Scaffidi-Argentina, F.; Werle, H.
1995-09-01
Since beryllium is considered as one of the best neutron multiplier materials in the blanket of the next generation fusion reactors, several studies have been started to evaluate its behaviour under irradiation during both operating and accidental conditions. Based on safety considerations, tritium produced in beryllium during neutron irradiation represents one important issue, therefore it is necessary to investigate tritium transport processes by using a comprehensive mathematical model and comparing its predictions with well characterized experimental tests. Because of the difficulties in extrapolating the short-time tritium release tests to a longer time scale, also long-time annealing experiments with beryllium samples from the SIBELIUS irradiation. have been carried out at the Forschungszentrum Karlsruhe. Samples were annealed up to 12 months at temperatures up to 650{degrees}C. The inventory after annealing was determined by heating the samples up to 1050{degrees}C with a He+0.1 vo1% H{sub 2} purge gas. Furthermore, in order to investigate the likely effects of cracks formation eventually causing a faster tritium release from beryllium, the behaviour of samples irradiated at low temperature (40-50{degrees}C) but up to very high fast neutron fluences (0.8-3.9{center_dot}10{sup 22} cm{sup -2}, E{sub n}{ge}1 MeV) in the BR2 reactor has been investigated. Tritium was released by heating the beryllium samples up to 1050{degrees}C and purging them with He+0.1 vo1% H{sub 2}. Tritium release from high-irradiated beryllium samples showed a much faster kinetics than from the low-irradiated ones, probably because of crack formation caused by thermal stresses in the brittle material and/or by helium bubbles migration. The obtained experimental data have been compared with predictions of the code ANFIBE with the goal to better understand the physical mechanisms governing tritium behaviour in beryllium and to assess the prediction capabilities of the code.
OBJECT KINETIC MONTE CARLO SIMULATIONS OF CASCADE ANNEALING IN TUNGSTEN
Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.
2014-03-31
The objective of this work is to study the annealing of primary cascade damage created by primary knock-on atoms (PKAs) of various energies, at various temperatures in bulk tungsten using the object kinetic Monte Carlo (OKMC) method.
Understanding long-time vacancy aggregation in iron: A kinetic activation-relaxation technique study
NASA Astrophysics Data System (ADS)
Brommer, Peter; Béland, Laurent Karim; Joly, Jean-François; Mousseau, Normand
2014-10-01
Vacancy diffusion and clustering processes in body-centered-cubic (bcc) Fe are studied using the kinetic activation-relaxation technique (k-ART), an off-lattice kinetic Monte Carlo method with on-the-fly catalog building capabilities. For monovacancies and divacancies, k-ART recovers previously published results while clustering in a 50-vacancy simulation box agrees with experimental estimates. Applying k-ART to the study of clustering pathways for systems containing from one to six vacancies, we find a rich set of diffusion mechanisms. In particular, we show that the path followed to reach a hexavacancy cluster influences greatly the associated mean-square displacement. Aggregation in a 50-vacancy box also shows a notable dispersion in relaxation time associated with effective barriers varying from 0.84 to 1.1 eV depending on the exact pathway selected. We isolate the effects of long-range elastic interactions between defects by comparing to simulations where those effects are deliberately suppressed. This allows us to demonstrate that in bcc Fe, suppressing long-range interactions mainly influences kinetics in the first 0.3 ms, slowing down quick energy release cascades seen more frequently in full simulations, whereas long-term behavior and final state are not significantly affected.
Progress on long-time kinetic simulation of tokamak turbulence with very weak dissipation
NASA Astrophysics Data System (ADS)
Parker, Scott; Chen, Yang; Kahut, Jason
2006-04-01
Recent progress on convergence studies of long-time simulations for both electron-temperature-gradient (ETG) and ion-temperature-gradient driven microturbulence will be reported. It was surprising to us to find that low-noise ETG turbulence simulations are well-converged with rather modest particle number (30-70 million particles). Progress on the particle-continuum method [Vadlamani et al., Comp. Phys. Comm., 209 164 (2004)] will also be reported. The particle-continuum method is really a general class of a variety of methods and has been shown to solve the so-called ``growing weight problem" in two-dimensional simulations. The method is implemented in four-dimensions with the μ∇B force neglected. In this case, v is a constant of motion and resetting of the particle δf on a four-dimensional grid is more reasonable. Discussion of issues related to applying particle continuum method in five dimensions will also be presented. Work supported by DOE SciDAC Gyrokinetic Particle Simulation Center and Center for Plasma Edge Simulation.
Lee, Thomas; Bocquet, Lydéric; Coasne, Benoit
2016-01-01
Hydrocarbon recovery from unconventional reservoirs (shale gas) is debated due to its environmental impact and uncertainties on its predictability. But a lack of scientific knowledge impedes the proposal of reliable alternatives. The requirement of hydrofracking, fast recovery decay and ultra-low permeability-inherent to their nanoporosity-are specificities of these reservoirs, which challenge existing frameworks. Here we use molecular simulation and statistical models to show that recovery is hampered by interfacial effects at the wet kerogen surface. Recovery is shown to be thermally activated with an energy barrier modelled from the interface wetting properties. We build a statistical model of the recovery kinetics with a two-regime decline that is consistent with published data: a short time decay, consistent with Darcy description, followed by a fast algebraic decay resulting from increasingly unreachable energy barriers. Replacing water by CO2 or propane eliminates the barriers, therefore raising hopes for clean/efficient recovery. PMID:27327254
NASA Astrophysics Data System (ADS)
Lee, Thomas; Bocquet, Lydéric; Coasne, Benoit
2016-06-01
Hydrocarbon recovery from unconventional reservoirs (shale gas) is debated due to its environmental impact and uncertainties on its predictability. But a lack of scientific knowledge impedes the proposal of reliable alternatives. The requirement of hydrofracking, fast recovery decay and ultra-low permeability--inherent to their nanoporosity--are specificities of these reservoirs, which challenge existing frameworks. Here we use molecular simulation and statistical models to show that recovery is hampered by interfacial effects at the wet kerogen surface. Recovery is shown to be thermally activated with an energy barrier modelled from the interface wetting properties. We build a statistical model of the recovery kinetics with a two-regime decline that is consistent with published data: a short time decay, consistent with Darcy description, followed by a fast algebraic decay resulting from increasingly unreachable energy barriers. Replacing water by CO2 or propane eliminates the barriers, therefore raising hopes for clean/efficient recovery.
