3 (1,1) emission toward IRAS 05506; these data, together with the combined presence of far-IR emission, H2O and OH masers, and CO and CS J=2-1 emission, strongly argue for a dense, dusty star-forming core associated with IRAS 05506. IRAS 05506 is probably an intermediate-mass or massive protostar, and the very short timescale (200 yr) of its outflows indicates that it is very young. If IRAS 05506 is a massive star, then the lack of radio continuum and the late G to early K spectral type we find from our optical spectra imply that in this object we are witnessing the earliest stages of its life, while its temperature is still too low to provide sufficient UV flux for ionization.

  7. Mapping High-Velocity H-alpha and Lyman-alpha Emission from Supernova 1987A

    NASA Technical Reports Server (NTRS)

    France, Kevin; McCray, Richard; Fransson, Claes; Larsson, Josefin; Frank, Kari A.; Burrows, David N.; Challis, Peter; Kirshner, Robert P.; Chevalier, Roger A.; Garnavich, Peter; Heng, Kevin; Lawrence, Stephen S.; Lundqvist, Peter; Smith, Nathan; Sonneborn, George

    2015-01-01

    We present new Hubble Space Telescope images of high-velocity H-alpha and Lyman-alpha emission in the outer debris of SN 1987A. The H-alpha images are dominated by emission from hydrogen atoms crossing the reverse shock. For the first time we observe emission from the reverse shock surface well above and below the equatorial ring, suggesting a bipolar or conical structure perpendicular to the ring plane. Using the H-alpha imaging, we measure the mass flux of hydrogen atoms crossing the reverse shock front, in the velocity intervals (-7,500 < V(sub obs) < -2,800 km/s) and (1,000 < V(sub obs) < 7,500 km/s), ?M(sub H) = 1.2 × 10(exp -3) M/ y. We also present the first Lyman-alpha imaging of the whole remnant and new Chandra X-ray observations. Comparing the spatial distribution of the Lyman-alpha and X-ray emission, we observe that the majority of the high-velocity Lyman-alpha emission originates interior to the equatorial ring. The observed Lyman-alpha/H-alpha photon ratio, R(L-alpha/H-alpha) approx. = 17, is significantly higher than the theoretically predicted ratio of approx. = 5 for neutral atoms crossing the reverse shock front. We attribute this excess to Lyman-alpha emission produced by X-ray heating of the outer debris. The spatial orientation of the Lyman-alpha and X-ray emission suggests that X-ray heating of the outer debris is the dominant Lyman-alpha production mechanism in SN 1987A at this phase in its evolution.

  8. Observational parameters of the dusty plasma line during high velocity meteor streams

    NASA Astrophysics Data System (ADS)

    Musatenko, S.; Musatenko, Yu.; Kurochka, E.; Choliy, V.; Lastochkin, A.; Slipchenko, O.

    The parameters of the dusty plasma line were determined from the observations of the high velocity meteor streams: Perseids, Orionids, Leonids whose velocities are greater than 70 km/sec. The observed line frequency variation is in 12-60 Hz range. The outline of the line is asymmetric, it contains a set of peaks 2-3 Hz wide and some of them may be approximated by gaussian. In some cases the line is accompanied with higher frequency satellite at the distance 3-5 Hz. The spectral behavior of the line during observation time is very individual for concrete meteor shower. In the Leonids-2000 campaign the sharp line intensity maximum was registered between 02-04 LT, whereas during Leonids-2003 there were no maxima found. During Perseids-1999 the line was detectable all the night time. From these follows that dusty component of ionosphere plasma was either cloud shaped or consisted of streams of different scale. The line could be detected with high confidence during low or middle solar activity. We failed to detect the line when the storm (Dst=235nT, F10.7=195) took place during Perseids-2000 campaign. It was impossible for us to make some conclusion about the influence of solar bursts hard emission on the line characteristics due to poor statistics. Also, some of the low velocity meteor streams like Geminids-2000 may produce weak line. We have evidence of line arising even when regular meteor showers are absent (our experiment in June 2000 when no any of the streams were awaited). Basing on characteristics of plasma line the structure of dust clouds created by meteor streams in Earth ionosphere could be determined.

  9. Wind tunnel investigation of the effect of high relative velocities on the structural integrity of birds

    NASA Technical Reports Server (NTRS)

    Bresnahan, D. L.

    1972-01-01

    An experimental investigation was conducted in a supersonic wind tunnel to determine the effect a sudden high velocity headwind had on the physical deformation and structural breakup characteristics of birds. Several sizes of recently killed birds were dropped into the test section at free-stream Mach numbers ranging from 0.2 to 0.8 and photographed with high-speed motion-picture cameras. These conditions simulated flow conditions encountered when birds are ingested into the inlets of high speed aircraft, thereby constituting a safety hazard to the aircraft and its occupants. The investigation shows that, over the range of headwind conditions tested, the birds remained structurally intact and did not suffer any appreciable deformation or structural breakup.

  10. Phase contrast ultrashort TE: A more reliable technique for measurement of high-velocity turbulent stenotic jets.

    PubMed

    O'Brien, Kieran R; Myerson, Saul G; Cowan, Brett R; Young, Alistair A; Robson, Matthew D

    2009-09-01

    Accurate measurement of peak velocity is critical to the assessment of patients with stenotic valvular disease. Conventional phase contrast (PC) methods for imaging high-velocity jets in aortic stenosis are susceptible to intravoxel dephasing signal loss, which can result in unreliable measurements. The most effective method for reducing intravoxel dephasing is to shorten the echo time (TE); however, the amount that TE can be shortened in conventional sequences is limited. A new sequence incorporating velocity-dependent slice excitation and ultrashort TE (UTE) centric radial readout trajectories is proposed that reduces TE from 2.85 to 0.65 ms. In a high-velocity stenotic jet phantom, a conventional sequence had >5% flow error at a flow rate of only 400 mL/s (velocity >358 cm/s), whereas the PC-UTE showed excellent agreement (<5% error) at much higher flow rates (1080 mL/s, 965 cm/s). In vivo feasibility studies demonstrated that by measuring velocity over a shorter time the PC-UTE approach is more robust to intravoxel dephasing signal loss. It also has less inherent higher-order motion encoding. This sequence therefore demonstrates potential as a more robust method for measuring peak velocity and flow in high-velocity turbulent stenotic jets.

  11. Survivability of bare, individual Bacillus subtilis spores to high-velocity surface impact: Implications for microbial transfer through space

    NASA Astrophysics Data System (ADS)

    Barney, Brandon L.; Pratt, Sara N.; Austin, Daniel E.

    2016-06-01

    Laboratory experiments show that endospores of Bacillus subtilis survive impact against a solid surface at velocities as high as 299 ±28 m/s. During impact, spores experience and survive accelerations of at least 1010 m/s2. The spores were introduced into a vacuum chamber using an electrospray source and accelerated to a narrow velocity distribution by entrainment in a differentially pumped gas flow. Different velocity ranges were studied by modifying the gas flow parameters. The spores were electrically charged, allowing direct measurement of the velocity of each spore as it passed through an image charge detector prior to surface impact. Spores impacted a glass surface and were collected for subsequent analysis by culturing. Most spores survived impact at all measured velocities. These experiments differ fundamentally from other studies that show either shock or impact survivability of bacteria embedded within or on the surface of a projectile. Bacteria in the present experiments undergo a single interaction with a solid surface at the full impact velocity, in the absence of any other effects such as cushioning due to microbe agglomerations, deceleration due to air or vapor, or transfer of impact shock through solid or liquid media. During these full-velocity impact events, the spores experience extremely high decelerations. This study is the first reported instance of accelerations of this magnitude experienced during a bacteria impact event. These results are discussed in the context of potential transfer of viable microbes in space and other scenarios involving surface impacts at high velocities.

  12. The 1994 Northridge, California, earthquake: Investigation of rupture velocity, risetime, and high-frequency radiation

    USGS Publications Warehouse

    Hartzell, S.; Liu, P.; Mendoza, C.

    1996-01-01

    A hybrid global search algorithm is used to solve the nonlinear problem of calculating slip amplitude, rake, risetime, and rupture time on a finite fault. Thirty-five strong motion velocity records are inverted by this method over the frequency band from 0.1 to 1.0 Hz for the Northridge earthquake. Four regions of larger-amplitude slip are identified: one near the hypocenter at a depth of 17 km, a second west of the hypocenter at about the same depth, a third updip from the hypocenter at a depth of 10 km, and a fourth updip from the hypocenter and to the northwest. The results further show an initial fast rupture with a velocity of 2.8 to 3.0 km/s followed by a slow termination of the rupture with velocities of 2.0 to 2.5 km/s. The initial energetic rupture phase lasts for 3 s, extending out 10 km from the hypocenter. Slip near the hypocenter has a short risetime of 0.5 s, which increases to 1.5 s for the major slip areas removed from the hypocentral region. The energetic rupture phase is also shown to be the primary source of high-frequency radiation (1-15 Hz) by an inversion of acceleration envelopes. The same global search algorithm is used in the envelope inversion to calculate high-frequency radiation intensity on the fault and rupture time. The rupture timing from the low- and high-frequency inversions is similar, indicating that the high frequencies are produced primarily at the mainshock rupture front. Two major sources of high-frequency radiation are identified within the energetic rupture phase, one at the hypocenter and another deep source to the west of the hypocenter. The source at the hypocenter is associated with the initiation of rupture and the breaking of a high-stress-drop asperity and the second is associated with stopping of the rupture in a westerly direction.

  13. Anion production in high-velocity cluster-atom collisions; the electron capture process revisited

    NASA Astrophysics Data System (ADS)

    Béroff, K.; Chabot, M.; Martinet, G.; Pino, T.; Bouneau, S.; Le Padellec, A.; Féraud, G.; Do Thi, N.; Calvo, F.; Bordas, C.; Lépine, F.

    2013-01-01

    Anion production cross sections in collisions between Cn+, Cn carbon clusters (n ≤ 5) and helium atoms have been measured in high-velocity collisions (v = 2.25 and 2.6 au). This paper focuses on two of the three processes responsible for the Cn- production, namely double electron capture (DEC) onto Cn+ cations and single electron capture onto neutral (SECN) Cn. They were experimentally distinguished from a gaseous thickness dependence study. Dissociative and non-dissociative cross sections were measured and, in the case of DEC, all dissociative branching ratios measured; for these small systems, the C2- fragment was found magical. Data concerning electron capture in neutral-neutral collisions are extremely rare, especially at high velocity. Introduction of this measured process in the independent atom and electron (IAE) model allowed us to revisit and satisfactorily reproduce the so-far unexplained size evolution of single electron capture (SEC) cross sections in 2.6 au Cn+-He (n ≤ 10) collisions (Chabot et al 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2593-603). IAE calculations for DEC cross sections and their comparison with experiment suggest a loss of electron in anionic Cn- species after the collision, competing with fragmentation and depending on the size.

  14. Surface-to-borehole illumination of a high-velocity layer using marine VSP

    SciTech Connect

    MacBeth, C.; Liu, E.; Boyd, M.; Sweeney, K.

    1994-12-31

    Two marine walkaway VSP lines are recorded by three-component receivers positioned in a dolomite layer. The layer has a high seismic velocity relative to the surrounding rocks and may be fracture. The recorded wavefield is analyzed to determine whether this acquisition is suitable to image details of the internal structure of the layer. The principal arrivals in the wavefield are a dominant horizontally refracted compressional wave with a smooth unbroken moveout, converted shear-waves from shallow reflectors, and reverberation of these converted shear-waves within the high velocity layer. Anisotropic analyses of the converted shear-waves estimate an overburden birefringence of 3% and a polarization direction consistent with the known NW-SE maximum compressive stress. Full-wave modeling of the recorded wavefield aids identification of the various arrivals and constrains the attenuation and anisotropic properties of the layer, which appears laterally uniform with the most satisfactory model possessing low attenuation but a birefringence of no more than 5%. If the layer is cracked, these results are diagnostic of evenly distributed cracks with a scalelength smaller than a fraction of a wavelength.

  15. Estimation of Rotational Velocity of Baseball Using High-Speed Camera Movies

    NASA Astrophysics Data System (ADS)

    Inoue, Takuya; Uematsu, Yuko; Saito, Hideo

    Movies can be used to analyze a player's performance and improve his/her skills. In the case of baseball, the pitching is recorded by using a high-speed camera, and the recorded images are used to improve the pitching skills of the players. In this paper, we present a method for estimating of the rotational velocity of a baseball on the basis of movies recorded by high-speed cameras. Unlike in the previous methods, we consider the original seam pattern of the ball seen in the input movie and identify the corresponding image from a database of images by adopting the parametric eigenspace method. These database images are CG Images. The ball's posture can be determined on the basis of the rotational parameters. In the proposed method, the symmetric property of the ball is also taken into consideration, and the time continuity is used to determine the ball's posture. In the experiments, we use the proposed method to estimate the rotational velocity of a baseball on the basis of real movies and movies consisting of CG images of the baseball. The results of both the experiments prove that our method can be used to estimate the ball's rotation accurately.

  16. Energy evaluation of the High Velocity Algae Raceway Integrated Design (ARID-HV)

    NASA Astrophysics Data System (ADS)

    Attalah, Said

    The original ARID (Algae Raceway Integrated Design) raceway was an effective method to increase temperature toward the optimal growth range. However, the energy input was high and flow mixing was poor. Thus, the ARID-HV (High Velocity Algae Raceway Integrated Design) raceway was developed to reduce energy input requirements and improve flow mixing. This was accomplished by improving pumping efficiency and using a serpentine flow pattern in which the water flows through channels instead of over barriers. A prototype ARID-HV system was installed in Tucson, Arizona, and the constructability, reliability of components, drainage of channels, and flow and energy requirements of the ARID-HV raceway were evaluated. Each of the electrical energy inputs to the raceway (air sparger, air tube blower, canal lift pump, and channel recirculation pump) was quantified, some by direct measurement and others by simulation. An algae growth model was used to determine the algae production rate vs. flow depth and time of year. Then the electrical energy requirement of the most effective flow depth was calculated. Channel hydraulics was evaluated with Manning's equation and the corner head loss equation. In this way, the maximum length of channels for several raceway slopes and mixing velocities were determined. Algae production in the ARID-HV raceway was simulated with a temperature and light growth model. An energy efficient design for the ARID-HV raceway was developed.

  17. The collision of high-velocity clouds with a galactic disk

    NASA Technical Reports Server (NTRS)

    Tenorio-Tagle, G.; Bodenheimer, P.; Rozyczka, M.; Franco, J.

    1986-01-01

    Two-dimensional hydrodynamic simulations for the interaction of high-velocity clouds with a galactic disk are presented. The impinging clouds are assumed to be spherical and the target disk is represented by a constant density slab, n(g) = 1/cu cm, with a total width W(g) = 200 pc. The numerical experiments cover a wide range of cloud densities, between 0.1 and 100/cu cm, and velocities between 100 and 300 km/s. At a time approximately 10 to the 7th yr after impact, two types of final configurations are found. In the first case, the infalling cloud is completely shocked in a time short compared with the crossing time of the disk. Then, the generated cavity has time to grow sideways and large scale structures with a round shape, and in some cases nearly spherical, are produced. In the second case, which occurs for high density clouds, the cloud is shocked on a time scale longer than or comparable to the crossing time. The resultant cylindrical holes drilled across the entire disk have the dimensions of the impinging cloud. Cloud-galaxy interactions are compared with other energy sources and the morphologies of the resultant structures are suggested to resemble the large scale structures observed in H I.

  18. The Small-Scale Structure of High-Velocity Na I Absorption Toward M81

    NASA Astrophysics Data System (ADS)

    Roth, K. C.; Meyer, D. M.; Lauroesch, J. T.

    2000-12-01

    We present high-resolution (R=20,000) integral field spectra of the Na I absorption toward the nucleus of the nearby spiral galaxy M81 (NGC 3031) obtained in April 2000 with the WIYN 3.5-m telescope and the DensePak fiber optic bundle. Our DensePak map covers the central 27 x 43 arcsec of M81 at a spatial resolution of 4 arcsec which corresponds to a projected length scale of 63 pc at the distance of the galaxy (3.25 Mpc). These data were intended to explore the spatial extent of high-velocity (v = 110-130 km/s) gas seen in Na I, Mg I and Mg II absorption toward SN 1993J by Bowen et al. (1994), which they proposed is due to tidal material associated with interactions between M81 and nearby M82 (Yun, Ho & Lo 1993). No H I gas at these velocities has been detected in 21 cm interferometry maps near the position of SN 1993J (2.6 arcmin SW of the M81 nucleus). Our Na I map of the M81 core shows no evidence of the strong absorption seen at v = 110-130 km/s toward SN 1993J. However, our map does reveal a strong Na I component at v = 220 km/s in several fibers that appears to trace a filamentary structure running from the SW to the NE across the M81 nuclear region. The origin and distance of this filament are unknown. No H I gas at v = 220 km/s has previously been detected in 21 cm studies of the core. At the location of SN 1993J, Bowen et al. measured weak Mg II absorption at this velocity but found no evidence of corresponding Na I absorption. The only known H I gas that corresponds to this velocity in the M81 group are the H I streamers found around M82 by Yun, Ho, & Lo that they interpreted as tidally disrupted M82 disk material.

  19. A dynamic study of fragmentation and energy loss during high velocity impact

    NASA Technical Reports Server (NTRS)

    Zee, Ralph H.

    1992-01-01

    Research conducted under this contract can be divided into two main areas: hypervelocity (in the range up to 7 km/s) and high velocity (less than 1 km/s). Work in the former was performed at NASA-MSFC using the Light Gas Gun Facility. The lower velocity studies were conducted at Auburn University using the ballistic gun. The emphasis of the project was on the hypervelocity phenomenon especially in the characterization of the debris cloud formed by the primary impact events. Special devices were made to determine the angular distributions of momentum and energy of the debris cloud as a function of impact conditions. After several iteration processes, it was decided to concentrate on the momentum effort. Prototype devices were designed, fabricated, and tested. These devices were based on the conservation of momentum. Distributions of the debris cloud formed were measured by determining the amount of momentum transferred from the debris cloud to strategically placed pendulum measurement devices. The motion of the pendula was monitored using itegrated opto-interrupters. The distribution of momentum in the debris cloud was found to be a strong function of the impact condition. Small projectiles at high velocities were observed to produce finely dispersed debris whereas large projectiles generated discrete particles in the debris. Results also show that the momentum in the forward direction was enhanced due to the impact. This phenomenon of momentum multiplication was also observed in other studies and in computer simulations. It was initially planned to determine the energy distribution using deformation energy in a rod with strain gauges. Results from preliminary studies show that this technique is acceptable but too tedious. A new technique was explored based on measuring the heating effect of the debris cloud using an IR camera. The feasibility and sensitivity was established at Auburn University. This type of energy distribution measurement method can easily be

  20. High-velocity frictional experiments on dolerite and quartzite under controlled pore pressure

    NASA Astrophysics Data System (ADS)

    Togo, T.; Shimamoto, T.; Ma, S.

    2013-12-01

    High-velocity friction experiments on rocks with or without gouge have been conducted mostly under dry conditions and demonstrated dramatic weakening of faults at high velocities (e.g., Di Toro et al., 2011, Nature). Recent experiments under wet conditions (e.g., Ujiie and Tsutsumi, 2010, GRL; Faulkner et al., 2011, GRL) revealed very different behaviors from those of dry faults, but those experiments were done under drained conditions. Experiments with controlled pore pressure Pp are definitely needed to determine mechanical properties of faults under fluid-rich environments such as those in subduction zones. Thus we have developed a pressure vessel that can be attached to our rotary-shear low to high-velocity friction apparatus (Marui Co Ltd., MIS-233-1-76). With a current specimen holder, friction experiments can be done on hollow-cylindrical specimens of 15 and 40 mm in inner and outer diameters, respectively, at controlled Pp to 35 MPa, at effective normal stresses of 3~9 MPa, and at slip rates of 60 mm/year to 2 m/s. An effective normal stress can be applied with a 100 kN hydraulic actuator. We report an outline of the experimental system and preliminary high-velocity experiments on Shanxi dolerite and a quartzite from China that are composed of pyroxene and plagioclase and of almost pure quartz, respectively. High-velocity friction experiments were performed on hollow-cylindrical specimens of Shanxi dolerite at effective normal stresses of 0.13~1.07 MPa and at slip rates of 1, 10, 100 and 1000 mm/sec. All experiments were conducted first with the nitrogen gas filling the pressure vessel (dry tests) and then with a controlled pore-water pressure (wet tests). In the dry tests an axial force was kept at 1 kN and the nitrogen gas pressure was increased in steps to 5 MPa to change an effective normal stress. In the wet tests the specimens were soaked in distilled water in the vessel and Pp was applied by nitrogen gas in a similar manner as in the dry tests

  1. A DETAILED KINEMATIC MAP OF CASSIOPEIA A'S OPTICAL MAIN SHELL AND OUTER HIGH-VELOCITY EJECTA

    SciTech Connect

    Milisavljevic, Dan; Fesen, Robert A.

    2013-08-01

    We present three-dimensional (3D) kinematic reconstructions of optically emitting material in the young Galactic supernova remnant Cassiopeia A (Cas A). These Doppler maps have the highest spectral and spatial resolutions of any previous survey of Cas A and represent the most complete catalog of its optically emitting material to date. We confirm that the bulk of Cas A's optically bright ejecta populate a torus-like geometry tilted approximately 30 Degree-Sign with respect to the plane of the sky with a -4000 to +6000 km s{sup -1} radial velocity asymmetry. Near-tangent viewing angle effects and an inhomogeneous surrounding circumstellar material/interstellar medium environment suggest that this geometry and velocity asymmetry may not be faithfully representative of the remnant's true 3D structure or the kinematic properties of the original explosion. The majority of the optical ejecta are arranged in several well-defined and nearly circular ring-like structures with diameters between approximately 30'' (0.5 pc) and 2' (2 pc). These ejecta rings appear to be a common phenomenon of young core-collapse remnants and may be associated with post-explosion input of energy from plumes of radioactive {sup 56}Ni-rich ejecta that rise, expand, and compress non-radioactive material. Our optical survey encompasses Cas A's faint outlying ejecta knots and exceptionally high-velocity NE and SW streams of S-rich debris often referred to as ''jets''. These outer knots, which exhibit a chemical make-up suggestive of an origin deep within the progenitor star, appear to be arranged in opposing and wide-angle outflows with opening half-angles of Almost-Equal-To 40 Degree-Sign.

  2. Comparison of three baseball-specific 6-week training programs on throwing velocity in high school baseball players.

    PubMed

    Escamilla, Rafael F; Ionno, Michele; deMahy, M Scott; Fleisig, Glenn S; Wilk, Kevin E; Yamashiro, Kyle; Mikla, Tony; Paulos, Lonnie; Andrews, James R

    2012-07-01

    Throwing velocity is an important baseball performance variable for baseball pitchers, because greater throwing velocity results in less time for hitters to make a decision to swing. Throwing velocity is also an important baseball performance variable for position players, because greater throwing velocity results in decreased time for a runner to advance to the next base. This study compared the effects of 3 baseball-specific 6-week training programs on maximum throwing velocity. Sixty-eight high school baseball players 14-17 years of age were randomly and equally divided into 3 training groups and a nontraining control group. The 3 training groups were the Throwers Ten (TT), Keiser Pneumatic (KP), and Plyometric (PLY). Each training group trained 3 d·wk(-1) for 6 weeks, which comprised approximately 5-10 minutes for warm-up, 45 minutes of resistance training, and 5-10 for cool-down. Throwing velocity was assessed before (pretest) and just after (posttest) the 6-week training program for all the subjects. A 2-factor repeated measures analysis of variance with post hoc paired t-tests was used to assess throwing velocity differences (p < 0.05). Compared with pretest throwing velocity values, posttest throwing velocity values were significantly greater in the TT group (1.7% increase), the KP group (1.2% increase), and the PLY group (2.0% increase) but not significantly different in the control group. These results demonstrate that all 3 training programs were effective in increasing throwing velocity in high school baseball players, but the results of this study did not demonstrate that 1 resistance training program was more effective than another resistance training program in increasing throwing velocity.

  3. Comparison of three baseball-specific 6-week training programs on throwing velocity in high school baseball players.

    PubMed

    Escamilla, Rafael F; Ionno, Michele; deMahy, M Scott; Fleisig, Glenn S; Wilk, Kevin E; Yamashiro, Kyle; Mikla, Tony; Paulos, Lonnie; Andrews, James R

    2012-07-01

    Throwing velocity is an important baseball performance variable for baseball pitchers, because greater throwing velocity results in less time for hitters to make a decision to swing. Throwing velocity is also an important baseball performance variable for position players, because greater throwing velocity results in decreased time for a runner to advance to the next base. This study compared the effects of 3 baseball-specific 6-week training programs on maximum throwing velocity. Sixty-eight high school baseball players 14-17 years of age were randomly and equally divided into 3 training groups and a nontraining control group. The 3 training groups were the Throwers Ten (TT), Keiser Pneumatic (KP), and Plyometric (PLY). Each training group trained 3 d·wk(-1) for 6 weeks, which comprised approximately 5-10 minutes for warm-up, 45 minutes of resistance training, and 5-10 for cool-down. Throwing velocity was assessed before (pretest) and just after (posttest) the 6-week training program for all the subjects. A 2-factor repeated measures analysis of variance with post hoc paired t-tests was used to assess throwing velocity differences (p < 0.05). Compared with pretest throwing velocity values, posttest throwing velocity values were significantly greater in the TT group (1.7% increase), the KP group (1.2% increase), and the PLY group (2.0% increase) but not significantly different in the control group. These results demonstrate that all 3 training programs were effective in increasing throwing velocity in high school baseball players, but the results of this study did not demonstrate that 1 resistance training program was more effective than another resistance training program in increasing throwing velocity. PMID:22549085

  4. The Draco Nebula, a Molecular Cloud Associated with a High Velocity Cloud?

    NASA Technical Reports Server (NTRS)

    Mebold, U.; Kalberla, P. W. M.

    1984-01-01

    Extended and very faint bright nebulae are found in high galactic latitudes at the Palomar Observatory Sky Survey. Such a nebula, located in the constellation Draco and called Draco Nebula or Dracula, was found to be in detailed positional coincidence with a 21 cm emission line feature. Estimates of the minimum visual extinction from star counts ON and OFF Dracula and an estimated visual surface brightness indicate that Dracula fits the relation SBV = 24.2 - 2.5 log AV for dust clouds located above the galactic plane and reflecting the integrated starlight of the galactic disk. Hence Dracula is probably a reflection nebula. Indicators of molecular hydrogen in Dracula, molecules such as CO, were searched for by using a 2.5-m mm-telescope. Molecular hydrogen column densities were estimated. The dynamics of CO clumps was studied. Dracula has a close positional and possibly even astrophysical relationship to the high velocity cloud phenomenon.

  5. High domain wall velocities via spin transfer torque using vertical current injection

    PubMed Central

    Metaxas, Peter J.; Sampaio, Joao; Chanthbouala, André; Matsumoto, Rie; Anane, Abdelmadjid; Fert, Albert; Zvezdin, Konstantin A.; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Nishimura, Kazumasa; Nagamine, Yoshinori; Maehara, Hiroki; Tsunekawa, Koji; Cros, Vincent; Grollier, Julie

    2013-01-01

    Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm2. Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching. PMID:23670402

  6. High domain wall velocities via spin transfer torque using vertical current injection.

    PubMed

    Metaxas, Peter J; Sampaio, Joao; Chanthbouala, André; Matsumoto, Rie; Anane, Abdelmadjid; Fert, Albert; Zvezdin, Konstantin A; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Nishimura, Kazumasa; Nagamine, Yoshinori; Maehara, Hiroki; Tsunekawa, Koji; Cros, Vincent; Grollier, Julie

    2013-01-01

    Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm(2). Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching. PMID:23670402

  7. High domain wall velocities via spin transfer torque using vertical current injection

    NASA Astrophysics Data System (ADS)

    Metaxas, Peter J.; Sampaio, Joao; Chanthbouala, André; Matsumoto, Rie; Anane, Abdelmadjid; Fert, Albert; Zvezdin, Konstantin A.; Yakushiji, Kay; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Nishimura, Kazumasa; Nagamine, Yoshinori; Maehara, Hiroki; Tsunekawa, Koji; Cros, Vincent; Grollier, Julie

    2013-05-01

    Domain walls, nanoscale transition regions separating oppositely oriented ferromagnetic domains, have significant promise for use in spintronic devices for data storage and memristive applications. The state of these devices is related to the wall position and thus rapid operation will require a controllable onset of domain wall motion and high speed wall displacement. These processes are traditionally driven by spin transfer torque due to lateral injection of spin polarized current through a ferromagnetic nanostrip. However, this geometry is often hampered by low maximum wall velocities and/or a need for prohibitively high current densities. Here, using time-resolved magnetotransport measurements, we show that vertical injection of spin currents through a magnetic tunnel junction can drive domain walls over hundreds of nanometers at ~500 m/s using current densities on the order of 6 MA/cm2. Moreover, these measurements provide information about the stochastic and deterministic aspects of current driven domain wall mediated switching.

  8. Aerodynamic study on supersonic flows in high-velocity oxy-fuel thermal spray process

    NASA Astrophysics Data System (ADS)

    Katanoda, Hiroshi; Matsuoka, Takeshi; Kuroda, Seiji; Kawakita, Jin; Fukanuma, Hirotaka; Matsuo, Kazuyasu

    2005-06-01

    To clarify the characteristics of gas flow in high velocity oxy-fuel (HVOF) thermal spray gun, aerodynamic research is performed using a special gun. The gun has rectangular cross-sectional area and sidewalls of optical glass to visualize the internal flow. The gun consists of a supersonic nozzle with the design Mach number of 2.0 followed by a straight passage called barrel. Compressed dry air up to 0.78 MPa is used as a process gas instead of combustion gas which is used in a commercial HVOF gun. The high-speed gas flows with shock waves in the gun and jets are visualized by schlieren technique. Complicated internal and external flow-fields containing various types of shock wave as well as expansion wave are visualized.

  9. The effect of low- and high-velocity tendon excursion on the mechanical properties of human cadaver subsynovial connective tissue.

    PubMed

    Filius, Anika; Thoreson, Andrew R; Yang, Tai-Hua; Vanhees, Matthias; An, Kai-Nan; Zhao, Chunfeng; Amadio, Peter C

    2014-01-01

    Fibrosis of the subsynovial connective tissue (SSCT) in the carpal tunnel is the most common histological finding in carpal tunnel syndrome (CTS). Fibrosis may result from damaged SSCT. Previous studies found that with low-velocity (2 mm/s), tendon excursions can irreversibly damage the SSCT. We investigated the effect of tendon excursion velocity in the generation of SSCT damage. Nine human cadaver wrists were used. Three repeated cycles of ramp-stretch testing were performed simulating 40%, 60%, 90%, and 120% of the middle finger flexor tendon superficialis physiological excursion with an excursion velocity of 60 mm/s. Energy and force were calculated and normalized by values obtained in the first cycle for each excursion level. Data were compared with low-velocity excursion data. For high-velocity excursions, a significant drop in the excursion energy ratio was first observed at an excursion level of 60% physiological excursion (p < 0.024) and that for low-velocity excursions was first observed at 90% physiological excursion (p < 0.038). Furthermore, the energy ratio was lower at 60% for high velocities (p ≤ 0.039). Increasing velocity lowers the SSCT damage threshold. This finding may be relevant for understanding the pathogenesis of SSCT fibrosis, such as that accompanying CTS, and a relationship with occupational factors.

