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Sample records for high velocity oxygen-fuel

  1. A Numerical Study on Gas Phase Dynamics of High-Velocity Oxygen Fuel Thermal Spray

    NASA Astrophysics Data System (ADS)

    Baik, Jae-Sang; Park, Sun-Kyu; Kim, Youn-Jea

    2008-08-01

    The high-velocity oxygen fuel (HVOF) thermal spray is used for a particulate deposition process in which micro-sized particles are propelled and heated in a supersonic combusting gas stream. It is characterized by high gas velocity and high density and is being used in an increasing variety of coating applications, such as ceramic and composite coatings, to improve wear and abrasion resistance. The particle temperature and velocity are two of the most important parameters in HVOF thermal spraying, which affect the quality of the coatings. To understand the particle dynamics, it is necessary to study, first, the thermal flow characteristics in the HVOF system. In this study, a numerical analysis is performed to predict the gas dynamic behaviors, and the effect of the geometrical parameter is studied to optimize the nozzle design.

  2. 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.

  3. 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.

  4. Particle melting behavior during high-velocity oxygen fuel thermal spraying

    NASA Astrophysics Data System (ADS)

    He, J.; Ice, M.; Lavernia, E.

    2001-03-01

    Particle melting behavior during high-velocity oxygen fuel (HVOF) thermal spraying was investigated using Inconel 625 powders. The powder characteristics and coating properties were investigated using scanning electron microscopy (SEM), x-ray, and microhardness studies. Results indicated that the volume fraction of unmelted particles in the coatings was dependent on the proportion of powder within a specified size range, in these experiments, 30 to 50 µm. This particle size range was primarily determined by the particle temperature, which was measured during spraying. Particle temperature significantly decreased as particle size increased. The microhardness values for the coatings containing unmelted particles were predicted by a simple rule-of-mixtures equation for the case of a low volume fraction of unmelted particles. However, for the condition of high volume fraction of unmelted particles, the measured microhardness values did not compare favorably with the calculated values, probably due to the presence of porosity, which occurred in the form of voids found among unmelted particles. The microstructure and characteristics of the feedstock powder were retained in the corresponding coating under certain spray conditions.

  5. 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.

  6. 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.

  7. 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.

  8. A Comprehensive Pitting Study of High Velocity Oxygen Fuel Inconel 625 Coating by Using Electrochemical Testing Techniques

    NASA Astrophysics Data System (ADS)

    Niaz, Akbar; Khan, Sajid Ullah

    2016-01-01

    In the present work, Inconel 625 was coated on a mild steel substrate using a high velocity oxygen fuel coating process. The pitting propensity of the coating was tested by using open circuit potential versus time, potentiodynamic polarization, electrochemical potentiokinetic reactivation, and scanning electrochemical microscopy. The pitting propensity of the coating was compared with bulk Inconel 625 alloy. The results confirmed that there were regions of different electrochemical activities on the coating which have caused pitting corrosion.

  9. Numerical Investigation of Combustion and Flow Dynamics in a High Velocity Oxygen-Fuel Thermal Spray Gun

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Song, Qiuzhi; Yu, Zhiyi

    2016-02-01

    The combustion and flow behavior within a high velocity oxygen-fuel (HVOF) thermal spray gun is very complex and involves multiphase flow, heat transfer, chemical reactions, and supersonic/subsonic transitions. Additionally, this behavior has a significant effect on the formation of a coating. Non-premixed combustion models have been developed and are able to provide insight into the underlying physics of the process. Therefore, this investigation employs a non-premixed combustion model and the SST k - ω turbulence model to simulate the flow field of the JP5000 (Praxair-TAFA, US) HVOF thermal spray gun. The predicted temperature and velocity have a high level of agreement with experimental data when using the non-premixed combustion model. The results are focused on the fuel combustion, the subsequent gas dynamics within the HVOF gun, and the development of a supersonic free jet outside the gun. Furthermore, the oxygen/fuel inlet turbulence intensity, the fuel droplet size, and the oxygen/fuel ratio are investigated to determine their effect on the supersonic flow characteristics of the combustion gas.

  10. 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.

  11. Microstructure and properties of tungsten carbide coatings sprayed with various high-velocity oxygen fuel spray systems

    NASA Astrophysics Data System (ADS)

    Schwetzke, R.; Kreye, H.

    1999-09-01

    This article reports on a series of experiments with various high-velocity oxygen fuel spray systems (Jet Kote, Top Gun, Diamond Jet (DJ) Standard, DJ 2600 and 2700, JP-5000, Top Gun-K) using different WC-Co and WC-Co-Cr powders. The microstructure and phase composition of powders and coatings were analyzed by optical and scanning electron microscopy and x-ray diffraction. Carbon and oxygen content of the coatings were determined to study the decarburization and oxidation of the material during the spray process. Coatings were also characterized by their hardness, bond strength, abrasive wear, and corrosion resistance. The results demonstrate that the powders exhibit various degrees of phase transformation during the spray process depending on type of powder, spray system, and spray parameters. Within a relatively wide range, the extent of phase transformation has only little effect on coating properties. Therefore, coatings of high hardness and wear resistance can be produced with all HVOF spray systems when the proper spray powder and process parameters are chosen.

  12. Numerical analysis of particle impacting and bonding processes during high velocity oxygen fuel spraying process

    NASA Astrophysics Data System (ADS)

    Pan, Jiajing; Hu, Shengsun; Niu, Anning; Ding, Kunying; Yang, Lijun

    2016-03-01

    In this paper, the dynamic impact behavior of a particle and a substrate under different particle temperatures and velocities as well as using different materials for the particle and substrate were systematically studied. We found that the highest temperature occurred at the side edge of the particle after the collision, which is consistent with the distribution of equivalent plastic strain. The deformation of the particle and substrate was very severe at the first 40 ns, slowed down after 40 ns and remained almost unchanged after 80 ns. With the increase in the particle velocity, the effective combination area became larger, the equivalent plastic strain of the substrate is increased, and the equivalent plastic strain of the particle is decreased. As the initial temperature of particles increased, the effective combination area between the particle and substrate increased, and higher temperature and larger equivalent plastic strain of the particle could be obtained. With the increase in the substrate strength, the temperature and the equivalent plastic strain of the particle is increased, whereas the plastic deformation of the substrate is decreased.

  13. Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

    SciTech Connect

    He, J. Ice, M.; Dallek, S.; Lavernia, E.J.

    2000-02-01

    A nanostructured WC-12 pct Co coating was synthesized using mechanical milling and high velocity oxygen fuel (HVOF) thermal spraying. The variation of powder characteristics with milling time and the performance of the coatings were investigated using scanning electron microscope (SEM), X-ray, transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and microhardness measurements. There is no evidence that indicates the presence of an amorphous phase in the sintered WC-12 pct Co powder, and the binder phase in this powder is still crystalline Co. Mechanical milling of up to 20 hours did not lead to the formation of an amorphous phase in the sintered WC-12 pct Co powder. During the initial stages of the milling, the brittle carbide particles were first fractured into fragments and then embedded into the binder phase. This process gradually formed polycrystal nanocomposite powders of the Co binder phase and W carbide particles. The conventional cold welding and fracturing processes primarily occurred among the Co binder powders and polycrystal composite powders. The nanostructured WC-12 pct Co coatings, synthesized in the present study, consist of an amorphous matrix and carbides with an average particle diameter of 35 nm. The coating possesses an average microhardness of 1135 HV and higher resistance to indentation fracture than that of its conventional counterpart.

  14. 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.

  15. High-Velocity Oxygen Fuel Thermal Spray of Fe-Based Amorphous Alloy: a Numerical and Experimental Study

    NASA Astrophysics Data System (ADS)

    Ajdelsztajn, L.; Dannenberg, J.; Lopez, J.; Yang, N.; Farmer, J.; Lavernia, E. J.

    2009-09-01

    The fabrication of dense coatings with appropriate properties using a high velocity oxygen fuel (HVOF) spray process requires an in-depth understanding of the complete gas flow field and particle behavior during the process. A computational fluid dynamics (CFD) model is implemented to investigate the gas flow behavior that occurs during the HVOF process and a simplified one-dimensional decoupled model of the in-flight thermal behavior of the amorphous Fe-based powder particles was developed and applied for three different spray conditions. The numerical results were used to rationalize the different coating microstructures described in the experimental results. Low porosity and amorphous coatings were produced using two different particle size distributions (16 to 25 μm and 25 to 53 μm). The amorphous characteristics of the powder were retained in the coating due to melting and rapid solidification in the case of very fine powder or ligaments (<16 μm) and to the fact that the crystallization temperature was not reached in the case of the large particles (16 to 53 μm).

  16. 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.

  17. 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

    2016-04-01

    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.

  18. A new high-velocity oxygen fuel process for making finely structured and highly bonded inconel alloy layers from liquid feedstock

    NASA Astrophysics Data System (ADS)

    Ma, X. Q.; Roth, J.; Gandy, D. W.; Frederick, G. J.

    2006-12-01

    High-velocity oxygen fuel (HVOF) thermal spray processes are used in applications requiring the highest density and adhesion strength, which are not achievable in most other thermal spray processes. Similar to other thermal spray processes, however, a normal HVOF process is unable to apply fine powders less than 10 µm via a powder feeder. The advantages of using smaller and even nanosized particles in a HVOF process include uniform microstructure, higher cohesion and adhesion, full density, lower internal stress, and higher deposition efficiency. In this work, a new process has been developed for HVOF forming of fine-grained Inconel 625 alloy layers using a liquid feedstock containing small alloy particles. Process investigations have shown the benefits of making single and duplex layered coatings with full density and high bond strength, which are attributed to the very high kinetic energy of particles striking on the substrates and the better melting of the small particles.

  19. Effect of Particle and Injection Parameters on the Performance of a Dual-Stage High-Velocity Oxygen Fuel Thermal Spray System

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed N.; Shamim, Tariq

    2015-06-01

    For temperature-sensitive material (such as titanium) coatings, recently developed high-velocity oxygen fuel dual-stage thermal spray systems offer better control of particle oxidation and production of various coating structures. These advantages of the dual-stage thermal system are significantly influenced by the state of the coating particles being injected. Hence, the objective of the present study is to investigate the effects of particle size, shape, injection velocity, and injection angle on a dual-stage thermal spray system by employing a comprehensive mathematical model. The results demonstrate that the particle size, shape, injection velocity, and injection angle affect the particle velocity and temperature, which in turn may affect the coating quality. The results show that smaller particles have higher temperatures and velocities owing to decrease in particle thermal and mass inertia. Spherical particles have higher temperature and lower velocity than the non-spherical particles because of lower drag. The particle velocity and temperature also increase with the increase of the injection velocity. Similarly, the particles injection angle also plays an important role. Higher particle temperatures and velocities outside of the barrel are obtained if the particles are injected at oblique angles to the main gaseous flow.

  20. Effect of ultrasonic cavitation erosion on corrosion behavior of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating.

    PubMed

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

    2015-11-01

    The effect of ultrasonic cavitation erosion on electrochemical corrosion behavior of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating in 3.5 wt.% NaCl solution, was investigated using free corrosion potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in comparison with stainless steel 1Cr18Ni9Ti. The results showed that cavitation erosion strongly enhanced the cathodic current density, shifted the free corrosion potential in the anodic direction, and reduced the magnitude of impedance of the coating. The impedance of the coating decreased more slowly under cavitation conditions than that of the stainless steel 1Cr18Ni9Ti, suggesting that corrosion behavior of the coating was less affected by cavitation erosion than that of the stainless steel. PMID:26186856

  1. Influence of Heat Treatment on Corrosion Resistance of High-Velocity Oxygen-Fuel Sprayed WC-17Co Coatings on 42CrMo Steel

    NASA Astrophysics Data System (ADS)

    Sun, Wan-chang; Zhang, Pei; Zhang, Feng; Dong, Chu-xu; Zhang, Ju-mei; Cai, Hui

    2015-09-01

    The influence of heat treatment from 500 to 1100 °C on the 5 wt.% H2SO4 solution-induced corrosion resistance of high-velocity oxygen-fuel sprayed WC-17Co coatings on 42CrMo steel was investigated, by using x-ray diffractometer (XRD), scanning electron microscopy (SEM)-energy-dispersive spectrometer (EDS), and polarization curve methods. XRD analysis showed decrease in W2C phase intensity with recrystallization of amorphous Co and generation of new Co3W3C and Co6W6C phases with heat treatment. Porosity distribution did not follow a particular pattern; it initially increased and then decreased with increasing temperature. Corrosion resistance sequence of the as-sprayed and heat-treated coatings in 5 wt.% H2SO4 solution was C-5 > C-9 > C-A > C-7 > C-11. Furthermore, microstructure and phase structure of heat-treated coatings revealed the formation of different discontinuous plate-like oxide films on the surface of the heat-treated coatings which indicated the vital effect of binder structure on the corrosion resistance.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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).

  10. High geocentric velocity meteor ablation

    NASA Astrophysics Data System (ADS)

    Hill, K. A.; Rogers, L. A.; Hawkes, R. L.

    2005-12-01

    Interstellar origin meteoroids have now been detected using radar, image intensified video, large aperture radar and space dust impact techniques. Dynamical and radiation production mechanisms will eject some meteoroids from other planetary systems into orbits which will impact Earth with high geocentric velocities. In this paper we numerically model the ablation of high geocentric velocity (71 to 500~km s-1) meteors in order to predict the heights, light curves and trail lengths to be expected. We modeled three compositions and structures: asteroidal, cometary and porous cometary. Meteoroid masses ranging from 10-6 to 10-13~kg were used in the model. As expected, these high geocentric velocity meteors, when compared to other meteors, ablate higher in the atmosphere. For example a 300~km s-1 cometary structure meteor of mass 10-9~kg will have a peak luminosity at about 190 km. They will also have significantly longer trail lengths. The same 300~km s-1, 10-9~kg cometary meteor would be within 2 mag of its peak brightness for a vertical displacement of 60 km if incident at a zenith angle of 45°. The peak light intensity of these high geocentric velocity meteors changes only slowly with velocity. Although the incident kinetic energy per unit time increases dramatically, this is largely offset by a decrease in the optical luminous efficiency in this velocity regime according to our luminous efficiency model. The 300~km s-1, 10-9~kg cometary meteor would have an absolute meteor magnitude at peak luminosity of about +8.5 mag. Our results suggest that at least those high geocentric velocity meteors larger than about 10-8~kg should be observable with current meteor electro-optical technology although there may be observational biases against their detection. The results of this paper can be used to help optimize a search strategy for these very high geocentric velocity meteors.