Lee, Thomas; Bocquet, Lydéric; Coasne, Benoit
2016-01-01
Hydrocarbon recovery from unconventional reservoirs (shale gas) is debated due to its environmental impact and uncertainties on its predictability. But a lack of scientific knowledge impedes the proposal of reliable alternatives. The requirement of hydrofracking, fast recovery decay and ultra-low permeability—inherent to their nanoporosity—are specificities of these reservoirs, which challenge existing frameworks. Here we use molecular simulation and statistical models to show that recovery is hampered by interfacial effects at the wet kerogen surface. Recovery is shown to be thermally activated with an energy barrier modelled from the interface wetting properties. We build a statistical model of the recovery kinetics with a two-regime decline that is consistent with published data: a short time decay, consistent with Darcy description, followed by a fast algebraic decay resulting from increasingly unreachable energy barriers. Replacing water by CO2 or propane eliminates the barriers, therefore raising hopes for clean/efficient recovery. PMID:27327254
NASA Astrophysics Data System (ADS)
Mahmoud, Sami; Trochet, Mickaël; Restrepo, Oscar; Mousseau, Normand
The microscopic mechanisms associated with the evolution of metallic materials are still a matter of debate as both experimental and numerical approaches fail to provide a detailed atomic picture of their time evolution. Here, we use the kinetic activation-relaxation technique (k-ART), an unbiased off-lattice kinetic Monte Carlo method with on-the-fly catalog building to overcome these limitations and follow the atomistic evolution of a 10.000-atom grain boundary Ni system over macroscopic time scales. We first characterize the kinetic properties of four different empirical potentials, the embedded atom method (EAM), the first and second modified embedded atom method (MEAM1NN and MEAM2NN respectively) and the Reax force field (ReaxFF) potentials. Comparing the energetics, the elastic effects and the diffusion mechanisms for systems with one to three vacancies and one to three self-interstitials in nickel simulated over second time scale, we conclude that ReaxFF and EAM potentials are closest to experimental values. We then proceed to study the long-time evolution of a grain boundary with the Reax forcefield and to offer a detailed description of its energy landscape, including the exact description of short and long-range effects on self-diffusion along the interface
Annealing kinetics of electrodeposited lithium dendrites.
Aryanfar, Asghar; Cheng, Tao; Colussi, Agustin J; Merinov, Boris V; Goddard, William A; Hoffmann, Michael R
2015-10-01
The densifying kinetics of lithium dendrites is characterized with effective activation energy of Ea ≈ 6 - 7 kcal mol(-1) in our experiments and molecular dynamics computations. We show that heating lithium dendrites for 55 °C reduces the representative dendrites length λ¯(T,t) up to 36%. NVT reactive force field simulations on three-dimensional glass phase dendrites produced by our coarse grained Monte Carlo method reveal that for any given initial dendrite morphology, there is a unique stable atomic arrangement for a certain range of temperature, combined with rapid morphological transition (∼10 ps) within quasi-stable states involving concurrent bulk and surface diffusions. Our results are useful for predicting the inherent structural characteristics of lithium dendrites such as dominant coordination number. PMID:26450322
NASA Astrophysics Data System (ADS)
Bocquet, Lyderic
2015-11-01
In this talk I will discuss the transport of hydrocarbons across nanoporous media and analyze how this transport impacts at larger scales the long-time kinetics of hydrocarbon recovery from unconventional reservoirs (the so-called shale gas). First I will establish, using molecular simulation and statistical mechanics, that the continuum description - the so-called Darcy law - fails to predict transport within a nanoscale organic matrix. The non-Darcy behavior arises from the strong adsorption of the alkanes in the nanoporous material and the breakdown of hydrodynamics at the nanoscale, which contradicts the assumption of viscous flow. Despite this complexity, all permeances collapse on a master curve with an unexpected dependence on alkane length, which can be described theoretically by a scaling law for the permeance. Then I will show that alkane recovery from such nanoporous reservoirs is dynamically retarded due to interfacial effects occuring at the material's interface. This occurs especially in the hydraulic fracking situation in which water is used to open fractures to reach the hydrocarbon reservoirs. Despite the pressure gradient used to trigger desorption, the alkanes remain trapped for long times until water desorbs from the external surface. The free energy barrier can be predicted in terms of an effective contact angle on the composite nanoporous surface. Using a statistical description of the alkane recovery, I will then demonstrate that this retarded dynamics leads to an overall slow - algebraic - decay of the hydrocarbon flux. Such a behavior is consistent with algebraic decays of shale gas flux from various wells reported in the literature. This work was performed in collaboration with B. Coasne, K. Falk, T. Lee, R. Pellenq and F. Ulm, at the UMI CNRS-MIT, Massachusetts Institute of Technology, Cambridge, USA.
NASA Astrophysics Data System (ADS)
Gutiérrez, Ricardo; Garrahan, Juan P.
2016-07-01
Glasses prepared by physical vapour deposition have been shown to be remarkably more stable than those prepared by standard cooling protocols, with properties that appear to be similar to systems aged for extremely long times. When subjected to a rapid rise in temperature, ultrastable glasses anneal towards the liquid in a qualitatively different manner than ordinary glasses, with the seeming competition of different time and length scales. We numerically reproduce the phenomenology of ultrastable glass annealing with a kinetically constrained model, a three dimensional East model with soft constraints, in a setting where the bulk is in an ultrastable configuration and a free surface is permanently excited. Annealing towards the liquid state is given by the competition between the ballistic propagation of a front from the free surface and a much slower nucleation-like relaxation in the bulk. The crossover between these mechanisms also explains the change in behaviour with film thickness seen experimentally.
Defect production and annealing kinetics in elemental metals and semiconductors
NASA Astrophysics Data System (ADS)
de la Rubia, T. Diaz; Soneda, N.; Caturla, M. J.; Alonso, E. A.
1997-11-01
We present a review of recent results of molecular dynamics (MD) and kinetic Monte Carlo (KMC) simulations of defect production and annealing in irradiated metals and semiconductors. The MD simulations describe the primary damage state in elemental metals Fe, V and Au, and in an elemental semiconductor Si. We describe the production of interstitial and vacancy clusters in the cascades and highlight the differences among the various materials. In particular, we discuss how covalent bonding in Si affects defect production and amorphization resulting in a very different primary damage state from the metals. We also use MD simulations to extract prefactors and activation energies for migration of point defects, as well as to investigate the energetics, geometry and diffusivity of small vacancy and interstitial clusters. We show that, in the metals, small interstitial clusters are highly mobile and glide in one dimension along the direction of the Burger's vector. In silicon, we show that, in contrast to the metals, the neutral vacancy diffuses faster than the neutral self-interstitial. The results for the primary damage state and for the defect energetics and kinetics are then combined and used in a kinetic Monte Carlo simulation to investigate the escape efficiency of defects from their nascent cascade in metals, and the effect of dose rate on damage accumulation and amorphization in silicon. We show that in fee metals Au and Pb at or above stage V the escape probability is approximately 40% for 30 keV recoils so that the freely migrating defect fraction is approximately 10% of the dpa standard. In silicon, we show that damage accumulation at room temperature during light ion implantation can be significantly reduced by decreasing the dose rate. The results are compared to scanning tunneling microscopy experiments.
Chowdhury, Md Delwar Hossain; Um, Jae Gwang; Jang, Jin
2014-12-08
We have studied the effect of long time post-fabrication annealing on negative bias illumination stress (NBIS) of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film-transistors. Annealing for 100 h at 250 °C increased the field effect mobility from 14.7 cm{sup 2}/V s to 17.9 cm{sup 2}/V s and reduced the NBIS instability remarkably. Using X-ray photoelectron spectroscopy, the oxygen vacancy and OH were found to exist at the interfaces of a-IGZO with top and bottom SiO{sub 2}. Long time annealing helps to decrease the vacancy concentration and increase the metal-oxygen bonds at the interfaces; this leads to increase in the free carrier concentrations in a-IGZO and field-effect mobility. X-ray reflectivity measurement indicated the increment of a-IGZO film density of 5.63 g cm{sup −3} to 5.83 g cm{sup −3} (3.4% increase) by 100 h annealing at 250 °C. The increase in film density reveals the decrease of O vacancy concentration and reduction of weak metal-oxygen bonds in a-IGZO, which substantially helps to improve the NBIS stability.