  10. A new instrument to measure charged and neutral cometary dust particles at low and high impact velocities

    NASA Technical Reports Server (NTRS)

    Economon, T.; Simpson, J. A.; Tuzzolino, A. J.

    1986-01-01

    A new class of dust particle detector, the PVDF dust detector, was designed for space missions such as the Halley Comet missions where the particle impact velocity is very high. It is demonstrated that this same PVDF detector (operating in a different mode) also has the capability of detecting dust particles having low velocity (approx. 100 m/s). This low velocity detection capability is extremely important in terms of planned missions requiring measurement of low velocity dust particles such as comet rendezvous missions. An additional detecting element (charge induction cylinder) was also developed which, when combined with a PVDF detector, yields a system which will measure the charge (magnitude and sign) carried by a cometary particle as well as the particle velocity and mass for impact velocities in the range 100 to 500 m/s. Since the cylinder-PVDF detector system has a relatively small geometry factors, an array of PVDF detectors was included having a total sensing area of 0.1 sq m for measurements in regions of space where the dust flux is expected to be low. The characteristics of the detectors in this array have been chosen to provide optimum mass sensitivity for both low-velocity cometary dust as well as high-velocity asteroid associated and interplanetary dust.

  11. A novel platform to study magnetized high-velocity collisionless shocks

    DOE PAGES

    Higginson, D. P.; Korneev, Ph; Béard, J.; Chen, S. N.; d'Humières, E.; Pépin, H.; Pikuz, S.; Pollock, B.; Riquier, R.; Tikhonchuk, V.; et al

    2014-12-13

    An experimental platform to study the interaction of two colliding high-velocity (0.01–0.2c; 0.05–20 MeV) proton plasmas in a high strength (20 T) magnetic field is introduced. This platform aims to study the collision of magnetized plasmas accelerated via the Target-Normal-Sheath-Acceleration mechanism and initially separated by distances of a few hundred microns. The plasmas are accelerated from solid targets positioned inside a few cubic millimeter cavity located within a Helmholtz coil that provides up to 20 T magnetic fields. Various parameters of the plasmas at their interaction location are estimated. These show an interaction that is highly non-collisional, and that becomesmore » more and more dominated by the magnetic fields as time progresses (from 5 to 60 ps). Particle-in-cell simulations are used to reproduce the initial acceleration of the plasma both via simulations including the laser interaction and via simulations that start with preheated electrons (to save dramatically on computational expense). The benchmarking of such simulations with the experiment and with each other will be used to understand the physical interaction when a magnetic field is applied. In conclusion, the experimental density profile of the interacting plasmas is shown in the case without an applied magnetic magnetic field, so to show that without an applied field that the development of high-velocity shocks, as a result of particle-to-particle collisions, is not achievable in the configuration considered.« less

  12. Impact of High Velocity Interactions on Galaxy Evolution in Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Machacek, Marie E.; Jones, C.; Forman, W. R.; Kraft, R. P.; Ashby, M. L.; Hardcastle, M. J.

    2007-05-01

    Galaxy interactions in cool groups dominate galaxy evolution at high redshift. Observations of galaxies interacting in nearby galaxy groups, where the same dynamical processes that transform galaxies at high redshift can be studied in detail, are critical to our understanding of galaxy and group evolution. X-ray observations of hot gas features, e.g. surface brightness edges and wakes, reveal that high velocity interactions play a significant role in the transformation of galaxies in groups, yet, because these encounters are difficult to identify in other wavebands, few have been studied. We present two case studies of high velocity galaxy-galaxy and galaxy-gas interactions in galaxy groups: NGC4782(3C278) and NGC4783 in LGG316, and NGC6872 and NGC6876 in the Pavo group. From Chandra and XMM-Newton X-ray data, we measure the hot gas temperature, density and metal abundance in the galaxies and the intragroup medium (IGM) to characterize the thermodynamic state of the group, constrain 3D motions of the galaxies through the IGM, and determine the dominant processes transferring matter and energy between the galaxy and group gas. We compare these results with VLA observations of NGC4782/3 and Spitzer IRAC observations of NGC6872 and NGC6876 to study the impact of these interactions on nuclear activity, radio jet evolution, and star formation in these galaxies, and on the heating and enrichment of the IGM. This work was supported in part by the Smithsonian Institution, the Chandra Science Center, NASA contracts AR5-6011X, GO6-7068X, NNX06AG34G, JPL1279244 and the Royal Society.

  13. Highly Ionized Gas in the Galactic Halo and the High Velocity Clouds Toward PG 1116+215

    NASA Astrophysics Data System (ADS)

    Ganguly, R.; Sembach, K. R.; Tripp, T. M.; Savage, B. D.

    2003-12-01

    Recent observations of extragalactic objects with FUSE have revealed the presence of high ionization OVI absorption associated with high velocity clouds (HVCs), defined as gas which lies at absolute velocities beyond 100 km/s in the Local Standard of Rest. We have acquired high spectral resolution observations with STIS ( ˜ 10 km/s) and FUSE ( ˜ 20 km/s) of the quasar PG 1116+215. The spectra show absorption at Vlsr=184km/s from a wide range of ionization species:CIV, OI, OVI, MgII, SiII, SiIII, SiIV, and FeII. The strong and broad O VI absorption in this HVC extends from ˜ 120 to 230 km/s with a weak wing of absorption to 300km/s. Although the HVC is not seen in HI 21 cm emission down to N(HI) ˜ 2x1018 cm-2, it is seen in the HI Lyman series up to at least the 918.13Å line. In addition, we have non-detection constraints on the column denisties of CI, NI, NV, and SII. We can rule out photoionization in an ultra-low density (n ˜ 10-6 cm-3) Local Group medium adopted by some investigators to explain the O VI and O VII absorption detected in several directions. We are currently in the process of determining if these data either support or rule out other models of HVCs, such as the Warm-Hot Intergalactic Medium, Dark Matter dominated mini-halos, or interactions with a low density (10-4-10-5 cm-3) Galactic corona or Local Group medium. In addition, we will also use abundance infomation to study the enrichment history and constrain possible sources for the high velocity gas, such as tidal debris from cannibalized galaxies.

  14. Global properties of the HI high velocity sky. A statistical investigation based on the LAB survey

    NASA Astrophysics Data System (ADS)

    Kalberla, P. M. W.; Haud, U.

    2006-08-01

    Context.Since 1973, it has been known that some H i high velocity clouds (HVCs) have a core-envelope structure. Recent observations of compact HVCs confirm this, but more general investigations have been missing so far.Aims.We study the properties of all major HVC complexes from a sample compiled in 1991 by Wakker & van Woerden (WvW). Methods.We use the Leiden/Argentine/Bonn all sky 21-cm line survey and decompose the profiles into Gaussian components.Results.We find the WvW line widths and column densities to be underestimated by ~40%. In 1991, these line widths could not be measured directly, but had to be estimated with the help of higher resolution data. We find a well-defined multi-component structure for most of the HVC complexes. The cold HVC phase has lines with typical velocity dispersions of σ = 3 km s-1 and exists only within more extended broad line regions, typically with σ = 12 km s-1. The motions of the cores relative to the envelopes are characterized by Mach numbers M = (vcore-venvelope)/σenvelope ˜ 1.5. The center velocities of the cores within a HVC complex have typical dispersions of 20 km s-1. The well-defined two-component structure of some prominent HVC complexes in the outskirts of the Milky Way is remakable: Complex H lies approximately in the Galactic plane, and the most plausible distance estimate of R ˜ 33 kpc places it at the edge of the disk. The Magellanic Stream and the Leading Arm (complex EP) reach higher latitudes and are probably more distant, R ˜ 50 kpc. There might be some indications for an interaction between HVCs and disk gas at intermediate velocities. This is possible for complex H, M, C, WB, WD, WE, WC, R, G, GCP, and OA, but not for complex A, MS, ACVHV, EN, WA, and P. Conclusions.The line widths, determined by us, imply that estimates of HVC masses, as far as those derived from the WvW database are concerned, need to be scaled up by a factor 1.4. Correspondingly, guesses for the external pressure of a confining

  15. What Happens to a High Velocity Cloud When it Hits the Milky Way's Disk: Is Dark Matter Necessary for Survival?

    NASA Astrophysics Data System (ADS)

    Shelton, Robin L.; Galyardt, Jason

    2015-01-01

    Dark matter halos enshroud some of the most massive high velocity clouds. Their gravitational pull confines the clouds as they pass through the intergalactic medium. Given the ability of dark matter halos to stabilize their embedded baryonic clouds against hydrodynamic interactions that would otherwise disrupt them, it has further been suggested that dark matter halos could enable high velocity clouds to survive impacts with the Milky Way's disk. The survival of high velocity clouds, such as the Smith Cloud, during a passage through the disk has been cited as evidence for the presence of dark matter. However, a second actor, the magnetic field, may also be at play. In order to characterize, measure, and disentangle their effects, we have performed magnetohydrodynamic simulations of massive high velocity clouds as they impact a galactic disk. Here, we present the rate at which material dissipates in a variety of situations that include or exclude dark matter and magnetic fields.

  16. High Antiferromagnetic Domain Wall Velocity Induced by Néel Spin-Orbit Torques

    NASA Astrophysics Data System (ADS)

    Gomonay, O.; Jungwirth, T.; Sinova, J.

    2016-07-01

    We demonstrate the possibility to drive an antiferromagnetic domain wall at high velocities by fieldlike Néel spin-orbit torques. Such torques arise from current-induced local fields that alternate their orientation on each sublattice of the antiferromagnet and whose orientation depends primarily on the current direction, giving them their fieldlike character. The domain wall velocities that can be achieved by this mechanism are 2 orders of magnitude greater than the ones in ferromagnets. This arises from the efficiency of the staggered spin-orbit fields to couple to the order parameter and from the exchange-enhanced phenomena in antiferromagnetic texture dynamics, which leads to a low domain wall effective mass and the absence of a Walker breakdown limit. In addition, because of its nature, the staggered spin-orbit field can lift the degeneracy between two 180° rotated states in a collinear antiferromagnet, and it provides a force that can move such walls and control the switching of the states.

  17. Laminar burning velocities at high pressure for primary reference fuels and gasoline: Experimental and numerical investigation

    SciTech Connect

    Jerzembeck, S.; Peters, N.; Pepiot-Desjardins, P.; Pitsch, H.

    2009-02-15

    Spherical flames of n-heptane, iso-octane, PRF 87 and gasoline/air mixtures are experimentally investigated to determine laminar burning velocities and Markstein lengths under engine-relevant conditions by using the constant volume bomb method. Data are obtained for an initial temperature of 373 K, equivalence ratios varying from {phi}=0.7 to {phi}=1.2, and initial pressures from 10 to 25 bar. To track the flame front in the vessel a dark field He-Ne laser Schlieren measurement technique and digital image processing were used. The propagating speed with respect to the burned gases and the stretch rate are determined from the rate of change of the flame radius. The laminar burning velocities are obtained through a linear extrapolation to zero stretch. The experimentally determined Markstein numbers are compared to theoretical predictions. A reduced chemical kinetic mechanism for n-heptane and iso-octane was derived from the Lawrence Livermore comprehensive mechanisms. This mechanism was validated for ignition delay times and flame propagation at low and high pressures. In summary an overall good agreement with the various experimental data sets used in the validation was obtained. (author)

  18. Removal of interproximal dental biofilms by high-velocity water microdrops.

    PubMed

    Rmaile, A; Carugo, D; Capretto, L; Aspiras, M; De Jager, M; Ward, M; Stoodley, P

    2014-01-01

    The influence of the impact of a high-velocity water microdrop on the detachment of Streptococcus mutans UA159 biofilms from the interproximal (IP) space of teeth in a training typodont was studied experimentally and computationally. Twelve-day-old S. mutans biofilms in the IP space were exposed to a prototype AirFloss delivering 115 µL water at a maximum exit velocity of 60 m/sec in a 30-msec burst. Using confocal microscopy and image analysis, we obtained quantitative measurements of the percentage removal of biofilms from different locations in the IP space. The 3D geometry of the typodont and the IP spaces was obtained by micro-computed tomography (µ-CT) imaging. We performed computational fluid dynamics (CFD) simulations to calculate the wall shear stress (τw ) distribution caused by the drops on the tooth surface. A qualitative agreement and a quantitative relationship between experiments and simulations were achieved. The wall shear stress (τw ) generated by the prototype AirFloss and its spatial distribution on the teeth surface played a key role in dictating the efficacy of biofilm removal in the IP space.

  19. Detecting non-maxwellian electron velocity distributions at JET by high resolution Thomson scattering.

    PubMed

    Beausang, K V; Prunty, S L; Scannell, R; Beurskens, M N; Walsh, M J; de la Luna, E

    2011-03-01

    The present work is motivated by a long standing discrepancy between the electron temperature measurements of Thomson scattering (TS) and electron cyclotron emission (ECE) diagnostics for plasmas with strong auxiliary heating observed at both JET and TFTR above 6–7 keV, where in some cases the ECE electron temperature measurements can be 15%–20% higher than the TS measurements. Recent analysis based on ECE results at JET has shown evidence of distortions to the Maxwellian electron velocity distribution and a correlation with the TS and ECE discrepancies has been suggested. In this paper, a technique to determine the presence of non-Maxwellian behavior using TS diagnostics is outlined. The difficulties and limitations of modern TS system designs to determine the electron velocity distribution are also discussed. It is demonstrated that small deviations such as those suggested by previous ECE analysis could be potentially detected, depending on the spectral layout of the TS polychromators. The spectral layout of the JET high resolution Thomson scattering system is such that it could be used to determine these deviations between 1 and 6 keV, and the results presented here indicate that no evidence of non-Maxwellian behavior is observed in this range. In this paper, a modification to the current polychromator design is proposed, allowing non-Maxwellian distortions to be detected up to at least 10 keV. PMID:21585113

  20. Sound velocities in highly-oriented pyrolytic graphite shocked to 18 GPa: Orientational order dependence

    NASA Astrophysics Data System (ADS)

    Lucas, Marcel; Winey, J. M.; Gupta, Y. M.

    2015-06-01

    Previous studies on shocked highly oriented pyrolytic graphite (HOPG) indicated a link between the orientational order and the HOPG response above and below the graphite-to-diamond phase transformation onset (>18 GPa). To gain insight into this link, the response of ZYH- and ZYB-grade HOPG shocked to 18 GPa was examined by measuring particle velocity profiles and peak state sound speeds in front surface impact experiments. The measured peak stress-particle velocity states are the same for the two HOPG grades. In contrast, the measured sound speeds and longitudinal moduli in the peak states reveal significant differences: the sound speed and modulus for ZYH-grade HOPG increase smoothly with increasing stress, whereas those for ZYB-grade HOPG exhibit softening for peak stresses of 12-17 GPa and an abrupt increase for 17-18 GPa. Comparison with the calculated moduli reveals an elastic instability for ZYB-grade HOPG shocked above 15 GPa. These findings, together with those from the previous reports, suggest that the elastic instability for shocked ZYB-grade HOPG is likely a precursor to the rapid phase transformation observed for this grade. Work supported by DOE/NNSA.

  1. Removal of Interproximal Dental Biofilms by High-velocity Water Microdrops

    PubMed Central

    Rmaile, A.; Carugo, D.; Capretto, L.; Aspiras, M.; De Jager, M.; Ward, M.; Stoodley, P.

    2014-01-01

    The influence of the impact of a high-velocity water microdrop on the detachment of Streptococcus mutans UA159 biofilms from the interproximal (IP) space of teeth in a training typodont was studied experimentally and computationally. Twelve-day-old S. mutans biofilms in the IP space were exposed to a prototype AirFloss delivering 115 µL water at a maximum exit velocity of 60 m/sec in a 30-msec burst. Using confocal microscopy and image analysis, we obtained quantitative measurements of the percentage removal of biofilms from different locations in the IP space. The 3D geometry of the typodont and the IP spaces was obtained by micro-computed tomography (µ-CT) imaging. We performed computational fluid dynamics (CFD) simulations to calculate the wall shear stress (τw) distribution caused by the drops on the tooth surface. A qualitative agreement and a quantitative relationship between experiments and simulations were achieved. The wall shear stress (τw) generated by the prototype AirFloss and its spatial distribution on the teeth surface played a key role in dictating the efficacy of biofilm removal in the IP space. PMID:24170371

  2. Estimation of Fuel Rate on the Galactic Disk from High Velocity Clouds (HVCs) Infall

    NASA Astrophysics Data System (ADS)

    Sung, Kwang Hyun; Kwak, Kyujin

    2016-06-01

    Continuous accretion of metal-poor gas can explain the discrepancy between the number of observed G-Dwarfs and the number predicted by the “simple model” of galactic evolution. The maximum accretion rate estimated based upon approaching high velocity clouds (HVCs) can be up to ~0.4 M⊙yr-1 which is comparable with the accretion rate required by many chemical evolution models that is at least ~0.45 M⊙yr-1. However, it is not clear to what extent the exchange of gas between the disk and the cloud can occur when a HVC collides with the galactic disk. Therefore, we examined a series of HVC-Disk collision simulations using the FLASH2.5 hydrodynamics simulation code. Our simulation results show that an HVC will more likely take away substances from the galactic disk rather than adding new material to the disk. We define this as a “negative fuel rate” event. Further outcomes in our study present that the fuel rate, which is defined as how much material is transferred to the galactic disk from the colliding HVC, can change depending on the combination among density, radius and velocity of an approaching HVC as well as the modeled galactic disk.

  3. Detecting non-maxwellian electron velocity distributions at JET by high resolution Thomson scattering.

    PubMed

    Beausang, K V; Prunty, S L; Scannell, R; Beurskens, M N; Walsh, M J; de la Luna, E

    2011-03-01

    The present work is motivated by a long standing discrepancy between the electron temperature measurements of Thomson scattering (TS) and electron cyclotron emission (ECE) diagnostics for plasmas with strong auxiliary heating observed at both JET and TFTR above 6–7 keV, where in some cases the ECE electron temperature measurements can be 15%–20% higher than the TS measurements. Recent analysis based on ECE results at JET has shown evidence of distortions to the Maxwellian electron velocity distribution and a correlation with the TS and ECE discrepancies has been suggested. In this paper, a technique to determine the presence of non-Maxwellian behavior using TS diagnostics is outlined. The difficulties and limitations of modern TS system designs to determine the electron velocity distribution are also discussed. It is demonstrated that small deviations such as those suggested by previous ECE analysis could be potentially detected, depending on the spectral layout of the TS polychromators. The spectral layout of the JET high resolution Thomson scattering system is such that it could be used to determine these deviations between 1 and 6 keV, and the results presented here indicate that no evidence of non-Maxwellian behavior is observed in this range. In this paper, a modification to the current polychromator design is proposed, allowing non-Maxwellian distortions to be detected up to at least 10 keV.

  4. Estimation of Venus wind velocities from high-resolution infrared spectra. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Smith, M. A. H.

    1978-01-01

    Zonal velocity profiles in the Venus atmosphere above the clouds were estimated from measured asymmetries of HCl and HF infrared absorption lines in high-resolution Fourier interferometer spectra of the planet. These asymmetries are caused by both pressure-induced shifts in the positions of the hydrogen-halide lines perturbed by CO2 and Doppler shifts due to atmospheric motions. Particularly in the case of the HCl 2-0 band, the effects of the two types of line shifts can be easily isolated, making it possible to estimate a profile of average Venus equatorial zonal velocity as a function of pressure in the region roughly 60 to 70 km above the surface of the planet. The mean profiles obtained show strong vertical shear in the Venus zonal winds near the cloud-top level, and both the magnitude and direction of winds at all levels in this region appear to vary greatly with longitude relative to the sub-solar point.

  5. A high speed data acquisition and analysis system for transonic velocity, density, and total temperature fluctuations

    NASA Technical Reports Server (NTRS)

    Clukey, Steven J.

    1988-01-01

    The high speed Dynamic Data Acquisition System (DDAS) is described which provides the capability for the simultaneous measurement of velocity, density, and total temperature fluctuations. The system of hardware and software is described in context of the wind tunnel environment. The DDAS replaces both a recording mechanism and a separate data processing system. The data acquisition and data reduction process has been combined within DDAS. DDAS receives input from hot wires and anemometers, amplifies and filters the signals with computer controlled modules, and converts the analog signals to digital with real-time simultaneous digitization followed by digital recording on disk or tape. Automatic acquisition (either from a computer link to an existing wind tunnel acquisition system, or from data acquisition facilities within DDAS) collects necessary calibration and environment data. The generation of hot wire sensitivities is done in DDAS, as is the application of sensitivities to the hot wire data to generate turbulence quantities. The presentation of the raw and processed data, in terms of root mean square values of velocity, density and temperature, and the processing of the spectral data is accomplished on demand in near-real-time- with DDAS. A comprehensive description of the interface to the DDAS and of the internal mechanisms will be prosented. A summary of operations relevant to the use of the DDAS will be provided.

  6. Variability of the high-velocity outflow in the quasar PDS 456

    SciTech Connect

    Reeves, J. N.; Gofford, J.; Costa, M.; Matzeu, G.; Braito, V.; Sim, S. A.; Behar, E.; Kaspi, S.; Miller, L.; O'Brien, P.; Turner, T. J.; Ward, M.

    2014-01-01

    We present a comparison of two Suzaku X-ray observations of the nearby (z = 0.184), luminous (L {sub bol} ∼ 10{sup 47} erg s{sup –1}) type I quasar, PDS 456. A new 125 ks Suzaku observation in 2011 caught the quasar during a period of low X-ray flux and with a hard X-ray spectrum, in contrast with a previous 190 ks Suzaku observation in 2007 when the quasar appeared brighter and had a steep (Γ > 2) X-ray spectrum. The 2011 X-ray spectrum contains a pronounced trough near 9 keV in the quasar rest frame, which can be modeled with blueshifted iron K-shell absorption, most likely from the He- and H-like transitions of iron. The absorption trough is observed at a similar rest-frame energy as in the earlier 2007 observation, which appears to confirm the existence of a persistent high-velocity wind in PDS 456, at an outflow velocity of 0.25-0.30c. The spectral variability between 2007 and 2011 can be accounted for by variations in a partial covering absorber, increasing in covering fraction from the brighter 2007 observation to the hard and faint 2011 observation. Overall, the low-flux 2011 observation can be explained if PDS 456 is observed at relatively low inclination angles through a Compton-thick wind, originating from the accretion disk, which significantly attenuates the X-ray flux from the quasar.

  7. The First Distance Constraint on the Renegade High-velocity Cloud Complex WD

    NASA Astrophysics Data System (ADS)

    Peek, J. E. G.; Bordoloi, Rongmon; Sana, Hugues; Roman-Duval, Julia; Tumlinson, Jason; Zheng, Yong

    2016-09-01

    We present medium-resolution, near-ultraviolet Very Large Telescope/FLAMES observations of the star USNO-A0600-15865535. We adapt a standard method of stellar typing to our measurement of the shape of the Balmer ɛ absorption line to demonstrate that USNO-A0600-15865535 is a blue horizontal branch star, residing in the lower stellar halo at a distance of 4.4 kpc from the Sun. We measure the H & K lines of singly ionized calcium and find two isolated velocity components, one originating in the disk, and one associated with the high-velocity cloud complex WD. This detection demonstrated that complex WD is closer than ˜4.4 kpc and is the first distance constraint on the +100 km s-1 Galactic complex of clouds. We find that complex WD is not in corotation with the Galactic disk, which has been assumed for decades. We examine a number of scenarios and find that the most likely scenario is that complex WD was ejected from the solar neighborhood and is only a few kiloparsecs from the Sun.

  8. The First Distance Constraint on the Renegade High-velocity Cloud Complex WD

    NASA Astrophysics Data System (ADS)

    Peek, J. E. G.; Bordoloi, Rongmon; Sana, Hugues; Roman-Duval, Julia; Tumlinson, Jason; Zheng, Yong

    2016-09-01

    We present medium-resolution, near-ultraviolet Very Large Telescope/FLAMES observations of the star USNO-A0600-15865535. We adapt a standard method of stellar typing to our measurement of the shape of the Balmer ɛ absorption line to demonstrate that USNO-A0600-15865535 is a blue horizontal branch star, residing in the lower stellar halo at a distance of 4.4 kpc from the Sun. We measure the H & K lines of singly ionized calcium and find two isolated velocity components, one originating in the disk, and one associated with the high-velocity cloud complex WD. This detection demonstrated that complex WD is closer than ∼4.4 kpc and is the first distance constraint on the +100 km s‑1 Galactic complex of clouds. We find that complex WD is not in corotation with the Galactic disk, which has been assumed for decades. We examine a number of scenarios and find that the most likely scenario is that complex WD was ejected from the solar neighborhood and is only a few kiloparsecs from the Sun.

  9. H ii REGIONS WITHIN A COMPACT HIGH VELOCITY CLOUD. A NEARLY STARLESS DWARF GALAXY?

    SciTech Connect

    Bellazzini, M.; Magrini, L.; Mucciarelli, A.; Fraternali, F.; Ibata, R.; Martin, N.; Battaglia, G.; Testa, V.; Fumana, M.; Marchetti, A.; Correnti, M.

    2015-02-10

    Within the SECCO survey we identified a candidate stellar counterpart to the Ultra Compact High Velocity Cloud (UCHVC) HVC274.68+74.70-123 that was suggested by Adams et al. to be a possible mini halo within the Local Group of galaxies. The spectroscopic follow-up of the brightest sources within the candidate reveals the presence of two H ii regions whose radial velocity is compatible with a physical association with the UVHVC. The available data do not allow us to give a definite answer on the nature of the newly identified system. A few alternative hypotheses are discussed. However, the most likely possibility is that we have found a new faint dwarf galaxy residing in the Virgo cluster of galaxies, which we name SECCO 1. Independently of its actual distance, SECCO 1 displays a ratio of neutral hydrogen mass to V luminosity of M{sub H} {sub I}/L{sub V}≳20, by far the largest among local dwarfs. Hence, it appears to be a nearly starless galaxy and it may be an example of the missing links between normal dwarfs and the dark mini halos that are predicted to exist in large numbers according to the currently accepted cosmological model.

  10. Sound Velocities of Iron-Nickel and Iron-Nickel-Silicon Alloys at High Pressure

    NASA Astrophysics Data System (ADS)

    Miller, R. A.; Jackson, J. M.; Sturhahn, W.; Zhao, J.; Murphy, C. A.

    2014-12-01

    Seismological and cosmochemical studies suggest Earth's core is primarily composed of iron with ~5 to 10 wt% nickel and some light elements [e.g. 1]. To date, the concentration of nickel and the amount and identity of light elements remain poorly constrained due in part to the difficulty of conducting experimental measurements at core conditions. The vibrational properties of a variety iron alloys paired with seismic observations can help better constrain the composition of the core. We directly measured the partial phonon density of states of bcc- and hcp-structured Fe0.9Ni0.1 and Fe0.85Ni0.1Si0.05 at high pressures. The samples were compressed using a panoramic diamond anvil cell. A subset of the experiments were conducted using neon as a pressure transmitting medium. Measurements of high statistical quality were performed with nuclear resonant inelastic x-ray scattering (NRIXS) at sector 3-ID-B of the Advanced Photon Source [2, 3, 4]. The unit cell volume of each sample was determined at each compression point with in-situ x-ray diffraction at sector 3-ID-B before and after each NRIXS measurement. The Debye, compressional, and shear sound velocities were determined from the low energy region of the partial phonon density of states paired with the volume measurements. We will present partial phonon density of states and sound velocities for Fe0.9Ni0.1 and Fe0.85Ni0.1Si0.05 at high-pressure and compare with those of pure iron. References: [1] McDonough, W.F. (2004): Compositional Model for the Earth's Core. Elsevier Ltd., Oxford. [2] Murphy, C.A., J.M. Jackson, W. Sturhahn, and B. Chen (2011): Melting and thermal pressure of hcp-Fe from the phonon density of states, Phys. Earth Planet. Int., doi:10.1016/j.pepi.2011.07.001. [3] Murphy, C.A., J.M. Jackson, W. Sturhahn, and B. Chen (2011): Grüneisen parameter of hcp-Fe to 171 GPa, Geophys. Res. Lett., doi:10.1029/2011GL049531. [4] Murphy, C.A., J.M. Jackson, and W. Sturhahn (2013): Experimental constraints on the

  11. Determination of the meteoroid velocity distribution at the Earth using high-gain radar

    NASA Astrophysics Data System (ADS)

    Hunt, S. M.; Oppenheim, M.; Close, S.; Brown, P. G.; McKeen, F.; Minardi, M.

    2004-03-01

    Plasma formed in the immediate vicinity of a meteoroid as it descends through Earth's atmosphere enables high-gain radars such as those found at Kwajalein, Arecibo, and Jicamarca to detect ablating meteoroids. In the work presented here, we show that these head echo measurements preferentially detect more energetic meteoroids over less energetic ones and present a method of estimating the effects of this bias when measuring the velocity distributions. To do this, we apply ablation and ionization models to estimate a meteoroid's plasma production rate based on its initial kinetic energy and ionization efficiency. This analysis demonstrates that, almost regardless of the assumptions made, high-gain radars will preferentially detect faster and more massive meteoroids. Following the model used by Taylor (1995, Icarus 116, 154-158), we estimate the biases and then apply them to observed meteoroid velocity distributions. We apply this technique to observations of the North Apex meteoroid source made by the Advanced Research Project Agency Long Range Tracking and Instrumentation Radar (ALTAIR) at two frequencies (160 and 422 MHz) and compare results from the Harvard Radio Meteor Project (HRMP) at High Frequency (HF, 40.9 MHz). Both studies observe a peak in the distribution of North Apex meteoroids at approximately 56 km s -1. After correcting for biases using Taylor's method, the results suggest that the mass-weighted peak of the distribution lies near 20 km s -1 for both studies. We attribute these similarities to the fact that both radar systems depend upon similar ablation and ionization processes and thus have a common mass scale.

  12. Fault Geometry's and High Resolution Velocity Structure of The Colfiorito 1997 Earthquake Sequence

    NASA Astrophysics Data System (ADS)

    Chiaraluce, L.; Chiarabba, C.; Ellsworth, W. L.

    The Colfiorito region was struck by a series of moderate magnitude (5Mw6) n ormal faulting earthquakes in 1997 monitored in great detail by a dense, temporary, three componen t seismic network. We applied the double difference earthquake loca- tion met hod to travel time picks and waveform cross-correlation measurements, ob- taining high-resolution images of the seismicity (ý1600 hypocenters with errors less than 20 m) and peculiarity of the geometry of normal faults. In this study, we tried to better constrain velocity models by using the DD locations as reference location, kept fixed during the tomographic inversion. The three-dimensional Vp and Vp/Vs struc ture was computed inverting P-wave and S-P arrival times, revealing strong later al heterogeneity and details of the complex tectonic setting. We show the compar ison between results obtained by this new inversion and those found by previous studies, underlying the strong influence of improved starting locations in simpl ifying the in- version process and in obtaining more detailed velocity images. Fro m our results, we observe that the previously proposed geometrical discontinuiti es and lateral steps due to the inherited structures, that control the lateral e xtension and consequently fault segmentation, are better defined. All the princi pal shocks nucleated near the base of the seismogenic layer (6 km) and in regio ns of high Vp. Strong high Vp patches are delineated along the fault segments in dicating the main asperities ruptured during the main shocks. Moreover, the posi tion of the relatively young normal faults mostly on the back limb of the old thrust is also evident.