  11. 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.

  12. Simulations of High Velocity Clouds

    NASA Astrophysics Data System (ADS)

    Shelton, Robin

    Recently, a great deal of progress has been made toward understanding clouds of fast moving material within and near our Galaxy. Not only have observations revealed more clouds and enabled better distance estimates, but they have found large numbers of high velocity high ions. Observations of faint stars have revealed that our Galaxy is threaded with streams of stars, the likely remnants of subsumed dwarf galaxies. It has become apparent that the gas stripped from such galaxies likely contributed to the population of high velocity clouds (HVCs), making HVCs signposts of the Milky Way's growth via accretion. Theoretical and simulational work on this explanation for HVCs have advanced as have theoretical and simulational work on other explanations and on HVC-galaxy interactions. But, much work has yet to be done. Here, we propose a suite of multi-dimensional simulations of HVC-galaxy interactions designed to determine how HVCs affect the Galaxy and designed to determine the characteristics of the clouds and environmental gas that enable high velocity gas to be rich in high stage ions. This work will contribute toward NASA's strategic goal to discover how the universe works and evolves. The project will employ simulations and theory, while also producing results that will be helpful for deciphering vast numbers of observations taken by NASA telescopes.

  13. High Velocity Outflows in Quasars

    NASA Astrophysics Data System (ADS)

    Hamann, Fred; Rodriguez Hidalgo, Paola; Nestor, Daniel

    2006-02-01

    High velocity (HV) outflows are important components of SMBH growth and evolution. The ability of SMBHs to accrete matter and light up as AGN probably requires that outflows are present to carry away angular momentum. Outflows during the luminous AGN phase might also play a critical role in ``unveiling" young dust-enshrouded AGN and in ``polluting" the intergalactic medium with metals at high redshifts. Nonetheless, AGN outflows remain poorly understood. We have begun a program to study a nearly unexplored realm of AGN outflow parameter space: HV winds with v> 10,000 km/s up to v~ 0.2c but small velocity dispersions (narrow absorption lines), such that v/(Delta) v ≫ 1. These extreme outflows have been detected so far in just a few quasars, but they might be ubiquitous if, as expected, the flows subtend a small solid angle as seen from the central engine. Narrow-line HV flows merit specific attention because they pose unique challenges for theoretical models of the wind acceleration, mass loss rates, launch radii, etc. They might also comprise a significant fraction of absorbers previously attributed to unrelated (interveinng) gas or galaxies. We have compiled a list of bright quasars with candidate HV outflow lines (CIV 1550 A) in existing SDSS spectra. We now propose to observe ~50 of these candidates with the 2.1m GoldCam to i) identify/confirm some of the true outflow systems (based on line variability), ii) place a firm lower limit on the fraction of quasars with narrow-line HV outflows, iii) compile a short list of confirmed HV outflow sources for future study, and iv) use the combined SDSS and GoldCam data to measure or constrain basic outflow properties, such as the kinematics, locations, and physical conditions.

  14. 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!

  15. Modeling of Two-Phase Flow and Heat Transfer in Low-Temperature Oxygen-Fuel Spray Process

    NASA Astrophysics Data System (ADS)

    Shan, Y. G.; Shen, C. H.; Jia, L. B.; Mostaghimi, J.

    2014-01-01

    The low-temperature oxygen-fuel (LTOF) spray is a modification of high velocity oxygen fuel spray. In this process, the high-temperature gas is accelerated to supersonic speed through a Laval nozzle followed by a straight barrel. By injecting room temperature gas into the mixing chamber, the temperature of the gas can be controlled in a range of about 1000-2500 K, so that some oxygen and temperature-sensitive materials, such as titanium and copper, can avoid oxidation or decomposition during the spraying process. The purpose of this paper is to establish a 2-D mathematical model to simulate the supersonic gas dynamics and particles behavior in LTOF process. The temperature and velocity of the flow fields, and the trajectory and heating of in-flight particles are predicted for different operating parameters. The model is validated by experimental data in the literature. Effects of the mixing gas flow rates, particle sizes, and injection conditions on this process were investigated as well.

  16. 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.

  17. 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.

  18. High velocity knot in the Helix nebula

    SciTech Connect

    Meaburn, J.; Walsh, J.R.

    1980-01-01

    A high velocity (about 66 km/s) split feature about 15 arcseconds in extent has been detected in forbidden O II emission over a dark knot in the loop of the Helix nebula. This velocity splitting is much greater than the 20 km/s large scale splitting observed previously, and several mechanisms are proposed to account for this feature.

  19. Effect of High-Velocity Oxy-Fuel (HVOF) Thermal Spraying on Physical and Mechanical Properties of Type 316 Stainless Steel

    SciTech Connect

    Terry C. Totemeier

    2005-09-01

    Data on the microstructural, physical, and mechanical characteristics of high-velocity oxygen-fuel (HVOF)-sprayed type 316 stainless steel coatings are presented and compared with properties of wrought 316 stainless steel. Coatings were prepared at three different spray particle velocities; coating characteristics are presented as a function of velocity. The coatings had relatively low porosity and oxide contents and were significantly harder than annealed, wrought 316 stainless steel. The hardness difference is primarily attributed to high dislocation densities resulting from peening imparted by high-velocity spray particles. The coating hardness increased with increasing spray particle velocity, reflecting increased peening effects. The elastic modulus of the coatings was essentially identical to wrought material. The mean coefficient of thermal expansion of as-sprayed coatings was lower than wrought material, but the expansion of annealed coatings matched the wrought behavior.

  20. High velocity pulsed plasma thermal spray

    NASA Astrophysics Data System (ADS)

    Witherspoon, F. D.; Massey, D. W.; Kincaid, R. W.; Whichard, G. C.; Mozhi, T. A.

    2002-03-01

    The quality and durability of coatings produced by many thermal spray techniques could be improved by increasing the velocity with which coating particles impact the substrate. Additionally, better control of the chemical and thermal environment seen by the particles during flight is crucial to the quality of the coating. A high velocity thermal spray device is under development through a Ballistic Missile Defense Organization Small Business Innovation Research (SBIR) project, which provides significantly higher impact velocity for accelerated particles than is currently available with existing thermal spray devices. This device utilizes a pulsed plasma as the accelerative medium for powders introduced into the barrel. Recent experiments using a particle imaging diagnostic system showed that the device can accelerate stainless steel and WC-Co powders to velocities ranging from 1500 to 2200 m/s. These high velocities are accomplished without the use of combustible gases and without the need of a vacuum chamber, while maintaining an inert atmosphere for the particles during acceleration. The high velocities corresponded well to modeling predictions, and these same models suggest that velocities as high as 3000 m/s or higher are possible.

  1. 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.

  2. 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

  3. 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.

  4. High velocity impact resistance of composite materials

    NASA Astrophysics Data System (ADS)

    Justo, Jo; Marquer, A. T.

    2003-09-01

    Composite materials are used in applications that require protection against high velocity impacts by fragment simulating projectiles. In this work, the ballistic performance of two commercially available materials against a fragments simulating projectile (FSP) is studied. The materials used were an aramid fiber with a phenolic matrix and a polyethylene fiber with a thermoplastic film. Impact tests have been carried out, with velocities ranging from 300 m/s to 1260m/s. The projectile used is a 1.1g NATO FSP. Impact velocity and exit velocity are measured, to determine the V{50} and the energy absorbed in cases where perforation occurs. Assessment of the impact damaged area is done using ultrasonic C-scan inspection. Types of damage and damage mechanisms have been identified. Several mechanical tests have been carried out to determine the mechanical properties, at different strain rates. Future work in numerical simulation of impact will be done using commercial code AutodyntinycircledR ftom Century Dynamics.

  5. 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

  6. Transfer of nucleons at high relative velocities

    NASA Astrophysics Data System (ADS)

    Von Oertzen, W.

    1985-02-01

    We discuss nucleon transfer between bound states of nuclei at high relative velocities. It is shown that the tails of the internal momentum distributions of the nuclear states participating in the transition strongly influence the transfer probabilities at energies between 30-90 MeV/u. Data and DWBA calculations show an exponential decrease of the cross sections in this energy regime and we dub it TGV (Transfer à Grande Vitesse).

  7. High Resolution Velocity Structure in Eastern Turkey

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    We investigate the crust and upper mantle structure of eastern Turkey where the Anatolian, Arabian and Eurasian Plates meet, forming a complex tectonic regime. 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) provide a unique opportunity for studying the high resolution velocity structure of the region. Zor et al. (2003) found an average 46 km thick crust in the Anatolian plateau using a 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 functions alone, however, may result in an apparent depth-velocity trade-off [Ammon et al., 1990]. In order to improve upon this velocity model, we have combined the receiver functions with surface wave data using the joint inversion method of Julia et al. (2000). In this technique, the two sets of observations are combined into a single algebraic equation and each data set is weighted by an estimate of the uncertainty in the observations. The receiver functions are calculated using an iterative time-domain deconvolution technique. We also consider azimuthal changes in the receiver functions and have stacked them into different groups accordingly. We are improving our surface wave model by making Love and Rayleigh dispersion measurements at the ETSE stations and incorporating them into a regional group velocity model for periods between 10 and 100 seconds. Preliminary results indicate a strong trend in the long period group velocities toward the northeast, indicating slow upper mantle velocities in the area consistent with Pn, Sn and receiver function results. Starting models used for the joint inversions include both a 1-D model from a 12-ton dam shot recorded by ETSE [Gurbuz et al., 2004] and

  8. SIMULATIONS OF HIGH-VELOCITY CLOUDS. I. HYDRODYNAMICS AND HIGH-VELOCITY HIGH IONS

    SciTech Connect

    Kwak, Kyujin; Henley, David B.; Shelton, Robin L. E-mail: dbh@physast.uga.edu

    2011-09-20

    We present hydrodynamic simulations of high-velocity clouds (HVCs) traveling through the hot, tenuous medium in the Galactic halo. A suite of models was created using the FLASH hydrodynamics code, sampling various cloud sizes, densities, and velocities. In all cases, the cloud-halo interaction ablates material from the clouds. The ablated material falls behind the clouds where it mixes with the ambient medium to produce intermediate-temperature gas, some of which radiatively cools to less than 10,000 K. Using a non-equilibrium ionization algorithm, we track the ionization levels of carbon, nitrogen, and oxygen in the gas throughout the simulation period. We present observation-related predictions, including the expected H I and high ion (C IV, N V, and O VI) column densities on sightlines through the clouds as functions of evolutionary time and off-center distance. The predicted column densities overlap those observed for Complex C. The observations are best matched by clouds that have interacted with the Galactic environment for tens to hundreds of megayears. Given the large distances across which the clouds would travel during such time, our results are consistent with Complex C having an extragalactic origin. The destruction of HVCs is also of interest; the smallest cloud (initial mass {approx} 120 M{sub sun}) lost most of its mass during the simulation period (60 Myr), while the largest cloud (initial mass {approx} 4 x 10{sup 5} M{sub sun}) remained largely intact, although deformed, during its simulation period (240 Myr).

  9. 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.

  10. 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.

    2016-03-01

    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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Recent observations of the solar wind using the SWICS instrument on the Ulysses spacecraft have shown the presence of high-velocity 'tails' 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 percent of the solar wind density is involved in these tails, which are approximately exponential in shape and persist to V = V(B) + 10V(th) or beyond, where VB is the bulk velocity and V(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.

  17. 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.

  18. 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...

  19. 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...

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. The High Resolution Measurement of P and S Velocity

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Azuma, H.

    2013-12-01

    Seismic explorations, which give seismic velocity, such as seismic refraction method and the down hole - PS logging, are generally applied to the large - scale area. Typically, at these seismic explorations, the receivers spacing ranges from 1.0m to 20.0m and resolution which means a minimal area required to determine seismic velocity is 10 to 50m depending of the receivers spacing. On the other hand, recently, seismic exploration to the smaller area has been applied with increasing frequency. For the large-scale constructions which require severe safety, such as the power station, dam, tunnels, bridges, the rock physical properties in wide area of several hundred meter square, are necessary in order to assess the safety when those are built and an earthquake comes. However, field tests which give the physical properties are almost applied to the area of around 1 m square. In this case, the issue exists whether or not the small field test area is representative of the whole rock property in the site. For this issue, seismic explorations to the small area are adopted for the purpose of the comparison between seismic velocity in the field test area and in the whole site area. It is generally recognized that the accuracy of seismic velocity decrease with decreasing seismic measurement length and number of receivers. To achieve high accuracy with the seismic exploration to the smaller area, we should adjust the spacing closer between the receivers compared to the spacing used by the existing method, and increase the number of receivers. And also, by doing this, we can increase the resolution of velocity results. At first, before the investigation, we calculated the errors of velocity caused by picking error of the arrival time from slope of a straight line using the linear least squares method, based on the Theory of Errors. This method shows that we should use the high frequency seismic wave in order to achieve the increasing the accuracy with the short seismic

  6. Interferometry on diffuse surfaces in high-velocity measurements

    NASA Astrophysics Data System (ADS)

    Pronin, A.; Gupta, V.

    1993-08-01

    An interferometer is presented which is capable of measuring the free-surface velocities and displacements of both specular and diffuse surfaces. The setup utilizes a previously used principle of producing a virtual image of one mirror at the same distance from the photodiode as the second mirror of the interferometer, albeit with considerable simplification. It is shown that use of a He-Ne laser of only 5-mW power can produce high contrast displacement fringes from surfaces of materials with nonuniform microstructure, including composites. Substrates of carbon-carbon composites and polycrystalline alumina with nonuniform microstructure on the scale of 5-10 μm, and with peak velocities up to 150 m/s were considered. An experimental strategy which allows one to covert the optical setup to either a velocity or a displacement interferometer is also discussed. It is further shown that use of a fast photodiode and a high-speed digitizer with a 5-ps rise time provides a time resolution of 0.2 ns for recording the displacement fringes, and allows measuring free surface velocities up to 800 m/s. This is demonstrated by measuring such transient surface velocities with rise times of 1 ns on a specular Si surface. In all the experiments reported here, the surface velocities were produced by the reflection of a stress wave, which in turn was generated on the back surface of the substrate, using a Nd:YAG laser pulse.

