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Sample records for pressure-gradient soliton compression

  1. Similar solutions for the compressible laminar boundary layer with heat transfer and pressure gradient

    NASA Technical Reports Server (NTRS)

    Cohen, Clarence B; Reshotko, Eli

    1956-01-01

    Stewartson's transformation is applied to the laminar compressible boundary-layer equations and the requirement of similarity is introduced, resulting in a set of ordinary nonlinear differential equations previously quoted by Stewartson, but unsolved. The requirements of the system are Prandtl number of 1.0, linear viscosity-temperature relation across the boundary layer, an isothermal surface, and the particular distributions of free-stream velocity consistent with similar solutions. This system admits axial pressure gradients of arbitrary magnitude, heat flux normal to the surface, and arbitrary Mach numbers. The system of differential equations is transformed to integral system, with the velocity ratio as the independent variable. For this system, solutions are found by digital computation for pressure gradients varying from that causing separation to the infinitely favorable gradient and for wall temperatures from absolute zero to twice the free-stream stagnation temperature. Some solutions for separated flows are also presented.

  2. The Compressible Laminar Boundary Layer with Heat Transfer and Arbitrary Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Cohen, Clarence B; Reshotko, Eli

    1956-01-01

    An approximate method for the calculation of the compressible laminar boundary layer with heat transfer and arbitrary pressure gradient, based on Thwaites' correlation concept, is presented. With the definition of dimensionless shear and heat-transfer parameters and an assumed correlation of these parameters in terms of a momentum parameter, a complete system of relations for calculating skin friction and heat transfer results. Knowledge of velocity or temperature profiles is not necessary in using this calculation method. When the method is applied to a convergent-divergent, axially symmetric rocket nozzle, it shows that high rates of heat transfer are obtained at the initial stagnation point and at the throat of the nozzle. Also indicated are negative displacement thicknesses in the convergent portion of the nozzle; these occur because of the high density within the lower portions of the cooled boundary layer. (author)

  3. Calculation of turbulent boundary layers with heat transfer and pressure gradient utilizing a compressibility transformation. Part 3: Computer program manual

    NASA Technical Reports Server (NTRS)

    Schneider, J.; Boccio, J.

    1972-01-01

    A computer program is described capable of determining the properties of a compressible turbulent boundary layer with pressure gradient and heat transfer. The program treats the two-dimensional problem assuming perfect gas and Crocco integral energy solution. A compressibility transformation is applied to the equation for the conservation of mass and momentum, which relates this flow to a low speed constant property flow with simultaneous mass transfer and pressure gradient. The resulting system of describing equations consists of eight ordinary differential equations which are solved numerically. For Part 1, see N72-12226; for Part 2, see N72-15264.

  4. Charts and Tables for Estimating the Stability of the Compressible Laminar Boundary Layer with Heat Transfer and Arbitrary Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Tetervin, Neal

    1959-01-01

    The minimum critical Reynolds numbers for the similar solutions of the compressible laminar boundary layer computed by Cohen and Reshotko and also for the Falkner and Skan solutions as recomputed by Smith have been calculated by Lin's rapid approximate method for two-dimensional disturbances. These results enable the stability of the compressible laminar boundary layer with heat transfer and pressure gradient to be easily estimated after the behavior of the boundary layer has been computed by the approximate method of Cohen and Reshotko. The previously reported unusual result (NACA Technical Note 4037) that a highly cooled stagnation point flow is more unstable than a highly cooled flat-plate flow is again encountered. Moreover, this result is found to be part of the more general result that a favorable pressure gradient is destabilizing for very cool walls when the Mach number is less than that for complete stability. The minimum critical Reynolds numbers for these wall temperature ratios are, however, all larger than any value of the laminar-boundary-layer Reynolds number likely to be encountered. For Mach numbers greater than those for which complete stability occurs a favorable pressure gradient is stabilizing, even for very cool walls.

  5. Reynolds number and pressure gradient effects on compressible turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Acharya, M.; Kussoy, M. I.; Horstman, C. C.

    1978-01-01

    A detailed investigation of attached supersonic turbulent boundary layers over an extensive range of Reynolds numbers (12 x 10 to the 6th to 314 x 10 to the 6th) is presented. Experimental measurements were obtained for adverse pressure gradients ranging in magnitude from those of previous investigations to those approaching separation. The measurements include mean values of surface pressure and skin-friction, mean-flow profiles, and profiles of the three turbulent velocity fluctuation components and turbulent shear stress. Numerical solutions, employing three turbulence models of various degrees of complexity have been compared with the details of the measured flow fields. Generally, it was found that the more sophisticated turbulence models are superior to a mixing length model for predicting the Reynolds number and pressure gradient effects. However, some details of the turbulent fluctuations as well as the exact Reynolds number trends indicated by the data were not accurately predicted with any of the turbulence models considered.

  6. Cascaded photonic crystal fibers for three-stage soliton compression.

    PubMed

    Li, Qian; Cheng, Zihao

    2016-11-01

    Cascaded higher-order soliton compression in photonic crystal fibers (PCFs) is demonstrated, where both the hyperbolic secant and Gaussian input pulses are considered. Detailed fiber designs for three-stage higher-order soliton compression where soliton order is three or non-integer are presented. A highest compression factor of 221.32 has been achieved with only 49.48% pedestal energy.

  7. Enhanced soliton spectral tunneling effect of self-compressing nonautonomous colored femtosecond solitons

    NASA Astrophysics Data System (ADS)

    Perez-Torres, R.; Belyaeva, T. L.; Hernandez-Tenorio, C.; Kovachev, L. M.; Serkin, V. N.

    2010-10-01

    The discovery of stimulated Raman self-scattering (SRSS) effect of femtosecond optical solitons is acknowledged to be among the most notable achievements of nonlinear fiber optics. This effect is also often called intrapulse stimulated Raman scattering (ISRS), or soliton self-frequency shift (SSFS), thereby emphasizing the unusual regime of stimulated Raman scattering, when the spectrum of a high-power ultrashort laser pulse proves to be so broad that it covers the band of Raman resonances of the medium. The soliton-like wave packets with continuously shifted spectrum traveling not only in the ordinary space and time, but also in the spectral space, are known as colored femtosecond solitons. Colored solitons play an important role in the soliton supercontinuum generation. The most interesting features of colored optical solitons are connected with the possibility of their tunneling in the spectral domain through a potential barrier-like spectral inhomogeneity of group velocity dispersion (GVD), including the forbidden band of positive GVD. This effect is known as soliton spectral tunneling effect (SST). In this Report, we consider the influence of the soliton binding energy on dynamics of the SST effect assuming that the amplitude and duration of the tunneling soliton vary in time when the soliton spectrum approaches a forbidden GVD barrier. We show that soliton self-compressing effect has dramatic impact on the SST through forbidden spectral region of positive GVD.

  8. Compression stockings with a negative pressure gradient have a more pronounced effect on venous pumping function than graduated elastic compression stockings.

    PubMed

    Mosti, G; Partsch, H

    2011-08-01

    To measure the effect on the venous pumping function of a stocking providing a negative pressure gradient with higher pressures over the calf in comparison to a conventional graduated elastic compression stocking (GECS) in patients with advanced venous insufficiency. Experimental study. 30 patients with severe superficial chronic venous insufficiency were enrolled. Two elastic stocking designs exerting a pressure at ankle between 15 and 25 mm Hg were compared; a conventional GECS and a stocking exerting a higher pressure over the calf than over the ankle producing a "progressive" increase in compression (PECS). the venous calf pumping function was assessed by measuring the ejection fraction (EF) from the lower leg by a plethysmographic method during a standardised exercise. Interface pressure of the 2 compression devices was simultaneously recorded both at B1 = 12 cm above ankle, C = just above widest part of calf. The mean increase of EF produced by PECS was +75% (95 CI 48, 7-101,3) compared with +32% (95% CI 16, 8-48,6) with GECS (P < 0.001). There was a significant correlation between EF and the stocking pressure measured at calf level during standing and walking. Stockings exerting a higher pressure on the calf than on the ankle show a greater efficacy in increasing the venous ejection fraction from the leg. Copyright © 2011 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

  9. 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.

  10. Generation and compression of dissipative soliton using fiber arrays

    NASA Astrophysics Data System (ADS)

    Shakeri, Somayeh; Niknafs, Akram; Rooholamininejad, Hossein; Bahrampour, Alireza

    2017-01-01

    Compression of dissipative soliton (DS) and dissipative soliton resonance (DSR) have attracted considerable attention for generation of short pulse lasers. Generation of DS/DSR is investigated numerically in circular fiber array with optical central fiber. Parameter management can generate the DS and DSR in circular fiber array with central optical fiber and in normal or anomalous dispersion. The nonlinear circular fiber arrays can be used as an optical pulse compressor. In this paper, compression of DS and DSR versus the nonlinearity and dispersion parameters in circular fiber array with central fiber, are taken into investigation.

  11. Calculation of turbulent boundary layers with heat transfer and pressure gradient utilizing a compressibility transformation. Part 2: Constant property turbulent boundary layer flow with simultaneous mass transfer and pressure gradient

    NASA Technical Reports Server (NTRS)

    Boccio, J.; Economos, C.

    1972-01-01

    An analysis of the incompressible turbulent boundary layer, developing under the combined effects of mass transfer and pressure gradient, is presented in this paper. A strip-integral method is employed whereby two of the three governing equations are obtained by integrating the combined momentum and continuity equation to 50 percent and 100 percent, respectively, of the boundary-layer height. The latter equation is the usual momentum-integral equation; the former equation requires specification of shear. Accordingly, Clauser's equilibrium eddy-viscosity law is assumed valid at this point. The third and final equation is obtained by specifying that Stevenson's velocity profiles apply throughout the domain of interest, from which a skin-friction law can be derived. Comparisons of the numerical results with the experiments of McQuaid, which include combined effects of variable pressure gradient and mass transfer, show good agreement.

  12. Observation of soliton compression in silicon photonic crystals

    PubMed Central

    Blanco-Redondo, A.; Husko, C.; Eades, D.; Zhang, Y.; Li, J.; Krauss, T.F.; Eggleton, B.J.

    2014-01-01

    Solitons are nonlinear waves present in diverse physical systems including plasmas, water surfaces and optics. In silicon, the presence of two photon absorption and accompanying free carriers strongly perturb the canonical dynamics of optical solitons. Here we report the first experimental demonstration of soliton-effect pulse compression of picosecond pulses in silicon, despite two photon absorption and free carriers. Here we achieve compression of 3.7 ps pulses to 1.6 ps with <10 pJ energy. We demonstrate a ~1-ps free-carrier-induced pulse acceleration and show that picosecond input pulses are critical to these observations. These experiments are enabled by a dispersion-engineered slow-light photonic crystal waveguide and an ultra-sensitive frequency-resolved electrical gating technique to detect the ultralow energies in the nanostructured device. Strong agreement with a nonlinear Schrödinger model confirms the measurements. These results further our understanding of nonlinear waves in silicon and open the way to soliton-based functionalities in complementary metal-oxide-semiconductor-compatible platforms. PMID:24423977

  13. Compressible boundary layer with normal pressure gradients: Quasi-similarity equations - Their properties at the wall and at sharp and blunt leading edges.

    NASA Technical Reports Server (NTRS)

    Seginer, A.

    1972-01-01

    The failure of most viscous-inviscid interaction methods at strong interactions is attributed to the presence of a normal pressure gradient. A new theory is proposed for supersonic laminar boundary layers that can generate normal pressure gradients. The Navier-Stokes equations are reexamined by an order of magnitude analysis and all first and second order terms are retained. The approximation is found to be dependent not only on the boundary layer thickness but also on the ratio of the dimensionless viscosity and density. The equations are transformed into two quasi-similar, nonlinear, third order, ordinary integro-differential equations for the velocity and pressure as functions of a single transverse variable. The properties of the equations at the boundaries are discussed.

  14. Ion-acoustic compressive and rarefactive solitons in an electron-beam plasma system

    SciTech Connect

    Yadav, L.L.; Tiwari, R.S.; Sharma, S.R. )

    1994-03-01

    Using the general formulation of reductive perturbation method, the Korteweg--de Vries (KdV) equation is derived for an electron-beam plasma with hot isothermal beam and plasma electrons and warm ions. The soliton solution of the KdV equation is discussed in detail. It is found that above a critical velocity of electron-beam two additional ion-acoustic soliton branches appear. It is found that corresponding to two linear modes, the system supports the existence of compressive as well as rarefactive solitons depending upon the plasma parameters, while corresponding to other two wave modes, the system supports only rarefactive solitons. The effect of different parameters on the characteristics of solitons have been investigated in detail.

  15. Compressive and rarefactive DIA solitons beyond the KdV limit

    SciTech Connect

    Mamun, A. A.; Deeba, F.

    2012-04-15

    The modified Gardner equation (MGE), showing the existence of compressive and rarefactive dust-ion-acoustic (DIA) solitons in a nonplanar dusty plasma (containing inertial ions, Boltzmann electrons, and negatively charged stationary dust) beyond the KdV Korteweg-de Vries (KdV) limit, is derived and numerically solved. The basic features of the compressive and rarefactive cylindrical and spherical DIA solitons, which are found to exist beyond the KdV limit, i.e., exist for {mu} {approx} 2/3 (where {mu} = Z{sub n}n{sub d0}/n{sub i0}, z{sub d} is the number of electrons residing onto the dust grain surface, n{sub d0}(n{sub i0}) is the dust (ion) number density at equilibrium, and {mu} {approx} 2/3 means that {mu} is not equal to 2/3, but it is around 2/3) are identified. These solitons (which can be referred to as DIA Gardner solitons (DIA-GSs)) are completely different from the KdV solitons because {mu} = 2/3 corresponds to the vanishing of the nonlinear coefficient of the KdV equation, and {mu} {approx} 2/3 corresponds to extremely large amplitude KdV solitons for which the validity of the reductive perturbation method breaks down. It is also shown that the properties of the nonplanar (cylindrical and spherical) DIA-GSs are significantly different from those of the one dimensional planar ones.

  16. Optical Solitons

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.

    2005-08-01

    1. Optical solitons in fibres: theoretical review A. Hasegawa; 2. Solitons in optical fibres: an experimental account L. F. Mollenauer; 3. All-optical long-distance soliton-based transmission systems K. Smith and L. F. Mollenauer; 4. Nonlinear propagation effects in optical fibres: numerical studies K. J. Blow and N. J. Doran; 5. Soliton-soliton interactions C. Desem and P. L. Chu; 6. Soliton amplification in erbium-doped fibre amplifiers and its application to soliton communication M. Nakazawa; 7. Nonlinear transformation of laser radiation and generation of Raman solitons in optical fibres E. M. Dianov, A. B. Grudinin, A. M. Prokhorov and V. N. Serkin; 8. Generation and compression of femtosecond solitons in optical fibers P. V. Mamyshev; 9. Optical fibre solitons in the presence of higher order dispersion and birefringence C. R. Menyuk and Ping-Kong A. Wai; 10. Dark optical solitons A. M. Weiner; 11. Soliton Raman effects J. R. Taylor; Bibliography; Index.

  17. Optical Solitons

    NASA Astrophysics Data System (ADS)

    Taylor, J. R.

    1992-04-01

    1. Optical solitons in fibres: theoretical review A. Hasegawa; 2. Solitons in optical fibres: an experimental account L. F. Mollenauer; 3. All-optical long-distance soliton-based transmission systems K. Smith and L. F. Mollenauer; 4. Nonlinear propagation effects in optical fibres: numerical studies K. J. Blow and N. J. Doran; 5. Soliton-soliton interactions C. Desem and P. L. Chu; 6. Soliton amplification in erbium-doped fibre amplifiers and its application to soliton communication M. Nakazawa; 7. Nonlinear transformation of laser radiation and generation of Raman solitons in optical fibres E. M. Dianov, A. B. Grudinin, A. M. Prokhorov and V. N. Serkin; 8. Generation and compression of femtosecond solitons in optical fibers P. V. Mamyshev; 9. Optical fibre solitons in the presence of higher order dispersion and birefringence C. R. Menyuk and Ping-Kong A. Wai; 10. Dark optical solitons A. M. Weiner; 11. Soliton Raman effects J. R. Taylor; Bibliography; Index.

  18. Hydrofracturing, fluid pressure gradients and channel drainage

    NASA Astrophysics Data System (ADS)

    Koehn, Daniel; Toussaint, Renaud

    2017-04-01

    Build up of fluid overpressure and the development of fluid pressure gradients leads to hydrofracturing in the Earth's crust. We illustrate the complexity of the developing effective stress and fracture patterns with a hybrid numerical model linking pressure gradients to solid deformation. In the model fluid pressure rise below a seal leads to a decrease of the mean and differential stress of the solid. In a closed system where fluid pressure rise below a seal is not local, the main principle stresses flip with the effective horizontal stress becoming zero and the effective vertical stress tensile leading to horizontal hydrofractures. Such a system leads to the development of a hydraulic breccia if initially local high fluid pressure pulses produce vertical fractures. We argue that fluid pressure gradients have to be taken into account to understand effective stresses in the Earth's crust. Depending on the boundary conditions a reservoir with fluid overpressure is drained vertically or horizontally. At the moment when draining channels develop the surrounding solid matrix is slightly compressed. This can be seen as the selection of a compaction wavelength in the system. The channels are dynamic but prefer a given wavelength. We show that effective stresses react anisotropic to overpressure, that overpressure leads to fracture orientation flip and that dynamic opening and closing channels drain the system.

  19. Soliton compression to few-cycle pulses with a high quality factor by engineering cascaded quadratic nonlinearities.

    PubMed

    Zeng, Xianglong; Guo, Hairun; Zhou, Binbin; Bache, Morten

    2012-11-19

    We propose an efficient approach to improve few-cycle soliton compression with cascaded quadratic nonlinearities by using an engineered multi-section structure of the nonlinear crystal. By exploiting engineering of the cascaded quadratic nonlinearities, in each section soliton compression with a low effective order is realized, and high-quality few-cycle pulses with large compression factors are feasible. Each subsequent section is designed so that the compressed pulse exiting the previous section experiences an overall effective self-defocusing cubic nonlinearity corresponding to a modest soliton order, which is kept larger than unity to ensure further compression. This is done by increasing the cascaded quadratic nonlinearity in the new section with an engineered reduced residual phase mismatch. The low soliton orders in each section ensure excellent pulse quality and high efficiency. Numerical results show that compressed pulses with less than three-cycle duration can be achieved even when the compression factor is very large, and in contrast to standard soliton compression, these compressed pulses have minimal pedestal and high quality factor.

  20. Note on rarefactive and compressive ion-acoustic solitons in a plasma containing two ion species

    NASA Astrophysics Data System (ADS)

    McKenzie, J. F.; Verheest, F.; Doyle, T. B.; Hellberg, M. A.

    2005-10-01

    In a recent article the conditions for the existence of solitons in a plasma containing two ion species were analyzed within the framework of a fully nonlinear treatment. In particular, an upper limit for the critical collective Mach number (above which rarefactive solitons cease to exist) was obtained from the requirement that a charge neutral point in the rarefactive regime must be formed before the electron density, ne, experiences its "lid," i.e., where ne→0. Although this is a necessary condition it is not sufficient. In the present work a sufficient condition is derived by requiring that a rarefactive equilibrium point be reached before the limit is imposed by either the electron lid or the infinite compression of the second ion species. This requirement, along with the usual necessary condition for soliton formation, provides the parameter space window for the existence of rarefactive solitons. The analysis has also been generalized to include ions of finite mass of various charge for both the rarefactive and compressive cases.

  1. Deterministic single soliton generation and compression in microring resonators avoiding the chaotic region.

    PubMed

    Jaramillo-Villegas, Jose A; Xue, Xiaoxiao; Wang, Pei-Hsun; Leaird, Daniel E; Weiner, Andrew M

    2015-04-20

    A path within the parameter space of detuning and pump power is demonstrated in order to obtain a single cavity soliton (CS) with certainty in SiN microring resonators in the anomalous dispersion regime. Once the single CS state is reached, it is possible to continue a path to compress it, broadening the corresponding single free spectral range (FSR) Kerr frequency comb. The first step to achieve this goal is to identify the stable regions in the parameter space via numerical simulations of the Lugiato-Lefever equation (LLE). Later, using this identification, we define a path from the stable modulation instability (SMI) region to the stable cavity solitons (SCS) region avoiding the chaotic and unstable regions.

  2. Type-I cascaded quadratic soliton compression in lithium niobate: Compressing femtosecond pulses from high-power fiber lasers

    SciTech Connect

    Bache, Morten; Wise, Frank W.

    2010-05-15

    The output pulses of a commercial high-power femtosecond fiber laser or amplifier are typically around 300-500 fs with wavelengths of approximately 1030 nm and tens of microjoules of pulse energy. Here, we present a numerical study of cascaded quadratic soliton compression of such pulses in LiNbO{sub 3} using second-harmonic generation in a type-I phase-matching configuration. We find that because of competing cubic material nonlinearities, compression can only occur in the nonstationary regime, where group-velocity-mismatch-induced Raman-like nonlocal effects prevent compression to less than 100 fs. However, the strong group-velocity dispersion implies that the pulses can achieve moderate compression to durations of less than 130 fs in available crystal lengths. Most of the pulse energy is conserved because the compression is moderate. The effects of diffraction and spatial walk-off are addressed, and in particular the latter could become an issue when compressing such long crystals (around 10 cm long). We finally show that the second harmonic contains a short pulse locked to the pump and a long multi-picosecond red-shifted detrimental component. The latter is caused by the nonlocal effects in the nonstationary regime, but because it is strongly red-shifted to a position that can be predicted, we show that it can be removed using a bandpass filter, leaving a visible component of less than 100 fs at {lambda}=515 nm with excellent pulse quality.

  3. Self-compression of soliton-like laser pulses in the process of self-focusing

    NASA Astrophysics Data System (ADS)

    Balakin, A. A.; Litvak, A. G.; Mironov, V. A.; Skobelev, S. A.

    2017-09-01

    We study the possibility of efficient self-compression of femtosecond laser pulses in nonlinear media with anomalous dispersion of group velocity during the self-focusing of wave packets with a power several times greater than the critical self-focusing power. The results of qualitative analysis of the evolution of three-dimensional wave packets with the quasi-soliton field distribution are confirmed by the computer simulation. The simulation proves that the considered regime of compression of high-power laser pulses with initial durations of about ten optical cycles is stable relative to filamentation instability, due to the influence of the nonlinear dispersion. We demonstrate the possibility of self-compression of laser pulses at a multi-millijoule energy level and up to one optical cycle with an energy efficiency of more than 50%.

  4. Stimulated Raman self-scattering of femtosecond pulses. II. The self-compression of Schroedinger solitons in a spectrally inhomogeneous dispersion medium

    SciTech Connect

    Serkin, Vladimir N; Belyaeva, T L; Corro, G H; Granados, M Agueero

    2003-05-31

    It is shown that stimulated Raman self-scattering (SRSS) can be efficiently used for the compression of femtosecond optical solitons in optical fibres with the spectrally inhomogeneous frequency dependence of the group-velocity dispersion. The SRS dynamics is studied in detail near the point of the second-order zero dispersion. The saturation of compression of femtosecond solitons in spectrally inhomogeneous fibres in the zero-dispersion region is predicted. (solitons)

  5. Characterization and compression of dissipative-soliton-resonance pulses in fiber lasers

    PubMed Central

    Li, Daojing; Li, Lei; Zhou, Junyu; Zhao, Luming; Tang, Dingyuan; Shen, Deyuan

    2016-01-01

    We report numerical and experimental studies of dissipative-soliton-resonance (DSR) in a fiber laser with a nonlinear optical loop mirror. The DSR pulse presents temporally a flat-top profile and a clamped peak power. Its spectrum has a rectangle profile with characteristic steep edges. It shows a unique behavior as pulse energy increases: The rectangle part of the spectrum is unchanged while the newly emerging spectrum sits on the center part and forms a peak. Experimental observations match well with the numerical results. Moreover, the detailed evolution of the DSR pulse compression is both numerically and experimentally demonstrated for the first time. An experimentally obtained DSR pulse of 63 ps duration is compressed down to 760 fs, with low-intensity pedestals using a grating pair. Before being compressed to its narrowest width, the pulse firstly evolves into a cat-ear profile, and the corresponding autocorrelation trace shows a crown shape, which distinguishes itself from properties of other solitons formed in fiber lasers. PMID:27025189

  6. On the impact of adverse pressure gradient on the supersonic turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Wang, Qian-Cheng; Wang, Zhen-Guo; Zhao, Yu-Xin

    2016-11-01

    By employing the particle image velocimetry, the mean and turbulent characteristics of a Mach 2.95 turbulent boundary layer are experimentally investigated without the impact of curvature. The physical mechanism with which the streamwise adverse pressure gradient affects the supersonic boundary layer is revealed. The data are compared to that of the concave boundary layer with similar streamwise distributions of wall static pressure to clarify the separate impacts of the adverse pressure gradient and the concave curvature. The logarithmic law is observed to be well preserved for both of the cases. The dip below the logarithmic law is not observed in present investigation. Theoretical analysis indicates that it could be the result of compromise between the opposite impacts of the compression wave and the increased turbulent intensity. Compared to the zero pressure gradient boundary layer, the principal strain rate and the turbulent intensities are increased by the adverse pressure gradient. The shear layer formed due the hairpin packets could be sharpened by the compression wave, which leads to higher principal strain rate and the associated turbulent level. Due to the additional impact of the centrifugal instability brought by the concave wall, even higher turbulent intensities than that of the adverse pressure gradient case are introduced. The existence of velocity modes within the zero pressure gradient boundary layer suggests that the large scale motions are statistically well organized. The generation of new velocity modes due to the adverse pressure gradient indicates that the turbulent structure is changed by the adverse pressure gradient, through which more turbulence production that cannot be effectively predicted by the Reynolds-stress transport equations could be brought.

  7. Pressure-gradient fiber laser hydrophone

    NASA Astrophysics Data System (ADS)

    Zhang, Wentao; Zhang, Faxiang; Li, Fang; Liu, Yuliang

    2009-10-01

    A pressure-gradient fiber laser hydrophone (FLH) is demonstrated. Two brass diaphragms are installed at the end of a metal cylinder as the sensing element. There are two orifices at the middle of the cylinder. This structure can work as a pressure-gradient microphone in the acoustic field. Thus the DFB fiber laser fixed at the center of the two diaphragms is elongated or shortened due to the acoustic wave. Theoretical analysis is given based on the electro-acoustic theory. Experiments are carried out to test the performance of the hydrophone. A sensitivity of 100 nm/MPa has been achieved. Furthermore, the hydrostatic pressure is self-compensated and a ultra-thin dimension is achieved based on the proposed structure.

  8. Comment on "Electrostatic compressive and rarefactive shocks and solitons in relativistic plasmas occurring in polar regions of pulsar"

    NASA Astrophysics Data System (ADS)

    Hafez, M. G.; Talukder, M. R.; Hossain Ali, M.

    2016-05-01

    The aim of this comment is to show the solution of the KdVB equation used by Shah et al. (Astrophys. Space Sci. 335:529-537, 2011, doi: 10.1007/s10509-011-0766-y) is not correct. So, the numerical results that are predicted in this manuscript should not be helpful for further investigations in a plasma laboratory. For this reason, we have employed the Bernoulli's equation method to obtain the correct form of analytical solution to this equation, which is appropriate for the study of electrostatic compressive and rarefactive shocks and solitons in relativistic plasmas occurring in polar regions of pulsar.

  9. 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.

  10. Turbulence measurements in axisymmetric supersonic boundary layer flow in adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Gootzait, E.; Childs, M. E.

    1977-01-01

    Mean flow and turbulence measurements are presented for adiabatic compressible turbulent boundary layer flow in adverse pressure gradients. The gradients were induced on the wall of an axially symmetric wind tunnel by contoured centerbodies mounted on the wind tunnel centerline. The boundary layer turbulence downstream of a boundary layer bleed section in a zero pressure gradient was also examined. The measurements were obtained using a constant temperature hot-wire anemometer. The adverse pressure gradients were found to significantly alter the turbulence properties of the boundary layer. With flow through the bleed holes there was a measureable decrease in the rms longitudinal velocity fluctuations near the wall and the turbulent shear stress in the boundary layer was reduced.

  11. Turbulence measurements in axisymmetric supersonic boundary layer flow in adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Gootzait, E.; Childs, M. E.

    1976-01-01

    Measurements have been made of the mean-flow and turbulence properties in adiabatic turbulent boundary layer flows subjected to adverse pressure gradients. In the freestream region upstream of the adverse pressure gradient the Mach number was 3.86, the unit Reynolds number 5.3 million per foot. The boundary layer developed on the wall of an axisymmetric nozzle and straight test section. The pressure gradients at the test section wall were induced by contoured centerbodies mounted on the wind tunnel centerline. The flow under study simulated that which might be found in an axially symmetric engine inlet of a supersonic aircraft. The results obtained have shown good agreement to exist between the measured normalized turbulent velocity fluctuations and the results from other recent investigations of compressible boundary layers.

  12. Two techniques for temporal pulse compression in gas-filled hollow-core kagomé photonic crystal fiber.

    PubMed

    Mak, K F; Travers, J C; Joly, N Y; Abdolvand, A; Russell, P St J

    2013-09-15

    We demonstrate temporal pulse compression in gas-filled kagomé hollow-core photonic crystal fiber (PCF) using two different approaches: fiber-mirror compression based on self-phase modulation under normal dispersion, and soliton effect self-compression under anomalous dispersion with a decreasing pressure gradient. In the first, efficient compression to near-transform-limited pulses from 103 to 10.6 fs was achieved at output energies of 10.3 μJ. In the second, compression from 24 to 6.8 fs was achieved at output energies of 6.6 μJ, also with near-transform-limited pulse shapes. The results illustrate the potential of kagomé-PCF for postprocessing the output of fiber lasers. We also show that, using a negative pressure gradient, ultrashort pulses can be delivered directly into vacuum.

  13. Comment on ``Dynamically maintained steady-state pressure gradients''

    NASA Astrophysics Data System (ADS)

    Duncan, Todd L.

    2000-04-01

    Sheehan [Phys. Rev. E 57, 6660 (1998)] recently discussed the possibility of establishing a dynamically maintained, steady-state pressure gradient in a gas filling a cavity. In this Comment it is pointed out that the pressure gradients in such a system, if attainable in the laboratory, could be used to violate the second law of thermodynamics.

  14. Compressive and rarefactive dust-ion-acoustic Gardner solitons in a multi-component dusty plasma

    NASA Astrophysics Data System (ADS)

    Ema, S. A.; Ferdousi, M.; Mamun, A. A.

    2015-04-01

    The linear and nonlinear propagations of dust-ion-acoustic solitary waves (DIASWs) in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains have been investigated theoretically. The linear properties are analyzed by using the normal mode analysis and the reductive perturbation method is used to derive the nonlinear equations, namely, the Korteweg-de Vries (K-dV), the modified K-dV (mK-dV), and the Gardner equations. The basic features (viz., polarity, amplitude, width, etc.) of Gardner solitons (GS) are found to exist beyond the K-dV limit and these dust-ion-acoustic GS are qualitatively different from the K-dV and mK-dV solitons. It is observed that the basic features of DIASWs are affected by various plasma parameters (viz., electron nonextensivity, negative-to-positive ion number density ratio, electron-to-positive ion number density ratio, electron-to-positive ion temperature ratio, etc.) of the considered plasma system. The findings of our results obtained from this theoretical investigation may be useful in understanding the nonlinear structures and the characteristics of DIASWs propagating in both space and laboratory plasmas.

  15. Compressive and rarefactive dust-ion-acoustic Gardner solitons in a multi-component dusty plasma

    SciTech Connect

    Ema, S. A.; Ferdousi, M.; Mamun, A. A.

    2015-04-15

    The linear and nonlinear propagations of dust-ion-acoustic solitary waves (DIASWs) in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains have been investigated theoretically. The linear properties are analyzed by using the normal mode analysis and the reductive perturbation method is used to derive the nonlinear equations, namely, the Korteweg-de Vries (K-dV), the modified K-dV (mK-dV), and the Gardner equations. The basic features (viz., polarity, amplitude, width, etc.) of Gardner solitons (GS) are found to exist beyond the K-dV limit and these dust-ion-acoustic GS are qualitatively different from the K-dV and mK-dV solitons. It is observed that the basic features of DIASWs are affected by various plasma parameters (viz., electron nonextensivity, negative-to-positive ion number density ratio, electron-to-positive ion number density ratio, electron-to-positive ion temperature ratio, etc.) of the considered plasma system. The findings of our results obtained from this theoretical investigation may be useful in understanding the nonlinear structures and the characteristics of DIASWs propagating in both space and laboratory plasmas.

  16. Effect of laser annealing of pressure gradients in a diamond-anvil cell using common solid pressure media.

    PubMed

    Uts, Ilya; Glazyrin, Konstantin; Lee, Kanani K M

    2013-10-01

    Pressure media are one of the most effective deterrents of pressure gradients in diamond-anvil cell (DAC) experiments. The media, however, become less effective with increasing pressure, particularly for solid pressure media. One of the most popular ways of alleviating the increase in pressure gradients in DAC samples is through laser annealing of the sample. We explore the effectiveness of this technique for six common solid pressure media that include: alkali metal halides LiF, NaCl, KCl, CsCl, KBr, as well as amorphous SiO2. Pressure gradients are determined through the analysis of the first-order diamond Raman band across the sample before and after annealing the sample with a near-infrared laser to temperatures between ~2000 and 3000 K. As expected, we find that in the absence of sample chamber geometrical changes and diamond anvil damage, laser annealing reduces pressure gradients, albeit to varying amounts. We find that under ideal conditions, NaCl provides the best deterrent to pressure gradients before and after laser annealing, at least up to pressures of 60 GPa and temperatures between ~2000 and 3000 K. Amorphous SiO2, on the other hand, transforms in to harder crystalline stishovite upon laser annealing at high pressures resulting in increased pressure gradients upon further compression without laser annealing.

  17. Optimal disturbances in boundary layers subject to streamwise pressure gradient

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Tumin, Anatoli

    2003-01-01

    An analysis of the optimal non-modal growth of perturbations in a boundary layer in the presence of a streamwise pressure gradient is presented. The analysis is based on PSE equations for an incompressible fluid. Examples with Falkner-Scan profiles indicate that a favorable pressure gradient decreases the non-modal growth, while an unfavorable pressure gradient leads to an increase of the amplification. It is suggested that the transient growth mechanism be utilized to choose optimal parameters of tripping elements on a low-pressure turbine (LPT) airfoil. As an example, a boundary layer flow with a streamwise pressure gradient corresponding to the pressure distribution over a LPT airfoil is considered. It is shown that there is an optimal spacing of the tripping elements and that the transient growth effect depends on the starting point.

  18. The pressure gradient in the human respiratory tract

    NASA Astrophysics Data System (ADS)

    Chovancová, Michaela; Elcner, Jakub

    2014-03-01

    Respiratory airways cause resistance to air flow during inhalation and exhalation. The pressure gradient is necessary to transport the air from the mount (or nose) to pulmonary alveoli. The knowledge of pressure gradient (i.e. respiratory airways resistance) is also needed to solve the question of aerosol deposition in the human respiratory tract. The obtained data will be used as boundary conditions for CFD simulations of aerosol transport. Understanding of aerosol transport in the human lungs can help us to determine the health hazard of harmful particles. On the other hand it can be used to set the conditions for transport of medication to the desirable place. This article deals with the description of the mathematical equations defining the pressure gradient and resistance in the bronchial three and describes the geometry used in the calculation.

  19. Pressure Gradient Estimation Based on Ultrasonic Blood Flow Measurement

    NASA Astrophysics Data System (ADS)

    Nitta, Naotaka; Homma, Kazuhiro; Shiina, Tsuyoshi

    2006-05-01

    Mechanical load to the blood vessel wall, such as shear stress and pressure, which occurs in blood flow dynamics, contribute greatly to plaque rupture in arteriosclerosis and to biochemical activation of endothelial cells. Therefore, noninvasive estimations of these mechanical loads are able to provide useful information for the prevention of vascular diseases. Although the pressure is the dominant component of mechanical load, for practical purposes, the pressure gradient is also often important. So far, we have investigated the estimation of the kinematic viscosity coefficient using a combination of the Navier-Stokes equations and ultrasonic velocity measurement. In this paper, a method for pressure gradient estimation using the estimated kinematic viscosity coefficient is proposed. The validity of the proposed method was investigated on the basis of the analysis with the data obtained by computer simulation and a flow phantom experiment. These results revealed that the proposed method can provide a valid estimation of the pressure gradient.

  20. Pressure Gradients and Annealing Effects in Solid Helium-4

    NASA Astrophysics Data System (ADS)

    Suhel, Md. Abdul Halim

    The Kim and Chan experiment in 2004 gave the first experimental evidence of a possible supersolid state. Even though the origin of this state is not clear yet, several experimental and theoretical investigations suggest defects are responsible for this curious phase. We have used heat pulses and thermal quenching to study pressure gradients and annealing mechanisms in solid 4He crystals. Large pressure gradients exist in crystals grown at constant volume. These can be enhanced by phase transitions, thermal quenching or by partial melting. Annealing reduces defect densities and hence pressure gradients in crystals. Our measurements show that the pressure at different points in a crystal can behave differently, even if there is little change in the crystal's average pressure. We measured the activation energy that is associated with the annealing process.

  1. Enhanced magnetic reconnection in the presence of pressure gradients

    SciTech Connect

    Pueschel, M. J.; Terry, P. W.; Told, D.; Jenko, F.

    2015-06-15

    Magnetic reconnection in the presence of background pressure gradients is studied, with special attention to parallel (compressional) magnetic fluctuations. A process is reported that reconnects fields through coupling of drift-wave-type instabilities with current sheets. Its time scale is set not by the reconnecting field but by inhomogeneities of the background density or temperature. The observed features can be attributed to a pressure-gradient-driven linear instability which interacts with the reconnecting system but is fundamentally different from microtearing. In particular, this mode relies on parallel magnetic fluctuations and the associated drift. For turbulent reconnection, similar or even stronger enhancements are reported. In the solar corona, this yields a critical pressure gradient scale length of about 200 km below which this new process becomes dominant over the tearing instability.

  2. Evolution of a Planar Wake in Adverse Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Driver, David M.; Mateer, George G.

    2016-01-01

    In the interest of improving the predictability of high-lift systems at maximum lift conditions, a series of fundamental experiments were conducted to study the effects of adverse pressure gradient on a wake flow. Mean and fluctuating velocities were measured with a two-component laser-Doppler velocimeter. Data were obtained for several cases of adverse pressure gradient, producing flows ranging from no reversed flow to massively reversed flow. While the turbulent Reynolds stresses increase with increasing size of the reversed flow region, the gradient of Reynolds stress does not. Computations using various turbulence models were unable to reproduce the reversed flow.

  3. Accurate pressure gradient calculations in hydrostatic atmospheric models

    NASA Technical Reports Server (NTRS)

    Carroll, John J.; Mendez-Nunez, Luis R.; Tanrikulu, Saffet

    1987-01-01

    A method for the accurate calculation of the horizontal pressure gradient acceleration in hydrostatic atmospheric models is presented which is especially useful in situations where the isothermal surfaces are not parallel to the vertical coordinate surfaces. The present method is shown to be exact if the potential temperature lapse rate is constant between the vertical pressure integration limits. The technique is applied to both the integration of the hydrostatic equation and the computation of the slope correction term in the horizontal pressure gradient. A fixed vertical grid and a dynamic grid defined by the significant levels in the vertical temperature distribution are employed.

  4. 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.

  5. Time-domain near-infrared spectroscopy using a wavelength-tunable narrow-linewidth source by spectral compression of ultrashort soliton pulses.

    PubMed

    Nishizawa, Norihiko; Takahashi, Koji

    2011-10-01

    Time-domain absorption spectroscopy was demonstrated using a wideband, rapid wavelength-tunable, narrow-linewidth source based on an Er-doped ultrashort pulse fiber laser system. The spectrum of the Raman-shifted ultrashort soliton pulse was compressed using a comb-profile dispersion increasing fiber. Rapid wavelength sweeping was demonstrated using an electro-optical intensity modulator. The absorption spectrum of CH(2)Cl(2) liquid at 1625-1780 nm was observed in a 10 μs time-domain measurement. © 2011 Optical Society of America

  6. Asymptotically solvable model for a solitonic vortex in a compressible superfluid

    NASA Astrophysics Data System (ADS)

    Toikka, L. A.; Brand, J.

    2017-02-01

    Vortex motion is a complex problem due to the interplay between the short-range physics at the vortex core level and the long-range hydrodynamical effects. Here we show that the hydrodynamic equations of vortex motion in a compressible superfluid can be solved asymptotically in a model ‘slab’ geometry. Starting from an exact solution for an incompressible fluid, the hydrodynamic equations are solved with a series expansion in a small tunable parameter provided by the ratio of the healing length, characterising the vortex cores, to the slab width. The key dynamical properties of the vortex, the inertial and physical masses, are well defined and renormalizable. They are calculated at leading order beyond the logarithmic accuracy that has limited previous approaches. Subtracting the asymptotic solutions of the universal hydrodynamic problem from experimental observations of vortex motion exposes the physics of the vortex core and provides a window into interesting many-body phenomena that are currently poorly understood including the role of quantum pressure. Our results provide a solid framework for further detailed study of the vortex mass and vortex forces in strongly correlated and exotic superfluids.

  7. Novel pressure-gradient driven component for blood extraction

    NASA Astrophysics Data System (ADS)

    Fujioka, K.; Khumpuang, S.; Horede, M.; Sugiyama, S.

    2006-01-01

    Portable blood analysis devices are usually appreciable for applications in blood diagnostic system. We have designed and fabricated a low-cost and simple deal blood extraction device for a biomedical analysis. The device mainly composes of blood extraction tool and a functional bio-chemical analyzing element. In this work, we report the fabrication and pressure-gradient testing results of the blood extraction tool which consists of painless microneedle array and pressure-gradient tank. Microneedle array was fabricated by X-ray lithography using PCT (Plane-pattern to Cross-section Transfer) technique. The idea of our extraction device was simple but capability which is just to hold a sufficient pressure gradient between the tank and blood vessel. The device can draw the volume of blood up to 237 μl. The device was made of low-cost and disposable materials since it is expected to be used for single blood analysis system. In this work, we introduce design, fabrication and mechanism of the pressure gradient driven component including the extraction test results. The fabrication method of microneedle used in our system is also described.

  8. Optimal Disturbances in Boundary Layers Subject to Streamwise Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Tumin, Anatoli

    2003-01-01

    An analysis of the non-modal growth of perturbations in a boundary layer in the presence of a streamwise pressure gradient is presented. The analysis is based on PSE equations for an incompressible fluid. Examples with Falkner- Skan profiles indicate that a favorable pressure gradient decreases the non-modal growth while an unfavorable pressure gradient leads to an increase of the amplification. It is suggested that the transient growth mechanism be utilized to choose optimal parameters of tripping elements on a low-pressure turbine (LPT) airfoil. As an example, a boundary-layer flow with a streamwise pressure gradient corresponding to the pressure distribution over a LPT airfoil is considered. It is shown that there is an optimal spacing of the tripping elements and that the transient growth effect depends on the starting point. The amplification is found to be small at the LPT s very low Reynolds numbers, but there is a possibility to enhance the transient energy growth by means of wall cooling.

  9. Pressure Gradient Effects on Hypersonic Cavity Flow Heating

    NASA Technical Reports Server (NTRS)

    Everhart, Joel L.; Alter, Stephen J.; Merski, N. Ronald; Wood, William A.; Prabhu, Ramdas K.

    2007-01-01

    The effect of a pressure gradient on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated in support of the Space Shuttle Return-To-Flight Program. Two blunted-nose test surface geometries were developed, including an expansion plate test surface with nearly constant negative pressure gradient and a flat plate surface with nearly zero pressure gradient. The test surface designs and flow characterizations were performed using two-dimensional laminar computational methods, while the experimental boundary layer state conditions were inferred using the measured heating distributions. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process. Both open-flow and closed-flow cavities were tested on each test surface. The cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary conclusions based on an analysis of only the cavity centerline data indicate that the presence of the pressure gradient did not alter the open cavity heating for laminar-entry/laminar-exit flows, but did raise the average floor heating for closed cavities. The results of these risk-reduction studies will be used to formulate a heating assessment of potential damage scenarios occurring during future Space Shuttle flights.

  10. Pressure Gradient Effects on Hypersonic Cavity Flow Heating

    NASA Technical Reports Server (NTRS)

    Everhart, Joel L.; Alter, Stephen J.; Merski, N. Ronald; Wood, William A.; Prabhu, Ramadas K.

    2006-01-01

    The effect of a pressure gradient on the local heating disturbance of rectangular cavities tested at hypersonic freestream conditions has been globally assessed using the two-color phosphor thermography method. These experiments were conducted in the Langley 31-Inch Mach 10 Tunnel and were initiated in support of the Space Shuttle Return-To-Flight Program. Two blunted-nose test surface geometries were developed, including an expansion plate test surface with nearly constant negative pressure gradient and a flat plate surface with nearly zero pressure gradient. The test surface designs and flow characterizations were performed using two-dimensional laminar computational methods, while the experimental boundary layer state conditions were inferred using the measured heating distributions. Three-dimensional computational predictions of the entire model geometry were used as a check on the design process. Both open-flow and closed-flow cavities were tested on each test surface. The cavity design parameters and the test condition matrix were established using the computational predictions. Preliminary conclusions based on an analysis of only the cavity centerline data indicate that the presence of the pressure gradient did not alter the open cavity heating for laminar-entry/laminar-exit flows, but did raise the average floor heating for closed cavities. The results of these risk-reduction studies will be used to formulate a heating assessment of potential damage scenarios occurring during future Space Shuttle flights.

  11. Pressure Gradients in the Inner Surf and Outer Swash Zone

    NASA Astrophysics Data System (ADS)

    Kidwell, A.; Puleo, J. A.; Torres-Freyermuth, A.

    2010-12-01

    The swash zone is a highly dynamic region of the beach profile. Although there has been significant progression in understanding the complex hydrodynamics of the swash zone, an improvement in the understanding of the sediment transport mechanisms deserves further investigation. Prior studies have demonstrated that the existing formulations derived from the energetics-type formulation do not accurately and consistently predict sediment transport. Thus, measurements and numerical modeling can contribute in the improvement of the current predictive capability of sediment transport. A potential enhancement to nearshore sediment transport is the horizontal pressure gradient. However, measuring the dynamic pressure gradient in nearshore flows is a difficult task. For instance, standard pressure sensors are generally ill-suited for this type of measurement in shallow swash flows due to the obstructing size of the sensor and the potential for flow interference. With improved measurement apparati and techniques, it is possible to obtain measurements of the horizontal pressure gradient. Our current research includes laboratory and numerical model investigation of the horizontal pressure gradient in the inner surf and outer swash zone. An inexpensive differential pressure gauge is employed allowing for a pressure port on the order of 2 mm diameter. Four pressure sensor pairs are installed 1 cm above the bed with a cross-shore spacing of 8 cm. The sensors are deployed just outside of and at various locations within the outer swash zone to determine spatio-temporal pressure variations. The measurement of total pressure coupled with the corresponding free surface measurements from co-located capacitance wave gauges yields time series of the hydrostatic and dynamic pressure and pressure gradients. A VOF-type RANS model is employed in this investigation. Firstly, the numerical model is validated with swash measurements. Then, model simulations will be performed in order to

  12. Investigation on a pressure-gradient fiber laser hydrophone

    NASA Astrophysics Data System (ADS)

    Zhang, Wentao; Zhang, Faxiang; Li, Fang; Liu, Yuliang

    2010-09-01

    In this paper, a pressure-gradient fiber laser hydrophone is demonstrated. Two brass diaphragms are installed at the end of a metal cylinder as sensing elements. A distributed feedback fiber laser, fixed at the center of the two diaphragms, is elongated or shortened due to the acoustic wave. There are two orifices at the middle of the cylinder. So this structure can work as a pressure-gradient microphone in the acoustic field. Furthermore, the hydrostatic pressure is self-compensated and an ultra-thin dimension is achieved. Theoretical analysis is given based on the electro-acoustic theory. Field trials are carried out to test the performance of the hydrophone. A sensitivity of 100 nm MPa-1 has been achieved. Due to the small dimensions, no directivity is found in the test.

  13. Plasma Streamwise Vortex Generators in an Adverse Pressure Gradient

    NASA Astrophysics Data System (ADS)

    Kelley, Christopher; Corke, Thomas; Thomas, Flint

    2013-11-01

    A wind tunnel experiment was conducted to compare plasma streamwise vortex generators (PSVGs) and passive vortex generators (VGs). These devices were installed on a wing section by which the angle of attack could be used to vary the streamwise pressure gradient. The experiment was performed for freestream Mach numbers 0.1-0.2. Three-dimensional velocity components were measured using a 5-hole Pitot probe in the boundary layer. These measurements were used to quantify the production of streamwise vorticity and the magnitude of the reorientation term from the vorticity transport equation. The effect of Mach number, pressure gradient, operating voltage, and electrode length was then investigated for the PSVGs. The results indicate that the PSVGs could easily outperform the passive VGs and provide a suitable alternative for flow control.

  14. Computation of Turbulent Wake Flows in Variable Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Duquesne, N.; Carlson, J. R.; Rumsey, C. L.; Gatski, T. B.

    1999-01-01

    Transport aircraft performance is strongly influenced by the effectiveness of high-lift systems. Developing wakes generated by the airfoil elements are subjected to strong pressure gradients and can thicken very rapidly, limiting maximum lift. This paper focuses on the effects of various pressure gradients on developing symmetric wakes and on the ability of a linear eddy viscosity model and a non-linear explicit algebraic stress model to accurately predict their downstream evolution. In order to reduce the uncertainties arising from numerical issues when assessing the performance of turbulence models, three different numerical codes with the same turbulence models are used. Results are compared to available experimental data to assess the accuracy of the computational results.

  15. Pore-pressure gradients in the proximity of a submarine buried pipeline

    SciTech Connect

    Magda, W.

    1995-12-31

    This paper is concerned with the two-dimensional finite-element modeling of the wave-induced pore-pressure field in the proximity of a submarine pipeline buried in sandy seabed sediments subject to continuous loading of regular surface waves. Neglecting inertial forces, a linear elastic stress-strain relationship for the soil, and Darcy`s law for the flow of pore-fluid are assumed. The model takes into account the compressibility of both components (i.e., pore-fluid and soil skeleton) of the two-phase medium. The results of numerical computations are discussed with respect to the hydraulic gradient in the upper part of seabed sediments just above the buried submarine pipeline. The pore-pressure gradient is studied as a function of geometry (depth of burial) as well as soil and pore-fluid compressibility parameters where the later of which is defined in terms of soil saturation conditions.

  16. Integral analysis of boundary layer flows with pressure gradient

    NASA Astrophysics Data System (ADS)

    Wei, Tie; Maciel, Yvan; Klewicki, Joseph

    2017-09-01

    This Rapid Communication investigates boundary layer flows with a pressure gradient using a similarity/integral analysis of the continuity equation and momentum equation in the streamwise direction. The analysis yields useful analytical relations for Ve, the mean wall-normal velocity at the edge of the boundary layer, and for the skin friction coefficient Cf in terms of the boundary layer parameters and in particular βRC, the Rotta-Clauser pressure gradient parameter. The analytical results are compared with experimental and numerical data and are found to be valid. One of the main findings is that for large positive βRC (an important effect of an adverse pressure gradient), the friction coefficient is closely related to βRC as Cf∝1 /βRC , because δ /δ1,δ1/δ2=H , and d δ /d x become approximately constant. Here, δ is the boundary layer thickness, δ1 is the displacement thickness, δ2 is the momentum thickness, and H is the shape factor. Another finding is that the mean wall-normal velocity at the edge of the boundary layer is related to other flow variables as UeVe/uτ2=H +(1 +δ /δ1+H ) βRC , where Ue is the streamwise velocity at the edge of the boundary layer. At zero pressure gradient, this relation reduces to U∞V∞/uτ2=H , as recently derived by Wei and Klewicki [Phys. Rev. Fluids 1, 082401 (2016), 10.1103/PhysRevFluids.1.082401].

  17. On Localized Vapor Pressure Gradients Governing Condensation and Frost Phenomena.

    PubMed

    Nath, Saurabh; Boreyko, Jonathan B

    2016-08-23

    Interdroplet vapor pressure gradients are the driving mechanism for several phase-change phenomena such as condensation dry zones, interdroplet ice bridging, dry zones around ice, and frost halos. Despite the fundamental nature of the underlying pressure gradients, the majority of studies on these emerging phenomena have been primarily empirical. Using classical nucleation theory and Becker-Döring embryo formation kinetics, here we calculate the pressure field for all possible modes of condensation and desublimation in order to gain fundamental insight into how pressure gradients govern the behavior of dry zones, condensation frosting, and frost halos. Our findings reveal that in a variety of phase-change systems the thermodynamically favorable mode of nucleation can switch between condensation and desublimation depending upon the temperature and wettability of the surface. The calculated pressure field is used to model the length of a dry zone around liquid or ice droplets over a broad parameter space. The long-standing question of whether the vapor pressure at the interface of growing frost is saturated or supersaturated is resolved by considering the kinetics of interdroplet ice bridging. Finally, on the basis of theoretical calculations, we propose that there exists a new mode of frost halo that is yet to be experimentally observed; a bimodal phase map is developed, demonstrating its dependence on the temperature and wettability of the underlying substrate. We hope that the model and predictions contained herein will assist future efforts to exploit localized vapor pressure gradients for the design of spatially controlled or antifrosting phase-change systems.

  18. Estimation of pressure gradients at renal artery stenoses

    NASA Astrophysics Data System (ADS)

    Yim, Peter J.; Cebral, Juan R.; Weaver, Ashley; Lutz, Robert J.; Vasbinder, G. Boudewijn C.

    2003-05-01

    Atherosclerotic disease of the renal artery can reduce the blood flow leading to renovascular hypertension and ischemic nephopathy. The kidney responds to a decrease in blood flow by activation of the renin-angiotensin system that increases blood pressure and can result in severe hypertension. Percutaneous translumenal angioplasty (PTA) may be indicated for treatment of renovascular hypertension (RVH). However, direct measurement of renal artery caliber and degree of stenosis has only moderate specificity for detection of RVH. A confounding factor in assessment of the proximal renal artery is that diffuse atherosclerotic disease of the distal branches of the renal artery can produce the same effect on blood-flow as atherosclerotic disease of the proximal renal artery. A methodology is proposed for estimation of pressure gradients at renal artery stenoses from magnetic resonance imaging that could improve the evaluation of renal artery disease. In the proposed methodology, pressure gradients are estimated using computational fluid dynamics (CFD) modeling. Realistic CFD models are constructed from images of vessel shape and measurements of blood-flow rates which are available from magnetic resonance angiography (MRA) and phase-contrast magnetic resonance (MR) imaging respectively. CFD measurement of renal artery pressure gradients has been validated in a physical flow-through model.

  19. Statistical estimates for channel flows driven by a pressure gradient

    NASA Astrophysics Data System (ADS)

    Ramos, F.; Rosa, R.; Temam, R.

    2008-07-01

    We present rigorous estimates for some physical quantities related to turbulent and non-turbulent channel flows driven by a uniform pressure gradient. Such results are based on the concept of stationary statistical solutions, which is related to the notion of ensemble averages for flows in statistical equilibrium. We provide a lower bound estimate for the mean skin friction coefficient and improve on a previous upper bound estimate for the same quantity; both estimates are derived in terms of the Reynolds number. We also present lower and upper bound estimates for the mean rate of energy dissipation, the mean longitudinal bulk velocity (in the direction of the pressure gradient), and the mean kinetic energy in terms of various physical parameters. In particular, we obtain an upper bound related to the energy dissipation law, namely that the mean rate of energy dissipation is essentially bounded by a non-dimensional universal constant times the cube of the mean longitudinal bulk velocity over a characteristic macro-scale length. Finally, we investigate the scale-by-scale energy injection due to the pressure gradient, proving an upper bound estimate for the decrease of this energy injection as the scale length decreases.

  20. Vandenberg Air Force Base Pressure Gradient Wind Study

    NASA Technical Reports Server (NTRS)

    Shafer, Jaclyn A.

    2013-01-01

    Warning category winds can adversely impact day-to-day space lift operations at Vandenberg Air Force Base (VAFB) in California. NASA's Launch Services Program and other programs at VAFB use wind forecasts issued by the 30 Operational Support Squadron Weather Flight (30 OSSWF) to determine if they need to limit activities or protect property such as a launch vehicle. The 30 OSSWF tasked the AMU to develop an automated Excel graphical user interface that includes pressure gradient thresholds between specific observing stations under different synoptic regimes to aid forecasters when issuing wind warnings. This required the AMU to determine if relationships between the variables existed.

  1. Structure of the zero-pressure-gradient turbulent boundary layer.

    PubMed

    Barenblatt, G I; Chorin, A J; Hald, O H; Prostokishin, V M

    1997-07-22

    A processing of recent experimental data by Nagib and Hites [Nagib, H. & Hites, M. (1995) AIAA paper 95-0786, Reno, NV) shows that the flow in a zero-pressure-gradient turbulent boundary layer, outside the viscous sublayer, consists of two self-similar regions, each described by a scaling law. The results concerning the Reynolds-number dependence of the coefficients of the wall-region scaling law are consistent with our previous results concerning pipe flow, if the proper definition of the boundary layer Reynolds number (or boundary layer thickness) is used.

  2. Characteristics of turbulence in boundary layer with zero pressure gradient

    NASA Technical Reports Server (NTRS)

    Klebanoff, P S

    1955-01-01

    The results of an experimental investigation of a turbulent boundary layer with zero pressure gradient are presented. Measurements with the hot-wire anemometer were made of turbulent energy and turbulent shear stress, probability density and flattening factor of u-fluctuation (fluctuation in x-direction), spectra of turbulent energy and shear stress, and turbulent dissipation. The importance of the region near the wall and the inadequacy of the concept of local isotropy are demonstrated. Attention is given to the energy balance and the intermittent character of the outer region of the boundary layer. Also several interesting features of the spectral distribution of the turbulent motions are discussed.

  3. Effectiveness of Micro-Blowing Technique in Adverse Pressure Gradients

    NASA Technical Reports Server (NTRS)

    Welch, Gerard E.; Larosiliere, Louis M.; Hwang, Danny P.; Wood, Jerry R.

    2001-01-01

    The impact of the micro-blowing technique (MBT) on the skin friction and total drag of a strut in a turbulent, strong adverse-pressure-gradient flow is assessed experimentally over a range of subsonic Mach numbers (0.3 less than M less than 0.7) and reduced blowing fractions (0 less than or equal to 2F/C (sub f,o) less than or equal to 1.75). The MBT-treated strut is situated along the centerline of a symmetric 2-D diffuser with a static pressure rise coefficient of 0.6. In agreement with presented theory and earlier experiments in zero-pressure-gradient flows, the effusion of blowing air reduces skin friction significantly (e.g., by 60% at reduced blowing fractions near 1.75). The total drag of the treated strut with blowing is significantly lower than that of the treated strut in the limit of zero-blowing; further, the total drag is reduced below that of the baseline (solid-plate) strut, provided that the reduced blowing fractions are sufficiently high. The micro-blowing air is, however, deficient in streamwise momentum and the blowing leads to increased boundary-layer and wake thicknesses and shape factors. Diffuser performance metrics and wake surveys are used to discuss the impact of various levels of micro-blowing on the aerodynamic blockage and loss.

  4. Investigation of pressure gradient aware wall modeling in LES

    NASA Astrophysics Data System (ADS)

    Thiry, Olivier; Winckelmans, Gregoire; Duponcheel, Matthieu

    2015-11-01

    This work focuses on the investigation of various wall modeling strategies for the simulation of high Reynolds number wall-bounded turbulent flows with acceleration and/or deceleration. Our code is based on fourth order finite differences, is momentum conserving, and is energy conserving up to fourth order. We here use a ``channel flow'' set-up, with no slip and wall modeling at the bottom, with slip at the top, and with blowing and/or suction at the top in order to generate the desired acceleration-deceleration profile. Two strategies are investigated and compared. Pressure gradient corrected algebraic models are first considered, and we investigate various local averaging techniques so as to avoid imposing mean profile laws pointwise. RANS sub-layer models are then also considered, where the turbulent viscosity is corrected to account for pressure gradient effects and for resolved LES fluctuations effects. A wall-resolved LES was also performed to provide a reference solution. Research fellow (Ph.D. student) at the F.R.S. - FNRS (Belgium).

  5. Transition from resistive ballooning to neoclassical magnetohydrodynamic pressure-gradient-driven instability

    SciTech Connect

    Spong, D. A.; Shaing, K. C.; Carreras, B. A.; Charlton, L. A.; Callen, J. D.; Garcia, L.

    1988-10-01

    The linearized neoclassical magnetohydrodynamic equations, including perturbed neoclassical flows and currents, have been solved for parameter regimes where the neoclassical pressure-gradient-driven instability becomes important. This instability is driven by the fluctuating bootstrap current term in Ohm's law. It begins to dominate the conventional resistive ballooning mode in the banana-plateau collisionality regime ({mu}{sub e}/{nu}{sub e} approx {radical}{epsilon}/(1 + {nu}{sub *e}) > {epsilon}{sup 2}) and is characterized by a larger radial mode width and higher growth rate. The neoclassical instability persists in the absence of the usual magnetic field curvature drive and is not significantly affected by compressibility. Scalings with respect to {beta}, n (toroidal mode number), and {mu} (neoclassical viscosity) are examined using a large-aspect-ratio, three-dimensional initial-value code that solves linearized equations for the magnetic flux, fluid vorticity, density, and parallel ion flow velocity in axisymmetric toroidal geometry. 13 refs., 10 figs.

  6. Implicit Large-Eddy Simulations of Zero-Pressure Gradient, Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Sekhar, Susheel; Mansour, Nagi N.

    2015-01-01

    A set of direct simulations of zero-pressure gradient, turbulent boundary layer flows are conducted using various span widths (62-630 wall units), to document their influence on the generated turbulence. The FDL3DI code that solves compressible Navier-Stokes equations using high-order compact-difference scheme and filter, with the standard recycling/rescaling method of turbulence generation, is used. Results are analyzed at two different Re values (500 and 1,400), and compared with spectral DNS data. They show that a minimum span width is required for the mere initiation of numerical turbulence. Narrower domains ((is) less than 100 w.u.) result in relaminarization. Wider spans ((is) greater than 600 w.u.) are required for the turbulent statistics to match reference DNS. The upper-wall boundary condition for this setup spawns marginal deviations in the mean velocity and Reynolds stress profiles, particularly in the buffer region.

  7. Effect of Pressure Gradients on Plate Response and Radiation in a Supersonic Turbulent Boundary Layer

    NASA Technical Reports Server (NTRS)

    Frendi, Abdelkader

    1997-01-01

    Using the model developed by the author for zero-pressure gradient turbulent boundary layers, results are obtained for adverse and favorable pressure gradients. It is shown that when a flexible plate is located in an adverse pressure gradient area, it vibrates more than if it were in a favorable pressure gradient one. Therefore the noise generated by the plate in an adverse pressure gradient is much greater than that due to the plate in a favorable pressure gradient. The effects of Reynolds number and boundary layer thickness are also analyzed and found to have the same effect in both adverse and favorable pressure gradient cases. Increasing the Reynolds number is found to increase the loading on the plate and therefore acoustic radiation. An increase in boundary layer thickness is found to decrease the level of the high frequencies and therefore the response and radiation at these frequencies. The results are in good qualitative agreement with experimental measurements.

  8. Wake measurements in a strong adverse pressure gradient

    NASA Technical Reports Server (NTRS)

    Hoffenberg, R.; Sullivan, John P.; Schneider, S. P.

    1994-01-01

    The behavior of wakes in adverse pressure gradients is critical to the performance of high-lift systems for transport aircraft. Wake deceleration is known to lead to sudden thickening and the onset of reversed flow; this 'wake bursting' phenomenon can occur while surface flows remain attached. Although 'wake bursting' is known to be important for high-lift systems, no detailed measurements of 'burst' wakes have ever been reported. Wake bursting has been successfully achieved in the wake of a flat plate as it decelerated in a two-dimensional diffuser, whose sidewalls were forced to remain attached by use of slot blowing. Pilot probe surveys, L.D.V. measurements, and flow visualization have been used to investigate the physics of this decelerated wake, through the onset of reversed flow.

  9. Theory of neoclassical pressure-gradient-driven turbulence

    SciTech Connect

    Kwon, O.J. ); Diamond, P.H.; Biglari, H. General Atomics, Inc., San Diego, California 92138 )

    1990-02-01

    The nonlinear evolution and saturation of neoclassical pressure-gradient-driven turbulence (NPGDT), evolving from linearly unstable bootstrap-current modes, are investigated. The theoretical model is based on neoclassical magnetohydrodynamic (MHD) equations'' that are valid in the banana-plateau regimes of collisionality. Modes with poloidal wavelengths shorter than radial wavelengths are shown to be suppressed. From nonlinear saturation conditions, the turbulent pressure diffusivity is determined as an eigenvalue of the renormalized equations. Levels and radial scales of turbulence are determined from the pressure diffusivity and are shown to exceed mixing-length estimates by powers of a nonlinear enhancement factor. The problem of the electron heat transport resulting from stochastic magnetic fields driven by NPGDT is revisited. The reconsideration of the radial structure of magnetic flutter leads to estimates of the electron heat transport and magnetic fluctuation levels that differ qualitatively and quantitatively from previous calculations.

  10. Theory of neoclassical pressure-gradient-driven turbulence

    SciTech Connect

    Kwon, O.J.; Diamond, P.H.; Biglari, H.

    1988-11-01

    The nonlinear evolution and saturation of neoclassical pressure- gradient-driven turbulence (NPGDT), evolving from linearly unstable bootstrap current modes, are investigated. The theoretical model is based on '' neoclassical MHD equations'' which are valid in the banana-plateau regimes of collisionality. Modes with poloidal wavelengths shorter than radial wavelengths are shown to be suppressed. From nonlinear saturation conditions, the turbulent pressure diffusivity is determined as an eigenvalue of the renormalized equations. Levels and radial scales of turbulence are determined from the pressure diffusivity and are shown to exceed mixing length estimates by powers of a nonlinear enhancement factor. The problem of the electron heat transport due to stochastic magnetic fields driven by NPGDT is revisited. The reconsideration of the radial structure of magnetic flutter leads to estimates of the electron heat transport and magnetic fluctuation levels which differ qualitatively and quantitatively from previous calculations. 25 refs.

  11. Radio jet refraction in galactic atmospheres with static pressure gradients

    NASA Technical Reports Server (NTRS)

    Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

    1981-01-01

    A theory of double radio sources which have a 'Z' or 'S' morphology is proposed, based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy. The model describes a collimated jet of supersonic material bending self-consistently under the influence of external static pressure gradients. Gravity and magnetic fields are neglected in the simplest case except insofar as they determine the static pressure distribution. The calculation is a straightforward extension of a method used to calculate a ram-pressure model for twin radio trails ('C' morphology). It may also be described as a continuous-jet version of a buoyancy model proposed in 1973. The model has the added virtue of invoking a galactic atmosphere similar to those already indicated by X-ray measurements of some other radio galaxies and by models for the collimation of other radio jets.

  12. Radio jet refraction in galactic atmospheres with static pressure gradients

    NASA Technical Reports Server (NTRS)

    Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

    1981-01-01

    A theory based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy, is proposed for double radio sources with a Z or S morphology. The model describes a collimated jet of supersonic material that bends self-consistently under the influence of external static pressure gradients, and may alternatively be seen as a continuous-jet version of the buoyancy model proposed by Gull (1973). Emphasis is placed on (1) S-shaped radio sources identified with isolated galaxies, such as 3C 293, whose radio structures should be free of distortions resulting from motion relative to a cluster medium, and (2) small-scale, galaxy-dominated rather than environment-dominated S-shaped sources such as the inner jet structure of Fornax A.

  13. Pressure Gradient Effects On Two-Dimensional Plasma Expansion

    SciTech Connect

    Moon, S; Smith, R F; Dunn, J; Keenan, R; Nilsen, J; Hunter, J R; Filevich, J; Rocca, J J; Marconi, M C; Shlyaptsev, V N

    2004-10-05

    Recent advances in interferometry has allowed for the characterization of the electron density expansion within a laser produced plasma to within 10 {micro}m of the target surface and over picosecond timescales. This technique employs the high brightness output of the transient gain Ni-like Pd collisional x-ray laser at 14.7 nm to construct an effective moving picture of the two-dimensional (2-D) expansion of the plasma. We present experimentally measured density profiles of an expanding Al plasma generated through laser irradiation in a 14mm line focus geometry. Significant lateral expansion was observed at all times as well as a pronounced on-axis electron density dip. Detailed modeling with a 2-D plasma physics code gives good agreement to experimental observations. Large pressure gradients associated with the tight focal spot conditions are calculated to dominate in shaping the plasma density profile.

  14. Radio jet refraction in galactic atmospheres with static pressure gradients

    NASA Technical Reports Server (NTRS)

    Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

    1981-01-01

    A theory based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy, is proposed for double radio sources with a Z or S morphology. The model describes a collimated jet of supersonic material that bends self-consistently under the influence of external static pressure gradients, and may alternatively be seen as a continuous-jet version of the buoyancy model proposed by Gull (1973). Emphasis is placed on (1) S-shaped radio sources identified with isolated galaxies, such as 3C 293, whose radio structures should be free of distortions resulting from motion relative to a cluster medium, and (2) small-scale, galaxy-dominated rather than environment-dominated S-shaped sources such as the inner jet structure of Fornax A.

