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Sample records for induced pressure waves

  1. Utilization of sparker induced pressure waves to tenderize meat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study investigated the feasibility of tenderizing meat using high pressure waves generated from a sparker source. Beef strip loins were cut into steaks from the anterior end and one to two steaks from each strip loin were randomly selected to serve as non-treated controls and the remaining ste...

  2. Pressure induced Superconductivity in the Charge Density Wave Compound Tritelluride

    SciTech Connect

    Hamlin, J.J.; Zocco, D.A.; Sayles, T.A.; Maple, M.B.; Chu, J.-H.; Fisher, I.R.; /Stanford U., Geballe Lab.

    2010-02-15

    A series of high-pressure electrical resistivity measurements on single crystals of TbTe{sub 3} reveal a complex phase diagram involving the interplay of superconducting, antiferromagnetic and charge density wave order. The onset of superconductivity reaches a maximum of almost 4 K (onset) near {approx} 12.4 GPa.

  3. Wave-Induced Pressure Under an Internal Solitary Wave and Its Impact at the Bed

    NASA Astrophysics Data System (ADS)

    Rivera, Gustavo; Diamesis, Peter; Jenkins, James; Berzi, Diego

    2015-11-01

    The bottom boundary layer (BBL) under a mode-1 internal solitary wave (ISW) of depression propagating against an oncoming model barotropic current is examined using 2-D direct numerical simulation based on a spectral multidomain penalty method model. Particular emphasis is placed on the diffusion into the bed of the pressure field driven by the wake and any near-bed instabilities produced under specific conditions. To this end, a spectral nodal Galerkin approach is used for solving the diffusion equation for the wave-induced pressure. At sufficiently high ISW amplitude, the BBL undergoes a global instability which produces intermittent vortex shedding from within the separation bubble in the lee of the wave. The interplay between the bottom shear stress field and pressure perturbations during vortex ejection events and the subsequent evolution of the vortices is examined. The potential for bed failure upon the passage of the ISW trough and implications for resuspension of bottom particulate matter are both discussed in the context of specific sediment transport models.

  4. A simplified physical model of pressure wave dynamics and acoustic wave generation induced by laser absorption in the retina.

    PubMed

    Till, S J; Milsom, P K; Rowlands, G

    2004-07-01

    Shock waves have been proposed in the literature as a mechanism for retinal damage induced by ultra-short laser pulses. For a spherical absorber, we derive a set of linear equations describing the propagation of pressure waves. We show that the formation of shock fronts is due to the form of the absorber rather than the inclusion of nonlinear terms in the equations. The analytical technique used avoids the need for a Laplace transform approach and is easily applied to other absorber profiles. Our analysis suggests that the 'soft' nature of the membrane surrounding retinal melanosomes precludes shock waves as a mechanism for the retinal damage induced by ultra-short pulse lasers. The quantitative estimates of the pressure gradients induced by laser absorption which are made possible by this work, together with detailed meso-scale or molecular modelling, will allow alternative damage mechanisms to be identified. PMID:15210319

  5. Influence of ambient air pressure on the energy conversion of laser-breakdown induced blast waves

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Komurasaki, Kimiya; Arakawa, Yoshihiro

    2013-09-01

    Influence of ambient pressure on energy conversion efficiency from a Nd : glass laser pulse (λ = 1.053 µm) to a laser-induced blast wave was investigated at reduced pressure. Temporal incident and transmission power histories were measured using sets of energy meters and photodetectors. A half-shadowgraph half-self-emission method was applied to visualize laser absorption waves. Results show that the blast energy conversion efficiency ηbw decreased monotonically with the decrease in ambient pressure. The decrease was small, from 40% to 38%, for the pressure change from 101 kPa to 50 kPa, but the decrease was considerable, to 24%, when the pressure was reduced to 30 kPa. Compared with a TEA-CO2-laser-induced blast wave (λ = 10.6 µm), higher fraction absorption in the laser supported detonation regime ηLSD of 90% was observed, which is influenced slightly by the reduction of ambient pressure. The conversion fraction ηbw/ηLSD≈90% was achieved at pressure >50 kPa, which is significantly higher than that in a CO2 laser case.

  6. Rubber-induced uniform laser shock wave pressure for thin metal sheets microforming

    NASA Astrophysics Data System (ADS)

    Shen, Zongbao; Wang, Xiao; Liu, Huixia; Wang, Yayuan; Wang, Cuntang

    2015-02-01

    Laser shock microforming of thin metal sheets is a new high velocity forming technique, which employs laser shock wave to deform the thin metal sheets. The spatial distribution of forming pressure is mainly dependent on the laser beam. A new type of laser shock loading method is introduced which gives a uniform pressure distribution. A low density rubber is inserted between the laser beam and the thin metal sheets. The mechanism of rubber-induced smoothing effect on confined laser shock wave is proposed. Plasticine is used to perform the smoothing effect experiments due to its excellent material flow ability. The influence of rubber on the uniformity of laser shock wave pressure is studied by measuring the surface micro topography of the deformed plasticine. And the four holes forming experiment is used to verify the rubber-induced uniform pressure on thin metal sheets surface. The research results show the possibility of smoothing laser shock wave pressure using rubber. And the good surface quality can be obtained under rubber dynamic loading.

  7. Modeling wave-induced pore pressure and effective stress in a granular seabed

    NASA Astrophysics Data System (ADS)

    Scholtès, Luc; Chareyre, Bruno; Michallet, Hervé; Catalano, Emanuele; Marzougui, Donia

    2014-08-01

    The response of a sandy seabed under wave loading is investigated on the basis of numerical modeling using a multi-scale approach. To that aim, the discrete element method is coupled to a finite volume method specially enhanced to describe compressible fluid flow. Both solid and fluid phase mechanics are upscaled from considerations established at the pore level. Model's predictions are validated against poroelasticity theory and discussed in comparison with experiments where a sediment analog is subjected to wave action in a flume. Special emphasis is put on the mechanisms leading the seabed to liquefy under wave-induced pressure variation on its surface. Liquefaction is observed in both dilative and compactive regimes. It is shown that the instability can be triggered for a well-identified range of hydraulic conditions. Particularly, the results confirm that the gas content, together with the permeability of the medium are key parameters affecting the transmission of pressure inside the soil.

  8. Modeling wave-induced pore pressure and effective stress in a granular seabed

    NASA Astrophysics Data System (ADS)

    Scholtès, Luc; Chareyre, Bruno; Michallet, Hervé; Catalano, Emanuele; Marzougui, Donia

    2015-01-01

    The response of a sandy seabed under wave loading is investigated on the basis of numerical modeling using a multi-scale approach. To that aim, the discrete element method is coupled to a finite volume method specially enhanced to describe compressible fluid flow. Both solid and fluid phase mechanics are upscaled from considerations established at the pore level. Model's predictions are validated against poroelasticity theory and discussed in comparison with experiments where a sediment analog is subjected to wave action in a flume. Special emphasis is put on the mechanisms leading the seabed to liquefy under wave-induced pressure variation on its surface. Liquefaction is observed in both dilative and compactive regimes. It is shown that the instability can be triggered for a well-identified range of hydraulic conditions. Particularly, the results confirm that the gas content, together with the permeability of the medium are key parameters affecting the transmission of pressure inside the soil.

  9. Syrinx fluid transport: modeling pressure-wave-induced flux across the spinal pial membrane.

    PubMed

    Elliott, N S J

    2012-03-01

    Syrinxes are fluid-filled cavities of the spinal cord that characterize syringomyelia, a disease involving neurological damage. Their formation and expansion is poorly understood, which has hindered successful treatment. Syrinx cavities are hydraulically connected with the spinal subarachnoid space (SSS) enveloping the spinal cord via the cord interstitium and the network of perivascular spaces (PVSs), which surround blood vessels penetrating the pial membrane that is adherent to the cord surface. Since the spinal canal supports pressure wave propagation, it has been hypothesized that wave-induced fluid exchange across the pial membrane may play a role in syrinx filling. To investigate this conjecture a pair of one-dimensional (1-d) analytical models were developed from classical elastic tube theory coupled with Darcy's law for either perivascular or interstitial flow. The results show that transpial flux serves as a mechanism for damping pressure waves by alleviating hoop stress in the pial membrane. The timescale ratio over which viscous and inertial forces compete was explicitly determined, which predicts that dilated PVS, SSS flow obstructions, and a stiffer and thicker pial membrane-all associated with syringomyelia-will increase transpial flux and retard wave travel. It was also revealed that the propagation of a pressure wave is aided by a less-permeable pial membrane and, in contrast, by a more-permeable spinal cord. This is the first modeling of the spinal canal to include both pressure-wave propagation along the spinal axis and a pathway for fluid to enter and leave the cord, which provides an analytical foundation from which to approach the full poroelastic problem. PMID:22482686

  10. Landslide stability: Role of rainfall-induced, laterally propagating, pore-pressure waves

    USGS Publications Warehouse

    Priest, G.R.; Schulz, W.H.; Ellis, W.L.; Allan, J.A.; Niem, A.R.; Niem, W.A.

    2011-01-01

    The Johnson Creek Landslide is a translational slide in seaward-dipping Miocene siltstone and sandstone (Astoria Formation) and an overlying Quaternary marine terrace deposit. The basal slide plane slopes sub-parallel to the dip of the Miocene rocks, except beneath the back-tilted toe block, where it slopes inland. Rainfall events raise pore-water pressure in the basal shear zone in the form of pulses of water pressure traveling laterally from the headwall graben down the axis of the slide at rates of 1-6 m/hr. Infiltration of meteoric water and vertical pressure transmission through the unsaturated zone has been measured at ~50 mm/hr. Infiltration and vertical pressure transmission were too slow to directly raise head at the basal shear zone prior to landslide movement. Only at the headwall graben was the saturated zone shallow enough for rainfall events to trigger lateral pulses of water pressure through the saturated zone. When pressure levels in the basal shear zone exceeded thresholds defined in this paper, the slide began slow, creeping movement as an intact block. As pressures exceeded thresholds for movement in more of the slide mass, movement accelerated, and differential displacement between internal slide blocks became more pronounced. Rainfall-induced pore-pressure waves are probably a common landslide trigger wherever effective hydraulic conductivity is high and the saturated zone is located near the surface in some part of a slide. An ancillary finding is apparently greater accuracy of grouted piezometers relative to those in sand packs for measurement of pore pressures at the installed depth.

  11. Seismic attenuation: effects of interfacial impedance on wave-induced pressure diffusion

    NASA Astrophysics Data System (ADS)

    Qi, Qiaomu; Müller, Tobias M.; Rubino, J. Germán

    2014-12-01

    Seismic attenuation and dispersion in layered sedimentary structures are often interpreted in terms of the classical White model for wave-induced pressure diffusion across the layers. However, this interlayer flow is severely dependent on the properties of the interface separating two layers. This interface behaviour can be described by a pressure jump boundary condition involving a non-vanishing interfacial impedance. In this paper, we incorporate the interfacial impedance into the White model by solving a boundary value problem in the framework of quasi-static poroelasticity. We show that the White model predictions for attenuation and dispersion substantially change. These changes can be attributed to petrophysically plausible scenarios such as imperfect hydraulic contacts or the presence of capillarity.

  12. Pressure-induced quenching of the charge-density-wave state observed by x-ray diffraction

    SciTech Connect

    Sacchetti, A.

    2010-05-03

    We report an x-ray diffraction study on the charge-density-wave (CDW) LaTe{sub 3} and CeTe{sub 3} compounds as a function of pressure. We extract the lattice constants and the CDW modulation wave-vector, and provide direct evidence for a pressure-induced quenching of the CDW phase. We observe subtle differences between the chemical and mechanical compression of the lattice. We account for these with a scenario where the effective dimensionality in these CDW systems is dependent on the type of lattice compression and has a direct impact on the degree of Fermi surface nesting and on the strength of fluctuation effects.

  13. Wave numbers and pressure-induced shifts of Ar I atomic lines measured by Fourier transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Veza, Damir; Sansonetti, Craig J.; Salit, Marc L.; Travis, John C.

    2012-06-01

    Wave numbers and pressure-induced shifts of 19 blue argon emission lines belonging to the 3p56p-3p54s and 3p55p-3p54s transition arrays were measured with high accuracy using a UV/visible Fourier transform spectrometer (FTS). The measurements were made using electrodeless lamps containing traces of 198Hg and argon at pressures of 33 Pa (1/4 Torr), 400 Pa (3 Torr), 933 Pa (7 Torr) and 1333 Pa (10 Torr). Calibration of the FTS wave number scale was obtained using the four most prominent lines of 198Hg as internal standards. The pressure-induced shifts of the argon emission lines are in reasonable agreement with theoretical predictions. These results are of importance for astronomers and analytical chemists who use argon lines for practical wavelength standards as well as for theoreticians calculating argon-argon interactions and potential energy curves of diatomic argon molecules.

  14. Pressure-induced superconducting phase in the charge-density-wave compound terbium tritelluride.

    PubMed

    Hamlin, J J; Zocco, D A; Sayles, T A; Maple, M B; Chu, J-H; Fisher, I R

    2009-05-01

    A series of high-pressure electrical resistivity measurements on single crystals of TbTe3 reveal a complex phase diagram involving the interplay of superconducting, antiferromagnetic and charge-density-wave order. The onset of superconductivity reaches a maximum of almost 4 K (onset) near approximately 12.4 GPa. PMID:19518815

  15. Characteristics of pressure waves

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Air blast characteristics generated by most types of explosions are discussed. Data cover both negative and positive blast load phases and net transverse pressure as a function of time. The effects of partial or total confinement, atmospheric propagation, absorption of energy by ground shock or cratering, and transmission over irregular terrain on blast wave properties were also considered.

  16. Numerical simulation of pressure waves in the cochlea induced by a microwave pulse.

    PubMed

    Yitzhak, Nir M; Ruppin, Raphael; Hareuveny, Ronen

    2014-10-01

    The pressure waves developing at the cochlea by the irradiation of the body with a plane wave microwave pulse are obtained by numerical simulation, employing a two-step finite-difference time-domain (FDTD) algorithm. First, the specific absorption rate (SAR) distribution is obtained by solving the Maxwell equations on a FDTD grid. Second, the temperature rise due to this SAR distribution is used to formulate the thermoelastic equations of motion, which are discretized and solved by the FDTD method. The calculations are performed for anatomically based full body human models, as well as for a head model. The dependence of the pressure amplitude at the cochlea on the frequency, the direction of propagation, and the polarization of the incident electromagnetic radiation, as well as on the pulse width, was investigated. PMID:25099875

  17. Shock wave reflection induced detonation (SWRID) under high pressure and temperature condition in closed cylinder

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Qi, Y.; Liu, H.; Zhang, P.; He, X.; Wang, J.

    2016-07-01

    Super-knock is one of the major obstacles for improving power density in advanced internal combustion engines (ICE). This work studied the mechanism of super-knock initiation using a rapid compression machine that simulated conditions relevant to ICEs and provided excellent optical accessibility. Based on the high-speed images and pressure traces of the stoichiometric iso-octane/oxygen/nitrogen combustion under high-temperature and high-pressure conditions, it was observed that detonation was first initiated in the near-wall region as a result of shock wave reflection. Before detonation was initiated, the speed of the combustion wave front was less than that of the Chapman-Jouguet (C-J) detonation speed (around 1840 m/s). In the immediate vicinity of the initiation, the detonation speed was much higher than that of the C-J detonation.

  18. Shear waves in the diamond-anvil cell reveal pressure-induced instability in (Mg,Fe)O.

    PubMed

    Jacobsen, Steven D; Spetzler, Hartmut; Reichmann, Hans J; Smyth, Joseph R

    2004-04-20

    The emerging picture of Earth's deep interior from seismic tomography indicates more complexity than previously thought. The presence of lateral anisotropy and heterogeneity in Earth's mantle highlights the need for fully anisotropic elasticity data from mineral physics. A breakthrough in high-frequency (gigahertz) ultrasound has resulted in transmission of pure-mode elastic shear waves into a high-pressure diamond-anvil cell using a P-to-S elastic-wave conversion. The full elastic tensor (c(ij)) of high-pressure minerals or metals can be measured at extreme conditions without optical constraints. Here we report the effects of pressure and composition on shear-wave velocities in the major lower-mantle oxide, magnesiowüstite-(Mg,Fe)O. Magnesiowüstite containing more than approximately 50% iron exhibits pressure-induced c(44) shear-mode softening, indicating an instability in the rocksalt structure. The oxide closer to expected lower-mantle compositions ( approximately 20% iron) shows increasing shear velocities more similar to MgO, indicating that it also should have a wide pressure-stability field. A complete sign reversal in the c(44) pressure derivative points to a change in the topology of the (Mg,Fe)O phase diagram at approximately 50-60% iron. The relative stability of Mg-rich (Mg,Fe)O and the strong compositional dependence of shear-wave velocities (and partial differential c(44)/ partial differential P) in (Mg,Fe)O implies that seismic heterogeneity in Earth's lower mantle may result from compositional variations rather than phase changes in (Mg,Fe)O. PMID:15079080

  19. Shear waves in the diamond-anvil cell reveal pressure-induced instability in (Mg,Fe)O

    PubMed Central

    Jacobsen, Steven D.; Spetzler, Hartmut; Reichmann, Hans J.; Smyth, Joseph R.

    2004-01-01

    The emerging picture of Earth's deep interior from seismic tomography indicates more complexity than previously thought. The presence of lateral anisotropy and heterogeneity in Earth's mantle highlights the need for fully anisotropic elasticity data from mineral physics. A breakthrough in high-frequency (gigahertz) ultrasound has resulted in transmission of pure-mode elastic shear waves into a high-pressure diamond-anvil cell using a P-to-S elastic-wave conversion. The full elastic tensor (cij) of high-pressure minerals or metals can be measured at extreme conditions without optical constraints. Here we report the effects of pressure and composition on shear-wave velocities in the major lower-mantle oxide, magnesiowüstite-(Mg,Fe)O. Magnesiowüstite containing more than ≈50% iron exhibits pressure-induced c44 shear-mode softening, indicating an instability in the rocksalt structure. The oxide closer to expected lower-mantle compositions (≈20% iron) shows increasing shear velocities more similar to MgO, indicating that it also should have a wide pressure-stability field. A complete sign reversal in the c44 pressure derivative points to a change in the topology of the (Mg,Fe)O phase diagram at ≈50–60% iron. The relative stability of Mg-rich (Mg,Fe)O and the strong compositional dependence of shear-wave velocities (and ∂c44/∂P) in (Mg,Fe)O implies that seismic heterogeneity in Earth's lower mantle may result from compositional variations rather than phase changes in (Mg,Fe)O. PMID:15079080

  20. Fluid Pressure Increases in Hydrothermal Systems Induced by Seismic Waves: Possible Triggers of Earthquakes and Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Roeloffs, E.

    2002-12-01

    That seismic waves trigger microseismicity in hydrothermal settings hundreds of km from the epicenter is plausibly linked to seismic-wave-induced fluid pressure changes at these distances. Although fluid pressure decreases have been observed in diverse settings, in the hydrothermal system at Long Valley, California, that seismic waves from earthquakes increase fluid pressure or discharge. Other published data, from thermal springs in Japan, Yellowstone, and Klamath Falls, Oregon, support the idea that seismic waves have induced pressure and discharge changes and that, in hydrothermal systems, these changes are usually increases. Temperature increases in seafloor hydrothermal vents within days after earthquakes as distant as 220 km imply, moreover, that seismic waves enhance conductance of vertical fluid flow pathways. The influence of seismic waves (wavelengths of km), on hot, fluid-filled subsurface fractures (apertures of mm to cm) could proceed by several mechanisms. Local fluid flow induced at crack walls could remove mineral seals. Spatially uniform acceleration can move gas bubbles relative to denser liquid and solid phases. Thermal expansion can elevate pressure around hot fluid that has penetrated upward. By lowering effective stress and directly weakening faults that are themselves flow paths, seismic waves could initiate processes leading to volcanic eruptions or other earthquakes where sufficient subsurface magma or elastic strain energy have previously accumulated. This type of earthquake-volcano linkage could explain why volcanos statistically erupt more frequently up to 5 years after M>7 earthquakes hundreds of km distant. For example, 11 months elapsed after the Ms 7.8 Luzon (Phillipines) earthquake before Mount Pinatubo erupted on June 15, 1991, 100 km away. Steam emission and 3 M4+ earthquakes in the Pinatubo area followed within days of the Luzon event, however, and a hydrothermal explosion on April 2 started the continuous unrest that built to

  1. The Numerical Simulation of Unsteady Cavitation Evolution Induced by Pressure Wave

    NASA Astrophysics Data System (ADS)

    Khoo, B. C.; Zheng, J. G.

    2014-11-01

    The present study is focused on the numerical simulation of pressure wave propagation through the cavitating compressible liquid flow, its interaction with cavitation bubble and the resulting unsteady cavitation evolution. The compressibility effects of liquid water are taken into account and the cavitating flow is governed by one-fluid cavitation model which is based on the compressible Euler equations with the assumption that the cavitation is the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. Several aspects of the method employed to solve the governing equations are outlined. The unsteady features of cavitating flow due to the external perturbation, such as the cavitation deformation and collapse and consequent pressure increase are resolved numerically and discussed in detail. It is observed that the cavitation bubble collapse is accompanied by the huge pressure surge of order of 100 bar, which is thought to be responsible for the material erosion, noise, vibration and loss of efficiency of operating underwater devices.

  2. Effects of pressure characteristics on transfection efficiency in laser-induced stress wave-mediated gene delivery

    NASA Astrophysics Data System (ADS)

    Ando, Takahiro; Sato, Shunichi; Ashida, Hiroshi; Obara, Minoru

    2013-07-01

    Laser-induced stress waves (LISWs) generated by irradiating a light-absorbing medium with a pulsed laser can transiently increase the permeability of cell membranes for gene delivery. In this study, we investigated the effects of pressure characteristics of LISWs upon gene transfection efficiency using lasers with different pulse durations: a 6-ns pulsed Nd:YAG laser and 20-ns and 200-µs pulsed ruby lasers. LISWs were generated by irradiating a black rubber disk, on which a transparent plastic sheet was adhered for confinement of the laser-produced plasma. Rat dorsal skin was injected with plasmid DNA coding for luciferase, to which LISWs were applied. With nanosecond laser pulses, transfection efficiency increased linearly with increasing positive peak pressure in the range of 35 to 145 MPa, the corresponding impulse ranging from 10 to 40 Paṡs. With 200-µs laser pulses, on the other hand, efficient gene expression was observed by the application of LISWs even with a 10-fold-lower peak pressure (˜5 MPa), the corresponding impulse being as large as 430 Paṡs. These results indicate that even at low peak pressures, efficient transfection can be achieved by extending the pressure duration and hence by increasing the impulse of LISWs, while the averaged expression efficiencies were relatively low.

  3. Arterial pulse wave pressure transducer

    NASA Technical Reports Server (NTRS)

    Kim, C.; Gorelick, D.; Chen, W. (Inventor)

    1974-01-01

    An arterial pulse wave pressure transducer is introduced. The transducer is comprised of a fluid filled cavity having a flexible membrane disposed over the cavity and adapted to be placed on the skin over an artery. An arterial pulse wave creates pressure pulses in the fluid which are transduced, by a pressure sensitive transistor in direct contact with the fluid, into an electric signal. The electrical signal is representative of the pulse waves and can be recorded so as to monitor changes in the elasticity of the arterial walls.

  4. Source duration of stress and water-pressure induced seismicity derived from experimental analysis of P wave pulse width in granite

    NASA Astrophysics Data System (ADS)

    Masuda, K.

    2013-12-01

    Pulse widths of P waves in granite, measured in the laboratory, were analyzed to investigate source durations of rupture processes for water-pressure induced and stress-induced microseismicity. Much evidence suggests that fluids in the subsurface are intimately linked to faulting processes. Studies of seismicity induced by water injection are thus important for understanding the trigger mechanisms of earthquakes as well as for engineering applications such as hydraulic fracturing of rocks at depth for petroleum extraction. Determining the cause of seismic events is very important in seismology and engineering; however, water-pressure induced seismic events are difficult to distinguish from those induced by purely tectonic stress. To investigate this problem, we analyzed the waveforms of acoustic emissions (AEs) produced in the laboratory by both water-pressure induced and stress-induced microseismicity. We used a cylinder (50 mm in diameter and 100 mm in length) of medium-grained granite. We applied a differential stress of about 70% of fracture strength, to the rock sample under 40 MPa confining pressure and held it constant throughout the experiment. When the primary creep stage and acoustic emissions (AEs) caused by the initial loading had ceased, we injected distilled water into the bottom end of the sample at a constant pressure of 17 MPa until macroscopic fracture occurred. We analysed AE waveforms produced by stress-induced AEs which occurred before the water-injection and by water-pressure induced AEs which occurred after the water-injection. Pulse widths were measured from the waveform traces plotted from the digital data. To investigate the source duration of the rupture process, we estimated the pulse width at the source and normalized by event magnitude to obtain a scaled pulse width at the source. After the effects of event size and hypocentral distance were removed from observed pulse widths, the ratio of the scaled source durations of water-pressure

  5. Effects of pressure waves

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Two parameters, side on overpressure and side on impulse loads, and their application to the determination of structural damage to buildings and vehicles in the vicinity of an explosion are investigated. Special consideration was given to what constitutes damage and what level of damage is acceptable. Solutions were sorted through the examination of glass breakage, curve fit to bomb damage, overturning of marginal structures (buses, trucks, mobile homes) subject to toppling, and initiation of yielding in either beam or plate structural components. Three different empirical pressure versus impulse diagrams were presented - the first is for minor structural damage involving wrenched joints and partitions, the second is for major damage structural damage with load bearing members at least partially destroyed, and the third is for 50% to 75% of the building demolished. General guidelines were obtained from the results when the accurate structural details are unknown.

  6. Strong anharmonicity induces quantum melting of charge density wave in 2 H -NbSe2 under pressure

    NASA Astrophysics Data System (ADS)

    Leroux, Maxime; Errea, Ion; Le Tacon, Mathieu; Souliou, Sofia-Michaela; Garbarino, Gaston; Cario, Laurent; Bosak, Alexey; Mauri, Francesco; Calandra, Matteo; Rodière, Pierre

    2015-10-01

    The pressure and temperature dependence of the phonon dispersion of 2 H -NbSe2 is measured by inelastic x-ray scattering. A strong temperature dependent soft phonon mode, reminiscent of the charge density wave (CDW), is found to persist up to a pressure as high as 16 GPa, far above the critical pressure at which the CDW disappears at 0 K. By using ab initio calculations beyond the harmonic approximation, we obtain an accurate, quantitative description of the (P ,T ) dependence of the phonon spectrum. Our results show that the rapid destruction of the CDW under pressure is related to the zero mode vibrations—or quantum fluctuations—of the lattice renormalized by the anharmonic part of the lattice potential. The calculations also show that the low-energy longitudinal acoustic mode that drives the CDW transition barely contributes to superconductivity, explaining the insensitivity of the superconducting critical temperature to the CDW transition.

  7. The behavior of a compressible turbulent boundary layer in a shock-wave-induced adverse pressure gradient. Ph.D. Thesis - Washington Univ., Seattle, Aug. 1972

    NASA Technical Reports Server (NTRS)

    Rose, W. C.

    1973-01-01

    The results of an experimental investigation of the mean- and fluctuating-flow properties of a compressible turbulent boundary layer in a shock-wave-induced adverse pressure gradient are presented. The turbulent boundary layer developed on the wall of an axially symmetric nozzle and test section whose nominal free-stream Mach number and boundary-layer thickness Reynolds number were 4 and 100,000, respectively. The adverse pressure gradient was induced by an externally generated conical shock wave. Mean and time-averaged fluctuating-flow data, including the complete experimental Reynolds stress tensor and experimental turbulent mass- and heat-transfer rates are presented for the boundary layer and external flow, upstream, within and downstream of the pressure gradient. The mean-flow data include distributions of total temperature throughout the region of interest. The turbulent mixing properties of the flow were determined experimentally with a hot-wire anemometer. The calibration of the wires and the interpretation of the data are discussed. From the results of the investigation, it is concluded that the shock-wave - boundary-layer interaction significantly alters the turbulent mixing characteristics of the boundary layer.

  8. Fluid pressure waves trigger earthquakes

    NASA Astrophysics Data System (ADS)

    Mulargia, Francesco; Bizzarri, Andrea

    2015-03-01

    Fluids-essentially meteoric water-are present everywhere in the Earth's crust, occasionally also with pressures higher than hydrostatic due to the tectonic strain imposed on impermeable undrained layers, to the impoundment of artificial lakes or to the forced injections required by oil and gas exploration and production. Experimental evidence suggests that such fluids flow along preferred paths of high diffusivity, provided by rock joints and faults. Studying the coupled poroelastic problem, we find that such flow is ruled by a nonlinear partial differential equation amenable to a Barenblatt-type solution, implying that it takes place in form of solitary pressure waves propagating at a velocity which decreases with time as v ∝ t [1/(n - 1) - 1] with n ≳ 7. According to Tresca-Von Mises criterion, these waves appear to play a major role in earthquake triggering, being also capable to account for aftershock delay without any further assumption. The measure of stress and fluid pressure inside active faults may therefore provide direct information about fault potential instability.

  9. Enhanced Transfection Efficiency in Laser-Induced Stress Wave-Assisted Gene Transfer at Low Laser Fluence by Increasing Pressure Impulse

    NASA Astrophysics Data System (ADS)

    Takano, Shinta; Sato, Shunichi; Terakawa, Mitsuhiro; Asida, Hiroshi; Okano, Hideyuki; Obara, Minoru

    2008-03-01

    To improve transfection efficiency in gene delivery based on nanosecond pulsed laser-induced stress waves, we examined different types of transparent materials, a poly(ethylene terephthalate) sheet, poly(vinyl alcohol) gel, and water, which were placed on a laser target for plasma confinement. We found that the use of water was most effective for maintaining a large pressure impulse during multipulse laser irradiation and, as a result, high transfection efficiency was demonstrated in rat skin in vivo at a relatively low laser fluence of 0.7 J/cm2. At this fluence, steady laser transmission through quartz fibers was confirmed, allowing endoscopic application of our gene delivery technique.

  10. Rhythmic Pressure Waves Induce Mucin5AC Expression via an EGFR-Mediated Signaling Pathway in Human Airway Epithelial Cells

    PubMed Central

    Liu, Chunyi; Li, Qi; Kolosov, Victor P.; Perelman, Juliy M.

    2013-01-01

    Rhythmic pressure waves (RPW), mimicking the mechanical forces generated during normal breathing, play a key role in airway surface liquid (ASL) homeostasis. As a major component of ASL, we speculated that the mucin5AC (MUC5AC) expression must also be regulated by RPW. However, fewer researches have focused on this question. Therefore, our aim was to test the effect and mechanism of RPW on MUC5AC expression in cultured human bronchial epithelial cells. Compared with the relevant controls, the transcriptional level of MUC5AC and the protein expressions of MUC5AC, the phospho-epidermal growth factor receptor (p-EGFR), phospho-extracellular signal-related kinase (p-ERK), and phospho-Akt (p-Akt) were all significantly increased after mechanical stimulation. However, this effect could be significantly attenuated by transfecting with EGFR-siRNA. Similarly, pretreating with the inhibitor of ERK or phosphatidylinositol 3-kinases (PI3K)/Akt separately or jointly also significantly reduced MUC5AC expression. Collectively, these results indicate that RPW modulate MUC5AC expression via the EGFR-PI3K-Akt/ERK-signaling pathway in human bronchial epithelial cells. PMID:23768102

  11. Pressure measurements of nonplanar stress waves

    SciTech Connect

    Carlson, G.H.; Charest, J.A.