  7. SIMULATIONS OF HIGH-VELOCITY CLOUDS. II. ABLATION FROM HIGH-VELOCITY CLOUDS AS A SOURCE OF LOW-VELOCITY HIGH IONS

    SciTech Connect

    Henley, David B.; Kwak, Kyujin; Shelton, Robin L. E-mail: rls@physast.uga.edu

    2012-07-01

    In order to determine if the material ablated from high-velocity clouds (HVCs) is a significant source of low-velocity high ions (C IV, N V, and O VI) such as those found in the Galactic halo, we simulate the hydrodynamics of the gas and the time-dependent ionization evolution of its carbon, nitrogen, and oxygen ions. Our suite of simulations examines the ablation of warm material from clouds of various sizes, densities, and velocities as they pass through the hot Galactic halo. The ablated material mixes with the environmental gas, producing an intermediate-temperature mixture that is rich in high ions and that slows to the speed of the surrounding gas. We find that the slow mixed material is a significant source of the low-velocity O VI that is observed in the halo, as it can account for at least {approx}1/3 of the observed O VI column density. Hence, any complete model of the high ions in the halo should include the contribution to the O VI from ablated HVC material. However, such material is unlikely to be a major source of the observed C IV, presumably because the observed C IV is affected by photoionization, which our models do not include. We discuss a composite model that includes contributions from HVCs, supernova remnants, a cooling Galactic fountain, and photoionization by an external radiation field. By design, this model matches the observed O VI column density. This model can also account for most or all of the observed C IV, but only half of the observed N V.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 3D finite element simulations of high velocity projectile impact

    NASA Astrophysics Data System (ADS)

    Ožbolt, Joško; İrhan, Barış; Ruta, Daniela

    2015-09-01

    An explicit three-dimensional (3D) finite element (FE) code is developed for the simulation of high velocity impact and fragmentation events. The rate sensitive microplane material model, which accounts for large deformations and rate effects, is used as a constitutive law. In the code large deformation frictional contact is treated by forward incremental Lagrange multiplier method. To handle highly distorted and damaged elements the approach based on the element deletion is employed. The code is then used in 3D FE simulations of high velocity projectile impact. The results of the numerical simulations are evaluated and compared with experimental results. It is shown that it realistically predicts failure mode and exit velocities for different geometries of plain concrete slab. Moreover, the importance of some relevant parameters, such as contact friction, rate sensitivity, bulk viscosity and deletion criteria are addressed.

  13. 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.

  14. 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.

  15. HD 69686: A MYSTERIOUS HIGH VELOCITY B STAR

    SciTech Connect

    Huang, Wenjin; Gies, D. R.; McSwain, M. V. E-mail: gies@chara.gsu.ed

    2009-09-20

    We report on the discovery of a high velocity B star, HD 69686. We estimate its space velocity, distance, surface temperature, gravity, and age. With these data, we are able to reconstruct the trajectory of the star and to trace it back to its birthplace. We use evolutionary tracks for single stars to estimate that HD 69686 was born 73 Myr ago in the outer part of our Galaxy (r {approx} 12 kpc) at a position well below the Galactic plane (z {approx} -1.8 kpc), a very unusual birthplace for a B star. Along the star's projected path in the sky, we also find about 12 other stars having similar proper motions, and their photometry data suggest that they are located at the same distance as HD 69686 and probably have the same age. We speculate on the origin of this group by star formation in a high velocity cloud or as a Galactic merger fragment.

  16. A Search for High-Velocity Be Stars

    NASA Astrophysics Data System (ADS)

    Berger, D. H.; Gies, D. R.

    2001-07-01

    We present an analysis of the kinematics of Be stars based upon Hipparcos proper motions and published radial velocities. We find approximately 23 of the 344 stars in our sample have peculiar space motions greater than 40 km s-1 and up to 102 km s-1. We argue that these high-velocity stars are the result of either a supernova that disrupted a binary or ejection by close encounters of binaries in young clusters. Be stars spun up by binary mass transfer will appear as high-velocity objects if there was significant mass loss during the supernova explosion of the initially more massive star, but the generally moderate peculiar velocities of Be X-ray binaries indicate that the progenitors lose most of their mass prior to the supernova (in accordance with model predictions). Binary formation models for Be stars predict that most systems bypass the supernova stage (and do not receive runaway velocities) to create ultimately Be+white dwarf binaries. The fraction of Be stars spun up by binary mass transfer remains unknown, since the post-mass transfer companions are difficult to detect.

  17. 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

  18. 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.

  19. 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.

  20. VELOCITY SPECTRUM FOR H I AT HIGH LATITUDES

    SciTech Connect

    Chepurnov, A.; Lazarian, A.; Stanimirovic, S.; Heiles, Carl; Peek, J. E. G.

    2010-05-10

    In this paper, we present the results of the statistical analysis of high-latitude H I turbulence in the Milky Way. We have observed H I in the 21 cm line, obtained with the Arecibo{sup 3} L-Band Feed Array receiver at the Arecibo radio telescope. For recovering velocity statistics, we have used the velocity coordinate spectrum (VCS) technique. In our analysis, we have used direct fitting of the VCS model, as its asymptotic regimes are questionable for Arecibo's resolution, given the restrictions from thermal smoothing of the turbulent line. We have obtained a velocity spectral index of 3.87 {+-} 0.11, an injection scale of 140 {+-} 80 pc, and an H I cold phase temperature of 52 {+-} 11 K. The spectral index is steeper than the Kolmogorov index and can be interpreted as being due to shock-dominated turbulence.

  1. Constraints on the Orbit of High Velocity Cloud Complex A

    NASA Astrophysics Data System (ADS)

    Fernandes, Alexandre; Benjamin, R. A.; Penn, J. A.; Wakker, B. P.

    2013-01-01

    Galactic high-velocity clouds are generally thought to be circum-galactic clouds of neutral hydrogen gas orbiting the Milky Way at distances of a few to a few hundred kiloparsecs from the disk of the Milky Way. Recent efforts to bracket the distances to these clouds via searches for optical/ultraviolet absorption lines in the spectra of distant halo stars have led to new distances limits for many of the larger cloud "complexes". This advance allows for the calculation of more secure orbits for these clouds, with orbital estimates now available for the Magellanic Stream, GCN (Galactic Center Negative) complex, GCP (Galactic Center Positive, or Smith Cloud) complex, and Complex H. We present new constraints on the trajectory of high velocity cloud Complex A, matching the distance constraints, the radial velocity and gradient in the radial velocity. The dependence of these orbital parameters on the section of the complex matched, the model potential, tidal disruption, and drag forces are all presented. This work was partially supported by the National Science Foundation's REU program through NSF Award AST-1004881 and NASA Astrophysical Theory program award NNX10AI70G.

  2. Effect of velocity spread on operation of high power gyrotrons

    SciTech Connect

    Levush, B.; Cai, S.Y.; Antonsen, T.M. Jr.; Guss, W.C.; Basten, M.A.; Kreischer, K.E.; Temkin, R.

    1995-12-31

    The effect of velocity spread on the operation of 140 GHz gyrotrons has been studied. The performance of two cavities, with low and high Q, has been examined experimentally and theoretically. The simulation code MAGY was modified to include the measured velocity distribution function and the measured pitch angle in order to compare the measured efficiencies with the predicted efficiencies. Based on measurements, the inferred velocity spread at a beam current of 40 A is given by {l_angle}{delta}{upsilon}{sub {perpendicular}}/{upsilon}{sub {perpendicular}}{r_angle}{sub RMS} = 15%. Simulations with this spread produced efficiencies lower than those measured. However, it was found that assuming {l_angle}{delta}{upsilon}{sub {perpendicular}}/{upsilon}{sub {perpendicular}}{r_angle}{sub RMS} = 10% for 40 A current and using the experimentally determined dependence of the spread on the current the calculated efficiencies agree well with the measured efficiencies for the low Q cavity. The efficiency of the low Q gyrotron at 40 A beam current is only 27%. For the same beam current and velocity spread the efficiency of the high Q gyrotron was predicted to be 40% which agrees well with the measured efficiency of 39%.

  3. The formation of discrete high velocity molecular features

    NASA Astrophysics Data System (ADS)

    Hartquist, T. W.; Dyson, J. E.

    1987-10-01

    Clumps embedded in a flowing diffuse medium will be dissipated before ram pressure accelerates them substantially. Molecular hydrogen can be accelerated to high speeds by passing through a slow shock leading a shell at the edge of a wind-driven bubble if the density in the ambient medium drops rapidly enough to allow the shell to accelerate subsequently. The shell will be subject to the Rayleigh-Taylor instability which will drive transonic turbulence but will not initiate the formation of fragments having large density contrasts until the shell reaches sufficient speeds to become thermally unstable. The existence of high velocity discrete features in and the magnitude of the linewidth of the H2 emission from CRL 618 are explained with this acceleration mechanism. High velocity water masers may be formed in a similar fashion, but not Herbig-Haro objects.

  4. 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

  5. Galvanic porous silicon composites for high-velocity nanoenergetics.

    PubMed

    Becker, Collin R; Apperson, Steven; Morris, Christopher J; Gangopadhyay, Shubhra; Currano, Luke J; Churaman, Wayne A; Stoldt, Conrad R

    2011-02-01

    Porous silicon (PS) films ∼65-95 μm thick composed of pores with diameters less than 3 nm were fabricated using a galvanic etching approach that does not require an external power supply. A highly reactive, nanoenergetic composite was then created by impregnating the nanoscale pores with the strong oxidizer, sodium perchlorate (NaClO(4)). The combustion propagation velocity of the energetic composite was measured using microfabricated diagnostic devices in conjunction with high-speed optical imaging up to 930000 frames per second. Combustion velocities averaging 3050 m/s were observed for PS films with specific surface areas of ∼840 m(2)/g and porosities of 65-67%. PMID:21182311

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. High velocity compact clouds in the sagittarius C region

    SciTech Connect

    Tanaka, Kunihiko; Oka, Tomoharu; Matsumura, Shinji; Nagai, Makoto; Kamegai, Kazuhisa

    2014-03-01

    We report the detection of extremely broad emission toward two molecular clumps in the Galactic central molecular zone. We have mapped the Sagittarius C complex (–0.°61 < l < –0.°27, –0.°29 < b < 0.°04) in the HCN J = 4-3, {sup 13}CO J = 3-2, and H{sup 13}CN J = 1-0 lines with the ASTE 10 m and NRO 45 m telescopes, detecting bright emission with 80-120 km s{sup –1} velocity width (in full-width at zero intensity) toward CO–0.30–0.07 and CO–0.40–0.22, which are high velocity compact clouds (HVCCs) identified with our previous CO J = 3-2 survey. Our data reveal an interesting internal structure of CO–0.30–0.07 comprising a pair of high velocity lobes. The spatial-velocity structure of CO–0.40–0.22 can be also understood as a multiple velocity component, or a velocity gradient across the cloud. They are both located on the rims of two molecular shells of about 10 pc in radius. Kinetic energies of CO–0.30–0.07 and CO–0.40–0.22 are (0.8-2) × 10{sup 49} erg and (1-4) × 10{sup 49} erg, respectively. We propose several interpretations of their broad emission: collision between clouds associated with the shells, bipolar outflow, expansion driven by supernovae (SNe), and rotation around a dark massive object. These scenarios cannot be discriminated because of the insufficient angular resolution of our data, though the absence of a visible energy source associated with the HVCCs seems to favor the cloud-cloud collision scenario. Kinetic energies of the two molecular shells are 1 × 10{sup 51} erg and 0.7 × 10{sup 51} erg, which can be furnished by multiple SN or hypernova explosions in 2 × 10{sup 5} yr. These shells are candidates of molecular superbubbles created after past active star formation.

  11. 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.

  12. Velocity measurements on highly turbulent free surface flow using ADV

    NASA Astrophysics Data System (ADS)

    Cea, L.; Puertas, J.; Pena, L.

    2007-03-01

    The 3D instantaneous velocity recorded with an acoustic Doppler velocimeter (ADV) in a highly turbulent free surface flow is analysed using several filters in order to eliminate the corrupted data from the sample. The filters used include the minimum/maximum threshold, the acceleration threshold, and the phase-space threshold. Following some ideas of the phase-space filter, a new method based on the 3D velocity cross-correlation is proposed and tested. A way of computing the constants of the acceleration threshold method is proposed, so no parameters need to be fixed by the user, which makes the filtering process simpler, more objective and more efficient. All the samples analysed are highly turbulent. Nevertheless, the turbulence intensity and the air entrainment vary widely in the flow under study, which produces data records of different quality depending on the measurement point. The performance of the filtering methods when applied to samples of different quality, and the effects of the filtering process in the mean velocity, turbulent kinetic energy and frequency spectra are discussed.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Velocity Crossover Between Hydrous and Anhydrous Forsterite at High Pressures

    SciTech Connect

    Mao, Z.; Jacobsen, S; Smyth, R; Holl, C; Frost, D; Duffy, T

    2010-01-01

    The elastic properties of hydrous forsterite, Mg{sub 2-x}SiO{sub 4}H{sub 2x}, are relevant to interpreting seismic velocity anomalies in the Earth's mantle. In this study, we used Brillouin scattering to determine the single-crystal elasticity of forsterite with 0.9(1) wt.% H{sub 2}O (x = 0.14) to 14 GPa. Aggregate bulk and shear moduli of hydrous forsterite increase with pressure at a greater rate than those of the corresponding anhydrous phase. Compared with anhydrous forsterite, we observe a 7% increase in the pressure derivative of the bulk modulus (K{prime}{sub S0} = 4.50(5)), and a 25% increase in the pressure derivative of the shear modulus (G{prime}{sub 0} = 1.75(5)) for forsterite with near maximum possible water content. Using our results, we calculated the compressional, V{sub P}, and shear, V{sub S}, velocities of forsterite as a function of pressure at 300 K. Whereas V{sub P} and V{sub S} of hydrous forsterite are 0.6% and 0.4% slower than those of anhydrous forsterite at ambient pressure, velocity crossovers at {approx} 3-4 GPa result in higher hydrous forsterite velocities at pressures corresponding to depths below {approx} 120 km. At the pressure of the 410-km discontinuity, V{sub P} and V{sub S} of hydrous forsterite exceed those of anhydrous forsterite by 1.1(1)% and 1.9(1)%, respectively. This implies that incorporation of water could decrease the magnitude of the velocity contrast at 410-km depth between forsterite and wadsleyite. Although the effects of hydration on temperature derivatives of the elastic moduli of forsterite and wadsleyite are not yet known, from the current data we estimate that the presence of {approx} 0.4 wt.% H{sub 2}O in forsterite (at 60 mol%) could lower the P and S velocity contrast at 410-km depth to 3.8(4)% and 4.8(6)%, respectively. At high pressures, hydration also decreases the V{sub P}/V{sub S} ratio of forsterite, and lowers the maximum P wave azimuthal anisotropy and S wave splitting of forsterite.

