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Sample records for air arc gouging

  1. Shielded Metal Arc Welding and Carbon Arc Cutting--Air. Teacher Edition [and] Student Edition [and] Student Workbook. Third Edition.

    ERIC Educational Resources Information Center

    Harper, Eddie; Knapp, John

    This document contains the teacher and student texts and student workbook for a secondary-level course in shielded metal arc welding (SMAW) and carbon arc cutting that consists of units on the following topics: SMAW safety; SMAW equipment, applications, and techniques; hardfacing; and carbon arc cutting--air. The teacher edition includes the…

  2. Magnetically Diffused Radial Electric-Arc Air Heater Employing Water-Cooled Copper Electrodes

    NASA Technical Reports Server (NTRS)

    Mayo, R. F.; Davis, D. D., Jr.

    1962-01-01

    A magnetically rotated electric-arc air heater has been developed that is novel in that an intense magnetic field of the order of 10,000 to 25,000 gauss is employed. This field is supplied by a coil that is connected in series with the arc. Experimentation with this heater has shown that the presence of an intense magnetic field transverse to the arc results in diffusion of the arc and that the arc has a positive effective resistance. With the field coil in series with the arc, highly stable arc operation is obtained from a battery power supply. External ballast is not required to stabilize the arc when it is operating at maximum power level. The electrode erosion rate is so low that the airstream contamination is no more than 0.07 percent and may be substantially less.

  3. Theory of the arc discharge in air blast breakers

    SciTech Connect

    Vogel, H.F.

    1980-08-01

    The complete set of equations obtaining in the arc's length element are given. The arc length is determined when the external circuit equations are closed by an expression for the arc inductance as a function of the radius and length, in addition to our relationships for the radius and voltage gradients.

  4. Investigation on Plasma Jet Flow Phenomena During DC Air Arc Motion in Bridge-Type Contacts

    NASA Astrophysics Data System (ADS)

    Zhai, Guofu; Bo, Kai; Chen, Mo; Zhou, Xue; Qiao, Xinlei

    2016-05-01

    Arc plasma jet flow in the air was investigated under a bridge-type contacts in a DC 270 V resistive circuit. We characterized the arc plasma jet flow appearance at different currents by using high-speed photography, and two polished contacts were used to search for the relationship between roughness and plasma jet flow. Then, to make the nature of arc plasma jet flow phenomena clear, a simplified model based on magnetohydrodynamic (MHD) theory was established and calculated. The simulated DC arc plasma was presented with the temperature distribution and the current density distribution. Furthermore, the calculated arc flow velocity field showed that the circular vortex was an embodiment of the arc plasma jet flow progress. The combined action of volume force and contact surface was the main reason of the arc jet flow. supported by National Natural Science Foundation of China (Nos. 51307030, 51277038)

  5. Simulation and Experimental Analysis of Arc Motion Characteristics in Air Circuit Breaker

    NASA Astrophysics Data System (ADS)

    Niu, Chunping; Ding, Juwen; Wu, Yi; Yang, Fei; Dong, Delong; Fan, Xingyu; Rong, Mingzhe

    2016-03-01

    In this paper, to simulate the arc motion in an air circuit breaker (ACB), a three-dimensional magneto-hydrodynamic (MHD) model is developed, considering the influence of thermal radiation, the change of physical parameters of arc plasma and the nonlinear characteristic of ferromagnetic material. The distributions of pressure, temperature, gas flow and current density of arc plasma in the arc region are calculated. The simulation results show some phenomena which discourage arc interruption, such as back commutation and arc burning at the back of the splitter plate. To verify the simulation model, the arc motion is studied experimentally. The influences of the material and position of the innermost barrier plate are analyzed mainly. It proved that the model developed in this paper can efficiently simulate the arc motion. The results indicate that the insulation barrier plate close to the top of the splitter plate is conducive to the arc splitting, which leads to the significant increase of the arc voltage, so it is better for arc interruption. The research can provide methods and references to the optimization of ACB design. supported by National Key Basic Research Program of China (973 Program) (Nos. 2015CB251002, 6132620303), National Natural Science Foundation of China (Nos. 51221005, 51377128, 51577144), and the Fundamental Research Funds for the Central Universities, China

  6. The Influence of Contact Space on Arc Commutation Process in Air Circuit Breaker

    NASA Astrophysics Data System (ADS)

    Niu, Chunping; Ding, Juwen; Yang, Fei; Dong, Delong; Rong, Mingzhe; Xu, Dan

    2016-05-01

    In this paper, a 3D magneto-hydrodynamic (MHD) arc simulation model is applied to analyze the arc motion during current interruption in a certain air circuit breaker (ACB). The distributions of pressure, temperature, gas flow and current density of the arc plasma in the arc region are calculated, and the factors influencing the commutation process are analyzed according to the calculated results. Based on the airflow in the arc chamber, the causes of arc commutation asynchrony and the back commutation are investigated. It indicates that a reasonable contact space design is crucial to a successful arc commutation process. To verify the simulation results, the influence of contact space on arc voltage and arc commutation is tested. This research can provide methods and references to the optimization of ACB design. supported by National Key Basic Research Program of China (973 Program) (Nos. 2015CB251002, 6132620303) and National Natural Science Foundation of China (Nos. 51221005, 51377128, 51577144), and Science and Technology Project Through Grid State Corporation (No. SGSNKYOOKJJS1501564)

  7. Strengths of serpentinite gouges at elevated temperatures

    USGS Publications Warehouse

    Moore, Diane E.; Lockner, D.A.; Ma, S.; Summers, R.; Byerlee, J.D.

    1997-01-01

    Serpentinite has been proposed as a cause of both low strength and aseismic creep of fault zones. To test these hypotheses, we have measured the strength of chrysotile-, lizardite-, and antigorite-rich serpentinite gouges under hydrothermal conditions, with emphasis on chrysotile, which has thus far received little attention. At 25??C, the coefficient of friction, ??, of chrysotile gouge is roughly 0.2, whereas the lizardite- and antigorite-rich gouges are at least twice as strong. The very low room temperature strength of chrysotile is a consequence of its unusually high adsorbed water content. When the adsorbed water is removed, chrysotile is as strong as pure antigorite gouge at room temperature. Heating to ???200??C causes the frictional strengths of all three gouges to increase. Limited data suggest that different polytypes of a given serpentine mineral have similar strengths; thus deformation-induced changes in polytype should not affect fault strength. At 25??C, the chrysotile gouge has a transition from velocity strengthening at low velocities to velocity weakening at high velocities, consistent with previous studies. At temperatures up to ???200??C, however, chrysotile strength is essentially independent of velocity at low velocities. Overall, chrysotile has a restricted range of velocity-strengthening behavior that migrates to higher velocities with increasing temperature. Less information on velocity dependence is available for the lizardite and antigorite gouges, but their behavior is consistent with that outlined for chrysotile. The marked changes in velocity dependence and strength of chrysotile with heating underscore the hazards of using room temperature data to predict fault behavior at depth. The velocity behavior at elevated temperatures does not rule out serpentinite as a cause of aseismic slip, but in the presence of a hydrostatic fluid pressure gradient, all varieties of serpentine are too strong to explain the apparent weakness of faults such

  8. A frictional law for volcanic ash gouge

    NASA Astrophysics Data System (ADS)

    Lavallée, Y.; Hirose, T.; Kendrick, J. E.; De Angelis, S.; Petrakova, L.; Hornby, A. J.; Dingwell, D. B.

    2014-08-01

    Volcanic provinces are structurally active regions - undergoing continual deformation along faults. Within such fault structures, volcanic ash gouge, containing both crystalline and glassy material, may act as a potential fault plane lubricant. Here, we investigate the frictional properties of volcanic ash gouges with varying glass fractions using a rotary shear apparatus at a range of slip rates (1.3-1300 mm/s) and axial stresses (0.5-2.5 MPa). We show that the frictional behaviour of volcanic ash is in agreement with Byerlee's friction law at low slip velocities, irrespective of glass content. The results reveal a common non-linear reduction of the friction coefficient with slip velocity and yield a frictional law for fault zones containing volcanic ash gouge. Textural analysis reveals that strain localisation and the development of shear bands are more prominent at higher slip velocities (>10 mm/s). The textures observed here are similar to those recorded in ash gouge at the surface of extrusive spines at Mount St. Helens (USA). We use the rate-weakening component of the frictional law to estimate shear-stress-resistance reductions associated with episodic seismogenic slip events that accompany magma ascent pulses. We conclude that the internal structure of volcanic ash gouge may act as a kinematic marker of exogenic dome growth.

  9. Some features of horizontally oriented low-current electric arc in air

    SciTech Connect

    Tazmeev, Kh. K.; Tazmeev, B. Kh.

    2016-01-15

    The properties of an electric arc operating in open air at currents of lower than 1 A were studied experimentally. The rod cathode was oriented horizontally. Cylindrical rods and plane plates either installed strictly vertically in front of the cathode end or tilted at a certain angle served as the anode. It is shown that, with such an electrode configuration, it is possible to form a discharge channel much longer than the electrode gap length. Regimes of regular oscillations are revealed, and conditions for their appearance are established. The electric field strength in the arc column and the electron temperature near the anode are calculated.

  10. Spectroscopic Diagnostics and an Arc Jet Heated Air Plasma

    NASA Technical Reports Server (NTRS)

    Mack, Larry Howard, Jr.

    1996-01-01

    Spectral radiation measurements were made in the range of 200 to 900 nm across a section of the plenum of an arc jet wind tunnel using a series of optical fibers. The spectra contained line radiation from Oxygen and Nitrogen atoms and molecular radiation from N2(+), N2, and NO. Abel inversion technique is used to obtain radial distribution of the spectra. The analysis yielded radial profiles of the electronic excitation, vibrational and rotational temperatures of the flow field. Spectral fitting yielded branching ratios for different vibrational and rotational bands. Relatively mild flow conditions, i.e. enthalpy and mass flow rate, were used for prolonged measurements of up to and over two hours to establish the best experimental methods of temperature determinations. Signal to noise was improved by at least an order of magnitude enabling the molecular vibrational band heads of N2(+) (first negative system), N2 (second positive system), and NO (beta, gamma, delta, and epsilon systems) to be resolved in the lower ultraviolet wavelength regions. The increased signal to noise ratio also enabled partial resolution of the rotational lines of N2(+) and N2 in certain regions of minimal overlap. Comparison of the spectra with theoretical models such as the NEQAIR2 code are presented and show potential for fitting the spectra when reliable calibration is performed for the complete wavelength range.

  11. Analysis and Simulation of Hypervelocity Gouging Impacts

    DTIC Science & Technology

    2006-06-01

    Hypervelocity Gouging Test . . 8 -11 8.2.4 Further Results from the Comparison of CTH Simulations to the 1-D Penetration Theory . . . 8 - 13 8.2.5...more plasticity and gouge depth is generated and the temperature profile is correspondingly more significant. 8 - 13 Figure 8.14: Comparison of CTH...19a. NAME OF RESPONSIBLE PERSON 19b. TELEPHONE NUMBER (include area code) Standard Form 298 (Rev. 8 –98) Prescribed by ANSI Std. Z39.18 13 –06–2006

  12. Experimental study of the heat transfer process of air around atmospheric arc plasma

    NASA Astrophysics Data System (ADS)

    Salimi Meidanshahi, F.; Madanipour, Kh.; Shokri, Babak

    2011-05-01

    The experimental investigation of thermodynamic properties such heat and mass transfer of plasmas has many applications in different industries. Laboratory atmospheric arc plasma is studied in this work. The refractive index of the air around the plasma is changed because of convection phenomena. When the convection creates the air flowing around the plasma, the density and consequently, the refractive index of air are distributed symmetrically. Moiré deflectometry is a technique of wave front analysis which in both Talbot effect and moiré technique is applied for measuring phase objects. Deflection of light beam passing through the inhomogeneous medium is utilized to obtain the refractive index distribution. In experimental set-up, an expanded collimated He-Ne laser propagate through the arc plasma and the around air. The temperature distribution is obtained by use of thermo-optic coefficient of air. To calculate the thermo- optic coefficient and the refractive index of air for a given wavelength of light and given atmospheric conditions (air temperature, pressure, and humidity), the Edlén equation is used. The convective heat transfer coefficient is obtained by calculating the temperature gradient on the plasma border. This method is not expensive, complicated and sensitive to environmental vibrations.

  13. Non-Intrusive Magneto-Optic Detecting System for Investigations of Air Switching Arcs

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Zhang, Guogang; Dong, Jinlong; Liu, Wanying; Geng, Yingsan

    2014-07-01

    In current investigations of electric arc plasmas, experiments based on modern testing technology play an important role. To enrich the testing methods and contribute to the understanding and grasping of the inherent mechanism of air switching arcs, in this paper, a non-intrusive detecting system is described that combines the magneto-optic imaging (MOI) technique with the solution to inverse electromagnetic problems. The detecting system works in a sequence of main steps as follows: MOI of the variation of the arc flux density over a plane, magnetic field information extracted from the magneto-optic (MO) images, arc current density distribution and spatial pattern reconstruction by inverting the resulting field data. Correspondingly, in the system, an MOI set-up is designed based on the Faraday effect and the polarization properties of light, and an intelligent inversion algorithm is proposed that involves simulated annealing (SA). Experiments were carried out for high current (2 kA RMS) discharge cases in a typical low-voltage switchgear. The results show that the MO detection system possesses the advantages of visualization, high resolution and response, and electrical insulation, which provides a novel diagnostics tool for further studies of the arc.

  14. Frictional Strength of Hayward Fault Gouge

    NASA Astrophysics Data System (ADS)

    Morrow, C.; Moore, D.; Lockner, D.

    2007-12-01

    A recent 3-D geologic model of the Hayward fault in the San Francisco Bay Region shows that a number of different rock units are juxtaposed across the fault surface as a result of lateral displacement. The fault gouge formed therein is likely a mixture of these various rock types. To better model the mechanical behavior of the Hayward fault, which is known to both creep and have large earthquakes, frictional properties of mixtures of the principal rock types were determined in the laboratory. Room temperature triaxial shearing tests were conducted on binary and ternary mixtures of Great Valley Sequence graywacke, Franciscan jadeite-bearing metagraywacke, Franciscan pumpellyite-bearing metasandstone, Franciscan melange matrix, serpentinite and two-pyroxene gabbro. The gouge samples were crushed and sieved (<150 μm grains), then applied in a 1-mm layer between saw-cut sliding blocks. Each sample assemblage was saturated and sheared at constant pore water pressure of 1 MPa and normal stress of 51 MPa. Coefficients of friction, μ, ranged from a low of 0.38 for the serpentinite to a maximum of 0.85 for the gabbro. While the serpentinite and the Franciscan melange matrix were relatively weak, all other rock types obeyed Byerlee's Law. The friction coefficient of mixtures could be reliably predicted by a simple average based on dry weight percent of the end member strengths. This behavior is in contrast to some mixtures of common gouge materials such as montmorillonite+quartz, which exhibit non- linear frictional strength trends with varying weight percent of constituents. All materials tested except serpentinite were velocity strengthening, therefore promoting creeping behavior. The addition of serpentinite decreased a-b values of the gouge and increased the characteristic displacement, dc, of strength evolution. Because temperature strongly influences the mechanical properties of fault gouge as well as speeding chemical reactions between the constituents, elevated

  15. Analysis of the characteristics of DC nozzle arcs in air and guidance for the search of SF6 replacement gas

    NASA Astrophysics Data System (ADS)

    Liu, J.; Zhang, Q.; Yan, J. D.; Zhong, J.; Fang, M. T. C.

    2016-11-01

    It is shown that the arc model based on laminar flow cannot predict satisfactorily the voltage of an air arc burning in a supersonic nozzle. The Prandtl mixing length model (PML) and a modified k-epsilon turbulence model (MKE) are used to introduce turbulence enhanced momentum and energy transport. Arc voltages predicted by these two turbulence models are in good agreement with experiments at the stagnation pressure (P 0) of 10 bar. The predicted arc voltages by MKE for P 0  =  13 bar and 7 bar are in better agreement with experiments than those predicted by PML. MKE is therefore a preferred turbulence model for an air nozzle arc. There are two peaks in ρC P of air at 4000 K and 7000 K due, respectively, to the dissociation of oxygen and that of nitrogen. These peaks produce corresponding peaks in turbulent thermal conductivity, which results in very broad radial temperature profile and a large arc radius. Thus, turbulence indirectly enhances axial enthalpy transport, which becomes the dominant energy transport process for the overall energy balance of the arc column at high currents. When the current reduces, turbulent thermal conduction gradually becomes dominant. The temperature dependence of ρC P has a decisive influence on the radial temperature profile of a turbulent arc, thus the thermal interruption capability of a gas. Comparison between ρC P for air and SF6 shows that ρC P for SF6 has peaks below 4000 K. This renders a distinctive arc core and a small arc radius for turbulent SF6, thus superior arc quenching capability. It is suggested, for the first time, that ρC P provides guidance for the search of a replacement switching gas for SF6.

  16. Amorphous material in high strain experimental fault gouges

    SciTech Connect

    Yund, R.A.; Blanpied, M.L.; Tullis, T.E.; Weeks, J.D. )

    1990-09-10

    The microstructures of gouges produced in room temperature, rotary shear sliding experiments were examined by transmission electron microscopy. Gouges were produced by sliding on ground surfaces of granite, quartzite, or marble except for one experiment in which a 1-mm-thick simulated gouge layer was used. Water was added to the sliding surfaces of all but one sample. Crystal plastic processes play no role in the granite and quartzite gouges and a minor role in the marbles. All of the gouges consist of mostly submicron crystalline fragments; in addition, the granite gouges contain 5-60% amorphous material, and the quartzite gouge contains {approximately}50% amorphous material. In the granite samples the composition of the amorphous material commonly lies between K-rich and Na, Ca-rich feldspars, although portions may be silica-rich. The microstructural relations suggest that the amorphous material forms by comminution of fragments rather than by melting. The amount of amorphous material increases, and the size of the largest crystalline fragments decreases, with an increase in average shear strain, although the microstructure is nearly uniform throughout each granite gouge layer. These observations suggest that after slip becomes localized on Y shear surfaces and/or R{sub 1} Riedel shears the entire gouge layer must continue to undergo deformation. It is suggested that cyclic deformation in the gouge must occur to accommodate the passage of geometric irregularities on the active slip surfaces.

  17. The Investigation of Hypervelocity Gouging

    DTIC Science & Technology

    2007-11-02

    The Holloman High Speed Test Track (HHSTT) facility at Holloman Air Force Base, New Mexico , is a ground based test facility designed to test items...Friedrichs KO, and Lewy H, ‘ Uber die partiellen Differenzengleichungen der mathematischen Physik’, Mathematische Annalen Vol. 100, pp 32-74 (1928

  18. Ice gouge processes in the Alaskan Beaufort Sea

    USGS Publications Warehouse

    Rearic, Douglas M.; Ticken, Edward J.

    1988-01-01

    A generalized picture of ice gouge characteristics from shallow inshore depths to the outer shelf at about 60 m of water is presented. Data from recent studies show that the size and quantity of gouging increases in an offshore direction to depths of about 45 m where this trend then reverses and the features decrease in size and quantity as the shelf break is approached. Ice gouges are oriented east-west and this suggests that most gouging is caused by ice approaching from the east, possibly driven by the Beaufort Sea gyre. The most intense gouging occurs in the stamukhi zone, between 20 and 40 m of water, and is caused by a high rate of ice keel production owing to shearing forces between mobile and stable sea ice. Inshore of the stamukhi zone, ice gouging still presents a significant hazard but their greatly decreased size and number make it possible to design against this hazard.

  19. Plasma treatment of aqueous solutes: Some chemical properties of a gliding arc in humid air

    NASA Astrophysics Data System (ADS)

    Benstaali, B.; Moussa, D.; Addou, A.; Brisset, J.-L.

    1998-11-01

    The chemical properties of the gaseous species generated in a humid air gliding arc discharge are investigated. Aqueous solutions are used as the targets exposed to the plasma, and this allows to evidence strong acid and oxidizing effects on various solutes by means of spectrometric or potentiometric methods. The influence of some working parameters such as the input gas flow, the distance from the electrodes to the target or the electrode gap is examined on the chemical transform and simple experimental laws are derived. A general feature is observed for oxidation and suggests the occurrence of an auto-catalytic step in the relevant kinetic mechanism.

  20. Frictional healing in simulated anhydrite fault gouges: effects of water and CO2

    NASA Astrophysics Data System (ADS)

    Pluymakers, Anne; Bakker, Elisenda; Samuelson, Jon; Spiers, Christopher

    2014-05-01

    Currently, depleted hydrocarbon reservoirs are in many ways considered ideal for storage of CO2 and other gases. Faults are of major importance to CO2 storage because of their potential as leakage pathways, and also due to the possible seismic risk associated with fault reactivation. Both in the Netherlands and worldwide, anhydrite-rich rocks are a common topseal for many potential storage sites, making it likely that crosscutting faults will contain fault gouges rich in anhydrite. In order to assess the likelihood of fault reactivation and/or fault leakage, it is important to have a thorough understanding of the fault strength, velocity dependence and of the potential to regain frictional strength after fault movement (healing behavior) of anhydrite fault gouge. Starting with a natural anhydrite (>95wt% CaSO4), with minor quantities of dolomite (<5wt% (Ca,Mg)CO3), we conducted direct shear experiments on simulated anhydrite fault gouges with both a slide-hold-slide and velocity-stepping sequences. Pore fluid phase was varied (air, vacuum, water, dry/wet CO2), and pressure and temperature conditions used are representative for potential CO2 storage sites, with an effective normal stress of 25 MPa, a temperature of 120°C and, where used, a pore fluid pressure of 15 MPa. First results indicate that frictional healing in anhydrite is strongly influenced by the presence of water. Dry fault gouges exhibit no measurable frictional healing for hold times up to 1 hour, whereas wet gouges show significant healing and stress relaxation, even for short duration hold periods (30s), suggesting a fluid-assisted process such as pressure solution might be of importance. Interestingly, while many materials exhibit a log-linear dependence of frictional drop on hold time (i.e. "Dieterich-type" healing), our results for wet gouge indicate a non-linear increase of frictional drop with increasing hold time. To determine if pressure solution controls frictional healing we will perform

  1. Spatiotemporally resolved characteristics of a gliding arc discharge in a turbulent air flow at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Zhu, Jiajian; Gao, Jinlong; Ehn, Andreas; Aldén, Marcus; Larsson, Anders; Kusano, Yukihiro; Li, Zhongshan

    2017-01-01

    A gliding arc discharge was generated in a turbulent air flow at atmospheric pressure driven by a 35 kHz alternating current (AC) electric power. The spatiotemporally resolved characteristics of the gliding arc discharge, including glow-type discharges, spark-type discharges, short-cutting events and transitions among the different types of discharges, were investigated using simultaneously optical and electrical diagnostics. The glow-type discharge shows sinusoidal-like voltage and current waveforms with a peak current of hundreds of milliamperes. The frequency of the emission intensity variation of the glow-type discharge is the same as that of the electronic power dissipated in the plasma column. The glow-type discharge can transfer into a spark discharge characterized by a sharp peak current of several amperes and a sudden increase of the brightness in the plasma column. Transitions can also be found to take place from spark-type discharges to glow-type discharges. Short-cutting events were often observed as the intermediate states formed during the spark-glow transition. Three different types of short-cutting events have been observed to generate new current paths between two plasma channel segments, and between two electrodes, as well as between the channel segment and the electrodes, respectively. The short-cut upper part of the plasma column that was found to have no current passing through can be detected several hundreds of microseconds after the short-cutting event. The voltage recovery rate, the period of AC voltage-driving signal, the flow rates and the rated input powers were found to play an important role in affecting the transitions among the different types of discharges.

  2. Snowball gouge-aggregates formed in experimental fault gouges at seismic slip rates

    NASA Astrophysics Data System (ADS)

    Kim, J. H.; Ree, J. H.; Hirose, T.; Yang, K.; Kim, J. W.

    2015-12-01

    Clay-clast aggregates (CCA) have commonly been reported from experimental and natural fault gouges, but their formation process and mechanical meaning are not so clear. We call CCA snowball gouge aggregate (SGA) since its formation process is similar to that of snowball (see below) and CCA-like structure has been reported also from pure quartz and pure calcite gouges. Here, we discuss the formation process of SGA and its implication for faulting from experimental results of simulated gouges. We conducted high-velocity rotary shear experiments on Ca-bentonite gouges at a normal stress of 1 MPa, slip rate of 1.31 m/s, room temperature and room humidity conditions. Ca-bentonite gouge consists of montmorillonite (>95%) and other minor minerals including quartz and plagioclase. Upon displacement, the friction abruptly increases to the 1st peak (friction coefficient μ≈ 0.7) followed by slip weakening to reach a steady state (μ≈ 0.25~0.3). The simulated fault zone can be divided into slip-localization zone (SLZ) and low-slip-rate zone (LSZ) based on grain size. Spherical SGAs with their size ranging from 1 to 100 μm occur only in LSZ, and their proportion is more than 90%. Two types of SGA occur; SGA with and without a central clast. Both types of SGA show a concentric layering defined by the alternation of pore-rich (1-1.5 μm thick) and pore-poor layers (1.5-2 μm thick). Clay minerals locally exhibit a preferred orientation with their basal plane parallel to the layer boundary. We interpret that the pore-poor layers are clay-accumulated layers formed by rolling of SGA nuclei, and pore-rich layers correspond to the boundary between accumulated clay layers. Water produced from dehydration of clays due to frictional heating presumably acts as an adhesion agent of clay minerals during rolling of SGA. Since the number of layers within each SGA represents the number of rolling, the minimum

  3. Sliding behavior and deformation textures of heated illite gouge

    USGS Publications Warehouse

    Moore, Diane E.; Summers, R.; Byerlee, J.D.

    1989-01-01

    The run products of a series of triaxial friction experiments on an illite-rich gouge have been examined petrographically to study the relationship between textural development and sliding mode. The samples show a complete range of textures, from ones in which the entire gouge layer is deformed to ones in which the deformation is concentrated along narrow subsidiary shears and the rest of the gouge layer is massive. The samples with a pervasively developed deformation fabric slide stably, whereas the samples containing shear bands show stick-slip motion if the intersection angles between boundary-parallel and cross-cutting (Riedel) shears are also relatively high. These textural differences suggest that localization of shear combined with higher-angle Riedel shears are somehow involved in stick-slip motion. The orientation of Riedel-type shears in natural fault zones may also have potential as a paleoseismological tool. ?? 1989.

  4. Nanometric Gouge in High-Speed Shearing Experiments: Superplasticity?

    NASA Astrophysics Data System (ADS)

    Green, H. W.; Lockner, D. A.; Bozhilov, K. N.; Maddon, A.; Beeler, N. M.; Reches, Z.

    2010-12-01

    High-speed shearing experiments on solid rock samples typically generate a gouge with sub-micron grain size that appears to control the frictional resistance at velocities approaching 1 m/s (Reches & Lockner, Nature, in press). We conducted experiments on Kasota dolomite samples and observed profound weakening (friction drops from ~0.8 to ~ 0.2) under earthquake conditions (up to slip-velocity ~ 0.95 m/s and normal stress 28.4 MPa). During these runs the experimental fault had T ≥ 800°C and developed a shining, dark surface. We report here analysis of such a surface with scanning electron microscopy (SEM) and atomic force microscopy (AFM). SEM analysis shows a slickensided gouge made up of particles all ≤ 50nm with a large fraction ≤ 20nm. The spacing of the slickenside striations is less than 1 µm. Over large areas of the slickensided surface the nanometric gouge has been replaced by an undeformed, interlocking crystalline pavement of 100-300 nm grain size. Qualitative chemical analysis of this pavement surface by energy-dispersive X-ray spectroscopy reveals only a weak carbon peak, suggesting that the dolomite has been decarbonated. The development of a “pavement” of grain size ~200 nm in our experiments is remarkably similar to the observations of Han et al. (JGR, 2010, Fig. 14(d)). However, their experiments either did not develop such a nanometric gouge or it was completely replaced by the coarser pavement. These present observations of nanometric gouge that recrystallizes during the short time interval of elevated temperature following termination of deformation are reminiscent of the nanometric “gouge” produced in very high-pressure experiments (1-14 GPa) that have failed by transformation-induced faulting during the olivine-spinel transformation (Green and Burnley, Nature, 1989; Green et al., Nature, 1990). In the high-pressure experiments, the gouge consists of a nanocrystalline aggregate of the spinel phase that flowed at very high strain

  5. The Frictional Proprierties of Dolomite Gouges at Subseismic Slip Rates

    NASA Astrophysics Data System (ADS)

    Faoro, I.; De Paola, N.

    2011-12-01

    Field studies conducted on the slip zones of exhumed faults, developed in the same evaporitic sequences as the seismic sources of the Colfiorito earthquakes, suggest that localized slip occurred within narrow (<5mm) principal slip zones of fine-grained dolomite and Mg-rich calcite fault gouges. These are characterized by thin slip planes of localized deformation (500 micron). Recent friction experiments performed on dolomite gouge samples at seismic slip rates have shown a dramatic drop of frictional strength (f = 0.1-0.2) from the initial peak values in the Byerlee's range (f = 0.65-0.8). Despite these laboratory data supporting dynamic lubrication of experimental faults at seismic slip rates, the frictional properties and behaviour of dolomite at subseismic slip rates are still poorly understood. We performed a set of preliminary experiments at room temperature and humidity conditions with a low to high velocity rotary shear friction apparatus to investigate the frictional properties and mechanical behaviour of dolomite gouges deforming at sub-seismic slip rates. The gouge samples have been tested at slip rates comprised between 13.4 microns/s to 1.34 mm/s and normal stresses ranging between 2 and 20 MPa. At these sub-seismic slip rates dolomite gouges display strain hardening behaviour during experiments performed at constant slip rate and normal load. During cyclic slide-hold-slide experiments, the magnitude of strain hardening decreases for increasing number of the slide-hold-slide cycles, for a given hold time. This behaviour is particularly evident at the highest normal loads, where the dolomite shows almost strain neutral behaviour during the last cycles, i.e. peak friction is almost absent. Preliminary results during velocity steps experiments show velocity strengthening behaviour at all conditions. A set of preliminary experiments performed on dolomite gouges deformed against host blocks with different roughness shows that the frictional behaviour (strain

  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. Internal Structure of Taiwan Chelungpu Fault Zone Gouges

    NASA Astrophysics Data System (ADS)

    Song, Y.; Song, S.; Tang, M.; Chen, F.; Chen, Y.

    2005-12-01

    Gouge formation is found to exist in brittle faults at all scale (1). This fine-grain gouge is thought to control earthquake instability. And thus investigating the gouge textures and compositions is very important to an understanding of the earthquake process. Employing the transmission electron microscope (TEM) and a new transmission X-ray microscope (TXM), we study the internal structure of fault zone gouges from the cores of the Taiwan Chelungpu-fault Drilling Project (TCDP), which drilled in the fault zone of 1999 Chi-Chi earthquake. This X-ray microscope have installed at beamline BL01B of the Taiwan Light Source, National Synchrotron Radiation Research Center (NSRRC). It provides 2D imaging and 3D tomography at energy 8-11 keV with a spatial resolution of 25-60 nm, and is equipped with the Zernike-phase contrast capability for imaging light materials. In this work, we show the measurements of gouge texture, particle size distribution and 3D structure of the ultracataclasite in fault gouges within 12 cm about 1111.29 m depth. These characterizations in transition from the fault core to damage zone are related to the comminuting and the fracture energy in the earthquake faulting. The TXM data recently shows the particle size distributions of the ultracataclasite are between 150 nm and 900 nm in diameter. We will keep analyzing the characterization of particle size distribution, porosity and 3D structure of the fault zone gouges in transition from the fault core to damage zone to realize the comminuting and fracture surface energy in the earthquake faulting(2-5).The results may ascertain the implication of the nucleation, growth, transition, structure and permeability of the fault zones(6-8). Furthermore, it may be possible to infer the mechanism of faulting, the physical and chemical property of the fault, and the nucleation of the earthquake. References 1) B. Wilson, T. Dewerw, Z. Reches and J. Brune, Nature, 434 (2005) 749. 2) S. E. Schulz and J. P. Evans

  8. Ice-gouged microrelief on the floor of the eastern Chukchi Sea, Alaska: a reconnaissance survey

    USGS Publications Warehouse

    Toimil, Lawrence J.

    1978-01-01

    Side-scan sonar and bathymetric records obtained from 1,800 km of trackline from the eastern Chukchi Sea continental shelf, between water depths of 20 and 70 m show the ubiquitous presence of furrow-like linear depressions produced by gouging of the sea bed by ice keels. These sea bed micro-features are regionally widespread but are not uniformly distributed. Furthermore, the microrelief, texture, and lithologic structure of sea bed sediments have been significantly modified by the disruptive processes associated with ice gouge formation. An analysis of some 10,.200 individual gouges shows that the density of ice gouges increases with increasing latitude, increasing slope gradients, and decreasing water depth. Across the northern half of the shelf few trackline segments are free of ice gouges; in the southern portion numerous segments contain no ice gouges. However, ice gouges extend at least as far south as Cape Prince of Wales Shoal. Densities of over 200 gouges per km of trackline are not uncommon in water depths less than 30 m ,but no values higher than 50 km are encountered in water deeper than 50 m. No ice gouges have been observed in water depths exceeding 58 m. Saturation ice gouge densities (greater than 300/Pan) occur along the eastern side 6f Barrow Sea Valley and the northeast flank of Hanna Shoal. Maximum gouge incision depths per km of trackline are greatest in water 36 to 50 m deep . A maximum incision depth of 4.5 m occurs in the 35-40 m water depth interval. Individual ice gouge events wider than 100 m, most produced by multi-keeled ice fragments, are found between 31 and 45 m depths. The dominant azimuth of gouge furrows shows no preferred orientation on the Chukchi Sea shelf; only locally does bathmetric control of the trend of gouges appear. The occurrence of current-produced bedforms within individual ice gouges suggests an interaction between slow-moving grounded or gouging ice keels and swift currents. In other cases, current

  9. Distribution of air and serum PCDD/F levels of electric arc furnaces and secondary aluminum and copper smelters.

    PubMed

    Lee, Ching-Chang; Shih, Tung-Seng; Chen, Hsiu-Ling

    2009-12-30

    Metallurgical processes, such as smelting, can generate organic impurities such as organic chloride chemicals, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). The objective of this study was to elucidate the serum PCDD/F levels of 134 workers and ambient air levels around electric arc furnaces (EAF), secondary copper smelters and secondary aluminum smelters (ALSs) in Taiwan. The highest serum PCDD/F levels were found in the ALSs workers (21.9 pg WHO-TEQ/g lipid), with lower levels in copper smelter workers (21.5 pg WHO-TEQ/g lipid), and the lowest in the EAF plant workers (18.8 pg WHO-TEQ/g lipid). This was still higher than the levels for residents living within 5 km of municipal waste incinerators (14.0 pg WHO-TEQ/g lipid). For ambient samples, the highest ambient air PCDD/F level was in the copper smelters (12.4 pg WHO-TEQ/Nm(3)), with lower levels in ALSs (7.2 pg WHO-TEQ/Nm(3)), and the lowest in the EAF industry (1.8 pg WHO-TEQ/Nm(3)). The congener profiles were consistent in serum and in air samples collected in the copper smelters, but not for ALSs and EAF. In secondary copper smelters, the air PCDD/Fs levels might be directly linked to the PCDD/Fs accumulated in the workers due to the exceedingly stable congener pattern of the PCDD/F emission.

  10. Gouge initiation in high-velocity rocket sled testing

    NASA Astrophysics Data System (ADS)

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

    1994-07-01

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

  11. 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.

  12. Mechanical amorphization during experimental shearing of synthetic granite gouge

    NASA Astrophysics Data System (ADS)

    White, J. C.; Hadizadeh, J.; Tullis, T. E.; Goldsby, D. L.

    2009-04-01

    Frictional sliding experiments performed in a rotary shear machine at 25 MPa normal stress on 2-mm thick layers of simulated Westerly granite gouge (initial particle size 1-85 µm) have produced heterogeneous microstructures comprising comminuted material with internal layering. In SEM/BSE individual layers comprise grains of rounded and sub-rounded quartz and feldspar particles that vary in size from 20nm on one side to about 300nm on the other. Characterization of the gouge ultrastructure has been undertaken by analytical scanning transmission electron microscopy (STEM). Areas were selected from high-magnification SEM images and thinned in a focused ion beam instrument (FIB). This sampling procedure produces material of even electron transparency with perfect spatial registration to the optical and SEM microstructures. The sub-micrometre-scale laminar variation of grain size and porosity is confirmed by STEM. Shards of both feldspar and quartz are progressively comminuted to form the texture in which larger grains are surrounded by finer-comminuted matrix material. Grains of both of the latter primary mineral constituents are routinely less than 100 nm in size. Most significantly, the finest grained, least porous zones comprise small grain fragments embedded within an amorphous silicate matrix. By extension, one can infer that observation of these zones throughout the gouge is consistent with extensive amorphization during the shearing. The internal layering of the brecciated fragments, with asymmetric particle size and porosity grading, indicates that Y-slip surfaces localize displacement until particles that line the slip surface are reduced to a critical size that enables mechanically induced amorphization. Fluctuations in friction recorded during formation of this microstructure can be reasonably related to cyclic softening-hardening related to porosity loss and amorphization, with subsequent brecciation of the gouge during slip on multiple Y-slip surfaces.

  13. A new test method for the assessment of the arc tracking properties of wire insulation in air, oxygen enriched atmospheres and vacuum

    NASA Technical Reports Server (NTRS)

    Koenig, Dieter

    1994-01-01

    Development of a new test method suitable for the assessment of the resistance of aerospace cables to arc tracking for different specific environmental and network conditions of spacecraft is given in view-graph format. The equipment can be easily adapted for tests at different realistic electrical network conditions incorporating circuit protection and the test system works equally well whatever the test atmosphere. Test results confirm that pure Kapton insulated wire has bad arcing characteristics and ETFE insulated wire is considerably better in air. For certain wires, arc tracking effects are increased at higher oxygen concentrations and significantly increased under vacuum. All tests on different cable insulation materials and in different environments, including enriched oxygen atmospheres, resulted in a more or less rapid extinguishing of all high temperature effects at the beginning of the post-test phase. In no case was a self-maintained fire initiated by the arc.

  14. Vacuum-Induction, Vacuum-Arc, and Air-Induction Melting of a Complex Heat-Resistant Alloy

    NASA Technical Reports Server (NTRS)

    Decker, R. F.; Rowe, John P.; Freeman, J. W.

    1959-01-01

    The relative hot-workability and creep-rupture properties at 1600 F of a complex 55Ni-20Cr-15Co-4Mo-3Ti-3Al alloy were evaluated for vacuum-induction, vacuum-arc, and air-induction melting. A limited study of the role of oxygen and nitrogen and the structural effects in the alloy associated with the melting process was carried out. The results showed that the level of boron and/or zirconium was far more influential on properties than the melting method. Vacuum melting did reduce corner cracking and improve surface during hot-rolling. It also resulted in more uniform properties within heats. The creep-rupture properties were slightly superior in vacuum heats at low boron plus zirconium or in heats with zirconium. There was little advantage at high boron levels and air heats were superior at high levels of boron plus zirconium. Vacuum heats also had fewer oxide and carbonitride inclusions although this was a function of the opportunity for separation of the inclusions from high oxygen plus nitrogen heats. The removal of phosphorous by vacuum melting was not found to be related to properties. Oxygen plus nitrogen appeared to increase ductility in creep-rupture tests suggesting that vacuum melting removes unidentified elements detrimental to ductility. Oxides and carbonitrides in themselves did not initiate microcracks. Carbonitrides in the grain boundaries of air heats did initiate microcracks. The role of microcracking from this source and as a function of oxygen and nitrogen content was not clear. Oxygen and nitrogen did intensify corner cracking during hot-rolling but were not responsible for poor surface which resulted from rolling heats melted in air.

  15. Study of Nanodispersed Iron Oxides Produced in Steel Drilling by Contracted Electric-Arc Air Plasma Torch

    NASA Astrophysics Data System (ADS)

    Stefanov, P.; Galanov, D.; Vissokov, G.; Paneva, D.; Kunev, B.; Mitov, I.

    2008-06-01

    The optimal conditions on the plasma-forming gas flowrate, discharge current and voltage, distance between the plasma-torch nozzle and the metal plate surface for the process of penetration in and vaporization of steel plates by the contracted electric-arc air plasma torch accompanied by water quenching, were determined. The X-ray structural and phase studies as well as Mössbauer and electron microscope studies on the samples treated were performed. It was demonstrated that the vaporized elemental iron was oxidized by the oxygen present in the air plasma jet to form iron oxides (wüstite, magnetite, hematite), which, depending on their mass ratios, determined the color of the iron oxide pigments, namely, beginning from light yellow, through deep yellow, light brown, deep brown, violet, red-violet, to black. A high degree of dispersity of the iron oxides is thus produced, with an averaged diameter of the particles below 500 nm, and their defective crystal structure form the basis of their potential application as components of iron-containing catalysts and pigments.

  16. [X-ray diffraction and infrared spectrum analysis of fault gouge in Wenchuan seismic belt].

    PubMed

    Wang, Zheng-Yang; Cao, Jian-Jin; Luo, Song-Ying; Liao, Yi-Peng

    2014-05-01

    Wenchuan earthquake produced a series of co-seismic surface ruptures in Leigu and Zhaojiagou, and we collected samples of co-seismic fault gouge in the surface ruptures as well as the old gouge in the fault of Nanba. Testing The new and old fault gouge was tested with X-ray diffraction and infrared absorption spectra, and its characteristics such as mineral compositions, clay mineral contents and combinations were comprehensively analyzed. The results display obvious differences between the new and old fault gouge, showing that the old fault gouge is mainly composed of wall rock debris or milled powders, while the main components of new fault gouge are clay minerals. The assemblage of clay minerals composition shows that the environment of the fault activity was mainly warm and humid, and the clay minerals were mainly transformed by low temperature and low pressure dynamic metamorphism. And this also partly indicates that the latest way of the fault activity in this area may be a creeping. However the previous researches on the fault gouge of Wenchuan earthquake fault zone are mainly focused on its mechanical properties as well as its texture and structure, the research in this paper is to determine the physical and chemical environment of fault activity through the mineral compositions and clay mineral contents in the fault gouge characteristics, and this research has important scientific significance to the researches on the evolution of the fault environment and the activity mechanism of the earthquake.

  17. Ice gouge obliteration and sediment redistribution event: 1977-1978, Beaufort Sea, Alaska

    USGS Publications Warehouse

    Barnes, Peter W.; Reimnitz, Erk

    1979-01-01

    In 1978 major changes in shelf morphology were observed during a routine re-survey of part of the inner shelf region of the central Beaufort Sea. Regional observations are coupled with a detailed diving and side-scan study of a single ice gouge of known age to develop a detailed description of the altered seabed conditions. Hydrodynamic activity has caused extensive sediment reworking, obliterating ice gouges to water depths of at least 13 m and has caused ponding of sediment in ice gouge terrain in deeper waters. Ponded sediment is characterized as a soft, sometimes very poorly consolidated, mud unit underlain by a stiffer, more consolidated, silty clay. In places, stiff silty clay is exposed in windows in the sediment pond and displays a fine-textured ice gouge morphology. Rates of sediment reworking and redisposition from apparently episodic events are an order of magnitude greater than the average sediment accumulation rates on the Beaufort Sea shelf. Reported maximum ice gouge incision depths are not representative of maximum ice keel penetrations into the seabed because these sedimentation events preferentially infill gouges. Furthermore, because these sedimentation events concentrate sediments in gouge troughs, a series of overlapping and interfingering 'shoestring' deposits is developed which should characterize the ice gouge stratigraphy. The specific hydraulic mechanisms for sediment redistribution and sediment compaction observed in this study are only poorly understood.

  18. Role of autonomic reflex arcs in cardiovascular responses to air pollution exposure.

    PubMed

    Perez, Christina M; Hazari, Mehdi S; Farraj, Aimen K

    2015-01-01

    The body responds to environmental stressors by triggering autonomic reflexes in the pulmonary receptors, baroreceptors, and chemoreceptors to maintain homeostasis. Numerous studies have shown that exposure to various gases and airborne particles can alter the functional outcome of these reflexes, particularly with respect to the cardiovascular system. Modulation of autonomic neural input to the heart and vasculature following direct activation of sensory nerves in the respiratory system, elicitation of oxidative stress and inflammation, or through other mechanisms is one of the primary ways that exposure to air pollution affects normal cardiovascular function. Any homeostatic process that utilizes the autonomic nervous system to regulate organ function might be affected. Thus, air pollution and other inhaled environmental irritants have the potential to alter both local airway function and baro- and chemoreflex responses, which modulate autonomic control of blood pressure and detect concentrations of key gases in the body. While each of these reflex pathways causes distinct responses, the systems are heavily integrated and communicate through overlapping regions of the brainstem to cause global effects. This short review summarizes the function of major pulmonary sensory receptors, baroreceptors, and carotid body chemoreceptors and discusses the impacts of air pollution exposure on these systems.

  19. Correlation of clayey gouge in a surface exposure of the San Andreas fault with gouge at depth from SAFOD: Implications for the role of serpentinite in fault mechanics

    USGS Publications Warehouse

    Moore, Diane E.; Rymer, Michael J.

    2012-01-01

    Magnesium-rich clayey gouge similar to that comprising the two actively creeping strands of the San Andreas Fault in drill core from the San Andreas Fault Observatory at Depth (SAFOD) has been identified in a nearby outcrop of serpentinite within the fault zone at Nelson Creek. Each occurrence of the gouge consists of porphyroclasts of serpentinite and sedimentary rocks dispersed in a fine-grained, foliated matrix of Mg-rich smectitic clays. The clay minerals in all three gouges are interpreted to be the product of fluid-assisted, shear-enhanced reactions between quartzofeldspathic wall rocks and serpentinite that was tectonically entrained in the fault from a source in the Coast Range Ophiolite. We infer that the gouge at Nelson Creek connects to one or both of the gouge zones in the SAFOD core, and that similar gouge may occur at depths in between. The special significance of the outcrop is that it preserves the early stages of mineral reactions that are greatly advanced at depth, and it confirms the involvement of serpentinite and the Mg-rich phyllosilicate minerals that replace it in promoting creep along the central San Andreas Fault.

  20. Experimental investigations of mechanical healing of a simulated fault gouge

    NASA Astrophysics Data System (ADS)

    Messen, Y. H.; Corfdir, A.; Schmittbuhl, J.; Toussaint, R.

    2009-04-01

    In order to investigate the effect of fast healing from mechanical perturbations on the frictional behavior of fault surfaces, slide-hold-slide (SHS) experiments are often run in which holds are preceded by a rapid reduction of the shear stress, that triggers an increase of shear strength when resuming shear (i.e. The Tightening-up effect of unloading or Tu-effect). We present laboratory investigation where we explore the role of slip and stress perturbations before resuming the general loading of the frictional interface. Tests are performed with the Annular Simple Shear Apparatus (Navier/CERMES, Ecole des Ponts ParisTech, France) for studying such mechanical healing of a simulated fault gouge. A 100mm thick annular sample of siliceous sand (0.6mm diameter) is submitted to shear by the mean of a rotating cylinder in a semi-Couette geometry. We show that rather than small shear stress perturbations, small back-slips are responsible for significant restrengthening of the interface. Shear stress perturbations that do not lead to any significant inelastic back-slips, however, do not lead to restrengthening. A robust linear relationship between the amount of the back-slip and the strength increase is surprisingly obtained. This result suggests that small perturbations of the contact status in the granular assembly of gouge particles have a major influence on the fault restrengthening. Small displacements might have a much larger effect on the force chain transfer than stress perturbations.

  1. Experimental studies of compaction and dilatancy during frictional sliding on faults containing gouge

    USGS Publications Warehouse

    Morrow, C.A.; Byerlee, J.D.

    1989-01-01

    Transient strength changes are observed in fault gouge materials when the velocity of shearing is varied. A transient stress peak is produced when the strain rate in the gouge is suddenly increased, whereas a transient stress drop results from a sudden change to a slower strain rate. We have studied the mechanism responsible for these observations by performing frictional sliding experiments on sawcut granite samples filled with a layer of several different fault gouge types. Changes in pore volume and strength were monitored as the sliding velocity alternated between fast and slow rates. Pore volume increased at the faster strain rate, indicating a dilation of the gouge layer, whereas volume decreased at the slower rate indicating compaction. These results verify that gouge dilation is a function of strain rate. Pore volume changed until an equilibrium void ratio of the granular material was reached for a particular rate of strain. Using arguments from soil mechanics, we find that the dense gouge was initially overconsolidated relative to the equilibrium level, whereas the loose gouge was initially underconsolidated relative to this level. Therefore, the transient stress behavior must be due to the overconsolidated state of the gouge at the new rate when the velocity is increased and to the underconsolidated state when the velocity is lowered. Time-dependent compaction was also shown to cause a transient stress response similar to the velocity-dependent behavior. This may be important in natural fault gouges as they become consolidated and stronger with time. In addition, the strain hardening of the gouge during shearing was found to be a function of velocity, rendering it difficult to quantify the change in equilibrium shear stress when velocity is varied under certain conditions. ?? 1989.

  2. Grain size distribution of fault rocks: implication from natural gouges and high velocity friction experiments

    NASA Astrophysics Data System (ADS)

    Yang, X.; Chen, J.; Duan, B.

    2011-12-01

    The grain size distribution (GSD) is considered as an important parameter for the characterization of fault rocks. The relative magnitude of energy radiated as seismic waves to fracture energy plays a fundamental role to influence earthquake rupture dynamics. Currently, the details of grain size reduction mechanism and energy-budget are not well known. Here we present GSD measurements on fault rocks (gouge and breccias) in the main slip zone associated with the Wenchuan earthquake happened on 12 May, 2008, and on the gouges produced by high velocity friction (HVF) experiments. High velocity friction experiments were carried out on air dry granitic powder with grain size of 150 - 300 μm at normal stress of 1.0 MPa, a slip rate of 1.0 m / s and slip distances from 10 m to 30 m. On log-log plots of N(r) versus equivalent radius, two distinct linear parts can be discriminated with their intersection at 1 - 2 μm, defined as critical radius rc. One of power-law regime spans about 4 decades from 4 μm to 16 mm and the other covers a range of 0.2 - 2.0 μm. Larger fractal dimension from 2.7 to 3.5 are obtained for larger grain size regime, while lower values ranging from 1.7 to 2.1 for smaller size one. This two-stage distribution means the GSD is not self-similar (scale invariant) and the dominant ways of reducing grain size may be different from one another. XRD data show that the content of quartz drops greatly or disappears at 0.5 - 0.25 μm. GSD of HVF experimental products demonstrates similar feature to natural gouges. For instance, they all show the two-stage GSD with 1 - 2 μm of critical radius rc. The grains with their sizes of less than 1 μm appear rounded edges and equiaxial shapes. A variation in grain shapes can be observed in the grains larger than 5 μm. Some implications could be obtained from the measurements and experiments. (1) rc corresponds to the average value of grinding limit of rock-forming minerals. Further grain size reducing could be

  3. Experimental study on copper cathode erosion rate and rotational velocity of magnetically driven arcs in a well-type cathode non-transferred plasma torch operating in air

    NASA Astrophysics Data System (ADS)

    Chau, S. W.; Hsu, K. L.; Lin, D. L.; Tzeng, C. C.

    2007-04-01

    The cathode erosion rate, arc root velocity and output power of a well-type cathode (WTC), non-transferred plasma torch operating in air are studied experimentally in this paper. An external solenoid to generate a magnetically driven arc and a circular swirler to produce a vortex flow structure are equipped in the studied torch system, which is designed to reduce the erosion rate at the cathode. A least square technique is applied to correlate the system parameters, i.e. current, axial magnetic field and mass flow rate, with the cathode erosion rate, arc root velocity and system power output. In the studied WTC torch system, the cathode erosion has a major thermal erosion component and a minor component due to the ion-bombardment effect. The cathode erosion increases with the increase of current due to the enhancement in both Joule heating and ion bombardment. The axial magnetic field can significantly reduce the cathode erosion by reducing the thermal loading of cathode materials at the arc root and improving the heat transfer to gas near the cathode. But, the rise in the mass flow rate leads to the deterioration of erosion, since the ion-bombardment effect prevails over the convective cooling at the cathode. The most dominant system parameter to influence the arc root velocity is the axial magnetic field, which is mainly contributed to the magnetic force driving the arc. The growth in current has a negative impact on increasing the arc root velocity, because the friction force acting at the spot due to a severe molten condition becomes the dominant component counteracting the magnetic force. The mass flow rate also suppresses the arc root velocity, as a result of which the arc root moves in the direction against that of the swirled working gas. All system parameters such as current, magnetic field and gas flow rate increase with the increase in the torch output power. The experimental evidences suggest that the axial magnetic field is the most important parameter

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

    NASA Astrophysics Data System (ADS)

    Tachau, Robert David Mazur

    1991-02-01

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

  5. Frictional strength and velocity-dependence of serpentine gouges under hydrothermal conditions and their seismogeological implications

    USGS Publications Warehouse

    Ma, S.; Lockner, D.; Moore, D.; Summers, R.; Byerlee, J.

    1997-01-01

    The velocity - dependence of frictional strength of serpentine gouges has been measured at constant normal stress of 110 MPa, pore pressure of 10 MPa, temperature 25, 100 and 200??C , and at sliding rate ranging from 0. 001 to 10??m/s. At 25??C, the coefficient of friction of chrysotile gouge is very low (?????0. 2-0. 25), while lizardite and antigorite gouge are much stronger, with ?????0. 39 and 0. 45, respectively. The frictional strengths of chrysotile and antigorite gouges change little with a temperature increase to 200??C, whereas the strength of lizardite gouge increases substantially with increasing temperature. At 25??C, all three gouges show a transition from weak velocity weakening at high slip rates to velocity strengthening at low slip rates. With increasing temperature, the velocity dependence of each gouge shifts towards more positive values, especially at high slip rates. Based on this study and previous results, we suggest that the presence of serpentine in the fault zone may contribute to the occurrence of stable creep rather than earthquakes, but this effect may be limited to shallow depths. Although chrysotile is one of the weakest rock - forming minerals, it is still too strong to explain the weakness of the San Andreas fault deduced from heat flow data.

  6. The effects of sliding velocity on the frictional and physical properties of heated fault gouge

    USGS Publications Warehouse

    Moore, Diane E.; Summers, R.; Byerlee, J.D.

    1986-01-01

    The frictional properties of a crushed granite gouge and of gouges rich in montmorillonite, illite, and serpentine minerals have been investigated at temperatures as high as 600??C, confining pressures as high as 2.5 kbar, a pore pressure of 30 bar, and sliding velocities of 4.8 and 4.8??10-2 ??m/sec. The gouges showed nearly identical strength behaviors at the two sliding velocities; all four gouges, however, showed a greater tendency to stick-slip movement and somewhat higher stress drops in the experiments at 4.8??10-2 ??m/sec. Varying the sliding velocity also had an effect on the mineral assemblages and deformation textures developed in the heated gouges. The principal mineralogical difference was that at 400??C and 1 kbar confining pressure a serpentine breakdown reaction occurred in the experiments at 4.8??10-2 ??m/sec but not in those at 4.8 ??m/sec. The textures developed in the gouge layers were in part functions of the gouge type and the temperature, but changes in the sliding velocity affected, among other features, the degree of mineral deformation and the orientation of some fractures. ?? 1986 Birkha??user Verlag.

  7. Dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates.

    PubMed

    Proctor, B P; Mitchell, T M; Hirth, G; Goldsby, D; Zorzi, F; Platt, J D; Di Toro, G

    2014-11-01

    To investigate differences in the frictional behavior between initially bare rock surfaces of serpentinite and powdered serpentinite ("gouge") at subseismic to seismic slip rates, we conducted single-velocity step and multiple-velocity step friction experiments on an antigorite-rich and lizardite-rich serpentinite at slip rates (V) from 0.003 m/s to 6.5 m/s, sliding displacements up to 1.6 m, and normal stresses (σn ) up to 22 MPa for gouge and 97 MPa for bare surfaces. Nominal steady state friction values (μnss) in gouge at V = 1 m/s are larger than in bare surfaces for all σn tested and demonstrate a strong σn dependence; μnss decreased from 0.51 at 4.0 MPa to 0.39 at 22.4 MPa. Conversely, μnss values for bare surfaces remained ∼0.1 with increasing σn and V. Additionally, the velocity at the onset of frictional weakening and the amount of slip prior to weakening were orders of magnitude larger in gouge than in bare surfaces. Extrapolation of the normal stress dependence for μnss suggests that the behavior of antigorite gouge approaches that of bare surfaces at σn ≥ 60 MPa. X-ray diffraction revealed dehydration reaction products in samples that frictionally weakened. Microstructural analysis revealed highly localized slip zones with melt-like textures in some cases gouge experiments and in all bare surfaces experiments for V ≥ 1 m/s. One-dimensional thermal modeling indicates that flash heating causes frictional weakening in both bare surfaces and gouge. Friction values for gouge decrease at higher velocities and after longer displacements than bare surfaces because strain is more distributed.

  8. Powder lubrication of faults by powder rolls in gouge zones

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Powder-lubrication by fault gouge can be an effective mechanism of dynamic weakening of faults (Reches & Lockner, 2010); however, the physical mechanisms of this lubrication are poorly understood. While the flow of coarse-grained (> 100 μm) materials, e.g. glass beads or quartz sand, was extensively studied, the flow of fine-grained (< 1 μm) powders, e.g., fault-gouge and nano-powders, have remained enigmatic. We report here experimental results of a new efficient mechanism for powder lubrication. We conducted friction tests on high-velocity rotary shear apparatus (Reches & Lockner, 2010). Two types of experimental faults were tested: (1) faults made of solid, igneous rocks (granite, tonalite and diorite); and (2) fault-zones made of 2-3 mm thick layer of granular materials (oolites, calcite or gypsum) sheared in a confined cell. We performed 21 runs with total slip of 0.14-13 m, normal stress of 1.2-14.5 MPa, slip velocity of 0.012-0.97 m/s. The ultra-microscopic (SEM and AFM) analysis of the experimental slip surfaces revealed two outstanding features in 17 out of the 21 experiments: (1) localized fault-slip along Principal Slip Zones (PSZs) that are composed of a dense, shiny, cohesive crust, 0.5-1 micron thick, that overlaid a porous substrate, and (2) elongated rolls composed of gouge-powder into three-dimensional structures of closely-packed powder grains, (20-50 nm in size). The rolls are cylindrical, 0.75-1.4 micron wide, and 1.7-30 micron long, with smooth outer surface, and laminated, concentric layers of compacted grains. The rolls were exclusively found on the PSZs. Many rolls were destroyed fracturing and smearing on the PSZ, suggesting that the rolls underwent a life cycle of formation and destruction. Significant macroscopic friction reduction was measured in experiments with observed rolls, and no (or minor) friction reduction in the four experiments without rolls. The final, reduced friction coefficients have a general reciprocal relation to the

  9. Healing and sliding stability of simulated anhydrite fault gouge: Effects of water, temperature and CO2

    NASA Astrophysics Data System (ADS)

    Pluymakers, Anne M. H.; Niemeijer, André R.

    2015-08-01

    Anhydrite-bearing faults are currently of interest to 1) CO2-storage sites capped by anhydrite caprocks (such as those found in the North Sea) and 2) seismically active faults in evaporite formations (such as the Italian Apennines). In order to assess the likelihood of fault reactivation, the mode of fault slip and/or fault leakage, it is important to understand the evolution of frictional strength during periods of no slip and upon reloading (healing and relaxation behavior) and of the velocity dependence of friction of anhydrite fault gouge. Therefore, we performed slide-hold-slide experiments combined with a velocity-stepping sequence using simulated anhydrite fault gouge (> 95 wt.% CaSO4). Vacuum-dry and water-wet experiments were performed at temperatures ranging from 20 to 150 °C, and at an effective normal stress of 25 MPa. We also performed tests using dry CO2, water-wetted CO2 and CO2-saturated water as pore fluid, but only at 120 °C. If pore fluid was present, a fluid pressure of 15 MPa was present. Vacuum-dry samples exhibit similar frictional healing to samples containing lab-air, but healing is significantly enhanced in wet samples. Dry samples exhibit velocity-weakening behavior at T ≥ 120 °C, and wet samples exhibit velocity-strengthening behavior over the full temperature range. The presence of CO2 does not influence the healing behavior or the velocity-dependence of friction. Samples containing water-wetted CO2 exhibit behavior similar to wet samples. We infer that the healing in dry samples is controlled by plastic asperity creep (Dieterich-type), possibly through dislocation creep and/or twinning. In wet samples healing is inferred to be controlled by increases in contact area and cohesion by pressure solution. Using a pressure solution rate model to extrapolate healing by contact area growth indicates that the maximum re-strengthening through such a mechanism will only take days to tens of days.

  10. Discovery of 100-160-year-old iceberg gouges and their relation to halibut habitat in Glacier Bay, Alaska

    USGS Publications Warehouse

    Carlson, P.R.; Hooge, P.N.; Cochrane, G.R.

    2005-01-01

    Side-scan sonar and multibeam imagery of Glacier Bay, Alaska, revealed complex iceberg gouge patterns at water depths to 135 m on the floor of Whidbey Passage and south to the bay entrance. These previously undiscovered gouges likely formed more than 100 years ago as the glacier retreated rapidly up Glacier Bay. Gouged areas free of fine sediment supported greater biodiversity of Pacific halibut Hippoglossus stenolepsis than nearby sediment-filled gouges, probably due to increased habitat complexity. Small Pacific halibut were forund more frequently in sediment-free gouged areas, presumably due to higher prey abundance. In contrast, large Pacific halibut were found more frequently on soft substrates such as sediment-filled gouges, where they could bury themselves and ambush prey.

  11. Experimental and microstructural investigations of frictional heating and fluidization in clay-rich fault gouge

    NASA Astrophysics Data System (ADS)

    Ujiie, K.; Nakakoji, T.; Tsutsumi, A.

    2011-12-01

    Mature faults commonly contain a considerable amount of clay minerals in their core. The frictional properties and the co-seismic deformation mechanisms of clay-rich fault gouges are key controls of the co-seismic fault strength, rupture propagation, and tsunamigenesis in subduction zones. Recent microstructural observations of natural slip zones and high-velocity friction experiments on clay-rich fault gouges suggest that the clay-clast aggregates (CCA; the spherical aggregates defined by clasts surrounded by a cortex of concentric clay layer) and the grain size segregation could be new textural evidence for thermal pressurization associated with water vaporization and fluidization, respectively. However, the physical processes and frictional properties during the development of these textures remain not fully understood. We conducted friction experiments on clay-rich fault gouge taken from the megasplay fault zone in the Nankai subduction zone and examined the resulting microstructures. Friction experiments were conducted at a normal stress of 1.0 MPa and slip rates (V) of 0.0013-1.3 m/s under dry (room humidity) and wet (water saturated) conditions. In the dry tests at V=1.3 m/s, the peak friction of 0.6-0.7 decreases to the steady-state friction of 0.2, over slip weakening distances of ~10.9 m, which is closely correlated to gouge dilation. In contrast, there is no visible slip weakening in the dry tests at V=0.0013-0.13 m/s; friction coefficients remain high in the range of 0.6-0.9 until the end of the experiments and the gouge dilation is small or absent. However, CCA are observed in all dry tests, with their volume content in the fault gouge decreasing with a decrease in V. The calculated temperatures in the fault gouge during the experiments are lower than the temperature for water vaporization at 1.0 MPa (180°C) when V=0.0013-0.013 m/s. These results demonstrate that CCA are neither textural evidence of the reduction in frictional coefficient due to

  12. Texture evolution in calcite gouge formed at sub-seismic slip

    NASA Astrophysics Data System (ADS)

    Delle Piane, Claudio; Luzin, Vladimir; Timms, Nick E.; Ben Clennell, M.; Giwelli, Ausama

    2016-04-01

    Carbonate rocks are abundant in the upper crust and are notoriously seismogenic with Mw>6 earthquakes nucleating in fault zones in carbonate dominated units around the world. Field observations describe fault zones as characterised by a narrow principal slip zone at their core, containing fine, granular wear material referred to as fault gouge, produced during cumulative slip. The current literature on the link between texture and frictional properties of calcite gouges is very limited and somewhat contradictory: based on the study of a natural calcite gouge a link has been proposed between the presence of a crystallographic preferred orientation (CPO) and past seismic activity on the gouge hosting fault zone. However, similar features in terms of CPO were also identified on gouges experimentally generated at slip velocities well below the seismic ones, therefore questioning their interpretation as diagnostic of past seismic events. We studied the evolution of friction coefficient and texture on calcite gouges experimentally produced by means of high pressure direct shear experiments on large, water saturated, intact blocks of travertine (calcite 99 % wt.). Several blocks were deformed at room temperature up to different amounts of maximum displacements (20 mm, 70 mm and 120 mm) under an imposed sub-seismic slip rate of approximately 0.1 microns/s. Microstructural characterization of the deformed blocks was subsequently carried out on samples representing the highest strained portion s of each blocks (i.e. gouge zones). Local and bulk texture of the original and deformed materials was studied by means of electron backscattered diffraction (EBSD) and neutron diffraction, respectively. Direct shear experiments consistently indicate an evolution of the friction coefficient stabilizing at around values of 0.6 after 15 mm of slip. Macroscopic observations on the deformed blocks indicate that deformation is localised in a narrow band of extreme grain size reduction

  13. The frictional properties of a simulated gouge having a fractal particle distribution

    USGS Publications Warehouse

    Biegel, R.L.; Sammis, C.G.; Dieterich, J.H.

    1989-01-01

    The frictional properties of a layer of simulated Westerly granite fault gouge sandwiched between sliding blocks of Westerly granite have been measured in a high-speed servo-controlled double-direct shear apparatus. Most gouge layers were prepared to have a self-similar particle distribution with a fractal dimension of 2.6. The upper fractal limit was varied between 45 and 710 ??m. Some gouges were prepared with all particles in the range between 360 and 710 ??m. In each experiment the sliding velocity was cyclically alternated between 1 and 10 ??ms-1 and the coefficient of friction ??m and its transient parameters a, b and Dc were measured as functions of displacement. In addition to the particle size distribution, the following experimental variables were also investigated: the layer thickness (1 and 3 mm), the roughness of the sliding surfaces (Nos 60 and 600 grit) and the normal stress (10 and 25 MPa). Some of the sample assemblies were epoxy impregnated following a run so the gouge structure could be microscopically examined in thin section. We observed that gouges which were initially non-fractal evolved to a fractal distribution with dimension 2.6. Gouges which had an initial fractal distribution remained fractal. When the sliding blocks had smooth surfaces, the coefficient of friction was relatively low and was independent of the particle distribution. In these cases, strong velocity weakening was observed throughout the experiment and the transient parameters a, b and Dc, remained almost constant. When the sliding blocks had rough surfaces, the coefficient of friction was larger and more dependent on the particle distribution. Velocity strengthening was observed initially but evolved to velocity weakening with increased sliding displacement. All three transient parameters changed with increasing displacement. The a and b values were about three times as large for rough surfaces as for smooth. The characteristic displacement Dc was not sensitive to surface

  14. Textural development of clayey and quartzofeldspathic fault gouges relative to their sliding behavior

    USGS Publications Warehouse

    Moore, Diane E.; Byerlee, J.D.

