Advective velocity and energy dissipation rate in an oscillatory flow.
Haider, Ziaul; Hondzo, Miki; Porte-Agel, Fernando
2005-07-01
Characterizing the transport processes at the sediment-water interface along sloping boundaries in lakes and reservoirs is of fundamental interest in lake and reservoir water quality management. The turbulent bottom boundary layer (TBBL) along a slope, induced by the breaking of internal waves in a linearly stratified fluid, was investigated through laboratory measurements. Fast response micro-scale conductivity and temperature probes in conjunction with laser-Doppler velocimetry were used to measure the time series of salinity, temperature, and velocity along a sloping boundary. Turbulent energy spectra were computed from the velocity data using a time-dependent advective velocity and Taylor's hypothesis. The energy spectra were used to estimate the energy dissipation rate at different positions in the TBBL. The advective velocity in this near-zero mean shear flow is based on an integral time scale (T(int)). The integral time scale is related to the average frequency of the spectral energy density of the flow velocity. The energy dissipation rate estimated from the variable advective velocity with an averaging time window equal to the integral time scale (T=T(int)) was 43% higher than the energy dissipation rate estimated from a constant advective velocity. The estimated dissipation rates with T=T(int) were comparable to values obtained by curve-fitting a theoretical Batchelor spectrum for the temperature gradient spectra. This study proposes the integral time scale to be used for the oscillatory flows as (a) a time-averaging window to estimate the advective velocity and associated energy dissipation level, and (b) a normalizing parameter in the energy spectrum.
What is the energy dissipation rate in rotating turbulence?
NASA Astrophysics Data System (ADS)
Moisy, Frederic; Campagne, Antoine; Cortet, Pierre-Philippe; Gallet, Basile
2014-11-01
The scaling of the energy dissipation rate ɛ is one of the most fundamental open issues for rapidly rotating turbulence. For non-rotating 3D turbulence at large Reynolds number, it takes the classical form ɛ3 D ~=U3 / L , with U and L the characteristic velocity and length scales. Here, we propose a simple experiment aiming to probe directly the influence of the background rotation on ɛ: we measure the torque Γ acting on a propeller rotating at constant rate ω in a large volume of fluid rotating at Ω (the torque measurement being performed in the rotating frame). The normalized torque Kp = Γ / (ρR4 Hω2) (where R and H are the propeller radius and height) provides a direct measure of the normalized dissipation ɛ /ɛ3 D as a function of the Rossby number Ro = ω / Ω . For cyclonic propeller rotation (Ro > 0) we find a transition between Kp = constant at large Ro (no rotation) and Kp ~= Ro at small Ro (large rotation), in agreement with weakly nonlinear rotating turbulence prediction. The situation is more intricate for anticyclonic rotation (Ro < 0), showing a peak dissipation at intermediate Ro , and a decrease at small Ro but with a different scaling.
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
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
Mean shear regulates the intermittency of energy dissipation rate
NASA Astrophysics Data System (ADS)
Morshed, Khandakar; Dasi, Lakshmi
2012-11-01
We studied the multi-fractal properties of the instantaneous fluctuations of the turbulent kinetic energy dissipation rate, ɛ in the strongly anisotropic flow past a backward facing step. Measurements correspond to time-resolved PIV at Reynolds number, Re= 13600, 9000, and 5500 based on the free stream velocity and step height. Results indicate a significant dependence of the intermittent dissipation rate signal with respect to Re and local mean shear, S. Probability analysis showed that the fluctuations in ɛ are less skewed around its mean in regions of intense shear. The frequency of relatively intense bursts of intermittent fluctuations in ɛ appear to be dependent on the magnitude of these events. Lacunarity, a measure that characterizes such magnitude and temporal scale dependent intermittency of fluctuating signals, revealed that intermittency in ɛ reduces with S across all temporal scales. However, the intermittency of ɛ appears to increase with burst magnitudes. We discuss the implications of these results on the established multi-fractal picture of small-scale turbulence and the effects of large scale anisotropy.
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.
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
Seasonal Variation of turbulent Energy Dissipation Rates in the Polar Mesosphere
NASA Astrophysics Data System (ADS)
Singer, W.; Latteck, R.; Becker, E.
Turbulent energy dissipation rates have been derived from the width of the observed signal spectra obtained with a narrow beam Doppler radar operated at 3 17 MHz in Andenes 69 r N using a computationally intensive correction method to remove contributions from non-turbulent processes Vertical and oblique beams with a minimum half-power full-beam width of 6 6 r are used The radar provides estimates of turbulent energy dissipation rates in an altitude range from 50 to about 90 km with a time resolution of 1 h and a range resolution of 1 km since September 2003 Turbulent energy dissipation rates based on radar observations vary in the order of 2-10 mW kg around 70 km and between about 10 and 200 mW kg around 85 km in dependence on season During the occurrence of strong polar mesosphere winter echoes in January 2005 energy dissipation rates between 30 and about 100 mW kg are observed at altitudes from 55 to 65 km The radar estimates of turbulent energy dissipation rates are in reasonable agreement with climatologically winter and summer data from previous rocket soundings at Andenes as well as with time-resolved results 1-h resolution from the Kuehlungsborn Mechanistic General Circulation Model KMCM model for summer and winter conditions
Observations of the turbulent kinetic energy dissipation rate in the upper central South China Sea
NASA Astrophysics Data System (ADS)
Liang, Chang-Rong; Chen, Gui-Ying; Shang, Xiao-Dong
2017-05-01
Measurements of the turbulent kinetic energy dissipation rate ( ɛ), velocity, temperature, and salinity were obtained for the upper ocean of the central South China Sea (14.5° N, 117.0° E) during an experimental campaign from May 11 to 13, 2010. Dissipation in the diurnal mixed layer showed a diurnal variability that was strongly affected by the surface buoyancy flux. Dissipation was enhanced ( ɛ ˜ 10-7 W kg-1) at night due to the convective mixing and was weakened ( ɛ ˜ 10-9 W kg-1) in daytime due to the stratification. Dissipation in the thermocline varied with time under the influence of internal waves. Shear from high-frequency internal waves (period ˜8 h) played an important role in enhancing the turbulent mixing in the thermocline. In the period of strong high-frequency internal waves, the shear from high-frequency internal waves became strong and the depth-averaged ɛ in the thermocline was elevated by almost one order of magnitude. Compared with the dissipation in the thermocline, dissipation below was weaker (the time-averaged ɛ ˜ 10-10 W kg-1). The observation indicates that the dissipation rates during the measurements can be parameterized by the MacKinnon-Gregg model that is widely used in the continental shelf but are not in agreement with the Gregg-Henyey model used for the open ocean.
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.
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.
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.
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.
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.
Rate of Dissipation of the Energy of Low-Frequency Mechanical Disturbances in a Tire
NASA Astrophysics Data System (ADS)
Grinchuk, P. S.; Fisenko, S. P.
2016-11-01
An expression for the rate of dissipation of the energy of low-frequency mechanical disturbances in a tire, accounting for the tired wheel radius, velocity of motion, and loading, has been derived. After processing experimental data on heating the tread rubber of an oversize tire by the proposed method, it has been revealed that about 30% of the energy of deformations appearing in motion of a loaded tire is converted into heat, and the coefficient of heat transfer between the tire and air has been derived.
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.
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.
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.
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.
Response of mean turbulent energy dissipation rate and spectra to concentrated wall suction
NASA Astrophysics Data System (ADS)
Oyewola, O.; Djenidi, L.; Antonia, R. A.
2008-01-01
The response of mean turbulent energy dissipation rate and spectra to concentrated suction applied through a porous wall strip has been quantified. Both suction and no suction data of the spectra collapsed reasonably well for Kolmogorov normalised wavenumber k {1/*} > 0.2. Similar results were also observed for second-order structure functions (not shown) for Kolmogorov normalised radius r* < 10. Although, the quality of collapsed is poorer for transverse component, the result highlights that Kolmogorov similarity hypothesis is reasonably well satisfied. However, the suction results shows a significant departure from the no suction case of the Kolmogorov normalised spectra and second-order structure functions for k {1/*} < 0.2 and r* > 20, respectively. The departure at the larger scales with collapse at the small scales suggests that suction induce a change in the small-scale motion. This is also reflected in the alteration of mean turbulent energy dissipation rate and Taylor microscale Reynolds number. This change is a result of the weakening of the large-scale structures. The effect is increased as the suction rate is increased.
Johnson, Chris; Natarajan, Venkatesh; Antoniou, Chris
2014-01-01
Suspension mammalian cell cultures in aerated stirred tank bioreactors are widely used in the production of monoclonal antibodies. Given that production scale cell culture operations are typically performed in very large bioreactors (≥ 10,000 L), bioreactor scale-down and scale-up become crucial in the development of robust cell-culture processes. For successful scale-up and scale-down of cell culture operations, it is important to understand the scale-dependence of the distribution of the energy dissipation rates in a bioreactor. Computational fluid dynamics (CFD) simulations can provide an additional layer of depth to bioreactor scalability analysis. In this communication, we use CFD analyses of five bioreactor configurations to evaluate energy dissipation rates and Kolmogorov length scale distributions at various scales. The results show that hydrodynamic scalability is achievable as long as major design features (# of baffles, impellers) remain consistent across the scales. Finally, in all configurations, the mean Kolmogorov length scale is substantially higher than the average cell size, indicating that catastrophic cell damage due to mechanical agitation is highly unlikely at all scales. © 2014 American Institute of Chemical Engineers.
Mérida, Fernando; Chiu-Lam, Andreina; Bohórquez, Ana C.; Maldonado-Camargo, Lorena; Pérez, María-Eglée; Pericchi, Luis; Torres-Lugo, Madeline; Rinaldi, Carlos
2015-01-01
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 1,048 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. PMID:26273124
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.
On the Energy Dissipation Rate of Solutions to the Compressible Isentropic Euler System
NASA Astrophysics Data System (ADS)
Chiodaroli, Elisabetta; Kreml, Ondrej
2014-07-01
In this paper we extend and complement the results in Chiodaroli et al. (Global ill-posedness of the isentropic system of gas dynamics, 2014) on the well-posedness issue for weak solutions of the compressible isentropic Euler system in 2 space dimensions with pressure law p(ρ) = ρ γ , γ ≥ 1. First we show that every Riemann problem whose one-dimensional self-similar solution consists of two shocks admits also infinitely many two-dimensional admissible bounded weak solutions (not containing vacuum) generated by the method of De Lellis and Székelyhidi (Ann Math 170:1417-1436, 2009), (Arch Ration Mech Anal 195:225-260, 2010). Moreover we prove that for some of these Riemann problems and for 1 ≤ γ < 3 such solutions have a greater energy dissipation rate than the self-similar solution emanating from the same Riemann data. We therefore show that the maximal dissipation criterion proposed by Dafermos in (J Diff Equ 14:202-212, 1973) does not favour the classical self-similar solutions.
Turbulent energy dissipation rate in a tilting flume with a highly rough bed
NASA Astrophysics Data System (ADS)
Coscarella, F.; Servidio, S.; Ferraro, D.; Carbone, V.; Gaudio, R.
2017-08-01
Turbulent flows on highly rough beds, such as those occurring in natural watercourses, represent a longstanding and fascinating problem of hydraulics, motivating in the past few decades huge research on new models of turbulence. In this work, laboratory experiments are presented on a stream flowing on a heterogeneous pebble bed with varying slope. The analysis of the flow speed puts in evidence a clear inertial range, where the Kolmogorov 4/5-law for the streamwise velocity spatial increments holds. The law is used for a systematic estimation of the turbulent kinetic energy dissipation rate 𝜖 , here measured for three different bed slopes and hence for three different shear Reynolds numbers. The experiments presented here suggest that small scale turbulence has properties similar to the classical picture of homogeneous universal turbulence invoked by the Kolmogorov theory.
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.
Measurement of turbulent kinetic energy dissipation rates in the mesosphere by a 3 MHz Doppler radar
NASA Astrophysics Data System (ADS)
Latteck, R.; Singer, W.; Hocking, W. K.
A new narrow beam Doppler radar operating at 3.17 MHz has been installed close to the Andøya Rocket Range in Andenes, Norway in summer 2002 in order to improve the ground based capabilities for measurements of turbulence in the mesosphere. The main feature of the radar is a Mills Cross transmitting/receiving antenna consisting of 29 crossed half-wave dipoles. In combination with the modular transceiver system this provides high flexibility in beam forming and pointing. In general, vertical and oblique beams with a minimum one way half-power full-beam width (HPFW) of 6.6° are used. The observations are usually performed with a height resolution of 1 km and with off-zenith beams at 7.3° directed towards NW, NE, SE, and SW. Turbulence intensities have been estimated from the width of the observed signal spectra using an computationally intensive correction method which requires precise knowledge of the antenna radiation pattern. The program uses real-time measurements of the wind field in all determinations. Turbulent kinetic energy dissipation rates based on radar observations are presented and compared with corresponding climatological summer and winter profiles from rocket measurements, as well as with single profiles from model runs for selected periods from September 2003 to Summer 2004. The mean turbulent kinetic energy dissipation rates based on these radar measurements are about 5 mW/kg at 60 km altitude and about 20 mW/kg at 80 km, in reasonable agreement with mean turbulence intensities obtained from previous rocket soundings at Andenes.
Sikiö, Päivi; Jalali, Payman
2014-12-01
The hierarchical shell models of turbulence including a spatial dimension, namely, spatiotemporal tree models, reproduce the intermittent behavior of Navier-Stokes equations in both space and time dimensions corresponding to high Reynolds number turbulent flows. This model is used, for the first time in this paper, in a one-dimensional flow zone containing a dispersed-phase particle that can be used in the study of dispersed-phase flows. In this paper, a straightforward method has been used to introduce discrete phase into the spatiotemporal tree model that leads to an increased amount of turbulent energy dissipation rate in the vicinity of the discrete phase. The effects of particle insertion and particle size on the turbulent energy dissipation rate are demonstrated. Moreover, the space-scale behavior of the time-averaged turbulent energy dissipation rate in the presence of dispersed phase is demonstrated by means of continuous wavelet transform.
Kim, Daewook; 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(|A (1/2) u|(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.
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
Shenkman, Rustin M.; Godoy-Silva, Ruben; Papas, Klearchos K.; Chalmers, Jeffrey J.
2010-01-01
Acute physical stresses can occur in the procurement and isolation process and potentially can contribute to islet death or malfunction upon transplantation. A contractional flow device, previously used to subject suspended cells to well-defined hydrodynamic forces, has been modified and used to assess the vulnerability of porcine islets of Langerhans to hydrodynamic forces. The flow profiles and velocity gradients in this modified device were modeled using commercial CFD software and characterized, as in previous studies, with the scalar parameter, energy dissipation rate (EDR). Porcine islets were stressed in a single pass at various stress levels (i.e., values of EDR). Membrane integrity, oxygen uptake rate, caspase 3/7 activity, and insulin release were not affected by the levels of fluid stress tested up to an EDR of 2 × 103 W/m3. Visual observation of the stressed islets suggested that cells at the islet exterior were peeled away at EDR greater than 10,000 W/m3, however, this observation could not be confirmed using image analysis software, which determined the ratio of surface perimeter to total area. The result of this study suggests an upper limit in fluid stress to which islets can be subjected. Such upper limits assist in the design and operation of future islet processing equipment and processes. PMID:19191351
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
Turbulent kinetic energy dissipation rates in the polar mesosphere measured by a 3-MHz-Doppler radar
NASA Astrophysics Data System (ADS)
Latteck, R.; Singer, W.; Hocking, W. K.
2005-08-01
Turbulence produces changes in the spectral width of a backscattered radar signal which can be used to deduce turbulent energy dissipation rates at the region of the scatter. Since the radar signal spectrum is also influenced by the background wind field causing broadening effects of the spectrum, a system with a relative small beam width as well as corresponding methods to correct for the non-turbulent broadening of the spectrum are necessary for the estimation of reliable energy dissipation rates. The new narrow beam MF radar at Saura on Andøya island in northern Norway has got a Mills-Cross antenna with a minimum beam width of θ = 6.6° (Half-Power-Full-Width, one way) and a modular transceiver system which provides high flexibility in beam pointing as well as beam forming. An correction method for non-turbulent spectral broadening effects has been implemented for the estimation of turbulence intensities from the width of the observed signal spectra. The method requires the precise knowledge of the antenna radiation pattern and real-time measurements of the wind field. The critical steps of the estimation of the turbulent part of the signal spectrum are discussed. Turbulent kinetic energy dissipation rates based on the spectral width method are obtained with the Saura MF radar since September 2003. The radar results are compared with corresponding data from rocket measurements at Andenes under summer and winter conditions, as well as with the results from the Kühlungsborn Mechanistic Circulation Model (KMCM). The mean turbulent kinetic energy dissipation rates basing on these radar measurements are about 5 mW/kg at 60 km altitude and about 20 mW/kg at 80 km, in reasonable agreement with mean turbulence intensities obtained from previous rocket soundings at Andenes.
Pathak, Siddhartha; Lim, Ee J; Abadi, Parisa Pour Shahid Saeed; Graham, Samuel; Cola, Baratunde A; Greer, Julia R
2012-03-27
We report mechanical behavior and strain rate dependence of recoverability and energy dissipation in vertically aligned carbon nanotube (VACNT) bundles subjected to quasi-static uniaxial compression. We observe three distinct regimes in their stress-strain curves for all explored strain rates from 4 × 10(-2) down to 4 × 10(-4)/sec: (1) a short initial elastic section followed by (2) a sloped plateau with characteristic wavy features corresponding to buckle formation and (3) densification characterized by rapid stress increase. Load-unload cycles reveal a stiffer response and virtually 100% recoverability at faster strain rates of 0.04/sec, while the response is more compliant at slower rates, characterized by permanent localized buckling and significantly reduced recoverability. We propose that it is the kinetics of attractive adhesive interactions between the individual carbon nanotubes within the VACNT matrix that governs morphology evolution and ensuing recoverability. In addition, we report a 6-fold increase in elastic modulus and gradual decrease in recoverability (down to 50%) when VACNT bundles are unloaded from postdensification stage as compared with predensification. Finally, we demonstrate energy dissipation capability, as revealed by hysteresis in load-unload cycles. These findings, together with high thermal and electrical conductivities, position VACNTs in the "unattained-as-of-to-date-space" in the material property landscape. © 2012 American Chemical Society
NASA Astrophysics Data System (ADS)
Guo, Yafang; Liu, Alan Z.; Gardner, Chester S.
2017-06-01
Turbulence is ubiquitous in the mesopause region, where the atmospheric stability is low and wave breaking is frequent. Measuring turbulence is challenging in this region and is traditionally done by rocket soundings and radars. In this work, we show for the first time that the modern Na wind/temperature lidar located at Andes Lidar Observatory in Cerro Pachón, Chile, is able to directly measure the turbulence perturbations in temperature and vertical wind between 85 and 100 km. Using 150 h of lidar observations, we derived the frequency (ω) and vertical wave number (m) spectra for both gravity wave and turbulence, which follow the power law with slopes consistent with theoretical models. The eddy heat flux generally decreases with altitude from about -0.5 Km s-1 at 85 km to -0.1 Km s-1 at 100 km, with a local maximum of -0.6 Km s-1 at 93 km. The derived mean turbulence thermal diffusivity and energy dissipation rate are 43 m2 s-1 and 37 mW kg-1, respectively. The mean net cooling resulted from the heat transport and energy dissipation is -4.9 ± 1.5 K d-1, comparable to that due to gravity wave transport at -7.9 ± 1.9 K d-1. Turbulence key parameters show consistency with turbulence theories.
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
NASA Astrophysics Data System (ADS)
Wacławczyk, Marta; Ma, Yong-Feng; Kopeć, Jacek; Malinowski, Szymon
2017-04-01
Evaluation of turbulent kinetic energy (TKE) dissipation rate (ɛ) from the low- and moderate-resolution in situ airborne measurements is problematic and scarce. Due to various problems related to e.g. inhomogeneity of turbulence along the aircraft and artifacts related to inevitable aerodynamic problems, estimation of ɛ using the traditional methods such as power spectra or structure functions are complex and far from being standardized. Therefore, we try to introduce alternative methods to increase robustness of ɛ retrievals from such low-resolution airborne measurements. In this study we propose two approaches to estimate ɛ based on the zero-crossing method by Sreenivasan et al. (1983). The original formulation requires a fine resolution of the measured signal, down to the smallest dissipative scales. However, due to finite sampling frequency, as well as measurement errors, velocity time series obtained from airborne experiments are characterized by the presence of effective spectral cut-offs. In contrast to the original formulation the proposed approaches are suitable for use with signals originated from such experiments. The fittingness of the new approaches is tested using measurement data obtained during the Physics of Stratocumulus Top (POST) airborne research campaign. Sreenivasan K., Prabhu A. and Narasimha R., 1983: Zero-crossings in turbulent signals, J. Fluid Mech., 137, 251-272.
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.
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.
Damage Prediction of Projectile Penetration Process Based on Energy Dissipation Rate.
1985-08-01
terms of at least a length parameter, say Z in Figure 1(a), that describes the degree of uniformity or homo - geneity of the stress or energy state...but those acting on the plane with the same . , dV/dA value as that in the uniaxial test. In view of equations (5) and (6), homo - geneity of the...i k C~~~~~a zL C -na-u 50 2 C CC 3 i c a s’ CUC~~~- LCI"i -~i. C u -- - C C2 C- C - u-c. a 5ULcta C Cuv -COI-a WEt 1 . EcC i-li ’ t o- C j 2 wC o4 icXl
Energy dissipation in sheared granular flows
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.
NASA Astrophysics Data System (ADS)
Lefeuvre, N.; Thiesset, F.; Djenidi, L.; Antonia, R. A.
2014-09-01
A numerical simulation based on the lattice Boltzmann method is carried out in the wake of a square cylinder with the view to investigating possible surrogates for the instantaneous turbulent kinetic energy dissipation rate, ɛ, as well as its mean value, overline{ɛ }. Various surrogate approximations of ɛ, based on local isotropy (ɛiso), local axisymmetry along the streamwise direction x (ɛa, x) and the transverse direction y (ɛa, y), local homogeneity (ɛhom), and homogeneity in the transverse plane, (ɛ4x), are assessed. All the approximations are in agreement with overline{ɛ } when the distance downstream of the obstacle is larger than about 40 diameters. Closer to the obstacle, the agreement remains reasonable only for overline{ɛ }_{a,x}, overline{ɛ }_{hom} and overline{ɛ }_{4x}. The probability density functions (PDF) and joint PDFs of ɛ and its surrogates show that ɛ4x correlates best with ɛ while ɛiso and ɛhom present the smallest correlation. The results indicate that ɛ4x is a very good surrogate for ɛ and can be used for correctly determining the behaviour of ɛ.
NASA Astrophysics Data System (ADS)
Rippeth, T. P.; Simpson, J. H.; Inall, M. E.; Williams, E.
Simultaneous measurements of the rates of turbulent energy dissipation (epsilon) and production (P) have been made over a period of 24 hours at a tidally energetic site in the Northern Irish Sea in a water depth of 25 m. Epsilon profiles from 5 m below the surface to 15 cm above the sea bed were obtained using a FLY microstructure pro- filer while P profiles were determined from a bottom mounted high frequency ADCP (Acoustic Doppler Current Profiler) using the variance method. In homogeneous flow of the kind observed, the turbulence regime should approximate to local equillibrium so that, with no buoyancy forces involved, epsilon and P should co-vary with mean values which are equal. The results show a close tracking of epsilon and P for most of the observational period but with a mean ratio of epsilon/ P = 0.5 +/- 0.07, a significant departure from unity, but within the range of uncertainty previously estimated for the epsilon measurements. A marked phase lag of between 5 and 20 minutes between the maximum P and the maximum epsilon is interpreted using a simple model in terms of decay rate of TKE. Two other significant differences between the two sets of mea- surements are attributed to errors in the stress estimate due to (i) inherent ADCP noise and (ii) strong surface wave activity resulting in anomalously high stress estimates covering near half the water column at times. Consideration of the former has enabled an estimate of the lowest P threshold measurable using the variance technique which for the chosen averaging parameters was~10-4 W/m3.
Resonant Enhancement of Turbulent Energy Dissipation
Cekli, Hakki Ergun; Tipton, Carl; Water, Willem van de
2010-07-23
We periodically modulate a turbulent wind-tunnel flow with an active grid. We find a resonant enhancement of the mean turbulent dissipation rate at a modulation frequency which equals the large-eddy turnover rate. Thus, we find the best frequency to inject energy into a turbulent flow. The resonant response is characterized by the emergence of vortical structures in the flow and depends on the spatial mode of the stirring grid.
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.
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.
ENERGY DISSIPATION PROCESSES IN SOLAR WIND TURBULENCE
Wang, Y.; Wei, F. S.; Feng, X. S.; Sun, T. R.; Zuo, P. B.; Xu, X. J.; Zhang, J.
2015-12-15
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.
Estimation of turbulent kinetic energy dissipation
NASA Astrophysics Data System (ADS)
Chen, Huey-Long; Hondzo, Miki; Rao, A. Ramachandra
2001-06-01
The kinetic energy dissipation rate is one of the key intrinsic fluid flow parameters in environmental fluid dynamics. In an indirect method the kinetic energy dissipation rate is estimated from the Batchelor spectrum. Because the Batchelor spectrum has a significant difference between the highest and lowest spectral values, the spectral bias in the periodogram causes the lower spectral values at higher frequencies to increase. Consequently, the accuracy in fitting the Batchelor spectrum is affected. In this study, the multitaper spectral estimation method is compared to conventional methods in estimating the synthetic temperature gradient spectra. It is shown in the results that the multitaper spectra have less bias than the Hamming window smoothed spectra and the periodogram in estimating the synthetic temperature gradient spectra. The results of fitting the Batchelor spectrum based on four error functions are compared. When the theoretical noise spectrum is available and delineated at the intersection of the estimated spectrum, the fitting results of the kinetic energy dissipation rate corresponding to the four error functions do not have significant differences. However, when the noise spectrum is unknown and part of the Batchelor spectrum overlaps the region where the noise spectrum dominates, the weighted chi-square distributed error function has the best fitting results.
Collisional dissipation rate in shearing flows of granular liquid crystals
NASA Astrophysics Data System (ADS)
Berzi, Diego; Thai-Quang, Nha; Guo, Yu; Curtis, Jennifer
2017-05-01
We make use of discrete-element-method numerical simulations of inelastic frictionless cylinders in simple shearing at different length-to-diameter ratios and solid volume fractions to analyze the rate of collisional dissipation of the fluctuation kinetic energy. We show that the nonspherical geometry of the particles is responsible, by inducing rotation, for increasing the dissipation rate of the fluctuation kinetic energy with respect to that for frictionless spheres. We also suggest that the partial alignment of the cylinders induced by shearing concurs with the particle inelasticity in generating correlation in the velocity fluctuations and thus affecting the collisional dissipation rate as the solid volume fraction increases. Finally, we propose simple phenomenological modifications to the expression of the collisional dissipation rate of kinetic theory of granular gases to take into account our findings.
Wetlands as energy-dissipating systems.
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.
Material Systems for Blast-Energy Dissipation
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.
Energy dissipation in magnetohydrodynamic turbulence: coherent structures or 'nanoflares'?
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.
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.
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.
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.
The joint dissipation rate for multiple scalars in differential diffusion.
NASA Astrophysics Data System (ADS)
Vedula, Prakash; Yeung, P. K.; Fox, R. O.
1999-11-01
We continue recent numerical studies of scalar dissipation fluctuations in turbulent mixing, with current emphasis on modeling and extension to differential diffusion for scalars with different molecular diffusivities. Data are taken from high-resolution direct numerical simulations for homogeneous scalar fields with uniform mean gradient. Amplification of scalar gradients by strain rate fluctuations in principal axes is of greatest interest, with a nearly universal time scale slightly less than 2 Kolmogorov time scales. Preferential alignment of scalar gradients with the most compressive strain rate conditioned upon the energy dissipation is observed in studies of both the dissipation rate of each scalar and their joint dissipation rate (which appears in the covariance equation). The gradient correlation between scalars with Schmidt numbers 1/8 to 1 is strongest in the most compressive strain direction. The Lagrangian PDF model for the joint dissipation (Fox 1999, Phys. Fluids 11, 1550) contains closures for each of the terms in the conditional joint dissipation rate balance equation. The DNS data are used to validate and improve the conditional closures, as well as to check for Reynolds and Schmidt number dependencies.
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.
Asynchonous Binaries, Energy Dissipation and Turbulent Viscosity
NASA Astrophysics Data System (ADS)
Koenigsberger, G.; Brott, I.; Moreno, E.
2015-07-01
Stars in binary systems are generally modeled under the assumption that they are in an equilibrium configuration and, in particular, that the stellar rotation angular velocity equals the orbital angular velocity. However, asynchronous rotation is more common than generally recognized. All eccentric systems undergo asynchronous rotation and the angular velocity of rotation of many stars in circular orbits differs from that of the orbital angular velocity. Combined with the external gravitational potential, this asynchronous rotation causes shearing motions in the stellar layers and, given that the stellar material is not inviscid, kinetic energy is dissipated into heat. In 1968, Zdeněk Kopal addressed the question of whether the tidal shear energy dissipation rates, Ė, in asynchronous binaries can lead to an internal stellar structure that differs from that in an analogous single star. His calculation, based on the assumption that the viscosity is purely molecular, led him to conclude that Ė is insignificant and therefore has no effect on the internal stellar structure. However, Kopal also pointed out the important caveat that if turbulent viscosity prevailed, then larger values of Ė would obtain. We have revisited the question of the magnitude of Ė using the TIDES code (Moreno 2011) and examined its dependence on viscosity for several layers of a ZAMS 30 M⊙ star with a 20 M⊙ companion in a 6-day eccentric orbit. We find that conditions for turbulent viscosity are favored when the star expands after leaving the main sequence. For example, when the 30 M⊙ star is 5 Myr old and rotating near its corrotation speed, turbulent viscosity might be expected to appear in all layers at distances greater than 60% of the maximum stellar radius. As a consequence, tidal shear energy dissipation may constitute a non-negligible effect in a large number of close binary systems, with possibly interesting consequences for their internal structure and evolution.
Intermittent energy dissipation by turbulent reconnection
NASA Astrophysics Data System (ADS)
Fu, H. S.; Vaivads, A.; Khotyaintsev, Y. V.; André, M.; Cao, J. B.; Olshevsky, V.; Eastwood, J. P.; Retinò, A.
2017-01-01
Magnetic reconnection—the process responsible for many explosive phenomena in both nature and laboratory—is efficient at dissipating magnetic energy into particle energy. To date, exactly how this dissipation happens remains unclear, owing to the scarcity of multipoint measurements of the "diffusion region" at the sub-ion scale. Here we report such a measurement by Cluster—four spacecraft with separation of 1/5 ion scale. We discover numerous current filaments and magnetic nulls inside the diffusion region of magnetic reconnection, with the strongest currents appearing at spiral nulls (O-lines) and the separatrices. Inside each current filament, kinetic-scale turbulence is significantly increased and the energy dissipation, E' ṡ j, is 100 times larger than the typical value. At the jet reversal point, where radial nulls (X-lines) are detected, the current, turbulence, and energy dissipations are surprisingly small. All these features clearly demonstrate that energy dissipation in magnetic reconnection occurs at O-lines but not X-lines.
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.
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.
Energy dissipation associated with crack extension in an elastic-plastic material
NASA Technical Reports Server (NTRS)
Shivakumar, K. N.; Crews, J. H., Jr.
1987-01-01
Crack extension in elastic-plastic material involves energy dissipation through the creation of new crack surfaces and additional yielding around the crack front. An analytical procedure, using a two-dimensional elastic-plastic finite element method, was developed to calculate the energy dissipation components during a quasi-static crack extension. The fracture of an isotropic compact specimen was numerically simulated using the critical crack-tip-opening-displacement (CTOD) growth criterion. Two specimen sizes were analyzed for three values of critical CTOD. Results from the analyses showed that the total energy dissipation rate consisted of three components: the crack separation energy rate, the plastic energy dissipation rate, and the residual strain energy rate. All three energy dissipation components and the total energy dissipation rate initially increased with crack extension and finally reached constant values.
Balsa wood as an energy dissipator
NASA Technical Reports Server (NTRS)
Knoell, A. C.
1973-01-01
Studies have been undertaken to determine response of balsa wood in variety of environmental conditions. Response is dependent upon state of balsa wood as well as environment to which it is exposed, but certain combinations of conditions serve to increase significantly energy-dissipating capacity of wood relative to its normal capacity.
Fuel cell generator energy dissipator
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
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.
NASA Astrophysics Data System (ADS)
Li, Qiang; Rapp, Markus; Schrön, Anne; Schneider, Andreas; Stober, Gunter
2016-12-01
We present the derivation of turbulent energy dissipation rate ɛ from a total of 522 days of observations with the Middle Atmosphere Alomar Radar SYstem (MAARSY) mesosphere-stratosphere-troposphere (MST) radar running tropospheric experiments during the period of 2010-2013 as well as with balloon-borne radiosondes based on a campaign in the summer 2013. Spectral widths are converted to ɛ after the removal of the broadening effects due to the finite beam width of the radar. With the simultaneous in situ measurements of ɛ with balloon-borne radiosondes at the MAARSY radar site, we compare the ɛ values derived from both techniques and reach an encouraging agreement between them. Using all the radar data available, we present a preliminary climatology of atmospheric turbulence in the UTLS (upper troposphere and lower stratosphere) region above the MAARSY site showing a variability of more than 5 orders of magnitude inherent in turbulent energy dissipation rates. The derived ɛ values reveal a log-normal distribution with a negative skewness, and the ɛ profiles show an increase with height which is also the case for each individual month. Atmospheric turbulence based on our radar measurements reveals a seasonal variation but no clear diurnal variation in the UTLS region. Comparison of ɛ with the gradient Richardson number Ri shows that only 1.7 % of all the data with turbulence occur under the condition of Ri < 1 and that the values of ɛ under the condition of Ri < 1 are significantly larger than those under Ri > 1. Further, there is a roughly negative correlation between ɛ and Ri that is independent of the scale dependence of Ri. Turbulence under active dynamical conditions (velocity of horizontal wind U > 10 m s-1) is significantly stronger than under quiet conditions (U < 10 m s-1). Last but not least, the derived ɛ values are compared with the corresponding vertical shears of background wind velocity showing a linear relation with a corresponding
NASA Astrophysics Data System (ADS)
Sikiö, Päivi; Tynjälä, Tero; Jalali, Payman
2017-01-01
In this article, a spatiotemporal dynamical system model (tree model) is utilized for investigating the features of forced and unforced turbulence in a dispersed phase two-phase system. The tree model includes a variable for spatial dimension in addition to variables of wavenumber and time, which display both spatial and temporal intermittencies. The focus of this paper is to study the turbulence modulation due to the presence of rigid particles. The study considers particles with the sizes of 32, 64, and 128 times the Kolmogorov length scale. Specifically, the study of the energy dissipation rate (EDR) at the particle-fluid interface is considered. Two models, namely, A and B with different types of interaction connections between nearby shells, are used first to compare the results of the particle-laden case with decaying turbulence. The number of tree connections in the model is found to affect the amount of augmentation of EDR near the particle surface. Model B is studied further with different sizes of particles in forced turbulence cases and compared to the unladen case with the same parameters. Also, the model expression is studied in the forced turbulence case of dual particles separated by given distances. The results of spatiotemporal shell models provide new approach of handling high Reynolds turbulence in dispersed phase multiphase systems.
Magnetotail energy dissipation during an auroral substorm
Panov, E.V.; Baumjohann, W.; Wolf, R.A.; Nakamura, R.; Angelopoulos, V.; Weygand, J. M.; Kubyshkina, M.V.
2016-01-01
Violent releases of space plasma energy from the Earth’s magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1km/s. This observed auroral activity appears sufficient to dissipate the released energy. PMID:27917231
Magnetotail energy dissipation during an auroral substorm
NASA Astrophysics Data System (ADS)
Panov, Evgeny V.; Baumjohann, Wolfgang; Wolf, Richard A.; Nakamura, Rumi; Angelopoulos, Vassilis; Weygand, James M.; Kubyshkina, Marina V.
2017-04-01
Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1 km s-1. This observed auroral activity appears sufficient to dissipate the released energy.
Magnetotail energy dissipation during an auroral substorm.
Panov, E V; Baumjohann, W; Wolf, R A; Nakamura, R; Angelopoulos, V; Weygand, J M; Kubyshkina, M V
2016-12-01
Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1km/s. This observed auroral activity appears sufficient to dissipate the released energy.
Magnetotail energy dissipation during an auroral substorm
NASA Astrophysics Data System (ADS)
Panov, E. V.; Baumjohann, W.; Wolf, R. A.; Nakamura, R.; Angelopoulos, V.; Weygand, J. M.; Kubyshkina, M. V.
2016-12-01
Violent releases of space plasma energy from the Earth's magnetotail during substorms produce strong electric currents and bright aurora. But what modulates these currents and aurora and controls dissipation of the energy released in the ionosphere? Using data from the THEMIS fleet of satellites and ground-based imagers and magnetometers, we show that plasma energy dissipation is controlled by field-aligned currents (FACs) produced and modulated during magnetotail topology change and oscillatory braking of fast plasma jets at 10-14 Earth radii in the nightside magnetosphere. FACs appear in regions where plasma sheet pressure and flux tube volume gradients are non-collinear. Faster tailward expansion of magnetotail dipolarization and subsequent slower inner plasma sheet restretching during substorm expansion and recovery phases cause faster poleward then slower equatorward movement of the substorm aurora. Anharmonic radial plasma oscillations build up displaced current filaments and are responsible for discrete longitudinal auroral arcs that move equatorward at a velocity of about 1 km s-1. This observed auroral activity appears sufficient to dissipate the released energy.
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.
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.
Energy Storage and Dissipation in Random Copolymers during Biaxial Loading
NASA Astrophysics Data System (ADS)
Cho, Hansohl; Boyce, Mary
2012-02-01
Random copolymers composed of hard and soft segments in a glassy and rubbery state at the ambient conditions exhibit phase-separated morphologies which can be tailored to provide hybrid mechanical behaviors of the constituents. Here, phase-separated copolymers with hard and soft contents which form co-continuous structures are explored through experiments and modeling. The mechanics of the highly dissipative yet resilient behavior of an exemplar polyurea are studied under biaxial loading. The hard phase governs the initially stiff response followed by a highly dissipative viscoplasticity where dissipation arises from viscous relaxation as well as structural breakdown in the network structure that still provides energy storage resulting in the shape recovery. The soft phase provides additional energy storage that drives the resilience in high strain rate events. Biaxial experiments reveal the anisotropy and loading history dependence of energy storage and dissipation, validating the three-dimensional predictive capabilities of the microstructurally-based constitutive model. The combination of a highly dissipative and resilient behavior provides a versatile material for a myriad of applications ranging from self-healing microcapsules to ballistic protective coatings.
Energy relaxation of a dissipative quantum oscillator
Kumar, Pradeep; Pollak, Eli
2014-12-21
The dissipative harmonic oscillator is studied as a model for vibrational relaxation in a liquid environment. Continuum limit expressions are derived for the time-dependent average energy, average width of the population, and the vibrational population itself. The effect of the magnitude of the solute-solvent interaction, expressed in terms of a friction coefficient, solvent temperature, and initial energy of the oscillator on the relaxation has been studied. These results shed light on the recent femtosecond stimulated Raman scattering probe of the 1570 cm{sup −1} −C=C− stretching mode of trans-Stilbene in the first (S{sub 1}) excited electronic state. When the oscillator is initially cold with respect to the bath temperature, its average energy and width increase in time. When it is initially hot, the average energy and width decrease with time in qualitative agreement with the experimental observations.
Energy relaxation of a dissipative quantum oscillator.
Kumar, Pradeep; Pollak, Eli
2014-12-21
The dissipative harmonic oscillator is studied as a model for vibrational relaxation in a liquid environment. Continuum limit expressions are derived for the time-dependent average energy, average width of the population, and the vibrational population itself. The effect of the magnitude of the solute-solvent interaction, expressed in terms of a friction coefficient, solvent temperature, and initial energy of the oscillator on the relaxation has been studied. These results shed light on the recent femtosecond stimulated Raman scattering probe of the 1570 cm(-1) -C=C- stretching mode of trans-Stilbene in the first (S1) excited electronic state. When the oscillator is initially cold with respect to the bath temperature, its average energy and width increase in time. When it is initially hot, the average energy and width decrease with time in qualitative agreement with the experimental observations.
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.
Floating hydrometer with energy dissipating baffle
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.
Mechanochemistry for shock wave energy dissipation
NASA Astrophysics Data System (ADS)
Shaw, William L.; Ren, Yi; Moore, Jeffrey S.; Dlott, Dana D.
2017-01-01
Using a laser-driven flyer-plate apparatus to launch 75 μm thick Al flyers up to 2.8 km/s, we developed a technique for detecting the attenuation of shock waves by mechanically-driven chemical reactions. The attenuating sample was spread on an ultrathin Au mirror deposited onto a glass window having a known Hugoniot. As shock energy exited the sample and passed through the mirror, into the glass, photonic Doppler velocimetry monitored the velocity profile of the ultrathin mirror. Knowing the window Hugoniot, the velocity profile could be quantitatively converted into a shock energy flux or fluence. The flux gave the temporal profile of the shock front, and showed how the shock front was reshaped by passing through the dissipative medium. The fluence, the time-integrated flux, showed how much shock energy was transmitted through the sample. Samples consisted of microgram quantities of carefully engineered organic compounds selected for their potential to undergo negative-volume chemistry. Post mortem analytical methods were used to confirm that shock dissipation was associated with shock-induced chemical reactions.
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.
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.
Energy-dependent path of dissipation in nanomechanical resonators.
Güttinger, Johannes; Noury, Adrien; Weber, Peter; Eriksson, Axel Martin; Lagoin, Camille; Moser, Joel; Eichler, Christopher; Wallraff, Andreas; Isacsson, Andreas; Bachtold, Adrian
2017-07-01
Energy decay plays a central role in a wide range of phenomena, such as optical emission, nuclear fission, and dissipation in quantum systems. Energy decay is usually described as a system leaking energy irreversibly into an environmental bath. Here, we report on energy decay measurements in nanomechanical systems based on multilayer graphene that cannot be explained by the paradigm of a system directly coupled to a bath. As the energy of a vibrational mode freely decays, the rate of energy decay changes abruptly to a lower value. This finding can be explained by a model where the measured mode hybridizes with other modes of the resonator at high energy. Below a threshold energy, modes are decoupled, resulting in comparatively low decay rates and giant quality factors exceeding 1 million. Our work opens up new possibilities to manipulate vibrational states, engineer hybrid states with mechanical modes at completely different frequencies, and to study the collective motion of this highly tunable system.