  2. Velocity alignment leads to high persistence in confined cells.

    PubMed

    Camley, Brian A; Rappel, Wouter-Jan

    2014-06-01

    Many cell types display random motility on two-dimensional substrates but crawl persistently in a single direction when confined in a microchannel or on an adhesive micropattern. Does this imply that the motility mechanism of confined cells is fundamentally different from that of unconfined cells? We argue that both free- and confined-cell migration may be described by a generic model of cells as "velocity-aligning" active Brownian particles previously proposed to solve a completely separate problem in collective cell migration. Our model can be mapped to a diffusive escape over a barrier and analytically solved to determine the cell's orientation distribution and repolarization rate. In quasi-one-dimensional confinement, velocity-aligning cells maintain their direction for times that can be exponentially larger than their persistence time in the absence of confinement. Our results suggest an important connection between single- and collective-cell migration: high persistence in confined cells corresponds with fast alignment of velocity to cell-cell forces. PMID:25019812

  3. 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.

  4. Decision making in high-velocity environments: implications for healthcare.

    PubMed

    Stepanovich, P L; Uhrig, J D

    1999-01-01

    Healthcare can be considered a high-velocity environment and, as such, can benefit from research conducted in other industries regarding strategic decision making. Strategic planning is not only relevant to firms in high-velocity environments, but is also important for high performance and survival. Specifically, decision-making speed seems to be instrumental in differentiating between high and low performers; fast decision makers outperform slow decision makers. This article outlines the differences between fast and slow decision makers, identifies five paralyses that can slow decision making in healthcare, and outlines the role of a planning department in circumventing these paralyses. Executives can use the proposed planning structure to improve both the speed and quality of strategic decisions. The structure uses planning facilitators to avoid the following five paralyses: 1. Analysis. Decision makers can no longer afford the luxury of lengthy, detailed analysis but must develop real-time systems that provide appropriate, timely information. 2. Alternatives. Many alternatives (beyond the traditional two or three) need to be considered and the alternatives must be evaluated simultaneously. 3. Group Think. Decision makers must avoid limited mind-sets and autocratic leadership styles by seeking out independent, knowledgeable counselors. 4. Process. Decision makers need to resolve conflicts through "consensus with qualification," as opposed to waiting for everyone to come on board. 5. Separation. Successful implementation requires a structured process that cuts across disciplines and levels. PMID:10537497

  5. High-velocity cometary dust enters the atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Tricarico, P.

    2015-06-01

    When comet C/2013 A1 (Siding Spring) passed nearby Mars in 2014, it offered an unprecedented opportunity to observe the interaction between the dust tail of the comet and the atmosphere of Mars. Here I provide an overview of a recent series of four articles reporting observations from three satellites fortuitously orbiting Mars at the appropriate time (MAVEN, MEX, and MRO). These observations reveal high-velocity ablation and ionization of metals from the comet, the diffusion and transport processes that operated in Mars' atmosphere, and the abundance of these metals in the comet.

  6. 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.

  7. 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

  8. 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.

  9. High-Velocity H I Gas in Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Koo, Bon-Chul

    1993-05-01

    Using the Hat Creek 85 foot telescope, we had carried out a survey of H I 21 cm emission lines toward all 103 known northern supernova remnants (SNRs) in order to find rapidly expanding SNR shells (Koo & Heiles 1991). We detected 15 SNRs that have associated high-velocity (HV) H I gas, most of which are quite likely the gas accelerated by the SN blast wave. Although the large beam-size (FWHM~ 30') of the 85 foot telescope prevented us to see the structure of the HV H I gas, the H I mass distribution in line-of-sight velocity suggested clumpy shell structures in several SNRs. In order to resolve the structure of the HV H I gas, we have been carrying out high-resolution H I 21 cm line observations using the Arecibo telescope and the VLA. We report preliminary results on two SNRs, CTB 80 and W51. In CTB 80, the VLA observations revealed fast moving H I clumps, which have a dense (n_H ~ 100 cm(-3) ) core surrounded by a relatively diffuse envelope. The clumps are small, 3 pc to 5 pc, and have velocities between +40 km s(-1) and +80 km s(-1) with respect to the systematic velocity of CTB 80. The clumps have relatively large momentum per unit volume, which implies that they have been swept-up at an early stage of the SNR evolution. By analyzing the Arecibo data, we found that the interstellar medium around CTB 80 is far from being uniform and homogeneous, which explains the peculiar morphology of CTB 80 in infrared and radio continuum. In W51, HV H I gas moving up to v_LSR>+150 km s(-1) has been detected. The H I distribution is elongated along the northwest-southeast direction, and the peak is very close to an X-ray bright region. We discuss the implications of our results in relation to the X-ray and the radio continuum morphology of W51. This work was supported in part by NON DIRECTED RESEARCH FUND, Korea Research Foundation, 1992.

  10. 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.

  11. 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.

  12. 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.

  13. High Velocity Horizontal Motions at the Edge of Sunspot Penumbrae

    NASA Astrophysics Data System (ADS)

    Hagenaar-Daggett, Hermance J.; Shine, R.

    2010-05-01

    The outer edges of sunspot penumbrae have long been noted as a region of interesting dynamics including formation of MMFs, extensions and retractions of the penumbral tips, fast moving (2-3 km/s) bright features dubbed"streakers", and localized regions of high speed downflows interpreted as Evershed "sinks". Using 30s cadence movies of high spatial resolution G band and Ca II H images taken by the Hinode SOT/FPP instrument from 5-7 Jan 2007, we have been investigating the penumbra around a sunspot in AR 10933. In addition to the expected phenomena, we also see occasional small dark crescent-shaped features with high horizontal velocities (6.5 km/s) in G band movies. These appear to be emitted from penumbral tips. They travel about 1.5 Mm developing a bright wake that evolves into a slower moving (1-2 km/s) bright feature. In some cases, there may be an earlier outward propagating disturbance within the penumbra. We have also analyzed available Fe 6302 Stokes V images to obtain information on the magnetic field. Although only lower resolution 6302 images made with a slower cadence are available for these particular data sets, we can establish that the features have the opposite magnetic polarity of the sunspot. This observation may be in agreement with simulations showing that a horizontal flux tube develops crests that move outward with a velocity as large as 10 km/s. This work was supported by NASA contract NNM07AA01C.

  14. 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.

  15. 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.

  16. Spherically symmetric high-velocity plasma expansions into background gases

    NASA Technical Reports Server (NTRS)

    Tan, T.-H.; Borovsky, J. E.

    1986-01-01

    Spherically symmetric plasmas with high expansion velocities have been produced by irradiating targets with eight beams from the Helios CO2 laser in the presence of gases at various pressures. Attention was given to the properties of the target-emitted ions in order to obtain information about the ion-acceleration mechanisms in plasma expansions. Photoionization of the ambient gases by the soft X-ray emission from the laser-irradiated targets produced background plasmas, permitting plasma counterstreaming experiments to be performed in spherical geometry. Successful laser-target coupling in the presence of back-ground gases is obtained; modification of the ion acceleration in accordance with isothermal-expansion models is observed; and an absence of collective coupling between collisionless counterstreaming plasmas is found.

  17. Stetson Revisited: Identifying High-Velocity Early-Type Stars

    NASA Astrophysics Data System (ADS)

    Kinman, T. D.

    1999-02-01

    Our current knowledge of the local blue horizontal branch (BHB) and other high-velocity early-type stars largely depends upon Stetson's survey (in the 1980s) that was based on the SAO catalog. He selected the stars by their reduced proper motion as a function of spectral type. We argue that it is worth repeating Stetson's work using a more recent proper motion source such as the PPM catalog (published 1991) which (inter alia) contains many more stars with spectral types than the SAO. A photometric program is described (using the 0.9-m telescope at full moon) to observe the candidate stars (mostly with V<=10 mag.) and so identify the interesting stars (BHB, RR Lyrae, SW Phoenicis variables, Blue stragglers) that may be expected among them. The new data would materially improve our knowledge of the local space densities of these stars (Kinman 1998).

  18. Heterogeneous fragmentation of metallic liquid microsheet with high velocity gradient

    NASA Astrophysics Data System (ADS)

    An-Min, He; Pei, Wang; Jian-Li, Shao

    2016-01-01

    Large-scale molecular dynamics simulations are performed to study the fragmentation of metallic liquid sheets with high velocity gradient. Dynamic fragmentation of the system involves the formation of a network of fragments due to the growth and coalescence of holes, decomposition of the network into filaments, and further breakup of the filaments into spherical clusters. The final size distribution of the fragmented clusters in the large volume limit is found to obey a bilinear exponential form, which is resulted from the heterogeneous breakup of quasi-cylindrical filaments. The main factors contributing to fragmentation heterogeneity are introduced, including strain rate inhomogeneity and matter distribution nonuniformity of fragments produced during decomposition of the network structure. Project supported by the Science and Technology Development Foundation of China Academy of Engineering Physics (Grant Nos. 2013A0201010 and 2015B0201039) and the National Natural Science Foundation of China (Grant No. 11402032).

  19. Introduction to High-Velocity Suspension Flame Spraying (HVSFS)

    NASA Astrophysics Data System (ADS)

    Gadow, Rainer; Killinger, Andreas; Rauch, Johannes

    2008-12-01

    High-velocity suspension flame spraying (HVSFS) has been developed to thermally spray suspensions containing micron, submicron, and nanoparticles with hypersonic speed. For this purpose, the suspension is introduced directly into the combustion chamber of a modified HVOF torch. The aim in mind is to achieve dense coatings with a refined microstructure. Especially from nanostructured coatings superior physical properties are expected for many potential applications. Direct spraying of suspensions offers flexibility in combining and processing different materials. It is a cost-saving process and allows the allocation of entirely new application fields. The paper gives an overview of the HVSFS spray method and will present some actual results that have been achieved by spraying the nanooxide ceramic materials Al2O3, TiO2, 3YSZ, and Cr2O3.

  20. Magnetized collisionless shock studies using high velocity plasmoids

    NASA Astrophysics Data System (ADS)

    Weber, Thomas; Intrator, Thomas; Gao, Kevin

    2012-10-01

    Magnetized collisionless shocks are ubiquitous throughout the cosmos and are observed to accelerate particles to relativistic velocities, amplify magnetic fields, transport energy, and create non-thermal distributions. They exhibit transitional scale lengths much shorter than the collisional mean free path and are mediated by collective interactions rather than Coulomb collisions. The Magnetized Shock Experiment (MSX) leverages advances in Field Reversed Configuration (FRC) plasmoid formation and acceleration to produce highly supersonic and super-Alfvènic supercritical shocks with pre-existing magnetic field at perpendicular, parallel or oblique angles to the direction of propagation. Adjustable shock speed, density, and magnetic field provide unique access to a range of parameter space relevant to a variety of naturally occurring shocks. This effort examines experimentally, analytically, and numerically the physics of collisionless shock formation, structure, and kinetic effects in a laboratory setting and draw comparisons between experimental data and astronomical observations. Approved for Public Release: LA-UR-12-22886

  1. 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.

  2. Distance limits to intermediate- and high-velocity clouds

    NASA Astrophysics Data System (ADS)

    Smoker, J. V.; Fox, A. J.; Keenan, F. P.

    2011-08-01

    We present optical spectra of 403 stars and quasi-stellar objects in order to obtain distance limits towards intermediate- and high-velocity clouds (IHVCs), including new Fibre-fed Extended Range Optical Spectrograph (FEROS) observations plus archival ELODIE, FEROS, High Resolution Echelle Spectrometer (HIRES) and Ultraviolet and Visual Echelle Spectrograph (UVES) data. The non-detection of Ca II K interstellar (IS) absorption at a velocity of -130 to -60 km s-1 towards HDE 248894 (d˜ 3 kpc) and HDE 256725 (d˜ 8 kpc) in data at signal-to-noise ratio (S/N) > 450 provides a new firm lower distance limit of 8 kpc for the anti-centre shell HVC. Similarly, the non-detection of Ca II K IS absorption towards HD 86248 at S/N ˜ 500 places a lower distance limit of 7.6 kpc for Complex EP, unsurprising since this feature is probably related to the Magellanic System. The lack of detection of Na I D at S/N = 35 towards Mrk 595 puts an improved upper limit for the Na I column density of log (NNaD <) 10.95 cm-2 towards this part of the Cohen Stream where Ca II was detected by Wakker et al. Absorption at ˜-40 km s-1 is detected in Na I D towards the Galactic star PG 0039+049 at S/N = 75, placing a firm upper distance limit of 1 kpc for the intermediate-velocity cloud south (IVS), where a tentative detection had previously been obtained by Centurión et al. Ca II K and Na I D absorption is detected at -53 km s-1 towards HD 93521, which confirms the upper distance limit of 2.4 kpc for part of the IV arch complex obtained using the International Ultraviolet Explorer (IUE) data by Danly. Towards HD 216411 in Complex H a non-detection in Na D towards gas with log(?) = 20.69 cm-2 puts a lower distance limit of 6.6 kpc towards this HVC complex. Additionally, Na I D absorption is detected at -43.7 km s-1 in the star HD 218915 at a distance of 5.0 kpc in gas in the same region of the sky as Complex H. Finally, the Na I/Ca II and Ca II/H I ratios of the current sample are found to lie

  3. 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. PMID:7749000

  4. 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.

