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Sample records for energy dissipation rates

  1. Quantified Energy Dissipation Rates in the Terrestrial Bow Shock. 2; Waves and Dissipation

    NASA Technical Reports Server (NTRS)

    Wilson, L. B., III; Sibeck, D. G.; Breneman, A. W.; Le Contel, O.; Cully, C.; Turner, D. L.; Angelopoulos, V.; Malaspina, D. M.

    2014-01-01

    We present the first quantified measure of the energy dissipation rates, due to wave-particle interactions, in the transition region of the Earth's collision-less bow shock using data from the Time History of Events and Macro-Scale Interactions during Sub-Storms spacecraft. Our results show that wave-particle interactions can regulate the global structure and dominate the energy dissipation of collision-less shocks. In every bow shock crossing examined, we observed both low-frequency (less than 10 hertz) and high-frequency (approximately or greater than10 hertz) electromagnetic waves throughout the entire transition region and into the magnetosheath. The low-frequency waves were consistent with magnetosonic-whistler waves. The high-frequency waves were combinations of ion-acoustic waves, electron cyclotron drift instability driven waves, electrostatic solitary waves, and whistler mode waves. The high-frequency waves had the following: (1) peak amplitudes exceeding delta B approximately equal to 10 nanoteslas and delta E approximately equal to 300 millivolts per meter, though more typical values were delta B approximately equal to 0.1-1.0 nanoteslas and delta E approximately equal to 10-50 millivolts per meter (2) Poynting fluxes in excess of 2000 microWm(sup -2) (micro-waves per square meter) (typical values were approximately 1-10 microWm(sup -2) (micro-waves per square meter); (3) resistivities greater than 9000 omega meters; and (4) associated energy dissipation rates greater than 10 microWm(sup -3) (micro-waves per cubic meter). The dissipation rates due to wave-particle interactions exceeded rates necessary to explain the increase in entropy across the shock ramps for approximately 90 percent of the wave burst durations. For approximately 22 percent of these times, the wave-particle interactions needed to only be less than or equal to 0.1 percent efficient to balance the nonlinear wave steepening that produced the shock waves. These results show that wave

  2. Effect of mean velocity shear on the dissipation rate of turbulent kinetic energy

    NASA Technical Reports Server (NTRS)

    Yoshizawa, Akira; Liou, Meng-Sing

    1992-01-01

    The dissipation rate of turbulent kinetic energy in incompressible turbulence is investigated using a two-scale DIA. The dissipation rate is shown to consist of two parts; one corresponds to the dissipation rate used in the current turbulence models of eddy-viscosity type, and another comes from the viscous effect that is closely connected with mean velocity shear. This result can elucidate the physical meaning of the dissipation rate used in the current turbulence models and explain part of the discrepancy in the near-wall dissipation rates between the current turbulence models and direct numerical simulation of the Navier-Stokes equation.

  3. Energy dissipator

    NASA Technical Reports Server (NTRS)

    Delafuente, Horacio M. (Inventor); Nagy, Kornel (Inventor); Wesselski, Clarence J. (Inventor)

    1993-01-01

    An all metal energy dissipator construction is disclosed for dissipating kinetic energy force (F) by rolling balls which are forced by a tapered surface on an expandable sleeve to frictionally load a force rod. The balls are maintained in an initial position by a plate member which is biased by a spring member. A spring member returns the force rod to its initial position after a loading force is removed.

  4. Turbulence Kinetic Energy Budgets and Dissipation Rates in Disturbed Stable Boundary Layers

    SciTech Connect

    Lundquist, J K; Piper, M; Kosovic, B

    2004-06-18

    An important parameter in the numerical simulation of atmospheric boundary layers is the dissipation length scale, l{sub {var_epsilon}}. It is especially important in weakly to moderately stable conditions, in which a tenuous balance between shear production of turbulence, buoyant destruction of turbulence, and turbulent dissipation is maintained. In large-scale models, the dissipation rate is often parameterized using a diagnostic equation based on the production of turbulent kinetic energy (TKE) and an estimate of the dissipation length scale. Proper parameterization of the dissipation length scale from experimental data requires accurate estimation of the rate of dissipation of TKE from experimental data. Using data from the MICROFRONTS and CASES-99 field programs, we evaluate turbulent kinetic energy (TKE), TKE dissipation rate {var_epsilon}, and dissipation length l{sub {var_epsilon}} over a range of stability regimes represented by a stable boundary layer (SBL), a destabilizing intrusion (by first a cold front and second a density current) and recovery. These data may be utilized to test recent parameterizations of dissipation rate {var_epsilon} and l{sub {var_epsilon}} in order to determine the suitability of these models for inclusion in mesoscale models for numerical weather prediction or pollution dispersion prediction.

  5. Lumley's energy cascade dissipation rate model for boundary-free turbulent shear flows

    NASA Technical Reports Server (NTRS)

    Duncan, B. S.

    1992-01-01

    True dissipation occurs mainly at the highest wavenumbers where the eddy sizes are comparatively small. These high wavenumbers receive their energy through the spectral cascade of energy starting with the largest eddies spilling energy into the smaller eddies, passing through each wavenumber until it is dissipated at the microscopic scale. However, a small percentage of the energy does not spill continuously through the cascade but is instantly passed to the higher wavenumbers. Consequently, the smallest eddies receive a certain amount of energy almost immediately. As the spectral energy cascade continues, the highest wavenumber needs a certain time to receive all the energy which has been transferred from the largest eddies. As such, there is a time delay, of the order of tau, between the generation of energy by the largest eddies and the eventual dissipation of this energy. For equilibrium turbulence at high Reynolds numbers, there is a wide range where energy is neither produced by the large eddies nor dissipated by viscosity, but is conserved and passed from wavenumber to higher wavenumbers. The rate at which energy cascades from one wavenumber to another is proportional to the energy contained within that wavenumber. This rate is constant and has been used in the past as a dissipation rate of turbulent kinetic energy. However, this is true only in steady, equilibrium turbulence. Most dissipation models contend that the production of dissipation is proportional to the production of energy and that the destruction of dissipation is proportional to the destruction of energy. In essence, these models state that the change in the dissipation rate is proportional to the change in the kinetic energy. This assumption is obviously incorrect for the case where there is no production of turbulent energy, yet energy continues to cascade from large to small eddies. If the time lag between the onset on the energy cascade to the destruction of energy at the microscale can be

  6. Quantified Energy Dissipation Rates in the Terrestrial Bow Shock. 1.; Analysis Techniques and Methodology

    NASA Technical Reports Server (NTRS)

    Wilson, L. B., III; Sibeck, D. G.; Breneman, A.W.; Le Contel, O.; Cully, C.; Turner, D. L.; Angelopoulos, V.; Malaspina, D. M.

    2014-01-01

    We present a detailed outline and discussion of the analysis techniques used to compare the relevance of different energy dissipation mechanisms at collisionless shock waves. We show that the low-frequency, quasi-static fields contribute less to ohmic energy dissipation, (-j · E ) (minus current density times measured electric field), than their high-frequency counterparts. In fact, we found that high-frequency, large-amplitude (greater than 100 millivolts per meter and/or greater than 1 nanotesla) waves are ubiquitous in the transition region of collisionless shocks. We quantitatively show that their fields, through wave-particle interactions, cause enough energy dissipation to regulate the global structure of collisionless shocks. The purpose of this paper, part one of two, is to outline and describe in detail the background, analysis techniques, and theoretical motivation for our new results presented in the companion paper. The companion paper presents the results of our quantitative energy dissipation rate estimates and discusses the implications. Together, the two manuscripts present the first study quantifying the contribution that high-frequency waves provide, through wave-particle interactions, to the total energy dissipation budget of collisionless shock waves.

  7. Emergence of rate-independent dissipation from viscous systems with wiggly energies

    NASA Astrophysics Data System (ADS)

    Mielke, Alexander

    2012-11-01

    We consider the passage from viscous systems to rate-independent system in the limit of vanishing viscosity and for wiggly energies. Our new convergence approach is based on the {({R},{R}^*)} formulation of De Giorgi, where we pass to the Γ limit in the dissipation functional. The difficulty is that the type of dissipation changes from a quadratic functional to one that is homogeneous of degree 1, thus leading to hysteresis. The analysis uses the decomposition of the restoring force into a macroscopic part and a fluctuating part, where the latter is handled via homogenization.

  8. Energy dissipation in substorms

    NASA Technical Reports Server (NTRS)

    Weiss, Loretta A.; Reiff, P. H.; Moses, J. J.; Heelis, R. A.; Moore, B. D.

    1992-01-01

    The energy dissipated by substorms manifested in several ways is discussed: the Joule dissipation in the ionosphere; the energization of the ring current by the injection of plasma sheet particles; auroral election and ion acceleration; plasmoid ejection; and plasma sheet ion heating during the recovery phase. For each of these energy dissipation mechanisms, a 'rule of thumb' formula is given, and a typical dissipation rate and total energy expenditure is estimated. The total energy dissipated as Joule heat (approximately) 2 x 10(exp 15) is found about twice the ring current injection term, and may be even larger if small scale effects are included. The energy expended in auroral electron precipitation, on the other hand, is smaller than the Joule heating by a factor of five. The energy expended in refilling and heating the plasma sheets is estimated to be approximately 5 x 10(exp 14)J, while the energy lost due to plasmoid ejection is between (approximately) (10 exp 13)(exp 14)J.

  9. Determination of turbulent energy dissipation rate directly from MF-radar determined velocity

    NASA Astrophysics Data System (ADS)

    Hall, C. M.; Nozawa, S.; Manson, A. H.; Meek, C. E.

    2000-02-01

    MF radar systems are able to determine horizontal neutral winds in the mesosphere and, to some extent in the lower thermosphere by cross-correlations of signals received at spaced antennas. Essentially, by also computing auto-correlations, signal fading may be measured which in turn is thought to be largely attributable to turbulence. Hitherto, estimates of upper limits for the turbulent energy dissipation rate have been derived from the characteristic fading times. In this paper, we propose that power spectra of the velocity components themselves may be used to yield estimates of turbulent energy dissipation rate. 2-minute resolution velocities from the Universities of Saskatchewan, Tromsø and Nagoya joint MF radar at 69°N, 19°E are used in a pilot analysis to illustrate and ratify the method.

  10. Characteristics of turbulent kinetic energy dissipation rate and turbidity near the coast of East China Sea

    NASA Astrophysics Data System (ADS)

    Zhang, Yanwei; Xu, Huiping; Qin, Rufu; Xu, Changwei; Fan, Daidu

    2016-09-01

    The East China Sea (ECS) has a high suspended-sediment concentration because of the influence of the Changjiang River, indicated by high turbidity in the water. Considering the islands offthe coast and the complex topography, and the strong influence of tides and wind, the coast offthe ECS is a typical region with strong oceanic mixing processes. The changes in the dynamic processes near the bottom play an important role in the control of water turbidity. The turbulent kinetic energy dissipation rate ( ɛ ) is a parameter that shows the strength of ocean mixing. This is estimated based on a structure method using current velocity that is measured by a high-frequency Acoustic Doppler Current Profiler (ADCP) from a seafloor observatory in the ECS. The results indicate strong ocean mixing processes with a mean ɛ value of 5.7×10-5 W/kg and distinct tidal variations in the dissipation rate. Conversely, the variation of the water turbidity leads to changes in the water dynamical structure near the bottom. Comparing the dissipation rate with the turbidity near the bottom boundary layer, we find that the high turbidity mimics strong ocean mixing.

  11. Characteristics of turbulent kinetic energy dissipation rate and turbidity near the coast of East China Sea

    NASA Astrophysics Data System (ADS)

    Zhang, Yanwei; Xu, Huiping; Qin, Rufu; Xu, Changwei; Fan, Daidu

    2016-01-01

    The East China Sea (ECS) has a high suspended-sediment concentration because of the influence of the Changjiang River, indicated by high turbidity in the water. Considering the islands offthe coast and the complex topography, and the strong influence of tides and wind, the coast offthe ECS is a typical region with strong oceanic mixing processes. The changes in the dynamic processes near the bottom play an important role in the control of water turbidity. The turbulent kinetic energy dissipation rate ( ɛ ) is a parameter that shows the strength of ocean mixing. This is estimated based on a structure method using current velocity that is measured by a high-frequency Acoustic Doppler Current Profiler (ADCP) from a seafloor observatory in the ECS. The results indicate strong ocean mixing processes with a mean ɛ value of 5.7×10-5 W/kg and distinct tidal variations in the dissipation rate. Conversely, the variation of the water turbidity leads to changes in the water dynamical structure near the bottom. Comparing the dissipation rate with the turbidity near the bottom boundary layer, we find that the high turbidity mimics strong ocean mixing.

  12. Optimization of synthesis and peptization steps to obtain iron oxide nanoparticles with high energy dissipation rates

    NASA Astrophysics Data System (ADS)

    Mérida, Fernando; Chiu-Lam, Andreina; Bohórquez, Ana C.; Maldonado-Camargo, Lorena; Pérez, María-Eglée; Pericchi, Luis; Torres-Lugo, Madeline; Rinaldi, Carlos

    2015-11-01

    Magnetic Fluid Hyperthermia (MFH) uses heat generated by magnetic nanoparticles exposed to alternating magnetic fields to cause a temperature increase in tumors to the hyperthermia range (43-47 °C), inducing apoptotic cancer cell death. As with all cancer nanomedicines, one of the most significant challenges with MFH is achieving high nanoparticle accumulation at the tumor site. This motivates development of synthesis strategies that maximize the rate of energy dissipation of iron oxide magnetic nanoparticles, preferable due to their intrinsic biocompatibility. This has led to development of synthesis strategies that, although attractive from the point of view of chemical elegance, may not be suitable for scale-up to quantities necessary for clinical use. On the other hand, to date the aqueous co-precipitation synthesis, which readily yields gram quantities of nanoparticles, has only been reported to yield sufficiently high specific absorption rates after laborious size selective fractionation. This work focuses on improvements to the aqueous co-precipitation of iron oxide nanoparticles to increase the specific absorption rate (SAR), by optimizing synthesis conditions and the subsequent peptization step. Heating efficiencies up to 1048 W/gFe (36.5 kA/m, 341 kHz; ILP=2.3 nH m2 kg-1) were obtained, which represent one of the highest values reported for iron oxide particles synthesized by co-precipitation without size-selective fractionation. Furthermore, particles reached SAR values of up to 719 W/gFe (36.5 kA/m, 341 kHz; ILP=1.6 nH m2 kg-1) when in a solid matrix, demonstrating they were capable of significant rates of energy dissipation even when restricted from physical rotation. Reduction in energy dissipation rate due to immobilization has been identified as an obstacle to clinical translation of MFH. Hence, particles obtained with the conditions reported here have great potential for application in nanoscale thermal cancer therapy.

  13. Energy dissipation rate of a sample-induced thermal fluctuating field in the tip of a probe microscope

    NASA Astrophysics Data System (ADS)

    Dorofeyev, I. A.

    1998-03-01

    Fluctuation electrodynamics was used as a basis to obtain an expression for the dissipation power of a thermal electromagnetic field of a heated plane sample in the tip of a probe microscope, as a function of the value of a gap between them. We have shown that the energy dissipation rate is inversely proportional to the tip-sample distance cubed.

  14. Estimates of turbulent kinetic energy dissipation rate for a stratified flow in a wind tunnel

    NASA Astrophysics Data System (ADS)

    Puhales, Franciano Scremin; Demarco, Giuliano; Martins, Luis Gustavo Nogueira; Acevedo, Otávio Costa; Degrazia, Gervásio Annes; Welter, Guilherme Sausen; Costa, Felipe Denardin; Fisch, Gilberto Fernando; Avelar, Ana Cristina

    2015-08-01

    In this work a method to estimate turbulent kinetic energy dissipation rate (TKEDR) was presented. The technique uses the second-order structure function and Kolmogorov's law for inertial subrange. This methodology was applied on both neutral and stable stratification wind tunnel data, where the frozen turbulence hypothesis was assumed. The experiments were made with Reynolds Number ranging from 103 up to 104. The results show difference between the neutral and stable cases, but this gap decreases with the mean wind speed. Furthermore, TKEDR evaluated was used to describe the inertial subrange in the longitudinal velocity spectrum with a good agreement with the experimental data.

  15. An Estimation of Turbulent Kinetic Energy and Energy Dissipation Rate Based on Atmospheric Boundary Layer Similarity Theory

    NASA Technical Reports Server (NTRS)

    Han, Jongil; Arya, S. Pal; Shaohua, Shen; Lin, Yuh-Lang; Proctor, Fred H. (Technical Monitor)

    2000-01-01

    Algorithms are developed to extract atmospheric boundary layer profiles for turbulence kinetic energy (TKE) and energy dissipation rate (EDR), with data from a meteorological tower as input. The profiles are based on similarity theory and scalings for the atmospheric boundary layer. The calculated profiles of EDR and TKE are required to match the observed values at 5 and 40 m. The algorithms are coded for operational use and yield plausible profiles over the diurnal variation of the atmospheric boundary layer.

  16. Do inertial wave interactions control the rate of energy dissipation of rotating turbulence?

    NASA Astrophysics Data System (ADS)

    Cortet, Pierre-Philippe; Campagne, Antoine; Machicoane, Nathanael; Gallet, Basile; Moisy, Frederic

    2015-11-01

    The scaling law of the energy dissipation rate, ɛ ~U3 / L (with U and L the characteristic velocity and lengthscale), is one of the most robust features of fully developed turbulence. How this scaling is affected by a background rotation is still a controversial issue with importance for geo and astrophysical flows. At asymptotically small Rossby numbers Ro = U / ΩL , i.e. in the weakly nonlinear limit, wave-turbulence arguments suggest that ɛ should be reduced by a factor Ro . Such scaling has however never been evidenced directly, neither experimentally nor numerically. We report here direct measurements of the injected power, and therefore of ɛ, in an experiment where a propeller is rotating at a constant rate in a large volume of fluid rotating at Ω. In co-rotation, we find a transition between the wave-turbulence scaling at small Ro and the classical Kolmogorov law at large Ro . The transition between these two regimes is characterized from experiments varying the propeller and tank dimensions. In counter-rotation, the scenario is much richer with the observation of an additional peak of dissipation, similar to the one found in Taylor-Couette experiments.

  17. Kinetic and thermal energy dissipation rates in two-dimensional Rayleigh-Taylor turbulence

    NASA Astrophysics Data System (ADS)

    Zhou, Quan; Jiang, Lin-Feng

    2016-04-01

    The statistical properties of the kinetic ɛu and thermal ɛθ energy dissipation rates in two-dimensional Rayleigh-Taylor (RT) turbulence are studied by means of direct numerical simulations at small Atwood number and unit Prandtl number. Although ɛθ is important but ɛu can be neglected in the energy transport processes, the probability density functions of ɛu and ɛθ both show self-similarity properties during the RT evolution. The distributions are well fitted by a stretched exponential function and found to depart distinctly from the log-normal distribution for small amplitudes. Within the turbulent range, the intense dissipation events occur near the interfaces of hot and cold fluids, leading to a strong positive correlation between ɛu and ɛθ. Our results further reveal that although there is no constant fractal dimension for the fluid interfaces within the inertial range, the local fractal dimensions obtained at different times share similar scale-dependence.

  18. Measurement of turbulent kinetic energy dissipation rates in the mesosphere by a 3 MHz Doppler radar

    NASA Astrophysics Data System (ADS)

    Singer, W.; Latteck, R.; Hocking, W. K.

    A new narrow beam Doppler radar at 3.17 MHz has been installed close to the Andöya Rocket Range in Andenes, Norway in summer 2002 to improve the ground based capabilities for measurements of turbulence in the mesosphere. The main feature of the radar is the transmitting/receiving antenna (Mills Cross antenna of 29 crossed half-wave dipoles) which provides in combination with the modular transceiver system high flexibility in beam forming and pointing. In general, vertical and oblique beams with a minimum beam width of about 7 (FWHP, one way) are used; the observations are done with a height resolution of 1 km. Off-zenith beams at 7.3 are directed towards NW, NE, SE, and SW. In addition, beams with different widths at the same pointing angle can be formed for the application of dual-beam width techniques. Turbulence intensities are estimated from the width of the observed signal spectra. Exact and approximate methods of removing non-turbulent processes such as wind shear and beam width broadening are applied. The exact, but computer time consuming correction method requires the knowledge of the antenna radiation pattern and of the measured wind field. The standard approximation is based on background winds and beam width, the dual-beam width approximation needs the beam width only. Examples of the various methods are discussed. Results of measurements of turbulent kinetic energy dissipation rates obtained with the exact correction method for beam and shear broadening are presented for the period September 2003 to January 2004. In September, mean turbulent kinetic energy dissipation rates amount about 5 mW/kg at 60km and about 20 mW/kg at 80km in agreement with mean turbulence intensities obtained from rocket soundings at Andenes.

  19. Global Existence and Energy Decay Rates for a Kirchhoff-Type Wave Equation with Nonlinear Dissipation

    PubMed Central

    Kim, Dojin; Hong, Keum-Shik; Jung, Il Hyo

    2014-01-01

    The first objective of this paper is to prove the existence and uniqueness of global solutions for a Kirchhoff-type wave equation with nonlinear dissipation of the form Ku′′ + M(|A1/2u|2)Au + g(u′) = 0 under suitable assumptions on K, A, M(·), and g(·). Next, we derive decay estimates of the energy under some growth conditions on the nonlinear dissipation g. Lastly, numerical simulations in order to verify the analytical results are given. PMID:24977217

  20. Evaluation of the Turbulent Kinetic Energy Dissipation Rate Inside Canopies by Zero- and Level-Crossing Density Methods

    NASA Astrophysics Data System (ADS)

    Poggi, D.; Katul, G. G.

    2010-08-01

    Inferring the vertical variation of the mean turbulent kinetic energy dissipation rate ( ɛ) inside dense canopies remains a basic research problem to be confronted. Using detailed laser Doppler anemometry (LDA) measurements collected within a densely arrayed rod canopy, traditional and newly proposed methods to infer ɛ profiles are compared. The traditional methods for estimating ɛ at a given layer include isotropic relationships applied to the viscous dissipation scales that are resolved by LDA measurements, higher order structure function methods, and residuals of the turbulent kinetic energy budget in which production and transport terms are all independently inferred. The newly proposed method extends earlier approaches based on zero-crossing statistics, which were shown to be promising in a number of laboratory flows. The extension to account for an arbitrary threshold (hereafter referred to as the level-crossing method) instead of zero-crossing minimizes the effects of instrument noise on the inferred ɛ. While none of the ɛ methods employed here can be titled as ‘measured’, these methods differ in their underlying assumptions and simplifications. Above the canopy, where a balance between production and dissipation rate of turbulent kinetic energy is expected, the agreement among all the methods is reasonably good. In the lower-to-middle layers of the canopy, all the methods agree except for those based on a structure-function inference of ɛ. This departure can be attributed to the lack of a well-defined inertial subrange in these layers. In the upper canopy layers, the disagreements between the methods are largest. Even the higher order structure-function methods disagree with each other when ɛ is inferred from third- and fifth-order moments. However, for all layers within the canopy, the proposed zero- and threshold-crossing methods agree well with estimates of ɛ derived from the isotropic relationship applied to the viscous dissipation range

  1. Dissipation of Tidal Energy

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The moon's gravity imparts tremendous energy to the Earth, raising tides throughout the global oceans. What happens to all this energy? This question has been pondered by scientists for over 200 years, and has consequences ranging from the history of the moon to the mixing of the oceans. Richard Ray at NASA's Goddard Space Flight Center, Greenbelt, Md. and Gary Egbert of the College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Ore. studied six years of altimeter data from the TOPEX/Poseidon satellite to address this question. According to their report in the June 15 issue of Nature, about 1 terawatt, or 25 to 30 percent of the total tidal energy dissipation, occurs in the deep ocean. The remainder occurs in shallow seas, such as on the Patagonian Shelf. 'By measuring sea level with the TOPEX/Poseidon satellite altimeter, our knowledge of the tides in the global ocean has been remarkably improved,' said Richard Ray, a geophysicist at Goddard. The accuracies are now so high that this data can be used to map empirically the tidal energy dissipation. (Red areas, above) The deep-water tidal dissipation occurs generally near rugged bottom topography (seamounts and mid-ocean ridges). 'The observed pattern of deep-ocean dissipation is consistent with topographic scattering of tidal energy into internal motions within the water column, resulting in localized turbulence and mixing', said Gary Egbert an associate professor at OSU. One important implication of this finding concerns the possible energy sources needed to maintain the ocean's large-scale 'conveyor-belt' circulation and to mix upper ocean heat into the abyssal depths. It is thought that 2 terawatts are required for this process. The winds supply about 1 terawatt, and there has been speculation that the tides, by pumping energy into vertical water motions, supply the remainder. However, all current general circulation models of the oceans ignore the tides. 'It is possible that properly

  2. 'Reduced' magnetohydrodynamics and minimum dissipation rates

    NASA Technical Reports Server (NTRS)

    Montgomery, David

    1992-01-01

    It is demonstrated that all solutions of the equations of 'reduced' magnetohydrodynamics approach a uniform-current, zero-flow state for long times, given a constant wall electric field, uniform scalar viscosity and resistivity, and uniform mass density. This state is the state of minimum energy dissipation rate for these boundary conditions. No steady-state turbulence is possible. The result contrasts sharply with results for full three-dimensional magnetohydrodynamics before the reduction occurs.

  3. Dissipation Rate of Turbulent Kinetic Energy in Diel Vertical Migrations: Comparison of ANSYS Fluent Model to Measurements

    NASA Astrophysics Data System (ADS)

    Dean, Cayla; Soloviev, Alexander; Hirons, Amy; Frank, Tamara; Wood, Jon

    2015-04-01

    Recent studies suggest that diel vertical migrations of zooplankton may have an impact on ocean mixing, though details are not completely clear. A strong sound scattering layer of zooplankton undergoing diel vertical migrations was observed in Saanich Inlet, British Colombia, Canada by Kunze et al. (2006). In this study, a shipboard 200-kHz echosounder was used to track vertical motion of the sound scattering layer, and microstructure profiles were collected to observe turbulence. An increase of dissipation rate of turbulent kinetic energy by four to five orders of magnitude was measured during diel vertical migrations of zooplankton in one case (but not observed during other cases). A strong sound scattering layer undergoing diel vertical migration was also observed in the Straits of Florida via a bottom mounted acoustic Doppler current profiler at 244 m isobath. A 3-D non-hydrostatic computational fluid dynamics model with Lagrangian particle injections (a proxy for migrating zooplankton) via a discrete phase model was used to simulate the effect of diel vertical migrations on the turbulence for both Saanich Inlet and the Straits of Florida. The model was initialized with idealized (but based on observation) density and velocity profiles. Particles, with buoyancy adjusted to serve as a proxy for vertically swimming zooplankton, were injected to simulate diel vertical migration cycles. Results of models run with extreme concentrations of particles showed an increase in dissipation rate of turbulent kinetic energy of approximately five orders of magnitude over background turbulence during migration of particles in both Saanich Inlet and the Straits of Florida cases (though direct relation of the turbulence produced by buoyant particles and swimming organisms isn't straightforward). This increase was quantitatively consistent, with turbulence measurements by Kunze et al. (2006). When 10 times fewer particles were injected into the model, the effect on dissipation

  4. Lightning - Estimates of the rates of energy dissipation and nitrogen fixation

    NASA Technical Reports Server (NTRS)

    Borucki, W. J.; Chameides, W. L.

    1984-01-01

    The nitrogen needed by plants can normally not be directly obtained from the nitrogen present in molecular form in the atmosphere. The reason for this situation is related to the great energy required to break the N-N bond. Only a few organisms, such as algae and certain bacteria, can 'fix' nitrogen. An abiological process for breaking the N-N bond is provided by lightning. The present investigation is concerned with this possibility. It is found that lightning produces approximately 2.6 x 10 to the 9th kg N per year. There are, however, uncertainties, which are mainly related to the energy of a lightning flash.

  5. A Reynolds-averaged turbulence modeling approach using three transport equations for the turbulent viscosity, kinetic energy, and dissipation rate

    NASA Astrophysics Data System (ADS)

    Yoshizawa, Akira; Abe, Hiroyuki; Matsuo, Yuichi; Fujiwara, Hitoshi; Mizobuchi, Yasuhiro

    2012-07-01

    A Reynolds-averaged approach to turbulent shear flows is sought with resort to a three-equation method. Its novelty is the introduction of a turbulent-viscosity transport equation through the transport equation for the Reynolds stress in addition to those for the turbulent kinetic energy and the dissipation rate. The latter two equations are used for evaluating the dimensional coefficients in the former. The aim of this model is to enhance the capability to cope with nonstationary and advection effects in various turbulent flows. The adaptability to them is confirmed through the application to homogeneous-shear and supersonic free-shear flows. In particular, the reasonable prediction is obtained in the latter where the growth rate of the shear layer is suppressed with the increase in the convective Mach number. The present model is also applied to a three-dimensional flow past a wing tip as an instance of complex aeronautical flows, and the excessive diffusion of the trailing vortices is shown to be suppressed. The turbulent-viscosity representation for the Reynolds stress is systematically supplemented with nonlinear effects of mean-velocity gradient tensors, and its adequacy is verified in a channel flow.

  6. Energy dissipation in sheared granular flows

    SciTech Connect

    Karion, A.; Hunt, M.L.

    1999-11-01

    Granular material flows describe flows of solid particles in which the interstitial fluid plays a negligible role in the flow mechanics. Examples include the transport of coal, food products, detergents, pharmaceutical tablets, and toner particles in high-speed printers. Using a two-dimensional discrete element computer simulation of a bounded, gravity-free Couette flow of particles, the heat dissipation rate per unit area is calculated as a function of position in the flow as well as overall solid fraction. The computation results compare favorably with the kinetic theory analysis for rough disks. The heat dissipation rate is also measured for binary mixtures of particles for different small to large solid fraction ratios, and for diameter ratios of ten, five, and two. The dissipation rates increase significantly with overall solid fraction as well as local strain rates and granular temperatures. The thermal energy equation is solved for a Couette flow with one adiabatic wall and one at constant temperature. Solutions use the simulation measurements of the heat dissipation rate, solid fraction, and granular temperature to show that the thermodynamic temperature increases with solid fraction and decreases with particle conductivity. In mixtures, both the dissipation rate and the thermodynamic temperature increase with size ratio and with decreasing ratio of small to large particles.

  7. Spacecraft detumbling through energy dissipation

    NASA Technical Reports Server (NTRS)

    Fitz-Coy, Norman; Chatterjee, Anindya

    1993-01-01

    The attitude motion of a tumbling, rigid, axisymmetric spacecraft is considered. A methodology for detumbling the spacecraft through energy dissipation is presented. The differential equations governing this motion are stiff, and therefore an approximate solution, based on the variation of constants method, is developed and utilized in the analysis of the detumbling strategy. Stability of the detumbling process is also addressed.

  8. Energy dissipating structures in turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Farge, Marie; Nguyen van Yen, Romain; Schneider, Kai

    2011-11-01

    We present numerical experiments of a dipole crashing into a wall, a generic event in two-dimensional incompressible flows with solid boundaries. The Reynolds number Re is varied from 985 to 7880, and no-slip boundary conditions are approximated by Navier boundary conditions with a slip length proportional to Re-1 . Energy dissipation is shown to first set up within a vorticity sheet of thickness proportional to Re-1 in the neighborhood of the wall, and to continue as this sheet rolls up into a spiral and detaches from the wall. The energy dissipation rate integrated over these regions appears to converge towards Rey -independent values, indicating the existence of energy dissipating structures that persist in the vanishing viscosity limit. Details can be found in Nguyen van yen, Farge and Schneider, PRL, 106, 184502 (2011).

  9. Tidal Energy Dissipation from Topex/Poseidon

    NASA Technical Reports Server (NTRS)

    Ray, Richard D.; Egbert, G. D.; Smith, David E. (Technical Monitor)

    2000-01-01

    In a recent paper ({\\it Nature, 405,} 775, 2000) we concluded that 25 to 30\\% of the ocean's tidal energy dissipation, or about 1 terawatt, occurs in the deep ocean, with the remaining 2.6 TW in shallow seas. The physical mechanism for deep-ocean dissipation is apparently scattering of the surface tide into internal modes; Munk and Wunsch have suggested that this mechanism may provide half the power needed for mixing the deep-ocean. This paper builds further evidence for $1\\pm 0.2$ TW of deep-ocean dissipation. The evidence is extracted from tidal elevations deduced from seven years of Topex/Poseidon satellite altimeter data. The dissipation rate Is formed as a balance between the rate of working by tidal forces and the energy flux divergence. While dynamical assumptions are required to compute fluxes, area integrals of the energy balance are, owing to the tight satellite constraints, remarkably insensitive to these assumptions. A large suite of tidal solutions based on a wide range of dynamical assumptions, on perturbations to bathymetric models, and on simulated elevation data are used to assess this sensitivity. These and Monte Carlo error fields from a generalized inverse model are used to establish error uncertainties.

  10. Energy Dissipation Processes in Solar Wind Turbulence

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Wei, F. S.; Feng, X. S.; Xu, X. J.; Zhang, J.; Sun, T. R.; Zuo, P. B.

    2015-12-01

    Turbulence is a chaotic flow regime filled by irregular flows. The dissipation of turbulence is a fundamental problem in the realm of physics. Theoretically, dissipation ultimately cannot be achieved without collisions, and so how turbulent kinetic energy is dissipated in the nearly collisionless solar wind is a challenging problem. Wave particle interactions and magnetic reconnection (MR) are two possible dissipation mechanisms, but which mechanism dominates is still a controversial topic. Here we analyze the dissipation region scaling around a solar wind MR region. We find that the MR region shows unique multifractal scaling in the dissipation range, while the ambient solar wind turbulence reveals a monofractal dissipation process for most of the time. These results provide the first observational evidences for intermittent multifractal dissipation region scaling around a MR site, and they also have significant implications for the fundamental energy dissipation process.

