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Sample records for active deflagration front

  1. Properties of Deflagration Fronts and Models for Type IA Supernovae

    NASA Astrophysics Data System (ADS)

    Domínguez, I.; Höflich, P.

    2000-01-01

    Detailed models of the explosion of a white dwarf that include self-consistent calculations of the light curve and spectra provide a link between observational quantities and the underlying explosion model. These calculations assume spherical geometry and are based on parameterized descriptions of the burning front. Recently, the first multidimensional calculations for nuclear burning fronts have been performed. Although a fully consistent treatment of the burning fronts is beyond the current state of the art, these calculations provide a new and better understanding of the physics. Several new descriptions for flame propagation have been proposed by Khokhlov et al. and Niemeyer et al. Using various descriptions for the propagation of a nuclear deflagration front, we have studied the influence on the results of previous analyses of Type Ia supernovae, namely, the nucleosynthesis and structure of the expanding envelope. Our calculations are based on a set of delayed detonation models with parameters that give a good account of the optical and infrared light curves and of the spectral evolution. In this scenario, the burning front first propagates in a deflagration mode and subsequently turns into a detonation. The explosions and light curves are calculated using a one-dimensional Lagrangian radiation-hydro code including a detailed nuclear network. We find that the results of the explosion are rather insensitive to details of the description of the deflagration front, even if its speed and the time from the transition to detonation differ almost by a factor of 2. For a given white dwarf (WD) and a fixed transition density, the total production of elements changes by less than 10%, and the distribution in the velocity space changes by less than 7%. Qualitatively, this insensitivity of the final outcome of the explosion to the details of the flame propagation during the (slow) deflagration phase can be understood as follows: for plausible variations in the speed of

  2. Bubble velocity in the nonlinear Rayleigh-Taylor instability at a deflagration front

    SciTech Connect

    Modestov, Mikhail; Bychkov, Vitaly; Betti, Riccardo; Eriksson, Lars-Erik

    2008-04-15

    The Rayleigh-Taylor instability at a deflagration front is studied systematically using extensive direct numerical simulations. It is shown that, for a sufficiently large gravitational field, the effects of bubble rising dominate the deflagration dynamics. It is demonstrated both analytically and numerically that the deflagration speed is described asymptotically by the Layzer theory in the limit of large acceleration. In the opposite limit of small and zero gravitational field, intrinsic properties of the deflagration front become important. In that case, the deflagration speed is determined by the velocity of a planar front and by the Darrieus-Landau instability. Because of these effects, the deflagration speed is larger than predicted by the Layzer theory. An analytical formula for the deflagration speed is suggested, which matches two asymptotic limits of large and small acceleration. The formula is in good agreement with the numerical data in a wide range of Froude numbers. The present results are also in agreement with previous numerical simulations on this problem.

  3. Counterpart of the Darrieus-Landau instability at a magnetic deflagration front

    NASA Astrophysics Data System (ADS)

    Jukimenko, O.; Modestov, M.; Dion, C. M.; Marklund, M.; Bychkov, V.

    2016-04-01

    The magnetic instability at the front of the spin avalanche in a crystal of molecular magnets is considered. This phenomenon reveals similar features with the Darrieus-Landau instability, inherent to classical combustion flame fronts. The instability growth rate and the cutoff wavelength are investigated with respect to the strength of the external magnetic field, both analytically in the limit of an infinitely thin front and numerically for finite-width fronts. The presence of quantum tunneling resonances is shown to increase the growth rate significantly, which may lead to a possible transition from deflagration to detonation regimes. Different orientations of the crystal easy axis are shown to exhibit opposite stability properties. In addition, we suggest experimental conditions that could evidence the instability and its influence on the magnetic deflagration velocity.

  4. Fast and slow magnetic deflagration fronts in type I X-ray bursts

    NASA Astrophysics Data System (ADS)

    Cavecchi, Yuri; Levin, Yuri; Watts, Anna L.; Braithwaite, Jonathan

    2016-06-01

    Type I X-ray bursts are produced by thermonuclear runaways that develop on accreting neutron stars. Once one location ignites, the flame propagates across the surface of the star. Flame propagation is fundamental in order to understand burst properties like rise time and burst oscillations. Previous work quantified the effects of rotation on the front, showing that the flame propagates as a deflagration and that the front strongly resembles a hurricane. However, the effect of magnetic fields was not investigated, despite the fact that magnetic fields strong enough to have an effect on the propagating flame are expected to be present on many bursters. In this paper, we show how the coupling between fluid layers introduced by an initially vertical magnetic field plays a decisive role in determining the character of the fronts that are responsible for the type I bursts. In particular, on a star spinning at 450 Hz (typical among the bursters), we test seed magnetic fields of 107-1010 G and find that for the medium fields the magnetic stresses that develop during the burst can speed up the velocity of the burning front, bringing the simulated burst rise time close to the observed values. By contrast, in a magnetic slow rotator like IGR J17480-2446, spinning at 11 Hz, a seed field ≳109 G is required to allow localized ignition and the magnetic field plays an integral role in generating the burst oscillations observed during the bursts.

  5. Deflagration Wave Profiles

    SciTech Connect

    Menikoff, Ralph

    2012-04-03

    Shock initiation in a plastic-bonded explosives (PBX) is due to hot spots. Current reactive burn models are based, at least heuristically, on the ignition and growth concept. The ignition phase occurs when a small localized region of high temperature (or hot spot) burns on a fast time scale. This is followed by a growth phase in which a reactive front spreads out from the hot spot. Propagating reactive fronts are deflagration waves. A key question is the deflagration speed in a PBX compressed and heated by a shock wave that generated the hot spot. Here, the ODEs for a steady deflagration wave profile in a compressible fluid are derived, along with the needed thermodynamic quantities of realistic equations of state corresponding to the reactants and products of a PBX. The properties of the wave profile equations are analyzed and an algorithm is derived for computing the deflagration speed. As an illustrative example, the algorithm is applied to compute the deflagration speed in shock compressed PBX 9501 as a function of shock pressure. The calculated deflagration speed, even at the CJ pressure, is low compared to the detonation speed. The implication of this are briefly discussed.

  6. Active learning of Pareto fronts.

    PubMed

    Campigotto, Paolo; Passerini, Andrea; Battiti, Roberto

    2014-03-01

    This paper introduces the active learning of Pareto fronts (ALP) algorithm, a novel approach to recover the Pareto front of a multiobjective optimization problem. ALP casts the identification of the Pareto front into a supervised machine learning task. This approach enables an analytical model of the Pareto front to be built. The computational effort in generating the supervised information is reduced by an active learning strategy. In particular, the model is learned from a set of informative training objective vectors. The training objective vectors are approximated Pareto-optimal vectors obtained by solving different scalarized problem instances. The experimental results show that ALP achieves an accurate Pareto front approximation with a lower computational effort than state-of-the-art estimation of distribution algorithms and widely known genetic techniques.

  7. On the thermal conductivity due to collisions between relativistic degenerate electrons. [for stellar opacity calculations and propagation of deflagration fronts of compact stellar remnants

    NASA Technical Reports Server (NTRS)

    Timmes, F. X.

    1992-01-01

    A numerical integration is undertaken of the integral expression for the thermal conductivity due to collisions of relativistic degenerate electrons and compared to the limiting-case analytic formula. The integration is designed to encompass all temperature/electron-plasma-frequency temperature ratios between the melting temperature and the Fermi temperature. High accuracy fits are demonstrated by interpolating the values of the integrals of the function and by using an asymptotic function by Urpin and Yakovlev (1980). The numerically integrated expression compares favorably to the limiting-case analytic asymptotic formula by Urpin and Yakovlev, and the results are valid for temperatures above and below the electron-plasma-frequency temperature. The present techniques can be used in stellar opacity calculations and in the study of the propagation of deflagration fronts of compact stellar remnants.

  8. Experiments on hydrogen deflagration

    NASA Astrophysics Data System (ADS)

    Sato, Y.; Iwabuchi, H.; Groethe, M.; Merilo, E.; Chiba, S.

    Deflagrations of hydrogen mixed with air have been studied in an open space and inside a shock tube to provide fundamental data needed for safety evaluations and validation of computer models. The open space tests were performed in 5.2- and 37-m 3 rectangular tents and in a 300-m 3 hemispherical tent that were filled with quiescent, homogenous mixtures ranging from 15 to 57% hydrogen by volume. The mixture was contained by a very thin plastic membrane that was cut just prior to igniting the mixture with a spark at the bottom center to prevent confinement of the mass flow. The information collected included flame front propagation monitored with ionization probes, the pressure-time histories of the resulting blast, and radiated heat obtained from thermal flux sensors. In these experiments the following results were obtained. (i) Deflagration of 30% hydrogen generated a much higher overpressure than deflagration of 9.5% natural gas. (ii) The flame propagation velocity and generated pressure were remarkably influenced by the hydrogen concentration. (iii) Turbulence caused by obstacles within the gas mixture and increasing the gas mixture volume increased the speed of the flame propagation and the overpressure. (iv) The combustion inside a tube also showed a high-speed deflagration. These results are useful to re-examine the existing codes and standards.

  9. EDC-37 Deflagration Rates at Elevated Pressures

    SciTech Connect

    Maienschein, J L; Koerner, J G

    2008-01-31

    We report deflagration rates on EDC-37 at high pressures. Experiments are conducted using the Lawrence Livermore National Laboratory High Pressure Strand Burner (HPSB) apparatus. The HPSB contains a deflagrating sample in a small volume, high pressure chamber. The sample consists of nine, 6.35 mm diameter, 6.35 mm length cylinders stacked on end, with burn wires placed between cylinders. Sample deflagration is limited to the cross-sectional surface of the cylinder by coating the cylindrical surface of the tower with Halthane 88-2 epoxy. Sample deflagration is initiated on one end of the tower by a B/KNO{sub 3} and HNS igniter train. Simultaneous temporal pressure history and burn front time of arrival measurements yield the laminar deflagration rate for a range of pressures and provide insight into deflagration uniformity. These measurements are one indicator of overall thermal explosion violence. Specific details of the experiment and the apparatus can be found in the literature.

  10. LX-17 Deflagration at High Pressures and Temperatures

    SciTech Connect

    Koerner, J; Maienschein, J; Black, K; DeHaven, M; Wardell, J

    2006-10-23

    We measure the laminar deflagration rate of LX-17 (92.5 wt% TATB, 7.5 wt% Kel-F 800) at high pressure and temperature in a strand burner, thereby obtaining reaction rate data for prediction of thermal explosion violence. Simultaneous measurements of flame front time-of-arrival and temporal pressure history allow for the direct calculation of deflagration rate as a function of pressure. Additionally, deflagrating surface areas are calculated in order to provide quantitative insight into the dynamic surface structure during deflagration and its relationship to explosion violence. Deflagration rate data show that LX-17 burns in a smooth fashion at ambient temperature and is represented by the burn rate equation B = 0.2P{sup 0.9}. At 225 C, deflagration is more rapid and erratic. Dynamic deflagrating surface area calculations show that ambient temperature LX-17 deflagrating surface areas remain near unity over the pressure range studied.

  11. Deflagration to detonation transition in combustible gas mixtures

    SciTech Connect

    Smirnov, N.N.; Panfilov, I.I.

    1995-04-01

    This paper presents the results of a computational investigation of the process of deflagration to detonation transition in a combustible gas mixture. The type of combustion (i.e., deflagration or detonation) supported by a two-step reaction scheme is studied as a function of the activation energies. It is shown that both a deflagration to detonation transition and a deflagration wave that lags behind a leading shock are possible. Two types of deflagration to detonation transitions are found theoretically: initiation of detonation from the flame zone and initiation of detonation along a contact discontinuity in the compressed gas near the primary shock wave.

  12. Deflagration plasma thruster

    NASA Technical Reports Server (NTRS)

    Cheng, D. Y.; Chang, C. N.

    1984-01-01

    This paper introduces the application of the magnetized plasma deflagration process to space propulsion. The deflagration process has the unique capability of efficiently converting input energy into kinetic energy in the accelerating direction. To illustrate the totally divergent characters of 'snowplow' detonation and deflagration discharges, examples of the differences between deflagration and detonation 'snowplow' discharges are expressed in terms of current densities, temperature, and particle velocities. Magnetic field profiles of the deflagration mode of discharges are measured. Typical attainable plasma characteristics are described in terms of velocity, electron temperature, and density, as well as measurement techniques. Specific impulses measured by piezo-electric probe and pendulum methods are presented. The influence of the transmission line in the discharge circuits on plasma velocity is measured by means of a microwave time-of-flight method. The results for the deflagration thruster are compared with other space thrusters. Further research areas are identified.

  13. Deflagration Behavior of PBX 9501 at Elevated Temperature and Pressure

    SciTech Connect

    Maienschein, J L; Koerner, J G

    2008-04-15

    We report the deflagration behavior of PBX 9501 at pressures up to 300 MPa and temperatures of 150-180 C where the sample has been held at the test temperature for several hours before ignition. The purpose is to determine the effect on the deflagration behavior of material damage caused by prolonged exposure to high temperature. This conditioning is similar to that experienced by an explosive while it being heated to eventual explosion. The results are made more complicated by the presence of a significant thermal gradient along the sample during the temperature ramp and soak. Three major conclusions are: the presence of nitroplasticizer makes PBX 9501 more thermally sensitive than LX-04 with an inert Viton binder; the deflagration behavior of PBX 9501 is more extreme and more inconsistent than that of LX-04; and something in PBX 9501 causes thermal damage to 'heal' as the deflagration proceeds, resulting in a decelerating deflagration front as it travels along the sample.

  14. Modelling propagation of deflagration waves out of hot spots

    NASA Astrophysics Data System (ADS)

    Partom, Yehuda

    2015-06-01

    It is widely accepted that shock initiation and detonation of heterogeneous explosives come about by a two-step process known as ignition and growth. In the first step a shock sweeping an explosive cell (control volume) creates hot spots that become ignition sites. In the second step deflagration waves (or burn waves) propagate out of those hot spots and transform the reactant in the cell into reaction products. The macroscopic (or average) reaction rate of the reactant in a cell depends on the speed of those deflagration waves and on the average distance between neighbouring hot spots. Here we simulate the propagation of deflagration waves out of hot spots on the mesoscale in axial symmetry using a 2D hydrocode, to which we add heat conduction and bulk reaction. The propagation speed of the deflagration wave depends on both pressure and temperature, where pressure dependence is dominant at low shock level, and temperature dependence is dominant at a higher shock level. From the simulation we obtain deflagration (or burn) fronts emanating out of the hot spots. For intermediate shock levels the deflagration waves consume the explosive between hot spots. For higher shock levels the deflagration waves strengthen to become detonation waves on the mesoscale. From the simulation results we extract average deflagration wave speeds and show how they depend on reaction rate and on other material parameters.

  15. Experiments on Magnetic Deflagration

    NASA Astrophysics Data System (ADS)

    Tejada, Javier

    2011-03-01

    Magnetic deflagration was first observed in molecular magnets [1,2] and then in glassy magnetic materials like manganites [3,4] and intermetallic systems like Gd 5 Ge 4. The role of the chemical energy is played by the magnetic energy of the material. In the case of a molecular magnet, this is Zeeman energy, while in manganites and Gd 5 Ge 4 the free energy is a combination of the Zeeman energy and the energy of the metastable magnetic phase. In molecular magnets both the ignition process and the speed of the flame are assisted by quantum spin reversal. There also exists some evidence of the transition from deflagration to detonation. Various experimental techniques have been used to detect the speed of the magnetic flame. They include SQUID magnetometry, Hall bars and coils. Magnetic deflagration has been ignited by local heating, application of external fields, by surface acoustic waves and microwaves. High frequency EPR measurements of the population of spin levels permitted observation of magnetic deflagration in real time. The talk will review these experiments and their interpretation.

  16. Quantum magnetic deflagration in acetate.

    PubMed

    Hernández-Mínguez, A; Hernandez, J M; Macià, F; García-Santiago, A; Tejada, J; Santos, P V

    2005-11-18

    We report controlled ignition of magnetization reversal avalanches by surface acoustic waves in a single crystal of acetate. Our data show that the speed of the avalanche exhibits maxima on the magnetic field at the tunneling resonances of Mn(12). Combined with the evidence of magnetic deflagration in Mn(12) acetate, this suggests a novel physical phenomenon: deflagration assisted by quantum tunneling. PMID:16384178

  17. Quantum magnetic deflagration in acetate.

    PubMed

    Hernández-Mínguez, A; Hernandez, J M; Macià, F; García-Santiago, A; Tejada, J; Santos, P V

    2005-11-18

    We report controlled ignition of magnetization reversal avalanches by surface acoustic waves in a single crystal of acetate. Our data show that the speed of the avalanche exhibits maxima on the magnetic field at the tunneling resonances of Mn(12). Combined with the evidence of magnetic deflagration in Mn(12) acetate, this suggests a novel physical phenomenon: deflagration assisted by quantum tunneling.

  18. Time-resolved Measurements of Spontaneous Magnetic Deflagration of Mn12 tBuAc

    NASA Astrophysics Data System (ADS)

    Chen, Yizhang; Kent, A. D.; Zhang, Qing; Sarachik, M. P.; Baker, M. L.; Garanin, D. A.; Mhesn, Najah; Lampropoulos, Christos

    Magnetic deflagration in molecular magnets has been triggered by heat pulses and acoustic waves. In this work we report spontaneous magnetic deflagration (i.e. deflagration that occurs without an external trigger) in the axially symmetric single molecule magnet Mn12 tBuAc . Magnetic hysteresis measurements show steps due to resonant quantum tunneling (RQT) below 1K, confirming the spin-Hamiltonian parameters for this material and previous results. Deflagration speeds measured with a newly constructed higher bandwidth (2MHz) setup will be presented as a function of transverse and longitudinal fields Hx ⊗Hz both on and off resonance. A large increase in front velocity near RQT steps is observed in experiments with swept transverse fields and will be discussed in light of models of deflagration. Work supported by NSF-DMR-1309202 (NYU); ARO W911NF-13-1-0125 (CCNY); DMR-1161571(Lehman); Cottrell College Science Award (UNF).

  19. Propagation of avalanches in Mn12-acetate: magnetic deflagration.

    PubMed

    Suzuki, Yoko; Sarachik, M P; Chudnovsky, E M; McHugh, S; Gonzalez-Rubio, R; Avraham, Nurit; Myasoedov, Y; Zeldov, E; Shtrikman, H; Chakov, N E; Christou, G

    2005-09-30

    Local time-resolved measurements of fast reversal of the magnetization of single crystals of Mn12-acetate indicate that the magnetization avalanche spreads as a narrow interface that propagates through the crystal at a constant velocity that is roughly 2 orders of magnitude smaller than the speed of sound. We argue that this phenomenon is closely analogous to the propagation of a flame front (deflagration) through a flammable chemical substance. PMID:16241690

  20. Propagation of avalanches in Mn12-acetate: magnetic deflagration.

    PubMed

    Suzuki, Yoko; Sarachik, M P; Chudnovsky, E M; McHugh, S; Gonzalez-Rubio, R; Avraham, Nurit; Myasoedov, Y; Zeldov, E; Shtrikman, H; Chakov, N E; Christou, G

    2005-09-30

    Local time-resolved measurements of fast reversal of the magnetization of single crystals of Mn12-acetate indicate that the magnetization avalanche spreads as a narrow interface that propagates through the crystal at a constant velocity that is roughly 2 orders of magnitude smaller than the speed of sound. We argue that this phenomenon is closely analogous to the propagation of a flame front (deflagration) through a flammable chemical substance.

  1. Quantum ignition of deflagration in the Fe8 molecular magnet

    NASA Astrophysics Data System (ADS)

    Leviant, Tom; Keren, Amit; Zeldov, Eli; Myasoedov, Yuri

    2014-10-01

    We report spatially resolved, time-dependent, magnetization reversal measurements of an Fe8 single molecular magnet using a microscopic Hall bar array. We found that a deflagration process, where molecules reverse their spin direction along a moving front, can be ignited quantum mechanically (T →0) at a resonance field, with no phonon pulse. The avalanche front velocity is of the order of 1m/s and is sensitive to field gradients and sweep rates. We also measured the thermal diffusivity κ in Fe8. This allows us to estimate the "flame" temperature.

  2. Deflagration Behavior of HMX-Based Explosives at High Temperatures and Pressures

    SciTech Connect

    Maienschein, J L; Wardell, J F

    2003-11-20

    We report the deflagration behavior of several HMX-based explosives at pressure from 10-600 MPa and temperatures from 20-180 C. We have made laminar burn rate measurements with the LLNL High Pressure Strand Burner, in which burn wires are used to record the time-of-arrival of the burn front in the cylindrical sample as a function of pressure. The explosive samples are 6.4 mm in diameter and 63 mm long, with ten burn wires embedded at different positions in the sample. Burning on the cylindrical surface is inhibited with an epoxy layer. With this direct measurement we do not have to account for product gas equation of state or heat losses in the system, and the burn wires allow detection of irregular burning. We find that formulation details are very important to overall deflagration behavior - the presence of 10% or less by weight of binder leads to physical deconsolidation and rapid deflagration at high pressures, and a larger particle size distribution leads to slower deflagration. High temperatures have a relatively minor effect on the deflagration rate until the beta-to-delta phase transition temperature is reached, beyond which the deflagration rate increases approximately 40-fold.

  3. The Role of Binder in Deflagrating HMX-based Explosives

    NASA Astrophysics Data System (ADS)

    Tringe, J. W.; Levie, H. W.; Glascoe, E. A.; Greenwood, D. W.; de Haven, M. R.; Molitoris, J. D.; Springer, H. K.

    2011-06-01

    Deflagration rates are known to be a strong function of temperature and pressure, but chemical reactions facilitated by the explosive's binder can also play an important role. Here we report a study of two HMX-based formulations, PBX-9501 (HMX 95%, estane 2.5%, bdnpa 1.25%, and bdnpf 1.25%) and LX-10 (HMX 95%, Viton-A 5%), which we use to investigate the origins of violence in thermal explosions. We employ flash x-ray radiography to directly image the rates at which reaction fronts proceed in a confined vessel. Photonic Doppler velocimetry (PDV) characterizes the vessel wall motion as a function of time. Our results show that thermal explosions of PBX-9501, with its more reactive binder, are more violent than explosions of LX-10. In LX-10, we observe quenched deflagration and limited violence. In PBX-9501, however, a higher deflagration rate is developed and sustained even after vessel rupture. Thermal explosions of initially-confined PBX-9501 therefore are more complete and significantly more violent. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  4. Gravitational waves from deflagration bubbles in first-order phase transitions

    SciTech Connect

    Megevand, Ariel

    2008-10-15

    The walls of bubbles in a first-order phase transition can propagate either as detonations, with a velocity larger than the speed of sound, or deflagrations, which are subsonic. We calculate the gravitational radiation that is produced by turbulence during a phase transition which develops via deflagration bubbles. We take into account the fact that a deflagration wall is preceded by a shock front which distributes the latent heat throughout space and influences other bubbles. We show that turbulence can induce peak values of {omega}{sub GW} as high as {approx}10{sup -9}. We discuss the possibility of detecting at LISA (Laser Interferometer Space Antennae) gravitational waves produced in the electroweak phase transition with wall velocities v{sub w} < or approx. 10{sup -1}, which favor electroweak baryogenesis.

  5. Benchmarking Of Improved DPAC Transient Deflagration Analysis Code

    SciTech Connect

    Laurinat, James E.; Hensel, Steve J.

    2013-03-21

    The transient deflagration code DPAC (Deflagration Pressure Analysis Code) has been upgraded for use in modeling hydrogen deflagration transients. The upgraded code is benchmarked using data from vented hydrogen deflagration tests conducted at the HYDRO-SC Test Facility at the University of Pisa. DPAC originally was written to calculate peak deflagration pressures for deflagrations in radioactive waste storage tanks and process facilities at the Savannah River Site. Upgrades include the addition of a laminar flame speed correlation for hydrogen deflagrations and a mechanistic model for turbulent flame propagation, incorporation of inertial effects during venting, and inclusion of the effect of water vapor condensation on vessel walls. In addition, DPAC has been coupled with CEA, a NASA combustion chemistry code. The deflagration tests are modeled as end-to-end deflagrations. The improved DPAC code successfully predicts both the peak pressures during the deflagration tests and the times at which the pressure peaks.

  6. The Darrieus-Landau instability in fast deflagration and laser ablation

    SciTech Connect

    Bychkov, Vitaly; Modestov, Mikhail; Marklund, Mattias

    2008-03-15

    The problem of the Darrieus-Landau instability at a discontinuous deflagration front in a compressible flow is solved. Numerous previous attempts to solve this problem suffered from the deficit of boundary conditions. Here, the required additional boundary condition is derived rigorously taking into account the internal structure of the front. The derived condition implies a constant mass flux at the front; it reduces to the classical Darrieus-Landau condition in the limit of an incompressible flow. It is demonstrated that in general the solution to the problem depends on the type of energy source in the flow. In the common case of a strongly localized source, compression effects make the Darrieus-Landau instability considerably weaker. Particularly, the instability growth rate is reduced for laser ablation in comparison to the classical incompressible case. The instability disappears completely in the Chapman-Jouguet regime of ultimately fast deflagration.

  7. Observations and Modeling of the Component Mechanisms in Deflagration

    NASA Astrophysics Data System (ADS)

    Smilowitz, Laura; Henson, Bryan; Oschwald, David; Novak, Alan; Holmes, Matthew

    2013-06-01

    We have used dynamic x-ray and proton radiography to observe the behavior of a series of HMX based energetic materials formulations undergoing thermal explosions. The result of these observations is a mechanism for deflagration based on both gas phase convective burning and solid phase conductive burning. The velocities for both the convective and conductive burns are tied together by the single combustion pressure driving both in a single experiment. The convective rate is directly measured as the burn front in the radiographs. The pressure associated with that rate is inferred from independently measured burn rate verses pressure data. This same pressure is then assumed to drive the conductive burning which begins as the convective burn front lights the material surface. Using a single, independently validated particle size distribution for damaged HMX, the combination of pressure driven convective lighting and conductive consumption is then calculated and compared to the measured transmission data sets. This same model with different initial pressurizations is used to successfully model deflagration in PBX9501, PBXN-9, and LX-07. In addition, a correlation between initial pressurization, convective/conductive velocity, and final ``reaction violence'' is observed. This leads us to the use of convective velocity as a metric for final energy release rate and therefore overall reaction violence.

  8. The delayed-detonation model of a type Ia supernovae. 1: The deflagration phase

    NASA Technical Reports Server (NTRS)

    Arnett, David; Livne, Eli

    1994-01-01

    The nature of the 'delayed detonation' mechanism of Khokhlov for the explosion of Type Ia supernovae is investigated by using two-dimensional numerical hydrodynamics simulations. A new algorithm is used to treat the deflagration front. Assuming that it propagates locally at the laminar flame speed, the deflagration is insufficient to unbind the star. Expansion shuts of the flame; much of this small production of iron group nuclei occurs at lower densities, which reduces the electron-capture problem. The burning front does become wrinkled, but the wavelength of the instability is much larger than the computational grid size and is resolved; this is consistent with previous analysis. Because the degenerate star has an adiabatic exponent only slightly above 4/3, the energy released by deflagration drives a pulsation of large amplitude. During the first expansion phase, adiabatic cooling shuts off the burning, and a Rayleigh-Taylor instability then gives mixing of high-entropy ashes with low-entropy fuel. During the first contraction phase, compressional heating reignites the material. This paper deals with the deflagration phase, from the onset of burning, through expansion and quenching of the flame, to the first contraction.

  9. The deflagration-to-detonation transition in granular HMX

    SciTech Connect

    McAfee, J.M.; Asay, B.; Campbell, A.W.; Ramsay, J.B.

    1991-01-01

    The transition from deflagration to detonation in porous beds of explosive and propellant has received considerable attention both experimentally and theoretically. In many cases, the use of a hot-gas-producing igniter complicates the interpretation and subsequent modeling of experiments because considerable effort is required to account for the effect of the igniter gases on the granular bed. Hot-wire ignition is less intrusive; however, the ignition front is not planar. Thus the early events in these experiments cannot be approximated as one-dimensional. We have studied the deflagration-to-detonation behavior of granular HMX confined in steel tubes with x-radiography, light emission, stress gauges, and various pin techniques. Simplification and consistency of results were obtained by igniting the HMX with a piston (initially at rest and in contact with the HMX) driven into the bed. A gasless igniter is used to stare the burning of the piston propellant (low-density HMX) providing the piston with a smooth initial motion. Analysis of the data gives a detailed picture of the DDT process under these conditions. The qualitative and quantitative experimental results show the transition from the burning to detonation is discontinuous. The results are discussed in terms of a descriptive model.

  10. CFD simulation of hydrogen deflagration in a vented room

    NASA Astrophysics Data System (ADS)

    Tolias, I. C.; Venetsanos, A. G.; Markatos, N. C.; Kiranoudis, C. T.

    2015-09-01

    In the present work, CFD simulations of hydrogen deflagration in a real scale vented room are performed. Two ignition points were simulated: at the wall opposite to the vent (back ignition) and at the center of the chamber (center ignition). The overpressure time series and flame front velocities are compared with the experimental results. The combustion model is based on the turbulent flame speed concept. The turbulent flame speed is calculated based on a modification of Yakhot's equation, in order to account for all the main physical mechanisms which appear in hydrogen deflagrations. Special attention is given to the simulation of Rayleigh-Taylor instability. This instability occurs at the vent area and results in sudden explosion of the mixture that has been pushed outside the chamber at the initial stage of the explosion. The importance of this external explosion to the generated overpressures inside the chamber is highlighted. The agreement between experimental and computational results is satisfactory in both back ignition and center ignition cases.

  11. Mesoscale Modeling of Deflagration-Induced Deconsolidation in Polymer-Bonded Explosives

    NASA Astrophysics Data System (ADS)

    Springer, H. Keo; Reaugh, J. E.; Glascoe, E. A.; Kercher, J. R.; Friedman, G.

    2011-06-01

    Initially intact polymer-bonded explosives can transition from conductive burning to more violent convective burning via rapid deconsolidation at higher pressures. The pressure-dependent infiltration of cracks and pores, i.e., damage, by product gases at the burn-front is a key step in the transition to convective burning. However, the relative influence of pre-existing damage and deflagration-induced damage on the transition to convective burning is not well understood. The objective of this study is to investigate the role of explosive constituent properties, microstructure, and deflagration velocity on deconsolidation. We performed simulations using the multi-physics hydrocode, ALE3D. HMX was used as the model energetic grain. We used a JWL form for the unreacted and reacted equation-of-state of the HMX. Simplified strength and failure models were used for the HMX and the binder. The propensity for deconsolidation increased with increasing grain volume fraction, increasing porosity, decreasing binder strength, and increasing deflagration velocity. These studies are important because they enable the development of deflagration-induced damage models, as well as the design of inherently safer explosives. This work performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344. This work was funded by the Joint DoD/DOE Munitions Technology Development Program.

  12. Deflagrations and detonations in thermonuclear supernovae.

    PubMed

    Gamezo, Vadim N; Khokhlov, Alexei M; Oran, Elaine S

    2004-05-28

    We study a type Ia supernova explosion using three-dimensional numerical simulations based on reactive fluid dynamics. We consider a delayed-detonation model that assumes a deflagration-to-detonation transition. In contrast with the pure deflagration model, the delayed-detonation model releases enough energy to account for a healthy explosion, and does not leave carbon, oxygen, and intermediate-mass elements in central parts of a white dwarf. This removes the key disagreement between simulations and observations, and makes a delayed detonation the mostly likely mechanism for type Ia supernovae. PMID:15245271

  13. Deflagrations and detonations in thermonuclear supernovae.

    PubMed

    Gamezo, Vadim N; Khokhlov, Alexei M; Oran, Elaine S

    2004-05-28

    We study a type Ia supernova explosion using three-dimensional numerical simulations based on reactive fluid dynamics. We consider a delayed-detonation model that assumes a deflagration-to-detonation transition. In contrast with the pure deflagration model, the delayed-detonation model releases enough energy to account for a healthy explosion, and does not leave carbon, oxygen, and intermediate-mass elements in central parts of a white dwarf. This removes the key disagreement between simulations and observations, and makes a delayed detonation the mostly likely mechanism for type Ia supernovae.

  14. Critical deflagration waves leading to detonation onset under different boundary conditions

    NASA Astrophysics Data System (ADS)

    Lin, Wei; Zhou, Jin; Fan, Xiao-Hua; Lin, Zhi-Yong

    2015-01-01

    High-speed turbulent critical deflagration waves before detonation onset in H2-air mixture propagated into a square cross section channel, which was assembled of optional rigid rough, rigid smooth, or flexible walls. The corresponding propagation characteristic and the influence of the wall boundaries on the propagation were investigated via high-speed shadowgraph and a high-frequency pressure sampling system. As a comprehensive supplement to the different walls effect investigation, the effect of porous absorbing walls on the detonation propagation was also investigated via smoke foils and the high-frequency pressure sampling system. Results are as follows. In the critical deflagration stage, the leading shock and the closely following turbulent flame front travel at a speed of nearly half the CJ detonation velocity. In the preheated zone, a zonary flame arises from the overlapping part of the boundary layer and the pressure waves, and then merges into the mainstream flame. Among these wall boundary conditions, the rigid rough wall plays a most positive role in the formation of the zonary flame and thus accelerates the transition of the deflagration to detonation (DDT), which is due to the boost of the boundary layer growth and the pressure wave reflection. Even though the flexible wall is not conducive to the pressure wave reflection, it brings out a faster boundary layer growth, which plays a more significant role in the zonary flame formation. Additionally, the porous absorbing wall absorbs the transverse wave and yields detonation decay and velocity deficit. After the absorbing wall, below some low initial pressure conditions, no re-initiation occurs and the deflagration propagates in critical deflagration for a relatively long distance. Project supported by the National Natural Science Foundation of China (Grant No. 51206182).

  15. Different stages of flame acceleration from slow burning to Chapman-Jouguet deflagration.

    PubMed

    Valiev, Damir M; Bychkov, Vitaly; Akkerman, V'yacheslav; Eriksson, Lars-Erik

    2009-09-01

    Numerical simulations of spontaneous flame acceleration are performed within the problem of flame transition to detonation in two-dimensional channels. The acceleration is studied in the extremely wide range of flame front velocity changing by 3 orders of magnitude during the process. Flame accelerates from realistically small initial velocity (with Mach number about 10(-3)) to supersonic speed in the reference frame of the tube walls. It is shown that flame acceleration undergoes three distinctive stages: (1) initial exponential acceleration in the quasi-isobaric regime, (2) almost linear increase in the flame speed to supersonic values, and (3) saturation to a stationary high-speed deflagration velocity. The saturation velocity of deflagration may be correlated with the Chapman-Jouguet deflagration speed. The acceleration develops according to the Shelkin mechanism. Results on the exponential flame acceleration agree well with previous theoretical and numerical studies. The saturation velocity is in line with previous experimental results. Transition of flame acceleration regime from the exponential to the linear one, and then to the constant velocity, happens because of gas compression both ahead and behind the flame front. PMID:19905222

  16. Different stages of flame acceleration from slow burning to Chapman-Jouguet deflagration.

    PubMed

    Valiev, Damir M; Bychkov, Vitaly; Akkerman, V'yacheslav; Eriksson, Lars-Erik

    2009-09-01

    Numerical simulations of spontaneous flame acceleration are performed within the problem of flame transition to detonation in two-dimensional channels. The acceleration is studied in the extremely wide range of flame front velocity changing by 3 orders of magnitude during the process. Flame accelerates from realistically small initial velocity (with Mach number about 10(-3)) to supersonic speed in the reference frame of the tube walls. It is shown that flame acceleration undergoes three distinctive stages: (1) initial exponential acceleration in the quasi-isobaric regime, (2) almost linear increase in the flame speed to supersonic values, and (3) saturation to a stationary high-speed deflagration velocity. The saturation velocity of deflagration may be correlated with the Chapman-Jouguet deflagration speed. The acceleration develops according to the Shelkin mechanism. Results on the exponential flame acceleration agree well with previous theoretical and numerical studies. The saturation velocity is in line with previous experimental results. Transition of flame acceleration regime from the exponential to the linear one, and then to the constant velocity, happens because of gas compression both ahead and behind the flame front.

  17. A study of deflagration and detonation in multiphase hydrocarbon-air mixtures

    SciTech Connect

    Smirnov, N.N.; Tyurnikov, M.V. . Dept. of Mechanics and Mathematics)

    1994-01-01

    This article represents a theoretical and experimental study of the problems of deflagration and detonation structure in heterogeneous media, which contains an oxidant in the gaseous phase and fuel in the form of either dispersed droplets in the oxidant flow or a thin film on the chamber walls. Detonation in such systems is shown to have a complex unsteady-state structure: the detonation front can exhibit mobile discontinuities and can pulsate periodically. A physical model of pulsating and spin detonation in heterogeneous media is developed. A system of governing equations with boundary conditions is composed that makes it possible to simulate mathematically the transition of deflagration to detonation. The transition process and the initiation of detonation are calculated numerically and studied experimentally. The comparison shows good agreement of theoretical and experimental results.

  18. Investigations on deflagration to detonation transition in porous energetic materials. Final report

    SciTech Connect

    Stewart, D.S.

    1999-07-01

    The research carried out by this contract was part of a larger effort funded by LANL in the areas of deflagration to detonation in porous energetic materials (DDT) and detonation shock dynamics in high explosives (DSD). In the first three years of the contract the major focus was on DDT. However, some researchers were carried out on DSD theory and numerical implementation. In the last two years the principal focus of the contract was on DSD theory and numerical implementation. However, during the second period some work was also carried out on DDT. The paper discusses DDT modeling and DSD modeling. Abstracts are included on the following topics: modeling deflagration to detonation; DSD theory; DSD wave front tracking; and DSD program burn implementation.

  19. Front Range Infrastructure Resources Project: water-resources activities

    USGS Publications Warehouse

    Robson, Stanley G.; Heiny, Janet S.

    1998-01-01

    Infrastructure, such as roads, buildings, airports, and dams, is built and maintained by use of large quantities of natural resources such as aggregate (sand and gravel), energy, and water. As urban area expand, local sources of these resource are becoming inaccessible (gravel cannot be mined from under a subdivision, for example), or the cost of recovery of the resource becomes prohibitive (oil and gas drilling in urban areas is costly), or the resources may become unfit for some use (pollution of ground water may preclude its use as a water supply). Governmental land-use decision and environmental mandates can further preclude development of natural resources. If infrastructure resources are to remain economically available. current resource information must be available for use in well-reasoned decisions bout future land use. Ground water is an infrastructure resource that is present in shallow aquifers and deeper bedrock aquifers that underlie much of the 2,450-square-mile demonstration area of the Colorado Front Range Infrastructure Resources Project. In 1996, mapping of the area's ground-water resources was undertaken as a U.S. Geological Survey project in cooperation with the Colorado Department of Natural Resources, Division of Water Resources, and the Colorado Water Conservation Board.

  20. The Impact of Oil and Natural Gas Activity on Ozone Formation in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Hornbrook, R. S.; Apel, E. C.; Hills, A. J.; Blake, D. R.; Blake, N. J.; Schroeder, J.; Fried, A.; Weibring, P.; Richter, D.; Walega, J.; Mauldin, L.; Cantrell, C. A.; Hall, S. R.; Ullmann, K.; Weinheimer, A. J.; Montzka, D.; Orlando, J. J.; Tyndall, G. S.; Campos, T. L.; Stell, M. H.; Heikes, B.; Treadaway, V.; O'Sullivan, D. W.; Huey, L. G.; Tanner, D.; Cohen, R. C.; Flocke, F. M.; Pfister, G.; Knote, C. J.; Emmons, L. K.

    2014-12-01

    The 2014 Front Range Air Pollution and Photochemistry Experiment (FRAPPE) was a ground-based and airborne field study designed to characterize and understand air quality in the Colorado Front Range, where National Ambient Air Quality Standards (NAAQS) ozone levels are frequently exceeded during summertime. A primary goal of the study was to determine the factors controlling surface ozone in the Front Range. As part of the project, measurements of many trace gases were observed on board the NSF/NCAR C-130 by a suite of instrumentation, including the NCAR Trace Organic Gas Analyzer (TOGA), which made measurements of a set of volatile organic compounds (VOCs). VOCs are crucial for characterizing emissions and photochemical processing in the Front Range, as well as the air transported into the region. During recent years, oil and natural gas (O&NG) activity in the Front Range has been growing rapidly. Ratios of observed aromatic hydrocarbons, butanes and pentanes demonstrate distinct fingerprinting that can be used to distinguish both between different types of O&NG activities and between O&NG extraction regions in the FRAPPE study region and beyond. Using the observed hydrocarbon data along with other trace gas observations, we will compare contributions of O&NG emissions to OH reactivities in different regions in the Front Range, and present box model results demonstrating the impact of O&NG activities on ozone formation.

  1. The Impact of Oil and Natural Gas Activity on Ozone Formation in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Hornbrook, R. S.; Apel, E. C.; Hills, A. J.; Blake, D. R.; Blake, N. J.; Schroeder, J.; Fried, A.; Weibring, P.; Richter, D.; Walega, J.; Mauldin, L.; Cantrell, C. A.; Hall, S. R.; Ullmann, K.; Weinheimer, A. J.; Montzka, D.; Orlando, J. J.; Tyndall, G. S.; Campos, T. L.; Stell, M. H.; Heikes, B.; Treadaway, V.; O'Sullivan, D. W.; Huey, L. G.; Tanner, D.; Cohen, R. C.; Flocke, F. M.; Pfister, G.; Knote, C. J.; Emmons, L. K.

    2015-12-01

    The 2014 Front Range Air Pollution and Photochemistry Experiment (FRAPPE) was a ground-based and airborne field study designed to characterize and understand air quality in the Colorado Front Range, where National Ambient Air Quality Standards (NAAQS) ozone levels are frequently exceeded during summertime. A primary goal of the study was to determine the factors controlling surface ozone in the Front Range. As part of the project, measurements of many trace gases were observed on board the NSF/NCAR C-130 by a suite of instrumentation, including the NCAR Trace Organic Gas Analyzer (TOGA), which made measurements of a set of volatile organic compounds (VOCs). VOCs are crucial for characterizing emissions and photochemical processing in the Front Range, as well as the air transported into the region. During recent years, oil and natural gas (O&NG) activity in the Front Range has been growing rapidly. Ratios of observed aromatic hydrocarbons, butanes and pentanes demonstrate distinct fingerprinting that can be used to distinguish both between different types of O&NG activities and between O&NG extraction regions in the FRAPPE study region and beyond. Using the observed hydrocarbon data along with other trace gas observations, we will compare contributions of O&NG emissions to OH reactivities in different regions in the Front Range, and present box model results demonstrating the impact of O&NG activities on ozone formation.

  2. Species and temperature profiles in ignition and deflagration of HMX

    SciTech Connect

    Parr, T.; Hanson-Parr, D.

    1987-01-01

    This paper reports on progress made in a program investigating the chemistry and kinetics of the ignition and combustion of solid propellants and their ingredients. Experiments were performed using imaging Planar Laser Induced Fluorescence (PLIF) to measure species and temperture profiles during CO/sub 2/ laser ignition and steady state deflagration of HMX. All experiments were done at one atmosphere. Time resolved PLIF images were obtained for NO/sub 2/, NO, CN, NH, H/sub 2/CO, OH, and OH rotational temperatures during ignition and deflagration of HMX. CN and NH form at reasonably large heights off the sample surface in gas phase ignition kernels at finite delays, and reform into relatively thin flame sheets which snap back towards the sample surface. NO/sub 2/ and NO are initial products during laser ignition, beginning to form at minimum delay times and producing tall plumes until ignition occurs in the gas phase. The NO/sub 2/ and NO PLIF signals are then confined to an expanding spherical shell plus a steady state solid core between the sample surface and the CN or NH flame sheet. Thus it appears that NO/sub 2/ and NO are early decomposition products which are consumed in a flame separated significantly from the surface. The CN and NH are produced in this flame as transient radicals. OH is produced at the same delay as CN and NH but extends very far beyond the thin CNNH flame front. OH rotational temperature profiles rise sharply at the CNNH flame sheet and level off at about 2772 degrees K beyond it. Evidence is given that the flames are two phase even for neat HMX. Little or no evidence for H/sub 2/CO was seen during ignition of HMX. Although large concentrations are seen during ignition of a nitramine composite propellant, this signal appears to be due to formaldehyde from decomposition of the PEG binder.

  3. Physical changes within a large tropical hydroelectric reservoir induced by wintertime cold front activity

    NASA Astrophysics Data System (ADS)

    Curtarelli, M. P.; Alcântara, E. H.; Rennó, C. D.; Stech, J. L.

    2014-08-01

    We investigated the influence of wintertime cold front activity on the physical processes within a large tropical reservoir located in Brazil. The period chosen for this study consisted of 49 days between 28 April 2010 and 15 July 2010. This period was defined based on information from the Brazilian Center for Weather Forecasting and Climate Studies (CPTEC), data collected in situ and the interpretation of remotely sensed images. To better understand the governing processes that drive changes in the heat balance, differential cooling and mixing dynamics, a simulation was performed that utilized a three-dimensional hydrodynamic model enforced with in situ and remote sensing data. The results showed that during a cold front passage over the reservoir, the sensible and latent heat fluxes were enhanced by approximately 77 and 16%, respectively. The reservoir's daily averaged heat loss was up to 167% higher on the days with cold front activity than on the days without activity. The cold front passage also intensified the differential cooling process; in some cases the difference between the water temperature of the littoral and pelagic zones reached up to 8 °C. The occurrence of cold front passages impacted the diurnal mixed layer (DML), by increasing the turbulent energy input (∼54%) and the DML depth (∼41%). Our results indicate that the cold front events are one of the main meteorological disturbances driving the physical processes within hydroelectric reservoirs located in tropical South America during the wintertime. Hence, cold front activity over these aquatic systems has several implications for water quality and reservoir management in Brazil.

  4. Deflagration transient study of the CIF incinerator

    SciTech Connect

    Hang, T.

    2000-01-03

    The Consolidated Incineration Facility (CIF) treats solid and liquid RCRA hazardous and mixed wastes generated at the Savannah River Site (SRS). The transient responses of the CIF system to a deflagration, caused by an accidental charge of a modest quantity of solvent (e.g. toluene) into the rotary kiln, were a major safety concern. Using a dynamic computer model, a study was conducted to analyze the transient system responses to the rapid temperature and pressure surge in the kiln. The objective of the study was to determined the maximum pressure, temperature, and gas flow rate in each CIF component (rotary kiln, secondary combustion chamber, quencher, scrubber/cyclone, mist eliminator, reheaters, HEPAs, and ID fans). The resulting data provided a basis for the subsequent structural analysis. This paper will describe the CIF deflagration study in some detail, and present the results of the simulation scenarios.

  5. Front motion and localized states in an asymmetric bistable activator-inhibitor system with saturation

    NASA Astrophysics Data System (ADS)

    Yochelis, Arik; Garfinkel, Alan

    2008-03-01

    We study the spatiotemporal properties of coherent states (peaks, holes, and fronts) in a bistable activator-inhibitor system that exhibits biochemical saturated autocatalysis, and in which fronts do not preserve spatial parity symmetry. Using the Gierer-Meinhardt prototype model, we find the conditions in which two distinct pinning regions are formed. The first pinning type is known in the context of variational systems while the second is structurally different due to the presence of a heteroclinic bifurcation between two uniform states. The bifurcation also separates the parameter regions of counterpropagating fronts, leading in turn to the growth or contraction of activator domains. These phenomena expand the range of pattern formation theory and its biomedical applications: activator domain retraction suggests potential therapeutic strategies for patterned pathologies, such as cardiovascular calcification.

  6. Low-frequency wave activity related to dipolarization fronts detected by MMS in the magnetotail

    NASA Astrophysics Data System (ADS)

    Le Contel, O.; Retino, A.; Breuillard, H.; Mirioni, L.; Roux, A.; Chust, T.; Chasapis, A.; Lavraud, B.; Lindqvist, P. A.; Khotyaintsev, Y. V.; Vaivads, A.; Fu, H.; Marklund, G. T.; Nakamura, R.; Burch, J. L.; Torbert, R. B.; Moore, T. E.; Ergun, R.; Goodrich, K.; Needell, J.; Chutter, M.; Rau, D.; Dors, I.; Russell, C. T.; Magnes, W.; Strangeway, R. J.; Le, G.; Bromund, K. R.; Plaschke, F.; Fischer, D.; Leinweber, H. K.; Anderson, B. J.; Argall, M. R.; Slavin, J. A.; Kepko, L.; Baumjohann, W.; Pollock, C. J.; Mauk, B.; Fuselier, S. A.

    2015-12-01

    Dipolarization fronts are often associated to reconnection jets in the magnetotail current sheet and are sites of important energy dissipation and particle energization. Since the launch on March 12th and until the 9th of July 2015, the MMS constellation has been moving from dawn to dusk in a string of pearls formation. Although particle instruments were rarely operating and only FIELDS instrument suite was often gathering data, the MMS spacecraft have detected numerous dipolarization fronts, in particular on May 15th. Since 9th of July, the MMS evolved into a tetrahedral configuration with an average inter-satellite distance of 160 km and was still able to detect dipolarization fronts in the dusk magnetotail. As the Larmor radius of thermal protons is about 500 km in this region and dipolarization fronts have a typical thickness of the order of the Larmor radius, such a separation allows us to investigate in detail the microphysics of dipolarization fronts. In this study, we focus in particular on low-frequency electromagnetic wave activity related to the fronts and discuss possible mechanisms of particle heating and acceleration both at large scales (string of pearls configuration) and at kinetic scales (tetrahedral configuration).

  7. Structure and Stability of Deflagrations in Porous Energetic Materials

    SciTech Connect

    stephen B. Margolis; Forman A. Williams

    1999-03-01

    Theoretical two-phase-flow analyses have recently been developed to describe the structure and stability of multi-phase deflagrations in porous energetic materials, in both confined and unconfined geometries. The results of these studies are reviewed, with an emphasis on the fundamental differences that emerge with respect to the two types of geometries. In particular, pressure gradients are usually negligible in unconfined systems, whereas the confined problem is generally characterized by a significant gas-phase pressure difference, or overpressure, between the burned and unburned regions. The latter leads to a strong convective influence on the burning rate arising from the pressure-driven permeation of hot gases into the solid/gas region and the consequent preheating of the unburned material. It is also shown how asymptotic models that are suitable for analyzing stability may be derived based on the largeness of an overall activation-energy parameter. From an analysis of such models, it is shown that the effects of porosity and two-phase flow are generally destabilizing, suggesting that degraded propellants, which exhibit greater porosity than their pristine counterparts, may be more readily subject to combustion instability and nonsteady deflagration.

  8. PBXN-9 Ignition Kinetics and Deflagration Rates

    SciTech Connect

    Glascoe, E; Maienschein, J; Burnham, A; Koerner, J; Hsu, P; Wemhoff, A

    2008-04-24

    The ignition kinetics and deflagration rates of PBXN-9 were measured using specially designed instruments at LLNL and compared with previous work on similar HMX based materials. Ignition kinetics were measured based on the One Dimensional Time-to-Explosion combined with ALE3D modeling. Results of these experiments indicate that PBXN-9 behaves much like other HMX based materials (i.e. LX-04, LX-07, LX-10 and PBX-9501) and the dominant factor in these experiments is the type of explosive, not the type of binder/plasticizer. In contrast, the deflagration behavior of PBXN-9 is quite different from similar high weight percent HMX based materials (i.e LX-10, LX-07 and PBX-9501). PBXN-9 burns in a laminar manner over the full pressure range studied (0-310 MPa) unlike LX-10, LX-07, and PBX-9501. The difference in deflagration behavior is attributed to the nature of the binder/plasticizer alone or in conjunction with the volume of binder present in PBXN-9.

  9. Deflagration Behavior of PBXN-109 and Composition B at High Pressures and Temperatures

    SciTech Connect

    Maienschein, J L; Wardell, J F

    2002-03-11

    We report deflagration rate measurements on PBXN-109 (RDWAVHTPB) and Composition B (RXDTTNThrvax) at pressures from 1,500-100,000 psi (10-700 MPa). This was done with the LLNL High Pressure Strand Burner, in which embedded wires are used to record the time-of-arrival of the burn front in the cylindrical sample as a function of pressure. The propellant samples are 6.4 mm in diameter and 6.4 mm long, with burn wires inserted between samples. Burning on the cylindrical surface is inhibited with an epoxy or polyurethane layer. With this direct measurement we do not have to account for product gas equation of state or heat losses in the system, and the burn wires allow detection of irregular burning. We report deflagration results for PBXN-109 as received, and also after it has been damaged by heating. The burn behavior of pristine PBXN-109 is very regular, and exhibits a reduction in pressure exponent from 1.32 to 0.85 at pressures above 20,000 psi (135 MPa). When PBXN-109 is thermally damaged by heating to 170-180 C, the deflagration rate is increased by more than a factor of 10. This appears to be a physical effect, as the faster burning may be explained by an increase in surface area. Our results with Composition B show an apparent 2nd order pressure dependence for initial deflagration, followed by deconsolidation and onset of very rapid and erratic burning. The deconsolidation may be the result of the TNT melting as heat flows into the sample.

  10. Pre-ignition confinement and deflagration violence in LX-10 and PBX 9501

    SciTech Connect

    Tringe, J. W. Glascoe, E. A.; McClelland, M. A.; Greenwood, D.; Chambers, R. D.; Springer, H. K.; Levie, H. W.

    2014-08-07

    In thermal explosions of the nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)-based explosives LX-10 and PBX-9501, the pre-ignition spatial and temporal heating profile defines the ignition location. The ignition location then determines the extent of inertial confinement and the violence of the resulting deflagration. In this work, we present results of experiments in which ∼23 g cylinders of LX-10 and PBX 9501 in thin-walled aluminum confinement vessels were subjected to identical heating profiles but which presented starkly different energy release signatures. Post-explosion LX-10 containment vessels were completely fragmented, while the PBX 9501 vessels were merely ruptured. Flash x-ray radiography images show that the initiation location for the LX-10 is a few mm farther from the end caps of the vessel relative to the initiation location of PBX 9501. This difference increases deflagration confinement for LX-10 at the time of ignition and extends the pressurization time during which the deflagration front propagates in the explosive. The variation in the initiation location, in turn, is determined by the thermal boundary conditions, which differ for these two explosives because of the larger coefficient of thermal expansion and greater thermal stability of the Viton binder in LX-10 relative to the estane and bis(2,2-dinitropropyl) acetal/formal binder of the PBX 9501. The thermal profile and initiation location were modeled for LX-10 using the hydrodynamics and structures code ALE3D; results indicate temperatures in the vicinity of the ignition location in excess of 274 °C near the time of ignition. The conductive burn rates for these two explosives, as determined by flash x-ray radiography, are comparable in the range 0.1–0.2 mm/μs, somewhat faster than rates observed by strand burner experiments for explosives in the temperature range 150–180 °C and pressures up to 100 MPa. The thinnest-wall aluminum containment vessels

  11. Pre-ignition confinement and deflagration violence in LX-10 and PBX 9501

    NASA Astrophysics Data System (ADS)

    Tringe, J. W.; Glascoe, E. A.; McClelland, M. A.; Greenwood, D.; Chambers, R. D.; Springer, H. K.; Levie, H. W.

    2014-08-01

    In thermal explosions of the nitramine octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)-based explosives LX-10 and PBX-9501, the pre-ignition spatial and temporal heating profile defines the ignition location. The ignition location then determines the extent of inertial confinement and the violence of the resulting deflagration. In this work, we present results of experiments in which ˜23 g cylinders of LX-10 and PBX 9501 in thin-walled aluminum confinement vessels were subjected to identical heating profiles but which presented starkly different energy release signatures. Post-explosion LX-10 containment vessels were completely fragmented, while the PBX 9501 vessels were merely ruptured. Flash x-ray radiography images show that the initiation location for the LX-10 is a few mm farther from the end caps of the vessel relative to the initiation location of PBX 9501. This difference increases deflagration confinement for LX-10 at the time of ignition and extends the pressurization time during which the deflagration front propagates in the explosive. The variation in the initiation location, in turn, is determined by the thermal boundary conditions, which differ for these two explosives because of the larger coefficient of thermal expansion and greater thermal stability of the Viton binder in LX-10 relative to the estane and bis(2,2-dinitropropyl) acetal/formal binder of the PBX 9501. The thermal profile and initiation location were modeled for LX-10 using the hydrodynamics and structures code ALE3D; results indicate temperatures in the vicinity of the ignition location in excess of 274 °C near the time of ignition. The conductive burn rates for these two explosives, as determined by flash x-ray radiography, are comparable in the range 0.1-0.2 mm/μs, somewhat faster than rates observed by strand burner experiments for explosives in the temperature range 150-180 °C and pressures up to 100 MPa. The thinnest-wall aluminum containment vessels presented here

  12. Local strains in waste tank deflagration analysis

    SciTech Connect

    Bryan, B.J.; Flanders, H.E. Jr.

    1993-10-01

    In recent years extensive effort has been expended to qualify buried nuclear waste storage tanks under accident conditions. One of these conditions is deflagration of the combustible gases which may build up over time. While much work has been done to calculate the general strain state, less effort has been made to address the local strains at structural discontinuities. An analytical method is presented for calculating these local strains and combining them with the general strain state. A closed form solution of the local strains is compared to a finite element solution.

  13. Numerical modeling of deflagration mode in coaxial plasma guns

    NASA Astrophysics Data System (ADS)

    Sitaraman, Hariswaran; Raja, Laxminarayan

    2012-10-01

    Pulsed coaxial plasma guns have been used in several applications in the field of space propulsion, nuclear fusion and materials processing. These devices operate in two modes based on the delay between gas injection and breakdown initiation. Larger delay led to the plasma detonation mode where a compression wave in the form of a luminous front propagates from the breech to the muzzle. Shorter delay led to the more efficient deflagration mode characterized by a relatively diffuse plasma with higher resistivity. The overall physics of the discharge in the two modes of operation and in particular the latter remain relatively unexplored. Here we perform a computational modeling study by solving the non-ideal Magneto-hydrodynamics equations for the quasi-neutral plasma in the coaxial plasma gun. A finite volume formulation on an unstructured mesh framework with an implicit scheme is used to do stable computations. The final work will present details of important species in the plasma, particle energies and Mach number at the muzzle. A comparison of the plasma parameters will be made with the experiments reported in ref. [1]. [4pt] [1] F. R. Poehlmann et al., Phys. Plasmas 17, 123508 (2010)

  14. Deflagration-to-detonation transition in granular HMX

    NASA Technical Reports Server (NTRS)

    Campbell, A. W.

    1980-01-01

    Granular HMX of three degrees of fineness was packed into heavy-walled steel tubes closed at both ends. Ignition was obtained at one end using an intimate mixture of finely divided titanium and boron as an igniter that produced heat with little gas. The distance to detonation was determined by examination of the resulting tube fragments. By inserting tightly-fitted neoprene diaphragms periodically into the HMX column, it was shown that the role of convective combustion was limited to the initial stage of the deflagration to detonation (DDT) process. Experiments in which various combinations of two of the three types of HMX were loaded into the same tube showed that heating by adiabatic shear of explosive grains was an essential factor in the final buildup to detonation. A description of the DDT process is developed in which conductive burning is followed in turn by convective burning, bed collapse with plug formation, onset of accelerated burning at the front of the plug through heating by intercrystalline friction and adiabatic shear, and intense shock formation resulting in high-order detonation.

  15. TURBULENCE IN A THREE-DIMENSIONAL DEFLAGRATION MODEL FOR TYPE Ia SUPERNOVAE. II. INTERMITTENCY AND THE DEFLAGRATION-TO-DETONATION TRANSITION PROBABILITY

    SciTech Connect

    Schmidt, W.; Niemeyer, J. C.; Ciaraldi-Schoolmann, F.; Roepke, F. K.; Hillebrandt, W.

    2010-02-20

    The delayed detonation model describes the observational properties of the majority of Type Ia supernovae very well. Using numerical data from a three-dimensional deflagration model for Type Ia supernovae, the intermittency of the turbulent velocity field and its implications on the probability of a deflagration-to-detonation (DDT) transition are investigated. From structure functions of the turbulent velocity fluctuations, we determine intermittency parameters based on the log-normal and the log-Poisson models. The bulk of turbulence in the ash regions appears to be less intermittent than predicted by the standard log-normal model and the She-Leveque model. On the other hand, the analysis of the turbulent velocity fluctuations in the vicinity of the flame front by Roepke suggests a much higher probability of large velocity fluctuations on the grid scale in comparison to the log-normal intermittency model. Following Pan et al., we computed probability density functions for a DDT for the different distributions. The determination of the total number of regions at the flame surface, in which DDTs can be triggered, enables us to estimate the total number of events. Assuming that a DDT can occur in the stirred flame regime, as proposed by Woosley et al., the log-normal model would imply a delayed detonation between 0.7 and 0.8 s after the beginning of the deflagration phase for the multi-spot ignition scenario used in the simulation. However, the probability drops to virtually zero if a DDT is further constrained by the requirement that the turbulent velocity fluctuations reach about 500 km s{sup -1}. Under this condition, delayed detonations are only possible if the distribution of the velocity fluctuations is not log-normal. From our calculations follows that the distribution obtained by Roepke allow for multiple DDTs around 0.8 s after ignition at a transition density close to 1 x 10{sup 7} g cm{sup -3}.

  16. Onset of a propagating self-sustained spin reversal front in a magnetic system.

    PubMed

    Subedi, P; Vélez, S; Macià, F; Li, S; Sarachik, M P; Tejada, J; Mukherjee, S; Christou, G; Kent, A D

    2013-05-17

    The energy released in a magnetic material by reversing spins as they relax toward equilibrium can lead to a dynamical instability that ignites self-sustained rapid relaxation along a deflagration front that propagates at a constant subsonic speed. Using a trigger heat pulse and transverse and longitudinal magnetic fields, we investigate and control the crossover between thermally driven magnetic relaxation and magnetic deflagration in single crystals of Mn(12)-acetate. PMID:25167444

  17. Onset of a propagating self-sustained spin reversal front in a magnetic system.

    PubMed

    Subedi, P; Vélez, S; Macià, F; Li, S; Sarachik, M P; Tejada, J; Mukherjee, S; Christou, G; Kent, A D

    2013-05-17

    The energy released in a magnetic material by reversing spins as they relax toward equilibrium can lead to a dynamical instability that ignites self-sustained rapid relaxation along a deflagration front that propagates at a constant subsonic speed. Using a trigger heat pulse and transverse and longitudinal magnetic fields, we investigate and control the crossover between thermally driven magnetic relaxation and magnetic deflagration in single crystals of Mn(12)-acetate.

  18. Estimation of the front-to-total activity ratio for wire screens using CFD simulation.

    PubMed

    Chen, B; Zhuo, W

    2015-11-01

    Wire screens are widely used for sampling radioactive aerosols. The front-to-total activity ratio is a critical factor in describing the self-shielding effect of the wire screens. In this study, computational fluid dynamic method was applied to simulate the deposition of aerosols on the surface of the wire screens. Four different types of screens were investigated for particle size varying from 1 nm to 10 µm. Experimental verification was carried out in a radon chamber. The results showed good agreement between experimental data interception and the simulation. Significant differences on the front-to-total activity ratio for the different types of screens were observed when the size of particle was <20 nm.