  15. Characterizing developing adverse pressure gradient flows subject to surface roughness

    NASA Astrophysics Data System (ADS)

    Brzek, Brian; Chao, Donald; Turan, Özden; Castillo, Luciano

    2010-04-01

    An experimental study was conducted to examine the effects of surface roughness and adverse pressure gradient (APG) on the development of a turbulent boundary layer. Hot-wire anemometry measurements were carried out using single and X-wire probes in all regions of a developing APG flow in an open return wind tunnel test section. The same experimental conditions (i.e., T ∞, U ref, and C p) were maintained for smooth, k + = 0, and rough, k + = 41-60, surfaces with Reynolds number based on momentum thickness, 3,000 < Re θ < 40,000. The experiment was carefully designed such that the x-dependence in the flow field was known. Despite this fact, only a very small region of the boundary layer showed a balance of the various terms in the integrated boundary layer equation. The skin friction computed from this technique showed up to a 58% increase due to the surface roughness. Various equilibrium parameters were studied and the effect of roughness was investigated. The generated flow was not in equilibrium according to the Clauser (J Aero Sci 21:91-108, 1954) definition due to its developing nature. After a development region, the flow reached the equilibrium condition as defined by Castillo and George (2001), where Λ = const, is the pressure gradient parameter. Moreover, it was found that this equilibrium condition can be used to classify developing APG flows. Furthermore, the Zagarola and Smits (J Fluid Mech 373:33-79, 1998a) scaling of the mean velocity deficit, U ∞δ*/δ, can also be used as a criteria to classify developing APG flows which supports the equilibrium condition of Castillo and George (2001). With this information a ‘full APG region’ was defined.

  16. A turbulent burst model for boundary layer flows with pressure gradient

    NASA Astrophysics Data System (ADS)

    Thomas, L. C.; Benton, D. J.

    The object of this paper is to develop a surface renewal model of the turbulent burst phenomenon for momentum and energy transfer in the wall region for turbulent boundary layer flows with pressure gradient. In addition to obtaining inner laws for the distributions in velocity and temperature, predictions are obtained for the effect of pressure gradient on the mean burst frequency and on the turbulent Prandtl number within the wall region for slight favorable and mild adverse pressure gradients.

  17. Modeling of Propagation of Interacting Cracks Under Hydraulic Pressure Gradient

    SciTech Connect

    Huang, Hai; Mattson, Earl Douglas; Podgorney, Robert Karl

    2015-04-01

    A robust and reliable numerical model for fracture initiation and propagation, which includes the interactions among propagating fractures and the coupling between deformation, fracturing and fluid flow in fracture apertures and in the permeable rock matrix, would be an important tool for developing a better understanding of fracturing behaviors of crystalline brittle rocks driven by thermal and (or) hydraulic pressure gradients. In this paper, we present a physics-based hydraulic fracturing simulator based on coupling a quasi-static discrete element model (DEM) for deformation and fracturing with conjugate lattice network flow model for fluid flow in both fractures and porous matrix. Fracturing is represented explicitly by removing broken bonds from the network to represent microcracks. Initiation of new microfractures and growth and coalescence of the microcracks leads to the formation of macroscopic fractures when external and/or internal loads are applied. The coupled DEM-network flow model reproduces realistic growth pattern of hydraulic fractures. In particular, simulation results of perforated horizontal wellbore clearly demonstrate that elastic interactions among multiple propagating fractures, fluid viscosity, strong coupling between fluid pressure fluctuations within fractures and fracturing, and lower length scale heterogeneities, collectively lead to complicated fracturing patterns.

  18. Luminescence from cavitation bubbles deformed in uniform pressure gradients

    NASA Astrophysics Data System (ADS)

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed

    2017-09-01

    Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single-collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelength range, 300-900 nm) from the individual collapses of laser-induced bubbles in water. By varying the bubble size, driving pressure, and perceived gravity level aboard parabolic flights, we probed the limit from aspherical to highly spherical bubble collapses. Luminescence was detected for bubbles of maximum radii within the previously uncovered range, R0=1.5 -6 mm, for laser-induced bubbles. The relative luminescence energy was found to rapidly decrease as a function of the bubble asymmetry quantified by the anisotropy parameter ζ , which is the dimensionless equivalent of the Kelvin impulse. As established previously, ζ also dictates the characteristic parameters of bubble-driven microjets. The threshold of ζ beyond which no luminescence is observed in our experiment closely coincides with the threshold where the microjets visibly pierce the bubble and drive a vapor jet during the rebound. The individual fitted blackbody temperatures range between Tlum=7000 and Tlum=11 500 K but do not show any clear trend as a function of ζ . Time-resolved measurements using a high-speed photodetector disclose multiple luminescence events at each bubble collapse. The averaged full width at half-maximum of the pulse is found to scale with R0 and to range between 10 and 20 ns.

  19. Optimal Disturbances in Boundary Layers Subject to Streamwise Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Tumin, Anatoli; Ashpis, David E.

    2003-01-01

    Laminar-turbulent transition in shear flows is still an enigma in the area of fluid mechanics. The conventional explanation of the phenomenon is based on the instability of the shear flow with respect to infinitesimal disturbances. The conventional hydrodynamic stability theory deals with the analysis of normal modes that might be unstable. The latter circumstance is accompanied by an exponential growth of the disturbances that might lead to laminar-turbulent transition. Nevertheless, in many cases, the transition scenario bypasses the exponential growth stage associated with the normal modes. This type of transition is called bypass transition. An understanding of the phenomenon has eluded us to this day. One possibility is that bypass transition is associated with so-called algebraic (non-modal) growth of disturbances in shear flows. In the present work, an analysis of the optimal disturbances/streamwise vortices associated with the transient growth mechanism is performed for boundary layers in the presence of a streamwise pressure gradient. The theory will provide the optimal spacing of the control elements in the spanwise direction and their placement in the streamwise direction.

  20. Solitons riding on solitons and the quantum Newton's cradle

    NASA Astrophysics Data System (ADS)

    Ma, Manjun; Navarro, R.; Carretero-González, R.

    2016-02-01

    The reduced dynamics for dark and bright soliton chains in the one-dimensional nonlinear Schrödinger equation is used to study the behavior of collective compression waves corresponding to Toda lattice solitons. We coin the term hypersoliton to describe such solitary waves riding on a chain of solitons. It is observed that in the case of dark soliton chains, the formulated reduction dynamics provides an accurate an robust evolution of traveling hypersolitons. As an application to Bose-Einstein condensates trapped in a standard harmonic potential, we study the case of a finite dark soliton chain confined at the center of the trap. When the central chain is hit by a dark soliton, the energy is transferred through the chain as a hypersoliton that, in turn, ejects a dark soliton on the other end of the chain that, as it returns from its excursion up the trap, hits the central chain repeating the process. This periodic evolution is an analog of the classical Newton's cradle.

  1. Solitons riding on solitons and the quantum Newton's cradle.

    PubMed

    Ma, Manjun; Navarro, R; Carretero-González, R

    2016-02-01

    The reduced dynamics for dark and bright soliton chains in the one-dimensional nonlinear Schrödinger equation is used to study the behavior of collective compression waves corresponding to Toda lattice solitons. We coin the term hypersoliton to describe such solitary waves riding on a chain of solitons. It is observed that in the case of dark soliton chains, the formulated reduction dynamics provides an accurate an robust evolution of traveling hypersolitons. As an application to Bose-Einstein condensates trapped in a standard harmonic potential, we study the case of a finite dark soliton chain confined at the center of the trap. When the central chain is hit by a dark soliton, the energy is transferred through the chain as a hypersoliton that, in turn, ejects a dark soliton on the other end of the chain that, as it returns from its excursion up the trap, hits the central chain repeating the process. This periodic evolution is an analog of the classical Newton's cradle.

  2. Effects of pressure gradient on global Alfvén eigenmodes in reversed field pinch

    NASA Astrophysics Data System (ADS)

    Cai, Huishan; Fu, Guoyong; Lin, Liang; Liu, D. Y.; Ding, Weixing; Brower, D. L.; Hu, Y. J.

    2014-02-01

    The effects of pressure gradient on the existence of global Alfvén eigenmodes (GAE) in Reversed Field Pinch are studied by numerical calculation. It is found that GAEs near the plasma core can exist when pressure gradient is sufficiently large. The calculated mode frequency and structure are consistent with the experimental results in the Madison Symmetric Torus.

  3. The second law and chemically-induced, steady-state pressure gradients: controversy, corroboration and caveats

    NASA Astrophysics Data System (ADS)

    Sheehan, D. P.

    2001-02-01

    Experimental results are reported supporting key aspects of a recently proposed chemical pressure gradient (D.P. Sheehan, Phys. Rev. E 57 (1998) 6660). This pressure gradient has been invoked in a paradox involving the second law of thermodynamics (T.L. Duncan, Phys. Rev. E 61 (2000) 4661).

  4. Effects of pressure gradient on global Alfvén eigenmodes in reversed field pinch

    SciTech Connect

    Cai, Huishan; Fu, Guoyong; Lin, Liang; Ding, Weixing; Brower, D. L.; Liu, D. Y.; Hu, Y. J.

    2014-02-15

    The effects of pressure gradient on the existence of global Alfvén eigenmodes (GAE) in Reversed Field Pinch are studied by numerical calculation. It is found that GAEs near the plasma core can exist when pressure gradient is sufficiently large. The calculated mode frequency and structure are consistent with the experimental results in the Madison Symmetric Torus.

  5. Quantitative Analysis of Cerebrospinal Fluid Pressure Gradients in Healthy Volunteers and Patients with Normal Pressure Hydrocephalus

    PubMed Central

    HAYASHI, Naokazu; MATSUMAE, Mitsunori; YATSUSHIRO, Satoshi; HIRAYAMA, Akihiro; ABDULLAH, Afnizanfaizal; KURODA, Kagayaki

    2015-01-01

    Magnetic resonance imaging (MRI) can depict not only anatomical information, but also physiological factors such as velocity and pressure gradient. Measurement of these physiological factors is necessary to understand the cerebrospinal fluid (CSF) environment. In this study we quantified CSF motion in various parts of the CSF space, determined changes in the CSF environment with aging, and compared CSF pressure gradient between patients with idiopathic normal pressure hydrocephalus (iNPH) and healthy elderly volunteers. Fifty-seven healthy volunteers and six iNPH patients underwent four-dimensional (4D) phase-contrast (PC) MRI. CSF motion was observed and the pressure gradient of CSF was quantified in the CSF space. In healthy volunteers, inhomogeneous CSF motion was observed whereby the pressure gradient markedly increased in the center of the skull and gradually decreased in the periphery of the skull. For example, the pressure gradient at the ventral surface of the brainstem was 6.6 times greater than that at the convexity of the cerebrum. The pressure gradient was statistically unchanged with aging. The pressure gradient of patients with iNPH was 3.2 times greater than that of healthy volunteers. The quantitative analysis of 4D-PC MRI data revealed that the pressure gradient of CSF can be used to understand the CSF environment, which is not sufficiently given by subjective impression of the anatomical image. PMID:26226976

  6. Effect of Axial Pressure Gradient on the Bifurcation Structure of Viscous Vortex Breakdown

    NASA Astrophysics Data System (ADS)

    Vyazmina, Elena; Nichols, Joseph; Chomaz, Jean-Marc; Schmid, Peter

    2007-11-01

    Incompressible open swirling flows are studied by means of direct numerical simulation (DNS) and linear stability analysis. The bifurcation structure is obtained by varying control parameters including: the swirl parameter S, the Reynolds number Re, and the nondimensional external pressure gradientβ. Nonlinear steady states are traced by pseudo-arclength continuation using the Recursive Projection Method (RPM) applied to the fully nonlinear DNS. For zero pressure gradient and large Re, the bifurcation curve shows a characteristic fold representing the existence of multiple solutions associated with vortex breakdown. Large favorable pressure gradients prevent vortex breakdown giving access to new stable or unstable branches corresponding to high swirl number, breakdown-free states. These branches are traced back to the case with zero pressure gradient by applying continuation into the pressure gradient parameter.

  7. Noncommutative Solitons

    SciTech Connect

    Lechtenfeld, Olaf

    2008-03-06

    Solitonic objects play a central role in gauge and string theory (as, e.g., monopoles, black holes, D-branes, etc.). Certain string backgrounds produce a noncommutative deformation of the low-energy effective field theory, which allows for new types of solitonic solutions. I present the construction, moduli spaces and dynamics of Moyal-deformed solitons, exemplified in the 2+1 dimensional Yang-Mills-Higgs theory and its Bogomolny system, which is gauge-fixed to an integrable chiral sigma model (the Ward model). Noncommutative solitons for various 1+1 dimensional integrable systems (such as sine-Gordon) easily follow by dimensional and algebraic reduction. Supersymmetric extensions exist as well and are related to twistor string theory.

  8. Rarefactive and compressive soliton waves in unmagnetized dusty plasma with non-thermal electron and ion distribution

    SciTech Connect

    Eslami, Esmaeil Baraz, Rasoul

    2014-02-15

    Sagdeev's pseudo potential method is employed to study dust acoustic solitary waves in an unmagnetized plasma containing negatively charged dusts with non-thermal electron and ion. The range of parameters for the existence of solitary waves using the analytical expression of the Sagdeev potential has been found. It is observed that, depending on the values of the plasma parameters like ion to electron temperature ratio σ, non-thermal parameters β and γ, electron to ion density ratio μ, and the value of the Mach number M, both rarefactive and compressive solitary waves may exist.

  9. On soliton propagation in biomembranes and nerves

    PubMed Central

    Heimburg, Thomas; Jackson, Andrew D.

    2005-01-01

    The lipids of biological membranes and intact biomembranes display chain melting transitions close to temperatures of physiological interest. During this transition the heat capacity, volume and area compressibilities, and relaxation times all reach maxima. Compressibilities are thus nonlinear functions of temperature and pressure in the vicinity of the melting transition, and we show that this feature leads to the possibility of soliton propagation in such membranes. In particular, if the membrane state is above the melting transition solitons will involve changes in lipid state. We discuss solitons in the context of several striking properties of nerve membranes under the influence of the action potential, including mechanical dislocations and temperature changes. PMID:15994235

  10. On soliton propagation in biomembranes and nerves.

    PubMed

    Heimburg, Thomas; Jackson, Andrew D

    2005-07-12

    The lipids of biological membranes and intact biomembranes display chain melting transitions close to temperatures of physiological interest. During this transition the heat capacity, volume and area compressibilities, and relaxation times all reach maxima. Compressibilities are thus nonlinear functions of temperature and pressure in the vicinity of the melting transition, and we show that this feature leads to the possibility of soliton propagation in such membranes. In particular, if the membrane state is above the melting transition solitons will involve changes in lipid state. We discuss solitons in the context of several striking properties of nerve membranes under the influence of the action potential, including mechanical dislocations and temperature changes.

  11. Effect of Laser Annealing of Common Solid Pressure Media on Pressure Gradients in a Diamond Anvil Cell

    NASA Astrophysics Data System (ADS)

    Uts, I.; Glazyrin, K.; Lee, K. K.

    2012-12-01

    Advances in experimental techniques allow for the studying of geophysics and planetary science related materials under high pressure and high temperature conditions. With the intrinsic limits of the multianvil apparatus, compression in a diamond anvil cell (DAC) has become the preferred method for creating the extreme conditions of planetary interiors. High pressures up to 1 Mbar can be routinely obtained in laboratories with the use of DACs. Additionally, as in situ laser heating is becoming progressively more affordable for DACs, it is becoming more common to find laser heating setups in many large scale facilities. After the sample material, the pressure medium is the second most important ingredient for a successful high pressure DAC experiment. Not every pressure medium is equally suitable for every experiment. For example, solid pressure media are more persistent than gaseous pressure media if high temperature heating is required. The melting point of the former is much higher, and melting of pressure media may induce undesirable sample shift in the pressure chamber. However, the most important characteristic of a pressure medium is its ability to maintain hydrostaticity in the DAC. The media, particularly solid pressure media, become less effective with increasing pressure. One of the most popular ways of alleviating pressure gradients is through laser annealing of the sample. We explore the effectiveness of this technique in relation to common pressure media, namely, alkali metal halides NaCl, CsCl, KCl, LiF, and oxide MgO. The samples were laser annealed at temperatures above 2000 K. Pressure gradients were determined through the analysis of diamond Raman and ruby fluorescence peaks before and after annealing the sample with a near-infrared laser. We find that the effect of annealing varies for different materials. For some (NaCl and KCl), it reduces pressure gradients considerably, but for the others (MgO), the effect of annealing is less profound.

  12. Instantaneous PIV/PTV-based pressure gradient estimation: a framework for error analysis and correction

    NASA Astrophysics Data System (ADS)

    McClure, Jeffrey; Yarusevych, Serhiy

    2017-08-01

    A framework for the exact determination of the pressure gradient estimation error in incompressible flows given erroneous velocimetry data is derived which relies on the calculation of the curl and divergence of the pressure gradient error over the domain and then the solution of a div-curl system to reconstruct the pressure gradient error field. In practice, boundary conditions for the div-curl system are unknown, and the divergence of the pressure gradient error requires approximation. The effect of zero pressure gradient error boundary conditions and approximating the divergence are evaluated using three flow cases: (1) a stationary Taylor vortex; (2) an advecting Lamb-Oseen vortex near a boundary; and (3) direct numerical simulation of the turbulent wake of a circular cylinder. The results show that the exact form of the pressure gradient error field reconstruction converges onto the exact values, within truncation and round-off errors, except for a small flow field region near the domain boundaries. It is also shown that the approximation for the divergence of the pressure gradient error field retains the fidelity of the reconstruction, even when velocity field errors are generated with substantial spatial variation. In addition to the utility of the proposed technique to improve the accuracy of pressure estimates, the reconstructed error fields provide spatially resolved estimates for instantaneous PIV/PTV-based pressure error.

  13. Relationship between exercise pressure gradient and haemodynamic progression of aortic stenosis.

    PubMed

    Ringle, Anne; Levy, Franck; Ennezat, Pierre-Vladimir; Le Goffic, Caroline; Castel, Anne-Laure; Delelis, François; Menet, Aymeric; Malaquin, Dorothée; Graux, Pierre; Vincentelli, André; Tribouilloy, Christophe; Maréchaux, Sylvestre

    We hypothesized that large exercise-induced increases in aortic mean pressure gradient can predict haemodynamic progression during follow-up in asymptomatic patients with aortic stenosis. We retrospectively identified patients with asymptomatic moderate or severe aortic stenosis (aortic valve area<1.5cm(2) or<1cm(2)) and normal ejection fraction, who underwent an exercise stress echocardiography at baseline with a normal exercise test and a resting echocardiography during follow-up. The relationship between exercise-induced increase in aortic mean pressure gradient and annualised changes in resting mean pressure gradient during follow-up was investigated. Fifty-five patients (mean age 66±15 years; 45% severe aortic stenosis) were included. Aortic mean pressure gradient significantly increased from rest to peak exercise (P<0.001). During a median follow-up of 1.6 [1.1-3.2] years, resting mean pressure gradient increased from 35±13mmHg to 48±16mmHg, P<0.0001. Median annualised change in resting mean pressure gradient during follow-up was 5 [2-11] mmHg. Exercise-induced increase in aortic mean pressure gradient did correlate with annualised changes in mean pressure gradient during follow-up (r=0.35, P=0.01). Hemodynamic progression of aortic stenosis was faster in patients with large exercise-induced increase in aortic mean pressure gradient (≥20mmHg) as compared to those with exercise-induced increase in aortic mean pressure gradient<20mmHg (median annualised increase in mean pressure gradient 19 [6-28] vs. 4 [2-10] mmHg/y respectively, P=0.002). Similar results were found in the subgroup of 30 patients with moderate aortic stenosis. Large exercise-induced increases in aortic mean pressure gradient correlate with haemodynamic progression of stenosis during follow-up in patients with asymptomatic aortic stenosis. Further studies are needed to fully establish the role of ESE in the decision-making process in comparison to other prognostic markers in asymptomatic

  14. Temporal solitons in air

    NASA Astrophysics Data System (ADS)

    Voronin, A. A.; Zheltikov, A. M.

    2017-02-01

    Analysis of the group-velocity dispersion (GVD) of atmospheric air with a model that includes the entire manifold of infrared transitions in air reveals a remarkably broad and continuous anomalous-GVD region in the high-frequency wing of the carbon dioxide rovibrational band from approximately 3.5 to 4.2 μm where atmospheric air is still highly transparent and where high-peak-power sources of ultrashort midinfrared pulses are available. Within this range, anomalous dispersion acting jointly with optical nonlinearity of atmospheric air is shown to give rise to a unique three-dimensional dynamics with well-resolved soliton features in the time domain, enabling a highly efficient whole-beam soliton self-compression of such pulses to few-cycle pulse widths.

  15. Soliton production with nonlinear homogeneous lines

    DOE PAGES

    Elizondo-Decanini, Juan M.; Coleman, Phillip D.; Moorman, Matthew W.; ...

    2015-11-24

    Low- and high-voltage Soliton waves were produced and used to demonstrate collision and compression using diode-based nonlinear transmission lines. Experiments demonstrate soliton addition and compression using homogeneous nonlinear lines. We built the nonlinear lines using commercially available diodes. These diodes are chosen after their capacitance versus voltage dependence is used in a model and the line design characteristics are calculated and simulated. Nonlinear ceramic capacitors are then used to demonstrate high-voltage pulse amplification and compression. The line is designed such that a simple capacitor discharge, input signal, develops soliton trains in as few as 12 stages. We also demonstrated outputmore » voltages in excess of 40 kV using Y5V-based commercial capacitors. The results show some key features that determine efficient production of trains of solitons in the kilovolt range.« less

  16. Soliton production with nonlinear homogeneous lines

    SciTech Connect

    Elizondo-Decanini, Juan M.; Coleman, Phillip D.; Moorman, Matthew W.; Petney, Sharon Joy Victor; Dudley, Evan C.; Youngman, Kevin; Penner, Tim Dwight; Fang, Lu; Myers, Katherine M.

    2015-11-24

    Low- and high-voltage Soliton waves were produced and used to demonstrate collision and compression using diode-based nonlinear transmission lines. Experiments demonstrate soliton addition and compression using homogeneous nonlinear lines. We built the nonlinear lines using commercially available diodes. These diodes are chosen after their capacitance versus voltage dependence is used in a model and the line design characteristics are calculated and simulated. Nonlinear ceramic capacitors are then used to demonstrate high-voltage pulse amplification and compression. The line is designed such that a simple capacitor discharge, input signal, develops soliton trains in as few as 12 stages. We also demonstrated output voltages in excess of 40 kV using Y5V-based commercial capacitors. The results show some key features that determine efficient production of trains of solitons in the kilovolt range.

  17. Gravitationally-Induced, Dynamically-Maintained, Steady-State Pressure Gradients

    NASA Astrophysics Data System (ADS)

    Sheehan, D. P.; Glick, J.

    Under sealed blackbody cavity conditions, pressure gradients typically take three forms: (a) statistical fluctuations, (b) transients associated with the system relaxing toward equilibrium, and (c) equilibrium pressure gradients, such as those associated with static gravitational potentials. In this paper a new type of pressure gradient is introduced, one which arises if a gravitator has surfaces with different trapping probabilities for suprathermal gas collisions. Three-dimensional test particle simulations of this system using realistic physical parameters support this hypothesis. This gas phase is inherently nonequilibrium in character and represents an unstudied thermodynamic regime involving low-density gas-surface interactions. This is the gravitational analog of a previously studied, chemically-induced pressure gradient [D. P. Sheehan, Phys. Rev. E57, 6660 (1998)].

  18. Experimental analysis of the boundary layer transition with zero and positive pressure gradient

    NASA Technical Reports Server (NTRS)

    Arnal, D.; Jullen, J. C.; Michel, R.

    1980-01-01

    The influence of a positive pressure gradient on the boundary layer transition is studied. The mean velocity and turbulence profiles of four cases are examined. As the intensity of the pressure gradient is increased, the Reynolds number of the transition onset and the length of the transition region are reduced. The Tollmein-Schlichting waves disturb the laminar regime; the amplification of these waves is in good agreement with the stability theory. The three dimensional deformation of the waves leads finally to the appearance of turbulence. In the case of zero pressure gradient, the properties of the turbulent spots are studied by conditional sampling of the hot-wire signal; in the case of positive pressure gradient, the turbulence appears in a progressive manner and the turbulent spots are much more difficult to characterize.

  19. Nonisothermal turbulent boundary-layer adverse pressure gradient large scale thermal structure measurements

    SciTech Connect

    Bagheri, N.; White, B.R.; Lei, T.

    1994-01-01

    Hot-wire anemometry measurements in an incompressible turbulent boundary-layer flow over a heated flat plate under equilibrium adverse-pressure-gradient conditions (beta = 1.8) were made for two different temperature difference cases (10 and 15 C) between the wall and the freestream. Space-time correlations of temperature fluctuations (T`) were obtained with a pair of subminiature temperature fluctuation probes. The mean convection velocities, the mean inclination angles, and coherence characteristics of the T` large-scale structure were determined. The present temperature structures measurements for a nonisothermal boundary layer are compared to the zero-pressure-gradient case with identical temperature differences previously reported, in which the mean convection velocity of the T` structure was a function of position y(sup +) and independent of the limited temperature-difference cases tested. The three major findings of the present study, as compared to the zero-pressure-gradient case, are (1) the mean convection speed of the T` structure under beta = 1.8 pressure-gradient conditions was found to be substantially lower in the logarithmic core region than the zero-pressure-gradient case. Additionally, the mean convection speed is felt by the authors to be a function of pressure-gradient parameter beta; (2) the mean inclination angle of the T` structure to the wall under the adverse-pressure-gradient flow was 32 deg, which compares favorably to the 30-deg value of the zero-pressure-gradient case; and (3) the limited data suggests that the mean convection velocity of the T` structure is a function of y(sup +) and independent of the limited temperature-difference cases tested. 11 refs.

  20. Data Assimilation in an Ocean Model of the Mediterranean Sea Forced by the Atmospheric Pressure Gradient

    NASA Astrophysics Data System (ADS)

    Dobricic, Srdjan; Oddo, Paolo; Pinardi, Nadia

    2012-03-01

    Recently the atmospheric pressure gradient forcing has been implemented in the oceanographic model used in the Mediterranean Forecasting System data assimilation scheme. Experiments show that there is an impact on how the temperature and salinity is updated in the assimilation when the ocean model is forced by the atmospheric pressure gradient. It is, however, necessary to perform longer data assimilation experiments to quantify the impact on the quality of the MFS analyses of the state of the Mediterranean Sea.

  1. Secondary subharmonic instability of boundary layers with pressure gradient and suction

    NASA Technical Reports Server (NTRS)

    El-Hady, Nabil M.

    1988-01-01

    Three-dimensional linear secondary instability is investigated for boundary layers with pressure gradient and suction in the presence of a finite amplitude TS wave. The focus is on principal parametric resonance responsible for a strong growth of subharmonics in a low disturbance environment. Calculations are presented for the effect of pressure gradients and suction on controlling the onset and amplification of the secondary instability.

  2. Limits to the H-mode pedestal pressure gradient in DIII-D

    SciTech Connect

    Groebner, R. J.; Snyder, P. B.; Osborne, T. H.; Leonard, A. W.; Rhodes, T. L.; Zeng, L.; Unterberg, Ezekial A; Yan, Z.; Mckee, G. R.; Lasnier, C. J.; Boedo, J.A.; Watkins, J. G.

    2010-01-01

    The spatial and temporal evolution of the total pedestal pressure profile has been measured during the pedestal evolution between successive edge localized modes (ELMs) of type-I ELMing H-mode discharges in DIII-D. Measurements are used to test a model that predicts that kinetic ballooning modes (KBMs) provide a strong constraint on the pedestal pressure gradient obtained during an inter-ELM cycle and cause the pedestal width to scale as the square root of the pedestal poloidal beta. Discharges in two different parameter regimes are examined for evidence that the evolution of the pressure gradient reaches a limit prior to the onset of an ELM. Both discharges show evidence of rapid evolution of the pressure profile very early in the recovery phase from an ELM. In one discharge, the pressure gradient reached approximate steady state within similar to 3 ms after the ELM event. In the other discharge, the pressure gradient just inboard of the last closed flux surface reached steady state early in the ELM recovery phase even as the pedestal expanded into the core and the maximum pressure gradient continued to rise during the remainder of the ELM cycle. Simple quantitative theoretical metrics show that pressure gradients in both discharges reached levels that were large enough to excite KBMs. In addition, the peeling-ballooning theory for the onset of type-I ELMs and the EPED1 model for pedestal height and width make predictions consistent with the data of both discharges.

  3. On determining characteristic length scales in pressure-gradient turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Vinuesa, R.; Bobke, A.; Örlü, R.; Schlatter, P.

    2016-05-01

    In the present work, we analyze three commonly used methods to determine the edge of pressure gradient turbulent boundary layers: two based on composite profiles, the one by Chauhan et al. ["Criteria for assessing experiments in zero pressure gradient boundary layers," Fluid Dyn. Res. 41, 021404 (2009)] and the one by Nickels ["Inner scaling for wall-bounded flows subject to large pressure gradients," J. Fluid Mech. 521, 217-239 (2004)], and the other one based on the condition of vanishing mean velocity gradient. Additionally, a new method is introduced based on the diagnostic plot concept by Alfredsson et al. ["A new scaling for the streamwise turbulence intensity in wall-bounded turbulent flows and what it tells us about the `outer' peak," Phys. Fluids 23, 041702 (2011)]. The boundary layers developing over the suction and pressure sides of a NACA4412 wing section, extracted from a direct numerical simulation at chord Reynolds number Rec = 400 000, are used as the test case, besides other numerical and experimental data from favorable, zero, and adverse pressure-gradient flat-plate turbulent boundary layers. We find that all the methods produce robust results with mild or moderate pressure gradients, although the composite-profile techniques require data preparation, including initial estimations of fitting parameters and data truncation. Stronger pressure gradients (with a Rotta-Clauser pressure-gradient parameter β larger than around 7) lead to inconsistent results in all the techniques except the diagnostic plot. This method also has the advantage of providing an objective way of defining the point where the mean streamwise velocity is 99% of the edge velocity and shows consistent results in a wide range of pressure gradient conditions, as well as flow histories. Collapse of intermittency factors obtained from a wide range of pressure-gradient and Re conditions on the wing further highlights the robustness of the diagnostic plot method to determine the

  4. Soliton turbulence

    NASA Technical Reports Server (NTRS)

    Tchen, C. M.

    1986-01-01

    Theoretical and numerical works in atmospheric turbulence have used the Navier-Stokes fluid equations exclusively for describing large-scale motions. Controversy over the existence of an average temperature gradient for the very large eddies in the atmosphere suggested that a new theoretical basis for describing large-scale turbulence was necessary. A new soliton formalism as a fluid analogue that generalizes the Schrodinger equation and the Zakharov equations has been developed. This formalism, processing all the nonlinearities including those from modulation provided by the density fluctuations and from convection due to the emission of finite sound waves by velocity fluctuations, treats large-scale turbulence as coalescing and colliding solitons. The new soliton system describes large-scale instabilities more explicitly than the Navier-Stokes system because it has a nonlinearity of the gradient type, while the Navier-Stokes has a nonlinearity of the non-gradient type. The forced Schrodinger equation for strong fluctuations describes the micro-hydrodynamical state of soliton turbulence and is valid for large-scale turbulence in fluids and plasmas where internal waves can interact with velocity fluctuations.

  5. Quantifying Dynamic Changes in Plantar Pressure Gradient in Diabetics with Peripheral Neuropathy

    PubMed Central

    Lung, Chi-Wen; Hsiao-Wecksler, Elizabeth T.; Burns, Stephanie; Lin, Fang; Jan, Yih-Kuen

    2016-01-01

    Diabetic foot ulcers remain one of the most serious complications of diabetes. Peak plantar pressure (PPP) and peak pressure gradient (PPG) during walking have been shown to be associated with the development of diabetic foot ulcers. To gain further insight into the mechanical etiology of diabetic foot ulcers, examination of the pressure gradient angle (PGA) has been recently proposed. The PGA quantifies directional variation or orientation of the pressure gradient during walking and provides a measure of whether pressure gradient patterns are concentrated or dispersed along the plantar surface. We hypothesized that diabetics at risk of foot ulceration would have smaller PGA in key plantar regions, suggesting less movement of the pressure gradient over time. A total of 27 participants were studied, including 19 diabetics with peripheral neuropathy and 8 non-diabetic control subjects. A foot pressure measurement system was used to measure plantar pressures during walking. PPP, PPG, and PGA were calculated for four foot regions – first toe (T1), first metatarsal head (M1), second metatarsal head (M2), and heel (HL). Consistent with prior studies, PPP and PPG were significantly larger in the diabetic group compared with non-diabetic controls in the T1 and M1 regions, but not M2 or HL. For example, PPP was 165% (P = 0.02) and PPG was 214% (P < 0.001) larger in T1. PGA was found to be significantly smaller in the diabetic group in T1 (46%, P = 0.04), suggesting a more concentrated pressure gradient pattern under the toe. The proposed PGA may improve our understanding of the role of pressure gradient on the risk of diabetic foot ulcers. PMID:27486576

  6. A Study of Wake Development and Structure in Constant Pressure Gradients

    NASA Technical Reports Server (NTRS)

    Thomas, Flint O.; Nelson, R. C.; Liu, Xiaofeng

    2000-01-01

    Motivated by the application to high-lift aerodynamics for commercial transport aircraft, a systematic investigation into the response of symmetric/asymmetric planar turbulent wake development to constant adverse, zero, and favorable pressure gradients has been conducted. The experiments are performed at a Reynolds number of 2.4 million based on the chord of the wake generator. A unique feature of this wake study is that the pressure gradients imposed on the wake flow field are held constant. The experimental measurements involve both conventional LDV and hot wire flow field surveys of mean and turbulent quantities including the turbulent kinetic energy budget. In addition, similarity analysis and numerical simulation have also been conducted for this wake study. A focus of the research has been to isolate the effects of both pressure gradient and initial wake asymmetry on the wake development. Experimental results reveal that the pressure gradient has a tremendous influence on the wake development, despite the relatively modest pressure gradients imposed. For a given pressure gradient, the development of an initially asymmetric wake is different from the initially symmetric wake. An explicit similarity solution for the shape parameters of the symmetric wake is obtained and agrees with the experimental results. The turbulent kinetic energy budget measurements of the symmetric wake demonstrate that except for the convection term, the imposed pressure gradient does not change the fundamental flow physics of turbulent kinetic energy transport. Based on the turbulent kinetic energy budget measurements, an approach to correct the bias error associated with the notoriously difficult dissipation estimate is proposed and validated through the comparison of the experimental estimate with a direct numerical simulation result.

  7. Dorsomedial/Perifornical Hypothalamic Stimulation Increases Intraocular Pressure, Intracranial Pressure, and the Translaminar Pressure Gradient

    PubMed Central

    Samuels, Brian C.; Hammes, Nathan M.; Johnson, Philip L.; Shekhar, Anantha; McKinnon, Stuart J.; Allingham, R. Rand

    2012-01-01

    Purpose. Intraocular pressure (IOP) fluctuation has recently been identified as a risk factor for glaucoma progression. Further, decreases in intracranial pressure (ICP), with postulated increases in the translaminar pressure gradient across the lamina cribrosa, has been reported in glaucoma patients. We hypothesized that circadian fluctuations in IOP and the translaminar pressure gradient are influenced, at least in part, by central autonomic regulatory neurons within the dorsomedial and perifornical hypothalamus (DMH/PeF). This study examined whether site-directed chemical stimulation of DMH/PeF neurons evoked changes in IOP, ICP, and the translaminar pressure gradient. Methods. The GABAA receptor antagonist bicuculline methiodide (BMI) was stereotaxically microinjected into the DMH/PeF region of isoflurane-anesthetized male Sprague-Dawley rats (n = 19). The resulting peripheral cardiovascular (heart rate [HR] and mean arterial pressure [MAP]), IOP, and ICP effects were recorded and alterations in the translaminar pressure gradient calculated. Results. Chemical stimulation of DMH/PeF neurons evoked significant increases in HR (+69.3 ± 8.5 beats per minute); MAP (+22.9 ± 1.6 mm Hg); IOP (+7.1 ± 1.9 mm Hg); and ICP (+3.6 ± 0.7 mm Hg) compared with baseline values. However, the peak IOP increase was significantly delayed compared with ICP (28 vs. 4 minutes postinjection), resulting in a dramatic translaminar pressure gradient fluctuation. Conclusions. Chemical stimulation of DMH/PeF neurons evokes substantial increases in IOP, ICP, and the translaminar pressure gradient in the rat model. Given that the DMH/PeF neurons may be a key effector pathway for circadian regulation of autonomic tone by the suprachiasmatic nucleus, these findings will help elucidate novel mechanisms modulating circadian fluctuations in IOP and the translaminar pressure gradient. PMID:23033392

  8. Thermophoresis of dissolved molecules and polymers: Consideration of the temperature-induced macroscopic pressure gradient.

    PubMed

    Semenov, Semen; Schimpf, Martin

    2004-01-01

    The movement of molecules and homopolymer chains dissolved in a nonelectrolyte solvent in response to a temperature gradient is considered a consequence of temperature-induced pressure gradients in the solvent layer surrounding the solute molecules. Local pressure gradients are produced by nonuniform London-van der Waals interactions, established by gradients in the concentration (density) of solvent molecules. The density gradient is produced by variations in solvent thermal expansion within the nonuniform temperature field. The resulting expression for the velocity of the solute contains the Hamaker constants for solute-solvent and solute-solute interactions, the radius of the solute molecule, and the viscosity and cubic coefficient of thermal expansion of the solvent. In this paper we consider an additional force that arises from directional asymmetry in the interaction between solvent molecules. In a closed cell, the resulting macroscopic pressure gradient gives rise to a volume force that affects the motion of dissolved solutes. An expression for this macroscopic pressure gradient is derived and the resulting force is incorporated into the expression for the solute velocity. The expression is used to calculate thermodiffusion coefficients for polystyrene in several organic solvents. When these values are compared to those measured in the laboratory, the consistency is better than that found in previous reports, which did not consider the macroscopic pressure gradient that arises in a closed thermodiffusion cell. The model also allows for the movement of solute in either direction, depending on the relative values of the solvent and solute Hamaker constants.

  9. Pressure gradient effects on the development of hairpin vortices in an initially laminar boundary layer

    NASA Astrophysics Data System (ADS)

    Taylor, Blaine Keith

    An experimental study was conducted in Lehigh University's low-speed water channel to examine the effects of a zero, adverse, and favorable pressure gradients on the development of single hairpin vortices. Single hairpin vortices were generated in an initially laminar environment using controlled fluid injection through a streamwise slot at a Re(delta)* = 380, 440, and 570. Behavior of hairpin structures was determined by the use of dye and hydrogen bubble flow visualization techniques. Visualization results indicate that as a single hairpin vortex convects downstream a complicated growth process due to viscous-inviscid interactions and Biot-Savart deformation results in the generation of secondary and subsidiary vortices, eventually yielding a turbulent spot-like structure. The hairpin vortex structures are observed to be strongly affected by the presence of a pressure gradient, undergoing significant spatial growth changes, as well as experiencing significant flow structure modifications. As the hairpin initiation location is moved further into an adverse pressure gradient, the hairpin vortex lifts and rotates farther away from the surface relative to the behavior in a zero pressure gradient. Regions of low and high-velocity fluid near the surface are accentuated within an adverse pressure gradient, which amplifies the low-speed streak formation and breakdown process, accelerating the formation of vortical substructures and ejection of fluid from the surface.

  10. Intraarterial Pressure Gradients After Randomized Angioplasty or Stenting of Iliac Artery Lesions

    SciTech Connect

    Tetteroo, Eric; Haaring, Cees; Graaf, Yolanda van der; Schaik, Jan P.J. van; Engelen, A.D. van; Mali, Willem P.T.M.

    1996-11-15

    Purpose: To determine initial technical results of percutaneous transluminal angioplasty (PTA) and stent procedures in the iliac artery, mean intraarterial pressure gradients were recorded before and after each procedure. Methods: We randomly assigned 213 patients with typical intermittent claudication to primary stent placement (n= 107) or primary PTA (n= 106), with subsequent stenting in the case of a residual mean pressure gradient of > 10 mmHg (n= 45). Eligibility criteria included angiographic iliac artery stenosis (> 50% diameter reduction) and/or a peak systolic velocity ratio > 2.5 on duplex examination. Mean intraarterial pressures were simultaneously recorded above and below the lesion, at rest and also during vasodilatation in the case of a resting gradient {<=} 10 mmHg. Results: Pressure gradients in the primary stent group were 14.9 {+-} 10.4 mmHg before and 2.9 {+-} 3.5 mmHg after stenting. Pressure gradients in the primary PTA group were 17.3 {+-} 11.3 mmHg pre-PTA, 4.2 {+-} 5.4 mmHg post-PTA, and 2.5 {+-} 2.8 mmHg after selective stenting. Compared with primary stent placement, PTA plus selective stent placement avoided application of a stent in 63% (86/137) of cases, resulting in a considerable cost saving. Conclusion: Technical results of primary stenting and PTA plus selective stenting are similar in terms of residual pressure gradients.

  11. On determining characteristic length scales in pressure gradient turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Vinuesa, Ricardo; Örlü, Ramis; Schlatter, Philipp

    2016-04-01

    In the present work we analyze three methods used to determine the edge of pressure gradient turbulent boundary layers: two based on composite profiles, the one by Chauhan et al. (Fluid Dyn. Res. 41:021401, 2009) and the one by Nickels (J. Fluid Mech. 521:217-239, 2004), and the other one based on the condition of vanishing mean velocity gradient. Additionally, a new method is introduced based on the diagnostic plot concept by Alfredsson et al. (Phys. Fluids 23:041702, 2011). The boundary layer developing over the suction side of a NACA4412 wing profile, extracted from a direct numerical simulation at Rec = 400,000, is used as the test case. We find that all the methods produce robust results with mild or moderate pressure gradients, but stronger pressure gradients (with β larger than around 7) lead to inconsistent results in all the techniques except the diagnostic plot. This method also has the advantage of providing an objective way of defining the point where the mean streamwise velocity is 99% of the edge velocity, and shows consistent results in a wide range of pressure gradient conditions, as well as flow histories. Therefore, the technique based on the diagnostic plot is a robust method to determine the boundary layer thickness (equivalent to δ99) and edge velocity in pressure gradient turbulent boundary layers.

  12. Vertical two-phase flow regimes and pressure gradients: Effect of viscosity

    SciTech Connect

    Da Hlaing, Nan; Sirivat, Anuvat; Siemanond, Kitipat; Wilkes, James O.

    2007-05-15

    The effect of liquid viscosity on the flow regimes and the corresponding pressure gradients along the vertical two-phase flow was investigated. Experiment was carried out in a vertical transparent tube of 0.019 m in diameter and 3 m in length and the pressure gradients were measured by a U-tube manometer. Water and a 50 vol.% glycerol solution were used as the working fluids whose kinematic viscosities were 0.85 x 10{sup -6} and 4.0 x 10{sup -6} m{sup 2}/s, respectively. In our air-liquid annular two-phase flow, the liquid film of various thicknesses flowed adjacent to the wall and the gas phase flowed at the center of the tube. The superficial air velocity, j{sub air}, was varied between 0.0021 and 58.7 m/s and the superficial liquid velocity, j{sub liquid}, was varied between 0 and 0.1053 m/s. In the bubble, the slug and the slug-churn flow regimes, the pressure gradients decreased with increasing Reynolds number. But in the annular and the mist flow regimes, pressure gradients increased with increasing Reynolds number. Finally, the experimentally measured pressure gradient values were compared and are in good agreement with the theoretical values. (author)

  13. Non-linear aspects of Görtler instability in boundary layers with pressure gradient

    NASA Astrophysics Data System (ADS)

    Rogenski, J. K.; de Souza, L. F.; Floryan, J. M.

    2016-12-01

    The laminar flow over a concave surface may undergo transition to a turbulent state driven by secondary instabilities initiated by the longitudinal vortices known as Görtler vortices. These vortices distort the boundary layer structure by modifying the streamwise velocity component in both spanwise and wall-normal directions. Numerical simulations have been conducted to identify the role of the external pressure gradients in the development and saturation of the vortices. The results show that flows with adverse pressure gradients reach saturation upstream from the saturation location for neutral and favorable pressure gradients. In the transition region, the mean spanwise shear stress is about three times larger than in the flow without the vortices.

  14. Coherent structures of a self-similar adverse pressure gradient turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Sekimoto, Atsushi; Kitsios, Vassili; Atkinson, Callum; Jiménez, Javier; Soria, Julio

    2016-11-01

    The turbulence statistics and structures are studied in direct numerical simulation (DNS) of a self-similar adverse pressure gradient turbulent boundary layer (APG-TBL). The self-similar APG-TBL at the verged of separation is achieved by a modification of the far-field boundary condition to produce the desired pressure gradient. The turbulence statistics in the self-similar region collapse by using the scaling of the external velocity and the displacement thickness. The coherent structures of the APG-TBL are investigated and compared to those of zero-pressure gradient case and homogeneous shear flow. The support of the ARC, NCI and Pawsey SCC funded by the Australian and Western Australian governments as well as the support of PRACE funded by the European Union are gratefully acknowledged.

  15. The influence of free-stream turbulence on turbulent boundary layers with mild adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Hoffmann, J. A.; Kassir, S. M.; Larwood, S. M.

    1989-01-01

    The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent boundary layers is presented for the cases of zero and mild adverse pressure gradients. With free-stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free-stream, both of which act to improve the transmission of momentum from the free-stream to the boundary layers.

  16. The influence of free-stream turbulence on turbulent boundary layers with mild adverse pressure gradients

    NASA Technical Reports Server (NTRS)

    Hoffmann, Jon A.

    1988-01-01

    The influence of near isotropic free-stream turbulence on the shape factors and skin friction coefficients of turbulent bounday layers is presented for the cases of zero and mild adverse pressure gradients. With free-stream turbulence, improved fluid mixing occurs in boundary layers with adverse pressure gradients relative to the zero pressure gradient condition, with the same free-stream turbulence intensity and length scale. Stronger boundary layers with lower shape factors occur as a result of a lower ratio of the integral scale of turbulence to the boundary layer thickness, and to vortex stretching of the turbulent eddies in the free stream, both of which act to improve the transmission of momentum from the free stream to the boundary layers.

  17. Experimental and numerical study of a turbulent boundary layer with pressure gradients

    NASA Technical Reports Server (NTRS)

    Spalart, Philippe R.; Watmuff, Jonathan H.

    1993-01-01

    Results are presented of an experimental and numerical study of a turbulent boundary layer with pressure gradients conducted using the recent 'fringe method' with its numerical advantages and good inflow quality. After an inflow transient good agreement is observed; the differences, of up to 13 percent, are discussed. Moderate deviations from the law of the wall are found in the velocity profiles of the simulation. They are fully correlated with the pressure gradient, are in fair quantitative agreement with the experimental results of Nagano et al. (1992), and are roughly the opposite of uncorrected mixing-length-model predictions. Large deviations from the wall scaling are observed for other quantities, notably for the turbulence dissipation rate. The a(1) structure parameter drops mildly in the upper layer with adverse pressure gradient.

  18. Arterial Pressure Gradients during Upright Posture and 30 deg Head Down Tilt

    NASA Technical Reports Server (NTRS)

    Sanchez, E. R; William, J. M.; Ueno, T.; Ballard, R. E.; Hargens, A. R.; Holton, Emily M. (Technical Monitor)

    1997-01-01

    Gravity alters local blood pressure within the body so that arterial pressures in the head and foot are lower and higher, respectively, than that at heart level. Furthermore, vascular responses to local alterations of arterial pressure are probably important to maintain orthostatic tolerance upon return to the Earth after space flight. However, it has been difficult to evaluate the body's arterial pressure gradient due to the lack of noninvasive technology. This study was therefore designed to investigate whether finger arterial pressure (FAP), measured noninvasively, follows a normal hydrostatic pressure gradient above and below heart level during upright posture and 30 deg head down tilt (HDT). Seven healthy subjects gave informed consent and were 19 to 52 years old with a height range of 158 to 181 cm. A Finapres device measured arterial pressure at different levels of the body by moving the hand from 36 cm below heart level (BH) to 72 cm above heart level (AH) in upright posture and from 36 cm BH to 48 cm AH during HDT in increments of 12 cm. Mean FAP creased by 85 mmHg transitioning from BH to AH in upright posture, and the pressure gradient calculated from hydrostatic pressure difference (rho(gh)) was 84 mmHg. In HDT, mean FAP decreased by 65 mmHg from BH to AH, and the calculated pressure gradient was also 65 mmHg. There was no significant difference between the measured FAP gradient and the calculated pressure gradient, although a significant (p = 0.023) offset was seen for absolute arterial pressure in upright posture. These results indicate that arterial pressure at various levels can be obtained from the blood pressure at heart level by calculating rho(gh) + an offset. The offset equals the difference between heart level and the site of measurement. In summary, we conclude that local blood pressure gradients can be measured by noninvasive studies of FAP.

  19. Arterial Pressure Gradients during Upright Posture and 30 deg Head Down Tilt

    NASA Technical Reports Server (NTRS)

    Sanchez, E. R; William, J. M.; Ueno, T.; Ballard, R. E.; Hargens, A. R.; Holton, Emily M. (Technical Monitor)

    1997-01-01

    Gravity alters local blood pressure within the body so that arterial pressures in the head and foot are lower and higher, respectively, than that at heart level. Furthermore, vascular responses to local alterations of arterial pressure are probably important to maintain orthostatic tolerance upon return to the Earth after space flight. However, it has been difficult to evaluate the body's arterial pressure gradient due to the lack of noninvasive technology. This study was therefore designed to investigate whether finger arterial pressure (FAP), measured noninvasively, follows a normal hydrostatic pressure gradient above and below heart level during upright posture and 30 deg head down tilt (HDT). Seven healthy subjects gave informed consent and were 19 to 52 years old with a height range of 158 to 181 cm. A Finapres device measured arterial pressure at different levels of the body by moving the hand from 36 cm below heart level (BH) to 72 cm above heart level (AH) in upright posture and from 36 cm BH to 48 cm AH during HDT in increments of 12 cm. Mean FAP creased by 85 mmHg transitioning from BH to AH in upright posture, and the pressure gradient calculated from hydrostatic pressure difference (rho(gh)) was 84 mmHg. In HDT, mean FAP decreased by 65 mmHg from BH to AH, and the calculated pressure gradient was also 65 mmHg. There was no significant difference between the measured FAP gradient and the calculated pressure gradient, although a significant (p = 0.023) offset was seen for absolute arterial pressure in upright posture. These results indicate that arterial pressure at various levels can be obtained from the blood pressure at heart level by calculating rho(gh) + an offset. The offset equals the difference between heart level and the site of measurement. In summary, we conclude that local blood pressure gradients can be measured by noninvasive studies of FAP.

  20. Acoustic solitons in inhomogeneous pair-ion plasmas

    SciTech Connect

    Shah, Asif; Mahmood, S.; Haque, Q.

    2010-12-15

    The acoustic solitons are investigated in inhomogeneous unmagnetized pair ion plasmas. The Korteweg-de Vries (KdV) like equation with an additional term due to density gradients is deduced by employing reductive perturbation technique. It is noticed that pair-ion plasma system is conducive for the propagation of compressive as well as rarefactive solitons. The increase in the temperature ratio causes the amplitude of the rarefactive soliton to decrease. However, the amplitude of the compressive solitons is found to be increased as the temperature ratio of ions is enhanced. The amplitude of both compressive and rarefactive solitons is found to be increased as the density gradient parameter is increased. The equlibrium density profile is assumed to be exponential. The numerical results are shown for illustration.

  1. Role of Pressure Gradient on Intrinsic Toroidal Rotation in Tokamak Plasmas

    SciTech Connect

    Yoshida, M.; Kamada, Y.; Takenaga, H.; Sakamoto, Y.; Urano, H.; Oyama, N.; Matsunaga, G.

    2008-03-14

    The toroidal plasma rotation generated by the external momentum input and by the plasma itself (intrinsic rotation) has been separated through a novel momentum transport analysis in the JT-60U tokamak device. The toroidal rotation, which is not determined by the momentum transport coefficients and the external momentum input, has been observed. It is found that this intrinsic rotation is locally determined by the local pressure gradient and increases with increasing pressure gradient. This trend is almost the same for various plasmas: low and high confinement mode, co and counterrotating plasmas.

  2. FIRST MEASUREMENT OF PRESSURE GRADIENT-DRIVEN CURRENTS IN TOKAMAK EDGE PLASMAS

    SciTech Connect

    THOMAS DM; LEONARD AW; LAO LL; OSBORNE TH; MUELLER HW; FINKENTHAL DK

    2003-11-01

    Localized currents driven by pressure gradients play a pivotal role in the magnetohydrodynamic stability of toroidal plasma confinement devices. We have measured the currents generated in the edge of L- (low) and H- (high confinement) mode discharges on the DIII-D tokamak, utilizing the Zeeman effect in an injected lithium beam to obtain high resolution profiles of the poloidal magnetic field. We find current densities in excess of 1 MA/m{sup 2} in a 1 to 2 cm region near the peak of the edge pressure gradient. These values are sufficient to challenge edge stability theories based on specific current formation models.

  3. Approximate Solution of a Laminar Flow over a Flat Plate with Suction and Pressure Gradient.

    DTIC Science & Technology

    1984-01-01

    8217nature ywpartment Chair) Date Department of Mechanical Enoineerino Accesslon Por U nIn C, LA ICC -’ .", J, f ! i C I o D irnt rbut ion / A*.-.1 lilt...reduced to a no suction and no pressure gradient condi t ion . Blasius Thesis Linear Prandtl Pohlhausen S(x) 5.8 4.318 3.464 4.64 5.835 S 1 1.729 1.727...2, but he was able to overcome that limitation with another function. 4.2 Suction and Pressure Gradient at Seoaration From Chapter 3 the velocity

  4. Non-autonomous bright matter wave solitons in spinor Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Kanna, T.; Babu Mareeswaran, R.; Sakkaravarthi, K.

    2014-01-01

    We investigate the dynamics of bright matter wave solitons in spin-1 Bose-Einstein condensates with time modulated nonlinearities. We obtain soliton solutions of an integrable autonomous three-coupled Gross-Pitaevskii (3-GP) equations using Hirota's method involving a non-standard bilinearization. The similarity transformations are developed to construct the soliton solutions of non-autonomous 3-GP system. The non-autonomous solitons admit different density profiles. An interesting phenomenon of soliton compression is identified for kink-like nonlinearity coefficient with Hermite-Gaussian-like potential strength. Our study shows that these non-autonomous solitons undergo non-trivial collisions involving condensate switching.

  5. The Effect of Adverse Pressure Gradient on Turbulent Burst Structure in Low-Reynolds Number Equilibrium Boundary Layers

    DTIC Science & Technology

    1990-01-01

    pressure gradient and a strong (relative to the mild case) pressure gradient. The objeetive-of the study was to determine the effect of pressure... determine the various boundary layer integral parameters and to create velocity records needed to calculate the period of the bursting cycle. Over the range...role in the production of turbulence and in momentum transport. For this reason, this study undertakes to determine the effect of pressure gradient on

  6. Nonlinear tunneling of optical soliton in 3 coupled NLS equation with symbolic computation

    NASA Astrophysics Data System (ADS)

    Mani Rajan, M. S.; Mahalingam, A.; Uthayakumar, A.

    2014-07-01

    We investigated the soliton solution for N coupled nonlinear Schrödinger (CNLS) equations. These equations are coupled due to the cross-phase-modulation (CPM). Lax pair of this system is obtained via the Ablowitz-Kaup-Newell-Segur (AKNS) scheme and the corresponding Darboux transformation is constructed to derive the soliton solution. One and two soliton solutions are generated. Using two soliton solutions of 3 CNLS equation, nonlinear tunneling of soliton for both with and without exponential background has been discussed. Finally cascade compression of optical soliton through multi-nonlinear barrier has been discussed. The obtained results may have promising applications in all-optical devices based on optical solitons, study of soliton propagation in birefringence fiber systems and optical soliton with distributed dispersion and nonlinearity management.

  7. Barrier island breach evolution: Alongshore transport and bay-ocean pressure gradient interactions

    NASA Astrophysics Data System (ADS)

    Safak, Ilgar; Warner, John C.; List, Jeffrey H.

    2016-12-01

    Physical processes controlling repeated openings and closures of a barrier island breach between a bay and the open ocean are studied using aerial photographs and atmospheric and hydrodynamic observations. The breach site is located on Pea Island along the Outer Banks, separating Pamlico Sound from the Atlantic Ocean. Wind direction was a major control on the pressure gradients between the bay and the ocean to drive flows that initiate or maintain the breach opening. Alongshore sediment flux was found to be a major contributor to breach closure. During the analysis period from 2011 to 2016, three hurricanes had major impacts on the breach. First, Hurricane Irene opened the breach with wind-driven flow from bay to ocean in August 2011. Hurricane Sandy in October 2012 quadrupled the channel width from pressure gradient flows due to water levels that were first higher on the ocean side and then higher on the bay side. The breach closed sometime in Spring 2013, most likely due to an event associated with strong alongshore sediment flux but minimal ocean-bay pressure gradients. Then, in July 2014, Hurricane Arthur briefly opened the breach again from the bay side, in a similar fashion to Irene. In summary, opening and closure of breaches are shown to follow a dynamic and episodic balance between along-channel pressure gradient driven flows and alongshore sediment fluxes.

  8. Reply to ``Comment on `Dynamically maintained steady-state pressure gradients' ''

    NASA Astrophysics Data System (ADS)

    Sheehan, D. P.

    2000-04-01

    A reply is made to Duncan's Comment [T. L. Duncan, Phys. Rev. E 61, 4661 (2000)] on my earlier paper [D. P. Sheehan, Phys. Rev. E 57, 6660 (1998)] in which he raises an apparent second-law paradox arising from dynamically maintained, steady-state pressure gradients. Resolutions to this paradox are considered in light of current theoretical and experimental understanding.

  9. Barrier island breach evolution: Alongshore transport and bay-ocean pressure gradient interactions

    USGS Publications Warehouse

    Safak, Ilgar; Warner, John C.; List, Jeffrey

    2016-01-01

    Physical processes controlling repeated openings and closures of a barrier island breach between a bay and the open ocean are studied using aerial photographs and atmospheric and hydrodynamic observations. The breach site is located on Pea Island along the Outer Banks, separating Pamlico Sound from the Atlantic Ocean. Wind direction was a major control on the pressure gradients between the bay and the ocean to drive flows that initiate or maintain the breach opening. Alongshore sediment flux was found to be a major contributor to breach closure. During the analysis period from 2011 to 2016, three hurricanes had major impacts on the breach. First, Hurricane Irene opened the breach with wind-driven flow from bay to ocean in August 2011. Hurricane Sandy in October 2012 quadrupled the channel width from pressure gradient flows due to water levels that were first higher on the ocean side and then higher on the bay side. The breach closed sometime in Spring 2013, most likely due to an event associated with strong alongshore sediment flux but minimal ocean-bay pressure gradients. Then, in July 2014, Hurricane Arthur briefly opened the breach again from the bay side, in a similar fashion to Irene. In summary, opening and closure of breaches are shown to follow a dynamic and episodic balance between along-channel pressure gradient driven flows and alongshore sediment fluxes.

  10. Analytic Formulation and Numerical Implementation of an Acoustic Pressure Gradient Prediction

    NASA Technical Reports Server (NTRS)

    Lee, Seongkyu; Brentner, Kenneth S.; Farassat, Fereidoun

    2007-01-01

    The scattering of rotor noise is an area that has received little attention over the years, yet the limited work that has been done has shown that both the directivity and intensity of the acoustic field may be significantly modified by the presence of scattering bodies. One of the inputs needed to compute the scattered acoustic field is the acoustic pressure gradient on a scattering surface. Two new analytical formulations of the acoustic pressure gradient have been developed and implemented in the PSU-WOPWOP rotor noise prediction code. These formulations are presented in this paper. The first formulation is derived by taking the gradient of Farassat's retarded-time Formulation 1A. Although this formulation is relatively simple, it requires numerical time differentiation of the acoustic integrals. In the second formulation, the time differentiation is taken inside the integrals analytically. The acoustic pressure gradient predicted by these new formulations is validated through comparison with the acoustic pressure gradient determined by a purely numerical approach for two model rotors. The agreement between analytic formulations and numerical method is excellent for both stationary and moving observers case.

  11. A General Pressure Gradient Formulation for Ocean Models - Part II: Energy, Momentum, and Bottom Torque Consistency

    NASA Technical Reports Server (NTRS)

    Song, Y.; Wright, D.

    1998-01-01

    A formulation of the pressure gradient force for use in models with topography-following coordinates is proposed and diagnostically analyzed by Song. We investigate numerical consistency with respect to global energy conservation, depth-integrated momentum changes, and the represent of the bottom pressure torque.

  12. Effect of adverse pressure gradient on high speed boundary layer transition

    NASA Astrophysics Data System (ADS)

    Franko, Kenneth J.; Lele, Sanjiva

    2014-02-01

    The effect of adverse pressure gradients (APG) on boundary layer stability, breakdown, and heat-transfer overshoot is investigated. Flat plate isothermal boundary layers initially at Mach 6 with APG imposed through the freestream boundary condition are simulated using suction and blowing to produce boundary layer instabilities. The three different transition mechanisms compared are first mode oblique breakdown, second mode oblique breakdown, and second mode fundamental resonance. For all of the transition mechanisms, an adverse pressure gradient increases the linear growth rates and quickens the transition to turbulence. However, the nonlinear breakdown for all three transition mechanisms is qualitatively the same as for a zero pressure gradient boundary layer. First mode oblique breakdown leads to the earliest transition location and an overshoot in heat transfer in the transitional region. Both types of Mack second mode forcing lead to a transitional boundary layer but even with the increased growth rates and N factors produced by the adverse pressure gradient, the breakdown process is still more gradual than first mode oblique breakdown because the primary Mack second mode instabilities saturate and produce streaks that breakdown further downstream.

  13. Validation of Reynolds Stress Transport Models with Velocity/Pressure-Gradient Models in Wall- Bounded Flows

    NASA Astrophysics Data System (ADS)

    Fernandez, Juan D. C.; Poroseva, Svetlana; Murman, Scott

    2014-11-01

    In the traditional formulation of Reynolds Stress Transport (RST) turbulence models, velocity/pressure-gradient correlations are decomposed into pressure-strain correlations and pressure diffusion terms that are modeled separately. In our study, a potential of a different modeling approach for improving simulation results in the near-wall area is investigated. No decomposition of velocity/pressure-gradient correlations is attempted. New linear models for such correlations have been recently developed and successfully validated against DNS data in two-dimensional incompressible turbulent flows such as a zero-pressure gradient boundary layer over a flat plate and a fully-developed channel flow. The models correctly reproduce DNS profiles of velocity/pressure-gradient correlations up to the wall with the same model coefficients in different geometries and at different Reynolds numbers. These models are currently implemented in transport equations for Reynolds stresses. The compatibility of models for such correlations with existing models for the dissipation tensor and turbulent diffusion is investigated. Simulations are conducted with open-source software OpenFOAM and in-house code in two-dimensional wall-bounded flows. A part of the material is based upon work supported by NASA under Award NNX12AJ61A.

  14. Evaluation of turbulence models for prediction of separated turbulent boundary layer under unsteady adverse pressure gradients

    NASA Astrophysics Data System (ADS)

    Park, Junshin; You, Donghyun

    2014-11-01

    Predicitive capabilites of Reynolds-averaged Navier-Stokes (RANS) techniques for separated flow under unsteady adverse pressure gradients have been assessed using SST k - ω model and Spalart-Allmaras model by comparing their results with direct numerical simulation (DNS) results. Both DNS and RANS have been conducted with a zero pressure gradient, a steady adverse pressure gradient, and an unsteady adverse pressure gradient, respectively. Comparative studies show that both RANS models predict earlier separation and fuller velocity profiles at the reattachment zone than DNS in the unsteady case, while reasonable agreements with DNS are observed for steady counterparts. Causes for differences in the predictive capability of RANS for steady and unsteady cases, are explained by examining the Reynolds stress term and eddy viscosity term in detail. The Reynolds stress and eddy viscosity are under-predicted by both RANS models in the unsteady case. The origin of the under-prediction of the Reynolds stress with both RANS models is revealed by investigating Reynolds stress budget terms obtained from DNS. Supported by the National Research Foundation of Korea Grant NRF-2012R1A1A2003699 and the Brain Korea 21+ program.

  15. Some features of surface pressure fluctuations in turbulent boundary layers with zero and favorable pressure gradients

    NASA Technical Reports Server (NTRS)

    Mcgrath, B. E.; Simpson, R. L.

    1987-01-01

    Measurements of surface pressure fluctuation spectra, coherence and convective wave speeds from zero and favorable pressure gradient turbulent boundary layers are reported for momentum Reynolds numbers from 3000 to 18,800. The acceleration parameter K is near 2 x 10 to the -7 power for the favorable pressure gradient flow. The outer variables, U sub e, tau sub w and delta sub 1 non-dimensionalize and collapse the spectra for the low to middle range of frequencies for most test cases. The grouping using the inner variable, U sub tau and gamma, collapse the spectra for the middle to high range of frequencies for all test cases. The value of p'/tau sub w was near 3.8 and 2.8 for the smallest values of d+ in the zero and favorable pressure gradient flows, respectively. The coherence exhibits a decay that is not exponential in some cases, but the Corcos similarity parameters omega Delta x/U sub c and omega Delta z/U sub c collapse the data for all test cases. The ratio of U sub c/U sub e increases with omega delta sub 1/U sub e up to omega delta sub 1/U sub e on the order of unity, where U sub c/U sub e becomes nearly constant. This was observed in the present results for both streamwise pressure gradient flows. The experimental results presented show good agreement with previous research.

  16. A General Pressure Gradient Formulation for Ocean Models - Part II: Energy, Momentum, and Bottom Torque Consistency

    NASA Technical Reports Server (NTRS)

    Song, Y.; Wright, D.

    1998-01-01

    A formulation of the pressure gradient force for use in models with topography-following coordinates is proposed and diagnostically analyzed by Song. We investigate numerical consistency with respect to global energy conservation, depth-integrated momentum changes, and the represent of the bottom pressure torque.

  17. Nonisothermal flow of a polymeric liquid under a pulsating pressure gradient

    SciTech Connect

    Shul'man, Z.P.; Khusid, B.M.; Shabunina, Z.A.

    1987-03-01

    Increasing flow rates is a major problem in transporting petroleum as well as polymer solutions and melts. Industrial methods are often directed to reducing the effective viscosity: heating and pulsation. The latter is related to the nonlinearity in the properties. This paper studies the effects of pressure-gradient pulsations on the nonisothermal flow of a nonlinear liquid with memory in an annular channel.

  18. Alveolar septal patterning during compensatory lung growth: Part II the effect of parenchymal pressure gradients.

    PubMed

    Haber, Shimon; Weisbord, Michal; Mentzer, Steven J; Tsuda, Akira

    2017-05-21

    In most mammals, compensatory lung growth occurs after the removal of one lung (pneumonectomy). Although the mechanism of alveolar growth is unknown, the patterning of complex alveolar geometry over organ-sized length scales is a central question in regenerative lung biology. Because shear forces appear capable of signaling the differentiation of important cells involved in neoalveolarization (fibroblasts and myofibroblasts), interstitial fluid mechanics provide a potential mechanism for the patterning of alveolar growth. The movement of interstitial fluid is created by two basic mechanisms: 1) the non-uniform motion of the boundary walls, and 2) parenchymal pressure gradients external to the interstitial fluid. In a previous study (Haber et al., Journal of Theoretical Biology 400: 118-128, 2016), we investigated the effects of non-uniform stretching of the primary septum (associated with its heterogeneous mechanical properties) during breathing on generating non-uniform Stokes flow in the interstitial space. In the present study, we analyzed the effect of parenchymal pressure gradients on interstitial flow. Dependent upon lung microarchitecture and physiologic conditions, parenchymal pressure gradients had a significant effect on the shear stress distribution in the interstitial space of primary septa. A dimensionless parameter δ described the ratio between the effects of a pressure gradient and the influence of non-uniform primary septal wall motion. Assuming that secondary septa are formed where shear stresses were the largest, it is shown that the geometry of the newly generated secondary septa was governed by the value of δ. For δ smaller than 0.26, the alveolus size was halved while for higher values its original size was unaltered. We conclude that the movement of interstitial fluid, governed by parenchymal pressure gradients and non-uniform primary septa wall motion, provides a plausible mechanism for the patterning of alveolar growth. Copyright © 2017

  19. Influence of imaging quality on magnetic resonance-based pressure gradient measurements

    NASA Astrophysics Data System (ADS)

    Delles, Michael; Rengier, Fabian; Ley, Sebastian; von Tengg-Kobligk, Hendrik; Kauczor, Hans-Ulrich; Unterhinninghofen, Roland; Dillmann, Rüdiger

    2010-03-01

    In cardiovascular diagnostics, the knowledge of blood pressure is essential for the physician. Nowadays, blood pressures are usually obtained by catheter measurements or sphygmomanometric methods. These techniques suffer from different drawbacks in terms of invasiveness, observable vessels and the resolution of the pressure values, respectively. Magnetic resonance imaging (MRI) offers a promising approach to establish a method for blood pressure measurements that is able to overcome these difficulties. Phase-contrast MRI is used to acquire velocity-encoded data. Fluid pressure gradients can be derived from the measured velocities using the Navier-Stokes equations. Unfortunately, this technique is known to suffer from a strong sensitivity to imaging quality. Especially the low signal-to-noise ratios (SNR) of phase contrast MRI data combined with the limited spatial and temporal resolution could severely reduce the reliability of computations. In this paper, we analyze computations of blood pressure gradients based on phase contrast MRI measurements of steady and pulsatile flow in a phantom. The influence of image quality of the velocity-encoded data as well as of different segmentation techniques is evaluated. In case of steady flow, the pressure gradient values computed via Navier-Stokes equations show good agreement with theoretical values if physical a-priori knowledge is incorporated. If a pulsatile aortic flow profile is applied, the computed pressure gradients generally match catheter measurements well. Nevertheless, an underestimation of pressure gradient peaks is observed. Different segmentation techniques influence the size of root mean squared errors between computation and measurement as well as their reduction by the use of higher SNRs.