    1981-01-01

    Measuring the pressure of non-planar stress waves using thin piezo-resistive gages requires correcting for induced strain parallel to the sensing elements. A technique has been developed that permits such measurements, making use of a dual element gage. One element, Manganin, is sensitive to stress both parallel and perpendicular to the sensing element; the other element, Constantan, is primarily sensitive to stress parallel to the sensing element. The change in resistance in the Constantan element is thereby used to correct for the strain effect parallel to the Manganin element axis. Individual and combined Manganin and Constantan elements were subjected to controlled gas gun impact tests in the pressure and strain ranges of 0 to 50 kbar and 0 to 7%, respectively. From planar wave tests, the piezoresistivity of Constantan was found to be positive but negligible in comparison with Manganin. From combined stress and strain environments, the compression and tension strain factors of Constantan were found to be constant and equal to 2.06. The strain factors of Manganin were found to increase from 1.2 to 2.0 asymptotically in the range of 0 to 3% strain. It was experimentally demonstrated that, because of the closeness of their strain factors, the Manganin-Constantan dual element gage could be used in the differential recording mode to yield pressure directly. In this mode the gage is a strain compensating gage. Analytical techniques have also been developed for more accurate strain compensation.

  12. Non-β-blocking R-carvedilol enantiomer suppresses Ca2+ waves and stress-induced ventricular tachyarrhythmia without lowering heart rate or blood pressure.

    PubMed

    Zhang, Jingqun; Zhou, Qiang; Smith, Chris D; Chen, Haiyan; Tan, Zhen; Chen, Biyi; Nani, Alma; Wu, Guogen; Song, Long-Sheng; Fill, Michael; Back, Thomas G; Chen, S R Wayne

    2015-09-01

    Carvedilol is the current β-blocker of choice for suppressing ventricular tachyarrhythmia (VT). However, carvedilol's benefits are dose-limited, attributable to its potent β-blocking activity that can lead to bradycardia and hypotension. The clinically used carvedilol is a racemic mixture of β-blocking S-carvedilol and non-β-blocking R-carvedilol. We recently reported that novel non-β-blocking carvedilol analogues are effective in suppressing arrhythmogenic Ca(2+) waves and stress-induced VT without causing bradycardia. Thus, the non-β-blocking R-carvedilol enantiomer may also possess this favourable anti-arrhythmic property. To test this possibility, we synthesized R-carvedilol and assessed its effect on Ca(2+) release and VT. Like racemic carvedilol, R-carvedilol directly reduces the open duration of the cardiac ryanodine receptor (RyR2), suppresses spontaneous Ca(2+) oscillations in human embryonic kidney (HEK) 293 cells, Ca(2+) waves in cardiomyocytes in intact hearts and stress-induced VT in mice harbouring a catecholaminergic polymorphic ventricular tachycardia (CPVT)-causing RyR2 mutation. Importantly, R-carvedilol did not significantly alter heart rate or blood pressure. Therefore, the non-β-blocking R-carvedilol enantiomer represents a very promising prophylactic treatment for Ca(2+)- triggered arrhythmia without the bradycardia and hypotension often associated with racemic carvedilol. Systematic clinical assessments of R-carvedilol as a new anti-arrhythmic agent may be warranted. PMID:26348911

  13. Improvement of erectile dysfunction by the active pepide from Urechis unicinctus by high temperature/pressure and ultra - wave assisted lysis in Streptozotocin Induced Diabetic Rats

    PubMed Central

    Kim, Kang Sup; Bae, Woong Jin; Kim, Su Jin; Kang, Kyong-Hwa; Kim, Se-Kwon; Cho, Hyuk Jin; Hong, Sung-Hoo; Lee, Ji Youl; Kim, Sae Woong

    2016-01-01

    ABSTRACT Introduction: We investigate the effect of active peptide from Urechis unicinctus (UU) by high temperature/pressure and ultra-wave assisted lysis on erectile dysfunction in streptozotocin-induced diabetic rats. Materials and Methods: Forty 12-week-old Sprague-Dawley rats were used in this study. Diabetes was induced by a one-time intraperitoneal injection of streptozotocin (50mg/kg). One week later, the diabetic rats were randomly divided into four groups: normal control, untreated diabetes control, and groups treated with 100 or 500mg/kg/d UU peptide. Rats were fed with UU peptide by intragastric administration for 8 weeks. After 8 weeks, penile hemodynamic function was evaluated in all groups by measuring the intracavernosal pressure after electrostimulating the cavernous nerve. Nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) activities were measured and endothelial nitric oxide synthase (eNOS) and neuronal NOS (nNOS) protein expression was determined by Western blot. Results: Maximum intracavernosal pressure in diabetic control rats decreased significantly compared to normal control rats, and was increased significantly compared to untreated diabetic rats after UU peptide supplementation. Treatment with the higher dose of UU peptide significantly increased the NO and cGMP levels compared with the diabetic control group. Decreased activity and expression eNOS and nNOS were found in the diabetic rats compared with the normal control group. Decreased eNOS and nNOS in diabetic rats were improved by UU peptide administration. Conclusions: Active peptide from UU ameliorates erectile function in a streptozotocin induced diabetic rat model of erectile dysfunction. PMID:27564297

  14. Investigation of Pressurized Wave Bearings

    NASA Technical Reports Server (NTRS)

    Keith, Theo G., Jr.; Dimofte, Florin

    2003-01-01

    The wave bearing has been pioneered and developed by Dr. Dimofte over the past several years. This bearing will be the main focus of this research. It is believed that the wave bearing offers a number of advantages over the foil bearing, which is the bearing that NASA is currently pursuing for turbomachinery applications. The wave bearing is basically a journal bearing whose film thickness varies around the circumference approximately sinusoidally, with usually 3 or 4 waves. Being a rigid geometry bearing, it provides precise control of shaft centerlines. The wave profile also provides good load capacity and makes the bearing very stable. Manufacturing techniques have been devised that should allow the production of wave bearings almost as cheaply as conventional full-circular bearings.

  15. Influence of Plasma Pressure Fluctuation on RF Wave Propagation

    NASA Astrophysics Data System (ADS)

    Liu, Zhiwei; Bao, Weimin; Li, Xiaoping; Liu, Donglin; Zhou, Hui

    2016-02-01

    Pressure fluctuations in the plasma sheath from spacecraft reentry affect radio-frequency (RF) wave propagation. The influence of these fluctuations on wave propagation and wave properties is studied using methods derived by synthesizing the compressible turbulent flow theory, plasma theory, and electromagnetic wave theory. We study these influences on wave propagation at GPS and Ka frequencies during typical reentry by adopting stratified modeling. We analyzed the variations in reflection and transmission properties induced by pressure fluctuations. Our results show that, at the GPS frequency, if the waves are not totally reflected then the pressure fluctuations can remarkably affect reflection, transmission, and absorption properties. In extreme situations, the fluctuations can even cause blackout. At the Ka frequency, the influences are obvious when the waves are not totally transmitted. The influences are more pronounced at the GPS frequency than at the Ka frequency. This suggests that the latter can mitigate blackout by reducing both the reflection and the absorption of waves, as well as the influences of plasma fluctuations on wave propagation. Given that communication links with the reentry vehicles are susceptible to plasma pressure fluctuations, the influences on link budgets should be taken into consideration. supported by the National Basic Research Program of China (No. 2014CB340205) and National Natural Science Foundation of China (No. 61301173)

  16. Pressure diffusion waves in porous media

    SciTech Connect

    Silin, Dmitry; Korneev, Valeri; Goloshubin, Gennady

    2003-04-08

    Pressure diffusion wave in porous rocks are under consideration. The pressure diffusion mechanism can provide an explanation of the high attenuation of low-frequency signals in fluid-saturated rocks. Both single and dual porosity models are considered. In either case, the attenuation coefficient is a function of the frequency.

  17. Blast wave parameters at diminished ambient pressure

    NASA Astrophysics Data System (ADS)

    Silnikov, M. V.; Chernyshov, M. V.; Mikhaylin, A. I.

    2015-04-01

    Relation between blast wave parameters resulted from a condensed high explosive (HE) charge detonation and a surrounding gas (air) pressure has been studied. Blast wave pressure and impulse differences at compression and rarefaction phases, which traditionally determine damage explosive effect, has been analyzed. An initial pressure effect on a post-explosion quasi-static component of the blast load has been investigated. The analysis is based on empirical relations between blast parameters and non-dimensional similarity criteria. The results can be directly applied to flying vehicle (aircraft or spacecraft) blast safety analysis.

  18. Turbulence measurements in a compressible boundary layer subjected to a shock-wave-induced adverse pressure gradient.

    NASA Technical Reports Server (NTRS)

    Rose, W. C.

    1973-01-01

    The rms intensities of fluctuating mass flux and total temperature and their correlation coefficients are given for the case of an adiabatic, Mach 4, axisymmetric shock-wave boundary-layer interaction. Data were obtained upstream, within, and downstream of the interaction by the use of constant temperature hot-wire anemometer. Turbulence spectra and quantitative behavior from oscilloscope traces are shown at selected locations. The measurements indicate that certain frequencies of the turbulence are increased as a result of the interaction and that the mass flux and total temperature fluctuations remain highly correlated over most of the boundary layer throughout the interaction. The present data are also transformed to rms intensities of fluctuating static temperature and velocity and compared with existing data obtained in adiabatic flows.

  19. Modulated pressure waves in large elastic tubes.

    PubMed

    Mefire Yone, G R; Tabi, C B; Mohamadou, A; Ekobena Fouda, H P; Kofané, T C

    2013-09-01

    Modulational instability is the direct way for the emergence of wave patterns and localized structures in nonlinear systems. We show in this work that it can be explored in the framework of blood flow models. The whole modified Navier-Stokes equations are reduced to a difference-differential amplitude equation. The modulational instability criterion is therefore derived from the latter, and unstable patterns occurrence is discussed on the basis of the nonlinear parameter model of the vessel. It is found that the critical amplitude is an increasing function of α, whereas the region of instability expands. The subsequent modulated pressure waves are obtained through numerical simulations, in agreement with our analytical expectations. Different classes of modulated pressure waves are obtained, and their close relationship with Mayer waves is discussed. PMID:24089964

  20. Modulated pressure waves in large elastic tubes

    NASA Astrophysics Data System (ADS)

    Mefire Yone, G. R.; Tabi, C. B.; Mohamadou, A.; Ekobena Fouda, H. P.; Kofané, T. C.

    2013-09-01

    Modulational instability is the direct way for the emergence of wave patterns and localized structures in nonlinear systems. We show in this work that it can be explored in the framework of blood flow models. The whole modified Navier-Stokes equations are reduced to a difference-differential amplitude equation. The modulational instability criterion is therefore derived from the latter, and unstable patterns occurrence is discussed on the basis of the nonlinear parameter model of the vessel. It is found that the critical amplitude is an increasing function of α, whereas the region of instability expands. The subsequent modulated pressure waves are obtained through numerical simulations, in agreement with our analytical expectations. Different classes of modulated pressure waves are obtained, and their close relationship with Mayer waves is discussed.

  1. Wave pressure acting on V-shaped floating breakwater in random seas

    NASA Astrophysics Data System (ADS)

    Yu, Yang; Ding, Ning; Lin, Jie; Hou, Jiajia

    2015-12-01

    Wave pressure on the wet surface of a V-shaped floating breakwater in random seas is investigated. Considering the diffraction effect, the unit velocity potential caused by the single regular waves around the breakwater is solved using the finite-depth Green function and boundary element method, in which the Green function is solved by integral method. The Response-Amplitude Operator (RAO) of wave pressure is acquired according to the Longuet-Higgins' wave model and the linear Bernoulli equation. Furthermore, the wave pressure's response spectrum is calculated according to the wave spectrum by discretizing the frequency domain. The wave pressure's characteristic value corresponding to certain cumulative probability is determined according to the Rayleigh distribution of wave heights. The numerical results and field test results are compared, which indicates that the wave pressure calculated in random seas agrees with that of field measurements. It is found that the bigger angle between legs will cause the bigger pressure response, while the increase in leg length does not influence the pressure significantly. The pressure at the side of head sea is larger than that of back waves. When the incident wave angle changes from 0° to 90°, the pressure at the side of back waves decreases clearly, while at the side of head sea, the situation is more complicated and there seems no obvious tendency. The concentration of wave energy around low frequency (long wavelength) will induce bigger wave pressure, and more attention should be paid to this situation for the structure safety.

  2. Pressure wave charged repetitively pulsed gas laser

    DOEpatents

    Kulkarny, Vijay A.

    1982-01-01

    A repetitively pulsed gas laser in which a system of mechanical shutters bracketing the laser cavity manipulate pressure waves resulting from residual energy in the cavity gas following a lasing event so as to draw fresh gas into the cavity and effectively pump spent gas in a dynamic closed loop.

  3. Implications of pressure diffusion for shock waves

    NASA Technical Reports Server (NTRS)

    Ram, Ram Bachan

    1989-01-01

    The report deals with the possible implications of pressure diffusion for shocks in one dimensional traveling waves in an ideal gas. From this new hypothesis all aspects of such shocks can be calculated except shock thickness. Unlike conventional shock theory, the concept of entropy is not needed or used. Our analysis shows that temperature rises near a shock, which is of course an experimental fact; however, it also predicts that very close to a shock, density increases faster than pressure. In other words, a shock itself is cold.

  4. Pressure waves generated by steady flames.

    NASA Technical Reports Server (NTRS)

    Kuhl, A. L.; Kamel, M. M.; Oppenheim, A. K.

    1973-01-01

    Analysis of pressure waves that can be generated by clouds of explosive gas mixtures in a free atmosphere which is initially at a uniform state. The treatment is restricted only to the final stage of constant flame velocity when the flowfield is self-similar. By the introduction of reduced blast-wave parameters as phase-plane coordinates, the problem is resolved into the determination of the appropriate integral curves on this plane. Results, including space profiles of gasdynamic parameters, have been computed for a specific case of a hydrocarbon-air mixture characterized by a specific heat ratio of 1.3, sound speed at NTP of 345 m/sec, and volumetric expansion ratio corresponding to constant pressure deflagration of 7. Maximum overpressure ratios that can be generated by such flames in point-and line-symmetrical waves range from .00053, for the lower bound in the burning speed, up to 6 for the deflagration, while, for the average speeds of 5 to 10 m/sec, they are at a level of 0.05 to 0.10.

  5. Wave-Induced Groundwater Flows in a Freshwater Beach Aquifer

    NASA Astrophysics Data System (ADS)

    Malott, S. S.; Robinson, C. E.; O'Carroll, D. M.

    2014-12-01

    Wave-induced recirculation across the sediment-water interface can impact the transport of pollutants through a beach aquifer and their ultimate flux into coastal waters. The fate of nutrients (e.g. from septic and agricultural sources) and fecal indicator bacteria (e.g. E. coil) near the sediment-water interface are of particular concern as these pollutants often lead to degradation of recreational water quality and nearshore ecosystems. This paper presents detailed field measurements of groundwater flows in a freshwater beach aquifer on Lake Huron over periods of intensified wave conditions. Quantifying wave-driven processes in a freshwater beach aquifer enables wave effects to be studied in isolation from density and tidal effects that complicate groundwater flows in marine beaches. Water exchange across the sediment-water interface and groundwater flow patterns were measured using groundwater wells, arrays of vertically nested pressure transducers and manometers. Results show that wave action induces rapid infiltration/exfiltration across the sediment-water interface and a larger recirculation cell through the beach aquifer. Field data is used to validate a numerical groundwater model of wave-induced groundwater flows. While prior studies have simulated the effects of waves on beach groundwater flows, this study is the first attempt to validate these sophisticated modeling approaches. Finally, field data illustrating the impact of wave-induced groundwater flows on nutrient and bacteria fate and transport in beach aquifers will also be presented.

  6. Surface wave propagation characteristics in atmospheric pressure plasma column

    NASA Astrophysics Data System (ADS)

    Pencheva, M.; Benova, E.; Zhelyazkov, I.

    2007-04-01

    In the typical experiments of surface wave sustained plasma columns at atmospheric pressure the ratio of collision to wave frequency (ν/ω) is much greater than unity. Therefore, one might expect that the usual analysis of the wave dispersion relation, performed under the assumption ν/ω = 0, cannot give adequate description of the wave propagation characteristics. In order to study these characteristics we have analyzed the wave dispersion relationship for arbitrary ν/ω. Our analysis includes phase and wave dispersion curves, attenuation coefficient, and wave phase and group velocities. The numerical results show that a turning back point appears in the phase diagram, after which a region of backward wave propagation exists. The experimentally observed plasma column is only in a region where wave propagation coefficient is higher than the attenuation coefficient. At the plasma column end the electron density is much higher than that corresponding to the turning back point and the resonance.

  7. Numerical Study of Unsteady Supercavitation Perturbed by a Pressure Wave

    NASA Astrophysics Data System (ADS)

    Zheng, J. G.; Khoo, B. C.

    2016-06-01

    The unsteady features of supercavitation disturbed by an introduced pressure wave are investigated numerically using a one-fluid cavitation model. The supercavitating flow is assumed to be the homogeneous mixture of liquid and vapour which are locally under both kinetic and thermodynamic equilibrium. The compressibility effects of liquid water are taken into account to model the propagation of pressure wave through flow and its interaction with supercavitation bubble. The interaction between supercavity enveloping an underwater flat-nose cylinder and pressure wave is simulated and the resulting unsteady behavior of supercavitation is illustrated. It is observed that the supercavity will become unstable under the impact of the pressure wave and may collapse locally, which depends on the strength of perturbation. The huge pressure surge accompanying the collapse of supercavitation may cause the material erosion, noise, vibration and efficiency loss of operating underwater devices.

  8. Coalescence of two pressure waves associated with stream interactions

    NASA Technical Reports Server (NTRS)

    Whang, Y. C.; Burlaga, L. F.

    1984-01-01

    An MHD unsteady 1-D model is used to simulate the interaction and coalescence of two pressure waves in the outer heliosphere. Each of the two pressure waves was a compression region bounded by a shock pair. Computer simulation using Voyager data as input demonstrates the interaction and coalescence process involving one pressure wave associated with a fast stream and the other pressure wave without a fast stream. The process produced a significant change in the magnetic field and plasma signatures. The propagation of the forward and reverse shocks first widened the radial dimension of the shock compression region with increasing heliocentric distances. The shocks belonging to two neighboring compression regions eventually collided and two compression regions began to overlap with each other. This type of interaction is a dominant dynamical process in the outer heliosphere, and significantly and irreversible alters the structure of the medium.

  9. Induced topological pressure for topological dynamical systems

    SciTech Connect

    Xing, Zhitao; Chen, Ercai

    2015-02-15

    In this paper, inspired by the article [J. Jaerisch et al., Stochastics Dyn. 14, 1350016, pp. 1-30 (2014)], we introduce the induced topological pressure for a topological dynamical system. In particular, we prove a variational principle for the induced topological pressure.

  10. Corotating pressure waves without streams in the solar wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.

    1983-01-01

    Voyager 1 and 2 magnetic field and plasma data are presented which demonstrate the existence of large scale, corotating, non-linear pressure waves between 2 AU and 4 AU that are not accompanied by fast streams. The pressure waves are presumed to be generated by corotating streams near the Sun. For two of the three pressure waves that are discussed, the absence of a stream is probably a real, physical effect, viz., a consequence of deceleration of the stream by the associated compression wave. For the third pressure wave, the apparent absence of a stream may be a geometrical effect; it is likely that the stream was at latitudes just above those of the spacecraft, while the associated shocks and compression wave extended over a broader range of latitudes so that they could be observed by the spacecraft. It is suggested that the development of large-scale non-linear pressure waves at the expense of the kinetic energy of streams produces a qualitative change in the solar wind in the outer heliosphere. Within a few AU the quasi-stationary solar wind structure is determined by corotating streams whose structure is determined by the boundary conditions near the Sun.

  11. Novel wave power analysis linking pressure-flow waves, wave potential, and the forward and backward components of hydraulic power.

    PubMed

    Mynard, Jonathan P; Smolich, Joseph J

    2016-04-15

    Wave intensity analysis provides detailed insights into factors influencing hemodynamics. However, wave intensity is not a conserved quantity, so it is sensitive to diameter variations and is not distributed among branches of a junction. Moreover, the fundamental relation between waves and hydraulic power is unclear. We, therefore, propose an alternative to wave intensity called "wave power," calculated via incremental changes in pressure and flow (dPdQ) and a novel time-domain separation of hydraulic pressure power and kinetic power into forward and backward wave-related components (ΠP±and ΠQ±). Wave power has several useful properties:1) it is obtained directly from flow measurements, without requiring further calculation of velocity;2) it is a quasi-conserved quantity that may be used to study the relative distribution of waves at junctions; and3) it has the units of power (Watts). We also uncover a simple relationship between wave power and changes in ΠP±and show that wave reflection reduces transmitted power. Absolute values of ΠP±represent wave potential, a recently introduced concept that unifies steady and pulsatile aspects of hemodynamics. We show that wave potential represents the hydraulic energy potential stored in a compliant pressurized vessel, with spatial gradients producing waves that transfer this energy. These techniques and principles are verified numerically and also experimentally with pressure/flow measurements in all branches of a central bifurcation in sheep, under a wide range of hemodynamic conditions. The proposed "wave power analysis," encompassing wave power, wave potential, and wave separation of hydraulic power provides a potent time-domain approach for analyzing hemodynamics. PMID:26873972

  12. Estimating Sinusoidal Pressure Waves In A Pump Volute

    NASA Technical Reports Server (NTRS)

    Szabo, Roland J.; Chon, Juliet T.

    1994-01-01

    Closed-form equation approximates principal traveling-wave sinusoidal components of fluctuations of pressure in volute of centrifugal pump. Equation incorporated into Blade Vane Interaction Code (BVIC) computer program, which produces estimates for various pump speeds and various locations in volute. Intended use of BVIC in analysis of undesired interactions between pressure field and pump structure.

  13. The wave-induced boundary layer under long internal waves

    NASA Astrophysics Data System (ADS)

    Lin, Yuncheng; Redekopp, Larry G.

    2011-08-01

    The boundary layer formed under the footprint of an internal solitary wave is studied by numerical simulation for waves of depression in a two-layer model of the density stratification. The inviscid outer flow, in the perspective of boundary-layer theory, is based on an exact solution for the long wave-phase speed, yielding a family of fully nonlinear solitary wave solutions of the extended Korteweg-de Vries equation. The wave-induced boundary layer corresponding to this outer flow is then studied by means of simulation employing the Reynolds-averaged Navier-Stokes (RANS) formulation coupled with a turbulence closure model validated for wall-bounded flows. Boundary-layer characteristics are computed for an extensive range of environmental conditions and wave amplitudes. Boundary-layer transition, identified by monitoring the eddy viscosity, is correlated in terms of a boundary-layer Reynolds number. The frictional drag is evaluated for laminar, transitional, and turbulent cases, and correlations are presented for the friction coefficient plus relevant measures of the boundary-layer thickness.

  14. Acoustic Wave Propagation in Pressure Sense Lines

    NASA Technical Reports Server (NTRS)

    Vitarius, Patrick; Gregory, Don A.; Wiley, John; Korman, Valentin

    2003-01-01

    Sense lines are used in pressure measurements to passively transmit information from hostile environments to areas where transducers can be used. The transfer function of a sense line can be used to obtain information about the measured environment from the protected sensor. Several properties of this transfer function are examined, including frequency dependence, Helmholtz resonance, and time of flight delay.

  15. Diaphragm Pressure Wave Generator Developments at Industrial Research Ltd

    NASA Astrophysics Data System (ADS)

    Caughley, A. J.; Emery, N.; Glasson, N. D.

    2010-04-01

    Industrial Research Ltd (IRL) have been developing a unique diaphragm based pressure wave generator technology for pulse tube and Stirling cryocoolers. Our system uses a metal diaphragm to separate the clean cryocooler gas circuit from a conventionally lubricated mechanical driver, thus producing a clean pressure wave with a long life drive that does not require the precision manufacture and associated costs of large linear motors. The first successful diaphragm pressure wave generator produced 3.2 kW of acoustic power at an electro-acoustic efficiency of 72% with a swept volume of 200 ml and a prototype has now accumulated over 2500 hours running. This paper describes recent developments in the technology. To explore scaling, a small diaphragm pressure wave generator with a swept volume of 20 ml has been constructed and has delivered 454 W of acoustic power at an electro-acoustic efficiency of 60%. Improvements have been made to the hydraulic force amplifier mechanism for driving the diaphragms resulting in a cheaper and lighter mechanism than the mechanical linkage originally used. To meet a customer's specific requirements, the 200 ml pressure wave generator's stroke was extended to achieve 240 ml of swept volume thereby increasing its acoustic power delivery to 4.1 kW without compromising efficiency.

  16. Dual mode acoustic wave sensor for precise pressure reading

    NASA Astrophysics Data System (ADS)

    Mu, Xiaojing; Kropelnicki, Piotr; Wang, Yong; Randles, Andrew Benson; Chuan Chai, Kevin Tshun; Cai, Hong; Gu, Yuan Dong

    2014-09-01

    In this letter, a Microelectromechanical system acoustic wave sensor, which has a dual mode (lateral field exited Lamb wave mode and surface acoustic wave (SAW) mode) behavior, is presented for precious pressure change read out. Comb-like interdigital structured electrodes on top of piezoelectric material aluminium nitride (AlN) are used to generate the wave modes. The sensor membrane consists of single crystalline silicon formed by backside-etching of the bulk material of a silicon on insulator wafer having variable device thickness layer (5 μm-50 μm). With this principle, a pressure sensor has been fabricated and mounted on a pressure test package with pressure applied to the backside of the membrane within a range of 0 psi to 300 psi. The temperature coefficient of frequency was experimentally measured in the temperature range of -50 °C to 300 °C. This idea demonstrates a piezoelectric based sensor having two modes SAW/Lamb wave for direct physical parameter—pressure readout and temperature cancellation which can operate in harsh environment such as oil and gas exploration, automobile and aeronautic applications using the dual mode behavior of the sensor and differential readout at the same time.

  17. Two-phase flow model for energetic proton beam induced pressure waves in mercury target systems in the planned European Spallation Source

    NASA Astrophysics Data System (ADS)

    Barna, I. F.; Imre, A. R.; Rosta, L.; Mezei, F.

    2008-12-01

    Two-phase flow calculations are presented to investigate the thermo-hydraulical effects of the interaction between 2 ms long 1.3 GeV proton pulses with a closed mercury loop which can be considered as a model system of the target of the planned European Spallation Source (ESS) facility. The two-fluid model consists of six first-order partial differential equations that present one dimensional mass, momentum and energy balances for mercury vapor and liquid phases are capable to describe quick transients like cavitation effects or shock waves. The absorption of the proton beam is represented as instantaneous heat source in the energy balance equations. Densities and internal energies of the mercury liquid-vapor system is calculated from the van der Waals equation, but general method how to obtain such properties using arbitrary equation of state is also presented. A second order accurate high-resolution shock-capturing numerical scheme is applied with different kind of limiters in the numerical calculations. Our analysis show that even 75 degree temperature heat shocks cannot cause considerable cavitation effects in mercury.

  18. Acoustic waves in gases with strong pressure gradients

    NASA Technical Reports Server (NTRS)

    Zorumski, William E.

    1989-01-01

    The effect of strong pressure gradients on the acoustic modes (standing waves) of a rectangular cavity is investigated analytically. When the cavity response is represented by a sum of modes, each mode is found to have two resonant frequencies. The lower frequency is near the Viaesaela-Brundt frequency, which characterizes the buoyant effect, and the higher frequency is above the ordinary acoustic resonance frequency. This finding shows that the propagation velocity of the acoustic waves is increased due to the pressure gradient effect.

  19. Pressure induced ageing of polymers

    NASA Technical Reports Server (NTRS)

    Emri, I.; Knauss, W. G.

    1988-01-01

    The nonlinearly viscoelastic response of an amorphous homopolymer is considered under aspects of time dependent free volume behavior. In contrast to linearly viscoelastic solids, this model couples shear and volume deformation through a shift function which influences the rate of molecular relaxation or creep. Sample computations produce all those qualitative features one observes normally in uniaxial tension including the rate dependent formation of a yield point as a consequence of the history of an imposed pressure.

  20. Theoretical pressure distribution and wave drags for conical boattails

    NASA Technical Reports Server (NTRS)

    Jack, John R

    1953-01-01

    Afterbody pressure distributions and wave drag were calculated using a second-order theory for a variety of conical boattails at zero angle of attack. Results are presented for Mach numbers from 1.5 to 4.5, area ratios from 0.200 to 0.800, and boattail angle from 3 degrees to 11 degrees. The results indicate that for a given boattail angle, the wave drag decreases with increasing Mach number and area ratio. The wave drag, for a constant area ratio, increases with increasing boattail angle. For a specific Mach number, area ratio, and fineness ratio, a comparison of the wave-drag coefficients for conical, tangent-parabolic, and secant-parabolic boattails showed the conical boattail to have the smallest wave drag.

  1. Rapid miniature fiber optic pressure sensors for blast wave measurements

    NASA Astrophysics Data System (ADS)

    Zou, Xiaotian; Wu, Nan; Tian, Ye; Niezrecki, Christopher; Chen, Julie; Wang, Xingwei

    2013-02-01

    Traumatic brain injury (TBI) is a serious potential threat to soldiers who are exposed to explosions. Since the pathophysiology of TBI associated with a blast wave is not clearly defined, it is crucial to have a sensing system to accurately quantify the blast wave dynamics. This paper presents an ultra-fast fiber optic pressure sensor based on Fabry-Perot (FP) interferometric principle that is capable of measuring the rapid pressure changes in a blast event. The blast event in the experiment was generated by a starter pistol blank firing at close range, which produced a more realistic wave profile compared to using compressed air driven shock tubes. To the authors' knowledge, it is also the first study to utilize fiber optic pressure sensors to measure the ballistics shock wave of a pistol firing. The results illustrated that the fiber optic pressure sensor has a rise time of 200 ns which demonstrated that the sensor has ability to capture the dynamic pressure transient during a blast event. Moreover, the resonant frequency of the sensor was determined to be 4.11 MHz, which agrees well with the specific designed value.

  2. Air pressure waves from Mount St. Helens eruptions

    SciTech Connect

    Reed, J.W.

    1987-10-20

    Weather station barograph records as well as infrasonic recordings of the pressure wave from the Mount St. Helens eruption of May 18, 1980, have been used to estimate an equivalent explosion airblast yield for this event. Pressure amplitude versus distance patterns in various directions compared with patterns from other large explosions, such as atmospheric nuclear tests, the Krakatoa eruption, and the Tunguska comet impact, indicate that the wave came from an explosion equivalent of a few megatons of TNT. The extent of tree blowdown is considerably greater than could be expected from such an explosion, and the observed forest damage is attributed to outflow of volcanic material. The pressure-time signature obtained at Toledo, Washington, showed a long, 13-min duration negative phase as well as a second, hour-long compression phase, both probably caused by ejacta dynamics rather than standard explosion wave phenomenology. The peculiar audibility pattern, with the blast being heard only at ranges beyond about 100 km, is explicable by finite amplitude propagation effects. Near the source, compression was slow, taking more than a second but probably less than 5 s, so that it went unnoticed by human ears and susceptible buildings were not damaged. There was no damage as Toledo (54 km), where the recorded amplitude would have broken windows with a fast compression. An explanation is that wave emissions at high elevation angles traveled to the upper stratosphere, where low ambient air pressures caused this energetic pressure oscillation to form a shock wave with rapid, nearly instantaneous compression. Atmospheric refraction then returned part of this wave to ground level at long ranges, where the fast compressions were clearly audible. copyright American Geophysical Union 1987

  3. Measurement of Blast Waves from Bursting Pressureized Frangible Spheres

    NASA Technical Reports Server (NTRS)

    Esparza, E. D.; Baker, W. E.

    1977-01-01

    Small-scale experiments were conducted to obtain data on incident overpressure at various distances from bursting pressurized spheres. Complete time histories of blast overpressure generated by rupturing glass spheres under high internal pressure were obtained using eight side-on pressure transducers. A scaling law is presented, and its nondimensional parameters are used to compare peak overpressures, arrival times, impulses, and durations for different initial conditions and sizes of blast source. The nondimensional data are also compared, whenever possible, with results of theoretical calculations and compiled data for Pentolite high explosive. The scaled data are repeatable and show significant differences from blast waves generated by condensed high-explosives.

  4. Attenuation characteristics of nonlinear pressure waves propagating in pipes

    NASA Technical Reports Server (NTRS)

    Shih, C. C.