  19. Thermonuclear supernovae: simulations of the deflagration stage and their implications.

    PubMed

    Gamezo, Vadim N; Khokhlov, Alexei M; Oran, Elaine S; Chtchelkanova, Almadena Y; Rosenberg, Robert O

    2003-01-01

    Large-scale, three-dimensional numerical simulations of the deflagration stage of a thermonuclear supernova explosion show the formation and evolution of a highly convoluted turbulent flame in the gravitational field of an expanding carbon-oxygen white dwarf. The flame dynamics are dominated by the gravity-induced Rayleigh-Taylor instability that controls the burning rate. The thermonuclear deflagration releases enough energy to produce a healthy explosion. The turbulent flame, however, leaves large amounts of unburned and partially burned material near the star center, whereas observations that imply these materials are present only in outer layers. This disagreement could be resolved if the deflagration triggers a detonation. PMID:12446871

  20. Thermonuclear supernovae: simulations of the deflagration stage and their implications.

    PubMed

    Gamezo, Vadim N; Khokhlov, Alexei M; Oran, Elaine S; Chtchelkanova, Almadena Y; Rosenberg, Robert O

    2003-01-01

    Large-scale, three-dimensional numerical simulations of the deflagration stage of a thermonuclear supernova explosion show the formation and evolution of a highly convoluted turbulent flame in the gravitational field of an expanding carbon-oxygen white dwarf. The flame dynamics are dominated by the gravity-induced Rayleigh-Taylor instability that controls the burning rate. The thermonuclear deflagration releases enough energy to produce a healthy explosion. The turbulent flame, however, leaves large amounts of unburned and partially burned material near the star center, whereas observations that imply these materials are present only in outer layers. This disagreement could be resolved if the deflagration triggers a detonation.

  1. Autotrophic and heterotrophic abundance and activity associated with a nearshore front off the Georgia coast, U.S.A.

    NASA Astrophysics Data System (ADS)

    Jacobsen, T. R.; Pomeroy, L. R.; Blanton, J. O.

    1983-11-01

    The nearshore frontal zone off the coast of Georgia was found to be an area of high phytoplankton and bacterioplankton abundance and activity. Phytoplankton and bacterioplankton populations on the seaward side of the frontal zone had significantly higher photosynthetic and heterotrophic potentials than the nearshore side of the front. Phytoplankton species composition changed across the front, verifying that the front is a barrier to cross shelf mixing. Nearshore, large chain forming diatoms dominated, while smaller single cell diatoms and cyanobacteria dominated the seaward side of the front. Increased bacterioplankton activity was found associated with phytoplankton photosynthetic activity. Light appeared to be the major factor controlling photosynthesis across the frontal zone. Nitrogen, phosphorus and silica were present in similar concentrations, well above levels that would limit photosynthesis, on both sides of the front. Therefore the outflow of nutrients from rivers or estuaries did not influence primary production directly.

  2. Self-similar blast waves incorporating deflagrations of variable speed

    NASA Technical Reports Server (NTRS)

    Guirguis, R. H.; Kamel, M. M.; Oppenheim, A. K.

    1983-01-01

    The present investigation is concerned with the development of a systematic approach to the problem of self-similar blast waves incorporating nonsteady flames. The regime covered by the presented solutions is bounded on one side by an adiabatic strong explosion and, on the other, by deflagration propagating at an infinite acceleration. Results for a representative set of accelerations are displayed, taking into account the full range of propagation speeds from zero to velocities corresponding to the Chapman-Jouguet deflagration. It is found that the distribution of stored energy in the undisturbed medium determines the acceleration of the deflagration-shock wave system. The obtained results reveal the existence of a simple relation between the location of the deflagration and its Mach number.

  3. Effects of two-phase flow on the deflagration of porous energetic materials

    SciTech Connect

    Margolis, S.B.; Williams, F.A.

    1994-07-01

    Theoretical analyses are developed for the multi-phase deflagration of porous energetic solids, such as degraded nitramine propellants, that experience significant gas flow in the solid preheat region and are characterized by the presence of exothermic reactions in a bubbling melt layer at their surfaces. Relative motion between the gas and condensed phases is taken into account in both regions, and expressions for the mass burning rate and other quantities of interest, such as temperature and volume-fraction profiles, are derived by activation-energy asymptotics. The model extends recent work by allowing for gas flow in the unburned solid, and by incorporating pressure effects through the gas-phase equation of state. As a consequence, it is demonstrated how most aspects of the deflagration wave, including its structure, propagation speed and final temperature, depend on the local pressure in the two-phase regions.

  4. On the mechanism of the deflagration-to-detonation transition in a hydrogen-oxygen mixture

    SciTech Connect

    Liberman, M. A.; Ivanov, M. F.; Kiverin, A. D.; Kuznetsov, M. S.; Rakhimova, T. V.; Chukalovskii, A. A.

    2010-10-15

    The flame acceleration and the physical mechanism underlying the deflagration-to-detonation transition (DDT) have been studied experimentally, theoretically, and using a two-dimensional gasdynamic model for a hydrogen-oxygen gas mixture by taking into account the chain chemical reaction kinetics for eight components. A flame accelerating in a tube is shown to generate shock waves that are formed directly at the flame front just before DDT occurred, producing a layer of compressed gas adjacent to the flame front. A mixture with a density higher than that of the initial gas enters the flame front, is heated, and enters into reaction. As a result, a high-amplitude pressure peak is formed at the flame front. An increase in pressure and density at the leading edge of the flame front accelerates the chemical reaction, causing amplification of the compression wave and an exponentially rapid growth of the pressure peak, which 'drags' the flame behind. A high-amplitude compression wave produces a strong shock immediately ahead of the reaction zone, generating a detonation wave. The theory and numerical simulations of the flame acceleration and the new physical mechanism of DDT are in complete agreement with the experimentally observed flame acceleration, shock formation, and DDT in a hydrogen-oxygen gas mixture.

  5. Front end optimization for the monolithic active pixel sensor of the ALICE Inner Tracking System upgrade

    NASA Astrophysics Data System (ADS)

    Kim, D.; Aglieri Rinella, G.; Cavicchioli, C.; Chanlek, N.; Collu, A.; Degerli, Y.; Dorokhov, A.; Flouzat, C.; Gajanana, D.; Gao, C.; Guilloux, F.; Hillemanns, H.; Hristozkov, S.; Junique, A.; Keil, M.; Kofarago, M.; Kugathasan, T.; Kwon, Y.; Lattuca, A.; Mager, M.; Sielewicz, K. M.; Marin Tobon, C. A.; Marras, D.; Martinengo, P.; Mazza, G.; Mugnier, H.; Musa, L.; Pham, T. H.; Puggioni, C.; Reidt, F.; Riedler, P.; Rousset, J.; Siddhanta, S.; Snoeys, W.; Song, M.; Usai, G.; Van Hoorne, J. W.; Yang, P.

    2016-02-01

    ALICE plans to replace its Inner Tracking System during the second long shut down of the LHC in 2019 with a new 10 m2 tracker constructed entirely with monolithic active pixel sensors. The TowerJazz 180 nm CMOS imaging Sensor process has been selected to produce the sensor as it offers a deep pwell allowing full CMOS in-pixel circuitry and different starting materials. First full-scale prototypes have been fabricated and tested. Radiation tolerance has also been verified. In this paper the development of the charge sensitive front end and in particular its optimization for uniformity of charge threshold and time response will be presented.

  6. Chemical Energy Release in Several Recently Discovered Detonation and Deflagration Flows

    NASA Astrophysics Data System (ADS)

    Tarver, Craig M.

    2010-10-01

    Several recent experiments on complex detonation and deflagration flows are analyzed in terms of the chemical energy release required to sustain these flows. The observed double cellular structures in detonating gaseous nitromethane-oxygen and NO2-fuel (H2, CH4, and C2H6) mixtures are explained by the amplification of two distinct pressure wave frequencies by two exothermic reactions, the faster reaction forming vibrationally excited NO* and the slower reaction forming highly vibrationally excited N2**. The establishment of a Chapman-Jouguet (C-J) deflagration behind a weak shock wave, the C-J detonation established after a head-on collision with a shock front, and the C-J detonation conditions established in reactive supersonic flows are quantitatively calculated using the chemical energy release of a H2 + Cl2 mixture. For these three reactive flows, these calculations illustrate that different fractions of the exothermic chemical energy are used to sustain steady-state propagation. C-J detonation calculations on the various initial states using the CHEETAH chemical equilibrium code are shown to be in good agreement with experimental detonation velocity measurements for the head-on collision and supersonic flow detonations.

  7. Deflagration to detonation experiments in granular HMX

    SciTech Connect

    Burnside, N.J.; Son, S.F.; Asay, B.W.; Dickson, P.M.

    1998-03-01

    In this paper the authors report on continuing work involving a series of deflagration-to-detonation transition (DDT) experiments in which they study the piston-initiated DDT of heavily confined granular cyclotetramethylenetetranitramine (HMX). These experiments were designed to he useful in model development and evaluation. A main focus of these experiments is the effect of density on the DDT event. Particle size distribution and morphology are carefully characterized. In this paper they present recent surface area analysis. Earlier studies demonstrated extensive fracturing and agglomeration in samples at densities as low as 75% TMD as evidenced by dramatic decreases in particle size distribution due to mild stimulus. This is qualitatively confirmed with SEM images and quantitatively studied with gas absorption surface area analysis. Also, in this paper they present initial results using a microwave interferometer technique. Dynamic calibration of the technique was performed, a 35 GHz signal is used to increase resolution, and the system has been designed to be inexpensive for repeated experiments. The distance to where deformation of the inner wall begins for various densities is reported. This result is compared with the microwave interferometer measurements.

  8. Traveling circumferential unstable wave of cylindrical flame front

    NASA Astrophysics Data System (ADS)

    Trilis, A. V.; Vasiliev, A. A.; Sukhinin, S. V.

    2016-06-01

    The researches of stability of cylindrical front of deflagration combustion in an annular combustion chamber were made using phenomenological model. The flame front is described as discontinuity of gasdynamic parameters. It is considered that the combustion products are under chemical equilibrium. The combustible mixture and the combustion products are ideal gases. The velocity of deflagration combustion is determined using the Chapman-Jouget theory. It depends on the temperature of combustible mixture only. It is found that the combustible flame front is unstable for several types of small disturbances in the system Mechanics of instabilities are examined using both the numeric and analytical methods. The cases of evolution of the unstable waves rotating in circular channel are presented.

  9. On the stability of subsonic thermal fronts

    SciTech Connect

    Ibanez S, Miguel H.; Shchekinov, Yuri; Bessega L, Maria C.

    2005-08-15

    The stability of subsonic thermal fronts against corrugation is analyzed and an exact dispersion relation is obtained taking into account the compressibility of the gas. For heat fronts, this dispersion equation has an unstable root ({omega}{sub ex}) corresponding to the Landau-Darrieus unstable mode ({omega}{sub 0}) modified by the compressional effects. In particular, the exact solution shows a conspicuous maximum very close to the value of the intake Mach number M{sub 1} at which a Chapman-Jouguet deflagration wave behind the heat front is formed. Cooling fronts are stable for corrugation-like disturbances. A maximum damping as well as a maximum in the frequency occur at a value of M{sub 1} depending on the value of the normalized cooling q.

  10. The Deflagration of Energetic Crystals at Pressures above the Weak Shock Limit

    NASA Astrophysics Data System (ADS)

    Goveas, Stephen; Bourne, Neil; Millett, Jeremy

    2013-06-01

    The response of inert solid to shock loading may be divided into two regimes of contrasting behaviour. In the lower of these, the material deforms in a regime below the theoretical strength of the material where deformation is triggered at discrete flaws within the microstructure at grain boundaries, second-phase particles, or vacancies within the lattice at the higher pressures. There comes a point however, where the theoretical strength of the material is overcome and response becomes truly homogeneous behind the shock front and this point corresponds to the limit of weak shock behaviour within the crystal. Recent work of Zaug discussing burning rate of HMX as a function of pressure is reviewed and the onset of rapid deflagration is shown to commence as the WSL is exceeded. Implications for the shock response of energetic materials are discussed.

  11. Active deformation of the northern front of the Eastern Great Caucasus

    NASA Astrophysics Data System (ADS)

    Niviere, Bertrand; Gagala, Lukasz; Callot, Jean-Paul; Regard, Vincent; Ringenbach, Jean-Claude

    2016-04-01

    The Arabia-Eurasia collision involved a mosaic of island arcs and microcontinents. Their accretion to the complex paleogeographic margin of Neotethys was marked by numerous collisional events. The Greater Caucasus constitute the northernmost tectonic element of this tectonic collage, developed as a back arc extensional zone now inverted, which relationships to the onset of Arabia-Eurasia continental collision and/or to the reorganization of the Arabia-Eurasia plate boundary at ˜5 Ma remain controversial. Structurally, the Greater Caucasus are a former continental back arc rift, now the locus of ongoing continental shortening. Modern geodetic observations suggest that in the west, the strain north of the Armenian Plateau is accommodated almost exclusively along the margins of the Greater Caucasus. This differs from regions further east where strain accommodation is distributed across both the Lesser and Greater Caucasus, and within the Greater Caucasus range, with a unique southward vergence. We question here the amount and mechanisms by which the Eastern Greater Caucasus accommodate part of the Arabia-Eurasia convergence. Morphostructural analysis of the folded late Pleistocene marine terrace along the northern slope of the Eastern Greater Caucasus evidences an on going tectonic activity in the area where GPS measurements record no motion. Most of the recent foreland deformation is accommodated by south-vergent folds and thrust, i. e. opposite to the vergence of the Caucasus frontal northern thrust. A progressive unconformity in the folded beds shows that it was already active during the late Pliocene. Cosmogenic dating of the terrace and kinematic restoration of the remnant terrace, linked to the subsurface geology allows for the estimation of a shortening rate ranging from a few mm/yr to 1 cm/yr over the last 5 Myr along the greater Caucasus northern front. Thus more than one third of the shortening between the Kura block / Lesser Caucasus domain and the Stable

  12. Seismic and satellite observations of calving activity at major glacier fronts in Greenland

    NASA Astrophysics Data System (ADS)

    Danesi, Stefania; Salimbeni, Simone; Urbini, Stefano; Pondrelli, Silvia; Margheriti, Lucia

    2016-04-01

    The interaction between oceans and large outlet glaciers in polar regions contributes to the budget of the global water cycle. We have observed the dynamic of sizeable outlet glaciers in Greenland by the analysis of seismic data collected by the regional seismic network Greenland Ice Sheet Monitoring Network (GLISN) trying also to find out correspondence in the glacier tongue evolution derived by the observation of satellite images. By studying the long-period seismic signals at stations located at the mouth of large fjords (e.g. ILULI, NUUG, KULLO), we identify major calving events through the detection of the ground flexure in response to seiche waves generated by iceberg detachments. 
For the time spanning the period between 2010-2014, we fill out calving-event catalogues which can be useful for the estimation of spatial and temporal variations in volume of ice loss at major active fronts in Greenland.

  13. Non-Invasive Measurement of Adrenocortical Activity in Blue-Fronted Parrots (Amazona aestiva, Linnaeus, 1758).

    PubMed

    Ferreira, João C P; Fujihara, Caroline J; Fruhvald, Erika; Trevisol, Eduardo; Destro, Flavia C; Teixeira, Carlos R; Pantoja, José C F; Schmidt, Elizabeth M S; Palme, Rupert

    2015-01-01

    Parrots kept in zoos and private households often develop psychological and behavioural disorders. Despite knowing that such disorders have a multifactorial aetiology and that chronic stress is involved, little is known about their development mainly due to a poor understanding of the parrots' physiology and the lack of validated methods to measure stress in these species. In birds, blood corticosterone concentrations provide information about adrenocortical activity. However, blood sampling techniques are difficult, highly invasive and inappropriate to investigate stressful situations and welfare conditions. Thus, a non-invasive method to measure steroid hormones is critically needed. Aiming to perform a physiological validation of a cortisone enzyme immunoassay (EIA) to measure glucocorticoid metabolites (GCM) in droppings of 24 Blue-fronted parrots (Amazona aestiva), two experiments were designed. During the experiments all droppings were collected at 3-h intervals. Initially, birds were sampled for 24 h (experiment 1) and one week later assigned to four different treatments (experiment 2): Control (undisturbed), Saline (0.2 mL of 0.9% NaCl IM), Dexamethasone (1 mg/kg IM) and Adrenocorticotropic hormone (ACTH; 25 IU IM). Treatments (always one week apart) were applied to all animals in a cross-over study design. A daily rhythm pattern in GCM excretion was detected but there were no sex differences (first experiment). Saline and dexamethasone treatments had no effect on GCM (not different from control concentrations). Following ACTH injection, GCM concentration increased about 13.1-fold (median) at the peak (after 3-9 h), and then dropped to pre-treatment concentrations. By a successful physiological validation, we demonstrated the suitability of the cortisone EIA to non-invasively monitor increased adrenocortical activity, and thus, stress in the Blue-fronted parrot. This method opens up new perspectives for investigating the connection between behavioural

  14. Non-Invasive Measurement of Adrenocortical Activity in Blue-Fronted Parrots (Amazona aestiva, Linnaeus, 1758)

    PubMed Central

    Ferreira, João C. P.; Fujihara, Caroline J.; Fruhvald, Erika; Trevisol, Eduardo; Destro, Flavia C.; Teixeira, Carlos R.; Pantoja, José C. F.; Schmidt, Elizabeth M. S.; Palme, Rupert

    2015-01-01

    Parrots kept in zoos and private households often develop psychological and behavioural disorders. Despite knowing that such disorders have a multifactorial aetiology and that chronic stress is involved, little is known about their development mainly due to a poor understanding of the parrots’ physiology and the lack of validated methods to measure stress in these species. In birds, blood corticosterone concentrations provide information about adrenocortical activity. However, blood sampling techniques are difficult, highly invasive and inappropriate to investigate stressful situations and welfare conditions. Thus, a non-invasive method to measure steroid hormones is critically needed. Aiming to perform a physiological validation of a cortisone enzyme immunoassay (EIA) to measure glucocorticoid metabolites (GCM) in droppings of 24 Blue-fronted parrots (Amazona aestiva), two experiments were designed. During the experiments all droppings were collected at 3-h intervals. Initially, birds were sampled for 24 h (experiment 1) and one week later assigned to four different treatments (experiment 2): Control (undisturbed), Saline (0.2 mL of 0.9% NaCl IM), Dexamethasone (1 mg/kg IM) and Adrenocorticotropic hormone (ACTH; 25 IU IM). Treatments (always one week apart) were applied to all animals in a cross-over study design. A daily rhythm pattern in GCM excretion was detected but there were no sex differences (first experiment). Saline and dexamethasone treatments had no effect on GCM (not different from control concentrations). Following ACTH injection, GCM concentration increased about 13.1-fold (median) at the peak (after 3–9 h), and then dropped to pre-treatment concentrations. By a successful physiological validation, we demonstrated the suitability of the cortisone EIA to non-invasively monitor increased adrenocortical activity, and thus, stress in the Blue-fronted parrot. This method opens up new perspectives for investigating the connection between behavioural

  15. Non-Invasive Measurement of Adrenocortical Activity in Blue-Fronted Parrots (Amazona aestiva, Linnaeus, 1758).

    PubMed

    Ferreira, João C P; Fujihara, Caroline J; Fruhvald, Erika; Trevisol, Eduardo; Destro, Flavia C; Teixeira, Carlos R; Pantoja, José C F; Schmidt, Elizabeth M S; Palme, Rupert

    2015-01-01

    Parrots kept in zoos and private households often develop psychological and behavioural disorders. Despite knowing that such disorders have a multifactorial aetiology and that chronic stress is involved, little is known about their development mainly due to a poor understanding of the parrots' physiology and the lack of validated methods to measure stress in these species. In birds, blood corticosterone concentrations provide information about adrenocortical activity. However, blood sampling techniques are difficult, highly invasive and inappropriate to investigate stressful situations and welfare conditions. Thus, a non-invasive method to measure steroid hormones is critically needed. Aiming to perform a physiological validation of a cortisone enzyme immunoassay (EIA) to measure glucocorticoid metabolites (GCM) in droppings of 24 Blue-fronted parrots (Amazona aestiva), two experiments were designed. During the experiments all droppings were collected at 3-h intervals. Initially, birds were sampled for 24 h (experiment 1) and one week later assigned to four different treatments (experiment 2): Control (undisturbed), Saline (0.2 mL of 0.9% NaCl IM), Dexamethasone (1 mg/kg IM) and Adrenocorticotropic hormone (ACTH; 25 IU IM). Treatments (always one week apart) were applied to all animals in a cross-over study design. A daily rhythm pattern in GCM excretion was detected but there were no sex differences (first experiment). Saline and dexamethasone treatments had no effect on GCM (not different from control concentrations). Following ACTH injection, GCM concentration increased about 13.1-fold (median) at the peak (after 3-9 h), and then dropped to pre-treatment concentrations. By a successful physiological validation, we demonstrated the suitability of the cortisone EIA to non-invasively monitor increased adrenocortical activity, and thus, stress in the Blue-fronted parrot. This method opens up new perspectives for investigating the connection between behavioural

  16. Front structure and dynamics in dense colonies of motile bacteria: Role of active turbulence

    NASA Astrophysics Data System (ADS)

    Chatterjee, Rayan; Joshi, Abhijeet A.; Perlekar, Prasad

    2016-08-01

    We study the spreading of a bacterial colony undergoing turbulentlike collective motion. We present two minimalistic models to investigate the interplay between population growth and coherent structures arising from turbulence. Using direct numerical simulation of the proposed models we find that turbulence has two prominent effects on the spatial growth of the colony: (a) the front speed is enhanced, and (b) the front gets crumpled. Both these effects, which we highlight by using statistical tools, are markedly different in our two models. We also show that the crumpled front structure and the passive scalar fronts in random flows are related in certain regimes.

  17. Front structure and dynamics in dense colonies of motile bacteria: Role of active turbulence.

    PubMed

    Chatterjee, Rayan; Joshi, Abhijeet A; Perlekar, Prasad

    2016-08-01

    We study the spreading of a bacterial colony undergoing turbulentlike collective motion. We present two minimalistic models to investigate the interplay between population growth and coherent structures arising from turbulence. Using direct numerical simulation of the proposed models we find that turbulence has two prominent effects on the spatial growth of the colony: (a) the front speed is enhanced, and (b) the front gets crumpled. Both these effects, which we highlight by using statistical tools, are markedly different in our two models. We also show that the crumpled front structure and the passive scalar fronts in random flows are related in certain regimes. PMID:27627334

  18. Significance of an Active Volcanic Front in the Far Western Aleutian Arc

    NASA Astrophysics Data System (ADS)

    Yogodzinski, G. M.; Kelemen, P. B.; Hoernle, K.

    2015-12-01

    Discovery of a volcanic front west of Buldir Volcano, the western-most emergent Aleutian volcano, demonstrates that the surface expression of Aleutian volcanism falls below sea level just west of 175.9° E longitude, but is otherwise continuous from mainland Alaska to Kamchatka. The newly discovered sites of western Aleutian seafloor volcanism are the Ingenstrem Depression, a 60 km-long structural depression just west of Buldir, and an unnamed area 300 km further west, referred to as the Western Cones. These locations fall along a volcanic front that stretches from Buldir to Piip Seamount near the Komandorsky Islands. Western Aleutian seafloor volcanic rocks include large quantities of high-silica andesite and dacite, which define a highly calc-alkaline igneous series and carry trace element signatures that are unmistakably subduction-related. This indicates that subducting oceanic lithosphere is present beneath the westernmost Aleutian arc. The rarity of earthquakes below depths of 200 km indicates that the subducting plate is unusually hot. Some seafloor volcanoes are 6-8 km wide at the base, and so are as large as many emergent Aleutian volcanoes. The seafloor volcanoes are submerged in water depths >3000 m because they sit on oceanic lithosphere of the Bering Sea. The volcanic front is thus displaced to the north of the ridge of arc crust that underlies the western Aleutian Islands. This displacement, which developed since approximately 6 Ma when volcanism was last active on the islands, must be a consequence of oblique convergence in a system where the subducting plate and large blocks of arc crust are both moving primarily in an arc-parallel sense. The result is a hot-slab system where low subduction rates probably limit advection of hot mantle to the subarc, and produce a relatively cool and perhaps stagnant mantle wedge. The oceanic setting and highly oblique subduction geometry also severely limit rates of sediment subduction, so the volcanic rocks, which

  19. The Deflagration Stage of Chandrasekhar Mass Models for Type Ia Supernovae. I. Early Evolution

    NASA Astrophysics Data System (ADS)

    Malone, C. M.; Nonaka, A.; Woosley, S. E.; Almgren, A. S.; Bell, J. B.; Dong, S.; Zingale, M.

    2014-02-01

    We present high-resolution, full-star simulations of the post-ignition phase of Type Ia supernovae using the compressible hydrodynamics code Castro. Initial conditions, including the turbulent velocity field and ignition site, are imported directly from a simulation of the last few hours of presupernova convection using a low Mach number code, Maestro. Adaptive mesh refinement allows the initial burning front to be modeled with an effective resolution of 36,8643 zones (136 m zone-1). The initial rise and expansion of the deflagration front are tracked until burning reaches the star's edge and the role of the background turbulence on the flame is investigated. The effect of artificially moving the ignition location closer to the star's center is explored. The degree to which turbulence affects the burning front decreases with increasing ignition radius since the buoyancy force is stronger at larger radii. Even central ignition—in the presence of a background convective flow field—is rapidly carried off-center as the flame is carried by the flow field. We compare our results to analytic models for burning thermals, and find that they reproduce the general trends of the bubble's size and mass, but underpredict the amount of buoyant acceleration due to simplifying assumptions of the bubble's properties. Overall, we find that the amount of mass that burns prior to flame break out is small, consistent with a "gravitationally confined detonation" occurring at a later epoch, but additional burning will occur following breakout that may modify this conclusion.

  20. Plasma-assisted ignition and deflagration-to-detonation transition.

    PubMed

    Starikovskiy, Andrey; Aleksandrov, Nickolay; Rakitin, Aleksandr

    2012-02-13

    Non-equilibrium plasma demonstrates great potential to control ultra-lean, ultra-fast, low-temperature flames and to become an extremely promising technology for a wide range of applications, including aviation gas turbine engines, piston engines, RAMjets, SCRAMjets and detonation initiation for pulsed detonation engines. The analysis of discharge processes shows that the discharge energy can be deposited into the desired internal degrees of freedom of molecules when varying the reduced electric field, E/n, at which the discharge is maintained. The amount of deposited energy is controlled by other discharge and gas parameters, including electric pulse duration, discharge current, gas number density, gas temperature, etc. As a rule, the dominant mechanism of the effect of non-equilibrium plasma on ignition and combustion is associated with the generation of active particles in the discharge plasma. For plasma-assisted ignition and combustion in mixtures containing air, the most promising active species are O atoms and, to a smaller extent, some other neutral atoms and radicals. These active particles are efficiently produced in high-voltage, nanosecond, pulse discharges owing to electron-impact dissociation of molecules and electron-impact excitation of N(2) electronic states, followed by collisional quenching of these states to dissociate the molecules. Mechanisms of deflagration-to-detonation transition (DDT) initiation by non-equilibrium plasma were analysed. For longitudinal discharges with a high power density in a plasma channel, two fast DDT mechanisms have been observed. When initiated by a spark or a transient discharge, the mixture ignited simultaneously over the volume of the discharge channel, producing a shock wave with a Mach number greater than 2 and a flame. A gradient mechanism of DDT similar to that proposed by Zeldovich has been observed experimentally under streamer initiation.

  1. Plasma-assisted ignition and deflagration-to-detonation transition.

    PubMed

    Starikovskiy, Andrey; Aleksandrov, Nickolay; Rakitin, Aleksandr

    2012-02-13

    Non-equilibrium plasma demonstrates great potential to control ultra-lean, ultra-fast, low-temperature flames and to become an extremely promising technology for a wide range of applications, including aviation gas turbine engines, piston engines, RAMjets, SCRAMjets and detonation initiation for pulsed detonation engines. The analysis of discharge processes shows that the discharge energy can be deposited into the desired internal degrees of freedom of molecules when varying the reduced electric field, E/n, at which the discharge is maintained. The amount of deposited energy is controlled by other discharge and gas parameters, including electric pulse duration, discharge current, gas number density, gas temperature, etc. As a rule, the dominant mechanism of the effect of non-equilibrium plasma on ignition and combustion is associated with the generation of active particles in the discharge plasma. For plasma-assisted ignition and combustion in mixtures containing air, the most promising active species are O atoms and, to a smaller extent, some other neutral atoms and radicals. These active particles are efficiently produced in high-voltage, nanosecond, pulse discharges owing to electron-impact dissociation of molecules and electron-impact excitation of N(2) electronic states, followed by collisional quenching of these states to dissociate the molecules. Mechanisms of deflagration-to-detonation transition (DDT) initiation by non-equilibrium plasma were analysed. For longitudinal discharges with a high power density in a plasma channel, two fast DDT mechanisms have been observed. When initiated by a spark or a transient discharge, the mixture ignited simultaneously over the volume of the discharge channel, producing a shock wave with a Mach number greater than 2 and a flame. A gradient mechanism of DDT similar to that proposed by Zeldovich has been observed experimentally under streamer initiation. PMID:22213667

  2. PLEKHG3 enhances polarized cell migration by activating actin filaments at the cell front.

    PubMed

    Nguyen, Trang Thi Thu; Park, Wei Sun; Park, Byung Ouk; Kim, Cha Yeon; Oh, Yohan; Kim, Jin Man; Choi, Hana; Kyung, Taeyoon; Kim, Cheol-Hee; Lee, Gabsang; Hahn, Klaus M; Meyer, Tobias; Heo, Won Do

    2016-09-01

    Cells migrate by directing Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42) activities and by polymerizing actin toward the leading edge of the cell. Previous studies have proposed that this polarization process requires a local positive feedback in the leading edge involving Rac small GTPase and actin polymerization with PI3K likely playing a coordinating role. Here, we show that the pleckstrin homology and RhoGEF domain containing G3 (PLEKHG3) is a PI3K-regulated Rho guanine nucleotide exchange factor (RhoGEF) for Rac1 and Cdc42 that selectively binds to newly polymerized actin at the leading edge of migrating fibroblasts. Optogenetic inactivation of PLEKHG3 showed that PLEKHG3 is indispensable both for inducing and for maintaining cell polarity. By selectively binding to newly polymerized actin, PLEKHG3 promotes local Rac1/Cdc42 activation to induce more local actin polymerization, which in turn promotes the recruitment of more PLEKHG3 to induce and maintain cell front. Thus, autocatalytic reinforcement of PLEKHG3 localization to the leading edge of the cell provides a molecular basis for the proposed positive feedback loop that is required for cell polarization and directed migration. PMID:27555588

  3. PLEKHG3 enhances polarized cell migration by activating actin filaments at the cell front

    PubMed Central

    Nguyen, Trang Thi Thu; Park, Wei Sun; Park, Byung Ouk; Kim, Cha Yeon; Oh, Yohan; Kim, Jin Man; Choi, Hana; Kyung, Taeyoon; Kim, Cheol-Hee; Lee, Gabsang; Hahn, Klaus M.; Meyer, Tobias; Heo, Won Do

    2016-01-01

    Cells migrate by directing Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42) activities and by polymerizing actin toward the leading edge of the cell. Previous studies have proposed that this polarization process requires a local positive feedback in the leading edge involving Rac small GTPase and actin polymerization with PI3K likely playing a coordinating role. Here, we show that the pleckstrin homology and RhoGEF domain containing G3 (PLEKHG3) is a PI3K-regulated Rho guanine nucleotide exchange factor (RhoGEF) for Rac1 and Cdc42 that selectively binds to newly polymerized actin at the leading edge of migrating fibroblasts. Optogenetic inactivation of PLEKHG3 showed that PLEKHG3 is indispensable both for inducing and for maintaining cell polarity. By selectively binding to newly polymerized actin, PLEKHG3 promotes local Rac1/Cdc42 activation to induce more local actin polymerization, which in turn promotes the recruitment of more PLEKHG3 to induce and maintain cell front. Thus, autocatalytic reinforcement of PLEKHG3 localization to the leading edge of the cell provides a molecular basis for the proposed positive feedback loop that is required for cell polarization and directed migration. PMID:27555588

  4. Steady Deflagration of PBX-9501 Within a Copper Cylinder

    SciTech Connect

    Pemberton, Steven J.; Herrera, Dennis H.; Herrera, Tommy J.; Arellano, Jesus C.; Sandoval, Thomas D.

    2012-06-26

    A copper cylinder cook-off experiment has been designed to cause steady deflagration in PBX-9501 explosive material. The design is documented and preliminary copper expansion results are presented for steady deflagration with a reaction speed of 1092 +/- 24 m/s. The expansion of reaction products from the detonation of an explosive is something that is well understood, and reasonably simulated using documented equations of state (EOS) for many explosives of interest. These EOS were historically measured using a 'standard' copper cylinder test design; this design comprised an annealed, oxygen-free high conductivity (OFHC) copper tube filled with explosive material and detonated from one end. Expansion of the copper wall was measured as a function of time using either a streak camera (for classic testing), or more recently using laser velocimetry techniques. Expansion data were then used to derive the EOS in various preferred forms - which are not discussed here for the sake of brevity. [Catanach, et. al., 1999] When an explosive deflagrates rather than detonating, simulation becomes more difficult. Reaction products are released on a slower time scale, and the reactions are much more affected by the geometry and local temperature within the reaction environment. It is assumed that the standard, documented EOS will no longer apply. In an effort to establish a first order approximation of deflagration product behavior, a cook-off test has been designed to cause steady deflagration in PBX-9501 explosive material, and to record the copper expansion profile as a function of time during this test. The purpose of the current paper is to document the initial test design and report some preliminary results. A proposal for modification of the design is also presented.

  5. Are boundary conditions in surface productivity at the Southern Polar Front reflected in benthic activity?

    NASA Astrophysics Data System (ADS)

    Brandt, Angelika; Vanreusel, Ann; Bracher, Astrid; Jule Marie Hoppe, Clara; Lins, Lidia; Meyer-Löbbecke, Anna; Altenburg Soppa, Mariana; Würzberg, Laura

    2014-10-01

    In austral summer 2012, during the expedition ANT-XXVIII/3 on board RV Polarstern, two sites were sampled 1600 km apart in the South Polar Front area (52°S) at the boundary of different productivity regimes for meio- and macrobenthos using a multiple-corer and an epibenthic sledge, respectively. Patterns in density and abundance data were compared between different size classes of the benthos and interpreted in relation to surface primary productivity data and sediment oxygen consumption. We tested the hypothesis that long-term satellite-derived surface phytoplankton biomass, in situ real time biomass, and productivity measurements at the surface and throughout the euphotic zone are reflected in abyssal benthos densities, abundances and activity. Specifically, we investigated the effect of boundary conditions for lower and higher surface productivity. Surface and integrated to 100 m depth biomass and primary productivity measurements vary stations, with the lowest values at station 85 (0.083 mg Chl-a m-3 at surface, 9 mg Chl-a m-2 and 161 mg C m-2 d-1- integrated over the first 100 m depth), and the highest values at station 86 (2.231 mg Chl-a m-3 at surface, 180 mg Chl-a m-2 and 2587 mg C m-2 d-1 integrated over first 100 m depth). Total meiofaunal densities varied between 102 and 335 individuals/10 cm². Densities were the highest at station 86-30 (335 individuals) and lowest at station 81-13 (102 individuals). Total macrofaunal densities (individuals/1000 m²) varied between 26 individuals at station 81-17 and 194 individuals at station 86-24. However, three EBS hauls were taken at station 86 with a minimum of 80 and a maximum of 194 individuals. Sediment oxygen consumption did not vary significantly between stations from east to west. Bentho-pelagic coupling of meio- and macrobenthic communities could not be observed in the South Polar Front at the boundary conditions from low to high surface productivity between stations 81 and 86.

  6. Deflagration of HMX-Based Explosives at High Temperatures and Pressures

    SciTech Connect

    Maienschein, J L; Wardell, J F; DeHaven, M R; Black, C K

    2004-05-12

    We measure the deflagration behavior of energetic materials at extreme conditions (up to 520K and 1 GPa) in the LLNL High Pressure Strand Burner, thereby obtaining reaction rate data for prediction of violence of thermal explosions. The apparatus provides both temporal pressure history and flame time-of-arrival information during deflagration, allowing direct calculation of deflagration rate as a function of pressure. Samples may be heated before testing. Here we report the deflagration behavior of several HMX-based explosives at pressures of 10-600 MPa and temperatures of 300-460 K. We find that formulation details are very important to overall deflagration behavior. Formulations with high binder content (>15 wt%) deflagrate smoothly over the entire pressure range regardless of particle size, with a larger particle size distribution leading to a slower reaction. The deflagration follows a power law function with the pressure exponent being unity. Formulations with lower binder content ({le} 10% or less by weight) show physical deconsolidation at pressures over 100-200 MPA, with transition to a rapid erratic deflagration 10-100 times faster. High temperatures have a relatively minor effect on the deflagration rate until the HMX {beta} {yields} {delta} phase transition occurs, after which the deflagration rate increases by more than a factor of 10.

  7. Design and optimization of a deflagration to detonation transition (ddt) section

    NASA Astrophysics Data System (ADS)

    Romo, Francisco X.

    Throughout the previous century, hydrocarbon-fueled engines have used and optimized the `traditional' combustion process called deflagration (subsonic combustion). An alternative form of combustion, detonation (supersonic combustion), can increase the thermal efficiency of the process by anywhere from 20 - 50%. Even though several authors have studied detonation waves since the 1890's and a plethora of papers and books have been published, it was not until 2008 that the first detonation-powered flight took place. It lasted for 10 seconds at 100 ft. altitude. Achieving detonation presents its own challenges: some fuels are not prone to detonate, severe vibrations caused by the cyclic nature of the engine and its intense noise are some of the key areas that need further research. Also, to directly achieve detonation either a high-energy, bulky, ignition system is required, or the combustion chamber must be fairly long (5 ft. or more in some cases). In the latter method, a subsonic flame front accelerates within the combustion chamber until it reaches supersonic speeds, thus detonation is attained. This is called deflagration-todetonation transition (DDT). Previous papers and experiments have shown that obstacles, such as discs with an orifice, located inside the combustion chamber can shorten the distance required to achieve detonation. This paper describes a hands-on implementation of a DDT device. Different disc geometries inside the chamber alter the wave characteristics at the exit of the tube. Although detonation was reached only when using pure oxygen, testing identified an obstacle configuration for LPG and air mixtures that increased pressure and wave speed significantly when compared to baseline or other obstacle configurations. Mixtures of LPG and air were accelerated to Mach 0.96 in the downstream frame of reference, which would indicate a transition to detonation was close. Reasons for not achieving detonation may include poor fuel and oxidizer mixing

  8. Extremely reduced motion in front of screens: investigating real-world physical activity of adolescents by accelerometry and electronic diary.

    PubMed

    Streb, Judith; Kammer, Thomas; Spitzer, Manfred; Hille, Katrin

    2015-01-01

    This paper reports accelerometer and electronic dairy data on typical daily activities of 139 school students from grade six and nine. Recordings covered a typical school day for each student and lasted on average for 23 h. Screen activities (watching television and using the computer) are compared to several other activities performed while sitting (e.g., playing, eating, sitting in school, and doing homework). Body movement was continuously recorded by four accelerometers and transformed into a motion sore. Our results show that extremely low motion scores, as if subjects were freezing, emerge to a greater extent in front of screens compared to other investigated activities. Given the substantial amount of time young people spend in front of screens and the rising obesity epidemic, our data suggest a mechanism for the association of screen time and obesity. PMID:25955531

  9. Active Uplift At The Taiwan Belt Front Revealed By River Profiles:the Hsiaomei Anticline Area

    NASA Astrophysics Data System (ADS)

    Chen, R.-F.; Angelier, J.; Hu, J.-C.; Deffontaines, B.; Tsai, H.

    A river profile may reveal tectonic deformation through comparison with a smoothed theoretical function based on simple assumptions, provided that its relationships with the erosion-accumulation phenomena have been deciphered. The Taiwan orogeny re- sults from the collision between the Luzon volcanic arc of the Philippine Sea plate and the Chinese continental margin of the Eurasian plate. As an active collision zone between the Luzon arc and the China continental margin, the Taiwan mountain belt, particularly its south-central part, is undergoing strong crustal shortening and rapid uplift. In the central part of the island, rock uplift rates are matched by erosion rates calculated from sediment yields and exhumation rates. In the foothills of southwestern Taiwan we focus on the longitudinal profiles of twelve rivers near Chiayi area. Based on the fit with mathematical functions, we characterize a significant positive anomaly in terms of shape, amplitude and location. River data from 1/5,000 topographic maps were used to define a set of parameters related to the classical exponential equation of the longitudinal profiles. We obtained an accepted fit for a set of 5-7 parameters of the polynomial exponent, that is, a degree 4-6. The anomaly is spatially consistent and does not show correlation with variations in erosional-depositional phenomena, including variations in lithology of the rock formations. The anomaly thus reflects tectonic uplift, in good agreement with other sources of information, including the GPS data that indicate active E-W shortening of about 1 cm/yr in this area. The posi- tive anomaly detected in ten river profiles diminishes and vanishes in the northernmost and southernmost river profiles. It reflects continuing folding and uplift within an ellip- tic area elongated N-S, which corresponds to the present-day growth of the Hsiaomei anticline at the front of Taiwan belt.

  10. Turbulent Deflagrated Flame Interaction with a Fluidic Jet Flow for Deflagration-to-Detonation Flame Acceleration

    NASA Astrophysics Data System (ADS)

    Chambers, Jessica; McGarry, Joseph; Ahmed, Kareem

    2015-11-01

    Detonation is a high energetic mode of pressure gain combustion. Detonation combustion exploits the pressure rise to augment high flow momentum and thermodynamic cycle efficiencies. The driving mechanism of deflagrated flame acceleration to detonation is turbulence generation and induction. A fluidic jet is an innovative method for the production of turbulence intensities and flame acceleration. Compared to traditional obstacles, the jet reduces the pressure losses and heat soak effects while providing turbulence generation control. The investigation characterizes the turbulent flame-flow interactions. The focus of the study is on classifying the turbulent flame dynamics and the temporal evolution of turbulent flame regime. The turbulent flame-flow interactions are experimentally studied using a LEGO Detonation facility. Advanced high-speed laser diagnostics, particle image velocimetry (PIV), planar laser induced florescence (PLIF), and Schlieren imaging are used in analyzing the physics of the interaction and flame acceleration. Higher turbulence induction is observed within the turbulent flame after contact with the jet, leading to increased flame burning rates. The interaction with the fluidic jet results in turbulent flame transition from the thin reaction zones to the broken reaction regime.

  11. Eigenvalue analysis and calculations for the deflagration of porous energetic materials in the merged-flame regime

    SciTech Connect

    Ilincic, N.; Margolis, S.B.

    1996-07-01

    Analytical and numerical calculations of the structure and burning rate of a deflagrating porous energetic material are presented for the limiting case of merged condensed and gas-phase reaction zones. The reaction scheme is modeled by a global two-step mechanism, applicable to certain types of degraded nitramine propellants and consisting of sequential condensed and gaseous steps. Taking into account important effects due to multiphase flow and exploiting the limit of large activation energies, a theoretical analysis may be developed based on activation-energy asymptotics. For steady, planar deflagration, this leads to an eigenvalue problem for the inner reaction-zone, the solution of which determines the burning rate. Numerical solutions give a reasonably complete description of the dependence of the structure and burning rate on the various parameters in the problem, and show excellent agreement with analytical results that are obtained in a more limited parameter regime in which most of the heat release is produced by the condensed-phase reaction and the porosity of the solid is small. These calculations indicate the significant influences of two-phase flow and the multiphase, multi-step chemistry on the deflagration structure and the burning rate, and thus serve to define an important parameter regime that supports the intrusion of the primary gas flame into the two-phase condensed decomposition region at the propellant surface.

  12. Deflagration Rate Measurements of Three Insensitive High Explosives: LLM-105, TATB, and DAAF

    SciTech Connect

    Glascoe, E A; Maienschein, J L; Lorenz, K T; Tan, N; Koerner, J G

    2010-03-08

    The pressure dependent deflagration rates of LLM-105, DAAF and TATB based formulations were measured in the LLNL high pressure strand burner. The role of binder amount, explosive type, and thermal damage and their effects on the deflagration rate will be discussed. One DAAF formulation, two different formulations of LLM-105, and four formulations of TATB were studied; results indicate that binder amount and type play a minor role in the deflagration behavior. This is in sharp contrast to the HMX based formulations which strongly depend on binder amount and type. The effect of preheating these samples was considerably more dramatic. In the case of LLM-105, preheating the sample appears to have little effect on the deflagration rate. In contrast, preheating DAAF and TATB formulations causes the deflagration rate to accelerate. The thermal and mechanical properties of these formulations will be discussed in the context of their pressure and temperature dependent deflagration rates.

  13. PRESSURE AND TEMPERATURE DEPENDENT DEFLAGRATION RATE MEASUREMENTS OF LLM-105 AND TATB BASED EXPLOSIVES

    SciTech Connect

    Glascoe, E A; Tan, N; Koerner, J; Lorenz, K T; Maienschein, J L

    2009-11-10

    The pressure dependent deflagration rates of LLM-105 and TATB based formulations were measured in the LLNL high pressure strand burner. The role of binder amount, explosive type, and thermal damage and their effects on the deflagration rate will be discussed. Two different formulations of LLM-105 and three formulations of TATB were studied and results indicate that binder amount and type play a minor role in the deflagration behavior. This is in sharp contrast to the HMX based formulations which strongly depend on binder amount and type. The effect of preheating these samples was considerably more dramatic. In the case of LLM-105, preheating the sample appears to have little effect on the deflagration rate. In contrast, preheating TATB formulations causes the deflagration rate to accelerate and become erratic. The thermal and mechanical properties of these formulations will be discussed in the context of their pressure and temperature dependent deflagration rates.

  14. Temperature activated absorption during laser-induced damage: The evolution of laser-supported solid-state absorption fronts

    SciTech Connect

    Carr, C W; Bude, J D; Shen, N; Demange, P

    2010-10-26

    Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  15. Deflagration-to-detonation transition in PETN and HMX

    SciTech Connect

    Dinegar, R.H.

    1983-02-01

    The deflagration-to-detonation transition (DDT) can be made to occur in both PETN and HMX. The reaction is sensitive to the degree of subdivision and the compactness of the explosive in which the transition takes place. It apparently happens better with explosives of small specific surface loaded at low density. Experiments using thin metal shims between the donor and transition-explosive charges suggest that transition-explosive compression makes an important contribution to the DDT process.

  16. Detonating Failed Deflagration Model of Thermonuclear Supernovae. I. Explosion Dynamics

    NASA Astrophysics Data System (ADS)

    Plewa, Tomasz

    2007-03-01

    We present a detonating failed deflagration model of Type Ia supernovae. In this model, the thermonuclear explosion of a massive white dwarf follows an off-center deflagration. We conduct a survey of asymmetric ignition configurations initiated at various distances from the stellar center. In all cases studied, we find that only a small amount of stellar fuel is consumed during deflagration phase, no explosion is obtained, and the released energy is mostly wasted on expanding the progenitor. Products of the failed deflagration quickly reach the stellar surface, polluting and strongly disturbing it. These disturbances eventually evolve into small and isolated shock-dominated regions that are rich in fuel. We consider these regions as seeds capable of forming self-sustained detonations that, ultimately, result in the thermonuclear supernova explosion. Preliminary nucleosynthesis results indicate that the model supernova ejecta are typically composed of about 0.1-0.25 Msolar of silicon group elements and 0.9-1.2 Msolar of iron group elements and are essentially carbon-free. The ejecta have a composite morphology, are chemically stratified, and display a modest amount of intrinsic asymmetry. The innermost layers are slightly egg shaped with the axis ratio ~1.2-1.3 and dominated by the products of silicon burning. This central region is surrounded by a shell of silicon group elements. The outermost layers of ejecta are highly inhomogeneous and contain products of incomplete oxygen burning with only small admixture of unburned stellar material. The explosion energies are ~(1.3-1.5)×1051 ergs.

  17. Response of a Type III waste tank to hydrogen deflagration

    SciTech Connect

    Gong, Chung; Jerrell, J.W.; Pelfrey, J.R.; Yau, W.W.F.

    1992-05-01

    The type III waste tank is built with ASTM A516 Grade 70 steel shells in the shape of a torus with a central concrete core. The tank is buried underground and covered with a four foot thick reinforced concrete slab. The tank is enriched by 2.5 foot thick reinforced concrete wall. Between the tank surface and the wall there is a 2.5 foot annular space. The tank itself is called the ``primary liner.`` The interior surface of the concrete wall is line with steel plates, called the ``secondary liner.`` The base of the tank rests on a concrete mat. Underneath the mat the secondary liner extends from the wall to the central column surfaces. The bottom liner is attached to the reinforced concrete foundation. Based on the conditions that the tank is filled with liquid wastes to 50% of the design capacity, and that the accumulation of hydrogen becomes 20% inside its free board, the resulting deflagration would cause an overpressure of 100 psig in the tank [Wallace and Yau, 1986]. The task of this analysis is to simulate the ``hydrogen deflagration`` scenario in the Type III Waste Tank complex. During the deflagration, the stresses in the steel tank would be expected to exceed the elastic limit of the steel and the tank would then undergo large deformation. The concrete roof slab could be fractured by the expansion of the tank. The central concrete column would start to exhibit large deformation first. All the structural members in the system are expected to interact drastically during the deflagration.

  18. Response of a Type III waste tank to hydrogen deflagration

    SciTech Connect

    Gong, Chung; Jerrell, J.W.; Pelfrey, J.R.; Yau, W.W.F.

    1992-01-01

    The type III waste tank is built with ASTM A516 Grade 70 steel shells in the shape of a torus with a central concrete core. The tank is buried underground and covered with a four foot thick reinforced concrete slab. The tank is enriched by 2.5 foot thick reinforced concrete wall. Between the tank surface and the wall there is a 2.5 foot annular space. The tank itself is called the primary liner.'' The interior surface of the concrete wall is line with steel plates, called the secondary liner.'' The base of the tank rests on a concrete mat. Underneath the mat the secondary liner extends from the wall to the central column surfaces. The bottom liner is attached to the reinforced concrete foundation. Based on the conditions that the tank is filled with liquid wastes to 50% of the design capacity, and that the accumulation of hydrogen becomes 20% inside its free board, the resulting deflagration would cause an overpressure of 100 psig in the tank (Wallace and Yau, 1986). The task of this analysis is to simulate the hydrogen deflagration'' scenario in the Type III Waste Tank complex. During the deflagration, the stresses in the steel tank would be expected to exceed the elastic limit of the steel and the tank would then undergo large deformation. The concrete roof slab could be fractured by the expansion of the tank. The central concrete column would start to exhibit large deformation first. All the structural members in the system are expected to interact drastically during the deflagration.

  19. The deflagration stage of Chandrasekhar mass models for type Ia supernovae. I. Early evolution

    SciTech Connect

    Malone, C. M.; Woosley, S. E.; Dong, S.; Nonaka, A.; Almgren, A. S.; Bell, J. B.; Zingale, M.

    2014-02-10

    We present high-resolution, full-star simulations of the post-ignition phase of Type Ia supernovae using the compressible hydrodynamics code Castro. Initial conditions, including the turbulent velocity field and ignition site, are imported directly from a simulation of the last few hours of presupernova convection using a low Mach number code, Maestro. Adaptive mesh refinement allows the initial burning front to be modeled with an effective resolution of 36,864{sup 3} zones (136 m zone{sup –1}). The initial rise and expansion of the deflagration front are tracked until burning reaches the star's edge and the role of the background turbulence on the flame is investigated. The effect of artificially moving the ignition location closer to the star's center is explored. The degree to which turbulence affects the burning front decreases with increasing ignition radius since the buoyancy force is stronger at larger radii. Even central ignition—in the presence of a background convective flow field—is rapidly carried off-center as the flame is carried by the flow field. We compare our results to analytic models for burning thermals, and find that they reproduce the general trends of the bubble's size and mass, but underpredict the amount of buoyant acceleration due to simplifying assumptions of the bubble's properties. Overall, we find that the amount of mass that burns prior to flame break out is small, consistent with a gravitationally confined detonation' occurring at a later epoch, but additional burning will occur following breakout that may modify this conclusion.

  20. Muscle activation characteristics of the front leg during baseball swings with timing correction for sudden velocity decrease.

    PubMed

    Ohta, Yoichi; Nakamoto, Hiroki; Ishii, Yasumitsu; Ikudome, Sachi; Takahashi, Kyohei; Shima, Norihiro

    2014-01-01

    This study aimed to clarify the activation characteristics of the vastus lateralis muscle in the front leg during timing correction for a sudden decrease in the velocity of a target during baseball swings. Eleven male collegiate baseball players performed coincident timing tasks that comprised constant velocity of 8 m/s (unchanged) and a sudden decrease in velocity from 8 to 4 m/s (decreased velocity). Electromyography (EMG) revealed that the muscle activation was typically monophasic when responding unchanged conditions. The type of muscle activation during swings in response to decreased velocity condition was both monophasic and biphasic. When biphasic activation appeared in response to decreased velocity, the impact time and the time to peak EMG amplitude were significantly prolonged and the timing error was significantly smaller than that of monophasic activation. However, the EMG onset from the target start was consistent both monophasic and biphasic activation in response to conditions of decreased velocity. In addition, batters with small timing errors in response to decreased velocity were more likely to generate biphasic EMG activation. These findings indicated that timing correction for a sudden decrease in the velocity of an oncoming target is achieved by modifying the muscle activation characteristics of the vastus lateralis muscle of front leg from monophasic to biphasic to delay reaching peak muscle activation and thus prolong impact time. Therefore, the present findings suggests that the extent of timing errors in response to decreased velocity is influenced by the ability to correct muscle activation after its initiation rather than by delaying the initiation timing of muscle activation during baseball swings.

  1. Muscle activation characteristics of the front leg during baseball swings with timing correction for sudden velocity decrease.

    PubMed

    Ohta, Yoichi; Nakamoto, Hiroki; Ishii, Yasumitsu; Ikudome, Sachi; Takahashi, Kyohei; Shima, Norihiro

    2014-01-01

    This study aimed to clarify the activation characteristics of the vastus lateralis muscle in the front leg during timing correction for a sudden decrease in the velocity of a target during baseball swings. Eleven male collegiate baseball players performed coincident timing tasks that comprised constant velocity of 8 m/s (unchanged) and a sudden decrease in velocity from 8 to 4 m/s (decreased velocity). Electromyography (EMG) revealed that the muscle activation was typically monophasic when responding unchanged conditions. The type of muscle activation during swings in response to decreased velocity condition was both monophasic and biphasic. When biphasic activation appeared in response to decreased velocity, the impact time and the time to peak EMG amplitude were significantly prolonged and the timing error was significantly smaller than that of monophasic activation. However, the EMG onset from the target start was consistent both monophasic and biphasic activation in response to conditions of decreased velocity. In addition, batters with small timing errors in response to decreased velocity were more likely to generate biphasic EMG activation. These findings indicated that timing correction for a sudden decrease in the velocity of an oncoming target is achieved by modifying the muscle activation characteristics of the vastus lateralis muscle of front leg from monophasic to biphasic to delay reaching peak muscle activation and thus prolong impact time. Therefore, the present findings suggests that the extent of timing errors in response to decreased velocity is influenced by the ability to correct muscle activation after its initiation rather than by delaying the initiation timing of muscle activation during baseball swings. PMID:25918848

  2. Muscle Activation Characteristics of the Front Leg During Baseball Swings with Timing Correction for Sudden Velocity Decrease

    PubMed Central

    Ohta, Yoichi; Nakamoto, Hiroki; Ishii, Yasumitsu; Ikudome, Sachi; Takahashi, Kyohei; Shima, Norihiro

    2015-01-01

    This study aimed to clarify the activation characteristics of the vastus lateralis muscle in the front leg during timing correction for a sudden decrease in the velocity of a target during baseball swings. Eleven male collegiate baseball players performed coincident timing tasks that comprised constant velocity of 8 m/s (unchanged) and a sudden decrease in velocity from 8 to 4 m/s (decreased velocity). Electromyography (EMG) revealed that the muscle activation was typically monophasic when responding unchanged conditions. The type of muscle activation during swings in response to decreased velocity condition was both monophasic and biphasic. When biphasic activation appeared in response to decreased velocity, the impact time and the time to peak EMG amplitude were significantly prolonged and the timing error was significantly smaller than that of monophasic activation. However, the EMG onset from the target start was consistent both monophasic and biphasic activation in response to conditions of decreased velocity. In addition, batters with small timing errors in response to decreased velocity were more likely to generate biphasic EMG activation. These findings indicated that timing correction for a sudden decrease in the velocity of an oncoming target is achieved by modifying the muscle activation characteristics of the vastus lateralis muscle of front leg from monophasic to biphasic to delay reaching peak muscle activation and thus prolong impact time. Therefore, the present findings suggests that the extent of timing errors in response to decreased velocity is influenced by the ability to correct muscle activation after its initiation rather than by delaying the initiation timing of muscle activation during baseball swings. PMID:25918848

  3. Fronts, fish, and predators

    NASA Astrophysics Data System (ADS)

    Belkin, Igor M.; Hunt, George L.; Hazen, Elliott L.; Zamon, Jeannette E.; Schick, Robert S.; Prieto, Rui; Brodziak, Jon; Teo, Steven L. H.; Thorne, Lesley; Bailey, Helen; Itoh, Sachihiko; Munk, Peter; Musyl, Michael K.; Willis, Jay K.; Zhang, Wuchang

    2014-09-01

    Ocean fronts play a key role in marine ecosystems. Fronts shape oceanic landscapes and affect every trophic level across a wide range of spatio-temporal scales, from meters to thousands of kilometers, and from days to millions of years. At some fronts, there is an elevated rate of primary production, whereas at others, plankton is aggregated by advection and by the behavior of organisms moving against gradients in temperature, salinity, light irradiance, hydrostatic pressure and other physico-chemical and biological factors. Lower trophic level organisms - phytoplankton and zooplankton - that are aggregated in sufficient densities, attract organisms from higher trophic levels, from planktivorous schooling fish to squid, large piscivorous fish, seabirds and marine mammals. Many species have critical portions of their life stages or behaviors closely associated with fronts, including spawning, feeding, ontogenetic development, migrations, and other activities cued to frontal dynamics. At different life stages, an individual species or population might be linked to different fronts. The nature and strength of associations between fronts and biota depend on numerous factors such as the physical nature and spatio-temporal scales of the front and the species and their life stages in question. In other words, fronts support many different niches and micro/macro-habitats over a wide range of spatial and temporal scales.

  4. Deflagration-to-Detonation Transition in Unconfined Media

    NASA Astrophysics Data System (ADS)

    Poludnenko, Alexei; Gardiner, Thomas; Oran, Elaine

    2011-11-01

    Deflagration-to-detonation transition (DDT) can occur in environments ranging from experimental and industrial systems on Earth to astrophysical thermonuclear supernovae explosions. In recent years, substantial progress has been made in elucidating the nature of this process in confined systems with walls, obstacles, etc. It remains unclear, however, whether a subsonic turbulent flame in an unconfined environment can undergo a DDT. We present simulations of premixed flames in stoichiometric H2-air and CH4-air mixtures interacting with high-intensity turbulence. These calculations demonstrate the DDT in unconfined systems unassisted by shocks or obstacles. We discuss the mechanism of this process and its implications.

  5. Strategies for understanding the deflagration-to-detonation transition

    SciTech Connect

    Asay, B.W.

    1992-01-01

    The deflagration-to-detonation (DDT) phenomenon has been studied for many years. However, no comprehensive model of the DDT process is available. It is important to understand the mechanism by which an explosive will detonate when the source of ignition is a weak shock or flame, and to able to predict this response. We have identified several key areas of the DDT problem which need to be understood before any such prediction can be made, and have established a modest program to obtain a more fundamental understanding of the behavior of explosive under the conditions that can lead to DDT.

  6. Strategies for understanding the deflagration-to-detonation transition

    SciTech Connect

    Asay, B.W.

    1992-05-01

    The deflagration-to-detonation (DDT) phenomenon has been studied for many years. However, no comprehensive model of the DDT process is available. It is important to understand the mechanism by which an explosive will detonate when the source of ignition is a weak shock or flame, and to able to predict this response. We have identified several key areas of the DDT problem which need to be understood before any such prediction can be made, and have established a modest program to obtain a more fundamental understanding of the behavior of explosive under the conditions that can lead to DDT.

  7. Active faulting south of the Himalayan Front: Establishing a new plate boundary

    NASA Astrophysics Data System (ADS)

    Yeats, Robert S.; Thakur, V. C.

    2008-06-01

    New tectonic uplifts south of the Salt Range Thrust and Himalayan Front Thrust (HFT) represent an outward step of the plate boundary from the principal tectonic displacement zone into the Indo-Gangetic Plain. In Pakistan, the Lilla Anticline deforms fine-grained overbank deposits of the Jhelum River floodplain 15 km south of the Salt Range. The anticline is overpressured in Eocambrian non-marine strata. In northwest India south of Dehra Dun, the Piedmont Fault (PF) lies 15 km south of the HFT. Coalescing fans derived from the Himalaya form a piedmont (Old Piedmont Zone) 15-20 km wide east of the Yamuna River. This zone is uplifted as much as 15-20 m near the PF, and bedding is tilted 5-7° northeast. Holocene thermoluminescence-optically-stimulated luminescence dates for sediments in the Old Piedmont Zone suggest that the uplift rate might be as high as several mm/a. The Old Piedmont Zone is traced northwest 200 km and southeast another 200 km to the Nepal border. These structures, analogous to protothrusts in subduction zones, indicate that the Himalayan plate boundary is not a single structure but a series of structures across strike, including reactivated parts of the Main Boundary Thrust north of the range front, the HFT sensu stricto, and stepout structures on the Indo-Gangetic Plain. Displacement rates on all these structures must be added to determine the local India-Himalaya convergence rate.

  8. Mesoscale modeling of deflagration-induced deconsolidation in polymer-bonded explosives

    NASA Astrophysics Data System (ADS)

    Springer, Harry Keo; Glascoe, Elizabeth A.; Reaugh, John E.; Kercher, James; Maienschein, Jon L.

    2012-03-01

    Initially undamaged polymer-bonded explosives can transition from conductive burning to more violent convective burning via rapid deconsolidation at higher pressures. The pressure-dependent infiltration of cracks and pores, i.e., damage, by product gases at the burn-front is a key step in the transition to convective burning. However, the relative influence of pre-existing damage and the evolution of deflagration-induced damage during the transition to convective burning is not well understood. The objective of this study is to investigate the role of microstructure and initial pressurization on deconsolidation. We performed simulations using the multi-physics hydrocode, ALE3D. HMX-Viton A served as our model explosive. A Prout-Tompkins chemical kinetic model, Vielle's Law pressure-dependent burning, Gruneisen equation-of-state, and simplified strength model were used for the HMX. The propensity for deconsolidation increased with increasing defect size and decreasing initial pressurization, as measured by the increase in burning surface area. These studies are important because they enable the development of continuum-scale damage models and the design of inherently safer explosives.

  9. MESOSCALE MODELING OF DEFLAGRATION-INDUCED DECONSOLIDATION IN POLYMER-BONDED EXPLOSIVES

    SciTech Connect

    Springer, H K; Glascoe, E A; Reaugh, J E; Kercher, J R; Maienschein, J L

    2011-08-01

    Initially undamaged polymer-bonded explosives can transition from conductive burning to more violent convective burning via rapid deconsolidation at higher pressures. The pressure-dependent infiltration of cracks and pores, i.e., damage, by product gases at the burn-front is a key step in the transition to convective burning. However, the relative influence of pre-existing damage and the evolution of deflagration-induced damage during the transition to convective burning is not well understood. The objective of this study is to investigate the role of microstructure and initial pressurization on deconsolidation. We performed simulations using the multi-physics hydrocode, ALE3D. HMX-Viton A served as our model explosive. A Prout-Tompkins chemical kinetic model, Vielle's Law pressure-dependent burning, Gruneisen equation-of-state, and simplified strength model were used for the HMX. The propensity for deconsolidation increased with increasing defect size and decreasing initial pressurization, as measured by the increase in burning surface area. These studies are important because they enable the development of continuum-scale damage models and the design of inherently safer explosives.