  13. Optical Emission from High Velocity Clouds and the Nature of HVCs

    NASA Astrophysics Data System (ADS)

    Weiner, B. J.; Vogel, S. N.; Williams, T. B.

    1999-12-01

    The nature and origin of the high-velocity clouds of neutral hydrogen remain controversial, and the distances of most HVCs are poorly constrained. Only the large northern HVC complexes M and A have upper distance limits, of <5 and 4--10 kpc, from absorption against halo stars (Danly et al 1993, van Woerden et al 1999). These HVCs have diffuse H-alpha emission of 80--200 milli-Rayleighs (mR) (Tufte, Reynolds & Haffner 1998). We report results from a search of 20 high velocity clouds for faint diffuse optical emission lines in H-alpha and [N II], using a Fabry-Perot at the Las Campanas 2.5-m telescope. A few small complexes are ``bright,'' with H-alpha emission from 100--400 mR and high [N II]/H-alpha. Many HVCs are very faint in H-alpha: HVCs from the Anticenter, Galactic Center Negative, and Extreme Positive complexes have H-alpha from <15 to 30 mR. We construct a simple model for the ionizing flux emergent from the galaxy, normalized by the northern ``bright'' HVCs with known distances and H-alpha fluxes. If the H-alpha from HVCs is produced by ionizing flux escaping from the Galaxy, the H-alpha flux can be used to infer distances for HVCs. The model places the very faint HVCs at distances of 20--60 kpc, in the outer Galactic halo. If H-alpha can be produced by other mechanisms, than these distances could be lower limits. Independent of the model or mechanism, the HVCs that are very faint in H-alpha should be much farther away than the nearby ``bright'' HVCs. The faint HVCs are too far away to be produced by a Galactic fountain, and represent a significant amount of gas accreting onto the Galaxy. This work has been supported by a Carnegie Barbara McClintock Fellowship.

  14. Ultradiscrete optimal velocity model: A cellular-automaton model for traffic flow and linear instability of high-flux traffic

    NASA Astrophysics Data System (ADS)

    Kanai, Masahiro; Isojima, Shin; Nishinari, Katsuhiro; Tokihiro, Tetsuji

    2009-05-01

    In this paper, we propose the ultradiscrete optimal velocity model, a cellular-automaton model for traffic flow, by applying the ultradiscrete method for the optimal velocity model. The optimal velocity model, defined by a differential equation, is one of the most important models; in particular, it successfully reproduces the instability of high-flux traffic. It is often pointed out that there is a close relation between the optimal velocity model and the modified Korteweg-de Vries (mkdV) equation, a soliton equation. Meanwhile, the ultradiscrete method enables one to reduce soliton equations to cellular automata which inherit the solitonic nature, such as an infinite number of conservation laws, and soliton solutions. We find that the theory of soliton equations is available for generic differential equations and the simulation results reveal that the model obtained reproduces both absolutely unstable and convectively unstable flows as well as the optimal velocity model.

  15. Generalized logarithmic scaling for high-order moments of the longitudinal velocity component explained by the random sweeping decorrelation hypothesis

    NASA Astrophysics Data System (ADS)

    Katul, Gabriel G.; Banerjee, Tirtha; Cava, Daniela; Germano, Massimo; Porporato, Amilcare

    2016-09-01

    Expressions for the logarithmic variations of the normalized turbulent longitudinal velocity (u2p ¯ +) 1 /p with normalized distance z/δ from a boundary for high-order (p) moments in the intermediate region of wall bounded flows characterized by thickness δ are derived. The ansatz that ( u2p¯ +) 1 /pvariationin ln(z/δ) originates from a compound effect of random sweeping and -1 power-law scaling in the longitudinal velocity spectrum Eu(k) is discussed, where k is the wavenumber. Using velocity time series sampled above a uniform ice sheet, an Eu(k) ˜ k-1 scaling is confirmed for kz < 1 and kδ > 1. The data were then used to analyze assumptions required for the utility of the random sweeping decorrelation (RSD) hypothesis connecting the k-1 power-law with log-scaling in (u2p ¯ +) 1 /p. It has been found out that while the RSD hypothesis is operationally applicable to scales associated with attached eddies bounded by kz < 1 and kδ > 1, significant interactions among high-order turbulent velocity and velocity increments lead to the conclusion that the RSD hypothesis cannot be exactly valid. Its operational utility stems from the observations that some of the interaction terms among the high-order velocity and velocity increments act in opposite directions thereby canceling their additive effects in RSD.

  16. Detection Of New High Velocity Clouds Using The Leiden-Argentina-Bonn Hi All-sky Survey

    NASA Astrophysics Data System (ADS)

    Engel, Tyler; Wakker, B.; Witt, C.; Gostisha, M. C.; Thomson, E.; Stratman, L.; Benjamin, R. A.

    2011-01-01

    We describe a new effort to use the Leiden/Argentina/Bonn (LAB) Galactic HI survey to update the high-velocity clouds catalog of Wakker and van Woerden (1991). The LAB survey (Kalberla et al 2005) combined the Leiden-Dwingeloo survey (Hartmann and Burton 1997) with a complementary southern sky survey (Arnal et al 2000). This survey provides improved angular spacing (0.5 deg vs. 1 deg) and velocity resolution (1 km/s vs. 16 km/s), although it was less sensitive than previous surveys. We describe how we fit the LAB high velocity gas with Gaussian components, providing three levels of review for the quality of fits, and compare the resulting high velocity cloud catalog to previous results for galactic latitudes greater than b=45 degrees. This research was supported by NASA ATP grant NNX10AI70G to the University of Wisconsin-Whitewater.

  17. Simulation of High Velocity Impact on Composite Structures - Model Implementation and Validation

    NASA Astrophysics Data System (ADS)

    Schueler, Dominik; Toso-Pentecôte, Nathalie; Voggenreiter, Heinz

    2016-08-01

    High velocity impact on composite aircraft structures leads to the formation of flexural waves that can cause severe damage to the structure. Damage and failure can occur within the plies and/or in the resin rich interface layers between adjacent plies. In the present paper a modelling methodology is documented that captures intra- and inter-laminar damage and their interrelations by use of shell element layers representing sub-laminates that are connected with cohesive interface layers to simulate delamination. This approach allows the simulation of large structures while still capturing the governing damage mechanisms and their interactions. The paper describes numerical algorithms for the implementation of a Ladevèze continuum damage model for the ply and methods to derive input parameters for the cohesive zone model. By comparison with experimental results from gas gun impact tests the potential and limitations of the modelling approach are discussed.

  18. The structural and dynamical aspects of boron nitride nanotubes under high velocity impacts.

    PubMed

    Machado, Leonardo D; Ozden, Sehmus; Tiwary, ChandraSekhar; Autreto, Pedro A S; Vajtai, Robert; Barrera, Enrique V; Galvao, Douglas S; Ajayan, Pulickel M

    2016-06-01

    This communication report is a study on the structural and dynamical aspects of boron nitride nanotubes (BNNTs) shot at high velocities (∼5 km s(-1)) against solid targets. The experimental results show unzipping of BNNTs and the formation of hBN nanoribbons. Fully atomistic reactive molecular dynamics simulations were also carried out to gain insights into the BNNT fracture patterns and deformation mechanisms. Our results show that longitudinal and axial tube fractures occur, but the formation of BN nanoribbons from fractured tubes was only observed for some impact angles. Although some structural and dynamical features of the impacts are similar to the ones reported for CNTs, because BNNTs are more brittle than CNTs this results in a larger number of fractured tubes but with fewer formed nanoribbons. PMID:27189765

  19. Specific heat and sound velocity at the relevant competing phase of high-temperature superconductors

    PubMed Central

    Varma, Chandra M.; Zhu, Lijun

    2015-01-01

    Recent highly accurate sound velocity measurements reveal a phase transition to a competing phase in YBa2Cu3O6+δ that is not identified in available specific heat measurements. We show that this signature is consistent with the universality class of the loop current-ordered state when the free-energy reduction is similar to the superconducting condensation energy, due to the anomalous fluctuation region of such a transition. We also compare the measured specific heat with some usual types of transitions, which are observed at lower temperatures in some cuprates, and find that the upper limit of the energy reduction due to them is about 1/40th the superconducting condensation energy. PMID:25941376

  20. Specific heat and sound velocity at the relevant competing phase of high-temperature superconductors.

    PubMed

    Varma, Chandra M; Zhu, Lijun

    2015-05-19

    Recent highly accurate sound velocity measurements reveal a phase transition to a competing phase in YBa2Cu3O6+δ that is not identified in available specific heat measurements. We show that this signature is consistent with the universality class of the loop current-ordered state when the free-energy reduction is similar to the superconducting condensation energy, due to the anomalous fluctuation region of such a transition. We also compare the measured specific heat with some usual types of transitions, which are observed at lower temperatures in some cuprates, and find that the upper limit of the energy reduction due to them is about 1/40th the superconducting condensation energy. PMID:25941376

  1. Background solar velocity spectrum at high and low phases of solar activity cycle

    NASA Astrophysics Data System (ADS)

    Régulo, C.; Roca Cortés, T.; Vázquez Ramió, H.

    2002-12-01

    Using GOLF/SOHO data a detailed analysis of the solar background spectrum has been performed at high and low phases of solar activity cycle. The analysis includes not only the non-periodic components of the background power spectrum but also the periodic ones. Apart from the solar activity, other causes produce similar effects in the data, particularly the different depths in the solar atmosphere where the measurements are done, because due to the sun-satellite relative velocity, we are observing at different positions in the line profile. Another effect is that different line wings are used in the observation at two different epochs, before and after SOHO loss and recovery which, unfortunately, coincide with minimum and maximum of solar activity. In this work we have tried to separate all these effects in order to really understand what is being seen in the data and ultimately extract the effects of solar activity on the acoustic background solar spectrum.

  2. Three-dimensional finite element analysis for high velocity impact. [of projectiles from space debris

    NASA Technical Reports Server (NTRS)

    Chan, S. T. K.; Lee, C. H.; Brashears, M. R.

    1975-01-01

    A finite element algorithm for solving unsteady, three-dimensional high velocity impact problems is presented. A computer program was developed based on the Eulerian hydroelasto-viscoplastic formulation and the utilization of the theorem of weak solutions. The equations solved consist of conservation of mass, momentum, and energy, equation of state, and appropriate constitutive equations. The solution technique is a time-dependent finite element analysis utilizing three-dimensional isoparametric elements, in conjunction with a generalized two-step time integration scheme. The developed code was demonstrated by solving one-dimensional as well as three-dimensional impact problems for both the inviscid hydrodynamic model and the hydroelasto-viscoplastic model.

  3. Study of Iron oxide nanoparticles using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Ushakov, M. V.; Šepelák, V.; Semionkin, V. A.; Morais, P. C.

    2016-01-01

    Iron oxide (magnetite and maghemite) nanoparticles developed for magnetic fluids were studied using Mössbauer spectroscopy with a high velocity resolution at 295 and 90 K. The recorded Mössbauer spectra have demonstrated that usual physical models based on octahedral and tetrahedral sites were not suitable for fitting. Alternatively, the Mössbauer spectra were nicely fitted using a large number of magnetic sextets. The obtained results showed that the Mössbauer spectra and the assessed parameters were different for nanoparticles as-prepared and dispersed in the dispersing fluid at 295 K. We claim that this finding is mainly due to the interaction of polar molecules with Iron cations at nanoparticle's surface or due to the surface coating using carboxylic-terminated molecules. It is assumed that the large number of spectral components may be related to complexity of the nanoparticle's characteristics and deviations from stoichiometry, including in the latter the influence of the oxidation of magnetite towards maghemite.

  4. Ringlike spin segregation of binary mixtures in a high-velocity rotating drum

    NASA Astrophysics Data System (ADS)

    Decai, Huang; Ming, Lu; Gang, Sun; Yaodong, Feng; Min, Sun; Haiping, Wu; Kaiming, Deng

    2012-03-01

    This study presents molecular dynamics simulations on the segregation of binary mixtures in a high-velocity rotating drum. Depending on the ratio between the particle radius and density, similarities to the Brazil-nut effect and its reverse form are shown in the ringlike spin segregation patterns in radial direction. The smaller and heavier particles accumulated toward the drum wall, whereas the bigger and lighter particles accumulated toward the drum center. The effects of particle radius and density on the segregation states were quantified and the phase diagram of segregation in the ρb/ρs - rb/rs space was plotted. The observed phenomena can be explained by the combined percolation and the buoyancy effects.

  5. Some consequences to ion source behavior of high plasma drift velocity

    SciTech Connect

    Brown, I. G.; Monteiro, O. R.; Bilek, M. M. M.; Keidar, M.; Oks, E. M.; Vizir, A.

    2000-02-01

    We consider the case of energetic ion beam formation when the ion streaming velocity within the source plasma is substantial, i.e., when the ions have a drift speed (in the positive downstream direction) that is on the order of or greater than the ion acoustic speed in the plasma. Some interesting consequences can follow, including the capability of a negatively biased substrate located in the plasma stream to maintain high bias voltage, and of an ion source with no extractor or ''conventionally poor'' extractor providing a kind of plasma immersion ion implantation mode of operation. Here we summarize the kind of plasma geometry in which this situation can occur, and describe some experimental observations we've made of these effects, with reference to a simple theoretical basis for the mechanism. (c) 2000 American Institute of Physics.

  6. Cosmic Fire Hydrants: The nature of 11 high-velocity water masers in our Galaxy

    NASA Astrophysics Data System (ADS)

    Harvey-Smith, Lisa; Walsh, Andrew; Breen, Shari; Green, jimi; Purcell, Cormac; Longmore, Steve N.

    2015-08-01

    Water masers act as excellent cosmic markers for the motion of dynamic astronomical regions such as young massive circumstellar disks and outflows from evolved stars. Studying fast water masers gives us a very rare insight into two very a significant stages of stellar evolution.In high-mass star forming regions, water masers are formed in the walls of conical outflows, in collimated jets and in some cases under the influence of a circumstellar disk wind. High-resolution studies of these masers therefore enable us to probe the accretion mechanism for massive star formation. Water masers in post-Asymptotic Giant Branch (AGB) stars probe the very brief phase of aspherical mass-loss before the outer layers of the circumstellar envelope are ionised and the star becomes a Planetary Nebula. The process of aspherical Planetary Nebula formation is still the subject of considerable debate, with the binary hypothesis and magnetic collimation of fast winds being the leading explanations at present.We selected the eleven water maser sites from the H2O Southern Galactic Plane Survey that have differential radial velocities greater than 200 km/s. The water maser sites were subsequently re-observed at higher angular resolution to localise the maser positions with respect to other astronomical emission in the vicinity and where possible, to probe the internal velocity gradients. We conducted a multi-wavelength study of these sites of water masers to determine the stage of stellar evolution, their physical size and a number of other attributes. We present several significant new results and open questions that demand further investigation.

  7. High-velocity frictional strength across the Tohoku-Oki megathrust determined from surface drilling torque

    NASA Astrophysics Data System (ADS)

    Ujiie, K.; Inoue, T.; Ishiwata, J.

    2015-12-01

    Frictional strength at seismic slip rates is a key to evaluate fault weakening and rupture propagation during earthquakes. The Japan Trench First Drilling Project (JFAST) drilled through the shallow plate-boundary thrust, where huge displacements of ~50 m occurred during the 2011 Tohoku-Oki earthquake. To determine the downhole frictional strength at drilled site (Site C0019), we analyzed surface drilling data. The equivalent slip rate estimated from the rotation rate and inner and outer radiuses of the drill bit ranges from 0.8 to 1.3 m/s. The measured torque includes the frictional torque between the drilling string and borehole wall, the viscous torque between the drilling string and seawater/drilling fluid, and the drilling torque between the drill bit and sediments. We subtracted the former two from the measured torque using the torque data during bottom-up rotating operations at several depths. Then, the shear stress was calculated from the drilling torque taking the configuration of the drill bit into consideration. The normal stress was estimated from the weight on bit data and the projected area of the drill bit. Assuming negligible cohesion, the frictional strength was obtained by dividing shear stress by normal stress. The results show a clear contrast in high-velocity frictional strength across the plate-boundary thrust: the friction coefficient of frontal prism sediments (hemipelagic mudstones) in hanging wall is 0.1-0.2, while that in subducting sediments (hemipelagic to pelagic mudstones and chert) in footwall increases to 0.2-0.4. The friction coefficient of smectite-rich pelagic clay in the plate-boundary thrust is ~0.1, which is consistent with that obtained from high-velocity (1.3 m/s) friction experiments and temperature measurements. We conclude that surface drilling torque provides useful data to obtain a continuous downhole frictional strength.

  8. High resolution applications of seismic tomography: low velocity anomalies and static corrections using wave-equation datuming

    NASA Astrophysics Data System (ADS)

    Flecha, I.; Marti, D.; Escuder, J.; Perez-Estaun, A.; Carbonell, R.

    2003-04-01

    A detailed characterization of the internal structure and physical properties of shallow surface can be obtained using high-resolution seismic tomography. Two applications of high resolution seismic tomography are presented in this study. Several synthetics simulations have been carried out to asses the resolving power of this methodology in different cases. The first studied case is the detection of low velocity anomalies in the shallow subsoil. Underground cavities (mines), water flows (formation wich loose sand), etc., are geological features present in the shallow subsurface characterized by low seismic velocities, and are targets of considerable social interest. We have considered a 400m×50m two dimensional velocity model consisting of a background velocity gradient in depth from 3 to 4 Km/s which included a rectangular low velocity anomaly (300 m/s). This anomaly was placed between 10m and 30m in depth and between 180m and 220m in length. The inversions schemes provided estimates of the velocity, however the tomograms and the ray tracing diagrams indicated a low resolution for the anomaly. In the second case we have applied wave-equation datuming to pre-stack layer replacement. The standard seismic data processing applies a vertical time shift to the data traces. However, it is not a good option when we are dealing with rugged topography or bathymetry, and when the media presents a high heterogeneity. Wave-equation datuming extrapolates seismic time data to some level datum keeping consistency between raypaths and wavefield propagation. It improves considerably seismic reflectors imaging. In order to implement this technique a velocity model is required, and usually a constant velocity is used to propagate the wavefield; instead of it we have used seismic tomography to provide an accurate velocity model.

  9. THE RELATION BETWEEN EJECTA VELOCITY, INTRINSIC COLOR, AND HOST-GALAXY MASS FOR HIGH-REDSHIFT TYPE Ia SUPERNOVAE

    SciTech Connect

    Foley, Ryan J.

    2012-04-01

    Recently, using a large low-redshift sample of Type Ia supernovae (SNe Ia), we discovered a relation between SN Ia ejecta velocity and intrinsic color that improves the distance precision of SNe Ia and reduces potential systematic biases related to dust reddening. No SN Ia cosmological results have yet made a correction for the 'velocity-color' relation. To test the existence of such a relation and constrain its properties at high redshift, we examine a sample of 75 SNe Ia discovered and observed by the Sloan Digital Sky Survey-II Supernova Survey and Supernova Legacy Survey. From each spectrum, we measure ejecta velocities at maximum brightness for the Ca H and K and Si II {lambda}6355 features, v{sup 0}{sub CaHandK} and v{sup 0}{sub SiII}, respectively. Using SN light curve parameters, we determine the intrinsic B{sub max} - V{sub max} for each SN. Similar to what was found at low redshift, we find that SNe Ia with higher ejecta velocity tend to be intrinsically redder than SNe Ia with lower ejecta velocity. The distributions of ejecta velocities for SNe Ia at low and high redshift are similar, indicating that current cosmological results should have little bias related to the velocity-color relation. Additionally, we find a slight (2.4{sigma} significant) trend between SN Ia ejecta velocity and host-galaxy mass such that SNe Ia in high-mass host galaxies tend to have lower ejecta velocities as probed by v{sup 0}{sub CaHandK}. These results emphasize the importance of spectroscopy for SN Ia cosmology.

  10. Determining the frequency, depth and velocity of preferential flow by high frequency soil moisture monitoring.

    PubMed

    Hardie, Marcus; Lisson, Shaun; Doyle, Richard; Cotching, William

    2013-01-01

    Preferential flow in agricultural soils has been demonstrated to result in agrochemical mobilisation to shallow ground water. Land managers and environmental regulators need simple cost effective techniques for identifying soil - land use combinations in which preferential flow occurs. Existing techniques for identifying preferential flow have a range of limitations including; often being destructive, non in situ, small sampling volumes, or are subject to artificial boundary conditions. This study demonstrated that high frequency soil moisture monitoring using a multi-sensory capacitance probe mounted within a vertically rammed access tube, was able to determine the occurrence, depth, and wetting front velocity of preferential flow events following rainfall. Occurrence of preferential flow was not related to either rainfall intensity or rainfall amount, rather preferential flow occurred when antecedent soil moisture content was below 226 mm soil moisture storage (0-70 cm). Results indicate that high temporal frequency soil moisture monitoring may be used to identify soil type - land use combinations in which the presence of preferential flow increases the risk of shallow groundwater contamination by rapid transport of agrochemicals through the soil profile. However use of high frequency based soil moisture monitoring to determine agrochemical mobilisation risk may be limited by, inability to determine the volume of preferential flow, difficulty observing macropore flow at high antecedent soil moisture content, and creation of artificial voids during installation of access tubes in stony soils. PMID:23159761

  11. Determining the frequency, depth and velocity of preferential flow by high frequency soil moisture monitoring.

    PubMed

    Hardie, Marcus; Lisson, Shaun; Doyle, Richard; Cotching, William

    2013-01-01

    Preferential flow in agricultural soils has been demonstrated to result in agrochemical mobilisation to shallow ground water. Land managers and environmental regulators need simple cost effective techniques for identifying soil - land use combinations in which preferential flow occurs. Existing techniques for identifying preferential flow have a range of limitations including; often being destructive, non in situ, small sampling volumes, or are subject to artificial boundary conditions. This study demonstrated that high frequency soil moisture monitoring using a multi-sensory capacitance probe mounted within a vertically rammed access tube, was able to determine the occurrence, depth, and wetting front velocity of preferential flow events following rainfall. Occurrence of preferential flow was not related to either rainfall intensity or rainfall amount, rather preferential flow occurred when antecedent soil moisture content was below 226 mm soil moisture storage (0-70 cm). Results indicate that high temporal frequency soil moisture monitoring may be used to identify soil type - land use combinations in which the presence of preferential flow increases the risk of shallow groundwater contamination by rapid transport of agrochemicals through the soil profile. However use of high frequency based soil moisture monitoring to determine agrochemical mobilisation risk may be limited by, inability to determine the volume of preferential flow, difficulty observing macropore flow at high antecedent soil moisture content, and creation of artificial voids during installation of access tubes in stony soils.

  12. Are high p-wave velocity sediments on thin Tethyan crust, deep-water carbonates?

    NASA Astrophysics Data System (ADS)

    Gutscher, Marc-Andre; Graindorge, David; Klingelhoefer, Frauke; Dellong, David; Kopp, Heidrun; Sallares, Valenti; Bartolome, Rafael; Gallais, Flora

    2016-04-01

    Seismic reflection profiles from the Central Mediterranean and Gulf of Cadiz regions indicate the widespread presence of a seismic unit, marked by strong continuous reflectors, directly overlying the basement. Seismic velocity analysis from seismic reflection and refraction studies indicate high p-wave velocities of 3.5 - 4.5 km/s in this layer. These same seismic studies image a thin crust, typically 6-9 km thick, in most cases thought to be oceanic in nature and related to the Tethys oceanic domain separating Africa (Gondwana) from Laurussia. We interpret this 2-3 km thick reflective layer to be carbonates, deposited in the late Triassic, Jurassic and early Cretaceous in the Tethys Ocean, in deep marine basins. Few drilling studies have penetrated into this layer. In one case (DSDP site 135, drilled at 4152 m water depth on Coral Patch Ridge in the western Gulf of Cadiz), Aptian (early Cretaceous) marls and limestone were drilled (560-689 m sub-seafloor depth). The Calcite compensation depth during the Jurassic to Early Cretaceous was about 4000 m to 3500 m according to compilations from the Atlantic and Indian Oceans and is consistent with deposition of deep-water carbonates. For the NW Moroccan margin (Mazagan transect near El Jadida) there is a 2 km thick sedimentary layer with p-wave velocities of 4.0 - 4.5 km/s at the base of a 4 - 6 km thick sedimentary section. This layer extends from seafloor thought to be oceanic crust (west of the West African Coast magnetic anomaly) across a domain of thin/transitional crust with abundant Triassic salt diapirs to the foot of the margin. This reflective basal layer is also observed in reflection and refraction profiles from the Seine abyssal plain, below the toe of the Cadiz accretionary wedge (S. Algarve margin), in the Ionian abyssal plain and below the toe of the Calabrian accretionary wedge, all regions floored by this thin Tethyan crust. Work is in progress to determine the exact nature of this crust.

  13. WSRT HI imaging of ultra-compact high velocity clouds: gas-bearing dark matter minihalos?

    NASA Astrophysics Data System (ADS)

    Adams, Elizabeth A.; Oosterloo, Tom; Giovanelli, Riccardo; Haynes, Martha P.; Cannon, John M.; Faerman, Yakov; Janesh, William; Janowiecki, Steven; Munoz, Ricardo; Rhode, Katherine L.; Salzer, John Joseph; Sternberg, Amiel

    2015-01-01

    A long standing problem in cosmology is the mismatch between the number of low mass dark matter halos predicted by simulations and the number of low mass galaxies observed in the Local Volume. We recently presented a set of isolated ultra-compact high velocity clouds (UCHVCs) identified within the dataset of the Arecibo Legacy Fast ALFA (ALFALFA) HI line survey that are consistent with representing low-mass gas-bearing dark matter halos within the Local Volume (Adams+ 2013). At distances of ~1 Mpc, the UCHVCs have HI masses of ~10^5 Msun and indicative dynamical masses of 10^7-10^8 Msun. The HI diameters of the UCHVCs range from 4' to 20', or 1 to 6 kpc at a distance of 1 Mpc.We have selected the most compact and isolated UCHVCs with the highest average column densities as representing the best galaxy candidates. These systems have been observed with the Westerbork Synthesis Radio Telescope (WSRT) to enable higher spatial resolution (~60") studies of the HI distribution. The HI morphology revealed by the WSRT data offers clues to the environment and origin of the UCHVCs, the kinematics of the HI allow the underlying mass distribution to be constrained, and the combination of spatial and spectral resolution allow the detection of a cold neutral medium component to the HI. The WSRT HI observations discriminate among the selected galaxy candidates for those objects that are most likely gas-bearing dark matter halos.One UCHVC, AGC198606, is of particular interest as it is located 16 km/s and 1.2 degrees from Leo T and has similar HI properties within the ALFALFA dataset. The WSRT HI observations reveal a smooth HI morphology and a velocity gradient along the HI major axis of the system consistent with rotation. These properties are consistent with the hypothesis that this object is a gas-bearing low-mass dark matter halo.

  14. H II Regions Within a Compact High Velocity Cloud. A Nearly Starless Dwarf Galaxy?

    NASA Astrophysics Data System (ADS)

    Bellazzini, M.; Magrini, L.; Mucciarelli, A.; Beccari, G.; Ibata, R.; Battaglia, G.; Martin, N.; Testa, V.; Fumana, M.; Marchetti, A.; Correnti, M.; Fraternali, F.

    2015-02-01

    Within the SECCO survey we identified a candidate stellar counterpart to the Ultra Compact High Velocity Cloud (UCHVC) HVC274.68+74.70-123 that was suggested by Adams et al. to be a possible mini halo within the Local Group of galaxies. The spectroscopic follow-up of the brightest sources within the candidate reveals the presence of two H ii regions whose radial velocity is compatible with a physical association with the UVHVC. The available data do not allow us to give a definite answer on the nature of the newly identified system. A few alternative hypotheses are discussed. However, the most likely possibility is that we have found a new faint dwarf galaxy residing in the Virgo cluster of galaxies, which we name SECCO 1. Independently of its actual distance, SECCO 1 displays a ratio of neutral hydrogen mass to V luminosity of {{M}H I}/{{L}V}≳ 20, by far the largest among local dwarfs. Hence, it appears to be a nearly starless galaxy and it may be an example of the missing links between normal dwarfs and the dark mini halos that are predicted to exist in large numbers according to the currently accepted cosmological model. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University; and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota, and University of Virginia.

  15. Cognate xenoliths in Mt. Etna lavas: witnesses of the high-velocity body beneath the volcano

    NASA Astrophysics Data System (ADS)

    Corsaro, Rosa Anna; Rotolo, Silvio Giuseppe; Cocina, Ornella; Tumbarello, Gianvito

    2014-01-01

    Various xenoliths have been found in lavas of the 1763 ("La Montagnola"), 2001, and 2002-03 eruptions at Mt. Etna whose petrographic evidence and mineral chemistry exclude a mantle origin and clearly point to a cognate nature. Consequently, cognate xenoliths might represent a proxy to infer the nature of the high-velocity body (HVB) imaged beneath the volcano by seismic tomography. Petrography allows us to group the cognate xenoliths as follows: i) gabbros with amphibole and amphibole-bearing mela-gabbros, ii) olivine-bearing leuco-gabbros, iii) leuco-gabbros with amphibole, and iv) Plg-rich leuco gabbros. Geobarometry estimates the crystallization pressure of the cognate xenoliths between 1.9 and 4.1 kbar. The bulk density of the cognate xenoliths varies from 2.6 to 3.0 g/cm3. P wave velocities (V P ), calculated in relation to xenolith density, range from 4.9 to 6.1 km/s. The integration of mineralogical, compositional, geobarometric data, and density-dependent V P with recent literature data on 3D V P seismic tomography enabled us to formulate the first hypothesis about the nature of the HVB which, in the depth range of 3-13 km b.s.l., is likely made of intrusive gabbroic rocks. These are believed to have formed at the "solidification front", a marginal zone that encompasses a deep region (>5 km b.s.l.) of Mt. Etna's plumbing system, within which magma crystallization takes place. The intrusive rocks were afterwards fragmented and transported as cognate xenoliths by the volatile-rich and fast-ascending magmas of the 1763 "La Montagnola", 2001 and 2002-03 eruptions.

  16. Calibration of relative sensitivity factors for impact ionization detectors with high-velocity silicate microparticles

    NASA Astrophysics Data System (ADS)

    Fiege, Katherina; Trieloff, Mario; Hillier, Jon K.; Guglielmino, Massimo; Postberg, Frank; Srama, Ralf; Kempf, Sascha; Blum, Jürgen

    2014-10-01

    Impact ionization mass spectrometers, e.g., the Cosmic Dust Analyzer (CDA) onboard the Cassini spacecraft can quantitatively analyze the chemical composition of impacting particles, if the ionization efficiencies of the elements to be quantified are appropriately calibrated. Although silicates are an abundant dust species inside and outside the Solar System, an experimental calibration was not available for elements typically found in silicates. We performed such a calibration by accelerating orthopyroxene dust of known composition with a modified Van de Graaff accelerator to velocities of up to 37.9 km s-1 and subsequent analyses by a high resolution impact ionization mass spectrometer, the Large Area Mass Analyzer (LAMA). The orthopyroxene dust, prepared from a natural rock sample, contains ∼90% orthopyroxene and ∼10% additional mineral species, such as clinopyroxene, spinel, amphibole, olivine and glasses, which are present as impurities within the orthopyroxene, due to inclusion or intergrowth. Hence, the dust material can be regarded as a multi-mineral mixture. After analyses, we find that most particle data cluster at a composition ascribed to pure orthopyroxene. Some data scatter is caused by stochastic effects, other data scatter is caused by the chemically different mineral impurities. Our data indicate that these minor mineral phases can be recognized within a multi-mineral mixture. Here, for the first time, we present experimentally derived relative sensitivity factors (RSFs) for impact ionization mass spectroscopy of silicates, enabling the quantitative determination of the composition of cosmic dust grains. Orthopyroxene data were used to infer RSFs for Na, Mg, Al, Si, Ca, Ti, Fe and K, for particles with radii ranging from 0.04 μm to 0.2 μm and velocities between 19 and 37.9 km s-1, impacting on a Rh-target.

