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Статті в журналах з теми "Non-equilibrium energies"
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Dellago, Christoph, and Gerhard Hummer. "Computing Equilibrium Free Energies Using Non-Equilibrium Molecular Dynamics." Entropy 16, no. 1 (December 27, 2013): 41–61. http://dx.doi.org/10.3390/e16010041.
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Ross, David, Elizabeth A. Strychalski, Christopher Jarzynski, and Samuel M. Stavis. "Equilibrium free energies from non-equilibrium trajectories with relaxation fluctuation spectroscopy." Nature Physics 14, no. 8 (May 28, 2018): 842–47. http://dx.doi.org/10.1038/s41567-018-0153-5.
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Suman Kalyan, M., G. Anjan Prasad, V. S. S. Sastry, and K. P. N. Murthy. "A note on non-equilibrium work fluctuations and equilibrium free energies." Physica A: Statistical Mechanics and its Applications 390, no. 7 (April 2011): 1240–47. http://dx.doi.org/10.1016/j.physa.2010.11.018.
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Liewen, Chen, Ge Lingxiao, Zhang Xiaodong, and Zhang Fengshou. "Isospin equilibrium and non-equilibrium in heavy-ion collisions at intermediate energies." Journal of Physics G: Nuclear and Particle Physics 23, no. 2 (February 1, 1997): 211–18. http://dx.doi.org/10.1088/0954-3899/23/2/008.
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Grudzevich, O., S. Yavshits, and Y. Martirosyan. "Non-equilibrium nucleon spectra from reactions at intermediate energies." Radiation Protection Dosimetry 126, no. 1-4 (May 13, 2007): 101–3. http://dx.doi.org/10.1093/rpd/ncm021.
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VOSKRESENSKY, D. N., D. BLASCHKE, G. RÖPKE, and H. SCHULZ. "NON-EQUILIBRIUM APPROACH TO DENSE HADRONIC MATTER." International Journal of Modern Physics E 04, no. 01 (March 1995): 1–45. http://dx.doi.org/10.1142/s021830139500002x.
Повний текст джерелаАнотація:
A general approach to the kinetics of a hadronic many-particle system is formulated employing a nonequilibrium diagram technique. The investigation of medium effects is based on the analysis of the coupled set of nonequilibrium Dyson equations for the π, N, and Δ components. Some model approaches to their solution are considered. The results are applied to the study of expanding hadronic fireballs containing pions, nucleons, and deltas as produced in the course of heavy-ion collisions at energies provided by the GSI-SIS up to the CERN-SpS.
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Michael, Fredrick, and M. D. Johnson. "Replacing leads by self-energies using non-equilibrium Green's functions." Physica B: Condensed Matter 339, no. 1 (November 2003): 31–38. http://dx.doi.org/10.1016/s0921-4526(03)00447-2.
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Basilevsky, M. V., I. V. Rostov, and M. D. Newton. "A frequency-resolved cavity model (FRCM) for treating equilibrium and non-equilibrium solvation energies." Chemical Physics 232, no. 1-2 (June 1998): 189–99. http://dx.doi.org/10.1016/s0301-0104(98)00101-3.
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Newton, M. D., M. V. Basilevsky, and I. V. Rostov. "A frequency-resolved cavity model (FRCM) for treating equilibrium and non-equilibrium solvation energies." Chemical Physics 232, no. 1-2 (June 1998): 201–10. http://dx.doi.org/10.1016/s0301-0104(98)00102-5.
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Rosati, Roberto, Koloman Wagner, Samuel Brem, Raül Perea-Causín, Jonas D. Ziegler, Jonas Zipfel, Takashi Taniguchi, Kenji Watanabe, Alexey Chernikov, and Ermin Malic. "Non-equilibrium diffusion of dark excitons in atomically thin semiconductors." Nanoscale 13, no. 47 (2021): 19966–72. http://dx.doi.org/10.1039/d1nr06230a.
Повний текст джерелаАнотація:
Combining microscopic theory and spatiotemporal photoluminescence experiments we reveal an unconventional, time-dependent exciton diffusion in atomically thin semiconductors. This behavior originates from hot dark excitons with large excess energies.
Дисертації з теми "Non-equilibrium energies"
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Nicholls, David Conway. "Nebular metallicities in isolated dwarf irregular galaxies." Phd thesis, 2014. http://hdl.handle.net/1885/11923.
Повний текст джерелаАнотація:
The motive for this work was to investigate whether small, isolated gas-rich galaxies show
evidence of chemical evolution, by studying their nebular metallicities. I have identified
a sample of 83 objects chosen for low luminosity and mass, the presence of active star
formation, and isolation from other galaxies and galaxy clusters that might generate tidal
effects or enrich the intergalactic medium. From these I have measured the spectra of 35
objects, using theWiFeS IFU spectrograph on the ANU 2.3m telescope at Siding Spring.