Magnetization kinetics in tension and field annealed Fe-based amorphous alloys
NASA Astrophysics Data System (ADS)
Hasegawa, Ryusuke; Takahashi, Kengo; Francoeur, Bruno; Couture, Pierre
2013-05-01
Magnetization kinetics in tension-annealed and field-annealed amorphous magnetic materials indicates that strain and magnetic fields are equally effective in inducing and relaxing local structural and magnetic anisotropy changes. This observation is based on the thermomagnetic aging of the magnetic properties obtained in the materials studied.
Growth of Ni2Si by rapid thermal annealing: Kinetics and moving species
NASA Astrophysics Data System (ADS)
Ma, E.; Lim, B. S.; Nicolet, M.-A.; Natan, M.
1987-10-01
The growth kinetics is characterized and the moving species is identified for the formation of Ni2Si by Rapid Thermal Annealing (RTA) of sequentially deposited Si and Ni films on a <100> Si substrate. The interfacial Ni2Si layer grows as the square root of time, indicating that the suicide growth process is diffusion-limited. The activation energy is 1.25±0.2 eV in the RTA temperature range of 350 450° C. The results extend those of conventional steady-state furnace annealing quite fittingly, and a common activation energy of 1.3±0.2 eV is deduced from 225° to 450° C. The marker experiment shows that Ni is the dominant moving species during Ni2Si formation by RTA, as is the case for furnace annealing. It is concluded that the two annealing techniques induce the same growth mechanisms in Ni2Si formation.
Interrogating the Effects of Radiation Damage Annealing on Helium Diffusion Kinetics in Apatite
NASA Astrophysics Data System (ADS)
Willett, C. D.; Fox, M.; Shuster, D. L.
2015-12-01
Apatite (U-Th)/He thermochronology is commonly used to study landscape evolution and potential links between climate, erosion and tectonics. The technique relies on a quantitative understanding of (i) helium diffusion kinetics in apatite, (ii) an evolving 4He concentration, (iii) accumulating damage to the crystal lattice caused by radioactive decay[1], and (iv) the thermal annealing of such damage[2],[3], which are each functions of both time and temperature. Uncertainty in existing models of helium diffusion kinetics has resulted in conflicting conclusions, especially in settings involving burial heating through geologic time. The effects of alpha recoil damage annealing are currently assumed to follow the kinetics of fission track annealing (e.g., reference [3]), although this assumption is difficult to fully validate. Here, we present results of modeling exercises and a suite of experiments designed to interrogate the effects of damage annealing on He diffusivity in apatite that are independent of empirical calibrations of fission track annealing. We use the existing experimental results for Durango apatite[2] to develop and calibrate a new function that predicts the effects of annealing temperature and duration on measured diffusivity. We also present a suite of experiments conducted on apatite from Sierra Nevada, CA granite to establish whether apatites with different chemical compositions have the same behavior as Durango apatite. Crystals were heated under vacuum to temperatures between 250 and 500°C for 1, 10, or 100 hours. The samples were then irradiated with ~220 MeV protons to produce spallogenic 3He, the diffusant then used in step-heating diffusion experiments. We compare the results of these experiments and model calibrations to existing models. Citations: [1]Shuster, D., Flowers R., and Farley K., (2006), EPSL 249(3-4), 148-161; [2]Shuster, D. and Farley, K., (2009), GCA 73 (1), 6183-6196; [3]Flowers, R., Ketcham, R., Shuster, D. and Farley, K
NASA Astrophysics Data System (ADS)
Boboev, I. R.; Strizhko, L. S.; Bobozoda, Sh.; Gorbunov, E. P.
2016-03-01
The results of kinetic studies on the removal of arsenic from scorodite using sulfidizing annealing are presented. The reaction order with respect to the reactant and the activation energy are established from the experimental data. The rate-determining step of the sulfidizing annealing process is determined. The main reactions that occur during the sulfidizing of arsenic in scorodite are proposed on the basis of the obtained results and confirmed by thermodynamic calculations and chemical analyses. The major results of testing this technology, as applied to the refractory oxidized ores in which arsenic is mainly concentrated in scorodite, are presented. Arsenic removal from this ore is confirmed by chemical and quantitative X-ray diffraction analyses and by qualitative phase analysis. Industrial use of this technology provides safe and efficient processing of refractory gold-containing ores, where arsenic is mainly concentrated in scorodite.
Kinetics of F center annealing and colloid formation in Al2O3
NASA Astrophysics Data System (ADS)
Kotomin, E. A.; Kuzovkov, V. N.; Popov, A. I.; Vila, R.
2016-05-01
The diffusion-controlled kinetics of the F center annealing in Al2O3 (sapphire, corundum) is simulated theoretically for the two regimes: after neutron irradiation when the immobile F centers are annihilated with complementary defects - mobile interstitial oxygen ions, and in thermochemically reduced (additively colored) crystals where mobile F centers aggregate and create the metal colloids. A comparison of the experimental and theoretical kinetics allowed us to estimate the migration energies for the F centers and interstitial oxygen ions. It is obtained that the pre-exponents in diffusion coefficients for defects in different neutron irradiated samples can vary by two orders of magnitude which is attributed by presence of numerous traps for mobile interstitial oxygen ions.
Kinetics modeling of precipitation with characteristic shape during post-implantation annealing
Li, Kun-Dar Chen, Kwanyu
2015-11-15
In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion dose, temperature and crystallographic symmetry on the processes of faceted precipitation were also demonstrated. To comprehend the kinetic mechanism, the simulation results were further analyzed quantitatively by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponents obtained from the regression curves varied from 1.47 to 0.52 for different conditions. With the increase of ion dose and temperature, the nucleation and growth of precipitations were expedited in accordance with the shortened incubation time and the raised coefficient of growth rate. A miscellaneous shape of precipitates in various crystallographic symmetry systems could be simulated through this anisotropic model. From the analyses of the kinetics, more fundamental information about the nucleation and growth mechanism of faceted precipitation during post-implantation annealing was acquired for future application.
Kinetics modeling of precipitation with characteristic shape during post-implantation annealing
NASA Astrophysics Data System (ADS)
Li, Kun-Dar; Chen, Kwanyu
2015-11-01
In this study, we investigated the precipitation with characteristic shape in the microstructure during post-implantation annealing via a theoretical modeling approach. The processes of precipitates formation and evolution during phase separation were based on a nucleation and growth mechanism of atomic diffusion. Different stages of the precipitation, including the nucleation, growth and coalescence, were distinctly revealed in the numerical simulations. In addition, the influences of ion dose, temperature and crystallographic symmetry on the processes of faceted precipitation were also demonstrated. To comprehend the kinetic mechanism, the simulation results were further analyzed quantitatively by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) equation. The Avrami exponents obtained from the regression curves varied from 1.47 to 0.52 for different conditions. With the increase of ion dose and temperature, the nucleation and growth of precipitations were expedited in accordance with the shortened incubation time and the raised coefficient of growth rate. A miscellaneous shape of precipitates in various crystallographic symmetry systems could be simulated through this anisotropic model. From the analyses of the kinetics, more fundamental information about the nucleation and growth mechanism of faceted precipitation during post-implantation annealing was acquired for future application.
Movahedi, M.; Kokabi, A.H.; Seyed Reihani, S.M.; Najafi, H.; Farzadfar, S.A.; Cheng, W.J.; Wang, C.J.