  17. Study of Optical Mode Scrambling of Fiber Optics for High Precision Radial Velocity Measurements

    NASA Astrophysics Data System (ADS)

    Cassette, Anthony; Ge, Jian; Jeram, Sarik; Klanot, Khaya; Ma, Bo; Varosi, Frank

    2016-01-01

    Optical Fibers have been used throughout Astronomy for spectroscopy with spectrographs located some distance away from the telescope. This fiber-fed design has greatly increased precision for radial velocity (RV) measurements. However, due to the incomplete fiber illumination mode scrambling in the radial direction, high resolution spectrographs with regular circular fibers have suffered RV uncertainties on the order of a few to tens of m/s with stellar observations, which largely limited their sensitivity in detecting and characterizing low mass planets around stars. At the University of Florida, we studied mode scrambling gain of a few different optical devices, such as three-lens optical double scramblers, octagonal fibers and low numerical aperture fibers with a goal to find an optimal mode scrambling solution for the TOU optical very high resolution spectrograph (R=100,000, 0.38-0.9 microns) and FIRST near infrared high resolution spectrograph (R=60,000, 0.9-1.8 microns) for the on-going Dharma Planet Survey. This presentation will report our lab measurement results and also stellar RV measurements at the observatories.

  18. Measurement of Correlation Between Flow Density, Velocity, and Density*velocity(sup 2) with Far Field Noise in High Speed Jets

    NASA Technical Reports Server (NTRS)

    Panda, Jayanta; Seasholtz, Richard G.; Elam, Kristie A.

    2002-01-01

    To locate noise sources in high-speed jets, the sound pressure fluctuations p', measured at far field locations, were correlated with each of radial velocity v, density rho, and phov(exp 2) fluctuations measured from various points in jet plumes. The experiments follow the cause-and-effect method of sound source identification, where correlation is related to the first, and correlation to the second source terms of Lighthill's equation. Three fully expanded, unheated plumes of Mach number 0.95, 1.4 and 1.8 were studied for this purpose. The velocity and density fluctuations were measured simultaneously using a recently developed, non-intrusive, point measurement technique based on molecular Rayleigh scattering. It was observed that along the jet centerline the density fluctuation spectra S(sub rho) have different shapes than the radial velocity spectra S(sub v), while data obtained from the peripheral shear layer show similarity between the two spectra. Density fluctuations in the jet showed significantly higher correlation, than either rhov(sub 2) or v fluctuations. It is found that a single point correlation from the peak sound emitting region at the end of the potential core can account for nearly 10% of all noise at 30 to the jet axis. The correlation, representing the effectiveness of a longitudinal quadrupole in generating noise 90 to the jet axis, is found to be zero within experimental uncertainty. In contrast rhov(exp 2) fluctuations were better correlated with sound pressure fluctuation at the 30 location. The strongest source of sound is found to lie at the centerline and beyond the end of potential core.

  19. High strain rate metalworking with vaporizing foil actuator: Control of flyer velocity by varying input energy and foil thickness

    NASA Astrophysics Data System (ADS)

    Vivek, A.; Hansen, S. R.; Daehn, Glenn S.

    2014-07-01

    Electrically driven rapid vaporization of thin metallic foils can generate a high pressure which can be used to launch flyers at high velocities. Recently, vaporizing foil actuators have been applied toward a variety of impulse-based metal working operations. In order to exercise control over this useful tool, it is imperative that an understanding of the effect of characteristics of the foil actuator on its ability for mechanical impulse generation is developed. Here, foil actuators made out of 0.0508 mm, 0.0762 mm, and 0.127 mm thick AA1145 were used for launching AA2024-T3 sheets of thickness 0.508 mm toward a photonic Doppler velocimeter probe. Launch velocities ranging between 300 m/s and 1100 m/s were observed. In situ measurement of velocity, current, and voltage assisted in understanding the effect of burst current density and deposited electrical energy on average pressure and velocity with foil actuators of various thicknesses. For the pulse generator, geometry, and flyer used here, the 0.0762 mm thick foil was found to be optimal for launching flyers to high velocities over short distances. Experimenting with annealed foil actuators resulted in no change in the temporal evolution of flyer velocity as compared to foil actuators of full hard temper. A physics-based analytical model was developed and found to have reasonable agreement with experiment.

  20. High strain rate metalworking with vaporizing foil actuator: control of flyer velocity by varying input energy and foil thickness.

    PubMed

    Vivek, A; Hansen, S R; Daehn, Glenn S

    2014-07-01

    Electrically driven rapid vaporization of thin metallic foils can generate a high pressure which can be used to launch flyers at high velocities. Recently, vaporizing foil actuators have been applied toward a variety of impulse-based metal working operations. In order to exercise control over this useful tool, it is imperative that an understanding of the effect of characteristics of the foil actuator on its ability for mechanical impulse generation is developed. Here, foil actuators made out of 0.0508 mm, 0.0762 mm, and 0.127 mm thick AA1145 were used for launching AA2024-T3 sheets of thickness 0.508 mm toward a photonic Doppler velocimeter probe. Launch velocities ranging between 300 m/s and 1100 m/s were observed. In situ measurement of velocity, current, and voltage assisted in understanding the effect of burst current density and deposited electrical energy on average pressure and velocity with foil actuators of various thicknesses. For the pulse generator, geometry, and flyer used here, the 0.0762 mm thick foil was found to be optimal for launching flyers to high velocities over short distances. Experimenting with annealed foil actuators resulted in no change in the temporal evolution of flyer velocity as compared to foil actuators of full hard temper. A physics-based analytical model was developed and found to have reasonable agreement with experiment. PMID:25085167

  1. High strain rate metalworking with vaporizing foil actuator: Control of flyer velocity by varying input energy and foil thickness

    SciTech Connect

    Vivek, A. Hansen, S. R.; Daehn, Glenn S.

    2014-07-15

    Electrically driven rapid vaporization of thin metallic foils can generate a high pressure which can be used to launch flyers at high velocities. Recently, vaporizing foil actuators have been applied toward a variety of impulse-based metal working operations. In order to exercise control over this useful tool, it is imperative that an understanding of the effect of characteristics of the foil actuator on its ability for mechanical impulse generation is developed. Here, foil actuators made out of 0.0508 mm, 0.0762 mm, and 0.127 mm thick AA1145 were used for launching AA2024-T3 sheets of thickness 0.508 mm toward a photonic Doppler velocimeter probe. Launch velocities ranging between 300 m/s and 1100 m/s were observed. In situ measurement of velocity, current, and voltage assisted in understanding the effect of burst current density and deposited electrical energy on average pressure and velocity with foil actuators of various thicknesses. For the pulse generator, geometry, and flyer used here, the 0.0762 mm thick foil was found to be optimal for launching flyers to high velocities over short distances. Experimenting with annealed foil actuators resulted in no change in the temporal evolution of flyer velocity as compared to foil actuators of full hard temper. A physics-based analytical model was developed and found to have reasonable agreement with experiment.

  2. Burst Speed of Wild Fishes under High-Velocity Flow Conditions Using Stamina Tunnel with Natural Guidance System in River

    NASA Astrophysics Data System (ADS)

    Izumi, Mattashi; Yamamoto, Yasuyuki; Yataya, Kenichi; Kamiyama, Kohhei

    Swimming experiments were conducted on wild fishes in a natural guidance system stamina tunnel (cylindrical pipe) installed in a fishway of a local river under high-velocity flow conditions (tunnel flow velocity : 211 to 279 cm·s-1). In this study, the swimming characteristics of fishes were observed. The results show that (1) the swimming speeds of Tribolodon hakonensis (Japanese dace), Phoxinus lagowshi steindachneri (Japanese fat-minnow), Plecoglossus altivelis (Ayu), and Zacco platypus (Pale chub) were in proportion to their body length under identical water flow velocity conditions; (2) the maximum burst speed of Japanese dace and Japanese fat-minnow (measuring 4 to 6 cm in length) was 262 to 319 cm·s-1 under high flow velocity conditions (225 to 230 cm·s-1), while the maximum burst speed of Ayu and Pale chub (measuring 5 cm to 12 cm in length) was 308 to 355 cm·s-1 under high flow velocity conditions (264 to 273 cm·s-1) ; (3) the 50cm-maximum swimming speed of swimming fishes was 1.07 times faster than the pipe-swimming speed; (4) the faster the flow velocity, the shorter the swimming distance became.

  3. Frictional behavior of talc at seismic slip rates: preliminary results from high-velocity experiments.

    NASA Astrophysics Data System (ADS)

    Boutareaud, S.; Hirose, T.; Doan, M. L.; Andréani, M.; Calugaru, D. G.

    2009-04-01

    Talc is one of the few minerals not following the Byerlee law, its static friction velocity is 0.2-0.25. Talc has been identified in the San Andreas Fault, and is expected to occur within subduction zone. Talc can then affect their seismic behavior. Yet, the details of its frictional properties are poorly known, especially at seismic velocities. Our study aims at understanding its behavior at these velocities. The properties of the talc were studied during high-velocity rotary-shear experiments carried out at from 0.01 m/s to 1.31 m/s, at normal stresses of 0.6 to 1.4 MPa, using the frictional testing apparatus of the JAMSTEC. The experimental gouge is a pure natural talc schist powder (99.9% wt). The samples were test used in dry (i.e. at room moisture conditions) or wet conditions. During experiments, we were able to measure simulated fault thickness evolution, moisture release and to calculate friction coefficient. Even though it is from the start a weak material, talc schist follows a slip weakening law, which appears to depend strongly on the saturation of the sample. Dry samples sliding at speed of 1.31m/s an exponential decrease of friction coefficient from a peak value of 0.98-0.71 to a steady state value between 0.18 and 0.59. This weakening is strongly dependent on normal stress. Dry sample also experienced large gouge dilation. Results from experiments on wet samples are different. The friction peak values of 0.52-0.36 drop to a steady state value between 0.1 and 0.18. Moreover the steady state friction seems to be independent on the applied normal stress. Finally, the wet samples do not experience dilation, but a large release of water steam. This preliminary work suggests two different weakening processes for dry and wet conditions, respectively. To understand the talc friction behavior, we performed studies on talc schist decomposition, in case flash heating would locally alter the talc structure. Differential thermal analysis (DTA) combined to

  4. Force Criterion Prediction of Damage for Carbon/Epoxy Composite Panels Impacted by High Velocity Ice

    NASA Astrophysics Data System (ADS)

    Rhymer, Jennifer D.

    The use of advanced fiber-reinforced polymer matrix composites in load-bearing aircraft structures is increasing, as evident by the various composites-intensive transport aircraft presently under development. A major impact source of concern for these structures is hail ice, which affects design and skin-sizing (skin thickness determination) at various locations of the aircraft. Impacts onto composite structures often cause internal damage that is not visually detectable due to the high strength and resiliency of the composite material (unlike impacts onto metallic structures). This internal damage and its effect on the performance of the structure are of great concern to the aircraft industry. The prediction of damage in composite structures due to SHI impact has been accomplished via experimental work, explicit dynamic nonlinear finite element analysis (FEA) and the definition of design oriented relationships. Experiments established the critical threshold and corresponding analysis provided contact force results not readily measurable in high velocity SHI impact experiments. The design oriented relationships summarize the FEA results and experimental database into contact force estimation curves that can be easily applied for damage prediction. Failure thresholds were established for the experimental conditions (panel thickness ranging from 1.56 to 4.66 mm and ice diameters from 38.1 to 61.0 mm). Additionally, the observations made by high-speed video during the impact event, and ultrasonic C-scan post-impact, showed how the ice failed during impact and the overall shape and location of the panel damage. Through analysis, the critical force, the force level where damage occurs above but not below, of a SHI impact onto the panel was found to be dependent only on the target structure. However, the peak force generated during impact was dependent on both the projectile and target. Design-oriented curves were generated allowing the prediction of the allowable

  5. Ionic mechanisms maintaining action potential conduction velocity at high firing frequencies in an unmyelinated axon.

    PubMed

    Cross, Kevin P; Robertson, R Meldrum

    2016-05-01

    The descending contralateral movement detector (DCMD) is a high-performance interneuron in locusts with an axon capable of transmitting action potentials (AP) at more than 500 Hz. We investigated biophysical mechanisms for fidelity of high-frequency transmission in this axon. We measured conduction velocities (CVs) at room temperature during exposure to 10 mmol/L cadmium, a calcium current antagonist, and found significant reduction in CV with reduction at frequencies >200 Hz of ~10%. Higher temperatures induced greater CV reductions during exposure to cadmium across all frequencies of ~20-30%. Intracellular recordings during 15 min of exposure to cadmium or nickel, also a calcium current antagonist, revealed an increase in the magnitude of the afterhyperpolarization potential (AHP) and the time to recover to baseline after the AHP (Medians for Control: -19.8%; Nickel: 167.2%; Cadmium: 387.2%), that could be due to a T-type calcium current. However, the removal of extracellular calcium did not mimic divalent cation exposure suggesting calcium currents are not the cause of the AHP increase. Computational modeling showed that the effects of the divalent cations could be modeled with a persistent sodium current which could be blocked by high concentrations of divalent cations. Persistent sodium current shortened the AHP duration in our models and increased CV for high-frequency APs. We suggest that faithful, high-frequency axonal conduction in the DCMD is enabled by a mechanism that shortens the AHP duration like a persistent or resurgent sodium current. PMID:27225630

  6. Whole-body and segmental muscle volume are associated with ball velocity in high school baseball pitchers

    PubMed Central

    Yamada, Yosuke; Yamashita, Daichi; Yamamoto, Shinji; Matsui, Tomoyuki; Seo, Kazuya; Azuma, Yoshikazu; Kida, Yoshikazu; Morihara, Toru; Kimura, Misaka

    2013-01-01

    The aim of the study was to examine the relationship between pitching ball velocity and segmental (trunk, upper arm, forearm, upper leg, and lower leg) and whole-body muscle volume (MV) in high school baseball pitchers. Forty-seven male high school pitchers (40 right-handers and seven left-handers; age, 16.2 ± 0.7 years; stature, 173.6 ± 4.9 cm; mass, 65.0 ± 6.8 kg, years of baseball experience, 7.5 ± 1.8 years; maximum pitching ball velocity, 119.0 ± 9.0 km/hour) participated in the study. Segmental and whole-body MV were measured using segmental bioelectrical impedance analysis. Maximum ball velocity was measured with a sports radar gun. The MV of the dominant arm was significantly larger than the MV of the non-dominant arm (P < 0.001). There was no difference in MV between the dominant and non-dominant legs. Whole-body MV was significantly correlated with ball velocity (r = 0.412, P < 0.01). Trunk MV was not correlated with ball velocity, but the MV for both lower legs, and the dominant upper leg, upper arm, and forearm were significantly correlated with ball velocity (P < 0.05). The results were not affected by age or years of baseball experience. Whole-body and segmental MV are associated with ball velocity in high school baseball pitchers. However, the contribution of the muscle mass on pitching ball velocity is limited, thus other fundamental factors (ie, pitching skill) are also important. PMID:24379713

  7. Whole-body and segmental muscle volume are associated with ball velocity in high school baseball pitchers.

    PubMed

    Yamada, Yosuke; Yamashita, Daichi; Yamamoto, Shinji; Matsui, Tomoyuki; Seo, Kazuya; Azuma, Yoshikazu; Kida, Yoshikazu; Morihara, Toru; Kimura, Misaka

    2013-01-01

    The aim of the study was to examine the relationship between pitching ball velocity and segmental (trunk, upper arm, forearm, upper leg, and lower leg) and whole-body muscle volume (MV) in high school baseball pitchers. Forty-seven male high school pitchers (40 right-handers and seven left-handers; age, 16.2 ± 0.7 years; stature, 173.6 ± 4.9 cm; mass, 65.0 ± 6.8 kg, years of baseball experience, 7.5 ± 1.8 years; maximum pitching ball velocity, 119.0 ± 9.0 km/hour) participated in the study. Segmental and whole-body MV were measured using segmental bioelectrical impedance analysis. Maximum ball velocity was measured with a sports radar gun. The MV of the dominant arm was significantly larger than the MV of the non-dominant arm (P < 0.001). There was no difference in MV between the dominant and non-dominant legs. Whole-body MV was significantly correlated with ball velocity (r = 0.412, P < 0.01). Trunk MV was not correlated with ball velocity, but the MV for both lower legs, and the dominant upper leg, upper arm, and forearm were significantly correlated with ball velocity (P < 0.05). The results were not affected by age or years of baseball experience. Whole-body and segmental MV are associated with ball velocity in high school baseball pitchers. However, the contribution of the muscle mass on pitching ball velocity is limited, thus other fundamental factors (ie, pitching skill) are also important. PMID:24379713

  8. Whole-body and segmental muscle volume are associated with ball velocity in high school baseball pitchers.

    PubMed

    Yamada, Yosuke; Yamashita, Daichi; Yamamoto, Shinji; Matsui, Tomoyuki; Seo, Kazuya; Azuma, Yoshikazu; Kida, Yoshikazu; Morihara, Toru; Kimura, Misaka

    2013-01-01

    The aim of the study was to examine the relationship between pitching ball velocity and segmental (trunk, upper arm, forearm, upper leg, and lower leg) and whole-body muscle volume (MV) in high school baseball pitchers. Forty-seven male high school pitchers (40 right-handers and seven left-handers; age, 16.2 ± 0.7 years; stature, 173.6 ± 4.9 cm; mass, 65.0 ± 6.8 kg, years of baseball experience, 7.5 ± 1.8 years; maximum pitching ball velocity, 119.0 ± 9.0 km/hour) participated in the study. Segmental and whole-body MV were measured using segmental bioelectrical impedance analysis. Maximum ball velocity was measured with a sports radar gun. The MV of the dominant arm was significantly larger than the MV of the non-dominant arm (P < 0.001). There was no difference in MV between the dominant and non-dominant legs. Whole-body MV was significantly correlated with ball velocity (r = 0.412, P < 0.01). Trunk MV was not correlated with ball velocity, but the MV for both lower legs, and the dominant upper leg, upper arm, and forearm were significantly correlated with ball velocity (P < 0.05). The results were not affected by age or years of baseball experience. Whole-body and segmental MV are associated with ball velocity in high school baseball pitchers. However, the contribution of the muscle mass on pitching ball velocity is limited, thus other fundamental factors (ie, pitching skill) are also important.

  9. Combustion Velocity of Benzine-Benzol-Air Mixtures in High-Speed Internal-Combustion Engines

    NASA Technical Reports Server (NTRS)

    Schnauffer, Kurt

    1932-01-01

    The present paper describes a device whereby rapid flame movement within an internal-combustion engine cylinder may be recorded and determined. By the aid of a simple cylindrical contact and an oscillograph the rate of combustion within the cylinder of an airplane engine during its normal operation may be measured for gas intake velocities of from 30 to 35 m/s and for velocities within the cylinder of from 20 to 25 m/s. With it the influence of mixture ratios, of turbulence, of compression ratio and kind of fuel on combustion velocity may be determined. Besides the determination of the influence of the above factors on combustion velocity, the degree of turbulence may also be determined. As a unit of reference in estimating the degree of turbulence, the intake velocity of the charge is chosen.

  10. In vitro performance of ceramic coatings obtained by high velocity oxy-fuel spray.

    PubMed

    Melero, H; Garcia-Giralt, N; Fernández, J; Díez-Pérez, A; Guilemany, J M

    2014-01-01

    Hydroxyapatite coatings obtained by plasma-spraying have been used for many years to improve biological performance of bone implants, but several studies have drawn attention to the problems arising from high temperatures and the lack of mechanical properties. In this study, plasma-spraying is substituted by high velocity oxy-fuel (HVOF) spray, with lower temperatures reached, and TiO2 is added in low amounts to hydroxyapatite in order to improve the mechanical properties. Four conditions have been tested to evaluate which are those with better biological properties. Viability and proliferation tests, as well as differentiation assays and morphology observation, are performed with human osteoblast cultures onto the studied coatings. The hydroxyapatite-TiO2 coatings maintain good cell viability and proliferation, especially the cases with higher amorphous phase amount and specific surface, and promote excellent differentiation, with a higher ALP amount for these cases than for polystyrene controls. Observation by SEM corroborates this excellent behaviour. In conclusion, these coatings are a good alternative to those used industrially, and an interesting issue would be improving biological behaviour of the worst cases, which in turn show the better mechanical properties.

  11. Numerical Analysis of Multicomponent Suspension Droplets in High-Velocity Flame Spray Process

    NASA Astrophysics Data System (ADS)

    Gozali, Ebrahim; Mahrukh, Mahrukh; Gu, Sai; Kamnis, Spyros

    2014-08-01

    The liquid feedstock or suspension as a different mixture of liquid fuel ethanol and water is numerically studied in high-velocity suspension flame spray (HVSFS) process, and the results are compared for homogenous liquid feedstock of ethanol and water. The effects of mixture on droplet aerodynamic breakup, evaporation, combustion, and gas dynamics of HVSFS process are thoroughly investigated. The exact location where the particle heating is initiated (above the carrier liquid boiling point) can be controlled by increasing the water content in the mixture. In this way, the particle inflight time in the high-temperature gas regions can be adjusted avoiding adverse effects from surface chemical transformations. The mixture is modeled as a multicomponent droplet, and a convection/diffusion model, which takes into account the convective flow of evaporating material from droplet surface, is used to simulate the suspension evaporation. The model consists of several sub-models that include premixed combustion of propane-oxygen, non-premixed ethanol-oxygen combustion, modeling of multicomponent droplet breakup and evaporation, as well as heat and mass transfer between liquid droplets and gas phase.

  12. Experimental Characterization of Magnetogasdynamic Phenomena in Ultra-High Velocity Pulsed Plasma Jets

    NASA Astrophysics Data System (ADS)

    Loebner, Keith; Wang, Benjamin; Cappelli, Mark

    2014-10-01

    The formation and propagation of high velocity plasma jets in a pulsed, coaxial, deflagration-type discharge is examined experimentally. A sensitive, miniaturized, immersed probe array is used to map out magnetic flux density and associated radial current density as a function of time and axial position. This array is also used to probe the magnetic field gradient across the exit of the accelerator and in the jet formation region. Sensitive interferometry via a continuous-wave helium-neon laser source is used to probe the structure of the plasma jet over multiple chords and axial locations. A two dimensional plasma density gradient profile at an instant in time during jet formation is compiled via Shack-Hartmann wavefront sensor analysis. The qualitative characteristics of rarefaction and/or shock wave formation as a function of chamber back-pressure is examined via fast-framing ICCD imaging. These measurements are compared to existing resistive MHD simulations of the coaxial deflagration accelerator and the ensuing rarefaction jet that is expelled from the electrode assembly. The physical mechanisms governing the behavior of the discharge and the formation of these high energy density plasma jets are proposed and validated against both theoretical models and numerically simulated behavior. This research was conducted with Government support under and awarded by DoD, Air Force Office of Scientific Research, National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a.

  13. Suspension High Velocity Oxy-Fuel (SHVOF)-Sprayed Alumina Coatings: Microstructure, Nanoindentation and Wear

    NASA Astrophysics Data System (ADS)

    Murray, J. W.; Ang, A. S. M.; Pala, Z.; Shaw, E. C.; Hussain, T.

    2016-10-01

    Suspension high velocity oxy-fuel spraying can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from submicron-sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt.% amorphous phase and 26 wt.% crystalline phase (95 wt.% gamma and 3 wt.% alpha alumina), while the 72-kW coating contained lower 58 wt.% amorphous phase and 42 wt.% crystalline phases (73 wt.% was alpha and 26 wt.% gamma). The 101-kW coating had a dry sliding specific wear rate between 4 and 4.5 × 10-5 mm3/Nm, 2 orders of magnitude higher than the 72-kW coating wear rate of 2-4.2 × 10-7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pullout of the coating was responsible for the wear of the 101-kW coating, explained by mean fracture toughness three times lower than the 72-kW coating, owing to the almost complete absence of alpha alumina.

  14. Monochromatic multicomponent fluorescence sedimentation velocity for the study of high-affinity protein interactions

    PubMed Central

    Zhao, Huaying; Fu, Yan; Glasser, Carla; Andrade Alba, Eric J; Mayer, Mark L; Patterson, George; Schuck, Peter

    2016-01-01

    The dynamic assembly of multi-protein complexes underlies fundamental processes in cell biology. A mechanistic understanding of assemblies requires accurate measurement of their stoichiometry, affinity and cooperativity, and frequently consideration of multiple co-existing complexes. Sedimentation velocity analytical ultracentrifugation equipped with fluorescence detection (FDS-SV) allows the characterization of protein complexes free in solution with high size resolution, at concentrations in the nanomolar and picomolar range. Here, we extend the capabilities of FDS-SV with a single excitation wavelength from single-component to multi-component detection using photoswitchable fluorescent proteins (psFPs). We exploit their characteristic quantum yield of photo-switching to imprint spatio-temporal modulations onto the sedimentation signal that reveal different psFP-tagged protein components in the mixture. This novel approach facilitates studies of heterogeneous multi-protein complexes at orders of magnitude lower concentrations and for higher-affinity systems than previously possible. Using this technique we studied high-affinity interactions between the amino-terminal domains of GluA2 and GluA3 AMPA receptors. DOI: http://dx.doi.org/10.7554/eLife.17812.001 PMID:27436096

  15. High-contrast Imaging of Intermediate-mass Giants with Long-term Radial Velocity Trends

    NASA Astrophysics Data System (ADS)

    Ryu, Tsuguru; Sato, Bun'ei; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro H.; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; Harakawa, Hiroki; Abe, Lyu; Ando, Hiroyasu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Hełminiak, Krzysztof G.; Henning, Thomas; Hodapp, Klaus W.; Ida, Shigeru; Ishii, Miki; Itoh, Yoichi; Iye, Masanori; Izumiura, Hideyuki; Janson, Markus; Kambe, Eiji; Kandori, Ryo; Knapp, Gillian R.; Kokubo, Eiichiro; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W.; Mede, Kyle; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Takeda, Yoichi; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Yoshida, Michitoshi; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-07-01

    A radial velocity (RV) survey for intermediate-mass giants has been in operation for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct-imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to γ Hya B ({0.61}-0.14+0.12{M}⊙ ), HD 5608 B (0.10+/- 0.01{M}⊙ ), and HD 109272 B (0.28+/- 0.06{M}⊙ ). For the remaining targets (ι Dra, 18 Del, and HD 14067), we exclude companions more massive than 30-60 M Jup at projected separations of 1″-7″. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets ι Dra b, HD 5608 b, and HD 14067 b.

  16. Flow mechanism of Forchheimer's cubic equation in high-velocity radial gas flow through porous media

    SciTech Connect

    Ezeudembah, A.S.; Dranchuk, P.M.

    1982-01-01

    Formal derivation of Forchheimer's cubic equation is made by considering the kinetic energy equation of mean flow and dimensional relations for one-dimensional, linear, incompressible fluid flow. By the addition of the cubic term, this equation is regarded as a modified Forchheimer's quadratic equation which accounts for the flow rates obtained beyond the laminar flow condition. The cubic equation spans a wide range of flow rates and regimes. For suitable use in gas flow studies, this equation has been adapted, modified, and corrected for the gas slippage effect. The physical basis of the cubic term has been established by using boundary layer theory to explain the high-velocity, high-pressure flow behavior through a porous path. Gamma, the main parameter in the cubic term, is related directly to a characteristic, dimensionless shape factor which is significant at higher flow rates. It is inversely related to viscosity, but has no dependence on the gas slippage coefficient in the higher flow regime. 25 references.

  17. Velocity Measurements of a Pistol Shrimp's Micro Water Jet Using High Speed PIV

    NASA Astrophysics Data System (ADS)

    Torres, J.; Washington, K.; Wong, S.; Zarzecki, M.; Cheng, Y.; Diez, F. J.

    2007-11-01

    The pistol shrimp generates a high speed micro water jet that was studied experimentally using time resolved particle image velocimetry. The pistol shrimp, with an average size of about 5.5 cm, is considered to be one of the loudest animals in the world. The sound generated can reach intensity levels as high as 200 db. In the past, it was believed that the loud noise was produced by the shrimp closing its claws. Recent research has revealed that the sound is actually generated by a bubble that is created when the claw is shut. The generated bubble is followed by a micro jet. This process is used by the shrimp to stunt and attack preys and to defend itself. In this cavitation process, the bubble is created by a sudden drop in pressure as the claw closes at speeds of 100 km/hr. The temperature inside the bubble can range from 5,000 to 10000 degrees Kelvin and generates infrared light. This whole process is estimated to last around 300 microseconds. The phenomenon of the bubble itself is believed to take at most 10 nanoseconds. This research focuses in visualizing the bubble and the micro jet produced during the closing of the claw and characterizing the velocity field generated by the micro jet by taking PIV images at a rate of up to 40,000 frames per second.

  18. Studying counterstreaming high velocity plasma flows relevant to astrophysical collisionless shock

    NASA Astrophysics Data System (ADS)

    Ross, James Steven; Amendt, Peter; Divol, Laurent; Pollock, Brad; Remington, Bruce; Ryutov, Dmitri; rozmus, Wojciech; Turnbull, David; Froula, Dustin; morita, taichi; Sakawa, Youichi; Takabe, Hideke; Drake, R. Paul; Kuranz, Carolyn C.; Gregori, Gianluca; Meinecke, Jena; Koenig, Michel; Spitkovsky, Anatoly; Park, Hye-Sook

    2015-08-01

    In a broad range of low-density astrophysical plasmas the flow has a high Mach number, making the ion-ion collisional mean free path very large compared to the scale lengths of various observed astrophysical shocks. These shocks are believed to be “collisionless,” driven by plasma instabilities and self-generated magnetic fields. A series of experiments at the NIF and Omega laser facilities is underway to study the formation of collisionless shocks under scaled laboratory conditions, using high velocity counterstreaming and interpenetrating plasma flows. Double CH2, and CH/CD planar foils have been irradiated with a laser intensity of ~1016 W/cm2. The laser-ablated plasma between the two foils was characterized using a suite of diagnostics, including Thomson scattering and x-ray radiography. On the Omega laser facility clear interpenetration and instability growth are observed, although our experimental conditions reached only ~50 ion skin depths (c/wpi) and were insufficient to fully form a collisionless shock. Initial NIF experimental results using 50x more laser energy than the Omega experiments will be presented.

  19. High-Velocity Gas in the SN1991T/3C273 Sightline

    NASA Astrophysics Data System (ADS)

    Meyer, David M.