    1974-01-01

    A series of experiments was conducted to investigate temporal and spatial velocity distributions of fluid flow in 3-in. open-end pipes of various lengths up to 210 ft, produced by the propagation of nonlinear pressure waves of various intensities. Velocity profiles across each of five sections along the pipes were measured as a function of time with the use of hot-film and hot-wire anemometers for two pressure waves produced by a piston. Peculiar configurations of the velocity profiles across the pipe section were noted, which are uncommon for steady pipe flow. Theoretical consideration was given to this phenomenon of higher velocity near the pipe wall for qualitative confirmation. Experimentally time-dependent velocity distributions along the pipe axis were compared with one-dimensional theoretical results obtained by the method of characteristics with or without diffusion term for the purpose of determining the attenuation characteristics of the nonlinear wave propagation in the pipes.

  5. Free-surface wave-induced separation

    SciTech Connect

    Zhang, Z.J.; Stern, F.

    1996-09-01

    Free-surface wave-induced separation is studied for a surface-piercing NACA 0024 foil over a range of Froude numbers (0, .2, .37, .55) through computational fluid dynamics of the unsteady Reynolds-averaged Navier-Stokes and the continuity equations with the Baldwin-Lomax turbulence model, exact nonlinear kinematic and approximate dynamic free-surface boundary conditions, and a body/free-surface conforming grid. The flow conditions and uncertainty analysis are discussed. A topological rule for a surface-piercing body is derived and verified. Steady-flow results are presented and analyzed with regard to the wave and viscous flow and the nature of the separation.

  6. Gravitational waves induced by spinor fields

    NASA Astrophysics Data System (ADS)

    Feng, Kaixi; Piao, Yun-Song

    2015-07-01

    In realistic model building, spinor fields with various masses are present. During inflation, a spinor field may induce gravitational waves as a second order effect. In this paper, we calculate the contribution of a single massive spinor field to the power spectrum of primordial gravitational wave by using a retarded Green propagator. We find that the correction is scale invariant and of order H4/MP4 for arbitrary spinor mass mψ. Additionally, we also observe that when mψ≳H , the dependence of correction on mψ/H is nontrivial.

  7. Magnetospheric ULF waves with increasing amplitude related to solar wind dynamic pressure changes: The Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations

    NASA Astrophysics Data System (ADS)

    Shen, X. C.; Zong, Q.-G.; Shi, Q. Q.; Tian, A. M.; Sun, W. J.; Wang, Y. F.; Zhou, X. Z.; Fu, S. Y.; Hartinger, M. D.; Angelopoulos, V.

    2015-09-01

    Ultralow frequency (ULF) waves play an important role in transferring energy by buffeting the magnetosphere with solar wind pressure impulses. The amplitudes of magnetospheric ULF waves, which are induced by solar wind dynamic pressure enhancements or shocks, are thought to damp in one half a wave cycle or an entire wave cycle. We report in situ observations of solar wind dynamic pressure impulse-induced magnetospheric ULF waves with increasing amplitudes. We found six ULF wave events induced by solar wind dynamic pressure enhancements with slow but clear wave amplitude increase. During three or four wave cycles, the amplitudes of ion velocities and electric field of these waves increased continuously by 1.3-4.4 times. Two significant events were selected to further study the characteristics of these ULF waves. We found that the wave amplitude growth is mainly contributed by the toroidal mode wave. Three possible mechanisms of causing the wave amplitude increase are discussed. First, solar wind dynamic pressure perturbations, which are observed in a duration of 20-30 min, might transfer energy to the magnetospheric ULF waves continually. Second, the wave amplitude increase in the radial electric field may be caused by superposition of two wave modes, a standing wave excited by the solar wind dynamic impulse and a propagating compressional wave directly induced by solar wind oscillations. When superposed, the two wave modes fit observations as does a calculation that superposes electric fields from two wave sources. Third, the normal of the solar wind discontinuity is at an angle to the Sun-Earth line. Thus, the discontinuity will affect the dayside magnetopause continuously for a long time.

  8. Application of Monochromatic Ocean Wave Forecasts to Prediction of Wave-Induced Currents

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1975-01-01

    Stoke's wave-induced currents are compared, for variety of wind conditions resulting in partially developed seas and for two water depths, with currents induced by average and significant monochromatic waves related to Bretschneider spectrum.

  9. Internal wave-turbulence pressure above sloping sea bottoms

    NASA Astrophysics Data System (ADS)

    van Haren, Hans

    2011-12-01

    An accurate bottom pressure sensor has been moored at different sites varying from a shallow sea strait via open ocean guyots to a 1900 m deep Gulf of Mexico. All sites show more or less sloping bottom topography. Focusing on frequencies (σ) higher than tidal, the pressure records are remarkably similar, to within the 95% statistical significance bounds, in the internal gravity wave continuum (IWC) band up to buoyancy frequency N. The IWC has a relatively uniform spectral slope: log(P(σ)) = -αlog(σ), α = 2 ± 1/3. The spectral collapse is confirmed from independent internal hydrostatic pressure estimate, which suggests a saturated IWC. For σ > N, all pressure-spectra transit to a bulge that differs in magnitude. This bulge is commonly attributed to long surface waves. For the present data it is suggested to be due to stratified turbulence-internal wave coupling, which is typically large over sloping topography. The bulge drops off at a more or less common frequency of 2-3 × 10-2 Hz, which is probably related with typical turbulent overturning scales.

  10. Propagation of waves in a medium with high radiation pressure

    NASA Technical Reports Server (NTRS)

    Bisnovatyy-Kogan, G. S.; Blinnikov, S. I.

    1979-01-01

    The propagation and mutual transformation of acoustic and thermal waves are investigated in media with a high radiative pressure. The equations of hydrodynamics for matter and the radiative transfer equations in a moving medium in the Eddington approximation are used in the investigation. Model problems of waves in a homogeneous medium with an abrupt jump in opacity and in a medium of variable opacity are presented. The characteristic and the times of variability are discussed. Amplitude for the brightness fluctuations for very massive stars are discussed.

  11. Plateau Waves of Intracranial Pressure and Partial Pressure of Cerebral Oxygen.

    PubMed

    Lang, Erhard W; Kasprowicz, Magdalena; Smielewski, Peter; Pickard, John; Czosnyka, Marek

    2016-01-01

    This study investigates 55 intracranial pressure (ICP) plateau waves recorded in 20 patients after severe traumatic brain injury (TBI) with a focus on a moving correlation coefficient between mean arterial pressure (ABP) and ICP, called PRx, which serves as a marker of cerebrovascular reactivity, and a moving correlation coefficient between ABP and cerebral partial pressure of oxygen (pbtO2), called ORx, which serves as a marker for cerebral oxygen reactivity. ICP and ICPamplitude increased significantly during the plateau waves, whereas CPP and pbtO2 decreased significantly. ABP, ABP amplitude, and heart rate remained unchanged. In 73 % of plateau waves PRx increased during the wave. ORx showed an increase during and a decrease after the plateau waves, which was not statistically significant. Our data show profound cerebral vasoparalysis on top of the wave and, to a lesser extent, impairment of cerebral oxygen reactivity. The different behavior of the indices may be due to the different latencies of the cerebral blood flow and oxygen level control mechanisms. While cerebrovascular reactivity is a rapidly reacting mechanism, cerebral oxygen reactivity is slower. PMID:27165902

  12. Time-resolved wave profile measurements in copper to Megabar pressures

    SciTech Connect

    Chhabildas, L C; Asay, J R

    1981-01-01

    Many time-resolved techniques have been developed which have greatly aided in the understanding of dynamic material behavior such as the high pressure-dynamic strength of materials. In the paper, time-resolved measurements of copper (at shock-induced high pressures and temperatures) are used to illustrate the capability of using such techniques to investigate high pressure strength. Continuous shock loading and release wave profiles have been made in copper to 93 GPa using velocity interferometric techniques. Fine structure in the release wave profiles from the shocked state indicates an increase in shear strength of copper to 1.5 GPa at 93 GPa from its ambient value of 0.08 GPa.

  13. Computation of the pressure field generated by surface acoustic waves in microchannels.

    PubMed

    Darinskii, A N; Weihnacht, M; Schmidt, H

    2016-07-01

    The high-frequency pressure induced by a surface acoustic wave in the fluid filling a microchannel is computed by solving the full scattering problem. The microchannel is fabricated inside a container attached to the top of a piezoelectric substrate where the surface wave propagates. The finite element method is used. The pressure found in this way is compared with the pressure obtained by solving boundary-value problems formulated on the basis of simplifications which have been introduced in earlier papers by other research studies. The considered example shows that the difference between the results can be significant, ranging from several tens of percent up to several times in different points inside the channel. PMID:27314212

  14. An oxygen pressure sensor using surface acoustic wave devices

    NASA Technical Reports Server (NTRS)

    Leighty, Bradley D.; Upchurch, Billy T.; Oglesby, Donald M.

    1993-01-01

    Surface acoustic wave (SAW) piezoelectric devices are finding widespread applications in many arenas, particularly in the area of chemical sensing. We have developed an oxygen pressure sensor based on coating a SAW device with an oxygen binding agent which can be tailored to provide variable sensitivity. The coating is prepared by dissolving an oxygen binding agent in a toluene solution of a copolymer which is then sprayed onto the surface of the SAW device. Experimental data shows the feasibility of tailoring sensors to measure the partial pressure of oxygen from 2.6 to 67 KPa (20 to 500 torr). Potential applications of this technology are discussed.

  15. Air pressure waves from Mount St. Helens eruptions

    SciTech Connect

    Reed, J.W.

    1980-01-01

    Barograms from a number of National Weather Service stations were assembled for the May 18, 1980, eruption and compared to airblast wave propagations from large explosions. Wave amplitudes at 50 to 300 km distances were about what might be expected from a nuclear explosion of between 1 megaton and 10 megaton yield. Pressure-time signatures could not be resolved for the first compression phase, because of the slow paper recording speed. The 900 s negative phase duration was much too long for comparison with the negative phase of an explosion. Nevertheless, positive and negative amplitudes were about equal, as often observed at long distances from explosions. Calculations have been made for a simple finite amplitude propagation model. These show rough bounds on the source compression rate, to give the observed inaudible waves at least to 54 km distance, yet cause audibly rapid compression at Seattle, near 150 km, and beyond.

  16. Pressure-induced metallization of silane

    SciTech Connect

    Chen,X.; Struzhkin, V.; Song, Y.; Goncharov, A.; Ahart, M.; Liu, Z.; Mao, H.; Hemley, R.

    2008-01-01

    There is a great interest in electronic transitions in hydrogen-rich materials under extreme conditions. It has been recently suggested that the group IVa hydrides such as methane (CH4), silane (SiH4), and germane (GeH4) become metallic at far lower pressures than pure hydrogen at equivalent densities because the hydrogen is chemically compressed in group IVa hydride compounds. Here we report measurements of Raman and infrared spectra of silane under pressure. We find that SiH4 undergoes three phase transitions before becoming opaque at 27-30 GPa. The vibrational spectra indicate the material transforms to a polymeric (framework) structure in this higher pressure range. Room-temperature infrared reflectivity data reveal that the material exhibits Drude-like metallic behavior above 60 GPa, indicating the onset of pressure-induced metallization.

  17. Wavelet analysis of blood pressure waves in vasovagal syncope

    NASA Astrophysics Data System (ADS)

    Marrone, A.; Polosa, A. D.; Scioscia, G.; Stramaglia, S.; Zenzola, A.

    1999-09-01

    We describe the multiresolution wavelet analysis of blood pressure waves in vasovagal syncope affected patients compared with healthy people. We argue that there exist discriminating criteria which allow us to isolate particular features, common to syncope-affected patients sample, indicating a tentative, alternative diagnosis methodology for this syndrome. We perform a throughout analysis both in the Haar basis and in a Gaussian one, with an attempt to grasp the underlying dynamics.

  18. Shock pressures induced in condensed matter by laser ablation.

    PubMed

    Swift, Damian C; Tierney, Thomas E; Kopp, Roger A; Gammel, J Tinka

    2004-03-01

    The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m(2). States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the velocity history of the opposite surface. By varying the energy in the laser pulse, relations were inferred between the irradiance and the induced pressure. For samples in vacuo, an irradiance constant in time does not produce a constant pressure. Radiation hydrodynamics simulations were used to investigate the relationship between the precise pulse shape and the pressure history. In this regime of time and irradiance, it was possible to reproduce the experimental data to within their uncertainty by including conductivity-dependent deposition of laser energy, heat conduction, gray radiation diffusion, and three temperature hydrodynamics in the treatment of the plasma, with ionizations calculated using the Thomas-Fermi equation. States induced in the solid sample were fairly insensitive to the details of modeling in the plasma, so Hugoniot points may be estimated from experiments of this type given a reasonable model of the plasma. More useful applications include the generation of dynamic loading to investigate compressive strength and phase transitions, and for sample recovery. PMID:15089414

  19. Shock pressures induced in condensed matter by laser ablation

    NASA Astrophysics Data System (ADS)

    Swift, Damian C.; Tierney, Thomas E.; Kopp, Roger A.; Gammel, J. Tinka

    2004-03-01

    The Trident laser was used to induce shock waves in samples of solid elements, with atomic numbers ranging from Be to Au, using pulses of 527 nm light around 1 ns long with irradiances of the order of 0.1 to 10 PW/m2. States induced by the resulting ablation process were investigated using laser Doppler velocimetry to measure the velocity history of the opposite surface. By varying the energy in the laser pulse, relations were inferred between the irradiance and the induced pressure. For samples in vacuo, an irradiance constant in time does not produce a constant pressure. Radiation hydrodynamics simulations were used to investigate the relationship between the precise pulse shape and the pressure history. In this regime of time and irradiance, it was possible to reproduce the experimental data to within their uncertainty by including conductivity-dependent deposition of laser energy, heat conduction, gray radiation diffusion, and three temperature hydrodynamics in the treatment of the plasma, with ionizations calculated using the Thomas-Fermi equation. States induced in the solid sample were fairly insensitive to the details of modeling in the plasma, so Hugoniot points may be estimated from experiments of this type given a reasonable model of the plasma. More useful applications include the generation of dynamic loading to investigate compressive strength and phase transitions, and for sample recovery.

  20. Pressure-induced phase transition in pentacene

    NASA Astrophysics Data System (ADS)

    Farina, L.; Brillante, A.; Della Valle, R. G.; Venuti, E.; Amboage, M.; Syassen, K.

    2003-07-01

    We have recently studied two solid phases of bulk pentacene (polymorphs H and C) by means of lattice phonon Raman spectroscopy. The assignment, previously based on lattice dynamics calculations alone, is now verified by X-ray diffraction measurements, conclusively confirming the existence of both polymorphs. Furthermore, Raman phonon spectra indicate a pressure-induced phase transition where the polymorph C (lower density phase) transforms to the H form (higher density phase). The onset pressure for the phase transition is only 0.2 GPa. The phase change is irreversible.

  1. Pressure-induced transformations in molecular crystals

    SciTech Connect

    Taylor, R.D.; Hearne, G.R. |; Pasternak, M.P.

    1995-09-01

    A review is given on the unique features of the Moessbauer spectroscopy (MS) which by virtue of the quadrupole interaction and the lattice dynamics allows one to characterize some structural properties in the pressure-induced amorphous state of molecular crystals. Experiments were performed in GeI{sub 4}, SnI{sub 4} and SnBr{sub 4} by means of {sup 119}Sn and {sup 129}I MS with pressures to 35 GPa at cryogenic temperatures using diamond anvil cells.

  2. Numerical Investigations of High Pressure Acoustic Waves in Resonators

    NASA Technical Reports Server (NTRS)

    Athavale, Mahesh; Pindera, Maciej; Daniels, Christopher C.; Steinetz, Bruce M.

    2004-01-01

    This presentation presents work on numerical investigations of nonlinear acoustic phenomena in resonators that can generate high-pressure waves using acoustic forcing of the flow. Time-accurate simulations of the flow in a closed cone resonator were performed at different oscillation frequencies and amplitudes, and the numerical results for the resonance frequency and fluid pressure increase match the GRC experimental data well. Work on cone resonator assembly simulations has started and will involve calculations of the flow through the resonator assembly with and without acoustic excitation. A new technique for direct calculation of resonance frequency of complex shaped resonators is also being investigated. Script-driven command procedures will also be developed for optimization of the resonator shape for maximum pressure increase.

  3. Experimental Study Of Metallurgical Evolutions In Metallic Alloys Induced By Laser Generated High Pressure Shocks

    NASA Astrophysics Data System (ADS)

    Fabbro, R.; Fournier, J.; Fabre, E.; Leberichel, E.; Hannau, Th; Corbet, C.

    1986-11-01

    Some preliminary results are presented concerning the damages and the evolutions of metallurgical properties of Fe-C alloys induced by laser shock waves at two different laser wavelengths. In the present work, changes induced by laser shocking have been measured : pressure, microhardness, residual stresses. In addition microstructural variations at the surface and in depth have been observed.

  4. Cavitation inception by the backscattering of pressure waves from a bubble interface

    NASA Astrophysics Data System (ADS)

    Takahira, Hiroyuki; Ogasawara, Toshiyuki; Mori, Naoto; Tanaka, Moe

    2015-10-01

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t0 to a characteristic time of wave propagation tS, η = t0/ts, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  5. Microcantilever Actuation by Laser Induced Photoacoustic Waves.

    PubMed

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided. PMID:26814360

  6. Microcantilever Actuation by Laser Induced Photoacoustic Waves

    PubMed Central

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided. PMID:26814360

  7. Long waves induced motions to rigid spheroids

    NASA Astrophysics Data System (ADS)

    Zhou, Hongkun; Hong, Lianjin

    2015-05-01

    Responses of unconstrained and rigid spheroidal bodies subjected to long sound waves are analyzed by means of approaching hydrodynamic method. It is shown that in the low-frequency approximation the amplitude of translational velocity is completely determined by the density as well as the acoustic added mass which is equal to hydrodynamic one associated with the body. The inconformity of responses to sound waves in virtue of geometric asymmetry is also presented. In addition, rotational movement engendered by acoustic oblique incidence is discussed, and it represents as the modulated angular oscillation similar to the beat-frequency vibration. All these analyses on acoustically induced motions provide a theoretical evidence for developing spheroidal inertial vector receivers.

  8. Microcantilever Actuation by Laser Induced Photoacoustic Waves

    NASA Astrophysics Data System (ADS)

    Gao, Naikun; Zhao, Dongfang; Jia, Ran; Liu, Duo

    2016-01-01

    We present here a combined theoretical and experimental investigation on effective excitation of microcantilever by using photoacoustic waves. The photoacoustic waves arose from a vibrating Al foil induced by an intensity-modulated laser. We demonstrate that, superior to photothermal excitation, this new configuration avoids direct heating of the microcantilever, thus minimizing undesired thermal effects on the vibration of microcantilever, while still keeps the advantage of being a remote, non-contact excitation method. We also measured the vibration amplitude of the microcantilever as a function of distance between the microcantilever and the Al foil and found that the amplitudes decay gradually according to the inverse distance law. This method is universal and can be adopted in bio-microelectromechanical systems (BioMEMs) for the detection of small signals where detrimental thermal effects must be avoided.

  9. Radiation-pressure-driven dust waves inside bursting interstellar bubbles

    NASA Astrophysics Data System (ADS)

    Ochsendorf, B. B.; Verdolini, S.; Cox, N. L. J.; Berné, O.; Kaper, L.; Tielens, A. G. G. M.

    2014-06-01

    Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log (L/L⊙) ≲ 5.2, form and expand because of the thermal pressure that accompanies the ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept-up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, which demonstrates the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions and provide direct evidence that bubbles are relieving their pressure into the interstellar medium through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We explore a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in ultraluminous infrared galaxies, merging galaxies, and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

  10. Current-induced spin wave Doppler shift

    NASA Astrophysics Data System (ADS)

    Bailleul, Matthieu

    2010-03-01

    In metal ferromagnets -namely Fe, Co and Ni and their alloys- magnetism and electrical transport are strongly entangled (itinerant magnetism). This results in a number of properties such as the tunnel and giant magnetoresistance (i.e. the dependence of the electrical resistance on the magnetic state) and the more recently addressed spin transfer (i.e. the ability to manipulate the magnetic state with the help of an electrical current). The spin waves, being the low-energy elementary excitations of any ferromagnet, also exist in itinerant magnets, but they are expected to exhibit some peculiar properties due the itinerant character of the carriers. Accessing these specific properties experimentally could shed a new light on the microscopic mechanism governing itinerant magnetism, which -in turn- could help in optimizing material properties for spintronics applications. As a simple example of these specific properties, it was predicted theoretically that forcing a DC current through a ferromagnetic metal should induce a shift of the frequency of the spin waves [1,2]. This shift can be identified to a Doppler shift undergone by the electron system when it is put in motion by the electrical current. We will show how detailed spin wave measurements allow one to access this current-induced Doppler shift [3]. From an experimental point of view, we will discuss the peculiarities of propagating spin wave spectroscopy experiments carried out at a sub-micrometer length-scale and with MHz frequency resolution. Then, we will discuss the measured value of the Doppler shift in the context of both the old two-current model of spin-polarized transport and the more recent model of adiabatic spin transfer torque. [4pt] [1] P.Lederer and D.L. Mills, Phys.Rev. 148, 542 (1966).[0pt] [2] J. Fernandez-Rossier et al., Phys. Rev. B 69, 174412 (2004)[0pt] [3] V. Vlaminck and M. Bailleul, Science 322, 410 (2008).

  11. Mild neurotrauma indicates a range-specific pressure response to low level shock wave exposure.

    PubMed

    Vandevord, Pamela J; Bolander, Richard; Sajja, Venkata Siva Sai Sujith; Hay, Kathryn; Bir, Cynthia A

    2012-01-01

    Identifying the level of overpressure required to create physiological deficits is vital to advance prevention, diagnostic, and treatment strategies for individuals exposed to blasts. In this study, a rodent model of primary blast neurotrauma was employed to determine the pressure at which acute neurological alterations occurred. Rats were exposed to a single low intensity shock wave at a pressure of 0, 97, 117, or 153 kPa. Following exposure, rats were assessed for acute cognitive alterations using the Morris water maze and motor dysfunction using the horizontal ladder test. Subsequently, histological analyses of three brain regions (primary motor cortex, the hippocampal dentate gyrus region, and the posteromedial cortical amygdala) were conducted. Histological parameters included measuring the levels of glial fibrillary acidic protein (GFAP) to identify astrocyte activation, cleaved caspase-3 for early apoptosis identification and Fluoro-Jade B (FJB) which labels degenerating neurons within the brain tissue. The results demonstrated that an exposure to a single 117 kPa shock wave revealed a significant change in overall neurological deficits when compared to controls and the other pressures. The animals showed significant alterations in water maze parameters and a histological increase in the number of GFAP, caspase-3, and FJB-positive cells. It is suggested that when exposed to a low level shock wave, there may be a biomechanical response elicited by a specific pressure range which can cause low level neurological deficits within the rat. These data indicate that neurotrauma induced from a shock wave may lead to cognitive deficits in short-term learning and memory of rats. Additional histological evidence supports significant and diffuse glial activation and cellular damage. Further investigation into the biomechanical aspects of shock wave exposure is required to elucidate this pressure range-specific phenomenon. PMID:21994066

  12. Pressure wave generated by the Mount St. Helens eruption

    SciTech Connect

    Banister, J.B.

    1984-06-20

    Histories of the air pressure wave radiated from the eruption of Mount St. Helens on May 18, 1980, were calculated for two models of the eruption cloud expansion. The first considered the wave radiated from an accelerated plane surface, while the second examined the wave radiated from an expanding hemisphere. Two histories of eruption cloud motion based on photographs were used. Peak positive overpressures were about the same for these cloud motion histories of expansion into a hemisphere was assumed. If an accelerated planar source model was used, the peak positive pressures have again about the same value in east and west direction, but values are about half in the north and south direction. Observed peak overpressures at microbarograph stations are somewhat higher than the calculated with the most marked departures at the greater surface ranges. These observed overpressures may have been about half the correct values, however. Microbarograph records show a weaker rarefaction than calculated histories or none at all. This can be explained, in part, by a lack of a real motion coherence in the slowing eruption cloud. If it is also possible the net ash cloud volume increased considerably after its vertical growth ceased and weakened the negative phase as well as lengthening the positive phase.

  13. Application of monochromatic ocean wave forecasts to prediction of wave-induced currents

    NASA Technical Reports Server (NTRS)

    Poole, L. R.

    1975-01-01

    The use of monochromatic wind-wave forecasts in prediction of wind-wave-induced currents was assessed. Currents were computed for selected combinations of wind conditions by using a spectrum approach which was developed by using the Bretschneider wave spectrum for partially developed wind seas. These currents were compared with currents computed by using the significant and average monochromatic wave parameters related to the Bretschneider spectrum. Results indicate that forecasts of significant wave parameters can be used to predict surface wind-wave-induced currents. Conversion of these parameters to average wave parameters can furnish reasonable estimates of subsurface current values.

  14. Pressure-induced diffusion in natural garnets

    NASA Astrophysics Data System (ADS)

    Floess, David; Vrijmoed, Johannes; Baumgartner, Lukas; Podladchikov, Yuri

    2015-04-01

    Recent efforts in metamorphic petrology suggest that significant pressure gradients exist on the grain-scale and provide tools for its quantification [1,2]. Here we propose that pressure gradients around coesite inclusions induced diffusion of major elements within garnet crystals upon exhumation. This is based on the fact that the molar mass of garnet endmembers vary between 403 and 497 g/mol, thus up to 23 %. Whiteschists from the Dora Maira Massive in the Western Alps underwent eclogite facies metamorphism (3.3-4.3 GPa, 720-780 °C) during the Alpine event at 35 Ma [3]. Coesite included in garnet (py0.96gr0.02alm0.02) during the HP stage was partially transformed to quartz during the subsequent, rapid exhumation (from 3.5 to 1 GPa within 2 Ma [4]). Coesite is preserved by maintaining a high pressure on the inclusion wall due to the large volume change of the phase transition. The surface of the host garnet experiences a lower pressure controlled by the exhumation P-T path. This pressure difference should induce diffusion of major elements in the garnet surrounding the inclusion. Element distribution maps show well-defined Fe-rich, Ca-poor halos surrounding the coesite-inclusions. The observed diffusion profiles are in agreement with predictions, assuming a positive ΔP around the inclusions. The results are based on thermodynamic equilibrium calculations assuming heterogeneous pressure [5]. Hence, the observed profiles are interpreted as an equilibrium state reflecting the pressure (stress) distribution within the crystal and can be used as tool to constrain the exhumation path. Understanding the effect of pressure gradients on diffusion and, alternatively, the generation of pressure due to relaxation of chemical gradients by diffusion, is crucial for interpreting P-T-t paths of zoned minerals correctly. [1] Baumgartner et al. (2010), GSA meeting Denver. [2] Tajčmanová et al. (2014) CMP 32, 195-207. [3] Compagnoni & Rolfo (2003), UHP Metamorphism - EMU notes 5

  15. Measurement of sound speed vs. depth in South Pole ice: pressure waves and shear waves

    SciTech Connect

    IceCube Collaboration; Klein, Spencer

    2009-06-04

    We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at {approx}5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background.

  16. Wave-induced response of poro-elastic offshore foundations

    SciTech Connect

    Toha, F.X.

    1983-01-01

    A plane strain analysis based on Biot's theory of consolidation is utilized to investigate the pore-water pressures and displacements induced by steady-state linear planar waves beneath offshore gravity structures placed on poro-elastic seabed of finite thickness. The response is characterized by three controlling parameters, i.e., poroelasticity factor, fluid compressibility factor, and Poisson's Ratio. A parametric study, using a range of the controlling parameters encountered in practice, indicates that the response is governed primarily by the poro-elasticity factor and to a lesser extent by Poisson's Ratio (fluid compressibility factor has negligible influence for saturated soils). For offshore gravity structures, the wave-induced moment and horizontal force exerted by the structure on the foundation contribute most to the overall response while the influence of sea water pressure penetration through the sea bottom is, in general, negligible. For smaller structures, however, the latter influence dominates the response for soils as fine as silty sand. The maximum shear strain amplitudes evaluated imply that the soil response remains primarily in the linear elastic range, even for severe storm loadings. An experimental procedure was developed for the measurement of a composite poro-elastic property which combines all the pertinent soil properties. Two test configurations were found to be suitable depending on the hydraulic conductivity of the soil considered. The results of test on nine specimens reconstituted from three soil samples conform with the theoretical estimates and indicate that the developed procedure is viable.

  17. Wave Acceleration Induced Sediment Transport in the Surf Zone

    NASA Astrophysics Data System (ADS)

    Hoefel, F.; Elgar, S.

    2002-12-01

    A bedload sediment transport formulation (Drake and Calantoni, 2001) that accounts for the effects of near-bottom wave-orbital velocity acceleration skewness predicts onshore sandbar migration observed near Duck, NC. Including acceleration effects in an energetics sediment transport model results in improved skill in reproducing cross-shore sandbar migration patterns observed over a 40 day period during which the bar moved both offshore in storms and onshore between storms. These results suggest that skewed acceleration time series, associated with the pitched forward shapes of nearly breaking and broken waves, play an important role in wave-induced sediment transport in the surf zone. The passage of steep wave fronts results in spikes in acceleration when orbital velocities are directed onshore, producing strong horizontal pressure gradient forces that act on the sediment. In contrast to velocity skewness, which remains approximately constant across the surf zone, acceleration skewness is observed to increase from small values offshore to a maximum near the bar crest, and then to decrease toward the shoreline, producing cross-shore spatial gradients in acceleration-driven transport that are consistent with erosion offshore and accretion onshore of the bar crest. As the sandbar migrates shoreward, the maximum of acceleration skewness also moves onshore, causing a positive feedback mechanism that promotes continued onshore sediment transport motion provided the forcing remains constant. Funded by ARO, ONR, and NOPP.

  18. Model of a small surface wave discharge at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Ivanov, A.; Kiss'ovski, Zh

    2016-05-01

    Self-consistent model of a small microwave plasma source based on a surface wave sustained discharge at 2.45 GHz is presented in this study. The model includes dispersion relation of azimuthally symmetric surface waves, sustaining the discharge in a high permittivity ceramic tube (εd = 9.3) and the radial distribution of the field components at curtain values of the electron density are obtained. The electron Boltzmann equation under the local approximation is solved together with the heavy particle balance equations. A detailed collisional-radiative model for argon discharge at atmospheric pressure is implemented in the model. The changes in the EEDF shape and the mean electron energy with the value of the electron density are investigated. Results show that the EEDF is close to Maxwellian at our experimental conditions for the plasma density above 2.1020 (m-3).

  19. Spectroscopy During Laser Induced Shock Wave Lithotripsy

    NASA Astrophysics Data System (ADS)

    Engelhardt, R.; Meyer, W.; Hering, P.

    1988-06-01

    In the course of laser induced shock wave lithotripsy (LISL) by means of a flashlamp pumped dye laser a plasma is formed on the stone's surface. Spectral analysis of the plasma flash leads to chemical stone analysis during the procedure. A time resolved integral analysis of scattered and laser induced fluorescence light makes stone detection possible and avoids tissue damage. We used a 200 μm fiber to transmit a 2 μs, 50 mJ pulse to the stone's surface and a second 200 μ fiber for analysis. This transmission system is small and flexible enough for controlled endoscopic use in the treatment of human ureter or common bile duct stones. Under these conditions the stone selective effect of lasertripsy leads only to minor tissue injury.

  20. Estimating explosive performance from laser-induced shock waves

    NASA Astrophysics Data System (ADS)

    Gottfried, Jennifer

    2015-06-01

    A laboratory-scale method for predicting explosive performance (e.g., detonation velocity and pressure) based on milligram quantities of material is currently being developed. This technique is based on schlieren imaging of the shock wave generated in air by the formation of a laser-induced plasma on the surface of an energetic material. A large suite of pure and composite conventional energetic materials has been tested. Based on the observed linear correlation between the laser-induced shock velocity and the measured performance from full-scale detonation testing, this method is a potential screening tool for the development of new energetic materials and formulations prior to detonation testing. Recent results on the extension of this method to metal-containing energetic materials will be presented.