In analysing spectra extracted from the WiFeS data cubes, I found that standard ‘strong
line’ methods using emission line ratios to measure atomic abundances, gave either erratic
or no results. I found that for those galaxies showing the [O iii] 4363Å auroral line, the
metallicities determined using the standard ‘electron temperature’ methodwere inconsistent
with previous published work. This led me to investigate the conventional assumption that
electrons in Hii regions are in thermal equilibrium. I show that the non-equilibrium ‘ ’
electron energy distribution, found almost universally in solar system plasmas, can explain
the long recognised ‘abundance discrepancy’ between recombination line and collisional line
abundance calculations in nebular metallicity measurements. This has added an important
new dimension to the analysis of nebular spectra.
Using the extensively revised Mappings photoionisation modelling code and new atomic
data to analyse the spectra of two exceptionally isolated dwarf galaxies, I find that they
exhibit metallicities similar to galaxies in more crowded environments, and appear to have
evolved quite normally, through periodic star formation and subsequent enrichment of
their interstellar media.
I present a new approach for calculating total oxygen abundance using electron temperatures
that appears to give more consistent results than earlier methods. I apply this to my
measured spectra, together with the revised Mappings photoionisation modelling code, to
explore the physical parameters affecting the measurement of nebular metallicities. In particular,
I find strong evidence for several of the observed nebulae being—in part—optically
thin. I use the models to show that nebular optical depth affects measured abundances and
temperatures, and that electron densities also have an important role. I develop models that
give a very good match to the observations.
I conclude that the measurement of abundances and temperatures in Hii regions is a more
complex question than had generally been assumed, and important physical parameters
affecting the measurement processes have in the past not been taken fully into account.
Книги з теми "Non-equilibrium energies"
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Sherwood, Dennis, and Paul Dalby. Phase equilibria. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198782957.003.0015.
Повний текст джерелаАнотація:
This chapter extends the discussion of gas phase equilibria to phase equilibria. The central concept is the vapour pressure, and the key proof is that the criterion for phase equilibrium is the equality of the molar Gibbs free energies, or chemical potentials, of each phase. This then leads to the Clapeyron and Clausius-Clapeyron equations. A notable feature of this chapter is the discussion of non-ideal gases, answering the question “Given that, by definition, an ideal gas can never liquefy, what is it about a real gas that enables the gas to change phase into a liquid?”. A unique feature of this discussion is the rigorous analysis of the Gibbs free energy of a van der Waals gas under compression, and the proof of the ‘Maxwell construction’.
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Fox, Raymond. The Use of Self. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780190616144.001.0001.
Повний текст джерелаАнотація:
This monograph presents recent advances in neural network (NN) approaches and applications to chemical reaction dynamics. Topics covered include: (i) the development of ab initio potential-energy surfaces (PES) for complex multichannel systems using modified novelty sampling and feedforward NNs; (ii) methods for sampling the configuration space of critical importance, such as trajectory and novelty sampling methods and gradient fitting methods; (iii) parametrization of interatomic potential functions using a genetic algorithm accelerated with a NN; (iv) parametrization of analytic interatomic potential functions using NNs; (v) self-starting methods for obtaining analytic PES from ab inito electronic structure calculations using direct dynamics; (vi) development of a novel method, namely, combined function derivative approximation (CFDA) for simultaneous fitting of a PES and its corresponding force fields using feedforward neural networks; (vii) development of generalized PES using many-body expansions, NNs, and moiety energy approximations; (viii) NN methods for data analysis, reaction probabilities, and statistical error reduction in chemical reaction dynamics; (ix) accurate prediction of higher-level electronic structure energies (e.g. MP4 or higher) for large databases using NNs, lower-level (Hartree-Fock) energies, and small subsets of the higher-energy database; and finally (x) illustrative examples of NN applications to chemical reaction dynamics of increasing complexity starting from simple near equilibrium structures (vibrational state studies) to more complex non-adiabatic reactions. The monograph is prepared by an interdisciplinary group of researchers working as a team for nearly two decades at Oklahoma State University, Stillwater, OK with expertise in gas phase reaction dynamics; neural networks; various aspects of MD and Monte Carlo (MC) simulations of nanometric cutting, tribology, and material properties at nanoscale; scaling laws from atomistic to continuum; and neural networks applications to chemical reaction dynamics. It is anticipated that this emerging field of NN in chemical reaction dynamics will play an increasingly important role in MD, MC, and quantum mechanical studies in the years to come.
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Raff, Lionel, Ranga Komanduri, Martin Hagan, and Satish Bukkapatnam. Neural Networks in Chemical Reaction Dynamics. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199765652.001.0001.