  11. Energy Dissipation in Magnetohydrodynamic Turbulence: Coherent Structures or Nanoflares?

    NASA Astrophysics Data System (ADS)

    Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos; Tobias, Steven

    2014-10-01

    Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be highly intermittent, occurring mainly in current sheets. However, the question remains whether the overall energy dissipation is dominated by small (dissipation-scale) structures or by large (inertial-range) structures. To systematically investigate this question, we develop and apply a procedure to identify and characterize dissipative structures in numerical simulations of reduced MHD. We find that the probability distribution of energy dissipation rates exhibits a power law tail with index very close to the critical value of -2.0, indicating that structures of all intensities contribute equally to the overall energy dissipation. We then measure the characteristic spatial scales of structures using two methods: one based on the linear scales across the structure and the other based on the Minkowski functionals, which rigorously characterize the morphology of any shape. We find that energy dissipation is dominated by coherent structures with lengths and widths uniformly distributed across the inertial range, while thicknesses lie deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and more numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. The current sheets therefore exhibit features of both coherent structures and nanoflares.

  12. Wetlands as energy-dissipating systems.

    PubMed

    Pokorný, Jan; Květ, Jan; Rejšková, Alžběta; Brom, Jakub

    2010-12-01

    Since wetlands are ecosystems that have an ample supply of water, they play an important role in the energy budgets of their respective landscapes due to their capacity to shift energy fluxes in favor of latent heat. Rates of evapotranspiration in wetlands are commonly as high as 6-15 mm day⁻¹, testifying to the large amount of energy that is dissipated through this process. Emergent or semi-emergent wetland macrophytes substantially influence the solar energy distribution due to their high capacity for transpiration. Wetland ecosystems in eutrophic habitats show a high primary production of biomass because of the highly efficient use of solar energy in photosynthesis. In wetlands associated with the slow decomposition of dead organic matter, such as oligotrophic marshes or fens and bogs, the accumulation of biomass is also high, in spite of the rather low primary production of biomass. Most of the energy exchange in water-saturated wetlands is, however, linked with heat balance, whereby the largest proportion of the incoming energy is dissipated during the process of evapotranspiration. An example is shown of energy fluxes during the course of a day in the wetland ecosystem of Mokré Louky (Wet Meadows) near Třeboň. The negative consequences of the loss of wetlands for the local and regional climate are discussed. PMID:21086105

  13. An improvement in the calculation of the efficiency of oxidative phosphorylation and rate of energy dissipation in mitochondria

    NASA Astrophysics Data System (ADS)

    Ghafuri, Mohazabeh; Golfar, Bahareh; Nosrati, Mohsen; Hoseinkhani, Saman

    2014-12-01

    The process of ATP production is one of the most vital processes in living cells which happens with a high efficiency. Thermodynamic evaluation of this process and the factors involved in oxidative phosphorylation can provide a valuable guide for increasing the energy production efficiency in research and industry. Although energy transduction has been studied qualitatively in several researches, there are only few brief reviews based on mathematical models on this subject. In our previous work, we suggested a mathematical model for ATP production based on non-equilibrium thermodynamic principles. In the present study, based on the new discoveries on the respiratory chain of animal mitochondria, Golfar's model has been used to generate improved results for the efficiency of oxidative phosphorylation and the rate of energy loss. The results calculated from the modified coefficients for the proton pumps of the respiratory chain enzymes are closer to the experimental results and validate the model.

  14. Energy dissipation in magnetohydrodynamic turbulence: coherent structures or 'nanoflares'?

    SciTech Connect

    Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos; Tobias, Steven M.

    2014-11-10

    We investigate the intermittency of energy dissipation in magnetohydrodynamic (MHD) turbulence by identifying dissipative structures and measuring their characteristic scales. We find that the probability distribution of energy dissipation rates exhibits a power-law tail with an index very close to the critical value of –2.0, which indicates that structures of all intensities contribute equally to energy dissipation. We find that energy dissipation is uniformly spread among coherent structures with lengths and widths in the inertial range. At the same time, these structures have thicknesses deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and more numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. This implies that in the limit of high Reynolds number, energy dissipation occurs in thin, tightly packed current sheets which nevertheless span a continuum of scales up to the system size, exhibiting features of both coherent structures and nanoflares previously conjectured as a coronal heating mechanism.

  15. Energy Dissipation in Magnetohydrodynamic Turbulence: Coherent Structures or "Nanoflares"?

    NASA Astrophysics Data System (ADS)

    Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos; Tobias, Steven M.

    2014-11-01

    We investigate the intermittency of energy dissipation in magnetohydrodynamic (MHD) turbulence by identifying dissipative structures and measuring their characteristic scales. We find that the probability distribution of energy dissipation rates exhibits a power-law tail with an index very close to the critical value of -2.0, which indicates that structures of all intensities contribute equally to energy dissipation. We find that energy dissipation is uniformly spread among coherent structures with lengths and widths in the inertial range. At the same time, these structures have thicknesses deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and more numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. This implies that in the limit of high Reynolds number, energy dissipation occurs in thin, tightly packed current sheets which nevertheless span a continuum of scales up to the system size, exhibiting features of both coherent structures and nanoflares previously conjectured as a coronal heating mechanism.

  16. Nonlinear Internal Waves - Evolution and Energy Dissipation

    NASA Astrophysics Data System (ADS)

    Orr, M.; Mignerey, P.

    2003-04-01

    Nonlinear internal waves have been observed propagating up the slope of the South China Sea during the recent ONR Asian Seas International Acoustics Experiment. Energy dissipation rates have been extracted. The location of the initiation of the depression to elevation conversion has been identified. Scaling parameters have been extracted and used to initialize a two-layer evolution equation model simulation. Mode1, 2 linear and nonlinear internal waves and instabilities have been observed near the shelf break of the United States of America New Jersey Shelf. Acoustic flow visualization records will be presented. Work supported by the Office of Naval Research (ONR) Ocean Acoustics Program and ONR's NRL base funding.

  17. A Note on Kinetic Energy, Dissipation and Enstrophy

    NASA Technical Reports Server (NTRS)

    Wu, Jie-Zhi; Zhou, Ye; Fan, Meng

    1998-01-01

    The dissipation rate of a Newtonian fluid with constant shear viscosity can be shown to include three constituents: dilatation, vorticity, and surface strain. The last one is found to make no contributions to the change of kinetic energy. These dissipation constituents arc used to identify typical compact turbulent flow structures at high Reynolds numbers. The incompressible version of the simplified kinetic-energy equation is then cast to a novel form, which is free from the work rate done by surface stresses but in which the full dissipation re-enters.

  18. Magnetic energy dissipation in force-free jets

    NASA Technical Reports Server (NTRS)

    Choudhuri, Arnab Rai; Konigl, Arieh

    1986-01-01

    It is shown that a magnetic pressure-dominated, supersonic jet which expands or contracts in response to variations in the confining external pressure can dissipate magnetic energy through field-line reconnection as it relaxes to a minimum-energy configuration. In order for a continuous dissipation to occur, the effective reconnection time must be a fraction of the expansion time. The dissipation rate for the axisymmetric minimum-energy field configuration is analytically derived. The results indicate that the field relaxation process could be a viable mechanism for powering the synchrotron emission in extragalactic jets if the reconnection time is substantially shorter than the nominal resistive tearing time in the jet.

  19. Material Systems for Blast-Energy Dissipation

    SciTech Connect

    James Schondel; Henry S. Chu

    2010-10-01

    Lightweight panels have been designed to protect buildings and vehicles from blast pressures by activating energy dissipation mechanisms under the influence of blast loading. Panels were fabricated which featured a variety of granular materials and hydraulic dissipative deformation mechanisms and the test articles were subjected to full-scale blast loading. The force time-histories transmitted by each technology were measured by a novel method that utilized inexpensive custom-designed force sensors. The array of tests revealed that granular materials can effectively dissipate blast energy if they are employed in a way that they easily crush and rearrange. Similarly, hydraulic dissipation can effectively dissipate energy if the panel features a high fraction of porosity and the panel encasement features low compressive stiffness.

  20. Strain Rates and Scalar Dissipation Rates in Gaseous Transverse Jets

    NASA Astrophysics Data System (ADS)

    Shoji, Takeshi; Gevorkyan, Levon; Besnard, Andrea; Karagozian, Ann

    2015-11-01

    This experimental study quantifies local strain rates and scalar dissipation rates for the non-reactive gaseous jet in crossflow (JICF) using simultaneous acetone planar laser-induced fluorescence (PLIF) imaging and stereo particle image velocimetry (PIV). Flush nozzle and flush pipe injectors are used to create jets consisting of mixtures of He and N2, with varying exit velocity profiles, jet-to-crossflow momentum flux ratios J, and density ratios S. Strain rates in the vicinity of windward and lee-side jet shear layers are quantified based both on scalar dissipation rates extracted from PLIF measurements within locally 1D layer-like structures and on vector fields extracted from PIV measurements. Strain rates from the simultaneous measurements are in very good qualitative agreement with one another on the jets' windward and lee sides, and are also consistent with flame ignition locations in comparable reactive JICF experiments. Quantitative differences in strain fields are most pronounced at lower J values, corresponding to absolutely unstable shear layers and high local strain fields, although these differences are affected by the PLIF spatial resolution for a range of flow conditions. Extraction of dominant mode structures via POD will also be presented. Supported by NSF grant CBET-1437014 & AFOSR grant FA9550-15-1-0261 (A004376801).

  1. Scalar dissipation rate statistics in turbulent swirling jets

    NASA Astrophysics Data System (ADS)

    Stetsyuk, V.; Soulopoulos, N.; Hardalupas, Y.; Taylor, A. M. K. P.

    2016-07-01

    The scalar dissipation rate statistics were measured in an isothermal flow formed by discharging a central jet in an annular stream of swirling air flow. This is a typical geometry used in swirl-stabilised burners, where the central jet is the fuel. The flow Reynolds number was 29 000, based on the area-averaged velocity of 8.46 m/s at the exit and the diameter of 50.8 mm. The scalar dissipation rate and its statistics were computed from two-dimensional imaging of the mixture fraction fields obtained with planar laser induced fluorescence of acetone. Three swirl numbers, S, of 0.3, 0.58, and 1.07 of the annular swirling stream were considered. The influence of the swirl number on scalar mixing, unconditional, and conditional scalar dissipation rate statistics were quantified. A procedure, based on a Wiener filter approach, was used to de-noise the raw mixture fraction images. The filtering errors on the scalar dissipation rate measurements were up to 15%, depending on downstream positions from the burner exit. The maximum of instantaneous scalar dissipation rate was found to be up to 35 s-1, while the mean dissipation rate was 10 times smaller. The probability density functions of the logarithm of the scalar dissipation rate fluctuations were found to be slightly negatively skewed at low swirl numbers and almost symmetrical when the swirl number increased. The assumption of statistical independence between the scalar and its dissipation rate was valid for higher swirl numbers at locations with low scalar fluctuations and less valid for low swirl numbers. The deviations from the assumption of statistical independence were quantified. The conditional mean of the scalar dissipation rate, the standard deviation of the scalar dissipation rate fluctuations, the weighted probability of occurrence of the mean conditional scalar dissipation rate, and the conditional probability are reported.

  2. A Mechanism of Energy Dissipation in Cyanobacteria

    PubMed Central

    Berera, Rudi; van Stokkum, Ivo H.M.; d'Haene, Sandrine; Kennis, John T.M.; van Grondelle, Rienk; Dekker, Jan P.

    2009-01-01

    When grown under a variety of stress conditions, cyanobacteria express the isiA gene, which encodes the IsiA pigment-protein complex. Overexpression of the isiA gene under iron-depletion stress conditions leads to the formation of large IsiA aggregates, which display remarkably short fluorescence lifetimes and thus a strong capacity to dissipate energy. In this work we investigate the underlying molecular mechanism responsible for chlorophyll fluorescence quenching. Femtosecond transient absorption spectroscopy allowed us to follow the process of energy dissipation in real time. The light energy harvested by chlorophyll pigments migrated within the system and eventually reaches a quenching site where the energy is transferred to a carotenoid-excited state, which dissipates it by decaying to the ground state. We compare these findings with those obtained for the main light-harvesting complex in green plants (light-harvesting complex II) and artificial light-harvesting antennas, and conclude that all of these systems show the same mechanism of energy dissipation, i.e., one or more carotenoids act as energy dissipators by accepting energy via low-lying singlet-excited S1 states and dissipating it as heat. PMID:19289052

  3. Energy dissipation in multifrequency atomic force microscopy.

    PubMed

    Pukhova, Valentina; Banfi, Francesco; Ferrini, Gabriele

    2014-01-01

    The instantaneous displacement, velocity and acceleration of a cantilever tip impacting onto a graphite surface are reconstructed. The total dissipated energy and the dissipated energy per cycle of each excited flexural mode during the tip interaction is retrieved. The tip dynamics evolution is studied by wavelet analysis techniques that have general relevance for multi-mode atomic force microscopy, in a regime where few cantilever oscillation cycles characterize the tip-sample interaction. PMID:24778976

  4. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    NASA Astrophysics Data System (ADS)

    Soto-Aquino, D.; Rinaldi, C.

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given.

  5. Dissipation of wave energy and turbulence in a shallow coral reef lagoon

    NASA Astrophysics Data System (ADS)

    Huang, Zhi-Cheng; Lenain, Luc; Melville, W. Kendall; Middleton, Jason H.; Reineman, Benjamin; Statom, Nicholas; McCabe, Ryan M.

    2012-03-01

    Simultaneous in situ measurements of waves, currents and turbulence are presented to describe dissipation rates of wave energy and turbulent kinetic energy in the windward coral reef-lagoon system at Lady Elliot Island (LEI), Australia. The dissipation of wave energy in the lagoon is tidally modulated and strongly correlates with frictional dissipation due to the presence of the extremely rough bottom boundary. The observed turbulent kinetic energy (TKE) dissipation rate, ɛ, in this wave-dominated lagoon is much larger than recently reported values for unidirectional flows over natural fringing coral reefs. The correlation between the wave dissipation and ɛ is examined. The average rate of dissipation induced by the rough turbulent flow was estimated directly from the observed ɛ coupled with both a depth-integrated approach and with a bottom boundary layer scaling. Rates of TKE dissipation estimated using the two approaches approximate well, within a factor of 1.5 to 2.4, to the surface-wave energy dissipation rate. The wave dissipation and friction factor in the lagoon can be described by a spectral wave-frictional model with a bottom roughness length scale that is approximately constant across the lagoon. We also present estimates of dissipation induced by the canopy drag force of the coral heads. The dissipation in this case is enhanced and becomes more significant for the total energy dissipation when the water depth in the lagoon is comparable to the height of the coral heads.

  6. Scalar dissipation rates in non-conservative transport systems

    PubMed Central

    Engdahl, Nicholas B.; Ginn, Timothy R.; Fogg, Graham E.

    2014-01-01

    This work considers how the inferred mixing state of diffusive and advective-diffusive systems will vary over time when the solute masses are not constant over time. We develop a number of tools that allow the scalar dissipation rate to be used as a mixing measure in these systems without calculating local concentration gradients. The behavior of dissipation rates are investigated for single and multi-component kinetic reactions and a commonly studied equilibrium reaction. The scalar dissipation rate of a tracer experiencing first order decay can be determined exactly from the decay constant and the dissipation rate of a passive tracer, and the mixing rate of a conservative component is not the superposition of the solute specific mixing rates. We then show how the behavior of the scalar dissipation rate can be determined from a limited subset of an infinite domain. Corrections are derived for constant and time dependent limits of integration the latter is used to approximate dissipation rates in advective-diffusive systems. Several of the corrections exhibit similarities to the previous work on mixing, including non-Fickian mixing. This illustrates the importance of accounting for the effects that reaction systems or limited monitoring areas may have on the inferred mixing state. PMID:23584457

  7. Landing Energy Dissipation for Manned Reentry Vehicles

    NASA Technical Reports Server (NTRS)

    1960-01-01

    Landing Energy Dissipation for Manned Reentry Vehicles. The film shows experimental investigations to determine the landing-energy-dissipation characteristics for several types of landing gear for manned reentry vehicles. The landing vehicles are considered in two categories: those having essentially vertical-descent paths, the parachute-supported vehicles, and those having essentially horizontal paths, the lifting vehicles. The energy-dissipation devices include crushable materials such as foamed plastics and honeycomb for internal application in couch-support systems, yielding metal elements as part of the structure of capsules or as alternates for oleos in landing-gear struts, inflatable bags, braking rockets, and shaped surfaces for water impact. [Entire movie available on DVD from CASI as Doc ID 20070030945. Contact help@sti.nasa.gov

  8. Landing Energy Dissipation for Manned Reentry Vehicles

    NASA Technical Reports Server (NTRS)

    Fisher, Loyd. L.

    1960-01-01

    The film shows experimental investigations to determine the landing-energy-dissipation characteristics for several types of landing gear for manned reentry vehicles. The landing vehicles are considered in two categories: those having essentially vertical-descent paths, the parachute-supported vehicles, and those having essentially horizontal paths, the lifting vehicles. The energy-dissipation devices include crushable materials such as foamed plastics and honeycomb for internal application in couch-support systems, yielding metal elements as part of the structure of capsules or as alternates for oleos in landing-gear struts, inflatable bags, braking rockets, and shaped surfaces for water impact.

  9. Fuel cell generator energy dissipator

    SciTech Connect

    Veyo, S.E.; Dederer, J.T.; Gordon, J.T.; Shockling, L.A.

    2000-02-15

    An apparatus and method are disclosed for eliminating the chemical energy of fuel remaining in a fuel cell generator when the electrical power output of the fuel cell generator is terminated. During a generator shut down condition, electrically resistive elements are automatically connected across the fuel cell generator terminals in order to draw current, thereby depleting the fuel inventory in the generator. The invention provides a safety function in eliminating the fuel energy, and also provides protection to the fuel cell stack by eliminating overheating.

  10. Fuel cell generator energy dissipator

    DOEpatents

    Veyo, Stephen Emery; Dederer, Jeffrey Todd; Gordon, John Thomas; Shockling, Larry Anthony

    2000-01-01

    An apparatus and method are disclosed for eliminating the chemical energy of fuel remaining in a fuel cell generator when the electrical power output of the fuel cell generator is terminated. During a generator shut down condition, electrically resistive elements are automatically connected across the fuel cell generator terminals in order to draw current, thereby depleting the fuel

  11. Energy flow and energy dissipation in a free surface.

    NASA Astrophysics Data System (ADS)

    Goldburg, Walter; Cressman, John

    2005-11-01

    Turbulent flows on a free surface are strongly compressible [1] and do not conserve energy in the absence of viscosity as bulk fluids do. Despite violation of assumptions essential to Kolmogorov's theory of 1941 (K41) [2, 3], surface flows show strong agreement with Kolmogorov scaling, though intermittency is larger there. Steady state turbulence is generated in a tank of water, and the spatially averaged energy flux is measured from the four-fifth's law at each instant of time. Likewise, the energy dissipation rate as measured from velocity gradients is also a random variable in this experiment. The energy flux - dissipation rate cross-correlation is measured to be correlated in incompressible bulk flows, but strongly anti-correlated on the surface. We argue that the reason for this discrepancy between surface and bulk flows is due to compressible effects present on the surface. [1] J. R. Cressman, J. Davoudi, W. I. Goldburg, and J. Schumacher, New Journal of Physics, 6, 53, 2004. [2] U. Frisch. Turbulence: The legacy of A. N. Kolmogorov, Cambridge University Press, Cambridge, 1995. [3] A. N. Kolmogorov, Doklady Akad. Nauk SSSR, 32, 16, 1941.

  12. Critical behavior in earthquake energy dissipation

    NASA Astrophysics Data System (ADS)

    Wanliss, J.; Muñoz, V.; Pastén, D.; Toledo, B.; Valdivia, J. A.

    2015-04-01

    We explore bursty multiscale energy dissipation from earthquakes flanked by latitudes 29 and 35.5° S, and longitudes 69.501 and 73.944° W (in the Chilean central zone). Our work compares the predictions of a theory of nonequilibrium phase transitions with nonstandard statistical signatures of earthquake complex scaling behaviors. For temporal scales less than than 84 h, time development of earthquake radiated energy activity follows an algebraic arrangement consistent with estimates from the theory of nonequilibrium phase transitions. There are no characteristic scales for probability distributions of sizes and lifetimes of the activity bursts in the scaling region. The power-law exponents describing the probability distributions suggest that the main energy dissipation takes place due to largest bursts of activity, such as major earthquakes, as opposed to smaller activations which contribute less significantly though they have greater relative occurrence. The results obtained provide statistical evidence that earthquake energy dissipation mechanisms are essentially "scale-free," displaying statistical and dynamical self-similarity. Our results provide some evidence that earthquake radiated energy and directed percolation belong to a similar universality class.

  13. ENHANCED DISSIPATION RATE OF MAGNETIC FIELD IN STRIPED PULSAR WINDS BY THE EFFECT OF TURBULENCE

    SciTech Connect

    Takamoto, Makoto; Inoue, Tsuyoshi; Inutsuka, Shu-ichiro E-mail: inouety@phys.aoyama.ac.jp

    2012-08-10

    In this paper, we report on turbulent acceleration of the dissipation of the magnetic field in the post-shock region of a Poynting flux-dominated flow, such as the Crab pulsar wind nebula. We have performed two-dimensional resistive relativistic magnetohydrodynamics simulations of subsonic turbulence driven by the Richtmyer-Meshkov instability at the shock fronts of the Poynting flux-dominated flows in pulsar winds. We find that turbulence stretches current sheets which substantially enhances the dissipation of the magnetic field, and that most of the initial magnetic field energy is dissipated within a few eddy-turnover times. We also develop a simple analytical model for turbulent dissipation of the magnetic field that agrees well with our simulations. The analytical model indicates that the dissipation rate does not depend on resistivity even in the small resistivity limit. Our findings can possibly alleviate the {sigma}-problem in the Crab pulsar wind nebulae.

  14. Modeling the dissipation rate in rotating turbulent flows

    NASA Technical Reports Server (NTRS)

    Speziale, Charles G.; Raj, Rishi; Gatski, Thomas B.

    1990-01-01

    A variety of modifications to the modeled dissipation rate transport equation that have been proposed during the past two decades to account for rotational strains are examined. The models are subjected to two crucial test cases: the decay of isotropic turbulence in a rotating frame and homogeneous shear flow in a rotating frame. It is demonstrated that these modifications do not yield substantially improved predictions for these two test cases and in many instances give rise to unphysical behavior. An alternative proposal, based on the use of the tensor dissipation rate, is made for the development of improved models.

  15. Energy localization in weakly dissipative resonant chains.

    PubMed

    Kovaleva, Agnessa

    2016-08-01

    Localization of energy in oscillator arrays has been of interest for a number of years, with special attention paid to the role of nonlinearity and discreteness in the formation of localized structures. This work examines a different type of energy localization arising due to the presence of dissipation in nonlinear resonance arrays. As a basic model, we consider a Klein-Gordon chain of finite length subjected to a harmonic excitation applied at an edge of the chain. It is shown that weak dissipation may be a key factor preventing the emergence of resonance in the entire chain, even if its nondissipative analog is entirely captured into resonance. The resulting process in the dissipative oscillator array represents large-amplitude resonant oscillations in a part of the chain adjacent to the actuator and small-amplitude oscillations in the distant part of the chain. The conditions of the emergence of resonance as well as the conditions of energy localization are derived. An agreement between the obtained analytical results and numerical simulations is demonstrated. PMID:27627299

  16. Landing Energy Dissipation for Manned Reentry Vehicles

    NASA Technical Reports Server (NTRS)

    Fisher, Lloyd J., Jr.

    1960-01-01

    Analytical and experimental investigations have been made to determine the landing-energy-dissipation characteristics for several types of landing gear for manned reentry vehicles. The landing vehicles are considered in two categories: those having essentially vertical-descent paths, the parachute-supported vehicles, and those having essentially horizontal paths, the lifting vehicles. The energy-dissipation devices discussed are crushable materials such as foamed plastics and honeycomb for internal application in couch-support systems, yielding metal elements as part of the structure of capsules or as alternates for oleos in landing-gear struts, inflatable bags, braking rockets, and shaped surfaces for water impact. It appears feasible to readily evaluate landing-gear systems for internal or external application in hard-surface or water landings by using computational procedures and free-body landing techniques with dynamic models. The systems investigated have shown very interesting energy-dissipation characteristics over a considerable range of landing parameters. Acceptable gear can be developed along lines similar to those presented if stroke requirements and human-tolerance limits are considered.

  17. Energy localization in weakly dissipative resonant chains

    NASA Astrophysics Data System (ADS)

    Kovaleva, Agnessa

    2016-08-01

    Localization of energy in oscillator arrays has been of interest for a number of years, with special attention paid to the role of nonlinearity and discreteness in the formation of localized structures. This work examines a different type of energy localization arising due to the presence of dissipation in nonlinear resonance arrays. As a basic model, we consider a Klein-Gordon chain of finite length subjected to a harmonic excitation applied at an edge of the chain. It is shown that weak dissipation may be a key factor preventing the emergence of resonance in the entire chain, even if its nondissipative analog is entirely captured into resonance. The resulting process in the dissipative oscillator array represents large-amplitude resonant oscillations in a part of the chain adjacent to the actuator and small-amplitude oscillations in the distant part of the chain. The conditions of the emergence of resonance as well as the conditions of energy localization are derived. An agreement between the obtained analytical results and numerical simulations is demonstrated.

  18. Low Energy Dissipation Nano Device Research

    NASA Astrophysics Data System (ADS)

    Yu, Jenny

    2015-03-01

    The development of research on energy dissipation has been rapid in energy efficient area. Nano-material power FET is operated as an RF power amplifier, the transport is ballistic, noise is limited and power dissipation is minimized. The goal is Green-save energy by developing the Graphene and carbon nantube microwave and high performance devices. Higher performing RF amplifiers can have multiple impacts on broadly field, for example communication equipment, (such as mobile phone and RADAR); higher power density and lower power dissipation will improve spectral efficiency which translates into higher system level bandwidth and capacity for communications equipment. Thus, fundamental studies of power handling capabilities of new RF (nano)technologies can have broad, sweeping impact. Because it is critical to maximizing the power handling ability of grephene and carbon nanotube FET, the initial task focuses on measuring and understanding the mechanism of electrical breakdown. We aim specifically to determine how the breakdown voltage in graphene and nanotubes is related to the source-drain spacing, electrode material and thickness, and substrate, and thus develop reliable statistics on the breakdown mechanism and probability.

  19. On the structure of turbulence dissipation rate under unsteady breaking waves

    NASA Astrophysics Data System (ADS)

    Derakhti, Morteza; Kirby, James

    2015-11-01

    During the last decade, extensive laboratory and field measurements have been conducted for the estimation and parameterization of the turbulence dissipation rate under unsteady breaking waves, showing a large amount of scatter depending on the selected estimation, type and scale of the considered breaking waves. To further elucidate the physical processes involved in turbulence generation and dissipation mechanisms, Derakhti & Kirby, JFM, (2014) examined shear- and bubble-induced dissipation. They used a 3D VOF-based Navier-Stokes solver extended to incorporate entrained bubble populations using an Eulerian-Eulerian formulation for a poly-disperse bubble phase, and found that the total bubble-induced dissipation accounts for more than 50% of the total dissipation in the breaking region (the results were presented at DFD13, Abstract 001799). In this presentation, we will examine the 3D distribution of breaking-induced turbulent kinetic energy and dissipation rate during the active breaking period. The role of breaking-induced vortical structures in the transport of turbulent motions will be addressed as well. Finally, the accuracy of the available analytic scaling relations of the intensity and depth dependence of wave breaking turbulence dissipation rate will be discussed. NSF, Physical Oceanography Program, grant OCE-1435147.

  20. Intermittent Energy Dissipation in Magnetohydrodynamic Turbulence: Applications to the Solar Corona and Solar Wind

    NASA Astrophysics Data System (ADS)

    Zhdankin, Vladimir

    2015-11-01

    Energy dissipation is highly intermittent in large-scale turbulent plasmas, being localized in space and in time. This intermittency is manifest by the presence of coherent structures such as current (and vorticity) sheets, which account for a large fraction of the overall energy dissipation and may serve as sites for magnetic reconnection and particle acceleration. The statistical analysis of these dissipative structures is a robust and informative methodology for probing the underlying dynamics, both in numerical simulations and in observations. In this talk, the statistical properties of current sheets in numerical simulations of driven magnetohydrodynamic (MHD) turbulence are described, including recent results obtained from applying new methods for characterizing their morphology. Instantaneously, the overall energy dissipation is found to be evenly spread among current sheets spanning a continuum of energy dissipation rates and inertial-range sizes, while their thicknesses are localized deep inside the dissipation range. The temporal dynamics are then investigated by tracking the current sheets in time and considering the statistics of the resulting four-dimensional spatiotemporal structures, which correspond to dissipative events or flares in astrophysical systems. These dissipative events are found to exhibit robust power-law distributions and scaling relations, and are often highly complex, long-lived, and weakly asymmetric in time. Based on the distribution for their dissipated energies, the strongest dissipative events are found to dominate the overall energy dissipation in the system. These results are compared to the observed statistics of solar flares, and some possible implications for the solar wind are also described.

  1. Field observations of turbulent dissipation rate profiles immediately below the air-water interface

    NASA Astrophysics Data System (ADS)

    Wang, Binbin; Liao, Qian

    2016-06-01

    Near surface profiles of turbulence immediately below the air-water interface were measured with a free-floating Particle Image Velocimetry (PIV) system on Lake Michigan. The surface-following configuration allowed the system to measure the statistics of the aqueous-side turbulence in the topmost layer immediately below the water surface (z≈0˜15 cm, z points downward with 0 at the interface). Profiles of turbulent dissipation rate (ɛ) were investigated under a variety of wind and wave conditions. Various methods were applied to estimate the dissipation rate. Results suggest that these methods yield consistent dissipation rate profiles with reasonable scattering. In general, the dissipation rate decreases from the water surface following a power law relation in the top layer, ɛ˜z-0.7, i.e., the slope of the decrease was lower than that predicted by the wall turbulence theory, and the dissipation was considerably higher in the top layer for cases with higher wave ages. The measured dissipation rate profiles collapse when they were normalized with the wave speed, wave height, water-side friction velocity, and the wave age. This scaling suggests that the enhanced turbulence may be attributed to the additional source of turbulent kinetic energy (TKE) at the "skin layer" (likely due to micro-breaking), and its downward transport in the water column.

  2. VISCOUS ENERGY DISSIPATION IN FROZEN CRYOGENS

    SciTech Connect

    Meitner, S. J.; Pfotenhauer, J. M.; Andraschko, M. R.

    2008-03-16

    ITER is an international research and development project with the goal of demonstrating the feasibility of fusion power. The fuel for the ITER plasma is injected in the form of frozen deuterium pellets; the current injector design includes a batch extruder, cooled by liquid helium. A more advanced fuel system will produce deuterium pellets continuously using a twin-screw extruder, cooled by a cryocooler. One of the critical design parameters for the advanced system is the friction associated with the shearing planes of the frozen deuterium in the extruder; the friction determines the required screw torque as well as the cryocooler heat load.An experiment has been designed to measure the energy dissipation associated with shearing frozen deuterium. Deuterium gas is cooled to its freezing point in the gap between a stationary outer canister and a rotating inner cylinder. The dissipation is measured mechanically and through calorimetric means. The experiment has also been used to measure dissipation in other cryogens, such as neon, as a function of rotational velocity and temperature. This paper describes the design and construction of the experiment and presents measurements over a range of cryogens and test conditions.

  3. Floating hydrometer with energy dissipating baffle

    SciTech Connect

    Kownurko, W.A.

    1987-11-24

    This patent describes a floating hydrometer employable for purposes of obtaining measurements of the presence of suspended solids in a fluid substance contained in a receptacle comprising: a. a probe portion operative as an instrument-bearing housing; b. an elongated tubular element having a hollow interior and at least one open end so as to enable the flow into the hollow interior of the elongated tubular element through the open end; and c. energy dissipating baffle means having a first mode of action and a second mode of action and including a member having a hollow interior.

  4. The Dissipation Rate Transport Equation and Subgrid-Scale Models in Rotating Turbulence

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Ye, Zhou

    1997-01-01

    The dissipation rate transport equation remains the most uncertain part of turbulence modeling. The difficulties arc increased when external agencies like rotation prevent straightforward dimensional analysis from determining the correct form of the modelled equation. In this work, the dissipation rate transport equation and subgrid scale models for rotating turbulence are derived from an analytical statistical theory of rotating turbulence. In the strong rotation limit, the theory predicts a turbulent steady state in which the inertial range energy spectrum scales as k(sup -2) and the turbulent time scale is the inverse rotation rate. This scaling has been derived previously by heuristic arguments.

  5. Energy dissipation in a rolling aircraft tire

    NASA Technical Reports Server (NTRS)

    Tielking, John T.

    1988-01-01

    The project is extending an existing finite element tire model to calculate the energy dissipation in a free-rolling aircraft tire and temperature buildup in the tire carcass. The model will provide a means of calculating the influence of tire design on the distribution of tire temperature. Current focus is on energy loss measurements of aircraft tire material. The feasibility of taking test specimens directly from the tire carcass for measurements of viscoelastic properties was demonstrated. The interaction of temperature and frequency effects on material loss properties was studied. The tire model was extended to calculate the cyclic energy change in a tire during rolling under load. Input data representing the 40 by 14 aircraft tire whose material loss properties were measured are being used.

  6. Estimation of Eddy Dissipation Rates from Mesoscale Model Simulations

    NASA Technical Reports Server (NTRS)

    Ahmad, Nashat N.; Proctor, Fred H.

    2012-01-01

    The Eddy Dissipation Rate is an important metric for representing the intensity of atmospheric turbulence and is used as an input parameter for predicting the decay of aircraft wake vortices. In this study, the forecasts of eddy dissipation rates obtained from the current state-of-the-art mesoscale model are evaluated for terminal area applications. The Weather Research and Forecast mesoscale model is used to simulate the planetary boundary layer at high horizontal and vertical mesh resolutions. The Bougeault-Lacarrer and the Mellor-Yamada-Janji schemes implemented in the Weather Research and Forecast model are evaluated against data collected during the National Aeronautics and Space Administration s Memphis Wake Vortex Field Experiment. Comparisons with other observations are included as well.

  7. Estimates of M2 Tidal Energy Dissipation from TOPEX/Poseidon Altimeter Data

    NASA Technical Reports Server (NTRS)

    Egbert, Gary D.; Ray, Richard D.