  20. Cascaded generation of coherent Raman dissipative solitons.

    PubMed

    Kharenko, Denis S; Bednyakova, Anastasia E; Podivilov, Evgeniy V; Fedoruk, Mikhail P; Apolonski, Alexander; Babin, Sergey A

    2016-01-01

    The cascaded generation of a conventional dissipative soliton (at 1020 nm) together with Raman dissipative solitons of the first (1065 nm) and second (1115 nm) orders inside a common fiber laser cavity is demonstrated experimentally and numerically. With sinusoidal (soft) spectral filtering, the generated solitons are mutually coherent at a high degree and compressible down to 300 fs. Numerical simulation shows that an even higher degree of coherence and shorter pulses could be achieved with step-like (hard) spectral filtering. The approach can be extended toward a high-order coherent Raman dissipative soliton source offering numerous applications such as frequency comb generation, pulse synthesis, biomedical imaging, and the generation of a coherent mid-infrared supercontinuum.

  1. Shortcut to adiabatic control of soliton matter waves by tunable interaction

    PubMed Central

    Li, Jing; Sun, Kun; Chen, Xi

    2016-01-01

    We propose a method for shortcut to adiabatic control of soliton matter waves in harmonic traps. The tunable interaction controlled by Feshbach resonance is inversely designed to achieve fast and high-fidelity compression of soliton matter waves as compared to the conventional adiabatic compression. These results pave the way to control the nonlinear dynamics for matter waves and optical solitons by using shortcuts to adiabaticity. PMID:28009007

  2. Direct numerical simulation of turbulent boundary layers under unsteady pressure gradients

    NASA Astrophysics Data System (ADS)

    Bromby, William; You, Donghyun

    2011-11-01

    Direct numerical simulations are performed to improve the understanding of unsteady separation processes of turbulent boundary layers characterizing the performance and efficiency of many aerodynamic applications such as helicopter rotor blades, wind turbine blades, pitching and flapping airfoils and wings, and rotating turbomachines. A time varying blowing-suction velocity distribution is imposed along the upper boundary to introduce unsteady adverse pressure gradients to the turbulent boundary layer. The distinct characteristics of turbulent boundary layers under unsteady adverse pressure gradients including unsteady boundary-layer detachment and reattachment, and production and dissipation of turbulent kinetic energy and vorticity, are revealed by a systematic comparison with steady attached/separated turbulent boundary layers. Supported by the Army Research Office Grant W911NF1010348. Done...processed 2146 records...17:52:29 Beginning APS data extraction...17:52:30

  3. Polynomial regularization for robust MRI-based estimation of blood flow velocities and pressure gradients.

    PubMed

    Delles, Michael; Rengier, Fabian; Ley, Sebastian; von Tengg-Kobligk, Hendrik; Kauczor, Hans-Ulrich; Dillmann, Rüdiger; Unterhinninghofen, Roland

    2011-01-01

    In cardiovascular diagnostics, phase-contrast MRI is a valuable technique for measuring blood flow velocities and computing blood pressure values. Unfortunately, both velocity and pressure data typically suffer from the strong image noise of velocity-encoded MRI. In the past, separate approaches of regularization with physical a-priori knowledge and data representation with continuous functions have been proposed to overcome these drawbacks. In this article, we investigate polynomial regularization as an exemplary specification of combining these two techniques. We perform time-resolved three-dimensional velocity measurements and pressure gradient computations on MRI acquisitions of steady flow in a physical phantom. Results based on the higher quality temporal mean data are used as a reference. Thereby, we investigate the performance of our approach of polynomial regularization, which reduces the root mean squared errors to the reference data by 45% for velocities and 60% for pressure gradients.

  4. Applicability of the isotropic vorticity theory to an adverse pressure gradient flow

    NASA Astrophysics Data System (ADS)

    Arora, S. C.; Azad, R. S.

    1980-03-01

    The isotropic vorticity theory is examined for an adverse pressure gradient flow on the basis of experimental data obtained in a conical diffuser. This conical diffuser is the same as that used by Okwuobi and Azad (1973), having an 8-deg included angle and an area ratio of 4:1 with fully developed pipe flow at the entry. The experiments are conducted in a low-speed open-circuit wind tunnel. It is shown that the rates and ratio of production and dissipation of the turbulent vorticity are constant in the core region of the diffuser but increase significantly in the wall layer. The validity of the analysis of Batchelor and Townsend (1947) for isotropic vorticity is discussed. The results suggest that even in a shear flow subjected to adverse pressure gradient, the isotropic theory of vorticity can be applied to a region far removed from the wall.

  5. Experimental Measurements of a High Reynolds Num- ber Adverse Pressure Gradient Turbulent Boundary Layer

    NASA Astrophysics Data System (ADS)

    Atkinson, Callum; Amili, Omid; Stanislas, Michel; Cuvier, Christophe; Foucaut, Jean-Marc; Srinath, Sricharan; Laval, Jean-Philippe; Kaehler, Christian; Hain, Rainer; Scharnowski, Sven; Schroeder, Andreas; Geisler, Reinhard; Agocs, Janos; Roese, Anni; Willert, Christian; Klinner, Joachim; Soria, Julio

    2016-11-01

    The study of adverse pressure gradient turbulent boundary layers is complicated by the need to characterise both the local pressure gradient and it's upstream flow history. It is therefore necessary to measure a significant streamwise domain at a resolution sufficient to resolve the small scales features. To achieve this collaborative particle image velocimetry (PIV) measurements were performed in the large boundary layer wind-tunnel at the Laboratoire de Mecanique de Lille, including: planar measurements spanning a streamwise domain of 3.5m using 16 cameras covering 15 δ spanwise wall-normal stereo-PIV measurements, high-speed micro-PIV of the near wall region and wall shear stress; and streamwise wall-normal PIV in the viscous sub layer. Details of the measurements and preliminary results will be presented.

  6. Risk Factors Involved in Central-to-Radial Arterial Pressure Gradient During Cardiac Surgery.

    PubMed

    Fuda, Giuseppe; Denault, André; Deschamps, Alain; Bouchard, Denis; Fortier, Annik; Lambert, Jean; Couture, Pierre

    2016-03-01

    A central-to-radial arterial pressure gradient may occur after cardiopulmonary bypass (CPB), which, in some patients, may last for a prolonged time after CPB. Whenever there is a pressure gradient, the radial artery pressure measure may underestimate a more centrally measured systemic pressure, which may result in a misguided therapeutic strategy. It is clinically important to identify the risk factors that may predict the appearance of a central-to-radial pressure gradient, because more central sites of measurements might then be considered to monitor systemic arterial pressure in high-risk patients. The objective of this study was to assess preoperative and intraoperative risk factors for central-to-radial pressure gradient. Seventy-three patients undergoing cardiac surgery using CPB were included in this prospective observational study. A significant central-to-radial arterial pressure gradient was defined as a difference of 25 mm Hg in systolic pressure or 10 mm Hg in mean arterial pressure for a minimum of 5 minutes. Preoperative data included demographics, presence of comorbidities, and medications. Intraoperative data included type of surgery, CPB and aortic clamping time, use of inotropic drugs, and vasodilators or vasopressors agents. The diameter of the radial and femoral artery was measured before the induction of anesthesia using B-mode ultrasonography. Thirty-three patients developed a central-to-radial arterial pressure gradient (45%). Patients with a significant pressure gradient had a smaller weight (71.0 ± 16.9 vs 79.3 ± 17.3 kg, P = 0.041), a smaller height (162.0 ± 9.6 vs 166.3 ± 8.6 cm, P = 0.047), a smaller radial artery diameter (0.24 ± 0.03 vs 0.29 ± 0.05 cm, P < 0.001), and were at a higher risk as determined by the Parsonnet score (30.3 ± 24.9 vs 17.0 ± 10.9, P = 0.007). In addition, a longer aortic clamping time (85.8 ± 51.0 vs 64.2 ± 29.3 minutes, P = 0.036), mitral and complex surgery (P = 0.007 and P = 0.017, respectively

  7. Sound scattering by rigid oblate spheroids, with implication to pressure gradient microphones

    NASA Technical Reports Server (NTRS)

    Maciulaitis, A.; Seiner, J.; Norum, T. D.

    1976-01-01

    The frequency limit below which sound scattering by a microphone body is sufficiently small to permit accurate pressure gradient measurements was determined. The sound pressure was measured at various points on the surface of a rigid oblate spheroid illuminated by spherical waves generated by a point source at a large distance from the spheroid, insuring an essentially plane sound field. The measurements were made with small pressure microphones flush mounted from the inside of the spheroid model. Numerical solutions were obtained for a variety of spheroid shapes, including that of the experimental model. Very good agreement was achieved between the experimental and theoretical results. It was found that scattering effects are insignificant if the ratio of the major circumference of the spheroid to the wavelength of the incident sound is less than about 0.7, this number being dependent upon the shape of the spheroid. This finding can be utilized in the design of pressure gradient microphones.

  8. Vertical two-phase flow regimes and pressure gradients under the influence of SDS surfactant

    SciTech Connect

    Duangprasert, Tanabordee; Sirivat, Anuvat; Siemanond, Kitipat; Wilkes, James O.

    2008-01-15

    Two-phase gas/liquid flows in vertical pipes have been systematically investigated. Water and SDS surfactant solutions at various concentrations were used as the working fluids. In particular, we focus our work on the influence of surfactant addition on the flow regimes, the corresponding pressure gradients, and the bubble sizes and velocity. Adding the surfactant lowers the air critical Reynolds numbers for the bubble-slug flow and the slug flow transitions. The pressure gradients of SDS solutions are lower than those of pure water especially in the slug flow and the slug-churn flow regimes, implying turbulent drag reduction. At low Re{sub air}, the bubble sizes of the surfactant solution are lower than those of pure water due to the increase in viscosity. With increasing and at high Re{sub air}, the bubble sizes of the SDS solution become greater than those of pure water which is attributed to the effect of surface tension. (author)

  9. Roll-up of vorticity in adverse-pressure-gradient boundary layers

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Durbin, P. A.; Leib, S. J.

    1987-01-01

    It is shown how the unsteady, nonlinear critical-layer equation determines the evolution of instability waves in a weak adverse-pressure-gradient boundary layer. Numerical solutions show that the nonlinearity halts the growth of these inviscidly unstable waves. The stabilizing effect of nonlinearity, in the present case, can be described as a consequence of either the increase (toward zero) of the phase jump across the critical layer or the roll-up of the critical-layer disturbance vorticity.

  10. Experimental Investigation of a Supersonic Boundary Layer Including Favorable Pressure Gradient Effects

    DTIC Science & Technology

    2011-07-21

    United States Government. EXPERIMENTAL INVESTIGATION OF A SUPERSONIC BOUNDARY LAYER INCLUDING FAVORABLE PRESSURE GRADIENT EFFECTS THESIS Presented to...flow to be disturbed from its original state . Aside from providing a non-intrusive method of measurement, LDV has the advantage of measuring the...providing some useful test of turbulence modeling. 4. Well-defined experimental boundary conditions: All incoming conditions (especially the state of

  11. Topological Solitons in Physics.

    ERIC Educational Resources Information Center

    Parsa, Zohreh

    1979-01-01

    A broad definition of solitons and a discussion of their role in physics is given. Vortices and magnetic monopoles which are examples of topological solitons in two and three spatial dimensions are described in some detail. (BB)

  12. Some Properties of Solitons

    NASA Astrophysics Data System (ADS)

    Brizhik, L. S.; Eremko, A. A.; Ferreira, L. A.; Piette, B. M.. A. G.; Zakrzewski, W. J.

    We present a general review of some aspects of the dynamics of topological solitons in 1 and 2 dimensions. We discuss some recent work on the scattering of solitons on potential obstructions and in the presence of some external fields.

  13. Ponderable soliton stars

    NASA Technical Reports Server (NTRS)

    Chiu, Hong-Yee

    1990-01-01

    The theory of Lee and Pang (1987), who obtained solutions for soliton stars composed of zero-temperature fermions and bosons, is applied here to quark soliton stars. Model soliton stars based on a simple physical model of the proton are computed, and the properties of the solitons are discussed, including the important problem of the existence of a limiting mass and thus the possible formation of black holes of primordial origin. It is shown that there is a definite mass limit for ponderable soliton stars, so that during cooling a soliton star might reach a stage beyond which no equilibrium configuration exists and the soliton star probably will collapse to become a black hole. The radiation of ponderable soliton stars may alter the short-wavelength character of the cosmic background radiation, and may be observed as highly redshifted objects at z of about 100,000.

  14. Reevaluation of compressible-flow Preston tube calibrations

    NASA Technical Reports Server (NTRS)

    Allen, J. M.

    1977-01-01

    Revised zero-pressure-gradient, adiabatic wall skin-friction-balance data covering a Mach number range from 1.6 to 4.6 led to a reevaluation of existing compressible flow Preston tube calibration equations.

  15. Sound Localization in Lizards: Functioning of a Pressure-Gradient Receiver

    NASA Astrophysics Data System (ADS)

    van Hemmen, J. Leo

    2009-03-01

    Because of their small interaural distance, lizards as well as some other animals have developed a special hearing mechanism, the ``pressure-gradient receiver''. The lizard peripheral auditory system differs from the mammalian one by a coupling of the two eardrums through the internal mouth cavity. We present a three-dimensional analytical model of the pressure-gradient receiver. The central aspect of the coupling of the membranes through the mouth cavity is realized by means of the boundary conditions. Moreover, the lizard's middle ear, a simple lever construction called columella, is asymmetrically attached to the tympanic membrane. This has motivated us to solve the problem of how the middle ear influences the spatial-amplitude profile and the frequency distribution of the tympanic membrane vibration. Finally, we show results from numerical simulations of the eigenfunctions and eigenfrequencies in a lizard's internal mouth cavity bounded by the eardrums. To this end, we have constructed the complex geometry from a cast imprint of the cavity with the help of three-dimensional scans. Our results led to an interesting speculation regarding the neurobiological use of the pressure-gradient system.

  16. Analytic Formulation and Numerical Implementation of an Acoustic Pressure Gradient Prediction

    NASA Technical Reports Server (NTRS)

    Lee, Seongkyu; Brentner, Kenneth S.; Farassat, F.; Morris, Philip J.

    2008-01-01

    Two new analytical formulations of the acoustic pressure gradient have been developed and implemented in the PSU-WOPWOP rotor noise prediction code. The pressure gradient can be used to solve the boundary condition for scattering problems and it is a key aspect to solve acoustic scattering problems. The first formulation is derived from the gradient of the Ffowcs Williams-Hawkings (FW-H) equation. This formulation has a form involving the observer time differentiation outside the integrals. In the second formulation, the time differentiation is taken inside the integrals analytically. This formulation avoids the numerical time differentiation with respect to the observer time, which is computationally more efficient. The acoustic pressure gradient predicted by these new formulations is validated through comparison with available exact solutions for a stationary and moving monopole sources. The agreement between the predictions and exact solutions is excellent. The formulations are applied to the rotor noise problems for two model rotors. A purely numerical approach is compared with the analytical formulations. The agreement between the analytical formulations and the numerical method is excellent for both stationary and moving observer cases.

  17. Computations of Turbulent Boundary Layers Subjected to Various Localized Pressure Gradients

    NASA Astrophysics Data System (ADS)

    Vinuesa Motilva, Ricardo; Nagib, Hassan

    2009-11-01

    Four different localized pressure gradient configurations were computed using a commercially available code by means of four RANS turbulence models (SA, k-ɛ, SST and RSM), and compared with experimental measurements of the mean flow quantities and the wall shear stress. The pressure gradients were imposed on high Reynolds number, 2-D turbulent boundary layer developing on a flat plate by changing the ceiling geometry. Two converging humps (at x=2m and x=5.5m from the leading edge of the plate) and two diverging humps at the same locations were considered. The SST model produced the best agreement with experiments. A complimentary study about how the models deal with numerical transition was done by solving a zero pressure gradient (ZPG) configuration. We find that the major differences between the results from the models when predicting mean flow quantities are essentially produced by the numerical transition process. This process does not belong to the models themselves, and it is a procedure by which the software transforms the simple laminar boundary conditions at the inlet into inflow conditions which characterize the turbulent flow when turbulence has already been developed. Therefore, models requiring the simplest inflow conditions lead to better results and consequently models such as the RSM suffer the most and ultimately lead to inferior results.

  18. DNS of self-similar adverse pressure gradient turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Soria, Julio; Kitsios, Vassili; Sekimoto, Atsushi; Atkinson, Callum; Jiménez, Javier

    2016-11-01

    A direct numerical simulation (DNS) of a self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) at the verge of separation has been set-up and carried out. The DNS APG TBL has a displacement thickness based Reynolds number that ranges up to 30,000. The conditions for self-similarity and appropriate scaling will be highlighted, with the first and second order velocity statistical profiles non-dimensionalised using this scaling. The details of the DNS and the required boundary conditions that are necessary to establish this self-similar APG-TBL will be presented. The statistical properties of the self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) DNS will presented, as will the profiles of the terms in the momentum equation, spanwise/wall-normal kinetic energy spectrum and two-point correlations, which will be compared to those of a zero pressure gradient turbulent boundary layer. NCI and Pawsey SCC funded by the Australian and Western Australian governments as well as the support of PRACE funded by the European Union are gratefully acknowledged.

  19. A three-dimensional turbulent boundary layer undergoing transverse strain and streamwise pressure gradient

    NASA Technical Reports Server (NTRS)

    Hebbar, S. K.; Driver, D. M.

    1985-01-01

    Results from an experimental investigation designed to provide data on both mean and turbulence quantities in the axisymmetric, swirling boundary layer (with and without pressure gradient) flowing over a stationary cylinder downstreams of a spinning cylindrical section are presented. The pressure gradient was introduced into the flow field by a 25.4 mm-high, forward-facing, circular step mounted on the stationary cylinder, the step height being nearly equal to the thickness of the approaching boundary layer. All the measurements were made at a nominal upstream reference Reynolds number of 2.4 x 10 to the 6th power/m (corresponding to an upstream reference velocity of 36 to 37 m/sec) with the rotation of the spinner set to make its peripheral speed equal the reference velocity. The data reported included measurements of surface pressure and the mean surface shear-stress vector taken with a miniature, directional, surface-fence gage. These measurements were supplemented by oil-flow visualization studies of the stationary cylinder. The data indicates that the streamwise pressure gradient controls the development of the streamwise component of wall shear, but leaves the peripheral component of wall shear practically unaffected.

  20. The F-Region Gravity and Pressure Gradient Current Systems: A Review

    NASA Astrophysics Data System (ADS)

    Alken, P.; Maute, A.; Richmond, A. D.

    2016-07-01

    The ionospheric gravity and pressure-gradient current systems are most prominent in the low-latitude F-region due to the plasma density enhancement known as the equatorial ionization anomaly (EIA). This enhancement of plasma density which builds up during the day and lasts well into the evening supports a toroidal gravity current which flows eastward around the Earth in the F-region during the daytime and evening, and eventually returns westward through the E-region. The existence of pressure-gradients in the EIA region also gives rise to a poloidal diamagnetic current system, whose flow direction acts to reduce the ambient geomagnetic field inside the plasma. The gravity and pressure-gradient currents are among the weaker ionospheric sources, with current densities of a few nA/m2, however they produce clear signatures of about 5-7 nT in magnetic measurements made by low-Earth orbiting satellites. In this work, we review relevant observational and modeling studies of these two current systems and present new results from a 3D ionospheric electrodynamics model which allows us to visualize the entire flow pattern of these currents throughout the ionosphere as well as calculate their magnetic perturbations.

  1. Influence of pressure gradient on streamwise skewness factor in turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Dróżdż, Artur

    2014-08-01

    The paper shows an effect of favourable and adverse pressure gradients on turbulent boundary layer. The skewness factor of streamwise velocity component was chosen as a measure of the pressure gradient impact. It appears that skewness factor is an indicator of convection velocity of coherent structures, which is not always equal to the average flow velocity. The analysis has been performed based upon velocity profiles measured with hot-wire technique in turbulent boundary layer with pressure gradient corresponding to turbomachinery conditions. The results show that the skewness factor decreases in the flow region subjected to FPG and increases in the APG conditions. The changes of convection velocity and skewness factor are caused by influence of large-scale motion through the mechanism called amplitude modulation. The large-scale motion is less active in FPG and more active in APG, therefore in FPG the production of vortices is random (there are no high and low speed regions), while in the APG the large-scale motion drives the production of vortices. Namely, the vortices appear only in the high-speed regions, therefore have convection velocity higher than local mean velocity. The convection velocity affects directly the turbulent sweep and ejection events. The more flow is dominated by large-scale motion the higher values takes both the convection velocity of small-scale structures and sweep events induced by them.

  2. Pressure gradient sensors for bearing determination in shallow water tracking ranges

    NASA Astrophysics Data System (ADS)

    Stein, Peter J.; Euerle, Steven E.; Menoche, Richard K.; Janiesch, Robert E.

    1996-04-01

    Underwater acoustic tracking has traditionally used only the arrival time of tracking pings to localize targets. This implies that the ping transmitted from a target must be received at a minimum of three separate nodes (receiver locations) in order to determine the position. For deep water ranges this was acceptable. In shallow water, where propagation ranges are limited, this requires a large number of nodes. This makes shallow water ranges very costly. An effort is underway to use pressure gradient hydrophones as receivers and measure the bearing of the ping arrival along with arrival time, thereby locating the target using only one tracking node. This allows for increased node spacing and greatly reduced cost. However, the accuracy required for training ranges is on the order of 1 degree. Further, the directional receiver must be housed so as to withstand impacts from fishing operations. Research including design, fabrication, and testing of conventional and unconventional pressure gradient hydrophones, the housing, and signal processing methods are discussed. Extensive testing has already been conducted using a 1″ diameter by 5″ long multimode hydrophone. A shallow water tracking test was conducted at the NUWC Lake Seneca test facility. The results demonstrate the feasibility of tracking using a single pressure gradient hydrophone with an accuracy of 50 yds out to 2 kyds. The effects of multiple paths and scattering are also discussed.

  3. Self-similar turbulent boundary layer with imposed pressure gradient. Four flow regimes

    SciTech Connect

    Vigdorovich, I. I.

    2014-11-15

    Self-similar flows of an incompressible fluid in a turbulent boundary layer, when the free-stream velocity is a power function (with the exponent m) of the longitudinal coordinate, have been studied. It has been shown that there are four different self-similar flow regimes corresponding to four individual similarity parameters one of which is the known Clauser parameter and the three other parameters have been established for the first time. At adverse pressure gradient, when the exponent m lies in a certain range depending on Reynolds number, the problem has two solutions with different values of the boundary-layer thickness and skin friction; consequently, hysteresis in a pre-separation flow is possible. Separation occurs not at the minimal value of m that corresponds to the strongest adverse pressure gradient, but at m = −0.216 −0.4 Re{sub p}{sup −1/3} + O(Re{sub p}{sup −2/3}), where Re{sub p} is the Reynolds number based on longitudinal pressure gradient. The theoretical results are in good agreement with experimental data.

  4. The F-Region Gravity and Pressure Gradient Current Systems: A Review

    NASA Astrophysics Data System (ADS)

    Alken, P.; Maute, A.; Richmond, A. D.

    2017-03-01

    The ionospheric gravity and pressure-gradient current systems are most prominent in the low-latitude F-region due to the plasma density enhancement known as the equatorial ionization anomaly (EIA). This enhancement of plasma density which builds up during the day and lasts well into the evening supports a toroidal gravity current which flows eastward around the Earth in the F-region during the daytime and evening, and eventually returns westward through the E-region. The existence of pressure-gradients in the EIA region also gives rise to a poloidal diamagnetic current system, whose flow direction acts to reduce the ambient geomagnetic field inside the plasma. The gravity and pressure-gradient currents are among the weaker ionospheric sources, with current densities of a few nA/m2, however they produce clear signatures of about 5-7 nT in magnetic measurements made by low-Earth orbiting satellites. In this work, we review relevant observational and modeling studies of these two current systems and present new results from a 3D ionospheric electrodynamics model which allows us to visualize the entire flow pattern of these currents throughout the ionosphere as well as calculate their magnetic perturbations.

  5. Investigation on nonautonomous soliton management in generalized external potentials via dispersion and nonlinearity

    NASA Astrophysics Data System (ADS)

    Vijayalekshmi, S.; Mani Rajan, M. S.; Mahalingam, A.; Uthayakumar, A.

    2015-09-01

    We investigate the controllable behavior of nonautonomous soliton in external potentials with variable dispersion and nonlinearity management functions, which describes the propagation of optical pulses in an inhomogeneous fiber system. We derive the Lax pair with a variable spectral parameter and the exact multi-soliton solution is generated via Darboux transformation. Based on these solutions, several novel optical solitons are constructed by selecting appropriate functions and the main evolution features of these waves are shown by some interesting figures with computer simulation. As few examples, breathers in periodic potential, soliton compression in an exponentially dispersion decreasing fiber and interaction of boomerang solitons are discussed. The presented results have applications in the study of nonautonomous soliton birefringence-managed switching architecture. These results are potentially useful in the management of nonautonomous soliton with external potentials in the optical soliton communications and long-haul telecommunication networks.

  6. Helmholtz dark solitons.

    PubMed

    Chamorro-Posada, P; McDonald, G S

    2003-05-15

    A general dark-soliton solution of the Helmholtz equation (with defocusing Kerr nonlinearity) that has on- and off-axis, gray and black, paraxial and Helmholtz solitons as particular solutions, is reported. Modifications to soliton transverse velocity, width, phase period, and existence conditions are derived and explained in geometrical terms. Simulations verify analytical predictions and also demonstrate spontaneous formation of Helmholtz solitons and transparency of their interactions.

  7. Studies on soliton energy at critical and noncritical densities of negative ions in an inhomogeneous magnetized warm plasma

    SciTech Connect

    Singh, Dhananjay K.; Malik, Hitendra K.

    2007-11-15

    Considering an inhomogeneous plasma having finite-temperature negative and positive ions, and the isothermal electrons in the presence of an external magnetic field, the solitons at noncritical and critical densities of the negative ions are studied through Korteweg-deVries (KdV) and modified Korteweg-deVries (mKdV) equations, respectively. The compressive (rarefactive) KdV solitons are found to propagate when the negative ion concentration is less (greater) than the critical density of the negative ions. At the critical density, both the compressive and the rarefactive solitons of equal amplitudes are found to occur. The energies of the compressive KdV soliton and the mKdV solitons are found to increase and that of the rarefactive KdV soliton is found to decrease with the negative ion density. Soliton energy for both the KdV and the mKdV solitons gets lowered under the effect of stronger magnetic field. The effect of ion temperature is to increase the energy of the compressive KdV soliton, whereas the energy of the rarefactive KdV soliton as well as of the mKdV solitons gets decreased. The variation of the energy with the obliqueness of the magnetic field is different for the KdV and the mKdV solitons.

  8. Dipole soliton-vortices.

    PubMed

    Kartashov, Yaroslav V; Ferrando, Albert; García-March, Miguel-Angel

    2007-08-01

    On universal symmetry grounds, we analyze the existence of a new type of discrete-symmetry vortex solitons that can be considered as coherent states of dipole solitons carrying a nonzero topological charge. Remarkably, they can be also interpreted as excited angular Bloch states. The stability of new soliton states is elucidated numerically.

  9. Dissipative photonic lattice solitons.

    PubMed

    Ultanir, Erdem A; Stegeman, George I; Christodoulides, Demetrios N

    2004-04-15

    We show that discrete dissipative optical lattice solitons are possible in waveguide array configurations that involve periodically patterned semiconductor optical amplifiers and saturable absorbers. The characteristics of these low-power soliton states are investigated, and their propagation constant eigenvalues are mapped on Floquet-Bloch band diagrams. The prospect of observing such low-power dissipative lattice solitons is discussed in detail.

  10. Surface Pressure Gradient and Carbon Dioxide Degassing Survey at Cumbre Vieja Volcano, La Palma, Canary Islands

    NASA Astrophysics Data System (ADS)

    Alfaya, A.; López, F.; Padron, E.; Hernández, P. A.; Salazar, J. M.; Pérez, N. M.

    2002-12-01

    La Palma (730 Km2) is one of the youngest island of the Canarian archipelago. Recent volcanic activity is concentrated on the southern part of the island, where Cumbre Vieja volcano (220 Km2) has been constructed during the last 1 Ma reaching an elevation of 1,898 m above sea level. Six historical eruptions had occurred at Cumbre Vieja, and the most recent event took place in the southern part of the volcano (Teneguía volcano, 1971). The main structural features are three major volcanic rift-zones of N-S, NE, and NW orientations. Since fumarolic activity is absent at Cumbre Vieja, coupled surface pressure gradient and carbon dioxide degassing monitoring could be potential geophysical and geochemical tools for its volcanic surveillance. Surface pressure gradient and carbon dioxide degassing survey of 619 observation sites was carried out from July 19 to August 13, 2002, at Cumbre Vieja volcano. Pressure gradient measurements were performed by means of a Setra 239 Model pressure transducer, and soil CO2 efflux measurements were performed by means of a portable NDIR sensor according to the accumulation chamber method. At each sampling site, soil gas samples were collected at 40 cm deep using a metallic probe and analyzed for CO2 contents by means of a Omnistar QMS within 24 hours. Surface pressure gradient ranged from -36 to 90 Pam-1. Soil CO2 efflux ranged from negligible values to 1,300 gm-2d-1, and soil gas CO2 content ranged from 0.03 to 1.1 %V. Statistical graphical analysis showed two different populations for the CO2 efflux data and their mean values are 1.4 and 52 gm-2d-1, respectively. For this 2002 survey, the total output of diffuse CO2 emission was estimated about 1,340 td-1, which lies within the range of previous surveys (1,250-2,500 td-1). Spatial distribution of the data showed an excellent agreement between surface pressure gradient and CO2 degassing at Cumbre Vieja, where the highest observed values were detected in and around the volcanic vent

  11. Favorable pressure gradient turbulent flow over straight and inclined ribs on both channel walls

    NASA Astrophysics Data System (ADS)

    Tachie, Mark F.; Shah, Mohammad K.

    2008-09-01

    This paper reports on experimental study of turbulent flows over straight and inclined transverse ribs of square and triangular cross sections attached to the bottom and top walls of an asymmetric converging channel. The pitch-to-height ratio of the ribs was 10. A particle image velocimetry technique was used to conduct extensive velocity measurements at channel midspan and in planes close to the leading and trailing edges of the inclined ribs. From these measurements, spatial averaged profiles of the mean velocity and higher order statistics were obtained to study the effects of rib geometry, pressure gradient, spanwise plane, and rib inclination on the flow characteristics. The results show that rib geometry has no significant effects on the mean flow and turbulent quantities. The roughness effects produced by the straight ribs outweighed pressure gradient effects in the inner region of the flow. As a result, the skin friction coefficient is nearly independent of pressure gradient. The Reynolds shear stress and turbulent transport of the shear stress are also independent of pressure gradient. On the contrary, favorable pressure gradient decreased the Reynolds normal stresses in the outer region and increased the magnitudes of the triple velocity correlations and transport of turbulent kinetic energy (TKE). The three-dimensional secondary motion produced by the inclined ribs distorted the mean flow pattern and substantially diminished the ribs' effectiveness to augment skin friction and turbulence. For example, the skin friction over the inclined ribs is only 50%-70% of the value measured over the straight ribs. Furthermore, the size of equivalent sand grain required to produce the same amount of drag is one-tenth to one-third of the rib height for the inclined ribs compared to two- to fourfold for the straight ribs. The inclined ribs also reduced the level of the Reynolds stresses, triple velocity correlations, and transport of both the turbulent kinetic energy

  12. Large amplitude ion-acoustic solitons in dusty plasmas

    SciTech Connect

    Tiwari, R. S.; Jain, S. L.; Mishra, M. K.

    2011-08-15

    Characteristics of ion-acoustic soliton in dusty plasma, including the dynamics of heavily charged massive dust grains, are investigated following the Sagdeev Potential formalism. Retaining fourth order nonlinearities of electric potential in the expansion of the Sagdeev Potential in the energy equation for a pseudo particle and integrating the resulting energy equation, large amplitude soliton solution is determined. Variation of amplitude (A), half width (W) at half maxima and the product P = AW{sup 2} of the Korteweg-deVries (KdV), dressed and large amplitude soliton as a function of wide range of dust concentration are numerically studied for recently observed parameters of dusty plasmas. We have also presented the region of existence of large amplitude ion-acoustic soliton in the dusty plasma by analyzing the structure of the pseudo potential. It is found that in the presence of positively charged dust grains, system supports only compressive solitons, on the other hand, in the presence of negatively charged dust grains, the system supports compressive solitons up to certain critical concentration of dust grains and above this critical concentration, the system can support rarefactive solitons also. The effects of dust concentration, charge, and mass of the dust grains, on the characteristics of KdV, dressed and large amplitude the soliton, i.e., amplitude (A), half width at half maxima (W), and product of amplitude (A) and half width at half maxima (P = AW{sup 2}), are discussed in detail.

  13. Supersolitons: Solitonic Excitations in Atomic Soliton Chains

    SciTech Connect

    Novoa, David; Michinel, Humberto; Perez-Garcia, Victor M.

    2008-10-03

    We show that, by tuning interactions in nonintegrable vector nonlinear Schroedinger equations modeling Bose-Einstein condensates and other relevant physical systems, it is possible to achieve a regime of elastic particlelike collisions between solitons. This would allow one to construct a Newton's cradle with solitons and supersolitons: localized collective excitations in solitary-wave chains.

  14. Solitons in nonlinear optics

    SciTech Connect

    Maimistov, Andrei I

    2010-11-13

    The classic examples of optical phenomena resulting in the appearance of solitons are self-focusing, self-induced transparency, and parametric three-wave interaction. To date, the list of the fields of nonlinear optics and models where solitons play an important role has significantly expanded. Now long-lived or stable solitary waves are called solitons, including, for example, dissipative, gap, parametric, and topological solitons. This review considers nonlinear optics models giving rise to the appearance of solitons in a narrow sense: solitary waves corresponding to the solutions of completely integrable systems of equations basic for the models being discussed. (review)

  15. PHz-Wide Spectral Interference Through Coherent Plasma-Induced Fission of Higher-Order Solitons

    NASA Astrophysics Data System (ADS)

    Köttig, F.; Tani, F.; Travers, J. C.; Russell, P. St. J.

    2017-06-01

    We identify a novel regime of soliton-plasma interactions in which high-intensity ultrashort pulses of intermediate soliton order undergo coherent plasma-induced fission. Experimental results obtained in gas-filled hollow-core photonic crystal fiber are supported by rigorous numerical simulations. In the anomalous dispersion regime, the cumulative blueshift of higher-order input solitons with ionizing intensities results in pulse splitting before the ultimate self-compression point, leading to the generation of robust pulse pairs with PHz bandwidths. The novel dynamics closes the gap between plasma-induced adiabatic soliton compression and modulational instability.

  16. Visualization of turbulent wedges under favorable pressure gradients using shear-sensitive and temperature-sensitive liquid crystals.

    PubMed

    Chong, Tze-Pei; Zhong, Shan; Hodson, Howard P

    2002-10-01

    Turbulent wedges induced by a three-dimensional surface roughness placed on a flat plate were studied using both shear sensitive and temperature sensitive liquid crystals, respectively denoted by SSLC and TSLC. The experiments were carried out at a free-stream velocity of 28 m/sec at three different favorable pressure gradients. The purpose of this investigation was to examine the spreading angles of the turbulent wedges, as indicated by their associated surface shear stresses and heat transfer characteristics, and to obtain more insight about the behavior of transitional momentum and thermal boundary layers when a streamwise pressure gradient exists. It was shown that under a zero pressure gradient the spreading angles indicated by the two types of liquid crystals are the same, but the difference increases as the level of the favorable pressure gradient increases. The result from the present study is important for modelling the transition of thermal boundary layers over gas turbine blades.

  17. Numerical simulations of the bending of narrow-angle-tail radio jets by ram pressure or pressure gradients

    NASA Technical Reports Server (NTRS)

    Soker, Noam; Sarazin, Craig L.; O'Dea, Christopher P.

    1988-01-01

    Three-dimensional numerical hydrodynamic simulations are used to study the bending of radio jets. The simulations are compared with observations of jets in narrow-angle-tail radio sources. Two mechanisms for the observed bending are considered: direct bending of quasi-continuous jets by ram pressure from intergalactic gas and bending by pressure gradients in the interstellar gas of the host galaxy, the pressure gradients themselves being the result of ram pressure by intergalactic gas. It is shown that the pressure gradients are much less effective in bending jets, implying that the jets have roughly 30 times lower momentum fluxes if they are bent by this mechanism. Ram-pressure bending produces jets with 'kidney-shaped' cross sections; when observed from the side, these jets appear to have diffuse extensions on the downstream side. On the other hand, pressure-gradient bending causes the jets to be densest near their upstream side.

  18. Stability of the flow in a soft tube deformed due to an applied pressure gradient

    NASA Astrophysics Data System (ADS)

    Verma, M. K. S.; Kumaran, V.

    2015-04-01

    A linear stability analysis is carried out for the flow through a tube with a soft wall in order to resolve the discrepancy of a factor of 10 for the transition Reynolds number between theoretical predictions in a cylindrical tube and the experiments of Verma and Kumaran [J. Fluid Mech. 705, 322 (2012), 10.1017/jfm.2011.55]. Here the effect of tube deformation (due to the applied pressure difference) on the mean velocity profile and pressure gradient is incorporated in the stability analysis. The tube geometry and dimensions are reconstructed from experimental images, where it is found that there is an expansion and then a contraction of the tube in the streamwise direction. The mean velocity profiles at different downstream locations and the pressure gradient, determined using computational fluid dynamics, are found to be substantially modified by the tube deformation. The velocity profiles are then used in a linear stability analysis, where the growth rates of perturbations are calculated for the flow through a tube with the wall modeled as a neo-Hookean elastic solid. The linear stability analysis is carried out for the mean velocity profiles at different downstream locations using the parallel flow approximation. The analysis indicates that the flow first becomes unstable in the downstream converging section of the tube where the flow profile is more pluglike when compared to the parabolic flow in a cylindrical tube. The flow is stable in the upstream diverging section where the deformation is maximum. The prediction for the transition Reynolds number is in good agreement with experiments, indicating that the downstream tube convergence and the consequent modification in the mean velocity profile and pressure gradient could reduce the transition Reynolds number by an order of magnitude.

  19. Perpendicular propagation of electromagnetic solitons in magnetized thermal pair plasmas

    NASA Astrophysics Data System (ADS)

    Verheest, Frank

    2016-02-01

    The properties of perpendicularly propagating large amplitude electromagnetic solitons are investigated in a thermal, magnetized pair plasma. To obtain a tractable description, these solitons are assumed to be charge neutral and have a linearly polarized magnetic field, and thus represent the nonlinear extension of part of the linear extraordinary mode. From a Sagdeev pseudopotential analysis it transpires that these solitons are compressive and characterized by a wave magnetic field parallel to the static field. The existence domain in compositional parameter space shows pressure-dependent maxima for the soliton velocities, densities and total magnetic field. Physically, an increase in pressure yields a decrease in the acceptable maxima. This is also illustrated on typical pseudopotential and soliton profiles.

  20. Direct numerical simulations of turbulent thermal boundary layers subjected to adverse streamwise pressure gradients

    NASA Astrophysics Data System (ADS)

    Araya, Guillermo; Castillo, Luciano

    2013-09-01

    An innovative method for prescribing turbulent thermal inflow information in spatially developing boundary layers under streamwise pressure gradients is introduced for attached flows. The approach is tested and validated in a suite of Direct Numerical Simulations (DNS) of thermal boundary layers for zero (ZPG) and adverse (APG) pressure gradients with momentum thickness Reynolds numbers (Reθ) up to 3000. The turbulent thermal data are generated based on the dynamic multi-scale approach proposed by Araya et al. ["A dynamic multi-scale approach for turbulent inflow boundary conditions in spatially evolving flows," J. Fluid Mech. 670, 581-605 (2011)], which is extended to include thermal field simulations in the present article. The approach is based on the original rescaling-recycling method developed by Lund, Wu, and Squires ["Generation of turbulent inflow data for spatially developing boundary layer simulations," J. Comput. Phys. 140, 233-258 (1998)] for ZPG flows. Isothermal walls are considered for the thermal field and the molecular Prandtl number is 0.71. In addition, only inlet momentum/thermal boundary layer thicknesses must be prescribed while other flow parameters such as the inlet friction velocity, uτ, and friction temperature, Θτ, are computed dynamically based on the flow solution obtained downstream by means of a test plane. This plane is located between the inlet and recycle stations. Based on the unique and extensive DNS results of heat transfer obtained in this investigation, the effects of Reynolds numbers and adverse pressure gradients on the flow and thermal parameters are also explored and visualized. The principal outcome of adverse pressure gradient on the flow parameters has been determined as a secondary peak, particularly on the streamwise velocity fluctuations in the outer region, which shows clear evidence of energy production in the outer flow and not only in the buffer layer as traditionally known. Nevertheless, this peak is not so

  1. Turbulence model investigations on the boundary layer flow with adverse pressure gradients

    NASA Astrophysics Data System (ADS)

    Yong, Zhao; Zhi, Zong; Li, Zou; Tianlin, Wang

    2015-06-01

    In this paper, a numerical study of flow in the turbulence boundary layer with adverse and pressure gradients (APGs) is conducted by using Reynolds-averaged Navier-Stokes (RANS) equations. This research chooses six typical turbulence models, which are critical to the computing precision, and to evaluating the issue of APGs. Local frictional resistance coefficient is compared between numerical and experimental results. The same comparisons of dimensionless averaged velocity profiles are also performed. It is found that results generated by Wilcox (2006) k- w are most close to the experimental data. Meanwhile, turbulent quantities such as turbulent kinetic energy and Reynolds-stress are also studied.

  2. Correlation of heat transfer for the zero pressure gradient hypersonic laminar boundary layer for several gases

    NASA Technical Reports Server (NTRS)

    Cook, W. J.

    1973-01-01

    A theoretical study of heat transfer for zero pressure gradient hypersonic laminar boundary layers for various gases with particular application to the flows produced in an expansion tube facility was conducted. A correlation based on results obtained from solutions to the governing equations for five gases was formulated. Particular attention was directed toward the laminar boundary layer shock tube splitter plates in carbon dioxide flows generated by high speed shock waves. Computer analysis of the splitter plate boundary layer flow provided information that is useful in interpreting experimental data obtained in shock tube gas radiation studies.

  3. New Pressure Gradient Equations for Lumped-Parameter Interior Ballistic Codes

    DTIC Science & Technology

    1990-05-01

    chambrage effects are important factors in respect to the time- dependent behavior of the pressure gradient. The result of the RGA gradient equation... dependence of both V. and d 21np/dt 2 . The Drojectile acceleration is given by P = goABPB gQAP,L.5 MM "(L.25) To get the base pressure Pg dependence ...v)) or a- - 14(t)z (L.69) where k1(t) = k, = C "- ,j. (L,.70) k, depends upon the base pressure PB = P(z.P (one of the values we wish to solve for

  4. Gap heating with pressure gradients. [for Shuttle Orbiter thermal protection system tiles

    NASA Technical Reports Server (NTRS)

    Scott, C. D.; Maraia, R. J.

    1979-01-01

    The heating rate distribution and temperature response on the gap walls of insulating tiles is analyzed to determine significant phenomena and parameters in flows where there is an external surface pressure gradient. Convective heating due to gap flow, modeled as fully developed pipe flow, is coupled with a two-dimensional thermal model of the tiles that includes conduction and radiative heat transfer. To account for geometry and important environmental parameters, scale factors are obtained by curve-fitting measured temperatures to analytical solutions. These scale factors are then used to predict the time-dependent gap heat flux and temperature response of tile gaps on the Space Shuttle Orbiter during entry.

  5. Local pressure gradients due to incipience of boiling in subcooled flows

    SciTech Connect

    Ruggles, A.E.; McDuffee, J.L.

    1995-09-01

    Models for vapor bubble behavior and nucleation site density during subcooled boiling are integrated with boundary layer theory in order to predict the local pressure gradient and heat transfer coefficient. Models for bubble growth rate and bubble departure diameter are used to scale the movement of displaced liquid in the laminar sublayer. An added shear stress, analogous to a turbulent shear stress, is derived by considering the liquid movement normal to the heated surface. The resulting mechanistic model has plausible functional dependence on wall superheat, mass flow, and heat flux and agrees well with data available in the literature.

  6. LES - IB analysis of a flow in channel with an adverse pressure gradient.

    NASA Astrophysics Data System (ADS)

    Księżyk, M.; Tyliszczak, A.

    2016-10-01

    This paper presents results of Large Eddy Simulation (LES) of a flow in a channel with an adverse pressure gradient. The applied computational code (SAILOR) is based on a high-order compact finite difference scheme on half-staggered meshes and is combined with an Immersed Boundary (IB) method. The IB method is implemented using the direct forcing approach in a simplified stepwise variant. The results are verified using the experimental data and the general agreement is good. The observed discrepancies are small close to the inlet section and increase along the channel length where strong flow separation occurs.

  7. Self-consistent high-Reynolds-number asymptotics for zero-pressure-gradient turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Monkewitz, Peter A.; Chauhan, Kapil A.; Nagib, Hassan M.

    2007-11-01

    The asymptotic behavior of mean velocity and integral parameters in flat plate turbulent boundary layers under zero pressure gradient are studied for Reynolds numbers approaching infinity. Using the classical two-layer approach of Millikan, Rotta, and Clauser with a logarithmic velocity profile in the overlap region between "inner" and "outer" layers, a fully self-consistent leading-order description of the mean velocity profile and all integral parameters is developed. It is shown that this description fits most high Reynolds number data, and in particular their Reynolds number dependence, exceedingly well; i.e., within experimental errors.

  8. Structure of the zero-pressure-gradient turbulent boundary layer

    PubMed Central

    Barenblatt, G. I.; Chorin, A. J.; Hald, O. H.; Prostokishin, V. M.

    1997-01-01

    A processing of recent experimental data by Nagib and Hites [Nagib, H. & Hites, M. (1995) AIAA paper 95-0786, Reno, NV) shows that the flow in a zero-pressure-gradient turbulent boundary layer, outside the viscous sublayer, consists of two self-similar regions, each described by a scaling law. The results concerning the Reynolds-number dependence of the coefficients of the wall-region scaling law are consistent with our previous results concerning pipe flow, if the proper definition of the boundary layer Reynolds number (or boundary layer thickness) is used. PMID:11038559

  9. Direct numerical simulation of a self-similar adverse pressure gradient turbulent boundary layer at the verge of separation

    NASA Astrophysics Data System (ADS)

    Kitsios, V.; Sekimoto, A.; Atkinson, C.; Sillero, J. A.; Borrell, G.; Gungor, A. G.; Jiménez, J.; Soria, J.

    2017-10-01

    The statistical properties are presented for the direct numerical simulation (DNS) of a self-similar adverse pressure gradient (APG) turbulent boundary layer (TBL) at the verge of separation. The APG TBL has a momentum thickness based Reynolds number range from $Re_{\\delta_2}=570$ to $13800$, with a self-similar region from $Re_{\\delta_2} = 10000$ to $12300$. Within this domain the average non-dimensional pressure gradient parameter $\\beta=39$, where for a unit density $\\beta=\\delta_1 P_e^\\prime / \\tau_w$, with $\\delta_1$ the displacement thickness, $\\tau_w$ the mean shear stress at the wall, and $P_e^\\prime$ the farfield pressure gradient. This flow is compared to previous zero pressure gradient (ZPG) and mild APG TBL ($\\beta=1$) results of similar Reynolds number. All flows are generated via the DNS of a TBL on a flat surface with farfield boundary conditions tailored to apply the desired pressure gradient. The conditions for self-similarity, and the appropriate length and velocity scales are derived. The mean and Reynolds stress profiles are shown to collapse when non-dimensionalised on the basis of these length and velocity scales. As the pressure gradient increases the flow has properties less like a ZPG TBL and more akin to a free shear layer.

  10. Dissipative solitons in pair-ion plasmas

    SciTech Connect

    Ghosh, Samiran; Adak, Ashish Khan, Manoranjan

    2014-01-15

    The effects of ion-neutral collisions on the dynamics of the nonlinear ion acoustic wave in pair-ion plasma are investigated. The standard perturbative approach leads to a Korteweg-de Vries equation with a linear damping term for the dynamics of the finite amplitude wave. The ion-neutral collision induced dissipation is responsible for the linear damping. The analytical solution and numerical simulation reveal that the nonlinear wave propagates in the form of a weakly dissipative compressive solitons. Furthermore, the width of the soliton is proportional to the amplitude of the wave for fixed soliton velocity. Results are discussed in the context of the fullerene pair-ion plasma experiment.

  11. Mixed mode transition in zero and adverse pressure gradient boundary layers

    NASA Astrophysics Data System (ADS)

    Bose, Rikhi; Durbin, Paul

    2015-11-01

    Flow regimes exist where interaction of Klebanoff streaks and the Tollmien-Sclichting waves trigger transition but either mode is individually insufficient. Such interaction between orderly and bypass routes of transition is called Mixed mode transition. In zero pressure gradient boundary layers, mixed mode transition follows three routes depending upon strength of these perturbation modes. At high free-stream turbulence intensity (Tu), bypass transition is dominant and the flow is very weakly sensitive to the TS mode strength. In the presence of a strong TS mode, low Tu triggers secondary instability of the TS wave forming Λ vortices. The Λ vortices are forced response due to the weak streaks rather than resonance mechanism seen in monochromatic excitations. When both of these modes are weak, secondary instability of streaks trigger consequent breakdown to turbulent spots. Three-dimensional visualization of the perturbation fields shows toroidal n = 0 and helical n = 1 modes observed in instability of axisymmetric jets and wakes. In adverese pressure gradient boundary layers, the presence of an inflection point significantly increases the growth rate of TS mode thereby strengthening the secondary instability route and the interaction is more interesting. This work was supported by NSF grant CBET-1228195. Computer time was provided by the Extreme Science and Engineering Discovery Environment (XSEDE).

  12. Mitral inertance in humans: critical factor in Doppler estimation of transvalvular pressure gradients

    NASA Technical Reports Server (NTRS)

    Nakatani, S.; Firstenberg, M. S.; Greenberg, N. L.; Vandervoort, P. M.; Smedira, N. G.; McCarthy, P. M.; Thomas, J. D.

    2001-01-01

    The pressure-velocity relationship across the normal mitral valve is approximated by the Bernoulli equation DeltaP = 1/2 rhoDeltav(2) + M. dv/dt, where DeltaP is the atrioventricular pressure difference, rho is blood density, v is transmitral flow velocity, and M is mitral inertance. Although M is indispensable in assessing transvalvular pressure differences from transmitral flow, this term is poorly understood. We measured intraoperative high-fidelity left atrial and ventricular pressures and simultaneous transmitral flow velocities by using transesophageal echocardiography in 100 beats (8 patients). We computed mean mitral inertance (M) by M = integral((DeltaP)-(1/2 x rho v(2))dt/integral(dv/dt)dt and we assessed the effect of the inertial term on the transmitral pressure-flow relation. ranged from 1.03 to 5.96 g/cm(2) (mean = 3.82 +/- 1.22 g/cm(2)). DeltaP calculated from the simplified Bernoulli equation (DeltaP = 1/2. rhov(2)) lagged behind (44 +/- 11 ms) and underestimated the actual peak pressures (2.3 +/- 1.1 mmHg). correlated with left ventricular systolic pressure (r = -0.68, P < 0.0001) and transmitral pressure gradients (r = 0.65, P < 0.0001). Because mitral inertance causes the velocity to lag significantly behind the actual pressure gradient, it needs to be considered when assessing diastolic filling and the pressure difference across normal mitral valves.

  13. Flow Control Device Evaluation for an Internal Flow with an Adverse Pressure Gradient

    NASA Technical Reports Server (NTRS)

    Jenkins, Luther N.; Gorton, Susan Althoff; Anders, Scott G.

    2002-01-01

    The effectiveness of several active and passive devices to control flow in an adverse pressure gradient with secondary flows present was evaluated in the 15 Inch Low Speed Tunnel at NASA Langley Research Center. In this study, passive micro vortex generators, micro bumps, and piezoelectric synthetic jets were evaluated for their flow control characteristics using surface static pressures, flow visualization, and 3D Stereo Digital Particle Image Velocimetry. Data also were acquired for synthetic jet actuators in a zero flow environment. It was found that the micro vortex generator is very effective in controlling the flow environment for an adverse pressure gradient, even in the presence of secondary vortical flow. The mechanism by which the control is effected is a re-energization of the boundary layer through flow mixing. The piezoelectric synthetic jet actuators must have sufficient velocity output to produce strong longitudinal vortices if they are to be effective for flow control. The output of these devices in a laboratory or zero flow environment will be different than the output in a flow environment. In this investigation, the output was higher in the flow environment, but the stroke cycle in the flow did not indicate a positive inflow into the synthetic jet.

  14. Experimental feasibility of investigating acoustic waves in Couette flow with entropy and pressure gradients

    NASA Technical Reports Server (NTRS)

    Parrott, Tony L.; Zorumski, William E.; Rawls, John W., Jr.

    1990-01-01

    The feasibility is discussed for an experimental program for studying the behavior of acoustic wave propagation in the presence of strong gradients of pressure, temperature, and flow. Theory suggests that gradients effects can be experimentally observed as resonant frequency shifts and mode shape changes in a waveguide. A convenient experimental geometry for such experiments is the annular region between two co-rotating cylinders. Radial temperature gradients in a spinning annulus can be generated by differentially heating the two cylinders via electromagnetic induction. Radial pressure gradients can be controlled by varying the cylinder spin rates. Present technology appears adequate to construct an apparatus to allow independent control of temperature and pressure gradients. A complicating feature of a more advanced experiment, involving flow gradients, is the requirement for independently controlled cylinder spin rates. Also, the boundary condition at annulus terminations must be such that flow gradients are minimally disturbed. The design and construction of an advanced apparatus to include flow gradients will require additional technology development.

  15. Myocardial fractional flow reserve: a biplane angiocardiographic alternative to the pressure gradient method

    NASA Astrophysics Data System (ADS)

    Schrijver, Marc; Slump, Cornelis H.; Storm, Corstiaan J.

    2001-05-01

    Pijls and De Bruyne (1993) developed a method employing intravascular blood pressure gradients to calculate the Myocardial Fractional Flow Reserve (FFR). This flow reserve is a better indication of the functional severity of a coronary stenosis than percentage diameter or luminal area reduction as provided by traditional Quantitative Coronary Angiography (QCA). However, to use this method, all of the relevant artery segments have to be select intra-operatively. After the procedure, only the segments for which a pressure reading is available can be graded. We previously introduced another way to assess the functional severity of stenosis using angiographic projections: the Relative Coronary Flow Reserve (RCFR). It is based on standard densitometric blood velocity and flow reserve methods, but without the need to estimate the geometry of the artery. This paper demonstrates that this RCFR method yields -- in theory -- the same results as the FFR, and can be given an almost identical interpretation. This provides the opportunity to use the RCFR retrospectively, when pressure gradients are not available for the segment(s) of interest.

  16. Internal pressure gradient errors in σ-coordinate ocean models in high resolution fjord studies

    NASA Astrophysics Data System (ADS)

    Berntsen, Jarle; Thiem, Øyvind; Avlesen, Helge

    2015-08-01

    Terrain following ocean models are today applied in coastal areas and fjords where the topography may be very steep. Recent advances in high performance computing facilitate model studies with very high spatial resolution. In general, numerical discretization errors tend to zero with the grid size. However, in fjords and near the coast the slopes may be very steep, and the internal pressure gradient errors associated with σ-models may be significant even in high resolution studies. The internal pressure gradient errors are due to errors when estimating the density gradients in σ-models, and these errors are investigated for two idealized test cases and for the Hardanger fjord in Norway. The methods considered are the standard second order method and a recently proposed method that is balanced such that the density gradients are zero for the case ρ = ρ(z) where ρ is the density and z is the vertical coordinate. The results show that by using the balanced method, the errors may be reduced considerably also for slope parameters larger than the maximum suggested value of 0.2. For the Hardanger fjord case initialized with ρ = ρ(z) , the errors in the results produced with the balanced method are orders of magnitude smaller than the corresponding errors in the results produced with the second order method.

  17. Direct and Large Eddy Simulation of turbulent channel flow with periodic pressure gradient.

    NASA Astrophysics Data System (ADS)

    Scotti, Alberto; Piomelli, Ugo; Trowbridge, John

    1999-11-01

    The flow inside blood vessels or in internal combustion engines, or the motion due to gravity waves in shallow waters, have in common the fact that the external forcing that maintains the flow is unsteady. Despite their importance and ubiquitousness, however, turbulent flows with an imposed unsteadiness have received relatively little attention. Spalart [NASA Technical Memorandum 89460 (1987)] performed DNS of boundary-layer turbulence subject to a periodic pressure gradient with zero mean. More recently, Binder et al. [J. Fluid Mec., 267 (1995)] have measured turbulence statistics in a channel flow driven by an unsteady, periodic pressure gradient. We have performed direct numerical simulations of the same problem using a pseudospectral code. The database has been found in good agreement with the published results. We have explored the temporal and spatial relationship between the Reynold stress and the phase-averaged rate of strain. We find that, in agreement with the experiments, the computed eddy viscosity -uv/dU/dy is not in phase with the rate of strain; conventional eddy viscosity models are thus inadequate to deal with unsteadiness. It is arguable that, for unsteady flows, large-eddy simulations provide a better approach, since the small unresolved scales should adjust faster to changes in the rate of strain field. In particular, we explore a priori the performance of models based on the Germano identity.

  18. Pressure gradient effects on heat transfer to reusable surface insulation tile-array gaps

    NASA Technical Reports Server (NTRS)

    Throckmorton, D. A.

    1975-01-01

    An experimental investigation was performed to determine the effect of pressure gradient on the heat transfer within space shuttle reusable surface insulation (RSI) tile-array gaps under thick, turbulent boundary-layer conditions. Heat-transfer and pressure measurements were obtained on a curved array of full-scale simulated RSI tiles in a tunnel-wall boundary layer at a nominal free-stream Mach number and free-stream Reynolds numbers. Transverse pressure gradients of varying degree were induced over the model surface by rotating the curved array with respect to the flow. Definition of the tunnel-wall boundary-layer flow was obtained by measurement of boundary-layer pitot pressure profiles, wall pressure, and heat transfer. Flat-plate heat-transfer data were correlated and a method was derived for prediction of heat transfer to a smooth curved surface in the highly three-dimensional tunnel-wall boundary-layer flow. Pressure on the floor of the RSI tile-array gap followed the trends of the external surface pressure. Heat transfer to the surface immediately downstream of a transverse gap is higher than that for a smooth surface at the same location. Heating to the wall of a transverse gap, and immediately downstream of it, at its intersection with a longitudinal gap is significantly greater than that for the simple transverse gap.

  19. Measurement of the Turbulence Kinetic Energy Budget of a Turbulent Planar Wake Flow in Pressure Gradients

    NASA Technical Reports Server (NTRS)

    Liu, Xiao-Feng; Thomas, Flint O.; Nelson, Robert C.

    2001-01-01

    Turbulence kinetic energy (TKE) is a very important quantity for turbulence modeling and the budget of this quantity in its transport equation can provide insight into the flow physics. Turbulence kinetic energy budget measurements were conducted for a symmetric turbulent wake flow subjected to constant zero, favorable and adverse pressure gradients in year-three of research effort. The purpose of this study is to clarify the flow physics issues underlying the demonstrated influence of pressure gradient on wake development and provide experimental support for turbulence modeling. To ensure the reliability of these notoriously difficult measurements, the experimental procedure was carefully designed on the basis of an uncertainty analysis. Four different approaches, based on an isotropic turbulence assumption, a locally axisymmetric homogeneous turbulence assumption, a semi-isotropy assumption and a forced balance of the TKE equation, were applied for the estimate of the dissipation term. The pressure transport term is obtained from a forced balance of the turbulence kinetic energy equation. This report will present the results of the turbulence kinetic energy budget measurement and discuss their implication on the development of strained turbulent wakes.

  20. Mitral inertance in humans: critical factor in Doppler estimation of transvalvular pressure gradients

    NASA Technical Reports Server (NTRS)

    Nakatani, S.; Firstenberg, M. S.; Greenberg, N. L.; Vandervoort, P. M.; Smedira, N. G.; McCarthy, P. M.; Thomas, J. D.

    2001-01-01

    The pressure-velocity relationship across the normal mitral valve is approximated by the Bernoulli equation DeltaP = 1/2 rhoDeltav(2) + M. dv/dt, where DeltaP is the atrioventricular pressure difference, rho is blood density, v is transmitral flow velocity, and M is mitral inertance. Although M is indispensable in assessing transvalvular pressure differences from transmitral flow, this term is poorly understood. We measured intraoperative high-fidelity left atrial and ventricular pressures and simultaneous transmitral flow velocities by using transesophageal echocardiography in 100 beats (8 patients). We computed mean mitral inertance (M) by M = integral((DeltaP)-(1/2 x rho v(2))dt/integral(dv/dt)dt and we assessed the effect of the inertial term on the transmitral pressure-flow relation. ranged from 1.03 to 5.96 g/cm(2) (mean = 3.82 +/- 1.22 g/cm(2)). DeltaP calculated from the simplified Bernoulli equation (DeltaP = 1/2. rhov(2)) lagged behind (44 +/- 11 ms) and underestimated the actual peak pressures (2.3 +/- 1.1 mmHg). correlated with left ventricular systolic pressure (r = -0.68, P < 0.0001) and transmitral pressure gradients (r = 0.65, P < 0.0001). Because mitral inertance causes the velocity to lag significantly behind the actual pressure gradient, it needs to be considered when assessing diastolic filling and the pressure difference across normal mitral valves.

  1. Feasibility of skin-friction diagnostics based on surface pressure gradient field

    NASA Astrophysics Data System (ADS)

    Liu, Tianshu; Misaka, Takashi; Asai, Keisuke; Obayashi, Shigeru; Wu, Jie-Zhi

    2016-12-01

    An intrinsic relation is given between the skin-friction vector and the surface pressure gradient through the boundary enstrophy flux (BEF), and it is used to study the possibility to extract some skin-friction structures from a surface pressure field. This attempt contains two related parts. In the first part, when the BEF field is given, a projected skin-friction field in the image plane can be sought from a surface pressure image based on a variational solution of an optical-flow-like equation. This approach is validated in several classical flows. The second part deals with a practical problem in which the BEF field is not known a priori. In this case, a so-called auxiliary skin-friction field is determined from a surface pressure image alone by using the same variational approach. The auxiliary skin-friction field has the magnitude proportional to the skin-friction magnitude and the direction of the negative surface pressure gradient. The physical meaning of the auxiliary skin-friction field and its applicability to global skin-friction diagnostics are discussed.

  2. Acoustic receptivity due to weak surface inhomogeneities in adverse pressure gradient boundary layers

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan; Ng, Lian; Streett, Craig

    1995-01-01

    The boundary layer receptivity to free-stream acoustic waves in the presence of localized surface disturbances is studied for the case of incompressible Falkner-Skan flows with adverse pressure gradients. These boundary layers are unstable to both viscous and inviscid (i.e., inflectional) modes, and the finite Reynolds number extension of the Goldstein-Ruban theory provides a convenient method to compare the efficiency of the localized receptivity processes in these two cases. The value of the efficiency function related to the receptivity caused by localized distortions in surface geometry is relatively insensitive to the type of instability mechanism, provided that the same reference length scale is used to normalize the efficiency function for each type of instability. In contrast, when the receptivity is induced by variations in wall suction velocity or in wall admittance distribution, the magnitudes of the related efficiency functions, as well as the resulting coupling coefficients, are smaller for inflectional (i.e., Rayleigh) modes than for the viscous Tollmien-Schlichting waves. The reduced levels of receptivity can be attributed mainly to the shorter wavelengths and higher frequencies of the inflectional modes. Because the most critical band of frequencies shifts toward higher values, the overall efficiency of the wall suction- and the wall admittance-induced receptivity decreases with an increase in the adverse pressure gradient.