  1. Tunnel pressure waves - A smartphone inquiry on rail travel

    NASA Astrophysics Data System (ADS)

    Müller, Andreas; Hirth, Michael; Kuhn, Jochen

    2016-02-01

    When traveling by rail, you might have experienced the following phenomenon: The train enters a tunnel, and after some seconds a noticeable pressure change occurs, as perceived by your ears or even by a rapid wobbling of the train windows. The basic physics is that pressure waves created by the train travel down the tunnel, are reflected at its other end, and travel back until they meet the train again. Here we will show (i) how this effect can be well understood as a kind of large-scale outdoor case of a textbook paradigm, and (ii) how, e.g., a prediction of the tunnel length from the inside of a moving train on the basis of this model can be validated by means of a mobile phone measurement.

  2. Pressure-induced Polymerization in Substituted Acetylenes

    NASA Astrophysics Data System (ADS)

    Chellappa, Raja; Dattelbaum, Dana; Sheffield, Stephen; Robbins, David

    2011-06-01

    A fundamental understanding of shock-induced chemical reactions in organics is still lacking and there are limited studies devoted to determining reaction mechanisms, evolution of bonding, and effect of functional group substitutions. The fast timescale of reactions occurring during shock compression create significant experimental challenges (diagnostics) to fully quantify the mechanisms involved. Static compression provides a complementary route to investigate the equilibrium phase space and metastable intermediates during high pressure chemistry, although at a much slower timescale. In this study, we present our results from our ongoing high pressure in situ synchrotron x-ray diffraction and vibrational spectroscopy experiments on substituted acetylenes: tert-butyl acetylene [TBA: (CH3)3 -C ≡CH] and ethynyl trimethylsilane [ETMS: (CH3)3 -Si ≡CH]. We observed that the onset pressure of chemical reactions (at room temperature) in these compounds is significantly higher in static compression (TBA: 11 GPa and ETMS: 26 GPa) when compared to shock input pressures (TBA: 6.1 GPa and ETMS: 6.6 GPa). The products were polymeric in nature, recovered to ambient conditions with little degradation and fully characterized using spectroscopy, calorimetry, and other techniques to identify reaction mechanisms. LDRD-DR (PI: Dana Dattelbaum)

  3. On the Generation of Multiple Atmospheric Pressure Waves Observed During Violent Volcanic Eruptions.

    NASA Astrophysics Data System (ADS)

    Medici, E. F.; Waite, G. P.

    2015-12-01

    One or more atmospheric pressure waves followed by a supersonic jet may be generated during the over pressurized vapor-solid-liquid mixture ejection of a violent volcanic eruption. The source of these multiple atmospheric pressure waves could have different origins. Among the physical mechanisms that could explain these behaviors are pulsating eruptions, the dynamics of shock waves, coupled pressure wave-supersonic jet interaction, or a combination of all these factors. In order to elucidate the causes of these complex fluid flow dynamics, a series of analog volcanic eruption experiments using an atmospheric shock tube were performed. During the testing, single and multiple pressure waves and the subsequent supersonic jet were generated. The controlled laboratory conditions enable studies of the most relevant variables potentially responsible for the formation of the multiple pressure waves. The tests were performed using dry, compressed nitrogen at standard room temperature that was free of particles. Yet, under this idealization of a real volcanic eruption, multiple pressure waves were observed on the high-speed video imaging and recorded on the pressure transducer. The amount of energy being released on each test was varied to achieve different discharge dynamics and the formation of single and multiple pressure waves. The preliminary experimental observations indicate a coupled pressure wave-jet interaction as source of multiple pressure waves.

  4. Pressure-induced metal-insulator transition in spinel compound CuV 2S 4

    NASA Astrophysics Data System (ADS)

    Okada, H.; Koyama, K.; Hedo, M.; Uwatoko, Y.; Watanabe, K.

    2008-04-01

    In order to investigate the pressure effect on electrical properties of CuV 2S 4, we performed the electrical resistivity measurements under high pressures up to 8 GPa for a high-quality polycrystalline sample. The charge density wave (CDW) transition temperatures increase with increasing pressure. The residual resistivity rapidly increases with increasing pressure over 4 GPa, and the temperature dependence of the electrical resistivity at 8 GPa exhibits a semiconducting behavior below about 150 K, indicating that a pressure-induced metal-insulator transition occurs in CuV 2S 4 at 8 GPa.

  5. Pressure-Induced Foaming of Metals

    NASA Astrophysics Data System (ADS)

    García-Moreno, Francisco; Mukherjee, Manas; Jiménez, Catalina; Banhart, John

    2015-05-01

    Pressure-induced foaming (PIF) of metals is a foaming technique in which blowing agent free compacted metal powders are foamed. The method consists of heating hot-compacted metallic precursors to above their melting temperature under gas overpressure and foaming them by pressure release. This study focuses on PIF of Al99.7 and AlSi7 alloys under both air or Ar and overpressures up to 9 bar. In situ x-ray radioscopy allows us to follow the foaming process and to perform quantitative analyses of expansion, foam morphology, and coalescence rate. Mass spectrometry helps to identify hydrogen as the foaming gas. Adsorbates on the former powder particles are found to be the primary gas source. Various advantages of this new method are identified and discussed.

  6. Internal wave pressure, velocity, and energy flux from density perturbations

    NASA Astrophysics Data System (ADS)

    Allshouse, Michael R.; Lee, Frank M.; Morrison, Philip J.; Swinney, Harry L.

    2016-05-01

    Determination of energy transport is crucial for understanding the energy budget and fluid circulation in density varying fluids such as the ocean and the atmosphere. However, it is rarely possible to determine the energy flux field J =p u , which requires simultaneous measurements of the pressure and velocity perturbation fields p and u , respectively. We present a method for obtaining the instantaneous J (x ,z ,t ) from density perturbations alone: A Green's function-based calculation yields p ; u is obtained by integrating the continuity equation and the incompressibility condition. We validate our method with results from Navier-Stokes simulations: The Green's function method is applied to the density perturbation field from the simulations and the result for J is found to agree typically to within 1% with J computed directly using p and u from the Navier-Stokes simulation. We also apply the Green's function method to density perturbation data from laboratory schlieren measurements of internal waves in a stratified fluid and the result for J agrees to within 6 % with results from Navier-Stokes simulations. Our method for determining the instantaneous velocity, pressure, and energy flux fields applies to any system described by a linear approximation of the density perturbation field, e.g., to small-amplitude lee waves and propagating vertical modes. The method can be applied using our matlab graphical user interface EnergyFlux.

  7. Wave-induced dynamics of flexible blades

    NASA Astrophysics Data System (ADS)

    Luhar, M.; Nepf, H. M.

    2016-02-01

    We present an experimental and numerical study that describes the motion of flexible blades, scaled to be dynamically similar to natural aquatic vegetation, forced by wave-induced oscillatory flows. For the conditions tested, blade motion is governed primarily by two dimensionless variables: (i) the Cauchy number, $Ca$, which represents the ratio of the hydrodynamic forcing to the restoring force due to blade stiffness, and (ii) the ratio of the blade length to the wave orbital excursion, $L$. For flexible blades with $Ca \\gg 1$, the relationship between drag and velocity can be described by two different scaling laws at the large- and small-excursion limits. For large excursions ($L \\ll 1$), the flow resembles a unidirectional current and the scaling laws developed for steady-flow reconfiguration studies hold. For small excursions ($L \\gg 1$), the beam equations may be linearized and a different scaling law for drag applies. The experimental force measurements suggest that the small-excursion scaling applies even for intermediate cases with $L \\sim O(1)$. The numerical model employs the well-known Morison force formulation, and adequately reproduces the observed blade dynamics and measured hydrodynamic forces without the use of any fitted parameters. For $Ca \\gg 1$, the movement of the flexible blades reduces the measured and modeled hydrodynamic drag relative to a rigid blade of the same morphology. However, in some cases with $Ca \\sim O(1)$, the measured hydrodynamic forces generated by the flexible blades exceed those generated by rigid blades, but this is not reproduced in the model. Observations of blade motion suggest that this unusual behavior is related to an unsteady vortex shedding event, which the simple numerical model cannot reproduce. Finally, we also discuss implications for the modeling of wave energy dissipation over canopies of natural aquatic vegetation.

  8. Optical Estimation of Depth Induced Wave Breaking Distributions over Complex Bathymetry

    NASA Astrophysics Data System (ADS)

    Keen, A. S.; Holman, R. A.

    2012-12-01

    Parametric depth-induced-breaking dissipation models have shown great skill at predicting time averaged wave heights across the surf zone. First proposed by Battjes & Janssen (1978), these models balance the incoming wave energy flux with a roller dissipation term. This roller dissipation term is estimated by calculating the dissipation for one characteristic broken wave and then multiplying this quantity by the fraction of broken waves. To describe the fraction of broken waves, a typical assumption asserts that wave heights are nearly Rayleigh distributed [Thornton & Guza (1983)] allowing a sea state to be described by only a few parameters. While many experiments have validated the cross shore wave height profiles, few field experiments have been performed to analyze the probability distribution of breaking wave heights over a barred beach profile. The goal of the present research is to determine the distribution of broken and unbroken wave heights across a natural barred beach profile. Field data collected during the Surf Zone Optics experiment (a Multi-disciplinary University Research Initiative) in Duck, North Carolina, consisted of an array of in-situ pressure sensors and optical remote sensing cameras. Sea surface elevation time series from the in-situ pressure sensors are used here to resolve wave height distributions at multiple locations across the surf zone. Breaking wave height distributions are resolved based upon a combination of the pressure sensor and optically based breaker detection algorithm. Since breaking is easily able to be tracked by video imaging, breaking waves are flagged in the sea surface elevation series and binned into a broken wave height distribution. Results of this analysis are compared with model predictions based upon the Battjes & Janssen (1978), Thornton & Guza (1983) and Janssen & Battjes (2007) models to assess the validity of each wave height distribution model.

  9. A Boussinesq-scaled, pressure-Poisson water wave model

    NASA Astrophysics Data System (ADS)

    Donahue, Aaron S.; Zhang, Yao; Kennedy, Andrew B.; Westerink, Joannes J.; Panda, Nishant; Dawson, Clint

    2015-02-01

    Through the use of Boussinesq scaling we develop and test a model for resolving non-hydrostatic pressure profiles in nonlinear wave systems over varying bathymetry. A Green-Nagdhi type polynomial expansion is used to resolve the pressure profile along the vertical axis, this is then inserted into the pressure-Poisson equation, retaining terms up to a prescribed order and solved using a weighted residual approach. The model shows rapid convergence properties with increasing order of polynomial expansion which can be greatly improved through the application of asymptotic rearrangement. Models of Boussinesq scaling of the fully nonlinear O (μ2) and weakly nonlinear O (μN) are presented, the analytical and numerical properties of O (μ2) and O (μ4) models are discussed. Optimal basis functions in the Green-Nagdhi expansion are determined through manipulation of the free-parameters which arise due to the Boussinesq scaling. The optimal O (μ2) model has dispersion accuracy equivalent to a Padé [2,2] approximation with one extra free-parameter. The optimal O (μ4) model obtains dispersion accuracy equivalent to a Padé [4,4] approximation with two free-parameters which can be used to optimize shoaling or nonlinear properties. In comparison to experimental results the O (μ4) model shows excellent agreement to experimental data.

  10. Effect of the initial pressure of multicomponent bubble media on the characteristics of detonation waves

    NASA Astrophysics Data System (ADS)

    Sychev, A. I.

    2016-05-01

    The effect of the initial pressure of multicomponent bubble media on the conditions of initiation, the structure, the velocity, and the pressure of detonation waves is experimentally studied. The variation of the initial pressure of a bubble medium is found to be an effective method to control the parameters of bubble detonation waves.

  11. Optimizing OBS data using shielding and by removing ocean wave loading noise with Pressure and Horizontal Pressure Gradient Sensor Data

    NASA Astrophysics Data System (ADS)

    Webb, Spahr C.; Barclay, Andrew H.

    2016-04-01

    Ocean bottom seismometer (OBS) data, particularly from sites in shallow water are notoriously noisy. Ocean currents generate forces on an unshielded OBS sensor causing time varying tilt that greatly raises noise levels. Shallow burial can mitigate this source of noise, but is expensive and difficult to accomplish, particularly for large fleets of instruments. Large shields can provide significant reduction in noise levels as demonstrated with Cascadia Array OBS data. A recent test deployment investigated the relative motion of the shield and the sensor within the shield, providing guidance on the effectiveness of shielding. Even with shielding or burial, deformation of the seafloor caused by loading by the ocean waves raises seismic noise levels. We have previously shown the vertical component noise can be reduced using data from pressure sensors to predict the vertical deformation and remove it from the vertical record. We recently deployed a new OBS instrument in shallow water (80m) that measured two horizontal components of pressure gradient and show these data can be used to reduce wave induced deformation noise from horizontal component seismic data.

  12. Producing ion waves from acoustic pressure waves in pulsed ICP: Modeling vs. Experiments

    NASA Astrophysics Data System (ADS)

    Despiau-Pujo, Emilie; Cunge, Gilles; Darnon, Maxime; Sadeghi, Nader; Braithwaite, Nicholas

    2015-09-01

    Neutral depletion is an important phenomenon in CW high-density plasmas, mostly caused by gas heating - with a small contribution due to electron pressure Pe - under typical material processing conditions. In pulsed ICP, neutral depletion plays an important role on radical transport in the afterglow. At the beginning of the afterglow, Pe drops rapidly (10 μs) by electron cooling and the gas cools down as well. It generates a neutral pressure gradient between the plasma bulk and the reactor walls, which in turn forces the cold surrounding gas to move rapidly towards the center, thus launching an acoustic wave in the reactor. Fast gas displacement is evidenced by measuring Al atoms drift velocity in the early afterglow of a Cl2/Ar discharge by time-resolved LIF, the acoustic wave in the chamber being observed by mass spectrometry. 2D fluid simulations of Cl2 pulsed ICP predict similar results. These phenomena are further studied during both the plasma ignition and afterglow using modeling and experiments. Strong oscillations are observed both on the Cl2 neutral densities and on the ion flux. As neutrals are pushed towards (or outwards) the chamber walls by the pressure gradient, ions are also pushed in that direction through collisions, as well captured by our ion flux probe.

  13. Influence of flow and pressure on wave propagation in the canine aorta.

    NASA Technical Reports Server (NTRS)

    Histand, M. B.; Anliker, M.

    1973-01-01

    Data on wave speed acquired from 20 anesthetized dogs showed that the thoracic aorta was essentially nondispersive for small artificially generated pressure waves traveling in the downstream or the upstream direction and having frequencies between 40 and 120 Hz. The amplitude of these waves decayed exponentially with the distance traveled. Theoretical studies are cited which have shown that changes in wave speed due to variations in pressure and flow produce marked nonlinear effects in hemodynamics.

  14. Mass Spectrometry of Atmospheric Pressure Surface Wave Discharges

    NASA Astrophysics Data System (ADS)

    Ridenti, M. A.; Souza-Corrêa, J. A.; Amorim, J.

    2016-05-01

    By applying mass spectrometry techniques, we carried out measurements of ionic mass spectrum and their energy distribution in order to investigate an atmospheric argon discharge by using a surfatron surface-wave device. The mass and energy distribution measurements were performed with fixed flow rate (2.5 SLM) of pure argon gas (99.999%) and different Ar-O2 gas mixture compositions (99-1, 98-2 and 97-3). The mass spectra and energy distributions were recorded for Ar+, O+, O+ 2, N+ and N2 +. The axial distribution profiles of ionic mass and their energy were obtained for different experimental conditions as a function of the plasma length. The results showed that the peak of the positive ion energy distributions shifted to higher energies and also that the distribution width increased as the distance between the sampling orifice and the launcher gap was increased. It was also found that under certain experimental conditions the ion flux of atomic species were higher than the ion flux of their diatomic counterpart. The motivation of this study was to obtain a better understanding of a surface wave discharge in atmospheric pressure that may play a key role on new second generation biofuel technologies.

  15. Cavitation inception by the backscattering of pressure waves from a bubble interface

    SciTech Connect

    Takahira, Hiroyuki Ogasawara, Toshiyuki Mori, Naoto Tanaka, Moe

    2015-10-28

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t{sub 0} to a characteristic time of wave propagation t{sub S}, η = t{sub 0}/t{sub s}, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  16. Frequency and wavelength prediction of ultrasonic induced liquid surface waves.

    PubMed

    Mahravan, Ehsan; Naderan, Hamid; Damangir, Ebrahim

    2016-12-01

    A theoretical investigation of parametric excitation of liquid free surface by a high frequency sound wave is preformed, using potential flow theory. Pressure and velocity distributions, resembling the sound wave, are applied to the free surface of the liquid. It is found that for impinging wave two distinct capillary frequencies will be excited: One of them is the same as the frequency of the sound wave, and the other is equal to the natural frequency corresponding to a wavenumber equal to the horizontal wavenumber of the sound wave. When the wave propagates in vertical direction, mathematical formulation leads to an equation, which has resonance frequency equal to half of the excitation frequency. This can explain an important contradiction between the frequency and the wavelength of capillary waves in the two cases of normal and inclined interaction of the sound wave and the free surface of the liquid. PMID:27566141

  17. Statistical properties of wave groups described by group-induced long waves

    NASA Astrophysics Data System (ADS)

    Lin, Weiqi; Huang, Peiji

    1992-03-01

    A new method using group-induced second-order long waves (GSLW) to describe wave groups is presented in this paper on the basis of the GSLW theory by Longuet-Higgins and Steward (1964). In the method, the parabolic relationship between GSLW and the wave envelope is first deduced, and then the distribution function of GSLW amplitude is derived. Thus, the formulae in terms of the moments of GSLW and short wave spectra for the average time duration and the mean length of runs of wave heights exceeding a certain level can be derived. A new groupiness factor equivalent to half the mean wave number in wave groups is defined by taking into account the widths of spectra of GSLW and short waves. Compared with theoretical results of others, ours are closer to measured wave data.

  18. Experimental particle acceleration by water evaporation induced by shock waves

    NASA Astrophysics Data System (ADS)

    Scolamacchia, T.; Alatorre Ibarguengoitia, M.; Scheu, B.; Dingwell, D. B.; Cimarelli, C.

    2010-12-01

    Shock waves are commonly generated during volcanic eruptions. They induce sudden changes in pressure and temperature causing phase changes. Nevertheless, their effects on flowfield properties are not well understood. Here we investigate the role of gas expansion generated by shock wave propagation in the acceleration of ash particles. We used a shock tube facility consisting of a high-pressure (HP) steel autoclave (450 mm long, 28 mm in internal diameter), pressurized with Ar gas, and a low-pressure tank at atmospheric conditions (LP). A copper diaphragm separated the HP autoclave from a 180 mm tube (PVC or acrylic glass) at ambient P, with the same internal diameter of the HP reservoir. Around the tube, a 30 cm-high acrylic glass cylinder, with the same section of the LP tank (40 cm), allowed the observation of the processes occurring downstream from the nozzle throat, and was large enough to act as an unconfined volume in which the initial diffracting shock and gas jet expand. All experiments were performed at Pres/Pamb ratios of 150:1. Two ambient conditions were used: dry air and air saturated with steam. Carbon fibers and glass spheres in a size range between 150 and 210 μm, were placed on a metal wire at the exit of the PVC tube. The sudden decompression of the Ar gas, due to the failure of the diaphragm, generated an initial air shock wave. A high-speed camera recorded the processes between the first 100 μsec and several ms after the diaphragm failure at frame rates ranging between 30,000 and 50,000 fps. In the experiments with ambient air saturated with steam, the high-speed camera allowed to visualize the condensation front associated with the initial air shock; a maximum velocity of 788 m/s was recorded, which decreases to 524 m/s at distance of 0.5 ±0.2 cm, 1.1 ms after the diaphragm rupture. The condensation front preceded the Ar jet front exhausting from the reservoir, by 0.2-0.5 ms. In all experiments particles velocities following the initial

  19. A thoracic mechanism of mild traumatic brain injury due to blast pressure waves.

    PubMed

    Courtney, A C; Courtney, M W

    2009-01-01

    The mechanisms by which blast pressure waves cause mild-to-moderate traumatic brain injury (mTBI) are an open question. Possibilities include acceleration of the head, direct passage of the blast wave via the cranium, and propagation of the blast wave to the brain via a thoracic mechanism. The hypothesis that the blast pressure wave reaches the brain via a thoracic mechanism is considered in light of ballistic and blast pressure wave research. Ballistic pressure waves, caused by penetrating ballistic projectiles or ballistic impacts to body armor, can only reach the brain via an internal mechanism and have been shown to cause cerebral effects. Similar effects have been documented when a blast pressure wave has been applied to the whole body or focused on the thorax in animal models. While vagotomy reduces apnea and bradycardia due to ballistic or blast pressure waves, it does not eliminate neural damage in the brain, suggesting that the pressure wave directly affects the brain cells via a thoracic mechanism. An experiment is proposed which isolates the thoracic mechanism from cranial mechanisms of mTBI due to blast wave exposure. Results have implications for evaluating risk of mTBI due to blast exposure and for developing effective protection. PMID:18829180

  20. Effects of Blood Pressure and Sex on the Change of Wave Reflection: Evidence from Gaussian Fitting Method for Radial Artery Pressure Waveform

    PubMed Central

    Liu, Chengyu; Zhao, Lina; Liu, Changchun

    2014-01-01

    An early return of the reflected component in the arterial pulse has been recognized as an important indicator of cardiovascular risk. This study aimed to determine the effects of blood pressure and sex factor on the change of wave reflection using Gaussian fitting method. One hundred and ninety subjects were enrolled. They were classified into four blood pressure categories based on the systolic blood pressures (i.e., ≤110, 111–120, 121–130 and ≥131 mmHg). Each blood pressure category was also stratified for sex factor. Electrocardiogram (ECG) and radial artery pressure waveforms (RAPW) signals were recorded for each subject. Ten consecutive pulse episodes from the RAPW signal were extracted and normalized. Each normalized pulse episode was fitted by three Gaussian functions. Both the peak position and peak height of the first and second Gaussian functions, as well as the peak position interval and peak height ratio, were used as the evaluation indices of wave reflection. Two-way ANOVA results showed that with the increased blood pressure, the peak position of the second Gaussian significantly shorten (P<0.01), the peak height of the first Gaussian significantly decreased (P<0.01) and the peak height of the second Gaussian significantly increased (P<0.01), inducing the significantly decreased peak position interval and significantly increased peak height ratio (both P<0.01). Sex factor had no significant effect on all evaluation indices (all P>0.05). Moreover, the interaction between sex and blood pressure factors also had no significant effect on all evaluation indices (all P>0.05). These results showed that blood pressure has significant effect on the change of wave reflection when using the recently developed Gaussian fitting method, whereas sex has no significant effect. The results also suggested that the Gaussian fitting method could be used as a new approach for assessing the arterial wave reflection. PMID:25384042

  1. Autapse-induced target wave, spiral wave in regular network of neurons

    NASA Astrophysics Data System (ADS)

    Qin, HuiXin; Ma, Jun; Wang, ChunNi; Chu, RunTong

    2014-10-01

    Autapse is a type of synapse that connects axon and dendrites of the same neuron, and the effect is often detected by close-loop feedback in axonal action potentials to the owned dendritic tree. An artificial autapse was introduced into the Hindmarsh-Rose neuron model, and a regular network was designed to detect the regular pattern formation induced by autapse. It was found that target wave emerged in the network even when only a single autapse was considered. By increasing the (autapse density) number of neurons with autapse, for example, a regular area (2×2, 3×3, 4×4, 5×5 neurons) under autapse induced target wave by selecting the feedback gain and time-delay in autapse. Spiral waves were also observed under optimized feedback gain and time delay in autapses because of coherence-like resonance in the network induced by some electric autapses connected to some neurons. This confirmed that the electric autapse has a critical role in exciting and regulating the collective behaviors of neurons by generating stable regular waves (target waves, spiral waves) in the network. The wave length of the induced travelling wave (target wave, spiral wave), because of local effect of autapse, was also calculated to understand the waveprofile in the network of neurons.

  2. Visualization of ultrasonically induced shear wave propagation using phase sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Nguyen, Thu-Mai; Song, Shaozhen; Arnal, Bastien; Wong, Emily Y.; Wang, Ruikang K.; O'Donnell, Matthew

    2014-02-01

    Shear wave elastography measures the stiffness of soft tissues from the speed of propagating shear waves induced in tissue. Optical coherence tomography (OCT) is a promising detection modality given its high sensitivity and spatial resolution, making it suitable for elastic characterization of skin, peripheral vasculature or ocular tissues. For clinical applications, it would be valuable to use a non-contact shear source. Thus, we propose acoustic radiation force as a remote shear source combined with OCT for visualization. A single-element focused transducer (central frequency 7.5 MHz) was used to apply a maximal pressure of ~3 MPa for 100 μs in agar phantoms. It induced shear waves with an amplitude of several hundreds of nanometers and a broadband spectrum in the kilohertz range. Phasesensitive OCT was used to track shear waves at an equivalent frame rate of 47 kHz. We reconstructed shear modulus maps in a heterogeneous phantom. In addition, we use 3-ms long coded excitation to increase the displacement signal-to-noise ratio. We applied digital pulse compression to the resulting displacement field to obtain a gain of ~15 dB compared to standard pulse excitation while maintaining the US pressure level and the shear wave spatial and temporal resolution. This is a promising result for shear wave generation at low US pressures (~ 1 MPa).

  3. Wave energy and wave-induced flow reduction by full-scale model Posidonia oceanica seagrass

    NASA Astrophysics Data System (ADS)

    Manca, E.; Cáceres, I.; Alsina, J. M.; Stratigaki, V.; Townend, I.; Amos, C. L.

    2012-12-01

    This paper presents results from experiments in a large flume on wave and flow attenuation by a full-scale artificial Posidonia oceanica seagrass meadow in shallow water. Wave height and in-canopy wave-induced flows were reduced by the meadow under all tested regular and irregular wave conditions, and were affected by seagrass density, submergence and distance from the leading edge. The energy of irregular waves was reduced at all components of the spectra, but reduction was greater at the peak spectral frequency. Energy dissipation factors were largest for waves with small orbital amplitudes and at low wave Reynolds numbers. An empirical model, commonly applied to predict friction factors by rough beds, proved applicable to the P. oceanica bed. However at the lowest Reynolds numbers, under irregular waves, the data deviated significantly from the model. In addition, the wave-induced flow dissipation in the lower canopy increased with increasing wave orbital amplitude and increasing density of the mimics. The analysis of the wave-induced flow spectra confirm this trend: the reduction of flow was greatest at the longer period component of the spectra. Finally, we discuss the implications of these findings for sediment dynamics and the role of P. oceanica beds in protecting the shore from erosion.

  4. Earthquake Induced Water Waves in Washington State

    NASA Astrophysics Data System (ADS)

    Barberopoulou, A.; Qamar, A.; Pratt, T. L.

    2003-12-01

    The Mw 7.9 Denali earthquake of 3 November 2002 caused minor damage to at least 20 houseboats by initiating water waves in Lake Union, Seattle, Washington. Damage caused by unusual water activity is not uncommon in Washington State. Newspaper reports show that damage also has been caused by water waves in the Seattle area during local or distant earthquakes in 1899 (Yakutat Bay Alaska earthquake), 1949 (Olympia earthquake) and 1965 (Seattle-Tacoma earthquake). Analysis of Pacific Northwest Seismic Network (PNSN) recordings of the Denali earthquake demonstrates that large water waves are due in part to local amplification of seismic waves by the underlying Seattle sedimentary basin. Simple formulae predict water wave amplitudes only half or smaller than those reported for swimming pools and lakes. Resonance initiated by multiple cycles of surface waves, focusing, and near-shore effects could further amplify the water waves. To understand the type and origins of these water waves, we are examining the response of a water body of rectangular shape and rectangular cross-section subjected to hypothetical forcing functions, and to forcing functions derived from seismograph records of major earthquakes. The results provide estimates of the potential wave heights during future large earthquakes on the nearby subduction zone or on local faults.

  5. Mechanism of membrane poration by shock wave induced nanobubble collapse: a molecular dynamics study.

    PubMed

    Adhikari, Upendra; Goliaei, Ardeshir; Berkowitz, Max L

    2015-05-21

    We performed coarse-grained molecular dynamics simulations in order to understand the mechanism of membrane poration by shock wave induced nanobubble collapse. Pressure profiles obtained from the simulations show that the shock wave initially hits the membrane and is followed by a nanojet produced by the nanobubble collapse. While in the absence of the nanobubble, the shock wave with an impulse of up to 18 mPa s does not create a pore in the membrane, in the presence of a nanobubble even a smaller impulse leads to the poration of the membrane. Two-dimensional pressure maps depicting the pressure distributed over the lateral area of the membrane reveal the differences between these two cases. In the absence of a nanobubble, shock pressure is evenly distributed along the lateral area of the membrane, while in the presence of a nanobubble an unequal distribution of pressure on the membrane is created, leading to the membrane poration. The size of the pore formed depends on both shock wave velocity and shock wave duration. The results obtained here show that these two properties can be tuned to make pores of various sizes. PMID:25903048

  6. Investigations of High Pressure Acoustic Waves in Resonators with Seal-Like Features

    NASA Technical Reports Server (NTRS)

    Daniels, Christopher C.; Steinetz, Bruce M.; Finkbeiner, Joshua R.; Li, Xiao-Fan; Raman, Ganesh

    2004-01-01

    1) Standing waves with maximum pressures of 188 kPa have been produced in resonators containing ambient pressure air; 2) Addition of structures inside the resonator shifts the fundamental frequency and decreases the amplitude of the generated pressure waves; 3) Addition of holes to the resonator does reduce the magnitude of the acoustic waves produced, but their addition does not prohibit the generation of large magnitude non-linear standing waves; 4) The feasibility of reducing leakage using non-linear acoustics has been confirmed.

  7. An application of Love SH waves for the viscosity measurement of triglycerides at high pressures

    NASA Astrophysics Data System (ADS)

    Rostocki, A. J.; Siegoczyński, R. M.; Kiełczyński, P.; Szalewski, M.

    2010-03-01

    A new ultrasonic method of viscosity measurements at a high-pressure conditions has been presented. The method is based on the Love wave amplitude measurement. The same electronic setup as in the Bleustein-Gulyaev (B-G) wave method applied by the authors recently for a high-pressure measurement was adopted. The new sensors were made of metallic materials, which make them more reliable at high-pressure conditions. The method has been successfully applied for the viscosity measurement of some triglycerides at high-pressure conditions up to 1 GPa. The results have been compared with the earlier results obtained using B-G waves. This comparison has shown that Love wave method sensors are more reliable than B-G wave sensors and are also cheaper in fabrication, although the sensitivity of Love wave sensors is lower. During the measurement, the phase transitions in the investigated liquids were observed.

  8. Laser induced plane acoustic wave generation, propagation, and interaction with rigid structures in water

    NASA Astrophysics Data System (ADS)

    Ko, Seung H.; Ryu, Sang G.; Misra, Nipun; Pan, Heng; Grigoropoulos, Costas P.; Kladias, Nick; Panides, Elias; Domoto, Gerald A.

    2008-10-01

    Short pulsed laser induced single acoustic wave generation, propagation, interaction with rigid structures, and focusing in water are experimentally and numerically studied. A large area short duration single plane acoustic wave was generated by the thermoelastic interaction of a homogenized nanosecond pulsed laser beam with a liquid-solid interface and propagated at the speed of sound in water. Laser flash schlieren photography was used to visualize the transient interaction of the plane acoustic wave with various submerged rigid structures [(a) a single block, (b) double blocks, (c) 33° tilted single block, and (d) concave cylindrical acoustic lens configurations]. Excellent agreement between the experimental results and numerical simulation is observed. Our simulation results demonstrate that the laser induced planar acoustic wave can be focused down to several tens of micron size and several bars in pressure.

  9. a Low Cost Pressure Wave Generator Using Diaphragms

    NASA Astrophysics Data System (ADS)

    Caughley, A. J.; Haywood, D. J.; Wang, C.