    2001-01-01

    Most of the tidal energy dissipation in the ocean occurs in shallow seas, as has long been recognized. However, recent work has suggested that a significant fraction of the dissipation, perhaps 1 TW or more, occurs in the deep ocean. This paper builds further evidence for that conclusion. More than 6 years of data from the TOPEX/Poseidon satellite altimeter are used to map the tidal dissipation rate throughout the world ocean. The dissipation rate is estimated as a balance between the rate of working by tidal forces and the energy flux divergence, computed using currents derived by least squares fitting of the altimeter data and the shallow water equations. Such calculations require dynamical assumptions, in particular about the nature of dissipation. To assess sensitivity of dissipation estimates to input assumptions, a large suite of tidal inversions based on a wide range of drag parameterizations and employing both real and synthetic altimeter data are compared. These experiments and Monte Carlo error fields from a generalized inverse model are used to establish error uncertainties for the dissipation estimates. Owing to the tight constraints on tidal elevation fields provided by the altimeter, area integrals of the energy balance are remarkably insensitive to required dynamical assumptions. Tidal energy dissipation is estimated for all major shallow seas (excluding individual polar seas) and compared with previous model and data-based estimates. Dissipation in the open ocean is significantly tnhanced around major bathymetric features, in a manner consistent with simple theories the generation of baroclinic tides.

  8. Energy dissipation in viscous-plastic sea-ice models

    NASA Astrophysics Data System (ADS)

    Bouchat, Amélie; Tremblay, Bruno

    2014-02-01

    In viscous-plastic (VP) sea-ice models, small deformations are approximated by irreversible viscous deformations, introducing a nonphysical energy sink. As the spatial resolution and the degree of numerical convergence of the models increase, linear kinematic features (LKFs) are better resolved and more states of stress lie in the viscous regime. Energy dissipation in this nonphysical viscous regime therefore increases. We derive a complete kinetic energy (KE) balance for sea ice, including plastic and viscous energy sinks to study energy dissipation. The main KE balance is between the energy input by the wind and the dissipation by the water drag and the internal stresses (dissipating 87% and 13% of the energy input on an annual average). The internal stress term is mostly important in winter when ice-ice interactions are dominant. The energy input that is not dissipated locally is redistributed laterally by the internal stresses into regions of dissipation by small-scale deformations (LKFs). Of the 13% dissipated annually by the internal stress term, 93% is dissipated in plastic friction along LKFs (14% in ridging, 79% in shearing) and 7% is stored as potential energy in ridges. For all time and spatial scales tested, the frictional viscous dissipation is negligible in the KE balance. This conclusion remains valid regardless of the degree of numerical convergence of the simulations. Overall, the results confirm the applicability, from an energetical point of view, of the VP approximation.

  9. Energy dissipation in Exosat tanks: Test results

    NASA Astrophysics Data System (ADS)

    Marce, J. L.; Torres, L.; Assemat, D.; Michel, S.

    1981-03-01

    Results of tests performed with inertia ratio and filling ratio scanning on Ariane tanks are presented. The Exosat launch requires the use of a fourth stage (P 0.7). The Exosat + P 0.7 assembly is spin stabilized with a spin rate of 50 rpm during transfer orbit. The unstable assembly is fitted with an active nutation damping system. To size this, it is necessary to know the time constant of nutation build up essentially due to fuel motion in the propane tanks and the hydrazine tank of Exosat. The major source of dissipation is the hydrazine tank for which an hysteresis phenomenon on diaphragm position was observed; the worst time constants of nutation build up, deduced from tests are 2.5 mn before P 0.7 and 1.9 mn after P 0.7 firing, taking into account the appropriate safety factors.

  10. Harvesting dissipated energy with a mesoscopic ratchet.

    PubMed

    Roche, B; Roulleau, P; Jullien, T; Jompol, Y; Farrer, I; Ritchie, D A; Glattli, D C

    2015-01-01

    The search for new efficient thermoelectric devices converting waste heat into electrical energy is of major importance. The physics of mesoscopic electronic transport offers the possibility to develop a new generation of nanoengines with high efficiency. Here we describe an all-electrical heat engine harvesting and converting dissipated power into an electrical current. Two capacitively coupled mesoscopic conductors realized in a two-dimensional conductor form the hot source and the cold converter of our device. In the former, controlled Joule heating generated by a voltage-biased quantum point contact results in thermal voltage fluctuations. By capacitive coupling the latter creates electric potential fluctuations in a cold chaotic cavity connected to external leads by two quantum point contacts. For unequal quantum point contact transmissions, a net electrical current is observed proportional to the heat produced. PMID:25828578

  11. Harvesting dissipated energy with a mesoscopic ratchet

    NASA Astrophysics Data System (ADS)

    Roche, B.; Roulleau, P.; Jullien, T.; Jompol, Y.; Farrer, I.; Ritchie, D. A.; Glattli, D. C.

    2015-04-01

    The search for new efficient thermoelectric devices converting waste heat into electrical energy is of major importance. The physics of mesoscopic electronic transport offers the possibility to develop a new generation of nanoengines with high efficiency. Here we describe an all-electrical heat engine harvesting and converting dissipated power into an electrical current. Two capacitively coupled mesoscopic conductors realized in a two-dimensional conductor form the hot source and the cold converter of our device. In the former, controlled Joule heating generated by a voltage-biased quantum point contact results in thermal voltage fluctuations. By capacitive coupling the latter creates electric potential fluctuations in a cold chaotic cavity connected to external leads by two quantum point contacts. For unequal quantum point contact transmissions, a net electrical current is observed proportional to the heat produced.

  12. Light energy dissipation under water stress conditions

    SciTech Connect

    Stuhlfauth, T.; Scheuermann, R.; Fock, H.P. )

    1990-04-01

    Using {sup 14}CO{sub 2} gas exchange and metabolite analyses, stomatal as well as total internal CO{sub 2} uptake and evolution were estimated. Pulse modulated fluorescence was measured during induction and steady state of photosynthesis. Leaf water potential of Digitalis lanata EHRH. plants decreased to {minus}2.5 megapascals after withholding irrigation. By osmotic adjustment, leaves remained turgid and fully exposed to irradiance even at severe water stress. Due to the stress-induced reduction of stomatal conductance, the stomatal CO{sub 2} exchange was drastically reduced, whereas the total CO{sub 2} uptake and evolution were less affected. Stomatal closure induced an increase in the reassimilation of internally evolved CO{sub 2}. This CO{sub 2}-recycling consumes a significant amount of light energy in the form of ATP and reducing equivalents. As a consequence, the metabolic demand for light energy is only reduced by about 40%, whereas net photosynthesis is diminished by about 70% under severe stress conditions. By CO{sub 2} recycling, carbon flux, enzymatic substrate turnover and consumption of light energy were maintained at high levels, which enabled the plant to recover rapidly after rewatering. In stressed D. lanata plants a variable fluorescence quenching mechanism, termed coefficient of actinic light quenching, was observed. Besides water conservation, light energy dissipation is essential and involves regulated metabolic variations.

  13. Estimation of turbulence dissipation rate by Large eddy PIV method in an agitated vessel

    NASA Astrophysics Data System (ADS)

    Kysela, Bohuš; Jašíková, Darina; Konfršt, Jiří; Šulc, Radek; Ditl, Pavel

    2015-05-01

    The distribution of turbulent kinetic energy dissipation rate is important for design of mixing apparatuses in chemical industry. Generally used experimental methods of velocity measurements for measurement in complex geometries of an agitated vessel disallow measurement in resolution of small scales close to turbulence dissipation ones. Therefore, Particle image velocity (PIV) measurement method improved by large eddy Ply approach was used. Large eddy PIV method is based on modeling of smallest eddies by a sub grid scale (SGS) model. This method is similar to numerical calculations using Large Eddy Simulation (LES) and the same SGS models are used. In this work the basic Smagorinsky model was employed and compared with power law approximation. Time resolved PIV data were processed by Large Eddy PIV approach and the obtained results of turbulent kinetic dissipation rate were compared in selected points for several operating conditions (impeller speed, operating liquid viscosity).

  14. Cloud-Scale Vertical Velocity and Turbulent Dissipation Rate Retrievals

    DOE Data Explorer

    Shupe, Matthew

    2013-05-22

    Time-height fields of retrieved in-cloud vertical wind velocity and turbulent dissipation rate, both retrieved primarily from vertically-pointing, Ka-band cloud radar measurements. Files are available for manually-selected, stratiform, mixed-phase cloud cases observed at the North Slope of Alaska (NSA) site during periods covering the Mixed-Phase Arctic Cloud Experiment (MPACE, late September through early November 2004) and the Indirect and Semi-Direct Aerosol Campaign (ISDAC, April-early May 2008). These time periods will be expanded in a future submission.

  15. Dissipative control of energy flow in interconnected systems

    NASA Technical Reports Server (NTRS)

    Kishimoto, Y.; Bernstein, D. S.; Hall, S. R.

    1993-01-01

    Dissipative energy flow controllers are designed for interconnected modal subsystems. Active feedback controllers for vibration suppression are then viewed as either an additional subsystem or a dissipative coupling. These controllers, which are designed by the LQG positive real control approach, maximize energy flow from a specified modal subsystem.

  16. Energy dissipation of rockfalls by coppice structures

    NASA Astrophysics Data System (ADS)

    Ciabocco, G.; Boccia, L.; Ripa, M. N.

    2009-06-01

    The objective of this work is to develop elements to improve understanding of the behaviour of a coppice in relation to the phenomenon of falling boulders. The first section proposes an amendment to the equation for calculating the index which describes the probability of impact between a rock and plants in managed coppice forests. A study was carried out, using models to calculate the kinetic energy of a falling boulder along a slope considering the kinetic energy dissipated during the impact with the structure of forest plants managed by coppice. The output of the simulation models were then compared with the real dynamics of falling boulders in field tests using digital video. It emerged from an analysis of the results of this comparison that a modification to the 1989 Gsteiger equation was required, in order to calculate the "Average Distance between Contacts" (ADC). To this purpose, the concept of "Structure of Interception", proposed in this paper, was developed, valid as a first approach for describing the differences in the spatial distribution of stems between coppice and forest. This study also aims to provide suggestions for forestry management, in order to maintain or increase the protective capacity of a coppice managed with conventional techniques for the area studied, modifying the dendrometric characteristics.

  17. A dimensionless model of impact piezoelectric energy harvesting with dissipation

    NASA Astrophysics Data System (ADS)

    Fu, Xinlei; Liao, Wei-Hsin

    2016-04-01

    Impact excitation is common in the environment. Impact piezoelectric energy harvesting could realize frequency up-conversion. However, the dissipation mechanism in impact piezoelectric energy harvesting has not been investigated so far. There is no comprehensive model to be able to analyze the impact piezoelectric energy harvesting thoroughly. This paper is aimed to develop a generalized model that considers dissipation mechanism of impact piezoelectric energy harvesting. In this electromechanical model, Hertzian contact theory and impact dissipation mechanism are identified as constitutive mechanisms. The impact force is compared and the energy distribution is analyzed so that input energy corresponds to impact dissipated energy, structural damping dissipated energy and harvested electrical energy. We then nondimensionalize the developed model and define five dimensionless parameters with attributed physical meanings, including dimensionless parameters of impact dissipation, mass ratio, structural damping, electromechanical coupling, and electrical load. We conclude it is more accurate to consider impact dissipation mechanism to predict impact force and harvested energy. The guideline for improving harvested energy based on parametric studies of dimensionless model is to increase mass ratio, to minimize structural damping, to maximize electromechanical coupling, to use optimal load resistance for impedance matching, and to choose proper impact velocity .

  18. Turbulence in Continental Stratocumulus, Part II: Eddy Dissipation Rates and Large-Eddy Coherent Structures

    NASA Astrophysics Data System (ADS)

    Fang, Ming; Albrecht, Bruce A.; Ghate, Virendra P.; Kollias, Pavlos

    2014-03-01

    This study first illustrates the utility of using the Doppler spectrum width from millimetre wavelength radar to calculate the energy dissipation rate and then to use the energy dissipation rate to study turbulence structure in a continental stratocumulus cloud. It is shown that the turbulence kinetic energy dissipation rate calculated from the radar-measured Doppler spectrum width agrees well with that calculated from the Doppler velocity power spectrum. During the 16-h stratocumulus cloud event, the small-scale turbulence contributes 40 % of the total velocity variance at cloud base, 50 % at normalized cloud depth = 0.8 and 70 % at cloud top, which suggests that small-scale turbulence plays a critical role near the cloud top where the entrainment and cloud-top radiative cooling act. The 16-h mean vertical integral length scale decreases from about 160 m at cloud base to 60 m at cloud top, and this signifies that the larger scale turbulence dominates around cloud base whereas the small-scale turbulence dominates around cloud top. The energy dissipation rate, total variance and squared spectrum width exhibit diurnal variations, but unlike marine stratocumulus they are high during the day and lowest around sunset at all levels; energy dissipation rates increase at night with the intensification of the cloud-top cooling. In the normalized coordinate system, the averaged coherent structure of updrafts is characterized by low energy dissipation rates in the updraft core and higher energy dissipation rates surround the updraft core at the top and along the edges. In contrast, the energy dissipation rate is higher inside the downdraft core indicating that the downdraft core is more turbulent. The turbulence around the updraft is weaker at night and stronger during the day; the opposite is true around the downdraft. This behaviour indicates that the turbulence in the downdraft has a diurnal cycle similar to that observed in marine stratocumulus whereas the turbulence

  19. Temporal intermittency of energy dissipation in magnetohydrodynamic turbulence.

    PubMed

    Zhdankin, Vladimir; Uzdensky, Dmitri A; Boldyrev, Stanislav

    2015-02-13

    Energy dissipation in magnetohydrodynamic (MHD) turbulence is known to be highly intermittent in space, being concentrated in sheetlike coherent structures. Much less is known about intermittency in time, another fundamental aspect of turbulence which has great importance for observations of solar flares and other space or astrophysical phenomena. In this Letter, we investigate the temporal intermittency of energy dissipation in numerical simulations of MHD turbulence. We consider four-dimensional spatiotemporal structures, "flare events," responsible for a large fraction of the energy dissipation. We find that although the flare events are often highly complex, they exhibit robust power-law distributions and scaling relations. We find that the probability distribution of dissipated energy has a power-law index close to α≈1.75, similar to observations of solar flares, indicating that intense dissipative events dominate the heating of the system. We also discuss the temporal asymmetry of flare events as a signature of the turbulent cascade. PMID:25723225

  20. Vertical kinetic energy and turbulent dissipation in the ocean

    NASA Astrophysics Data System (ADS)

    Thurnherr, A. M.; Kunze, E.; Toole, J. M.; St. Laurent, L.; Richards, K. J.; Ruiz-Angulo, A.

    2015-09-01

    Oceanic internal waves are closely linked to turbulence. Here a relationship between vertical wave number (kz) spectra of fine-scale vertical kinetic energy (VKE) and turbulent dissipation ɛ is presented using more than 250 joint profiles from five diverse dynamic regimes, spanning latitudes between the equator and 60°. In the majority of the spectra VKE varies as kz-2. Scaling VKE with √ɛ collapses the off-equatorial spectra to within √2 but underestimates the equatorial spectrum. The simple empirical relationship between VKE and ɛ fits the data better than a common shear-and-strain fine-scale parameterization, which significantly underestimates ɛ in the two data sets that are least consistent with the Garrett-Munk (GM) model. The new relationship between fine-scale VKE and dissipation rate can be interpreted as an alternative, single-parameter scaling for turbulent dissipation in terms of fine-scale internal wave vertical velocity that requires no reference to the GM model spectrum.

  1. Estimating wave energy dissipation in the surf zone using thermal infrared imagery

    NASA Astrophysics Data System (ADS)

    Carini, Roxanne J.; Chickadel, C. Chris; Jessup, Andrew T.; Thomson, Jim

    2015-06-01

    Thermal infrared (IR) imagery is used to quantify the high spatial and temporal variability of dissipation due to wave breaking in the surf zone. The foam produced in an actively breaking crest, or wave roller, has a distinct signature in IR imagery. A retrieval algorithm is developed to detect breaking waves and extract wave roller length using measurements taken during the Surf Zone Optics 2010 experiment at Duck, NC. The remotely derived roller length and an in situ estimate of wave slope are used to estimate dissipation due to wave breaking by means of the wave-resolving model by Duncan (1981). The wave energy dissipation rate estimates show a pattern of increased breaking during low tide over a sand bar, consistent with in situ turbulent kinetic energy dissipation rate estimates from fixed and drifting instruments over the bar. When integrated over the surf zone width, these dissipation rate estimates account for 40-69% of the incoming wave energy flux. The Duncan (1981) estimates agree with those from a dissipation parameterization by Janssen and Battjes (2007), a wave energy dissipation model commonly applied within nearshore circulation models.

  2. Energy/dissipation-preserving Birkhoffian multi-symplectic methods for Maxwell's equations with dissipation terms

    NASA Astrophysics Data System (ADS)

    Su, Hongling; Li, Shengtai

    2016-04-01

    In this paper, we propose two new energy/dissipation-preserving Birkhoffian multi-symplectic methods (Birkhoffian and Birkhoffian box) for Maxwell's equations with dissipation terms. After investigating the non-autonomous and autonomous Birkhoffian formalism for Maxwell's equations with dissipation terms, we first apply a novel generating functional theory to the non-autonomous Birkhoffian formalism to propose our Birkhoffian scheme, and then implement a central box method to the autonomous Birkhoffian formalism to derive the Birkhoffian box scheme. We have obtained four formal local conservation laws and three formal energy global conservation laws. We have also proved that both of our derived schemes preserve the discrete version of the global/local conservation laws. Furthermore, the stability, dissipation and dispersion relations are also investigated for the schemes. Theoretical analysis shows that the schemes are unconditionally stable, dissipation-preserving for Maxwell's equations in a perfectly matched layer (PML) medium and have second order accuracy in both time and space. Numerical experiments for problems with exact theoretical results are given to demonstrate that the Birkhoffian multi-symplectic schemes are much more accurate in preserving energy than both the exponential finite-difference time-domain (FDTD) method and traditional Hamiltonian scheme. We also solve the electromagnetic pulse (EMP) propagation problem and the numerical results show that the Birkhoffian scheme recovers the magnitude of the current source and reaction history very well even after long time propagation.

  3. Identification of energy dissipation mechanisms in CNT-reinforced nanocomposites.

    PubMed

    Gardea, Frank; Glaz, Bryan; Riddick, Jaret; Lagoudas, Dimitris C; Naraghi, Mohammad

    2016-03-11

    In this paper we present our recent findings on the mechanisms of energy dissipation in polymer-based nanocomposites obtained through experimental investigations. The matrix of the nanocomposite was polystyrene (PS) which was reinforced with carbon nanotubes (CNTs). To study the mechanical strain energy dissipation of nanocomposites, we measured the ratio of loss to storage modulus for different CNT concentrations and alignments. CNT alignment was achieved via hot-drawing of PS-CNT. In addition, CNT agglomeration was studied via a combination of SEM imaging and Raman scanning. We found that at sufficiently low strains, energy dissipation in composites with high CNT alignment is not a function of applied strain, as no interfacial slip occurs between the CNTs and PS. However, below the interfacial slip strain threshold, damping scales monotonically with CNT content, which indicates the prevalence of CNT-CNT friction dissipation mechanisms within agglomerates. At higher strains, interfacial slip also contributes to energy dissipation. However, the increase in damping with strain, especially when CNT agglomerates are present, does not scale linearly with the effective interface area between CNTs and PS, suggesting a significant contribution of friction between CNTs within agglomerates to energy dissipation at large strains. In addition, for the first time, a comparison between the energy dissipation in randomly oriented and aligned CNT composites was made. It is inferred that matrix plasticity and tearing caused by misorientation of CNTs with the loading direction is a major cause of energy dissipation. The results of our research can be used to design composites with high energy dissipation capability, especially for applications where dynamic loading may compromise structural stability and functionality, such as rotary wing structures and antennas. PMID:26866611

  4. Identification of energy dissipation mechanisms in CNT-reinforced nanocomposites

    NASA Astrophysics Data System (ADS)

    Gardea, Frank; Glaz, Bryan; Riddick, Jaret; Lagoudas, Dimitris C.; Naraghi, Mohammad

    2016-03-01

    In this paper we present our recent findings on the mechanisms of energy dissipation in polymer-based nanocomposites obtained through experimental investigations. The matrix of the nanocomposite was polystyrene (PS) which was reinforced with carbon nanotubes (CNTs). To study the mechanical strain energy dissipation of nanocomposites, we measured the ratio of loss to storage modulus for different CNT concentrations and alignments. CNT alignment was achieved via hot-drawing of PS-CNT. In addition, CNT agglomeration was studied via a combination of SEM imaging and Raman scanning. We found that at sufficiently low strains, energy dissipation in composites with high CNT alignment is not a function of applied strain, as no interfacial slip occurs between the CNTs and PS. However, below the interfacial slip strain threshold, damping scales monotonically with CNT content, which indicates the prevalence of CNT-CNT friction dissipation mechanisms within agglomerates. At higher strains, interfacial slip also contributes to energy dissipation. However, the increase in damping with strain, especially when CNT agglomerates are present, does not scale linearly with the effective interface area between CNTs and PS, suggesting a significant contribution of friction between CNTs within agglomerates to energy dissipation at large strains. In addition, for the first time, a comparison between the energy dissipation in randomly oriented and aligned CNT composites was made. It is inferred that matrix plasticity and tearing caused by misorientation of CNTs with the loading direction is a major cause of energy dissipation. The results of our research can be used to design composites with high energy dissipation capability, especially for applications where dynamic loading may compromise structural stability and functionality, such as rotary wing structures and antennas.

  5. Reynolds-stress and dissipation rate budgets in a turbulent channel flow

    NASA Technical Reports Server (NTRS)

    Mansour, N. N.; Kim, J.; Moin, P.

    1987-01-01

    The budgets for the Reynolds stresses and for the dissipation rate of the turbulence kinetic energy are computed using direct simulation data of a turbulent channel flow. The budget data reveal that all the terms in the budget become important close to the wall. For inhomogeneous pressure boundary conditions, the pressure-strain term is split into a return term, a rapid term, and a Stokes term. The Stokes term is important close to the wall. The rapid and return terms play different roles depending on the component of the term. A split of the velocity pressure-gradient term into a redistributive term and a diffusion term is proposed, which should be simpler to model. The budget data is used to test existing closure models for the pressure-strain term, the dissipation rate, and the transport rate. In general, further work is needed to improve the models.

  6. Robust Stabilization of Uncertain Systems Based on Energy Dissipation Concepts

    NASA Technical Reports Server (NTRS)

    Gupta, Sandeep

    1996-01-01

    Robust stability conditions obtained through generalization of the notion of energy dissipation in physical systems are discussed in this report. Linear time-invariant (LTI) systems which dissipate energy corresponding to quadratic power functions are characterized in the time-domain and the frequency-domain, in terms of linear matrix inequalities (LMls) and algebraic Riccati equations (ARE's). A novel characterization of strictly dissipative LTI systems is introduced in this report. Sufficient conditions in terms of dissipativity and strict dissipativity are presented for (1) stability of the feedback interconnection of dissipative LTI systems, (2) stability of dissipative LTI systems with memoryless feedback nonlinearities, and (3) quadratic stability of uncertain linear systems. It is demonstrated that the framework of dissipative LTI systems investigated in this report unifies and extends small gain, passivity, and sector conditions for stability. Techniques for selecting power functions for characterization of uncertain plants and robust controller synthesis based on these stability results are introduced. A spring-mass-damper example is used to illustrate the application of these methods for robust controller synthesis.

  7. Energy Spectrum in the Dissipation Range of Fluid Turbulence

    NASA Technical Reports Server (NTRS)

    Martinez, D. O.; Chen, S.; Doolen, G. D.; Kraichnan, R. H.; Wang, L.-P.; Zhou, Y.

    1996-01-01

    High resolution, direct numerical simulations of the three-dimensional incompressible Navier-Stokes equations are carried out to study the energy spectrum in the dissipation range. An energy spectrum of the form A(k/k( sub d))(sup alpha) exp[- betak/k(sub d) is confirmed. The possible values of the parameters alpha and beta, as well as their dependence on Revnolds numbers and length scales, are investigated, showing good agreement with recent theoretical predictions. A "bottleneck'-type effect is reported at k/k(sub d) approximately 4, exhibiting a possible transition from near-dissipation to far- dissipation.

  8. Probing postsaddle nuclear dissipation with excitation energy at scission

    NASA Astrophysics Data System (ADS)

    Ye, W.; Tian, J.

    2016-04-01

    Using the stochastic Langevin model coupled with a statistical decay model, we study postsaddle dissipation properties in fission by analyzing the excitation energy at scission (Esc*) measured in fissioning nuclei 179Re and Fm,256254. The postsaddle dissipation strength (β ) required to fit Esc* data is found to be larger for Fm,256254 than light 179Re which has a smaller postsaddle deformation compared to heavy Fm,256254, showing a rise of nuclear dissipation strength at a greater deformation. Furthermore, we explore the influence of initial excitation energy of a fissioning system 246Cf on the sensitivity of its Esc* to β , and find that the sensitivity is significantly enhanced with increasing the initial excitation energy. Our finding suggests that, on the experimental side, to more accurately probe the postsaddle dissipation strength through the measurement of Esc*, it is best to yield those fissioning systems with high energy.

  9. Energy Dissipation by Tides and Librations in Synchronous Satellites

    NASA Technical Reports Server (NTRS)

    Bills, B. G.; Ray, R. D.

    2000-01-01

    Energy dissipation associated with physical librations of large synchronous satellites may be important for maintaining internal fluid layers. Depending on the depth and viscosity of the fluid layer, viscous heating from librations may exceeed that from tides.

  10. Energy dissipation characteristics of magnetosensitive elastomer under impact loading

    NASA Astrophysics Data System (ADS)

    Leng, D.; Sun, L.; Sun, J.; Chen, W.; Ma, F.; Li, W.; Lin, Y.

    2013-02-01

    Magnetosensitive (MS) elastomers are a class of material that ferro-magnetic particles dispersed in rubber or elastomer whose mechanical properties change with the external magnetic fields. To investigate energy dissipation properties of MS elastomers, experimental method is adopted. Firstly, this paper presents a new fabrication method of a magnetosensitive elastomers with particles in millimeter scale distributed in ideal isotropic or in chain. Then, a drop hammer testing setup is developed to measure the energy dissipation and study the impact behaviour of magnetosensitive elastomers (MSEs). For the same volume fraction and size of particle, the dissipated energy per unit length of MSEs increases with the magnetic field increasing, and chain-like structured MSEs dissipate more energy than homogenous MSEs under the same external magnetic field.

  11. Rolling friction and energy dissipation in a spinning disc

    PubMed Central

    Ma, Daolin; Liu, Caishan; Zhao, Zhen; Zhang, Hongjian

    2014-01-01

    This paper presents the results of both experimental and theoretical investigations for the dynamics of a steel disc spinning on a horizontal rough surface. With a pair of high-speed cameras, a stereoscopic vision method is adopted to perform omnidirectional measurements for the temporal evolution of the disc's motion. The experiment data allow us to detail the dynamics of the disc, and consequently to quantify its energy. From our experimental observations, it is confirmed that rolling friction is a primary factor responsible for the dissipation of the energy. Furthermore, a mathematical model, in which the rolling friction is characterized by a resistance torque proportional to the square of precession rate, is also proposed. By employing the model, we perform qualitative analysis and numerical simulations. Both of them provide results that precisely agree with our experimental findings. PMID:25197246

  12. Turbulent viscosity and Jupiter's tidal Q. [energy dissipation function

    NASA Technical Reports Server (NTRS)

    Goldreich, P.; Nicholson, P. D.

    1977-01-01

    A recent estimate of tidal dissipation by turbulent viscosity in Jupiter's convective interior predicts that the current value of the planet's tidal Q is roughly 5 million. We point out a fundamental error in this calculation, and show that turbulent dissipation alone implies that at present Q is about 50 trillion. Our reduced estimate for the rate of tidal dissipation shows conclusively that tidal torques have produced only negligible modifications of the orbits of the Galilean satellites over the age of the solar system.

  13. Scaling laws for the upper ocean temperature dissipation rate

    NASA Astrophysics Data System (ADS)

    Bogucki, Darek J.; Huguenard, K.; Haus, B. K.; Özgökmen, T. M.; Reniers, A.; Laxague, N. J. M.

    2015-02-01

    Our understanding of temperature dissipation rate χ within the upper ocean boundary layer, which is critical for climate forecasts, is very limited. Near-surface turbulence also affects dispersion of contaminants and biogeochemical tracers. Using high-resolution optical turbulence measurements, scaling laws for χ are investigated under forcing states where either the daytime heat flux or the wind stress forcing is dominant. We find that χ remains constant over 1.5 times the significant wave height, while over a layer below, χ decays based on the local surface forcing. When the heat flux is dominant, traditional scaling based on the Monin-Obukhov similarity theory remains valid; χ ∝ z-1. When the wind stress dominates, we observe the emergence of a new scaling, χ ∝ z-1/2, which is explained by invoking the effect of small-scale coherent structures on vertical heat transport. These results have implications for improved modeling of the ocean's heat and CO2 intake.

  14. Turbulent energy dissipation and intermittency in ambipolar diffusion magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Momferratos, G.; Lesaffre, P.; Falgarone, E.; Pineau des Forêts, G.

    2014-09-01

    The dissipation of kinetic and magnetic energy in the interstellar medium (ISM) can proceed through viscous, Ohmic or ambipolar diffusion (AD). It occurs at very small scales compared to the scales at which energy is presumed to be injected. This localized heating may impact the ISM evolution but also its chemistry, thus providing observable features. Here, we perform 3D spectral simulations of decaying magnetohydrodynamic turbulence including the effects of AD. We find that the AD heating power spectrum peaks at scales in the inertial range, due to a strong alignment of the magnetic and current vectors in the dissipative range. AD affects much greater scales than the AD scale predicted by dimensional analysis. We find that energy dissipation is highly concentrated on thin sheets. Its probability density function follows a lognormal law with a power-law tail which hints at intermittency, a property which we quantify by use of structure function exponents. Finally, we extract structures of high dissipation, defined as connected sets of points where the total dissipation is most intense and we measure the scaling exponents of their geometric and dynamical characteristics: the inclusion of AD favours small sizes in the dissipative range.

  15. Dissipative dynamics in a finite chaotic environment: Relationship between damping rate and Lyapunov exponent

    NASA Astrophysics Data System (ADS)

    Xavier, J. C.; Strunz, W. T.; Beims, M. W.

    2015-08-01

    We consider the energy flow between a classical one-dimensional harmonic oscillator and a set of N two-dimensional chaotic oscillators, which represents the finite environment. Using linear response theory we obtain an analytical effective equation for the system harmonic oscillator, which includes a frequency dependent dissipation, a shift, and memory effects. The damping rate is expressed in terms of the environment mean Lyapunov exponent. A good agreement is shown by comparing theoretical and numerical results, even for environments with mixed (regular and chaotic) motion. Resonance between system and environment frequencies is shown to be more efficient to generate dissipation than larger mean Lyapunov exponents or a larger number of bath chaotic oscillators.

  16. Energy dissipation in an adaptive molecular circuit

    NASA Astrophysics Data System (ADS)

    Wang, Shou-Wen; Lan, Yueheng; Tang, Lei-Han

    2015-07-01

    The ability to monitor nutrient and other environmental conditions with high sensitivity is crucial for cell growth and survival. Sensory adaptation allows a cell to recover its sensitivity after a transient response to a shift in the strength of extracellular stimulus. The working principles of adaptation have been established previously based on rate equations which do not consider fluctuations in a thermal environment. Recently, Lan et al (2012 Nat. Phys. 8 422-8) performed a detailed analysis of a stochastic model for the Escherichia coli sensory network. They showed that accurate adaptation is possible only when the system operates in a nonequilibrium steady-state (NESS). They further proposed an energy-speed-accuracy (ESA) trade-off relation. We present here analytic results on the NESS of the model through a mapping to a one-dimensional birth-death process. An exact expression for the entropy production rate is also derived. Based on these results, we are able to discuss the ESA relation in a more general setting. Our study suggests that the adaptation error can be reduced exponentially as the methylation range increases. Finally, we show that a nonequilibrium phase transition exists in the infinite methylation range limit, despite the fact that the model contains only two discrete variables.

  17. The Dissipation Rate In The Wind-induced Ekman Boundary Layer

    NASA Astrophysics Data System (ADS)

    Roget, E.; Figueroa, M.; Lozovatsky, I.

    Turbulent measurements in the near-surface oceanic boundary layer carried out at the trans-Atlantic section (along 53N) in 2001 are used to study variations of the intensity of ocean mixing influenced by various atmospheric forcing including stormy winds. Measurements were taken from the Russian r/v Akademik Ioffe (IO RAN) during its 9th research cruise. Atmospheric data were obtained in the course of regular standard meteorological observations. Microstructure oceanographic measurements were made from the sea surface down to the depth of about 200 m using a profiler developed by SeaSun Technology GmbH (Germany). The profiler was equipped by an airfoil sensor to measure small-scale shear with further calculation of the kinetic energy dissipation rate, fast and slow temperature sensors, a conductivity probe, and a pressure sensor. To control level of vibrations during downcasts, acceleration signal was recorded and fur- ther analyzed with respect to the airfoil record. The data were transmitted onboard via a thin cable of almost neutral buoyancy that was realized with a slightly higher speed than the falling speed of the profiler to reduce possible vibrations caused by cable ten- sion. Upper 5-10 meters of the measurements were eliminated from the analysis due to the ship-induced contaminations. The background hydrological information was ob- tained by a ship-mounted ADCP and a Neil Brown profiler. The ADCP measurements showed that wind-induced drift currents usually occupy the upper 30-40 meter layer under moderate winds (Va < 10 m/s). The decimal logarithm of dissipation rate in this layer varies from -6 to -8 W/kg depending on the age of the wind-induced turbulence. When the measurements were made after an intense storm (Va > 25 m/s), the depth of the Ekman layer increased to about 80 m keeping high dissipation (log10eps > -6 W/kg) across the whole layer. The dissipation at the higher depths, in the thermohalo- cline, usually had an intermittent nature with a

  18. Airborne lidar measurements of wave energy dissipation in a coral reef lagoon system

    NASA Astrophysics Data System (ADS)

    Huang, Zhi-Cheng; Reineman, Benjamin D.; Lenain, Luc; Melville, W. Kendall; Middleton, Jason H.