  10. Deflagration-to-detonation transition project. Quarterly report, December 1979-February 1980

    SciTech Connect

    Lieberman, M.L.

    1980-09-01

    Progress in a project on deflagration-to-detonation transition (DDT) is reported. The activities of this project pertain primarily to the development of small, safe, low-voltage, hot-wire detonators. Its major goals are: the formulation of a modeling capability for DDT of the explosive 2-(5-cyanotetrazolato)pentaamminecobalt (III) perchlorate (CP); the development of improved DDT materials; the establishment of a data base for corrosion, compatibility, and reliability of CP-loaded detonators; and the design and development of advanced DDT components. Information is included on materials development, component development, and compatibility studies encompassing the thermal and chemical stability of CP in contact with the component materials. (LCL)

  11. Potential VOC Deflagrations in a Vented TRU Drum

    SciTech Connect

    Mukesh, GUPTA

    2005-04-07

    The objective of the analysis is to examine the potential for lid ejection from a vented transuranic (TRU) waste drum due to pressure buildup caused by the deflagration of hydrogen and volatile organic compounds (VOCs) inside the drum. In this analysis, the AICC pressure for a stoichiometric mixture of VOCs is calculated and then compared against the experimental peak pressure of stoichiometric combustion of propane and hexane in a combustion chamber. The experimental peak pressures of propane and hexane are about 12 percent lower than the calculated AICC pressure. Additional losses in the drum are calculated due to venting of the gases, drum bulging, waste compaction, and heat losses from the presence of waste in the drum. After accounting for these losses, the final pressures are compared to the minimum observed pressure that ejects the lid from a TRU drum. The ejection pressure of 105 psig is derived from data that was recorded for a series of tests where hydrogen-air mixtures were ignited inside sealed TRU drums. Since the calculated pressures are below the minimum lid ejection pressure, none of the VOCs and the hydrogen (up to 4 percent) mixtures present in the TRU waste drum is expected to cause lid ejection if ignited. The analysis of potential VOC deflagrations in a vented TRU drum can be applied across the DOE-Complex since TRU waste is stored in drums throughout the complex.

  12. Measuring seeing with a Shack-Hartmann wave-front sensor during an active-optics experiment.

    PubMed

    Zhang, Yong; Yang, Dehua; Cui, Xiangqun

    2004-02-01

    We describe the measurement of atmospheric enclosure seeing along a 120-m light path by use of a Shack-Hartmann wave-front sensor (S-H WFS) for the first time to our knowledge in the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) outdoor active-optics experiment system, based on the differential image motion method and a S-H WFS. Seeing estimates that were gained with the S-H WFS were analyzed and found to be in close agreement with the actual seeing conditions, the estimates of refractive-index structure constant, and the thin-mirror active optics results, which usually include the shape sensing precision and the active correction precision of the experimental system. Finally, some countermeasures against poor seeing conditions were considered and adopted.

  13. Small-scale deflagration cylinder test with velocimetry wall-motion diagnostics

    SciTech Connect

    Hooks, Daniel E; Hill, Larry G; Pierce, Timothy H

    2010-01-01

    Predicting the likelihood and effects of outcomes resultant from thermal initiation of explosives remains a significant challenge. For certain explosive formulations, the general outcome can be broadly predicted given knowledge of certain conditions. However, there remain unexplained violent events, and increased statistical understanding of outcomes as a function of many variables, or 'violence categorization,' is needed. Additionally, the development of an equation of state equivalent for deflagration would be very useful in predicting possible detailed event consequences using traditional hydrodynamic detonation moders. For violence categorization, it is desirable that testing be efficient, such that it is possible to statistically define outcomes reliant on the processes of initiation of deflagration, steady state deflagration, and deflagration to detonation transitions. If the test simultaneously acquires information to inform models of violent deflagration events, overall predictive capabilities for event likelihood and consequence might improve remarkably. In this paper we describe an economical scaled deflagration cylinder test. The cyclotetramethylene tetranitramine (HMX) based explosive formu1lation PBX 9501 was tested using different temperature profiles in a thick-walled copper cylindrical confiner. This test is a scaled version of a recently demonstrated deflagration cylinder test, and is similar to several other thermal explosion tests. The primary difference is the passive velocimetry diagnostic, which enables measurement of confinement vessel wall velocities at failure, regardless of the timing and location of ignition.

  14. Hydrodynamic Instabilities of Acid-Base Reaction Fronts: Active Role of a Color Indicator

    NASA Astrophysics Data System (ADS)

    Riolfo, L. A.; Almarcha, C.; Trevelyan, P. M. J.; El Hasi, C.; Zalts, A.; D'Onofrio, A.; de Wit, A.

    2010-11-01

    Chemical reactions are able to trigger hydrodynamic flows by, for example changing the density of the solutions across the reactive interfaces. In this work we present an experimental and theoretical study of the buoyancy-driven hydrodynamic instabilities that can occur when two miscible reactive solutions of an acid-base system are put in contact in the gravity field. We compare situations where a hydrochloric acid aqueous solution is put on top of a sodium hydroxide aqueous solution with or without a color indicator (Bromocresol Green). We also analyze the situation where a hydrochloric acid is put on top of an aqueous solution of a color indicator without any base. We show that the patterns observed and the instabilities taking place strongly depend on the presence of a color indicator. Using a reaction-diffusion model for the concentrations of all species (including the color indicator) we analyze the different possible sources of destabilization of the acid-base front and explain the various instabilities observed in each experimental system.

  15. In-use measurement of the activity, fuel use, and emissions of front-loader refuse trucks

    NASA Astrophysics Data System (ADS)

    Sandhu, Gurdas S.; Frey, H. Christopher; Bartelt-Hunt, Shannon; Jones, Elizabeth

    2014-08-01

    Field measurements were made for six front-loader refuse trucks for over 560 miles (901 km) and 47 h of operation using a portable emissions measurement system, electronic control unit data logger, and global positioning system receivers. Daily activity, fuel use rates, and emission rates are quantified in terms of operating mode bins defined by the U.S. Environmental Protection Agency for the MOVES emission factor model. On average, 44 (±4) percent of time was spent at idle, 5 (±1) percent braking or decelerating, 11 (±2) percent coasting, 23 (±3) percent cruising or accelerating at low speed (up to 25 mph, 40.2 kmph), 10 (±2) percent cruising or accelerating at moderate speed (25-50 mph, 40.2 to 80.4 kmph), and 7 (±3) percent cruising or accelerating at high speed (50 mph, 80.4 kmph or higher). Fuel use and emission rates varied among operating modes by factors of 6-24. The estimated daily activity cycle average fuel economy ranges from 2.3 to 3.2 mpg (0.98-1.4 kmpl). The PM emission rates for trucks with diesel particulate filters are 98 percent lower compared to those without. Variation in truck weight lead to differences in average fuel use and emission rates of 20 percent or less, except for hydrocarbons. The variation in the empirically-based daily activity cycle average rates were highly correlated with MOVES estimates, except for hydrocarbons. The data collected here are useful for quantifying daily activity specific to front-loaders, and for developing fuel use and emission estimates and models for this type of vehicle.

  16. Engineering models of deflagration-to-detonation transition

    SciTech Connect

    Bdzil, J.B.; Son, S.F.

    1995-07-01

    For the past two years, Los Alamos has supported research into the deflagration-to-detonation transition (DDT) in damaged energetic materials as part of the explosives safety program. This program supported both a theory/modeling group and an experimentation group. The goal of the theory/modeling group was to examine the various modeling structures (one-phase models, two-phase models, etc.) and select from these a structure suitable to model accidental initiation of detonation in damaged explosives. The experimental data on low-velocity piston supported DDT in granular explosive was to serve as a test bed to help in the selection process. Three theoretical models have been examined in the course of this study: (1) the Baer-Nunziato (BN) model, (2) the Stewart-Prasad-Asay (SPA) model and (3) the Bdzil-Kapila-Stewart model. Here we describe these models, discuss their properties, and compare their features.

  17. Deflagration rates of secondary explosives under static MPa - GPa pressure

    NASA Astrophysics Data System (ADS)

    Zaug, Joseph; Young, Christopher; Glascoe, Elizabeth; Maienschein, Jon; Hart, Elaine; Long, Gregory; Black, Collin; Sykora, Gregory; Wardell, Jeffrey

    2009-06-01

    We discuss our measurements of the chemical reaction propagation rate (RPR) as a function of pressure using diamond anvil cell (DAC) and strand burner technologies. Materials investigated include HMX and RDX crystalline powders, LX-04 (85% HMX and 15% Viton A), and Comp B (63% RDX, 36% TNT, 1% wax). The anomalous correspondence between crystal structure, including in some instances isostructural phase transitions, on pressure dependant RPRs of TATB, HMX, Nitromethane, and Viton are elucidated using micro -IR and -Raman spectroscopies. The contrast between DAC GPa and strand burner MPa regime measurements yields insight into explosive material burn phenomena. Here we highlight pressure dependent physicochemical mechanisms that appear to affect the deflagration rate of precompressed energetic materials.

  18. Deflagration-to-detonation transition in granular HMX

    SciTech Connect

    Campbell, A.W.

    1980-01-01

    Experimental studies of the deflagration-to-detonation transition (DDT) in chemical explosives, specifically, granular HMX, are reviewed. The picture of the DDT process as presented here results from an attempt to incorporate common experimental observations which have heretofore been puzzling. It differs from that presented by G.B. Kistiakowsky in that the role of convective combustion is terminated and mechanical processes are postulated as the means of continuing the reaction buildup until shock waves are formed. In order to validate this picture it will be necessary both to review the experimental literature for observations which may not be reconcilable with it, and to subject each step in the proposed DDT process to detailed scrutiny. (LCL)

  19. Performance Impact of Deflagration to Detonation Transition Enhancing Obstacles

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.; Schauer, Frederick; Hopper, David

    2012-01-01

    A sub-model is developed to account for the drag and heat transfer enhancement resulting from deflagration-to-detonation (DDT) inducing obstacles commonly used in pulse detonation engines (PDE). The sub-model is incorporated as a source term in a time-accurate, quasi-onedimensional, CFD-based PDE simulation. The simulation and sub-model are then validated through comparison with a particular experiment in which limited DDT obstacle parameters were varied. The simulation is then used to examine the relative contributions from drag and heat transfer to the reduced thrust which is observed. It is found that heat transfer is far more significant than aerodynamic drag in this particular experiment.

  20. DEFLAGRATION RATES OF SECONDARY EXPLOSIVES UNDER STATIC MPA - GPA PRESSURE

    SciTech Connect

    Zaug, J; Young, C; Long, G; Maienschein, J; Glascoe, E; Hansen, D; Wardell, J; Black, C; Sykora, G

    2009-07-30

    We provide measurements of the chemical reaction propagation rate (RPR) as a function of pressure using diamond anvil cell (DAC) and strand burner technologies. Materials investigated include HMX and RDX crystalline powders, LX-04 (85% HMX and 15% Viton A), and Composition B (63% RDX, 36% TNT, 1% wax). The anomalous correspondence between crystal structure, including in some instances isostructural phase transitions, on pressure dependent RPRs of HMX and RDX are correlated to confocal micro-Raman spectroscopic results. The contrast between DAC GPa and strand burner MPa regime measurements yield insight into explosive material burn phenomena. Here we highlight pressure dependent physicochemical mechanisms that appear to affect the deflagration rate of precompressed energetic materials.

  1. Deflagration studies on waste Tank 101-SY: Test plan

    SciTech Connect

    Cashdollar, K.L.; Zlochower, I.A.; Hertzberg, M.

    1991-07-01

    Waste slurries produced during the recovery of plutonium and uranium from irradiated fuel are stored in underground storage tanks. While a variety of waste types have been generated, of particular concern are the wastes stored in Tank 101-SY. A slurry growth-gas evolution cycle has been observed since 1981. The waste consists of a thick slurry, consisting of a solution high in NaOH, NaNO{sub 3}, NaAlO{sub 2}, dissolved organic complexants (EDTA, HEDTA, NTA, and degradation products), other salts (sulfates and phosphates), and radionuclides (primarily cesium and strontium). During a gas release the major gaseous species identified include: hydrogen and nitrous oxide (N{sub 2}O). Significant amounts of nitrogen may also be present. Traces of ammonia, carbon oxides, and other nitrogen oxides are also detected. Air and water vapor are also present in the tank vapor space. The purpose of the deflagration study is to determine risks of the hydrogen, nitrous oxide, nitrogen, and oxygen system. To be determined are pressure and temperature as a function of composition of reacting gases and the concentration of gases before and after the combustion event. Analyses of gases after the combustion event will be restricted to those tests that had an initial concentration of {le}8% hydrogen. This information will be used to evaluate safety issues related to periodic slurry growth and flammable gas releases from Tank 101-SY. the conditions to be evaluated will simulate gases in the vapor space above the salt cake as well as gases that potentially are trapped in pockets within/under the waste. The deflagration study will relate experimental laboratory results to conditions in the existing tanks.

  2. Comparative analysis of active drag using the MAD system and an assisted towing method in front crawl swimming.

    PubMed

    Formosa, Daniel P; Toussaint, Huub M; Mason, Bruce R; Burkett, Brendan

    2012-12-01

    The measurement of active drag in swimming is a biomechanical challenge. This research compared two systems: (i) measuring active drag (MAD) and (ii) assisted towing method (ATM). Nine intermediate-level swimmers (19.7 ± 4.4 years) completed front crawl trials with both systems during one session. The mean (95% confidence interval) active drag for the two systems, at the same maximum speed of 1.68 m/s (1.40-1.87 m/s), was significantly different (p = .002) with a 55% variation in magnitude. The mean active drag was 82.3 N (74.0-90.6 N) for the MAD system and 148.3 N (127.5-169.1 N) for the ATM system. These differences were attributed to variations in swimming style within each measurement system. The inability to measure the early catch phase and kick, along with the fixed length and depth hand place requirement within the MAD system generated a different swimming technique, when compared with the more natural free swimming ATM protocol. A benefit of the MAD system was the measurement of active drag at various speeds. Conversely, the fixed towing speed of the ATM system allowed a natural self-selected arm stroke (plus kick) and the generation of an instantaneous force-time profile.

  3. Flammable gas deflagration consequence calculations for the tankwaste remediation system basis for interim operation

    SciTech Connect

    Van Vleet, R.J., Westinghouse Hanford

    1996-09-23

    This paper calculates the radiological dose consequences and the toxic exposures for deflagration accidents at various Tank Waste Remediation System facilities. These will be used in support of the Tank Waste Remediation System Basis for Interim Operation.

  4. Steady deflagration of HMX with simple kinetics: A gas phase chain reaction model

    SciTech Connect

    Ward, M.J.; Brewster, M.Q.; Son, S.F.

    1998-08-01

    A new approach is presented for modeling steady combustion of energetic solids, in particular HMX. A simplified, global, gas phase chain reaction kinetic mechanism is employed. Specifically, a zero-order, high activation energy thermal decomposition initiation reaction in the condensed phase followed by a second-order, low activation energy chain reaction in the gas phase is assumed. A closed-form solution is obtained, which is based on the activation energy asymptotics analysis of Lengelle in the condensed phase and the assumption of zero activation energy in the gas phase. Comparisons between the model and a variety of experimental observations over a wide range of pressures and initial temperatures are presented and demonstrate the validity of the approach. The model provides excellent agreement with burning rate data (including sensitivity to pressure and initial temperature) and temperature profile data (in particular the gas phase). This suggests that in the realm of simplified, approximate kinetics modeling of energetic solids, the low gas phase activation energy limit is a more appropriate model than the classical high activation energy limit or heuristic flame sheet models. The model also indicates that the condensed phase reaction zone plays an important role in determining the deflagration rate of HMX, underscoring the need for better understanding of the chemistry in this zone.

  5. Adenosine: front and center in linking nutrition and metabolism to neuronal activity

    PubMed Central

    Greene, Robert W.

    2011-01-01

    Many individuals with epilepsy benefit from consuming a ketogenic diet, which is similar to the more commonly known Atkins diet. The underlying molecular reason for this has not been determined. However, in this issue of the JCI, Masino et al. have elucidated the mechanism responsible for the antiepileptic effects of the ketogenic diet in mice. The diet is shown to decrease expression of the enzyme adenosine kinase (Adk), which is responsible for clearing the endogenous antiepileptic agent adenosine (Ado) from the extracellular CNS space. Decreased expression of Adk results in increased extracellular Ado, activation of inhibitory Ado A1 receptors, and decreased seizure generation, the desired therapeutic effect. The authors’ work serves to emphasize the importance of controlling Adk expression, not only as the mechanism of action of the ketogenic diet, but also as a potential target of future therapies. PMID:21701073

  6. A hybrid active optical system for wave front preservation and variable focal distance

    NASA Astrophysics Data System (ADS)

    Cocco, Daniele; Bortoletto, Gianluca; Sergo, Rudi; Sostero, Giovanni; Cudin, Ivan

    2010-05-01

    A new Free Electron Laser (FEL) user facility, named FERMI@Elettra, is under construction at Sincrotrone Trieste (Italy). It is based on a seeded scheme to provide an almost perfect transform limited beam with fully spatial coherence. The wavelength range will be 100-3 nm with fundamental and will go down to 1 nm by using higher harmonics. It will be operative by autumn 2010. The exceptional characteristics of the source must be preserved until the experimental chamber, where a large set of different experiments will be performed. This condition poses very tight requirements to the design of the beamlines and, in particular, to the focusing optics. Here we will present the active optics system developed for Fermi but intended to be used also on the Elettra beamlines. It is based on the adoption of a hybrid active system composed by UHV compatible stepping motors and piezo ceramic actuators. These mirrors are supposed to provide focal distances from 0.8 m to infinity with an angle of incidence up to a few degrees and residual shape errors below 10 or 5 nm (depending on the wavelength). In this way it is possible to work with an almost perfect focused coherent beam as well as with a uniform defocused or unfocused image. The metrology results on the first 400 mm long mirror will be shown and the actuator system described. A strain gauge assembly, calibrated in Elettra by means of a long trace profiler, and controlled by a custom made electronic system developed by us, is used as a direct in situ encoder.

  7. Manufacture and deflagration of an atomic hydrogen propellant

    NASA Technical Reports Server (NTRS)

    Rosen, G.

    1974-01-01

    It is observed that the use of very low temperatures (in the range from 0.1 to 1.5 K) produced by advanced cryogenic apparatus and the use of very strong magnetic fields (in the range from 50 to 100 kG) produced by superconducting magnets can yield a significant improvement in the atomic hydrogen trapping effectiveness of an H2 matrix. The use of a radioactive beta-ray emiter isotope may yield H-H2 propellants (with a specific impulse of about 740 sec) by secondary electron impact dissociations of H2 in an impregnated matrix maintained below 1 K in a strong magnetic field. Another method for manufacturing an H-H2 propellant involves bombardment of supercooled solid H2 with a cyclotron-produced beam of 10-MeV hydrogen atoms. The matrix-isolated atomic hydrogen must be used directly without prior melting as a solid propellant, and an analysis of the steady deflagration is presented.

  8. Integrated chassis control of active front steering and yaw stability control based on improved inverse nyquist array method.

    PubMed

    Zhu, Bing; Chen, Yizhou; Zhao, Jian

    2014-01-01

    An integrated chassis control (ICC) system with active front steering (AFS) and yaw stability control (YSC) is introduced in this paper. The proposed ICC algorithm uses the improved Inverse Nyquist Array (INA) method based on a 2-degree-of-freedom (DOF) planar vehicle reference model to decouple the plant dynamics under different frequency bands, and the change of velocity and cornering stiffness were considered to calculate the analytical solution in the precompensator design so that the INA based algorithm runs well and fast on the nonlinear vehicle system. The stability of the system is guaranteed by dynamic compensator together with a proposed PI feedback controller. After the response analysis of the system on frequency domain and time domain, simulations under step steering maneuver were carried out using a 2-DOF vehicle model and a 14-DOF vehicle model by Matlab/Simulink. The results show that the system is decoupled and the vehicle handling and stability performance are significantly improved by the proposed method.

  9. Integrated Chassis Control of Active Front Steering and Yaw Stability Control Based on Improved Inverse Nyquist Array Method

    PubMed Central

    2014-01-01

    An integrated chassis control (ICC) system with active front steering (AFS) and yaw stability control (YSC) is introduced in this paper. The proposed ICC algorithm uses the improved Inverse Nyquist Array (INA) method based on a 2-degree-of-freedom (DOF) planar vehicle reference model to decouple the plant dynamics under different frequency bands, and the change of velocity and cornering stiffness were considered to calculate the analytical solution in the precompensator design so that the INA based algorithm runs well and fast on the nonlinear vehicle system. The stability of the system is guaranteed by dynamic compensator together with a proposed PI feedback controller. After the response analysis of the system on frequency domain and time domain, simulations under step steering maneuver were carried out using a 2-DOF vehicle model and a 14-DOF vehicle model by Matlab/Simulink. The results show that the system is decoupled and the vehicle handling and stability performance are significantly improved by the proposed method. PMID:24782676

  10. Three-dimensional pure deflagration models with nucleosynthesis and synthetic observables for Type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Fink, Michael; Kromer, Markus; Seitenzahl, Ivo R.; Ciaraldi-Schoolmann, Franco; Röpke, Friedrich K.; Sim, Stuart A.; Pakmor, Rüdiger; Ruiter, Ashley J.; Hillebrandt, Wolfgang

    2014-02-01

    We investigate whether pure deflagration models of Chandrasekhar-mass carbon-oxygen white dwarf stars can account for one or more subclass of the observed population of Type Ia supernova (SN Ia) explosions. We compute a set of 3D full-star hydrodynamic explosion models, in which the deflagration strength is parametrized using the multispot ignition approach. For each model, we calculate detailed nucleosynthesis yields in a post-processing step with a 384 nuclide nuclear network. We also compute synthetic observables with our 3D Monte Carlo radiative transfer code for comparison with observations. For weak and intermediate deflagration strengths (energy release Enuc ≲ 1.1 × 1051 erg), we find that the explosion leaves behind a bound remnant enriched with 3 to 10 per cent (by mass) of deflagration ashes. However, we do not obtain the large kick velocities recently reported in the literature. We find that weak deflagrations with Enuc ˜ 0.5 × 1051 erg fit well both the light curves and spectra of 2002cx-like SNe Ia, and models with even lower explosion energies could explain some of the fainter members of this subclass. By comparing our synthetic observables with the properties of SNe Ia, we can exclude the brightest, most vigorously ignited models as candidates for any observed class of SN Ia: their B - V colours deviate significantly from both normal and 2002cx-like SNe Ia and they are too bright to be candidates for other subclasses.

  11. Computer Simulations to Study the High-Pressure Deflagration of HMX

    NASA Astrophysics Data System (ADS)

    Reaugh, John E.

    2004-07-01

    The accepted micro-mechanical picture of the build-up of detonation in solid explosives from a shock is that imperfections are a source of hot spots. The hot spots ignite and link up in the reaction zone by high-pressure deflagration. Although the deflagration is subsonic, there are so many ignition sites that the pressure build-up is rapid enough to strengthen the initial shock. Quantitative advances in this research require a detailed understanding of deflagration at the high pressure, 1 to 50 GPa, which is present in the reaction zone. We performed direct numerical simulations of high-pressure deflagrations using a simplified global (3-reaction) chemical kinetics scheme. We used ALE-3D to calculate coupled chemical reactions, heat transfer, and hydrodynamic flow for finite-difference zones comprising a mixture of reactants and products at pressure and temperature equilibrium. The speed of isobaric deflagrations depends on the pressure and initial temperature. We show how this dependence changes with kinetic parameters, including the order of the last reaction step and the heat of formation of the species formed, relative to the reactant.

  12. Computer Simulations to Study the High-Pressure Deflagration of HMX

    SciTech Connect

    Reaugh, J E

    2003-07-11

    The accepted micro-mechanical picture of the build-up of detonation in solid explosives from a shock is that imperfections are a source of hot spots. The hot spots ignite and link up in the reaction zone by high-pressure deflagration. Although the deflagration is subsonic, there are so many ignition sites that the pressure build-up is rapid enough to strengthen the initial shock. Quantitative advances in this research require a detailed understanding of deflagration at the high pressure, 1 to 50 GPa, which is present in the reaction zone. We performed direct numerical simulations of high-pressure deflagrations using a simplified global (3-reaction) chemical kinetics scheme. We used ALE-3D to calculate coupled chemical reactions, heat transfer, and hydrodynamic flow for finite-difference zones comprising a mixture of reactants and products at pressure and temperature equilibrium. The speed of isobaric deflagrations depends on the pressure and initial temperature. We show how this dependence changes with kinetic parameters, including the order of the last reaction step and the heat of formation of the species formed, relative to the reactant.

  13. Two-Dimensional Failure Waves and Ignition Fronts in Premixed Combustion

    NASA Technical Reports Server (NTRS)

    Vedarajan, T. G.; Buckmaster J.; Ronney, P.

    1998-01-01

    This paper is a continuation of our work on edge-flames in premixed combustion. An edge-flame is a two-dimensional structure constructed from a one-dimensional configuration that has two stable solutions (bistable equilibrium). Edge-flames can display wavelike behavior, advancing as ignition fronts or retreating as failure waves. Here we consider two one-dimensional configurations: twin deflagrations in a straining flow generated by the counterflow of fresh streams of mixture: and a single deflagration subject to radiation losses. The edge-flames constructed from the first configuration have positive or negative speeds, according to the value of the strain rate. But our numerical solutions strongly suggest that only positive speeds (corresponding to ignition fronts) can exist for the second configuration. We show that this phenomenon can also occur in diffusion flames when the Lewis numbers are small. And we discuss the asymptotics of the one-dimensional twin deflagration configuration. an overlooked problem from the 70s.

  14. Neotectonics and structure of the Himalayan deformation front in the Kashmir Himalaya, India: Implication in defining what controls a blind thrust front in an active fold-thrust belt

    NASA Astrophysics Data System (ADS)

    Gavillot, Y. G.; Meigs, A.; Yule, J. D.; Rittenour, T. M.; Malik, M. O. A.

    2014-12-01

    Active tectonics of a deformation front constrains the kinematic evolution and structural interaction between the fold-thrust belt and most-recently accreted foreland basin. In Kashmir, the Himalayan Frontal thrust (HFT) is blind, characterized by a broad fold, the Suruin-Mastargh anticline (SMA), and displays no emergent faults cutting either limb. A lack of knowledge of the rate of shortening and structural framework of the SMA hampers quantifying the earthquake potential for the deformation front. Our study utilized the geomorphic expression of dated deformed terraces on the Ujh River in Kashmir. Six terraces are recognized, and three yield OSL ages of 53 ka, 33 ka, and 0.4 ka. Vector fold restoration of long terrace profiles indicates a deformation pattern characterized by regional uplift across the anticlinal axis and back-limb, and by fold limb rotation on the forelimb. Differential uplift across the fold trace suggests localized deformation. Dip data and stratigraphic thicknesses suggest that a duplex structure is emplaced at depth along the basal décollement, folding the overlying roof thrust and Siwalik-Muree strata into a detachment-like fold. Localized faulting at the fold axis explains the asymmetrical fold geometry. Folding of the oldest dated terrace, suggest that rock uplift rates across the SMA range between 2.0-1.8 mm/yr. Assuming a 25° dipping ramp for the blind structure on the basis of dip data constraints, the shortening rate across the SMA ranges between 4.4-3.8 mm/yr since ~53 ka. Of that rate, ~1 mm/yr is likely absorbed by minor faulting in the near field of the fold axis. Given that Himalaya-India convergence is ~18.8-11 mm/yr, internal faults north of the deformation front, such as the Riasi thrust absorbs more of the Himalayan shortening than does the HFT in Kashmir. We attribute a non-emergent thrust at the deformation front to reflect deformation controlled by pre-existing basin architecture in Kashmir, in which the thick succession

  15. Cloud Front

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02171 Cloud Front

    These clouds formed in the south polar region. The faintness of the cloud system likely indicates that these are mainly ice clouds, with relatively little dust content.

    Image information: VIS instrument. Latitude -86.7N, Longitude 212.3E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  16. A comparison of deflagration rates at elevated pressures and temperatures with thermal explosion results

    NASA Astrophysics Data System (ADS)

    Glascoe, Elizabeth A.; Springer, Harry Keo; Tringe, Joseph; Maienschein, Jon L.

    2012-03-01

    The deflagration rate of HMX-based explosives has previously been correlated with the violence of thermal explosion experiments. In particular, HMX-based materials that experience deconsolidative burning at elevated pressures (i.e. P = 200 - 600 MPa) also produce significantly more violent thermal explosions. We now report deflagration rates at elevated temperatures (i.e. T = 150 - 180C) and moderate pressures (i.e. P = 10 - 100 MPa). These conditions more closely mimic the pressures and temperatures of an explosive shortly after ignition of a thermal explosion. Here, we discuss the deflagration rates of HMX-based explosives at elevated temperatures and their usefulness to predict the thermal explosion violence of the same materials.

  17. Microscopic simulations of supersonic and subsonic exothermic chemical wave fronts and transition to detonation.

    PubMed

    Lemarchand, A; Nowakowski, B; Dumazer, G; Antoine, C

    2011-01-21

    We perform microscopic simulations using the direct simulation Monte Carlo approach to an exothermic chemical wave front of Fisher-Kolmogorov, Petrovsky, Piskunov-type in a one-dimensional gaseous medium. The results confirm the existence of a transition from a weak detonation or deflagration to a Chapman-Jouguet detonation wave, that we already investigated at the macroscopic scale [G. Dumazer et al., Phys. Rev. E 78, 016309 (2008)]. In the domain of weak detonation or deflagration, the discrepancy between the propagation speeds deduced from the simulations and the macroscopic balance equations of hydrodynamics is explained by two microscopic effects, the discretization of the variables, known as cutoff effect, and the departure from local equilibrium. Remarkably, the propagation speed of a Chapman-Jouguet detonation wave is not sensitive to these perturbations of microscopic origin. PMID:21261344

  18. Microscopic simulations of supersonic and subsonic exothermic chemical wave fronts and transition to detonation.

    PubMed

    Lemarchand, A; Nowakowski, B; Dumazer, G; Antoine, C

    2011-01-21

    We perform microscopic simulations using the direct simulation Monte Carlo approach to an exothermic chemical wave front of Fisher-Kolmogorov, Petrovsky, Piskunov-type in a one-dimensional gaseous medium. The results confirm the existence of a transition from a weak detonation or deflagration to a Chapman-Jouguet detonation wave, that we already investigated at the macroscopic scale [G. Dumazer et al., Phys. Rev. E 78, 016309 (2008)]. In the domain of weak detonation or deflagration, the discrepancy between the propagation speeds deduced from the simulations and the macroscopic balance equations of hydrodynamics is explained by two microscopic effects, the discretization of the variables, known as cutoff effect, and the departure from local equilibrium. Remarkably, the propagation speed of a Chapman-Jouguet detonation wave is not sensitive to these perturbations of microscopic origin.

  19. Visualization of deflagration-to-detonation transitions in a channel with repeated obstacles using a hydrogen-oxygen mixture

    NASA Astrophysics Data System (ADS)

    Maeda, S.; Minami, S.; Okamoto, D.; Obara, T.

    2016-09-01

    The deflagration-to-detonation transition in a 100 mm square cross-section channel was investigated for a highly reactive stoichiometric hydrogen oxygen mixture at 70 kPa. Obstacles of 5 mm width and 5, 10, and 15 mm heights were equally spaced 60 mm apart at the bottom of the channel. The phenomenon was investigated primarily by time-resolved schlieren visualization from two orthogonal directions using a high-speed video camera. The detonation transition occurred over a remarkably short distance within only three or four repeated obstacles. The global flame speed just before the detonation transition was well below the sound speed of the combustion products and did not reach the sound speed of the initial unreacted gas for tests with an obstacle height of 5 and 10 mm. These results indicate that a detonation transition does not always require global flame acceleration beyond the speed of sound for highly reactive combustible mixtures. A possible mechanism for this detonation initiation was the mixing of the unreacted and reacted gas in the vicinity of the flame front convoluted by the vortex present behind each obstacle, and the formation of a hot spot by the shock wave. The final onset of the detonation originated from the unreacted gas pocket, which was surrounded by the obstacle downstream face and the channel wall.

  20. Visualization of deflagration-to-detonation transitions in a channel with repeated obstacles using a hydrogen-oxygen mixture

    NASA Astrophysics Data System (ADS)

    Maeda, S.; Minami, S.; Okamoto, D.; Obara, T.

    2016-05-01

    The deflagration-to-detonation transition in a 100 mm square cross-section channel was investigated for a highly reactive stoichiometric hydrogen oxygen mixture at 70 kPa. Obstacles of 5 mm width and 5, 10, and 15 mm heights were equally spaced 60 mm apart at the bottom of the channel. The phenomenon was investigated primarily by time-resolved schlieren visualization from two orthogonal directions using a high-speed video camera. The detonation transition occurred over a remarkably short distance within only three or four repeated obstacles. The global flame speed just before the detonation transition was well below the sound speed of the combustion products and did not reach the sound speed of the initial unreacted gas for tests with an obstacle height of 5 and 10 mm. These results indicate that a detonation transition does not always require global flame acceleration beyond the speed of sound for highly reactive combustible mixtures. A possible mechanism for this detonation initiation was the mixing of the unreacted and reacted gas in the vicinity of the flame front convoluted by the vortex present behind each obstacle, and the formation of a hot spot by the shock wave. The final onset of the detonation originated from the unreacted gas pocket, which was surrounded by the obstacle downstream face and the channel wall.

  1. Pyrotechnic hazards classification and evaluation program test report. Heat flux study of deflagrating pyrotechnic munitions

    NASA Technical Reports Server (NTRS)

    Fassnacht, P. O.

    1971-01-01

    A heat flux study of deflagrating pyrotechnic munitions is presented. Three tests were authorized to investigate whether heat flux measurements may be used as effective hazards evaluation criteria to determine safe quantity distances for pyrotechnics. A passive sensor study was conducted simultaneously to investigate their usefulness in recording events and conditions. It was concluded that heat flux measurements can effectively be used to evaluate hazards criteria and that passive sensors are an inexpensive tool to record certain events in the vicinity of deflagrating pyrotechnic stacks.

  2. Modeling and computation of deflagration-to-detonation transition in reactive granular materials

    SciTech Connect

    Baer, M.R.; Benner, R.E.; Gross, R.J.; Nunziato, J.W.

    1985-01-01

    In this paper, we present a multiphase flow model of the combustion of a gas-permeable reactive granular material. In particular, we focus on a model of the physical-chemical processes associated with the transition from deflagration to detonation in granular explosives and propellants. Two numerical strategies are discussed that are aimed toward multidimensional computations. Comparison of our results with experimental data for the explosives CP and HMX suggests that a thermodynamically consistent model can describe the flame spread processes associated with convective burning, compressive deflagration, and detonation.

  3. Managing Contradictions from the Middle: A Cultural Historical Activity Theory Investigation of Front-Line Supervisors' Learning Lives

    ERIC Educational Resources Information Center

    Lord, Ramo J.

    2009-01-01

    This study focused on front-line supervisors in a union shop, steel-production plant and how they learn to successfully negotiate their role with in the corporation's division of labor. Negotiating their role means continued practice in how issues of standpoint, agency, power, oppression, habits, knowledge, related business concerns, mediating…

  4. Autoignition due to hydraulic resistance and deflagration-to-detonation transition

    SciTech Connect

    Kagan, L.; Sivashinsky, G.

    2008-07-15

    A further development of the friction-based concept of the deflagration-to-detonation transition is presented. Employing Zeldovich's quasi-one-dimensional formulation for combustion in hydraulically resisted flows, the autoignition of the unburned gas subjected to the friction-induced precompression and preheating is assessed. It is shown that autoignition, triggering the transition, is readily attainable for quite realistic parameters. (author)

  5. Temperature effects on failure thickness and deflagration-to-detonation transition in PBX 9502 and TATB

    SciTech Connect

    Asay, B.W.; McAfee, J.B.

    1993-01-01

    The deflagration-to-detonation (DDT) behavior of TATB has been investigated at high temperatures and severe confinement. comparison is made to other common explosives under similar confinement. TATB did not DDT under these conditions. The failure thickness of PBX 9502 at 250[degrees]C has also been determined. Two mm appears to be the limiting value at this temperature.

  6. Temperature effects on failure thickness and deflagration-to-detonation transition in PBX 9502 and TATB

    SciTech Connect

    Asay, B.W.; McAfee, J.B.

    1993-04-01

    The deflagration-to-detonation (DDT) behavior of TATB has been investigated at high temperatures and severe confinement. comparison is made to other common explosives under similar confinement. TATB did not DDT under these conditions. The failure thickness of PBX 9502 at 250{degrees}C has also been determined. Two mm appears to be the limiting value at this temperature.

  7. Do electron-capture supernovae make neutron stars?. First multidimensional hydrodynamic simulations of the oxygen deflagration

    NASA Astrophysics Data System (ADS)

    Jones, S.; Röpke, F. K.; Pakmor, R.; Seitenzahl, I. R.; Ohlmann, S. T.; Edelmann, P. V. F.

    2016-09-01

    Context. In the classical picture, electron-capture supernovae and the accretion-induced collapse of oxygen-neon white dwarfs undergo an oxygen deflagration phase before gravitational collapse produces a neutron star. These types of core collapse events are postulated to explain several astronomical phenomena. In this work, the oxygen deflagration phase is simulated for the first time using multidimensional hydrodynamics. Aims: By simulating the oxygen deflagration with multidimensional hydrodynamics and a level-set-based flame approach, new insights can be gained into the explosive deaths of 8-10 M⊙ stars and oxygen-neon white dwarfs that accrete material from a binary companion star. The main aim is to determine whether these events are thermonuclear or core-collapse supernova explosions, and hence whether neutron stars are formed by such phenomena. Methods: The oxygen deflagration is simulated in oxygen-neon cores with three different central ignition densities. The intermediate density case is perhaps the most realistic, being based on recent nuclear physics calculations and 1D stellar models. The 3D hydrodynamic simulations presented in this work begin from a centrally confined flame structure using a level-set-based flame approach and are performed in 2563 and 5123 numerical resolutions. Results: In the simulations with intermediate and low ignition density, the cores do not appear to collapse into neutron stars. Instead, almost a solar mass of material becomes unbound from the cores, leaving bound remnants. These simulations represent the case in which semiconvective mixing during the electron-capture phase preceding the deflagration is inefficient. The masses of the bound remnants double when Coulomb corrections are included in the equation of state, however they still do not exceed the effective Chandrasekhar mass and, hence, would not collapse into neutron stars. The simulations with the highest ignition density (log 10ρc = 10.3), representing the case

  8. Optimization of the deflagration to detonation transition: reduction of length and time of transition

    NASA Astrophysics Data System (ADS)

    Sorin, R.; Zitoun, R.; Desbordes, D.

    2006-06-01

    The aim of this experimental investigation is the study of Deflagration to Detonation Transition (DDT) in tubes in order to (i) reduce both run-up distance and time of transition ( L DDT and t DDT) in connection with Pulsed Detonation Engine applications and to (ii) attempt to scale L DDT with λCJ (the detonation cellular structure width). In DDT, the production of turbulence during the long flame run-up can lead to L DDT values of several meters. To shorten L DDT, an experimental set-up is designed to quickly induce highly turbulent initial flow. It consists of a double chamber terminated with a perforated plate of high Blockage Ratio (BR) positioned at the beginning of a 26 mm inner diameter tube containing a “Shchelkin spiral” of BR ≈ 0.5. The study involves stoichiometric reactive mixtures of H2, CH4, C3H8, and C2H4 with oxygen and diluted with N2 in order to obtain the same cell width λCJ≈10 mm at standard conditions. The results show that a shock-flame system propagating with nearly the isobaric speed of sound of combustion products, called the choking regime, is rapidly obtained. This experimental set-up allows a L DDT below 40 cm for the mixtures used and a ratio L DDT/λCJ ranging from 23 to 37. The transition distance seems to depend on the reduced activation energy ( E a/ RT c) and on the normalized heat of reaction ( Q/ a 0 2). The higher these quantities are, the shorter the ratio L DDT/λCJ is.

  9. Front-line ownership: imagine.

    PubMed

    Matlow, Anne

    2013-01-01

    When used in a military context, the term front line refers to the interface between enemies in action on the battlefield. In a non-military context, the front line is the site where the core activity defining a particular industry takes place, and those working there are key to successful operations. In healthcare, the need to improve patient safety has become a global imperative, and an armamentarium of strategies, tools and technological approaches have been adapted or developed for this context. Often neglected, however, have been strategies to engage the healthcare workers, those at the front line, in the cause.In order for healthcare to function error free, we must assume the characteristics of high-reliability organizations. In particular, the ability to bounce back, to be resilient in the face of a catastrophe, is of paramount importance. Those working at the front line may have the answers. We need to create an opportunity for them to be heard.`

  10. Front matter.

    PubMed

    2015-01-01

    has defined four basic areas to be managed in the new care model: address the big data challenges; foster meaningful innovation; understand and address the potential new risks; and support concerted effort to un-silo communities for a virtual care future. The multilateral benefits of pHealth technologies for all stakeholder communities including patients, citizens, health professionals, politicians, healthcare establishments, and companies from the biomedical technology, pharmaceutical, and telecommunications domain gives enormous potential, not only for medical quality improvement and industrial competitiveness, but also for managing health care cost. The pHealth 2015 Conference thankfully benefits from the experience and the lessons learned from the organizing committees of previous pHealth events, particularly 2009 in Oslo, 2010 in Berlin, 2011 in Lyon, 2012 in Porto, 2013 in Tallinn, and 2014 Vienna. The 2009 conference brought up the interesting idea of having special sessions, focusing on a particular topic, and being organized by a mentor/moderator. The Berlin event in 2010 initiated workshops on particular topics prior to the official kick-off of the conference. Lyon in 2011 initiated the launch of socalled dynamic demonstrations allowing the participants to dynamically show software and hardware solutions on the fly without needing a booth. Implementing preconference events, the pHealth 2012 in Porto gave attendees a platform for presenting and discussing recent developments and provocative ideas that helped to animate the sessions. Highlight of pHealth 2013 in Tallinn was the special session on European projects' success stories, but also presentations on the newest paradigm changes and challenges coming up with Big Data, Analytics, Translational and Nano Medicine, etc. Vienna in 2014 focused on lessons learned from international and national R&D activities and practical solutions, and especially from the new EU Framework Program for Research and Innovation

  11. Front matter.

    PubMed

    2015-01-01

    has defined four basic areas to be managed in the new care model: address the big data challenges; foster meaningful innovation; understand and address the potential new risks; and support concerted effort to un-silo communities for a virtual care future. The multilateral benefits of pHealth technologies for all stakeholder communities including patients, citizens, health professionals, politicians, healthcare establishments, and companies from the biomedical technology, pharmaceutical, and telecommunications domain gives enormous potential, not only for medical quality improvement and industrial competitiveness, but also for managing health care cost. The pHealth 2015 Conference thankfully benefits from the experience and the lessons learned from the organizing committees of previous pHealth events, particularly 2009 in Oslo, 2010 in Berlin, 2011 in Lyon, 2012 in Porto, 2013 in Tallinn, and 2014 Vienna. The 2009 conference brought up the interesting idea of having special sessions, focusing on a particular topic, and being organized by a mentor/moderator. The Berlin event in 2010 initiated workshops on particular topics prior to the official kick-off of the conference. Lyon in 2011 initiated the launch of socalled dynamic demonstrations allowing the participants to dynamically show software and hardware solutions on the fly without needing a booth. Implementing preconference events, the pHealth 2012 in Porto gave attendees a platform for presenting and discussing recent developments and provocative ideas that helped to animate the sessions. Highlight of pHealth 2013 in Tallinn was the special session on European projects' success stories, but also presentations on the newest paradigm changes and challenges coming up with Big Data, Analytics, Translational and Nano Medicine, etc. Vienna in 2014 focused on lessons learned from international and national R&D activities and practical solutions, and especially from the new EU Framework Program for Research and Innovation

  12. Front Matter.

    PubMed

    2016-01-01

    On behalf of the Scientific Program Committee, I extend a warm welcome to the IMIA-NI members, students, practitioners, informatics researchers, industry partners, and others interested in health and nursing informatics who have come to attend the NI 2016, 13th International Congress on Nursing Informatics. NI 2016 is a biennial conference of the IMIA-NI and the leading scientific meeting for health and nursing informatics research and practice. NI 2016 presents work not only from the discipline of nursing but also from many other disciplines and specialties including both basic and applied informatics. The theme of NI 2016 is eHealth for all: Every level collaboration - From project to realization. The theme reflects the major challenges we face in healthcare today, that is, the need to collaborate at every level to achieve our goal of Health For All. NI 2016 offers a variety of topics on the conference theme. The mission of the Scientific Program Committee is to solicit for, evaluate and schedule NI 2016 conference program to be consistent with the goal of the IMIA-NI. We received 445 submissions for papers, posters, short communications, panels, workshops, demonstrations, student competitions and tutorials from more than 40 countries. Each submission was reviewed by three reviewers selected from a panel of more than 963 experts. Reviewers' feedback was provided to the authors and every effort was made to ensure the best submissions given the constraints of the conference timetable. In the end, a total of 332 submissions were selected. The result of the Scientific Program Committee's activity is reflected in the Conference Program and Proceedings. The proceedings contain OA full papers, indexed in MEDLINE, and also workshops, panels and posters summaries. The Scientific Program Committee has prepared a wonderful program. We have six keynote speakers addressing the state-of-the-art for health and nursing informatics ranging from data, to healthcare delivery to the

  13. Front Matter.

    PubMed

    2016-01-01

    On behalf of the Scientific Program Committee, I extend a warm welcome to the IMIA-NI members, students, practitioners, informatics researchers, industry partners, and others interested in health and nursing informatics who have come to attend the NI 2016, 13th International Congress on Nursing Informatics. NI 2016 is a biennial conference of the IMIA-NI and the leading scientific meeting for health and nursing informatics research and practice. NI 2016 presents work not only from the discipline of nursing but also from many other disciplines and specialties including both basic and applied informatics. The theme of NI 2016 is eHealth for all: Every level collaboration - From project to realization. The theme reflects the major challenges we face in healthcare today, that is, the need to collaborate at every level to achieve our goal of Health For All. NI 2016 offers a variety of topics on the conference theme. The mission of the Scientific Program Committee is to solicit for, evaluate and schedule NI 2016 conference program to be consistent with the goal of the IMIA-NI. We received 445 submissions for papers, posters, short communications, panels, workshops, demonstrations, student competitions and tutorials from more than 40 countries. Each submission was reviewed by three reviewers selected from a panel of more than 963 experts. Reviewers' feedback was provided to the authors and every effort was made to ensure the best submissions given the constraints of the conference timetable. In the end, a total of 332 submissions were selected. The result of the Scientific Program Committee's activity is reflected in the Conference Program and Proceedings. The proceedings contain OA full papers, indexed in MEDLINE, and also workshops, panels and posters summaries. The Scientific Program Committee has prepared a wonderful program. We have six keynote speakers addressing the state-of-the-art for health and nursing informatics ranging from data, to healthcare delivery to the

  14. Front Matter.

    PubMed

    2016-01-01

    Can bad health informatics kill? A similar question has been asked a decade ago by one of the editors of this book on evidence-based health informatics [1]. And indeed, when informatics methodology and information and communication technology (ICT) are used inappropriately this can cause severe negative effects. On the other hand we will probably all agree with her, when she writes in the same article that it "is evident that the use of modern ICT offers tremendous opportunities to support health care professionals and to increase efficiency, effectiveness and appropriateness of care" [1]. Even earlier, more than 15 years ago, the other editor stated that it "is unfortunately a truism in health care informatics… that evaluation is undertaken rarely and inadequately" and he concludes, among others, that "integrated information systems also give new opportunity to provide effective health care service evaluation, and thus a much more robust future evidence base" [2]. As perspective he writes that "a deeper and longer-term evaluation philosophy is needed which does not stop after the initial confirmation of system functioning, but continues on with a deepening into the effects on the individual clinical services, and then on the host user organisation" [2]. Both colleagues worked during recent years continuously and intensively on how to better evaluate health care processes and outcomes in the context of health information systems, so that informatics tools and information management strategies are not 'just' applied in this context, but that their evidence has also been evaluated according to current good scientific practice. It is probably no surprise to find later joint papers of them on evidence-based health informatics, reporting about their international activities there [3]. Today there is indeed still a discrepancy in making decisions on health information system architectures, infrastructures and tools, related to considerable investments for health care

  15. Direct numerical simulation of ignition front propagation in a constant volume with temperature inhomogeneities. I. Fundamental analysis and diagnostics

    SciTech Connect

    Chen, Jacqueline H.; Hawkes, Evatt R.; Sankaran, Ramanan; Mason, Scott D.; Im, Hong G.

    2006-04-15

    The influence of thermal stratification on autoignition at constant volume and high pressure is studied by direct numerical simulation (DNS) with detailed hydrogen/air chemistry with a view to providing better understanding and modeling of combustion processes in homogeneous charge compression-ignition engines. Numerical diagnostics are developed to analyze the mode of combustion and the dependence of overall ignition progress on initial mixture conditions. The roles of dissipation of heat and mass are divided conceptually into transport within ignition fronts and passive scalar dissipation, which modifies the statistics of the preignition temperature field. Transport within ignition fronts is analyzed by monitoring the propagation speed of ignition fronts using the displacement speed of a scalar that tracks the location of maximum heat release rate. The prevalence of deflagrative versus spontaneous ignition front propagation is found to depend on the local temperature gradient, and may be identified by the ratio of the instantaneous front speed to the laminar deflagration speed. The significance of passive scalar mixing is examined using a mixing timescale based on enthalpy fluctuations. Finally, the predictions of the multizone modeling strategy are compared with the DNS, and the results are explained using the diagnostics developed. (author)

  16. [Fire disaster due to deflagration of a propane gas-air mixture].

    PubMed

    Nadjem, Hadi; Vogt, Susanne; Simon, Karl-Heinz; Pollak, Stefan; Geisenberger, Dorothee; Kramer, Lena; Pircher, Rebecca; Perdekampl, Markus Große; Thierauf-Emberger, Annette

    2015-01-01

    On 26 Nov 2012, a serious fire occurred at Neustadt/Black Forest in which 14 persons in a sheltered workshop died and 10 other individuals were injured. The fire was caused by the unbridled escape of propane gas due to accidental disconnection of the screw fixing between a gas bottle and a catalytic heater. Deflagration of the propane gas-air mixture set the workshop facilities on fire. In spite of partly extensive burns the fatally injured victims could be rapidly identified. The results of the fire investigations at the scene and the autopsy findings are presented. Carboxyhemoglobin concentrations ranged between 8 and 56 % and signs of fire fume inhalation were present in all cases. Three victims had eardrum ruptures due to the sudden increase in air pressure during the deflagration. PMID:26548032

  17. Radial magnetic compression in the expelled jet of a plasma deflagration accelerator

    NASA Astrophysics Data System (ADS)

    Loebner, Keith T. K.; Underwood, Thomas C.; Mouratidis, Theodore; Cappelli, Mark. A.

    2016-02-01

    A spectroscopic study of a pulsed plasma deflagration accelerator is carried out that confirms the existence of a strong compression in the emerging jet at the exit plane of the device. An imaging spectrometer is used to collect broadened Hα emission from a transaxial slice of the emerging jet at high spatial resolution, and the radial plasma density profile is computed from Voigt fits of the Abel inverted emissivity profiles. The plasma temperature, determined via Doppler broadening of impurity line emission, is compared against the temperature predictions of a radial magnetohydrodynamic equilibrium model applied to the measured density profiles. Empirical scaling laws developed for the plasma density, combined with the measured and predicted temperatures, indicate that a radially equilibrated Z-pinch is formed within the expelled plasma jet at the exit plane during the deflagration process.

  18. Nitramine flame chemistry and deflagration interpreted in terms of a flame model

    SciTech Connect

    Ben-Reuven, M.; Caveny, L.H.

    1981-10-01

    The diversity of chemical kinetic time scales associated with nitramine decomposition has led to incorporation of two simultaneous overall reactions in the vapor phase mode of deflagration. This allowed derivation of an asymptotic burning rate formula, showing variable pressure dependence. The comprehensive model considers a reacting melt layer, coupled to the gas field through conservation conditions satisfied by all chemical species and enthalpy, and is solved numerically. The structure of the deflagration wave near the propellant surface is obtained, along with the overall pressure dependence of the surface temperature and the flame speed eigenvalue, comparing RDX and HMX. A mechanism of coupling between secondary reactions and heat feedback to the surface is proposed, and a quantitative measure of the effect of condensed phase exothermicity on burning rate is demonstrated.

  19. [Fire disaster due to deflagration of a propane gas-air mixture].

    PubMed

    Nadjem, Hadi; Vogt, Susanne; Simon, Karl-Heinz; Pollak, Stefan; Geisenberger, Dorothee; Kramer, Lena; Pircher, Rebecca; Perdekampl, Markus Große; Thierauf-Emberger, Annette

    2015-01-01

    On 26 Nov 2012, a serious fire occurred at Neustadt/Black Forest in which 14 persons in a sheltered workshop died and 10 other individuals were injured. The fire was caused by the unbridled escape of propane gas due to accidental disconnection of the screw fixing between a gas bottle and a catalytic heater. Deflagration of the propane gas-air mixture set the workshop facilities on fire. In spite of partly extensive burns the fatally injured victims could be rapidly identified. The results of the fire investigations at the scene and the autopsy findings are presented. Carboxyhemoglobin concentrations ranged between 8 and 56 % and signs of fire fume inhalation were present in all cases. Three victims had eardrum ruptures due to the sudden increase in air pressure during the deflagration.

  20. Peak pressures from hydrogen deflagrations in the PFP thermal stabilization glovebox

    SciTech Connect

    Van Keuren, J.C.

    1998-08-11

    This document describes the calculations of the peak pressures due to hydrogen deflagrations in the glovebox used for thermal stabilization (glovebox HC-21A) in PFP. Two calculations were performed. The first considered the burning of hydrogen released from a 7 inch Pu can in the Inert Atmosphere Confinement (IAC) section of the glovebox. The peak pressure increase was 12400 Pa (1.8 psi). The second calculation considered burning of the hydrogen from 25 g of plutonium hydride in the airlock leading to the main portion of the glovebox. Since the glovebox door exposes most of the airlock when open, the deflagration was assumed to pressurize the entire glovebox. The peak pressure increase was 3860 Pa (0.56 psi).

  1. Flame acceleration in channels with obstacles in the deflagration-to-detonation transition

    SciTech Connect

    Valiev, Damir; Bychkov, Vitaly; Akkerman, V'yacheslav; Law, Chung K.; Eriksson, Lars-Erik

    2010-05-15

    It was demonstrated recently in Bychkov et al. [Bychkov et al., Phys. Rev. Lett. 101 (2008) 164501], that the physical mechanism of flame acceleration in channels with obstacles is qualitatively different from the classical Shelkin mechanism. The new mechanism is much stronger, and is independent of the Reynolds number. The present study provides details of the theory and numerical modeling of the flame acceleration. It is shown theoretically and computationally that flame acceleration progresses noticeably faster in the axisymmetric cylindrical geometry as compared to the planar one, and that the acceleration rate reduces with increasing Mach number and thereby the gas compressibility. Furthermore, the velocity of the accelerating flame saturates to a constant value that is supersonic with respect to the wall. The saturation state can be correlated to the Chapman-Jouguet deflagration as well as the fast flames observed in experiments. The possibility of transition from deflagration-to-detonation in the obstructed channels is demonstrated. (author)

  2. The role and importance of porosity in the deflagration rates of HMX-based materials

    SciTech Connect

    Glascoe, E A; Hsu, P C; Springer, H K

    2011-03-15

    The deflagration behavior of thermally damaged HMX-based materials will be discussed. Strands of material were burned at pressures ranging from 10-300 MPa using the LLNL high pressure strand burner. Strands were heated in-situ and burned while still hot; temperatures range from 90-200 C and were chosen in order to allow for thermal damage of the material without significant decomposition of the HMX. The results indicate that multiple variables affect the burn rate but the most important are the polymorph of HMX and the nature and thermal stability of the non-HE portion of the material. Characterization of the strands indicate that the thermal soak produces significant porosity and permeability in the sample allowing for significantly faster burning due to the increased surface area and new pathways for flame spread into the material. Specifically, the deflagration rates of heated PBXN-9, LX-10, and PBX-9501 will be discussed and compared.

  3. Magneto-hydrodynamics simulation study of deflagration mode in co-axial plasma accelerators

    SciTech Connect

    Sitaraman, Hariswaran; Raja, Laxminarayan L.

    2014-01-15

    Experimental studies by Poehlmann et al. [Phys. Plasmas 17(12), 123508 (2010)] on a coaxial electrode magnetohydrodynamic (MHD) plasma accelerator have revealed two modes of operation. A deflagration or stationary mode is observed for lower power settings, while higher input power leads to a detonation or snowplow mode. A numerical modeling study of a coaxial plasma accelerator using the non-ideal MHD equations is presented. The effect of plasma conductivity on the axial distribution of radial current is studied and found to agree well with experiments. Lower conductivities lead to the formation of a high current density, stationary region close to the inlet/breech, which is a characteristic of the deflagration mode, while a propagating current sheet like feature is observed at higher conductivities, similar to the detonation mode. Results confirm that plasma resistivity, which determines magnetic field diffusion effects, is fundamentally responsible for the two modes.

  4. A report on the deflagration-to-detonation transition (DDT) in the high explosive LX-04

    SciTech Connect

    Hare, D E; Forbes, J W; Garcia, F; Granholm, R H; Tarver, C M; Vandersall, K S; Sandusky, H W

    2004-06-30

    The deflagration-to-detonation transition (DDT) was investigated for 1.874 g/cc (98.8 % of theoretical maximum density) LX-04 in moderate confinement (4340 steel tube at R{sub C} 32 with 1.020 inch inside diameter and 0.235 inch thick wall) at both ambient initial temperature (roughly 20 C) and at an initial temperature of 186 C. No transition to detonation was observed in a 295 mm column length for either case.

  5. Ultrafast Chemistry under Nonequilibrium Conditions and the Shock to Deflagration Transition at the Nanoscale

    DOE PAGES

    Wood, Mitchell A.; Cherukara, Mathew J.; Kober, Edward M.; Strachan, Alejandro

    2015-06-13

    We use molecular dynamics simulations to describe the chemical reactions following shock-induced collapse of cylindrical pores in the high-energy density material RDX. For shocks with particle velocities of 2 km/s we find that the collapse of a 40 nm diameter pore leads to a deflagration wave. Molecular collisions during the collapse lead to ultrafast, multistep chemical reactions that occur under nonequilibrium conditions. WE found that exothermic products formed during these first few picoseconds prevent the nanoscale hotspot from quenching. Within 30 ps, a local deflagration wave develops. It propagates at 0.25 km/s and consists of an ultrathin reaction zone ofmore » only ~5 nm, thus involving large temperature and composition gradients. Contrary to the assumptions in current models, a static thermal hotspot matching the dynamical one in size and thermodynamic conditions fails to produce a deflagration wave indicating the importance of nonequilibrium loading in the criticality of nanoscale hot spots. These results provide insight into the initiation of reactive decomposition.« less

  6. A comparison of deflagration rates, at elevated pressures and temperatures, with thermal explosion results

    NASA Astrophysics Data System (ADS)

    Glascoe, Elizabeth; Springer, H. Keo; Tringe, Joseph W.; Maienschein, Jon L.

    2011-06-01

    Previously, the deflagration rate and behavior of HMX-based explosives have been correlated with the violence of thermal explosion experiments. In particular, HMX materials that experience deconsolidative burning at elevated pressures (i.e. P = 200 - 600 MPa) also produce significantly more violent thermal explosions. Recently, we have measured the deflagration rates of HMX-based explosives at elevated temperatures (i.e. T = 150 - 180C) and moderate pressures (i.e. P = 10 - 100 MPa). These conditions more closely mimic the pressure and temperatures of an explosive shortly after ignition of a thermal explosion. We will discuss the deflagration rates of HMX based explosives at elevated temperatures and make comparisons with thermal explosion studies on the same materials. The Joint DoD-DOE Munitions Technology Development Program is acknowledged for funding. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  7. Ultrafast Chemistry under Nonequilibrium Conditions and the Shock to Deflagration Transition at the Nanoscale

    SciTech Connect

    Wood, Mitchell A.; Cherukara, Mathew J.; Kober, Edward M.; Strachan, Alejandro

    2015-06-13

    We use molecular dynamics simulations to describe the chemical reactions following shock-induced collapse of cylindrical pores in the high-energy density material RDX. For shocks with particle velocities of 2 km/s we find that the collapse of a 40 nm diameter pore leads to a deflagration wave. Molecular collisions during the collapse lead to ultrafast, multistep chemical reactions that occur under nonequilibrium conditions. WE found that exothermic products formed during these first few picoseconds prevent the nanoscale hotspot from quenching. Within 30 ps, a local deflagration wave develops. It propagates at 0.25 km/s and consists of an ultrathin reaction zone of only ~5 nm, thus involving large temperature and composition gradients. Contrary to the assumptions in current models, a static thermal hotspot matching the dynamical one in size and thermodynamic conditions fails to produce a deflagration wave indicating the importance of nonequilibrium loading in the criticality of nanoscale hot spots. These results provide insight into the initiation of reactive decomposition.

  8. Flame-powered trigger device for activating explosion suppression barrier

    SciTech Connect

    Cortese, R.A.; Sapko, M.J.

    1991-01-01

    This paper reports that the U.S. Bureau of Mines has developed a flame-radiation-powered trigger device to explosively activate suppression barriers to quench gas and coal dust explosions. The major component of the device is a silicon solar panel, which concerts radiation from the developing explosion into electrical energy to initiate an electric detonator, which releases an extinguishing agent into the advancing flame front. Solar panels that are rated to produce 20 W of electrical power when exposed to the sunlight are producing about 200 W when exposed to a full-scale dust explosion. The solar panel is electrically isolated from the detonator by a pressure-sensitive switch until the arrival of the precursor pressure pulse, which always precedes a deflagration. This combination of pressure arming and flame-powered photogenerator prevents false barrier activation and requires no external power supply.

  9. Effects of high activation energies on acoustic timescale detonation initiation

    NASA Astrophysics Data System (ADS)

    Regele, J. D.; Kassoy, D. R.; Vasilyev, O. V.

    2012-08-01

    Acoustic timescale Deflagration-to-Detonation Transition (DDT) has been shown to occur through the generation of compression waves emitted by a hot spot or reaction centre where the pressure and temperature increase with little diminution of density. In order to compensate for the multi-scale nature of the physico-chemical processes, previous numerical simulations in this area have been limited to relatively small activation energies. In this work, a computational study investigates the effect of increased activation energy on the time required to form a detonation wave and the change in behaviour of each hot spot as the activation energy is increased. The simulations use a localised spatially distributed thermal power deposition of limited duration into a finite volume of reactive gas to facilitate DDT. The Adaptive Wavelet-Collocation Method is used to solve efficiently the 1-D reactive Euler equations with one-step Arrhenius kinetics. The DDT process as described in previous work is characterised by the formation of hot spots during an initial transient period, explosion of the hot spots and creation of an accelerating reaction front that reaches the lead shock and forms an overdriven detonation wave. Current results indicate that as the activation energy is raised the chemical heat release becomes more temporally distributed. Hot spots that produce an accelerating reaction front with low activation energies change behaviour with increased activation energy so that no accelerating reaction front is created. An acoustic timescale ratio is defined that characterises the change in behaviour of each hot spot.