  3. Observations of wave-induced pore pressure gradients and bed level response on a surf zone sandbar

    NASA Astrophysics Data System (ADS)

    Anderson, Dylan; Cox, Dan; Mieras, Ryan; Puleo, Jack A.; Hsu, Tian-Jian

    2017-06-01

    Horizontal and vertical pressure gradients may be important physical mechanisms contributing to onshore sediment transport beneath steep, near-breaking waves in the surf zone. A barred beach was constructed in a large-scale laboratory wave flume with a fixed profile containing a mobile sediment layer on the crest of the sandbar. Horizontal and vertical pore pressure gradients were obtained by finite differences of measurements from an array of pressure transducers buried within the upper several centimeters of the bed. Colocated observations of erosion depth were made during asymmetric wave trials with wave heights between 0.10 and 0.98 m, consistently resulting in onshore sheet flow sediment transport. The pore pressure gradient vector within the bed exhibited temporal rotations during each wave cycle, directed predominantly upward under the trough and then rapidly rotating onshore and downward as the wavefront passed. The magnitude of the pore pressure gradient during each phase of rotation was correlated with local wave steepness and relative depth. Momentary bed failures as deep as 20 grain diameters were coincident with sharp increases in the onshore-directed pore pressure gradients, but occurred at horizontal pressure gradients less than theoretical critical values for initiation of the motion for compact beds. An expression combining the effects of both horizontal and vertical pore pressure gradients with bed shear stress and soil stability is used to determine that failure of the bed is initiated at nonnegligible values of both forces.Plain Language SummaryThe <span class="hlt">pressure</span> <span class="hlt">gradient</span> present within the seabed beneath breaking waves may be an important physical mechanism transporting sediment. A large-scale laboratory was used to replicate realistic surfzone conditions in controlled tests, allowing for horizontal and vertical <span class="hlt">pressure</span> <span class="hlt">gradient</span> magnitudes and the resulting sediment bed response to be observed with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvL.114k3901B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvL.114k3901B"><span>Adiabatic <span class="hlt">Soliton</span> Laser</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bednyakova, Anastasia; Turitsyn, Sergei K.</p> <p>2015-03-01</p> <p>The key to generating stable optical pulses is mastery of nonlinear light dynamics in laser resonators. Modern techniques to control the buildup of laser pulses are based on nonlinear science and include classical <span class="hlt">solitons</span>, dissipative <span class="hlt">solitons</span>, parabolic pulses (similaritons) and various modifications and blending of these methods. Fiber lasers offer remarkable opportunities to apply one-dimensional nonlinear science models for the design and optimization of very practical laser systems. Here, we propose a new concept of a laser based on the adiabatic amplification of a <span class="hlt">soliton</span> pulse in the cavity—the adiabatic <span class="hlt">soliton</span> laser. The adiabatic change of the <span class="hlt">soliton</span> parameters during evolution in the resonator relaxes the restriction on the pulse energy inherent in traditional <span class="hlt">soliton</span> lasers. Theoretical analysis is confirmed by extensive numerical modeling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25606940','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25606940"><span>Dissipative Raman <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kalashnikov, Vladimir L; Sorokin, Evgeni</p> <p>2014-12-01</p> <p>A new type of dissipative <span class="hlt">solitons</span>--dissipative Raman <span class="hlt">solitons</span>--are revealed on the basis of numerical study of the generalized complex nonlinear Ginzburg-Landau equation. The stimulated Raman scattering significantly affects the energy scalability of the dissipative <span class="hlt">solitons</span>, causing splitting to multiple pulses. We show, that an appropriate increase of the group-delay dispersion can suppress the multipulsing instability due to formation of the dissipative Raman <span class="hlt">soliton</span>, which is chirped, has a Stokes-shifted spectrum, and chaotic modulation on its trailing edge. The strong perturbation of a <span class="hlt">soliton</span> envelope caused by the stimulated Raman scattering confines the energy scalability preventing the so-called dissipative <span class="hlt">soliton</span> resonance. We show, that in practical implementations, a spectral filter can extend the stability regions of high-energy pulses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4740180','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4740180"><span>Pure-quartic <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Blanco-Redondo, Andrea; Martijn, de Sterke C.; Sipe, J.E.; Krauss, Thomas F.; Eggleton, Benjamin J.; Husko, Chad</p> <p>2016-01-01</p> <p>Temporal optical <span class="hlt">solitons</span> have been the subject of intense research due to their intriguing physics and applications in ultrafast optics and supercontinuum generation. Conventional bright optical <span class="hlt">solitons</span> result from the interaction of anomalous group-velocity dispersion and self-phase modulation. Here we experimentally demonstrate a class of bright <span class="hlt">soliton</span> arising purely from the interaction of negative fourth-order dispersion and self-phase modulation, which can occur even for normal group-velocity dispersion. We provide experimental and numerical evidence of shape-preserving propagation and flat temporal phase for the fundamental pure-quartic <span class="hlt">soliton</span> and periodically modulated propagation for the higher-order pure-quartic <span class="hlt">solitons</span>. We derive the approximate shape of the fundamental pure-quartic <span class="hlt">soliton</span> and discover that is surprisingly Gaussian, exhibiting excellent agreement with our experimental observations. Our discovery, enabled by precise dispersion engineering, could find applications in communications, frequency combs and ultrafast lasers. PMID:26822758</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870033952&hterms=formalism+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dformalism%2Btheory','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870033952&hterms=formalism+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dformalism%2Btheory"><span>Statistical foundation of the fluid analogue of the <span class="hlt">soliton</span> formalism</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tchen, C. M.</p> <p>1986-01-01</p> <p>A fully nonlinear analysis is used to develop a general <span class="hlt">soliton</span> formalism for the description of the nonlinear evolution of <span class="hlt">soliton</span> fluctuations in both plasmas and classical fluids. From the Navier-Stokes equations for plasmas and <span class="hlt">compressible</span> fluids of two scales, two equations for the propagation of density waves are derived. A fast <span class="hlt">soliton</span> field is spontaneously created by rarefaction, and a slow density wave modulates the field intensity as a ponderomotive force. Constitutive properties are demonstrated using a Lagrangian-kinetic formalism of the fluctuation-dissipation theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870033952&hterms=fluids+properties+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfluids%2Bproperties%2Bdensity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870033952&hterms=fluids+properties+density&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfluids%2Bproperties%2Bdensity"><span>Statistical foundation of the fluid analogue of the <span class="hlt">soliton</span> formalism</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tchen, C. M.</p> <p>1986-01-01</p> <p>A fully nonlinear analysis is used to develop a general <span class="hlt">soliton</span> formalism for the description of the nonlinear evolution of <span class="hlt">soliton</span> fluctuations in both plasmas and classical fluids. From the Navier-Stokes equations for plasmas and <span class="hlt">compressible</span> fluids of two scales, two equations for the propagation of density waves are derived. A fast <span class="hlt">soliton</span> field is spontaneously created by rarefaction, and a slow density wave modulates the field intensity as a ponderomotive force. Constitutive properties are demonstrated using a Lagrangian-kinetic formalism of the fluctuation-dissipation theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19730029969&hterms=1589&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D%2526%25231589','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19730029969&hterms=1589&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3D%2526%25231589"><span>Multiple <span class="hlt">soliton</span> production and the Korteweg-de Vries equation.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hershkowitz, N.; Romesser, T.; Montgomery, D.</p> <p>1972-01-01</p> <p><span class="hlt">Compressive</span> square-wave pulses are launched in a double-plasma device. Their evolution is interpreted according to the Korteweg-de Vries description of Washimi and Taniuti. Square-wave pulses are an excitation for which an explicit solution of the Schrodinger equation permits an analytical prediction of the number and amplitude of emergent <span class="hlt">solitons</span>. Bursts of energetic particles (pseudowaves) appear above excitation voltages greater than an electron thermal energy, and may be mistaken for <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22072219','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22072219"><span>Multipole plasmonic lattice <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kou Yao; Ye Fangwei; Chen Xianfeng</p> <p>2011-09-15</p> <p>We theoretically demonstrate a variety of multipole plasmonic lattice <span class="hlt">solitons</span>, including dipoles, quadrupoles, and necklaces, in two-dimensional metallic nanowire arrays with Kerr-type nonlinearities. Such <span class="hlt">solitons</span> feature complex internal structures with an ultracompact mode size approaching or smaller than one wavelength. Their mode sizes and the stability characteristics are studied in detail within the framework of coupled mode theory. The conditions to form and stabilize these highly confined <span class="hlt">solitons</span> are within the experimentally achievable range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990ApJ...354..302C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990ApJ...354..302C"><span>Massive <span class="hlt">soliton</span> stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chiu, Hong-Yee</p> <p>1990-05-01</p> <p>The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of <span class="hlt">soliton</span> stars. The possibility of primordial creation of <span class="hlt">soliton</span> stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside <span class="hlt">soliton</span> stars, the luminosity of <span class="hlt">soliton</span> stars is not determined by its radiative transfer characteristics, and the surface temperature of <span class="hlt">soliton</span> stars can be the same as its interior temperature. It is possible that <span class="hlt">soliton</span> stars are intense X-ray radiators at large distances. <span class="hlt">Soliton</span> stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside <span class="hlt">soliton</span> stars during early epochs of the universe. In addition, if <span class="hlt">soliton</span> stars exist they could assume the role played by massive black holes in galactic centers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900045148&hterms=Friedberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DFriedberg','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900045148&hterms=Friedberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DFriedberg"><span>Massive <span class="hlt">soliton</span> stars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chiu, Hong-Yee</p> <p>1990-01-01</p> <p>The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of <span class="hlt">soliton</span> stars. The possibility of primordial creation of <span class="hlt">soliton</span> stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside <span class="hlt">soliton</span> stars, the luminosity of <span class="hlt">soliton</span> stars is not determined by its radiative transfer characteristics, and the surface temperature of <span class="hlt">soliton</span> stars can be the same as its interior temperature. It is possible that <span class="hlt">soliton</span> stars are intense X-ray radiators at large distances. <span class="hlt">Soliton</span> stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside <span class="hlt">soliton</span> stars during early epochs of the universe. In addition, if <span class="hlt">soliton</span> stars exist they could assume the role played by massive black holes in galactic centers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011OptL...36.3470K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011OptL...36.3470K"><span><span class="hlt">Solitons</span> in geometric potentials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kartashov, Yaroslav V.; Szameit, Alexander; Keil, Robert; Vysloukh, Victor A.; Torner, Lluis</p> <p>2011-09-01</p> <p>We show that the geometrically induced potential existing in undulated slab waveguides dramatically affects the properties of <span class="hlt">solitons</span>. In particular, whereas <span class="hlt">solitons</span> residing in the potential maxima do not feature power thresholds and are stable, their counterparts residing in the potential minima are unstable and may exhibit a power threshold for their existence. Additionally, the geometric potential is shown to support stable multipole <span class="hlt">solitons</span> that cannot be supported by straight waveguides. Finally, the geometric potential results in the appearance of the effective barriers that prevent transverse <span class="hlt">soliton</span> motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5706','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5706"><span><span class="hlt">Solitons</span> in Granular Chains</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Manciu, M.; Sen, S.; Hurd, A.J.</p> <p>1999-04-12</p> <p>The authors consider a chain of elastic (Hertzian) grains that repel upon contact according to the potential V = a{delta}{sup u}, u > 2, where {delta} is the overlap between the grains. They present numerical and analytical results to show that an impulse initiated at an end of a chain of Hertzian grains in contact eventually propagates as a <span class="hlt">soliton</span> for all n > 2 and that no <span class="hlt">solitons</span> are possible for n {le} 2. Unlike continuous, they find that colliding <span class="hlt">solitons</span> in discrete media initiative multiple weak <span class="hlt">solitons</span> at the point of crossing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900045148&hterms=friedberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfriedberg','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900045148&hterms=friedberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dfriedberg"><span>Massive <span class="hlt">soliton</span> stars</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chiu, Hong-Yee</p> <p>1990-01-01</p> <p>The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of <span class="hlt">soliton</span> stars. The possibility of primordial creation of <span class="hlt">soliton</span> stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside <span class="hlt">soliton</span> stars, the luminosity of <span class="hlt">soliton</span> stars is not determined by its radiative transfer characteristics, and the surface temperature of <span class="hlt">soliton</span> stars can be the same as its interior temperature. It is possible that <span class="hlt">soliton</span> stars are intense X-ray radiators at large distances. <span class="hlt">Soliton</span> stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside <span class="hlt">soliton</span> stars during early epochs of the universe. In addition, if <span class="hlt">soliton</span> stars exist they could assume the role played by massive black holes in galactic centers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5231370','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5231370"><span>Beyond <span class="hlt">Pressure</span> <span class="hlt">Gradients</span>: The Effects of Intervention on Heart Power in Aortic Coarctation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brüning, Jan; Hellmeier, Florian; Nordmeyer, Sarah; da Silva, Tiago Ferreira; Schubert, Stephan; Berger, Felix; Kuehne, Titus; Kelm, Marcus</p> <p>2017-01-01</p> <p>Background In aortic coarctation, current guidelines recommend reducing <span class="hlt">pressure</span> <span class="hlt">gradients</span> that exceed given thresholds. From a physiological standpoint this should ideally improve the energy expenditure of the heart and thus prevent long term organ damage. Objectives The aim was to assess the effects of interventional treatment on external and internal heart power (EHP, IHP) in patients with aortic coarctation and to explore the correlation of these parameters to <span class="hlt">pressure</span> <span class="hlt">gradients</span> obtained from heart catheterization. Methods In a collective of 52 patients with aortic coarctation 25 patients received stenting and/or balloon angioplasty, and 20 patients underwent MRI before and after an interventional treatment procedure. EHP and IHP were computed based on catheterization and MRI measurements. Along with the power efficiency these were combined in a cardiac energy profile. Results By intervention, the catheter gradient was significantly reduced from 21.8±9.4 to 6.2±6.1mmHg (p<0.001). IHP was significantly reduced after intervention, from 8.03±5.2 to 4.37±2.13W (p < 0.001). EHP was 1.1±0.3 W before and 1.0±0.3W after intervention, p = 0.044. In patients initially presenting with IHP above 5W intervention resulted in a significant reduction in IHP from 10.99±4.74 W to 4.94±2.45W (p<0.001), and a subsequent increase in power efficiency from 14 to 26% (p = 0.005). No significant changes in IHP, EHP or power efficiency were observed in patients initially presenting with IHP < 5W. Conclusion It was demonstrated that interventional treatment of coarctation resulted in a decrease in IHP. <span class="hlt">Pressure</span> <span class="hlt">gradients</span>, as the most widespread clinical parameters in coarctation, did not show any correlation to changes in EHP or IHP. This raises the question of whether they should be the main focus in coarctation interventions. Only patients with high IHP of above 5W showed improvement in IHP and power efficiency after the treatment procedure. Trial Registration clinicaltrials</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ZNatA..71..751R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ZNatA..71..751R"><span>Unexpected Behavior on Nonlinear Tunneling of Chirped Ultrashort <span class="hlt">Soliton</span> Pulse in Non-Kerr Media with Raman Effect</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rajan, M. S. Mani</p> <p>2016-08-01</p> <p>In this manuscript, the ultrashort <span class="hlt">soliton</span> pulse propagation through nonlinear tunneling in cubic quintic media is investigated. The effect of chirping on propagation characteristics of the <span class="hlt">soliton</span> pulse is analytically investigated using similarity transformation. In particular, we investigate the propagation dynamics of ultrashort <span class="hlt">soliton</span> pulse through dispersion barrier for both chirp and chirp-free <span class="hlt">soliton</span>. By investigating the obtained <span class="hlt">soliton</span> solution, we found that chirping has strong influence on <span class="hlt">soliton</span> dynamics such as pulse <span class="hlt">compression</span> with amplification. These two important dynamics of chirped <span class="hlt">soliton</span> in cubic quintic media open new possibilities to improve the <span class="hlt">solitonic</span> communication system. Moreover, we surprisingly observe that a dispersion well is formed for the chirped case whereas a barrier is formed for the chirp-free case, which has certain applications in the construction of logic gate devices to achieve ultrafast switching.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/837193','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/837193"><span>Influence of <span class="hlt">Pressure-gradient</span> and Shear on Ballooning Stability in Stellarators</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>S.R. Hudson; C.C. Hegna; N. Nakajima</p> <p>2005-02-28</p> <p>Pressure-driven, ideal ballooning stability calculations are often used to predict the achievable plasma in stellarator configurations. In this paper, the sensitivity of ballooning stability to plasmas profile variations is addressed. A simple, semi-analytic method for expressing the ballooning growth rate, for each field line, as a polynomial function of the variation in the <span class="hlt">pressure</span> <span class="hlt">gradient</span> and the average magnetic shear from an original equilibrium has recently been introduced [Phys. Plasmas 11:9 (September 2004) L53]. This paper will apply the expression to various stellarator configurations and comment on the validity of various truncated forms of the polynomial expression. In particular, it is shown that in general it is insufficient to consider only the second order terms as previously assumed, and that higher order terms must be included to obtain accurate predictions of stability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140016390','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140016390"><span>Direct Numerical Simulation and Theories of Wall Turbulence with a Range of <span class="hlt">Pressure</span> <span class="hlt">Gradients</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Coleman, G. N.; Garbaruk, A.; Spalart, P. R.</p> <p>2014-01-01</p> <p>A new Direct Numerical Simulation (DNS) of Couette-Poiseuille flow at a higher Reynolds number is presented and compared with DNS of other wall-bounded flows. It is analyzed in terms of testing semi-theoretical proposals for universal behavior of the velocity, mixing length, or eddy viscosity in <span class="hlt">pressure</span> <span class="hlt">gradients</span>, and in terms of assessing the accuracy of two turbulence models. These models are used in two modes, the traditional one with only a dependence on the wall-normal coordinate y, and a newer one in which a lateral dependence on z is added. For pure Couette flow and the Couette-Poiseuille case considered here, this z-dependence allows some models to generate steady streamwise vortices, which generally improves the agreement with DNS and experiment. On the other hand, it complicates the comparison between DNS and models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840034660&hterms=mass+transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmass%2Btransfer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840034660&hterms=mass+transfer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dmass%2Btransfer"><span>Wall mass transfer and <span class="hlt">pressure</span> <span class="hlt">gradient</span> effects on turbulent skin friction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Watson, R. D.; Balasubramanian, R.</p> <p>1984-01-01</p> <p>The effects of mass injection and <span class="hlt">pressure</span> <span class="hlt">gradients</span> on the drag of surfaces were studied theoretically with the aid of boundary-layer and Navier-Stokes codes. The present investigation is concerned with the effects of spatially varying the injection in the case of flat-plate drag. Effects of suction and injection on wavy wall surfaces are also explored. Calculations were performed for 1.2 m long surfaces, one flat and the other sinusoidal with a wavelength of 30.5 cm. Attention is given to the study of the effect of various spatial blowing variations on flat-plate skin friction reduction, local skin friction coefficient calculated by finite difference boundary-layer code and Navier-Stokes code, and the effect of phase-shifting sinusoidal mass transfer on the drag of a sinusoidal surface.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16659971','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16659971"><span>Effects of Abscisic Acid and of Hydrostatic <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> on Water Movement through Excised Sunflower Roots.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Glinka, Z</p> <p>1977-05-01</p> <p>The effect of abscisic acid on the exudation rate from decapitated roots of sunflower plants (Helianthus annuus L.) was investigated in the presence and absence of an imposed hydrostatic <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The magnitude of the abscisic acid effect was constant even when suctions up to 60 cm Hg were applied to the cut stumps.When roots were bathed in a THO-labeled nutrient solution, the course of the appearance of radioactivity in the exudate, expressed as a function of exudate volume, was not affected by abscisic acid treatment but was strongly speeded up by applying suction.The implications of those findings with regard to the water pathway through the root and the location of the abscisic acid effect are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MsT..........3I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MsT..........3I"><span>Experimental and Numerical Studies of Flows over Forward Facing Steps in <span class="hlt">Pressure</span> <span class="hlt">Gradients</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iftekhar, Hassan</p> <p></p> <p>This thesis reports experimental and numerical studies of the effects of adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> (APG) and Reynolds numbers on flows over forward facing steps (FFS). For the experimental work, particle image velocimetry was used to conduct velocity measurements at several locations downstream of the FFS. Proper orthogonal decomposition and two-point correlation were applied to the experimental data to study the large scale structures. For the numerical analysis, turbulence models in ANSYS Fluent were used to study the reattachment length XL for blockage ratios from 5.8% to 29.5% and step inclination angles from 22.5° to 135°. The experimental results show that XL increases with the increase in Reynolds number without APG, but remains nearly constant for increasing APG. The CFD results show that as the step angle is increased, XL decreased. Furthermore, increasing the blockage at constant Reynolds number, the XL values decrease.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980JMecE..22..213A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980JMecE..22..213A"><span>Natural transition of boundary layers - The effects of turbulence, <span class="hlt">pressure</span> <span class="hlt">gradient</span>, and flow history</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abu-Ghannam, B. J.; Shaw, R.</p> <p>1980-10-01</p> <p>Natural transition of boundary layers is investigated for a flat plate in a low-speed wind tunnel with free-stream turbulence intensities ranging from 0.3 to 5 percent, and with <span class="hlt">pressure-gradient</span> histories typical of turbomachinery blades without separation. Empirical relationships are proposed for the prediction of the start and end of transition, as well as the development of the boundary layer during transition. These relations are based on the recent measurements made with a hot-wire anemometer, and augmented, mainly for the start of transition, by results of previously reported research. Finally, these experimental relationships are used in conjunction with well established methods to predict the entire unseparated boundary layer. To utilize the prediction, all that is required is a knowledge of the free-stream turbulence level and the free-stream velocity distribution, which itself can be derived from potential flow theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28081900','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28081900"><span>Broadening of analyte streams due to a transverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> in free-flow isoelectric focusing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dutta, Debashis</p> <p>2017-02-10</p> <p>Pressure-driven cross-flows can arise in free-flow isoelectric focusing systems (FFIEF) due to a non-uniform electroosmotic flow velocity along the channel width induced by the pH gradient in this direction. In addition, variations in the channel cross-section as well as unwanted differences in hydrostatic heads at the buffer/sample inlet ports can also lead to such <span class="hlt">pressure-gradients</span> which besides altering the equilibrium position of the sample zones have a tendency to substantially broaden their widths deteriorating the separations. In this situation, a thorough assessment of stream broadening due to transverse <span class="hlt">pressure-gradients</span> in FFIEF devices is necessary in order to establish accurate design rules for the assay. The present article describes a mathematical framework to estimate the noted zone dispersion in FFIEF separations based on the method-of-moments approach under laminar flow conditions. A closed-form expression has been derived for the spatial variance of the analyte streams at their equilibrium positions as a function of the various operating parameters governing the assay performance. This expression predicts the normalized stream variance under the chosen conditions to be determined by two dimensionless Péclet numbers evaluated based on the transverse pressure-driven and electrophoretic solute velocities in the separation chamber, respectively. Moreover, the analysis shows that while the stream width can be expected to increase with an increase in the value of the first Péclet number, the opposite trend will be followed with respect to the latter. The noted results have been validated using Monte Carlo simulations that also establish a time/length scale over which the predicted equilibrium stream width is attained in the system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1014451','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1014451"><span>Probability density function method for variable-density <span class="hlt">pressure-gradient</span>-driven turbulence and mixing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bakosi, Jozsef; Ristorcelli, Raymond J</p> <p>2010-01-01</p> <p>Probability density function (PDF) methods are extended to variable-density <span class="hlt">pressure-gradient</span>-driven turbulence. We apply the new method to compute the joint PDF of density and velocity in a non-premixed binary mixture of different-density molecularly mixing fluids under gravity. The full time-evolution of the joint PDF is captured in the highly non-equilibrium flow: starting from a quiescent state, transitioning to fully developed turbulence and finally dissipated by molecular diffusion. High-Atwood-number effects (as distinguished from the Boussinesq case) are accounted for: both hydrodynamic turbulence and material mixing are treated at arbitrary density ratios, with the specific volume, mass flux and all their correlations in closed form. An extension of the generalized Langevin model, originally developed for the Lagrangian fluid particle velocity in constant-density shear-driven turbulence, is constructed for variable-density <span class="hlt">pressure-gradient</span>-driven flows. The persistent small-scale anisotropy, a fundamentally 'non-Kolmogorovian' feature of flows under external acceleration forces, is captured by a tensorial diffusion term based on the external body force. The material mixing model for the fluid density, an active scalar, is developed based on the beta distribution. The beta-PDF is shown to be capable of capturing the mixing asymmetry and that it can accurately represent the density through transition, in fully developed turbulence and in the decay process. The joint model for hydrodynamics and active material mixing yields a time-accurate evolution of the turbulent kinetic energy and Reynolds stress anisotropy without resorting to gradient diffusion hypotheses, and represents the mixing state by the density PDF itself, eliminating the need for dubious mixing measures. Direct numerical simulations of the homogeneous Rayleigh-Taylor instability are used for model validation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=pendulum&pg=4&id=EJ1037447','ERIC'); return false;" href="http://eric.ed.gov/?q=pendulum&pg=4&id=EJ1037447"><span>Semirelativity and Kink <span class="hlt">Solitons</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Nowak, Mariusz Karol</p> <p>2014-01-01</p> <p>It is hard to observe relativistic effects in everyday life. However, table experiments using a mechanical transmission line for <span class="hlt">solitons</span> may be an efficient and simple way to show effects such as Lorentz contraction in a classroom. A kink <span class="hlt">soliton</span> is a deformation of a lattice of several dozen or more pendulums placed on a wire and connected by a…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyD..316...43K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyD..316...43K"><span>Lossless polariton <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Komineas, Stavros; Shipman, Stephen P.; Venakides, Stephanos</p> <p>2016-02-01</p> <p>Photons and excitons in a semiconductor microcavity interact to form exciton-polariton condensates. These are governed by a nonlinear quantum-mechanical system involving exciton and photon wavefunctions. We calculate all non-traveling harmonic <span class="hlt">soliton</span> solutions for the one-dimensional lossless system. There are two frequency bands of bright <span class="hlt">solitons</span> when the inter-exciton interactions produce an attractive nonlinearity and two frequency bands of dark <span class="hlt">solitons</span> when the nonlinearity is repulsive. In addition, there are two frequency bands for which the exciton wavefunction is discontinuous at its symmetry point, where it undergoes a phase jump of π. A band of continuous dark <span class="hlt">solitons</span> merges with a band of discontinuous dark <span class="hlt">solitons</span>, forming a larger band over which the <span class="hlt">soliton</span> far-field amplitude varies from 0 to ∞; the discontinuity is initiated when the operating frequency exceeds the free exciton frequency. The far fields of the <span class="hlt">solitons</span> in the lowest and highest frequency bands (one discontinuous and one continuous dark) are linearly unstable, whereas the other four bands have linearly stable far fields, including the merged band of dark <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=Particle+AND+physics+AND+educations&pg=5&id=EJ1037447','ERIC'); return false;" href="https://eric.ed.gov/?q=Particle+AND+physics+AND+educations&pg=5&id=EJ1037447"><span>Semirelativity and Kink <span class="hlt">Solitons</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Nowak, Mariusz Karol</p> <p>2014-01-01</p> <p>It is hard to observe relativistic effects in everyday life. However, table experiments using a mechanical transmission line for <span class="hlt">solitons</span> may be an efficient and simple way to show effects such as Lorentz contraction in a classroom. A kink <span class="hlt">soliton</span> is a deformation of a lattice of several dozen or more pendulums placed on a wire and connected by a…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10991164','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10991164"><span>Dipole-mode vector <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Garcia-Ripoll; Perez-Garcia; Ostrovskaya; Kivshar</p> <p>2000-07-03</p> <p>We find a new type of optical vector <span class="hlt">soliton</span> that originates from trapping of a dipole mode by the <span class="hlt">soliton</span>-induced waveguides. These <span class="hlt">solitons</span>, which appear as a consequence of the vector nature of the two-component system, are more stable than the previously found optical vortex <span class="hlt">solitons</span> and represent a new type of extremely robust nonlinear vector structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3000527','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3000527"><span><span class="hlt">Soliton</span> absorption spectroscopy</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kalashnikov, V. L.; Sorokin, E.</p> <p>2010-01-01</p> <p>We analyze optical <span class="hlt">soliton</span> propagation in the presence of weak absorption lines with much narrower linewidths as compared to the <span class="hlt">soliton</span> spectrum width using the novel perturbation analysis technique based on an integral representation in the spectral domain. The stable <span class="hlt">soliton</span> acquires spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary <span class="hlt">soliton</span> propagation and to an absorber inside a passively modelocked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurement in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improving of the sensitivity and spectroscopic accuracy making the <span class="hlt">soliton</span> absorption spectroscopy a promising novel measurement technique. PMID:21151755</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910036729&hterms=Film+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DFilm%2Btheory','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910036729&hterms=Film+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DFilm%2Btheory"><span>Internally mounted thin-liquid-film skin-friction meter - Comparison with floating element method with and without <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hornung, Hans; Seto, Jeffrey</p> <p>1991-01-01</p> <p>A new, robust oil film skin friction meter was designed and constructed. This enables skin friction measurements remotely and from within the model, as well as avoiding the need to know the location of the leading edge of the film. The instrument was tested by comparing measurements with those given by a floating element gage in a zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> flat plate turbulent boundary layer. Both instruments agreed satisfactorily with the well-known curve for this case. Significant discrepancies between the two instruments were observed in the case of adverse and favorable <span class="hlt">pressure</span> <span class="hlt">gradients</span>. The discrepancies were of opposite sign for opposite-sign <span class="hlt">pressure</span> <span class="hlt">gradients</span> as is consistent with the error expected from floating-element gages. Additional confidence in the oil film technique is supplied by the good agreement of the behavior of the film profile with predictions from lubrication theory.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730006564','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730006564"><span>The turbulent boundary layer on a porous plate: An experimental study of the heat transfer behavior with adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blackwell, B. F.; Kays, W. M.; Moffat, R. J.</p> <p>1972-01-01</p> <p>An experimental investigation of the heat transfer behavior of the near equilibrium transpired turbulent boundary layer with adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> has been carried out. Stanton numbers were measured by an energy balance on electrically heated plates that form the bottom wall of the wind tunnel. Two adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> were studied. Two types of transpiration boundary conditions were investigated. The concept of an equilibrium thermal boundary layer was introduced. It was found that Stanton number as a function of enthalpy thickness Reynolds number is essentially unaffected by adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> with no transpiration. Shear stress, heat flux, and turbulent Prandtl number profiles were computed from mean temperature and velocity profiles. It was concluded that the turbulent Prandtl number is greater than unity in near the wall and decreases continuously to approximately 0.5 at the free stream.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ExFl...57..151H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ExFl...57..151H"><span>FFT integration of instantaneous 3D <span class="hlt">pressure</span> <span class="hlt">gradient</span> fields measured by Lagrangian particle tracking in turbulent flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huhn, F.; Schanz, D.; Gesemann, S.; Schröder, A.</p> <p>2016-09-01</p> <p><span class="hlt">Pressure</span> <span class="hlt">gradient</span> fields in unsteady flows can be estimated through flow measurements of the material acceleration in the fluid and the assumption of the governing momentum equation. In order to derive pressure from its gradient, almost exclusively two numerical methods have been used to spatially integrate the <span class="hlt">pressure</span> <span class="hlt">gradient</span> until now: first, direct path integration in the spatial domain, and second, the solution of the Poisson equation for pressure. Instead, we propose an alternative third method that integrates the <span class="hlt">pressure</span> <span class="hlt">gradient</span> field in Fourier space. Using a FFT function, the method is fast and easy to implement in programming languages for scientific computing. We demonstrate the accuracy of the integration scheme on a synthetic pressure field and apply it to an experimental example based on time-resolved material acceleration data from high-resolution Lagrangian particle tracking with the Shake-The-Box method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19940028441','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19940028441"><span>Modification of the MML turbulence model for adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> flows. M.S. Thesis - Akron Univ., 1993</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Conley, Julianne M.</p> <p>1994-01-01</p> <p>Computational fluid dynamics is being used increasingly to predict flows for aerospace propulsion applications, yet there is still a need for an easy to use, computationally inexpensive turbulence model capable of accurately predicting a wide range of turbulent flows. The Baldwin-Lomax model is the most widely used algebraic model, even though it has known difficulties calculating flows with strong adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> and large regions of separation. The modified mixing length model (MML) was developed specifically to handle the separation which occurs on airfoils and has given significantly better results than the Baldwin-Lomax model. The success of these calculations warrants further evaluation and development of MML. The objective of this work was to evaluate the performance of MML for zero and adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> flows, and modify it as needed. The Proteus Navier-Stokes code was used for this study and all results were compared with experimental data and with calculations made using the Baldwin-Lomax algebraic model, which is currently available in Proteus. The MML model was first evaluated for zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> flow over a flat plate, then modified to produce the proper boundary layer growth. Additional modifications, based on experimental data for three adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> flows, were also implemented. The adapted model, called MMLPG (modified mixing length model for <span class="hlt">pressure</span> <span class="hlt">gradient</span> flows), was then evaluated for a typical propulsion flow problem, flow through a transonic diffuser. Three cases were examined: flow with no shock, a weak shock and a strong shock. The results of these calculations indicate that the objectives of this study have been met. Overall, MMLPG is capable of accurately predicting the adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> flows examined in this study, giving generally better agreement with experimental data than the Baldwin-Lomax model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS32A..06A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS32A..06A"><span>Instantaneous Sediment Bed Level Response to Wave-induced Pore-<span class="hlt">pressure</span> <span class="hlt">Gradients</span> on a Surfzone Sandbar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anderson, D. L.; Cox, D. T.; Mieras, R.; Puleo, J. A.; Hsu, T. J.</p> <p>2016-12-01</p> <p>Proposed physical mechanisms contributing to onshore sediment transport over sandbar crests and subsequent sandbar migration include boundary layer streaming, Stokes drift, and <span class="hlt">pressure</span> <span class="hlt">gradients</span>. Both horizontal and vertical gradients may be a physical link for predicting sediment transport because they relate to the strong fluid accelerations at the bed induced by steep, near-breaking waves. To understand the fluid forcing and bed response, a barred beach was constructed in a large-scale wave flume with a fixed profile to control the global wave shoaling and breaking. A moveable sediment layer was placed on the crest of the sandbar to quantify instantaneous sediment bed levels co-located with pore pressure measurements within the upper several centimeters of the bed. A wide range of wave asymmetries were forced over the same profile in individual trials of regular waves to isolate bed response due to wave motions. The total <span class="hlt">pressure</span> <span class="hlt">gradient</span> vector derived within the bed exhibited temporal rotations during each wave cycle, directed predominantly upwards under the trough and then rapidly rotating onshore and downwards as the wave front passed. Sharp increases in the onshore-directed <span class="hlt">pressure</span> <span class="hlt">gradient</span> were correlated with rapid decreases in the bed level on the order of centimeters occurring in less than 0.5 seconds. The initiation of the bed level decrease was coincident with large onshore directed <span class="hlt">pressure</span> <span class="hlt">gradients</span> corresponding to non-dimensional Sleath parameter values between 0.1 and 0.2, and preceded onshore-directed sheet flow sediment transport. Downward-directed vertical <span class="hlt">pressure</span> <span class="hlt">gradients</span> increased rapidly during bed failure, remained downward during sheet flow, and were minimal under the wave trough. The magnitude of bed level decrease was positively correlated with the degree of wave asymmetry and exhibited additional dependency on the magnitude of bed shear stress, suggesting <span class="hlt">pressure</span> <span class="hlt">gradients</span> are important for initiation of transport while total</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20787348','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20787348"><span>Ion-acoustic dressed <span class="hlt">solitons</span> in a dusty plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tiwari, R.S.; Mishra, M.K.</p> <p>2006-06-15</p> <p>Using the reductive perturbation method, equations for ion-acoustic waves governing the evolution of first- and second-order potentials in a dusty plasma including the dynamics of charged dust grains have been derived. The renormalization procedure of Kodama and Taniuti is used to obtain a steady state nonsecular solution of these equations. The variation of velocity and width of the Korteweg-de Vries (KdV) as well as dressed <span class="hlt">solitons</span> with amplitude have been studied for different concentrations and charge multiplicity of dust grains. The higher-order perturbation corrections to the KdV <span class="hlt">soliton</span> description significantly affect the characteristics of the <span class="hlt">solitons</span> in dusty plasma. It is found that in the presence of positively charged dust grains the system supports only <span class="hlt">compressive</span> <span class="hlt">solitons</span>. However, the plasma with negatively charged dust grains can support <span class="hlt">compressive</span> <span class="hlt">solitons</span> only up to a certain concentration of dust. Above this critical concentration of negative charge, the dusty plasma can support rarefactive <span class="hlt">solitons</span>. An expression for the critical concentration of negatively charged dust in terms of charge and mass ratio of dust grains with plasma ions is also derived.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23a2302R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23a2302R"><span>Ion-acoustic Gardner <span class="hlt">Solitons</span> in electron-positron-ion plasma with two-electron temperature distributions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rehman, Momin A.; Mishra, M. K.</p> <p>2016-01-01</p> <p>The ion-acoustic <span class="hlt">solitons</span> in collisionless plasma consisting of warm adiabatic ions, isothermal positrons, and two temperature distribution of electrons have been studied. Using reductive perturbation method, Korteweg-de Vries (K-dV), the modified K-dV (m-KdV), and Gardner equations are derived for the system. The <span class="hlt">soliton</span> solution of the Gardner equation is discussed in detail. It is found that for a given set of parameter values, there exists a critical value of β=Tc/Th, (ratio of cold to hot electron temperature) below which only rarefactive KdV <span class="hlt">solitons</span> exist and above it <span class="hlt">compressive</span> KdV <span class="hlt">solitons</span> exist. At the critical value of β, both <span class="hlt">compressive</span> and rarefactive m-KdV <span class="hlt">solitons</span> co-exist. We have also investigated the <span class="hlt">soliton</span> in the parametric regime where the KdV equation is not valid to study <span class="hlt">soliton</span> solution. In this region, it is found that below the critical concentration the system supports rarefactive Gardner <span class="hlt">solitons</span> and above it <span class="hlt">compressive</span> Gardner <span class="hlt">solitons</span> are found. The effects of temperature ratio of two-electron species, cold electron concentration, positron concentration on the characteristics of <span class="hlt">solitons</span> are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvL.118l5101G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvL.118l5101G"><span>Role of Magnetosonic <span class="hlt">Solitons</span> in Perpendicular Collisionless Shock Reformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gueroult, Renaud; Ohsawa, Yukiharu; Fisch, Nathaniel J.</p> <p>2017-03-01</p> <p>The nature of the magnetic structure arising from ion specular reflection in shock <span class="hlt">compression</span> studies is examined by means of 1D particle-in-cell simulations. Propagation speed, field profiles, and supporting currents for this magnetic structure are shown to be consistent with a magnetosonic <span class="hlt">soliton</span>. Coincidentally, this structure and its evolution are typical of foot structures observed in perpendicular shock reformation. To reconcile these two observations, we propose, for the first time, that shock reformation can be explained as the result of the formation, growth, and subsequent transition to a supercritical shock of a magnetosonic <span class="hlt">soliton</span>. This argument is further supported by the remarkable agreement found between the period of the <span class="hlt">soliton</span> evolution cycle and classical reformation results. This new result suggests that the unique properties of <span class="hlt">solitons</span> can be used to shed new light on the long-standing issue of shock nonstationarity and its role on particle acceleration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4789996','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4789996"><span>Comparison of hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> and endoscopic grading of esophageal varices</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lee, EunJi; Kim, Yong Jae; Goo, Dong Erk; Yang, Seung Boo; Kim, Hyun-Joo; Jang, Jae Young; Jeong, Soung Won</p> <p>2016-01-01</p> <p>AIM: To determine the correlation between the hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> and the endoscopic grade of esophageal varices. METHODS: From September 2009 to March 2013, a total of 176 measurements of hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (HVPG) were done in 146 patients. Each transjugular HVPG was measured twice, first using an end whole catheter (EH-HVPG), and then using a balloon catheter (B-HVPG). The HVPG was compared with the endoscopic grade of esophageal varices (according to the general rules for recording endoscopic findings of esophagogastric varices), which was recorded within a month of the measurement of HVPG. RESULTS: The study included 110 men and 36 women, with a mean age of 56.1 years (range, 43-76 years). The technical success rate of the pressure measurements was 100% and there were no complication related to the procedures. Mean HVPG was 15.3 mmHg as measured using the end hole catheter method and 16.5 mmHg as measured using the balloon catheter method. Mean HVPG (both EH-HVPG and B-HVPG) was not significantly different among patients with different characteristics, including sex and comorbid factors, except for cases with hepatocellular carcinoma (B-HVPG, P = 0.01; EH-HVPG, P = 0.02). Portal hypertension (> 12 mmHg HVPG) occurred in 66% of patients according to EH-HVPG and 83% of patients according to B-HVGP, and significantly correlated with Child’s status (B-HVPG, P < 0.000; EH-HVGP, P < 0.000) and esophageal varies observed upon endoscopy (EH-HVGP, P = 0.003; B-HVGP, P = 0.006). One hundred and thirty-five endoscopies were performed, of which 15 showed normal findings, 27 showed grade 1 endoscopic esophageal varices, 49 showed grade 2 varices, and 44 showed grade 3 varices. When comparing endoscopic esophageal variceal grades and HVPG using univariate analysis, the P value was 0.004 for EH-HVPG and 0.002 for B-HVPG. CONCLUSION: Both EH-HVPG and B-HVPG showed a positive correlation with the endoscopic grade of esophageal varices, with B</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17280167','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17280167"><span>Helmholtz-Manakov <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Christian, J M; McDonald, G S; Chamorro-Posada, P</p> <p>2006-12-01</p> <p>A different spatial <span class="hlt">soliton</span>-bearing wave equation is introduced, the Helmholtz-Manakov (HM) equation, for describing the evolution of broad multicomponent self-trapped beams in Kerr-type media. By omitting the slowly varying envelope approximation, the HM equation can describe accurately vector <span class="hlt">solitons</span> propagating and interacting at arbitrarily large angles with respect to the reference direction. The HM equation is solved using Hirota's method, yielding four different classes of Helmholtz <span class="hlt">soliton</span> that are vector generalizations of their scalar counterparts. General and particular forms of the three invariants of the HM system are also reported.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22309112','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22309112"><span>Coherent <span class="hlt">soliton</span> communication lines</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yushko, O. V. Redyuk, A. A.; Fedoruk, M. P.; Turitsyn, S. K.</p> <p>2014-11-15</p> <p>The data transmission in coherent fiber-optical communication lines using <span class="hlt">solitons</span> with a variable phase is studied. It is shown that nonlinear coherent structures (<span class="hlt">solitons</span>) can be applied for effective signal transmission over a long distance using amplitude and optical-phase keying of information. The optimum ratio of the pulse width to the bit slot at which the spectral efficiency (transmitted bits per second and hertz) is maximal is determined. It is shown that <span class="hlt">soliton</span> fiber-optical communication lines can ensure data transmission at a higher spectral efficiency as compared to traditional communication lines and at a high signal-to-noise ratio.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22095488','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22095488"><span>Cavity <span class="hlt">soliton</span> billiards</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Prati, F.; Lugiato, L. A.; Tissoni, G.; Brambilla, M.</p> <p>2011-11-15</p> <p>The motion of a self-propelled cavity <span class="hlt">soliton</span> in a laser where the pump profile acts as a square billiard is investigated. In the long-term dynamics, only closed trajectories are possible, exhibiting nonspecular reflections with striking similarities to walking droplets in a vibrated liquid bath. Open orbits can be achieved either by introducing scattering defects in the pump profile or in the presence of more than two <span class="hlt">solitons</span>, due to their interaction. Such dynamical properties can be exploited for applications such as a compact <span class="hlt">soliton</span>-force microscope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyB..501..117L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyB..501..117L"><span>Bipolar <span class="hlt">solitons</span> of the focusing nonlinear Schrödinger equation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Zhongxuan; Feng, Qi; Lin, Chengyou; Chen, Zhaoyang; Ding, Yingchun</p> <p>2016-11-01</p> <p>The focusing nonlinear Schrödinger equation (NLSE) is a universal model for studying solitary waves propagation in nonlinear media. The NLSE is especially important in understanding how <span class="hlt">solitons</span> on a condensate background (SCB) appear from a small perturbation through modulation instability. We study theoretically the one- and two-<span class="hlt">soliton</span> solutions of the NLSE in presence of a condensate by using the dressing method. It is found that a class of bipolar elliptically polarized <span class="hlt">solitons</span> with the choice of specific parameters in the one- and two-<span class="hlt">soliton</span> solutions. Collisions among these <span class="hlt">solitons</span> are studied by qualitative analysis and graphical illustration. We also generalize the concept of the quasi-Akhmediev breather to the bipolar <span class="hlt">solitons</span> and show how it can be used for wave profile <span class="hlt">compression</span> down to the extremely short duration. Our results extend previous studies in this area of the SCB and play an important role in the theory of freak wave.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790025267','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790025267"><span>Survey and bibliography on attainment of laminar flow control in air using <span class="hlt">pressure</span> <span class="hlt">gradient</span> and suction, volume 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bushnell, D. M.; Tuttle, M. H.</p> <p>1979-01-01</p> <p>A survey was conducted and a bibliography compiled on attainment of laminar flow in air through the use of favorable <span class="hlt">pressure</span> <span class="hlt">gradient</span> and suction. This report contains the survey, summaries of data for both ground and flight experiments, and abstracts of referenced reports. Much early information is also included which may be of some immediate use as background material for LFC applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985asme.confU....M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985asme.confU....M"><span>The influence of the radial <span class="hlt">pressure</span> <span class="hlt">gradient</span> on the blade root loss in an annular subsonic nozzle cascade</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meng, D.; Weng, Z.; Xiang, Y.</p> <p>1985-09-01</p> <p>This paper presents a method for predicting the blade root loss in an annular nozzle cascade in which consideration is given to the influence of the radial <span class="hlt">pressure</span> <span class="hlt">gradient</span> (RPG) on it. The variation of blade root losses under different RPG is obtained experimentally, and finite element method is used to calculate the pressure distribution in the blade passage.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4322945','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4322945"><span>A MATHEMATICAL ANALYSIS OF PHYSIOLOGICAL AND MOLECULAR MECHANISMS THAT MODULATE <span class="hlt">PRESSURE</span> <span class="hlt">GRADIENTS</span> AND FACILITATE VENTRICULAR EXPANSION IN HYDROCEPHALUS</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>WILKIE, KATHLEEN P.; NAGRA, GURJIT; JOHNSTON, MILES</p> <p>2014-01-01</p> <p>Perhaps the greatest paradox in the hydrocephalus field is the failure of researchers to consistently measure transmantle <span class="hlt">pressure</span> <span class="hlt">gradients</span> (ventricle to subarachnoid space) in either human or animal models of the communicating form of the disorder. Without such a gradient, conceptualization of how ventricular distention occurs is difficult. Based on evidence from both a mathematical model [35] and experiments in skin [51], we observed that the intraventricular injection of anti-β1 integrin antibodies in rat brains results in a reduction of periventricular pressures to values below those monitored in the ventricles. In addition, many of these animals developed hydrocephalus [30]. We conclude that the dissociation of β1 integrins from the surrounding matrix fibers generates <span class="hlt">pressure</span> <span class="hlt">gradients</span> favouring ventricular expansion suggesting a novel mechanism for hydrocephalus development. Several issues, however, need further clarification. If hydrostatic pressure declines in the periventricular tissues then fluid absorption must occur. Aquaporin-4 (AQP4) is a likely candidate for this absorption as it is the predominant water channel in the brain. Indeed, when capillary function is negated, periventricular interstitial fluid pressures increase after anti-β1 integrin antibody administration. This suggests that capillary absorption of parenchymal water may play a pivotal role in the generation of <span class="hlt">pressure</span> <span class="hlt">gradients</span> in our hydrocephalus model. Focusing on these issues, we present two poroelastic models to investigate the role of intramantle <span class="hlt">pressure</span> <span class="hlt">gradients</span> in ventriculomegaly and to determine if integrin-matrix disassociation represents a complete causative mechanism for hydrocephalus development. PMID:25678938</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040112441&hterms=ischemia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dischemia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040112441&hterms=ischemia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dischemia"><span>Estimation of diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> by Doppler M-mode echocardiography</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greenberg, N. L.; Vandervoort, P. M.; Firstenberg, M. S.; Garcia, M. J.; Thomas, J. D.</p> <p>2001-01-01</p> <p>Previous studies have shown that small intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> (IVPG) are important for efficient filling of the left ventricle (LV) and as a sensitive marker for ischemia. Unfortunately, there has previously been no way of measuring these noninvasively, severely limiting their research and clinical utility. Color Doppler M-mode (CMM) echocardiography provides a spatiotemporal velocity distribution along the inflow tract throughout diastole, which we hypothesized would allow direct estimation of IVPG by using the Euler equation. Digital CMM images, obtained simultaneously with intracardiac pressure waveforms in six dogs, were processed by numerical differentiation for the Euler equation, then integrated to estimate IVPG and the total (left atrial to left ventricular apex) pressure drop. CMM-derived estimates agreed well with invasive measurements (IVPG: y = 0.87x + 0.22, r = 0.96, P < 0.001, standard error of the estimate = 0.35 mmHg). Quantitative processing of CMM data allows accurate estimation of IVPG and tracking of changes induced by beta-adrenergic stimulation. This novel approach provides unique information on LV filling dynamics in an entirely noninvasive way that has previously not been available for assessment of diastolic filling and function.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..DFDR20007C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..DFDR20007C"><span>Large eddy simulation of zero-<span class="hlt">pressure-gradient</span> turbulent boundary layer based on different scaling laws</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cheng, Wan; Samtaney, Ravi</p> <p>2013-11-01</p> <p>We present results of large eddy simulation (LES) for a smooth-wall, zero-<span class="hlt">pressure-gradient</span> turbulent boundary layer. We employ the stretched vortex sub-grid-scale model in the simulations augmented by a wall model. Our wall model is based on the virtual-wall model introduced by Chung & Pullin (J. Fluid Mech 2009). An essential component of their wall model is an ODE governing the local wall-normal velocity gradient obtained using inner-scaling ansatz. We test two variants of the wall model based on different similarity laws: one is based on a log-law and the other on a power-law. The specific form of the power law scaling utilized is that proposed by George & Castillo (Appl. Mech. Rev. 1997), dubbed the ``GC Law''. Turbulent inflow conditions are generated by a recycling method, and applying scaling laws corresponding to the two variants of the wall model, and a uniform way to determine the inlet friction velocity. For Reynolds number based on momentum thickness, Reθ , ranging from 104 to 1012 it is found that the velocity profiles generally follow the log law form rather than the power law. For large Reynolds number asymptotic behavior, LES based on different scaling laws the boundary layer thickness and turbulent intensities do not show much difference. Supported by a KAUST funded project on large eddy simulation of turbulent flows. The IBM Blue Gene P Shaheen at KAUST was utilized for the simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvF...1h2401W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvF...1h2401W"><span>Scaling properties of the mean wall-normal velocity in zero-<span class="hlt">pressure-gradient</span> boundary layers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Tie; Klewicki, Joseph</p> <p>2016-12-01</p> <p>The scaling properties of the mean wall-normal velocity V (x ,y ) in zero-<span class="hlt">pressure-gradient</span> laminar and turbulent boundary-layer flows are investigated using numerical simulation data, physical experiment data, and integral analyses of the governing equations. The maximum mean wall-normal velocity V∞ and the boundary-layer thickness δ are evidenced to be the proper scaling for V over most if not all of the boundary layer. This is different from the behavior of the mean streamwise velocity U or the turbulent shear stress T =-ρ <u v > , which depend on different characteristic length scales in the regions near and away from the surface, respectively. The reason for this apparent difference in scaling behaviors is described physically relative to the downstream development of the U velocity profile and the mechanisms of boundary-layer growth. Insights pertaining to this are further surmised from an analytical relationship for the ratio of the displacement to momentum thickness, i.e., shape factor H . Integral analyses using the continuity and mean momentum equation show that U∞V∞/uτ2=H , where uτ is the friction velocity. Both the laminar similarity solution and direct numerical simulation data in post-transitional flows convincingly support this relation. Over the transitional regime, data of sufficiently high quality are lacking to check if this relation remains valid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040141463&hterms=pressure+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dpressure%2Bmodel','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141463&hterms=pressure+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dpressure%2Bmodel"><span>Doppler echo evaluation of pulmonary venous-left atrial <span class="hlt">pressure</span> <span class="hlt">gradients</span>: human and numerical model studies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Firstenberg, M. S.; Greenberg, N. L.; Smedira, N. G.; Prior, D. L.; Scalia, G. M.; Thomas, J. D.; Garcia, M. J.</p> <p>2000-01-01</p> <p>The simplified Bernoulli equation relates fluid convective energy derived from flow velocities to a <span class="hlt">pressure</span> <span class="hlt">gradient</span> and is commonly used in clinical echocardiography to determine pressure differences across stenotic orifices. Its application to pulmonary venous flow has not been described in humans. Twelve patients undergoing cardiac surgery had simultaneous high-fidelity pulmonary venous and left atrial pressure measurements and pulmonary venous pulsed Doppler echocardiography performed. Convective gradients for the systolic (S), diastolic (D), and atrial reversal (AR) phases of pulmonary venous flow were determined using the simplified Bernoulli equation and correlated with measured actual pressure differences. A linear relationship was observed between the convective (y) and actual (x) pressure differences for the S (y = 0.23x + 0.0074, r = 0.82) and D (y = 0.22x + 0.092, r = 0.81) waves, but not for the AR wave (y = 0. 030x + 0.13, r = 0.10). Numerical modeling resulted in similar slopes for the S (y = 0.200x - 0.127, r = 0.97), D (y = 0.247x - 0. 354, r = 0.99), and AR (y = 0.087x - 0.083, r = 0.96) waves. Consistent with numerical modeling, the convective term strongly correlates with but significantly underestimates actual gradient because of large inertial forces.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5309885','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5309885"><span>A Simple Method for Noninvasive Quantification of <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Across the Pulmonary Valve</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhou, Xueying; Xing, Changyang; Feng, Yang; Duan, Yunyou; Zheng, Qiangsun; Wang, Zuojun; Liu, Jie; Cao, Tiesheng; Yuan, Lijun</p> <p>2017-01-01</p> <p><span class="hlt">Pressure</span> <span class="hlt">gradient</span> across the pulmonary valve (PVPG) is an important hemodynamic variable used in the management of patients with cardiovascular and pulmonary disease. However, a reliable noninvasive method is unavailable. We hypothesized that a progressive Muller maneuver would elicit the pulmonary valve premature opening (PVPO) in diastole and that this event would be detectable by Doppler echocardiography. The intrathoracic pressure (ITP) decrease during this maneuver equals PVPG, which may be assessed with a custom airway pressure measurement device. A total of 102 subjects were enrolled in the study. At the earliest appearance of PVPO, the ITP decrease was recorded as the PVPG. PVPG was also simultaneously measured and compared by other two methods: right heart catheterization in 43 subjects, and routine Doppler echocardiography (pulmonary regurgitation jet) in the other 59 subjects. The results measured by different approaches were compared using the Bland-Altman analysis. PVPG assessed via PVPO showed strong agreement with PVPG measured by catheterization or routine Doppler echocardiography methods, with Lin concordance correlation coefficients of 0.91 and 0.70, respectively. In conclusion, PVPO provides a new noninvasive method of quantification of PVPG. PMID:28198458</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23539394','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23539394"><span>Are there any alternative methods to hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> in portal hypertension assessment?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Procopeţ, Bogdan; Tantau, Marcel; Bureau, Christophe</p> <p>2013-03-01</p> <p>Portal hypertension is a major consequence of any chronic liver disease and it represents the main mechanism of complication occurrence. Therefore, the assessment of portal hypertension presence is one of the most important steps in the management of any chronic liver diseases. The most accurate tool for portal pressure assessment is hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (HVPG) measurement, which has diagnostic and prognostic relevance. In this paper we review the methodology of HVPG measuring, together with the clinical relevance of this technique. Portal hypertension is defined as a HVPG higher than 5 mmHg, but clinically significant portal hypertension that predisposes to clinical decompensation is defined as HVPG higher than 10 mmHg. HVPG is useful for portal hypertension treatment monitoring. A decrease in HVPG greater than 20% or under the threshold of 12 mmHg is considered to be protective against portal hypertension-related events. Even if HVPG measurement is a safe procedure, it is still considered an invasive technique and not widely available. Therefore, non-invasive markers of portal hypertension were searched for. Until now only liver stiffness measurement by transient elastography has proved to be sufficiently accurate but there is still heterogeneity among the cut-off values for portal hypertension diagnosis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28198458','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28198458"><span>A Simple Method for Noninvasive Quantification of <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Across the Pulmonary Valve.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, Xueying; Xing, Changyang; Feng, Yang; Duan, Yunyou; Zheng, Qiangsun; Wang, Zuojun; Liu, Jie; Cao, Tiesheng; Yuan, Lijun</p> <p>2017-02-15</p> <p><span class="hlt">Pressure</span> <span class="hlt">gradient</span> across the pulmonary valve (PVPG) is an important hemodynamic variable used in the management of patients with cardiovascular and pulmonary disease. However, a reliable noninvasive method is unavailable. We hypothesized that a progressive Muller maneuver would elicit the pulmonary valve premature opening (PVPO) in diastole and that this event would be detectable by Doppler echocardiography. The intrathoracic pressure (ITP) decrease during this maneuver equals PVPG, which may be assessed with a custom airway pressure measurement device. A total of 102 subjects were enrolled in the study. At the earliest appearance of PVPO, the ITP decrease was recorded as the PVPG. PVPG was also simultaneously measured and compared by other two methods: right heart catheterization in 43 subjects, and routine Doppler echocardiography (pulmonary regurgitation jet) in the other 59 subjects. The results measured by different approaches were compared using the Bland-Altman analysis. PVPG assessed via PVPO showed strong agreement with PVPG measured by catheterization or routine Doppler echocardiography methods, with Lin concordance correlation coefficients of 0.91 and 0.70, respectively. In conclusion, PVPO provides a new noninvasive method of quantification of PVPG.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDH32006W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDH32006W"><span>Scaling properties of the mean wall-normal velocity in the zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> boundary layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wei, Tie; Klewicki, Joseph</p> <p>2016-11-01</p> <p>The scaling properties of the mean wall-normal velocity, V (x , y) , in zero-<span class="hlt">pressure-gradient</span> laminar and turbulent boundary layer flows is investigated using numerical simulation data, physical experiment data, and integral analyses of governing equations. The maximum mean wall-normal velocity, V∞, and the boundary layer thickness, δ, are evidenced to be the proper scaling for V over most if not the entire boundary layer. This is different from the behavior of the mean streamwise velocity (U) or the turbulent shear stress (T = - ρ < uv >), which depend on different characteristic length scales in the regions near to and away from the surface. Insights pertaining to this are further surmised from an analytical relationship for the ratio of the displacement to momentum thickness, i.e., shape factor, H. Integral analyses using the continuity and mean momentum equation show that (U∞V∞) /uτ2 = H , where uτ is the friction velocity. Both the laminar similarity solution and DNS data in post-transitional flows convincingly support this relation. Over the transitional regime, sufficiently high quality data is still lacking to check if this relation remains valid.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10760253','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10760253"><span>Characteristic length scale of the intermediate structure in zero-<span class="hlt">pressure-gradient</span> boundary layer flow.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Barenblatt, G I; Chorin, A J; Prostokishin, V M</p> <p>2000-04-11</p> <p>In a turbulent boundary layer over a smooth flat plate with zero <span class="hlt">pressure</span> <span class="hlt">gradient</span>, the intermediate structure between the viscous sublayer and the free stream consists of two layers: one adjacent to the viscous sublayer and one adjacent to the free stream. When the level of turbulence in the free stream is low, the boundary between the two layers is sharp, and both have a self-similar structure described by Reynolds-number-dependent scaling (power) laws. This structure introduces two length scales: one-the wall-region thickness-determined by the sharp boundary between the two intermediate layers and the second determined by the condition that the velocity distribution in the first intermediate layer be the one common to all wall-bounded flows and in particular coincide with the scaling law previously determined for pipe flows. Using recent experimental data, we determine both these length scales and show that they are close. Our results disagree with the classical model of the "wake region."</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19960021498&hterms=fahr&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfahr','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19960021498&hterms=fahr&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dfahr"><span>Pick-up ion <span class="hlt">pressure</span> <span class="hlt">gradients</span> modulating the solar wind dynamics</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fahr, Hans J.; Fichtner, Horst</p> <p>1995-01-01</p> <p>Neutral interstellar atoms penetrate deeply into the inner heliosphere before they become ionized by various processes. As ions they are picked-up by the frozen-in magnetic fields and are convected outwards with the solar wind plasma. Thereby the primary plasma flow is mass, momentum, and energy-loaded. The dynamics of the distant multi-constituent solar wind is, however, not solely determined by these loading processes, but is also affected by the wave-mediated pick-up ion <span class="hlt">pressure</span> <span class="hlt">gradients</span> derivable from the pick-up ion distribution function. The action of the radial components of these pressures essentially counter balances the decelerating effect of the solar wind momentum loading, diminishing strongly the deceleration of the distant solar wind. Furthermore the latitudinal components of the pick-up ion pressures induce latitudinal forces acting on the multiconstituent solar plasma outflow and inducing nonradial bulk flow components. The enforced nonradial outflow geometry on the upwind hemisphere may partly be responsible for the magnetic flux deficit which was claimed since several years in the PIONEER-10 magnetic flux data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750048838&hterms=gases+reales&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dgases%2Breales','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750048838&hterms=gases+reales&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dgases%2Breales"><span>Correlation of boundary layer quantities for hypersonic laminar flows with zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> for several gases</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cook, W. J.</p> <p>1975-01-01</p> <p>The laminar boundary layer has been theoretically studied for six gases for flows over cold walls with zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> at Mach numbers between 5.5 and 12.5 to correlate boundary layer quantities for the various gases. The flow conditions considered correspond to those that can be generated in test facilities such as the shock tunnel and the expansion tube. Computed results obtained using real gas properties indicate that the Eckert number based on edge conditions serves to correlate the results in terms of the wall shear stress and enthalpy gradient, the Stanton number, and the momentum thickness for the various gases within plus or minus 10 per cent for Te = Tw and Te approximately 3Tw. Computed Reynolds analogy factors exhibit very good agreement with those predicted by the Colburn analogy. Velocity and displacement thicknesses correlate well with Eckert number for Te = Tw, but fail to correlate for Te approximately 3Tw. Differences in results are traced to property variations. Results show that the Eckert number is a significant correlating variable for the flows considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4381184','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4381184"><span>Staging of liver fibrosis or cirrhosis: The role of hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> measurement</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Suk, Ki Tae; Kim, Dong Joon</p> <p>2015-01-01</p> <p>Liver fibrosis is a common histological change of chronic liver injury and it is closely related with portal hypertension which is hemodynamic complication of chronic liver disease. Currently, liver fibrosis has been known as a reversible dynamic process in previous literatures. Although liver biopsy is a gold standard for assessing the stage of liver fibrosis, it may not completely represent the stage of liver fibrosis because of sampling error or semi-quantative measurement. Recent evidences suggested that histologic, clinical, hemodynamic, and biologic features are closely associated in patients with chronic liver disease. Hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (HVPG) measurement has been known as a modality to evaluate the portal pressure. The HVPG measurement has been used clinically for fibrosis diagnosis, risk stratification, preoperative screening for liver resection, monitoring the efficacy of medical treatments, and assessing the prognosis of liver fibrosis. Therefore, the HVPG measurement can be used to monitor areas the chronic liver disease but also other important areas of chronic liver disease. PMID:25848485</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840039067&hterms=ordinary+differential+equation+models&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dordinary%2Bdifferential%2Bequation%2Bmodels','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840039067&hterms=ordinary+differential+equation+models&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dordinary%2Bdifferential%2Bequation%2Bmodels"><span>A new turbulence closure model for boundary layer flows with strong adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> and separation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, D. A.; King, L. S.</p> <p>1984-01-01</p> <p>A new turbulence closure model designed specifically to treat two-dimensional, turbulent boundary layers with strong adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> and attendant separation, is presented. The influence of history effects are modeled by using an ordinary differential equation (ODE) derived from the turbulence kinetic-energy equation, to describe the streamwise development of the maximum Reynolds shear stress in conjunction with an assumed eddy-viscosity distribution which has as its velocity scale the maximum Reynolds shear stress. In the outer part of the boundary layer, the eddy viscosity is treated as a free parameter which is adjusted in order to satisfy the ODE for the maximum shear stress. Because of this, the model s not simply an eddy-viscosity model, but contains features of a Reynolds-stress model. Comparisons with experiments are presented which clearly show the proposed model to be superior to the Cebeci-Smith model in treating strongly retarded and separated flows. In contrast to two-equation, eddy-viscosity models, it requires only slightly more computational effort than simple models like the Cebeci-Smith model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040141463&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgreenberg','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141463&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgreenberg"><span>Doppler echo evaluation of pulmonary venous-left atrial <span class="hlt">pressure</span> <span class="hlt">gradients</span>: human and numerical model studies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Firstenberg, M. S.; Greenberg, N. L.; Smedira, N. G.; Prior, D. L.; Scalia, G. M.; Thomas, J. D.; Garcia, M. J.</p> <p>2000-01-01</p> <p>The simplified Bernoulli equation relates fluid convective energy derived from flow velocities to a <span class="hlt">pressure</span> <span class="hlt">gradient</span> and is commonly used in clinical echocardiography to determine pressure differences across stenotic orifices. Its application to pulmonary venous flow has not been described in humans. Twelve patients undergoing cardiac surgery had simultaneous high-fidelity pulmonary venous and left atrial pressure measurements and pulmonary venous pulsed Doppler echocardiography performed. Convective gradients for the systolic (S), diastolic (D), and atrial reversal (AR) phases of pulmonary venous flow were determined using the simplified Bernoulli equation and correlated with measured actual pressure differences. A linear relationship was observed between the convective (y) and actual (x) pressure differences for the S (y = 0.23x + 0.0074, r = 0.82) and D (y = 0.22x + 0.092, r = 0.81) waves, but not for the AR wave (y = 0. 030x + 0.13, r = 0.10). Numerical modeling resulted in similar slopes for the S (y = 0.200x - 0.127, r = 0.97), D (y = 0.247x - 0. 354, r = 0.99), and AR (y = 0.087x - 0.083, r = 0.96) waves. Consistent with numerical modeling, the convective term strongly correlates with but significantly underestimates actual gradient because of large inertial forces.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040112441&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgreenberg','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040112441&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgreenberg"><span>Estimation of diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> by Doppler M-mode echocardiography</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greenberg, N. L.; Vandervoort, P. M.; Firstenberg, M. S.; Garcia, M. J.; Thomas, J. D.</p> <p>2001-01-01</p> <p>Previous studies have shown that small intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> (IVPG) are important for efficient filling of the left ventricle (LV) and as a sensitive marker for ischemia. Unfortunately, there has previously been no way of measuring these noninvasively, severely limiting their research and clinical utility. Color Doppler M-mode (CMM) echocardiography provides a spatiotemporal velocity distribution along the inflow tract throughout diastole, which we hypothesized would allow direct estimation of IVPG by using the Euler equation. Digital CMM images, obtained simultaneously with intracardiac pressure waveforms in six dogs, were processed by numerical differentiation for the Euler equation, then integrated to estimate IVPG and the total (left atrial to left ventricular apex) pressure drop. CMM-derived estimates agreed well with invasive measurements (IVPG: y = 0.87x + 0.22, r = 0.96, P < 0.001, standard error of the estimate = 0.35 mmHg). Quantitative processing of CMM data allows accurate estimation of IVPG and tracking of changes induced by beta-adrenergic stimulation. This novel approach provides unique information on LV filling dynamics in an entirely noninvasive way that has previously not been available for assessment of diastolic filling and function.