    1990-01-01

    Many of the secondary fault structures developed during triaxial friction experiments have been generally correlated with the structures of natural fault zones. Therefore, any physical differences that can be found between laboratory samples that slide stably and those that show stick-slip motion may help to identify the cause of earthquakes. We have examined petrographically the run products of many triaxial friction experiments using clayey and quartzofeldspathic gouges, which comprise the principal types of natural fault gouge material. The examined samples were tested under a wide range of temperature, confining and fluid pressure, and velocity conditions. The clayey and quartzofeldspathic gouges show some textural differences, owing to their different mineral contents and grain sizes and shapes. In the clayey gouges, for example, a clay mineral fabric and kink band sets are commonly developed, whereas in the quartzofeldspathic gouges fracturing and crushing of the predominately quartz and feldspar grains are important processes. For both types of gouge, however, and whatever the pressure-temperature-velocity conditions of the experiments, the transition from stable sliding to stick-slip motion is correlated with: (i) a change from pervasive deformation of the gouge layer to localized slip in subsidiary shears; and (ii) an increase in the angle betweem the shears that crosscut the gouge layer (Riedel shears) and ones that form along the gouge-rock cylinder boundaries (boundary shears). This suggests that the localization of shear within a fault zone combined with relatively high Riedel-shear angles are somehow connected with earthquakes. Secondary fracture sets similar to Riedel shears have been identified at various scales in major strike-slip faults such as the San Andreas of the western United States (Wallace, 1973) and the Luhuo and Fuyun earthquake faults of China (Deng and Zhang, 1984; Deng et al., 1986). The San Andreas also contains locked and creeping

  15. Dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates

    PubMed Central

    Proctor, B P; Mitchell, T M; Hirth, G; Goldsby, D; Zorzi, F; Platt, J D; Di Toro, G

    2014-01-01

    To investigate differences in the frictional behavior between initially bare rock surfaces of serpentinite and powdered serpentinite (“gouge”) at subseismic to seismic slip rates, we conducted single-velocity step and multiple-velocity step friction experiments on an antigorite-rich and lizardite-rich serpentinite at slip rates (V) from 0.003 m/s to 6.5 m/s, sliding displacements up to 1.6 m, and normal stresses (σn) up to 22 MPa for gouge and 97 MPa for bare surfaces. Nominal steady state friction values (μnss) in gouge at V = 1 m/s are larger than in bare surfaces for all σn tested and demonstrate a strong σn dependence; μnss decreased from 0.51 at 4.0 MPa to 0.39 at 22.4 MPa. Conversely, μnss values for bare surfaces remained ∼0.1 with increasing σn and V. Additionally, the velocity at the onset of frictional weakening and the amount of slip prior to weakening were orders of magnitude larger in gouge than in bare surfaces. Extrapolation of the normal stress dependence for μnss suggests that the behavior of antigorite gouge approaches that of bare surfaces at σn ≥ 60 MPa. X-ray diffraction revealed dehydration reaction products in samples that frictionally weakened. Microstructural analysis revealed highly localized slip zones with melt-like textures in some cases gouge experiments and in all bare surfaces experiments for V ≥ 1 m/s. One-dimensional thermal modeling indicates that flash heating causes frictional weakening in both bare surfaces and gouge. Friction values for gouge decrease at higher velocities and after longer displacements than bare surfaces because strain is more distributed. Key Points Gouge friction approaches that of bare surfaces at high normal stress Dehydration reactions and bulk melting in serpentinite in < 1 m of slip Flash heating causes dynamic frictional weakening in gouge and bare surfaces PMID:26167425

  16. Dynamics of Particle Size Distribution in Slide-Hold Tests on Laboratory Gouge Zones

    NASA Astrophysics Data System (ADS)

    Muhuri, S. K.; Dewers, T. A.; Scott, T. E.

    2001-12-01

    Slide-hold tests using triaxially-loaded precut forcing blocks and artificial gouge examine contrasts in gouge particle size dynamics during frictional sliding and annealing or healing stages. A series of room-dry sliding experiments were conducted to various shear strains using dry gypsum gouge in between precut steel forcing members. A separate series of experiments saturated with distilled water was conducted at a pore pressure of 6.9 MPa (effective pressure of 13.8 MPa identical to the dry tests). The latter experiments were taken to a constant shear strain but were held under shear loading for various lengths of time (0.01-10 hours) after slip. Pore-volume change was monitored during hold periods. Particle size distribution (PSD) of gouge was measured using a laser particle size analyzer with a measurement range of 0.4-2000 microns. Stress-strain behavior for both dry and wet tests revealed multiple stress drops or stick-slip events and were similar suggesting no marked strengthening or weakening effect due to presence of water over the time scale of sliding. Gouge PSD's were fit to a log-normal distribution function and then analyzed in terms of the moments of mass-size distributions. The best log-normal fits were obtained in the coarser fraction of the gouge (larger than peak size). PSD means decreased with shear while higher moments such as skewness increased with shear. Particle number-size relationships computed from the mass-size distributions revealed a fractal nature of the gouge with excellent fits obtained for fine and intermediate fractions (smaller than peak size). A fractal dimension (D) around 2.6 consistent with previous work on both natural and experimental fault gouge was obtained. There appears to be a correlation between D and the amount of shear strain and an inverse relationship between D and the maximum particle size. Empirical distributions such as the Weibull, Rosin-Rammler distribution functions and others provide good approximations

  17. The Melt Transition in Mature, Fluid-Saturated Gouge

    NASA Astrophysics Data System (ADS)

    Rempel, A. W.

    2006-12-01

    Mechanisms that link the evolution of fault strength and temperature during earthquakes have been studied extensively, with accumulating constraints from theoretical, field and laboratory investigations promoting increased confidence in our understanding of the dominant physical interactions. In mature fault zones that have accommodated many large earthquakes and are characterized by gouge layers that greatly exceed the thickness of the ~ mm-scale "principal slip surfaces" in which shear is localized, the thermal pressurization of pore fluids is expected to be particularly important for reducing the fault strength and limiting the extent of shear heating. Nevertheless, for sufficiently large slip distances and reasonable estimates of hydraulic transport properties and other controlling variables, the predicted temperature increases are sometimes able to reach the onset of melting, particularly at mid to lower seismogenic depths (e.g. 10km). Reported field observations of quenched glassy melt products, known as pseudotachylytes, are much more common on young faults, particularly where slip is initiated between coherent rock surfaces, rather than in exhumed mature fault zones, where thermal pressurization is likely to be more important and macroscopic melting appears to be rare. Those pseudotachylyte layers that are recovered from mature fault zones display a range of thicknesses and crystal contents, which indicate that significant shear heating continued long after the onset of melting, with work performed against the viscous resistance of a partially molten slurry. Models that describe the transition to melting in a finite shear zone that is initially saturated with pore fluids are presented with two main conceptual challenges: 1. the energy input for frictional heating is generally assumed to be proportional to the effective stress, which vanishes when macroscopic melt layers are produced and thermodynamic considerations require that the melt pressure balance the

  18. An unload-induced direct-shear model for granular gouge friction in rock discontinuities.

    PubMed

    Wu, Wei; Zou, Yang; Li, Xing; Zhao, Jian

    2014-09-01

    The experimental study introduces an unload-induced direct-shear model to investigate the frictional slip of a layer of simulated granular gouges induced by the combination of a decreasing normal stress and a constant shear stress. A frictional equilibrium state of the gouge layer is initially established under fixed normal and shear stresses. The normal stress is proposed to decrease at a constant unloading rate to induce the frictional slip of the gouge layer, and the shear stress is proposed to keep a constant value during the test. A displacement meter and load cells synchronously measure the slip displacement and the applied normal and shear stresses, respectively. The normal and shear stresses sharply decrease with the frictional slip, owing to damage of gouge contacts. The frictional slip is then gradually arrested with new formation of gouge contacts. A greater initial shear stress induces larger normal and shear stress reductions and a smaller slip displacement. The strain energy stored in the discontinuous system before the frictional slip is found to affect the slip displacement. The advantages and the limitations of this model are discussed at the end.

  19. Thermo-Chemical Pressurization of Fault Gouges During Coseismic Slip

    NASA Astrophysics Data System (ADS)

    Brantut, N.; Schubnel, A.; Corvisier, J.

    2008-12-01

    This work deals with thermo-hydro-mechanical couplings within fault gouges during coseismic slip, including effects of possible thermal dehydration of hydrous minerals. The framework of thermal pressurization of pore fluid is extend to include the dehydration effect as a source term for pore pressure and a sink for temperature. The dehydration kinetics is modelled by a first order reaction rate which is bounded by the ratio between heating rate and the reaction enthalpy variation. We first solve analytically the equations in the case of no fluid and heat transport and with a constant reaction rate. It shows that the dehydration reaction, if the rate constant is of the order of 1~s-1, induces a pore pressure increase that can grow beyond the normal stress apllied on the fault. At the same time, the temperature slightly decreases as the reaction progresses. If the kinetics is calculated from the ratio between frictional heating and enthalpy variation, the temperature is kept constant during the reaction, and the pore pressure increases asymptotically to the normal stress. This corresponds to a transient equilibrium where the pressurization is maintained by the mineral reaction. Then we model the phenomenon more precisely by taking into account transport of fluid and heat and we use an Arrhenius law to calculate the rate constant as function of temperature. The overall behaviour of the system is characterized by a sudden increase of pore pressure and an almost constant temperature as the reaction starts. The parameters values are then discussed, showing that overpressures can occur for low reaction temperatures, low enthalpy change, deep faults and/or thick slipping zones. It shows that dehydration is an effective mechanism for delaying or preventing melting during coseismic slip, if the mass fraction of released water is larger than ~ 1%.

  20. The coefficient of friction of chrysotile gouge at seismogenic depths

    USGS Publications Warehouse

    Moore, Diane E.; Lockner, D.A.; Tanaka, H.; Iwata, K.

    2004-01-01

    We report new strength data for the serpentine mineral chrysotile at effective normal stresses, ??sn between 40 and 200 MPa in the temperature range 25??-280??C. Overall, the coefficient of friction, ?? (= shear stress/effective normal stress) of water-saturated chrysotile gouge increases both with increasing temperature and ??sn, but the rates vary and the temperature-related increases begin at ???100??C. As a result, a frictional strength minimum (?? = 0.1) occurs at low ??sn at about 100??C. Maximum strength (?? = 0.55) results from a combination of high normal stress and high temperature. The low-strength region is characterized by velocity strengthening and the high-strength region by velocity-weakening behavior. Thoroughly dried chrysotile has ?? = 0.7 and is velocity-weakening. The frictional properties of chrysolite can be explained in its tendency to adsorb large amounts of water that acts as a lubricant during shear. The water is progressively driven off the fiber surfaces with increasing temperature and pressure, causing chrysotile to approach its dry strength. Depth profiles for a chrysotile-lined fault constructed from these data would pass through a strength minimum at ???3 km depth, where sliding should be stable. Below that depth, strength increases rapidly as does the tendency for unstable (seismic) slip. Such a trend would not have been predicted from the room-temperature data. These results therefore illustrate the potential hazards of extrapolating room-temperature friction data to predict fault zone behavior at depth. This depth profile for chrysotile is consistent with the pattern of slip on the Hayward fault, which creeps aseismically at shallow depths but which may be locked below 5 km depth. ?? 2004 by V. H. Winston and Son, Inc. All rights reserved.

  1. Comparisons between gouge and bare surface friction of serpentinite at seismic slip velocities: Implications for dynamic weakening of gouge-bearing faults

    NASA Astrophysics Data System (ADS)

    Proctor, B.; Mitchell, T. M.; Hirth, G.; Goldsby, D. L.; Di Toro, G.; Zorzi, F.

    2013-12-01

    High-velocity friction (HVF) experiments on bare rock surfaces have revealed various dynamic weakening processes (e.g., flash weakening, gel weakening, melt lubrication) that likely play a fundamental role in coseismic fault weakening. However, faults generally contain a thin layer of gouge separating the solid wallrocks, thus it is important to understand how the presence of gouge modifies the efficiency of these weakening processes at seismic slip rates. We explored the frictional behavior of bare surfaces and powdered samples of an antigorite-rich serpentinite (ARS) and a lizardite-rich serpentinite (LRS) at earthquake slip rates. HVF experiments were conducted with slip displacements ranging from ~0.5 to 2m, at velocities ranging from 0.002m/s to 6.5 m/s, and with normal stresses ranging from 2-22 MPa for gouge and 5-100MPa for bare surfaces. Our results demonstrate that the friction coefficient (μ) of powdered serpentine is significantly larger than that of bare surfaces under otherwise identical conditions. Bare surface friction decreases over a weakening distance of a few centimeters to a nominally steady-state value of ~0.1 at velocities greater than 0.1m/s. The nominal steady-state friction decreases non-linearly with increasing normal stress from 0.14 to 0.045 at 5 and ~100MPa respectfully at a slip velocity of 1m/s. Additionally, the recovery of frictional strength during deceleration depends on total displacement; samples slipped for ~50mm recover faster than samples slipped for ~0.5m. Microstructural analysis of bare surfaces deformed at the highest normal stresses revealed translucent glass-like material on the slip surfaces and XRD analysis of wear material revealed an increasing presence of olivine and enstatite with increasing normal stress. In contrast, gouge requires an order of magnitude higher velocity than bare surfaces to induce frictional weakening, has a larger weakening distance and higher steady state friction values for equivalent

  2. Analysis of processes in DC arc plasma torches for spraying that use air as plasma forming gas

    NASA Astrophysics Data System (ADS)

    Frolov, V.; Ivanov, D.; Toropchin, A.

    2014-11-01

    Developed in Saint Petersburg State Polytechnical University technological processes of air-plasma spraying of wear-resistant, regenerating, hardening and decorative coatings used in number of industrial areas are described. The article contains examples of applications of air plasma spraying of coatings as well as results of mathematical modelling of processes in air plasma torches for spraying.

  3. The effect of mineral bond strength and adsorbed water on fault gouge frictional strength

    USGS Publications Warehouse

    Morrow, C.A.; Moore, Diane E.; Lockner, D.A.

    2000-01-01

    Recent studies suggest that the tendency of many fault gouge minerals to take on adsorbed or interlayer water may strongly influence their frictional strength. To test this hypothesis, triaxial sliding experiments were conducted on 15 different single-mineral gouges with various water-adsorbing affinities. Vacuum dried samples were sheared at 100 MPa, then saturated with water and sheared farther to compare dry and wet strengths. The coefficients of friction, μ, for the dry sheet-structure minerals (0.2-0.8), were related to mineral bond strength, and dropped 20-60% with the addition of water. For non-adsorbing minerals (μ = 0.6-0.8), the strength remained unchanged after saturation. These results confirm that the ability of minerals to adsorb various amounts of water is related to their relative frictional strengths, and may explain the anomalously low strength of certain natural fault gouges.

  4. 46 CFR 56.70-15 - Procedure.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... repairs. (1) All defects in welds requiring repair must be removed by a flame or arc-gouging, grinding... original weld. (2) Preheating may be required for flame-gouging or arc-gouging certain alloy materials of the air hardening type in order to prevent surface checking or cracking adjacent to the flame or...

  5. 46 CFR 56.70-15 - Procedure.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... repairs. (1) All defects in welds requiring repair must be removed by a flame or arc-gouging, grinding... original weld. (2) Preheating may be required for flame-gouging or arc-gouging certain alloy materials of the air hardening type in order to prevent surface checking or cracking adjacent to the flame or...

  6. Triaxial testing of Lopez Fault gouge at 150 MPa mean effective stress

    USGS Publications Warehouse

    Scott, D.R.; Lockner, D.A.; Byerlee, J.D.; Sammis, C.G.

    1994-01-01

    Triaxial compression experiments were performed on samples of natural granular fault gouge from the Lopez Fault in Southern California. This material consists primarily of quartz and has a self-similar grain size distribution thought to result from natural cataclasis. The experiments were performed at a constant mean effective stress of 150 MPa, to expose the volumetric strains associated with shear failure. The failure strength is parameterized by the coefficient of internal friction ??, based on the Mohr-Coulomb failure criterion. Samples of remoulded Lopez gouge have internal friction ??=0.6??0.02. In experiments where the ends of the sample are constrained to remain axially aligned, suppressing strain localisation, the sample compacts before failure and dilates persistently after failure. In experiments where one end of the sample is free to move laterally, the strain localises to a single oblique fault at around the point of failure; some dilation occurs but does not persist. A comparison of these experiments suggests that dilation is confined to the region of shear localisation in a sample. Overconsolidated samples have slightly larger failure strengths than normally consolidated samples, and smaller axial strains are required to cause failure. A large amount of dilation occurs after failure in heavily overconsolidated samples, suggesting that dilation is occurring throughout the sample. Undisturbed samples of Lopez gouge, cored from the outcrop, have internal friction in the range ??=0.4-0.6; the upper end of this range corresponds to the value established for remoulded Lopez gouge. Some kind of natural heterogeneity within the undisturbed samples is probably responsible for their low, variable strength. In samples of simulated gouge, with a more uniform grain size, active cataclasis during axial loading leads to large amounts of compaction. Larger axial strains are required to cause failure in simulated gouge, but the failure strength is similar to that of

  7. Role of fault gouge dilatancy on aseismic deformation transients

    NASA Astrophysics Data System (ADS)

    Liu, Yajing; Rubin, Allan M.

    2010-10-01

    In the vicinity of episodic aseismic transients in several subduction zones, the presence of interstitial fluids and near-lithostatic pore pressure has been proposed to interpret seismic observations of high P to S wave speed ratio and high Poisson's ratio. Under such conditions, fault stabilization by dilatancy-induced suction during increased shear strain rates becomes very efficient. We analyze the frictional and hydraulic conditions for spontaneous transients on a fluid-infiltrated fault including dilatancy and pore compaction in the framework of rate and state friction with a "membrane diffusion" approximation. In both a simplified spectral model and a 2-D Cascadia-like subduction fault model, the fault response is mainly controlled by three nondimensional parameters: (1) W/h*, the along-dip width of the high pore pressure, velocity-weakening fault relative to a characteristic nucleation size, (2) a drainage parameter U, the relative time scales for fluid diffusion and friction evolution, and (3) a dilatancy parameter E, the relative contributions to stress drop from dilatancy and friction evolution. The incorporation of dilatancy enables aseismic transients at much larger values of W/h* than is possible under conditions of constant pore pressure. An analytic estimate of the maximum slip velocity as a function of W/h*, E, and U is derived and agrees reasonably well with the simulation results. The dependence of the properties of modeled transients on the drainage parameter U is similar to that on the dilatancy parameter E. For U (E) less than 1, maximum velocity decreases, while recurrence period remains relatively constant. For U (E) greater than 1, maximum velocity approaches the steady state velocity, and recurrence period approaches the period at neutral stability. In the subduction fault model using gabbro gouge friction properties, the slip per episode and the recurrence period increase with W/h*, generally following the trend defined without dilatancy

  8. Cathodic arcs

    SciTech Connect

    Anders, Andre

    2003-10-29

    Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas standout due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bias. Industrial processes often use cathodic arc plasma in reactive mode. In contrast, the science of arcs has focused on the case of vacuum arcs. Future research directions include closing the knowledge gap for reactive mode, large area coating, linear sources and filters, metal plasma immersion process, with application in high-tech and biomedical fields.

  9. Frictional properties of simulated anhydrite-dolomite fault gouge and implications for seismogenic potential

    NASA Astrophysics Data System (ADS)

    Pluymakers, A. M. H.; Niemeijer, A. R.; Spiers, C. J.

    2016-03-01

    The frictional properties of anhydrite-dolomite fault gouges, and the effects of CO2 upon them, are of key importance in assessing the risks associated with CO2 storage in reservoir formations capped by anhydrite-dolomite sequences, and in understanding seismicity occurring in such formations (such as the Italian Apennines). Therefore, we performed velocity-stepping direct-shear experiments on simulated dolomite, anhydrite and 50:50 anhydrite/dolomite gouges, at representative in-situ conditions (120 °C and σne = 25 MPa). They were conducted under vacuum, or else using water or CO2-saturated water as pore fluid (Pf = 15 MPa). Friction coefficients varied between 0.55 and 0.7. All dry samples exhibited velocity-weakening behavior, whereas all wet samples exhibited velocity-strengthening behavior, without or with CO2. This is consistent with trends previously reported for such gouges. A compilation of literature data shows that the transition from velocity-strengthening to velocity-weakening occurs in these materials between 80 and 120 °C when dry, and between 100 and 150 °C when wet. This implies little seismogenic potential for wet dolomite, anhydrite and mixed gouges under CO2 storage conditions at 2-4 km depth. Seismic slip in the Italian Apennines at depths of ∼6 km and beyond may be explained by the velocity-weakening behavior expected in anhydrite and especially dolomite at temperatures above 150 °C.

  10. Clay clast aggregates in gouges: New textural evidence for seismic faulting

    NASA Astrophysics Data System (ADS)

    Boutareaud, SéBastien; Boullier, Anne-Marie; AndréAni, Muriel; Calugaru, Dan-Gabriel; Beck, Pierre; Song, Sheng-Rong; Shimamoto, Toshihiko

    2010-02-01

    Spherical aggregates named clay-clast aggregates (CCAs) have been reported from recent investigations on retrieved clay-bearing fault gouges from shallow depth seismogenic faults and rotary shear experiments conducted on clay-bearing gouge at seismic slip rates. The formation of CCAs appears to be related to the shearing of a smectite-rich granular material that expands and becomes fluidized. We have conducted additional high-velocity rotary shear experiments and low-velocity double-shear experiments. We demonstrate that a critical temperature depending on dynamic pressure-temperature conditions is needed for the formation of CCAs. This temperature corresponds to the phase transition of pore water from liquid to vapor or to critical, which induced gouge pore fluid expansion and therefore a thermal pressurization of the fault. A detailed examination by energy dispersive X-ray spectrometry (EDX-SEM) element mapping, SEM, and transmission electron microscopy (TEM) shows strong similar characteristics of experimental and natural CCAs with a concentric well-organized fabric of the cortex and reveals that their development may result from the combination of electrostatic and capillary forces in a critical reactive medium during the dynamic slip weakening. Accordingly, the occurrence of CCAs in natural clay-rich fault gouges constitutes new unequivocal textural evidence for shallow depth thermal pressurization and consequently for past seismic faulting.

  11. Timing and conditions of clay fault gouge formation on the Naxos detachment (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Mancktelow, N.; Zwingmann, H.; Mulch, A.

    2016-10-01

    Clay fault gouge from the Naxos detachment (locally up to 1.0-1.5 m thick) is reported and dated for the first time. K-Ar ages on eight clay size fractions from the detachment and a minor fault in the immediate footwall have a narrow range, from 10.3 to 9.0 Ma, with an average of 9.7 ± 0.5 Ma (±1σ). These results are in excellent accord with regional and local age constraints, independently demonstrating the reliability of the method. Hydrogen δD values fall in the range -89 to -95‰, indicating interaction with infiltrating meteoric water during gouge formation, which is consistent with deposition of freshwater sediments in the hanging wall at the same time. Clay mineralogy in the detachment gouge is predominantly mixed layer illite-smectite with subordinate 1 M illite and kaolinite but without higher-temperature 2 M1 illite/mica. Clay fault gouge predominantly formed over a limited time and temperature range, potentially acting as a weak lubricant promoting movement on the Naxos detachment, with correspondingly rapid exhumation and cooling of the underlying footwall.

  12. Experimental investigation of supersonic low pressure air plasma flows obtained with different arc-jet operating conditions

    SciTech Connect

    Lago, Viviana; Ndiaye, Abdoul-Aziz

    2012-11-27

    A stationary arc-jet plasma flow at low pressure is used to simulate some properties of the gas flow surrounding a vehicle during its entry into celestial body's atmospheres. This paper presents an experimental study concerning plasmas simulating a re-entry into our planet. Optical measurements have been carried out for several operating plasma conditions in the free stream, and in the shock layer formed in front of a flat cylindrical plate, placed in the plasma jet. The analysis of the spectral radiation enabled the identification of the emitting species, the determination of the rotational and vibrational temperatures in the free-stream and in the shock layer and the determination of the distance of the shock to the flat plate face. Some plasma fluid parameters like, stagnation pressure, specific enthalpy and heat flux have been determined experimentally along the plasma-jet axis.

  13. Temperature - Fluid Pressure controls on the mechanical evolution of shale-carbonate composite gouge: Implications for natural faults

    NASA Astrophysics Data System (ADS)

    Haywood, J. C.; Kennedy, L.; Faulkner, D. R.

    2010-12-01

    Carbonate and phyllosilicate-rich fault gouges are common in fault zones worldwide, particularly in fold and thrust belts. Limestone-on-shale thrust faults are commonly comprised of a carbonate hangingwall and a shale footwall. Generally a cataclasite develops in both the carbonate and shale materials and between them is a zone of mixing in which the shale cataclasite contains clasts of carbonate cataclasite. Both hangingwall and footwall cataclasites are commonly foliated but the extent of partitioning of strain between shale and carbonate cataclasites is unknown. Frictional sliding experiments were conducted on carbonate and shale composite gouges to examine the effect of gouge composition, temperature (T) and pore fluid pressure (Pf) on the strength, stability, and microstructural evolution of these gouge zones. Triaxial frictional sliding experiments were conducted at a displacement rate of 4.5 µm/s on 20mm diameter by 50mm length cores containing a 1 mm thick, gouge layer coating a 30° angle sawcut. Porous Berea Sandstone (φ ~ 17%) comprised the upper forcing block while impermeable Badshot Dolomite comprised the lower forcing block. The synthetic gouge was a mixture of quartz-bearing phyllosilicate-rich shale (31% quartz, 39% muscovite, 18% clinochlore, 11% feldspar) and reagent grade calcite powder (80% calcite, 20% dolomite). Experiments were performed on endmember compositions and on 75%, 50% and 25% mixtures of shale and carbonate. Baseline, room temperature experiments on water saturated (but drained) gouge were conducted at 70 MPa confining pressure (Pc). Under these conditions, the 100% shale gouge is the weakest (μ ~ .65). The 100% carbonate gouge is the strongest (μ ~.87), and the composite gouges are intermediate in strength (μ ~ .7 - .75). All gouge compositions show stable sliding and slight strain hardening. Experiments at 150°C were conducted with a Pf of 15 MPa and a Pc of 85MPa (Pc effective = 70 MPa). Under these conditions, 100% shale

  14. Air annealing effects on the optical properties of ZnO SnO2 thin films deposited by a filtered vacuum arc deposition system

    NASA Astrophysics Data System (ADS)

    Çetinörgü, E.; Goldsmith, S.; Boxman, R. L.

    2006-03-01

    ZnO-SnO2 transparent and conducting thin films were deposited on microscope glass substrates by a filtered vacuum arc deposition (FVAD) system. The cathode was prepared with 50%:50% atomic concentration of Zn:Sn. The films were annealed in air at 500 °C for 1 h. Structural and compositional analyses were obtained using XRD and XPS diagnostics. X-ray diffraction analysis indicated that as-deposited and air-annealed thin ZnO-SnO2 films were amorphous. The atomic ratio of Zn to Sn in the film obtained using the 50%:50% cathode as determined by XPS analysis was ~2.7:1 in the bulk film. The optical properties were determined from normal incidence transmission measurements. Film transmission in the visible was 70% to 90%, affected by interference effects. Annealed films did not show higher transmission in the VIS compared to as-deposited films. Assuming that the interband electron transition is direct, the optical band gap was found to be in the range 3.34-3.61 eV for both as-deposited and annealed films. However, the average Eg for annealed films was 3.6 eV, larger by 0.2 eV than that of as-deposited. The refractive index n increased while the extinction index k decreased significantly with annealing.

  15. Gas Tungsten Arc Welding and Plasma Arc Cutting. Teacher Edition.

    ERIC Educational Resources Information Center

    Fortney, Clarence; And Others

    This welding curriculum guide treats two topics in detail: the care of tungsten electrodes and the entire concept of contamination control and the hafnium electrode and its importance in dual-air cutting systems that use compressed shop air for plasma arc cutting activities. The guide contains three units of instruction that cover the following…

  16. The Influence of Calcite on The Mechanical Behavior of Quartz-Bearing Gouge

    NASA Astrophysics Data System (ADS)

    Carpenter, Brett; Di Stefano, Giuseppe; Collettini, Cristiano

    2015-04-01

    Mechanical heterogeneities along faults can result in diverse and complex fault slip. These heterogeneities can vary spatially and temporally and may result from changes in fault structure or frictional properties. The accumulation of calcite in non-carbonate faults, via cementation or entrainment, is likely to alter the frictional properties of that fault gouge. Furthermore, widespread observations of calcite as cement, veins, or cataclasites in non-carbonate hosted faults indicates that calcite is readily available and could play an important role during fault reactivation at shallow- and mid-crustal earthquakes. We report on laboratory experiments designed to explore the mechanical behavior of quartz/calcite mixtures as a means to better understand the evolution in behavior of quartz-bearing gouge in the presence of exotic calcite. We sheared mixtures of powdered Carrara marble (>98% CaCO3) and disaggregated Ottawa sand (99.8% SiO2) at constant normal stresses of 5 and 50 MPa under saturated conditions at room temperature. We performed slide-hold-slide tests, 1-3,000 seconds, and velocity stepping tests, 0.1-1000 µm/s, to measure the amount of frictional healing and velocity dependence of friction respectively. At low normal stress, the addition of calcite to quartz-based synthetic fault gouge results in increases in the steady-state frictional strength, and rates of frictional healing and creep relaxation of the gouge. In particular, with the addition of as little as 2.5 wt% calcite, the frictional healing rate increases by 30%. Microstructural observations indicate that shear is accommodated by distributed deformation throughout the gouge layer and that calcite undergoes significantly more comminution compared to quartz. Large quartz grains frequently show minor rounding of angular edges with fine-grained calcite often penetrating fractures. The in-situ addition of calcite to fault gouge, by either the circulation of fluids or the involvement of carbonate

  17. 3D microstructural and microchemical characteristics of SAFOD fault gouge: implications for understanding fault creep

    NASA Astrophysics Data System (ADS)

    Warr, Laurence; Wojatschke, Jasmaria; Carpenter, Brett; Marone, Chris; Schleicher, Anja; van der Pluijm, Ben

    2013-04-01

    Fault creep on the SAFOD section of the San Andreas Fault occurs along mechanically weak fault gouge characterized by high proportions of hydrous clay minerals, namely smectite, illite-smectite and chlorite-smectite phases. These minerals are concentrated along closely spaced, interconnected polished slip surfaces that give the gouge its characteristic scaly fabric. Although it is generally accepted that the creep behavior of the gouge relates to the concentration of these minerals, the precise mechanisms by which clay minerals weaken rock is currently a topic of debate. In this contribution we present the first results from a "slice-and-view" study of SAFOD gouge material by focused ion beam - scanning electron microscopy (Zeiss Auriga FIB/SEM), which allows the reconstruction of the microstructure and microchemistry of mineralized slip surfaces in 3D. The core and cuttings samples studied were selected from ca. 3297 m measured depth and represent some of the weakest materials yet recovered from the borehole, with a frictional coefficient of ca. 0.10 and a healing rate close to zero. This gouge contains abundant serpentine and smectite minerals, the latter of which was identified by X-ray diffraction to be saponite, after Mg- and glycol intercalation. Imaging and chemical analyses reveal nanometer scale thin alteration seams of saponite clay distributed throughout the ca. 50 micron thick sheared serpentinite layer that coats the slip surfaces. The base of this layer is defined by cataclastically deformed iron oxide minerals. The 3D fabric implies the orientation of the hydrated smectite minerals, which are interconnected and lie commonly sub parallel to the slip surface, are responsible for the gouge creep behavior in the laboratory. These minerals, and related interlayered varieties, are particularly weak due to their thin particle size and large quantities of adsorbed water, properties that are expected to persist down to mid-crustal depth (ca. 10 km). Creep of

  18. Clay minerals in Alpine Fault gouge: First results from the DFDP-1B pilot hole

    NASA Astrophysics Data System (ADS)

    van der Pluijm, B. A.; Schleicher, A. M.

    2012-12-01

    Clay mineralization is increasingly recognized as a key process along fault systems in the upper crust. The Alpine Fault in New Zealand is a major active fault zone with locally large earthquakes. Samples from this fault zone offer excellent opportunity to investigate recent and ancient rupture zones, and the mechanical role of clay mineral transformations and fluid-rock interactions in particular. The Alpine Fault drilling project (DFDP-project) on the South Island of New Zealand sampled two shallow pilot holes; DFDP-1A was drilled down to 100.6 m and DFDP-1B drilled down to 151.4 m. Five samples from borehole DFDP-1B have been investigated by X-ray diffraction, X-ray texture goniometry and electron microscopy. These samples were taken at ~143.3 m (sections 69_2 to 69_2) and ~128.1 m depth (sections 59_1 to 59_1); the latter is the area of principal slip. The bulk rock mineralogy shows similar compositions in all samples with quartz, phyllosilicates (muscovite, chlorite), calcite, zeolite and clay minerals; the dominant clay phases in all samples are illite and chlorite. Importantly, abundant discrete smectite is uniquely present in gouge zones at sections 69_2 (~143.4 m) and 59_1 (~128.1 m). Smectite was likely formed by dissolution-precipitation reactions during displacement and movement of aqueous fluids along permeable fractures, at the expense of host rock minerals. Electron microscopy of fault gouge at section 69_2 shows small illite and smectite particles with pseudo-hexagonal shapes and variable amounts of K, Ca, Mg and Fe, growing adjacent to each other. Some distinct illite and smectite mineral veins form epitaxially on quartz-feldspar mineral surfaces. Clay fabric intensity, measured by X-ray goniometry, is higher outside the gouge zones (true cataclasite, section 69_1) with average fabric intensities of m.r.d. 3.5. Both gouge zones at sections 59_2 and 69_1 exhibit uniformly weak fabrics for illite and chlorite (m.r.d. ~2.5 on average). The weak

  19. 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

  20. The Influence of Exotic Calcite on the Mechanical Behavior of Quartz Bearing Fault Gouge

    NASA Astrophysics Data System (ADS)

    Carpenter, B. M.; Di Stefano, G.; Collettini, C.

    2014-12-01

    The interseismic recovery of frictional strength is a fundamental part of the seismic cycle. This restrengthening, and related phenomena, plays a key role in determining the stability and mode of tectonic faulting. Recent experimental data has shown that gouge mineralogy has a strong influence on the rate of frictional healing, with calcite-dominated gouges showing the highest rates. Combining these data with widespread observations of calcite as cement or veins in non-carbonate hosted faults, indicates that the presence of calcite within a fault gouge could play an important role in shallow- and mid-crustal earthquakes. We report on laboratory experiments designed to explore the mechanical behavior of quartz/calcite mixtures as a means to better understand the evolution of fault behavior in faults where carbonate materials are present. We sheared mixtures of powdered Carrara marble (>98% CaCO3) and disaggregated Ottawa sand (99.8% SiO2) at constant normal stress of 5 MPa under saturated conditions at room temperature. We performed slide-hold-slide tests, 1-3,000 seconds, and velocity stepping tests, 0.1-1000 μm/s, to measure the amount of frictional healing and velocity dependence of friction respectively. Small subsets of experiments were conducted at different boundary conditions. Preliminary results show that the presence of calcite in quartz-based fault gouge has a hardening effect, both in overall frictional strength, where the strength of our mixtures increases with increasing calcite content, and in single experiments, where mixtures with low percentages of calcite show a consistent strain-hardening trend. We also observe that the rates of frictional healing and creep relaxation increase with increasing calcite content. Finally, our results show that the addition of as little as 2.5% calcite within a fault gouge results in a 30% increase in the rate of frictional healing, with further increases in calcite content resulting in larger increases in the rate

  1. Dynamic weakening of fault gouge affected by thermal conductivity of host specimen: implications for the high-velocity weakening mechanisms

    NASA Astrophysics Data System (ADS)

    Yao, Lu; Ma, Shengli; Shimamoto, Toshihiko; Niemeijer, André

    2015-04-01

    Since many high-velocity weakening mechanisms are thermal in origin, we study the effects of thermal conductivity of host specimen on fault gouge friction behavior at seismic slip rates. By using host specimens made of brass, stainless steel, Ti-Al-V alloy and gabbro with thermal conductivities of 123, 15, 5.8 and 3.25 W/m/K, respectively, the experiments in this study produce completely different temperature conditions within the same gouge under the same slip rates and normal stresses. Fault gouges used in the experiments are a natural illite- and quartz-rich gouge from Longmenshan fault zone and pure periclase (MgO) nanopowder. High-velocity weakening of gouges were more pronounced with decreasing thermal conductivity of the specimens. Particularly, almost no dynamic weakening was observed in the tests performed with brass host specimens, while tests with specimens of gabbro and Ti-Al-V alloy exhibits quite similar dramatic weakening behaviors. Such differences in gouge frictional behavior cannot be explained by original flash heating model, since asperity contacts within the slip zone and experimental conditions are still same, even though host specimens are different. Microstructure observations under scanning and transmission electron microscopes reveal that slip zone materials tend to change from individual ultrafine nanograins to larger sintered grains or aggregates, with decreasing thermal conductivities of host specimens. Calculated temperature together with observed microstructure indicate that bulk temperature rise may be also play an important role in fault weakening, as predicted by a recent theoretical analysis of the role of flash heating within the gouge zone [Proctor et al., 2014]. Current results demonstrate the importance of frictional heating in causing the dynamic weakening of gouge, and the powder lubrication hypothesis is not consistent with our experimental data.

  2. Elements of arc welding

    SciTech Connect

    Not Available

    1993-07-01

    This paper looks at the following arc welding techniques: (1) shielded metal-arc welding; (2) submerged-arc welding; (3) gas metal-arc welding; (4) flux-cored arc welding; (5) electrogas welding; (6) gas tungsten-arc welding; and (7) plasma-arc welding.

  3. Laboratory observations of time-dependent frictional strengthening and stress relaxation in natural and synthetic fault gouges

    NASA Astrophysics Data System (ADS)

    Carpenter, B. M.; Ikari, M. J.; Marone, C.

    2016-02-01

    Interseismic recovery of fault strength (healing) following earthquake failure is a fundamental requirement of the seismic cycle and likely plays a key role in determining the stability and slip behavior of tectonic faults. We report on laboratory measurements of time- and slip-dependent frictional strengthening for natural and synthetic gouges to evaluate the role of mineralogy in frictional strengthening. We performed slide-hold-slide (SHS) shearing experiments on nine natural fault gouges and eight synthetic gouges at conditions of 20 MPa normal stress, 100% relative humidity (RH), large shear strain (~15), and room temperature. Phyllosilicate-rich rocks show the lowest rates of frictional strengthening. Samples rich in quartz and feldspar exhibit intermediate rates of frictional strengthening, and calcite-rich gouges show the largest values. Our results show that (1) the rates of frictional strengthening and creep relaxation scale with frictional strength, (2) phyllosilicate-rich fault gouges have low strength and healing characteristics that promote stable, aseismic creep, (3) most natural fault gouges exhibit intermediate rates of frictional strengthening, consistent with a broad range of fault slip behaviors, and (4) calcite-rich fault rocks show the highest rates of frictional strengthening, low values of dilation upon reshear, and high frictional strengths, all of which would promote seismogenic behavior.

  4. Friction properties and deformation mechanisms of halite(-mica) gouges from low to high sliding velocities

    NASA Astrophysics Data System (ADS)

    Buijze, Loes; Niemeijer, André R.; Han, Raehee; Shimamoto, Toshihiko; Spiers, Christopher J.

    2017-01-01

    The evolution of friction as a function of slip rate is important in understanding earthquake nucleation and propagation. Many laboratory experiments investigating friction of fault rocks are either conducted in the low velocity regime (10-8-10-4 ms-1) or in the high velocity regime (0.01-1 m s-1). Here, we report on the evolution of friction and corresponding operating deformation mechanisms in analog gouges deformed from low to high slip rates, bridging the gap between these low and high velocity regimes. We used halite and halite-muscovite gouges to simulate processes, governing friction, active in upper crustal quartzitic fault rocks, at conditions accessible in the laboratory. The gouges were deformed over a 7 orders of magnitude range of slip rate (10-7-1 m s-1) using a low-to-high velocity rotary shear apparatus, using a normal stress of 5 MPa and room-dry humidity. Microstructural analysis was conducted to study the deformation mechanisms. Four frictional regimes as a function of slip rate could be recognized from the mechanical data, showing a transitional regime and stable sliding (10-7-10-6 m s-1), unstable sliding and weakening (10-6-10-3 m s-1), hardening (10-2-10-1 m s-1) and strong weakening (10-1-1 m s-1). Each of the four regimes can be associated with a distinct microstructure, reflecting a transition from mainly brittle deformation accompanied by pressure solution healing to temperature activated deformation mechanisms. Additionally, the frictional response of a sliding gouge to a sudden acceleration of slip rate to seismic velocities was investigated. These showed an initial strengthening, the amount of which depended on the friction level at which the step was made, followed by strong slip weakening.

  5. Comparative mineral chemistry and textures of SAFOD fault gouge and damage-zone rocks

    USGS Publications Warehouse

    Moore, Diane E.

    2014-01-01

    Creep in the San Andreas Fault Observatory at Depth (SAFOD) drillhole is localized to two foliated gouges, the central deforming zone (CDZ) and southwest deforming zone (SDZ). The gouges consist of porphyroclasts of serpentinite and sedimentary rock dispersed in a foliated matrix of Mg-smectite clays that formed as a result of shearing-enhanced reactions between the serpentinite and quartzofeldspathic rocks. The CDZ takes up most of the creep and exhibits differences in mineralogy and texture from the SDZ that are attributable to its higher shearing rate. In addition, a ∼0.2-m-wide sector of the CDZ at its northeastern margin (NE-CDZ) is identical to the SDZ and may represent a gradient in creep rate across the CDZ. The SDZ and NE-CDZ have lower clay contents and larger porphyroclasts than most of the CDZ, and they contain veinlets and strain fringes of calcite in the gouge matrix not seen elsewhere in the CDZ. Matrix clays in the SDZ and NE-CDZ are saponite and corrensite, whereas the rest of the CDZ lacks corrensite. Saponite is younger than corrensite, reflecting clay crystallization under declining temperatures, and clays in the more actively deforming portions of the CDZ have better equilibrated to the lower-temperature conditions.

  6. A note on the effect of fault gouge composition on the stability of frictional sliding

    USGS Publications Warehouse

    Summers, R.; Byerlee, J.

    1977-01-01

    The frictional properties of fault gouge have been studied at confining pressures to 6 kbars. If the gouge is composed of strong materials such as crushed granite or quartz sand, the frictional strength is high, and violent stick-slip occurs at confining pressures above approximately 1.5 kbars. If the gouge is composed of minerals such as illite, kaolinite, chlorite, or antigorite, which have weak bonding forces between the structural layers, the frictional strength is slightly lower, but violent stick-slip still occurs under high confining pressure. The expanding clays, montmorillonite and vermiculite, which have free water between their structural layers, slide stably at confining pressures as high as 6.25 kbars and exhibit low friction. A similar stable behavior with lowered strength is observed in water-saturated quartz sand when the water is confined within the fault zone during deformation. The results of this series of experiments support water being the stabilizing influence when it is either (1) trapped within or between rocks of low permeability and can provide a high pore pressure when the rocks are deformed, or (2) loosely bonded in a mineral structure, as in the hydrated clays, where it can produce a pseudo-pore pressure when the clay is compressed. In both these cases, the effective stress can be reduced and the deformation stabilized. ?? 1977.

  7. Fault Slip Controlled By Gouge Rheology: A Model For Slow Earthquakes

    NASA Astrophysics Data System (ADS)

    Amoruso, A.; Crescentini, L.; Dragoni, M.; Piombo, A.

    During 1997 several slow earthquakes have been recorded by a geodetic interferom- eter located beneath Gran Sasso in Central Italy. The strain rise times of the events range from tens to thousands of seconds, strain amplitudes are of the order of 10-9. Amplitudes scale with the square root of the rise time and this suggests a diffusive behavior of the slip propagation along the fault. In this work we assume that slip dif- fusion is due to the presence of a gouge layer between fault faces, with a visco-plastic rheology. Fault gouge behavior is elastic if shear stress is less than yield stress. If the yield stress is reached, gouge behaves as an incompressible Newtonian fluid. Fluid velocity diffuses in the directions of fault length and fault thickness, with different characteristic times. This model reproduces the relation between amplitude and rise time of measured strain signals. Synthetic straingrams, obtained for a horizontally layered flat earth and a source located at a few km from the instrument, are in good agreement with observed signals.

  8. Sea-floor gouges caused by migrating gray whales off northern California

    USGS Publications Warehouse

    Cacchione, D.A.; Drake, D.E.; Field, M.E.; Tate, G.B.

    1987-01-01

    Side-scan sonar records collected during March and April 1981 and 1982 off northern California contain elongate depressions whose sizes and shapes are similar to sea-floor gouges made by feeding gray whales (Eschrichtius robustus) in the northern Bering Sea and in shallow embayments off British Columbia. The discovery of the whale gouges in the sonar records was unexpected, and supports some of the previous speculation that gray whales feed opportunistically during migration. Gouges occupy about 0.032% of the 7.6 km2 of sea floor that was surveyed, which represents about 575 metric tons of excavated material. Although seemingly minor in amount, the total amount of bottom sediment removed from the central and northern California continental shelf by gray whale activities year after year represents macroscale biologically induced erosion and could have significant geological implications in shelf erosion and depositional schemes. This is the only published evidence of benthic feeding by gray whales along their migration route off northern California. ?? 1987.

  9. Frictional Properties of Experimentally Sheared Gouges from the 2011 Mw 9.0 Tohoku-Oki Earthquake Fault Zone

    NASA Astrophysics Data System (ADS)

    Mittempergher, S.; Smith, S. A. F.; Remitti, F.; Gualtieri, A.; Di Toro, G.

    2014-12-01

    Smectite-rich fault gouge recovered during IODP exp. 343 (J-FAST project) from the plate-boundary slip zone of the 2011 Mw 9.0 Tohoku-oki earthquake was deformed at slip velocities of 10 -5 - 3 m s -1 with theSlow to High Velocity Apparatus (SHIVA) at INGV, Rome. Experiments were performed "room-dry" (40-60% humidity, 8.5 -12.5 MPa normal stress) or "water-dampened" (0.5 ml distilled water, 3.5 MPa normal stress), with displacements up to 1m. Mineralogy and microstructures of pre and post-experiment material was investigated by quantitative X Ray Powder Diffraction (XRPD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The starting material is composed of smectite (beidellite, 55.8 wt.%), illite (17.2 wt.%), quartz (8.5 wt.%), plagioclase (7.4 wt.%), K-feldspar (7.1 wt.%) and kaolinite (5 wt.%). At all investigated slip velocities, water-dampened gouges have peak and steady state frictional strengths (0.04<μ<0.1) lower than room dry gouges and are velocity-neutral to velocity-weakening. Under room-dry conditions, the gouges are velocity-strengthening at intermediate velocities (0.001 - 0.1 m s -1 , 0.25<μ<0.35) and strongly velocity-weakening at slip velocities > 0.1 m s -1 (μ<0.1). A detectable amount of amorphous material formed in room-dry experiments at low and high-slip velocities, likely by comminution and disordering of smectite.Room-dry gouges deformed at low slip velocities are foliated (P foliation) and cut by a series of shear bands lying either sub-parallel (Y) or at low angles to gouge layer boundaries (R). At high slip velocities, room-dry gouges contain a weak P foliation and a single, prominent Y shear. Deformed water-dampened gouges display homogeneous internal texture, lacking foliation or systematically organized fracture sets. In room-dry gouges, velocity strengthening at intermediate slip velocities and a pronounced peak friction at high slip velocities, represent an energy barrier to seismic rupture

  10. Slip-localization within confined gouge powder sheared at moderate to high slip-velocity

    NASA Astrophysics Data System (ADS)

    Reches, Zeev; Chen, Xiaofeng; Morgan, Chance; Madden, Andrew

    2015-04-01

    Slip along faults in the upper crust is always associated with comminution and formation of non-cohesive gouge powder that can be lithified to cataclasite. Typically, the fine-grained powders (grain-size < 1 micron) build a 1-10 cm thick inner-core of a fault-zone. The ubiquitous occurrence of gouge powder implies that gouge properties may control the dynamic weakening of faults. Testing these properties is the present objective. We built a Confined ROtary Cell, CROC, with a ring-shape, ~3 mm thick gouge chamber, with 62.5 and 81.2 mm of inner and outer diameters. The sheared powder is sealed by two sets of seals pressurized by nitrogen. In CROC, we can control the pore-pressure and to inject fluids, and to monitor CO2 and H2O concentration; in addition, we monitor the standard mechanical parameters (slip velocity, stresses, dilation, and temperature). We tested six types of granular materials (starting grain-size in microns): Talc (<250), Kasota dolomite (125-250), ooides grains (125-250), San Andreas fault zone powder (< 840), montmorillonite powder (1-2), kaolinite powder and gypsum. The experimental slip-velocity ranged 0.001-1 m/s, slip distances from a few tens of cm to tens of m, effective normal stress up to 6.1 MPa. The central ultra-microscopic (SEM) observation is that almost invariably the slip was localized along principal-slip-zone (PSZ) within the granular layer. Even though the starting material was loose, coarse granular material, the developed PSZ was cohesive, hard, smooth and shining. The PSZ is about 1 micron thick, and built of agglomerated, ultra-fine grains (20-50 nm) that were pulverized from the original granular material. We noted that PSZs of the different tested compositions display similar characteristics in terms of structure, grain size, and roughness. Further, we found striking similarities between PSZ in the granular samples and the PZS that developed along experimental faults made of solid rock that were sheared at similar

  11. The friction experiments using simulated fault gouge: Rowe's constant energy ratio

    NASA Astrophysics Data System (ADS)

    Hirata, M.; Muto, J.; Nagahama, H.; Otsuki, K.

    2013-12-01

    Rowe (1962) introduced a concept called minimum energy ratio principle to get a stress-dilatancy relation of granular materials under axisymmetric stress condition, and postulated that the ratio of rate of dissipation of energy in internal friction to rate of supply of energy in the direction of the major principal stress shall be a minimum and a constant value. However, the physical basis of this principle or physical meanings of the minimum incremental energy ratio have been questioned by many investigators. So we conducted friction experiments using simulated fault gouge in a gas-medium apparatus to test Rowe's hypothesis of constant energy ratio. The friction experiments using simulated fault gouge in a gas-medium apparatus was conducted under the confining pressure 140-180 MPa, and strain rate 10-3 /s. Dry quartz powders for gouge were sandwiched into two gabbro cylinders, which were 20 mm in diameter, 40 mm in length, and cut by a 50o to their cylindrical axis. To clarify mechanical behaviors of fault gouge, we repeated holding loads at several desired values, and used strain gauges glued onto a gauge layer directly with the high-speed data acquisition systems. During holding stage, we obtained the ratio of energy rate of the major principal compressional stress to minor compression stresses, or the energy rate ratio of input energy to output one. The ratio of energy rates showed a constant value in lower energy rates, on the other hand, it deviated from the constant value in higher energy rates. According to Rowe's theory of the constant energy ratio, the change in the ratio of energy rate indicates the change in angle of internal friction. Riedel shear angle related to internal friction angle decreases with shear strain (Gu and Wong, 1994), so it can be said that the change in internal friction angle is related to microstructure development. Therefore, the energy ratio in the lower energy rates is constant and the ratio in the higher energy rates varies

  12. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  13. Highly plastic behavior and fluidization of gouge; implications for fault and landslide mechanics and for the generation of mud volcanoes

    NASA Astrophysics Data System (ADS)

    Shimamoto, Toshihiko; Aoki, Kazuhiro; Seshimo, Kazuyoshi; Hu, Wei; Ma, Shengli; Yao, Lu; Xiong, Ran; Xiao, Yinke

    2016-04-01

    We address an issue on "how low gouge friction can be with an increasing amount of pore fluid" (an unexplored problem in fault mechanics), as studied with a rotary-shear low to high-velocity friction apparatus in Beijing using host specimens of Ti-Al-V alloy with a Teflon sleeve. A friction experiment was conducted on about 1 mm-thick, smectite-rich gouge from Shionohira fault zone, Fukushima, Japan, with 80 wt% of initial pore water, at a normal stress of 1 MPa, and with velocity steps of 17 times ranging in 0.21 microns/s to 2.1 m/s. Friction coefficients at slow rates were initially 0.003 to 0.005 with abundant water, but the coefficients increased to about 0.2 owing to the loss of water during the drained tests. Gouge was squeezed out slowly from host-specimen/Teflon interface as very thin paper-like flakes during a part of the run, indicating highly plastic behavior of gouge. The initial friction was by far the lowest ever reported! A dry high-velocity friction experiment on the same gouge (normal stress 2 MPa, velocity 2.1 m/s) revealed fluidization of gouge due to vaporized water released during decomposition of clay minerals. Friction coefficient increased to its peak (~ 0.8), followed by nearly exponential decay to a steady-state value of ~ 0.2. Then the friction coefficient began to decrease almost linearly with displacement down to ca. 0.07, deviating from an exponential decay. The gouge was lost almost instantly in less than one second, terminating the run. Temperature, measured at the sliding surface, began to decrease at the onset of the nearly linear weakening, strongly suggesting dehydration of clays (endothermic reactions). We interpret the results that steam pressure increased in gouge till a limit to cause a small explosion of gouge. Gouge can fluidize! A series of low to intermediate-velocity experiments on slip-zone materials from Kualiangzi landslide, Sichuan, China, demonstrated that the initial friction coefficient was less than 0.1 with a

  14. Dependence of frictional strength on compositional variations of Hayward fault rock gouges

    USGS Publications Warehouse

    Morrow, Carolyn A.; Moore, Diane E.; Lockner, David A.

    2010-01-01

    The northern termination of the locked portion of the Hayward Fault near Berkeley, California, is found to coincide with the transition from strong Franciscan metagraywacke to melange on the western side of the fault. Both of these units are juxtaposed with various serpentinite, gabbro and graywacke units to the east, suggesting that the gouges formed within the Hayward Fault zone may vary widely due to the mixing of adjacent rock units and that the mechanical behavior of the fault would be best modeled by determining the frictional properties of mixtures of the principal rock types. To this end, room temperature, water-saturated, triaxial shearing tests were conducted on binary and ternary mixtures of fine-grained gouges prepared from serpentinite and gabbro from the Coast Range Ophiolite, a Great Valley Sequence graywacke, and three different Franciscan Complex metasedimentary rocks. Friction coefficients ranged from 0.36 for the serpentinite to 0.84 for the gabbro, with four of the rock types having coefficients of friction ranging from 0.67-0.84. The friction coefficients of the mixtures can be predicted reliably by a simple weighted average of the end-member dry-weight percentages and strengths for all samples except those containing serpentinite. For the serpentinite mixtures, a linear trend between end-member values slightly overestimates the coefficients of friction in the midcomposition ranges. The range in strength for these rock admixtures suggests that both theoretical and numerical modeling of the fault should attempt to account for variations in rock and gouge properties.

  15. Physicochemical Processes and the Evolution of Strength in Calcite Fault Gouge at Room Temperature

    NASA Astrophysics Data System (ADS)

    Carpenter, B. M.; Viti, C.; Collettini, C.

    2015-12-01

    The presence of calcite in and near faults, as the dominant material, cement, or vein fill, indicates that the mechanical behavior of carbonate-dominated material likely plays an important role in shallow- and mid-crustal faulting. Furthermore, a variety of physical and chemical processes control the evolution of strength and style of slip along seismogenic faults and thus play a critical role in the seismic cycle. Determining the role and contributions of these types of mechanisms is essential to furthering our understanding of the processes and timescales that lead to the strengthening of faults during interseismic periods and their behavior during the earthquake nucleation process. To further our understanding of these processes, we performed laboratory-shearing experiments on calcite gouge at normal stresses from 1 to 100 MPa, under conditions of saturation and at room temperature. We performed velocity stepping (0.1-1000μm/s) and slide-hold-slide (1-3000s) tests, to measure the velocity dependence of friction and the amount of frictional strengthening respectively, under saturated conditions with pore fluid that was in equilibrium with CaCO3. At 5 MPa normal stress, we also varied the environmental conditions by performing experiments under conditions of 5% RH and 50 % RH, and saturation with: silicone oil, demineralized water, and the equilibrated solution combined with 0.5M NaCl. Finally, we collected post experimental samples for microscopic analysis. Our combined analyses of rate-dependence, strengthening behavior, and microstructures show that calcite fault gouge transitions from brittle to semi-brittle behavior at high normal stress and low sliding velocities. Furthermore, our results also highlight how changes in pore water chemistry can have significant influence on the mechanical behavior of calcite gouge in both the laboratory and in natural faults. Our observations have important implications for earthquake nucleation and propagation on faults in

  16. Benthic Gouge Marks in the Canadian Beaufort Sea: Associations Between Whales and Methane Seeps?

    NASA Astrophysics Data System (ADS)

    Smalls, P. T.; Paull, C. K.; Dallimore, S.

    2015-12-01

    Numerous distinctive depressions were observed on the seafloor during twenty-eight remotely operated vehicle (ROV) dives conducted on the shelf edge and upper slope of the Canadian Beaufort Sea. Surface ship and autonomous underwater vehicle (AUV) multibeam bathymetric maps were used to identify potential methane seepage sites, such as areas with persistent water column acoustic anomalies and the tops of mud volcanoes. ROV dives were conducted at these sites and at background sites for stratigraphic sampling. The high abundance of these distinctive depressions stimulated an analysis of the video observations made on these ROV dives. Depressions were analyzed to document their characteristics, to help determine their origin, and to establish whether their frequency varies with bottom type. One hundred fifty-two of the depressions observed had shared characteristics consisting of an "oval-shaped" depression with raised ridged edges that extended laterally along the flanks, and traces of uplifted sediment either in or around the depression. Similar depressions have been called "gouge marks" and attributed to bottom feeding beaked whales in previous studies. The size and water depth of the measured depressions matched well with beak sizes and feeding depths of beaked whale species known to exist in this area. This supports the conclusion that beaked whales created the depressions. The occurrence of these gouge marks and the estimates of the total area observed on these ROV dives (~45,000 m2), suggests they are common (e.g., ~4,000 per km2) features on the seafloor in this area of the Arctic. Gouges were also found 2.25 times more often at suspected methane seep-sites when normalized for depth and area. This suggests that the whales are preferentially attracted to seepage sites. While the reason for this possible preferential feeding behavior is unknown, it provides an intriguing avenue for further research.

  17. Sea floor gouges and pits in deep fjords, Baffin Island: Possible mammalian feeding traces

    NASA Astrophysics Data System (ADS)

    Hein, F. J.; Syvitski, J. P. M.

    1989-06-01

    Pisces submersible dives within Baffin Island fjords have revealed the common occurrence of pits on the sea floor, at water depths between 40 and 326 m. The size of these pits are in the decimeter to meter range. Through indirect evidence (by comparison of morphologic features to pits or gouges of known origin) they are believed to be feeding traces of narwhal, beluga, or bowhead whales. If so, they are the deepest mammalian feeding traces yet reported. Bioerosion by large foraging mammals may be a more common sea floor process than previously thought.

  18. Probing Magnetically the Paleotemperature in a Gouge: The Example from the Chinshui Shales from the Chelungpu Fault

    NASA Astrophysics Data System (ADS)

    Chou, Y. M.; Aubourg, C.; Lee, T. Q.; Song, S. R.; Yeh, E. C.

    2015-12-01

    The frictional heating is considered as a large component of earthquake energy releasing. However, probing the paleotemperature in fault gouge is still a challenge. The magnetic minerals could be neoformed/altered by thermal process within fault zone. In this study, we aim to estimate the paleotemperature by using low-temperature magnetic analyses (10K-300K) of wall rock (Chinshui Shale) and fault gouge zone from Taiwan Chelungpu-fault Drilling Project (TCDP). A piece of hanging wall rock sample from FZB1194 (fault zone within Hole-B at depth of 1,194 m) was grinded to powder and was stepwise heated within argon atmosphere from 90 to 550 ºC for one hour. The starting material is characterized by a very high content of nanoparticles. During laboratory heating, we observed the gradual destruction of the content of nanoparticles in the range 120°C up to 350°C, and the disappearance of Verwey transition at temperature higher than 350°C. The FZB1194 and FZB1243 were sampled from upper to lower parts including deformed sediments, black material disks, and black gouge zones. The magnetic analysis results show trends that we attribute to paleotemperature reached within the gouge. The deformed sediments seem unheated with respect to Chinshui Shales. In contrast, the proxy of paleotemperature of black material disk and gouge indicate >350°C and <250°C respectively. Tracking paleotemperature along a profile permits to identify several seismic events in the same gouge zone.

  19. The implication of gouge mineralogy evolution on fault creep: an example from The North Anatolian Fault, Turkey

    NASA Astrophysics Data System (ADS)

    Kaduri, M.; Gratier, J. P.; Renard, F.; Cakir, Z.; Lasserre, C.

    2015-12-01

    Aseismic creep is found along several sections of major active faults at shallow depth, such as the North Anatolian Fault in Turkey, the San Andreas Fault in California (USA), the Longitudinal Valley Fault in Taiwan, the Haiyuan fault in China and the El Pilar Fault in Venezuela. Identifying the mechanisms controlling creep and their evolution with time and space represents a major challenge for predicting the mechanical evolution of active faults, the interplay between creep and earthquakes, and the link between short-term observations from geodesy and the geological setting. Hence, studying the evolution of initial rock into damaged rock, then into gouge, is one of the key question for understanding the origin of fault creep. In order to address this question we collected samples from a dozen well-preserved fault outcrops along creeping and locked sections of the North Anatolian Fault. We used various methods such as microscopic and geological observations, EPMA, XRD analysis, combined with image processing, to characterize their mineralogy and strain. We conclude that (1) there is a clear correlation between creep localization and gouge composition. The locked sections of the fault are mostly composed of massive limestone. The creeping sections comprises clay gouges with 40-80% low friction minerals such as smectite, saponite, kaolinite, that facilitates the creeping. (2) The fault gouge shows two main structures that evolve with displacement: anastomosing cleavage develop during the first stage of displacement; amplifying displacement leads to layering development oblique or sub-parallel to the fault. (3) We demonstrate that the fault gouge result from a progressive evolution of initial volcanic rocks including dissolution of soluble species that move at least partially toward the damage zones and alteration transformations by fluid flow that weaken the gouge and strengthen the damage zone.

  20. Blackening of fault gouge by comminution and pyrolysis of carbonaceous materials during earthquake slip

    NASA Astrophysics Data System (ADS)

    Kaneki, Shunya; Hirono, Tetsuro

    2016-05-01

    Black fault gouges sometimes develop, mainly in sedimentary rocks, but the cause of the color transformation is not well understood. Here we demonstrated the blackening of synthetic mixtures of montmorillonite and bituminous coal and of montmorillonite and magnetite in milling, heating, and friction experiments. Mixed samples with a higher volume fraction of coal or magnetite before the experiments showed lower L* values (lightness index; lower values indicate darker blacks), because coal and magnetite are intrinsically black. The milling and heating experiments showed that the L* values of mixed samples of montmorillonite and coal drastically decreased with longer milling times and higher temperatures. The L* values of mixed samples of montmorillonite and magnetite also decreased with longer milling times, but no notable change was observed in the samples after the heating experiments. Because comminution by milling induces granulation of the constituent materials, blackening of the experimental samples was primarily caused by dispersal through the sample of fine black particles such as coal and magnetite, but it could be strengthened by adsorption onto host particles of organic gases produced by pyrolysis of carbonaceous material at high temperature. The friction experiment with mixed samples of montmorillonite and coal produced the remarkably low L* values. Friction induces both comminution and heating of samples, so the blackening could be greater than after either milling or heating alone. Therefore, relatively black fault gouges, compared with the surrounding host rocks, might have experienced comminution and heating, probably related to earthquake slip. Thus, black coloration could be one of the important information on fieldwork.

  1. Preferred orientation of phyllosilicates: Comparison of fault gouge, shale and schist

    NASA Astrophysics Data System (ADS)

    Wenk, Hans-Rudolf; Kanitpanyacharoen, Waruntorn; Voltolini, Marco

    2010-04-01

    Samples of fault gouge from the San Andreas Fault drill hole (SAFOD), a shale from the North Sea sedimentary basin and schists from metamorphic rocks in the Alps have been analyzed with high energy synchrotron X-rays to determine preferred orientation of mica and clay minerals. The method relies on obtaining 2D diffraction images which are then processed with the crystallographic Rietveld method, implemented in the software MAUD, allowing for deconvolution of phases and extraction of their orientation distributions. It is possible to distinguish between detrital illite/muscovite and authigenic illite/smectite, kaolinite and chlorite, and muscovite and biotite, with strongly overlapping peaks in the diffraction pattern. The results demonstrate that phyllosilicates show large texture variations in various environments, where different mechanisms produce the rock microfabrics: fault gouge fabrics are quite weak and asymmetric with maxima for (001) in the range of 1.5-2.5 multiples of random distribution (m.r.d.). This is attributed to heterogeneous deformation with randomization, as well as dissolution-precipitation reactions. Shale fabrics have maxima ranging from 3 to 9 m.r.d. and this is due to sedimentation and compaction. The strongest fabrics were observed in metamorphic schists (10-14 m.r.d.) and developed by deformation as well as recrystallization in a stress field. In the analyzed samples, fabrics of co-existing quartz are weak. All phyllosilicate textures can be explained by orientation of (001) platelets, with no additional constraints on a-axes.

  2. Dynamic friction in sheared fault gouge: Implications of acoustic vibration on triggering and slow slip

    NASA Astrophysics Data System (ADS)

    Lieou, Charles K. C.; Elbanna, Ahmed E.; Carlson, Jean M.

    2016-03-01

    Friction and deformation in granular fault gouge are among various dynamic interactions associated with seismic phenomena that have important implications for slip mechanisms on earthquake faults. To this end, we propose a mechanistic model of granular fault gouge subject to acoustic vibrations and shear deformation. The grain-scale dynamics is described by the Shear-Transformation-Zone theory of granular flow, which accounts for irreversible plastic deformation in terms of flow defects whose density is governed by an effective temperature. Our model accounts for stick-slip instabilities observed at seismic slip rates. In addition, as the vibration intensity increases, we observe an increase in the temporal advancement of large slip events, followed by a plateau and gradual decrease. Furthermore, slip becomes progressively slower upon increasing the vibration intensity. The results shed important light on the physical mechanisms of earthquake triggering and slow slip and provide essential elements for the multiscale modeling of earthquake ruptures. In particular, the results suggest that slow slip may be triggered by tremors.

  3. High shear strain behaviour of synthetic muscovite fault gouges under hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Van Diggelen, Esther W. E.; De Bresser, Johannes H. P.; Peach, Colin J.; Spiers, Christopher J.

    2010-11-01

    Major continental fault zones typically contain phyllosilicates and have long been recognised as zones of persistent weakness. To establish whether the presence of micas can explain this weakness, we studied the frictional behaviour of simulated muscovite fault gouge by performing rotary shear experiments in the temperature range 20-700 °C, under constant effective normal stresses of 20-100 MPa, a fixed fluid pressure of 100 MPa and at sliding velocities of 0.03-3.7 μm/s, reaching shear strains up to 100. Cataclasis causes substantial grain size reduction up to 600 °C. With increasing strain, both pervasive and localized cataclasis and related compaction result in strain hardening, until steady state is reached. This reflects the progressive development of a continuous network of fine grained, hardening bands. Coarse grained relict lenses between these bands show folded and kinked muscovite grains indicative of ductile mechanisms. Samples deformed at 700 °C show evidence for chemical alteration and partial melting. Since our data suggest that muscovite gouge strengthens with depth and strain, it is questionable whether its presence can contribute to the long-term weakness of major crustal fault zones, unless a substantial decrease in strength occurs at shear strain rates lower than attained in our study.

  4. Preferred orientation of phyllosilicates: Comparison of fault gouge, shale and schist

    SciTech Connect

    Wenk, Hans-Rudolf; Kanitpanyacharoen, Waruntorn; Voltolini, Marco

    2010-08-04

    Samples of fault gouge from the San Andreas Fault drill hole (SAFOD), a shale from the North Sea sedimentary basin and schists from metamorphic rocks in the Alps have been analyzed with high energy synchrotron X-rays to determine preferred orientation of mica and clay minerals. The method relies on obtaining 2D diffraction images which are then processed with the crystallographic Rietveld method, implemented in the software MAUD, allowing for deconvolution of phases and extraction of their orientation distributions. It is possible to distinguish between detrital illite/muscovite and authigenic illite/smectite, kaolinite and chlorite, and muscovite and biotite, with strongly overlapping peaks in the diffraction pattern. The results demonstrate that phyllosilicates show large texture variations in various environments, where different mechanisms produce the rock microfabrics: fault gouge fabrics are quite weak and asymmetric with maxima for (001) in the range of 1.5-2.5 multiples of random distribution (m.r.d.). This is attributed to heterogeneous deformation with randomization, as well as dissolution-precipitation reactions. Shale fabrics have maxima ranging from 3 to 9 m.r.d. and this is due to sedimentation and compaction. The strongest fabrics were observed in metamorphic schists (10-14 m.r.d.) and developed by deformation as well as recrystallization in a stress field. In the analyzed samples, fabrics of co-existing quartz are weak. All phyllosilicate textures can be explained by orientation of (001) platelets, with no additional constraints on a-axes.

  5. Evaluation of pyrolysis and arc tracking on candidate wire insulation designs for space applications

    NASA Technical Reports Server (NTRS)

    Stueber, Thomas J.; Hrovat, Kenneth

    1994-01-01

    The ability of wire insulation materials and constructions to resist arc tracking was determined and the damage caused by initial arcing and restrike events was assessed. Results of arc tracking tests on various insulation constructions are presented in view-graph format. Arc tracking tests conducted on Champlain, Filotex, and Teledyne Thermatics indicate the Filotex is least likely to arc track. Arc tracking occurs more readily in air than it does in vacuum.