  10. Luminescence ages for alluvial-fan deposits in Southern Death Valley: Implications for climate-driven sedimentation along a tectonically active mountain front

    USGS Publications Warehouse

    Sohn, M.F.; Mahan, S.A.; Knott, J.R.; Bowman, D.D.

    2007-01-01

    Controversy exists over whether alluvial-fan sedimentation along tectonically active mountain fronts is driven by climatic changes or tectonics. Knowing the age of sedimentation is the key to understanding the relationship between sedimentation and its cause. Alluvial-fan deposits in Death Valley and throughout the arid southwestern United States have long been the subjects of study, but their ages have generally eluded researchers until recently. Most mapping efforts have recognized at least four major relative-age groupings (Q1 (oldest), Q2, Q3, and Q4 (youngest)), using observed changes in surface soils and morphology, relation to the drainage net, and development of desert pavement. Obtaining numerical age determinations for these morphologic stages has proven challenging. We report the first optically stimulated luminescence (OSL) ages for three of these four stages deposited within alluvial-fans along the tectonically active Black Mountains of Death Valley. Deposits showing distinct, remnant bar and swale topography (Q3b) have OSL ages from 7 to 4 ka., whereas those with moderate to poorly developed desert pavement and located farther above the active channel (Q3a) have OSL ages from 17 to 11 ka. Geomorphically older deposits with well-developed desert pavement (Q2d) have OSL ages ???25 ka. Using this OSL-based chronology, we note that alluvial-fan deposition along this tectonically active mountain front corresponds to both wet-to-dry and dry-to-wet climate changes recorded globally and regionally. These findings underscore the influence of climate change on alluvial fan deposition in arid and semi-arid regions. ?? 2007 Elsevier Ltd and INQUA.

  11. Front Matter: Volume 8454

    NASA Astrophysics Data System (ADS)

    SPIE, Proceedings of

    2012-05-01

    This PDF file contains the front matter associated with SPIE Proceedings Volume 8454, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

  12. Deflagration-to-detonation transition in inertial-confinement-fusion baseline targets.

    PubMed

    Gauthier, P; Chaland, F; Masse, L

    2004-11-01

    By means of highly resolved one-dimensional hydrodynamics simulations, we provide an understanding of the burn process in inertial-confinement-fusion baseline targets. The cornerstone of the phenomenology of propagating burn in such laser-driven capsules is shown to be the transition from a slow unsteady reaction-diffusion regime of thermonuclear combustion (some sort of deflagration) to a fast detonative one. Remarkably, detonation initiation follows the slowing down of a shockless supersonic reaction wave driven by energy redeposition from the fusion products themselves. Such a route to detonation is specific to fusion plasmas. PMID:15600681

  13. Deflagration Rates of Secondary Explosives Under Static MPA—GPA Pressure

    NASA Astrophysics Data System (ADS)

    Zaug, Joseph M.; Young, Christopher E.; Long, Gregory T.; Maienschein, Jon L.; Glascoe, Elizabeth A.; Hansen, Donald W.; Wardell, Jeffery F.; Black, C. Kevin; Sykora, Gregory B.

    2009-12-01

    We provide measurements of the chemical reaction propagation rate (RPR) as a function of pressure using diamond anvil cell (DAC) and strand burner technologies. Materials investigated include HMX and RDX crystalline powders, LX-04 (85% HMX and 15% Viton A), and Composition B (63% RDX, 36% TNT, 1% wax). The anomalous correspondence between crystal structure, including in some instances isostructural phase transitions, on pressure dependent RPRs of HMX and RDX are correlated to confocal micro-Raman spectroscopic results. The contrast between DAC GPa and strand burner MPa regime measurements yield insight into explosive material burn phenomena. Here we highlight physicochemical mechanisms that appear to affect the deflagration rate of precompressed energetic materials.

  14. Deflagration-to-detonation in granular HMX: Ignition, kinetics, and shock formation

    SciTech Connect

    McAfee, J.M.; Asay, B.W.; Bdzil, J.B.

    1993-06-01

    Experimental studies and analysis of the deflagration-to detonation transition (DDT) in granular HMX are continued. Experiments performed using a direct-gasless igniter exhibit the same phenomenology as those ignited with a piston. Simple kinetics and mechanics describe the formation of the {approximately}100% TMD plug in terms of competing pressurization processes. A mass-conservation analysis of the experimentally observed structures shows how the low velocities characteristic of convective burning are amplified to shock-wave velocities through non-convective processes.

  15. Deflagration-to-detonation transition in inertial-confinement-fusion baseline targets.

    PubMed

    Gauthier, P; Chaland, F; Masse, L

    2004-11-01

    By means of highly resolved one-dimensional hydrodynamics simulations, we provide an understanding of the burn process in inertial-confinement-fusion baseline targets. The cornerstone of the phenomenology of propagating burn in such laser-driven capsules is shown to be the transition from a slow unsteady reaction-diffusion regime of thermonuclear combustion (some sort of deflagration) to a fast detonative one. Remarkably, detonation initiation follows the slowing down of a shockless supersonic reaction wave driven by energy redeposition from the fusion products themselves. Such a route to detonation is specific to fusion plasmas.

  16. Deflagration-to-detonation transition in inertial-confinement-fusion baseline targets

    SciTech Connect

    Gauthier, P.; Chaland, F.; Masse, L.

    2004-11-01

    By means of highly resolved one-dimensional hydrodynamics simulations, we provide an understanding of the burn process in inertial-confinement-fusion baseline targets. The cornerstone of the phenomenology of propagating burn in such laser-driven capsules is shown to be the transition from a slow unsteady reaction-diffusion regime of thermonuclear combustion (some sort of deflagration) to a fast detonative one. Remarkably, detonation initiation follows the slowing down of a shockless supersonic reaction wave driven by energy redeposition from the fusion products themselves. Such a route to detonation is specific to fusion plasmas.

  17. a New Approach of the Deflagration to Detonation Transition in SNIa Thermonuclear Supernovae

    NASA Astrophysics Data System (ADS)

    Chièze, Jean Pierre; Charignon, Camille

    2015-03-01

    A wide class of type Ia thermonuclear supernovae models relies on the transition from the subsonic deflagration combustion regime to the supersonic detonation regime of the carbon and oxygen mixture of an accreting white dwarf, near the Chandrasekhar mass. We show that this can actually be achieved in a cold C+O white dwarf near the Chandrasekhar mass, with seed sound waves of relatively low Mach number M ˜ 0.02. Moreover, even weaker perturbations, with velocity perturbations as low as M ˜ 0.003 can trigger a detonation wave in SNIa progenitors models wich include the presence of a thin helium surface layer.

  18. The piston-flow interaction as a model for the deflagration-to-detonation transition

    SciTech Connect

    Brailovsky, Irina; Kagan, Leonid; Sivashinsky, Gregory

    2011-01-15

    The piston-flow interaction induced by a piston pushing hydraulically resisted gas through a long tube is discussed. It is shown that the hydraulic resistance causes a significant precompression and preheating of the gas adjacent to the piston's edge. In the case of an explosive premixture this development may lead to a localized autoignition triggering detonation. It is suggested that the problem may serve as a guide for understanding the deflagration-to-detonation transition in tubes, with the piston modeling the impact of the advancing flame. (author)

  19. Simulations of flame acceleration and deflagration-to-detonation transitions in methane-air systems

    SciTech Connect

    Kessler, D.A.; Gamezo, V.N.; Oran, E.S.

    2010-11-15

    Flame acceleration and deflagration-to-detonation transitions (DDT) in large obstructed channels filled with a stoichiometric methane-air mixture are simulated using a single-step reaction mechanism. The reaction parameters are calibrated using known velocities and length scales of laminar flames and detonations. Calculations of the flame dynamics and DDT in channels with obstacles are compared to previously reported experimental data. The results obtained using the simple reaction model qualitatively, and in many cases, quantitatively match the experiments and are found to be largely insensitive to small variations in model parameters. (author)

  20. Apparatus and method for rapid detection of explosives residue from the deflagration signature thereof

    DOEpatents

    Funsten, Herbert O.; McComas, David J.

    1997-01-01

    Apparatus and method for rapid detection of explosives residue from the deflagration signature thereof. A property inherent to most explosives is their stickiness, resulting in a strong tendency of explosive particulate to contaminate the environment of a bulk explosive. An apparatus for collection of residue particulate, burning the collected particulate, and measurement of the optical emission produced thereby is described. The present invention can be utilized for real-time screening of personnel, cars, packages, suspected devices, etc., and provides an inexpensive, portable, and noninvasive means for detecting explosives.

  1. Apparatus and method for rapid detection of explosives residue from the deflagration signature thereof

    DOEpatents

    Funsten, H.O.; McComas, D.J.

    1999-06-15

    Apparatus and method are disclosed for rapid detection of explosives residue from the deflagration signature thereof. A property inherent to most explosives is their stickiness, resulting in a strong tendency of explosive particulate to contaminate the environment of a bulk explosive. An apparatus for collection of residue particulate, burning the collected particulate, and measurement of the ultraviolet emission produced thereby, is described. The present invention can be utilized for real-time screening of personnel, cars, packages, suspected devices, etc., and provides an inexpensive, portable, and noninvasive means for detecting explosives. 4 figs.

  2. Apparatus and method for rapid detection of explosives residue from the deflagration signature thereof

    DOEpatents

    Funsten, Herbert O.; McComas, David J.

    1999-01-01

    Apparatus and method for rapid detection of explosives residue from the deflagration signature thereof. A property inherent to most explosives is their stickiness, resulting in a strong tendency of explosive particulate to contaminate the environment of a bulk explosive. An apparatus for collection of residue particulate, burning the collected particulate, and measurement of the ultraviolet emission produced thereby, is described. The present invention can be utilized for real-time screening of personnel, cars, packages, suspected devices, etc., and provides an inexpensive, portable, and noninvasive means for detecting explosives.

  3. X-ray emission from the remnant of a carbon deflagration supernova - SN 1572 (Tycho)

    SciTech Connect

    Itoh, H.; Masai, K.; Nomoto, K.

    1988-11-01

    A spherically symmetric hydrodynamic code is used to study the evolution of a young supernova remnant on the basis of a carbon deflagration model for type Ia supernovae. The nonequilibrium X-ray emission has been determined for the elemental composition of the model. The discrepancy between the derived intensity of the Fe D-alpha line blend and the observed value is eliminated by assuming that the stratification of the elemental composition in the supernova ejecta is partially removed by mixing. 59 references.

  4. Deflagration Rates and Molecular Bonding Trends of Statically Compressed Secondary Explosives

    SciTech Connect

    Zaug, J M; Foltz, M F; Hart, E

    2010-03-09

    We discuss our measurements of the chemical reaction propagation rate as a function of pressure. Materials investigated have included CL-20, HMX, TATB, and RDX crystalline powders, LX-04, Comp B, and nitromethane. The anomalous correspondence between crystal structure, including in some instances isostructural phase transitions, on pressure-dependant RPRs of TATB, HMX, Nitromethane, CL-20, and PETN have been elucidated using micro-IR and -Raman spectroscopies. Here we specifically highlight pressure-dependent physicochemical mechanisms affecting the deflagration rate of nitromethane and epsilon-CL-20. We find that pressure induced splitting of symmetric stretch NO{sub 2} vibrations can signal the onset of increasingly more rapid combustion reactions.

  5. Self-deflagration rates of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). [burning tate, thermal stability

    NASA Technical Reports Server (NTRS)

    Boggs, T. L.; Price, C. F.; Zurn, D. E.; Atwood, A. I.; Eisel, J. L.

    1980-01-01

    The thermal stability and resistance to impact was investigated for the ingredient TABA. Particular attention was given to determining the use of TABA as a possible alternative ingredient or substitute for HMX in explosives and high energy propellants. The burn rate of TABA was investigated as a function of pressure. It was concluded that the self deflagration rate of TABA is an order of magnitude lower than HMX over the range 2000-15000 psi; TABA will not sustain self deflagration at low pressures (less than or equal to 1500 psi) in the sample configuration and apparatus used.

  6. Flame-powered trigger device for activating explosion-suppression barrier. Rept. of Investigations/1991

    SciTech Connect

    Cortese, R.A.; Sapko, M.J.

    1991-01-01

    The U.S. Bureau of Mines has developed a flame-radiation-powered trigger device to explosively activate suppression barriers to quench gas and coal dust explosions. The major component of the device is a silicon solar panel, which converts radiation from the developing explosion into electrical energy to initiate an electric detonator, which releases an extinguishing agent into the advancing flame front. Solar panels that are rated to produce 20 W of electrical power when exposed to the sunlight are producing about 200 W when exposed to a full-scale dust explosion. The solar panel is electrically isolated from the detonator by a pressure-sensitive switch until the arrival of the precursor pressure pulse, which always precedes a deflagration. The combination of pressure arming and flame-powered photogenerator prevents false barrier activation and requires no external power supply.

  7. Negative Ion Density Fronts

    SciTech Connect

    Igor Kaganovich

    2000-12-18

    Negative ions tend to stratify in electronegative plasmas with hot electrons (electron temperature Te much larger than ion temperature Ti, Te > Ti ). The boundary separating a plasma containing negative ions, and a plasma, without negative ions, is usually thin, so that the negative ion density falls rapidly to zero-forming a negative ion density front. We review theoretical, experimental and numerical results giving the spatio-temporal evolution of negative ion density fronts during plasma ignition, the steady state, and extinction (afterglow). During plasma ignition, negative ion fronts are the result of the break of smooth plasma density profiles during nonlinear convection. In a steady-state plasma, the fronts are boundary layers with steepening of ion density profiles due to nonlinear convection also. But during plasma extinction, the ion fronts are of a completely different nature. Negative ions diffuse freely in the plasma core (no convection), whereas the negative ion front propagates towards the chamber walls with a nearly constant velocity. The concept of fronts turns out to be very effective in analysis of plasma density profile evolution in strongly non-isothermal plasmas.

  8. TURBULENCE IN A THREE-DIMENSIONAL DEFLAGRATION MODEL FOR TYPE Ia SUPERNOVAE. I. SCALING PROPERTIES

    SciTech Connect

    Ciaraldi-Schoolmann, F.; Schmidt, W.; Niemeyer, J. C.; Roepke, F. K.; Hillebrandt, W.

    2009-05-10

    We analyze the statistical properties of the turbulent velocity field in the deflagration model for Type Ia supernovae. In particular, we consider the question of whether turbulence is isotropic and consistent with the Kolmogorov theory at small length scales. Using numerical data from a high-resolution simulation of a thermonuclear supernova explosion, spectra of the turbulence energy and velocity structure functions are computed. We show that the turbulent velocity field is isotropic at small length scales and follows a scaling law that is consistent with the Kolmogorov theory until most of the nuclear fuel is burned. At length scales greater than a certain characteristic scale that agrees with the prediction of Niemeyer and Woosley, turbulence becomes anisotropic. Here, the radial velocity fluctuations follow the scaling law of the Rayleigh-Taylor instability, whereas the angular component still obeys the Kolmogorov scaling. In the late phase of the explosion, this characteristic scale drops below the numerical resolution of the simulation. The analysis confirms that a subgrid-scale model for the unresolved turbulence energy is required for the consistent calculation of the flame speed in deflagration models of Type Ia supernovae, and that the assumption of isotropy on these scales is appropriate.

  9. The type Iax supernova, SN 2015H. A white dwarf deflagration candidate

    NASA Astrophysics Data System (ADS)

    Magee, M. R.; Kotak, R.; Sim, S. A.; Kromer, M.; Rabinowitz, D.; Smartt, S. J.; Baltay, C.; Campbell, H. C.; Chen, T.-W.; Fink, M.; Gal-Yam, A.; Galbany, L.; Hillebrandt, W.; Inserra, C.; Kankare, E.; Le Guillou, L.; Lyman, J. D.; Maguire, K.; Pakmor, R.; Röpke, F. K.; Ruiter, A. J.; Seitenzahl, I. R.; Sullivan, M.; Valenti, S.; Young, D. R.

    2016-05-01

    We present results based on observations of SN 2015H which belongs to the small group of objects similar to SN 2002cx, otherwise known as type Iax supernovae. The availability of deep pre-explosion imaging allowed us to place tight constraints on the explosion epoch. Our observational campaign began approximately one day post-explosion, and extended over a period of about 150 days post maximum light, making it one of the best observed objects of this class to date. We find a peak magnitude of Mr = -17.27± 0.07, and a (Δm15)r = 0.69 ± 0.04. Comparing our observations to synthetic spectra generated from simulations of deflagrations of Chandrasekhar mass carbon-oxygen white dwarfs, we find reasonable agreement with models of weak deflagrations that result in the ejection of ~0.2 M⊙ of material containing ~0.07 M⊙ of 56Ni. The model light curve however, evolves more rapidly than observations, suggesting that a higher ejecta mass is to be favoured. Nevertheless, empirical modelling of the pseudo-bolometric light curve suggests that ≲0.6 M⊙ of material was ejected, implying that the white dwarf is not completely disrupted, and that a bound remnant is a likely outcome.

  10. Observation and interpretation of thermal instabilities at the front face of actively cooled limiters in TORE-SUPRA

    SciTech Connect

    Guilhem, D.; Hogan, J.T.; Mitteau, R.; Phillips, V.

    1995-12-01

    In TORE-SUPRA, actively cooled modular limiters (time constant = 2 s) covered with carbon have been used to exhaust the convective heat flux continuously up to 700 kW steady state (design value) without thermal instability, i.e., 4.5 MW/m{sup 2} on average. Steady state surface temperatures in the range 600 C (with 1.45 MW of Lower Hybrid waves) were routinely obtained. However, sudden surface temperature excursions from 600 C to 1,900 C, called ``super-brilliances``, were observed during ohmic or heated plasmas, taking place locally over 20 ms, which led to a new equilibrium. This new equilibrium correspond to a local increased power flux density to the limiter as confirmed by calorimetric measurements. Shot after shot, an increasing number of independent overheated zones (up to 4) were observed on the limiter ridge, the closest location to Last Closed Flux Surface (LCFS). The power extracted by the limiter then was {approximately} 1.1 MW (6.9 MW/m{sup 2} average and 15 MW/m{sup 2} maximum). Experimental data and possible mechanisms leading to a finite increased heat flux to the limiter surface are reviewed and comparisons with modelization are made.

  11. Effects of fluctuations on propagating fronts

    NASA Astrophysics Data System (ADS)

    Panja, Debabrata

    Propagating fronts are seen in varieties of nonequilibrium pattern forming systems in Physics, Chemistry and Biology. In the last two decades, many researchers have contributed to the understanding of the underlying dynamics of the propagating fronts. Of these, the deterministic and mean-field dynamics of the fronts were mostly understood in late 1980s and 1990s. On the other hand, although the earliest work on the effect of fluctuations on propagating fronts dates back to early 1980s, the subject of fluctuating fronts did not reach its adolescence until the mid 1990s. From there onwards the last few years witnessed a surge in activities in the effect of fluctuations on propagating fronts. Scores of papers have been written on this subject since then, contributing to a significant maturity of our understanding, and only recently a full picture of fluctuating fronts has started to emerge. This review is an attempt to collect all the works on fluctuating (propagating) fronts in a coherent and cogent manner in proper perspective. It is based on the idea of making our knowledge in this field available to a broader audience, and it is also expected to help to collect bits and pieces of loose thread-ends together for possible further investigation.

  12. Deflagration-to-detonation transition in gases in tubes with cavities

    NASA Astrophysics Data System (ADS)

    Smirnov, N. N.; Nikitin, V. F.; Phylippov, Yu. G.

    2010-12-01

    The existence of a supersonic second combustion mode — detonation — discovered by Mallard and Le Chatelier and by Berthélot and Vieille in 1881 posed the question of mechanisms for transition from one mode to the other. In the period 1959-1969, experiments by Salamandra, Soloukhin, Oppenheim, and their coworkers provided insights into this complex phenomenon. Since then, among all the phenomena related to combustion processes, deflagration-to-detonation transition is, undoubtedly, the most intriguing one. Deflagration-to-detonation transition (DDT) in gases is connected with gas and vapor explosion safety issues. Knowing mechanisms of detonation onset control is of major importance for creating effective mitigation measures addressing two major goals: to prevent DDT in the case of mixture ignition, or to arrest the detonation wave in the case where it has been initiated. A new impetus to the increase in interest in deflagration-to-detonation transition processes was given by the recent development of pulse detonation devices. The probable application of these principles to creation of a new generation of engines put the problem of effectiveness of pulse detonating devices at the top of current research needs. The effectiveness of the pulse detonation cycle turned out to be the key factor characterizing the Pulse Detonation Engine (PDE), whose operation modes were shown to be closely related to periodical onset and degeneration of a detonation wave. Those unsteady-state regimes should be self-sustained to guarantee a reliable operation of devices using the detonation mode of burning fuels as a constitutive part of their working cycle. Thus deflagration-to-detonation transition processes are of major importance for the issue. Minimizing the predetonation length and ensuring stability of the onset of detonation enable one to increase the effectiveness of a PDE. The DDT turned out to be the key factor characterizing the PDE operating cycle. Thus, the problem of

  13. Role of prokaryotic biomasses and activities in carbon and phosphorus cycles at a coastal, thermohaline front and in offshore waters (Gulf of Manfredonia, Southern Adriatic Sea).

    PubMed

    Monticelli, L S; Caruso, G; Decembrini, F; Caroppo, C; Fiesoletti, F

    2014-04-01

    The Western areas of the Adriatic Sea are subjected to inputs of inorganic nutrients and organic matter that can modify the trophic status of the waters and consequently, the microbiological processes involved in the carbon and phosphorus biogeochemical cycles, particularly in shallow coastal environments. To explore this topic, a survey was carried out during the spring of 2003 in a particular hydrodynamic area of the Gulf of Manfredonia, where the potential (P) and real (R) rates of four different microbial exoenzymatic activities (EEA) (α [αG] and ß glucosidases [ßG], leucine aminopeptidase [LAP], and alkaline phosphatase [AP]) as well as the P and R rates of prokaryotic heterotrophic production (PHP), AP as well as the P and R rates of PHP, primary production (PPnet), the prokaryotic and phototrophic stocks and basic hydrological parameters were examined. Three different water masses were found, with a thermohaline front (THF) being detected between the warmer and less saline coastal waters and colder and saltier offshore Adriatic waters. Under the general oligotrophic conditions of the entire Gulf, a decreasing gradient from the coastal toward the offshore areas was detected, with PHP, PPnet, stocks and EEA (αG, ßG, AP) being directly correlated with the temperature and inversely correlated with the salinity, whereas opposite relationships were observed for LAP activity. No enhancement of microbiological activities or stocks was observed at the THF. The use of P or R rates of microbiological activities, which decrease particularly for EEA, could result in discrepancies in interpreting the efficiency of several metabolic processes.

  14. The role of gas phase reactions in the deflagration-to-detonation transition of high energy propellants

    NASA Technical Reports Server (NTRS)

    Boggs, T. L.; Price, C. F.; Atwood, A. I.; Zurn, D. E.; Eisel, J. L.; Derr, R. L.

    1980-01-01

    The inadequacies of the two commonly used assumptions are shown, along with the need for considering gas phase reactions. Kinetic parameters that describe the gas phase reactions for several ingredients are provided, and the first steps in convective combustion leading to deflagration to detonation transition are described.

  15. Laboratory experiments on fronts

    NASA Astrophysics Data System (ADS)

    Chia, F.; Griffiths, R. W.; Linden, P. F.

    We describe a laboratory model of an upwelling front in a two-layer stratification. In the model the interface between the two layers slopes upwards toward a vertical boundary (or coastline) and can intersect the free surface to produce a front. Fluid motion in each layer is density driven and, in the undisturbed state, is in quasi-geostrophic balance. The front is observed to be unstable to (ageostrophic) disturbances with an along-front wavelength proportional to the Rossby radius of deformation. At very large amplitudes these unstable waves form closed circulations. However, in contrast to the behaviour of fronts far from vertical boundaries, where cyclone-anticyclone vortex pairs are formed, the presence of the coastline inhibits formation of anticyclonic eddies in the upper layer and enhances cyclonic rings of upper layer fluid which lie above cyclonic eddies in the lower layer. The cyclones move away from the vertical boundary and (as is also the case when no vertical boundary is present) they appear at the surface as eddies containing lower layer fluid on the seaward side of the mean frontal position.

  16. Modeling 1-D deflagration to detonation transition (DDT) in porous explosive

    SciTech Connect

    Weston, A.M.; Lee, E.L.

    1985-04-04

    A one-dimensional Lagrange hydrodynamic computer model is presented that describes gas flow, compaction, ignition, and deflagration processes in deformable porous beds. The model makes use of a consumable finite element cell that allows gas to flow through a compacting matrix. The model can be regarded as structural in the sense that the initial cell dimension is directly related to mean particle size. Experimental investigation of the DDT phenomenon are typically carried out using long thick-walled tubes filled with a granular porous bed of reactive material. In this configuration, much of the process can be described by flow in one dimension. We present calculations that simulate both squib initiated and piston initiated experiments on porous HMX to point out various observed features. Our purpose is to establish a basis for setting bounds on the physical parameters that describe such transient reaction processes. 16 refs., 17 figs., 1 tab.

  17. Deflagration to detonation in HMX under high confinement. [HMX confined in steel tubes

    SciTech Connect

    McAfee, J.M.; Campbell, A.W.; Asay, B.W.

    1987-01-01

    The deflagration-to-detonation behavior of HMX confined in steel tubes was studied by means of x radiography, light emission, and various pin techniques. Unlike most reported experiments, the HMX bed was ignited by driving a piston (initially at rest and in contact with the HMX) into the bed with the pressure generated from burning, low-density HMX on the opposite side of the piston. Because a gasless igniter is used to start the burning of the low-density HMX, the piston has a relatively smooth initial motion. Analysis of the data from these experiments gives a rather detailed picture of the DDT process under these conditions. 2 refs., 19 figs.

  18. Study on the Mechanism of the Deflagration to Detonation Transition Process of Explosive

    NASA Astrophysics Data System (ADS)

    Wei, Lan; Dong, Hefei; Pan, Hao; Hu, Xiaomian; Zhu, Jianshi

    2014-10-01

    We present a numerical study of the mechanisms of the deflagration to detonation transition (DDT) process of explosives to assess its thermal stability. We treated the modeling system as a mixture of solid explosives and gaseous reaction products. We utilized a one-dimensional two-phase flow modeling approach with a space-time conservation element and solution element (CE/SE) method. Simulation results show that in the chemical reaction process a plug area of high density with relatively slow chemical reactions preceeds the new violent reactions and the consequent detonation. We found that steady detonation occurs at the regions where physical characteristics, such as pressure, density, temperature, and velocity, peak simultaneously. These simulation results agree well with high-temperature DDT tube experiments.

  19. Deflagration-to-detonation characteristics of a laser exploding bridge detonator

    NASA Astrophysics Data System (ADS)

    Welle, E. J.; Fleming, K. J.; Marley, S. K.

    2006-08-01

    Evaluation of laser initiated explosive trains has been an area of extreme interest due to the safety benefits of these systems relative to traditional electro-explosive devices. A particularly important difference is these devices are inherently less electro-static discharge (ESD) sensitive relative to traditional explosive devices due to the isolation of electrical power and associated materials from the explosive interface. This paper will report work conducted at Sandia National Laboratories' Explosive Components Facility, which evaluated the initiation and deflagration-to-detonation characteristics of a Laser Driven Exploding Bridgewire detonator. This paper will report and discuss characteristics of Laser Exploding Bridgewire devices loaded with hexanitrohexaazaisowurtzitane (CL-20) and tetraammine-cis-bis-(5-nitro-2H-tetrazolato-N2) cobalt (III) perchlorate (BNCP).

  20. Stability of quasi-steady deflagrations in confined porous energetic materials

    SciTech Connect

    Alexander M. Telengator; Stephen B. Margolis; Forman A. Williams

    2000-03-01

    Previous analyses have shown that unconfined deflagrations propagating through both porous and nonporous energetic materials can exhibit a thermal/diffusive instability that corresponds to the onset of various oscillatory modes of combustion. For porous materials, two-phase-flow effects, associated with the motion of the gas products relative to the condensed material, play a significant role that can shift stability boundaries with respect to those associated with the nonporous problem. In the present work, additional significant effects are shown to be associated with confinement, which produces an overpressure in the burned-gas region that leads to reversal of the gas flow and hence partial permeation of the hot gases into the unburned porous material. This results in a superadiabatic effect that increases the combustion temperature and, consequently, the burning rate. Under the assumption of gas-phase quasi-steadiness, an asymptotic model is presented that facilitates a perturbation analysis of both the basic solution, corresponding to a steadily propagating planar combustion wave, and its stability. The neutral stability boundaries collapse to the previous results in the absence of confinement, but different trends arising from the presence of the gas-permeation layer are predicted for the confined problem. Whereas two-phase-flow effects are generally destabilizing in the unconfined geometry, the effects of increasing overpressure and hence combustion temperature associated with confinement are shown to be generally stabilizing with respect to thermal/diffusive instability, analogous to the effects of decreasing heat losses on combustion temperature and stability in single-phase deflagrations.

  1. Evaluating systematic dependencies of type Ia supernovae : the influence of deflagration to detonation density.

    SciTech Connect

    Jackson, A. P.; Calder, A. C.; Townsley, D. M.; Chamulak, D. A.; Brown, E. F.; Timmes, F. X.

    2010-09-01

    We explore the effects of the deflagration to detonation transition (DDT) density on the production of {sup 56}Ni in thermonuclear supernova (SN) explosions (Type Ia supernovae). Within the DDT paradigm, the transition density sets the amount of expansion during the deflagration phase of the explosion and therefore the amount of nuclear statistical equilibrium (NSE) material produced. We employ a theoretical framework for a well-controlled statistical study of two-dimensional simulations of thermonuclear SNe with randomized initial conditions that can, with a particular choice of transition density, produce a similar average and range of {sup 56}Ni masses to those inferred from observations. Within this framework, we utilize a more realistic 'simmered' white dwarf progenitor model with a flame model and energetics scheme to calculate the amount of {sup 56}Ni and NSE material synthesized for a suite of simulated explosions in which the transition density is varied in the range (1-3) x 10{sup 7} g cm{sup -3}. We find a quadratic dependence of the NSE yield on the log of the transition density, which is determined by the competition between plume rise and stellar expansion. By considering the effect of metallicity on the transition density, we find the NSE yield decreases by 0.055 {+-} 0.004 M {circle_dot} for a 1 Z {circle_dot} increase in metallicity evaluated about solar metallicity. For the same change in metallicity, this result translates to a 0.067 {+-} 0.004 M {circle_dot} decrease in the {sup 56}Ni yield, slightly stronger than that due to the variation in electron fraction from the initial composition. Observations testing the dependence of the yield on metallicity remain somewhat ambiguous, but the dependence we find is comparable to that inferred from some studies.

  2. One-step reduced kinetics for lean hydrogen-air deflagration

    SciTech Connect

    Fernandez-Galisteo, D.; Sanchez, A.L.; Linan, A.; Williams, F.A.

    2009-05-15

    A short mechanism consisting of seven elementary reactions, of which only three are reversible, is shown to provide good predictions of hydrogen-air lean-flame burning velocities. This mechanism is further simplified by noting that over a range of conditions of practical interest, near the lean flammability limit all reaction intermediaries have small concentrations in the important thin reaction zone that controls the hydrogen-air laminar burning velocity and therefore follow a steady state approximation, while the main species react according to the global irreversible reaction 2H{sub 2} + O{sub 2} {yields} 2H{sub 2}O. An explicit expression for the non-Arrhenius rate of this one-step overall reaction for hydrogen oxidation is derived from the seven-step detailed mechanism, for application near the flammability limit. The one-step results are used to calculate flammability limits and burning velocities of planar deflagrations. Furthermore, implications concerning radical profiles in the deflagration and reasons for the success of the approximations are clarified. It is also demonstrated that adding only two irreversible direct recombination steps to the seven-step mechanism accurately reproduces burning velocities of the full detailed mechanism for all equivalence ratios at normal atmospheric conditions and that an eight-step detailed mechanism, constructed from the seven-step mechanism by adding to it the fourth reversible shuffle reaction, improves predictions of O and OH profiles. The new reduced-chemistry descriptions can be useful for both analytical and computational studies of lean hydrogen-air flames, decreasing required computation times. (author)

  3. EVALUATING SYSTEMATIC DEPENDENCIES OF TYPE Ia SUPERNOVAE: THE INFLUENCE OF DEFLAGRATION TO DETONATION DENSITY

    SciTech Connect

    Jackson, Aaron P.; Calder, Alan C.; Townsley, Dean M.; Chamulak, David A.; Brown, Edward F.; Timmes, F. X.

    2010-09-01

    We explore the effects of the deflagration to detonation transition (DDT) density on the production of {sup 56}Ni in thermonuclear supernova (SN) explosions (Type Ia supernovae). Within the DDT paradigm, the transition density sets the amount of expansion during the deflagration phase of the explosion and therefore the amount of nuclear statistical equilibrium (NSE) material produced. We employ a theoretical framework for a well-controlled statistical study of two-dimensional simulations of thermonuclear SNe with randomized initial conditions that can, with a particular choice of transition density, produce a similar average and range of {sup 56}Ni masses to those inferred from observations. Within this framework, we utilize a more realistic 'simmered' white dwarf progenitor model with a flame model and energetics scheme to calculate the amount of {sup 56}Ni and NSE material synthesized for a suite of simulated explosions in which the transition density is varied in the range (1-3) x10{sup 7} g cm{sup -3}. We find a quadratic dependence of the NSE yield on the log of the transition density, which is determined by the competition between plume rise and stellar expansion. By considering the effect of metallicity on the transition density, we find the NSE yield decreases by 0.055 {+-} 0.004 M {sub sun} for a 1 Z{sub sun} increase in metallicity evaluated about solar metallicity. For the same change in metallicity, this result translates to a 0.067 {+-} 0.004 M{sub sun} decrease in the {sup 56}Ni yield, slightly stronger than that due to the variation in electron fraction from the initial composition. Observations testing the dependence of the yield on metallicity remain somewhat ambiguous, but the dependence we find is comparable to that inferred from some studies.

  4. Mesoscale challenge of extending atomistic scale chemistry of initiation reactions to deflagration-to-detonation transition

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Santanu

    2015-06-01

    Predictive simulations connecting chemistry that follow the shock or thermal initiation of energetic materials to subsequent deflagration or detonation events is currently outside the realm of possibilities. Molecular dynamics and first-principles based dynamics have made progress in understanding reactions in picosecond to nanosecond time scale. However, connecting the events that leads to deflagration will require simulations using much larger length and time scale to connect the full reaction network. This constitutes a mesoscale challenge in energetic materials research. Recent advances in addressing this mesoscale chemistry challenge in other domains will be discussed. Development in coarse-grain simulations and accelerating reactive MD simulations faces the challenge of simplifying the chemistry by making assumptions on the mechanism with consequences on the outcome. For example, results from thermal ignition of different phases of RDX shows a complex reaction and deterministic behavior for critical temperature before ignition. First-principles calculations for validation of key pathways observed will be discussed. The kinetics observed is dependent on the hot spot temperature, system size and thermal conductivity. Smaller hot spots in simulations needed higher temperature for ignition of the solid. For cases where ignition is observed, the incubation period is dominated by intermolecular and intramolecular hydrogen transfer reactions. The gradual temperature and pressure increase in the incubation period is accompanied by accumulation of heavier polyradicals. The polyradicals with triazine rings from the RDX molecules intact undergo ring-opening reactions which fuel a series of rapid exothermic chemical reactions. Our ongoing work on connecting mesoscale and continuum scale will be discussed. Funding from DTRA Grant # HDTRA1-13-1-0018 acknowledged.

  5. A new mechanism for deflagration-to-detonation in porous granular explosives

    NASA Astrophysics Data System (ADS)

    Gifford, M. J.; Luebcke, P. E.; Field, J. E.

    1999-08-01

    An investigation has been carried out into the differences between the deflagration-to-detonation (DDT) process as it occurs in low density [˜30% theoretical maximum density (TMD)] columns of conventional grain size (˜180 μm) pentaerythritol tetranitrate (PETN) and in ultrafine PETN with a grain size ˜1 μm. The principle technique for observing the process utilized charges confined within a steel housing fitted with a polycarbonate slit window. This allowed direct recording of the transition using high speed streak photography. The explosive was thermally ignited using a pyrotechnic mixture with low gaseous emission to minimize any prepressurization of the charge. In addition to the photographic records of the events, the outputs of photodiodes along the length of the column were monitored in order to determine the rate at which the reaction proceeds. The results obtained show that the DDT process in the larger grain PETN at low density was similar in structure to the DDT process at higher densities. In contrast a different mechanism leads to detonation in columns composed of the smaller grain size PETN when packed to densities less than 50% TMD. After ignition hot gases propagate along the column both compacting and igniting material as they pass. After the gases have reached the downstream end of the column, the column continues to burn and the pressure and temperature increase. Some time later initiation takes place at a point along the burning column, and detonation waves propagate in both directions from this point. The detonation waves propagate from the initiation point at speeds that would normally be associated with material compacted to around 60% TMD. The process appears to be in effect a deflagration-to-localized thermal explosion detonation transition.

  6. Front Range Branch Officers

    NASA Astrophysics Data System (ADS)

    The Front Range Branch of AGU has installed officers for 1990: Ray Noble, National Center for Atmospheric Research, chair; Sherry Oaks, U.S. Geological Survey, chair-elect; Howard Garcia, NOAA, treasurer; Catharine Skokan, Colorado School of Mines, secretary. JoAnn Joselyn of NOAA is past chair. Members at large are Wallace Campbell, NOAA; William Neff, USGS; and Stephen Schneider, NCAR.

  7. Nanoparticle Oscillations and Fronts

    SciTech Connect

    Lagzi, Istvan; Kowalczyk, Bartlomiej; Wang, Dawei; Grzybowski, Bartosz A.

    2010-09-30

    Chemical oscillations can be coupled to the dynamic self-assembly of nanoparticles. Periodic pH changes translate into protonation and deprotonation of the ligands that stabilize the nanoparticles, thus altering repulsive and attractive interparticle forces. In a continuous stirred-tank reactor, rhythmic aggregation and dispersion is observed; in spatially distributed media, propagation of particle aggregation fronts is seen.

  8. A study on the characteristics of the deflagration of hydrogen-air mixture under the effect of a mesh aluminum alloy.

    PubMed

    Pang, Lei; Wang, Chenxu; Han, Mengxing; Xu, Zilong

    2015-12-15

    Mesh aluminum alloys (MAAs) have been widely used in military and civilian applications to suppress the explosion of flammable gases (fluids) inside containers. However, MAAs have not been tested in or applied to the hydrogen suppression-explosions. Hence, a typical MAA product, i.e., one that has been in wide use, is selected as the experimental material in the present study. The characteristics of the deflagration of hydrogen-air mixture inside an MAA-filled tube are investigated, and the effects of the filling density of the MAA and the concentration of hydrogen in air on the deflagration are examined. The suppressing effect of the MAA on the deflagration of hydrogen-air mixture is compared with its effect on the deflagration of a typical hydrocarbon fuel in air. The results show that not only is the existing MAA product unable to effectively suppress the deflagration of hydrogen-air mixture, but it also increases the maximum explosion pressure, which is opposite to the satisfactory suppressing effect of the MAA product on the deflagration of hydrocarbon fuels such as methane. The results of this study provide a scientific basis for the effective prevention of explosion accidents with hydrogen and for the development of explosion-suppression products. PMID:26124063

  9. A study on the characteristics of the deflagration of hydrogen-air mixture under the effect of a mesh aluminum alloy.

    PubMed

    Pang, Lei; Wang, Chenxu; Han, Mengxing; Xu, Zilong

    2015-12-15

    Mesh aluminum alloys (MAAs) have been widely used in military and civilian applications to suppress the explosion of flammable gases (fluids) inside containers. However, MAAs have not been tested in or applied to the hydrogen suppression-explosions. Hence, a typical MAA product, i.e., one that has been in wide use, is selected as the experimental material in the present study. The characteristics of the deflagration of hydrogen-air mixture inside an MAA-filled tube are investigated, and the effects of the filling density of the MAA and the concentration of hydrogen in air on the deflagration are examined. The suppressing effect of the MAA on the deflagration of hydrogen-air mixture is compared with its effect on the deflagration of a typical hydrocarbon fuel in air. The results show that not only is the existing MAA product unable to effectively suppress the deflagration of hydrogen-air mixture, but it also increases the maximum explosion pressure, which is opposite to the satisfactory suppressing effect of the MAA product on the deflagration of hydrocarbon fuels such as methane. The results of this study provide a scientific basis for the effective prevention of explosion accidents with hydrogen and for the development of explosion-suppression products.

  10. 9. DETAIL OF INTERIOR OF FRONT PORCH SHOWING FRONT ENTRY ...

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

    9. DETAIL OF INTERIOR OF FRONT PORCH SHOWING FRONT ENTRY (LEFT) AND BLANK WALL (CENTER) CORRESPONDING TO LOCATION OF INTERIOR VAULTS. VIEW TO SOUTHEAST. - Boise Project, Boise Project Office, 214 Broadway, Boise, Ada County, ID

  11. 35. EAST FRONT OF POWERHOUSE AND CAR BARN: East front ...

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

    35. EAST FRONT OF POWERHOUSE AND CAR BARN: East front of powerhouse and car barn. 'Annex' is right end of building. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

  12. 4. BARRACKS, WITH PARKING LOT IN FRONT, FRONT AND RIGHT ...

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

    4. BARRACKS, WITH PARKING LOT IN FRONT, FRONT AND RIGHT SIDES, LOOKING SOUTH. - NIKE Missile Base SL-40, Barracks No. 2, North end of base, southeast of Barracks No. 1 & northeast of Mess Hall, Hecker, Monroe County, IL

  13. 1. BARRACKS, WITH PARKING LOT IN FRONT, FRONT, LOOKING SOUTHWEST. ...

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

    1. BARRACKS, WITH PARKING LOT IN FRONT, FRONT, LOOKING SOUTHWEST. - NIKE Missile Base SL-40, Barracks No. 2, North end of base, southeast of Barracks No. 1 & northeast of Mess Hall, Hecker, Monroe County, IL

  14. 3. VIEW NORTH, SOUTHWEST FRONT, SOUTHEAST SIDE Front and side ...

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

    3. VIEW NORTH, SOUTHWEST FRONT, SOUTHEAST SIDE Front and side elevation. Note gasoline sign post added. Flush store window not altered, 1900 clapboard siding and panelling remaining. - 510 Central Avenue (Commercial Building), Ridgely, Caroline County, MD

  15. ARIEL front end

    NASA Astrophysics Data System (ADS)

    Marchetto, M.; Baartman, R. A.; Laxdal, R. E.

    2014-01-01

    The ARIEL project at TRIUMF will greatly expand the variety and availability of radioactive ion beams (RIBs) (Laxdal, Nucl Inst Methods Phys Res B 204:400-409, 2003). The ARIEL front end connects the two ARIEL target stations to the existing ISAC facility to expand delivery to two and eventually three simultaneous RIB beams with up to two simultaneous accelerated beams (Laxdal et al. 2008). The low-energy beam transport lines and mass separators are designed for maximum flexibility to allow a variety of operational modes in order to optimize the radioactive ion beam delivery. A new accelerator path is conceived for high mass delivery from an EBIS charge state breeder. The front-end design utilizes the experience gained in 15 years of ISAC beam delivery.

  16. Theory of pinned fronts

    NASA Astrophysics Data System (ADS)

    Weissmann, Haim; Shnerb, Nadav M.; Kessler, David A.

    2016-01-01

    The properties of a front between two different phases in the presence of a smoothly inhomogeneous external field that takes its critical value at the crossing point is analyzed. Two generic scenarios are studied. In the first, the system admits a bistable solution and the external field governs the rate in which one phase invades the other. The second mechanism corresponds to a continuous transition that, in the case of reactive systems, takes the form of a transcritical bifurcation at the crossing point. We solve for the front shape and for the response of competitive fronts to external noise, showing that static properties and also some of the dynamical features cannot discriminate between the two scenarios. A reliable indicator turns out to be the fluctuation statistics. These take a Gaussian form in the bifurcation case and a double-peaked shape in a bistable system. Our results are discussed in the context of biological processes, such as species and communities dynamics in the presence of a resource gradient.

  17. Radiative thermal conduction fronts

    NASA Technical Reports Server (NTRS)

    Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

    1990-01-01

    The discovery of the O VI interstellar absorption lines in our Galaxy by the Copernicus observatory was a turning point in our understanding of the Interstellar Medium (ISM). It implied the presence of widespread hot (approx. 10 to the 6th power K) gas in disk galaxies. The detection of highly ionized species in quasi-stellar objects' absorption spectra may be the first indirect observation of this hot phase in external disk galaxies. Previous efforts to understand extensive O VI absorption line data from our Galaxy were not very successful in locating the regions where this absorption originates. The location at interfaces between evaporating ISM clouds and hot gas was favored, but recent studies of steady-state conduction fronts in spherical clouds by Ballet, Arnaud, and Rothenflug (1986) and Bohringer and Hartquist (1987) rejected evaporative fronts as the absorption sites. Researchers report here on time-dependent nonequilibrium calculations of planar conductive fronts whose properties match well with observations, and suggest reasons for the difference between the researchers' results and the above. They included magnetic fields in additional models, not reported here, and the conclusions are not affected by their presence.

  18. The Physics of Deflagration-to-Detonation Transition in Type Ia Supernovae

    NASA Astrophysics Data System (ADS)

    Poludnenko, Alexei

    BACKGROUND: The scenario currently best capable of explaining the observational properties of normal bright type Ia supernovae (SNIa), which are of primary importance for cosmology, is the delayed detonation model of the explosion of a white dwarf star with the mass near the Chandrasekhar limit in a single-degenerate binary system. In this model, the explosion starts as a subsonic deflagration that later transitions to a supersonic detonation (deflagration-to-detonation transition, or DDT). Significant progress has been made over the years both experimentally and numerically in elucidating the physics of DDT in terrestrial confined systems. It remains unclear, however, whether and how a detonation can be formed in an unpressurized, unconfined system such as the interior of a WD. Modern large-scale multidimensional models of SNIa cannot capture the DDT process and, thus, are forced to make two crucial assumptions, namely (a) that DDT does occur at some point, and (b) when and where it occurs. As a result, delayed detonation is a parameterized model that must be "tuned" in order to obtain the proper match with the observations. This substantially hinders the possibility of investigating potential sources of systematic errors in the calibration of normal bright SNIa as standard candles. Recently we have carried out a systematic study of the high-speed turbulence-flame interaction through first-principles direct numerical simulations (DNS) using reaction models similar to those describing terrestrial chemical flames. Our analysis has shown that at sufficiently high turbulent intensities, subsonic turbulent flames in unconfined environments, such as the WD interior, are indeed inherently susceptible to DDT. The associated mechanism is based on the unsteady evolution of turbulent flames faster than the Chapman-Jouguet deflagrations. This process is qualitatively different from the traditional spontaneous reaction wave model and does not require the formation of

  19. THERMAL FRONTS IN SOLAR FLARES

    SciTech Connect

    Karlický, Marian

    2015-12-01

    We studied the formation of a thermal front during the expansion of hot plasma into colder plasma. We used a three-dimensional electromagnetic particle-in-cell model that includes inductive effects. In early phases, in the area of the expanding hot plasma, we found several thermal fronts, which are defined as a sudden decrease of the local electron kinetic energy. The fronts formed a cascade. Thermal fronts with higher temperature contrast were located near plasma density depressions, generated during the hot plasma expansion. The formation of the main thermal front was associated with the return-current process induced by hot electron expansion and electrons backscattered at the front. A part of the hot plasma was trapped by the thermal front while another part, mainly with the most energetic electrons, escaped and generated Langmuir and electromagnetic waves in front of the thermal front, as shown by the dispersion diagrams. Considering all of these processes and those described in the literature, we show that anomalous electric resistivity is produced at the location of the thermal front. Thus, the thermal front can contribute to energy dissipation in the current-carrying loops of solar flares. We estimated the values of such anomalous resistivity in the solar atmosphere together with collisional resistivity and electric fields. We propose that the slowly drifting reverse drift bursts, observed at the beginning of some solar flares, could be signatures of the thermal front.

  20. Thermal Fronts in Solar Flares

    NASA Astrophysics Data System (ADS)

    Karlický, Marian

    2015-12-01

    We studied the formation of a thermal front during the expansion of hot plasma into colder plasma. We used a three-dimensional electromagnetic particle-in-cell model that includes inductive effects. In early phases, in the area of the expanding hot plasma, we found several thermal fronts, which are defined as a sudden decrease of the local electron kinetic energy. The fronts formed a cascade. Thermal fronts with higher temperature contrast were located near plasma density depressions, generated during the hot plasma expansion. The formation of the main thermal front was associated with the return-current process induced by hot electron expansion and electrons backscattered at the front. A part of the hot plasma was trapped by the thermal front while another part, mainly with the most energetic electrons, escaped and generated Langmuir and electromagnetic waves in front of the thermal front, as shown by the dispersion diagrams. Considering all of these processes and those described in the literature, we show that anomalous electric resistivity is produced at the location of the thermal front. Thus, the thermal front can contribute to energy dissipation in the current-carrying loops of solar flares. We estimated the values of such anomalous resistivity in the solar atmosphere together with collisional resistivity and electric fields. We propose that the slowly drifting reverse drift bursts, observed at the beginning of some solar flares, could be signatures of the thermal front.

  1. Simple front tracking

    SciTech Connect

    Glimm, J.; Grove, J.W.; Li, X.; Zhao, N.

    1999-04-01

    A new and simplified front tracking algorithm has been developed as an aspect of the extension of this algorithm to three dimensions. Here the authors emphasize two main results: (1) a simplified description of the microtopology of the interface, based on interface crossings with cell block edges, and (2) an improved algorithm for the interaction of a tracked contact discontinuity with an untracked shock wave. For the latter question, they focus on the post interaction jump at the contact, which is a purely 1D issue. Comparisons to other methods, including the level set method, are included.

  2. [Instantaneous emission spectra of epoxypropane in the process of deflagration to detonation transition].

    PubMed

    Li, Ping; Yuan, Chang-ying; Hu, Dong; Liu, Jun-chao; Zhu-mei, Sun; Dong, Shi; Xiao, Hai-bo

    2004-07-01

    Using an intensified CCD spectroscopic detector (Princeton Instruments, ICCD PI-Max 1024 RB) which can be gated in as little as 5 ns, the synchronization of the measuring system was controlled by a digital delay generator (Stanford Research Systems, DG535), the DG535 was triggered externally by a lab-made electrical pulse generator which transformed the optical trigger signal to an electrical signal, and the light signal from the end window of an explosion shock tube was delivered by an 1 mm in diameter plastic optical fiber to the entrance slit of the spectrometer (grating of 150 g x mm(-1) , central wavelength of 550 nm). The spectrum measurement of the epoxypropane in the process of deflagration to detonation transition (DDT) was then made. The instantaneous emission spectra of epoxypropane at different time of the DDT process with an exposure time of several microseconds were acquired. Results show that at the beginning of the DDT process, the emitted light was very weak and the line spectra of atoms were observed mainly; in the middle process of the DDT, the emitted light became strong and the spectra observed consisted of line spectra of atoms, band spectra of molecules plus continuous spectrum of the thermal radiation; when the detonation was formed, the emitted light got very strong, and the spectra acquired consisted of both line spectra of atoms and band spectra of molecules superimposed on the strong continuum of the thermal radiation. PMID:15766070

  3. Tantalum dust deflagration in a bag filter dust-collecting device.

    PubMed

    Matsuda, T; Yamaguma, M

    2000-10-01

    An accidental tantalum powder deflagration with casualties occurred during the operation of a bag filter dust-collecting device. To understand the mechanism of the incident and its material hazards, experiments for determining the combustibility and ignition characteristics of the tantalum powder were performed. The magnitude of the tantalum dust explosion is classified as severe (K(st)=273), contrary to the classification found in the preceding literature. The minimum ignition energies for both a dust cloud and a dust layer of the tantalum powder were also found to be far lower than previous values. Judging from the observation of the surface with an SEM, the coral-like structure of each particle of the tantalum powder can enhance its fire and explosion hazards and affect its sensitivity to electrostatic sparks by increasing in particle surface area. A thin, non-conductive oxide layer of the tantalum powder surface has a high resistivity and generates electrostatic charge when rubbed with conductive materials like the wall of the collecting device. The authors conclude that the possible cause of the ignition was electrostatic discharge resulting from charging electrostatically. PMID:10946117

  4. The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode As Deflagrations?

    SciTech Connect

    Phillips, M.M.; Li, W.; Frieman, J.A.; Blinnikov, S.I.; DePoy, D.; Prieto, J.L.; Milne, P.; Contreras, C.; Folatelli, Gaston; Morrell, N.; Hamuy, M.; Suntzeff, N.B.; Roth, M.; Gonzalez, S.; Krzeminski, W.; Filippenko, A.V.; Freedman, W.L.; Chornock, R.; Jha, S.; Madore, B.F.; Persson, S.E.; /Las Campanas Observ. /UC, Berkeley, Astron. Dept. /Chicago U., Astron. Astrophys. Ctr. /KICP, Chicago /Fermilab /Moscow, ITEP /Garching, Max Planck Inst. /Ohio State U., Dept. Astron. /Arizona U., Astron. Dept. - Steward Observ. /Chile U., Santiago /Texas A-M /Carnegie Inst. Observ. /KIPAC, Menlo Park /Caltech, IPAC /Notre Dame U. /South African Astron. Observ. /Cape Town U. /Washington U., Seattle, Astron. Dept. /New Mexico State U. /Chicago U., FLASH /Baltimore, Space Telescope Sci.

    2006-11-14

    We present extensive u{prime}g{prime}r{prime}i{prime} BV RIY JHK{sub s} photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called 'the most peculiar known type Ia supernova'. Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal type Ia supernovae. Our Y JH photometry of SN 2005hk reveals the same peculiarity in the near-infrared. By combining our optical and near-infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from {approx} 10 days before to {approx}60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near-infrared wavelengths, are all in reasonable agreement with model calculations of a 3D deflagration which produces {approx} 0.25 M{sub {circle_dot}} of {sup 56}Ni.

  5. The development of laser ignited deflagration-to-detonation transition (DDT) detonators and pyrotechnic actuators

    SciTech Connect

    Merson, J.A.; Salas, F.J.

    1994-05-01

    The use of laser ignited explosive components has been recognized as a safety enhancement over existing electrical explosive devices (EEDs). Sandia has been pursuing the development of optical ordnance for many years with recent emphasis on developing optical deflagration-to-detonation (DDT) detonators and pyrotechnic actuators. These low energy optical ordnance devices can be ignited with either a semiconductor diode laser, laser diode arrays or a solid state rod laser. By using a semiconductor laser diode, the safety improvement can be made without sacrificing performance since the input energy required for the laser diode and the explosive output are similar to existing electrical systems. The use of higher powered laser diode arrays or rod lasers may have advantages in fast DDT applications or lossy optical environments such as long fiber applications and applications with numerous optical connectors. Recent results from our continued study of optical ignition of explosive and pyrotechnic materials are presented. These areas of investigation can be separated into three different margin categories: (1) the margin relative to intended inputs ( i.e. powder performance as a function of laser input variation), (2) the margin relative to anticipated environments (i.e. powder performance as a function of thermal environment variation), and (3) the margin relative to unintended environments (i.e. responses to abnormal environments or safety).

  6. Tantalum dust deflagration in a bag filter dust-collecting device.

    PubMed

    Matsuda, T; Yamaguma, M

    2000-10-01

    An accidental tantalum powder deflagration with casualties occurred during the operation of a bag filter dust-collecting device. To understand the mechanism of the incident and its material hazards, experiments for determining the combustibility and ignition characteristics of the tantalum powder were performed. The magnitude of the tantalum dust explosion is classified as severe (K(st)=273), contrary to the classification found in the preceding literature. The minimum ignition energies for both a dust cloud and a dust layer of the tantalum powder were also found to be far lower than previous values. Judging from the observation of the surface with an SEM, the coral-like structure of each particle of the tantalum powder can enhance its fire and explosion hazards and affect its sensitivity to electrostatic sparks by increasing in particle surface area. A thin, non-conductive oxide layer of the tantalum powder surface has a high resistivity and generates electrostatic charge when rubbed with conductive materials like the wall of the collecting device. The authors conclude that the possible cause of the ignition was electrostatic discharge resulting from charging electrostatically.

  7. Mechanisms of deflagration-to-detonation transition under initiation by high-voltage nanosecond discharges

    SciTech Connect

    Rakitin, Aleksandr E.; Starikovskii, Andrei Yu.

    2008-10-15

    An experimental study of detonation initiation in a stoichiometric propane-oxygen mixture by a high-voltage nanosecond gas discharge was performed in a detonation tube with a single-cell discharge chamber. The discharge study performed in this geometry showed that three modes of discharge development were realized under the experimental conditions: a spark mode with high-temperature channel formation, a streamer mode with nonuniform gas excitation, and a transient mode. Under spark and transient initiation, simultaneous ignition inside the discharge channel occurred, forming a shock wave and leading to a conventional deflagration-to-detonation transition (DDT) via an adiabatic explosion. The DDT length and time at 1 bar of initial pressure in the square smooth tube with a 20-mm transverse size amounted to 50 mm and 50{mu}s, respectively. The streamer mode of discharge development at an initial pressure of 1 bar resulted in nonuniform mixture excitation and a successful DDT via a gradient mechanism, which was confirmed by high-speed time resolved ICCD imaging. The gradient mechanism implied a longer DDT time of 150{mu}s, a DDT run-up distance of 50 mm, and an initiation energy of 1 J, which is two orders of magnitude less than the direct initiation energy for a planar detonation under these conditions. (author)

  8. [Instantaneous emission spectra of epoxypropane in the process of deflagration to detonation transition].

    PubMed

    Li, Ping; Yuan, Chang-ying; Hu, Dong; Liu, Jun-chao; Zhu-mei, Sun; Dong, Shi; Xiao, Hai-bo

    2004-07-01

    Using an intensified CCD spectroscopic detector (Princeton Instruments, ICCD PI-Max 1024 RB) which can be gated in as little as 5 ns, the synchronization of the measuring system was controlled by a digital delay generator (Stanford Research Systems, DG535), the DG535 was triggered externally by a lab-made electrical pulse generator which transformed the optical trigger signal to an electrical signal, and the light signal from the end window of an explosion shock tube was delivered by an 1 mm in diameter plastic optical fiber to the entrance slit of the spectrometer (grating of 150 g x mm(-1) , central wavelength of 550 nm). The spectrum measurement of the epoxypropane in the process of deflagration to detonation transition (DDT) was then made. The instantaneous emission spectra of epoxypropane at different time of the DDT process with an exposure time of several microseconds were acquired. Results show that at the beginning of the DDT process, the emitted light was very weak and the line spectra of atoms were observed mainly; in the middle process of the DDT, the emitted light became strong and the spectra observed consisted of line spectra of atoms, band spectra of molecules plus continuous spectrum of the thermal radiation; when the detonation was formed, the emitted light got very strong, and the spectra acquired consisted of both line spectra of atoms and band spectra of molecules superimposed on the strong continuum of the thermal radiation.

  9. The development of laser ignited deflagration-to-detonation transition (DDT) detonators and pyrotechnic actuators

    SciTech Connect

    Merson, J.A.; Salas, F.J.; Harlan, J.G.

    1993-11-01

    The use of laser ignited explosive components has been recognized as a safety enhancement over existing electrical explosive devices (EEDs). Sandia has been pursuing the development of optical ordnance for many years with recent emphasis on developing optical deflagration-to-detonation (DDT) detonators and pyrotechnic actuators. These low energy optical ordnance devices can be ignited with either a semiconductor diode laser, laser diode arrays or a solid state rod laser. By using a semiconductor laser diode, the safety improvement can be made without sacrificing performance since the input energy required for the laser diode and the explosive output are similar to existing electrical systems. The use of higher powered laser diode arrays or rod lasers may have advantages in fast DDT applications or lossy optical environments such as long fiber applications and applications with numerous optical connectors. Recent results from our continued study of optical ignition of explosive and pyrotechnic materials are presented. These areas of investigation can be separated into three different margin categories: (1) the margin relative to intended inputs (i.e. powder performance as a function of laser input variation), (2) the margin relative to anticipated environments (i.e. powder performance as a function of thermal environment variation), and (3) the margin relative to unintended environments (i.e. responses to abnormal environments or safety).

  10. Deflagration-induced flash of solid pyrotechnics as pumps for high-energy solid state lasers

    NASA Astrophysics Data System (ADS)

    Kang, Xiaoli; Liu, Liming; Tang, Yongjian

    2013-09-01

    Using the flash produced by deflagration of solid pyrotechnics to pump the laser gain medium is a potentially effective way to develop portable high power lasers. The purpose of this work is to examine the effect of some optimization or modifications in terms of compositions and distribution of the pyrotechnic pumping sources on the laser output. The optimization means the transmittance of the output couple. Modifications include: (1) pyrotechnic compositions are improved by adding small amounts of nano Al powders; (2) distribution of pumping light around the laser rod is changed through changing the discrete pyrotechnic tablets into continuous pyrotechnic bars. Results showed that laser output energy reached the maximum of 656 mJ when the transmittance of output mirror raised to10%; after adding nano Al powders into pyrotechnic compositions, laser energy increased by 80% at addition of 2% in the case of discrete distribution, while in the case of continuous distribution, even the mass of pyrotechnics was halved, laser energy still increased to the maximum of 442 mJ with 1% nano Al added. Besides, typical temporal waveform and spot of the laser as well as the light radiation performance of the pyrotechnic tablet are measured to help analyze the laser output performance. It is suggested that the mechanisms of the three modifications we employed are different though they all lead to increase in laser output.

  11. Observation and modeling of deflagration-to-detonation (DDT) transition in low-density HMX

    NASA Astrophysics Data System (ADS)

    Tringe, Joseph; Vandersall, Kevin; Reaugh, Jack; Levie, Harold; Henson, Bryan; Smilowitz, Laura; Parker, Gary

    2015-06-01

    We employ simultaneous flash x-ray radiography and streak imaging, together with a multi-phase finite element model, to understand deflagration-to-detonation transition (DDT) phenomena in low-density (~ 1.2 gm/cm3) powder of the explosive cyclotetramethylene-tetranitramine (HMX). HMX powder was lightly hand-tamped in a 12.7 mm diameter column, relatively lightly-confined in an optically-transparent polycarbonate cylinder with wall thickness 25.4 mm. We observe apparent compaction of the powder in advance of the detonation transition, both by x-ray contrast and by the motion of small steel spheres pre-emplaced throughout the length of explosive. High-speed imaging along the explosive cylinder length provides a temporally continuous record of the transition that is correlated with the high-resolution x-ray image record. Preliminary simulation of these experiments with the HERMES model implemented in the ALE3D code enables improved understanding of the explosive particle burning, compaction and detonation phenomena which are implied by the observed reaction rate and transition location within the cylinder. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. Measurement of the flow properties within a copper tube containing a deflagrating explosive

    SciTech Connect

    Hill, Larry G; Morris, John S; Jackson, Scott I

    2009-01-01

    We report on the propagation of deflagration waves in the high explosive (HE) PBX 9501 (95 wt % HMX, 5 wt% binder). Our test configuration, which we call the def1agration cylinder test (DFCT), is fashioned after the detonation cylinder test (DTCT) that is used to calibrate the JWL detonation product equation of state (EOS). In the DFCT, the HE is heated to a uniform slightly subcritical temperature, and is ignited at one end by a hot wire. For some configurations and initial conditions, we observe a quasi-steady wave that flares the tube into a funnel shape, stretching it to the point of rupture. This behavior is qualitatively like the DTCT, such that, by invoking certain additional approximations that we discuss, its behavior can be analyzed by the same methods. We employ an analysis proposed by G.I. Taylor to infer the pressure-volume curve for the burning, expanding flow. By comparing this result to the EOS of HMX product gas alone. we infer that only {approx}20 wt% of the HMX has burned at tube rupture. This result confirms pre-existing observations about the role of convective burning in HMX cookoff explosions.