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2357502','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2357502"><span>The effect of <span class="hlt">pressure</span> <span class="hlt">gradient</span> and thermolactyl control gloves in arthritic patients with swollen hands.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Oosterveld, F G; Rasker, J J</p> <p>1990-06-01</p> <p>In this study the effect of <span class="hlt">pressure</span> <span class="hlt">gradient</span> gloves was compared with that of control gloves by eight patients with rheumatoid arthritis (RA) and diffusely and symmetrically swollen hands. In the morning at fixed times, grip strength, circumference of PIP joints and proximal phalanges, nocturnal pain and morning stiffness in the hands were measured. Significant improvement of circumference of PIP joints (P less than 0.001) and proximal phalanges (P less than 0.01) were found. On wearing the control gloves, some improvement was also found, but only the circumference of PIP joints decreased significantly (P less than 0.05). Nocturnal pain and morning stiffness diminished significantly on wearing both types of glove. Grip strength improved, but not significantly with both. No significant differences were detected between the effects of wearing the two types of glove. No correlation was found between the decreased swelling in the hands as measured by PIP joint circumference or circumference of the proximal phalanges and the decreased nocturnal pain or morning stiffness. This study provided no explanation for the beneficial effect of the gloves. It was shown that for some patients with painful and swollen hands, wearing gloves at night may give relief.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DPPU10025R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DPPU10025R"><span>Ion <span class="hlt">pressure</span> <span class="hlt">gradient</span> effects on Kelvin-Helmholtz and interchange instabilities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Russell, David; Myra, James</p> <p>2016-10-01</p> <p>In the flow-free state, radial force-balance implies that the poloidal components of the ExB and ion diamagnetic drifts, grad(Pi) / n, are mirrored : vE + vdi = 0. Analysis of the linearized fluid equations shows that the mirrored state is stable in the absence of the interchange drive, grad(Pe +Pi) / n, i.e., the K-H instability is absent. With the interchange drive present, the mirrored-state growth rate passes through a global minimum value with increasing ion <span class="hlt">pressure</span> <span class="hlt">gradient</span>, due to sheared ExB flow and diamagnetic suppression, admitting a stability interval in a neighborhood of the minimum if other damping mechanisms are present. The K-H instability is recovered, absent the interchange drive, if force-balance is generalized to include neoclassical poloidal flows (vE + vdi + vnc = 0, vnc grad(Ti)), so that mirroring is lost. Implications for achieving a quiescent H-mode are discussed, and SOLT simulations, which include nonlinear ion pressure effects, are compared with the linear picture. Work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-97ER54392.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3880383','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3880383"><span>A <span class="hlt">pressure-gradient</span> mechanism for vortex shedding in constricted channels</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Boghosian, M. E.; Cassel, K. W.</p> <p>2013-01-01</p> <p>Numerical simulations of the unsteady, two-dimensional, incompressible Navier–Stokes equations are performed for a Newtonian fluid in a channel having a symmetric constriction modeled by a two-parameter Gaussian distribution on both channel walls. The Reynolds number based on inlet half-channel height and mean inlet velocity ranges from 1 to 3000. Constriction ratios based on the half-channel height of 0.25, 0.5, and 0.75 are considered. The results show that both the Reynolds number and constriction geometry have a significant effect on the behavior of the post-constriction flow field. The Navier–Stokes solutions are observed to experience a number of bifurcations: steady attached flow, steady separated flow (symmetric and asymmetric), and unsteady vortex shedding downstream of the constriction depending on the Reynolds number and constriction ratio. A sequence of events is described showing how a sustained spatially growing flow instability, reminiscent of a convective instability, leads to the vortex shedding phenomenon via a proposed streamwise <span class="hlt">pressure-gradient</span> mechanism. PMID:24399860</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790008471','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790008471"><span>Acoustic scattering by circular cylinders of various aspect ratios. [<span class="hlt">pressure</span> <span class="hlt">gradient</span> microphones</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maciulaitis, A.</p> <p>1979-01-01</p> <p>The effects of acoustic scattering on the useful frequency range of <span class="hlt">pressure</span> <span class="hlt">gradient</span> microphones were investigated experimentally between ka values of 0.407 and 4.232 using two circular cylindrical models (L/D = 0.5 and 0.25) having a 25 cm outside diameter. Small condenser microphones, attached to preamplifiers by flexible connectors, were installed from inside the cylindrical bodies, and flush mounted on the exterior surface of the cylinders. A 38 cm diameter woofer in a large speaker enclosure was used as the sound source. Surface pressure augmentation and phase differences were computed from measured data for various sound wave incidence angles. Results are graphically compared with theoretical predictions supplied by NASA for ka = 0.407, 2.288, and 4.232. All other results are tabulated in the appendices. With minor exceptions, the experimentally determined pressure augmentations agreed within 0.75 dB with theoretical predictions. The agreement for relative phase angles was within 5 percent without any exceptions. Scattering parameter variations with ka and L/D ratio, as computed from experimental data, are also presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721146','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721146"><span>Hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> predicts development of hepatocellular carcinoma independently of severity of cirrhosis☆</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ripoll, Cristina; Groszmann, Roberto J.; Garcia-Tsao, Guadalupe; Bosch, Jaime; Grace, Norman; Burroughs, Andrew; Planas, Ramon; Escorsell, Angels; Garcia-Pagan, Juan Carlos; Makuch, Robert; Patch, David; Matloff, Daniel S.</p> <p>2013-01-01</p> <p>Background/Aims A total of 213 patients with compensated cirrhosis, portal hypertension and no varices were included in a trial evaluating beta-blockers in preventing varices. Predictors of the development of hepatocellular carcinoma (HCC), including hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (HVPG) were analyzed. Methods Baseline laboratory tests, ultrasound and HVPG measurements were performed. Patients were followed prospectively every three months until development of varices or variceal bleeding or end of the study in 09/02. The endpoint was HCC development according to standard diagnostic criteria. Univariate and multivariate Cox regression models were developed to identify predictors of HCC. Results In a median follow-up of 58 months 26/213 (12.2%) patients developed HCC. Eight patients were transplanted and 28 patients died without HCC. Twenty-one (84%) HCC developed in patients with HCV. On multivariate analysis HVPG (HR 1.18; 95%CI 1.08–1.29), albumin (HR 0.34; 95%CI 0.14–0.83) and viral etiology (HR 4.59; 95%CI 1.51–13.92) were independent predictors of HCC development. ROC curves identified 10 mmHg of HVPG as the best cutoff; those who had an HVPG above this value had a 6-fold increase in the HCC incidence. Conclusions Portal hypertension is an independent predictor of HCC development. An HVPG >10 mmHg is associated with a 6-fold increase of HCC risk. PMID:19303163</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26368200','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26368200"><span>Probe-controlled <span class="hlt">soliton</span> frequency shift in the regime of optical event horizon.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gu, Jie; Guo, Hairun; Wang, Shaofei; Zeng, Xianglong</p> <p>2015-08-24</p> <p>In optical analogy of the event horizon, temporal pulse collision and mutual interactions are mainly between an intense solitary wave (<span class="hlt">soliton</span>) and a dispersive probe wave. In such a regime, here we numerically investigate the probe-controlled <span class="hlt">soliton</span> frequency shift as well as the <span class="hlt">soliton</span> self-<span class="hlt">compression</span>. In particular, in the dispersion landscape with multiple zero dispersion wavelengths, bi-directional <span class="hlt">soliton</span> spectral tunneling effects is possible. Moreover, we propose a mid-infrared <span class="hlt">soliton</span> self-<span class="hlt">compression</span> to the generation of few-cycle ultrashort pulses, in a bulk of quadratic nonlinear crystals in contrast to optical fibers or cubic nonlinear media, which could contribute to the community with a simple and flexible method to experimental implementations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA278322','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA278322"><span>Analysis and Calculation by Integral Methods of Laminar <span class="hlt">Compressible</span> Boundary Layer with Heat Transfer and with and Without <span class="hlt">Pressure</span> <span class="hlt">Gradient</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1955-01-01</p> <p>hI ’Uher an I ’lI 5 l’i it ’ ll t/, Iis I 4’(l i0o l ir o ll th dllt’ \\\\ Ill’ Iv trl’ sf1411 e111/ 41. ’ developed. Ths111 rflclto 1i’e tilt hidt...551)v LAIABO iRLAYEoin ANALYS;ISvo olid Ir conrariit liiimer, a cmmetiiR Vait ofra eq *11 viilli v iate! 1 K i nnd -doc (re .3) 1111 q l~~ofa sprateiof...where44 seq(jll(’h 1. ThuIllS-. o14Jpj41i4g cquat11ion. 40l 4)1 14414 37 14fil q/ (A- 1)! opi,, :;S) i l( 1114’ lli lo1414141 oIf Ilvilt- Ir lsfl rate14I</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721058','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3721058"><span>Chronic Liver Disease: Noninvasive Subharmonic Aided Pressure Estimation of Hepatic Venous <span class="hlt">Pressure</span> <span class="hlt">Gradient</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Eisenbrey, John R.; Dave, Jaydev K.; Halldorsdottir, Valgerdur G.; Merton, Daniel A.; Miller, Cynthia; Gonzalez, José M.; Machado, Priscilla; Park, Suhyun; Dianis, Scott; Chalek, Carl L.; Kim, Christopher E.; Baliff, Jeffrey P.; Thomenius, Kai E.; Brown, Daniel B.; Navarro, Victor</p> <p>2013-01-01</p> <p>Purpose: To compare subharmonic aided pressure estimation (SHAPE) with pressure catheter–based measurements in human patients with chronic liver disease undergoing transjugular liver biopsy. Materials and Methods: This HIPAA-compliant study had U.S. Food and Drug Administration and institutional review board approval, and written informed consent was obtained from all participants. Forty-five patients completed this study between December 2010 and December 2011. A clinical ultrasonography (US) scanner was modified to obtain SHAPE data. After transjugular liver biopsy with pressure measurements as part of the standard of care, 45 patients received an infusion of a microbubble US contrast agent and saline. During infusion, SHAPE data were collected from a portal and hepatic vein and were compared with invasive measurements. Correlations between data sets were determined by using the Pearson correlation coefficient, and statistical significance between groups was determined by using the Student t test. Results:- The 45 study patients included 27 men and 18 women (age range, 19–71 years; average age, 55.8 years). The SHAPE gradient between the portal and hepatic veins was in good overall agreement with the hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (HVPG) (R = 0.82). Patients at increased risk for variceal hemorrhage (HVPG ≥ 12 mm Hg) had a significantly higher mean subharmonic gradient than patients with lower HVPGs (1.93 dB ± 0.61 [standard deviation] vs −1.47 dB ± 0.29, P < .001), with a sensitivity of 100% and a specificity of 81%, indicating that SHAPE may be a useful tool for the diagnosis of clinically important portal hypertension. Conclusion: Preliminary results show SHAPE to be an accurate noninvasive technique for estimating portal hypertension. © RSNA, 2013 Supplemental material: http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.13121769/-/DC1 PMID:23525208</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21083455','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21083455"><span>Restoration of Liver Function and Portosystemic <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> after TIPSS and Late TIPSS Occlusion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Maedler, U.; Hansmann, J.; Duex, M.; Noeldge, G.; Sauer, P.; Richter, G.M.</p> <p>2002-03-15</p> <p>TIPSS (transjugular intrahepatic portosystemic shunt) may be indicated to control bleeding from esophageal and gastric varicose veins, to reduce ascites, and to treat patients with Budd-Chiari syndrome and veno-occlusive disease. Numerous measures to improve the safety and methodology of the procedure have helped to increase the technical and clinical success. Follow-up of TIPSS patients has revealed shunt stenosis to occur more often in patients with preserved liver function (Child A, Child B). In addition, the extent of liver cirrhosis is the main factor that determines prognosis in the long term. Little is known about the effects of TIPSS with respect to portosystemic hemodynamics. This report deals with a cirrhotic patient who stopped drinking 7 months prior to admission. He received TIPSS to control ascites and recurrent esophageal bleeding. Two years later remarkable hypertrophy of the left liver lobe and shunt occlusion was observed. The portosystemic <span class="hlt">pressure</span> <span class="hlt">gradient</span> dropped from 24 mmHg before TIPSS to 11 mmHg and remained stable after shunt occlusion. The Child's B cirrhosis prior to TIPSS turned into Child's A cirrhosis and remained stable during the follow-up period of 32 months. This indicates that liver function of TIPSS patients may recover due to hypertrophy of the remaining non-cirrhotic liver tissue. In addition the hepatic hemodynamics may return to normal. In conclusion, TIPSS cannot cure cirrhosis but its progress may be halted if the cause can be removed. This may result in a normal portosystemic gradient, leading consequently to shunt occlusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010APS..DPPGI2004Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010APS..DPPGI2004Y"><span><span class="hlt">Pressure-Gradient</span>-Limiting Instability Dynamics in the H-mode Pedestal on DIII-D</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yan, Z.</p> <p>2010-11-01</p> <p>Detailed 2D measurements of long-wavelength density fluctuations in the pedestal region with beam emission spectroscopy during the inter-ELM phase indicate two distinct bands of fluctuations propagating in opposite poloidal directions in the plasma frame: one lower frequency band (20-150 kHz) advects in the ion-diamagnetic drift direction (ion mode), and a higher frequency band (200-400 kHz) advects in the electron diamagnetic drift direction (electron mode). Interestingly, the mode amplitudes are modulated with the ELM cycle with the ion mode having some features qualitatively similar to those predicted for kinetic ballooning modes (KBM). Experiments have focused on determining the role of current and <span class="hlt">pressure</span> <span class="hlt">gradient</span>-driven instabilities in determining the H-mode pedestal structure. Detailed analysis of the temporal evolution reveals complex dynamics. The ion mode amplitude increases rapidly after an ELM and then saturates, consistent with the dynamics of the pedestal electron pressure, while the electron mode is quasi-stationary between ELMs. The decorrelation time of the ion mode is <5,s (τcxcs/a<=1), the radial correlation length is of order 10,ρi and the poloidal wave-number kθρi˜0.1. The mode velocity is comparable to the diamagnetic velocity. In related Quiescent H-mode experiments, pedestals with high electron pressure and high ExB shearing rates exhibit a set of high-frequency coherent modes propagating in the ion diamagnetic direction. These modes also exhibit KBM-like characteristics, but do not develop into fully turbulent structures. Numerical simulations are in progress to help identify the underlying instabilities and nature of these modes, and ultimately help validate nonlinear models of the H-mode pedestal structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5583542','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5583542"><span>Estimating <span class="hlt">pressure</span> <span class="hlt">gradients</span> by auscultation: How technology (echocardiography) can help improve clinical skills</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kadle, Rohini L; Phoon, Colin K L</p> <p>2017-01-01</p> <p>AIM To extend our previously-published experience in estimating <span class="hlt">pressure</span> <span class="hlt">gradients</span> (PG) via physical examination in a large patient cohort. METHODS From January 1, 1997 through December 31, 2009, an attending pediatric cardiologist compared clinical examination (EXAM) with Doppler-echo (ECHO), in 1193 patients with pulmonic stenosis (PS, including tetralogy of Fallot), aortic stenosis (AS), and ventricular septal defect (VSD). EXAM PG estimates were based primarily on a murmur’s pitch, grade, and length. ECHO peak instantaneous PG was derived from the modified Bernoulli equation. Patients were 0-38.4 years old (median 4.8). RESULTS For all patients, EXAM correlated highly with ECHO: ECHO = 0.99 (EXAM) + 3.2 mmHg; r = +0.89; P < 0.0001. Agreement was excellent (mean difference = -2.9 ± 16.1 mmHg). In 78% of all patients, agreement between EXAM and ECHO was within 15 mmHg and within 5 mmHg in 45%. Clinical estimates of PS PG were more accurate than of AS and VSD. A palpable precordial thrill and increasing loudness of the murmur predicted higher gradients (P < 0.0001). Weight did not influence accuracy. A learning curve was evident, such that the most recent quartile of patients showed ECHO = 1.01 (EXAM) + 1.9, r = +0.92, P < 0.0001; during this time, the attending pediatric cardiologist had been > 10 years in practice. CONCLUSION Clinical examination can accurately estimate PG in PS, AS, or VSD. Continual correlation of clinical findings with echocardiography can lead to highly accurate diagnostic skills. PMID:28932358</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23804669','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23804669"><span>Cardiovascular design in fin whales: high-stiffness arteries protect against adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> at depth.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lillie, M A; Piscitelli, M A; Vogl, A W; Gosline, J M; Shadwick, R E</p> <p>2013-07-15</p> <p>Fin whales have an incompliant aorta, which, we hypothesize, represents an adaptation to large, depth-induced variations in arterial transmural pressures. We hypothesize these variations arise from a limited ability of tissues to respond to rapid changes in ambient ocean pressures during a dive. We tested this hypothesis by measuring arterial mechanics experimentally and modelling arterial transmural pressures mathematically. The mechanical properties of mammalian arteries reflect the physiological loads they experience, so we examined a wide range of fin whale arteries. All arteries had abundant adventitial collagen that was usually recruited at very low stretches and inflation pressures (2-3 kPa), making arterial diameter largely independent of transmural pressure. Arteries withstood significant negative transmural pressures (-7 to -50 kPa) before collapsing. Collapse was resisted by recruitment of adventitial collagen at very low stretches. These findings are compatible with the hypothesis of depth-induced variation of arterial transmural pressure. Because transmural pressures depend on thoracic pressures, we modelled the thorax of a diving fin whale to assess the likelihood of significant variation in transmural pressures. The model predicted that deformation of the thorax body wall and diaphragm could not always equalize thoracic and ambient pressures because of asymmetrical conditions on dive descent and ascent. Redistribution of blood could partially compensate for asymmetrical conditions, but inertial and viscoelastic lag necessarily limits tissue response rates. Without pressure equilibrium, particularly when ambient pressures change rapidly, internal <span class="hlt">pressure</span> <span class="hlt">gradients</span> will develop and expose arteries to transient pressure fluctuations, but with minimal hemodynamic consequence due to their low compliance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040087555&hterms=ethanol&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dethanol','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040087555&hterms=ethanol&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dethanol"><span>Improvement in diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> in patients with HOCM after ethanol septal reduction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rovner, Aleksandr; Smith, Rebecca; Greenberg, Neil L.; Tuzcu, E. Murat; Smedira, Nicholas; Lever, Harry M.; Thomas, James D.; Garcia, Mario J.</p> <p>2003-01-01</p> <p>We sought to validate measurement of intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> (IVPG) and analyze their change in patients with hypertrophic obstructive cardiomyopathy (HOCM) after ethanol septal reduction (ESR). Quantitative analysis of color M-mode Doppler (CMM) images may be used to estimate diastolic IVPG noninvasively. Noninvasive IVPG measurement was validated in 10 patients undergoing surgical myectomy. Echocardiograms were then analyzed in 19 patients at baseline and after ESR. Pulsed Doppler data through the mitral valve and pulmonary venous flow were obtained. CMM was used to obtain the flow propagation velocity (Vp) and to calculate IVPG off-line. Left atrial pressure was estimated with the use of previously validated Doppler equations. Data were compared before and after ESR. CMM-derived IVPG correlated well with invasive measurements obtained before and after surgical myectomy [r = 0.8, P < 0.01, Delta(CMM - invasive IVPG) = 0.09 +/- 0.45 mmHg]. ESR resulted in a decrease of resting LVOT systolic gradient from 62 +/- 10 to 29 +/- 5 mmHg (P < 0.001). There was a significant increase in the Vp and IVPG (from 48 +/- 5to 74 +/- 7 cm/s and from 1.5 +/- 0.2 to 2.6 +/- 0.3 mmHg, respectively, P < 0.001 for both). Estimated left atrial pressure decreased from 16.2 +/- 1.1 to 11.5 +/- 0.9 mmHg (P < 0.001). The increase in IVPG correlated with the reduction in the LVOT gradient (r = 0.6, P < 0.01). Reduction of LVOT obstruction after ESR is associated with an improvement in diastolic suction force. Noninvasive measurements of IVPG may be used as an indicator of diastolic function improvement in HOCM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18079461','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18079461"><span>Transpulmonary <span class="hlt">pressure</span> <span class="hlt">gradient</span> verifies pulmonary hypertension is initiated by increased arterial resistance in broilers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lorenzoni, A G; Anthony, N B; Wideman, R F</p> <p>2008-01-01</p> <p>Previous hemodynamic evaluations demonstrated that pulmonary arterial pressure (PAP) is higher in broilers that are susceptible to pulmonary hypertension syndrome (PHS, ascites) than in broilers that are resistant to PHS. We compared key pulmonary hemodynamic parameters in broilers from PHS-susceptible and PHS-resistant lines (selected for 12 generations under hypobaric hypoxia) and in broilers from a relaxed (control) line. In experiment 1 the PAP was measured in male broilers in which a flow probe positioned on one pulmonary artery permitted the determination of cardiac output and pulmonary vascular resistance (PVR). The PAP and relative PVR were higher in susceptible broilers than in relaxed and resistant broilers, whereas absolute and relative cardiac output did not differ between lines. In experiment 2 male and female broilers from the 3 lines were catheterized to measure pressures in the wing vein, right atrium, right ventricle, pulmonary artery, and pulmonary veins (WP, wedge pressure). The transpulmonary <span class="hlt">pressure</span> <span class="hlt">gradient</span> (TPG) was calculated as (PAP-WP), with PAP quantifying precapillary pressure and WP approximating postcapillary pulmonary venous pressure. When compared with resistant and relaxed broilers, PAP values in susceptible broilers were > or =10 mmHg higher, TPG values were > or =8 mmHg higher, and WP values were < or =2 mmHg higher, regardless of sex. The combined hemodynamic criteria (elevated PAP and PVR combined with a proportionally elevated TPG) demonstrate that susceptibility to PHS can be attributed primarily to pulmonary arterial hypertension associated with increased precapillary (arteriole) resistance rather than to pulmonary venous hypertension caused by elevated postcapillary (venous and left atrial) resistance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2761583','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2761583"><span>Sildenafil does not influence hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> in patients with cirrhosis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clemmesen, Jens Otto; Giraldi, Annamaria; Ott, Peter; Dalhoff, Kim; Hansen, Bent Adel; Larsen, Fin Stolze</p> <p>2008-01-01</p> <p>AIM: To investigate if sildenafil increases splanchnic blood flow and changes the hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (HVPG) in patients with cirrhosis. Phosphodiesterase type-5 inhibitors are valuable in the treatment of erectile dysfunction and pulmonary hypertension in patients with end-stage liver disease. However, the effect of phosphodiesterase type-5 inhibitors on splanchnic blood flow and portal hypertension remains essentially unknown. METHODS: Ten patients with biopsy proven cirrhosis (five females/five males, mean age 54 ± 8 years) and an HVPG above 12 mmHg were studied after informed consent. Measurement of splanchnic blood flow and the HVPG during liver vein catheterization were done before and 80 min after oral administration of 50 mg sildenafil. Blood flow was estimated by use of indocyanine green clearance technique and Fick's principle, with correction for non-steady state. RESULTS: The plasma concentration of sildenafil was 222 ± 136 ng/mL 80 min after administration. Mean arterial blood pressure decreased from 77 ± 7 mmHg to 66 ± 12 mmHg, P = 0.003, while the splanchnic blood flow and oxygen consumption remained unchanged at 1.14 ± 0.71 L/min and 2.3 ± 0.6 mmol/min, respectively. Also the HVPG remained unchanged (18 ± 2 mmHg vs 16 ± 2 mmHg) with individual changes ranging from -8 mmHg to +2 mmHg. In seven patients, HVPG decreased and in three it increased. CONCLUSION: In spite of arterial blood pressure decreases 80 min after administration of the phosphodiesterase type-5 inhibitor sildenafil, the present study could not demonstrate any clinical relevant influence on splanchnic blood flow, oxygen consumption or the HVPG. PMID:18985812</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040087555&hterms=lever&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlever','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040087555&hterms=lever&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dlever"><span>Improvement in diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> in patients with HOCM after ethanol septal reduction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rovner, Aleksandr; Smith, Rebecca; Greenberg, Neil L.; Tuzcu, E. Murat; Smedira, Nicholas; Lever, Harry M.; Thomas, James D.; Garcia, Mario J.</p> <p>2003-01-01</p> <p>We sought to validate measurement of intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> (IVPG) and analyze their change in patients with hypertrophic obstructive cardiomyopathy (HOCM) after ethanol septal reduction (ESR). Quantitative analysis of color M-mode Doppler (CMM) images may be used to estimate diastolic IVPG noninvasively. Noninvasive IVPG measurement was validated in 10 patients undergoing surgical myectomy. Echocardiograms were then analyzed in 19 patients at baseline and after ESR. Pulsed Doppler data through the mitral valve and pulmonary venous flow were obtained. CMM was used to obtain the flow propagation velocity (Vp) and to calculate IVPG off-line. Left atrial pressure was estimated with the use of previously validated Doppler equations. Data were compared before and after ESR. CMM-derived IVPG correlated well with invasive measurements obtained before and after surgical myectomy [r = 0.8, P < 0.01, Delta(CMM - invasive IVPG) = 0.09 +/- 0.45 mmHg]. ESR resulted in a decrease of resting LVOT systolic gradient from 62 +/- 10 to 29 +/- 5 mmHg (P < 0.001). There was a significant increase in the Vp and IVPG (from 48 +/- 5to 74 +/- 7 cm/s and from 1.5 +/- 0.2 to 2.6 +/- 0.3 mmHg, respectively, P < 0.001 for both). Estimated left atrial pressure decreased from 16.2 +/- 1.1 to 11.5 +/- 0.9 mmHg (P < 0.001). The increase in IVPG correlated with the reduction in the LVOT gradient (r = 0.6, P < 0.01). Reduction of LVOT obstruction after ESR is associated with an improvement in diastolic suction force. Noninvasive measurements of IVPG may be used as an indicator of diastolic function improvement in HOCM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..12110698Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..12110698Z"><span>Alfvén wings in the lunar wake: The role of <span class="hlt">pressure</span> <span class="hlt">gradients</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, H.; Khurana, K. K.; Kivelson, M. G.; Fatemi, S.; Holmström, M.; Angelopoulos, V.; Jia, Y. D.; Wan, W. X.; Liu, L. B.; Chen, Y. D.; Le, H. J.; Shi, Q. Q.; Liu, W. L.</p> <p>2016-11-01</p> <p>Strongly conducting or magnetized obstacles in a flowing plasma generate structures called Alfvén wings, which mediate momentum transfer between the obstacle and the plasma. Nonconducting obstacles such as airless planetary bodies can generate such structures, which, however, have so far been seen only in sub-Alfvénic regime. A novel statistical analysis of simultaneous measurements made by two ARTEMIS satellites, one in the solar wind upstream of the Moon and one in the downstream wake, and comparison of the data with results of a three-dimensional hybrid model of the interaction reveal that the perturbed plasma downstream of the Moon generates Alfvén wings in super-Alfvénic solar wind. In the wake region, magnetic field lines bulge toward the Moon and the plasma flows are significantly perturbed. We use the simulation to show that some of the observed bends of the field result from field-aligned currents. The perturbations in the wake thus arise from a combination of compressional and Alfvénic perturbations. Because of the super-Alfvénic background flow of the solar wind, the two Alfvén wings fold back to form a small intersection angle. The currents that form the Alfvén wing in the wake are driven by both plasma flow deceleration and a gradient of plasma pressure, positive down the wake from the region just downstream of the Moon. Such Alfvén wing structures, caused by <span class="hlt">pressure</span> <span class="hlt">gradients</span> in the wake and the resulting plasma slowdown, should exist downstream of any nonconducting body in a super-Alfvénic plasma flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19523943','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19523943"><span>Histomorphometric measurements in human and dog optic nerve and an estimation of optic nerve <span class="hlt">pressure</span> <span class="hlt">gradients</span> in human.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Balaratnasingam, Chandrakumar; Morgan, William H; Johnstone, Victoria; Pandav, Surinder S; Cringle, Stephen J; Yu, Dao-Yi</p> <p>2009-11-01</p> <p>Intraocular pressure and cerebrospinal fluid (CSF) pressure are important determinants of the trans-laminar <span class="hlt">pressure</span> <span class="hlt">gradient</span> which is believed to be important in the pathogenesis of glaucomatous optic nerve degeneration. Computational models and finite element calculations of optic nerve head biomechanics have been previously used to predict pressures and stresses in the human optic nerve. The purpose of this report is to morphometrically compare the optic nerve laminar and pia mater structure between humans and dogs, and to use previously reported tissue pressure measurements in the dog optic nerve to estimate individual-specific human optic nerve pressures and <span class="hlt">pressure</span> <span class="hlt">gradients</span>. High resolution light microscopy was used to acquire quantitative histological measurements from sagittal sections taken from the middle of the optic nerve in 34 human cadaveric eyes and 10 dog eyes. Parameters measured included the pre-laminar and lamina cribrosa thickness, distance from posterior boundary of lamina cribrosa to inner limiting membrane (ILM), shortest distance between anterior lamina cribrosa surface and subarachnoid space, shortest distance between ILM and inner surface of pia mater in contact with the subarachnoid space and optic nerve diameter. Pia mater thickness in the proximal 4 mm of post-laminar nerve was also determined. There was no significant difference in lamina cribrosa thickness between dog and human eyes (P = 0.356). The distance between the intraocular and subarachnoid space was greater in dogs (P < 0.001). Pia mater thickness was greatest at the termination of subarachnoid space in both species. In humans, pia mater thickness decreased over the proximal 500 mum to reach a constant value of approximately 60 mum. In dogs this decrease occurred over 1000 mum to reach a constant diameter of approximately 30 mum. Using previous measurements of optic nerve pressures and <span class="hlt">pressure</span> <span class="hlt">gradients</span> in dogs we estimate that at an IOP of 15 mmHg and a CSF pressure of 0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyU...59..642T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyU...59..642T"><span>Dissipative <span class="hlt">solitons</span> in fiber lasers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turitsyn, S. K.; Rosanov, N. N.; Yarutkina, I. A.; Bednyakova, A. E.; Fedorov, S. V.; Shtyrina, O. V.; Fedoruk, M. P.</p> <p>2016-07-01</p> <p>Dissipative <span class="hlt">solitons</span> (also known as auto-<span class="hlt">solitons</span>) are stable, nonlinear, time- or space-localized solitary waves that occur due to the balance between energy excitation and dissipation. We review the theory of dissipative <span class="hlt">solitons</span> applied to fiber laser systems. The discussion context includes the classical Ginzburg-Landau and Maxwell-Bloch equations and their modifications that allow describing laser-cavity-produced waves. Practical examples of laser systems generating dissipative <span class="hlt">solitons</span> are discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24877932','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24877932"><span>Noncommuting momenta of topological <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Watanabe, Haruki; Murayama, Hitoshi</p> <p>2014-05-16</p> <p>We show that momentum operators of a topological <span class="hlt">soliton</span> may not commute among themselves when the <span class="hlt">soliton</span> is associated with the second cohomology H2 of the target space. The commutation relation is proportional to the winding number, taking a constant value within each topological sector. The noncommutativity makes it impossible to specify the momentum of a topological <span class="hlt">soliton</span>, and induces a Magnus force.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvL.112s1804W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvL.112s1804W"><span>Noncommuting Momenta of Topological <span class="hlt">Solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Watanabe, Haruki; Murayama, Hitoshi</p> <p>2014-05-01</p> <p>We show that momentum operators of a topological <span class="hlt">soliton</span> may not commute among themselves when the <span class="hlt">soliton</span> is associated with the second cohomology H2 of the target space. The commutation relation is proportional to the winding number, taking a constant value within each topological sector. The noncommutativity makes it impossible to specify the momentum of a topological <span class="hlt">soliton</span>, and induces a Magnus force.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21011275','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21011275"><span><span class="hlt">Soliton-soliton</span> scattering in dipolar Bose-Einstein condensates</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nath, R.; Santos, L.; Pedri, P.</p> <p>2007-07-15</p> <p>We analyze the scattering of bright <span class="hlt">solitons</span> in dipolar Bose-Einstein condensates placed in unconnected layers. Whereas for short-range interactions unconnected layers are independent, a remarkable consequence of the dipole interaction is the appearance of nonlocal interlayer effects. In particular, we show that both for one- and two-dimensional <span class="hlt">solitons</span> the interlayer interaction leads to an effective molecular potential between disconnected <span class="hlt">solitons</span>, which induces a complex scattering physics between them, that includes inelastic fusion into <span class="hlt">soliton</span> molecules, and strong inelastic resonances. In addition, contrary to the short-range interacting case, a two-dimensional <span class="hlt">soliton</span> scattering is possible, in which inelastic spiraling occurs, resembling phenomena in photorefractive materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017OptFT..37...11M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017OptFT..37...11M"><span>Ultrashort dark <span class="hlt">solitons</span> interactions and nonlinear tunneling in the modified nonlinear Schrödinger equation with variable coefficient</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Musammil, N. M.; Porsezian, K.; Nithyanandan, K.; Subha, P. A.; Tchofo Dinda, P.</p> <p>2017-09-01</p> <p>We present the study of the dark <span class="hlt">soliton</span> dynamics in an inhomogeneous fiber by means of a variable coefficient modified nonlinear Schrödinger equation (Vc-MNLSE) with distributed dispersion, self-phase modulation, self-steepening and linear gain/loss. The ultrashort dark <span class="hlt">soliton</span> pulse evolution and interaction is studied by using the Hirota bilinear (HB) method. In particular, we give much insight into the effect of self-steepening (SS) on the dark <span class="hlt">soliton</span> dynamics. The study reveals a shock wave formation, as a major effect of SS. Numerically, we study the dark <span class="hlt">soliton</span> propagation in the continuous wave background, and the stability of the <span class="hlt">soliton</span> solution is tested in the presence of photon noise. The elastic collision behaviors of the dark <span class="hlt">solitons</span> are discussed by the asymptotic analysis. On the other hand, considering the nonlinear tunneling of dark <span class="hlt">soliton</span> through barrier/well, we find that the tunneling of the dark <span class="hlt">soliton</span> depends on the height of the barrier and the amplitude of the <span class="hlt">soliton</span>. The intensity of the tunneling <span class="hlt">soliton</span> either forms a peak or valley and retains its shape after the tunneling. For the case of exponential background, the <span class="hlt">soliton</span> tends to <span class="hlt">compress</span> after tunneling through the barrier/well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22072453','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22072453"><span>Ion-acoustic <span class="hlt">solitons</span> in negative ion plasma with two-electron temperature distributions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mishra, M. K.; Tiwari, R. S.; Chawla, J. K.</p> <p>2012-06-15</p> <p>Ion-acoustic <span class="hlt">solitons</span> in a warm positive and negative ion species with different masses, concentrations, and charge states with two electron temperature distributions are studied. Using reductive perturbation method, Korteweg de-Vries (KdV) and modified-KdV (m-KdV) equations are derived for the system. The <span class="hlt">soliton</span> solution of the KdV and m-KdV equations is discussed in detail. It is found that if the ions have finite temperatures, then there exist two types of modes, namely slow and fast ion-acoustic modes. It is also investigated that the parameter determining the nature of <span class="hlt">soliton</span> (i.e., whether the system will support <span class="hlt">compressive</span> or rarefactive <span class="hlt">solitons</span>) is different for slow and fast modes. For the slow mode, the parameter is the relative temperature of the two ion species; whereas for the fast mode, it is the relative concentration of the two ion species. At a critical concentration of negative ions, both <span class="hlt">compressive</span> and rarefactive <span class="hlt">solitons</span> coexist. The amplitude and width of the <span class="hlt">solitons</span> are discussed in detail at critical concentration for m-KdV <span class="hlt">solitons</span>. The effect of the relative temperature of the two-electron and cold-electron concentration on the characteristics of the <span class="hlt">solitons</span> are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JFM...215..101L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JFM...215..101L"><span>A visual study of the coherent structure of the turbulent boundary layer in flow with adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lian, Qi Xiang</p> <p>1990-06-01</p> <p>Experimental investigations were carried out on the coherent structures of turbulent boundary layers in flow with adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> and, in the vicinity of separation, extensive visual observations using the hydrogen-bubble technique were performed. In a flow with adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span>, the structures are larger, and thus more details were observed. By a suitable manipulation of the generation of hydrogen-bubble time lines, some new results were obtained in observing plan views near the wall. The long streaks downstream along the interface regions between low-speed and high-speed streaks are continually stretching, and their velocity may be greater than that of high-speed streaks; the hydrogen bubbles in the long streaks generally have a longer life. Streamwise (x, y) vortices were also observed along the interface regions between high-speed and low-speed streaks. Transverse (z) vortices were observed at the front of the high-speed regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhFl...23a5101D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhFl...23a5101D"><span>A wall-layer model for large-eddy simulations of turbulent flows with/out <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Duprat, C.; Balarac, G.; Métais, O.; Congedo, P. M.; Brugière, O.</p> <p>2011-01-01</p> <p>In this work, modeling of the near-wall region in turbulent flows is addressed. A new wall-layer model is proposed with the goal to perform high-Reynolds number large-eddy simulations of wall bounded flows in the presence of a streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The model applies both in the viscous sublayer and in the inertial region, without any parameter to switch from one region to the other. An analytical expression for the velocity field as a function of the distance from the wall is derived from the simplified thin-boundary equations and by using a turbulent eddy coefficient with a damping function. This damping function relies on a modified van Driest formula to define the mixing-length taking into account the presence of a streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The model is first validated by a priori comparisons with direct numerical simulation data of various flows with and without streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span> and with eventual flow separation. Large-eddy simulations are then performed using the present wall model as wall boundary condition. A plane channel flow and the flow over a periodic arrangement of hills are successively considered. The present model predictions are compared with those obtained using the wall models previously proposed by Spalding, Trans. ASME, J. Appl. Mech 28, 243 (2008) and Manhart et al., Theor. Comput. Fluid Dyn. 22, 243 (2008). It is shown that the new wall model allows for a good prediction of the mean velocity profile both with and without streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span>. It is shown than, conversely to the previous models, the present model is able to predict flow separation even when a very coarse grid is used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8608K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8608K"><span><span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Error of Spectral Element Dynamical Core associated with Topographic Forcing: Comparison with the Spherical Harmonics Dynamical Core</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kang, Hyun-Gyu; Cheong, Hyeong-Bin; Jeong, Han-Byeol; Kim, Won-Ho</p> <p>2015-04-01</p> <p>Response characteristics of the spectral element hydrostatic dynamical core on the cubed sphere to the global topographic forcing are investigated in terms of <span class="hlt">pressure</span> <span class="hlt">gradient</span> error, and it is compared with the spherical harmonics hydrostatic dynamical core. The vertical hybrid-pressure coordinate and finite difference method are introduced to both dynamical cores, and explicit and implicit hyper-diffusion schemes are applied to spectral element dynamical core and spherical harmonics dynamical core, respectively. The model atmosphere at initial time is set to the quiescent environment so that the term affecting on the time tendency of the momentum equation at the first time step is the <span class="hlt">pressure</span> <span class="hlt">gradient</span> term only which is influenced by the observed surface topography. During 6 days of time integration, the spurious flow is generated due to inaccurate numerical approximations of <span class="hlt">pressure</span> <span class="hlt">gradient</span> term for each dynamical core. High zonal wind speed which can be regarded as numerical error is occurred commonly in two dynamical cores around steep topography (e.g., the Tibetan Plateau, the Rocky Mountains, and the Andes Mountains), but the maximum zonal wind speed at day 6 of spectral element dynamical core is 8-9 times larger than that of spherical harmonics dynamical core. The vertically averaged kinetic energy spectrum at day 6 shows very different trend between two dynamical cores. By performing the experiments with the scale-separated topography, it turns out that these kinetic energy spectrum trends are mainly caused by the small-scale topography. A simple change of <span class="hlt">pressure</span> <span class="hlt">gradient</span> term into log-pressure form is found to significantly reduce numerical error (up to 63% of maximum wind speed in case of spectral element dynamical core) and noise-like small-scale phenomena.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017OcMod.116....1E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017OcMod.116....1E"><span>High-order accurate finite-volume formulations for the <span class="hlt">pressure</span> <span class="hlt">gradient</span> force in layered ocean models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Engwirda, Darren; Kelley, Maxwell; Marshall, John</p> <p>2017-08-01</p> <p>Discretisation of the horizontal <span class="hlt">pressure</span> <span class="hlt">gradient</span> force in layered ocean models is a challenging task, with non-trivial interactions between the thermodynamics of the fluid and the geometry of the layers often leading to numerical difficulties. We present two new finite-volume schemes for the <span class="hlt">pressure</span> <span class="hlt">gradient</span> operator designed to address these issues. In each case, the horizontal acceleration is computed as an integration of the contact pressure force that acts along the perimeter of an associated momentum control-volume. A pair of new schemes are developed by exploring different control-volume geometries. Non-linearities in the underlying equation-of-state definitions and thermodynamic profiles are treated using a high-order accurate numerical integration framework, designed to preserve hydrostatic balance in a non-linear manner. Numerical experiments show that the new methods achieve high levels of consistency, maintaining hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer geometries, non-linear equations-of-state and non-uniform vertical stratification profiles. These results suggest that the new <span class="hlt">pressure</span> <span class="hlt">gradient</span> formulations may be appropriate for general circulation models that employ hybrid vertical coordinates and/or terrain-following representations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......243T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......243T"><span>Experimental Study of Turbulent Flow over Inclined Ribs in Adverse <span class="hlt">Pressure</span> <span class="hlt">Gradient</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsikata, Jonathan Mawuli</p> <p></p> <p>This thesis is an experimental study of turbulent flows over smooth and rough walls in a channel that consists of an upstream parallel section to produce a fully developed channel flow and a diverging section to produce an adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> (APG) flow. The roughness elements used were two-dimensional square ribs of nominal height k = 3 mm. The ribs were secured to the lower wall of the channel and spaced to produce the following three pitches: 2k, 4k and 8 k, corresponding to d-type, intermediate and k-type rough walls, respectively. For each rough wall type, the ribs were inclined at 90°, 45° and 30° to the approach flow. The velocity measurements were performed using a particle image velocimetry technique. The results showed that rib roughness enhanced the drag characteristics, and the degree of enhancement increased with increasing pitch. The level of turbulence production and Reynolds stresses were significantly increased by roughness beyond the roughness sublayer. It was observed that the population, sizes and the level of organization of hairpin vortices varied with roughness and more intense quadrant events were found over the smooth wall than the rough walls. APG reinforced wall roughness in augmenting the equivalent sand grain roughness height, turbulence production and Reynolds stresses. APG also reduced the sizes of the hairpin packets but strengthened the quadrant events in comparison to the results obtained in the parallel section. The secondary flow induced by inclined ribs significantly altered the distributions of the flow characteristics across the span of the channel. Generally, the mean flow was less uniform close to the trailing edge of the ribs compared to the flows at the mid-span and close to the leading edge of the ribs. The Reynolds stresses and hairpin packets were distinctly larger close to the trailing edge of the ribs. Rib inclination also decreased the drag characteristics and significantly modified the distributions of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000070465','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000070465"><span>Preventing Damaging <span class="hlt">Pressure</span> <span class="hlt">Gradients</span> at the Walls of an Inflatable Space System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scialdone, John J.</p> <p>2000-01-01</p> <p>An inflatable structural system to deploy a space system such as a solar shield, an antenna or another similar instrument, requires a stiffening element after it is extended by the inflated gas pressure. The stiffening element has to be packaged in a folded configuration before the deployment. It must be relatively small, lightweight, non-damaging to the inflated system, and be able to become stiff in a short time. One stiffening method is to use a flexible material inserted in the deployable system, which, upon a temperature curing, can become stiff and is capable to support the entire structure. There are two conditions during the space operations when the inflated volume could be damaged: during the transonic region of the launch phase and when the curing of the rigidizing element occurs. In both cases, an excess of pressure within the volume containing the rigid element could burst the walls of the low-pressure gas inflated portion of the system. This paper investigates those two conditions and indicates the vents, which will prevent those damaging overpressures. Vent openings at the non-inflated volumes have been calculated for the conditions existing during the launch. Those vents allow the initially folded volume to exhaust the trapped atmospheric gas at approximately the same rate as the ambient pressure drops. That will prevent <span class="hlt">pressure</span> <span class="hlt">gradients</span> across the container walls which otherwise could be as high as 14.7 psi. The other condition occurring during the curing of the stiffening element has been investigated. This has required the testing of the element to obtain the gas generation during the curing and the transformation from a pliable material to a rigid one. The tested material is a composite graphite/epoxy weave. The outgassing of the uncured sample at 121C was carried with the Cahn Microbalance and with other outgassing facilities including the micro-CVCM ASTM E-595 facility. The tests provided the mass of gas evolved during the test. That data</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000090512','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000090512"><span>Preventing Damaging <span class="hlt">Pressure</span> <span class="hlt">Gradients</span> at the Walls of an Inflatable Space System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Scialdone, John J.; Powers, Edward I. (Technical Monitor)</p> <p>2000-01-01</p> <p>An inflatable structural system to deploy a space system such as a solar shield, an antenna or another similar instrument requires a stiffening element after it is extended by the inflated gas pressure. The stiffening element has to be packaged in folded configuration before the deployment. It must be relatively small, lightweight, non-damaging to the inflated system and be able to become stiff in a short time. One stiffening method is to use a flexible material inserted in the deployable system, which, upon a temperature curing, can become stiff and is capable of supporting the entire structure. There are two conditions during the space operations when the inflated volume could be damaged: during the transonic region of the launch phase and when the curing of the rigidizing element occurs. In both cases, an excess of pressure within the volume containing the rigid element could burst the walls of the low-pressure gas inflated portion of the system. This paper investigates those two conditions and indicates the vents, which will prevent those damaging overpressures. Vent openings at the non-inflated volumes have been calculated for the conditions existing during the launch. Those vents allow the initially folded volume to exhaust the trapped atmospheric gas at approximately the same rate as the ambient pressure drops. That will prevent <span class="hlt">pressure</span> <span class="hlt">gradients</span> across the container walls which otherwise could be as high as 14.7 psi. The other condition occurring during the curing of the stiffening element has been investigated. This has required the testing of the element to obtain the gas generation during the curing and the transformation from a pliable material to a rigid on The tested material is a composite graphite/epoxy weave. The outgassing of the uncured sample at 121 deg Celcius was carried with the Cahn Microbalance and with other outgassing facilities including the micro-CVCM ASTM E-595 facility. The test provided the mass of gas evolved during the test. That</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...631296B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...631296B"><span><span class="hlt">Soliton</span> driven angiogenesis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bonilla, L. L.; Carretero, M.; Terragni, F.; Birnir, B.</p> <p>2016-08-01</p> <p>Angiogenesis is a multiscale process by which blood vessels grow from existing ones and carry oxygen to distant organs. Angiogenesis is essential for normal organ growth and wounded tissue repair but it may also be induced by tumours to amplify their own growth. Mathematical and computational models contribute to understanding angiogenesis and developing anti-angiogenic drugs, but most work only involves numerical simulations and analysis has lagged. A recent stochastic model of tumour-induced angiogenesis including blood vessel branching, elongation, and anastomosis captures some of its intrinsic multiscale structures, yet allows one to extract a deterministic integropartial differential description of the vessel tip density. Here we find that the latter advances chemotactically towards the tumour driven by a <span class="hlt">soliton</span> (similar to the famous Korteweg-de Vries <span class="hlt">soliton</span>) whose shape and velocity change slowly. Analysing these collective coordinates paves the way for controlling angiogenesis through the <span class="hlt">soliton</span>, the engine that drives this process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890054720&hterms=compressible+flow+adiabatic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcompressible%2Bflow%2Badiabatic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890054720&hterms=compressible+flow+adiabatic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcompressible%2Bflow%2Badiabatic"><span>A skin friction law for <span class="hlt">compressible</span> turbulent flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barnwell, Richard W.; Wahls, Richard A.</p> <p>1989-01-01</p> <p>An algebraic skin friction law is derived for adiabatic, <span class="hlt">compressible</span>, equilibrium, turbulent boundary layer flow. An outer solution in terms of the Clauser defect stream function is matched to an inner empirical expression composed of <span class="hlt">compressible</span> laws of the wall and wake. The modified Crocco temperature-velocity relationship and the Clauser eddy viscousity model are used in the outer solution. The skin friction law pertains for all <span class="hlt">pressure</span> <span class="hlt">gradients</span> in the incompressible through supersonic range and for small <span class="hlt">pressure</span> <span class="hlt">gradients</span> in the hypersonic range. Excellent comparisons with experiment are obtained in the appropriate parameter ranges. The application to numerical computation is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatPh..13...53Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatPh..13...53Y"><span>Stokes <span class="hlt">solitons</span> in optical microcavities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yang, Qi-Fan; Yi, Xu; Yang, Ki Youl; Vahala, Kerry</p> <p>2017-01-01</p> <p><span class="hlt">Solitons</span> are wave packets that resist dispersion through a self-induced potential well. They are studied in many fields, but are especially well known in optics on account of the relative ease of their formation and control in optical fibre waveguides. Besides their many interesting properties, <span class="hlt">solitons</span> are important to optical continuum generation, in mode-locked lasers, and have been considered as a natural way to convey data over great distances. Recently, <span class="hlt">solitons</span> have been realized in microcavities, thereby bringing the power of microfabrication methods to future applications. This work reports a <span class="hlt">soliton</span> not previously observed in optical systems, the Stokes <span class="hlt">soliton</span>. The Stokes <span class="hlt">soliton</span> forms and regenerates by optimizing its Raman interaction in space and time within an optical potential well shared with another <span class="hlt">soliton</span>. The Stokes and the initial <span class="hlt">soliton</span> belong to distinct transverse mode families and benefit from a form of <span class="hlt">soliton</span> trapping that is new to microcavities and <span class="hlt">soliton</span> lasers in general. The discovery of a new optical <span class="hlt">soliton</span> can impact work in other areas of photonics, including nonlinear optics and spectroscopy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AIPC.1479..536B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AIPC.1479..536B"><span>Classically spinning and isospinning <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Battye, Richard A.; Haberichter, Mareike</p> <p>2012-09-01</p> <p>We investigate classically spinning topological <span class="hlt">solitons</span> in (2+1)- and (3+1)-dimensional models; more explicitely spinning sigma model <span class="hlt">solitons</span> in 2+1 dimensions and Skyrme <span class="hlt">solitons</span> in 2+1 and 3+1 dimensions. For example, such types of <span class="hlt">solitons</span> can be used to describe quasiparticle excitations in ferromagnetic quantum Hall systems or to model spin and isospin states of nuclei. The standard way to obtain <span class="hlt">solitons</span> with quantised spin and isospin is the semiclassical quantization procedure: One parametrizes the zero-mode space - the space of energy-degenerate <span class="hlt">soliton</span> configurations generated from a single <span class="hlt">soliton</span> by spatial translations and rotations in space and isospace - by collective coordinates which are then taken to be time-dependent. This gives rise to additional dynamical terms in the Hamiltonian which can then be quantized following semiclassical quantization rules. A simplification which is often made in the literature is to apply a simple adiabatic approximation to the (iso)rotational zero modes of the <span class="hlt">soliton</span> by assuming that the <span class="hlt">soliton</span>'s shape is rotational frequency independent. Our numerical results on classically spinning arbitrarily deforming <span class="hlt">soliton</span> solutions clearly show that <span class="hlt">soliton</span> deformation cannot be ignored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22560317','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22560317"><span>Accessible <span class="hlt">solitons</span> of fractional dimension</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhong, Wei-Ping; Belić, Milivoj; Zhang, Yiqi</p> <p>2016-05-15</p> <p>We demonstrate that accessible <span class="hlt">solitons</span> described by an extended Schrödinger equation with the Laplacian of fractional dimension can exist in strongly nonlocal nonlinear media. The <span class="hlt">soliton</span> solutions of the model are constructed by two special functions, the associated Legendre polynomials and the Laguerre polynomials in the fraction-dimensional space. Our results show that these fractional accessible <span class="hlt">solitons</span> form a <span class="hlt">soliton</span> family which includes crescent <span class="hlt">solitons</span>, and asymmetric single-layer and multi-layer necklace <span class="hlt">solitons</span>. -- Highlights: •Analytic solutions of a fractional Schrödinger equation are obtained. •The solutions are produced by means of self-similar method applied to the fractional Schrödinger equation with parabolic potential. •The fractional accessible <span class="hlt">solitons</span> form crescent, asymmetric single-layer and multilayer necklace profiles. •The model applies to the propagation of optical pulses in strongly nonlocal nonlinear media.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/254136','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/254136"><span>Weakly relativistic <span class="hlt">solitons</span> in a cold plasma with electron inertia</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kalita, B.C.; Barman, S.N.; Goswami, G.</p> <p>1996-01-01</p> <p>Ion-acoustic <span class="hlt">solitons</span> have been investigated in a cold plasma in the presence of electron inertia through the derivation of the Korteweg{endash}de Vries (KdV) equation taking into account of weakly relativistic effects. Interestingly, relativistic <span class="hlt">solitons</span> of both <span class="hlt">compressive</span> and rarefactive characters are found to exist at the negligible difference of {ital u}{sub 0}/{ital c} and {ital v}{sub 0}/{ital c} ({ital u}{sub 0}, {ital v}{sub 0} being the initial speeds of streaming electrons and ions respectively, and {ital c}, the velocity of light) of the order 1{times}10{sup -7}. {copyright} {ital 1996 American Institute of Physics.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16599743','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16599743"><span>Moving embedded lattice <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Malomed, B A; Fujioka, J; Espinosa-Cerón, A; Rodríguez, R F; González, S</p> <p>2006-03-01</p> <p>It was recently proved that <span class="hlt">solitons</span> embedded in the spectrum of linear waves may exist in discrete systems, and explicit solutions for isolated unstable embedded lattice <span class="hlt">solitons</span> (ELS) of a differential-difference version of a higher-order nonlinear Schrodinger equation were found [Gonzalez-Perez-Sandi, Fujioka, and Malomed, Physica D 197, 86 (2004)]. The discovery of these ELS gives rise to relevant questions such as the following: (1) Are there continuous families of ELS? (2) Can ELS be stable? (3) Is it possible for ELS to move along the lattice? (4) How do ELS interact? The present work addresses these questions by showing that a novel equation (a discrete version of a complex modified Korteweg-de Vries equation that includes next-nearest-neighbor couplings) has a two-parameter continuous family of exact ELS. These <span class="hlt">solitons</span> can move with arbitrary velocities across the lattice, and the numerical simulations demonstrate that these ELS are completely stable. Moreover, the numerical tests show that these ELS are robust enough to withstand collisions, and the result of a collision is only a shift in the positions of the <span class="hlt">solitons</span>. The model may apply to the description of a Bose-Einstein condensate with dipole-dipole interactions between the atoms, trapped in a deep optical-lattice potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11736300','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11736300"><span>Ring <span class="hlt">solitons</span> on vortices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kevrekidis, P G; Nistazakis, H E; Frantzeskakis, D J; Malomed, B A; Bishop, A R</p> <p>2001-12-01</p> <p>Interaction of a ring dark or antidark <span class="hlt">soliton</span> (RDS and RADS, respectively) with a vortex is considered in the defocusing nonlinear Schrödinger equation with cubic (for RDS) or saturable (for RADS) nonlinearities. By means of direct simulations, it is found that the interaction gives rise to either an almost isotropic or a spiral-like pattern. A transition between them occurs at a critical value of the RDS or RADS amplitude, the spiral pattern appearing if the amplitude exceeds the critical value. An initial ring <span class="hlt">soliton</span> created on top of the vortex splits into a pair of rings moving inward and outward. In the subcritical case, the inbound ring reverses its polarity, bouncing from the vortex core, without conspicuous effect on the core. In the transcritical case, the bounced ring <span class="hlt">soliton</span> suffers a spiral deformation, while the vortex changes its position and structure and also loses its axial symmetry. Through a variational-type approach to the system's Hamiltonian, we additionally find that the vortex-RDS and vortex-RADS interactions are, respectively, attractive and repulsive. Simulations with the vortex placed eccentrically with respect to the RDS or RADS reveal the generation of strongly localized multispot dark and/or antidark coherent structures. The occurrence of spiral-like patterns in many numerical experiments prompted an attempt to generate a spiral dark <span class="hlt">soliton</span>, but the latter is found to suffer a core instability that converts it into a rotating dipole emitting waves in the outward direction.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/40203393','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/40203393"><span>Walking cavity <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Skryabin, Dmitry V.; Champneys, Alan R.</p> <p>2001-06-01</p> <p>A family of walking <span class="hlt">solitons</span> is obtained for the degenerate optical parametric oscillator below threshold. The loss-driven mechanism of velocity selection for these structures is described analytically and numerically. Our approach is based on understanding the role played by the field momentum and generic symmetry properties and, therefore, it can be easily generalized to other dissipative multicomponent models with walk off.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060041530&hterms=pressure+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dpressure%2Bmodel','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060041530&hterms=pressure+model&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dpressure%2Bmodel"><span>A General <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Formulation for Ocean Models, Part 1: Scheme Design and Diagnostic Analysis, Part II: Energy, Momentum, and Bottom Torque Consistency</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Song, Y. T.</p> <p>1998-01-01</p> <p>A Jacobian formulation of the <span class="hlt">pressure</span> <span class="hlt">gradient</span> force for use in models with topography following coordinates is proposed. It can be used in conjunction with any vertical coordinate system and is easily implemented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830054819&hterms=sigma+model&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsigma%2Bmodel','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830054819&hterms=sigma+model&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsigma%2Bmodel"><span>A comparison of methods for computing the sigma-coordinate <span class="hlt">pressure</span> <span class="hlt">gradient</span> force for flow over sloped terrain in a hybrid theta-sigma model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Johnson, D. R.; Uccellini, L. W.</p> <p>1983-01-01</p> <p>In connection with the employment of the sigma coordinates introduced by Phillips (1957), problems can arise regarding an accurate finite-difference computation of the <span class="hlt">pressure</span> <span class="hlt">gradient</span> force. Over steeply sloped terrain, the calculation of the sigma-coordinate <span class="hlt">pressure</span> <span class="hlt">gradient</span> force involves computing the difference between two large terms of opposite sign which results in large truncation error. To reduce the truncation error, several finite-difference methods have been designed and implemented. The present investigation has the objective to provide another method of computing the sigma-coordinate <span class="hlt">pressure</span> <span class="hlt">gradient</span> force. Phillips' method is applied for the elimination of a hydrostatic component to a flux formulation. The new technique is compared with four other methods for computing the <span class="hlt">pressure</span> <span class="hlt">gradient</span> force. The work is motivated by the desire to use an isentropic and sigma-coordinate hybrid model for experiments designed to study flow near mountainous terrain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060041530&hterms=ocean+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Docean%2Benergy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060041530&hterms=ocean+energy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Docean%2Benergy"><span>A General <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Formulation for Ocean Models, Part 1: Scheme Design and Diagnostic Analysis, Part II: Energy, Momentum, and Bottom Torque Consistency</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Song, Y. T.</p> <p>1998-01-01</p> <p>A Jacobian formulation of the <span class="hlt">pressure</span> <span class="hlt">gradient</span> force for use in models with topography following coordinates is proposed. It can be used in conjunction with any vertical coordinate system and is easily implemented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960015858','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960015858"><span>A Study of the Development of Steady and Periodic Unsteady Turbulent Wakes Through Curved Channels at Positive, Zero, and Negative Streamwise <span class="hlt">Pressure</span> <span class="hlt">Gradients</span>, Part 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schobeiri, M. T.; John, J.</p> <p>1996-01-01</p> <p>The turbomachinery wake flow development is largely influenced by streamline curvature and streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The objective of this investigation is to study the development of the wake under the influence of streamline curvature and streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The experimental investigation is carried out in two phases. The first phase involves the study of the wake behind a stationary circular cylinder (steady wake) in curved channels at positive, zero, and negative streamwise <span class="hlt">pressure</span> <span class="hlt">gradients</span>. The mean velocity and Reynolds stress components are measured using a X-hot-film probe. The measured quantities obtained in probe coordinates are transformed to a curvilinear coordinate system along the wake centerline and are presented in similarity coordinates. The results of the steady wakes suggest strong asymmetry in velocity and Reynolds stress components. However, the velocity defect profiles in similarity coordinates are almost symmetrical and follow the same distribution as the zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> straight wake. The results of Reynolds stress distributions show higher values on the inner side of the wake than the outer side. Other quantities, including the decay of maximum velocity defect, growth of wake width, and wake integral parameters, are also presented for the three different <span class="hlt">pressure</span> <span class="hlt">gradient</span> cases of steady wake. The decay rate of velocity defect is fastest for the negative streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span> case and slowest for the positive <span class="hlt">pressure</span> <span class="hlt">gradient</span> case. Conversely, the growth of the wake width is fastest for the positive streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span> case and slowest for the negative streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The second phase studies the development of periodic unsteady wakes generated by the circular cylinders of the rotating wake generator in a curved channel at zero streamwise <span class="hlt">pressure</span> <span class="hlt">gradient</span>. Instantaneous velocity components of the periodic unsteady wakes, measured with a stationary X-hot-film probe, are analyzed by the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24787565','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24787565"><span>Analysis of the intraocular jet flows and <span class="hlt">pressure</span> <span class="hlt">gradients</span> induced by air and fluid infusion: mechanism of focal chorioretinal damage.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Yong Joon; Jo, Sungkil; Moon, Daruchi; Joo, Youngcheol; Choi, Kyung Seek</p> <p>2014-05-01</p> <p>To comprehend the mechanism of focal chorioretinal damage by analysis of the pressure distribution and dynamic pressure induced by infused air during fluid-air exchange. A precise simulation featuring a model eye and a fluid circuit was designed to analyze fluid-air exchange. The pressure distribution, flow velocity, and dynamic pressure induced by infusion of air into an air-filled eye were analyzed using an approach based on fluid dynamics. The size of the port and the infusion pressure were varied during simulated iterations. We simulated infusion of an air-filled eye with balanced salt solution (BSS) to better understand the mechanism of chorioretinal damage induced by infused air. Infused air was projected straight toward a point on the retina contralateral to the infusion port (the "vulnerable point"). The highest pressure was evident at the vulnerable point, and the lowest pressure was recorded on most retinal areas. Simulations using greater infusion pressure and a port of larger size were associated with elevations in dynamic pressure and the <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The <span class="hlt">pressure</span> <span class="hlt">gradients</span> were 2.8 and 5.1 mm Hg, respectively, when infusion pressures of 30 and 50 mm Hg were delivered through a 20-gauge port. The <span class="hlt">pressure</span> <span class="hlt">gradient</span> associated with BSS infusion was greater than that created by air, but lasted for only a moment. Our simulation explains the mechanism of focal chorioretinal damage in numerical terms. Infused air induces a prolonged increase in focal pressure on the vulnerable point, and this may be responsible for visual field defects arising after fluid-air exchange. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920069951&hterms=Kdv&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DKdv','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920069951&hterms=Kdv&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DKdv"><span>Formation of quasiparallel Alfven <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hamilton, R. L.; Kennel, C. F.; Mjolhus, E.</p> <p>1992-01-01</p> <p>The formation of quasi-parallel Alfven <span class="hlt">solitons</span> is investigated through the inverse scattering transformation (IST) for the derivative nonlinear Schroedinger (DNLS) equation. The DNLS has a rich complement of <span class="hlt">soliton</span> solutions consisting of a two-parameter <span class="hlt">soliton</span> family and a one-parameter bright/dark <span class="hlt">soliton</span> family. In this paper, the physical roles and origins of these <span class="hlt">soliton</span> families are inferred through an analytic study of the scattering data generated by the IST for a set of initial profiles. The DNLS equation has as limiting forms the nonlinear Schroedinger (NLS), Korteweg-de-Vries (KdV) and modified Korteweg-de-Vries (MKdV) equations. Each of these limits is briefly reviewed in the physical context of quasi-parallel Alfven waves. The existence of these limiting forms serves as a natural framework for discussing the formation of Alfven <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21528745','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21528745"><span>Shaping <span class="hlt">solitons</span> by lattice defects</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dong Liangwei; Ye Fangwei</p> <p>2010-11-15</p> <p>We demonstrate the existence of shape-preserving self-localized nonlinear modes in a two-dimensional photonic lattice with a flat-topped defect that covers several lattice sites. The balance of diffraction, defocusing nonlinearity, and optical potential induced by lattices with various forms of defects results in novel families of <span class="hlt">solitons</span> featuring salient properties. We show that the <span class="hlt">soliton</span> shape can be controlled by varying the shape of lattice defects. The existence domains of fundamental and vortex <span class="hlt">solitons</span> in the semi-infinite gap expand with the defect amplitude. Vortex <span class="hlt">solitons</span> in the semi-infinite gap with rectangular intensity distributions will break into dipole <span class="hlt">solitons</span> when the propagation constant exceeds a critical value. In the semi-infinite and first-finite gaps, we find that lattices with rectangular defects can support stable vortex <span class="hlt">solitons</span> which exhibit noncanonical phase structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JFM...221....1K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JFM...221....1K"><span>On the evolution of the turbulent spot in a laminar boundary layer with a favourable <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Katz, Y.; Seifert, A.; Wygnanski, I.</p> <p>1990-12-01</p> <p>An investigation is conducted of the evolution of a turbulent spot in an accelerating boundary layer which faithfully resembles the flow in the vicinity of a stagnation point theoretically characterized by Falkner and Skan. The spot's rate of growth was substantially inhibited by the favorable <span class="hlt">pressure</span> <span class="hlt">gradient</span> in all three directions. Dimensional analysis was used to identify and correlate the independent variables responsible for the spot's size, convection speed, and relative rate of growth. The arrowhead shape of the spot gave way to a rounded triangular shape whose trailing interface was straight and perpendicular to the direction of streaming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950008193','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950008193"><span>A Modified Mixing Length Turbulence Model for Zero and Adverse <span class="hlt">Pressure</span> <span class="hlt">Gradients</span>. M.S. Thesis - Akron Univ., 1993</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Conley, Julianne M.; Leonard, B. P.</p> <p>1994-01-01</p> <p>The modified mixing length (MML) turbulence model was installed in the Proteus Navier-Stokes code, then modified to make it applicable to a wider range of flows typical of aerospace propulsion applications. The modifications are based on experimental data for three flat-plate flows having zero, mild adverse, and strong adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span>. Three transonic diffuser test cases were run with the new version of the model in order to evaluate its performance. All results are compared with experimental data and show improvements over calculations made using the Baldwin-Lomax turbulence model, the standard algebraic model in Proteus.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750052813&hterms=fe&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfe','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750052813&hterms=fe&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dfe"><span>Application of a general boundary layer analysis to turbulent boundary layers subjected to strong favorable <span class="hlt">pressure</span> <span class="hlt">gradients</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kreskovsky, J. P.; Shamroth, S. J.; Mcdonald, H.</p> <p>1975-01-01</p> <p>Theoretical predictions of turbulent boundary layer development under the influence of strong favorable <span class="hlt">pressure</span> <span class="hlt">gradients</span> made using a finite-difference calculation procedure are compared to experimental data. Comparisons are presented for low speed flows with and without wall heat transfer as well as for supersonic flows with adiabatic walls. The turbulence model used is governed by an integral form of the turbulence kinetic energy equation and the results are compared with predictions made using a conventional equilibrium turbulence model based upon Prandtl's mixing length, a Clauser-type eddy viscosity model used by Cebecci and Mosinskis, and a two-equation turbulence energy model of Launder and Jones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21230428','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21230428"><span>Role of hydrodynamic interactions in the migration of polyelectrolytes driven by a <span class="hlt">pressure</span> <span class="hlt">gradient</span> and an electric field.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kekre, Rahul; Butler, Jason E; Ladd, Anthony J C</p> <p>2010-11-01</p> <p>Experiments have shown that DNA molecules in capillary electrophoresis migrate across field lines if a <span class="hlt">pressure</span> <span class="hlt">gradient</span> is applied simultaneously. We suggest that this migration results from an electrically driven flow field around the polyelectrolyte, which generates additional contributions to the center-of-mass velocity if the overall polymer conformation is asymmetric. This hypothesis leads to a coarse-grained polymer model, without explicit charges, that quantitatively explains the experimentally observed migration. The simulations contradict the widely held notion that charge neutrality eliminates the effects of hydrodynamic interactions in electrically driven flows of polyelectrolytes. We predict a measurable increase in the electrophoretic velocity of a sheared polyelectrolyte that depends on chain length.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17351250','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17351250"><span><span class="hlt">Pressure</span> <span class="hlt">gradients</span> along whole culms and leaf sheaths, and other aspects of humidity-induced gas transport in Phragmites australis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Afreen, F; Zobayed, S M A; Armstrong, J; Armstrong, W</p> <p>2007-01-01</p> <p>Emergent aquatic macrophytes growing in waterlogged anaerobic sediments overlain by deep water require particularly efficient ventilating systems. In Phragmites australis (Cav.) Trin. ex Steud, pressurized gas flows, generated by humidity-induced diffusion of air into leaf sheaths, enhance oxygen transport to below-ground parts and aid in the removal of respiratory CO2 and sediment-generated CO2 and methane. Although modelling and flow measurements have pointed to the probable involvement of all leaf sheaths in the flow process and the development of <span class="hlt">pressure</span> <span class="hlt">gradients</span> along the whole lengths of living culm and leaf sheaths, direct measurements of <span class="hlt">pressure</span> <span class="hlt">gradients</span> have never been reported. The aim of this study was to search for <span class="hlt">pressure</span> <span class="hlt">gradient</span> development in Phragmites culms and leaf sheaths and to determine their magnitudes and distribution. In addition, dynamic (with gas flow) and static pressures (no flow condition) and their relationship to flows, leaf sheath areas, and living-to-dead culm ratios were further investigated. Dynamic pressures (DeltaPd) recorded in the pith cavities of intact (non-excised) leafy culms, pneumatically isolated from the below-ground parts and venting through an artificial bore-hole near the base, revealed a curvilinear gradient of pressure 'asymptoting' towards the tips of the culms. Similarly, DeltaPd in upper and lower parts of leaf sheaths increased with distance from the base of the culm, with values in the upper parts always being greater. Curvilinear gradients of pressure were also found along pneumatically isolated individual leaf sheaths, but radial channels linking the leaf sheath aerenchyma with the pith cavity of the culm appeared to offer little resistance to flow. In keeping with predictions, static pressure differentials (DeltaPs) achieved in intact and excised culms and single leaf sheaths on intact culms proved to be relatively independent of leaf sheath area, whereas the potential for developing convective flows</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810012482','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810012482"><span>The influence of a high <span class="hlt">pressure</span> <span class="hlt">gradient</span> on unsteady velocity perturbations in the case of a turbulent supersonic flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dussauge, J. P.; Debieve, J. F.