  5. Laboratory investigations involving high-velocity oxygen atoms

    NASA Technical Reports Server (NTRS)

    Leger, Lubert J.; Koontz, Steven L.; Visentine, James T.; Cross, Jon B.

    1989-01-01

    Facilities for measuring material reactive characteristics have been under development for several years and span the atom energy range from thermal to 5 eV, the orbital collision energy. One of the high-atom energy facilities (The High Intensity/Energy Atomic Oxygen Source) capable of simulating the reactive part of LEO is described, along with results of beam characterization and preliminary material studies. The oxygen atom beam source was a continuous wave plasma produced by focusing a high-power CO2 laser through a lens system into a rare gas/molecular oxygen mixture chamber at elevated temperature. Material samples were exposed to the high velocity beam through an external feedthrough. The facility showed good stability in continued operation for more than 100 hours, producing fluences of 10 to the 21st to 10 to the 22nd atoms/sq cm. Reaction efficiencies and surface morphology have been measured for several materials at energies of 1.5 and 2.8 eV, matching with data generated from previous space flights. Activation energies for carbon and Kapton as measured in this facility were 800 cal/mole.

  6. 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

  7. 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.

  8. 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).

  9. Process gases for high velocity oxy-fuel thermal spraying

    SciTech Connect

    Creffield, G.K.; Chapman, I.F.; Cole, M.A.; Page, W.J.; McDonough, T.

    1994-12-31

    The importance of fuel and other process gases for high velocity oxy-fuel (HVOF) thermal spraying and especially the delivery of them to the point of use is well recognized. Problems associated with the supply of liquid fuel gases, at the high flow rates and pressures required by this process, have been addressed. Considerable development work has gone into designing an appropriate liquid withdrawal and vaporizer system for propylene, which overcomes these previous difficulties and enables users to maintain adequate fuel gas flow rates in order to ensure optimum operating conditions for the production of high quality coatings. A feature of the thermal spray process is that the temperature of the workpiece is kept low, typically below 150 C, in order to reduce residual stresses in the coating and to protect heat sensitive substrates. Traditionally this has been by compressed air, however, improved cooling has been achieved using carbon dioxide. Specially designed equipment is now available which provides and directs a cold mixture of carbon dioxide gas and solid particles (snow) via suitable nozzles, on the workpiece. The position of the cooling stream can be varied, depending on the application. These developments emphasize the importance now attached to providing dedicated gas installation packages for HVOF.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. High velocity vortex channeling in vicinal YBCO thin films

    PubMed Central

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

    2012-01-01

    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. PMID:23482832

  15. 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. PMID:23482832

  16. Magnetized Collisionless Shock Studies Using High Velocity Plasmoids

    NASA Astrophysics Data System (ADS)

    Weber, Thomas; Intrator, T.

    2013-04-01

    Magnetized collisionless shocks are ubiquitous throughout the cosmos and are observed to accelerate particles to relativistic velocities, amplify magnetic fields, transport energy, and create non-thermal distributions. They exhibit transitional scale lengths much shorter than the collisional mean free path and are mediated by collective interactions rather than Coulomb collisions. The Magnetized Shock Experiment (MSX) leverages advances in Field Reversed Configuration (FRC) plasmoid formation and acceleration to produce highly supersonic and super-Alfvénic supercritical shocks with pre-existing magnetic field at perpendicular, parallel or oblique angles to the direction of propagation. Adjustable shock speed, density, and magnetic field provide unique access to a range of parameter space relevant to a variety of naturally occurring shocks. This effort examines experimentally, analytically, and numerically the physics of collisionless shock formation, structure, and kinetic effects in a laboratory setting and draw comparisons between experimental data and astronomical observations. Supported by DOE Office of Fusion Energy Sciences and National Nuclear Security Administration under LANS contract DE-AC52-06NA25369 Approved for Public Release: LA-UR-12-22886

  17. Magnetized collisionless shock studies using high velocity plasmoids

    NASA Astrophysics Data System (ADS)

    Weber, T.; Intrator, T.; Gao, K.

    2012-12-01

    Magnetized collisionless shocks are ubiquitous throughout the cosmos and are observed to accelerate particles to relativistic velocities, amplify magnetic fields, transport energy, and create non-thermal distributions. They exhibit transitional scale lengths much shorter than the collisional mean free path and are mediated by collective interactions rather than Coulomb collisions. The Magnetized Shock Experiment (MSX) leverages advances in Field Reversed Configuration (FRC) plasmoid formation and acceleration to produce highly supersonic and super-Alfvènic supercritical shocks with pre-existing magnetic field at perpendicular, parallel or oblique angles to the direction of propagation. Adjustable shock speed, density, and magnetic field provide unique access to a range of parameter space relevant to a variety of naturally occurring shocks. This effort examines experimentally, analytically, and numerically the physics of collisionless shock formation, structure, and kinetic effects in a laboratory setting and draw comparisons between experimental data and astronomical observations. Supported by DOE Office of Fusion Energy Sciences and National Nuclear Security Administration under LANS contract DE-AC52-06NA25369 Approved for Public Release: LA-UR-12-22886

  18. Do high-velocity clouds form by thermal instability?

    NASA Astrophysics Data System (ADS)

    Binney, James; Nipoti, Carlo; Fraternali, Filippo

    2009-08-01

    We examine the proposal that the HI `high-velocity' clouds (HVCs) surrounding the Milky Way and other disc galaxies form by condensation of the hot galactic corona via thermal instability. Under the assumption that the galactic corona is well represented by a non-rotating, stratified atmosphere, we find that for this formation mechanism to work the corona must have an almost perfectly flat entropy profile. In all other cases, the growth of thermal perturbations is suppressed by a combination of buoyancy and thermal conduction. Even if the entropy profile were nearly flat, cold clouds with sizes smaller than 10kpc could form in the corona of the Milky Way only at radii larger than 100kpc, in contradiction with the determined distances of the largest HVC complexes. Clouds with sizes of a few kpc can form in the inner halo only in low-mass systems. We conclude that unless even slow rotation qualitatively changes the dynamics of a corona, thermal instability is unlikely to be a viable mechanism for formation of cold clouds around disc galaxies.

  19. A study of high-velocity combustion wire molybdenum coatings

    NASA Astrophysics Data System (ADS)

    Modi, S. C.; Calla, Eklavya

    2001-09-01

    In this paper, coatings manufactured using the high-velocity combustion wire (HVCW) spray process have been studied. Molybdenum coatings were prepared in this study, and wavelength dispersive x-ray analysis (WDX) investigations were carried out to ascertain the oxygen content of the coating and its distribution. The x-ray diffraction (XRD) analysis of the coating was also carried out to determine the phases present in the coating. Based on the above data, the authors explain the HVCW-sprayed molybdenum coating microstructure properties. These coatings were also sprayed using a modified aircap design. The parameters varied for the molybdenum coatings by HVCW and were (1) the distance of the substrate from the spray gun and (2) the wire feed rate of the gun. The wear test and coefficient of friction measurements were also carried out for the coatings. Air plasma spraying of Mo-25% NiCrBSi coatings was carried out, and these coatings were further checked for wear friction properties.

  20. Spectroscopy of High Velocity Compact Toroids on CTIX

    NASA Astrophysics Data System (ADS)

    Jungwirth, Nick; Horton, Robert; Klauser, Ruth; Hwang, David

    2010-11-01

    High density toroidal plasmas can reach speeds exceeding 200 km/s using coaxial accelerators such as CTIX at UC Davis. Applications of these compact toroids (CTs) include the fueling of next generation tokamaks and stellarators. An important CT diagnostic is to monitor atomic line radiation from CT ions. In this investigation we develop a reliable method of measuring a broad range (40 nm) of the CT spectrum from multiple positions. Our system employs fiber-optic cables to transmit the signal to a spectrometer operating in the 300-1300 nm range. A gated, intensified, CCD camera surveys the CT emission spectrum at a fixed time over a range of wavelengths. Additionally, a photomultiplier is used to investigate the time dependence of particular wavelengths of interest (monochrometer mode). Such measurements enable the study of CT temperature, density, impurity content, and CT velocity. The fiber-optic system will first be used to survey the emission spectrum of CTIX in typical operation, and to identify candidate lines for monochrometer operation.

  1. Nonintrusive, multipoint velocity measurements in high-pressure combustion flows

    NASA Technical Reports Server (NTRS)

    Allen, M.; Davis, S.; Kessler, W.; Legner, H.; Mcmanus, K.; Mulhall, P.; Parker, T.; Sonnenfroh, D.

    1993-01-01

    A combined experimental and analytical effort was conducted to demonstrate the applicability of OH Doppler-shifted fluorescence imaging of velocity distributions in supersonic combustion gases. The experiments were conducted in the underexpanded exhaust flow from a 6.8 atm, 2400 K, H2-O2-N2 burner exhausting into the atmosphere. In order to quantify the effects of in-plane variations of the gas thermodynamic properties on the measurement accuracy, a set of detailed measurements of the OH (1,0) band collisional broadening and shifting in H2-air gases was produced. The effect of pulse-to-pulse variations in the dye laser bandshape was also examined in detail and a modification was developed which increased in the single pulse bandwidth, thereby increasing the intraimage velocity dynamic range as well as reducing the sensitivity of the velocity measurement to the gas property variations. Single point and imaging measurements of the velocity field in the exhaust flowfield were compared with 2D, finite-rate kinetics simulations of the flowfield. Relative velocity accuracies of +/- 50 m/s out of 1600 m/s were achieved in time-averaged imaging measurements of the flow over an order of magnitude variation in pressure and a factor of two variation in temperature.

  2. Two high resolution velocity vector analyzers for cosmic dust particles

    NASA Technical Reports Server (NTRS)

    Auer, S.

    1975-01-01

    Two new methods are described to measure velocities and angles of incidence of charged cosmic dust particles with precisions of about 1% and 1 deg, respectively. Both methods employ four one-dimensional position-sensitive detectors in series. The first method utilizes a charge-dividing technique while the second utilizes a time-of-flight technique for determining the position of a particle inside the instrument. The velocity vectors are measured although mechanical interaction between the particle and the instrument is completely avoided. Applications to cosmic dust composition and collection experiments are discussed. The range of radii of measurable particles is from about 0.01 to 100 microns at velocities from 1 to 80 km/sec.

  3. 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.

  4. High Proper Motion Stars. III. Radial Velocities of 24 Late-Type Dwarfs

    NASA Astrophysics Data System (ADS)

    Dawson, P. C.; De Robertis, M. M.

    1998-11-01

    We report 27 radial velocity measurements for 24 stars, all with annual proper motions larger than 1". For 17 of these, no velocities have previously been published. We identify a few stars that may be spectroscopic binaries and a sdK star of spectacularly high space velocity.

  5. PERFORMANCE OF A HIGH-VELOCITY PULSE-JET FILTER, II

    EPA Science Inventory

    The report gives results of a study of the performance of a high-velocity pulse-jet filter. Such filtration has distinct advantages over low-velocity filtration in that the equipment required to clean a gas stream is reduced in size and initial cost as velocity increases. Althoug...

  6. PERFORMANCE OF A HIGH-VELOCITY PULSE-JET FILTER, III

    EPA Science Inventory

    The report gives results of a continuing study of the performance of a high-velocity pulse-jet filter. Such filtration has distinct advantages over low-velocity filtration in that the equipment required to clean a gas stream is reduced in size and initial cost as filtration veloc...

  7. 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

  8. Treatment protocol for high velocity/high energy gunshot injuries to the face.

    PubMed

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

    2012-03-01

    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

  9. 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.

  10. High velocity sliding at polycrystalline ductile metal interfaces

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    We present the results of large scale 3-dimensional NonEquilibrium Molecular Dynamics (NEMD) simulations for Al-Al and Al-Ta interfaces for sliding velocities in the range 20-4000 m/s at pressures of 15 GPa. System sizes include 8 M, 26 M and 138 M atoms for times to 40 ns. We discuss polycrystalline samples with initial grain sizes of 13 nm and 20 nm. For velocities above a size dependent critical velocity, vc, the frictional force per unit area agrees with single crystal simulations. For velocities below vc, the polycrystalline interfaces evolve to a new steady state grain size distribution characterized by very large plastic deformation with larger grain sizes, time dependent coarsening and refinement, a graded size distribution in the direction normal to the sliding interface, and significantly larger frictional forces per unit area compared to similar single crystal sliding interfaces. We also find that for the Al-Ta interface the frictional properties are determined by the weaker Al material. 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.

  11. 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.

  12. Influence of oxygenated fuels on the emissions from three pre-1985 light-duty passenger vehicles

    SciTech Connect

    Stump, F.D.; Knapp, K.T.; Ray, W.D.; Siudak, P.D.; Snow, R.F.

    1994-06-01

    Tailpipe and evaporative emissions from three pre-1985 passenger motor vehicles operating on an oxygenated blend fuel and on a nonoxgenated base fuel were characterized. Emission data were collected for vehicles operating over the Federal Test Procedure at 40, 75, and 90 F to simulate ambient driving conditions. The two fuels tested were a commercial summer grade regular gasoline (the nonoxgenated base fuel) and an oxygenated fuel containing 9.5 percent methyl ter-butyl ether (MTBE), more olefins, and fewer aromatics than the base fuel. The emissions measured were total hydrocarbons (THCs), speciated hydrocarbons, speciated aldehydes, carbon monoxide (CO), oxides of nitrogen (NOX), benzene, and 1,3-butadiene. This study showed no pattern of tailpipe regulated emission reduction when oxygenated fuel was used. THC, CO, benzene, and 1,3-butadiene emissions from both fuels and all vehicles, in general, decreased with increasing test temperature, whereas NOX emissions, in general, increased with increasing test temperature.

  13. Effectiveness of mandated oxygenated fuel usage to reduce carbon monoxide exhaust levels in Colorado

    SciTech Connect

    Cagle, G.A.