Energy-dependent path of dissipation in nanomechanical resonators
NASA Astrophysics Data System (ADS)
Güttinger, Johannes; Noury, Adrien; Weber, Peter; Eriksson, Axel Martin; Lagoin, Camille; Moser, Joel; Eichler, Christopher; Wallraff, Andreas; Isacsson, Andreas; Bachtold, Adrian
2017-07-01
Energy decay plays a central role in a wide range of phenomena, such as optical emission, nuclear fission, and dissipation in quantum systems. Energy decay is usually described as a system leaking energy irreversibly into an environmental bath. Here, we report on energy decay measurements in nanomechanical systems based on multilayer graphene that cannot be explained by the paradigm of a system directly coupled to a bath. As the energy of a vibrational mode freely decays, the rate of energy decay changes abruptly to a lower value. This finding can be explained by a model where the measured mode hybridizes with other modes of the resonator at high energy. Below a threshold energy, modes are decoupled, resulting in comparatively low decay rates and giant quality factors exceeding 1 million. Our work opens up new possibilities to manipulate vibrational states, engineer hybrid states with mechanical modes at completely different frequencies, and to study the collective motion of this highly tunable system.
Neuromorphic quantum computation with energy dissipation
Kinjo, Mitsunaga; Sato, Shigeo; Nakamiya, Yuuki; Nakajima, Koji
2005-11-15
Real parallel computing with a quantum computer attracts vast interest due to its extreme high potential. We propose a neuromorphic quantum computation algorithm based on an adiabatic Hamiltonian evolution with energy dissipation. This algorithm can be applied to problems if a cost function can be expressed in a quadratic form. This requirement results from the fact that our Hamiltonian is designed by following a method similar to an artificial neural network (ANN). The state of an ANN is often trapped at local minima, and the network outputs an error. Since the state of a quantum system with the proposed algorithm is always in the ground state according to the adiabatic theorem, it is not necessary to be concerned that the quantum state is trapped at local minima. However, there is no guarantee that a quantum algorithm based on an adiabatic Hamiltonian evolution with degeneration or level crossing is successfully executed. We show successful numerical simulation results with the proposed algorithm by introducing energy dissipation to keep the quantum state staying in the ground state, and then we show an application to the n-queen problem, which is one of the combinatorial optimization problems.
Hayashi, Taiyu; Itatani, Keiichi; Inuzuka, Ryo; Shimizu, Nobutaka; Shindo, Takahiro; Hirata, Yoichiro; Miyaji, Kagami
2015-11-01
Vector flow mapping (VFM) is a novel echocardiographic technology which enables visualization of the intraventricular flow velocity vector. Dissipative energy loss (EL) derived from the velocity vector field of intraventricular blood flow is considered to reflect the efficiency of blood flow, and could be an indicator of left ventricular function. We aimed to determine the reference values of the EL derived from VFM within the left ventricle. VFM analysis was performed using echocardiography in 64 healthy children. The velocity vector fields of the intra-left ventricular blood flow were obtained from the apical 5-chamber view, and the EL values during systole and diastole were calculated. The measurements were averaged over three cardiac cycles, and indexed to body surface area (BSA). The mean subject age was 6.8±4.3 years. The mean EL was 4.10±2.35mW/m/m(2) BSA during systole and 16.24±11.63mW/m/m(2) BSA during diastole. On multivariate analysis, age and heart rate (HR) were independent predictors of systolic EL, whereas age, HR, and E wave peak velocity were independent predictors of diastolic EL. The regression equations used to predict the BSA-indexed systolic and diastolic EL were as follows: log10 (systolic EL)=-0.0332-0.00213×age (months)+0.00789×HR (beats/min) (adjusted R(2), 0.833; p<0.0001); and log10 (diastolic EL)=0.277-0.00346×age (months)+0.00570×HR (beats/min)+0.00564×E wave peak velocity (cm/s) (adjusted R(2), 0.867; p<0.0001). The systolic and diastolic EL were positively correlated with HR and negatively correlated with age. Moreover, the diastolic EL was positively correlated with the E wave peak velocity. The present study provides reference values for the systolic and diastolic EL that can be used in future studies examining patients with heart disease. Copyright © 2014 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.
Energy dissipation in flows through curved spaces
Debus, J.-D.; Mendoza, M.; Succi, S.; Herrmann, H. J.
2017-01-01
Fluid dynamics in intrinsically curved geometries is encountered in many physical systems in nature, ranging from microscopic bio-membranes all the way up to general relativity at cosmological scales. Despite the diversity of applications, all of these systems share a common feature: the free motion of particles is affected by inertial forces originating from the curvature of the embedding space. Here we reveal a fundamental process underlying fluid dynamics in curved spaces: the free motion of fluids, in the complete absence of solid walls or obstacles, exhibits loss of energy due exclusively to the intrinsic curvature of space. We find that local sources of curvature generate viscous stresses as a result of the inertial forces. The curvature- induced viscous forces are shown to cause hitherto unnoticed and yet appreciable energy dissipation, which might play a significant role for a variety of physical systems involving fluid dynamics in curved spaces. PMID:28195148
Energy dissipation in flows through curved spaces
NASA Astrophysics Data System (ADS)
Debus, J.-D.; Mendoza, M.; Succi, S.; Herrmann, H. J.
2017-02-01
Fluid dynamics in intrinsically curved geometries is encountered in many physical systems in nature, ranging from microscopic bio-membranes all the way up to general relativity at cosmological scales. Despite the diversity of applications, all of these systems share a common feature: the free motion of particles is affected by inertial forces originating from the curvature of the embedding space. Here we reveal a fundamental process underlying fluid dynamics in curved spaces: the free motion of fluids, in the complete absence of solid walls or obstacles, exhibits loss of energy due exclusively to the intrinsic curvature of space. We find that local sources of curvature generate viscous stresses as a result of the inertial forces. The curvature- induced viscous forces are shown to cause hitherto unnoticed and yet appreciable energy dissipation, which might play a significant role for a variety of physical systems involving fluid dynamics in curved spaces.
Evaluation of the turbulent kinetic dissipation rate in an agitated vessel
NASA Astrophysics Data System (ADS)
Kysela, Bohus; Konfrst, Jiri; Chara, Zdenek; Sulc, Radek; Jasikova, Darina
The design of agitated tanks depends on operating conditions and processes for that are used for. An important parameter for the scale-up modelling is the dissipation rate of the turbulent kinetic energy. The dissipation rate is commonly assumed to be a function of the impeller power input. But this approach gives no information about distribution of the dissipation rate inside the agitated volume. In this paper the distributions of the dissipation rate inside the agitated vessels are estimated by evaluations of the CFD (Computational Fluid Dynamics). The results obtained from RANS (Reynolds Averaged Navier-Stokes equations) k-ɛ turbulent model and LES (Large Eddy Simulations) with Smagorinsky SGS (Sub Grid Scale) model are compared. The agitated vessels with standard geometry equipped with four baffles and stirred by either a standard Rushton turbine or a high shear impeller were investigated. The results are compared with mean dissipation rate estimated from the total impeller power input.
Energy dissipation of moved magnetic vortices
NASA Astrophysics Data System (ADS)
Magiera, Martin P.
2013-09-01
A two-dimensional easy-plane ferromagnetic substrate, interacting with a dipolar tip which is magnetised perpendicularly with respect to the easy plane is studied numerically by solving the Landau-Lifshitz Gilbert equation. The dipolar tip stabilises a vortex structure which is dragged through the system and dissipates energy. An analytical expression for the friction force in the v {\\rightarrow} 0 limit based on the Thiele equation is presented. The limitations of this result which predicts a diverging friction force in the thermodynamic limit, are demonstrated by a study of the size dependence of the friction force. While for small system sizes the dissipation depends logarithmically on the system size, it saturates at a specific velocity-dependent value. This size can be regarded as an effective vortex size and it is shown how this effective vortex size agrees with the infinite extension of a vortex in the thermodynamic limit. A magnetic friction number is defined which represents a general criterion for the validity of the Thiele equation and quantifies the degree of nonlinearity in the response of a driven spin configuration.
If there is dissipation the particle can gain energy
NASA Astrophysics Data System (ADS)
Egydio de Carvalho, R.
2015-10-01
In this work, we summarize two different mechanisms to gain energy from the presence of dissipation in a time-dependent non-linear system. The particles can gain energy, in the average, from two different scenarios: i) for very week dissipation with the creation of an attractor with high velocity, and ii) in the opposite limit, for very strong dissipation, the particles can also gain energy from a boundary crisis. From the thermodynamic viewpoint both results are totally acceptable.
Energy dissipation in a fluidic nanomechanical resonator
NASA Astrophysics Data System (ADS)
Sader, John; Burg, Thomas; Manalis, Scott
2008-11-01
The fluid-structure interaction of resonating microcantilevers in fluid has been widely studied and is a cornerstone in nanomechanical sensor development. Operation in fluid environments presents significant challenges due to the strong enhancement of fluid damping effects with miniaturization. Recently, Burg et al. [Nature, Vol. 446, 1066 (2007)] proposed a new type of microcantilever device whereby a microfluidic channel was embedded inside the cantilever, which resulted in unprecedented sensitivity. We study the fluid dynamics of these devices by presenting a theoretical model and experimental measurements. Significantly, it is found that energy dissipation in these devices is not a monotonic function of fluid viscosity. A direct consequence is that miniaturization does not necessarily result in degradation in the quality factor, which may indeed be enhanced. This highly desirable feature is unprecedented in current nanomechanical devices and permits direct miniaturization to enhance sensitivity in liquid environments.
Light energy dissipation under water stress conditions
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.
Dissipation of Turbulent Kinetic Energy in the Atmospheric Boundary Layer: Observations and Theory
NASA Astrophysics Data System (ADS)
Blumen, W.
2002-05-01
Two aspects of atmospheric dissipation will be examined, namely, the measurement of dissipation in frontal zones that are embedded in the boundary layer, and a theoretical examination of the dissipation length, used for parameterization purposes in some numerical models. The observations were acquired during two field programs carried out in southeast Kansas:MICROFRONTS-1995 and CASES-1999. Data were collected by both hot-wire and sonic anemometers. The hot-wire voltages were converted to wind speeds and the dissipation computed under the assumption of local isotropy. Taylor's hypothesis, including correction terms, was applied to convert spatial to time derivatives, since these data were collected on towers and presented as time series. This approach represents the direct dissipation method. The inertial method computes the dissipation from inertial subrange measurements, making use of the Kolmogorov five-thirds law and Taylor's hypothesis. The turbulent kinetic energy dissipation rate ɛ increased by over an order of magnitude in the frontal zone that passed the MICROFRONTS tower array, from values of the order of ɛ =0.01m2s-3 in the prefrontal region. After passage of the front the dissipation rate relaxed back to prefrontal values. The dissipation rate within the frontal zone that passed through the CASES site could not be determined because of flow distortion by the tower. Both prefrontal and post frontal dissipation rates were similar in magnitude to those measured during MICROFRONTS.In each case, no significant differences in the magnitudes of ɛ determined by the direct dissipation and inertial dissipation calculations, were evident. Numerical models require a parameterization of the dissipation rate ɛ that is appropriate for the unresolved scales of motion. One approach is to employ the dissipation length l as a surrogate for ɛ , where l=e3/2/ɛ and e is the turbulent kinetic energy. The aim is to represent l as a function of the vertical wind shear and
Scalar dissipation rates in non-conservative transport systems
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
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.
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.
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 .
Thermal energy dissipation and xanthophyll cycles beyond the Arabidopsis model.
García-Plazaola, José Ignacio; Esteban, Raquel; Fernández-Marín, Beatriz; Kranner, Ilse; Porcar-Castell, Albert
2012-09-01
Thermal dissipation of excitation energy is a fundamental photoprotection mechanism in plants. Thermal energy dissipation is frequently estimated using the quenching of the chlorophyll fluorescence signal, termed non-photochemical quenching. Over the last two decades, great progress has been made in the understanding of the mechanism of thermal energy dissipation through the use of a few model plants, mainly Arabidopsis. Nonetheless, an emerging number of studies suggest that this model represents only one strategy among several different solutions for the environmental adjustment of thermal energy dissipation that have evolved among photosynthetic organisms in the course of evolution. In this review, a detailed analysis of three examples highlights the need to use models other than Arabidopsis: first, overwintering evergreens that develop a sustained form of thermal energy dissipation; second, desiccation tolerant plants that induce rapid thermal energy dissipation; and third, understorey plants in which a complementary lutein epoxide cycle modulates thermal energy dissipation. The three examples have in common a shift from a photosynthetically efficient state to a dissipative conformation, a strategy widely distributed among stress-tolerant evergreen perennials. Likewise, they show a distinct operation of the xanthophyll cycle. Expanding the list of model species beyond Arabidopsis will enhance our knowledge of these mechanisms and increase the synergy of the current studies now dispersed over a wide number of species.
Constraining Tidal Dissipation in Stars and Destruction Rates of Exoplanets
NASA Astrophysics Data System (ADS)
Jackson, Brian; Penev, K.; Barnes, R.
2011-01-01
Several recent studies have shown that the orbits of most transiting extra-solar planets, with periods of order a few days, are not stable against tidal decay. If the host star rotates slowly enough, tidal dissipation within the star causes the planet to spiral in over many millions or billions of years. Because the rate of tidal decay increases rapidly as orbital semi-major axis drops, planets that start out very close to their host stars are quickly destroyed, while planets farther out require more time. We calculate the times left for known transiting exoplanets as a function of the rate of tidal dissipation within the host star. For a population of such planets, we expect to observe a minority of planets near the end of their lives since those planets will only survive for a short time more. For an assumed tidal dissipation rate, if we find instead that a majority of transiting planets have only a small fraction of the lifetimes left before destruction, we can conclude the assumed tidal dissipation rate is too large. Thus, we can estimate the rate of tidal dissipation within planet-hosting stars by considering the distributions of times left of transiting planets for a range of assumed dissipation rates. We must also account for important selection and observational biases. Our results based on such an analysis suggest stellar dissipation rates corresponding to tidal Q-values of 106 and larger are consistent with observations, while values of 105 and smaller are not. Given these constraints, we estimate the rates of tidal destruction of transiting exoplanets.
Dissipative or conservative cosmology with dark energy?
NASA Astrophysics Data System (ADS)
Szydlowski, M.; Hrycyna, O.
2007-12-01
All evolutional paths for all admissible initial conditions of FRW cosmological models with dissipative dust fluid (described by dark matter, baryonic matter and dark energy) are analyzed using dynamical system approach. With that approach, one is able to see how generic the class of solutions leading to the desired property -- acceleration -- is. The theory of dynamical systems also offers a possibility of investigating all possible solutions and their stability with tools of Newtonian mechanics of a particle moving in a 1-dimensional potential which is parameterized by the cosmological scale factor. We demonstrate that flat cosmology with bulk viscosity can be treated as a conservative system with a potential function of the Chaplygin gas type. We also confront viscous models with SNIa observations. The best fitted models are obtained by minimizing the $\\chi^{2}$ function which is illustrated by residuals and $\\chi^{2}$ levels in the space of model independent parameters. The general conclusion is that SNIa data supports the viscous model without the cosmological constant. The obtained values of $\\chi^{2}$ statistic are comparable for both the viscous model and LCDM model. The Bayesian information criteria are used to compare the models with different power law parameterization of viscous effects. Our result of this analysis shows that SNIa data supports viscous cosmology more than the LCDM model if the coefficient in viscosity parameterization is fixed. The Bayes factor is also used to obtain the posterior probability of the model.
Modeling scalar flux and the energy and dissipation equations
NASA Technical Reports Server (NTRS)
Yoshizawa, A.
1987-01-01
Closure models derived from the Two-Scale Direct-Interaction Approximation were compared with data from direct simulations of turbulence. Attention was restricted to anisotropic scalar diffusion models, models for the energy dissipation equation, and models for energy diffusion.
Temporal intermittency of energy dissipation in magnetohydrodynamic turbulence.
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.
ENHANCED DISSIPATION RATE OF MAGNETIC FIELD IN STRIPED PULSAR WINDS BY THE EFFECT OF TURBULENCE
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.
Topographic generation of submesoscale centrifugal instability and energy dissipation
Gula, Jonathan; Molemaker, M. Jeroen; McWilliams, James C.
2016-01-01
Most of the ocean kinetic energy is contained in the large scale currents and the vigorous geostrophic eddy field, at horizontal scales of order 100 km. To achieve equilibrium the geostrophic currents must viscously dissipate their kinetic energy at much smaller scale. However, geostrophic turbulence is characterized by an inverse cascade of energy towards larger scale, and the pathways of energy toward dissipation are still in question. Here, we present a mechanism, in the context of the Gulf Stream, where energy is transferred from the geostrophic flow to submesoscale wakes through anticyclonic vertical vorticity generation in the bottom boundary layer. The submesoscale turbulence leads to elevated local dissipation and mixing outside the oceanic boundary layers. This process is generic for boundary slope currents that flow in the direction of Kelvin wave propagation. Topographic generation of submesoscale flows potentially provides a new and significant route to energy dissipation for geostrophic flows. PMID:27681822
Topographic generation of submesoscale centrifugal instability and energy dissipation
NASA Astrophysics Data System (ADS)
Gula, Jonathan; Molemaker, M. Jeroen; McWilliams, James C.
2016-09-01
Most of the ocean kinetic energy is contained in the large scale currents and the vigorous geostrophic eddy field, at horizontal scales of order 100 km. To achieve equilibrium the geostrophic currents must viscously dissipate their kinetic energy at much smaller scale. However, geostrophic turbulence is characterized by an inverse cascade of energy towards larger scale, and the pathways of energy toward dissipation are still in question. Here, we present a mechanism, in the context of the Gulf Stream, where energy is transferred from the geostrophic flow to submesoscale wakes through anticyclonic vertical vorticity generation in the bottom boundary layer. The submesoscale turbulence leads to elevated local dissipation and mixing outside the oceanic boundary layers. This process is generic for boundary slope currents that flow in the direction of Kelvin wave propagation. Topographic generation of submesoscale flows potentially provides a new and significant route to energy dissipation for geostrophic flows.
Topographic generation of submesoscale centrifugal instability and energy dissipation.
Gula, Jonathan; Molemaker, M Jeroen; McWilliams, James C
2016-09-29
Most of the ocean kinetic energy is contained in the large scale currents and the vigorous geostrophic eddy field, at horizontal scales of order 100 km. To achieve equilibrium the geostrophic currents must viscously dissipate their kinetic energy at much smaller scale. However, geostrophic turbulence is characterized by an inverse cascade of energy towards larger scale, and the pathways of energy toward dissipation are still in question. Here, we present a mechanism, in the context of the Gulf Stream, where energy is transferred from the geostrophic flow to submesoscale wakes through anticyclonic vertical vorticity generation in the bottom boundary layer. The submesoscale turbulence leads to elevated local dissipation and mixing outside the oceanic boundary layers. This process is generic for boundary slope currents that flow in the direction of Kelvin wave propagation. Topographic generation of submesoscale flows potentially provides a new and significant route to energy dissipation for geostrophic flows.
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.
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.
Thermodynamic Study of Energy Dissipation in Adiabatic Superconductor Logic
NASA Astrophysics Data System (ADS)
Takeuchi, Naoki; Yamanashi, Yuki; Yoshikawa, Nobuyuki
2015-09-01
Because of its extremely high energy efficiency, adiabatic superconductor logic is one of the most promising candidates for the realization of a practical reversible computer. In a previous study, we proposed a logically and physically reversible logic gate using adiabatic superconductor logic, and numerically demonstrated reversible computing. In the numerical calculation, we assumed that the average energy dissipation at finite temperature corresponds to that at zero temperature. However, how the phase difference of a Josephson junction in adiabatic superconductor logic behaves at finite temperature is not yet well understood, and whether thermal noise can induce a nonadiabatic state change remains unclear. In the present study, we investigate energy dissipation in adiabatic superconductor logic at finite temperature through numerical analyses using the Monte Carlo method. We investigate the average and standard deviation of the energy dissipation through both numerical calculation and analytical estimation. Finally, we discuss the minimum energy dissipation required for adiabatic switching operations.
Designing energy dissipation properties via thermal spray coatings
Brake, Matthew R. W.; Hall, Aaron Christopher; Madison, Jonathan D.
2016-12-14
The coefficient of restitution is a measure of energy dissipation in a system across impact events. Often, the dissipative qualities of a pair of impacting components are neglected during the design phase. This research looks at the effect of applying a thin layer of metallic coating, using thermal spray technologies, to significantly alter the dissipative properties of a system. We studied the dissipative properties across multiple impacts in order to assess the effects of work hardening, the change in microstructure, and the change in surface topography. The results of the experiments indicate that any work hardening-like effects are likely attributable to the crushing of asperities, and the permanent changes in the dissipative properties of the system, as measured by the coefficient of restitution, are attributable to the microstructure formed by the thermal spray coating. Furthermore, the microstructure appears to be robust across impact events of moderate energy levels, exhibiting negligible changes across multiple impact events.
Enhanced turbulence and energy dissipation at ocean fronts.
D'Asaro, Eric; Lee, Craig; Rainville, Luc; Harcourt, Ramsey; Thomas, Leif
2011-04-15
The ocean surface boundary layer mediates air-sea exchange. In the classical paradigm and in current climate models, its turbulence is driven by atmospheric forcing. Observations at a 1-kilometer-wide front within the Kuroshio Current indicate that the rate of energy dissipation within the boundary layer is enhanced by one to two orders of magnitude, suggesting that the front, rather than the atmospheric forcing, supplied the energy for the turbulence. The data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence. The resulting boundary layer is stratified in contrast to the classically well-mixed layer. These effects will be strongest at the intense fronts found in the Kuroshio Current, the Gulf Stream, and the Antarctic Circumpolar Current, all of which are key players in the climate system.
Delayed correlation between turbulent energy injection and dissipation.
Pearson, Bruce R; Yousef, Tarek A; Haugen, Nils Erland L; Brandenburg, Axel; Krogstad, Per-Age
2004-11-01
The dimensionless kinetic energy dissipation rate C(epsilon) is estimated from numerical simulations of statistically stationary isotropic box turbulence that is slightly compressible. The Taylor microscale Reynolds number (Re(lambda)) range is 20< or approximately equal to Re(lambda) < or approximately equal to 220 and the statistical stationarity is achieved with a random phase forcing method. The strong Re(lambda) dependence of C(epsilon) abates when Re(lambda) approximately 100 after which C(epsilon) slowly approaches approximately 0.5, a value slightly different from previously reported simulations but in good agreement with experimental results. If C(epsilon) is estimated at a specific time step from the time series of the quantities involved it is necessary to account for the time lag between energy injection and energy dissipation. Also, the resulting value can differ from the ensemble averaged value by up to +/-30%. This may explain the spread in results from previously published estimates of C(epsilon).
Fluctuations of the dissipated energy in a granular system
NASA Astrophysics Data System (ADS)
Lasanta, Antonio; Hurtado, Pablo I.; Garrido, Pedro L.; Brey, J. Javier
2011-03-01
Large fluctuations, play an important role in many fields of science as they crucially determine the fate of a system. The statistics of these fluctuations encodes essential information on the physics of the system at hand. This is particularly important in systems far from equilibrium, where no general theory exists up to date capable of predicting macroscopic and fluctuating behavior in terms of microscopic physics.The study of fluctuations far from equilibrium may open the door to such general theory. In this work we follow this path by studying the fluctuations of the dissipated energy in an oversimplified model of a granular system. The model, first proposed and solved by Levanony and Levine [1], is a simple one dimensional diffusive lattice system which includes energy dissipation as a main ingredient. When subject to boundary heat baths, the system reaches an steady state characterized by a highly nonlinear temperature profile and a nonzero average energy dissipation. For long but finite times, the time-averaged dissipated energy fluctuates, obeying a large deviation principle. We study the large deviation function (LDF) of the dissipated energy by means of advanced Monte Carlo techniques [2], arriving to the following results: (i) the LDF of the dissipated energy has only a positive branch, meaning that for long times only positive dissipation is expected, (ii) as a result of microscopic time-irreversibility, the LDF does not obeys the Gallavotti-Cohen fluctuation theorem, (iii) the LDF is Gaussian around the average dissipation, but non-Gaussian, asymmetric tails quickly develop away from the average, and (iv) the granular system adopts a precise optimal profile in order to facilitate a given dissipation fluctuation, different from the steady profile. We compare our numerical results with predictions based on hydrodynamic fluctuation theory [3], finding good agreement.
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.
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.
Reversibility and energy dissipation in adiabatic superconductor logic.
Takeuchi, Naoki; Yamanashi, Yuki; Yoshikawa, Nobuyuki
2017-03-06
Reversible computing is considered to be a key technology to achieve an extremely high energy efficiency in future computers. In this study, we investigated the relationship between reversibility and energy dissipation in adiabatic superconductor logic. We analyzed the evolution of phase differences of Josephson junctions in the reversible quantum-flux-parametron (RQFP) gate and confirmed that the phase differences can change time reversibly, which indicates that the RQFP gate is physically, as well as logically, reversible. We calculated energy dissipation required for the RQFP gate to perform a logic operation and numerically demonstrated that the energy dissipation can fall below the thermal limit, or the Landauer bound, by lowering operation frequencies. We also investigated the 1-bit-erasure gate as a logically irreversible gate and the quasi-RQFP gate as a physically irreversible gate. We calculated the energy dissipation of these irreversible gates and showed that the energy dissipation of these gate is dominated by non-adiabatic state changes, which are induced by unwanted interactions between gates due to logical or physical irreversibility. Our results show that, in reversible computing using adiabatic superconductor logic, logical and physical reversibility are required to achieve energy dissipation smaller than the Landauer bound without non-adiabatic processes caused by gate interactions.
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.
Ubiquitous mechanisms of energy dissipation in noncontact atomic force microscopy.
Ghasemi, S Alireza; Goedecker, Stefan; Baratoff, Alexis; Lenosky, Thomas; Meyer, Ernst; Hug, Hans J
2008-06-13
Atomistic simulations considering larger tip structures than hitherto assumed reveal novel dissipation mechanisms in noncontact atomic force microscopy. The potential energy surfaces of realistic silicon tips exhibit many energetically close local minima that correspond to different structures. Most of them easily deform, thus causing dissipation arising from hysteresis in force versus distance characteristics. Furthermore, saddle points which connect local minima can suddenly switch to connect different minima. Configurations driven into metastability by the tip motion can thus suddenly access lower energy structures when thermal activation becomes allowed within the time required to detect the resulting average dissipation.
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.
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.
Su, Hongling; Li, Shengtai
2016-02-03
In this study, 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 versionmore » 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. Finally, 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.« less
Su, Hongling; Li, Shengtai
2016-02-03
In this study, 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. Finally, 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.
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.
Improved observations of turbulence dissipation rates from wind profiling radars
NASA Astrophysics Data System (ADS)
McCaffrey, Katherine; Bianco, Laura; Wilczak, James M.
2017-07-01
Observations of turbulence dissipation rates in the planetary boundary layer are crucial for validation of parameterizations in numerical weather prediction models. However, because dissipation rates are difficult to obtain, they are infrequently measured through the depth of the boundary layer. For this reason, demonstrating the ability of commonly used wind profiling radars (WPRs) to estimate this quantity would be greatly beneficial. During the XPIA field campaign at the Boulder Atmospheric Observatory, two WPRs operated in an optimized configuration, using high spectral resolution for increased accuracy of Doppler spectral width, specifically chosen to estimate turbulence from a vertically pointing beam. Multiple post-processing techniques, including different numbers of spectral averages and peak processing algorithms for calculating spectral moments, were evaluated to determine the most accurate procedures for estimating turbulence dissipation rates using the information contained in the Doppler spectral width, using sonic anemometers mounted on a 300 m tower for validation. The optimal settings were determined, producing a low bias, which was later corrected. Resulting estimations of turbulence dissipation rates correlated well (R2 = 0. 54 and 0. 41) with the sonic anemometers, and profiles up to 2 km from the 449 MHz WPR and 1 km from the 915 MHz WPR were observed.
Improved observations of turbulence dissipation rates from wind profiling radars
McCaffrey, Katherine; Bianco, Laura; Wilczak, James M.
2017-07-20
Observations of turbulence dissipation rates in the planetary boundary layer are crucial for validation of parameterizations in numerical weather prediction models. However, because dissipation rates are difficult to obtain, they are infrequently measured through the depth of the boundary layer. For this reason, demonstrating the ability of commonly used wind profiling radars (WPRs) to estimate this quantity would be greatly beneficial. During the XPIA field campaign at the Boulder Atmospheric Observatory, two WPRs operated in an optimized configuration, using high spectral resolution for increased accuracy of Doppler spectral width, specifically chosen to estimate turbulence from a vertically pointing beam. Multiplemore » post-processing techniques, including different numbers of spectral averages and peak processing algorithms for calculating spectral moments, were evaluated to determine the most accurate procedures for estimating turbulence dissipation rates using the information contained in the Doppler spectral width, using sonic anemometers mounted on a 300 m tower for validation. Furthermore, the optimal settings were determined, producing a low bias, which was later corrected. Resulting estimations of turbulence dissipation rates correlated well (R2 = 0.54 and 0.41) with the sonic anemometers, and profiles up to 2 km from the 449 MHz WPR and 1 km from the 915 MHz WPR were observed.« less
Improved observations of turbulence dissipation rates from wind profiling radars
McCaffrey, Katherine; Bianco, Laura; Wilczak, James M.
2017-01-01
Observations of turbulence dissipation rates in the planetary boundary layer are crucial for validation of parameterizations in numerical weather prediction models. However, because dissipation rates are difficult to obtain, they are infrequently measured through the depth of the boundary layer. For this reason, demonstrating the ability of commonly used wind profiling radars (WPRs) to estimate this quantity would be greatly beneficial. During the XPIA field campaign at the Boulder Atmospheric Observatory, two WPRs operated in an optimized configuration, using high spectral resolution for increased accuracy of Doppler spectral width, specifically chosen to estimate turbulence from a vertically pointing beam. Multiple post-processing techniques, including different numbers of spectral averages and peak processing algorithms for calculating spectral moments, were evaluated to determine the most accurate procedures for estimating turbulence dissipation rates using the information contained in the Doppler spectral width, using sonic anemometers mounted on a 300 m tower for validation. The optimal settings were determined, producing a low bias, which was later corrected. Resulting estimations of turbulence dissipation rates correlated well (R^{2} = 0. 54 and 0. 41) with the sonic anemometers, and profiles up to 2 km from the 449 MHz WPR and 1 km from the 915 MHz WPR were observed.
Scalar dissipation rate measurements in a starting jet
NASA Astrophysics Data System (ADS)
Soulopoulos, N.; Hardalupas, Y.; Taylor, A. M. K. P.
2014-03-01
Measurements of the scalar dissipation rate are taken in an impulsively started gas jet, using planar laser-induced fluorescence. The measurements are well-resolved spatially. The deteriorating effect of experimental noise on this experiment is treated with a Wiener filter, which is shown to be applicable to this large-scale inhomogeneous flow. The accuracy of the scalar dissipation rate is within 20 %, as determined from an explicit calculation of the filtering errors. The residual fields that remain after the filtering are analysed in detail, and their statistical properties show that these resemble white noise to a good approximation. The level of corrections is minimal for the scalar field but it is of the order of 40 % for the scalar dissipation rate. An examination of the filtering operation using modelled spectra and the measured spatial resolution shows that the Wiener filter produces errors in the estimate of the scalar dissipation rate ˜30 %, for Taylor-scale Reynolds number up to 1,000. The implications of this modelling are discussed with respect to common experimental situations and point out the relative merits of improving the spatial resolution as compared to improvements in the signal-to-noise ratio.
Iprodione residues and dissipation rates in tobacco leaves and soil.
Wang, Xiuguo; Xu, Guangjun; Wang, Fenglong; Sun, Huiqing; Li, Yiqiang
2012-10-01
Field experiments were conducted in two different locations to determine the residue levels and dissipation rates of iprodione in tobacco leaves and soil. Iprodione 50% wettable powder formulation was sprayed once at 12.50 g/ha to study the dissipation behavior and three to four times at 8.33 g/ha (recommended dose) and 12.50 g/ha (1.5 times the recommended field dose) to determine the residue levels of iprodione in tobacco leaves and soil after repeated applications. Iprodione residues in both green tobacco leaves and soil dissipated to about 50% of the initial deposits after 7 days and then further dissipated to more than 90% after 35 days.The dissipation of iprodione followed first order kinetics and the calculated half-life values (T (1/2)) were 5.64-8.80 days in green tobacco leaves and 7.50-9.93 days in soil, respectively. Iprodione residue levels in flue-cured tobacco leaves 21 days after the third and fourth applications ranged from 7.61 to 40.98 mg/kg. Meanwhile, the residues detected in soil decreased to 0.010-0.117 mg/kg 21 days after the last treatment.
Rolling friction and energy dissipation in a spinning disc
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
Rolling friction and energy dissipation in a spinning disc.
Ma, Daolin; Liu, Caishan; Zhao, Zhen; Zhang, Hongjian
2014-09-08
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.
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.
Temporal, Spatial, Statistical Distribution of the Rate of Dissipation of TKE in Islay Sound
NASA Astrophysics Data System (ADS)
Lueck, R. G.; Wolk, F.; Black, K.
2016-02-01
Turbulence measurements were conducted with a vertical turbulence microstructure profiler (VMP) in the Sound of Islay, a tidal channel that is slated for of tidal energy extraction. The work is part of the Turbulence in the Marine Environment (TiME) project. The magnitude and variability of the measured rate of dissipation of turbulent kinetic energy (ɛ) in this environment are remarkable, and this data set provides new information for site assessments, numerical flow models, and engineering designs of tidal energy extraction devices. The data were collected during spring tides and during maximum current speeds, which exceeded 4 m s-1 in both directions. The turbulence is very intense with ɛ reaching up to 2×10-3 W kg-1, placing these data among the highest rates of dissipation measured in open natural water. A total of 108 profiles were collected along two north-south transect lines. The lines were separated in the east-west by 1600 m and straddle the location of a moored turbulence float and a bottom-mounted ADCP. There are no significant statistical variations in neither the meridional nor the zonal directions. However, the rate of dissipation is two times larger during current flow to the west compared to flow to the east, even though current to the west is slightly weaker than to the east. Turbulence data from the vertical profiles agree well with those from the moored platform. The average and median rate of dissipation increases with increasing depth. The mean rate is projected to reach 1 and 2×10-3 W kg-1 at the bottom. The rate of dissipation is distributed lognormally with the standard deviation of 0.6, which means that there is a high probability of dissipation rates that are 10 times larger than the mean rate.
Area theorem and energy quantization for dissipative optical solitons
Renninger, William H.; Chong, Andy; Wise, Frank W.
2011-01-01
Soliton area theorems express the pulse energy as a function of the pulse shape and the system parameters. From an analytical solution to the cubic-quintic Ginzbug-Landau equation, we derive an area theorem for dissipative optical solitons. In contrast to area theorems for conservative optical solitons, the energy does not scale inversely with the pulse duration, and in addition there is an upper limit to the energy. Energy quantization explains the existence of, and conditions for, multiple-pulse solutions. The theoretical predictions are confirmed with numerical simulations and experiments in the context of dissipative soliton fiber lasers. PMID:21765589
Modeling of the metabolic energy dissipation for restricted tumor growth.
Pajic-Lijakovic, Ivana; Milivojevic, Milan
2017-08-29
Energy dissipation mostly represents unwanted outcome but in the biochemical processes it may alter the biochemical pathways. However, it is rarely considered in the literature although energy dissipation and its alteration due to the changes in cell microenvironment may improve methods for guiding chemical and biochemical processes in the desired directions. Deeper insight into the changes of metabolic activity of tumor cells exposed to osmotic stress or irradiation may offer the possibility of tumor growth reduction. In this work effects of the osmotic stress and irradiation on the thermodynamical affinity of tumor cells and their damping effects on metabolic energy dissipation were investigated and modeled. Although many various models were applied to consider the tumor restrictive growth they have not considered the metabolic energy dissipation. In this work a pseudo rheological model in the form of "the metabolic spring-pot element" is formulated to describe theoretically the metabolic susceptibility of tumor spheroid. This analog model relates the thermodynamical affinity of cell growth with the volume expansion of tumor spheroid under isotropic loading conditions. Spheroid relaxation induces anomalous nature of the metabolic energy dissipation which causes the damping effects on cell growth. The proposed model can be used for determining the metabolic energy "structure" in the context of restrictive cell growth as well as for predicting optimal doses for cancer curing in order to tailor the clinical treatment for each person and each type of cancer.
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.
Accuracy improvement in dissipated energy measurement by using phase information
NASA Astrophysics Data System (ADS)
Shiozawa, D.; Inagawa, T.; Washio, T.; Sakagami, T.
2017-04-01
In this paper, a technique for improving the accuracy of a dissipated energy measurement based on the phase information—called the phase 2f lock-in infrared method—is proposed. In the conventional 2f lock-in infrared method, the dissipated energy is obtained as the double frequency component of the measured temperature change. In this work, a phase analysis of the double frequency component has been conducted. It is found that the double frequency component includes the influence of the energy dissipation and harmonic vibration of the fatigue testing machine, and the phase difference between the thermoelastic temperature change and the double frequency component is a specific value. The phase 2f lock-in method utilizes a specific phase of the dissipated energy and is effective for removing the noise component such as the thermoelastic temperature change due to the harmonic vibration of fatigue testing machine. This method provides an improvement in the accuracy of the fatigue-limit estimate and the detection of future crack initiation points based on the dissipated energy.
Derivation and application of the energy dissipation factor in the design of fishways
Towler, Brett; Mulligan, Kevin; Haro, Alexander J.
2015-01-01
Reducing turbulence and associated air entrainment is generally considered advantageous in the engineering design of fish passage facilities. The well-known energy dissipation factor, or EDF, correlates with observations of the phenomena. However, inconsistencies in EDF forms exist and the bases for volumetric energy dissipation rate criteria are often misunderstood. A comprehensive survey of EDF criteria is presented. Clarity in the application of the EDF and resolutions to these inconsistencies are provided through formal derivations; it is demonstrated that kinetic energy represents only 1/3 of the total energy input for the special case of a broad-crested weir. Specific errors in published design manuals are identified and resolved. New, fundamentally sound, design equations for culvert outlet pools and standard Denil Fishway resting pools are developed. The findings underscore the utility of EDF equations, demonstrate the transferability of volumetric energy dissipation rates, and provide a foundation for future refinement of component-, species-, and life-stage-specific EDF criteria.
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.
Energy dissipation in the Nagel-Schreckenberg model with open boundary condition
NASA Astrophysics Data System (ADS)
Zhang, Wei; Zhang, Wei
2014-01-01
In this paper, we numerically investigate energy dissipation caused by traffic in the Nagel-Schreckenberg (NaSch) model with open boundary conditions (OBC). Boundary results in excess energy dissipation. The effects of the stochastic boundary conditions on energy dissipation are discussed. The behaviors of energy dissipation in different traffic phase are distinct. As an order parameter, energy dissipation rate E d characterizes the phase transition behaviors well. It is shown that there is no true free-flow state in nondeterministic NaSch model with OBC. We refer to this non-true free-flow state as quasi-free-flow (QFF) phase in which there are interactions between vehicles caused by stochastic braking but no backward moving jam exists. In the maximum current phase, E d is minimal thus the social payoff is maximal. Energy dissipation profiles in QFF, jammed and maximum current phase are presented. Theoretical analyses are in good agreement with numerical results for the case v max = 1.
Alternate energy dissipation? Phenolic metabolites and the xanthophyll cycle.
Close, Dugald C; Beadle, Chris L
2003-04-01
The dynamics of phenolic galloylglucoses (di-, tri-, tetra- and penta-galloylglucose), flavonoids (quercitin and quercitin glycosides) and sideroxylonal were compared with that of xanthophyll cycle-dependent energy dissipation during rapid induction of chilling-dependent photo-inhibition. Pre-dawn xanthophyll cycle engagement of seedlings of Eucalyptus nitens transferred from mild nursery conditions to a low temperature controlled environment increased logarithmically during eight days of treatment. Photochemical efficiency and flavonoids decreased after four days of treatment and non-photochemical quenching after two days of treatment. Galloylglucoses and sideroxylonal decreased linearly during treatment. These results demonstrate that rapid changes in foliar phenolic levels are associated with abrupt changes in the plant environment. It is argued that under these growth-chamber conditions, the xanthophyll cycle facilitated dissipation of excess light energy, lessening the requirement for the dissipation of energy or antioxidant activity through phenolic metabolites.
Protein-mediated energy-dissipating pathways in mitochondria.
Starkov, Anatoly A
2006-05-15
Mitochondrial production of reactive oxygen species (ROS) is a well-established fact of fundamental importance to aging and etiology of many pathologies with serious public health implications. The ROS production is an innate property of mitochondrial biochemistry inseparable from the oxidative metabolism. Recent discoveries indicate that in addition to several ROS-detoxifying enzyme systems, which remove ROS, mitochondria may also be able to limit their ROS production by the mechanism comprising several protein-mediated energy-dissipating ("uncoupling") pathways. Although the physiological significance and in vivo modus operandi of these pathways remain to be elucidated, several proteins potentially capable of energy dissipation are known. This mini-review addresses the identity of mitochondrial protein-mediated energy-dissipating pathways and the experimental evidence to their role in controlling ROS production.
Protein-mediated energy-dissipating pathways in mitochondria.
Starkov, Anatoly A
2006-10-27
Mitochondrial production of reactive oxygen species (ROS) is a well-established fact of fundamental importance to aging and etiology of many pathologies with serious public health implications. The ROS production is an innate property of mitochondrial biochemistry inseparable from the oxidative metabolism. Recent discoveries indicate that in addition to several ROS-detoxifying enzyme systems, which remove ROS, mitochondria may also be able to limit their ROS production by the mechanism comprising several protein-mediated energy-dissipating ("uncoupling") pathways. Although the physiological significance and in vivo modus operandi of these pathways remain to be elucidated, several proteins potentially capable of energy dissipation are known. This mini-review addresses the identity of mitochondrial protein-mediated energy-dissipating pathways and the experimental evidence to their role in controlling ROS production.
Energy Dissipating Devices in Falling Rock Protection Barriers
NASA Astrophysics Data System (ADS)
Castanon-Jano, L.; Blanco-Fernandez, E.; Castro-Fresno, D.; Ballester-Muñoz, F.
2017-03-01
Rockfall is a phenomenon which, when uncontrolled, may cause extensive material damage and personal injury. One of the structures used to avoid accidents caused by debris flows or rockfalls is flexible barriers. The energy dissipating devices which absorb the energy generated by rock impact and reduce the mechanical stresses in the rest of the elements of the structure are an essential part of these kinds of structures. This document proposes an overview of the performance of energy dissipating devices, as well as of the role that they fulfil in the barrier. Furthermore, a compilation and a description of the dissipating elements found in the literature are proposed. Additionally, an analysis has been performed of the aspects taken into account in the design, such as experimental (quasi-static and dynamic) tests observing the variation of the behaviour curve depending on the test speed and numerical simulations by means of several finite element software packages.
Effects of bearing surfaces on lap joint energy dissipation
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.
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.
Modeling compaction-induced energy dissipation of granular HMX
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.
Non-dissipative energy capture of confined liquid in nanopores
Xu, Baoxing; Chen, Xi; Lu, Weiyi; Zhao, Cang; Qiao, Yu
2014-05-19
In the past, energy absorption of protection/damping materials is mainly based on energy dissipation, which causes a fundamental conflict between the requirements of safety/comfort and efficiency. In the current study, a nanofluidic “energy capture” system is reported, which is based on nanoporous materials and nonwetting liquid. Both molecular dynamics simulations and experiments show that as the liquid overcomes the capillary effect and infiltrates into the nanopores, the mechanical energy of a stress wave could be temporarily stored by the confined liquid phase and isolated from the wave energy transmission path. Such a system can work under a relatively low pressure for mitigating high-pressure stress waves, not necessarily involved in any energy dissipation processes.