2014-04-01
In this study, we explored the growth kinetics of the Al–Fe intermetallic (IM) layer at the joint interface of the St-12/Al-5083 friction stir lap welds during post-weld annealing treatment at 350, 400 and 450 °C for 30 to 180 min. Optical microscope (OM), field emission gun scanning electron microscope (FEG-SEM) and transmission electron microscope (TEM) were employed to investigate the structure of the weld zone. The thickness and composition of the IM layers were evaluated using image analysis system and electron back-scatter diffraction (EBSD), respectively. Moreover, kernel average misorientation (KAM) analysis was performed to evaluate the level of stored energy in the as-welded state. The results showed that the growth kinetics of the IM layer was not governed by a parabolic diffusion law. Presence of the IM compounds as well as high stored energy near the joint interface of the as-welded sample was recognized to be the origin of the observed deviation from the parabolic diffusion law. - Highlights: • This work provided a new insight into growth kinetics of Al–Fe IM thickness. • The growth kinetics of IM layer was not governed by a parabolic diffusion law. • IM near the joint interface was the origin of deviation from the parabolic law. • High stored energy at joint interface was origin of deviation from parabolic law.
Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.
2015-07-01
The results of object kinetic Monte Carlo (OKMC) simulations of the annealing of primary cascade damage in bulk tungsten using a comprehensive database of cascades obtained from molecular dynamics (Setyawan et al.) are described as a function of primary knock-on atom (PKA) energy at temperatures of 300, 1025 and 2050 K. An increase in SIA clustering coupled with a decrease in vacancy clustering with increasing temperature, in addition to the disparate mobilities of SIAs versus vacancies, causes an interesting effect of temperature on cascade annealing. The annealing efficiency (the ratio of the number of defects after and before annealing) exhibits an inverse U-shape curve as a function of temperature. The capabilities of the newly developed OKMC code KSOME (kinetic simulations of microstructure evolution) used to carry out these simulations are described.
NASA Astrophysics Data System (ADS)
Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.
2015-07-01
The results of object kinetic Monte Carlo (OKMC) simulations of the annealing of primary cascade damage in bulk tungsten using a comprehensive database of cascades obtained from molecular dynamics (Setyawan et al.) are described as a function of primary knock-on atom (PKA) energy at temperatures of 300, 1025 and 2050 K. An increase in SIA clustering coupled with a decrease in vacancy clustering with increasing temperature, in addition to the disparate mobilities of SIAs versus vacancies, causes an interesting effect of temperature on cascade annealing. The annealing efficiency (the ratio of the number of defects after and before annealing) exhibits an inverse U-shape curve as a function of temperature. The capabilities of the newly developed OKMC code KSOME (kinetic simulations of microstructure evolution) used to carry out these simulations are described.
Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.; Roche, Kenneth J.; Kurtz, Richard J.; Wirth, Brian D.
2015-07-01
Object kinetic Monte Carlo (OKMC) simulations have been performed to investigate various aspects of cascade aging in bulk tungsten and to determine the sensitivity of the results to the kinetic parameters. The primary focus is on how the kinetic parameters affect the initial recombination of defects in the first few ns of a simulation. The simulations were carried out using the object kinetic Monte Carlo (OKMC) code KSOME (kinetic simulations of microstructure evolution), using a database of cascades obtained from results of molecular dynamics (MD) simulations at various primary knock-on atom (PKA) energies and directions at temperatures of 300, 1025 and 2050 K. The OKMC model was parameterized using defect migration barriers and binding energies from ab initio calculations. Results indicate that, due to the disparate mobilities of SIA and vacancy clusters in tungsten, annealing is dominated by SIA migration even at temperatures as high as 2050 K. For 100 keV cascades initiated at 300 K recombination is dominated by annihilation of large defect clusters. But for all other PKA energies and temperatures most of the recombination is due to the migration and rotation of small SIA clusters, while all the large SIA clusters escape the cubic simulation cell. The inverse U-shape behavior exhibited by the annealing efficiency as a function of temperature curve, especially for cascades of large PKA energies, is due to asymmetry in SIA and vacancy clustering assisted by the large difference in mobilities of SIAs and vacancies. This annealing behavior is unaffected by the dimensionality of SIA migration persists over a broad range of relative mobilities of SIAs and vacancies.
Kinetics and dynamics of annealing during sub-gel phase formation in phospholipid bilayers
Páli, Tibor; Bartucci, Rosa; Horváth, László I.; Marsh, Derek
1993-01-01
The saturation transfer electron spin resonance (STESR) spectra of spin-labeled phosphatidylcholine have been used to follow the kinetics of conversion from the gel phase to the sub-gel phase in aqueous bilayers of dipalmitoyl phosphatidylcholine. This is a simple, well-defined model system for lipid domain formation in membranes. The integrated intensity of the STESR spectrum from the chain-labeled lipid first increases and then decreases with time of incubation in the gel phase at 0°C. The first, more rapid phase of the kinetics is attributed to the conversion of germ nuclei to growth nuclei of the sub-gel phase. The increase in STESR intensity corresponds to the reduction in chain mobility of spin labels located in the gel phase at the boundaries of the growth nuclei and correlates with the increase in the diagnostic STESR line height ratios over this time range. The second, slower phase of the kinetics is attributed to growth of the domains of the sub-gel phase. The decrease in STESR intensity over this time regime corresponds to exclusion of the spin-labeled lipids from the tightly packed sub-gel phase and correlates quantitatively with calibrations of the spin label concentration dependence of the STESR intensity in the gel phase. The kinetics of formation of the sub-gel phase are consistent with the classical model for domain formation and growth. At 0°C, the half-time for conversion of germ nuclei to growth nuclei is ∼7.7 h and domain growth of the sub-gel phase is characterized by a rate constant of 0.025 h-1. The temperature dependence of the STESR spectra from samples annealed at 0°C suggests that the subtransition takes place via dissolution of sub-gel phase domains, possibly accompanied by domain fission. PMID:19431899
NASA Astrophysics Data System (ADS)
Mazaheri, Y.; Kermanpur, A.; Najafizadeh, A.; Kalashami, A. Ghatei
2016-03-01
Ultrafine-grained, dual-phase (UFG DP) steels were produced by a new route using an uncommon cold-rolling and subsequent intercritical annealing of ferrite/martensite duplex starting microstructures. The effects of processing parameters such as rolling reduction, intercritical annealing temperature, and time on the microstructural evaluations have been studied. UFG DP steels with an average grain size of about 1 to 2 μm were achieved by short intercritical annealing of the 80 pct cold-rolled duplex microstructures. The kinetics of ferrite recrystallization and austenite formation were studied based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The proposed model for describing the isothermal austenite formation kinetics was applied successfully to the nonisothermal conditions. It was found that complete recrystallization of ferrite before the austenite formation led to the formation of a large extent randomly distributed austenite in the ferrite matrix and a chain-networked structure.
Influence of Oxygen Ion Implantation on the Damage and Annealing Kinetics of Iron-Implanted Sapphire
Hunn, J.D.; McHargue, C.J.
1999-11-14
The effects of implanted oxygen on the damage accumulation in sapphire which was previously implanted with iron was studied for (0001) sapphire implanted with iron and then with oxygen. The energies were chosen to give similar projected ranges. One series was implanted with a 1:l ratio (4x10{sup 16} ions/cm{sup 2} each) and another with a ratio of 2:3 (4x10{sup 16} fe{sup +}/cm{sup 2}; 6x10{sup 16} O{sup +}/cm{sup 2}). Retained damage, X, in the Al-sublattice, was compared to that produced by implantation of iron alone. The observed disorder was less for the dual implantations suggesting that implantation of oxygen enhanced dynamic recovery during implantation. Samples were annealed for one hour at 800 and 1200 C in an oxidizing and in a reducing atmosphere. No difference was found in the kinetics of recovery in the Al-sublattice between the two dual implant conditions. However, the rate of recovery was different for each from samples implanted with iron alone.