    2008-03-01

    The high cost of Pressure Wave Generators (PWGs) is a major barrier to the more widespread use of high-efficiency pulse tube and Stirling cryocoolers. This paper describes the development and testing of a low-cost industrial-style PWG which employs metal diaphragms. The use of diaphragms removes the need for rubbing or clearance seals, and eliminates contamination problems by hermetically separating the gas circuit and the lubricated driving mechanism. A conventional low-cost electric motor is used for power input, via a novel high-efficiency kinematic linkage. A first prototype of the diaphragm PWG produced 3.2 kW of PV power with a measured electro-acoustic efficiency of 72%. Accelerated testing predicts a diaphragm life time in excess of 40,000 hours. An additional advantage of the use of diaphragms is the ability to directly cool the gas in the compression space. This eliminates or significantly reduces the requirement for an after cooler, and further decreases the cost of the whole cryocooler system. A pulse tube cryocooler has been successfully run at Industrial Research Ltd to 59K with the diaphragm PWG and no aftercooler. Another pulse tube cryocooler with the diaphragm PWG is undergoing development at Cryomech, the results of which will be given in another presentation.

  10. Nonlinear upper hybrid waves and the induced density irregularities

    SciTech Connect

    Kuo, Spencer P.

    2015-08-15

    Upper hybrid waves are excited parametrically by the O-mode high-frequency heater waves in the ionospheric heating experiments. These waves grow to large amplitudes and self-induced density perturbations provide nonlinear feedback. The lower hybrid resonance modifies the nonlinear feedback driven by the ponderomotive force; the nonlinear equation governing the envelope of the upper hybrid waves is derived. Solutions in symmetric alternating functions, in non-alternating periodic functions, as well as in solitary functions are shown. The impact of lower hybrid resonance on the envelope of the upper hybrid waves is explored; the results show that both the spatial period and amplitude are enlarged. The average fluctuation level of induced density irregularities is also enhanced. In the soliton form, the induced density cavity is widened considerably.

  11. Predicting S-wave velocities for unconsolidated sediments at low effective pressure

    USGS Publications Warehouse

    Lee, Myung W.

    2010-01-01

    Accurate S-wave velocities for shallow sediments are important in performing a reliable elastic inversion for gas hydrate-bearing sediments and in evaluating velocity models for predicting S-wave velocities, but few S-wave velocities are measured at low effective pressure. Predicting S-wave velocities by using conventional methods based on the Biot-Gassmann theory appears to be inaccurate for laboratory-measured velocities at effective pressures less than about 4-5 megapascals (MPa). Measured laboratory and well log velocities show two distinct trends for S-wave velocities with respect to P-wave velocity: one for the S-wave velocity less than about 0.6 kilometer per second (km/s) which approximately corresponds to effective pressure of about 4-5 MPa, and the other for S-wave velocities greater than 0.6 km/s. To accurately predict S-wave velocities at low effective pressure less than about 4-5 MPa, a pressure-dependent parameter that relates the consolidation parameter to shear modulus of the sediments at low effective pressure is proposed. The proposed method in predicting S-wave velocity at low effective pressure worked well for velocities of water-saturated sands measured in the laboratory. However, this method underestimates the well-log S-wave velocities measured in the Gulf of Mexico, whereas the conventional method performs well for the well log velocities. The P-wave velocity dispersion due to fluid in the pore spaces, which is more pronounced at high frequency with low effective pressures less than about 4 MPa, is probably a cause for this discrepancy.

  12. Defect induced guided waves mode conversion

    NASA Astrophysics Data System (ADS)

    Wandowski, Tomasz; Kudela, Pawel; Malinowski, Pawel; Ostachowicz, Wieslaw

    2016-04-01

    This paper deals with analysis of guided waves mode conversion phenomenon in fiber reinforced composite materials. Mode conversion phenomenon may take place when propagating elastic guided waves interact with discontinuities in the composite waveguide. The examples of such discontinuities are sudden thickness change or delamination between layers in composite material. In this paper, analysis of mode conversion phenomenon is based on full wave-field signals. In the full wave-field approach signals representing propagation of elastic waves are gathered from dense mesh of points that span over investigated area of composite part. This allow to animate the guided wave propagation. The reported analysis is based on signals resulting from numerical calculations and experimental measurements. In both cases defect in the form of delamination is considered. In the case of numerical research, Spectral Element Method (SEM) is utilized, in which a mesh is composed of 3D elements. Numerical model includes also piezoelectric transducer. Full wave-field experimental measurements are conducted by using piezoelectric transducer for guided wave excitation and Scanning Laser Doppler Vibrometer (SLDV) for sensing.

  13. The Pressure in a Deep-Water Stokes Wave of Greatest Height

    NASA Astrophysics Data System (ADS)

    Lyons, Tony

    2016-02-01

    In this paper we investigate the qualitative behaviour of the pressure function beneath an extreme Stokes wave over infinite depth. The presence of a stagnation point at the wave-crest of an extreme Stokes wave introduces a number of mathematical difficulties resulting in the irregularity of the free surface profile. It will be proven that the pressure decreases in the horizontal direction between a crest-line and subsequent trough-line, except along these lines themselves where the pressure is stationary with respect to the horizontal coordinate. In addition we will prove that the pressure strictly increases with depth throughout the fluid body.

  14. The Pressure in a Deep-Water Stokes Wave of Greatest Height

    NASA Astrophysics Data System (ADS)

    Lyons, Tony

    2016-06-01

    In this paper we investigate the qualitative behaviour of the pressure function beneath an extreme Stokes wave over infinite depth. The presence of a stagnation point at the wave-crest of an extreme Stokes wave introduces a number of mathematical difficulties resulting in the irregularity of the free surface profile. It will be proven that the pressure decreases in the horizontal direction between a crest-line and subsequent trough-line, except along these lines themselves where the pressure is stationary with respect to the horizontal coordinate. In addition we will prove that the pressure strictly increases with depth throughout the fluid body.

  15. Biological effect of shock waves on rat brain: pathological evaluation by compact Ho:YAG-laser-induced cavitational shock wave generator

    NASA Astrophysics Data System (ADS)

    Nakagawa, Atsuhiro; Hirano, T.; Kusaka, Y.; Sato, Motoyuki; Shirane, R.; Takayama, Kazuya; Yoshimoto, Takashi

    2003-07-01

    To introduce shock wave as a new treatment modality for the lesions in the vicinity of brain and skull, pressure-dependent brain damages after exposure of shock wave were investigated. A novel compact Ho:YAG laser-induced cavitational shock wave generator (diameter: 15 mm, weight: 20g) was used intstead of clinical lithotriptors due to their wide distribution of shock waves. In the first part, we have developed and investigated characteristics of present generator by means of high-speed photography, shadowgraphy, and pressure measurement. Generation of localized shock wave without harmful effect of laser was observed after irradiation of Ho:YAG laser in the brass tube with internal water supply. Mechanical effect of accompanying laser-induced liquid jet was mitigated after placement of latex diaphragm with acrylic water reservoir. Maximum overpressure of generated shock wave was 15 MPa before placement of diaphragm, and 5 MPa after placement of diaphragm. In the second part, shock wave-induced brain damages were investigated in 5 male Sprague-Dawley rats. While subarachnoid hemorrhage could be observed between 1 and 5 MPa, intracerebral hemorrhage, and laceration of tissue were also observed above 5 MPa. We therefore conclude that overpressure of exposing shock wave over brain surface should be managed under 1 MPa.

  16. Trichoscopy of Noncicatricial Pressure-induced Alopecia Resembling Alopecia Areata.

    PubMed

    Papaiordanou, Francine; da Silveira, Bruno Rebelo Lages; Piñeiro-Maceira, Juan; Pirmez, Rodrigo

    2016-01-01

    Pressure-induced alopecia is an unusual cause of hair loss, and reports of its trichoscopic features are scarce. In this paper, we describe a case of pressure-induced alopecia in which trichoscopic and histopathological findings overlap with those described for alopecia areata. PMID:27601865

  17. Trichoscopy of Noncicatricial Pressure-induced Alopecia Resembling Alopecia Areata

    PubMed Central

    Papaiordanou, Francine; da Silveira, Bruno Rebelo Lages; Piñeiro-Maceira, Juan; Pirmez, Rodrigo

    2016-01-01

    Pressure-induced alopecia is an unusual cause of hair loss, and reports of its trichoscopic features are scarce. In this paper, we describe a case of pressure-induced alopecia in which trichoscopic and histopathological findings overlap with those described for alopecia areata. PMID:27601865

  18. Influence of the initial pressure in bubble media on the detonation wave parameters

    NASA Astrophysics Data System (ADS)

    Sychev, A. I.

    2015-04-01

    The influence of the initial pressure in bubble media on the initiation, structure, velocity, and pressure of detonation waves in single-component bubble media is studied. The test medium (bubbles of a stoichiometric acetylene-oxygen mixture in a hydroglyceric solution) falls under the category of "chemically inactive liquid—bubbles of a chemically active gas." It is found that one can effectively control the parameters of bubble detonation waves by varying the initial pressure in the bubble medium.

  19. Practical and highly sensitive elemental analysis for aqueous samples containing metal impurities employing electrodeposition on indium-tin oxide film samples and laser-induced shock wave plasma in low-pressure helium gas.

    PubMed

    Kurniawan, Koo Hendrik; Pardede, Marincan; Hedwig, Rinda; Abdulmadjid, Syahrun Nur; Lahna, Kurnia; Idris, Nasrullah; Jobiliong, Eric; Suyanto, Hery; Suliyanti, Maria Margaretha; Tjia, May On; Lie, Tjung Jie; Lie, Zener Sukra; Kurniawan, Davy Putra; Kagawa, Kiichiro

    2015-09-01

    We have conducted an experimental study exploring the possible application of laser-induced breakdown spectroscopy (LIBS) for practical and highly sensitive detection of metal impurities in water. The spectrochemical measurements were carried out by means of a 355 nm Nd-YAG laser within N2 and He gas at atmospheric pressures as high as 2 kPa. The aqueous samples were prepared as thin films deposited on indium-tin oxide (ITO) glass by an electrolysis process. The resulting emission spectra suggest that concentrations at parts per billion levels may be achieved for a variety of metal impurities, and it is hence potentially feasible for rapid inspection of water quality in the semiconductor and pharmaceutical industries, as well as for cooling water inspection for possible leakage of radioactivity in nuclear power plants. In view of its relative simplicity, this LIBS equipment offers a practical and less costly alternative to the standard use of inductively coupled plasma-mass spectrometry (ICP-MS) for water samples, and its further potential for in situ and mobile applications. PMID:26368882

  20. Pressure-induced disproportionation in CuBr

    NASA Astrophysics Data System (ADS)

    Skelton, E. F.; Webb, A. W.; Qadri, S. B.; Ingalls, R. G.; Traquada, J. M.

    1983-04-01

    CuBr has been pressurized to 8.3 GPa in four separate runs. Prima facie evidence of pressure-induced disproportionation of cuprous bromide into cupric bromide has been observed on release of pressure from 7 GPa. Evidence is also seen of a phase change in CuBr2 above 5.5 GPa.

  1. Relationship between orientation to a blast and pressure wave propagation inside the rat brain.

    PubMed

    Chavko, Mikulas; Watanabe, Tomas; Adeeb, Saleena; Lankasky, Jason; Ahlers, Stephen T; McCarron, Richard M

    2011-01-30

    Exposure to a blast wave generated during an explosion may result in brain damage and related neurological impairments. Several mechanisms by which the primary blast wave can damage the brain have been proposed, including: (1) a direct effect of the shock wave on the brain causing tissue damage by skull flexure and propagation of stress and shear forces; and (2) an indirect transfer of kinetic energy from the blast, through large blood vessels and cerebrospinal fluid (CSF), to the central nervous system. To address a basic question related to the mechanisms of blast brain injury, pressure was measured inside the brains of rats exposed to a low level of blast (~35kPa), while positioned in three different orientations with respect to the primary blast wave; head facing blast, right side exposed to blast and head facing away from blast. Data show different patterns and durations of the pressure traces inside the brain, depending on the rat orientation to blast. Frontal exposures (head facing blast) resulted in pressure traces of higher amplitude and longer duration, suggesting direct transmission and reflection of the pressure inside the brain (dynamic pressure transfer). The pattern of the pressure wave inside the brain in the head facing away from blast exposures assumes contribution of the static pressure, similar to hydrodynamic pressure to the pressure wave inside the brain. PMID:21129403

  2. Head-on collision of shock wave induced vortices with solid and perforated walls

    NASA Astrophysics Data System (ADS)

    Kontis, K.; An, R.; Zare-Behtash, H.; Kounadis, D.

    2008-01-01

    An experimental study has been conducted to examine the interaction of shock wave induced vortices with a flat plate and a perforated plate. The experiments were carried out using a 30mm internal diameter shock-tube at Mach numbers 1.31, 1.49, and 1.61 under critical driver conditions. Air was used both in the driver and driven sections. High-speed schlieren photography was employed to study the flow development and the resulting interactions with the plates. Wall pressure measurements on both plates were also carried out in order to study the flow interactions quantitatively. The experimental results indicated that a region of strong flow development is generated near the wall surface, due to the flow interactions of reflected waves and oncoming induced vortices. This flow behavior causes the generation of multiple pressure fluctuations on the wall. In the case of the perforated plate, a weaker initial reflected wave is produced, which is followed by compression waves, due to the internal reflections within the plate. The transmitted wave is reduced in strength, compared to the initial incident shock wave.

  3. A Non-Intrusive Pressure Sensor by Detecting Multiple Longitudinal Waves.

    PubMed

    Zhou, Hongliang; Lin, Weibin; Ge, Xiaocheng; Zhou, Jian

    2016-01-01

    Pressure vessels are widely used in industrial fields, and some of them are safety-critical components in the system-for example, those which contain flammable or explosive material. Therefore, the pressure of these vessels becomes one of the critical measurements for operational management. In the paper, we introduce a new approach to the design of non-intrusive pressure sensors, based on ultrasonic waves. The model of this sensor is built based upon the travel-time change of the critically refracted longitudinal wave (LCR wave) and the reflected longitudinal waves with the pressure. To evaluate the model, experiments are carried out to compare the proposed model with other existing models. The results show that the proposed model can improve the accuracy compared to models based on a single wave. PMID:27527183

  4. Rogue wave formation under the action of quasi-stationary pressure

    NASA Astrophysics Data System (ADS)

    Abrashkin, A. A.; Oshmarina, O. E.

    2016-05-01

    The process of rogue wave formation on deep water is considered. A wave of extreme amplitude is born against the background of uniform waves (Gerstner waves) under the action of external pressure on free surface. The pressure distribution has a form of a quasi-stationary "pit". The fluid motion is supposed to be a vortex one and is described by an exact solution of equations of 2D hydrodynamics for an ideal fluid in Lagrangian coordinates. Liquid particles are moving around circumferences of different radii in the absence of drift flow. Values of amplitude and wave steepness optimal for rogue wave formation are found numerically. The influence of vorticity distribution and pressure drop on parameters of the fluid is investigated.

  5. Propagation of pore pressure diffusion waves in saturated dual-porosity media (II)

    NASA Astrophysics Data System (ADS)

    Yang, Duoxing; Li, Qi; Zhang, Lianzhong

    2016-04-01

    A mechanism has been established for pressure diffusion waves in dual-porosity media. Pressure diffusion waves are heavily damped with relatively low velocities and short wavelengths. The characteristic frequency dominates the attenuation behavior of pressure diffusions and separates wave fields into two asymptotic regimes: relaxed and unrelaxed. Characteristic delay times control the pressure diffusion between the matrix and the fractures. The transition zones in wavelength and attenuation peak shift toward high frequencies when the characteristic delay time decreases. In contrast, the transition zones in both phase and group velocity shift toward low frequencies as the characteristic time of the delay increases. In a spatially dependent diffusivity field, the pressure diffusion waves in dual-porosity media obey an accumulation-depletion law.

  6. Biological effects of laser-induced stress waves

    SciTech Connect

    Doukas, A.; Lee, S.; McAuliffe, D.

    1995-12-31

    Laser-induced stress waves can be generated by one of the following mechanisms: Optical breakdown, ablation or rapid heating of an absorbing medium. These three modes of laser interaction with matter allow the investigation of cellular and tissue responses to stress waves with different characteristics and under different conditions. The most widely studied phenomena are those of the collateral damage seen in photodisruption in the eye and in 193 run ablation of cornea and skin. On the other hand, the therapeutic application of laser-induced stress waves has been limited to the disruption of noncellular material such as renal stones, atheromatous plaque and vitreous strands. The effects of stress waves to cells and tissues can be quite disparate. Stress waves can fracture tissue, damage cells, and increase the permeability of the plasma membrane. The viability of cell cultures exposed to stress waves increases with the peak stress and the number of pulses applied. The rise time of the stress wave also influences the degree of cell injury. In fact, cell viability, as measured by thymidine incorporation, correlates better with the stress gradient than peak stress. Recent studies have also established that stress waves induce a transient increase of the permeability of the plasma membrane in vitro. In addition, if the stress gradient is below the damage threshhold, the cells remain viable. Thus, stress waves can be useful as a means of drug delivery, increasing the intracellular drug concentration and allowing the use of drugs which are impermeable to the cell membrane. The present studies show that it is important to create controllable stress waves. The wavelength tunability and the micropulse structure of the free electron laser is ideal for generating stress waves with independently adjustable parameters, such as rise time, duration and peak stress.

  7. Quench-induced correlation waves, and quantum grenades

    NASA Astrophysics Data System (ADS)

    Corson, John; Bohn, John

    2016-05-01

    We investigate the wave packet dynamics of a pair of particles that undergoes a rapid change of scattering length. Such quenches have recently become experimentally feasible with fast magnetic-field ramps and optical switching in the vicinity of a Feshbach resonance. The short-range interactions are modelled in the zero-range limit, where the quench is accomplished by switching the boundary condition of the wave function at vanishing particle separation. This generates a correlation wave that propagates rapidly to nonzero particle separations. We have derived universal, analytic results for this process that lead to a simple phase-space picture of quench-induced scattering. Intuitively, the strength of the correlation wave relates to the initial contact of the system. A natural consequence is that the waves are significant when the quench dissociates, at least partially, a bound state. These waves can propagate with high energy from one lattice site to another, potentially triggering highly non-equilibrium dynamics.

  8. Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon

    NASA Astrophysics Data System (ADS)

    Torres-Freyermuth, A.; Mariño-Tapia, I.; Coronado, C.; Salles, P.; Medellín, G.; Pedrozo-Acuña, A.; Silva, R.; Candela, J.; Iglesias-Prieto, R.

    2012-12-01

    Wave-induced extreme water levels in the Puerto Morelos fringing reef lagoon are investigated by means of a phase-resolving non-hydrostatic wave model (SWASH). This model solves the nonlinear shallow water equations including non-hydrostatic pressure. The one-dimensional version of the model is implemented in order to investigate wave transformation in fringing reefs. Firstly, the numerical model is validated with (i) laboratory experiments conducted on a physical model (Demirbilek et al., 2007)and (ii) field observations (Coronado et al., 2007). Numerical results show good agreement with both experimental and field data. The comparison against the physical model results, for energetic wave conditions, indicates that high- and low-frequency wave transformation is well reproduced. Moreover, extreme water-level conditions measured during the passage of Hurricane Ivan in Puerto Morelos are also estimated by the numerical tool. Subsequently, the model is implemented at different along-reef locations in Puerto Morelos. Extreme water levels, wave-induced setup, and infragravity wave energy are estimated inside the reef lagoon for different storm wave conditions (Hs >2 m). The numerical results revealed a strong correlation between the offshore sea-swell wave energy and the setup. In contrast, infragravity waves are shown to be the result of a more complex pattern which heavily relies on the reef geometry. Indeed, the southern end of the reef lagoon provides evidence of resonance excitation, suggesting that the reef barrier may act as either a natural flood protection morphological feature, or as an inundation hazard enhancer depending on the incident wave conditions.

  9. On pressure-shear plate impact for studying the kinetics of stress-induced phase transformations

    NASA Astrophysics Data System (ADS)

    Escobar, Joanne C.; Clifton, Rodney J.

    1992-07-01

    Pressure-shear plate impact experiments are proposed for studying the kinetics of stress-induced phase transformations. The purpose of this paper is to determine loading conditions and specimen orientations which can be expected to activate a single habit plane variant parallel to the impact plane, thereby simplifying the study of the kinetics of the transformation through monitoring the wave profiles associated with the propagating phase boundary. The Wechsler Lieberman-Read phenomenological theory was used to determine habit plane indices and directions of shape deformation for a Cu-Al-Ni shape memory alloy which undergoes a martensitic phase transformation under stress. Elastic waves generated by pressure-shear impact were analyzed for wave propagation in the direction of the normal to a habit plane. A critical resolved shear stress criterion was used to predict variants which are expected to be activated for a range of impact velocities and relative magnitudes of the normal and transverse components of the impact velocity.

  10. Particle transport induced by electrostatic wave fluctuations

    NASA Astrophysics Data System (ADS)

    Rosalem, K. C.; Roberto, M.; Caldas, I. L.

    2015-10-01

    Particle transport driven by electrostatic waves at the plasma edge is numerically investigated, for large aspect ratio tokamaks, by considering a kinetic model derived from guiding-center equations of motion. Initially, the transport is estimated for trajectories obtained from differential equations for a wave spectrum generated by a dominant spatial mode and three time modes. Then, in case of infinite time modes, the differential equations of motion are used to introduce a symplectic map that allows to analyze the particle transport. The particle transport barriers are observed for spatial localized dominant perturbation and infinite modes. In presence of infinite spatial modes, periodic islands arise in between chaotic trajectories at the plasma edge.

  11. Impact induced solitary wave propagation through a woodpile structure

    NASA Astrophysics Data System (ADS)

    Kore, R.; Waychal, A.; Agarwal, S.; Yadav, P.; Uddin, Ahsan; Sahoo, N.; Shelke, A.

    2016-02-01

    In this paper, we investigate solitary wave propagation through a one-dimensional woodpile structure excited by low and high velocity impact. Woodpile structures are a sub-class of granular metamaterial, which supports propagation of nonlinear waves. Hertz contact law governs the behavior of the solitary wave propagation through the granular media. Towards an experimental study, a woodpile structure was fabricated by orthogonally stacking cylindrical rods. A shock tube facility has been developed to launch an impactor on the woodpile structure at a velocity of 30 m s-1. Embedded granular chain sensors were fabricated to study the behavior of the solitary wave. The impact induced stress wave is studied to investigate solitary wave parameters, i.e. contact force, contact time, and solitary wave velocity. With the aid of the experimental setup, numerical simulations, and a theoretical solution based on the long wavelength approximation, formation of the solitary wave in the woodpile structure is validated to a reasonable degree of accuracy. The nondispersive and compact supported solitary waves traveling at sonic wave velocity offer unique properties that could be leveraged for application in nondestructive testing and structural health monitoring.

  12. Pressure-induced referred pain is expanded by persistent soreness.

    PubMed

    Doménech-García, V; Palsson, T S; Herrero, P; Graven-Nielsen, T

    2016-05-01

    Several chronic pain conditions are accompanied with enlarged referred pain areas. This study investigated a novel method for assessing referred pain. In 20 healthy subjects, pressure pain thresholds (PPTs) were recorded and pressure stimuli (120% PPT) were applied bilaterally for 5 and 60 seconds at the infraspinatus muscle to induce local and referred pain. Moreover, PPTs were measured bilaterally at the shoulder, neck, and leg before, during, and after hypertonic saline-induced referred pain in the dominant infraspinatus muscle. The pressure and saline-induced pain areas were assessed on drawings. Subsequently, delayed onset muscle soreness was induced using eccentric exercise of the dominant infraspinatus muscle. The day-1 assessments were repeated the following day (day 2). Suprathreshold pressure stimulations and saline injections into the infraspinatus muscle caused referred pain to the frontal aspect of the shoulder/arm in all subjects. The 60-second pressure stimulation caused larger referred pain areas compared with the 5-second stimulation (P < 0.01). Compared with pressure stimulation, the saline-induced referred pain area was larger (P < 0.02). After saline-induced pain, the PPTs at the infraspinatus and supraspinatus muscles were reduced (P < 0.05), and the 5-second pressure-induced referred pain area was larger than baseline. Pressure pain thresholds at the infraspinatus and supraspinatus muscles were reduced at day 2 in the delayed onset muscle soreness side (P < 0.05). Compared with day 1, larger pressure and saline-induced referred pain areas were observed on day 2 (P < 0.05). Referred pain to the shoulder/arm was consistently induced and enlarged after 1 day of muscle soreness, indicating that the referred pain area may be a sensitive biomarker for sensitization of the pain system. PMID:26808146

  13. The pressure-induced calcium deposition on crosslinked polyurethanes.

    PubMed

    Shunmugakumar, N; Jayabalan, M

    1992-06-01

    The pressure-induced calcium deposition in crosslinked polyurethane was studied. Two polyurethane systems, IPDI-PTMG/PPG-TMP and SMDI-PTMG/PPG-TMP were subjected to calcification under induced pressure. Calcium deposition in IPDI polymers was linear with the increase of soft segment (PTMG) content whereas in SMDI polymers the reverse trend was observed. Decreased phase mixing and hydrophilicity in the polymer (SMDI based) having increased soft segment content was attributed to the decreased calcification. The enhanced amount of calcium deposition under pressure indicates the possible influence of pressure on calcification. PMID:10078255

  14. Pressure induced swelling in microporous materials

    DOEpatents

    Vogt, Thomas; Hriljac, Joseph A.; Lee, Yongjae

    2006-07-11

    A method for capturing specified materials which includes contacting a microporous material with a hydrostatic fluid having at least one specified material carried therein, under pressure which structurally distorts the lattice sufficiently to permit entry of the at least one specified material. The microporous material is capable of undergoing a temporary structural distortion which alters resting lattice dimensions under increased ambient pressure and at least partially returning to rest lattice dimensions when returned to ambient pressure. The pressure of the fluid is then reduced to permit return to at least partial resting lattice dimension while the at least one specified material is therein. By this method, at least one specified material is captured in the microporous material to form a modified microporous material.

  15. Using Clifford Algebra to Understand the Nature of Negative Pressure Waves

    NASA Astrophysics Data System (ADS)

    McClellan, Gene

    2014-03-01

    The geometric algebra of 3-D Euclidean space, a sub-discipline of Clifford algebra, is a useful tool for analyzing wave propagation. We use geometric algebra to explore the concept of negative pressure. In free space a straightforward extension of Maxwell's equations using geometric algebra yields a theory in which classical electromagnetic waves coexist with nonelectromagnetic waves having retrograde momentum. By retrograde momentum we mean waves carrying momentum pointing in the opposite direction of energy flow. If such waves exist, they would have negative pressure. In rebounding from a wall, they would pull rather than push. In this presentation we use standard methods of analyzing energy and momentum conservation and their flow through the surface of an enclosed volume to illustrate the properties of both the electromagnetic and nonelectromagnetic solutions of the extended Maxwell equations. The nonelectromagnetic waves consist of coupled scalar and electric waves and coupled magnetic and pseudoscalar waves. They superimpose linearly with electromagnetic waves. We show that the nonelectromagnetic waves, besides having negative pressure, propagate with the speed of light and do not interact with conserved electric currents. Hence, they have three properties in common with dark energy.

  16. Elastic wave velocities of a MORB at pressures of the mantle transition region

    NASA Astrophysics Data System (ADS)

    Kono, Y.; Higo, Y.; Ohfuji, H.; Ohnishi, I.; Inoue, T.; Irifune, T.

    2006-12-01

    Ultrasonic P- and S-wave velocities of synthetic basalt at around 18 GPa and 1100 °C with MORB composition were measured up to 16 GPa under room temperature conditions. The basalt was synthesized in advance from MORB glass, and was found to consist of well-sintered, microcrystalline garnet and stishovite. Ultrasonic measurement was carried out in a multi-anvil apparatus. Details of the experimental procedures were described in Higo et al. (2006). Pressures were estimated from the load-pressure calibration using ZnTe pressure standard. The result showed a significant increase in both P- and S-wave velocities with increasing pressure, while the pressure dependence of P-wave velocity was larger than that of S-wave velocity. The pressure derivatives of P- and S-wave velocities are 0.07 and 0.02 (km/s)/GPa, respectively. Bulk (K) and shear (G) moduli and their pressure derivatives were calculated directly from the experimentally determined P- and S-wave velocities. The calculated K0 and G0 values were 174 and 104 GPa, respectively. The pressure derivatives of K (4.8) and G (1.5) of the basalt are markedly higher than those of major mineral constituents of mantle transition zone, that is, wadsleyite (4.2 and 1.5, respectively) (Li et al., 2001), ringwoodite (Fo91) (4.3 and 1.2, respectively) and majorite with pyrolite minus olivine composition (4.3 and 1.1, respectively) (Higo et al., unpublished data), for example. Stronger pressure dependence of P- and S-wave velocities is indicated in basaltic composition, as compared with those in pyrolitic or peridotitic compositions under the P-T conditions of the mantle transition zone. Combined ultrasonic and in situ X-ray measurements under high pressure and high temperature conditions for the present MORB composition are also currently being pursued at SPring-8.

  17. Transition from 1D to 2D Laser-Induced Ultrasonic Wave Propagation in an Extended Plate

    NASA Astrophysics Data System (ADS)

    Laloš, Jernej; Požar, Tomaž; Možina, Janez

    2016-05-01

    Optodynamic interaction between a laser pulse and the surface of an opaque, solid elastic object produces transient waves that propagate and reverberate within the object. They can be, in general, categorized into three distinctive types which are all formed through different mechanisms: ablation-induced waves, light-pressure-induced waves, and thermoelastic waves. In this paper, out-of-plane displacements of such waves are simulated at the epicentral position on the opposite side of an extended plane-parallel elastic plate. Wave propagation is mathematically described by Green's transfer functions convolved with suitable time profiles of the incoming laser pulses. The simulated size of the circularly symmetric laser-illuminated area on the plate surface is varied to show the limit-to-limit transition of the displacement waveforms: from a 2D point source to an infinite 1D source.

  18. Xe/+/ -induced ion-cyclotron harmonic waves

    NASA Astrophysics Data System (ADS)

    Jones, D.

    Xenon ion sources on an ejectable package separated from the main payload during the flights of Porcupine rockets F3 and F4 which were launched from Kiruna, Sweden on March 19 and 31, 1979, respectively. The effects of the xenon ion beam, detected by the LF (f less than 16 kHz) wideband electric field experiment and analyzed by using a sonograph, are discussed. Particular attention is given to the stimulation of the ion-cyclotron harmonic waves which are usually linked to the local proton gyro-frequency, but are sometimes related to half that frequency. It was found that in a plasma dominated by O(+) ions, a small amount (1-10%) of protons could cause an effect such that the O(+) cyclotron harmonic waves are set up by the hydrogen ions, the net result being the observation of harmonic emissions separated by the hydrogen ion gyro frequency.

  19. Inducing Peer Pressure to Promote Cooperation

    PubMed Central

    Mani, Ankur; Rahwan, Iyad; Pentland, Alex

    2013-01-01

    Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the ‘tragedy of the commons’ in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome. PMID:23619166

  20. Inducing peer pressure to promote cooperation.

    PubMed

    Mani, Ankur; Rahwan, Iyad; Pentland, Alex

    2013-01-01

    Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the 'tragedy of the commons' in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome. PMID:23619166

  1. Inducing Peer Pressure to Promote Cooperation

    NASA Astrophysics Data System (ADS)

    Mani, Ankur; Rahwan, Iyad; Pentland, Alex

    2013-04-01

    Cooperation in a large society of self-interested individuals is notoriously difficult to achieve when the externality of one individual's action is spread thin and wide on the whole society. This leads to the `tragedy of the commons' in which rational action will ultimately make everyone worse-off. Traditional policies to promote cooperation involve Pigouvian taxation or subsidies that make individuals internalize the externality they incur. We introduce a new approach to achieving global cooperation by localizing externalities to one's peers in a social network, thus leveraging the power of peer-pressure to regulate behavior. The mechanism relies on a joint model of externalities and peer-pressure. Surprisingly, this mechanism can require a lower budget to operate than the Pigouvian mechanism, even when accounting for the social cost of peer pressure. Even when the available budget is very low, the social mechanisms achieve greater improvement in the outcome.