  13. Study on the Mechanism of the Deflagration to Detonation Transition Process of Explosive

    NASA Astrophysics Data System (ADS)

    Ying, Yangjun; Hu, Xiaomian; Wei, Lan

    2014-03-01

    In this paper we presented a numerical study of the mechanisms of the deflagration to detonation transition (DDT) process of explosives to assess its thermal stability. We treated the modeling system as a mixture of solid explosives and gaseous reaction products. We utilized a one-dimensional two-phase flow modeling approach with space-time conservation element and solution element (CE/SE) method. Simulation results show a plug area of high density with relatively slow chemical reactions, whose forward boundary is the fast running shock wave, and rearward boundary is the burning wave.We identified a criterion of steady detonation through a detailed analysis of the characteristics of the reaction process: steady detonation occurs at locations where different physical quantities, such as pressure, density, temperature and velocity, reach peak values simultaneously.We also simulated the high temperature DDT tube experiments of HMX-based high explosive. We found good agreement between the simulation results of detonation velocity and run length determined by the above criterion and the experimental results.

  14. New Front End Technology

    SciTech Connect

    Pennington, D; Jovanovic, I; Comaskey, B J

    2001-02-01

    The next generation of Petawatt class lasers will require the development of new laser technology. Optical parametric chirped pulse amplification (OPCPA) holds a potential to increase the peak power level to >10 PW with existing grating technology through ultrashort pulses. Furthermore, by utilizing a new type of front-end system based on optical parametric amplification, pulses can be produced with substantially higher contrast than with Ti:sapphire regenerative amplifier technology. We performed extensive study of OPCPA using a single crystal-based OPA. We developed a replacement for Ti:sapphire regenerative amplifier for high peak power lasers based on OPCPA, with an output of 30 mJ, at 10 Hz repetition rate and 16.5 nm spectral bandwidth. We developed a 3D numerical model for OPCPA and we performed a theoretical study of influences of pump laser beam quality on optical parametric amplification. Our results indicate that OPCPA represents a valid replacement for Ti:sapphire in the front end of high energy short pulse lasers.

  15. Vehicle front wheel assist drive overspeed control system

    SciTech Connect

    Riehl, D.C.

    1987-01-13

    This patent describes a front wheel drive speed control system for a vehicle having a rear wheel drive and an assisting front wheel drive, comprising: (a) a hydraulic pump means operably connected by a hydraulic circuit to a hydraulic motor at each driven front wheel to cause rotation of that wheel; (b) an overrunning clutch assembly interposed between the motor and each associated wheel, engageable to facilitate rotation of the driven front wheel in both forward and reverse directions; (c) a speed sensing means has main rear wheel drive sensor mounted with a vehicle transmission output to the driven rear wheels thereof operable to provide pulse signals indicative of the speed of rotation of the driven rear wheels; (d) a driven front wheel sensor mounted with the vehicle and operable to provide pulse signals indicative of the speed of rotation of the driven front wheel; (e) a comparator means operable to compare the rate of rear wheel pulse signals with a first predetermined rate to produce a front wheel enabling signal when the rear wheel pulse signals are below the first predetermined rate; and (f) a front wheel drive operating circuit means connected to the comparator means to receive the front wheel enabling signal and operable to activate the hydraulic pump means to cause rotation of the front wheel.

  16. From the front

    SciTech Connect

    Price, Stephen

    2009-01-01

    The causes of recent dynamic thinning of Greenland's outlet glaciers have been debated. Realistic simulations suggest that changes at the marine fronts of these glaciers are to blame, implying that dynamic thinning will cease once the glaciers retreat to higher ground. For the last decade, many outlet glaciers in Greenland that terminate in the ocean have accelerated, thinned, and retreated. To explain these dynamic changes, two hypotheses have been discussed. Atmospheric warming has increased surface melting and may also have increased the amount of meltwater reaching the glacier bed, increasing lubrication at the base and hence the rate of glacier sliding. Alternatively, a change in the delicate balance of forces where the glacier fronts meet the ocean could trigger the changes. Faezeh Nick and colleagues5 present ice-sheet modeling experiments that mimic the observations on Helheim glacier, East Greenland, and suggest that the dynamic behaviour of outlet glaciers follows from perturbations at their marine fronts. Greenland's ice sheet loses mass partly through surface melting and partly through fast flowing outlet glaciers that connect the vast plateau of inland ice with the ocean. Earlier ice sheet models have failed to reproduce the dynamic variability exhibited by ice sheets over time. It has therefore not been possible to distinguish with confidence between basal lubrication from surface meltwater and changes at the glaciers' marine fronts as causes for the observed changes on Greenland's outlet glaciers. But this distinction bears directly on future sea-level rise, the raison d'etre of much of modern-day glaciology: If the recent dynamic mass loss Greenland's outlet glaciers is linked to changing atmospheric temperatures, it may continue for as long as temperatures continue to increase. On the other hand, if the source of the dynamic mass loss is a perturbation at the ice-ocean boundary, these glaciers will lose contact with that perturbation after a finite

  17. Time Line Visualization of Research Fronts.

    ERIC Educational Resources Information Center

    Morris, Steven A.; Yen, G.; Wu, Zheng; Asnake, Benyam

    2003-01-01

    Research fronts, defined as clusters of documents that tend to cite a fixed, time invariant set of base documents, are plotted as time lines for visualization and exploration. Illustrates the construction, exploration, and interpretation of time lines for identifying and visualizing temporal changes in research activity through journal articles.…

  18. FLAMES IN TYPE Ia SUPERNOVA: DEFLAGRATION-DETONATION TRANSITION IN THE OXYGEN-BURNING FLAME

    SciTech Connect

    Woosley, S. E.; Kerstein, A. R.; Aspden, A. J. E-mail: arkerst@sandia.gov

    2011-06-10

    The flame in a Type Ia supernova is a conglomerate structure that, depending on density, may involve separate regions of carbon, oxygen, and silicon burning, all propagating in a self-similar, subsonic front. The separation between these three burning regions increases as the density declines until eventually, below about 2 x 10{sup 7} g cm{sup -3}, only carbon burning remains active, the other two burning phases having 'frozen out' on stellar scales. Between 2 and 3 x 10{sup 7} g cm{sup -3}, however, there remains an energetic oxygen-burning region that trails the carbon burning by an amount that is sensitive to the turbulence intensity. As the carbon flame makes a transition to the distributed regime (Karlovitz number {approx}> 10), the characteristic separation between the carbon- and oxygen-burning regions increases dramatically, from a fraction of a meter to many kilometers. The oxygen-rich mixture between the two flames is created at a nearly constant temperature, and turbulence helps to maintain islands of well-mixed isothermal fuel as the temperature increases. The delayed burning of these regions can be supersonic and could initiate a detonation.

  19. Bioconvection and front formation of Paramecium tetraurelia

    NASA Astrophysics Data System (ADS)

    Kitsunezaki, So; Komori, Rie; Harumoto, Terue

    2007-10-01

    We have investigated the bioconvection of Paramecium tetraurelia in high-density suspensions made by centrifugal concentration. When a suspension is kept at rest in a Hele-Shaw cell, a crowded front of paramecia is formed in the vicinity of the bottom and it propagates gradually toward the water-air interface. Fluid convection occurs under this front, and it is driven persistently by the upward swimming of paramecia. The roll structures of the bioconvection become turbulent with an increase in the depth of the suspension; they also change rapidly as the density of paramecia increases. Our experimental results suggest that lack of oxygen in the suspension causes the active individual motions of paramecia to induce the formation of this front.

  20. On a front line.

    PubMed Central

    Jones, L.

    1995-01-01

    Like the patients, doctors in Sarajevo depend largely on humanitarian aid; everyone in the public sector has worked without pay for almost three years. The hospital is on a front line; yet the psychiatric department continues to function, even conducting large scale studies of psychosocial aspects of war in Bosnia-Hercegovina. The type of inpatient morbidity and treatment patterns have changed. A plethora of psychosocial rehabilitation programmes has emerged, including counselling, drop in centres, and attending to special needs of elderly people, schoolchildren, and women. The most prominent psychological symptoms were exhaustion at the prospect of a third winter of war and bewilderment at the Western stereotype of Bosnians as Muslim fundamentalists. Images p1052-a p1053-a PMID:7728062

  1. Two dimensional numerical prediction of deflagration-to-detonation transition in porous energetic materials.

    PubMed

    Narin, B; Ozyörük, Y; Ulas, A

    2014-05-30

    This paper describes a two-dimensional code developed for analyzing two-phase deflagration-to-detonation transition (DDT) phenomenon in granular, energetic, solid, explosive ingredients. The two-dimensional model is constructed in full two-phase, and based on a highly coupled system of partial differential equations involving basic flow conservation equations and some constitutive relations borrowed from some one-dimensional studies that appeared in open literature. The whole system is solved using an optimized high-order accurate, explicit, central-difference scheme with selective-filtering/shock capturing (SF-SC) technique, to augment central-diffencing and prevent excessive dispersion. The sources of the equations describing particle-gas interactions in terms of momentum and energy transfers make the equation system quite stiff, and hence its explicit integration difficult. To ease the difficulties, a time-split approach is used allowing higher time steps. In the paper, the physical model for the sources of the equation system is given for a typical explosive, and several numerical calculations are carried out to assess the developed code. Microscale intergranular and/or intragranular effects including pore collapse, sublimation, pyrolysis, etc. are not taken into account for ignition and growth, and a basic temperature switch is applied in calculations to control ignition in the explosive domain. Results for one-dimensional DDT phenomenon are in good agreement with experimental and computational results available in literature. A typical shaped-charge wave-shaper case study is also performed to test the two-dimensional features of the code and it is observed that results are in good agreement with those of commercial software. PMID:24721693

  2. Three-dimensional Simulations of Pure Deflagration Models for Thermonuclear Supernovae

    NASA Astrophysics Data System (ADS)

    Long, Min; Jordan, George C., IV; van Rossum, Daniel R.; Diemer, Benedikt; Graziani, Carlo; Kessler, Richard; Meyer, Bradley; Rich, Paul; Lamb, Don Q.

    2014-07-01

    We present a systematic study of the pure deflagration model of Type Ia supernovae (SNe Ia) using three-dimensional, high-resolution, full-star hydrodynamical simulations, nucleosynthetic yields calculated using Lagrangian tracer particles, and light curves calculated using radiation transport. We evaluate the simulations by comparing their predicted light curves with many observed SNe Ia using the SALT2 data-driven model and find that the simulations may correspond to under-luminous SNe Iax. We explore the effects of the initial conditions on our results by varying the number of randomly selected ignition points from 63 to 3500, and the radius of the centered sphere they are confined in from 128 to 384 km. We find that the rate of nuclear burning depends on the number of ignition points at early times, the density of ignition points at intermediate times, and the radius of the confining sphere at late times. The results depend primarily on the number of ignition points, but we do not expect this to be the case in general. The simulations with few ignition points release more nuclear energy E nuc, have larger kinetic energies E K, and produce more 56Ni than those with many ignition points, and differ in the distribution of 56Ni, Si, and C/O in the ejecta. For these reasons, the simulations with few ignition points exhibit higher peak B-band absolute magnitudes M B and light curves that rise and decline more quickly; their M B and light curves resemble those of under-luminous SNe Iax, while those for simulations with many ignition points are not.

  3. Turbulent flame speeds in ducts and the deflagration/detonation transition

    SciTech Connect

    Bradley, D.; Lawes, M.; Liu, Kexin

    2008-07-15

    A methodology is proposed for determining whether a deflagration-to-detonation transition (DDT) might occur for flame propagation along a duct with baffles, closed at the ignition end. A flammable mixture can attain a maximum turbulent burning velocity. If this is sufficiently high, a strong shock is formed ahead of the flame. It is assumed that this maximum burning velocity is soon attained and on the basis of previous studies, this value can be obtained for the given conditions. The increase in temperature and pressure of the reactants, due to the shock, further increases the maximum turbulent burning velocity. The gas velocity ahead of the flame is linked to one-dimensional shock wave equations in a numerical analysis. The predicted duct flame speeds with the appropriate maximum turbulent burning velocities are in good agreement with those measured in the slow and fast flame regimes of a range of CH{sub 4}-air and H{sub 2}-air mixtures. DDTs are possible if autoignition of the reactants occurs in the time available, and if the projected flame speed approaches the Chapman-Jouguet velocity at the same temperature and pressure. Prediction of the first condition requires values of the autoignition delay time of the mixture at the shocked temperatures and pressures. Prediction of the second requires values of the laminar burning velocity and Markstein number. With the appropriate values of these parameters, it is shown numerically that there is no DDT with CH{sub 4}-air. With H{sub 2}-air, the onset of DDT occurs close to the values of equivalence ratio at which it has been observed experimentally. The effects of different duct sizes also are predicted, although details of the DDT cannot be predicted. Extension of the study to a wider range of fuels requires more data on their laminar burning velocities and Markstein numbers at higher temperatures and pressures and on autoignition delay times at lower temperatures and pressures. (author)

  4. Origins of the deflagration-to-detonation transition in gas-phase combustion

    SciTech Connect

    Oran, Elaine S.; Gamezo, Vadim N.

    2007-01-15

    This paper summarizes a 10-year theoretical and numerical effort to understand the deflagration-to-detonation transition (DDT). To simulate DDT from first principles, it is necessary to resolve the relevant scales ranging from the size of the system to the flame thickness, a range that can cover up to 12 orders of magnitude in real systems. This computational challenge resulted in the development of numerical algorithms for solving coupled partial and ordinary differential equations and a new method for adaptive mesh refinement to deal with multiscale phenomena. Insight into how, when, and where DDT occurs was obtained by analyzing a series of multidimensional numerical simulations of laboratory experiments designed to create a turbulent flame through a series of shock-flame interactions. The simulations showed that these interactions are important for creating the conditions in which DDT can occur. Flames enhance the strength of shocks passing through a turbulent flame brush and generate new shocks. In turn, shock interactions with flames create and drive the turbulence in flames. The turbulent flame itself does not undergo a transition, but it creates conditions in nearby unreacted material that lead to ignition centers, or 'hot spots,' which can then produce a detonation through the Zeldovich gradient mechanism involving gradients of reactivity. Obstacles and boundary layers, through their interactions with shocks and flames, help to create environments in which hot spots can develop. Other scenarios producing reactivity gradients that can lead to detonations include flame-flame interactions, turbulent mixing of hot products with reactant gases, and direct shock ignition. Major unresolved questions concern the properties of nonequilibrium, shock-driven turbulence, stochastic properties of ignition events, and the possibility of unconfined DDT. (author)

  5. Three-dimensional simulations of pure deflagration models for thermonuclear supernovae

    SciTech Connect

    Long, Min; Jordan, George C. IV; Van Rossum, Daniel R.; Diemer, Benedikt; Graziani, Carlo; Kessler, Richard; Rich, Paul; Lamb, Don Q.; Meyer, Bradley

    2014-07-10

    We present a systematic study of the pure deflagration model of Type Ia supernovae (SNe Ia) using three-dimensional, high-resolution, full-star hydrodynamical simulations, nucleosynthetic yields calculated using Lagrangian tracer particles, and light curves calculated using radiation transport. We evaluate the simulations by comparing their predicted light curves with many observed SNe Ia using the SALT2 data-driven model and find that the simulations may correspond to under-luminous SNe Iax. We explore the effects of the initial conditions on our results by varying the number of randomly selected ignition points from 63 to 3500, and the radius of the centered sphere they are confined in from 128 to 384 km. We find that the rate of nuclear burning depends on the number of ignition points at early times, the density of ignition points at intermediate times, and the radius of the confining sphere at late times. The results depend primarily on the number of ignition points, but we do not expect this to be the case in general. The simulations with few ignition points release more nuclear energy E{sub nuc}, have larger kinetic energies E{sub K}, and produce more {sup 56}Ni than those with many ignition points, and differ in the distribution of {sup 56}Ni, Si, and C/O in the ejecta. For these reasons, the simulations with few ignition points exhibit higher peak B-band absolute magnitudes M{sub B} and light curves that rise and decline more quickly; their M{sub B} and light curves resemble those of under-luminous SNe Iax, while those for simulations with many ignition points are not.

  6. Neutrinos from type Ia supernovae: The deflagration-to-detonation transition scenario

    DOE PAGES

    Wright, Warren P.; Nagaraj, Gautam; Kneller, James P.; Scholberg, Kate; Seitenzahl, Ivo R.

    2016-07-19

    It has long been recognized that the neutrinos detected from the next core-collapse supernova in the Galaxy have the potential to reveal important information about the dynamics of the explosion and the nucleosynthesis conditions as well as allowing us to probe the properties of the neutrino itself. The neutrinos emitted from thermonuclear—type Ia—supernovae also possess the same potential, although these supernovae are dimmer neutrino sources. For the first time, we calculate the time, energy, line of sight, and neutrino-flavor-dependent features of the neutrino signal expected from a three-dimensional delayed-detonation explosion simulation, where a deflagration-to-detonation transition triggers the complete disruption ofmore » a near-Chandrasekhar mass carbon-oxygen white dwarf. We also calculate the neutrino flavor evolution along eight lines of sight through the simulation as a function of time and energy using an exact three-flavor transformation code. We identify a characteristic spectral peak at ˜10 MeV as a signature of electron captures on copper. This peak is a potentially distinguishing feature of explosion models since it reflects the nucleosynthesis conditions early in the explosion. We simulate the event rates in the Super-K, Hyper-K, JUNO, and DUNE neutrino detectors with the SNOwGLoBES event rate calculation software and also compute the IceCube signal. Hyper-K will be able to detect neutrinos from our model out to a distance of ˜10 kpc. Here, at 1 kpc, JUNO, Super-K, and DUNE would register a few events while IceCube and Hyper-K would register several tens of events.« less

  7. The influence of initial temperature on flame acceleration and deflagration-to-detonation transition

    SciTech Connect

    Ciccarelli, G.; Boccio, J.L.; Ginsberg, T.

    1996-07-01

    The influence of initial mixture temperature on deflagration-to-detonation transition (DDT) has been investigated experimentally. The experiments were carried out in a 27-cm-inner diameter, 21.3-meter-long heated detonation tube, which was equipped with periodic orifice plates to promote flame acceleration. Hydrogen-air-steam mixtures were tested at a range of temperatures up to 650K and at an initial pressure of 0.1 MPa. In most cases, the limiting hydrogen mole fraction which resulted in transition to detonation corresponded to the mixture whose detonation cell size, {lambda}, was approximately equal to the inner diameter of the orifice plate, d (e.g., d/{lambda}{approximately}1). The only exception was in dry hydrogen-air mixtures at 650K where the DDT limit was observed to be 11 percent hydrogen, corresponding to a value of d/{lambda} equal to 5.5. For a 10.5 percent hydrogen mixture at 650K, the flame accelerated to a maximum velocity of about 120 m/s and then decelerated to below 2 m/s. This observation indicates that the d/{lambda} = 1 DDT limit criterion provides a necessary condition but not a sufficient one for the onset of DDT in obstacle-laden ducts. In this particular case, the mixture initial condition (i.e., temperature) resulted in the inability of the mixture to sustain flame acceleration to the point where DDT could occur. It was also observed that the distance required for the flame to accelerate to the onset of detonation was a function of both the hydrogen mole fraction and the mixture initial temperature. For example, decreasing the hydrogen mole fraction or increasing the initial mixture temperature resulted in longer transition distances.

  8. Neutrinos from type Ia supernovae: The deflagration-to-detonation transition scenario

    NASA Astrophysics Data System (ADS)

    Wright, Warren P.; Nagaraj, Gautam; Kneller, James P.; Scholberg, Kate; Seitenzahl, Ivo R.

    2016-07-01

    It has long been recognized that the neutrinos detected from the next core-collapse supernova in the Galaxy have the potential to reveal important information about the dynamics of the explosion and the nucleosynthesis conditions as well as allowing us to probe the properties of the neutrino itself. The neutrinos emitted from thermonuclear—type Ia—supernovae also possess the same potential, although these supernovae are dimmer neutrino sources. For the first time, we calculate the time, energy, line of sight, and neutrino-flavor-dependent features of the neutrino signal expected from a three-dimensional delayed-detonation explosion simulation, where a deflagration-to-detonation transition triggers the complete disruption of a near-Chandrasekhar mass carbon-oxygen white dwarf. We also calculate the neutrino flavor evolution along eight lines of sight through the simulation as a function of time and energy using an exact three-flavor transformation code. We identify a characteristic spectral peak at ˜10 MeV as a signature of electron captures on copper. This peak is a potentially distinguishing feature of explosion models since it reflects the nucleosynthesis conditions early in the explosion. We simulate the event rates in the Super-K, Hyper-K, JUNO, and DUNE neutrino detectors with the SNOwGLoBES event rate calculation software and also compute the IceCube signal. Hyper-K will be able to detect neutrinos from our model out to a distance of ˜10 kpc . At 1 kpc, JUNO, Super-K, and DUNE would register a few events while IceCube and Hyper-K would register several tens of events.

  9. Shock-flame Interactions and Deflagration-to-Detonation Transition in Type Ia Supernovae.

    NASA Astrophysics Data System (ADS)

    Gamezo, Vadim N.; Oran, E. S.

    2007-05-01

    We study shock-flame interactions on small scales as a possible mechanism for deflagration-to-detonation transition (DDT) in an exploding carbon-oxygen white dwarf. Thermonuclear flames are modeled using reactive Navier-Stokes equations coupled with a 13-species alpha-network. Two-dimensional numerical simulations that resolve carbon and oxygen burning scales show that shock-flame interactions produce turbulent flames through Richtmyer-Meshkov instabilities and accelerate shocks. This may result in DDT when shocks become strong enough to produce hot spots in unburned carbon-oxygen mixture. In contrast to terrestrial chemical systems, for which similar phenomena are well known, we observe an additional mechanism for shock acceleration related to different length scales of carbon and oxygen burning in a white dwarf. The slow oxygen burning can release almost as much energy as the fast carbon burning, and occurs in a hot material where carbon is already depleted. Shocks that propagate through the hot and relatively thick oxygen burning zone can pick up energy and even produce detonations driven only by the oxygen burning. When this oxygen detonation enters the cold unburned material, it can ignite it and produce a regular carbon-oxygen detonation. Our simulations show this can occur for densities below 8x10^7 g/cm^3. For higher densities, shocks produced by oxygen detonations are too weak to ignite carbon. This work was supported in part by the NASA ATP program (NRA NNH05ZDA001N-AT) and by the Naval Research Laboratory (NRL) through the Office of Naval Research.

  10. Two dimensional numerical prediction of deflagration-to-detonation transition in porous energetic materials.

    PubMed

    Narin, B; Ozyörük, Y; Ulas, A

    2014-05-30

    This paper describes a two-dimensional code developed for analyzing two-phase deflagration-to-detonation transition (DDT) phenomenon in granular, energetic, solid, explosive ingredients. The two-dimensional model is constructed in full two-phase, and based on a highly coupled system of partial differential equations involving basic flow conservation equations and some constitutive relations borrowed from some one-dimensional studies that appeared in open literature. The whole system is solved using an optimized high-order accurate, explicit, central-difference scheme with selective-filtering/shock capturing (SF-SC) technique, to augment central-diffencing and prevent excessive dispersion. The sources of the equations describing particle-gas interactions in terms of momentum and energy transfers make the equation system quite stiff, and hence its explicit integration difficult. To ease the difficulties, a time-split approach is used allowing higher time steps. In the paper, the physical model for the sources of the equation system is given for a typical explosive, and several numerical calculations are carried out to assess the developed code. Microscale intergranular and/or intragranular effects including pore collapse, sublimation, pyrolysis, etc. are not taken into account for ignition and growth, and a basic temperature switch is applied in calculations to control ignition in the explosive domain. Results for one-dimensional DDT phenomenon are in good agreement with experimental and computational results available in literature. A typical shaped-charge wave-shaper case study is also performed to test the two-dimensional features of the code and it is observed that results are in good agreement with those of commercial software.

  11. FACILITY 1042. FRONT OBLIQUE SHOWING ROYAL PALMS LINING FRONT WALK. ...

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

    FACILITY 1042. FRONT OBLIQUE SHOWING ROYAL PALMS LINING FRONT WALK. VIEW FACING SOUTHEAST - U.S. Naval Base, Pearl Harbor, Naval Housing Area Hale Alii, Junior Officers' Quarters Type, 9-10 Hale Alii Avenue, 1-2 Eighth Street, Pearl City, Honolulu County, HI

  12. Measurement and ALE3D Simulation of Violence in a Deflagration Experiment With LX-10 and Aermet-100 Alloy

    SciTech Connect

    Knap, J; McClelland, M A; Maienschein, J L; Howard, W M; Nichols, A L; deHaven, M R; Strand, O T

    2006-06-22

    We describe the results of a Scaled-Thermal-Explosion-eXperiment (STEX) for LX-10 (94.7 % HMX, 5.3 % Viton A) confined in an AerMet 100 (iron-cobalt-nickel alloy) tube with reinforced end caps. The experimental measurements are compared with predictions of an Arbitrary-Lagrangian-Eulerian (ALE3D) computer model. ALE3D is a three-dimensional multi-physics computer code capable of solving coupled equations describing thermal, mechanical and chemical behavior of materials. In particular, we focus on the processes linked to fracture and fragmentation of the AerMet tube driven by the LX-10 deflagration.

  13. Dynamic compaction of granular materials in a tube with wall friction, applied to deflagration-to-detonation transition

    SciTech Connect

    Hill, L.G.; Kapila, A.K.

    1995-09-01

    A theoretical problem is considered in which a granular material is pushed through a tube of arbitrary cross-section by a constant velocity piston against the resistance of compaction work and wall friction. The crushing of the material is dictated by a simple yet physically reasonable compaction law. By considering two special cases - the limit of vanishing friction and the quasistatic limit - we identify the two basic compaction wave structures. We then consider the general case in which the two waves interact. Estimates suggest that for typical deflagration-to-detonation tests explosive at the wall melts on time scales short compared to the experiment.

  14. Offshore Deformation Front in Miaoli Area

    NASA Astrophysics Data System (ADS)

    Chiang, P.; Gwo-shyn, S.

    2015-12-01

    Taiwan is located at the junction of the Eurasian Plate and the Philippine Sea Plate. It's because arc-continent collision occurs in the western Taiwan, resulting in the orogeny has formed a fold-and-thrust belt, developing a series of thrusts aligned in north-south direction. The thrust faults, locating in the central island, are the oldest and have almost inactive. Westward to the island, the faults become younger, dipping angles are smaller, and motions were stronger. On the west side, the foot of the Taiwan Western Foothill is considered the youngest thrust faults located along west Taiwan. Scholars recognized them as so-called the deformation front, and they also believed that the deformation front is located in between the compressive terrain uplifted area and the extensional subsidence area. Therefore, this front line is on the boundary of two different tectonic zones. This study investigates the trace of the deformation front in Miaoli area. Previous studies suggested that the west side of Miaoli collision zone should be fault-bounded, and is located in the seabed. However, in the geological map, there is no geologic evidence that appears on land and so-called active faults related with this deformation front. In the near coast seafloor, according to the reflection earthquakes data from the Institute of Oceanography of NTU, we can only see the offshore strata have been uplifted, and the data also shows that seabed is only covered by thin layer of sediments. This study indicates that in offshore place within three kilometers, shallow formations show a special layer of slime which was extruded to be corrugated transversely. Accordingly, we believe that this slime layer should be pressurized and filled with muddy water. Such features should be further investigated with other geological and geophysical survey data to check if they belong to the structural product of the deformation front.

  15. Surface properties of ocean fronts

    NASA Technical Reports Server (NTRS)

    Wolff, P. M.; Hubert, W. E.

    1976-01-01

    Background information on oceanic fronts is presented and the results of several models which were developed to study the dynamics of oceanic fronts and their effects on various surface properties are described. The details of the four numerical models used in these studies are given in separate appendices which contain all of the physical equations, program documentation and running instructions for the models.

  16. Snowplow Injection Front Effects

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Chandler, M. O.; Buzulukova, N.; Collinson, G. A.; Kepko, E. L.; Garcia-Sage, K. S.; Henderson, M. G.; Sitnov, M. I.

    2013-01-01

    As the Polar spacecraft apogee precessed through the magnetic equator in 2001, Polar encountered numerous substorm events in the region between geosynchronous orbit and 10 RE geocentric distance; most of them in the plasma sheet boundary layers. Of these, a small number was recorded near the neutral sheet in the evening sector. Polar/Thermal Ion Dynamics Experiment provides a unique perspective on the lowest-energy ion plasma, showing that these events exhibited a damped wavelike character, initiated by a burst of radially outward flow transverse to the local magnetic field at approximately 80 km/s. They then exhibit strongly damped cycles of inward/outward flow with a period of several minutes. After one or two cycles, they culminated in a hot plasma electron and ion injection, quite similar to those observed at geosynchronous orbit. Cold plasmaspheric plasmas comprise the outward flow cycles, while the inward flow cycles contain counterstreaming field-parallel polar wind-like flows. The observed wavelike structure, preceding the arrival of an earthward moving substorm injection front, suggests an outward displacement driven by the inward motion at local times closer to midnight, that is, a "snowplow" effect. The damped in/out flows are consistent with interchange oscillations driven by the arrival at the observed local time by an injection originating at greater radius and local time.

  17. Fronts in Large Marine Ecosystems

    NASA Astrophysics Data System (ADS)

    Belkin, Igor M.; Cornillon, Peter C.; Sherman, Kenneth

    2009-04-01

    Oceanic fronts shape marine ecosystems; therefore front mapping and characterization are among the most important aspects of physical oceanography. Here we report on the first global remote sensing survey of fronts in the Large Marine Ecosystems (LME). This survey is based on a unique frontal data archive assembled at the University of Rhode Island. Thermal fronts were automatically derived with the edge detection algorithm of Cayula and Cornillon (1992, 1995, 1996) from 12 years of twice-daily, global, 9-km resolution satellite sea surface temperature (SST) fields to produce synoptic (nearly instantaneous) frontal maps, and to compute the long-term mean frequency of occurrence of SST fronts and their gradients. These synoptic and long-term maps were used to identify major quasi-stationary fronts and to derive provisional frontal distribution maps for all LMEs. Since SST fronts are typically collocated with fronts in other water properties such as salinity, density and chlorophyll, digital frontal paths from SST frontal maps can be used in studies of physical-biological correlations at fronts. Frontal patterns in several exemplary LMEs are described and compared, including those for: the East and West Bering Sea LMEs, Sea of Okhotsk LME, East China Sea LME, Yellow Sea LME, North Sea LME, East and West Greenland Shelf LMEs, Newfoundland-Labrador Shelf LME, Northeast and Southeast US Continental Shelf LMEs, Gulf of Mexico LME, and Patagonian Shelf LME. Seasonal evolution of frontal patterns in major upwelling zones reveals an order-of-magnitude growth of frontal scales from summer to winter. A classification of LMEs with regard to the origin and physics of their respective dominant fronts is presented. The proposed classification lends itself to comparative studies of frontal ecosystems.

  18. High-speed OH-PLIF imaging of deflagration-to-detonation transition in H2-air mixtures

    NASA Astrophysics Data System (ADS)

    Boeck, Lorenz R.; Mével, Rémy; Fiala, Thomas; Hasslberger, Josef; Sattelmayer, Thomas

    2016-06-01

    Planar laser-induced fluorescence (PLIF) is considered a standard experimental technique in combustion diagnostics. However, it has only been occasionally applied to explosion experiments with fast combustion regimes. It has been shown that single-shot OH-PLIF with high pulse energies yields clear fluorescence images of fast deflagrations and also detonations. This paper presents the first application of high-speed OH-PLIF at 20 kHz repetition rate to a deflagration-to-detonation transition experiment. Hydrogen-air mixtures at initial atmospheric pressure and ambient temperature are investigated. Satisfactory results are obtained for flame speeds up to about 500 m/s. Flame instabilities and turbulence-flame interactions are observed. Two factors limit the applicability of HS OH-PLIF toward higher flame speeds: excessive flame luminescence masking the HS OH-PLIF signal and strong absorption of laser light by the flame. The variation in OH-PLIF signal-to-background ratio across a DDT process is studied using a 1D laminar premixed flame simulation extended by spectroscopic models.

  19. Atomistic picture of the shock to deflagration transition in a solid explosive: ultra-fast chemistry under non-equilibrium

    NASA Astrophysics Data System (ADS)

    Wood, Mitchell; Cherukara, Mathew; Kober, Edward; Strachan, Alejandro

    2015-03-01

    We use large-scale molecular dynamics (MD) simulations to describe the chemical reactions following the shock-induced collapse of cylindrical pores in the high-energy density material RDX. For shocks with particle velocities of 2km/s, we find that the collapse of a 40 nm diameter pore leads to a deflagration wave, resulting in the first atomic-level description of this process. Pore collapse leads to ultra-fast, multi-step chemical reactions that occur under non-equilibrium conditions. The formation of exothermic product molecules within a few picoseconds of the pore collapse prevents the nanoscale hot spot from quenching. Within 30 ps, a local deflagration wave develops which propagates at speeds of ~ 0.25 km/s and consists of an ultra-thin reaction zone of only ~ 5 nm, thus involving large temperature and composition gradients. These results provide insight into the initiation of detonation, which is critical to understanding the performance and safety of this class of materials.

  20. Deflagrations in hybrid CONe white dwarfs: a route to explain the faint Type Iax supernova 2008ha

    NASA Astrophysics Data System (ADS)

    Kromer, M.; Ohlmann, S. T.; Pakmor, R.; Ruiter, A. J.; Hillebrandt, W.; Marquardt, K. S.; Röpke, F. K.; Seitenzahl, I. R.; Sim, S. A.; Taubenberger, S.

    2015-07-01

    Stellar evolution models predict the existence of hybrid white dwarfs (WDs) with a carbon-oxygen core surrounded by an oxygen-neon mantle. Being born with masses ˜1.1 M⊙, hybrid WDs in a binary system may easily approach the Chandrasekhar mass (MCh) by accretion and give rise to a thermonuclear explosion. Here, we investigate an off-centre deflagration in a near-MCh hybrid WD under the assumption that nuclear burning only occurs in carbon-rich material. Performing hydrodynamics simulations of the explosion and detailed nucleosynthesis post-processing calculations, we find that only 0.014 M⊙ of material is ejected while the remainder of the mass stays bound. The ejecta consist predominantly of iron-group elements, O, C, Si and S. We also calculate synthetic observables for our model and find reasonable agreement with the faint Type Iax SN 2008ha. This shows for the first time that deflagrations in near-MCh WDs can in principle explain the observed diversity of Type Iax supernovae. Leaving behind a near-MCh bound remnant opens the possibility for recurrent explosions or a subsequent accretion-induced collapse in faint Type Iax SNe, if further accretion episodes occur. From binary population synthesis calculations, we find the rate of hybrid WDs approaching MCh to be of the order of 1 per cent of the Galactic SN Ia rate.

  1. The effect of initial temperature on flame acceleration and deflagration-to-detonation transition phenomenon

    SciTech Connect

    Ciccarelli, G.; Boccio, J.L.; Ginsberg, T.; Finfrock, C.; Gerlach, L.; Tagawa, H.; Malliakos, A.

    1998-05-01

    The High-Temperature Combustion Facility at BNL was used to conduct deflagration-to-detonation transition (DDT) experiments. Periodic orifice plates were installed inside the entire length of the detonation tube in order to promote flame acceleration. The orifice plates are 27.3-cm-outer diameter, which is equivalent to the inner diameter of the tube, and 20.6-cm-inner diameter. The detonation tube length is 21.3-meters long, and the spacing of the orifice plates is one tube diameter. A standard automobile diesel engine glow plug was used to ignite the test mixture at one end of the tube. Hydrogen-air-steam mixtures were tested at a range of temperatures up to 650K and at an initial pressure of 0.1 MPa. In most cases, the limiting hydrogen mole fraction which resulted in DDT corresponded to the mixture whose detonation cell size, {lambda}, was equal to the inner diameter of the orifice plate, d (e.g., d/{lambda}=1). The only exception was in the dry hydrogen-air mixtures at 650K where the DDT limit was observed to be 11 percent hydrogen, corresponding to a value of d/{lambda} equal to 5.5. For a 10.5 percent hydrogen mixture at 650K, the flame accelerated to a maximum velocity of about 120 mIs and then decelerated to below 2 mIs. By maintaining the first 6.1 meters of the vessel at the ignition end at 400K, and the rest of the vessel at 650K, the DDT limit was reduced to 9.5 percent hydrogen (d/{lambda}=4.2). This observation indicates that the d/{lambda}=1 DDT limit criteria provides a necessary condition but not a sufficient one for the onset of DDT in obstacle laden ducts. In this particular case, the mixture initial condition (i.e., temperature) resulted in the inability of the mixture to sustain flame acceleration to the point where DDT could occur. It was also observed that the distance required for the flame to accelerate to the point of detonation initiation, referred to as the run-up distance, was found to be a function of both the hydrogen mole fraction

  2. 6. OVERALL VIEW OF THE FRONT AND THE TOWER, LOOKING ...

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

    6. OVERALL VIEW OF THE FRONT AND THE TOWER, LOOKING WEST FROM THE ACTIVE PIER OF BAY SHIP AND YACHT COMPANY. COAST GUARD CUTTER SHERMAN AT RIGHT. - United Engineering Company Shipyard, Crane, 2900 Main Street, Alameda, Alameda County, CA

  3. An explanation of unstable wetting fronts in soils

    NASA Astrophysics Data System (ADS)

    Steenhuis, Tammo; Parlange, Jean-Yves; Kung, Samuel; Stoof, Cathelijne; Baver, Christine

    2016-04-01

    Despite the findings of Raats on unstable wetting front almost a half a century ago, simulating wetting fronts in soils is still an area of active research. One of the critical questions currently is whether Darcy law is valid at the wetting front. In this talk, we pose that in many cases for dry soils, Darcy's law does not apply because the pressure field across the front is not continuous. Consequently, the wetting front pressure is not dependent on the pressure ahead of the front but is determined by the radius of water meniscuses and the dynamic contact angle of the water. If we further assume since the front is discontinuous, that water flows at one pore at the time, then by using the modified Hoffman relationship - relating the dynamic contact angle to the pore water velocity - we find the elevated pressures at the wetting front typical for unstable flows that are similar to those observed experimentally in small diameter columns. The theory helps also explain the funnel flow phenomena observed in layered soils.

  4. Radiative magnetized thermal conduction fronts

    NASA Technical Reports Server (NTRS)

    Borkowski, Kazimierz J.; Balbus, Steven A.; Fristrom, Carl C.

    1990-01-01

    The evolution of plane-parallel magnetized thermal conduction fronts in the interstellar medium (ISM) was studied. Separating the coronal ISM phase and interstellar clouds, these fronts have been thought to be the site of the intermediate-temperature regions whose presence was inferred from O VI absorption-line studies. The front evolution was followed numerically, starting from the initial discontinuous temperature distribution between the hot and cold medium, and ending in the final cooling stage of the hot medium. It was found that, for the typical ISM pressure of 4000 K/cu cm and the hot medium temperature of 10 to the 6th K, the transition from evaporation to condensation in a nonmagnetized front occurs when the front thickness is 15 pc. This thickness is a factor of 5 smaller than previously estimated. The O VI column densities in both evaporative and condensation stages agree with observations if the initial hot medium temperature Th exceeds 750,000 K. Condensing conduction fronts give better agreement with observed O VI line profiles because of lower gas temperatures.

  5. Restless rays, steady wave fronts.

    PubMed

    Godin, Oleg A

    2007-12-01

    Observations of underwater acoustic fields with vertical line arrays and numerical simulations of long-range sound propagation in an ocean perturbed by internal gravity waves indicate that acoustic wave fronts are much more stable than the rays comprising these wave fronts. This paper provides a theoretical explanation of the phenomenon of wave front stability in a medium with weak sound-speed perturbations. It is shown analytically that at propagation ranges that are large compared to the correlation length of the sound-speed perturbations but smaller than ranges at which ray chaos develops, end points of rays launched from a point source and having a given travel time are scattered primarily along the wave front corresponding to the same travel time in the unperturbed environment. The ratio of root mean square displacements of the ray end points along and across the unperturbed wave front increases with range as the ratio of ray length to correlation length of environmental perturbations. An intuitive physical explanation of the theoretical results is proposed. The relative stability of wave fronts compared to rays is shown to follow from Fermat's principle and dimensional considerations. PMID:18247745

  6. Io in Front of Jupiter

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Jupiter's four largest satellites, including Io, the golden ornament in front of Jupiter in this image from NASA's Cassini spacecraft, have fascinated Earthlings ever since Galileo Galilei discovered them in 1610 in one of his first astronomical uses of the telescope.

    Images from Cassini that will be released over the next several days capture each of the four Galilean satellites in their orbits around the giant planet.

    This true-color composite frame, made from narrow angle images taken on Dec. 12, 2000, captures Io and its shadow in transit against the disk of Jupiter. The distance of the spacecraft from Jupiter was 19.5 million kilometers (12.1 million miles). The image scale is 117 kilometers (73 miles) per pixel.

    The entire body of Io, about the size of Earth's Moon, is periodically flexed as it speeds around Jupiter and feels, as a result of its non-circular orbit, the periodically changing gravitational pull of the planet. The heat arising in Io's interior from this continual flexure makes it the most volcanically active body in the solar system, with more than 100 active volcanoes. The white and reddish colors on its surface are due to the presence of different sulfurous materials. The black areas are silicate rocks.

    Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C.

  7. Pentan isomers compound flame front structure

    SciTech Connect

    Mansurov, Z.A.; Mironenko, A.W.; Bodikov, D.U.; Rachmetkaliev, K.N.

    1995-08-13

    The fuels (hexane, pentane, diethyl ether) and conditions investigated in this study are relevant to engine knock in spark- ignition engines. A review is provided of the field of low temperature hydrocarbon oxidation. Studies were made of radical and stable intermediate distribution in the front of cool flames: Maximum concentrations of H atoms and peroxy radicals were observed in the luminous zone of the cool flame front. Peroxy radicals appear before the luminous zone at 430 K due to diffusion. H atoms were found in cool flames of butane and hexane. H atoms diffuses from the luminous zone to the side of the fresh mixture, and they penetrate into the fresh mixture to a small depth. Extension of action sphear of peroxy radicals in the fresh mixture is much greater than that of H atoms due to their small activity and high concentrations.

  8. Electromagnetic energy conversion at reconnection fronts.

    PubMed

    Angelopoulos, V; Runov, A; Zhou, X-Z; Turner, D L; Kiehas, S A; Li, S-S; Shinohara, I

    2013-09-27

    Earth's magnetotail contains magnetic energy derived from the kinetic energy of the solar wind. Conversion of that energy back to particle energy ultimately powers Earth's auroras, heats the magnetospheric plasma, and energizes the Van Allen radiation belts. Where and how such electromagnetic energy conversion occurs has been unclear. Using a conjunction between eight spacecraft, we show that this conversion takes place within fronts of recently reconnected magnetic flux, predominantly at 1- to 10-electron inertial length scale, intense electrical current sheets (tens to hundreds of nanoamperes per square meter). Launched continually during intervals of geomagnetic activity, these reconnection outflow flux fronts convert ~10 to 100 gigawatts per square Earth radius of power, consistent with local magnetic flux transport, and a few times 10(15) joules of magnetic energy, consistent with global magnetotail flux reduction. PMID:24072917

  9. Electromagnetic energy conversion at reconnection fronts.

    PubMed

    Angelopoulos, V; Runov, A; Zhou, X-Z; Turner, D L; Kiehas, S A; Li, S-S; Shinohara, I

    2013-09-27

    Earth's magnetotail contains magnetic energy derived from the kinetic energy of the solar wind. Conversion of that energy back to particle energy ultimately powers Earth's auroras, heats the magnetospheric plasma, and energizes the Van Allen radiation belts. Where and how such electromagnetic energy conversion occurs has been unclear. Using a conjunction between eight spacecraft, we show that this conversion takes place within fronts of recently reconnected magnetic flux, predominantly at 1- to 10-electron inertial length scale, intense electrical current sheets (tens to hundreds of nanoamperes per square meter). Launched continually during intervals of geomagnetic activity, these reconnection outflow flux fronts convert ~10 to 100 gigawatts per square Earth radius of power, consistent with local magnetic flux transport, and a few times 10(15) joules of magnetic energy, consistent with global magnetotail flux reduction.

  10. The Front Line.

    ERIC Educational Resources Information Center

    Unks, Gerald

    1979-01-01

    The author draws an analogy between today's school system and an assembly line, deploring the notion that all children are taught the same thing at the same time, ending in humiliation, disgrace, and failure for some, and nonchallenging academic activities for others. (KC)

  11. PRODUCTION OF THE p-PROCESS NUCLEI IN THE CARBON-DEFLAGRATION MODEL FOR TYPE Ia SUPERNOVAE

    SciTech Connect

    Kusakabe, Motohiko; Iwamoto, Nobuyuki; Nomoto, Ken'ichi E-mail: iwamoto.nobuyuki@jaea.go.jp

    2011-01-01

    We calculate the nucleosynthesis of proton-rich isotopes in the carbon-deflagration model for Type Ia supernovae (SNe Ia). The seed abundances are obtained by calculating the s-process nucleosynthesis that is expected to occur in the repeating helium shell flashes on the carbon-oxygen (CO) white dwarf (WD) during mass accretion from a binary companion. When the deflagration wave passes through the outer layer of the CO WD, p-nuclei are produced by photodisintegration reactions on s-nuclei in a region where the peak temperature ranges from 1.9 to 3.6 x 10{sup 9} K. We confirm the sensitivity of the p-process on the initial distribution of s-nuclei. We show that the initial C/O ratio in the WD does not affect much the yield of p-nuclei. On the other hand, the abundance of {sup 22}Ne left after s-processing has a large influence on the p-process via the {sup 22}Ne({alpha},n) reaction. We find that about 50% of p-nuclides are co-produced when normalized to their solar abundances in all adopted cases of seed distribution. Mo and Ru, which are largely underproduced in Type II supernovae (SNe II), are produced more than in SNe II although they are underproduced with respect to the yield levels of other p-nuclides. The ratios between p-nuclei and iron in the ejecta are larger than the solar ratios by a factor of 1.2. We also compare the yields of oxygen, iron, and p-nuclides in SNe Ia and SNe II and suggest that SNe Ia could make a larger contribution than SNe II to the solar system content of p-nuclei.

  12. Design of an Ultra-Efficient GaN High Power Amplifier for Radar Front-Ends Using Active Harmonic Load-Pull

    NASA Technical Reports Server (NTRS)

    Thrivikraman, Tushar; Hoffman, James

    2012-01-01

    This work presents a new measurement technique, mixed-signal active harmonic load-pull (MSALP) developed by Anterverta-mw in partnership with Maury Microwave, that allows for wide-band ultra-high efficiency amplifiers to be designed using GaN technology. An overview of the theory behind active load-pull is presented and why load-pull is important for high-power device characterization. In addition, an example procedure is presented that outlines a methodology for amplifier design using this measurement system. Lastly, measured results of a 10W GaN amplifier are presented. This work aims to highlight the benefit of using this sophisticated measurement systems for to optimize amplifier design for real radar waveforms that in turn will simplify implementation of space-based radar systems

  13. Feeding ecology and activity pattern of black-fronted titi monkeys (Callicebus nigrifrons) in a semideciduous tropical forest of southern Brazil.

    PubMed

    Caselli, Christini Barbosa; Setz, Eleonore Zulnara Freire

    2011-10-01

    Most aspects of the ecology and behavior of Callicebus nigrifrons are still unknown. The information available about this species is mainly based on a few studies that also focused on other Callicebus. We examined the feeding behavior and activity pattern of a free-ranging pair of C. nigrifrons between March and November 2007 in an area of semideciduous tropical forest of southeastern Brazil. The study site is located at the southern limit of the Tropical Zone and is characterized by pronounced seasonality. As observed for other Callicebus monkeys, fruits were the most consumed food resource, accounting for 53% of the diet, which was complemented mainly by leaves (16%) but also by invertebrates and flowers (10% of each). A great variety of plant families (28) and species (62) were included in the diet. The titis spent 35% of their time feeding, distributing the remaining time between resting (30%) and traveling (24%). Data presented here indicate that C. nigrifrons prefer high-quality food items (fruit pulp), adding low-quality food items (such as leaves) as the availability of the higher-quality foods decreases. The amount of time spent traveling and resting did not change between seasons, but the time invested in feeding increased during the lean period. The activity pattern was not related to fruit availability, but in months with lower temperatures, monkeys spent more time feeding. We suggest that the feeding ecology and activity pattern of C. nigrifrons reflect adaptations related to annual fluctuations in food availability and temperature, respectively.

  14. Lagrangian fronts in the ocean

    NASA Astrophysics Data System (ADS)

    Prants, S. V.; Budyansky, M. V.; Uleysky, M. Yu.

    2014-05-01

    We introduce the concept of Lagrangian fronts (LFs) in the ocean and describe their importance for analyzing water mixing and transport and the specific features and differences from hydrological fronts. A method of calculating LFs in a given velocity field is proposed. Based on altimeter velocity fields from AVISO data in the northwestern Pacific, we calculate the Lagrangian synoptic maps and identify LFs of different spatial and temporal scales. Using statistical analysis of saury catches in different years according to the Goskomrybolovstvo (State Fisheries Committee of the Russian Federation), we show that LFs can serve as good indicators of places that are favorable for fishing.

  15. Front tracking for gas dynamics

    SciTech Connect

    Chern, I.L.; Glimm, J.; McBryan, O.; Plohr, B.; Yaniv, S.

    1984-05-01

    Front tracking is an adaptive computational method in which a lower dimensional moving grid is fitted to and follows the dynamical evolution of distinguished waves in a fluid flow. The method takes advantage of known analytic solutions, derived from the Rankine-Hugoniot relations, for idealized discontinuities. In this paper the method is applied to the Euler equations describing compressible gas dynamics. The main thrust here is validation of the front tracking method: we present results on a series of test problems for which comparison answers can be obtained by independent methods.

  16. Front tracking for gas dynamics

    SciTech Connect

    Chern, I.; Glimm, J.; McBryan, O.; Plohr, B.; Yaniv, S.

    1986-01-01

    Front tracking is an adaptive computational method in which a lower dimensional moving grid is fitted to and follows the dynamical evolution of distinguished waves in a fluid flow. The method takes advantage of known analytic solutions, derived from the Rankine-Hugoniot relations, for idealized discontinuities. In this paper the method is applied to the Euler equations describing compressible gas dynamics. The main thrust here is validation of the front tracking method: we present results on a series of test problems for which comparison answers can be obtained by independent methods.

  17. Propagating substorm injection fronts

    NASA Technical Reports Server (NTRS)

    Moore, T. E.; Arnoldy, R. L.; Feynman, J.; Hardy, D. A.

    1981-01-01

    It is argued that a series of two-satellite observations leads to a clarification of substorm plasma injection, in which boundary motion plays a major role. Emphasis is put on a type of event characterized by abrupt, dispersionless changes in electron intensity and a coincident perturbation that consists of both a field magnitude increase and a small rotation toward more dipolar orientation. Comparing plasma observations at two points, it is found that in active, preinjection conditions the two most important features of the plasma sheet are: (1) the low-energy convection boundary for near-zero energy particles, determined by the magnitude of the large-scale convection electric field; and (2) the precipitation-flow boundary layer between the hot plasma sheet and the atmospherically contaminated inner plasma sheet.

  18. Upper plate deformation and seismic barrier in front of Nazca subduction zone: The Chololo Fault System and active tectonics along the Coastal Cordillera, southern Peru

    NASA Astrophysics Data System (ADS)

    Audin, Laurence; Lacan, Pierre; Tavera, Hernando; Bondoux, Francis

    2008-11-01

    The South America plate boundary is one of the most active subduction zone. The recent Mw = 8.4 Arequipa 2001 earthquake ruptured the subduction plane toward the south over 400 km and stopped abruptly on the Ilo Peninsula. In this exact region, the subduction seismic crisis induced the reactivation of continental fault systems in the coastal area. We studied the main reactivated fault system that trends perpendicular to the trench by detailed mapping of fault related-geomorphic features. Also, at a longer time scale, a recurrent Quaternary transtensive tectonic activity of the CFS is expressed by offset river gullies and alluvial fans. The presence of such extensional fault systems trending orthogonal to the trench along the Coastal Cordillera in southern Peru is interpreted to reflect a strong coupling between the two plates. In this particular case, stress transfer to the upper plate, at least along the coastal fringe, appears to have induced crustal seismic events that were initiated mainly during and after the 2001 earthquake. The seafloor roughness of the subducting plate is usually thought to be a cause of segmentation along subduction zones. However, after comparing and discussing the role of inherited structures within the upper plate to the subduction zone segmentation in southern Peru, we suggest that the continental structure itself may exert some feedback control on the segmentation of the subduction zone and thus participate to define the rupture pattern of major subduction earthquakes along the southern Peru continental margin.

  19. [Front Block distraction].

    PubMed

    Esnault, Olivier

    2015-03-01

    The contribution of the segmental osteotomies in the ortho-surgical protocols is no longer to demonstrate and found a new lease of life thanks to the combination with the bone distraction techniques. The osteotomy of Köle, initially described to close infraclusies, and then used to level very marked curves of Spee has more recently been used to correct anterior crowding. This support is therefore aimed at patients with an incisor and canine Class 2 but molar Class 1 with an isolated mandibular footprint. With minimal orthodontic preparation we can create in two weeks bilateral diastemas that will then be used to align the incisivocanin crowding without stripping or bicuspid extractions. Dental orthodontic movements can be resumed one month after the end of the distraction. This technique is therefore likely to avoid bicuspid extraction and replace some sagittal osteotomy advancement by correction of the overjet. It also helps to correct a incisors labial or lingual tipping playing on differential activation of the cylinders and the distractor. This segmental surgery can be combined with Le Fort 1 surgeries with correction of the transverse and associated meanings, but in a second time, to a mandibular advancement and/or a genioplasty. PMID:25888045

  20. The structure of mountain fronts

    NASA Astrophysics Data System (ADS)

    Vann, I. R.; Graham, R. H.; Hayward, A. B.

    Commonly the part of a mountain front which is visible at the surface consists of foreland-dipping thrust belt rocks elevated above their regional structural position and overlain more or less conformably by molasse. Several explanations for their geometry are possible. (1) Major detachments exist within or beneath the molasse resulting in transport of the foreland basin. Examples of this geometry come from the Swiss Molasse Plain, the Southern Pyrenees and the Mackenzie Mountains of Canada. (2) Displacement is lost on major backthrusts beneath the frontal monocline. Examples cited here are the Rockies of Alberta, the Sulaiman Ranges of Pakistan, the Mackenzies, and the Andes in Peru. (3) Thrust sheets travelled over an old land surface and syntectonic molasse contemporaneously offlaps the topographic high of the thrust front. This phenomenon occurs along the Alpine thrust front in Haute Provence. (4) The frontal fold represents deformation above a large-scale thrust tip. No unequivocal example of tip line strain at this scale has been recorded although this type of deformation may occur in the Brooks Range of Alaska. In many areas mountain fronts show a combination of these idealized geometries.

  1. Advanced RF Front End Technology

    NASA Technical Reports Server (NTRS)

    Herman, M. I.; Valas, S.; Katehi, L. P. B.

    2001-01-01

    The ability to achieve low-mass low-cost micro/nanospacecraft for Deep Space exploration requires extensive miniaturization of all subsystems. The front end of the Telecommunication subsystem is an area in which major mass (factor of 10) and volume (factor of 100) reduction can be achieved via the development of new silicon based micromachined technology and devices. Major components that make up the front end include single-pole and double-throw switches, diplexer, and solid state power amplifier. JPL's Center For Space Microsystems - System On A Chip (SOAC) Program has addressed the challenges of front end miniaturization (switches and diplexers). Our objectives were to develop the main components that comprise a communication front end and enable integration in a single module that we refer to as a 'cube'. In this paper we will provide the latest status of our Microelectromechanical System (MEMS) switches and surface micromachined filter development. Based on the significant progress achieved we can begin to provide guidelines of the proper system insertion for these emerging technologies. Additional information is contained in the original extended abstract.

  2. Align the Front End First.

    ERIC Educational Resources Information Center

    Perry, Jim

    1995-01-01

    Discussion of management styles and front-end analysis focuses on a review of Douglas McGregor's theories. Topics include Theories X, Y, and Z; leadership skills; motivational needs of employees; intrinsic and extrinsic rewards; and faulty implementation of instructional systems design processes. (LRW)

  3. Front instability in stratified media

    NASA Astrophysics Data System (ADS)

    Beltrame, Philippe

    2013-04-01

    Preferential flow in unsaturated soil may due to local heterogeneities like worm burrows but also to front instability leading to unstable finger flow (fingered pattern) in sandy textured soils. This last spontaneous preferential flow cannot be described by the standard Richards equation. Cueto-Felgueroso and Juanes proposed recently a phase field model in order to take into account a macroscopic surface tension effect at the front [1]. Their model simulates successfully the interface instability of an advancing front. We aim at simulating and understanding front instability passing a textural soil discontinuity for which the finger flow is particularly visible. We consider sand layers with different characteristics such as granulometry. Moreover, the wettability is taken into account by adding a hydrophobic term in the free energy of the phase field model. The hydrophobicity part is not only relevant for repellent soil but also to model the ultra-thin films [2]. Therefore, in our framework, this may have an influence at the front because the water saturation is nearly zero. Such a wettability influence on infiltration in porous media has recently been measured in [3]. The governing equation is analogous to the lubrication equation for which we pointed out the specific numerical difficulties [4]. A numerical code to perform time integration and bifurcation analysis was developed in [4] allowing to determine the onset of instability and its resulting dynamics in the parameter space [5]. We compute the parameter range for which the front stops when reaching the layers interface. As in [4], there is two main mechanisms that allow water to cross over the discontinuity. A first mechanism, called «depinning», leads to an intermittent flow and the second one, to a front instability and then to a finger flow. There is a parameter domain where both instabilities are present leading to a complex spatio-temporal dynamics. Finally, it is noteworthy that the wettability

  4. Reaction front formation in contaminant plumes

    NASA Astrophysics Data System (ADS)

    Cribbin, Laura B.; Winstanley, Henry F.; Mitchell, Sarah L.; Fowler, Andrew C.; Sander, Graham C.

    2014-12-01

    The formation of successive fronts in contaminated groundwater plumes by subsoil bacterial action is a commonly accepted feature of their propagation, but it is not obviously clear from a mathematical standpoint quite how such fronts are formed or propagate. In this paper we show that these can be explained by combining classical reaction-diffusion theory involving just two reactants (oxidant and reductant), and a secondary reaction in which a reactant on one side of such a front is (re-)formed on the other side of the front via diffusion of its product across the front. We give approximate asymptotic solutions for the reactant profiles, and the propagation rate of the front.

  5. Weather fronts and acute myocardial infarction

    NASA Astrophysics Data System (ADS)

    Kveton, Vit

    1991-03-01

    Some methodological aspects are discussed of the investigation of acute infarct myocarditis (AIM) in relation to weather fronts. Results of a new method of analysis are given. Data were analysed from about the hour of the onset of symptoms, and led to the diagnosis of AIM either immediately or within a few hours or days (3019 cases observed over 4.5 years during 1982 1986 in Plzen, Czechoslovakia). Weather classification was based on three factors (the type of the foregoing front, the type of the subsequent front, the time section of the time interval demarcated by the passage of the surfaces of the fronts). AIM occurrence increased in particular types of weather fronts: (i) by 30% during 7 12 h after a warm front, if the time span between fronts exceeded 24 h; (ii) by 10% in time at least 36 h distant from the foregoing cold or occlusion front and from the succeeding warm or occlusion front; (iii) by 20% during 0 2 h before the passage of the front, provided the foregoing front was not warm and the interval between fronts exceeded 5 h. AIM occurrence decreased by 15% 20% for time span between fronts > 24 h at times 6 11, 6 23 and 6 35 h before a coming warm or occlusion front (for interfrontal intervals 25 48, 49 72 and possibly > 72 h), and also at 12 23 and possibly 12 35 h before a cold front (for intervals 49 72 and possibly > 72 h), if the foregoing front was cold or an occlusion front.

  6. Multi Front-End Engineering

    NASA Astrophysics Data System (ADS)

    Botterweck, Goetz

    Multi Front-End Engineering (MFE) deals with the design of multiple consistent user interfaces (UI) for one application. One of the main challenges is the conflict between commonality (all front-ends access the same application core) and variability (multiple front-ends on different platforms). This can be overcome by extending techniques from model-driven user interface engineering.We present the MANTRA approach, where the common structure of all interfaces of an application is modelled in an abstract UI model (AUI) annotated with temporal constraints on interaction tasks. Based on these constraints we adapt the AUI, e.g., to tailor presentation units and dialogue structures for a particular platform. We use model transformations to derive concrete, platform-specific UI models (CUI) and implementation code. The presented approach generates working prototypes for three platforms (GUI, web, mobile) integrated with an application core via web service protocols. In addition to static evaluation, such prototypes facilitate early functional evaluations by practical use cases.

  7. Slow slip and the transition from fast to slow fronts in the rupture of frictional interfaces.

    PubMed

    Trømborg, Jørgen Kjoshagen; Sveinsson, Henrik Andersen; Scheibert, Julien; Thøgersen, Kjetil; Amundsen, David Skålid; Malthe-Sørenssen, Anders

    2014-06-17

    The failure of the population of microjunctions forming the frictional interface between two solids is central to fields ranging from biomechanics to seismology. This failure is mediated by the propagation along the interface of various types of rupture fronts, covering a wide range of velocities. Among them are the so-called slow fronts, which are recently discovered fronts much slower than the materials' sound speeds. Despite intense modeling activity, the mechanisms underlying slow fronts remain elusive. Here, we introduce a multiscale model capable of reproducing both the transition from fast to slow fronts in a single rupture event and the short-time slip dynamics observed in recent experiments. We identify slow slip immediately following the arrest of a fast front as a phenomenon sufficient for the front to propagate further at a much slower pace. Whether slow fronts are actually observed is controlled both by the interfacial stresses and by the width of the local distribution of forces among microjunctions. Our results show that slow fronts are qualitatively different from faster fronts. Because the transition from fast to slow fronts is potentially as generic as slow slip, we anticipate that it might occur in the wide range of systems in which slow slip has been reported, including seismic faults. PMID:24889640

  8. Temperature and pressure influence on explosion pressures of closed vessel propane-air deflagrations.

    PubMed

    Razus, Domnina; Brinzea, Venera; Mitu, Maria; Oancea, Dumitru

    2010-02-15

    An experimental study on pressure evolution during closed vessel explosions of propane-air mixtures was performed, for systems with various initial concentrations and pressures ([C(3)H(8)]=2.50-6.20 vol.%, p(0)=0.3-1.2 bar). The explosion pressures and explosion times were measured in a spherical vessel (Phi=10 cm), at various initial temperatures (T(0)=298-423 K) and in a cylindrical vessel (Phi=10 cm; h=15 cm), at ambient initial temperature. The experimental values of explosion pressures are examined against literature values and compared to adiabatic explosion pressures, computed by assuming chemical equilibrium within the flame front. The influence of initial pressure, initial temperature and fuel concentration on explosion pressures and explosion times are discussed. At constant temperature and fuel/oxygen ratio, the explosion pressures are linear functions of total initial pressure, as reported for other fuel-air mixtures. At constant initial pressure and composition, both the measured and calculated (adiabatic) explosion pressures are linear functions of reciprocal value of initial temperature. Such correlations are extremely useful for predicting the explosion pressures of flammable mixtures at elevated temperatures and/or pressures, when direct measurements are not available.