Zhang, Huanhuan; Xu, Lin; Lai, Yuqing; Shi, Tongfei
2016-06-28
On a non-wetting solid substrate, the solvent annealing process of a thin polymer film includes the swelling process and the dewetting process. Owing to difficulties in the in situ analysis of the two processes simultaneously, a quantitative study on the solvent annealing process of thin polymer films on the non-wetting solid substrate is extremely rare. In this paper, we design an experimental method by combining spectroscopic ellipsometry with optical microscopy to achieve the simultaneous in situ study. Using this method, we investigate the influence of the structure of swollen film on its dewetting kinetics during the solvent annealing process. The results show that for a thin PS film with low Mw (Mw = 4.1 kg mol(-1)), acetone molecules can form an ultrathin enriched layer between the PS film and the solid substrate during the swelling process. The presence of the acetone enriched layer accounts for the exponential kinetic behavior in the case of a thin PS film with low Mw. However, the acetone enriched layer is not observed in the case of a thin PS film with high Mw (Mw = 400 kg mol(-1)) and the slippage effect of polymer chains is valid during the dewetting process. PMID:27254136
Treml, Benjamin E; Jacobs, Alan G; Bell, Robert T; Thompson, Michael O; Hanrath, Tobias
2016-02-10
Much of the promise of nanomaterials derives from their size-dependent, and hence tunable, properties. Impressive advances have been made in the synthesis of nanoscale building blocks with precisely tailored size, shape and composition. Significant attention is now turning toward creating thin film structures in which size-dependent properties can be spatially programmed with high fidelity. Nonequilibrium processing techniques present exciting opportunities to create nanostructured thin films with unprecedented spatial control over their optical and electronic properties. Here, we demonstrate single scan laser spike annealing (ssLSA) on CdSe nanocrystal (NC) thin films as an experimental test bed to illustrate how the size-dependent photoluminescence (PL) emission can be tuned throughout the visible range and in spatially defined profiles during a single annealing step. Through control of the annealing temperature and time, we discovered that NC fusion is a kinetically limited process with a constant activation energy in over 2 orders of magnitude of NC growth rate. To underscore the broader technological implications of this work, we demonstrate the scalability of LSA to process large area NC films with periodically modulated PL emission, resulting in tunable emission properties of a large area film. New insights into the processing-structure-property relationships presented here offer significant advances in our fundamental understanding of kinetics of nanomaterials as well as technological implications for the production of nanomaterial films. PMID:26536402
Kinetics of hardness evolution during annealing of gamma-irradiated polycarbonate
Yeh, S. H.; Chen, P. Y.; Lee, Sanboh; Harmon, Julie
2012-12-01
This study focuses on the evolution in microhardness values that accompany isothermal annealing in gamma-irradiated polycarbonate (PC). Hardness increases with increasing annealing time, temperature, and gamma radiation dose. A model composed of a mixture of first and zero order structure relaxation is proposed to interpret the hardness data. The rate constant data fit the Arrhenius equation, and the corresponding activation energy decreases with increasing dose. The extent of structural relaxation that controls the hardness in post-annealed PC increases with increasing annealing temperature and dose. The model demonstrates that hardness evolution in PC is an endothermic process. By contrast, when the model is applied to irradiated poly(methyl methacrylate) and hydroxyethyl methacrylate copolymer, hardness evolution is an exothermic process.
Kinetics of Solute Partitioning During Intercritical Annealing of a Medium-Mn Steel
NASA Astrophysics Data System (ADS)
Kamoutsi, H.; Gioti, E.; Haidemenopoulos, Gregory N.; Cai, Z.; Ding, H.
2015-11-01
The evolution of austenite fraction and solute partitioning (Mn, Al, and C) during intercritical annealing was calculated for a medium-Mn steel containing 11 pct Mn. Austenite growth takes place in three stages. The first stage is growth under non-partitioning local equilibrium (NPLE) controlled by carbon diffusion in ferrite. The second stage is growth under partitioning local equilibrium (PLE) controlled by diffusion of Mn in ferrite. The third stage is shrinkage of austenite under PLE controlled by diffusion of Mn in austenite. During PLE growth, the austenite is progressively enriched in Mn. Compositional spikes evolve early during NPLE growth and broaden with annealing temperature and time.
A kinetic model of single-strand annealing for the repair of DNA double-strand breaks.
Taleei, Reza; Weinfeld, Michael; Nikjoo, Hooshang
2011-02-01
Ionising radiation induces different types of DNA damage, including single-strand breaks, double-strand breaks (DSB) and base damages. DSB are considered to be the most critical lesion to be repaired. The three main competitive pathways in the repair of DSB are non-homologous end joining (NHEJ), homologous recombination (HR) and single-strand annealing (SSA). SSA is a non-conservative repair pathway requiring direct repeat sequences for the repair process. In this work, a biochemical kinetic model is presented to describe the SSA repair pathway. The model consists of a system of non-linear ordinary differential equations describing the steps in the repair pathway. The reaction rates were estimated by comparing the model results with the experimental data for chicken DT40 cells exposed to 20 Gy of X-rays. The model successfully predicts the repair of the DT40 cells with the reaction rates derived from the 20-Gy X-ray experiment. The experimental data and the kinetic model show fast and slow DSB repair components. The half time and fractions of the slow and the fast components of the repair were compared for the model and the experiments. Mathematical and computational modelling in biology has played an important role in predicting biological mechanisms and stimulating future experimentation. The present model of SSA adds to the modelling of NHEJ and HR to provide a more complete description of DSB repair pathways. PMID:21183536
Decarburization and grain growth kinetics during the annealing of electrical steels
Oldani, C.R.
1996-12-01
Electrical steels are generally described as thin steel sheets of variable thickness (from 0.27 to 0.76 mm), whose function is to efficiently transport the magnetic flux in electrical equipments. The electromagnetic properties expected from these materials are low magnetic losses and a high permeability. It can be said that a cyclically magnetized-demagnetized material is not free of energy losses because a portion of the power, the loss, is irreversibly transformed into heat. These steels are usually produced in a partially processed condition and they reach their maximum magnetic potential during the final steps of manufacture at the user`s plant. Efficient control of the operations by which the sheets are submitted is essential to obtain the optimum steel yield in the magnetic circuit they are made for. In these operations a decarburization annealing heat treatment produces important effects such as removing punching residual tensions, decarburization to very low carbon content, ferritic grain growth and a favorable magnetic crystallographic texture.
NASA Astrophysics Data System (ADS)
Peters, Andrew J.; Lawson, Richard A.; Nation, Benjamin D.; Ludovice, Peter J.; Henderson, Clifford L.