    1989-01-01

    An examination of Colorado Automobile Inspection and Readjustment (A.I.R.) two-speed exhaust emissions testing results was undertaken to evaluate changes in carbon monoxide exhaust levels due to the use of oxygenated fuels. Vehicles utilized within the study were separated according to their various emission control technologies: precatalyst (1938 to 1974), catalyst (1975 to 1980), and closed-loop (1981 to 1988). It was found that pre-catalyst and catalyst vehicles utilizing oxygenated fuels had significant reductions in carbon monoxide exhaust levels at 2,500 R.P.M. Results for closed-loop vehicles at 2,500 R.P.M. showed no significant reductions in carbon monoxide exhaust levels. Further examination of idle data for closed-loop vehicles indicated that a small percentage of these vehicles were considered gross-emitters based on the 1.5 percent cut-point set in Colorado. Results of the study indicated that the impact of oxygenated fuels, as well as the rationale for using such fuels as a carbon monoxide reduction strategy, may be difficult to justify as newer, more sophisticated light-duty vehicles comprise a larger proportion of the overall vehicle population in Colorado.

  14. High Precision Measurement of Stellar Radial Velocity Variations

    NASA Technical Reports Server (NTRS)

    Cochran, W. D.

    1984-01-01

    A prototype instrument for measurement of stellar radial velocity variations to a precision of a few meters per second is discussed. The instrument will be used to study low amplitude stellar non-radial oscillations, to search for binary systems with large mass ratios, and ultimately to search for extrasolar planetary systems. The instrument uses a stable Fabry-Perot etalon, in reflection, to impose a set of fixed reference absorption lines on the stellar spectrum before it enters the coude spectrograph of the McDonald Observatory 2.7-m telescope. The spectrum is recorded on the Octicon detector, which consists of eight Reticon arrays placed end to end. Radial velocity variations of the star are detected by measuring the shift of the stellar lines with respect the artificial Fabry-Perot lines, and correcting for the known motions in the solar system.

  15. High-Velocity Jets in Recurrent Nova Outbursts

    NASA Astrophysics Data System (ADS)

    Kato, Mariko; Hachisu, Izumi

    2003-04-01

    Very fast bipolar mass outflows are suggested from emission-line profiles during the early stage of outbursts in the recurrent nova U Sco. The ejection velocity reaches 5000 or 6000 km s-1 at the optical peak and gradually decreases in time. Such properties have not been reproduced so far in nova theories. We propose a jet-shaped mass outflow as a mechanism of acceleration up to several thousand kilometers per second. The mass flow is accelerated where the jet is shaped, which is deep inside the region where the spherically symmetric winds would be accelerated. The terminal jet velocity depends sensitively on the white dwarf mass but weakly on other parameters.

  16. Vortex shedding flow meter performance at high flow velocities

    NASA Technical Reports Server (NTRS)

    Siegwarth, J. D.

    1986-01-01

    In some of the ducts of the Space Shuttle Main Engine (SSME), the maximum liquid oxygen flow velocities approach 10 times those at which liquid flow measurements are normally made. The hydrogen gas flow velocities in other ducts exceed the maximum for gas flow measurement by more than a factor of 3. The results presented here show from water flow tests that vortex shedding flow meters of the appropriate design can measure water flow to velocities in excess of 55 m/s, which is a Reynolds number of about 2 million. Air flow tests have shown that the same meter can measure flow to a Reynolds number of at least 22 million. Vortex shedding meters were installed in two of the SSME ducts and tested with water flow. Narrow spectrum lines were obtained and the meter output frequencies were proportional to flow to + or - 0.5% or better over the test range with no flow conditioning, even though the ducts had multiple bends preceeding the meter location. Meters with the shedding elements only partially spanning the pipe and some meters with ring shaped shedding elements were also tested.

  17. 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.

  18. 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.

  19. 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

  20. Detection of a second high-velocity component in the highly ionized wind from PG 1211+143

    NASA Astrophysics Data System (ADS)

    Pounds, Ken; Lobban, Andrew; Reeves, James; Vaughan, Simon

    2016-04-01

    An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG1211+143 in 2014 has revealed a more complex highly ionized, high-velocity outflow. The detection of previously unresolved spectral structure in Fe K absorption finds a second outflow velocity component of the highly ionized wind, with an outflow velocity of v ˜ 0.066 ± 0.003c, in addition to a still higher velocity outflow of v ˜ 0.129 ± 0.002c consistent with that first seen in 2001. We note that chaotic accretion, consisting of many prograde and retrograde events, offers an intriguing explanation of the dual velocity wind. In that context the persisting outflow velocities could relate to physically distinct orientations of the inner accretion flow, with prograde accretion yielding a higher launch velocity than retrograde accretion in a ratio close to that observed.

  1. 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.

  2. Ultrafine particle size distribution during high velocity impact of high density metals

    NASA Astrophysics Data System (ADS)

    Buonanno, Giorgio; Stabile, Luca; Ruggiero, Andrew; Iannitti, Gianluca; Bonora, Nicola

    2012-03-01

    In the event of high-energy penetrator impact, people involved in battlefield scenarios are exposed to the additional hazard stemming from ultrafine metallic particles, i.e. exposure, inhalation, and respiration of aerolized metals. In order to have reliable quantitative measurement of the aerosol particles generated under controlled impact conditions, an experimental set-up was designed to perform impact tests with light gas-gun in chamber. During the impact events, aerosol particle size distributions and total concentrations were measured with a one-second time resolution. In this study preliminary results relative to high purity copper projectile impact at different velocities are presented.

  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. 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%.

  5. High spatial range velocity measurements in a high Reynolds number turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    de Silva, C. M.; Gnanamanickam, E. P.; Atkinson, C.; Buchmann, N. A.; Hutchins, N.; Soria, J.; Marusic, I.

    2014-02-01

    Here, we detail and analyse a multi-resolution particle image velocity measurement that resolves the wide range of scales prevalent in a zero pressure gradient turbulent boundary layer at high Reynolds numbers (up to Reτ ≈ 20 000). A unique configuration is utilised, where an array of eight high resolution cameras at two magnification levels are used simultaneously to obtain a large field of view, while still resolving the smaller scales prevalent in the flow. Additionally, a highly magnified field of view targeted at the near wall region is employed to capture the viscous sublayer and logarithmic region, with a spatial resolution of a few viscous length scales. Flow statistics from these measurements show good agreement with prior, well resolved hot-wire anemometry measurements. Analysis shows that the instantaneous wall shear stress can be reliably computed, which is historically known to be challenging in boundary layers. A statistical assessment of the wall shear stress shows good agreement with existing correlations, prior experimental and direct numerical simulation data, extending this view to much higher Reynolds numbers. Furthermore, conditional analysis using multiple magnification levels is detailed, to study near-wall events associated with high skin friction fluctuations and their associated overlaying structures in the log region. Results definitively show that the passage of very large-scale positive (or negative) velocity fluctuations are associated with increased (or reduced) small-scale variance in wall shear stress fluctuations.

  6. High-velocity, high-excitation neutral carbon in a cloud in the Vela supernova remnant

    NASA Technical Reports Server (NTRS)

    Jenkins, Edward B.; Wallerstein, George

    1995-01-01

    HD 72089 is situated behind the Vela supernova remnant, and the interstellar absorption lines in the spectrum of this star are remarkable for two reasons. First, there are six distinct velocity components that span the (heliocentric) velocity range -60 to +121 km/s in the lines of Na I and Ca II. Second, two of the components at high velocity, one at +85 km/s and another at +121.5 km/s, have densities that are large enough to produce observable lines from neutral carbon. The gas moving at +121.5 km/s has such a large pressure that the excited fine-structure levels of the ground electronic state of C I are collisionally populated nearly in proportion to their level degeneracies. This high-velocity gas exhibits unusually low column densities of Mg I and Na I, compared to that of C I. We propose that the +121.5 km/s component represents gas that has cooled and recombined in a zone that follows a shock driven into a cloud by the very recent passage of a supernova blast wave. A representative preshock density of n(sub H) approximately = 13/cc and velocity v(sub s) = 100 km/s is indicated by the strength of diffuse (O III) emission lines seen in directions very near HD 72089. The strong collisional population of excited C I and apparent absence of excited levels of O I give a most favorable fit to the conditions 1000 less than n(sub H) less than 2900/cc over a temperature range 300 less than T less than 1000 K. The fact that the compression is not substantially more than this indicates that the preshock gas may have had an embedded, transverse magnetic field with a strength B greater than or approximately = 1 micro-G. The large dynamical pressure of the supernova blast wave that would be needed to create the cloud shock that we describe implies that the energy of the supernova was 8 x 10(exp 51) ergs, if the Vela remnant is 500 pc away. We can bring this value much closer to typical supernova energies E less than or approximately = 10(exp 51) ergs if the distance to the

  7. Influence of oxygenated fuels on the emissions from three pre-1985 light-duty passenger vehicles

    SciTech Connect

    Stump, F.D.; Knapp, K.T.; Ray, W.D. ); Siudak, P.D.; Snow, R.F. )

    1994-06-01

    Tailpipe and evaporative emissions from three pre-1985 passenger motor vehicles operating on an oxygenated blend fuel and on a nonoxygenated base fuel were characterized. Emission data were collected for vehicles operating over the Federal Test Procedure at 40, 75, and 90[degree]F to simulate ambient driving conditions. The two fuels tested were a commercial summer grade regular gasoline (the nonoxygenated base fuel) and an oxygenated fuel containing 9.5 percent methyl tert-butyl ether (MTBE), more olefins, and fewer aromatics than the base fuel. The emissions measured were total hydrocarbons (THCs), speciated hydrocarbons, speciated aldehydes, carbon monoxide (CO), oxides of nitrogen (NO[sub x]), benzene, and 1,3-butadiene. This study showed no pattern of tailpipe regulated emission reduction when oxygenated fuel was used. Tailpipe emissions from the 1984 Buick Century without a catalyst and the 1977 Mustang with catalyst decreased with the MTBE fuel. However, emissions from the 1984 Buick Century and the 1980 Chevrolet Citation, both fitted with catalysts increased. The vehicles emitted more 1,3-butadiene and, in general, more NO[sub x] when operated with the base fuel. THC, CO, benzene, and 1,3-butadiene emissions from both fuels and all vehicles, in general, decreased with increasing test temperature, whereas NO[sub x] emissions, in general, increased with increasing test temperature. 14 refs., 1 fig., 9 tabs.

  8. 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.

  9. 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.

  10. Thin Shell, High Velocity, High-Foot ICF 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.; Doeppner, T.; Hinkel, D. E.; Berzak Hopkins, L. F.; Le Pape, S.; Macphee, A. G.; Pak, A.; Park, H.-S.; Patel, P. K.; Robey, H. F.; Remington, B. A.; Salmonson, J. D.; Springer, P. T.; Tommasini, R.

    2014-10-01

    Experiments have recently been conducted at the National Ignition Facility utilizing ICF capsule ablators that are 175 μm in thickness, 10% thinner than the nominal thickness capsule used throughout the High-Foot and most of the National Ignition Campaigns. 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. Early results have shown good repeatability, with little to no hydrodynamic mix into the DT hot-spot, and >1/2 the yield coming from α-particle self-heating. This work performed under the auspices of U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  11. Ultra Low Velocity Zone existence in the high shear velocity region beneath Cocos Plate, Central America, and the Caribbean

    NASA Astrophysics Data System (ADS)

    Yu, S.; Garnero, E.; Shim, S. H. D.; Zhao, C.

    2014-12-01

    The lowermost mantle beneath subduction is typically characterized by higher than average shear wave speeds, often with the presence of one or more D" discontinuities. These regions are considered the cooler parts of the convective cycle, in contrast to warmer zones of convective return flow, namely, the vicinity of large low shear velocity provinces (LLSVPs). Ultra-low velocity zones (ULVZs) have been long characterized as related to elevated temperature (and/or chemistry) of LLSVP regions. However, some past work has suggested evidence for ULVZ in the presumed cooler regions. In this study we investigate the region beneath the Cocos Plate, Central America, and the Carribbean for ULVZ using high quality broadband Transportable Array data from EarthScope's USArray for the presence of ULVZs. We utilize an ScS-stripping technique that combines a precursor and postcursor to ScS that arise from ULVZ structure, if present. The precursor is a reflection off the top of the ULVZ, while the postcursor is a core-reflection with an added reverberation between the ULVZ top and the core-mantle boundary (CMB). We collected data from deep South American earthquakes recorded in North America and stack data in geographic bins. We find clear evidence for a ULVZ beneath the Gulf of Mexico, but the rest of the study area appears to lack any significant structure. The structure we find is of the order of 100 km wide. The ULVZ properties will be constrained by comparison to predictions from synthetic seismograms. We explore hypotheses for the origin of a ULVZ in a high shear velocity region. These include mineralogical heterogeneities that convective currents have collected; notable possibilities are accumulated melts from subducted materials, such as ocean crust basalts and banded-iron formation. If water can be transported by subducted slabs to the deep mantle, it can significantly decrease the melting temperature of mantle materials and cause such anomalies. A ULVZ a relatively cold

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Corrosion inhibitor selection for arctic and subsea high-velocity flowlines

    SciTech Connect

    Dougherty, J.A.

    2000-03-01

    Qualifying corrosion inhibitors for use in high-velocity multiphase flowlines in arctic or subsea environments is discussed. The criteria include high-velocity flow loop corrosion tests, pumpability through 0.125-in. (0.318-cm) capillary at low temperatures, compatibility with nylon 11, emulsion tendency testing, and partitioning characteristics. Laboratory and field data show the importance of using these criteria for inhibitor selection.

  18. 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.

  19. 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.

  20. 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.

  1. High-resolution shallow-seismic experiments in sand. Part 2: Velocities in shallow unconsolidated sand

    SciTech Connect

    Bachrach, R.; Dvorkin, J.; Nur, A.