    2012-03-01

    Quantification of the turbulent kinetic energy dissipation rate in the water column, ɛ, is very important for assessing nutrient uptake rates of corals and therefore the health of coral reef lagoon systems. However, the availability of such data is limited. Recently, at Lady Elliot Island (LEI), Australia, we showed that there was a strong correlation between in situ measurements of surface-wave energy dissipation and ɛ. Previously, Reineman et al. (2009), we showed that a small airborne scanning lidar system could measure the surface wavefield remotely. Here we present measurements demonstrating the use of the same airborne lidar to remotely measure surface wave energy fluxes and dissipation and thereby estimate ɛ in the LEI reef-lagoon system. The wave energy flux and wave dissipation rate across the fore reef and into the lagoon are determined from the airborne measurements of the wavefield. Using these techniques, observed spatial profiles of energy flux and wave energy dissipation rates over the LEI reef-lagoon system are presented. The results show that the high lidar backscatter intensity and point density coming from the high reflectivity of the foam from depth-limited breaking waves coincides with the high wave-energy dissipation rates. Good correlations between the airborne measurements and in situ observations demonstrate that it is feasible to apply airborne lidar systems for large-scale, long-term studies in monitoring important physical processes in coral reef environments. When added to other airborne techniques, the opportunities for efficient monitoring of large reef systems may be expanded significantly.

  19. Estimating Energy Dissipation Due to Wave Breaking in the Surf Zone Using Infrared Imagery

    NASA Astrophysics Data System (ADS)

    Carini, Roxanne J.

    Wave breaking is the largest forcing mechanism in the surf zone. Therefore, quantifying energy dissipation due to wave breaking is important for improving models that seek to predict nearshore circulation, wave-current interactions, air-sea gas exchange, erosion and accretion of sediment, and storm surge. Wave energy dissipation is difficult to measure with in situ instruments, and even the most reliable estimates are limited to point measurements. Using remote sensing technologies, specifically infrared (IR) imagery, the high spatial and temporal variability of wave breaking may be sampled. Duncan (1981) proposed a model (D81) for dissipation on a wave-by-wave basis, based on wave slope and roller length, the crest-perpendicular length of the aerated region of a breaking wave. The wave roller is composed of active foam, which, in thermal IR images, appears brighter than the surrounding water and the residual foam, the foam left behind in the wake of a breaking wave. Using IR imagery taken during the Surf Zone Optics 2010 experiment at Duck, NC, and exploiting the distinct signature of active foam, a retrieval algorithm was developed to identify and extract breaking wave roller length. Roller length was then used to estimate dissipation rate via the D81 formulation. The D81 dissipation rate estimates compare reasonably to in situ dissipation estimates at a point. When the D81 estimates are compared to the bulk energy flux into the surf zone, it is found that wave breaking dissipates approximately 25-36% of the incoming wave energy. The D81 dissipation rate estimates also agree closely with those from a dissipation parameterization proposed by Janssen and Battjes (2007) (JB07) and commonly applied within larger nearshore circulation models. The JB07 formulation, however, requires additional physical parameters (wave height and water depth) that are often sparsely sampled and are difficult to attain from remote sensing alone. The power of the D81 formulation lies in

  20. Effects of bearing surfaces on lap joint energy dissipation

    SciTech Connect

    Kess, H. R.; Rosnow, N. J.; Sidle, B. C.

    2001-01-01

    Energy is dissipated in mechanical systems in several forms. The major contributor to damping in bolted lap joints is friction, and the level of damping is a function of stress distribution in the bearing surfaces. This study examines the effects of bearing surface configuration on lap joint energy dissipation. The examination is carried out through the analysis of experimental results in a nonlinear framework. Then finite element models are constructed in a nonlinear framework to simulate the results. The experimental data were analyzed using piecewise linear log decrement. Phenomenological and non-phenomenological mathematical models were used to simulate joint behavior. Numerical results of experiments and analyses are presented.

  1. Hemodynamic Energy Dissipation in the Cardiovascular System: Generalized Theoretical Analysis on Disease States

    PubMed Central

    Dasi, Lakshmi P.; Pekkan, Kerem; de Zelicourt, Diane; Sundareswaran, Kartik S.; Krishnankutty, Resmi; Delnido, Pedro J.; Yoganathan, Ajit P.

    2010-01-01

    Background We present a fundamental theoretical framework for analysis of energy dissipation in any component of the circulatory system and formulate the full energy budget for both venous and arterial circulations. New indices allowing disease-specific subject-to-subject comparisons and disease-to-disease hemodynamic evaluation (quantifying the hemodynamic severity of one vascular disease type to the other) are presented based on this formalism. Methods and Results Dimensional analysis of energy dissipation rate with respect to the human circulation shows that the rate of energy dissipation is inversely proportional to the square of the patient body surface area and directly proportional to the cube of cardiac output. This result verified the established formulae for energy loss in aortic stenosis that was solely derived through empirical clinical experience. Three new indices are introduced to evaluate more complex disease states: (1) circulation energy dissipation index (CEDI), (2) aortic valve energy dissipation index (AV-EDI), and (3) total cavopulmonary connection energy dissipation index (TCPCEDI). CEDI is based on the full energy budget of the circulation and is the proper measure of the work performed by the ventricle relative to the net energy spent in overcoming frictional forces. It is shown to be 4.01 ± 0.16 for healthy individuals and above 7.0 for patients with severe aortic stenosis. Application of CEDI index on single-ventricle venous physiology reveals that the surgically created Fontan circulation, which is indeed palliative, progressively degrades in hemodynamic efficiency with growth (p <0.001), with the net dissipation in a typical Fontan patient (Body surface area = 1.0 m2) being equivalent to that of an average case of severe aortic stenosis. AV-EDI is shown to be the proper index to gauge the hemodynamic severity of stenosed aortic valves as it accurately reflects energy loss. It is about 0.28 ± 0.12 for healthy human valves. Moderate

  2. Impact of nonlinear waves on the dissipation of internal tidal energy at a shelf break

    NASA Astrophysics Data System (ADS)

    Inall, Mark E.; Rippeth, Tom P.; Sherwin, Toby J.

    2000-04-01

    The vertical and temporal structure of the dissipation of turbulent kinetic energy within the internal tide at a location 5 km shoreward of the shelf break on the Malin Shelf has been determined using a combination of the free-falling light yo-yo profiler and acoustic doppler current profilers. Two distinct internal wave regimes were encountered: period I in which large-amplitude high-frequency nonlinear internal waves (NIWs) occurred (around neap tides) and period II in which the internal wave spectral continuum was not dominated by any particular frequency band (around spring tides). Empirical orthogonal function analysis shows that for the low-frequency waves, 76% of the variance was described by mode 1, rising to 95% for the high-frequency waves. During period I the dissipation and vertical mixing were characterized by the NIWs, and 70% of the dissipation occurred in the bottom boundary layer. During period II the depth-integrated dissipation was more evenly distributed throughout the tidal cycle, whereas vertical mixing was greatly enhanced during a single hour long episode of elevated thermocline dissipation coincident with weakened stratification. During both periods I and II ˜30% of the total measured dissipation occurred within the thermocline when averaged over 12.4 hours; the remainder occurred within the bottom boundary layer(BBL). Tidal average values for depth-integrated dissipation and vertical eddy diffusivity for period I (II) were 1.1×10-2 W m-2 (4.0×10-2 W m-2) and 5 cm2 s-1 (12 cm2 s-1), respectively. Decay rates and internal damping are discussed, and vertical heat fluxes are estimated. Observed dissipation rates are compared with a simple model for BBL dissipation.

  3. Modeling compaction-induced energy dissipation of granular HMX

    SciTech Connect

    Gonthier, K.A.; Menikoff, R.; Son, S.F.; Asay, B.W.

    1998-12-31

    A thermodynamically consistent model is developed for the compaction of granular solids. The model is an extension of the single phase limit of two-phase continuum models used to describe Deflagration-to-Detonation Transition (DDT) experiments. The focus is on the energetics and dissipation of the compaction process. Changes in volume fraction are partitioned into reversible and irreversible components. Unlike conventional DDT models, the model is applicable from the quasi-static to dynamic compaction regimes for elastic, plastic, or brittle materials. When applied to the compaction of granular HMX (a brittle material), the model predicts results commensurate with experiments including stress relaxation, hysteresis, and energy dissipation. The model provides a suitable starting point for the development of thermal energy localization sub-scale models based on compaction-induced dissipation.

  4. Energy dissipation and transport in carbon nanotubes and graphene

    NASA Astrophysics Data System (ADS)

    Vallabhaneni, Ajit Kumar

    The emergence of new carbon-based nanomaterials, like carbon nanotubes and graphene, in the past decade has provided new opportunities in many areas of scientific research. Despite their promise, the devices based on these materials are facing several challenges that need to be addressed to reap complete advantage of their extraordinary properties. In the current work, we studied the intrinsic scattering processes among the energy carriers and how it effects the energy dissipation and transport in these devices which would set the upper limit on their performance. In the first half of this work, the energy dissipation in carbon nanotube resonators is studied using molecular dynamics simulations. We studied various ways to calculate the quality factor (Q) which quantifies the efficiency of a resonator from the temporal response. We have also pointed out the drawbacks of the previously proposed methods which lead to incorrect conclusions on the temperature dependence of Q. A new method based on a band-pass filter is proposed which can be used to calculate the Q of any mode within the linear regime. Then, using the same method, the impact of the CNT size (length and diameter) on Q is studied and comparisons are made with classical theoretical models is made wherever applicable. A non-classical dependence on size is clearly observed for both primary axial and transverse mode vibrations emphasizing the significance of nanoscale phenomena like ballistic transport and size effects. Later the impact of higher-order modes on the Q is considered, where it was observed that Q decreases with increasing order of the mode. Finally, the effect of the presence of the defects and the challenges it poses in the design of NEMS devices is discussed. In the second half of the thesis, the energy transport in laser irradiated graphene and the effect of non-equilibrium between energy carriers on thermal conductivity measurements in experiments are discussed We primarily used a first

  5. Excess kinetic energy dissipation in materials

    SciTech Connect

    Corrales, Louis R.; Chartier, Alain; Devanathan, Ram

    2005-01-12

    Molecular dynamics computer simulations are used to study the evolution of thermal spikes arising from PKAs in zircon and copper. The effects of thermostats employed to remove energy from the system is characterized and compared to the case where kinetic energy is not removed from the system. Strong effects on the trajectory of the collision sequence is found for zircon, but in contrast, little effects are found for copper.

  6. Development of a model for baffle energy dissipation in liquid fueled rocket engines

    NASA Astrophysics Data System (ADS)

    Miller, Nathan A.

    In this thesis the energy dissipation from a combined hub and blade baffle structure in a combustion chamber of a liquid-fueled rocket engine is modeled and computed. An analytical model of the flow stabilization due to the effect of combined radial and hub blades was developed. The rate of energy dissipation of the baffle blades was computed using a corner-flow model that included unsteady flow separation and turbulence effects. For the inviscid portion of the flow field, a solution methodology was formulated using an eigenfunction expansion and a velocity potential matching technique. Parameters such as local velocity, elemental path length, effective viscosity, and local energy dissipation rate were computed as a function of the local angle alpha for a representative baffle blade, and compared to results predicted by the Baer-Mitchell blade dissipation model. The sensitivity of the model to the overall engine acoustic oscillation mode, blade length, and thickness was also computed and compared to previous results. Additional studies were performed to determine the sensitivity to input parameters such as the dimensionless turbulence coefficient, the location of the potential difference in the generation of the dividing streamline, the number of baffle blades and the size of the central hub. Stability computations of a test engine indicated that when the baffle length is increased, the baffles provide increased stabilization effects. The model predicts greatest dissipation for radial modes with a hub radius at approximately half the chamber's radius.

  7. Energy Dissipating Structures Produced by Walls in Two-Dimensional Flows at Vanishing Viscosity

    NASA Astrophysics Data System (ADS)

    Nguyen van Yen, Romain; Farge, Marie; Schneider, Kai

    2011-05-01

    We perform numerical experiments of a dipole crashing into a wall, a generic event in two-dimensional incompressible flows with solid boundaries. The Reynolds number (Re) is varied from 985 to 7880, and no-slip boundary conditions are approximated by Navier boundary conditions with a slip length proportional to Re-1. Energy dissipation is shown to first set up within a vorticity sheet of thickness proportional to Re-1 in the neighborhood of the wall, and to continue as this sheet rolls up into a spiral and detaches from the wall. The energy dissipation rate integrated over these regions appears to converge towards Re-independent values, indicating the existence of energy dissipating structures that persist in the vanishing viscosity limit.

  8. Energy Dissipation Mechanisms in 2D Meteor Impacts

    NASA Astrophysics Data System (ADS)

    Lane, Andrew; Daniels, Karen E.; Utter, Brian; Behringer, R. P.

    2003-11-01

    The morphology of meteor craters has historically been studied via static analysis, after the fact, of what are highly dynamic impact events. As such, there are long-standing questions about the means through which a meteor comes to rest and forms a crater. Using high speed video analysis on a 2D lab-scale system, we characterize the dynamics of a "meteor" impacting on a granular bed. In this case, the particles are made of a photoelastic material, so that it is possible to measure the instantaneous elastic energy stored in the bed. To understand the energy dissipation mechanisms involved in slowing the meteor, we track the kinetic, potential, and elastic energies associated with individual grains. Two initial and tentative findings from this work are: 1) Damped oscillations occur as the energy is dissipated within the granular material; and 2) The angle of impact strongly influences the dynamics and final state.

  9. Does the Rate of Collisionless Magnetic Reconnection Depend on the Dissipation Mechanism?

    NASA Technical Reports Server (NTRS)

    Aunai, Nicolas; Hesse, Michael; Black, Carrie; Evans, Rebekah; Kuznetsova, Maria

    2012-01-01

    The importance of the electron dissipation effect on the reconnection rate is investigated in the general case of asymmetric collisionless magnetic reconnection. Contrary to the standard collisionless reconnection model, it is found that the reconnection rate, and the macroscopic evolution of the reconnecting system, crucially depend on the nature of the dissipation mechanism and that the Hall effect alone is not able to sustain fast reconnection.

  10. Modeling Energy Dissipation in Slag-Covered Steel Baths in Steelmaking Ladles

    NASA Astrophysics Data System (ADS)

    Mazumdar, Dipak; Guthrie, Roderick I. L.

    2010-10-01

    Physical and mathematical modeling of energy dissipation phenomena in a gas-stirred ladle with, and without, an overlying second-phase liquid have been carried out at relatively low gas flow rate and specific energy input rate. Data from the literature are applied to infer the extent of energy dissipation caused by various mechanisms. An analysis reveals that bubble slippage and friction at the vessel walls dominate energy dissipation in such systems, each contributing roughly one third of the input energy. The remainder is dissipated because of turbulence in the bulk of the liquid, the formation of a spout, and interactions between the upper phase and the bulk liquid when an overlying liquid is present. Remarkably, the overlying liquid despite its small volume (~3 pct to 13 pct of the bulk), is found to dissipate about 10 pct of input energy. To understand the way the total input energy is dissipated via the overlying liquid, flow and mixing studies were carried out with different types of upper phase liquids. Tracer dispersion studies conducted with Petroleum ether as the overlying liquid show reasonably intense flow within the upper phase with no noticeable entrainment around the spout. In contrast, a thick layer of highly viscous upper phase liquid such as mustard oil shows extensive deformation of the upper phase around the spout, but no discernable motion within. However, remarkably, the thickness of the upper phase rather than its physical properties was found to influence bath hydrodynamics and mixing most significantly. A mechanism based on the rerouting of the surfacing plume and the attendant reversal of flow in the vicinity of the spout is advocated to explain energy dissipation caused by the overlying liquid. This finding is rationalized with our experimental results on composition adjustment with sealed argon bubbling (CAS) alloy addition procedures reported more than two decades ago, wherein flow reversal caused by the baffle in the immediate

  11. Energy spectrum, dissipation, and spatial structures in reduced Hall magnetohydrodynamic

    SciTech Connect

    Martin, L. N.; Dmitruk, P.; Gomez, D. O.

    2012-05-15

    We analyze the effect of the Hall term in the magnetohydrodynamic turbulence under a strong externally supported magnetic field, seeing how this changes the energy cascade, the characteristic scales of the flow, and the dynamics of global magnitudes, with particular interest in the dissipation. Numerical simulations of freely evolving three-dimensional reduced magnetohydrodynamics are performed, for different values of the Hall parameter (the ratio of the ion skin depth to the macroscopic scale of the turbulence) controlling the impact of the Hall term. The Hall effect modifies the transfer of energy across scales, slowing down the transfer of energy from the large scales up to the Hall scale (ion skin depth) and carrying faster the energy from the Hall scale to smaller scales. The final outcome is an effective shift of the dissipation scale to larger scales but also a development of smaller scales. Current sheets (fundamental structures for energy dissipation) are affected in two ways by increasing the Hall effect, with a widening but at the same time generating an internal structure within them. In the case where the Hall term is sufficiently intense, the current sheet is fully delocalized. The effect appears to reduce impulsive effects in the flow, making it less intermittent.

  12. Mechanochemistry for Shock Wave Energy Dissipation

    NASA Astrophysics Data System (ADS)

    Shaw, William; Ren, Yi; Su, Zhi; Moore, Jeffrey; Suslick, Kenneth; Dlott, Dana

    2015-06-01

    Using our laser-driven flyer-plate apparatus we have developed a technique for detecting mechanically driven chemical reactions that attenuate shock waves. In these experiments 75 μm laser-driven flyer-plates travel at speeds of up to 2.8 km/s. Photonic Doppler velocimetry is used to monitor both the flight speed and the motions of an embedded mirror behind the sample on the supporting substrate. Since the Hugoniot of the substrate is known, mirror motions can be converted into the transmitted shock wave flux and fluence through a sample. Flux shows the shock profile whereas fluence represents the total energy transferred per unit area, and both are measured as a function of sample thickness. Targets materials are micrograms of carefully engineered organic and inorganic compounds selected for their potential to undergo negative volume, endothermic reactions. In situ fluorescence measurements and a suite of post mortem analytical methods are used to detect molecular chemical reactions that occur due to impact.

  13. Energy dissipation during sublimation from porous media

    NASA Astrophysics Data System (ADS)

    Keller, H. U.; Skorov, Yu. V.

    2002-09-01

    Several physical processes during the sublimation from and inside porous media have been investigated in detail in a series our papers (Skorov et al., 1999, Icarus 140, 173, Skorov et al., 2001, Icarus 153, 180, Davidsson and Skorov, 2002, Icarus 156, 223, Davidsson and Skorov, 2002, Icarus, in press) in order to analyse the gas production of cometary nuclei . New features are the absorption of the irradiation within the uppermost layers of the pores (rather than on the surface), taking into account the gas pressure of the coma, and temperature dependent condensation and sublimation coefficients. Detailed kinetic calculations revealed deviations from the canonical gasdynamic models. We will summarize the impact of these new calculations on the physics of sublimation from a cometary nucleus. The absorption of the irradiation below the surface leads to a decrease of sublimation flux near the subsolar point but to an increase near the evening terminator and nightside of a rotating nucleus. More absorbed energy is available to be transferred into the interior of the nucleus. This effect and consequences for the development of cometary nuclei will be discussed.

  14. Energy dissipation of highly charged ions on Al oxide films.

    PubMed

    Lake, R E; Pomeroy, J M; Sosolik, C E

    2010-03-01

    Slow highly charged ions (HCIs) carry a large amount of potential energy that can be dissipated within femtoseconds upon interaction with a surface. HCI-insulator collisions result in high sputter yields and surface nanofeature creation due to strong coupling between the solid's electronic system and lattice. For HCIs interacting with Al oxide, combined experiments and theory indicate that defect mediated desorption can explain reasonably well preferential O atom removal and an observed threshold for sputtering due to potential energy. These studies have relied on measuring mass loss on the target substrate or probing craters left after desorption. Our approach is to extract highly charged ions onto the Al oxide barriers of metal-insulator-metal tunnel junctions and measure the increased conductance in a finished device after the irradiated interface is buried under the top metal layer. Such transport measurements constrain dynamic surface processes and provide large sets of statistics concerning the way individual HCI projectiles dissipate their potential energy. Results for Xe(q +) for q = 32, 40, 44 extracted onto Al oxide films are discussed in terms of postirradiation electrical device characteristics. Future work will elucidate the relationship between potential energy dissipation and tunneling phenomena through HCI modified oxides. PMID:21389384

  15. Energy dissipation of highly charged ions on Al oxide films

    NASA Astrophysics Data System (ADS)

    Lake, R. E.; Pomeroy, J. M.; Sosolik, C. E.

    2010-03-01

    Slow highly charged ions (HCIs) carry a large amount of potential energy that can be dissipated within femtoseconds upon interaction with a surface. HCI-insulator collisions result in high sputter yields and surface nanofeature creation due to strong coupling between the solid's electronic system and lattice. For HCIs interacting with Al oxide, combined experiments and theory indicate that defect mediated desorption can explain reasonably well preferential O atom removal and an observed threshold for sputtering due to potential energy. These studies have relied on measuring mass loss on the target substrate or probing craters left after desorption. Our approach is to extract highly charged ions onto the Al oxide barriers of metal-insulator-metal tunnel junctions and measure the increased conductance in a finished device after the irradiated interface is buried under the top metal layer. Such transport measurements constrain dynamic surface processes and provide large sets of statistics concerning the way individual HCI projectiles dissipate their potential energy. Results for Xeq + for q = 32, 40, 44 extracted onto Al oxide films are discussed in terms of postirradiation electrical device characteristics. Future work will elucidate the relationship between potential energy dissipation and tunneling phenomena through HCI modified oxides.

  16. Energy dissipation in small-scale shape-change dynamics.

    PubMed

    Gammaitoni, L

    2012-02-01

    Shape is an important feature of physical systems, although very seldom is it addressed in the framework of a quantitative description approach. In this paper we propose to interpret the shape of things as a physical manifestation of the content of information associated with each thing and show that a change of shape in a physical system is necessarily connected with a change of its entropy and thus involves energy. We estimate the amount of energy dissipated during a shape change and propose experimental tests to be performed in nanoscale systems to verify this prediction by measuring the expected dissipation in a few simple cases. Relevant implications in the design of future zero-power logic switches are discussed. PMID:22463138

  17. Landauer limit of energy dissipation in a magnetostrictive particle.

    PubMed

    Roy, Kuntal

    2014-12-10

    According to Landauer's principle, a minimum amount of energy proportional to temperature must be dissipated during the erasure of a classical bit of information compensating the entropy loss, thereby linking the information and thermodynamics. Here, we show that the Landauer limit of energy dissipation is achievable in a shape-anisotropic single-domain magnetostrictive nanomagnet having two mutually anti-parallel degenerate magnetization states that store a bit of information. We model the magnetization dynamics using the stochastic Landau-Lifshitz-Gilbert equation in the presence of thermal fluctuations and show that on average the Landauer bound is satisfied, i.e. it is in accordance with the generalized Landauer's principle for small systems with stochastic fluctuations. PMID:25379608

  18. Universal energy transport law for dissipative and diffusive phase transitions

    NASA Astrophysics Data System (ADS)

    Nadkarni, Neel; Daraio, Chiara; Abeyaratne, Rohan; Kochmann, Dennis M.

    2016-03-01

    We present a scaling law for the energy and speed of transition waves in dissipative and diffusive media. By considering uniform discrete lattices and continuous solids, we show that—for arbitrary highly nonlinear many-body interactions and multistable on-site potentials—the kinetic energy per density transported by a planar transition wave front always exhibits linear scaling with wave speed and the ratio of energy difference to interface mobility between the two phases. We confirm that the resulting linear superposition applies to highly nonlinear examples from particle to continuum mechanics.

  19. Tidal energy fluxes and dissipation on the European continental shelf

    NASA Astrophysics Data System (ADS)

    Davies, Alan M.; Kwong, Simon C. M.

    2000-09-01

    The spatial distribution of the energy flux, energy dissipation, current magnitude, and surface elevation amplitude of the major tidal constituents over the northwest European shelf are examined in detail. These distributions are obtained from the harmonic analysis of a 6 month three-dimensional simulation of 28 tidal constituents. The model currents are validated by a comparison of computed tidal harmonics against those derived from a harmonic analysis of up to 278 current time series. A similar comparison is performed for tidal elevations based on 257 tide gauges. Calculations show that for the most significant tidal constituents (e.g., M2, S2 and K2) there is a major energy flux in the deep water along the shelf edge off the northwest of Scotland, with some energy leaking onto the shelf and into the North Sea. A second source of energy is across the shelf edge at the southern end of the Celtic Sea, with this energy flux propagating into the Irish Sea and southern North Sea, where the majority of the energy is dissipation in the shallow regions. Significantly different distributions are found for the diurnal and shallow water constituents, and the spatial distributions of energy flux and dissipation of the various constituents are considered. The accuracy of separating tidal current harmonics using model data of less than a synodic period is examined with reference to the S2 and K2 tide. Calculations suggest that the accuracy of computed currents comparable to those obtained from observations can be obtained from an analysis of a 60 day period compared with the synodic period for S2 and K2 of 182 days, a significant saving in computer time.

  20. A New Eddy Dissipation Rate Formulation for the Terminal Area PBL Prediction System(TAPPS)

    NASA Technical Reports Server (NTRS)

    Charney, Joseph J.; Kaplan, Michael L.; Lin, Yuh-Lang; Pfeiffer, Karl D.

    2000-01-01

    The TAPPS employs the MASS model to produce mesoscale atmospheric simulations in support of the Wake Vortex project at Dallas Fort-Worth International Airport (DFW). A post-processing scheme uses the simulated three-dimensional atmospheric characteristics in the planetary boundary layer (PBL) to calculate the turbulence quantities most important to the dissipation of vortices: turbulent kinetic energy and eddy dissipation rate. TAPPS will ultimately be employed to enhance terminal area productivity by providing weather forecasts for the Aircraft Vortex Spacing System (AVOSS). The post-processing scheme utilizes experimental data and similarity theory to determine the turbulence quantities from the simulated horizontal wind field and stability characteristics of the atmosphere. Characteristic PBL quantities important to these calculations are determined based on formulations from the Blackadar PBL parameterization, which is regularly employed in the MASS model to account for PBL processes in mesoscale simulations. The TAPPS forecasts are verified against high-resolution observations of the horizontal winds at DFW. Statistical assessments of the error in the wind forecasts suggest that TAPPS captures the essential features of the horizontal winds with considerable skill. Additionally, the turbulence quantities produced by the post-processor are shown to compare favorably with corresponding tower observations.

  1. Computational model for noncontact atomic force microscopy: energy dissipation of cantilever.

    PubMed

    Senda, Yasuhiro; Blomqvist, Janne; Nieminen, Risto M

    2016-09-21

    We propose a computational model for noncontact atomic force microscopy (AFM) in which the atomic force between the cantilever tip and the surface is calculated using a molecular dynamics method, and the macroscopic motion of the cantilever is modeled by an oscillating spring. The movement of atoms in the tip and surface is connected with the oscillating spring using a recently developed coupling method. In this computational model, the oscillation energy is dissipated, as observed in AFM experiments. We attribute this dissipation to the hysteresis and nonconservative properties of the interatomic force that acts between the atoms in the tip and sample surface. The dissipation rate strongly depends on the parameters used in the computational model. PMID:27420398

  2. Computational model for noncontact atomic force microscopy: energy dissipation of cantilever

    NASA Astrophysics Data System (ADS)

    Senda, Yasuhiro; Blomqvist, Janne; Nieminen, Risto M.

    2016-09-01

    We propose a computational model for noncontact atomic force microscopy (AFM) in which the atomic force between the cantilever tip and the surface is calculated using a molecular dynamics method, and the macroscopic motion of the cantilever is modeled by an oscillating spring. The movement of atoms in the tip and surface is connected with the oscillating spring using a recently developed coupling method. In this computational model, the oscillation energy is dissipated, as observed in AFM experiments. We attribute this dissipation to the hysteresis and nonconservative properties of the interatomic force that acts between the atoms in the tip and sample surface. The dissipation rate strongly depends on the parameters used in the computational model.

  3. Statistics of the dissipated energy in driven diffusive systems.

    PubMed

    Lasanta, A; Hurtado, Pablo I; Prados, A

    2016-03-01

    Understanding the physics of non-equilibrium systems remains one of the major open questions in statistical physics. This problem can be partially handled by investigating macroscopic fluctuations of key magnitudes that characterise the non-equilibrium behaviour of the system of interest; their statistics, associated structures and microscopic origin. During the last years, some new general and powerful methods have appeared to delve into fluctuating behaviour that have drastically changed the way to address this problem in the realm of diffusive systems: macroscopic fluctuation theory (MFT) and a set of advanced computational techniques that make it possible to measure the probability of rare events. Notwithstanding, a satisfactory theory is still lacking in a particular case of intrinsically non-equilibrium systems, namely those in which energy is not conserved but dissipated continuously in the bulk of the system (e.g. granular media). In this work, we put forward the dissipated energy as a relevant quantity in this case and analyse in a pedagogical way its fluctuations, by making use of a suitable generalisation of macroscopic fluctuation theory to driven dissipative media. PMID:27007607

  4. The Southern Ocean FINEstructure project: Turbulent dissipation and mixing rates and mechanisms in a Southern Ocean mixing hotspot.

    NASA Astrophysics Data System (ADS)

    Waterman, S.; Naveira Garabato, A. C.; Polzin, K. L.

    2012-04-01

    The Southern Ocean FINE structure project is an observational field study designed to investigate various mechanisms of ocean mixing and the roles that they play in the larger-scale circulation in a standing meander of the Antarctic Circumpolar Current (ACC) north of the Kerguelen Plateau. The region is potentially of special significance to closing both the Southern Ocean overturning circulation and the momentum budget of ACC. By presenting both a large-scale topographic obstacle and small-scale topographic roughness in the path of multiple ACC jets, it is a likely site for both enhanced adiabatic and diabatic mixing processes. We present the first results of the project which relate to the rates and mechanisms of turbulent energy dissipation and turbulent mixing in the region. From the first-ever full-depth microstructure measurements in the Southern Ocean, we map the observed turbulent kinetic energy dissipation and diapycnal mixing rates in this mixing hotspot. We next explore some of the physical mechanisms that observations and theory suggest may underpin the observed distributions. This exploration leads us to a characterization of the internal wave field in the region, and a study of some of the processes related to its generation, evolution and eventual dissipation. Results show that the observed turbulent energy dissipation and mixing rates are highly spatially variable. Systematic structure with depth and proximity to rough topography suggest a link with the local internal wave field, which can be characterized as consisting of near-inertial waves propagating from the surface downwards and higher frequency internal waves potentially sourced at the bottom propagating upwards, both being modified by a background shear as they propagate. Turbulent dissipation is high in regions where internal wave energy is high, however, the rates of turbulent dissipation and mixing are, in key places, generally lower than anticipated from the observed internal wave energy

  5. The South Carolina Coastal Erosion Study: Wind Wave Energy Dissipation

    NASA Astrophysics Data System (ADS)

    Demir, H.; Work, P. A.; Voulgaris, G.

    2004-12-01

    As part of the South Carolina Coastal Erosion Study (SCCES) wave and current data were collected offshore of Myrtle Beach, SC for 2 months in 2001-02. This field measurement campaign was the second of a three-part experiment series. While the overall objective of the study is to describe the processes governing the circulation, wave propagation and sediment transport along the northern South Carolina coast, this presentation focuses on the wave energy dissipation over a heterogeneous seafloor over a distance of 6 km. The data were collected between November 9, 2001 and January 17, 2002. The instruments were placed along a transect crossing a large sand shoal in an area otherwise largely deprived of sand, at depths of 8 to 12 meters. The four instruments used, in order of decreasing distance from shore, were 600 and1200 KHz RDI ADCP's, a Nortek Aquadopp and a Sontek Argonaut-XR. Bathymetry and bottom characteristics such as depth and thickness of sand layer are available through USGS's coastal relief model and side scan surveys. Wind data are supplied by a large-scale numerical wind model. Its output is compared with wind data collected at Frying Pan Shoals buoy and at an anemometer placed at Spring Maid pier after the experiment. The SWAN wave model (Booij et al. 1999) was used to model the spectral wave transformation from the offshore buoy to the inner stations and to compare the observed wave energy dissipation to the available models. There was no extreme storm event during the deployment period. The maximum significant wave height observed was 1.6 meters at the offshore wave station, and the mean wave height was 0.8 meters. The mean period was between 5 and 7 seconds most of the time. Significant wave energy dissipation (up to 40% decrease in wave energy flux) across 6 km was observed. A shift of the spectral peak and a change in the spectral shape was observed in many events, which were not generally reproduced by the model. Sand and rock bottom

  6. Analytical Theory of the Destruction Terms in Dissipation Rate Transport Equations

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert; Zhou, Ye

    1996-01-01

    Modeled dissipation rate transport equations are often derived by invoking various hypotheses to close correlations in the corresponding exact equations. D. C. Leslie suggested that these models might be derived instead from Kraichnan's wavenumber space integrals for inertial range transport power. This suggestion is applied to the destruction terms in the dissipation rate equations for incompressible turbulence, buoyant turbulence, rotating incompressible turbulence, and rotating buoyant turbulence. Model constants like C(epsilon 2) are expressed as integrals; convergence of these integrals implies the absence of Reynolds number dependence in the corresponding destruction term. The dependence of C(epsilon 2) on rotation rate emerges naturally; sensitization of the modeled dissipation rate equation to rotation is not required. A buoyancy related effect which is absent in the exact transport equation for temperature variance dissipation, but which sometimes improves computational predictions, also arises naturally. Both the presence of this effect and the appropriate time scale in the modeled transport equation depend on whether Bolgiano or Kolmogorov inertial range scaling applies. A simple application of these methods leads to a preliminary, dissipation rate equation for rotating buoyant turbulence.