2016-01-01
State-of-the-art block copolymer (BCP)-directed self-assembly (DSA) methods still yield defect densities orders of magnitude higher than is necessary in semiconductor fabrication despite free-energy calculations that suggest equilibrium defect densities are much lower than is necessary for economic fabrication. This disparity suggests that the main problem may lie in the kinetics of defect removal. This work uses a coarse-grained model to study the rates, pathways, and dependencies of healing a common defect to give insight into the fundamental processes that control defect healing and give guidance on optimal process conditions for BCP-DSA. It is found that bulk simulations yield an exponential drop in defect heal rate above χN˜30. Thin films show no change in rate associated with the energy barrier below χN˜50, significantly higher than the χN values found previously for self-consistent field theory studies that neglect fluctuations. Above χN˜50, the simulations show an increase in energy barrier scaling with 1/2 to 1/3 of the bulk systems. This is because thin films always begin healing at the free interface or the BCP-underlayer interface, where the increased A-B contact area associated with the transition state is minimized, while the infinitely thick films cannot begin healing at an interface.
Coarse-grained molecular dynamics modeling of the kinetics of lamellar BCP defect annealing
NASA Astrophysics Data System (ADS)
Peters, Andrew J.; Lawson, Richard A.; Nation, Benjamin D.; Ludovice, Peter J.; Henderson, Clifford L.
2015-03-01
Directed self-assembly of block copolymers (BCPs) is a process that has received great interest in the field of nanomanufacturing in the past decade, and great strides towards forming high quality aligned patterns have been made. But state of the art methods still yield defectivities orders of magnitude higher than is necessary in semi-conductor fabrication even though free energy calculations suggest that equilibrium defectivities are much lower than is necessary for economic semi-conductor fabrication. This disparity suggests that the main problem may lie in the kinetics of defect removal. This work uses a coarse-grained model to study the rates, pathways, and dependencies of healing a common defect to give insight into the fundamental processes that control defect healing and give guidance on optimal process conditions for BCP-DSA. It is found that infinitely thick films yield an exponential drop in defect heal rate above χN ~ 30. Below χN ~ 30, the rate of transport was similar to the rate at which the transition state was reached so that the overall rate changed only slightly. The energy barrier in periodic simulations increased with 0.31 χN on average. Thin film simulations show no change in rate associated with the energy barrier below χN ~ 50, and then show an increase in energy barrier scaling with 0.16χN. Thin film simulations always begin to heal at either the free interface or the BCP-underlayer interface where the increased A-B contact area associated with the transition state will be minimized, while the infinitely thick films must start healing in the bulk where the A-B contact area is increased. It is also found that cooperative chain movement is required for the defect to start healing.
Uberuaga, B. P.; Voter, A. F.; Sickafus, K. E.; Bacorisen, D.; Smith, Roger; Ball, J. A.; Grimes, R. W.
2007-03-01
Building upon work in which we examined defect production and stability in spinels, we now turn to defect kinetics. Using temperature accelerated dynamics (TAD), we characterize the kinetics of defects in three spinel oxides: magnesium aluminate MgAl{sub 2}O{sub 4}, magnesium gallate MgGa{sub 2}O{sub 4}, and magnesium indate MgIn{sub 2}O{sub 4}. These materials have varying tendencies to disorder on the cation sublattices. In order to understand chemical composition effects, we first examine defect kinetics in perfectly ordered, or normal, spinels, focusing on point defects on each sublattice. We then examine the role that cation disorder has on defect mobility. Using TAD, we find that disorder creates local environments which strongly trap point defects, effectively reducing their mobility. We explore the consequences of this trapping via kinetic Monte Carlo (KMC) simulations on the oxygen vacancy (V{sub O}) in MgGa{sub 2}O{sub 4}, finding that V{sub O} mobility is directly related to the degree of inversion in the system.
Kim, Seung-Hyun; Park, Gyu-Tae; Park, Jong-Jin; Park, Young-Bae
2015-11-01
The effects of annealing, thermomigration (TM), and electromigration (EM) on the intermetallic com- pound (IMC) growth kinetics of Cu/Sn-2.5Ag microbumps were investigated using in-situ scanning electron microscopy at 120-165 degrees C with a current density of 1.5 x 10(5) A/cm2. The IMC growth kinetics was controlled by a diffusion-dominant mechanism and a chemical-reaction-dominant mechanism with annealing and current-stressing conditions, respectively. Before all of the Sn was fully transformed into IMCs, the activation energies of the Cu3Sn IMCs were 0.54 eV, 0.50 eV, and 0.40 eV for annealing, TM, and EM, respectively, which is closely related to the acceleration effect of the interfacial reaction by electron wind force under current stressing. After all of the Sn was fully transformed into IMCs by reacting with Cu, the Cu3Sn IMC growth rates of the three structures became similar due to the reduced and similar diffusion rates inside the IMCs with and without current stressing. PMID:26726558
Long-time limit of correlation functions
NASA Astrophysics Data System (ADS)
Franosch, Thomas
2014-08-01
Auto-correlation functions in an equilibrium stochastic process are well-characterized by Bochner's theorem as Fourier transforms of a finite symmetric Borel measure. The existence of a long-time limit of these correlation functions depends on the spectral properties of the measure. Here we provide conditions applicable to a wide class of dynamical theories guaranteeing the existence of the long-time limit. We discuss the implications in the context of the mode-coupling theory of the glass transition where a non-trivial long-time limit signals an idealized glass state.
NASA Astrophysics Data System (ADS)
Etesami, S. A.; Enayati, M. H.
2016-05-01
The recrystallization behavior of 80 pct, cold-rolled, low-carbon, dual-phase steel during intercritical annealing for different times was studied. The annealed microstructures showed that the recrystallization initially occurred in the deformed martensitic regions. The values of Avrami exponent for recrystallization varied from 3.8 to 4 with an activation energy of 46.9 kJ/mol. This study also introduced a novel method for the production of bimodal grain structures in low-carbon, ferrite-martensite steel.
NASA Astrophysics Data System (ADS)
Etesami, S. A.; Enayati, M. H.
2016-07-01
The recrystallization behavior of 80 pct, cold-rolled, low-carbon, dual-phase steel during intercritical annealing for different times was studied. The annealed microstructures showed that the recrystallization initially occurred in the deformed martensitic regions. The values of Avrami exponent for recrystallization varied from 3.8 to 4 with an activation energy of 46.9 kJ/mol. This study also introduced a novel method for the production of bimodal grain structures in low-carbon, ferrite-martensite steel.
Swain, Mitali Singh, Surendra; Basu, Saibal; Bhattacharya, Debarati; Gupta, Mukul
2014-12-14
Ni-aluminides are an important class of intermetallics from technological point of view. Ni-Al phase diagram has been studied in detail experimentally as well as theoretically. It is known that if annealed at low temperature, the first alloy phase is usually NiAl{sub 3} according to Bené's rule. It is also understood that heat of formation may get modified by local densities of the constituents forming the alloy. In this regard, it is important to identify a kinetic length scale for defining “local density” in a system. We have deposited ultrathin multilayers of Ni and Al of layer thickness in tens of nanometres with Ni:Al stoichiometric ratio as 3:1 and 1:3, respectively. Considering these stoichiometry, Ni{sub 3}Al and NiAl{sub 3} are the thermodynamically favoured alloy phases in these samples. We used x-ray reflectivity, polarized neutron reflectivity, x-ray diffraction, and secondary ion mass spectroscopy to follow the alloy formation after annealing and identified the alloy phases at interfaces with nanometre resolution. Diffusion length of Ni and Al was obtained using Darken's law. Our results predict that ‘diffusion length’ is the unique length scale that connects kinetics to local density. In another interesting observation, using “virtual Kirkendall markers” at the interfaces, we showed asymmetry in consumption of Al for alloy formation, at Al on Ni (Al/Ni) and Ni on Al (Ni/Al) interfaces by comparing as-deposited and annealed states with respect to the markers.