  6. The influence of climate change on the intensity of ice gouging at the Kara Sea bottom by hummocky formations

    NASA Astrophysics Data System (ADS)

    Ogorodov, Stanislav; Arkhipov, Vasily; Kokin, Osip; Natalia, Shabanova

    2016-04-01

    Sea ice as a zonal factor is an important passive and active relief-forming agent in the coastal-shelf zone of the Arctic and other freezing seas. The most dangerous process in relation to the hydrotechnical facilities is ice gouging - destructive mechanical impact of the ice of the ground, connected with the dynamics of the ice cover, formation of hummocks and stamukhas under the influence of hydrometeorologic factors and of the relief of the coastal-shelf zone. Underestimation of the ice gouging intensity can lead to damage of the engineering facilities, while excessive deepening increases the expenses of the construction. Finding the optimal variant and, by this, decreasing the risks of extreme situations is a relevant task of the science and practice. This task is complicated by the fact that the oil and gas infrastructure within the coastal and shelf areas of the freezing seas is currently being developed in the conditions of global climate change. In the present work, several results of the repeated sounding of bottom ice gouging microrelief within the area of the underwater pipeline crossing of the Baydaratskaya Bay, Kara Sea, are presented. Based on the results of the monitoring, as well as the analysis of literature sources and modeling it has been established that under the conditions of climate warming and sea ice reduction, the zone of the most intensive ice gouging is shifted landwards, on shallower water areas.

  7. Generation of Billow-like Wavy Folds by Thermal Pressurization in a Seismic Slip Plane of Nojima Fault Gouge

    NASA Astrophysics Data System (ADS)

    Fukuzawa, T.; Nakamura, N.

    2015-12-01

    Nojima fault gouge has recorded physical processes during seismic slip, and one can find billow-like wavy folds along slip planes in the gouge. The fold patterns are similar to the ones of Kelvin Helmholtz (KH)-instability which occurs in fluid. Therefore, the presence of such folds suggests the fluidization of gouge materials. This instability occurs at the interface between two fluids of different densities shearing at different velocities (Thorpe, 2005), and in low viscous fluid (Woods, 1969). If a temperature range for the generation of such billow-like folds could be determined, we can constrain the weakening mechanism of frictional strength of faults. Here we show rock magnetic studies to prove the temperature rise in the generation of the billow-like folds, using a scanning magneto-impedance magnetic microscope. Its results showed the folds and the slip zones have been magnetized by the production of magnetite through thermal decomposition of siderite in the gouge. The thermal decomposition of siderite generally occurs at over about 350℃. This heating implies that thermal pressurization or melting were the driving mechanism of faulting. In order to clarify which mechanism mainly drove in the fault gouge, we constrained the temperature and viscosity condition of each melting model and thermal pressurization model from the perspective of the existence of the KH-instability. The melting model generates no such instability because of high viscosity (10 Pa·s), even if we postulate relatively high temperature melting (1300℃). On the other hands, we found that the thermal pressurization model can forced the fault slip zone very low viscosity (1.0×10-3 Pa·s) enough to generate KH-instability, which requires a shear stress of at most 0.25 Pa during faulting. It is supposed that the existence of the low viscosity fluid and the frictional heating decreased the frictional strength of the Nojima fault at an ancient large seismic activity, accelerating the fault

  8. Comparative analysis of masseter fiber architecture in tree-gouging (Callithrix jacchus) and nongouging (Saguinus oedipus) callitrichids.

    PubMed

    Taylor, Andrea B; Vinyard, Christopher J

    2004-09-01

    Common marmosets (Callithrix jacchus) and cotton-top tamarins (Saguinus oedipus) (Callitrichidae, Primates) share a broadly similar diet of fruits, insects, and tree exudates. Common marmosets, however, differ from tamarins by actively gouging trees with their anterior teeth to elicit tree exudate flow. During tree gouging, marmosets produce relatively large jaw gapes, but do not necessarily produce relatively large bite forces at the anterior teeth. We compared the fiber architecture of the masseter muscle in tree-gouging Callithrix jacchus (n = 10) to nongouging Saguinus oedipus (n = 8) to determine whether the marmoset masseter facilitates producing these large gapes during tree gouging. We predict that the marmoset masseter has relatively longer fibers and, hence, greater potential muscle excursion (i.e., a greater range of motion through increased muscle stretch). Conversely, because of the expected trade-off between excursion and force production in muscle architecture, we predict that the cotton-top tamarin masseter has more pinnate fibers and increased physiological cross-sectional area (PCSA) as compared to common marmosets. Likewise, the S. oedipus masseter is predicted to have a greater proportion of tendon relative to muscle fiber as compared to the common marmoset masseter. Common marmosets have absolutely and relatively longer masseter fibers than cotton-top tamarins. Given that fiber length is directly proportional to muscle excursion and by extension contraction velocity, this result suggests that marmosets have masseters designed for relatively greater stretching and, hence, larger gapes. Conversely, the cotton-top tamarin masseter has a greater angle of pinnation (but not significantly so), larger PCSA, and higher proportion of tendon. The significantly larger PCSA in the tamarin masseter suggests that their masseter has relatively greater force production capabilities as compared to marmosets. Collectively, these results suggest that the fiber

  9. Weld arc simulator

    DOEpatents

    Burr, Melvin J.

    1990-01-30

    An arc voltage simulator for an arc welder permits the welder response to a variation in arc voltage to be standardized. The simulator uses a linear potentiometer connected to the electrode to provide a simulated arc voltage at the electrode that changes as a function of electrode position.

  10. Permeability Evolution in Natural Fractures Subject to Cyclic Loading and Gouge Formation

    NASA Astrophysics Data System (ADS)

    Vogler, Daniel; Amann, Florian; Bayer, Peter; Elsworth, Derek

    2016-09-01

    Increasing fracture aperture by lowering effective normal stress and by inducing dilatant shearing and thermo-elastic effects is essential for transmissivity increase in enhanced geothermal systems. This study investigates transmissivity evolution for fluid flow through natural fractures in granodiorite at the laboratory scale. Processes that influence transmissivity are changing normal loads, surface deformation, the formation of gouge and fracture offset. Normal loads were varied in cycles between 1 and 68 MPa and cause transmissivity changes of up to three orders of magnitude. Similarly, small offsets of fracture surfaces of the order of millimeters induced changes in transmissivity of up to three orders of magnitude. During normal load cycling, the fractures experienced significant surface deformation, which did not lead to increased matedness for most experiments, especially for offset fractures. The resulting gouge material production may have caused clogging of the main fluid flow channels with progressing loading cycles, resulting in reductions of transmissivity by up to one order of magnitude. During one load cycle, from low to high normal loads, the majority of tests show hysteretic behavior of the transmissivity. This effect is stronger for early load cycles, most likely when surface deformation occurs, and becomes less pronounced in later cycles when asperities with low asperity strength failed. The influence of repeated load cycling on surface deformation is investigated by scanning the specimen surfaces before and after testing. This allows one to study asperity height distribution and surface deformation by evaluating the changes of the standard deviation of the height, distribution of asperities and matedness of the fractures. Surface roughness, as expressed by the standard deviation of the asperity height distribution, increased during testing. Specimen surfaces that were tested in a mated configuration were better mated after testing, than

  11. Clast-fabric development in a shearing granular material: Implications for subglacial till and fault gouge

    USGS Publications Warehouse

    Hooyer, T.S.; Iverson, N.R.

    2000-01-01

    Elongate clasts in subglacial till and in fault gouge align during shearing, but the relation between clast-fabric strength and cumulative shear strain for such materials is effectively unknown. This relation was explored in experiments with a large ring-shear device in which a till and a viscous putty that contained isolated clasts were sheared to high strains. As expected, rotation of clasts in the putty is closely approximated by the theory of G.B. Jeffrey, who derived the orbits of rigid ellipsoids in a slowly shearing fluid. Clast rotation in the till, however, is strikingly different. Rather than orbiting through the shear plane as predicted by Jeffery, most clasts rotate into the shear plane and remain there, resulting in strong fabrics regardless of the aspect ratios and initial orientations of clasts. This divergent behavior is likely due to slip of the till matrix along the surfaces of clasts, which is a natural expectation in a granular material but violates the no-slip condition of Jeffery's model. These results do not support the widespread belief that subglacial till deformation results in weak clast fabrics. Thus, many tills with weak fabrics thought to have been sheared subglacially to high strains, like many basal tills of the Laurentide Ice Sheet, may have been sheared only slightly with little effect on either ice-sheet dynamics or sediment transport. In addition, these results indicate that in simple shear the rotation of clasts in till and in fault gouge is best analyzed with the model of A. March, who treated inclusions as passive markers.

  12. Frictional processes in smectite-rich gouges sheared at slow to high slip rates

    NASA Astrophysics Data System (ADS)

    Aretusini, Stefano; Mittempergher, Silvia; Gualtieri, Alessandro; Di Toro, Giulio

    2015-04-01

    The slipping zones of shallow sections of megathrusts and of large landslides are often smectite-rich (e.g., montmorillonite type). Consequently, similar "frictional" processes operating at high slip rates (> 1 m/s) might be responsible of the large slips estimated in megathrust (50 m for the 2011 Tohoku Mw 9.1 earthquake) and measured in large landslides (500 m for the 1963 Vajont slide, Italy). At present, only rotary shear apparatuses can reproduce simultaneously the large slips and slip rates of these events. Noteworthy, the frictional processes proposed so far (thermal and thermochemical pressurization, etc.) remain rather obscure. Here we present preliminary results obtained with the ROtary Shear Apparatus (ROSA) installed at Padua University. Thirty-one experiments were performed at ambient conditions on pure end-members of (1) smectite-rich standard powders (STx-1b: ~68 wt% Ca-montmorillonite, ~30 wt% opal-CT and ~2 wt% quartz), (2) quartz powders (qtz) and (3) on 80:20 = Stx-1b:qtz mixtures. The gouges were sandwiched between two (1) hollow (25/15 mm external/internal diameter) or (2) solid (25 mm in diameter) stainless-steel made cylinders and confined by inner and outer Teflon rings (only outer for solid cylinders). Gouges were sheared at a normal stress of 5 MPa, slip rates V from 300 μm/s to 1.5 m/s and total slip of 3 m. The deformed gouges were investigated with quantitative (Rietveld method with internal standard) X-ray powder diffraction (XRPD) and Scanning Electron Microscopy (SEM). In the smectite-rich standard endmember, (1) for 300 μm/s ≤ V ≤ 0.1 m/s, initial friction coefficient (μi) was 0.6±0.05 whereas the steady-state friction coefficient (μss) was velocity and slip strengthening (μss 0.85±0.05), (2) for 0.1 m/s < V < 0.3 m/s, velocity and slip neutral (μi = μss = 0.62±0.08) and (3) for V > 0.8 m/s, velocity and slip weakening (μi = 0.7±0.1 and μss = 0.25±0.05). In the 80:20 Stx-1b:qtz mixtures, (1) for 300 μm/s ≤ V

  13. Comparison of Arc Tracking Tests in Various Aerospace Environments

    NASA Technical Reports Server (NTRS)

    Stueber, Thomas J.; Hammoud, Ahmad; McCall, David

    1996-01-01

    Momentary short-circuit arcs between a polyimide insulated wire with defective insulation and another conductor may cause pyrolization of the insulation resulting in a conductive path capable of sustaining the arc. These sustained arcs may propagate along the wires or to neighboring wires leading to complete failure of the wire bundle. Wire insulation susceptibility to arc tracking may be dependent on its environment. Because all wire insulation types tested to date arc track, a test procedure has been developed to compare different insulation types with respect to their arc tracking susceptibility. This test procedure is presented along with a comparison of arc tracking in the following three environments: (1) Air at atmospheric pressure and 1 gravitational(g) force; (2) Vacuum (2.67 x 10(exp -3) Pa) and 1g, and (3) Air at atmospheric pressure and microgravity (less than 0.04g).

  14. High-velocity frictional properties and microstructures of clay-rich fault gouge in megasplay fault zone, Nankai subduction zone

    NASA Astrophysics Data System (ADS)

    Ujiie, K.; Tsutsumi, A.

    2010-12-01

    In accretionary margins, a large out-of-sequence fault system (the megasplay fault) commonly branches from the megathrust and intersects the seafloor along the lower slope of the margin. Detailed seismic reflection surveys and theoretical studies have suggested that the propagation of earthquake rupture occurred repeatedly along the megasplay fault during great subduction earthquakes. Recently, IODP Expedition 316 drilled into the shallow portion of the megasplay fault zone in the Nankai subduction zone offshore the Kii Peninsula, southwest Japan and found the evidence for the slip localization and past frictional heating along ~10-mm-thick dark gouges in the microbreccia. Thus, high-velocity frictional properties of the megasplay fault material are crucial for understanding whether the megasplay fault efficiently transfers displacement toward the seafloor and fosters a tsunami genesis during a subduction earthquake. We conducted high-velocity friction experiments on clay-rich fault gouge taken from the Nankai megasplay fault zone at a slip rate of 1.3 m/s and normal stresses of 0.6-2.0 MPa under dry and wet conditions. After the experiments, the microstructures of the fault gouges were examined by optical microscope and SEM. In the dry tests, dehydration of clay minerals occurred by frictional heating, and the slip weakening is related to the fault gouge expansion due to a water phase transition from liquid to vapor. The water is derived from the dehydration of clay minerals by frictional heating. The resulting microstructure in the gouge layer is a random distribution of spherical clay-clast aggregates (CCA) in the optically isotropic, dark matrix. In the wet tests, the slip weakening is caused by pore-fluid pressurization resulting from shear-enhanced compaction of the water-saturated gouge and frictional heating. Compared to the dry tests, the wet tests show smaller dynamic stress drops and slip weakening distance. The steady-state shear stress in the wet tests

  15. Influence of Temperature on Frictional Strength and Healing Properties of Water Saturated Granular Fault Gouges During Dynamic Slip Instabilities

    NASA Astrophysics Data System (ADS)

    Scuderi, M.; Marone, C.

    2012-12-01

    The seismic potential of faults, as well as mechanical strength and frictional instability are controlled by the evolution of the real contact area within the fault gouge. Fault gouge is characterized by granular and clay rich material, as the result of continuous wear produced by dynamic or quasi-static slip along the fault plane. In this context, water and thermally-activated physicochemical reactions play a fundamental role in controlling the evolution of friction, via asperity contact properties and processes including hydrolytic weakening, adsorption/desorption, and/or intergranular pressure-solution (IPS). To investigate the role of granular processes and temperature in faulting, we performed shear experiments in water-saturated simulated gouges. We sheared layers of synthetic fault gouge composed of soda-lime glass beads (dia. 105-149 mm) in a double direct shear configuration within a true-triaxial pressure vessel under controlled fluid pressure using DI water. Effective normal stress (σn) was kept constant during shear at 5 MPa, and layer thickness was constantly monitored via a DCDT attached to the ram. Shear stress (τ) was applied via a constant shear displacement rate at layers boundaries. We performed velocity step experiments, during which shearing velocity was increased stepwise from 0.3 to 300 μm/s, and slide-hold-slide tests, with hold times from 1 to 1000 s. During each experiment temperature was kept constant at values of 25, 50 and 75C. Our experiments were conducted in a stick-slip sliding regime. At the end of each run, simulated gouge layers were carefully collected and impregnated with epoxy resin for SEM analysis. For all experiments, stress drop (Δτ) decreases roughly linearly with the log of velocity. With increasing temperature Δτ increases and the velocity dependence varies. Frictional healing is characterized by β = 0.023 change in friction per decade at T = 25C, increasing to β = 0.037 at T = 50C. We find that maximum

  16. Gas arc constriction for plasma arc welding

    NASA Technical Reports Server (NTRS)

    McGee, William F. (Inventor); Rybicki, Daniel J. (Inventor)

    1994-01-01

    A welding torch for plasma arc welding apparatus has an inert gas applied circumferentially about the arc column externally of the constricting nozzle so as to apply a constricting force on the arc after it has exited the nozzle orifice and downstream of the auxiliary shielding gas. The constricting inert gas is supplied to a plenum chamber about the body of the torch and exits through a series of circumferentially disposed orifices in an annular wall forming a closure at the forward end of the constricting gas plenum chamber. The constricting force of the circumferential gas flow about the arc concentrates and focuses the arc column into a more narrow and dense column of energy after exiting the nozzle orifice so that the arc better retains its energy density prior to contacting the workpiece.

  17. Driven Motion and Instability of an Atmospheric Pressure Arc

    SciTech Connect

    Max Karasik

    1999-12-01

    Atmospheric pressure arcs are used extensively in applications such as welding and metallurgy. However, comparatively little is known of the physics of such arcs in external magnetic fields and the mechanisms of the instabilities present. In order to address questions of equilibrium and stability of such arcs, an experimental arc furnace is constructed and operated in air with graphite cathode and steel anode at currents 100-250 A. The arc is diagnosed with a gated intensified camera and a collimated photodiode array, as well as fast voltage and current probes.

  18. Arc Deflection Length Affected by Transverse Rotating Magnetic Field with Lateral Gas

    NASA Astrophysics Data System (ADS)

    Shiino, Toru; Ishii, Yoko; Yamamoto, Shinji; Iwao, Toru; High Current Energy Laboratory (HiCEL) Team

    2016-10-01

    Gas metal arc welding using shielding gas is often used in the welding industry. However, the arc deflection affected by lateral gas is problem because of inappropriate heat transfer. Shielding gas is used in order to prevent the instability affected by the arc deflection. However, the shielding gas causes turbulence, then blowhole of weld defect occurs because the arc affected by the instability is contaminated by the air. Thus, the magnetic field is applied to the arc in order to stabilize the arc using low amount of shielding gas. The method of applying the transverse rotating magnetic field (RMF) to the arc is one of the methods to prevent the arc instability. The RMF drives the arc because of electromagnetic force. The driven arc is considered to be prevented to arc deflection of lateral gas because the arc is restrained by the magnetic field because of the driven arc. In addition, it is assume the RMF prevented to the arc deflection of lateral gas from the multiple directions. In this paper, the arc deflection length affected by the RMF with lateral gas was elucidated in order to know the effect of the RMF for arc stabilization. Specifically, the arc deflection length affected by the magnetic frequency and the magnetic flux density is measured by high speed video camera. As a result, the arc deflection length decreases with increasing magnetic frequency, and the arc deflection length increases with increasing the magnetic flux density.

  19. Helium and Carbon Systematics of the Sangihe Arc, Indonesia: Tracing Volatile Sources in an Arc-Arc Collision

    NASA Astrophysics Data System (ADS)

    Jaffe, L. A.; Hilton, D. R.; Fischer, T. P.; Hartono, U.

    2002-12-01

    The Sangihe and Halmahera arcs in northeastern Indonesia are presently colliding, forming the world's only extant example of an arc-arc collision. We report the first helium and carbon isotopic and relative abundance data from the Sangihe Arc volcanoes as a means to trace magma origins in this complicated tectonic region. Gas chemistry and N-isotopes from the same localities are reported in a companion paper (Clor et al, this volume). There is a distinct regional pattern in He and CO2 variations along the north-south strike of the Sangihe Arc. The two northernmost volcanoes (Awu and Karangetang) have 3He/4He <= 6.4RA (where RA = air 3He/4He), CO2/3He >= 30x109, and δ13C >= -2.0‰ . In contrast, the southern volcanoes along the arc (Ruang, Lokon, Mahawu) have 3He/4He >= 7.0RA, CO2/3He < 7x109 and δ13C < -3.0‰ . The southern volcanoes, therefore, sample volatiles more typical of island arc volcanoes. Resolving the CO2 into component structures (mantle-derived, plus slab-derived organic and limestone CO2 - following the approach of Sano and Marty, Chem. Geol., 1995), the northern volcanoes contain higher than average slab-derived limestone contributions. For example, limestone-derived CO2 makes up > 90% of the total CO2 at Karangetang and ~98% at Awu. These values compare with an average limestone contribution of ~65% in the southern Sangihe arc and ~73% in other arcs worldwide. We are investigating possible reasons for the enhanced limestone contributions in the northern Sangihe arc. The sedimentary mélange wedge is thickest in the north (up to 15km) - where the arcs initially collided. The greater availability of sediment may result in a greater input of subducted sediment, thereby providing enhanced dilution of mantle wedge C inputs. Alternatively, subducted sediments may be more carbonate-rich in the northern segment of the arc. This may reflect obduction of shallow, organic-bearing sediments onto the over-riding plate, leaving only pelagic carbonates to

  20. Arc spot welding technique for underwater use

    SciTech Connect

    Koga, H.; Ide, Y.; Ogawa, Y.

    1995-12-31

    An arc spot welding equipment with special local cavity shroud was developed for underwater salvaging activity. Arc spot welding for lapped plates is an effective method to recover defects. This method in surface is so simple to use widely in the field of railways and chemical plants manufacturing. But there is some problems on the reliability of joint strength and bead shapes. A special arc spot nozzle to improve welding quality was developed. A small outlet of air jet at the bottom of the nozzle was created to maintain the swirl flow of shielding gas and certain rejection of excessive molten metal. This nozzle covers the welding part completely, then it also works as a local cavity shroud under water. This paper describes the design and function of the nozzle for CO{sub 2} arc spot welding system. A programmable controller manages the welding sequence of shielding gas flow, air jet flow, and arcing time. This welding gun is operated manually, but the operation is only to press the gun on the weld point. After that welding will proceed automatically, and arcing time is about three seconds. Whole time for welding which includes pre and post gas flow time is less than ten seconds for surface use, it is required some more additional pre drying process of welding point for underwater use to guarantee the high quality welding results. Fundamental analysis of welding conditions and the effects of air jet were considered.

  1. Paleomagnetic constraints of seismic thermal signatures and coseismic geo-current in the Nojima fault gouge, Japan

    NASA Astrophysics Data System (ADS)

    Kitagawa, T.; Nakamura, N.

    2005-12-01

    The Nojima fault gouge is an alternating layer of fine-grained gouge (gray, cohesive) and pseudotachylyte (black, brittle), derived from the adjacent low-magnetic granite. Each layer is thinner than a few millimeters, and corresponds to one seismic slip event. Previous X-ray diffraction study showed that the gray-color gouge includes siderite and lepidocrocite, while the black-color pseudotachylyte includes magnetite. The bulk sample showed a strong intensity of natural remanent magnetization (NRM), being 400 times more intense than the granite. Two hypotheses to describe this higher remanence have been presented as 1) the thermal decomposition of mafic minerals to magnetite by friction melting of fine-grained gouge, and 2) the thermal dehydration of lepidocrocite to ferromagnetic maghemite through flash heating of the gouge. Both hypotheses indirectly estimated the temperature rise of up to at least 700°C, resulting that the pseudotachylyte should acquire a thermal remanence during seismic slip. Although thermal remanence records a thermal history at the time of flash heating during seismic slip, the bulk sample analysis averages the thermal history information of each seismic slip event. Nevertheless, there has been no paleomagnetic study of the alternating gouge by 'layer-by-layer'. Here, we report a direct estimation for the temperature rise of pseudotachylyte by the layer-by-layer analysis through step-wise thermal demagnetization by SQUID magnetometer and scanning electron microscopy (SEM). The thermal demagnetization was performed for small chips of pseudotachylyte in total 64 measurements, and 42 subsamples show relatively strong intensity and stable demagnetization patterns. Moreover, the orientations of high coercivity component are randomly oriented even in a centimeter apart along the same layer, being no hemispherical bias. SEM observation reveals that a remanence carrier is submicron-sized inclusions of iron, which is identified as magnetite through

  2. Studying the Effect of the Air-Cap Configuration in Twin-Wire Arc-Spraying Process on the Obtained Flow Characteristics Using Design of Experiment Oriented Fluid Simulation

    NASA Astrophysics Data System (ADS)

    Tillmann, W.; Abdulgader, M.; Anjami, N.; Hagen, L.

    2015-01-01

    The computational fluid dynamics approach is adopted in this work using the design of experiments to reveal the effect of the air-cap configurations on the obtained gas velocity, the shear stresses, the high velocity zone, and the convergence of the obtained spraying plume in the twin-wire arc-spraying process. The parameters, which are revealed to optimize the air-cap configuration, are the throat diameter, the convergence angle of the throat inlet, the throat length, and the distance between the throat outlet and the intersection point of the approaching wires. The throat length is dependent upon the other configuration parameters. Outlet gas velocity, the turbulence in the flow, and the exerted shear stresses at wire tips are directly affected by the dominating flow regimes near the intersection point of the approaching wires. The presence of wires and the contact tips in the gas flow has enormous impact on the obtained flow characteristics. Air-cap throat diameter and the distance between throat outlet and intersection point determine the shape and length of the obtained high velocity zone in the spraying plum.

  3. Frictional-viscous transition in simulated calcite fault gouge sheared at 550°C

    NASA Astrophysics Data System (ADS)

    Verberne, Berend Antonie; Niemeijer, André R.; de Bresser, Johannes H. P.; Spiers, Christopher J.

    2015-04-01

    Understanding the strength and slip stability of fault rocks throughout the frictional-viscous transition is important for understanding the mechanisms controlling seismogenesis. We report ring shear experiments on simulated calcite fault gouge (median grain size ~20 μm), consisting of i) tests performed at an effective normal stress (σneff) of 50 MPa at constant sliding velocities (v) of 0.1 and 100 μm/s, and ii) σneff-stepping tests at constant v = 0.1 and 10 μm/s, using sequentially increased σneff values within the range from 30 to 140 MPa. Each test was performed wet at a fixed temperature of 550°C, and sheared gouges recovered from constant σneff tests were used for microstructure analyses. Our results show that samples sheared at σneff = 50 MPa, at v = 0.1 μm/s, have a steady-state shear strength (τss) of ~46 MPa, and are characterized by a microstructure consisting of 10 to 30 µm sized elongated grains embedded in a matrix of ~1 to 5 μm sized polygonal grains. By contrast, samples sheared at σneff = 50 MPa at v = 100 μm/s, showed τss ≈ 38 MPa, and a microstructure consisting of a matrix of 1 to 40 μm sized angular to sub-rounded grains cut by a sharply-defined, 30 to 40 µm wide, boundary-parallel shear band composed of ~0.3 to 1 μm sized polygonal grains, characterized by strong, uniform, birefringence colours, and uniform extinction, suggestive of a crystallographic preferred orientation (CPO). Plots of shear strength against σneff, showed a clear deviation from linearity for σneff-stepping tests conducted at 0.1 µm/s, whereas for those conducted at 10 µm/s, the τ- σneff dependence was well-described with a straight line. Our results suggest that, in experiments conducted at low slip rates (v = 0.1 μm/s), the shear strain was accommodated by pervasive, frictional-viscous flow, whereas for samples sheared at high rates (v > 10 μm/s), this occurred via localized, frictional slip. Using a recent microphysical model involving a

  4. Rotating arc spark plug

    DOEpatents

    Whealton, John H.; Tsai, Chin-Chi

    2003-05-27

    A spark plug device includes a structure for modification of an arc, the modification including arc rotation. The spark plug can be used in a combustion engine to reduce emissions and/or improve fuel economy. A method for operating a spark plug and a combustion engine having the spark plug device includes the step of modifying an arc, the modifying including rotating the arc.

  5. DC arc weld starter

    DOEpatents

    Campiotti, Richard H.; Hopwood, James E.

    1990-01-01

    A system for starting an arc for welding uses three DC power supplies, a high voltage supply for initiating the arc, an intermediate voltage supply for sustaining the arc, and a low voltage welding supply directly connected across the gap after the high voltage supply is disconnected.

  6. Blackening of fault gouge by comminution and pyrolysis of carbonaceous materials during earthquake slip

    NASA Astrophysics Data System (ADS)

    Kaneki, S.; Hirono, T.

    2015-12-01

    Fault gouges often exhibit various colors (white-pink-green-brown-gray-black), and particularly those developed in sedimentary rocks show gray to black. However, the physicochemical process for the color transition accompanied with seismic slip has not yet been fully understood. On the other hand, determination of the peak temperature during slip is crucial to identify the faulting mechanism during an earthquake, so that various temperature proxies have been proposed. For example, 1) magnetite formation at high temperature of ≥400 °C, 2) anomalies in the concentrations of fluid-mobile trace elements (Sr, Cs, Rb, and Li) and in the Sr isotope ratios, indicating presence of high-temperature fluid of ≥350 °C, 3) dehydroxylation of clay minerals, 4) thermal decomposition of carbonate minerals, and 5) thermal maturation of carbonaceous material examined by vitrinite reflectance measurement and by infrared and Raman spectroscopies. However, these proxies required high-level analyses in laboratory, so easy method to detect the record of high temperature preliminarily on field would be expected. In this study, we reproduced the blackening of synthetic fault sample by using high-velocity friction apparatus, thermogravimetric, and milling machine, and evaluated the color transition and organic chemical property of the samples by using UV-visible/NIR spectrophotometer and pyrolysis-gas chromatography-mass spectrometry. We discuss the process of the blackening taking comminution and pyrolysis of carbonaceous materials into consideration.

  7. A study of different fault slip modes governed by the gouge material composition in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Kocharyan, G. G.; Novikov, V. A.; Ostapchuk, A. A.; Pavlov, D. V.

    2017-01-01

    Described are results of laboratory experiments which revealed regularities of gradual transition from stick-slip mode to aseismic creep. The behaviour of model gouge-filled fault was investigated with experimental setup of the spring-bock model. It was experimentally proven that small variations of a percentage of materials with velocity strengthening and velocity weakening properties in the fault principal slip zone may result in significant variation of the portion of seismic energy radiated during a fault slip event. The tests simulated different modes of interblock sliding whose characteristic values of scaled kinetic energy varied by several orders of magnitude, while differences in contact strength and shear stress drop remained relatively small. The obtained results led to the conclusion that the earthquake radiation efficiency and the fault slip mode are governed by the ratio of two parameters-maximum fault slip-weakening rate and shear stiffness of the enclosing massif. The ratio can be essentially changed by small variations of the material composition of the fault principal slip zone.

  8. A study of different fault slip modes governed by the gouge material composition in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Kocharyan, G. G.; Novikov, V. A.; Ostapchuk, A. A.; Pavlov, D. V.

    2016-11-01

    Described are results of laboratory experiments which revealed regularities of gradual transition from stick-slip mode to aseismic creep. The behavior of model gouge-filled fault was investigated with experimental setup of the spring-bock model. It was experimentally proven that small variations of a percentage of materials with velocity strengthening and velocity weakening properties in the fault principal slip zone may result in significant variation of the portion of seismic energy radiated during a fault slip event. The tests simulated different modes of inter-block sliding whose characteristic values of scaled kinetic energy varied by several orders of magnitude, while differences in contact strength and shear stress drop remained relatively small. The obtained results led to the conclusion that the earthquake radiation efficiency and the fault slip mode are governed by the ratio of two parameters - maximum fault slip-weakening rate and shear stiffness of the enclosing massif. The ratio can be essentially changed by small variations of the material composition of the fault principal slip zone.

  9. Discrete Slip, Amorphous Silica and Pore Structure of Slickensided Gouge Layers in 2004-2006 Mt. St. Helens Lava Domes

    NASA Astrophysics Data System (ADS)

    White, J. C.; Kennedy, L. A.; Russell, J. K.; Friedlander, B.

    2012-12-01

    Spines of dacite lava formed during the 2004-2006 Mt. St. Helens (MSH) effusion event are enveloped by extrusion gouges created during upward movement of crystallized magma. Multiple slickenside sets form one of the most distinctive feature types within this gouge carapace. Macroscopically, slickenside surfaces are seen to be composite features composed of discrete slip surfaces in Y- and R-shear orientations. In general, the spacing between the slip surfaces decreases toward the outer, exposed slickensided surface until they appear to coalesce. Slickensides are formed in association with all MSH spines, unlike some other fault rock fabrics within the gouge; therefore, their morphology can be inferred to be independent of syn-faulting residence time. As a significant record of the extrusion process, the MSH slickensides have been characterized by analytical scanning/transmission electron microscopy (STEM) to elucidate the mechanisms of energy dissipation and material transport. At the scale of these observations, the individual surfaces within a slickenside set comprise comminution bands (10-20 μm wide), each bounded by a discrete slip surface. The internal structure of these shear bands consists of a consistent sense of decreasing grain size toward the slip surface away and away from the spire core; grain size is routinely less than 100nm within the bands. The 1-5 μm wide slip layers that bound comminution bands are variously composed of amorphous silica or polycrystalline aggregates of sub-100nm grain size plagioclase, k-feldspar and quartz. Grain aggregates in the slip layer form an extended fabric parallel to the displacement direction, creating a "flow" foliation at edges of the shears. Specific to the slip bands are nano-scale pores, often silica-filled, whose circular cross-sections indicate the presence of fluids throughout slickenside formation. It is contended that the development of discrete slip surfaces is consistent with formation of the gouge by

  10. Amorphization and Frictional Processes in Smectite-Quartz Gouge Mixtures Sheared from Sub-seismic to Seismic Slip Rates

    NASA Astrophysics Data System (ADS)

    Aretusini, S.; Mittempergher, S.; Spagnuolo, E.; Di Toro, G.; Gualtieri, A.; Plümper, O.

    2015-12-01

    Slipping zones in shallow sections of megathrusts and large landslides are often made of smectite and quartz gouge mixtures. Experiments aimed at investigating the frictional processes operating at high slip rates (>1 m/s) may unravel the mechanics of these natural phenomena. Here we present a new dataset obtained with two rotary shear apparatus (ROSA, Padua University; SHIVA, INGV-Rome). Experiments were performed at room humidity and temperature on four mixtures of smectite (Ca-Montmorillonite) and quartz with 68, 50, 25, 0 wt% of smectite. The gouges were slid for 3 m at normal stress of 5 MPa and slip rate V from 300 µm/s to 1.5 m/s. Temperature during the experiments was monitored with four thermocouples and modeled with COMSOL Multiphysics. In smectite-rich mixtures, the friction coefficient µ evolved with slip according to three slip rate regimes: in regime 1 (V<0.1 m/s) initial slip-weakening was followed by slip-strengthening; in regime 2 (0.10.3 m/s) µ had strong slip-weakening behavior. Instead, in quartz-rich mixtures the gouge had a monotonic slip-weakening behavior, independently of V. Temperature modelling showed that the fraction of work rate converted into heat decreased with increasing smectite content and slip rate. Quantitative X-ray powder diffraction (Rietveld method) indicates that the production of amorphous material from smectite breakdown increased with frictional work but was independent of work rate. Scanning Electron Microscopy investigation evidenced strain localization and presence of dehydrated clays for V≥0.3 m/s; instead, for V<0.3 m/s, strain was distributed and the gouge layer pervasively foliated. In conclusion, amorphization of the sheared gouges was not responsible of the measured frictional weakening. Instead, slip-weakening was concomitant to strain localization and possible vaporization of water adsorbed on smectite grain surfaces.

  11. Frictional Properties and Microstructure of Calcite-Rich Fault Gouges Sheared at Sub-Seismic Sliding Velocities

    NASA Astrophysics Data System (ADS)

    Verberne, B. A.; Spiers, C. J.; Niemeijer, A. R.; De Bresser, J. H. P.; De Winter, D. A. M.; Plümper, O.

    2014-10-01

    We report an experimental and microstructural study of the frictional properties of simulated fault gouges prepared from natural limestone (96 % CaCO3) and pure calcite. Our experiments consisted of direct shear tests performed, under dry and wet conditions, at an effective normal stress of 50 MPa, at 18-150 °C and sliding velocities of 0.1-10 μm/s. Wet experiments used a pore water pressure of 10 MPa. Wet gouges typically showed a lower steady-state frictional strength ( μ = 0.6) than dry gouges ( μ = 0.7-0.8), particularly in the case of the pure calcite samples. All runs showed a transition from stable velocity strengthening to (potentially) unstable velocity weakening slip above 80-100 °C. All recovered samples showed patchy, mirror-like surfaces marking boundary shear planes. Optical study of sections cut normal to the shear plane and parallel to the shear direction showed both boundary and inclined shear bands, characterized by extreme grain comminution and a crystallographic preferred orientation. Cross-sections of boundary shears, cut normal to the shear direction using focused ion beam—SEM, from pure calcite gouges sheared at 18 and 150 °C, revealed dense arrays of rounded, ~0.3 μm-sized particles in the shear band core. Transmission electron microscopy showed that these particles consist of 5-20 nm sized calcite nanocrystals. All samples showed evidence for cataclasis and crystal plasticity. Comparing our results with previous models for gouge friction, we suggest that frictional behaviour was controlled by competition between crystal plastic and granular flow processes active in the shear bands, with water facilitating pressure solution, subcritical cracking and intergranular lubrication. Our data have important implications for the depth of the seismogenic zone in tectonically active limestone terrains. Contrary to recent claims, our data also demonstrate that nanocrystalline mirror-like slip surfaces in calcite(-rich) faults are not

  12. Birth of an island arc : Stuctural and Kinematics records of upper plate deformation. Example of St Barthelemy, Lesser Antilles (French West Indies).

    NASA Astrophysics Data System (ADS)

    Legendre, L.; Philippon, M. M.; Mazabraud, Y.; Jean-Frederic, L.

    2015-12-01

    The Lesser Antilles subduction initiated in Lower Cretaceous at the eastern tip of the Caribbean plate where Atlantic is subducting westward bellow Caribbean plate. The associated island arc extends from St Martin (to the north) to Grenada Island (to the south). The northern half of the volcanic arc presents a peculiar morphology with (i) an eastern outer arc that was active from Eocene to Oligocene from St Martin to Martinique and (ii) a western inner one from Saba to Martinique which is active since the Miocene attesting for a westward jump of the volcanic arc at that time. The long-term deformation pattern and kinematics affecting the Lesser Antilles arcand its evolution from Eocene to Miocene, before its westward jump, remain poorly constrained. This study aims at constraining the deformation pattern expressed in the eastern outer arc of the Lesser Antilles during Eocene time, which is contemporaneous with arc formation. To achieve this goal, St Barthelemy Isand (St Barth) is a key target as it consists of Eocene volcanites inter layered with carbonate platform sequences, intruded by Oligocene dykes and pipes. During fieldwork, we accurately mapped the main tectonic features that affect the island, and characterized the mineralogy of the gouges and fluid circulation along the main faults. The kinematics data were used to perform inversions in order to recover the paleostate of stress and datable minerals found in fault gouge will be further used to constrain the timing of fault activity. We discuss the observed deformations within the regional tectonic framework and the birth of the Lesser Antilles volcanic arc. Firstly, we recover the Eocene local paleostress in St Barth corresponding to the first stages of island arc building. Secondly, we discuss the Eo-Oligocene evolution of the stress field at the island scale. Thirdly, thanks to the observed mineralogy we decipher the different deformation stages that occurred at distinct structural levels.

  13. Mineralogical Controls of Fault Healing in Natural and Simulated Gouges with Implications for Fault Zone Processes and the Seismic Cycle

    NASA Astrophysics Data System (ADS)

    Carpenter, B. M.; Ikari, M.; Marone, C.

    2011-12-01

    The frictional strength and stability of tectonic faults is determined by asperity contact processes, granular deformation, and fault zone fabric development. The evolution of grain-scale contact area during the seismic cycle likely exhibits significant control on overall fault stability by influencing frictional restrengthening, or healing, during the interseismic period, and the rate-dependence of sliding friction, which controls earthquake nucleation and the mode of fault slip. We report on laboratory experiments designed to explore the affect of mineralogy on fault healing. We conducted frictional shear experiments in a double-direct shear configuration at room temperature, 100% relative humidity, and a normal stress of 20 MPa. We used samples from a wide range of natural faults, including outcrop samples and core recovered during scientific drilling. Faults include: Alpine (New Zealand), Zuccale (Italy), Rocchetta (Italy), San Gregorio (California), Calaveras (California), Kodiak (Alaska), Nankai (Japan), Middle America Trench (Costa Rica), and San Andreas (California). To isolate the role of mineralogy, we also tested simulated fault gouges composed of talc, montmorillonite, biotite, illite, kaolinite, quartz, andesine, and granite. Frictional healing was measured at an accumulated shear strain of ~15 within the gouge layers. We conducted slide-hold-slide tests ranging from 3 to 3000 seconds. The main suite of experiments used a background shearing rate of 10 μm/s; these were augmented with sub-suites at 1 and 100 μm/s. We find that phyllosilicate-rich gouges (e.g. talc, montmorillonite, San Andreas Fault) show little to no healing over all hold times. We find the highest healing rates (β ≈ 0.01, Δμ per decade in time, s) in gouges from the Alpine and Rocchetta faults, with the rest of our samples falling into an intermediate range of healing rates. Nearly all gouges exhibit log-linear healing rates with the exceptions of San Andreas Fault gouge and

  14. The Effects of Fault Composition and Microstructures on Fault Weakness: A Study of Synthetic and Natural Clay-Rich Fault Gouges

    NASA Astrophysics Data System (ADS)

    Kenigsberg, A.; Saffer, D. M.; Ryan, K. L.; Marone, C.

    2015-12-01

    The mechanical weakness of faults has long been a fundamental issue in faulting and earthquake mechanics studies. Studies of core and outcrop samples obtained from major faults, including the San Andreas Fault and subduction megathrusts, and laboratory friction experiments on natural and synthetic fault gouges all document that clay minerals are one likely explanation for fault weakness. While laboratory experiments have shown that clays are frictionally weak, with friction coefficients (μ) as low as 0.08-0.2 for smectite family minerals, and that μ varies systematically with clay content, the effects of microstructure, composition, and the evolution of friction throughout shearing of clay-rich gouges is not well understood. To investigate these processes, we conducted shearing experiments on two-phase synthetic gouges of varying proportions of quartz and Ca-montmorillonite. We then studied the resulting microstructures to test the hypothesis that as clay-rich gouges are sheared, clay minerals align and form discrete through-going surfaces that lead to reduced strength. Experiments were run in a double direct shear geometry at room temperature and normal stresses of 25 MPa. Samples were sheared at a constant velocity of 10μm/s. Sheared "wafers" were recovered for scanning electron microscope (SEM) analyses. Our preliminary results yield values of μ = 0.35-0.62 for mixtures ranging from 10%-90% clay, and document a decrease in μ with clay content, consistent with previous studies. Additionally, we observe a characteristic peak and then drop in shear strength at the beginning of shearing. The magnitude of this peak increases with clay content. Ongoing analysis of fabrics will systematically assess the relationship between microstructures, clay alignment, and the evolution of friction for our synthetic gouges as well as for a suite of natural clay-rich fault rocks from exhumed subduction thrusts. We expect that with clay content and shear strain increases

  15. Characteristics of Atmospheric Pressure Rotating Gliding Arc Plasmas

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Zhu, Fengsen; Tu, Xin; Bo, Zheng; Cen, Kefa; Li, Xiaodong

    2016-05-01

    In this work, a novel direct current (DC) atmospheric pressure rotating gliding arc (RGA) plasma reactor has been developed for plasma-assisted chemical reactions. The influence of the gas composition and the gas flow rate on the arc dynamic behaviour and the formation of reactive species in the N2 and air gliding arc plasmas has been investigated by means of electrical signals, high speed photography, and optical emission spectroscopic diagnostics. Compared to conventional gliding arc reactors with knife-shaped electrodes which generally require a high flow rate (e.g., 10-20 L/min) to maintain a long arc length and reasonable plasma discharge zone, in this RGA system, a lower gas flow rate (e.g., 2 L/min) can also generate a larger effective plasma reaction zone with a longer arc length for chemical reactions. Two different motion patterns can be clearly observed in the N2 and air RGA plasmas. The time-resolved arc voltage signals show that three different arc dynamic modes, the arc restrike mode, takeover mode, and combined modes, can be clearly identified in the RGA plasmas. The occurrence of different motion and arc dynamic modes is strongly dependent on the composition of the working gas and gas flow rate. supported by National Natural Science Foundation of China (No. 51576174), the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120101110099) and the Fundamental Research Funds for the Central Universities (No. 2015FZA4011)

  16. Rethinking Recycling in Arcs

    NASA Astrophysics Data System (ADS)

    Kelemen, P.; Behn, M. D.; Jagoutz, O.

    2012-12-01

    Hacker et al EPSL 2011 and Behn et al Nature Geosci 2011 investigated pathways for return of buoyant, subducted material to arc crust. These include (1) diapirs rising into the hot mantle wedge, with extensive melts adding a component to arc magmas, (2) flow of material back up a relatively cold "subduction channel", adding solids to the lower crust and small-degree partial melts to the upper crust, (3) flow from the forearc along the base of arc crust, and (4) imbrication of forearc material into arc crust. These processes add felsic, incompatible-element-rich components to arc crust. The flux of incompatible elements such as Th in arc lavas, thought to be mainly recycled from subducted sediments, is > sediment subduction flux. There are large uncertainties: arc crustal growth rates are imprecise; young, primitive arc lavas may not be representative of magmatic flux into arc crust; sediment subduction flux may have varied. Nevertheless, this result is found for all arcs examined, using recently published growth rates. Perhaps arc growth rates that include subduction erosion are systematically overestimated. Instead or in addition, maybe significant Th comes from material other than sediments. Here, we consider the implications of pathways 1-4 for arc growth rates and incompatible element enrichment, in the context of subduction erosion and arc-arc collision. Subducting arc lithologies can become separated, with only felsic components returned to arc crust. Buoyant lithologies are mobile in viscous instabilities at > 700-800°C. Whereas thin layers such as sediments may become mobile all at once, instabilities may periodically strip the hottest parts from the top of thick buoyant layers, replacing them with hot mantle. In arc-arc collision, the top of a subducting plate starts at about 0°C on the seafloor, so heating is slow. In subduction erosion, forearc material in the subducting package can be > 200°C before erosion so buoyant lithologies reach 700-800

  17. Arc initiation in cathodic arc plasma sources

    SciTech Connect

    Anders, Andre

    2002-01-01

    A "triggerless" arc initiation method and apparatus is based on simply switching the arc supply voltage to the electrodes (anode and cathode). Neither a mechanical trigger electrode nor a high voltage flashover from a trigger electrode is required. A conducting path between the anode and cathode is provided, which allows a hot spot to form at a location where the path connects to the cathode. While the conductive path is eroded by the cathode spot action, plasma deposition ensures the ongoing repair of the conducting path. Arc initiation is achieved by simply applying the relatively low voltage of the arc power supply, e.g. 500 V-1 kV, with the insulator between the anode and cathode coated with a conducting layer and the current at the layer-cathode interface concentrated at one or a few contact points. The local power density at these contact points is sufficient for plasma production and thus arc initiation. A conductive surface layer, such as graphite or the material being deposited, is formed on the surface of the insulator which separates the cathode from the anode. The mechanism of plasma production (and arc initiation) is based on explosive destruction of the layer-cathode interface caused by joule heating. The current flow between the thin insulator coating and cathode occurs at only a few contact points so the current density is high.

  18. Effect of carbonate content on the mechanical behaviour of clay fault-gouges

    NASA Astrophysics Data System (ADS)

    Bakker, Elisenda; Niemeijer, André; Hangx, Suzanne; Spiers, Chris

    2015-04-01

    Carbon dioxide capture and storage (CCS) in depleted oil and gas reservoirs is considered to be the most promising technology to achieve large-scale reduction in anthropogenic emissions. In order to retain the stored CO2 from the atmosphere for the very long-term, i.e. on timescales of the order of 103-104 years, it is essential to maintain the integrity of the caprock, and more specifically of any faults penetrating the seal. When selecting suitable CO2-storage reservoirs, pre-exisiting faults within the caprock require close attention, as changes in the stress state resulting from CO2-injection may induce fault slip motion which might cause leakage. Little is known about the effect of fluid-rock interactions on the mineral composition, mechanical properties and the integrity and sealing capacity of the caprock. Previous studies on the effect of mineral composition on the frictional properties of fault gouges have shown that friction is controlled by the dominant phase unless there is a frictionally weak, through-going fabric. However, the effect on stability is less clear. Since long-term CO2-exposure might cause chemical reactions, potentially resulting in the dissolution or precipitation of carbonate minerals, a change in mineralogy could affect the mechanical stability of a caprock significantly. Calcite, for example, is known to be prone to micro-seismicity and shows a transition from velocity-strengthening to velocity-weakening behaviour around 100-150°C. Therefore, we investigated the effect of varying clay:carbonate ratios on fault friction behaviour, fault reactivation potential and slip stability, i.e. seismic vs. aseismic behaviour. Three types of simulated fault gouges were used: i) carbonate-free, natural clay-rich caprock samples, consisting of predominantly phyllosilicates (~80%) and quartz ~20%), ii) pure calcite, and iii) mixtures of carbonate-free clay-rich caprock and pure calcite, with predetermined clay:carbonate ratios. For the natural clay

  19. Frictional properties of fault zone gouges from the J-FAST drilling project (Mw 9.0 2011 Tohoku-Oki earthquake)

    NASA Astrophysics Data System (ADS)

    Remitti, F.; Smith, S. A. F.; Mittempergher, S.; Gualtieri, A. F.; Di Toro, G.

    2015-04-01

    Smectite-rich fault gouges recovered during Integrated Ocean Drilling Program Expedition 343 (Japan Trench Fast Drilling Project (J-FAST)) from the plate boundary slip zone of the 2011 Mw 9.0 Tohoku-Oki earthquake were deformed at slip velocities of 10 µm s-1 to 3.5 m s-1 and normal stresses up to 12 MPa. Water-dampened gouges (1) are weaker (apparent friction coefficient, μ* <0.1) than room-humidity gouges (apparent friction coefficient, μ* ~0.1-0.35) at all slip velocities, (2) are velocity insensitive to velocity weakening at all slip velocities, unlike room-humidity gouges that are velocity strengthening at intermediate velocities (V = 0.001-0.1 m s-1), and (3) have negligible peak μ* at high slip velocities (V > 0.1 m s-1). A significant amount of amorphous material formed in room-humidity experiments at low- and high-slip velocities, likely by comminution and disordering of smectite. Our results indicate that the frictional properties of water-dampened gouges could have facilitated propagation of the Tohoku-oki rupture to the trench and large coseismic slip at shallow depths.

  20. Frictional and hydraulic behaviour of carbonate fault gouge during fault reactivation - An experimental study

    NASA Astrophysics Data System (ADS)

    Delle Piane, Claudio; Giwelli, Ausama; Clennell, M. Ben; Esteban, Lionel; Nogueira Kiewiet, Melissa Cristina D.; Kiewiet, Leigh; Kager, Shane; Raimon, John

    2016-10-01

    We present a novel experimental approach devised to test the hydro-mechanical behaviour of different structural elements of carbonate fault rocks during experimental re-activation. Experimentally faulted core plugs were subject to triaxial tests under water saturated conditions simulating depletion processes in reservoirs. Different fault zone structural elements were created by shearing initially intact travertine blocks (nominal size: 240 × 110 × 150 mm) to a maximum displacement of 20 and 120 mm under different normal stresses. Meso-and microstructural features of these sample and the thickness to displacement ratio characteristics of their deformation zones allowed to classify them as experimentally created damage zones (displacement of 20 mm) and fault cores (displacement of 120 mm). Following direct shear testing, cylindrical plugs with diameter of 38 mm were drilled across the slip surface to be re-activated in a conventional triaxial configuration monitoring the permeability and frictional behaviour of the samples as a function of applied stress. All re-activation experiments on faulted plugs showed consistent frictional response consisting of an initial fast hardening followed by apparent yield up to a friction coefficient of approximately 0.6 attained at around 2 mm of displacement. Permeability in the re-activation experiments shows exponential decay with increasing mean effective stress. The rate of permeability decline with mean effective stress is higher in the fault core plugs than in the simulated damage zone ones. It can be concluded that the presence of gouge in un-cemented carbonate faults results in their sealing character and that leakage cannot be achieved by renewed movement on the fault plane alone, at least not within the range of slip measureable with our apparatus (i.e. approximately 7 mm of cumulative displacement). Additionally, it is shown that under sub seismic slip rates re-activated carbonate faults remain strong and no frictional

  1. Long arc stabilities with various arc gas flow rates

    NASA Astrophysics Data System (ADS)

    Maruyama, K.; Takeda, K.; Sugimoto, M.; Noguchi, Y.

    2014-11-01

    A new arc torch for use in magnetically driven arc device was developed with a commercially available TIG welding arc torch. The torch has a water-cooling system to the torch nozzle and has a nozzle nut to supply a swirling-free plasma gas flow. Its endurance against arc thermal load is examined. Features of its generated arc are investigated.

  2. The Evolution of P-wave Velocity in Fault Gouge: Initial Results for Samples from the SAFOD Volume.

    NASA Astrophysics Data System (ADS)

    Knuth, M. W.; Tobin, H. J.; Marone, C.

    2008-12-01

    We present initial results from a new technique for observing the evolution of elastic properties in sheared fault zone materials via acoustic wave velocity. The relationship between the mechanical strength of fault gouge and acoustic velocity during active deformation has important implications not only for a physical understanding of elasticity in deforming granular media, but also for the interpretation of the seismic velocity at the field scale. Experiments are conducted at atmospheric temperature and saturation state in a double-direct-shear testing apparatus, with normal stress stepped from 1 to 19 MPa to interrogate behavior during compaction, and sheared at a rate of 10 microns/second to observe changes in velocity with increasing strain. Tests are divided between those involving continuous shear to a displacement of 22.5 mm, and those with intervals of 3.75 mm shear separated by unloading and reloading sequences in normal stress. Velocity is measured by time-of-flight between two piezoelectric P-wave transducers set into the sample configuration on either side of the shearing layers. Samples tested include common laboratory standards for simulated fault gouge and field samples taken from representative localities in the 3D rock volume containing the San Andreas Fault Observatory at Depth experiment in Parkfield, California. The velocities of sand and clay end-member gouges are observed to behave differently under shear, and mixtures of quartz sand and montmorillonite behave differently from both end-member materials. Initial results suggest that particle sorting exerts a strong influence on both the absolute velocity and the evolution of velocity in response to increasing shear strain where the elastic properties of the grains are similar. We also observe a first-order relationship between the coefficient of friction and P-wave velocity that appears to be related to grain reorganization at the onset of shear following initial compaction.

  3. Origin, Behavior and Texture of Clay Minerals in Mongolian Active Fault of Bogd and Comparison with SAFOD Fault Gouge

    NASA Astrophysics Data System (ADS)

    Wenk, H.; Buatier, M.; Chauvet, A.; Kanitpanyacharoen, W.

    2010-12-01

    Fault gouges are generally considered as the highly deformed zone corresponding to the localization of shear during seismic events. Clays are ubiquitous minerals in fault gouges but the origin is unclear. They can form as a result of break up of inherited phyllosilicates during faulting, or during co- or post- deformation events or even during interseismic creeping. In this study, we aim to characterize the origin and nature of the clay minerals, to observe the microtexture and preferred orientation of clay at various scales in order to understand the behavior of clay mineral in seismic faults. The investigation relied on x-ray powder patterns, SEM, TEM and high energy synchrotron x-ray diffraction. The major clay components are smectite, illite-smectite, illite-mica and kaolinite. Our observations suggest that the protolith and the fault rock of the Bogd and paleo-Bogd faults in Mongolia were highly altered by fluids. The fluid-rock interactions allows clay minerals to form and to precipitate kaolinite and smectite. Thus, newly formed clay minerals are heterogeneously distributed in the fault zone. The decrease of smectite component of the highly deformed samples suggests a dehydration process during deformation, leading to illite precipitation. From synchrotron diffraction images, volume fractions and preferred orientation were analyzed. Our analysis shows that texture strength of constituent clays is very weak ranging from 1.05 to 2.59 m.r.d., which is consistent with similar data from SAFOD fault gouge. The clays minerals of the Bogd fault favors the slip weakening behavior of the fault.

  4. Friction of Megathrust Gouges at in-Situ Subduction Zone Conditions: Strength, Rate Dependence, and Microphysical Mechanisms

    NASA Astrophysics Data System (ADS)

    Den Hartog, S. A. M.; Marone, C.; Niemeijer, A. R.; Saffer, D. M.

    2014-12-01

    Slip along subduction megathrusts generally ranges from seismogenic, to slow slip events (SSE) and aseismic creep. Although temperature and clay mineralogy are widely believed to play key roles in governing modes of slip, little is known about the microphysical mechanisms controlling this diverse behaviour, and laboratory friction data for realistic materials at in-situ conditions are few. Recently, we have published a series of large strain, rotary shear experiments on synthetic gouges consisting of phyllosilicates and quartz, sheared at in-situ PT conditions and low sliding velocities V (1-100 µm/s) relevant to earthquake nucleation. Here, we report new results for natural megathrust materials exhumed from different depths on Shikoku, SW Japan. These natural gouges were deformed at sample-specific, peak in-situ PT conditions with fluid overpressure ratios λ between 0.4 and 0.9, and V=0.1-100 µm/s. The simulated and natural materials show broadly consistent behaviour with rate strengthening [(a-b)>0] at T<~200-300°C (Regime 1), rate weakening [(a-b)<0] that would potentially allow nucleation of unstable slip at T up to ~400-500°C (Regime 2) and again rate strengthening at T>~500° C (Regime 3). These observations suggest the potential for earthquake nucleation in Regime 2. In addition, (a-b) tends to become more positive with increasing λ and with increasing V up to ~200-300°C, suggesting possible SSE nucleation in Regime 1, where high λ values have a stabilizing effect. These observations can be explained by a quantitative microphysical model for the steady state frictional behaviour of illite-quartz gouges, which includes rate independent slip on phyllosilicates and time dependent pressure solution of quartz clasts.

  5. Welding arc plasma physics

    NASA Technical Reports Server (NTRS)

    Cain, Bruce L.

    1990-01-01

    The problems of weld quality control and weld process dependability continue to be relevant issues in modern metal welding technology. These become especially important for NASA missions which may require the assembly or repair of larger orbiting platforms using automatic welding techniques. To extend present welding technologies for such applications, NASA/MSFC's Materials and Processes Lab is developing physical models of the arc welding process with the goal of providing both a basis for improved design of weld control systems, and a better understanding of how arc welding variables influence final weld properties. The physics of the plasma arc discharge is reasonably well established in terms of transport processes occurring in the arc column itself, although recourse to sophisticated numerical treatments is normally required to obtain quantitative results. Unfortunately the rigor of these numerical computations often obscures the physics of the underlying model due to its inherent complexity. In contrast, this work has focused on a relatively simple physical model of the arc discharge to describe the gross features observed in welding arcs. Emphasis was placed of deriving analytic expressions for the voltage along the arc axis as a function of known or measurable arc parameters. The model retains the essential physics for a straight polarity, diffusion dominated free burning arc in argon, with major simplifications of collisionless sheaths and simple energy balances at the electrodes.

  6. Frictional properties of the Mount St. Helens gouge: Chapter 20 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

    USGS Publications Warehouse

    Moore, Peter L.; Iverson, Neal R.; Iverson, Richard M.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

    2008-01-01

    Rate-weakening friction is a requirement for stick-slip behavior that is satisfied by the Mount St. Helens gouge. Indeed, regular stick-slip oscillations were observed in two experiments performed at the highest normal stress and lowest rates of shear. The conditions under which this stick-slip motion occurred indicate that the gouge also satisfies a second criterion for stick-slip behavior of materials exhibiting rateand-state dependent friction-gouge stiffness exceeds that of the ascending magma that drives upward motion of the plug. The presence of highly compliant magma as a driving element may be crucial for generating stick-slip instabilities at the shallow earthquake focal depths observed during the eruption.

  7. WSTF electrical arc projects

    NASA Astrophysics Data System (ADS)

    Linley, Larry

    1994-09-01

    The objectives of these projects include the following: validate method used to screen wire insulation with arc tracking characteristics; determine damage resistance to arc as a function of source voltage and insulation thickness; investigate propagation characteristics of Kapton at low voltages; and investigate pyrolytic properties of polyimide insulated (Kapton) wire for low voltage (less than 35 VDC) applications. Supporting diagrams and tables are presented.

  8. WSTF electrical arc projects

    NASA Technical Reports Server (NTRS)

    Linley, Larry

    1994-01-01

    The objectives of these projects include the following: validate method used to screen wire insulation with arc tracking characteristics; determine damage resistance to arc as a function of source voltage and insulation thickness; investigate propagation characteristics of Kapton at low voltages; and investigate pyrolytic properties of polyimide insulated (Kapton) wire for low voltage (less than 35 VDC) applications. Supporting diagrams and tables are presented.

  9. TIGER Arc Modification Application

    SciTech Connect

    Armstrong, Hillary

    1995-03-06

    The application enables the geometric correction of TIGER arcs to a more accurate spatial data set. This is done in a structured automated environment according to Census Bureau guidelines and New Mexico state GIS standards. Arcs may be deleted, added, combined, split, and moved relative to a coverage or image displayed in the background.

  10. Gouge-zone or solid-rock: An experimental view on fault frictional behavior

    NASA Astrophysics Data System (ADS)

    Reches, Z.

    2015-12-01

    Natural faults always include zone(s) of breccia, gouge or cataclasite that localize the slip. In contrast, many rock mechanics experiments are conducted on experimental faults made of rough, solid blocks without fault-rock zones. We experimentally compare the frictional strength of solid experimental faults with fault-zones made of granular material in high-velocity/long-distance runs. The frictional evolution of solid and granular dolomite fault was tested in a rotary apparatus at slip velocity up to 1 m/s and normal stress up to 7 MPa. The granular samples were composed of the 125-250 microns fraction of the crushed dolomite. They were sheared in a confined, rotary cell with continuous monitoring of CO2 and H2O and mechanical data. The tests showed that the granular samples required longer slip-distances and higher velocities to evolve to a frictional strength similar to the solid samples. Yet, both sample types display similar evolution trends, including slip-weakening at velocities above ~0.05 m/s, and drastic velocity-weakening as slip velocity approached 1 m/s. At velocity above 0.3 m/s, a shining principal-slip-zone developed spontaneously with identical microstructure in both solid and granular sample: thickness < 1 micron and sintered, 20-40 nm nano-grains. This development was associated with intense emission of CO2 (Fig. 1). In a similar testing approach and conditions, we tested the friction evolution of granular granite from the San-Andreas fault-zone at Tejon-Pass, CA. These samples remained strong, μ =0.8-0.9, at velocities up to 0.8 m/s and slip-distances up to 3 m, in contrast to known frictional evolution of solid faults made of granite and tonalite. We envision that at the present slip-velocity/normal-stress, the dolomite samples reached a stage of thermally activated phase-transition and associated weakening, whereas the granitic samples were below such transition. Fig. 1. Evolotion of slip-velocity, friction, temperature and CO2 emission in

  11. The timing of fault motion in Death Valley from Illite Age Analysis of fault gouge

    NASA Astrophysics Data System (ADS)

    Lynch, E. A.; Haines, S. H.; Van der Pluijm, B.

    2014-12-01

    We constrained the timing of fluid circulation and associated fault motion in the Death Valley region of the US Basin and Range Province from Illite Age Analysis (IAA) of fault gouge at seven Low-Angle Normal Fault (LANF) exposures in the Black Mountains and Panamint Mountains, and in two nearby areas. 40Ar/39Ar ages of neoformed, illitic clay minerals in these fault zones range from 2.8 Ma to 18.6 Ma, preserving asynchronous fault motion across the region that corresponds to an evolving history of crustal block movements during Neogene extensional deformation. From north to south, along the western side of the Panamint Range, the Mosaic Canyon fault yields an authigenic illite age of 16.9±2.9 Ma, the Emigrant fault has ages of less than 10-12 Ma at Tucki Mountain and Wildrose Canyon, and an age of 3.6±0.17 Ma was obtained for the Panamint Front Range LANF at South Park Canyon. Across Death Valley, along the western side of the Black Mountains, Ar ages of clay minerals are 3.2±3.9 Ma, 12.2±0.13 Ma and 2.8±0.45 Ma for the Amargosa Detachment, the Gregory Peak Fault and the Mormon Point Turtleback detachment, respectively. Complementary analysis of the δH composition of neoformed clays shows a primarily meteoric source for the mineralizing fluids in these LANF zones. The ages fall into two geologic timespans, reflecting activity pulses in the Middle Miocene and in the Upper Pliocene. Activity on both of the range front LANFs does not appear to be localized on any single portion of these fault systems. Middle Miocene fault rock ages of neoformed clays were also obtained in the Ruby Mountains (10.5±1.2 Ma) to the north of the Death Valley region and to the south in the Whipple Mountains (14.3±0.19 Ma). The presence of similar, bracketed times of activity indicate that LANFs in the Death Valley region were tectonically linked, while isotopic signatures indicate that faulting pulses involved surface fluid penetration.

  12. Strength and stability of calcite gouge sheared at 20-600°C

    NASA Astrophysics Data System (ADS)

    Verberne, Berend A.; Niemeijer, André R.; Spiers, Christopher J.

    2014-05-01

    As strong earthquakes often nucleate at depths corresponding to the frictional-viscous transition, it is important to understand the velocity dependence of fault zone shear strength throughout the transition. We conducted ring shear experiments on simulated pure calcite gouges at constant temperatures (T) of 22, 100, 200, 400, 490, 500, 540, and 590°C, while performing displacement rate stepping tests within the range v=0.01-100 μm/s. All experiments used a constant pore water pressure (10-60 MPa) and a constant effective normal stress (50 MPa). For experiments conducted at T≡22°C, the results showed a near-constant strength (τ≡30-37 MPa) and stable velocity strengthening at all displacements. For T>22°C, a peak strength (τpk≡33-56 MPa) developed at low displacements (0.5-2 mm), followed by weakening to a near-constant (average) value (τ≡15-42 MPa) depending on slip rate. Velocity weakening was observed in each experiment conducted at T≡100-540°C, where the magnitude of velocity weakening generally increased with increasing temperature and decreasing slip rate, which often resulted in unstable slip i.e. stick-slips. At 500°C, at v=0.01 μm/s, stick-slip showed a strength drop from ~41 to ~13 MPa, hence a stress release of nearly 70%! Experiments conducted at T≡590°C showed stable sliding throughout and velocity strengthening. Recovered sheared microstructures of samples deformed at T≡22°C showed shear bands characterized by a sub-micron grain size and a Crystallographic Preferred Orientation (CPO), similar to microstructures from earlier experiments conducted using a direct-shear geometry. For samples deformed at T>400°C, ultra-fine grained shear bands with a CPO also developed. However, strongly elongated grains up to 30 μm in size adjacent and bending into the shear band suggest that plasticity played a role in accommodating some of the deformation. Our results demonstrate that calcite fault rocks can slide unstably at temperatures as

  13. Lazy arc consistency

    SciTech Connect

    Schiex, T.; Gaspin, C.; Regin, J.C.; Verfaillie, G.

    1996-12-31

    Arc consistency filtering is widely used in the framework of binary constraint satisfaction problems: with a low complexity, inconsistency may be detected and domains are filtered. In this paper, we show that when detecting inconsistency is the objective, a systematic domain filtering is useless and a lazy approach is more adequate. Whereas usual arc consistency algorithms produce the maximum arc consistent sub-domain, when it exists, we propose a method, called LAC{tau}, which only looks for any arc consistent sub-domain. The algorithm is then extended to provide the additional service of locating one variable with a minimum domain cardinality in the maximum arc consistent sub-domain, without necessarily computing all domain sizes. Finally, we compare traditional AC enforcing and lazy AC enforcing using several benchmark problems, both randomly generated CSP and real life problems.

  14. Acoustically induced slip in sheared granular layers: Application to dynamic earthquake triggering: TRIGGERED SLIP IN SHEARED GRANULAR GOUGE

    SciTech Connect

    Ferdowsi, Behrooz; Griffa, Michele; Guyer, Robert A.; Johnson, Paul A.; Marone, Chris; Carmeliet, Jan

    2015-11-19

    A fundamental mystery in earthquake physics is “how can an earthquake be triggered by distant seismic sources?” We use discrete element method simulations of a granular layer, during stick slip, that is subject to transient vibrational excitation to gain further insight into the physics of dynamic earthquake triggering. We also observe delayed triggering of slip in the granular gouge, using Coulomb friction law for grains interaction. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance; i.e., transient vibration and triggered slip are simultaneous. Moreover, the critical strain is of order 10-6, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic decrease in coordination number and the weakening of the contact force network. Associated with this frictional weakening is a pronounced decrease in the elastic modulus of the layer. The study has important implications for mechanisms of triggered earthquakes and induced seismic events and points out the underlying processes in response of the fault gouge to dynamic transient stresses.

  15. Acoustically induced slip in sheared granular layers: Application to dynamic earthquake triggering: TRIGGERED SLIP IN SHEARED GRANULAR GOUGE

    DOE PAGES

    Ferdowsi, Behrooz; Griffa, Michele; Guyer, Robert A.; ...