Excess kinetic energy dissipation in materials
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.
Designing energy dissipation properties via thermal spray coatings
Brake, Matthew R. W.; Hall, Aaron Christopher; Madison, Jonathan D.
2016-12-14
The coefficient of restitution is a measure of energy dissipation in a system across impact events. Often, the dissipative qualities of a pair of impacting components are neglected during the design phase. This research looks at the effect of applying a thin layer of metallic coating, using thermal spray technologies, to significantly alter the dissipative properties of a system. We studied the dissipative properties across multiple impacts in order to assess the effects of work hardening, the change in microstructure, and the change in surface topography. The results of the experiments indicate that any work hardening-like effects are likely attributablemore » to the crushing of asperities, and the permanent changes in the dissipative properties of the system, as measured by the coefficient of restitution, are attributable to the microstructure formed by the thermal spray coating. Furthermore, the microstructure appears to be robust across impact events of moderate energy levels, exhibiting negligible changes across multiple impact events.« less
Dasi, Lakshmi P; Pekkan, Kerem; de Zelicourt, Diane; Sundareswaran, Kartik S; Krishnankutty, Resmi; Delnido, Pedro J; Yoganathan, Ajit P
2009-04-01
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. 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 (TCPC-EDI). 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 m(2)) 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 aortic stenosis has an AV-EDI one
ENERGY DISSIPATION IN MAGNETIC NULL POINTS AT KINETIC SCALES
Olshevsky, Vyacheslav; Lapenta, Giovanni; Divin, Andrey; Eriksson, Elin; Markidis, Stefano
2015-07-10
We use kinetic particle-in-cell and MHD simulations supported by an observational data set to investigate magnetic reconnection in clusters of null points in space plasma. The magnetic configuration under investigation is driven by fast adiabatic flux rope compression that dissipates almost half of the initial magnetic field energy. In this phase powerful currents are excited producing secondary instabilities, and the system is brought into a state of “intermittent turbulence” within a few ion gyro-periods. Reconnection events are distributed all over the simulation domain and energy dissipation is rather volume-filling. Numerous spiral null points interconnected via their spines form null lines embedded into magnetic flux ropes; null point pairs demonstrate the signatures of torsional spine reconnection. However, energy dissipation mainly happens in the shear layers formed by adjacent flux ropes with oppositely directed currents. In these regions radial null pairs are spontaneously emerging and vanishing, associated with electron streams and small-scale current sheets. The number of spiral nulls in the simulation outweighs the number of radial nulls by a factor of 5–10, in accordance with Cluster observations in the Earth's magnetosheath. Twisted magnetic fields with embedded spiral null points might indicate the regions of major energy dissipation for future space missions such as the Magnetospheric Multiscale Mission.
Peculiarities of light energy dissipation in uniaxial gyrotropic crystals
Mityurich, G.S.; Starodubtsev, E.G.
1994-10-01
The energy dissipation of electromagnetic waves in uniaxial gyrotropic crystals of types 32, 422, and 622 for arbitrary anisotropic and gyrotropic properties in the presence of multibeam optical interference is theoretically studied. The possibility of measuring the gyrotropic parameters of such crystals by photothermoacoustic techniques is shown, and conditions of the measurement optimization are found. 11 refs., 3 figs.
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 millimetrewavelength 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 stratocumuluswhereas the turbulence diurnal
Intrinsic Energy Dissipation Limits in Nano and Micromechanical Resonators
NASA Astrophysics Data System (ADS)
Iyer, Srikanth Subramanian
Resonant microelectromechanical Systems (MEMS) have enabled miniaturization of high-performance inertial sensors, radio-frequency filters, timing references and mass-based chemical sensors. Despite the increasing prevalence of MEMS resonators for these applications, the energy dissipation in these structures is not well-understood. Accurate prediction of the energy loss and the resulting quality factor (Q) has significant design implications because it is directly related to device performance metrics including sensitivity for resonant sensors, bandwidth for radio-frequency filters and phase-noise for timing references. In order to assess the future potential for MEMS resonators it is critically important to evaluate the energy dissipation limits, which will dictate the ultimate performance resonant MEMS devices can achieve. This work focuses on the derivation and evaluation of the intrinsic mechanical energy dissipation limit for single-crystal nano and micromechanical resonators due to anharmonic phonon-phonon scattering in the Akhiezer regime. The energy loss is derived using perturbation theory and the linearized Boltzmann transport equation for phonons, and includes the direction and polarization dependent mode-Gruneisen parameters in order to capture the strain-induced anharmonicity among phonon branches. Evaluation of the quality factor limit reveals that Akhiezer damping, previously thought to depend only on material properties, has a strong dependence on crystal orientation and resonant mode shape. The robust model provides a dissipation limit for all resonant modes including shear-mode vibrations, which have significantly reduced energy loss because dissipative phonon-phonon scattering is restricted to volume-preserving phonon branches, indicating that Lame or wine-glass mode resonators will have the highest upper limit on mechanical efficiency. Finally, the analytical dissipation model is integrated with commercial finite element software in order to
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
Cloud-Scale Vertical Velocity and Turbulent Dissipation Rate Retrievals
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.
Energy Dissipation and Noise Correlations in Biochemical Sensing
NASA Astrophysics Data System (ADS)
Govern, Christopher C.; ten Wolde, Pieter Rein
2014-12-01
To measure chemical concentrations, cells need to extract information from stochastic receptor signals via signaling networks which are also inherently stochastic. Here, we study how the accuracy of sensing depends on the correlations between these extrinsic and intrinsic sources of noise. We find that the sensing precision of signaling networks that are not driven out of equilibrium is fundamentally limited by the fluctuation-dissipation theorem, which generates a tradeoff between the removal of extrinsic and intrinsic noise. As a result, the sensing precision of equilibrium systems is limited by the number of receptors; the downstream network can never improve sensing. To lift the tradeoff, energy dissipation is essential. This allows the receptor to transduce the signal as a catalyst and enables time integration of the receptor state. To beat the sensing limit of equilibrium systems, a canonical nonequilibrium signaling network based on the push-pull motif needs to dissipate at least 1 kBT per receptor.
Energy dissipation in oscillating flow through straight and coiled pipes
Olson, J.R.; Swift, G.W.
1996-10-01
The energy dissipation is reported for oscillating flow in U-shaped pipes with 180{degree}, 540{degree}, and 900{degree} curves at the base of the U. Analysis permits separation of the dissipation in the straight and curved portions of the pipe. Using water, water/glycerine mixtures, liquid nitrogen, and helium gas, the dissipation was measured for fluid flow regimes (Reynolds number, quality factor, and pipe curvature) which have not previously been reported. Measured loss in the straight portion is compared to numerical solutions using a turbulent quasisteady representation of the wall shear stress. Measured loss in the curved portion is compared to simple theory. The results are applicable to thermoacoustic devices. {copyright} {ital 1996 Acoustical Society of America.}
Dissipation and energy balance in electronic dynamics of Na clusters
NASA Astrophysics Data System (ADS)
Vincendon, Marc; Suraud, Eric; Reinhard, Paul-Gerhard
2017-06-01
We investigate the impact of dissipation on the energy balance in the electron dynamics of metal clusters excited by strong electro-magnetic pulses. The dynamics is described theoretically by Time-Dependent Density-Functional Theory (TDDFT) at the level of Local Density Approximation (LDA) augmented by a self interaction correction term and a quantum collision term in Relaxation-Time Approximation (RTA). We evaluate the separate contributions to the total excitation energy, namely energy exported by electron emission, potential energy due to changing charge state, intrinsic kinetic and potential energy, and collective flow energy. The balance of these energies is studied as function of the laser parameters (frequency, intensity, pulse length) and as function of system size and charge. We also look at collisions with a highly charged ion and here at the dependence on the impact parameter (close versus distant collisions). Dissipation turns out to be small where direct electron emission prevails namely for laser frequencies above any ionization threshold and for slow electron extraction in distant collisions. Dissipation is large for fast collisions and at low laser frequencies, particularly at resonances. Contribution to the Topical Issue "Dynamics of Systems at the Nanoscale", edited by Andrey Solov'yov and Andrei Korol.
NASA Astrophysics Data System (ADS)
Yang, H.; Sinha, S. K.; Feng, Y.; Jeremic, B.
2016-12-01
The M5.8 earthquake occurred in Pawnee, Oklahoma on September 3rd 2016 is the strongest seismic event recorded in Oklahoma. Soil structure interaction (SSI) played an important role in this tragic event. As a major aspect of SSI analysis, the propagation and dissipation of seismic energy will be studied in depth, with particular focus on the ground motion recorded in this earthquake. Seismic energy propagates from seismic source to the SSI system and is dissipated within and around the SSI system. Energy dissipation with the SSI system is related to inelastic behavior of soil, rock, contact zone (foundation-soil/rock), structural components and energy dissipators. Accurate evaluation of seismic energy can be used to optimize SSI system for safety and economy. The SSI system can be designed so that majority of seismic energy is dissipated within soil and soil-foundation contact zone, away from the structure.Accurate and theoretically sound modeling of propagation and dissipation is essential to use of seismic energy for design and assessment. The rate of plastic work is defined as the product of stress and the rate of plastic strain. On the other hand, plastic dissipation is defined as a form of heat transfer. The difference between these two quantities, which has been neglected in many studies, is a plastic part of the free energy. By considering energy storage and dissipation at both micro (particle) scale and macro (continuum) scale, it can be shown that the plastic free energy is an intrinsic attribute at the continuum scale due to particle rearrangement. Proper application of thermodynamics to finite element simulations, plastic dissipation can be correctly modeled. Examples will be used to illustrate above point on both constitutive, single element and SSI model scales. In addition, propagation of seismic energy, its dissipation (timing and location) will be used to illustrate use in design and assessment.
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.
Tidal Energy Dissipation over long Geological Time Scales
NASA Astrophysics Data System (ADS)
Daher, H.; Adcroft, A.; Ansong, J. K.; Arbic, B. K.; Austermann, J.; Mitrovica, J. X.; Maloof, A. C.
2016-02-01
Over most of the history of the Earth-Moon system, tidal dissipation has been substantially lower than it is today. This is somewhat perplexing because in the past the moon was closer to the Earth and therefore tidal forces were larger. Previous work on this problem, done with highly idealized models, has shown that tidal dissipation is sensitive to Earth's rotation rate and the configuration of continents, which together set the time scale of the ocean's normal modes and hence their degree of resonance with the tidal forcing. Here, we employ a state-of-the-art global high-resolution ocean model, forced by the M2 tidal constituent, to explore the history of tidal resonance in a model with realistic bathymetries and continental geometries. Increasing Earth's rotation rate, while keeping geometries and bathymetries fixed to present-day values, yields substantially lower dissipation rates, consistent with the results of idealized models. We also show results from simulations with different continental configurations, increased tidal forcings, and smoother coastlines that mimic hundreds of millions of years without glacioeustasy in the Archaean and Proterozoic, to help unravel the puzzle of tidal dissipation over long geological time scales.
Influence of media characteristics on energy dissipation in filter backwashing.
Turan, Mustafa; Sabah, Eyup; Gulsen, Hakki; Celik, Mehmet S
2003-09-15
Effective cleaning of granular filters during backwashing processes needs maximum turbulence and maximum shear in the fluid particle field. The energy dissipation in a backwashed filter as a particulate fluidized bed arises due to the suspending and random motions of particles and turbulent fluctuations in the bed. Size, density, and sphericity of the filter materials greatly influence the fluidization behavior of the media. In this study, a new model is proposed for predicting the energy dissipation parameters namely the hydrodynamic shear stress (tau(a)), the velocity gradient (G(a)), the turbulence dissipation coefficient (C(a)), and the turbulence parameter (C(a)0.5/Re) in backwashing of filters for different types of filter materials (sand, anthracite, and glass ball). The hydrodynamic shear stress is the dominant mechanism of filter cleaning and appears to increase with increasing the density and size of the filter media particles. Using the basic set of data, a step by step procedure is developed to compute the velocity gradient G(a), the turbulence dissipation coefficient C(a), the hydrodynamic shear stress tau(a), and the turbulent parameter (C(a)0.5/ Re).
Energy dissipation in Ex-Vivo Porcine Liver during Electrosurgery.
Karaki, Wafaa; Akyildiz, Ali; De, Suvranu; Borca Tasciuc, Diana-Andra
2016-07-27
This paper explores energy dissipation in ex-vivo liver tissue during radiofrequency current excitation with application in electrosurgery. Tissue surface temperature for monopolar electrode configuration is measured using infrared thermometry. The experimental results are fitted to a finite element model for transient heat transfer taking into account energy storage and conduction in order to extract information about "apparent" specific heat, which encompasses storage and phase change. The average apparent specific heat determined for low temperatures is in agreement with published data. However, at temperatures approaching the boiling point of water, apparent specific heat increased by a factor of five, indicating that vaporization plays an important role in the energy dissipation through latent heat loss.
Magnetic energy dissipation and mean magnetic field generation in planar convection-driven dynamos.
Tilgner, A
2014-07-01
A numerical study of dynamos in rotating convecting plane layers is presented which focuses on magnetic energies and dissipation rates and the generation of mean fields (where the mean is taken over horizontal planes). The scaling of the magnetic energy with the flux Rayleigh number is different from the scaling proposed in spherical shells, whereas the same dependence of the magnetic dissipation length on the magnetic Reynolds number is found for the two geometries. Dynamos both with and without mean field exist in rapidly rotating convecting plane layers.
Energy dissipation dataset for reversible logic gates in quantum dot-cellular automata.
Bahar, Ali Newaz; Rahman, Mohammad Maksudur; Nahid, Nur Mohammad; Hassan, Md Kamrul
2017-02-01
This paper presents an energy dissipation dataset of different reversible logic gates in quantum-dot cellular automata. The proposed circuits have been designed and verified using QCADesigner simulator. Besides, the energy dissipation has been calculated under three different tunneling energy level at temperature T=2 K. For estimating the energy dissipation of proposed gates; QCAPro tool has been employed.
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.
Turbulent collision statistics of cloud droplets at low dissipation rates
NASA Astrophysics Data System (ADS)
Banerjee, Sandipan
Collisions of sedimenting droplets in a turbulent flow is of great importance in cloud physics. Collision efficiency and collision enhancement over gravitational collision by air turbulence govern the growth of the cloud droplets leading to warm rain initiation and precipitation dynamics. In this thesis we present direct numerical simulation (DNS) results for collision statistics of droplets in turbulent flows of low dissipation rates (in the range of 3 cm2/s3-100 cm2/s3) relevant to strato-cumulus clouds. First, we revisit the case of gravitational collision in still fluid to validate the details of the collision detection algorithm used in our code. We compare the collision statistics with either new analytical predictions regarding the percentages of different collision types, or results from published papers. The effect of initial conditions on the collision statistics and statistical uncertainties are analyzed both analytically and through the simulation data. Second, we consider the case of weak turbulence (as in strato-cumulus clouds). In this case the particle motion is mainly driven by gravity. The standard deviation (or the uncertainty) of the average collision statistics is examined analytically in terms of time correlation function of the data. We then report new DNS results of collision statistics in a turbulent flow, showing how air turbulence increases the geometric colli- sion statistics and the collision efficiency. We find that the collision-rate enhancement due to turbulence depends nonlinearly on the flow dissipation rate. This result calls for a more careful parameterization of the collision statistics in strato-cumulus clouds. Due to the low flow dissipation rate in stratocumulus clouds, a related challenge is low droplet Stokes number. Here the Stokes number is the ratio of droplet inertial response time to the flow Kolmogorov time. A very low Stokes number implies that the numerical integration time step is now governed by the droplet
Energy dissipation of highly charged ions on Al oxide films.
Lake, R E; Pomeroy, J M; Sosolik, C E
2010-03-03
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.
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
Stable schemes for dissipative particle dynamics with conserved energy
NASA Astrophysics Data System (ADS)
Stoltz, Gabriel
2017-07-01
This article presents a new numerical scheme for the discretization of dissipative particle dynamics with conserved energy. The key idea is to reduce elementary pairwise stochastic dynamics (either fluctuation/dissipation or thermal conduction) to effective single-variable dynamics, and to approximate the solution of these dynamics with one step of a Metropolis-Hastings algorithm. This ensures by construction that no negative internal energies are encountered during the simulation, and hence allows to increase the admissible timesteps to integrate the dynamics, even for systems with small heat capacities. Stability is only limited by the Hamiltonian part of the dynamics, which suggests resorting to multiple timestep strategies where the stochastic part is integrated less frequently than the Hamiltonian one.
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.
Reynolds-stress and dissipation-rate budgets in a turbulent channel flow
NASA Technical Reports Server (NTRS)
Mansour, N. N.; Kim, J.; Moin, P.
1988-01-01
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.
Damping and energy dissipation in soft tissue vibrations during running.
Khassetarash, Arash; Hassannejad, Reza; Enders, Hendrik; Ettefagh, Mir Mohammad
2015-01-21
It has been well accepted that the vibrations of soft tissue cannot be simulated by a single sinusoidal function. In fact, these vibrations are a combination of several vibration modes. In this study, these modes are extracted applying a recently developed method namely, partly ensemble empirical mode decomposition (PEEMD). Then, a methodology for estimating the damping properties and energy dissipation caused by damping for each mode is used. Applying this methodology on simulated signals demonstrates high accuracy. This methodology is applied to the acceleration signals of the gastrocnemius muscle during sprinting and the differences between the damping properties of different vibration modes were identified. The results were 1) the damping property of high-frequency mode was higher than that for low-frequency modes. 2) All identified modes were in under damped condition, therefore, the vibrations had an oscillatory nature. 3) The damping ratios of lower modes are about 100% increased compared to higher modes. 4) The energy dissipation occurred in lower modes were much more than that for higher mode; According to the power spectrum of the ground reaction force (GRF), which is the input force into the body, the recent finding supports the muscle tuning paradigm. It is suggested that the damping properties and energy dissipation can be used to distinguish between different running conditions (surface, fatigue, etc.).
Rapid Quantification of Energy Absorption and Dissipation Metrics for PPE Padding Materials
2010-01-22
Oct 2009 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Rapid Quantification of Energy Absorption & Dissipation Metrics for PPE 55332EGII Padding ...Engineering Seminar Series, Spring 2009 [2] Rapid Quantification of Energy Absorption & Dissipation Metrics for PPE Padding Materials: Final...55332EGII – Part2.pdf, and Part 3, respectively. [1] Rapid Quantification of Energy Absorption & Dissipation Metrics for PPE Padding Materials: Final
Statistics of the dissipated energy in driven diffusive systems.
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.
Mechanism of active transport: free energy dissipation and free energy transduction.
Tanford, C
1982-01-01
The thermodynamic pathway for "chemiosmotic" free energy transduction in active transport is discussed with an ATP-driven Ca2+ pump as an illustrative example. Two innovations are made in the analysis. (i) Free energy dissipated as heat is rigorously excluded from overall free energy bookkeeping by focusing on the dynamic equilibrium state of the chemiosmotic process. (ii) Separate chemical potential terms for free energy donor and transported ions are used to keep track of the thermodynamic state of each substrate through the reaction cycle. These procedures clarify the mechanism of free energy transduction, even without step-by-step analysis. The results show that free energy exchange must occur in its entirety among protein-bound species. Imposition of conditions for an adequate rate of physiological function further indicates (i) that the standard free energy of hydrolysis of protein-bound ATP (to yield protein-bound products) needs to differ substantially from the standard free energy of hydrolysis in solution and (ii) that binding sites for the transported ions must have different affinities when facing opposite sides of the membrane. The results also demonstrate that step-by-step "basic" free energy changes (often used in the form of free energy level diagrams) are inherently unsuited for analysis of the mechanism of free energy transduction. PMID:6216483
Air-bearing spin facility for measuring energy dissipation
NASA Technical Reports Server (NTRS)
Peterson, R. L.
1976-01-01
The air-bearing spin facility was developed to determine experimentally the effect of energy dissipation upon the motion of spinning spacecraft. The facility consists of an air-bearing spin table, a telemetry system, a command system, and a ground control station. The air-bearing spin table was designed to operate in a vacuum chamber. Tests were run on spacecraft components such as fuel tanks, nutation dampers, reaction wheels, and active nutation damper systems. Each of these items affected the attitude of a spinning spacecraft. An experimental approach to determine these effects was required because the dissipation of these components could not be adequately analyzed. The results of these experiments have been used, with excellent results, to predict spacecraft motion.
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
Energy dissipation in inelastic flow of cohesionless granular media
NASA Astrophysics Data System (ADS)
Okada, Naoyuki
In a granular mass which supports the externally applied loads through contact friction, the external work is partly stored and partly dissipated by friction or other mechanisms. In many applications involving relatively small pressures and hard granules, the dissipation by frictional sliding constitutes the major energy absorbing mechanism. Based on micromechanics, it is shown that the external work supplied to a water-saturated sand mass is mainly dissipated through friction between contacting granules. The frictional energy is formulated as a linear function of effective pressure. The model results are compared with the cyclic shearing experiments. A large hollow cylindrical torsional apparatus is used for the experiments, with sand as the test material. This thesis consists of three related parts. First, the results of a study of the cyclic shear deformation behavior under undrained conditions are presented. Experiments are conducted under strain-controlled conditions with various strain amplitudes. The relation between the excess pore water pressure and the corresponding external work in cyclic shearing is studied experimentally. Then, the results of a micromechanical model are compared with the experimental measurements. It is shown that the internal energy dissipation can be expressed as the history of the effective pressure and a single parameter. Second, the cyclic shear deformation behavior under drained conditions is studied. It is shown experimentally that the total volume decreases after each cycle, while the corresponding shear modulus increases. It is found that the energy dissipation coefficient is not constant in drained tests, but that these coefficients for undrained and drained tests approach each other as the number of cycles is increased. Third, the effect of the residual strain on the undrained cyclic shear deformation characteristics is experimentally studied. Experiments are conducted under both stress- and strain-controlled conditions, and
Konow, Nicolai; Roberts, Thomas J
2015-04-07
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.
Developing high energy dissipative soliton fiber lasers at 2 micron
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
Developing high energy dissipative soliton fiber lasers at 2 micron.
Huang, Chongyuan; Wang, Cong; Shang, Wei; Yang, Nan; Tang, Yulong; Xu, Jianqiu
2015-09-08
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.
NASA Astrophysics Data System (ADS)
McCaffrey, K.; Bianco, L.; Wilczak, J. M.; Johnston, P. E.
2015-12-01
When forecasting winds at a wind plant for energy production, the turbulence parameterizations are crucial for understanding wind plant performance. Recent research shows that the turbulence (eddy) dissipation rate in planetary boundary layer (PBL) parameterization schemes introduces significant uncertainty in the Weather Research and Forecasting (WRF) model. Thus, developing the capability to measure dissipation rates in the PBL will allow for identification of weaknesses in, and improvements to the parameterizations. We use data from a 915-MHz wind profiling radar at the Boulder Atmospheric Observatory, collected during the XPIA campaign in spring 2015, to identify the critical parameters for measuring eddy dissipation rates using the spectral width method. Radar set-up parameters (e.g., spectral resolution), post-processing techniques (e.g., filtering for non-atmospheric signals), and spectral averaging, are optimized to capture the most accurate power spectrum for measuring spectral widths for use in the computation of the eddy dissipation rates. These estimates are compared to six heights of turbulence-measuring sonic anemometers from 50 - 300 m on a co-located 300 m tower as verification, showing encouraging results. These methods are then applied to the wind profiling radar data being collected in the Wind Forecasting Improvement Project 2 (WFIP2), a DOE funded campaign that aims to improve the ability to forecast hub-height winds from WRF-based models. This campaign uses of a suite of field observations, including many wind profiling radars, in the Columbia River Gorge, a location with complex terrain where turbulence parameterizations are critical for wind energy prediction.
Energy Dissipation and Transport in Carbon Nanotube Devices
NASA Astrophysics Data System (ADS)
Pop, Eric
2011-03-01
Power consumption is a significant challenge in electronics, often limiting the performance of integrated circuits from mobile devices to massive data centers. Carbon nanotubes have emerged as potentially energy-efficient future devices and interconnects, with both large mobility and thermal conductivity. This talk will focus on understanding and controlling energy dissipation [1-3] and transport [4-6] in carbon nanotubes, with applications to low-energy devices, interconnects, heat sinks, and memory elements. Experiments have been used to gain new insight into the fundamental behavior of such devices, and to better inform practical device models. The results suggest much room for energy optimization in nanoelectronics through the design of geometry, interfaces, and materials..
NASA Astrophysics Data System (ADS)
Taguchi, E.; Stammer, D.; Zahel, W.
2014-07-01
Energy dissipation rates of eight major semidiurnal and diurnal tidal constituents are inferred using a barotropic data assimilative tide model with 7.5' spatial resolution. Dynamical residuals and dynamical residual power, estimated through the assimilation procedure as a correction for model uncertainties, constitute an essential contribution to deep-ocean and shallow-seas dissipation rates. Resulting total dissipation rates amount to 3.54 TW, of which 2.44 TW (69%) are accounted for by the M2 component alone. Concentrating on the deep ocean (> 1000 m water depth), the dissipation by all eight constituents amounts to 1.42 TW, and 0.93 TW just for the M2 component. These results are higher by 19% and 38% than dissipation rates estimated by Egbert and Ray (2003), respectively. Of the globally dissipated 2.44TWM2 energy, 1.24 TW are estimated to arise from bottom drag and eddy turbulence, 1.20 TW from residual power. For just the deep ocean, respective numbers amount to 0.10 TW for bottom drag and eddy turbulence, 1.07 TW for barotropic-to-baroclinic energy conversion due to the internal wave drag. Interpreting negative residual power -0.24 TW as a potential tidal energy source, a net surface-to-internal tide M2 energy conversion would amount to 0.83 TW.
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.
Computational model for noncontact atomic force microscopy: energy dissipation of cantilever.
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.
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.
Assessment of fine-scale parameterizations of turbulent dissipation rates in the Southern Ocean
NASA Astrophysics Data System (ADS)
Takahashi, A.; Hibiya, T.
2016-12-01
To sustain the global overturning circulation, more mixing is required in the ocean than has been observed. The most likely candidates for this missing mixing are breaking of wind-induced near-inertial waves and bottom-generated internal lee waves in the sparsely observed Southern Ocean. Nevertheless, there is a paucity of direct microstructure measurements in the Southern Ocean where energy dissipation rates have been estimated mostly using fine-scale parameterizations. In this study, we assess the validity of the existing fine-scale parameterizations in the Antarctic Circumpolar Current (ACC) region using the data obtained from simultaneous full-depth measurements of micro-scale turbulence and fine-scale shear/strain carried out south of Australia during January 17 to February 2, 2016. Although the fine-scale shear/strain ratio (Rω) is close to the Garrett-Munk (GM) value at the station north of Subtropical Front, the values of Rω at the stations south of Subantarctic Front well exceed the GM value, suggesting that the local internal wave spectra are significantly biased to lower frequencies. We find that not all of the observed energy dissipation rates at these locations are well predicted using Gregg-Henyey-Polzin (GHP; Gregg et al., 2003) and Ijichi-Hibiya (IH; Ijichi and Hibiya, 2015) parameterizations, both of which take into account the spectral distortion in terms of Rω; energy dissipation rates at some locations are obviously overestimated by GHP and IH, although only the strain-based Wijesekera (Wijesekera et al., 1993) parameterization yields fairly good predictions. One possible explanation for this result is that a significant portion of the observed shear variance at these locations might be attributed to kinetic-energy-dominant small-scale eddies associated with the ACC, so that fine-scale strain rather than Rω becomes a more appropriate parameter to characterize the actual internal wave field.
Entropy production and energy dissipation in symmetric redox supercapacitors
NASA Astrophysics Data System (ADS)
Palma-Aramburu, N.; Santamaría-Holek, I.
2017-08-01
In this work we propose a theoretical model that accounts for the main features of the loading-unloading process of a symmetric redox MnO2-based supercapacitor dominated by fast electrochemical reactions at the electrodes. The model is formulated on the basis of nonequilibrium thermodynamics from which we are able to deduce generalized expressions for the electrochemical affinity, the load-voltage and the current-voltage equations that constitute generalizations of the current-overpotential and Butler-Volmer equations, and that are used to describe experimental voltagram data with good agreement. These equations allowed us to derive the behavior of the energy dissipated per cycle showing that it has a nonmonotonic behavior and that in the operation regime it follows a power-law behavior as a function of the frequency. The existence of a maximum for the energy dissipated as a function of the frequency suggests the that the corresponding optimal operation frequency should be similar in value to ωmax.
Dynamically controlled energy dissipation for fast magnetic vortex switching
NASA Astrophysics Data System (ADS)
Badea, R.; Berezovsky, J.
2017-09-01
Manipulation of vortex states in magnetic media provides new routes towards information storage and processing technology. The typical slow relaxation times (˜100 ns) of magnetic vortex dynamics may present an obstacle to the realization of these applications. Here, we investigate how a vortex state in a ferromagnetic microdisk can be manipulated in a way that translates the vortex core while enhancing energy dissipation to rapidly damp the vortex dynamics. We use time-resolved differential magneto-optical Kerr effect microscopy to measure the motion of the vortex core in response to applied magnetic fields. We first map out how the vortex core becomes sequentially trapped by pinning sites as it translates across the disk. After applying a fast magnetic field step to translate the vortex from one pinning site to another, we observe long-lived dynamics of the vortex as it settles to the new equilibrium. We then demonstrate how the addition of a short (<10 ns) magnetic field pulse can induce additional energy dissipation, strongly damping the long-lived dynamics. A model of the vortex dynamics using the Thiele equation of motion explains the mechanism behind this effect.
Adams, W W; Demmig-Adams, B; Rosenstiel, T N; Ebbert, V
2001-01-01
Two very distinctive responses of photosynthesis to winter conditions have been identified. Mesophytic species that continue to exhibit growth during the winter typically exhibit higher maximal rates of photosynthesis during the winter or when grown at lower temperatures compared to individuals examined during the summer or when grown at warmer temperatures. In contrast, sclerophytic evergreen species growing in sun-exposed sites typically exhibit lower maximal rates of photosynthesis in the winter compared to the summer. On the other hand, shaded individuals of those same sclerophytic evergreen species exhibit similar or higher maximal rates of photosynthesis in the winter compared to the summer. Employment of the xanthophyll cycle in photoprotective energy dissipation exhibits similar characteristics in the two groups of plants (mesophytes and shade leaves of sclerophytic evergreens) that exhibit upregulation of photosynthesis during the winter. In both, zeaxanthin + antheraxanthin (Z + A) are retained and PS II remains primed for energy dissipation only on nights with subfreezing temperatures, and this becomes rapidly reversed upon exposure to increased temperatures. In contrast, Z + A are retained and PS II remains primed for energy dissipation over prolonged periods during the winter in sun leaves of sclerophytic evergreen species, and requires days of warming to become fully reversed. The rapid disengagement of this energy dissipation process in the mesophytes and shade sclerophytes apparently permits a rapid return to efficient photosynthesis and increased activity on warmer days during the winter. This may be associated with a decreasing opportunity for photosynthesis in source leaves relative to the demand for photosynthesis in the plant's sinks. In contrast, the sun-exposed sclerophytes - with a relatively high source to sink ratio - maintain PS II in a state primed for high levels of energy dissipation activity throughout much of the winter. Independent
Energy transfer and dissipation in forced isotropic turbulence
NASA Astrophysics Data System (ADS)
Linkmann, Moritz; McComb, W. David; Berera, Arjun; Yoffe, Samuel
2014-11-01
A model for the Reynolds number dependence of the dimensionless dissipation rate Cɛ is derived from the dimensionless Kármán-Howarth equation, resulting in Cɛ =Cɛ , ∞ + C /RL , 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. The model equation is fitted to data from direct numerical simulations (DNS) of forced isotropic turbulence for integral scale Reynolds numbers up to RL = 5875 (Rλ = 435), which results in an asymptote for Cɛ in the infinite Reynolds number limit Cɛ , ∞ = 0 . 47 +/- 0 . 01 . Since the coefficients in the model equation are scale-dependent while the dimensionless dissipation rate is not, we modelled the scale dependences of the coefficients by an ad hoc profile function such that they cancel out, leaving the model equation scale-independent, as it must be. The profile function was compared to DNS data to very good agreement, provided we restrict the comparison to scales small enough to be well resolved in our simulations. This work has made use of the resources provided by the UK supercomputing service HECToR, made available through the Edinburgh Compute and Data Facility (ECDF). A.B. is supported by STFC, S.R.Y. and M.F.L. are funded by EPSRC.
Energy shaping and dissipation: Underwater vehicle stabilization using internal rotors
NASA Astrophysics Data System (ADS)
Woolsey, Craig Arthur
This dissertation concerns nonlinear feedback stabilization of mechanical systems using energy-based methods. Nonlinear techniques are appealing because they can yield large regions of attraction for feedback-stabilized equilibria. Energy-based methods are particularly attractive for mechanical systems because these methods preserve a physical view of a system's dynamics and because they yield Lyapunov functions. For conservative systems, proof of stability typically requires the existence of a Lyapunov function. For systems with damping, Lyapunov functions can be used to design feedback dissipation to ensure or enhance asymptotic stability and to obtain more global conclusions. Both as a case study of a particular control methodology and as a practical contribution in the area of underwater vehicle control, we consider stabilization of an underwater vehicle using internal rotors as actuators. The methodology used to develop stabilizing control laws consists of three steps. The first step involves shaping the kinetic energy of the conservative dynamics. For the underwater vehicle, the control term in this step may be interpreted as modifying the system inertia. In the second step, feedback dissipation is designed based on a Lyapunov function developed in the first step. In the third step, it is verified that the effect of external damping due to viscous forces does not destroy the stability results. This method is applied first to a vehicle whose centers of gravity and buoyancy coincide and then to a vehicle with noncoincident centers of gravity and buoyancy. The method of controlled Lagrangians, developed in recent years, is a generalization of the idea of kinetic energy shaping. The method applies to underactuated mechanical systems (systems with more degrees of freedom than independent actuators). Motivated by the results of the investigation into the effect of external damping on an underwater vehicle with internal rotors, we study the effect of damping on more
Energy Dissipation in Calico Hills Tuff due to Pore Collapse
NASA Astrophysics Data System (ADS)
Lockner, D. A.; Morrow, C. A.
2008-12-01
Laboratory tests indicate that the weakest portions of the Calico Hills tuff formation are at or near yield stress under in situ conditions and that the energy expended during incremental loading can be more than 90 percent irrecoverable. The Calico Hills tuff underlies the Yucca Mountain waste repository site at a depth of 400 to 500 m within the unsaturated zone. The formation is highly variable in the degree of both vitrification and zeolitization. Since 1980, a number of boreholes penetrated this formation to provide site characterization for the YM repository. In the past, standard strength measurements were conducted on core samples from the drillholes. However, a significant sampling bias occurred in that tests were preferentially conducted on highly vitrified, higher-strength samples. In fact, the most recent holes were drilled with a dry coring technique that would pulverize the weakest layers, leaving none of this material for testing. We have re-examined Calico Hills samples preserved at the YM Core Facility and selected the least vitrified examples (some cores exceeded 50 percent porosity) for mechanical testing. Three basic tests were performed: (i) hydrostatic crushing tests (to 350 MPa), (ii) standard triaxial deformation tests at constant effective confining pressure (to 70 MPa), and (iii) plane strain tests with initial conditions similar to in situ stresses. In all cases, constant pore pressure of 10 MPa was maintained using argon gas as a pore fluid and pore volume loss was monitored during deformation. The strongest samples typically failed along discrete fractures in agreement with standard Mohr-Coulomb failure. The weaker, high porosity samples, however, would fail by pure pore collapse or by a combined shear-induced compaction mechanism similar to failure mechanisms described for porous sandstones and carbonates. In the plane-strain experiments, energy dissipation due to pore collapse was determined for eventual input into dynamic wave
A modal approach to modeling spatially distributed vibration energy dissipation.
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.
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.
2015-05-11
PREVIOUS VERSIONS I Turbulent kinetic energy and temperature variance dissipation in laboratory generated Rayleigh-Bénard turbulence designed to... energy and temperature variance dissipation rates in the tank, for different convective strengths. Optical image degradation in the tank is then...dynamics simulations of convective turbulence emulating the tank environment. These numerical simulations supplement the sparse laboratory measurements
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.
Polarization swings reveal magnetic energy dissipation in blazars
Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; Guo, Fan; Li, Hui
2015-05-01
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.
Friction-based energy dissipation unit for circuit breaker
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.
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.
Plastic deformation enabled energy dissipation in a bionanowire structured armor.
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.
POLARIZATION SWINGS REVEAL MAGNETIC ENERGY DISSIPATION IN BLAZARS
Zhang, Haocheng; Böttcher, Markus; Chen, Xuhui; Guo, Fan; Li, Hui
2015-05-01
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 sometimes 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.
Polarization Swings Reveal Magnetic Energy Dissipation in Blazars
NASA Astrophysics Data System (ADS)
Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; Guo, Fan; Li, Hui
2015-05-01
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 sometimes 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.
Polarization swings reveal magnetic energy dissipation in blazars
Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; ...
2015-05-01
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
Dissipation of 'dark energy' by cortex in knowledge retrieval.
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. Copyright © 2013 Elsevier B.V. All rights reserved.
Energy flux measurement from the dissipated energy in capillary wave turbulence.
Deike, Luc; Berhanu, Michael; Falcon, Eric
2014-02-01
We study experimentally the influence of dissipation on stationary capillary wave turbulence on the surface of a liquid by changing its viscosity. We observe that the frequency power-law scaling of the capillary spectrum departs significantly from its theoretical value when the dissipation is increased. The energy dissipated by capillary waves is also measured and found to increase nonlinearly with the mean power injected within the liquid. Here we propose an experimental estimation of the energy flux at every scale of the capillary cascade. The latter is found to be nonconstant through the scales. For fluids of low enough viscosity, we found that both capillary spectrum scalings with the frequency and the newly defined mean energy flux are in good agreement with wave turbulence theory. The Kolmogorov-Zakharov constant is then experimentally estimated and compared to its theoretical value.
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.
Log-stable law of energy dissipation as a framework of turbulence intermittency.
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.
Symmetry Energy Effects on Low Energy Dissipative Heavy Ion Collisions
NASA Astrophysics Data System (ADS)
Rizzo, C.; Baran, V.; Colonna, M.; Di Toro, M.; Odsuren, M.
2011-02-01
We investigate the reaction path followed by Heavy Ion Collisions with exotic nuclear beams at low energies. We focus on the interplay between reaction mechanisms, fusion vs. break-up (fast-fission, deep-inelastic), that in exotic systems is expected to be influenced by the symmetry energy term at densities around the normal value. The method described here, based on the event by event evolution of phase space quadrupole collective modes, will nicely allow to extract the fusion probability at relatively early times, when the transport results are reliable. Fusion probabilities for reactions induced by 132Sn on 64,58Ni targets at 10 AMeV are evaluated. We obtain larger fusion cross sections for the more n-rich composite system, and, for a given reaction, with a soft symmetry term above saturation. A collective charge equilibration mechanism (the Dynamical Dipole Resonance, DDR) is revealed in both fusion and break-up events, depending on the stiffness of the symmetry term just below saturation. Finally we investigate the effect of the mass asymmetry in the entrance channel for systems with the same overall isospin content and similar initial charge asymmetry. As expected we find reduced fusion probabilities for the more mass symmetric case, while the DDR strength appears not much affected. This is a nice confirmation of the prompt nature of such collective isovector mode.
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
NASA Astrophysics Data System (ADS)
Caswell, T. E.; Cooper, R. F.; Goldsby, D. L.
2015-12-01
Many outer planet satellites possess thick, icy crusts over an ocean of liquid water. Maintaining an ocean over geologic time requires internal heating by tidal dissipation, but the mechanisms of tidal dissipation in ice are poorly resolved. The physics of dissipation in the geological context (the "high temperature background") are dominated by stress-induced chemical diffusion, which has a distinct length-scale dependence that is frequently cited as the grain size. The experiments of McCarthy [2009], however, measured attenuation simultaneously with steady-state creep in polycrystalline ice and showed distinctly grain size-insensitive dissipation. These data can instead be normalized by the steady-state creep stress, implying that the deformation-induced microstructure dominates the length scale of diffusion. Thus, the relationship between deformation-induced microstructure and dissipation is critical to understanding how tidal dissipation affects (or, perhaps, effects) the geodynamics of icy satellites. To characterize the role of deformation microstructure in strain-energy dissipation, we conducted creep and stress-reduction experiments on polycrystalline ice. The stress (0.5-5 MPa), grain size (30 & 245 μm) and temperature (233K) of the experiments place our specimens in the rheological regimes of grain boundary sliding (geometrically accommodated by basal glide) or dislocation creep, both of which accrue significant plastic strain by the motion of lattice dislocations. Stress-reductions allow a specific deformation-induced microstructure—that produced in steady-state creep—to be probed for its effective viscosity (or "hardness") at a variety of stresses. This "constant-hardness creep compliance" is affected by deviatoric stress, but not by grain size, confirming a characteristic length scale for relaxation that is dictated by deformation. The microstructures of deformed samples, analyzed via cryogenic electron backscatter diffraction (EBSD) and reflected
Mesoscale simulations of shockwave energy dissipation via chemical reactions
NASA Astrophysics Data System (ADS)
Antillon, Edwin; Strachan, Alejandro
2015-06-01
We use a particle-based mesoscale model that incorporates chemical reactions at a coarse-grained level to study the response of materials under shockwave-loading conditions. An additional implicit variable (the particle size) is used to describe volume-reducing chemical reactions using an intra-molecular potential inspired by Transition State Theory, while the dynamics of the center-of-mass motion evolves according to inter-particle forces. The equations of motion are derived from a Hamiltonian and the model captures both: total energy conservation and Galilean invariance. We demonstrate that this model captures complex thermo-mechanical-chemical processes, and we use these features to explore materials with the capabilities to dissipate shocks-wave energy due to ballistic impacts. Our results characterize how the parameters of the chemical model affect shock-wave attenuation, and we elucidate on how the coupling between the different energy-transferring mechanisms influences nucleation of chemistry for conditions away from equilibrium.
G: Fracture energy, friction and dissipation in earthquakes.
Nielsen, S; Spagnuolo, E; Violay, M; Smith, S; Di Toro, G; Bistacchi, A
2016-01-01
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 Gf : the post-failure integral of the dynamic weakening curve. If the dominant dissipative process in earthquakes is friction, G(') and Gf 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/s(2)). The resulting fracture energy Gf is similar to the seismological estimates, with Gf and G(') being comparable over most of the slip range. However, Gf appears to saturate after several meters of slip, while in most of the reported earthquake sequences, G(') appears to increase further and surpasses Gf at large magnitudes. We analyze several possible causes of such discrepancy, in particular, additional off-fault damage in large natural earthquakes.
Spectral Energy Transfer and Dissipation of Magnetic Energy from Fluid to Kinetic Scales
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.