NASA Astrophysics Data System (ADS)
Swain, Mitali; Singh, Surendra; Basu, Saibal; Bhattacharya, Debarati; Gupta, Mukul
2014-12-01
Ni-aluminides are an important class of intermetallics from technological point of view. Ni-Al phase diagram has been studied in detail experimentally as well as theoretically. It is known that if annealed at low temperature, the first alloy phase is usually NiAl3 according to Bené's rule. It is also understood that heat of formation may get modified by local densities of the constituents forming the alloy. In this regard, it is important to identify a kinetic length scale for defining "local density" in a system. We have deposited ultrathin multilayers of Ni and Al of layer thickness in tens of nanometres with Ni:Al stoichiometric ratio as 3:1 and 1:3, respectively. Considering these stoichiometry, Ni3Al and NiAl3 are the thermodynamically favoured alloy phases in these samples. We used x-ray reflectivity, polarized neutron reflectivity, x-ray diffraction, and secondary ion mass spectroscopy to follow the alloy formation after annealing and identified the alloy phases at interfaces with nanometre resolution. Diffusion length of Ni and Al was obtained using Darken's law. Our results predict that `diffusion length' is the unique length scale that connects kinetics to local density. In another interesting observation, using "virtual Kirkendall markers" at the interfaces, we showed asymmetry in consumption of Al for alloy formation, at Al on Ni (Al/Ni) and Ni on Al (Ni/Al) interfaces by comparing as-deposited and annealed states with respect to the markers.
NASA Technical Reports Server (NTRS)
Stecura, S.
1976-01-01
Oxygen was added to T-111 (Ta-8W-2Hf, wt. %) at 820 and 990 C at an oxygen pressure of about 0.0003 torr. The technique employed permitted predetermined and reproducible doping of T-111 up to 3.0 at. % oxygen. Based on the temperature dependence of the doping reaction, it is concluded that the initial rates of oxygen pickup are probably controlled by solution of oxygen into the T-111 lattice. Although hafnium oxides are more stable than those of tantalum or tungsten, analyses of extracted residues indicate that the latter oxides predominate in the as-doped specimens, presumably because of the higher concentrations of tantalum and tungsten in the alloy. However, high-temperature annealing promotes gettering of dissolved oxygen and of other oxides to form hafnium oxides. Small amounts of tantalum and tungsten oxides were still present after high-temperature annealing. Tungsten oxide (WO3) volatilizes slightly from the surface of T-111 at 990 C. The vaporization of WO3 has no apparent affect on the doping reaction.
Effect of thermal annealing on the kinetics of rehydroxylation of Eu3+:La2O3 nanocrystals.
Méndez, Maria; Cesteros, Yolanda; Marsal, Lluís Francesc; Giguère, Alexandre; Drouin, Dominique; Salagre, Pilar; Formentín, Pilar; Pallarès, Josep; Aguiló, Magdalena; Díaz, Francesc; Carvajal, Joan Josep
2012-06-01
Europium-doped lanthanum oxide (5 mol % Eu(3+):La(2)O(3)) was prepared by calcining europium-doped lanthanum hydroxide (5 mol % Eu(3+):La(OH)(3)) previously synthesized by a simple hydrothermal method. Interestingly, we observed different emission Eu(3+) signatures depending on the phase of the host (lanthanum oxide or hydroxide) by cathodoluminescence. Taking into account that lanthanum oxide easily rehydroxylates in air, for the first time, we report the use of cathodoluminiscence as a novel characterization technique to follow the lanthanum oxide rehydroxylation reaction versus time according to different annealing procedures. Additionally, differential thermal-thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction techniques were used to identify the phases formed from the Eu(3+):La(OH)(3) depending on temperature and to study the evolution of La(2)O(3) to La(OH)(3) versus time. The results showed that the higher the temperature and the longer the annealing time, the higher the resistance to rehydroxylation of the Eu(3+):La(2)O(3) sample. PMID:22621467
Long time behaviour of a stochastic nanoparticle
NASA Astrophysics Data System (ADS)
Étoré, Pierre; Labbé, Stéphane; Lelong, Jérôme
2014-09-01
In this article, we are interested in the behaviour of a single ferromagnetic mono-domain particle submitted to an external field with a stochastic perturbation. This model is the first step toward the mathematical understanding of thermal effects on a ferromagnet. In a first part, we present the stochastic model and prove that the associated stochastic differential equation is well defined. The second part is dedicated to the study of the long time behaviour of the magnetic moment and in the third part we prove that the stochastic perturbation induces a non-reversibility phenomenon. Last, we illustrate these results through numerical simulations of our stochastic model. The main results presented in this article are on the one hand the rate of convergence of the magnetization toward the unique stable equilibrium of the deterministic model and on the other hand a sharp estimate of the hysteresis phenomenon induced by the stochastic perturbation (remember that with no perturbation, the magnetic moment remains constant).
Long time behavior of unsteady flow computations
NASA Technical Reports Server (NTRS)
Hariharan, S. I.
1992-01-01
This paper addresses a specific issue of time accuracy in the calculation of external aerodynamic problems. The class of problems discussed consists of inviscid compressible subsonic flows. These problems are governed by a convective equation. A key issue that is not understood is the long time behavior of the solution. This is important if one desires transient calculations of problems governed by the Euler equations or its derivatives such as the small disturbance equations or the potential formulations for the gust problem. Difficulties arise for two dimensional problems where the time rate decay solutions of the wave equation is slow. In concert with the above mentioned problem, exterior flows require proper modeling of the boundary conditions. In particular, this requires the truncation of infinite regions into finite regions with the aid of artificial boundaries. These boundary conditions must be consistent with the physics of the unbounded problem as well as consistent in time and space. Our treatment of the problem is discussed in detail and examples are given to verify the results.
Long-time Correlations in Electromyography Signals
NASA Astrophysics Data System (ADS)
Zurcher, Ulrich; Maynard, Rachel
2006-10-01
We have previously reported that the mean-square displacement calculated from electromyography time series of low back muscles exhibit a plateau-like behavior for intermediate times [50 ,ms < t < 0.5 ,s], so that < [xt- x0]^2 > ˜t^0. This behavior is unexpected, and indicates the presence of long-time correlations in the signal. For fractal Brownian motion, the Hurst exponent calculated from the mean-square displacement and the exponent from the spectral density P ( f) ˜1/f^α, α= 2 H + 1. For the EMG time series y^0i= xi, we have generated iterated time series, yi^n+1 = [y2 i ^n + y2i+1]/2, and have calculated the corresponding time correlation functions, C^n ( t) = < xi+ t^n xi^n>/<(xi^n)^2 >. We find that the correlation functions converge to a simple limit, C(0) = 1, C(1) = -0.5 and C(n) =0 for n >=2. This limit is consistent with the plateau behavior of the mean- square displacement. We discuss the connection between the behavior of the iterated correlation functions and the properties of the spectrum.
NASA Astrophysics Data System (ADS)
Pitale, Shreyas S.; Sharma, Suchinder K.; Dubey, R. N.; Qureshi, M. S.; Malik, M. M.