  9. Observations of gravity waves at atmospheric fronts

    NASA Astrophysics Data System (ADS)

    Abusamah, Azizan B. Hj

    1990-09-01

    An observational study of pressure perturbations associated with the passage of atmospheric fronts over the British Isles using a triangular array of sensitive microbarographs reveals the preponderance of gravity wave activities in the vicinity of the surface cold front (SCF). Examination of the time series of these pressure perturbations in the frequency domain shows an enhancement for frequencies less than the local buoyancy frequency N after the passage of the SCF. The spectral analysis also shows two predominant frequency peaks usually located near N and N/2 s(exp -1). Isolating these frequencies shows that there is a systematic amplitude modulation with an amplification near the SCF and at a region 2-3 hours before and after the SCF passage. The cross-correlation analysis reveals that the gravity waves in the post SCF region propagate towards the SCF. As these waves approach the SCF, the across front component of the phase speed decreases and the direction of propagation of the wave rotates in an anticlockwise manner. It is found that a consistent description of the gravity waves can only be made if first the waves are assumed to be ducted, i.e. there is a reflecting layer aloft, and second that as these waves propagate through the frontal environment, due to the inhomogeneity, they are refracted. A number of conceptual models are then developed to account for the observed wave behavior in a frontal region. In this investigation it is shown that the stable layer associated with the frontal zone can form a good upper reflector for non-hydrostatic gravity waves. It is also argued that the slope of this layer plays an important role in the refraction of the observed gravity waves. A model of wave propagation in a wedge is then used to account for this slope.

  10. [Determination of reaction products of epoxypropane in the process of deflagration to detonation transition by emission spectroscopy].

    PubMed

    Li, Ping; Hu, Dong; Yuan, Chang-Ying; Xiao, Hai-Bo; Liu, Jun-Chao; Sun, Zhu-Mei; Dong, Shi

    2005-12-01

    After solving problems of the synchronization of the measuring system, the detection of weak light, and the avoidance of false trigger signal, the instantaneous emission spectra of epoxypropane in the process of deflagration to detonation transition (DDT) with the exposure time of 1-16 micros and the resolution of 0.2 nm were measured. The spectra were acquired from side windows of an explosion shock tube 0.1 m in inner diameter and 4.0 m in length. The measuring system is made up of an intensified spectroscopic detector ICCD, a SpectraPro-275 spectrograph, and a digital delay generator DG535. By analyzing the spectra obtained, the reaction products OH, CH, C2, C3, CO, CO2, CHO and CH2O were identified according to their characteristic electronic and vibrational bands, which indicates that these molecules and radicals were produced during the DDT process of epoxypropane. The determination of reaction products can provide experimental basis for analyzing and understanding the microscopic mechanism of DDT process. PMID:16544471

  11. The p-Process in the Carbon Deflagration Model for Type Ia Supernovae and Chronology of the Solar System Formation

    SciTech Connect

    Kusakabe, Motohiko; Iwamoto, Nobuyuki; Nomoto, Ken'ichi

    2006-07-12

    We study nucleosynthesis of p-nuclei in the carbon deflagration model for Type Ia supernovae (SNe Ia) by assuming that seed nuclei are produced by the s-process in accreting layers on a carbon-oxygen white dwarf during mass accretion from a binary companion. We find that about 50 % of the p-nuclides are synthesized in proportion to the solar abundance and that p-isotopes of Mo and Ru which are significantly underproduced in Type II supernovae (SNe II) are produced up to a level close to other p-nuclei. Comparing the yields of iron and p-nuclei in SNe Ia we find that SNe Ia can contribute to the galactic evolution of the p-nuclei. Next, we consider nucleochronology of the solar system formation by using four radioactive nuclides and apply the result of the p-process nucleosynthesis to simple galactic chemical evolution models. We find that when assumed three phases of interstellar medium are mixed by the interdiffusion with the timescale of about 40 Myr 53Mn/55Mn value in the early solar system is consistent with a meteoritic value. In addition, we put constraints to a scenario that SNe Ia induce the core collapse of the molecular cloud, which leads to the formation of the solar system.

  12. [Determination of reaction products of epoxypropane in the process of deflagration to detonation transition by emission spectroscopy].

    PubMed

    Li, Ping; Hu, Dong; Yuan, Chang-Ying; Xiao, Hai-Bo; Liu, Jun-Chao; Sun, Zhu-Mei; Dong, Shi

    2005-12-01

    After solving problems of the synchronization of the measuring system, the detection of weak light, and the avoidance of false trigger signal, the instantaneous emission spectra of epoxypropane in the process of deflagration to detonation transition (DDT) with the exposure time of 1-16 micros and the resolution of 0.2 nm were measured. The spectra were acquired from side windows of an explosion shock tube 0.1 m in inner diameter and 4.0 m in length. The measuring system is made up of an intensified spectroscopic detector ICCD, a SpectraPro-275 spectrograph, and a digital delay generator DG535. By analyzing the spectra obtained, the reaction products OH, CH, C2, C3, CO, CO2, CHO and CH2O were identified according to their characteristic electronic and vibrational bands, which indicates that these molecules and radicals were produced during the DDT process of epoxypropane. The determination of reaction products can provide experimental basis for analyzing and understanding the microscopic mechanism of DDT process.

  13. DEFLAGRATION-TO-DETONATION TRANSITION IN LX-04 AS A FUNCTION OF LOADING DENSITY, TEMPERATURE, AND CONFINEMENT

    SciTech Connect

    Sandusky, H W; Granholm, R H; Bohl, D G; Hare, D E; Vandersall, K S; Garcia, F

    2005-06-01

    The potential for deflagration-to-detonation transition (DDT) in LX-04 (85/15 HMX/Viton) is being evaluated as a function of loading density, temperature, and confinement. In the high confinement arrangement, a matrix of tests will be performed with the LX-04 loaded at {approx}50, 70, 90, and {approx}99 %TMD; and temperatures of ambient, 160 C, and 190 C, at each loading density. A more limited set of tests at medium confinement will be conducted. As expected, LX-04 does not undergo DDT at near TMD loadings in both medium and high confinement, although the later still results in significant fragmentation. In high confinement at pour density (50.3 %TMD), LX-04 does not transit to detonation at 160 C, but does at ambient and 190 C with the shortest run distance to detonation (l) at ambient temperature. With a 70% TMD loading at ambient temperature, l was even less. The limited ambient temperature measurements for l in high confinement are similar to previous data for 91/9 HMX/wax, which has nearly the same %volume of HMX as LX-04.

  14. DEFLAGRATION-TO-DETONATION TRANSITION IN LX-04 AS A FUNCTION OF LOADING DENSITY, TEMPERATURE, AND CONFINEMENT

    SciTech Connect

    Sandusky, H W; Granholm, R H; Bohl, D G; Vandersall, K S; Hare, D E; Garcia, F

    2006-06-20

    The potential for deflagration-to-detonation transition (DDT) in LX-04 (85/15 HMX/Viton) is being evaluated as a function of loading density, temperature, and confinement. In the high confinement arrangement, a matrix of tests is nearly completed with the LX-04 loaded at {approx} 51, 70, 90, and {approx} 99% of theoretical maximum density (TMD); and temperatures of ambient, 160 C, and 190 C at each loading density. A more limited set of tests with {approx}99 %TMD loadings at medium confinement were conducted at temperatures of ambient and 186 C. LX-04 does not undergo DDT at near TMD loadings in both medium and high confinement, although the latter still results in significant fragmentation. Most porous beds in high confinement undergo DDT, with the minimum run distance to detonation (l) for a 70 %TMD loading at ambient temperature. LX-04 does not transit to detonation for a pour density (51.3 %TMD) loading at 160 C, but does at 190 C with a longer l than at ambient. The limited ambient temperature measurements for l in high confinement are similar to previous data for 91/9 HMX/wax, which has nearly the same %volume of HMX as LX-04.

  15. Seabird diving behaviour reveals the functional significance of shelf-sea fronts as foraging hotspots

    NASA Astrophysics Data System (ADS)

    Cox, S. L.; Miller, P. I.; Embling, C. B.; Scales, K. L.; Bicknell, A. W. J.; Hosegood, P. J.; Morgan, G.; Ingram, S. N.; Votier, S. C.

    2016-09-01

    Oceanic fronts are key habitats for a diverse range of marine predators, yet how they influence fine-scale foraging behaviour is poorly understood. Here, we investigated the dive behaviour of northern gannets Morus bassanus in relation to shelf-sea fronts. We GPS (global positioning system) tracked 53 breeding birds and examined the relationship between 1901 foraging dives (from time-depth recorders) and thermal fronts (identified via Earth Observation composite front mapping) in the Celtic Sea, Northeast Atlantic. We (i) used a habitat-use availability analysis to determine whether gannets preferentially dived at fronts, and (ii) compared dive characteristics in relation to fronts to investigate the functional significance of these oceanographic features. We found that relationships between gannet dive probabilities and fronts varied by frontal metric and sex. While both sexes were more likely to dive in the presence of seasonally persistent fronts, links to more ephemeral features were less clear. Here, males were positively correlated with distance to front and cross-front gradient strength, with the reverse for females. Both sexes performed two dive strategies: shallow V-shaped plunge dives with little or no active swim phase (92% of dives) and deeper U-shaped dives with an active pursuit phase of at least 3 s (8% of dives). When foraging around fronts, gannets were half as likely to engage in U-shaped dives compared with V-shaped dives, independent of sex. Moreover, V-shaped dive durations were significantly shortened around fronts. These behavioural responses support the assertion that fronts are important foraging habitats for marine predators, and suggest a possible mechanistic link between the two in terms of dive behaviour. This research also emphasizes the importance of cross-disciplinary research when attempting to understand marine ecosystems.

  16. Seabird diving behaviour reveals the functional significance of shelf-sea fronts as foraging hotspots

    PubMed Central

    Miller, P. I.; Embling, C. B.; Bicknell, A. W. J.; Hosegood, P. J.; Morgan, G.; Ingram, S. N.

    2016-01-01

    Oceanic fronts are key habitats for a diverse range of marine predators, yet how they influence fine-scale foraging behaviour is poorly understood. Here, we investigated the dive behaviour of northern gannets Morus bassanus in relation to shelf-sea fronts. We GPS (global positioning system) tracked 53 breeding birds and examined the relationship between 1901 foraging dives (from time-depth recorders) and thermal fronts (identified via Earth Observation composite front mapping) in the Celtic Sea, Northeast Atlantic. We (i) used a habitat-use availability analysis to determine whether gannets preferentially dived at fronts, and (ii) compared dive characteristics in relation to fronts to investigate the functional significance of these oceanographic features. We found that relationships between gannet dive probabilities and fronts varied by frontal metric and sex. While both sexes were more likely to dive in the presence of seasonally persistent fronts, links to more ephemeral features were less clear. Here, males were positively correlated with distance to front and cross-front gradient strength, with the reverse for females. Both sexes performed two dive strategies: shallow V-shaped plunge dives with little or no active swim phase (92% of dives) and deeper U-shaped dives with an active pursuit phase of at least 3 s (8% of dives). When foraging around fronts, gannets were half as likely to engage in U-shaped dives compared with V-shaped dives, independent of sex. Moreover, V-shaped dive durations were significantly shortened around fronts. These behavioural responses support the assertion that fronts are important foraging habitats for marine predators, and suggest a possible mechanistic link between the two in terms of dive behaviour. This research also emphasizes the importance of cross-disciplinary research when attempting to understand marine ecosystems. PMID:27703698

  17. A HIGH FIDELITY SAMPLE OF COLD FRONT CLUSTERS FROM THE CHANDRA ARCHIVE

    SciTech Connect

    Owers, Matt S.; Nulsen, Paul E. J.; Markevitch, Maxim; Couch, Warrick J.

    2009-10-20

    This paper presents a sample of 'cold front' clusters selected from the Chandra archive. The clusters are selected based purely on the existence of surface brightness edges in their Chandra images which are modeled as density jumps. A combination of the derived density and temperature jumps across the fronts is used to select nine robust examples of cold front clusters: 1ES0657 - 558, Abell 1201, Abell 1758N, MS1455.0+2232, Abell 2069, Abell 2142, Abell 2163, RXJ1720.1+2638, and Abell 3667. This sample is the subject of an ongoing study aimed at relating cold fronts to cluster merger activity, and understanding how the merging environment affects the cluster constituents. Here, temperature maps are presented along with the Chandra X-ray images. A dichotomy is found in the sample in that there exists a subsample of cold front clusters which are clearly mergers based on their X-ray morphologies, and a second subsample of clusters which harbor cold fronts, but have surprisingly relaxed X-ray morphologies, and minimal evidence for merger activity at other wavelengths. For this second subsample, the existence of a cold front provides the sole evidence for merger activity at X-ray wavelengths. We discuss how cold fronts can provide additional information which may be used to constrain merger histories, and also the possibility of using cold fronts to distinguish major and minor mergers.

  18. 1. VIEW SOUTHWARD FROM SOUTHWEST CORNER FRONT AND ARCH STREETS ...

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

    1. VIEW SOUTHWARD FROM SOUTHWEST CORNER FRONT AND ARCH STREETS (2. N. Front Street starts at left) - North Front Street Area Study, 2-66 North Front Street (Commercial Buildings), Philadelphia, Philadelphia County, PA

  19. Front and backside processed thin film electronic devices

    DOEpatents

    Evans, Paul G.; Lagally, Max G.; Ma, Zhenqiang; Yuan, Hao-Chih; Wang, Guogong; Eriksson, Mark A.

    2012-01-03

    This invention provides thin film devices that have been processed on their front- and backside. The devices include an active layer that is sufficiently thin to be mechanically flexible. Examples of the devices include back-gate and double-gate field effect transistors, double-sided bipolar transistors and 3D integrated circuits.

  20. Marangoni instability in the iodate-arsenous acid reaction front

    NASA Astrophysics Data System (ADS)

    Pópity-Tóth, Éva; Pótári, Gábor; Erdős, István; Horváth, Dezső; Tóth, Ágota

    2014-07-01

    Horizontally propagating chemical fronts leading to the formation of a single stable convection roll are investigated in the iodate-arsenous acid reaction with arsenous acid stoichiometrically limiting, leaving the surface active iodine present in the product mixture. In sufficiently thin solution layers with open upper surface, the contribution of Marangoni instability is significantly enhanced. Acting in the same direction as buoyancy driven instability, it distorts the entire tilted reaction front that becomes 50% more elongated. The corresponding three-dimensional calculations based on the empirical rate-law of the reaction corroborate the experimental findings.

  1. Marangoni instability in the iodate–arsenous acid reaction front

    SciTech Connect

    Pópity-Tóth, Éva; Pótári, Gábor; Erdős, István; Tóth, Ágota; Horváth, Dezső

    2014-07-28

    Horizontally propagating chemical fronts leading to the formation of a single stable convection roll are investigated in the iodate–arsenous acid reaction with arsenous acid stoichiometrically limiting, leaving the surface active iodine present in the product mixture. In sufficiently thin solution layers with open upper surface, the contribution of Marangoni instability is significantly enhanced. Acting in the same direction as buoyancy driven instability, it distorts the entire tilted reaction front that becomes 50% more elongated. The corresponding three-dimensional calculations based on the empirical rate-law of the reaction corroborate the experimental findings.

  2. Relating Global Precipitation to Atmospheric Fronts

    NASA Astrophysics Data System (ADS)

    Catto, J. L.; Jakob, C.; Nicholls, N.

    2012-12-01

    Atmospheric fronts are important for the day-to-day variability of weather in the midlatitudes, particularly during winter when extratropical storm-tracks are at their maximum intensity. Fronts are often associated with heavy rain, and strongly affect the local space-time distribution of rainfall. Although global climate models should be expected to represent the baroclinic systems within which the fronts are embedded, the fronts themselves and precipitation processes within them are of much smaller scale. As a consequence, models with the typical horizontal resolution of contemporary climate models do not necessarily accurately capture these features. A recently developed objective front identification method applied to reanalysis data is combined with global rainfall data to investigate how precipitation and extremes of precipitation around the globe are associated with atmospheric fronts. Having established the observed distribution of fronts and their role in producing precipitation and extremes, the occurrence of fronts and the associated precipitation can then be evaluated in state-of-the-art climate models. This provides a process-oriented method of model evaluation where the errors in the model can be decomposed into contributions from errors in front frequency and errors in frontal and non-frontal precipitation intensity. Finally, how fronts and their associated precipitation, may change in the future, especially the extremes, can be investigated.

  3. Laser-supported solid-state absorption fronts in silica

    NASA Astrophysics Data System (ADS)

    Carr, C. W.; Bude, J. D.; Demange, P.

    2010-11-01

    We develop a model based on simulation and extensive experimentation that explains the behavior of solid-state laser-supported absorption fronts generated in fused silica during high intensity (up to 5GW/cm2 ) laser exposure. Both experiments and simulations show that the absorption front velocity is constant in time and is nearly linear in laser intensity. Further, this model can explain the dependence of laser damage site size on these parameters. We show that these absorption fronts naturally result from the combination of high-temperature-activated deep subband-gap optical absorptivity, free-electron transport, and thermal diffusion in defect-free silica for temperatures up to 15000K and pressures <10GPa . The regime of parameter space critical to this problem spans and extends that measured by other means. It serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  4. Propagation failures, breathing fronts, and nonannihilation collisions in the ferroin-bromate-pyrocatechol system.

    PubMed

    Harati, Mohammad; Wang, Jichang

    2009-06-01

    The emergence of propagating pulses was investigated with the photosensitive ferroin-bromate-pyrocatechol reaction in capillary tubes, in which various interesting spatiotemporal behaviors such as propagation failure, breathing fronts, and transitions between propagating pulses and fronts have been observed. Rather than a mutual annihilation, the collision of a propagating pulse and a growing front forces the front to recede gradually. A phase diagram in the pyrocatechol-bromate concentration space shows that the pulse instabilities take place throughout the conditions at which the system generates wave activities, suggesting that the presence of coupled autocatalytic feedbacks may facilitate the onset of pulse instabilities.

  5. Light-Front Holographic QCD

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    The relation between the hadronic short-distance constituent quark and gluon particle limit and the long-range confining domain is yet one of the most challenging aspects of particle physics due to the strong coupling nature of Quantum Chromodynamics, the fundamental theory of the strong interactions. The central question is how one can compute hadronic properties from first principles; i.e., directly from the QCD Lagrangian. The most successful theoretical approach thus far has been to quantize QCD on discrete lattices in Euclidean space-time. Lattice numerical results follow from computation of frame-dependent moments of distributions in Euclidean space and dynamical observables in Minkowski spacetime, such as the time-like hadronic form factors, are not amenable to Euclidean lattice computations. The Dyson-Schwinger methods have led to many important insights, such as the infrared fixed point behavior of the strong coupling constant, but in practice, the analyses are limited to ladder approximation in Landau gauge. Baryon spectroscopy and the excitation dynamics of nucleon resonances encoded in the nucleon transition form factors can provide fundamental insight into the strong-coupling dynamics of QCD. New theoretical tools are thus of primary interest for the interpretation of the results expected at the new mass scale and kinematic regions accessible to the JLab 12 GeV Upgrade Project. The AdS/CFT correspondence between gravity or string theory on a higher-dimensional anti-de Sitter (AdS) space and conformal field theories in physical space-time has led to a semiclassical approximation for strongly-coupled QCD, which provides physical insights into its nonperturbative dynamics. The correspondence is holographic in the sense that it determines a duality between theories in different number of space-time dimensions. This geometric approach leads in fact to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light-front

  6. A High-Resolution Numerical Method for a Two-Phase Model of Deflagration-to-Detonation Transition

    NASA Astrophysics Data System (ADS)

    Gonthier, Keith A.; Powers, Joseph M.

    2000-09-01

    A conservative, upwind numerical method is formulated for the solution of a two-phase (reactive solid and inert gas) model of deflagration-to-detonation transition (DDT) in granular energetic solids. The model, which is representative of most two-phase DDT models, accounts for complete nonequilibrium between phases and constitutes a nonstrictly hyperbolic system of equations having parabolic degeneracies. The numerical method is based on Godunov's methodology and utilizes a new approximate solution for the two-phase Riemann problem for arbitrary equations of state. The approximate solution is similar to the Roe-type Riemann solution for single-phase systems. The method is able to accurately capture strong shocks associated with each phase without excessive smearing or spurious oscillations and can accurately resolve fine-scale detonation structure resulting from interaction between phases. The utility of the method is demonstrated by comparing numerical predictions with known solutions for three test cases: (1) a two-phase shock tube problem; (2) the evolution of a steady compaction wave in a granular material resulting from weak piston impact (∼100 m/s); and (3) the evolution of a steady two-phase detonation wave in an energetic granular material resulting from weak piston impact. The nominally second-order accurate numerical method is shown to have global convergence rates of 1.001 and 1.670 for inert test cases with (case 1) and without (case 2) discontinuities, respectively. For the reactive test case having a discontinuity (case 3), a convergence rate of 1.834 was predicted for coarse grids that seemed to be approaching the expected value of unity with increasing resolution.

  7. Front propagation and rejuvenation in flipping processes

    SciTech Connect

    Ben-naim, Eli; Krapivsky, P I; Antal, T; Ben - Avrahm, D

    2008-01-01

    We study a directed flipping process that underlies the performance of the random edge simplex algorithm. In this stochastic process, which takes place on a one-dimensional lattice whose sites may be either occupied or vacant, occupied sites become vacant at a constant rate and simultaneously cause all sites to the right to change their state. This random process exhibits rich phenomenology. First, there is a front, defined by the position of the leftmost occupied site, that propagates at a nontrivial velocity. Second, the front involves a depletion zone with an excess of vacant sites. The total excess {Delta}{sub k} increases logarithmically, {Delta}{sub k} {approx_equal}ln k, with the distance k from the front. Third, the front exhibits ageing -- young fronts are vigorous but old fronts are sluggish. We investigate these phenomena using a quasi-static approximation, direct solutions of small systems and numerical simulations.

  8. Condensation Front Migration in a Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Davis, Sanford S.

    2004-01-01

    Condensation front dynamics are investigated in the mid-solar nebula region. A quasi-steady model of the evolving nebula is combined with equilibrium vapor pressure curves to determine evolutionary condensation fronts for selected species. These fronts are found to migrate inwards from the far-nebula to final positions during a period of 10(exp 7) years. The physical process governing this movement is a combination of local viscous heating and luminescent heating from the central star. Two luminescent heating models are used and their effects on the ultimate radial position of the condensation front are discussed. At first the fronts move much faster than the nebular accretion velocity, but after a time the accreting gas and dust overtakes the slowing condensation front.

  9. Progress in front propagation research

    NASA Astrophysics Data System (ADS)

    Fort, Joaquim; Pujol, Toni

    2008-08-01

    We review the progress in the field of front propagation in recent years. We survey many physical, biophysical and cross-disciplinary applications, including reduced-variable models of combustion flames, Reid's paradox of rapid forest range expansions, the European colonization of North America during the 19th century, the Neolithic transition in Europe from 13 000 to 5000 years ago, the description of subsistence boundaries, the formation of cultural boundaries, the spread of genetic mutations, theory and experiments on virus infections, models of cancer tumors, etc. Recent theoretical advances are unified in a single framework, encompassing very diverse systems such as those with biased random walks, distributed delays, sequential reaction and dispersion, cohabitation models, age structure and systems with several interacting species. Directions for future progress are outlined.

  10. The upgraded Tevatron front end

    NASA Astrophysics Data System (ADS)

    Glass, M.; Zagel, J.; Smith, P.; Marsh, W.; Smolucha, J.

    1990-08-01

    We are replacing the computers which support the CAMAC crates in the Fermilab accelerator control system. We want a significant performance increase, but we still want to be able to service scores of different varieties of CAMAC cards in a manner essentially transparent to console applications software. Our new architecture is based on symmetric multiprocessing. Several processors on the same bus, each running identical software, work simultaneously at satisfying different pieces of a console's request for data. We dynamically adjust the load between the processors. We can obtain more processing power by simply plugging in more processors cards and rebooting. We describe in this paper what we believe to be the interesting architectural features of the new front-end computers. We also note how we use some of the advanced features of the Multibus™ II bus and the Intel 80386 processor design to achieve reliability and expandability of both hardware and software.

  11. Muon front end for the neutrino factory

    NASA Astrophysics Data System (ADS)

    Rogers, C. T.; Stratakis, D.; Prior, G.; Gilardoni, S.; Neuffer, D.; Snopok, P.; Alekou, A.; Pasternak, J.

    2013-04-01

    In the neutrino factory, muons are produced by firing high-energy protons onto a target to produce pions. The pions decay to muons and pass through a capture channel known as the muon front end, before acceleration to 12.6 GeV. The muon front end comprises a variable frequency rf system for longitudinal capture and an ionization cooling channel. In this paper we detail recent improvements in the design of the muon front end.

  12. Front blind spot crashes in Hong Kong.

    PubMed

    Cheng, Yuk Ki; Wong, Koon Hung; Tao, Chi Hang; Tam, Cheok Ning; Tam, Yiu Yan; Tsang, Cheuk Nam

    2016-09-01

    In 2012-2014, our laboratory had investigated a total of 9 suspected front blind spot crashes, in which the medium and heavy goods vehicles pulled away from rest and rolled over the pedestrians, who were crossing immediately in front of the vehicles. The drivers alleged that they did not see any pedestrians through the windscreens or the front blind spot mirrors. Forensic assessment of the goods vehicles revealed the existence of front blind spot zones in 3 out of these 9 accident vehicles, which were attributed to the poor mirror adjustments or even the absence of a front blind spot mirror altogether. In view of this, a small survey was devised involving 20 randomly selected volunteers and their goods vehicles and 5 out of these vehicles had blind spots at the front. Additionally, a short questionnaire was conducted on these 20 professional lorry drivers and it was shown that most of them were not aware of the hazards of blind spots immediately in front of their vehicles, and many did not use the front blind spot mirrors properly. A simple procedure for quick measurements of the coverage of front blind spot mirrors using a coloured plastic mat with dimensional grids was also introduced and described in this paper.

  13. Helices in the wake of precipitation fronts.

    PubMed

    Thomas, Shibi; Lagzi, István; Molnár, Ferenc; Rácz, Zoltán

    2013-08-01

    A theoretical study of the emergence of helices in the wake of precipitation fronts is presented. The precipitation dynamics is described by the Cahn-Hilliard equation and the fronts are obtained by quenching the system into a linearly unstable state. Confining the process onto the surface of a cylinder and using the pulled-front formalism, our analytical calculations show that there are front solutions that propagate into the unstable state and leave behind a helical structure. We find that helical patterns emerge only if the radius of the cylinder R is larger than a critical value R>R(c), in agreement with recent experiments. PMID:24032809

  14. Wave front fragmentation due to ventricular geometry in a model of the rabbit heart

    NASA Astrophysics Data System (ADS)

    Rogers, Jack M.

    2002-09-01

    The role of the heart's complex shape in causing the fragmentation of activation wave fronts characteristic of ventricular fibrillation (VF) has not been well studied. We used a finite element model of cardiac propagation capable of simulating functional reentry on curved two-dimensional surfaces to test the hypothesis that uneven surface curvature can cause local propagation block leading to proliferation of reentrant wave fronts. We found that when reentry was induced on a flat sheet, it rotated in a repeatable meander pattern without breaking up. However, when a model of the rabbit ventricles was formed from the same medium, reentrant wave fronts followed complex, nonrepeating trajectories. Local propagation block often occurred when wave fronts propagated across regions where the Gaussian curvature of the surface changed rapidly. This type of block did not occur every time wave fronts crossed such a region; rather, it only occurred when the wave front was very close behind the previous wave in the cycle and was therefore propagating into relatively inexcitable tissue. Close wave front spacing resulted from nonstationary reentrant propagation. Thus, uneven surface curvature and nonstationary reentrant propagation worked in concert to produce wave front fragmentation and complex activation patterns. None of the factors previously thought to be necessary for local propagation block (e.g., heterogeneous refractory period, steep action potential duration restitution) were present. We conclude that the complex geometry of the heart may be an important determinant of VF activation patterns.

  15. A spiral wave front beacon for underwater navigation: basic concept and modeling.

    PubMed

    Hefner, Brian T; Dzikowicz, Benjamin R

    2011-06-01

    A spiral wave front source produces an acoustic field that has a phase that is proportional to the azimuthal angle about the source. The concept of a spiral wave front beacon is developed by combining this source with a reference source that has a phase that is constant with the angle. The phase difference between these sources contains information about the receiver's azimuthal angle relative to the beacon and can be used for underwater navigation. To produce the spiral wave front, two sources are considered: a "physical-spiral" source, which produces the appropriate phase by physically deforming the active element of the source into a spiral, and a "phased-spiral" source, which uses an array of active elements, each driven with the appropriate phase, to produce the spiral wave front. Using finite element techniques, the fields produced by these sources are examined in the context of the spiral wave front beacon, and the advantages of each source are discussed.

  16. The APS beamline front end vacuum system

    SciTech Connect

    Nielsen, R.W.

    1993-10-15

    This report discusses the design of the vacuum system for the advanced photon source beamline front ends. Included in this report are discussions on: vacuum calculations, the differential pump; front end vacuum set points; cleaning methods and agents; and continuing and completed research and development.

  17. Observations of Gravity Waves at Atmospheric Fronts

    NASA Astrophysics Data System (ADS)

    Abu Samah, Azizan B. Hj.

    1990-01-01

    Available from UMI in association with The British Library. An observational study of pressure perturbations associated with the passage of atmospheric fronts over the British Isles using a triangular array of sensitive microbarographs reveals the preponderance of gravity wave activities in the vicinity of the surface cold front (SCF). Examination of the time series of these pressure perturbations in the frequency domain shows an enhancement for frequencies less than the local buoyancy frequency N after the passage of the SCF. The spectral analysis also shows two predominant frequency peaks usually located near N and N/2 s ^{-1}. Isolating these frequencies shows that there is a systematic amplitude modulation with an amplification near the SCF and at a region 2-3 hours before and after the SCF passage. The cross-correlation analysis reveals that the gravity waves in the post SCF region propagate towards the SCF. As these waves approach the SCF, the across front component of the phase speed decreases and the direction of propagation of the wave rotates in an anticlockwise manner. It is found that a consistent description of the gravity waves can only be made if first the waves are assumed to be ducted, i.e. there is a reflecting layer aloft, and second that as these waves propagate through the frontal environment, due to the inhomogeneity, they are refracted. A number of conceptual models are then developed to account for the observed wave behaviour in a frontal region. In this investigation it is shown that the stable layer associated with the frontal zone can form a good upper reflector for non-hydrostatic gravity waves. It is also argued that the slope of this layer plays an important role in the refraction of the observed gravity waves. A model of wave propagation in a wedge is then used to account for this slope. This model however predicts a clockwise rotation of the direction of propagation as the wave propagates toward the SCF. This rotation is the opposite

  18. Front end for GPS receivers

    NASA Technical Reports Server (NTRS)

    Thomas, Jr., Jess Brooks (Inventor)

    1999-01-01

    The front end in GPS receivers has the functions of amplifying, down-converting, filtering and sampling the received signals. In the preferred embodiment, only two operations, A/D conversion and a sum, bring the signal from RF to filtered quadrature baseband samples. After amplification and filtering at RF, the L1 and L2 signals are each sampled at RF at a high selected subharmonic rate. The subharmonic sample rates are approximately 900 MHz for L1 and 982 MHz for L2. With the selected subharmonic sampling, the A/D conversion effectively down-converts the signal from RF to quadrature components at baseband. The resulting sample streams for L1 and L2 are each reduced to a lower rate with a digital filter, which becomes a straight sum in the simplest embodiment. The frequency subsystem can be very simple, only requiring the generation of a single reference frequency (e.g. 20.46 MHz minus a small offset) and the simple multiplication of this reference up to the subharmonic sample rates for L1 and L2. The small offset in the reference frequency serves the dual purpose of providing an advantageous offset in the down-converted carrier frequency and in the final baseband sample rate.

  19. Relativistic ionization fronts in gas jets

    NASA Astrophysics Data System (ADS)

    Lemos, Nuno; Dias, J. M.; Gallacher, J. G.; Issac, R. C.; Fonseca, R. A.; Lopes, N. C.; Silva, L. O.; Mendonça, J. T.; Jaroszynski, D. A.

    2006-10-01

    A high-power ultra-short laser pulse propagating through a gas jet, ionizes the gas by tunnelling ionization, creating a relativistic plasma-gas interface. The relativistic ionization front that is created can be used to frequency up-shift electromagnetic radiation either in co-propagation or in counter-propagation configurations. In the counter-propagation configuration, ionization fronts can act as relativistic mirrors for terahertz radiation, leading to relativistic double Doppler frequency up-shift to the visible range. In this work, we identified and explored, the parameters that optimize the key features of relativistic ionization fronts for terahertz radiation reflection. The relativistic ionization front generated by a high power laser (TOPS) propagating in a supersonic gas jet generated by a Laval nozzle has been fully characterized. We have also performed detailed two-dimensional relativistic particle-in-cell simulations with Osiris 2.0 to analyze the generation and propagation of the ionization fronts.

  20. Coherent structures for front propagation in fluids

    NASA Astrophysics Data System (ADS)

    Mitchell, Kevin; Mahoney, John

    2014-03-01

    Our goal is to characterize the nature of reacting flows by identifying important ``coherent'' structures. We follow the recent work by Haller, Beron-Vera, and Farazmand which formalized the notion of lagrangian coherent structures (LCSs) in fluid flows. In this theory, LCSs were derived from the Cauchy-Green strain tensor. We adapt this perspective to analogously define coherent structures in reacting flows. By this we mean a fluid flow with a reaction front propagating through it such that the propagation does not affect the underlying flow. A reaction front might be chemical (Belousov-Zhabotinsky, flame front, etc.) or some other type of front (electromagnetic, acoustic, etc.). While the recently developed theory of burning invariant manifolds (BIMs) describes barriers to front propagation in time-periodic flows, this current work provides an important complement by extending to the aperiodic setting. Funded by NSF Grant CMMI-1201236.

  1. Thin front propagation in random shear flows.

    PubMed

    Chinappi, M; Cencini, M; Vulpiani, A

    2006-01-01

    Front propagation in time-dependent laminar flows is investigated in the limit of very fast reaction and very thin fronts--i.e., the so-called geometrical optics limit. In particular, we consider fronts stirred by random shear flows, whose time evolution is modeled in terms of Ornstein-Uhlembeck processes. We show that the ratio between the time correlation of the flow and an intrinsic time scale of the reaction dynamics (the wrinkling time tw) is crucial in determining both the front propagation speed and the front spatial patterns. The relevance of time correlation in realistic flows is briefly discussed in light of the bending phenomenon--i.e., the decrease of propagation speed observed at high flow intensities.

  2. First-Principles Petascale Simulations for Predicting Deflagration to Detonation Transition in Hydrogen-Oxygen Mixtures

    SciTech Connect

    Khokhlov, Alexei; Austin, Joanna

    2015-03-02

    Hydrogen has emerged as an important fuel across a range of industries as a means of achieving energy independence and to reduce emissions. DDT and the resulting detonation waves in hydrogen-oxygen can have especially catastrophic consequences in a variety of industrial and energy producing settings related to hydrogen. First-principles numerical simulations of flame acceleration and DDT are required for an in-depth understanding of the phenomena and facilitating design of safe hydrogen systems. The goals of this project were (1) to develop first-principles petascale reactive flow Navier-Stokes simulation code for predicting gaseous high-speed combustion and detonation (HSCD) phenomena and (2) demonstrate feasibility of first-principles simulations of rapid flame acceleration and deflagrationto- detonation transition (DDT) in stoichiometric hydrogen-oxygen mixture (2H2 + O2). The goals of the project have been accomplished. We have developed a novel numerical simulation code, named HSCD, for performing first-principles direct numerical simulations of high-speed hydrogen combustion. We carried out a series of validating numerical simulations of inert and reactive shock reflection experiments in shock tubes. We then performed a pilot numerical simulation of flame acceleration in a long pipe. The simulation showed the transition of the rapidly accelerating flame into a detonation. The DDT simulations were performed using BG/Q Mira at the Argonne National Laboratiory, currently the fourth fastest super-computer in the world. The HSCD is currently being actively used on BG/QMira for a systematic study of the DDT processes using computational resources provided through the 2014-2016 INCITE allocation ”First-principles simulations of high-speed combustion and detonation.” While the project was focused on hydrogen-oxygen and on DDT, with appropriate modifications of the input physics (reaction kinetics, transport coefficients, equation of state) the code has a much

  3. Dipolarization front and current disruption

    NASA Astrophysics Data System (ADS)

    Lui, A. T. Y.

    2016-10-01

    The modification of current density on the dawn-dusk cross section of the magnetotail with the earthward approach of a dipolarization front (DF) is examined through the recently published results of a three-dimensional (3-D) particle-in-cell (PIC) simulation. It is found that the current density intensifies by 37% abruptly within 1.5 ion gyrotime as the DF approaches and shows localized regions with north-south extrusions. After reaching its peak value, it undergoes a drastic current reduction (DCR) by 65% within 2 ion gyrotime. Breakdown of the frozen-in condition occurs in the neutral sheet region in association with DCR, demonstrating the non-MHD behavior of the phenomenon. The evolution of current density from this 3-D PIC simulation bears several similarities to those observed for the current disruption (CD) phenomenon, such as explosive growth and disruption of the current density leading to a breakdown of the frozen-in condition. The evolution is also similar to those from a previous two-dimensional (2-D) PIC simulation specially designed to investigate the nonlinear evolution of the cross-field current instability for CD. One interpretation of these findings is that CD and substorm triggering can be associated with earthward intrusion of a DF into the near-Earth plasma sheet as indicated by previous Cluster and Time History of Events and Macroscale Interactions during Substorms observations. An alternative interpretation is that both DF and CD are consequences of a global evolution from an ion-tearing-like instability of the magnetotail.

  4. Life on the front lines.

    PubMed

    Hern, W M

    1994-01-01

    Warren Hern's reminiscences about his experiences as medical director of the Boulder (Colorado) Abortion Clinic and as an abortion provider in private practice provide support for his statement, "Every doctor in America who does abortions lives under a death threat." Shortly after the clinic was opened, a group of anti-abortion physicians pressured the Boulder County Medical Society to pass a resolution declaring the clinic a "clear and present danger" that should be shut down by local health boards. As the only freestanding abortion clinic in the state in the mid-1970's, the Boulder center was targeted by the Right-to-Life Committee picketers and Dr. Hern was harassed in his home and in public. When Dr. Hern left the clinic a year later to establish a private practice specializing in pregnancy termination, the picketers followed. After release of a textbook he prepared on abortion practice, the publisher was deluged with hate mail and threats of boycott, leading them to withdraw the text from its list. Violent attacks on abortion clinics accelerated after Reagan's election and bullets were fired into Hern's waiting room. Randall Terry, national head of Operation Rescue, prayed for Hern's death at a rally in front of his clinic. By the time Dr. David Gunn was assassinated by an anti-abortionist in March 1993, there had been over 1285 acts of violence against abortion facilities and more than 100 facilities had been completely destroyed. The transgression for which Dr. Gunn was murdered was that he sought to save the lives and futures of countless women and support their right to become full participants in society.

  5. Cold Fronts in Cold Dark Matter Clusters

    NASA Astrophysics Data System (ADS)

    Nagai, Daisuke; Kravtsov, Andrey V.

    2003-04-01

    Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters. These features, called cold fronts, are characterized by an increase in surface brightness by a factor >~2 over 10-50 kpc accompanied by a drop in temperature of a similar magnitude. The existence of such sharp gradients can be used to put interesting constraints on the physics of the intracluster medium (ICM) if their mechanism and longevity are well understood. Here, we present results of a search for cold fronts in high-resolution simulations of galaxy clusters in cold dark matter models. We show that sharp gradients with properties similar to those of observed cold fronts naturally arise in cluster mergers when the shocks heat gas surrounding the merging subcluster, while its dense core remains relatively cold. The compression induced by supersonic motions and shock heating during the merger enhance the amplitude of gas density and temperature gradients across the front. Our results indicate that cold fronts are nonequilibrium transient phenomena and can be observed for a period of less than a billion years. We show that the velocity and density fields of gas surrounding the cold front can be very irregular, which would complicate analyses aiming to put constraints on the physical conditions of the ICM in the vicinity of the front.

  6. Problems and solutions for drawing fronts objectively

    NASA Astrophysics Data System (ADS)

    McCann, Donald W.; Whistler, James P.

    2001-06-01

    A recent requirement charged to the Aviation Weather Center (AWC) is to produce significant weather charts for aviation users with, among other forecast products, forecast locations of significant fronts. To increase forecaster productivity, the AWC decided to evaluate the possibility that fronts should be first drawn objectively. Hewson (1998) describes the basic technique which uses a variation on the Renard & Clarke (1965) frontal locator function to find the fronts. The AWC had to overcome many problems in implementing Hewson's techniques. This paper illuminates the problems and describes the AWC solutions. As a result of the AWC's success, objective frontal analyses and forecasts are now a reality, and the productivity of forecasters increased.

  7. Collisionless ion dynamics in the shock front

    NASA Astrophysics Data System (ADS)

    Gedalin, Michael

    2016-07-01

    In the vicinity of the shock front the dynamics of ions is governed by the macroscopic regular electric and magnetic field of the shock. Upon crossing the shock the thermal ions form a non-gyrotropic distribution. The pressure of these non-gyrotropic ions shapes the downstream magnetic field. High-energy ions behave in the shock front as test particles under the influence on the macroscopic fields. The reflection and transmission coefficients of high-energy ions at an oblique shock front is not sensitive to the shock structure and depends only on the global magnetic field change at the shock.

  8. Consumer preferences for front-of-pack calories labelling

    PubMed Central

    van Kleef, Ellen; van Trijp, Hans; Paeps, Frederic; Fernández-Celemín, Laura

    2008-01-01

    Objective In light of the emerging obesity pandemic, front-of-pack calories labels may be an important tool to assist consumers in making informed healthier food choices. However, there is little prior research to guide key decisions on whether caloric content should be expressed in absolute terms or relative to recommended daily intake, whether it should be expressed in per serving or per 100 g and whether the information should be further brought alive for consumers in terms of what the extra calorie intake implies in relation to activity levels. The present study aimed at providing more insight into consumers’ appreciation of front-of-pack labelling of caloric content of food products and their specific preferences for alternative execution formats for such information in Europe. Design For this purpose, eight executions of front-of-pack calorie flags were designed and their appeal and information value were extensively discussed with consumers through qualitative research in four different countries (Germany, The Netherlands, France and the UK). Results The results show that calories are well-understood and that participants were generally positive about front-of-pack flags, particularly when flags are uniform across products. The most liked flags are the simpler flags depicting only the number of calories per serving or per 100 g, while more complex flags including references to daily needs or exercise and the flag including a phrase referring to balanced lifestyle were least preferred. Some relevant differences between countries were observed. Although participants seem to be familiar with the notion of calories, they do not seem to fully understand how to apply them. Conclusion From the results, managerial implications for the design and implementation of front-of-pack calorie labelling as well as important directions for future research are discussed. PMID:17601362

  9. Heat conduction fronts in planetary nebulae

    NASA Technical Reports Server (NTRS)

    Soker, Noam

    1994-01-01

    We present arguments which suggest that many of the x-ray, some optical, and some UV observations of planetary nebulae, can be explained by the presence of heat conduction fronts. The heat flows from the hot bubble formed by the shocked fast wind to the cool shell and halo. Heat conduction fronts are likely to account for emission of x rays from plasma at lower temperature than the expected temperature of the hot bubble. In the presence of magnetic fields, only a small fraction of the fast wind luminosity emerges as radiation. Heat conduction fronts can naturally produce some unusual line flux ratios, which are observed in some planetary nebulae. Heat conduction fronts may heat the halo and cause some material at the inner surface of the shell to expand slower than the rest of the shell. In the presence of an asymmetrical magnetic field, this flow, the x-ray intensity, and the emission lines, may acquire asymmetrical structure as well.

  10. Optimizing emergency department front-end operations.

    PubMed

    Wiler, Jennifer L; Gentle, Christopher; Halfpenny, James M; Heins, Alan; Mehrotra, Abhi; Mikhail, Michael G; Fite, Diana

    2010-02-01

    As administrators evaluate potential approaches to improve cost, quality, and throughput efficiencies in the emergency department (ED), "front-end" operations become an important area of focus. Interventions such as immediate bedding, bedside registration, advanced triage (triage-based care) protocols, physician/practitioner at triage, dedicated "fast track" service line, tracking systems and whiteboards, wireless communication devices, kiosk self check-in, and personal health record technology ("smart cards") have been offered as potential solutions to streamline the front-end processing of ED patients, which becomes crucial during periods of full capacity, crowding, and surges. Although each of these operational improvement strategies has been described in the lay literature, various reports exist in the academic literature about their effect on front-end operations. In this report, we present a review of the current body of academic literature, with the goal of identifying select high-impact front-end operational improvement solutions. PMID:19556030

  11. Leap Day 2012 Severe Storm Front

    NASA Video Gallery

    This movie was created using GOES-13 visible and infrared satellite imagery from Feb. 28 at 1245 UTC (7:45 a.m. EST) through March 1, and shows the progression of the cold front and associated low ...

  12. Front-End Analysis Cornerstone of Logistics

    NASA Technical Reports Server (NTRS)

    Nager, Paul J.

    2000-01-01

    The presentation provides an overview of Front-End Logistics Support Analysis (FELSA), when it should be performed, benefits of performing FELSA and why it should be performed, how it is conducted, and examples.

  13. Nonperturbative light-front Hamiltonian methods

    NASA Astrophysics Data System (ADS)

    Hiller, J. R.

    2016-09-01

    We examine the current state-of-the-art in nonperturbative calculations done with Hamiltonians constructed in light-front quantization of various field theories. The language of light-front quantization is introduced, and important (numerical) techniques, such as Pauli-Villars regularization, discrete light-cone quantization, basis light-front quantization, the light-front coupled-cluster method, the renormalization group procedure for effective particles, sector-dependent renormalization, and the Lanczos diagonalization method, are surveyed. Specific applications are discussed for quenched scalar Yukawa theory, ϕ4 theory, ordinary Yukawa theory, supersymmetric Yang-Mills theory, quantum electrodynamics, and quantum chromodynamics. The content should serve as an introduction to these methods for anyone interested in doing such calculations and as a rallying point for those who wish to solve quantum chromodynamics in terms of wave functions rather than random samplings of Euclidean field configurations.

  14. Propelling efficiency of front-crawl swimming.

    PubMed

    Toussaint, H M; Beelen, A; Rodenburg, A; Sargeant, A J; de Groot, G; Hollander, A P; van Ingen Schenau, G J

    1988-12-01

    In this study the propelling efficiency (ep) of front-crawl swimming, by use of the arms only, was calculated in four subjects. This is the ratio of the power used to overcome drag (Pd) to the total mechanical power (Po) produced including power wasted in changing the kinetic energy of masses of water (Pk). By the use of an extended version of the system to measure active drag (MAD system), Pd was measured directly. Simultaneous measurement of O2 uptake (VO2) enabled the establishment of the relationship between the rate of the energy expenditure (PVO2) and Po (since when swimming on the MAD system Po = Pd). These individual relationships describing the mechanical efficiency (8-12%) were then used to estimate Po in free swimming from measurements of VO2. Because Pd was directly measured at each velocity studied by use of the MAD system, ep could be calculated according to the equation ep = Pd/(Pd + Pk) = Pd/Po. For the four top class swimmers studied, ep was found to range from 46 to 77%. Total efficiency, defined as the product of mechanical and propelling efficiency, ranged from 5 to 8%. PMID:3215850

  15. Nanocomposites for Underwater Deflagration

    SciTech Connect

    Shawn C. Stacey; Michelle L. Pantoya; Daniel J. Prentice; Eric D. Steffler; Michael A. Daniels

    2009-10-01

    Nanometer aluminum fuel particles demonstrate orders of magnitude higher ignition sensitivity and reactivity than micrometer aluminum particles. This enhanced ignition sensitivity could enable a submerged reaction to propagate and react to completion without quenching. Energetic composites consisting of micrometer Al fuel particles cannot react submerged because too much energy from the reaction is lost to the surrounding water, causing the reactants to quench. However, Al nanoparticles can be synthesized with significantly higher surface-area-to-volume ratios that enable them to exhibit new and unique combustion properties that are much improved over their micron scale counterparts.

  16. Speed of pulled fronts with a cutoff.

    PubMed

    Benguria, R D; Depassier, M C

    2007-05-01

    We study the effect of a small cutoff epsilon on the velocity of a pulled front in one dimension by means of a variational principle. We obtain a lower bound on the speed dependent on the cutoff, for which the two leading order terms correspond to the Brunet-Derrida expression. To do so we cast a known variational principle for the speed of propagation of fronts in different variables which makes it more suitable for applications. PMID:17677021

  17. Does Your Front Desk Staff Maximize Collections?

    PubMed

    Weinstock, Donna

    2015-01-01

    As collections become more difficult, practices need to use the front desk to help collect payments from patients when they are face to face. Training staff and giving them the tools to ask for money allows them to collect efficiently. Improve your collections by involving your front desk employees. Educate your patients to allow them to come to their visits prepared. It will save the practice time and money. PMID:26399028

  18. Does Your Front Desk Staff Maximize Collections?

    PubMed

    Weinstock, Donna

    2015-01-01

    As collections become more difficult, practices need to use the front desk to help collect payments from patients when they are face to face. Training staff and giving them the tools to ask for money allows them to collect efficiently. Improve your collections by involving your front desk employees. Educate your patients to allow them to come to their visits prepared. It will save the practice time and money.

  19. Turbulent transport model of wind shear in thunderstorm gust fronts and warm fronts

    NASA Technical Reports Server (NTRS)

    Lewellen, W. S.; Teske, M. E.; Segur, H. C. O.

    1978-01-01

    A model of turbulent flow in the atmospheric boundary layer was used to simulate the low-level wind and turbulence profiles associated with both local thunderstorm gust fronts and synoptic-scale warm fronts. Dimensional analyses of both type fronts provided the physical scaling necessary to permit normalized simulations to represent fronts for any temperature jump. The sensitivity of the thunderstorm gust front to five different dimensionless parameters as well as a change from axisymmetric to planar geometry was examined. The sensitivity of the warm front to variations in the Rossby number was examined. Results of the simulations are discussed in terms of the conditions which lead to wind shears which are likely to be most hazardous for aircraft operations.

  20. Life on the front lines.

    PubMed

    Hern, W M

    1993-01-01

    honor those who advanced the cause of women's rights. They honored the physician who had to shout over hecklers to make his remarks heard. After a year of operation, the physician encountered differences with the Board of Directors of the clinic. Soon after that, he resigned and opened his own clinic with a bank loan of $7000. Within 4 years, his clinic had expanded, and he purchased its building. The harassment from antiabortion protesters continued, with broken windows, pickets, and, in February 1988, bullets fired through the front windows of the waiting room. This necessitated the installation of bullet-proof glass and a security system which cost $17,000. As of March 1, 1993, there had been 1285 acts of violence towards abortion clinics, which led to the destruction of more than 100. On March 10 of that year, a physician who performed abortions in Florida was gunned down by an anti-abortion protestor. People who provide abortions hope for legal protection and respect for their civil liberties, but they will continue to provide this service even if conditions do not improve.

  1. Interaction of a cold front with a sea-breeze front Numerical simulations

    NASA Astrophysics Data System (ADS)

    Rhodin, A.

    1995-08-01

    This paper presents simulations of a front which passed the coast between the North Sea and northern Germany and thereby experienced some modifications of its mesoscale characteristics. The event was observed during the field experiment FRONTEX'89. The two-dimensional non-hydrostatic simulations presented in this paper resemble some of the observed characteristics and yield a detailed description of the evolution of the surface front. Over the sea several narrow frontal rain bands develop in the boundary layer which becomes unstable due to the increasing sea surface temperature near the coast. The rain bands move forward relative to the front due to the cross frontal circulation which is enhanced by the release of latent heat in the ascending warm air and by the cooling of the cold air below by evaporating precipitation. Over the heated land surface a sea-breeze front develops ahead of the synoptic-scale cold front. The strong frontal gradients of the sea-breeze front mask the broader frontal zone of the cold front at the ground. The sea-breeze front triggers deep convection ahead of the cold front in the afternoon and takes over all characteristics of the synoptic-scale front in the evening. The simulations show the mechanisms that caused the observed evolution and modification of the synoptic-scale cold front. They emphasize the strong influence of the surface heat fluxes on the characteristics of fronts on the mesoscale. The most important feature of the numerical model, necessary for the proper representation of the frontal characteristics on the mesoscale, is its high resolution. The simulations are restricted by the difficulties of finding an initial state and appropriate boundary conditions so that the results fit the observations for a long time period and that spin-up problems are avoided.

  2. COLD FRONTS AND GAS SLOSHING IN GALAXY CLUSTERS WITH ANISOTROPIC THERMAL CONDUCTION

    SciTech Connect

    ZuHone, J. A.; Markevitch, M.; Lee, D.

    2013-01-10

    Cold fronts in cluster cool cores should be erased on short timescales by thermal conduction, unless protected by magnetic fields that are 'draped' parallel to the front surfaces, suppressing conduction perpendicular to the sloshing fronts. We present a series of MHD simulations of cold front formation in the core of a galaxy cluster with anisotropic thermal conduction, exploring a parameter space of conduction strengths parallel and perpendicular to the field lines. Including conduction has a strong effect on the temperature distribution of the core and the appearance of the cold fronts. Though magnetic field lines are draping parallel to the front surfaces, preventing conduction directly across them, the temperature jumps across the fronts are nevertheless reduced. The geometry of the field is such that the cold gas below the front surfaces can be connected to hotter regions outside via field lines along directions perpendicular to the plane of the sloshing motions and along sections of the front that are not perfectly draped. This results in the heating of this gas below the front on a timescale of a Gyr, but the sharpness of the density and temperature jumps may nevertheless be preserved. By modifying the gas density distribution below the front, conduction may indirectly aid in suppressing Kelvin-Helmholtz instabilities. If conduction along the field lines is unsuppressed, we find that the characteristic sharp jumps seen in Chandra observations of cold front clusters do not form. Therefore, the presence of cold fronts in hot clusters is in contradiction with our simulations with full Spitzer conduction. This suggests that the presence of cold fronts in hot clusters could be used to place upper limits on conduction in the bulk of the intracluster medium. Finally, the combination of sloshing and anisotropic thermal conduction can result in a larger flux of heat to the core than either process in isolation. While still not sufficient to prevent a cooling

  3. Marine fronts are important fishing areas for demersal species at the Argentine Sea (Southwest Atlantic Ocean)

    NASA Astrophysics Data System (ADS)

    Alemany, Daniela; Acha, Eduardo M.; Iribarne, Oscar O.

    2014-03-01

    The high primary and secondary production associated with frontal systems attract a diversity of organisms due to high prey availability; this is why a strong relationship between fronts and pelagic fisheries has been shown worldwide. In the Argentine Sea, demersal resources are the most important, both in economical and in ecological sense; so we hypothesize that fronts are also preferred fishing areas for demersal resources. We evaluated the relationship between spatial distribution of fishing effort and oceanographic fronts, analyzing three of the most important frontal systems located in the Argentine Sea: the shelf-break front, the southern Patagonia front and the mid-shelf front. Individual vessel satellite monitoring system data (VMS; grouped by fleet type: ice-trawlers, freezer-trawlers and jigging fleet) were studied and fishing events were identified. Fishing events per area were used as a proxy of fishing effort and its spatial distribution by fleet type was visualized and analyzed with Geographic Information Systems. Oceanographic fronts were defined using polygons based on satellite chlorophyll amplitude values, and the percentage of fishing events within each polygon was calculated. Results showed a positive association between fronts and fishing activities of the different fleets, which suggests the aggregation of target species in these zones. The coupling of the freezer-trawler and jigging fleets (that operate on lower trophic level species; Macruronus magellanicus and Illex argentinus respectively) with fronts was higher than the ice-trawler fleet, targeting species of higher trophic level (Merluccius hubbsi). Marine fronts represent important fishing areas, even for demersal resources, as the distribution of fishing fleets and fishing effort are positively associated with frontal zones.

  4. Laser supported solid state absorption fronts in silica

    SciTech Connect

    Carr, C W; Bude, J D

    2010-02-09

    We develop a model based on simulation and experiment that explains the behavior of solid-state laser-supported absorption fronts generated in fused silica during high intensity (up to 5GW/cm{sup 2}) laser exposure. We find that the absorption front velocity is constant in time and is nearly linear in laser intensity. Further, this model can explain the dependence of laser damage site size on these parameters. This behavior is driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. The regime of parameter space critical to this problem spans and extends that measured by other means. It serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  5. Pareto Fronts in Clinical Practice for Pinnacle

    SciTech Connect

    Janssen, Tomas; Kesteren, Zdenko van; Franssen, Gijs; Damen, Eugène; Vliet, Corine van

    2013-03-01

    Purpose: Our aim was to develop a framework to objectively perform treatment planning studies using Pareto fronts. The Pareto front represents all optimal possible tradeoffs among several conflicting criteria and is an ideal tool with which to study the possibilities of a given treatment technique. The framework should require minimal user interaction and should resemble and be applicable to daily clinical practice. Methods and Materials: To generate the Pareto fronts, we used the native scripting language of Pinnacle{sup 3} (Philips Healthcare, Andover, MA). The framework generates thousands of plans automatically from which the Pareto front is generated. As an example, the framework is applied to compare intensity modulated radiation therapy (IMRT) with volumetric modulated arc therapy (VMAT) for prostate cancer patients. For each patient and each technique, 3000 plans are generated, resulting in a total of 60,000 plans. The comparison is based on 5-dimensional Pareto fronts. Results: Generating 3000 plans for 10 patients in parallel requires on average 96 h for IMRT and 483 hours for VMAT. Using VMAT, compared to IMRT, the maximum dose of the boost PTV was reduced by 0.4 Gy (P=.074), the mean dose in the anal sphincter by 1.6 Gy (P=.055), the conformity index of the 95% isodose (CI{sub 95%}) by 0.02 (P=.005), and the rectal wall V{sub 65} {sub Gy} by 1.1% (P=.008). Conclusions: We showed the feasibility of automatically generating Pareto fronts with Pinnacle{sup 3}. Pareto fronts provide a valuable tool for performing objective comparative treatment planning studies. We compared VMAT with IMRT in prostate patients and found VMAT had a dosimetric advantage over IMRT.

  6. QCD and Light-Front Dynamics

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /SLAC /Southern Denmark U., CP3-Origins /Costa Rica U.

    2011-01-10

    AdS/QCD, the correspondence between theories in a dilaton-modified five-dimensional anti-de Sitter space and confining field theories in physical space-time, provides a remarkable semiclassical model for hadron physics. Light-front holography allows hadronic amplitudes in the AdS fifth dimension to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The result is a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound state wavefunctions as a function of the invariant mass of the constituents. The hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. Higher Fock states with extra quark-anti quark pairs also arise. The soft-wall model also predicts the form of the nonperturbative effective coupling and its {beta}-function. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method to systematically include QCD interaction terms. Some novel features of QCD are discussed, including the consequences of confinement for quark and gluon condensates. A method for computing the hadronization of quark and gluon jets at the amplitude level is outlined.

  7. Light-Front Holography and the Light-Front Schrodinger Equation

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy

    2012-08-15

    One of the most important nonperturbative methods for solving QCD is quantization at fixed light-front time {tau} = t+z=c - Dirac's 'Front Form'. The eigenvalues of the light-front QCD Hamiltonian predict the hadron spectrum and the eigensolutions provide the light-front wavefunctions which describe hadron structure. More generally, we show that the valence Fock-state wavefunctions of the light-front QCD Hamiltonian satisfy a single-variable relativistic equation of motion, analogous to the nonrelativistic radial Schrodinger equation, with an effective confining potential U which systematically incorporates the effects of higher quark and gluon Fock states. We outline a method for computing the required potential from first principles in QCD. The holographic mapping of gravity in AdS space to QCD, quantized at fixed light-front time, yields the same light front Schrodinger equation; in fact, the soft-wall AdS/QCD approach provides a model for the light-front potential which is color-confining and reproduces well the light-hadron spectrum. One also derives via light-front holography a precise relation between the bound-state amplitudes in the fifth dimension of AdS space and the boost-invariant light-front wavefunctions describing the internal structure of hadrons in physical space-time. The elastic and transition form factors of the pion and the nucleons are found to be well described in this framework. The light-front AdS/QCD holographic approach thus gives a frame-independent first approximation of the color-confining dynamics, spectroscopy, and excitation spectra of relativistic light-quark bound states in QCD.

  8. Front-end electronics for the LZ experiment

    NASA Astrophysics Data System (ADS)

    Morad, James; LZ Collaboration

    2016-03-01

    LZ is a second generation direct dark matter detection experiment with 5.6 tonnes of liquid xenon active target, which will be instrumented as a two-phase time projection chamber (TPC). The peripheral xenon outside the active TPC (``skin'') will also be instrumented. In addition, there will be a liquid scintillator based outer veto surrounding the main cryostat. All of these systems will be read out using photomultiplier tubes. I will present the designs for front-end electronics for all these systems, which have been optimized for shaping times, gains, and low noise. Preliminary results from prototype boards will also be presented.

  9. Light-Front Quantization of Gauge Theories

    SciTech Connect

    Brodskey, Stanley

    2002-12-01

    Light-front wavefunctions provide a frame-independent representation of hadrons in terms of their physical quark and gluon degrees of freedom. The light-front Hamiltonian formalism provides new nonperturbative methods for obtaining the QCD spectrum and eigensolutions, including resolvant methods, variational techniques, and discretized light-front quantization. A new method for quantizing gauge theories in light-cone gauge using Dirac brackets to implement constraints is presented. In the case of the electroweak theory, this method of light-front quantization leads to a unitary and renormalizable theory of massive gauge particles, automatically incorporating the Lorentz and 't Hooft conditions as well as the Goldstone boson equivalence theorem. Spontaneous symmetry breaking is represented by the appearance of zero modes of the Higgs field leaving the light-front vacuum equal to the perturbative vacuum. I also discuss an ''event amplitude generator'' for automatically computing renormalized amplitudes in perturbation theory. The importance of final-state interactions for the interpretation of diffraction, shadowing, and single-spin asymmetries in inclusive reactions such as deep inelastic lepton-hadron scattering is emphasized.

  10. View of McKenzieRichey garage showing front opening, the false front, ...

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

    View of McKenzie-Richey garage showing front opening, the false front, metal roofing and horizontal plank siding, facing northeast - McKenzie Property, Garage, North Bank of Sailor Gulch, 750 feet northwest of intersection of U.S.F.S. Roads 651 & 349, Placerville, Boise County, ID

  11. Friction forces on phase transition fronts

    SciTech Connect

    Mégevand, Ariel

    2013-07-01

    In cosmological first-order phase transitions, the microscopic interaction of the phase transition fronts with non-equilibrium plasma particles manifests itself macroscopically as friction forces. In general, it is a nontrivial problem to compute these forces, and only two limits have been studied, namely, that of very slow walls and, more recently, ultra-relativistic walls which run away. In this paper we consider ultra-relativistic velocities and show that stationary solutions still exist when the parameters allow the existence of runaway walls. Hence, we discuss the necessary and sufficient conditions for the fronts to actually run away. We also propose a phenomenological model for the friction, which interpolates between the non-relativistic and ultra-relativistic values. Thus, the friction depends on two friction coefficients which can be calculated for specific models. We then study the velocity of phase transition fronts as a function of the friction parameters, the thermodynamic parameters, and the amount of supercooling.