Fermi Gamma-Ray Pulsars: Understanding the High-energy Emission from Dissipative Magnetospheres
NASA Astrophysics Data System (ADS)
Kalapotharakos, Constantinos; Harding, Alice K.; Kazanas, Demosthenes; Brambilla, Gabriele
2017-06-01
Based on the Fermi observational data, we reveal meaningful constraints for the dependence of the macroscopic conductivity (σ) of dissipative pulsar magnetosphere models on the corresponding spin-down rate, \\dot{{ E }}. Our models are refinements of the FIDO (Force-free Inside, Dissipative Outside) models, which have dissipative regions that are restricted on the equatorial current sheet outside of the the light-cylinder. Taking into account the observed cutoff energies of all of the Fermi pulsars and assuming that (a) the corresponding γ-ray pulsed emission is due to curvature radiation at the radiation-reaction-limit regime, and (b) this emission is produced at the equatorial current sheet near the light cylinder, we show that the Fermi data provide clear indications about the corresponding accelerating electric-field components. A direct comparison between the Fermi cutoff energies and the model ones reveals that σ increases with \\dot{{ E }} for high \\dot{{ E }}-values, while it saturates for low ones. This comparison indicates also that the corresponding gap width increases toward low \\dot{{ E }}-values. Assuming the Goldreich-Julian flux for the emitting particles, we calculate the total γ-ray luminosity (L γ ). A comparison between the dependence of the Fermi L γ -values and the model ones on \\dot{{ E }} indicates an increase of the emitting particle multiplicity with \\dot{{ E }}. Our modeling, guided by the Fermi data alone, enhances our understanding of the physical mechanisms behind the high-energy emission in pulsar magnetospheres.
Gaugler, Mario; Wirz, Dieter; Ronken, Sarah; Hafner, Mirjam; Göpfert, Beat; Friederich, Niklaus F; Elke, Reinhard
2015-04-01
To test meniscal mechanical properties such as the dynamic modulus of elasticity E* and the loss angle δ at two loading frequencies ω at different locations of the menisci and compare it to E* and δ of hyaline cartilage in indentation mode with spherical indenters. On nine pairs of human menisci, the dynamic E*-modulus and loss angle δ (as a measure of the energy dissipation) were determined. The measurements were performed at two different strain rates (slow sinusoidal and fast single impact) to show the strain rate dependence of the material. The measurements were compared to previous similar measurements with the same equipment on human hyaline cartilage. The resultant E* at fast indentation (median 1.16 MPa) was significantly higher, and the loss angle was significantly lower (median 10.2°) compared to slow-loading mode's E* and δ (median 0.18 MPa and 16.9°, respectively). Further, significant differences for different locations are shown. On the medial meniscus, the anterior horn shows the highest resultant dynamic modulus. In dynamic measurements with a spherical indenter, the menisci are much softer and less energy-dissipating than hyaline cartilage. Further, the menisci are stiffer and less energy-dissipating in the middle, intermediate part compared to the meniscal base. In compression, the energy dissipation of meniscus cartilage plays a minor role compared to hyaline cartilage. At high impacts, energy dissipation is less than on low impacts, similar to cartilage.
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
Energy dissipation in driven granular matter in the absence of gravity.
Sack, Achim; Heckel, Michael; Kollmer, Jonathan E; Zimber, Fabian; Pöschel, Thorsten
2013-07-05
We experimentally investigate the energy dissipation rate in sinusoidally driven boxes which are partly filled by granular material under conditions of weightlessness. We identify two different modes of granular dynamics, depending on the amplitude of driving, A. For intense forcing, A>A(0), the material is found in the collect-and-collide regime where the center of mass of the granulate moves synchronously with the driven container, while for weak forcing, Adissipation mechanisms, leading to different scaling with amplitude and frequency of the excitation and with the mass of the granulate. For the collect-and-collide regime, we explain the dependence on frequency and amplitude of the excitation by means of an effective one-particle model. For both regimes, the results may be collapsed to a single curve characterizing the physics of granular dampers.
Valencak, T G; Hackländer, K; Ruf, T
2010-08-15
It has been suggested that maximum sustained metabolic rate (SusMR) in mammals as reached, for instance, during lactation, is due to a limited capacity for heat dissipation. Here, we experimentally tested whether heat dissipation limitation (HDL) also constrains energy turnover in lactating European hares. Experimentally, we made use of the fact that hares nurse their young only once per day, which allowed us to keep females and young either at the same or at different ambient temperatures. During the last lactation week (week 4) females kept at thermoneutrality (22 degrees C), irrespective of the cold load of their young, had significantly lower rates of metabolisable energy intake (MEI) than cold-exposed mothers (5 degrees C), as predicted by the HDL hypothesis. However, in week 2 of lactation females at thermoneutrality rearing cold-exposed young were able to increase MEI to levels indistinguishable from those of cold-exposed females. Thus, even at thermoneutral temperature females reached maximum rates of energy turnover, which was inconsistent with the HDL hypothesis. We conclude that SusMR in lactating European hares typically results not from physiological constraints but from an active restriction of their energy turnover in order to maximise lifetime reproductive success.
NASA Astrophysics Data System (ADS)
Linkmann, Moritz; Berera, Arjun; Goldstraw, Erin E.
2017-01-01
This paper examines the behavior of the dimensionless dissipation rate Cɛ for stationary and nonstationary magnetohydrodynamic (MHD) turbulence in the presence of external forces. By combining with previous studies for freely decaying MHD turbulence, we obtain here both the most general model equation for Cɛ applicable to homogeneous MHD turbulence and a comprehensive numerical study of the Reynolds number dependence of the dimensionless total energy dissipation rate at unity magnetic Prandtl number. We carry out a series of medium to high resolution direct numerical simulations of mechanically forced stationary MHD turbulence in order to verify the predictions of the model equation for the stationary case. Furthermore, questions of nonuniversality are discussed in terms of the effect of external forces as well as the level of cross- and magnetic helicity. The measured values of the asymptote Cɛ ,∞ lie between 0.193 ≤Cɛ ,∞≤0.268 for free decay, where the value depends on the initial level of cross- and magnetic helicities. In the stationary case we measure Cɛ ,∞=0.223 .
Linkmann, Moritz; Berera, Arjun; Goldstraw, Erin E
2017-01-01
This paper examines the behavior of the dimensionless dissipation rate C_{ɛ} for stationary and nonstationary magnetohydrodynamic (MHD) turbulence in the presence of external forces. By combining with previous studies for freely decaying MHD turbulence, we obtain here both the most general model equation for C_{ɛ} applicable to homogeneous MHD turbulence and a comprehensive numerical study of the Reynolds number dependence of the dimensionless total energy dissipation rate at unity magnetic Prandtl number. We carry out a series of medium to high resolution direct numerical simulations of mechanically forced stationary MHD turbulence in order to verify the predictions of the model equation for the stationary case. Furthermore, questions of nonuniversality are discussed in terms of the effect of external forces as well as the level of cross- and magnetic helicity. The measured values of the asymptote C_{ɛ,∞} lie between 0.193≤C_{ɛ,∞}≤0.268 for free decay, where the value depends on the initial level of cross- and magnetic helicities. In the stationary case we measure C_{ɛ,∞}=0.223.
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.
Does the Rate of Collisionless 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 them acroscopic 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.
Structural Health Monitoring of a Bridge with Energy Dissipators
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.
Energy dissipation in fragmented geomaterials associated with impacting oscillators
NASA Astrophysics Data System (ADS)
Khudyakov, Maxim; Pasternak, Elena; Dyskin, Arcady
2016-04-01
In wave propagation through fragmented geomaterials forced by periodic loadings, the elements (fragments) strike against each other when passing through the neutral position (position with zero mutual rotation), quickly damping the oscillations. Essentially the impacts act as shock absorbers albeit localised at the neutral points. In order to analyse the vibrations of and wave propagation in such structures, a differential equation of a forced harmonic oscillator was investigated, where the each time the system passes through the neutral point the velocity gets reduced by multiplying it with the restitution coefficient which characterise the impact of the fragments. In forced vibrations the impact times depend on both the forced oscillations and the restitution coefficient and form an irregular sequence. Numerical solution of the differential equation was performed using Mathematica software. Along with vibration diagrams, the dependence of the energy dissipation on the ratio of the forcing frequency to the natural frequency was obtained. For small positive values of the restitution coefficient (less than 0.5), the asymmetric oscillations were found, and the phase of the forced vibrations determined the direction of the asymmetry. Also, at some values of the forcing frequencies and the restitution coefficient chaotic behaviour was found.
Energy dissipation and radical scavenging by the plant phenylpropanoid pathway.
Grace, S C; Logan, B A
2000-01-01
Environmental stresses such as high light, low temperatures, pathogen infection and nutrient deficiency can lead to increased production of free radicals and other oxidative species in plants. A growing body of evidence suggests that plants respond to these biotic and abiotic stress factors by increasing their capacity to scavenge reactive oxygen species. Efforts to understand this acclimatory process have focused on the components of the 'classical' antioxidant system, i.e. superoxide dismutase, ascorbate peroxidase, catalase, monodehydroascorbate reductase, glutathione reductase and the low molecular weight antioxidants ascorbate and glutathione. However, relatively few studies have explored the role of secondary metabolic pathways in plant response to oxidative stress. A case in point is the phenylpropanoid pathway which is responsible for the synthesis of a diverse array of phenolic metabolites such as flavonoids, tannins, hydroxycinnamate esters and the structural polymer lignin. These compounds are often induced by stress and serve specific roles in plant protection, i.e. pathogen defence, ultraviolet screening, antiherbivory, or structural components of the cell wall. This review will highlight a novel antioxidant function for the taxonomically widespread phenylpropanoid metabolite chlorogenic acid (CGA; 5-O-caffeoylquinic acid) and assess its possible role in abiotic stress tolerance. The relationship between CGA biosynthesis and photosynthetic carbon metabolism will also be discussed. Based on the properties of this model phenolic metabolite, we propose that under stress conditions phenylpropanoid biosynthesis may represent an alternative pathway for photochemical energy dissipation that has the added benefit of enhancing the antioxidant capacity of the cell. PMID:11128003
Structural Health Monitoring of a Bridge with Energy Dissipators
NASA Astrophysics Data System (ADS)
Amaddeo, Carmen; Benzoni, Gianmario; D'Amore, Enzo
2008-07-01
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.
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.
NASA Astrophysics Data System (ADS)
Zhang, Junshi; Chen, Hualing; Li, Dichen
2017-09-01
Subject to a high voltage, leakage current and induced electrical energy dissipation inevitably occur during the actuation of dielectric elastomers (DEs). In this article, a theoretical model is developed to investigate the dissipative performance of DEs in dynamic actuation. Effects of three different actuation conditions, including DE materials’ viscoelasticity intensity, amplitude of applied voltage, and mechanical tensile force, are considered. Numerical calculations are employed to detect the dynamic dissipative performance of DEs including leakage current, electrical power density, and electrical energy density in certain vibrational periods. Leakage current and induced electrical energy dissipation are enhanced with the enlargement of amplitude of applied voltage and mechanical force, and are suppressed as the intensity of DEs’ viscoelastic creep increases. The electrical energy for dissipation and actuation is also analyzed and compared.
Decay of energy and suppression of Fermi acceleration in a dissipative driven stadium-like billiard.
Livorati, André L P; Caldas, Iberê L; Leonel, Edson D
2012-06-01
The behavior of the average energy for an ensemble of non-interacting particles is studied using scaling arguments in a dissipative time-dependent stadium-like billiard. The dynamics of the system is described by a four dimensional nonlinear mapping. The dissipation is introduced via inelastic collisions between the particles and the moving boundary. For different combinations of initial velocities and damping coefficients, the long time dynamics of the particles leads them to reach different states of final energy and to visit different attractors, which change as the dissipation is varied. The decay of the average energy of the particles, which is observed for a large range of restitution coefficients and different initial velocities, is described using scaling arguments. Since this system exhibits unlimited energy growth in the absence of dissipation, our results for the dissipative case give support to the principle that Fermi acceleration seems not to be a robust phenomenon.
NASA Astrophysics Data System (ADS)
Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha
2012-07-01
Switching the magnetization of a shape-anisotropic 2-phase multiferroic nanomagnet with voltage-generated stress is known to dissipate very little energy (<1 aJ for a switching time of ˜0.5 ns) at 0 K temperature. Here, we show by solving the stochastic Landau-Lifshitz-Gilbert equation that switching can be carried out with ˜100% probability in less than 1 ns while dissipating less than 1.5 aJ at room temperature. This makes nanomagnetic logic and memory systems, predicated on stress-induced magnetic reversal, one of the most energy-efficient computing hardware extant. We also study the dependence of energy dissipation, switching delay, and the critical stress needed to switch, on the rate at which stress on the nanomagnet is ramped up or down.
Dissipation of Mesoscale Energy by Vortex-Topography Interaction
NASA Astrophysics Data System (ADS)
Bishnu, S.; Dewar, W. K.
2016-12-01
Energy is introduced into the oceans primarily at large scales by means of wind, tides and surface buoyancy forcing. This energy is transferred to the smaller mesoscale field through the geostrophic instability processes. The mesoscale field appears not to have accelerated appreciably over the last several decades, so we can assume that the mesoscale loses energy at roughly the same rate it receives energy. Interestingly, how the mesoscale loses energy is not quite clear. We have been exploring topographic interaction as a pathway by which the mesoscale may lose energy to unbalanced forward cascading flows. To demonstrate this phenomenon, an approximate model theory is developed which consists of solving a reduced set of the momentum equations in density coordinates for any topographic configuration. The equations are solved using a high order spectral element technique and the results verified with MITgcm simulations.
NASA Astrophysics Data System (ADS)
Hackerott, João A.; Bakhoday Paskyabi, Mostafa; Reuder, Joachim; de Oliveira, Amauri P.; Kral, Stephan T.; Marques Filho, Edson P.; Mesquita, Michel dos Santos; de Camargo, Ricardo
2017-06-01
We discuss scalar similarities and dissimilarities based on analysis of the dissipation terms in the variance budget equations, considering the turbulent kinetic energy and the variances of temperature, specific humidity and specific CO_2 content. For this purpose, 124 high-frequency sampled segments are selected from the Boundary Layer Late Afternoon and Sunset Turbulence experiment. The consequences of dissipation similarity in the variance transport are also discussed and quantified. The results show that, for the convective atmospheric surface layer, the non-dimensional dissipation terms can be expressed in the framework of Monin-Obukhov similarity theory and are independent of whether the variable is temperature or moisture. The scalar similarity in the dissipation term implies that the characteristic scales of the atmospheric surface layer can be estimated from the respective rate of variance dissipation, the characteristic scale of temperature, and the dissipation rate of temperature variance.
NASA Astrophysics Data System (ADS)
Meakin, P.; Basagaoglu, H.; Succi, S.; Welhan, J.
2005-12-01
The onset of nonlinear flow in three-dimensional random disordered porous flow domains was analyzed using participation numbers based on local kinetic energies, and energy dissipation rates computed via non-equilibrium kinetic tensors. A three-dimensional lattice Boltzmann model was used to simulate gravity-driven single-phase flow over a range of Reynolds numbers that included the crossover from linear to nonlinear flow. The simulations results indicated that the kinetic energy participation number characterized the onset of nonlinear flow in terms of transition to a more dispersed (uniform) distribution of kinetic energy densities as the flow rate increased. However, the energy dissipation participation number characterized the onset of nonlinear flow in terms of a transition to a more locally concentrated distribution of energy dissipation densities at higher flows. The flow regime transition characterized by the energy dissipation participation number occurred over a nearly equal or a narrower range of Reynolds numbers compared to the transition characterized by the kinetic energy participation number. The results also revealed that the boundary conditions (periodic vs. no-slip) parallel to the main flow direction have an insignificant effect on the magnitude of the critical Reynolds number, that characterizes the onset of nonlinear effects, although they did influence the spatial correlations of the pore-scale kinetic energy and the energy dissipation densities in all Cartesian directions. Flow domains with periodic boundaries resulted in less-localized (more dispersed) steady-state flows than domains with no-slip boundaries. These results should be useful for designing future experiment like those of Zeria et al. 2005 (Transport in Porous Media, 60:159-181) that would have significant potential implications in diverse fields.
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
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.
Dissipative quantum dynamics in low-energy collisions of complex nuclei
Diaz-Torres, A.; Hinde, D. J.; Dasgupta, M.; Milburn, G. J.; Tostevin, J. A.
2008-12-15
Model calculations that include the effects of irreversible, environmental couplings on top of a coupled-channels dynamical description of the collision of two complex nuclei are presented. The Liouville-von Neumann equation for the time evolution of the density matrix of a dissipative system is solved numerically providing a consistent transition from coherent to decoherent (and dissipative) dynamics during the collision. Quantum decoherence and dissipation are clearly manifested in the model calculations. Energy dissipation, due to the irreversible decay of giant-dipole vibrational states of the colliding nuclei, is shown to result in a hindrance of quantum tunneling and fusion.
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.
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.
Mechanisms for impulsive energy dissipation and small-scale effects in microgranular media.
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.
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.
Dissipation and Vertical Energy Transport in Radiation-dominated Accretion Disks
NASA Astrophysics Data System (ADS)
Blaes, Omer; Krolik, Julian H.; Hirose, Shigenobu; Shabaltas, Natalia
2011-06-01
Standard models of radiation-supported accretion disks generally assume that diffusive radiation flux is solely responsible for vertical heat transport. This requires that heat must be generated at a critical rate per unit volume if the disk is to be in hydrostatic and thermal equilibrium. This raises the question of how heat is generated and how energy is transported in MHD turbulence. By analysis of a number of radiation/MHD stratified shearing-box simulations, we show that the divergence of the diffusive radiation flux is indeed capped at the critical rate, but deep inside the disk, substantial vertical energy flux is also carried by advection of radiation. Work done by radiation pressure is a significant part of the energy budget, and much of this work is dissipated later through damping by radiative diffusion. We show how this damping can be measured in the simulations and identify its physical origins. Radiative damping accounts for as much as tens of percent of the total dissipation and is the only realistic physical mechanism for dissipation of turbulence that can actually be resolved in numerical simulations of accretion disks. Buoyancy associated with dynamo-driven, highly magnetized, nearly isobaric nonlinear slow magnetosonic fluctuations is responsible for the radiation advection flux and also explains the persistent periodic magnetic upwelling seen at all values of the radiation to gas pressure ratio. The intimate connection between radiation advection and magnetic buoyancy is the first example we know of in astrophysics in which a dynamo has direct impact on the global energetics of a system.
DISSIPATION AND VERTICAL ENERGY TRANSPORT IN RADIATION-DOMINATED ACCRETION DISKS
Blaes, Omer; Shabaltas, Natalia; Krolik, Julian H.; Hirose, Shigenobu
2011-06-01
Standard models of radiation-supported accretion disks generally assume that diffusive radiation flux is solely responsible for vertical heat transport. This requires that heat must be generated at a critical rate per unit volume if the disk is to be in hydrostatic and thermal equilibrium. This raises the question of how heat is generated and how energy is transported in MHD turbulence. By analysis of a number of radiation/MHD stratified shearing-box simulations, we show that the divergence of the diffusive radiation flux is indeed capped at the critical rate, but deep inside the disk, substantial vertical energy flux is also carried by advection of radiation. Work done by radiation pressure is a significant part of the energy budget, and much of this work is dissipated later through damping by radiative diffusion. We show how this damping can be measured in the simulations and identify its physical origins. Radiative damping accounts for as much as tens of percent of the total dissipation and is the only realistic physical mechanism for dissipation of turbulence that can actually be resolved in numerical simulations of accretion disks. Buoyancy associated with dynamo-driven, highly magnetized, nearly isobaric nonlinear slow magnetosonic fluctuations is responsible for the radiation advection flux and also explains the persistent periodic magnetic upwelling seen at all values of the radiation to gas pressure ratio. The intimate connection between radiation advection and magnetic buoyancy is the first example we know of in astrophysics in which a dynamo has direct impact on the global energetics of a system.
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.
Impact of a mean current on internal tide energy dissipation at the critical latitude
NASA Astrophysics Data System (ADS)
Richet, O.; Muller, C. J.; Chomaz, J. M.
2016-02-01
In many regions of the ocean, the abyssal flow is dominated by tidal flow. A large fraction of the tidal energy input in the ocean is dissipated via the generation of internal waves above rough topography. Idealised simulations suggest that internal tide energy is transferred and dissipated at smallerscales by the formation of a resonant triad between near-inertial waves, internal tides and subharmonics waves. Furthermore, the energy dissipation is enhanced at the critical latitude (28.8o), corresponding to the Parametric Subharmonic Instability (PSI). In the ocean, the presence of background flow, for instance due to the passage of a mesoscale eddy, can modify energy transfer mechanisms and the amount of energy dissipation. In this study, we investigate the generation and dissipation of internal tides in the presence of a background flow. We use a high-resolution two-dimensional nonhydrostatic numerical model (the MITgcm), with realistic multiscale topography representing the Brazil basin region. The purpose of this study is to understand the impact of the mean flow on the generation and dissipation of tidal waves. Our particular interest is how the maximum of energy dissipation at the critical latitude is impacted by the mean flow.
Impact of a mean current on internal tide energy dissipation at the critical latitude
NASA Astrophysics Data System (ADS)
Richet, Océane; Chomaz, Jean-Marc; Muller, Caroline
2015-11-01
In many regions of the ocean, the abyssal flow is dominated by tidal flow. A large fraction of the tidal energy input in the ocean is dissipated via the generation of internal waves above rough topography. Idealised simulations suggest that internal tide energy is transferred and dissipated at smallerscales by the formation of a resonant triad between near-inertial waves, internal tides and subharmonics waves. Furthermore, the energy dissipation is enhanced at the critical latitude (28.8°), corresponding to the Parametric Subharmonic Instability (PSI). In the ocean, the presence of background flow, for instance due to the passage of a mesoscale eddy, can modify energy transfer mechanisms and the amount of energy dissipation. In this study, we investigate the generation and dissipation of internal tides in the presence of a background flow. We use a high-resolution two-dimensional nonhydrostatic numerical model (the MITgcm), with realistic multiscale topography representing the Brazil basin region. The purpose of this study is to understand the impact of the mean flow on the generation and dissipation of tidal waves. Our particular interest is how the maximum of energy dissipation at the critical latitude is impacted by the mean flow.
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.
NASA Astrophysics Data System (ADS)
Coughenour, C.
2012-12-01
One of the enduring problems in physical oceanography has been that of tidal dynamics and the effective tidal torque that serves to slow Earth's axial rotation. In the late 20th century, with the aid of satellite altimetry and other technologies, a suite of reliable estimates was finally placed on the magnitude of this torque and other, related parameters in the current epoch. Tidal drag accounts for a 20 microsecond/year increase in mean day length, a 3.5 terawatt dissipation of energy in the oceans (Kantha et al., 1998), and a lunar retreat rate of 3.82 cm/yr (Dickey et al., 1994). Despite these significant advances, however, the problem of tidal dissipation in the geologic past remains largely unresolved. This is due, in part, to difficulties in numerical modeling of past tidal regimes that stem from uncertainties in ocean basin configurations and lunar distances. Tidal deposits can record, to high resolution, the primary astronomical periodicities responsible for the generation of the tidal currents under which transport and deposition occur. With reliable lunar orbital period data obtained from tidal deposits, the past Earth-Moon distance and length of day can be calculated. This task requires careful spectral analysis and consideration of sedimentological factors that may add noise and/or discontinuities to the signal. For deposits representing less than one year of deposition, the necessary assumptions are that Earth's moment of inertia has not changed significantly over the time interval of interest and that the solar component of tidal dissipation can be well-approximated. With consideration of the total angular momentum of the Earth-Moon couplet, we derive a method to calculate lunar distance and length of day. The efficacy of this method and its assumptions is tested via the multi-year sequence of data obtained from the late Precambrian Elatina Formation of Australia and comparing results obtained from the full suite of data by Williams (2000). We go on
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.
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.
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.
Energy input and dissipation in a temperate lake during the spring transition
NASA Astrophysics Data System (ADS)
Woolway, R. Iestyn; Simpson, John H.
2017-08-01
ADCP and temperature chain measurements have been used to estimate the rate of energy input by wind stress to the water surface in the south basin of Windermere. The energy input from the atmosphere was found to increase markedly as the lake stratified in spring. The efficiency of energy transfer ( Eff), defined as the ratio of the rate of working in near-surface waters ( RW) to that above the lake surface ( P 10), increased from ˜0.0013 in vertically homogenous conditions to ˜0.0064 in the first 40 days of the stratified regime. A maximum value of Eff˜0.01 was observed when, with increasing stratification, the first mode internal seiche period decreased to match the diurnal wind period of 24 h. The increase in energy input, following the onset of stratification was reflected in enhancement of the mean depth-varying kinetic energy without a corresponding increase in wind forcing. Parallel estimates of energy dissipation in the bottom boundary layer, based on determination of the structure function show that it accounts for ˜15% of RW in stratified conditions. The evolution of stratification in the lake conforms to a heating stirring model which indicates that mixing accounts for ˜21% of RW. Taken together, these estimates of key energetic parameters point the way to the development of full energy budgets for lakes and shallow seas.
Yahyaoui, W; Harnois, J; Carpentier, R
1998-11-27
When plant leaves or chloroplasts are exposed to illumination that exceeds their photosynthetic capacity, photoprotective mechanisms such as described by the energy-dependent (non-photochemical) quenching of chlorophyll fluorescence are involved. The protective action is attributed to an increased rate constant for thermal dissipation of absorbed quanta. We applied photoacoustic spectroscopy to monitor thermal dissipation in spinach thylakoid membranes together with simultaneous measurement of chlorophyll fluorescence in the presence of inhibitors of opposite action on the formation of delta pH across the thylakoid membrane (tentoxin and nigericin/valinomycin). A linear relationship between the appearance of fluorescence quenching during formation of the delta pH and the reciprocal variation of thermal dissipation was demonstrated. Dicyclohexylcarbodiimide, which is known to prevent protonation of the minor light-harvesting complexes of photosystem II, significantly reduced the formation of fluorescence quenching and the concurrent increase in thermal dissipation. However, the addition of exogenous ascorbate to activate the xanthophyll de-epoxidase increased non-photochemical fluorescence quenching without affecting the measured thermal dissipation. It is concluded that a portion of energy-dependent fluorescence quenching that is independent of de-epoxidase activity can be readily measured by photoacoustic spectroscopy as an increase in thermal deactivation processes.
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
Chloroplast thylakoid structure in evergreen leaves employing strong thermal energy dissipation.
Demmig-Adams, Barbara; Muller, Onno; Stewart, Jared J; Cohu, Christopher M; Adams, William W
2015-11-01
In nature, photosynthetic organisms cope with highly variable light environments--intensities varying over orders of magnitudes as well as rapid fluctuations over seconds-to-minutes--by alternating between (a) highly effective absorption and photochemical conversion of light levels limiting to photosynthesis and (b) powerful photoprotective thermal dissipation of potentially damaging light levels exceeding those that can be utilized in photosynthesis. Adjustments of the photosynthetic apparatus to changes in light environment involve biophysical, biochemical, and structural adjustments. We used electron micrographs to assess overall thylakoid grana structure in evergreen species that exhibit much stronger maximal levels of thermal energy dissipation than the more commonly studied annual species. Our findings indicate an association between partial or complete unstacking of thylakoid grana structure and strong reversible thermal energy dissipation that, in contrast to what has been reported for annual species with much lower maximal levels of energy dissipation, is similar to what is seen under photoinhibitory conditions. For a tropical evergreen with tall grana stacks, a loosening, or vertical unstacking, of grana was seen in sun-grown plants exhibiting pronounced pH-dependent, rapidly reversible thermal energy dissipation as well as for sudden low-to-high-light transfer of shade-grown plants that responded with photoinhibition, characterized by strong dark-sustained, pH-independent thermal energy dissipation and photosystem II (PSII) inactivation. On the other hand, full-sun exposed subalpine confers with rather short grana stacks transitioned from autumn to winter via conversion of most thylakoids from granal to stromal lamellae concomitant with photoinhibitory photosynthetic inactivation and sustained thermal energy dissipation. We propose that these two types of changes (partial or complete unstacking of grana) in thylakoid arrangement are both associated with
Nanotribology of shear and energy dissipation by interstitials in nanotube assemblies
NASA Astrophysics Data System (ADS)
Lin, Yu; Zhao, Yufeng; Couchman, Luise S.; Yakobson, Boris I.
2004-03-01
While normal-force and spacing between graphene layers is well understood, physics and degree of resistance to inter-layer shear remains controversial (e.g., in case of load transfer within multiwall tubes or within the arrays of single-wall tubes). Essentially zero-friction is assumed in context of nano-bearings and oscillators, however the load transfer in MWNT and within the rope-bundles of SWNT is quite measurable and its enhancement remains critically important for structural applications. We investigate theoretically dynamics of lattice-defect or interstitial relaxation in the course of applied shear, identify probable "transition states" and compute the associated energy barriers. We further relate the rate of energy dissipation in a "macroscopic" glide with the molecular dynamics in smaller atomistic scale. Obtained understanding can be useful for advances in composite material design.
NASA Astrophysics Data System (ADS)
Tailleux, Rémi
2013-07-01
Although it plays a key role in the theory of stratified turbulence, the concept of available potential energy (APE) dissipation has remained until now a rather mysterious quantity, owing to the lack of rigorous result about its irreversible character or energy conversion type. Here, we show by using rigorous energetics considerations rooted in the analysis of the Navier-Stokes for a fully compressible fluid with a nonlinear equation of state that the APE dissipation is an irreversible energy conversion that dissipates kinetic energy into internal energy, exactly as viscous dissipation. These results are established by showing that APE dissipation contributes to the irreversible production of entropy, and by showing that it is a part of the work of expansion/contraction. Our results provide a new interpretation of the entropy budget, that leads to a new exact definition of turbulent effective diffusivity, which generalizes the Osborn-Cox model, as well as a rigorous decomposition of the work of expansion/contraction into reversible and irreversible components. In the context of turbulent mixing associated with parallel shear flow instability, our results suggests that there is no irreversible transfer of horizontal momentum into vertical momentum, as seems to be required when compressible effects are neglected, with potential consequences for the parameterizations of momentum dissipation in the coarse-grained Navier-Stokes equations.
Xia, H; Ma, X; Tu, Y
2008-01-01
The dissipation behaviour of endosulfan in dry made-tea leaves of oolong and green tea was compared to establish whether there was any difference in dissipation rates between the two teas. The dissipation of endosulfan in oolong and green tea corresponded with a first-order kinetics curve. The average half-life of endosulfan (n = 12) was 1.60 +/- 0.44 days in green tea and 2.01 +/- 0.55 days in oolong tea, showing a statistically significant difference, and indicating that the dissipation of the pesticide was significantly slower in oolong tea than that in green tea. Although the initial levels of residual endosulfan were lower in oolong tea, due to the slower dissipation rate, the residues 5-7 days after application were higher in oolong than in green tea. It is suggested that the minimum interval between endosulfan application and tea leaf harvesting is 7 days for green tea and 10 days for oolong tea in the case where the maximum residue limit of endosulfan in made-tea is fixed as 10 mg kg(-1).
Ge, Hao; Qian, Hong
2013-06-01
Nonequilibrium thermodynamics of a system situated in a sustained environment with influx and efflux is usually treated as a subsystem in a larger, closed "universe." A question remains with regard to what the minimally required description for the surrounding of such an open driven system is so that its nonequilibrium thermodynamics can be established solely based on the internal stochastic kinetics. We provide a solution to this problem using insights from studies of molecular motors in a chemical nonequilibrium steady state (NESS) with sustained external drive through a regenerating system or in a quasisteady state (QSS) with an excess amount of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and inorganic phosphate (Pi). We introduce the key notion of minimal work that is needed, W(min), for the external regenerating system to sustain a NESS (e.g., maintaining constant concentrations of ATP, ADP and Pi for a molecular motor). Using a Markov (master-equation) description of a motor protein, we illustrate that the NESS and QSS have identical kinetics as well as the second law in terms of the same positive entropy production rate. The heat dissipation of a NESS without mechanical output is exactly the W(min). This provides a justification for introducing an ideal external regenerating system and yields a free-energy balance equation between the net free-energy input F(in) and total dissipation F(dis) in an NESS: F(in) consists of chemical input minus mechanical output; F(dis) consists of dissipative heat, i.e. the amount of useful energy becoming heat, which also equals the NESS entropy production. Furthermore, we show that for nonstationary systems, the F(dis) and F(in) correspond to the entropy production rate and housekeeping heat in stochastic thermodynamics and identify a relative entropy H as a generalized free energy. We reach a new formulation of Markovian nonequilibrium thermodynamics based on only the internal kinetic equation without further
NASA Astrophysics Data System (ADS)
Ge, Hao; Qian, Hong
2013-06-01
Nonequilibrium thermodynamics of a system situated in a sustained environment with influx and efflux is usually treated as a subsystem in a larger, closed “universe.” A question remains with regard to what the minimally required description for the surrounding of such an open driven system is so that its nonequilibrium thermodynamics can be established solely based on the internal stochastic kinetics. We provide a solution to this problem using insights from studies of molecular motors in a chemical nonequilibrium steady state (NESS) with sustained external drive through a regenerating system or in a quasisteady state (QSS) with an excess amount of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and inorganic phosphate (Pi). We introduce the key notion of minimal work that is needed, Wmin, for the external regenerating system to sustain a NESS (e.g., maintaining constant concentrations of ATP, ADP and Pi for a molecular motor). Using a Markov (master-equation) description of a motor protein, we illustrate that the NESS and QSS have identical kinetics as well as the second law in terms of the same positive entropy production rate. The heat dissipation of a NESS without mechanical output is exactly the Wmin. This provides a justification for introducing an ideal external regenerating system and yields a free-energy balance equation between the net free-energy input Fin and total dissipation Fdis in an NESS: Fin consists of chemical input minus mechanical output; Fdis consists of dissipative heat, i.e. the amount of useful energy becoming heat, which also equals the NESS entropy production. Furthermore, we show that for nonstationary systems, the Fdis and Fin correspond to the entropy production rate and housekeeping heat in stochastic thermodynamics and identify a relative entropy H as a generalized free energy. We reach a new formulation of Markovian nonequilibrium thermodynamics based on only the internal kinetic equation without further reference to
Landau-Zener transitions mediated by an environment: population transfer and energy dissipation.
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.
Landau-Zener transitions mediated by an environment: Population transfer and energy dissipation
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.
Estimation of turbulent energy dissipation in the boundary layer using Smoke Image Velocimetry
NASA Astrophysics Data System (ADS)
Mikheev, N. I.; Goltsman, A. E.; Saushin, I. I.; Dushina, O. A.
2017-08-01
Turbulent energy dissipation in the turbulent boundary layer has been estimated experimentally. Dissipation has been derived from dynamics of two-component instantaneous velocity vector fields measured by an optical method. Smoke Image Velocimetry technique based on digital processing of smoke visualization of flow and adapted to relatively large smoke displacement between two consecutive video frames has been employed. The obtained dissipation profiles have been compared with measurements by multi-sensor hot-wire anemometers, stereo PIV, Tomo-3D-PTV with VIC+, and DNS results.
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.
Anomalous dissipation and kinetic-energy distribution in pipes at very high Reynolds numbers
NASA Astrophysics Data System (ADS)
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 104, 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.
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.
Anomalous dissipation and kinetic-energy distribution in pipes at very high Reynolds numbers.
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.
Onset of energy dissipation in ballistic atomic wires.
Agraït, Nicolás; Untiedt, Carlos; Rubio-Bollinger, Gabino; Vieira, Sebastián
2002-05-27
Electronic transport at finite voltages in free-standing gold atomic chains of up to seven atoms in length is studied at low temperatures using a scanning tunneling microscope. The conductance vs voltage curves show that transport in these single-mode ballistic atomic wires is nondissipative up to a finite voltage threshold of the order of several mV. The onset of dissipation and resistance within the wire corresponds to the excitation of the atomic vibrations by the electrons traversing the wire and is very sensitive to strain.
Limiting Energy Dissipation Induces Glassy Kinetics in Single-Cell High-Precision Responses.
Das, Jayajit
2016-03-08
Single cells often generate precise responses by involving dissipative out-of-thermodynamic-equilibrium processes in signaling networks. The available free energy to fuel these processes could become limited depending on the metabolic state of an individual cell. How does limiting dissipation affect the kinetics of high-precision responses in single cells? I address this question in the context of a kinetic proofreading scheme used in a simple model of early-time T cell signaling. Using exact analytical calculations and numerical simulations, I show that limiting dissipation qualitatively changes the kinetics in single cells marked by emergence of slow kinetics, large cell-to-cell variations of copy numbers, temporally correlated stochastic events (dynamic facilitation), and ergodicity breaking. Thus, constraints in energy dissipation, in addition to negatively affecting ligand discrimination in T cells, can create a fundamental difficulty in determining single-cell kinetics from cell-population results. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Limiting Energy Dissipation Induces Glassy Kinetics in Single-Cell High-Precision Responses
Das, Jayajit
2016-01-01
Single cells often generate precise responses by involving dissipative out-of-thermodynamic-equilibrium processes in signaling networks. The available free energy to fuel these processes could become limited depending on the metabolic state of an individual cell. How does limiting dissipation affect the kinetics of high-precision responses in single cells? I address this question in the context of a kinetic proofreading scheme used in a simple model of early-time T cell signaling. Using exact analytical calculations and numerical simulations, I show that limiting dissipation qualitatively changes the kinetics in single cells marked by emergence of slow kinetics, large cell-to-cell variations of copy numbers, temporally correlated stochastic events (dynamic facilitation), and ergodicity breaking. Thus, constraints in energy dissipation, in addition to negatively affecting ligand discrimination in T cells, can create a fundamental difficulty in determining single-cell kinetics from cell-population results. PMID:26958894
Assessment of accuracy of CFD simulations through quantification of a numerical dissipation rate
NASA Astrophysics Data System (ADS)
Domaradzki, J. A.; Sun, G.; Xiang, X.; Chen, K. K.
2016-11-01
The accuracy of CFD simulations is typically assessed through a time consuming process of multiple runs and comparisons with available benchmark data. We propose that the accuracy can be assessed in the course of actual runs using a simpler method based on a numerical dissipation rate which is computed at each time step for arbitrary sub-domains using only information provided by the code in question (Schranner et al., 2015; Castiglioni and Domaradzki, 2015). Here, the method has been applied to analyze numerical simulation results obtained using OpenFOAM software for a flow around a sphere at Reynolds number of 1000. Different mesh resolutions were used in the simulations. For the coarsest mesh the ratio of the numerical dissipation to the viscous dissipation downstream of the sphere varies from 4.5% immediately behind the sphere to 22% further away. For the finest mesh this ratio varies from 0.4% behind the sphere to 6% further away. The large numerical dissipation in the former case is a direct indicator that the simulation results are inaccurate, e.g., the predicted Strouhal number is 16% lower than the benchmark. Low numerical dissipation in the latter case is an indicator of an acceptable accuracy, with the Strouhal number in the simulations matching the benchmark. Supported by NSF.
Borque, Paloma; Luke, Edward; Kollias, Pavlos
2016-05-27
Coincident profiling observations from Doppler lidars and radars are used to estimate the turbulence energy dissipation rate (ε) using three different data sources: (i) Doppler radar velocity (DRV), (ii) Doppler lidar velocity (DLV), and (iii) Doppler radar spectrum width (DRW) measurements. Likewise, the agreement between the derived ε estimates is examined at the cloud base height of stratiform warm clouds. Collocated ε estimates based on power spectra analysis of DRV and DLV measurements show good agreement (correlation coefficient of 0.86 and 0.78 for both cases analyzed here) during both drizzling and nondrizzling conditions. This suggests that unified (below and above cloud base) time-height estimates of ε in cloud-topped boundary layer conditions can be produced. This also suggests that eddy dissipation rate can be estimated throughout the cloud layer without the constraint that clouds need to be nonprecipitating. Eddy dissipation rate estimates based on DRW measurements compare well with the estimates based on Doppler velocity but their performance deteriorates as precipitation size particles are introduced in the radar volume and broaden the DRW values. And, based on this finding, a methodology to estimate the Doppler spectra broadening due to the spread of the drop size distribution is presented. Furthermore, the uncertainties in ε introduced by signal-to-noise conditions, the estimation of the horizontal wind, the selection of the averaging time window, and the presence of precipitation are discussed in detail.
Borque, Paloma; Luke, Edward; Kollias, Pavlos
2016-05-27
Coincident profiling observations from Doppler lidars and radars are used to estimate the turbulence energy dissipation rate (ε) using three different data sources: (i) Doppler radar velocity (DRV), (ii) Doppler lidar velocity (DLV), and (iii) Doppler radar spectrum width (DRW) measurements. Likewise, the agreement between the derived ε estimates is examined at the cloud base height of stratiform warm clouds. Collocated ε estimates based on power spectra analysis of DRV and DLV measurements show good agreement (correlation coefficient of 0.86 and 0.78 for both cases analyzed here) during both drizzling and nondrizzling conditions. This suggests that unified (below and abovemore » cloud base) time-height estimates of ε in cloud-topped boundary layer conditions can be produced. This also suggests that eddy dissipation rate can be estimated throughout the cloud layer without the constraint that clouds need to be nonprecipitating. Eddy dissipation rate estimates based on DRW measurements compare well with the estimates based on Doppler velocity but their performance deteriorates as precipitation size particles are introduced in the radar volume and broaden the DRW values. And, based on this finding, a methodology to estimate the Doppler spectra broadening due to the spread of the drop size distribution is presented. Furthermore, the uncertainties in ε introduced by signal-to-noise conditions, the estimation of the horizontal wind, the selection of the averaging time window, and the presence of precipitation are discussed in detail.« less
Borque, Paloma; Luke, Edward; Kollias, Pavlos
2016-05-27
Coincident profiling observations from Doppler lidars and radars are used to estimate the turbulence energy dissipation rate (ε) using three different data sources: (i) Doppler radar velocity (DRV), (ii) Doppler lidar velocity (DLV), and (iii) Doppler radar spectrum width (DRW) measurements. Likewise, the agreement between the derived ε estimates is examined at the cloud base height of stratiform warm clouds. Collocated ε estimates based on power spectra analysis of DRV and DLV measurements show good agreement (correlation coefficient of 0.86 and 0.78 for both cases analyzed here) during both drizzling and nondrizzling conditions. This suggests that unified (below and above cloud base) time-height estimates of ε in cloud-topped boundary layer conditions can be produced. This also suggests that eddy dissipation rate can be estimated throughout the cloud layer without the constraint that clouds need to be nonprecipitating. Eddy dissipation rate estimates based on DRW measurements compare well with the estimates based on Doppler velocity but their performance deteriorates as precipitation size particles are introduced in the radar volume and broaden the DRW values. And, based on this finding, a methodology to estimate the Doppler spectra broadening due to the spread of the drop size distribution is presented. Furthermore, the uncertainties in ε introduced by signal-to-noise conditions, the estimation of the horizontal wind, the selection of the averaging time window, and the presence of precipitation are discussed in detail.
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.
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. © 2016. Published by The Company of Biologists Ltd.
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.