    1998-07-01

    The authors conducted a shallow high-resolution seismic reflection and refraction experiment on a sandy beach. The depth of investigation was about 2 m. They interpret the data using the Hertz-Mindlin contact theory combined with Gassmann`s equation. These were used to obtain the vertical velocity profile. Then the profile was computed from seismic data using the turning-rays approximation. The normal moveout (NMO) velocity at the depth of 2 m matches the velocity profile. As a result, they developed a method to invert measured velocity from first arrivals, i.e., velocity versus distance into velocity versus depth using only one adjustable parameter. This parameter contains all the information about the internal structure and elasticity of the sand. The lowest velocity observed was about 40 m/s. It is noteworthy that the theoretical lower bound for velocity in dry sand with air is as low as 13 m/s. The authors find that modeling sand as a quartz sphere pack does not quantitatively agree with the measured data. However, the theoretical functional form proves to be useful for the inversion.

  2. The high-force region of the force-velocity relation in frog skinned muscle fibres.

    PubMed

    Lou, F; Sun, Y B

    1993-07-01

    The force-velocity relation has been studied during calcium-induced contracture of chemically skinned fibres from the semitendinosus muscle of Rana temporaria with special interest focused on the high-load region. The force-velocity curve was hyperbolic at low and intermediate loads but departed below the hyperbola as the load exceeded about 80% of the isometric force (P0). The force intercept (P*0) of the hyperbola derived from force-velocity data truncated at 0.78 P0 was higher than P0 (P*0/P0 = 1.14 +/- 0.04). At submaximum Ca2+ concentration, where the isometric force of the fibre was 65-75% of the maximum value, the force-velocity data still departed below the hyperbola at high loads (P*0/P0 = 1.09 +/- 0.04). The departure of the force-velocity data from the hyperbola at high force was also found at high ionic strength (250 mM), but not at low ionic strength (150 mM) (P*0/P0 = 1.09 +/- 0.03 and 0.98 +/- 0.03, respectively). The force-velocity relations derived under different experimental conditions could be fitted well by a modified version of Hill's (1938) hyperbolic equation (Edman 1988) using similar numerical values of k1 and k2 in the latter equation. The results indicate that the force-velocity relation in skinned muscle fibres is biphasic, and that the two curvatures, as in intact muscle fibres, are closely related to one another. Furthermore the evidence supports the hypothesis that the altered shape of the force-velocity relation at high loads is not related to the force level per se but rather to the speed of shortening of the contractile system (Edman 1992). PMID:8213180

  3. Ablative accelerative of small particles to high velocity by focused laser radiation

    NASA Astrophysics Data System (ADS)

    Goela, J. S.; Green, B. D.

    1986-01-01

    The results of a feasibility study of ablatively accelerating small particles to extremely high velocities using focused laser radiation are reported. The effects of particle size, melt, and breakup due to shear and compressive and centrifugal forces as well as particle stability in the beam are included. Ultimate velocities are limited by available laser sources, but velocities exceeding 10 to the 7th cm/sec appear possible. The conversion efficiency of laser energy into particle kinetic energy may exceed 10 to the 7th.

  4. 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.

  5. Ultrafine particle size distribution during high velocity impact of high density metals

    NASA Astrophysics Data System (ADS)

    Buonanno, Giorgio; Stabile, Luca; Ruggiero, Andrew; Iannitti, Gianluca; Bonora, Nicola

    2011-06-01

    In the event of kinetic energy penetrator impact, survival personnel is exposed to the additional hazard stemming from ultrafine metallic particles, i.e. exposure, inhalation, and respiration of aerolized metals. Aerosol particle size distribution is an important parameter that influences aerosol transport and deposition processes. In order to have reliable quantitative measure of the aerosol particles generated under controlled impact conditions, an experimental set-up has been developed. Both non penetrating and penetrating impacts tests have been designed and performed with light gas-gun in chamber. During the impact, size distribution, total concentration and chemical composition of ultrafine particles have been measured and correlated with impact parameters (such as energy and velocity). In order to avoid measurement contamination, as a result of undesired participating materials, target and projectile have been made of the same metal and tests have been performed in clean environmental chamber. In this study the results relative to high purity copper are presented.

  6. 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.

  7. Mixed convection in turbulent film boiling on a vertical ellipsoid under high and low velocity liquid

    NASA Astrophysics Data System (ADS)

    Hu, Hai-Ping

    2011-04-01

    The theoretical study researched into heat transfer of turbulent film boiling on an isothermal ellipsoid under high and low velocity liquid. The flowing velocity of the saturated liquid at the boundary layer is determined by potential flow theory. The larger the eccentricity parameter is the smaller the mean Nusselt number will be. Besides, for the cases of turbulent film boiling under the flowing liquid, the increase in the Froude number will bring out an increase in the mean Nusselt number.

  8. 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.

  9. Group velocity matching in high-order harmonic generation driven by mid-infrared lasers

    NASA Astrophysics Data System (ADS)

    Hernández-García, C.; Popmintchev, T.; Murnane, M. M.; Kapteyn, H. C.; Plaja, L.; Becker, A.; Jaron-Becker, A.

    2016-07-01

    We analyze the role of group-velocity matching (GVM) in the macroscopic build up of the high-harmonic signal generated in gas targets at high pressures. A definition of the walk-off length, associated with GVM, in the non-perturbative intensity regime of high-harmonic generation is given. Semiclassical predictions based on this definition are in excellent agreement with full quantum simulations. We demonstrate that group velocity matching is a relevant factor in high harmonic generation and the isolation of attosecond pulses driven by long wavelength lasers and preferentially selects contributions from the short quantum trajectories.

  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. High precision UTDR measurements by sonic velocity compensation with reference transducer.

    PubMed

    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

  13. HIGH-RESOLUTION OBSERVATIONS AND THE PHYSICS OF HIGH-VELOCITY CLOUD A0

    SciTech Connect

    Verschuur, Gerrit L.

    2013-04-01

    The neutral hydrogen structure of high-velocity cloud A0 (at about -180 km s{sup -1}) has been mapped with a 9.'1 resolution. Gaussian decomposition of the profiles is used to separately map families of components defined by similarities in center velocities and line widths. About 70% of the H I gas is in the form of a narrow, twisted filament whose typical line widths are of the order of 24 km s{sup -1}. Many bright features with narrow line widths of the order of 6 km s{sup -1}, clouds, are located in and near the filament. A third category with properties between those of the filament and clouds appears in the data. The clouds are not always co-located with the broader line width filament emission as seen projected on the sky. Under the assumption that magnetic fields underlie the presence of the filament, a theorem is developed for its stability in terms of a toroidal magnetic field generated by the flow of gas along field lines. It is suggested that the axial magnetic field strength may be derived from the excess line width of the H I emission over and above that due to kinetic temperature by invoking the role of Alfven waves that create what is in essence a form of magnetic turbulence. At a distance of 200 pc the axial and the derived toroidal magnetic field strengths in the filament are then about 6 {mu}G while for the clouds they are about 4 {mu}G. The dependence of the derived field strength on distance is discussed.

  14. 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.

  15. A simple approach for determining detonation velocity of high explosive at any loading density.

    PubMed

    Keshavarz, Mohammad Hossein

    2005-05-20

    A simple empirical relationship is introduced between detonation velocity at any loading density and chemical composition of high explosive as well as its gas phase heat of formation, which is calculated by group additivity rules. The present work may be applied to any explosive that contains the elements of carbon, hydrogen, nitrogen and oxygen with no difficulties. The new correlation can easily be applied for determining detonation velocity of explosives with loading densities less than 1g/cm3 as well as greater than 1g/cm3. Calculated detonation velocities by this procedure for both pure and explosive formulations show good agreement with respect to measured detonation velocity over a wide range of loading density. PMID:15885403

  16. 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.

  17. 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.

  18. Discovery of High-Velocity Gas in Absorption Associated with the Supernova Remnant W28

    NASA Astrophysics Data System (ADS)

    Ritchey, Adam M.; Wallerstein, G.

    2013-01-01

    We report the discovery of high-velocity interstellar absorption components observed toward the star CD-23 13777, an O-type supergiant located behind the supernova remnant W28. The interstellar Na I and Ca II profiles in this direction comprise numerous absorption components with velocities ranging from -150 km s-1 to +140 km s-1. The presence of gas at both high positive and high negative velocities indicates that the line of sight to CD-23 13777 probes both sides of the expanding shell of the remnant. The strongest interstellar absorption occurs at a velocity of +7.5 km s-1, consistent with the velocities of several nearby OH (1720 MHz) masers, which themselves are indicative of shock interactions between the supernova remnant and an adjacent molecular cloud. Moreover, the CD-23 13777 sight line passes very near a source of both GeV and TeV gamma rays, which likely result from collisions between high-energy particles, accelerated by the remnant, and the dense molecular gas in its vicinity. The identification of this line of sight as an exquisite probe of the interaction between the supernova remnant and the ambient molecular cloud paves the way for future observations in the UV and visible, which will enable a more detailed understanding of the physical conditions in the shocked gas and yield elemental abundances that can be used to study the chemical enrichment of the interstellar medium by the supernova explosion.

  19. Estimating hurricane vertical velocity from Doppler radar for high-resolution hurricane model initialization

    NASA Astrophysics Data System (ADS)

    Lee, J.

    2013-12-01

    A mesoscale vorticity method derives the hurricane inner-core vertical velocity from the vorticity variations in space and in time estimated from a deep layer of wind measurements obtained from Doppler radar. The vorticity method derives the hurricane inner core vertical velocity and thus, the divergent wind based on the mesoscale vorticity equation. The inner-core divergent wind inferred dynamically and rotational wind estimated from radar data form the total horizontal wind which is dynamically balanced with the derived vertical velocity. The derived high-resolution balance wind field is suitable for high resolution hurricane models initialization. The vorticity method is tested using a high-resolution non-hydrostatic hurricane model with radar data from Hurricane Danny which made landfall along the Alabama coast in 1997. Numerical experiments with a high resolution non-hydrostatic hurricane model show positive radar data impacts on track and intensity forecasts, in particular, substantial improvements on the hurricane inner core velocity field, can be obtained with the vertical velocity and thus inner-core divergent wind inferred from the mesoscale vorticity method.

  20. A high velocity impact experiment of micro-scale ice particles using laser-driven system

    NASA Astrophysics Data System (ADS)

    Yu, Hyeonju; Kim, Jungwook; Yoh, Jack J.

    2014-11-01

    A jet engine for high speed air breathing propulsion is subject to continuous wear as a result of impacts of micro-scale ice particles during a flight in the atmosphere. The inlet duct and compressor blades are exposed to on-coming frozen moisture particles that may result in the surface damage and significantly shorten the designed lifetime of the aircraft. Under such prolonged high-speed impact loading, the performance parameters such as flight instability and power loss of a jet engine can be significantly degraded. In this work, a laser-driven system was designed to accelerate micro-scale ice particles to the velocity up to Mach 2 using a Q-switched Nd:YAG laser beam at 100-600 mJ with 1064 nm wavelength and 9 ns pulse duration. The high speed images (Phantom v711) and double exposure shadowgraphs were used to calculate the average velocity of ice particles and their deceleration. Velocity Interferometer System for Any Reflector measurements were also utilized for the analysis of free surface velocity of a metal foil in order to understand the interfacial dynamics between the impacting particles and accepting metal target. The velocity of our ice particles is sufficiently fast for studying the effect of moisture particle collision on an air-breathing duct of high speed aircraft, and thus the results can provide insight into how minute space debris or micrometeorites cause damage to the orbiting spacecraft at large.

  1. CONTINUED ASSESSMENT OF A HIGH-VELOCITY FABRIC FILTRATION SYSTEM USED TO CONTROL FLY ASH EMISSIONS

    EPA Science Inventory

    The report gives results of a full-scale investigation of the performance of a variety of filter media, to provide technical and economic information under high-velocity conditions (high gas/cloth ratio). The fly ash emission studies demonstrated that woven fiberglass fabrics and...

  2. 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.

  3. 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…

  4. Efficient and reproducible high resolution spiral myocardial phase velocity mapping of the entire cardiac cycle

    PubMed Central

    2013-01-01

    Background Three-directional phase velocity mapping (PVM) is capable of measuring longitudinal, radial and circumferential regional myocardial velocities. Current techniques use Cartesian k-space coverage and navigator-gated high spatial and high temporal resolution acquisitions are long. In addition, prospective ECG-gating means that analysis of the full cardiac cycle is not possible. The aim of this study is to develop a high temporal and high spatial resolution PVM technique using efficient spiral k-space coverage and retrospective ECG-gating. Detailed analysis of regional motion over the entire cardiac cycle, including atrial systole for the first time using MR, is presented in 10 healthy volunteers together with a comprehensive assessment of reproducibility. Methods A navigator-gated high temporal (21 ms) and spatial (1.4 × 1.4 mm) resolution spiral PVM sequence was developed, acquiring three-directional velocities in 53 heartbeats (100% respiratory-gating efficiency). Basal, mid and apical short-axis slices were acquired in 10 healthy volunteers on two occasions. Regional and transmural early systolic, early diastolic and atrial systolic peak longitudinal, radial and circumferential velocities were measured, together with the times to those peaks (TTPs). Reproducibilities were determined as mean ± SD of the signed differences between measurements made from acquisitions performed on the two days. Results All slices were acquired in all volunteers on both occasions with good image quality. The high temporal resolution allowed consistent detection of fine features of motion, while the high spatial resolution allowed the detection of statistically significant regional and transmural differences in motion. Colour plots showing the regional variations in velocity over the entire cardiac cycle enable rapid interpretation of the regional motion within any given slice. The reproducibility of peak velocities was high with the reproducibility of early

  5. Impact pressures of turbulent high-velocity jets plunging in pools with flat bottom

    NASA Astrophysics Data System (ADS)

    Manso, P. A.; Bollaert, E. F. R.; Schleiss, A. J.

    2007-01-01

    Dynamic pressures created by the impact of high-velocity turbulent jets plunging in a water pool with flat bottom were investigated. Pressure fluctuations were sampled at 1 kHz at the jet outlet and at the pool bottom using piezo-resistive pressure transducers, jet velocities of up to 30 m/s and pool depth to jet diameter ratios from 2.8 to 11.4. The high-velocity jets entrain air in the pool in conditions similar to prototype applications at water release structures of dams. The intermittent character of plunge pool flows was investigated for shallow and deep pools, based on high order moments and time correlations. Maximum intermittency was observed for pool depths at 5.6 jet diameters, which approximate the core development length. Wall pressure skewness was shown to allow identifying the zone of influence of downward and upward moving currents.