    Meyer & Roth (1991) have recently obtained high SIN observations of the Ca II absorption toward SN1991T and 3C273 which exhibit weak components at vLSR=-87, +215, and +263 km s^-1 toward SN1991T that are absent in the adjacent (sep.=1.4degrees) 3C273 sightline. In this proposal, we discuss our plans to test the local hypothesis for these high-velocity clouds (HVCs) by observing the interstellar Mg II absorption toward several stars in the SN1991T/3C273 field with IUE. Although the many HVCs observed in H I 21 cm emission have not yet been conclusively detected in metal absorption against any Galactic source (Wakker 1991), our particular search is worthwhile given that: (1) the general issue of HVC distances remains unclear due to metallicity uncertainties and, (2) the SN1991T/3C273 sightline presents a possibly unique case where there is radio continuum evidence of a local disturbance.

  20. Monochromatic multicomponent fluorescence sedimentation velocity for the study of high-affinity protein interactions.

    PubMed

    Zhao, Huaying; Fu, Yan; Glasser, Carla; Andrade Alba, Eric J; Mayer, Mark L; Patterson, George; Schuck, Peter

    2016-01-01

    The dynamic assembly of multi-protein complexes underlies fundamental processes in cell biology. A mechanistic understanding of assemblies requires accurate measurement of their stoichiometry, affinity and cooperativity, and frequently consideration of multiple co-existing complexes. Sedimentation velocity analytical ultracentrifugation equipped with fluorescence detection (FDS-SV) allows the characterization of protein complexes free in solution with high size resolution, at concentrations in the nanomolar and picomolar range. Here, we extend the capabilities of FDS-SV with a single excitation wavelength from single-component to multi-component detection using photoswitchable fluorescent proteins (psFPs). We exploit their characteristic quantum yield of photo-switching to imprint spatio-temporal modulations onto the sedimentation signal that reveal different psFP-tagged protein components in the mixture. This novel approach facilitates studies of heterogeneous multi-protein complexes at orders of magnitude lower concentrations and for higher-affinity systems than previously possible. Using this technique we studied high-affinity interactions between the amino-terminal domains of GluA2 and GluA3 AMPA receptors. PMID:27436096

  1. High-contrast Imaging of Intermediate-mass Giants with Long-term Radial Velocity Trends

    NASA Astrophysics Data System (ADS)

    Ryu, Tsuguru; Sato, Bun’ei; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro H.; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; Harakawa, Hiroki; Abe, Lyu; Ando, Hiroyasu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Hełminiak, Krzysztof G.; Henning, Thomas; Hodapp, Klaus W.; Ida, Shigeru; Ishii, Miki; Itoh, Yoichi; Iye, Masanori; Izumiura, Hideyuki; Janson, Markus; Kambe, Eiji; Kandori, Ryo; Knapp, Gillian R.; Kokubo, Eiichiro; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W.; Mede, Kyle; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Takeda, Yoichi; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Yoshida, Michitoshi; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-07-01

    A radial velocity (RV) survey for intermediate-mass giants has been in operation for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct-imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to γ Hya B ({0.61}-0.14+0.12{M}ȯ ), HD 5608 B (0.10+/- 0.01{M}ȯ ), and HD 109272 B (0.28+/- 0.06{M}ȯ ). For the remaining targets (ι Dra, 18 Del, and HD 14067), we exclude companions more massive than 30–60 M Jup at projected separations of 1″–7″. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets ι Dra b, HD 5608 b, and HD 14067 b.

  2. Velocity Resolved---Scalar Modeled Simulations of High Schmidt Number Turbulent Transport

    NASA Astrophysics Data System (ADS)

    Verma, Siddhartha

    The objective of this thesis is to develop a framework to conduct velocity resolved - scalar modeled (VR-SM) simulations, which will enable accurate simulations at higher Reynolds and Schmidt (Sc) numbers than are currently feasible. The framework established will serve as a first step to enable future simulation studies for practical applications. To achieve this goal, in-depth analyses of the physical, numerical, and modeling aspects related to Sc " 1 are presented, specifically when modeling in the viscous-convective subrange. Transport characteristics are scrutinized by examining scalar-velocity Fourier mode interactions in Direct Numerical Simulation (DNS) datasets and suggest that scalar modes in the viscous-convective subrange do not directly affect large-scale transport for high Sc . Further observations confirm that discretization errors inherent in numerical schemes can be sufficiently large to wipe out any meaningful contribution from subfilter models. This provides strong incentive to develop more effective numerical schemes to support high Sc simulations. To lower numerical dissipation while maintaining physically and mathematically appropriate scalar bounds during the convection step, a novel method of enforcing bounds is formulated, specifically for use with cubic Hermite polynomials. Boundedness of the scalar being transported is effected by applying derivative limiting techniques, and physically plausible single sub-cell extrema are allowed to exist to help minimize numerical dissipation. The proposed bounding algorithm results in significant performance gain in DNS of turbulent mixing layers and of homogeneous isotropic turbulence. Next, the combined physical/mathematical behavior of the subfilter scalar-flux vector is analyzed in homogeneous isotropic turbulence, by examining vector orientation in the strain-rate eigenframe. The results indicate no discernible dependence on the modeled scalar field, and lead to the identification of the tensor

  3. Electrospray Charging of Minerals: Surface Chemistry and Applications to High-Velocity Microparticle Impacts

    NASA Astrophysics Data System (ADS)

    Daly, T.; Call, S.; Austin, D. E.

    2010-12-01

    Electrospray is a soft ionization technique commonly used to charge large biomolecules; it has, however, also been applied to inorganic compounds. We are extending this technique to mineral microparticles. Electrospray-charged mineral microparticles are interesting in the context of surface science because surface chemistry dictates where and how charge carriers can bond to mineral surfaces. In addition, using electrospray to charge mineral particles allows these particles to be electrostatically accelerated as projectiles in high- and hyper-velocity impacts. Since current techniques for producing high- and hyper-velocity microparticle impacts are largely limited to metal or metal-coated projectiles, using minerals as projectiles is a significant innovation. Electrospray involves three steps: creation of charged droplets containing solute/particles, evaporation and bifurcation of droplets, and desolvation of the solute/particles. An acidified solution is slowly pumped through a needle in a strong DC field, which causes the solution to break into tiny, charged droplets laden with protons. Solvent evaporates from the electrosprayed droplets as they move through the electric field toward a grounded plate, causing the charge on the droplet to increase relative to its mass. When the electrosprayed droplet’s charge becomes such that the droplet is no longer stable, it bifurcates, and each of the resulting droplets carries some of the original droplet’s charge. Evaporation and bifurcation continues until the solute particle is completely desolvated. The result is a protonated solute molecule or particle. We built an instrument that electrosprays particles into vacuum and measures them using an image charge detector. Mineral microparticles were prepared by grinding natural mineral samples to ~2 µm diameter. These microparticles are then added to a 4:1 methanol:water solution to create a 0.005% w/v suspension. The suspension is electrosprayed into vacuum, where the

  4. Monitoring High Velocity Salt Tracer via 4D Electrical Resistivity Tomography - Possibility for Salt Tracer Tomography

    NASA Astrophysics Data System (ADS)

    Doro, K. O.; Cirpka, O. A.; Patzelt, A.; Leven, C.

    2014-12-01

    Hydrogeological testing in a tomographic sequence as shown by the use of hydraulic tomography, allows an improvement of the spatial resolution of subsurface parameters. In this regard, recent studies show increasing interest in tracer tomography which involves sequential and spatially separated tracer injections and the measurement of their corresponding tracer breakthrough at different locations and depths. Such concentration measurements however require large experimental efforts and can be simplified by geophysical tracer monitoring techniques such as electrical resistivity. In this study, we present the use of 4-D, cross-hole electrical resistivity tomography (ERT) for monitoring salt tracer experiments in high velocity flow fields. For our study, we utilized a set up that enables the conduction of salt tracer experiments with complete recovery within 84 hours over a transport distance of 16 m. This allows the repetition of the experiments with different injection depths for a tomographic salt tracer testing. For ERT monitoring, we designed modular borehole electrodes for repeated usage in a flexible manner. We also assess the use of a high speed resistivity data acquisition mode for field scale tracer monitoring ensuring high spatial and temporal resolution without sacrificing data accuracy. We applied our approach at the Lauswiesen test site, Tübingen, Germany. In our 10 m × 10 m tracer monitoring domain with 16 borehole electrodes, we acquired 4650 data points in less than 18 minutes for each monitoring cycle. Inversion results show that the tracer could be successfully imaged using this approach. The results show that repeated salt tracer tests can be efficiently monitored at a high resolution with ERT which gives the possibility for salt tracer tomography at field scale. Our results also provide a data base for extending current hydrogeophysical inversion approaches to field scale data.

  5. The Use of the Propellant Specific Impulse for the Prediction of the Prompt and Terminal Gurney Velocity of High Explosives

    NASA Astrophysics Data System (ADS)

    Frem, Dany

    2016-10-01

    Simple relationships are presented for the calculation of both prompt and terminal Gurney velocity of chemical high explosives. By considering that a given explosive behaves like a propellant, its specific impulse ? was calculated using Mader's ISPBKW code; it was found that the density impulse (?where ? is the explosive density and ? is an empirically optimized variable) performance factor correlates well with the terminal Gurney velocity of both ideal and nonideal explosives. Furthermore, the cylinder wall energy can be computed from (?from which the prompt Gurney velocity can be obtained through the application of the Gurney's cylinder equation. It was concluded that (? is a powerful factor for the prediction of the Gurney velocities, especially for nonideal compositions.

  6. Sound velocity of hcp-Fe at high pressure: experimental constraints, extrapolations and comparison with seismic models

    NASA Astrophysics Data System (ADS)

    Antonangeli, Daniele; Ohtani, Eiji

    2015-12-01

    Determining the sound velocity of iron under extreme thermodynamic conditions is essential for a proper interpretation of seismic observations of the Earth's core but is experimentally challenging. Here, we review techniques and methodologies used to measure sound velocities in metals at megabar pressures, with specific focus on the compressional sound velocity of hexagonal close-packed iron. A critical comparison of literature results, coherently analyzed using consistent metrology (pressure scale, equation of state), allows us to propose reference relations for the pressure and density dependence of the compressional velocity of hexagonal close-packed iron at ambient temperature. This provides a key base line upon which to add complexity, including high-temperature effects, pre-melting effects, effects of nickel and/or light element incorporation, necessary for an accurate comparison with seismic models, and ultimately to constrain Earth's inner core composition.

  7. The StEllar Counterparts of COmpact high velocity clouds (SECCO) survey. I. Photos of ghosts

    NASA Astrophysics Data System (ADS)

    Bellazzini, M.; Beccari, G.; Battaglia, G.; Martin, N.; Testa, V.; Ibata, R.; Correnti, M.; Cusano, F.; Sani, E.

    2015-03-01

    We present an imaging survey that searches for the stellar counterparts of recently discovered ultra-compact high-velocity H i clouds (UCHVC). It has been proposed that these clouds are candidate mini-haloes in the Local Group and its surroundings within a distance range of 0.25-2.0 Mpc. Using the Large Binocular Telescope we obtained wide-field (≃ 23' × 23') g- and r-band images of the twenty-five most promising and most compact clouds amongst the fifty-nine that have been identified. Careful visual inspection of all the images does not reveal any stellar counterpart that even slightly resembles Leo P, the only local dwarf galaxy that was found as a counterpart to a previously detected high-velocity cloud. Only a possible distant (D> 3.0 Mpc) counterpart to HVC274.68+74.70-123 has been identified in our images. The point source photometry in the central 17.3' × 7.7' chips reaches r ≤ 26.5 and is expected to contain most of the stellar counterparts to the UCHVCs. However, no obvious stellar over-density is detected in any of our fields, in marked contrast to our comparison Leo P field, in which the dwarf galaxy is detected at a >30σ-significance level. Only HVC352.45+59.06+263 may be associated with a weak over-density, whose nature cannot be ascertained with our data. Sensitivity tests show that our survey would have detected any dwarf galaxy dominated by an old stellar population, with an integrated absolute magnitude of MV ≤ - 8.0 and a half-light radius of rh ≤ 300 pc that lies within 1.5 Mpc of us, thereby confirming that it is unlikely that the observed UCHVCs are associated with the stellar counterparts typical of known Local Group dwarf galaxies. Based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration amongst institutions in the United States, Italy, and Germany. LBT Corporation partners are The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica

  8. 3 mm band line survey toward the high-velocity compact cloud CO-0.40-0.22

    NASA Astrophysics Data System (ADS)

    Oka, T.; Tanaka, K.; Matsumura, S.; Miura, K.; Takekawa, S.; Takahata, Y.; Nishino, Akihiko

    2014-05-01

    High-velocity compact clouds (HVCCs) are a population of molecular clouds which have compact appearance (d < 10 pc) and large velocity width (Δ V > 50 km s-1), and are found in the central molecular zone of our Galaxy. We performed a 3 mm band line survey toward CO-0.40-0.22, a spatially unresolved HVCC with an extremely large velocity width (Δ V ≃ 90 km s-1), using the Mopra 22 m telescope. We surveyed the frequency range between 76 GHz and 116 GHz with a 0.27 MHz frequency resolution. We detect at least 54 lines from 32 molecules. Many line profiles show a prominent peak at vLSR ˜ 70 km s-1 with very large velocity width, indicating they are emitted by the HVCC. Detections of largish molecules are indicative of non-equilibrium chemistry. We extracted some prominent lines based on velocity structure, intensity ratios, and PCA analyses. Shock diagnostic lines (SiO, SO, CH3OH, HNCO) and dense gas probes (HCN, HCO+) appear to be prominent. Excitation analysis of CH3OH lines show an enhancement in T rot in the negative high-velocity end of the profile. These results suggest that CO-0.40-0.22 has experienced a shock, acceleration, compression, and heating in the recent past.

  9. Abnormal acoustic wave velocities in basaltic and (Fe,Al)-bearing silicate glasses at high pressures

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Lin, Jung-Fu

    2014-12-01

    We have measured acoustic VP and VS velocities of (Fe,Al)-bearing MgSiO3 silicate glasses and an Icelandic basalt glass up to 25 GPa. The velocity profiles of the (Fe,Al)-bearing and basaltic silicate glasses display decreased VP and VS with minima at approximately 5 and 2 GPa, respectively, which could be explained by the mode softening in the aluminosilicate networks. Our results represent the first observation of such velocity softening extending into the chemically complex basaltic glass at a relatively low transition pressure, which is likely due to its degree of polymerization, while the Fe and Al substitutions reduce sound velocities in MgSiO3 glass. If the velocity softening in the basaltic and silicate glasses can be used as analogs for understanding melts in Earth's interior, these observations suggest that the melt fraction needed to account for the velocity reduction in the upper mantle low-velocity zone may be smaller than previously thought.

  10. Self-consistent analysis of high drift velocity measurements with the STARE system

    NASA Technical Reports Server (NTRS)

    Reinleitner, L. A.; Nielsen, E.

    1985-01-01

    The use of the STARE and SABRE coherent radar systems as valuable tools for geophysical research has been enhanced by a new technique called the Superimposed-Grid-Point method. This method permits an analysis of E-layer plasma irregularity phase velocity versus flow angle utilizing only STARE or SABRE data. As previous work with STARE has indicated, this analysis has clearly shown that the cosine law assumption breaks down for velocities near and exceeding the local ion acoustic velocities. Use of this method is improving understanding of naturally-occurring plasma irregularities in the E-layer.

  11. Searching for dark matter annihilation in the Smith high-velocity cloud

    SciTech Connect

    Drlica-Wagner, Alex; Gómez-Vargas, Germán A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-07-20

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use γ-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant γ-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (∼ 3 × 10{sup –26} cm{sup 3} s{sup –1}) for dark matter masses ≲ 30 GeV annihilating via the b b-bar or τ{sup +}τ{sup –} channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  12. A High-velocity Cloud Impact Forming a Supershell in the Milky Way

    NASA Astrophysics Data System (ADS)

    Park, Geumsook; Koo, Bon-Chul; Kang, Ji-hyun; Gibson, Steven J.; Peek, J. E. G.; Douglas, Kevin A.; Korpela, Eric J.; Heiles, Carl E.

    2016-08-01

    Neutral atomic hydrogen (H i) gas in interstellar space is largely organized into filaments, loops, and shells, the most prominent of which are “supershells.” These gigantic structures, which require ≳ 3× {10}52 erg to form, are generally thought to be produced by either the explosion of multiple supernovae (SNe) in OB associations or, alternatively, by the impact of high-velocity clouds (HVCs) falling into the Galactic disk. Here, we report the detection of a kiloparsec (kpc)-size supershell in the outskirts of the Milky Way with the compact HVC 040 + 01-282 (hereafter, CHVC040) at its geometrical center using the “Inner-Galaxy Arecibo L-band Feed Array” H i 21 cm survey data. The morphological and physical properties of both objects suggest that CHVC040, which is either a fragment of a nearby disrupted galaxy or a cloud that originated from an intergalactic accreting flow, collided with the disk ˜5 Myr ago to form the supershell. Our results show that some compact HVCs can survive their trip through the Galactic halo and inject energy and momentum into the Milky Way disk.

  13. Cryogenic spray vaporization in high-velocity helium, argon and nitrogen gasflows

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1993-01-01

    Effects of gas properties on cryogenic liquid-jet atomization in high-velocity helium, nitrogen, and argon gas flows were investigated. Volume median diameter, D(sub v.5e), data were obtained with a scattered-light scanning instrument. By calculating the change in spray drop size, -Delta D(sub v.5)(exp 2), due to droplet vaporization, it was possible to calculate D(sub v.5C). D(sub v.5C) is the unvaporized characteristic drop size formed at the fuel-nozzle orifice. This drop size was normalized with respect to liquid-jet diameter, D(sub O). It was then correlated with several dimensionless groups to give an expression for the volume median diameter of cryogenic LN2 sprays. This expression correlates drop size D(sub v.5c) with aerodynamic and liquid-surface forces so that it can be readily determined in the design of multiphase-flow propellant injectors for rocket combustors.

  14. Cryogenic spray vaporization in high-velocity helium, argon and nitrogen gasflows

    NASA Astrophysics Data System (ADS)

    Ingebo, Robert D.

    1993-10-01

    Effects of gas properties on cryogenic liquid-jet atomization in high-velocity helium, nitrogen, and argon gas flows were investigated. Volume median diameter, D(sub v.5e), data were obtained with a scattered-light scanning instrument. By calculating the change in spray drop size, -Delta D(sub v.5)(exp 2), due to droplet vaporization, it was possible to calculate D(sub v.5C). D(sub v.5C) is the unvaporized characteristic drop size formed at the fuel-nozzle orifice. This drop size was normalized with respect to liquid-jet diameter, D(sub O). It was then correlated with several dimensionless groups to give an expression for the volume median diameter of cryogenic LN2 sprays. This expression correlates drop size D(sub v.5c) with aerodynamic and liquid-surface forces so that it can be readily determined in the design of multiphase-flow propellant injectors for rocket combustors.

  15. A High-velocity Cloud Impact Forming a Supershell in the Milky Way

    NASA Astrophysics Data System (ADS)

    Park, Geumsook; Koo, Bon-Chul; Kang, Ji-hyun; Gibson, Steven J.; Peek, J. E. G.; Douglas, Kevin A.; Korpela, Eric J.; Heiles, Carl E.

    2016-08-01

    Neutral atomic hydrogen (H i) gas in interstellar space is largely organized into filaments, loops, and shells, the most prominent of which are “supershells.” These gigantic structures, which require ≳ 3× {10}52 erg to form, are generally thought to be produced by either the explosion of multiple supernovae (SNe) in OB associations or, alternatively, by the impact of high-velocity clouds (HVCs) falling into the Galactic disk. Here, we report the detection of a kiloparsec (kpc)-size supershell in the outskirts of the Milky Way with the compact HVC 040 + 01‑282 (hereafter, CHVC040) at its geometrical center using the “Inner-Galaxy Arecibo L-band Feed Array” H i 21 cm survey data. The morphological and physical properties of both objects suggest that CHVC040, which is either a fragment of a nearby disrupted galaxy or a cloud that originated from an intergalactic accreting flow, collided with the disk ˜5 Myr ago to form the supershell. Our results show that some compact HVCs can survive their trip through the Galactic halo and inject energy and momentum into the Milky Way disk.

  16. Searching for Dark Matter Annihilation in the Smith High-Velocity Cloud

    NASA Technical Reports Server (NTRS)

    Drlica-Wagner, Alex; Gomez-Vargas, German A.; Hewitt, John W.; Linden, Tim; Tibaldo, Luigi

    2014-01-01

    Recent observations suggest that some high-velocity clouds may be confined by massive dark matter halos. In particular, the proximity and proposed dark matter content of the Smith Cloud make it a tempting target for the indirect detection of dark matter annihilation. We argue that the Smith Cloud may be a better target than some Milky Way dwarf spheroidal satellite galaxies and use gamma-ray observations from the Fermi Large Area Telescope to search for a dark matter annihilation signal. No significant gamma-ray excess is found coincident with the Smith Cloud, and we set strong limits on the dark matter annihilation cross section assuming a spatially extended dark matter profile consistent with dynamical modeling of the Smith Cloud. Notably, these limits exclude the canonical thermal relic cross section (approximately 3 x 10 (sup -26) cubic centimeters per second) for dark matter masses less than or approximately 30 gigaelectronvolts annihilating via the B/B- bar oscillation or tau/antitau channels for certain assumptions of the dark matter density profile; however, uncertainties in the dark matter content of the Smith Cloud may significantly weaken these constraints.

  17. Comparison of plantar pressure distribution in adolescent runners at low vs. high running velocity.

    PubMed

    Fourchet, François; Kelly, Luke; Horobeanu, Cosmin; Loepelt, Heiko; Taiar, Redha; Millet, Grégoire P

    2012-04-01

    This study aimed to compare foot plantar pressure distribution while jogging and running in highly trained adolescent runners. Eleven participants performed two constant-velocity running trials either at jogging (11.2 ± 0.9 km/h) or running (17.8 ± 1.4 km/h) pace on a treadmill. Contact area (CA in cm(2)), maximum force (F(max) in N), peak pressure (PP in kPa), contact time (CT in ms), and relative load (force time integral in each individual region divided by the force time integral for the total plantar foot surface, in %) were measured in nine regions of the right foot using an in-shoe plantar pressure device. Under the whole foot, CA, F(max) and PP were lower in jogging than in running (-1.2% [p<0.05], -12.3% [p<0.001] and -15.1% [p<0.01] respectively) whereas CT was higher (+20.1%; p<0.001). Interestingly, we found an increase in relative load under the medial and central forefoot regions while jogging (+6.7% and +3.7%, respectively; [p<0.05]), while the relative load under the lesser toes (-8.4%; p<0.05) was reduced. In order to prevent overloading of the metatarsals in adolescent runners, excessive mileage at jogging pace should be avoided. PMID:22205042

  18. Measuring ion velocity distribution functions through high-aspect ratio holes in inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Cunge, G.; Darnon, M.; Dubois, J.; Bezard, P.; Mourey, O.; Petit-Etienne, C.; Vallier, L.; Despiau-Pujo, E.; Sadeghi, N.

    2016-02-01

    Several issues associated with plasma etching of high aspect ratio structures originate from the ions' bombardment of the sidewalls of the feature. The off normal angle incident ions are primarily due to their temperature at the sheath edge and possibly to charging effects. We have measured the ion velocity distribution function (IVDF) at the wafer surface in an industrial inductively coupled plasma reactor by using multigrid retarding field analyzers (RFA) in front of which we place 400 μm thick capillary plates with holes of 25, 50, and 100 μm diameters. The RFA then probes IVDF at the exit of the holes with Aspect Ratios (AR) of 16, 8, and 4, respectively. The results show that the ion flux dramatically drops with the increase in AR. By comparing the measured IVDF with an analytical model, we concluded that the ion temperature is 0.27 eV in our plasma conditions. The charging effects are also observed and are shown to significantly reduce the ion energy at the bottom of the feature but only with a "minor" effect on the ion flux and the shape of the IVDF.

  19. Comparison of plantar pressure distribution in adolescent runners at low vs. high running velocity.

    PubMed

    Fourchet, François; Kelly, Luke; Horobeanu, Cosmin; Loepelt, Heiko; Taiar, Redha; Millet, Grégoire P

    2012-04-01

    This study aimed to compare foot plantar pressure distribution while jogging and running in highly trained adolescent runners. Eleven participants performed two constant-velocity running trials either at jogging (11.2 ± 0.9 km/h) or running (17.8 ± 1.4 km/h) pace on a treadmill. Contact area (CA in cm(2)), maximum force (F(max) in N), peak pressure (PP in kPa), contact time (CT in ms), and relative load (force time integral in each individual region divided by the force time integral for the total plantar foot surface, in %) were measured in nine regions of the right foot using an in-shoe plantar pressure device. Under the whole foot, CA, F(max) and PP were lower in jogging than in running (-1.2% [p<0.05], -12.3% [p<0.001] and -15.1% [p<0.01] respectively) whereas CT was higher (+20.1%; p<0.001). Interestingly, we found an increase in relative load under the medial and central forefoot regions while jogging (+6.7% and +3.7%, respectively; [p<0.05]), while the relative load under the lesser toes (-8.4%; p<0.05) was reduced. In order to prevent overloading of the metatarsals in adolescent runners, excessive mileage at jogging pace should be avoided.

  20. Stability analysis of confined V-shaped flames in high-velocity streams.

    PubMed

    El-Rabii, Hazem; Joulin, Guy; Kazakov, Kirill A

    2010-06-01

    The problem of linear stability of confined V-shaped flames with arbitrary gas expansion is addressed. Using the on-shell description of flame dynamics, a general equation governing propagation of disturbances of an anchored flame is obtained. This equation is solved analytically for V-flames anchored in high-velocity channel streams. It is demonstrated that dynamics of the flame disturbances in this case is controlled by the memory effects associated with vorticity generated by the perturbed flame. The perturbation growth rate spectrum is determined, and explicit analytical expressions for the eigenfunctions are given. It is found that the piecewise linear V structure is unstable for all values of the gas expansion coefficient. Despite the linearity of the basic pattern, however, evolutions of the V-flame disturbances are completely different from those found for freely propagating planar flames or open anchored flames. The obtained results reveal strong influence of the basic flow and the channel walls on the stability properties of confined V-flames. PMID:20866527

  1. Imprints of a high-velocity wind on the soft X-ray spectrum of PG1211+143

    NASA Astrophysics Data System (ADS)

    Pounds, K. A.; Lobban, A.; Reeves, J. N.; Vaughan, S.; Costa, M.

    2016-07-01

    An extended XMM-Newton observation of the luminous narrow-line Seyfert galaxy PG1211+143 in 2014 has revealed a more complex high-velocity wind, with components distinguished in velocity, ionization level, and column density. Here we report soft X-ray emission and absorption features from the ionized outflow, finding counterparts of both high-velocity components, v ˜ 0.129c and v ˜ 0.066c, recently identified in the highly ionized Fe K absorption spectrum. The lower ionization of the comoving soft X-ray absorbers imply a distribution of higher density clouds embedded in the main outflow, while much higher column densities for the same flow component in the hard X-ray spectra suggest differing sightlines to the continuum X-ray source.

  2. On the Metallicity and Origin of the Smith High-velocity Cloud

    NASA Astrophysics Data System (ADS)

    Fox, Andrew J.; Lehner, Nicolas; Lockman, Felix J.; Wakker, Bart P.; Hill, Alex S.; Heitsch, Fabian; Stark, David V.; Barger, Kathleen A.; Sembach, Kenneth R.; Rahman, Mubdi

    2016-01-01

    The Smith Cloud (SC) is a gaseous high-velocity cloud (HVC) in an advanced state of accretion, only 2.9 kpc below the Galactic plane and due to impact the disk in ≈27 Myr. It is unique among HVCs in having a known distance (12.4 ± 1.3 kpc) and a well-constrained 3D velocity (296 km s-1), but its origin has long remained a mystery. Here we present the first absorption-line measurements of its metallicity, using Hubble Space Telescope/COS UV spectra of three active galactic nuclei lying behind the Cloud together with Green Bank Telescope 21 cm spectra of the same directions. Using Voigt-profile fitting of the S ii λλ1250, 1253, 1259 triplet together with ionization corrections derived from photoionization modeling, we derive the sulfur abundance in each direction; a weighted average of the three measurements gives [S/H] = -0.28 ± 0.14, or {0.53}-0.15+0.21 solar metallicity. The finding that the SC is metal-enriched lends support to scenarios where it represents recycled Galactic material, rather than the remnant of a dwarf galaxy or accreting intergalactic gas. The metallicity and trajectory of the Cloud are both indicative of an origin in the outer disk. However, its large mass and prograde kinematics remain to be fully explained. If the cloud has accreted cooling gas from the corona during its fountain trajectory, as predicted in recent theoretical work, its current mass would be higher than its launch mass, alleviating the mass concern. Based on observations taken under program 13840 of the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555, and under program GBT09A_17 of the Robert C. Byrd Green Bank Telescope (GBT) of the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

  3. Si IV Column Densities Predicted from Non-equilibrium Ionization Simulations of Turbulent Mixing Layers and High-velocity Clouds

    NASA Astrophysics Data System (ADS)

    Kwak, Kyujin; Shelton, Robin L.; Henley, David B.

    2015-10-01

    We present predictions of the Si iv ions in turbulent mixing layers (TMLs) between hot and cool gas and in cool high-velocity clouds (HVCs) that travel through a hot halo, complementing the C iv, N v, and O vi predictions in Kwak & Shelton, Kwak et al., and Henley et al. We find that the Si iv ions are most abundant in regions where the hot and cool gases first begin to mix or where the mixed gas has cooled significantly. The predicted column densities of high velocity Si iv and the predicted ratios of Si iv to C iv and O vi found on individual sightlines in our HVC simulations are in good agreement with observations of high velocity gas. Low velocity Si iv is also seen in the simulations, as a result of decelerated gas in the case of the HVC simulations and when looking along directions that pass perpendicular to the direction of motion in the TML simulations. The ratios of low velocity Si iv to C iv and O vi in the TML simulations are in good agreement with those recorded for Milky Way halo gas, while the ratio of Si iv to O vi from the decelerated gas in the HVC simulations is lower than that observed at normal velocity in the Milky Way halo. We attribute the shortfall of normal velocity Si iv to not having modeled the effects of photoionization and, following Henley et al., consider a composite model that includes decelerated HVC gas, supernova remnants, galactic fountain gas, and the effect of photoionization.

  4. An Experimental Study on rock properties through the change of velocity measurement of high porosity in red sandstone

    NASA Astrophysics Data System (ADS)

    Wu, H.; Zhu, W.