Повний текст джерелаАнотація:
This monograph presents recent advances in neural network (NN) approaches and applications to chemical reaction dynamics. Topics covered include: (i) the development of ab initio potential-energy surfaces (PES) for complex multichannel systems using modified novelty sampling and feedforward NNs; (ii) methods for sampling the configuration space of critical importance, such as trajectory and novelty sampling methods and gradient fitting methods; (iii) parametrization of interatomic potential functions using a genetic algorithm accelerated with a NN; (iv) parametrization of analytic interatomic potential functions using NNs; (v) self-starting methods for obtaining analytic PES from ab inito electronic structure calculations using direct dynamics; (vi) development of a novel method, namely, combined function derivative approximation (CFDA) for simultaneous fitting of a PES and its corresponding force fields using feedforward neural networks; (vii) development of generalized PES using many-body expansions, NNs, and moiety energy approximations; (viii) NN methods for data analysis, reaction probabilities, and statistical error reduction in chemical reaction dynamics; (ix) accurate prediction of higher-level electronic structure energies (e.g. MP4 or higher) for large databases using NNs, lower-level (Hartree-Fock) energies, and small subsets of the higher-energy database; and finally (x) illustrative examples of NN applications to chemical reaction dynamics of increasing complexity starting from simple near equilibrium structures (vibrational state studies) to more complex non-adiabatic reactions. The monograph is prepared by an interdisciplinary group of researchers working as a team for nearly two decades at Oklahoma State University, Stillwater, OK with expertise in gas phase reaction dynamics; neural networks; various aspects of MD and Monte Carlo (MC) simulations of nanometric cutting, tribology, and material properties at nanoscale; scaling laws from atomistic to continuum; and neural networks applications to chemical reaction dynamics. It is anticipated that this emerging field of NN in chemical reaction dynamics will play an increasingly important role in MD, MC, and quantum mechanical studies in the years to come.
Частини книг з теми "Non-equilibrium energies"
1
Kumar, Jishad. "Dissipative Quantum System and Energy Balance." In Quantum Field Theory [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106474.
Повний текст джерелаАнотація:
We discuss how various parts of a quantum many-body system exchange energies at thermal equilibrium. To show this, we assume a quantum system is coupled to a many-body environment (at thermal equilibrium with a bigger environment) consisting of a large number of independent and non-interacting quantum harmonic oscillators above a stable ground state. Once the coupling to a large environment is switched on, the system dissipates its energy continuously to the environment until it reaches equilibrium with the latter. We use the Quantum Langevin equation to show such energy exchange at equilibrium. We conclude that different parts of a physical system can exchange energies even at absolute zero temperature.
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D’yachenko, A. T., and I. A. Mitropolsky. "Non-equilibrium Equation of State in the Approximation of the Local Density Functional and Its Application to the Emission of High-Energy Particles in Collisions of Heavy Ions." In Density Functional Theory Calculations. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.92247.
Повний текст джерелаАнотація:
The non-equilibrium equation of state is found in the approximation of the functional on the local density, and its application to the description of the emission of protons and pions in heavy ion collisions is considered. The non-equilibrium equation of state is studied in the context of the hydrodynamic approach. The compression stage, the expansion stage, and the freeze-out stage of the hot spot formed during the collisions of heavy ions are considered. The energy spectra of protons and subthreshold pions produced in collisions of heavy ions are calculated with inclusion of the nuclear viscosity effects and compared with experimental data for various combinations of colliding nuclei with energies of several tens of MeV per nucleon.
3
Bujalowski, Wlodzimierz, and Maria J. Jezewska. "Quantitative determination of equilibrium binding isotherms for multiple ligand-macromolecule interactions using spectroscopic methods." In Spectrophotometry and Spectrofluorimetry. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780199638130.003.0009.