  6. High Resolution Interseismic Velocity Model of the San Andreas Fault From GPS and InSAR

    NASA Astrophysics Data System (ADS)

    Tong, X.; Sandwell, D. T.; Smith-Konter, B. R.

    2011-12-01

    We recover the interseismic deformation along the entire San Andreas Fault System (SAFS) at a spatial resolution of 200 meters by combining InSAR and GPS observations using a dislocation model. Previous efforts to compare 17 different GPS-derived strain rate models of the SAFS shows that GPS data alone cannot uniquely resolve the rapid velocity gradients near faults, which are critical for understanding the along-strike variations in stress accumulation rate and associated earthquake hazard. To improve the near-fault velocity resolution, we integrate new GPS observations with InSAR observations, initially from ALOS (Advanced Land Observation Satellite launched by Japan Aerospace Exploration Agency) ascending data (spanning 2006.5-2010), using a remove/restore approach. More than 1100 interferograms were processed with the newly developed InSAR processing software GMTSAR. The integration uses a dislocation-based velocity model to interpolate the Line-Of-Sight (LOS) velocity at the full resolution of the InSAR data in radar coordinates. The residual between the model and InSAR LOS velocity are stacked and high-pass filtered, then added back to the model. This LOS velocity map covers almost entire San Andreas Fault System (see Figure 1) from Maacama Fault to the north to the Superstition Hills Fault to the south. The average standard deviation of the LOS velocity model ranges from 2 to 4 mm/yr. Our initial results show previously unknown details in along-strike variations in surface fault creep. Moreover, the high resolution velocity field can resolve asperities in these "creeping" sections that are important for understanding moment accumulation rates and seismic hazards. We find that much of the high resolution velocity signal is related to non-tectonic processes (e.g., ground subsidence and uplift) sometimes very close to the fault zone. The near-fault deformation signal extracted from this velocity map can provide tighter constraints on fault slip rates and

  7. 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.

  8. 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.

  9. 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.

  10. High-velocity Clouds in the Galactic All Sky Survey. I. Catalog

    NASA Astrophysics Data System (ADS)

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

  11. 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.

  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. 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.

  14. High-velocity drag friction in granular media near the jamming point.

    PubMed

    Takehara, Yuka; Okumura, Ko

    2014-04-11

    Drag friction that acts on a disk in a two-dimensional granular medium is studied at high packing fractions. We concentrate on a high-velocity region, in which the dynamic component of the force, obtained as an average of a strongly fluctuating force, clearly scales with velocity squared. We find that the total force composed of dynamic and static components, as well as its fluctuation, diverges with practically the same exponent as the packing fraction approaches the jamming point. To explain the critical behavior, we propose a simple theory equipped with a diverging length scale, which agrees well with the data and elucidates physical pictures for the divergence. PMID:24766018

  15. Sound Velocities and Validity of Birch's Law for Ultra-High Pressure Metals and Ionic Solids

    NASA Astrophysics Data System (ADS)

    Ware, L.; Boness, D. A.

    2014-12-01

    Recent detection of super-Earths has expanded interest in ultra-high pressure, temperature minerals and elements to help constrain the composition and physical properties of the interiors of these large planets. To understand Earth's interior, Birch's Law and velocity-density systematics has long been important. Recent published DAC experimental measurements of sound velocities in iron are inconsistent with each other with regard to the validity of Birch's Law. We examine the range of validity of Birch's Law for several metallic elements, including iron, and ionic solids shocked into the ultra-high pressure, temperature fluid state and make comparisons to the recent DAC data.

  16. 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.

  17. 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

  18. 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.

  19. The radial velocity technique and the discovery of exoplanets as seen by high school students.

    NASA Astrophysics Data System (ADS)

    Alves, Mauro; Gusev, Anatoly; Pugacheva, Galina; Martin, Inacio; Lyra, Cassia

    2012-07-01

    Presently, the existence of more than 750 exoplanets has been confirmed. The radial velocity technique has proven to be the most effective means to detect planets orbiting other stars. In this technique, which is based on the Doppler effect, the observation of the displacement of spectral lines is used to infer the presence of exoplanets orbiting distant stars. Despite the apparent complexity of this technique, high-school students not only can understand its basic principles, but also create simple programs and software to represent and simulate changes in the radial velocity of a star. Thus, as an extracurricular activity, high-school students developed a simple computer program using the C programming language to simulate the influence of a planet orbiting a star in order to obtain radial velocity curves. The radial velocity curve depends on the masses of the star and planet, and orbital parameters such as orbital period, semi-major axis, eccentricity, inclination, argument of periapsis, longitude of the ascending node and mean anomaly. The software allows the variation of these parameters so that the influence of any planet (or system of planets) in orbit of a star can be simulated and the corresponding changes in the radial velocity be observed. For comparison purposes, the radial velocity curve of the Sun under the influence of Jupiter and Saturn are compared with the radial velocity curves of other stars with known exoplanets. This activity became a multidisciplinary study of an interesting physical phenomenon. To obtain the desired results, the students had to learn new concepts and use different tools, which was very rewarding to them.

  20. Inferring the high velocity of landslides in Valles Marineris on Mars from morphological analysis

    NASA Astrophysics Data System (ADS)

    Mazzanti, Paolo; De Blasio, Fabio Vittorio; Di Bastiano, Camilla; Bozzano, Francesca

    2016-01-01

    The flow characteristics and velocities of three landslides in Valles Marineris on Mars are investigated using detailed morphological analyses of high-resolution images and dynamical calculations based on the run-up and curvature of the landslide deposits. The morphologies of the landslides are described, especially concerning those characteristics that can provide information on the dynamics and velocity. The long runout and estimated high velocities, often exceeding 100 m/s, confirm a low basal friction experienced by these landslides. Because subaqueous landslides on Earth exhibit reduced friction, we explore the scenario of sub-lacustrine failures, but find little support to this hypothesis. The environmental conditions that better explain the low friction and the presence of longitudinal furrows suggest an aerial environment with a basal soft and naturally lubricating medium on which friction diminished gradually; in this perspective, ice is the most promising candidate.

  1. 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

  2. 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.

  3. Sound Velocities of Fe-C and Fe-Si alloying liquids at high pressures

    NASA Astrophysics Data System (ADS)

    Jing, Z.; Han, J.; Yu, T.; Wang, Y.

    2014-12-01

    Geophysical and geochemical observations suggest light elements such as S, Si, C, O, H, etc., are likely present in the Earth's outer core and the molten cores of other terrestrial planets and moons including Mercury, Mars, Earth's Moon, and Ganymede. In order to constrain the abundances of light elements in planetary cores, it is crucial to determine the density and sound velocity of Fe-light element alloying liquids under core conditions. In this study, sound velocities of Fe-rich liquids were determined by combining the ultrasonic measurements with synchrotron X-ray radiography and diffraction techniques under high-pressure and temperature conditions from 1 to 6 GPa and 1573 to 1973 K. An Fe-C composition (Fe-5wt%C) and four Fe-Si compositions (Fe-10wt%Si, Fe-17wt%Si, Fe-25wt%Si, and FeSi) were studied. Compared to our previous results on the velocity of Fe and Fe-S liquids at high pressures (Jing et al., 2014, Earth Planet. Sci. Lett. 396, 78-87), the presence of both C and Si increases the velocity of liquid Fe, in contrast to the effect of S. The measured velocities of Fe-C and Fe-Si liquids increase with compression and decrease slightly with increasing temperature. Combined with 1-atm density data in the literature, the high-pressure velocity data provide tight constraints on the equations of state and thermodynamic properties such as the adiabatic temperature gradient for Fe-C and Fe-Si liquids. We will discuss these results with implications to planetary cores.

  4. 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.

  5. 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.

  6. 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

  7. ASSESSMENT OF A HIGH-VELOCITY FABRIC FILTRATION SYSTEM USED TO CONTROL FLY ASH EMISSIONS

    EPA Science Inventory

    The report gives results of a full-scale investigation (following a pilot plant study) of applying high-velocity fabric filtration to coal-fired boiler fly ash control. Two filter systems were applied separately to two 60,000 lb steam/hr coal-fired boilers. Performance evaluated ...

  8. Ballistics and the management of ureteral injuries from high velocity missiles.

    PubMed

    Stutzman, R E

    1977-12-01

    The management of 21 patients with 22 ureteral injuries from high velocity missiles is described and 6 cases are reported in detail. Ballistics should be considered in all wounds of violence. Débridement, internal stents, proximal diversion and thorough drainage are advocated. PMID:926271

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. The Effects of Drag and Tidal Forces on the Orbits of High-Velocity Clouds

    NASA Astrophysics Data System (ADS)

    Fernandes, Alexandre; Benjamin, R. A.

    2013-06-01

    Over the past several years, orbital constraints have been obtained for several high velocity cloud complexes surrounding the Milky Way: Complex GCP (Smith Cloud), Complex A, Complex H, Complex GCN, and the Magellanic Stream. We summarize what is known about the orbits of these clouds and and discuss how well each of these complexes fits a balistic trajectory, and discuss how the length of a complex across the sky is related to the inital "fragmentation" and velocity dispersion of the clouds. We then introduce gas drag into the simulation of the orbits of these complexes. We present analytical tests of our numerical method and characterize the departure of the clouds from the ballistic trajectory as a function of drag parameters (ambient gas density and velocity and cloud column density). Using the results of these simulations we comment on the survivability and ultimate fate of HVC in the context of the different models of drag forces.

  16. 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

  17. 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

  18. 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.

  19. 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

  20. High-Velocity Resistance Exercise Protocols in Older Women: Effects on Cardiovascular Response

    PubMed Central

    da Silva, Rodrigo P.; Novaes, Jefferson; Oliveira, Ricardo J.; Gentil, Paulo; Wagner, Dale; Bottaro, Martim

    2007-01-01

    Acute cardiovascular responses to different high-velocity resistance exercise protocols were compared in untrained older women. Twelve apparently healthy volunteers (62.6 ± 2.9 y) performed three different protocols in the bench press (BP). All protocols involved three sets of 10 repetitions performed with a 10RM load and 2 minutes of rest between sets. The continuous protocol (CP) involved ten repetitions with no pause between repetitions. The discontinuous protocols were performed with a pause of five (DP5) or 15 (DP15) seconds between the fifth and sixth repetitions. Heart rate (HR), systolic blood pressure (SBP), rate pressure product (RPP), Rating of Perceived Exertion (RPE), and blood lactate (BLa) were assessed at baseline and at the end of all exercise sets. Factorial ANOVA was used to compare the cardiovascular response among different protocols. Compared to baseline, HR and RPP were significantly (p < 0.05) higher after the third set in all protocols. HR and RPP were significantly (p < 0.05) lower in DP5 and DP15 compared with CP for the BP exercise. Compared to baseline, RPE increased significantly (p < 0.05) with each subsequent set in all protocols. Blood lactate concentration during DP5 and DP15 was significantly lower than CP. It appears that discontinuous high-velocity resistance exercise has a lower cardiovascular demand than continuous resistance exercise in older women. Key pointsThe assessment of cardiovascular responses to high-velocity resistance exercise in older individuals is very important for exercise prescription and rehabilitation in elderly population.Discontinuous protocol decrease myocardial oxygen consumption (HR x SBP) during the performance of dynamic high-velocity resistance exercise in older women.The decrease in RPP (~ 8.5%) during the discontinuous protocol has clinical implications when developing high-velocity resistance exercise strategies for elderly individuals. PMID:24149492

  1. 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

  2. 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.

  3. 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.

  4. 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. PMID:16797640

  5. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-01-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  6. Design and test of a superconducting structure for high-velocity ions

    SciTech Connect

    Delayen, J.R.; Kennedy, W.L.; Roche, C.T.

    1992-10-01

    Following the successful development of a niobium coaxial half-wave structure we have designed, built and tested a new half-wave geometry: the spoke resonator. This geometry is better suited for high frequency resonators and for the acceleration of high velocity ions. The prototype cavity is a 2-gap structure resonating at 855 MHz, and optimized for particle velocity of 0.30 c. It is easier to manufacture than the coaxial half-wave resonator and the geometry can be straightforwardly extended to multigap designs. Rf-tests have been performed on this cavity both prior to and after high temperature annealing. An accelerating gradient of 7.2 MV/m (cw) and 7.8 MV/m (pulsed) was observed at 4.2 K. After annealing, a low power Q{sub 0} of 1.2 {times}10{sup 8} was observed with small Q degradation due to field emission at high accelerating fields.

  7. 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.

  8. The high-velocity outflow in the proto-planetary nebula Hen 3-1475

    NASA Astrophysics Data System (ADS)

    Riera, A.; García-Lario, P.; Manchado, A.; Bobrowsky, M.; Estalella, R.

    2003-04-01

    The proto-planetary nebula Hen 3-1475 shows a remarkable highly collimated optical jet with an S-shaped string of three pairs of knots and extremely high velocities. We present here a detailed analysis of the overall morphology, kinematic structure and the excitation conditions of these knots based on deep ground-based high dispersion spectroscopy complemented with high spatial resolution spectroscopy obtained with STIS onboard HST, and WFPC2 [N II] images. The spectra obtained show double-peaked, extremely wide emission line profiles, and a decrease of the radial velocities with distance to the source in a step-like fashion. We find that the emission line ratios observed in the intermediate knots are consistent with a spectrum arising from the recombination region of a shock wave with shock velocities ranging from 100 to 150 km s-1. We propose that the ejection velocity is varying as a function of time with a quasi-periodic variability (with timescale of the order of 100 years) and the direction of ejection is also varying with a precession period of the order of 1500 years. Some slowing down with distance along the axis of the Hen 3-1475 jet may be due to the entrainment process and/or to the enviromental drag. This scenario is supported by geometric and kinematic evidence: firstly, the decrease of the radial velocities along the Hen 3-1475 jet in a step like fashion; secondly, the kinematic structure observed in the knots; thirdly, the point-symmetric morphology together with the high proper motions shown by several knots; and finally the fact that the shock velocity predicted from the observed spectra of the shocked knots is much slower than the velocities at which these knots move outwards with respect to the central source. Based on observations made during service time with the 2.5 m Isaac Newton Telescope operated on La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de

  9. 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.

  10. 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.