Relationship between dynamical entropy and energy dissipation far from thermodynamic equilibrium
Green, Jason R.; Costa, Anthony B.; Grzybowski, Bartosz A.; Szleifer, Igal
2013-01-01
Connections between microscopic dynamical observables and macroscopic nonequilibrium (NE) properties have been pursued in statistical physics since Boltzmann, Gibbs, and Maxwell. The simulations we describe here establish a relationship between the Kolmogorov–Sinai entropy and the energy dissipated as heat from a NE system to its environment. First, we show that the Kolmogorov–Sinai or dynamical entropy can be separated into system and bath components and that the entropy of the system characterizes the dynamics of energy dissipation. Second, we find that the average change in the system dynamical entropy is linearly related to the average change in the energy dissipated to the bath. The constant energy and time scales of the bath fix the dynamical relationship between these two quantities. These results provide a link between microscopic dynamical variables and the macroscopic energetics of NE processes. PMID:24065832
Relationship between dynamical entropy and energy dissipation far from thermodynamic equilibrium.
Green, Jason R; Costa, Anthony B; Grzybowski, Bartosz A; Szleifer, Igal
2013-10-08
Connections between microscopic dynamical observables and macroscopic nonequilibrium (NE) properties have been pursued in statistical physics since Boltzmann, Gibbs, and Maxwell. The simulations we describe here establish a relationship between the Kolmogorov-Sinai entropy and the energy dissipated as heat from a NE system to its environment. First, we show that the Kolmogorov-Sinai or dynamical entropy can be separated into system and bath components and that the entropy of the system characterizes the dynamics of energy dissipation. Second, we find that the average change in the system dynamical entropy is linearly related to the average change in the energy dissipated to the bath. The constant energy and time scales of the bath fix the dynamical relationship between these two quantities. These results provide a link between microscopic dynamical variables and the macroscopic energetics of NE processes.
NASA Astrophysics Data System (ADS)
Gabriel, T. S. J.; Scheeres, D. J.
2016-11-01
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.
Effective dissipation: Breaking time-reversal symmetry in driven microscopic energy transmission
NASA Astrophysics Data System (ADS)
Brown, Aidan I.; Sivak, David A.
2016-09-01
At molecular scales, fluctuations play a significant role and prevent biomolecular processes from always proceeding in a preferred direction, raising the question of how limited amounts of free energy can be dissipated to obtain directed progress. We examine the system and process characteristics that efficiently break time-reversal symmetry at fixed energy loss; in particular for a simple model of a molecular machine, an intermediate energy barrier produces unusually high asymmetry for a given dissipation. We relate the symmetry-breaking factors found in this model to recent observations of biomolecular machines.
NASA Astrophysics Data System (ADS)
Jrad, Hanen; Dion, Jean Luc; Renaud, Franck; Tawfiq, Imad; Haddar, Mohamed
2017-05-01
This paper focuses on energy losses caused by inner damping and friction in an elastomeric rotational joint. A description of the design of a new experimental device intended to characterize dynamic stiffness in rotational elastomeric joint is presented. An original method based on Lagrange's equations, which allows accurately measuring forces and torques only with accelerometers, is proposed in order to identify dissipated energy in the rotational elastomeric joint. A rheological model developed taking into account dependence of the torque and the angular displacement (rotation). Experimental results and simulations used to quantify the dissipated energy in order to evaluate the damping ratio are presented and discussed.
NASA Astrophysics Data System (ADS)
Jrad, Hanen; Dion, Jean Luc; Renaud, Franck; Tawfiq, Imad; Haddar, Mohamed
2016-10-01
This paper focuses on energy losses caused by inner damping and friction in an elastomeric rotational joint. A description of the design of a new experimental device intended to characterize dynamic stiffness in rotational elastomeric joint is presented. An original method based on Lagrange's equations, which allows accurately measuring forces and torques only with accelerometers, is proposed in order to identify dissipated energy in the rotational elastomeric joint. A rheological model developed taking into account dependence of the torque and the angular displacement (rotation). Experimental results and simulations used to quantify the dissipated energy in order to evaluate the damping ratio are presented and discussed.
Identification of a mechanism of photoprotective energy dissipation in higher plants.
Ruban, Alexander V; Berera, Rudi; Ilioaia, Cristian; van Stokkum, Ivo H M; Kennis, John T M; Pascal, Andrew A; van Amerongen, Herbert; Robert, Bruno; Horton, Peter; van Grondelle, Rienk
2007-11-22
Under conditions of excess sunlight the efficient light-harvesting antenna found in the chloroplast membranes of plants is rapidly and reversibly switched into a photoprotected quenched state in which potentially harmful absorbed energy is dissipated as heat, a process measured as the non-photochemical quenching of chlorophyll fluorescence or qE. Although the biological significance of qE is established, the molecular mechanisms involved are not. LHCII, the main light-harvesting complex, has an inbuilt capability to undergo transformation into a dissipative state by conformational change and it was suggested that this provides a molecular basis for qE, but it is not known if such events occur in vivo or how energy is dissipated in this state. The transition into the dissipative state is associated with a twist in the configuration of the LHCII-bound carotenoid neoxanthin, identified using resonance Raman spectroscopy. Applying this technique to study isolated chloroplasts and whole leaves, we show here that the same change in neoxanthin configuration occurs in vivo, to an extent consistent with the magnitude of energy dissipation. Femtosecond transient absorption spectroscopy, performed on purified LHCII in the dissipative state, shows that energy is transferred from chlorophyll a to a low-lying carotenoid excited state, identified as one of the two luteins (lutein 1) in LHCII. Hence, it is experimentally demonstrated that a change in conformation of LHCII occurs in vivo, which opens a channel for energy dissipation by transfer to a bound carotenoid. We suggest that this is the principal mechanism of photoprotection.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Zhao, Jieliang; Huang, He; Yan, Shaoze
2017-03-01
Whether for insects or for aircrafts, landing is one of the indispensable links in the verification of airworthiness safety. The mechanisms by which insects achieve a fast and stable landing remain unclear. An intriguing example is provided by honeybees (Apis mellifera ligustica), which use the swinging motion of their abdomen to dissipate residual flying energy and to achieve a smooth, stable, and quick landing. By using a high-speed camera, we observed that touchdown is initiated by honeybees extending their front legs or antennae and then landing softly on a wall. After touchdown, they swing the rest of their bodies until all flying energy is dissipated. We suggested a simplified model with mass-spring dampers for the body of the honeybee and revealed the mechanism of flying energy transfer and dissipation in detail. Results demonstrate that body translation and abdomen swinging help honeybees dissipate residual flying energy and orchestrate smooth landings. The initial kinetic energy of flying is transformed into the kinetic energy of the abdomen's rotary movement. Then, the kinetic energy of rotary movement is converted into thermal energy during the swinging cycle. This strategy provides more insight into the mechanism of insect flying, which further inspires better design on aerial vehicle with better landing performance.
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.
Mechanism of vibrational energy dissipation of free OH groups at the air–water interface
Hsieh, Cho-Shuen; Campen, R. Kramer; Okuno, Masanari; Backus, Ellen H. G.; Nagata, Yuki; Bonn, Mischa
2013-01-01
Interfaces of liquid water play a critical role in a wide variety of processes that occur in biology, a variety of technologies, and the environment. Many macroscopic observations clarify that the properties of liquid water interfaces significantly differ from those of the bulk liquid. In addition to interfacial molecular structure, knowledge of the rates and mechanisms of the relaxation of excess vibrational energy is indispensable to fully understand physical and chemical processes of water and aqueous solutions, such as chemical reaction rates and pathways, proton transfer, and hydrogen bond dynamics. Here we elucidate the rate and mechanism of vibrational energy dissipation of water molecules at the air–water interface using femtosecond two-color IR-pump/vibrational sum-frequency probe spectroscopy. Vibrational relaxation of nonhydrogen-bonded OH groups occurs at a subpicosecond timescale in a manner fundamentally different from hydrogen-bonded OH groups in bulk, through two competing mechanisms: intramolecular energy transfer and ultrafast reorientational motion that leads to free OH groups becoming hydrogen bonded. Both pathways effectively lead to the transfer of the excited vibrational modes from free to hydrogen-bonded OH groups, from which relaxation readily occurs. Of the overall relaxation rate of interfacial free OH groups at the air–H2O interface, two-thirds are accounted for by intramolecular energy transfer, whereas the remaining one-third is dominated by the reorientational motion. These findings not only shed light on vibrational energy dynamics of interfacial water, but also contribute to our understanding of the impact of structural and vibrational dynamics on the vibrational sum-frequency line shapes of aqueous interfaces. PMID:24191016
Mechanism of vibrational energy dissipation of free OH groups at the air-water interface.
Hsieh, Cho-Shuen; Campen, R Kramer; Okuno, Masanari; Backus, Ellen H G; Nagata, Yuki; Bonn, Mischa
2013-11-19
Interfaces of liquid water play a critical role in a wide variety of processes that occur in biology, a variety of technologies, and the environment. Many macroscopic observations clarify that the properties of liquid water interfaces significantly differ from those of the bulk liquid. In addition to interfacial molecular structure, knowledge of the rates and mechanisms of the relaxation of excess vibrational energy is indispensable to fully understand physical and chemical processes of water and aqueous solutions, such as chemical reaction rates and pathways, proton transfer, and hydrogen bond dynamics. Here we elucidate the rate and mechanism of vibrational energy dissipation of water molecules at the air-water interface using femtosecond two-color IR-pump/vibrational sum-frequency probe spectroscopy. Vibrational relaxation of nonhydrogen-bonded OH groups occurs at a subpicosecond timescale in a manner fundamentally different from hydrogen-bonded OH groups in bulk, through two competing mechanisms: intramolecular energy transfer and ultrafast reorientational motion that leads to free OH groups becoming hydrogen bonded. Both pathways effectively lead to the transfer of the excited vibrational modes from free to hydrogen-bonded OH groups, from which relaxation readily occurs. Of the overall relaxation rate of interfacial free OH groups at the air-H2O interface, two-thirds are accounted for by intramolecular energy transfer, whereas the remaining one-third is dominated by the reorientational motion. These findings not only shed light on vibrational energy dynamics of interfacial water, but also contribute to our understanding of the impact of structural and vibrational dynamics on the vibrational sum-frequency line shapes of aqueous interfaces.
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.
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.
Shear effects on energy dissipation from an elastic beam on a rigid foundation
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
Shear effects on energy dissipation from an elastic beam on a rigid foundation
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.
Energy dissipation and contour integral characterizing fracture behavior of incremental plasticity
NASA Astrophysics Data System (ADS)
He, Qi-Lin; Wu, Lin-Zhi; Li, Ming; Chen, Hong-Bo
2011-04-01
J ep-integral is derived for characterizing the fracture behavior of elastic-plastic materials. The J ep-integral differs from Rice's J-integral in that the free energy density rather than the stress working density is employed to define energy-momentum tensor. The J ep-integral is proved to be path-dependent regardless of incremental plasticity and deformation plasticity. The J ep-integral possesses clearly clear physical meaning: (1) the value J {tip/ep} evaluated on the infinitely small contour surrounding the crack tip represents the crack tip energy dissipation; (2) when the global steadystate crack growth condition is approached, the value of J {far-ss/ep} calculated along the boundary contour equals to the sum of crack tip dissipation and bulk dissipation of plastic zone. The theoretical results are verified by simulating mode I crack problems.
Estimation of the kinetic energy dissipation in fall-arrest system and manikin during fall impact.
Wu, John Z; Powers, John R; Harris, James R; Pan, Christopher S
2011-04-01
Fall-arrest systems (FASs) have been widely applied to provide a safe stop during fall incidents for occupational activities. The mechanical interaction and kinetic energy exchange between the human body and the fall-arrest system during fall impact is one of the most important factors in FAS ergonomic design. In the current study, we developed a systematic approach to evaluate the energy dissipated in the energy absorbing lanyard (EAL) and in the harness/manikin during fall impact. The kinematics of the manikin and EAL during the impact were derived using the arrest-force time histories that were measured experimentally. We applied the proposed method to analyse the experimental data of drop tests at heights of 1.83 and 3.35 m. Our preliminary results indicate that approximately 84-92% of the kinetic energy is dissipated in the EAL system and the remainder is dissipated in the harness/manikin during fall impact. The proposed approach would be useful for the ergonomic design and performance evaluation of an FAS. STATEMENT OF RELEVANCE: Mechanical interaction, especially kinetic energy exchange, between the human body and the fall-arrest system during fall impact is one of the most important factors in the ergonomic design of a fall-arrest system. In the current study, we propose an approach to quantify the kinetic energy dissipated in the energy absorbing lanyard and in the harness/body system during fall impact.
2014-06-01
Distribution List 20 iv INTENTIONALLY LEFT BLANK. 1 The constant energy dissipative particle dynamics ( DPD -E) method is implemented into the Large-Scale...User Manual and Source Code for a LAMMPS Implementation of Constant Energy Dissipative Particle Dynamics ( DPD -E) by James P. Larentzos...Energy Dissipative Particle Dynamics ( DPD -E) James P. Larentzos Engility Corporation John K. Brennan, Joshua D. Moore, and William D. Mattson
Structural development and energy dissipation in simulated silicon apices.
Jarvis, Samuel Paul; Kantorovich, Lev; Moriarty, Philip
2013-12-20
In this paper we examine the stability of silicon tip apices by using density functional theory (DFT) calculations. We find that some tip structures - modelled as small, simple clusters - show variations in stability during manipulation dependent on their orientation with respect to the sample surface. Moreover, we observe that unstable structures can be revealed by a characteristic hysteretic behaviour present in the F(z) curves that were calculated with DFT, which corresponds to a tip-induced dissipation of hundreds of millielectronvolts resulting from reversible structural deformations. Additionally, in order to model the structural evolution of the tip apex within a low temperature NC-AFM experiment, we simulated a repeated tip-surface indentation until the tip structure converged to a stable termination and the characteristic hysteretic behaviour was no longer observed. Our calculations suggest that varying just a single rotational degree of freedom can have as measurable an impact on the tip-surface interaction as a completely different tip structure.
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
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.
1975-08-01
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Energy Dissipation Capacity of Reinforced Concrete Beams Strengthened with CFRP Strips
NASA Astrophysics Data System (ADS)
Hong, Sungnam; Park, Sun-Kyu
2016-05-01
Cyclic loading tests were performed to investigate the energy dissipation capacities of reinforced concrete (RC) beams strengthened with carbon-fiber-reinforced polymer (CFRP) strips. Four RC beams were manufactured and three-point loaded. Responses of the strengthened beams to the cyclic loadings were measured, including deflections at the center of their span and strains of the CFRP strips and reinforcing steel rebars. Based on test results, the energy dissipation capacity of the strengthened beams were evaluated in comparison with that of an unstrengthened control beam.
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.
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.
Moroz, Adam
2009-06-11
The maximum energy dissipation principle is employed to nonlinear chemical thermodynamics in terms of distance variable (generalized displacement) from the global equilibrium, applying the optimal control interpretation to develop a variational formulation. The cost-like functional was chosen to support the suggestion that such a formulation corresponds to the maximum energy dissipation principle. Using this approach, the variational framework was proposed for a nonlinear chemical thermodynamics, including a general cooperative kinetics model. The formulation is in good agreement with standard linear nonequilibrium chemical thermodynamics.
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.
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.
Wave energy dissipation due to mudbanks formed off southwest coast of India
NASA Astrophysics Data System (ADS)
Samiksha, S. V.; Vethamony, P.; Rogers, W. Erick; Pednekar, P. S.; Babu, M. T.; Dineshkumar, P. K.
2017-09-01
Mudbanks (MBs) are a unique natural phenomenon, and form along the southwest coast of India during the southwest monsoon. They are characterized by a calm-water region, bordered by a rough sea. In order to quantify the wave energy dissipation, wave data were collected at two water depths (15 m and 7 m) before and during the period of formation of MBs off Alappuzha, Kerala. The observations indicate that MBs exist even in deeper water beyond 15 m water depth, contrary to earlier findings that they only form in depths of 0-5 m. The analysis showed 65-70% wave height attenuation. As spectral density evolves with shoaling, energy dissipation was examined using the concept of wave energy flux. The combination of high frequency dissipation and nonlinear energy transfer from higher-frequency to low-frequency waves resulted in a reduction of energy across a wide frequency range. The WAVEWATCH III® (WW3) model with wave-mud interaction physics was used to capture the signature of wave energy dissipation due to MBs. The accuracy of prediction of significant wave heights (Hs) of the WW3 model was verified using Hs of measured waves and ERA- Interim (ECMWF Reanalysis Interim data). The model accurately reproduced both the wave heights in the MB region and their general characteristics. The measurements and model results complement each other in explaining changes associated with an apparent shift of the MBs.
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.
Estimate of the Time Rate of Entropy Dissipation for Systems of Conservation Laws
NASA Astrophysics Data System (ADS)
Sever, Michael
1996-09-01
A priori estimates for weak solutions of nonlinear systems of conservation laws remain in short supply. In this note we obtain an estimate of the rate of total entropy dissipation for initial/boundary value problems for such systems, of any dimension and in any number of space variables. The essential assumptions made are those of a strictly convex entropy density, anL∞estimate on the solution, and initial data of "bounded variation" as described here.
Zhong, Yue; Liu, Yanting; Wu, Ting; Song, Huizi; Chen, Zhongxiu; Zhu, Wei; Cai, Yuyan; Zhang, Wen; Bai, Wenjuan; Tang, Hong; Rao, Li
2016-05-01
Dissipative energy loss derived from vector flow mapping represents the viscous dissipation of turbulent blood flow. We aimed to determine the left ventricular (LV) energy loss in patients with end-stage renal disease (ESRD). Patients with ESRD and a preserved LV ejection fraction, who consisted of a group receiving peritoneal dialysis, a group receiving hemodialysis, and a group receiving preparation for dialysis initiation, were examined by echocardiography; a group of healthy control participants were examined as well. Vector flow mapping analysis was then performed from the apical 4-chamber view to calculate the energy loss during diastole and systole in the left ventricle. Conventional transthoracic echocardiography and LV energy loss calculations were successfully performed in 63 cases and 50 controls. The patients with ESRD had significantly higher diastolic energy loss [median (interquartile range), 71.73 (46.08-106.75) versus 23.32 (17.17-29.26) mW/m; P < .001] and higher systolic energy loss [25.28 (19.03-33.93) versus 12.52 (9.35-16.47) mW/m; P < .001]. A significant difference in diastolic energy loss between the peritoneal dialysis and preparation groups was found [54.92 (39.28-89.94) versus 84.82 (62.58-171.4) mW/m; P = .04]. In patients with ESRD, the log-transformed diastolic energy loss had a significant association with the peak early diastolic transmitral flow velocity (P = .011), peak early diastolic transmitral flow velocity-to-peak early diastolic mitral annular flow velocity ratio (P = .001), LV mass index (P = .017), and heart rate (P = .003). Impaired blood flow efficiency was detected in patients with ESRD by using dissipative energy loss derived from vector flow mapping. The energy loss value could be a novel parameter for evaluating the ventricular workload of uremic hearts in terms of fluid mechanics. © 2016 by the American Institute of Ultrasound in Medicine.
NASA Technical Reports Server (NTRS)
Maddalon, D. V.
1974-01-01
Questions concerning the energy efficiency of aircraft compared to ground transport are considered, taking into account as energy intensity the energy consumed per passenger statute mile. It is found that today's transport aircraft have an energy intensity potential comparable to that of ground modes. Possibilities for improving the energy density are also much better in the case of aircraft than in the case of ground transportation. Approaches for potential reductions in aircraft energy consumption are examined, giving attention to steps for increasing the efficiency of present aircraft and to reductions in energy intensity obtainable by the introduction of new aircraft utilizing an advanced technology. The use of supercritical aerodynamics is discussed along with the employment of composite structures, advances in propulsion systems, and the introduction of very large aircraft. Other improvements in fuel economy can be obtained by a reduction of skin-friction drag and a use of hydrogen fuel.
Tumbling asteroid rotation with the YORP torque and inelastic energy dissipation
NASA Astrophysics Data System (ADS)
Breiter, S.; Murawiecka, M.
2015-05-01
The Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect and rotational energy dissipation due to inelastic deformations are two key mechanisms affecting rotation of tumbling asteroids in long term. Each of the effects used to be discussed separately. We present the first results concerning a simulation of their joint action. Asteroids (3103) Eger and (99942) Apophis, as well as their scaled variants, are used as test bodies. Plugging in the dissipation destroys limit cycles of the pure YORP, but creates a new asymptotic state of stationary tumbling with a fixed rotation period. The present model does not contradict finding Eger in the principal axis rotation. For Apophis, the model suggests that its current rotation state should be relatively young. In general, the fraction of initial conditions leading to the principal axis rotation is too small, compared to the actual data. The model requires a stronger energy dissipation and weaker YORP components in the nutation angle and obliquity.
Heat dissipation of high rate Li-SOCl sub 2 primary cells
NASA Astrophysics Data System (ADS)
Cho, Y. I.; Halpert, G.; Deligiannis, E.
1986-09-01
The heat dissipation problem occurring in the lithium thionyl chloride cells discharged at relatively high rates under normal discharge conditions is examined. Four heat flow paths were identified, and the thermal resistances of the relating cell components along each flow path were accordingly calculated. From the thermal resistance network analysis, it was demonstrated that about 90 percent of the total heat produced within the cell should be dissipated along the radial direction in a spirally wound cell. In addition, the threshold value of the heat generation rate at which cell internal temperature could be maintained below 100 C, was calculated from total thermal resistance and found to be 2.9 W. However, these calculations were made only at the cell components' level, and the transient nature of the heat accumulation and dissipation was not considered. A simple transient model based on the lumped-heat-capacity concept was developed to predict the time-dependent cell temperature at different discharge rates. The overall objective was to examine the influence of cell design variable from the heat removal point of view under normal discharge conditions and to make recommendations to build more efficient lithium cells.
Endo, Tsuyoshi; Uebayashi, Nozomu; Ishida, Satoshi; Ikeuchi, Masahiro; Sato, Fumihiko
2014-08-01
In the field, plants are exposed to fluctuating light, where photosynthesis occurs under conditions far from a steady state. Excess energy dissipation associated with energy quenching of chlorophyll fluorescence (qE) functions as an efficient photo-protection mechanism in photosystem II. PsbS is an important regulator of qE, especially for the induction phase of qE. Beside the regulatory energy dissipation, some part of energy is lost through relaxation of excited chlorophyll molecules. To date, several models to quantify energy loss through these dissipative pathways in PSII have been proposed. In this short review, we compare and evaluate these models for PSII energy allocation when they are applied to non-steady state photosynthesis. As a case study, an investigation on energy allocation to qE-associated dissipation at PSII under non-steady state photosynthesis using PsbS-deficient rice transformants is introduced. Diurnal and seasonal changes in PSII energy allocation in rice under natural light are also presented. Future perspective of studies on PSII energy allocation is discussed.
NASA Astrophysics Data System (ADS)
Bianco, L.; McCaffrey, K.; Wilczak, J. M.; Olson, J. B.; Kenyon, J.
2016-12-01
When forecasting winds at a wind plant for energy production, the turbulence parameterizations in the forecast models are crucial for understanding wind plant performance. Recent research shows that the turbulence (eddy) dissipation rate in planetary boundary layer (PBL) parameterization schemes introduces significant uncertainty in the Weather Research and Forecasting (WRF) model. Thus, developing the capability to measure dissipation rates in the PBL will allow for identification of weaknesses in, and improvements to the parameterizations. During a preliminary field study at the Boulder Atmospheric Observatory in spring 2015, a 915-MHz wind profiling radar (WPR) measured dissipation rates concurrently with sonic anemometers mounted on a 300-meter tower. WPR set-up parameters (e.g., spectral resolution), post-processing techniques (e.g., filtering for non-atmospheric signals), and spectral averaging were optimized to capture the most accurate Doppler spectra for measuring spectral widths for use in the computation of the eddy dissipation rates. These encouraging results lead to the implementation of the observing strategy on a 915-MHz WPR in Wasco, OR, operating as part of the Wind Forecasting Improvement Project 2 (WFIP2). These observations are compared to dissipation rates calculated from the High-Resolution Rapid Refresh model, a WRF-based mesoscale numerical weather prediction model run for WFIP2 at 3000 m horizontal grid spacing and with a nest, which has 750-meter horizontal grid spacing, in the complex terrain region of the Columbia River Gorge. The observed profiles of dissipation rates are used to evaluate the PBL parameterization schemes used in the HRRR model, which are based on the modeled turbulent kinetic energy and a tunable length scale.
Energy dissipation and error probability in fault-tolerant binary switching
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
Phase space scales of free energy dissipation in gradient-driven gyrokinetic turbulence
NASA Astrophysics Data System (ADS)
Hatch, D. R.; Jenko, F.; Bratanov, V.; Navarro, A. Bañón; Navarro
2014-08-01
A reduced four-dimensional (integrated over perpendicular velocity) gyrokinetic model of slab ion temperature gradient-driven turbulence is used to study the phase-space scales of free energy dissipation in a turbulent kinetic system over a broad range of background gradients and collision frequencies. Parallel velocity is expressed in terms of Hermite polynomials, allowing for a detailed study of the scales of free energy dynamics over the four-dimensional phase space. A fully spectral code - the DNA code - that solves this system is described. Hermite free energy spectra are significantly steeper than would be expected linearly, causing collisional dissipation to peak at large scales in velocity space even for arbitrarily small collisionality. A key cause of the steep Hermite spectra is a critical balance - an equilibration of the parallel streaming time and the nonlinear correlation time - that extends to high Hermite number n. Although dissipation always peaks at large scales in all phase space dimensions, small-scale dissipation becomes important in an integrated sense when collisionality is low enough and/or nonlinear energy transfer is strong enough. Toroidal full-gyrokinetic simulations using the Gene code are used to verify results from the reduced model. Collision frequencies typically found in present-day experiments correspond to turbulence regimes slightly favoring large-scale dissipation, while turbulence in low-collisionality systems like ITER and space and astrophysical plasmas is expected to rely increasingly on small-scale dissipation mechanisms. This work is expected to inform gyrokinetic reduced modeling efforts like Large Eddy Simulation and gyrofluid techniques.
Earthquake Energy Dissipation in Light of High-Velocity, Slip-Pulse Shear Experiments
NASA Astrophysics Data System (ADS)
Reches, Z.; Liao, Z.; Chang, J. C.
2014-12-01
We investigated the energy dissipation during earthquakes by analysis of high-velocity shear experiments conducted on room-dry, solid samples of granite, tonalite, and dolomite sheared at slip-velocity of 0.0006-1m/s, and normal stress of 1-11.5MPa. The experimental fault were loaded in one of three modes: (1) Slip-pulse of abrupt, intense acceleration followed by moderate deceleration; (2) Impact by a spinning, heavy flywheel (225 kg); and (3) Constant velocity loading. We refer to energy dissipation in terms of power-density (PD=shear stress*slip-velocity; units of MW/m^2), and Coulomb-energy-density (CED= mechanical energy/normal stress; units of m). We present two aspects: Relative energy dissipation of the above loading modes, and relative energy dissipation between impact experiments and moderate earthquakes. For the first aspect, we used: (i) the lowest friction coefficient of the dynamic weakening; (ii) the work dissipated before reaching the lowest friction; and (iii) the cumulative mechanical work during the complete run. The results show that the slip-pulse/impact modes are energy efficient relatively to the constant-velocity mode as manifested by faster, more intense weakening and 50-90% lower energy dissipation. Thus, for a finite amount of pre-seismic crustal energy, the efficiency of slip-pulse would amplify earthquake instability. For the second aspect, we compare the experimental CED of the impact experiments to the reported breakdown energy (EG) of moderate earthquakes, Mw = 5.6 to 7.2 (Chang et al., 2012). In is commonly assumed that the seismic EG is a small fraction of the total earthquake energy, and as expected in 9 out of 11 examined earthquakes, EG was 0.005 to 0.07 of the experimental CED. We thus speculate that the experimental relation of Coulomb-energy-density to total slip distance, D, CED = 0.605 × D^0.933, is a reasonable estimate of total earthquake energy, a quantity that cannot be determined from seismic data.
Verhoeven, A. S.; Demmig-Adams, B.; Adams III, W. W.
1997-01-01
The involvement of the xanthophyll cycle in photoprotection of N-deficient spinach (Spinacia oleracea L. cv Nobel) was investigated. Spinach plants were fertilized with 14 mM nitrate (control, high N) versus 0.5 mM (low N) fertilizer, and grown under both high- and low-light conditions. Plants were characterized from measurements of photosynthetic oxygen exchange and chlorophyll fluorescence, as well as carotenoid and cholorophyll analysis. Compared with the high-N plants, the low-N plants showed a lower capacity for photosynthesis and a lower chlorophyll content, as well as a lower rate of photosystem II photosynthetic electron transport and a corresponding increase in thermal energy dissipation activity measured as nonphotochemical fluorescence quenching. The low-N plants displayed a greater fraction of the total xanthophyll cycle pool as zeaxanthin and antheraxanthin at midday, and an increase in the ratio of xanthophyll cycle pigments to total chlorophyll. These results indicate that under N limitation both the light-collecting system and the photosynthetic rate decrease. However, the increased dissipation of excess energy shows that there is excess light absorbed at midday. We conclude that spinach responds to N limitation by a combination of decreased light collection and increased thermal dissipation involving the xanthophyll cycle. PMID:12223645
Dissipation rate and residue distribution of dufulin in tomato and soil under field conditions.
Zhu, Huijun; Shi, Mengmeng; Hu, Deyu; Zhang, Kankan; Zhang, Yuping; Lu, Ping; Zeng, Song; Yang, Song; Song, Baoan
2014-06-01
Dissipation rate and residue distribution of dufulin in tomato and soil under field conditions were investigated in Guiyang, Tianjin, and Haikou during 2011-2012, using ultra-performance liquid chromatography. Average recoveries of dufulin in tomato and soil ranged from 91.03 % to 95.16 % and 94.35 % to 98.34 %, respectively, with relative standard deviations of 1.16 %-3.97 %. Dufulin dissipation followed first-order kinetics. Dufulin had half-lives of 2.8, 4.7, and 9.0 days in tomato and 6.1, 8.2, and 17.2 days in soil in Guiyang, Tianjin, and Haikou, respectively. At harvest, dufulin residues in tomato samples collected 5 days after the last application at 3 times recommended dosage applied every 5 days were below 1.0 mg kg(-1).
NASA Astrophysics Data System (ADS)
Frank, T. D.; Kim, S.; Dotov, D. G.
2013-11-01
Canonical-dissipative nonequilibrium energy distributions play an important role in the life sciences. In one of the most fundamental forms, such energy distributions correspond to two-parametric normal distributions truncated to the left. We present an implicit moment method involving the first and second energy moments to estimate the distribution parameters. It is shown that the method is consistent with Cohen's 1949 formula. The implementation of the algorithm is discussed and the range of admissible parameter values is identified. In addition, an application to an earlier study on human oscillatory hand movements is presented. In this earlier study, energy was conceptualized as the energy of a Hamiltonian oscillator model. The canonical-dissipative approach allows for studying the systematic change of the model parameters with oscillation frequency. It is shown that the results obtained with the implicit moment method are consistent with those derived in the earlier study by other means.
Dissipation of excess excitation energy of the needle leaves in Pinus trees during cold winters.
Zhang, A O; Cui, Zhen-Hai; Yu, Jia-Lin; Hu, Zi-Ling; Ding, Rui; Ren, Da-Ming; Zhang, Li-Jun
2016-12-01
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.
Influence of a large-scale field on energy dissipation in magnetohydrodynamic turbulence
NASA Astrophysics Data System (ADS)
Zhdankin, Vladimir; Boldyrev, Stanislav; Mason, Joanne
2017-07-01
In magnetohydrodynamic (MHD) turbulence, the large-scale magnetic field sets a preferred local direction for the small-scale dynamics, altering the statistics of turbulence from the isotropic case. This happens even in the absence of a total magnetic flux, since MHD turbulence forms randomly oriented large-scale domains of strong magnetic field. It is therefore customary to study small-scale magnetic plasma turbulence by assuming a strong background magnetic field relative to the turbulent fluctuations. This is done, for example, in reduced models of plasmas, such as reduced MHD, reduced-dimension kinetic models, gyrokinetics, etc., which make theoretical calculations easier and numerical computations cheaper. Recently, however, it has become clear that the turbulent energy dissipation is concentrated in the regions of strong magnetic field variations. A significant fraction of the energy dissipation may be localized in very small volumes corresponding to the boundaries between strongly magnetized domains. In these regions, the reduced models are not applicable. This has important implications for studies of particle heating and acceleration in magnetic plasma turbulence. The goal of this work is to systematically investigate the relationship between local magnetic field variations and magnetic energy dissipation, and to understand its implications for modelling energy dissipation in realistic turbulent plasmas.
NASA Astrophysics Data System (ADS)
Callaghan, A. H.; Deane, G. B.; Stokes, M. D.
2016-11-01
Oceanic air-entraining breaking waves fundamentally influence weather and climate through bubble-mediated ocean-atmosphere exchanges, and influence marine engineering design by impacting statistics of wave heights, crest heights, and wave loading. However, estimating individual breaking wave energy dissipation in the field remains a fundamental problem. Using laboratory experiments, we introduce a new method to estimate energy dissipation by individual breaking waves using above-water images of evolving foam. The data show the volume of the breaking wave two-phase flow integrated in time during active breaking scales linearly with wave energy dissipated. To determine the volume time-integral, above-water images of surface foam provide the breaking wave timescale and horizontal extent of the submerged bubble plume, and the foam decay time provides an estimate of the bubble plume penetration depth. We anticipate that this novel remote sensing method will improve predictions of air-sea exchanges, validate models of wave energy dissipation, and inform ocean engineering design.
Excitation energy and nuclear dissipation probed with evaporation-residue cross sections
Ye, W.
2011-04-15
Using a Langevin equation coupled with a statistical decay model, we calculate the excess of evaporation-residue cross sections over its standard statistical-model value as a function of nuclear dissipation strength for {sup 200}Hg compound nuclei (CNs) under two distinct types of initial conditions for populated CNs: (i) high excitation energy but low angular momentum (produced via proton-induced spallation reactions at GeV energies and via peripheral heavy-ion collisions at relativistic energies) and (ii) high angular momentum but low excitation energy (produced through fusion mechanisms). We find that the conditions of case (ii) not only amplify the effect of dissipation on the evaporation residues, but also substantially increase the sensitivity of this excess to nuclear dissipation. These results suggest that, in experiments, to obtain accurate information of presaddle nuclear dissipation strength by measuring evaporation-residue cross sections, it is best to choose the heavy-ion-induced fusion reaction approach to yield excited compound nuclei.
Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data
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.
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
2016-12-01
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.
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.
Perreault, François; Ait Ali, Nadia; Saison, Cyril; Popovic, Radovan; Juneau, Philippe
2009-07-17
In this study, we investigated the energy dissipation processes via photosystem II and photosystem I activity in green alga Chlamydomonas reinhardtii exposed to dichromate inhibitory effect. Quantum yield of photosystem II and also photosystem I were highly decreased by dichromate effect. Such inhibition by dichromate induced strong quenching effect on rapid OJIP fluorescence transients, indicating deterioration of photosystem II electron transport via plastoquinone pool toward photosystem I. The decrease of energy dissipation dependent on electron transport of photosystem II and photosystem I by dichromate effect was associated with strong increase of non-photochemical energy dissipation processes. By showing strong effect of dichromate on acceptor side of photosystem I, we indicated that dichromate inhibitory effect was not associated only with PSII electron transport. Here, we found that energy dissipation via photosystem I was limited by its electron acceptor side. By the analysis of P700 oxido-reduction state with methylviolagen as an exogenous PSI electron transport mediator, we showed that PSI electron transport discrepancy induced by dichromate effect was also caused by inhibitory effect located beyond photosystem I. Therefore, these results demonstrated that dichromate has different sites of inhibition which are associated with photosystem II, photosystem I and electron transport sink beyond photosystems.
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.
Energy dissipation from a correlated system driven out of equilibrium
Rameau, J. D.; Freutel, S.; Kemper, A. F.; ...
2016-12-20
We report that in complex materials various interactions have important roles in determining electronic properties. Angle-resolved photoelectron spectroscopy (ARPES) is used to study these processes by resolving the complex single-particle self-energy and quantifying how quantum interactions modify bare electronic states. However, ambiguities in the measurement of the real part of the self-energy and an intrinsic inability to disentangle various contributions to the imaginary part of the self-energy can leave the implications of such measurements open to debate. Here we employ a combined theoretical and experimental treatment of femtosecond time-resolved ARPES (tr-ARPES) show how population dynamics measured using tr-ARPES can bemore » used to separate electron–boson interactions from electron–electron interactions. In conclusion, we demonstrate a quantitative analysis of a well-defined electron–boson interaction in the unoccupied spectrum of the cuprate Bi2Sr2CaCu2O8+x characterized by an excited population decay time that maps directly to a discrete component of the equilibrium self-energy not readily isolated by static ARPES experiments.« less
Energy dissipation from a correlated system driven out of equilibrium
NASA Astrophysics Data System (ADS)
Rameau, J. D.; Freutel, S.; Kemper, A. F.; Sentef, M. A.; Freericks, J. K.; Avigo, I.; Ligges, M.; Rettig, L.; Yoshida, Y.; Eisaki, H.; Schneeloch, J.; Zhong, R. D.; Xu, Z. J.; Gu, G. D.; Johnson, P. D.; Bovensiepen, U.
2016-12-01
In complex materials various interactions have important roles in determining electronic properties. Angle-resolved photoelectron spectroscopy (ARPES) is used to study these processes by resolving the complex single-particle self-energy and quantifying how quantum interactions modify bare electronic states. However, ambiguities in the measurement of the real part of the self-energy and an intrinsic inability to disentangle various contributions to the imaginary part of the self-energy can leave the implications of such measurements open to debate. Here we employ a combined theoretical and experimental treatment of femtosecond time-resolved ARPES (tr-ARPES) show how population dynamics measured using tr-ARPES can be used to separate electron-boson interactions from electron-electron interactions. We demonstrate a quantitative analysis of a well-defined electron-boson interaction in the unoccupied spectrum of the cuprate Bi2Sr2CaCu2O8+x characterized by an excited population decay time that maps directly to a discrete component of the equilibrium self-energy not readily isolated by static ARPES experiments.
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…
Energy dissipation from a correlated system driven out of equilibrium
Rameau, J. D.; Freutel, S.; Kemper, A. F.; Sentef, M. A.; Freericks, J. K.; Avigo, I.; Ligges, M.; Rettig, L.; Yoshida, Y.; Eisaki, H.; Schneeloch, J.; Zhong, R. D.; Xu, Z. J.; Gu, G. D.; Johnson, P. D.; Bovensiepen, U.
2016-01-01
In complex materials various interactions have important roles in determining electronic properties. Angle-resolved photoelectron spectroscopy (ARPES) is used to study these processes by resolving the complex single-particle self-energy and quantifying how quantum interactions modify bare electronic states. However, ambiguities in the measurement of the real part of the self-energy and an intrinsic inability to disentangle various contributions to the imaginary part of the self-energy can leave the implications of such measurements open to debate. Here we employ a combined theoretical and experimental treatment of femtosecond time-resolved ARPES (tr-ARPES) show how population dynamics measured using tr-ARPES can be used to separate electron–boson interactions from electron–electron interactions. We demonstrate a quantitative analysis of a well-defined electron–boson interaction in the unoccupied spectrum of the cuprate Bi2Sr2CaCu2O8+x characterized by an excited population decay time that maps directly to a discrete component of the equilibrium self-energy not readily isolated by static ARPES experiments. PMID:27996009
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…
Energy dissipation from a correlated system driven out of equilibrium
Rameau, J. D.; Freutel, S.; Kemper, A. F.; Sentef, M. A.; Freericks, J. K.; Avigo, I.; Ligges, M.; Rettig, L.; Yoshida, Y.; Eisaki, H.; Schneeloch, J.; Zhong, R. D.; Xu, Z. J.; Gu, G. D.; Johnson, P. D.; Bovensiepen, U.
2016-12-20
We report that in complex materials various interactions have important roles in determining electronic properties. Angle-resolved photoelectron spectroscopy (ARPES) is used to study these processes by resolving the complex single-particle self-energy and quantifying how quantum interactions modify bare electronic states. However, ambiguities in the measurement of the real part of the self-energy and an intrinsic inability to disentangle various contributions to the imaginary part of the self-energy can leave the implications of such measurements open to debate. Here we employ a combined theoretical and experimental treatment of femtosecond time-resolved ARPES (tr-ARPES) show how population dynamics measured using tr-ARPES can be used to separate electron–boson interactions from electron–electron interactions. In conclusion, we demonstrate a quantitative analysis of a well-defined electron–boson interaction in the unoccupied spectrum of the cuprate Bi_{2}Sr_{2}CaCu_{2}O_{8+x} characterized by an excited population decay time that maps directly to a discrete component of the equilibrium self-energy not readily isolated by static ARPES experiments.
Yamada, Yasuhiro; Yamaji, Youhei; Imada, Masatoshi
2015-11-06
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.
NASA Astrophysics Data System (ADS)
Moroz, Adam
2008-05-01
In this work we revise the applicability of the optimal control and variational approach to the maximum energy dissipation (MED) principle in non-equilibrium thermodynamics. The optimal control analogies for the kinetical and potential parts of thermodynamic Lagrangian (in the form of a sum of the positively defined thermodynamic potential and positively defined dissipative function) have been considered. An interpretation of thermodynamic momenta is discussed with respect to standard optimal control applications, which employ dynamic constraints. Also included is interpretation in terms of the least action principle.
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
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
Dissipative Double-Well Potential for Cold Atoms: Kramers Rate and Stochastic Resonance
NASA Astrophysics Data System (ADS)
Stroescu, Ion; Hume, David B.; Oberthaler, Markus K.
2016-12-01
We experimentally study particle exchange in a dissipative double-well potential using laser-cooled atoms in a hybrid trap. We measure the particle hopping rate as a function of barrier height, temperature, and atom number. Single-particle resolution allows us to measure rates over more than 4 orders of magnitude and distinguish the effects of loss and hopping. Deviations from the Arrhenius-law scaling at high barrier heights occur due to cold collisions between atoms within a well. By driving the system periodically, we characterize the phenomenon of stochastic resonance in the system response.
Dissipative Double-Well Potential for Cold Atoms: Kramers Rate and Stochastic Resonance.
Stroescu, Ion; Hume, David B; Oberthaler, Markus K
2016-12-09
We experimentally study particle exchange in a dissipative double-well potential using laser-cooled atoms in a hybrid trap. We measure the particle hopping rate as a function of barrier height, temperature, and atom number. Single-particle resolution allows us to measure rates over more than 4 orders of magnitude and distinguish the effects of loss and hopping. Deviations from the Arrhenius-law scaling at high barrier heights occur due to cold collisions between atoms within a well. By driving the system periodically, we characterize the phenomenon of stochastic resonance in the system response.
Control of flow around a circular cylinder for minimizing energy dissipation.
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)JFLSA70022-112010.1017/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
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
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.
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
2015-10-28
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.