    2015-11-19

    A fundamental mystery in earthquake physics is “how can an earthquake be triggered by distant seismic sources?” We use discrete element method simulations of a granular layer, during stick slip, that is subject to transient vibrational excitation to gain further insight into the physics of dynamic earthquake triggering. We also observe delayed triggering of slip in the granular gouge, using Coulomb friction law for grains interaction. We find that at a critical vibrational amplitude (strain) there is an abrupt transition from negligible time-advanced slip (clock advance) to full clock advance; i.e., transient vibration and triggered slip are simultaneous. Moreover, themore » critical strain is of order 10-6, similar to observations in the laboratory and in Earth. The transition is related to frictional weakening of the granular layer due to a dramatic decrease in coordination number and the weakening of the contact force network. Associated with this frictional weakening is a pronounced decrease in the elastic modulus of the layer. The study has important implications for mechanisms of triggered earthquakes and induced seismic events and points out the underlying processes in response of the fault gouge to dynamic transient stresses.« less

  16. Arc Inception Mechanism on a Solar Array Immersed in a Low-Density Plasma

    NASA Technical Reports Server (NTRS)

    Vayner, B.; Galofaro, J.; Ferguson, D.

    2001-01-01

    In this report, results are presented of an experimental and theoretical study of arc phenomena and snapover for two samples of solar arrays immersed in argon plasma. The effects of arcing and snapover are investigated. I-V curves are measured, and arc and snapover inception voltages and arc rates are determined within the wide range of plasma parameters. A considerable increase in arc rate due to absorption of molecules from atmospheric air has been confirmed. It is shown that increasing gas pressure causes increasing ion current collection and, consequently, arc rate even though the effect of conditioning also takes place. Arc sites have been determined by employing a video-camera. It is confirmed that keeping sample under high vacuum for a long time results in shifting arc threshold voltage well below -300 V. The results obtained seem to be important for the understanding of arc inception mechanism.

  17. High-Velocity Friction Experiments on the Longmenshan Fault Gouge towards the Understanding of Dynamic Rupture Propagation of the 2008 Wenchuan Earthquake

    NASA Astrophysics Data System (ADS)

    Togo, T.; Shimamoto, T.; Ma, S.; Wen, X.; Hirose, T.; Lei, X.

    2009-12-01

    Disastrous Wenchuan earthquake (12 May 2009, Mw 7.9) was accompanied by surface ruptures of about 280 km in EW extension along existing Longmenshan fault system (e.g., Lin et al., 2009, Tectonophysics). We have conducted high-velocity friction experiments on fault gouge from this fault in order to understand the mechanisms of dynamic fault motion that caused this earthquake. Fault gouge was collected from Hongkou outcrop of Yingxiu-Beichuan fault on the western part of the Longmenshan fault system (site 6 of Lin et al., 2009). XRD analyses revealed that gouge contains quartz, muscovite, kaolinite and chlorite. Experiments were done on gouge of about 1 mm in thickness between a pair of solid cylindrical specimens of Belfast gabbro of about 25 mm in diameter under dry or wet conditions, using the first high-velocity testing machine and a rotary-shear low-to-high-velocity friction apparatus (the second machine). Slip rates and normal stresses were varied, respectively, from 0.009 to 1.30 m/s and from 0.6 to 4.9 MPa. Deionized water of 0.25grams in weight was added to gouge for wet runs. Dry fault gouge exhibit quite similar behaviors to those reported previously, characterized by dramatic slip weakening at high slip rates. A series of tests at slip rate of 0.3 m/s with normal stresses varied from 0.61 to 3.04 MPa shows that Coulomb’s law of friction holds for both peak and steady-state friction with frictional coefficients of 0.65 and 0.12, respectively. The steady-state friction markedly decreases from around 0.75 to about 0.2 as slip rate increases from 0.01 to 1.3 m/s, even though the peak frictional coefficient remains at around 0.8 for the same range of slip rates. The change in friction from peak to steady state is characterized by nearly exponential decay from peak to steady-state. The slip-weakening distance, Dc, defined as the displacement required for 95% reduction from peak to steady-state friction, decreases very systematically with increasing slip rate

  18. Cloud Arcs in the Western Pacific

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Small cumulus clouds in this natural-color view from the Multi-angle Imaging SpectroRadiometer have formed a distinctive series of quasi-circular arcs. Clues regarding the formation of these arcs can be found by noting that larger clouds exist in the interior of each arc.

    The interior clouds are thicker and likely to be more convectively active than the other clouds, causing much of the air near the centers of the arcs to rise. This air spreads out horizontally in all directions as it rises and continues to spread out as it begins to sink back to the surface. This pushes any existing small cumulus clouds away from the central region of convection.

    As the air sinks, it also warms, preventing other small clouds from forming, so that the regions just inside the arcs are kept clear. At the arcs, the horizontal flow of sinking air is now quite weak and on meeting the undisturbed air it can rise again slightly -- possibly assisting in the formation of new small cumulus clouds. Although examples of the continuity of air, in which every rising air motion must be compensated by a sinking motion elsewhere, are very common, the degree of organization exhibited here is relatively rare, as the wind field at different altitudes usually disrupts such patterns. The degree of self organization of this cloud image, whereby three or four such circular events form a quasi-periodic pattern, probably also requires a relatively uncommon combination of wind, temperature and humidity conditions for it to occur.

    The image was acquired by MISR's nadir camera on March 11, 2002, and is centered west of the Marshall Islands. Enewetak Atoll is discernible through thin cloud as the turquoise band near the right-hand edge of the image.

    The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and views almost the entire globe every 9 days. This image is a portion of the data acquired during Terra orbit 11863, and covers an area of about 380

  19. Tokamak ARC damage

    SciTech Connect

    Murray, J.G.; Gorker, G.E.

    1985-01-01

    Tokamak fusion reactors will have large plasma currents of approximately 10 MA with hundreds of megajoules stored in the magnetic fields. When a major plasma instability occurs, the disruption of the plasma current induces voltage in the adjacent conducting structures, giving rise to large transient currents. The induced voltages may be sufficiently high to cause arcing across sector gaps or from one protruding component to another. This report reviews a tokamak arcing scenario and provides guidelines for designing tokamaks to minimize the possibility of arc damage.

  20. Electric arc saw apparatus

    DOEpatents

    Deichelbohrer, Paul R [Richland, WA

    1986-01-01

    A portable, hand held electric arc saw has a small frame for supporting an electrically conducting rotary blade which serves as an electrode for generating an electric arc to erode a workpiece. Electric current is supplied to the blade by biased brushes and a slip ring which are mounted in the frame. A pair of freely movable endless belts in the form of crawler treads stretched between two pulleys are used to facilitate movement of the electric arc saw. The pulleys are formed of dielectric material to electrically insulate the crawler treads from the frame.

  1. Welding arc initiator

    DOEpatents

    Correy, Thomas B.

    1989-01-01

    An improved inert gas shielded tungsten arc welder is disclosed of the type wherein a tungsten electrode is shielded within a flowing inert gas, and, an arc, following ignition, burns between the energized tungsten electrode and a workpiece. The improvement comprises in combination with the tungsten electrode, a starting laser focused upon the tungsten electrode which to ignite the electrode heats a spot on the energized electrode sufficient for formation of a thermionic arc. Interference problems associated with high frequency starters are thus overcome.

  2. Welding arc initiator

    DOEpatents

    Correy, T.B.

    1989-05-09

    An improved inert gas shielded tungsten arc welder is disclosed of the type wherein a tungsten electrode is shielded within a flowing inert gas, and, an arc, following ignition, burns between the energized tungsten electrode and a workpiece. The improvement comprises in combination with the tungsten electrode, a starting laser focused upon the tungsten electrode which to ignite the electrode heats a spot on the energized electrode sufficient for formation of a thermionic arc. Interference problems associated with high frequency starters are thus overcome. 3 figs.

  3. Frictional properties of saponite-rich gouge from a serpentinite-bearing fault zone along the Gokasho-Arashima Tectonic Line, central Japan

    USGS Publications Warehouse

    Sone, Hiroki; Shimamoto, Toshihiko; Moore, Diane E.

    2012-01-01

    We studied a serpentinite-bearing fault zone in Gokasho-Arashima Tectonic Line, Mie Prefecture, central Japan, characterizing its internal structures, mineral assemblage, permeability, and frictional properties. The fault core situated between the serpentinite breccia and the adjacent sedimentary rocks is characterized by a zone locally altered to saponite. The clayey gouge layer separates fault rocks of serpentinite origin containing talc and tremolite from fault rocks of sedimentary origin containing chlorite but no quartz. The minerals that formed within the fault are the products of metasomatic reaction between the serpentinite and the siliceous rocks. Permeability measurements show that serpentinite breccia and fault gouge have permeability of 10−14–10−17 m2 and 10−15–10−18 m2, respectively, at 5–120 MPa confining pressure. Frictional coefficient of the saponite-rich clayey fault gouge ranged between 0.20 and 0.35 under room-dry condition, but was reduced to 0.06–0.12 when saturated with water. The velocity dependence of friction was strongly positive, mostly ranging between 0.005 and 0.006 in terms of a–b values. The governing friction law is not constrained yet, but we find that the saponite-rich gouge possesses an evolutional behavior in the opposite direction to that suggested by the rate and state friction law, in addition to its direct velocity dependence.

  4. Metal halide arc discharge lamp having short arc length

    NASA Technical Reports Server (NTRS)

    Muzeroll, Martin E. (Inventor)

    1994-01-01

    A metal halide arc discharge lamp includes a sealed light-transmissive outer jacket, a light-transmissive shroud located within the outer jacket and an arc tube assembly located within the shroud. The arc tube assembly includes an arc tube, electrodes mounted within the arc tube and a fill material for supporting an arc discharge. The electrodes have a spacing such that an electric field in a range of about 60 to 95 volts per centimeter is established between the electrodes. The diameter of the arc tube and the spacing of the electrodes are selected to provide an arc having an arc diameter to arc length ratio in a range of about 1.6 to 1.8. The fill material includes mercury, sodium iodide, scandium tri-iodide and a rare gas, and may include lithium iodide. The lamp exhibits a high color rendering index, high lumen output and high color temperature.

  5. Brittle-to-viscous behaviour of quartz gouge in shear experiments

    NASA Astrophysics Data System (ADS)

    Richter, Bettina; Stunitz, Holger; Heilbronner, Renée

    2016-04-01

    In order to study the microstructure development across the brittle-viscous transition and to derive the corresponding flow laws, we performed shear experiments on quartz gouge in a Griggs-type deformation apparatus. The starting material is a crushed quartz single crystal (sieved grain size <100 μm) with 0.2 wt% water added. The experiments were conducted at temperatures between 500 ° C and 1000 ° C at confining pressures of 0.5 GPa, 1.0 GPa or 1.5 GPa. Four strain-rate-stepping experiments were conducted at strain rates between ˜2.5 x 10-6 s-1 and ˜2.5 x 10-4 s-1. Other experiments were conducted at constant strain rates of ˜2.5 x 10-6 s-1, ˜2.5 x 10-5 s-1, ˜2.5 x 10-4 s-1 and ˜2.5 x 10-3 s-1. At high confining pressure, the strength of the samples decreases with increasing temperature for all strain rates. The largest decrease occurred between 650 ° C and 700 ° C at shear strain rates of ˜2.5 x 10-5 s-1. At the same time, the pressure dependence of strength is positive for T ≤ 650 ° C while an inverse pressure dependence is observed at T > 650 ° C. For T < 700 ° C, the friction coefficient decreases slightly with increasing temperature, from 700-1000 ° C it shows a strong temperature dependence. Between 650 ° C and 700 ° C at shear strain rates of ˜2.5 x 10-5 s-1 a change in the deformation process occurs from one dominated by cataclastic flow to one dominated by crystal plasticity. The microstructure reveals a less abrupt transition in terms of operating processes, because brittle and viscous processes are equally active around 650 ° C. With increasing temperature the volume fraction of recrystallised grains increases, and at 900 ° C - 1000 ° C recrystallisation is nearly complete at strains of γ ˜ 3. The crystallographic preferred orientation of the c-axis evolves from a random distribution at low temperatures towards two peripheral maxima at intermediate temperatures. At high temperatures the c-axis show a single Y-maximum. At high

  6. Arc Voltage Between Deion Grid Affected by Division of Arc in Magnetic Driven Arc

    NASA Astrophysics Data System (ADS)

    Inuzuka, Yutaro; Yamato, Takashi; Yamamoto, Shinji; Iwao, Toru

    2016-10-01

    Magnetic driven arc has been applied to DC breaker and fault current limiters. However, it has not been researched, especially stagnation and re-strike of the arc. In this paper, the arc voltage between deion grid affected by division of arc in magnetic driven arc and arc behavior are measured by using the oscilloscope and HSVC (High Speed Video Camera). As a result, arc voltage increased because of division of the arc. The arc mean moving speed increases with increasing the external magnetic field. However, when the arc was not stalemate, the arc moving speed does not change so much. The arc re-strike time increases and stalemate time decreases with increasing the external magnetic field. Therefore, the anode spot moving speed increases 8 times because arc re-strike occurs easily with the external magnetic field. Thus, the erosion of electrodes decreases and the arc movement becomes the smooth. When the arc is divided, the arc voltage increased because of the electrode fall voltage. Therefore, the arc voltage increases with increasing the number of deion grid.

  7. Filtered cathodic arc source

    DOEpatents

    Falabella, S.; Sanders, D.M.

    1994-01-18

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge is described. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45[degree] to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles. 3 figures.

  8. Filtered cathodic arc source

    DOEpatents

    Falabella, Steven; Sanders, David M.

    1994-01-01

    A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45.degree. to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles.

  9. Emissions of chromium (VI) from arc welding.

    PubMed

    Heung, William; Yun, Myoung-Jin; Chang, Daniel P Y; Green, Peter G; Halm, Chris

    2007-02-01

    The presence of Cr in the +6 oxidation state (Cr[VI]) is still observed in ambient air samples in California despite steps taken to reduce emissions from plating operations. One known source of emission of Cr(VI) is welding, especially with high Cr-content materials, such as stainless steels. An experimental effort was undertaken to expand and update Cr(VI) emission factors by conducting tests on four types of arc-welding operations: gas-metal arc welding (GMAW), shielded metal arc welding (SMAW), fluxcore arc welding, and pulsed GMAW. Standard American Welding Society hood results were compared with a total enclosure method that permitted isokinetic sampling for particle size-cut measurement, as well as total collection of the aerosol. The fraction of Cr(VI) emitted per unit mass of Cr electrode consumed was determined. Consistent with AP-42 data, initial results indicate that a significant fraction of the total Cr in the aerosol is in the +6 oxidation state. The fraction of Cr(VI) and total aerosol mass produced by the different arc welding methods varies with the type of welding process used. Self-shielded electrodes that do not use a shield gas, for example, SMAW, produce greater amounts of Cr(VI) per unit mass of electrode consumed. The formation of Cr(VI) from standard electrode wires used for welding mild steel was below the method detection limit after eliminating an artifact in the analytical method used.

  10. Electric arc saw apparatus

    DOEpatents

    Deichelbohrer, P.R.

    1983-08-08

    A portable, hand-held electric arc saw apparatus comprising a small frame for supporting an electrically conducting rotary blade which serves as an electrode for generating an electric arc between the blade and a workpiece of opposite polarity. Electrically conducting means are provided on said frame for transmitting current to said blade. A pair of freely movable endless belts in the form of crawler treads are employed to facilitate movement of the apparatus relative to the workpiece.

  11. High T-P frictional strength and stability of exhumed fault core gouges, Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Boulton, C. J.; Moore, D. E.; Lockner, D. A.; Toy, V. G.; Townend, J.; Sutherland, R.

    2013-12-01

    Borehole temperature measurements acquired during the Deep Fault Drilling Project (DFDP-1) reveal a high geothermal gradient at shallow depths on the central Alpine Fault, New Zealand [62.6×2.1°C/km; Sutherland et al., 2012]. To investigate how an elevated geothermal gradient might affect fault strength and stability, eighteen hydrothermal shearing experiments have been performed using samples of two fault gouges recovered from depths of 90 m and 128 m. Using a triaxial deformation apparatus, ten experiments were conducted following a lithostatic pressure gradient (average crustal density, ρ, = 2650 kg/m3), hydrostatic pore fluid pressure (pore fluid factor, λ, = 0.40), and a 35°C/km geothermal gradient. Six experiments were conducted at equivalent effective normal stresses with elevated temperatures, and two experiments were conducted at room temperature, σn'=31.2 MPa. Sliding velocities varied between 0.01 μm/s and 3 μm/s. The coefficient of friction of montmorillonite-bearing DFDP-1B brown gouge was observed to increase markedly with temperature and pressure (T=70°C to 210°C, σn'=31.2 MPa to 93.6 MPa), from μ=0.49 to μ=0.74; it also underwent a stability transition from positive to negative rate dependence at 140°C, σn'=62.4 MPa. The chlorite/white mica-bearing DFDP-1A blue gouge was frictionally strong (μ=0.61-0.76) across a range of experimental conditions (T=70°C to 350°C, σn'=31.2 MPa to 156 MPa) and underwent a stability transition from positive to negative rate dependence at 210°C, σn'≥31.2 MPa. To investigate the conditions necessary for shear failure to occur on a fault plane composed of the 1A blue gouge, the experimentally determined coefficient of friction (μ=0.70 at T=210°C and σn'=62.4 MPa to 93.6 MPa) was used with the seismologically determined stress tensor [Boese et al., 2012] in a three-dimensional analysis following the method of Leclère and Fabbri [2013]. A low stress ratio, (σ2-σ3)/(σ1-σ3)≤0.30, and/or pore

  12. Experimental constraints on the energy budget of dynamic gouge formation: effects of rock strength, material heterogeneity, and initial flaw characteristics

    NASA Astrophysics Data System (ADS)

    Griffith, Ashley; Barber, Troy; Borjas, Christopher; Ghaffari, Hamed

    2016-04-01

    Fault core materials are characterized by substantial grain size reduction relative to host and damage zone rocks. The properties of these materials control fault strength and frictional behavior, and they record valuable information about rupture and slip processes. At high strain rates and large stress amplitudes characteristic of earthquake rupture tips, rock failure passes through a fragmentation transition from discrete fracture to pulverization; therefore much of the observed grain size reduction at the leading edge of propagating earthquake ruptures. Past examinations of particle size distributions in gouge formed in the cores of natural faults have led to contrasting conclusions that during a single event, the energy associated with creation of new surface area during this grain size reduction can be as large as 50%, or as little as <1% of the earthquake energy budget; however these estimates are difficult to confirm due to (A) challenges associated with accurate particle size measurement and (B) uncertainty regarding the variety of (not-necessarily coseismic) physico-chemical processes that may contribute to the observed grain size reduction. Here we study the micromechanics and energy budget of dynamic rock fragmentation under impulsive compressive loads using a Split Hopkinson Pressure Bar. We present new experimental results on Arkansas Novaculite and Westerly Granite coupled with microstructural observations and BET surface area measurements of post-mortem specimens. We show that the energy partitioned into creation of new surface areas approaches a significant portion of the total dissipated energy during our experiments, but this partitioning can be buffered by the presence of flaws and/or significant material heterogeneity. The results of this work have important implications for lithologic controls on gouge formation and energy partitioning during earthquakes.

  13. Consolidating NASA's Arc Jets

    NASA Technical Reports Server (NTRS)

    Balboni, John A.; Gokcen, Tahir; Hui, Frank C. L.; Graube, Peter; Morrissey, Patricia; Lewis, Ronald

    2015-01-01

    The paper describes the consolidation of NASA's high powered arc-jet testing at a single location. The existing plasma arc-jet wind tunnels located at the Johnson Space Center were relocated to Ames Research Center while maintaining NASA's technical capability to ground-test thermal protection system materials under simulated atmospheric entry convective heating. The testing conditions at JSC were reproduced and successfully demonstrated at ARC through close collaboration between the two centers. New equipment was installed at Ames to provide test gases of pure nitrogen mixed with pure oxygen, and for future nitrogen-carbon dioxide mixtures. A new control system was custom designed, installed and tested. Tests demonstrated the capability of the 10 MW constricted-segmented arc heater at Ames meets the requirements of the major customer, NASA's Orion program. Solutions from an advanced computational fluid dynamics code were used to aid in characterizing the properties of the plasma stream and the surface environment on the calorimeters in the supersonic flow stream produced by the arc heater.

  14. Control of arc length during gas metal arc welding

    SciTech Connect

    Madigan, R.B.; Quinn, T.P.

    1994-12-31

    An arc-length control system has been developed for gas metal arc welding (GMAW) under spray transfer welding conditions. The ability to monitor and control arc length during arc welding allows consistent weld characteristics to be maintained and therefore improves weld quality. Arc length control has only been implemented for gas tungsten arc welding (GTAW), where an automatic voltage control (AVC) unit adjusts torch-to-work distance. The system developed here compliments the voltage- and current-sensing techniques commonly used for control of GMAW. The system consists of an arc light intensity sensor (photodiode), a Hall-effect current sensor, a personal computer and software implementing a data interpretation and control algorithms. Arc length was measured using both arc light and arc current signals. Welding current was adjusted to maintain constant arc length. A proportional-integral-derivative (PID) controller was used. Gains were automatically selected based on the desired welding conditions. In performance evaluation welds, arc length varied from 2.5 to 6.5 mm while welding up a sloped workpiece (ramp in CTWD) without the control. Arc length was maintained within 1 mm of the desired (5 mm ) with the control.

  15. Radiation of long and high power arcs

    NASA Astrophysics Data System (ADS)

    Cressault, Y.; Bauchire, J. M.; Hong, D.; Rabat, H.; Riquel, G.; Sanchez, F.; Gleizes, A.

    2015-10-01

    The operators working on electrical installations of low, medium and high voltages can be accidentally exposed to short-circuit arcs ranging from a few kA to several tens of kA. To protect them from radiation, according to the exposure limits, we need to characterize the radiation emitted by the powerful arc. Therefore, we have developed a general experimental and numerical study in order to estimate the spectral irradiance received at a given distance from the arc. The experimental part was based on a very long arc (up to 2 m) with high ac current (between 4 and 40 kA rms, duration 100 ms) using 3 kinds of metallic contacts (copper, steel and aluminium). We measured the irradiance received 10m from the axis of the arc, and integrated on 4 spectral intervals corresponding to the UV, visible, IRA  +  B and IRC. The theoretical part consisted of calculating the radiance of isothermal plasmas in mixtures of air and metal vapour, integrated over the same spectral intervals as defined in the experiments. The comparison between the theoretical and experimental results has allowed the defining of three isothermal radiation sources whose combination leads to a spectral irradiation equivalent to the experimental one. Then the calculation allowed the deduction of the spectral description of the irradiance over all the wavelength range, between 200 nm and 20 μm. The final results indicate that the influence of metal is important in the visible and UVA ranges whereas the IR radiation is due to the air plasma and surrounding hot gas and fumes.

  16. Arc electrode interaction study

    NASA Technical Reports Server (NTRS)

    Zhou, X.; Berns, D.; Heberlein, J.

    1994-01-01

    The project consisted of two parts: (1) the cathode interaction studies which were a continuation of previous work and had the objective of increasing our understanding of the microscopic phenomena controlling cathode erosion in arc jet thrusters, and (2) the studies of the anode attachment in arc jet thrusters. The cathode interaction studies consisted of (1) a continuation of some modeling work in which the previously derived model for the cathode heating was applied to some specific gases and electrode materials, and (2) experimental work in which various diagnostics was applied to the cathode. The specific diagnostics used were observation of the cathode tip during arcing using a Laser Strobe Video system in conjunction with a tele-microscope, a monochromator with an optical multichannel analyzer for the determination of the cathode temperature distribution, and various ex situ materials analysis methods. The emphasis of our effort was shifted to the cathode materials analysis because a parallel project was in place during the second half of 1993 with a visiting scientist pursuing arc electrode materials studies. As a consequence, the diagnostic investigations of the arc in front of the cathode had to be postponed to the first half of 1994, and we are presently preparing these measurements. The results of last year's study showed some unexpected effects influencing the cathode erosion behavior, such as increased erosion away from the cathode tip, and our understanding of these effects should improve our ability to control cathode erosion. The arc jet anode attachment studies concentrated on diagnostics of the instabilities in subsonic anode attachment arc jet thrusters, and were supplemental measurements to work which was performed by one of the authors who spent the summer as an intern at NASA Lewis Research Center. A summary of the results obtained during the internship are included because they formed an integral part of the study. Two tasks for 1994, the

  17. Pulsed Long Arc Welding

    NASA Astrophysics Data System (ADS)

    Krampit, N. Yu

    2016-04-01

    The paper presents a method and an appliance for pulsed arc welding. The method supports dosage of energy required for melting each bead of electrode metal starting from the detachment of a bead. The appliance including a sensor to register bead detachment shows this moment due to the voltage burst in the arc space. Transferred beads of electrode metal are of similar size because of the dosage of energy used for melting each bead, as the consequence, the process is more stable and starting conditions to transfer electrode metal are similar, as the result, a produced weld is improved.

  18. ARc Welding (Industrial Processing Series).

    DTIC Science & Technology

    ARC WELDING , *BIBLIOGRAPHIES), (*ARC WELDS, BIBLIOGRAPHIES), ALUMINUM ALLOYS, TITANIUM ALLOYS, CHROMIUM ALLOYS, METAL PLATES, SPOT WELDING , STEEL...INERT GAS WELDING , MARAGING STEELS, MICROSTRUCTURE, HEAT RESISTANT ALLOYS, HEAT RESISTANT METALS, WELDABILITY, MECHANICAL PROPERTIES, MOLYBDENUM ALLOYS, NICKEL ALLOYS, RESISTANCE WELDING

  19. Thermal Arc Spray Overview

    NASA Astrophysics Data System (ADS)

    Hafiz Abd Malek, Muhamad; Hayati Saad, Nor; Kiyai Abas, Sunhaji; Mohd Shah, Noriyati

    2013-06-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  20. Variable polarity arc welding

    NASA Technical Reports Server (NTRS)

    Bayless, E. O., Jr.

    1991-01-01

    Technological advances generate within themselves dissatisfactions that lead to further advances in a process. A series of advances in welding technology which culminated in the Variable Polarity Plasma Arc (VPPA) Welding Process and an advance instituted to overcome the latest dissatisfactions with the process: automated VPPA welding are described briefly.

  1. Gas tungsten arc welder

    DOEpatents

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

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

  2. Arc Length Gone Global

    ERIC Educational Resources Information Center

    Boudreaux, Gregory M.; Wells, M. Scott

    2007-01-01

    Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

  3. Hall-effect arc protector

    DOEpatents

    Rankin, Richard A.; Kotter, Dale K.

    1997-01-01

    The Hall-Effect Arc Protector is used to protect sensitive electronics from high energy arcs. The apparatus detects arcs by monitoring an electrical conductor, of the instrument, for changes in the electromagnetic field surrounding the conductor which would be indicative of a possible arcing condition. When the magnitude of the monitored electromagnetic field exceeds a predetermined threshold, the potential for an instrument damaging are exists and the control system logic activates a high speed circuit breaker. The activation of the breaker shunts the energy imparted to the input signal through a dummy load to the ground. After the arc condition is terminated, the normal signal path is restored.

  4. Hall-effect arc protector

    DOEpatents

    Rankin, R.A.; Kotter, D.K.

    1997-05-13

    The Hall-Effect Arc Protector is used to protect sensitive electronics from high energy arcs. The apparatus detects arcs by monitoring an electrical conductor, of the instrument, for changes in the electromagnetic field surrounding the conductor which would be indicative of a possible arcing condition. When the magnitude of the monitored electromagnetic field exceeds a predetermined threshold, the potential for an instrument damaging are exists and the control system logic activates a high speed circuit breaker. The activation of the breaker shunts the energy imparted to the input signal through a dummy load to the ground. After the arc condition is terminated, the normal signal path is restored. 2 figs.

  5. Semicircular Rashba arc spin polarizer

    SciTech Connect

    Bin Siu, Zhuo; Jalil, Mansoor B. A.; Ghee Tan, Seng

    2014-05-07

    In this work, we study the generation of spin polarized currents using curved arcs of finite widths, in which the Rashba spin orbit interaction (RSOI) is present. Compared to the 1-dimensional RSOI arcs with zero widths studied previously, the finite width presents charge carriers with another degree of freedom along the transverse width of the arc, in addition to the longitudinal degree of freedom along the circumference of the arc. The asymmetry in the transverse direction due to the difference in the inner and outer radii of the arc breaks the antisymmetry of the longitudinal spin z current in a straight RSOI segment. This property can be exploited to generate spin z polarized current output from the RSOI arc by a spin unpolarized current input. The sign of the spin current can be manipulated by varying the arc dimensions.

  6. 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.

  7. HOLLOW CARBON ARC DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-10-11

    A device is described for producing an energetic, direct current, hollow, carbon-arc discharge in an evacuated container and within a strong magnetic field. Such discharges are particularly useful not only in dissociation and ionization of high energy molecular ion beams, but also in acting as a shield or barrier against the instreaming of lowenergy neutral particles into a plasma formed within the hollow discharge when it is used as a dissociating mechanism for forming the plasma. There is maintained a predetermined ratio of gas particles to carbon particles released from the arc electrodes during operation of the discharge. The carbon particles absorb some of the gas particles and are pumped along and by the discharge out of the device, with the result that smaller diffusion pumps are required than would otherwise be necessary to dispose of the excess gas.

  8. Arc jet diagnostics tests

    NASA Technical Reports Server (NTRS)

    Willey, Ronald J.

    1989-01-01

    Two objectives were addressed during a 10 week 1988 NASA/ASEE summer faculty fellowship at the Johnson Space Center Atmospheric Reentry Materials Structures Evaluation Facility (ARMSEF). These objectives were the evaluation of mass spectrometry for the measurement of atomic and molecular species in an arc jet environment, and the determination of atomic recombination coefficients for reaction cured glass (RCG) coated high temperature surface insulation (HRSI) materials subjected to simulated reentry conditions. Evaluation of mass spectrometry for the measurement of atomic and molecular species provided some of the first measurements of point compositions in arc jet tunnel environments. A major objective of this project centered around the sampling residence time. A three staged vacuum sampling system pulled the molecules and atoms from the arc jet to a quadrupole ionization mass spectrometer in 400 milliseconds. Conditions investigated included a composition survey across the nozzle exit at 3 cm z-distance from the nozzle exit for 3 different currents. Also, a point composition survey was taken around a shock created by the presence of a blunt body.

  9. Arc reattachment driven by a turbulent boundary layer: implications for the sweeping of lightning arcs along aircraft

    NASA Astrophysics Data System (ADS)

    Guerra-Garcia, C.; Nguyen, N. C.; Peraire, J.; Martinez-Sanchez, M.

    2016-09-01

    A lightning channel attached to an aircraft in flight will be swept along the aircraft’s surface in response to the relative velocity between the arc’s root (attached to a moving electrode) and the bulk of the arc, which is stationary with respect to the air. During this process, the reattachment of the arc to new locations often occurs. The detailed description of this swept stroke is still at an early stage of research, and it entails the interaction between an electrical arc and the flow boundary layer. In this paper we examine the implications of the structure of the boundary layer for the arc sweeping and reattachment process by considering different velocity profiles, both for laminar and turbulent flow, as well as a high fidelity description, using large eddy simulation, of transitional flow over an airfoil. It is found that the local velocity fluctuations in a turbulent flow may be important contributors to the reattachment of the arc, through a combination of an increased potential drop along the arc and local approaches of the arc to the surface. Specific flow features, such as the presence of a laminar recirculation bubble, can also contribute to the possibility of reattachment.

  10. Controlling Arc Length in Plasma Welding

    NASA Technical Reports Server (NTRS)

    Iceland, W. F.

    1986-01-01

    Circuit maintains arc length on irregularly shaped workpieces. Length of plasma arc continuously adjusted by control circuit to maintain commanded value. After pilot arc is established, contactor closed and transfers arc to workpiece. Control circuit then half-wave rectifies ac arc voltage to produce dc control signal proportional to arc length. Circuit added to plasma arc welding machines with few wiring changes. Welds made with circuit cleaner and require less rework than welds made without it. Beads smooth and free of inclusions.

  11. Models for Jupiter's decametric arcs

    NASA Technical Reports Server (NTRS)

    Warwick, J. W.

    1981-01-01

    Arc-shaped structures that dominate Jupiter's decametric emission are discussed in terms of a magnetic fine structure. The sequence of arcs manifest the occurence of widespread fine structures similar to the white ovals on Jupiter's visible surface. An arc concave toward increasing time occurs at the east limb passage, and an arc convex occurs at the west limb passage, which is consistent with the early source producing vertex early arcs, and the late source producing vertex late arcs. Due to the geometry of the Io plasma torus (IPT) which is arranged so that Io skims the northern surface of the IPT, for any connection between Io and Jupiter's surface that involves Alfven waves, the propagation time, the refraction and the directional defocusing of these waves must be strongly influenced by the amount of Alfven wave path length between the instantaneous position of Io and the surface of the IPT.

  12. Joan of Arc.

    PubMed

    Foote-Smith, E; Bayne, L

    1991-01-01

    For centuries, romantics have praised and historians and scientists debated the mystery of Joan of Arc's exceptional achievements. How could an uneducated farmer's daughter, raised in harsh isolation in a remote village in medieval France, have found the strength and resolution to alter the course of history? Hypotheses have ranged from miraculous intervention to creative psychopathy. We suggest, based on her own words and the contemporary descriptions of observers, that the source of her visions and convictions was in part ecstatic epileptic auras and that she joins the host of creative religious thinkers suspected or known to have epilepsy, from St. Paul and Mohammed to Dostoevsky, who have changed western civilization.

  13. APPARATUS FOR ARC WELDING

    DOEpatents

    Lingafelter, J.W.

    1960-04-01

    An apparatus is described in which a welding arc created between an annular electrode and a workpiece moves under the influence of an electromagnetic field about the electrode in a closed or annular path. This mode of welding is specially suited to the enclosing of nuclear-fuel slugs in a protective casing. For example, a uranium slug is placed in an aluminum can, and an aluminum closure is welded to the open end of the can along a closed or annular path conforming to the periphery of the end closure.

  14. Arcing on dc power systems

    NASA Technical Reports Server (NTRS)

    Moores, Greg; Heller, R. P.; Sutanto, Surja; Dugal-Whitehead, Norma R.

    1992-01-01

    Unexpected and undesirable arcing on dc power systems can produce hazardous situations aboard space flights. The potential for fire and shock might exist in a situation where there is a broken conductor, a loose power connection, or a break in the insulation of the power cable. Such arcing has been found to be reproducible in a laboratory environment. Arcing tests show that the phenomena can last for several seconds and yet be undetectable by present protection schemes used in classical power relaying and remote power controller applications. This paper characterizes the arcing phenomena and suggests future research that is needed.

  15. Environmental Influence of Gravity and Pressure on Arc Tracking of Insulated Wires Investigated

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Momentary short-circuit arcs between a defective polyimide-insulated wire and another conductor may thermally char (pyrolize) the insulating material. The charred polyimide, being conductive, can sustain the short-circuit arc, which may propagate along the wire through continuous pyrolization of the polyimide insulation (arc tracking). If the arcing wire is part of a multiple-wire bundle, the polyimide insulation of other wires within the bundle may become thermally charred and start arc tracking also (flash over). Such arc tracking can lead to complete failure of an entire wire bundle, causing other critical spacecraft or aircraft failures. Unfortunately, all tested candidate wire insulations for aerospace vehicles were susceptible to arc tracking. Therefore, a test procedure was designed at the NASA Lewis Research Center to select the insulation type least susceptible to arc tracking. This test procedure addresses the following three areas of concern: (1) probability of initiation, (2) probability of reinitiation (restrike), and (3) extent of arc tracking damage (propagation rate). Item 2 (restrike probability) is an issue if power can be terminated from and reapplied to the arcing wire (by a switch, fuse, or resettable circuit breaker). The degree of damage from an arcing event (item 3) refers to how easily the arc chars nearby insulation and propagates along the wire pair. Ease of nearby insulation charring can be determined by measuring the rate of arc propagation. Insulation that chars easily will propagate the arc faster than insulation that does not char very easily. A popular polyimide insulated wire for aerospace vehicles, MIL-W-81381, was tested to determine a degree of damage from an arcing event (item 3) in the following three environments: (1) microgravity with air at 1-atm pressure, (2) 1g with air at 1 atm, and (3) 1g within a 10^-6 Torr vacuum. The microgravity 1-atm air was the harshest environment, with respect to the rate of damage of arc

  16. Optical diagnostics of a gliding arc.

    PubMed

    Sun, Z W; Zhu, J J; Li, Z S; Aldén, M; Leipold, F; Salewski, M; Kusano, Y

    2013-03-11

    Dynamic processes in a gliding arc plasma generated between two diverging electrodes in ambient air driven by 31.25 kHz AC voltage were investigated using spatially and temporally resolved optical techniques. The life cycles of the gliding arc were tracked in fast movies using a high-speed camera with framing rates of tens to hundreds of kHz, showing details of ignition, motion, pulsation, short-cutting, and extinction of the plasma column. The ignition of a new discharge occurs before the extinction of the previous discharge. The developed, moving plasma column often short-cuts its current path triggered by Townsend breakdown between the two legs of the gliding arc. The emission from the plasma column is shown to pulsate at a frequency of 62.5 kHz, i.e., twice the frequency of the AC power supply. Optical emission spectra of the plasma radiation show the presence of excited N2, NO and OH radicals generated in the plasma and the dependence of their relative intensities on both the distance relative to the electrodes and the phase of the driving AC power. Planar laser-induced fluorescence of the ground-state OH radicals shows high intensity outside the plasma column rather than in the center suggesting that ground-state OH is not formed in the plasma column but in its vicinity.

  17. Four frictional regimes as a function of slip rate in halite and halite-muscovite gouge deformed from low to high velocities

    NASA Astrophysics Data System (ADS)

    Buijze, Loes; Niemeijer, Andre R.; Han, Raehee; Shimamoto, Toshihiko; Spiers, Christopher J.

    2014-05-01

    The evolution of friction as a function of slip velocity is an important factor in understanding earthquake nucleation and propagation. The velocity dependence of the coefficient of friction may not be constant but vary with slip rate. When such variations in the sign (velocity weakening vs. strengthening) and/or magnitude of the velocity dependence of friction are included in numerical modelling of rupture, it is observed that more complex and more realistic rupture patterns are produced compared to using a single constant velocity dependence. It is thus important to study the coefficient of friction over the entire range of velocities relevant to earthquake nucleation and propagation, which may be done in the laboratory. Most laboratory experiments are either conducted at low velocities (10-8 - 10-4 ms-1) or high velocities (0.01 - 1 ms-1). Few experiments however bridge the gap between these two regimes. Also, reproducing in situ conditions is difficult during high velocity experiments since normal stress is often limited, pore pressure is hard to control and often room temperature is used. In this research we aim to study the evolution of friction of a single material from low to high slip rates, which deforms via processes representative to upper crustal deformation of quartzite fault rock (with phyllosilicates) at conditions accessible at low and high velocities. Analogue halite and halite-muscovite gouges were deformed over a 7 orders of magnitude slip range (0.1 μms-1 - 1 ms-1) using a low-to-high velocity rotary shear apparatus at Hiroshima University. The applied normal stress was 5 MPa, the experiments took place at room temperature and gouges were room-dry. Microstructural analysis was conducted to study the deformation mechanisms. Four frictional regimes as a function of slip rate could be recognized from the mechanical data, and each regime was associated with a distinct microstructure, reflecting a transition from mainly brittle-dominated to more

  18. Integrated primary flight display: the sky arc

    NASA Astrophysics Data System (ADS)

    Voulgaris, Theodore J.; Metalis, Sam A.; Mobley, R. S.

    1995-05-01

    Flight instrument interpretability has been a key piloting issue because it is directly related to operator performance and inversely related to operator error. To improve interpretability we have developed the Sky Arc, a new symbology initially developed for attitude control, particularly for a helmet-mounted display. It consists of an integrated set of graphic symbols which vary in a continuous, analog fashion with changing flight parameters. The Sky Arc currently integrates, pitch, roll, heading, air speed, and terrain avoidance. The display can be integrated into a head down display, a head up display, or a helmet mounted display. In this preliminary study the usability of the Sky Arc as an attitude indicator was compared to a conventional head-up display pitch ladder symbology. The test involved six test subject pilots and a medium-fidelity simulator. The pilots were asked to fully recover from a series of unusual attitude conditions that were presented on the simulator. The time taken to recover and the correctness of the recovery procedure served as the objective evaluation measures. A Likert-type rating scale and open-ended subject matter expert opinions served as the subjective measures of evaluation. To examine whether there was a relationship between usability of the attitude indicator and difficulty of the unusual attitude, the workload levels involved in performing the unusual attitude recoveries were grouped into three levels, low, medium, and high. At each workload level there were four conditions, for a total of 12 different conditions. Each pilot was asked to recovery twice from each condition, for a total of 24 unusual attitude recovery trials. The test trials were counterbalanced and displayed in a prearranged order. No differences due to difficulty of the unusual attitude were detected. Overall, the study revealed that the Sky Arc led to generally faster recoveries than did the standard display, as well as higher subjective preference ratings

  19. Electric arc welding gun

    DOEpatents

    Luttrell, Edward; Turner, Paul W.

    1978-01-01

    This invention relates to improved apparatus for arc welding an interior joint formed by intersecting tubular members. As an example, the invention is well suited for applications where many similar small-diameter vertical lines are to be welded to a long horizontal header. The improved apparatus includes an arc welding gun having a specially designed welding head which is not only very compact but also produces welds that are essentially free from rolled-over solidified metal. The welding head consists of the upper end of the barrel and a reversely extending electrode holder, or tip, which defines an acute angle with the barrel. As used in the above-mentioned example, the gun is positioned to extend upwardly through the vertical member and the joint to be welded, with its welding head disposed within the horizontal header. Depending on the design of the welding head, the barrel then is either rotated or revolved about the axis of the vertical member to cause the electrode to track the joint.

  20. Fault gouge analyses: K-Ar illite dating, clay mineralogy and tectonic significance—a study from the Sierras Pampeanas, Argentina

    NASA Astrophysics Data System (ADS)

    Bense, Frithjof A.; Wemmer, Klaus; Löbens, Stefan; Siegesmund, Siegfried

    2014-01-01

    We introduce a method for the detailed interpretation of K-Ar illite fine-fraction ages of fault gouges from non-sedimentary host rocks. Ages are cross-evaluated with several independent parameters, e.g. illite crystallinity, illite polytype quantification, grain size, mineralogical observations, K-Ar muscovite and biotite host-rock cooling ages as well as low-temperature thermochronological data (AFT, AHe, ZHe). This interpretation approach is applied to a regional study in order to constrain the `deformation path' of the Eastern Sierras Pampeanas in NW Argentina. In the course of this study, a large number of gouge-bearing fault zones were systematically sampled and analysed. Obtained K-Ar illite fine-fraction ages range from Devonian to Cretaceous times, documenting a long-lasting brittle fault activity in this region. Ages >320 Ma are synchronous with a period of intra-Carboniferous compressional tectonism, whereas Permo-Triassic ages are contemporaneous to a flat-slab subduction episode of the Farallon plate beneath the South American plate. Middle to Late Permian and Early Triassic ages as well as Early Jurassic to Middle Cretaceous ages correlate with extensional tectonics in this region. Additionally, K-Ar illite ages reveal a propagation of brittle deformation from north to south in the Sierras de Córdoba and San Luis. Data integrity and consistency with other chronometers and geological evidence show that the here suggested interpretation is valid and can provide a powerful tool to evaluate cooling and deformation histories. Despite of that, we could show that the reliability of fault gouge data strongly depends on the regional cooling.

  1. Alternating-Polarity Arc Welding

    NASA Technical Reports Server (NTRS)

    Schwinghamer, R. J.

    1987-01-01

    Brief reversing polarity of welding current greatly improves quality of welds. NASA technical memorandum recounts progress in art of variable-polarity plasma-arc (VPPA) welding, with emphasis on welding of aluminum-alloy tanks. VPPA welders offer important advantages over conventional single-polarity gas/tungsten arc welders.

  2. TAMA. TIGER Arc Modification Application

    SciTech Connect

    Armstrong, H

    1994-06-03

    The application enables the geometric correction of TIGER arcs to a more accurate spatial data set. This is done in a structured automated environment according to Census Bureau guidelines and New Mexico state GIS standards. Arcs may be deleted, added, combined, split, and moved relative to a coverage or image displayed in the background.

  3. Of Eggs and Arcs

    NASA Astrophysics Data System (ADS)

    Burns, Joseph A.; Thomas, P. C.; Helfenstein, P.; Tiscareno, M. S.; Hedman, M. M.; Agarwal, M.

    2012-10-01

    New scenarios for the origins of Saturn’s rings/interior moons have directed scientific attention to the region just exterior to Saturn’s main rings. Four satellites (Aegaeon = Ae; Anthe = An; Methone = Me; Pallene = Pa) discovered by the Cassini mission on either side of Mimas’s orbit perhaps comprise a distinct class of ring-moon. They are tiny (R = 0.3-2.5 km); three (AeAnMe) are trapped in co-rotation resonances with Mimas and reside within ring-arcs; and at least two (MePa) have remarkably regular shapes. Images with pixel scales as fine as 27 m taken in May 2012 reveal Methone to be ovoid within 10 m (from sub-pixel limb detection) and devoid of any craters (>130 m) across its 9 km2 of surface; Pallene and even tiny Aegaeon have similar appearances in lesser-quality images. Numerical simulations demonstrate that particles comprising the surrounding ring-arcs populate the same resonances as their embedded moons; escape speeds from the moons are < 0.5 m/s, smaller than the 2 m/s that dynamically characterize the resonant well. We investigate the gentle transfer of particles back and forth between the ring-arcs and any embedded bodies. In this environment, the moons’ shapes are smooth equipotentials; electrostatic effects may also determine how grains settle to surfaces. Considering these shapes to represent equipotential surfaces for rotating, tidally distorted, homogeneous bodies, we infer mean satellite densities of 250+/-60 (Pa), 310+/-30 (Me), and 540+/-120 (Ae) kg m-3. About half of Methone’s leading hemisphere is covered by a sharply bounded, lemon-shaped, relatively dark region, having a form reminiscent of Mimas’s thermal anomaly (Howett et al. 2011). Its (601 nm) albedo is 13% lower than the bounding brighter material. An irregularly shaped, even-darker (by 4%) blotch straddles the apex of the moon’s motion. Impacts with circum-planetary meteoroids and plasma are likely responsible for these features.

  4. Arc fault detection system

    DOEpatents

    Jha, K.N.

    1999-05-18

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard. 1 fig.

  5. Arc fault detection system

    DOEpatents

    Jha, Kamal N.

    1999-01-01

    An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard.

  6. Frictional behavior of natural clay-rich fault gouges from ODP Leg 190, Nankai Trough, offshore Japan

    NASA Astrophysics Data System (ADS)

    McKiernan, A.; Lockner, D.; Saffer, D. M.

    2005-12-01

    The decollement at subduction interfaces localizes within sediments carried by the subducting plate, and therefore understanding the frictional behavior of these sediments provides insight into the initiation of the decollement and the nature of slip along it. Variations in frictional behavior due to the conversion of smectite to illite may affect the strength of subduction interfaces and the updip limit of the seismogenic zone. Recent work has shown that illite exhibits velocity strengthening behavior, and this study expands on previous experimental conditions by testing saturated, intact, natural samples, which are sheared parallel to the incipient plate-boundary fault. Here we present results from a mineralogically-varied suite of intact samples from Ocean Drilling Program (ODP) Leg 190, site 1174, offshore Japan. These samples range in bulk illite abundance from 21-35 wt. % and in total clay content from 45-67 wt. %. Thus our experiments provide a natural test of mineralogically-controlled frictional variability, and act as a pilot study into the role of depositional fabrics in shearing. Samples were prepared as ``wafers,'' where ODP cores were cut parallel to the depositional surface to produce thin, intact, rectangular layers, which were then sheared between Berea Sandstone and Westerly Granite driving blocks. Prepared layers of intact gouge were saturated at a controlled fluid pressure of 1 MPa, and sheared in a triaxial apparatus at normal stresses of 20, 50, 120, and 150 MPa. Initial sample thickness varied from ~1-7 mm, with maximum shear strains of ~1.5-10. Corrections were made primarily for displacement-based area change (contact area is decreased by ~40% at a maximum displacement of 10 mm) and jacket strength (linear increase in measured shear stress with displacement). Preliminary results show 1) values of μ (~0.25-0.4) similar to that previously reported for clay mixtures; 2) velocity strengthening behavior (a-b > 0) in all cases, consistent with

  7. Arc spot grouping: An entanglement of arc spot cells

    SciTech Connect

    Kajita, Shin; Hwangbo, Dogyun; Ohno, Noriyasu; Tsventoukh, Mikhail M.; Barengolts, Sergey A.

    2014-12-21

    In recent experiments, clear transitions in velocity and trail width of an arc spot initiated on nanostructured tungsten were observed on the boundary of the thick and thin nanostructured layer regions. The velocity of arc spot was significantly decreased on the thick nanostructured region. It was suggested that the grouping decreased the velocity of arc spot. In this study, we try to explain the phenomena using a simple random walk model that has properties of directionality and self-avoidance. And grouping feature was added by installing an attractive force between spot cells with dealing with multi-spots. It was revealed that an entanglement of arc spot cells decreased the spot velocity, and spot cells tend to stamp at the same location many times.

  8. Convergent evolution of the arginine deiminase pathway: the ArcD and ArcE arginine/ornithine exchangers.

    PubMed

    Noens, Elke E E; Lolkema, Juke S

    2017-02-01

    The arginine deiminase (ADI) pathway converts L-arginine into L-ornithine and yields 1 mol of ATP per mol of L-arginine consumed. The L-arginine/L-ornithine exchanger in the pathway takes up L-arginine and excretes L-ornithine from the cytoplasm. Analysis of the genomes of 1281 bacterial species revealed the presence of 124 arc gene clusters encoding the pathway. About half of the clusters contained the gene encoding the well-studied L-arginine/L-ornithine exchanger ArcD, while the other half contained a gene, termed here arcE, encoding a membrane protein that is not a homolog of ArcD. The arcE gene product of Streptococcus pneumoniae was shown to take up L-arginine and L-ornithine with affinities of 0.6 and 1 μmol/L, respectively, and to catalyze metabolic energy-independent, electroneutral exchange. ArcE of S. pneumoniae could replace ArcD in the ADI pathway of Lactococcus lactis and provided the cells with a growth advantage. In contrast to ArcD, ArcE catalyzed translocation of the pathway intermediate L-citrulline with high efficiency. A short version of the ADI pathway is proposed for L-citrulline catabolism and the presence of the evolutionary unrelated arcD and arcE genes in different organisms is discussed in the context of the evolution of the ADI pathway.

  9. Nature of convection-stabilized dc arcs in dual-flow nozzle geometry. I - The cold flow field and dc arc characteristics. II - Optical diagnostics and theory

    NASA Technical Reports Server (NTRS)

    Serbetci, Ilter; Nagamatsu, H. T.

    1990-01-01

    Steady-state low-current air arcs in a dual-flow nozzle system are studied experimentally. The cold flow field with no arc is investigated using a 12.7-mm diameter dual-flow nozzle in a steady-flow facility. Mach number and mass flux distributions are determined for various nozzle-pressure ratios and nozzle-gap spacing. It is found that the shock waves in the converging-diverging nozzles result in a decrease in overal resistance by about 15 percent. Also, Schlieren and differential interferometry techniques are used to visualize the density gradients within the arc plasma and thermal mantle. Both optical techniques reveal a laminar arc structure for a reservoir pressure of 1 atm at various current levels. Experimentally determined axial static pressure and cold-flow mass flux rate distributions and a channel-flow model with constant arc temperatre are used to solve the energy integral for the arc radius as a function of axial distance. The arc electric field strength, voltage, resistance, and power are determined with Ohm's law and the total heat transfer is related to arc power.

  10. Arc of opportunity.

    PubMed

    Delaney, Adam Vai

    2011-07-01

    Born in Port Moresby, Papua New Guinea, the author had a 20 year career in diplomacy, political affairs, and development policy analysis at the Pacific Islands Forum, the United Nations in New York; the Prime Minister's Department in Papua New Guinea (PNG) and in the Foreign Ministry of PNG. He has also been involved in theatre for over a decade in PNG, and participated in a three-month program at the Eugene O'Neill Theatre Center in Connecticut, USA. He is currently the Business Development Manager at the Torres Strait Regional Authority (Commonwealth) on Thursday Island. Since 1975 the Australian government's overseas development policy has supported various sectoral programs in its neighbouring countries, in particular Papua New Guinea and the Solomon Islands. The "creative" field has not been prominent in this strategy. While natural resources and the sports sectors have gained much greater attention, in terms of being viable international commercial enterprises, the arts, have remained stagnant. In this paper the need for joint programs genuinely supporting "wellbeing" and promoting social enterprise throughout the "arc of opportunity" is described to harness Melanesian creativity to compete successfully in world-markets, starting with penetration of the largest economy at its door-step: Australia.

  11. Percussive arc welding apparatus

    DOEpatents

    Hollar, Jr., Donald L.

    2002-01-01

    A percussive arc welding apparatus includes a generally cylindrical actuator body having front and rear end portions and defining an internal recess. The front end of the body includes an opening. A solenoid assembly is provided in the rear end portion in the internal recess of the body, and an actuator shaft assembly is provided in the front end portion in the internal recess of the actuator body. The actuator shaft assembly includes a generally cylindrical actuator block having first and second end portions, and an actuator shaft having a front end extending through the opening in the actuator body, and the rear end connected to the first end portion of the actuator block. The second end portion of the actuator block is in operational engagement with the solenoid shaft by a non-rigid connection to reduce the adverse rebound effects of the actuator shaft. A generally transversely extending pin is rigidly secured to the rear end of the shaft. One end of the pin is received in a slot in the nose housing sleeve to prevent rotation of the actuator shaft during operation of the apparatus.

  12. PC-based arc ignition and arc length control system for gas tungsten arc welding

    SciTech Connect

    Liu, Y. ); Cook, G.E.; Barnett, R.J.; Springfield, J.F. . School of Engineering)

    1992-10-01

    In this paper, a PC-based digital control system for gas tungsten arc welding (GTAW) is presented. This system controls the arc ignition process, the arc length, and the process of welding termination. A DT2818 made by Data Translation is used for interface and A/D and D/A conversions. The digital I/O ports of the DT2818 are used for control of wirefeed, shield gas, cooling water, welding power supply, etc. The DT2818 is housed in a PC. The welding signals and status are displayed on the screen for in-process monitoring. A user can control the welding process by the keyboard.

  13. More About Arc-Welding Process for Making Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Benavides, Jeanette M.; Leidecker, Henning

    2005-01-01

    High-quality batches of carbon nanotubes are produced at relatively low cost in a modified atmospheric-pressure electric-arc welding process that does not include the use of metal catalysts. What would normally be a welding rod and a weldment are replaced by an amorphous carbon anode rod and a wider, hollow graphite cathode rod. Both electrodes are water-cooled. The cathode is immersed in ice water to about 0.5 cm from the surface. The system is shielded from air by flowing helium during arcing. As the anode is consumed during arcing at 20 to 25 A, it is lowered to maintain it at an approximately constant distance above the cathode. The process causes carbon nanotubes to form on the lowest 5 cm of the anode. The arcing process is continued until the anode has been lowered to a specified height. The nanotube-containing material is then harvested. The additional information contained in the instant report consists mostly of illustrations of carbon nanotubes and a schematic diagram of the arc-welding setup, as modified for the production of carbon nanotubes.

  14. Physicochemical Processes of Frictional Healing and Lithification: Effects of Normal Stress and Water on Stick-Slip Stress Drop and Friction in Synthetic Fault Gouge

    NASA Astrophysics Data System (ADS)

    Scuderi, M.; Carpenter, B. M.; Marone, C.

    2011-12-01

    Earthquakes are dynamic phenomena characterized by slip instability along a preexisting zone of weakness (fault zone) within more competent rock. Fault zones are characterized by granular and clay-rich wear material (fault gouge) produced by dynamic and quasi-static slip processes. The mechanical strength, frictional stability, and seismic potential of a fault are strongly influenced by the evolution of grain contacts within the fault zone. In this context, water plays an important role at mineral surfaces and within contact junction via processes such as hydrolithic weakening, adsorption/desorption and pressure solution. To investigate the role of water in faulting, we performed shear experiments using synthetic fault gouge as a function of relative humidity (RH) and normal stress (σn). We sheared layers of glass beads and granular rock of known initial grain size (dia. 105 to 149 μm) in a double direct shear configuration. Normal stress was kept constant during shear at values of 2.5, 5 and 10 MPa. Shear (τ) stress was applied via a constant displacement rate at the layer boundaries, and shearing velocity was varied from 0.3 to 300 μm/s. Careful calibration of apparatus stiffness plus an external DCDT, mounted directly across the shear zone, were used to measure slip velocity of the fault zone. During each experiment, RH was kept constant at values of 5, 50 and 100%. Our experiments were conducted in the stick-slip sliding regime. For σn = 2.5 MPa, stress drop, (Δτ), is constant from 0.3 to 10 μm/s and decreases linearly with log velocity above 10 μm/s. Maximum shear stress τmax shows the same trend. At σn = 10 MPa, Δτ decreases linearly with log velocity over the entire velocity range. We find that maximum friction μmax increases systematically with increasing RH, in contrast to previous results for angular quartz and nominally-bare surfaces. In agreement with previous studies, our results indicate that frictional behavior of simulated fault gouge

  15. Heat transfer in GTA welding arcs

    NASA Astrophysics Data System (ADS)

    Huft, Nathan J.

    Heat transfer characteristics of Gas Tungsten Arc Welding (GTAW) arcs with arc currents of 50 to 125 A and arc lengths of 3 to 11 mm were measured experimentally through wet calorimetry. The data collected were used to calculate how much heat reported to the cathode and anode and how much was lost from the arc column. A Visual Basic for Applications (VBA) macro was written to further analyze the data and account for Joule heating within the electrodes and radiation and convection losses from the arc, providing a detailed account of how heat was generated and dissipated within the system. These values were then used to calculate arc efficiencies, arc column voltages, and anode and cathode fall voltages. Trends were noted for variances in the arc column voltage, power dissipated from the arc column, and the total power dissipated by the system with changing arc length. Trends for variances in the anode and cathode fall voltages, total power dissipated, Joule heating within the torches and electrodes with changing arc current were also noted. In addition, the power distribution between the anode and cathode for each combination of arc length and arc current was examined. Keywords: Gas Tungsten Arc Welding, GTAW, anode fall, cathode fall, heat transfer, wet calorimetry

  16. The Effect of Flow Distribution on the Concentration of NO Produced by Pulsed Arc Discharge

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Bao, Bin; Wang, Heli; Liang, Haiyan; He, Junjia; He, Zhenghao; Li, Jin

    2007-12-01

    As a new method to cure acute respiratory distress syndrome (ARDS), high blood pressure and some illnesses related to the lung, NO has recently received more attention. Thermal plasmas produced by arc discharge can create medical NO, but the concentration of NO2 produced by arc discharge must be controlled simultaneously. This paper investigates the characteristics and regulations of NO production at different flow distribution by pulsed arc discharge in dry air with a special pulsed power. The experimental results show that the flow distribution has a considerable effect on the NO concentration, the stabilization of NO. The production of NO2 could be controlled and the ratio of NO2/NO was decreased to about 10% in the arc discharge. Therefore, the arc discharge could produce stable inhaled NO for medical treatment by changing the flow distribution.

  17. Dosimetric and delivery characterizations of full-arc and half-arc volumetric-modulated arc therapy for maxillary cancer.

    PubMed

    Miura, Hideharu; Fujiwara, Masayuki; Tanooka, Masao; Doi, Hiroshi; Inoue, Hiroyuki; Takada, Yasuhiro; Kamikonya, Norihiko; Hirota, Shozo

    2012-09-01

    We compared the efficiency and accuracy of full-arc and half-arc volumetric-modulated arc therapy (VMAT) delivery for maxillary cancer. Plans for gantry rotation angles of 360° and 180° (full-arc and half-arc VMAT) were created for six maxillary cancer cases with the Monaco treatment planning system, and delivered using an Elekta Synergy linear accelerator. Full-arc and half-arc VMAT were compared with regard to homogeneity index (HI), conformity index (CI), mean dose to normal brain, total monitor units (MU), delivery times, root mean square (r.m.s.) gantry accelerations (°/s(2)), and r.m.s. gantry angle errors (°). The half-arc VMAT plans achieved comparable HI and CI to the full-arc plans. Mean doses to the normal brain and brainstem with the half-arc VMAT plans were on average 16% and 17% lower than those with the full-arc VMAT plans. For other organs at risk (OARs), no significant DVH differences were observed between plans. Half-arc VMAT resulted in 11% less total MU and 20% shorter delivery time than the full-arc VMAT, while r.m.s. gantry acceleration and r.m.s. gantry angle error during half-arc VMAT delivery were 30% and 23% less than those during full-arc VMAT delivery, respectively. Furthermore, the half-arc VMAT plans were comparable with the full-arc plans regarding dose homogeneity and conformity in maxillary cancer, and provided a statistical decrease in mean dose to OAR, total MU, delivery time and gantry angle error. Half-arc VMAT plans may be a suitable treatment option in radiotherapy for maxillary cancer.

  18. Evacuated FM08 Fuses Carry a Sustained Arc in a Bus over 75 VDC

    NASA Technical Reports Server (NTRS)

    Leidecker, Henning; Slonaker, J.

    1999-01-01

    The FM08 style fuse is specified to interrupt an overcurrent of up to 300 A in a bus of up to 125 VDC, but this applies only when its barrel is filled with air. When placed into a space-grade vacuum, the FM08 style fuse exhausts its air within a year. Then, the probability of an enduring arc is high for all ratings when the bus is above 75 VDC, and the overcurrent is large. The arc endures until something else interrupts the current. The fuse can violently eject metal vapor or other material during the sustained arcing. The evacuated FM08 does not develop a sustained arc when interrupted in a bus of 38 VDC or less, at least when there is little inductance in the circuit. This is consistent with its successful use in many spacecraft having buses in the range 24 to 36 volts.

  19. High pressure neon arc lamp

    DOEpatents

    Sze, Robert C.; Bigio, Irving J.

    2003-07-15

    A high pressure neon arc lamp and method of using the same for photodynamic therapies is provided. The high pressure neon arc lamp includes a housing that encloses a quantity of neon gas pressurized to about 500 Torr to about 22,000 Torr. At each end of the housing the lamp is connected by electrodes and wires to a pulse generator. The pulse generator generates an initial pulse voltage to breakdown the impedance of the neon gas. Then the pulse generator delivers a current through the neon gas to create an electrical arc that emits light having wavelengths from about 620 nanometers to about 645 nanometers. A method for activating a photosensitizer is provided. Initially, a photosensitizer is administered to a patient and allowed time to be absorbed into target cells. Then the high pressure neon arc lamp is used to illuminate the target cells with red light having wavelengths from about 620 nanometers to about 645 nanometers. The red light activates the photosensitizers to start a chain reaction that may involve oxygen free radicals to destroy the target cells. In this manner, a high pressure neon arc lamp that is inexpensive and efficiently generates red light useful in photodynamic therapy is provided.

  20. Clines Arc through Multivariate Morphospace.

    PubMed

    Lohman, Brian K; Berner, Daniel; Bolnick, Daniel I

    2017-04-01

    Evolutionary biologists typically represent clines as spatial gradients in a univariate character (or a principal-component axis) whose mean changes as a function of location along a transect spanning an environmental gradient or ecotone. This univariate approach may obscure the multivariate nature of phenotypic evolution across a landscape. Clines might instead be plotted as a series of vectors in multidimensional morphospace, connecting sequential geographic sites. We present a model showing that clines may trace nonlinear paths that arc through morphospace rather than elongating along a single major trajectory. Arcing clines arise because different characters diverge at different rates or locations along a geographic transect. We empirically confirm that some clines arc through morphospace, using morphological data from threespine stickleback sampled along eight independent transects from lakes down their respective outlet streams. In all eight clines, successive vectors of lake-stream divergence fluctuate in direction and magnitude in trait space, rather than pointing along a single phenotypic axis. Most clines exhibit surprisingly irregular directions of divergence as one moves downstream, although a few clines exhibit more directional arcs through morphospace. Our results highlight the multivariate complexity of clines that cannot be captured with the traditional graphical framework. We discuss hypotheses regarding the causes, and implications, of such arcing multivariate clines.

  1. Mechanical behavior and microstructure of simulated calcite fault gouge sheared at 20-600°C: Implications for natural faults in limestones

    NASA Astrophysics Data System (ADS)

    Verberne, Berend A.; Niemeijer, André R.; De Bresser, Johannes H. P.; Spiers, Christopher J.

    2015-12-01

    We report ring shear experiments on simulated calcite fault gouges performed at fixed temperatures (T) within the range from 20°C to 600°C. The experiments were performed wet, using pore fluid pressures (Pf) of 10 ≤ Pf ≤ 60 MPa. One series of experiments employed a constant effective normal stress (σneff) of 50 MPa, while in a second series, σneff was sequentially stepped from 30 to 100 MPa. In all experiments, sliding velocity (v) was stepped in the range from 0.03 to 100 µm/s. The results showed stable, velocity-strengthening behavior at 20°C, but velocity weakening at 100°C to 550°C (for all v steps to <3 µm/s), which was frequently accompanied by stick slip. At 600°C, velocity strengthening occurred. Microstructural observations suggest increasing importance of ductile deformation with increasing temperature, as reflected by a localized shear band structure at 20°C giving way to a pervasive, shear plane-parallel grain shape fabric at 600°C. Using existing flow equations for dense calcite polycrystals, we show that dislocation and/or diffusion creep of 10-30 µm-sized bulk gouge grains likely played a role in experiments performed at T ≥ 400°C. We suggest that the observed velocity-weakening behavior can be explained by a slip mechanism involving dilatant granular flow in competition with creep-controlled compaction. Our results have important implications for the breadth of the seismogenic zone in limestone terrains and for the interpretation of natural fault rock microstructures. Specifically, while samples sheared at 400-550°C exhibited essentially brittle/frictional mechanical behavior (stick slip), the corresponding microstructures resembled that of a mylonite.

  2. Effect of clay content and mineralogy on frictional sliding behavior of simulated gouges: Binary and ternary mixtures of quartz, illite, and montmorillonite

    NASA Astrophysics Data System (ADS)

    Tembe, Sheryl; Lockner, David A.; Wong, Teng-Fong

    2010-03-01

    We investigated the frictional sliding behavior of simulated quartz-clay gouges under stress conditions relevant to seismogenic depths. Conventional triaxial compression tests were conducted at 40 MPa effective normal stress on saturated saw cut samples containing binary and ternary mixtures of quartz, montmorillonite, and illite. In all cases, frictional strengths of mixtures fall between the end-members of pure quartz (strongest) and clay (weakest). The overall trend was a decrease in strength with increasing clay content. In the illite/quartz mixture the trend was nearly linear, while in the montmorillonite mixtures a sigmoidal trend with three strength regimes was noted. Microstructural observations were performed on the deformed samples to characterize the geometric attributes of shear localization within the gouge layers. Two micromechanical models were used to analyze the critical clay fractions for the two-regime transitions on the basis of clay porosity and packing of the quartz grains. The transition from regime 1 (high strength) to 2 (intermediate strength) is associated with the shift from a stress-supporting framework of quartz grains to a clay matrix embedded with disperse quartz grains, manifested by the development of P-foliation and reduction in Riedel shear angle. The transition from regime 2 (intermediate strength) to 3 (low strength) is attributed to the development of shear localization in the clay matrix, occurring only when the neighboring layers of quartz grains are separated by a critical clay thickness. Our mixture data relating strength degradation to clay content agree well with strengths of natural shear zone materials obtained from scientific deep drilling projects.

  3. Effect of clay content and mineralogy on frictional sliding behavior of simulated gouges: binary and ternary mixtures of quartz, illite, and montmorillonite

    USGS Publications Warehouse

    Tembe, Sheryl; Lockner, David A.; Wong, Teng-Fong

    2010-01-01

    We investigated the frictional sliding behavior of simulated quartz-clay gouges under stress conditions relevant to seismogenic depths. Conventional triaxial compression tests were conducted at 40 MPa effective normal stress on saturated saw cut samples containing binary and ternary mixtures of quartz, montmorillonite, and illite. In all cases, frictional strengths of mixtures fall between the end-members of pure quartz (strongest) and clay (weakest). The overall trend was a decrease in strength with increasing clay content. In the illite/quartz mixture the trend was nearly linear, while in the montmorillonite mixtures a sigmoidal trend with three strength regimes was noted. Microstructural observations were performed on the deformed samples to characterize the geometric attributes of shear localization within the gouge layers. Two micromechanical models were used to analyze the critical clay fractions for the two-regime transitions on the basis of clay porosity and packing of the quartz grains. The transition from regime 1 (high strength) to 2 (intermediate strength) is associated with the shift from a stress-supporting framework of quartz grains to a clay matrix embedded with disperse quartz grains, manifested by the development of P-foliation and reduction in Riedel shear angle. The transition from regime 2 (intermediate strength) to 3 (low strength) is attributed to the development of shear localization in the clay matrix, occurring only when the neighboring layers of quartz grains are separated by a critical clay thickness. Our mixture data relating strength degradation to clay content agree well with strengths of natural shear zone materials obtained from scientific deep drilling projects.