  7. GEM-CEDAR Study of Ionospheric Energy Input and Joule Dissipation

    NASA Technical Reports Server (NTRS)

    Rastaetter, Lutz; Kuznetsova, Maria M.; Shim, Jasoon

    2012-01-01

    We are studying ionospheric model performance for six events selected for the GEM-CEDAR modeling challenge. DMSP measurements of electric and magnetic fields are converted into Poynting Flux values that estimate the energy input into the ionosphere. Models generate rates of ionospheric Joule dissipation that are compared to the energy influx. Models include the ionosphere models CTIPe and Weimer and the ionospheric electrodynamic outputs of global magnetosphere models SWMF, LFM, and OpenGGCM. This study evaluates the model performance in terms of overall balance between energy influx and dissipation and tests the assumption that Joule dissipation occurs locally where electromagnetic energy flux enters the ionosphere. We present results in terms of skill scores now commonly used in metrics and validation studies and we can measure the agreement in terms of temporal and spatial distribution of dissipation (i.e, location of auroral activity) along passes of the DMSP satellite with the passes' proximity to the magnetic pole and solar wind activity level.

  8. Magnetization dynamics, Bennett clocking and associated energy dissipation in multiferroic logic.

    PubMed

    Fashami, Mohammad Salehi; Roy, Kuntal; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2011-04-15

    It has been recently shown that the magnetization of a multiferroic nanomagnet, consisting of a magnetostrictive layer elastically coupled to a piezoelectric layer, can be rotated by a large angle if a tiny voltage of a few tens of millivolts is applied to the piezoelectric layer. The potential generates stress in the magnetostrictive layer and rotates its magnetization by ~90° to implement Bennett clocking in nanomagnetic logic chains. Because of the small voltage needed, this clocking method is far more energy efficient than those that would employ spin transfer torque or magnetic fields to rotate the magnetization. In order to assess if such a clocking scheme can also be reasonably fast, we have studied the magnetization dynamics of a multiferroic logic chain with nearest-neighbor dipole coupling using the Landau-Lifshitz-Gilbert (LLG) equation. We find that clock rates of 2.5 GHz are feasible while still maintaining the exceptionally high energy efficiency. For this clock rate, the energy dissipated per clock cycle per bit flip is ~52,000 kT at room temperature in the clocking circuit for properly designed nanomagnets. Had we used spin transfer torque to clock at the same rate, the energy dissipated per clock cycle per bit flip would have been ~4 x 10⁸ kT, while with current transistor technology we would have expended ~10⁶ kT. For slower clock rates of 1 GHz, stress-based clocking will dissipate only ~200 kT of energy per clock cycle per bit flip, while spin transfer torque would dissipate about 10⁸ kT. This shows that multiferroic nanomagnetic logic, clocked with voltage-generated stress, can emerge as a very attractive technique for computing and signal processing since it can be several orders of magnitude more energy efficient than current technologies. PMID:21389584

  9. Magnetization dynamics, Bennett clocking and associated energy dissipation in multiferroic logic

    NASA Astrophysics Data System (ADS)

    Salehi Fashami, Mohammad; Roy, Kuntal; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2011-04-01

    It has been recently shown that the magnetization of a multiferroic nanomagnet, consisting of a magnetostrictive layer elastically coupled to a piezoelectric layer, can be rotated by a large angle if a tiny voltage of a few tens of millivolts is applied to the piezoelectric layer. The potential generates stress in the magnetostrictive layer and rotates its magnetization by ~ 90° to implement Bennett clocking in nanomagnetic logic chains. Because of the small voltage needed, this clocking method is far more energy efficient than those that would employ spin transfer torque or magnetic fields to rotate the magnetization. In order to assess if such a clocking scheme can also be reasonably fast, we have studied the magnetization dynamics of a multiferroic logic chain with nearest-neighbor dipole coupling using the Landau-Lifshitz-Gilbert (LLG) equation. We find that clock rates of 2.5 GHz are feasible while still maintaining the exceptionally high energy efficiency. For this clock rate, the energy dissipated per clock cycle per bit flip is ~ 52 000 kT at room temperature in the clocking circuit for properly designed nanomagnets. Had we used spin transfer torque to clock at the same rate, the energy dissipated per clock cycle per bit flip would have been ~ 4 × 108 kT, while with current transistor technology we would have expended ~ 106 kT. For slower clock rates of 1 GHz, stress-based clocking will dissipate only ~ 200 kT of energy per clock cycle per bit flip, while spin transfer torque would dissipate about 108 kT. This shows that multiferroic nanomagnetic logic, clocked with voltage-generated stress, can emerge as a very attractive technique for computing and signal processing since it can be several orders of magnitude more energy efficient than current technologies.

  10. Developing high energy dissipative soliton fiber lasers at 2 micron

    PubMed Central

    Huang, Chongyuan; Wang, Cong; Shang, Wei; Yang, Nan; Tang, Yulong; Xu, Jianqiu

    2015-01-01

    While the recent discovered new mode-locking mechanism - dissipative soliton - has successfully improved the pulse energy of 1 μm and 1.5 μm fiber lasers to tens of nanojoules, it is still hard to scale the pulse energy at 2 μm due to the anomalous dispersion of the gain fiber. After analyzing the intracavity pulse dynamics, we propose that the gain fiber should be condensed to short lengths in order to generate high energy pulse at 2 μm. Numerical simulation predicts the existence of stable 2 μm dissipative soliton solutions with pulse energy over 10 nJ, comparable to that achieved in the 1 μm and 1.5 μm regimes. Experimental operation confirms the validity of the proposal. These results will advance our understanding of mode-locked fiber lasers at different wavelengths and lay an important step in achieving high energy ultrafast laser pulses from anomalous dispersion gain media. PMID:26348563

  11. Developing high energy dissipative soliton fiber lasers at 2 micron

    NASA Astrophysics Data System (ADS)

    Huang, Chongyuan; Wang, Cong; Shang, Wei; Yang, Nan; Tang, Yulong; Xu, Jianqiu

    2015-09-01

    While the recent discovered new mode-locking mechanism - dissipative soliton - has successfully improved the pulse energy of 1 μm and 1.5 μm fiber lasers to tens of nanojoules, it is still hard to scale the pulse energy at 2 μm due to the anomalous dispersion of the gain fiber. After analyzing the intracavity pulse dynamics, we propose that the gain fiber should be condensed to short lengths in order to generate high energy pulse at 2 μm. Numerical simulation predicts the existence of stable 2 μm dissipative soliton solutions with pulse energy over 10 nJ, comparable to that achieved in the 1 μm and 1.5 μm regimes. Experimental operation confirms the validity of the proposal. These results will advance our understanding of mode-locked fiber lasers at different wavelengths and lay an important step in achieving high energy ultrafast laser pulses from anomalous dispersion gain media.

  12. Developing high energy dissipative soliton fiber lasers at 2 micron.

    PubMed

    Huang, Chongyuan; Wang, Cong; Shang, Wei; Yang, Nan; Tang, Yulong; Xu, Jianqiu

    2015-01-01

    While the recent discovered new mode-locking mechanism--dissipative soliton--has successfully improved the pulse energy of 1 μm and 1.5 μm fiber lasers to tens of nanojoules, it is still hard to scale the pulse energy at 2 μm due to the anomalous dispersion of the gain fiber. After analyzing the intracavity pulse dynamics, we propose that the gain fiber should be condensed to short lengths in order to generate high energy pulse at 2 μm. Numerical simulation predicts the existence of stable 2 μm dissipative soliton solutions with pulse energy over 10 nJ, comparable to that achieved in the 1 μm and 1.5 μm regimes. Experimental operation confirms the validity of the proposal. These results will advance our understanding of mode-locked fiber lasers at different wavelengths and lay an important step in achieving high energy ultrafast laser pulses from anomalous dispersion gain media. PMID:26348563

  13. Mechanisms of Surface Wave Energy Dissipation over a Fluid Mud Sediment Suspension

    NASA Astrophysics Data System (ADS)

    Traykovski, P.; Trowbridge, J. H.; Kineke, G. C.

    2014-12-01

    Field observations from the spring of 2008 on the Louisiana shelf were used to elucidate the mechanisms of wave energy dissipation over a muddy seafloor. After a period of high discharge from the Atchafalaya River acoustic measurements showed the presence of 20 cm thick mobile fluid mud layers during and after wave events. While total wave energy dissipation (D) was greatest during the high energy periods, these periods had relatively low normalized attenuation rates (Κ = Dissipation/Energy Flux). During declining wave energy conditions, as the fluid mud layer settled, the attenuation process became more efficient with high Κ and low D. The transition from high D and low Κ to high Κ and low D was caused by a transition from turbulent to laminar flow in the fluid mud layer as measured by a Pulse-coherent Doppler profiler. Measurements of the oscillatory boundary layer velocity profile in the fluid mud layer during laminar flow reveal a very thick wave boundary layer with curvature filling the entire fluid mud layer, suggesting a kinematic viscosity two to three orders of magnitude greater than clear water. This high viscosity is also consistent with a high wave attenuation rates measured by across shelf energy flux differences. The transition to turbulence was forced by instabilities on the lutocline, with wavelengths consistent with the dispersion relation for this two layer system. The measurements also provide new insight into the dynamics of wave supported turbidity flows during the transition from a laminar to turbulent fluid mud layer.

  14. Dissipation of 'dark energy' by cortex in knowledge retrieval.

    PubMed

    Capolupo, Antonio; Freeman, Walter J; Vitiello, Giuseppe

    2013-03-01

    We have devised a thermodynamic model of cortical neurodynamics expressed at the classical level by neural networks and at the quantum level by dissipative quantum field theory. Our model is based on features in the spatial images of cortical activity newly revealed by high-density electrode arrays. We have incorporated the mechanism and necessity for so-called dark energy in knowledge retrieval. We have extended the model first using the Carnot cycle to define our measures for energy, entropy and temperature, and then using the Rankine cycle to incorporate criticality and phase transitions. We describe the dynamics of two interactive fields of neural activity that express knowledge, one at high and the other at low energy density, and the two operators that create and annihilate the fields. We postulate that the extremely high density of energy sequestered briefly in cortical activity patterns can account for the vividness, richness of associations, and emotional intensity of memories recalled by stimuli. PMID:23333569

  15. Fluctuating systems under cyclic perturbations: Relation between energy dissipation and intrinsic relaxation processes

    NASA Astrophysics Data System (ADS)

    Camerin, Fabrizio; Frezzato, Diego

    2016-08-01

    This study focuses on fluctuating classical systems in contact with a thermal bath, and whose configurational energetics undergoes cyclic transformations due to interaction with external perturbing agents. Under the assumptions that the configurational dynamics is a stochastic Markov process in the overdamped regime and that the nonequilibrium configurational distribution remains close to the underlying equilibrium one, we derived an analytic approximation of the average dissipated energy per cycle in the asymptotic limit (i.e., after many cycles of perturbation). The energy dissipation is then readily translated into average entropy production, per cycle, in the environment. The accuracy of the approximation was tested by comparing the outcomes with the exact values obtained by stochastic simulations of a model case: a "particle on a ring" that fluctuates in a bistable potential perturbed in two different ways. As pointed out in previous studies on the stochastic resonance phenomenon, the dependence of the average dissipation on the perturbation period may unveil the inner spectrum of the system's fluctuation rates. In this respect, the analytical approximation presented here makes it possible to unveil the connection between average dissipation, intrinsic rates and modes of fluctuation of the system at the unperturbed equilibrium, and features of the perturbation itself (namely, the period of the cycle and the projections of the energy perturbation over the system's modes). The possibilities of employing the analytical results as a guide to devising and rationalizing a sort of "spectroscopic calorimetry" experiment, and of employing them in strategies aiming to optimize the system's features on the basis of a target average dissipation, are briefly discussed.

  16. Mixing and scalar dissipation rate statistics in a starting gas jet

    NASA Astrophysics Data System (ADS)

    Soulopoulos, N.; Hardalupas, Y.; Taylor, A. M. K. P.

    2015-12-01

    We quantify the temporal development of the mixing field of a starting jet by measuring the mixture fraction and the scalar dissipation rate and their statistics in an isothermal, impulsively started, gaseous jet. The scalar measurements are performed using planar laser induced fluorescence and, with appropriate processing of the resulting images, allow scalar dissipation rate measurements within 20%. The probability density functions of the mixture fraction, measured within a region of the order of 3 times the Batchelor length scale of the flow, are bimodal and skewed around a well-mixed radial location, which depends on the downstream distance and the time after the start of injection. The instantaneous distributions of the scalar dissipation rate reveal regions of high mixing at the jet periphery and at the developing vortex ring. The normalised probability density function (pdf) of the scalar dissipation rate at various flow positions and times after the start of injection has the same characteristic shape but differs from the usually suggested lognormal distribution at both low and high dissipation values; the same, also, holds true for the pdf conditioned on different values of the mixture fraction. The mean of the scalar dissipation rate conditional on mixture fraction shows a variation across the mixture fraction range, which differs between flow locations and times after the start of injection; however, at later times and for larger downstream distances the conditional mean between flow locations has similar distributions. Implications of the measurements for the auto-ignition of gaseous jets are examined and demonstrate that near the nozzle exit or at earlier times conditions are un-favourable for auto-ignition.

  17. Topology of energy fluxes in vortex dissipative soliton structures

    NASA Astrophysics Data System (ADS)

    Rosanov, N. N.; Fedorov, S. V.

    2016-07-01

    We consider and compare two-dimensional dissipative vortex solitons and their complexes in wide-aperture lasers and in exciton–polariton lasers; there is an incoherent pump and saturable absorption in both schemes presented. Our emphasis is on the study of the soliton’s internal structure. It can be revealed by the topology of energy fluxes and related energetic characteristics, because they are of primary importance for dissipative solitons representing the balance of energy input and output within the domains of field localization. For electromagnetic radiation in a nonlinear medium, it is difficult to separate energy between the field and the medium. The situation is simpler for paraxial beams and media with fast response (negligible dispersion), where we present the characterization of weak and strong soliton coupling based on the topology of spatial distributions of the Poynting vector and its divergence. Finally, we analyze the effect of nonresonant defocusing Kerr-like nonlinearity on vortex soliton existence and present different scenarios of soliton structural decay for sufficiently strong Kerr nonlinearity.

  18. Energy dissipation pathways in Photosystem 2 of the diatom, Phaeodactylum tricornutum, under high-light conditions.

    PubMed

    Kuzminov, Fedor I; Gorbunov, Maxim Y

    2016-02-01

    To prevent photooxidative damage under supraoptimal light, photosynthetic organisms evolved mechanisms to thermally dissipate excess absorbed energy, known as non-photochemical quenching (NPQ). Here we quantify NPQ-induced alterations in light-harvesting processes and photochemical reactions in Photosystem 2 (PS2) in the pennate diatom Phaeodactylum tricornutum. Using a combination of picosecond lifetime analysis and variable fluorescence technique, we examined the dynamics of NPQ activation upon transition from dark to high light. Our analysis revealed that NPQ activation starts with a 2-3-fold increase in the rate constant of non-radiative charge recombination in the reaction center (RC); however, this increase is compensated with a proportional increase in the rate constant of back reactions. The resulting alterations in photochemical processes in PS2 RC do not contribute directly to quenching of antenna excitons by the RC, but favor non-radiative dissipation pathways within the RC, reducing the yields of spin conversion of the RC chlorophyll to the triplet state. The NPQ-induced changes in the RC are followed by a gradual ~ 2.5-fold increase in the yields of thermal dissipation in light-harvesting complexes. Our data suggest that thermal dissipation in light-harvesting complexes is the major sink for NPQ; RCs are not directly involved in the NPQ process, but could contribute to photoprotection via reduction in the probability of (3)Chl formation. PMID:26220363

  19. Energy dissipation in intercalated carbon nanotube forests with metal layers

    NASA Astrophysics Data System (ADS)

    Boddu, Veera M.; Brenner, Matthew W.

    2016-02-01

    Vertically aligned carbon nanotube (CNT) forests were synthesized to study their quasi-static mechanical properties in a layered configuration with metallization. The top and bottom surfaces of CNT forests were metalized with Ag, Fe, and In using paste, sputtering, and thermal evaporation, respectively. Stacks of one, two, and three layers of these forests were assembled and compressed to measure their mechanical properties. The samples were strain limited to 0.7, and the results indicate that energy dissipation is approximately linear with respect to the number of layers and relatively independent of metal type. The energy per unit volume was approximately the same for all samples. Successive stacking of CNT forests reduces local buckling events, which is enhanced with a thick Ag deposition on the CNT forest surface. Young's modulus was also observed to increase as the number of layers was increased. These results are useful in the design of composite materials for high energy absorption and high stiffness applications.

  20. Spectral wave flow attenuation within submerged canopies: Implications for wave energy dissipation

    NASA Astrophysics Data System (ADS)

    Lowe, Ryan J.; Falter, James L.; Koseff, Jeffrey R.; Monismith, Stephen G.; Atkinson, Marlin J.

    2007-05-01

    Communities of benthic organisms can form very rough surfaces (canopies) on the seafloor. Previous studies have shown that an oscillatory flow induced by monochromatic surface waves will drive more flow inside a canopy than a comparable unidirectional current. This paper builds on these previous studies by investigating how wave energy is attenuated within canopies under spectral wave conditions, or random wave fields defined by many frequencies. A theoretical model is first developed to predict how flow attenuation within a canopy varies among the different wave components and predicts that shorter-period components will generally be more effective at driving flow within a canopy than longer-period components. To investigate the model performance, a field experiment was conducted on a shallow reef flat in which flow was measured both inside and above a model canopy array. Results confirm that longer-period components in the spectrum are significantly more attenuated than shorter-period components, in good agreement with the model prediction. This paper concludes by showing that the rate at which wave energy is dissipated by a canopy is closely linked to the flow structure within the canopy. Under spectral wave conditions, wave energy within a model canopy array is dissipated at a greater rate among the shorter-period wave components. These observations are consistent with previous observations of how wave energy is dissipated by the bottom roughness of a coral reef.

  1. Energy transfer in systems with random forcing and nonlinear dissipation

    NASA Astrophysics Data System (ADS)

    Pignol, Ricardo Jorge

    The purpose of this thesis is to study energy transfer in nonlinear systems. In the first part, I focus on a model of two nonlinearly coupled (complex) oscillators subject to stochastic forcing and nonlinear dissipation. This model arises from isolating an individual resonant quartet in a general dispersive system, and reducing it further by exploiting some of the system's symmetries. It turns out that the reduced model exhibits a rich and complex behavior encountered in far larger systems, with two qualitatively distinct regimes arising as one varies the system's single non-dimensional parameter: one that can be characterized as a perturbation of thermal equilibrium, and another highly constrained state, with phase and amplitude locking , and singular invariant measures. The relative simplicity of the reduced model allows a thorough numerical and theoretical treatment (including a closed expression for the system's invariant measures) that furnishes valuable insight on the energy transfer process in systems with much higher dimensionality. In the second part, the damped oscillator is replaced by an individual mode of the inviscid Burgers equation. Here, the dissipation occurs through shocks. Despite the complexity resulting from the inclusion of a nonlinear partial differential equation, I show that much of this system's behavior can be inferred precisely from a reduction to one of the cases studied in the first part.

  2. Global vs local energy dissipation: The energy cycle of the turbulent von Kármán flow

    NASA Astrophysics Data System (ADS)

    Kuzzay, Denis; Faranda, Davide; Dubrulle, Bérengère

    2015-07-01

    In this paper, we investigate the relations between global and local energy transfers in a turbulent von Kármán flow. The goal is to understand how and where energy is dissipated in such a flow and to reconstruct the energy cycle in an experimental device where local as well as global quantities can be measured. In order to do so, we use particle image velocimetry (PIV) measurements and we model the Reynolds stress tensor to take subgrid scales into account. This procedure involves a free parameter that is calibrated using angular momentum balance. We then estimate the local and global mean injected and dissipated powers for several types of impellers, for various Reynolds numbers, and for various flow topologies. These PIV estimates are then compared with direct injected power estimates provided by torque measurements at the impellers. The agreement between PIV estimates and direct measurements depends on the flow topology. In symmetric situations, we are able to capture up to 90% of the actual global energy dissipation rate. However, our results become increasingly inaccurate as the shear layer responsible for most of the dissipation approaches one of the impellers and cannot be resolved by our PIV setup. Finally, we show that a very good agreement between PIV estimates and direct measurements is obtained using a new method based on the work of Duchon and Robert ["Inertial energy dissipation for weak solutions of incompressible Euler and Navier-Stokes equations," Nonlinearity 13, 249-225 (2000)] which generalizes the Kármán-Howarth equation to nonisotropic, nonhomogeneous flows. This method provides parameter-free estimates of the energy dissipation rate as long as the smallest resolved scale lies in the inertial range. These results are used to evidence a well-defined stationary energy cycle within the flow in which most of the energy is injected at the top and bottom impellers and dissipated within the shear layer. The influence of the mean flow geometry

  3. Log-stable law of energy dissipation as a framework of turbulence intermittency.

    PubMed

    Mouri, Hideaki

    2015-03-01

    To describe the small-scale intermittency of turbulence, a self-similarity is assumed for the probability density function of a logarithm of the rate of energy dissipation smoothed over a length scale among those in the inertial range. The result is an extension of Kolmogorov's classical theory [A. N. Kolmogorov, Dokl. Akad. Nauk SSSR 30, 301 (1941)], i.e., a one-parameter framework where the logarithm obeys some stable distribution. Scaling laws are obtained for the dissipation rate and for the two-point velocity difference. They are consistent with theoretical constraints and with the observed scaling laws. Also discussed is the physics that determines the value of the parameter. PMID:25871212

  4. Log-stable law of energy dissipation as a framework of turbulence intermittency

    NASA Astrophysics Data System (ADS)

    Mouri, Hideaki

    2015-03-01

    To describe the small-scale intermittency of turbulence, a self-similarity is assumed for the probability density function of a logarithm of the rate of energy dissipation smoothed over a length scale among those in the inertial range. The result is an extension of Kolmogorov's classical theory [A. N. Kolmogorov, Dokl. Akad. Nauk SSSR 30, 301 (1941)], i.e., a one-parameter framework where the logarithm obeys some stable distribution. Scaling laws are obtained for the dissipation rate and for the two-point velocity difference. They are consistent with theoretical constraints and with the observed scaling laws. Also discussed is the physics that determines the value of the parameter.

  5. Energy transfer and dissipation in forced isotropic turbulence

    NASA Astrophysics Data System (ADS)

    McComb, W. D.; Berera, A.; Yoffe, S. R.; Linkmann, M. F.

    2015-04-01

    A model for the Reynolds-number dependence of the dimensionless dissipation rate Cɛ was derived from the dimensionless Kármán-Howarth equation, resulting in Cɛ=Cɛ ,∞+C /RL+O (1 /RL2) , where RL is the integral scale Reynolds number. The coefficients C and Cɛ ,∞ arise from asymptotic expansions of the dimensionless second- and third-order structure functions. This theoretical work was supplemented by direct numerical simulations (DNSs) of forced isotropic turbulence for integral scale Reynolds numbers up to RL=5875 (Rλ=435 ), which were used to establish that the decay of dimensionless dissipation with increasing Reynolds number took the form of a power law RLn with exponent value n =-1.000 ±0.009 and that this decay of Cɛ was actually due to the increase in the Taylor surrogate U3/L . The model equation was fitted to data from the DNS, which resulted in the value C =18.9 ±1.3 and in an asymptotic value for Cɛ in the infinite Reynolds-number limit of Cɛ ,∞=0.468 ±0.006 .

  6. Energy transfer and dissipation in forced isotropic turbulence.

    PubMed

    McComb, W D; Berera, A; Yoffe, S R; Linkmann, M F

    2015-04-01

    A model for the Reynolds-number dependence of the dimensionless dissipation rate C(ɛ) was derived from the dimensionless Kármán-Howarth equation, resulting in C(ɛ)=C(ɛ,∞)+C/R(L)+O(1/R(L)(2)), where R(L) is the integral scale Reynolds number. The coefficients C and C(ɛ,∞) arise from asymptotic expansions of the dimensionless second- and third-order structure functions. This theoretical work was supplemented by direct numerical simulations (DNSs) of forced isotropic turbulence for integral scale Reynolds numbers up to R(L)=5875 (R(λ)=435), which were used to establish that the decay of dimensionless dissipation with increasing Reynolds number took the form of a power law R(L)(n) with exponent value n=-1.000±0.009 and that this decay of C(ɛ) was actually due to the increase in the Taylor surrogate U(3)/L. The model equation was fitted to data from the DNS, which resulted in the value C=18.9±1.3 and in an asymptotic value for C(ɛ) in the infinite Reynolds-number limit of C(ɛ,∞)=0.468±0.006. PMID:25974586

  7. A modal approach to modeling spatially distributed vibration energy dissipation.

    SciTech Connect

    Segalman, Daniel Joseph

    2010-08-01

    The nonlinear behavior of mechanical joints is a confounding element in modeling the dynamic response of structures. Though there has been some progress in recent years in modeling individual joints, modeling the full structure with myriad frictional interfaces has remained an obstinate challenge. A strategy is suggested for structural dynamics modeling that can account for the combined effect of interface friction distributed spatially about the structure. This approach accommodates the following observations: (1) At small to modest amplitudes, the nonlinearity of jointed structures is manifest primarily in the energy dissipation - visible as vibration damping; (2) Correspondingly, measured vibration modes do not change significantly with amplitude; and (3) Significant coupling among the modes does not appear to result at modest amplitudes. The mathematical approach presented here postulates the preservation of linear modes and invests all the nonlinearity in the evolution of the modal coordinates. The constitutive form selected is one that works well in modeling spatially discrete joints. When compared against a mathematical truth model, the distributed dissipation approximation performs well.

  8. Assessing the numerical dissipation rate and viscosity in CFD simulations of fluid flows

    NASA Astrophysics Data System (ADS)

    Schranner, F. S.; Domaradzki, J. A.; Hickel, S.; Adams, N. A.

    2014-11-01

    We describe a method for quantifying the effective numerical dissipation rate and the effective numerical viscosity in Computational Fluid Dynamics simulations. Differently from the previous approach that was formulated in spectral space, the proposed method is developed in a physical-space representation and allows for determining numerical dissipation rates and viscosities locally, i.e., at the individual cell level or for arbitrary subdomains of the computational domain. The method is self-contained using only results produced by the Navier-Stokes solver being investigated. Since no extraneous information is required, the method is suitable for a straightforward quantification of the numerical dissipation as a post-processing step. We demonstrate the method's capabilities on the example of implicit large-eddy simulations of three-dimensional Taylor-Green vortex flows that exhibit laminar, transitional, and turbulent flow behavior at different stages of time evolution. For validation, we compare the numerical dissipation rate obtained using this method with exact reference data obtained with an accurate, spectral-space approach. Supported by Deutsche Forschungsgemeinschaft and Alexander von Humboldt Foundation.

  9. Dissipative Field Theory

    SciTech Connect

    Kheirandish, F.; Amooshahi, M.

    2008-11-18

    Quantum field theory of a damped vibrating string as the simplest dissipative scalar field theory is investigated by introducing a minimal coupling method. The rate of energy flowing between the system and its environment is obtained.

  10. Energy dissipation in micron- and submicron-thick single crystal diamond mechanical resonators

    NASA Astrophysics Data System (ADS)

    Liao, Meiyong; Toda, Masaya; Sang, Liwen; Hishita, Shunichi; Tanaka, Shuji; Koide, Yasuo

    2014-12-01

    The authors report the resonance frequency and the energy dissipation of single crystal diamond cantilevers with different dimensions, which were fabricated by ion implantation assisted technique. The resonance frequency well followed the inverse power law relationship with the length of the cantilevers and exhibited a high reproducibility with varying the dimensions. The energy dissipation decreased with increasing the cantilever length and saturated or reduced at a certain value. For the shorter cantilevers, clamping loss governed the energy dissipation. As the cantilever length increased to a certain value, defects relaxation or surface effect became dominant. The possible origins for these energy dissipations were discussed.

  11. The series elastic shock absorber: tendon elasticity modulates energy dissipation by muscle during burst deceleration

    PubMed Central

    Konow, Nicolai; Roberts, Thomas J.

    2015-01-01

    During downhill running, manoeuvring, negotiation of obstacles and landings from a jump, mechanical energy is dissipated via active lengthening of limb muscles. Tendon compliance provides a ‘shock-absorber’ mechanism that rapidly absorbs mechanical energy and releases it more slowly as the recoil of the tendon does work to stretch muscle fascicles. By lowering the rate of muscular energy dissipation, tendon compliance likely reduces the risk of muscle injury that can result from rapid and forceful muscle lengthening. Here, we examine how muscle–tendon mechanics are modulated in response to changes in demand for energy dissipation. We measured lateral gastrocnemius (LG) muscle activity, force and fascicle length, as well as leg joint kinematics and ground-reaction force, as turkeys performed drop-landings from three heights (0.5–1.5 m centre-of-mass elevation). Negative work by the LG muscle–tendon unit during landing increased with drop height, mainly owing to greater muscle recruitment and force as drop height increased. Although muscle strain did not increase with landing height, ankle flexion increased owing to increased tendon strain at higher muscle forces. Measurements of the length–tension relationship of the muscle indicated that the muscle reached peak force at shorter and likely safer operating lengths as drop height increased. Our results indicate that tendon compliance is important to the modulation of energy dissipation by active muscle with changes in demand and may provide a mechanism for rapid adjustment of function during deceleration tasks of unpredictable intensity. PMID:25716796

  12. Spin reorientation of a nonsymmetric body with energy dissipation

    NASA Technical Reports Server (NTRS)

    Cenker, R. J.

    1973-01-01

    Stable rotating semi-rigid bodies were demonstrated analytically, and verified in flights such as Explorer 1 and ATS-5 satellites. The problem arises from the two potential orientations which the final spin vector can take after large angle reorientation from minor to major axis, i.e., along the positive or negative axis of the maximum inertia. Reorientation of a satellite initially spinning about the minor axis using an energy dissipation device may require that the final spin orientation be controlled. Examples of possible applications are the Apogee Motor Assembly with Paired Satellites (AMAPS) configuration, where proper orientation of the thruster is required; and reorientation of ATS-5, where the spin sensitive nature of the despin device (yo-yo mechanism) requires that the final spin vector point is a specified direction.

  13. Friction-based energy dissipation unit for circuit breaker

    SciTech Connect

    Kar, R.; Rainer, J.H.

    1995-12-31

    This paper describes a friction-based energy dissipation unit (EDU) that has been designed to introduce supplemental damping into a circuit breaker. The brittle porcelain insulator posts of a 330 kV SF6 breaker were thus subjected to reduced forces from a design earthquake specified to have a peak ground acceleration of 1.05 g. Pull and release tests were performed to determine the dynamic properties, i.e., natural frequency, damping ratio, and mode shapes. Calculations of response of the circuit breaker to the 1940 El Centro N-S component shows that the EDU reduces the bending moment at the base of the porcelain column by a factor of three.

  14. Plastic deformation enabled energy dissipation in a bionanowire structured armor.

    PubMed

    Li, Haoze; Yue, Yonghai; Han, Xiaodong; Li, Xiaodong

    2014-05-14

    It has been challenging to simultaneously achieve high strength and toughness in engineered materials because of the trade-off relation between the two distinct properties. Nature, however, has elegantly solved this problem. Seashells, commonly referred to as nature's armors, exhibit an unusual resilience against predatory attacks. In this letter, we report an unexpected phenomenon in a bionanowire structured armor-conch shell where the shell's basic building blocks, i.e., the third-order lamellae, exhibit an exceptional plasticity with a maximum strain of 0.7% upon mechanical loading. We attribute such a plastic deformation behavior to the lamella's unique nanoparticle-biopolymer architecture, in which the biopolymer mediates the rotation of aragonite nanoparticles in response to external attacks. We also found that electron beam irradiation facilitates the lamella's plasticity. These findings advance our understanding of seashell's energy dissipating strategy and provide new design guidelines for developing high performance bioinspired materials and sensors. PMID:24745628

  15. Interfacial energy dissipation in a cellulose nanowhisker composite

    NASA Astrophysics Data System (ADS)

    Rusli, Rafeadah; Eichhorn, Stephen J.

    2011-08-01

    Cyclic tensile and compressive deformation is applied to cellulose nanowhisker-epoxy resin based model nanocomposites. The molecular deformation of the cellulose nanowhiskers within the epoxy resin matrix is followed using a Raman spectroscopy technique, whereby shifts in the position of a band located at ~ 1095 cm - 1 are shown to correlate directly with a breakdown in the interfaces between the resin and the nanowhiskers and between nanowhiskers themselves. A theoretical model is used to determine the dissipation of energy at the interfaces between whiskers and at the whisker-matrix interface. This approach is shown to be useful for interpreting the local micromechanics of these materials by providing a quantitative measure of the quality of the interface.

  16. Polarization swings reveal magnetic energy dissipation in blazars

    SciTech Connect

    Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; Guo, Fan; Li, Hui

    2015-04-30

    The polarization signatures of blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, large (≳ 180°) polarization angle swings are observed. We suggest that such phenomena can be interpreted as arising from light-travel-time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability, and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change in its polarization signatures. This unprecedented combination of spectral, variability, and polarization information in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic-field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.

  17. Polarization swings reveal magnetic energy dissipation in blazars

    DOE PAGESBeta

    Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; Guo, Fan; Li, Hui

    2015-04-30

    The polarization signatures of blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, large (≳ 180°) polarization angle swings are observed. We suggest that such phenomena can be interpreted as arising from light-travel-time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability, and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change in its polarization signatures. This unprecedented combination of spectral, variability, and polarization informationmore » in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic-field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.« less

  18. Scaling exponents for energy transport and dissipation in binary vibro-fluidized granular beds

    NASA Astrophysics Data System (ADS)

    Wildman, R. D.; Huntley, J. M.

    2003-10-01

    A binary three-dimensional highly fluidized vibrated granular bed has been investigated for the first time using positron emission particle tracking. Packing fraction distributions and granular temperature profiles are calculated for each species and the response to changes in the amplitude of vibration and the number of grains are determined. It is found that the binary system, though supporting two separate granular temperature profiles, responds to changes in vibration velocity in a broadly similar fashion to a monosized granular bed. This assessment is supported by an analysis of the steady-state energy input/dissipation rate balance equation, which contains terms describing the collisional dissipation between like and unlike grains. However, this theory also suggests that if one fraction dominates over another then the two phases could show different scaling relationships between the granular temperature of each phase and the base peak velocity.