Повний текст джерелаАнотація:
Thermodynamic studies provide information that is necessary in order to understand the forces that drive the formation of ligand-macromolecule complexes. Knowledge of the energetics of these interactions is also indispensable for characterization of functionally important structural changes that occur within the studied complexes. Quantitative examination of the equilibrium interactions are designed to provide the answers to the questions: What is the stoichiometry of the formed complexes? How strong or how specific are the interactions? Are there any cooperative interactions among the binding sites and/or the bound ligand molecules? Are the binding sites intrinsically heterogeneous? What are the molecular forces involved in the formation of the studied complexes, or, in other words, how do the equilibrium binding and kinetic parameters depend on solution variables (temperature, pressure, pH, salt concentration, etc.)? Equilibrium isotherms for the binding of a ligand to a macromolecule represent the relationship between the degree of ligand binding (moles of ligands bound per mole of a macromolecule) and the free ligand concentration. A true thermodynamic binding isotherm is model-independent and reflects only this relationship. Only then, when such an isotherm is obtained, can one proceed to extract physically meaningful interaction parameters that characterize the free energies of interaction. This is accomplished by comparing the experimental isotherms to theoretical predictions based on specific binding models that incorporate known molecular aspects, such as intrinsic binding constants, cooperativity parameters, allosteric equilibrium constants, discrete character of the binding sites or overlap of potential binding sites, etc. (see below). Any method used to quantitatively study ligand binding to a macromolecule must relate the extent of the complex formation to the free ligand concentration in solution. Numerous techniques have been developed to study equilibrium properties of specific and non-specific ligand-macromolecule interactions in which binding is directly monitored, including equilibrium dialysis, ultrafiltration, column chromatography, filter binding assay and gel electrophoresis (1-6). These direct methods are very straightforward; however, they are usually time consuming and some, like filter binding or gel shift assays, are non-equilibrium techniques which require many controls before the reliable equilibrium binding data can be obtained.
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Raff, Lionel, Ranga Komanduri, Martin Hagan, and Satish Bukkapatnam. "Empirical Potential-Energy Surfaces Fitting Using Feed forward Neural Networks." In Neural Networks in Chemical Reaction Dynamics. Oxford University Press, 2012. http://dx.doi.org/10.1093/oso/9780199765652.003.0012.
Повний текст джерелаАнотація:
When the system of interest becomes too complex to permit the use of ab initio methods to obtain the system potential-energy surfaces (PES), empirical potential surfaces are frequently employed to represent the force fields present in the system under investigation. In most cases, the functional forms present in these potentials are selected on the basis of chemical and physical intuitions. The parameters of the surface are frequently adjusted to fit a very small set of experimental data that comprise bond energies, equilibrium bond distances and angles, fundamental vibrational frequencies, and perhaps measured barrier heights to reactions of interest. Such potentials generally yield only qualitative or semiquantitative descriptions of the system dynamics. Several research groups have significantly improved the accuracy of the values of the experimental properties computed using empirical potential surfaces by fitting the chosen functional form for the potential to the force fields obtained from trajectories using ab initio Car-Parrinello molecular dynamics simulations. The fitting to the force fields is usually done using a least-squares fitting approach. This method has been employed by Izvekov et al. to obtain effective non-polarizable three-site force fields for liquid water. Carré et al. have employed such a procedure to obtain a new pair potential for silica. In their investigation, the vector of potential parameters was fitted using an iterative Levenberg-Marquardt algorithm. Tangney and Scandolo have also developed an interatomic force field for liquid SiO2 in which the parameters were fitted to the forces, stresses, and energies obtained from ab initio calculations. Ercolessi and Adams have used a quasi-Newtonian procedure to fit an empirical potential for aluminum to data obtained from first-principals computations. Empirical potentials can be improved by making the parameters parameterized functions of the coordinates defining the instantaneous positions of the atoms of the system. This approach has been successfully employed by numerous investigators The difficulty with this procedure is that the number of parameters that must be adjusted increases rapidly. Appropriate fitting of these parameters requires a much more extensive database. Finally, the actual fitting process can often be tedious, difficult, and time-consuming.
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Tuck, Adrian F. "Temperature Intermittency and Ozone Photodissociation." In Atmospheric Turbulence. Oxford University Press, 2008. http://dx.doi.org/10.1093/oso/9780199236534.003.0008.
Повний текст джерелаАнотація:
During the last two missions performed by the ER-2 in the Arctic lower stratosphere, POLARIS in the summer of 1997 and SOLVE during the winter of 1999–2000, an unexpected correlation emerged when the data were subjected to analysis by generalized scale invariance. It was between the intermittency of temperature, a number which can be determined for each segment of analysable flight from the temperature measurements, and the average over the flight segment of the photodissociation rate of ozone, which was calculable as a time series along the flight segment by taking the product of the 1Hz measurements of the local ozone concentration and the 1Hz measurements of the ozone photodissociation coefficient. In searching for a physical explanation of this correlation, it was realized that the common link between the quantities was that ozone photodissociation produces photofragments of atomic and molecular oxygen that recoil very fast, while temperature itself is the integral of the translational energy of all air molecules. The next step therefore was to ask if the intermittency of temperature was correlated with the average of the temperature itself over the flight segment: it was. One might think that because ozone is present at about 20km altitude in mixing ratios of about 2−3×10−6, the rapid quenching of the translational energies of the recoiling photofragments by molecular nitrogen and molecular oxygen would prevent any possible effects from showing up in the bulk, observed temperature. However, during the POLARIS mission, it was possible to fly the ER-2 near the terminator, the boundary between day and night, because at Arctic latitudes the planet was rotating slowly enough that it could fly legs in the same, stagnant air mass in both sunlight and darkness. These flights showed that the heating rate was significant, about 0.2Kper hour, and since heating in the stratosphere arises from the absorption of solar radiation by ozone, which leads to photodissociation, there is a prima facie case for considering non-local thermodynamic equilibrium effects from the recoiling fast photofragments. Two arguments may be deployed at this point, both from the theoretical literature; there are as yet no experiments on the translational speed distributions of atmospheric molecules.
