Atomistic Visualization of Ballistic Phonon Transport

2007 ◽  
Author(s):  
Neil Zuckerman ◽  
Jennifer R. Lukes
Keyword(s):  
Heat Transfer ◽  
High Frequency ◽  
Energy Transport ◽  
Imaging Techniques ◽  
Phonon Transport ◽  
Dynamics Simulation ◽  
Short Time Scale ◽  
Ballistic Phonons ◽  
Short Time ◽  
Phonon Focusing

Heat transfer in solid materials at short time scales, short length scales, and low temperatures is governed by the transport of ballistic phonons. In anisotropic crystals, the energy carried by these phonons is strongly channeled into well-defined directions in a phenomenon known as phonon focusing. Presented here is a new molecular dynamics simulation approach for visualizing acoustic phonon focusing in anisotropic crystals. An advantage of this approach over experimental phonon imaging techniques is that it allows examination of phonon propagation at selected modes and frequencies. The spatial, mode, and frequency dependence of ballistic energy transport gained with this approach will be useful for understanding heat transfer issues in high frequency electronics and short time scale laser-material interactions.

Weakness of short-term synchronization among respiratory nerve activities during fictive vomiting

1992 ◽  
Vol 263 (2) ◽  
pp. R339-R347 ◽  
Author(s):  
M. I. Cohen ◽  
A. D. Miller ◽  
R. Barnhardt ◽  
C. F. Shaw
Keyword(s):  
Time Scale ◽  
High Frequency ◽  
Pattern Generator ◽  
High Frequency Oscillation ◽  
Short Time Scale ◽  
Coherence Analysis ◽  
Frequency Range ◽  
Frequency Oscillation ◽  
Short Term ◽  
Short Time

In decerebrate, paralyzed cats, phrenic (PHR) and lumbar abdominal (ABD) nerve discharges during both neural respiration and fictive vomiting (FV) were subjected to spectral and coherence analyses. During respiration, PHR discharge exhibited high-frequency oscillation (HFO), manifested as a narrow spectral peak (range 57-90 Hz) in autospectra and left-right coherence spectra. During FV, the following occurred: 1) the HFO peak disappeared and was replaced by a broad peak with higher modal frequency (range 84-120 Hz), indicating elimination of inputs from the medullary inspiratory pattern generator. 2) Left-right PHR coherence spectra had no distinct peaks, indicating that correlations between opposite PHR discharges were now not frequency specific. 3) Although ABD and PHR autospectra were similar, PHR-ABD coherences were near zero, indicating lack of common inputs on a short time scale. 4) Nonzero coherences between ABD nerves were confined to ipsilateral pairs. Thus coherence analysis indicates that the outputs of the vomiting pattern generator are temporally dispersed on a short time scale and are not necessarily common to different motoneuron populations.

scholarly journals The Mathematical Analysis On The Effect Of Strong Nonlinearity On Steady-State Self-Focusing And Filamentation Of Whistlers In A Plasma

2016 ◽  
Vol 5 (1) ◽  
pp. 18
Author(s):  
Ghanshyam Rai
Keyword(s):  
Time Scale ◽  
High Frequency ◽  
Small Scale ◽  
Nonuniform Heating ◽  
Short Time Scale ◽  
Strong Nonlinearity ◽  
Self Focusing ◽  
Long Time ◽  
Short Time ◽  
Very High

<div><p><em>A high-power Gaussian Whistler propagating in a magnatoplasma becomes self-focused because of (i) ponderomotive force and (ii) nonuniform heating nonlinearities (i) being dominant for t &lt;&lt; T and (ii) being dominant for t &gt; t<sub>E</sub>. On short time scale (t &lt;&lt; t<sub>E</sub> ) whistlers of all frequencies can be focused (the self – focusing length is very large for ω= </em><em> /2 and decreases rapidly on both sides), whereas on the long time scale (t &gt; t<sub>E</sub>) only high frequency whistlers (ω&gt; </em><em> /2) are focused. At very high powers the plasma is depleted almost completely from the axial region and self-focusing does not occur, rather, defocusing takes place. </em></p><p><em>            A plane uniform whistler of high intensity is seen to be unstable for small scale fluctuations, i.e., it must break up into filaments in course of it propagation. The growth rate increases with decreasing scale length of perturbation and is seen to be a saturating function of power density of the beam. </em></p></div>

scholarly journals Dynamics and interactions of highly resolved marine plankton via automated high frequency sampling