</p> <p>1980-01-01</p> <p>The amplification or reduction of unsteady velocity perturbations under the influence of strong flow acceleration or deceleration was studied. Supersonic flows with large velocity, <span class="hlt">pressure</span> <span class="hlt">gradients</span>, and the conditions in which the velocity fluctuations depend on the action of the average gradients of pressure and velocity rather than turbulence, are described. Results are analyzed statistically and interpreted as a return to laminar process. It is shown that this return to laminar implies negative values in the turbulence production terms for kinetic energy. A simple geometrical representation of the Reynolds stress production is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013IJMPS..22..675U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013IJMPS..22..675U"><span><span class="hlt">Soliton</span> Pulse Analysis in GaInP Photonic Crystal Waveguide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Upadhyay, P. K.; Nagar, A. K.</p> <p></p> <p><span class="hlt">Solitons</span> are nonlinear waves that remain invariant as they propagate. Precise control of dispersion and nonlinear effects govern <span class="hlt">soliton</span> propagation. In recent years Photonic crystals (PhCs) have attracted a great deal of attention due to the facility to engineer and enhance both their nonlinear and dispersive effects. In this article we show <span class="hlt">soliton</span> pulse analysis in GaInP Photonic Crystal Waveguides using AUTO bifurcation analysis tool. We have demonstrated pulse <span class="hlt">compression</span> at moderately slow velocities in GaInP Photonic Crystal Waveguides. This is enabled by the enhanced self phase modulation and strong negative group velocity dispersion in the Photonic Crystal Waveguides.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhL.107x1107Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhL.107x1107Z"><span>All-fiber nonlinearity- and dispersion-managed dissipative <span class="hlt">soliton</span> nanotube mode-locked laser</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Z.; Popa, D.; Wittwer, V. J.; Milana, S.; Hasan, T.; Jiang, Z.; Ferrari, A. C.; Ilday, F. Ö.</p> <p>2015-12-01</p> <p>We report dissipative <span class="hlt">soliton</span> generation from an Yb-doped all-fiber nonlinearity- and dispersion-managed nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative <span class="hlt">solitons</span> with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally <span class="hlt">compressed</span> to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22486223','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22486223"><span>All-fiber nonlinearity- and dispersion-managed dissipative <span class="hlt">soliton</span> nanotube mode-locked laser</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhang, Z.; Popa, D. Wittwer, V. J.; Milana, S.; Hasan, T.; Jiang, Z.; Ferrari, A. C.; Ilday, F. Ö.</p> <p>2015-12-14</p> <p>We report dissipative <span class="hlt">soliton</span> generation from an Yb-doped all-fiber nonlinearity- and dispersion-managed nanotube mode-locked laser. A simple all-fiber ring cavity exploits a photonic crystal fiber for both nonlinearity enhancement and dispersion compensation. The laser generates stable dissipative <span class="hlt">solitons</span> with large linear chirp in the net normal dispersion regime. Pulses that are 8.7 ps long are externally <span class="hlt">compressed</span> to 118 fs, outperforming current nanotube-based Yb-doped fiber laser designs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28569889','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28569889"><span><span class="hlt">Soliton</span>-plasma nonlinear dynamics in mid-IR gas-filled hollow-core fibers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Selim Habib, Md; Markos, Christos; Bang, Ole; Bache, Morten</p> <p>2017-06-01</p> <p>We investigate numerically <span class="hlt">soliton</span>-plasma interaction in a noble-gas-filled silica hollow-core anti-resonant fiber pumped in the mid-IR at 3.0 μm. We observe multiple <span class="hlt">soliton</span> self-<span class="hlt">compression</span> stages due to distinct stages where either the self-focusing or the self-defocusing nonlinearity dominates. Specifically, the parameters may be tuned so the competing plasma self-defocusing nonlinearity only dominates over the Kerr self-focusing nonlinearity around the <span class="hlt">soliton</span> self-<span class="hlt">compression</span> stage, where the increasing peak intensity on the leading pulse edge initiates a competing self-defocusing plasma nonlinearity acting nonlocally on the trailing edge, effectively preventing <span class="hlt">soliton</span> formation there. As the plasma switches off after the self-<span class="hlt">compression</span> stage, self-focusing dominates again, initiating another <span class="hlt">soliton</span> self-<span class="hlt">compression</span> stage in the trailing edge. This process is accompanied by supercontinuum generation spanning 1-4 μm. We find that the spectral coherence drops as the secondary <span class="hlt">compression</span> stage is initiated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013NatSR...3E2272K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013NatSR...3E2272K"><span>Biological <span class="hlt">soliton</span> in multicellular movement</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuwayama, Hidekazu; Ishida, Shuji</p> <p>2013-07-01</p> <p><span class="hlt">Solitons</span> have been observed in various physical phenomena. Here, we show that the distinct characteristics of <span class="hlt">solitons</span> are present in the mass cell movement of non-chemotactic mutants of the cellular slime mould Dictyostelium discoideum. During starvation, D. discoideum forms multicellular structures that differentiate into spore or stalk cells and, eventually, a fruiting body. Non-chemotactic mutant cells do not form multicellular structures; however, they do undergo mass cell movement in the form of a pulsatile <span class="hlt">soliton</span>-like structure (SLS). We also found that SLS induction is mediated by adhesive cell-cell interactions. These observations provide novel insights into the mechanisms of biological <span class="hlt">solitons</span> in multicellular movement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995stia.book.....G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995stia.book.....G"><span><span class="hlt">Soliton</span> Theory and Its Applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gu, Chaohao</p> <p></p> <p><span class="hlt">Soliton</span> theory is an important branch of applied mathematics and mathematical physics. An active and productive field of research, it has important applications in fluid mechanics, nonlinear optics, classical and quantum fields theories etc. This book presents a broad view of <span class="hlt">soliton</span> theory. It gives an expository survey of the most basic ideas and methods, such as physical background, inverse scattering, Backlünd transformations, finite-dimensional completely integrable systems, symmetry, Kac-moody algebra, <span class="hlt">solitons</span> and differential geometry, numerical analysis for nonlinear waves, and gravitational <span class="hlt">solitons</span>. Besides the essential points of the theory, several applications are sketched and some recent developments, partly by the authors and their collaborators, are presented.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70034727','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70034727"><span><span class="hlt">Pressure-gradient</span>-driven nearshore circulation on a beach influenced by a large inlet-tidal shoal system</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Shi, F.; Hanes, D.M.; Kirby, J.T.; Erikson, L.; Barnard, P.; Eshleman, J.</p> <p>2011-01-01</p> <p>The nearshore circulation induced by a focused pattern of surface gravity waves is studied at a beach adjacent to a major inlet with a large ebb tidal shoal. Using a coupled wave and wave-averaged nearshore circulation model, it is found that the nearshore circulation is significantly affected by the heterogeneous wave patterns caused by wave refraction over the ebb tidal shoal. The model is used to predict waves and currents during field experiments conducted near the mouth of San Francisco Bay and nearby Ocean Beach. The field measurements indicate strong spatial variations in current magnitude and direction and in wave height and direction along Ocean Beach and across the ebb tidal shoal. Numerical simulations suggest that wave refraction over the ebb tidal shoal causes wave focusing toward a narrow region at Ocean Beach. Due to the resulting spatial variation in nearshore wave height, wave-induced setup exhibits a strong alongshore nonuniformity, resulting in a dramatic change in the pressure field compared to a simulation with only tidal forcing. The analysis of momentum balances inside the surf zone shows that, under wave conditions with intensive wave focusing, the alongshore <span class="hlt">pressure</span> <span class="hlt">gradient</span> associated with alongshore nonuniform wave setup can be a dominant force driving circulation, inducing heterogeneous alongshore currents. <span class="hlt">Pressure-gradient</span>- forced alongshore currents can exhibit flow reversals and flow convergence or divergence, in contrast to the uniform alongshore currents typically caused by tides or homogeneous waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001IJNAM..25..307G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001IJNAM..25..307G"><span>Finite element analysis of land subsidence above depleted reservoirs with pore <span class="hlt">pressure</span> <span class="hlt">gradient</span> and total stress formulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gambolati, Giuseppe; Ferronato, Massimiliano; Teatini, Pietro; Deidda, Roberto; Lecca, Giuditta</p> <p>2001-04-01</p> <p>The solution of the poroelastic equations for predicting land subsidence above productive gas/oil fields may be addressed by the principle of virtual works using either the effective intergranular stress, with the pore <span class="hlt">pressure</span> <span class="hlt">gradient</span> regarded as a distributed body force, or the total stress incorporating the pore pressure. In the finite element (FE) method both approaches prove equivalent at the global assembled level. However, at the element level apparently the equivalence does not hold, and the strength source related to the pore pressure seems to generate different local forces on the element nodes. The two formulations are briefly reviewed and discussed for triangular and tetrahedral finite elements. They are shown to yield different results at the global level as well in a three-dimensional axisymmetric porous medium if the FE integration is performed using the average element-wise radius. A modification to both formulations is suggested which allows to correctly solve the problem of a finite reservoir with an infinite <span class="hlt">pressure</span> <span class="hlt">gradient</span>, i.e. with a pore pressure discontinuity on its boundary.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27810603','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27810603"><span>Overdrainage after ventriculoperitoneal shunting in a patient with a wide depressed skull bone defect: The effect of atmospheric <span class="hlt">pressure</span> <span class="hlt">gradient</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, Lixiang; Yu, Jinlu; Sun, Lichao; Han, Yanwu; Wang, Guangming</p> <p>2016-01-01</p> <p>In patients with traumatic brain injury, an effective approach for managing refractory intracranial hypertension is wide decompressive craniectomy. Postoperative hydrocephalus is a frequent complication requiring cerebrospinal fluid (CSF) diversion. A 50-year-old male who underwent decompressive craniectomy after traumatic brain injury. He developed hydrocephalus postoperatively, and accordingly we placed a ventriculoperitoneal shunt. However, an imbalance between the intra- and extra-cranial atmospheric pressures led to overdrainage, and he suffered cognitive disorders and extremity weakness. He remained supine for 5days to avoid the effect of gravity on CSF diversion. After 20days, we performed a cranioplasty using a titanium plate. The postoperative course was uneventful, and the patient achieved satisfactory recovery. The gravitational effect and the atmospheric <span class="hlt">pressure</span> <span class="hlt">gradient</span> effect are two factors associated in the ventriculoperitoneal (VP) shunt treatment of hydrocephalus for the patient who had decompressive craniectomy. These effects can be eliminated by supine bed rest and cranioplasty. We herein emphasize the efficacy of VP shunt, supine bed rest and cranioplasty in treating hydrocephalus patients who have undergone craniectomy. A flexible application of these procedures to change the gravitational effect and the atmospheric <span class="hlt">pressure</span> <span class="hlt">gradient</span> effect should promote a favorable outcome. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020027465&hterms=platzer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dplatzer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020027465&hterms=platzer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dplatzer"><span>Study of the Effect of Two-Dimensional Cavities on the Boundary Layer in an Adverse <span class="hlt">Pressure</span> <span class="hlt">Gradient</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Margason, Richard J.; Platzer, Max F.; Olson, Lawrence E. (Technical Monitor)</p> <p>1995-01-01</p> <p>One concept for high lift aerodynamics is the trapped-vortex. Recently it has been suggested that several spoilers located at different chordwise locations on an airfoil could be deployed to form several cavities in the chordwise direction. This may provide a means of increasing upper surface camber and thereby increase wing lift. It is envisioned that the cavities would be located on an airfoil in its pressure recovery region. Investigations of the effect of one or more cavities on the adjacent boundary layer in an adverse boundary layer were not found in a literature survey. Since flow separation can be caused by flow over cavities, boundary layer measurements were made in the vicinity of cavities which were located in an adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> to study the associated flow in an effort to identify any benefits. The experimental data from the present investigation indicate a minimal impact on the boundary layer profiles is caused by the presence of cavities in either a constant pressure freestream or an adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The data from the experimental investigation has been obtained and analyzed. The computational investigation using an incompressible Navier-Stokes code show that reasonable results are being obtained when they are compared with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22410426','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22410426"><span>Composite nonlinear structure within the magnetosonic <span class="hlt">soliton</span> interactions in a spin-1/2 degenerate quantum plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Han, Jiu-Ning Luo, Jun-Hua; Li, Jun-Xiu; Li, Sheng-Chang; Liu, Shi-Wei; Yang, Yang; Duan, Wen-Shan; Han, Juan-Fang</p> <p>2015-06-15</p> <p>We study the basic physical properties of composite nonlinear structure induced by the head-on collision of magnetosonic <span class="hlt">solitons</span>. Solitary waves are assumed to propagate in a quantum electron-ion magnetoplasma with spin-1/2 degenerate electrons. The main interest of the present work is to investigate the time evolution of the merged composite structure during a specific time interval of the wave interaction process. We consider three cases of colliding-situation, namely, <span class="hlt">compressive</span>-rarefactive <span class="hlt">solitons</span> interaction, <span class="hlt">compressive-compressive</span> <span class="hlt">solitons</span> interaction, and rarefactive-rarefactive <span class="hlt">solitons</span> interaction, respectively. Compared with the last two colliding cases, the changing process of the composite structure is more complex for the first situation. Moreover, it is found that they are obviously different for the last two colliding cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790010770&hterms=genres&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgenres','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790010770&hterms=genres&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dgenres"><span>Calculation methods for <span class="hlt">compressible</span> turbulent boundary layers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bushnell, D. M.; Cary, A. M., Jr.; Harris, J. E.</p> <p>1976-01-01</p> <p>Calculation procedures for non-reacting <span class="hlt">compressible</span> two- and three-dimensional turbulent boundary layers were reviewed. Integral, transformation and correlation methods, as well as finite difference solutions of the complete boundary layer equations summarized. Alternative numerical solution procedures were examined, and both mean field and mean turbulence field closure models were considered. Physics and related calculation problems peculiar to <span class="hlt">compressible</span> turbulent boundary layers are described. A catalog of available solution procedures of the finite difference, finite element, and method of weighted residuals genre is included. Influence of <span class="hlt">compressibility</span>, low Reynolds number, wall blowing, and <span class="hlt">pressure</span> <span class="hlt">gradient</span> upon mean field closure constants are reported.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23454958','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23454958"><span><span class="hlt">Solitons</span> in spiraling Vogel lattices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kartashov, Yaroslav V; Vysloukh, Victor A; Torner, Lluis</p> <p>2013-01-15</p> <p>We address light propagation in Vogel optical lattices and show that such lattices support a variety of stable <span class="hlt">soliton</span> solutions in both self-focusing and self-defocusing media, whose propagation constants belong to domains resembling gaps in the spectrum of a truly periodic lattice. The azimuthally rich structure of Vogel lattices allows generation of spiraling <span class="hlt">soliton</span> motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28249402','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28249402"><span>Dynamics of vector dark <span class="hlt">solitons</span> propagation and tunneling effect in the variable coefficient coupled nonlinear Schrödinger equation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Musammil, N M; Porsezian, K; Subha, P A; Nithyanandan, K</p> <p>2017-02-01</p> <p>We investigate the dynamics of vector dark <span class="hlt">solitons</span> propagation using variable coefficient coupled nonlinear Schrödinger (Vc-CNLS) equation. The dark <span class="hlt">soliton</span> propagation and evolution dynamics in the inhomogeneous system are studied analytically by employing the Hirota bilinear method. It is apparent from our asymptotic analysis that the collision between the dark <span class="hlt">solitons</span> is elastic in nature. The various inhomogeneous effects on the evolution and interaction between dark <span class="hlt">solitons</span> are explored, with a particular emphasis on nonlinear tunneling. It is found that the tunneling of the <span class="hlt">soliton</span> depends on a condition related to the height of the barrier and the amplitude of the <span class="hlt">soliton</span>. The intensity of the tunneling <span class="hlt">soliton</span> either forms a peak or a valley, thus retaining its shape after tunneling. For the case of exponential background, the <span class="hlt">soliton</span> tends to <span class="hlt">compress</span> after tunneling through the barrier/well. Thus, a comprehensive study of dark <span class="hlt">soliton</span> pulse evolution and propagation dynamics in Vc-CNLS equation is presented in the paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Chaos..27b3113M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Chaos..27b3113M"><span>Dynamics of vector dark <span class="hlt">solitons</span> propagation and tunneling effect in the variable coefficient coupled nonlinear Schrödinger equation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Musammil, N. M.; Porsezian, K.; Subha, P. A.; Nithyanandan, K.</p> <p>2017-02-01</p> <p>We investigate the dynamics of vector dark <span class="hlt">solitons</span> propagation using variable coefficient coupled nonlinear Schrödinger (Vc-CNLS) equation. The dark <span class="hlt">soliton</span> propagation and evolution dynamics in the inhomogeneous system are studied analytically by employing the Hirota bilinear method. It is apparent from our asymptotic analysis that the collision between the dark <span class="hlt">solitons</span> is elastic in nature. The various inhomogeneous effects on the evolution and interaction between dark <span class="hlt">solitons</span> are explored, with a particular emphasis on nonlinear tunneling. It is found that the tunneling of the <span class="hlt">soliton</span> depends on a condition related to the height of the barrier and the amplitude of the <span class="hlt">soliton</span>. The intensity of the tunneling <span class="hlt">soliton</span> either forms a peak or a valley, thus retaining its shape after tunneling. For the case of exponential background, the <span class="hlt">soliton</span> tends to <span class="hlt">compress</span> after tunneling through the barrier/well. Thus, a comprehensive study of dark <span class="hlt">soliton</span> pulse evolution and propagation dynamics in Vc-CNLS equation is presented in the paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvB..92b0402K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvB..92b0402K"><span>Thermophoresis of an antiferromagnetic <span class="hlt">soliton</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Se Kwon; Tchernyshyov, Oleg; Tserkovnyak, Yaroslav</p> <p>2015-07-01</p> <p>We study the dynamics of an antiferromagnetic <span class="hlt">soliton</span> under a temperature gradient. To this end, we start by phenomenologically constructing the stochastic Landau-Lifshitz-Gilbert equation for an antiferromagnet with the aid of the fluctuation-dissipation theorem. We then derive the Langevin equation for the <span class="hlt">soliton</span>'s center of mass by the collective coordinate approach. An antiferromagentic <span class="hlt">soliton</span> behaves as a classical massive particle immersed in a viscous medium. By considering a thermodynamic ensemble of <span class="hlt">solitons</span>, we obtain the Fokker-Planck equation, from which we extract the average drift velocity of a <span class="hlt">soliton</span>. The diffusion coefficient is inversely proportional to a small damping constant α , which can yield a drift velocity of tens of m/s under a temperature gradient of 1 K/mm for a domain wall in an easy-axis antiferromagnetic wire with α ˜10-4 .</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvD..94l5013C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvD..94l5013C"><span><span class="hlt">Solitons</span> in generalized Galileon theories</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Carrillo González, Mariana; Masoumi, Ali; Solomon, Adam R.; Trodden, Mark</p> <p>2016-12-01</p> <p>We consider the existence and stability of <span class="hlt">solitons</span> in generalized Galileons, scalar-field theories with higher-derivative interactions but second-order equations of motion. It has previously been proven that no stable, static <span class="hlt">solitons</span> exist in a single Galileon theory using an argument invoking the existence of zero modes for the perturbations. Here we analyze the applicability of this argument to generalized Galileons and discuss how this may be avoided by having potential terms in the energy functional for the perturbations or by including time dependence. Given the presence of potential terms in the Lagrangian for the perturbations, we find that stable, static <span class="hlt">solitons</span> are not ruled out in conformal and (anti-)de Sitter Galileons. For the case of Dirac-Born-Infeld and conformal Galileons, we find that <span class="hlt">solitonic</span> solutions moving at the speed of light exist, the former being stable and the latter unstable if the background <span class="hlt">soliton</span> satisfies a certain condition.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...814569Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...814569Y"><span>Breather <span class="hlt">soliton</span> dynamics in microresonators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Mengjie; Jang, Jae K.; Okawachi, Yoshitomo; Griffith, Austin G.; Luke, Kevin; Miller, Steven A.; Ji, Xingchen; Lipson, Michal; Gaeta, Alexander L.</p> <p>2017-02-01</p> <p>The generation of temporal cavity <span class="hlt">solitons</span> in microresonators results in coherent low-noise optical frequency combs that are critical for applications in spectroscopy, astronomy, navigation or telecommunications. Breather <span class="hlt">solitons</span> also form an important part of many different classes of nonlinear wave systems, manifesting themselves as a localized temporal structure that exhibits oscillatory behaviour. To date, the dynamics of breather <span class="hlt">solitons</span> in microresonators remains largely unexplored, and its experimental characterization is challenging. Here we demonstrate the excitation of breather <span class="hlt">solitons</span> in two different microresonator platforms based on silicon nitride and on silicon. We investigate the dependence of the breathing frequency on pump detuning and observe the transition from period-1 to period-2 oscillation. Our study constitutes a significant contribution to understanding the <span class="hlt">soliton</span> dynamics within the larger context of nonlinear science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28232720','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28232720"><span>Breather <span class="hlt">soliton</span> dynamics in microresonators.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yu, Mengjie; Jang, Jae K; Okawachi, Yoshitomo; Griffith, Austin G; Luke, Kevin; Miller, Steven A; Ji, Xingchen; Lipson, Michal; Gaeta, Alexander L</p> <p>2017-02-24</p> <p>The generation of temporal cavity <span class="hlt">solitons</span> in microresonators results in coherent low-noise optical frequency combs that are critical for applications in spectroscopy, astronomy, navigation or telecommunications. Breather <span class="hlt">solitons</span> also form an important part of many different classes of nonlinear wave systems, manifesting themselves as a localized temporal structure that exhibits oscillatory behaviour. To date, the dynamics of breather <span class="hlt">solitons</span> in microresonators remains largely unexplored, and its experimental characterization is challenging. Here we demonstrate the excitation of breather <span class="hlt">solitons</span> in two different microresonator platforms based on silicon nitride and on silicon. We investigate the dependence of the breathing frequency on pump detuning and observe the transition from period-1 to period-2 oscillation. Our study constitutes a significant contribution to understanding the <span class="hlt">soliton</span> dynamics within the larger context of nonlinear science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19293847','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19293847"><span>Dissipative ring <span class="hlt">solitons</span> with vorticity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Soto-Crespo, J M; Akhmediev, N; Mejia-Cortés, C; Devine, N</p> <p>2009-03-16</p> <p>We study dissipative ring <span class="hlt">solitons</span> with vorticity in the frame of the (2+1)-dimensional cubic-quintic complex Ginzburg-Landau equation. In dissipative media, radially symmetric ring structures with any vorticity m can be stable in a finite range of parameters. Beyond the region of stability, the <span class="hlt">solitons</span> lose the radial symmetry but may remain stable, keeping the same value of the topological charge. We have found bifurcations into <span class="hlt">solitons</span> with n-fold bending symmetry, with n independent on m. <span class="hlt">Solitons</span> without circular symmetry can also display (m + 1)-fold modulation behaviour. A sequence of bifurcations can transform the ring <span class="hlt">soliton</span> into a pulsating or chaotic state which keeps the same value of the topological charge as the original ring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5333125','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5333125"><span>Breather <span class="hlt">soliton</span> dynamics in microresonators</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yu, Mengjie; Jang, Jae K.; Okawachi, Yoshitomo; Griffith, Austin G.; Luke, Kevin; Miller, Steven A.; Ji, Xingchen; Lipson, Michal; Gaeta, Alexander L.</p> <p>2017-01-01</p> <p>The generation of temporal cavity <span class="hlt">solitons</span> in microresonators results in coherent low-noise optical frequency combs that are critical for applications in spectroscopy, astronomy, navigation or telecommunications. Breather <span class="hlt">solitons</span> also form an important part of many different classes of nonlinear wave systems, manifesting themselves as a localized temporal structure that exhibits oscillatory behaviour. To date, the dynamics of breather <span class="hlt">solitons</span> in microresonators remains largely unexplored, and its experimental characterization is challenging. Here we demonstrate the excitation of breather <span class="hlt">solitons</span> in two different microresonator platforms based on silicon nitride and on silicon. We investigate the dependence of the breathing frequency on pump detuning and observe the transition from period-1 to period-2 oscillation. Our study constitutes a significant contribution to understanding the <span class="hlt">soliton</span> dynamics within the larger context of nonlinear science. PMID:28232720</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGP...114..216G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGP...114..216G"><span>On the h-almost Ricci <span class="hlt">soliton</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gomes, J. N.; Wang, Qiaoling; Xia, Changyu</p> <p>2017-04-01</p> <p>We introduce the concept h-almost Ricci <span class="hlt">soliton</span> which extends naturally the almost Ricci <span class="hlt">soliton</span> by Pigola-Rigoli-Rimoldi-Setti and show that a compact nontrivial h-almost Ricci <span class="hlt">soliton</span> of dimension no less than three with h having defined signal and constant scalar curvature is isometric to a standard sphere with the potential function well determined. We also consider the h-Ricci <span class="hlt">soliton</span> which is a particular case of the h-almost Ricci <span class="hlt">soliton</span> and a generalization of the Ricci <span class="hlt">soliton</span> and give characterizations for a special class of gradient h-Ricci <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11397526','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11397526"><span>Spatio-temporal mapping of intracardiac <span class="hlt">pressure</span> <span class="hlt">gradients</span>. A solution to Euler's equation from digital postprocessing of color Doppler M-mode echocardiograms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bermejo, J; Antoranz, J C; Yotti, R; Moreno, M; García-Fernández, M A</p> <p>2001-05-01</p> <p>Doppler assessment of intracardiac <span class="hlt">pressure</span> <span class="hlt">gradients</span> using the simplified Bernoulli equation is inaccurate in the absence of a restricted orifice. The purpose of this study is to develop a new general method to map instantaneous <span class="hlt">pressure</span> <span class="hlt">gradients</span> inside the heart using Doppler echocardiography. Color Doppler M-mode recordings are digitally postprocessed with a software algorithm that decodes flow velocity and fits a bivariate spatio-temporal tensor-product smoothing spline. Temporal and spatial accelerations are then calculated by analytical derivation of the fitted velocity data, allowing solution of both inertial and convective terms of Euler's equation. A database of 39 transmitral inflow and transaortic outflow color Doppler M-mode recordings from 20 patients with a number of cardiac conditions was analysed, along with matched pulsed-wave spectral recordings. A close agreement was observed between the spectral and postprocessed color Doppler velocity values (error = 0.8 +/- 11.7 cm/s), validating the data decoding and fitting process. Spatio-temporal <span class="hlt">pressure-gradient</span> maps were obtained from all studies, allowing visualisation of instantaneous <span class="hlt">pressure</span> <span class="hlt">gradients</span> from the atrium to the apex during left ventricular filling, and from the apex to the outflow tract during ejection. Instantaneous pressure differences between localised intracardiac sample points closely matched previously published catheterization findings, both in magnitude and waveform shape. Our method shows that intracardiac instantaneous <span class="hlt">pressure</span> <span class="hlt">gradients</span> can be analysed noninvasively using color Doppler M-mode echocardiography combined with image postprocessing methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24580162','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24580162"><span>Gray <span class="hlt">solitons</span> on the surface of water.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chabchoub, A; Kimmoun, O; Branger, H; Kharif, C; Hoffmann, N; Onorato, M; Akhmediev, N</p> <p>2014-01-01</p> <p>The dynamics of surface gravity water waves can be described by the self-defocusing nonlinear Schrödinger equation. Recent observations of black <span class="hlt">solitons</span> on the surface of water confirmed its validity for finite, below critical depth. The black <span class="hlt">soliton</span> is a limiting case of a family of gray <span class="hlt">soliton</span> solutions with finite amplitude depressions. Here, we report observations of gray <span class="hlt">solitons</span> in water waves, thus, complementing our previous observations of black <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21528744','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21528744"><span>Fully localized two-dimensional embedded <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yang Jianke</p> <p>2010-11-15</p> <p>We report the prediction of fully localized two-dimensional embedded <span class="hlt">solitons</span>. These <span class="hlt">solitons</span> are obtained in a quasi-one-dimensional waveguide array which is periodic along one spatial direction and localized along the orthogonal direction. Under appropriate nonlinearity, these <span class="hlt">solitons</span> are found to exist inside the Bloch bands (continuous spectrum) of the waveguide and thus are embedded <span class="hlt">solitons</span>. These embedded <span class="hlt">solitons</span> are fully localized along both spatial directions. In addition, they are fully stable under perturbations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000APS..DFD.BD005C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000APS..DFD.BD005C"><span>Computation of Flow in a Circular Cylinder Driven by Coaxial Screw Rotation and an Opposing <span class="hlt">Pressure</span> <span class="hlt">Gradient</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cotrell, David L.; Pearlstein, Arne J.</p> <p>2000-11-01</p> <p>We report computations of the velocity field for flows driven by rotation of a screw in a circular cylinder with an applied opposing <span class="hlt">pressure</span> <span class="hlt">gradient</span>. Use of a helical coordinate system in a frame rotating with the screw reduces the flow calculation to a steady one, which is taken to be fully-developed in the helical direction. The full incompressible Navier-Stokes equations in primitive-variables form are solved numerically using a finite-element method employing quadrilateral elements with quadratic velocity and linear pressure interpolation. A consistent penalty method is used to satisfy incompressibility. The screw cross-section is rectangular. The effect of screw clearance and other geometric parameters on the velocity field will be discussed for low and intermediate Reynolds numbers and compared to the Stokes flow case.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21282103','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21282103"><span>Observation of a critical <span class="hlt">pressure</span> <span class="hlt">gradient</span> for the stabilization of interchange modes in simple magnetized toroidal plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Federspiel, L.; Labit, B.; Ricci, P.; Fasoli, A.; Furno, I.; Theiler, C.</p> <p>2009-09-15</p> <p>The existence of a critical <span class="hlt">pressure</span> <span class="hlt">gradient</span> needed to drive the interchange instability is experimentally demonstrated in the simple magnetized torus TORoidal Plasma EXperiment [A. Fasoli et al., Phys. Plasmas 13, 055902 (2006)]. This gradient is reached during a scan in the neutral gas pressure p{sub n}. Around a critical value for p{sub n}, depending on the magnetic configuration and on the injected rf power, a small increase in the neutral gas pressure triggers a transition in the plasma behavior. The pressure profile is locally flattened, stabilizing the interchange mode observed at lower neutral gas densities. The measured value for the critical gradient is close to the linear theory estimate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22688582','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22688582"><span>Marked discrepancy in <span class="hlt">pressure</span> <span class="hlt">gradient</span> between Doppler and catheter examinations on Medtronic Mosaic valve in aortic position.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ito, Toshiaki; Maekawa, Atsuo; Fujii, Genyo; Sawaki, Sadanari; Hoshino, Satoshi; Hayashi, Yasunari</p> <p>2012-12-01</p> <p>A 71-year-old woman underwent aortic valve replacement with 23 mm Medtronic Mosaic Ultra valve 4 years ago because of aortic stenosis. Although she had been asymptomatic since the operation, echocardiography showed 4 m/s of transprosthetic valve flow that implied early prosthetic valve failure. Catheter examination revealed that the mean transvalvular <span class="hlt">pressure</span> <span class="hlt">gradient</span> during systole was 15.1 mmHg on simultaneous pressure recording, and calculated valve area 1.82 cm(2). Her body surface area was 1.56 m(2). Prosthetic valve failure and prosthesis-patient mismatch were both denied. The discrepancy between Doppler study data and catheter data seemed to be due to fluid dynamical pressure recovery phenomenon. Net pressure difference between the left ventricle and the aorta may be significantly smaller than that estimated using Bernoulli's equation from transvalvular flow speed in some patients after aortic valve replacement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800009140','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800009140"><span>First results of a study on turbulent boundary layers in oscillating flow with a mean adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Houdeville, R.; Cousteix, J.</p> <p>1979-01-01</p> <p>The development of a turbulent unsteady boundary layer with a mean <span class="hlt">pressure</span> <span class="hlt">gradient</span> strong enough to induce separation, in order to complete the extend results obtained for the flat plate configuration is presented. The longitudinal component of the velocity is measured using constant temperature hot wire anemometer. The region where negative velocities exist is investigated with a laser Doppler velocimeter system with BRAGG cells. The boundary layer responds by forced pulsation to the perturbation of potential flow. The unsteady effects observed are very important. The average location of the zero skin friction point moves periodically at the perturbation frequency. Average velocity profiles from different instants in the cycle are compared. The existence of a logarithmic region enables a simple calculation of the maximum phase shift of the velocity in the boundary layer. An attempt of calculation by an integral method of boundary layer development is presented, up to the point where reverse flow starts appearing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..DFD.KL001T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..DFD.KL001T"><span>Zero <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Flat Plate Boundary Layer Experiments Using Synchronized PIV and a Hot Wire Anemometry Rake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tutkun, M.; Johansson, P. B. V.; George, W. K.; Stanislas, M.; Foucaut, J. M.; Kostas, J.; Coudert, S.; Delville, J.</p> <p>2006-11-01</p> <p>Zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> flat plate boundary layer experiments have been performed in the 20 meter long test section of the Laboratoire de M'ecanique de Lille, LML, wind tunnel. Measurements were carried out at Reθ=10 000 and Reθ=20 000 using synchronized PIV and a hot wire anemometry rake. The boundary layer thickness at the measurement location was about 30 cm. A hot wire rake of 143 probes was placed in the test section of the wind tunnel to provide the time history of the boundary layer. 2 stereo PIV systems in the wallnormal-spanwise (YZ) plane, and 1 stereo PIV system to record in the streamwise-wallnormal (XY) were used. One high repetition PIV system was used in streamwise-spanwise (XZ) plane. The sampling frequency of the XZ PIV system was 3000 VF/s at Reθ=20 000 and 1500 VF/s at Reθ=10 000.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840012420','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840012420"><span>An experimental study of the properties of surface pressure fluctuations in strong adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> turbulent boundary layers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Simpson, R. L.</p> <p>1984-01-01</p> <p>Experimental data were obtained on blade self-noise generation by strong adverse-<span class="hlt">pressure-gradient</span> attached boundary layers and by separated turbulent boundary layers that accompany stall. Two microphones were calibrated, placed in plastic housing, and installed in a wind tunnel where observations of acoustic and turbulent signals permitted decomposition of the surface pressure fluctuation signals into the propagated acoustic part and the turbulent-flow generated portion. To determine the convective wave speed of the turbulent contributions, the microphones were spaced a small distance apart in the streamwise direction and correlations were obtained. The turbulent surface pressure spectra upstream of detachment and downstream of the beginning of separation are discussed as well as measurements of turbulent velocity spectra and wavespeeds.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JOptB...5.....D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JOptB...5.....D"><span>CALL FOR PAPERS: Optical <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Drummond, P. D.; Haelterman, Marc; Vilaseca, R.</p> <p>2003-06-01</p> <p>A topical issue of Journal of Optics B: Quantum and Semiclassical Optics will be devoted to recent advances in optical <span class="hlt">solitons</span>. The topics to be covered will include, but are not limited to: bulletProperties, control and dynamics of temporal <span class="hlt">solitons</span> bulletProperties, control and dynamics of spatial <span class="hlt">solitons</span> bulletCavity <span class="hlt">solitons</span> in passive and active resonators bulletThree-dimensional spatial <span class="hlt">solitons</span> bulletDark, bright, grey <span class="hlt">solitons</span>; interface dynamics bulletCompound or vector <span class="hlt">solitons</span>; incoherent <span class="hlt">solitons</span> bulletLight and matter <span class="hlt">solitons</span> in BEC bulletNonlinear localized structures in microstructured and nanostructured materials (photonic crystals, etc) bulletAngular momentum effects associated with localized light structures; vortex <span class="hlt">solitons</span> bulletQuantum effects associated with localized light structures bulletInteraction of <span class="hlt">solitons</span> with atoms and other media bulletApplications of optical <span class="hlt">solitons</span> The DEADLINE for submission of contributions is 31 July 2003 to allow the topical issue to appear in about February 2004. All papers will be peer-reviewed in accordance with the normal refereeing procedures and standards of Journal of Optics B: Quantum and Semiclassical Optics. Advice on publishing your work in the journal may be found at www.iop.org/journals/authors/jopb. Submissions should ideally be in either standard LaTeX form or Microsoft Word. There are no page charges for publication. In addition to the usual 50 free reprints, the corresponding author of each paper published will receive a complimentary copy of the topical issue. Contributions to the topical issue should if possible be submitted electronically at www.iop.org/journals/jopb. or by e-mail to jopb@iop.org. Authors unable to submit online or by e-mail may send hard copy contributions (enclosing the electronic code) to: Dr Claire Bedrock (Publisher), Journal of Optics B: Quantum and Semiclassical Optics, Institute of Physics Publishing, Dirac House, Temple Back, Bristol BS1 6BE, UK. All</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhDT.......234C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhDT.......234C"><span>A Computational Study on the Effects of Dynamic Roughness Application to Separated Transitional Flows Affected by Adverse <span class="hlt">Pressure</span> <span class="hlt">Gradient</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Campitelli, Gennaro</p> <p></p> <p>The study of transitional flows is considered crucial for many practical engineering applications. In fact, a comprehensive understanding of the laminar-turbulent transition phenomenon often helps to improve the overall performance of apparatuses such as airfoils, wind turbines, hulls and turbomachinery blades. In addition to understanding and prediction of transitional flows, active research continues in the area of boundary layer control, which includes control of phenomena such as flow separation and transition. For instance, optimum geometrical shaping may be followed by the adoption on the wall-surface of riblets to adjust <span class="hlt">pressure</span> <span class="hlt">gradient</span> and reduce drag. Further "flow control" may also be acquired by introducing active devices able to modify the flow field in order to accomplish a desired aerodynamic task. Such flow manipulation is often achieved by using time-dependent forcing mechanisms which promote natural instabilities amplifying the control effectiveness. Localized energy inputs such as Lorentz-force actuator, piezoelectric flaps and synthetic jets all produce a consistent boundary layer mixing enhancement with lift increase and drag abatement. The current numerical study attempts to demonstrate the efficacy of dynamic roughness (DR) on altering separated-reattached transitional flows under adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span>. It has already been proven how DR, acting on the boundary sublayer perturbation, is able to suppress (partially or completely) the typical leading edge separation for an airfoil at different angles of attack. This makes DR particularly suitable for separated flow control applications where the shear layer reattaches presenting the characteristic laminar separation bubble. A numerical sensitivity study has been conducted with an efficient orthogonal design taking into account four different control parameters on three levels (actuation frequency, humps height, rows displacement, synchronization) to provide an optimum DR setup which limits</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985RSPTA.315..423S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985RSPTA.315..423S"><span>Davydov <span class="hlt">Solitons</span> in Polypeptides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scott, A. C.</p> <p>1985-08-01</p> <p>The experimental evidence for self-trapping of amide-I (CO stretching) vibrational energy in crystalline acetanilide (a model protein) is reviewed and related to A. S. Davydov's theory of <span class="hlt">solitons</span> as a mechanism for energy storage and transport in protein. Particular attention is paid to the construction of quantum states that contain N amide-I vibrational quanta. It is noted that the `N = 2' state is almost exactly resonant with the free energy that is released upon hydrolysis of adenosine triphosphate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6443952','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6443952"><span>Davydov <span class="hlt">solitons</span> in polypeptides</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Scott, A.</p> <p>1984-10-01</p> <p>The experimental evidence for self-trapping of amide-I (CO stretching) vibrational energy in crystalline acetanilide (a model protein) is reviewed and related to A. S. Davydov's theory of <span class="hlt">solitons</span> as a mechanism for energy storage and transport in protein. Particular attention is paid to the construction of quantum states that contain N amide-I vibrational quanta. It is noted that the N = 2 state is almost exactly resonant with the free energy that is released upon hydrolysis of adenosine triphosphate. 30 references, 4 figures, 3 tables.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.2231S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.2231S"><span>Deceleration of the small <span class="hlt">solitons</span> in the <span class="hlt">soliton</span> lattice: KdV-type framework</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shurgalina, Ekaterina; Gorshkov, Konstantin; Talipova, Tatiana; Pelinovsky, Efim</p> <p>2016-04-01</p> <p>As it is known the solitary waves (<span class="hlt">solitons</span>) in the KdV-systems move with speed which exceeds the speed of propagation of long linear waves (sound speed). Due to interaction between them, <span class="hlt">solitons</span> do not lose their individuality (elastic interaction). Binary interaction of neigborough <span class="hlt">solitons</span> is the major contribution in the dynamics of <span class="hlt">soliton</span> gas. Taking into account the integrability of the classic and modified Korteweg-de Vries equations the process of the <span class="hlt">soliton</span> interaction can be analyzed in the framework of the rigorous analytical two-<span class="hlt">soliton</span> solutions. Main physical conclusion from this solution is the phase shift which is positive for large <span class="hlt">solitons</span> and negative for small <span class="hlt">solitons</span>. This fact influences the average velocity of individual <span class="hlt">soliton</span> in the <span class="hlt">soliton</span> lattice or <span class="hlt">soliton</span> gas. We demonstrate that <span class="hlt">soliton</span> of relative small amplitude moves in <span class="hlt">soliton</span> gas in average in opposite (negative) direction, meanwhile a free <span class="hlt">soliton</span> moves always in the right direction. Approximated analytical theory is created for the <span class="hlt">soliton</span> motion in the periodic lattice of big <span class="hlt">solitons</span> of the same amplitudes, and the critical amplitude of the small <span class="hlt">soliton</span> changed its averaged speed is found. Numerical simulation is conducted for a statistical assembly of <span class="hlt">solitons</span> with random amplitudes and phases. The application of developed theory to the long surface and internal waves is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991PhRvL..67.1177K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991PhRvL..67.1177K"><span>Resonant <span class="hlt">soliton</span>-impurity interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kivshar, Yuri S.; Fei, Zhang; Vázquez, Luis</p> <p>1991-09-01</p> <p>We describe a new type of <span class="hlt">soliton</span>-impurity interaction and demonstrate that the <span class="hlt">soliton</span> can be totally reflected by an attractive impurity if its initial velocity lies in certain resonance ``windows.'' This effect has an analogy with the resonance phenomena in kink-antikink collisions [Campbell, Schonfeld, and Wingate, Physica (Amsterdam) 9D, 1 (1983)], and it can be explained by a resonant energy exchange between the <span class="hlt">soliton</span> and the impurity mode. Taking the sine-Gordon and φ4 models as examples, we find a number of resonance windows by numerical simulations and develop a collective-coordinate approach to describe the effect analytically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993NuPhB.405..451S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993NuPhB.405..451S"><span>Quantum reduplication of classical <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sveshnikov, Konstantin</p> <p>1993-09-01</p> <p>The possible existence of a series of quantum copies of classical <span class="hlt">soliton</span> solutions is discussed, which do not exist when the effective Planck constant of the theory γ tends to zero. Within the conventional weak-coupling expansion in √ γ such non-classical <span class="hlt">solitons</span> are O(√ γ) in energy and therefore lie in between the true classical solutions and elementary quantum excitations. Analytic results concerning the shape functions, masses and characteristic scales of such quantum excitations are given for <span class="hlt">soliton</span> models of a self-interacting scalar field. Stability properties and quantization of fluctuations in the neighborhood of these configurations are also discussed in detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPIE10193E..0HT','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPIE10193E..0HT"><span>Chirped <span class="hlt">soliton</span>: new type of <span class="hlt">solitons</span> for photonics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Trofimov, Vyacheslav A.; Lysak, Tatiana M.; Zakharova, Irina G.</p> <p>2017-05-01</p> <p>We investigate a novel type of <span class="hlt">solitons</span> - chirped <span class="hlt">solitons</span>- in the various problems of photonics which deals with the femtosecond laser pulse propagation in the media with nonlinear non-stationary absorption. This type of <span class="hlt">solitons</span> is characterized by the complicated pulse chirp and allows self-similar propagation of laser radiation at the distances up to several dispersion lengths. In our analytical considerations, we develop approximate formulas which describe the nonlinear chip and the <span class="hlt">soliton</span> shape. We confirm our analytical results by the numerical simulation of the considered problems: femtosecond laser pulse propagation in the media with nanorods or in the fused silica with taking into account non-stationary multi-photon absorption, nonlinear refraction, nanorods melting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21408284','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21408284"><span>Nonautonomous matter-wave <span class="hlt">solitons</span> near the Feshbach resonance</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Serkin, V. N.; Belyaeva, T. L.; Hasegawa, Akira</p> <p>2010-02-15</p> <p>By means of analytical and numerical methods, we reveal the main features of nonautonomous matter-wave <span class="hlt">solitons</span> near the Feshbach resonance in a one-dimensional Bose-Einstein condensate confined by a harmonic potential with a varying-in-time longitudinal trapping frequency. Based on the generalized nonautonomous Gross-Pitaevskii model, we show that <span class="hlt">solitons</span> in nonautonomous physical systems exist only under certain conditions so that varying-in-time nonlinearity and confining harmonic potential cannot be chosen independently; they satisfy the exact integrability scenarios and complement each other. We focus on the most physically important examples where the applied magnetic field is either a linearly or a periodically varying-in-time function. In the case of periodically varying scattering length, variations of confining harmonic potential are found to be sign-reversible (periodic attractive and repulsive) to support the <span class="hlt">soliton</span>-management regime. We investigate the losses of validity of one-dimensional (1D) approximation in the cases when, by the joint action of varying-in-time nonlinearity and confining potential, the atom cloud can be <span class="hlt">compressed</span> from an initially elongated quasi-1D cigar-shaped geometry to a final ball-shaped three-dimensional geometry and the induced <span class="hlt">soliton</span> collapse may occur.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SuMi..102..323T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SuMi..102..323T"><span><span class="hlt">Soliton</span> solutions for Davydov <span class="hlt">solitons</span> in α-helix proteins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taghizadeh, N.; Zhou, Qin; Ekici, M.; Mirzazadeh, M.</p> <p>2017-02-01</p> <p>The propagation equation for describing Davydov <span class="hlt">solitons</span> in α-helix proteins has been investigated analytically. There are seven integration tools to extract analytical <span class="hlt">soliton</span> solutions. They are the Ricatti equation expansion approach, ansatz scheme, improved extended tanh-equation method, the extend exp(-Ψ(τ)) -expansion method, the extended Jacobi elliptic function expansion method, the extended trial equation method and the extended G ' / G - expansion method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JPlPh..67..353M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JPlPh..67..353M"><span>The fluid-dynamic paradigm of the dust-acoustic <span class="hlt">soliton</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McKenzie, J. F.</p> <p>2002-06-01</p> <p>In most studies, the properties of dust-acoustic <span class="hlt">solitons</span> are derived from the first integral of the Poisson equation, in which the shape of the pseudopotential determines both the conditions in which a <span class="hlt">soliton</span> may exist and its amplitude. Here this first integral is interpreted as conservation of total momentum, which, along with the Bernoulli-like energy equations for each species, may be cast as the structure equation for the dust (or heavy-ion) speed in the wave. In this fluid-dynamic picture, the significance of the sonic points of each species becomes apparent. In the wave, the heavy-ion (or dust) flow speed is supersonic (relative to its sound speed), whereas the protons and electrons are subsonic (relative to their sound speeds), and the dust flow is driven towards its sonic point. It is this last feature that limits the strength (amplitude) of the wave, since the equilibrium point (the centre of the wave) must be reached before the dust speed becomes sonic. The wave is characterized by a <span class="hlt">compression</span> in the heavies and a <span class="hlt">compression</span> (rarefaction) in the electrons and a rarefaction (<span class="hlt">compression</span>) in the protons if the heavies have positive (negative) charge, and the corresponding potential is a hump (dip). These features are elucidated by an exact analytical <span class="hlt">soliton</span>, in a special case, which provides the fully nonlinear counterpoint to the weakly nonlinear sech2-type <span class="hlt">solitons</span> associated with the Korteweg de Vries equation, and indicates the parameter regimes in which <span class="hlt">solitons</span> may exist.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJTP...55.4075R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJTP...55.4075R"><span>Bell's Theorem and Entangled <span class="hlt">Solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rybakov, Yu. P.; Kamalov, T. F.</p> <p>2016-09-01</p> <p>Entangled <span class="hlt">solitons</span> construction being introduced in the nonlinear spinor field model, the Einstein—Podolsky—Rosen (EPR) spin correlation is calculated and shown to coincide with the quantum mechanical one for the 1/2-spin particles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001PhRvB..64c5418A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001PhRvB..64c5418A"><span>Longitudinal <span class="hlt">solitons</span> in carbon nanotubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Astakhova, T. Yu.; Gurin, O. D.; Menon, M.; Vinogradov, G. A.</p> <p>2001-07-01</p> <p>We present results on <span class="hlt">soliton</span> excitations in carbon nanotubes (CNT's) using Brenner's many-body potential. Our numerical simulations demonstrate high <span class="hlt">soliton</span> stability in (10,10) CNT's. The interactions of <span class="hlt">solitons</span> and solitary excitation with CNT defect are found to be inelastic if the excitations and defects length scales are comparable, resulting in a substantial part of <span class="hlt">soliton</span> energy being distributed inhomogeneously over the defect bonds. In these solitary-excitation-cap collisions the local energy of a few bonds in the cap can exceed the average energy by an order of magnitude and more. This phenomenon, denoted the ``Tsunami effect,'' can contribute dynamically to the recently proposed ``kinky chemistry.'' We also present results of changes in the local density of states and variations in the atomic partial charges estimated at different time instants of the solitary-excitation Tsunami at the nanotube cap.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhLB..765..352M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhLB..765..352M"><span>Thermodynamic volume of cosmological <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mbarek, Saoussen; Mann, Robert B.</p> <p>2017-02-01</p> <p>We present explicit expressions of the thermodynamic volume inside and outside the cosmological horizon of Eguchi-Hanson <span class="hlt">solitons</span> in general odd dimensions. These quantities are calculable and well-defined regardless of whether or not the regularity condition for the <span class="hlt">soliton</span> is imposed. For the inner case, we show that the reverse isoperimetric inequality is not satisfied for general values of the <span class="hlt">soliton</span> parameter a, though a narrow range exists for which the inequality does hold. For the outer case, we find that the mass Mout satisfies the maximal mass conjecture and the volume is positive. We also show that, by requiring Mout to yield the mass of dS spacetime when the <span class="hlt">soliton</span> parameter vanishes, the associated cosmological volume is always positive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhLB..762...80A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhLB..762...80A"><span>Hairy AdS <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anabalón, Andrés; Astefanesei, Dumitru; Choque, David</p> <p>2016-11-01</p> <p>We construct exact hairy AdS <span class="hlt">soliton</span> solutions in Einstein-dilaton gravity theory. We examine their thermodynamic properties and discuss the role of these solutions for the existence of first order phase transitions for hairy black holes. The negative energy density associated to hairy AdS <span class="hlt">solitons</span> can be interpreted as the Casimir energy that is generated in the dual filed theory when the fermions are antiperiodic on the compact coordinate.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984PhRvB..30.4703E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984PhRvB..30.4703E"><span><span class="hlt">Soliton</span> structure in crystalline acetanilide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eilbeck, J. C.; Lomdahl, P. S.; Scott, A. C.</p> <p>1984-10-01</p> <p>The theory of self-trapping of amide I vibrational energy in crystalline acetanilide is studied in detail. A spectrum of stationary, self-trapped (<span class="hlt">soliton</span>) solutions is determined and tested for dynamic stability. Only those solutions for which the amide I energy is concentrated near a single molecule were found to be stable. Exciton modes were found to be unstable to decay into <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6141072','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6141072"><span><span class="hlt">Soliton</span> structure in crystalline acetanilide</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Eilbeck, J.C.; Lomdahl, P.S.; Scott, A.C.</p> <p>1984-10-15</p> <p>The theory of self-trapping of amide I vibrational energy in crystalline acetanilide is studied in detail. A spectrum of stationary, self-trapped (<span class="hlt">soliton</span>) solutions is determined and tested for dynamic stability. Only those solutions for which the amide I energy is concentrated near a single molecule were found to be stable. Exciton modes were found to be unstable to decay into <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15578142','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15578142"><span>Kinks of the transplant renal artery without accompanying intraarterial <span class="hlt">pressure</span> <span class="hlt">gradient</span> do not require correction: five-year outcome study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chua, Gim Chuah; Snowden, Sue; Patel, Uday</p> <p>2004-01-01</p> <p>Significant transplant renal artery stenosis (TRAS) results in an intraarterial <span class="hlt">pressure</span> <span class="hlt">gradient</span> and increasing graft dysfunction correctable by endovascular therapy. Kinks of the transplant artery cause velocity gradients on Doppler ultrasound, but some will have no intraarterial <span class="hlt">pressure</span> <span class="hlt">gradient</span> across the kink. It is not known whether these nonflow limiting kinks progress further to threaten graft function and should undergo endovascular correction. This is a longitudinal study of conservatively managed arterial kinks to define their natural history. Fourteen patients who had undergone angiography over a 5-year period for suspected TRAS had kinks of the renal artery. True intraarterial pressures were measured in all cases by slow withdrawal of an end-hole catheter after intraarterial injection of a vasodilator. Those with a significant pressure change (> or =10% change in peak systolic pressure across the area of suspicion) underwent endovascular treatment. The rest were managed conservatively, with maximal antihypertensive therapy. Outcome of all 14 cases was determined by follow-up of creatinine levels, blood pressure (BP) control and graft outcome over a 3-5-year period (median 4 years). Of the 14 patients with kinks, 10 were male and 4 female; age range 23-67 years (mean 47 years). Eleven had received cadaveric transplants and 3 were allografts; 12 had end-to-side and 2 end-to-end anastomosis, 11/14 cases had an intraarterial pressure ratio of <10% and at median 4 years follow-up on conservative treatment, the serum creatinine of these 11 patients did not differ significantly from those who underwent successful endovascular treatment (mean 118 micromol/l versus 149 micromol/l; p = 0.30, Mann Whitney test). Mean blood pressure was 137/82 mmHg, with a range of 124-155/56-95 mmHg. Only one patient has required an unexplainable increase in antihypertensive medication. Grafts (2/11) were lost and both had chronic rejection on histology. There were no</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21088202','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21088202"><span>Kinks of the Transplant Renal Artery Without Accompanying Intraarterial <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Do Not Require Correction: Five-Year Outcome Study</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chua, Gim Chuah; Snowden, Sue; Patel, Uday</p> <p>2004-11-15</p> <p>Significant transplant renal artery stenosis (TRAS) results in an intraarterial <span class="hlt">pressure</span> <span class="hlt">gradient</span> and increasing graft dysfunction correctable by endovascular therapy. Kinks of the transplant artery cause velocity gradients on Doppler ultrasound, but some will have no intraarterial <span class="hlt">pressure</span> <span class="hlt">gradient</span> across the kink. It is not known whether these nonflow limiting kinks progress further to threaten graft function and should undergo endovascular correction. This is a longitudinal study of conservatively managed arterial kinks to define their natural history. Fourteen patients who had undergone angiography over a 5-year period for suspected TRAS had kinks of the renal artery. True intraarterial pressures were measured in all cases by slow withdrawal of an end-hole catheter after intraarterial injection of a vasodilator. Those with a significant pressure change ({>=}10% change in peak systolic pressure across the area of suspicion) underwent endovascular treatment. The rest were managed conservatively, with maximal antihypertensive therapy. Outcome of all 14 cases was determined by follow-up of creatinine levels, blood pressure (BP) control and graft outcome over a 3-5-year period (median 4 years). Of the 14 patients with kinks, 10 were male and 4 female; age range 23-67 years (mean 47 years). Eleven had received cadaveric transplants and 3 were allografts; 12 had end-to-side and 2 end-to-end anastomosis, 11/14 cases had an intraarterial pressure ratio of <10% and at median 4 years follow-up on conservative treatment, the serum creatinine of these 11 patients did not differ significantly from those who underwent successful endovascular treatment (mean 118 {mu}mol/l versus 149 {mu}mol/l; p = 0.30, Mann Whitney test). Mean blood pressure was 137/82 mmHg, with a range of 124-155/56-95 mmHg. Only one patient has required an unexplainable increase in antihypertensive medication. Grafts (2/11) were lost and both had chronic rejection on histology. There were no unexplained</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140000685','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140000685"><span>Multiphase Transport in Porous Media: Gas-Liquid Separation Using Capillary <span class="hlt">Pressure</span> <span class="hlt">Gradients</span> International Space Station (ISS) Flight Experiment Development</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wheeler, Richard R., Jr.; Holtsnider, John T.; Dahl, Roger W.; Deeks, Dalton; Javanovic, Goran N.; Parker, James M.; Ehlert, Jim</p> <p>2013-01-01</p> <p>Advances in the understanding of multiphase flow characteristics under variable gravity conditions will ultimately lead to improved and as of yet unknown process designs for advanced space missions. Such novel processes will be of paramount importance to the success of future manned space exploration as we venture into our solar system and beyond. In addition, because of the ubiquitous nature and vital importance of biological and environmental processes involving airwater mixtures, knowledge gained about fundamental interactions and the governing properties of these mixtures will clearly benefit the quality of life here on our home planet. The techniques addressed in the current research involving multiphase transport in porous media and gas-liquid phase separation using capillary <span class="hlt">pressure</span> <span class="hlt">gradients</span> are also a logical candidate for a future International Space Station (ISS) flight experiment. Importantly, the novel and potentially very accurate Lattice-Boltzmann (LB) modeling of multiphase transport in porous media developed in this work offers significantly improved predictions of real world fluid physics phenomena, thereby promoting advanced process designs for both space and terrestrial applications.This 3-year research effort has culminated in the design and testing of a zero-g demonstration prototype. Both the hydrophilic (glass) and hydrophobic (Teflon) media Capillary <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> (CPG) cartridges prepared during the second years work were evaluated. Results obtained from ground testing at 1-g were compared to those obtained at reduced gravities spanning Martian (13-g), Lunar (16-g) and zero-g. These comparisons clearly demonstrate the relative strength of the CPG phenomena and the efficacy of its application to meet NASAs unique gas-liquid separation (GLS) requirements in non-terrestrial environments.LB modeling software, developed concurrently with the zero-g test effort, was shown to accurately reproduce observed CPG driven gas-liquid separation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhRvA..58.2542S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhRvA..58.2542S"><span>Spatial <span class="hlt">solitons</span> in semiconductor microcavities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Spinelli, L.; Tissoni, G.; Brambilla, M.; Prati, F.; Lugiato, L. A.</p> <p>1998-09-01</p> <p>We consider a semiconductor microcavity driven by a coherent and stationary holding beam, in two distinct configurations. In the first, no carriers are injected in the multiple-quantum-well structure and the optical nonlinearity is governed by an excitonic resonance. The second corresponds to that of a vertical-cavity surface-emitting laser kept slightly below threshold. We describe both configurations using a unified model that includes both field diffraction and carrier diffusion. We calculate numerically both the time evolution and the stationary profile of the <span class="hlt">solitonic</span> solutions, using a generalization of the radial integration technique introduced by Firth and Scroggie [Phys. Rev. Lett. 76, 1623 (1996)]. We analyze the instability that forms spatial patterns and especially cavity spatial <span class="hlt">solitons</span>. We predict the existence of these <span class="hlt">solitons</span> in various parametric domains for both configurations. We demonstrate that these results are independent of the periodic boundary conditions used in the simulations. We show that, introducing a simple phase modulation in the holding beam, one can eliminate the motions of <span class="hlt">solitons</span> that arise from noise and from amplitude gradients. The <span class="hlt">solitons</span> are robust with respect to parametric variations, to carrier diffusion, and even to some amount of self-defocusing. This picture points to the possibility of realizing arrays of <span class="hlt">solitonic</span> pixels using semiconductor microresonators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JPS...161..901L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPS...161..901L"><span>Novel <span class="hlt">compressive</span> seals for solid oxide fuel cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le, Shiru; Sun, Kening; Zhang, Naiqing; An, Maozhong; Zhou, Derui; Zhang, Jingdong; Li, Donggang</p> <p></p> <p>Traditional seals for planar solid oxide fuel cells (pSOFCs) are rigid glass and glass-ceramic, which have caused the problem of being unable to replace malfunctioning components. Non-glass sealants have become a recent trend. In this paper, fumed silica-infiltrated alumina-silica fiber paper gaskets were investigated as a novel <span class="hlt">compressive</span> seal for planar solid oxide fuel cells. The leak rates decreased with increase of the silica-infiltration amount and the <span class="hlt">compressive</span> load. Samples pre-stressed at 10 MPa indicated far superior sealing characteristics, with leak rates as low as 0.04 sccm cm -1 at a 1 MPa <span class="hlt">compressive</span> stress and a 10 kPa <span class="hlt">pressure</span> <span class="hlt">gradient</span>, and 0.05 sccm cm -1 for 0.05 MPa, and a 1.4 kPa <span class="hlt">pressure</span> <span class="hlt">gradient</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997PhyA..236..243S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997PhyA..236..243S"><span>Asymptotic theory of two-phase gas-solid flow through a vertical tube at moderate <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sergeev, Y. A.; Zhurov, A. I.</p> <p>1997-02-01</p> <p>Based on the equations, constitutive relations and boundary conditions of the kinetic theory of colliding particles in a gas-solid suspension, the approximate theory of the steady, developed vertical flow of a gas-particulate mixture is developed for the case of moderate gas <span class="hlt">pressure</span> <span class="hlt">gradient</span> in a vertical tube. The basic equations and boundary conditions show a singular behaviour of the solution of the problem at the wall. The method of matched asymptotic expansions is applied to develop a boundary layer-type theory for the flow parameters of the particulate phase. The basic equations in the bulk flow are reduced to a system of two ordinary integrodifferential equations for the particle-phase concentration and mean kinetic energy of particle velocity fluctuations (particle-phase pseudotemperature). The distributions of the particle concentration and velocity are found in both the bulk and the boundary layer. The solutions shows the bifurcation of flow parameters, and an explicit criterion is derived to identify a range of the given macroscopic parameters corresponding to upward or downward particulate flow. The integrated parameters (total fluxes of the gas and particle phase) are calculated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1375953-pattern-parallel-edge-plasma-flows-due-pressure-gradients-recycling-resonant-magnetic-perturbations-diii','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1375953-pattern-parallel-edge-plasma-flows-due-pressure-gradients-recycling-resonant-magnetic-perturbations-diii"><span>The pattern of parallel edge plasma flows due to <span class="hlt">pressure</span> <span class="hlt">gradients</span>, recycling, and resonant magnetic perturbations in DIII-D</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Frerichs, H.; Schmitz, Oliver; Evans, Todd; ...</p> <p>2015-07-13</p> <p>High resolution plasma transport simulations with the EMC3-EIRENE code have been performed to address the parallel plasma flow structure in the boundary of a poloidal divertor configuration with non-axisymmetric perturbations at DIII-D. Simulation results show that a checkerboard pattern of flows with alternating direction is generated inside the separatrix. This pattern is aligned with the position of the main resonances (i.e. where the safety factor is equal to rational values q = m/n for a perturbation field with base mode number n): m pairs of alternating forward and backward flow channel exist for each resonance. The poloidal oscillations are alignedmore » with the subharmonic Melnikov function, which indicates that the plasma flow is generated by parallel <span class="hlt">pressure</span> <span class="hlt">gradients</span> along perturbed field lines. Lastly, an additional scrape-off layer-like domain is introduced by the perturbed separatrix which guides field lines from the interior to the divertor targets, resulting in an enhanced outward flow that is consistent with the experimentally observed particle pump-out effect. However, while the lobe structure of the perturbed separatrix is very well reflected in the temperature profile, the same lobes can appear to be smaller in the flow profile due to a competition between high upstream pressure and downstream particle sources driving flows in opposite directions.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4437633','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4437633"><span>Ex-Vivo Lymphatic Perfusion System for Independently Controlling <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> and Transmural Pressure in Isolated Vessels</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kornuta, Jeffrey A.; Dixon, J. Brandon</p> <p>2015-01-01</p> <p>In addition to external forces, collecting lymphatic vessels intrinsically contract to transport lymph from the extremities to the venous circulation. As a result, the lymphatic endothelium is routinely exposed to a wide range of dynamic mechanical forces, primarily fluid shear stress and circumferential stress, which have both been shown to affect lymphatic pumping activity. Although various ex-vivo perfusion systems exist to study this innate pumping activity in response to mechanical stimuli, none are capable of independently controlling the two primary mechanical forces affecting lymphatic contractility: transaxial <span class="hlt">pressure</span> <span class="hlt">gradient</span>, ΔP, which governs fluid shear stress; and average transmural pressure, Pavg, which governs circumferential stress. Hence, the authors describe a novel ex-vivo lymphatic perfusion system (ELPS) capable of independently controlling these two outputs using a linear, explicit model predictive control (MPC) algorithm. The ELPS is capable of reproducing arbitrary waveforms within the frequency range observed in the lymphatics in vivo, including a time-varying ΔP with a constant Pavg, time-varying ΔP and Pavg, and a constant ΔP with a time-varying Pavg. In addition, due to its implementation of syringes to actuate the working fluid, a post-hoc method of estimating both the flow rate through the vessel and fluid wall shear stress over multiple, long (5 sec) time windows is also described. PMID:24809724</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhPl...22g2508F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhPl...22g2508F"><span>The pattern of parallel edge plasma flows due to <span class="hlt">pressure</span> <span class="hlt">gradients</span>, recycling, and resonant magnetic perturbations in DIII-D</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Frerichs, H.; Schmitz, O.; Evans, T.; Feng, Y.; Reiter, D.</p> <p>2015-07-01</p> <p>High resolution plasma transport simulations with the EMC3-EIRENE code have been performed to address the parallel plasma flow structure in the boundary of a poloidal divertor configuration with non-axisymmetric perturbations at DIII-D. Simulation results show that a checkerboard pattern of flows with alternating direction is generated inside the separatrix. This pattern is aligned with the position of the main resonances (i.e., where the safety factor is equal to rational values q = m / n for a perturbation field with base mode number n): m pairs of alternating forward and backward flow channel exist for each resonance. The poloidal oscillations are aligned with the subharmonic Melnikov function, which indicates that the plasma flow is generated by parallel <span class="hlt">pressure</span> <span class="hlt">gradients</span> along perturbed field lines. An additional scrape-off layer-like domain is introduced by the perturbed separatrix which guides field lines from the interior to the divertor targets, resulting in an enhanced outward flow that is consistent with the experimentally observed particle pump-out effect. However, while the lobe structure of the perturbed separatrix is very well reflected in the temperature profile, the same lobes can appear to be smaller in the flow profile due to a competition between high upstream pressure and downstream particle sources driving flows in opposite directions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5381827','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5381827"><span>Transient elastography versus hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> for diagnosing portal hypertension: a systematic review and meta-analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Gaeun; Kim, Moon Young; Baik, Soon Koo</p> <p>2017-01-01</p> <p>Background/Aims Transient elastography (TE) has been proposed as a promising noninvasive alternative to hepatic venous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (HVPG) for detecting portal hypertension (PH). However, previous studies have yielded conflicting results. We gathered evidence from literature on the clinical usefulness of TE versus HVPG for assessing PH. Methods We conducted a systematic review by searching databases for relevant literature evaluating the clinical usefulness of non-invasive TE for assessing PH in patients with cirrhosis. A literature search in Ovid Medline, EMBASE and the Cochrane Library was performed for all studies published prior to December 30, 2015. Results Eight studies (1,356 patients) met our inclusion criteria. For the detection of PH (HVPG ≥6 mmHg), the summary sensitivity and specificity were 0.88 (95% confidence interval [CI] 0.86-0.90) and 0.74 (95% CI 0.67-0.81), respectively. Regarding clinically significant PH (HVPG ≥10 mmHg), the summary sensitivity and specificity were 0.85 (95% CI 0.63-0.97) and 0.71 (95% CI 0.50-0.93), respectively. The overall correlation estimate of TE and HVPG was large (0.75, 95% CI: 0.65; 0.82, P<0.0001). Conclusions TE showed high accuracy and correlation for detecting the severity of PH. Therefore, TE shows promise as a reliable and non-invasive procedure for the evaluation of PH that should be integrated into clinical practice. PMID:28263953</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015DyAtO..71...83S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015DyAtO..71...83S"><span>Using the mean <span class="hlt">pressure</span> <span class="hlt">gradient</span> and NCEP/NCAR reanalysis to estimate the strength of the South Atlantic Anticyclone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salcedo-Castro, Julio; de Camargo, Ricardo; Marone, Eduardo; Sepúlveda, Héctor H.</p> <p>2015-09-01</p> <p>A new methodology is proposed to estimate the strength of the South Atlantic Anticyclone (SAA), using the gridded sea level pressure (SLP) of the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis data. The top quartile (1017.3 hPa) of the SLP data was found a reasonable criterion to delimit the SAA area. Consequently, we defined the SAA area as the quadrangle containing 80% of the observations with pressure >1017.3 hPa. In this quadrangle, an area weighted <span class="hlt">pressure</span> <span class="hlt">gradient</span> (AWPG) was computed for the whole area and for the north-south and west-east halves. When compared with maximum pressure, the AWPG showed a better correlation with the significant wave height (SWH) and wind speed (WS) derived from altimetry. The mean value of the AWPG was 8 × 10-4 Pa/m, with representative values of 9.1 × 10-4 Pa/m and 7.4 × 10-4 Pa/m for austral winter and summer, respectively. The phase difference between the monthly AWPG in the north and south sub-quadrangles accounts for the evolution of the spatial pattern of the anticyclone throughout a year. This quantitative approach proved to be a useful estimate of the strength of South Atlantic Anticyclone. Further improvements of this approach are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JThSc..21...49A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JThSc..21...49A"><span>Direct numerical simulation of convective heat transfer in a zero-<span class="hlt">pressure</span>- <span class="hlt">gradient</span> boundary layer with supercritical water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Azih, C.; Brinkerhoff, J. R.; Yaras, M. I.