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Schweitzer, George K., and Lester L. Pesterfield. "The Carbon Group." In The Aqueous Chemistry of the Elements. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780195393354.003.0010.
Повний текст джерелаАнотація:
The elements which constitute the Carbon Group of the Periodic Table are carbon C, silicon Si, germanium Ge, tin Sn, and lead Pb. All five of the elements have atoms characterized by an outer electron structure of ns2np2 with n representing the principal quantum number. This electron arrangement signals the possibility of oxidation states of IV and II. Such is the case with the II oxidation state becoming more stable from C to Pb. As one descends the group, there is a marked change from non-metallic (C) to metallic character (Pb). Reflecting very high ionization energies, C, Si, and Ge do not form a simple cation, they instead bond covalently. In line with the trends just mentioned, the inorganic aqueous chemistry moves from anionic (C) to cationic (Pb). The inorganic aqueous solution chemistry of C is represented by four acids and their anionic derivatives: carbonic acid H2CO3, oxalic acid H2C2O4, formic acid HOOCH, and acetic acid HOOCCH3. Note that in all of these the ionizing H+ ions are not attached to C but to O. The inorganic aqueous chemistry of Si is dominated by anions SiO(OH)3− and SiO2(OH)2−2 and their many polymeric forms and by the hexafluorosilicate anion SiF6−2. Ge is very similar to Si. Cationic species, largely absent in all three previous elements, are shown in both Sn and Pb. The covalent single bond radii of C, Si, and Ge are 77, 118, and 122 pm, and the ionic radii in pm of the other two elements are Sn+2(118), Sn+4 (83), Pb+2 (133), Pb+4 (92). a. E–pH diagrams. In order to understand the E–pH relationships of the aqueous species of C, it is important to consider both the thermodynamic and the kinetic relationships. Thermodynamics tells us whether a reaction will occur but it says nothing about how fast. The rate is a kinetic matter. When acetic acid HC2H3O2 is entered into a C species E–pH diagram, Figure 8.1 results. This figure shows that at equilibrium HC2H3O2 is not stable and disproportionates into H2CO3 and CH4. The same E–pH diagram results when formic acid HOOCH or when oxalic acid H2C2O4 is entered.
Тези доповідей конференцій з теми "Non-equilibrium energies"
1
Raman, Ashok, D. G. Walker, and T. S. Fisher. "Non-Equilibrium Thermal Effects in Power Transistors." In ASME 2001 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/imece2001/htd-24402.
Повний текст джерелаАнотація:
Abstract The present work considers electro-thermal simulation of LDMOS devices and associated non-equilibrium effects. Simulations have been performed on three kinds of LDMOS i.e. bulk Si, partial SOI and full SOI. From the analysis, the extent of thermal non-equilibrium is determined from phonon temperature contours and electron energies in each case. The results indicate that, under similar operating conditions, non-equilibrium is more significant in the case of full SOI devices. Time development of acoustic phonon and lattice temperatures, obtained using two different heat source terms, was studied. This study provided insight into the difference between localized device heating in the electrically active region. The variation of optical and acoustic phonon temperatures with time is presented, and is used to identify time scales where thermal non-equilibrium would be significant.
2
D'yachenko, A. T., K. A. Gridnev, I. A. Mitropolsky, and W. Greiner. "A NON-EQUILIBRIUM EQUATION OF STATE IN HEAVY-ION COLLISIONS AT INTERMEDIATE ENERGIES." In International Symposium on Exotic Nuclei EXON-2014. WORLD SCIENTIFIC, 2015. http://dx.doi.org/10.1142/9789814699464_0043.
Повний текст джерела
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Xue, S., P. Proulx, M. I. Boulos, and T. Murphy. "A Thermal and Chemical Non-Equilibrium Model for Multi-Component Ar-H2 Plasma." In ITSC2005, edited by E. Lugscheider. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2005. http://dx.doi.org/10.31399/asm.cp.itsc2005p0305.