2017 ◽  
Author(s):  
David M. Needham ◽  
Erin B. Fichot ◽  
Ellice Wang ◽  
Lyria Berdjeb ◽  
Jacob A. Cram ◽  
...  
Keyword(s):  
High Frequency ◽  
18S Rrna ◽  
18S Rrna Gene ◽  
Short Time Scale ◽  
Rrna Gene ◽  
Gene Sequences ◽  
Ecological Processes ◽  
New Information ◽  
Abundant Phytoplankton ◽  
Short Time

AbstractShort time-scale observations are valuable for understanding microbial ecological processes. We assessed dynamics in relative abundance and potential activities by sequencing the small sub-unit ribosomal RNA gene (rRNA gene) and rRNA molecules (rRNA) ofBacteria,Archaea, andEukaryotaonce to twice-daily between March 2014 and May 2014 from the surface ocean off Catalina Island, California. TypicallyOstreococcus, Braarudosphaera, Teleaulax, and Synechococcusdominated phytoplankton sequences (including chloroplasts) while SAR11,Sulfitobacter, andFluviicoladominated non-phytoplanktonBacteriaandArchaea. We observed short-lived increases of diatoms, mostlyPseudo-nitzschiaandChaetoceros, with quickly respondingBacteriaandArchaeaincludingFlavobacteriaceae(Polaribacter&Formosa),Roseovarius, andEuryarchaeota(MGII), notably the exact amplicon sequence variants we observed responding similarly to another diatom bloom nearby, three years prior. We observed correlations representing known interactions among abundant phytoplankton rRNA sequences, demonstrating the biogeochemical and ecological relevance of such interactions: 1) The kleptochloroplastidic ciliateMesodinium18S rRNA gene sequences and a singleTeleaulaxtaxon (via 16S rRNA gene sequences) were correlated (Spearmanr=0.83) yet uncorrelated to aTeleaulax18S rRNA gene OTU, or any other taxon (consistent with a kleptochloroplastidic or karyoklepty relationship) and 2) the photosynthetic prymnesiophyteBraarudosphaera bigelowiiand two strains of diazotrophic cyanobacterium UCYN-A were correlated and each taxon was also correlated to other taxa, includingB. bigelowiito a verrucomicrobium and a dictyochophyte phytoplankter (allr> 0.8). We also report strong correlations (r> 0.7) between various ciliates, bacteria, and phytoplankton, suggesting interactions via currently unknown mechanisms. These data reiterate the utility of high-frequency time-series to show rapid microbial reactions to stimuli, and provide new information aboutin-situdynamics of previously recognized and hypothesized interactions.

Anomalous Diffusion in Short-Pulse Laser Interactions With Random Media

1996 ◽  
Vol 118 (3) ◽  
pp. 781-786 ◽  
Author(s):  
M. C. Hipwell ◽  
C.-L. Tien
Keyword(s):  
Time Scales ◽  
Anomalous Diffusion ◽  
Time Scale ◽  
Random Media ◽  
Energy Transport ◽  
Short Pulse ◽  
Homogeneous Medium ◽  
Short Time Scale ◽  
Short Time ◽  
The Impact

This work applies fractal percolation theory to examine the impact of anomalous diffusion in short time-scale applications of random media. It is shown that there exist three regimes of heat transport corresponding to transport over the basic percolation unit (particle), the fractal cluster, and the homogeneous medium. Scaling is performed to determine the characteristic time scales of anomalous diffusion. The dependence of these time scales on both material properties and structure is examined to assess the impact of the anomalous diffusion regime on short time-scale energy transport. Additional criteria that determine the importance of anomalous diffusion relative to other transport phenomena and properties, such as radiation and thermal boundary resistance, are established.