Vasic, Borislav; Matkovic, Aleksandar; Gajic, Rados
2017-09-21
We investigate phase imaging of supported graphene using amplitude modulation atomic force microscopy (AFM), so called, tapping mode. The phase contrast between graphene and neighbouring substrate grows at hard tapping conditions and the contrast is enhanced compared to the topographic one. Therefore, the phase measurements could enable a high contrast imaging of graphene and related two dimensional materials and heterostructures, not achievable with conventional AFM based topographic measurements. Obtained phase maps are then transformed into energy dissipation maps which are important for graphene applications in various mechanical systems. From fundamental point of view, the energy dissipation gives further insights into mechanical properties. Reliable measurements, obtained in the repulsive regime, show that the energy dissipation on graphene covered substrate is lower than on bare one, so graphene provides a certain shielding in tip-substrate interaction. According to obtained phase curves and their derivatives, as well as according to correlation measurements based on AFM nanoindentation and force modulation microscopy, we conclude that the main dissipation channels in graphene-substrate systems are short range hysteresis and long range interfacial forces. © 2017 IOP Publishing Ltd.
Vertical Kinetic Energy of Internal Gravity Waves and Turbulent Dissipation in the Ocean
NASA Astrophysics Data System (ADS)
Thurnherr, Andreas; St. Laurent, Louis; Richards, Kelvin; Toole, John
2015-04-01
Internal gravity waves in the ocean are closely associated with turbulence and mixing. The relationship between IGWs and turbulence is usually interpreted in the framework of the Garret-Munk model, a prescription for open-ocean internal-wave energy as a function of several environmental parameters. Here, we evaluate the relationship between internal-wave energy and turbulence directly, using more than 250 joint profiles of turbulent dissipation from microstructure, and vertical velocity from CTD/LADCP measurements. The observations include profiles from a wide variety of dynamical regimes and latitudes between the equator and 60°. In most profiles, finescale vertical kinetic energy (VKE) varies as kz-2, where kz is the vertical wave number. Scaling VKE with dissipation collapses all off-equatorial data-set average spectra to within √2 or better. The dissipation-normalized spectrum can be interpreted as a new single-parameter (dissipation) model for internal-wave VKE, which is considerably simpler and more accurate than the corresponding Garrett-Munk model.
Correlation between non-Gaussian statistics of a scalar and its dissipation rate in turbulent flows.
Mi, Jianchun
2006-07-01
This paper reports an experimental study on the correlation between the deviation from Gaussianity of the probability density function (PDF) of a fluctuating scalar and the dependence of the scalar dissipation on the scalar itself in turbulent flows. The study demonstrates that the departure of the scalar PDF from Gaussianity reflects the degree to which the dissipation rate depends statistically on the scalar. Of important significance, present results obtained from wake and jet flows, together with those deduced from previous work on various turbulent flows, appear to point to a generic expression for the total correlation. This expression suggests that the analytical result of O'Brien and Jiang [Phys. Fluids A 3, 3121 (1991)], derived for homogeneous turbulence, should be also valid for inhomogeneous turbulence. That is, the statistical independence of the scalar dissipation and the scalar itself appears to act as the sufficient and necessary condition for the scalar PDF to be Gaussian in any stationary turbulence. It follows that the independence assumption, often used in combustion modeling, is reasonable only in the flow region where the scalar PDF is closely Gaussian.
Energy Dissipation and Landau Damping in Two- and Three-dimensional Plasma Turbulence
NASA Astrophysics Data System (ADS)
Li, Tak Chu; Howes, Gregory G.; Klein, Kristopher G.; TenBarge, Jason M.
2016-12-01
Plasma turbulence is ubiquitous in space and astrophysical plasmas, playing an important role in plasma energization, but the physical mechanisms leading to dissipation of the turbulent energy remain to be definitively identified. Kinetic simulations in two dimensions (2D) have been extensively used to study the dissipation process. How the limitation to 2D affects energy dissipation remains unclear. This work provides a model of comparison between two- and three-dimensional (3D) plasma turbulence using gyrokinetic simulations; it also explores the dynamics of distribution functions during the dissipation process. It is found that both 2D and 3D nonlinear gyrokinetic simulations of a low-beta plasma generate electron velocity-space structures with the same characteristics as that of the linear Landau damping of Alfvén waves in a 3D linear simulation. The continual occurrence of the velocity-space structures throughout the turbulence simulations suggests that the action of Landau damping may be responsible for the turbulent energy transfer to electrons in both 2D and 3D, and makes possible the subsequent irreversible heating of the plasma through collisional smoothing of the velocity-space fluctuations. Although, in the 2D case where variation along the equilibrium magnetic field is absent, it may be expected that Landau damping is not possible, a common trigonometric factor appears in the 2D resonant denominator, leaving the resonance condition unchanged from the 3D case. The evolution of the 2D and 3D cases is qualitatively similar. However, quantitatively, the nonlinear energy cascade and subsequent dissipation is significantly slower in the 2D case.
Plasma Jet Braking: Energy Dissipation and Nonadiabatic Electrons
Khotyaintsev, Yu. V.; Cully, C. M.; Vaivads, A.; Andre, M.; Owen, C. J.
2011-04-22
We report in situ observations by the Cluster spacecraft of wave-particle interactions in a magnetic flux pileup region created by a magnetic reconnection outflow jet in Earth's magnetotail. Two distinct regions of wave activity are identified: lower-hybrid drift waves at the front edge and whistler-mode waves inside the pileup region. The whistler-mode waves are locally generated by the electron temperature anisotropy, and provide evidence for ongoing betatron energization caused by magnetic flux pileup. The whistler-mode waves cause fast pitch-angle scattering of electrons and isotropization of the electron distribution, thus making the flow braking process nonadiabatic. The waves strongly affect the electron dynamics and thus play an important role in the energy conversion chain during plasma jet braking.
Power drainage and energy dissipation in lossy but perfect lenses
NASA Astrophysics Data System (ADS)
Rosenblatt, Gilad; Orenstein, Meir
2017-05-01
It has recently been shown that passive lens designs can retain perfect lensing despite intrinsic loss in the comprising left-handed materials. Here we show that energy conservation is not at odds with the operation of such lossy perfect lenses: The irreversible transfer of electromagnetic power to the lossy material dictates that a smaller portion of the power emitted by the source arrives at the image, but image fidelity remains absolute. Moreover, the power that does arrive at the perfect image must drain from the system there. This is shown to apply to any layered perfect lens based on left-handed media, including the well-known Veselago lens. Combined with what is known about Maxwell's fisheye lens, our results suggest that power drainage is universal to all perfect lenses and is intrinsic to any perfect image. Properly addressing this unique power dynamics is therefore essential to any successful realization of practical perfect lenses with existing metamaterials.
Plasma Jet Braking: Energy Dissipation and Nonadiabatic Electrons
NASA Astrophysics Data System (ADS)
Khotyaintsev, Yu. V.; Cully, C. M.; Vaivads, A.; André, M.; Owen, C. J.
2011-04-01
We report in situ observations by the Cluster spacecraft of wave-particle interactions in a magnetic flux pileup region created by a magnetic reconnection outflow jet in Earth’s magnetotail. Two distinct regions of wave activity are identified: lower-hybrid drift waves at the front edge and whistler-mode waves inside the pileup region. The whistler-mode waves are locally generated by the electron temperature anisotropy, and provide evidence for ongoing betatron energization caused by magnetic flux pileup. The whistler-mode waves cause fast pitch-angle scattering of electrons and isotropization of the electron distribution, thus making the flow braking process nonadiabatic. The waves strongly affect the electron dynamics and thus play an important role in the energy conversion chain during plasma jet braking.
Plasma jet braking: energy dissipation and nonadiabatic electrons.
Khotyaintsev, Yu V; Cully, C M; Vaivads, A; André, M; Owen, C J
2011-04-22
We report in situ observations by the Cluster spacecraft of wave-particle interactions in a magnetic flux pileup region created by a magnetic reconnection outflow jet in Earth's magnetotail. Two distinct regions of wave activity are identified: lower-hybrid drift waves at the front edge and whistler-mode waves inside the pileup region. The whistler-mode waves are locally generated by the electron temperature anisotropy, and provide evidence for ongoing betatron energization caused by magnetic flux pileup. The whistler-mode waves cause fast pitch-angle scattering of electrons and isotropization of the electron distribution, thus making the flow braking process nonadiabatic. The waves strongly affect the electron dynamics and thus play an important role in the energy conversion chain during plasma jet braking.
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.
Chen, Ming; Anderson, Erik; Hill, Geoffrey; Chen, John J; Patrianakos, Thomas
2015-01-01
To compare cumulative dissipated energy between two phacoemulsification machines. An ambulatory surgical center, Honolulu, Hawaii, USA. Retrospective chart review. 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. 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. The Centurion phacoemulsification system required less energy to remove a cataractous lens in comparison to the Infiniti phacoemulsification system.
Experimental study of breaking and energy dissipation in surface waves
NASA Astrophysics Data System (ADS)
Ruiz Chavarria, Gerardo; Le Gal, Patrice; Le Bars, Michael
2014-11-01
We present an experimental study of the evolution of monochromatic waves produced by a parabolic wave maker. Because of the parabolic shape of the wave front, the waves exhibit spatial focusing and their amplitude dramatically increases over distances of a few wavelengths. Unlike linear waves, the amplitude of the free surface deformation cannot exceed a certain threshold and when this happens the waves break. In order to give a criterion for the appearance of breaking, we calculate the steepness defined as ɛ = H/ λ (where H is the wave height and λ their wavelength) for waves of frequencies in the range 4-10 Hz. We found that wave breaking develops when ɛ attains approximately a value of 0.10. We also evaluate the lost of energy carried by the waves during their breaking by a detailed and accurate measurement of their amplitude using an optical Fourier transform profilometry. G. Ruiz Chavarria acknowledges DGAPA-UNAM by support under Project IN 116312 (Vorticidad y ondas no lineales en fluidos).
NASA Astrophysics Data System (ADS)
Hibiya, Toshiyuki; Furuichi, Naoki; Robertson, Robin
2012-12-01
Shear-based and/or strain-based fine-scale parameterizations of turbulent dissipation rates in the deep ocean become erroneous near topographic features where internal wave spectra deviate from Garrett-Munk (GM). Although the Gregg-Henyey-Polzin (GHP) parameterization incorporates this spectral deviation, the applicability remains uncertain. We evaluate “α” and “β” representing the local internal wave energy in the high frequency (2f < ω < N) and low frequency (f < ω < 2f) bands, respectively, scaled by their corresponding values in GM using fine-scale vertical shear and strain simultaneously measured near mixing hotspots. The local internal wave spectra are biased toward higher frequencies (α/β ≫ 1) over rough bathymetry where high frequency internal waves are generated, whereas they are biased toward lower frequencies (α/β ≪ 1) at latitudes where high vertical wavenumber, near-inertial shears are created by parametric subharmonic instabilities. Compared with the shear-based and/or strain-based parameterizations, GHP more accurately estimates turbulent dissipation rates by compensating for deviations from GM.
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.
NASA Astrophysics Data System (ADS)
Steenkamp, Joalet Dalene; Hockaday, Christopher James; Gous, Johan Petrus; Nzima, Thabo Witness
2017-09-01
Submerged-arc furnace technology is applied in the primary production of ferroalloys. Electrical energy is dissipated to the process via a combination of arcing and resistive heating. In processes where a crater forms between the charge zone and the reaction zone, electrical energy is dissipated mainly through arcing, e.g., in coke-bed based processes, through resistive heating. Plant-based measurements from a device called "Arcmon" indicated that in silicomanganese (SiMn) production, at times up to 15% of the electrical energy used is transferred by arcing, 30% in high-carbon ferromanganese (HCFeMn) production, compared with 5% in ferrochromium and 60% in ferrosilicon production. On average, the arcing is much less at 3% in SiMn and 5% in HCFeMn production.
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.
NASA Astrophysics Data System (ADS)
Steenkamp, Joalet Dalene; Hockaday, Christopher James; Gous, Johan Petrus; Nzima, Thabo Witness
2017-06-01
Submerged-arc furnace technology is applied in the primary production of ferroalloys. Electrical energy is dissipated to the process via a combination of arcing and resistive heating. In processes where a crater forms between the charge zone and the reaction zone, electrical energy is dissipated mainly through arcing, e.g., in coke-bed based processes, through resistive heating. Plant-based measurements from a device called "Arcmon" indicated that in silicomanganese (SiMn) production, at times up to 15% of the electrical energy used is transferred by arcing, 30% in high-carbon ferromanganese (HCFeMn) production, compared with 5% in ferrochromium and 60% in ferrosilicon production. On average, the arcing is much less at 3% in SiMn and 5% in HCFeMn production.
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.
Mechanical energy transfer and dissipation in fibrous beta-sheet-rich proteins
NASA Astrophysics Data System (ADS)
Xu, Zhiping; Buehler, Markus J.
2010-06-01
Mechanical properties of structural protein materials are crucial for our understanding of biological processes and disease states. Through utilization of molecular simulation based on stress wave tracking, we investigate mechanical energy transfer processes in fibrous beta-sheet-rich proteins that consist of highly ordered hydrogen bond (H-bond) networks. By investigating four model proteins including two morphologies of amyloids, beta solenoids, and silk beta-sheet nanocrystals, we find that all beta-sheet-rich protein fibrils provide outstanding elastic moduli, where the silk nanocrystal reaches the highest value of ≈40GPa . However, their capacities to dissipate mechanical energy differ significantly and are controlled strongly by the underlying molecular structure of H-bond network. Notably, silk beta-sheet nanocrystals feature a ten times higher energy damping coefficient than others, owing to flexible intrastrand motions in the transverse directions. The results demonstrate a unique feature of silk nanocrystals, their capacity to simultaneously provide extreme stiffness and energy dissipation capacity. Our results could help one to explain the remarkable properties of silks from an atomistic and molecular perspective, in particular its great toughness and energy dissipation capacity, and may enable the design of multifunctional nanomaterials with outstanding stiffness, strength, and impact resistance.
Mechanical energy transfer and dissipation in fibrous beta-sheet-rich proteins.
Xu, Zhiping; Buehler, Markus J
2010-06-01
Mechanical properties of structural protein materials are crucial for our understanding of biological processes and disease states. Through utilization of molecular simulation based on stress wave tracking, we investigate mechanical energy transfer processes in fibrous beta-sheet-rich proteins that consist of highly ordered hydrogen bond (H-bond) networks. By investigating four model proteins including two morphologies of amyloids, beta solenoids, and silk beta-sheet nanocrystals, we find that all beta-sheet-rich protein fibrils provide outstanding elastic moduli, where the silk nanocrystal reaches the highest value of ≈40 GPa. However, their capacities to dissipate mechanical energy differ significantly and are controlled strongly by the underlying molecular structure of H-bond network. Notably, silk beta-sheet nanocrystals feature a ten times higher energy damping coefficient than others, owing to flexible intrastrand motions in the transverse directions. The results demonstrate a unique feature of silk nanocrystals, their capacity to simultaneously provide extreme stiffness and energy dissipation capacity. Our results could help one to explain the remarkable properties of silks from an atomistic and molecular perspective, in particular its great toughness and energy dissipation capacity, and may enable the design of multifunctional nanomaterials with outstanding stiffness, strength, and impact resistance.
Heber, Ulrich; Soni, Vineet; Strasser, Reto J
2011-05-01
During desiccation, fluorescence emission and stable light-dependent charge separation in the reaction centers (RCs) of photosystem II (PSII) declined strongly in three different lichens: in Parmelia sulcata with an alga as the photobiont, in Peltigera neckeri with a cyanobacterium and in the tripartite lichen Lobaria pulmonaria. Most of the decline of fluorescence was caused by a decrease in the quantum efficiency of fluorescence emission. It indicated the activation of photoprotective thermal energy dissipation. Photochemical activity of the RCs was retained even after complete desiccation. It led to light-dependent absorption changes and found expression in reversible increases in fluorescence or in fluorescence quenching. Lowering the temperature changed the direction of fluorescence responses in P. sulcata. The observations are interpreted to show that reversible light-induced increases in fluorescence emission in desiccated lichens indicate the functionality of the RCs of PSII. Photoprotection is achieved by the drainage of light energy to dissipating centers outside the RCs before stable charge separation can take place. Reversible quenching of fluorescence by strong illumination is suggested to indicate the conversion of the RCs from energy conserving to energy dissipating units. This permits them to avoid photoinactivation. On hydration, re-conversion occurs to energy-conserving RCs. Copyright © Physiologia Plantarum 2010.
NASA Astrophysics Data System (ADS)
Akopian, Samvel Ts.
2015-06-01
A concept of seismic system (SS), which is responsible for the preparation of an ensemble of strong earthquakes, is considered as an open dissipative system exchanging energy and entropy with the environment. Open dissipative SS allow one to describe the equilibrium and non-equilibrium states of SS, and the lithosphere evolution under different plate tectonic settings on the basis of seismostatistics. Several new seismic parameters (`seismic temperature', `seismic time', dissipation function, efficiency, inelastic energy, dynamical probability) are defined and proposed for better understanding and describing the dynamical processes. The Sakhalin SS is considered to illustrate the behaviour of proposed parameters. By analogy to Liouville's equation in thermodynamics, it is shown that there is no criterion of instability in the domain where the Gutenberg-Richter law is true. In the proposed approach, the instability origination and the formation of seismogenic structures in the lithosphere are based on the energy versus information entropy power law; the existence of `time arrow' also proceeds from such a dependence. Application of energy and trajectory diagrams enables to describe the preparation of strong earthquakes within an ensemble in terms of slow and fast timescales. These diagrams help perform the spatiotemporal-energy monitoring of the instability origination in the lithosphere. It is shown that the information entropy parameter can serve as a measure of the unknown external energy flow into the system (this energy is supplied for the elastic radiation energy in the earthquake sources and for inelastic processes in the system volume). The property of the ensemble of strong earthquakes is periodically to restore the SS equilibrium state that enables to describe the SS energy balance. The results offer possibilities to estimate the fraction of inelastic energy released by the SS medium during the preparation and occurrence of seismic catastrophes. The
Kopecky, J; Azarkovich, M; Pfündel, E E; Shuvalov, V A; Heber, U
2005-03-01
Modulated chlorophyll fluorescence was used to compare dissipation of light energy as heat in photosystem II of homoiohydric and poikilohydric photosynthetic organisms which were either hydrated or dehydrated. In hydrated chlorolichens with an alga as the photobiont, fluorescence quenching revealed a dominant mechanism of energy dissipation which was based on a protonation reaction when zeaxanthin was present. CO2 was effective as a weak protonating agent and actinic light was not necessary. In a hydrated cyanobacterial lichen, protonation by CO2 was ineffective to initiate energy dissipation. This was also true for leaves of higher plants. Thus, regulation of zeaxanthin-dependent energy dissipation by protonation was different in leaves and in chlorolichens. A mechanism of energy dissipation different from that based on zeaxanthin became apparent on dehydration of both lichens and leaves. Quenching of maximum or Fm fluorescence increased strongly during dehydration. In lichens, this was also true for so-called basal or Fo fluorescence. In contrast to zeaxanthin-dependent quenching, dehydration-induced quenching could not be inhibited by dithiothreitol. Both zeaxanthin-dependent and dehydration-induced quenching cooperated in chlorolichens to increase thermal dissipation of light energy if desiccation occurred in the light. In cyanolichens, which do not possess a zeaxanthin cycle, only desiccation-induced thermal energy dissipation was active in the dry state. Fluorescence emission spectra of chlorolichens revealed stronger desiccation-induced suppression of 685-nm fluorescence than of 720-nm fluorescence. In agreement with earlier reports of , fluorescence excitation data showed that desiccation reduced flow of excitation energy from chlorophyll b of the light harvesting complex II to emitting centres more than flow from chlorophyll a of core pigments. The data are discussed in relation to regulation and localization of thermal energy dissipation mechanisms. It is
Yeow, C H; Lee, P V S; Goh, J C H
2009-08-25
Lack of the necessary magnitude of energy dissipation by lower extremity joint muscles may be implicated in elevated impact stresses present during landing from greater heights. These increased stresses are experienced by supporting tissues like cartilage, ligaments and bones, thus aggravating injury risk. This study sought to investigate frontal plane kinematics, kinetics and energetics of lower extremity joints during landing from different heights. Eighteen male recreational athletes were instructed to perform drop-landing tasks from 0.3- to 0.6-m heights. Force plates and motion-capture system were used to capture ground reaction force and kinematics data, respectively. Joint moment was calculated using inverse dynamics. Joint power was computed as a product of joint moment and angular velocity. Work was defined as joint power integrated over time. Hip and knee joints delivered significantly greater joint power and eccentric work (p<0.05) than the ankle joint at both landing heights. Substantial increase (p<0.05) in eccentric work was noted at the hip joint in response to increasing landing height. Knee and hip joints acted as key contributors to total energy dissipation in the frontal plane with increase in peak ground reaction force (GRF). The hip joint was the top contributor to energy absorption, which indicated a hip-dominant strategy in the frontal plane in response to peak GRF during landing. Future studies should investigate joint motions that can maximize energy dissipation or reduce the need for energy dissipation in the frontal plane at the various joints, and to evaluate their effects on the attenuation of lower extremity injury risk during landing.
NASA Astrophysics Data System (ADS)
Glasgow, Scott Alan; Corson, John; Verhaaren, Chris
2010-07-01
Free energies of dissipative media are reviewed. Then we use free-energy-optimal excitation and de-excitation fields to generate a dielectric’s time-reversal spectrum, with several properties: a) The spectrum generalizes the time-reversal parity from “even” and “odd” of conservative systems to an interval [-1,+1] of “time-reversal eigenvalues” λ in dissipative media. b) It yields eigenmodes that are complete: any state of the medium is optimally excitable or de-excitable by them. c) These excitations are orthogonal with respect to the work function of the medium and, so, d) characterize field excitations for the given medium that, when superimposed, only do work on the medium, not on each other via the medium-field interaction mechanism. Notions of en masse potential and kinetic energy in the dissipative medium arise through even (λ=+1) and odd (λ=-1) parity, but also other energy notions via alternative parity (|λ|<1) under time reversal.
The energy dissipative mechanisms of the particle-fiber interface in a textile composite
NASA Astrophysics Data System (ADS)
McAllister, Quinn Patrick
Impact resistant fabrics comprised of woven high performance fibers (e.g., Kevlar) have exhibited improved energy dissipative capability with the inclusion of nano- to micrometer sized particles. Upon impact, the particles embed and gouge adjacent fiber surfaces. While the particle-fiber interactions appear to be a primary mechanism for the increase in energy dissipation, the fundamentals of the nano- to micrometer sized gouging response of high performance fibers and the dissipation of energy due to particle gouging have not been studied previously. In this research, nanoindentation and nanoscratching techniques, which exploit probe sizes in the range of nano- to micrometers, were used to study the particle-fiber contact and develop nanoscale structure-property relationships of single Kevlar fibers. Atomic force microscopy based methods were used to create high resolution stiffness maps of fiber cross-sections, the results of which indicated that the stiffness of Kevlar 49 fibers is independent of radial position, while Kevlar KM2 fibers exhibit a reduced stiffness "shell" region (up to ˜300-350 nm thick). Instrumented indentation was used to evaluate the local response of Kevlar fibers with respect to orientation and contact size. For radial indentation, modifications to the traditional indentation analysis were developed to account for fiber curvature and finite size effects. A critical contact size was established above which the fiber response was independent of indenter size. This "homogeneous" response was used to estimate the local material properties of the Kevlar fibers through the application of an analytical model for indentation of a transversely isotropic material. The local properties of both fibers differed from their previously measured bulk properties, which was likely due, at least in part, to the deformation mechanisms of the fiber microstructure during indentation. Nanoindentation and nanoscratch tests were then conducted to study the
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.
Lane-changing behavior and its effect on energy dissipation using full velocity difference model
NASA Astrophysics Data System (ADS)
Wang, Jian; Ding, Jian-Xun; Shi, Qin; Kühne, Reinhart D.
2016-07-01
In real urban traffic, roadways are usually multilane with lane-specific velocity limits. Most previous researches are derived from single-lane car-following theory which in the past years has been extensively investigated and applied. In this paper, we extend the continuous single-lane car-following model (full velocity difference model) to simulate the three-lane-changing behavior on an urban roadway which consists of three lanes. To meet incentive and security requirements, a comprehensive lane-changing rule set is constructed, taking safety distance and velocity difference into consideration and setting lane-specific speed restriction for each lane. We also investigate the effect of lane-changing behavior on distribution of cars, velocity, headway, fundamental diagram of traffic and energy dissipation. Simulation results have demonstrated asymmetric lane-changing “attraction” on changeable lane-specific speed-limited roadway, which leads to dramatically increasing energy dissipation.
Dissipation of Energy by Dry Granular Matter in a Rotating Cylinder
NASA Astrophysics Data System (ADS)
Sack, Achim; Pöschel, Thorsten
2016-06-01
We study experimentally the dissipation of energy in a rotating cylinder which is partially filled by granular material. We consider the range of angular velocity corresponding to continous and stationary flow of the granulate. In this regime, the stationary state depends on the angular velocity and on the filling mass. For a wide interval of filling levels we find a universal behavior of the driving torque required to sustain the stationary state as a function of the angular velocity. The result may be of relevance to industrial applications, e.g. to understand the power consumption of ball mills or rotary kilns and also for damping applications where mechanical energy has to be dissipated in a controlled way.
Determination of energy dissipation of a spider silk structure under impulsive loading
NASA Astrophysics Data System (ADS)
Alencastre, Jorge; Mago, Carlos; Rivera, Richard
2015-09-01
Various researches and studies have demonstrated that spider silk is much stronger and more deformable than a steel string of the same diameter from a mechanical approach. These excellent properties have caused many scientific disciplines to get involved, such as bio-mechanics, bio-materials and bio-mimetics, in order to create a material of similar properties and characteristics. It should be noted that the researches and studies have been oriented mainly as a quasi-static model. For this research, the analysis has taken a dynamic approach and determined the dissipation energy of a structure which is made of spider silk "Dragline" and produced by the Argiope-Argentata spider, through an analytical-experimental way, when being subjected to impulsive loading. Both experimental and analytical results, the latter obtained by using adjusted models, have given high levels of dissipation energy during the first cycle of vibration, which are consistent with the values suggested by other authors.
a Minimum Energy Dissipation Model for River Networks and Their Associated Topographies
NASA Astrophysics Data System (ADS)
Sun, T.; Meakin, P.; JØSsang, T.
The model for the river networks presented here is based on minimum energy dissipation principles. The foundation for this model is the empirical relationship s ~ Qα between the link slope s in channel networks and the mean annual discharge Q in that link. The associated landscapes were constructed using a range of values for the exponent α. The surfaces appear to be more complex than simple self-affine fractals. The boundaries of drainage basins covering the entire drainage area were found to have an effective fractal dimension about 1.10 for all values of α in the range - 1 < α < 0. A universal power-law size (area) distribution is also found for the drainage basins obtained from this minimum energy dissipation model.
Dissipation of Energy by Dry Granular Matter in a Rotating Cylinder
Sack, Achim; Pöschel, Thorsten
2016-01-01
We study experimentally the dissipation of energy in a rotating cylinder which is partially filled by granular material. We consider the range of angular velocity corresponding to continous and stationary flow of the granulate. In this regime, the stationary state depends on the angular velocity and on the filling mass. For a wide interval of filling levels we find a universal behavior of the driving torque required to sustain the stationary state as a function of the angular velocity. The result may be of relevance to industrial applications, e.g. to understand the power consumption of ball mills or rotary kilns and also for damping applications where mechanical energy has to be dissipated in a controlled way. PMID:27255925
Zhou Fulin; Tan Ping; Cui Jie; Xian Qiaoling; Wei Lushun; Huang Dongyang
2008-07-08
This paper briefly introduces the recent research, testing analysis, design and application on seismic isolation, energy dissipation, tuned mass damper and active control for buildings and bridges in mainland China. Paper introduces some typical researches, testing and analysis, including the mechanical tests for bearings and control devices, and the shaking table tests for structural models with different control systems. Paper also introduces the Chinese design codes for structures with seismic isolation and energy dissipation. Paper describes the recent application status and typical examples, especially introduces the largest isolation buildings group in the world, and the using passive and semi active control for structures. Also the paper makes discussion some problems existed on passive and active control technique now and the tendency of development on seismic control in future.
Zhang, Yanwen; Stocks, George 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.
2015-10-28
A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel to binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.
NASA Astrophysics Data System (ADS)
Zilletti, Michele; Elliott, Stephen J.; Rustighi, Emiliano
2012-08-01
The tuning of a dynamic vibration absorber is considered such that either the kinetic energy of the host structure is minimised or the power dissipation within the absorber is maximised. If the host structure is approximated as a damped single degree of freedom, the optimal values for the ratio of the absorber's natural frequency to the host structure and the optimal damping ratio of the absorber are shown to be the same whether the kinetic energy of the host structure is minimised or the power dissipation of the absorber is maximised. It is also demonstrated that the total power input into the system does not depend on the two parameters but only on the host structure's mass.
Dissipation of Energy by Dry Granular Matter in a Rotating Cylinder.
Sack, Achim; Pöschel, Thorsten
2016-06-03
We study experimentally the dissipation of energy in a rotating cylinder which is partially filled by granular material. We consider the range of angular velocity corresponding to continous and stationary flow of the granulate. In this regime, the stationary state depends on the angular velocity and on the filling mass. For a wide interval of filling levels we find a universal behavior of the driving torque required to sustain the stationary state as a function of the angular velocity. The result may be of relevance to industrial applications, e.g. to understand the power consumption of ball mills or rotary kilns and also for damping applications where mechanical energy has to be dissipated in a controlled way.
Energy dissipation by whistler turbulence: Three-dimensional particle-in-cell simulations
Chang, Ouliang; Peter Gary, S.; Wang, Joseph
2014-05-15
Three-dimensional particle-in-cell simulations of whistler turbulence are carried out on a collisionless, homogeneous, magnetized plasma model. The simulations use an initial ensemble of relatively long wavelength whistler modes and follow the temporal evolution of the fluctuations as they cascade into a broadband, anisotropic, turbulent spectrum at shorter wavelengths. For relatively small levels of the initial fluctuation energy ϵ{sub e}, linear collisionless damping provides most of the dissipation of the turbulence. But as ϵ{sub e} and the total dissipation increase, linear damping becomes less important and, especially at β{sub e} ≪ 1, nonlinear processes become stronger. The PDFs and kurtoses of the magnetic field increments in the simulations suggest that intermittency in whistler turbulence generally increases with increasing ϵ{sub e} and β{sub e}. Correlation coefficient calculations imply that the current structure dissipation also increases with increasing ϵ{sub e} and β{sub e}, and that the nonlinear dissipation processes in these simulations are primarily associated with regions of localized current structures.
Wang, Xiuguo; Xiang, Zhenbo; Yan, Xiaoyang; Sun, Huiqing; Li, Yiqiang; Pan, Canping
2013-08-01
A two-year field experiment was conducted in two different locations to investigate the dissipation rate and residual fate of thiamethoxam in tobacco leaves and soil by high performance liquid chromatography with UV detection. The average recoveries for green, cured tobacco leaves and soil ranged from 89.7 %-94.8 %, 90.6 %-94.4 % and 89.0%-92.8 %, respectively, with relative standard deviations between 2.7 % and 9.2 %. The dissipation rates of thiamethoxam were described by first-order kinetics and its half-life values were in the range of 3.9-4.4 days in green tobacco leaves and 12.0-19.1 days in soil, respectively. The residue levels of thiamethoxam at harvest time ranged from 0.020-0.541 mg/kg in cured tobacco leaves, and 0.005-0.019 mg/kg in soil, respectively.
Frank, H.A.; Cua, A.; Young, A.; Gosztola, D.; Wasielewski, M.R.
1994-09-01
Understanding the way in which excess solar energy is dissipated by photosynthetic membranes under high light stress is a major problem in photosynthesis studies. This paper reports femtosecond time-resolved, fast-transient optical spectroscopic analyses of three important xanthophylls: violaxanthin, antheraxanthin, zeoaxanthin. The results support the notion that the enzymatic reactions that interconvert these xanthophylls act as a kind of ``molecular gear shift`` controlling whether the molecules function as light-harvesting pigments performing forward energy transfer or as fluorescence quenchers performing reverse energy transfer.
Diameter-dependent dissipation of vibration energy of cantilevered multiwall carbon nanotubes.
Sawaya, Shintaro; Arie, Takayuki; Akita, Seiji
2011-04-22
This study investigated the mechanical properties of vibrating cantilevered multiwall carbon nanotubes in terms of energy loss in a vibrating nanotube. Young's moduli of the nanotubes show a clear dependence of the perfection of the sp(2) carbon network, as determined from Raman spectroscopy. The energy loss corresponding to the inverse of the quality factor increases with increasing tube diameter, although the nanotube maintains high mechanical strength around 0.5 TPa. This fact implies that the vibration energy is dissipated mainly not by defects, but by van der Waals interactions between walls.
Homman, Ahmed-Amine; Maillet, Jean-Bernard; Roussel, Julien; Stoltz, Gabriel
2016-01-14
This work presents new parallelizable numerical schemes for the integration of dissipative particle dynamics with energy conservation. So far, no numerical scheme introduced in the literature is able to correctly preserve the energy over long times and give rise to small errors on average properties for moderately small time steps, while being straightforwardly parallelizable. We present in this article two new methods, both straightforwardly parallelizable, allowing to correctly preserve the total energy of the system. We illustrate the accuracy and performance of these new schemes both on equilibrium and nonequilibrium parallel simulations.
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.
NASA Astrophysics Data System (ADS)
Retinò, Alessandro
2016-04-01
The Universe is permeated by hot, turbulent magnetized plasmas. They are found in active galactic nuclei, supernova remnants, the intergalactic and interstellar medium, as well as in the solar corona, the solar wind and the Earth's magnetosphere. Turbulent plasmas are also found in laboratory devices such as e.g. tokamaks. Our comprehension of the plasma Universe is largely based on measurements of electromagnetic radiation such as light or X-rays which originate from particles that are heated and accelerated as a result of energy dissipation in turbulent environments. Therefore it is of key importance to study and understand how plasma is energized by turbulence. Most of the energy dissipation occurs at kinetic scales, where plasma no longer behaves as a fluid and the properties of individual plasma species (electrons, protons and other ions) become important. THOR (Turbulent Heating ObserveR - http://thor.irfu.se/) is a space mission currently in Study Phase as candidate for M-class mission within the Cosmic Vision program of the European Space Agency. The scientific theme of the THOR mission is turbulent energy dissipation and particle energization in space plasmas, which ties in with ESA's Cosmic Vision science. The main focus is on turbulence and shock processes, however areas where the different fundamental processes interact, such as reconnection in turbulence or shock generated turbulence, are also of high importance. The THOR mission aims to address fundamental questions such as how plasma is heated and particles are accelerated by turbulent fluctuations at kinetic scales, how energy is partitioned among different plasma components and how dissipation operates in different regimes of turbulence. To reach the goal, a careful design of the THOR spacecraft and its payload is ongoing, together with a strong interaction with numerical simulations. Here we present the science of THOR mission and we discuss implications of THOR observations for space
NASA Astrophysics Data System (ADS)
Sakai, Y.; Nakajima, M.; Hasegawa, J.; Kikuchi, T.; Horioka, K.
2016-03-01
Beam behavior during longitudinal bunch compression of charged particles was investigated using a compact simulator device based on electron beams. Beam current waveforms and bunch compression ratios were measured as a function of the initial beam current. We found that the current waveform became blunt and the compression ratio degraded at higher beam currents. These results indicate that space-charge fields dissipate the kinetic energy of beam particles.
Chaudhuri, Swetaprovo; Kolla, Hemanth; Dave, Himanshu L.; ...
2017-07-07
The flame structure corresponding to lean hydrogen–air premixed flames in intense sheared turbulence in the thin reaction zone regime is quantified from flame thickness and conditional scalar dissipation rate statistics, obtained from recent direct numerical simulation data of premixed temporally-evolving turbulent slot jet flames. It is found that, on average, these sheared turbulent flames are thinner than their corresponding planar laminar flames. Extensive analysis is performed to identify the reason for this counter-intuitive thinning effect. The factors controlling the flame thickness are analyzed through two different routes i.e., the kinematic route, and the transport and chemical kinetics route. The kinematicmore » route is examined by comparing the statistics of the normal strain rate due to fluid motion with the statistics of the normal strain rate due to varying flame displacement speed or self-propagation. It is found that while the fluid normal straining is positive and tends to separate iso-scalar surfaces, the dominating normal strain rate due to self-propagation is negative and tends to bring the iso-scalar surfaces closer resulting in overall thinning of the flame. The transport and chemical kinetics route is examined by studying the non-unity Lewis number effect on the premixed flames. The effects from the kinematic route are found to couple with the transport and chemical kinetics route. In addition, the intermittency of the conditional scalar dissipation rate is also examined. It is found to exhibit a unique non-monotonicity of the exponent of the stretched exponential function, conventionally used to describe probability density function tails of such variables. As a result, the non-monotonicity is attributed to the detailed chemical structure of hydrogen-air flames in which heat release occurs close to the unburnt reactants at near free-stream temperatures.« less
Heber, Ulrich
2012-09-01
Conservation of light energy in photosynthesis is possible only in hydrated photoautotrophs. It requires complex biochemistry and is limited in capacity. Charge separation in reaction centres of photosystem II initiates energy conservation but opens also the path to photooxidative damage. A main mechanism of photoprotection active in hydrated photoautotrophs is controlled by light. This is achieved by coupling light flux to the protonation of a special thylakoid protein which activates thermal energy dissipation. This mechanism facilitates the simultaneous occurrence of energy conservation and energy dissipation but cannot completely prevent damage by light. Continuous metabolic repair is required to compensate damage. More efficient photoprotection is needed by desiccation-tolerant photoautotrophs. Loss of water during desiccation activates ultra-fast energy dissipation in mosses and lichens. Desiccation-induced energy dissipation neither requires a protonation reaction nor light but photoprotection often increases when light is present during desiccation. Two different mechanisms contribute to photoprotection of desiccated photoautotrophs. One facilitates energy dissipation in the antenna of photosystem II which is faster than energy capture by functional reaction centres. When this is insufficient for full photoprotection, the other one permits energy dissipation in the reaction centres themselves.
Laboratory Study of surface-gravity wave energy dissipation due to breaking.
NASA Astrophysics Data System (ADS)
Savelyev, I.; Donelan, M.; Haus, B.; Slinn, D.
2006-12-01
Detailed quantitative analysis of wave energy dissipation is required for air-sea interaction modeling. The main mechanism of wave energy dissipation - wave breaking - is poorly studied because of the lack of theoretical and experimental techniques needed for such complex phenomena. In the University of Miami an Air-Sea Interaction Sea-Water Tank was constructed to study processes on air- sea interface using the most modern experimental techniques. That includes wind tunnel (0-25 m/s); programmable wave-maker; water temperature control; water current control; turbulence instrumentation including: hot-film anemometry; particle image velocimetry; wave instrumentation including: laser slope and height gauges; capacitance height gauges; two-dimensional slope-imaging devices, etc. Using these techniques, the fine structure of breaking waves was studied. In order for phenomena to be reproducible, a breaking wave was created by a paddle using a `wave focusing' technique with no wind forcing. Three dimensional velocity vectors in the vertical plane were obtained with 1 mm resolution. Experimental results were compared with existing models, such as direct numerical simulation and an exactly solved linear problem with similar boundary and initial conditions. Turbulent components of water motion velocities during wave breaking were separated and the turbulent kinetic energy distribution and dissipation dynamics was studied.
NASA Astrophysics Data System (ADS)
Zhang, Wen-Ming; Yan, Han; Jiang, Hui-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang
2016-04-01
In this paper, the dynamics of suspended microchannel resonators which convey internal flows with opposite directions are investigated. The fluid-structure interactions between the laminar fluid flow and oscillating cantilever are analyzed by comprehensively considering the effects of velocity profile, flow viscosity and added flowing particle. A new model is developed to characterize the dynamic behavior of suspended microchannel resonators with the fluid-structure interactions. The stability, frequency shift and energy dissipation of suspended microchannel resonators are analyzed and discussed. The results demonstrate that the frequency shifts induced by the added flowing particle which are obtained from the new model have a good agreement with the experimental data. The steady mean flow can cause the frequency shift and influence the stability of the dynamic system. As the flow velocity reaches the critical value, the coupled-mode flutter occurs via a Hamiltonian Hopf bifurcation. The perturbation flow resulted from the vibration of the microcantilever leads to energy dissipation, while the steady flow does not directly cause the damping which increases with the increasing of the flow velocity predicted by the classical model. It can also be found that the steady flow firstly changes the mode shape of the cantilever and consequently affects the energy dissipation.
Li, Ling; Ortiz, Christine
2014-05-01
Hierarchical composite materials design in biological exoskeletons achieves penetration resistance through a variety of energy-dissipating mechanisms while simultaneously balancing the need for damage localization to avoid compromising the mechanical integrity of the entire structure and to maintain multi-hit capability. Here, we show that the shell of the bivalve Placuna placenta (~99 wt% calcite), which possesses the unique optical property of ~80% total transmission of visible light, simultaneously achieves penetration resistance and deformation localization via increasing energy dissipation density (0.290 ± 0.072 nJ μm(-3)) by approximately an order of magnitude relative to single-crystal geological calcite (0.034 ± 0.013 nJ μm(-3)). P. placenta, which is composed of a layered assembly of elongated diamond-shaped calcite crystals, undergoes pervasive nanoscale deformation twinning (width ~50 nm) surrounding the penetration zone, which catalyses a series of additional inelastic energy dissipating mechanisms such as interfacial and intracrystalline nanocracking, viscoplastic stretching of interfacial organic material, and nanograin formation and reorientation.
NASA Astrophysics Data System (ADS)
Li, Ling; Ortiz, Christine
2014-05-01
Hierarchical composite materials design in biological exoskeletons achieves penetration resistance through a variety of energy-dissipating mechanisms while simultaneously balancing the need for damage localization to avoid compromising the mechanical integrity of the entire structure and to maintain multi-hit capability. Here, we show that the shell of the bivalve Placuna placenta (~99 wt% calcite), which possesses the unique optical property of ~80% total transmission of visible light, simultaneously achieves penetration resistance and deformation localization via increasing energy dissipation density (0.290 ± 0.072 nJ μm-3) by approximately an order of magnitude relative to single-crystal geological calcite (0.034 ± 0.013 nJ μm-3). P. placenta, which is composed of a layered assembly of elongated diamond-shaped calcite crystals, undergoes pervasive nanoscale deformation twinning (width ~50 nm) surrounding the penetration zone, which catalyses a series of additional inelastic energy dissipating mechanisms such as interfacial and intracrystalline nanocracking, viscoplastic stretching of interfacial organic material, and nanograin formation and reorientation.
Aspinall-O'Dea, Mark; Wentworth, Mark; Pascal, Andy; Robert, Bruno; Ruban, Alexander; Horton, Peter
2002-12-10
Dissipation of excess light energy in plant photosynthetic membranes plays an important role in the response of plants to the environment, providing short-term balancing between the intensity of sunlight and photosynthetic capacity. The carotenoid zeaxanthin and the photosystem II subunit PsbS play vital roles in this process, but the mechanism of their action is largely unexplained. Here we report that the isolated photosystem II subunit PsbS was able to bind exogenous zeaxanthin, the binding resulting in a strong red shift in the absorption spectrum, and the appearance of characteristic features in the resonance Raman spectrum and a distinct circular dichroism spectrum, indicating pigment-protein, as well as specific pigment-pigment, interaction. A strong shift in the absorption spectrum of PsbS phenylalanine residues after zeaxanthin binding was observed. It is concluded that zeaxanthin binding to PsbS is the origin of the well known energy dissipation-related 535-nm absorption change that we showed in vivo to arise from activation of 1-2 molecules of this pigment. The altered properties of zeaxanthin and PsbS that result from this interaction provide the first direct indication about how they regulate energy dissipation.