  19. Mechanisms of surface wave energy dissipation over a high-concentration sediment suspension

    NASA Astrophysics Data System (ADS)

    Traykovski, Peter; Trowbridge, John; Kineke, Gail

    2015-03-01

    Field observations from the spring of 2008 on the Louisiana shelf were used to elucidate the mechanisms of wave energy dissipation over a muddy seafloor. After a period of high discharge from the Atchafalaya River, acoustic measurements showed the presence of 20 cm thick mobile fluid-mud layers during and after wave events. While total wave energy dissipation (D) was greatest during the high energy periods, these periods had relatively low normalized attenuation rates (κ = Dissipation/Energy Flux). During declining wave-energy conditions, as the fluid-mud layer settled, the attenuation process became more efficient with high κ and low D. The transition from high D and low κ to high κ and low D was caused by a transition from turbulent to laminar flow in the fluid-mud layer as measured by a Pulse-coherent Doppler profiler. Measurements of the oscillatory boundary layer velocity profile in the fluid-mud layer during laminar flow reveal a very thick wave boundary layer with curvature filling the entire fluid-mud layer, suggesting a kinematic viscosity 2-3 orders of magnitude greater than that of clear water. This high viscosity is also consistent with a high wave-attenuation rates measured by across-shelf energy flux differences. The transition to turbulence was forced by instabilities on the lutocline, with wavelengths consistent with the dispersion relation for this two-layer system. The measurements also provide new insight into the dynamics of wave-supported turbidity flows during the transition from a laminar to turbulent fluid-mud layer.

  20. G: Fracture energy, friction and dissipation in earthquakes

    NASA Astrophysics Data System (ADS)

    Nielsen, S.; Spagnuolo, E.; Violay, M.; Smith, S.; Di Toro, G.; Bistacchi, A.

    2016-03-01

    Recent estimates of fracture energy G ' in earthquakes show a power-law dependence with slip u which can be summarized as G ' ∝ u a where a is a positive real slightly larger than one. For cracks with sliding friction, fracture energy can be equated to G f : the post-failure integral of the dynamic weakening curve. If the dominant dissipative process in earthquakes is friction, G ' and G f should be comparable and show a similar scaling with slip. We test this hypothesis by analyzing experiments performed on various cohesive and non-cohesive rock types, under wet and dry conditions, with imposed deformation typical of seismic slip (normal stress of tens of MPa, target slip velocity > 1 m/s and fast accelerations ≈ 6.5 m/s2). The resulting fracture energy G f is similar to the seismological estimates, with G f and G ' being comparable over most of the slip range. However, G f appears to saturate after several meters of slip, while in most of the reported earthquake sequences, G ' appears to increase further and surpasses G f at large magnitudes. We analyze several possible causes of such discrepancy, in particular, additional off-fault damage in large natural earthquakes.

  1. Mapping Closure Approximation to Conditional Dissipation Rate for Turbulent Scalar Mixing

    NASA Technical Reports Server (NTRS)

    He, Gouwei; Rubinstein, R.

    2000-01-01

    A novel mapping closure approximation (MCA) technique is developed to construct a model for the conditional dissipation rate (CDR) of a scalar in homogeneous turbulence. It is shown that the CDR model from amplitude mapping closure is incorrect in asymptotic behavior for unsymmetric binary mixing. The correct asymptotic behavior can be described by the CDR model formulated by the MCA technique. The MCA approach is outlined for constructing successive approximation to probability density function (PDF) and conditional moment.

  2. Evaluation of leaf energy dissipation by the Photochemical Reflectance

    NASA Astrophysics Data System (ADS)

    Raddi, S.; Magnani, F.

    Starting from the early paper by Heber (1969), several studies have demonstrated a subtle shift in leaf spectroscopic characteristics (both absorbance and reflectance) in response to rapid changes in environmental conditions. More recent work, briefly reviewed here, has also demonstrated the existence of two components in the maked peak centered at 505-540 nm: an irreversible component, attributed to the interconversion of leaf xanthophylls, and a reversible component at slightly longer wavelengths, resulting from conformational changes induced by the buildup of a pH gradient across the thylakoid membrane associated with photosynthetic electron transport. Both processes (xanthophyll de-epoxidation and conformational changes) are known to contribute to the dissipation of excess energy in Photosystem II (PSII). Leaf spectroscopy could therefore provide a powerful non-invasive tool for the determination of leaf photosynthetic processes. This led to the development of the normalized spectral index PRI (Photochemical Reflectance Index; Gamon, Penuelas &Field 1992; Gamon, Serrano &Surfus 1997), which relates the functional signal at 531 nm to a reference signal at 570 nm. The index has been found to track diurnal changes in xanthophyll de-epoxidation state, radiation use efficiency and fluorescence in response to light, both at the leaf and more recently at the canopy level. A common relationship has also beenreported across species and functional types, although such a generality has not always been confirmed. Recent reports (Stylinski et al. 2000) have also hinted of a possible link between PRI and leaf photosynthetic potential, possibly through the correlation between xanthophyll content and electron transport machinery in the chloroplast. Such a link, if confirmed, could prove very useful for the remote sensing and modelling ofvegetation. Some of these open questions were addressed in the present study. The correlation between leaf function and reflectance was

  3. Elliptic-blending second-moment turbulence closure using an algebraic anisotropic dissipation rate tensor model

    NASA Astrophysics Data System (ADS)

    Shin, Jong-Keun; Seo, Jeong-Sik; Choi, Young-Don

    2009-06-01

    This study describes the amendment of an algebraic anisotropic dissipation rate model (ADRM) and its application to various turbulent flows to test the model's performance. Modeling anisotropies for the turbulence dissipation rate is considered by an analysis of the exact transport equation for the dissipation rate tensor. The second-moment closure, which is based on the explicit amended ADRM, is proposed and it is closely linked to the elliptic-blending model that is used for the prediction of Reynolds stresses. To develop and calibrate the present elliptic-blending second-moment closure that uses the amended ADRM, firstly, the distributions of both the mean velocity and Reynolds stress are solved for flows in a fully developed non-rotating channel and a straight square duct. And then, the fully developed turbulent flows in a rotating channel and a rotating straight square duct are predicted to test the ability of the explicit amended ADRM that is combined with the rotation effect. The prediction results are directly compared with the DNS and the large-eddy simulation (LES) to assess the performance of the new model predictions and to show their reasonable agreement with the DNS and LES data for all the flow fields that are analyzed for the present study. This paper is a modified version of the original article from the Proceedings of the 5th International Symposium on Turbulence and Shear Flow Phenomena held in Munich, Germany on 27-29 August 2007.

  4. Two-point, high-repetition-rate Rayleigh thermometry in flames: techniques to correct for apparent dissipation induced by noise.

    PubMed

    Wang, G H; Clemens, N T; Varghese, P L

    2005-11-01

    High-repetition-rate, two-point Rayleigh thermometry is used to measure the thermal dissipation in turbulent nonpremixed jet flames. Scalar-dissipation measurements are very important in turbulent combustion but are often strongly influenced by noise effects. Dissipation is proportional to the squared gradient of the scalar, and noise produces an "apparent dissipation" that can dominate the measured dissipation, particularly at high resolution. Two independent techniques are presented that enable correction for the apparent thermal dissipation, provided that the smallest spatial scales are resolved. A model for shot-noise-limited data is developed that predicts the magnitude of the apparent dissipation at any measurement location and gives the minimum value of the apparent dissipation for measurements that are not shot-noise limited. These techniques are applied to the Rayleigh thermometry data, and they are shown to be largely self-consistent and consistent with theoretical expectations. The apparent dissipation is significantly larger than the true dissipation, demonstrating the importance of data correction in this noise-limited, fully spatially resolved regime. PMID:16270563

  5. Energy conservation in dissipative processes: Teacher expectations and strategies associated with imperceptible thermal energy

    NASA Astrophysics Data System (ADS)

    Daane, Abigail R.; McKagan, Sarah B.; Vokos, Stamatis; Scherr, Rachel E.

    2015-06-01

    Research has demonstrated that many students and some teachers do not consistently apply the conservation of energy principle when analyzing mechanical scenarios. In observing elementary and secondary teachers engaged in learning activities that require tracking and conserving energy, we find that challenges to energy conservation often arise in dissipative scenarios in which kinetic energy transforms into thermal energy (e.g., a ball rolls to a stop). We find that teachers expect that when they can see the motion associated with kinetic energy, they should be able to perceive the warmth associated with thermal energy. Their expectations are violated when the warmth produced is imperceptible. In these cases, teachers reject the idea that the kinetic energy transforms to thermal energy. Our observations suggest that apparent difficulties with energy conservation may have their roots in a strong and appropriate association between forms of energy and their perceptible indicators. We see teachers resolve these challenges by relating the original scenario to an exaggerated version in which the dissipated thermal energy is associated with perceptible warmth. Using these exaggerations, teachers infer that thermal energy is present to a lesser degree in the original scenario. They use this exaggeration strategy to track and conserve energy in dissipative scenarios.

  6. Temperature rise due to mechanical energy dissipation in undirectional thermoplastic composites(AS4/PEEK)

    NASA Technical Reports Server (NTRS)

    Georgious, I. T.; Sun, C. T.

    1992-01-01

    The history of temperature rise due to internal dissipation of mechanical energy in insulated off-axis uniaxial specimens of the unidirectional thermoplastic composite (AS4/PEEK) has been measured. The experiment reveals that the rate of temperature rise is a polynomial function of stress amplitude: It consists of a quadratic term and a sixth power term. This fact implies that the specific heat of the composite depends on the stretching its microstructure undergoes during deformation. The Einstein theory for specific heat is used to explain the dependence of the specific heat on the stretching of the microstructure.

  7. Spectral Energy Transfer and Dissipation of Magnetic Energy from Fluid to Kinetic Scales

    SciTech Connect

    Bowers, K.; Li, H.

    2007-01-19

    We investigate the magnetic energy transfer from the fluid to kinetic scales and dissipation processes using three-dimensional fully kinetic particle-in-cell plasma simulations. The nonlinear evolution of a sheet pinch is studied where we show that it exhibits both fluid scale global relaxation and kinetic scale collisionless reconnection at multiple resonant surfaces. The interactions among collisionless tearing modes destroy the original flux surfaces and produce stochastic fields, along with generating sheets and filaments of intensified currents. In addition, the magnetic energy is transferred from the original shear length scale both to the large scales due to the global relaxation and to the smaller, kinetic scales for dissipation. The dissipation is dominated by the thermal or pressure effect in the generalized Ohm's law, and electrons are preferentially accelerated.

  8. Spectral energy transfer and dissipation of magnetic energy from fluid to kinetic scales.

    PubMed

    Bowers, K; Li, H

    2007-01-19

    We investigate the magnetic energy transfer from the fluid to kinetic scales and dissipation processes using three-dimensional fully kinetic particle-in-cell plasma simulations. The nonlinear evolution of a sheet pinch is studied where we show that it exhibits both fluid scale global relaxation and kinetic scale collisionless reconnection at multiple resonant surfaces. The interactions among collisionless tearing modes destroy the original flux surfaces and produce stochastic fields, along with generating sheets and filaments of intensified currents. In addition, the magnetic energy is transferred from the original shear length scale both to the large scales due to the global relaxation and to the smaller, kinetic scales for dissipation. The dissipation is dominated by the thermal or pressure effect in the generalized Ohm's law, and electrons are preferentially accelerated. PMID:17358690

  9. Fractional characteristic times and dissipated energy in fractional linear viscoelasticity

    NASA Astrophysics Data System (ADS)

    Colinas-Armijo, Natalia; Di Paola, Mario; Pinnola, Francesco P.

    2016-08-01

    In fractional viscoelasticity the stress-strain relation is a differential equation with non-integer operators (derivative or integral). Such constitutive law is able to describe the mechanical behavior of several materials, but when fractional operators appear, the elastic and the viscous contribution are inseparable and the characteristic times (relaxation and retardation time) cannot be defined. This paper aims to provide an approach to separate the elastic and the viscous phase in the fractional stress-strain relation with the aid of an equivalent classical model (Kelvin-Voigt or Maxwell). For such equivalent model the parameters are selected by an optimization procedure. Once the parameters of the equivalent model are defined, characteristic times of fractional viscoelasticity are readily defined as ratio between viscosity and stiffness. In the numerical applications, three kinds of different excitations are considered, that is, harmonic, periodic, and pseudo-stochastic. It is shown that, for any periodic excitation, the equivalent models have some important features: (i) the dissipated energy per cycle at steady-state coincides with the Staverman-Schwarzl formulation of the fractional model, (ii) the elastic and the viscous coefficients of the equivalent model are strictly related to the storage and the loss modulus, respectively.

  10. Structural Health Monitoring of a Bridge with Energy Dissipators

    SciTech Connect

    Amaddeo, Carmen; D'Amore, Enzo; Benzoni, Gianmario

    2008-07-08

    After natural events like the 1994 Northridge (USA), the 1995 Kobe (Japan), the 1999 Chi-Chi (Taiwan) and the 1999 Duzce (Turkey) earthquakes it became evident that the demand for bridge structures could greatly benefit from the application of isolation/energy dissipation techniques. Despite the level of maturity achieved in the field of seismic isolation, open questions still remain on the durability of seismic response modification devices (SRMD) under working conditions. The option of removal of sample devices from the bridge structure to verify their performance characteristics involves a significant economical effort, particularly if associated to disruption of the regular traffic. It provides also a device response verification difficult to correlate to the global structural performance. Health monitoring techniques offer a valuable alternative. The main objective of this research is the definition of an effective health monitoring approach to be applied to bridges protected with the most common seismic response modification devices (SRMD). The proposed methodology was validated with the use of records from a bridge equipped with viscous dampers. The record were obtained before and after damage occurred. The procedure proved to be accurate in detecting early degradations of the device characteristics as well as of the structural elements directly connected to the devices.

  11. Methods for reducing energy dissipation in cosmetic gloves.

    PubMed

    Herder, J L; Cool, J C; Plettenburg, D H

    1998-06-01

    For cosmetic reasons, hand prostheses are provided with cosmetic gloves. Their pleasing appearance, however, is accompanied by poor mechanical behavior, resulting in a negative influence on prosthesis operation. Glove stiffness is high and nonlinear, and internal friction in the glove material causes energy dissipation (hysteresis). In this article, two methods for reducing hysteresis in cosmetic gloves are proposed, that may be applied independently or in combination. Glove modification. Altering the mechanical properties of the glove itself is the first method that is presented. It was found possible to reduce both stiffness and hysteresis about 50% by forming grooves into the inside of the glove. Together with the evaluation of this method, several properties of the cosmetic glove were determined. Motion optimization. Additionally, a second method for reducing hysteresis was developed. The amount of hysteresis is influenced by the way the glove is forced to deform. The prosthesis mechanism, determining this deformation, was designed for minimum hysteresis and maximum cosmesis. For the prosthesis-glove combination used in this study, thumb motion optimization reduced hysteresis by about 65%. PMID:9651892

  12. Homogenization and improvement in energy dissipation of nonlinear composites

    NASA Astrophysics Data System (ADS)

    Verma, Luv; Sivakumar, Srinivasan M.; Vedantam, S.

    2016-04-01

    Due to their high strength to weight and stiffness to weight ratio, there is a huge shift towards the composite materials from the conventional metals, but composites have poor damage resistance in the transverse direction. Undergoing impact loads, they can fail in wide variety of modes which severely reduces the structural integrity of the component. This paper deals with the homogenization of glass-fibers and epoxy composite with a material introduced as an inelastic inclusion. This nonlinearity is being modelled by kinematic hardening procedure and homogenization is done by one of the mean field homogenization technique known as Mori-Tanaka method. The homogenization process consider two phases, one is the matrix and another is the inelastic inclusion, thus glass-fibers and epoxy are two phases which can be considered as one phase and act as a matrix while homogenizing non-linear composite. Homogenization results have been compared to the matrix at volume fraction zero of the inelastic inclusions and to the inelastic material at volume fraction one. After homogenization, increase of the energy dissipation into the composite due to addition of inelastic material and effects onto the same by changing the properties of the matrix material have been discussed.

  13. Dissipation of modified entropic gravitational energy through gravitational waves

    NASA Astrophysics Data System (ADS)

    de Matos, Clovis Jacinto

    2012-01-01

    The phenomenological nature of a new gravitational type interaction between two different bodies derived from Verlinde's entropic approach to gravitation in combination with Sorkin's definition of Universe's quantum information content, is investigated. Assuming that the energy stored in this entropic gravitational field is dissipated under the form of gravitational waves and that the Heisenberg principle holds for this system, one calculates a possible value for an absolute minimum time scale in nature tau=15/16 Λ^{1/2}hbar G/c4˜9.27×10^{-105} seconds, which is much smaller than the Planck time t P =( ħG/ c 5)1/2˜5.38×10-44 seconds. This appears together with an absolute possible maximum value for Newtonian gravitational forces generated by matter Fg=32/30c7/Λ hbar G2˜ 3.84× 10^{165} Newtons, which is much higher than the gravitational field between two Planck masses separated by the Planck length F gP = c 4/ G˜1.21×1044 Newtons.

  14. Extrema principles of entrophy production and energy dissipation in fluid mechanics

    NASA Technical Reports Server (NTRS)

    Horne, W. Clifton; Karamcheti, Krishnamurty

    1988-01-01

    A survey is presented of several extrema principles of energy dissipation as applied to problems in fluid mechanics. An exact equation is derived for the dissipation function of a homogeneous, isotropic, Newtonian fluid, with terms associated with irreversible compression or expansion, wave radiation, and the square of the vorticity. By using entropy extrema principles, simple flows such as the incompressible channel flow and the cylindrical vortex are identified as minimal dissipative distributions. The principal notions of stability of parallel shear flows appears to be associated with a maximum dissipation condition. These different conditions are consistent with Prigogine's classification of thermodynamic states into categories of equilibrium, linear nonequilibrium, and nonlinear nonequilibrium thermodynamics; vortices and acoustic waves appear as examples of dissipative structures. The measurements of a typical periodic shear flow, the rectangular wall jet, show that direct measurements of the dissipative terms are possible.

  15. Extrema principles of entropy production and energy dissipation in fluid mechanics

    NASA Technical Reports Server (NTRS)

    Horne, W. Clifton; Karamcheti, Krishnamurty

    1988-01-01

    A survey is presented of several extrema principles of energy dissipation as applied to problems in fluid mechanics. An exact equation is derived for the dissipation function of a homogeneous, isotropic, Newtonian fluid, with terms associated with irreversible compression or expansion, wave radiation, and the square of the vorticity. By using entropy extrema principles, simple flows such as the incompressible channel flow and the cylindrical vortex are identified as minimal dissipative distributions. The principal notions of stability of parallel shear flows appear to be associated with a maximum dissipation condition. These different conditions are consistent with Prigogine's classification of thermodynamic states into categories of equilibrium, linear nonequilibrium, and nonlinear nonequilibrium thermodynamics; vortices and acoustic waves appear as examples of dissipative structures. The measurements of a typical periodic shear flow, the rectangular wall jet, show that direct measurements of the dissipative terms are possible.

  16. Mechanisms for impulsive energy dissipation and small-scale effects in microgranular media.

    PubMed

    Bunyan, Jonathan; Vakakis, Alexander F; Tawfick, Sameh

    2015-12-01

    We study impulse response in one-dimensional homogeneous microgranular chains on a linear elastic substrate. Microgranular interactions are analytically described by the Schwarz contact model which includes nonlinear compressive as well as snap-to and from-contact adhesive effects forming a hysteretic loop in the force deformation relationship. We observe complex transient dynamics, including disintegration of solitary pulses, local clustering, and low-to-high-frequency energy transfers resulting in enhanced energy dissipation. We study in detail the underlying dynamics of cluster formation in the impulsively loaded medium and relate enhanced energy dissipation to the rate of cluster formation. These unusual and interesting dynamical phenomena are shown to be robust over a range of physically feasible conditions and are solely scale effects since they are attributed to surface forces, which have no effect at the macroscale. We establish a universal relation between the reclustering rate and the effective damping in these systems. Our findings demonstrate that scale effects generating new nonlinear features can drastically affect the dynamics and acoustics of microgranular materials. PMID:26764681

  17. Mechanisms for impulsive energy dissipation and small-scale effects in microgranular media

    NASA Astrophysics Data System (ADS)

    Bunyan, Jonathan; Vakakis, Alexander F.; Tawfick, Sameh

    2015-12-01

    We study impulse response in one-dimensional homogeneous microgranular chains on a linear elastic substrate. Microgranular interactions are analytically described by the Schwarz contact model which includes nonlinear compressive as well as snap-to and from-contact adhesive effects forming a hysteretic loop in the force deformation relationship. We observe complex transient dynamics, including disintegration of solitary pulses, local clustering, and low-to-high-frequency energy transfers resulting in enhanced energy dissipation. We study in detail the underlying dynamics of cluster formation in the impulsively loaded medium and relate enhanced energy dissipation to the rate of cluster formation. These unusual and interesting dynamical phenomena are shown to be robust over a range of physically feasible conditions and are solely scale effects since they are attributed to surface forces, which have no effect at the macroscale. We establish a universal relation between the reclustering rate and the effective damping in these systems. Our findings demonstrate that scale effects generating new nonlinear features can drastically affect the dynamics and acoustics of microgranular materials.

  18. Heat dissipation does not suppress an immune response in laboratory mice divergently selected for basal metabolic rate (BMR).

    PubMed

    Książek, Aneta; Konarzewski, Marek

    2016-05-15

    The capacity for heat dissipation is considered to be one of the most important constraints on rates of energy expenditure in mammals. To date, the significance of this constraint has been tested exclusively under peak metabolic demands, such as during lactation. Here, we used a different set of metabolic stressors, which do not induce maximum energy expenditures and yet are likely to expose the potential constraining effect of heat dissipation. We compared the physiological responses of mice divergently selected for high (H-BMR) and low basal metabolic rate (L-BMR) to simultaneous exposure to the keyhole limpet haemocyanin (KLH) antigen and high ambient temperature (Ta). At 34°C (and at 23°C, used as a control), KLH challenge resulted in a transient increase in core body temperature (Tb) in mice of both line types (by approximately 0.4°C). Warm exposure did not produce line-type-dependent differences in Tb (which was consistently higher by ca. 0.6°C in H-BMR mice across both Ta values), nor did it result in the suppression of antibody synthesis. These findings were also supported by the lack of between-line-type differences in the mass of the thymus, spleen or lymph nodes. Warm exposure induced the downsizing of heat-generating internal organs (small intestine, liver and kidneys) and an increase in intrascapular brown adipose tissue mass. However, these changes were similar in scope in both line types. Mounting a humoral immune response in selected mice was therefore not affected by ambient temperature. Thus, a combined metabolic challenge of high Ta and an immune response did not appreciably compromise the capacity to dissipate heat, even in the H-BMR mice. PMID:26944492

  19. Slip Damping in Vibrating Layered Beams and Leaf Springs: Energy Dissipated and Optimum Considerations

    NASA Astrophysics Data System (ADS)

    Badrakhan, F.

    1994-06-01

    The general expression for the energy dissipated by Coulomb friction in layered beams, valid for any number of layers and for any slipping level, is derived. The expression of optimum pressure for maximum energy dissipation is also derived. It is shown, in particular, that this optimum pressure does not guarantee minimum vibration amplitude at resonance if the beam is excited by a harmonic force. The results obtained, concerning the energy dissipated and the optimum pressure, are adapted to the case of leaf springs, for which the concept of optimum pressure seems to be more meaningful.

  20. Quantifying the energy dissipation of overriding plate deformation in three-dimensional subduction models

    NASA Astrophysics Data System (ADS)

    Chen, Zhihao; Schellart, Wouter P.; Duarte, João. C.

    2015-01-01

    In a subduction system the force and the energy required to deform the overriding plate are generally thought to come from the negative buoyancy of the subducted slab and its potential energy, respectively. Such deformation might involve extension and back-arc basin formation or shortening and mountain building. How much of the slab's potential energy is consumed during overriding plate deformation remains unknown. In this work, we present dynamic three-dimensional laboratory experiments of progressive subduction with an overriding plate to quantify the force (FOPD) that drives overriding plate deformation and the associated energy dissipation rate (ΦOPD), and we compare them with the negative buoyancy (FBU) of the subducted slab and its total potential energy release rate (ΦBU), respectively. We varied the viscosity ratio between the plates and the sublithospheric upper mantle with ηSP/ηUM = 157-560 and the thickness of the overriding plate with TOP = 0.5-2.5 cm (scaling to 25-125 km in nature). The results show that FOPD/FBU has average values of 0.5-2.0%, with a maximum of 5.3%, and ΦOPD/ΦBU has average values of 0.05-0.30%, with a maximum of 0.41%. The results indicate that only a small portion of the negative buoyancy of the slab and its potential energy are used to deform the overriding plate. Our models also suggest that the force required to deform the overriding plate is of comparable magnitude as the ridge push force. Furthermore, we show that in subduction models with an overriding plate bending dissipation at the subduction zone hinge remains low (3-15% during steady state subduction).

  1. Low dust charging rate induced weakly dissipative dust acoustic solitary waves: Role of nonthermal ions

    SciTech Connect

    Chaudhuri, Tushar Kanti; Khan, Manoranjan; Gupta, M. R.; Ghosh, Samiran

    2007-10-15

    The effects of low dust charging rate compared to the dust oscillation frequency and nonthermal ions on small but finite amplitude nonlinear dust acoustic wave have been investigated. It is seen that because of the low dust charging rate, the nonlinear wave exhibits weakly dissipative solitary wave that is governed by a modified form of the Korteweg-de Vries equation. The solitary wave possesses both rarefactive and compressive soliton solution depending on the values of ion nonthermality parameter a. An analytical solution reveals that because of the simultaneous effects of low dust charging rate and nonthermal ions, the wave amplitude may grow exponentially with time if the ion nonthermality parameter (a) exceeds a critical value provided the ion-electron temperature ratio ({sigma}{sub i}) is less than 0.11.

  2. The role of energy dissipation of polymeric scaffolds in the mechanobiological modulation of chondrogenic expression.

    PubMed

    Abdel-Sayed, Philippe; Darwiche, Salim E; Kettenberger, Ulrike; Pioletti, Dominique P

    2014-02-01

    Mechanical stimulation has been proposed to induce chondrogenesis in cell-seeded scaffolds. However, the effects of mechanical stimuli on engineered cartilage may vary substantially between different scaffolds. This advocates for the need to identify an overarching mechanobiological variable. We hypothesize that energy dissipation of scaffolds subjected to dynamic loading may be used as a mechanobiology variable. The energy dissipation would furnish a general criterion to adjust the mechanical stimulation favoring chondrogenesis in scaffold. Epiphyseal chondro-progenitor cells were then subject to unconfined compression 2 h per day during four days in different scaffolds, which differ only by the level of dissipation they generated while keeping the same loading conditions. Scaffolds with higher dissipation levels upregulated the mRNA of chondrogenic markers. In contrast lower dissipation of scaffolds was associated with downregulation of chondrogenic markers. These results showed that energy dissipation could be considered as a mechanobiology variable in cartilage. This study also indicated that scaffolds with energy dissipation level close to the one of cartilage favors chondrogenic expression when dynamical loading is present. PMID:24331703

  3. Power and energy dissipation in subsequent return strokes as predicted by a new return stroke model

    NASA Technical Reports Server (NTRS)

    Cooray, Vernon

    1991-01-01

    Recently, Cooray introduced a new return stroke model which is capable of predicting the temporal behavior of the return stroke current and the return stroke velocity as a function of the height along the return stroke channel. The authors employed this model to calculate the power and energy dissipation in subsequent return strokes. The results of these calculations are presented here. It was concluded that a large fraction of the total energy available for the dart leader-subsequent stroke process is dissipated in the dart leader stage. The peak power per unit length dissipated in a subsequent stroke channel element decreases with increasing height of that channel element from ground level. For a given channel element, the peak power dissipation increases with increasing current in that channel element. The peak electrical power dissipation in a typical subsequent return stroke is about 1.5 times 10(exp 11) W. The energy dissipation in a subsequent stroke increases with increasing current in the return stroke channel, and for a typical subsequent stroke, the energy dissipation per unit length is about 5.0 times 10(exp 3) J/m.

  4. On the dissipation of the rotation energy of dust grains in interstellar magnetic fields

    NASA Astrophysics Data System (ADS)

    Papoular, R.

    2016-04-01

    A new mechanism is described, analysed and visualized, for the dissipation of suprathermal rotation energy of molecules in magnetic fields, a necessary condition for their alignment. It relies upon the Lorentz force perturbing the motion of every atom of the structure, as each is known to carry its own net electric charge because of spatial fluctuations in electron density. If the molecule is large enough that the frequency of its lowest frequency phonon lies near or below the rotation frequency, then the rotation couples with the molecular normal modes and energy flows from the former to the latter. The rate of this exchange is very fast, and the vibrational energy is radiated away in the IR at a still faster rate, which completes the removal of rotation energy. The energy decay rate scales like the field intensity, the initial angular velocity, the number of atoms in the grain and the inverse of the moment of inertia. It does not depend on the susceptibility. Here, the focus is on carbon-rich molecules which are diamagnetic. The same process must occur if the molecule is paramagnetic or bathes in an electric field instead. A semi-empirical method of chemical modelling was used extensively to illustrate and quantify these concepts as applied to a hydrocarbon molecule. The motion of a rotating molecule in a field was monitored in time so as to reveal the energy transfer and visualize the evolution of its orientation towards the stable configuration.

  5. Energy dissipation and heat exchange in magnetorheological suspensions in a rotating magnetic field

    SciTech Connect

    Shul'man, Z.P.; Kordonskii, V.I.; Gorodkin, S.R.; Kashevskii, B.E.; Prokhorov, I.V.

    1987-07-01

    The authors present the results of experiments on the effect of the rheological properties of magnetic suspensions and the regime parameters on energy dissipation and heat transport in a rotating magnetic field.

  6. Landau-Zener transitions mediated by an environment: Population transfer and energy dissipation

    SciTech Connect

    Dodin, Amro; Simine, Lena; Segal, Dvira; Garmon, Savannah

    2014-03-28

    We study Landau-Zener transitions between two states with the addition of a shared discretized continuum. The continuum allows for population decay from the initial state as well as indirect transitions between the two states. The probability of nonadiabatic transition in this multichannel model preserves the standard Landau-Zener functional form except for a shift in the usual exponential factor, reflecting population transfer into the continuum. We provide an intuitive explanation for this behavior assuming individual, independent transitions between pairs of states. In contrast, the ground state survival probability at long time shows a novel, non-monotonic, functional form with an oscillatory behavior in the sweep rate at low sweep rate values. We contrast the behavior of this open-multistate model to other generalized Landau-Zener models incorporating an environment: the stochastic Landau-Zener model and the dissipative case, where energy dissipation and thermal excitations affect the adiabatic region. Finally, we present evidence that the continuum of states may act to shield the two-state Landau-Zener transition probability from the effect of noise.

  7. Landau-Zener transitions mediated by an environment: population transfer and energy dissipation.

    PubMed

    Dodin, Amro; Garmon, Savannah; Simine, Lena; Segal, Dvira

    2014-03-28

    We study Landau-Zener transitions between two states with the addition of a shared discretized continuum. The continuum allows for population decay from the initial state as well as indirect transitions between the two states. The probability of nonadiabatic transition in this multichannel model preserves the standard Landau-Zener functional form except for a shift in the usual exponential factor, reflecting population transfer into the continuum. We provide an intuitive explanation for this behavior assuming individual, independent transitions between pairs of states. In contrast, the ground state survival probability at long time shows a novel, non-monotonic, functional form with an oscillatory behavior in the sweep rate at low sweep rate values. We contrast the behavior of this open-multistate model to other generalized Landau-Zener models incorporating an environment: the stochastic Landau-Zener model and the dissipative case, where energy dissipation and thermal excitations affect the adiabatic region. Finally, we present evidence that the continuum of states may act to shield the two-state Landau-Zener transition probability from the effect of noise. PMID:24697472

  8. Finescale parameterizations of energy dissipation in a region of strong internal tides and sheared flow, the Lucky-Strike segment of the Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Pasquet, Simon; Bouruet-Aubertot, Pascale; Reverdin, Gilles; Turnherr, Andreas; Laurent, Lou St.

    2016-06-01

    The relevance of finescale parameterizations of dissipation rate of turbulent kinetic energy is addressed using finescale and microstructure measurements collected in the Lucky Strike segment of the Mid-Atlantic Ridge (MAR). There, high amplitude internal tides and a strongly sheared mean flow sustain a high level of dissipation rate and turbulent mixing. Two sets of parameterizations are considered: the first ones (Gregg, 1989; Kunze et al., 2006) were derived to estimate dissipation rate of turbulent kinetic energy induced by internal wave breaking, while the second one aimed to estimate dissipation induced by shear instability of a strongly sheared mean flow and is a function of the Richardson number (Kunze et al., 1990; Polzin, 1996). The latter parameterization has low skill in reproducing the observed dissipation rate when shear unstable events are resolved presumably because there is no scale separation between the duration of unstable events and the inverse growth rate of unstable billows. Instead GM based parameterizations were found to be relevant although slight biases were observed. Part of these biases result from the small value of the upper vertical wavenumber integration limit in the computation of shear variance in Kunze et al. (2006) parameterization that does not take into account internal wave signal of high vertical wavenumbers. We showed that significant improvement is obtained when the upper integration limit is set using a signal to noise ratio criterion and that the spatial structure of dissipation rates is reproduced with this parameterization.