  12. Optimal back-to-front airplane boarding.

    PubMed

    Bachmat, Eitan; Khachaturov, Vassilii; Kuperman, Ran

    2013-06-01

    The problem of finding an optimal back-to-front airplane boarding policy is explored, using a mathematical model that is related to the 1+1 polynuclear growth model with concave boundary conditions and to causal sets in gravity. We study all airplane configurations and boarding group sizes. Optimal boarding policies for various airplane configurations are presented. Detailed calculations are provided along with simulations that support the main conclusions of the theory. We show that the effectiveness of back-to-front policies undergoes a phase transition when passing from lightly congested airplanes to heavily congested airplanes. The phase transition also affects the nature of the optimal or near-optimal policies. Under what we consider to be realistic conditions, optimal back-to-front policies lead to a modest 8-12% improvement in boarding time over random (no policy) boarding, using two boarding groups. Having more than two groups is not effective. PMID:23848727

  13. Foam front propagation in anisotropic oil reservoirs.

    PubMed

    Grassia, P; Torres-Ulloa, C; Berres, S; Mas-Hernández, E; Shokri, N

    2016-04-01

    The pressure-driven growth model is considered, describing the motion of a foam front through an oil reservoir during foam improved oil recovery, foam being formed as gas advances into an initially liquid-filled reservoir. In the model, the foam front is represented by a set of so-called "material points" that track the advance of gas into the liquid-filled region. According to the model, the shape of the foam front is prone to develop concave sharply curved concavities, where the orientation of the front changes rapidly over a small spatial distance: these are referred to as "concave corners". These concave corners need to be propagated differently from the material points on the foam front itself. Typically the corner must move faster than those material points, otherwise spurious numerical artifacts develop in the computed shape of the front. A propagation rule or "speed up" rule is derived for the concave corners, which is shown to be sensitive to the level of anisotropy in the permeability of the reservoir and also sensitive to the orientation of the corners themselves. In particular if a corner in an anisotropic reservoir were to be propagated according to an isotropic speed up rule, this might not be sufficient to suppress spurious numerical artifacts, at least for certain orientations of the corner. On the other hand, systems that are both heterogeneous and anisotropic tend to be well behaved numerically, regardless of whether one uses the isotropic or anisotropic speed up rule for corners. This comes about because, in the heterogeneous and anisotropic case, the orientation of the corner is such that the "correct" anisotropic speed is just very slightly less than the "incorrect" isotropic one. The anisotropic rule does however manage to keep the corner very slightly sharper than the isotropic rule does.

  14. Foam front propagation in anisotropic oil reservoirs.

    PubMed

    Grassia, P; Torres-Ulloa, C; Berres, S; Mas-Hernández, E; Shokri, N

    2016-04-01

    The pressure-driven growth model is considered, describing the motion of a foam front through an oil reservoir during foam improved oil recovery, foam being formed as gas advances into an initially liquid-filled reservoir. In the model, the foam front is represented by a set of so-called "material points" that track the advance of gas into the liquid-filled region. According to the model, the shape of the foam front is prone to develop concave sharply curved concavities, where the orientation of the front changes rapidly over a small spatial distance: these are referred to as "concave corners". These concave corners need to be propagated differently from the material points on the foam front itself. Typically the corner must move faster than those material points, otherwise spurious numerical artifacts develop in the computed shape of the front. A propagation rule or "speed up" rule is derived for the concave corners, which is shown to be sensitive to the level of anisotropy in the permeability of the reservoir and also sensitive to the orientation of the corners themselves. In particular if a corner in an anisotropic reservoir were to be propagated according to an isotropic speed up rule, this might not be sufficient to suppress spurious numerical artifacts, at least for certain orientations of the corner. On the other hand, systems that are both heterogeneous and anisotropic tend to be well behaved numerically, regardless of whether one uses the isotropic or anisotropic speed up rule for corners. This comes about because, in the heterogeneous and anisotropic case, the orientation of the corner is such that the "correct" anisotropic speed is just very slightly less than the "incorrect" isotropic one. The anisotropic rule does however manage to keep the corner very slightly sharper than the isotropic rule does. PMID:27090239

  15. Front variability and surface ocean features of the presumed southern bluefin tuna spawning grounds in the tropical southeast Indian Ocean

    NASA Astrophysics Data System (ADS)

    Nieblas, Anne-Elise; Demarcq, Hervé; Drushka, Kyla; Sloyan, Bernadette; Bonhommeau, Sylvain

    2014-09-01

    The southern bluefin tuna (SBT, Thunnus maccoyii) is an ecologically and economically valuable fish. However, surprisingly little is known about its critical early life history, a period when mortality is several orders of magnitude higher than at any other life stage, and when larvae are highly sensitive to environmental conditions. Ocean fronts can be important in creating favourable spawning conditions, as they are a convergence of water masses with different properties that can concentrate planktonic particles and lead to enhanced productivity. In this study, we examine the front activity within the only region where SBT have been observed to spawn: the tropical southeast Indian Ocean between Indonesia and Australia (10°S-20°S, 105°E-125°E). We investigate front activity and its relationship to ocean dynamics and surface features of the region. Results are also presented for the entire Indian Ocean (30°N-45°S, 20°E-140°E) to provide a background context. We use an extension of the Cayula and Cornillon algorithm to detect ocean fronts from satellite images of sea surface temperature (SST) and chlorophyll-a concentration (chl-a). Front occurrence represents the probability of occurrence of a front at each pixel of an image. Front intensity represents the magnitude of the difference between the two water masses that make up a front. Relative to the rest of the Indian Ocean, both SST and chl-a fronts in the offshore spawning region are persistent in occurrence and weak in intensity. Front occurrence and intensity along the Australian coast are high, with persistent and intense fronts found along the northwest and west coasts. Fronts in the tropical southeast Indian Ocean are shown to have strong annual variability and some moderate interannual variability. SST front occurrence is found to lead the Southern Oscillation Index by one year, potentially linked to warming and wind anomalies in the Indian Ocean. The surface ocean characteristics of the offshore

  16. Light-front nuclear shell-model

    SciTech Connect

    Johnson, M.B.

    1990-01-01

    I examine the effects of nuclear structure on high-energy, high-momentum transfer processes, specifically the EMC effect. For pedagogical reasons, a fictitious but simple two-body system consisting of two equal-mass particles interacting in a harmonic oscillator potential has been chosen. For this toy nucleus, I utilize a widely-used link between instant-form and light-front dynamics, formulating nuclear structure and deep-inelastic scattering consistently in the laboratory system. Binding effects are compared within conventional instant-form and light-front dynamical frameworks, with appreciable differences being found in the two cases. 20 refs.

  17. Numerical and experimental study of thermal explosions in LX-10 and PBX 9501: Influence of thermal damage on deflagration processes

    NASA Astrophysics Data System (ADS)

    Tringe, J. W.; Kercher, J. R.; Springer, H. K.; Glascoe, E. A.; Levie, H. W.; Hsu, P.; Willey, T. M.; Molitoris, J. D.

    2013-07-01

    We employ in-situ flash x-ray imaging, together with a detailed multiphase convective burn model, to demonstrate how explosives' binder characteristics influence the burning processes in thermal explosions. Our study focuses on the HMX-based explosives LX-10 and PBX 9501. While the HMX (cyclotetramethylene-tetranitramine) crystallite size distributions for these two explosives are nearly identical before heating, our experiments and simulations indicate that after heating, variations result due to differences in binder composition. Post-ignition flash x-ray images reveal that the average density decreases at late times more rapidly in PBX 9501 than LX-10, suggesting a faster conductive burning rate in PBX-9501. Heated permeability measurements in LX-10 and PBX 9501 demonstrate that the binder system characteristics influence the evolution of connected porosity. Once ignited, connected porosity provides pathways for product gas heating ahead of the reaction front and additional surface area for burning, facilitating the transition from conductive to convective burning modes. A multiphase convective burn model implemented in the ALE3D code is used to better understand the influence on burn rates of material properties such as porosity and effective thermally damaged particle size. In this context, particles are defined as gas-impermeable binder-coated crystallites and agglomerations with a set of effective radii reff. Model results demonstrate quantitative agreement with containment wall velocity for confined PBX 9501 and LX-10, and qualitative agreement with density as a function of position in the burning explosive. The model predicts a decrease in post-ignition containment wall velocity with larger radii in reff. These experimental data and model results together provide insight into the initiation and propagation of the reaction wave that defines the convective burn front in HMX-based explosives, a necessary step toward predicting violence under a broad range of

  18. Size effect and detonation front curvature

    SciTech Connect

    Souers, P. C., LLNL

    1997-07-01

    Heat flow in a cylinder with internal heating is used as a basis for deriving a simple theory of detonation front curvature, leading to the prediction of quadratic curve shapes. A thermal conductivity of 50 MW/mm{sup 2} is found for TATB samples.

  19. Positional Velar Fronting: An Updated Articulatory Account

    ERIC Educational Resources Information Center

    Byun, Tara McAllister

    2012-01-01

    This study develops the hypothesis that the child-specific phenomenon of positional velar fronting can be modeled as the product of phonologically encoded articulatory limitations unique to immature speakers. Children have difficulty executing discrete tongue movements, preferring to move the tongue and jaw as a single unit. This predisposes the…

  20. A preliminary ultrasound study of velar fronting

    NASA Astrophysics Data System (ADS)

    Wodzinski, Sylvie M.; Frisch, Stefan A.

    2003-10-01

    The purpose of this study is to (1) evaluate the effectiveness of ultrasound imaging to measure velar consonant closure location, and (2) conduct a thorough study of velar fronting by measuring several productions of velar stops in the context of every English vowel. Word onset velar stops were measured in both words (CV or CVC) and nonwords (VCV) within a carrier phrase. Other coarticulatory influences were minimized by using words with no coda or labial coda consonants (e.g., ``Say a gap again,'' ``Say /oIkoI/ again''). Measurements were made at the point of maximal closure. Closure location was measured using the radial angle from the center of the ultrasound probe to the center of the velar closure. Pilot data for one subject has been analyzed to date. Closure location appears consistent across all central and back vowels. For front vowels, the degree of fronting of the velar appears to be correlated with the frontness of the vowel. Measures of closure location for diphthongs followed the back vowel pattern in the word targets. For nonwords, the closure location was influenced by the preceding diphthong offset quality and the following diphthong onset quality. Theoretical implications for the phonetics/phonology interface will be discussed.

  1. Advocacy on the Front Lines of CTE

    ERIC Educational Resources Information Center

    Reese, Susan

    2011-01-01

    Career and technical education (CTE) in the 21st century is more relevant and rigorous than ever before. It prepares students to compete in the global workplace, it inspires lifelong learning, and it helps prevent at-risk students from dropping out of school because it keeps them engaged in the learning process. Those who work on the front lines…

  2. Motivation and Front-End Analysis.

    ERIC Educational Resources Information Center

    Harless, Joe

    1978-01-01

    Relates Front-End Analysis (FEA) to motivation by categorizing it as either Diagnostic FEA or Planning FEA. The former is used to diagnose existing problems and prescribe motivational programs; the latter assumes that motivational programs must be implemented, along with other programs, to build the optimum environment to support the performance.…

  3. QCD and Light-Front Holography

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2010-10-27

    The soft-wall AdS/QCD model, modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics. The model predicts a zero-mass pion for zero-mass quarks and a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number N. Light-Front Holography maps the amplitudes which are functions of the fifth dimension variable z of anti-de Sitter space to a corresponding hadron theory quantized on the light front. The resulting Lorentz-invariant relativistic light-front wave equations are functions of an invariant impact variable {zeta} which measures the separation of the quark and gluonic constituents within the hadron at equal light-front time. The result is to a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryon light-quark bound states, which in turn predict the behavior of the pion and nucleon form factors. The theory implements chiral symmetry in a novel way: the effects of chiral symmetry breaking increase as one goes toward large interquark separation, consistent with spectroscopic data, and the the hadron eigenstates generally have components with different orbital angular momentum; e.g., the proton eigenstate in AdS/QCD with massless quarks has L = 0 and L = 1 light-front Fock components with equal probability. The soft-wall model also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function which agrees with the effective coupling {alpha}{sub g1} extracted from the Bjorken sum rule. The AdS/QCD model can be systematically improved by using its complete orthonormal solutions to diagonalize the full QCD light-front Hamiltonian or by applying the Lippmann-Schwinger method in order to systematically include the QCD interaction terms. A new perspective on quark and gluon condensates is also reviewed.

  4. Fine-scale recognition and use of mesoscale fronts by foraging Cape gannets in the Benguela upwelling region

    NASA Astrophysics Data System (ADS)

    Sabarros, Philippe S.; Grémillet, David; Demarcq, Hervé; Moseley, Christina; Pichegru, Lorien; Mullers, Ralf H. E.; Stenseth, Nils C.; Machu, Eric

    2014-09-01

    Oceanic structures such as mesoscale fronts may become hotspots of biological activity through concentration and enrichment processes. These fronts generally attract fish and may therefore be targeted by marine top-predators. In the southern Benguela upwelling system, such fronts might be used as environmental cues by foraging seabirds. In this study we analyzed high-frequency foraging tracks (GPS, 1 s sampling) of Cape gannets Morus capensis from two colonies located on the west and east coast of South Africa in relation to mesoscale fronts detected on daily high-resolution chlorophyll-a maps (MODIS, 1 km). We tested the association of (i) searching behavior and (ii) diving activity of foraging birds with mesoscale fronts. We found that Cape gannets shift from transiting to area-restricted search mode (ARS) at a distance from fronts ranging between 2 and 11 km (median is 6.7 km). This suggests that Cape gannets may be able to sense fronts (smell or vision) or other predators, and that such detection triggers an intensified investigation of their surroundings (i.e. ARS). Also we found that diving probability increases near fronts in 11 out of 20 tracks investigated (55%), suggesting that Cape gannets substantially use fronts for feeding; in the remaining cases (45%), birds may have used other cues for feeding including fishing vessels, particularly for gannets breeding on the west coast. We demonstrated in this study that oceanographic structures such as mesoscale fronts are important environmental cues used by a foraging seabird within the rich waters of an upwelling system. There is now need for further investigations on how Cape gannets actually detect these fronts.

  5. Fronts and frontogenesis as revealed by high time resolution data

    NASA Technical Reports Server (NTRS)

    Frank, A. E.; Barber, D. A.

    1977-01-01

    Upper air sounding are used to examine a cold front of average intensity. Vertical cross sections of potential temperature and wind, and horizontal analyses were compared and adjusted for consistency. These analyses were then used to study the evolution of the front, found to consist of a complex system of fronts occurring at all levels of the troposphere. Low level fronts were strongest at the surface and rapidly weakened with height. Fronts in the midddle troposphere were much more intense. The warm air ahead of the fronts was nearly barotropic, while the cold air behind was baroclinic through deep layers. A deep mixed layer was observed to grow in this cold air.

  6. Urea hydrolysis and calcium carbonate reaction fronts

    NASA Astrophysics Data System (ADS)

    Fox, D. T.; Redden, G. D.; Henriksen, J.; Fujita, Y.; Guo, L.; Huang, H.

    2010-12-01

    The mobility of toxic or radioactive metal contaminants in subsurface environments can be reduced by the formation of mineral precipitates that form co-precipitates with the contaminants or that isolate them from the mobile fluid phase. An engineering challenge is to control the spatial distribution of precipitation reactions with respect to: 1) the location of a contaminant, and 2) where reactants are introduced into the subsurface. One strategy being explored for immobilizing contaminants, such as Sr-90, involves stimulating mineral precipitation by forming carbonate ions and hydroxide via the in situ, microbially mediated hydrolysis of urea. A series of column experiments have been conducted to explore how the construction or design of such an in situ reactant production strategy can affect the temporal and spatial distribution of calcium carbonate precipitation, and how the distribution is coupled to changes in permeability. The columns were constructed with silica gel as the porous media. An interval midway through the column contained an adsorbed urease enzyme in order to simulate a biologically active zone. A series of influent solutions were injected to characterize hydraulic properties of the column (e.g., bromide tracer), profiles of chemical conditions and reaction products as the enzyme catalyzes urea hydrolysis (e.g., pH, ammonia, urea), and changes that occur due to CaCO3 precipitation with the introduction of a calcium+urea solutions. In one experiment, hydraulic conductivity was reduced as precipitate accumulated in a layer within the column that had a higher fraction of fine grained silica gel. Subsequent reduction of permeability and flow (for a constant head condition) resulted in displacement of the hydrolysis and precipitation reaction profiles upstream. In another experiment, which lacked the physical heterogeneity (fine grained layer), the precipitation reaction did not result in loss of permeability or flow velocity and the reaction profile

  7. Mineral replacement front propagation in deformed rocks

    NASA Astrophysics Data System (ADS)

    Beaudoin, Nicolas; Koehn, Daniel; Kelka, Ulrich

    2015-04-01

    Fluid migrations are a major agent of contaminant transport leading to mineral replacement in rocks, impacting their properties as porosity, permeability, and rheology. Understanding the physical and chemical mechanisms that govern mineralogical replacement during and after deformation is required to better understand complex interplays between fluid and rocks that are involved in faulting, seismic cycle, and resource distribution in the upper crust. Dolomitization process related to hydrothermal fluid flow is one of the most studied and debated replacement processes in earth sciences. Dolomitization of limestone is of economic importance as well, as it stands as unconventional oil reservoirs and is systematically observed in Mississippian-Valley Type ore deposit. Despite recent breakthrough about dolomitization processes at large-scale, the small-scale propagation of the reaction front remains unclear. It is poorly documented in the occurrence of stylolites and fractures in the medium while pressure-solution and fracture network development are the most efficient deformation accomodation mechanism in limestone from early compaction to layer-parallel shortening. Thus, the impact of such network on geometry of replaced bodies and on replacement front propagation deserves specific attention. This contribution illustrates the role of fracture and stylolites on the propagation of a reaction front. In a 2 dimensional numerical model we simulate the dolomitization front propagation in a heterogeneous porous medium. The propagation of the reaction front is governed by the competition between advection and diffusion processes, and takes into account reaction rates, disorder in the location of the potential replacement seeds, and permeability heterogeneities. We add stylolites and fractures that can act as barriers or drains to fluid flow according to their orientation and mineralogical content, which can or cannot react with the contaminant. The patterns produced from

  8. Solidification fronts in supercooled liquids: how rapid fronts can lead to disordered glassy solids.

    PubMed

    Archer, A J; Robbins, M J; Thiele, U; Knobloch, E

    2012-09-01

    We determine the speed of a crystallization (or, more generally, a solidification) front as it advances into the uniform liquid phase after the system has been quenched into the crystalline region of the phase diagram. We calculate the front speed by assuming a dynamical density functional theory (DDFT) model for the system and applying a marginal stability criterion. Our results also apply to phase field crystal (PFC) models of solidification. As the solidification front advances into the unstable liquid phase, the density profile behind the advancing front develops density modulations and the wavelength of these modulations is a dynamically chosen quantity. For shallow quenches, the selected wavelength is precisely that of the crystalline phase and so well-ordered crystalline states are formed. However, when the system is deeply quenched, we find that this wavelength can be quite different from that of the crystal, so the solidification front naturally generates disorder in the system. Significant rearrangement and aging must subsequently occur for the system to form the regular well-ordered crystal that corresponds to the free energy minimum. Additional disorder is introduced whenever a front develops from random initial conditions. We illustrate these findings with simulation results obtained using the PFC model. PMID:23030925

  9. Trace metal fronts in European shelf waters

    NASA Astrophysics Data System (ADS)

    Kremling, K.

    1983-05-01

    The Hebrides shelf edge area is characterized by strong horizontal salinity gradients (fronts) which mark the boundary between Scottish coastal and oceanic waters1,2. The results presented here, obtained in summer 1981 on a transect between the open North Atlantic and the German Bight (Fig. 1), confirm that the hydrographical front is accompanied by dramatic increases in inorganic nutrients (phosphate, silicate) and dissolved trace elements such as Cd, Cu, Mn, and 226Ra (Figs 2 and 3). These data (together with measurements from North Sea regions) suggest that the trace metals are mobilized from partly reduced (organic-rich) sediments and vertically mixed into the surface waters3. The regional variations evident from the transect are interpreted as being the result of the hydrography prevailing in waters around the British Isles4.

  10. Slow Progress in Dune (Right Front Wheel)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The right front wheel of NASA's Mars Exploration Rover Opportunity makes slow but steady progress through soft dune material in this movie clip of frames taken by the rover's front hazard identification camera over a period of several days. The sequence starts on Opportunity's 460th martian day, or sol (May 10, 2005) and ends 11 days later. In eight drives during that period, Opportunity advanced a total of 26 centimeters (10 inches) while spinning its wheels enough to have driven 46 meters (151 feet) if there were no slippage. The motion appears to speed up near the end of the clip, but that is an artifact of individual frames being taken less frequently.

  11. Slow Progress in Dune (Left Front Wheel)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The left front wheel of NASA's Mars Exploration Rover Opportunity makes slow but steady progress through soft dune material in this movie clip of frames taken by the rover's front hazard identification camera over a period of several days. The sequence starts on Opportunity's 460th martian day, or sol (May 10, 2005) and ends 11 days later. In eight drives during that period, Opportunity advanced a total of 26 centimeters (10 inches) while spinning its wheels enough to have driven 46 meters (151 feet) if there were no slippage. The motion appears to speed up near the end of the clip, but that is an artifact of individual frames being taken less frequently.

  12. Front contact solar cell with formed emitter

    DOEpatents

    Cousins, Peter John

    2012-07-17

    A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

  13. Front contact solar cell with formed emitter

    DOEpatents

    Cousins, Peter John

    2014-11-04

    A bipolar solar cell includes a backside junction formed by an N-type silicon substrate and a P-type polysilicon emitter formed on the backside of the solar cell. An antireflection layer may be formed on a textured front surface of the silicon substrate. A negative polarity metal contact on the front side of the solar cell makes an electrical connection to the substrate, while a positive polarity metal contact on the backside of the solar cell makes an electrical connection to the polysilicon emitter. An external electrical circuit may be connected to the negative and positive metal contacts to be powered by the solar cell. The positive polarity metal contact may form an infrared reflecting layer with an underlying dielectric layer for increased solar radiation collection.

  14. Multiclass gene selection using Pareto-fronts.

    PubMed

    Rajapakse, Jagath C; Mundra, Piyushkumar A

    2013-01-01

    Filter methods are often used for selection of genes in multiclass sample classification by using microarray data. Such techniques usually tend to bias toward a few classes that are easily distinguishable from other classes due to imbalances of strong features and sample sizes of different classes. It could therefore lead to selection of redundant genes while missing the relevant genes, leading to poor classification of tissue samples. In this manuscript, we propose to decompose multiclass ranking statistics into class-specific statistics and then use Pareto-front analysis for selection of genes. This alleviates the bias induced by class intrinsic characteristics of dominating classes. The use of Pareto-front analysis is demonstrated on two filter criteria commonly used for gene selection: F-score and KW-score. A significant improvement in classification performance and reduction in redundancy among top-ranked genes were achieved in experiments with both synthetic and real-benchmark data sets.

  15. Comparison of Bacillus atrophaeus spore viability following exposure to detonation of C4 and to deflagration of halogen-containing thermites

    SciTech Connect

    Tringe, J. W.; Letant, S. E.; Dugan, L. C.; Levie, H. W.; Kuhl, A. L.; Murphy, G. A.; Alves, S. W.; Vandersall, K. S.; Pantoya, M. L.

    2013-12-17

    We found that energetic materials are being considered for the neutralization of spore-forming bacteria. In this study, the neutralization effects of a monomolecular explosive were compared to the effects of halogen-containing thermites. Bacillus atrophaeus spores were exposed to the post-detonation environment of a 100 g charge of the military explosive C-4 at a range of 50 cm. These tests were performed in the thermodynamically closed environment of a 506-l barometric calorimeter. Associated temperatures were calculated using a thermodynamic model informed by calculations with the Cheetah thermochemicalcode. Temperatures in the range of 2300–2800 K were calculated to persist for nearly the full 4 ms pressure observation time. After the detonation event, spores were characterized using optical microscopy and the number of viable spores was assessed. These results showed live spore survival rates in the range of 0.01%–1%. For the thermite tests, a similar, smaller-scale configuration was employed that examined the spore neutralization effects of two thermites: aluminum with iodine pentoxide andaluminum with potassium chlorate. Only the former mixture resulted in spore neutralization. Our results indicate that the detonation environment produced by an explosive with no chemical biocides may provide effective spore neutralization similar to a deflagrating thermite containing iodine.

  16. Comparison of Bacillus atrophaeus spore viability following exposure to detonation of C4 and to deflagration of halogen-containing thermites

    SciTech Connect

    Tringe, J. W.; Létant, S. E.; Dugan, L. C.; Levie, H. W.; Kuhl, A. L.; Murphy, G. A.; Alves, S. W.; Vandersall, K. S.; Pantoya, M. L.

    2013-12-21

    Energetic materials are being considered for the neutralization of spore-forming bacteria. In this study, the neutralization effects of a monomolecular explosive were compared to the effects of halogen-containing thermites. Bacillus atrophaeus spores were exposed to the post-detonation environment of a 100 g charge of the military explosive C-4 at a range of 50 cm. These tests were performed in the thermodynamically closed environment of a 506-l barometric calorimeter. Associated temperatures were calculated using a thermodynamic model informed by calculations with the Cheetah thermochemical code. Temperatures in the range of 2300–2800 K were calculated to persist for nearly the full 4 ms pressure observation time. After the detonation event, spores were characterized using optical microscopy and the number of viable spores was assessed. Results showed live spore survival rates in the range of 0.01%–1%. For the thermite tests, a similar, smaller-scale configuration was employed that examined the spore neutralization effects of two thermites: aluminum with iodine pentoxide and aluminum with potassium chlorate. Only the former mixture resulted in spore neutralization. These results indicate that the detonation environment produced by an explosive with no chemical biocides may provide effective spore neutralization similar to a deflagrating thermite containing iodine.

  17. Comparison of Bacillus atrophaeus spore viability following exposure to detonation of C4 and to deflagration of halogen-containing thermites

    DOE PAGES

    Tringe, J. W.; Letant, S. E.; Dugan, L. C.; Levie, H. W.; Kuhl, A. L.; Murphy, G. A.; Alves, S. W.; Vandersall, K. S.; Pantoya, M. L.

    2013-12-17

    We found that energetic materials are being considered for the neutralization of spore-forming bacteria. In this study, the neutralization effects of a monomolecular explosive were compared to the effects of halogen-containing thermites. Bacillus atrophaeus spores were exposed to the post-detonation environment of a 100 g charge of the military explosive C-4 at a range of 50 cm. These tests were performed in the thermodynamically closed environment of a 506-l barometric calorimeter. Associated temperatures were calculated using a thermodynamic model informed by calculations with the Cheetah thermochemicalcode. Temperatures in the range of 2300–2800 K were calculated to persist for nearly themore » full 4 ms pressure observation time. After the detonation event, spores were characterized using optical microscopy and the number of viable spores was assessed. These results showed live spore survival rates in the range of 0.01%–1%. For the thermite tests, a similar, smaller-scale configuration was employed that examined the spore neutralization effects of two thermites: aluminum with iodine pentoxide andaluminum with potassium chlorate. Only the former mixture resulted in spore neutralization. Our results indicate that the detonation environment produced by an explosive with no chemical biocides may provide effective spore neutralization similar to a deflagrating thermite containing iodine.« less

  18. Comparison of Bacillus atrophaeus spore viability following exposure to detonation of C4 and to deflagration of halogen-containing thermites

    NASA Astrophysics Data System (ADS)

    Tringe, J. W.; Létant, S. E.; Dugan, L. C.; Levie, H. W.; Kuhl, A. L.; Murphy, G. A.; Alves, S. W.; Vandersall, K. S.; Pantoya, M. L.

    2013-12-01

    Energetic materials are being considered for the neutralization of spore-forming bacteria. In this study, the neutralization effects of a monomolecular explosive were compared to the effects of halogen-containing thermites. Bacillus atrophaeus spores were exposed to the post-detonation environment of a 100 g charge of the military explosive C-4 at a range of 50 cm. These tests were performed in the thermodynamically closed environment of a 506-l barometric calorimeter. Associated temperatures were calculated using a thermodynamic model informed by calculations with the Cheetah thermochemical code. Temperatures in the range of 2300-2800 K were calculated to persist for nearly the full 4 ms pressure observation time. After the detonation event, spores were characterized using optical microscopy and the number of viable spores was assessed. Results showed live spore survival rates in the range of 0.01%-1%. For the thermite tests, a similar, smaller-scale configuration was employed that examined the spore neutralization effects of two thermites: aluminum with iodine pentoxide and aluminum with potassium chlorate. Only the former mixture resulted in spore neutralization. These results indicate that the detonation environment produced by an explosive with no chemical biocides may provide effective spore neutralization similar to a deflagrating thermite containing iodine.

  19. Phase front design with metallic pillar arrays.

    PubMed

    Verslegers, Lieven; Catrysse, Peter B; Yu, Zongfu; Shin, Wonseok; Ruan, Zhichao; Fan, Shanhui

    2010-03-15

    We demonstrate numerically, using a three-dimensional finite-difference frequency-domain method, the ability to design a phase front using an array of metallic pillars. We show that in such structures, the local phase delay upon transmission can be tuned by local geometry. We apply this knowledge to demonstrate a metallic microlens. The presented design principles apply to a wider range of wavelength-size integrated photonic components.

  20. The Foley Acoustic Wave Front Slides

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2004-04-01

    In 1912 Arthur L. Foley of Indiana University published an article in Physical Review about his technique for photographing acoustic wave fronts. Subsequently, the Central Scientific Company published a series of glass lantern slides of his illustrations. These have been unavailable for about 60 years. Here I discuss how Foley made his slides and give examples of use to the present-day physics teacher.

  1. Stability analysis of unsteady ablation fronts

    SciTech Connect

    Betti, R.; McCrory, R.L.; Verdon, C.P. )

    1993-11-08

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  2. Stability analysis of unsteady ablation fronts

    NASA Astrophysics Data System (ADS)

    Betti, R.; McCrory, R. L.; Verdon, C. P.

    1993-08-01

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  3. Stability analysis of unsteady ablation fronts

    SciTech Connect

    Betti, R.; McCrory, R.L.; Verdon, C.P.

    1993-08-01

    The linear stability analysis of unsteady ablation fronts, is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

  4. Stability analysis of unsteady ablation fronts

    NASA Astrophysics Data System (ADS)

    Betti, R.; McCrory, R. L.; Verdon, C. P.

    1993-11-01

    The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code orchid.

  5. Detached plasma in Saturn's front side magnetosphere

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.

    1983-01-01

    Plasma observations in the outer front side Saturnian magnetosphere are discussed which indicate the existence of dense flux tubes outside the plasma sheets. It is suggested that flux tubes are detached from the plasma sheet by a centifugally driven flute instability. The same instability leads to a dispersal of Titan-injected plasma. It is shown that the detached flux tubes will probably break open as they convect into the nightside magnetotail and lose their content in the form of a planetary wind.

  6. Solar cell having improved front surface metallization

    SciTech Connect

    Lillington, D.R.; Mardesich, N.; Dill, H.G.; Garlick, G.F.J.

    1987-09-15

    This patent describes a solar cell comprising: a first layer of gallium arsenide semiconductor material of an N+ conductivity; a second layer of gallium arsenide semiconductor material of an N conductivity overlying the first layer; a third layer of gallium arsenide semiconductor material of a P conductivity overlying the N conductivity layer and forming a P-N junction therebetween. A layer of aluminium gallium arsenide semiconductor material of a p conductivity overlying the front major surface of the P conductivity third layer and having an exposed surface essentially parallel to the front major surface and at least one edge; a plurality of metallic contact lines made of a first metal alloy composition and being spaced apart by a first predetermined distance traversing the exposed surface and extending through the aluminium gallium arsenide layer to the front major surface and making electrical contact to the third layer; a plurality of longitudinally disposed metallic grid lines made of a second metal alloy composition and being spaced apart by a second predetermined distance located on the exposed surface of the aluminium gallium arsenide layer and which cross the metallic contact lines and make electrical contact to the metallic lines; a flat metallic strip disposed on the aluminium gallium arsenide layer exposed surface near the edge, the strip electrically coupling the metallic grid lines to one another; and a back contact located on the back major surface.

  7. A compaction front in North Sea chalk

    NASA Astrophysics Data System (ADS)

    Japsen, P.; Dysthe, D. K.; Hartz, E. H.; Stipp, S. L. S.; Yarushina, V. M.; Jamtveit, B.

    2011-11-01

    North Sea chalk from 18 wells shows a pronounced porosity drop, from ˜20% to less than 10% over a compaction front of less than 300 m. The position of the compaction front is independent of stratigraphic position, temperature, and actual depth, but closely tied to an effective stress (load stress minus fluid pressure) of ˜17 MPa. These observations require a strongly nonlinear rheology with a marked increase in compaction rate at a specific effective stress. Grain-scale observations demonstrate that the compaction front coincides with marked grain coarsening and recrystallization of fossils and fossil fragments. We propose that this nonlinear rheology is caused by stress-driven failure of the larger pores and the associated generation of reactive surface area by subcritical crack propagation away from these pores. Before the onset of this instability, compaction by pressure solution is slowed down by the inhibitory effect of organic compounds associated with the fossils. Although the compaction mechanism is mainly by pressure solution, the rheological response to burial may still be dominantly plastic and controlled by the (fracturing controlled) rate of exposure of reactive surface area. The nonlinear compaction of chalk has significant implications for the evolution of petroleum systems in the central North Sea, both with respect to sea-floor subsidence above hydrocarbon-producing chalk reservoirs and for the formation of low-porosity pressure seals within the chalk.

  8. Colloid Formation at Waste Plume Fronts

    SciTech Connect

    Wan, Jiamin; Tokunaga, Tetsu K.; Saiz, Eduardo; Larsen, Joern T.; Zheng, Zuoping; Couture, Rex A.

    2004-05-22

    Highly saline and caustic tank waste solutions containing radionuclides and toxic metals have leaked into sediments at U. S. Department of Energy (DOE) facilities such as the Hanford Site (Washington State). Colloid transport is frequently invoked to explain migration of radionuclides and metals in the subsurface. To understand colloid formation during interactions between highly reactive fluids and sediments and its impact on contaminant transport, we simulated tank waste solution (TWS) leakage processes in laboratory columns at ambient and elevated (70 C) temperatures. We found that maximum formation of mobile colloids occurred at the plume fronts (hundreds to thousands times higher than within the plume bodies or during later leaching). Concentrations of suspended solids were as high as 3 mass%, and their particle-sizes ranged from tens of nm to a few {micro}m. Colloid chemical composition and mineralogy depended on temperature. During infiltration of the leaked high Na{sup +} waste solution, rapid and completed Na{sup +} replacement of exchangeable Ca{sup 2+} and Mg{sup 2+} from the sediment caused accumulation of these divalent cations at the moving plume front. Precipitation of supersaturated Ca{sup 2+}/Mg{sup 2+}-bearing minerals caused dramatic pH reduction at the plume front. In turn, the reduced pH caused precipitation of other minerals. This understanding can help predict the behavior of contaminant trace elements carried by the tank waste solutions, and could not have been obtained through conventional batch studies.

  9. Phenomenological Theory of the Photoevaporation Front Instability

    SciTech Connect

    Ryutov, D D; Kane, J O; Mizuta, A; Pound, M W; Remington, B A

    2006-04-10

    The dynamics of photoevaporated molecular clouds is determined by the ablative pressure acting on the ionization front. An important step in the understanding of the ensuing motion is to develop the linear stability theory for the initially flat front. Despite the simplifications introduced by the linearization, the problem remains quite complex and still draws a lot of attention. The complexity is related to the large number of effects that have to be included in the analysis: acceleration of the front, possible temporal variation of the intensity of the ionizing radiation, the tilt of the radiation flux with respect to the normal to the surface, and partial absorption of the incident radiation in the ablated material. In this paper, we describe a model where all these effects can be taken into account simultaneously, and a relatively simple and universal dispersion relation can be obtained. The proposed phenomenological model may prove to be a helpful tool in assessing the feasibility of the laboratory experiments directed towards scaled modeling of astrophysical phenomena.

  10. Phenomenological Theory of the Photoevaporation Front Instability

    NASA Astrophysics Data System (ADS)

    Ryutov, D. D.; Kane, J. O.; Mizuta, A.; Pound, M. W.; Remington, B. A.

    2007-01-01

    The dynamics of photoevaporated molecular clouds is determined by the ablative pressure acting on the ionization front. An important step in the understanding of the ensuing motion is to develop the linear stability theory for an initially flat front. Despite the simplifications introduced by linearization, the problem remains quite complex and still draws a lot of attention. The complexity is related to the large number of effects that have to be included in the analysis: acceleration of the front, possible temporal variation of the intensity of the ionizing radiation, the tilt of the radiation flux with respect to the normal to the surface, and partial absorption of the incident radiation in the ablated material. In this paper, we describe a model where all these effects can be taken into account simultaneously, and a relatively simple and universal dispersion relation can be obtained. The proposed phenomenological model may prove to be a helpful tool in assessing the feasibility of the laboratory experiments directed towards scaled modeling of astrophysical phenomena.

  11. Kinetic information from detonation front curvature

    SciTech Connect

    Souers, P. C., LLNL

    1998-06-15

    The time constants for time-dependent modeling may be estimated from reaction zone lengths, which are obtained from two sources One is detonation front curvature, where the edge lag is close to being a direct measure The other is the Size Effect, where the detonation velocity decreases with decreasing radius as energy is lost to the cylinder edge A simple theory that interlocks the two effects is given A differential equation for energy flow in the front is used, the front is described by quadratic and sixth-power radius terms The quadratic curvature comes from a constant power source of energy moving sideways to the walls Near the walls, the this energy rises to the total energy of detonation and produces the sixth-power term The presence of defects acting on a short reaction zone can eliminate the quadratic part while leaving the wall portion of the cuvature A collection of TNT data shows that the reaction zone increases with both the radius and the void fraction

  12. Front lighted shadowgraphic method and apparatus

    DOEpatents

    Stone, William J.

    1985-02-26

    High contrast silhouette images of a substantially opaque object are obtained using front illumination techniques. The object is frontally illuminated by light of a first polarization. A frontal surface of the object reflects the incident light to an observation station. The polarization of incident light bypassing the object and incident on a background is changed. The background light is reflected to the observation station, and the intensity of one of the two, differently polarized, reflected images is substantially reduced with respect to the other. Apparatus for carrying out the method includes a first polarizer for polarizing frontally incident illuminating light, a second polarizer behind the object and a reflective surface behind the second polarizer. A polarization analyzer, located in front of the object, is used to extinguish one of the two reflected images. Apparatus for carrying out the invention in instruments having a polarized light source and a polarization analyzer includes a combination of a polarizing material, for contacting a rear surface of the object, and a reflective surface provided adjacent the rear surface of the polarizing material. The combination is applied to the rear surface of the object. Back-surface mirrors of pleochroic substrates applied to thin film physical vapor deposited electronic circuit elements enable front lighted shadowgraphic imaging of the elements.

  13. 11. Front elevation of building 101, administration, recreation, and storage ...

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

    11. Front elevation of building 101, administration, recreation, and storage building, showing front sentry box on far right, looking west - Nike Missile Battery MS-40, County Road No. 260, Farmington, Dakota County, MN

  14. TRACES OF ORIGINAL PARTITIONS AT JUNCTURE OF FRONT ROOM, REAR ...

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

    TRACES OF ORIGINAL PARTITIONS AT JUNCTURE OF FRONT ROOM, REAR ROOM AND HALL, SECOND FLOOR. ALSO SHOWS ORIGINAL STUCCO CORNICE OF FRONT AND REAR ROOMS (LEFT) AND HALL (RIGHT) - Kid-Chandler House, 323 Walnut Street, Philadelphia, Philadelphia County, PA

  15. 1. FRONT CORNER, LOOKING NORTHEAST, TOP HALF OF 'DUTCH DOORS' ...

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

    1. FRONT CORNER, LOOKING NORTHEAST, TOP HALF OF 'DUTCH DOORS' LEANING AGAINST FRONT WALL. - A. D. Wilcox Drift Mine, Boiler Cabin, Linda Creek near Dalton Highway, Bettles, Yukon-Koyukuk Census Area, AK

  16. Security Station and Front Entrance to hospital property, looking northeast ...

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

    Security Station and Front Entrance to hospital property, looking northeast - U.S. Veterans Hospital, Jefferson Barracks, Security Station & Front Gate, VA Medical Center, Jefferson Barracks Division 1 Jefferson Barracks Drive, Saint Louis, Independent City, MO

  17. 2. VIEW SOUTHEAST, WEST FRONT OF BUILDINGS 25. 26; NORTH ...

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

    2. VIEW SOUTHEAST, WEST FRONT OF BUILDINGS 25. 26; NORTH FRONT OF BUILDING 24: ROOF GABLE OF BUILDING 27 - U.S. Plant Introduction Station, Soil Conservation Service Cluster, 11601 Old Pond Road, Glenn Dale, Prince George's County, MD

  18. 26. General view of Front Street looking from north to ...

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

    26. General view of Front Street looking from north to south from vicinity of Rue Lafayette to intersection of Rue Horne & beyond - Front Street (Commercial Buildings), Natchitoches, Natchitoches Parish, LA

  19. 7. VIEW OF CONNECTING WALL BETWEEN FRONT AND REAR ROOMS ...

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

    7. VIEW OF CONNECTING WALL BETWEEN FRONT AND REAR ROOMS OF SECOND FLOOR, SHOWING SIMPLE GREEK REVIVAL MANTLE. LOOKING WEST; TAKEN FROM FRONT ROOM. - Manlius Thomas House, 125 North Mulberry Street, Georgetown, Scott County, KY

  20. 253. 441 SOUTH NINETEENTH STREET, WEST FRONT AND SOUTH SIDE, ...

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

    253. 441 SOUTH NINETEENTH STREET, WEST FRONT AND SOUTH SIDE, AND 1829, SOUTH FRONT AND WEST SIDE, TOWARD NORTHEAST - Russell Neighborhood, Bounded by Congress & Esquire Alley, Fifteenth & Twenty-first Streets, Louisville, Jefferson County, KY

  1. 11. Photocopy of old photo shows the front facade partially ...

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

    11. Photocopy of old photo shows the front facade partially hidden by trees. It dates from circa 1883 and includes the porch with Ionic columns. From an unknown source. - John Tremper House, 3 North Front Street, Kingston, Ulster County, NY

  2. 2. LAUNCH CONTROL SUPPORT BUILDING WEST FRONT AND VEHICLE STORAGE ...

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

    2. LAUNCH CONTROL SUPPORT BUILDING WEST FRONT AND VEHICLE STORAGE BUILDING SOUTHWEST FRONT. VIEW TO EAST. - Minuteman III ICBM Launch Control Facility November-1, 1.5 miles North of New Raymer & State Highway 14, New Raymer, Weld County, CO

  3. EXCAVATION OF EAST (FRONT) BASEMENT WELL AND DRAINAGE SYSTEM, WITH ...

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

    EXCAVATION OF EAST (FRONT) BASEMENT WELL AND DRAINAGE SYSTEM, WITH ARCHED ENTRY INTO BASEMENT UNDER FRONT ENTRY IN BACKGROUND, LOOKING NORTH (NOTE GALLETING IN BRICK FOUNDATION) - Belair, Tulip Grove Drive, Belair-at-Bowie, Bowie, Prince George's County, MD

  4. Wintertime sea surface temperature fronts in the Taiwan Strait

    NASA Astrophysics Data System (ADS)

    Chang, Yi; Shimada, Teruhisa; Lee, Ming-An; Lu, Hsueh-Jung; Sakaida, Futoki; Kawamura, Hiroshi

    2006-12-01

    We present wintertime variations and distributions of sea surface temperature (SST) fronts in the Taiwan Strait by applying an entropy-based edge detection method to 10-year (1996-2005) satellite SST images with grid size of 0.01°. From climatological monthly mean maps of SST gradient magnitude in winter, we identify four significant SST fronts in the Taiwan Strait. The Mainland China Coastal Front is a long frontal band along the 50-m isobath near the Chinese coast. The sharp Peng-Chang Front appears along the Peng-Hu Channel and extends northward around the Chang-Yuen Ridge. The Taiwan Bank Front evolves in early winter. As the winter progresses, the front becomes broad and moves toward the Chinese coast, connecting to the Mainland China Coastal Front. The Kuroshio Front extends northeastward from the northeastern tip of Taiwan with a semicircle-shape curving along the 100-m isobath.

  5. Subtropical Shelf Front off eastern South America

    NASA Astrophysics Data System (ADS)

    Piola, Alberto R.; Campos, Edmo J. D.; MöLler, Osmar O.; Charo, Marcela; Martinez, Carlos

    2000-03-01

    Historical hydrographic data from the continental shelf off eastern South America are used to examine the thermohaline properties of the water masses in the region between 20°S and 40°S. The continental shelf water masses are originated by dilution of open ocean waters of the western boundary currents of the South Atlantic Ocean. On the basis of temperature-salinity relation, two distinct water masses are identified, namely, the Subantarctic Shelf Water and the Subtropical Shelf Water. Subantarctic Shelf Water originates by dilution of Subantarctic Water, primarily in the southeast Pacific, due to excess precipitation and continental runoff and enters the continental shelf near 55°S. The Subtropical Shelf Water is modified South Atlantic Central Water diluted by continental runoff from the coast of Brazil. In addition, substantial dilution of the upper shelf waters takes place at the mouth of Río de la Plata (approximately located at 36°S) and, in a lesser extent, at the Patos-Mirim Lagoon (at 32°S). The Río de la Plata and the Patos outflows form a low-salinity tongue that caps the shelf water leading to a salinity decrease to values <30. The low-salinity tongue extends northward over the shelf penetrating farther north in winter than in summer. The extent of the low-salinity water has a strong impact on the vertical stratification and acts to limit winter convection to the layer above the halocline. There is little or no indication of mixing between Subantarctic Shelf Water and Subtropical Shelf Water. An intense temperature, salinity, and nutrient front separates these water masses. The front is oriented along the north-south direction, located on average near the 50 m isobath at 32°S and extends southward toward the shelf break near 36°S. Between 32° and 34°S the Subtropical Shelf Front follows the 100 to 200 m isobaths and separates Subantarctic Shelf Water from the oceanic South Atlantic Central Water. On the basis of the temperature and salinity

  6. 16 CFR 1512.13 - Requirements for front fork.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Requirements for front fork. 1512.13 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.13 Requirements for front fork. The front fork shall... fork test, § 1512.18(k)(1), without visible evidence of fracture. Sidewalk bicycles need not meet...

  7. 16 CFR 1512.13 - Requirements for front fork.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Requirements for front fork. 1512.13 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.13 Requirements for front fork. The front fork shall... fork test, § 1512.18(k)(1), without visible evidence of fracture. Sidewalk bicycles need not meet...

  8. 16 CFR 1512.13 - Requirements for front fork.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Requirements for front fork. 1512.13 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.13 Requirements for front fork. The front fork shall... fork test, § 1512.18(k)(1), without visible evidence of fracture. Sidewalk bicycles need not meet...

  9. 16 CFR 1512.13 - Requirements for front fork.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Requirements for front fork. 1512.13 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.13 Requirements for front fork. The front fork shall... fork test, § 1512.18(k)(1), without visible evidence of fracture. Sidewalk bicycles need not meet...

  10. 16 CFR 1512.13 - Requirements for front fork.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Requirements for front fork. 1512.13 Section... REGULATIONS REQUIREMENTS FOR BICYCLES Regulations § 1512.13 Requirements for front fork. The front fork shall... fork test, § 1512.18(k)(1), without visible evidence of fracture. Sidewalk bicycles need not meet...

  11. 11. VIEW NORTH, SOUTH FRONT OF MAIN OFFICE UNIT (BUILDING ...

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

    11. VIEW NORTH, SOUTH FRONT OF MAIN OFFICE UNIT (BUILDING I, 2); SOUTH AND EAST FRONTS OF SEED STORAGE BUILDING (BUILDING 21); EAST FRONT OF GREENHOUSE #1 (BUILDING 5) - U.S. Plant Introduction Station, 11601 Old Pond Road, Glenn Dale, Prince George's County, MD

  12. 1. EXTERIOR VIEW OF FRONT OF CLUB HOUSE. BOAT HOUSE ...

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

    1. EXTERIOR VIEW OF FRONT OF CLUB HOUSE. BOAT HOUSE AND DOCK TO THE RIGHT. PICTURE TAKEN FROM FRONT YARD OF COTTAGE 231, CAMERA FACING SOUTHWEST. SMALL WOOD FRAME SHED IN FRONT OF CLUB HOUSE STORES FIRE HOSE BUILT AFTER 1980. - Swan Falls Village, Clubhouse 011, Snake River, Kuna, Ada County, ID

  13. "How Can We Stay Healthy When You're Throwing All of This in Front of Us?" Findings from Focus Groups and Interviews in Middle Schools on Environmental Influences on Nutrition and Physical Activity

    ERIC Educational Resources Information Center

    Bauer, Katherine W.; Yang, Y. Wendy; Austin, S. Bryn

    2004-01-01

    This study aimed to identify factors in school physical and social environments that may facilitate or compete with programs and policies to improve student physical activity and nutrition. Focus groups and interviews were conducted with students, faculty, and staff of two public middle schools. Participants identified numerous aspects of the…

  14. Detailed bathymetry and magnetic anomaly in the Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after approximately 2.1 Ma

    NASA Astrophysics Data System (ADS)

    Sato, Taichi; Oda, Hirokuni; Ishizuka, Osamu; Arai, Kohsaku

    2014-12-01

    Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed approximately 20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least approximately 2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

  15. Detailed bathymetry and magnetic anomaly inthe Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after ~2.1 Ma

    NASA Astrophysics Data System (ADS)

    Sato, T.; Oda, H.; Ishizuka, O.; Arai, K.

    2014-12-01

    Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed ~20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least ~2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

  16. Water Films: Moisture that Extends Beyond the Capillary Wetting Front

    NASA Astrophysics Data System (ADS)

    Dragila, M. I.; Ambrowiak, G.

    2015-12-01

    Imbibition dynamics were investigated by measuring upward imbibition rates in laboratory vertical columns that were filled with sandy loam soil media. The contribution of films and capillary water which drives the infiltrating wetting front was successfully quantified. It was demonstrated that films move ahead of the wetting front only after capillary water has ceased driving percolation, and that the hydraulic diffusion coefficient (Dh) of film flow varied from 10-70% of the hydraulic diffusion coefficient of capillary water. The magnitude of Dh depended upon particle size distribution, surface roughness and initial moisture content of the media. What is the potential value of this mechanism in soil moisture dynamics research? (1) In coarse textured soils with low capillary potential, film that stretches well beyond the capillary wetting front can provide moisture to microbiota and mycorhyza, thereby increasing nutrient diffusion to a broader area than by capillary based models (e.g., modeling of drip irrigation systems). Even though the potential role of films in these processes has been previously discussed, the magnitude of potential moisture delivery has not been measured. (2) Films surging ahead of a decelerating capillary front may reduce the effect of subsurface water repellency. It is known that over time, moisture decreases both the contact angle of water against silica and water repellent soils. Therefore, in time, a film may predispose sandy soil to greater imbibition capacity. (3) The need to maximize water efficiency becomes exceedingly important in drought threatened, semi-arid irrigated agriculture. A thoughtful, yet realistic balance must be reached between water conservation and crop production. As our climate changes and water needs increase, protecting against crop failure will require a more comprehensive understanding of the mechanisms that control soil moisture dynamics. This study adds to this conversation by investigating higher level

  17. "How can we stay healthy when you're throwing all of this in front of us?" Findings from focus groups and interviews in middle schools on environmental influences on nutrition and physical activity.

    PubMed

    Bauer, Katherine W; Yang, Y Wendy; Austin, S Bryn

    2004-02-01

    This study aimed to identify factors in school physical and social environments that may facilitate or compete with programs and policies to improve student physical activity and nutrition. Focus groups and interviews were conducted with students, faculty, and staff of two public middle schools. Participants identified numerous aspects of the school environments as significant. Competition, teasing and bullying, time, and safety were described as major barriers for students to be physically active during physical education class, on sports teams, and before and after school. The quality of the food served, easy access to nonnutritious snacks, limited time for lunch period, and weight concerns emerged as significant reasons why students do not eat nutritious meals in school. When developing programs and policies to improve the health of students, environmental influences that undermine efforts to improve student health behaviors must be addressed. PMID:14768656

  18. Universal power law for front propagation in all fiber resonators.

    PubMed

    Coulibaly, S; Taki, M; Tlidi, M

    2014-01-13

    We consider a bistable system consisting of all fiber cavity driven by an external injected continuous wave. We report on front propagation in a high finesse cavity. We study the asymptotic behavior of the front velocity. We show that the front velocity is affected by the distance from the critical point associated with bistability. We provide a scaling low governing its evolution near the up-switching point of the bistable curve. We show also that the velocity of front propagation obeys a generic power law when the front velocity approaches asymptotically its linear growing value.

  19. Novel Perspectives from Light-Front QCD, Super-Conformal Algebra, and Light-Front Holography

    SciTech Connect

    Brodsky, Stanley J.

    2015-12-01

    Light-Front Quantization – Dirac’s “Front Form” – provides a physical, frame-independent formalism for hadron dynamics and structure. Observables such as structure functions, transverse momentum distributions, and distribution amplitudes are defined from the hadronic LFWFs. One obtains new insights into the hadronic mass scale, the hadronic spectrum, and the functional form of the QCD running coupling in the nonperturbative domain using light-front holography. In addition, superconformal algebra leads to remarkable supersymmetric relations between mesons and baryons. I also discuss evidence that the antishadowing of nuclear structure functions is nonuniversal; i.e., flavor dependent, and why shadowing and antishadowing phenomena may be incompatible with the momentum and other sum rules for the nuclear parton distribution functions.

  20. Imaging Slow Slip Fronts in Cascadia With High-Precision Tremor Locations

    NASA Astrophysics Data System (ADS)

    Rubin, A. M.; Armbruster, J. G.

    2012-12-01

    We use the method of Armbruster and Kim [AGU 2010] to obtain tremor locations using 4-second windows, focusing on a few spots beneath southern Vancouver Island activated by slow slip events from 2003 to 2005. The method compares horizontal-component waveforms (not envelopes) at 3 stations separated by 10-20 km. From local earthquakes "caught" by the detector it appears that the coherent signal consists of the direct S arrival but not the S coda. Using 150-s windows, Armbruster and Kim found "wispy" sources of tremor that in some regions were reproducible between the 2003, 2004, and 2005 events to within 1 km. In time, their tremor locations trace out quasi-linear trajectories on the fault surface that migrate tens of times faster than the main front, as has been reported elsewhere [e.g., Ghosh et al., 2010; Vidale et al., AGU 2011]. By moving to 4-s windows, we find that these long-time-window locations very often represent the spatial "average" of secondary fronts behind the main front. These secondary fronts tend to (a) start within about 1 km of the main tremor front and propagate back along strike, akin to the "rapid tremor reversals" of Houston et al. [2011] but on a smaller scale (5 km rather than 50); (b) less commonly do the reverse, ending at the main front; or (c) propagate up- or down-dip at or within 1-2 kilometers of the main front. Rare events propagate in other directions. The fronts that move along strike can be as narrow as 1 km in the propagation direction but can exceed 5 km in the orthogonal direction. Those that propagate along dip are typically also narrow (~ 1 km) in the strike direction; if they are even narrower in the propagation direction this is below our resolution. Characteristic propagation speeds are 10 km/hr along strike and several times faster along dip. For those along-dip migrations that occur at the main front, the larger propagation speed is plausibly an "apparent" velocity as the main front intersects an along-dip alignment

  1. Functional description of APS beamline front ends

    SciTech Connect

    Kuzay, T.

    1993-02-01

    Traditional synchrotron sources were designed to produce bending magnet radiation and have proven to be an essential scientific tool. Currently, a new generation of synchrotron sources is being built that will be able to accommodate a large number of insertion device (ID) and high quality bending magnet (BM) sources. One example is the 7-GeV Advanced Photon Source (APS) now under construction at Argonne National Laboratory. The research and development effort at the APS is designed to fully develop the potential of this new generation of synchrotron sources. Of the 40 straight sections in the APS storage ring, 34 will be available for IDs. The remaining six sections are reserved for the storage ring hardware and diagnostics. Although the ring incorporates 80 BMs, only 40 of them can be used to extract radiation. The accelerator hardware shadows five of these 40 bending magnets, so the maximum number of BM sources on the lattice is 35. Generally, a photon beamline consists of four functional sections. The first section is the ID or the BM, which provides the radiation source. The second section, which is immediately outside the storage ring but inside a concrete shielding tunnel, is the front end, which is designed to control, define, and/or confine the x-ray beam. In the case of the APS, the front ends are designed to confine the photon beam. The third section, just outside the concrete shielding tunnel and on the experimental floor, is the first optics enclosure, which contains optics to filter and monochromatize the photon beam. The fourth section of a beamline consists of beam transports, additional optics, and experiment stations to do the scientific investigations. This document describes only the front ends of the APS beamlines.

  2. Propagating Dipolarization Fronts Earthward of 6 Earth Radii

    NASA Astrophysics Data System (ADS)

    Malaspina, D.; Andersson, L.; Ergun, R.; Wygant, J. R.; Bonnell, J. W.; Kletzing, C.; Reeves, G. D.; Skoug, R. M.; Larsen, B.

    2014-12-01

    During geomagnetically active conditions, the Van Allen Probes observe magnetic dipolarizations associated with enhancements in > 1 keV electron energy flux and the presence of nonlinear electric field structures (e.g. double layers and phase space holes) in the inner magnetosphere (4-6 Re). These dipolarization events are observed most frequently between dusk and midnight, though some appear between midnight and dawn. In some cases, nonlinear electric field power shows abrupt onset that is nearly simultaneous with electron energy flux enhancements across a range of energies. By comparing magnetic field, electric field, and particle data from both spacecraft, recorded when the twin Van Allen Probes are in close proximity, it is found that some of these abrupt onset features can be identified as earthward-propagating fonts with speeds on the order of 30 km/s. The presence of coherent propagating dipolarization fronts well inside the nominal flow breaking region (9 - 12 Re) suggests that earthward plasma flows may influence the magnetospheric plasma environment at the radial distances associated with the ring current and radiation belts. Possible mechanisms for this influence include the localized injection of particles adiabatically energized by their earthward transport, and wave-particle interactions related to the high amplitude parallel electric fields associated with the nonlinear electric field structures observed near these propagating fronts.

  3. Front-like entire solutions for equations with convection

    NASA Astrophysics Data System (ADS)

    Crooks, E. C. M.; Tsai, Je-Chiang

    We construct families of front-like entire solutions for problems with convection, both for bistable and monostable reaction-diffusion-convection equations, and, via vanishing-viscosity arguments, for bistable and monostable balance laws. The unified approach employed is inspired by ideas of Chen and Guo and based on a robust method using front-dependent sub and supersolutions. Unlike convectionless problems, the equations studied here lack symmetry between increasing and decreasing travelling waves, which affects the choice of sub and supersolutions used. Our entire solutions include both those that behave like two fronts coming together and annihilating as time increases, and, for bistable equations, those that behave like two fronts merging to propagate like a single front. We also characterise the long-time behaviour of each family of entire solutions, which in the case of solutions constructed from a monostable front merging with a bistable front answers a question that was open even for reaction-diffusion equations without convection.

  4. The importance of oceanographic fronts to marine birds and mammals of the southern oceans

    NASA Astrophysics Data System (ADS)

    Bost, C. A.; Cotté, C.; Bailleul, F.; Cherel, Y.; Charrassin, J. B.; Guinet, C.; Ainley, D. G.; Weimerskirch, H.

    2009-10-01

    long distances from colonies, showing variable foraging strategies as a function of the distances involved. Diving birds such as King penguins, that travel at a higher cost and lower speed, rely on the predictable spatial distribution of mesopelagic fish found close to the Polar Front. They may use the currents associated with eddies as oceanographic cues in the active search for frontal zones. Once in these areas they dive preferentially in and below the depth of the thermocline where catches per unit effort are high. Elephant seals concentrate foraging activity principally inside or at the boundary of cyclonic eddies. These mesoscale features appear to offer exceptional productivity favourable for foraging by various diving top predators. The connection between biophysical parameters at fronts and predators is likely to be made through biological enhancement. Top predators appear to forage at locations where prey are advected by physical processes and others where prey are produced locally. Long-term research on at-sea distributions and demographic parameters of top predators are essential to assess the consequences of potential shift in front distributions in relation to global warming. Such environmental changes would add to the impact of fish extraction by the industrial fisheries on the southern food webs.

  5. Light-Front Perturbation Without Spurious Singularities

    NASA Astrophysics Data System (ADS)

    Przeszowski, Jerzy A.; Dzimida-Chmielewska, Elżbieta; Żochowski, Jan

    2016-07-01

    A new form of the light front Feynman propagators is proposed. It contains no energy denominators. Instead the dependence on the longitudinal subinterval x^2_L = 2 x+ x- is explicit and a new formalism for doing the perturbative calculations is invented. These novel propagators are implemented for the one-loop effective potential and various 1-loop 2-point functions for a massive scalar field. The consistency with results for the standard covariant Feynman diagrams is obtained and no spurious singularities are encountered at all. Some remarks on the calculations with fermion and gauge fields in QED and QCD are added.

  6. AIRS Storm Front Approaching California (animation)

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Click on the image for the AIRS Storm Front Approaching California Animation

    NASA's Atmospheric Infrared Sounder instrument is able to peel back cloud cover to reveal 3-D structure of a storm's water vapor content, information that can be used to improve weather forecast models.

    In this animation the initial visible cloud image series shows a front moving toward the West Coast of the United States as a low pressure area moves into the Pacific Northwest. The 'Pineapple Express,' a stream of moisture that originates in the tropics South of Hawaii and usually crosses Mexico to enter New Mexico and Texas, has shifted Westward and is also visible moving into Baja California. The area preceding the front appears to be relatively clear in the visible images.

    As the view shifts from the visible to the infrared wavelengths which highlight water vapor, we see both cloud areas contain heavy burdens of moisture. The area which appears clear in the visible images is seen to contain water vapor near the coastline as well. The viewpoint then rotates so that we can see the vertical cross section of the fronts. The variability of the vertical extent of water vapor and the amount is now clearly visible. The storm moving in from the Gulf of Alaska is more heavily laden with water vapor than that moving in from the Southwest. The moisture is concentrated in the lower atmosphere. The colors indicate the amount of water vapor present. Blue areas denote low water vapor content; green areas are medium water vapor content; red areas signify high water vapor content. The vertical grid for the final frame ranges from 250 millibar pressure at the top to 1000 millibar pressure at the bottom. The top is about 10 km (6.2 miles) above the surface of the Earth.

    The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in

  7. Covariance Constraints for Light Front Wave Functions

    NASA Astrophysics Data System (ADS)

    Müller, D.

    2016-06-01

    Light front wave functions (LFWFs) are often utilized to model parton distributions and form factors where their transverse and longitudinal momenta are tied to each other in some manner that is often guided by convenience. On the other hand, the cross talk of transverse and longitudinal momenta is governed by Poincaré symmetry and thus popular LFWF models are often not usable to model more intricate quantities such as generalized parton distributions. In this contribution a closer look to this issue is given and it is shown how to overcome the issue for two-body LFWFs.

  8. Nonperturbative calculations in light-front QED

    SciTech Connect

    Chabysheva, Sophia S.