  4. Successive reactivation of older structures under variable heat flow conditions evidenced by K-Ar fault gouge dating in Sierra de Ambato, northern Argentine broken foreland

    NASA Astrophysics Data System (ADS)

    Nóbile, Julieta C.; Collo, Gilda; Dávila, Federico M.; Martina, Federico; Wemmer, Klaus

    2015-12-01

    The Argentine broken foreland has been the subject of continuous research to determine the uplift and exhumation history of the region. High-elevation mountains are the result of N-S reverse faults that disrupted a W-E Miocene Andean foreland basin. In the Sierra de Ambato (northern Argentine broken foreland) the reverse faults offset Neogene sedimentary rocks (Aconquija Fm., ˜9 Ma) and affect the basement comprising Paleozoic metamorphic rocks that have been dated at ˜477-470 Ma. In order to establish a chronology of these faults affecting the previous continuous basin we date the formation age of clay minerals associated with fault gouge using the K-Ar dating technique. Clay mineral formation is a fundamental process in the evolution of faults under the brittle regime (<<300 °C). K-Ar ages (9 fractions from 3 samples collected along a transect in the Sierra de Ambato) vary from Late Devonian to Late Triassic (˜360-220 Ma). This age distribution can be explained by a long lasting brittle deformation history with a minimum age of ˜360 Ma and a last clay minerals forming event at ˜220 Ma. Moreover, given the progression of apparent ages decreasing from coarse to fine size fractions (˜360-311 Ma for 2-1 μm grain size fraction, ˜326-286 Ma for 1-0.2 μm and ˜291-219 Ma of <0.2 μm), we modeled discrete deformation events at ˜417 Ma (ending of the Famatinian cycle), ˜317-326 Ma (end of Gondwanic orogeny), and ˜194-279 Ma (Early Permian - Jurassic deformation). According to our data, the Neogene reactivation would not have affected the K-Ar system neither generated a significant clay minerals crystallization in the fault gouge, although an exhumation of more than 2 Km is recorded in this period from stratigraphic data.

  5. Performance and operating characteristics of the arc-driven Langley 6-inch shock tube

    NASA Technical Reports Server (NTRS)

    Nealy, J. E.

    1972-01-01

    Performance characteristics for the arc-driven Langley 6-inch shock tube were determined for driver energies from 0.62 to 5 MJ. Voltage, current and pressure histories of the arc driver were recorded, and driver efficiencies were determined from measured shock velocities. Time-resolved spectra for test gases of air, carbon monoxide, xenon, and a mixture of 80 percent helium and 20 percent hydrogen are presented.

  6. Thermal blanket metallic film groundstrap and second surface mirror vulnerability to arc discharges

    NASA Technical Reports Server (NTRS)

    Inouye, G. T.; Sanders, N. L.; Komatsu, G. K.; Valles, J. R.; Sellen, J. M., Jr.

    1979-01-01

    Available data on the geosynchronous orbit energetic plasma environment were examined, and a crude model was generated to permit an estimation to be made of the number of arc discharges per year to which a thermal blanket groundstrap would be subjected. Laboratory experiments and a survey of the literature on arc discharge characteristics were performed to define typical and worst case arc discharge current waveforms. In-air tests of different groundstrap configurations to a standardized test pulse were performed and a wide variability of durability values were found. A groundstrap technique, not used thus far, was found to be far superior than the others.

  7. Preliminary Study of the Feasibility of Inverse Problem Algorithms Used for Arc Magnetic Measurement Method

    NASA Astrophysics Data System (ADS)

    Wang, Qian; Li, Xingwen; Song, Haoyong; Rong, Mingzhe

    2010-04-01

    Non-contact magnetic measurement method is an effective way to study the air arc behavior experimentally One of the crucial techniques is to solve an inverse problem for the electromagnetic field. This study is devoted to investigating different algorithms for this kind of inverse problem preliminarily, including the preconditioned conjugate gradient method, penalty function method and genetic algorithm. The feasibility of each algorithm is analyzed. It is shown that the preconditioned conjugate gradient method is valid only for few arc segments, the estimation accuracy of the penalty function method is dependent on the initial conditions, and the convergence of genetic algorithm should be studied further for more segments in an arc current.

  8. Welding arc length control system

    NASA Technical Reports Server (NTRS)

    Iceland, William F. (Inventor)

    1993-01-01

    The present invention is a welding arc length control system. The system includes, in its broadest aspects, a power source for providing welding current, a power amplification system, a motorized welding torch assembly connected to the power amplification system, a computer, and current pick up means. The computer is connected to the power amplification system for storing and processing arc weld current parameters and non-linear voltage-ampere characteristics. The current pick up means is connected to the power source and to the welding torch assembly for providing weld current data to the computer. Thus, the desired arc length is maintained as the welding current is varied during operation, maintaining consistent weld penetration.

  9. Two color interferometric electron density measurement in an axially blown arc

    NASA Astrophysics Data System (ADS)

    Stoller, Patrick; Carstensen, Jan; Galletti, Bernardo; Doiron, Charles; Sokolov, Alexey; Salzmann, René; Simon, Sandor; Jabs, Philipp

    2016-09-01

    High voltage circuit breakers protect the power grid by interrupting the current in case of a short circuit. To do so an arc is ignited between two contacts as they separate; transonic gas flow is used to cool and ultimately extinguish the arc at a current-zero crossing of the alternating current. A detailed understanding of the arc interruption process is needed to improve circuit breaker design. The conductivity of the partially ionized gas remaining after the current-zero crossing, a key parameter in determining whether the arc will be interrupted or not, is a function of the electron density. The electron density, in turn, is a function of the detailed dynamics of the arc cooling process, which does not necessarily occur under local thermodynamic equilibrium (LTE) conditions. In this work, we measure the spatially resolved line-integrated index of refraction in a near-current-zero arc stabilized in an axial flow of synthetic air with two nanosecond pulsed lasers at wavelengths of 532 nm and 671 nm. Generating a stable, cylindrically symmetric arc enables us to determine the three-dimensional index of refraction distribution using Abel inversion. Due to the wavelength dependence of the component of the index of refraction related to the free electrons, the information at two different wavelengths can be used to determine the electron density. This information allows us to determine how important it is to take into account non-equilibrium effects for accurate modeling of the physics of decaying arcs.

  10. Temporal evolution characteristics of an annular-mode gliding arc discharge in a vortex flow

    SciTech Connect

    Zhao, Tian-Liang; Liu, Jing-Lin; Li, Xiao-Song; Liu, Jin-Bao; Song, Yuan-Hong; Xu, Yong; Zhu, Ai-Min

    2014-05-15

    An annular-mode gliding arc discharge powered by a 50 Hz alternating current (ac) supply was studied in a vortex flow of dry and humid air. Its temporal evolution characteristics were investigated by electrical measurement, temporally resolved imaging, and temporally resolved optical emission spectroscopic measurements. Three discharge stages of arc-ignition, arc-gliding, and arc-extinction were clearly observed in each half-cycle of the discharge. During the arc-gliding stage, the intensity of light emission from the arc root at the cathode was remarkably higher than that at other areas. The spectral intensity of N{sub 2}(C{sup 3}Π{sub u}−B{sup 3}Π{sub g}) during the arc-ignition stage was much higher than that during the arc-gliding stage, which was contrary to the temporal evolutions of spectral intensities for N{sub 2}{sup +}(B{sup 2}Σ{sub u}{sup +}−X{sup 2}Σ{sub g}{sup +}) and OH(A{sup 2}Σ{sup +}−X{sup 2}Π{sub i}). Temporally resolved vibrational and rotational temperatures of N{sub 2} were also presented and decreased with increasing the water vapor content.

  11. Unzipping of the volcano arc, Japan

    USGS Publications Warehouse

    Stern, R.J.; Smoot, N.C.; Rubin, M.

    1984-01-01

    A working hypothesis for the recent evolution of the southern Volcano Arc, Japan, is presented which calls upon a northward-progressing sundering of the arc in response to a northward-propagating back-arc basin extensional regime. This model appears to explain several localized and recent changes in the tectonic and magrnatic evolution of the Volcano Arc. Most important among these changes is the unusual composition of Iwo Jima volcanic rocks. This contrasts with normal arc tholeiites typical of the rest of the Izu-Volcano-Mariana and other primitive arcs in having alkaline tendencies, high concentrations of light REE and other incompatible elements, and relatively high silica contents. In spite of such fractionated characteristics, these lavas appear to be very early manifestations of a new volcanic and tectonic cycle in the southern Volcano Arc. These alkaline characteristics and indications of strong regional uplift are consistent with the recent development of an early stage of inter-arc basin rifting in the southern Volcano Arc. New bathymetric data are presented in support of this model which indicate: 1. (1) structural elements of the Mariana Trough extend north to the southern Volcano Arc. 2. (2) both the Mariana Trough and frontal arc shoal rapidly northwards as the Volcano Arc is approached. 3. (3) rugged bathymetry associated with the rifted Mariana Trough is replaced just south of Iwo Jima by the development of a huge dome (50-75 km diameter) centered around Iwo Jima. Such uplifted domes are the immediate precursors of rifts in other environments, and it appears that a similar situation may now exist in the southern Volcano Arc. The present distribution of unrifted Volcano Arc to the north and rifted Mariana Arc to the south is interpreted not as a stable tectonic configuration but as representing a tectonic "snapshot" of an arc in the process of being rifted to form a back-arc basin. ?? 1984.

  12. Total Marrow Irradiation With RapidArc Volumetric Arc Therapy

    SciTech Connect

    Aydogan, Bulent; Yeginer, Mete; Kavak, Gulbin O.; Fan, John; Radosevich, James A.; Gwe-Ya, Kim

    2011-10-01

    Purpose: To develop a volumetric arc therapy (VMAT)-total marrow irradiation (TMI) technique for patients with hematologic malignancies. Methods and Materials: VMAT planning was performed for 6 patients using RapidArc technology. The planning target volume consisted of all the bones in the body from the head to the mid-femur, excluding the extremities, except for the humerus, plus a 3.0-mm margin. The organs at risk included the lungs, heart, liver, kidneys, bowels, brain, eyes, and oral cavity. The VMAT-TMI technique consisted of three plans: the head and neck, the chest, and the pelvis, each with three 330{sup o} arcs. The plans were prescribed to ensure, at a minimum, 95% planning target volume dose coverage with the prescription dose (percentage of volume receiving dose of {>=}12 Gy was 95%). The treatments were delivered and verified using MapCheck and ion chamber measurements. Results: The VMAT-TMI technique reported in the present study provided comparable dose distributions with respect to the fixed gantry linear accelerator intensity-modulated TMI. RapidArc planning was less subjective and easier, and, most importantly, the delivery was more efficient. RapidArc reduced the treatment delivery time to approximately 18 min from 45 min with the fixed gantry linear accelerator intensity-modulated TMI. When the prescription dose coverage was reduced to 85% from 95% and the mandible and maxillary structures were not included in the planning target volume as reported in a tomotherapy study, a considerable organ at risk dose reduction of 4.2-51% was observed. The average median dose for the lungs and lenses was reduced to 5.6 Gy from 7.2 Gy and 2.4 Gy from 4.5 Gy, respectively. Conclusion: The RapidArc VMAT technique improved the treatment planning, dose conformality, and, most importantly, treatment delivery efficiency. The results from our study suggest that the RapidArc VMAT technology can be expected to facilitate the clinical transition of TMI.

  13. Arc-textured high emittance radiator surfaces

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A. (Inventor)

    1991-01-01

    High emittance radiator surfaces are produced by arc-texturing. This process produces such a surface on a metal by scanning it with a low voltage electric arc from a carbon electrode in an inert environment.

  14. Warm storage for arc magmas

    NASA Astrophysics Data System (ADS)

    Barboni, Mélanie; Boehnke, Patrick; Schmitt, Axel K.; Harrison, T. Mark; Shane, Phil; Bouvier, Anne-Sophie; Baumgartner, Lukas

    2016-12-01

    Felsic magmatic systems represent the vast majority of volcanic activity that poses a threat to human life. The tempo and magnitude of these eruptions depends on the physical conditions under which magmas are retained within the crust. Recently the case has been made that volcanic reservoirs are rarely molten and only capable of eruption for durations as brief as 1,000 years following magma recharge. If the “cold storage” model is generally applicable, then geophysical detection of melt beneath volcanoes is likely a sign of imminent eruption. However, some arc volcanic centers have been active for tens of thousands of years and show evidence for the continual presence of melt. To address this seeming paradox, zircon geochronology and geochemistry from both the frozen lava and the cogenetic enclaves they host from the Soufrière Volcanic Center (SVC), a long-lived volcanic complex in the Lesser Antilles arc, were integrated to track the preeruptive thermal and chemical history of the magma reservoir. Our results show that the SVC reservoir was likely eruptible for periods of several tens of thousands of years or more with punctuated eruptions during these periods. These conclusions are consistent with results from other arc volcanic reservoirs and suggest that arc magmas are generally stored warm. Thus, the presence of intracrustal melt alone is insufficient as an indicator of imminent eruption, but instead represents the normal state of magma storage underneath dormant volcanoes.

  15. Metal vapor arc ion plating

    DOEpatents

    Bertram, L.A.; Fisher, R.W.; Mattox, D.M.; Zanner, F.J.

    1986-09-09

    A method and apparatus for ion plating are described. The apparatus uses more negative than a first electrode voltage in a vacuum arc remelt system to attract low energy ions from the anode electrode to the article to be plated. 2 figs.

  16. Warm storage for arc magmas.

    PubMed

    Barboni, Mélanie; Boehnke, Patrick; Schmitt, Axel K; Harrison, T Mark; Shane, Phil; Bouvier, Anne-Sophie; Baumgartner, Lukas

    2016-12-06

    Felsic magmatic systems represent the vast majority of volcanic activity that poses a threat to human life. The tempo and magnitude of these eruptions depends on the physical conditions under which magmas are retained within the crust. Recently the case has been made that volcanic reservoirs are rarely molten and only capable of eruption for durations as brief as 1,000 years following magma recharge. If the "cold storage" model is generally applicable, then geophysical detection of melt beneath volcanoes is likely a sign of imminent eruption. However, some arc volcanic centers have been active for tens of thousands of years and show evidence for the continual presence of melt. To address this seeming paradox, zircon geochronology and geochemistry from both the frozen lava and the cogenetic enclaves they host from the Soufrière Volcanic Center (SVC), a long-lived volcanic complex in the Lesser Antilles arc, were integrated to track the preeruptive thermal and chemical history of the magma reservoir. Our results show that the SVC reservoir was likely eruptible for periods of several tens of thousands of years or more with punctuated eruptions during these periods. These conclusions are consistent with results from other arc volcanic reservoirs and suggest that arc magmas are generally stored warm. Thus, the presence of intracrustal melt alone is insufficient as an indicator of imminent eruption, but instead represents the normal state of magma storage underneath dormant volcanoes.

  17. Vacuum Gas Tungsten Arc Welding

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  18. Graphite electrode DC arc furnace. Innovative technology summary report

    SciTech Connect

    1999-05-01

    The Graphite Electrode DC Arc Furnace (DC Arc) is a high-temperature thermal process, which has been adapted from a commercial technology, for the treatment of mixed waste. A DC Arc Furnace heats waste to a temperature such that the waste is converted into a molten form that cools into a stable glassy and/or crystalline waste form. Hazardous organics are destroyed through combustion or pyrolysis during the process and the majority of the hazardous metals and radioactive components are incorporated in the molten phase. The DC Arc Furnace chamber temperature is approximately 593--704 C and melt temperatures are as high as 1,500 C. The DC Arc system has an air pollution control system (APCS) to remove particulate and volatiles from the offgas. The advantage of the DC Arc is that it is a single, high-temperature thermal process that minimizes the need for multiple treatment systems and for extensive sorting/segregating of large volumes of waste. The DC Arc has the potential to treat a wide range of wastes, minimize the need for sorting, reduce the final waste volumes, produce a leach resistant waste form, and destroy organic contaminants. Although the DC arc plasma furnace exhibits great promise for treating the types of mixed waste that are commonly present at many DOE sites, several data and technology deficiencies were identified by the Mixed Waste Focus Area (MWFA) regarding this thermal waste processing technique. The technology deficiencies that have been addressed by the current studies include: establishing the partitioning behavior of radionuclides, surrogates, and hazardous metals among the product streams (metal, slag, and offgas) as a function of operating parameters, including melt temperature, plenum atmosphere, organic loading, chloride concentration, and particle size; demonstrating the efficacy of waste product removal systems for slag and metal phases; determining component durability through test runs of extended duration, evaluating the effect of

  19. STRUVE arc and EUPOS® stations

    NASA Astrophysics Data System (ADS)

    Lasmane, Ieva; Kaminskis, Janis; Balodis, Janis; Haritonova, Diana

    2013-04-01

    The Struve Geodetic Arc was developed in Years 1816 to 1855, 200 years ago. Historic information on the points of the Struve Geodetic Arc are included in the UNESCO World Heritage list in 2005. Nevertheless, the sites of many points are still not identified nor included in the data bases nowadays. Originally STRUVE arc consisted of 258 main triangles with 265 triangulation points. Currently 34 of the original station points are identified and included in the in the UNESCO World Heritage list. identified original measurement points of the Meridian Arc are located in Sweden (7 points), Norway (15), Finland (83), Russia (1), Estonia (22), Latvia (16), Lithuania (18), Belorussia (28), Ukraine (59) and Moldova (27). In Year 2002 was initiated another large coverage project - European Position Determination System "EUPOS®". Currently there are about 400 continuously operating GNSS (Global Navigation Satellite Systems) stations covering EU countries Estonia, Latvia, Lithuania, Poland, Czech Republic, Slovakia, Hungary, Bulgaria, Romania and East European countries Ukraine and Moldavia. EUPOS® network is a ground based GNSS augmentation system widely used for geodesy, land surveying, geophysics and navigation. It gives the opportunity for fast and accurate position determination never available before. It is an honorable task to use the EUPOS® system for research of the Struve triangulation former sites. Projects with Struve arc can popularize geodesy, geo-information and its meaning in nowadays GIS and GNSS systems. Struve Arc and its points is unique cooperation cross-border object which deserve special attention because of their natural beauty and historical value for mankind. GNSS in geodesy discovers a powerful tool for the verification and validation of the height values of geodetic leveling benchmarks established historically almost 200 years ago. The differential GNSS and RTK methods appear very useful to identify vertical displacement of landscape by means of

  20. Laboratory experiments on arc deflection and instability

    SciTech Connect

    Zweben, S.; Karasik, M.

    2000-03-21

    This article describes experiments on arc deflection instability carried out during the past few years at the Princeton University Plasma Physics Laboratory (PPPL). The approach has been that of plasma physicists interested in arcs, but they believe these results may be useful to engineers who are responsible for controlling arc behavior in large electric steel furnaces.

  1. Magnification Bias in Gravitational Arc Statistics

    SciTech Connect

    Caminha, G. B.; Estrada, J.; Makler, M.

    2013-08-29

    The statistics of gravitational arcs in galaxy clusters is a powerful probe of cluster structure and may provide complementary cosmological constraints. Despite recent progresses, discrepancies still remain among modelling and observations of arc abundance, specially regarding the redshift distribution of strong lensing clusters. Besides, fast "semi-analytic" methods still have to incorporate the success obtained with simulations. In this paper we discuss the contribution of the magnification in gravitational arc statistics. Although lensing conserves surface brightness, the magnification increases the signal-to-noise ratio of the arcs, enhancing their detectability. We present an approach to include this and other observational effects in semi-analytic calculations for arc statistics. The cross section for arc formation ({\\sigma}) is computed through a semi-analytic method based on the ratio of the eigenvalues of the magnification tensor. Using this approach we obtained the scaling of {\\sigma} with respect to the magnification, and other parameters, allowing for a fast computation of the cross section. We apply this method to evaluate the expected number of arcs per cluster using an elliptical Navarro--Frenk--White matter distribution. Our results show that the magnification has a strong effect on the arc abundance, enhancing the fraction of arcs, moving the peak of the arc fraction to higher redshifts, and softening its decrease at high redshifts. We argue that the effect of magnification should be included in arc statistics modelling and that it could help to reconcile arcs statistics predictions with the observational data.

  2. Making Conductive Polymers By Arc Tracking

    NASA Technical Reports Server (NTRS)

    Daech, Alfred F.

    1992-01-01

    Experimental technique for fabrication of electrically conductive polymeric filaments based on arc tracking, in which electrical arc creates conductive carbon track in material that initially was insulator. Electrically conductive polymeric structures made by arc tracking aligned along wire on which formed. Alignment particularly suited to high conductivity and desirable in materials intended for testing as candidate superconductors.

  3. Arc-starting aid for GTA welding

    NASA Technical Reports Server (NTRS)

    Whiffen, E. L.

    1977-01-01

    Three-in-one handtool combining arc-gap gage, electrode tip sander, and electrode projection gate, effectively improves initiation on gas tungsten arc (GTA), automatic skate-welding machines. Device effects ease in polishing electrode tips and setting exactly initial arc gap before each weld pass.

  4. Thermal analysis of an arc heater electrode with a rotating arc foot

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Shepard, Charles E.

    1993-01-01

    A smoothly rotating arc foot and an arc foot that jumps between multiple sticking points were analyzed using analytic formulations and numerical solution procedures. For each case the temperature distribution for a copper electrode was obtained for the plausible range of operating conditions. It is shown that the smoothly rotating arc foot is an extremely safe mode of operation, whereas the jumping arc foot produces excessively high electrode surface temperatures which are not greatly alleviated by increasing the average rotational frequency of the arc foot. It is suggested to eliminate arc-foot rotation and rely on the distribution of fixed electrodes with stationary arc attachment to avoid electrode failure at high current.

  5. Progressive enrichment of arc magmas caused by the subduction of seamounts under Nishinoshima volcano, Izu-Bonin Arc, Japan

    NASA Astrophysics Data System (ADS)

    Sano, Takashi; Shirao, Motomaro; Tani, Kenichiro; Tsutsumi, Yukiyasu; Kiyokawa, Shoichi; Fujii, Toshitsugu

    2016-06-01

    The chemical composition of intraplate seamounts is distinct from normal seafloor material, meaning that the subduction of seamounts at a convergent margin can cause a change in the chemistry of the mantle wedge and associated arc magmas. Nishinoshima, a volcanic island in the Izu-Bonin Arc of Japan, has been erupting continuously over the past 2 years, providing an ideal opportunity to examine the effect of seamount subduction on the chemistry of arc magmas. Our research is based on the whole-rock geochemistry and the chemistry of minerals within lavas and air-fall scoria from Nishinoshima that were erupted before 1702, in 1973-1974, and in 2014. The mineral phases within the analyzed samples crystallized under hydrous conditions (H2O = 3-4 wt.%) at temperatures of 970 °C-990 °C in a shallow (3-6 km depth) magma chamber. Trace element data indicate that the recently erupted Nishinoshima volcanics are much less depleted in the high field strength elements (Nb, Ta, Zr, Hf) than other volcanics within the Izu-Bonin Arc. In addition, the level of enrichment in the Nishinoshima magmas has increased in recent years, probably due to the addition of material from HIMU-enriched (i.e., high Nb/Zr and Ta/Hf) seamounts on the Pacific Plate, which is being subducted westwards beneath the Philippine Sea Plate. This suggests that the chemistry of scoria from Nishinoshima volcano records the progressive addition of components derived from subducted seamounts.

  6. ION PRODUCING MECHANISM (ARC EXTERNAL TO BLOCK)

    DOEpatents

    Brobeck, W.H.

    1958-09-01

    This patent pentains to an ion producing mechanism employed in a calutron which has the decided advantage of an increased amount of ionization effectuated by the arc, and a substantially uniform arc in poiat of time, i arc location and along the arc length. The unique features of the disclosed ion source lie in the specific structural arrangement of the source block, gas ionizing passage, filament shield and filament whereby the arc is established both within the ionizing passage and immediately outside the exit of the ionizing passage at the block face.

  7. A mechanism that triggers double arcing during plasma arc cutting

    NASA Astrophysics Data System (ADS)

    Nemchinsky, Valerian

    2009-10-01

    Double arcing (DA) is a phenomenon when a transferred arc, flowing inside an electrically insulated nozzle, breaks into two separate arcs: one that connects the cathode and the nozzle and another that connects the nozzle and a work-piece. It is a commonly accepted opinion that the reason for DA is high voltage drop in the plasma inside the nozzle. However, the specific mechanism that triggers the DA development is not clear. In this paper, we propose such a mechanism. Dielectric films deposited inside the nozzle's orifice play the key role in this mechanism. These films are charged by ion current from plasma. A strong electric field is created inside the film and at the boundary of the film and clean metal of the nozzle. This gives rise to a thermo-field electron emission from the clean metal that borders the film. Emitted electrons are accelerated at the voltage drop between the nozzle and plasma. These electrons produce extra ions, which in turn move back to the film and additionally charge it. This sequence of events leads to explosive instability if the voltage drop inside the nozzle is high enough. Experiments to check the proposed mechanism are suggested.

  8. The Molucca Sea revisited: Evolution of an arc-arc collision

    SciTech Connect

    Milsom, J. )

    1991-03-01

    The Molucca Sea is the site of the collision between the opposed Sangihe and Halmahera arcs and is floored by the coalesced accretionary wedges to the two subduction zones. In the north, the sea is bounded by the southern islands of the Philippine Archipelago, while in the south it abuts on the Sula Spur Continental Fragment. Free air and Bouguer anomaly values in its central part are among the lowest recorded offshore anywhere on the globe and provide severe constraints on structural and evolutionary models for the area. Further constraints are provided by the patterns of regional seismicity, which show earthquakes to be virtually confined to the two Benioff zones. Recently obtained geological data from the Halmahera Arc, together with results from the 1988 cruise of the RRS Charles Darwin and reflection seismic data from the southern part of the sea allow refinements to be made to previous interpretations. An understanding of the area is of importance from an exploration point of view because the Mesozoic sediments of the Sula Spur, which are believed to have been laid down at the margin of Gondwanaland, are generally considered to have hydrocarbon potential.

  9. Ultransonic velocity measurements in sheared granular layers: Implications for the evolution of dynamic elastic moduli of compositionally-diverse cataclastic fault gouges

    NASA Astrophysics Data System (ADS)

    Knuth, Matthew William

    The objective of this project was to investigate the mechanical and elastic evolution of laboratory fault gouge analogs during active shear. To do this, I designed, constructed, and implemented a new technique for measuring changes in the elastic properties of granular layers subjected to shear deformation. Granular layers serve as an experimental analog to gouge layers forming in cataclastic faults. The technique combines a double-direct shear configuration with a method of determining ultrasonic elastic compressional and shear wavespeed. Experimental results are divided into chapters based on application to fundamental mechanics or to field cases. The first set of experiments allowed us to develop the technique and apply it to a range of end- member materials including quartz sands, montmorillonite clays, and mixtures of sand and clay. Emphasis is placed on normal stress unload-reload cycles and the resulting behavior as clay content is varied within the layer. We observe consistent decrease in wavespeed with shear for sand, and nonlinear but increasing wavespeed for clay and the sand/clay mixture. The second set of experiments involves the application of this technique to measurements conducted under fluid saturation and controlled pressure conditions, examining the behavior of materials from the Nankai Trough Accretionary Prism under shear. I introduce the effects of variable displacement rate and hold time, with implications for fault stability and rate-and-state frictional sliding. The experiments demonstrate a consistent inverse relationship between sliding velocity and wavespeed, and an increase in wavespeed associated with holds. The third set of experiments deals with velocity through stick-slipping glass beads, which has implications for fundamental granular mechanics questions involving velocity-weakening materials. I find that wavespeed decreases in the time between events and increases at "slips", suggesting a strong control related to changes in

  10. Destruction of hazardous military wastes using plasma arc technology

    SciTech Connect

    Kanaras, L.; Qazi, M.

    1996-12-31

    A Plasma Arc Technology (PAT) system treats hazardous wastes in a furnace, at temperatures of 2,000 C, or higher, using a plasma torch. The organic components vaporize, decompose or oxidize. The off-gases consist of hydrogen, carbon monoxide, carbon dioxide and nitric oxides. A wet air scrubber is used to remove most of these gases. The scrubber water is treated and recycled. Metal-bearing solids are melted or vaporized. The solids are usually recovered as molten metal, or as non-leachable vitrified slag, suitable for disposal in a landfill. A Plasma Arc Centrifugal Treatment system was used to evaluate this technology for destruction of four military hazardous wastes: sludge from Longhorn Army Ammunition Plant, TX; blast media from Letterkenny Army Depot, PA; medical incineration ash from Aberdeen Proving Ground, MD; and contaminated soil from open burning/open detonation ground at Picatinny Arsenal, NJ.

  11. Filters for cathodic arc plasmas

    DOEpatents

    Anders, Andre; MacGill, Robert A.; Bilek, Marcela M. M.; Brown, Ian G.

    2002-01-01

    Cathodic arc plasmas are contaminated with macroparticles. A variety of magnetic plasma filters has been used with various success in removing the macroparticles from the plasma. An open-architecture, bent solenoid filter, with additional field coils at the filter entrance and exit, improves macroparticle filtering. In particular, a double-bent filter that is twisted out of plane forms a very compact and efficient filter. The coil turns further have a flat cross-section to promote macroparticle reflection out of the filter volume. An output conditioning system formed of an expander coil, a straightener coil, and a homogenizer, may be used with the magnetic filter for expanding the filtered plasma beam to cover a larger area of the target. A cathodic arc plasma deposition system using this filter can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.

  12. Prediction of the cathodic arc root behaviour in a hollow cathode thermal plasma torch

    NASA Astrophysics Data System (ADS)

    Freton, Pierre; Gonzalez, Jean-Jacques; Escalier, Gaelle

    2009-10-01

    The upper part of a well type cathode (WTC) plasma torch is modelled for several conditions in an air medium in the presence of an electric arc. The plasma flow created by the electric arc is described and the results compared with the data from the literature. Special attention is paid to the description of arc root attachment and to its movement due to the balance of forces. A fine description of the magnetic field produced by the external solenoid is reported. The model is based on the @Fluent software implemented with specific developments to be adapted to the thermal plasma domain. The paper shows the necessity to provide an accurate description of the external magnetic field due to the strong influence of the radial magnetic field component. Overall, we propose an original approach for arc root movement description which contributes to the understanding of the flow behaviour in the WTC torch.

  13. The SOAR Gravitational Arc Survey

    NASA Astrophysics Data System (ADS)

    Makler, M.; Furlanetto, C.; Santiago, B. X.; Caminha, G. B.; Cypriano, E.; Cibirka, N.; Pereira, M. E. S.; Bom, C. R. D.; Lima, M. P.; Brandt, C. H.; Neto, A. F.; Estrada, J.; Lin, H.; Hao, J.; McKay, T. M.; da Costa, L. N.; Maia, M. A. G.

    2014-10-01

    We present the first results of the SOAR Gravitational Arc Survey (SOGRAS). The survey imaged 47 clusters in two redshift intervals centered at z=0.27 and z=0.55, targeting the richest clusters in each interval. Images were obtained in the g', r' and i' bands with a median seeing of 0.83, 0.76 and 0.71 arcsec, respectively, in these filters. Most of the survey clusters are located within the Sloan Digital Sky Survey (SDSS) Stripe-82 region and all of them are in the SDSS footprint. We present the first results of the survey, including the 6 best strong lensing systems, photometric and morphometric catalogs of the galaxy sample, and cross matches of the clusters and galaxies with complementary samples (spectroscopic redshifts, photometry in several bands, X-ray and Sunyaev Zel'dovich clusters, etc.), exploiting the synergy with other surveys in Stripe-82. We apply several methods to characterize the gravitational arc candidates, including the Mediatrix method (Bom et al. 2012) and ArcFitting (Furlanetto et al. 2012), and for the subtraction of galaxy cluster light. Finally, we apply strong lensing inversion techniques to the best systems, providing constraints on their mass distribution. The analyses of a spectral follow-up with Gemini and the derived dynamical masses are presented in a poster submitted to this same meeting (Cibirka et al.). Deeper follow-up images with Gemini strengthen the case for the strong lensing nature of the candidates found in this survey.

  14. Tracing crustal and slab contributions to arc magmatism in the Lesser Antilles island arc using helium and carbon relationships in geothermal fluids

    SciTech Connect

    Soest, M.C. van; Hilton, D.R. |; Kreulen, R.

    1998-10-01

    The authors report helium and carbon isotope and CO{sub 2}/{sup 3}He ratios from a regional survey of geothermal fluids from the Lesser Antilles island arc, an arc system where there is compelling geochemical evidence for the superimposition of a crustal component onto mantle-derived magmas. A predominant mantle helium isotope signature is observed throughout the arc. The highest ratios coincide with MORB helium ({approximately}8R{sub A} where R{sub A} = air {sup 3}He/{sup 4}He) and occur towards the center of the arc (the islands of Martinique, Dominica, Guadeloupe, and Montserrat). In the south and north of the arc (Grenada, St. Vincent, St. Lucia in the south and Nevis and Saba in the north) {sup 3}He/{sup 4}He ratios are lower and lie between 4.9 and 6.8R{sub A}. This regional variation is also apparent in the carbon isotope systematics: the central portion of the arc (Martinique to Montserrat) have {delta}{sup 13}C(CO{sub 2}) values between {minus}2{per_thousand} and {minus}4{per_thousand} (vs PDB), heavier than the range observed in MORB ({minus}4 to {minus}9{per_thousand}). The south of the arc (Grenada to St. Lucia) is characterized by MORB-like carbon isotope ratios (centered on {minus}6{per_thousand}). CO{sub 2}/{sup 3}He ratios are significantly higher than the MORB value ({approximately}2 {times} 10{sup 9}) for the entire arc. The values in the central islands fall close to 10{sup 10} whereas the southern volcanoes have higher ratios between 10{sup 10}--10{sup 13}.

  15. Review of switching arcs and plasma chemistry

    NASA Astrophysics Data System (ADS)

    Benenson, D. M.; Gilmour, A. S., Jr.; Dollinger, R. E.; Nagamatsu, H. T.; Pfender, E.; Warder, R. C., Jr.

    1980-05-01

    Physical processes in switching arcs are considered in such applications as circuit interruption (in high pressure, high voltage gas blast circuit breakers and vacuum arc interrupters), fault current limiting (principally through vacuum arc devices), and pulse power systems (using vacuum arcs). The physics of arc heaters, associated with processes in the anode region, are described. Analytical models of (1) the current zero region and interrupter performance of gas blast interrupters and (2) the heat transfer mechanisms in the anode region of arc heaters, are discussed. Selected diagnostic techniques are presented. Applications of plasma chemistry involving the high pressure, equilibrium (thermal) plasma are noted. Low pressure (nonequilibrium) plasma processing is described through mechanisms associated with coating, deposition, and etching applications.

  16. ARC length control for plasma welding

    NASA Technical Reports Server (NTRS)

    Iceland, William F. (Inventor)

    1988-01-01

    A control system to be used with a plasma arc welding apparatus is disclosed. The plasma arc welding apparatus includes a plasma arc power supply, a contactor, and an electrode assembly for moving the electrode relative to a work piece. The electrode assembly is raised or lowered by a drive motor. The present apparatus includes a plasma arc adapter connected across the power supply to measure the voltage across the plasma arc. The plasma arc adapter forms a dc output signal input to a differential amplifier. A second input is defined by an adjustable resistor connected to a dc voltage supply to permit operator control. The differential amplifier forms an output difference signal provided to an adder circuit. The adder circuit then connects with a power amplifier which forms the driving signal for the motor. In addition, the motor connects to a tachometor which forms a feedback signal delivered to the adder to provide damping, therby avoiding servo loop overshoot.

  17. Plasma arc torch with coaxial wire feed

    DOEpatents

    Hooper, Frederick M

    2002-01-01

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

  18. Water in Aleutian Arc Volcanoes

    NASA Astrophysics Data System (ADS)

    Plank, T.; Zimmer, M. M.; Hauri, E. H.

    2011-12-01

    In the past decade, baseline data have been obtained on pre-eruptive water contents for several volcanic arcs worldwide. One surprising observation is that parental magmas contain ~ 4 wt% H2O on average at each arc worldwide [1]. Within each arc, the variation from volcano to volcano is from 2 to 6 w% H2O, with few exceptions. The similar averages at different arcs are unexpected given the order of magnitude variations in the concentration of other slab tracers. H2O is clearly different from other tracers, however, being both a major driver of melting in the mantle and a major control of buoyancy and viscosity in the crust. Some process, such as mantle melting or crustal storage, apparently modulates the water content of mafic magmas at arcs. Mantle melting may deliver a fairly uniform product to the Moho, if the wet melt process includes a negative feedback. On the other hand, magmas with variable water content may be generated in the mantle, but a crustal filter may lead to magma degassing up to a common mid-to-upper crustal storage region. Testing between these two end-member scenarios is critical to our understanding of subduction dehydration, global water budgets, magmatic plumbing systems, melt generation and eruptive potential. The Alaska-Aleutian arc is a prime location to explore this fundamental problem in the subduction water cycle, because active volcanoes vary more than elsewhere in the world in parental H2O contents (based on least-degassed, mafic melt inclusions hosted primarily in olivine). For example, Shishaldin volcano taps magma with among the lowest H2O contents globally (~ 2 wt%) and records low pressure crystal fractionation [2], consistent with a shallow magma system (< 1 km bsl). At the other extreme, Augustine volcano is fed by a mafic parent that contains among the highest H2O globally (~ 7 wt%), and has evolved by deep crystal fractionation [2], consistent with a deep magma system (~ 14 km bsl). Do these magmas stall at different depths

  19. Nomenclature of SLC Arc beamline components

    SciTech Connect

    Silva, J.; Weng, W.T.

    1986-04-10

    This note defines I and C formal names for beamline components in the Arc as specified in the TRANSPORT decks ARCN FINAL and ARCS FINAL of June 5, 1985. The formal name consists of three fields: the primary name, the zone and the unit number. The general principles and guidelines are explained in Reference 1. The rationale and the final resolutions of the naming conventions for the Arc are explained.

  20. Overvoltage protector using varistor initiated arc

    DOEpatents

    Brainard, John P.

    1982-01-01

    Coaxial conductors are protected against electrical overvoltage by at least one element of non-electroded varistor material that adjoins each other varistor element and conductor with which it contacts. With this construction, overvoltage current initiated through the varistor material arcs at the point contacts between varistor elements and, as the current increases, the arcs increase until they become a continuous arc between conductors, bypassing the varistor material.

  1. Magnetic-cusp, cathodic-arc source

    DOEpatents

    Falabella, Steven

    1995-01-01

    A magnetic-cusp for a cathodic-arc source wherein the arc is confined to the desired cathode surface, provides a current path for electrons from the cathode to the anode, and utilizes electric and magnetic fields to guide ions from the cathode to a point of use, such as substrates to be coated. The magnetic-cusp insures arc stability by an easy magnetic path from anode to cathode, while the straight-through arrangement leads to high ion transmission.

  2. Miniaturized cathodic arc plasma source

    DOEpatents

    Anders, Andre; MacGill, Robert A.

    2003-04-15

    A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about 1/4 inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism. The movable cathode rod is housed in a cooled metal shield or tube which serves as both a current conductor, thus reducing ohmic heat produced in the cathode, and as the heat sink for heat generated at or near the cathode. Cooling of the cathode housing tube is done by contact with coolant at a place remote from the active cathode surface. The source is operated in pulsed mode at relatively high currents, about 1 kA. The high arc current can also be used to operate the magnetic filter. A cathodic arc plasma deposition system using this source can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.

  3. Arc Synthesis of Fullerenes from the Carbide of Waste Cloths

    NASA Astrophysics Data System (ADS)

    Hayashi, Koichiro; Mieno, Tetsu

    2000-09-01

    A great many scraps of cotton cloth are disposed of as industrial waste through making clothes. The purpose of this study is to transform the waste into very valuable carbon compounds, that is, fullerenes. The scraps were piled and carbonized in air at 1050°C. By carbonization, the weight of the scraps decreased to 16-18%. Carbide from the scraps was used as the raw material for synthesizing fullerenes with the \\mbi{J}×\\mbi{B} arc discharge method. The soot that was deposited on the inside of the vacuum chamber contained C60 (>0.05 wt%), C70 and higher fullerenes.

  4. Eastern Aleutian volcanic arc digital model - version 1.0

    USGS Publications Warehouse

    Saltus, R.W.; Barnett, Adrienne

    2000-01-01

    A 3-dimensional model (Figure 1) of the interaction of oceanic and continental tectonic plates along the eastern portion of the Aleutian volcanic arc helps in the visualization of basic tectonic, geodetic, and geophysical data in this active plate boundary region. The model is constrained by topographic, bathymetric, and seismic data and by the principle of isostasy. Examination of free-air gravity anomalies over the region indicates where the flexural strength of the down-going oceanic slab disturbs local isostatic balance and where low-density sediments have accumulated in the trench and forearc regions.

  5. Lightning Induced Arcing an LDRD Report

    SciTech Connect

    JORGENSON,ROY E.; WARNE,LARRY K.; KUNHARDT,ERICH E.

    2000-12-01

    The purpose of this research was to develop a science-based understanding of the early-time behavior of electric surface arcing in air at atmospheric pressure. As a first step towards accomplishing this, we used a kinetic approach to model an electron swarm as it evolved in a neutral gas under the influence of an applied electric field. A computer code was written in which pseudo-particles, each representing some number of electrons, were accelerated by an electric field. The electric field due to the charged particles was calculated efficiently using a tree algorithm. Collision of the electrons with the background gas led to the creation of new particles through the processes of ionization and photoionization. These processes were accounted for using measured cross-section data and Monte Carlo methods. A dielectric half-space was modeled by imaging the charges in its surface. Secondary electron emission from the surface, resulting in surface charging, was also calculated. Simulation results show the characteristics of a streamer in three dimensions. A numerical instability was encountered before the streamer matured to form branching.

  6. Plasma arc melting of zirconium

    SciTech Connect

    Tubesing, P.K.; Korzekwa, D.R.; Dunn, P.S.

    1997-12-31

    Zirconium, like some other refractory metals, has an undesirable sensitivity to interstitials such as oxygen. Traditionally, zirconium is processed by electron beam melting to maintain minimum interstitial contamination. Electron beam melted zirconium, however, does not respond positively to mechanical processing due to its large grain size. The authors undertook a study to determine if plasma arc melting (PAM) technology could be utilized to maintain low interstitial concentrations and improve the response of zirconium to subsequent mechanical processing. The PAM process enabled them to control and maintain low interstitial levels of oxygen and carbon, produce a more favorable grain structure, and with supplementary off-gassing, improve the response to mechanical forming.

  7. The Abundance of Large Arcs From CLASH

    NASA Astrophysics Data System (ADS)

    Xu, Bingxiao; Postman, Marc; Meneghetti, Massimo; Coe, Dan A.; Clash Team

    2015-01-01

    We have developed an automated arc-finding algorithm to perform a rigorous comparison of the observed and simulated abundance of large lensed background galaxies (a.k.a arcs). We use images from the CLASH program to derive our observed arc abundance. Simulated CLASH images are created by performing ray tracing through mock clusters generated by the N-body simulation calibrated tool -- MOKA, and N-body/hydrodynamic simulations -- MUSIC, over the same mass and redshift range as the CLASH X-ray selected sample. We derive a lensing efficiency of 15 ± 3 arcs per cluster for the X-ray selected CLASH sample and 4 ± 2 arcs per cluster for the simulated sample. The marginally significant difference (3.0 σ) between the results for the observations and the simulations can be explained by the systematically smaller area with magnification larger than 3 (by a factor of ˜4) in both MOKA and MUSIC mass models relative to those derived from the CLASH data. Accounting for this difference brings the observed and simulated arc statistics into full agreement. We find that the source redshift distribution does not have big impact on the arc abundance but the arc abundance is very sensitive to the concentration of the dark matter halos. Our results suggest that the solution to the "arc statistics problem" lies primarily in matching the cluster dark matter distribution.

  8. Atmospheric spreading of protons in auroral arcs

    NASA Technical Reports Server (NTRS)

    Iglesias, G. E.; Vondrak, R. R.

    1974-01-01

    A model is developed to calculate the effect of atmospheric spreading on the flux and angular distribution of protons in homogeneous auroral arcs. An expression is derived that indicates the angular distribution in the atmosphere as a function of distance from arc center, neutral scale height, arc width, and initial angular distribution. The results of the model agree favorably with those based on Monte-Carlo calculations. From these results the enhancement factors needed to compute the original proton current above the atmosphere are obtained. A technique is indicated for determining the incident angular distribution from rocket-based measurements of the arc width and angular distribution.

  9. Automatic Control Of Length Of Welding Arc

    NASA Technical Reports Server (NTRS)

    Iceland, William F.

    1991-01-01

    Nonlinear relationships among current, voltage, and length stored in electronic memory. Conceptual microprocessor-based control subsystem maintains constant length of welding arc in gas/tungsten arc-welding system, even when welding current varied. Uses feedback of current and voltage from welding arc. Directs motor to set position of torch according to previously measured relationships among current, voltage, and length of arc. Signal paths marked "calibration" or "welding" used during those processes only. Other signal paths used during both processes. Control subsystem added to existing manual or automatic welding system equipped with automatic voltage control.

  10. Metals purification by improved vacuum arc remelting

    DOEpatents

    Zanner, Frank J.; Williamson, Rodney L.; Smith, Mark F.

    1994-12-13

    The invention relates to improved apparatuses and methods for remelting metal alloys in furnaces, particularly consumable electrode vacuum arc furnaces. Excited reactive gas is injected into a stationary furnace arc zone, thus accelerating the reduction reactions which purify the metal being melted. Additionally, a cooled condensation surface is disposed within the furnace to reduce the partial pressure of water in the furnace, which also fosters the reduction reactions which result in a purer produced ingot. Methods and means are provided for maintaining the stationary arc zone, thereby reducing the opportunity for contaminants evaporated from the arc zone to be reintroduced into the produced ingot.

  11. Unstable behavior of anodic arc discharge for synthesis of nanomaterials

    DOE PAGES

    Gershman, Sophia; Raitses, Yevgeny

    2016-07-27

    A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

  12. Unstable behavior of anodic arc discharge for synthesis of nanomaterials

    SciTech Connect

    Gershman, Sophia; Raitses, Yevgeny

    2016-07-27

    A short carbon arc operating with a high ablation rate of the graphite anode exhibits a combined motion of the arc and the arc attachment to the anode. A characteristic time scale of this motion is in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. Thermal processes in the arc plasma region interacting with the ablating anode are considered as possible causes of this unstable arc behavior. It is also hypothesized that the arc motion could potentially cause mixing of the various nanoparticles synthesized in the arc in the high ablation regime.

  13. Tracing crustal and slab contributions to arc magmatism in the lesser antilles island arc using helium and carbon relationships in geothermal fluids

    NASA Astrophysics Data System (ADS)

    van Soest, M. C.; Hilton, D. R.; Kreulen, R.

    1998-10-01

    We report helium and carbon isotope and CO 2/ 3He ratios from a regional survey of geothermal fluids from the Lesser Antilles island arc, an arc system where there is compelling geochemical evidence for the superimposition of a crustal component onto mantle-derived magmas. A predominant mantle helium isotope signature is observed throughout the arc. The highest ratios coincide with MORB helium (˜8R A where R A = air 3He/ 4He) and occur towards the centre of the arc (the islands of Martinique, Dominica, Guadeloupe, and Montserrat). In the south and north of the arc (Grenada, St. Vincent, St. Lucia in the south and Nevis and Saba in the north) 3He/ 4He ratios are lower and lie between 4.9 and 6.8R A. This regional variation is also apparent in the carbon isotope systematics: the central portion of the arc (Martinique to Montserrat) have δ 13C(CO 2) values between -2‰ and -4‰ (vs. PDB), heavier than the range observed in MORB (-4 to -9‰). The south of the arc (Grenada to St.Lucia) is characterized by MORB-like carbon isotope ratios (centred on -6‰). CO 2/ 3He ratios are significantly higher than the MORB value (˜2 × 10 9) for the entire arc. The values in the central islands fall close to 10 10 whereas the southern volcanoes have higher ratios between 10 10-10 13. Assuming the Lesser Antilles mantle wedge has a MORB-like helium and carbon composition our data can be explained by mixing of mantle wedge carbon with at least two other carbon components: an isotopically-heavy marine limestone endmember of slab-derivation and an isotopically-lighter component representing either slab-derived organic carbon and/or an upper crustal component with a large fraction of organic carbon. The helium-carbon systematics of the central portion of the arc are consistent with a large slab-derived marine limestone input to the carbon inventory, and we calculate a non-mantle:mantle carbon flux of 5.7:1. MORB-like helium isotope ratios, which are sensitive to perturbation by

  14. Apollo’s Warriors: United States Air Force Special Operations during the Cold War

    DTIC Science & Technology

    1997-01-01

    nation for controlling and exploiting the air and space environment. We are the nation’s Air Force—the only service that pro- vides air and space power...groups, the four ARC units performed a number of national -level, clandestine, and covert operations behind the Iron Curtain. Backing up this small force...four states activated their own Air National Guard ARC units as a ready reserve force to support special operations. The role of USAF special

  15. Quantum Oscillations from Fermi Arcs

    NASA Astrophysics Data System (ADS)

    Pereg-Barnea, Tamar; Refael, Gil; Franz, Marcel; Weber, Heidi; Seradjeh, Babak

    2009-03-01

    Recent experiments[1] in a variety of High Tc superconductors revel 1/B oscillations in the vortex-liquid state. The period of oscillations in underdoped samples is short and can be translated, via the Onsager relation to an area in k-space which makes up a few percents of the Brillouin zone. Quantum oscillations are usually thought of as arising from closed orbits in momentum space along the Fermi surface and are used to measure the Fermi vector. Thus, the observation of quantum oscillations in the cuprates seems to be at odds with the observation of Fermi arcs in ARPES experiments[2] due to their fragmented Fermi surface topology. In this talk we show that quantum oscillations can arise from a partially gapped Fermi surface. We adopt a phenomenological model of arcs which terminate at a regime with a superconducting gap of d-wave symmetry to describe the pseudo gap phase. Without invoking any additional order, quantization of energy is found well below the gap maximum. Semiclassically the quantization condition arises from closed orbits in real-space. When translated to momentum space, the area enclosed by the orbits is much smaller than that of the full Fermi surface. [1]N. Doiron-Leyaraud et al. nature 447, 565 (2007) [2]Kanigel et al. Nature Physics 2 447 (2006)

  16. Measurement of Velocity Induced by a Propagating Arc Magnetohydrodynamic Plasma Actuator

    NASA Astrophysics Data System (ADS)

    Choi, Young Joon; Gray, Miles; Sirohi, Jayant; Raja, Laxminarayan

    2016-09-01

    Plasma actuators can substantially improve the maneuverability and efficiency of aerial vehicles. These solid state devices have low mass, small volume, and high bandwidth that make them excellent alternatives to conventional mechanical actuators. In particular, a Rail Plasma Actuator (RailPAc) has the potential to delay flow separation on an aerodynamic surface by generating a large body force. A RailPAc consists of parallel rails and an electrical arc that propagates along the rails with a self-induced Lorentz force. The motion of the arc transfers momentum to the surrounding neutral air. A study was conducted to understand how the motion and shape of a propagating arc couples with the fluid momentum. In particular, we used Particle Imaging Velocimetry (PIV) and seedless PIV based on Background Oriented Schlieren (BOS) technique to measure the induced velocity of a propagating arc in one atmosphere. Results obtained provide insight into how the flow field responds to the passage of a RailPAc electrical arc. A complete description of the RailPAc actuation mechanism can be obtained if the fluid momentum measurements from PIV and seedless PIV are compared to the transit characteristics of an arc. US ARL Grant W911NF1410226.

  17. Physicochemical processes of frictional healing: Effects of water on stick-slip stress drop and friction of granular fault gouge

    NASA Astrophysics Data System (ADS)

    Scuderi, Marco M.; Carpenter, Brett M.; Marone, Chris

    2014-05-01

    Understanding the micromechanical processes that dictate the evolution of fault strength during the seismic cycle is a fundamental problem in earthquake physics. We report on laboratory experiments that investigate the role of water during repetitive stick-slip frictional sliding, with particular emphasis on the grain-scale and atomic-scale mechanisms of frictional restrengthening (healing). Our experiments are designed to test underlying concepts of rate and state friction laws. We sheared layers of soda-lime glass beads in a double direct shear configuration at a constant normal stress of 5 MPa. Shear stress was applied via a constant displacement rate from 0.3 to 300 µm/s. During each experiment, relative air humidity (RH) was kept constant at values of 5, 50, or 100%. Our data show a systematic increase in maximum friction (μmax), stick-slip friction drop (Δμ), and frictional healing rate, with increasing RH. The highest values of interevent dilation occur at 100% RH. Postexperiment scanning electron microscope observations reveal details of contact junction processes, showing a larger grain-to-grain contact area at higher RH. We find that the evolution of contact area depends inversely on slip velocity and directly on RH. Our results illuminate the fundamental processes that dictate stick-slip frictional sliding and provide important constraints on the mechanisms of rate and state friction.

  18. Arc-heated gas flow experiments for hypersonic propulsion applications

    NASA Astrophysics Data System (ADS)

    Roseberry, Christopher Matthew

    Although hydrogen is an attractive fuel for a hypersonic air-breathing vehicle in terms of reaction rate, flame temperature, and energy content per unit mass, the substantial tank volume required to store hydrogen imposes a drag penalty to performance that tends to offset these advantages. An alternative approach is to carry a hydrocarbon fuel and convert it on-board into a hydrogen-rich gas mixture to be injected into the engine combustors. To investigate this approach, the UTA Arc-Heated Wind Tunnel facility was modified to run on methane rather than the normally used nitrogen. Previously, this facility was extensively developed for the purpose of eventually performing experiments simulating scramjet engine flow along a single expansion ramp nozzle (SERN) in addition to more generalized applications. This formidable development process, which involved modifications to every existing subsystem along with the incorporation of new subsystems, is described in detail. Fortunately, only a minor plumbing reconfiguration was required to prepare the facility for the fuel reformation research. After a failure of the arc heater power supply, a 5.6 kW plasma-cutting torch was modified in order to continue the arc pyrolysis experiments. The outlet gas flow from the plasma torch was sampled and subsequently analyzed using gas chromatography. The experimental apparatus converted the methane feedstock almost completely into carbon, hydrogen and acetylene. A high yield of hydrogen, consisting of a product mole fraction of roughly 0.7, was consistently obtained. Unfortunately, the energy consumption of the apparatus was too excessive to be feasible for a flight vehicle. However, other researchers have pyrolyzed hydrocarbons using electric arcs with much less power input per unit mass.

  19. Fixing the Mobility Air Forces New Way

    DTIC Science & Technology

    2013-03-01

    the ARC normally has a 1:5 Mobilization to Dwell ( M2D ). In order to understand what this new way changed and why it is important, it is necessary to... M2D . In measurements of AC and ARC workloads, a trend of decreasing ratios means the aircrew workload is increasing. When the AC ratio decreases...to properly convert the ARC 1:5 M2D to an accurate D2D ratio in order to use a common measure of workloads.15 According to the Air Force Reserve

  20. Fault gouge evolution during rupture and healing: Continual active-seismic observations across laboratory-scale fault zones

    NASA Astrophysics Data System (ADS)

    Krysta, M.; Kusmierczyk-Michulec, J.; Nikkinen, M.; Carter, J. A.

    2011-12-01

    In order to support its mission of monitoring compliance with the treaty banning nuclear explosions, the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) operates four global networks of, respectively, seismic, infrasound, hydroacoustic sensors and air samplers accompanied with radionuclide detectors. The role of the International Data Centre (IDC) of CTBTO is to associate the signals detected in the monitoring networks with the physical phenomena which emitted these signals, by forming events. One of the aspects of associating detections with emitters is the problem of inferring the sources of radionuclides from the detections made at CTBTO radionuclide network stations. This task is particularly challenging because the average transport distance between a release point and detectors is large. Complex processes of turbulent diffusion are responsible for efficient mixing and consequently for decreasing the information content of detections with an increasing distance from the source. The problem is generally addressed in a two-step process. In the first step, an atmospheric transport model establishes a link between the detections and the regions of possible source location. In the second step this link is inverted to infer source information from the detections. In this presentation, we will discuss enhancements of the presently used regression-based inversion algorithm to reconstruct a source of radionuclides. To this aim, modern inversion algorithms accounting for prior information and appropriately regularizing an under-determined reconstruction problem will be briefly introduced. Emphasis will be on the CTBTO context and the choice of inversion methods. An illustration of the first tests will be provided using a framework of twin experiments, i.e. fictitious detections in the CTBTO radionuclide network generated with an atmospheric transport model.

  1. Non-equilibrium modelling of transferred arcs

    NASA Astrophysics Data System (ADS)

    Haidar, J.

    1999-02-01

    A two-temperature, variable-density, arc model has been developed for description of high-current free-burning arcs, including departures from thermodynamic and chemical equilibrium in the plasma. The treatment includes the arc, the anode and the cathode and considers the separate energy balance of the electrons and the heavy particles, together with the continuity equations for these species throughout the plasma. The output includes a two-dimensional distribution for the temperatures and densities both of the electrons and of the heavy particles, plasma velocity, current density and electrical potential throughout the arc. For a 200 A arc in pure argon at 1 atm, we calculate large differences between the temperatures of the electrons and the heavy particles in the plasma region near the cathode tip, together with large departures from local chemical plasma equilibrium. In the main body of the arc at high plasma temperatures, we predict minor differences between the temperatures of the electrons and the heavy particles, which are inconsistent with recent measurements using laser-scattering techniques showing differences of up to several thousand degrees. However, we find that, for the region in front of the cathode tip, the ground-state level of the neutral atoms is overpopulated relative to the corresponding populations under conditions of LTE, in agreement with experimental observations. These departures from LTE are caused by the injection of a large mass flow of cold gas into the arc core due to arc constriction at the tip of the cathode.

  2. Risk assessment of metal vapor arcing

    NASA Technical Reports Server (NTRS)

    Hill, Monika C. (Inventor); Leidecker, Henning W. (Inventor)

    2009-01-01

    A method for assessing metal vapor arcing risk for a component is provided. The method comprises acquiring a current variable value associated with an operation of the component; comparing the current variable value with a threshold value for the variable; evaluating compared variable data to determine the metal vapor arcing risk in the component; and generating a risk assessment status for the component.

  3. Preventing Arc Welding From Damaging Electronics

    NASA Technical Reports Server (NTRS)

    Sargent, Noel; Mareen, D.

    1988-01-01

    Shielding technique developed to protect sensitive electronic equipment from damage due to electromagnetic disturbances produced by arc welding. Established acceptable alternative in instances in which electronic equipment cannot be removed prior to arc welding. Guidelines established for open, unshielded welds. Procedure applicable to robotics or computer-aided manufacturing.

  4. Feature extraction of arc tracking phenomenon

    NASA Technical Reports Server (NTRS)

    Attia, John Okyere

    1995-01-01

    This document outlines arc tracking signals -- both the data acquisition and signal processing. The objective is to obtain the salient features of the arc tracking phenomenon. As part of the signal processing, the power spectral density is obtained and used in a MATLAB program.

  5. Purification of tantalum by plasma arc melting

    DOEpatents

    Dunn, Paul S.; Korzekwa, Deniece R.

    1999-01-01

    Purification of tantalum by plasma arc melting. The level of oxygen and carbon impurities in tantalum was reduced by plasma arc melting the tantalum using a flowing plasma gas generated from a gas mixture of helium and hydrogen. The flowing plasma gases of the present invention were found to be superior to other known flowing plasma gases used for this purpose.

  6. Steady rotation of the Cascade arc

    USGS Publications Warehouse

    Wells, Ray E.; McCaffrey, Robert

    2013-01-01

    Displacement of the Miocene Cascade volcanic arc (northwestern North America) from the active arc is in the same sense and at nearly the same rate as the present clockwise block motions calculated from GPS velocities in a North American reference frame. Migration of the ancestral arc over the past 16 m.y. can be explained by clockwise rotation of upper-plate blocks at 1.0°/m.y. over a linear melting source moving westward 1–4.5 km/m.y. due to slab rollback. Block motion and slab rollback are in opposite directions in the northern arc, but both are westerly in the southern extensional arc, where rollback may be enhanced by proximity to the edge of the Juan de Fuca slab. Similarities between post–16 Ma arc migration, paleomagnetic rotation, and modern GPS block motions indicate that the secular block motions from decadal GPS can be used to calculate long-term strain rates and earthquake hazards. Northwest-directed Basin and Range extension of 140 km is predicted behind the southern arc since 16 Ma, and 70 km of shortening is predicted in the northern arc. The GPS rotation poles overlie a high-velocity slab of the Siletzia terrane dangling into the mantle beneath Idaho (United States), which may provide an anchor for the rotations.

  7. Orbital evolution of Neptune's ring arcs

    NASA Astrophysics Data System (ADS)

    Giuliatti-Winter, Silvia; Madeira, Gustavo

    2016-10-01

    Voyager 2 spacecraft sent several images of the Neptune's ring system in 1989. These images show a set of arcs (Courage, Liberté, Egalité and Fraternité), previously detected by stellar occultation in 1984, embedded in the tenuous Adams ring. In order to maintain the confinement of the arcs against the spreading, Renner et al. (2015) proposeda model which the Adams ring has a collection of small coorbital satellites placed in specific positions. These coorbitals would be responsible for maintaining the arcs particles. In this work we analyse the orbital evolution of the particles coorbital to the satellites by adding the effects of the solar radiation force. Our numerical results show that due to this dissipative effect the smallest particles, 1μm in size, leave the arc in less than 10years. Larger particles leave the arc, but can stay confined between the coorbital satellites. De Pater et al. (2005) suggested that a small moonlet embedded in the arc Fraternité can be the source of the arcs and even theAdams ring through an erosion mechanism. Our preliminary results showed that a moonlet up to 200m in radius can stay in the arc without causing any significant variation in the eccentricities of the coorbitals and the particles.

  8. Crustal structure of the Kermadec arc from MANGO seismic refraction profiles

    NASA Astrophysics Data System (ADS)

    Bassett, Dan; Kopp, Heidrun; Sutherland, Rupert; Henrys, Stuart; Watts, Anthony B.; Timm, Christian; Scherwath, Martin; Grevemeyer, Ingo; Ronde, Cornel E. J.

    2016-10-01

    Three active-source seismic refraction profiles are integrated with morphological and potential field data to place the first regional constraints on the structure of the Kermadec subduction zone. These observations are used to test contrasting tectonic models for an along-strike transition in margin structure previously known as the 32°S boundary. We use residual bathymetry to constrain the geometry of this boundary and propose the name Central Kermadec Discontinuity (CKD). North of the CKD, the buried Tonga Ridge occupies the fore-arc with VP 6.5-7.3 km s-1 and residual free-air gravity anomalies constrain its latitudinal extent (north of 30.5°S), width (110 ± 20 km), and strike ( 005° south of 25°S). South of the CKD the fore-arc is structurally homogeneous downdip with VP 5.7-7.3 km s-1. In the Havre Trough back-arc, crustal thickness south of the CKD is 8-9 km, which is up to 4 km thinner than the northern Havre Trough and at least 1 km thinner than the southern Havre Trough. We suggest that the Eocene arc did not extend along the current length of the Tonga-Kermadec trench. The Eocene arc was originally connected to the Three Kings Ridge, and the CKD was likely formed during separation and easterly translation of an Eocene arc substrate during the early Oligocene. We suggest that the first-order crustal thickness variations along the Kermadec arc were inherited from before the Neogene and reflect Mesozoic crustal structure, the Cenozoic evolution of the Tonga-Kermadec-Hikurangi margin and along-strike variations in the duration of arc volcanism.

  9. Carbon arc ignition improved by simple auxiliary circuit

    NASA Technical Reports Server (NTRS)

    1965-01-01

    High voltage, low current pulse in series with arc power supply efficiently ignites a carbon arc. The easily and economically produced circuit is useful with arc burners and searchlights and with plasma jets.

  10. Crustal thickening drives arc front migration

    NASA Astrophysics Data System (ADS)

    Karlstrom, Leif; Lee, Cin-Ty; Manga, Michael

    2014-05-01

    The location of volcanic arcs, relative to the trench evolves over time. Arc front migration has been observed in relic (Sierra Nevada, Andes) as well as active (Cascades) arcs, sometimes with cycles of retreat and return of the front towards the trench over millions of years. Other arcs, particularly where back-arc extension dominates, migrate more slowly, if at all. Coupled with arc migration there are systematic changes in the geochemistry of magmas such as the ratio of trace elements La/Yb and 87Sr/86Sr isotopes (e.g., Haschke et al., 2002). The position of active volcanic arcs relative to the trench is controlled by the location where melt is generated in the mantle wedge, in turn controlled by the geometry of subduction, and the processes that focus rising melt. Arc front migration is commonly attributed to variation in dip angle of the downgoing slab, delamination of overthickened crust, or to subduction erosion. Here we present an alternative hypothesis. Assuming mantle wedge melting is a largely temperature-dependant process, the maximum isotherm in the wedge sets arc front location. Isotherm location depends on slab angle, subduction velocity and wedge thermal diffusivity (England and Katz, 2010). It also depends on crustal thickness, which evolves as melt is transferred from the wedge to the crust. Arc front migration can thus occur purely through magmatic thickening of crust and lithosphere. Thickening rate is determined by the mantle melt flux into the crust, modulated by tectonics and surface erosion. It is not steady in time, as crustal thickening progressively truncates the mantle melt column and eventually shuts it off. Thus slab angle need not change, and in the absence of other contribution processes front location and crustal thickness have long-time steady state values. We develop a quantitative model for arc front migration that is consistent with published arc front data, and explains why arc fronts do not move when there is extension, such

  11. Gliding arc triggered microwave plasma arc at atmospheric pressure for coal gasification application

    NASA Astrophysics Data System (ADS)

    Jain, Vishal; Visani, A.; Patil, C.; Patel, B. K.; Sharma, P. K.; John, P. I.; Nema, S. K.

    2014-08-01

    Plasma torch is device that efficiently converts electrical energy in to thermal energy for various high temperature applications. The conventional plasma torch comprises of consumable electrodes namely anode and cathode electrodes. The replacement of these electrodes is a complex process owing to its cooling and process shut down requirements. However, microwave plasma arc is electrode-less plasma arc system that is an alternative method to conventional arc technology for generating plasma arc. In this technique, microwave power is efficiently coupled to generate plasma arc by using the property of polar molecule to absorb microwave power. The absorption of microwave power is in form of losses due to intermolecular friction and high collisions between the molecules. This is an efficient method because all microwave power can be absorbed by plasma arc. The main feature of microwave plasma arc is its large uniform high temperature column which is not possible with conventional arc discharge methods. Such type of plasma discharge is very useful in applications where sufficient residence time for treat materials is required. Microwave arc does not require any consumable electrodes and hence, it can be operated continuously that makes it very useful for hazardous effluent treatment applications. Further, microwave cannot ionize neutral particles at atmospheric pressure and hence, a gliding arc is initiated between two thin electrodes in the cavity by applying very low power high voltage (3kV) AC source. In this report, the method for generating microwave arc of 1kW power using commercial microwave oven is elaborated.

  12. Low voltage arc formation in railguns

    DOEpatents

    Hawke, R.S.

    1985-08-05

    A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile.

  13. Low voltage arc formation in railguns

    DOEpatents

    Hawke, R.S.

    1987-11-17

    A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile. 2 figs.

  14. Low voltage arc formation in railguns

    DOEpatents

    Hawke, Ronald S.

    1987-01-01

    A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile.

  15. 'European approach' to arc flash risk.

    PubMed

    Baillie, Jonathan

    2011-11-01

    DuPont claims that electrical arc, and the resulting "arc flash", are among the deadliest, least understood hazards of electricity", and can potentially occur in many industrial and other applications, including hospital plant rooms. Technical and engineering personnel from DuPont Engineering Technology, DuPont Personal Protection, and external independent experts, have thus collaborated to develop "a European approach to electrical arc risk assessment". The resulting free online resource, the DuPont Arc-Guide, sets out key steps to minimise serious arc flash incident risk, and details a range of optional, paid-for tailored risk assessment services, and an accompanying secure web portal, offering more in-depth guidance on this important, but apparently often overlooked, issue. HEJ editor Jonathan Baillie reports.

  16. An advanced arc track resistant airframe wire

    NASA Technical Reports Server (NTRS)

    Beatty, J.