</p> <p>2012-02-01</p> <p>Experimental research has long shown that forced-convective heat transfer in wall-bounded turbulent flows of fluids in the supercritical thermodynamic state is not accurately predicted by correlations that have been developed for single-phase fluids in the subcritical thermodynamic state. In the present computational study, the statistical properties of turbulent flow as well as the development of coherent flow structures in a zero-<span class="hlt">pressure-gradient</span> flat-plate boundary layer are investigated in the absence of body forces, where the working fluid is in the supercritical thermodynamic state. The simulated boundary layers are developed to a friction Reynolds number of 250 for two heat-flux to mass-flux ratios corresponding to cases where normal heat transfer and improved heat transfer are observed. In the case where improved heat transfer is observed, spanwise spacing of the near-wall coherent flow structures is reduced due to a relatively less stable flow environment resulting from the lower magnitudes of the wall-normal viscosity-gradient profile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/6109503','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/6109503"><span>[Comparison of two E.E.C. baths by study of the oncotic pressure-pulmonary artery <span class="hlt">pressure</span> <span class="hlt">gradient</span>].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>D'Enfert, J; Mathieu-Daudé, J C; Grolleau, D; Saussine, M; Allien, M; Chaptal, P A; du Cailar, J</p> <p>1980-01-01</p> <p>Variations in oncotic pressure-pulmonary artery diastolic <span class="hlt">pressure</span> <span class="hlt">gradient</span> and in intrapulmonary shunt were studied in two groups of patients undergoing surgery with extracorporeal circulation for aortocoronary bypass of excision of an aneurysm. The two groups, differed only in terms of the E.C.C. bath (Group A: Ringer Lactate; Group B: DDextran 60,000). The effects of E.C.C. on these parameters were as follows: - decrease in both groups in the gradient (OP-PAP) (respectively P < 0.001 and P < 0.01) but with a more marked decrease in group A than in group B (P < 0.05) with non-negativisation of the gradient in that group; - non-significant variations in Qs/Qt in both groups without any correlation with gradient (OP-PAP). The onset of pulmonary oedema associated with a decrease in gradient (OP-PAP) leads to the suggestion of the use of Dextrans in pathological situations where OP is low or PAP high and all the more so when both of these factors are present.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..DFDD20007S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..DFDD20007S"><span>Two-point correlations for zero-<span class="hlt">pressure-gradient</span> turbulent boundary layers and channels at Reτ ~ 1000 - 2000</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sillero, Juan A.; Jiménez, Javier; Moser, Robert D.</p> <p>2012-11-01</p> <p>Two-point 5-dimensional correlations Cξξ (x ;x' ; y ;y' Δz) are investigated to educe the structure of the velocity and pressure fluctuations in zero-<span class="hlt">pressure-gradient</span> turbulent boundary layers in the range Reθ = 2780 - 6680 , and in matching channels at Reτ ~ 1000 - 2000 . Eddies in channels are coherent over longer distances than in boundary layers, especially for Cuu in the direction of the flow. At the 5% level, the maximum streamwise length of Cuu is O (6 δ) for boundary layers and O (15 h) for channels. The corresponding lengths for the transverse velocities and for the pressure are shorter, O (δ- 2 δ) , and of the same order for both flows. Integral correlation lengths in the streamwise and spanwise directions grow away from the wall, except for Luu , x, which peaks at y ~ 0 . 6 h in channels and at y ~ 0 . 2 δ in boundary layers, probably due to the outer intermittency in the latter. Above the buffer layer, Cuu is inclined by ~ 10 -12o from the wall, the wall-normal velocity and the pressure are roughly vertical, and Cww is inclined by ~30o . Those features seem unaffected by the Reynolds number and by the type of flow. Funded by CICYT, INCITE and ERC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840052446&hterms=pedrosa&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpedrosa','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840052446&hterms=pedrosa&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpedrosa"><span>Convective heat transfer studies at high temperatures with <span class="hlt">pressure</span> <span class="hlt">gradient</span> for inlet flow Mach number of 0.45</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pedrosa, A. C. F.; Nagamatsu, H. T.; Hinckel, J. A.</p> <p>1984-01-01</p> <p>Heat transfer measurements were determined for a flat plate with and without <span class="hlt">pressure</span> <span class="hlt">gradient</span> for various free stream temperatures, wall temperature ratios, and Reynolds numbers for an inlet flow Mach number of 0.45, which is a representative inlet Mach number for gas turbine rotor blades. A shock tube generated the high temperature and pressure air flow, and a variable geometry test section was used to produce inlet flow Mach number of 0.45 and accelerate the flow over the plate to sonic velocity. Thin-film platinum heat gages recorded the local heat flux for laminar, transition, and turbulent boundary layers. The free stream temperatures varied from 611 R (339 K) to 3840 R (2133 K) for a T(w)/T(r,g) temperature ratio of 0.87 to 0.14. The Reynolds number over the heat gages varied from 3000 to 690,000. The experimental heat transfer data were correlated with laminar and turbulent boundary layer theories for the range of temperatures and Reynolds numbers and the transition phenomenon was examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3913518','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3913518"><span>Experimental Study on the Flow Regimes and <span class="hlt">Pressure</span> <span class="hlt">Gradients</span> of Air-Oil-Water Three-Phase Flow in Horizontal Pipes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Al-Hadhrami, Luai M.; Shaahid, S. M.; Tunde, Lukman O.; Al-Sarkhi, A.</p> <p>2014-01-01</p> <p>An experimental investigation has been carried out to study the flow regimes and <span class="hlt">pressure</span> <span class="hlt">gradients</span> of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and <span class="hlt">pressure</span> <span class="hlt">gradients</span> have been studied. The experiments have been conducted at 20°C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3 m/s to 3 m/s and air velocity varied from 0.29 m/s to 52.5 m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The <span class="hlt">pressure</span> <span class="hlt">gradients</span> have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the <span class="hlt">pressure</span> <span class="hlt">gradients</span> increased with the increase in the superficial liquid velocity. The <span class="hlt">pressure</span> <span class="hlt">gradient</span> first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed. PMID:24523645</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24523645','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24523645"><span>Experimental study on the flow regimes and <span class="hlt">pressure</span> <span class="hlt">gradients</span> of air-oil-water three-phase flow in horizontal pipes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Al-Hadhrami, Luai M; Shaahid, S M; Tunde, Lukman O; Al-Sarkhi, A</p> <p>2014-01-01</p> <p>An experimental investigation has been carried out to study the flow regimes and <span class="hlt">pressure</span> <span class="hlt">gradients</span> of air-oil-water three-phase flows in 2.25 ID horizontal pipe at different flow conditions. The effects of water cuts, liquid and gas velocities on flow patterns and <span class="hlt">pressure</span> <span class="hlt">gradients</span> have been studied. The experiments have been conducted at 20 °C using low viscosity Safrasol D80 oil, tap water and air. Superficial water and oil velocities were varied from 0.3 m/s to 3 m/s and air velocity varied from 0.29 m/s to 52.5 m/s to cover wide range of flow patterns. The experiments were performed for 10% to 90% water cuts. The flow patterns were observed and recorded using high speed video camera while the pressure drops were measured using pressure transducers and U-tube manometers. The flow patterns show strong dependence on water fraction, gas velocities, and liquid velocities. The observed flow patterns are stratified (smooth and wavy), elongated bubble, slug, dispersed bubble, and annular flow patterns. The <span class="hlt">pressure</span> <span class="hlt">gradients</span> have been found to increase with the increase in gas flow rates. Also, for a given superficial gas velocity, the <span class="hlt">pressure</span> <span class="hlt">gradients</span> increased with the increase in the superficial liquid velocity. The <span class="hlt">pressure</span> <span class="hlt">gradient</span> first increases and then decreases with increasing water cut. In general, phase inversion was observed with increase in the water cut. The experimental results have been compared with the existing unified Model and a good agreement has been noticed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016OptCo.380..108Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016OptCo.380..108Z"><span>Abnormal single or composite dissipative <span class="hlt">solitons</span> generation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhong, Xianqiong; Liu, Dingyao; Cheng, Ke; Sheng, Jianan</p> <p>2016-12-01</p> <p>The evolution dynamics of the initial finite energy Airy pulses and Airy pulse pairs are numerically investigated in the cubic-quintic complex Ginzberg-Laudau equation governed dissipative system. Depending on different initial excitations and system parameters, abnormal double, triple, and quadruple composite dissipative <span class="hlt">solitons</span> as well as single dissipative <span class="hlt">solitons</span> can be observed. The composite dissipative <span class="hlt">solitons</span> may consist of identical or different types of pulsating <span class="hlt">solitons</span>. Moreover, the creeping <span class="hlt">solitons</span> and the single ordinary pulsating <span class="hlt">solitons</span> can even appear in the parameter regions where originally the other types of pulsating <span class="hlt">solitons</span> exist. Besides, before evolving into each abnormal dissipative <span class="hlt">soliton</span>, the initial finite energy Airy pulse or pulse pairs generally exhibit very interesting and unique early evolution behavior.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22250948','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22250948"><span>Geometric <span class="hlt">solitons</span> of Hamiltonian flows on manifolds</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Song, Chong; Sun, Xiaowei; Wang, Youde</p> <p>2013-12-15</p> <p>It is well-known that the LIE (Locally Induction Equation) admit <span class="hlt">soliton</span>-type solutions and same <span class="hlt">soliton</span> solutions arise from different and apparently irrelevant physical models. By comparing the <span class="hlt">solitons</span> of LIE and Killing magnetic geodesics, we observe that these <span class="hlt">solitons</span> are essentially decided by two families of isometries of the domain and the target space, respectively. With this insight, we propose the new concept of geometric <span class="hlt">solitons</span> of Hamiltonian flows on manifolds, such as geometric Schrödinger flows and KdV flows for maps. Moreover, we give several examples of geometric <span class="hlt">solitons</span> of the Schrödinger flow and geometric KdV flow, including magnetic curves as geometric Schrödinger <span class="hlt">solitons</span> and explicit geometric KdV <span class="hlt">solitons</span> on surfaces of revolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/871827','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/servlets/purl/871827"><span><span class="hlt">Soliton</span> quenching NLTL impulse circuit with a pulse forming network at the output</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>McEwan, Thomas E.; Dallum, Gregory E.</p> <p>1998-01-01</p> <p>An impulse forming circuit is disclosed which produces a clean impulse from a nonlinear transmission line <span class="hlt">compressed</span> step function without customary <span class="hlt">soliton</span> ringing by means of a localized pulse shaping and differentiating network which shunts the nonlinear transmission line output to ground.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/672704','DOE-PATENT-XML'); return false;" href="http://www.osti.gov/scitech/biblio/672704"><span><span class="hlt">Soliton</span> quenching NLTL impulse circuit with a pulse forming network at the output</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>McEwan, T.E.; Dallum, G.E.</p> <p>1998-09-08</p> <p>An impulse forming circuit is disclosed which produces a clean impulse from a nonlinear transmission line <span class="hlt">compressed</span> step function without customary <span class="hlt">soliton</span> ringing by means of a localized pulse shaping and differentiating network which shunts the nonlinear transmission line output to ground. 5 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA559827','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA559827"><span>On-chip Electrical <span class="hlt">Soliton</span> Oscillators for Picosecond Pulse Self-Generation and THz Electronics</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2012-01-17</p> <p>nonlinear line substantially sharpens the pulse . This work is in contrast to our earlier circular <span class="hlt">soliton</span> oscillator... sharpening mechanism provided at the open end of the nonlinear line further <span class="hlt">compresses</span> the pulse . In an experimental prototype (discrete prototype for proof... nonlinear properties, to ensure oscillation stability. The nonlinear line substantially sharpens the pulse . This work is in contrast to our</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013IJMPA..2850136M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013IJMPA..2850136M"><span>The <span class="hlt">Soliton-Soliton</span> Interaction in the Chiral Dilaton Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mantovani-Sarti, Valentina; Park, Byung-Yoon; Vento, Vicente</p> <p>2013-10-01</p> <p>We study the interaction between two B = 1 states in the Chiral Dilaton Model where baryons are described as nontopological <span class="hlt">solitons</span> arising from the interaction of chiral mesons and quarks. By using the hedgehog solution for B = 1 states we construct, via a product ansatz, three possible B = 2 configurations to analyse the role of the relative orientation of the hedgehog quills in the dynamics of the <span class="hlt">soliton-soliton</span> interaction and investigate the behavior of these solutions in the range of long/intermediate distance. One of the solutions is quite binding due to the dynamics of the π and σ fields at intermediate distance and should be used for nuclear matter studies. Since the product ansatz break down as the two <span class="hlt">solitons</span> get close, we explore the short range distance regime with a model that describes the interaction via a six-quark bag ansatz. We calculate the interaction energy as a function of the inter-<span class="hlt">soliton</span> distance and show that for small separations the six quarks bag, assuming a hedgehog structure, provides a stable bound state that at large separations connects with a special configuration coming from the product ansatz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhRvE..61.2010K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhRvE..61.2010K"><span>Analytical solution for photorefractive screening <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Królikowski, Wieslaw; Luther-Davies, Barry; McCarthy, Glen; Bledowski, Aleksander</p> <p>2000-02-01</p> <p>We study formation and interaction of one-dimensional screening <span class="hlt">solitons</span> in a photorefractive medium with sublinear dependence of the photoconductivity on light intensity. We find an exact analytical solution to the corresponding nonlinear Schrödinger equation. We show that these <span class="hlt">solitons</span> are stable in propagation and their interaction is generic for <span class="hlt">solitons</span> of saturable nonlinearity. In particular, they may fuse or ``give birth'' to new <span class="hlt">solitons</span> upon collision.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5596803','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5596803"><span>Spontaneous transition from flat to cylindrical <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Frycz, P.; Infeld, E. )</p> <p>1989-07-24</p> <p>Flat, cylindrical, and spherical <span class="hlt">soliton</span> solutions to various model equations are known. Many of these exact solutions have been seen in numerical simulations. However, there are few simulations that actually show that exact flat <span class="hlt">solitons</span> can break up into an array of exact cylindrical or spherical <span class="hlt">solitons</span> and follow this on a step by step basis. This Letter presents the first of these two kinds of transition for the Zakharov-Kuznetsov equation governing ion acoustic <span class="hlt">solitons</span> in strongly magnetized plasmas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21408494','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21408494"><span>Slow oscillations of dispersion-managed <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hartwig, H.; Boehm, M.; Hause, A.; Mitschke, F.</p> <p>2010-03-15</p> <p>In dispersion-managed fibers, <span class="hlt">soliton</span>-like solutions with periodically recurring shapes exist. These so called dispersion-managed <span class="hlt">solitons</span> are relevant for fiber-optic telecommunication. In this article we address their behavior when there is deviation from the stationary solution, which is accompanied by the excitation of a long-lived periodic oscillation. We give a possible interpretation by applying <span class="hlt">soliton</span> radiation beat analysis, a method capable of analyzing the <span class="hlt">soliton</span> content.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10970520','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10970520"><span>Observation of dipole-mode vector <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Krolikowski; Ostrovskaya; Weilnau; Geisser; McCarthy; Kivshar; Denz; Luther-Davies</p> <p>2000-08-14</p> <p>We report on the first experimental observation of a novel type of optical vector <span class="hlt">soliton</span>, a dipole-mode <span class="hlt">soliton</span>, recently predicted theoretically. We show that these vector <span class="hlt">solitons</span> can be generated in a photorefractive medium employing two different processes: a phase imprinting, and a symmetry-breaking instability of a vortex-mode vector <span class="hlt">soliton</span>. The experimental results display remarkable agreement with the theory, and confirm the robust nature of these radially asymmetric two-component solitary waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997PhRvE..55.7720S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997PhRvE..55.7720S"><span>Properties of an optical <span class="hlt">soliton</span> gas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schwache, A.; Mitschke, F.</p> <p>1997-06-01</p> <p>We consider light pulses propagating in an optical fiber ring resonator with anomalous dispersion. New pulses are fed into the resonator in synchronism with its round-trip time. We show that solitary pulse shaping leads to a formation of an ensemble of subpulses that are identified as <span class="hlt">solitons</span>. All <span class="hlt">solitons</span> in the ensemble are in perpetual relative motion like molecules in a fluid; thus we refer to the ensemble as a <span class="hlt">soliton</span> gas. Properties of this <span class="hlt">soliton</span> gas are determined numerically.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27594309','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27594309"><span>Progressive <span class="hlt">compression</span> versus graduated <span class="hlt">compression</span> for the management of venous insufficiency.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shepherd, Jan</p> <p>2016-09-01</p> <p>Venous leg ulceration (VLU) is a chronic condition associated with chronic venous insufficiency (CVI), where the most frequent complication is recurrence of ulceration after healing. Traditionally, graduated <span class="hlt">compression</span> therapy has been shown to increase healing rates and also to reduce recurrence of VLU. Graduated <span class="hlt">compression</span> occurs because the circumference of the limb is narrower at the ankle, thereby producing a higher pressure than at the calf, which is wider, creating a lower pressure. This phenomenon is explained by the principle known as Laplace's Law. Recently, the view that <span class="hlt">compression</span> therapy must provide a graduated <span class="hlt">pressure</span> <span class="hlt">gradient</span> has been challenged. However, few studies so far have focused on the potential benefits of progressive <span class="hlt">compression</span> where the pressure profile is inverted. This article will examine the contemporary concept that progressive <span class="hlt">compression</span> may be as effective as traditional graduated <span class="hlt">compression</span> therapy for the management of CVI.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhPl...24h2514Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhPl...24h2514Y"><span>Effect of entropy on <span class="hlt">soliton</span> profile in ITG driven magneto-plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yaqub Khan, M.; Iqbal, Javed</p> <p>2017-08-01</p> <p>Interconnection of entropy with the density and temperature of plasmas leads us to investigate the effect of entropy on different plasma related phenomena. By using Braginskii's transport equations and a transformation, the linear dispersion relation and the KdV equation for the ion temperature gradient (ITG) mode having entropy drift are derived. It is found that this mode supports only <span class="hlt">compressive</span> <span class="hlt">solitons</span>. Due to entropy drift, a parameter ηi=Ln/LT is observed in the KdV equation. We found that the <span class="hlt">soliton</span> profile is sensitive to entropy, i.e., due to the changes in the entropy amplitude and the width of <span class="hlt">solitons</span>. It is also observed that the increasing ion temperature and increasing magnetic field affect the shape of the <span class="hlt">soliton</span>. The results are briefly compared with the well-known results of the <span class="hlt">soliton</span> profile, and a change in the structure of the <span class="hlt">soliton</span> profile is found by introducing entropy in the ITG mode. This work may be helpful in the study of entropy based models and in understanding the formation of nonlinear solitary waves driven by the ITG mode in magnetically confined plasmas in the presence of entropy. For illustration, the model has been applied to tokamak plasmas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060040270&hterms=Schrodinger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSchrodinger','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060040270&hterms=Schrodinger&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DSchrodinger"><span><span class="hlt">Soliton</span> resonance in bose-einstein condensate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zak, Michail; Kulikov, I.</p> <p>2002-01-01</p> <p>A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced <span class="hlt">soliton</span> and 'eigen-<span class="hlt">solitons</span>' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark <span class="hlt">solitons</span> in an attractive / repulsive Bose condensate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22482325','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22482325"><span>Critical density of a <span class="hlt">soliton</span> gas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>El, G. A.</p> <p>2016-02-15</p> <p>We quantify the notion of a dense <span class="hlt">soliton</span> gas by establishing an upper bound for the integrated density of states of the quantum-mechanical Schrödinger operator associated with the Korteweg–de Vries <span class="hlt">soliton</span> gas dynamics. As a by-product of our derivation, we find the speed of sound in the <span class="hlt">soliton</span> gas with Gaussian spectral distribution function.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18197238','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18197238"><span>Spiraling multivortex <span class="hlt">solitons</span> in nonlocal nonlinear media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Buccoliero, Daniel; Desyatnikov, Anton S; Krolikowski, Wieslaw; Kivshar, Yuri S</p> <p>2008-01-15</p> <p>We demonstrate the existence of a broad class of higher-order rotating spatial <span class="hlt">solitons</span> in nonlocal nonlinear media. We employ the generalized Hermite-Laguerre-Gaussian ansatz for constructing multivortex <span class="hlt">soliton</span> solutions and study numerically their dynamics and stability. We discuss in detail the tripole <span class="hlt">soliton</span> carrying two spiraling phase dislocations, or self-trapped optical vortices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22378387','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22378387"><span>Observation of vector <span class="hlt">solitons</span> with hidden vorticity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Izdebskaya, Yana V; Rebling, Johannes; Desyatnikov, Anton S; Kivshar, Yuri S</p> <p>2012-03-01</p> <p>This letter reports the first experimental observation, to our knowledge, of optical vector <span class="hlt">solitons</span> composed of two incoherently coupled vortex components. We employ nematic liquid crystal to generate stable vector <span class="hlt">solitons</span> with counterrotating vortices and hidden vorticity. In contrast, the <span class="hlt">solitons</span> with explicit vorticity and corotating vortex components show azimuthal splitting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009PhRvA..80b3806T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009PhRvA..80b3806T"><span><span class="hlt">Soliton</span> modulation instability in fiber lasers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, D. Y.; Zhao, L. M.; Wu, X.; Zhang, H.</p> <p>2009-08-01</p> <p>We report experimental evidence of <span class="hlt">soliton</span> modulation instability in erbium-doped fiber lasers. An alternate type of spectral sideband generation was always experimentally observed on the <span class="hlt">soliton</span> spectrum of the erbium-doped <span class="hlt">soliton</span> fiber lasers when energy of the formed <span class="hlt">solitons</span> reached beyond a certain threshold value. Following this spectral sideband generation, if the pump power of the lasers was further increased, either a new <span class="hlt">soliton</span> would be formed or the existing <span class="hlt">solitons</span> would experience dynamical instabilities, such as the period-doubling bifurcations or period-doubling route to chaos. We point out that the mechanism for this <span class="hlt">soliton</span> spectral sideband generation is the modulation instability of the <span class="hlt">solitons</span> in the lasers. We further show that, owing to the internal energy balance of a dissipative <span class="hlt">soliton</span>, modulation instability itself does not destroy the stable <span class="hlt">soliton</span> evolution in a laser cavity. It is the strong resonant wave coupling between the <span class="hlt">soliton</span> and dispersive waves that leads to the dynamic instability of the <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12653362','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12653362"><span>Stable spatial <span class="hlt">solitons</span> in semiconductor optical amplifiers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ultanir, E A; Michaelis, D; Lederer, F; Stegeman, G I</p> <p>2003-02-15</p> <p>The existence of stable dissipative spatial <span class="hlt">solitons</span> at low intensities in patterned electrode semiconductor optical amplifiers (SOAs) is predicted theoretically. In contrast to conventional SOAs, this system may support stable <span class="hlt">solitons</span> because the inherent saturating losses provide subcritical bifurcations for both the plane-wave and the <span class="hlt">soliton</span> solution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12857133','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12857133"><span>Stable dissipative <span class="hlt">solitons</span> in semiconductor optical amplifiers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ultanir, Erdem A; Stegeman, George I; Michaelis, Dirk; Lange, Christoph H; Lederer, Falk</p> <p>2003-06-27</p> <p>We have observed for the first time stable spatial <span class="hlt">solitons</span> in semiconductor optical amplifiers. <span class="hlt">Soliton</span> destabilization due to the growth of background noise was suppressed by using patterned electrodes on the device. Numerical simulations fit very well with the experiment results. We show that it is possible to excite these <span class="hlt">solitons</span> with about 60 mW input power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060040270&hterms=einstein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Deinstein','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060040270&hterms=einstein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Deinstein"><span><span class="hlt">Soliton</span> resonance in bose-einstein condensate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zak, Michail; Kulikov, I.</p> <p>2002-01-01</p> <p>A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced <span class="hlt">soliton</span> and 'eigen-<span class="hlt">solitons</span>' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark <span class="hlt">solitons</span> in an attractive / repulsive Bose condensate.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010PhDT.......112T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010PhDT.......112T"><span>Characterization of the influence of a favorable <span class="hlt">pressure</span> <span class="hlt">gradient</span> on the basic structure of a mach 5.0 high reynolds number supersonic turbulent boundary layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tichenor, Nathan Ryan</p> <p></p> <p>High-speed high Reynolds number boundary layer flows with mechanical non-equilibrium effects have numerous practical applications; examples include access-to-space ascent, re-entry and descent, and military hypersonic systems. However, many of the basic turbulent flow processes in this regime are poorly understood and are beyond the realm of modern direct numerical simulations Previous studies have shown that curvature driven <span class="hlt">pressure</span> <span class="hlt">gradients</span> significantly alter the state of the turbulence in high-speed boundary layers; the turbulence levels have been shown to decrease by large amounts (up to 100%) and the Reynolds shear stress has been shown to change sign. However, most of our understanding is based on point measurement techniques such as hot-wire and Laser Doppler anemometry acquired at low to moderate supersonic Mach numbers (i.e., M = 2-3). After reviewing the available literature, the following scientific questions remain unanswered pertaining to the effect of favorable <span class="hlt">pressure</span> <span class="hlt">gradients</span>: (1) How is state of the mean flow and turbulence statistics altered? (2) How is the structure of wall turbulence; break-up, stretch or a combination? (3) How are the Reynolds stress component production mechanisms altered? (4) What is the effect of Mach number on the above processes? To answer these questions and to enhance the current database, an experimental analysis was performed to provide high fidelity documentation of the mean and turbulent flow properties using two-dimensional particle image velocimetry (PIV) along with flow visualizations of a high speed (M = 4.88), high Reynolds number (Retheta ≈ 36,000) supersonic turbulent boundary layer with curvature-driven favorable <span class="hlt">pressure</span> <span class="hlt">gradients</span> (a nominally zero, a weak, and a strong favorable <span class="hlt">pressure</span> <span class="hlt">gradient</span>). From these data, detailed turbulence analyses were performed including calculating classical mean flow and turbulence statistics, examining turbulent stress production, and performing quadrant</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27628359','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27628359"><span>80  nJ ultrafast dissipative <span class="hlt">soliton</span> generation in dumbbell-shaped mode-locked fiber laser.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, He; Chen, Sheng-Ping; Jiang, Zong-Fu; Hou, Jing</p> <p>2016-09-15</p> <p>A novel all-fiberized dumbbell-shaped mode-locked fiber laser was developed to directly generate 80 nJ dissipative <span class="hlt">solitons</span>, which can be linearly <span class="hlt">compressed</span> from 85 to 1.2 ps externally with a diffraction grating pair. The pulse peak power reached 42 kW after <span class="hlt">compression</span>. With the most available pump power, stable dissipative <span class="hlt">soliton</span> bundles with up to 628 nJ bundle energy were obtained. The corresponding average output power reached 2.2 W. The employment of dual-nonlinear-optical-loop mirrors and large-mode-area fibers in the cavity played an essential role in improving structural compactness and producing high-energy ultrafast pulses. To the best of our knowledge, these are the most energetic <span class="hlt">compressible</span> dissipative <span class="hlt">solitons</span> generated from a strictly all-fiber cavity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhR...507...43K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhR...507...43K"><span>Bifurcations of <span class="hlt">solitons</span> and their stability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuznetsov, E. A.; Dias, F.</p> <p>2011-10-01</p> <p>In spite of the huge progress in studies on solitary waves in the seventies and eighties of the XX century as well as their practical importance, the theory of <span class="hlt">solitons</span> is far from being complete. Only in 1989, Longuet-Higgins in his numerical experiments discovered one-dimensional <span class="hlt">solitons</span> for gravity-capillary waves in deep water. These <span class="hlt">solitons</span> essentially differed from those in shallow water where the KDV equation could be used. Being localized, these <span class="hlt">solitons</span>, unlike the KDV <span class="hlt">solitons</span>, contain many oscillations in their shape. The number of oscillations was found to increase while approaching the maximal phase velocity for linear gravity-capillary waves and simultaneously the <span class="hlt">soliton</span> amplitude was demonstrated to vanish. In fact, it was the first time ever that the bifurcation of <span class="hlt">solitons</span> was observed. This review discusses bifurcations of <span class="hlt">solitons</span>, both supercritical and subcritical, with applications to fluids and nonlinear optics as well. The main attention is paid to the universality of <span class="hlt">soliton</span> behavior and stability of <span class="hlt">solitons</span> while approaching supercritical bifurcations. For all physical models considered in this review, <span class="hlt">solitons</span> are stationary points of the corresponding Hamiltonian for the fixed integrals of motion, i.e., the total momentum, number of quasi-particles, etc. Two approaches are used for the <span class="hlt">soliton</span> stability analysis. The first method is based on the Lyapunov theory and another one is connected with the linear stability criterion of the Vakhitov-Kolokolov type. The Lyapunov stability proof is maintained by means of application of the integral majorized inequalities being sequences of the Sobolev embedding theorem. This allows one to demonstrate the boundedness of the Hamiltonians and show that <span class="hlt">solitons</span>, as stationary points, which realize the minimum (or maximum) of the Hamiltonian, are stable in the Lyapunov sense. In the case of unstable <span class="hlt">solitons</span>, the nonlinear stage of their instability near the bifurcation point results in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11016507','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11016507"><span>Can a linear electrical analog model of a mechanical valve predict flow by using a <span class="hlt">pressure</span> <span class="hlt">gradient</span>?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Graen, M D; Ewert, D L; Glower, J S; Gray, L A; Koenig, S C</p> <p>2000-01-01</p> <p>The objective was to determine whether a previously developed technique for biological aortic valves could predict flow through a mechanical valve. An electrical analog model of the aortic valve that includes compliance, resistance, and inertance parameters, and corresponding second order differential equations was used to predict flow given a <span class="hlt">pressure</span> <span class="hlt">gradient</span>, as previously reported. Simulated pressures and flow were recorded by using a pulse duplicator system. The heart rate was varied from 60 to 180 bpm, and the stroke volume was varied from 22 to 67 cc. Resistance, inertance, and compliance parameters of the governing differential equation were estimated by using a least-squares fit to the measured flow at 120 bpm and 50 cc stroke volume. By using these parameter estimates, flow was calculated for other heart rates and stroke volumes. To achieve a better flow prediction, a nonlinear filter (third order polynomial range calibration equation) was applied to the output of the linear model (flow). The mean error, full-scale error, and spectral error in magnitude and phase between measured and predicted flow were compared. Error in mean flow ranged from 3% at medium flow rates to 90% at low flow rates. The maximum and minimum full scale errors were 12% and 5%, respectively. Error in the harmonics of measured and calculated flow ranged from 0% to 55%. Larger errors were usually present at the higher harmonics. The agreement between measured and calculated flow was better at normal and high flows but rather poor at low flows. The nonlinear filter (range calibration equation) was unable to account for the discrepancies between the measured and calculated flow over all flow ranges. It seems that this linear model and nonlinear filter have limited application, and an alternate nonlinear approach may produce better results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.454..213T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.454..213T"><span>Evidence for impact induced <span class="hlt">pressure</span> <span class="hlt">gradients</span> on the Allende CV3 parent body: Consequences for fluid and volatile transport</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tait, Alastair W.; Fisher, Kent R.; Srinivasan, Poorna; Simon, Justin I.</p> <p>2016-11-01</p> <p>Carbonaceous chondrites, such as those associated with the Vigarano (CV) parent body, exhibit a diverse range of oxidative/reduced alteration mineralogy (McSween, 1977). Although fluids are often cited as the medium by which this occurs (Rubin, 2012), a mechanism to explain how this fluid migrates, and why some meteorite subtypes from the same planetary body are more oxidized than others remains elusive. In our study we examined a slab of the well-known Allende (CV3OxA) meteorite. Using several petrological techniques (e.g., Fry's and Flinn) and Computerized Tomography (CT) we discover it exhibits a strong penetrative planar fabric, resulting from strain partitioning among its major components: Calcium-Aluminum-rich Inclusions (CAIs) (64.5%CT) > matrix (21.5%Fry) > chondrules (17.6%CT). In addition to the planar fabric, we found a strong lineation defined by the alignment of the maximum elongation of flattened particles interpreted to have developed by an impact event. The existence of a lineation could either be non-coaxial deformation, or the result of a mechanically heterogeneous target material. In the later case it could have formed due to discontinuous patches of sub-surface ice and/or fabrics developed through prior impact compaction (MacPherson and Krot, 2014), which would have encouraged preferential flow within the target material immediately following the impact, compacting pore spaces. We suggest that structurally controlled movement of alteration fluids in the asteroid parent body along <span class="hlt">pressure</span> <span class="hlt">gradients</span> contributed to the formation of secondary minerals, which may have ultimately lead to the different oxidized subtypes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22208017','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22208017"><span>The Role of Postintervention Pullback <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> in Percutaneous Transluminal Angioplasty for Central Vein Stenosis in Dialysis Patients</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lin, Yu-Sheng; Yang, Cheng-Hsu; Chu, Chi-Ming; Fang, Chi-Yung Chen, Chien-Jen; Hsu, Jen-Te Yang, Teng-Yao; Hang, Chi-Ling Wu, Chiung-Jen</p> <p>2013-10-15</p> <p>Purpose: The severity of residual stenosis (RS) sometimes cannot be accurately measured by angiography during central vein intervention. This study evaluated the role of pullback pressure measurement during central vein stenosis (CVS) intervention. Methods: A retrospective review enrolled 94 consecutive dialysis patients who underwent CVS interventions but not stenting procedures. Patients were classified into 2 groups by either angiography or <span class="hlt">pressure</span> <span class="hlt">gradient</span> (PG) criteria, respectively. Groups divided by angiographic result were successful group (RS {<=}30 %) and acceptable group (50 % {>=} RS > 30 %), while groups divided by PG were low PG group (PG {<=}5 mmHg) and high PG group (PG >5 mmHg). Baseline characteristics and 12-month patency rates between the groups were analyzed. Results: The angiography results placed 63 patients in the successful group and 31 patients in the acceptable group. The patency rate at 12 month was not statistically different (P = 0.167). When the patients were reclassified by the postintervention pullback PG, the patency rate at 12 months was significant (P = 0.048). Further analysis in groups redivided by different combinations of RS and PG criteria identified significant differences in the group with both RS {<=}30 % and PG {<=}5 mmHg compared with those with either RS >30 % (P = 0.047) or PG >5 mmHg (P = 0.027). In addition, there was a significant difference between those with both RS {<=}30 % and PG {<=}5 mmHg compared with those with both RS >30 % and PG >5 mmHg (P = 0.027). Conclusion: Postintervention PG can better predict long-term outcomes after angioplasty for CVS in nonstented dialysis patients than angiography.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15512946','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15512946"><span>Effect of hydrostatic <span class="hlt">pressure</span> <span class="hlt">gradients</span> and Na2EDTA on permeability of human Schlemm's canal cell monolayers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burke, A G; Zhou, W; O'Brien, E T; Roberts, B C; Stamer, W D</p> <p>2004-06-01</p> <p>Elevated intraocular pressure in those with glaucoma appears to be a function of increased resistance to movement of aqueous humor through the conventional outflow pathway. The majority of resistance in both normal and glaucomatous eyes is generated in the region between the juxtacanalicular trabecular meshwork and the inner wall of Schlemm's canal. To accommodate transient elevations in pressure, we hypothesize that conventional outflow increases rapidly due to changes in complexity of intercellular junctions between cells of the inner wall of Schlemm's canal. To test this hypothesis we examined specifically the effects of hydrostatic <span class="hlt">pressure</span> <span class="hlt">gradients</span> and the calcium chelator, Na2EDTA, on permeability of cultured human Schlemm's canal cell monolayers in isolation. Human Schlemm's Canal cells were isolated, cultured and then seeded onto permeable supports and maintained in culture to allow intercellular junctions to mature. With a minimum net transendothelial electrical resistance of 10 Ohm cm2, cells were placed into an Ussing-type chamber and hydraulic conductivity was calculated from pressure and flow measurements that were continuously recorded. Simultaneously, transendothelial electrical resistance was measured manually at fixed intervals. In parallel experiments, cell margins were monitored in real time by videomicroscopy. During the baseline measurement period when cells were exposed to pressure but not Na2EDTA, hydraulic conductivity was constant but transendothelial electrical resistance decreased continuously at rate of 0.24 Ohm cm2/minute. After Na2EDTA treatment, no significant change in transendothelial electrical resistance was measured while, hydraulic conductivity of Schlemm's Canal monolayers increased significantly by 125%; corresponding to noticeable intercellular separations. Restoration of cell-cell contact was observed by videomicroscopy 30 minutes following washout of Na2EDTA and functionally after 2 hours. Responses of Schlemm's Canal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993PhDT........53S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993PhDT........53S"><span>The fluid mechanics of a high aspect ratio slot with an impressed <span class="hlt">pressure</span> <span class="hlt">gradient</span> and secondary injection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sobanik, John Bertram</p> <p>1993-01-01</p> <p>A high aspect ratio slot flow (which emulates the gas leakage path in a gas turbine engine outer turbine air seal) is studied by use of a high aspect ratio slot using water as the working fluid. The cross section of the geometry is similar to a 'T', the slot being the vertical stroke and the main flow being the cross bar. A <span class="hlt">pressure</span> <span class="hlt">gradient</span> in the axial direction is created by blocking the main flow at a discreet location with an orifice plate (or blade tip simulator), located above the slot. Seven individually metered secondary flow injectors are located periodically along the bottom of the wall of the slot. Two slot widths, 1/8 and 1/4 inch, were investigated for length to width aspect ratios of 384 and 192 and height to width aspect ratios 33.2 and 16.6 respectively. Orifice plate pressure drops sufficient to give Reynolds numbers based upon half width of the slot, without secondary injection turned on, of 2350 and 4700 in the 1/8 inch slot and 4700 and 9400 in the 1/4 inch slot were run. Various secondary injection scenarios were added to the flow, the cases most studied being the no-injection and the all injectors flowing equal mass rates. Total injection rates for all seven injectors of 3.78 and 7.56 slot volumes per second were run. Laser velocimetry data and flow visualization pictures using fluorescein dye in the secondary flow are compared with computational results form the TEACH 3-D computer code. Major features and trends of the flow are captured by the computational model. Recommendations for further improvement of the numerical accuracy involves modification of the TEACH 3-D code to allow the 'slip condition' on all confining boundaries of the flow, or using a code which permits the 'slip condition' on all boundaries as a built-in option.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28703367','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28703367"><span>Temporal relationship between instantaneous <span class="hlt">pressure</span> <span class="hlt">gradients</span> and peak-to-peak systolic ejection gradient in congenital aortic stenosis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boe, Brian A; Norris, Mark D; Zampi, Jeffrey D; Rocchini, Albert P; Ensing, Gregory J</p> <p>2017-07-12</p> <p>We sought to identify a time during cardiac ejection when the instantaneous <span class="hlt">pressure</span> <span class="hlt">gradient</span> (IPG) correlated best, and near unity, with peak-to-peak systolic ejection gradient (PPSG) in patients with congenital aortic stenosis. Noninvasive echocardiographic measurement of IPG has limited correlation with cardiac catheterization measured PPSG across the spectrum of disease severity of congenital aortic stenosis. A major contributor is the observation that these measures are inherently different with a variable relationship dependent on the degree of stenosis. Hemodynamic data from cardiac catheterizations utilizing simultaneous pressure measurements from the left ventricle (LV) and ascending aorta (AAo) in patients with congenital valvar aortic stenosis was retrospectively reviewed over the past 5 years. The cardiac cycle was standardized for all patients using the percentage of total LV ejection time (ET). Instantaneous gradient at 5% intervals of ET were compared to PPSG using linear regression and Bland-Altman analysis. A total of 22 patients underwent catheterization at a median age of 13.7 years (interquartile range [IQR] 10.3-18.0) and median weight of 51.1 kg (IQR 34.2-71.6). The PPSG was 46.5 ± 12.6 mm Hg (mean ± SD) and correlated suboptimally with the maximum and mean IPG. The midsystolic IPG (occurring at 50% of ET) had the strongest correlation with the PPSG ( PPSG = 0.97(IPG50%)-1.12, R(2)  = 0.88), while the IPG at 55% of ET was closest to unity ( PPSG = 0.997(IPG55%)-1.17, R(2)  = 0.87). The commonly measured maximum and mean IPG are suboptimal estimates of the PPSG in congenital aortic stenosis. Using catheter-based data, IPG at 50%-55% of ejection correlates well with PPSG. This may allow for a more accurate estimation of PPSG via noninvasive assessment of IPG. © 2017 Wiley Periodicals, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890013463','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890013463"><span>An experimental investigation of a low Reynolds number turbulent boundary layer subject to an adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Watmuff, Jonathan H.</p> <p>1989-01-01</p> <p>A very low Reynolds number turbulent boundary layer subject to an adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> is studied. The aim is to obtain highly accurate mean-flow and turbulence measurements under conditions that can be closely related to the numerical simulations of Philippe Spalart for the purposes of CFD validation. Much of the Boundary Layer Wind Tunnel was completely rebuilt with a new wider contraction and working section which will improve compatibility with the simulations. A unique sophisticated high-speed computer controlled 3-D probe traversing mechanism was integrated into the test section. Construction of the tunnel and traverse is discussed in some detail. The hardware is now complete, and measurements are in progress. The mean-flow data indicate that a suitably two-dimensional base flow was established. Automation of the probe positioning and data acquistion have led to a decreased running time for total pressure measurements. However, the most significant benefits are expected to occur when using hot-wire probes. Calibrations can be performed automatically and there is no need to handle fragile probes when moving between measuring stations. Techniques are being developed which require sampling of the signals from moving hot-wire probes on the basis of their position in the flow. Measurements can be made in high intensity turbulence by flying probes upstream at high speed so that the relative magnitude of the turbulent velocity fluctuations are reduced. In regions, where the turbulence intensity is not too large, the probe can also be repetitively scanned across very dense spatial grids in other directions. With this technique, a complete profile can be measured in about 1/3 the time and with a spatial density about 50 times that obtainable using a stationary probe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4663650','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4663650"><span>Functional Heart Valve Scaffolds Obtained by Complete Decellularization of Porcine Aortic Roots in a Novel Differential <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Perfusion System</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sierad, Leslie Neil; Shaw, Eliza Laine; Bina, Alexander; Brazile, Bryn; Rierson, Nicholas; Patnaik, Sourav S.; Kennamer, Allison; Odum, Rebekah; Cotoi, Ovidiu; Terezia, Preda; Branzaniuc, Klara; Smallwood, Harrison; Deac, Radu; Egyed, Imre; Pavai, Zoltan; Szanto, Annamaria; Harceaga, Lucian; Suciu, Horatiu; Raicea, Victor; Olah, Peter; Simionescu, Agneta; Liao, Jun; Movileanu, Ionela</p> <p>2015-01-01</p> <p>There is a great need for living valve replacements for patients of all ages. Such constructs could be built by tissue engineering, with perspective of the unique structure and biology of the aortic root. The aortic valve root is composed of several different tissues, and careful structural and functional consideration has to be given to each segment and component. Previous work has shown that immersion techniques are inadequate for whole-root decellularization, with the aortic wall segment being particularly resistant to decellularization. The aim of this study was to develop a differential <span class="hlt">pressure</span> <span class="hlt">gradient</span> perfusion system capable of being rigorous enough to decellularize the aortic root wall while gentle enough to preserve the integrity of the cusps. Fresh porcine aortic roots have been subjected to various regimens of perfusion decellularization using detergents and enzymes and results compared to immersion decellularized roots. Success criteria for evaluation of each root segment (cusp, muscle, sinus, wall) for decellularization completeness, tissue integrity, and valve functionality were defined using complementary methods of cell analysis (histology with nuclear and matrix stains and DNA analysis), biomechanics (biaxial and bending tests), and physiologic heart valve bioreactor testing (with advanced image analysis of open–close cycles and geometric orifice area measurement). Fully acellular porcine roots treated with the optimized method exhibited preserved macroscopic structures and microscopic matrix components, which translated into conserved anisotropic mechanical properties, including bending and excellent valve functionality when tested in aortic flow and pressure conditions. This study highlighted the importance of (1) adapting decellularization methods to specific target tissues, (2) combining several methods of cell analysis compared to relying solely on histology, (3) developing relevant valve-specific mechanical tests, and (4) in vitro testing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24917414','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24917414"><span>Effects of flecainide on left ventricular <span class="hlt">pressure</span> <span class="hlt">gradient</span> and symptoms in obstructive hypertrophic cardiomyopathy: a comparison of flecainide and disopyramide.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Haruki, Shintaro; Minami, Yuichiro; Suzuki, Atsushi; Hagiwara, Nobuhisa</p> <p>2015-09-01</p> <p>It remains unclear whether flecainide, a Class I antiarrhythmic drug, improves left ventricular <span class="hlt">pressure</span> <span class="hlt">gradient</span> (LVPG) or symptoms in patients with obstructive hypertrophic cardiomyopathy (HCM). Our study evaluated the long-term efficacy of flecainide, compared to disopyramide, when administered orally, on LVPG and symptoms in obstructive HCM patients. Among 164 obstructive HCM patients, 15 were administered oral flecainide therapy and 33 administered oral disopyramide therapy. LVPG declined from 79.8 ± 36.6 to 39.2 ± 36.7 mmHg (p = 0.003) after flecainide therapy and from 74.5 ± 26.4 to 31.4 ± 24.8 mmHg (p < 0.001) after disopyramide therapy. The percent reduction in LVPG was -47.9 ± 43.2 % in patients treated with flecainide, comparable to the results for those treated with disopyramide (-57.1 ± 33.0 %; p = 0.425). We found no significant differences in improvement in NYHA functional class between patients treated with flecainide and those treated with disopyramide (p = 0.331). Patients treated with flecainide exhibited no significant adverse side effects, and there was no need for myectomy or alcohol septal ablation to reduce LVPG and symptoms. Improvements in LVPG and symptoms were similar in patients treated with flecainide and patients treated with disopyramide, suggesting that flecainide is a potentially useful alternative for symptomatic obstructive HCM patients, particularly those with disopyramide-induced vagolytic side effects, narrow angle glaucoma, or prostatic hyperplasia and pre-existing urination difficulties. Our data must be viewed with caution, however, in view of the small number of study patients. Flecainide therapy will require further proof of safety before it can be routinely recommended in patients with symptomatic obstructive HCM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26467108','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26467108"><span>Functional Heart Valve Scaffolds Obtained by Complete Decellularization of Porcine Aortic Roots in a Novel Differential <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> Perfusion System.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sierad, Leslie Neil; Shaw, Eliza Laine; Bina, Alexander; Brazile, Bryn; Rierson, Nicholas; Patnaik, Sourav S; Kennamer, Allison; Odum, Rebekah; Cotoi, Ovidiu; Terezia, Preda; Branzaniuc, Klara; Smallwood, Harrison; Deac, Radu; Egyed, Imre; Pavai, Zoltan; Szanto, Annamaria; Harceaga, Lucian; Suciu, Horatiu; Raicea, Victor; Olah, Peter; Simionescu, Agneta; Liao, Jun; Movileanu, Ionela; Harpa, Marius; Simionescu, Dan Teodor</p> <p>2015-12-01</p> <p>There is a great need for living valve replacements for patients of all ages. Such constructs could be built by tissue engineering, with perspective of the unique structure and biology of the aortic root. The aortic valve root is composed of several different tissues, and careful structural and functional consideration has to be given to each segment and component. Previous work has shown that immersion techniques are inadequate for whole-root decellularization, with the aortic wall segment being particularly resistant to decellularization. The aim of this study was to develop a differential <span class="hlt">pressure</span> <span class="hlt">gradient</span> perfusion system capable of being rigorous enough to decellularize the aortic root wall while gentle enough to preserve the integrity of the cusps. Fresh porcine aortic roots have been subjected to various regimens of perfusion decellularization using detergents and enzymes and results compared to immersion decellularized roots. Success criteria for evaluation of each root segment (cusp, muscle, sinus, wall) for decellularization completeness, tissue integrity, and valve functionality were defined using complementary methods of cell analysis (histology with nuclear and matrix stains and DNA analysis), biomechanics (biaxial and bending tests), and physiologic heart valve bioreactor testing (with advanced image analysis of open-close cycles and geometric orifice area measurement). Fully acellular porcine roots treated with the optimized method exhibited preserved macroscopic structures and microscopic matrix components, which translated into conserved anisotropic mechanical properties, including bending and excellent valve functionality when tested in aortic flow and pressure conditions. This study highlighted the importance of (1) adapting decellularization methods to specific target tissues, (2) combining several methods of cell analysis compared to relying solely on histology, (3) developing relevant valve-specific mechanical tests, and (4) in vitro testing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017LTP....43..274K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017LTP....43..274K"><span>The vortex structure of magnetic <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kovalev, A. S.</p> <p>2017-02-01</p> <p><span class="hlt">Soliton</span> excitations in the general form are considered using the classical model, in a two-dimensional easy-plane ferromagnet. Equations are derived and solved for small-amplitude two-parameter dynamic <span class="hlt">solitons</span>. It is demonstrated that they have a vortex structure and that as their amplitude increases, the excitations turn into coupled quadrupole vortex states that are characterized by two dynamic parameters: the <span class="hlt">soliton</span> velocity and its internal precession frequency. The limit transitions of vortex <span class="hlt">solitons</span> in the general form into vortex dipoles, magnetic lamps, and magnon droplets, are analyzed. The obtained results are compared against the corresponding information about <span class="hlt">solitons</span> in one-dimensional magnetic systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/836463','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/836463"><span>Quark structure of chiral <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dmitri Diakonov</p> <p>2004-05-01</p> <p>There is a prejudice that the chiral <span class="hlt">soliton</span> model of baryons is something orthogonal to the good old constituent quark models. In fact, it is the opposite: the spontaneous chiral symmetry breaking in strong interactions explains the appearance of massive constituent quarks of small size thus justifying the constituent quark models, in the first place. Chiral symmetry ensures that constituent quarks interact very strongly with the pseudoscalar fields. The ''chiral <span class="hlt">soliton</span>'' is another word for the chiral field binding constituent quarks. We show how the old SU(6) quark wave functions follow from the ''<span class="hlt">soliton</span>'', however, with computable relativistic corrections and additional quark-antiquark pairs. We also find the 5-quark wave function of the exotic baryon Theta+.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17995127','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17995127"><span>Thermal diffusion of Boussinesq <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arévalo, Edward; Mertens, Franz G</p> <p>2007-10-01</p> <p>We consider the problem of the <span class="hlt">soliton</span> dynamics in the presence of an external noisy force for the Boussinesq type equations. A set of ordinary differential equations (ODEs) of the relevant coordinates of the system is derived. We show that for the improved Boussinesq (IBq) equation the set of ODEs has limiting cases leading to a set of ODEs which can be directly derived either from the ill-posed Boussinesq equation or from the Korteweg-de Vries (KdV) equation. The case of a <span class="hlt">soliton</span> propagating in the presence of damping and thermal noise is considered for the IBq equation. A good agreement between theory and simulations is observed showing the strong robustness of these excitations. The results obtained here generalize previous results obtained in the frame of the KdV equation for lattice <span class="hlt">solitons</span> in the monatomic chain of atoms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28289992','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28289992"><span>Dual <span class="hlt">compression</span> is not an uncommon type of iliac vein <span class="hlt">compression</span> syndrome.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shi, Wan-Yin; Gu, Jian-Ping; Liu, Chang-Jian; Lou, Wen-Sheng; He, Xu</p> <p>2017-03-13</p> <p>Typical iliac vein <span class="hlt">compression</span> syndrome (IVCS) is characterized by <span class="hlt">compression</span> of left common iliac vein (LCIV) by the overlying right common iliac artery (RCIA). We described an underestimated type of IVCS with dual <span class="hlt">compression</span> by right and left common iliac arteries (LCIA) simultaneously. Thirty-one patients with IVCS were retrospectively included. All patients received trans-catheter venography and computed tomography (CT) examinations for diagnosing and evaluating IVCS. Late venography and reconstructed CT were used for evaluating the anatomical relationship among LCIV, RCIA and LCIA. Imaging manifestations as well as demographic data were collected and evaluated by two experienced radiologists. Sole and dual <span class="hlt">compression</span> were found in 32.3% (n = 10) and 67.7% (n = 21) of 31 patients respectively. No statistical differences existed between them in terms of age, gender, LCIV diameter at the maximum <span class="hlt">compression</span> point, <span class="hlt">pressure</span> <span class="hlt">gradient</span> across stenosis, and the percentage of <span class="hlt">compression</span> level. On CT and venography, sole <span class="hlt">compression</span> was commonly presented with a longitudinal <span class="hlt">compression</span> at the orifice of LCIV while dual <span class="hlt">compression</span> was usually presented as two types: one had a lengthy stenosis along the upper side of LCIV and the other was manifested by a longitudinal <span class="hlt">compression</span> near to the orifice of external iliac vein. The presence of dual <span class="hlt">compression</span> seemed significantly correlated with the tortuous LCIA (p = 0.006). Left common iliac vein can be presented by dual <span class="hlt">compression</span>. This type of <span class="hlt">compression</span> has typical manifestations on late venography and CT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890011582','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890011582"><span>Stability of <span class="hlt">compressible</span> boundary layers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nayfeh, Ali H.</p> <p>1989-01-01</p> <p>The stability of <span class="hlt">compressible</span> 2-D and 3-D boundary layers is reviewed. The stability of 2-D <span class="hlt">compressible</span> flows differs from that of incompressible flows in two important features: There is more than one mode of instability contributing to the growth of disturbances in supersonic laminar boundary layers and the most unstable first mode wave is 3-D. Whereas viscosity has a destabilizing effect on incompressible flows, it is stabilizing for high supersonic Mach numbers. Whereas cooling stabilizes first mode waves, it destabilizes second mode waves. However, second order waves can be stabilized by suction and favorable <span class="hlt">pressure</span> <span class="hlt">gradients</span>. The influence of the nonparallelism on the spatial growth rate of disturbances is evaluated. The growth rate depends on the flow variable as well as the distance from the body. Floquet theory is used to investigate the subharmonic secondary instability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21000552','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21000552"><span>Phase structure of <span class="hlt">soliton</span> molecules</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hause, A.; Hartwig, H.; Seifert, B.; Stolz, H.; Boehm, M.; Mitschke, F.</p> <p>2007-06-15</p> <p>Temporal optical <span class="hlt">soliton</span> molecules were recently demonstrated; they potentially allow further increase of data rates in optical telecommunication. Their binding mechanism relies on the internal phases, but these have not been experimentally accessible so far. Conventional frequency-resolved optical gating techniques are not suited for measurement of their phase profile: Their algorithms fail to converge due to zeros both in their temporal and their spectral profile. We show that the VAMPIRE (very advanced method of phase and intensity retrieval of E-fields) method performs reliably. With VAMPIRE the phase profile of <span class="hlt">soliton</span> molecules has been measured, and further insight into the mechanism is obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007PhRvA..75f3836H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007PhRvA..75f3836H"><span>Phase structure of <span class="hlt">soliton</span> molecules</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hause, A.; Hartwig, H.; Seifert, B.; Stolz, H.; Böhm, M.; Mitschke, F.</p> <p>2007-06-01</p> <p>Temporal optical <span class="hlt">soliton</span> molecules were recently demonstrated; they potentially allow further increase of data rates in optical telecommunication. Their binding mechanism relies on the internal phases, but these have not been experimentally accessible so far. Conventional frequency-resolved optical gating techniques are not suited for measurement of their phase profile: Their algorithms fail to converge due to zeros both in their temporal and their spectral profile. We show that the VAMPIRE (very advanced method of phase and intensity retrieval of E -fields) method performs reliably. With VAMPIRE the phase profile of <span class="hlt">soliton</span> molecules has been measured, and further insight into the mechanism is obtained.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20782654','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20782654"><span>Negative mass <span class="hlt">solitons</span> in gravity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cebeci, Hakan; Sarioglu, Oezguer; Tekin, Bayram</p> <p>2006-03-15</p> <p>We first reconstruct the conserved (Abbott-Deser) charges in the spin-connection formalism of gravity for asymptotically (Anti)-de Sitter spaces, and then compute the masses of the AdS <span class="hlt">soliton</span> and the recently found Eguchi-Hanson <span class="hlt">solitons</span> in generic odd dimensions, unlike the previous result obtained for only five dimensions. These solutions have negative masses compared to the global AdS or AdS/Z{sub p} spacetimes. As a separate note, we also compute the masses of the recent even dimensional Taub-NUT-Reissner-Nordstroem metrics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGP...114..138B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGP...114..138B"><span>Algebraic Ricci <span class="hlt">solitons</span> of three-dimensional Lorentzian Lie groups</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Batat, W.; Onda, K.</p> <p>2017-04-01</p> <p>We study algebraic Ricci <span class="hlt">solitons</span> of three-dimensional Lorentzian Lie groups. All algebraic Ricci <span class="hlt">solitons</span> that we obtain are solvsolitons. In particular, we obtain new <span class="hlt">solitons</span> on G2, G5, and G6, and we prove that, contrary to the Riemannian case, Lorentzian Ricci <span class="hlt">solitons</span> need not be algebraic Ricci <span class="hlt">solitons</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JThSc...9...23B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JThSc...9...23B"><span>Power law or logarithmic law? — A data analysis for zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> turbulent boundary layers with low Reδ2</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Buschmann, Matthias</p> <p>2000-03-01</p> <p>The paper presents an analysis of two-dimensional zero <span class="hlt">pressure</span> <span class="hlt">gradient</span> (ZPG) turbulent boundary layers (TBL) with regard to the application of power laws. Only TBL with low Reynolds number 300 < Reδ2 < 6200 are taken into account. It is found that a certain region of the mean velocity profile can be described with a power law of the formu +=C Pow{*}y +a. This power law region is not a priori identical with the overlap region. An algorithm for the determination of the wall skin friction using the power law is proposed. The method was applied with good result to ZPG TBL and to adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> (APG) TBL. To bridge the gap between the wall and the power law region an approach for the turbulent viscosity is suggested.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PhDT........62S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PhDT........62S"><span><span class="hlt">Soliton</span> interactions and the formation of <span class="hlt">solitonic</span> patterns</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sears, Suzanne M.</p> <p></p> <p>From the stripes of a zebra, to the spirals of cream in a hot cup of coffee, we are surrounded by patterns in the natural world. But why are there patterns? Why drives their formation? In this thesis we study some of the diverse ways patterns can arise due to the interactions between solitary waves in nonlinear systems, sometimes starting from nothing more than random noise. What follows is a set of three studies. In the first, we show how a nonlinear system that supports <span class="hlt">solitons</span> can be driven to generate exact (regular) Cantor set fractals. As an example, we use numerical simulations to demonstrate the formation of Cantor set fractals by temporal optical <span class="hlt">solitons</span>. This fractal formation occurs in a cascade of nonlinear optical fibers through the dynamical evolution of a single input <span class="hlt">soliton</span>. In the second study, we investigate pattern formation initiated by modulation instability in nonlinear partially coherent wave fronts and show that anisotropic noise and/or anisotropic correlation statistics can lead to ordered patterns such as grids and stripes. For the final study, we demonstrate the spontaneous clustering of <span class="hlt">solitons</span> in partially coherent wavefronts during the final stages of pattern formation initiated by modulation instability and noise. Experimental observations are in agreement with theoretical predictions and are confirmed using numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720022609','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720022609"><span>The turbulent boundary layer on a porous plate: An experimental study of the fluid mechanics for adverse free stream <span class="hlt">pressure</span> <span class="hlt">gradients</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anderson, P. S.; Kays, W. M.; Moffat, R. J.</p> <p>1972-01-01</p> <p>An experimental investigation of transpired turbulent boundary layers in zero and adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> has been carried out. Profiles of: (1) the mean velocity, (2) the three intensities of the turbulent fluctuations, and (3) the Reynolds stress were obtained by hot-wire anemometry. The friction coefficients were measured by using an integrated form of the boundary layer equation to extrapolate the measured shear stress profiles to the wall.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840015581','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840015581"><span>Investigation of the effects of <span class="hlt">pressure</span> <span class="hlt">gradient</span>, temperature and wall temperature ratio on the stagnation point heat transfer for circular cylinders and gas turbine vanes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nagamatsu, H. T.; Duffy, R. E.</p> <p>1984-01-01</p> <p>Low and high pressure shock tubes were designed and constructed for the purpose of obtaining heat transfer data over a temperature range of 390 to 2500 K, pressures of 0.3 to 42 atm, and Mach numbers of 0.15 to 1.5 with and without <span class="hlt">pressure</span> <span class="hlt">gradient</span>. A square test section with adjustable top and bottom walls was constructed to produce the favorable and adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> over the flat plate with heat gages. A water cooled gas turbine nozzle cascade which is attached to the high pressure shock tube was obtained to measuse the heat flux over pressure and suction surfaces. Thin-film platinum heat gages with a response time of a few microseconds were developed and used to measure the heat flux for laminar, transition, and turbulent boundary layers. The laminar boundary heat flux on the shock tube wall agreed with Mirel's flat plate theory. Stagnation point heat transfer for circular cylinders at low temperature compared with the theoretical prediction, but for a gas temperature of 922 K the heat fluxes were higher than the predicted values. Preliminary flat plate heat transfer data were measured for laminar, transition, and turbulent boundary layers with and without <span class="hlt">pressure</span> <span class="hlt">gradients</span> for free-stream temperatures of 350 to 2575 K and flow Mach numbers of 0.11 to 1.9. The experimental heat flux data were correlated with the laminar and turbulent theories and the agreement was good at low temperatures which was not the case for higher temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750006922','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750006922"><span>An experimental investigation of heat transfer to reusable surface insulation tile array gaps in a turbulent boundary layer with <span class="hlt">pressure</span> <span class="hlt">gradient</span>. M.S. Thesis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Throckmorton, D. A.</p> <p>1975-01-01</p> <p>An experimental investigation was performed to determine the effect of <span class="hlt">pressure</span> <span class="hlt">gradient</span> on the heat transfer to space shuttle reusable surface insulation (RSI) tile array gaps under thick, turbulent boundary layer conditions. Heat transfer and pressure measurements were obtained on a curved array of full-scale simulated RSI tiles in a tunnel wall boundary layer at a nominal freestream Mach number of 10.3 and freestream unit Reynolds numbers of 1.6, 3.3, and and 6.1 million per meter. Transverse <span class="hlt">pressure</span> <span class="hlt">gradients</span> were induced over the model surface by rotating the curved array with respect to the flow. Definition of the tunnel wall boundary layer flow was obtained by measurement of boundary layer pitot pressure profiles, and flat plate wall pressure and heat transfer. Flat plate wall heat transfer data were correlated and a method was derived for prediction of smooth, curved array heat transfer in the highly three-dimensional tunnel wall boundary layer flow and simulation of full-scale space shuttle vehicle <span class="hlt">pressure</span> <span class="hlt">gradient</span> levels was assessed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18510603','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18510603"><span>Gastroesophageal <span class="hlt">pressure</span> <span class="hlt">gradients</span> in gastroesophageal reflux disease: relations with hiatal hernia, body mass index, and esophageal acid exposure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Vries, Durk R; van Herwaarden, Margot A; Smout, André J P M; Samsom, Melvin</p> <p>2008-06-01</p> <p>The roles of intragastric pressure (IGP), intraesophageal pressure (IEP), gastroesophageal <span class="hlt">pressure</span> <span class="hlt">gradient</span> (GEPG), and body mass index (BMI) in the pathophysiology of gastroesophageal reflux disease (GERD) and hiatal hernia (HH) are only partly understood. In total, 149 GERD patients underwent stationary esophageal manometry, 24-h pH-metry, and endoscopy. One hundred three patients had HH. Linear regression analysis showed that each kilogram per square meter of BMI caused a 0.047-kPa increase in inspiratory IGP (95% confidence interval [CI] 0.026-0.067) and a 0.031-kPa increase in inspiratory GEPG (95% CI 0.007-0.055). Each kilogram per square meter of BMI caused expiratory IGP to increase with 0.043 kPa (95% CI 0.025-0.060) and expiratory IEP with 0.052 kPa (95% CI 0.027-0.077). Each added year of age caused inspiratory IEP to decrease by 0.008 kPa (95% CI -0.015-0.001) and inspiratory GEPG to increase by 0.008 kPa (95% CI 0.000-0.015). In binary logistic regression analysis, HH was predicted by inspiratory and expiratory IGP (odds ratio [OR] 2.93 and 2.62, respectively), inspiratory and expiratory GEPG (OR 3.19 and 2.68, respectively), and BMI (OR 1.72/5 kg/m(2)). In linear regression analysis, HH caused an average 5.09% increase in supine acid exposure (95% CI 0.96-9.22) and an average 3.46% increase in total acid exposure (95% CI 0.82-6.09). Each added year of age caused an average 0.10% increase in upright acid exposure and a 0.09% increase in total acid exposure (95% CI 0.00-0.20 and 0.00-0.18). BMI predicts IGP, inspiratory GEPG, and expiratory IEP. Age predicts inspiratory IEP and GEPG. Presence of HH is predicted by IGP, GEPG, and BMI. GEPG is not associated with acid exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040088758&hterms=cardiopulmonary+function&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcardiopulmonary%2Bfunction','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040088758&hterms=cardiopulmonary+function&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dcardiopulmonary%2Bfunction"><span>Relationship between early diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span>, an index of elastic recoil, and improvements in systolic and diastolic function</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Firstenberg, M. S.; Smedira, N. G.; Greenberg, N. L.; Prior, D. L.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.</p> <p>2001-01-01</p> <p>BACKGROUND: Early diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> (IVPGs) have been proposed to relate to left ventricular (LV) elastic recoil and early ventricular "suction." Animal studies have demonstrated relationships between IVPGs and systolic and diastolic indices during acute ischemia. However, data on the effects of improvements in LV function in humans and the relationship to IVPGs are lacking. METHODS AND RESULTS: Eight patients undergoing CABG and/or infarct exclusion surgery had a triple-sensor high-fidelity catheter placed across the mitral valve intraoperatively for simultaneous recording of left atrial (LA), basal LV, and apical LV pressures. Hemodynamic data obtained before bypass were compared with those with similar LA pressures and heart rates obtained after bypass. From each LV waveform, the time constant of LV relaxation (tau), +dP/dt(max), and -dP/dt(max) were determined. Transesophageal echocardiography was used to determined end-diastolic (EDV) and end-systolic (ESV) volumes and ejection fractions (EF). At similar LA pressures and heart rates, IVPG increased after bypass (before bypass 1.64+/-0.79 mm Hg; after bypass 2.67+/-1.25 mm Hg; P<0.01). Significant improvements were observed in ESV, as well as in apical and basal +dP/dt(max), -dP/dt(max), and tau (each P<0.05). Overall, IVPGs correlated inversely with both ESV (IVPG=-0.027[ESV]+3.46, r=-0.64) and EDV (IVPG=-0.027[EDV]+4.30, r=-0.70). Improvements in IVPGs correlated with improvements in apical tau (Deltatau =5.93[DeltaIVPG]+4.76, r=0.91) and basal tau (Deltatau =2.41[DeltaIVPG]+5.13, r=-0.67). Relative changes in IVPGs correlated with changes in ESV (DeltaESV=-0.97[%DeltaIVPG]+23.34, r=-0.79), EDV (DeltaEDV=-1.16[%DeltaIVPG]+34.92, r=-0.84), and EF (DeltaEF=0.38[%DeltaIVPG]-8.39, r=0.85). CONCLUSIONS: Improvements in LV function also increase IVPGs. These changes in IVPGs, suggestive of increases in LV suction and elastic recoil, correlate directly with improvements in LV relaxation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040088758&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgreenberg','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040088758&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dgreenberg"><span>Relationship between early diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span>, an index of elastic recoil, and improvements in systolic and diastolic function</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Firstenberg, M. S.; Smedira, N. G.; Greenberg, N. L.; Prior, D. L.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.</p> <p>2001-01-01</p> <p>BACKGROUND: Early diastolic intraventricular <span class="hlt">pressure</span> <span class="hlt">gradients</span> (IVPGs) have been proposed to relate to left ventricular (LV) elastic recoil and early ventricular "suction." Animal studies have demonstrated relationships between IVPGs and systolic and diastolic indices during acute ischemia. However, data on the effects of improvements in LV function in humans and the relationship to IVPGs are lacking. METHODS AND RESULTS: Eight patients undergoing CABG and/or infarct exclusion surgery had a triple-sensor high-fidelity catheter placed across the mitral valve intraoperatively for simultaneous recording of left atrial (LA), basal LV, and apical LV pressures. Hemodynamic data obtained before bypass were compared with those with similar LA pressures and heart rates obtained after bypass. From each LV waveform, the time constant of LV relaxation (tau), +dP/dt(max), and -dP/dt(max) were determined. Transesophageal echocardiography was used to determined end-diastolic (EDV) and end-systolic (ESV) volumes and ejection fractions (EF). At similar LA pressures and heart rates, IVPG increased after bypass (before bypass 1.64+/-0.79 mm Hg; after bypass 2.67+/-1.25 mm Hg; P<0.01). Significant improvements were observed in ESV, as well as in apical and basal +dP/dt(max), -dP/dt(max), and tau (each P<0.05). Overall, IVPGs correlated inversely with both ESV (IVPG=-0.027[ESV]+3.46, r=-0.64) and EDV (IVPG=-0.027[EDV]+4.30, r=-0.70). Improvements in IVPGs correlated with improvements in apical tau (Deltatau =5.93[DeltaIVPG]+4.76, r=0.91) and basal tau (Deltatau =2.41[DeltaIVPG]+5.13, r=-0.67). Relative changes in IVPGs correlated with changes in ESV (DeltaESV=-0.97[%DeltaIVPG]+23.34, r=-0.79), EDV (DeltaEDV=-1.16[%DeltaIVPG]+34.92, r=-0.84), and EF (DeltaEF=0.38[%DeltaIVPG]-8.39, r=0.85). CONCLUSIONS: Improvements in LV function also increase IVPGs. These changes in IVPGs, suggestive of increases in LV suction and elastic recoil, correlate directly with improvements in LV relaxation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhPl...23h2111L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhPl...23h2111L"><span>PIC simulation of <span class="hlt">compressive</span> and rarefactive dust ion-acoustic solitary waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Zhong-Zheng; Zhang, Heng; Hong, Xue-Ren; Gao, Dong-Ning; Zhang, Jie; Duan, Wen-Shan; Yang, Lei</p> <p>2016-08-01</p> <p>The nonlinear propagations of dust ion-acoustic solitary waves in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains have been investigated by the particle-in-cell method. By comparing the simulation results with those obtained from the traditional reductive perturbation method, it is observed that the rarefactive KdV <span class="hlt">solitons</span> propagate stably at a low amplitude, and when the amplitude is increased, the prime wave form evolves and then gradually breaks into several small amplitude solitary waves near the tail of <span class="hlt">soliton</span> structure. The <span class="hlt">compressive</span> KdV <span class="hlt">solitons</span> propagate unstably and oscillation arises near the tail of <span class="hlt">soliton</span> structure. The finite amplitude rarefactive and <span class="hlt">compressive</span> Gardner <span class="hlt">solitons</span> seem to propagate stably.