    2010-12-22

    The methods of light-front quantization and Pauli-Villars regularization are applied to a nonperturbative calculation of the dressed-electron state in quantum electrodynamics. This is intended as a test of the methods in a gauge theory, as a precursor to possible methods for the nonperturbative solution of quantum chromodynamics. The electron state is truncated to include at most two photons and no positrons in the Fock basis, and the wave functions of the dressed state are used to compute the electrons's anomalous magnetic moment. A choice of regularization that preserves the chiral symmetry of the massless limit is critical for the success of the calculation.

  9. Injury Risk for Children in Rear Impacts: Role of the Front Seat Occupant

    PubMed Central

    Jermakian, Jessica Steps; Arbogast, Kristy B.; Durbin, Dennis R.; Kallan, Michael J.

    2008-01-01

    As more children move to the rear rows, there is a need to understand the rear impact environment for children to guide future regulatory and due care activities in this impact direction. A probability sample of 1,035 restrained child occupants, aged 0–12 years, seated in a second row outboard position in rear impact tow-away crashes, weighted to represent 10,079 children, was collected from an on-going child specific crash surveillance system between 3/1/00 and 12/31/06. These data were analyzed to quantify the overall injury risk and the influence of both front seat occupant presence and reported front seat back deformation on injury risk. Overall risk of AIS 2+ injury for restrained child occupants seated in the rear row outboard position in rear impact crashes was 2.3%. Occupants were seated in front of these children in 71% of cases and deformation of the front seat back into the child’s space was reported in 8% of cases. For those children with seatback deformation occurring directly in front of them, there was a doubling of the injury risk (4.8% vs. 2.1%, adjusted OR=2.4, 95% CI=1.2–4.8). This paper provides the first population-based estimates of the injury risk of rear row-seated children in rear impact crash events and points to the importance of understanding the role of front seat back design on rear impact injury risk for both the front seat and rear seat occupants. PMID:19026228

  10. Injury risk for children in rear impacts: role of the front seat occupant.

    PubMed

    Jermakian, Jessica Steps; Arbogast, Kristy B; Durbin, Dennis R; Kallan, Michael J

    2008-10-01

    As more children move to the rear rows, there is a need to understand the rear impact environment for children to guide future regulatory and due care activities in this impact direction. A probability sample of 1,035 restrained child occupants, aged 0-12 years, seated in a second row outboard position in rear impact tow-away crashes, weighted to represent 10,079 children, was collected from an on-going child specific crash surveillance system between 3/1/00 and 12/31/06. These data were analyzed to quantify the overall injury risk and the influence of both front seat occupant presence and reported front seat back deformation on injury risk. Overall risk of AIS 2+ injury for restrained child occupants seated in the rear row outboard position in rear impact crashes was 2.3%. Occupants were seated in front of these children in 71% of cases and deformation of the front seat back into the child's space was reported in 8% of cases. For those children with seatback deformation occurring directly in front of them, there was a doubling of the injury risk (4.8% vs. 2.1%, adjusted OR=2.4, 95% CI=1.2-4.8). This paper provides the first population-based estimates of the injury risk of rear row-seated children in rear impact crash events and points to the importance of understanding the role of front seat back design on rear impact injury risk for both the front seat and rear seat occupants. PMID:19026228

  11. A compaction front in North Sea chalk

    NASA Astrophysics Data System (ADS)

    Japsen, P.; Dysthe, D. K.; Hartz, E. H.; Jamtveit, B.

    2012-04-01

    North Sea chalk from 18 wells shows a pronounced porosity drop, from ˜20% to less than 10% over a compaction front of less than 300 m. The position of the compaction frontis independent of stratigraphic position, temperature, and actual depth, but closely tied to an effective stress of ˜17 MPa. These observations require a strongly nonlinear rheology with a marked increase in compaction rate at a specific effective stress. Grain-scale observations demonstrate that the compaction front coincides with marked grain coarsening and recrystallization of fossils and fossil fragments. We propose that this nonlinear rheology is caused by stress-driven failure of the larger pores and the associated generation of reactive surface area by subcritical crack propagation away from these pores. Before the onset of this instability, compaction by pressure solution is slowed down by the inhibitory effect of organic compounds associated with the fossils. Although the compaction mechanism is mainly by pressure solution, the rheological response to burial may still be dominantly plastic and controlled by the (fracturing controlled) rate of exposure of reactive surface area. The nonlinear compaction of chalk has significant implications for the evolution of petroleum systems in the central North Sea, both with respect to sea-floor subsidence above hydrocarbon-producing chalk reservoirs and for the formation of low-porosity pressure seals within the chalk.

  12. Universal Millimeter-Wave Radar Front End

    NASA Technical Reports Server (NTRS)

    Perez, Raul M.

    2010-01-01

    A quasi-optical front end allows any arbitrary polarization to be transmitted by controlling the timing, amplitude, and phase of the two input ports. The front end consists of two independent channels horizontal and vertical. Each channel has two ports transmit and receive. The transmit signal is linearly polarized so as to pass through a periodic wire grid. It is then propagated through a ferrite Faraday rotator, which rotates the polarization state 45deg. The received signal is propagated through the Faraday rotator in the opposite direction, undergoing a further 45 of polarization rotation due to the non-reciprocal action of the ferrite under magnetic bias. The received signal is now polarized at 90deg relative to the transmit signal. This signal is now reflected from the wire grid and propagated to the receive port. The horizontal and vertical channels are propagated through, or reflected from, another wire grid. This design is an improvement on the state of the art in that any transmit signal polarization can be chosen in whatever sequence desired. Prior systems require switching of the transmit signal from the amplifier, either mechanically or by using high-power millimeter-wave switches. This design can have higher reliability, lower mass, and more flexibility than mechanical switching systems, as well as higher reliability and lower losses than systems using high-power millimeter-wave switches.

  13. AFEII Analog Front End Board Design Specifications

    SciTech Connect

    Rubinov, Paul; /Fermilab

    2005-04-01

    This document describes the design of the 2nd iteration of the Analog Front End Board (AFEII), which has the function of receiving charge signals from the Central Fiber Tracker (CFT) and providing digital hit pattern and charge amplitude information from those charge signals. This second iteration is intended to address limitations of the current AFE (referred to as AFEI in this document). These limitations become increasingly deleterious to the performance of the Central Fiber Tracker as instantaneous luminosity increases. The limitations are inherent in the design of the key front end chips on the AFEI board (the SVXIIe and the SIFT) and the architecture of the board itself. The key limitations of the AFEI are: (1) SVX saturation; (2) Discriminator to analog readout cross talk; (3) Tick to tick pedestal variation; and (4) Channel to channel pedestal variation. The new version of the AFE board, AFEII, addresses these limitations by use of a new chip, the TriP-t and by architectural changes, while retaining the well understood and desirable features of the AFEI board.

  14. Identifying Lagrangian fronts with favourable fishery conditions

    NASA Astrophysics Data System (ADS)

    Prants, S. V.; Budyansky, M. V.; Uleysky, M. Yu.

    2014-08-01

    Lagrangian fronts (LFs) in the ocean are defined as boundaries between surface waters with strongly different Lagrangian properties. They can be accurately detected in a given velocity field by computing synoptic maps for displacements of synthetic tracers and other Lagrangian indicators. We use Pacific saury catch and location data for a number of commercial fishery seasons in the region of the northwest Pacific with one of the richest fishery in the world. It is shown statistically that the saury fishing grounds with maximal catches are not randomly distributed over the region but located mainly along the sharp LFs where productive cold waters of the Oyashio Current, warmer waters of the southern branch of the Soya Current, and waters of warm-core Kuroshio rings converge. Computation of those fronts in altimetric geostrophic velocity fields both in the years with the First and Second Oyashio Intrusions shows that in spite of different oceanographic conditions LF locations may serve as good indicators of potential fishing grounds. Possible biophysical reasons for saury aggregation near sharp LFs are discussed. We propose a mechanism for effective export of nutrient rich waters based on stretching of material lines in the vicinity of hyperbolic objects in the ocean. The developed method, based on identifying LFs in any velocity fields, is quite general and may be applied to find potential fishing grounds for the other pelagic fish.

  15. Biomechanics of front and back squat exercises

    NASA Astrophysics Data System (ADS)

    Braidot, A. A.; Brusa, M. H.; Lestussi, F. E.; Parera, G. P.

    2007-11-01

    Squat constitutes one of the most popular exercises to strengthen the muscles of the lower limbs. It is considered one of the most widely spread exercises for muscle sport training and is part of the competition movements comprised within olympic weight-lifting. In physical rehabilitation, squats are used for muscular recovery after different injuries of the lower limbs, especially the knee. In previous anterior cruciate ligament injuries, the mini-squats are generally used, in a knee flexion motion range from 0° to 50° because in this range the shear forces, the tibiofemoral and patellofemoral compression forces decrease related to greater flexion angles. The aim of this work is to make a comparative bidimensional study of the kinematic and dynamic variables of the excecution of the parallel squat exercise with the front and back bar. It is observed in the knee a better development of energy with the front bar, allowing a better muscular exercise with the same load. The mean power absorbed by the hip with the back bar is considerably greater, associated to the speed of the gesture.

  16. Shearlet-based detection of flame fronts

    NASA Astrophysics Data System (ADS)

    Reisenhofer, Rafael; Kiefer, Johannes; King, Emily J.

    2016-03-01

    Identifying and characterizing flame fronts is the most common task in the computer-assisted analysis of data obtained from imaging techniques such as planar laser-induced fluorescence (PLIF), laser Rayleigh scattering (LRS), or particle imaging velocimetry (PIV). We present Complex Shearlet-Based Ridge and Edge Measure (CoShREM), a novel edge and ridge (line) detection algorithm based on complex-valued wavelet-like analyzing functions—so-called complex shearlets—displaying several traits useful for the extraction of flame fronts. In addition to providing a unified approach to the detection of edges and ridges, our method inherently yields estimates of local tangent orientations and local curvatures. To examine the applicability for high-frequency recordings of combustion processes, the algorithm is applied to mock images distorted with varying degrees of noise and real-world PLIF images of both OH and CH radicals. Furthermore, we compare the performance of the newly proposed complex shearlet-based measure to well-established edge and ridge detection techniques such as the Canny edge detector, another shearlet-based edge detector, and the phase congruency measure.

  17. Spatially hybrid computations for streamer discharges with generic features of pulled fronts: I. Planar fronts

    SciTech Connect

    Li Chao Ebert, Ute Hundsdorfer, Willem

    2010-01-01

    Streamers are the first stage of sparks and lightning; they grow due to a strongly enhanced electric field at their tips; this field is created by a thin curved space charge layer. These multiple scales are already challenging when the electrons are approximated by densities. However, electron density fluctuations in the leading edge of the front and non-thermal stretched tails of the electron energy distribution (as a cause of X-ray emissions) require a particle model to follow the electron motion. But present computers cannot deal with all electrons in a fully developed streamer. Therefore, super-particle have to be introduced, which leads to wrong statistics and numerical artifacts. The method of choice is a hybrid computation in space where individual electrons are followed in the region of high electric field and low density while the bulk of the electrons is approximated by densities (or fluids). We here develop the hybrid coupling for planar fronts. First, to obtain a consistent flux at the interface between particle and fluid model in the hybrid computation, the widely used classical fluid model is replaced by an extended fluid model. Then the coupling algorithm and the numerical implementation of the spatially hybrid model are presented in detail, in particular, the position of the model interface and the construction of the buffer region. The method carries generic features of pulled fronts that can be applied to similar problems like large deviations in the leading edge of population fronts, etc.

  18. Role of molecular dynamics on descriptions of shock-front processes

    SciTech Connect

    Karo, A.M.

    1981-07-22

    By means of a computational approach based on classical molecular dynamics, we can begin to form a realistic picture of shock-induced processes occurring at the shock front and resulting from the detailed, violent motion associated with shock motion on an atomic scale. Prototype studies of phase transitions will be discussed. We will also examine the interaction of the shock front with defects, surfaces, voids, and inclusions, and across grain boundaries. We will focus on the critical question of how mechanical energy imparted to a condensed material by shock loading is converted to the activation energy required to overcome some initial energy barrier in an initiation process.

  19. Theoretical Analysis of Interferometer Wave Front Tilt and Fringe Radiant Flux on a Rectangular Photodetector

    PubMed Central

    Smith, Robert; Fuss, Franz Konstantin

    2013-01-01

    This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where these opto-electronic devices are employed for partial fringe counting. Formulas are derived for radiant flux across the detector for variable location within the fringe pattern and with varying wave front angle. The results indicate that the flux is a damped sine function of the wave front angle, with a decay constant of the ratio of wavelength to detector width. The modulation amplitude of the dynamic fringe pattern reduces to zero at wave front angles that are an integer multiple of this ratio and the results show that the polarity of the radiant flux changes exclusively at these multiples. Varying tilt angle causes radiant flux oscillations under an envelope curve, the frequency of which is dependent on the location of the detector with the fringe pattern. It is also shown that a fringe count of zero can be obtained for specific photodetector locations and wave front angles where the combined effect of fringe contraction and fringe tilt can have equal and opposite effects. Fringe tilt as a result of a wave front angle of 0.05° can introduce a phase measurement difference of 16° between a photodetector/pixel located 20 mm and one located 100 mm from the optical origin. PMID:24018954

  20. Observations of nonlinear internal waves at a persistent coastal upwelling front

    NASA Astrophysics Data System (ADS)

    Walter, Ryan K.; Stastna, Marek; Woodson, C. Brock; Monismith, Stephen G.

    2016-04-01

    We collected high-resolution observations of nonlinear internal waves (NLIWs) at a persistent upwelling front in the shallow coastal environment (~20 m) of northern Monterey Bay, CA. The coastal upwelling front forms between recently upwelled waters and warmer stratified waters that are trapped in the bay (upwelling shadow). The front propagates up and down the coast in the along-shore direction as a buoyant plume front due to modulation by strong diurnal wind forcing. The evolution of the coastal upwelling front, and the subsequent modulation of background environmental conditions, is examined using both individual events and composite day averages. We demonstrate that regional-scale upwelling and local diurnal wind forcing are key components controlling local stratification and the formation of internal wave guides that allow for high-frequency internal wave activity. Finally, we discuss the ability of theoretical models to describe particularly large-amplitude internal waves that exist in the presence of a strong background shear and test a fully nonlinear model (i.e., the Dubreil-Jacotin-Long equation).

  1. Theoretical analysis of interferometer wave front tilt and fringe radiant flux on a rectangular photodetector.

    PubMed

    Smith, Robert; Fuss, Franz Konstantin

    2013-09-06

    This paper is a theoretical analysis of mirror tilt in a Michelson interferometer and its effect on the radiant flux over the active area of a rectangular photodetector or image sensor pixel. It is relevant to sensor applications using homodyne interferometry where these opto-electronic devices are employed for partial fringe counting. Formulas are derived for radiant flux across the detector for variable location within the fringe pattern and with varying wave front angle. The results indicate that the flux is a damped sine function of the wave front angle, with a decay constant of the ratio of wavelength to detector width. The modulation amplitude of the dynamic fringe pattern reduces to zero at wave front angles that are an integer multiple of this ratio and the results show that the polarity of the radiant flux changes exclusively at these multiples. Varying tilt angle causes radiant flux oscillations under an envelope curve, the frequency of which is dependent on the location of the detector with the fringe pattern. It is also shown that a fringe count of zero can be obtained for specific photodetector locations and wave front angles where the combined effect of fringe contraction and fringe tilt can have equal and opposite effects. Fringe tilt as a result of a wave front angle of 0.05° can introduce a phase measurement difference of 16° between a photodetector/pixel located 20 mm and one located 100 mm from the optical origin.

  2. Increased zooplankton PAH concentrations across hydrographic fronts in the East China Sea.

    PubMed

    Hung, Chin-Chang; Ko, Fung-Chi; Gong, Gwo-Ching; Chen, Kuo-Shu; Wu, Jian-Ming; Chiang, Hsin-Lun; Peng, Sen-Chueh; Santschi, Peter H

    2014-06-15

    The Changjiang has transported large quantities of polycyclic aromatic hydrocarbons (PAHs) to the East China Sea (ECS), but information of these pollutants in zooplankton is limited. To understand PAHs pollution in zooplankton in the ECS, total concentrations of PAHs in zooplankton from surface waters were measured. Values of PAHs ranged from 2 to 3500 ng m(-3) in the ECS, with highest PAHs levels located at the salinity front between the Changjiang Diluted Water (CDW) and the mid-shelf waters. In contrast, concentrations of zooplankton PAHs in the mid-shelf and outer-shelf waters were significantly lower (2-23 ng m(-3)) than those in the CDW. These results demonstrate that PAHs are conspicuously accumulated in zooplankton at the salinity front between the CDW and the mid-shelf waters. These higher levels of PAHs in zooplankton at the salinity front may be further biomagnified in marine organisms of higher trophic levels through their feeding activities. PMID:24775063

  3. A Theoretical Study of Propagation and Extinction of Nonsteady Spherical Flame Fronts

    NASA Technical Reports Server (NTRS)

    Ronney, P. D.; Sivashinsky, G. I.

    1989-01-01

    Freely propagating expanding spherical flame fronts are studied analytically using the method of activation energy asymptotics. Effects of Lewis number (Le), curvature, heat loss, and thermal expansion on propagation rates and extinction conditions are examined. The behavior of spherical flame fronts is found to be determined primarily by the values of Le and a heat-loss parameter. Results are compared to recent experimental observations of spherical flame fronts in mixtures near the flammability limits; for Le less than 1, it is found that many of the features of these experimental results are described by the analysis presented here. For Le greater than 1, however, unrealistic dynamic behavior is predicted due to the nature of diffusive-thermal instabilities under these conditions.

  4. Focusing solenoids for the HINS Linac front end

    SciTech Connect

    Terechkine, I.; Appollinari, G.; Di-Marco, J.; Huang, Y.; Orris, D.; Page, T.; Rabehl, R.; Tartaglia, M.; Tompkins, J.; /Fermilab

    2008-10-01

    The low energy part of a linac for the High Intensity Neutrino Source (HINS) project at Fermilab will use superconducting solenoids as beam focusing elements (lenses). While the lenses for the conventional DTL-type accelerating section of the front end require individual cryostats, in the superconducting accelerating sections solenoids will be installed inside RF cryomodules. Some of the lenses in the conventional and in the superconducting sections are equipped with horizontal and vertical steering dipoles. Lenses for the DTL section are in the stage of production with certification activities ongoing at Fermilab. For the superconducting sections of the linac, a prototype lens has been built and tested. Each lens will be installed in the transport channel of the accelerator so that its magnetic axis is on the beamline. Corresponding technique has been developed at Fermilab and is used during the certification process. This report summarizes design features, parameters, and test results of the focusing lenses.

  5. Perspectives from the front lines of tobacco control.

    PubMed

    Burrus, Barri; Northridge, Mary E; Hund, Lisa; Green, Molly; Braithwaite, Kisha; Sabol, Barbara; Healton, Cheryl; Treadwell, Henrie M; Wenter, Dana; Dolina, Suzanne; Vallone, Donna; Duke, Jennifer; Batson, Jane; Blackwood, Julie; Bristow, Zuzanne; Demps, Wambui; Ferguson, Cheryl; Laton, Cindy; Mack, Melany; Perez, Leda; Pizarro, Marta; Ragonesi, Cheryl; Ruland, Jodie; Smith, Lucille; Walters, Gayle; North, Sharon R

    2006-02-01

    This research is designed to share valuable experiences and transferable principles from program staff of the Legacy/Community Voices initiative who have been involved in planning, implementing, evaluating, and sustaining tobacco control activities in underserved communities. Interviews were conducted with 13 front line staff from 9 sites: Alameda County, California; Detroit, Michigan; El Paso, Texas; Ingham County, Michigan; Miami, Florida; New Mexico; North Carolina; Northern Manhattan; and West Virginia. A model emerged from these interviews that places the life cycle of a program in a central position, with many of the identified themes (working with local champions, obtaining support from multiple partners, increasing organizational capacity) repeated throughout, albeit in different forms at different stages. Reflecting upon wisdom gained and identifying best processes for such work may help ensure that tobacco control programs are developed that are culturally safe and effective in meeting the needs of diverse communities throughout the United States.

  6. STS-110 crew in front of countdown clock after TCDT

    NASA Technical Reports Server (NTRS)

    2002-01-01

    KENNEDY SPACE CENTER, FLA. -- Before departing for Houston, the STS-110 crew poses in front of the countdown clock that faces the grandstand at the Press Site. Standing left to right are Commander Michael Bloomfield, Mission Specialists Rex Walheim and Jerry Ross, Pilot Stephen Frick, and Mission Specialists Ellen Ochoa, Lee Morin and Steven Smith. The crew was at KSC for Terminal Countdown Demonstration Test activities that included payload familiarization and a simulated launch countdown. Scheduled for launch April 4, the 11-day STS-110 mission will feature Space Shuttle Atlantis docking with the International Space Station (ISS) and delivering the S0 truss, the centerpiece-segment of the primary truss structure that will eventually extend over 300 feet.

  7. CME front and severe space weather

    NASA Astrophysics Data System (ADS)

    Balan, N.; Skoug, R.; Tulasi Ram, S.; Rajesh, P. K.; Shiokawa, K.; Otsuka, Y.; Batista, I. S.; Ebihara, Y.; Nakamura, T.

    2014-12-01

    Thanks to the work of a number of scientists who made it known that severe space weather can cause extensive social and economic disruptions in the modern high-technology society. It is therefore important to understand what determines the severity of space weather and whether it can be predicted. We present results obtained from the analysis of coronal mass ejections (CMEs), solar energetic particle (SEP) events, interplanetary magnetic field (IMF), CME-magnetosphere coupling, and geomagnetic storms associated with the major space weather events since 1998 by combining data from the ACE and GOES satellites with geomagnetic parameters and the Carrington event of 1859, the Quebec event of 1989, and an event in 1958. The results seem to indicate that (1) it is the impulsive energy mainly due to the impulsive velocity and orientation of IMF Bz at the leading edge of the CMEs (or CME front) that determine the severity of space weather. (2) CMEs having high impulsive velocity (sudden nonfluctuating increase by over 275 km s-1 over the background) caused severe space weather (SvSW) in the heliosphere (failure of the solar wind ion mode of Solar Wind Electron Proton Alpha Monitor in ACE) probably by suddenly accelerating the high-energy particles in the SEPs ahead directly or through the shocks. (3) The impact of such CMEs which also show the IMF Bz southward from the leading edge caused SvSW at the Earth including extreme geomagnetic storms of mean DstMP < -250 nT during main phases, and the known electric power outages happened during some of these SvSW events. (4) The higher the impulsive velocity, the more severe the space weather, like faster weather fronts and tsunami fronts causing more severe damage through impulsive action. (5) The CMEs having IMF Bz northward at the leading edge do not seem to cause SvSW on Earth, although, later when the IMF Bz turns southward, they can lead to super geomagnetic storms of intensity (Dstmin) less than even -400 nT.

  8. Enhanced reactivity of mechanically-activated nano-scale gasless reactive materials consolidated via the cold-spray technique

    NASA Astrophysics Data System (ADS)

    Bacciochini, Antoine; Radulescu, Matei; Meydanoglu, Onur; Charron-Tousignant, Yannick; van Dyke, Jason; Jodoin, Bertrand; Nganbe, Michel; Yandouzi, Mohamed; Lee, Julian J.

    2011-06-01

    It has been speculated that gasless reactive systems can sustain supersonic detonations waves, provided the local decomposition rate is sufficiently fast and the initial density is sufficiently close to the theoretical maximal density. The present study presents a novel method to prepare nano-scale energetic materials with high reactivity, vanishing porosity, structural integrity and arbitrary shape. The experiments have focused on the Ni-Al system. To increase the reactivity, an initial mechanical activation was achieved by the technique of ball milling. The consolidation of the materials used the supersonic cold gas spray technique, where the particles are accelerated to high speeds and consolidated via plastic deformation upon impact, forming activated nano-composites in arbitrary shapes with close to zero porosity. This technique permits to retain the micro-structures in the powders and prevents any reactions during the consolidation phase. Deflagration tests of the obtained samples showed an increase in the deflagration rate by up to two orders of magnitude.

  9. Light-Front Holography, Light-Front Wavefunctions, and Novel QCD Phenomena

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    Light-Front Holography is one of the most remarkable features of the AdS/CFT correspondence. In spite of its present limitations it provides important physical insights into the nonperturbative regime of QCD and its transition to the perturbative domain. This novel framework allows hadronic amplitudes in a higher dimensional anti-de Sitter (AdS) space to be mapped to frame-independent light-front wavefunctions of hadrons in physical space-time. The model leads to an effective confining light-front QCD Hamiltonian and a single-variable light-front Schroedinger equation which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. The coordinate z in AdS space is uniquely identified with a Lorentz-invariant coordinate {zeta} which measures the separation of the constituents within a hadron at equal light-front time and determines the off-shell dynamics of the bound-state wavefunctions, and thus the fall-off as a function of the invariant mass of the constituents. The soft-wall holographic model modified by a positive-sign dilaton metric, leads to a remarkable one-parameter description of nonperturbative hadron dynamics - a semi-classical frame-independent first approximation to the spectra and light-front wavefunctions of meson and baryons. The model predicts a Regge spectrum of linear trajectories with the same slope in the leading orbital angular momentum L of hadrons and the radial quantum number n. The hadron eigensolutions projected on the free Fock basis provides the complete set of valence and non-valence light-front Fock state wavefunctions {Psi}{sub n/H} (x{sub i}, k{sub {perpendicular}i}, {lambda}{sub i}) which describe the hadron's momentum and spin distributions needed to compute the direct measures of hadron structure at the quark and gluon level, such as elastic and transition form factors, distribution amplitudes, structure functions, generalized parton distributions and transverse

  10. Front lighted optical tooling method and apparatus

    DOEpatents

    Stone, W.J.

    1983-06-30

    An optical tooling method and apparatus uses a front lighted shadowgraphic technique to enhance visual contrast of reflected light. The apparatus includes an optical assembly including a fiducial mark, such as cross hairs, reflecting polarized light with a first polarization, a polarizing element backing the fiducial mark and a reflective surface backing the polarizing element for reflecting polarized light bypassing the fiducial mark and traveling through the polarizing element. The light reflected by the reflecting surface is directed through a second pass of the polarizing element toward the frontal direction with a polarization differing from the polarization of the light reflected by the fiducial mark. When used as a tooling target, the optical assembly may be mounted directly to a reference surface or may be secured in a mounting, such as a magnetic mounting. The optical assembly may also be mounted in a plane defining structure and used as a spherometer in conjunction with an optical depth measuring instrument.

  11. Flame front configuration of turbulent premixed flames

    SciTech Connect

    Furukawa, Junichi; Maruta, Kaoru; Hirano, Toshisuke

    1998-02-01

    The present study is performed to explore dependence of the wrinkle scale of propane-air turbulent premixed flames on the characteristics of turbulence in the nonreacting flow, burner size, and mixture ratio. The wrinkle scales are examined and expressed in the frequency distribution of the radii of flame front curvatures. The average wrinkle scale depends not only on the characteristics of turbulence in the nonreacting flow but also on burner diameter and mixture ratio. The average wrinkle scale of a lean propane-air flame is larger than those of the near stoichiometric and rich flames. The smallest wrinkle scale of turbulent premixed flame is in the range of 0.75--1.0 mm, which is much larger than the Kolmogorov scale of turbulence in the nonreacting flow.

  12. Salinity fronts in the tropical Pacific Ocean

    PubMed Central

    Kao, Hsun-Ying; Lagerloef, Gary S E

    2015-01-01

    This study delineates the salinity fronts (SF) across the tropical Pacific, and describes their variability and regional dynamical significance using Aquarius satellite observations. From the monthly maps of the SF, we find that the SF in the tropical Pacific are (1) usually observed around the boundaries of the fresh pool under the intertropical convergence zone (ITCZ), (2) stronger in boreal autumn than in other seasons, and (3) usually stronger in the eastern Pacific than in the western Pacific. The relationship between the SF and the precipitation and the surface velocity are also discussed. We further present detailed analysis of the SF in three key tropical Pacific regions. Extending zonally around the ITCZ, where the temperature is nearly homogeneous, we find the strong SF of 1.2 psu from 7° to 11°N to be the main contributor of the horizontal density difference of 0.8 kg/m3. In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection. In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature. The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics. PMID:26213676

  13. Opportunity Rolls Free Again (Left Front Wheel)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This animated piece illustrates the recent escape of NASA's Mars Exploration Rover Opportunity from dangerous, loose material on the vast plains leading to the rover's next long-term target, 'Victoria Crater.'

    A series of images of the rover's left front wheel, taken by the front hazard-avoidance camera, make up this brief movie. It chronicles the challenge Opportunity faced to free itself from a ripple dubbed 'Jammerbugt.' The rover's wheels became partially embedded in the ripple at the end of a drive on Opportunity's 833rd Martian day, or sol (May 28, 2006). The images in this clip were taken on sols 836 through 841 (May 31 through June 5, 2006).

    Scientists and engineers who had been elated at the meters of progress the rover had been making in earlier drives were happy for even centimeters of advance per sol as they maneuvered their explorer through the slippery material of Jammerbugt. The wheels reached solid footing on a rock outcrop on the final sol of this sequence.

    The science and engineering teams appropriately chose the ripple's informal from name the name of a bay on the north coast of Denmark. Jammerbugt, or Jammerbugten, loosely translated, means Bay of Lamentation or Bay of Wailing. The shipping route from the North Sea to the Baltic passes Jammerbugt on its way around the northern tip of Jutland. This has always been an important trade route and many ships still pass by the bay. The prevailing wind directions are typically northwest to southwest with the strongest winds and storms tending to blow from the northwest. A northwesterly wind will blow straight into the Jammerbugt, towards shore. Therefore, in the age of sail, many ships sank there during storms. The shore is sandy, but can have strong waves, so running aground was very dangerous even though there are no rocks.

    Fortunately, Opportunity weathered its 'Jammerbugt' and is again on its way toward Victoria Crater.

  14. Opportunity Rolls Free Again (Right Front Wheel)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This animated piece illustrates the recent escape of NASA's Mars Exploration Rover Opportunity from dangerous, loose material on the vast plains leading to the rover's next long-term target, 'Victoria Crater.'

    A series of images of the rover's right front wheel, taken by the front hazard-avoidance camera, make up this brief movie. It chronicles the challenge Opportunity faced to free itself from a ripple dubbed 'Jammerbugt.' The rover's wheels became partially embedded in the ripple at the end of a drive on Opportunity's 833rd Martian day, or sol (May 28, 2006). The images in this clip were taken on sols 836 through 841 (May 31 through June 5, 2006).

    Scientists and engineers who had been elated at the meters of progress the rover had been making in earlier drives were happy for even centimeters of advance per sol as they maneuvered their explorer through the slippery material of Jammerbugt. The wheels reached solid footing on a rock outcrop on the final sol of this sequence.

    The science and engineering teams appropriately chose the ripple's informal from name the name of a bay on the north coast of Denmark. Jammerbugt, or Jammerbugten, loosely translated, means Bay of Lamentation or Bay of Wailing. The shipping route from the North Sea to the Baltic passes Jammerbugt on its way around the northern tip of Jutland. This has always been an important trade route and many ships still pass by the bay. The prevailing wind directions are typically northwest to southwest with the strongest winds and storms tending to blow from the northwest. A northwesterly wind will blow straight into the Jammerbugt, towards shore. Therefore, in the age of sail, many ships sank there during storms. The shore is sandy, but can have strong waves, so running aground was very dangerous even though there are no rocks.

    Fortunately, Opportunity weathered its 'Jammerbugt' and is again on its way toward Victoria Crater.

  15. Action Minimising Fronts in General FPU-type Chains

    NASA Astrophysics Data System (ADS)

    Herrmann, Michael

    2011-02-01

    We study atomic chains with nonlinear nearest neighbour interactions and prove the existence of fronts (heteroclinic travelling waves with constant asymptotic states). Generalising recent results of Herrmann and Rademacher we allow for non-convex interaction potentials and find fronts with non-monotone profile. These fronts minimise an action integral and can only exists if the asymptotic states fulfil the macroscopic constraints and if the interaction potential satisfies a geometric graph condition. Finally, we illustrate our findings by numerical simulations.

  16. 2. EXTERIOR FRONT (SOUTHEAST) SIDE OF BUILDING 117 SHOWING MAIN ...

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

    2. EXTERIOR FRONT (SOUTHEAST) SIDE OF BUILDING 117 SHOWING MAIN RESIDENTIAL STREET IN LOWER FOREGROUND, CEMENT-LAID ROCK RETAINING WALL IN FRONT OF HOUSE, AND CONCRETE STEPS AND WALKWAY TO FRONT PORCH AND DOOR. NOTE SLIDING GLASS DOOR REPLACEMENT FOR ORIGINAL DOOR WHICH HAS SUBSEQUENTLY BEEN REMODELED BACK TO A SINGLE ENTRY DOOR. VIEW TO NORTHWEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA

  17. Dr. von Braun In Front of a Display of Missiles

    NASA Technical Reports Server (NTRS)

    1960-01-01

    In this photo, Director of the US Army Ballistic Missile Agency (ABMA) Development Operations Division, Dr. Wernher von Braun, is standing before a display of Army missiles celebrating ABMA's Fourth Open House. The missiles in the background include (left to right) a satellite on a Juno II shroud with a Nike Ajax pointing left in front of a Jupiter missile. The Lacrosse is in front of the Juno II. The Nike Hercules points skyward in front of the Juno II and the Redstone.

  18. 5. SUPERINTENDENT'S COTTAGE WEST WALL AND NORTH FRONT SHOWING CONCRETE ...

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

    5. SUPERINTENDENT'S COTTAGE WEST WALL AND NORTH FRONT SHOWING CONCRETE BLOCK UTILITY ROOM ADDITION. - Tucson Plant Materials Center, Superintendent's Cottage, 3241 North Romero Road, Tucson, Pima County, AZ

  19. EAST (FRONT) AND NORTH SIDE OF DOUBLE FURNACE AND NORTH ...

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

    EAST (FRONT) AND NORTH SIDE OF DOUBLE FURNACE AND NORTH SIDE OF SINGLE FURNACE, SOUTHWEST. - Tannehill Furnace, 12632 Confederate Parkway, Tannehill Historical State Park, Bucksville, Tuscaloosa County, AL

  20. View of north front and west sides of hall, facing ...

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

    View of north front and west sides of hall, facing south - International Longshoremen's & Warehousemen's Union Hall, Naval Civil Engineering Laboratory, Port Hueneme Road, Port Hueneme, Ventura County, CA

  1. 1. FRONT FACADE (Photograph of photograph in possession of Turner ...

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

    1. FRONT FACADE (Photograph of photograph in possession of Turner Associates and Nicholas Satterlee Associates, Washington, DC, 1973.) - 1 & 2 Logan Circle (House), Washington, District of Columbia, DC

  2. Stability of a Shock-Decelerated Ablation Front

    SciTech Connect

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Schmitt, A. J.; Obenschain, S. P.; Metzler, N.; Zalesak, S. T.; Gardner, J. H.; Oh, J.; Harding, E. C.

    2009-08-21

    Experimental study of a shock-decelerated ablation front is reported. A planar solid plastic target is accelerated by a laser across a vacuum gap and collides with a lower-density plastic foam layer. While the target is accelerated, a fast Rayleigh-Taylor (RT) growth of the seeded single-mode perturbation at the ablation front is observed. After the collision, the velocity of the ablation front is seen to remain constant. The reshock quenches the RT growth but does not trigger any Richtmyer-Meshkov growth at the ablation front, which is shown to be consistent with both theory and simulations.

  3. SOUTHEAST FRONT ELEVATION, LOOKING NORTHWEST, SHOWING PHILADELPHIA THANKSGIVING PARADE ...

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

    SOUTHEAST FRONT ELEVATION, LOOKING NORTHWEST, SHOWING PHILADELPHIA THANKSGIVING PARADE - Free Library of Philadelphia, Thomas Holme Branch, 7810 Frankford Avenue, Philadelphia, Philadelphia County, PA

  4. TENANT HOUSE, WINDOW DETAIL, NORTH FRONT, LOOKING SOUTH Irvine ...

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

    TENANT HOUSE, WINDOW DETAIL, NORTH FRONT, LOOKING SOUTH - Irvine Ranch Agricultural Headquarters, Carillo Tenant House, Southwest of Intersection of San Diego & Santa Ana Freeways, Irvine, Orange County, CA

  5. DETAIL VIEW OF SOUTH FRONT DOORS, FACING NORTHEAST. Douglas ...

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

    DETAIL VIEW OF SOUTH FRONT DOORS, FACING NORTHEAST. - Douglas Aircraft Company Long Beach Plant, Aircraft Wing & Fuselage Assembly Building, 3855 Lakewood Boulevard, Long Beach, Los Angeles County, CA

  6. 89. PHOTOCOPY OF DRAWING LOUISVILLE WATER COMPANY, GENERAL, FRONT ELEVATION, ...

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

    89. PHOTOCOPY OF DRAWING LOUISVILLE WATER COMPANY, GENERAL, FRONT ELEVATION, ALLIS-CHALMERS - Kennecott Copper Corporation, On Copper River & Northwestern Railroad, Kennicott, Valdez-Cordova Census Area, AK

  7. 90. PHOTOCOPY OF DRAWING LOUISVILLE WATER COMPANY, GENERAL, FRONT ELEVATION, ...

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

    90. PHOTOCOPY OF DRAWING LOUISVILLE WATER COMPANY, GENERAL, FRONT ELEVATION, ALLIS-CHALMERS - Kennecott Copper Corporation, On Copper River & Northwestern Railroad, Kennicott, Valdez-Cordova Census Area, AK

  8. Interior, living room toward front porch of east unit ...

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

    Interior, living room toward front porch of east unit - Fitzsimons General Hospital, Noncomissioned Officers' Quarters, West Loosley Avenue & North Hickey Street, Southeast Corner, Aurora, Adams County, CO

  9. Wave-front analysis of personal eye protection.

    PubMed

    Eppig, Timo; Zoric, Katja; Speck, Alexis; Zelzer, Benedikt; Götzelmann, Jens; Nagengast, Dieter; Langenbucher, Achim

    2012-07-30

    Shack-Hartmann wave-front sensing has been successfully applied to many fields of optical testing including the human eye itself. We propose wave-front measurement for testing protective eye wear for production control and investigation of aberrations. Refractive power data is derived from the wave-front data and compared to a subjective measurement technique based on a focimeter. Additional image quality classification was performed with a multivariate model using objective parameters to resample a subjectively determined visual quality. Wave-front measurement advances optical testing of protective eye wear and may be used for objective quality control.

  10. Front contact solar cell with formed electrically conducting layers on the front side and backside

    DOEpatents

    Cousins, Peter John

    2012-06-26

    A bipolar solar cell includes a backside junction formed by a silicon substrate and a first doped layer of a first dopant type on the backside of the solar cell. A second doped layer of a second dopant type makes an electrical connection to the substrate from the front side of the solar cell. A first metal contact of a first electrical polarity electrically connects to the first doped layer on the backside of the solar cell, and a second metal contact of a second electrical polarity electrically connects to the second doped layer on the front side of the solar cell. An external electrical circuit may be electrically connected to the first and second metal contacts to be powered by the solar cell.

  11. Exploring the Wichita Mountain front - With new parameters

    SciTech Connect

    Schneider, R.E. )

    1991-08-01

    Understanding the short south flank of the Anadarko basin has been limited by a lack of well control and extremely poor seismic data in this complex trend. This flank lies immediately south of the synclinal axis of the Anadarko basin and has been uplifted nearly 40,000 ft in a space of 5 to 10 mi. Variously called the Wichita Mountain front or the buried Wichita-Amarillo mountains, this trend separates-the deep Anadarko basin from the Hardeman or Palo Duro basin to the south. With tensional forces during the Acadian and Wichitan orogenies, then compressional movement in the Late Pennsylvanian (the Arbuckle orogeny), this 250-mi trend traverses more than half of southwestern Oklahoma. It extends from the Arbuckle Mountains westward into the Texas Panhandle and is noted for its early shallow oil and gas fields in its uppermost blocks. For the past 25 years deeper drilling, especially in Beckham County, Oklahoma, and Wheeler County, Texas, has found huge quantities of gas in the lower Paleozoic carbonates. These limestones and dolomites in the Hunton and Arbuckle are becoming attractive targets because of the recent activity at Cottonwood Creek, Susie Pi-Hoodle (Alden area), and the new Park Avenue well south of Cordell. In February 1991 an extensive 460-mi survey of 28 seismic lines was completed - shooting with the intent to image the intermediate fault blocks that bring those carbonates up from 40,000 ft of burial to the surface along the Wichita Mountain front. For the first time, detailed high-resolution data has been obtained in previously poor-to-questionable record areas. Including a series of dip lines from West Mayfield to Lawton that show the structural style and types of hydrocarbon traps that are attracting large exploration dollars, this talk till also discuss the new parameters needed to obtain high-quality data.

  12. Instability of an infiltration-driven dissolution-precipitation front with a nonmonotonic porosity profile

    NASA Astrophysics Data System (ADS)

    Kondratiuk, Paweł; Dutka, Filip; Szymczak, Piotr

    2016-04-01

    Infiltration of a rock by an external fluid very often drives it out of chemical equilibrium. As a result, alteration of the rock mineral composition occurs. It does not however proceed uniformly in the entire rock volume. Instead, one or more reaction fronts are formed, which are zones of increased chemical activity, separating the altered (product) rock from the yet unaltered (primary) one. The reaction fronts propagate with velocities which are usually much smaller than those of the infiltrating fluid. One of the simplest examples of such alteration is the dissolution of some of the minerals building the primary rock. For instance, calcium carbonate minerals in the rock matrix can be dissolved by infiltrating acidic fluids. In such a case the product rock has higher porosity and permeability than the primary one. Due to positive feedbacks between the reactant transport, fluid flow, and porosity generation, the reaction fronts in porosity-generating replacement systems are inherently unstable. An arbitrarily small protrusion of the front gets magnified and develops into a highly porous finger-like or funnel-like structure. This feature of dissolution fronts, dubbed the "reactive-infiltration instability" [1], is responsible for the formation of a number of geological patterns, such as solution pipes or various karst forms. It is also of practical importance, since spontaneous front breakup and development of localized highly porous flow paths (a.k.a. "wormholes") is favourable by petroleum engineers, who apply acidization to oil-bearing reservoirs in order to increase their permeability. However, more complex chemical reactions might occur during infiltration of a rock by a fluid. In principle, the products of dissolution might react with other species present either in the fluid or in the rock and reprecipitate [2]. The dissolution and precipitation fronts develop and and begin to propagate with equal velocities, forming a single dissolution-precipitation front

  13. The CF6 jet engine performance improvement: New front mount

    NASA Technical Reports Server (NTRS)

    Fasching, W. A.

    1979-01-01

    The New Front Mount was evaluated in component tests including stress, deflection/distortion and fatigue tests. The test results demonstrated a performance improvement of 0.1% in cruise sfc, 16% in compressor stall margin and 10% in compressor stator angle margin. The New Front Mount hardware successfully completed 35,000 simulated flight cycles endurance testing.

  14. 76 FR 63656 - Front Range Resource Advisory Council Meeting Cancellation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-13

    ... Bureau of Land Management Front Range Resource Advisory Council Meeting Cancellation AGENCY: Bureau of... (FACA), notice is hereby given that the Front Range Resource Advisory Council meeting scheduled for... scheduled for October 19, 2011, 9:15 a.m. to 4:30 p.m. FOR FURTHER INFORMATION CONTACT: Tina Brown,...

  15. Muon Front-End for the Neutrino Factory

    NASA Astrophysics Data System (ADS)

    Fernow, R. C.

    2006-05-01

    The front end at a neutrino factory includes all the systems necessary for capturing the pion beam produced at the target and for preparing the transverse and longitudinal phase space of the resulting muon beam for subsequent acceleration to high energies. We compare front end configurations for a number of neutrino factory designs.

  16. 8. EXTERIOR OF FRONT (SOUTH) SIDE OF BUILDING 102 SHOWING ...

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

    8. EXTERIOR OF FRONT (SOUTH) SIDE OF BUILDING 102 SHOWING THE SHED-ROOFED PORCH, THE TWO MAIN FRONT DOORS (ON EITHER SIDE OF THE INSIDE ELBOW OF THIS SIDE OF THE HOUSE), AND AN EARLY CHIMNEY WITH CORBELED BRICK CAP. VIEW TO NORTHWEST. - Bishop Creek Hydroelectric System, Plant 6, Cashbaugh-Kilpatrick House, Bishop Creek, Bishop, Inyo County, CA

  17. INTERIOR VIEW OF THE LIVING ROOM AND FRONT ENTRY. NOTE ...

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

    INTERIOR VIEW OF THE LIVING ROOM AND FRONT ENTRY. NOTE THE ORIGINAL TONGUE-AND-GROOVE WOOD FLOORING, CANEC PANEL CEILING, AND FRONT DOOR OF VERTICAL BOARDS WITH V-JOINTS. VIEW FACING NORTH. - Hickam Field, NCO Housing Type 2, 301 Eleventh Street, Honolulu, Honolulu County, HI

  18. Pattern formation in the wake of triggered pushed fronts

    NASA Astrophysics Data System (ADS)

    Goh, Ryan; Scheel, Arnd

    2016-08-01

    Pattern-forming fronts are often controlled by an external stimulus which progresses through a stable medium at a fixed speed, rendering it unstable in its wake. By controlling the speed of excitation, such stimuli, or ‘triggers’, can mediate pattern forming fronts which freely invade an unstable equilibrium and control which pattern is selected. In this work, we analytically and numerically study when the trigger perturbs an oscillatory pushed free front. In such a situation, the resulting patterned front, which we call a pushed trigger front, exhibits a variety of phenomenon, including snaking, non-monotonic wave-number selection, and hysteresis. Assuming the existence of a generic oscillatory pushed free front, we use heteroclinic bifurcation techniques to prove the existence of trigger fronts in an abstract setting motivated by the spatial dynamics approach. We then derive a leading order expansion for the selected wave-number in terms of the trigger speed. Furthermore, we show that such a bifurcation curve is governed by the difference of certain strong-stable and weakly-stable spatial eigenvalues associated with the decay of the free pushed front. We also study prototypical examples of these phenomena in the cubic-quintic complex Ginzburg Landau equation and a modified Cahn-Hilliard equation.

  19. 4. VIEW NORTHWEST, NORTH FRONT OF SOIL CONSERVATION SERVICE CLUSTER ...

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

    4. VIEW NORTHWEST, NORTH FRONT OF SOIL CONSERVATION SERVICE CLUSTER (BUILDINGS 24, 25, 26); NORTH FRONT OF QUARANTINE HEADHOUSE (BUILDING 27) - U.S. Plant Introduction Station, Soil Conservation Service Cluster, 11601 Old Pond Road, Glenn Dale, Prince George's County, MD

  20. 34. PHOTOCOPY OF PHOTOGRAPH SHOWING PERIOD FIRE ENGINE IN FRONT ...

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

    34. PHOTOCOPY OF PHOTOGRAPH SHOWING PERIOD FIRE ENGINE IN FRONT OF BUILDING 99. NOTE ORIGINAL DOORS ON EAST FRONT. DATE: JANUARY 6, 1938. PHOTOGRAPHER UNKNOWN. THIS PHOTO IS AN ENLARGEMENT FROM A 4'x5' NEGATIVE. - Mare Island Naval Shipyard, Firehouse, Vallejo, Solano County, CA

  1. Modeling the interacting detonation fronts observed by low energy radiography

    SciTech Connect

    Aufderheide, M; Egan, P O; Morgan, D L; Vantine, H C

    1998-09-18

    We have completed a series of experiments in which we made radiographs of interacting detonation fronts in a high explosive. Although the fronts and interactions were observed, the experimental data were insufficient to distinguish between two computer models which we employed to simulate the experiments.

  2. More distant view than previous photograph of front and side ...

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

    More distant view than previous photograph of front and side (west) of building 253, along with fronts of buildings 254, 255, 256, and 257. Looking northeast from corner of W.J. Avenue and N. 10th Street. - Fitzsimons General Hospital, Building 253, North side of East O'Neil Avenue between Tenth & Twelfth Streets, Aurora, Adams County, CO

  3. Rapid acceleration of protons upstream of earthward propagating dipolarization fronts

    PubMed Central

    Ukhorskiy, AY; Sitnov, MI; Merkin, VG; Artemyev, AV

    2013-01-01

    [1] Transport and acceleration of ions in the magnetotail largely occurs in the form of discrete impulsive events associated with a steep increase of the tail magnetic field normal to the neutral plane (Bz), which are referred to as dipolarization fronts. The goal of this paper is to investigate how protons initially located upstream of earthward moving fronts are accelerated at their encounter. According to our analytical analysis and simplified two-dimensional test-particle simulations of equatorially mirroring particles, there are two regimes of proton acceleration: trapping and quasi-trapping, which are realized depending on whether the front is preceded by a negative depletion in Bz. We then use three-dimensional test-particle simulations to investigate how these acceleration processes operate in a realistic magnetotail geometry. For this purpose we construct an analytical model of the front which is superimposed onto the ambient field of the magnetotail. According to our numerical simulations, both trapping and quasi-trapping can produce rapid acceleration of protons by more than an order of magnitude. In the case of trapping, the acceleration levels depend on the amount of time particles stay in phase with the front which is controlled by the magnetic field curvature ahead of the front and the front width. Quasi-trapping does not cause particle scattering out of the equatorial plane. Energization levels in this case are limited by the number of encounters particles have with the front before they get magnetized behind it. PMID:26167430

  4. Front elevation, note threestory addition to rear dating from 1915. ...

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

    Front elevation, note three-story addition to rear dating from 1915. In foreground is original two-story building of English bond brick. Openings on the street front have stone sills below each opening - Pioneer Building, 2679 East Grand Boulevard, Detroit, MI

  5. 3. VIEW SHOWING FRONT HALF OF NORTH SIDE OF BURLEY ...

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

    3. VIEW SHOWING FRONT HALF OF NORTH SIDE OF BURLEY SUBSTATION, LOOKING SOUTHWEST. BREAK BETWEEN 1913-1914 AND 1921 CONSTRUCTION PHASES, LOCATED BELOW AND ABOVE RIGHT EDGE OF SECOND WINDOW, FRONT LEFT OF PHOTOGRAPH - Bonneville Power Administration Burley Substation, 1221 Albion Avenue, Burley, Cassia County, ID

  6. 49 CFR 393.44 - Front brake lines, protection.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 5 2013-10-01 2013-10-01 false Front brake lines, protection. 393.44 Section 393... ACCESSORIES NECESSARY FOR SAFE OPERATION Brakes § 393.44 Front brake lines, protection. On every bus, if equipped with air brakes, the braking system shall be so constructed that in the event any brake line...

  7. 49 CFR 393.44 - Front brake lines, protection.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 5 2014-10-01 2014-10-01 false Front brake lines, protection. 393.44 Section 393... ACCESSORIES NECESSARY FOR SAFE OPERATION Brakes § 393.44 Front brake lines, protection. On every bus, if equipped with air brakes, the braking system shall be so constructed that in the event any brake line...

  8. 49 CFR 393.44 - Front brake lines, protection.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 5 2012-10-01 2012-10-01 false Front brake lines, protection. 393.44 Section 393... ACCESSORIES NECESSARY FOR SAFE OPERATION Brakes § 393.44 Front brake lines, protection. On every bus, if equipped with air brakes, the braking system shall be so constructed that in the event any brake line...

  9. 33. EAST FRONT AND SOUTH SIDE OF POWERHOUSE 1965: ...

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

    33. EAST FRONT AND SOUTH SIDE OF POWERHOUSE - 1965: Photocopy of July 1965 photograph showing south side and east front of powerhouse and car barn. Note addition of the decorative canopy at the corner of the building. At this date the structure displayed a coat of light green paint. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA

  10. 2. VIEW OF PARK SIGNAGE AT FRONT ROYAL. SIGN SAYS: ...

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

    2. VIEW OF PARK SIGNAGE AT FRONT ROYAL. SIGN SAYS: "NORTH ENTRANCE SHENANDOAH NATIONAL PARK." LOCATED ON EXIT SIDE OF ROAD. LOOKING SOUTHWEST, MILE 0.0. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

  11. View of front (north) and east walls of the Office, ...

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

    View of front (north) and east walls of the Office, Childs power plant. Rock cairn in front frames the 1976 National Historic Mechanical Engineering plaque. Looking southeast - Childs-Irving Hydroelectric Project, Childs System, Office, Forest Service Road 708/502, Camp Verde, Yavapai County, AZ

  12. Fronts and Thermohaline Structure of the Brazil Current Confluence System

    NASA Astrophysics Data System (ADS)

    Severov, Dimitri

    and Thermohaline Structure of the Brazil Current Confluence System (BCCS) are stud-ied from climatic data, "Marathon Exp. Leg.8, 1984"data, and two Sea surface temperature (SST) data bases: "Meteor satellite"(1989-1994) and "ds277-Reynolds" (1981-2000).The South Atlantic Central Water (SACW) is divided in two main types: tropical (TW) and subtropical water (ST). Water masses, fronts, inter-frontal and frontal zones are analysed and classified: a) the water masses: Tropical Low-Salinity Water, Tropical Surface Water, Tropical Tropospheric Water, Subtropical Low-Salinity Water, Subtropical Surface Water, Subtropical Tropospheric Water. T,S characteristics of intermediate, deep and bottom water defined by different authors are confirmed and completed; b) the Inter-frontal Zones: Tropical/Brazil Current Zone, Sub-tropical Zone and Subantarctic Zone; c) the Frontal Zones: Subtropical, Subantarctic and Polar, and d) the Fronts: Subtropical Front of the Brazil Current, Principal Subtropical Front, North Subtropical Front, Subtropical Surface Front, South Subtropical Front, Subantarctic Surface Front, Subantarctic Front and Polar Front. Several stable T-S relationships are found below the friction layer and at the Fronts. The maximum gradient of the oceanographic characteris-tics occurs at the Brazil Current Front, which can be any of the subtropical fronts, depending on season. Minimum mean depth of the pycnocline coincides with the fronts of the BCCS, indicating the paths of low-salinity shelf waters into the open ocean. D. N. Severov (a) , V. Pshennikov (b) and A.V. Remeslo (c) a -Sección Oceanologé Facultad de Ciencia, Universidad de la Republica, Igué 4225, 11400 ıa, a Montevideo, Uruguay. Tel. (598-2) 525-8618, Fax (598-2) 525-8617, mail: dima@fcien.edu.uy b -Instituto de Física, Facultad de Ciencias, Universidad de la Republica, Igué 4225, 11400 Mon-a tevideo, Uruguay, mail: seva@fisica.edu.uy c -Atlantic Research Inst. For Fisheries Oceanology (Atlant

  13. The mechanical efficiency of front crawl swimming.

    PubMed

    Toussaint, H M; Knops, W; De Groot, G; Hollander, A P

    1990-06-01

    In this study the gross efficiency of swimming was determined in a group of male (N = 6) and female (N = 4) competitive swimmers. The gross efficiency is defined as the ratio of the power output (W) to the power input (W). In a range of swimming velocities (0.95-1.6 m.s-1), the power input (rate of energy expenditure, 445-1137 W) was calculated from the oxygen uptake values (1.33-3.25 1 O2.min-1). The total power output (26-108 W) was directly measured during front crawl swimming using a system of underwater push-off pads instrumented with a force transducer (MAD-system). Using the MAD-system, the effect on total body drag due to the addition of the respiratory apparatus was evaluated to be negligible. The gross efficiency ranged from 5 to 9.5%. At equal swimming speed, the male competitive swimmers demonstrated a higher gross efficiency. However, this was due to the higher power output required by the male swimmers at a given speed. Gross efficiency was dependent on the absolute power output such that as power output increased so did the calculated gross efficiency. At the same power output, the values for the gross efficiency do not differ between the male and female competitive swimmers. PMID:2381310

  14. Flame front geometry in premixed turbulent flames

    SciTech Connect

    Shepherd, I.G. ); Ashurst, W.T. )

    1991-12-01

    Experimental and numerical determinations of flame front curvature and orientation in premixed turbulent flames are presented. The experimental data is obtained from planar, cross sectional images of stagnation point flames at high Damkoehler number. A direct numerical simulation of a constant energy flow is combined with a zero-thickness, constant density flame model to provide the numerical results. The computational domain is a 32{sup 3} cube with periodic boundary conditions. The two-dimensional curvature distributions of the experiments and numerical simulations compare well at similar q{prime}/S{sub L} values with means close to zero and marked negative skewness. At higher turbulence levels the simulations show that the distributions become symmetric about zero. These features are also found in the three dimensional distributions of curvature. The simulations support assumptions which make it possible to determine the mean direction cosines from the experimental data. This leads to a reduction of 12% in the estimated flame surface area density in the middle of the flame brush. 18 refs.

  15. Detonation Front Curvatures and Detonation Rates

    NASA Astrophysics Data System (ADS)

    Lauderbach, Lisa M.; Lorenz, K. Thomas; Lee, Edward L.; Souers, P. Clark

    2015-06-01

    We have normalized the LLNL library of detonation front curvatures by dividing lags by the edge lag and radii by the edge radius. We then fit the normalized data to the equation L = AR2 + BR8, where L is the normalized lag and R is the normalized radius. We attribute the quadratic term to thermal processes and the 8th-power term to shock processes. We compare the % of the quadratic term J at the edge with detonation rates obtained from the size effect. One class of results is made up of fine-grained, uniform explosives with large lags, where a low detonation rate leads to a high J and vice versa. This provides a rough way of estimating unknown rates if the unknown explosive is of high quality. The other, equally-large class contains rough-grained materials, often with small lags and small radii. These have curves that do not fit the equation but superfically often look quadratic. Some HMX and PETN curvatures even show a ``sombrero'' effect. Code models show that density differences of 0.03 g/cc in ram-pressed parts can cause pseudo-quadratic curves and even sombreros. Modeling is used to illustrate J at the lowest and highest possible detonation rates. This work performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  16. The PHENIX Drift Chamber Front End Electroncs

    NASA Astrophysics Data System (ADS)

    Pancake, C.; Velkovska, J.; Pantuev, V.; Fong, D.; Hemmick, T.

    1998-04-01

    The PHENIX Drift Chamber (DC) is designed to operate in the high particle flux environment of the Relativistic Heavy Ion Collider and provide high resolution track measurements. It is segmented into 80 keystones with 160 readout channels each. The Front End Electronics (FEE) developed to meet the demanding operating conditions and the large number of readout channels of the DC will be discussed. It is based on two application specific integrated circuits: the ASD8 and the TMC-PHX1. The ASD8 chip contains 8 channels of bipolar amplifier-shaper-discriminator with 6 ns shaping time and ≈ 20 ns pulse width, which satisfies the two track resolution requirements. The TMC-PHX1 chip is a high-resolution multi-hit Time-to-Digital Converter. The outputs from the ASD8 are digitized in the Time Memory Cell (TMC) every (clock period)/32 or 0.78 ns (at 40 MHz), which gives the intrinsic time resolution of the system. A 256 words deep dual port memory keeps 6.4 μs time history of data at 40 MHz clock. Each DC keystone is supplied with 4 ASD8/TMC boards and one FEM board, which performs the readout of the TMC-PHX1's, buffers and formats the data to be transmitted over the Glink. The slow speed control communication between the FEM and the system is carried out over ARCNET. The full readout chain and the data aquisition system are being tested.

  17. Front lighted optical tooling method and apparatus

    DOEpatents

    Stone, William J.

    1985-06-18

    An optical tooling method and apparatus uses a front lighted shadowgraphic technique to enhance visual contrast of reflected light. The apparatus includes an optical assembly including a fiducial mark, such as cross hairs, reflecting polarized light with a first polarization, a polarizing element backing the fiducial mark and a reflective surface backing the polarizing element for reflecting polarized light bypassing the fiducial mark and traveling through the polarizing element. The light reflected by the reflecting surface is directed through a second pass of the polarizing element toward the frontal direction with a polarization differing from the polarization of the light reflected by the fiducial mark. When used as a tooling target, the optical assembly may be mounted directly to a reference surface or may be secured in a mounting, such as a magnetic mounting. The optical assembly may also be mounted in a plane defining structure and used as a spherometer in conjunction with an optical depth measuring instrument. A method of measuring a radius of curvature of an unknown surface includes positioning the spherometer on a surface between the surface and a depth measuring optical instrument. As the spherometer is frontally illuminated, the distance from the depth measuring instrument to the fiducial mark and the underlying surface are alternately measured and the difference in these measurements is used as the sagittal height to calculate a radius of curvature.

  18. Translational genetics: advancing fronts for craniofacial health.

    PubMed

    D'Souza, R N; Dunnwald, M; Dunnvald, M; Frazier-Bowers, S; Polverini, P J; Wright, J T; de Rouen, T; Vieira, A R

    2013-12-01

    Scientific opportunities have never been better than today! The completion of the Human Genome project has sparked hope and optimism that cures for debilitating conditions can be achieved and tailored to individuals and communities. The availability of reference genome sequences and genetic variations as well as more precise correlations between genotype and phenotype have facilitated the progress made in finding solutions to clinical problems. While certain craniofacial and oral diseases previously deemed too difficult to tackle have benefited from basic science and technological advances over the past decade, there remains a critical need to translate the fruits of several decades' worth of basic and clinical research into tangible therapies that can benefit patients. The fifth Annual Fall Focused Symposium, "Translational Genetics - Advancing Fronts for Craniofacial Health", was created by the American Association for Dental Research (AADR) to foster its mission to advance interdisciplinary research that is directed toward improving oral health. The symposium showcased progress made in identifying molecular targets that are potential therapeutics for common and rare dental diseases and craniofacial disorders. Speakers focused on translational and clinical applications of their research and, where applicable, on strategies for new technologies and therapeutics. The critical needs to transfer new knowledge to the classroom and for further investment in the field were also emphasized. The symposium underscored the importance of basic research, chairside clinical observations, and population-based studies in driving the new translational connections needed for the development of cures for the most common and devastating diseases involving the craniofacial complex. PMID:24097854

  19. Formation mechanisms of magnetotail dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Fu, Huishan

    2016-07-01

    Dipolarization fronts (DFs) are frequently detected in the Earth's magnetotail. How these DFs are formed is still poorly understood. Three possible mechanisms have been suggested in previous simulations: (1) jet braking, (2) transient reconnection, and (3) spontaneous formation. Among these three mechanisms, the first has been verified by using spacecraft observation, while the second and third have not. In this study, we show Cluster observation of DFs inside reconnection diffusion region. This observation provides in situ evidence of the second mechanism: transient reconnection can produce DFs. We suggest that the DFs detected in the near-Earth region (XGSM > -10 RE) are primarily attributed to jet braking, while the DFs detected in the mid- or far-tail region (XGSM < -15 RE) are primarily attributed to transient reconnection or spontaneous formation. In the jet-braking mechanism, the high-speed flow 'pushes' the pre-existing plasmas to produce the DF, so that there is causality between high-speed flow and DF. In the transient-reconnection mechanism, there is no causality between high-speed flow and DF, because the frozen-in condition is violated.

  20. Light-Front Holography: A First Approximation to QCD

    SciTech Connect

    de Teramond, Guy F.; Brodsky, Stanley J.

    2008-10-03

    Starting from the Hamiltonian equation of motion in QCD, we identify an invariant light-front coordinate {zeta} which allows the separation of the dynamics of quark and gluon binding from the kinematics of constituent spin and internal orbital angular momentum. The result is a single variable light-front Schroedinger equation for QCD which determines the eigenspectrum and the light-front wavefunctions of hadrons for general spin and orbital angular momentum. This light-front wave equation is equivalent to the equations of motion which describe the propagation of spin-J modes on anti-de Sitter (AdS) space. This allows us to establish formally a gauge/gravity correspondence between an effective gravity theory defined on AdS5 and light front QCD.