    1995-01-01

    Tensolite, a custom cable manufacturer specializing in high temperature materials as the dielectric medium, develops an advance arc track resistant airframe wire called Tufflite 2000. Tufflite 2000 has the following advantages over the other traditional wires: lighter weight and smaller in diameter; excellent wet and dry arc track resistance; superior dynamic cut-through performance even at elevated temperatures; flight proven performance on Boeing 737 and 757 airplanes; and true 260 C performance by utilizing Nickel plated copper conductors. This paper reports the different tests performed on Tufflite 2000: accelerated aging, arc resistance (wet and dry), dynamic cut through, humidity resistance, wire-to-wire abrasion, flammability, smoke, weight, notch sensitivity, flexibility, and markability. It particularly focuses on the BSI (British Standards Institute) dry arc resistance test and BSI wet arc tracking.

  17. Arc burst pattern analysis fault detection system

    NASA Technical Reports Server (NTRS)

    Russell, B. Don (Inventor); Aucoin, B. Michael (Inventor); Benner, Carl L. (Inventor)

    1997-01-01

    A method and apparatus are provided for detecting an arcing fault on a power line carrying a load current. Parameters indicative of power flow and possible fault events on the line, such as voltage and load current, are monitored and analyzed for an arc burst pattern exhibited by arcing faults in a power system. These arcing faults are detected by identifying bursts of each half-cycle of the fundamental current. Bursts occurring at or near a voltage peak indicate arcing on that phase. Once a faulted phase line is identified, a comparison of the current and voltage reveals whether the fault is located in a downstream direction of power flow toward customers, or upstream toward a generation station. If the fault is located downstream, the line is de-energized, and if located upstream, the line may remain energized to prevent unnecessary power outages.

  18. Numerical simulation of ac plasma arc thermodynamics

    NASA Astrophysics Data System (ADS)

    Wu, Han-Ming; Carey, G. F.; Oakes, M. E.

    1994-05-01

    A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequnecy range of 10-10(exp 2) Hz which includes most industry ac arc frequencies.

  19. Numerical Simulation of AC Plasma Arc Thermodynamics

    NASA Astrophysics Data System (ADS)

    Wu, Han-Ming; Carey, G. F.; Oakes, M. E.

    1994-05-01

    A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequency range of 10-102 Hz which includes most industry ac arc frequencies.

  20. The Ophiolite - Oceanic Fore-Arc Connection

    NASA Astrophysics Data System (ADS)

    Reagan, M. K.; Pearce, J. A.; Stern, R. J.; Ishizuka, O.; Petronotis, K. E.

    2014-12-01

    Miyashiro (1973, EPSL) put forward the hypothesis that many ophiolites are generated in subduction zone settings. More recently, ophiolitic sequences including MORB-like basalts underlying boninites or other subduction-related rock types have been linked to near-trench spreading during subduction infancy (e.g., Stern and Bloomer, 1992, GSA Bull.; Shervais, 2001, G-cubed; Stern et al., 2012, Lithos.). These contentions were given strong support by the results of Shinkai 6500 diving in the Izu-Bonin-Mariana (IBM) fore-arc (e.g., Reagan et al., 2010, G-cubed; Ishizuka et al., 2011, EPSL; Reagan et al., 2013, EPSL). Based on widely spaced dives and grab sampling at disbursed dive stops, these studies concluded that the most abundant and most submerged volcanic rocks in the IBM fore-arc are MORB-like basalts (fore-arc basalts or FAB), and that these basalts appear to be part of a crustal sequence of gabbro, dolerite, FAB, boninite, and normal arc lavas overlying depleted peridotite. This ophiolitic sequence was further postulated to make up most or all of the IBM fore-arc from Guam to Japan, with similar magmatic ages (52 Ma FAB to 45 Ma arc) north to south, reflecting a western-Pacific wide subduction initiation event. At the time of this writing, IODP Expedition 352 is about to set sail, with a principal goal of drilling the entire volcanic sequence in the Bonin fore-arc. This drilling will define the compositional gradients through the volcanic sequence associated with subduction initiation and arc infancy, and test the hypothesized oceanic fore-arc - ophiolite genetic relationship. A primary goal of this expedition is to illustrate how mantle compositions and melting processes evolved during decompression melting of asthenosphere during subduction initiation to later flux melting of depleted mantle. These insights will provide important empirical constraints for geodynamic models of subduction initiation and early arc development.

  1. Plasma arc welding weld imaging

    NASA Technical Reports Server (NTRS)

    Rybicki, Daniel J. (Inventor); Mcgee, William F. (Inventor)

    1994-01-01

    A welding torch for plasma arc welding apparatus has a transparent shield cup disposed about the constricting nozzle, the cup including a small outwardly extending polished lip. A guide tube extends externally of the torch and has a free end adjacent to the lip. First and second optical fiber bundle assemblies are supported within the guide tube. Light from a strobe light is transmitted along one of the assemblies to the free end and through the lip onto the weld site. A lens is positioned in the guide tube adjacent to the second assembly and focuses images of the weld site onto the end of the fiber bundle of the second assembly and these images are transmitted along the second assembly to a video camera so that the weld site may be viewed continuously for monitoring the welding process.

  2. Zircon Recycling in Arc Intrusions

    NASA Astrophysics Data System (ADS)

    Miller, J.; Barth, A.; Matzel, J.; Wooden, J.; Burgess, S.

    2008-12-01

    Recycling of zircon has been well established in arc intrusions and arc volcanoes, but a better understanding of where and how zircons are recycled can help illuminate how arc magma systems are constructed. To that end, we are conducting age, trace element (including Ti-in-zircon temperatures; TzrnTi) and isotopic studies of zircons from the Late Cretaceous (95-85 Ma) Tuolumne Intrusive Suite (TIS) in the Sierra Nevada Batholith (CA). Within the TIS zircons inherited from ancient basement sources and/or distinctly older host rocks are uncommon, but recycled zircon antecrysts from earlier periods of TIS-related magmatism are common and conspicuous in the inner and two most voluminous units of the TIS, the Half Dome and Cathedral Peak Granodiorites. All TIS units have low bulk Zr ([Zr]<150 ppm) and thus low calculated zircon saturation temperatures (Tzrnsat). Within the Half Dome and Cathedral Peak, TzrnTi values are predominantly at or below average Tzrnsat, and there is no apparent correlation between age and TzrnTi. At temperatures appropriate for granodiorite/tonalite melt generation (at or above biotite dehydration; >825°C), [Zr] in the TIS is a factor of 2 to 3 lower than saturation values. Low [Zr] in TIS rocks might be attributed to a very limited supply of zircon in the source, by disequilibrium melting and rapid melt extraction [1], by melting reactions involving formation of other phases that can incorporate appreciable Zr [2], or by removal of zircon at an earlier stage of magma evolution. Based on a preliminary compilation of literature data, low [Zr] is common to Late Cretaceous N.A. Cordilleran granodioritic/tonalitic intrusions (typically <200 ppm and frequently 100-150 ppm for individual large intrusions or intrusive suites). We infer from this that [Zr] in anatectic melts is probably not limited by zircon supply and is primarily controlled by melting parameters. Comparison of the data from TIS with one of these intrusions, the smaller but otherwise

  3. Gliding arc surface modification of carrot nanofibre coating - perspective for composite processing

    NASA Astrophysics Data System (ADS)

    Kusano, Y.; Berglund, L.; Aitomäki, Y.; Oksman, K.; Madsen, B.

    2016-07-01

    Surfaces of carrot nanofibre coatings were modified by a gliding arc in atmospheric pressure air. The treatment strengthened wetting of deionized water and glycerol, increased an oxygen content, C-O and C=O, and moderately roughened the surfaces. In the perspective of composite materials, these changes to the nanofibres can potentially improve their processability when they are to be impregnated with a polymeric matrix. However, longer exposure to the gliding arc reduced oxidation and roughness of the surface, and thus there exists an optimum condition to achieve good wetting to solvents.

  4. Shielding conditions of local cavity for underwater arc spot welding

    SciTech Connect

    Ogawa, Y.; Koga, H.

    1996-12-01

    Arc spot welding to join lapped plates is an effective maintenance operation for emergent recovering technique of defects under water. The welding operation is easy and effective except for an excessive amount of weld metal for deep penetration. A special nozzle for CO{sub 2} arc spot welding was designed to maintain this defect. A large amount of swirl shielding gas flow is adopted to discharge the excessive weld metal and to reduce digging action of weld pool. An additional high speed air jet is supplied to reinforce these effects. Almost flat weld bead is obtained by using of this nozzle. The effect of swirl shielding flow and additional air jet on the pressure is studied. When an excessive axial gas flow is used, a pressure at the weld pool becomes high enough to press down the weld surface below original surface level of base plate, and some molten metal is splashed out. Then, it is difficult to get a sound weld geometry. A swirl gas flow is tried to reduce the static pressure on the weld pool. The pressure on the weld pool by the swirl flow becomes much lower compared to the case by axial flow. When the swirl flow is used, a flat bead can be obtained. But some molten metal which is blown out by the swirl gas is resolidified at the edge of the nozzle. The additional high speed air jet is required to blow out the splashed metal from the nozzle completely. It has a suction effect itself. The pressure on the weld pool is also decreased. But the interaction between the swirl flow and the additional jet shows a complicated manner. This paper discusses the interaction between main shielding gas flow and the additional air jet to guarantee the good shielding condition for underwater use.

  5. Theoretical analysis of ARC constriction

    SciTech Connect

    Stoenescu, M.L.; Brooks, A.W.; Smith, T.M.

    1980-12-01

    The physics of the thermionic converter is governed by strong electrode-plasma interactions (emissions surface scattering, charge exchange) and weak interactions (diffusion, radiation) at the maximum interelectrode plasma radius. The physical processes are thus mostly convective in thin sheaths in front of the electrodes and mostly diffusive and radiative in the plasma bulk. The physical boundaries are open boundaries to particle transfer (electrons emitted or absorbed by the electrodes, all particles diffusing through some maximum plasma radius) and to convective, conductive and radiative heat transfer. In a first approximation the thermionic converter may be described by a one-dimensional classical transport theory. The two-dimensional effects may be significant as a result of the sheath sensitivity to radial plasma variations and of the strong sheath-plasma coupling. The current-voltage characteristic of the converter is thus the result of an integrated current density over the collector area for which the boundary conditions at each r determine the regime (ignited/unignited) of the local current density. A current redistribution strongly weighted at small radii (arc constriction) limits the converter performance and opens questions on constriction reduction possibilities. The questions addressed are the followng: (1) what are the main contributors to the loss of current at high voltage in the thermionic converter; and (2) is arc constriction observable theoretically and what are the conditions of its occurrence. The resulting theoretical problem is formulated and results are given. The converter electrical current is estimated directly from the electron and ion particle fluxes based on the spatial distribution of the electron/ion density n, temperatures T/sub e/, T/sub i/, electrical voltage V and on the knowledge of the transport coefficients. (WHK)

  6. Analysis of arc emission spectra of stainless steel electric arc furnace slag affected by fluctuating arc voltage.

    PubMed

    Aula, Matti; Mäkinen, Ari; Fabritius, Timo

    2014-01-01

    Control of chromium oxidation in the electric arc furnace (EAF) is a significant problem in stainless steel production due to variations of the chemical compositions in the EAF charge. One potential method to control chromium oxidation is to analyze the emission spectrum of the electric arc in order to find indicators of rising chromium content in slag. The purpose of this study was to determine if slag composition can be gained by utilizing electric arc emission spectra in the laboratory environment, despite electric arc voltage fluctuations and varying slag composition. The purpose of inducing voltage fluctuation was to simulate changes in the industrial EAF process. The slag samples were obtained from Outokumpu Stainless Oy Tornio Works, and three different arc currents were used. The correlation analysis showed that the emission spectra offer numerous peak ratios with high correlations to the X-ray fluorescence-measured slag CrO(x)/FeO(x) and MnO/SiO2 ratios. These ratios are useful in determining if the reduction agents have been depleted in the EAF. The results suggest that analysis of laboratory-scale electric arc emission spectra is suitable for indicating the high CrO(x) or MnO content of the slag despite the arc fluctuations. Reliable analysis of other slag components was not successful.

  7. Propagation of back-arc extension into the arc lithosphere in the southern New Hebrides volcanic arc

    NASA Astrophysics Data System (ADS)

    Patriat, M.; Collot, J.; Danyushevsky, L.; Fabre, M.; Meffre, S.; Falloon, T.; Rouillard, P.; Pelletier, B.; Roach, M.; Fournier, M.

    2015-09-01

    New geophysical data acquired during three expeditions of the R/V Southern Surveyor in the southern part of the North Fiji Basin allow us to characterize the deformation of the upper plate at the southern termination of the New Hebrides subduction zone, where it bends eastward along the Hunter Ridge. Unlike the northern end of the Tonga subduction zone, on the other side of the North Fiji Basin, the 90° bend does not correspond to the transition from a subduction zone to a transform fault, but it is due to the progressive retreat of the New Hebrides trench. The subduction trench retreat is accommodated in the upper plate by the migration toward the southwest of the New Hebrides arc and toward the south of the Hunter Ridge, so that the direction of convergence remains everywhere orthogonal to the trench. In the back-arc domain, the active deformation is characterized by propagation of the back-arc spreading ridge into the Hunter volcanic arc. The N-S spreading axis propagates southward and penetrates in the arc, where it connects to a sinistral strike-slip zone via an oblique rift. The collision of the Loyalty Ridge with the New Hebrides arc, less than two million years ago, likely initiated this deformation pattern and the fragmentation of the upper plate. In this particular geodynamic setting, with an oceanic lithosphere subducting beneath a highly sheared volcanic arc, a wide range of primitive subduction-related magmas has been produced including adakites, island arc tholeiites, back-arc basin basalts, and medium-K subduction-related lavas.

  8. Arc statistics with realistic cluster potentials

    NASA Astrophysics Data System (ADS)

    Bartelmann, Matthias; Steinmetz, Matthias; Weiss, Achim

    1995-07-01

    We construct a sample of numerical models for clusters of galaxies and employ these to investigate their capability of imaging background sources into long arcs. The clusters are simulated within the CDM cosmogonic scheme in an Einstein-de Sitter universe. Emphasis is laid on the statistics of the arcs formed, and optical depths for arc formation are determined. We also compare the results to predictions based on simplified, radially symmetric cluster models. We find that the capability of the numerically modeled clusters to produce long arcs is increased by a factor of <~50 compared to a sample of softened isothermal spheres with the same observable parameters (core radii and velocity dispersions), and that they are comparably efficient as singular isothermal spheres with the same velocity dispersion. This largely enhanced capability to produce large arcs of the numerical cluster models can be understood in terms of substructure and intrinsic asymmetry, which enhance the tidal field (shear) of the clusters compared to the radially symmetric cases. We also find that the intrinsic ellipticity of the background sources has a noticeable influence on arc statistics; the optical depth for arcs with a length-to-width ratio of >~10 is significantly larger for elliptical than for circular background sources.

  9. Crustal recycling and the aleutian arc

    SciTech Connect

    Kay, R.W.; Kay, S.M. )

    1988-06-01

    Two types of crustal recycling transfer continental crust back into its mantle source. The first of these, upper crustal recycling, involves elements that have been fractionated by the hydrosphere-sediment system, and are subducted as a part of the oceanic crust. The subduction process (S-process) then fractionates these elements, and those not removed at shallow tectonic levels and as excess components of arc magmas are returned to the mantle. Newly determined trace element composition of Pacific oceanic sedimants are variable and mixing is necessary during the S-process, if sediment is to provide excess element in the ratios observed in Aleutian arc magmas. Only a small fraction of the total sediment subducted at the Aleutian trench is required to furnish the excess elements in Aleutian arc magmas. Ba and {sub 10}Be data indicate that this small fraction includes a contribution from the youngest subducted sediment. The second type of recycling, lower crustal recycling, involves crystal cumulates of both arc and oceanic crustal origin, and residues from crustal melting within arc crust. Unlike the silicic sediments, recycled lower crust is mafic to ultramafic in composition. Trace element analyses of xenoliths representing Aleutian arc lower crust are presented. Recycling by delamination of lower crust and attached mantle lithosphere may occur following basalt eclogite phase transformations that are facilitated by terrane suturing events that weld oceanic island arcs to the continents. The relative importance of upper and lower crustal recycling exerts a primary control on continental crustal composition.

  10. Masking, persistence, and transfer in rotating arcs.

    PubMed

    Geremek, Adam; Stürzel, Frank; da Pos, Osvaldo; Spillmann, Lothar

    2002-10-01

    We demonstrate that the apparent length of a thin white arc on a black disk, rotating concentrically at 2.5 rps, varies with angular length and exposure duration. While short arcs (9-18 degrees ) gradually expand, long arcs (36-72 degrees ) first undergo a brief contraction, before they also expand. On average, perceived elongation asymptotes after 15 s equivalent to visual persistencies ranging from 68 to 170 ms. Using bi- and tri-colored arcs, we find that the apparent increase in length derives from the rear end of the rotating stimulus, while the initial shrinkage derives from contraction of the middle. After 15 s of adaptation, perceived length of the arc decays to actual stimulus length within an average of 6 s and, upon re-exposure of the arc, reaches its former value after only 5 s (priming). When the rotating arc is presented first to one eye and then to the other, apparent elongation transfers partially (46%), suggesting a contribution by the binocular cells in the visual cortex. A partial transfer (26%) also occurs from clockwise to counterclockwise rotation. When tested interocularly, the directional transfer is more pronounced (47%) and equals the interocular transfer under equidirectional conditions, suggesting that the directional transfer (cw versus ccw) might derive from non-directional cortical units. Whereas the initial contraction may be attributable to backward masking, the observed elongation likely reflects a cumulative build-up of after-discharge in cortical neurons over time.

  11. Initial development of the Banda Volcanic Arc

    SciTech Connect

    Hartono, H.M.S. )

    1990-06-01

    The initial development of the Banda Volcanic Arc can be determined by obtaining absolute ages of granites or volcanics, stratigraphy of the Eocene Metan Volcanics of Timor as the oldest formation containing Banda Volcanic Arc extrusives, and tectonic analysis. Banda Arc volcanism is the result of subduction of oceanic crust under the volcanic arc. The time of initial subduction is related to initial seafloor spreading between Australia and Antarctica, which is identical to geomagnetic polarity time 34 (82 mybp). Therefore, 82 mybp can be used as one of the criteria to determine the birth of the Banda Volcanic Arc. With present available time data for determining the birth of the Banda Volcanic Arc, the minimum age coincides with the age of the Metan Volcanics (Eocene, 39-56 mybp) and the maximum age coincides with initial seafloor spreading between Australia and Antarctica (82 mybp). This time span is too long. With the assumption that it needs some time to develop from transcurrent faulting to subduction and volcanism, it is proposed that the initial development of Banda Arc volcanism was during early Tertiary.

  12. Acoustic characteristics of electric arc furnaces

    NASA Astrophysics Data System (ADS)

    Cherednichenko, V. S.; Bikeev, R. A.; Cherednichenko, A. V.; Ognev, A. M.

    2016-06-01

    A mathematical model is constructed to describe the appearance and development of the noise characteristics of superpower electric arc furnaces. The noise formation is shown to be related to the pulsation of the axial plasma flows in arc discharges because of the electrodynamic pressure oscillations caused by the interaction of the self-magnetic field with the current passing in an arc. The pressure in the arc axis changes at a frequency of 100 Hz at the maximum operating pressure of 66 kPa for an arc current of 80 kA. The main ac arc sound frequencies are multiples of 100 Hz, which is supported in the practice of operation of electric arc furnaces. The sound intensity in the furnace laboratory reaches 160 dB and is decreased to 115-120 dB in the working furnace area due to shielding by the furnace jacket, the molten metal, and the molten slag. The appropriateness of increasing the hermetic sealing of electric furnaces and creating furnaces operating at low currents and high transformer voltages is corroborated.

  13. Towards a theory for Neptune's arc rings

    NASA Astrophysics Data System (ADS)

    Goldreich, P.; Tremaine, S.; Borderies, N.

    1986-08-01

    It is proposed that the incomplete rings of Neptune consist of a number of short arcs centered on the corotation resonances of a single satellite. The satellite must have a radius of the order of 100 km or more and move on an inclined orbit. Corotation resonances are located at potential maxima. Thus, mechanical energy dissipated by interparticle collisions must be continually replenished to prevent the arcs from spreading. It is shown that each corotation resonance is associated with a nearby Lindblad resonance, which excites the ring particles' orbital eccentricity, thus supplying the energy required to maintain the arc. The ultimate energy reservoir is the satellite's orbital energy. Therefore, interaction with the arcs damps the satellite's orbital inclination. The self-gravity of the arcs limits their contraction and enforces a relation between arc length and mass. The estimated arc masses are so small, of the order of 10 to the 16th g, that the satellite's orbital inclination suffers negligible decay over the age of the solar system. The inferred surface mass densities are comparable to those found in the major rings of Saturn and Uranus.

  14. Towards a theory for Neptune's arc rings

    NASA Technical Reports Server (NTRS)

    Goldreich, P.; Tremaine, S.; Borderies, N.

    1986-01-01

    It is proposed that the incomplete rings of Neptune consist of a number of short arcs centered on the corotation resonances of a single satellite. The satellite must have a radius of the order of 100 km or more and move on an inclined orbit. Corotation resonances are located at potential maxima. Thus, mechanical energy dissipated by interparticle collisions must be continually replenished to prevent the arcs from spreading. It is shown that each corotation resonance is associated with a nearby Lindblad resonance, which excites the ring particles' orbital eccentricity, thus supplying the energy required to maintain the arc. The ultimate energy reservoir is the satellite's orbital energy. Therefore, interaction with the arcs damps the satellite's orbital inclination. The self-gravity of the arcs limits their contraction and enforces a relation between arc length and mass. The estimated arc masses are so small, of the order of 10 to the 16th g, that the satellite's orbital inclination suffers negligible decay over the age of the solar system. The inferred surface mass densities are comparable to those found in the major rings of Saturn and Uranus.

  15. Reconstruction of Late Cretaceous Magmatic Arcs in the Northern Andes: Single Versus Multiple Arc Systems

    NASA Astrophysics Data System (ADS)

    Cardona, A.; Jaramillo, J. S.; Leon, S.; Hincapie, S.; Mejia, D.; Patino, A. M.; Vanegas, J.; Zapata, S.; Valencia, V.; Jimenez, G.; Monsalve, G.

    2014-12-01

    Although magmatic rocks are major tracers of the geological evolution of convergent margins, pre-collisional events such as subduction erosion, collisional thrusting or late collisional strike slip segmentation may difficult the recognizing of multiple arc systems and therefore the existence of paleogeographic scenarios with multiple subduction systems. New field, U-Pb geochronology and whole rock geochemistry constraints from the northwestern segment of the Central Cordillera in the states of Antioquia and Caldas (Colombia) are used to understand the nature of the Late Cretaceous arc magmatism and evaluate the existence of single or multiple Pacific and Caribbean arc systems in the growth of the Northwestern Andes. The new results integrated with additional field and published information is used to suggest the existence of at least three different magmatic arcs. (1) An Eastern Continental arc built within a well defined Permian to Triassic continental crust that record a protracted 90-70 Ma magmatic evolution, (2) a 90-80 arc formed within attenuated continental crust and associated oceanic crust, (3) 90-88 Ma arc formed over a Late Cretaceous plateau crust. The eastern arcs were formed as part of double eastern vergent subduction system, where the most outboard arc represent a fringing arc formed over detached fragments of continental crust, whereas the easternmost continental arc growth by the closure an subduction of and older and broad Triassic to Early Jurassic back-arc ocean. Its closure also end up in ophiolite emplacement. The third allochtonous oceanic arc was formed over the Caribbean plateau crust and was accreted to the continental margin in the Late Cretaceous. Ongoing paleomagnetic, deformational, gravimetric and basin analysis will be integrate to test this model and understand the complex Late Cretaceous tectonic evolution of the Northern Andes.

  16. A simple prescription for simulating and characterizing gravitational arcs

    NASA Astrophysics Data System (ADS)

    Furlanetto, C.; Santiago, B. X.; Makler, M.; de Bom, C.; Brandt, C. H.; Neto, A. F.; Ferreira, P. C.; da Costa, L. N.; Maia, M. A. G.

    2013-01-01

    Simple models of gravitational arcs are crucial for simulating large samples of these objects with full control of the input parameters. These models also provide approximate and automated estimates of the shape and structure of the arcs, which are necessary for detecting and characterizing these objects on massive wide-area imaging surveys. We here present and explore the ArcEllipse, a simple prescription for creating objects with a shape similar to gravitational arcs. We also present PaintArcs, which is a code that couples this geometrical form with a brightness distribution and adds the resulting object to images. Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to images of real gravitational arcs. We validate this fitting technique using simulated arcs and apply it to CFHTLS and HST images of tangential arcs around clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a Sérsic profile for the source, recovers the total signal in real images typically within 10%-30%. The ArcEllipse+Sérsic models also automatically recover visual estimates of length-to-width ratios of real arcs. Residual maps between data and model images reveal the incidence of arc substructure. They may thus be used as a diagnostic for arcs formed by the merging of multiple images. The incidence of these substructures is the main factor that prevents ArcEllipse models from accurately describing real lensed systems.

  17. Modeling Multi-Arc Spraying Systems

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.

    2016-06-01

    The use of plasma as energy source in thermal spraying enables among others the processing of feed stock materials with very high melting temperatures as coating materials. New generation multi-arc plasma spraying systems are widely spread and promise several advantages in comparison to the conventional single-arc systems. Numerical modeling of multi-arc plasma spraying offers the possibility to increase the understanding about this process. This study focuses on the numerical modeling of three-cathode spraying systems, introducing the recent activities in this field and discussing the numerical aspects which influence the prediction power of the models.

  18. Metal vapor arc switch electromagnetic accelerator technology

    NASA Technical Reports Server (NTRS)

    Mongeau, P. P.

    1984-01-01

    A multielectrode device housed in an insulator vacuum vessel, the metal vapor vacuum switch has high power capability and can hold off voltages up to the 100 kilovolt level. Such switches can be electronically triggered and can interrupt or commutate at a zero current crossing. The physics of arc initiation, arc conduction, and interruption are examined, including material considerations; inefficiencies; arc modes; magnetic field effects; passive and forced extinction; and voltage recovery. Heating, electrode lifetime, device configuration, and external circuit configuration are discussed. The metal vapor vacuum switch is compared with SCRs, GTOs, spark gaps, ignitrons, and mechanical breakers.

  19. Magnetic-cusp, cathodic-arc source

    DOEpatents

    Falabella, S.

    1995-11-21

    A magnetic-cusp for a cathodic-arc source wherein the arc is confined to the desired cathode surface, provides a current path for electrons from the cathode to the anode, and utilizes electric and magnetic fields to guide ions from the cathode to a point of use, such as substrates to be coated. The magnetic-cusp insures arc stability by an easy magnetic path from anode to cathode, while the straight-through arrangement leads to high ion transmission. 3 figs.

  20. Linear volcanic segments in the Sunda Arc, Indonesia: Implications for arc lithosphere control upon volcano distribution

    NASA Astrophysics Data System (ADS)

    Macpherson, C. G.; Pacey, A.; McCaffrey, K. J.

    2012-12-01

    The overall curvature of many subduction zones is immediately apparent and the term island arc betrays the common assumption that subduction zone magmatism occurs in curved zones. This assumption can be expressed by approximating island arcs as segments of small circles on the surface of a sphere. Such treatments predict that the location of arc volcanoes is related to their vertical separation from the slab (in fact, the depth to seismicity in the slab) and require that the primary control on the locus of magmatism lies either within the subducted slab or the mantle wedge that separates the subducted and overriding lithospheric plates. The concept of curved arcs ignores longstanding observations that magmatism in many subduction systems occurs as segments of linearly arranged volcanic centres. Further evidence for this distribution comes from the close relationship between magmatism and large scale, arc-parallel fabrics in some arcs. Similarly, exposures of deep arc crust or mantle often reveal elongation of magmatic intrusions sub-parallel to the inferred trend of the arc. The Sunda Arc forms the Indonesian islands from Sumatra to Alor and provides an important test for models of volcano distribution for several reasons. First, Sunda has hosted abundant historic volcanic activity. Second, with the notable exception of Krakatau, every volcano in the arc is subaerial from base to cone and, therefore, can be readily identified where there is a suitable extent of local mapping that can be used to ground-truth satellite imagery. Third, there are significant changes in the stress regime along the length of the arc, allowing the influence of the upper plate to be evaluated by comparison of different arc segments. Finally, much of the Sunda Arc has proved difficult to accommodate in models that try to relate volcano distribution to the depth to the subducted slab. We apply an objective line-fitting protocol; the Hough Transform, to explore the distribution of volcanoes

  1. Arc - arc collisional tectonics within the Central Mobile Belt of the Newfoundland Appalachians

    NASA Astrophysics Data System (ADS)

    Zagorevski, A.; Rogers, N.; van Staal, C. R.; McNicoll, V. J.; Valverde-Vaquero, P.

    2007-12-01

    The Central Mobile Belt of Newfoundland Appalachians records the Ordovician arc - arc collision between the peri-Laurentian Red Indian Lake Arc of the Annieopsquotch accretionary tract (c. 480-460 Ma), and the peri- Gondwanan Victoria - Popelogan Arc (c. 473-453 Ma), which marks the closure of the Cambro-Ordovician Iapetus Ocean. Although the arc systems are in part coeval, they are distinguishable by the preservation of distinct structural histories and stratigraphies, unique basement characteristics as demonstrated by lead isotopic values of volcanic massive sulphide deposits and faunal differences. A modern analogue of such an arc - arc collision is observed in the Molucca and Solomon seas of the southwest Pacific. From such modern analogues it is evident that the Victoria - Popelogan Arc occupied a lower-plate setting during collision. This tectonic setting is demonstrated by subsidence of the Victoria - Popelogan Arc similar to the collision induced subsidence that is developed on the Australian active margin and Halmahera arcs of the Southwest Pacific. The timing of Victoria - Popelogan Arc subsidence is constrained by three age dates that form the last vestiges of arc volcanism (457 ± 2; 456.8 ± 3.1; 457 ± 3.6 Ma). These volcanic rocks are immediately overlain by Caradocian black shale of the Point Leamington Formation that marks the base of the Badger Group and the initiation of a successor basin. Caradocian black shale is noticeably absent from the top of the Red Indian Lake Arc with this time interval instead represented by a sub-Silurian unconformity, formed in response to collisional uplift. Emergence of the peri- Laurentian margin is demonstrated by detritus from it preserved in the Badger Group, which as it stratigraphically overlies the peri-Gondwanan Victoria - Popelogan Arc, requires that Iapetus was closed by this time. Following this collision, subduction stepped back into the outboard Tetagouche - Exploits back-arc basin. Whereas correlative

  2. 33 CFR 334.1290 - In Bering Sea, Shemya Island Area, Alaska; meteorological rocket launching facility, Alaskan Air...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., Alaska; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. 334.1290 Section...; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. (a) The danger zone. An arc of a... Force, Headquarters 6th Weather Wing (MAC), Andrews Air Force Base, Washington, D.C. 20331. (40...

  3. 33 CFR 334.1290 - In Bering Sea, Shemya Island Area, Alaska; meteorological rocket launching facility, Alaskan Air...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., Alaska; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. 334.1290 Section...; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. (a) The danger zone. An arc of a... Force, Headquarters 6th Weather Wing (MAC), Andrews Air Force Base, Washington, D.C. 20331. (40...

  4. 33 CFR 334.1290 - In Bering Sea, Shemya Island Area, Alaska; meteorological rocket launching facility, Alaskan Air...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., Alaska; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. 334.1290 Section...; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. (a) The danger zone. An arc of a... Force, Headquarters 6th Weather Wing (MAC), Andrews Air Force Base, Washington, D.C. 20331. (40...

  5. 33 CFR 334.1290 - In Bering Sea, Shemya Island Area, Alaska; meteorological rocket launching facility, Alaskan Air...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., Alaska; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. 334.1290 Section...; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. (a) The danger zone. An arc of a... Force, Headquarters 6th Weather Wing (MAC), Andrews Air Force Base, Washington, D.C. 20331. (40...

  6. 33 CFR 334.1290 - In Bering Sea, Shemya Island Area, Alaska; meteorological rocket launching facility, Alaskan Air...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., Alaska; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. 334.1290 Section...; meteorological rocket launching facility, Alaskan Air Command, U.S. Air Force. (a) The danger zone. An arc of a... Force, Headquarters 6th Weather Wing (MAC), Andrews Air Force Base, Washington, D.C. 20331. (40...

  7. Investigation of arc length versus flange thickness while using an arc voltage controller

    SciTech Connect

    Daumeyer, G.J.

    1994-11-01

    An arc voltage controller (AVC) for gas tungsten arc welding will change arc length when flange thickness changes while all other variables, including AVC setting, are held constant. A procedure for calibrating an LVDT (linear variable displacement transducer) used for electrode assembly motion monitoring was proven for laboratory setups and special investigations. A partial characterization on the deadband and sensitivity control settings of the Cyclomatic AVC was completed.

  8. Lifespans of Cascade Arc volcanoes

    NASA Astrophysics Data System (ADS)

    Calvert, A. T.

    2015-12-01

    Compiled argon ages reveal inception, eruptive episodes, ages, and durations of Cascade stratovolcanoes and their ancestral predecessors. Geologic mapping and geochronology show that most Cascade volcanoes grew episodically on multiple scales with periods of elevated behavior lasting hundreds of years to ca. 100 kyr. Notable examples include the paleomag-constrained, few-hundred-year-long building of the entire 15-20 km3 Shastina edifice at Mt. Shasta, the 100 kyr-long episode that produced half of Mt. Rainier's output, and the 30 kyr-long episode responsible for all of South and Middle Sister. Despite significant differences in timing and rates of construction, total durations of active and ancestral volcanoes at discrete central-vent locations are similar. Glacier Peak, Mt. Rainier, Mt. Adams, Mt. Hood, and Mt. Mazama all have inception ages of 400-600 ka. Mt. St. Helens, Mt. Jefferson, Newberry Volcano, Mt. Shasta and Lassen Domefield have more recent inception ages of 200-300 ka. Only the Sisters cluster and Mt. Baker have established eruptive histories spanning less than 50 kyr. Ancestral volcanoes centered 5-20 km from active stratocones appear to have similar total durations (200-600 kyr), but are less well exposed and dated. The underlying mechanisms governing volcano lifecycles are cryptic, presumably involving tectonic and plumbing changes and perhaps circulation cycles in the mantle wedge, but are remarkably consistent along the arc.

  9. Submarine evidence for large-scale debris avalanches in the Lesser Antilles Arc

    NASA Astrophysics Data System (ADS)

    Deplus, Christine; Le Friant, Anne; Boudon, Georges; Komorowski, Jean-Christophe; Villemant, Benoit; Harford, Chloe; Ségoufin, Jacques; Cheminée, Jean-Louis

    2001-10-01

    Results from a recent marine geophysical survey demonstrate the importance of the process of flank collapse in the growth and evolution of volcanoes along an island arc. The Aguadomar cruise, aboard the French R/V L'Atalante, surveyed the flanks of the Lesser Antilles Arc between the islands of Montserrat and St. Lucia. Analysis of the data shows that flank collapse events occurred on active volcanoes all along the arc and resulted in debris avalanches, some of them being of large magnitude. The debris avalanche deposits display hummocky topography on the swath bathymetry, speckled pattern on backscatter images, hyperbolic facies on 3.5 kHz echosounder data and chaotic units on air gun seismic profiles. They extend from horseshoe-shaped structures previously identified on the subaerial part of the volcanoes. In the southern part of the arc, large-scale debris avalanche deposits were identified on the floor of the Grenada Basin west of active volcanoes on Dominica, Martinique and St. Lucia. The extent of debris avalanche deposits off Dominica is about 3500 km 2. The debris avalanches have resulted from major flank collapse events which may be mainly controlled by the large-scale structure of the island arc and the presence of the deep Grenada Basin. In the northern part of the arc, several debris avalanche deposits were also identified around the island of Montserrat. With smaller extent (20-120 km 2), they are present on the east, south and west submarine flanks of Soufriere Hills volcano which has been erupting since July 1995. Flank collapse is thus a recurrent process in the recent history of this volcano. The marine data are also relevant for a discussion of the transport mechanisms of debris avalanches on the seafloor surrounding a volcanic island arc.

  10. Stretched arc discharge in produced water.

    PubMed

    Cho, Y I; Wright, K C; Kim, H S; Cho, D J; Rabinovich, A; Fridman, A

    2015-01-01

    The objective of the present study was to investigate the feasibility of stretching an arc discharge in produced water to increase the volume of produced water treated by plasma. Produced water is the wastewater generated by hydraulic fracturing of shale during the production phase in shale-oil or shale-gas exploration. The electric conductivity of produced water is in the range of 50-200 mS/cm, which provides both a challenge and opportunity for the application of plasmas. Stretching of an arc discharge in produced water was accomplished using a ground electrode and two high-voltage electrodes: one positioned close to the ground electrode and the other positioned farther away from the ground. The benefit of stretching the arc is that the contact between the arc and water is significantly increased, resulting in more efficient plasma treatment in both performance and energy cost.

  11. Arc tracks on nanostructured surfaces after microbreakdowns

    NASA Astrophysics Data System (ADS)

    Sinelnikov, D.; Bulgadaryan, D.; Hwangbo, D.; Kajita, S.; Kolodko, D.; Kurnaev, V.; Ohno, N.

    2016-09-01

    Studying of initial steps of unipolar arc ignition process is important for reduction of probability of arcing between the plasma and the wall in thermonuclear devices. Tungsten nano-fuzz surface formed by helium plasma irradiation at high fluences and temperatures is a perfect material for arc ignition. Snowflake-like craters were detected on the fuzzy surfaces after short micro-breakdowns. Such sort of craters have not been observed before on any other metallic surfaces. These specific traces are formed due to unique properties of the fuzz structure. The nano-fuzz could be easily melted and vaporized by micro-breakdown current, due to its porosity and bad thermal conductivity, and formation of low conducting metallic vapour under the cathode spot causes discharge movement to the nearest place. Thus, even low current arc can easily move and leave traces, which could be easily observed by a secondary electron microscope.

  12. Tracking Sediment Subduction Along the Sangihe Volcanic Arc, Indonesia Using Volatile Chemistry and N-isotopes

    NASA Astrophysics Data System (ADS)

    Clor, L. E.; Fischer, T. P.; Hilton, D. R.; Sharp, Z.; Hartono, U.

    2002-12-01

    We report the first data on volatile emissions from the Sangihe Volcanic Arc to trace sediment subduction. The Sangihe Arc is part of an unusual tectonic setting where the Molucca Sea Plate subducts beneath both the Sangihe and Halmahera Arcs, resulting in oblique arc-arc collision. The northern parts of Sangihe and Halmahera are fused, while the south has not yet collided. Collision has resulted in sediment obduction onto the facing arcs, decoupling it from the oceanic plate below. To study the geochemical effects of collision, we collected gases at eight locations along Sangihe Arc at fumaroles and hot springs. Our results complement CO2-He systematics of the same samples (Jaffe et al., this volume). Gas samples were analyzed for major volatiles and N isotopes. Typical N2/He for subduction zones are 1000-25,000, while MORB and OIB are lower (10-100) due to the lack of sediment-derived N input. Most Sangihe samples have N2/He that deviate from the subduction signature (330-2825). The N isotopic (δ15N) value of air is 0‰ by definition, -3 to -5‰ in the upper mantle, and +7‰ in marine sediments. δ15N values for Sangihe samples range from -7 to +2‰ . Variations in N2/He ratios and δ15N data (tracers of hemipelagic sediment) correlate with latitude, with values decreasing to the north suggesting that subduction of hemipelagic sediment is less significant in the north than the south. The N2-He systematics suggest that arc-arc collision, more advanced in the north (where N2/He=537 and δ15N=-7‰ at Ruang Volcano), has caused the sediment package to become less coupled to the underlying ocean crust. The higher values in the south (N2/He=1977 and δ15N=+2‰ at Ambang Volcano) suggest that sediment is still subducting there, as the collision is less developed. Alternatively, sediment composition may vary along strike of the arc, with hemipelagic and carbonate-rich sediments subducted in the south and north, respectively.

  13. 49 CFR 195.226 - Welding: Arc burns.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Welding: Arc burns. 195.226 Section 195.226 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.226 Welding: Arc burns. (a) Each arc burn must be repaired. (b) An arc burn...

  14. 49 CFR 195.226 - Welding: Arc burns.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Welding: Arc burns. 195.226 Section 195.226 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.226 Welding: Arc burns. (a) Each arc burn must be repaired. (b) An arc burn...

  15. 49 CFR 195.226 - Welding: Arc burns.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Welding: Arc burns. 195.226 Section 195.226 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.226 Welding: Arc burns. (a) Each arc burn must be repaired. (b) An arc burn...

  16. 49 CFR 195.226 - Welding: Arc burns.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Welding: Arc burns. 195.226 Section 195.226 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.226 Welding: Arc burns. (a) Each arc burn must be repaired. (b) An arc burn...

  17. Arc voltage measurements of the hyperbaric MIG process

    SciTech Connect

    Huismann, G.; Hoffmeister, H.

    1996-12-01

    As a vital part of the MIG process, the arc controls the stability of the process, the melting of the filler wire and the base material. In order to control and describe the arc behavior, it is necessary to know the voltage- current- arc length relations, or the arc characteristics. Knowledge of arc characteristics is necessary for control of the MIG process and further automation of welding systems, in particular, at hyperbaric welding. In literature, information on arc characteristics for hyperbaric open arc pulsed process is not available so far. Therefore, in the present work, arc characteristics were measured for a pressure range of 1 to 16 bar. In measuring arc voltages and arc lengths of MIG arcs, specific problems are encountered as compared to TIG arcs where the distance between the electrode and work piece can be taken as the arc length and the ohmic voltage drop in the tungsten electrode is low. The movement of the electrode in the MIG process and the deformation of the molten wire end together with weld pool fluctuations are providing a complex system. For determining the arc characteristics certain simplifications are thus required which have been applied in this work. This paper presents a new concept on measuring arc lengths and voltages in the open MIG arc.

  18. 49 CFR 195.226 - Welding: Arc burns.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 3 2010-10-01 2010-10-01 false Welding: Arc burns. 195.226 Section 195.226 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... PIPELINE Construction § 195.226 Welding: Arc burns. (a) Each arc burn must be repaired. (b) An arc burn...

  19. Basins in ARC-continental collisions

    USGS Publications Warehouse

    Draut, Amy E.; Clift, Peter D.; Busby, Cathy; Azor, Antonio

    2012-01-01

    Arc-continent collisions occur commonly in the plate-tectonic cycle and result in rapidly formed and rapidly collapsing orogens, often spanning just 5-15 My. Growth of continental masses through arc-continent collision is widely thought to be a major process governing the structural and geochemical evolution of the continental crust over geologic time. Collisions of intra-oceanic arcs with passive continental margins (a situation in which the arc, on the upper plate, faces the continent) involve a substantially different geometry than collisions of intra-oceanic arcs with active continental margins (a situation requiring more than one convergence zone and in which the arc, on the lower plate, backs into the continent), with variable preservation potential for basins in each case. Substantial differences also occur between trench and forearc evolution in tectonically erosive versus tectonically accreting margins, both before and after collision. We examine the evolution of trenches, trench-slope basins, forearc basins, intra-arc basins, and backarc basins during arc-continent collision. The preservation potential of trench-slope basins is low; in collision they are rapidly uplifted and eroded, and at erosive margins they are progressively destroyed by subduction erosion. Post-collisional preservation of trench sediment and trench-slope basins is biased toward margins that were tectonically accreting for a substantial length of time before collision. Forearc basins in erosive margins are usually floored by strong lithosphere and may survive collision with a passive margin, sometimes continuing sedimentation throughout collision and orogeny. The low flexural rigidity of intra-arc basins makes them deep and, if preserved, potentially long records of arc and collisional tectonism. Backarc basins, in contrast, are typically subducted and their sediment either lost or preserved only as fragments in melange sequences. A substantial proportion of the sediment derived from

  20. Arc distribution during the vacuum arc remelting of Ti-6Al-4V

    SciTech Connect

    Woodside, Charles Rigel; King, Paul E.; Nordlund, Chris

    2013-01-01

    Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot–Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.

  1. Sensitivity of collapsed arc QA method for delivery errors in Volumetric Modulated Arc Therapy (VMAT)

    NASA Astrophysics Data System (ADS)

    Young, Tony; Xing, Aitang; Vial, Philp; Thwaites, David; Holloway, Lois; Arumugam, Sankar

    2015-01-01

    In this paper the sensitivity of an Electronic Portal Imaging Device (EPID) to detecting introduced Volumetric Arc Therapy (VMAT) treatment errors was studied using the Collapsed Arc method. Two clinical Head and Neck (H&N) and Prostate treatment plans had gantry dependent dose and MLC errors introduced to the plans. These plans were then delivered to an Elekta Synergy Linear Accelerator EPID and compared to the original treatment planning system Collapsed Arc dose matrix. With the Collapsed Arc technique the EPID was able to detect MLC errors down to 2mm and dose errors of down to 3% depending on the treatment plan complexity and gamma tolerance used.

  2. Arc Distribution During the Vacuum Arc Remelting of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Woodside, C. Rigel; King, Paul E.; Nordlund, Chris

    2013-02-01

    Currently, the temporal distribution of electric arcs across the ingot during vacuum arc remelting (VAR) is not a known or monitored process parameter. Previous studies indicate that the distribution of arcs can be neither diffuse nor axisymmetric about the center of the furnace. Correct accounting for the heat flux, electric current flux, and mass flux into the ingot is critical to achieving realistic solidification models of the VAR process. The National Energy Technology Laboratory has developed an arc position measurement system capable of locating arcs and determining the arc distribution within an industrial VAR furnace. The system is based on noninvasive magnetic field measurements and a VAR specific form of the Biot-Savart law. The system was installed on a coaxial industrial VAR furnace at ATI Albany Operations in Albany, OR. This article reports on the different arc distributions observed during production of Ti-6Al-4V. It is shown that several characteristic arc distribution modes can develop. This behavior is not apparent in the existing signals used to control the furnace, indicating the measurement system is providing new information. It is also shown that the different arc distribution modes observed may impact local solidification times, particularly at the side wall.

  3. Aligning Plasma-Arc Welding Oscillations

    NASA Technical Reports Server (NTRS)

    Norris, Jeff; Fairley, Mike

    1989-01-01

    Tool aids in alignment of oscillator probe on variable-polarity plasma-arc welding torch. Probe magnetically pulls arc from side to side as it moves along joint. Tensile strength of joint depends on alignment of weld bead and on alignment of probe. Operator installs new tool on front of torch body, levels it with built-in bubble glass, inserts probe in slot on tool, and locks probe in place. Procedure faster and easier and resulting alignment more accurate and repeatable.

  4. Metal Vapor Arcing Risk Assessment Tool

    NASA Technical Reports Server (NTRS)

    Hill, Monika C.; Leidecker, Henning W.

    2010-01-01

    The Tin Whisker Metal Vapor Arcing Risk Assessment Tool has been designed to evaluate the risk of metal vapor arcing and to help facilitate a decision toward a researched risk disposition. Users can evaluate a system without having to open up the hardware. This process allows for investigating components at risk rather than spending time and money analyzing every component. The tool points to a risk level and provides direction for appropriate action and documentation.

  5. Visualization of Gas Tungsten Arc Weld Pools

    DTIC Science & Technology

    1991-09-01

    flow visualization of Gas Tungsten Arc weld pools for HY-80 steel is presented using a pulsed laser light source and a conventional night~vision...visualization of Gas Tungsten Arc weld pools for HY-80 steel is presented using a pulsed laser light source and a conventional night-vision image-intensifier...effects of electromagnetic stirring on GTA welds in austenitic stainless steel . Changes in shape and solidification structure of welds observed

  6. Air Research

    EPA Pesticide Factsheets

    EPA's air research provides the critical science to develop and implement outdoor air regulations under the Clean Air Act and puts new tools and information in the hands of air quality managers and regulators to protect the air we breathe.

  7. Ion source with improved primary arc collimation

    DOEpatents

    Dagenhart, William K.

    1985-01-01

    An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power, thereby preventing the exposure of the anode to the full arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

  8. Dynamics of a discrete auroral arc

    NASA Technical Reports Server (NTRS)

    Bruening, K.; Goertz, C. K.

    1986-01-01

    Porcupine Flight 4 data were used to determine the field-aligned currents associated with a southward moving discrete auroral arc in the postmidnight sector. Three different methods were used for determining the field-aligned current which should give identical results if the arcs are quasi-stationary and no parallel electric field exists between the payload and the dynamo region of the ionosphere. As long as the rocket is above the arc, the three methods agree. The integral of precipitating electron flux, the local magnetic field perturbations, and the divergence of the horizontal Pedersen current all indicate an upward current of 5 + or - 3 microamperes/sq m. Immediately north of the arc a strong downward current of about 10-20 microamperes/sq m is detected. The magnitude, however, is not well known because the rocket's velocity relative to the arc cannot be clearly established. Further north of the southward moving arc, the two methods that can be applied (magnetic field perturbations and divergence of the horizontal Pedersen current) yield contradictory results not only about the magnitude of the current but also about the direction of the current. It is suggested that this discrepancy is due to time-dependent electric field.

  9. Dynamics of a discrete auroral arc

    NASA Astrophysics Data System (ADS)

    Bruening, K.; Goertz, C. K.

    1986-06-01

    Porcupine Flight 4 data were used to determine the field-aligned currents associated with a southward moving discrete auroral arc in the postmidnight sector. Three different methods were used for determining the field-aligned current which should give identical results if the arcs are quasi-stationary and no parallel electric field exists between the payload and the dynamo region of the ionosphere. As long as the rocket is above the arc, the three methods agree. The integral of precipitating electron flux, the local magnetic field perturbations, and the divergence of the horizontal Pedersen current all indicate an upward current of 5 + or - 3 microamperes/sq m. Immediately north of the arc a strong downward current of about 10-20 microamperes/sq m is detected. The magnitude, however, is not well known because the rocket's velocity relative to the arc cannot be clearly established. Further north of the southward moving arc, the two methods that can be applied (magnetic field perturbations and divergence of the horizontal Pedersen current) yield contradictory results not only about the magnitude of the current but also about the direction of the current. It is suggested that this discrepancy is due to time-dependent electric field.

  10. Magnesium isotope geochemistry in arc volcanism.

    PubMed

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-28

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ(26)Mg of the Martinique Island lavas varies from -0.25 to -0.10, in contrast to the narrow range that characterizes the mantle (-0.25 ± 0.04, 2 SD). These high δ(26)Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid-mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration.

  11. Magnesium isotope geochemistry in arc volcanism

    NASA Astrophysics Data System (ADS)

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from -0.25 to -0.10, in contrast to the narrow range that characterizes the mantle (-0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid-mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration.

  12. Apparatus for gas-metal arc deposition

    DOEpatents

    Buhrmaster, Carol L.; Clark, Denis E.; Smartt, Herschel B.

    1991-01-01

    Apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment with the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspenion of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite.

  13. Method for gas-metal arc deposition

    DOEpatents

    Buhrmaster, C.L.; Clark, D.E.; Smartt, H.B.

    1990-11-13

    Method and apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites are disclosed. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment with the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspension of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite. 1 fig.

  14. Method for gas-metal arc deposition

    DOEpatents

    Buhrmaster, Carol L.; Clark, Denis E.; Smartt, Herschel B.

    1990-01-01

    Method and apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment wiht the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspension of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite.

  15. Technique for the comparison of light spectra from natural and laboratory generated lightning current arcs

    NASA Astrophysics Data System (ADS)

    Mitchard, D.; Clark, D.; Carr, D.; Haddad, A.

    2016-08-01

    A technique was developed for the comparison of observed emission spectra from lightning current arcs generated through self-breakdown in air and the use of two types of initiation wire, aluminum bronze and nichrome, against previously published spectra of natural lightning events. A spectrograph system was used in which the wavelength of light emitted by the lightning arc was analyzed to derive elemental interactions. A lightning impulse of up to 100 kA was applied to a two hemispherical tungsten electrode configuration which allowed the effect of the lightning current and lightning arc length to be investigated. A natural lightning reference spectrum was reconstructed from literature, and generated lightning spectra were obtained from self-breakdown across a 14.0 mm air gap and triggered along initiation wires of length up to 72.4 mm. A comparison of the spectra showed that the generated lightning arc induced via self-breakdown produced a very similar spectrum to that of natural lightning, with the addition of only a few lines from the tungsten electrodes. A comparison of the results from the aluminum bronze initiation wire showed several more lines, whereas results from the nichrome initiation wire differed greatly across large parts of the spectrum. This work highlights the potential use for spectrographic techniques in the study of lightning interactions with surrounding media and materials, and in natural phenomena such as recently observed ball lightning.

  16. Mercury and Iodine systematics of volcanic arc fluids

    NASA Astrophysics Data System (ADS)

    Varekamp, J. C.; Kading, T.; Fehn, U.; Lu, Z.

    2008-12-01

    The mantle has low Mercury and Iodine concentrations, but these elements occur in volcanic gases and hydrothermal fluids at ppb (Hg) and ppm (Iodine) levels. Possibly, the Hg and Iodine concentrations in volcanic fluids reflect subducted sediment sources in arc magmas. Iodine is a biophilic element, and I129/I values indicate that subducted sediment (especially organic matter) is an important Iodine source for arc magmas. It is uncertain if this is true for Hg as well, although in the surface environment Hg is commonly associated with organic matter. We present 60 new analyses of Hg and I in fluids from volcanoes in Central America, New Zealand, Japan, and the Cascades. A first assessment suggests that Iodine is released to some degree in the early stage of subduction in the forearc, whereas Hg may be released largely below the main volcanic arc. Isotope and trace element signatures of volcanic rocks of the investigated volcanoes show no simple correlation with Hg or Iodine abundances. The acid hot spring fluids of Copahue volcano (Argentina) carried ~ 200 ppt Hg in January 1999, ~80 ppt Hg in March 2008, and 90 ppt Hg in the crater lake in March 1997. The dissolved Hg fluxes from the Copahue hydrothermal system are ~300 gr Hg/year in 1999 and ~130 gr Hg/year in 2008. The bulk hydrothermal Hg flux (particle bound+dissolved) in 2008 was ~ 350 gr Hg/year. The potential Mercury evasion from these hydrothermal spring fluids into the air has not yet been incorporated in these estimates.

  17. THE REDSHIFT DISTRIBUTION OF GIANT ARCS IN THE SLOAN GIANT ARCS SURVEY

    SciTech Connect

    Bayliss, Matthew B.; Gladders, Michael D.; Koester, Benjamin P.; Oguri, Masamune; Hennawi, Joseph F.; Sharon, Keren; Dahle, Haakon

    2011-01-20

    We measure the redshift distribution of a sample of 28 giant arcs discovered as a part of the Sloan Giant Arcs Survey. Gemini/GMOS-North spectroscopy provides precise redshifts for 24 arcs, and 'redshift desert' constrains for the remaining 4 arcs. This is a direct measurement of the redshift distribution of a uniformly selected sample of bright giant arcs, which is an observable that can be used to inform efforts to predict giant arc statistics. Our primary giant arc sample has a median redshift z = 1.821 and nearly two-thirds of the arcs, 64%, are sources at z {approx}> 1.4, indicating that the population of background sources that are strongly lensed into bright giant arcs resides primarily at high redshift. We also analyze the distribution of redshifts for 19 secondary strongly lensed background sources that are not visually apparent in Sloan Digital Sky Survey imaging, but were identified in deeper follow-up imaging of the lensing cluster fields. Our redshift sample for the secondary sources is not spectroscopically complete, but combining it with our primary giant arc sample suggests that a large fraction of all background galaxies that are strongly lensed by foreground clusters reside at z {approx}> 1.4. Kolmogorov-Smirnov tests indicate that our well-selected, spectroscopically complete primary giant arc redshift sample can be reproduced with a model distribution that is constructed from a combination of results from studies of strong-lensing clusters in numerical simulations and observational constraints on the galaxy luminosity function.

  18. Crustal thickening drives arc front migration

    NASA Astrophysics Data System (ADS)

    Karlstrom, L.; Lee, C.; Manga, M.

    2012-12-01

    The position of active volcanism relative to the trench in arcs depends on melt focusing processes within the mantle wedge and the geometric parameters of subduction. Arc front migration has been observed in relic (Sierra Nevada, Andes) as well as active (Cascades) arcs, sometimes with cycles of retreat and return of the front towards the trench over millions of years. Other arcs, particularly where backarc extension dominates, exhibit a more stationary front in time relative to the trench. In addition, crustal indices of magmatism as measured by the ratio of trace elements La/Yb or isotopes 87}Sr/{86Sr covary with arc front migration (e.g., Haschke et al., 2002). Arc front migration is commonly attributed to variation in dip angle of the downgoing slab, delamination of overthickened crust, or to subduction erosion. Here we present an alternative hypothesis. Assuming mantle wedge melting is a largely temperature-dependant process, the maximum isotherm in the wedge sets arc front location. Isotherm location depends on slab angle, subduction velocity and wedge thermal diffusivity (England and Katz, 2010). It also depends on crustal thickness, which evolves as melt is transferred from the wedge to the crust. Arc front migration can thus occur purely through magmatic thickening of crust. Thickening proceeds through intrusive as well as extrusive volcanism, modulated by tectonics and surface erosion. Migration rate is set by the mantle melt flux into the crust, which decreases as thickening occurs. Thus slab angle need not change, and in the absence of other contribution processes front location and crustal thickness have long-time steady state values. We develop an analytic model of this process that produces migration rates consistent with published data and explains arc fronts that do not move (dominated by extension, such as in the case of intra-oceanic arcs). We present new geochemical and age data from the Peninsular Ranges Batholith that are also consistent with

  19. Increasing deforestation at the Arc of Deforestation in Brazil

    NASA Astrophysics Data System (ADS)

    Silva, Maria Elisa; Pereira, Gabriel; Rocha, Rosmeri

    2013-04-01

    In this study we investigated the impact on regional climate due to the deforestation of Amazonian region. The deforestation was applied specifically to the area at the edge of the Amazonian region in Brazil, named Arc of Deforestation, where the deforestation actually occurs. The numerical experiments were conducted with the regional climate model RegCM3, used by many scientific groups around the world. The simulations performed by the model were conducted for the Brazil's central-southeast region rainy season, which can be defined between October and March. Each rainy season was separately simulated, being July-1st always the first day and March-31th the last one. Some alterations were made in the model specifications in order to better simulate the climate over South America. Land cover information was updated by more recent data. The older data compiled for 1992 was replaced by that compiled for 2005 (GLCC2005). Besides the global coverage updating, Cerrado information over Brazil obtained from the Brazilian Environmental Ministry was included to cover information. Based on results from others studies, carried out to South America, we changed the root and total soil layers depth, they were enlarged to 3.0 and 4.5 meters, respectively. This change can provide more humidity to the atmosphere and then increase the amount of convective precipitation. The spatial and time resolution considered for all simulations were, respectively, 50 km and 30 min. The domain was defined considering the South America region centered in 55W e 22S, with 160 and 120 points in longitudinal and latitudinal directions, respectively. The vertical resolution was described by 18 levels. The convective precipitation was computed by Grell scheme. Initial and boundary conditions were defined by Reanalysis I dataset. Sea surface temperature was those compiled by NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, and was obtained from their Web site. Spatial patterns of simulated air temperature at low

  20. The performance of the progressive resolution optimizer (PRO) for RapidArc planning in targets with low-density media.

    PubMed

    Kan, Monica W K; Leung, Lucullus H T; Yu, Peter K N

    2013-11-04

    A new version of progressive resolution optimizer (PRO) with an option of air cavity correction has been implemented for RapidArc volumetric-modulated arc therapy (RA). The purpose of this study was to compare the performance of this new PRO with the use of air cavity correction option (PRO10_air) against the one without the use of the air cavity correction option (PRO10_no-air) for RapidArc planning in targets with low-density media of different sizes and complexities. The performance of PRO10_no-air and PRO10_air was initially compared using single-arc plans created for four different simple heterogeneous phantoms with virtual targets and organs at risk. Multiple-arc planning of 12 real patients having nasopharyngeal carcinomas (NPC) and ten patients having non-small cell lung cancer (NSCLC) were then performed using the above two options for further comparison. Dose calculations were performed using both the Acuros XB (AXB) algorithm with the dose to medium option and the analytical anisotropic algorithm (AAA). The effect of using intermediate dose option after the first optimization cycle in PRO10_air and PRO10_no-air was also investigated and compared. Plans were evaluated and compared using target dose coverage, critical organ sparing, conformity index, and dose homogeneity index. For NSCLC cases or cases for which large volumes of low-density media were present in or adjacent to the target volume, the use of the air cavity correction option in PRO10 was shown to be beneficial. For NPC cases or cases for which small volumes of both low- and high-density media existed in the target volume, the use of air cavity correction in PRO10 did not improve the plan quality. Based on the AXB dose calculation results, the use of PRO10_air could produce up to 18% less coverage to the bony structures of the planning target volumes for NPC cases. When the intermediate dose option in PRO10 was used, there was negligible difference observed in plan quality between

  1. Heat sink effects in variable polarity plasma arc welding

    NASA Technical Reports Server (NTRS)

    Abdelmessih, Amanie N.

    1991-01-01

    The Space Shuttle External Tank is fabricated by the variable polarity plasma arc (VPPA) welding process. In VPPA welding, a noble gas, usually argon, is directed through an arc to emerge from the torch as a hot plasma jet. This jet is surrounded by a shielding gas, usually helium, to protect the weld from contamination with air. The high velocity, hot plasma jet completely penetrates the workpiece (resembling a line heat source) when operated in the 'keyhole' mode. The metal melts on touching the side of the jet, as the torch travels in the perpendicular direction to the direction of the jet, and melted metal moves around the plasma jet in the keyhole forming a puddle which solidifies behind the jet. Heat sink effects are observed when there are irregularities in the workpiece configuration, especially, if these irregularities are close to the weld bead. These heat sinks affect the geometry of the weld bead, i.e., in extreme cases they could cause defects such as incomplete fusion. Also, different fixtures seem to have varying heat sink effects. The objective of this research is to study the effect of irregularities in workpiece configuration and fixture differences (heat sink effects) on the weld bead geometry with the ultimate objective to compensate for the heat sink effects and achieve a perfect weld. Experiments were performed on different workpiece geometries and compared to approximate models.

  2. Thermal Treatment of Solid Wastes Using the Electric Arc Furnace

    SciTech Connect

    O'Connor, W.K.; Turner, P.C.

    1999-09-01

    A thermal waste treatment facility has been developed at the Albany Research Center (ARC) over the past seven years to process a wide range of heterogeneous mixed wastes, on a scale of 227 to 907 kg/h (500 to 2,000 lb/h). The current system includes a continuous feed system, a 3-phase AC, 0.8 MW graphite electrode arc furnace, and a dedicated air pollution control system (APCS) which includes a close-coupled thermal oxidizer, spray cooler, baghouse, and wet scrubber. The versatility of the complete system has been demonstrated during 5 continuous melting campaigns, ranging from 11 to 25 mt (12 to 28 st) of treated wastes per campaign, which were conducted on waste materials such as (a) municipal incinerator ash, (b) simulated low-level radioactive, high combustible-bearing mixed wastes, (c) simulated low-level radioactive liquid tank wastes, (d) heavy metal contaminated soils, and (e) organic-contaminated dredging spoils. In all cases, the glass or slag products readily passed the U.S. Environmental Protection Agency (EPA) Toxicity Characteristic Leachability Program (TCLP) test. Additional studies are currently under way on electric utility wastes, steel and aluminum industry wastes, as well as zinc smelter residues. Thermal treatment of these solid waste streams is intended to produce a metallic product along with nonhazardous glass or slag products.

  3. arcControlTower: the System for Atlas Production and Analysis on ARC

    NASA Astrophysics Data System (ADS)

    Filipčič, Andrej; ATLAS Collaboration

    2011-12-01

    PanDA, the Atlas management and distribution system for production and analysis jobs on EGEE and OSG clusters, is based on pilot jobs to increase the throughput and stability of the job execution on grid. The ARC middleware uses a specific approach which tightly connects the job requirements with cluster capabilities like resource usage, software availability and caching of input files. The pilot concept renders the ARC features useless. The arcControlTower is the job submission system which merges the pilot benefits and ARC advantages. It takes the pilot payload from the panda server and submits the jobs to the Nordugrid ARC clusters as regular jobs, with all the job resources known in advance. All the pilot communication with the PanDA server is done by the arcControlTower, so it plays the role of a pilot factory and the pilot itself. There are several advantages to this approach: no grid middleware is needed on the worker nodes, the fair-share between the production and user jobs is tuned with the arcControlTower load parameters, the jobs can be controlled by ARC client tools. The system could be extended to other submission systems using central distribution.

  4. Heat flow and arc efficiency at high pressures in argon and helium tungsten arcs

    SciTech Connect

    Katsaounis, A. )

    1993-09-01

    For control of welding underwater robotic systems, the arc characteristics and the heat quotation in cathode, arc column and anode (weld) were measured in GTAW with argon and helium shielding gas using the calorimetric method. The measurements were performed mainly in a pressure chamber. The pressure, the current and the arc length were varied from 0.1-6.0 MPa, 50-300 A and 2-11 mm, respectively. It was observed that the welding voltage is strongly dependent on system pressure for both shielding gases and an explicit minimum voltage/current was obtained for the argon arc characteristics at approximately 100 A. Furthermore, the field strength and the heat emission from the arc column increased exponentially with the pressure. A simple relation was developed to predict heat emission from the arc column and, consequently, for the arc efficiency. In addition, a calculation model for engineering use was derived based on the Ellenbaas-Heller equation to calculate the-heat flux from the arc to the weld (for both gases).

  5. Effect of acoustic field parameters on arc acoustic binding during ultrasonic wave-assisted arc welding.

    PubMed

    Xie, Weifeng; Fan, Chenglei; Yang, Chunli; Lin, Sanbao

    2016-03-01

    As a newly developed arc welding method, power ultrasound has been successfully introduced into arc and weld pool during ultrasonic wave-assisted arc welding process. The advanced process for molten metals can be realized by utilizing additional ultrasonic field. Under the action of the acoustic wave, the plasma arc as weld heat source is regulated and its characteristics make an obvious change. Compared with the conventional arc, the ultrasonic wave-assisted arc plasma is bound significantly and becomes brighter. To reveal the dependence of the acoustic binding force on acoustic field parameters, a two-dimensional acoustic field model for ultrasonic wave-assisted arc welding device is established. The influences of the radiator height, the central pore radius, the radiator radius, and curvature radius or depth of concave radiator surface are discussed using the boundary element method. Then the authors analyze the resonant mode by this relationship curve between acoustic radiation power and radiator height. Furthermore, the best acoustic binding ability is obtained by optimizing the geometric parameters of acoustic radiator. In addition, three concave radiator surfaces including spherical cap surface, paraboloid of revolution, and rotating single curved surface are investigated systematically. Finally, both the calculation and experiment suggest that, to obtain the best acoustic binding ability, the ultrasonic wave-assisted arc welding setup should be operated under the first resonant mode using a radiator with a spherical cap surface, a small central pore, a large section radius and an appropriate curvature radius.

  6. GUI for studying the parameters influence of the electric arc model for a three-phase electric arc furnace

    NASA Astrophysics Data System (ADS)

    Ghiormez, L.; Prostean, O.; Panoiu, M.; Panoiu, C.

    2017-01-01

    This paper presents an analysis regarding the modeling of the behavior for a three-phase electric arc furnace installation. Therefore, a block diagram is implemented in Simulink that represents the modeling of the entire electric arc furnace installation. This block diagram contains also the modeling of the electric arc which is the element that makes the electric arc furnace behaving as a nonlinear load. The values for the model parameters of the electric arc furnace installation are like the ones from the real installation taken into consideration. Other model parameters are the electric arc model ones. In order to study the influence of the parameters of the electric arc models, it is developed a Matlab program that contains the graphical user interfaces. These interfaces make connection with the models of the electric arc implemented in Simulink. The interfaces allow the user to modify parameters for each of the electric arc model. Current and voltage of the electric arc are the variables taken into account to study the influence of the parameters on the electric arc models. Waveforms for voltage and current of the electric arc are illustrated when a parameter of the model is modified in order to analyze the importance of this parameter on the electric arc model. Also, for each of the models is presented the voltage-current characteristic of the electric arc because this characteristic gives information about the behavior of the electric arc furnace installation.

  7. The Composition of Water-Rich Components in the Sources of Back Arc and Arc Magmas

    NASA Astrophysics Data System (ADS)

    Kelley, K. A.; Hauri, E. H.