  2. Pressure-induced polyamorphism in salty water.

    PubMed

    Bove, L E; Klotz, S; Philippe, J; Saitta, A M

    2011-03-25

    We investigated the metastable phase diagram of an ionic salt aqueous solution, LiCl:6D₂O, at high pressure and low temperature by neutron diffraction measurements and computer simulations. We show that the presence of salt triggers a stepwise transformation, under annealing at high pressure, to a new very high-density amorphous form. The transition occurs abruptly at 120 K and 2 GPa, is reversible, and is characterized by a sizeable enthalpy release. Simulations suggest that the polyamorphic transition is linked to a local structural reorganization of water molecules around the Li ions. PMID:21517327

  3. Ion radial transport induced by ICRF waves in tokamaks

    SciTech Connect

    Chen, L.; Vaclavik, J.; Hammett, G.W.

    1987-05-01

    The wave-induced fluxes of energetic-trapped ions during ICRF heating of tokamak plasmas are calculated using quasilinear equations. A simple single particle model of this transport mechanism is also given. Both a convective flux proportional to k/sub phi/vertical bar E/sub +/vertical bar/sup 2/ and a diffusive flux proportional to k/sub phi//sup 2/vertical bar E/sub +/vertical bar/sup 2/ are found. Here, k/sub phi/ is the toroidal wave number and E/sub +/ is the left-hand polarized wave field. The convective flux may become significant for large k/sub phi/ if the wave spectrum is asymmetric in k/sub phi/. But for the conditions of most previous experiments, these calculations indicate that radial transport driven directly by the ICRF wave is unimportant.

  4. Laser control of filament-induced shock wave in water

    NASA Astrophysics Data System (ADS)

    Potemkin, F. V.; Mareev, E. I.; Podshivalov, A. A.; Gordienko, V. M.

    2014-09-01

    We discovered that tight focusing of Cr:forsterite femtosecond laser radiation in water provides the unique opportunity of long filament generation. The filament becomes a source of numerous spherical shock waves whose radius tends to saturate with the increase of energy. These overlapping waves create a contrast cylindrical shock wave. The laser-induced shock wave parameters such as shape, amplitude and speed can be effectively controlled by varying energy and focusing geometry of the femtosecond pulse. Aberrations added to the optical scheme lead to multiple dotted plasma sources for shock wave formation, spaced along the optical axis. Increasing the laser energy launches filaments at each dot that enhance the length of the entire filament and as a result, the shock impact on the material.

  5. Pacemaker interactions induce reentrant wave dynamics in engineered cardiac culture

    NASA Astrophysics Data System (ADS)

    Borek, Bartłomiej; Shajahan, T. K.; Gabriels, James; Hodge, Alex; Glass, Leon; Shrier, Alvin

    2012-09-01

    Pacemaker interactions can lead to complex wave dynamics seen in certain types of cardiac arrhythmias. We use experimental and mathematical models of pacemakers in heterogeneous excitable media to investigate how pacemaker interactions can be a mechanism for wave break and reentrant wave dynamics. Embryonic chick ventricular cells are cultured invitro so as to create a dominant central pacemaker site that entrains other pacemakers in the medium. Exposure of those cultures to a potassium channel blocker, E-4031, leads to emergence of peripheral pacemakers that compete with each other and with the central pacemaker. Waves emitted by faster pacemakers break up over the slower pacemaker to form reentrant waves. Similar dynamics are observed in a modified FitzHugh-Nagumo model of heterogeneous excitable media with two distinct sites of pacemaking. These findings elucidate a mechanism of pacemaker-induced reentry in excitable media.

  6. Measuring high pressure equation of state of polystyrene using laser driven shock wave

    NASA Astrophysics Data System (ADS)

    Shu, Hua; Huang, Xiuguang; Ye, Junjian; Wu, Jiang; Jia, Guo; Fang, Zhiheng; Xie, Zhiyong; Zhou, Huazhen; Fu, Sizu

    2015-11-01

    High precision polystyrene equation of state data were measured using laser-driven shock waves with pressures from 180 GPa to 700 GPa. α quartz was used as standard material, the shock wave trajectory in quartz and polystyrene was measured using the Velocity Interferometer for Any Reflector (VISAR). Instantaneous shock velocity in quartz and polystyrene was obtained when the shock wave pass the interface. This provided ~1% precision in shock velocity measurements.

  7. Theoretical calculation of plane wave speeds for alkali metals under pressure.

    NASA Technical Reports Server (NTRS)

    Eftis, J.; Macdonald, D. E.; Arkilic, G. M.

    1971-01-01

    Theoretical calculations of the variation with pressure of small amplitude plane wave speeds are performed for sodium and potassium at zero temperature. The results obtained for wave speeds associated with volume dependent second-order elastic coefficients show better agreement with experimental data than for wave speeds associated with shear dependent coefficients. This result is believed to be due to omission of the band structure correction to the strain energy density.

  8. [Research on the Method of Blood Pressure Monitoring Based on Multiple Parameters of Pulse Wave].

    PubMed

    Miao, Changyun; Mu, Dianwei; Zhang, Cheng; Miao, Chunjiao; Li, Hongqiang

    2015-10-01

    In order to improve the accuracy of blood pressure measurement in wearable devices, this paper presents a method for detecting blood pressure based on multiple parameters of pulse wave. Based on regression analysis between blood pressure and the characteristic parameters of pulse wave, such as the pulse wave transit time (PWTT), cardiac output, coefficient of pulse wave, the average slope of the ascending branch, heart rate, etc. we established a model to calculate blood pressure. For overcoming the application deficiencies caused by measuring ECG in wearable device, such as replacing electrodes and ECG lead sets which are not convenient, we calculated the PWTT with heart sound as reference (PWTT(PCG)). We experimentally verified the detection of blood pressure based on PWTT(PCG) and based on multiple parameters of pulse wave. The experiment results showed that it was feasible to calculate the PWTT from PWTT(PCG). The mean measurement error of the systolic and diastolic blood pressure calculated by the model based on multiple parameters of pulse wave is 1.62 mm Hg and 1.12 mm Hg, increased by 57% and 53% compared to those of the model based on simple parameter. This method has more measurement accuracy. PMID:26964321

  9. Pressure pulse induced-damage in live biological samples

    NASA Astrophysics Data System (ADS)

    Bo, C.; Balzer, J.; Godfrey, S.; Francois, M.; Saffell, J. L.; Rankin, S. M.; Proud, W. G.; Brown, K. A.

    2012-08-01

    Developing a cellular and molecular understanding of the nature of traumatic and post-traumatic effects of blast on live biological samples is critical for improving clinical outcomes. To analyze the effects of blast waves upon the cellular structures and the underlying physiological and biochemical changes, we have constructed an experimental platform capable of delivering compression waves, of amplitudes relevant to blast, to cell suspensions in a contained environment. Initial characterization of the system shows that cell cultures can be subjected to high-intensity compression waves up to 15 MPa in pressure and duration of 80 ± 10μs. Studies of mouse mesenchymal stem cells subjected to two different pressure impulses were analysed by cell counting, cell viability assays and microscopic evaluation: the experiments present evidence suggestive of increased levels of damage and loss of cellular integrity compared to uncompressed cell cultures.

  10. Observable induced gravitational waves from an early matter phase

    SciTech Connect

    Alabidi, Laila; Sasaki, Misao; Kohri, Kazunori; Sendouda, Yuuiti E-mail: kohri@post.kek.jp E-mail: sendouda@cc.hirosaki-u.ac.jp

    2013-05-01

    Assuming that inflation is succeeded by a phase of matter domination, which corresponds to a low temperature of reheating T{sub r} < 10{sup 9}GeV, we evaluate the spectra of gravitational waves induced in the post-inflationary universe. We work with models of hilltop-inflation with an enhanced primordial scalar spectrum on small scales, which can potentially lead to the formation of primordial black holes. We find that a lower reheat temperature leads to the production of gravitational waves with energy densities within the ranges of both space and earth based gravitational wave detectors.

  11. Monochromatic waves induced by large-scale parametric forcing.

    PubMed

    Nepomnyashchy, A; Abarzhi, S I

    2010-03-01

    We study the formation and stability of monochromatic waves induced by large-scale modulations in the framework of the complex Ginzburg-Landau equation with parametric nonresonant forcing dependent on the spatial coordinate. In the limiting case of forcing with very large characteristic length scale, analytical solutions for the equation are found and conditions of their existence are outlined. Stability analysis indicates that the interval of existence of a monochromatic wave can contain a subinterval where the wave is stable. We discuss potential applications of the model in rheology, fluid dynamics, and optics. PMID:20365907

  12. Current-induced spin-wave Doppler shift.

    PubMed

    Vlaminck, Vincent; Bailleul, Matthieu

    2008-10-17

    Spin transfer appears to be a promising tool for improving spintronics devices. Experiments that quantitatively access the magnitude of the spin transfer are required for a fundamental understanding of this phenomenon. By inductively measuring spin waves propagating along a permalloy strip subjected to a large electrical current, we observed a current-induced spin wave Doppler shift that we relate to the adiabatic spin transfer torque. Because spin waves provide a well-defined system for performing spin transfer, we anticipate that they could be used as an accurate probe of spin-polarized transport in various itinerant ferromagnets. PMID:18927387

  13. Pressure-induced superconductivity in europium metal

    SciTech Connect

    Debessai, M.; Matsuoka, T.; Hamlin, J.J.; Bi, W.; Meng, Y.; Shimizu, K.; Schilling, J.S.

    2010-05-24

    Of the 52 known elemental superconductors among the 92 naturally occurring elements in the periodic table, fully 22 only become superconducting under sufficiently high pressure. In the rare-earth metals, the strong local magnetic moments originating from the 4f shell suppress superconductivity. For Eu, however, Johansson and Rosengren have suggested that sufficiently high pressures should promote one of its 4f electrons into the conduction band, changing Eu from a strongly magnetic (J=7/2) 4f{sup 7}-state into a weak Van Vleck paramagnetic (J=0) 4f{sup 6}-state, thus opening the door for superconductivity, as in Am (5f{sup 6}). We report that Eu becomes superconducting above 1.8 K for pressures exceeding 80 GPa, T{sub c} increasing linearly with pressure to 142 GPa at the rate +15 mK/GPa. Eu thus becomes the 53rd elemental superconductor in the periodic table. Synchrotron x-ray diffraction studies to 92 GPa at ambient temperature reveal four structural phase transitions.

  14. Observations of height-dependent pressure-perturbation structure of a strong mesoscale gravity wave

    NASA Technical Reports Server (NTRS)

    Starr, David O'C.; Korb, C. L.; Schwemmer, Geary K.; Weng, Chi Y.

    1992-01-01

    Airborne observations using a downward-looking, dual-frequency, near-infrared, differential absorption lidar system provide the first measurements of the height-dependent pressure-perturbation field associated with a strong mesoscale gravity wave. A pressure-perturbation amplitude of 3.5 mb was measured within the lowest 1.6 km of the atmosphere over a 52-km flight line. Corresponding vertical displacements of 250-500 m were inferred from lidar-observed displacement of aerosol layers. Accounting for probable wave orientation, a horizontal wavelength of about 40 km was estimated. Satellite observations reveal wave structure of a comparable scale in concurrent cirrus cloud fields over an extended area. Smaller-scale waves were also observed. Local meteorological soundings are analyzed to confirm the existence of a suitable wave duct. Potential wave-generation mechanisms are examined and discussed. The large pressure-perturbation wave is attributed to rapid amplification or possible wave breaking of a gravity wave as it propagated offshore and interacted with a very stable marine boundary layer capped by a strong shear layer.

  15. Electromagnetic cyclotron waves in the dayside subsolar outer magnetosphere generated by enhanced solar wind pressure: EMIC wave coherency

    NASA Astrophysics Data System (ADS)

    Remya, B.; Tsurutani, B. T.; Reddy, R. V.; Lakhina, G. S.; Hajra, R.

    2015-09-01

    Electromagnetic ion (proton) cyclotron (EMIC) waves and whistler mode chorus are simultaneously detected in the Earth's dayside subsolar outer magnetosphere. The observations were made near the magnetic equator 3.1°-1.5° magnetic latitude at 1300 magnetic local time from L = 9.9 to 7.0. It is hypothesized that the solar wind external pressure caused preexisting energetic 10-100 keV protons and electrons to be energized in the T⊥ component by betatron acceleration and the resultant temperature anisotropy (T⊥>T∥) formed led to the simultaneous generation of both EMIC (ion) and chorus (electron) waves. The EMIC waves had maximum wave amplitudes of ˜6 nT in a ˜60 nT ambient field B0. The observed EMIC wave amplitudes were about ˜10 times higher than the usually observed chorus amplitudes (˜0.1-0.5 nT). The EMIC waves are found to be coherent to quasi-coherent in nature. Calculations of relativistic ˜1-2 MeV electron pitch angle transport are made using the measured wave amplitudes and wave packet lengths. Wave coherency was assumed. Calculations show that in a ˜25-50 ms interaction with an EMIC wave packet, relativistic electron can be transported ˜27° in pitch. Assuming dipole magnetic field lines for a L = 9 case, the cyclotron resonant interaction is terminated ˜±20° away from the magnetic equator due to lack of resonance at higher latitudes. It is concluded that relativistic electron anomalous cyclotron resonant interactions with coherent EMIC waves near the equatorial plane is an excellent loss mechanism for these particles. It is also shown that E > 1 MeV electrons cyclotron resonating with coherent chorus is an unlikely mechanism for relativistic microbursts. Temporal structures of ˜30 keV precipitating protons will be ˜2-3 s which will be measurable at the top of the ionosphere.

  16. Engineering biphoton wave packets with an electromagnetically induced grating

    SciTech Connect

    Wen Jianming; Xiao Min; Zhai Yanhua; Du Shengwang

    2010-10-15

    We propose to shape biphoton wave packets with an electromagnetically induced grating in a four-level double-{Lambda} cold atomic system. We show that the induced hybrid grating plays an essential role in directing the new fields into different angular positions, especially for the zeroth-order diffraction. A number of interesting features appears in the shaped two-photon wave forms. For example, broadening or narrowing the spectrum would be possible in the proposed scheme even without the use of a cavity.

  17. Wave Journal Bearing. Part 2: Experimental Pressure Measurements and Fractional Frequency Whirl Threshold for Wave and Plain Journal Bearings

    NASA Technical Reports Server (NTRS)

    Walker, James F.; Dimofte, Florin; Addy, Harold E., Jr.

    1995-01-01

    A new hydrodynamic bearing concept, the wave journal bearing, is being developed because it has better stability characteristics than plain journal bearings while maintaining similar load capacity. An analysis code to predict the steady state and dynamic performance of the wave journal bearing is also part of the development. To verify numerical predictions and contrast the wave journal bearing's stability characteristics to a plain journal bearing, tests were conducted at NASA Lewis Research Center using an air bearing test rig. Bearing film pressures were measured at 16 ports located around the bearing circumference at the middle of the bearing length. The pressure measurements for both a plain journal bearing and a wave journal bearing compared favorably with numerical predictions. Both bearings were tested with no radial load to determine the speed threshold for self-excited fractional frequency whirl. The plain journal bearing started to whirl immediately upon shaft start-up. The wave journal did not incur self-excited whirl until 800 to 900 rpm as predicted by the analysis. Furthermore, the wave bearing's geometry limited the whirl orbit to less than the bearing's clearance. In contrast, the plain journal bearing did not limit the whirl orbit, causing it to rub.

  18. Bicycling induced pudendal nerve pressure neuropathy.

    PubMed

    Silbert, P L; Dunne, J W; Edis, R H; Stewart-Wynne, E G

    1991-01-01

    Pudendal neuropathies are well recognised as part of more generalised peripheral neuropathies; however, focal abnormalities of the pudendal nerve due to cycling-related injuries have been infrequently reported. We describe two patients who developed pudendal neuropathies secondary to pressure effects on the perineum from racing-bicycle saddles. Both were male competitive athletes, one of whom developed recurrent numbness of the penis and scrotum after prolonged cycling; the other developed numbness of the penis, an altered sensation of ejaculation, with disturbance of micturition and reduced awareness of defecation. Both patients improved with alterations in saddle position and riding techniques. We conclude that pudendal nerve pressure neuropathy can result from prolonged cycling, particularly when using a poor riding technique. PMID:1821826

  19. The Propagation of Nonlinear Pressure Waves Through Regions of Non-Uniform Temperature

    NASA Astrophysics Data System (ADS)

    Dizinno, Nicholas; Vradis, George; Otugen, Volkan

    2006-11-01

    A numerical study of wave propagation through gases with non-uniform temperature distributions will be presented. The aim of this study is to determine the impact of temperature gradients on high-intensity pressure waves of various initial wave forms. Emphasis is paid to wave reflection and transmission. Ultimately, the performance of thermal barriers in attenuating nonlinear waves is evaluated. The concept of using regions of hot gas inside an ambient environment has potential in aeroacoustic applications, such as jet screech mitigation. This analysis considers the one-dimensional compressible unsteady Euler's equations with an ideal gas state equation. The domain is composed of two regions with uniform and equal gas properties separated by a third region with higher gas temperature (lower density). Pressure is uniform throughout the domain. We introduce various high-intensity wave forms into this medium. Our investigation studies how the shape and extent of the thermal zone affect transmission and reflection of the wave. This is done for a range of wave and thermal field parameters. A Fourier analysis will study the frequency content of the incident, transmitted and reflected waves. These results will help determine the effectiveness of using thermal barriers for nonlinear wave attenuation.

  20. Pressure gradient induced generation of microbubbles

    NASA Astrophysics Data System (ADS)

    Evangelio, Alvaro; Campo-Cortes, Francisco; Gordillo, Jose Manuel

    2015-11-01

    It is well known that the controlled production of monodisperse bubbles possesses uncountable applications in medicine, pharmacy and industry. Here we provide with a detailed physical description of the bubble formation processes taking place in a type of flow where the liquid pressure gradient can be straightforwardly controlled. In our experiments, a gas flow rate discharges through a cylindrical needle into a pressurized chamber. The pressure gradient created from the exit of the injection needle towards the entrance of a extraction duct promotes the stretching of the gas ligament downstream. In our analysis, which is supported by an exhaustive experimental study in which the liquid viscosity is varied by three orders of magnitude, different regimes can be distinguished depending mainly on the Reynolds number. Through our physical modeling, we provide closed expressions for both the bubbling frequencies and for the bubble diameters as well as the conditions under which a monodisperse generation is obtained in all regimes found. The excellent agreement between our expressions and the experimental data fully validates our physical modeling.

  1. Ultrafast Time Response Pressure-Sensitive Paint for Unsteady Shock-Wave Research

    NASA Astrophysics Data System (ADS)

    Numata, Daiju; Asai, Keisuke

    Pressure-Sensitive Paint (PSP) is an optical pressure measurement technique widely used in aerodynamic experiments, and has been applied to unsteady shock-wave phenomena [1, 2]. However, one of the largest problems to apply PSP to high-speed and unsteady phenomena is the response time of PSP.

  2. Wave-particle interactions induced by SEPAC on Spacelab 1 Wave observations

    NASA Technical Reports Server (NTRS)

    Taylor, W. W. L.; Obayashi, T.; Kawashima, N.; Sasaki, S.; Yanagisawa, M.; Burch, J. L.; Reasoner, D. L.; Roberts, W. T.

    1985-01-01

    Space experiments with particle accelerators (SEPAC) flew on Spacelab 1 in November and December 1983. SEPAC included an accelerator which emitted electrons into the ionospheric plasma with energies up to 5 keV and currents up to 300 mA. The SEPAC equipment also included an energetic plasma generator, a neutral gas generator, and an extensive array of diagnostics. The diagnostics included plasma wave detectors, and energetic electron analyzer, a photometer, a high sensitivity television camera, a Langmuir probe and a pressure gage. Twenty-eight experiments were performed during the mission to investigate beam-plasma interactions, electron beam dynamics, plasma beam propagation, and vehicle charging. The wave-particle interactions were monitored by the plasma wave instrumentation, by the energetic electron detector and by the optical detectors. All show evidence of wave-particle interactions, which are described in this paper.

  3. Two Dimensional Finite Element Analysis for the Effect of a Pressure Wave in the Human Brain

    NASA Astrophysics Data System (ADS)

    Ponce L., Ernesto; Ponce S., Daniel

    2008-11-01

    Brain injuries in people of all ages is a serious, world-wide health problem, with consequences as varied as attention or memory deficits, difficulties in problem-solving, aggressive social behavior, and neuro degenerative diseases such as Alzheimer's and Parkinson's. Brain injuries can be the result of a direct impact, but also pressure waves and direct impulses. The aim of this work is to develop a predictive method to calculate the stress generated in the human brain by pressure waves such as high power sounds. The finite element method is used, combined with elastic wave theory. The predictions of the generated stress levels are compared with the resistance of the arterioles that pervade the brain. The problem was focused to the Chilean mining where there are some accidents happen by detonations and high sound level. There are not formal medical investigation, however these pressure waves could produce human brain damage.

  4. Atmospheric planetary waves induced by solar rotation

    NASA Technical Reports Server (NTRS)

    Krivolutsky, A. A.

    1989-01-01

    It is known that there are variations in the atmospheric processes with a period close to that of the rotation of the Sun (27 days). The variations are discovered in tropospheric processes, rainfalls, geopotential and in stratosphere. The main theoretical problem is the identification of the physical process by which these heterogeneous solar and meteorological phenomena are connected. Ivanovsky and Krivolutsky proposed that the periodic heating of the ozone layer by the short wave radiation would be the reason of excitation the 27-day oscillations. It was also assumed that excitement takes place in condition of resonance with an excited mode corresponding to the conditions present in the stratospheric circulations. The possibility is discussed of the resonant excitation and presentation is made of the data analysis results which support this idea.

  5. Amplification of Pressure Waves during Vibrational Equilibration of Excited Chemical Reaction Products

    SciTech Connect

    Tarver, C M

    2004-05-11

    The Non-Equilibrium Zeldovich - von Neumann - Doring (NEZND) theory of self-sustaining detonation identified amplification of pressure wavelets during equilibration of vibrationally excited reaction products in the reaction zone as the physical mechanism by which exothermic chemical energy release sustains detonation waves. This mechanism leads to the formation of the well-known, complex three-dimensional structure of a self-sustaining detonation wave. This amplification mechanism is postulated to be a general property of subsonic and supersonic reactive flows occurring during: shock to detonation transition (SDT); hot spot ignition and growth; deflagration to detonation transition (DDT); flame acceleration by shock or compression waves; and acoustic (sound) wave amplification. The existing experimental and theoretical evidence for pressure wave amplification by chemical energy release into highly vibrationally excited product molecules under these reactive flow conditions is reviewed in this paper.

  6. Pressure-induced magnetic instability in Pd-Ni alloys

    NASA Astrophysics Data System (ADS)

    Oomi, Gendo; Iwai, Sadanori; Ohashi, Masashi; Nakano, Tomohito

    2012-12-01

    The electrical resistivity ρ(T) of dilute Pd-Ni alloys has been measured at high pressure up to 3 GPa. It is found that the ρ(T) of the ferromagnetic Pd-Ni alloy shows an anomalous temperature dependence near the critical pressure Pc, where the ferromagnetism disappears. The results are analysed in the framework of quantum critical behaviour induced by pressure. The effect of magnetic field on the ρ(T) is also examined. Different behaviour of magnetoresistance against pressure was found depending on the alloy concentration and discussed in connection with an instability of ferromagnetism.

  7. Barocaloric effect and the pressure induced solid state refrigerator

    SciTech Connect

    Oliveira, N. A. de

    2011-03-01

    The current refrigerators are based on the heating and cooling of fluids under external pressure variation. The great inconvenience of this refrigeration technology is the damage caused to the environment by the refrigerant fluids. In this paper, we discuss the magnetic barocaloric effect, i.e., the heating or cooling of magnetic materials under pressure variation and its application in the construction of refrigerators using solid magnetic compounds as refrigerant materials and pressure as the external agent. The discussion presented in this paper points out that such a pressure induced solid state refrigerator can be very interesting because it is not harmful to the environment and can exhibit a good performance.

  8. Slipstream-induced pressure fluctuations on a wing panel

    NASA Astrophysics Data System (ADS)

    Ljunggren, Sten; Samuelsson, Ingemar; Widig, Kurt

    1989-10-01

    Propeller-induced pressure fluctuations have been measured on a wind-tunnel model. The results show that the main contribution on the wing panels can be attributed to the propeller tip vortex, which gives a pressure level at least 20 dB above the level from the inner parts of the propeller. The pressure fluctuations are predominantly periodic and the spectrum shows strong peaks at the blade passage frequency and its harmonics. The pressure level at the blade passage frequency is approximately the same on wing panel and fuselage, while the level of the higher harmonics is substantially higher on the wing panel than on the fuselage.

  9. Characterization of laser-driven shock waves in solids using a fiber optic pressure probe

    SciTech Connect

    Cranch, Geoffrey A.; Lunsford, Robert; Grun, Jacob; Weaver, James; Compton, Steve; May, Mark; Kostinski, Natalie

    2013-11-08

    Measurement of laser-driven shock wave pressure in solid blocks of polymethyl methacrylate is demonstrated using fiber optic pressure probes. Three probes based on a fiber Fabry–Perot, fiber Bragg grating, and interferometric fiber tip sensor are tested and compared. Shock waves are generated using a high-power laser focused onto a thin foil target placed in close proximity to the test blocks. The fiber Fabry–Perot sensor appears capable of resolving the shock front with a rise time of 91 ns. As a result, the peak pressure is estimated, using a separate shadowgraphy measurement, to be 3.4 GPa.

  10. Surface modification by subsurface pressure induced diffusion

    SciTech Connect

    Zimmermann, Claus G.

    2012-01-23

    Polycrystalline Ag, covered with a nm thin siloxane layer, was irradiated with ultraviolet light in vacuum at 500 K. Ag particles of different aspect ratios, 50-1000 nm in size, formed on the surface, including a small fraction of nanorods. Pressurized water vapor bubbles are created in the subsurface region by hydrogen radicals photo-chemically released by the siloxane layer. They provide the driving force for a diffusive material flux along grain boundaries to the surface. This mechanism was modeled and found to agree with the experimental timescale: approximately 300 h are required for a 1000 nm particle to form.

  11. Quantification of wave reflection in the human aorta from pressure alone: a proof of principle.

    PubMed

    Westerhof, Berend E; Guelen, Ilja; Westerhof, Nico; Karemaker, John M; Avolio, Alberto

    2006-10-01

    Wave reflections affect the proximal aortic pressure and flow waves and play a role in systolic hypertension. A measure of wave reflection, receiving much attention, is the augmentation index (AI), the ratio of the secondary rise in pressure and pulse pressure. AI can be limiting, because it depends not only on the magnitude of wave reflection but also on wave shapes and timing of incident and reflected waves. More accurate measures are obtainable after separation of pressure in its forward (P(f)) and reflected (P(b)) components. However, this calculation requires measurement of aortic flow. We explore the possibility of replacing the unknown flow by a triangular wave, with duration equal to ejection time, and peak flow at the inflection point of pressure (F(tIP)) and, for a second analysis, at 30% of ejection time (F(t30)). Wave form analysis gave forward and backward pressure waves. Reflection magnitude (RM) and reflection index (RI) were defined as RM=P(b)/P(f) and RI=P(b)/(P(f)+P(b)), respectively. Healthy subjects, including interventions such as exercise and Valsalva maneuvers, and patients with ischemic heart disease and failure were analyzed. RMs and RIs using F(tIP) and F(t30) were compared with those using measured flow (F(m)). Pressure and flow were recorded with high fidelity pressure and velocity sensors. Relations are: RM(tIP)=0.82RM(mf)+0.06 (R(2)=0.79; n=24), RM(t30)=0.79RM(mf)+0.08 (R(2)=0.85; n=29) and RI(tIP)=0.89RI(mf)+0.02 (R(2)=0.81; n=24), RI(t30)=0.83RI(mf)+0.05 (R(2)=0.88; n=29). We suggest that wave reflection can be derived from uncalibrated aortic pressure alone, even when no clear inflection point is distinguishable and AI cannot be obtained. Epidemiological studies should establish its clinical value. PMID:16940207

  12. Low-pressure sustainment of surface-wave microwave plasma with modified microwave coupler

    NASA Astrophysics Data System (ADS)

    Sasai, Kensuke; Suzuki, Haruka; Toyoda, Hirotaka

    2016-01-01

    Sustainment of long-scale surface-wave plasma (SWP) at pressures below 1 Pa is investigated for the application of the SWP as an assisting plasma source for roll-to-roll sputter deposition. A modified microwave coupler (MMC) for easier surface-wave propagation is proposed, on the basis of the concept of the power direction alignment of the slot antenna and surface-wave propagation. The superiority of the MMC-SWP over conventional SWPs is shown at a sustainment pressure as low as 0.6 Pa and an electron density as high as 3 × 1017 m-3. A polymer film is treated with the MMC-SWP at a low pressure of 0.6 Pa, and surface modification at a low pressure is proved using Ar plasma. These results show the availability of the MMC-SWP as the surface treatment plasma source that is compatible with sputter deposition in the same processing chamber.

  13. New ultrasonic Bleustein-Gulyaev wave method for measuring the viscosity of liquids at high pressure

    NASA Astrophysics Data System (ADS)

    Kiełczyński, P.; Szalewski, M.; Siegoczyński, R. M.; Rostocki, A. J.

    2008-02-01

    In this paper, a new method for measuring the viscosity of liquids at high pressure is presented. To this end the authors have applied an ultrasonic method using the Bleustein-Gulyaev (BG) surface acoustic wave. By applying the perturbation method, we can prove that the change in the complex propagation constant of the BG wave produced by the layer of liquid loading the waveguide surface is proportional to the shear mechanical impedance of the liquid. In the article, a measuring setup employing the BG wave for the purpose of measuring the viscosity of liquids at high pressure (up to 1GPa) is presented. The results of high-pressure viscosity measurements of triolein and castor oil are also presented. In this paper the model of a Newtonian liquid was applied. Using this new method it is also possible to measure the viscosity of liquids during the phase transition and during the decompression process (hysteresis of the dependence of viscosity on pressure).

  14. Inositol 1,4,5-trisphosphate induced calcium waves

    NASA Astrophysics Data System (ADS)

    Falcke, M.

    Traveling waves of high concentration of Ca2+ are observed in many different cells and have attracted great interest in experimental and theoretical biological research in recent years. They are created by the nonlinear dynamics of the release and uptake of Ca2+ by intracellular Ca2+ stores like the endoplasmatic or sarcoplasmatic reticulum. Their characteristics depend on other cellular organelles and components like mitochondria and Ca2+ buffers too. Here, we present some mathematical models and results of recent research on intracellular Ca2+ waves generated by the inositol 1,4,5-trisphosphate receptor channel including the modeling of Calcium induced Calcium release, buffer dynamics, impact of mitochondria on wave formation and the effect of the spatial discreteness of the channels releasing Ca2+. Modeling of the communication of Ca2+ waves to adjacent cells through gap junctions concludes this report.

  15. Modelling and Experimental Verification of Pressure Wave Following Gaseous Helium Storage Tank Rupture

    NASA Astrophysics Data System (ADS)

    Chorowski, M.; Grabowski, M.; Jędrusyna, A.; Wach, J.

    Helium inventory in high energy accelerators, tokamaks and free electron lasers may exceed tens of tons. The gaseous helium is stored in steel tanks under a pressure of about 20 bar and at environment temperature. Accidental rupture of any of the tanks filled with the gaseous helium will create a rapid energy release in form of physical blast. An estimation of pressure wave distribution following the tank rupture and potential consequences to the adjacent research infrastructure and buildings is a very important task, critical in the safety aspect of the whole cryogenic system. According to the present regulations the TNT equivalent approach is to be applied to evaluate the pressure wave following a potential gas storage tank rupture. A special test stand was designed and built in order to verify experimentally the blast effects in controlled conditions. In order to obtain such a shock wave a pressurized plastic tank was used. The tank was ruptured and the resulting pressure wave was recorded using a spatially-distributed array of pressure sensors connected to a high-speed data acquisition device. The results of the experiments and the comparison with theoretical values obtained from thermodynamic model of the blast are presented. A good agreement between the simulated and measured data was obtained. Recommendations regarding the applicability of thermodynamic model of physical blast versus TNT approach, to estimate consequences of gas storage tank rupture are formulated. The laboratory scale experimental results have been scaled to ITER pressurized helium storage tanks.