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22599906','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22599906"><span>PIC simulation of <span class="hlt">compressive</span> and rarefactive dust ion-acoustic solitary waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Li, Zhong-Zheng; Zhang, Heng; Hong, Xue-Ren; Gao, Dong-Ning; Zhang, Jie; Duan, Wen-Shan; Yang, Lei</p> <p>2016-08-15</p> <p>The nonlinear propagations of dust ion-acoustic solitary waves in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains have been investigated by the particle-in-cell method. By comparing the simulation results with those obtained from the traditional reductive perturbation method, it is observed that the rarefactive KdV <span class="hlt">solitons</span> propagate stably at a low amplitude, and when the amplitude is increased, the prime wave form evolves and then gradually breaks into several small amplitude solitary waves near the tail of <span class="hlt">soliton</span> structure. The <span class="hlt">compressive</span> KdV <span class="hlt">solitons</span> propagate unstably and oscillation arises near the tail of <span class="hlt">soliton</span> structure. The finite amplitude rarefactive and <span class="hlt">compressive</span> Gardner <span class="hlt">solitons</span> seem to propagate stably.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900051664&hterms=1582&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%25EF%25BF%25BD%2526%25231582','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900051664&hterms=1582&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3D%25EF%25BF%25BD%2526%25231582"><span>A study of turbulence on <span class="hlt">compression</span> ramps with k-epsilon and Reynolds stress models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lee, J.; Taulbee, D. B.; Holden, M. S.</p> <p>1990-01-01</p> <p>A theoretical study was conducted to determine the effects of adverse <span class="hlt">pressure</span> <span class="hlt">gradient</span> and <span class="hlt">compressibility</span> in modeling turbulent <span class="hlt">compressible</span> flows. The kinetic energy/dissipation and Reynolds stress model predictions are presented and compared with experimental data. The effects of <span class="hlt">compressibility</span>, which include the mass averaged fluctuation term, the pressure dilatation term, and the dilatation dissipation, are important in modeling the turbulent <span class="hlt">compressible</span> flows. The normal stresses and longitudinal strain rates also have an effect in the prediction of turbulent energy productions on the curved surfaces. A new <span class="hlt">compressible</span> formulation of the pressure strain term, which includes the dilatation effects, in the Reynolds stress equation is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21479022','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21479022"><span>Subwavelength vortical plasmonic lattice <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ye, Fangwei; Mihalache, Dumitru; Hu, Bambi; Panoiu, Nicolae C</p> <p>2011-04-01</p> <p>We present a theoretical study of vortical plasmonic lattice <span class="hlt">solitons</span>, which form in two-dimensional arrays of metallic nanowires embedded into nonlinear media with both focusing and defocusing Kerr nonlinearities. Their existence, stability, and subwavelength spatial confinement are investigated in detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5631998','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5631998"><span>Vibrational <span class="hlt">soliton</span>: an experimental overview</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bigio, I.J.</p> <p>1986-03-08</p> <p>To date the most convincing evidence of vibrational <span class="hlt">solitons</span> in biopolymers has been found in two very disparate systems: Davydov-like excitations in hydrogen-bonded linear chains (acetanilide and N-methylacetamide) which are not biopolymers but plausible structural paradigms for biopolymers, and longitudinal accoustic modes of possibly nonlinear character in biologically viable DNA. 17 refs., 4 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1984AmJPh..52..826O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1984AmJPh..52..826O"><span><span class="hlt">Solitons</span> in a wave tank</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Olsen, M.; Smith, H.; Scott, A. C.</p> <p>1984-09-01</p> <p>A wave tank experiment (first described by the nineteenth-century engineer and naval architect John Scott Russell) relates a linear eigenvalue problem from elementary quantum mechanics to a striking feature of modern nonlinear wave theory: multiple generation of <span class="hlt">solitons</span>. The tank experiment is intended for lecture demonstrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5234179','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5234179"><span><span class="hlt">Solitons</span> induced by boundary conditions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhou, R.L.</p> <p>1987-01-01</p> <p>Although <span class="hlt">soliton</span> phenomena have attracted wide attention since 1965, there are still not enough efforts paid to mixed-boundary - initial-value problems that are important in real physical cases. The main purpose of this thesis is to study carefully the various boundary-induced <span class="hlt">soliton</span> under different initial conditions. The author states with three sets of nonlinear equations: KdV equations and Boussinesq equations (for water); two-fluid equations for cold-ion plasma. He was interested in four types of problems involved with water <span class="hlt">solitons</span>: excitation by different time-dependent boundary conditions under different initial conditions; head-on and over-taking collisions; reflection at a wall and the excitation by pure initial conditions. For KdV equations, only cases one and four are conducted. The results from two fully nonlinear KdV and Boussinesq equations are compared, and agree extremely well. The Boussinesq equations permit solition head-on collisions and reflections, studied the first time. The results from take-over collision agree with KdV results. For the ion-acoustic plasma, a set of Boussinesq-type equations was derived from the standard two-fluid equations for the ion-acoustic plasma. It theoretically proves the essential nature of the solitary wave solutions of the cold-ion plasma. The ion acoustic <span class="hlt">solitons</span> are also obtained by prescribing a potential phi/sub 0/ at one grid point.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22307934','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22307934"><span><span class="hlt">Soliton</span> molecules: Experiments and optimization</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mitschke, Fedor</p> <p>2014-10-06</p> <p>Stable compound states of several fiber-optic <span class="hlt">solitons</span> have recently been demonstrated. In the first experiment their shape was approximated, for want of a better description, by a sum of Gaussians. Here we discuss an optimization strategy which helps to find preferable shapes so that the generation of radiative background is reduced.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA496574','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA496574"><span>Comparison of Engineering Correlations for Predicting Heat Transfer in Zero-<span class="hlt">pressure-gradient</span> <span class="hlt">Compressible</span> Boundary Layers with CFD and Experimental Data</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2008-08-01</p> <p>END >RUN 2 ISEN 1.0e0 SHCK 1.300 >END >RCT &REAC_PARAMETERS / >END > VOD &VODE_PARAMETERS / >END >END >--- Figure 2: Input file 1ns for cmpexp for Mach...SPC 2 N2 0.77 O2 0.23 >END >RUN 1 ISEN 1.0e0 >END >RCT &REAC_PARAMETERS / >END > VOD &VODE_PARAMETERS / >END >END >--- (a) 1ns &ZPG_QDOT_PARAMETERS...REAC_PARAMETERS / >END > VOD &VODE_PARAMETERS / >END >END >--- (a) 1ns &ZPG_QDOT_PARAMETERS T_wall = 300.0, platelength = 1.5, xpoints = 100, shockcase = 0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25116003','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25116003"><span>Multicolour nonlinearly bound chirped dissipative <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Babin, Sergey A; Podivilov, Evgeniy V; Kharenko, Denis S; Bednyakova, Anastasia E; Fedoruk, Mikhail P; Kalashnikov, Vladimir L; Apolonski, Alexander</p> <p>2014-08-13</p> <p>The dissipative <span class="hlt">soliton</span> regime is one of the most advanced ways to generate high-energy femtosecond pulses in mode-locked lasers. On the other hand, the stimulated Raman scattering in a fibre laser may convert the excess energy out of the coherent dissipative <span class="hlt">soliton</span> to a noisy Raman pulse, thus limiting its energy. Here we demonstrate that intracavity feedback provided by re-injection of a Raman pulse into the laser cavity leads to formation of a coherent Raman dissipative <span class="hlt">soliton</span>. Together, a dissipative <span class="hlt">soliton</span> and a Raman dissipative <span class="hlt">soliton</span> (of the first and second orders) form a two (three)-colour stable complex with higher total energy and broader spectrum than those of the dissipative <span class="hlt">soliton</span> alone. Numerous applications can benefit from this approach, including frequency comb spectroscopy, transmission lines, seeding femtosecond parametric amplifiers, enhancement cavities and multiphoton fluorescence microscopy.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21457003','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21457003"><span>Making beam splitters with dark <span class="hlt">soliton</span> collisions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Steiglitz, Ken</p> <p>2010-10-15</p> <p>We show with numerical simulations that for certain simple choices of parameters, the waveguides induced by colliding dark <span class="hlt">solitons</span> in a Kerr medium yield a complete family of beam splitters for trapped linear waves, ranging from total transmission to total deflection. The way energy is transferred from one waveguide to another is similar to that of a directional coupler, but no special fabrication is required. Dark <span class="hlt">soliton</span> beam splitters offer potential advantages over their bright <span class="hlt">soliton</span> counterparts: Their transfer characteristics do not depend on the relative phase or speed of the colliding <span class="hlt">solitons</span>; dark <span class="hlt">solitons</span> are generally more robust than bright <span class="hlt">solitons</span>; and the probe peaks at nulls of the pump, enhancing the signal-to-noise ratio for probe detection. The last factor is especially important for possible application to quantum information processing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApPhL.103a1103W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApPhL.103a1103W"><span>All-fiber ultrafast thulium-doped fiber ring laser with dissipative <span class="hlt">soliton</span> and noise-like output in normal dispersion by single-wall carbon nanotubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, QingQing; Chen, Tong; Li, Mingshan; Zhang, Botao; Lu, Yongfeng; Chen, Kevin P.</p> <p>2013-07-01</p> <p>An ultrafast thulium-doped fiber laser with large net normal dispersion has been developed to produce dissipative <span class="hlt">soliton</span> and noise-like outputs at 1.9 μm. The mode-locked operation was enabled by using single-wall carbon nanotubes as saturable absorber for all-fiber configuration. Dissipative <span class="hlt">soliton</span> in normal dispersion produced by the fiber laser oscillator was centered at 1947 nm with 4.1-nm FWHM bandwidth and 0.45 nJ/pulse. The output dissipative <span class="hlt">soliton</span> pulses were <span class="hlt">compressed</span> to 2.3 ps outside the laser cavity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860020303','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860020303"><span>Stability and control of <span class="hlt">compressible</span> flows over a surface with concave-conves curvature</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maestrello, L.; Bayliss, A.; Parikh, P.; Turkel, E.</p> <p>1986-01-01</p> <p>The active control of spatially unstable disturbances in a laminar, two-dimensional, <span class="hlt">compressible</span> boundary layer over a curved surface is numerically simulated. The control is effected by localized time-periodic surface heating. We consider two similar surfaces of different heights with concave-convex curvature. In one, the height is sufficiently large so that the favorable <span class="hlt">pressure</span> <span class="hlt">gradient</span> is sufficient to stabilize a particular disturbance. In the other case the <span class="hlt">pressure</span> <span class="hlt">gradient</span> induced by the curvature is destabilizing. It is shown that by using active control that the disturbance can be stabilized. The results demonstrate that the curvature induced mean <span class="hlt">pressure</span> <span class="hlt">gradient</span> significantly enhances the receptivity of the flow localized time-periodic surface heating and that this is a potentially viable mechanism in air.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9728E..36K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9728E..36K"><span>Mode-locked fiber laser with cascaded generation of coherent Raman dissipative <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kharenko, Denis S.; Bednyakova, Anastasia E.; Podivilov, Evgenii V.; Fedoruk, Mikhail P.; Apolonskiy, Alexander A.; Babin, Sergey A.</p> <p>2016-03-01</p> <p>We experimentally demonstrate a cascaded generation of a conventional dissipative <span class="hlt">soliton</span> (DS) at 1020 nm and Raman dissipative <span class="hlt">solitons</span> (RDS) of the first (1065 nm) and second (1115 nm) orders inside a common fiber laser cavity. The generated high-energy pulses are shown to be linearly-chirped and <span class="hlt">compressible</span> to 200-300 fs durations for all wavelengths. Moreover, the pulses are mutually coherent that has been confirmed by efficient coherent combining exhibiting ~75 fs and <40 fs interference fringes within the combined pulse envelope of a DS with the first-order RDS and the second-order RDS respectively. The numerical simulation was performed with sinusoidal (soft) and step-like (hard) spectral filters and took into account the discreetness of the laser elements. Shown that even higher degree of coherence and shorter pulses could be achieved with hard spectral filtering. This approach opens the door towards cascaded generation of multiple coherent dissipative <span class="hlt">solitons</span> in a broad spectral range (so-called dissipative <span class="hlt">soliton</span> comb). The demonstrated source of coherent dissipative <span class="hlt">solitons</span> can improve numerous areas such as frequency comb generation, pulse synthesis, biomedical imaging and the generation of coherent mid-infrared supercontinuum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JAP...119d3102B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JAP...119d3102B"><span>Wavelength conversion through <span class="hlt">soliton</span> self-frequency shift in tellurite microstructured fiber with picosecond pump pulse</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bi, Wanjun; Li, Xia; Xing, Zhaojun; Zhou, Qinling; Fang, Yongzheng; Gao, Weiqing; Xiong, Liangming; Hu, Lili; Liao, Meisong</p> <p>2016-01-01</p> <p>Wavelength conversion to the wavelength range that is not covered by commercially available lasers could be accomplished through the <span class="hlt">soliton</span> self-frequency shift (SSFS) effect. In this study, the phenomenon of SSFS pumped by a picosecond-order pulse in a tellurite microstructured fiber is investigated both theoretically and experimentally. The balance between the dispersion and the nonlinearity achieved by a 1958 nm pump laser induces a distinct SSFS effect. Attributed to the large spectral distance between the pump pulse and the fiber zero-dispersion wavelength, the SSFS is not cancelled due to energy shedding from the <span class="hlt">soliton</span> to the dispersive wave. Details about the physical mechanisms behind this phenomenon and the variations of the wavelength shift, the conversion efficiency are revealed based on numerical simulations. Owing to the large <span class="hlt">soliton</span> number N, the pulse width of the first split fundamental <span class="hlt">soliton</span> is approximately 40 fs, producing a pulse <span class="hlt">compression</span> factor of ˜38, much higher than that pumped by a femtosecond pulse. Experiments were also conducted to confirm the validity of the simulation results. By varying the pump power, a continuous <span class="hlt">soliton</span> shift from 1990 nm to 2264 nm was generated. The generation of SSFS in tellurite microstructured fibers with picosecond pump pulse can provide a new approach for wavelength conversion in the mid-infrared range and could be useful in medical and some other areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21020798','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21020798"><span><span class="hlt">Solitons</span> in the midst of chaos</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Seghete, Vlad; Menyuk, Curtis R.; Marks, Brian S.</p> <p>2007-10-15</p> <p>A system of coupled nonlinear Schroedinger equations describes pulse propagation in weakly birefringent optical fibers. <span class="hlt">Soliton</span> solutions of this system are found numerically through the shooting method. We employ Poincare surface of section plots - a standard dynamical systems approach - to analyze the phase space behavior of these solutions and neighboring trajectories. Chaotic behavior around the <span class="hlt">solitons</span> is apparent and suggests dynamical instability. A Lyapunov stability analysis confirms this result. Thus, <span class="hlt">solitons</span> exist in the midst of chaos.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21408326','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21408326"><span>Two-color interface vortex <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xu Zhiyong</p> <p>2010-02-15</p> <p>We study the existence and properties of vortex <span class="hlt">solitons</span> supported by an interface between two distinct optical lattices imprinted in nonlinear quadratic media. We analyze the impact of guiding parameters of lattices and phase mismatching conditions on the existence and stability of two-color interface vortex <span class="hlt">solitons</span>. The salient point is that interface vortex <span class="hlt">solitons</span> feature highly asymmetric profiles, and are stable throughout almost the entire existence domain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4893185','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4893185"><span>Half conformally flat gradient Ricci almost <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brozos-Vázquez, M.; Valle-Regueiro, X.</p> <p>2016-01-01</p> <p>The local structure of half conformally flat gradient Ricci almost <span class="hlt">solitons</span> is investigated, showing that they are locally conformally flat in a neighbourhood of any point where the gradient of the potential function is non-null. In opposition, if the gradient of the potential function is null, then the <span class="hlt">soliton</span> is a steady traceless κ-Einstein <span class="hlt">soliton</span> and is realized on the cotangent bundle of an affine surface. PMID:27279774</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21528753','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21528753"><span>Four-wave-mixing gap <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zhang Yanpeng; Wang Zhiguo; Zheng Huaibin; Yuan Chenzhi; Li Changbiao; Lu Keqing; Xiao Min</p> <p>2010-11-15</p> <p>We report an experimental demonstration of generating gap <span class="hlt">soliton</span> trains in a four-wave-mixing (FWM) signal. Such spatial FWM surfacelike gap <span class="hlt">soliton</span> trains are induced in a periodically modulated self-defocusing atomic medium by the cross-phase modulation, which can be reshaped under different experimental conditions, such as different atomic densities, nonlinear dispersions, and dressing fields. Controlling spatial gap <span class="hlt">solitons</span> can have important applications in image memory, processing, and communication.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21408900','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21408900"><span>Stable optical vortex <span class="hlt">solitons</span> in pair plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Berezhiani, V. I.; Shatashvili, N. L.; Mahajan, S. M.</p> <p>2010-05-15</p> <p>It is shown that the pair plasmas with small temperature asymmetry can support existence of localized as well as delocalized optical vortex <span class="hlt">solitons</span>. Coexistence of such <span class="hlt">solitons</span> is possible due to peculiar form of saturating nonlinearity which has a focusing-defocusing nature--for weak amplitudes being focusing becoming defocusing for higher amplitudes. It is shown that delocalized vortex <span class="hlt">soliton</span> is stable in entire region of its existence while single- and multicharged localized vortex <span class="hlt">solitons</span> are unstable for low amplitudes and become stable for relativistic amplitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvB..94x5432S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..94x5432S"><span>Coupled spatial multimode <span class="hlt">solitons</span> in microcavity wires</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Slavcheva, G.; Gorbach, A. V.; Pimenov, A.</p> <p>2016-12-01</p> <p>A modal expansion approach is developed and employed to investigate and elucidate the nonlinear mechanism behind the multistability and formation of coupled multimode polariton <span class="hlt">solitons</span> in microcavity wires. With pump switched on and realistic dissipation parameters, truncating the expansion up to the second-order wire mode, our model predicts two distinct coupled <span class="hlt">soliton</span> branches: stable and unstable. Modulational stability of the stationary homogeneous solution and <span class="hlt">soliton</span> branches stability are studied. Our simplified 1D model is in remarkably good agreement with the full 2D mean-field Gross-Pitaevskii model, reproducing correctly the <span class="hlt">soliton</span> existence domain upon variation of pump amplitude and the onset of multistability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhA...49G5201G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhA...49G5201G"><span><span class="hlt">Soliton</span> splitting in quenched classical integrable systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gamayun, O.; Semenyakin, M.</p> <p>2016-08-01</p> <p>We take a <span class="hlt">soliton</span> solution of a classical non-linear integrable equation and quench (suddenly change) its non-linearity parameter. For that we multiply the amplitude or the width of a <span class="hlt">soliton</span> by a numerical factor η and take the obtained profile as a new initial condition. We find the values of η for which the post-quench solution consists of only a finite number of <span class="hlt">solitons</span>. The parameters of these <span class="hlt">solitons</span> are found explicitly. Our approach is based on solving the direct scattering problem analytically. We demonstrate how it works for Korteweg-de Vries, sine-Gordon and non-linear Schrödinger integrable equations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010IJQC..110..127L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010IJQC..110..127L"><span>Davydov's <span class="hlt">solitons</span> in a homogeneous nucleotide chain</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lakhno, Victor D.</p> <p></p> <p>Charge transfer in homogeneous nucleotide chains is modeled on the basis of Holstein Hamiltonian. The path length of Davydov <span class="hlt">solitons</span> in these chains is being studied. It is shown that in a dispersionless case, when the <span class="hlt">soliton</span> velocity V is small, the path length grows exponentially as V decreases. In this case, the state of a moving <span class="hlt">soliton</span> is quasisteady. In the presence of dispersion determined by the dependenceΩ2 =Ω 02 + V 02κ2, the path length in the region 0 < V < V0 is equal to infinity. In this case, the phonon environment follows the charge motion. In the region V > V0, the <span class="hlt">soliton</span> motion is accompanied by emission of phonons which leads to a finite path length of a <span class="hlt">soliton</span>. The latter tends to infinity as V → V0 + 0 and V → ∞. The presence of dissipation leads to a finite <span class="hlt">soliton</span> path length. An equilibrium velocity of <span class="hlt">soliton</span> in an external electric field is calculated. It is shown that there is a maximum intensity of an electric field at which a steady motion of a <span class="hlt">soliton</span> is possible. The <span class="hlt">soliton</span> mobility is calculated for the stable or ohmic brunch.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21254532','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21254532"><span>Dynamics of Alfven <span class="hlt">solitons</span> in inhomogeneous plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xu Tao; Li Lili; Lue Xing; Zhang Cheng; Tian Bo</p> <p>2008-10-15</p> <p>To provide an analytical scheme for the dynamical behavior of nonlinear Alfven waves in inhomogeneous plasmas, this paper investigates a generalized variable-coefficient derivative nonlinear Schroedinger equation. In the sense of admitting the Lax pair and infinitely many conservation laws, the integrability of this equation is established under certain coefficient constraint which suggests which inhomogeneities support stable Alfven <span class="hlt">solitons</span>. The Hirota method is adopted to construct the one- and multi-Alfven-<span class="hlt">soliton</span> solutions. The inhomogeneous <span class="hlt">soliton</span> features are also discussed through analyzing some important physical quantities. A sample model is treated with our results, and graphical illustration presents two energy-radiating Alfven <span class="hlt">soliton</span> structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvE..96a2206K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvE..96a2206K"><span>Cascade replication of dissipative <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kochetov, Bogdan A.; Tuz, Vladimir R.</p> <p>2017-07-01</p> <p>We report a new effect of a cascade replication of dissipative <span class="hlt">solitons</span> from a single one. It is discussed in the framework of a common model based on the one-dimensional cubic-quintic complex Ginzburg-Landau equation in which an additional linear term is introduced to account the perturbation from a particular potential of externally applied force. The effect is demonstrated on the light beams propagating through a planar waveguide. The waveguide consists of a nonlinear layer able to guide dissipative <span class="hlt">solitons</span> and a magneto-optic substrate. In the waveguide an externally applied force is considered to be an inhomogeneous magnetic field which is induced by modulated electric currents flowing along a set of conducting wires adjusted on the top of the waveguide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JHEP...09..008C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JHEP...09..008C"><span>Regularized degenerate multi-<span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Correa, Francisco; Fring, Andreas</p> <p>2016-09-01</p> <p>We report complex {P}{T} -symmetric multi-<span class="hlt">soliton</span> solutions to the Korteweg de-Vries equation that asymptotically contain one-<span class="hlt">soliton</span> solutions, with each of them possessing the same amount of finite real energy. We demonstrate how these solutions originate from degenerate energy solutions of the Schrödinger equation. Technically this is achieved by the application of Darboux-Crum transformations involving Jordan states with suitable regularizing shifts. Alternatively they may be constructed from a limiting process within the context Hirota's direct method or on a nonlinear superposition obtained from multiple Bäcklund transformations. The proposed procedure is completely generic and also applicable to other types of nonlinear integrable systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28296135','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28296135"><span>Assessment of trans-aortic <span class="hlt">pressure</span> <span class="hlt">gradient</span> using a coronary pressure wire in patients with mechanical aortic and mitral valve prostheses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kherada, Nisharahmed; Brenes, Juan Carlos; Kini, Annapoorna S; Dangas, George D</p> <p>2017-03-15</p> <p>Accurate evaluation of trans-aortic valvular <span class="hlt">pressure</span> <span class="hlt">gradients</span> is challenging in cases where dual mechanical aortic and mitral valve prostheses are present. Non-invasive Doppler echocardiographic imaging has its limitations due to multiple geometric assumptions. Invasive measurement of trans-valvular gradients with cardiac catheterization can provide further information in patients with two mechanical valves, where simultaneous pressure measurements in the left ventricle and ascending aorta must be obtained. Obtaining access to the left ventricle via the mitral valve after a trans-septal puncture is not feasible in the case of a concomitant mechanical mitral valve, whereas left ventricular apical puncture technique is associated with high procedural risks. Retrograde crossing of a bileaflet mechanical aortic prosthesis with standard catheters is associated with the risk of catheter entrapment and acute valvular regurgitation. In these cases, the assessment of trans-valvular gradients using a 0.014˝ diameter coronary pressure wire technique has been described in a few case reports. We present the case of a 76-year-old female with rheumatic valvular heart disease who underwent mechanical aortic and mitral valve replacement in the past. She presented with decompensated heart failure and echocardiographic findings suggestive of elevated <span class="hlt">pressure</span> <span class="hlt">gradient</span> across the mechanical aortic valve prosthesis. The use of a high-fidelity 0.014˝ diameter coronary pressure guidewire resulted in the detection of a normal trans-valvular <span class="hlt">pressure</span> <span class="hlt">gradient</span> across the mechanical aortic valve. This avoided a high-risk third redo valve surgery in our patient. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA148396','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA148396"><span><span class="hlt">Solitons</span> and SeaSat,</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1984-08-01</p> <p>second statement is demonstrated to be false. The% Kadomtsev-.1etviashvile equation relevant to Internal Waves is shown not to have SOliL -solutions. This...more than one space dimension. The second statement is demonstrated to be false. The Kadomtsev-Petviashvile equation relevant to Internal Waves Is...observed by SeaSat has led to suggestions that the phenomena may be related to Internal 0 Wave <span class="hlt">Solitons</span>. Most observations were made under conditions for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvB..91d5424B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvB..91d5424B"><span>Discrete <span class="hlt">solitons</span> in graphene metamaterials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bludov, Yu. V.; Smirnova, D. A.; Kivshar, Yu. S.; Peres, N. M. R.; Vasilevskiy, M. I.</p> <p>2015-01-01</p> <p>We study nonlinear properties of multilayer metamaterials created by graphene sheets separated by dielectric layers. We demonstrate that such structures can support localized nonlinear modes described by the discrete nonlinear Schrödinger equation and that its solutions are associated with stable discrete plasmon <span class="hlt">solitons</span>. We also analyze the nonlinear surface modes in truncated graphene metamaterials being a nonlinear analog of surface Tamm states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27828402','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27828402"><span>Self-frequency-shifted <span class="hlt">solitons</span> in a polarization-maintaining, very-large-mode area, Er-doped fiber amplifier.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nicholson, J W; Desantolo, A; Kaenders, W; Zach, A</p> <p>2016-10-03</p> <p>We demonstrate <span class="hlt">soliton</span> self-frequency-shifted, femtosecond-pulse amplification in a newly-developed, polarization-maintaining, Er-doped, very-large-mode-area fiber amplifier. The PM-VLMA Er fiber had a core diameter of 50 μm, an effective area of ~1050 μm<sup>2</sup>, and Er absorption of 50 dB/m. The measured birefringence beat length of the PM-VLMA Er fiber was 14.1 mm. The <span class="hlt">soliton</span> wavelength could be shifted by more than 90 nm. The <span class="hlt">soliton</span> generation process resulted in remarkably clean, 86 fs pulses with 21 nJ energy at 1650 nm and 244 kW peak power from an all-fiber, fusion spliced system without bulk-optics for pulse <span class="hlt">compression</span>. The polarization extinction ratio of the <span class="hlt">soliton</span> was greater than 40 dB, and the M<sup>2</sup> was 1.1. The fully polarization-maintaining fiber laser system provides robust and stable <span class="hlt">soliton</span> generation. Peak-to-peak variation in the <span class="hlt">soliton</span> wavelength, measured over the course of an hour was only 0.03% and pulse energy variation was only 0.5%.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24921341','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24921341"><span>Highly coherent mid-IR supercontinuum by self-defocusing <span class="hlt">solitons</span> in lithium niobate waveguides with all-normal dispersion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Guo, Hairun; Zhou, Binbin; Zeng, Xianglong; Bache, Morten</p> <p>2014-05-19</p> <p>We numerically investigate self-defocusing <span class="hlt">solitons</span> in a lithium niobate (LN) waveguide designed to have a large refractive index (RI) change. The waveguide evokes strong waveguide dispersion and all-normal dispersion is found in the entire guiding band spanning the near-IR and the beginning of the mid-IR. Meanwhile, a self-defocusing nonlinearity is invoked by the cascaded (phase-mismatched) second-harmonic generation under a quasi-phase-matching pitch. Combining this with the all-normal dispersion, mid-IR <span class="hlt">solitons</span> can form and the waveguide presents the first all-nonlinear and <span class="hlt">solitonic</span> device where no linear dispersion (i.e. non-<span class="hlt">solitonic</span>) regimes exist within the guiding band. <span class="hlt">Soliton</span> <span class="hlt">compressions</span> at 2 μm and 3 μm are investigated, with nano-joule single cycle pulse formations and highly coherent octave-spanning supercontinuum generations. With an alternative design on the waveguide dispersion, the <span class="hlt">soliton</span> spectral tunneling effect is also investigated, with which few-cycle pico-joule pulses at 2 μm are formed by a near-IR pump.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16642146','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16642146"><span>Multipole vector <span class="hlt">solitons</span> in nonlocal nonlinear media.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kartashov, Yaroslav V; Torner, Lluis; Vysloukh, Victor A; Mihalache, Dumitru</p> <p>2006-05-15</p> <p>We show that multipole <span class="hlt">solitons</span> can be made stable via vectorial coupling in bulk nonlocal nonlinear media. Such vector <span class="hlt">solitons</span> are composed of mutually incoherent nodeless and multipole components jointly inducing a nonlinear refractive index profile. We found that stabilization of the otherwise highly unstable multipoles occurs below certain maximum energy flow. Such a threshold is determined by the nonlocality degree.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SuMi..103..161V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SuMi..103..161V"><span>Dispersive <span class="hlt">solitons</span> in magneto-optic waveguides</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vega-Guzman, Jose; Ullah, Malik Zaka; Asma, Mir; Zhou, Qin; Biswas, Anjan</p> <p>2017-03-01</p> <p>This paper obtains bright, dark and singular dispersive optical <span class="hlt">soliton</span> solutions with magneto-optic waveguides. The governing equation is the coupled Schrödinger-Hirota equation. The existence criteria of these <span class="hlt">solitons</span> are also presented. Both Kerr law and power law of nonlinearity are considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvA..96a3838S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvA..96a3838S"><span>Perturbed dissipative <span class="hlt">solitons</span>: A variational approach</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sahoo, Ambaresh; Roy, Samudra; Agrawal, Govind P.</p> <p>2017-07-01</p> <p>We adopt a variational technique to study the dynamics of perturbed dissipative <span class="hlt">solitons</span> whose evolution is governed by a Ginzburg-Landau equation (GLE). As a specific example of such <span class="hlt">solitons</span>, we consider a silicon-based active waveguide in which free carriers are generated through two-photon absorption. In this case, dissipative <span class="hlt">solitons</span> are perturbed by physical processes such as third-order dispersion, intrapulse Raman scattering, self-steepening, and free-carrier generation. To solve the variational problem, we adopt the Pereira-Stenflo <span class="hlt">soliton</span> as an ansatz since this <span class="hlt">soliton</span> is the exact solution of the unperturbed GLE. With this ansatz, we derive a set of six coupled differential equations exhibiting the dynamics of various pulse parameters. This set of equations provides considerable physical insight into the complex behavior of perturbed dissipative <span class="hlt">solitons</span>. Its predictions are found to be in good agreement with direct numerical simulations of the GLE. More specifically, the spectral and temporal shifts of the chirped <span class="hlt">soliton</span> induced by free carriers and intrapulse Raman scattering are predicted quite accurately. We also provide simple analytic expressions of these shifts by making suitable approximations. Our semianalytic treatment is useful for gaining physical insight into complex <span class="hlt">soliton</span>-evolution processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22220591','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22220591"><span>Nonplanar <span class="hlt">solitons</span> collision in ultracold neutral plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>El-Tantawy, S. A.; Moslem, W. M.; El-Metwally, M.; Sabry, R.; El-Labany, S. K.; Schlickeiser, R.</p> <p>2013-09-15</p> <p>Collisions between two nonplanar ion-acoustic <span class="hlt">solitons</span> in strongly coupled ultracold neutral plasmas composed of ion fluid and non-Maxwellian (nonthermal or superthermal) electron distributions are investigated. The extended Poincare-Lighthill-Kuo method is used to obtain coupled nonplanar Kortweg-de Vries equations for describing the system. The nonplanar phase shifts after the interaction of the two <span class="hlt">solitons</span> are calculated. It is found that the properties of the nonplanar colliding <span class="hlt">solitons</span> and its corresponding phase shifts are different from those in the planar case. The polarity of the colliding <span class="hlt">solitons</span> strongly depends on the type of the non-Maxwellian electron distributions. A critical nonthermality parameter β{sub c} is identified. For values of β ≤ β{sub c} <span class="hlt">solitons</span> with double polarity exist, while this behavior cannot occur for superthermal plasmas. The phase shift for nonthermal plasmas increases below β{sub c} for a positive <span class="hlt">soliton</span>, but it decreases for β > β{sub c} for a negative <span class="hlt">soliton</span>. For superthermal plasmas, the phase shift enhances rapidly for low values of spectral index κ and higher values of ions effective temperature ratio σ{sub *}. For 2 ≲ κ<10, the phase shift decreases but does not change for κ > 10. The nonlinear structure, as reported here, is useful for controlling the <span class="hlt">solitons</span> created in forthcoming ultracold neutral plasma experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20861525','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20861525"><span>Dissipative <span class="hlt">Solitons</span> that Cannot be Trapped</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pardo, Rosa; Perez-Garcia, Victor M.</p> <p>2006-12-22</p> <p>We show that dissipative <span class="hlt">solitons</span> in systems with high-order nonlinear dissipation cannot survive in the presence of trapping potentials of the rigid wall or asymptotically increasing type. <span class="hlt">Solitons</span> in such systems can survive in the presence of a weak potential but only with energies out of the interval of existence of linear quantum mechanical stationary states.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14759052','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14759052"><span>Coherent interactions of dissipative spatial <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ultanir, Erdem A; Stegeman, George I; Lange, Christoph H; Lederer, Falk</p> <p>2004-02-01</p> <p>We report observation of the interaction between two coherent dissipative spatial <span class="hlt">solitons</span> in a periodically patterned semiconductor optical amplifier with power levels of tens of milliwatts. The interactions are nonlocal and phase dependent and exhibit surprising features, such as <span class="hlt">soliton</span> birth. The experimental results are in good agreement with the numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18040515','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18040515"><span><span class="hlt">Soliton</span> algebra by vortex-beam splitting.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Minardi, S; Molina-Terriza, G; Di Trapani, P; Torres, J P; Torner, L</p> <p>2001-07-01</p> <p>We experimentally demonstrate the possibility of breaking up intense vortex light beams into stable and controllable sets of parametric <span class="hlt">solitons</span>. We report observations performed in seeded second-harmonic generation, but the scheme can be extended to all parametric processes. The number of generated <span class="hlt">solitons</span> is shown to be determined by a robust arithmetic rule.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPIE10090E..0DV','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPIE10090E..0DV"><span>Dissipative Kerr <span class="hlt">solitons</span> and microcavity frequency combs (Conference Presentation)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vahala, Kerry J.</p> <p>2017-02-01</p> <p>Dissipative Kerr <span class="hlt">soliton</span> mode locking in high-Q silica micro cavities is reviewed including resonator dispersion optimization. Phenomena relating to <span class="hlt">soliton</span> propagation in the micro cavity are studied including dispersive wave generation and <span class="hlt">soliton</span> trapping. Applications of the <span class="hlt">soliton</span> comb are described.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPhCS.822a2017L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPhCS.822a2017L"><span>Generalized wall function and its application to <span class="hlt">compressible</span> turbulent boundary layer over a flat plate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, J.; Wu, S. P.</p> <p>2017-04-01</p> <p>Wall function boundary conditions including the effects of <span class="hlt">compressibility</span> and heat transfer are improved for <span class="hlt">compressible</span> turbulent boundary flows. Generalized wall function formulation at zero-<span class="hlt">pressure</span> <span class="hlt">gradient</span> is proposed based on coupled velocity and temperature profiles in the entire near-wall region. The parameters in the generalized wall function are well revised. The proposed boundary conditions are integrated into Navier-Stokes computational fluid dynamics code that includes the shear stress transport turbulence model. Numerical results are presented for a <span class="hlt">compressible</span> boundary layer over a flat plate at zero-<span class="hlt">pressure</span> <span class="hlt">gradient</span>. Compared with experimental data, the computational results show that the generalized wall function reduces the first grid spacing in the directed normal to the wall and proves the feasibility and effectivity of the generalized wall function method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15004305','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15004305"><span><span class="hlt">Compressibility</span> Corrections to Closure Approximations for Turbulent Flow Simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cloutman, L D</p> <p>2003-02-01</p> <p>We summarize some modifications to the usual closure approximations for statistical models of turbulence that are necessary for use with <span class="hlt">compressible</span> fluids at all Mach numbers. We concentrate here on the gradient-flu approximation for the turbulent heat flux, on the buoyancy production of turbulence kinetic energy, and on a modification of the Smagorinsky model to include buoyancy. In all cases, there are <span class="hlt">pressure</span> <span class="hlt">gradient</span> terms that do not appear in the incompressible models and are usually omitted in <span class="hlt">compressible</span>-flow models. Omission of these terms allows unphysical rates of entropy change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960015572','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960015572"><span>Effects of Periodic Unsteady Wake Flow and <span class="hlt">Pressure</span> <span class="hlt">Gradient</span> on Boundary Layer Transition Along the Concave Surface of a Curved Plate. Part 3</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schobeiri, M. T.; Radke, R. E.</p> <p>1996-01-01</p> <p>Boundary layer transition and development on a turbomachinery blade is subjected to highly periodic unsteady turbulent flow, <span class="hlt">pressure</span> <span class="hlt">gradient</span> in longitudinal as well as lateral direction, and surface curvature. To study the effects of periodic unsteady wakes on the concave surface of a turbine blade, a curved plate was utilized. On the concave surface of this plate, detailed experimental investigations were carried out under zero and negative <span class="hlt">pressure</span> <span class="hlt">gradient</span>. The measurements were performed in an unsteady flow research facility using a rotating cascade of rods positioned upstream of the curved plate. Boundary layer measurements using a hot-wire probe were analyzed by the ensemble-averaging technique. The results presented in the temporal-spatial domain display the transition and further development of the boundary layer, specifically the ensemble-averaged velocity and turbulence intensity. As the results show, the turbulent patches generated by the wakes have different leading and trailing edge velocities and merge with the boundary layer resulting in a strong deformation and generation of a high turbulence intensity core. After the turbulent patch has totally penetrated into the boundary layer, pronounced becalmed regions were formed behind the turbulent patch and were extended far beyond the point they would occur in the corresponding undisturbed steady boundary layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChPhB..25b4701W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChPhB..25b4701W"><span>Numerical investigation of a coupled moving boundary model of radial flow in low-permeable stress-sensitive reservoir with threshold <span class="hlt">pressure</span> <span class="hlt">gradient</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wen-Chao, Liu; Yue-Wu, Liu; Cong-Cong, Niu; Guo-Feng, Han; Yi-Zhao, Wan</p> <p>2016-02-01</p> <p>The threshold <span class="hlt">pressure</span> <span class="hlt">gradient</span> and formation stress-sensitive effect as the two prominent physical phenomena in the development of a low-permeable reservoir are both considered here for building a new coupled moving boundary model of radial flow in porous medium. Moreover, the wellbore storage and skin effect are both incorporated into the inner boundary conditions in the model. It is known that the new coupled moving boundary model has strong nonlinearity. A coordinate transformation based fully implicit finite difference method is adopted to obtain its numerical solutions. The involved coordinate transformation can equivalently transform the dynamic flow region for the moving boundary model into a fixed region as a unit circle, which is very convenient for the model computation by the finite difference method on fixed spatial grids. By comparing the numerical solution obtained from other different numerical method in the existing literature, its validity can be verified. Eventually, the effects of permeability modulus, threshold <span class="hlt">pressure</span> <span class="hlt">gradient</span>, wellbore storage coefficient, and skin factor on the transient wellbore pressure, the derivative, and the formation pressure distribution are analyzed respectively. Project supported by the National Natural Science Foundation of China (Grant No. 51404232), the China Postdoctoral Science Foundation (Grant No. 2014M561074), and the National Science and Technology Major Project, China (Grant No. 2011ZX05038003).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980227967','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980227967"><span>A Simple Method for Determining Heat Transfer, Skin Friction, and Boundary-Layer Thickness for Hypersonic Laminar Boundary-Layer Flows in a <span class="hlt">Pressure</span> <span class="hlt">Gradient</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bertram, Mitchel H.; Feller, William V.</p> <p>1959-01-01</p> <p>A procedure based on the method of similar solutions is presented by which the skin friction, heat transfer, and boundary-layer thickness in a laminar hypersonic flow with <span class="hlt">pressure</span> <span class="hlt">gradient</span> may be rapidly evaluated if the pressure distribution is known. This solution, which at present is. restricted to power-law variations of pressure with surface distance, is presented for a wide range of exponents in the power law corresponding to both favorable and adverse <span class="hlt">pressure</span> <span class="hlt">gradients</span>. This theory has been compared to results from heat-transfer experiments on blunt-nose flat plates and a hemisphere cylinder at free-stream Mach numbers of 4 and 6.8. The flat-plate experiments included tests made at a Mach number of 6.8 over a range of angle of attack of +/- 10 deg. Reasonable agreement of the experimental and theoretical heat-transfer coefficients has been obtained as well as good correlation of the experimental results over the entire range of angle of attack studied. A similar comparison of theory with experiment was not feasible for boundary-layer-thickness data; however, the hypersonic similarity theory was found to account satisfactorily for the variation in boundary-layer thickness due to local pressure distribution for several sets of measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22303636','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22303636"><span>Magnetic turbulence and <span class="hlt">pressure</span> <span class="hlt">gradient</span> feedback effect of the 1/2 mode soft-hard magnetohydrodynamic limit in large helical device</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Varela, J.; Watanabe, K. Y.; Ohdachi, S.; Narushima, Y.</p> <p>2014-09-15</p> <p>The aim of this study was to analyze the feedback process between the magnetic turbulence and the <span class="hlt">pressure</span> <span class="hlt">gradients</span> in Large Helical Device (LHD) inward-shifted configurations as well as its role in the transition between the soft-hard magnetohydrodynamic (MHD) regimes for instabilities driven by the mode 1/2 in the middle plasma. In the present paper, we summarize the results of two simulations with different Lundquist numbers, S=2.5×10{sup 5} and 10{sup 6}, assuming a plasma in the slow reconnection regime. The results for the high Lundquist number simulation show that the magnetic turbulence and the <span class="hlt">pressure</span> <span class="hlt">gradient</span> in the middle plasma region of LHD are below the critical value to drive the transition to the hard MHD regime, therefore only relaxations in the soft MHD limit are triggered (1/2 sawtooth-like events) [Phys. Plasmas 19, 082512 (2012)]. In the case of the simulation with low Lundquist number, the system reaches the hard MHD limit and a plasma collapse is observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012NaPho...6...84G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012NaPho...6...84G"><span>Dissipative <span class="hlt">solitons</span> for mode-locked lasers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grelu, Philippe; Akhmediev, Nail</p> <p>2012-02-01</p> <p>Dissipative <span class="hlt">solitons</span> are localized formations of an electromagnetic field that are balanced through an energy exchange with the environment in presence of nonlinearity, dispersion and/or diffraction. Their growing use in the area of passively mode-locked lasers is remarkable: the concept of a dissipative <span class="hlt">soliton</span> provides an excellent framework for understanding complex pulse dynamics and stimulates innovative cavity designs. Reciprocally, the field of mode-locked lasers serves as an ideal playground for testing the concept of dissipative <span class="hlt">solitons</span> and revealing their unusual dynamics. This Review provides basic definitions of dissipative <span class="hlt">solitons</span>, summarizes their implications for the design of high-energy mode-locked fibre laser cavities, highlights striking emerging dynamics such as dissipative <span class="hlt">soliton</span> molecules, pulsations, explosions and rain, and finally provides an outlook for dissipative light bullets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12188854','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12188854"><span>Isotropic versus anisotropic modeling of photorefractive <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Belić, M R; Vujić, D; Stepken, A; Kaiser, F; Calvo, G F; Agulló-López, F; Carrascosa, M</p> <p>2002-06-01</p> <p>The question of the isotropic versus anisotropic modeling of incoherent spatial screening <span class="hlt">solitons</span> in photorefractive crystals is addressed by a careful theoretical and numerical analysis. Isotropic, or local, models allow for an extended spiraling of two interacting scalar <span class="hlt">solitons</span>, and for a prolonged propagation of vortex vector <span class="hlt">solitons</span>, whereas anisotropic, nonlocal, models prevent such phenomena. In the context of Kukhtarev's material equations, the difference in behavior is traced to the continuity equation for the current density. We further show that neither an indefinite spiraling of two <span class="hlt">solitons</span> nor stable propagation of vortex vector <span class="hlt">solitons</span> is generally possible in both isotropic and anisotropic models. Such systems do not conserve angular momentum, even in the case of an isotropic change in the index of refraction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhPl....7..883T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhPl....7..883T"><span>Ion-acoustic <span class="hlt">solitons</span> and double layers in a two-electron temperature plasma with hot isothermal electrons and cold ions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tagare, S. G.</p> <p>2000-03-01</p> <p>It is found that a two-electron temperature plasma with isothermal electrons and cold ions admits both <span class="hlt">compressive</span> and rarefactive <span class="hlt">solitons</span>, as well as <span class="hlt">compressive</span> and rarefactive double layers (depending on the concentration of low-temperature electrons). In this paper, a Korteweg-de Vries (K-dV) equation and a K-dV-type equation with cubic and fourth-order nonlinearity at the critical density of the low-temperature isothermal electrons are derived to discuss the properties of ion-acoustic <span class="hlt">solitons</span> in a two-electron temperature plasma. In the vicinity of the critical electron density of low-temperature isothermal electrons, we have derived a K-dV-type equation with mixed nonlinearity, and the solution of this equation will have both <span class="hlt">compressive</span> and rarefactive double layers for those values of critical electron density of low-temperature electrons for which ion-acoustic <span class="hlt">solitons</span> do not exist. By using quasipotential analysis, critical Mach numbers M1c and M2c are obtained such that <span class="hlt">compressive</span> ion-acoustic <span class="hlt">solitons</span> exist when 1<M<M1c and rarefactive ion-acoustic <span class="hlt">solitons</span> exist when 1<M<M2c.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28196896','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28196896"><span>Brownian motion of <span class="hlt">solitons</span> in a Bose-Einstein condensate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Aycock, Lauren M; Hurst, Hilary M; Efimkin, Dmitry K; Genkina, Dina; Lu, Hsin-I; Galitski, Victor M; Spielman, I B</p> <p>2017-03-07</p> <p>We observed and controlled the Brownian motion of <span class="hlt">solitons</span>. We launched <span class="hlt">solitonic</span> excitations in highly elongated [Formula: see text] Bose-Einstein condensates (BECs) and showed that a dilute background of impurity atoms in a different internal state dramatically affects the <span class="hlt">soliton</span>. With no impurities and in one dimension (1D), these <span class="hlt">solitons</span> would have an infinite lifetime, a consequence of integrability. In our experiment, the added impurities scatter off the much larger <span class="hlt">soliton</span>, contributing to its Brownian motion and decreasing its lifetime. We describe the <span class="hlt">soliton</span>'s diffusive behavior using a quasi-1D scattering theory of impurity atoms interacting with a <span class="hlt">soliton</span>, giving diffusion coefficients consistent with experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20975147','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20975147"><span>Small amplitude <span class="hlt">solitons</span> in a warm plasma with smaller and higher order relativistic effects</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kalita, B. C.; Das, R.</p> <p>2007-07-15</p> <p><span class="hlt">Solitons</span> have been investigated in a warm plasma through the Korteweg-de Vries (KdV) equation, considering a smaller relativistic effect for {gamma}{approx_equal}O(v{sup 2}/c{sup 2}) and {gamma}{sub e}{approx_equal}O(u{sup 2}/c{sup 2}) and higher relativistic effects for {gamma}{approx_equal}O(v{sup 4}/c{sup 4}) and {gamma}{sub e}{approx_equal}O(u{sup 4/}c{sup 4}). <span class="hlt">Compressive</span> fast ion-acoustic <span class="hlt">solitons</span> are observed to exist in the entire range (u{sub 0}-v{sub 0}) subject to a suitable mathematical condition satisfied by the initial streaming velocities u{sub 0},v{sub 0} of the electrons and the ions, respectively, electron to ion mass ratio Q(=m{sub e}/m{sub i}) and ion to electron temperature ratio {sigma}(=T{sub i}/T{sub e}). Further, rarefactive <span class="hlt">solitons</span> of pretty small amplitudes are observed in the small upper range of |u{sub 0}-v{sub 0}| for higher order relativistic effect which are found to change parabolically. It is essentially important to report in our model of plasma, that the higher order relativistic effect slows down the <span class="hlt">soliton</span> speed to V{<=}0.10 for all temperature ratios {sigma} for small amplitude waves. On the other hand, the smaller order relativistic effect permits the <span class="hlt">soliton</span> to exist even at a relatively much higher speed V<0.30. <span class="hlt">Solitons</span> of high (negligible) amplitudes are found to generate at the smaller (greater) difference of initial streamings (u{sub 0}-v{sub 0}) corresponding to both the relativistic effects.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22490967','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22490967"><span>Effects of hot electron inertia on electron-acoustic <span class="hlt">solitons</span> and double layers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Verheest, Frank; Hellberg, Manfred A.</p> <p>2015-07-15</p> <p>The propagation of arbitrary amplitude electron-acoustic <span class="hlt">solitons</span> and double layers is investigated in a plasma containing cold positive ions, cool adiabatic and hot isothermal electrons, with the retention of full inertial effects for all species. For analytical tractability, the resulting Sagdeev pseudopotential is expressed in terms of the hot electron density, rather than the electrostatic potential. The existence domains for Mach numbers and hot electron densities clearly show that both rarefactive and <span class="hlt">compressive</span> <span class="hlt">solitons</span> can exist. <span class="hlt">Soliton</span> limitations come from the cool electron sonic point, followed by the hot electron sonic point, until a range of rarefactive double layers occurs. Increasing the relative cool electron density further yields a switch to <span class="hlt">compressive</span> double layers, which ends when the model assumptions break down. These qualitative results are but little influenced by variations in compositional parameters. A comparison with a Boltzmann distribution for the hot electrons shows that only the cool electron sonic point limit remains, giving higher maximum Mach numbers but similar densities, and a restricted range in relative hot electron density before the model assumptions are exceeded. The Boltzmann distribution can reproduce neither the double layer solutions nor the switch in rarefactive/<span class="hlt">compressive</span> character or negative/positive polarity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19604512','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19604512"><span>Peak <span class="hlt">compression</span> factor of proteins.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gritti, Fabrice; Guiochon, Georges</p> <p>2009-08-14</p> <p>An experimental protocol is proposed in order to measure with accuracy and precision the band <span class="hlt">compression</span> factor G(12)(2) of a protein in gradient RPLC. Extra-column contributions to bandwidth and the dependency of both the retention factor and the reduced height equivalent to a theoretical plate (HETP) on the mobile phase composition were taken into account. The band <span class="hlt">compression</span> factor of a small protein (insulin, MW kDa) was measured on a 2.1mm x 50mm column packed with 1.7 microm C(4)-bonded bridged ethylsiloxane BEH-silica particles, for 1 microL samples of dilute insulin solution (<0.05g/L). A linear gradient profile of acetonitrile (25-28% acetonitrile in water containing 0.1% trifluoroacetic acid) was applied during three different gradient times (5, 12.5, and 20 min). The mobile phase flow rate was set at 0.20 mL/min in order to avoid heat friction effects (maximum column inlet pressure 180 bar). The band <span class="hlt">compression</span> factor of insulin is defined as the ratio of the experimental space band variance measured under gradient conditions to the reference space band variance, which would be observed if no thermodynamic <span class="hlt">compression</span> would take place during gradient elution. It was 0.56, 0.71, and 0.76 with gradient times of 5, 12.5, and 20 min, respectively. These factors are 20-30% smaller than the theoretical band <span class="hlt">compression</span> factors (0.79, 0.89, and 0.93) calculated from an equation derived from the well-known Poppe equation, later extended to any retention models and columns whose HETP depends on the mobile phase composition. This difference is explained in part by the omission in the model of the effect of the <span class="hlt">pressure</span> <span class="hlt">gradient</span> on the local retention factor of insulin during gradient elution. A much better agreement is obtained for insulin when this effect is taken into account. For lower molecular weight compounds, the <span class="hlt">pressure</span> <span class="hlt">gradient</span> has little effect but the finite retention of acetonitrile causes a distortion of the gradient shape during the migration of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26832559','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26832559"><span>Coexistence and interaction of vector and bound vector <span class="hlt">solitons</span> in a dispersion-managed fiber laser mode locked by graphene.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Song, Y F; Zhang, H; Zhao, L M; Shen, D Y; Tang, D Y</p> <p>2016-01-25</p> <p>We report on the experimental observation of vector and bound vector <span class="hlt">solitons</span> in a fiber laser passively mode locked by graphene. Localized interactions between vector <span class="hlt">solitons</span>, vector <span class="hlt">soliton</span> with bound vector <span class="hlt">solitons</span>, and vector <span class="hlt">soliton</span> with a bunch of vector <span class="hlt">solitons</span> are experimentally investigated. We show that depending on the <span class="hlt">soliton</span> interactions, various stable and dynamic multiple vector <span class="hlt">soliton</span> states could be formed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvE..95c2217C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvE..95c2217C"><span>Gap <span class="hlt">solitons</span> in Rabi lattices</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Zhaopin; Malomed, Boris A.</p> <p>2017-03-01</p> <p>We introduce a two-component one-dimensional system, which is based on two nonlinear Schrödinger or Gross-Pitaevskii equations (GPEs) with spatially periodic modulation of linear coupling ("Rabi lattice") and self-repulsive nonlinearity. The system may be realized in a binary Bose-Einstein condensate, whose components are resonantly coupled by a standing optical wave, as well as in terms of the bimodal light propagation in periodically twisted waveguides. The system supports various types of gap <span class="hlt">solitons</span> (GSs), which are constructed, and their stability is investigated, in the first two finite bandgaps of the underlying spectrum. These include on- and off-site-centered <span class="hlt">solitons</span> (the GSs of the off-site type are additionally categorized as spatially even and odd ones), which may be symmetric or antisymmetric, with respect to the coupled components. The GSs are chiefly stable in the first finite bandgap and unstable in the second one. In addition to that, there are narrow regions near the right edge of the first bandgap, and in the second one, which feature intricate alternation of stability and instability. Unstable <span class="hlt">solitons</span> evolve into robust breathers or spatially confined turbulent modes. On-site-centered GSs are also considered in a version of the system that is made asymmetric by the Zeeman effect, or by birefringence of the optical waveguide. A region of alternate stability is found in the latter case too. In the limit of strong asymmetry, GSs are obtained in a semianalytical approximation, which reduces two coupled GPEs to a single one with an effective lattice potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25238388','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25238388"><span><span class="hlt">Soliton</span> turbulence in shallow water ocean surface waves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Costa, Andrea; Osborne, Alfred R; Resio, Donald T; Alessio, Silvia; Chrivì, Elisabetta; Saggese, Enrica; Bellomo, Katinka; Long, Chuck E</p> <p>2014-09-05</p> <p>We analyze shallow water wind waves in Currituck Sound, North Carolina and experimentally confirm, for the first time, the presence of <span class="hlt">soliton</span> turbulence in ocean waves. <span class="hlt">Soliton</span> turbulence is an exotic form of nonlinear wave motion where low frequency energy may also be viewed as a dense <span class="hlt">soliton</span> gas, described theoretically by the <span class="hlt">soliton</span> limit of the Korteweg-deVries equation, a completely integrable <span class="hlt">soliton</span> system: Hence the phrase "<span class="hlt">soliton</span> turbulence" is synonymous with "integrable <span class="hlt">soliton</span> turbulence." For periodic-quasiperiodic boundary conditions the ergodic solutions of Korteweg-deVries are exactly solvable by finite gap theory (FGT), the basis of our data analysis. We find that large amplitude measured wave trains near the energetic peak of a storm have low frequency power spectra that behave as ∼ω-1. We use the linear Fourier transform to estimate this power law from the power spectrum and to filter densely packed <span class="hlt">soliton</span> wave trains from the data. We apply FGT to determine the <span class="hlt">soliton</span> spectrum and find that the low frequency ∼ω-1 region is <span class="hlt">soliton</span> dominated. The <span class="hlt">solitons</span> have random FGT phases, a <span class="hlt">soliton</span> random phase approximation, which supports our interpretation of the data as <span class="hlt">soliton</span> turbulence. From the probability density of the <span class="hlt">solitons</span> we are able to demonstrate that the <span class="hlt">solitons</span> are dense in time and highly non-Gaussian.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ChPhL..28h4204H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ChPhL..28h4204H"><span>Diode-Pumped <span class="hlt">Soliton</span> and Non-<span class="hlt">Soliton</span> Mode-Locked Yb:GYSO Lasers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, Jin-Ping; Liang, Xiao-Yan; Li, Jin-Feng; Zheng, Li-He; Su, Liang-Bi; Xu, Jun</p> <p>2011-08-01</p> <p>Diode-pumped <span class="hlt">soliton</span> and non-<span class="hlt">soliton</span> mode-locked Yb:(Gd1-x Yx)2SiO5(x = 0.5) lasers are demonstrated. Pulses as short as 1.4 ps are generated for the <span class="hlt">soliton</span> mode-locked operation, with a pair of SF10 prisms as the negative dispersion elements. The central wavelength is 1056 nm and the repetition rate is 48 MHz. For the non-<span class="hlt">soliton</span> mode locking, the output power could achieve ~1.2 W, and the pulse width is about 20 ps. The critical pulse energy in the <span class="hlt">soliton</span>-mode locked operation against the Q-switched mode locking is much lower than the critical pulse energy in the non-<span class="hlt">soliton</span> mode-locked operation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19860023270','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19860023270"><span>A comparison of experimental and theoretical results for leakage, <span class="hlt">pressure</span> <span class="hlt">gradients</span>, and rotordynamic coefficients for tapered annular gas seal</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Elrod, D. A.; Childs, D. W.</p> <p>1986-01-01</p> <p>A brief review of current annular seal theory and a discussion of the predicted effect on stiffness of tapering the seal stator are presented. An outline of Nelson's analytical-computational method for determining rotordynamic coefficients for annular <span class="hlt">compressible</span>-flow seals is included. Modifications to increase the maximum rotor speed of an existing air-seal test apparatus at Texas A&M University are described. Experimental results, including leakage, entrance-loss coefficients, pressure distributions, and normalized rotordynamic coefficients, are presented for four convergent-tapered, smooth-rotor, smooth-stator seals. A comparison of the test results shows that an inlet-to-exit clearance ratio of 1.5 to 2.0 provides the maximum direct stiffness, a clearance ratio of 2.5 provides the greatest stability, and a clearance ratio of 1.0 provides the least stability. The experimental results are compared to theoretical results from Nelson's analysis with good agreement. Test results for cross-coupled stiffness show less sensitivity of fluid prerotation than predicted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21215975','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21215975"><span>Response of single benthic metrics and multi-metric methods to anthropogenic <span class="hlt">pressure</span> <span class="hlt">gradients</span>, in five distinct European coastal and transitional ecosystems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Borja, Angel; Barbone, Enrico; Basset, Alberto; Borgersen, Gunhild; Brkljacic, Marijana; Elliott, Michael; Garmendia, Joxe Mikel; Marques, João Carlos; Mazik, Krysia; Muxika, Iñigo; Magalhães Neto, João; Norling, Karl; Rodríguez, J Germán; Rosati, Ilaria; Rygg, Brage; Teixeira, Heliana; Trayanova, Antoaneta</p> <p>2011-03-01</p> <p>In recent times many benthic indices have been proposed to assess the ecological quality of marine waters worldwide. In this study we compared single metrics and multi-metric methods to assess coastal and transitional benthic status along human <span class="hlt">pressure</span> <span class="hlt">gradients</span> in five distinct environments across Europe: Varna bay and lake (Bulgaria), Lesina lagoon (Italy), Mondego estuary (Portugal), Basque coast (Spain) and Oslofjord (Norway). Hence, 13 single metrics (abundance, number of taxa, and several diversity and sensitivity indices) and eight of the most common indices used within the European Water Framework Directive (WFD) for benthic assessment were selected: index of size spectra (ISS), Benthic assessment tool (BAT), Norwegian quality index (NQI), Multivariate AMBI (M-AMBI), Benthic quality index (BQI), (Benthic ecosystem quality index (BEQI), Benthic index based on taxonomic sufficiency (BITS), and infaunal quality index (IQI). Within each system, sampling sites were ordered in an increasing <span class="hlt">pressure</span> <span class="hlt">gradient</span> according to a preliminary classification based on professional judgement. The different indices are largely consistent in their response to <span class="hlt">pressure</span> <span class="hlt">gradient</span>, except in some particular cases (i.e. BITS, in all cases, or ISS when a low number of individuals is present). Inconsistencies between indicator responses were most pronounced in transitional waters (i.e. IQI, BEQI), highlighting the difficulties of the generic application of indicators to all marine, estuarine and lagoonal environments. However, some of the single (i.e. ecological groups approach, diversity, richness) and multi-metric methods (i.e. BAT, M-AMBI, NQI) were able to detect such gradients both in transitional and coastal environments, being these multi-metric methods more consistent in the detection than single indices. This study highlights the importance of survey design and good reference conditions for some indicators. The agreement observed between different methodologies and their</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=data+AND+storage+AND+devices&pg=6&id=EJ453314','ERIC'); return false;" href="http://eric.ed.gov/?q=data+AND+storage+AND+devices&pg=6&id=EJ453314"><span>Data <span class="hlt">Compression</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Bookstein, Abraham; Storer, James A.</p> <p>1992-01-01</p> <p>Introduces this issue, which contains papers from the 1991 Data <span class="hlt">Compression</span> Conference, and defines data <span class="hlt">compression</span>. The two primary functions of data <span class="hlt">compression</span> are described, i.e., storage and communications; types of data using <span class="hlt">compression</span> technology are discussed; <span class="hlt">compression</span> methods are explained; and current areas of research are…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22743443','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22743443"><span>Stable surface <span class="hlt">solitons</span> in truncated complex potentials.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>He, Yingji; Mihalache, Dumitru; Zhu, Xing; Guo, Lina; Kartashov, Yaroslav V</p> <p>2012-07-01</p> <p>We show that surface <span class="hlt">solitons</span> in the one-dimensional nonlinear Schrödinger equation with truncated complex periodic potential can be stabilized by linear homogeneous losses, which are necessary to balance gain in the near-surface channel arising from the imaginary part of potential. Such <span class="hlt">solitons</span> become stable attractors when the strength of homogeneous losses acquires values from a limited interval and they exist in focusing and defocusing media. The domains of stability of the surface <span class="hlt">solitons</span> shrink with an increase in the amplitude of the imaginary part of complex potential.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvE..95d2204L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvE..95d2204L"><span>Landau-Zener tunneling of <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loladze, Vazha; Khomeriki, Ramaz</p> <p>2017-04-01</p> <p>We consider Landau-Zener tunneling of <span class="hlt">solitons</span> in a weakly coupled two-channel system, for this purpose we construct a simple mechanical system using two weakly coupled chains of nonlinear oscillators with gradually decreasing (first chain) and increasing (second chain) masses. The model allows us to consider <span class="hlt">soliton</span> propagation and Landau-Zener tunneling between the chains. It is shown that <span class="hlt">soliton</span> tunneling characteristics become drastically dependent on its amplitude in nonlinear regime. The validity of the developed tunneling theory is justified via comparison with direct numerical simulations on oscillator ladder system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPhCS.890a2071U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPhCS.890a2071U"><span>Flat top <span class="hlt">solitons</span> on linear gaussian potential</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Umarov, B. A.; Aklan, N. A. B.; Rosly, M. R.; Hassan, T. H.</p> <p>2017-09-01</p> <p>The study of Nonlinear Schrodinger Equation has been wide focus from many researchers especially analysing the result of collision as it describes the <span class="hlt">soliton</span> propagation. This paper considers the <span class="hlt">soliton</span> scattering of cubic-quintic Nonlinear Schrodinger Equation on localized Gaussian potential. By applying Super-Gaussian ansatz as the trial function for variational approximation (VA) method, the <span class="hlt">soliton</span> interaction may acquire flat-top shape with appropriate parameters. The result of VA will be compared to numerical analysis to check the accuracy of analytical predictions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21408895','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21408895"><span><span class="hlt">Solitons</span> in curved space of constant curvature</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Batz, Sascha; Peschel, Ulf</p> <p>2010-05-15</p> <p>We consider spatial <span class="hlt">solitons</span> as, for example, self-confined optical beams in spaces of constant curvature, which are a natural generalization of flat space. Due to the symmetries of these spaces we are able to define respective dynamical parameters, for example, velocity and position. For positively curved space we find stable multiple-hump <span class="hlt">solitons</span> as a continuation from the linear modes. In the case of negatively curved space we show that no localized solution exists and a bright <span class="hlt">soliton</span> will always decay through a nonlinear tunneling process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28505861','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28505861"><span>Landau-Zener tunneling of <span class="hlt">solitons</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Loladze, Vazha; Khomeriki, Ramaz</p> <p>2017-04-01</p> <p>We consider Landau-Zener tunneling of <span class="hlt">solitons</span> in a weakly coupled two-channel system, for this purpose we construct a simple mechanical system using two weakly coupled chains of nonlinear oscillators with gradually decreasing (first chain) and increasing (second chain) masses. The model allows us to consider <span class="hlt">soliton</span> propagation and Landau-Zener tunneling between the chains. It is shown that <span class="hlt">soliton</span> tunneling characteristics become drastically dependent on its amplitude in nonlinear regime. The validity of the developed tunneling theory is justified via comparison with direct numerical simulations on oscillator ladder system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22072205','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22072205"><span>Transversely stable <span class="hlt">soliton</span> trains in photonic lattices</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Yang Jianke</p> <p>2011-09-15</p> <p>We report the existence of transversely stable <span class="hlt">soliton</span> trains in optics. These stable <span class="hlt">soliton</span> trains are found in two-dimensional square photonic lattices when they bifurcate from X-symmetry points with saddle-shaped diffraction inside the first Bloch band and their amplitudes are above a certain threshold. We also show that <span class="hlt">soliton</span> trains with low amplitudes or bifurcated from edges of the first Bloch band ({Gamma} and M points) still suffer transverse instability. These results are obtained in the continuous lattice model and are further corroborated by the discrete model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22490139','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22490139"><span>Rarefaction <span class="hlt">solitons</span> initiated by sheath instability</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Levko, Dmitry</p> <p>2015-09-15</p> <p>The instability of the cathode sheath initiated by the cold energetic electron beam is studied by the one-dimensional fluid model. Numerical simulations show the generation of travelling rarefaction <span class="hlt">solitons</span> at the cathode. It is obtained that the parameters of these <span class="hlt">solitons</span> strongly depend on the parameters of electron beam. The “stretched” variables are derived using the small-amplitude analysis. These variables are used in order to obtain the Korteweg-de Vries equation describing the propagation of the rarefaction <span class="hlt">solitons</span> through the plasma with cold energetic electron beam.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21443001','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21443001"><span>Spectral tunneling of lattice nonlocal <span class="hlt">solitons</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kartashov, Yaroslav V.; Torner, Lluis; Vysloukh, Victor A.</p> <p>2010-07-15</p> <p>We address spectral tunneling of walking spatial <span class="hlt">solitons</span> in photorefractive media with nonlocal diffusion component of the nonlinear response and an imprinted shallow optical lattice. In contrast to materials with local nonlinearities, where <span class="hlt">solitons</span> traveling across the lattice close to the Bragg angle suffer large radiative losses, in photorefractive media with diffusion nonlinearity resulting in self-bending, <span class="hlt">solitons</span> survive when their propagation angle approaches and even exceeds the Bragg angle. In the spatial frequency domain this effect can be considered as tunneling through the band of spatial frequencies centered around the Bragg frequency where the spatial group velocity dispersion is positive.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21020777','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21020777"><span>Dark <span class="hlt">solitons</span> in a superfluid Fermi gas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Antezza, Mauro; Dalfovo, Franco; Stringari, Sandro; Pitaevskii, Lev P.</p> <p>2007-10-15</p> <p>We investigate the behavior of dark <span class="hlt">solitons</span> in a superfluid Fermi gas along the BCS-BEC crossover by solving the Bogoliubov-de Gennes equations and looking for real and odd solutions for the order parameter. We show that in the resonance unitary region, where the scattering length is large, the density profile of the <span class="hlt">soliton</span> has a deep minimum, differently from what happens in the BCS regime. The superfluid gap is found to be significantly quenched by the presence of the <span class="hlt">soliton</span> due to the occurrence of Andreev fermionic bound states localized near the nodal plane of the order parameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AIPC..805..266E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AIPC..805..266E"><span><span class="hlt">Solitons</span> in Supersymmetric Gauge Theories</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eto, M.; Isozumi, Y.; Nitta, M.; Ohashi, K.; Sakai, N.</p> <p>2005-12-01</p> <p>Recent results on BPS <span class="hlt">solitons</span> in the Higgs phase of supersymmetric (SUSY) gauge theories with eight supercharges are reviewed. For U(NC) gauge theories with the NF(> NC) hypermultiplets in the fundamental representation, the total moduli space of walls are found to be the complex Grassmann manifold SU(NF)/[SU(NC) × SU(NF - NC) × U(1)]. The monopole in the Higgs phase has to accompany vortices, and preserves a 1/4 of SUSY. We find that walls are also allowed to coexist with them. We obtain all the solutions of such 1/4 BPS composite <span class="hlt">solitons</span> in the strong coupling limit. Instantons in the Higgs phase is also obtained as 1/4 BPS states. As another instructive example, we take U(1) × U(1) gauge theories with four hypermultiplets. We find that the moduli space is the union of several special Lagrangian submanifolds of the Higgs branch vacua of the corresponding massless theory. We also observe transmutation of walls and repulsion and attraction of BPS walls. This is a review of recent works on the subject, which was given at the conference by N. Sakai.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999JGR...10428295B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999JGR...10428295B"><span><span class="hlt">Soliton</span> approach to magnetic holes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baumgärtel, Klaus</p> <p></p> <p>``Magnetic holes'' (MHs), depressions in the magnetic field magnitude associated with enhancements in density and kinetic pressure, have been observed in the solar wind, the magnetosheaths of terrestrial planets and in the environments of comets, suggesting that this phenomenon may be a common occurrence in space plasmas. MHs are usually believed to result from the mirror instability which can develop in high-beta plasmas with a temperature anisotropy, T⊥/T∥>1. Motivated by the fact that solar wind MHs are often observed in a mirror mode stable environment [Winterhalter et al., 1994], this paper proposes a mechanism for the maintenance of MHs in an equilibrium plasma. We suggest an explanation in terms of magnetically rarefactive (``dark'') MHD <span class="hlt">solitons</span> with anticorrelation of magnetic field and density, which propagate with small velocities at large angles to the ambient magnetic field. This intrinsically nonlinear approach is based on a magnetohydrodynamic plasma description including Hall inertia effects and utilizes the well-developed <span class="hlt">soliton</span> theory of the Derivative Nonlinear Schrödinger Equation (DNLS) which appears as a partly adequate approximation to the parent Hall-MHD system. The approach introduces an alternative mechanism into the discussion over the physical nature of MHs that is not related to an instability and provides an explanation for various aspects of the observations including amplitude, thickness, and spatial structure of MHs.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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