    2007-12-01

    Arc and back-arc basin basalts are distinguished by geochemical signatures that are a complex function of the composition of crustal inputs form the subducting plate and the internal "factory" processes that extract materials from the slab and distribute them across the mantle wedge. Here, we use a global data set of basaltic melts from back arcs and arcs to examine relationships between four elements thought to be primary constituents of slab- derived materials: H2O, Na2O, K2O, and Cl. We use the methods of Kelley et al. (2006), coupled with recent constraints on mantle/melt DH2O and DCl (Hauri et al., 2006) to constrain concentrations of these elements in the mantle source, which compare directly with compositional models of the mantle and the slab-derived component beneath the Mariana trough (Stolper & Newman, 1994). The Mariana trough samples define linear trends in Na2O/H2O (1), K2O/H2O (0.2), and Cl/H2O (0.03) consistent with mixing between these two components. Four other back-arc basins (Sumisu, Central Lau, Manus, and E. Scotia) also fall along this trend in Na2O/H2O and K2O/H2O, suggesting that slab additions to most back-arc mantle sources have common major element characteristics. The Valu Fa Ridge segment of the southern Lau basin, however, trends away from other back arcs towards lower Na2O/H2O (0.1) and K2O/H2O (0.08). Such lower ratios are generally characteristic of arc sources in the Marianas and other arcs (e.g., Na2O/H2O=0.5-0.05), but also appear to be distinct for specific arc volcanoes. In back arcs, Cl may also be affected by late-stage magmatic assimilation of seawater, which drives up Cl/H2O and obscures primary trends, although some central Lau basin samples do point towards a mixing array coincident with the Mariana trough. Mariana arc sources have higher H2O and Cl concentrations than the Mariana trough, and indicate overall lower, but volcano-specific, Cl/H2O (0.02-0.01). In terms of these major-element constituents, arc volcanoes

  8. Research of Arc Chamber Optimization Techniques Based on Flow Field and Arc Joint Simulation

    NASA Astrophysics Data System (ADS)

    Zhong, Jianying; Guo, Yujing; Zhang, Hao

    2016-03-01

    The preliminary design of an arc chamber in the 550 kV SF6 circuit breaker was proposed in accordance with the technical requirements and design experience. The structural optimization was carried out according to the no-load flow field simulation results and verified by no-load pressure measurement. Based on load simulation results such as temperature field variation at the arc area and the tendency of post arc current under different recovery voltage, the second optimal design was completed and its correctness was certificated by a breaking test. Results demonstrate that the interrupting capacity of an arc chamber can be evaluated by the comparison of the gas medium recovery speed and post arc current growth rate.

  9. Gaseous and particulate emissions from a DC arc melter.

    PubMed

    Overcamp, Thomas J; Speer, Matthew P; Griner, Stewart J; Cash, Douglas M

    2003-01-01

    Tests treating soils contaminated with metal compounds and radionuclide surrogates were conducted in a DC arc melter. The soil melted, and glassy or ceramic waste forms with a separate metal phase were produced. Tests were run in the melter plenum with either air or N2 purge gases. In addition to nitrogen, the primary emissions of gases were CO2, CO, oxygen, methane, and oxides of nitrogen (NO(x)). Although the gas flow through the melter was low, the particulate concentrations ranged from 32 to 145 g/m3. Cerium, a nonradioactive surrogate for plutonium and uranium, was not enriched in the particulate matter (PM). The PM was enriched in cesium and highly enriched in lead.

  10. Earthquake location in island arcs

    USGS Publications Warehouse

    Engdahl, E.R.; Dewey, J.W.; Fujita, K.

    1982-01-01

    A comprehensive data set of selected teleseismic P-wave arrivals and local-network P- and S-wave arrivals from large earthquakes occurring at all depths within a small section of the central Aleutians is used to examine the general problem of earthquake location in island arcs. Reference hypocenters for this special data set are determined for shallow earthquakes from local-network data and for deep earthquakes from combined local and teleseismic data by joint inversion for structure and location. The high-velocity lithospheric slab beneath the central Aleutians may displace hypocenters that are located using spherically symmetric Earth models; the amount of displacement depends on the position of the earthquakes with respect to the slab and on whether local or teleseismic data are used to locate the earthquakes. Hypocenters for trench and intermediate-depth events appear to be minimally biased by the effects of slab structure on rays to teleseismic stations. However, locations of intermediate-depth events based on only local data are systematically displaced southwards, the magnitude of the displacement being proportional to depth. Shallow-focus events along the main thrust zone, although well located using only local-network data, are severely shifted northwards and deeper, with displacements as large as 50 km, by slab effects on teleseismic travel times. Hypocenters determined by a method that utilizes seismic ray tracing through a three-dimensional velocity model of the subduction zone, derived by thermal modeling, are compared to results obtained by the method of joint hypocenter determination (JHD) that formally assumes a laterally homogeneous velocity model over the source region and treats all raypath anomalies as constant station corrections to the travel-time curve. The ray-tracing method has the theoretical advantage that it accounts for variations in travel-time anomalies within a group of events distributed over a sizable region of a dipping, high

  11. Critical Length Criterion and the Arc Chain Model for Calculating the Arcing Time of the Secondary Arc Related to AC Transmission Lines

    NASA Astrophysics Data System (ADS)

    Cong, Haoxi; Li, Qingmin; Xing, Jinyuan; Li, Jinsong; Chen, Qiang

    2015-06-01

    The prompt extinction of the secondary arc is critical to the single-phase reclosing of AC transmission lines, including half-wavelength power transmission lines. In this paper, a low-voltage physical experimental platform was established and the motion process of the secondary arc was recorded by a high-speed camera. It was found that the arcing time of the secondary arc rendered a close relationship with its arc length. Through the input and output power energy analysis of the secondary arc, a new critical length criterion for the arcing time was proposed. The arc chain model was then adopted to calculate the arcing time with both the traditional and the proposed critical length criteria, and the simulation results were compared with the experimental data. The study showed that the arcing time calculated from the new critical length criterion gave more accurate results, which can provide a reliable criterion in term of arcing time for modeling and simulation of the secondary arc related with power transmission lines. supported by National Natural Science Foundation of China (Nos. 51277061 and 51420105011)

  12. Back-arc basin basalt systematics

    NASA Astrophysics Data System (ADS)

    Taylor, Brian; Martinez, Fernando

    2003-05-01

    The Mariana, east Scotia, Lau, and Manus back-arc basins (BABs) have spreading rates that vary from slow (<50 mm/yr) to fast (>100 mm/yr) and extension axes located from 10 to 400 km behind their island arcs. Axial lava compositions from these BABs indicate melting of mid-ocean ridge basalt (MORB)-like sources in proportion to the amount added of previously depleted, water-rich, arc-like components. The arc-like end-members are characterized by low Na, Ti and Fe, and by high H 2O and Ba/La; the MORB-like end-members have the opposite traits. Comparisons between basins show that the least hydrous compositions follow global MORB systematics and an inverse correlation between Na8 and Fe8. This is interpreted as a positive correlation between the average degree and pressure of mantle melting that reflects regional variations in mantle potential temperatures (Lau/Manus hotter than Mariana/Scotia). This interpretation accords with numerical model predictions that faster subduction-induced advection will maintain a hotter mantle wedge. The primary compositional trends within each BAB (a positive correlation between Fe8, Na8 and Ti8, and their inverse correlation with H 2O(8) and Ba/La) are controlled by variations in water content, melt extraction, and enrichments imposed by slab and mantle wedge processes. Systematic axial depth (as a proxy for crustal production) variations with distance from the island arc indicate that compositional controls on melting dominate over spreading rate. Hydrous fluxing enhances decompression melting, allowing depleted mantle sources just behind the island arc to melt extensively, producing shallow spreading axes. Flow of enriched mantle components around the ends of slabs may augment this process in transform-bounded back-arcs such as the east Scotia Basin. The re-circulation (by mantle wedge corner flow) to the spreading axes of mantle previously depleted by both arc and spreading melt extraction can explain the greater depths and thinner

  13. The geochemistry and petrogenesis of the Paleoproterozoic Green Mountain arc: A composite(?), bimodal, oceanic, fringing arc

    USGS Publications Warehouse

    Jones, D.S.; Barnes, C.G.; Premo, W.R.; Snoke, A.W.

    2011-01-01

    The inferred subduction affinity of the ~1780-Ma Green Mountain arc, a dominantly bimodal igneous terrane (together with immature marine and volcaniclastic sedimentary rocks) accreted to the southern margin of the Wyoming province, is integral to arc-accretion models of the Paleoproterozoic growth of southern Laurentia. Conversely, the dominantly bimodal nature of many putative arc-related igneous suites throughout southern Laurentia, including the Green Mountain arc, has also been used to support models of growth by extension of pre-existing crust. We report new geochemical and isotopic data from ~1780-Ma gabbroic and granodioritic to tonalitic rocks of the Big Creek Gneiss, interpreted as consanguineous with previously studied metavolcanic rocks of the Green Mountain Formation.The ~1780-Ma Big Creek Gneiss mafic rocks show clear geochemical signatures of a subduction origin and provide no supporting evidence for extensional tectonism. The ~1780-Ma Big Creek Gneiss felsic rocks are attributed to partial melting of mafic and/or mixed lower-crustal material. The bimodal nature of the suite results from the combination of arc basalts and felsic crustal melts. The lack of andesite is consistent with the observed tholeiitic differentiation trend of the mafic magmas. The lower e{open}Nd(1780Ma) values for the felsic rocks vs. the mafic rocks suggest that the unexposed lower crust of the arc may be older than the arc and that Trans-Hudson- or Penokean-aged rocks possibly form the substratum of the arc. Our results reinforce previous interpretations that arc-related magmatism played a key role in the Paleoproterozoic crustal growth of southern Laurentia, but also support the possibility of unexposed older crust as basement to the arcs. ?? 2011 Elsevier B.V.

  14. Crustal evolution of Eocene paleo arc around Ogasawara region obtained by seismic reflection survey

    NASA Astrophysics Data System (ADS)

    Yamashita, M.; Takahashi, N.; Kodaira, S.; Miura, S.; Ishizuka, O.; Tatsumi, Y.

    2011-12-01

    The Izu-Bonin (Ogasawara)-Mariana (IBM) arc is known to the typical oceanic island arc, and it is the most suitable area to understand the growth process of island arc. The existence of two paleo arc which consists of Oligocene and Eocene paleo age is known in IBM forearc region by geological and geophysical studies. The Ogasawara ridge is also known to locate the initial structure of arc evolution from geologic sampling of research submersible. In this region, IODP drilling site: IBM-2 is proposed in order to understand the temporal and spatial change in arc crust composition from 50 to 40Ma magmatism. Site IBM-2 consists of two offset drilling holes (BON-1, BON-2). BON-1 designed to first encounter forearc basalt and will reach the sheeted dykes. BON-2 will start in boninites and finish in fore arc basalts. The purpose of these drilling is sampling the full volcanic stratigraphy from gabbro to boninite. There is no seismic data around BON-1 and BON-2, therefore it is need to conduct the multi-channel seismic reflection survey. Japan Agency for Marine-Earth Science and Technology carried out multi-channel seismic reflection survey and wide-angle reflection survey using 7,800 cu.in. air gun, 5 km streamer with 444 ch hydrophones and 40 OBSs in March 2011. We obtained two seismic reflection profiles of lines KT06 and KT07 along the paleo arc around Ogasawara ridge. Line KT06 located the north side of Ogasawara ridge. Line KT07 located the trench side of Ogasawara ridge. Lines KT06 is also deployed the OBSs every 5 km interval. Thin sediments are covered with basement in both survey lines. There are some sediment filled in depression topography. The low-frequency reflection from the top of subducting Pacific plate is recognized in line KT06. The continuity of this reflection is not clear due to the complicated bathymetry. The displacement of basement in northern side of Ogasawara ridge is identified along the lineament of bathymetry in Line 06. This structure is

  15. Physics of arcing, and implications to sputter deposition

    SciTech Connect

    Anders, Andre

    2005-03-15

    Arc and glow discharges are defined based on their cathode processes. Arcs are characterized by collective electron emission, which can be stationary with hot cathodes (thermionic arcs), or non-stationary with cold cathodes (cathodic arcs). A brief review on cathodic arc properties serves as the starting point to better understand arcing phenomena in sputtering. Although arcing occurs in both metal and reactive sputtering, it is more of an issue in the reactive case. Arcing occurs if sufficiently high field strength leads to thermal runaway of an electron emission site. The role of insulating layers and surface potential adjustment through current leakage is highlighted. In the situation of magnetron sputtering with ''racetrack'', the need for a model with two spatial dimensions is shown. In many cases, arcing is initiated by breakdown of dielectric layers and inclusions. It is most efficiently prevented if formation and excessive charge-up of dielectric layers and inclusions can be avoided.

  16. Fluid simulation of carbon arc plasma

    NASA Astrophysics Data System (ADS)

    Hara, Kentaro; Raitses, Yevgeny; Kaganovich, Igor

    2016-09-01

    An arc discharge using graphite electrodes is known to produce carbon nanomaterials, e.g. nanotubes and fullerenes. In order to understand where and how such nanomaterials are synthesized, the plasma properties inside the arc discharge must be characterized. The mechanism of the carbon arc plasma is as follows. Carbon particles evaporate from the graphite anode, which is mainly heated by the electrons. Carbon atoms and ions condensate and form a deposit on the cathode, from which the electrons are thermionically emitted. A one-dimensional fluid model is developed to study the characteristics of the carbon arc plasma in atmospheric pressures. Sheath models for the anode and cathode are coupled to the fluid simulation to obtain the material temperature and sheath potential. In the model, thermal nonequilibrium is assumed and atomic carbon, dimer, and trimer are considered. A typical operating condition of a carbon arc plasma is discharge voltage of 20 V, discharge current of 60 A, the electron radius of 6 to 12 mm, and background pressure of 500 Torr. Transition from low to high ablation mode is obtained from the simulations with a smaller electrode radius and with a larger discharge current, which agrees with experimental observations. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  17. Ion source with improved primary arc collimation

    DOEpatents

    Dagenhart, W.K.

    1983-12-16

    An improved negative ion source is provided in which a self-biasing, molybdenum collimator is used to define the primary electron stream arc discharge from a filament operated at a negative potential. The collimator is located between the anode and the filament. It is electrically connected to the anode by means of an appropriate size resistor such that the collimator is biased at essentially the filament voltage during operation. Initially, the full arc voltage appears across the filament to collimator until the arc discharge strikes. Then the collimator biases itself to essentially filament potential due to current flow through the resistor thus defining the primary electron stream without intercepting any appreciable arc power. The collimator aperture is slightly smaller than the anode aperture to shield the anode from the arc power which, in the past, has caused overheating and erosion of the anode collimator during extended time pulsed-beam operation of the source. With the self-biasing collimator of this invention, the ion source may be operated from short pulse periods to steady-state without destroying the anode.

  18. Electric Arc and Electrochemical Surface Texturing Technologies

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; Rutledge, Sharon K.; Snyder, Scott A.

    1997-01-01

    Surface texturing of conductive materials can readily be accomplished by means of a moving electric arc which produces a plasma from the environmental gases as well as from the vaporized substrate and arc electrode materials. As the arc is forced to move across the substrate surface, a condensate from the plasma re-deposits an extremely rough surface which is intimately mixed and attached to the substrate material. The arc textured surfaces produce greatly enhanced thermal emittance and hold potential for use as high temperature radiator surfaces in space, as well as in systems which use radiative heat dissipation such as computer assisted tomography (CAT) scan systems. Electrochemical texturing of titanium alloys can be accomplished by using sodium chloride solutions along with ultrasonic agitation to produce a random distribution of craters on the surface. The crater size and density can be controlled to produce surface craters appropriately sized for direct bone in-growth of orthopaedic implants. Electric arc texturing and electrochemical texturing techniques, surface properties and potential applications will be presented.

  19. Welding torch with arc light reflector

    NASA Technical Reports Server (NTRS)

    Gordon, Stephen S. (Inventor)

    1986-01-01

    A welding torch arc light reflector is disclosed for welding torches having optical viewing systems. A schematic of a welding torch having an internal coaxial viewing system consisting of a lens which focuses the field of view of the weld scene of the workpiece onto the end of the fiberoptic bundle is provided. The transmitted image of the fiberoptic bundle is provided to a camera lens which focuses it onto a TV sensor array for transmission. To improve the parity of the image of the monitoring system, an arc light reflector is shown fitted to the end of the torch housing or gas cup. The arc light reflector has an internal conical section portion which is polished to serve as a mirror which reflects the bright arc light back onto the darker areas of the weld area and thereby provides a more detailed image for the monitoring system. The novelty of the invention lies in the use of an arc light reflector on welding torches having optical viewing systems.

  20. Welding torch with arc light reflector

    NASA Astrophysics Data System (ADS)

    Gordon, Stephen S.

    1986-12-01

    A welding torch arc light reflector is disclosed for welding torches having optical viewing systems. A schematic of a welding torch having an internal coaxial viewing system consisting of a lens which focuses the field of view of the weld scene of the workpiece onto the end of the fiberoptic bundle is provided. The transmitted image of the fiberoptic bundle is provided to a camera lens which focuses it onto a TV sensor array for transmission. To improve the parity of the image of the monitoring system, an arc light reflector is shown fitted to the end of the torch housing or gas cup. The arc light reflector has an internal conical section portion which is polished to serve as a mirror which reflects the bright arc light back onto the darker areas of the weld area and thereby provides a more detailed image for the monitoring system. The novelty of the invention lies in the use of an arc light reflector on welding torches having optical viewing systems.

  1. Channel model for AC electric arc

    NASA Astrophysics Data System (ADS)

    Larsen, H. L.

    1993-06-01

    This report contains the results from calculations of free-burning AC electric arcs in argon. In order to calculate the arc current and arc voltage, the external electric circuit must be taken into consideration. The external circuit is modeled by an equivalent circuit consisting of an ideal AC voltage source, a loss resistance, and an inductance. The qualitative behavior of the current-voltage characteristic is in agreement with observed characteristics, but experimental data are necessary in order to check whether the calculated power loss is reasonable. Non-symmetry was modeled by introducing different anode and cathode falls in the two half periods. An attempt at taking into account different cathode current densities in the two half periods, depending on whether the electrode or silicon melt is cathode, did not give satisfactory results. Thermionic emission was assumed in both half periods, but this may not be the right mechanism when the silicon melt is cathode. The time delay of the AC arc compared to the DC case is modeled by a time constant. It was shown that this preset time constant must be in agreement with the mean 'mechanical' relaxation time in the arc in order to fulfill the energy balance. By updating the time constant until this is achieved, the time constant is eliminated as a parameter that must be chosen a priori.

  2. Arc Conductance and Flow Velocity Affected by Transient Recovery Voltage

    NASA Astrophysics Data System (ADS)

    Fukuoka, Reo; Ishikawa, Yuya; Ono, Seisui; Sato, Ken; Yamamoto, Shinji; Iwao, Toru

    2016-09-01

    Recently, the stable supply of electric power is indispensable. The GCB (Gas Circuit Breaker) can prevent the spread of the fault current. However, it should have the reliability more. Therefore the GCB has been researched for performance improvement of the arc interruption of abnormal fault current without the fail. Therefore, it is important to prevent the breakdown such as the re-ignition and thermal re-ignition of arc after the arc interruption. It is necessary to reduce the arc conductance in order to prevent the re-ignition of arc. The arc conductance is derived from the temperature distribution and the volume of the arc. The temperature distribution of the arc is formed by convection. In this research, the arc conductance and flow velocity affected by transient recovery voltage are elucidated. The flow rate and temperature distribution of the arc is calculated with changing transient recovery voltage. In addition, the arc conductance is calculated in order to know the extinguish arc ability. As a result, when the transient recovery voltage increases, the probability of re-ignition increases. Therefore, the arc temperature and the arc conductance were increased.

  3. EDITORIAL Metal vapour in atmospheric-pressure arcs Metal vapour in atmospheric-pressure arcs

    NASA Astrophysics Data System (ADS)

    Murphy, Anthony B.

    2010-11-01

    Metal vapour has a significant, and in some cases dominant, influence in many applications of atmospheric-pressure plasmas, including arc welding, circuit interruption and mineral processing. While the influence of metal vapour has long been recognized, it is only recently that diagnostic and computational tools have been sufficiently well-developed to allow this influence to be more thoroughly examined and understood. Some unexpected findings have resulted: for example, that the presence of metal vapour in gas-metal arc welding leads to local minima in the temperature and current density in the centre of the arc. It has become clear that the presence of metal vapour, as well as having intrinsic scientific interest, plays an important role in determining the values of critical parameters in industrial applications, such as the weld penetration in arc welding and the extinction time in circuit breakers. In gas-tungsten arc welding, metal vapour concentrations are formed by evaporation of the weld pool, and are relatively low, typically at most a few per cent. Moreover, the convective flow of the plasma near the weld pool tends to direct the metal vapour plume radially outwards. In gas-metal arc welding, in contrast, metal vapour concentrations can reach over 50%. In this case, the metal vapour is produced mainly by evaporation of the wire electrode, and the strong downwards convective flow below the electrode concentrates the metal vapour in the central region of the arc. The very different metal concentrations and distributions in the two welding processes mean that the metal vapour has markedly different influences on the arc. In gas-tungsten arc welding, the current density distribution is broadened near the weld pool by the influence of the metal vapour on the electrical conductivity of the plasma, and the arc voltage is decreased. In contrast, in gas-metal arc welding, the arc centre is cooled by increased radiative emission and the arc voltage is increased. In

  4. Plasma arc heated secondary combustion chamber

    SciTech Connect

    Haun, R.; Paulson, B.; Schlienger, M.; Goerz, D.; Kerns, J.; Vernazza, J.

    1995-02-01

    This paper describes a secondary combustion chamber (SCC) for hazardous waste treatment systems that uses a plasma arc torch as the heat source. Developed under a cooperative research and development agreement (CRADA) between Retech, Inc. and Lawrence Livermore National Laboratory (LLNL), the unit is intended primarily to handle the off-gas from a Plasma Arc Centrifugal Treatment (PACT) system. ft is designed to heat the effluent gas which may contain volatile organic compounds, and maintain the gas temperature above 1000 C for two seconds or more. The benefits of using a plasma arc gas heater are described in comparison to a conventional fossil fuel heated SCC. Thermal design considerations are discussed. Analysis and experimental results are presented to show the effectiveness in destroying hazardous compounds and reducing the total volume of gaseous emissions.

  5. Understanding the Evolution of the Scotia Arc

    NASA Astrophysics Data System (ADS)

    Maldonado, Andrés.; Dalziel, Ian; Leat, Philip T.

    2013-07-01

    An international 3-day meeting in which participants discussed geodynamic and multidisciplinary topics related to the evolution of the Scotia Arc was held at the Andalucía Institute of Earth Sciences (Spanish Research Council (CSIC)/University of Granada (UGR)) in Granada, Spain. The Scotia Arc encompasses southern South America, the Antarctic Peninsula, and the intervening part of the Southern Ocean including the South Georgia and South Orkney crustal blocks and the volcanically active South Sandwich Arc. It is a region of critical importance because of its role as a developing ocean gateway during Eocene-Miocene times and because of its impact on global ocean circulation, with possible importance for Paleogene-Neogene paleoenvironmental change, early phases of development of Antarctic ice sheets, gene flow, and resulting biodiversity.

  6. APPARATUS AND METHOD FOR ARC WELDING

    DOEpatents

    Noland, R.A.; Stone, C.C.

    1960-05-10

    An apparatus and method are given for forming a welding arc which is rotated by a magnetic field very rapidly about an annular electrode so that a weld is produced simultaneously over all points of an annular or closed path. This invention inhibits outgassing from the jacket of a fuel slug which is being welded by adjusting the pressure throughout the welding cycle to establish a balance between the gas pressure within the jacket and that of the atmosphere surrounding the jacket. Furthermore, an improved control of the magnetic field producing rotation of the welding arc is disclosed whereby this rotation is prevented from splashing about the metal being welded as the welding arc makes it molten.

  7. Characterization of a high current pulsed arc using optical emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Sousa Martins, R.; Zaepffel, C.; Chemartin, L.; Lalande, Ph; Soufiani, A.

    2016-10-01

    In this paper, we present the investigation realized on an experimental setup that simulates an arc column subjected to the transient phase of a lightning current waveform in laboratory conditions. Optical emission spectroscopy is employed to assess space- and time-resolved properties of this high current pulsed arc. Different current peak levels are utilised in this work, ranging from 10 kA to 100 kA, with a peak time around 15 µs. Ionic lines of nitrogen and oxygen are used to determine the radial profiles of temperature and electron density of the arc channel over time from 2 µs to 36 µs. A combination of 192 N II and O II lines is considered in the calculation of the bound-bound contribution of the absorption coefficient of the plasma channel. Calculations of the optical thickness showed that self-absorption of these ionic lines in the arc column is important. To obtain temperature and electron density profiles in the arc, we solved the radiative transfer equation across the channel under an axisymmetric assumption and considering the channel formed by uniform concentric layers. For the 100 kA current peak level, the temperature reaches more than 38 000 K and the electron density reaches 5  ×  1018 cm-3. The pressure inside the channel is calculated using the air plasma composition at local thermodynamic equilibrium, and reaches 45 bar. The results are discussed and utilised to estimate the electrical conductivity of the arc channel.

  8. Interaction of graphite and ablative materials with CO2-laser, carbon-arc, and xenon-arc radiation. M.S. Thesis - George Washington Univ., Washington, D. C.

    NASA Technical Reports Server (NTRS)

    Brewer, W. D.

    1975-01-01

    The behavior of graphite and several charring ablators in a variety of high radiative heat flux environments was studied in various radiative environments produced by a CO2 laser and a carbon arc facility. Graphite was also tested in xenon arc radiation. Tests were conducted in air nitrogen, helium, and a mixture of CO2 and nitrogen, simulating the Venus atmosphere. The experimental results are compared with theoretical results obtained with a one dimensional charring ablator analysis and a two dimensional subliming ablator analysis. Photomicroscopy showed no significant differences in appearance or microstructure of the charring ablators or graphite after testing in the three different facilities, indicating that the materials respond fundamentally the same to the radiation of different frequencies. The performance of phenolic nylon and graphite was satisfactorily predicted with existing analyses and published material property data.

  9. Air Pollution

    MedlinePlus

    Air pollution is a mixture of solid particles and gases in the air. Car emissions, chemicals from factories, ... Ozone, a gas, is a major part of air pollution in cities. When ozone forms air pollution, it's ...

  10. Nonlinear identification of the total baroreflex arc.

    PubMed

    Moslehpour, Mohsen; Kawada, Toru; Sunagawa, Kenji; Sugimachi, Masaru; Mukkamala, Ramakrishna

    2015-12-15

    The total baroreflex arc [the open-loop system relating carotid sinus pressure (CSP) to arterial pressure (AP)] is known to exhibit nonlinear behaviors. However, few studies have quantitatively characterized its nonlinear dynamics. The aim of this study was to develop a nonlinear model of the sympathetically mediated total arc without assuming any model form. Normal rats were studied under anesthesia. The vagal and aortic depressor nerves were sectioned, the carotid sinus regions were isolated and attached to a servo-controlled piston pump, and the AP and sympathetic nerve activity (SNA) were measured. CSP was perturbed using a Gaussian white noise signal. A second-order Volterra model was developed by applying nonparametric identification to the measurements. The second-order kernel was mainly diagonal, but the diagonal differed in shape from the first-order kernel. Hence, a reduced second-order model was similarly developed comprising a linear dynamic system in parallel with a squaring system in cascade with a slower linear dynamic system. This "Uryson" model predicted AP changes 12% better (P < 0.01) than a linear model in response to new Gaussian white noise CSP. The model also predicted nonlinear behaviors, including thresholding and mean responses to CSP changes about the mean. Models of the neural arc (the system relating CSP to SNA) and peripheral arc (the system relating SNA to AP) were likewise developed and tested. However, these models of subsystems of the total arc showed approximately linear behaviors. In conclusion, the validated nonlinear model of the total arc revealed that the system takes on an Uryson structure.

  11. Magnesium isotope geochemistry in arc volcanism

    PubMed Central

    Teng, Fang-Zhen; Hu, Yan

    2016-01-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from −0.25 to −0.10, in contrast to the narrow range that characterizes the mantle (−0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid−mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration. PMID:27303032

  12. Nonlinear identification of the total baroreflex arc

    PubMed Central

    Moslehpour, Mohsen; Kawada, Toru; Sunagawa, Kenji; Sugimachi, Masaru

    2015-01-01

    The total baroreflex arc [the open-loop system relating carotid sinus pressure (CSP) to arterial pressure (AP)] is known to exhibit nonlinear behaviors. However, few studies have quantitatively characterized its nonlinear dynamics. The aim of this study was to develop a nonlinear model of the sympathetically mediated total arc without assuming any model form. Normal rats were studied under anesthesia. The vagal and aortic depressor nerves were sectioned, the carotid sinus regions were isolated and attached to a servo-controlled piston pump, and the AP and sympathetic nerve activity (SNA) were measured. CSP was perturbed using a Gaussian white noise signal. A second-order Volterra model was developed by applying nonparametric identification to the measurements. The second-order kernel was mainly diagonal, but the diagonal differed in shape from the first-order kernel. Hence, a reduced second-order model was similarly developed comprising a linear dynamic system in parallel with a squaring system in cascade with a slower linear dynamic system. This “Uryson” model predicted AP changes 12% better (P < 0.01) than a linear model in response to new Gaussian white noise CSP. The model also predicted nonlinear behaviors, including thresholding and mean responses to CSP changes about the mean. Models of the neural arc (the system relating CSP to SNA) and peripheral arc (the system relating SNA to AP) were likewise developed and tested. However, these models of subsystems of the total arc showed approximately linear behaviors. In conclusion, the validated nonlinear model of the total arc revealed that the system takes on an Uryson structure. PMID:26354845

  13. Axial Presentations of Regular Arcs on Mn

    PubMed Central

    Morse, Marston

    1972-01-01

    THEOREM 1. Let Mn be a Riemannian manifold of class Cm, m > 0. On Mn let g be a simple compact, sensed, regular arc whose local coordinates are functions of class Cm of the algebraic arc length s, measured along g from a prescribed point of g. There then exists a presentation (F: U, X) [unk] [unk]Mn such that g [unk] X, and each point p(s) of g is represented in the euclidean domain U by coordinates (x1,...,xn) = (s,0,...,0). PMID:16592036

  14. Grain refinement control in TIG arc welding

    NASA Technical Reports Server (NTRS)

    Iceland, W. F.; Whiffen, E. L. (Inventor)

    1975-01-01

    A method for controlling grain size and weld puddle agitation in a tungsten electrode inert gas welding system to produce fine, even grain size and distribution is disclosed. In the method the frequency of dc welding voltage pulses supplied to the welding electrode is varied over a preselected frequency range and the arc gas voltage is monitored. At some frequency in the preselected range the arc gas voltage will pass through a maximum. By maintaining the operating frequency of the system at this value, maximum weld puddle agitation and fine grain structure are produced.

  15. Arc-driven rail accelerator research

    NASA Technical Reports Server (NTRS)

    Ray, Pradosh K.

    1987-01-01

    Arc-driven rail accelerator research is analyzed by considering wall ablation and viscous drag in the plasma. Plasma characteristics are evaluated through a simple fluid-mechanical analysis considering only wall ablation. By equating the energy dissipated in the plasma with the radiation heat loss, the average properties of the plasma are determined as a function of time and rate of ablation. Locations of two simultaneously accelerating arcs were determined by optical and magnetic probes and fron streak camera photographs. All three measurements provide consistent results.

  16. Ion source based on the cathodic arc

    DOEpatents

    Sanders, D.M.; Falabella, S.

    1994-02-01

    A cylindrically symmetric arc source to produce a ring of ions which leave the surface of the arc target radially and are reflected by electrostatic fields present in the source to a point of use, such as a part to be coated, is described. An array of electrically isolated rings positioned in the source serves the dual purpose of minimizing bouncing of macroparticles and providing electrical insulation to maximize the electric field gradients within the source. The source also includes a series of baffles which function as a filtering or trapping mechanism for any macroparticles. 3 figures.

  17. Ion source based on the cathodic arc

    DOEpatents

    Sanders, David M.; Falabella, Steven

    1994-01-01

    A cylindrically symmetric arc source to produce a ring of ions which leave the surface of the arc target radially and are reflected by electrostatic fields present in the source to a point of use, such as a part to be coated. An array of electrically isolated rings positioned in the source serves the dual purpose of minimizing bouncing of macroparticles and providing electrical insulation to maximize the electric field gradients within the source. The source also includes a series of baffles which function as a filtering or trapping mechanism for any macroparticles.

  18. Plasma distribution of cathodic ARC deposition system

    SciTech Connect

    Anders, S.; Raoux, S.; Krishnan, K.; MacGill, R.A.; Brown, I.G.

    1996-08-01

    The plasma distribution using a cathodic arc plasma source with and without magnetic macroparticle filter has been determined by depositing on a transparent plastic substrate and measuring the film absorption. It was found that the width of the distribution depends on the arc current, and it also depends on the cathode material which leads to a spatial separation of the elements when an alloy cathode is used. By applying a magnetic multicusp field near the exit of the magnetic filter, it was possible to modify the plasma distribution and obtain a flat plasma profile with a constant and homogeneous elemental distribution.

  19. Geochemical differences between along-arc and across-arc volcanics in west-central Nicaragua

    NASA Astrophysics Data System (ADS)

    Geilert, Sonja; Freundt, Armin; Wörner, Gerhard; Kutterolf, Steffen

    2012-04-01

    The La Paz Centro - Malpaisillo Lineament (LPML) in west-central Nicaragua is a north-south striking, 20 km long chain of maars and cinder cones, which intersects the northwest-southeast striking main volcanic front. A tectonic control of LPML volcanism is likely but only evident for the Malpaisillo fissure at the northern end of the LPML. Previous work demonstrated geochemical variations implying changes in mantle-source composition (i.e., added slab components) along the Central American Volcanic Arc at spatial scales of some 10's of kilometers. Our study of the LPML shows that minor but systematic changes also occur across the arc within 20 km distance. Variations in trace element ratios such as Zr/Nb, Ba/Th, Ba/La, Th/Zr, U/La and La/Yb along the LPML, i.e. across the volcanic front indicate little change in the degree of partial melting but an increase particularly in the hemipelagic sediment component in the mantle source from the fore arc towards the arc front, followed by a decrease behind the arc. Interestingly, the slab component is most prominent just in front of the arc. About 60 km southeast of the LPML, the Nejapa-Miraflores volcanic and tectonic lineament, which marks a 20 km north-south offset in the arc, differs substantially from the LPML. There is a wide scatter in incompatible trace element ratios indicating a heterogeneous mantle source at small spatial scales (c. 1 km). This mantle heterogeneity may represent vertical rather than across-arc variations and is probably related to the arc offset, because in the absence of such offset at the LPML mantle source conditions vary much less but more systematically.

  20. The effect of plasma on solar cell array arc characteristics

    NASA Technical Reports Server (NTRS)

    Snyder, D. B.; Tyree, E.

    1984-01-01

    The influence from the ambient plasma on the arc characteristics of a negatively biased solar cell array was investigated. The arc characteristics examined were the peak current during an arc, the decay time as the arc terminates, and the charge lost during the arc. These arc characteristics were examined in a nitrogen plasma with charge densities ranging from 15,000 to 45,000 cu cm. Background gas pressures ranged from 8x1,000,000 to 6x100,000 torr. Over these ranges of parameters no significant effect on the arc characteristics were seen. Arc characteristics were also examined for three gas species: helium, nitrogen and argon. The helium arcs have higher peak currents and shorter decay times than nitrogen and argon arcs. There are slight differences in the arc characteristics between nitrogen and argon. These differences may be caused by the differences in mass of the respective species. Also, evidence is presented for an electron emission mechanism appearing as a precursor to solar array arcs. Occassionally the plasma generator could be turned off, and currents could still be detected in the vacuum system. When these currents are presented, arcs may occur.

  1. Influence of a transverse magnetic field on arc root movements in a dc plasma torch: Diamagnetic effect of arc column

    SciTech Connect

    Kim, Keun Su

    2009-03-23

    The effect of a transverse magnetic field on the anodic arc root movement inside a dc plasma torch has been investigated. The arc voltage fluctuation, which represents the degree of the arc instability, was reduced to 28.6% of the original value and the high frequency components in the voltage signal also decreased in their magnitudes. The inherent arc instability in a dc thermal plasma torch seems to be suppressed by a diamagnetic effect of the arc column. Furthermore, the measured voltage wave forms indicated that the arc root attachment mode would be controllable by a transverse magnetic field.

  2. Characterization of Submerged-Arc and Gas-Metal-Arc Weldments in HY-100 Steel.

    DTIC Science & Technology

    1983-12-01

    RD-R14i 939 CHARACTERIZATION OF SUBMERGED-ARC AND GAS-METAL-ARC / WELDMENTS IN HY-IBB STEEL (U) NAVAL POSTGRADUATE SCHOOL MONTEREY CA R E THERRIEN DEC...100 Steel 6. PIERFORMING ORG. REPORT NUM11ER I.7. AUTHOW) 11. CONTRACT OR GRANT NuMMER(.) Alfred E. Therrien _O P O R ME E E T R J C .T S’ .~ S...weld toughness in submerged arc welded (SAW) 4- HY-100 steel weldments precludes this process from large 4. scale HY-100 shipbuilding production

  3. DEVICE AND METHOD FOR PRODUCING A HIGH INTENSITY ARC DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-01-01

    A device is described for producing an energetic d-c carbon arc discharge between widely spaced electrodes with arc currents in excess of 100 amperes in a magnetic field of about 3000 gauss and witnin an evacuated enclo sure at a pressure of about 10/sup -5/ mm Hg. No defining electrodes are used in the device, thus essentially eliminating the problems of shorting which heretofore limited the amount of current that could be produced in an arc discharge. The energetic carbon arc discharge is sustained by the potential across the electrodes and by carbon ions and electrons released from the electrodes during arc operation. A large part of the potential drop of the arc occurs along the arc and many energetic electrons reach the anode because the arc pressure is relatively low, and few collisions occur. The carbon discharge is also an efficient ion pump.

  4. Automated Variable-Polarity Plasma-Arc Welding

    NASA Technical Reports Server (NTRS)

    Numes, A. C., Jr.; Bayless, E. O., Jr.; Jones, S. C., III; Munafo, P.; Munafo, A.; Biddle, A.; Wilson, W.

    1984-01-01

    Variable-polarity plasma-arc methods produces better welds at lower cost than gas-shielded tungsten-arc welding in assemblies. Weld porosity very low and costs of joint preparation, depeaking, inspection, and weld repair minimized.

  5. First UCCRN Assessment Report on Climate Change and Cities (ARC3) (Invited)

    NASA Astrophysics Data System (ADS)

    Rosenzweig, C.

    2010-12-01

    Urban areas are home to over half the world’s people and are emerging as the ‘First Responders’ of the climate change issue. The need for an ongoing global research effort to establish the current understanding of climate change adaptation and mitigation at the city level is urgent. To meet this goal a coalition of international researchers - the Urban Climate Change Research Network (UCCRN) - was formed in 2007 at the time of the C40 Large Cities Climate Summit in New York. Since then, the UCCRN has been preparing the First Assessment Report on Climate Change and Cities (ARC3), to be published by Cambridge University Press in late 2010/early 2011. The ~100 authors are international experts on climate change mitigation and adaptation from ~50 cities in both the developing and developed countries. Key topics and sectors addressed in ARC3 include methods for conducting urban vulnerability assessments, interactions of the urban heat island and air pollution with climate variability and climate change projections, energy, water and wastewater, transportation, public health, land use planning, and governance. Case studies of practical mitigation and adaptation measures currently being undertaken by cities around the world are presented in each chapter. ARC3 provides decision makers - mayors, city officials, sustainability officers and urban planners - with the information they need to address the challenging issues of climate change. The UCCRN/ARC3 process will provide an ongoing mechanism for advancing understanding of climate change and cities in the coming decades.

  6. Pairing, pseudogap and Fermi arcs in cuprates

    DOE PAGES

    Kaminski, Adam; Kondo, Takeshi; Takeuchi, Tsunehiro; ...

    2014-04-29

    We use Angle Resolved Photoemission Spectroscopy (ARPES) to study the relationship between the pseudogap, pairing and Fermi arcs in cuprates. High quality data measured over a wide range of dopings reveals a consistent picture of Fermiology and pairing in these materials. The pseudogap is due to an ordered state that competes with superconductivity rather than preformed pairs. Pairing does occur below Tpair ~ 150K and significantly above Tc, but well below T* and the doping dependence of this temperature scale is distinct from that of the pseudogap. The d-wave gap is present below Tpair, and its interplay with strong scatteringmore » creates “artificial” Fermi arcs for Tc ≤ T ≤ Tpair. However, above Tpair, the pseudogap exists only at the antipodal region. This leads to presence of real, gapless Fermi arcs close to the node. The length of these arcs remains constant up to T*, where the full Fermi surface is recovered. As a result, we demonstrate that these findings resolve a number of seemingly contradictory scenarios.« less

  7. Pairing, pseudogap and Fermi arcs in cuprates

    SciTech Connect

    Kaminski, Adam; Kondo, Takeshi; Takeuchi, Tsunehiro; Gu, Genda

    2014-04-29

    We use Angle Resolved Photoemission Spectroscopy (ARPES) to study the relationship between the pseudogap, pairing and Fermi arcs in cuprates. High quality data measured over a wide range of dopings reveals a consistent picture of Fermiology and pairing in these materials. The pseudogap is due to an ordered state that competes with superconductivity rather than preformed pairs. Pairing does occur below Tpair ~ 150K and significantly above Tc, but well below T* and the doping dependence of this temperature scale is distinct from that of the pseudogap. The d-wave gap is present below Tpair, and its interplay with strong scattering creates “artificial” Fermi arcs for Tc ≤ T ≤ Tpair. However, above Tpair, the pseudogap exists only at the antipodal region. This leads to presence of real, gapless Fermi arcs close to the node. The length of these arcs remains constant up to T*, where the full Fermi surface is recovered. As a result, we demonstrate that these findings resolve a number of seemingly contradictory scenarios.

  8. Cheaper Custom Shielding Cups For Arc Welding

    NASA Technical Reports Server (NTRS)

    Morgan, Gene E.

    1992-01-01

    New way of making special-purpose shielding cups for gas/tungsten arc welding from hobby ceramic greatly reduces cost. Pattern machined in plastic. Plaster-of-paris mold made, and liquid ceramic poured into mold. Cost 90 percent less than cup machined from lava rock.

  9. Neural-Network Modeling Of Arc Welding

    NASA Technical Reports Server (NTRS)

    Anderson, Kristinn; Barnett, Robert J.; Springfield, James F.; Cook, George E.; Strauss, Alvin M.; Bjorgvinsson, Jon B.

    1994-01-01

    Artificial neural networks considered for use in monitoring and controlling gas/tungsten arc-welding processes. Relatively simple network, using 4 welding equipment parameters as inputs, estimates 2 critical weld-bead paramaters within 5 percent. Advantage is computational efficiency.

  10. CW arc-lamp-pumped alexandrite lasers

    SciTech Connect

    Samelson, H.; Walling, J.C.; Wernikowski, T.; Harter, D.J.

    1988-06-01

    The performance characteristics of arc-lamp- (Xe and Hg) pumped, CW alexandrite lasers are described in detail. The modes of operation considered are free running, tuned, and repetitively Q-switched. The experimental arrangement and apparatus are also outlined. The experimental results are discussed in terms of a steady-state model, and the areas of agreement and difficulty are pointed out.

  11. F-Layer Polar Cap Arcs.

    DTIC Science & Technology

    1987-09-01

    the electric fields. The particles may also be accelerated; they typically have a * higher range of energies than that of their solar ,.-.., wind ...spread F masking in the ionogram indicates the presence of structured irregularities in the arcs. Irregularities also cause dmplitude scintillation. and

  12. Remote electrical arc suppression by laser filamentation.

    PubMed

    Schubert, Elise; Mongin, Denis; Kasparian, Jérôme; Wolf, Jean-Pierre

    2015-11-02

    We investigate the interaction of narrow plasma channels formed in the filamentation of ultrashort laser pulses, with a DC high voltage. The laser filaments prevent electrical arcs by triggering corona that neutralize the high-voltage electrodes. This phenomenon, that relies on the electric field modulation and free electron release around the filament, opens new prospects to lightning and over-voltage mitigation.

  13. Signal Analysis of Gas Tungsten Arc Welds

    NASA Technical Reports Server (NTRS)

    Eagar, T. W.

    1985-01-01

    Gas tungsten arc welding is a process in which the input parameters such as current, voltage and travel speed, can be easily controlled and/or monitored. However, weld quality is not solely a function of these parameters. An adaptive method of observing weld quality is desired to improve weld quality assurance. The use of dynamic electrical properties of the welding arc as a weld quality monitor was studied. The electrical properties of the arc are characterized by the current voltage transfer function. The hardware and software necessary to collect the data at a maximum rate of 45 kHz and to allow the off-line processing of this data are tested. The optimum input current waveform is determined. Bead-on-plate welds to observe such characteristics of the weld as the fundamental frequency of the puddle are studied. Future work is planned to observe changes of the arc response with changes in joint geometry, base metal chemistry, and shielding gas composition are discussed.

  14. Gas tungsten arc welder with electrode grinder

    DOEpatents

    Christiansen, David W.; Brown, William F.

    1984-01-01

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

  15. Arc tracking of cables for space applications

    NASA Technical Reports Server (NTRS)

    Koenig, D.; Frontzek, F. R.; Hanson, J.; Reher, H. J.; Judd, M. D.; Bryant, D.

    1995-01-01

    The main objective of this study is to develop a new test method that is suitable for the assessment of the resistance of aerospace cables to arc tracking for different specific environmental and network conditions of spacecrafts. This paper reports the purpose, test conditions, test specimen, test procedure, and test acceptance criteria of seven different (200-250 mm long) cables.

  16. Evaluation of the clinical usefulness of modulated arc treatment

    NASA Astrophysics Data System (ADS)

    Lee, Young Kyu; Jang, Hong Seok; Kim, Yeon Sil; Choi, Byung Ock; Kang, Young-Nam; Nam, Sang Hee; Park, Hyeong Wook; Kim, Shin Wook; Shin, Hun Joo; Lee, Jae Choon; Kim, Ji Na; Park, Sung Kwang; Kim, Jin Young

    2015-07-01

    The purpose of this study is to evaluate the clinical usefulness of modulated arc (mARC) treatment techniques. The mARC treatment plans for non-small-cell lung cancer (NSCLC) patients were made in order to verify the clinical usefulness of mARC. A pre-study was conducted to find the best plan condition for mARC treatment, and the usefulness of the mARC treatment plan was evaluated by comparing it with other Arc treatment plans such as tomotherapy and RapidArc plans. In the case of mARC, the optimal condition for the mARC plan was determined by comparing the dosimetric performance of the mARC plans developed by using various parameters, which included the photon energy (6 MV, 10 MV), the optimization point angle (6°- 10°intervals), and the total number of segments (36 - 59 segments). The best dosimetric performance of mARC was observed at a 10 MV photon energy, a point angle 6 degrees, and 59 segments. The treatment plans for the three different techniques were compared by using the following parameters: the conformity index (CI), homogeneity index (HI), the target coverage, the dose to the OARs, the number of monitor units (MU), the beam on time, and the normal tissue complication probability (NTCP). As a result, the three different treatment techniques showed similar target coverages. The mARC plan had the lowest V20 (volume of lung receiving > 20 Gy) and MU per fraction compared with both the RapidArc and the tomotherapy plans. The mARC plan reduced the beam on time as well. Therefore, the results of this study provide satisfactory evidence that the mARC technique can be considered as a useful clinical technique for radiation treatment.

  17. Uranium ARC Fission Reactor for Space Power and Propulsion

    DTIC Science & Technology

    1992-03-01

    thruster or MHD accelerator/generator. Uranium arc technology is being developed for use in space nuclear thermal and electric propulsion reactors. In...specific impulse propulsion or ultrahigh temperature power conversion. Fission events in the nuclear arc plasma provide for additional dissociation and...I Technical Objectives 3 2. URANIUM ARC FISSION REACTOR CONCEPT AND NUCLEAR -AUGMENTED THRUSTER CONCEPT 4 2.1 Physics Basis 4 2.2 Uranium Arc

  18. The Tertiary Arc Chain in the Western Pacific

    NASA Astrophysics Data System (ADS)

    Honza, E.

    1991-02-01

    The arcs bordering the Pacific Plate on the Western and Southwestern Pacific rim are reconstructed since their initiation in the Eocene and Oligocene. They occur in a zone forming an arc chain from the Western Pacific tropics to the eastern margin of Australia. They are the Bonin, Mariana, Yap, Palau, Halmahera, North New Guinea-West Melanesia, Solomon, Vanuatu, and Tonga-Kermadec Arcs, designated here the Tertiary Arc Chain. They are associated with the formation and consumption of backarc basins. Reversals of arc polarity and episodic subduction has occurred in some of them. The Tertiary Arc Chain is characterized by four major stages in its evolution which can be seen characteristically in some of the arcs. The first stage is the occurrence of the arc chain from the middle Eocene to earliest Oligocene. The second stage is the formation of the backarc basins from the early to late Oligocene. The third stage is the occurrence of double arcs on the inner side of the arc chain in the early to middle Miocene and the fourth stage is the reversal of arc polarities due to collisions since the late Miocene. The backarc basins associated with the arcs of the Tertiary Arc Chain have fixed limits of duration in their evolution. The backarc basins initially form 15 million years after the initiation of the volcanic arc. Several to 10 million years after the initial opening, backarc spreading terminates. Approximately 20 million years after the cessation of the backarc spreading, a second phase of opening occurs in the backarc region. In the case of arc collision, reversal of the arc polarity occurs if there is oceanic crust on the backarc side, and opening of a backarc basin occurs within several million years. These occurrences and durations have a variation of ca. 3-5 million years.

  19. H2O and CO2 in magmas from the Mariana arc and back arc systems

    NASA Astrophysics Data System (ADS)

    Newman, Sally; Stolper, Edward; Stern, Robert

    2000-05-01

    We examined the H2O and CO2 contents of glasses from lavas and xenoliths from the Mariana arc system, an intraoceanic convergent margin in the western Pacific, which contains an active volcanic arc, an actively spreading back arc basin, and active behind-the-arc cross-chain volcanoes. Samples include (1) glass rims from Mariana arc, Mariana trough, and cross-chain submarine lavas; (2) glass inclusions in arc and trough phenocrysts; and (3) glass inclusions from a gabbro + anorthosite xenolith from Agrigan (Mariana arc). Glass rims of submarine arc lavas contain 0.3-1.9 wt % H2O, and CO2 is below detection limits. Where they could be compared, glass inclusions in arc phenocrysts contain more H2O than their host glasses; most arc glasses and phenocryst inclusions contain no detectable CO2, with the exception of those from a North Hiyoshi shoshonite, which contains 400-600 ppm. The glass inclusions from the Agrigan xenolith contain 4-6% H2O, and CO2 is below the detection limit. Glasses from the cross-chain lavas are similar to those from the arc: H2O contents are 1.4-1.7 wt %, and CO2 is below detection limits. Volatile contents in Mariana trough lava glass rims are variable: 0.2-2.8 wt % H2O and 0-300 ppm CO2. Glass inclusions from trough phenocrysts have water contents similar to the host glass, but they can contain up to 875 ppm CO2. Volatile contents of melt inclusions from trough and arc lavas and from the xenolith imply minimum depths of crystallization of ~1-8 km. H2O and CO2 contents of Mariana trough glasses are negatively correlated, indicating saturation of the erupting magma with a CO2-H2O vapor at the pressure of eruption (~400 bars for these samples), with the vapor ranging from nearly pure CO2 at the CO2-rich end of the glass array to nearly pure H2O at the H2O-rich end. Degassing of these magmas on ascent and eruption leads to significant loss of CO2 (thereby masking preeruptive CO2 contents) but minimal disturbance of preeruptive H2O contents. For

  20. Load-Point Compliance for the Arc Bend-Arc Support Fracture Toughness Specimen

    DTIC Science & Technology

    1990-03-01

    co TECHNICAL REPORT ARCCB-TR-900 11(N LOAD-POINT COMPLIANCE FOR THE ARC BEND-ARC SUPPORT FRACTURE TOUGHNESS SPECIMEN FRANCIS I. BARATTA JOSEPH A...ORG. REPORT NUMBER 7. AUTHOR(@) 1. CONTRACT OR GRANT NUMBER(@) Francis I. Baratta , Joseph A. Kapp, and David S. Saunders (See Reverse) 9. PERFORMING...CLASSIFICATION OF THIS PAGEhan Date Entered) 7. AUTHORS (CONT’D) Francis I. Baratta U.S. Army Materials Technology Laboratory Watertown, MA 02172

  1. The arc arises: The links between volcanic output, arc evolution and melt composition

    NASA Astrophysics Data System (ADS)

    Brandl, Philipp A.; Hamada, Morihisa; Arculus, Richard J.; Johnson, Kyle; Marsaglia, Kathleen M.; Savov, Ivan P.; Ishizuka, Osamu; Li, He

    2017-03-01

    Subduction initiation is a key process for global plate tectonics. Individual lithologies developed during subduction initiation and arc inception have been identified in the trench wall of the Izu-Bonin-Mariana (IBM) island arc but a continuous record of this process has not previously been described. Here, we present results from International Ocean Discovery Program Expedition 351 that drilled a single site west of the Kyushu-Palau Ridge (KPR), a chain of extinct stratovolcanoes that represents the proto-IBM island arc, active for ∼25 Ma following subduction initiation. Site U1438 recovered 150 m of oceanic igneous basement and ∼1450 m of overlying sediments. The lower 1300 m of these sediments comprise volcaniclastic gravity-flow deposits shed from the evolving KPR arc front. We separated fresh magmatic minerals from Site U1438 sediments, and analyzed 304 glass (formerly melt) inclusions, hosted by clinopyroxene and plagioclase. Compositions of glass inclusions preserve a temporal magmatic record of the juvenile island arc, complementary to the predominant mid-Miocene to recent activity determined from tephra layers recovered by drilling in the IBM forearc. The glass inclusions record the progressive transition of melt compositions dominated by an early 'calc-alkalic', high-Mg andesitic stage to a younger tholeiitic stage over a time period of 11 Ma. High-precision trace element analytical data record a simultaneously increasing influence of a deep subduction component (e.g., increase in Th vs. Nb, light rare earth element enrichment) and a more fertile mantle source (reflected in increased high field strength element abundances). This compositional change is accompanied by increased deposition rates of volcaniclastic sediments reflecting magmatic output and maturity of the arc. We conclude the 'calc-alkalic' stage of arc evolution may endure as long as mantle wedge sources are not mostly advected away from the zones of arc magma generation, or the rate of

  2. Electric-arc synthesis of soot with high content of higher fullerenes in parallel arc

    NASA Astrophysics Data System (ADS)

    Dutlov, A. E.; Nekrasov, V. M.; Sergeev, A. G.; Bubnov, V. P.; Kareev, I. E.

    2016-12-01

    Soot with a relatively high content of higher fullerenes (C76, C78, C80, C82, C84, C86, etc.) is synthesized in a parallel arc upon evaporation of pure carbon electrodes. The content of higher fullerenes in soot extract amounts to 13.8 wt % when two electrodes are simultaneously burnt in electric-arc reactor. Such a content is comparable with the content obtained upon evaporation of composite graphite electrodes with potassium carbonate impurity.

  3. Volumetric Modulated Arc Radiotherapy for Vestibular Schwannomas

    SciTech Connect

    Lagerwaard, Frank J. Meijer, Otto W.M.; Hoorn, Elles A.P. van der; Verbakel, Wilko; Slotman, Ben J.; Senan, Suresh

    2009-06-01

    Purpose: To evaluate volumetric modulated arc radiotherapy (RapidArc [RA]), a novel approach allowing for rapid treatment delivery, for the treatment of vestibular schwannoma (VS). Methods and Materials: The RA plans were generated for a small (0.5 cm{sup 3}), intermediate (2.8 cm{sup 3}), and large (14.8 cm{sup 3}) VS. The prescription dose was 12.5 Gy to the encompassing 80% isodose. The RA plans were compared with conventional radiosurgery plans using both a single dynamic conformal arc (1DCA) and five noncoplanar dynamic conformal arcs (5DCA). Conformity indices (CI) and dose-volume histograms of critical organs were compared. The RA plan for the medium-sized VS was measured in a phantom using Gafchromic EBT films and compared with calculated dose distributions. Results: The RA planning was completed within 30 min in all cases, and calculated treatment delivery time (after patient setup) was 5 min vs. 20 min for 5DCA. A superior CI was achieved with RA, with a substantial decrease in low-dose irradiation of the normal brain achieved relative to 5DCA plans. Maximum doses to critical organs were similar for RA and 5DCA but were higher for 1DCA. Film measurements showed the differences between calculated and measured doses to be smaller than 1.5% in the high-dose area and smaller than 3% in the low-dose area. Conclusion: The RA plans consistently achieved a higher CI and decrease in areas of low-dose irradiation. This, together with shorter treatment delivery times, has led to RA replacing our conventional five-arc radiosurgery technique for VS.

  4. The Plio Quaternary Ambon arc, Eastern Indonesia

    NASA Astrophysics Data System (ADS)

    Honthaas, Christian; Maury, René C.; Priadi, Bambang; Bellon, Hervé; Cotten, Joseph

    1999-01-01

    Plio-Quaternary lavas and granites have been collected from Ambon, Seram, Kelang, Haruku, Saparua, Ambelau and Banda Api islands, Eastern Indonesia. They include low-K calc-alkaline basalts, andesites, dacites and rhyolites and high-K calc-alkaline andesites, dacites, rhyolites and granites. All these rocks present the usual chemical characteristics of island-arc magmas. The high-K suite of Ambon is mostly represented by cordierite-bearing dacites (known as ambonites) and granites. Low-K and high-K magmas were emplaced in neighbouring islands or even in the same island (Ambon), often concomitantly, during two magmatic pulses at 5-3.2 Ma and 2.3-1 Ma, respectively. We propose that the low-K suite results from the evolution of basaltic magmas derived from mantle melting above the Western Irian Jaya plate which subducts along the Seram trough. Intermediate and acidic rocks of the high-K suite (e.g. ambonites) are thought to derive from low-K mafic magmas through massive assimilation of the Seram-Ambon continental crust, as originally proposed by Van Bemmelen in 1949. The timing of magmatic events and the geochemical features of the studied lavas are clearly different from those of the southern part of the Banda arc, in which the low-K suite is lacking. In agreement with earlier seismic evidence for two different slabs subducting beneath the Seram-Ambon continental block and beneath the southern Banda arc (from Wetar to Manuk), respectively, we propose to recognise a new Plio-Quaternary island arc, i.e. the Ambon arc, extending west-east from Ambelau to the Banda Archipelago active low-K volcanoes through Kelang, southwestern Seram, Ambon, Haruku and Saparua.

  5. Interaction of Komatiitic Liquids With Archean Arcs

    NASA Astrophysics Data System (ADS)

    Kerrich, R.

    2006-12-01

    New, and compilations of, high precision data for 3.0 to 2.7 Ga komatiites of the Superior province show positive normalized anomalies of Nb relative to Th-La, and Nb/Th>8. These features are present in Al- undepleted (AUK) and Al-depleted komatiites(ADK) screened for minimal alteration and absence of crustal contamination. AUK possess positive Zr(Hf)/Sm anomalies, whereas ADK counterparts have negative anomalies. For AUK, positive (Nb,Zr)/REE anomalies are interpreted as oceanic lithosphere processed through a dehydration-dominated subduction zone and recycled into the mantle source of plumes. For ADK, HFSE/REE anomalies may reflect recycled oceanic lithosphere processed through a melt(TTG)-dominated subduction zone, melting of a plume with residual majorite garnet at >400 km, or some combination. Both AUK and ADK are associated with anhydrous intraplate plume-related magmas, based on field associations and Ti/V. A new compositional type of Neoarchean intraoceanic low-K (Ce) tholeiitic arc basalt has been identified. These are characterized by a spectrum of negative to positive (Nb,Ta,Zr,Hf)/REE anomalies, but systematic negative Ti/REE anomalies, where Nb antivaries with Zr/Nb, and Ni>300ppm. This type differs from low-K arc tholeiites of Archean and Phanerozoic age variably associated with andesites, dacites, rhyolites, and characterized by systematic negative anomalies of (Nb,Ta,P,Ti)/REE, with Ni<250ppm. The new type tholeiites are consistent with a model of earlier komatiitic liquids that stalled in, and fertilized, upper mantle. As an arc migrated through composite upper mantle, hydrous melting generated a basalt compositional spectrum from subdued AUK-like to classic arc-like HFSE/REE anomalies. Alternatively, contemporaneous AUK liquids leaked through a slab into the sub-arc mantle wedge, hybridizing with wedge peridotite melts.

  6. Unstable Behavior of Anodic Arc Discharge for Synthesis of Nanomaterials

    NASA Astrophysics Data System (ADS)

    Gershman, Sophia; Raitses, Yevgeny

    2016-09-01

    Fast imaging and electrical current measurements reveal unstable behavior of the carbon arc discharge for synthesis of nanomaterials. The arc column and the arc attachment region to the anode move in a somewhat sporadic way with a characteristic time in a 10-3 sec range. The arc exhibits a negative differential resistance before the arc motion occurs. A physical mechanism is proposed based on the thermal processes in the arc plasma region interacting with the ablating anode which leads to the shift of the arc to a new anode region. According to the transient heat transfer analysis, the time needed to heat a new anode region is also in a 10-3 sec range. For a 0.6 cm diameter anode used in our experiments, this time yields a frequency of about 200-300 Hz, comparable to the measured frequency of the arc motion. The voltage and current measurements show oscillations with a similar characteristic frequency. The thermal model is indirectly supported by the measured negative differential resistance of the arc discharge during arc oscillations. The observed unstable behavior of the arc may be responsible for the mixing of the flow of nanoparticles during the synthesis of nanoparticles leading to poor selectivity typical for the arc synthesis. The work was supported by US DOE under Contract No. DE-AC02-09CH11466.

  7. Arc-Jet Power Supply And Starting Circuit

    NASA Technical Reports Server (NTRS)

    Gruber, Robert P.

    1988-01-01

    Power efficiency high, current regulated, and starting automatic. New circuit for starting arc jets and controlling them in steady operation capable of high power efficiency and constructed in lightweight form. Feedback control system keeps arc-jet current nearly constant, once arc struck by starting pulse. Circuit made of commercially available components. Design capable of high power efficiency.

  8. 29 CFR 1926.351 - Arc welding and cutting.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Arc welding and cutting. 1926.351 Section 1926.351 Labor... (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Welding and Cutting § 1926.351 Arc welding and... for arc welding and cutting, and are of a capacity capable of safely handling the maximum...

  9. Dry and wet arc track propagation resistance testing

    NASA Technical Reports Server (NTRS)

    Beach, Rex

    1995-01-01

    The wet arc-propagation resistance test for wire insulation provides an assessment of the ability of an insulation to prevent damage in an electrical environment. Results of an arc-propagation test may vary slightly due to the method of arc initiation; therefore a standard test method must be selected to evaluate the general arc-propagation resistance characteristics of an insulation. This test method initiates an arc by dripping salt water over pre-damaged wires which creates a conductive path between the wires. The power supply, test current, circuit resistances, and other variables are optimized for testing 20 guage wires. The use of other wire sizes may require modifications to the test variables. The dry arc-propagation resistance test for wire insulation also provides an assessment of the ability of an insulation to prevent damage in an electrical arc environment. In service, electrical arcs may originate form a variety of factors including insulation deterioration, faulty installation, and chafing. Here too, a standard test method must be selected to evaluate the general arc-propagation resistance characteristics of an insulation. This test method initiates an arc with a vibrating blade. The test also evaluates the ability of the insulation to prevent further arc-propagation when the electrical arc is re-energized.

  10. Quantitative Spectral Radiance Measurements in the HYMETS Arc Jet

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Hires, Drew V.; Johansen, Craig T.; Bathel, Brett F.; Jones, Stephen B.; Gragg, Jeffrey G.; Splinter, Scott C.

    2012-01-01

    Calibrated spectral radiance measurements of gaseous emission spectra have been obtained from the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. A fiber-optic coupled spectrometer collected natural luminosity from the flow. Spectral radiance measurements are reported between 340 and 1000 nm. Both Silicon Carbide (SiC) and Phenolic Impregnated Carbon Ablator (PICA) samples were placed in the flow. Test gases studied included a mostly-N2 atmosphere (95% nitrogen, 5% argon), a simulated Earth Air atmosphere (75% nitrogen, 20% oxygen, 5% argon) and a simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon). The bulk enthalpy of the flow was varied as was the location of the measurement. For the intermediate flow enthalpy tested (20 MJ/kg), emission from the Mars simulant gas was about 10 times higher than the Air flow and 15 times higher than the mostly-N2 atmosphere. Shock standoff distances were estimated from the spectral radiance measurements. Within-run, run-to-run and day-to-day repeatability of the emission were studied, with significant variations (15-100%) noted.

  11. Natural gamma-radiation in the Aeolian volcanic arc.

    PubMed

    Chiozzi, P; Pasquale, V; Verdoya, M; Minato, S

    2001-11-01

    Pulse-height distributions of gamma-rays, obtained with a field NaI(Tl) scintillation spectrometer in numerous sites of the Lipari and Vulcano islands (Aeolian volcanic arc, Italy), were measured to determine the U, Th and K concentrations of the bedrock and the relative values of the air absorbed dose rate. U is spatially related to both Th and K and the Th/U ratio is on average 3.1-3.5. The magmatic evolution is reflected by the concentration of the three radioelements, as they are more abundant within the more felsic units of the volcanic series. The higher values of U (15.7-20.0 ppm) coincide with higher Th (48.3-65.9 ppm) and K (4.9-6.1%) concentrations associated with rhyolitic rocks of the third cycle (< 50 ky). The air absorbed dose rate varies from 20 to 470 nGy h(-1). The highest values (> 350 nGy h(-1)) are observed on outcrops of rhyolitic obsidian lava flows. The cosmic-ray contribution is also evaluated to estimate the total background radiation dose rate.

  12. The investigation of carbon nitride films prepared at various arc currents by vacuum cathode arc method

    NASA Astrophysics Data System (ADS)

    Zhou, Zhimin; Xia, Lifang

    2002-08-01

    The carbon nitride films have been prepared in the arc currents range of 20-60 A at the Ar/N2 atmosphere of 50/400 sccm by the vacuum cathode arc deposition method. The properties of the films were characterized by x-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and nanoindentation. The N concentration showed a maximum of 35 at% at 20 A and decreased gradually with the arc currents. The films below 40 A consisted of linear polymeric-like component and sp2 graphitic cluster. With the increasing of the arc current from 20 to 40 A, the ID/IG rose and the photoluminescence (PL) fell gradually, which resulted from the development of the sp2 graphitic phase and the decrease of the polymeric-like phase. As a result, the CC bonds increased and sp3CN and sp2CN decreased. Above 40 A, with the increasing of arc currents, ID/IG fell and the PL increased gradually, which reflected the decreasing of sp2 graphitic phase and the modification of C and N atoms in sp2 cluster. The CC bonds and sp3CN fell and the sp2CN rose. The nanohardness of films showed increasing tendency with the arc currents. The variation of the relative ratio and the average energy of N-containing species and C-containing species at the atmosphere would be responsible for the change in the properties of films.

  13. Numerical investigation of the double-arcing phenomenon in a cutting arc torch

    SciTech Connect

    Mancinelli, B. R.; Minotti, F. O.; Kelly, H.; Prevosto, L.

    2014-07-14

    A numerical investigation of the double-arcing phenomenon in a cutting arc torch is reported. The dynamics of the double-arcing were simulated by using a two-dimensional model of the gas breakdown development in the space-charge layer contiguous to the nozzle of a cutting arc torch operated with oxygen. The kinetic scheme includes ionization of heavy particles by electron impact, electron attachment, electron detachment, electron–ion recombination, and ion–ion recombination. Complementary measurements during double-arcing phenomena were also conducted. A marked rise of the nozzle voltage was found. The numerical results showed that the dynamics of a cathode spot at the exit of the nozzle inner surface play a key role in the raising of the nozzle voltage, which in turn allows more electrons to return to the wall at the nozzle inlet. The return flow of electrons thus closes the current loop of the double-arcing. The increase in the (floating) nozzle voltage is due to the fact that the increased electron emission at the spot is mainly compensated by the displacement current (the ions do not play a relevant role due to its low-mobility) until that the stationary state is achieved and the electron return flow fully-compensates the electron emission at the spot. A fairly good agreement was found between the model and the experiment for a spot emission current growth rate of the order of 7 × 10{sup 4} A/s.