Повний текст джерелаАнотація:
Abstract A thermal and chemical non-equilibrium model is developed for the modelling of multi-component supersonic induction Ar-H2 plasma flows. The species included in the modelling are electrons(e), hydrogen ion(H+), hydrogen atoms(H), hydrogen molecules(H2), Argon ions(Ar+) and Argon atoms(Ar). The negative hydrogen ions(H-), molecular hydrogen ions(H2+) and second order ionisation are neglected. The chemical reactions considered in the modelling are the H2 dissociations and the corresponding recombination, induced by Ar atom and H2, and the ionisations of the hydrogen and Argon and the corresponding recombination. All the heavy species are assumed to have the same temperature (Ti). The electron temperature (Te) is allowed to deviate from that of heavy species. The energies for these chemical reactions have been treated as the source terms for energy conservation equations. As a result, the contributions of these chemical reactions to the total enthalpy are removed. Therefore, the heavy species temperature can be obtained by solving the thermal kinetic energy equation, rather than the total enthalpy equation. Yos’s mixing law is used to calculate the contribution of vibrational and rotational energies of hydrogen molecules to the thermal conductivity of heavy species. The transport properties are calculated using the formulas derived by Hirschfelder, Curtiss and Bird. The data of collision integrals or collision cross-sections between species in the mixture are taken from Murphy, Devoto and Mason’s publications. The binary mass diffusion coefficients between the species in the mixture are also calculated from these collision integral data. The mass diffusion of species in the mixture are modelled under the dilute approximation at present since the mole fraction of the principal species, Argon, in the whole computational region is more than 90%. For charged species, Ambipolar diffusion coefficients are used. Mass balance equations are solved to obtain the mass fractions or mole fractions or the number densities of all the species except for electrons. The electron number density is determined by the condition of electrical neutrality. The developed model is applied to the modelling of inductive plasma flow, generated by the Tekna PL-35 torch model, under different pressures and then to the supersonic plasma flow. The model has been validated by comparing the transport properties under the LTE conditions from this model with the corresponding published values.
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Bulusu, A., and D. G. Walker. "Modeling of Electron Transport in Thin Films With Quantum and Scattering Effects." In ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73212.
Повний текст джерелаАнотація:
With device dimensions shrinking to nanoscales, quantum effects such as confinement and tunneling become significant in electron transport. In addition, thermal transport in devices is directly coupled to charge transport even in highly scaled devices. While electron-phonon scattering usually helps restore thermodynamic equilibrium, shrinking device dimensions may not ensure enough scattering to restore equilibrium. The simultaneous consideration of scattering effects, which is usually described as particle behavior, and quantum effects, which are wave in nature, is extremely difficult and computationally intensive. Most device transport simulation models are not mature enough to couple quantum effects with strong scattering effects. In this paper, we couple quantum effects and scattering influences on electron transport using the non-equilibrium Green’s function formalism. Results indicate a 45 to 70 percent decrease in channel current for the case of near-elastic, phase-breaking, electron-phonon scattering. The single phonon energies ranged from 2meV to 20meV. The results illustrate the importance of including scattering effects with quantum transport. In addition, the NEGF model is used to assess the effect of temperature on device characteristics of thin film superlattices whose applications include thermoelectric cooling of electronic and optoelectronic systems. Results show the predicted Seebeck coefficient to be in good agreement with the measured values.
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Fan, Angie, Calin Tarau, Richard Bonner, Tomas Palacios, and Massoud Kaviany. "2-D Simulation of Hot Electron-Phonon Interactions in a Submicron Gallium Nitride Device Using Hydrodynamic Transport Approach." In ASME 2012 Heat Transfer Summer Conference collocated with the ASME 2012 Fluids Engineering Division Summer Meeting and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ht2012-58322.
Повний текст джерелаАнотація:
In this study, a thermal and electrical coupled device solver is developed to simulate the energy transfer mechanism within a GaN FET with a gate length of 0.2 μm. The simulation simultaneously solves a set of hydrodynamic equations (derived from the Boltzmann Transport Equation) and the Poisson equation for electron, optical phonon and acoustic phonon energies, electron number density, electric field and electric potential. This approach has been previously established for gallium arsenide (GaAs) devices [36,37], but has not been extended to GaN due to the lack of readily available property values for GaN devices that are required. Via extensive literature study, high-fidelity properties for GaN were collected in analytical forms with respect to many dependencies, e.g. lattice temperature, electrical field, electron number density, doping rate, defects rate. These properties are then implemented into the developed code to provide a high accuracy sub-micron GaN device simulation. Simulations show that non-equilibrium heat generation is exhibited in a typical device while the drain current is reduced due to the decrease in electron mobility. Future analysis is needed to quantify the hot-electron effect on reducing the drain current and to discover more effective ways of heat removal.
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Chen, Chen, Zhidong Du, and Liang Pan. "Nanoscale Thermal Transport in Plasmonic Nanofocusing Structure With Strong Nonlocality." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-37334.