Possible network interactions indicated by bilaterally coherent fast rhythms in expiratory recurrent laryngeal nerve discharges

1993 ◽  
Vol 70 (5) ◽  
pp. 2192-2196 ◽  
Author(s):  
W. X. Huang ◽  
C. N. Christakos ◽  
M. I. Cohen ◽  
Q. He
Keyword(s):  
High Frequency ◽  
Laryngeal Nerve ◽  
Short Time Scale ◽  
Coherence Analysis ◽  
High Frequency Oscillations ◽  
Prolonged Duration ◽  
Almost All ◽  
Short Time ◽  
Two Sides ◽  
Pulmonary Stretch Receptor

1. In a search for correlated fast rhythms in recurrent laryngeal (RL) expiratory (E) activities, we performed spectral and coherence analysis on bilateral RL nerve discharges in 54 midcollicular decerebrate, paralyzed cats. 2. Inspiratory (I) RL activities showed in almost all cases high-frequency oscillations (HFO, range 50-100 Hz) that were bilaterally coherent and also coherent to HFOs in phrenic (PHR) activities. In contrast, bilaterally coherent rhythms (range 24-54 Hz) in RLE discharges were found in only a fraction of the cats (6/54); in the other cats (48/54) such coherences were absent even though the auto-spectra showed the presence of similar fast rhythms on the two sides. The bilateral RLE coherences were associated with increased amplitude and prolonged duration of RLE activity, such as occurred following removal of phasic pulmonary stretch receptor inputs by vagotomy or by no-inflation. 3. Thus, although coherent fast rhythms are uncommon in RLE discharges, their occurrence under some conditions indicates the presence of short-time-scale interactions between neurons involved in this activity. This suggests that such rhythms are a general feature of neural networks.

A Discussion of Nano-Length Scale Heat Conduction by Comparing the Ballistic-Diffusive Equation and Molecular Dynamics Simulation

2002 ◽  
Author(s):  
Pezhman Akbari ◽  
Boon-Keat Chui ◽  
Lisa Oravecz-Simpkins ◽  
John R. Lloyd
Keyword(s):  
Heat Transfer ◽  
Molecular Dynamics ◽  
Heat Conduction ◽  
Molecular Dynamics Simulation ◽  
Energy Transport ◽  
Dynamics Simulation ◽  
Length Scale ◽  
Conductive Heat ◽  
Using Data ◽  
Length Analysis

A discussion of two methods, the Ballistic-Diffusive, Chen [1,2], and Molecular Dynamics simulation, for solving heat conduction in the nano-length regime is presented. Using data from Chen [1,2], a solution to the Ballistic Diffusive equation is rescaled and compared with the Fourier solution. Results imply that care must be taken when rescaling and comparing equations used in the different length scale regimes because physical definitions (i.e. temperature) are not identical in the two regions (nano and macro length). Analysis of the molecular dynamics simulation shows its inadequacy to describe conductive heat transfer in the nanoscale. Based on the discussion, a modified energy transport map is devised.

Microscale Thermal Energy Transfer Between Thin Films with Vacuum Gap at Interface

2019 ◽  
Vol 44 (2) ◽  
pp. 123-142 ◽  
Author(s):  
Haider Ali ◽  
Bekir Sami Yilbas
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Energy Transfer ◽  
Radiative Heat ◽  
Near Field ◽  
Silicon Film ◽  
Phonon Transport ◽  
Ballistic Phonons ◽  
Vacuum Gap

Abstract Transfer of phonons through a silicon–diamond thin film pair with a nano-size gap at the interface is examined. The thin film pair is thermally disturbed by introducing 301 K at the silicon film left edge while keeping the other edges of the thin films at a low temperature (300 K). The radiative phonon transport equation is solved numerically to quantify the phonon intensity distribution in the combined films. The frequency dependent formulation of phonon transport is incorporated in the transient analysis. The thermal boundary resistance is adopted at the interface in the formulations. The near-field radiative heat transfer is also adopted at the gap interface, as the vacuum gap size falls within the Casimir limit. The predictions of thermal conductivity are validated through the thermocouple data. It is observed that predictions of thermal conductivity are in agreement with the experimental data. The ballistic phonons play a major role in energy transfer through the gap; their contribution is more significant than that of the near-field radiative heat transfer. Enlarging the size of the gap reduces the influence of the ballistic phonons on the energy transfer in the films. Increasing the silicon film thickness alters the energy transfer through the gap; in this case, the equivalent equilibrium temperature difference is increased at the interface.