  16. Shock pressure induced by glass-confined laser shock peening: Experiments, modeling and simulation

    SciTech Connect

    Wu Xianqian; Song Hongwei; Wei Yanpeng; Wang Xi; Huang Chenguang; Duan Zhuping

    2011-09-01

    The shock pressure generated by the glass confined regime in laser shock peening and its attenuation in the target material are investigated. First, the particle velocity of the target back free surface induced by laser generated shock pressure of this regime is measured using a photonic Doppler velocimetry system. The temporal profile of the particle velocity at the back free surface, where the elastic precursor is captured, manifests a powerful diagnostic capability of this newly developed photonic Doppler velocimetry system for tracking the velocity on short time scales in shock-wave experiments. Second, a coupling pressure analytical model, in which the material constitutive models of confined layers and target material are considered, is proposed to predict the plasma pressure profile at the surface of target. Furthermore, using the predicted shock pressure profile as the input condition, the dynamic response of the target under the shock pressure is simulated by LS-DYNA. The simulated back free surface velocity profile agrees well with that measured by the photonic Doppler velocimetry system. Finally, the attenuation behavior of stress waves and particle velocities in the depth of the target is analyzed, and it indicates an exponential decay. The corresponding empirical formulas for the attenuation behavior are given based on the numerical results.

  17. Eliminating pulse-induced artifacts in Urethral Pressure data.

    PubMed

    Klunder, Mario; Feuer, Ronny; Amend, Bastian; Kelp, Alexandra; Stenzl, Arnulf; Sievert, Karl-Dietrich; Sawodny, Oliver; Ederer, Michael

    2015-08-01

    Urethral Pressure Profilometry (UPP) is a tool in the diagnosis of urinary incontinence. The pressure profile along the urethra is measured by a special catheter in order to assess the contraction strength of the sphincter muscle. The use of microtip catheters with several pressure sensors and an integrated acceleration sensor enables signal reconstruction of the pressure distribution on the urethra's inside. Experimental data from minipigs exhibit artifact patterns in the pressure data. It is shown that these artifacts are caused by vascular pulsation in the sphincter structure. We therefore investigate different methods exploiting the time-correlation of the artifacts to eliminate pulse-induced artifacts in the pressure data without compromising the actual signal. Evaluation of these methods applied to experimental data conclude this work showing that both an Input-Model and Principal Component Analysis Decorrelation are effective at removing the artifacts. PMID:26736868

  18. Pressure-induced metallization of molybdenum disulfide.

    PubMed

    Chi, Zhen-Hua; Zhao, Xiao-Miao; Zhang, Haidong; Goncharov, Alexander F; Lobanov, Sergey S; Kagayama, Tomoko; Sakata, Masafumi; Chen, Xiao-Jia

    2014-07-18

    X-ray diffraction, Raman spectroscopy, and electrical conductivity measurements of molybdenum disulfide MoS(2) are performed at pressures up to 81 GPa in diamond anvil cells. Above 20 GPa, we find discontinuous changes in Raman spectra and x-ray diffraction patterns which provide evidence for isostructural phase transition from 2H(c) to 2H(a) modification through layer sliding previously predicted theoretically. This first-order transition, which is completed around 40 GPa, is characterized by a collapse in the c-lattice parameter and volume and also by changes in interlayer bonding. After the phase transition completion, MoS(2) becomes metallic. The reversibility of the phase transition is identified from all these techniques. PMID:25083660

  19. The impact of hepatic pressurization on liver shear wave speed estimates in constrained versus unconstrained conditions

    NASA Astrophysics Data System (ADS)

    Rotemberg, V.; Palmeri, M.; Nightingale, R.; Rouze, N.; Nightingale, K.

    2012-01-01

    Increased hepatic venous pressure can be observed in patients with advanced liver disease and congestive heart failure. This elevated portal pressure also leads to variation in acoustic radiation-force-derived shear wave-based liver stiffness estimates. These changes in stiffness metrics with hepatic interstitial pressure may confound stiffness-based predictions of liver fibrosis stage. The underlying mechanism for this observed stiffening behavior with pressurization is not well understood and is not explained with commonly used linear elastic mechanical models. An experiment was designed to determine whether the stiffness increase exhibited with hepatic pressurization results from a strain-dependent hyperelastic behavior. Six excised canine livers were subjected to variations in interstitial pressure through cannulation of the portal vein and closure of the hepatic artery and hepatic vein under constrained conditions (in which the liver was not free to expand) and unconstrained conditions. Radiation-force-derived shear wave speed estimates were obtained and correlated with pressure. Estimates of hepatic shear stiffness increased with changes in interstitial pressure over a physiologically relevant range of pressures (0-35 mmHg) from 1.5 to 3.5 m s-1. These increases were observed only under conditions in which the liver was free to expand while pressurized. This behavior is consistent with hyperelastic nonlinear material models that could be used in the future to explore methods for estimating hepatic interstitial pressure noninvasively.

  20. A mechanism for sustained groundwater pressure changes induced by distant earthquakes

    USGS Publications Warehouse

    Brodsky, E.E.; Roeloffs, E.; Woodcock, D.; Gall, I.; Manga, M.

    2003-01-01

    Large sustained well water level changes (>10 cm) in response to distant (more than hundreds of kilometers) earthquakes have proven enigmatic for over 30 years. Here we use high sampling rates at a well near Grants Pass, Oregon, to perform the first simultaneous analysis of both the dynamic response of water level and sustained changes, or steps. We observe a factor of 40 increase in the ratio of water level amplitude to seismic wave ground velocity during a sudden coseismic step. On the basis of this observation we propose a new model for coseismic pore pressure steps in which a temporary barrier deposited by groundwater flow is entrained and removed by the more rapid flow induced by the seismic waves. In hydrothermal areas, this mechanism could lead to 4 ?? 10-2 MPa pressure changes and triggered seismicity.

  1. Characteristics of laser-induced shock wave injury to the inner ear of rats

    NASA Astrophysics Data System (ADS)

    Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro

    2014-12-01

    Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury.

  2. Characteristics of laser-induced shock wave injury to the inner ear of rats.

    PubMed

    Kurioka, Takaomi; Matsunobu, Takeshi; Niwa, Katsuki; Tamura, Atsushi; Kawauchi, Satoko; Satoh, Yasushi; Sato, Shunichi; Shiotani, Akihiro

    2014-12-01

    Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury. PMID:25467523

  3. Wave-induced topographic formstress in baroclinic channel flow

    NASA Astrophysics Data System (ADS)

    Olbers, Dirk; Lettmann, Karsten; Wolff, Jörg-Olaf

    2007-12-01

    Large-scale zonal flow driven across submarine topography establishes standing Rossby waves. In the presence of stratification, the wave pattern can be represented by barotropic and baroclinic Rossby waves of mixed planetary topographic nature, which are locked to the topography. In the balance of momentum, the wave pattern manifests itself as topographic formstress. This wave-induced formstress has the net effect of braking the flow and reducing the zonal transport. Locally, it may lead to acceleration, and the parts induced by the barotropic and baroclinic waves may have opposing effects. This flow regime occurs in the circumpolar flow around Antarctica. The different roles that the wave-induced formstress plays in homogeneous and stratified flows through a zonal channel are analyzed with the BARBI (BARotropic-Baroclinic-Interaction ocean model, Olbers and Eden, J Phys Oceanogr 33:2719-2737, 2003) model. It is used in complete form and in a low-order version to clarify the different regimes. It is shown that the barotropic formstress arises by topographic locking due to viscous friction and the baroclinic one due to eddy-induced density advection. For the sinusoidal topography used in this study, the transport obeys a law in which friction and wave-induced formstress act as additive resistances, and windstress, the effect of Ekman pumping on the density stratification, and the buoyancy forcing (diapycnal mixing of the stratified water column) of the potential energy stored in the stratification act as additive forcing functions. The dependence of the resistance on the system parameters (lateral viscosity ɛ, lateral diffusivity κ of eddy density advection, Rossby radius λ, and topography height δ) as well as the dependence of transport on the forcing functions are determined. While the current intensity in a channel with homogeneous density decreases from the viscous flat bottom case in an inverse quadratic law ~ δ -2 with increasing

  4. Optimization of pressure waveform, distribution and sequence in shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Zhou, Yufeng

    This work aims to improve shock wave lithotripsy (SWL) technology by increasing stone comminution efficiency while reducing simultaneously the propensity of tissue injury. First, the mechanism of vascular injury in SWL was investigated. Based on in vitro vessel phantom experiment and theoretical calculation, it was found that SWL-induced large intraluminal bubble expansion may constitute a primary mechanism for the rupture of capillaries and small blood vessels. However, when the large intraluminal bubble expansion is suppressed by inversion of the pressure waveform of the lithotripter shock wave (LSW), rupture of a 200-mum cellulose hollow fiber vessel phantom can be avoided. Based on these experimental observations and theoretical assessment of bubble dynamics using the Gilmore model an in situ pulse superposition technique was developed to reduce tissue injury without compromising stone comminution in SWL. A thin shell ellipsoidal reflector insert was fabricated to fit snugly with the original HM-3 reflector. Using the Hamilton model, the effects of reflector geometry on the pulse profile and sequence of the shock waves were evaluated qualitatively. Guided by this analysis, the design of the reflector insert had been refined to suppress the intraluminal bubble expansion, which was confirmed by high-speed imaging of bubble dynamics both in free field and inside a vessel phantom. The pulse pressure, beam size and stone comminution efficiency of the upgraded reflector were all found to be comparable to those of the original reflector. However, the greatest difference lies in the propensity for tissue injury. At the lithotripter focus, about 30 shocks are needed to cause a rupture of the vessel phantom using the original reflector, but no rupture can be produced after 200 shocks by the upgraded reflector. Overall, the upgraded reflector could significantly reduce the propensity of vessel rupture while maintaining satisfactory stone comminution. Second, to improve

  5. Prediction of the characteristics of two types of pressure waves in the cochlea: Theoretical considerations

    NASA Astrophysics Data System (ADS)

    Andoh, Masayoshi; Wada, Hiroshi

    2004-07-01

    The aim of this study was to predict the characteristics of two types of cochlear pressure waves, so-called fast and slow waves. A two-dimensional finite-element model of the organ of Corti (OC), including fluid-structure interaction with the surrounding lymph fluid, was constructed. The geometry of the OC at the basal turn was determined from morphological measurements of others in the gerbil hemicochlea. As far as mechanical properties of the materials within the OC are concerned, previously determined mechanical properties of portions within the OC were adopted, and unknown mechanical features were determined from the published measurements of static stiffness. Time advance of the fluid-structure scheme was achieved by a staggered approach. Using the model, the magnitude and phase of the fast and slow waves were predicted so as to fit the numerically obtained pressure distribution in the scala tympani with what is known about intracochlear pressure measurement. When the predicted pressure waves were applied to the model, the numerical result of the velocity of the basilar membrane showed good agreement with the experimentally obtained velocity of the basilar membrane documented by others. Thus, the predicted pressure waves appeared to be reliable. Moreover, it was found that the fluid-structure interaction considerably influences the dynamic behavior of the OC at frequencies near the characteristic frequency.

  6. Wave-induced seepage and its possible contribution to the formation of pockmarks in the Huanghe (Yellow) River delta

    NASA Astrophysics Data System (ADS)

    Wang, Hu; Liu, Hongjun; Zhang, Minsheng; Wang, Xiuhai

    2016-01-01

    Wave-induced seepage and its possible contribution to the formation of pockmarks in the Huanghe (Yellow) River delta were investigated experimentally and numerically. Laboratory experiments were carried out to explore the response of a layered silty seabed with various saturation conditions under cyclic wave loads, in which the pore pressure and seepage-related phenomena were particularly monitored. Numerical models to simulate wave-induced seepage in the seabed were presented and evaluated, then applied to the Huanghe River delta. The experimental results show that the excess pore pressure decreases more rapidly at the surface layer, while the seepage-related phenomena are more pronounced when large cyclic loads are applied and the underlying layer is less saturated. The proposed numerical models were verified by comparing with the experiments. The calculated seepage depth agreed well with the depth of the pockmarks in the Huanghe River delta. The experimental and numerical results and the existing insitu investigations indicate that the wave-induced seepage may be a direct cause of the pockmarks in the Huanghe River delta. Extreme storm waves and the dual-layered structure of hard surface layer and weak underlying layer are essential external and internal factors, respectively. Wave- or current-induced scour and transport are possible contributors to the reformation of pockmarks at a later stage.

  7. Pressure waves generated by metastable intermolecular composites in an aqueous environment

    NASA Astrophysics Data System (ADS)

    Maines, G.; Radulescu, M.; Bacciochini, A.; Jodoin, B.; Lee, J. J.

    2014-05-01

    In the present study, pressure waves generated by a metastable intermolecular composite (MIC) have been measured experimentally in an aqueous environment and correlated with flame speed measurements. Underwater experiments were performed in a 1.0 L high-pressure chamber mounted with high-resolution pressure transducers and designed with optical access. Samples consisting of a stoichiometric mixture of aluminium and copper(II)-oxide particles were evaluated. Two types of samples were synthesized; a mixture of micron-sized raw powders, and ball-milled powders with a fine-scale nano-structure. A planetary mill was used to refine reactant powders from micron- to nano-scale dimensions. The dynamics of the pressure wave and high-pressure gas bubble were monitored via pressure histories and high-speed Schlieren visualization. The effect of reactant particle size has been evaluated quantitatively. The dynamics of the pressure wave were correlated with the rate of expansion of the high-pressure gas bubble.

  8. Transport induced by ion cyclotron range of frequencies waves

    SciTech Connect

    Zhang, Debing Xu, Yingfeng; Wang, Shaojie

    2014-11-15

    The Vlasov equation, which includes the effect of the ion cyclotron range of frequencies (ICRF) waves, can be written as the Fokker-Planck equation which describes the quasilinear transport in phase space by using the Lie-transform method. The radial transport fluxes of particle, energy and parallel momentum driven by ICRF waves in the slab geometry have been derived. The results show that the ICRF-induced radial redistributions of particle, energy and parallel momentum are driven by the inhomogeneity in energy of the equilibrium distribution function, and related to the correlation between the excursion in the real space and the excursion in energy. For the case with strong asymmetry of k{sub y} spectrum, the ICRF-induced radial transport driven by the energy inhomogeneity dominates the ICRF-induced radial transport driven by the spatial inhomogeneity.

  9. Dehydration-induced porosity waves and episodic tremor and slip

    NASA Astrophysics Data System (ADS)

    Skarbek, Rob M.; Rempel, Alan W.

    2016-02-01

    Episodic tremor and slip (ETS) along the subduction interface takes place where there is abundant evidence for elevated, near-lithostatic pore pressures, at sufficiently great depths (30-45 km) that chemical dehydration reactions must act as their dominant source. We simulate fluid and heat flow while tracking the location of a vertically oriented, one-dimensional column of material as it subducts through the slow slip and tremor zone. The material in the column is transformed through a pressure-dependent and temperature-dependent dehydration reaction that we describe with a generalized nonlinear kinetic rate law. Column deformation is largely dominated by viscous creep, with a closure rate that depends linearly on porosity. This behavior causes the dehydration reaction to generate traveling porosity waves that transport increased fluid pressures within the slow slip region. To explore the possibility that the observed periodicity of slow slip and tremor in subduction zones can be explained by the migration of such porosity waves, we derive a dispersion relation that accurately describes our numerical results. We also obtain an expression for how the thickness of the dehydrating layer is expected to vary as a function of the parameters in the reaction rate law. Although the amplitudes of pore pressure perturbations rival those that are produced by known external forcings (e.g., tides or passing surface waves), our analysis suggests that given reasonable estimates of rock viscosity, permeabilities in the range 6.5×10-15 to 5×10-10 m2 are required for porosity wave trains to form at periods comparable to those of slow slip and tremor.

  10. A computational study of pressure wave reflections in the pulmonary arteries.

    PubMed

    Qureshi, M Umar; Hill, N A

    2015-12-01

    Experiments using wave intensity analysis suggest that the pulmonary circulation in sheep and dogs is characterized by negative or open-end type wave reflections, that reduce the systolic pressure. Since the pulmonary physiology is similar in most mammals, including humans, we test and verify this hypothesis by using a subject specific one-dimensional model of the human pulmonary circulation and a conventional wave intensity analysis. Using the simulated pressure and velocity, we also analyse the performance of the P-U loop and sum of squares techniques for estimating the local pulse wave velocity in the pulmonary arteries, and then analyse the effects of these methods on linear wave separation in the main pulmonary artery. P-U loops are found to provide much better estimates than the sum of squares technique at proximal locations, but both techniques accumulate progressive error at distal locations away from heart, particularly near junctions. The pulse wave velocity estimated using the sum of squares method also gives rise to an artificial early systolic backward compression wave. Finally, we study the influence of three types of pulmonary hypertension viz. pulmonary arterial hypertension, chronic thromboembolic pulmonary hypertension and pulmonary hypertension associated with hypoxic lung disease. Simulating these conditions by changing the relevant parameters in the model and then applying the wave intensity analysis, we observe that for each group the early systolic backward decompression wave reflected from proximal junctions is maintained, whilst the initial forward compression and the late systolic backward compression waves amplify with increasing pathology and contribute significantly to increases in systolic pressure. PMID:25754476

  11. Pressure induced phase transitions in ceramic compounds containing tetragonal zirconia

    SciTech Connect

    Sparks, R.G.; Pfeiffer, G.; Paesler, M.A.

    1988-12-01

    Stabilized tetragonal zirconia compounds exhibit a transformation toughening process in which stress applied to the material induces a crystallographic phase transition. The phase transition is accompanied by a volume expansion in the stressed region thereby dissipating stress and increasing the fracture strength of the material. The hydrostatic component of the stress required to induce the phase transition can be investigated by the use of a high pressure technique in combination with Micro-Raman spectroscopy. The intensity of Raman lines characteristic for the crystallographic phases can be used to calculate the amount of material that has undergone the transition as a function of pressure. It was found that pressures on the order of 2-5 kBar were sufficient to produce an almost complete transition from the original tetragonal to the less dense monoclinic phase; while a further increase in pressure caused a gradual reversal of the transition back to the original tetragonal structure.

  12. Experimental and Numerical Investigation of Pressure Wave Attenuation due to Bubbly Layers

    NASA Astrophysics Data System (ADS)

    Jayaprakash, Arvind; Fourmeau, Tiffany; Hsiao, Chao-Tsung; Chahine, Georges; Dynaflow Inc. Team

    2013-03-01

    In this work, the effects of dispersed microbubbles on a steep pressure wave and its attenuation are investigated both numerically and experimentally. Numerical simulations were carried out using a compressible Euler equation solver, where the liquid-gas mixture was modeled using direct numerical simulations involving discrete deforming bubbles. To reduce computational costs a 1D configuration is used and the bubbles are assumed distributed in layers and the initial pressure profile is selected similar to that of a one-dimensional shock tube problem. Experimentally, the pressure pulse was generated using a submerged spark electric discharge, which generates a large vapor bubble, while the microbubbles in the bubbly layer are generated using electrolysis. High speed movies were recorded in tandem with high fidelity pressure measurements. The dependence of pressure wave attenuation on the bubble radii, the void fraction, and the bubbly layer thickness were parametrically studied. It has been found that the pressure wave attenuation can be seen as due to waves reflecting and dispersing in the inter-bubble regions, with the energy absorbed by bubble volume oscillations and re-radiation. Layer thickness and small bubble sizes were also seen as having a strong effect on the attenuation with enhanced attenuation as the bubble size is reduced for the same void fraction. This study was supported by the Department of Energy, under SBIR Phase II Contract DE-FG02-07ER84839.

  13. Wave reflection quantification based on pressure waveforms alone--methods, comparison, and clinical covariates.

    PubMed

    Hametner, Bernhard; Wassertheurer, Siegfried; Kropf, Johannes; Mayer, Christopher; Holzinger, Andreas; Eber, Bernd; Weber, Thomas

    2013-03-01

    Within the last decade the quantification of pulse wave reflections mainly focused on measures of central aortic systolic pressure and its augmentation through reflections based on pulse wave analysis (PWA). A complementary approach is the wave separation analysis (WSA), which quantifies the total amount of arterial wave reflection considering both aortic pulse and flow waves. The aim of this work is the introduction and comparison of aortic blood flow models for WSA assessment. To evaluate the performance of the proposed modeling approaches (Windkessel, triangular and averaged flow), comparisons against Doppler measurements are made for 148 patients with preserved ejection fraction. Stepwise regression analysis between WSA and PWA parameters are performed to provide determinants of methodological differences. Against Doppler measurement mean difference and standard deviation of the amplitudes of the decomposed forward and backward pressure waves are comparable for Windkessel and averaged flow models. Stepwise regression analysis shows similar determinants between Doppler and Windkessel model only. The results indicate that the Windkessel method provides accurate estimates of wave reflection in subjects with preserved ejection fraction. The comparison with waveforms derived from Doppler ultrasound as well as recently proposed simple triangular and averaged flow waves showed that this approach may reduce variability and provide realistic results. PMID:23107159

  14. Radiation-induced decomposition of PETN and TATB under pressure

    SciTech Connect

    Giefers, Hubertus; Pravica, Michael; Liermann, Hanns-Peter; Yang, Wenge

    2008-10-02

    We have investigated decomposition of PETN and TATB induced by white synchrotron X-ray radiation in a diamond anvil cell at ambient temperature and two pressures, nearly ambient and about 6 GPa. The decomposition rate of TATB decreases significantly when it is pressurized to 5.9 GPa. The measurements were highly reproducible and allowed us to obtain decomposition rates and the order parameters of the reactions.

  15. Transepithelial pressure pulses induce nucleotide release in polarized MDCK cells.

    PubMed

    Praetorius, H A; Frøkiaer, J; Leipziger, J

    2005-01-01

    The release of nucleotides is involved in mechanosensation in various epithelial cells. Intriguingly, kidney epithelial cells are absolutely dependent on the primary cilium to sense changes in apical laminar flow. During fluid passage, the renal epithelial cells are subjected to various mechanical stimuli in addition to changes in the laminar flow rate. In the distal part of the collecting duct, the epithelial cells are exposed to pressure changes and possibly distension during papillary contractions. The aim of the present study was to determine whether nucleotide release contributes to mechanosensation in kidney epithelial cells, thereby establishing whether pressure changes are sufficient to produce nucleotide-mediated responses. Madin-Darby canine kidney (MDCK) cells grown on permeable supports were mounted in a closed double perfusion chamber on an inverted microscope. The intracellular Ca(2+) concentration ([Ca(2+)](i)) was monitored with the Ca(2+)-sensitive fluorescence probe fluo 4. Transepithelial pressure pulses of 30-80 mm Hg produced a transient increase in [Ca(2+)](i) of MDCK cells. This response is independent of the primary cilium, since it is readily observed in immature cells that do not yet express primary cilia. The amplitudes of the pressure-induced Ca(2+) transients varied with the applied chamber pressure in a quantity-dependent manner. The ATPase apyrase and the P2Y antagonist suramin significantly reduced the pressure-induced Ca(2+) transients. Applying apyrase or suramin to both sides of the preparation simultaneously nearly abolished the pressure-induced Ca(2+) response. In conclusion, these observations suggest that rapid pressure changes induce both apical and basolateral nucleotide release that contribute to mechanosensation in kidney epithelial cells. PMID:15367389

  16. Generation and Propagation of Long Waves due to Spatial and Temporal Pressure Distributions

    NASA Astrophysics Data System (ADS)

    Metin, A. D.; Yalçıner, A. C.; Ozyurt Tarakcıoglu, G.; Zaytsev, A.

    2015-12-01

    An abnormal wave event was observed between 23 and 27 June 2014 in the Mediterranean and Black Seas. First, sea level oscillations began in Ciutadella Inlet (Spain) after midnight of 22 June. The phenomena continued with observation of strong oscillations (up to 3 m wave height) in the Adriatic Sea, Mediterranean Sea and Black Sea on 25-26 June. Finally, at noon on 27 June on a calm and sunny day, the abnormal waves suddenly struck coasts of Odessa with 1-2 m wave height injuring a number of people. This tsunami-like event which is called meteotsunami is generated by different types of meteorological disturbances such as atmospheric gravity waves, pressure jumps and squall lines and the significant consequences necessitates the research to understand, model and simulate such events accurately. Thus, using the 2014 event as a case study, the waves generated by the change of atmospheric pressure distribution is studied. A static water level drop due to high atmospheric pressure in a region and rise due to low atmospheric pressure in another region deform the water level throughout the entire sea area. To compute the sea level change, the relation between the pressure difference and change of water level from normal position (ζ=0.99ΔP) is used where ζ is the change of water level (cm) according to the pressure difference from normal pressure ΔP. This relation gives that 1 hPa (1millibar) depression in air pressure from normal water level position (under 1000millibar) creates almost 1 cm rise in mean sea level. The respective small amplitude long waves propagate along the sea which is continuously excited by the spatial and temporal changes of atmospheric pressure. And, the amplification becomes important to understand the occurrence of unexpected water level changes, especially near the coastal zone. In this study, this long wave propagation due to water surface deformation is modelled by solving nonlinear shallow water equations. The model results are compared

  17. Structure of an oblique detonation wave induced by a wedge

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Liu, Y.-S.; Wu, D.; Wang, J.-P.

    2016-03-01

    The structure of an oblique detonation wave (ODW) induced by a wedge is investigated via numerical simulations and Rankine-Hugoniot analysis. The two-dimensional Euler equations coupled with a two-step chemical reaction model are solved. In the numerical results, four configurations of the Chapman-Jouguet (CJ) ODW reflection (overall Mach reflection, Mach reflection, regular reflection, and non-reflection) are observed to take place sequentially as the inflow Mach number increases. According to the numerical and analytical results, the change of the CJ ODW reflection configuration results from the interaction among the ODW, the CJ ODW, and the centered expansion wave.

  18. Pressure-induced structural phase transition, elastic and thermodynamic properties of ReC under high pressure

    NASA Astrophysics Data System (ADS)

    Lei, Hui-Ru; Zhu, Jun; Hao, Yan-Jun; Zhang, Lin; Zhao, Yu-Xin; Zhan, Guo-Fu

    2015-10-01

    The pressure-induced structural phase transition of rhenium monocarbon (ReC) is investigated via the projector augmented wave (PAW) method with the generalized gradient approximation (GGA). Using the first-principles calculations, the equilibrium structural parameters of ReC in rocksalt (NaCl), cesium chloride (CsCl), zinc blende (ZB), wurtzite (WZ), nickel arsenide (NiAs) and tungsten carbide (WC) types are successfully obtained, and the results are well consistent with other theoretical data. It is firstly noted that WC-ReC translates into CsCl-ReC at 510.50 GPa by analyzing the enthalpy difference versus pressure. From the calculated elastic constants, the aggregate elastic modulus (B, G, E), the Poisson's ratio (σ) and the Debye temperature ΘD of WC-type are also derived. It is observed that all the data of WC-ReC obtained increase monotonically with increasing pressure. Meanwhile, the thermodynamic properties of WC-ReC under high temperature and high pressure are investigated applying nonempirical Debye model in the quasi-harmonic approximation.

  19. Wave-induced fluid flow in random porous media: attenuation and dispersion of elastic waves.

    PubMed

    Müller, Tobias M; Gurevich, Boris

    2005-05-01

    A detailed analysis of the relationship between elastic waves in inhomogeneous, porous media and the effect of wave-induced fluid flow is presented. Based on the results of the poroelastic first-order statistical smoothing approximation applied to Biot's equations of poroelasticity, a model for elastic wave attenuation and dispersion due to wave-induced fluid flow in 3-D randomly inhomogeneous poroelastic media is developed. Attenuation and dispersion depend on linear combinations of the spatial correlations of the fluctuating poroelastic parameters. The observed frequency dependence is typical for a relaxation phenomenon. Further, the analytic properties of attenuation and dispersion are analyzed. It is shown that the low-frequency asymptote of the attenuation coefficient of a plane compressional wave is proportional to the square of frequency. At high frequencies the attenuation coefficient becomes proportional to the square root of frequency. A comparison with the 1-D theory shows that attenuation is of the same order but slightly larger in 3-D random media. Several modeling choices of the approach including the effect of cross correlations between fluid and solid phase properties are demonstrated. The potential application of the results to real porous materials is discussed. PMID:15957744

  20. Pressure dependence of the charge-density-wave gap in rare-earth tritellurides.

    PubMed

    Sacchetti, A; Arcangeletti, E; Perucchi, A; Baldassarre, L; Postorino, P; Lupi, S; Ru, N; Fisher, I R; Degiorgi, L

    2007-01-12

    We investigate the pressure dependence of the optical properties of CeTe3, which exhibits an incommensurate charge-density-wave (CDW) state already at 300 K. Our data are collected in the midinfrared spectral range at room temperature and at pressures between 0 and 9 GPa. The energy for the single particle excitation across the CDW gap decreases upon increasing the applied pressure, similarly to the chemical pressure by rare-earth substitution. The broadening of the bands upon lattice compression removes the perfect nesting condition of the Fermi surface and therefore diminishes the impact of the CDW transition on the electronic properties of RTe3. PMID:17358625

  1. Slowly breaking waves: the longevity of tidally induced spiral structure

    NASA Astrophysics Data System (ADS)

    Struck, Curtis; Dobbs, Clare L.; Hwang, Jeong-Sun

    2011-07-01

    We have discovered long-lived waves in two sets of numerical models of fast (marginally bound or unbound) flyby galaxy collisions, carried out independently with two different codes. In neither simulation set are the spirals the result of a collision-induced bar formation. Although there is variation in the appearance of the waves with time, they do not disappear and reform recurrently, as seen in other cases described in the literature. We also present an analytic theory that can account for the wave structure, not as propagating transients, nor as a fixed pattern propagating through the disc. While these waves propagate through the disc, they are mantained by the coherent oscillations initiated by the impulsive disturbance. Specifically, the analytic theory suggests that they are caustic waves in ensembles of stars pursuing correlated epicyclic orbits after the disturbance. This theory is an extension of that developed by Struck and collaborators for colliding ring galaxies. The models suggest that this type of wave may persist for a couple of Gyr, and galaxy interactions occur on comparable time-scales, so waves produced by the mechanism may be well represented in observed spirals. In particular, this mechanism can account for the tightly wound, and presumably long-lived, spirals seen in some nearby early-type galaxies. These spirals are also likely to be common in groups and clusters, where fast encounters between galaxies occur relatively frequently. However, as the spirals become tightly wound, and evolve to modest amplitudes, they may be difficult to resolve unless they are nearby. None the less, the effect may be one of several processes that result from galaxy harassment, and via wave-enhanced star formation, contributes to the Butcher-Oemler effect.

  2. Molecular modeling of high-pressure ramp waves in tantalum

    NASA Astrophysics Data System (ADS)

    Lane, J. Matthew D.; Lim, Hojun; Brown, Justin L.

    2015-03-01

    Ramp wave compression experiments of bcc metals under extreme conditions have produced differing measurements of material strength response. These variations are often attributed to differing experimental techniques, and varying material factors such as microstructure, and strain-rate. We present non-equilibrium molecular dynamics simulations of tantalum for single crystal and two polycrystalline nanostructures out to 250 GPa, over strain states ranging from 108 to 1011 1/s. Results will be compared to recent Z-machine strength experiments, meso-scale crystal plasticity models and continuum-scale polycrystalline model. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  3. Wave pattern in the wake of an arbitrary moving surface pressure disturbance

    NASA Astrophysics Data System (ADS)

    Miao, Sha; Liu, Yuming

    2015-12-01

    We study the problem of wave pattern in the wake of an arbitrary surface pressure disturbance that moves forward at constant speed U in deep water. We seek the dependence of the location of the maximum amplitude of waves upon the pressure distribution and the Froude number F ≡ U / √{ g L } , where L is the characteristic length of the pressure disturbance and g is the gravitational acceleration. We show by theoretical analysis and direct numerical evaluation that half of the included angle (ϕmax) of the V-shape corresponding to the maximum amplitude of the waves in the wake at large Froude numbers behaves asymptotically as ϕ max = C F - a for F > F c , with the constant a, coefficient C, and threshold value of Froude number F c all being functions of the pressure distribution. It is found that for most pressure disturbances, a equals 1, but a can equal 2 for special non-smooth pressure disturbances. The condition in terms of the order of discontinuity and distribution shape of the pressure disturbance for the result of a = 2 is provided. These findings imply that for ship wakes, ϕmax generally decreases with increasing F at large Froude numbers, while the exact value of ϕmax is dependent on ship geometry and F .