  9. Group velocity locked vector dissipative solitons in a high repetition rate fiber laser.

    PubMed

    Luo, Yiyang; Li, Lei; Liu, Deming; Sun, Qizhen; Wu, Zhichao; Xu, Zhilin; Tang, Dingyuan; Fu, Songnian; Zhao, Luming

    2016-08-01

    Vectorial nature of dissipative solitons (DSs) with high repetition rate is studied for the first time in a normal-dispersion fiber laser. Despite the fact that the formed DSs are strongly chirped and the repetition rate is greater than 100 MHz, polarization locked and polarization rotating group velocity locked vector DSs can be formed under 129.3 MHz fundamental mode-locking and 258.6 MHz harmonic mode-locking of the fiber laser, respectively. The two orthogonally polarized components of these vector DSs possess distinctly different central wavelengths and travel together at the same group velocity in the laser cavity, resulting in a gradual spectral edge and small steps on the optical spectrum, which can be considered as an auxiliary indicator of the group velocity locked vector DSs. Moreover, numerical simulations well confirm the experimental observations and further reveal the impact of the net cavity birefringence on the properties of the formed vector DSs. PMID:27505834

  10. The relationship between node degree and dissipation rate in networks of diffusively coupled oscillators and its significance for pancreatic beta cells

    NASA Astrophysics Data System (ADS)

    Gosak, Marko; Stožer, Andraž; Markovič, Rene; Dolenšek, Jurij; Marhl, Marko; Slak Rupnik, Marjan; Perc, Matjaž

    2015-07-01

    Self-sustained oscillatory dynamics is a motion along a stable limit cycle in the phase space, and it arises in a wide variety of mechanical, electrical, and biological systems. Typically, oscillations are due to a balance between energy dissipation and generation. Their stability depends on the properties of the attractor, in particular, its dissipative characteristics, which in turn determine the flexibility of a given dynamical system. In a network of oscillators, the coupling additionally contributes to the dissipation, and hence affects the robustness of the oscillatory solution. Here, we therefore investigate how a heterogeneous network structure affects the dissipation rate of individual oscillators. First, we show that in a network of diffusively coupled oscillators, the dissipation is a linearly decreasing function of the node degree, and we demonstrate this numerically by calculating the average divergence of coupled Hopf oscillators. Subsequently, we use recordings of intracellular calcium dynamics in pancreatic beta cells in mouse acute tissue slices and the corresponding functional connectivity networks for an experimental verification of the presented theory. We use methods of nonlinear time series analysis to reconstruct the phase space and calculate the sum of Lyapunov exponents. Our analysis reveals a clear tendency of cells with a higher degree, that is, more interconnected cells, having more negative values of divergence, thus confirming our theoretical predictions. We discuss these findings in the context of energetic aspects of signaling in beta cells and potential risks for pathological changes in the tissue.

  11. The relationship between node degree and dissipation rate in networks of diffusively coupled oscillators and its significance for pancreatic beta cells.

    PubMed

    Gosak, Marko; Stožer, Andraž; Markovič, Rene; Dolenšek, Jurij; Marhl, Marko; Rupnik, Marjan Slak; Perc, Matjaž

    2015-07-01

    Self-sustained oscillatory dynamics is a motion along a stable limit cycle in the phase space, and it arises in a wide variety of mechanical, electrical, and biological systems. Typically, oscillations are due to a balance between energy dissipation and generation. Their stability depends on the properties of the attractor, in particular, its dissipative characteristics, which in turn determine the flexibility of a given dynamical system. In a network of oscillators, the coupling additionally contributes to the dissipation, and hence affects the robustness of the oscillatory solution. Here, we therefore investigate how a heterogeneous network structure affects the dissipation rate of individual oscillators. First, we show that in a network of diffusively coupled oscillators, the dissipation is a linearly decreasing function of the node degree, and we demonstrate this numerically by calculating the average divergence of coupled Hopf oscillators. Subsequently, we use recordings of intracellular calcium dynamics in pancreatic beta cells in mouse acute tissue slices and the corresponding functional connectivity networks for an experimental verification of the presented theory. We use methods of nonlinear time series analysis to reconstruct the phase space and calculate the sum of Lyapunov exponents. Our analysis reveals a clear tendency of cells with a higher degree, that is, more interconnected cells, having more negative values of divergence, thus confirming our theoretical predictions. We discuss these findings in the context of energetic aspects of signaling in beta cells and potential risks for pathological changes in the tissue. PMID:26232966

  12. K-12 Teacher Understanding of Energy Conservation: Conceptual Metaphor, Dissipation, and Degradation

    NASA Astrophysics Data System (ADS)

    Daane, Abigail R.

    In K-12 educational settings, conservation of energy is typically presented in two ways: the conservation of energy principle (energy is neither created nor destroyed) and the sociopolitical need to conserve energy (we guard against energy being used up). These two meanings of conservation typically remain disconnected from each other and can appear contradictory, even after instruction. In an effort to support teachers in building robust understandings of energy from their existing knowledge, I designed a study to investigate the productive ideas in K-12 teachers' conversations about energy. A micro-analysis of discourse, gestures, and artifacts of professional development courses revealed teachers' productive ideas about three aspects of energy: conceptual metaphor, dissipation and degradation. In learning about energy, K-12 teachers come to use conceptual metaphors in their own language and value attending to students' metaphorical language as a means of formative assessment. Teachers' conversations about dissipation suggest that apparent difficulties with energy conservation may have their roots in a strong association between forms of energy (thermal) and their perceptible indicators (warmth). Teachers address this challenge by employing an exaggeration strategy to locate the dissipated thermal energy, making the energy indicator perceptible. Finally, teachers' unprompted statements about sociopolitical aspects of energy are related to both statements from the NGSS and aspects of energy degradation. I conclude that energy conservation can be better taught and learned in K-12 Education by: 1) understanding and applying conceptual metaphors about energy in K-12 settings, 2) using prior experiences to better understand dissipative energy processes involving imperceptible thermal energy, thereby understanding how energy conservation applies in all situations, and 3) connecting productive ideas about sociopolitical aspects of energy to canonical physics. Keywords

  13. Energy dissipation of Alfven wave packets deformed by irregular magnetic fields in solar-coronal arches

    NASA Technical Reports Server (NTRS)

    Similon, Philippe L.; Sudan, R. N.

    1989-01-01

    The importance of field line geometry for shear Alfven wave dissipation in coronal arches is demonstrated. An eikonal formulation makes it possible to account for the complicated magnetic geometry typical in coronal loops. An interpretation of Alfven wave resonance is given in terms of gradient steepening, and dissipation efficiencies are studied for two configurations: the well-known slab model with a straight magnetic field, and a new model with stochastic field lines. It is shown that a large fraction of the Alfven wave energy flux can be effectively dissipated in the corona.

  14. Dielectric elastomer energy harvesting: maximal converted energy, viscoelastic dissipation and a wave power generator

    NASA Astrophysics Data System (ADS)

    Lv, Xiongfei; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2015-11-01

    Dielectric elastomer (DE) is a smart soft material. It is able to produce large deformation under mechanical force and electric field, so that it can achieve mutual conversion between mechanical energy and electrical energy. Based on this property, dielectric elastomer can be used in energy harvesting field. In this paper, firstly, we analyzed the constitutive relation under different hyperelastic models (Gent and neo-Hookean model) based on both theoretical and experimental study. Secondly, we depicted the allowable areas in force-displacement and voltage-charge plane according to different failure modes, and then calculated the maximal energy density in one energy harvesting period. Thirdly, we studied the viscoelastic energy dissipation which can lose the input mechanical energy in the energy harvesting process. Finally, we designed and fabricated a wave power generator, and tested its performance. This paper is of deep significance to the future applications of DE generators.

  15. Rates of formation and dissipation of clumping reveal lagged responses in tropical tree populations.

    PubMed

    Detto, Matteo; Muller-Landau, Helene C

    2016-05-01

    The dynamics of spatial patterns of plant populations can provide important information about underlying processes, yet they have received relatively little attention to date. Here we investigate the rates of formation and dissipation of clusters and the relationship of these rates to the degree of aggregation (clumping) in models and in empirical data for tropical trees. In univariate models, exact solutions and simulations show that the rate of change of spatial patterns has a specific, linear relationship to the degree of aggregation at all scales. Shorter dispersal and/or weaker negative density dependence (NDD) result in both denser and longer-lasting clusters. In multivariate host-parasite models in contrast, the rate of change of spatial pattern is faster relative to the level of aggrega- tion. We then analyzed the dynamics of spatial patterns of stems ≥ 1 cm diameter in 221 tropical tree species from seven censuses spanning 28 yr. We found that for most species, the rates of change in spatial patterns were faster than predicted from univariate models given their aggregation. This indicates that more complex dynamics involving multivariate interactions induce time lags in responses to aggregation in these species. Such lags could arise, for example, if it takes time for natural enemies to locate aggregations of their hosts. This combination of theoretical and empirical results thus shows that complex multilevel models are needed to capture spatiotemporal dynamics of tropical forests and provides new insights into the processes structuring tropical plant communities. PMID:27349094

  16. Linear Multivariable Regression Models for Prediction of Eddy Dissipation Rate from Available Meteorological Data

    NASA Technical Reports Server (NTRS)

    MCKissick, Burnell T. (Technical Monitor); Plassman, Gerald E.; Mall, Gerald H.; Quagliano, John R.

    2005-01-01

    Linear multivariable regression models for predicting day and night Eddy Dissipation Rate (EDR) from available meteorological data sources are defined and validated. Model definition is based on a combination of 1997-2000 Dallas/Fort Worth (DFW) data sources, EDR from Aircraft Vortex Spacing System (AVOSS) deployment data, and regression variables primarily from corresponding Automated Surface Observation System (ASOS) data. Model validation is accomplished through EDR predictions on a similar combination of 1994-1995 Memphis (MEM) AVOSS and ASOS data. Model forms include an intercept plus a single term of fixed optimal power for each of these regression variables; 30-minute forward averaged mean and variance of near-surface wind speed and temperature, variance of wind direction, and a discrete cloud cover metric. Distinct day and night models, regressing on EDR and the natural log of EDR respectively, yield best performance and avoid model discontinuity over day/night data boundaries.

  17. Dissipation rates and residues of fungicide azoxystrobin in ginseng and soil at two different cultivated regions in China.

    PubMed

    Hou, Zhiguang; Wang, Xiumei; Zhao, Xiaofeng; Wang, Xinhong; Yuan, Xing; Lu, Zhongbin

    2016-07-01

    The maximum residue limit (MRL) for fungicide azoxystrobin in ginseng has not yet been established in China. This is partially due to the lack of its dissipation and residue data at China's main ginseng production areas. In this work, the dissipation rates and residue levels of azoxystrobin in ginseng roots, plant parts (stems and leaves), and soil in Beijing and Jilin Province, China were determined using gas chromatograph-mass spectrometry (GC-MS). The mean half-life of azoxystrobin in ginseng plant parts was 1.6 days with a dissipation rate of 90 % over 21 days. The mean half-life in soil was 2.8 days with a dissipation rate of 90 % over 30 days. Dissipation rates from two geographically separated experimental fields differed, suggesting that these were affected by local soil characteristics and climate. Maximum final residues of azoxystrobin in ginseng roots, plant parts, and soil were determined to be 0.343, 9.40, and 0.726 mg kg(-1), respectively. Our results, particularly the high residues of azoxystrobin observed in ginseng plant parts, provide a quantitative basis for revising the application of this pesticide to ginseng. PMID:27351188

  18. A case study of the energy dissipation of the gravity wave field based on satellite altimeter measurements

    NASA Technical Reports Server (NTRS)

    Huang, N. E.; Parsons, C. L.; Long, S. R.; Bliven, L. F.

    1983-01-01

    Wave breaking is proposed as the primary energy dissipation mechanism for the gravity wave field. The energy dissipation rate is calculated based on the statistical model proposed by Longuet-Higgins (1969) with a modification of the breaking criterion incorporating the surface stress according to Phillips and Banner (1974). From this modified model, an analytic expression is found for the wave attenuation rate and the half-life time of the wave field which depend only on the significant slope of the wave field and the ratio of friction velocity to initial wave phase velocity. These expressions explain why the freshly generated wave field does not last long, but why swells are capable of propagating long distances without substantial change in energy density. It is shown that breaking is many orders of magnitude more effective in dissipating wave energy than the molecular viscosity, if the significant slope is higher than 0.01. Limited observational data from satellite and laboratory are used to compare with the analytic results, and show good agreement.

  19. Dissipation from a Drifter

    NASA Astrophysics Data System (ADS)

    Thomson, J. M.; Talbert, J.

    2010-12-01

    Wave breaking and the associated dissipation of turbulent kinetic energy are important processes in accurately describing wave evolution and air-sea interaction. Quantitative observations of wave breaking dissipation are difficult because of rapid changes in surface elevation and advection of turbulence by wave orbital motions. A quasi-Lagrangian reference frame can mitigate these challenges, as demonstrated with the new Surface Wave Instrumentation Float with Tracking, or "SWIFT". The primary goal of SWIFT deployments is to observe near-surface turbulent fluid velocities using pulse-coherent acoustic Doppler current profilers (Nortek Aquadopp HR). Tests of SWIFT prototypes for both deep-water (whitecap) breaking and shallow-water (surfzone) breaking will be presented, in which dissipation is inferred from fitting velocity profiles to a spatial structure function, assuming isotropic turbulence. The drifters are tracked in realtime with the Automated Information System (AIS) used for commercial vessel traffic, and drifter motion is logged with onboard GPS and accelerometers. Onboard video recordings are used to confirm breaking events, which coincide with elevated dissipation rates. Breaking events also coincide with elevated acoustic backscatter, consistent with bubble injection by breaking waves. Example profiles of vertical velocity (upper panel) and dissipation rate (lower panel) versus time. The breaking wave at t = 54 s coincides with an elevated dissipation rate, compared with both background levels and larger non-breaking waves.

  20. A study of energy dissipation and critical speed of granular flow in a rotating cylinder

    NASA Astrophysics Data System (ADS)

    Dragomir, Sergiu C.; Sinnott, Mathew D.; Semercigil, S. Eren; Turan, Özden F.

    2014-12-01

    Tuned vibration absorbers may improve the safety of flexible structures which are prone to excessive oscillation magnitudes under dynamic loads. A novel absorber design proposes sloshing of granular material in a rotating cylinder where the granular material is the energy dissipating agent. As the conventional dissipative elements require maintenance due to the nature of their function, the new design may represent a virtually maintenance free alternative. The angular speed of the cylinder containing particles has a critical centrifuging speed, after which particles remain permanently in contact with the walls and there can be no further dissipation. Until the critical speed, however, dissipation increases proportionally with the angular speed. It is then vital to know the value of the critical speed as the limit of dissipation. The focus of the present study is on determination of the critical centrifuge speed. This critical speed is also of practical importance in bulk-material handling rotary mills, such as dryers and crushers. Experiments and numerical simulations, using Discrete Element Method, are used to determine the critical centrifuging speed. In addition, predictions are given and guidelines are offered for the choice of material properties to maximize the energy dissipation. As a result of a parametric study, the coefficient of friction is found to have the greatest significance on the centrifuging speed.

  1. Energy Dissipation End States of the Sphere Restricted Planar Three Body Problem with Collisional Interaction

    NASA Astrophysics Data System (ADS)

    Gabriel, T. S. J.; Scheeres, D. J.

    2016-08-01

    We perform a large number of gravitational granular mechanics simulations to investigate the role of energy dissipation in the sphere restricted planar three body problem where, for a given angular momentum, multiple end state configurations are available to the system. For the case of three equal spheres, previous studies have mapped all relative equilibria of the problem as a function of angular momentum. We find trends in the production of end states as a function of angular momentum and dissipation parameters, as well as outline the dynamical-mechanical interactions that generate these results. For strongly dissipative systems a relationship between the minimum energy function of the system and the end state dynamics is uncovered. In particular, the likelihood of achieving one end state over another is largely governed by the geometrical projection of the minimum energy function. In contrast, for systems with low energy dissipation the end state becomes a function of the relative depth of the different energy wells available to the system. This study highlights the importance of having well-defined dissipative properties of a gravitational granular system, such as those used to study the dynamics of rubble pile asteroids and planetary rings.

  2. Intrinsic noise, dissipation cost, and robustness of cellular networks: The underlying energy landscape of MAPK signal transduction

    PubMed Central

    Lapidus, Saul; Han, Bo; Wang, Jin

    2008-01-01

    We develop a probabilistic method for analyzing global features of a cellular network under intrinsic statistical fluctuations, which is important when there are finite numbers of molecules. By making a self-consistent mean field approximation of splitting the variables in order to reduce the large number of degrees of freedom, which is reasonable for a not very strongly interacting network, we discovered that the underlying energy landscape of the mitogen-activated protein kinases (MAPKs) signal transduction network (with experimentally measured or inferred parameters such as chemical reaction rate coefficients in the network) is funneled toward a global minimum characterized by the nonequilibrium steady-state fixed point of the system at the end of the signal transduction process. For this system, we also show that the energy landscape is robust against intrinsic fluctuations and random perturbation to the inherent chemical reaction rates. The ratio of the slope versus the roughness of the energy landscape becomes a quantitative measure of robustness and stability of the network. Furthermore, we quantify the dissipation cost of this nonequilibrium system through entropy production, caused by the nonequilibrium flux in the system. We found that a lower dissipation cost corresponds to a more robust network. This least dissipation property might provide a design principle for robust and functional networks. Finally, we find the possibility of bistable and oscillatory-like solutions, which are important for cell fate decisions, upon perturbations. The method described here can be used in a variety of biological networks. PMID:18420822

  3. Limits to sustained energy intake. XXIII. Does heat dissipation capacity limit the energy budget of lactating bank voles?

    PubMed

    Sadowska, Edyta T; Król, Elżbieta; Chrzascik, Katarzyna M; Rudolf, Agata M; Speakman, John R; Koteja, Paweł

    2016-03-01

    Understanding factors limiting sustained metabolic rate (SusMR) is a central issue in ecological physiology. According to the heat dissipation limit (HDL) theory, the SusMR at peak lactation is constrained by the maternal capacity to dissipate body heat. To test that theory, we shaved lactating bank voles (Myodes glareolus) to experimentally elevate their capacity for heat dissipation. The voles were sampled from lines selected for high aerobic exercise metabolism (A; characterized also by increased basal metabolic rate) and unselected control lines (C). Fur removal significantly increased the peak-lactation food intake (mass-adjusted least square means ± s.e.; shaved: 16.3 ± 0.3 g day(-1), unshaved: 14.4 ± 0.2 g day(-1); P<0.0001), average daily metabolic rate (shaved: 109 ± 2 kJ day(-1), unshaved: 97 ± 2 kJ day(-1); P<0.0001) and metabolisable energy intake (shaved: 215 ± 4 kJ day(-1), unshaved: 185 ± 4 kJ day(-1); P<0.0001), as well as the milk energy output (shaved: 104 ± 4 kJ day(-1); unshaved: 93 ± 4 kJ day(-1); P=0.021) and litter growth rate (shaved: 9.4 ± 0.7 g 4 days(-1), unshaved: 7.7 ± 0.7 g 4 days(-1); P=0.028). Thus, fur removal increased both the total energy budget and reproductive output at the most demanding period of lactation, which supports the HDL theory. However, digestive efficiency was lower in shaved voles (76.0 ± 0.3%) than in unshaved ones (78.5 ± 0.2%; P<0.0001), which may indicate that a limit imposed by the capacity of the alimentary system was also approached. Shaving similarly affected the metabolic and reproductive traits in voles from the A and C lines. Thus, the experimental evolution model did not reveal a difference in the limiting mechanism between animals with inherently different metabolic rates. PMID:26747907

  4. Roles of Energy Dissipation in a Liquid-Solid Transition of Out-of-Equilibrium Systems

    NASA Astrophysics Data System (ADS)

    Komatsu, Yuta; Tanaka, Hajime

    2015-07-01

    Self-organization of active matter as well as driven granular matter in nonequilibrium dynamical states has attracted considerable attention not only from the fundamental and application viewpoints but also as a model to understand the occurrence of such phenomena in nature. These systems share common features originating from their intrinsically out-of-equilibrium nature, and how energy dissipation affects the state selection in such nonequilibrium states remains elusive. As a simple model system, we consider a nonequilibrium stationary state maintained by continuous energy input, relevant to industrial processing of granular materials by vibration and/or flow. More specifically, we experimentally study roles of dissipation in self-organization of a driven granular particle monolayer. We find that the introduction of strong inelasticity entirely changes the nature of the liquid-solid transition from two-step (nearly) continuous transitions (liquid-hexatic-solid) to a strongly discontinuous first-order-like one (liquid-solid), where the two phases with different effective temperatures can coexist, unlike thermal systems, under a balance between energy input and dissipation. Our finding indicates a pivotal role of energy dissipation and suggests a novel principle in the self-organization of systems far from equilibrium. A similar principle may apply to active matter, which is another important class of out-of-equilibrium systems. On noting that interaction forces in active matter, and particularly in living systems, are often nonconservative and dissipative, our finding may also shed new light on the state selection in these systems.

  5. An investigation and modelling of energy dissipation through sloshing in an egg-shaped shell

    NASA Astrophysics Data System (ADS)

    Marsh, Adam P.; Prakash, Mahesh; Eren Semercigil, S.; Turan, Özden F.

    2011-12-01

    Sloshing absorbers work on a similar principle to that of tuned vibration absorbers. A sloshing absorber consists of a tank, partially filled with liquid. The absorber is attached to the structure to be controlled, and relies on the structure's motion to excite the liquid. Consequently, a sloshing wave is produced at the liquid free surface possessing energy dissipative qualities to suppress excessive vibrations of the structure. The hen's egg has evolved to dissipate vibration energy rapidly to protect its contents. An uncooked hen's egg's capability to rapidly dissipate potentially harmful energy, is due to sloshing of its contents. Hence, there may be lessons to learn from the natural design of an egg which could be employed in the engineered (artificial) design of a sloshing absorber. The primary objective of this work is to identify the physical events responsible for effective energy dissipation in an eggshell, at different fill levels. A secondary objective is to demonstrate the suitability of the Smoothed Particle Hydrodynamics (SPH) method for numerical predictions in such an unusually shaped shell. Through numerical predictions, the possibility of modifying the egg's design to further encourage dissipation patterns is explored briefly. Simple experiments are also presented to check the validity of the numerical predictions.

  6. Internal swells in the tropics: Near-inertial wave energy fluxes and dissipation during CINDY

    NASA Astrophysics Data System (ADS)

    Soares, S. M.; Natarov, A.; Richards, K. J.

    2016-05-01

    A developing MJO event in the tropical Indian Ocean triggered wind disturbances that generated inertial oscillations in the surface mixed layer. Subsequent radiation of near-inertial waves below the mixed layer produced strong turbulence in the pycnocline. Linear plane wave dynamics and spectral analysis are used to explain these observations, with the ultimate goal of estimating the wave energy flux in relation to both the energy input by the wind and the dissipation by turbulence. The results indicate that the wave packets carry approximately 30-40% of the wind input of inertial kinetic energy, and propagate in an environment conducive to the occurrence of a critical level set up by a combination of vertical gradients in background relative vorticity and Doppler shifting of wave frequency. Turbulent kinetic energy dissipation measurements demonstrate that the waves lose energy as they propagate in the transition layer as well as in the pycnocline, where approaching this critical level may have dissipated approximately 20% of the wave packet energy in a single event. Our analysis, therefore, supports the notion that appreciable amounts of wind-induced inertial kinetic energy escape the surface boundary layer into the interior. However, a large fraction of wave energy is dissipated within the pycnocline, limiting its penetration into the abyssal ocean.

  7. Effects of sterilization on the energy-dissipating properties of balsa wood

    NASA Technical Reports Server (NTRS)

    Sorkin, A. B.

    1969-01-01

    Technical report on the effects of sterilization on the energy-dissipating properties of balsa wood is given. Sterilization by ethylene oxide plus heat enhances the average specific energy of balsa while plastic impregnation followed by irradiation-induced polymerization does not.

  8. The effect of step height on energy dissipation in stepped spillways

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A two-dimensional, physical model was constructed to evaluate the energy dissipation on a 4(H):1(V) slope spillway chute. Step heights of 38 mm (1.5 inches), 76 mm (3.0 inches), and 152 mm (6 inches) were evaluated, and energy losses created by these steps were compared. Model unit discharges rang...

  9. Clinical application of fluctuation dissipation theory - Prediction of heart rate response to spontaneous breathing trial

    NASA Astrophysics Data System (ADS)

    Niestemski, Liang R.; Chen, Man; Prevost, Robert; McRae, Michael; Cholleti, Sharath; Najarro, Gabriel; Buchman, Timothy G.; Deem, Michael W.

    2013-03-01

    Contrary to the traditional view of the healthy physiological state as being a single static state, variation in physiologic variables has more recently been suggested to be a key component of the healthy state. Indeed, aging and disease are characterized by a loss of such variability. We apply the conceptual framework of fluctuation-dissipation theory (FDT) to predict the response to a common clinical intervention from historical fluctuations in physiologic time series data. The non-equilibrium FDT relates the response of a system to a perturbation to natural fluctuations in the stationary state of the system. We seek to understand with the FDT a common clinical perturbation, the spontaneous breathing trial (SBT), in which mechanical ventilation is briefly suspended while the patient breathes freely for a period of time. As a stress upon the heart of the patient, the SBT can be characterized as a perturbation of heart rate dynamics. A non-equilibrium, but steady-state FDT allows us to predict the heart rate recovery after the SBT stress. We show that the responses of groups of similar patients to the spontaneous breathing trial can be predicted by this approach. This mathematical framework may serve as part of the basis for personalized critical care.

  10. Shear effects on energy dissipation from an elastic beam on a rigid foundation

    DOE PAGESBeta

    Brink, Adam Ray; Quinn, D. Dane

    2015-10-20

    This paper describes the energy dissipation arising from microslip for an elastic shell incorporating shear and longitudinal deformation resting on a rough-rigid foundation. This phenomenon is investigated using finite element (FE) analysis and nonlinear geometrically exact shell theory. Both approaches illustrate the effect of shear within the shell and observe a reduction in the energy dissipated from microslip as compared to a similar system neglecting shear deformation. In particular, it is found that the shear deformation allows for load to be transmitted beyond the region of slip so that the entire interface contributes to the load carrying capability of themore » shell. The energy dissipation resulting from the shell model is shown to agree well with that arising from the FE model, and this representation can be used as a basis for reduced order models that capture the microslip phenomenon.« less

  11. Shear effects on energy dissipation from an elastic beam on a rigid foundation

    SciTech Connect

    Brink, Adam Ray; Quinn, D. Dane

    2015-10-20

    This paper describes the energy dissipation arising from microslip for an elastic shell incorporating shear and longitudinal deformation resting on a rough-rigid foundation. This phenomenon is investigated using finite element (FE) analysis and nonlinear geometrically exact shell theory. Both approaches illustrate the effect of shear within the shell and observe a reduction in the energy dissipated from microslip as compared to a similar system neglecting shear deformation. In particular, it is found that the shear deformation allows for load to be transmitted beyond the region of slip so that the entire interface contributes to the load carrying capability of the shell. The energy dissipation resulting from the shell model is shown to agree well with that arising from the FE model, and this representation can be used as a basis for reduced order models that capture the microslip phenomenon.

  12. The role of coral reef rugosity in dissipating wave energy and coastal protection

    NASA Astrophysics Data System (ADS)

    Harris, Daniel; Rovere, Alessio; Parravicini, Valeriano; Casella, Elisa

    2016-04-01

    Coral reefs are the most effective natural barrier in dissipating wave energy through breaking and bed friction. The attenuation of wave energy by coral reef flats is essential in the protection and stability of coral reef aligned coasts and reef islands. However, the effectiveness of wave energy dissipation by coral reefs may be diminished under future climate change scenarios with a potential reduction of coral reef rugosity due to increased stress environmental stress on corals. The physical roughness or rugosity of coral reefs is directly related to ecological diversity, reef health, and hydrodynamic roughness. However, the relationship between physical roughness and hydrodynamic roughness is not well understood despite the crucial role of bed friction in dissipating wave energy in coral reef aligned coasts. We examine the relationship between wave energy dissipation across a fringing reef in relation to the cross-reef ecological zonation and the benthic hydrodynamic roughness. Waves were measured by pressure transducers in a cross-reef transect on the reefs flats and post processed on a wave by wave basis to determine wave statistics such as significant wave height and wave period. Results from direct wave measurement were then used to calibrate a 1D wave dissipation model that incorporates dissipation functions due to bed friction and wave breaking. This model was used to assess the bed roughness required to produce the observed wave height dissipation during propagation from deep water and across the coral reef flats. Changes in wave dissipation was also examined under future scenarios of sea level rise and reduced bed roughness. Three dimensional models of the benthic reef structure were produced through structure-from-motion photogrammetry surveys. Reef rugosity was then determined from these surveys and related to the roughness results from the calibrated model. The results indicate that applying varying roughness coefficients as the benthic ecological

  13. Stably stratified shear turbulence: A new model for the energy dissipation length scale

    NASA Technical Reports Server (NTRS)

    Cheng, Y.; Canuto, V. M.

    1994-01-01

    A model is presented to compute the turbulent kinetic energy dissipation length scale l(sub epsilon) in a stably stratified shear flow. The expression for l(sub epsilon) is derived from solving the spectral balance equation for the turbulent kinetic energy. The buoyancy spectrum entering such equation is constructed using a Lagrangian timescale with modifications due to stratification. The final result for l(sub epsilon) is given in algebraic form as a function of the Froude number Fr and the flux Richardson number R(sub f), l(sub epsilon) = l(sub epsilon)(Fr, R(sub f). The model predicts that for R(sub f) less than R(sub fc), l(sub epsilon) decreases with stratification. An attractive feature of the present model is that it encompasses, as special cases, some seemingly different models for l(sub epsilon) that have been proposed in the past by Deardorff, Hunt et al., Weinstock, and Canuto and Minotti. An alternative form for the dissipation rate epsilon is also discussed that may be useful when one uses a prognostic equation for the heat flux. The present model is applicable to subgrid-scale models, which are needed in large eddy simulations (LES), as well as to ensemble average models. The model is applied to predict the variation of l(sub epsilon) with height z in the planetary boundary layer. The resulting l(sub epsilon) versus z profile reproduces very closely the nonmonotonic profile of l(sub epsilon) exhibited by many LES calculations, beginning with the one by Deardorff in 1974.

  14. Rock Drilling Performance Evaluation by an Energy Dissipation Based Rock Brittleness Index

    NASA Astrophysics Data System (ADS)

    Munoz, H.; Taheri, A.; Chanda, E. K.

    2016-08-01

    To reliably estimate drilling performance both tool-rock interaction laws along with a proper rock brittleness index are required to be implemented. In this study, the performance of a single polycrystalline diamond compact (PDC) cutter cutting and different drilling methods including PDC rotary drilling, roller-cone rotary drilling and percussive drilling were investigated. To investigate drilling performance by rock strength properties, laboratory PDC cutting tests were performed on different rocks to obtain cutting parameters. In addition, results of laboratory and field drilling on different rocks found elsewhere in literature were used. Laboratory and field cutting and drilling test results were coupled with values of a new rock brittleness index proposed herein and developed based on energy dissipation withdrawn from the complete stress-strain curve in uniaxial compression. To quantify cutting and drilling performance, the intrinsic specific energy in rotary-cutting action, i.e. the energy consumed in pure cutting action, and drilling penetration rate values in percussive action were used. The results show that the new energy-based brittleness index successfully describes the performance of different cutting and drilling methods and therefore is relevant to assess drilling performance for engineering applications.

  15. A parametric sensitivity study of entropy production and kinetic energy dissipation using the FAMOUS AOGCM

    NASA Astrophysics Data System (ADS)

    Pascale, Salvatore; Gregory, Jonathan M.; Ambaum, Maarten H. P.; Tailleux, Rémi

    2012-03-01

    The possibility of applying either the maximum entropy production conjecture of Paltridge (Q J R Meteorol Soc 101:475-484, 1975) or the conjecture of Lorenz (Generation of available potential energy and the intensity of the general circulation. Pergamon, Tarrytown, 1960) of maximum generation of available potential energy (APE) in FAMOUS, a complex but low-resolution AOGCM, is explored by varying some model parameters to which the simulated climate is highly sensitive, particularly the convective entrainment rate, ɛ, and cloud droplet-to-rain-conversion rate, c T . The climate response is analysed in terms of its entropy production and the strength of the Lorenz energy cycle. If either conjecture is true, the parameter values which yield the most realistic climate will also maximise the relevant quantity. No maximum is found in the total material entropy production, which is dominated by the hydrological cycle and tends to increase monotonically with global-mean temperature, which is not constant because the parameter variations affect the net input of solar radiation at the top of the atmosphere (TOA). In contrast, there is a non-monotonic, peaked behaviour in the generation of APE and entropy production associated with kinetic energy dissipation, with the standard FAMOUS values for ɛ and c T occurring nearly at the maximising ones. The maximum states are shown to be states of vigorous baroclinic activity. The peak in the generation of APE appears to be related to a trade-off between the mean vertical stability and horizontal stratification. Experiments are repeated for a simplified setup in which the net solar input at TOA is fixed. Again a peak in the generation of APE is found in association with the maximum baroclinic activity, but no trade-off of the kind shown by simple climate models is found between meridional heat transport and the meridional temperature gradient. We conclude that the maximum entropy production conjecture does not hold within the

  16. Energy conserving and potential-enstrophy dissipating schemes for the shallow water equations

    NASA Technical Reports Server (NTRS)

    Arakawa, Akio; Hsu, Yueh-Jiuan G.

    1990-01-01

    To incorporate potential enstrophy dissipation into discrete shallow water equations with no or arbitrarily small energy dissipation, a family of finite-difference schemes have been derived with which potential enstrophy is guaranteed to decrease while energy is conserved (when the mass flux is nondivergent and time is continuous). Among this family of schemes, there is a member that minimizes the spurious impact of infinite potential vorticities associated with infinitesimal fluid depth. The scheme is, therefore, useful for problems in which the free surface may intersect with the lower boundary.

  17. Hydration and energy dissipation measurements of biomolecules on a piezoelectric quartz oscillator by admittance analyses.