    2015-12-01

    The main research focus is to understand the effect of deformation on rock properties through the change of velocity measurement of high porosity in red sandstone. We have carried out the numerical simulation and laboratory experiments. We studied pulse compression of numerical simulation, which is based on the basic coded excitation principle. From the simulation results, in order to achieve the best effect to pulse compression of incentive transducer, cycle number of carrier frequencies of unit code element need to be chosen according to close degree of the specific signal band width and bandwidth transducer. For single frequency characteristics of piezoelectric ceramic transducer, we have compared to the performance of various transducers in our lab. When the transducer matching combines with coded excitation signal matching, experimental system platform of coded excitation was established. In this project, we analyzed the influence on different excitation signal with different modulation and its pulse compression result by transducer. To improve the resolution of detection of changes of wave velocity in rocks and solve the problem of attenuation in high porous rocks, different high porosity of red sandstones were used, which were processed into different size of rock samples. Coded excitation under uniaxial loading of rock experiments were used to test the variation of wave velocity in rock media under coded excitation conditions. This research detected the changes of wave velocity with the single pulse and coded excitation signal in rocks during dynamic loading, and the result shown that wave velocity of coded excitation signal was stable and reliable. With the ultrasound imaging experimental system set before, imaging experiments under uniaxial loading were performed on rock samples. In the loading process, four transmission methods of observation were used in the rock sample. Four sides of rock sample were respectively arranged a plurality of transducer and

  5. Shockwave determination of the shear velocity at very high pressures. [for determining properties of planetary interiors

    NASA Technical Reports Server (NTRS)

    Anderson, O. L.

    1972-01-01

    A shock wave experiment is described for confirming changes in density, from seismic interpretation, for determining the properties of planet interiors. The experiment focuses on the problem of measurements in a pressure region, where the shear velocity tends to vanish, or become very small. Pressure-sensitive lattice stability, and the equations for an atomic model of the NaCl lattice are discussed along with the particle velocity shock technique.

  6. Vortex Formation in a High Speed Dust Flow with Large Velocity Shear in RF Plasmas

    SciTech Connect

    Iizuka, Satoru; Gohda, Takuma

    2008-09-07

    We have investigated a rotation of a dust cloud disc with strong velocity shear in a radio frequency (RF) plasma. The flow pattern of the dusts was evaluated by the Navier Stokes Equation with shear viscosity due to the Coulomb interactions. We have clarified dynamic behaviors of the dusts and observed generation of micro-vortices around rotational center, when the velocity shear is enhanced.

  7. AXAOTHER XL -- A spreadsheet for determining doses for incidents caused by tornadoes or high-velocity straight winds

    SciTech Connect

    Simpkins, A.A.

    1996-09-01

    AXAOTHER XL is an Excel Spreadsheet used to determine dose to the maximally exposed offsite individual during high-velocity straight winds or tornado conditions. Both individual and population doses may be considered. Potential exposure pathways are inhalation and plume shine. For high-velocity straight winds the spreadsheet has the capability to determine the downwind relative air concentration, however for the tornado conditions, the user must enter the relative air concentration. Theoretical models are discussed and hand calculations are performed to ensure proper application of methodologies. A section has also been included that contains user instructions for the spreadsheet.

  8. Plane-wave and common-translation-factor treatments of He sup 2+ +H collisions at high velocities

    SciTech Connect

    Errea, L.F. ); Harel, C.; Jouin, H. ); Maidagan, J.M.; Mendez, L. ); Pons, B. ); Riera, A. )

    1992-11-01

    We complement previous work that showed that the molecular approach, modified with plane-wave translation factors, is able to reproduce the fall of charge-exchange cross sections in He{sup 2+}+H collisions, by presenting the molecular data, and studying the corresponding mechanism. We test the accuracy of simplifications of the method that have been employed in the literature, and that lead to very simple calculations. We show that the common-translation-factor method is also successful at high nuclear velocities, provided that sufficiently excited states are included in the basis; moreover, it yields a simple picture of the mechanism and a description of ionization processes at high velocities.

  9. Evolution of the High Velocity X-Ray Emission in SN 1987A

    NASA Astrophysics Data System (ADS)

    Dewey, Daniel; Haberl, F.; Dwarkadas, V. V.; Burrows, D. N.; Park, S.

    2011-01-01

    Chandra HETG observations of SN 1987A in late 1999 showed very broad lines with observed FWHM of order 7000 km/s (Michael et al. 2002). At this time (SN day 4600) the blastwave was already interacting with the HII region around the progenitor and optical spots had recently appeared. High-resolution spectra taken from May 2003 ( day 5900) to the present by XMM-Newton and Chandra have been well fit by models with FWHM less than 2000 km/s (Zhekov et al. 2005; Dewey et al. 2008; Sturm et al 2010). The emission is increasingly dominated by these narrower components as the blastwave encounters more of the dense equatorial ring. However emission from the HII region out of the ring plane is still expected at late times and would contribute a high-velocity component to the spectra. We analyze 6 epochs of SN 1987A grating data and include an additional very broad component in the spectral model. We find that deep HETG 2007 data are better fit when one quarter of the flux comes from a component with FWHM 8500 km/s, and that RGS 2003 data show an improved fit with a very-broad fraction that is between the 1999 and 2007 values. Later data continue a progression to lower, but still significant, very-broad fractions. The measurements are discussed in terms of the density and extent of the out-of-plane HII region, hydrodynamical simulations, and 3D models of SN 1987A's emission. Support for this work was provided by NASA/USA through contract NAS8-03060 to the Smithsonian Astrophysical Observatory (SAO) and further SAO sub-contracts TM9-0004X to VVD (U Chicago) and SV3-73016 to MIT for support of the CXC.

  10. Energy Productivity of the High Velocity Algae Raceway Integrated Design (ARID-HV)

    SciTech Connect

    Attalah, Said; Waller, Peter M.; Khawam, George; Ryan, Randy D.; Huesemann, Michael H.

    2015-06-03

    The original Algae Raceway Integrated Design (ARID) raceway was an effective method to increase algae culture temperature in open raceways. However, the energy input was high and flow mixing was poor. Thus, the High Velocity Algae Raceway Integrated Design (ARID-HV) raceway was developed to reduce energy input requirements and improve flow mixing in a serpentine flow path. A prototype ARID-HV system was installed in Tucson, Arizona. Based on algae growth simulation and hydraulic analysis, an optimal ARID-HV raceway was designed, and the electrical energy input requirement (kWh ha-1 d-1) was calculated. An algae growth model was used to compare the productivity of ARIDHV and conventional raceways. The model uses a pond surface energy balance to calculate water temperature as a function of environmental parameters. Algae growth and biomass loss are calculated based on rate constants during day and night, respectively. A 10 year simulation of DOE strain 1412 (Chlorella sorokiniana) showed that the ARID-HV raceway had significantly higher production than a conventional raceway for all months of the year in Tucson, Arizona. It should be noted that this difference is species and climate specific and is not observed in other climates and with other algae species. The algae growth model results and electrical energy input evaluation were used to compare the energy productivity (algae production rate/energy input) of the ARID-HV and conventional raceways for Chlorella sorokiniana in Tucson, Arizona. The energy productivity of the ARID-HV raceway was significantly greater than the energy productivity of a conventional raceway for all months of the year.

  11. Thick-lens velocity-map imaging spectrometer with high resolution for high-energy charged particles

    NASA Astrophysics Data System (ADS)

    Kling, N. G.; Paul, D.; Gura, A.; Laurent, G.; De, S.; Li, H.; Wang, Z.; Ahn, B.; Kim, C. H.; Kim, T. K.; Litvinyuk, I. V.; Cocke, C. L.; Ben-Itzhak, I.; Kim, D.; Kling, M. F.

    2014-05-01

    A novel design for a velocity-map imaging (VMI) spectrometer with high resolution over a wide energy range surpassing a standard VMI design is reported. The main difference to a standard three-electrode VMI is the spatial extension of the applied field using 11 electrodes forming a thick-lens. This permits measurements of charged particles with higher energies while achieving excellent resolving power over a wide range of energies. Using SIMION simulations, the thick-lens VMI is compared to a standard design for up to 360 eV electrons. The simulations also show that the new spectrometer design is suited for charged-particle detection with up to 1 keV using a repeller-electrode voltage of -30 kV. The experimental performance is tested by laser-induced ionization of rare gases producing electrons up to about 70 eV. The thick-lens VMI is useful for a wide variety of studies on atoms, molecules and nanoparticles in intense laser fields and high-photon-energy fields from high-harmonic-generation or free-electron lasers.

  12. High velocity flyer plates launched by magnetic pressure on pulsed power generator CQ-4 and applied in shock Hugoniot experiments

    NASA Astrophysics Data System (ADS)

    Zhang, Xuping; Wang, Guiji; Zhao, Jianheng; Tan, Fuli; Luo, Binqiang; Sun, Chengwei

    2014-05-01

    High velocity flyer plates with good flatness and some thickness have being widely used to the field of shock physics for characterizations of materials under dynamical loading. The techniques of magnetically driven high-velocity flyer plates are further researched based on our pulsed power generators CQ-4 and some good results got on Sandia's Z machine. With large current of several mega-amperes, the loading surface of electrode panel will suffer acute phase transitions caused from magnetic diffusion and Joule heating, and the thickness and flatness of the flyer plates will change with time. In order to obtain the flyer plates with high performances for shock physics, some researches on electrode panels were done by means of LS-DYNA980 software with electro-magnetic package. Two typical configurations for high velocity flyer plates were compared from distribution uniformity of magnetic field in simulation. The results show that the configuration with counter-bore with "notch" and "ear" is better than the other. Then, with the better configuration panels, some experiments were designed and done to validate the simulation results and obtain high velocity flyer plates with good flatness for one-dimensional strain shock experiments on CQ-4. The velocity profiles of the flyer plates were measured by displacement interferometer systems for any reflectors. And the planarity of flyer plates was measured by using the optical fiber pins array for recording the flyer arrival time. The peak velocities of 8.7 km/s with initial dimension of 10 × 7.2 × 0.62 mm for aluminum flyer plates have been achieved. And the flyer plate with initial size of 12 × 9.2 × 0.73 mm was accelerated to velocity of 6.5 km/s with the flatness of less than 11 ns in the central region of 6 mm in diameter and the effective thickness of about 0.220 mm. Based on these work, the symmetrical impact experiments were performed to obtain the high accuracy Hugoniot data of OFHC (oxygen free high conductance

  13. Calculation and measurement of a neutral air flow velocity impacting a high voltage capacitor with asymmetrical electrodes

    SciTech Connect

    Malík, M. Primas, J.; Kopecký, V.; Svoboda, M.

    2014-01-15

    This paper deals with the effects surrounding phenomenon of a mechanical force generated on a high voltage asymmetrical capacitor (the so called Biefeld-Brown effect). A method to measure this force is described and a formula to calculate its value is also given. Based on this the authors derive a formula characterising the neutral air flow velocity impacting an asymmetrical capacitor connected to high voltage. This air flow under normal circumstances lessens the generated force. In the following part this velocity is measured using Particle Image Velocimetry measuring technique and the results of the theoretically calculated velocity and the experimentally measured value are compared. The authors found a good agreement between the results of both approaches.

  14. Feasibility of using acoustic velocity meters for estimating highly organic suspended-solids concentrations in streams

    USGS Publications Warehouse

    Patino, Eduardo

    1996-01-01

    A field experiment was conducted at the Levee 4 canal site below control structure G-88 in the Everglades agricultural area in northwestern Broward County, Florida, to study the relation of acoustic attenuation to suspended-solids concentrations. Acoustic velocity meter and temperature data were obtained with concurrent water samples analyzed for suspended-solids concentrations. Two separate acoustic velocity meter frequencies were used, 200 and 500 kilohertz, to determine the sensitivity of acoustic attenuation to frequency for the measured suspended-solids concentration range. Suspended-solids concentrations for water samples collected at the Levee 4 canal site from July 1993 to September 1994 ranged from 22 to 1,058 milligrams per liter, and organic content ranged from about 30 to 93 percent. Regression analyses showed that attenuation data from the acoustic velocity meter (automatic gain control) and temperature data alone do not provide enough information to adequately describe the concentrations of suspended solids. However, if velocity is also included as one of the independent variables in the regression model, a satisfactory correlation can be obtained. Thus, it is feasible to use acoustic velocity meter instrumentation to estimate suspended-solids concentrations in streams, even when suspended solids are primarily composed of organic material. Using the most comprehensive data set available for the study (500 kiloherz data), the best fit regression model produces a standard error of 69.7 milligrams per liter, with actual errors ranging from 2 to 128 milligrams per liter. Both acoustic velocity meter transmission frequencies of 200 and 500 hilohertz produced similar results, suggesting that transducers of either frequency could be used to collect attenuation data at the study site. Results indicate that calibration will be required for each acoustic velocity meter system to the unique suspended-solids regime existing at each site. More robust solutions may

  15. Nickel-silver composition shows promise as catalyst for hydrogen-oxygen fuel cells

    NASA Technical Reports Server (NTRS)

    Magerl, J. A.; Murray, J. N.

    1970-01-01

    Carburized 3-1 nickel-silver preparation exhibits considerable catalytic activity, although not as high as platinum black. Cost and availability factors warrant further evaluation of nickel-silver materials.

  16. High Dynamic Velocity Range Particle Image Velocimetry Using Multiple Pulse Separation Imaging

    PubMed Central

    Persoons, Tim; O’Donovan, Tadhg S.

    2011-01-01

    The dynamic velocity range of particle image velocimetry (PIV) is determined by the maximum and minimum resolvable particle displacement. Various techniques have extended the dynamic range, however flows with a wide velocity range (e.g., impinging jets) still challenge PIV algorithms. A new technique is presented to increase the dynamic velocity range by over an order of magnitude. The multiple pulse separation (MPS) technique (i) records series of double-frame exposures with different pulse separations, (ii) processes the fields using conventional multi-grid algorithms, and (iii) yields a composite velocity field with a locally optimized pulse separation. A robust criterion determines the local optimum pulse separation, accounting for correlation strength and measurement uncertainty. Validation experiments are performed in an impinging jet flow, using laser-Doppler velocimetry as reference measurement. The precision of mean flow and turbulence quantities is significantly improved compared to conventional PIV, due to the increase in dynamic range. In a wide range of applications, MPS PIV is a robust approach to increase the dynamic velocity range without restricting the vector evaluation methods. PMID:22346564

  17. Field-derived relationships for flow velocity and resistance in high-gradient streams

    USGS Publications Warehouse

    Comiti, F.; Mao, L.; Wilcox, A.; Wohl, E.E.; Lenzi, M.A.

    2007-01-01

    We measured velocity and channel geometry in 10 reaches (bed gradient = 0.08-0.21) of a predominantly step-pool channel, the Rio Cordon, Italy, over a range of discharges (3-80% of the bankfull discharge). The resulting data were used to compute flow resistance. At-a-station hydraulic geometry relations indicate that in most reaches, the exponent describing the rate of velocity increases with discharge was between 0.48 and 0.6, which is within the range of published values for pool-riffle channels. The Rio Cordon data are also combined with published hydraulics data from step-pool streams to explore non-dimensional relationships between velocity and flow resistance and factors including unit discharge, channel gradient, and step geometry. Multiple regression analysis of this combined field dataset indicated that dimensionless unit discharge (q*) is the most important independent variable overall in explaining variations in velocity and flow resistance, followed by channel slope and the ratio of step height to step length. Empirical equations are provided both for dimensionless velocity and flow resistance, but prediction of the former variable appears more reliable. ?? 2007 Elsevier B.V. All rights reserved.

  18. A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT

    SciTech Connect

    Kunder, Andrea; Storm, J.; Rich, R. M.; Hawkins, K.; Poleski, R.; Johnson, C. I.; Shen, J.; Li, Z.-Y.; Cordero, M. J.; Nataf, D. M.; Bono, G.; Walker, A. R.; Koch, A.; De Propris, R.; Udalski, A.; Szymanski, M. K.; Soszynski, I.; Pietrzynski, G.; Ulaczyk, K.; Wyrzykowski, Ł.; and others

    2015-07-20

    We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of −372 ± 8 km s{sup −1} and true space velocity of −482 ± 22 km s{sup −1} relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, −2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal, at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.

  19. An Economical High Resolution Spectrograph Optimized for Radial Velocity Measurements at 5000 Angstroms.

    NASA Astrophysics Data System (ADS)

    Lyons, D.; Arion, D. N.

    2004-12-01

    A high resolution spectrometer was built and calibrated on an optical bench. The target resolution of the instrument was designed to allow accurate measurement of the Doppler shifts of the 5007 Angstrom O III line in planetary nebulae due to their expansion. The optical components of the instrument include two Meade ETX 90 Maksutov-Cassegrain telescopes, a Richardson Grating Laboratory reflection diffraction grating, nickel-plated glass slides used as slit apertures, and an SBIG ST-8E CCD imaging camera. The mounts for each of the optical components were machined out of aluminum bar and plate stock. The instrument was calibrated using He and Hg gas discharge tubes generating spectra of known wavelengths. A total of four sets of lines were imaged and analyzed to calibrate the instrument. The line shapes in the images were manually fit with functions approximating the pressure and Doppler broadening of the lines, as expected for the behavior of the lines emitted by the spectrum tubes. These fits were used to identify the line peak positions, which were then compared to standard line wavelengths to determine the instrument calibration. The He I line at 5015.678 Angstrom line was carefully analyzed to determine the system wavelength uncertainty, which determines the smallest resolvable difference in wavelength that the instrument can determine. The resulting operating resolution at 5007 Angstroms was found to be 206474, making the instrument capable of resolving Doppler shifts at 5007 Angstroms corresponding to +/- 1.4 kilometers per second. The program was thus successful in developing an instrument suitable for a variety of relatively low velocity Doppler measurements, especially those associated with planetary nebula expansions. Future work entails developing a mounting system to rigidly hold the instrument on a suitable telescope, while maintaining the necessary precision to retain the instrumental resolution. This work was supported in part by Carthage College

  20. Uvby-B Photometry of High Velocity Stars. Photometric Parallaxes and Preliminary Kinematic Results

    NASA Astrophysics Data System (ADS)

    Schuster, W. J.

    1990-11-01

    RESUMEN. Se han explorado dos metodos para la determinaci6n de paralajes fotometricos usando fotometrfa uv - . Estos metodos dependen de las relaciones estandar de Crawford (1975) y de Olsen (1984) y de colores y magnitudes sinteticas de VandenBerg y Bell (1985). Ambos metodos incluyen una correcci6n evolucionaria de forma f6c0. Se calculan las distancias para las 711 estrellas de alta velocidad y pobres en metales en el catalogo uvby-p de Schuster y Nissen (1988). Se comparan estas con las distancias de Sandage y Fouts (1987) y Laird, Carney y Latham (1988) para las estrellas en comtfin. Tambien son aplicables nuestros metodos a estrellas de paralaje. En general las comparaciones son satisfactorias y las sistematicas son despreciables o pequefias. Las distancias finales de nuestras 711 estrellas se aplican a un numero de problemas cinematicos. Se estudian algunos diagramas interesantes, tales como el diagrama de energia de Toomre y el diagrama V(rot) versus [Fe/H]. ABSTRACT Two methods for the determination of parallaxes using uvbyP photometry are being explored. These methods depend upon the standard relations of Crawford (1975) and of Olsen (1984) and upon synthetic colors and magnitudes of VandenBerg and Bell (1985). Both include an evolutionary correction of the form f6c0. Distances are calculated for the 711 high-velocity and metal-poor stars in the uvby-P catalogue of Schuster and Nissen (1988). These are compared to the distances of Sandage and Fouts (1987) and Laird, Carney, and Lathain (1988) for stars in common. Also our methods are applied to parallax stars. In general the comparisons are good with negligible or small systematic differences. The final distances of our 711 stars are applied to a number of kinematical problems. Several interesting diagrams are studied, sucl as Toomre energy diagram and the plot of V(rot) versus [Fe/H]. Key words: DISTANCES - PHOTOMETRY - STARS-POPULATION II

  1. COLLISIONS BETWEEN DARK MATTER CONFINED HIGH VELOCITY CLOUDS AND MAGNETIZED GALACTIC DISKS: THE SMITH CLOUD

    SciTech Connect

    Galyardt, Jason; Shelton, Robin L. E-mail: rls@physast.uga.edu

    2016-01-01

    The Galaxy’s population of High Velocity Clouds (HVCs) may include a subpopulation that is confined by dark matter minihalos and falling toward the Galactic disk. We present the first magnetohydrodynamic simulational study of dark-matter-dominated HVCs colliding with a weakly magnetized galactic disk. Our HVCs have baryonic masses of 5 × 10{sup 6}M{sub ⊙} and dark matter minihalo masses of 0, 3 × 10{sup 8}, or 1 × 10{sup 9} M{sub ⊙}. They are modeled on the Smith Cloud, which is said to have collided with the disk 70 Myr ago. We find that, in all cases, the cloud’s collision with the galactic disk creates a hole in the disk, completely disperses the cloud, and forms a bubble-shaped structure on the far side of the disk. In contrast, when present, the dark matter minihalo continues unimpeded along its trajectory. Later, as the minihalo passes through the bubble structure and galactic halo, it accretes up to 6.0 × 10{sup 5} M{sub ⊙} in baryonic material, depending on the strengths of the magnetic field and minihalo gravity. These simulations suggest that if the Smith Cloud is associated with a dark matter minihalo and collided with the Galactic disk, the minihalo has accreted the observed gas. However, if the Smith Cloud is dark-matter-free, it is on its first approach toward the disk. These simulations also suggest that the dark matter is most concentrated either at the head of the cloud or near the cloud, depending upon the strength of the magnetic field, a point that could inform indirect dark matter searches.

  2. Collisions between Dark Matter Confined High Velocity Clouds and Magnetized Galactic Disks: The Smith Cloud

    NASA Astrophysics Data System (ADS)

    Galyardt, Jason; Shelton, Robin L.

    2016-01-01

    The Galaxy’s population of High Velocity Clouds (HVCs) may include a subpopulation that is confined by dark matter minihalos and falling toward the Galactic disk. We present the first magnetohydrodynamic simulational study of dark-matter-dominated HVCs colliding with a weakly magnetized galactic disk. Our HVCs have baryonic masses of 5 × 106M⊙ and dark matter minihalo masses of 0, 3 × 108, or 1 × 109 M⊙. They are modeled on the Smith Cloud, which is said to have collided with the disk 70 Myr ago. We find that, in all cases, the cloud’s collision with the galactic disk creates a hole in the disk, completely disperses the cloud, and forms a bubble-shaped structure on the far side of the disk. In contrast, when present, the dark matter minihalo continues unimpeded along its trajectory. Later, as the minihalo passes through the bubble structure and galactic halo, it accretes up to 6.0 × 105 M⊙ in baryonic material, depending on the strengths of the magnetic field and minihalo gravity. These simulations suggest that if the Smith Cloud is associated with a dark matter minihalo and collided with the Galactic disk, the minihalo has accreted the observed gas. However, if the Smith Cloud is dark-matter-free, it is on its first approach toward the disk. These simulations also suggest that the dark matter is most concentrated either at the head of the cloud or near the cloud, depending upon the strength of the magnetic field, a point that could inform indirect dark matter searches.

  3. High Velocity Linear Induction Launcher with Exit-Edge Compensation for Testing of Aerospace Components

    NASA Technical Reports Server (NTRS)

    Kuznetsov, Stephen; Marriott, Darin

    2008-01-01

    Advances in ultra high speed linear induction electromagnetic launchers over the past decade have focused on magnetic compensation of the exit and entry-edge transient flux wave to produce efficient and compact linear electric machinery. The paper discusses two approaches to edge compensation in long-stator induction catapults with typical end speeds of 150 to 1,500 m/s. In classical linear induction machines, the exit-edge effect is manifest as two auxiliary traveling waves that produce a magnetic drag on the projectile and a loss of magnetic flux over the main surface of the machine. In the new design for the Stator Compensated Induction Machine (SCIM) high velocity launcher, the exit-edge effect is nulled by a dual wavelength machine or alternately the airgap flux is peaked at a location prior to the exit edge. A four (4) stage LIM catapult is presently being constructed for 180 m/s end speed operation using double-sided longitudinal flux machines. Advanced exit and entry edge compensation is being used to maximize system efficiency, and minimize stray heating of the reaction armature. Each stage will output approximately 60 kN of force and produce over 500 G s of acceleration on the armature. The advantage of this design is there is no ablation to the projectile and no sliding contacts, allowing repeated firing of the launcher without maintenance of any sort. The paper shows results of a parametric study for 500 m/s and 1,500 m/s linear induction launchers incorporating two of the latest compensation techniques for an air-core stator primary and an iron-core primary winding. Typical thrust densities for these machines are in the range of 150 kN/sq.m. to 225 kN/sq.m. and these compete favorably with permanent magnet linear synchronous machines. The operational advantages of the high speed SCIM launcher are shown by eliminating the need for pole-angle position sensors as would be required by synchronous systems. The stator power factor is also improved.

  4. A math model for high velocity sensoring with a focal plane shuttered camera.

    NASA Technical Reports Server (NTRS)

    Morgan, P.

    1971-01-01

    A new mathematical model is presented which describes the image produced by a focal plane shutter-equipped camera. The model is based upon the well-known collinearity condition equations and incorporates both the translational and rotational motion of the camera during the exposure interval. The first differentials of the model with respect to exposure interval, delta t, yield the general matrix expressions for image velocities which may be simplified to known cases. The exposure interval, delta t, may be replaced under certain circumstances with a function incorporating blind velocity and image position if desired. The model is tested using simulated Lunar Orbiter data and found to be computationally stable as well as providing excellent results, provided that some external information is available on the velocity parameters.

  5. Dynamic Measurements of High Explosive Velocity Fields using Particle Image Velocimetry

    NASA Astrophysics Data System (ADS)

    Wilson, Brandon; Wood, Wm. M.; Olson, Russ

    2015-06-01

    A non-invasive technique for measuring dynamic particle velocities using pRad images ahead and behind an HE detonation burn front is presented. The technique uses proven principles from particle image velocimetry (PIV). Time-resolved radiographs of detonated HE (PBX 9501 and 9502) doped with tungsten particles (<= 10 μ m) are captured at pRad at Los Alamos National Laboratory. From sequential radiographs, resolved velocity fields are measured by local cross-correlations of tungsten tracer positions. With this technique, we resolve the Taylor wave and can measure the particle velocity directly behind the detonation front. Results for single detonation waves and colliding detonation waves are presented. We also discuss the capabilities, limitations, applications, and future of this technique.

  6. Sound velocities in highly oriented pyrolytic graphite shocked to 18 GPa: Orientational order dependence and elastic instability

    NASA Astrophysics Data System (ADS)

    Lucas, Marcel; Winey, J. M.; Gupta, Y. M.

    2015-12-01

    Previous reports of rapid phase transformation above 18 GPa [Erskine and Nellis, Nature 349, 317 (1991)] and large elastic waves below 18 GPa [Lucas et al., J. Appl. Phys. 114, 093515 (2013)] for shock-compressed ZYB-grade highly oriented pyrolytic graphite (HOPG), but not for less oriented ZYH-grade HOPG, indicated a link between the orientational order dependence of the HOPG response above and below the phase transformation stress. To gain insight into this link and into the mechanical response of HOPG shocked to peak stresses approaching the phase transformation onset, the compressibility of ZYB- and ZYH-grade HOPG in the shocked state was examined using front surface impact experiments. Particle velocity histories and sound velocities were measured for peak stresses reaching 18 GPa. Although the locus of the measured peak stress-particle velocity states is indistinguishable for the two grades of HOPG, the measured sound velocities in the peak state reveal significant differences between the two grades. Specifically (1) the measured sound velocities are somewhat higher for ZYH-grade HOPG compared with ZYB-grade HOPG; (2) the measured sound velocities for ZYH-grade HOPG increase smoothly with compression, whereas those for ZYB-grade HOPG exhibit a significant reduction in the compression dependence from 12 GPa to 17 GPa and an abrupt increase from 17 GPa to 18 GPa; and (3) the longitudinal moduli, determined from the measured sound velocities, are smaller than the calculated bulk moduli for ZYB-grade HOPG shocked to peak stresses above 15 GPa, indicating the onset of an elastic instability. The present findings demonstrate that the softening of the longitudinal modulus (or elastic instability) presented here is linked to the large elastic waves and the rapid phase transformation reported previously—all observed only for shocked ZYB-grade HOPG. The elastic instability in shocked ZYB-grade HOPG is likely a precursor to the rapid phase transformation observed

  7. High-resolution seismic velocities and shallow structure of the San Andreas fault zone at Middle Mountain, Parkfield, California

    USGS Publications Warehouse

    Catchings, R.D.; Rymer, M.J.; Goldman, M.R.; Hole, J.A.; Huggins, R.; Lippus, C.

    2002-01-01

    A 5-km-long, high-resolution seismic imaging survey across the San Andreas fault (SAF) zone and the proposed San Andreas Fault Observatory at Depth (SAFOD) drill site near Parkfield, California, shows that velocities vary both laterally and vertically. Velocities range from 4.0 km/sec) probably correspond to granitic rock of the Salinian block, which is exposed a few kilometers southwest of the SAF. The depth to the top of probable granitic rock varies laterally along the seismic profile but is about 600 m below the surface at the proposed SAFOD site. We observe a prominent, lateral low-velocity zone (LVZ) beneath and southwest of the surface trace of the SAF. The LVZ is about 1.5 km wide at 300-m depth but tapers to about 600 m wide at 750-m depth. At the maximum depth of the velocity model (750 m), the LVZ is centered approximately 400 m southwest of the surface trace of the SAF. Similar velocities and velocity gradients are observed at comparable depths on both sides of the LVZ, suggesting that the LVZ is anomalous relative to rocks on either side of it. Velocities within the LVZ are lower than those of San Andreas fault gouge, and the LVZ is also anomalous with respect to gravity, magnetic, and resistivity measurements. Because of its proximity to the surface trace of the SAF, it is tempting to suggest that the LVZ represents a zone of fractured crystalline rocks at depth. However, the LVZ instead probably represents a tectonic sliver of sedimentary rock that now rests adjacent to or encompasses the SAF. Such a sliver of sedimentary rock implies fault strands on both sides and possibly within the sliver, suggesting a zone of fault strands at least 1.5 km wide at a depth of 300 m, tapering to about 600 m wide at 750-m depth. Fluids within the sedimentary sliver are probably responsible for observed low-resistivity values.

  8. DEVELOPMENT OF AN OPTICAL SYSTEM FOR HIGH-SPEED, SMALL-SCALE VELOCITY MEASUREMENTS

    SciTech Connect

    Davies, H. R.; Chapman, D. J.; Proud, W. G.; Vine, T. A.

    2009-12-28

    An optical system was developed to allow the accurate focussing and alignment of small samples for velocity analysis with streak photography Even at low magnifications, a narrow streak slit means that any vibration or instability in the system greatly reduces the accuracy of the velocity measurements achieved. The optical system was designed to reduce the effects of such vibration. A spatial mount and rotation stage were modified to allow three spatial axis and rotational freedom of a custom-made sample mount. Markers within the sample mount were used to achieve precise alignment of the sample with the optical axis of the streak camera.

  9. High-velocity emission in young supernova remnants: SN 1006 and SN 1572

    SciTech Connect

    Kirshner, R.; Winkler, P.F.; Chevalier, R.A.

    1987-04-01

    The paper reports the discovery of broad H-alpha emission from the SN 1006 remnant with a FWHM velocity of 2600 + or - 100 km/s. This emission is similar to that seen in the remnant of SN 1572 which has a FWHM for H-alpha of 1800 km/s. The nonradiative model was used to interpret the line widths and the derived shock velocity was compared with proper motion measurements to derive distances of 1.4-2.1 kpc to SN 1006 and 2.0-2.8 kpc to SN 1572. 24 references.