  14. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, Michael; Hornbach, Matthew J.; Le Friant, Anne; Ishizuka, Osamu; Stroncik, Nicole; Adachi, Tatsuya; Aljahdali, Mohammed; Boudon, Georges; Breitkreuz, Christoph; Fraass, Andrew; Fujinawa, Akihiko; Hatfield, Robert; Jutzeler, Martin; Kataoka, Kyoko; Lafuerza, Sara; Maeno, Fukashi; Martinez-Colon, Michael; McCanta, Molly; Morgan, Sally; Palmer, Martin R.; Saito, Takeshi; Slagle, Angela; Stinton, Adam J.; Subramanyam, K. S. V.; Tamura, Yoshihiko; Talling, Peter J.; Villemant, Benoit; Wall-Palmer, Deborah; Wang, Fei

    2012-08-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to <0.07 W/m2 at distances >15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present-day volcanism is confined to the region with the highest heat flow.

  15. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, M.; Hornbach, M. J.; Le Friant, A.; Ishizuka, O.; Stroncik, N.

    2012-12-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to < 0.07 W/m2 at distances > 15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present day volcanism is confined to the region with the highest heat flow.

  16. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, Michael; Hornbach, Matt; Le Friant, Anne; Ishizuka, Osamu

    2014-05-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to < 0.07 W/m2 at distances > 15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present day volcanism is confined to the region with the highest heat flow.

  17. Oceanic, island arc, and back-arc remnants into eastern Kamchatka accretionary complexes

    SciTech Connect

    Fedorchuk, A.V.; Vishnevskaya, V.S.; Izvekov, I.N. )

    1990-06-01

    The Kamchatsky Mts. accretionary complex in the Eastern Kamchatka orogenic belt was studied for identification of the oceanic and suprasubduction components into accretionary wedges. That complex is divided into two tectonic units. The Lower unit is formed sedimentary and tectonic melanges containing arc-related components (Late Senonian volcaniclastics and boninitic gabbro) and oceanic fragments (Fe-Ti-tholeiites, ocean island basalts, and pelagic sediments of Valanginian to Turonian age). The Upper unit consists of ductile deformed oceanic cumulates from troctolites to Fe-Ti-gabbro, 151 to 172 Ma, which are intruded MORB-like diabases with suprasubduction characteristics, 122 to 141 Ma, and are overlain by basalts similar to latter. The Lower and Upper units are separated by a SW-dipping thrust, which is related by an ophiolitoclastic olistostrome of Late Campanian to Early Maestrichtian age. Both units are covered by Paleocene authoclastic deposits. They are all thrusted over the early Neogene island arc complex, 16 to 20 Ma. The Lower unit of the Kamchatsky Mys accretionary complex was originated in a shear zone between a Late Cretaceous island arc and an Early Cretaceous oceanic plate. The Upper unit represents a Jurassic oceanic remnant that formed a basement of Early Cretaceous back-arc or fore-arc basin. Both units were superposed in the latest Cretaceous. The Kamchatsky Mys accretionary complex was emplaced into the Eastern Kamchatka orogenic belt during late Neogene by collision of the early Neogene island arc.

  18. Temperature and Nitric Oxide Generation in a Pulsed Arc Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Namihira, T.; Sakai, S.; Matsuda, M.; D., Wang; Kiyan, T.; Akiyama, H.; Okamoto, K.; Toda, K.

    2007-12-01

    Nitric oxide (NO) is increasingly being used in medical treatments of high blood pressure, acute respiratory distress syndrome and other illnesses related to the lungs. Currently a NO inhalation system consists of a gas cylinder of N2 mixed with a high concentration of NO. This arrangement is potentially risky due to the possibility of an accidental leak of NO from the cylinder. The presence of NO in the air leads to the formation of nitric dioxide (NO2), which is toxic to the lungs. Therefore, an on-site generator of NO would be highly desirable for medical doctors to use with patients with lung disease. To develop the NO inhalation system without a gas cylinder, which would include a high concentration of NO, NAMIHIRA et al have recently reported on the production of NO from room air using a pulsed arc discharge. In the present work, the temperature of the pulsed arc discharge plasma used to generate NO was measured to optimize the discharge condition. The results of the temperature measurements showed the temperature of the pulsed arc discharge plasma reached about 10,000 K immediately after discharge initiation and gradually decreased over tens of microseconds. In addition, it was found that NO was formed in a discharge plasma having temperatures higher than 9,000 K and a smaller input energy into the discharge plasma generates NO more efficiently than a larger one.

  19. Physical characteristics of gliding arc discharge plasma generated in a laval nozzle

    SciTech Connect

    Lu, S. Y.; Sun, X. M.; Li, X. D.; Yan, J. H.; Du, C. M.

    2012-07-15

    The dynamic behavior of gliding arc discharge generated in a Laval nozzle has been investigated by electrical diagnostics and a high-speed camera. The results show that the voltage waveform keeps the initial shape as the gas flow rate is small, while it becomes less stable with increasing flow rate. During the first half of a cycle, the voltage rises and after that it decreases. In nitrogen and oxygen, the break down voltage for the arc is between 3.3 and 5.5 kV, while it is between 3.3-7.5 kV in air. The waveform of current I remains almost stable; and for nitrogen and oxygen, the maximum value of current I is between 0.28 and 0.46 A. With increasing flow rate, the power consumption in air first increases and then decreases; it remains in the range of 110-217 W, and gradually increases in nitrogen and oxygen. The power consumption in oxygen is lower than that in nitrogen; the input of the energy density decreases with increasing flow rate for all the three gases. The development of the arc is tracked and recorded by a high-speed camera. The cycle is stable at 10 ms for flow rates up to 1 m{sup 3} h{sup -1}. At a higher flow rate, the cycle becomes unstable.

  20. NASA GRC and MSFC Space-Plasma Arc Testing Procedures

    NASA Technical Reports Server (NTRS)

    Ferguson, Dale C.; Vayner, Boris V.; Galofaro, Joel T,; Hillard, G. Barry; Vaughn, Jason; Schneider, Todd

    2005-01-01

    Tests of arcing and current collection in simulated space plasma conditions have been performed at the NASA Glenn Research Center (GRC) in Cleveland, Ohio, for over 30 years and at the Marshall Space Flight Center (MSFC) in Huntsville, Alabama, for almost as long. During this period, proper test conditions for accurate and meaningful space simulation have been worked out, comparisons with actual space performance in spaceflight tests and with real operational satellites have been made, and NASA has achieved our own internal standards for test protocols. It is the purpose of this paper to communicate the test conditions, test procedures, and types of analysis used at NASA GRC and MSFC to the space environmental testing community at large, to help with international space-plasma arcing-testing standardization. To be discussed are: 1.Neutral pressures, neutral gases, and vacuum chamber sizes. 2. Electron and ion densities, plasma uniformity, sample sizes, and Debuy lengths. 3. Biasing samples versus self-generated voltages. Floating samples versus grounded. 4. Power supplies and current limits. Isolation of samples from power supplies during arcs. 5. Arc circuits. Capacitance during biased arc-threshold tests. Capacitance during sustained arcing and damage tests. Arc detection. Prevention sustained discharges during testing. 6. Real array or structure samples versus idealized samples. 7. Validity of LEO tests for GEO samples. 8. Extracting arc threshold information from arc rate versus voltage tests. 9. Snapover and current collection at positive sample bias. Glows at positive bias. Kapon (R) pyrolisis. 10. Trigger arc thresholds. Sustained arc thresholds. Paschen discharge during sustained arcing. 11. Testing for Paschen discharge threshold. Testing for dielectric breakdown thresholds. Testing for tether arcing. 12. Testing in very dense plasmas (ie thruster plumes). 13. Arc mitigation strategies. Charging mitigation strategies. Models. 14. Analysis of test results

  1. NOTE: Monte Carlo simulation of RapidArc radiotherapy delivery

    NASA Astrophysics Data System (ADS)

    Bush, K.; Townson, R.; Zavgorodni, S.

    2008-10-01

    RapidArc radiotherapy technology from Varian Medical Systems is one of the most complex delivery systems currently available, and achieves an entire intensity-modulated radiation therapy (IMRT) treatment in a single gantry rotation about the patient. Three dynamic parameters can be continuously varied to create IMRT dose distributions—the speed of rotation, beam shaping aperture and delivery dose rate. Modeling of RapidArc technology was incorporated within the existing Vancouver Island Monte Carlo (VIMC) system (Zavgorodni et al 2007 Radiother. Oncol. 84 S49, 2008 Proc. 16th Int. Conf. on Medical Physics). This process was named VIMC-Arc and has become an efficient framework for the verification of RapidArc treatment plans. VIMC-Arc is a fully automated system that constructs the Monte Carlo (MC) beam and patient models from a standard RapidArc DICOM dataset, simulates radiation transport, collects the resulting dose and converts the dose into DICOM format for import back into the treatment planning system (TPS). VIMC-Arc accommodates multiple arc IMRT deliveries and models gantry rotation as a series of segments with dynamic MLC motion within each segment. Several verification RapidArc plans were generated by the Eclipse TPS on a water-equivalent cylindrical phantom and re-calculated using VIMC-Arc. This includes one 'typical' RapidArc plan, one plan for dual arc treatment and one plan with 'avoidance' sectors. One RapidArc plan was also calculated on a DICOM patient CT dataset. Statistical uncertainty of MC simulations was kept within 1%. VIMC-Arc produced dose distributions that matched very closely to those calculated by the anisotropic analytical algorithm (AAA) that is used in Eclipse. All plans also demonstrated better than 1% agreement of the dose at the isocenter. This demonstrates the capabilities of our new MC system to model all dosimetric features required for RapidArc dose calculations.

  2. Monte Carlo simulation of RapidArc radiotherapy delivery.

    PubMed

    Bush, K; Townson, R; Zavgorodni, S

    2008-10-07

    RapidArc radiotherapy technology from Varian Medical Systems is one of the most complex delivery systems currently available, and achieves an entire intensity-modulated radiation therapy (IMRT) treatment in a single gantry rotation about the patient. Three dynamic parameters can be continuously varied to create IMRT dose distributions-the speed of rotation, beam shaping aperture and delivery dose rate. Modeling of RapidArc technology was incorporated within the existing Vancouver Island Monte Carlo (VIMC) system (Zavgorodni et al 2007 Radiother. Oncol. 84 S49, 2008 Proc. 16th Int. Conf. on Medical Physics). This process was named VIMC-Arc and has become an efficient framework for the verification of RapidArc treatment plans. VIMC-Arc is a fully automated system that constructs the Monte Carlo (MC) beam and patient models from a standard RapidArc DICOM dataset, simulates radiation transport, collects the resulting dose and converts the dose into DICOM format for import back into the treatment planning system (TPS). VIMC-Arc accommodates multiple arc IMRT deliveries and models gantry rotation as a series of segments with dynamic MLC motion within each segment. Several verification RapidArc plans were generated by the Eclipse TPS on a water-equivalent cylindrical phantom and re-calculated using VIMC-Arc. This includes one 'typical' RapidArc plan, one plan for dual arc treatment and one plan with 'avoidance' sectors. One RapidArc plan was also calculated on a DICOM patient CT dataset. Statistical uncertainty of MC simulations was kept within 1%. VIMC-Arc produced dose distributions that matched very closely to those calculated by the anisotropic analytical algorithm (AAA) that is used in Eclipse. All plans also demonstrated better than 1% agreement of the dose at the isocenter. This demonstrates the capabilities of our new MC system to model all dosimetric features required for RapidArc dose calculations.

  3. Tangential electric fields in a drifting auroral arc

    NASA Astrophysics Data System (ADS)

    Yau, A. W.; Whalen, B. A.; Creutzberg, F.

    1981-04-01

    Rocket-borne ion convection velocity and ground-based optical measurements in an early evening, equatorward drifting, NW-SE oriented auroral arc are reported. Measurements indicate a detailed correspondence between the normal component of the ion convection velocity (the component normal to the auroral arc) and the drift motion of the auroral arc. The two velocities were identical on a time scale of minutes, and correlated strongly with each other in smaller-scale temporal variations. The correspondence implies a near-zero tangential electric field in an auroral arc, in the frame of reference of the arc. The observations have serious consequences for several auroral theories.

  4. Effects of arcing due to spacecraft charging on spacecraft survival

    NASA Technical Reports Server (NTRS)

    Rosen, A.; Sanders, N. L.; Ellen, J. M., Jr.; Inouye, G. T.

    1978-01-01

    A quantitative assessment of the hazard associated with spacecraft charging and arcing on spacecraft systems is presented. A literature survey on arc discharge thresholds and characteristics was done and gaps in the data and requirements for additional experiments were identified. Calculations of coupling of arc discharges into typical spacecraft systems were made and the susceptibility of typical spacecraft to disruption by arc discharges was investigated. Design guidelines and recommended practices to reduce or eliminate the threat of malfunction and failures due to spacecraft charging/arcing were summarized.

  5. Series and parallel arc-fault circuit interrupter tests.

    SciTech Connect

    Johnson, Jay Dean; Fresquez, Armando J.; Gudgel, Bob; Meares, Andrew

    2013-07-01

    While the 2011 National Electrical Codeª (NEC) only requires series arc-fault protection, some arc-fault circuit interrupter (AFCI) manufacturers are designing products to detect and mitigate both series and parallel arc-faults. Sandia National Laboratories (SNL) has extensively investigated the electrical differences of series and parallel arc-faults and has offered possible classification and mitigation solutions. As part of this effort, Sandia National Laboratories has collaborated with MidNite Solar to create and test a 24-string combiner box with an AFCI which detects, differentiates, and de-energizes series and parallel arc-faults. In the case of the MidNite AFCI prototype, series arc-faults are mitigated by opening the PV strings, whereas parallel arc-faults are mitigated by shorting the array. A range of different experimental series and parallel arc-fault tests with the MidNite combiner box were performed at the Distributed Energy Technologies Laboratory (DETL) at SNL in Albuquerque, NM. In all the tests, the prototype de-energized the arc-faults in the time period required by the arc-fault circuit interrupt testing standard, UL 1699B. The experimental tests confirm series and parallel arc-faults can be successfully mitigated with a combiner box-integrated solution.

  6. Characteristic of a triple-cathode vacuum arc plasma source.

    PubMed

    Xiang, W; Li, M; Chen, L

    2012-02-01

    In order to generate a better ion beam, a triple-cathode vacuum arc plasma source has been developed. Three plasma generators in the vacuum arc plasma source are equally located on a circle. Each generator initiated by means of a high-voltage breakdown between the cathode and the anode could be operated separately or simultaneously. The arc plasma expands from the cathode spot region in vacuum. In order to study the behaviors of expanding plasma plume generated in the vacuum arc plasma source, a Langmuir probe array is employed to measure the saturated ion current of the vacuum arc plasma source. The time-dependence profiles of the saturated current density of the triple vacuum arc plasma source operated separately and simultaneously are given. Furthermore, the plasma characteristic of this vacuum arc plasma source is also presented in the paper.

  7. Electric arc discharge damage to ion thruster grids

    NASA Technical Reports Server (NTRS)

    Beebe, D. D.; Nakanishi, S.; Finke, R. C.

    1974-01-01

    Arcs representative of those occurring between the grids of a mercury ion thruster were simulated. Parameters affecting an arc and the resulting damage were studied. The parameters investigated were arc energy, arc duration, and grid geometry. Arc attenuation techniques were also investigated. Potentially serious damage occurred at all energy levels representative of actual thruster operating conditions. Of the grids tested, the lowest open-area configuration sustained the least damage for given conditions. At a fixed energy level a long duration discharge caused greater damage than a short discharge. Attenuation of arc current using various impedances proved to be effective in reducing arc damage. Faults were also deliberately caused using chips of sputtered materials formed during the operation of an actual thruster. These faults were cleared with no serious grid damage resulting using the principles and methods developed in this study.

  8. SAR arcs we have seen: Evidence for variability in stable auroral red arcs

    NASA Astrophysics Data System (ADS)

    Mendillo, Michael; Baumgardner, Jeffrey; Wroten, Joei

    2016-01-01

    Since 1987, an all-sky airglow imaging system has operated from a site at the Millstone Hill/Haystack Observatory in Westford, MA. During the ~2.5 solar cycles from 1987 to 2014, many studies using all-sky images, in conjunction with incoherent scatter radar and satellite data, described subauroral, ionospheric disturbances observed during individual geomagnetic storms. The most prominent storm time optical feature from a subauroral site is a stable auroral red (SAR) arc. The standard use of a SAR arc's position is to locate the ionospheric footprint of the narrow plasmapause-ring current interaction region where heat conduction from the inner magnetosphere excites emission within the F layer trough. When mapped from an emission altitude of 400 km to the geomagnetic equatorial plane, SAR arcs from Millstone Hill give the location of the plasmapause at radial distances between 2 to 4.5 Earth radii. A total of 314 SAR arcs have been observed during the 27 years of imaging at Millstone Hill. We find no single morphology for all SAR arcs, but rather patterns that occasionally depart from stability in space and time. We have classified these into five categories: longevity, multiplicity, zonal structure, latitudinal inhomogeneity, and tilt with respect to geomagnetic coordinates. In each case, the implications for the inner magnetosphere sources that drive SAR arcs are explored. While individual SAR arc variability characteristics have been noted in previous studies, here we describe for the first time all five types from the same site—an aspect not yet addressed in either magnetosphere or ionosphere modeling studies.

  9. Structure and magnetic properties of surface alloyed Fe nanocapsules prepared by arc discharge

    NASA Astrophysics Data System (ADS)

    Si, P. Z.; Choi, C. J.; Brück, E.; Geng, D. Y.; Zhang, Z. D.

    2005-12-01

    C-Fe-Si alloy encapsulating Fe nanocapsules were fabricated by arc evaporating the mixture of Fe and SiC powders. The high temperature of the electric arc results in a surface reaction between SiC and Fe nanoparticles and therefore a uniform encapsulation of the Fe nanoparticles with its alloy. The size of the nanocapsules ranges from 10 to 60 nm while most shells are approximately 7 nm in thickness. Air oxidation to the as-prepared sample does not change the shell/core structure but the saturation magnetization and the coercivity are reduced. The characteristics of the nanocapsules were investigated systematically by using X-ray diffraction, transmission electron microscopy, energy dispersive spectra, X-ray photoelectron spectroscopy, and superconducting quantum interference device magnetometer.

  10. Evaporation Erosion During the Relay Contact Breaking Process Based on a Simplified Arc Model

    NASA Astrophysics Data System (ADS)

    Cui, Xinglei; Zhou, Xue; Zhai, Guofu; Peng, Xiyuan

    2016-05-01

    Evaporation erosion of the contacts is one of the fundamental failure mechanisms for relays. In this paper, the evaporation erosion characteristics are investigated for the copper contact pair breaking a resistive direct current (dc) 30 V/10 A circuit in the air. Molten pool simulation of the contacts is coupled with the gas dynamics to calculate the evaporation rate. A simplified arc model is constructed to obtain the contact voltage and current variations with time for the prediction of the current density and the heat flux distributions flowing from the arc into the contacts. The evaporation rate and mass variations with time during the breaking process are presented. Experiments are carried out to verify the simulation results. supported by National Natural Science Foundation of China (Nos. 51377038, 51307030)

  11. Common arc method for diffraction pattern orientation.

    PubMed

    Bortel, Gábor; Tegze, Miklós

    2011-11-01

    Very short pulses of X-ray free-electron lasers opened the way to obtaining diffraction signal from single particles beyond the radiation dose limit. For three-dimensional structure reconstruction many patterns are recorded in the object's unknown orientation. A method is described for the orientation of continuous diffraction patterns of non-periodic objects, utilizing intensity correlations in the curved intersections of the corresponding Ewald spheres, and hence named the common arc orientation method. The present implementation of the algorithm optionally takes into account Friedel's law, handles missing data and is capable of determining the point group of symmetric objects. Its performance is demonstrated on simulated diffraction data sets and verification of the results indicates a high orientation accuracy even at low signal levels. The common arc method fills a gap in the wide palette of orientation methods.

  12. Catalyst and doping methods for arc graphene

    NASA Astrophysics Data System (ADS)

    Cho, Hyunjin; Oh, InSeoup; Kang, JungHo; Park, Sungchan; Ku, Boncheol; Park, Min; Kwak, Soonjong; Khanra, Partha; Lee, Joong Hee; Jong Kim, Myung

    2014-11-01

    Nitrogen-doped graphene synthesis with ˜g scale has been accomplished using the arc discharge method. The defects formed in the synthesis process were reduced by adding various metal catalysts, among which Bi2O3 was found to be the most effective. Adding dopants to the starting materials increased the electrical conductivity of the graphene product, and the doping concentration in graphene was tuned by adjusting the amount of nitrogen dopants. A step-wise technique to fabricate graphene thin films was developed, including dispersion, separation, and filtering processes. The arc graphene can also find its potential application in supercapacitors, taking advantage of its large surface area and improved conductivity by doping.

  13. The Singing Arc:. the Oldest Memristor?

    NASA Astrophysics Data System (ADS)

    Ginoux, Jean-Marc; Rossetto, Bruno

    2013-01-01

    On April 30th 2008, the journal Nature announced that the missing circuit element, postulated thirty-seven years before by Professor Leon O. Chua has been found. Thus, after the capacitor, the resistor and the inductor, the existence of a fourth fundamental element of electronic circuits called "memristor" was established. In order to point out the importance of such a discovery, the aim of this article is first to propose an overview of the manner with which the three others have been invented during the past centuries. Then, a comparison between the main properties of the singing arc, i.e. a forerunner device of the triode used in Wireless Telegraphy, and that of the memristor will enable to state that the singing arc could be considered as the oldest memristor.

  14. Hybrid Arc Cell Studies: Status Report

    SciTech Connect

    Berg J. S.

    2012-09-28

    I report on the status, at the end of FY12, of the studies of an arc cell for a hybrid synchrotron accelerating from 375 GeV/c to 750 GeV/c in momentum. Garren produced a complete lattice that gives a good outline of the structure of a hybrid synchrotron lattice. It is, however, lacking in some details: it does not maintain a constant time of flight, it lacks chromaticity correction, its cell structure is not ideal for removing aberrations from chromaticity correction, and it probably needs more space between magnets. I have begun studying cell structures for the arc cells to optimize the lattice performance and cost. I present some preliminary results for two magnets per half cell. I then discuss difficulties encountered, some preliminary attempts at resolving them, and the future plans for this work.

  15. Electrical Safety and Arc Flash Protections

    SciTech Connect

    R. Camp

    2008-03-04

    Over the past four years, the Electrical Safety Program at PPPL has evolved in addressing changing regulatory requirements and lessons learned from accident events, particularly in regards to arc flash hazards and implementing NFPA 70E requirements. This presentation will discuss PPPL's approaches to the areas of electrical hazards evaluation, both shock and arc flash; engineered solutions for hazards mitigation such as remote racking of medium voltage breakers, operational changes for hazards avoidance, targeted personnel training and hazard appropriate personal protective equipment. Practical solutions for nominal voltage identification and zero voltage checks for lockout/tagout will also be covered. Finally, we will review the value of a comprehensive electrical drawing program, employee attitudes expressed as a personal safety work ethic, integrated safety management, and sustained management support for continuous safety improvement.

  16. Filtered cathodic arc deposition apparatus and method

    DOEpatents

    Krauss, Alan R.

    1999-01-01

    A filtered cathodic arc deposition method and apparatus for the production of highly dense, wear resistant coatings which are free from macro particles. The filtered cathodic arc deposition apparatus includes a cross shaped vacuum chamber which houses a cathode target having an evaporable surface comprised of the coating material, means for generating a stream of plasma, means for generating a transverse magnetic field, and a macro particle deflector. The transverse magnetic field bends the generated stream of plasma in the direction of a substrate. Macro particles are effectively filtered from the stream of plasma by traveling, unaffected by the transverse magnetic field, along the initial path of the plasma stream to a macro particle deflector. The macro particle deflector has a preformed surface which deflects macro particles away from the substrate.

  17. Shepherding model for Neptune's arc ring

    NASA Technical Reports Server (NTRS)

    Lissauer, J. J.

    1985-01-01

    A model to explain the confinement of the recently discovered incomplete arc ring around Neptune is developed. The ring may be azimuthally confined near a triangular (Trojan) point of an undiscovered satellite of Neptune. Radial diffusion of the ring particles can be prevented by shepherding torques of another moon. Two satellites with diameters of 100-200 km would be sufficient to confine the ring; such moons would be too small to have been photographed from earth.

  18. Mixing gasdynamic laser with nonequilibrium arc excitation

    NASA Astrophysics Data System (ADS)

    Antonov, G. G.; Kovshechnikov, V. B.; Rutberg, F. G.

    2016-05-01

    A mixing gasdynamic laser with nonuniform arc excitation is investigated using a model setup. Tentative analysis of the results indicates the appropriateness of using plasmatrons to improve the efficiency of mixing gasdynamic lasers by making carbon dioxide molecules vibrationally more nonuniform. In addition, a plasmatron serves as a preionization source both for a fast-flow gas-discharge laser and for a gasdynamic laser with combined pumping.

  19. Delivery quality assurance with ArcCHECK

    SciTech Connect

    Neilson, Christopher; Klein, Michael; Barnett, Rob; Yartsev, Slav

    2013-04-01

    Radiation therapy requires delivery quality assurance (DQA) to ensure that treatment is accurate and closely follows the plan. We report our experience with the ArcCHECK phantom and investigate its potential optimization for the DQA process. One-hundred seventy DQA plans from 84 patients were studied. Plans were classified into 2 groups: those with the target situated on the diodes of the ArcCHECK (D plans) and those with the target situated at the center (C plans). Gamma pass rates for 8 target sites were examined. The parameters used to analyze the data included 3%/3 mm with the Van Dyk percent difference criteria (VD) on, 3%/3 mm with the VD off, 2%/2 mm with the VD on, and x/3 mm with the VD on and the percentage dosimetric agreement “x” for diode plans adjusted. D plans typically displayed maximum planned dose (MPD) on the cylindrical surface containing ArcCHECK diodes than center plans, resulting in inflated gamma pass rates. When this was taken into account by adjusting the percentage dosimetric agreement, C plans outperformed D plans by an average of 3.5%. ArcCHECK can streamline the DQA process, consuming less time and resources than radiographic films. It is unnecessary to generate 2 DQA plans for each patient; a single center plan will suffice. Six of 8 target sites consistently displayed pass rates well within our acceptance criteria; the lesser performance of head and neck and spinal sites can be attributed to marginally lower doses and increased high gradient of plans.

  20. The Arc Cloud Complex. A Case Study.

    DTIC Science & Technology

    1984-08-01

    evaporationally-driven downdrafts. At the surface, The citations on the following pages follow the style of The Jounal gf the Atmospheric Sciences. 2...categories shown in Fig. 4. The wind direction behind the gust front is indicated by the arrows. A Type 2 pattern has a clear-cut, arc-shaped leading edge...500, 700, and 850 mb) from the NWS were reanalyzed by hand in order to seek indications -of the mesoscale features aloft which may have been

  1. Surface breakdown igniter for mercury arc devices

    DOEpatents

    Bayless, John R.

    1977-01-01

    Surface breakdown igniter comprises a semiconductor of medium resistivity which has the arc device cathode as one electrode and has an igniter anode electrode so that when voltage is applied between the electrodes a spark is generated when electrical breakdown occurs over the surface of the semiconductor. The geometry of the igniter anode and cathode electrodes causes the igniter discharge to be forced away from the semiconductor surface.

  2. HPF Implementation of ARC3D

    NASA Technical Reports Server (NTRS)

    Frumkin, Michael; Yan, Jerry

    1999-01-01

    We present an HPF (High Performance Fortran) implementation of ARC3D code along with the profiling and performance data on SGI Origin 2000. Advantages and limitations of HPF as a parallel programming language for CFD applications are discussed. For achieving good performance results we used the data distributions optimized for implementation of implicit and explicit operators of the solver and boundary conditions. We compare the results with MPI and directive based implementations.

  3. Multi-colour detection of gravitational arcs

    NASA Astrophysics Data System (ADS)

    Maturi, Matteo; Mizera, Sebastian; Seidel, Gregor

    2014-07-01

    Strong gravitational lensing provides fundamental insights into the understanding of the dark matter distribution in massive galaxies, galaxy clusters, and the background cosmology. Despite their importance, few gravitational arcs have been discovered so far. The urge for more complete, large samples and unbiased methods of selecting candidates increases. Several methods for the automatic detection of arcs have been proposed in the literature, but large amounts of spurious detections retrieved by these methods force observers to visually inspect thousands of candidates per square degree to clean the samples. This approach is largely subjective and requires a huge amount of checking by eye, especially considering the actual and upcoming wide-field surveys, which will cover thousands of square degrees. In this paper we study the statistical properties of the colours of gravitational arcs detected in the 37 deg2 of the CFHTLS-Archive-Research Survey (CARS). Most of them lie in a relatively small region of the (g' - r', r' - i') colour-colour diagram. To explain this property, we provide a model that includes the lensing optical depth expected in a ΛCDM cosmology that, in combination with the sources' redshift distribution of a given survey, in our case CARS, peaks for sources at redshift z ~ 1. By furthermore modelling the colours derived from the spectral energy distribution of the galaxies that dominate the population at that redshift, the model reproduces the observed colours well. By taking advantage of the colour selection suggested by both data and model, we automatically detected 24 objects out of 90 detected by eye checking. Compared with the single-band arcfinder, this multi-band filtering returns a sample complete to 83% and a contamination reduced by a factor of ~6.5. New gravitational arc candidates are also proposed.

  4. Development of a multiperspective optical measuring system for investigating decaying switching arcs at the nozzle exit of circuit breakers.

    PubMed

    Stoffels, M; Simon, S; Nikolic, P G; Stoller, P; Carstensen, J

    2017-03-01

    generates two gas jets, as described in [Exp. Fluids43, 241 (2007)EXFLDU0723-486410.1007/s00348-007-0331-1]. Experiments using a simple model of a circuit breaker, which provides optical access to an ∼1  kA arc that burns between two contacts and is blown through a nozzle system by synthetic air from a high pressure reservoir, are also described. The density in the decaying arc and surrounding gas flow is reconstructed, and the limitations of the technique, which are related to the temporal and spatial resolution, are addressed.

  5. Effect of cathode model on arc attachment for short high-intensity arc on a refractory cathode

    NASA Astrophysics Data System (ADS)

    Javidi Shirvan, Alireza; Choquet, Isabelle; Nilsson, Håkan

    2016-12-01

    Various models coupling the refractory cathode, the cathode sheath and the arc at atmospheric pressure exist. They assume a homogeneous cathode with a uniform physical state, and differ by the cathode layer and the plasma arc model. However even the most advanced of these models still fail in predicting the extent of the arc attachment when applied to short high-intensity arcs such as gas tungsten arcs. Cathodes operating in these conditions present a non-uniform physical state. A model taking into account the first level of this non-homogeneity is proposed based on physical criteria. Calculations are done for 5 mm argon arcs with a thoriated tungsten cathode. The results obtained show that radiative heating and cooling of the cathode surface are of the same order. They also show that cathode inhomogeneity has a significant effect on the arc attachment, the arc temperature and pressure. When changing the arc current (100 A, 200 A) the proposed model allows predicting trends observed experimentally that cannot be captured by the homogeneous cathode model unless restricting a priori the size of the arc attachment. The cathode physics is thus an important element to include to obtain a comprehensive and predictive arc model.

  6. Arc melter demonstration baseline test results

    SciTech Connect

    Soelberg, N.R.; Chambers, A.G.; Anderson, G.L.; Oden, L.L.; O`Connor, W.K.; Turner, P.C.

    1994-07-01

    This report describes the test results and evaluation for the Phase 1 (baseline) arc melter vitrification test series conducted for the Buried Waste Integrated Demonstration program (BWID). Phase 1 tests were conducted on surrogate mixtures of as-incinerated wastes and soil. Some buried wastes, soils, and stored wastes at the INEL and other DOE sites, are contaminated with transuranic (TRU) radionuclides and hazardous organics and metals. The high temperature environment in an electric arc furnace may be used to process these wastes to produce materials suitable for final disposal. An electric arc furnace system can treat heterogeneous wastes and contaminated soils by (a) dissolving and retaining TRU elements and selected toxic metals as oxides in the slag phase, (b) destroying organic materials by dissociation, pyrolyzation, and combustion, and (c) capturing separated volatilized metals in the offgas system for further treatment. Structural metals in the waste may be melted and tapped separately for recycle or disposal, or these metals may be oxidized and dissolved into the slag. The molten slag, after cooling, will provide a glass/ceramic final waste form that is homogeneous, highly nonleachable, and extremely durable. These features make this waste form suitable for immobilization of TRU radionuclides and toxic metals for geologic timeframes. Further, the volume of contaminated wastes and soils will be substantially reduced in the process.

  7. Finite element analysis of arc welding

    SciTech Connect

    Friedman, E.

    1980-01-01

    Analytical models of the gas tungsten-arc welding process into finite element computer programs provides a valuable tool for determining the welding thermal cycle, weld bead shape, and penetration characteristics, as well as for evaluating the stresses and distortions generated as a result of the temperature transients. The analysis procedures are applicable to planar or axisymmetric welds with arbitrary cross-sectional geometries, under quasistationary conditions. The method used for determining temperatures features an iteration procedure to accurately account for the latent heat absorbed during melting and liberated during solidification of the weld. By simulating the heat input from the arc to the workpiece by a normal distribution function, temperature transients, weld bead dimensions, and cooling rates are evaluated as functions of both the magnitude and distribution of heat input, weldment geometry, and weld speed (or duration of heating for stationary arcs). Modeling of the welding thermal cycle is a prerequisite to analytical treatments of metallurgical changes in weld metal and heat-affected zone material, residual stresses and distortions, and weld defects. A quasistationary formulation for moving welds enables temperatures to be calculated using a two-dimensional heat conduction computer program. The present limitation of high welding speed can, however, be relaxed without altering the two-dimensional framework of the procedure.

  8. Modify surfaces with ions and arcs

    SciTech Connect

    Banks, B.A. . Lewis Research Center)

    1993-12-01

    Ions, arcs, and atomic-oxygen techniques have been developed at NASA to texture metals, polymers, and biomaterials for a range of medical and industrial applications. NASA originally conducted research in the field of electron bombardment because the technology involves generation of high-velocity ions, which have the potential to produce much higher propellant exhaust velocities for spacecraft than chemical propulsion. As a consequence, considerable data were collected about the effects of ion beams on a wide range of materials. Based on this information, researchers designed specialized surface modification techniques such as ion beam sputter texturing, etching, and simultaneous deposition and etching. Arc-texturing technology was developed as a result of research on high-thermal-emittance radiators. In this process, an electric arc is formed between a carbon or silicon-carbide electrode and a moving metal surface, resulting in durable, microscopically rough surfaces that emit heat more efficiently than coated materials. Atomic-oxygen texturing is a by-product of studies about the effects of atomic oxygen on the surfaces of spacecraft. The purpose of the original research was to find coatings that could withstand atomic-oxygen attack, but it evolved into deliberate bombardment of polymeric materials to increase thermal emittance or reduce co-efficient of friction.

  9. Plasma magmavication of soils by nontransferred arc

    SciTech Connect

    Mayne, P.W.; Burns, S.E.; Circeo, L.J.

    2000-05-01

    Electrical plasma arcs create very high temperatures (T > 4,000 C) that can be specifically directed for the in-place melting of soils. This overview presents a summary of the basic features and capabilities of plasma torches having a nontransferred type of arc for the in situ vitrification of soils. Laboratory chamber experiments using 100 kW and 240 kW plasma systems and full-scale field trials using a 1 MW portable system have successfully melted a variety of soil types, including sands, silts, and clays. Within five minutes' exposure to the arc, a core region of magma forms within the soil matrix that expands radially outward and upward as the torch is pulled out vertically. Several days afterwards, the molten zone cools to form an artificial igneous rock similar to obsidian, basalt, or granite. The size of the vitrified mass is proportional to the electrical power demand. The plasma torch has a configuration similar to a flamethrower and will therefore be amenable to placement down boreholes for purposes of in situ ground modification and subsurface remediation.

  10. Geothermal resource potential of Cascade volcanic arc

    SciTech Connect

    Priest, G.R.

    1987-08-01

    The central and southern cascade volcanic arc has the following features that suggest a high potential for geothermal resources: (1) extensive Quaternary volcanism with some silicic to intermediate volcanoes, (2) hundreds of square kilometers with regional background heat flow in excess of 100 mW/m/sup 2/, (3) shallow (4-9 km) calculated depth to Curie point in the same areas that have heat flow in excess of 100 mW/m/sup 2/, (4) a thick pile of volcanic rock with moderate to low thermal conductivity, (5) hot springs with minimum reservoir temperatures of 174/sup 0/-186/sup 0/C (from the anhydrite geothermometer of Mariner, 1985), and (6) fault zones for fracture permeability. These features are the result of interactions between the North American plate (NAP), the Pacific plate (PP), and the subducted Gorda, Juan de Fuca, and Explorer plates (GJEP). Interactions between the NAP and the PP produce north-south compression and east-west extension, causing extensive development of north-south normal faults and partial melting episodes in upper mantle. Northeast-southwest convergence between the NAP and the GJEP produce subduction-related magmas and crustal deformation from northeast-southwest compression. NAP-GJEP interactions dominate in the northern part of the arc, whereas NAP-PP and NAP-GJEP interactions have combined in the central and southern part of the arc to produce rates of magmatism and heat flow higher than in the north.

  11. Sevoflurane induced amnesia inhibits hippocampal Arc expression partially through 5-hydroxytryptamine-7 receptors in the bilateral basolateral amygdala in rats.

    PubMed

    Zhang, Fujun; Feng, Xiaomei; Zeng, Qingwen; Wang, Bo; Wilhelmsen, Kevin; Li, Qiang; Cao, Xiaohua; Yu, Buwei

    2014-03-06

    This study aimed to investigate whether the regulation of 5-hydroxytryptamine-7 (5-HT7) receptors in the bilateral basolateral amygdala (BLA) could alter the amnesic effects of sevoflurane and change the hippocampal expression of Arc and neural apoptosis. Male Sprague-Dawley rats were randomized into ten groups. First, the animals received bilateral injection of SB269970 (20, 50, or 100 pmol/0.2 μl) or saline (0.2 μl) or AS-19 (2, 10, or 50 pmol/0.2 μl), followed by inhalation of 2% sevoflurane or air for 2h. Then, fear conditioning training was carried out, and the percentage of freezing was detected 24h later. Furthermore, hippocampal Arc protein level and neural apoptosis were measured. Pre-training inhalation of sevoflurane reduced the extent of freezing, and hippocampal Arc expression. The largest dose of SB269970 (100 pmol) could block sevoflurane-induced amnesia and reverse the inhibitive effect of sevoflurane on Arc expression, while the maximal dose of AS-19 could exacerbate the amnesic effect, and further inhibit Arc expression. Furthermore, pre-training inhalation of 2% sevoflurane for 6h could not induce neural apoptosis in the hippocampus. The amnesic effect of sevoflurane might partly attribute to its impairment of memory formation in the hippocampus via activation of 5-HT7 receptors in the BLA.

  12. Volumetric modulated arc radiotherapy for esophageal cancer

    SciTech Connect

    Vivekanandan, Nagarajan; Sriram, Padmanaban; Syam Kumar, S.A.; Bhuvaneswari, Narayanan; Saranya, Kamalakannan

    2012-04-01

    A treatment planning study was performed to evaluate the performance of volumetric arc modulation with RapidArc (RA) against 3D conformal radiation therapy (3D-CRT) and conventional intensity-modulated radiation therapy (IMRT) techniques for esophageal cancer. Computed tomgraphy scans of 10 patients were included in the study. 3D-CRT, 4-field IMRT, and single-arc and double-arc RA plans were generated with the aim to spare organs at risk (OAR) and healthy tissue while enforcing highly conformal target coverage. The planning objective was to deliver 54 Gy to the planning target volume (PTV) in 30 fractions. Plans were evaluated based on target conformity and dose-volume histograms of organs at risk (lung, spinal cord, and heart). The monitor unit (MU) and treatment delivery time were also evaluated to measure the treatment efficiency. The IMRT plan improves target conformity and spares OAR when compared with 3D-CRT. Target conformity improved with RA plans compared with IMRT. The mean lung dose was similar in all techniques. However, RA plans showed a reduction in the volume of the lung irradiated at V{sub 20Gy} and V{sub 30Gy} dose levels (range, 4.62-17.98%) compared with IMRT plans. The mean dose and D{sub 35%} of heart for the RA plans were better than the IMRT by 0.5-5.8%. Mean V{sub 10Gy} and integral dose to healthy tissue were almost similar in all techniques. But RA plans resulted in a reduced low-level dose bath (15-20 Gy) in the range of 14-16% compared with IMRT plans. The average MU needed to deliver the prescribed dose by RA technique was reduced by 20-25% compared with IMRT technique. The preliminary study on RA for esophageal cancers showed improvements in sparing OAR and healthy tissue with reduced beam-on time, whereas only double-arc RA offered improved target coverage compared with IMRT and 3D-CRT plans.

  13. Arc Jet Facility Test Condition Predictions Using the ADSI Code

    NASA Technical Reports Server (NTRS)

    Palmer, Grant; Prabhu, Dinesh; Terrazas-Salinas, Imelda

    2015-01-01

    The Aerothermal Design Space Interpolation (ADSI) tool is used to interpolate databases of previously computed computational fluid dynamic solutions for test articles in a NASA Ames arc jet facility. The arc jet databases are generated using an Navier-Stokes flow solver using previously determined best practices. The arc jet mass flow rates and arc currents used to discretize the database are chosen to span the operating conditions possible in the arc jet, and are based on previous arc jet experimental conditions where possible. The ADSI code is a database interpolation, manipulation, and examination tool that can be used to estimate the stagnation point pressure and heating rate for user-specified values of arc jet mass flow rate and arc current. The interpolation is performed in the other direction (predicting mass flow and current to achieve a desired stagnation point pressure and heating rate). ADSI is also used to generate 2-D response surfaces of stagnation point pressure and heating rate as a function of mass flow rate and arc current (or vice versa). Arc jet test data is used to assess the predictive capability of the ADSI code.

  14. Numerical modeling of volcanic arc development

    NASA Astrophysics Data System (ADS)

    Gerya, T.; Gorczyk, W.; Nikolaeva, K.

    2007-05-01

    We have created a new coupled geochemical-petrological-thermomechanical numerical model of subduction associated with volcanic arc development. The model includes spontaneous slab bending, subducted crust dehydration, aqueous fluid transport, mantle wedge melting and melt extraction resulting in crustal growth. Two major volcanic arc settings are modeled so far: active continental margins, and intraoceanic subduction. In case of Pacific-type continental margin two fundamentally different regimes of melt productivity are observed in numerical experiments which are in line with natural observations: (1) During continuous convergence with coupled plates highest amounts of melts are formed immediately after the initiation of subduction and then decrease rapidly with time due to the steepening of the slab inclination angle precluding formation of partially molten mantle wedge plumes; (2) During subduction associated with slab delamination and trench retreat resulting in the formation of a pronounced back arc basin with a spreading center in the middle melt production increases with time due to shallowing/stabilization of slab inclination associated with upward asthenospheric mantle flow toward the extension region facilitating propagation of hydrous partially molten plumes from the slab. In case of spontaneous nucleation of retreating oceanic subduction two scenarios of tecono-magmatic evolution are distinguished: (1) decay and, ultimately, the cessation of subduction and related magmatic activity, (2) increase in subduction rate (to up to ~12 cm/yr) and stabilization of subduction and magmatic arc growth. In the first case the duration of subduction correlates positively with the intensity of melt extraction: the period of continued subduction increases from 15,4 Myrs to 47,6 Myrs with the increase of melt extraction threshold from 1% to 9%. In scenario (1) the magmatic arc crust includes large amounts of rocks formed by melting of subducted crust atop the thermally

  15. Unraveling the diversity in arc volcanic eruption styles: Examples from the Aleutian volcanic arc, Alaska

    NASA Astrophysics Data System (ADS)

    Larsen, Jessica F.

    2016-11-01

    The magmatic systems feeding arc volcanoes are complex, leading to a rich diversity in eruptive products and eruption styles. This review focuses on examples from the Aleutian subduction zone, encompassed within the state of Alaska, USA because it exhibits a rich diversity in arc structure and tectonics, sediment and volatile influx feeding primary magma generation, crustal magma differentiation processes, with the resulting outcome the production of a complete range in eruption styles from its diverse volcanic centers. Recent and ongoing investigations along the arc reveal controls on magma production that result in diversity of eruptive products, from crystal-rich intermediate andesites to phenocryst-poor, melt-rich silicic and mafic magmas and a spectrum in between. Thus, deep to shallow crustal "processing" of arc magmas likely greatly influences the physical and chemical character of the magmas as they accumulate in the shallow crust, the flow physics of the magmas as they rise in the conduit, and eruption style through differences in degassing kinetics of the bubbly magmas. The broad spectrum of resulting eruption styles thus depends on the bulk magma composition, melt phase composition, and the bubble and crystal content (phenocrysts and/or microlites) of the magma. Those fundamental magma characteristics are in turn largely determined by the crustal differentiation pathway traversed by the magma as a function of tectonic location in the arc, and/or the water content and composition of the primary magmas. The physical and chemical character of the magma, set by the arc differentiation pathway, as it ascends towards eruption determines the kinetic efficiency of degassing versus the increasing internal gas bubble overpressure. The balance between degassing rate and the rate at which gas bubble overpressure builds then determines the conditions of fragmentation, and ultimately eruption intensity.

  16. Back-arc with frontal-arc component origin of Triassic Karmutsen basalt, British Columbia, Canada

    USGS Publications Warehouse

    Barker, F.; Sutherland, Brown A.; Budahn, J.R.; Plafker, G.

    1989-01-01

    The largely basaltic, ???4.5-6.2-km-thick, Middle to Upper Triassic Karmutsen Formation is a prominent part of the Wrangellian sequence. Twelve analyses of major and minor elements of representative samples of pillowed and massive basalt flows and sills from Queen Charlotte and Vancouver Islands are ferrotholeiites that show a range of 10.2-3.8% MgO (as normalized, H2O- and CO2-free) and related increases in TiO2 (1.0-2.5%), Zr (43-147 ppm) and Nb (5-16 ppm). Other elemental abundances are not related simply to MgO: distinct groupings are evident in Al2O3, Na2O and Cr, but considerable scatter is present in FeO* (FeO + 0.9Fe2O3) and CaO. Some of the variation is attributed to alteration during low-rank metamorphism or by seawater - including variation of Ba, Rb, Sr and Cu, but high-field-strength elements (Sc, Ti, Y, Zr and Nb) as well as Cr, Ni, Cu and rare-earth elements (REE's) were relatively immobile. REE's show chondrite-normalized patterns ranging from light-REE depleted to moderately light-REE enriched. On eleven discriminant plots these analyses fall largely into or across fields of within-plate basalt (WIP), normal or enriched mid-ocean-ridge tholeiite (MORB) and island-arc tholeiite (IAT). Karmutsen basalts are chemically identical to the stratigraphically equivalent Nikolai Greenstone of southern Alaska and Yukon Territory. These data and the fact that the Karmutsen rests on Sicker Group island-arc rocks of Paleozoic age suggest to us that: 1. (1) the basal arc, after minor carbonate-shale deposition, underwent near-axial back-arc rifting (as, e.g., the Mariana arc rifted at different times); 2. (2) the Karmutsen basalts were erupted along this rift or basin as "arc-rift" tholeiitite; and 3. (3) after subsequent deposition of carbonates and other rocks, and Jurassic magmatism, a large fragment of this basalt-sediment-covered island arc was accreted to North America as Wrangellia. The major- and minor-elemental abundances of Karmutsen basalt is modeled

  17. Optical arc sensor using energy harvesting power source

    NASA Astrophysics Data System (ADS)

    Choi, Kyoo Nam; Rho, Hee Hyuk

    2016-06-01

    Wireless sensors without external power supply gained considerable attention due to convenience both in installation and operation. Optical arc detecting sensor equipping with self sustaining power supply using energy harvesting method was investigated. Continuous energy harvesting method was attempted using thermoelectric generator to supply standby power in micro ampere scale and operating power in mA scale. Peltier module with heat-sink was used for high efficiency electricity generator. Optical arc detecting sensor with hybrid filter showed insensitivity to fluorescent and incandescent lamps under simulated distribution panel condition. Signal processing using integrating function showed selective arc discharge detection capability to different arc energy levels, with a resolution below 17J energy difference, unaffected by bursting arc waveform. The sensor showed possibility for application to arc discharge detecting sensor in power distribution panel. Also experiment with proposed continuous energy harvesting method using thermoelectric power showed possibility as a self sustainable power source of remote sensor.

  18. Arc Flash Boundary Calculations Using Computer Software Tools

    SciTech Connect

    Gibbs, M.D.

    2005-01-07

    Arc Flash Protection boundary calculations have become easier to perform with the availability of personal computer software. These programs incorporate arc flash protection boundary formulas for different voltage and current levels, calculate the bolted fault current at each bus, and use built in time-current coordination curves to determine the clearing time of protective devices in the system. Results of the arc flash protection boundary calculations can be presented in several different forms--as an annotation to the one-line diagram, as a table of arc flash protection boundary distances, and as printed placards to be attached to the appropriate equipment. Basic arc flash protection boundary principles are presented in this paper along with several helpful suggestions for performing arc flash protection boundary calculations.

  19. Computational Modeling of Arc-Slag Interaction in DC Furnaces

    NASA Astrophysics Data System (ADS)

    Reynolds, Quinn G.

    2017-02-01

    The plasma arc is central to the operation of the direct-current arc furnace, a unit operation commonly used in high-temperature processing of both primary ores and recycled metals. The arc is a high-velocity, high-temperature jet of ionized gas created and sustained by interactions among the thermal, momentum, and electromagnetic fields resulting from the passage of electric current. In addition to being the primary source of thermal energy, the arc jet also couples mechanically with the bath of molten process material within the furnace, causing substantial splashing and stirring in the region in which it impinges. The arc's interaction with the molten bath inside the furnace is studied through use of a multiphase, multiphysics computational magnetohydrodynamic model developed in the OpenFOAM® framework. Results from the computational solver are compared with empirical correlations that account for arc-slag interaction effects.

  20. Regulation of p53 tetramerization and nuclear export by ARC

    PubMed Central

    Foo, Roger S.-Y.; Nam, Young-Jae; Ostreicher, Marc Jason; Metzl, Mark D.; Whelan, Russell S.; Peng, Chang-Fu; Ashton, Anthony W.; Fu, Weimin; Mani, Kartik; Chin, Suet-Feung; Provenzano, Elena; Ellis, Ian; Figg, Nichola; Pinder, Sarah; Bennett, Martin R.; Caldas, Carlos; Kitsis, Richard N.

    2007-01-01

    Inactivation of the transcription factor p53 is central to carcinogenesis. Yet only approximately one-half of cancers have p53 loss-of-function mutations. Here, we demonstrate a mechanism for p53 inactivation by apoptosis repressor with caspase recruitment domain (ARC), a protein induced in multiple cancer cells. The direct binding in the nucleus of ARC to the p53 tetramerization domain inhibits p53 tetramerization. This exposes a nuclear export signal in p53, triggering Crm1-dependent relocation of p53 to the cytoplasm. Knockdown of endogenous ARC in breast cancer cells results in spontaneous tetramerization of endogenous p53, accumulation of p53 in the nucleus, and activation of endogenous p53 target genes. In primary human breast cancers with nuclear ARC, p53 is almost always WT. Conversely, nearly all breast cancers with mutant p53 lack nuclear ARC. We conclude that nuclear ARC is induced in cancer cells and negatively regulates p53. PMID:18087040

  1. Computational Modeling of Arc-Slag Interaction in DC Furnaces

    NASA Astrophysics Data System (ADS)

    Reynolds, Quinn G.

    2016-11-01

    The plasma arc is central to the operation of the direct-current arc furnace, a unit operation commonly used in high-temperature processing of both primary ores and recycled metals. The arc is a high-velocity, high-temperature jet of ionized gas created and sustained by interactions among the thermal, momentum, and electromagnetic fields resulting from the passage of electric current. In addition to being the primary source of thermal energy, the arc jet also couples mechanically with the bath of molten process material within the furnace, causing substantial splashing and stirring in the region in which it impinges. The arc's interaction with the molten bath inside the furnace is studied through use of a multiphase, multiphysics computational magnetohydrodynamic model developed in the OpenFOAM® framework. Results from the computational solver are compared with empirical correlations that account for arc-slag interaction effects.

  2. The Detection and Statistics of Giant Arcs behind CLASH Clusters

    NASA Astrophysics Data System (ADS)

    Xu, Bingxiao; Postman, Marc; Meneghetti, Massimo; Seitz, Stella; Zitrin, Adi; Merten, Julian; Maoz, Dani; Frye, Brenda; Umetsu, Keiichi; Zheng, Wei; Bradley, Larry; Vega, Jesus; Koekemoer, Anton

    2016-02-01

    We developed an algorithm to find and characterize gravitationally lensed galaxies (arcs) to perform a comparison of the observed and simulated arc abundance. Observations are from the Cluster Lensing And Supernova survey with Hubble (CLASH). Simulated CLASH images are created using the MOKA package and also clusters selected from the high-resolution, hydrodynamical simulations, MUSIC, over the same mass and redshift range as the CLASH sample. The algorithm's arc elongation accuracy, completeness, and false positive rate are determined and used to compute an estimate of the true arc abundance. We derive a lensing efficiency of 4 ± 1 arcs (with length ≥6″ and length-to-width ratio ≥7) per cluster for the X-ray-selected CLASH sample, 4 ± 1 arcs per cluster for the MOKA-simulated sample, and 3 ± 1 arcs per cluster for the MUSIC-simulated sample. The observed and simulated arc statistics are in full agreement. We measure the photometric redshifts of all detected arcs and find a median redshift zs = 1.9 with 33% of the detected arcs having zs > 3. We find that the arc abundance does not depend strongly on the source redshift distribution but is sensitive to the mass distribution of the dark matter halos (e.g., the c-M relation). Our results show that consistency between the observed and simulated distributions of lensed arc sizes and axial ratios can be achieved by using cluster-lensing simulations that are carefully matched to the selection criteria used in the observations.

  3. Occultation detection of a Neptunian ring-like arc

    NASA Technical Reports Server (NTRS)

    Hubbard, W. B.; Brahic, A.; Sicardy, B.; Roques, F.; Elicer, L.-R.; Vilas, F.

    1986-01-01

    The apparent closest approach of the star SAO186001 to Neptune was observed photoelectrically on July 22, 1984 at Cerro Tololo Inter-American Observatory. A 32-percent signal drop, lasting about 1.2 s, was probably caused by a partially transparent arc of material at a distance of 67,000 km from Neptune. Neptune's arc(s) do not vary smoothly with azimuth, unlike the rings of other Jovian planets.

  4. Liquid-Arc/Spark-Excitation Atomic-Emission Spectroscopy

    NASA Technical Reports Server (NTRS)

    Schlagen, Kenneth J.

    1992-01-01

    Constituents of solutions identified in situ. Liquid-arc/spark-excitation atomic-emission spectroscopy (LAES) is experimental variant of atomic-emission spectroscopy in which electric arc or spark established in liquid and spectrum of light from arc or spark analyzed to identify chemical elements in liquid. Observations encourage development of LAES equipment for online monitoring of process streams in such industries as metal plating, electronics, and steel, and for online monitoring of streams affecting environment.

  5. Physics of arcing, and implications to sputter deposition

    SciTech Connect

    Anders, Andre

    2003-12-15

    Arcing is a well-known, unwanted discharge regime observed on the surface of sputtering targets. The discharge voltage breaks down to less than 50 V while the current jumps to elevated levels. Arcing is unwanted because it prevents uniform deposition and creates particulates. The issue of arcing has been dealt with by target surface conditioning and by using modern power supplies that have arc suppression incorporated. With increasing quality requirements in terms of uniformity of coatings, and absence of particulates, especially for electrochromic and other advanced coatings applications, the issue of arcing warrants a closer examination with the goal to find other, physics-based, and hopefully better approaches of arcing prevention. From a physics point of view, the onset of arcing is nothing else than the transition of the discharge to a cathodic arc mode, which is characterized by the ignition of non-stationary arc spots. Arc spots operate by a sequence of microexplosions, enabling explosive electron emission, as opposed to secondary electron emission. Arc spots and their fragments have a size distribution in the micrometer and sub-micrometer range, and a characteristic time distribution that has components shorter than microseconds. Understanding the ignition conditions of arc spots are of central physical interest. Spot ignition is associated with electric field enhancement, which can be of geometric nature (roughness,particles), or chemical nature (e.g. oxide formation) and related local accumulation of surface charge. Therefore, it is clear that these issues are of particular concern when operating with high-density plasmas, such as in high-power pulsed sputtering, and when using reactive sputter gases.

  6. Analysis of optical perturbations of the SLC arcs

    SciTech Connect

    Weng, W.T.; Sands, M.

    1987-01-01

    This paper establishes the analytical framework in solving optical pertubations in a transport line in general and the SLC Arc specifically. The Formulation presented here is applicable to any transport system in a straightforward way. The equations of motion of a perturbed betatron function and dispersion function are presented. Sources of field errors for the SLC Arc system are discussed. Magnitudes of pertubations to the optical functions for the SLC Arc are estimated. (JDH)

  7. THE DETECTION AND STATISTICS OF GIANT ARCS BEHIND CLASH CLUSTERS

    SciTech Connect

    Xu, Bingxiao; Zheng, Wei; Postman, Marc; Bradley, Larry; Meneghetti, Massimo; Koekemoer, Anton; Seitz, Stella; Zitrin, Adi; Merten, Julian; Maoz, Dani; Frye, Brenda; Vega, Jesus

    2016-02-01

    We developed an algorithm to find and characterize gravitationally lensed galaxies (arcs) to perform a comparison of the observed and simulated arc abundance. Observations are from the Cluster Lensing And Supernova survey with Hubble (CLASH). Simulated CLASH images are created using the MOKA package and also clusters selected from the high-resolution, hydrodynamical simulations, MUSIC, over the same mass and redshift range as the CLASH sample. The algorithm's arc elongation accuracy, completeness, and false positive rate are determined and used to compute an estimate of the true arc abundance. We derive a lensing efficiency of 4 ± 1 arcs (with length ≥6″ and length-to-width ratio ≥7) per cluster for the X-ray-selected CLASH sample, 4 ± 1 arcs per cluster for the MOKA-simulated sample, and 3 ± 1 arcs per cluster for the MUSIC-simulated sample. The observed and simulated arc statistics are in full agreement. We measure the photometric redshifts of all detected arcs and find a median redshift z{sub s} = 1.9 with 33% of the detected arcs having z{sub s} > 3. We find that the arc abundance does not depend strongly on the source redshift distribution but is sensitive to the mass distribution of the dark matter halos (e.g., the c–M relation). Our results show that consistency between the observed and simulated distributions of lensed arc sizes and axial ratios can be achieved by using cluster-lensing simulations that are carefully matched to the selection criteria used in the observations.

  8. A New Survey for Giant Arcs

    SciTech Connect

    Hennawi, Joseph F.; Gladders, Michael D.; Oguri, Masamune; Dalal, Neal; Koester, Benjamin; Natarajan, Priyamvada; Strauss, Michael A.; Inada, Naohisa; Kayo, Issha; Lin, Huan; Lampeitl, Hubert; Annis, James; Bahcall, Neta A.; Schneider, Donald P.

    2006-11-15

    We report on the first results of an imaging survey to detect strong gravitational lensing targeting the richest clusters selected from the photometric data of the Sloan Digital Sky Survey (SDSS) with follow-up deep imaging observations from the Wisconsin Indiana Yale NOAO (WIYN) 3.5m telescope and the University of Hawaii 88-inch telescope (UH88). The clusters are selected from an area of 8000 deg{sup 2} using the Red Cluster Sequence technique and span the redshift range 0.1 {approx}< z {approx}< 0.6, corresponding to a comoving cosmological volume of {approx} 2Gpc{sup 3}. Our imaging survey thus targets a volume more than an order of magnitude larger than any previous search. A total of 240 clusters were imaged of which 141 had sub-arcsecond image quality. Our survey has uncovered 16 new lensing clusters with definite giant arcs, an additional 12 systems for which the lensing interpretation is very likely, and 9 possible lenses which contain shorter arclets or candidate arcs which are less certain and will require further observations to confirm their lensing origin. The number of new cluster lenses detected in this survey is likely > 30. Among these new systems are several of the most dramatic examples of strong gravitational lensing ever discovered with multiple bright arcs at large angular separation. These will likely become 'poster-child' gravitational lenses similar to Abell 1689 and CL0024+1654. The new lenses discovered in this survey will enable future systematic studies of the statistics of strong lensing and its implications for cosmology and our structure formation paradigm.

  9. Monitoring Temperature in High Enthalpy Arc-heated Plasma Flows using Tunable Diode Laser Absorption Spectroscopy

    NASA Technical Reports Server (NTRS)

    Martin, Marcel Nations; Chang, Leyen S.; Jeffries, Jay B.; Hanson, Ronald K.; Nawaz, Anuscheh; Taunk, Jaswinder S.; Driver, David M.; Raiche, George

    2013-01-01

    A tunable diode laser sensor was designed for in situ monitoring of temperature in the arc heater of the NASA Ames IHF arcjet facility (60 MW). An external cavity diode laser was used to generate light at 777.2 nm and laser absorption used to monitor the population of electronically excited oxygen atoms in an air plasma flow. Under the assumption of thermochemical equilibrium, time-resolved temperature measurements were obtained on four lines-of-sight, which enabled evaluation of the temperature uniformity in the plasma column for different arcjet operating conditions.

  10. Mariana Arc structure inferred from gravity and seismic data

    NASA Astrophysics Data System (ADS)

    Sager, W. W.

    1980-10-01

    A two-dimensional gravity model of the lithosphere was constructed along a seismic refraction line near 18°N latitude. Included in the model are crustal layers constrained by seismic refraction results, an estimate of the gravity anomaly caused by the subducting slab, and a model of the low-density mantle beneath the Mariana Trough. With a reasonable anomaly assumed for the slab it is shown that the gravity anomaly caused by the low-density mantle is greatest over the axial bathymetric high and tapers off to the sides. With the bottom of the low-density mantle set at 200 km the density contrast is -0.033 g/cm3. Other depths and densities are tried as well. Several notable anomalies are found on the crustal layers. East of the trench, the crust has been thinned slightly to account for an outer gravity high. Behind the landward wall of the trench, a small, low-density body is modeled to explain a slight offset of the minimum of the free air anomaly from the trench axis. A 50-mGal jump on the observed gravity over the volcanic line is explained by an unusual configuration of the frontal arc Moho.

  11. Hazards from High Intensity Lamps and Arcs

    NASA Technical Reports Server (NTRS)

    Sliney, D. H.

    1970-01-01

    The principal occupational health problem generally associated with high intensity arc lamps results from exposure of the eye and skin to ultraviolet radiation. Occasionally, the chorioretinal burns are of concern. The eye is generally more susceptible than the skin to injury from high intensity optical radiation sources whether ultraviolet, visible or infrared. Recent developments in technology have shown that some high intensity optical radiation sources which have output parameters greatly different from those encountered in the natural environment present a serious chorioretinal burn hazard.

  12. Arc Heater Capability Upgrade at AEDC

    DTIC Science & Technology

    2010-01-01

    pressure flow for expansion through a hypersonic nozzle into a subatmospheric test cell to provide flows at Mach numbers ranging from 3.4 to 7.0. The...H2 arc-heated wind tunnel specifications. Facility type Subatmospheric free-jet exhaust Max. run time Up to 30 min Nozzle Mach number 3.4–7.0 Nozzle...ground simulation testing of thermal protection systems, antenna transmission windows, hypersonic leading edges, and missile fore- bodies and nose tips

  13. Method for controlling gas metal arc welding

    DOEpatents

    Smartt, Herschel B.; Einerson, Carolyn J.; Watkins, Arthur D.

    1989-01-01

    The heat input and mass input in a Gas Metal Arc welding process are controlled by a method that comprises calculating appropriate values for weld speed, filler wire feed rate and an expected value for the welding current by algorithmic function means, applying such values for weld speed and filler wire feed rate to the welding process, measuring the welding current, comparing the measured current to the calculated current, using said comparison to calculate corrections for the weld speed and filler wire feed rate, and applying corrections.

  14. Plasma Arc Welding: How it Works

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur

    2004-01-01

    The physical principles of PAW from basic arcs to keyholing to variable polarity are outlined. A very brief account of the physics of PAW with an eye to the needs of a welder is presented. Understanding is usually (but not always) superior to handbooks and is required (unless dumb luck intervenes) for innovation. And, in any case, all welders by nature desire to know. A bit of history of the rise and fall of the Variable Polarity (VP) PA process in fabrication of the Space Shuttle External Tank is included.

  15. Sensing the gas metal arc welding process

    NASA Technical Reports Server (NTRS)

    Carlson, N. M.; Johnson, J. A.; Smartt, H. B.; Watkins, A. D.; Larsen, E. D.; Taylor, P. L.; Waddoups, M. A.

    1994-01-01

    Control of gas metal arc welding (GMAW) requires real-time sensing of the process. Three sensing techniques for GMAW are being developed at the Idaho National Engineering Laboratory (INEL). These are (1) noncontacting ultrasonic sensing using a laser/EMAT (electromagnetic acoustic transducer) to detect defects in the solidified weld on a pass-by-pass basis, (2) integrated optical sensing using a CCD camera and a laser stripe to obtain cooling rate and weld bead geometry information, and (3) monitoring fluctuations in digitized welding voltage data to detect the mode of metal droplet transfer and assure that the desired mass input is achieved.

  16. The ATLAS ARC backend to HPC

    NASA Astrophysics Data System (ADS)

    Haug, S.; Hostettler, M.; Sciacca, F. G.; Weber, M.

    2015-12-01

    The current distributed computing resources used for simulating and processing collision data collected by ATLAS and the other LHC experiments are largely based on dedicated x86 Linux clusters. Access to resources, job control and software provisioning mechanisms are quite different from the common concept of self-contained HPC applications run by particular users on specific HPC systems. We report on the development and the usage in ATLAS of a SSH backend to the Advanced Resource Connector (ARC) middleware to enable HPC compliant access and on the corresponding software provisioning mechanisms.

  17. Sensing the gas metal arc welding process

    SciTech Connect

    Carlson, N.M.; Johnson, J.A.; Smartt, H.B.; Watkins, A.D.; Larsen, E.D.; Taylor, P.L. ); Waddoups, M.A. )

    1992-01-01

    Control of gas metal arc welding (GMAW) requires real-time sensing of the process. Three sensing techniques for GMAW are being developed at the Idaho National Engineering Laboratory (INEL). These are (1) noncontacting ultrasonic sensing using a laser/EMAT (electromagnetic acoustic transducer) to detect defects in the solidified weld on a pass-bypass basis, (2) integrated optical sensing using a CCD camera and a laser stripe to obtain cooling rate and weld bead geometry information, and (3) monitoring fluctuations in digitized welding voltage data to detect the mode of metal droplet transfer and assure that the desired mass input is achieved.

  18. Sensing the gas metal arc welding process

    SciTech Connect

    Carlson, N.M.; Johnson, J.A.; Smartt, H.B.; Watkins, A.D.; Larsen, E.D.; Taylor, P.L.; Waddoups, M.A.

    1992-10-01

    Control of gas metal arc welding (GMAW) requires real-time sensing of the process. Three sensing techniques for GMAW are being developed at the Idaho National Engineering Laboratory (INEL). These are (1) noncontacting ultrasonic sensing using a laser/EMAT (electromagnetic acoustic transducer) to detect defects in the solidified weld on a pass-bypass basis, (2) integrated optical sensing using a CCD camera and a laser stripe to obtain cooling rate and weld bead geometry information, and (3) monitoring fluctuations in digitized welding voltage data to detect the mode of metal droplet transfer and assure that the desired mass input is achieved.

  19. ArcView Coal Evaluation User's Guide

    USGS Publications Warehouse

    Watson, William

    2007-01-01

    Purpose: The objective of the ArcView Coal Evaluation (ACE) is to estimate the amount and location of coal available to be mined by various coal mining technologies, based on the geologic coverages developed in the National Coal Resource Assessment (NCRA) which are the starting coverages used in the Geographic Information Systems (GIS) evaluation of coal resources. The ACE Users Guide provides many examples of how to apply technical limits based upon mining technology. The methods, which are iterative for any given mining technology, should transfer directly by mining technology to other coal beds.

  20. Method for controlling gas metal arc welding

    DOEpatents

    Smartt, H.B.; Einerson, C.J.; Watkins, A.D.

    1987-08-10

    The heat input and mass input in a Gas Metal Arc welding process are controlled by a method that comprises calculating appropriate values for weld speed, filler wire feed rate and an expected value for the welding current by algorithmic function means, applying such values for weld speed and filler wire feed rate to the welding process, measuring the welding current, comparing the measured current to the calculated current, using said comparison to calculate corrections for the weld speed and filler wire feed rate, and applying corrections. 3 figs., 1 tab.