  4. Pressure waves generated by metastable intermolecular composites in an aqueous environment

    NASA Astrophysics Data System (ADS)

    Maines, Geoff; Radulescu, Matei; Bacciochini, Antoine; Jodoin, Bertrand; Lee, Julian

    2013-06-01

    In the present study, pressure waves generated by a metastable intermolecular composite (MIC) have been measured experimentally in an aqueous environment. Experiments were performed in a 1.0 L high pressure chamber mounted with high resolution pressure transducers and designed with optical access. Samples consisting of a stoichiometric mixture of aluminum and copper(II)oxide particles were evaluated. Two types of samples were constructed; a mixture of micron-sized raw powders, and ball milled powders with a lamellated nanostructure. A planetary mill was used to refine reactant powders from micron- to nano-scale dimensions. Manual compaction and cold spray deposition techniques were used to consolidate powders in various densities. The dynamics of the pressure wave and high pressure gas bubble were monitored via pressure data and high-speed Schlieren visualization. The effects of reactant particle size and sample density have been evaluated quantitatively and compared with equilibrium calculations. Dynamics of the pressure wave were correlated with the amount of gas released and the rate of burning of the sample material. Work supported by DRDC Suffield (Dr. Julian J. Lee).

  5. The effect of convection and shear on the damping and propagation of pressure waves

    NASA Astrophysics Data System (ADS)

    Kiel, Barry Vincent

    Combustion instability is the positive feedback between heat release and pressure in a combustion system. Combustion instability occurs in the both air breathing and rocket propulsion devices, frequently resulting in high amplitude spinning waves. If unchecked, the resultant pressure fluctuations can cause significant damage. Models for the prediction of combustion instability typically include models for the heat release, the wave propagation and damping. Many wave propagation models for propulsion systems assume negligible flow, resulting in the wave equation. In this research the effect of flow on wave propagation was studied both numerically and experimentally. Two experiential rigs were constructed, one with axial flow to study the longitudinal waves, the other with swirling flow to study circumferential waves. The rigs were excited with speakers and the resultant pressure was measured simultaneously at many locations. Models of the rig were also developed. Equations for wave propagation were derived from the Euler Equations. The resultant resembled the wave equation with three additional terms, two for the effect of the convection and a one for the effect of shear of the mean flow on wave propagation. From the experimental and numerical data several conclusions were made. First, convection and shear both act as damping on the wave propagation, reducing the magnitude of the Frequency Response Function and the resonant frequency of the modes. Second, the energy extracted from the mean flow as a result of turbulent shear for a given condition is frequency dependent, decreasing with increasing frequency. The damping of the modes, measured for the same shear flow, also decreased with frequency. Finally, the two convective terms cause the anti-nodes of the modes to no longer be stationary. For both the longitudinal and circumferential waves, the anti-nodes move through the domain even for mean flow Mach numbers less than 0.10. It was concluded that convection

  6. The wave-induced sediment responses in the subaquous Yellow River delta, China: new insights into seabed inhomogeneity

    NASA Astrophysics Data System (ADS)

    Liu, X.; Jia, Y.; Zheng, J.; Shan, H.

    2014-12-01

    This paper presents the results of an experimental study of the wave-induced sediment responses in the subaqueous Yellow River delta. The pore pressure, sediment particle size composition, microstructure, physical and mechanical properties at different depths inside the seabed were observed during the experimental process under the weight of the soil and under the action of waves of different heights. The results showed that wave-induced sediment responses significantly controlled the occurrence and evolution of inhomogeneity in the strength and sediment distribution of a uniform-originated silty seabed. The variations in the strength, composition and structure of during the wave-sediment interaction processes are closely related to the pore water seepage inside the seabed. The driving machanism can be devided into three modes: transient seepage caused by pore pressure oscillation, seepage failure caused by pore pressure accumulation and liquefaction failure caused by pore pressure accumulation, during which the latter is the main cause of vertical transport of pore water carrying a large amount of fine particles inside the seabed of the subaqueous Yellow River delta. The array of features observed in these experiments can be incorporated into a new model of seabed stratification in uniform-originated silty sediments during wave-sediment interaction. In addition, the implications of this model for traditional sedimentology are explored from a sediment dynamic perspective.

  7. New experimental capabilities and theoretical insights of high pressure compression waves

    NASA Astrophysics Data System (ADS)

    Orlikowski, Daniel

    2007-06-01

    While some high pressure, compression wave research seeks ever high pressures(>10 Mbar), the exciting developments of high pressure research for gas-gun generated compression waves have spawned novel compression experiments as well as new theoretical insights into compression wave dissipation. The first half of the discussion covers the unique gradient density impactor (GDI) developed at LLNL, that has just matured into a viable tool to examine the material response along and significantly away from the principal paths of the Hugoniot and isentrope. This gives direct access to hot planetary isentropes or cyclic paths to understand hysteretic response at moderately high pressures (<5 Mbar). Recently, significant material design challenges pertaining to material control, planarity, parallel layers, and reproducibility have been overcome in the manufacturing of these impactors used to create (within 2μs) compression waves. These compression waves consist of the standard monotonic compression and of unique non-monotonic compression waves, which widens the field of research to include previously inaccessible parts of the thermodynamic phase diagram for a given material. These developments will be addressed in conjunction with hydrodynamic simulations discussing several interesting experiments that have taken place in the pursuit of understanding the high-pressure phase diagram of water and of understanding high-pressure strength. Closely connected to these compression experiments, in general, is the interpretation of the recorded particle velocity histories and the assumptions used to quantify those results, e.g. stress versus density. Therefore, a second theoretical discussion of solitary wave structure is given suggested by recent experimental observations. Dissipative and dispersive effects are expected to exist in general, however, these effects are not usually discussed within the context of the Korteweg-de Vries(KdV)-Burgers equation, thus, leading to a possible

  8. Helical guided waves in liquid-filled cylindrical shells subjected to static pressurization stress

    NASA Astrophysics Data System (ADS)

    Dubuc, Brennan; Ebrahimkhanlou, Arvin; Salamone, Salvatore

    2016-04-01

    Helical guided waves in pipelines are studied under the effects of pressurization stresses from a contained liquid. The pipeline is approximated by an "unwrapped" plate waveguide, and a transfer matrix method is used to solve for guided wave velocity and attenuation dispersion curves in a multilayered plate waveguide subject to an arbitrary triaxial state of initial stress. The matrix-based model is able to incorporate both elastic and viscoelastic solid materials, as well as approximate non-uniform distributions in initial stress through the thickness of a waveguide. Experiments on a steel pipe filled with pressurized water are carried out to validate the modeling approach.

  9. Cosmic shear from scalar-induced gravitational waves

    SciTech Connect

    Sarkar, Devdeep; Serra, Paolo; Cooray, Asantha; Ichiki, Kiyotomo; Baumann, Daniel

    2008-05-15

    Weak gravitational lensing by foreground density perturbations generates a gradient mode in the shear of background images. In contrast, cosmological tensor perturbations induce a nonzero curl mode associated with image rotations. In this note, we study the lensing signatures of both primordial gravitational waves from inflation and second-order gravitational waves generated from the observed spectrum of primordial density fluctuations. We derive the curl mode for galaxy lensing surveys at redshifts of 1-3 and for lensing of the cosmic microwave background at a redshift of 1100. We find that the curl mode angular power spectrum associated with secondary tensor modes for galaxy lensing surveys dominates over the corresponding signal generated by primary gravitational waves from inflation. However, both tensor contributions to the shear curl mode spectrum are below the projected noise levels of upcoming galaxy and cosmic microwave background lensing surveys and therefore are unlikely to be detectable.

  10. Enhancement of airborne shock wave by laser-induced breakdown of liquid column in laser shock cleaning

    SciTech Connect

    Jang, Deoksuk; Kim, Dongsik; Park, Jin-Goo

    2011-04-01

    In laser shock cleaning (LSC), the shock wave is generated by laser-induced breakdown of the ambient gas. The shock wave intensity has thus been a factor limiting the performance of the LSC process. In this work, a novel method of amplifying a laser-induced plasma-generated shock wave by the breakdown of a liquid column is proposed and analyzed. When the laser beam is focused on a microscale liquid column, a shock wave having a significantly amplified intensity compared to that generated by air breakdown alone can be generated in air. Therefore, substantially amplified cleaning force can be obtained. The dynamics of a shock wave induced by a Q-switched Nd:YAG laser was analyzed by laser flash shadowgraphy. The peak pressure of the laser-induced shock wave was approximately two times greater than that of air breakdown at the same laser fluence. The proposed method of shock wave generation is expected to be useful in various applications of laser shock processing, including surface cleaning.

  11. Wave induced density modification in RF sheaths and close to wave launchers

    SciTech Connect

    Van Eester, D.; Lu, Ling-Feng

    2015-12-10

    With the return to full metal walls - a necessary step towards viable fusion machines - and due to the high power densities of current-day ICRH (Ion Cyclotron Resonance Heating) or RF (radio frequency) antennas, there is ample renewed interest in exploring the reasons for wave-induced sputtering and formation of hot spots. Moreover, there is experimental evidence on various machines that RF waves influence the density profile close to the wave launchers so that waves indirectly influence their own coupling efficiency. The present study presents a return to first principles and describes the wave-particle interaction using a 2-time scale model involving the equation of motion, the continuity equation and the wave equation on each of the time scales. Through the changing density pattern, the fast time scale dynamics is affected by the slow time scale events. In turn, the slow time scale density and flows are modified by the presence of the RF waves through quasilinear terms. Although finite zero order flows are identified, the usual cold plasma dielectric tensor - ignoring such flows - is adopted as a first approximation to describe the wave response to the RF driver. The resulting set of equations is composed of linear and nonlinear equations and is tackled in 1D in the present paper. Whereas the former can be solved using standard numerical techniques, the latter require special handling. At the price of multiple iterations, a simple ’derivative switch-on’ procedure allows to reformulate the nonlinear problem as a sequence of linear problems. Analytical expressions allow a first crude assessment - revealing that the ponderomotive potential plays a role similar to that of the electrostatic potential arising from charge separation - but numerical implementation is required to get a feeling of the full dynamics. A few tentative examples are provided to illustrate the phenomena involved.

  12. Wave induced density modification in RF sheaths and close to wave launchers

    NASA Astrophysics Data System (ADS)

    Van Eester, D.; Crombé, K.; Lu, Ling-Feng

    2015-12-01

    With the return to full metal walls - a necessary step towards viable fusion machines - and due to the high power densities of current-day ICRH (Ion Cyclotron Resonance Heating) or RF (radio frequency) antennas, there is ample renewed interest in exploring the reasons for wave-induced sputtering and formation of hot spots. Moreover, there is experimental evidence on various machines that RF waves influence the density profile close to the wave launchers so that waves indirectly influence their own coupling efficiency. The present study presents a return to first principles and describes the wave-particle interaction using a 2-time scale model involving the equation of motion, the continuity equation and the wave equation on each of the time scales. Through the changing density pattern, the fast time scale dynamics is affected by the slow time scale events. In turn, the slow time scale density and flows are modified by the presence of the RF waves through quasilinear terms. Although finite zero order flows are identified, the usual cold plasma dielectric tensor - ignoring such flows - is adopted as a first approximation to describe the wave response to the RF driver. The resulting set of equations is composed of linear and nonlinear equations and is tackled in 1D in the present paper. Whereas the former can be solved using standard numerical techniques, the latter require special handling. At the price of multiple iterations, a simple 'derivative switch-on' procedure allows to reformulate the nonlinear problem as a sequence of linear problems. Analytical expressions allow a first crude assessment - revealing that the ponderomotive potential plays a role similar to that of the electrostatic potential arising from charge separation - but numerical implementation is required to get a feeling of the full dynamics. A few tentative examples are provided to illustrate the phenomena involved.

  13. In-situ determination of SH-channel wave velocity and the influence of overburden pressure

    SciTech Connect

    Reeves, J.J.; Major, M.W.

    1982-04-01

    In the Dutch Creek 1 Mine at Coal Basin, Colorado, SH-channel waves have been transmitted through floor coal underneath a gob (cave darea) produced by an advancing longwall panel. For any given source, only the receiver directly adjacent or closest to the source was monitored by the Geometrics ES 1210 F seismograph. Two sources were used to excite channel waves at each source location; one an explosive charge, the other a hammer blow. Tests showed that variation in overburden pressure on coal can be detected seismically using channel waves passing through the coal.

  14. Finite-amplitude pressure waves in the radial mode of a cylinder

    NASA Technical Reports Server (NTRS)

    Kubo, I.; Moore, F. K.

    1972-01-01

    A numerical study of finite-strength, isentropic pressure waves transverse to the axis of a circular cylinder was made for the radial resonant mode. The waves occur in a gas otherwise at rest, filling the cylinder. A method of characteristics was used for the numerical solution. For small but finite amplitudes, calculations indicate the existence of waves of permanent potential form. For larger amplitudes, a shock is indicated to occur. The critical value of the initial amplitude parameter in the power series is found to be 0.06 to 0.08, under various types of initial conditions.

  15. Experimental observation of standing wave effect in low-pressure very-high-frequency capacitive discharges

    SciTech Connect

    Liu, Yong-Xin; Gao, Fei; Liu, Jia; Wang, You-Nian

    2014-07-28

    Radial uniformity measurements of plasma density were carried out by using a floating double probe in a cylindrical (21 cm in electrode diameter) capacitive discharge reactor driven over a wide range of frequencies (27–220 MHz). At low rf power, a multiple-node structure of standing wave effect was observed at 130 MHz. The secondary density peak caused by the standing wave effect became pronounced and shifts toward the axis as the driving frequency further to increase, indicative of a much more shortened standing-wave wavelength. With increasing rf power, the secondary density peak shift toward the radial edge, namely, the standing-wave wavelength was increased, in good qualitative agreement with the previous theory and simulation results. At higher pressures and high frequencies, the rf power was primarily deposited at the periphery of the electrode, due to the fact that the waves were strongly damped as they propagated from the discharge edge into the center.

  16. Propagation of terahertz waves in an atmospheric pressure microplasma with Epstein electron density profile

    SciTech Connect

    Yuan Chengxun; Zhou Zhongxiang; Zhang, Jingwen W.; Sun Hongguo; Wang He; Du Yanwei; Xiang Xiaoli

    2011-03-15

    Propagation properties of terahertz (THz) waves in a bounded atmospheric-pressure microplasma (AMP) are analyzed in this study. A modified Epstein profile model is used to simulate the electron density distribution caused by the plasma sheaths. By introducing the dielectric constant of a Drude-Lorentz model and using the method of dividing the plasma into a series of subslabs with uniform electron density, the coefficients of power reflection, transmission, and absorption are derived for a bounded microplasma structure. The effects of size of microplasma, electron density profile, and collision frequency on the propagation of THz waves are analyzed numerically. The results indicate that the propagation of THz waves in AMPs depend greatly on the above three parameters. It is demonstrated that the THz wave can play an important role in AMPs diagnostics; meanwhile, the AMP can be used as a novel potential tool to control THz wave propagation.

  17. Modeling and simulation of pressure waves generated by nano-thermite reactions

    NASA Astrophysics Data System (ADS)

    Martirosyan, Karen S.; Zyskin, Maxim; Jenkins, Charles M.; (Yuki) Horie, Yasuyuki

    2012-11-01

    This paper reports the modeling of pressure waves from the explosive reaction of nano-thermites consisting of mixtures of nanosized aluminum and oxidizer granules. Such nanostructured thermites have higher energy density (up to 26 kJ/cm3) and can generate a transient pressure pulse four times larger than that from trinitrotoluene (TNT) based on volume equivalence. A plausible explanation for the high pressure generation is that the reaction times are much shorter than the time for a shock wave to propagate away from the reagents region so that all the reaction energy is dumped into the gaseous products almost instantaneously and thereby a strong shock wave is generated. The goal of the modeling is to characterize the gas dynamic behavior for thermite reactions in a cylindrical reaction chamber and to model the experimentally measured pressure histories. To simplify the details of the initial stage of the explosive reaction, it is assumed that the reaction generates a one dimensional shock wave into an air-filled cylinder and propagates down the tube in a self-similar mode. Experimental data for Al/Bi2O3 mixtures were used to validate the model with attention focused on the ratio of specific heats and the drag coefficient. Model predictions are in good agreement with the measured pressure histories.

  18. a New Approach of Dynamic Blood Pressure Measurement Based on the Time Domain Analysis of the Pulse Wave

    NASA Astrophysics Data System (ADS)

    Zimei, Su; Wei, Xu; Hui, Yu; Fei, Du; Jicun, Wang; Kexin, Xu

    2009-08-01

    In this study the pulse wave characteristics were used as a new approach to measure the human blood pressure. Based the principle of pulse wave and theory of the elastic vascular, the authors analyzed the characteristic of the pulse waveforms and revealed the characteristics points which could be used to represent the blood pressure. In this investigation the relevant mathematical feature was used to identify the relationship between the blood pressure and pulse wave parameters in a more accurate way. It also provided an experimental basis to carry out continuing non-invasive blood pressure monitoring using the pulse wave method.

  19. The quality of high pressure-induced and heat-induced yuzu marmalade

    NASA Astrophysics Data System (ADS)

    Kuwada, Hiroko; Jibu, Yuri; Teramoto, Ai; Fuchigami, Michiko

    2010-12-01

    Yuzu is a typical Japanese citrus with a desirable smell. The objectives of this study are to establish a process for pressure-induced marmalade (without both heating or the addition of pectin) and compare it with heat-induced marmalade. Sliced peel (flavedo) was soaked in 2% citric acid solution (pH 2.0). Albedo, endocarp and juice sacs were homogenized with 0.3% citric acid solution (pH 2.5). After soaking for 24 h, these were mixed and 50% or 60% sucrose of the total weight was added, then pressurized at 500 MPa or boiled (process A). Process B: all processing was done at pH 2.7. Peel of high pressure-induced marmalade maintained a natural color. Flavedo in heat-induced marmalade was softer than that of pressure-induced marmalade. There was no difference in viscosity between heat-induced and high pressure-induced marmalade. High pressure-induced marmalade with 50% sugar was preferred by a sensory test because fresh flavor and color were maintained.

  20. Ballistic quench-induced correlation waves in ultracold gases

    NASA Astrophysics Data System (ADS)

    Corson, John P.; Bohn, John L.

    2016-08-01

    We investigate the wave-packet dynamics of a pair of particles that undergoes a rapid change of scattering length. The short-range interactions are modeled in the zero-range limit, where the quench is accomplished by switching the boundary condition of the wave function at vanishing particle separation. This generates a correlation wave that propagates rapidly to nonzero particle separations. We have derived universal, analytic results for this process that lead to a simple phase-space picture of the quench-induced scattering. Intuitively, the strength of the correlation wave relates to the initial contact of the system. We find that, in one spatial dimension, the k-4 tail of the momentum distribution contains a ballistic contribution that does not originate from short-range pair correlations, and a similar conclusion can hold in other dimensionalities depending on the quench protocol. We examine the resultant quench-induced transport in an optical lattice in one dimension, and a semiclassical treatment is found to give quantitatively accurate estimates for the transport probabilities.

  1. On the toroidal plasma rotations induced by lower hybrid waves

    SciTech Connect

    Guan Xiaoyin; Fisch, Nathaniel J.; Qin Hong; Liu Jian

    2013-02-15

    A theoretical model is developed to explain the plasma rotations induced by lower hybrid waves in Alcator C-Mod. In this model, torodial rotations are driven by the Lorentz force on the bulk-electron flow across flux surfaces, which is a response of the plasma to the resonant-electron flow across flux surfaces induced by the lower hybrid waves. The flow across flux surfaces of the resonant electrons and the bulk electrons are coupled through the radial electric field initiated by the resonant electrons, and the friction between ions and electrons transfers the toroidal momentum to ions from electrons. An improved quasilinear theory with gyrophase dependent distribution function is developed to calculate the perpendicular resonant-electron flow. Toroidal rotations are determined using a set of fluid equations for bulk electrons and ions, which are solved numerically by a finite-difference method. Numerical results agree well with the experimental observations in terms of flow profile and amplitude. The model explains the strong correlation between torodial flow and internal inductance observed experimentally, and predicts both counter-current and co-current flows, depending on the perpendicular wave vectors of the lower hybrid waves.

  2. On the Toroidal Plasma Rotations Induced by Lower Hybrid Waves

    SciTech Connect

    Guan, Xiaoyin; Qin, Hong; Liu, Jian; Fisch, Nathaniel J.

    2012-11-14

    A theoretical model is developed to explain the plasma rotations induced by lower hybrid waves in Alcator C-Mod. In this model, torodial rotations are driven by the Lorentz force on the bulk electron flow across flux surfaces, which is a response of the plasma to the resonant-electron flow across flux surfaces induced by the lower hybrid waves. The flow across flux surfaces of the resonant electrons and the bulk electrons are coupled through the radial electric fi eld initiated by the resonant electrons, and the friction between ions and electrons transfers the toroidal momentum to ions from electrons. An improved quasilinear theory with gyrophase dependent distribution function is developed to calculate the perpendicular resonant-electron flow. Toroidal rotations are determined using a set of fluid equations for bulk electrons and ions, which are solved numerically by a fi nite- difference method. Numerical results agree well with the experimental observations in terms of flow pro file and amplitude. The model explains the strong correlation between torodial flow and internal inductance observed experimentally, and predicts both counter-current and co-current flows, depending on the perpendicular wave vectors of the lower hybrid waves. __________________________________________________

  3. High-pressure-induced water penetration into 3-isopropylmalate dehydrogenase

    SciTech Connect

    Nagae, Takayuki; Kawamura, Takashi; Chavas, Leonard M. G.; Niwa, Ken; Hasegawa, Masashi; Kato, Chiaki; Watanabe, Nobuhisa

    2012-03-01

    Structures of 3-isopropylmalate dehydrogenase were determined at pressures ranging from 0.1 to 650 MPa. Comparison of these structures gives a detailed picture of the swelling of a cavity at the dimer interface and the generation of a new cleft on the molecular surface, which are accompanied by water penetration. Hydrostatic pressure induces structural changes in proteins, including denaturation, the mechanism of which has been attributed to water penetration into the protein interior. In this study, structures of 3-isopropylmalate dehydrogenase (IPMDH) from Shewanella oneidensis MR-1 were determined at about 2 Å resolution under pressures ranging from 0.1 to 650 MPa using a diamond anvil cell (DAC). Although most of the protein cavities are monotonically compressed as the pressure increases, the volume of one particular cavity at the dimer interface increases at pressures over 340 MPa. In parallel with this volume increase, water penetration into the cavity could be observed at pressures over 410 MPa. In addition, the generation of a new cleft on the molecular surface accompanied by water penetration could also be observed at pressures over 580 MPa. These water-penetration phenomena are considered to be initial steps in the pressure-denaturation process of IPMDH.

  4. Pore-pressure gradients, stresses, and induced earthquakes

    SciTech Connect

    Segall, P. . Geophysics Dept. Geological Survey, Menlo Park, CA )

    1992-01-01

    In the theory of poroelasticity, spatial gradients in pore-pressure enter the equilibrium equations in the same way as distributed body forces. Pore-pressure gradients are thus associated with poroelastic stresses in the same way that temperature gradients associated with thermoelastic stresses. The author has suggested that pore-pressure gradients caused by pumping are responsible for earthquakes near some oil and gas fields. Seismic data from a number of active oil and gas fields in California, Texas, Alberta, and elsewhere clearly show that earthquakes are occurring near fields where pore pressures have declined by several 10's of MPa. These observations can not be explained by changes in effective stress alone, which predicts that decreasing pore-fluid pressures tend to stabilize faults. He believes that poro-elastic stresses resulting from pore-fluid extraction are responsible for earthquakes in these situations. Fluid injection also induces poro-elastic stresses, however it is difficult to separate this effect from the destabilizing effect of increased pore-pressure within fault zones. To test the poroelastic model for induced seismicity, theoretical predictions are compared to data from a deep gas field in the Pyrenean foreland. Hundreds of shallow, small to moderate earthquakes have occurred there since 1969. The earthquakes are tightly clustered near the gas field. Reservoir pressure had declined by 30 MPa at the onset of seismicity. The relationship between average reservoir pressure decline and subsidence is remarkably linear, lending support to the linear poroelastic model. Using laboratory derived material parameters and in situ reservoir pressure measurements, it is possible to predict the surface deformations and the change in stress field without adjustable parameters. The computed vertical displacements are in good agreement with the observed subsidence. The poroelastic stress changes at the onset of seismicity are of the order of a few bars.

  5. Pressure-induced conformational switch of an interfacial protein.

    PubMed

    Johnson, Quentin R; Lindsay, Richard J; Nellas, Ricky B; Shen, Tongye

    2016-06-01

    A special class of proteins adopts an inactive conformation in aqueous solution and activates at an interface (such as the surface of lipid droplet) by switching their conformations. Lipase, an essential enzyme for breaking down lipids, serves as a model system for studying such interfacial proteins. The underlying conformational switch of lipase induced by solvent condition is achieved through changing the status of the gated substrate-access channel. Interestingly, a lipase was also reported to exhibit pressure activation, which indicates it is drastically active at high hydrostatic pressure. To unravel the molecular mechanism of this unusual phenomenon, we examined the structural changes induced by high hydrostatic pressures (up to 1500 MPa) using molecular dynamics simulations. By monitoring the width of the access channel, we found that the protein undergoes a conformational transition and opens the access channel at high pressures (>100 MPa). Particularly, a disordered amphiphilic α5 region of the protein becomes ordered at high pressure. This positive correlation between the channel opening and α5 ordering is consistent with the early findings of the gating motion in the presence of a water-oil interface. Statistical analysis of the ensemble of conformations also reveals the essential collective motions of the protein and how these motions contribute to gating. Arguments are presented as to why heightened sensitivity to high-pressure perturbation can be a general feature of switchable interfacial proteins. Further mutations are also suggested to validate our observations. Proteins 2016; 84:820-827. © 2016 Wiley Periodicals, Inc. PMID:26967808

  6. Irreversibility of Pressure Induced Boron Speciation Change in Glass

    PubMed Central

    Smedskjaer, Morten M.; Youngman, Randall E.; Striepe, Simon; Potuzak, Marcel; Bauer, Ute; Deubener, Joachim; Behrens, Harald; Mauro, John C.; Yue, Yuanzheng

    2014-01-01

    It is known that the coordination number (CN) of atoms or ions in many materials increases through application of sufficiently high pressure. This also applies to glassy materials. In boron-containing glasses, trigonal BO3 units can be transformed into tetrahedral BO4 under pressure. However, one of the key questions is whether the pressure-quenched CN change in glass is reversible upon annealing below the ambient glass transition temperature (Tg). Here we address this issue by performing 11B NMR measurements on a soda lime borate glass that has been pressure-quenched at ~0.6 GPa near Tg. The results show a remarkable phenomenon, i.e., upon annealing at 0.9Tg the pressure-induced change in CN remains unchanged, while the pressurised values of macroscopic properties such as density, refractive index, and hardness are relaxing. This suggests that the pressure-induced changes in macroscopic properties of soda lime borate glasses compressed up to ~0.6 GPa are not attributed to changes in the short-range order in the glass, but rather to changes in overall atomic packing density and medium-range structures. PMID:24442182

  7. Irreversibility of pressure induced boron speciation change in glass.

    PubMed

    Smedskjaer, Morten M; Youngman, Randall E; Striepe, Simon; Potuzak, Marcel; Bauer, Ute; Deubener, Joachim; Behrens, Harald; Mauro, John C; Yue, Yuanzheng

    2014-01-01

    It is known that the coordination number (CN) of atoms or ions in many materials increases through application of sufficiently high pressure. This also applies to glassy materials. In boron-containing glasses, trigonal BO3 units can be transformed into tetrahedral BO4 under pressure. However, one of the key questions is whether the pressure-quenched CN change in glass is reversible upon annealing below the ambient glass transition temperature (Tg). Here we address this issue by performing (11)B NMR measurements on a soda lime borate glass that has been pressure-quenched at ~0.6 GPa near Tg. The results show a remarkable phenomenon, i.e., upon annealing at 0.9Tg the pressure-induced change in CN remains unchanged, while the pressurised values of macroscopic properties such as density, refractive index, and hardness are relaxing. This suggests that the pressure-induced changes in macroscopic properties of soda lime borate glasses compressed up to ~0.6 GPa are not attributed to changes in the short-range order in the glass, but rather to changes in overall atomic packing density and medium-range structures. PMID:24442182

  8. Mechanism of pressure-induced gelation of milk.

    PubMed

    Keenan, R D; Young, D J; Tier, C M; Jones, A D; Underdown, J

    2001-07-01

    The pressure-induced gelation of concentrated skimmed milk and milk-sugar mixtures was studied to discover the main components responsible for gelation. The major protein component responsible for gelation is micellar casein. Gelation occurs at similar pressures to casein micelle disintegration in dilute milk, and both can be prevented by inclusion of excess calcium chloride. Transmission electron micrographs show that the protein network is formed from particles with diameters approximately an order of magnitude smaller than those of intact casein micelles. Gelation occurs on decompression and is found to be baroreversible. Concentrations of sugar up to 30% reduce the critical concentration of casein required for gelation, but higher sugar concentrations inhibit gelation. A mechanism of gelation based on the aggregation of casein submicelles formed by pressure-induced disintegration of casein micelles is proposed. Observations on the effect of sucrose on gelation are discussed in terms of the influence of sugars on the solvent quality in aqueous casein systems. PMID:11453781

  9. Magnetic field induced spin-wave energy focusing

    NASA Astrophysics Data System (ADS)

    Perez, Noel; Lopez-Diaz, Luis

    2015-07-01

    Local temperature variations induced by spin-wave propagation are studied using a model that couples nonuniform magnetization dynamics and heat flow. We show that the remote heating at the sample edge reported recently [T. An et al., Nat. Mater. 12, 549 (2013)], 10.1038/nmat3628 is due to the geometry-induced gradual reduction of the effective field. We demonstrate that the same effect can be achieved by a reduction in the external field instead of a constriction at the edge and, furthermore, that both the location and the amount of energy to be delivered to the lattice can be controlled accurately this way.

  10. Plasma transport induced by kinetic Alfven wave turbulence

    SciTech Connect

    Izutsu, T.; Hasegawa, H.; Fujimoto, M.; Nakamura, T. K. M.

    2012-10-15

    At the Earth's magnetopause that separates the hot-tenuous magnetospheric plasma from the cold dense solar wind plasma, often seen is a boundary layer where plasmas of both origins coexist. Plasma diffusions of various forms have been considered as the cause of this plasma mixing. Here, we investigate the plasma transport induced by wave-particle interaction in kinetic Alfven wave (KAW) turbulence, which is one of the candidate processes. We clarify that the physical origin of the KAW-induced cross-field diffusion is the drift motions of those particles that are in Cerenkov resonance with the wave: E Multiplication-Sign B-like drift that emerges in the presence of non-zero parallel electric field component and grad-B drift due to compressional magnetic fluctuations. We find that KAW turbulence, which has a spectral breakpoint at which an MHD inertial range transits to a dissipation range, causes selective transport for particles whose parallel velocities are specified by the local Alfven velocity and the parallel phase velocity at the spectral breakpoint. This finding leads us to propose a new data analysis method for identifying whether or not a mixed plasma in the boundary layer is a consequence of KAW-induced transport across the magnetopause. The method refers to the velocity space distribution function data obtained by a spacecraft that performs in situ observations and, in principle, is applicable to currently available dataset such as that provided by the NASA's THEMIS mission.