  10. The multibeam Fabry-Perot velocimeter: Efficient measurement of high velocities

    SciTech Connect

    1996-07-01

    In support of the Laboratory`s scientific stockpile stewardship mission, we have developed a multibeam Fabry-Perot velocimetry system to more efficiently measure continuous velocities during our experiments. These data are invaluable for testing the adequacy of our hydrodynamic computer modeling codes. A new fiber optic system and Laboratory-designed optical devices allow us to obtain five or even ten continuous velocity records from an experiment using just one Fabry-Perot interferometer. Before the advent of this system, we could obtain only one record per interferometer. We have also developed a dual-cavity interferometer that greatly facilitates reading the interference fringes recorded during our experiments.

  11. Simultaneous structure and elastic wave velocity measurement of SiO[subscript 2] glass at high pressures and high temperatures in a Paris-Edinburgh cell

    SciTech Connect

    Kono, Yoshio; Park, Changyong; Sakamaki, Tatsuya; Kenny-Benson, Curtis; Shen, Guoyin; Wang, Yanbin

    2015-02-19

    An integration of multi-angle energy-dispersive x-ray diffraction and ultrasonic elastic wave velocity measurements in a Paris-Edinburgh cell enabled us to simultaneously investigate the structures and elastic wave velocities of amorphous materials at high pressure and high temperature conditions. We report the first simultaneous structure and elastic wave velocity measurement for SiO{sub 2} glass at pressures up to 6.8 GPa at around 500 C. The first sharp diffraction peak (FSDP) in the structure factor S(Q) evidently shifted to higher Q with increasing pressure, reflecting the shrinking of intermediate-range order, while the Si-O bond distance was almost unchanged up to 6.8 GPa. In correlation with the shift of FSDP position, compressional wave velocity (Vp) and Poisson's ratio increased markedly with increasing pressure. In contrast, shear wave velocity (Vs) changed only at pressures below 4 GPa, and then remained unchanged at {approx}4.0-6.8 GPa. These observations indicate a strong correlation between the intermediate range order variations and Vp or Poisson's ratio, but a complicated behavior for Vs. The result demonstrates a new capability of simultaneous measurement of structures and elastic wave velocities at high pressure and high temperature conditions to provide direct link between microscopic structure and macroscopic elastic properties of amorphous materials.

  12. Feasibility of a semi-automated method for cardiac conduction velocity analysis of high-resolution activation maps.

    PubMed

    Doshi, Ashish N; Walton, Richard D; Krul, Sébastien P; de Groot, Joris R; Bernus, Olivier; Efimov, Igor R; Boukens, Bastiaan J; Coronel, Ruben

    2015-10-01

    Myocardial conduction velocity is important for the genesis of arrhythmias. In the normal heart, conduction is primarily dependent on fiber direction (anisotropy) and may be discontinuous at sites with tissue heterogeneities (trabeculated or fibrotic tissue). We present a semi-automated method for the accurate measurement of conduction velocity based on high-resolution activation mapping following central stimulation. The method was applied to activation maps created from myocardium from man, sheep and mouse with anisotropic and discontinuous conduction. Advantages of the presented method over existing methods are discussed.

  13. Instantaneous 2D Velocity and Temperature Measurements in High Speed Flows Based on Spectrally Resolved Molecular Rayleigh Scattering

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.

    1995-01-01

    A Rayleigh scattering diagnostic for high speed flows is described for the simultaneous, instantaneous measurement of gas temperature and velocity at a number (up to about one hundred) of locations in a plane illuminated by an injection-seeded, frequency doubled Nd:YAG laser. Molecular Rayleigh scattered light is collected and passed through a planar mirror Fabry-Perot interferometer. The resulting image is analyzed to determine the gas temperature and bulk velocity at each of the regions. The Cramer Rao lower bound for measurement uncertainty is calculated. Experimental data is presented for a free jet and for preliminary measurements in the Lewis 4 inch by 10 inch supersonic wind tunnel.

  14. High-resolution interseismic velocity data along the San Andreas Fault from GPS and InSAR

    NASA Astrophysics Data System (ADS)

    Tong, X.; Sandwell, D. T.; Smith-Konter, B.

    2013-01-01

    We compared four interseismic velocity models of the San Andreas Fault based on GPS observations. The standard deviations of the predicted secular velocity from the four models are larger north of the San Francisco Bay area, near the creeping segment in Central California, and along the San Jacinto Fault and the East California Shear Zone in Southern California. A coherence spectrum analysis of the secular velocity fields indicates relatively high correlation among the four models at longer wavelengths (>15-40 km), with lower correlation at shorter wavelengths. To improve the short-wavelength accuracy of the interseismic velocity model, we integrated interferometric synthetic aperture radar (InSAR) observations, initially from Advanced Land Observing Satellite (ALOS) ascending data (spanning from the middle of 2006 to the end of 2010, totaling more than 1100 interferograms), with GPS observations using a Sum/Remove/Filter/Restore approach. The final InSAR line of sight data match the point GPS observations with a mean absolute deviation of 1.5 mm/yr. We systematically evaluated the fault creep rates along major faults of the San Andreas Fault and compared them with creepmeters and alignment array data compiled in Uniform California Earthquake Rupture Forecast, Version 2 (UCERF2). Moreover, this InSAR line of sight dataset can constrain rapid velocity gradients near the faults, which are critical for understanding the along-strike variations in stress accumulation rate and associated earthquake hazard.

  15. Sound velocity of Fe-S liquids at high pressure: Implications for the Moon's molten outer core

    SciTech Connect

    Jing, Zhicheng; Wang, Yanbin; Kono, Yoshio; Yu, Tony; Sakamaki, Tatsuya; Park, Changyong; Rivers, Mark L.; Sutton, Stephen R.; Shen, Guoyin

    2014-07-21

    Sound velocities of Fe and Fe–S liquids were determined by combining the ultrasonic measurements and synchrotron X-ray techniques under high pressure–temperature conditions from 1 to 8 GPa and 1573 K to 1973 K. Four different liquid compositions were studied including Fe, Fe–10 wt% S, Fe–20 wt% S, and Fe–27 wt% S. Our data show that the velocity of Fe-rich liquids increases upon compression and decreases with increasing sulfur content, whereas temperature has negligible effect on the velocity of Fe–S liquids. The sound velocity data were combined with ambient-pressure densities to fit the Murnaghan equation of state (EOS). Compared to the lunar seismic model, our velocity data constrain the sulfur content at 4±3 wt%, indicating a significantly denser (6.5±0.5 g/cm3) and hotter (1870-70+100 K) outer core than previously estimated. A new lunar structure model incorporating available geophysical observations points to a smaller core radius. Our model suggests a top–down solidification scenario for the evolution of the lunar core. Such “iron snow” process may have been an important mechanism for the growth of the inner core.

  16. Characterization and Fabrication of Spoke Cavities for High-Velocity Applications

    SciTech Connect

    Hopper, Christopher S.; Park, HyeKyoung; Delayen, Jean R.

    2014-02-01

    A 500 MHz, velocity-of-light, two-spoke cavity has been designed and optimized for possible use in a compact light source. Here we present the mechanical analysis and steps taken in fabrication of this cavity at Jefferson Lab.

  17. Portable Conduction Velocity Experiments Using Earthworms for the College and High School Neuroscience Teaching Laboratory

    ERIC Educational Resources Information Center

    Shannon, Kyle M.; Gage, Gregory J.; Jankovic, Aleksandra; Wilson, W. Jeffrey; Marzullo, Timothy C.

    2014-01-01

    The earthworm is ideal for studying action potential conduction velocity in a classroom setting, as its simple linear anatomy allows easy axon length measurements and the worm's sparse coding allows single action potentials to be easily identified. The earthworm has two giant fiber systems (lateral and medial) with different conduction…

  18. Are anthropometric, flexibility, muscular strength, and endurance variables related to clubhead velocity in low- and high-handicap golfers?

    PubMed

    Keogh, Justin W L; Marnewick, Michel C; Maulder, Peter S; Nortje, Jacques P; Hume, Patria A; Bradshaw, Elizabeth J

    2009-09-01

    The present study assessed the anthropometric profile (International Society for the Advancement of Kinanthropometry protocol), flexibility, muscular strength, and endurance of 20 male golfers. These data were collected in order to determine: a) the relationship between these kinanthropometric measures and clubhead velocity; and b) if these measures could distinguish low-handicap (LHG) and high-handicap (HHG) golfers. Ten LHG (handicap of 0.3 +/- 0.5) and 10 HHG (handicap of 20.3 +/- 2.4) performed 10 swings for maximum velocity and accuracy with their own 5-iron golf club at a wall-mounted target. LHG hit the target significantly more (115%) and had a 12% faster clubhead velocity than HHG (p < 0.01). The LHG also had significantly (28%) greater golf swing-specific cable woodchop (GSCWC) strength (p < 0.01) and tendencies for greater (30%) bench press strength and longer (5%) upper am and total arm (4%) length and less (24%) right hip internal rotation than HHG (0.01 < p < 0.05). GSCWC strength was significantly correlated to clubhead velocity (p < 0.01), with bench press and hack squat strength as well as upper arm and total arm length also approaching significance (0.01 < p < 0.05). Golfers with high GSCWC strength and perhaps greater bench press strength and longer arms may therefore be at a competitive advantage, as these characteristics allow the production of greater clubhead velocity and resulting ball displacement. Such results have implications for golf talent identification programs and for the prescription and monitoring of golf conditioning programs. While golf conditioning programs may have many aims, specific trunk rotation exercises need to be included if increased clubhead velocity is the goal. Muscular hypertrophy development may not need to be emphasized as it could reduce golf performance by limiting range of motion and/or increasing moment of inertia.

  19. Elastic properties of silicate melts at high pressure and implications for low velocity anomalies in the crust and mantle

    NASA Astrophysics Data System (ADS)

    Clark, A. N.; Lesher, C. E.

    2015-12-01

    Regions of low seismic velocities in the mantle and crust are commonly attributed to the presence of silicate melt or aqueous fluid. The elastic properties of silicate melts are typically modeled at high pressure using equations of state developed for crystalline materials. However, amorphous silicates spanning a wide range of composition and structure, i.e. SiO2 to MgSiO3, and including naturally occurring basalt compositions, exhibit a weak dependence of P-wave velocity on density in clear violation of Birch's law, which governs the behavior of crystalline materials. This anomalous behavior is attributed to the high degree of flexibility of the silicate network on loading that may be a general property of naturally occurring silicate melts at crustal and upper mantle conditions. If this is the case, P-wave velocities for silicate melts will be significantly less pressure dependent than previously assumed, which in turn will enhance the effects of melt fraction on lowering aggregate mantle seismic velocities. Here we present VP calculated for partially molten mantle up to 20 GPa showing that melt fractions purported to explain VP reductions associated with the lithosphere-asthenosphere boundary may be overestimated by 15%, while those reported for the transition zone may be overestimated to an even greater extent. Moreover, we predict that d lnVS/d lnVP (RSP) should vary little across low velocities regions within the upper mantle due solely to the presence of melt, but will be strongly influenced by how melt is distributed, consistent the work of [1]. Finally, RSP is found to be relatively insensitive to type of fluid present, contrary to conventional wisdom, and thus caution is warranted in attributing changes in RSP to either silicate melt or aqueous fluids. The implications of these findings for interpreting low velocity anomalies beneath hotspots and arcs (e.g. Iceland and Japan) will be discussed. [1] Takei, Y. (2002) JGR vol. 107

  20. Spatially-Resolved Velocity Measurements in Steady, High-Speed Reacting Flows Using Laser-Induced OH Fluorescence.

    NASA Astrophysics Data System (ADS)

    Klavuhn, Kurt G.

    The theoretical development and calibration of a nonintrusive, high-resolution, optical flowfield-diagnostic technique utilizing OH laser-induced fluorescence (OH LIF) for the measurement of velocity in steady, high-speed, reacting flows is reported. The particular high-speed, reacting flows of interest are those occurring in supersonic combustors for proposed hypersonic flight vehicles. The theory of the OH LIF strategy employed in this work is described, with emphasis on the optimization of the strategy for quantitative velocity measurements. A simplified model is derived for the calculation of expected signal levels from pulsed, narrow-linewidth, (1,0) band excitation of OH in flames when collecting filtered (1,1) and (0,0) band fluorescence with a gated detector. Several illumination techniques are presented for measuring the Doppler shift of the OH LIF while eliminating systematic errors. A unique reacting underexpanded jet was constructed for the calibration of the OH LIF velocity measurement technique over a wide range of flow conditions. A complete analysis of the distribution of flow properties in the jet flowfield is presented, including results from a full Navier-Stokes calculation with finite -rate chemistry. Comparisons of results from pointwise OH LIF velocity measurements along the centerline and planar OH LIF velocity measurements along the central plane of the reacting underexpanded jet with the numerical solution demonstrate the resolution, range, and accuracy of the technique. Measured and calculated velocities in the supersonic jet core agree on average to within +/-1.3% for the pointwise measurements and +/-2.2% for the planar measurements. The uncertainty (2 sigma) in the pointwise velocity measurements in the jet core was on average +/-6.0% for a single measurement and +/-3.5% for the average value of three scans. For the planar velocity measurements in the jet core, the uncertainty (2 sigma) was on average +/-4.9% for a single measurement

  1. Upper mantle low-velocity layers beneath the High Lava Plains imaged by scattered-wavefield migration

    NASA Astrophysics Data System (ADS)

    Chen, C.; James, D. E.; Wagner, L. S.

    2011-12-01

    The High Lava Plains (HLP) in eastern Oregon represents one of the most active intraplate magmatic provinces on Earth. This region's recent tectonic history is dominated by voluminous mid-Miocene outpourings of the Steens and Columbia River flood basalts, followed by a period of bimodal volcanic activities, generating two roughly orthogonal time-progressive rhyolitic hotspot tracks: the northeastern-trending Snake River Plain and the northwestern-trending High Lava Plains. The causes of this complex tectonomagmatic evolution are not well understood, and geophysical constraints have been lacking regarding the detailed crustal and upper mantle structure in this region. From 2006 to 2009, a passive seismic experiment with the deployment of 118 broadband seismic stations was carried out as part of the multidisciplinary High Lava Plains project, which aims to investigate the causes of continental intraplate tectonomagmatism. These stations covered central and eastern Oregon, northern Nevada, and southwestern Idaho, with average spacing of 15-20 km, yielding unprecedented data density in the HLP region. A number of tomographic and receiver function studies has revealed complex structures beneath HLP. These include irregular Moho topography across the HLP, and concentrated low velocity anomalies in the uppermost mantle beneath regions of Holocene volcanism in southeastern Oregon (including areas of the Owyhee Plateau), as well as beneath volcanic centers near Steens Mountain and Newberry volcano. We complement these previous studies by generating high-resolution seismic images from scattered wavefield to detect seismic discontinuities beneath the HLP. We process 80 high-quality teleseismic events with good azimuthal coverage using a 2-D teleseismic migration algorithm based on the Generalized Radon Transform. The resulting migration images indicate the presence of several main features: 1) a prominent and varying Moho topography: the Moho is at ~40 km depth east of the

  2. Titanium dioxide reinforced hydroxyapatite coatings deposited by high velocity oxy-fuel (HVOF) spray.

    PubMed

    Li, H; Khor, K A; Cheang, P

    2002-01-01

    Hydroxyapatite (HA) coatings with titania addition were produced by the high velocity oxy-fuel (HVOF) spray process. Mechanical properties of the as-sprayed coatings in terms of adhesive strength, shear strength and fracture toughness were investigated to reveal the effect of the titania reinforcement on HA. Qualitative phase analysis with X-ray diffraction (XRD) showed that mutual chemical reaction between TiO2 and HA, that formed CaTiO3 occurred during coating formation. Differential scanning calorimetry (DSC) analysis of the starting powders showed that the mutual chemical reaction temperature was approximately 1410 degrees C and the existence of TiO2 can effectively inhibit the decomposition of HA at elevated temperatures. The positive influence of TiO2 addition on the shear strength was revealed. The incorporation of 10 vol% TiO2 significantly improved the Young's modulus of HA coatings from 24.82 (+/- 2.44) GPa to 43.23 (+/- 3.20) GPa. It decreased to 38.51 (+/- 3.65) GPa as the amount of TiO2 increased to 20 vol%. However, the addition of TiO2 has a negative bias on the adhesive strength of HA coatings especially when the content of TiO2 reached 20 vol%. This is attributed to the weak chemical bonding and brittle phases existing at the splats' interface that resulted from mutual chemical reactions. The fracture toughness exhibited values of 0.48 (+/- 0.08) MPa m0.5, 0.60 (+/- 0.07) MPa m0.5 and 0.67 (+/- 0.06) MPa m0.5 for the HA coating, 10 vol% TiO2 blended HA coating and 20 vol% TiO2 blended HA coating respectively. The addition of TiO2 in HA coating with the amount of less than 20 vol% is suggested for satisfactory toughening effect in HVOF HA coating. PMID:11762858

  3. Telluric Line Effect on High Precision Radial Velocity Survey of K and M Dwarfs

    NASA Astrophysics Data System (ADS)

    Sithajan, Sirinrat; Ge, Jian; Wang, Ji

    2016-01-01

    The red and NIR region, where K and M dwarfs emit most of light, is the desirable region for radial velocity (RV) measurements for detecting low mass planets, but this wavelength region is heavily contaminated with telluric absorption lines. Variation in the telluric line depths and centroids can result in large RV measurement uncertainties, limiting the sensitivity to detect low mass planets. Here we use simulations to study effect of telluric removal and the residuals on RV measurements and determine the level of correction needed to minimize the effect. Simulated spectra from three representative spectrographs with spectral resolutions, R=60K, 80K, 100K and 120K for wavelength coverage at 0.38-0.62 μm (called the optical spectrograph), 0.38-0.90 μm (called the broad optical spectrograph) and 0.90-2.4 μm (called the NIR spectrograph), have been studied. Two methods are used to study the RV effect by the telluric lines. The first one is a 'Masking' method, in which the telluric lines are identified and removed from RV calculation. The other method is a 'Removal' method, in which all heavily saturated lines are masked out and the remaining lines are subtracted by synthetic atmospheric spectra to a desired level. Our results show that, in case of late M dwarfs, the broad optical spectrograph can gain additional RV sensitivity over the optical spectrograph if telluric lines can be modeled and subtracted to better than 10%, or all lines deeper than 5% are masked out from RV calculation. For the earlier type stars, it requires better than 2% modeling and subtracting precision with the broad optical spectrograph to gain additional Doppler sensitivity over the optical spectrograph. Besides the photon gain with the NIR spectrograph over the optical spectrograph for late M dwarf observations, the NIR can gain additional advantage of Doppler sensitivity over the optical tool for late M dwarfs when telluric residuals can be subtracted to below 1%. However, it is never

  4. Effects of pulsed, high-velocity water flow on larval robust redhorse and V-lip redhorse

    USGS Publications Warehouse

    Weyers, R.S.; Jennings, C.A.; Freeman, Mary C.

    2003-01-01

    The pulsed, high-velocity water flow characteristic of water-flow patterns downstream from hydropower-generating dams has been implicated in the declining abundance of both aquatic insects and fishes in dam-regulated rivers. This study examined the effects of 0, 4, and 12 h per day of pulsed, high-velocity water flow on the egg mortality, hatch length, final length, and survival of larval robust redhorse Moxostoma robusturn, a presumedly extinct species that was rediscovered in the 1990s, and V-lip redhorse M. collapsum (previously synonomized with the silver redhorse M. anisurum) over a 3-5 week period in three separate experiments. Twelve 38.0-L aquaria (four per treatment) were modified to simulate pulsed, high-velocity water flow (>35 cm/s) and stable, low-velocity water flow (<10 cm/s). Temperature, dissolved oxygen, zooplankton density, and water quality variables were kept the same across treatments. Fertilized eggs were placed in gravel nests in each aquarium. Hatch success was estimated visually at greater than 90%, and the mean larval length at 24 h posthatch was similar in each experiment. After emergence from the gravel nest, larvae exposed to 4 and 12 h of pulsed, high-velocity water flow grew significantly more slowly and had lower survival than those in the 0-h treatment. These results demonstrate that the altered water-flow patterns that typically occur when water is released during hydropower generation can have negative effects on the growth and survival of larval catostomid suckers.

  5. Spatial tuning of acoustofluidic pressure nodes by altering net sonic velocity enables high-throughput, efficient cell sorting

    SciTech Connect

    Jung, Seung-Yong; Notton, Timothy; Fong, Erika; Shusteff, Maxim; Weinberger, Leor S.

    2015-01-07

    Particle sorting using acoustofluidics has enormous potential but widespread adoption has been limited by complex device designs and low throughput. Here, we report high-throughput separation of particles and T lymphocytes (600 μL min-1) by altering the net sonic velocity to reposition acoustic pressure nodes in a simple two-channel device. Finally, the approach is generalizable to other microfluidic platforms for rapid, high-throughput analysis.

  6. Spatial tuning of acoustofluidic pressure nodes by altering net sonic velocity enables high-throughput, efficient cell sorting

    DOE PAGES

    Jung, Seung-Yong; Notton, Timothy; Fong, Erika; Shusteff, Maxim; Weinberger, Leor S.

    2015-01-07

    Particle sorting using acoustofluidics has enormous potential but widespread adoption has been limited by complex device designs and low throughput. Here, we report high-throughput separation of particles and T lymphocytes (600 μL min-1) by altering the net sonic velocity to reposition acoustic pressure nodes in a simple two-channel device. Finally, the approach is generalizable to other microfluidic platforms for rapid, high-throughput analysis.

  7. Ultra-compact high velocity clouds in the ALFALFA HI survey: Candidate Local Group galaxies?

    NASA Astrophysics Data System (ADS)

    Adams, Elizabeth Ann Kovenz

    The increased sensitivity and spatial resolution of the ALFALFA HI survey has resulted in the detection of ultra-compact high velocity clouds (UCHVCs). These objects are good candidates to represent low mass gas-rich galaxies in the Local Group and Local Volume with stellar populations that are too faint to be detected in extant optical surveys. This idea is referred to as the "minihalo hypothesis". We identify the UCHVCs within the ALFALFA dataset via the use of a 3D matched filtering signal identification algorithm. UCHVCs are selected based on a compact size (< 30'), separation from Galactic HI (|upsilon LSR| > 120 km s-1) and isolation. Within the 40% complete ALFALFA survey (alpha.40), 59 UCHVCs are identified; 19 are in a most-isolated subset and are the best galaxy candidates. Due to the presence of large HVC complexes in the fall sky, most notably the Magellanic Stream, the association of UCHVCs with existing structure cannot be ruled out. In the spring sky, the spatial and kinematic distribution of the UCHVCs is consistent with simulations of dark matter halos within the Local Group. In addition, the HI properties of the UCHVCs (if placed at 1 Mpc) are consistent with both theoretical and observational predictions for low mass gas-rich galaxies. Importantly, the HI properties of the UCHVCs are consistent with those of two recently discovered low mass gas-rich galaxies in the Local Group and Local Volume, Leo T and Leo P. Detailed follow-up observations are key for addressing the minihalo hypothesis. High resolution HI observations can constrain the environment of a UCHVC and offer evidence for a hosting dark matter halo through evidence of rotation support and comparison to theoretical models. Observations of one UCHVC at high resolution (15'') reveal the presence of a clumpy HI distribution, similar to both low mass galaxies and circumgalactic compact HVCs. An extended envelope containing ˜50% of the HI flux is resolved out by the array configuration

  8. Leaner Lifted-Flame Combustion Enabled by the Use of an Oxygenated Fuel in an Optical CI Engine

    DOE PAGES

    Gehmlich, Ryan K.; Dumitrescu, Cosmin E.; Wang, Yefu; Mueller, Charles J.

    2016-04-05

    Leaner lifted-flame combustion (LLFC) is a mixing-controlled combustion strategy for compression-ignition engines that does not produce soot because the equivalence ratio at the lift-off length, Φ(H), is less than or equal to approximately two. In addition to preventing soot formation, LLFC can simultaneously control emissions of nitrogen oxides because it is tolerant to the use of exhaust-gas recirculation for lowering in-cylinder temperatures. LLFC can be achieved through the use of oxygenated fuels and enhanced fuel/charge-gas mixing upstream of the lift-off length. Enhanced mixing can be obtained via higher injection pressures, smaller injector orifice diameters, lower intake-manifold and coolant temperatures, and/ormore » more retarded injection timings. This study focuses on the effects of an oxygenated fuel blend (T50) made up of 50% by volume tri-propylene glycol mono-methyl ether with a #2 ULSD emissions-certification fuel (CFA), compared against baseline testing of the CFA fuel without the oxygenate. Experimental measurements include crank-angle resolved natural luminosity (NL) and chemiluminescence (CL) imaging diagnostics. EGR is simulated by adding nitrogen and carbon dioxide to the intake charge to produce a 16% intake-oxygen mole fraction (XO2), and results are compared against cases with no charge dilution (i.e., 21% XO2). Initial experiments with a two-hole tip achieved soot-free LLFC at low loads with the T50 fuel, 240 MPa injection pressure, 50 °C intake-manifold temperature (IMT), 95 °C coolant temperature, and -5 crank-angle degree (CAD) after top-dead-center (ATDC) start of combustion (SOC) timing. The strategy was extended to more moderate loads by employing a 6-hole injector tip, where lowering the IMT to 30 °C, reducing the coolant temperature to 85 °C, and retarding the SOC timing to +5 CAD ATDC resulted in sustained LLFC at both 21% and 16% XO2 at up to 6.2 bar gross indicated mean effective pressure (gIMEP) with T50. The

  9. Indoor seismology by probing the Earth interior by using sound velocity measurements at high pressures and temperatures

    SciTech Connect

    Li,B.; Liebermann, R.

    2007-01-01

    The adiabatic bulk (K S) and shear (G) moduli of mantle materials at high pressure and temperature can be obtained directly by measuring compressional and shear wave velocities in the laboratory with experimental techniques based on physical acoustics. We present the application of the current state-of-the-art experimental techniques by using ultrasonic interferometry in conjunction with synchrotron x radiation to study the elasticity of olivine and pyroxenes and their high-pressure phases. By using these updated thermoelasticity data for these phases, velocity and density profiles for a pyrolite model are constructed and compared with radial seismic models. We conclude that pyrolite provides an adequate explanation of the major seismic discontinuities at 410- and 660-km depths, the gradient in the transition zone, as well as the velocities in the lower mantle, if the uncertainties in the modeling and the variations in different seismic models are considered. The characteristics of the seismic scaling factors in response to thermal anomalies suggest that anticorrelations between bulk sound and shear wave velocities, as well as the large positive density anomalies observed in the lower mantle, cannot be explained fully without invoking chemical variations.

  10. Indoor seismology by probing the Earth's interior by using sound velocity measurements at high pressures and temperatures.

    PubMed

    Li, Baosheng; Liebermann, Robert C

    2007-05-29

    The adiabatic bulk (K(S)) and shear (G) moduli of mantle materials at high pressure and temperature can be obtained directly by measuring compressional and shear wave velocities in the laboratory with experimental techniques based on physical acoustics. We present the application of the current state-of-the-art experimental techniques by using ultrasonic interferometry in conjunction with synchrotron x radiation to study the elasticity of olivine and pyroxenes and their high-pressure phases. By using these updated thermoelasticity data for these phases, velocity and density profiles for a pyrolite model are constructed and compared with radial seismic models. We conclude that pyrolite provides an adequate explanation of the major seismic discontinuities at 410- and 660-km depths, the gradient in the transition zone, as well as the velocities in the lower mantle, if the uncertainties in the modeling and the variations in different seismic models are considered. The characteristics of the seismic scaling factors in response to thermal anomalies suggest that anticorrelations between bulk sound and shear wave velocities, as well as the large positive density anomalies observed in the lower mantle, cannot be explained fully without invoking chemical variations.

  11. Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes

    NASA Astrophysics Data System (ADS)

    Yang, Jie; Shu, Ting; Fan, Yuwei

    2013-01-01

    Time-and-space resolved comparison of the expansion velocities of plasmas in the planar diode with cathodes made of carbon velvet and polymer velvet has been performed. The diode was powered by a 200 kV, 110 ns pulse, and the peak current density was nearly 477 A/cm2. A four-channel high speed framing camera (HSFC) was used to observe the formation and subsequent movement of the cathode plasmas. More accurate and valuable information about the two-dimensional (radial and axial) velocity components of the cathode plasmas was also acquired by utilizing the digital image processing methods. Additionally, the perveance model based on the Child-Langmuir law was used to calculate the expansion velocities of the diode plasmas from voltage and current profiles. Results from the two diagnostics were compared. Comparing the average values of the radial and axial velocity components indicated that the former was much larger than the latter during the initial period of the current. It was also found that the radial velocity of the carbon velvet cathode (190 cm/μs) was much larger than that (90 cm/μs) of the polymer velvet cathode. Moreover, the average values of both the radial and axial velocity components of the carbon velvet cathode were typically in the range of 2.5 ± 1.5 cm/μs, which were smaller than that of the polymer velvet cathode during the current flattop. These results, together with the comparison of calculated values from the perveance model, indicated that the diode with carbon velvet cathode was more robust as compared with the polymer velvet cathode for the same electron current densities.

  12. Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes

    SciTech Connect

    Yang Jie; Shu Ting; Fan Yuwei

    2013-01-28

    Time-and-space resolved comparison of the expansion velocities of plasmas in the planar diode with cathodes made of carbon velvet and polymer velvet has been performed. The diode was powered by a 200 kV, 110 ns pulse, and the peak current density was nearly 477 A/cm{sup 2}. A four-channel high speed framing camera (HSFC) was used to observe the formation and subsequent movement of the cathode plasmas. More accurate and valuable information about the two-dimensional (radial and axial) velocity components of the cathode plasmas was also acquired by utilizing the digital image processing methods. Additionally, the perveance model based on the Child-Langmuir law was used to calculate the expansion velocities of the diode plasmas from voltage and current profiles. Results from the two diagnostics were compared. Comparing the average values of the radial and axial velocity components indicated that the former was much larger than the latter during the initial period of the current. It was also found that the radial velocity of the carbon velvet cathode (190 cm/{mu}s) was much larger than that (90 cm/{mu}s) of the polymer velvet cathode. Moreover, the average values of both the radial and axial velocity components of the carbon velvet cathode were typically in the range of 2.5 {+-} 1.5 cm/{mu}s, which were smaller than that of the polymer velvet cathode during the current flattop. These results, together with the comparison of calculated values from the perveance model, indicated that the diode with carbon velvet cathode was more robust as compared with the polymer velvet cathode for the same electron current densities.

  13. Techniques for the measurements of the line of sight velocity of high altitude Barium clouds

    NASA Technical Reports Server (NTRS)

    Mende, S. B.

    1981-01-01

    It is demonstrated that for maximizing the scientific output of future ion cloud release experiments a new type of instrument is required which will measure the line of sight velocity of the ion cloud by the Doppler Technique. A simple instrument was constructed using a 5 cm diameter solid Fabry-Perot etalon coupled to a low light level integrating television camera. It was demonstrated that the system has both the sensitivity and spectral resolution for the detection of ion clouds and the measurement of their line of sight Doppler velocity. The tests consisted of (1) a field experiment using a rocket barium cloud release to check the sensitivity, (2) laboratory experiments to show the spectral resolving capabilities of the system. The instrument was found to be operational if the source was brighter than about 1 kilorayleigh and it had a wavelength resolution much better than .2A which corresponds to about 12 km/sec or an acceleration potential of 100 volts.