    PubMed

    Ozeki, Tomomitsu; Morita, Mizuki; Yoshimine, Hiroshi; Furusawa, Hiroyuki; Okahata, Yoshio

    2007-01-01

    By using a 27-MHz piezoelectric quartz oscillator connected with a vector network analyzer, we obtained resonance frequency decreases (-DeltaFwater) and energy dissipation increases (DeltaDwater) during binding of biotinylated bovine serum albumin, biotinylated ssDNA, biotinylated dsDNA, and biotinylated pullulan to a NeutrAvidin-immobilized 27-MHz quartz crystal microbalance (QCM) plate in aqueous solution, as well as in the wet air phase (98% humidity, -DeltaFwet and DeltaDwet) and in the dry air phase (-DeltaFair and DeltaDair). -DeltaFwater indicates the total mass of the molecule, bound water, and vibrated water in aqueous solutions. -DeltaFwet indicates the total mass of the molecule and bound water. -DeltaFair simply shows the real mass of the molecule on the QCM. In terms of results, (-DeltaFwet)/(-DeltaFair) values indicated the bound water ratios per unit biomolecular mass were on the order of pullulan (2.1-2.2) > DNAs = proteins (1.4-1.6) > polystyrene (1.0). The (-DeltaFwater)/(-DeltaFair) values indicated the hydrodynamic water (bound and vibrated water) ratios per unit biomolecular mass were on the order of dsDNA (6.5) > ssDNA = pullulan (3.5-4.4) > proteins (2.4-2.5) > polystyrene (1.0). Energy dissipation parameters per unit mass in water (DeltaDwater/(-DeltaFair)) were on the order of pullulan > dsDNA > ssDNA > proteins > polystyrene. Energy dissipation in the wet and dry air phases (DeltaDwet and DeltaDair) were negligibly small, which indicates even these biomolecules act as elastic membranes in the air phase (without aqueous solution). We obtained a good linear relationship between [(-DeltaFwater)/(-DeltaFair) - 1], which is indicative of hydration and DeltaDwater/(-DeltaFair) of proteins. The aforementioned values suggest that the energy dissipation of proteins was mainly caused by hydration and that proteins themselves are elastic molecules without energy dissipation in aqueous solutions. On the contrary, plots in cases of denatured proteins

  18. On the stability and energy dissipation in magnetized radio galaxy jets.

    NASA Astrophysics Data System (ADS)

    Bromberg, Omer; Tchekhovskoy, Alexander

    2016-07-01

    It is commonly accepted that the relativistic jets observed in radio galaxies are launched magnetically and are powered by the rotational energy of the central supermassive black hole. Such jets carry most of their energy in the form of electromagnetic Poynting flux. However by the time the ejecta reach the emission zone most of that energy is transferred to relativistic motions of the jet material with a large fraction given to non-thermal particles, which calls for an efficient dissipation mechanism to work within the jet without compromising its integrity. Understanding the energy dissipation mechanisms and stability of Poynting flux dominated jets is therefore crucial for modeling these astrophysical objects. In this talk I will present the first self consistent 3D simulations of the formation and propagation of highly magnetized (σ ˜25), relativistic jets in a medium. We find that the jets develop two types of instability: i) a local, "internal" kink mode which efficiently dissipates half of the magnetic energy into heat, and ii) a global "external" mode that grows on longer time scales and causes the jets to bend sideways and wobble. Low power jets propagating in media with flat density profiles, such as galaxy cluster cores, are susceptible to the global mode, and develop FRI like morphology. High power jets remain stable as they cross the cores, break out and accelerate to large distances, appearing as FRII jets. Thus magnetic kink instability can account for both the magnetic energy dissipation and the population dichotomy in radio galaxy jets.

  19. Predicting NonInertial Effects with Algebraic Stress Models which Account for Dissipation Rate Anisotropies

    NASA Technical Reports Server (NTRS)

    Jongen, T.; Machiels, L.; Gatski, T. B.

    1997-01-01

    Three types of turbulence models which account for rotational effects in noninertial frames of reference are evaluated for the case of incompressible, fully developed rotating turbulent channel flow. The different types of models are a Coriolis-modified eddy-viscosity model, a realizable algebraic stress model, and an algebraic stress model which accounts for dissipation rate anisotropies. A direct numerical simulation of a rotating channel flow is used for the turbulent model validation. This simulation differs from previous studies in that significantly higher rotation numbers are investigated. Flows at these higher rotation numbers are characterized by a relaminarization on the cyclonic or suction side of the channel, and a linear velocity profile on the anticyclonic or pressure side of the channel. The predictive performance of the three types of models are examined in detail, and formulation deficiencies are identified which cause poor predictive performance for some of the models. Criteria are identified which allow for accurate prediction of such flows by algebraic stress models and their corresponding Reynolds stress formulations.

  20. An analysis of lower-dimensional approximations to the scalar dissipation rate using direct numerical simulations of plane jet flames

    SciTech Connect

    Chen, Jackie; Sankaran, Ramanan; Hawkes, Evatt R

    2009-05-01

    The difficulty of experimental measurements of the scalar dissipation rate in turbulent flames has required researchers to estimate the true three-dimensional (3D) scalar dissipation rate from one-dimensional (1D) or two-dimensional (2D) gradient measurements. In doing so, some relationship must be assumed between the true values and their lower dimensional approximations. We develop these relationships by assuming a form for the statistics of the gradient vector orientation, which enables several new results to be obtained and the true 3D scalar dissipation PDF to be reconstructed from the lower-dimensional approximations. We use direct numerical simulations (DNS) of turbulent plane jet flames to examine the orientation statistics, and verify our assumptions and final results. We develop and validate new theoretical relationships between the lower-dimensional and true moments of the scalar dissipation PDF assuming a log-normal true PDF. We compare PDFs reconstructed from lower-dimensional gradient projections with the true values and find an excellent agreement for a 2D simulated measurement and also for a 1D simulated measurement perpendicular to the mean flow variations. Comparisons of PDFs of thermal dissipation from DNS with those obtained via reconstruction from 2D experimental measurements show a very close match, indicating this PDF is not unique to a particular flame configuration. We develop a technique to reconstruct the joint PDF of the scalar dissipation and any other scalar, such as chemical species or temperature. Reconstructed conditional means of the hydroxyl mass fraction are compared with the true values and an excellent agreement is obtained.

  1. Energy dissipation and error probability in fault-tolerant binary switching

    PubMed Central

    Fashami, Mohammad Salehi; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2013-01-01

    The potential energy profile of an ideal binary switch is a symmetric double well. Switching between the wells without energy dissipation requires time-modulating the height of the potential barrier separating the wells and tilting the profile towards the desired well at the precise juncture when the barrier disappears. This, however, demands perfect timing synchronization and is therefore fault-intolerant even in the absence of noise. A fault-tolerant strategy that requires no time modulation of the barrier (and hence no timing synchronization) switches by tilting the profile by an amount at least equal to the barrier height and dissipates at least that amount of energy in abrupt switching. Here, we present a third strategy that requires a time modulated barrier but no timing synchronization. It is therefore fault-tolerant, error-free in the absence of thermal noise, and yet it dissipates arbitrarily small energy in a noise-free environment since an arbitrarily small tilt is required for slow switching. This case is exemplified with stress induced switching of a shape-anisotropic single-domain soft nanomagnet dipole-coupled to a hard magnet. When thermal noise is present, we show analytically that the minimum energy dissipated to switch in this scheme is ~2kTln(1/p) [p = switching error probability]. PMID:24220310

  2. Relaxation dynamics in quantum dissipative systems: The microscopic effect of intramolecular vibrational energy redistribution

    SciTech Connect

    Uranga-Piña, L.; Tremblay, J. C.

    2014-08-21

    We investigate the effect of inter-mode coupling on the vibrational relaxation dynamics of molecules in weak dissipative environments. The simulations are performed within the reduced density matrix formalism in the Markovian regime, assuming a Lindblad form for the system-bath interaction. The prototypical two-dimensional model system representing two CO molecules approaching a Cu(100) surface is adapted from an ab initio potential, while the diatom-diatom vibrational coupling strength is systematically varied. In the weak system-bath coupling limit and at low temperatures, only first order non-adiabatic uni-modal coupling terms contribute to surface-mediated vibrational relaxation. Since dissipative dynamics is non-unitary, the choice of representation will affect the evolution of the reduced density matrix. Two alternative representations for computing the relaxation rates and the associated operators are thus compared: the fully coupled spectral basis, and a factorizable ansatz. The former is well-established and serves as a benchmark for the solution of Liouville-von Neumann equation. In the latter, a contracted grid basis of potential-optimized discrete variable representation is tailored to incorporate most of the inter-mode coupling, while the Lindblad operators are represented as tensor products of one-dimensional operators, for consistency. This procedure results in a marked reduction of the grid size and in a much more advantageous scaling of the computational cost with respect to the increase of the dimensionality of the system. The factorizable method is found to provide an accurate description of the dissipative quantum dynamics of the model system, specifically of the time evolution of the state populations and of the probability density distribution of the molecular wave packet. The influence of intra-molecular vibrational energy redistribution appears to be properly taken into account by the new model on the whole range of coupling strengths. It

  3. Loss of energy dissipation capacity from the deadzone in linear and nonlinear viscous damping devices

    NASA Astrophysics Data System (ADS)

    Tong, Mai; Liebner, Thomas

    2007-03-01

    In a viscous damping device under cyclic loading, after the piston reaches a peak stroke, the reserve movement that follows may sometimes experience a short period of delayed or significantly reduced device force output. A similar delay or reduced device force output may also occur at the damper’s initial stroke as it moves away from its neutral position. This phenomenon is referred to as the effect of “deadzone”. The deadzone can cause a loss of energy dissipation capacity and less efficient vibration control. It is prominent in small amplitude vibrations. Although there are many potential causes of deadzone such as environmental factors, construction, material aging, and manufacture quality, in this paper, its general effect in linear and nonlinear viscous damping devices is analyzed. Based on classical dynamics and damping theory, a simple model is developed to capture the effect of deadzone in terms of the loss of energy dissipation capacity. The model provides several methods to estimate the loss of energy dissipation within the deadzone in linear and sublinear viscous fluid dampers. An empirical equation of loss of energy dissipation capacity versus deadzone size is formulated, and the equivalent reduction of effective damping in SDOF systems has been obtained. A laboratory experimental evaluation is carried out to verify the effect of deadzone and its numerical approximation. Based on the analysis, a modification is suggested to the corresponding formulas in FEMA 356 for calculation of equivalent damping if a deadzone is to be considered.

  4. Dissipation of excess excitation energy of the needle leaves in Pinus trees during cold winters

    NASA Astrophysics Data System (ADS)

    Zhang, AO; Cui, Zhen-Hai; Yu, Jia-Lin; Hu, Zi-Ling; Ding, Rui; Ren, Da-Ming; Zhang, Li-Jun

    2016-05-01

    Photooxidative damage to the needle leaves of evergreen trees results from the absorption of excess excitation energy. Efficient dissipation of this energy is essential to prevent photodamage. In this study, we determined the fluorescence transients, absorption spectra, chlorophyll contents, chlorophyll a/b ratios, and relative membrane permeabilities of needle leaves of Pinus koraiensis, Pinus tabulaeformis, and Pinus armandi in both cold winter and summer. We observed a dramatic decrease in the maximum fluorescence (F m) and substantial absorption of light energy in winter leaves of all three species. The F m decline was not correlated with a decrease in light absorption or with changes in chlorophyll content and chlorophyll a/b ratio. The results suggested that the winter leaves dissipated a large amount of excess energy as heat. Because the cold winter leaves had lost normal physiological function, the heat dissipation depended solely on changes in the photosystem II supercomplex rather than the xanthophyll cycle. These findings imply that more attention should be paid to heat dissipation via changes in the photosystem complex structure during the growing season.

  5. Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data

    PubMed

    Egbert; Ray

    2000-06-15

    How and where the ocean tides dissipate their energy are long-standing questions that have consequences ranging from the history of the Moon to the mixing of the oceans. Historically, the principal sink of tidal energy has been thought to be bottom friction in shallow seas. There has long been suggestive evidence, however, that tidal dissipation also occurs in the open ocean through the scattering by ocean-bottom topography of surface tides into internal waves, but estimates of the magnitude of this possible sink have varied widely. Here we use satellite altimeter data from Topex/Poseidon to map empirically the tidal energy dissipation. We show that approximately 10(12) watts--that is, 1 TW, representing 25-30% of the total dissipation--occurs in the deep ocean, generally near areas of rough topography. Of the estimated 2 TW of mixing energy required to maintain the large-scale thermohaline circulation of the ocean, one-half could therefore be provided by the tides, with the other half coming from action on the surface of the ocean. PMID:10866194

  6. Stochastic friction force mechanism of energy dissipation in noncontact atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kantorovich, L. N.

    2001-12-01

    The tip-surface interaction in noncontact atomic force microscopy (NC-AFM) leads to energy dissipation, which has been used as another imaging mechanism of surface topography with atomic resolution. In this paper, using a rigorous approach based on the coarse graining method of (classical) nonequilibrium statistical mechanics, we derive the Fokker-Planck equation for the tip distribution function and then the Langevin equation (equation of motion) for the tip. We show that the latter equation contains a friction force leading to the energy dissipation. The friction force is related to the correlation function of the fluctuating tip-surface force in agreement with earlier treatments by other methods. Using a simple model of a plane surface in which only one surface atom interacts directly with the tip (it, however, interacts with other surface atoms), we calculate the friction coefficient and the corresponding dissipation energy as a function of the tip position. In our model all surface atoms are allowed to relax. Nevertheless, our calculations qualitatively agree with a previous much simpler treatment by Gauthier and Tsukada [Phys. Rev. B 60, 11 716 (1999)] that, at least for the plain terraces, the calculated dissipation energies appear to be much smaller than observed in experiments. We also demonstrate the validity of the Markovian approximation in studying the NC-AFM system.

  7. Sucrose-fueled, energy dissipative, transient formation of molecular hydrogels mediated by yeast activity.

    PubMed

    Angulo-Pachón, César A; Miravet, Juan F

    2016-04-01

    A biologically mediated, energy dissipative, reversible formation of fibrillar networks is reported. The process of gelation is linked to sucrose-fueled production of CO2 by baker's yeast (Saccharomyces cerevisiae). Continuous fueling of the system is required to maintain the self-assembled fibrillar network. PMID:27009800

  8. Significant Dissipation of Tidal Energy in the Deep Ocean Inferred from Satellite Altimeter Data

    NASA Technical Reports Server (NTRS)

    Egbert, G. D.; Ray, R. D.

    2000-01-01

    How and where the ocean tides dissipate their energy are longstanding questions that have consequences ranging from the history of the Moon to the mixing of the oceans. Historically, the principal sink of tidal energy has been thought to be bottom friction in shallow seas. There has long been suggestive however, that tidal dissipation also occurs in the open ocean through the scattering by ocean-bottom topography of surface tides into internal waves, but estimates of the magnitude of this possible sink have varied widely. Here we use satellite altimeter data from Topex/Poseidon to map empirically the tidal energy dissipation. We show that approximately 10(exp 12) watts-that is, 1 TW, representing 25-30% of the total dissipation-occurs in the deep ocean, generally near areas of rough topography. Of the estimated 2 TW of mixing energy required to maintain the large-scale thermohaline circulation of the ocean, one-half could therefore be provided by the tides, with the other half coming from action on the surface of the ocean.

  9. Exciton Lifetime Paradoxically Enhanced by Dissipation and Decoherence: Toward Efficient Energy Conversion of a Solar Cell.

    PubMed

    Yamada, Yasuhiro; Yamaji, Youhei; Imada, Masatoshi

    2015-11-01

    Energy dissipation and decoherence are at first glance harmful to acquiring the long exciton lifetime desired for efficient photovoltaics. In the presence of both optically forbidden (namely, dark) and allowed (bright) excitons, however, they can be instrumental, as suggested in photosynthesis. By simulating the quantum dynamics of exciton relaxations, we show that the optimized decoherence that imposes a quantum-to-classical crossover with the dissipation realizes a dramatically longer lifetime. In an example of a carbon nanotube, the exciton lifetime increases by nearly 2 orders of magnitude when the crossover triggers a stable high population in the dark excitons. PMID:26588415

  10. Exciton Lifetime Paradoxically Enhanced by Dissipation and Decoherence: Toward Efficient Energy Conversion of a Solar Cell

    NASA Astrophysics Data System (ADS)

    Yamada, Yasuhiro; Yamaji, Youhei; Imada, Masatoshi

    2015-11-01

    Energy dissipation and decoherence are at first glance harmful to acquiring the long exciton lifetime desired for efficient photovoltaics. In the presence of both optically forbidden (namely, dark) and allowed (bright) excitons, however, they can be instrumental, as suggested in photosynthesis. By simulating the quantum dynamics of exciton relaxations, we show that the optimized decoherence that imposes a quantum-to-classical crossover with the dissipation realizes a dramatically longer lifetime. In an example of a carbon nanotube, the exciton lifetime increases by nearly 2 orders of magnitude when the crossover triggers a stable high population in the dark excitons.

  11. Anomalous dissipation and kinetic-energy distribution in pipes at very high Reynolds numbers.

    PubMed

    Chen, Xi; Wei, Bo-Bo; Hussain, Fazle; She, Zhen-Su

    2016-01-01

    A symmetry-based theory is developed for the description of (streamwise) kinetic energy K in turbulent pipes at extremely high Reynolds numbers (Re's). The theory assumes a mesolayer with continual deformation of wall-attached eddies which introduce an anomalous dissipation, breaking the exact balance between production and dissipation. An outer peak of K is predicted above a critical Re of 10^{4}, in good agreement with experimental data. The theory offers an alternative explanation for the recently discovered logarithmic distribution of K. The concept of anomalous dissipation is further supported by a significant modification of the k-ω equation, yielding an accurate prediction of the entire K profile. PMID:26871016

  12. State transitions redistribute rather than dissipate energy between the two photosystems in Chlamydomonas.

    PubMed

    Nawrocki, Wojciech J; Santabarbara, Stefano; Mosebach, Laura; Wollman, Francis-André; Rappaport, Fabrice

    2016-01-01

    Photosynthesis converts sunlight into biologically useful compounds, thus fuelling practically the entire biosphere. This process involves two photosystems acting in series powered by light harvesting complexes (LHCs) that dramatically increase the energy flux to the reaction centres. These complexes are the main targets of the regulatory processes that allow photosynthetic organisms to thrive across a broad range of light intensities. In microalgae, one mechanism for adjusting the flow of energy to the photosystems, state transitions, has a much larger amplitude than in terrestrial plants, whereas thermal dissipation of energy, the dominant regulatory mechanism in plants, only takes place after acclimation to high light. Here we show that, at variance with recent reports, microalgal state transitions do not dissipate light energy but redistribute it between the two photosystems, thereby allowing a well-balanced influx of excitation energy. PMID:27249564

  13. Control of flow around a circular cylinder for minimizing energy dissipation

    NASA Astrophysics Data System (ADS)

    Naito, Hiroshi; Fukagata, Koji

    2014-11-01

    Control of flow around a circular cylinder is studied numerically aiming at minimization of the energy dissipation. First, we derive a mathematical relationship (i.e., identity) between the energy dissipation in an infinitely large volume and the surface quantities, so that the cost function can be expressed by the surface quantities only. Subsequently a control law to minimize the energy dissipation is derived by using the suboptimal control procedure [J. Fluid Mech. 401, 123 (1999), 10.1017/S002211209900659X]. The performance of the present suboptimal control law is evaluated by a parametric study by varying the value of the arbitrary parameter contained. Two Reynolds numbers, Re =100 and 1000, are investigated by two-dimensional simulations. Although no improvement is obtained at Re =100 , the present suboptimal control shows better results at Re =1000 than the suboptimal controls previously proposed. With the present suboptimal control, the dissipation and the drag are reduced by 58% and 44% as compared to the uncontrolled case, respectively. The suction around the front stagnation point and the blowing in the rear half are found to be weakened as compared to those in the previous suboptimal control targeting at pressure drag reduction. A predetermined control based on the control input profile obtained by the suboptimal control is also performed. The energy dissipation and the drag are found to be reduced as much as those in the present suboptimal control. It is also found that the present suboptimal and predetermined controls have better energy efficiencies than the suboptimal control previously proposed. Investigation at different control amplitudes reveals an advantage of the present control at higher amplitude. Toward its practical implementation, a localized version of the predetermined control is also examined, and it is found to work as effectively as the continuous case. Finally, the present predetermined control is confirmed to work well in a three

  14. Effects of uncertainty in position on the dissipation rates and the entanglement of two atoms collectively interacting with a reservoir

    NASA Astrophysics Data System (ADS)

    Castaños, L. O.; Jáuregui, R.

    2011-06-01

    We consider two two-level atoms interacting collectively with all the modes of the quantum electromagnetic field. The center-of-mass motion of each atom is quantized in three dimensions and each atom is placed in a harmonic oscillator potential. We describe a method that factorizes an approximate density operator of the two atoms in parts which evolve under different portions of the Hamiltonian. We apply this method to the system under consideration to study the effect of the uncertainty in the position of the atoms on the dissipation rates and on the entanglement between the internal degrees of freedom of the two atoms. We find that the uncertainty in position can give rise to smaller dissipation rates. This in turn affects the entanglement which may decay exponentially with smaller decay rates or may even decay asymptotically by a power law.

  15. Effects of uncertainty in position on the dissipation rates and the entanglement of two atoms collectively interacting with a reservoir

    SciTech Connect

    Castanos, L. O.; Jauregui, R.

    2011-06-15

    We consider two two-level atoms interacting collectively with all the modes of the quantum electromagnetic field. The center-of-mass motion of each atom is quantized in three dimensions and each atom is placed in a harmonic oscillator potential. We describe a method that factorizes an approximate density operator of the two atoms in parts which evolve under different portions of the Hamiltonian. We apply this method to the system under consideration to study the effect of the uncertainty in the position of the atoms on the dissipation rates and on the entanglement between the internal degrees of freedom of the two atoms. We find that the uncertainty in position can give rise to smaller dissipation rates. This in turn affects the entanglement which may decay exponentially with smaller decay rates or may even decay asymptotically by a power law.

  16. Energy dissipation of nanoconfined hydration layer: Long-range hydration on the hydrophilic solid surface

    PubMed Central

    Kim, Bongsu; Kwon, Soyoung; Mun, Hyosik; An, Sangmin; Jhe, Wonho

    2014-01-01

    The hydration water layer (HWL), a ubiquitous form of water on the hydrophilic surfaces, exhibits anomalous characteristics different from bulk water and plays an important role in interfacial interactions. Despite extensive studies on the mechanical properties of HWL, one still lacks holistic understanding of its energy dissipation, which is critical to characterization of viscoelastic materials as well as identification of nanoscale dissipation processes. Here we address energy dissipation of nanoconfined HWL between two atomically flat hydrophilic solid surfaces (area of ~120 nm2) by small amplitude-modulation, noncontact atomic force microscopy. Based on the viscoelastic hydration-force model, the average dissipation energy is ~1 eV at the tapping amplitude (~0.1 nm) of the tip. In particular, we determine the accurate HWL thickness of ~6 layers of water molecules, as similarly observed on biological surfaces. Such a long-range interaction of HWL should be considered in the nanoscale phenomena such as friction, collision and self-assembly. PMID:25267426

  17. Temperature dependence of energy dissipation on NaCl(001) in non-contact atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Langewisch, G.; Fuchs, H.; Schirmeisen, A.

    2010-08-01

    The dissipative tip-sample interactions are measured by dynamic force spectroscopy for silicon tips on NaCl(001) in ultrahigh vacuum in the attractive and repulsive force regimes. Force and dissipation versus distance curves were obtained for different sample temperatures ranging from 35 to 285 K. Detailed comparison in different distance regimes shows that neither the force nor energy dissipation exhibits a systematic variation with sample temperature.

  18. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    PubMed Central

    Zhang, Yanwen; Stocks, G. Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C.; Wang, Lumin; Béland, Laurent K.; Stoller, Roger E.; Samolyuk, German D.; Caro, Magdalena; Caro, Alfredo; Weber, William J.

    2015-01-01

    A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications. PMID:26507943

  19. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Yanwen; Stocks, G. Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C.; Wang, Lumin; Béland, Laurent K.; Stoller, Roger E.; Samolyuk, German D.; Caro, Magdalena; Caro, Alfredo; Weber, William J.

    2015-10-01

    A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications.

  20. Influence of chemical disorder on energy dissipation and defect evolution in concentrated solid solution alloys.

    PubMed

    Zhang, Yanwen; Stocks, G Malcolm; Jin, Ke; Lu, Chenyang; Bei, Hongbin; Sales, Brian C; Wang, Lumin; Béland, Laurent K; Stoller, Roger E; Samolyuk, German D; Caro, Magdalena; Caro, Alfredo; Weber, William J

    2015-01-01

    A grand challenge in materials research is to understand complex electronic correlation and non-equilibrium atomic interactions, and how such intrinsic properties and dynamic processes affect energy transfer and defect evolution in irradiated materials. Here we report that chemical disorder, with an increasing number of principal elements and/or altered concentrations of specific elements, in single-phase concentrated solid solution alloys can lead to substantial reduction in electron mean free path and orders of magnitude decrease in electrical and thermal conductivity. The subsequently slow energy dissipation affects defect dynamics at the early stages, and consequentially may result in less deleterious defects. Suppressed damage accumulation with increasing chemical disorder from pure nickel to binary and to more complex quaternary solid solutions is observed. Understanding and controlling energy dissipation and defect dynamics by altering alloy complexity may pave the way for new design principles of radiation-tolerant structural alloys for energy applications. PMID:26507943

  1. Analysis of energy dissipation and deposition in elastic bodies impacting at hypervelocities

    NASA Technical Reports Server (NTRS)

    Medina, David F.; Allahdadi, Firooz A.

    1992-01-01

    A series of impact problems were analyzed using the Eulerian hydrocode CTH. The objective was to quantify the amount of energy dissipated locally by a projectile-infinite plate impact. A series of six impact problems were formulated such that the mass and speed of each projectile were varied in order to allow for increasing speed with constant kinetic energy. The properties and dimensions of the plate were the same for each projectile impact. The resulting response of the plate was analyzed for global Kinetic Energy, global momentum, and local maximum shear stress. The percentage of energy dissipated by the various hypervelocity impact phenomena appears as a relative change of shear stress at a point away from the impact in the plate.

  2. Two Theorems on Dissipative Energy Losses in Capacitor Systems

    ERIC Educational Resources Information Center

    Newburgh, Ronald

    2005-01-01

    This article examines energy losses in charge motion in two capacitor systems. In the first charge is transferred from a charged capacitor to an uncharged one through a resistor. In the second a battery charges an originally uncharged capacitor through a resistance. Analysis leads to two surprising general theorems. In the first case the fraction…

  3. Prediction of heart rate response to conclusion of the spontaneous breathing trial by fluctuation dissipation theory

    NASA Astrophysics Data System (ADS)

    Chen, Man; Niestemski, Liang Ren; Prevost, Robert; McRae, Michael; Cholleti, Sharath; Najarro, Gabriel; Buchman, Timothy G.; Deem, Michael W.

    2013-02-01

    The non-equilibrium fluctuation dissipation theorem is applied to predict how critically ill patients respond to treatment, based upon data currently collected by standard hospital monitoring devices. This framework is demonstrated on a common procedure in critical care: the spontaneous breathing trial. It is shown that the responses of groups of similar patients to the spontaneous breathing trial can be predicted by the non-equilibrium fluctuation dissipation approach. This mathematical framework, when fully formed and applied to other clinical interventions, may serve as part of the basis for personalized critical care.

  4. Energy Dissipation and Defect Generation for Nanocrystalline Silicon Carbide

    SciTech Connect

    Gao, Fei; Chen, Dong; Hu, Wangyu; Weber, William J.

    2010-05-05

    Large-scale molecular dynamics simulations have been employed to study defect generation and primary damage state in nano crystalline (NC) SiC of average grain diameters from 5 to 21 nm. Primary knock-on atom (PKA) kinetic energies of 10 keV are simulated, and cascade structures in NC SiC with a grain size smaller than 12 nm are generally different from those generated in single crystalline SiC. It is found that the local stresses near the grain boundaries (GBs) strongly affect the behavior of the PKA and secondary recoil atoms (SRAs), and the GBs act as sinks for deposition of kinetic energy. A striking feature is that the PKA and SRAs preferentially deposit energy along the GBs for grains with average size less 12 nm, which results in atomic displacements primarily within the GBs; whereas for larger grain sizes, most defects are produced within the grains. There exists a crossover in defect production, which is manifested in switching from grain boundary damage to grain damage. The most common defects created in NC SiC are antisite defects, following by vacancies and interstitials, in contrast to those produced in a single crystalline SiC, where the dominate defects are Frenkel pairs. Defect production efficiency increases with increasing the grain size, with a typical value of 0.18 for small grains and rising to 0.5 for larger grains.

  5. Energy dissipation and defect generation in nanocrystalline silicon carbide

    SciTech Connect

    Gao, F.; Weber, W. J.; Chen, D.; Hu Wangyu

    2010-05-01

    Large-scale molecular-dynamics simulations have been employed to study defect generation and primary damage state in nanocrystalline (NC) SiC of average grain diameters from 5 to 21 nm. Primary knock-on atom (PKA) kinetic energies of 10 keV are simulated and cascade structures in NC SiC with a grain size smaller than 12 nm are generally different from those generated in single-crystalline SiC. It is found that the local stresses near the grain boundaries (GBs) strongly affect the behavior of the PKA and secondary recoil atoms (SRAs), and the GBs act as sinks for deposition of kinetic energy. A striking feature is that the PKA and SRAs preferentially deposit energy along the GBs for grains with average size less 12 nm, which results in atomic displacements primarily within the GBs; whereas for larger grain sizes, most defects are produced within the grains. The defect production within gains generally increases with increasing grain size, which is manifested in switching from grain boundary damage to grain damage. The most common defects created in NC SiC are antisite defects, following by vacancies and interstitials, in contrast to those produced in a single-crystalline SiC, where the dominate defects are Frenkel pairs. Defect production efficiency increases with increasing grain size, with a typical value of 0.18 for small grains and rising to 0.5 for larger grains.

  6. Fish Swimming: Patternsin the Mechanical Energy Generation, Transmission and Dissipation from Muscle Activation to Body Movement

    NASA Astrophysics Data System (ADS)

    Zhang, W.; Yu, Y. L.; Tong, B. G.

    2011-09-01

    The power consumption of the undulatory fish swimming is produced by active muscles. The mechanical energy generated by stimulated muscles is dissipated partly by the passive tissues of fish while it is being transmitted to the fluid medium. Furthermore, the effective energy, propelling fish movement, is a part of that delivered by the fish body. The process depends on the interactions of the active muscles, the passive tissues, and the water surrounding the fish body. In the previous works, the body-fluid interactions have been investigated widely, but it is rarely considered how the mechanical energy generates, transmits and dissipates in fish swimming. This paper addresses the regular patterns of energy transfer process from muscle activation to body movement for a cruising lamprey (LAMPREY), a kind of anguilliform swimmer. It is necessary to propose a global modelling of the kinematic chain, which is composed of active muscle force-moment model, fish-body dynamic model and hydrodynamic model in order. The present results show that there are traveling energy waves along the fish body from anterior to posterior, accompanied with energy storing and dissipating due to the viscoelastic property of internal tissues. This study is a preliminary research on the framework of kinematic chain coordination performance in fish swimming.

  7. Comparison of cumulative dissipated energy between the Infiniti and Centurion phacoemulsification systems

    PubMed Central

    Chen, Ming; Anderson, Erik; Hill, Geoffrey; Chen, John J; Patrianakos, Thomas

    2015-01-01

    Purpose To compare cumulative dissipated energy between two phacoemulsification machines. Setting An ambulatory surgical center, Honolulu, Hawaii, USA. Design Retrospective chart review. Methods A total of 2,077 consecutive cases of cataract extraction by phacoemulsification performed by five surgeons from November 2012 to November 2014 were included in the study; 1,021 consecutive cases were performed using the Infiniti Vision System, followed by 1,056 consecutive cases performed using the Centurion Vision System. Results The Centurion phacoemulsification system required less energy to remove a cataractous lens with an adjusted average energy reduction of 38% (5.09 percent-seconds) (P<0.001) across all surgeons in comparison to the Infiniti phacoemulsification system. The reduction in cumulative dissipated energy was statistically significant for each surgeon, with a range of 29%–45% (2.25–12.54 percent-seconds) (P=0.005–<0.001). Cumulative dissipated energy for both the Infiniti and Centurion systems varied directly with patient age, increasing an average of 2.38 percent-seconds/10 years. Conclusion The Centurion phacoemulsification system required less energy to remove a cataractous lens in comparison to the Infiniti phacoemulsification system. PMID:26229430

  8. Magneto-elastic artificial neurons with extremely low energy dissipation

    NASA Astrophysics Data System (ADS)

    Biswas, Ayan K.; Al-Rashid, Md Mamun; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-03-01

    We present a detailed analysis of artificial step transfer function neurons and binary weight synapses implemented with magneto-tunneling junctions whose soft layers are magnetostrictive nanomagnets switched with voltage generated mechanical strain. These devices are more energy-efficient than CMOS-based neurons or so-called spin neurons that are based on magnets switched with spin-polarized current. We studied their switching dynamics using stochastic Landau-Lifshitz-Gilbert simulations for two different geometries (elliptical and cylindrical) of the magnetostrictive nanomagnet. Our study revealed that while the step transition (firing) of the magnetic neuron is always very sharp at 0 K, the threshold is significantly broadened at room temperature, regardless of geometry and regardless of whether the magnet is switched with strain or spin-polarized current. While this could preclude some applications, the extreme energy-efficiency of these neurons makes them nearly ideal for use in certain types of neuromorphic computation. This work is supported by the NSF under grant ECCS-1124714 and CCF-1216614.

  9. Energy Dissipation at a Shock Front in Diamond: Simulation and Comparison with Phase Contrast Imaging Data

    NASA Astrophysics Data System (ADS)

    Beckwith, Martha; Schropp, Andreas; Ping, Yuan; Swift, Damian; Collins, Gilbert

    2015-06-01

    Understanding the behavior of carbon at high pressures and temperatures is essential for predicting the structure and evolution of giant planets, such as Uranus and Neptune. Shock compression experiments on pure carbon materials, such as diamond, can provide insight into their behavior at the extreme temperatures and pressures of the giant planets. Phase contrast imaging and hydrodynamic simulations were used to examine the propagation of a shock front in diamond. As the shock front propagates through the sample, a decrease in the shock amplitude and an increase in the shock width are observed, indicating that energy dissipative processes, such as viscosity, are apparent. In addition, fractures are observed in the diamond sample behind the shock, which could also contribute to the energy dissipation at the shock front. Work at LLNL performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  10. Shock Formation and Energy Dissipation of Slow Magnetosonic Waves in Coronal Plumes

    NASA Technical Reports Server (NTRS)

    Cuntz, M.; Suess, S. T.

    2003-01-01

    We study the shock formation and energy dissipation of slow magnetosonic waves in coronal plumes. The wave parameters and the spreading function of the plumes as well as the base magnetic field strength are given by empirical constraints mostly from SOHO/UVCS. Our models show that shock formation occurs at low coronal heights, i.e., within 1.3 bun, depending on the model parameters. In addition, following analytical estimates, we show that scale height of energy dissipation by the shocks ranges between 0.15 and 0.45 Rsun. This implies that shock heating by slow magnetosonic waves is relevant at most heights, even though this type of waves is apparently not a solely operating energy supply mechanism.