Повний текст джерелаАнотація:
Nanoscale optical energy concentration and focusing is crucial for many high-throughput nanomanufacturing applications, such as material processing, imaging and lithography. The use of surface plasmons has resulted in the rapid development of nanofocusing devices and techniques at spatial confinements as good as a few nanometers associated with strong nonlocal plasmonic response. However, operations of these plasmonic nanofocusing structures usually require extremely high optical energy density at nanoscale, which leads to intense structure heating and causes unreliable device functions and short device lifetimes. In many plasmonic applications, optical heating has become a very important issue, which has not been investigated intensively yet. In these structures, the ballistic transport and interface scattering of the energy carriers both become significant because the characteristic lengths of the devices are comparable to or smaller than the mean free paths of the carriers. A comprehensive model is desired to understand the heat generation and transport inside the plasmonic nanofocusing structures. This work studied the electromagnetic and optothermal responses of plasmonic nanofocusing nanostructures. At the nanometer length scale, the local optical response and diffusive thermal model are no longer sufficient to describe the device optothermal response because of the strong interactions between energy carriers and the ballistic nature of carriers. Here, we used the hydrodynamic Drude model to consider the nonlocality of plasmonic response and calculate the heat generation inside the metallic nanostructures. Starting from Boltzmann transport equation, we derived the energy transport equations for both electron and phonon systems under the relaxation-time approximations. The obtained multi-carrier ballistic-diffusive model was used to study the non-equilibrium heat transports inside the structures. We assume that the ballistic electrons originate from boundaries and the electron-photon couplings inside the structure, experiencing out-scattering only in the material. The optically-generated “hot” electrons are considered as ballistic and are treated separately from the “ordinary” electrons which are in local thermal equilibrium and have significantly lower energies. Meanwhile, the electron-phonon couplings are considered under the non-equilibrium conditions between the electron and phonon systems. Using our model, we further investigated the transient optothermal responses of a one-dimensional (1D) plasmonic nanofocusing structure. In comparison to the diffusive transport description, our multi-carrier ballistic-diffusive model can more accurately describe the optothermal responses of the plasmonic nanofocusing structures which are crucial for predicting the performance and the lifetime of the plasmonic nanofocusing devices.
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Avanessian, Tadeh, and Gisuk Hwang. "Adsorption-Controlled Thermal Diode: Nonequilibrium Molecular Dynamics Simulation." In ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icnmm2016-7936.
Повний текст джерелаАнотація:
A thermal diode is a system controlling the heat transfer preferentially in one direction. This serves as a basic building block to design advanced thermal management systems in energy saving applications and to provide implications to design new application such as thermal computers. The development of the thermal diode has been of great interest as electrical diodes have similarly made significant impacts on modern industries. Numerous studies have demonstrated thermal diode mechanisms using non-linear heat transfer mechanisms, but the main challenges in current systems are poor steady-state performance, slow transient response, and/or extremely difficult manufacturing for the viable solutions. In this study, an adsorption-based thermal diode is examined for a fast and efficient thermal diode mechanism as a completely new class, using a gas-filled, heterogeneous nanogap with asymmetric surface interactions in Knudsen regime. Ar gas atoms confined in Pt-based solid surfaces are selected to predict the degree of rectification, R ∼ 10, using non-equilibrium molecular dynamics simulation with the nanogap size of Lz = 20 nm and ΔT = 20 K for various average plate temperatures, 80 < T < 130 K. Different surface energies for the thermal diode is studied and a maximum degree of rectification, Rmax ∼ 10, is found at T = 80 K which results from the significant adsorption-controlled thermal accommodation coefficient (TAC). The obtained results provide insights into the design of advanced thermal management systems including thermal switches and thermal computing systems.
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Cai, Ziqi, Qingmin Zhang, Zhuang Shao, and Yuanming Li. "Molecular Dynamics Study on Thermal Conductivity of Unirradiated and Irradiated Symmetrical Tilt Grain Boundary 3C-SiC." In 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-92136.
Повний текст джерелаАнотація:
Abstract The cubic silicon carbide (3C-SiC) has been considered as a candidate structural material for several types of advanced nuclear reactors. The effects of cascade collision on thermal conductivity in symmetrical tilt grain boundary (GB) were studied by Molecular dynamics (MD) simulations. The thermal conductivity of 3C-SiC at Σ5(210)[001] GB was calculated using non-equilibrium molecular dynamics (NEMD) methods. A relatively small simulation unit was used to analyze the effect of different energies of incident PKA (primary knock-on atoms) on the thermal conductivity of 3C-SiC and to compare the results with perfect structure GB system. Finally, the vibrational density of states (VDOS) of atoms in the GB region was calculated to analyze the phonon mismatch at the interface. Calculations show that cascade collisions generated by energetic atoms will result in a decrease in thermal conductivity of the Σ5(210) GB system, but the effect varies in different regions, with a sharp decrease in thermal conductivity and an increase in thermal resistance for the intracrystalline region, while the magnitude of change in either thermal resistance or thermal conductivity is not significant in the GB region. Irradiated model shows a higher GB energy compared to the unirradiated model. For all irradiated models, lattice defects have a significant effect on the thermal conductivity of the GB system, depending on the spatial structure of the GBs. the results of the VDOS analysis suggest that an increase in the degree of atomic lattice mismatch near the interface is responsible for a further increase in the thermal resistance of the irradiated GB system.