  14. A holographic system that records front-surface detail of a scene moving at high velocity

    NASA Technical Reports Server (NTRS)

    Kurtz, R. L.; Loh, H. Y.

    1972-01-01

    A holographic technique that uses an elliptical orientation for the holographic arrangement is discussed. It is shown that the degree of image degradation is not only a function of exposure time but also of the system used. The form of the functional system dependence is given, as well as the results of several systems tested, which verify this dependence. It is further demonstrated that the important parameter is the total motion of the target. Using the experimentally determined resolution of front-surface detail from a target with a velocity of 17,546 centimeters per second, an upper limit on target velocity for resolution of front-surface detail for a given system can be predicted.

  15. Velocity distribution function of electrons plasma produced by high power laser pulse interacting aluminum target

    NASA Astrophysics Data System (ADS)

    Mahdieh, M. H.; Razi, E. M.

    2010-09-01

    This paper presents the experimental results of studying the distribution function of electrons plasma produced by irradiating aluminum target by nanosecond pulsed laser in vacuum. The laser beam was provided by second harmonic of a Q-switched Nd:YAG pulsed laser with ~10 nsec pulse duration and energy of 70 mJ. A home made Faraday cup was used for detecting the current signal. From analyzing the time of flight (TOF) experimental distribution function was determined. Comparing the experimental distribution function with Maxwell-Boltzamnn and effusion distribution functions, the electron temperature was estimated. From the experimental results, the velocity of maximum electron flux was determined. In this study the influence of the probe position and biasing voltage was investigated. The results show that the velocity of maximum electron flux and associated temperature rises with distance from the target surface. The results also show that effusion distribution function is more appropriate for modeling such plasma.

  16. On the X-Ray Low- and High-Velocity Outflows in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Ramirez, J. M.; Tombesi, F.

    2012-01-01

    An exploration of the relationship between bolometric luminosity and outflow velocity for two classes of X-ray outflows in a large sample of active galactic nuclei has been performed. We find that line radiation pressure could be one physical mechanism that might accelerate the gas we observe in warm absorber, v approx. 100-1000 km/s, and on comparable but less stringent grounds the ultrafast outflows, v approx. 0.03-0.3c. If comparable with the escape velocity of the system, the first is naturally located at distances of the dusty torus, '" I pc, and the second at subparsec scales, approx.0.01 pc, in accordance with large set of observational evidence existing in the literature. The presentation of this relationship might give us key clues for our understanding of the different physical mechanisms acting in the centre of galaxies, the feedback process and its impact on the evolution of the host galaxy.

  17. A comprehensive set of simulations of high-velocity collisions between main-sequence stars

    NASA Astrophysics Data System (ADS)

    Freitag, Marc; Benz, Willy

    2005-04-01

    We report on a very large set of simulations of collisions between two main-sequence (MS) stars. These computations were carried out with the smoothed particle hydrodynamics method. Realistic stellar structure models for evolved MS stars were used. In order to sample an extended domain of initial parameters space (masses of the stars, relative velocity and impact parameter), more than 14000 simulations were carried out. We considered stellar masses ranging between 0.1 and 75 Msolar and relative velocities up to a few thousand km s-1. To limit the computational burden, a resolution of 1000-32000 particles per star was used. The primary goal of this study was to build a complete data base from which the result of any collision can be interpolated. This allows us to incorporate the effects of stellar collisions with an unprecedented level of realism into dynamical simulations of galactic nuclei and other dense stellar clusters. We make the data describing the initial condition and outcome (mass and energy loss, angle of deflection) of all our simulations available on the Internet. We find that the outcome of collisions depends sensitively on the stellar structure and that, in most cases, using polytropic models is inappropriate. Published fitting formulae for the collision outcomes, established from a limited set of collisions, prove of limited use because they do not allow robust extrapolation to other stellar structures or relative velocities.

  18. Stochastic simulation for the propagation of high-frequency acoustic waves through a random velocity field

    NASA Astrophysics Data System (ADS)

    Lu, B.; Darmon, M.; Leymarie, N.; Chatillon, S.; Potel, C.

    2012-05-01

    In-service inspection of Sodium-Cooled Fast Reactors (SFR) requires the development of non-destructive techniques adapted to the harsh environment conditions and the examination complexity. From past experiences, ultrasonic techniques are considered as suitable candidates. The ultrasonic telemetry is a technique used to constantly insure the safe functioning of reactor inner components by determining their exact position: it consists in measuring the time of flight of the ultrasonic response obtained after propagation of a pulse emitted by a transducer and its interaction with the targets. While in-service the sodium flow creates turbulences that lead to temperature inhomogeneities, which translates into ultrasonic velocity inhomogeneities. These velocity variations could directly impact the accuracy of the target locating by introducing time of flight variations. A stochastic simulation model has been developed to calculate the propagation of ultrasonic waves in such an inhomogeneous medium. Using this approach, the travel time is randomly generated by a stochastic process whose inputs are the statistical moments of travel times known analytically. The stochastic model predicts beam deviations due to velocity inhomogeneities, which are similar to those provided by a determinist method, such as the ray method.

  19. Stochastic simulation for the propagation of high-frequency acoustic waves through a random velocity field

    SciTech Connect

    Lu, B.; Darmon, M.; Leymarie, N.; Chatillon, S.; Potel, C.

    2012-05-17

    In-service inspection of Sodium-Cooled Fast Reactors (SFR) requires the development of non-destructive techniques adapted to the harsh environment conditions and the examination complexity. From past experiences, ultrasonic techniques are considered as suitable candidates. The ultrasonic telemetry is a technique used to constantly insure the safe functioning of reactor inner components by determining their exact position: it consists in measuring the time of flight of the ultrasonic response obtained after propagation of a pulse emitted by a transducer and its interaction with the targets. While in-service the sodium flow creates turbulences that lead to temperature inhomogeneities, which translates into ultrasonic velocity inhomogeneities. These velocity variations could directly impact the accuracy of the target locating by introducing time of flight variations. A stochastic simulation model has been developed to calculate the propagation of ultrasonic waves in such an inhomogeneous medium. Using this approach, the travel time is randomly generated by a stochastic process whose inputs are the statistical moments of travel times known analytically. The stochastic model predicts beam deviations due to velocity inhomogeneities, which are similar to those provided by a determinist method, such as the ray method.

  20. Detection of High Velocity Absorption Components in the He I Lines of Eta Carinae near the Time of Periastron

    NASA Technical Reports Server (NTRS)

    Richardson, Noel D.; St-Jean, Lucas; Gull, Theodore R.; Madura, Thomas; Hillier, D. John; Teodoro, Mairan; Moffat, Anthony; Corcoran, Michael; Damineli, Augusto

    2014-01-01

    We have obtained a total of 58 high spectral resolution (R90,000) spectra of the massive binary star eta Carinae since 2012 in an effort to continue our orbital and long-term echelle monitoring of this extreme binary (Richardson et al. 2010, AJ, 139, 1534) with the CHIRON spectrograph on the CTIO 1.5 m telescope (Tokovinin et al. 2013, PASP, 125, 1336) in the 45507500A region. We have increased our monitoring efforts and observation frequency as the periastron event of 2014 has approached. We note that there were multiple epochs this year where we observe unusual absorption components in the P Cygni troughs of the He I triplet lines. In particular, we note high velocity absorption components related to the following epochs for the following lines: He I 4713: HJD 2456754- 2456795 (velocity -450 to -560 kms) He I 5876: HJD 2456791- 2456819 (velocity -690 to -800 kms) He I 7065: HJD 2456791- 2456810 (velocity -665 to -730 kms) Figures: Note that red indicates a high-velocity component noted above. He I 4713: http:www.astro.umontreal.carichardson4713.png He I 5876: http:www.astro.umontreal.carichardson5876.png He I 7065: http:www.astro.umontreal.carichardson7065.png These absorptions are likely related to the wind-wind collision region and bow shock, as suggested by the high-velocity absorption observed by Groh et al. (2010, AA, 519, 9) in the He I 10830 Atransition. In these cases, we suspect that we look along an arm of the shock cone and that we will see a fast absorption change from the other collision region shortly after periastron. We suspect that this is related to the multiple-components of the He II 4686 line that was noted by Walter (ATel6334), and is confirmed in our data. Further, high spectral resolution data are highly encouraged,especially for resolving powers greater than 50,000.These observations were obtained with the CTIO 1.5 m telescope, operated by the SMARTS Consortium, and were obtained through both SMARTS and NOAO programs 2012A-0216,2012B-0194

  1. Precise Astrometry in the Core of the Globular Cluster 47 Tuc: a Complete Census of High-Velocity Stars

    NASA Astrophysics Data System (ADS)

    Meylan, Georges

    1995-07-01

    Binary stars play an essential role during the late phases of the dynamical evolution of a globular cluster. They transfer energy to passing stars, and so can strongly influence the cluster evolution - enough to delay, halt, and even reverse core collapse. Hard binaries are known to exist in cluster cores, e.g., in the form of millisecond pulsars. The presence of hard binaries may also be revealed by searching for the by- products of close encounters: high-velocity stars. Two such stars were serendipitously discovered in the core of 47 Tuc by Meylan et al. (1991), and similar stars have since been detected by Pryor et al. (1994). This represents the limit of the radial velocity data which can be obtained from the ground. If more progress is to be made in the search for high- velocity stars in 47 Tuc it must be made by obtaining proper motions - a task for which only HST is suitable. We propose to use WFPC2 to obtain deep U (F300W) images of the core of 47 Tuc at three different epochs over two years. This will allow us to measure differential proper motions to a 1 sigma limit of 0.23 mas/yr - this corresponds to a 5 sigma detection of all stars with velocities greater than 22 km/s. The choice of F300W will allow stars to be measured over the whole color-magnitude diagram - from the red-giant branch to well down the main sequence. Such a complete census will provide unique constraints on relaxation processes, collision and ejection rates, and velocity distributions.

  2. Precise Astrometry in the Core of the Globular Cluster 47 Tuc: A Complete Census of High-Velocity Stars

    NASA Astrophysics Data System (ADS)

    Meylan, Georges

    1996-07-01

    Binary stars play an essential role during the late phases of the dynamical evolution of a globular cluster. They transfer energy to passing stars, and so can strongly influence the cluster evolution. Hard binaries are known to exist in cluster cores, e.g., in the form of millisecond pulsars. The presence of hard binaries may also be revealed by searching for the by- products of close encounters: high-velocity stars. Two such stars were serendipitously discovered in the core of 47 Tuc by Meylan et al. {1991}, and similar stars have since been detected by Pryor et al. {1994}. This represents the limit of the radial velocity data from the ground. If more progress is to be made in the search for high-velocity stars in 47 Tuc, it must be made by obtaining proper motions, a task for which only HST is suitable. We propose to continue {Cycle 5 observations are scheduled for the fall of 1995} to use WFPC2 to obtain deep U {F300W} images of the core of 47 Tuc at three different epochs over two years. This will allow us to measure differential proper motions to a 1-Sigma limit of 0.23 mas/yr - this corresponds to a 5-Sigma detection of all stars with velocities greater than 22 km/s. The choice of F300W will allow stars to be measured over the whole color-magnitude diagram, from the red-giant branch to well down the main sequence. Such a complete census will provide unique constraints on relaxation processes, collision and ejection rates, and velocity distribution, as a function of the stellar mass.

  3. Precise Astrometry in the Core of the Globular Cluster 47 Tuc: A Complete Census of High-Velocity Stars

    NASA Astrophysics Data System (ADS)

    Meylan, Georges

    1997-07-01

    We propose to obtain the third and final epoch for our measurement of differential proper motions in the core of 47 Tuc using deep U {F300W} and V {F555W} WFPC2 images over two years {1^st epoch: Oct. 1995; 2^nd: Cycle 6 scheduled}. The resulting motions will have a 1-Sigma uncertainty of 0.23 mas/yr - corresponds to a 5-Sigma detection of all stars with velocities greater than 22 km/s. The choice of F300W will allow stars to be measured over the whole color-magnitude diagram, from the red-giant branch to well down the main sequence. Such a complete census will provide unique constraints on relaxation processes, collision and ejection rates, and the velocity distribution, as a function of the stellar mass. Binary stars play an essential role during the late phases of the dynamical evolution of a globular cluster. They transfer energy to passing stars, and so can strongly influence the cluster evolution. Hard binaries are known to exist in cluster cores, e.g., in th e form of millisecond pulsars. Th e presence of hard binaries may also be revealed by searching for the by-products of close encounters: high-velocity stars. Two such stars were serendipitously discovered in the core of 47 Tuc by Meylan et al. {1991}, and similar stars have since been detected by Pryor et al. {1994}. This represents the limit of the radial velocity data from the ground. If more progress is to be made in the search for high-velocity stars in 47 Tuc, it must be made by obtaining proper motions, a task for which only HST is suitable.

  4. Optimization of magnetically accelerated, ultra-high velocity aluminum flyer plates for use in plate impact, shock wave experiments.

    SciTech Connect

    Cochrane, Kyle Robert; Knudson, Marcus D.; Slutz, Stephen A.; Lemke, Raymond William; Davis, J. P.; Harjes, Henry Charles III; Giunta, Anthony Andrew; Bliss, David Emery

    2005-05-01

    The intense magnetic field produced by the 20 MA Z accelerator is used as an impulsive pressure source to accelerate metal flyer plates to high velocity for the purpose of performing plate impact, shock wave experiments. This capability has been significantly enhanced by the recently developed pulse shaping capability of Z, which enables tailoring the rise time to peak current for a specific material and drive pressure to avoid shock formation within the flyer plate during acceleration. Consequently, full advantage can be taken of the available current to achieve the maximum possible magnetic drive pressure. In this way, peak magnetic drive pressures up to 490 GPa have been produced, which shocklessly accelerated 850 {micro}m aluminum (6061-T6) flyer plates to peak velocities of 34 km/s. We discuss magnetohydrodynamic (MHD) simulations that are used to optimize the magnetic pressure for a given flyer load and to determine the shape of the current rise time that precludes shock formation within the flyer during acceleration to peak velocity. In addition, we present results pertaining to plate impact, shock wave experiments in which the aluminum flyer plates were magnetically accelerated across a vacuum gap and impacted z-cut, {alpha}-quartz targets. Accurate measurements of resulting quartz shock velocities are presented and analyzed through high-fidelity MHD simulations enhanced using optimization techniques. Results show that a fraction of the flyer remains at solid density at impact, that the fraction of material at solid density decreases with increasing magnetic pressure, and that the observed abrupt decrease in the quartz shock velocity is well correlated with the melt transition in the aluminum flyer.

  5. Electron drift velocity in lattice-matched AlInN/AlN/GaN channel at high electric fields

    NASA Astrophysics Data System (ADS)

    Ardaravičius, L.; Ramonas, M.; Liberis, J.; Kiprijanovič, O.; Matulionis, A.; Xie, J.; Wu, M.; Leach, J. H.; Morkoç, H.

    2009-10-01

    Hot-electron transport was probed by nanosecond-pulsed measurements for a nominally undoped two-dimensional channel confined in a nearly lattice-matched Al0.82In0.18N/AlN/GaN structure at room temperature. The electric field was applied parallel to the interface, the pulsed technique enabled minimization of Joule heating. No current saturation was reached at fields up to 180 kV/cm. The effect of the channel length on the current is considered. The electron drift velocity is deduced under the assumption of uniform electric field and field-independent electron density. The highest estimated drift velocity reaches ˜3.2×107 cm/s when the AlN spacer thickness is 1 nm. At high fields, a weak (if any) dependence of the drift velocity on the spacer thickness is found in the range from 1 to 2 nm. The measured drift velocity is low for heterostructures with thinner spacers (0.3 nm).

  6. Influence of Processing Parameters on Residual Stress of High Velocity Oxy-Fuel Thermally Sprayed WC-Co-Cr Coating

    NASA Astrophysics Data System (ADS)

    Gui, M.; Eybel, R.; Asselin, B.; Radhakrishnan, S.; Cerps, J.

    2012-10-01

    Residual stress in high velocity oxy-fuel (HVOF) thermally sprayed WC-10Co-4Cr coating was studied based on design of experiment (DOE) with five factors of oxygen flow, fuel gas hydrogen flow, powder feed rate, stand-off distance, and surface speed of substrate. In each DOE run, the velocity and temperature of in-flight particle in flame, and substrate temperature were measured. Almen-type N strips were coated, and their deflections after coating were used for evaluation of residual stress level in the coating. The residual stress in the coating obtained in all DOE runs is compressive. In the present case of HVOF thermally sprayed coating, the residual stress is determined by three types of stress: peening, quenching, and cooling stress generated during spraying or post spraying. The contribution of each type stress to the final compressive residual stress in the coating depends on material properties of coating and substrate, velocity and temperature of in-flight particle, and substrate temperature. It is found that stand-off distance is the most important factor to affect the final residual stress in the coating, following by two-factor interaction of oxygen flow and hydrogen flow. At low level of stand-off distance, higher velocity of in-flight particle in flame and higher substrate temperature post spraying generate more peening stress and cooling stress, resulting in higher compressive residual stress in the coating.

  7. Titanium K-Shell X-Ray Production from High Velocity Wire Arrays Implosions on the 20-MA Z Accelerator

    SciTech Connect

    Apruzese, J.P.; Beg, F.N.; Clark, R.C.; Coverdale, C.A.; Davis, J.; Deeney, C.; Douglas, M.R.; Nash, T.J.; Ruiz-Comacho, J.; Spielman, R.B.; Struve, K.W.; Thornhill, J.W.; Whitney, K.G.

    1999-01-27

    The advent of the 20-MA Z accelerator [R.B. Spielman, C. Deeney, G.A. Chandler, et al., Phys. Plasmas 5, 2105, (1997)] has enabled implosions of large diameter, high-wire-number arrays of titanium to begin testing Z-pinch K-shell scaling theories. The 2-cm long titanium arrays, which were mounted on a 40-mm diameter, produced between 75{+-}15 to 125{+-}20 kJ of K-shell x-rays. Mass scans indicate that, as predicted, higher velocity implosions in the series produced higher x-ray yields. Spectroscopic analyses indicate that these high velocity implosions achieved peak electron temperatures from 2.7{+-}0.1 to 3.2{+-}0.2 keV and obtained a K-shell emission mass participation of up to 12%.

  8. A revised velocity-reversal and sediment-sorting model for a high-gradient, pool-riffle stream

    USGS Publications Warehouse

    Thompson, D.M.; Wohl, E.E.; Jarrett, R.D.

    1996-01-01

    Sediment-sorting processes related to varying channel-bed morphology were investigated from April to November 1993 along a 1-km pool-riffle and step-pool reach of North Saint Vrain Creek, a small mountain stream in the Rocky Mountains of northern Colorado. Measured cross-sectional areas of flow were used to suggest higher velocities in pools than in riffles at high flow. Three hundred and sixteen tracer particles, ranging in size from 16 mm to 256 mm, were placed in two separate pool-riffle-pool sequences and used to assess sediment-sorting patterns and sediment-transport competence variations. Tracer-particle depositional evidence indicated higher sediment-transport competence in pools than in riffles at high flow. Pool-riffle sediment sorting may be created by velocity reversals, and more localized sorting results from gravitational forces along the upstream sloping portion of the channel bed located at the downstream end of pools.

  9. Geometry Effects on Multipole Components and Beam Optics in High-Velocity Multi-Spoke Cavities

    SciTech Connect

    Hopper, Christopher S.; Deitrick, Kirsten E.; Delayen, Jean R.

    2013-12-01

    Velocity-of-light, multi-spoke cavities are being proposed to accelerate electrons in a compact light-source. There are strict requirements on the beam quality which require that the linac have only small non-uniformities in the accelerating field. Beam dynamics simulations have uncovered varying levels of focusing and defocusing in the proposed cavities, which is dependent on the geometry of the spoke in the vicinity of the beam path. Here we present results for the influence different spoke geometries have on the multipole components of the accelerating field and how these components, in turn, impact the simulated beam properties.

  10. A high speed data acquisition system for the analysis of velocity, density, and total temperature fluctuations at transonic speeds

    NASA Technical Reports Server (NTRS)

    Clukey, Steven J.; Jones, Gregory S.; Stainback, P. Calvin

    1988-01-01

    The use of a high-speed Dynamic Data Acquisition System (DDAS) to measure simultaneously velocity, density, and total temperature fluctuations is described. The DDAS is used to automate the acquisition of hot-wire calibration data. The data acquisition, data handling, and data reporting techiques used by DDAS are described. Sample data are used to compare results obtained with the DDAS with those obtained from the FM tape and post-test digitization method.

  11. Study of maghemite nanoparticles as prepared and coated with DMSA using Mössbauer spectroscopy with a high velocity resolution

    NASA Astrophysics Data System (ADS)

    Oshtrakh, M. I.; Ushakov, M. V.; Semionkin, V. A.; Lima, E. C. D.; Morais, P. C.

    2014-04-01

    Study of maghemite nanoparticles, native and coated with DMSA as magnetic fluid for biomedical applications, was carried out using Mössbauer spectroscopy with a high velocity resolution at 295 and 90 K. The obtained results demonstrated differences in Mössbauer hyperfine parameters for uncoated and DMSA-coated nanoparticles which were related to the interactions of DMSA molecules with Fe3+ ions on maghemite nanoparticle's surface.

  12. A Case Report of Spinal Cord Injury Patient From a High Velocity Gunshot Wound to the Lumbar Spine

    PubMed Central

    Kim, Juyong; Kim, Je Ho

    2013-01-01

    We report on operational and rehabilitation management, as well as the outcome, of a patient who with sustained spinal cord injury from a high velocity gunshot wound to the lumbar spine. More specifically, a patient with a gunshot wound to the spine is more likely to sustain a complete injury and have a poor prognosis. As such, there should be concerns regarding associated and extended injuries related to bullet fragmentation as well as the possibility of long-term sequelae. PMID:23526072

  13. Negative Differential Velocity in Artificial Crystals Probed by High Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Patanè, A.

    Progress in the synthesis and engineering of semiconductor materials has led to improved device performances and functionalities. In particular, in the last decade, there has been considerable interest in the physics and applications of highly-mismatched alloys in which small and highly-electronegative isovalent N-atoms are incorporated onto the anion sublattice of a III-V compound semiconductor.1 The most studied material is the GaAs1-xNx alloy. Our magnetotunnelling studies have shown that a small percentage of N (x < 1%) perturbs dramatically the electronic properties of the host GaAs crystal leading to a large increase of the electron effective mass and an unusual response of the energy-wavevector dispersions to hydrostatic pressure.2-6 These effects differ from the smoother variation of the energy band gap and electron effective mass with alloy composition observed in other semiconductor compounds, such as InyGa1-yAs. The incorporation of N in GaAs gives rise to a qualitatively different type of alloy phenomenon: N-impurities and N-clusters tend to localize the extended Bloch states of GaAs at resonant energies in the conduction band (CB), thus fragmenting the energy-wavevector dispersion relations. The possibility of tailoring the electronic properties of III-V compounds by N-incorporation has stimulated proposals for innovative devices in optoelectronics and high frequency (terahertz, THz) electronics.7 However, to date, the implementation of dilute nitrides in these technologies presents several challenges, including a degradation of the electron mobility. Also, despite a rapidly expanding body of work on the electronic properties of GaAs1-xNx, the range of N-concentrations over which this alloy behaves as a good conductor is not yet well established. Our magnetotransport experiments have revealed how the incorporation of N in GaAs affects the electrical conductivity. Our studies in n-type GaAs1-xNx epilayers revealed a large increase of the resistivity,

  14. THE HIGH-VELOCITY MOLECULAR OUTFLOWS IN MASSIVE CLUSTER-FORMING REGION G10.6-0.4

    SciTech Connect

    Liu Hauyu Baobab; Ho, Paul T. P.; Zhang Qizhou E-mail: pho@asiaa.sinica.edu.t

    2010-12-20

    We report the arcsecond resolution Submillimeter Array observations of the {sup 12}CO (2-1) transition in the massive cluster-forming region G10.6-0.4. In these observations, the high-velocity {sup 12}CO emission is resolved into individual outflow systems, which have a typical size scale of a few arcseconds. These molecular outflows are energetic and are interacting with the ambient molecular gas. By inspecting the shock signatures traced by CH{sub 3}OH, SiO, and HCN emissions, we suggest that abundant star formation activities are distributed over the entire 0.5 pc scale dense molecular envelope. The star formation efficiency over one global free-fall timescale (of the 0.5 pc molecular envelope, {approx}10{sup 5} years) is about a few percent. The total energy feedback of these high-velocity outflows is higher than 10{sup 47} erg, which is comparable to the total kinetic energy in the rotational motion of the dense molecular envelope. From order-of-magnitude estimations, we suggest that the energy injected from the protostellar outflows is capable of balancing the turbulent energy dissipation. No high-velocity bipolar molecular outflow associated with the central OB cluster is directly detected, which can be due to the photoionization.

  15. The High-velocity Molecular Outflows in Massive Cluster-forming Region G10.6-0.4

    NASA Astrophysics Data System (ADS)

    Liu, Hauyu Baobab; Ho, Paul T. P.; Zhang, Qizhou

    2010-12-01

    We report the arcsecond resolution Submillimeter Array observations of the 12CO (2-1) transition in the massive cluster-forming region G10.6-0.4. In these observations, the high-velocity 12CO emission is resolved into individual outflow systems, which have a typical size scale of a few arcseconds. These molecular outflows are energetic and are interacting with the ambient molecular gas. By inspecting the shock signatures traced by CH3OH, SiO, and HCN emissions, we suggest that abundant star formation activities are distributed over the entire 0.5 pc scale dense molecular envelope. The star formation efficiency over one global free-fall timescale (of the 0.5 pc molecular envelope, ~105 years) is about a few percent. The total energy feedback of these high-velocity outflows is higher than 1047 erg, which is comparable to the total kinetic energy in the rotational motion of the dense molecular envelope. From order-of-magnitude estimations, we suggest that the energy injected from the protostellar outflows is capable of balancing the turbulent energy dissipation. No high-velocity bipolar molecular outflow associated with the central OB cluster is directly detected, which can be due to the photoionization.

  16. Design and Development of High-Velocity Slurry Erosion Test Rig Using CFD

    NASA Astrophysics Data System (ADS)

    Grewal, H. S.; Agrawal, Anupam; Singh, H.

    2013-01-01

    Slurry erosion (SE) is commonly observed in almost all kinds of components and machineries involved in fluid (liquid) transfer and delivery. During design and development phase of these components, test rigs are usually required to evaluate their performance; however, only few detailed designs of test rigs are available for SE investigations. Among the existing designs of SE test rigs, most of them belong to rotary type. In the present study, design of a new type of SE test rig has been proposed, which is simpler in construction and working. This newly designed test rig could possibly eliminate some of the limitations (velocity-concentration interdependence and lack of acceleration distance) found in the existing set-ups. Calibration of the test rig was done for jet velocity and erodent concentration. Commissioning of the rig was undertaken by evaluating the effect of operating parameters (concentration and impingement angle) on the erosion rates of aluminum and cast iron. Results show that the rig was able to capture the traditional responses of ductile and brittle erosion behaviors being observed for these materials. Repeatability of the test rig was ensured, and the results were found to be within the acceptable error limits.

  17. Measurement of the line-of-sight velocity of high-altitude barium clouds A technique

    NASA Technical Reports Server (NTRS)

    Mende, S. B.; Harris, S. E.

    1982-01-01

    It is demonstrated that for maximizing the scientific output of future ionospheric and magnetospheric ion cloud release experiments a new type of instrument is required which will measure the line-of-sight velocity of the ion cloud by the Doppler technique. A simple instrument was constructed using a 5-cm diam solid Fabry-Perot etalon coupled to a low-light-level integrating TV camera. It was demonstrated that the system has both the sensitivity and spectral resolution for detection of ion clouds and measurement of their line-of-sight Doppler velocity. The tests consisted of (1) a field experiment using a rocket barium cloud release to check sensitivity, and (2) laboratory experiments to show the spectral resolving capabilities of the system. The instrument was found to be operational if the source was brighter than approximately 1 kR, and it had a wavelength resolution much better than 0.2 A, which corresponds to approximately 12 km/sec or in the case of barium ion an acceleration potential of 100 V. The instrument is rugged and, therefore, simple to use in field experiments or on flight instruments. The sensitivity limit of the instrument can be increased by increasing the size of the etalon.

  18. A Solid Film Lubricant Composition for Use at High Sliding Velocities in Liquid Nitrogen

    NASA Technical Reports Server (NTRS)

    Wisander, D. W.; Johnson, R. L.

    1960-01-01

    Solid-lubricant-containing compositions can be of value as films and solid bodies for bearing and seal surfaces in low-temperature liquefied gases. An experimental composition including polytetrafluoroethylene (PTFE), an epoxy resin, and lithium-alumina-silicate was studied in friction, wear, and endurance experiments in liquid nitrogen (-320 F). This composition was formulated to approximate the thermal expansion of metals used in cryogenic systems. Hemisphere (3/6-in. radius) rider specimens were used and in most experiments the load was 1000 g. Films (0.005-in. thick) on disk specimens gave good endurance life, low rider wear, and desirable friction (f = 0.02 to 0.07). They functioned at a higher sliding velocity (no failure at 16, 000 ft/min) with copper rider specimens than with stainless steel riders (failure at 9000 ft/min). Solid rider material of the experimental composition had good friction and wear properties at sliding velocities above 4000 ft/min. It is important to use the experimental composition with mating materials having good thermal conductivity.

  19. Measurement of the line-of-sight velocity of high-altitude barium clouds: a technique.

    PubMed

    Mende, S B; Harris, S E

    1982-09-15

    It is demonstrated that for maximizing the scientific output of future ionospheric and magnetospheric ion cloud release experiments a new type of instrument is required which will measure the line-of-sight velocity of the ion cloud by the Doppler technique. A simple instrument was constructed using a 5-cm diam solid Fabry-Perot etalon coupled to a low-light-level integrating TV camera. It was demonstrated that the system has both the sensitivity and spectral resolution for detection of ion clouds and measurement of their line-of-sight Doppler velocity. The tests consisted of (1) a field experiment using a rocket barium cloud release to check sensitivity, and (2) laboratory experiments to show the spectral resolving capabilities of the system. The instrument was found to be operational if the source was brighter than approximately 1 kR, and it had a wavelength resolution much better than 0.2 A, which corresponds to approximately 12 km/sec or in the case of barium ion an acceleration potential of 100 V. The instrument is rugged and, therefore, simple to use in field experiments or on flight instruments. The sensitivity limit of the instrument can be increased by increasing the size of the etalon.

  20. Damage of infrared-transparent materials exposed to rain environments at high velocities

    NASA Astrophysics Data System (ADS)

    Hackworth, J. V.

    1983-04-01

    Experimental and analytical work being done to determine the response of infared-transparent materials to water drop impact is surveyed. The work also seeks to guide the development of materials with improved erosion resistance and to develop methods to protect the less erosion resistant materials. A description is given of the installation where the work is being done. Here, an arm 2.75 m long rotates inside a chamber that is 8 m in diameter. The specimen is attached to the tip of the rotating arm, which can attain a velocity of Mach 3. The test chamber can be evacuated to 0.1 atm, although it is normally evacuated to 0.3 atm. The two different rain environments that can be created inside the chamber are then described. After discussing the response to water drop impact and to multiple drop impacts, attention is given to the effect of velocity and impact angle on the rate of erosion of zinc sulfide in rainfields. Methods are described for improving the erosion resistance of infrared windows.