NASA Astrophysics Data System (ADS)
Ding, Guoliang; Santare, Michael H.; Karlsson, Anette M.; Kusoglu, Ahmet
2016-06-01
Understanding the mechanisms of growth of defects in polymer electrolyte membrane (PEM) fuel cells is essential for improving cell longevity. Characterizing the crack growth in PEM fuel cell membrane under relative humidity (RH) cycling is an important step towards establishing strategies essential for developing more durable membrane electrode assemblies (MEA). In this study, a crack propagation criterion based on plastically dissipated energy is investigated numerically. The accumulation of plastically dissipated energy under cyclical RH loading ahead of the crack tip is calculated and compared to a critical value, presumed to be a material parameter. Once the accumulation reaches the critical value, the crack propagates via a node release algorithm. From the literature, it is well established experimentally that membranes reinforced with expanded polytetrafluoroethylene (ePTFE) reinforced perfluorosulfonic acid (PFSA) have better durability than unreinforced membranes, and through-thickness cracks are generally found under the flow channel regions but not land regions in unreinforced PFSA membranes. We show that the proposed plastically dissipated energy criterion captures these experimental observations and provides a framework for investigating failure mechanisms in ionomer membranes subjected to similar environmental loads.
2016-06-01
post-fire energy 15. NUMBER OF PAGES 79 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT Unclassified 18. SECURITY CLASSIFICATION OF...RAILGUN POWER SUPPLY ARCHITECTURES TO QUANTIFY THE ENERGY DISSIPATED AFTER THE PROJECTILE LEAVES THE RAILGUN by Mitchell C. Stewart June...SUPPLY ARCHITECTURES TO QUANTIFY THE ENERGY DISSIPATED AFTER THE PROJECTILE LEAVES THE RAILGUN 5. FUNDING NUMBERS 6. AUTHOR(S) Mitchell C
Borovsky, J.E.
1998-05-01
In this report, several lightning-channel parameters are calculated with the aid of an electrodynamic model of lightning. The electrodynamic model describes dart leaders and return strokes as electromagnetic waves that are guided along conducting lightning channels. According to the model, electrostatic energy is delivered to the channel by a leader, where it is stored around the outside of the channel; subsequently, the return stroke dissipates this locally stored energy. In this report this lightning-energy-flow scenario is developed further. Then the energy dissipated per unit length in lightning channels is calculated, where this quantity is now related to the linear charge density on the channel, not to the cloud-to-ground electrostatic potential difference. Energy conservation is then used to calculate the radii of lightning channels: their initial radii at the onset of return strokes and their final radii after the channels have pressure expanded. Finally, the risetimes for channel heating during return strokes are calculated by defining an energy-storage radius around the channel and by estimating the radial velocity of energy flow toward the channel during a return stroke. In three appendices, values for the linear charge densities on lightning channels are calculated, estimates of the total length of branch channels are obtained, and values for the cloud-to-ground electrostatic potential difference are estimated. {copyright} 1998 American Geophysical Union
Energy Input and Dissipation in the Ionosphere-Thermosphere (IT) System
NASA Astrophysics Data System (ADS)
Huang, C. Y.; Huang, Y.; Su, Y. J.; Sutton, E. K.; Hairston, M. R.
2015-12-01
AFRL The long-held view of energy input and dissipation into the IT system says that the primary region in which dynamic and electrodynamic processes occur is the auroral zone. Recent observations have indicated that this may not be completely true. The dominant form of energy input to the IT system is electromagnetic, and not particle precipitation. Poynting flux measured on DMSP spacecraft during storms indicates that energy can be deposited at all local times (LTs) in both hemispheres at polar latitudes as well as in the auroral zones. One major effect of this energy input is Joule heating of the ionosphere and thermosphere. We have analyzed the ion temperature measured by DMSP for a number of storms. During storm main phases, the increase in ion temperature maximizes at polar latitudes. We have processed neutral densities from CHAMP, GRACE and GOCE which show localized Joule heating at extremely high latitudes in both hemispheres. We conclude that energy input and dissipation occurs in the polar cap as well as in the auroral zones. Our results require a re-examination of the processes by which energy can enter the IT system, as well as where and how energy is transferred to ions and neutrals
NASA Astrophysics Data System (ADS)
van Egmond, W. J.; Saakes, M.; Porada, S.; Meuwissen, T.; Buisman, C. J. N.; Hamelers, H. V. M.
2016-09-01
Unlike traditional fossil fuel plants, the wind and the sun provide power only when the renewable resource is available. To accommodate large scale use of renewable energy sources for efficient power production and utilization, energy storage systems are necessary. Here, we introduce a scalable energy storage system which operates by performing cycles during which energy generated from renewable resource is first used to produce highly concentrated brine and diluate, followed up mixing these two solutions in order to generate power. In this work, we present theoretical results of the attainable energy density as function of salt type and concentration. A linearized Nernst-Planck model is used to describe water, salt and charge transport. We validate our model with experiments over wide range of sodium chloride concentrations (0.025-3 m) and current densities (-49 to +33 A m-2). We find that depending on current density, charge and discharge steps have significantly different thermodynamic efficiency. In addition, we show that at optimal current densities, mechanisms of energy dissipation change with salt concentration. We find the highest thermodynamic efficiency at low concentrate concentrations. When using salt concentrations above 1 m, water and co-ion transport contribute to high energy dissipation due to irreversible mixing.
NASA Technical Reports Server (NTRS)
Choueiri, Edgar Y.; Kelly, Arnold J.; Jahn, Robert G.
1992-01-01
In the present paper the linear stability description and weak turbulence theory are used to develop a second order description of wave-particle transport and anomalous dissipation. The goal is to arrive at anomalous transport coefficients that can be readily included in fluid flow codes. In particular, expressions are derived for the heating rates of ions and electrons by the unstable waves and for the electron-wave momentum exchange rate that controls the anomalous resistivity effect. Comparative calculations were undertaken assuming four different saturation models: ion trapping, electron trapping, ion resonance broadening, and thermodynamic bound. A foremost finding is the importance of the role of electron Hall parameter in scaling the level of anomalous dissipation for the parameter range of the MPD thruster plasma. Polynomial expressions of the relevant transport coefficients cast solely in terms of macroscopic parameters are also obtained for inclusion in plasma fluid codes for the self-consistent numerical simulation of real thruster flows including microturbulent effects.
NASA Astrophysics Data System (ADS)
Kaurov, Alexander A.
2016-06-01
We explore a time-dependent energy dissipation of the energetic electrons in the inhomogeneous intergalactic medium (IGM) during the epoch of cosmic reionization. In addition to the atomic processes, we take into account the inverse Compton (IC) scattering of the electrons on the cosmic microwave background photons, which is the dominant channel of energy loss for electrons with energies above a few MeV. We show that: (1) the effect on the IGM has both local (atomic processes) and non-local (IC radiation) components; (2) the energy distribution between hydrogen and helium ionizations depends on the initial energy of an electron; (3) the local baryon overdensity significantly affects the fractions of energy distributed in each channel; and (4) the relativistic effect of the atomic cross-section becomes important during the epoch of cosmic reionization. We release our code as open source for further modification by the community.
Meziane, A; Norris, A N; Shuvalov, A L
2011-10-01
Analytical and numerical modeling of the nonlinear interaction of shear wave with a frictional interface is presented. The system studied is composed of two homogeneous and isotropic elastic solids, brought into frictional contact by remote normal compression. A shear wave, either time harmonic or a narrow band pulse, is incident normal to the interface and propagates through the contact. Two friction laws are considered and the influence on interface behavior is investigated: Coulomb's law with a constant friction coefficient and a slip-weakening friction law which involves static and dynamic friction coefficients. The relationship between the nonlinear harmonics and the dissipated energy, and the dependence on the contact dynamics (friction law, sliding, and tangential stress) and on the normal contact stress are examined in detail. The analytical and numerical results indicate universal type laws for the amplitude of the higher harmonics and for the dissipated energy, properly non-dimensionalized in terms of the pre-stress, the friction coefficient and the incident amplitude. The results suggest that measurements of higher harmonics can be used to quantify friction and dissipation effects of a sliding interface.
Energy Dissipation in Multi-phase Infalling Clouds in Galaxy Halos
Murray, S D; Lin, D C
2004-06-15
During the epoch of large galaxy formation, thermal instability leads to the formation of a population of cool fragments which are embedded within a background of tenuous hot gas. The hot gas attains a quasi hydrostatic equilibrium. Although the cool clouds are pressure confined by the hot gas, they fall into the galactic potential, subject to drag from the hot gas. The release of gravitational energy due to the infall of the cool clouds is first converted into their kinetic energy which is subsequently dissipated as heat. The cool clouds therefore represent a potentially significant energy source for the background hot gas, depending upon the ratio of thermal energy deposited within the clouds versus the hot gas. In this paper, we show that most of dissipated energy is deposited in to the tenuous hot halo gas, which provides a source of internal energy to replenish its loss in the hot gas through Bremsstrahlung cooling and conduction into the cool clouds. Through this process, the multi-phase structure of the interstellar medium is maintained.
Liu Jianye; Guo Wenjun; Gao Yuanyi; Xing Yongzhong; Li Xiguo
2004-09-01
We investigate separately the isospin effects of Coulomb interaction and symmetry potential on the dissipation and fragmentation in the intermediate energy heavy ion collisions by using isospin-dependent quantum molecular dynamics model. The calculated results show that the Coulomb interaction induces the reductions of both isospin fractionation ratio and nuclear stopping (momentum dissipation). However, the Coulomb interaction not only does not change obviously the strong isospin effect of the symmetry potential on the isospin fractionation ratio but also does not change obviously that of in-medium two-body collision on the nuclear stopping. On the contrary, the symmetry potential induces the enhancement of the isospin fractionation ratio but it is insensitive to the nuclear stopping. Finally, the competition between the Coulomb interaction and symmetry potential induces the reductions of both isospin fractionation ratio and nuclear stopping for two forms of symmetry potentials in this paper.
Modeling energy dissipation induced by quasi-static compaction of granular HMX
Gonthier, K.A.; Menikoff, R.; Son, S.F.; Asay, B.W.
1998-07-01
A simple extension of a conventional two-phase continuum model of Deflagration-to-Detonation Transition (DDT) in energetic granular material is given to account for energy dissipation induced by quasi-static compaction. To this end, the conventional model equations are supplemented by a relaxation equation that accounts for irreversible changes in solid volume fraction due to intergranular friction, plastic deformation of granules, and granule fracture. The proposed model, which is consistent with the Second Law of Thermodynamics for a two-phase mixture, is demonstrated by applying it to the quasi-static compaction of granular HMX. The model predicts results commensurate with experimental data including stress relaxation and substantial dissipation; such phenomena have not been previously accounted for by two-phase DDT models. {copyright} {ital 1998 American Institute of Physics.}
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.
NASA Astrophysics Data System (ADS)
Fantz, U.; Friedl, R.; Briefi, S.
2015-05-01
The visual properties of a large plasmoid rising from a water container into the air for up to 450 ms are brought into correlation with the total energy dissipated into the system, and, in particular, with the energy used for plasma generation. The latter parameters are deduced from the time-resolved discharge current and voltage of the capacitor bank which is used as energy supply. By varying the experimental parameters, the energy dissipated to the system varies between 5 kJ and 30 kJ from which 10% to 30% is transferred to the plasma. Clear correlations are obtained for the size of the plasmoid changing from 15 cm to 35 cm in width, the ascent velocity ranging from 1 m/s to 2 m/s, and the rising height for which up to 85 cm is measured. For the relation of the autonomous phase with the energy transferred to the plasma, two trends are observed: 450 ms duration is achieved in maximum with the present setup being almost independent on the electrode gap, the voltage-on time, the water conductivity, or the type of salt dissolved in the water. On the other hand, an almost linear dependence is obtained by changing the capacitance.
Field dissipation of acetochlor in two New Zealand soils at two application rates.
Ma, Qingli; Rahman, Anis; Holland, Patrick T; James, Trevor K; McNaughton, Don E
2004-01-01
The persistence of pesticides in soils has both economic and environmental significance and is often used as a key parameter in pesticide risk assessment. Persistence of acetochlor [2'-ethyl-6'-methyl-N-(ethoxymethyl)-2-chloroacetylanilide] in two New Zealand field soils was measured over two years and the data were used to identify models that adequately describe acetochlor persistence in the field. Acetochlor was sprayed onto six fallow plots (3 x 9 m each) at each site at the recommended rate (2.5 kg a.i. ha(-1)) and at twice that rate. Acetochlor concentrations were measured in soil cores. Simple first-order kinetics (Model 1) adequately described acetochlor persistence in Hamilton clay loam soil (Humic Hapludull, Illuvial Spadic) at the high application rate, but overestimated it at the low application rate. A quadratic model (Model 2), a first-order double-exponential model (Model 3), a first-order biphasic model (Model 4), or a two-compartment model (Model 5) better described acetochlor persistence at the low application rate. The time for 50% (DT50) and 90% (DT90) of initial acetochlor loss was approximately 9 and 56 d, and 18 and 63 d at low and high application rates, respectively. The more complex Models 2 through 5 also better described the biphasic dissipation of acetochlor in Horotiu sandy loam soil (Typic Orthic Allophanic) than Model 1, with Model 1 significantly underestimating acetochlor concentrations on the day of application at both application rates. The DT50 and DT90 values were 5 and 29 d and 7 and 31 d at low and high application rates, respectively. Overall, application rate significantly affected the DT50 and DT90 values in the Hamilton soil, but not in the Horotiu soil. Faster acetochlor loss in the Horotiu soil possibly resulted from the higher soil organic carbon content that retained more acetochlor near the soil surface where higher temperature and photolysis accelerated the loss.
NASA Astrophysics Data System (ADS)
Yasumura, Kevin Youl
In 1986 the atomic force microscope (AFM) was invented by Binnig, Quate, and Gerber. Cantilever based force microscopy has been used in a wide range of fields including the study of biological samples, data storage media, and microelectronics. These AFM-based imaging techniques typically measure forces in the piconewton (10-12 N) range. Recent developments in microcantilever fabrication and optical fiber displacement sensors have allowed for the construction of force microscope systems that are capable of measuring forces in the attonewton (10-18 N) range. Applications such as magnetic resonance force microscopy (MRFM) require the cantilevers used to have subattonewton force resolution in order to eventually detect single nuclear spins. It is believed that improvements in cantilever and experimental design will allow for improved force resolution. A fundamental limit to the detection of small forces is thermomechanical noise. The thermal noise force limit, via the fluctuation dissipation theorem, is directly related to the amount of mechanical energy dissipation in the cantilever-based force sensor. Work has therefore been focused on developing an understanding of which mechanisms are limiting the force resolution of these microcantilever oscillators. Arrays of silicon nitride, single-crystal silicon, and polysilicon cantilevers have been fabricated and studied. By measuring the dependence of Q on cantilever material, geometry, and surface treatments, significant insight into the dissipation mechanisms has been obtained. For submicron thick cantilevers, Q is found to decrease with decreasing cantilever thickness, indicative of surface loss mechanisms. For single-crystal silicon cantilevers, significant increase in room temperature Q is obtained after 700 C heat treatment in either N 2 or forming gas. Thermoelastic dissipation is not a factor for submicron thick cantilevers, but is shown to be significant for silicon nitride cantilevers as thin as 2.3 um. At low
Solar transformities for the tidal energy received by the earth and the tidal energy dissipated globally can be calculated because both solar energy and the gravitational attraction of the sun and moon drive independent processes that produce an annual flux of geopotential energy...
Solar transformities for the tidal energy received by the earth and the tidal energy dissipated globally can be calculated because both solar energy and the gravitational attraction of the sun and moon drive independent processes that produce an annual flux of geopotential energy...
Development of a semi-active friction device to reduce vibration by energy dissipation
NASA Astrophysics Data System (ADS)
Buaka, Paulin; Masson, Patrice; Micheau, Philippe
2003-08-01
Aerospace structures such as antennas and solar panels often consist of truss elements which are connected by bolted joints. Friction damping in these bolted joint connections structures has been identified as a major source of damping. It has been proposed that an improvement in vibration reduction could be obtained by controlling the normal contact force using integrated piezoelectric elements in order to maximize the energy dissipated at the interface between the connected parts. This paper presents analytical and experimental results in order to demonstrate the interest of implementing semi-active vibration reduction by dissipating energy through dry friction contact surfaces. This work fits within the scope of a research project aiming at the development of a semi-active compact piezoelectric friction device which can be bonded to any light structure. In this device, a moving component will rub on two friction surfaces and the normal force on friction surfaces will be controlled so that the distance between moving component and friction surfaces is neither too small (to avoid shock and stiction that cancel the slip between two surfaces and then friction effect) or too large (lose of contact surface). This device will then be positioned on the structure in order to allow the maximum energy dissipation by friction to reduce the vibrations of the structure. Such semi-active device will ensure stability of the control approach and will avoid the spillover effect found with the active approach in addition to reduce energy consumption cost. In this paper, an analytical and experimental study is carried out on two beams assembled by a joint bolted to show the influence of the normal gripping force (tightening torque in this case), directly related to the friction force, on the damping of the modes.
Heber, Ulrich
2008-09-01
In order to survive sunlight in the absence of water, desiccation-tolerant green plants need to be protected against photooxidation. During drying of the chlorolichen Cladonia rangiformis and the cyanolichen Peltigera neckeri, chlorophyll fluorescence decreased and stable light-dependent charge separation in reaction centers of the photosynthetic apparatus was lost. The presence of light during desiccation increased loss of fluorescence in the chlorolichen more than that in the cyanolichen. Heating of desiccated Cladonia thalli, but not of Peltigera thalli, increased fluorescence emission more after the lichen had been dried in the light than after drying in darkness. Activation of zeaxanthin-dependent energy dissipation by protonation of the PsbS protein of thylakoid membranes was not responsible for the increased loss of chlorophyll fluorescence by the chlorolichen during drying in the light. Glutaraldehyde inhibited loss of chlorophyll fluorescence during drying. Desiccation-induced loss of chlorophyll fluorescence and of light-dependent charge separation are interpreted to indicate activation of a highly effective mechanism of photoprotection in the lichens. Activation is based on desiccation-induced conformational changes of a pigment-protein complex. Absorbed light energy is converted into heat within a picosecond or femtosecond time domain. When present during desiccation, light interacts with the structural changes of the protein providing increased photoprotection. Energy dissipation is inactivated and structural changes are reversed when water becomes available again. Reversibility of ultra-fast thermal dissipation of light energy avoids photo-damage in the absence of water and facilitates the use of light for photosynthesis almost as soon as water becomes available.
NASA Astrophysics Data System (ADS)
Longbiao, Li
2016-06-01
In this paper, the relationship between hysteresis dissipated energy and temperature rising of the external surface in fiber-reinforced ceramic-matrix composites (CMCs) during the application of cyclic loading has been analyzed. The temperature rise, which is caused by frictional slip of fibers within the composite, is related to the hysteresis dissipated energy. Based on the fatigue hysteresis theories considering fibers failure, the hysteresis dissipated energy and a hysteresis dissipated energy-based damage parameter changing with the increase of cycle number have been investigated. The relationship between the hysteresis dissipated energy, a hysteresis dissipated energy-based damage parameter and a temperature rise-based damage parameter have been established. The experimental temperature rise-based damage parameter of unidirectional, cross-ply and 2D woven CMCs corresponding to different fatigue peak stresses and cycle numbers have been predicted. It was found that the temperature rise-based parameter can be used to monitor the fatigue damage evolution and predict the fatigue life of fiber-reinforced CMCs.
The effect of the dissipation of energy on the hydrodynamics of the gas-particle fluidized beds
NASA Astrophysics Data System (ADS)
Bergstrom, D. J.; Haghgoo, Mohammad Reza; Spiteri, R. J.
2014-11-01
The flow structure in dense gas-particle fluidized beds is strongly affected by the dissipation of kinetic energy through particle collisions with each other and the wall. The energy dissipation reduces the kinetic energy of the particles. Consequently, larger clusters will be formed, and this in turn leads to the formation of larger bubbles. Therefore, it is insightful to investigate the instantaneous dissipation of energy in a fluidized bed in order to have a better understanding of the hydrodynamics of the particle phase. Visualization of the dissipation term will also clarify how much the walls contribute to the dissipation of energy in the overall system. In this study, a two-fluid model is used for the numerical simulation of an engineering-scale bubbling fluidized bed. The MFiX code is used to perform the simulations. A modified SIMPLE algorithm for multiphase flows is employed that uses a higher-order discretization scheme to accurately compute bubble shapes and the deferred correction method to enhance numerical stability. The results of the three-dimensional simulation are in good agreement with the limited experimental data. The dissipation of the kinetic energy of the particles is evaluated using the model relations based on the simulated particle velocity fields.
Dissipation of MeV ion energy in solids, structure formation and phase changes
NASA Astrophysics Data System (ADS)
Sen, P.; Aggarwal, G.; Tiwari, U.
1998-12-01
Instabilities arise out of dynamic events and can lead to nonequilibrium (self-organization) processes. Ion irradiation is by nature a nonequilibrium process and hence formation of structures, metastable or otherwise is to be expected. Recently, it has been theoretically predicted that metals under ion irradiation can lead to dissipative structure formation arising out of radiation damage and their subsequent annealing. The possibility of direct observation of such structures in metals under irradiation is however reduced due to nonavailability of a large concentration of defects (mainly point defects) at any point of time. In this experimental presentation we show that this can be overcome through the involvement of microstructural imperfections which rearrange during irradiation. Employing microstructurally impure specimens of Fe and Ni, it is shown that heavy ions dissipate their electronic energy to modify atomic arrangements at the microstructure. The increased concentration of defects (atomic rearrangements), amenable to statistical decay is shown to produce effects in the 4-probe resistivity measurements which we assign to dissipative structure formation.
The energy-momentum tensor for a dissipative fluid in general relativity
NASA Astrophysics Data System (ADS)
Pimentel, Oscar M.; Lora-Clavijo, F. D.; González, Guillermo A.
2016-10-01
Considering the growing interest of the astrophysicist community in the study of dissipative fluids with the aim of getting a more realistic description of the universe, we present in this paper a physical analysis of the energy-momentum tensor of a viscous fluid with heat flux. We introduce the general form of this tensor and, using the approximation of small velocity gradients, we relate the stresses of the fluid with the viscosity coefficients, the shear tensor and the expansion factor. Exploiting these relations, we can write the stresses in terms of the extrinsic curvature of the normal surface to the 4-velocity vector of the fluid, and we can also establish a connection between the perfect fluid and the symmetries of the spacetime. On the other hand, we calculate the energy conditions for a dissipative fluid through contractions of the energy-momentum tensor with the 4-velocity vector of an arbitrary observer. This method is interesting because it allows us to compute the conditions in a reasonably easy way and without considering any approximation or restriction on the energy-momentum tensor.
NASA Astrophysics Data System (ADS)
Honkan, Anant; Andreopoulos, Yiannis
1997-11-01
Experimental results are presented that reveal the structure of a two-dimensional turbulent boundary layer which has been investigated by measuring the time-dependent vorticity flux at the wall, vorticity vector, strain-rate tensor and dissipation-rate tensor in the near-wall region with spatial resolution of the order of 7 Kolmogorov viscous length scales. Considerations of the structure function of velocity and pressure, which constitute vorticity flux and vorticity, indicated that, in the limit of vanishing distance, the maximum attainable content of these quantities which corresponds to unrestricted resolution, is determined by Taylor's microscale. They also indicated that most of the contributions to vorticity or vorticity flux come from the uncorrelated part of the two signals involved. The measurements allowed the computation of all components of the vorticity stretching vector, which indicates the rate of change of vorticity on a Lagrangian reference frame if viscous effects are negligible, and several matrix invariants of the velocity gradient or strain-rate tensor and terms appearing in the transport equations of vorticity, strain rate and their squared fluctuations. The orientation of vorticity revealed several preferential directions. During bursts or sweeps vorticity is inclined at 35° to the longitudinal direction. It was also found that there is high probability of the vorticity vector aligning with the direction of the intermediate extensive strain corresponding to the middle eigenvector of the strain-rate matrix. The results of the joint probability distributions of the vorticity vector orientation angles showed that these angles may be related to those of hairpin vortex structures. All invariants considered exhibit a very strong intermittent behaviour which is characterized by large-amplitude bursts which may be of the order of 10 r.m.s. values. Small-scale motions dominated by high rates of turbulent kinetic energy dissipation and high enstrophy
AGE-RELATED FACTORS AFFECTING THE POST-YIELD ENERGY DISSIPATION OF HUMAN CORTICAL BONE
Nyman, Jeffry S.; Roy, Anuradha; Tyler, Jerrod H.; Acuna, Rae L.; Gayle, Heather J.; Wang, Xiaodu
2007-01-01
The risk of bone fracture depends in part on the quality of the tissue, not just the size and mass. This study assessed the post-yield energy dissipation of cortical bone in tension as a function of age and composition. Tensile specimens were prepared from tibiae of human cadavers in which male and female donors were divided into two age groups: middle aged (51 to 56 years old, n = 9) and elderly (72 to 90 years old, n = 8). By loading, unloading, and reloading a specimen with rest period inserted in between, tensile properties at incremental strain levels were assessed. In addition, the post-yield toughness was estimated and partitioned as follows: plastic strain energy related to permanent deformation, released elastic strain energy related to stiffness loss, and hysteresis energy related to viscous behavior. Porosity, mineral and collagen content, and collagen crosslinks of each specimen were also measured to determine the micro and ultrastructural properties of the tissue. It was found that age affected all the energy terms plus strength but not elastic stiffness. The post-yield energy terms were correlated with porosity, pentosidine (a marker of non-enzymatic crosslinks), and collagen content, all of which significantly varied with age. General linear models with the highest possible R2 value suggested that the pentosidine concentration and collagen content provided the best explanation of the age-related decrease in the post-yield energy dissipation of bone. Among them, pentosidine concentration had the greatest contribution to plastic strain energy and was the best explanatory variable of damage accumulation. PMID:17266142
Quantification of the Energy Dissipated by Alfven Waves in a Polar Coronal Hole
NASA Astrophysics Data System (ADS)
Hahn, M.; Savin, D. W.
2013-12-01
We present a measurement of the energy carried and dissipated by Alfven waves in a polar coronal hole. Alfven waves have been proposed as the energy source that heats the corona and drives the solar wind. Previous work has shown that line widths decrease with height in coronal holes, which is a signature of wave damping, but have been unable to quantify the energy lost by the waves. This is because line widths depend on both the non-thermal velocity vnt and the ion temperature Ti. We have implemented a means to separate the Ti and vnt contributions using the observation that, at low heights, the waves are undamped and the ion temperatures do not change with height. This enables us to determine the amount of energy carried by the waves at low heights, which is proportional to vnt. We find the initial energy flux density present was 6.7×0.7×10^5 erg cm^-2 s^-1, which is sufficient to heat the coronal hole and accelerate the solar wind during the 2007 - 2009 solar minimum. Additionally, we find that about 85% of this energy is dissipated below 1.5 R_sun, sufficiently low that thermal conduction can transport the energy throughout the coronal hole, heating it and driving the fast solar wind. The remaining energy is roughly consistent with what models show is needed to provide the extended heating above the sonic point for the fast solar wind. We have also studied Ti, which we found to be in the range of 1 - 2 MK, depending on the ion species.
NASA Astrophysics Data System (ADS)
Tian, Jingjing
Low-rise woodframe buildings with disproportionately flexible ground stories represent a significant percentage of the building stock in seismically vulnerable communities in the Western United States. These structures have a readily identifiable structural weakness at the ground level due to an asymmetric distribution of large openings in the perimeter wall lines and to a lack of interior partition walls, resulting in a soft story condition that makes the structure highly susceptible to severe damage or collapse under design-level earthquakes. The conventional approach to retrofitting such structures is to increase the ground story stiffness. An alternate approach is to increase the energy dissipation capacity of the structure via the incorporation of supplemental energy dissipation devices (dampers), thereby relieving the energy dissipation demands on the framing system. Such a retrofit approach is consistent with a Performance-Based Seismic Retrofit (PBSR) philosophy through which multiple performance levels may be targeted. The effectiveness of such a retrofit is presented via examination of the seismic response of a full-scale four-story building that was tested on the outdoor shake table at NEES-UCSD and a full-scale three-story building that was tested using slow pseudo-dynamic hybrid testing at NEES-UB. In addition, a Direct Displacement Design (DDD) methodology was developed as an improvement over current DDD methods by considering torsion, with or without the implementation of damping devices, in an attempt to avoid the computational expense of nonlinear time-history analysis (NLTHA) and thus facilitating widespread application of PBSR in engineering practice.
Werkhausen, Amelie; Albracht, Kirsten; Cronin, Neil J; Meier, Rahel; Bojsen-Møller, Jens; Seynnes, Olivier R
2017-09-07
The compliance of elastic elements allows muscles to dissipate energy safely during eccentric contractions. This buffering function is well documented in animal models but our understanding of its mechanism in humans is confined to non-specific tasks, requiring a subsequent acceleration of the body. The present study aimed to examine the behaviour of the human triceps surae muscle-tendon unit (MTU) during a pure energy dissipation task, under two loading conditions.Thirty-nine subjects performed a single-leg landing task, with- and without added mass. Ultrasound measurements were combined with 3D kinematics and kinetics to determine instantaneous length changes of MTUs, muscle fascicles, Achilles tendon and combined elastic elements.Gastrocnemius and soleus MTUs lengthened during landing. After a small concentric action, fascicles contracted eccentrically during most of the task, when the highest muscle activity occurred. Combined elastic elements lengthened until peak ankle moment and recoiled thereafter, whilst no recoil was observed for the Achilles tendon. Adding mass resulted in greater negative work and MTU lengthening, which were accompanied by a greater stretch of tendon and elastic elements and a greater recruitment of the soleus muscle, without any further fascicle strain.Hence, the buffering action of elastic elements delimits the maximal strain and lengthening velocity of active muscle fascicles and is commensurate with loading constraints. In the present task, energy dissipation was modulated via greater MTU excursion and more forceful eccentric contractions. The distinct strain pattern of the Achilles tendon supports the notion that different elastic elements may not systematically fulfil the same function. © 2017. Published by The Company of Biologists Ltd.
NREL module energy rating methodology
Whitaker, C.; Newmiller, J.; Kroposki, B.
1995-11-01
The goals of this project were to develop a tool for: evaluating one module in different climates; comparing different modules; provide a Q&D method for estimating periodic energy production; provide an achievable module rating; provide an incentive for manufacturers to optimize modules to non-STC conditions; and to have a consensus-based, NREL-sponsored activity. The approach taken was to simulate module energy for five reference days of various weather conditions. A performance model was developed.
Energy dissipation within the wave run-up at stepped revetments
NASA Astrophysics Data System (ADS)
Kerpen, Nils B.; Bung, Daniel B.; Valero, Daniel; Schlurmann, Torsten
2017-08-01
To understand the processes and energy dissipation performance caused by turbulence during the wave run-up over a stepped revetment, hydraulic model tests with steady flow conditions are conducted and correlated with unsteady flow conditions of the wave run-up within a short time frame. Under irregular waves, the run-up reduction over a stepped revetment is dependent on the Iribarren number and decreases for decreasing Iribarren numbers. Velocity gradients are found to be similar in a steady and unsteady flow regime near the pseudo-bottom.
NASA Astrophysics Data System (ADS)
Paulo, Álvaro San; García, Ricardo
2001-11-01
Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the quantities that control the amplitude reduction. The agreement obtained between analytical and numerical results supports the analytical method.
Simulation of the dissipated and stored energy under deformation and failure of metallic materials
Kostina, Anastasiia Plekhov, Oleg
2015-10-27
This work is devoted to the development of the statistical model of the structural defect evolution which was developed at the Institute of continuous media mechanics UB RAS. This model takes into account stochastic properties of the defect evolution process, nonlinear interaction of defects, and connection between microplasticity and damage accumulation. The obtained constitutive equations allow us to propose a model of the energy storage and dissipation in the process of plastic deformation and failure of metallic materials. The obtained relations were adapted for standard finite-element package. Applicability of this model was demonstrated in three-dimensional simulation of the strain localization and crack propagation in metals.
A biomolecular implementation of logically reversible computation with minimal energy dissipation.
Klein, J P; Leete, T H; Rubin, H
1999-10-01
Energy dissipation associated with logic operations imposes a fundamental physical limit on computation and is generated by the entropic cost of information erasure, which is a consequence of irreversible logic elements. We show how to encode information in DNA and use DNA amplification to implement a logically reversible gate that comprises a complete set of operators capable of universal computation. We also propose a method using this design to connect, or 'wire', these gates together in a biochemical fashion to create a logic network, allowing complex parallel computations to be executed. The architecture of the system permits highly parallel operations and has properties that resemble well known genetic regulatory systems.
Grafmüller, Andrea; Shillcock, Julian; Lipowsky, Reinhard
2009-04-08
The fusion of lipid bilayers is studied with dissipative particle dynamics simulations. First, to achieve control over membrane properties, the effects of individual simulation parameters are studied and optimized. Then, a large number of fusion events for a vesicle and a planar bilayer are simulated using the optimized parameter set. In the observed fusion pathway, configurations of individual lipids play an important role. Fusion starts with individual lipids assuming a splayed tail configuration with one tail inserted in each membrane. To determine the corresponding energy barrier, we measure the average work for interbilayer flips of a lipid tail, i.e., the average work to displace one lipid tail from one bilayer to the other. This energy barrier is found to depend strongly on a certain dissipative particle dynamics parameter, and, thus, can be adjusted in the simulations. Overall, three subprocesses have been identified in the fusion pathway. Their energy barriers are estimated to lie in the range 8-15 k(B)T. The fusion probability is found to possess a maximum at intermediate tension values. As one decreases the tension, the fusion probability seems to vanish before the tensionless membrane state is attained. This would imply that the tension has to exceed a certain threshold value to induce fusion.
Fingerprints of energy dissipation for exothermic surface chemical reactions: O2 on Pd(100)
NASA Astrophysics Data System (ADS)
Bukas, Vanessa J.; Mitra, Shubhrajyoti; Meyer, Jörg; Reuter, Karsten
2015-07-01
We present first-principles calculations of the sticking coefficient of O2 at Pd(100) to assess the effect of phononic energy dissipation on this kinetic parameter. For this, we augment dynamical simulations on six-dimensional potential energy surfaces (PESs) representing the molecular degrees of freedom with various effective accounts of surface mobility. In comparison to the prevalent frozen-surface approach, energy dissipation is found to qualitatively affect the calculated sticking curves. At the level of a generalized Langevin oscillator model, we achieve good agreement with experimental data. The agreement is similarly reached for PESs based on two different semi-local density-functional theory functionals. This robustness of the simulated sticking curve does not extend to the underlying adsorption mechanism, which is predominantly directly dissociative for one functional or molecularly trapped for the other. Completely different adsorption mechanisms therewith lead to rather similar sticking curves that agree equally well with the experimental data. This highlights the danger of the prevalent practice to extract corresponding mechanistic details from simple fingerprints of measured sticking data for such exothermic surface reactions.
Fingerprints of energy dissipation for exothermic surface chemical reactions: O2 on Pd(100).
Bukas, Vanessa J; Mitra, Shubhrajyoti; Meyer, Jörg; Reuter, Karsten
2015-07-21
We present first-principles calculations of the sticking coefficient of O2 at Pd(100) to assess the effect of phononic energy dissipation on this kinetic parameter. For this, we augment dynamical simulations on six-dimensional potential energy surfaces (PESs) representing the molecular degrees of freedom with various effective accounts of surface mobility. In comparison to the prevalent frozen-surface approach, energy dissipation is found to qualitatively affect the calculated sticking curves. At the level of a generalized Langevin oscillator model, we achieve good agreement with experimental data. The agreement is similarly reached for PESs based on two different semi-local density-functional theory functionals. This robustness of the simulated sticking curve does not extend to the underlying adsorption mechanism, which is predominantly directly dissociative for one functional or molecularly trapped for the other. Completely different adsorption mechanisms therewith lead to rather similar sticking curves that agree equally well with the experimental data. This highlights the danger of the prevalent practice to extract corresponding mechanistic details from simple fingerprints of measured sticking data for such exothermic surface reactions.
The Fusion of Membranes and Vesicles: Pathway and Energy Barriers from Dissipative Particle Dynamics
Grafmüller, Andrea; Shillcock, Julian; Lipowsky, Reinhard
2009-01-01
The fusion of lipid bilayers is studied with dissipative particle dynamics simulations. First, to achieve control over membrane properties, the effects of individual simulation parameters are studied and optimized. Then, a large number of fusion events for a vesicle and a planar bilayer are simulated using the optimized parameter set. In the observed fusion pathway, configurations of individual lipids play an important role. Fusion starts with individual lipids assuming a splayed tail configuration with one tail inserted in each membrane. To determine the corresponding energy barrier, we measure the average work for interbilayer flips of a lipid tail, i.e., the average work to displace one lipid tail from one bilayer to the other. This energy barrier is found to depend strongly on a certain dissipative particle dynamics parameter, and, thus, can be adjusted in the simulations. Overall, three subprocesses have been identified in the fusion pathway. Their energy barriers are estimated to lie in the range 8–15 kBT. The fusion probability is found to possess a maximum at intermediate tension values. As one decreases the tension, the fusion probability seems to vanish before the tensionless membrane state is attained. This would imply that the tension has to exceed a certain threshold value to induce fusion. PMID:19348749
Geometrical Dependence of Electrical Energy dissipated for Intra-Cloud Flashes using LMA Data
NASA Astrophysics Data System (ADS)
Salinas, V.; Bruning, E. C.
2015-12-01
Lightning Mapping Array (LMA) data were used to estimate total electrical energy dissipation for 73 intra-cloud flashes from a Mesoscale Convective System (MCS) that occurred near Lubbock, TX on June 6th, 2013. Charge volumes and spacing were estimated from the convex hull of VHF sources emitted by positive and negative breakdown. Energy was obtained by solving for the electric field and potential in two ways. For reference, a three-dimensional Poisson solver was used with the observed convex hull geometry. Analytical estimates were then made by applying the same charge volumes to simplified geometries: charged spheres, cylinders, and plane parallel discs. Charge density was retrieved by applying constraints of charge conservation and the presence of a breakeven electric field. The analytic geometries were compared to the convex hull method in order to quantify and evaluate the geometric dependence of the total energy dissipated. Preliminary results showed the cylindrical geometry produced values within the range of other values reported in the literature, and in close agreement with solutions for the convex-hull geometry.
Wave run-up on a high-energy dissipative beach
Ruggiero, P.; Holman, R.A.; Beach, R.A.
2004-01-01
Because of highly dissipative conditions and strong alongshore gradients in foreshore beach morphology, wave run-up data collected along the central Oregon coast during February 1996 stand in contrast to run-up data currently available in the literature. During a single data run lasting approximately 90 min, the significant vertical run-up elevation varied by a factor of 2 along the 1.6 km study site, ranging from 26 to 61% of the offshore significant wave height, and was found to be linearly dependent on the local foreshore beach slope that varied by a factor of 5. Run-up motions on this high-energy dissipative beach were dominated by infragravity (low frequency) energy with peak periods of approximately 230 s. Incident band energy levels were 2.5 to 3 orders of magnitude lower than the low-frequency spectral peaks and typically 96% of the run-up variance was in the infragravity band. A broad region of the run-up spectra exhibited an f-4 roll off, typical of saturation, extending to frequencies lower than observed in previous studies. The run-up spectra were dependent on beach slope with spectra for steeper foreshore slopes shifted toward higher frequencies than spectra for shallower foreshore slopes. At infragravity frequencies, run-up motions were coherent over alongshore length scales in excess of 1 km, significantly greater than decorrelation length scales on moderate to reflective beaches. Copyright 2004 by the American Geophysical Union.
Gruszecki, Wieslaw I; Grudzinski, Wojciech; Gospodarek, Małgorzata; Patyra, Magdalena; Maksymiec, Waldemar
2006-11-01
The xanthophyll cycle pigments, violaxanthin and zeaxanthin, present outside the light-harvesting pigment-protein complexes of Photosystem II (LHCII) considerably enhance specific aggregation of proteins as revealed by analysis of the 77 K chlorophyll a fluorescence emission spectra. Analysis of the infrared absorption spectra in the Amide I region shows that the aggregation is associated with formation of intermolecular hydrogen bonding between the alpha helices of neighboring complexes. The aggregation gives rise to new electronic energy levels, in the Soret region (530 nm) and corresponding to the Q spectral region (691 nm), as revealed by analysis of the resonance light scattering spectra. New electronic energy levels are interpreted in terms of exciton coupling of protein-bound photosynthetic pigments. The energy of the Q excitonic level of chlorophyll is not high enough to drive the light reactions of Photosystem II but better suited to transfer excitation energy to Photosystem I, which creates favourable energetic conditions for the state I-state II transition. The lack of fluorescence emission from this energy level, at physiological temperatures, is indicative of either very high thermal energy conversion rate or efficient excitation quenching by carotenoids. Chlorophyll a fluorescence was quenched up to 61% and 34% in the zeaxanthin- and violaxanthin-containing samples, respectively, as compared to pure LHCII. Enhanced aggregation of LHCII, observed in the presence of the xanthophyll cycle pigments, is discussed in terms of the switch between light-harvesting and energy dissipation systems.
Wave energy dissipation by intertidal sand waves on a mixed-sediment Beach
Adams, P.; Ruggiero, P.
2006-01-01
Within the surf zone, the energy expended by wave breaking is strongly influenced by nearshore bathymetry, which is often linked to the character and abundance of local sediments. Based upon a continuous, two year record of Argus Beach Monitoring System (ABMS) data on the north shore of Kachemak Bay in southcentral Alaska, we model the enhancement of wave energy dissipation by the presence of intertidal sand waves. Comparison of model results from simulations in the presence and absence of sand waves illustrates that these ephemeral morphological features can offer significant protection to the backing beach and sea cliff through two mechanisms: (1) by moving the locus of wave breaking seaward and (2) by increasing energy expenditure associated with the turbulence of wave breaking. Copyright ASCE 2006.
Energy dissipation and absorption capacity influence on experimental modal parameters of a PC girder
NASA Astrophysics Data System (ADS)
Luna Vera, O. S.; Kim, C. W.; Oshima, Y.
2017-05-01
This experimental investigation focuses on collecting vibration data after different loading scenarios in a PC girder while measuring the performance at the same time. The vibration data is used for modal analysis and since several samples were taken in each scenario with different impact hammer tips, a comparison of the outcomes is also possible. The performance is based on recorded displacements along the bottom surface of the girder, information that makes possible the calculation of energy absorbed before cracking and the energy dissipation that takes place after cracking. Furthermore, two major damage events, a tendon breakage and cracking, were induced and monitored respectively. This study also clarified the influence of change in energy on changes in modal parameters.
Exploring postsaddle nuclear dissipation with light-particle multiplicity at high energy
NASA Astrophysics Data System (ADS)
Wang, N.; Ye, W.