Heat Transfer in Nanostructures for Solid-State Energy Conversion

2001 ◽  
Vol 124 (2) ◽  
pp. 242-252 ◽  
Author(s):  
G. Chen ◽  
A. Shakouri
Keyword(s):  
Heat Transfer ◽  
Solid State ◽  
Energy Conversion ◽  
State Energy ◽  
Energy Transport ◽  
Quantum Wires ◽  
Energy Conversion Efficiency ◽  
Phonon Transport ◽  
Device Development ◽  
Conversion Technologies

Solid-state energy conversion technologies such as thermoelectric and thermionic refrigeration and power generation require materials with low thermal conductivity but good electrical conductivity and Seebeck coefficient, which are difficult to realize in bulk semiconductors. Nanostructures such as superlattices, quantum wires, and quantum dots provide alternative approaches to improve the solid-state energy conversion efficiency through size and interface effects on the electron and phonon transport. In this review, we discuss recent research and progress using nanostructures for solid-state energy conversion. The emphasis is placed on fundamental issues that distinguish energy transport and conversion between nanoscale and macroscale, as well as heat transfer issues related to device development and property characterization.

scholarly journals Origin of Blazar Activity

1999 ◽  
Vol 194 ◽  
pp. 256-268
Author(s):  
M. M. Romanova
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Energy Spectrum ◽  
Magnetic Fields ◽  
Time Scale ◽  
High Frequency ◽  
Short Time Scale ◽  
Poynting Flux ◽  
Electron Positron ◽  
Short Time

Models of Blazars based on the propagation of finite discontinuities or fronts in the Poynting flux jet from the innermost regions of an accretion disk around a black hole are discussed. Such fronts may be responsible for short time–scale (from less than hours to days) flares in different wavebands from high frequency radioband to TeV, with delay in low radio frequencies as a result of synchrotron self-absorption. The cases of magnetic fields of one and opposite polarities across the front are investigated. We find that annihilation of magnetic field in the front leads to higher energy spectrum of leptons and possibility of strong TeV flares. Electron–positron pairs form in most cases as a result of interaction between numerous synchrotron photons and SSC photons, and constitute the majority species, compared with the ions at subparsec scales. Frequent weak outbursts may be responsible for flickering core radiation in all wavebands, while the stronger outbursts may be observed as short time–scale flares.

Electrodynamical Model of Quasi-Efficient Financial Markets

1998 ◽  
Vol 01 (02n03) ◽  
pp. 143-148 ◽  
Author(s):  
Kirill N. Ilinski ◽  
Alexander S. Stepanenko
Keyword(s):  
Financial Markets ◽  
Portfolio Management ◽  
High Frequency ◽  
Quantum Electrodynamics ◽  
Quantitative Agreement ◽  
Short Time Scale ◽  
Market Participants ◽  
Smart Money ◽  
Real Market ◽  
Short Time

The modelling of financial markets presents a problem which is both theoretically challenging and practically important. The theoretical aspects concern the issue of market efficiency which may even have political implications (Cuthbertson, 1996), whilst the practical side of the problem has clear relevance to portfolio management (Elton and Gruber, 1995) and derivative pricing (Hull, 1997). Up till now all market models contain "smart money" traders and "noise" traders whose joint activity constitutes the market (De Long et al., 1990; Bak et al., 1997). On a short time scale this traditional separation does not seem to be realistic, and is hardly acceptable since all high-frequency market participants are professional traders and cannot be separated into "smart" and "noise". In this paper we present a "microscopic" model with homogenuous quasi-rational behaviour of traders, aiming to describe short time market behaviour. To construct the model we use an analogy between "screening" in quantum electrodynamics and an equilibration process in a market with temporal mispricing (Ilinski, 1997; Dunbar, 1998). As a result, we obtain the time-dependent distribution function of the returns which is in quantitative agreement with real market data and obeys the anomalous scaling relations recently reported for both high-frequency exchange rates (Ghashghaie et al., 1996, S&P500 (Mantegna and Stanley, 1994) and other stock market indices (Bouchaud and Sornette, 1994; Matacz, 1997).

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