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Gao, G., L. Pershin, and J. Mostaghimi. "Optical Emission Spectroscopic Diagnostics of Atmospheric Argon Radio Frequency Inductively Coupled Plasma." In ITSC2003, edited by Basil R. Marple and Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p1337.
Повний текст джерелаАнотація:
Abstract An experimental study is conducted to determine the property fields of 40 MHz argon radio frequency inductively coupled plasma using optical emission spectroscopy. The pure argon plasma was operated at the input power of 0.3 kW and under atmospheric pressure. 29 atomic argon lines with upper level energies ranging from 12.9 to 15.5 eV, continuum emission and line width are used to evaluate plasma parameters such as temperature and electron number density. Since 40 MHz plasma is in almost complete nonequilibrium, the validaty and accuracy of most usual spectroscopic methods are questioned. Analysis based on the Boltzmann diagram, line-to-continuum intensity ratio, population of continuum extrapolated level, and continuum intensity reveals the departure from thermodynamic equilibrium in the plasma. Among these methods, the Boltzmann diagram method is shown to provide reliable plasma excitation temperature as long as the Boltzmann plot is drawn based on enough spectra lines covering from infrared to ultraviolet regions. The continuum emission at wavelengths within visible region can give good estimation of the electron density by using excitation temperature in the continuum relation. The line-to-continuum is not a reliable method for the temperature measurement of nonequilibrim plasma. The electron density obtained from the Saha plot can provide rough estimation of the electron density. It is shown that the electron-atom interaction contribution to the continuum radiation is more important than being expected before for the argon plasma in our study. The non-axisymmetric distribution of the emission was found to exist within the coil zone of the plasma, which may affect the estimation of the local emission coefficient, and consequently the measured plasma fields.
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Jaubert, Jean-Noe¨l, Romain Privat, and Michel Molie`re. "Ethanol and Distillate Blends: A Thermodynamic Approach to Miscibility Issues." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22126.
Повний текст джерелаАнотація:
In the recent years, the quest for an ever wider cluster of sustainable primary energies has prompted an increasing number of attempts to combine the emission sobriety of bio fuels with the energy density advantage of fossil fuels. A number of compositions incorporating hydrocarbons, ethanol and in some cases limited amounts of water have been proposed, especially in the forms of micro emulsions, with a variable success. Indeed due to markedly different physical and chemical properties, ethanol and gasoil are able to blend and form homogeneous solutions only in limited proportion ranges. Indeed, such mixtures often give rise to liquid-liquid equilibrium. A key parameter is thus the Minimum Miscibility Temperature (MMT), i.e. the temperature above which ethanol and gasoil become completely miscible. In fact, commercial gasoils do not constitute a monolithic product but display in the contrary a large span of compositions that influence the stability of these blends. In this context, the LRGP laboratory (Laboratoire Re´actions et Ge´nie des Proce´de´s) has undertaken an investigation program intended to understand the factors underlying the stability of ethanol/gasoil blends. The approach is based on the calculation of the liquid-liquid phase diagrams formed by anhydrous ethanol and a mixture of various hydrocarbons representative of the diesel oil pool using the group contribution concept. Indeed, for correlating thermodynamic properties, it is often convenient to regard a molecule as an aggregate of functional groups; as a result, some thermodynamic properties (heat of mixing, activity coefficients) can be calculated by summing group contributions. In this study, the universal quasichemical functional group activity coefficient (UNIFAC) method has been employed as it appears to be particularly useful for making reasonable estimates for the studied non ideal mixtures for which data are sparse or totally absent. In any group-contribution method, the basic idea is that whereas there are thousands of chemical compounds of interest in chemical technology, the number of functional groups that constitute these compounds is much smaller. Therefore, if we assume that a physical property of a fluid is the sum of contributions made by the molecule’s functional groups, we obtain a possible technique for correlating the properties of a very large number of fluids in terms of a much smaller number of parameters that characterize the contributions of individual groups. This paper shows the large influence exerted by the paraffinic, aromatic and naphthenic character of the gasoil but also the sulfur content of the fossil fraction on the shape of the liquid-liquid phase diagram and on the value of the minimum miscibility temperature.