2013-05-01
Based on the stochastic Langevin equation coupled with a statistical decay model, we study the effects of deformation on the accuracy of extracting saddle-to-scission friction (β) by analyzing prescission neutron yields measured in heavy compound nuclei 248Fm, 252Fm, 256Fm, and 251Es. It is shown that accounting for the effect can appreciably reduce the value of β needed to fit data, and a friction value of (11-13)×1021 s-1 is obtained. Furthermore, we find that at low energy the sensitivity of light charged particles (LCPs) to β almost disappears, but the sensitive dependence of neutrons and LCPs on friction is substantially enhanced with increasing excitation energy. Our findings suggest that to obtain precise information of saddle-to-scission nuclear dissipation with particle emission, besides taking into account deformation effects in theoretical calculations, in experiments it is best to populate heavy fissioning systems with high energy.
Angular momentum role in cross-section energy coherence of heavy-ion dissipative collisions
De Rosa, A.; Inglima, G.; Rosato, E.; Sandoli, M. ); Cardella, G. ); Papa, M. ); Pappalardo, G. ); Rizzo, F.; Fortuna, G.; Montagnoli, G. (Dipartimento di Fisica, Universit
1989-08-01
The dissipative excitation functions of the {sup 19}F+{sup 63}Cu reaction have been measured in the energy range {ital E}{sub lab}=100 to 108 MeV in 250 keV energy steps at angles {theta}{sub lab}=10{degree},20{degree},30{degree},40{degree},50{degree}. The energy-coherence width of the cross section has been determined by means of the spectral-density method. The results concerning the {sup 19}F+{sup 63}Cu and {sup 28}Si+{sup 48}Ti reactions are compared to evidence the angular momentum effects on the cross-section autocorrelation function. The probability distribution of the cross section is considered in discussing the possible selective excitation of intermediate-system doorway states.
An equivalent dissipation rate model for capturing history effects in non-premixed flames
Kundu, Prithwish; Echekki, Tarek; Pei, Yuanjiang; ...
2016-11-11
The effects of strain rate history on turbulent flames have been studied in the. past decades with 1D counter flow diffusion flame (CFDF) configurations subjected to oscillating strain rates. In this work, these unsteady effects are studied for complex hydrocarbon fuel surrogates at engine relevant conditions with unsteady strain rates experienced by flamelets in a typical spray flame. Tabulated combustion models are based on a steady scalar dissipation rate (SDR) assumption and hence cannot capture these unsteady strain effects; even though they can capture the unsteady chemistry. In this work, 1D CFDF with varying strain rates are simulated using twomore » different modeling approaches: steady SDR assumption and unsteady flamelet model. Comparative studies show that the history effects due to unsteady SDR are directly proportional to the temporal gradient of the SDR. A new equivalent SDR model based on the history of a flamelet is proposed. An averaging procedure is constructed such that the most recent histories are given higher weights. This equivalent SDR is then used with the steady SDR assumption in 1D flamelets. Results show a good agreement between tabulated flamelet solution and the unsteady flamelet results. This equivalent SDR concept is further implemented and compared against 3D spray flames (Engine Combustion Network Spray A). Tabulated models based on steady SDR assumption under-predict autoignition and flame lift-off when compared with an unsteady Representative Interactive Flamelet (RIF) model. However, equivalent SDR model coupled with the tabulated model predicted autoignition and flame lift-off very close to those reported by the RIF model. This model is further validated for a range of injection pressures for Spray A flames. As a result, the new modeling framework now enables tabulated models with significantly lower computational cost to account for unsteady history effects.« less
An equivalent dissipation rate model for capturing history effects in non-premixed flames
Kundu, Prithwish; Echekki, Tarek; Pei, Yuanjiang; Som, Sibendu
2016-11-11
The effects of strain rate history on turbulent flames have been studied in the. past decades with 1D counter flow diffusion flame (CFDF) configurations subjected to oscillating strain rates. In this work, these unsteady effects are studied for complex hydrocarbon fuel surrogates at engine relevant conditions with unsteady strain rates experienced by flamelets in a typical spray flame. Tabulated combustion models are based on a steady scalar dissipation rate (SDR) assumption and hence cannot capture these unsteady strain effects; even though they can capture the unsteady chemistry. In this work, 1D CFDF with varying strain rates are simulated using two different modeling approaches: steady SDR assumption and unsteady flamelet model. Comparative studies show that the history effects due to unsteady SDR are directly proportional to the temporal gradient of the SDR. A new equivalent SDR model based on the history of a flamelet is proposed. An averaging procedure is constructed such that the most recent histories are given higher weights. This equivalent SDR is then used with the steady SDR assumption in 1D flamelets. Results show a good agreement between tabulated flamelet solution and the unsteady flamelet results. This equivalent SDR concept is further implemented and compared against 3D spray flames (Engine Combustion Network Spray A). Tabulated models based on steady SDR assumption under-predict autoignition and flame lift-off when compared with an unsteady Representative Interactive Flamelet (RIF) model. However, equivalent SDR model coupled with the tabulated model predicted autoignition and flame lift-off very close to those reported by the RIF model. This model is further validated for a range of injection pressures for Spray A flames. As a result, the new modeling framework now enables tabulated models with significantly lower computational cost to account for unsteady history effects.
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.
NASA Astrophysics Data System (ADS)
Brancati, Renato; Strano, Salvatore; Timpone, Francesco
2011-10-01
When in use, a tire dissipates energy according to various mechanisms: rolling resistance, viscosity, hysteresis, friction energy, etc. This dissipation of energy contributes to influencing tire temperature, contact conditions and the resulting friction coefficient. This research project deals with viscoelastic and hysteretic mechanisms, and presents an explicit expression of the energy dissipated by tire-road interactions caused by these mechanisms. It is based on the Dahl model with regard to the hysteretic force together with a spring and a frequency variable damping coefficient with regard to the viscoelastic one. The energy expression found in this way can be used in tire thermal models to determine one of the heat flows needed to estimate the contact temperature and to find out the actual friction coefficient to be used in real time tire-road interaction models. Experimental tests were carried out, for longitudinal interaction only, in order to evaluate the effectiveness of the proposed expression by identifying the parameters and validating the results.
NASA Astrophysics Data System (ADS)
Borderie, B.; Rivet, M. F.; Tassan-Got, L.
For several years a new field in nuclear physics has been opened by the opportunity to accelerate heavy ions through an energy domain including the Fermi energy of nucleons. The new domain has to be seen as a link between dissipative processes observed at low energies, dominated by mean field considerations, and high energy collisions for which nucleon-nucleon collisions play an important role. This paper reviews our present knowledge on peripheral collisions. A reminder of contiguous energy domains is done as well as their extension in the new field. Specific calculations are also presented. Finally a wide comparison between experiments and calculations is performed. A fast dissipative stage proves to be responsible for the dominant mechanisms involved, at least when the incident energy is lower than 50 MeV/nucleon. Un nouveau champ d'études de la physique nucléaire s'est ouvert depuis quelques années avec la possibilité de réaliser des collisions noyau-noyau dans un domaine en énergie franchissant l'énergie de Fermi des nucléons. Ce nouveau domaine constitue le lien entre les processus dissipatifs observés à basse énergie, dominés par le concept de champ moyen, et les réactions à grande énergie pour lesquelles les collisions nucléon-nucléon jouent un rôle important. Cet article sur les collisions périphériques fait le point sur l'état actuel de nos connaissances. Après un rappel des domaines en énergie connexes, de leurs eventuelles extensions dans le domaine considéré, des calculs spécifiques au domaine sont décrits. Enfin une importante comparaison calculs théoriques-expériences est présentée. Une dissipation en énergie très rapide est responsable des processus dominants observés jusqu'à des énergies incidentes d'environ 50 MeV/nucléon.
Large-Area Nanolattice Film with Enhanced Modulus, Hardness, and Energy Dissipation.
Bagal, Abhijeet; Zhang, Xu A; Shahrin, Rahnuma; Dandley, Erinn C; Zhao, Junjie; Poblete, Felipe R; Oldham, Christopher J; Zhu, Yong; Parsons, Gregory N; Bobko, Christopher; Chang, Chih-Hao
2017-08-22
We present an engineered nanolattice material with enhanced mechanical properties that can be broadly applied as a thin film over large areas. The nanolattice films consist of ordered, three-dimensional architecture with thin-shell tubular elements, resulting in favorable modulus-density scaling (n ~ 1.1), enhanced energy dissipation, and extremely large material recoverability for strains up to 20% under normal compressive loading. At 95.6% porosity, the nanolattice film has demonstrated modulus of 1.19 GPa and specific energy dissipation of 325.5 kJ/kg, surpassing previously reported values at similar densities. The largest length scale in the reported nanolattice is the 500 nm unit-cell lattice constant, allowing the film to behave more like a continuum material and be visually unobservable. Fabricated using three-dimensional colloidal nanolithography and atomic layer deposition, the process can be scaled for large-area patterning. The proposed nanolattice film can find applications as a robust multifunctional insulating film that can be applied in integrated photonic elements, optoelectronic devices, and microcircuit chips.
Energy-dissipating and self-repairing SMA-ECC composite material system
NASA Astrophysics Data System (ADS)
Li, Xiaopeng; Li, Mo; Song, Gangbing
2015-02-01
Structural component ductility and energy dissipation capacity are crucial factors for achieving reinforced concrete structures more resistant to dynamic loading such as earthquakes. Furthermore, limiting post-event residual damage and deformation allows for immediate re-operation or minimal repairs. These desirable characteristics for structural ‘resilience’, however, present significant challenges due to the brittle nature of concrete, its deformation incompatibility with ductile steel, and the plastic yielding of steel reinforcement. Here, we developed a new composite material system that integrates the unique ductile feature of engineered cementitious composites (ECC) with superelastic shape memory alloy (SMA). In contrast to steel reinforced concrete (RC) and SMA reinforced concrete (SMA-RC), the SMA-ECC beams studied in this research exhibited extraordinary energy dissipation capacity, minimal residual deformation, and full self-recovery of damage under cyclic flexural loading. We found that the tensile strain capacity of ECC, tailored up to 5.5% in this study, allows it to work compatibly with superelastic SMA. Furthermore, the distributed microcracking damage mechanism in ECC is critical for sufficient and reliable recovery of damage upon unloading. This research demonstrates the potential of SMA-ECC for improving resilience of concrete structures under extreme hazard events.
Zhang, Yanwen; Stocks, George Malcolm; Jin, Ke; ...
2015-10-28
A long-standing objective in materials research is to understand how energy is dissipated in both the electronic and atomic subsystems in irradiated materials, and how related non-equilibrium processes may affect defect dynamics and microstructure evolution. Here we show that alloy complexity in concentrated solid solution alloys having both an increasing number of principal elements and altered concentrations of specific elements can lead to substantial reduction in the electron mean free path and thermal conductivity, which has a significant impact on energy dissipation and consequentially on defect evolution during ion irradiation. Enhanced radiation resistance with increasing complexity from pure nickel tomore » binary and to more complex quaternary solid solutions is observed under ion irradiation up to an average damage level of 1 displacement per atom. Understanding how materials properties can be tailored by alloy complexity and their influence on defect dynamics may pave the way for new principles for the design of radiation tolerant structural alloys.« less
NASA Astrophysics Data System (ADS)
Reddy, B. D.
2011-11-01
A general set of flow laws and associated variational formulations are constructed for small-deformation rate-independent problems in strain-gradient plasticity. The framework is based on the thermodynamically consistent theory due to Gurtin and Anand (J Mech Phys Solids 53:1624-1649, 2005), and includes as variables a set of microstresses which have both energetic and dissipative components. The flow law is of associative type. It is expressed as a normality law with respect to a convex but otherwise arbitrary yield function, or equivalently in terms of the corresponding dissipation function. Two cases studied are, first, an extension of the classical Hill-Mises or J 2 flow law and second, a form written as a linear sum of the magnitudes of the plastic strain and strain gradient. This latter form is motivated by work of Evans and Hutchinson (Acta Mater 57:1675-1688, 2009) and Nix and Gao (J Mech Phys Solids 46:411-425, 1998), who show that it leads to superior correspondence with experimental results, at least for particular classes of problems. The corresponding yield function is obtained by a duality argument. The variational problem is based on the flow rule expressed in terms of the dissipation function, and the problem is formulated as a variational inequality in the displacement, plastic strain, and hardening parameter. Dissipative components of the microstresses, which are indeterminate, are absent from the formulation. Existence and uniqueness of solutions are investigated for the generalized Hill-Mises and linear-sum dissipation functions, and for various combinations of defect energy. The conditions for well-posedness of the problem depend critically on the choice of dissipation function, and on the presence or otherwise of a defect energy in the plastic strain or plastic strain gradient, and of internal-variable hardening.
On the evaluation of the sub-filter scalar variance and dissipation rate in large eddy simulation
NASA Astrophysics Data System (ADS)
Balarac, Guillaume; Pitsch, Heinz; Raman, Venkatramanan
2007-11-01
In large-eddy simulations, the energy containing scales of the turbulence are resolved and the small scales have to be modeled. This is very important for flows with combustion, where the heat release typically correlates well with the rate of molecular mixing on the smallest scales. The mixture fraction describing mixing between fuel and oxidizer plays a central role in turbulent non-premixed combustion modeling. In particular, the sub-filter mixture fraction variance and the mixture fraction dissipation rate describe molecular mixing. Models for these quantities have been proposed in the past, but the performance of these models is often not of satisfactory accuracy given their importance for predicting the heat release. In the present work, a model based on a Taylor series expansion is proposed following the approach of Clark et al. [J. Fluid Mech., 1979]. The model is tested in an a priori study, and effects of expansion order and filter kernel are assessed. The results are discussed based on the notion of ``irreducible error'' recently introduced by Moreau et al. [Phys. Fluids, 2006]. The model is compared with the dynamic model and the results are analyzed to understand the validity of assumptions made in the dynamic procedure. Further numerical issues related to LES using implicit filtering are discussed.
Tkatchenko, Alexandre; Ambrosetti, Alberto; DiStasio, Robert A
2013-02-21
Interatomic pairwise methods are currently among the most popular and accurate ways to include dispersion energy in density functional theory calculations. However, when applied to more than two atoms, these methods are still frequently perceived to be based on ad hoc assumptions, rather than a rigorous derivation from quantum mechanics. Starting from the adiabatic connection fluctuation-dissipation (ACFD) theorem, an exact expression for the electronic exchange-correlation energy, we demonstrate that the pairwise interatomic dispersion energy for an arbitrary collection of isotropic polarizable dipoles emerges from the second-order expansion of the ACFD formula upon invoking the random-phase approximation (RPA) or the full-potential approximation. Moreover, for a system of quantum harmonic oscillators coupled through a dipole-dipole potential, we prove the equivalence between the full interaction energy obtained from the Hamiltonian diagonalization and the ACFD-RPA correlation energy. This property makes the Hamiltonian diagonalization an efficient method for the calculation of the many-body dispersion energy. In addition, we show that the switching function used to damp the dispersion interaction at short distances arises from a short-range screened Coulomb potential, whose role is to account for the spatial spread of the individual atomic dipole moments. By using the ACFD formula, we gain a deeper understanding of the approximations made in the interatomic pairwise approaches, providing a powerful formalism for further development of accurate and efficient methods for the calculation of the dispersion energy.
NASA Astrophysics Data System (ADS)
Lan, Ganhui
2015-09-01
We present here the analytical relation between the gain of eukaryotic gradient sensing network and the associated thermodynamic cost. By analyzing a general incoherent type-1 feed-forward loop, we derive the gain function (G ) through the reaction network and explicitly show that G depends on the nonequilibrium factor (0 ≤γ ≤1 with γ =0 and 1 representing irreversible and equilibrium reaction systems, respectively), the Michaelis constant (KM), and the turnover ratio (rcat) of the participating enzymes. We further find the maximum possible gain is intrinsically determined by KM/Gmax=(1 /KM+2 ) /4 . Our model also indicates that the dissipated energy (measured by -lnγ ), from the intracellular energy-bearing bioparticles (e.g., ATP), is used to generate a force field Fγ∝(1 -√{γ }) that reshapes and disables the effective potential around the zero gain region, which leads to the ultrasensitive response to external chemical gradients.
Irreversible processes without energy dissipation in an isolated Lipkin-Meshkov-Glick model.
Puebla, Ricardo; Relaño, Armando
2015-07-01
For a certain class of isolated quantum systems, we report the existence of irreversible processes in which the energy is not dissipated. After a closed cycle in which the initial energy distribution is fully recovered, the expectation value of a symmetry-breaking observable changes from a value differing from zero in the initial state to zero in the final state. This entails the unavoidable loss of a certain amount of information and constitutes a source of irreversibility. We show that the von Neumann entropy of time-averaged equilibrium states increases in the same magnitude as a consequence of the process. We support this result by means of numerical calculations in an experimentally feasible system, the Lipkin-Meshkov-Glick model.
Numerical simulation of flare energy build-up and release via Joule dissipation. [solar MHD model
NASA Technical Reports Server (NTRS)
Wu, S. T.; Bao, J. J.; Wang, J. F.
1986-01-01
A new numerical MHD model is developed to study the evolution of an active region due to photospheric converging motion, which leads to magnetic-energy buildup in the form of electric current. Because this new MHD model has incorporated finite conductivity, the energy conversion occurs from magnetic mode to thermal mode through Joule dissipation. In order to test the causality relationship between the occurrence of flare and photospheric motion, a multiple-pole configuration with neutral point is used. Using these results it is found that in addition to the converging motion, the initial magnetic-field configuration and the redistribution of the magnetic flux at photospheric level enhance the possibility for the development of a flare.
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.
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.
Muscle work is biased toward energy generation over dissipation in non-level running
DeVita, Paul; Janshen, Lars; Rider, Patrick; Solnik, Stanislaw; Hortobágyi, Tibor
2008-01-01
This study tested the hypothesis that skeletal muscles generate more mechanical energy in gait tasks that raise the center of mass compared to the mechanical energy they dissipate in gait tasks that lower the center of mass despite equivalent changes in total mechanical energy. Thirteen adults ran on a 10° decline and incline surface at a constant average velocity. Three-dimensional (3D) joint powers were calculated from ground force and 3D kinematic data using inverse dynamics. Joint work was calculated from the power curves and assumed to be due to skeletal muscle–tendon actuators. External work was calculated from the kinematics of the pelvis through the gait cycle. Incline vs. decline running was characterized with smaller ground forces that operated over longer lever arms causing larger joint torques and work from these torques. Total lower extremity joint work was 28% greater in incline vs. decline running (1.32 vs. −1.03 J/kg m, p<0.001). Total lower extremity joint work comprised 86% and 71% of the total external work in incline (1.53 J/kg m) and decline running (−1.45 J/kg m), which themselves were not significantly different (p<0.180). We conjectured that the larger ground forces in decline vs. incline running caused larger accelerations of all body tissues and initiated a greater energy-dissipating response in these tissues compared to their response in incline running. The runners actively lowered themselves less during decline stance and descended farther as projectiles than they lifted themselves during incline stance and ascended as projectiles. These data indicated that despite larger ground forces in decline running, the reduced displacement during downhill stance phases limited the work done by muscle contraction in decline compared to incline running. PMID:19010471
Xiong, Liping; Lan, Ganhui
2015-01-01
Sustained molecular oscillations are ubiquitous in biology. The obtained oscillatory patterns provide vital functions as timekeepers, pacemakers and spacemarkers. Models based on control theory have been introduced to explain how specific oscillatory behaviors stem from protein interaction feedbacks, whereas the energy dissipation through the oscillating processes and its role in the regulatory function remain unexplored. Here we developed a general framework to assess an oscillator’s regulation performance at different dissipation levels. Using the Escherichia coli MinCDE oscillator as a model system, we showed that a sufficient amount of energy dissipation is needed to switch on the oscillation, which is tightly coupled to the system’s regulatory performance. Once the dissipation level is beyond this threshold, unlike stationary regulators’ monotonic performance-to-cost relation, excess dissipation at certain steps in the oscillating process damages the oscillator’s regulatory performance. We further discovered that the chemical free energy from ATP hydrolysis has to be strategically assigned to the MinE-aided MinD release and the MinD immobilization steps for optimal performance, and a higher energy budget improves the robustness of the oscillator. These results unfold a novel mode by which living systems trade energy for regulatory function. PMID:26317492
Huarancca Reyes, Thais; Scartazza, Andrea; Lu, Yu; Yamaguchi, Junji; Guglielminetti, Lorenzo
2016-08-01
Carbon (C) and nitrogen (N) nutrient sources are essential elements for metabolism, and their availability must be tightly coordinated for the optimal growth and development in plants. Plants are able to sense and respond to different C/N conditions via specific partitioning of C and N sources and the regulation of a complex cellular metabolic activity. We studied how the interaction between C and N signaling could affect carbohydrate metabolism, soluble sugar levels, photochemical efficiency of photosystem II (PSII) and the ability to drive the excess energy in Arabidopsis seedlings under moderated and disrupted C/N-nutrient conditions. Invertase and sucrose synthase activities were markedly affected by C/N-nutrient status depending on the phosphorylation status, suggesting that these enzymes may necessarily be modulated by their direct phosphorylation or phosphorylation of proteins that form complex with them in response to C/N stress. In addition, the enzymatic activity of these enzymes was also correlated with the amount of sugars, which not only act as substrate but also as signaling compounds. Analysis of chlorophyll fluorescence in plants under disrupted C/N condition suggested a reduction of electron transport rate at PSII level associated with a higher capacity for non-radiative energy dissipation in comparison with plants under moderated C/N condition. In conclusion, the tight coordination between C and N not only affects the carbohydrates metabolism and their concentration within plant tissues, but also the partitioning of the excitation energy at PSII level between radiative (electron transport) and non-radiative (heat) dissipation pathways. Copyright © 2016 Elsevier Masson SAS. All rights reserved.
Energy-conserving dissipative particle dynamics with temperature-dependent properties
Li, Zhen; Tang, Yu-Hang; Lei, Huan; Caswell, Bruce; Karniadakis, George E.
2014-05-01
The dynamic properties of fluid, including diffusivity and viscosity, are temperature-dependent and can significantly influence the flow dynamics of mesoscopic non-isothermal systems. To capture the correct temperature-dependence of a fluid, an energy-conserving dissipative particle dynamics (eDPD) model is developed by expressing the weighting terms of the dissipative force and the random force as functions of temperature. The diffusivity and viscosity of liquid water at various temperatures ranging from 273 K to 373 K are used as examples for verifying the proposed model. Simulations of a Poiseuille flow and a steady case of heat conduction for reproducing the Fourier law are carried out to validate the present eDPD formulation and the thermal boundary conditions. Results show that the present eDPD model recovers the standard DPD model when isothermal fluid systems are considered. For non-isothermal fluid systems, the present model can predict the diffusivity and viscosity consistent with available experimental data of liquid water at various temperatures. Moreover, an analytical formula for determining the mesoscopic heat friction is proposed. The validity of the formula is confirmed by reproducing the experimental data for Prandtl number of liquid water at various temperatures. The proposed method is demonstrated in water but it can be readily extended to other liquids. (C) 2014 Elsevier Inc. All rights reserved.
Zhou, Yanhong; Lam, Hon Ming; Zhang, Jianhua
2007-01-01
Photoprotection mechanisms of rice plants were studied when its seedlings were subjected to the combined stress of water and high light. The imposition of water stress, induced by PEG 6000 which was applied to roots, resulted in substantial inhibition of stomatal conductance and net photosynthesis under all irradiance treatments. Under high light stress, the rapid decline of photosynthesis with the development of water stress was accompanied by decreases in the maximum velocity of RuBP carboxylation by Rubisco (V(cmax)), the capacity for ribulose-1,5-bisphosphate regeneration (J(max)), Rubisco and stromal FBPase activities, and the quantum efficiency of photosystem II, in the absence of any stomatal limitation of CO(2) supply. Water stress significantly reduced the energy flux via linear electron transport (J(PSII)), but increased light-dependent and DeltapH- and xanthophyll-mediated thermal dissipation (J(NPQ)). It is concluded that the drought-induced inhibition of photosynthesis under different irradiances in the rice was due to both diffusive and metabolic limitations. Metabolic limitation of photosynthesis may be related to the adverse effects of some metabolic processes and the oxidative damage to the chloroplast. Meanwhile, an enhanced thermal dissipation is an important process to minimize the adverse effects of drought and high irradiance when CO(2) assimilation is suppressed.
Exploring elasticity and energy dissipation in mussel-inspired hydrogel transient networks
NASA Astrophysics Data System (ADS)
Grindy, Scott; Learsch, Robert; Holten-Andersen, Niels
Dynamic, reversible crosslinks have been shown to specifically control the mechanical properties of a wide variety of mechanically tough and resilient biomaterials. We have shown that reversible histidine-metal ion interactions, known to contribute to the strong mechanical properties and self-healing nature of mussel byssal threads, can be used to control and engineer the temporally-hierarchical mechanical properties of model hydrogels orthogonally from the spatial structure of the material. Here, we explore the scaling relationships in our model networks to further inform our abilities to control the relative elasticity and energy dissipation on hierarchical timescales. Scaling arguments suggest that the elasticity is dominated by long-range entanglements, while the dissipation is controlled by the exchange kinetics of the transient crosslinks. Further, we show that by using UV light, we can further control the viscoelastic properties of our mussel-inspired hydrogels in situ. This process opens the door for creating biocompatible hydrogel materials with arbitrary spatial control over their viscoelastic mechanical properties. Overall, we show that by understanding the interplay between bio-inspired dynamic crosslinks and soft matter physics allows us to rationally design high-strength hydrogels for specific states of dynamic loading.
Effect of particle size on energy dissipation in viscoelastic granular collisions
NASA Astrophysics Data System (ADS)
Antypov, Dmytro; Elliott, James A.; Hancock, Bruno C.
2011-08-01
We analyze the scaling properties of the Hertz-Kuwabara-Kono (HKK) model, which is commonly used in numerical simulations to describe the collision of macroscopic noncohesive viscoelastic spherical particles. Parameters describing the elastic and viscous properties of the material, its density, and the size of the colliding particles affect the restitution coefficient ɛ and collision time τ only via appropriate rescaling but do not change the shape of ɛ(v) and τ(v) curves, where v is the impact velocity. We have measured the restitution coefficient experimentally for relatively large (1 cm) particles of microcrystalline cellulose to deduce material parameters and then to predict collision properties for smaller microcrystalline cellulose (MCC) particles by assuming the scaling properties of the HKK model. In particular, we demonstrate that the HKK model predicts the restitution coefficient of microscopic particles of about 100 μm to be considerably smaller than that of the macroscopic particles. In fact, the energy dissipation is so large that only completely inelastic collisions occur for weakly attractive particles. We propose a straightforward self-consistent extension to the Johnson-Kendall-Roberts (JKR) model to include dissipative forces and discuss the implications of our findings for the behavior of experimental powder systems.
NASA Astrophysics Data System (ADS)
Zehe, E.; Blume, T.; Bloeschl, G.
2009-04-01
Helmholtz free energy. Thermodynamic equilibrium is a state of minimum free energy. The latter is determined by potential energy and capillary energy in soil, which in turn strongly depends on soil moisture, pore size distribution and depth to groundwater. The objective of this study is threefold. First, we will introduce the necessary theoretical background. Second we suggest ? based on simulations with a physically based hydrological model ? that water flow in connected preferential pathways assures a faster relaxation towards thermodynamic equilibrium through a faster drainage of ?excess water? and a faster redistribution of ?capillary water? within the soil. The latter process is of prime importance in case of cohesive soils where the pore size distribution is dominated by medium and small pores. Third, an application of a physically based hydrological model to predict water flow and runoff response from a pristine catchment in the Chilenean Andes underpins this hypothesis. Behavioral model structures that allow a good match of the observed hydrographs turned out to be most efficient in dissipating free energy by means of preferential flow. It seems that a population of connected preferential pathways is favourable both for resilience and stability of these soils during extreme events and to retain water resources for the ecosystem at the same time. We suggest that this principle of ?maximum energy dissipation? may on the long term help us to better understand why soil structures remain stable, threshold nature of preferential as well as offer a means to further reduce model structural uncertainty. Bloeschl, G. 2006. Idle thoughts on a unifying theory of catchment Hydrology. Geophysical Research Abstracts, Vol. 8, 10677, 2006 SRef-ID: 1607-7962/gra/EGU06-A-10677 European Geosciences Union 2006 Kleidon, A., and S. Schymanski (2008), Thermodynamics and optimality of the water budget on land: A review, Geophys. Res. Lett., 35, L20404, doi:10.1029/ 2008GL035393.
Unravelling Coherent Dynamics and Energy Dissipation in Photosynthetic Complexes by 2D Spectroscopy
Abramavicius, Darius; Voronine, Dmitri V.; Mukamel, Shaul
2008-01-01
Spectroscopic studies of light harvesting and the subsequent energy conversion in photosynthesis can track quantum dynamics happening on the microscopic level. The Fenna-Matthews-Olson complex of the photosynthetic green sulfur bacteria Chlorobium tepidum is a prototype efficient light-harvesting antenna: it stores the captured photon energy in the form of excitons (collective excitations), which are subsequently converted to chemical energy with almost 100% efficiency. These excitons show an elaborate relaxation pattern involving coherent and incoherent pathways. We make use of the complex chirality and fundamental symmetries of multidimensional optical signals to design new sequences of ultrashort laser pulses that can distinguish between coherent quantum oscillations and incoherent energy dissipation during the exciton relaxation. The cooperative dynamical features, which reflect the coherent nature of excitations, are amplified. The extent of quantum oscillations and their timescales in photosynthesis can be readily extracted from the designed signals, showing that cooperativity is maintained during energy transport in the Fenna-Matthews-Olson complex. The proposed pulse sequences may also be applied to reveal information on the robustness of quantum states in the presence of fluctuating environments in other nanoscopic complexes and devices. PMID:18192357
Unravelling coherent dynamics and energy dissipation in photosynthetic complexes by 2D spectroscopy.
Abramavicius, Darius; Voronine, Dmitri V; Mukamel, Shaul
2008-05-01
Spectroscopic studies of light harvesting and the subsequent energy conversion in photosynthesis can track quantum dynamics happening on the microscopic level. The Fenna-Matthews-Olson complex of the photosynthetic green sulfur bacteria Chlorobium tepidum is a prototype efficient light-harvesting antenna: it stores the captured photon energy in the form of excitons (collective excitations), which are subsequently converted to chemical energy with almost 100% efficiency. These excitons show an elaborate relaxation pattern involving coherent and incoherent pathways. We make use of the complex chirality and fundamental symmetries of multidimensional optical signals to design new sequences of ultrashort laser pulses that can distinguish between coherent quantum oscillations and incoherent energy dissipation during the exciton relaxation. The cooperative dynamical features, which reflect the coherent nature of excitations, are amplified. The extent of quantum oscillations and their timescales in photosynthesis can be readily extracted from the designed signals, showing that cooperativity is maintained during energy transport in the Fenna-Matthews-Olson complex. The proposed pulse sequences may also be applied to reveal information on the robustness of quantum states in the presence of fluctuating environments in other nanoscopic complexes and devices.
Wahadoszamen, Md; Margalit, Iris; Ara, Anjue Mane; van Grondelle, Rienk; Noy, Dror
2014-10-24
Understanding how specific protein environments affect the mechanisms of non-radiative energy dissipation within densely assembled chlorophylls in photosynthetic protein complexes is of great interest to the construction of bioinspired solar energy conversion devices. Mixing of charge-transfer and excitonic states in excitonically interacting chlorophylls was implicated in shortening excited states' lifetimes, but its relevance to active control of energy dissipation in natural systems is under considerable debate. Here we show that the degree of fluorescence quenching in two similar pairs of excitonically interacting bacteriochlorophyll derivatives is directly associated with increasing charge-transfer character in the excited state, and that the protein environment may control non-radiative dissipation by affecting the mixing of charge-transfer and excitonic states. The capability of local protein environments to determine the fate of excited states, and thereby to confer different functionalities to excitonically coupled dimers substantiates the dimer as the basic functional element of photosynthetic enzymes.
NASA Astrophysics Data System (ADS)
Cohen, Doron
2000-08-01
We make the first steps toward a generic theory for energy spreading and quantum dissipation. The Wall formula for the calculation of friction in nuclear physics and the Drude formula for the calculation of conductivity in mesoscopic physics can be regarded as two special results of the general formulation. We assume a time-dependent Hamiltonian H(Q, P; x(t)) with x(t)=Vt, where V is slow in a classical sense. The rate-of-change V is not necessarily slow in the quantum-mechanical sense. The dynamical variables (Q, P) may represent some "bath" which is being parametrically driven by x. This bath may consist of just a few degrees of freedom, but it is assumed to be classically chaotic. In the case of either the Wall or Drude formula, the dynamical variables (Q, P) may represent a single particle. In any case, dissipation means an irreversible systematic growth of the (average) energy. It is associated with the stochastic spreading of energy across levels. The latter can be characterized by a transition probability kernel Pt(n ∣ m), where n and m are level indices. This kernel is the main object of the present study. In the classical limit, due to the (assumed) chaotic nature of the dynamics, the second moment of Pt(n ∣ m) exhibits a crossover from ballistic to diffusive behavior. In order to capture this crossover within quantum mechanics, a proper theory for the quantal Pt(n ∣ m) should be constructed. We define the V regimes where either perturbation theory or semiclassical considerations are applicable in order to establish this crossover. In the limit ℏ→0 perturbation theory does not apply but semiclassical considerations can be used in order to argue that there is detailed correspondence, during the crossover time, between the quantal and the classical Pt(n ∣ m). In the perturbative regime there is a lack of such correspondence. Namely, Pt(n ∣ m) is characterized by a perturbative core-tail structure that persists during the crossover time. In
Ramanan, Charusheela; Berera, Rudi; Gundermann, Kathi; van Stokkum, Ivo; Büchel, Claudia; van Grondelle, Rienk
2014-09-01
Photosynthetic organisms have developed vital strategies which allow them to switch from a light-harvesting to an energy dissipative state at the level of the antenna system in order to survive the detrimental effects of excess light illumination. These mechanisms are particularly relevant in diatoms, which grow in highly fluctuating light environments and thus require fast and strong response to changing light conditions. We performed transient absorption spectroscopy on FCPa, the main light-harvesting antenna from the diatom Cyclotella meneghiniana, in the unquenched and quenched state. Our results show that in quenched FCPa two quenching channels are active and are characterized by differing rate constants and distinct spectroscopic signatures. One channel is associated with a faster quenching rate (16ns⁻¹) and virtually no difference in spectral shape compared to the bulk unquenched chlorophylls, while a second channel is associated with a slower quenching rate (2.7ns⁻¹) and exhibits an increased population of red-emitting states. We discuss the origin of the two processes in the context of the models proposed for the regulation of photosynthetic light-harvesting. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.
Constraints on Energy Dissipation in the Earth's Body Tide From Satellite Tracking and Altimetry
NASA Technical Reports Server (NTRS)
Ray, Richard D.; Eanes, Richard J.; Lemoine, Frank G.
1992-01-01
The phase lag by which the earth's body tide follows the tidal potential is estimated for the principal lunar semidiurnal tide M(sub 2). The estimate results from combining recent tidal solutions from satellite tracking data and from Topex/Poseidon satellite altimeter data. Each data type is sensitive to the body-tide lag: gravitationally for the tracking data, geometrically for the altimetry. Allowance is made for the lunar atmospheric tide. For the tidal potential Love number kappa(sub 2) we obtain a lag epsilon of 0.20 deg +/- 0.05 deg, implying an effective body-tide Q of 280 and body-tide energy dissipation of 110 +/- 25 gigawatts.
Non-Enzymatic RNA Backbone Proofreading through Energy-Dissipative Recycling.
Mariani, Angelica; Sutherland, John D
2017-06-01
Non-enzymatic oligomerization of activated ribonucleotides leads to ribonucleic acids that contain a mixture of 2',5'- and 3',5'-linkages, and overcoming this backbone heterogeneity has long been considered a major limitation to the prebiotic emergence of RNA. Herein, we demonstrate non-enzymatic chemistry that progressively converts 2',5'-linkages into 3',5'-linkages through iterative degradation and repair. The energetic costs of this proofreading are met by the hydrolytic turnover of a phosphate activating agent and an acylating agent. With multiple rounds of this energy-dissipative recycling, we show that all-3',5'-linked duplex RNA can emerge from a backbone heterogeneous mixture, thereby delineating a route that could have driven RNA evolution on the early earth. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Zhang, Pu; Heyne, Mary A.; To, Albert C.
2015-10-01
We investigate the damping enhancement in a class of biomimetic staggered composites via a combination of design, modeling, and experiment. In total, three kinds of staggered composites are designed by mimicking the structure of bone and nacre. These composite designs are realized by 3D printing a rigid plastic and a viscous elastomer simultaneously. Greatly-enhanced energy dissipation in the designed composites is observed from both the experimental results and theoretical prediction. The designed polymer composites have loss modulus up to ~500 MPa, higher than most of the existing polymers. In addition, their specific loss modulus (up to 0.43 km2/s2) is among the highest of damping materials. The damping enhancement is attributed to the large shear deformation of the viscous soft matrix and the large strengthening effect from the rigid inclusion phase.
NASA Astrophysics Data System (ADS)
Zilletti, Michele; Gardonio, Paolo; Elliott, Stephen J.
2014-09-01
In this study the active vibration control of a structure modelled as a single degree of freedom system and excited by a white noise force is considered. The control system consists of an inertial actuator driven with a signal proportional to the velocity of the structure under control measured by an ideal collocated sensor. The optimisation of the physical and control parameters of the control system such as the internal damping of the actuator, its natural frequency and the feedback gain of the controller are considered such that either the kinetic energy of the host structure is minimised or the power dissipated by the control system is maximised. This type of control system is only conditionally stable therefore a stability condition has to be satisfied by the optimisation process. The paper shows that the two optimisation criteria are equivalent.
NASA Astrophysics Data System (ADS)
Montalvão, D.; Silva, J. M. M.
2015-03-01
The identification of the modal parameters from frequency response functions is a subject that is not new. However, the starting point often comes from the equations that govern the dynamic motion. In this paper, a novel approach is shown, resulting from an analysis that starts on the dissipated energy per cycle of vibration. Numerical and experimental examples were used in order to assess the effectiveness of the proposed method. It was shown that, for lightly damped systems with conveniently spaced modes, it produced quite accurate results when compared to those obtained from the method of the inverse. The technique also proved to be simple enough to be used for quick estimates of the modal damping factors. Finally, this paper is a contribution to modal analysis and identification methods, as the developed technique has never been proposed before.
Natural convection heat transfer simulation using energy conservative dissipative particle dynamics.
Abu-Nada, Eiyad
2010-05-01
Dissipative particle dynamics with energy conservation (eDPD) was used to study natural convection via Rayleigh-Bénard (RB) problem and a differentially heated enclosure problem (DHE). The current eDPD model implemented the Boussinesq approximation to model the buoyancy forces. The eDPD results were compared to the finite volume solutions and it was found that the eDPD method predict the temperature and flow fields throughout the natural convection domains properly. The eDPD model recovered the basic features of natural convection, such as development of plumes, development of thermal boundary layers, and development of natural convection circulation cells (rolls). The eDPD results were presented via temperature isotherms, streamlines, velocity contours, velocity vector plots, and temperature and velocity profiles. Further useful quantities, such as Nusselt number was calculated from the eDPD results and found to be in good agreement with the finite volume calculations.
Energy dissipation in dielectrics after swift heavy-ion impact: A hybrid model
NASA Astrophysics Data System (ADS)
Osmani, O.; Medvedev, N.; Schleberger, M.; Rethfeld, B.
2011-12-01
The energy dissipation after irradiation of dielectrics with swift heavy ions is studied applying a combination of the Monte Carlo (MC) method and the two-temperature model (TTM). Within the MC calculation the transient dynamics of the electrons in the excited dielectric is described: the primary excitation and relaxation of the target electrons as well as the creation of secondary electrons. From the MC data, it was observed that the electron system can be considered as thermalized after a time of t≈100 fs after the ion impact. Then the TTM is applied to calculate the spatial and temporal evolution of the electron and lattice temperature via the electron-phonon coupling using the MC data as initial conditions. Additionally, this MC-TTM combination allows to compute material parameters of strongly excited matter.
Control of spin ambiguity during reorientation of an energy dissipating body
NASA Technical Reports Server (NTRS)
Kaplan, M. H.; Cenker, R. J.
1973-01-01
A quasi-rigid body initially spinning about its minor principal axis and experiencing energy dissipation will enter a tumbling mode and eventually reorient itself such that stable spin about its major principal axis is achieved. However, in this final state the body may be spinning in a positive or negative sense with respect to its major axis and aligned in a positive or negative sense with the inertially fixed angular momentum vector. This ambiguity can be controlled only through an active system. The associated dynamical formulations and simulations of uncontrolled reorientations are presented. Three control schemes are discussed and results offered for specific examples. These schemes include displacement of internal masses, spinning up of internal inertia, and reaction jets, all of which have demonstrated the ability to control spin ambiguity.
Non-linear dynamics in biological microtubules: solitons and dissipation-free energy transfer
NASA Astrophysics Data System (ADS)
Mavromatos, Nick E.
2017-08-01
I review some recent developments concerning soliton solutions in biological microtubules and their significance in transferring energy without dissipation. I discuss various types of soliton solutions, as well as ‘spikes’, of the associated non-linear Lagrange equations describing the dynamics of a ‘pseudo-spin non-linear σ-model’ that models the dynamics of a microtubule system with dipole-dipole interactions. These results will hopefully contribute to a better understanding of the functional properties of microtubules, including the motor protein dynamics and the information transfer processes. With regards to the latter we also speculate on the use of microtubules as ‘logical’ gates. Our considerations are classical, but the soliton solutions may have a microscopic quantum origin, which we briefly touch upon.
NASA Astrophysics Data System (ADS)
Zhukov, A. A.; Shapiro, D. S.; Remizov, S. V.; Pogosov, W. V.; Lozovik, Yu. E.
2017-02-01
We consider a superconducting qubit coupled to the nonstationary transmission line cavity with modulated frequency taking into account energy dissipation. Previously, it was demonstrated that in the case of a single nonadiabatical modulation of a cavity frequency there are two channels of a two-level system excitation which are due to the absorption of Casimir photons and due to the counterrotating wave processes responsible for the dynamical Lamb effect. We show that the parametric periodical modulation of the resonator frequency can increase dramatically the excitation probability. Remarkably, counterrotating wave processes under such a modulation start to play an important role even in the resonant regime. Our predictions can be used to control qubit-resonator quantum states as well as to study experimentally different channels of a parametric qubit excitation.
NASA Astrophysics Data System (ADS)
Rittmeyer, Simon P.; Ward, David J.; Gütlein, Patrick; Ellis, John; Allison, William; Reuter, Karsten
2016-11-01
Helium spin echo experiments combined with ab initio based Langevin molecular dynamics simulations are used to quantify the adsorbate-substrate coupling during the thermal diffusion of Na atoms on Cu(111). An analysis of trajectories within the local density friction approximation allows the contribution from electron-hole pair excitations to be separated from the total energy dissipation. Despite the minimal electronic friction coefficient of Na and the relatively small mass mismatch to Cu promoting efficient phononic dissipation, about (20 ±5 )% of the total energy loss is attributable to electronic friction. The results suggest a significant role of electronic nonadiabaticity in the rapid thermalization generally relied upon in adiabatic diffusion theories.