2010-01-01
Synthesis of Pr 3+ doped CaS phosphor has been reported through chemical co-precipitation route and post annealing in the presence of NaCl, KCl and NH 4Cl flux. Good crystallinity and cubic CaS phase is achieved after post-precipitation calcinations of powder at 900 °C for 1 h duration. Pseudo-spherical morphostructural features of micron-size particles are observed for phosphor prepared via chemical route. Phosphor samples are also prepared via solid-state carbothermal reduction technique for comparative studies and exhibit dendrite like structures. Prominent excitation bands at 276, 320 nm are observed for the present phosphor samples. The emission spectra show a duo-band feature at 495 and 580 nm where a spectral overlap of host lattice emission due to intrinsic defects and characteristic spectral features of Pr ion due to 3P 0- 1H 4, 3P 1- 1H 5, 1D 2- 3H 4 and 3P 0- 3F 2 transitions can be observed. The carbothermal route synthesized CaS:Pr shows spectral features of Pr ion due to 3P 0- 1H 4 and 3P 0- 3F j transitions. Electron spin resonance investigations reveal the presence of unintentional Mn 2+ through a sextet signature. F + electron trapping center is detected having g = 2.0034. Thermoluminescence glow curves possess a broad duo-band feature between room temperature -100 °C and >125 °C under host UV irradiation. Kinetic characterization using glow curve deconvolution reveals quasicontinuous distribution of traps having energy between 0.56 and 1.15 eV and frequency factors between 10 7 and 10 11/sec.
Simulated annealing versus quantum annealing
NASA Astrophysics Data System (ADS)
Troyer, Matthias
Based on simulated classical annealing and simulated quantum annealing using quantum Monte Carlo (QMC) simulations I will explore the question where physical or simulated quantum annealers may outperform classical optimization algorithms. Although the stochastic dynamics of QMC simulations is not the same as the unitary dynamics of a quantum system, I will first show that for the problem of quantum tunneling between two local minima both QMC simulations and a physical system exhibit the same scaling of tunneling times with barrier height. The scaling in both cases is O (Δ2) , where Δ is the tunneling splitting. An important consequence is that QMC simulations can be used to predict the performance of a quantum annealer for tunneling through a barrier. Furthermore, by using open instead of periodic boundary conditions in imaginary time, equivalent to a projector QMC algorithm, one obtains a quadratic speedup for QMC, and achieve linear scaling in Δ. I will then address the apparent contradiction between experiments on a D-Wave 2 system that failed to see evidence of quantum speedup and previous QMC results that indicated an advantage of quantum annealing over classical annealing for spin glasses. We find that this contradiction is resolved by taking the continuous time limit in the QMC simulations which then agree with the experimentally observed behavior and show no speedup for 2D spin glasses. However, QMC simulations with large time steps gain further advantage: they ``cheat'' by ignoring what happens during a (large) time step, and can thus outperform both simulated quantum annealers and classical annealers. I will then address the question how to optimally run a simulated or physical quantum annealer. Investigating the behavior of the tails of the distribution of runtimes for very hard instances we find that adiabatically slow annealing is far from optimal. On the contrary, many repeated relatively fast annealing runs can be orders of magnitude faster for
EON: software for long time simulations of atomic scale systems
NASA Astrophysics Data System (ADS)
Chill, Samuel T.; Welborn, Matthew; Terrell, Rye; Zhang, Liang; Berthet, Jean-Claude; Pedersen, Andreas; Jónsson, Hannes; Henkelman, Graeme
2014-07-01
The EON software is designed for simulations of the state-to-state evolution of atomic scale systems over timescales greatly exceeding that of direct classical dynamics. States are defined as collections of atomic configurations from which a minimization of the potential energy gives the same inherent structure. The time evolution is assumed to be governed by rare events, where transitions between states are uncorrelated and infrequent compared with the timescale of atomic vibrations. Several methods for calculating the state-to-state evolution have been implemented in EON, including parallel replica dynamics, hyperdynamics and adaptive kinetic Monte Carlo. Global optimization methods, including simulated annealing, basin hopping and minima hopping are also implemented. The software has a client/server architecture where the computationally intensive evaluations of the interatomic interactions are calculated on the client-side and the state-to-state evolution is managed by the server. The client supports optimization for different computer architectures to maximize computational efficiency. The server is written in Python so that developers have access to the high-level functionality without delving into the computationally intensive components. Communication between the server and clients is abstracted so that calculations can be deployed on a single machine, clusters using a queuing system, large parallel computers using a message passing interface, or within a distributed computing environment. A generic interface to the evaluation of the interatomic interactions is defined so that empirical potentials, such as in LAMMPS, and density functional theory as implemented in VASP and GPAW can be used interchangeably. Examples are given to demonstrate the range of systems that can be modeled, including surface diffusion and island ripening of adsorbed atoms on metal surfaces, molecular diffusion on the surface of ice and global structural optimization of nanoparticles.
Numerical techniques for the study of long-time correlations
Karney, C.F.F.
1985-05-01
In the study of long-time correlations extremely long orbits must be calculated. This may be accomplished much more reliably using fixed-point arithmetic. Use of this arithmetic on the Cray-1 computer is illustrated.
NASA Astrophysics Data System (ADS)
Kanel, G. I.; Razorenov, S. V.; Garkushin, G. V.; Pavlenko, A. V.; Malyugina, S. N.
2016-06-01
The paper presents the results of measurements of shock-wave compression profiles of VT1-0 titanium samples after rolling and in the annealed state. In the experiments, the pressure of shock compression and distance passed by the wave before emerging to the sample surface were varied. From measurements of the elastic precursor decay and compression rate in a plastic shock wave of different amplitudes, the plastic strain and the corresponding shear stresses in the initial and subsequent stages of high-rate deformation in an elastoplastic shock wave are determined. It is found that the reduction in the dislocation density as a result of annealing reduces the hardness of the material but significantly increases its dynamic yield strengh, corresponding to the strain rate above 104 s-1. With a reduction in the strain rate, this anomalous difference in the flow stresses is leveled off.
Lourenço, Sidney A; Dantas, Noelio O; Silva, Ricardo S
2012-08-21
Semimagnetic Pb(1-x)Mn(x)Se nanocrystals were synthesized by a fusion method in a glass matrix and characterized by optical absorption (OA), atomic/magnetic force microscopy (AFM/MFM), and photoluminescence techniques. MFM images strongly indicated the formation of Pb(1-x)Mn(x)Se magnetic phases in the glass system. Quantum dot size was manipulated by tuning annealing time. It was shown that Mn(2+) impurity affects nucleation, where Mn(2+)-doped samples present a redshift of the OA peak after a short annealing time and a blueshift after long annealing time compared to undoped PbSe NCs. This behavior was linked to the dependence of band-gap energy and the absorption selection rule on Mn(2+) concentration. Photoluminescence in the Pb(1-x)Mn(x)Se nanocrystals increases as the temperature rises up to a point and then decreases at higher temperatures. Anomalous increases in emission efficiency were analyzed by considering temperature induced carrier-transfer in semimagnetic Pb(1-x)Mn(x)Se quantum dots nanocrystals of different sizes. PMID:22766762
Kovalyuk, T. T. Maistruk, E. V.; Maryanchuk, P. D.
2014-12-15
The results of studies of the kinetic properties of Hg{sub 1−x−y}Cd{sub x}Eu{sub y}Se semiconductor crystals in the ranges of temperatures T = 77–300 K and magnetic fields H = 0.5–5 kOe before and after heat treatment of the samples in Se vapors are reported. It is established that annealing of the samples in Se vapors induces a decrease in the electron concentration. From the concentration dependence of the electron effective mass at the Fermi level, the band gap, the matrix element of interband interaction, and the electron effective mass at the bottom of the conduction band are determined.
Spectra of thermoprogrammed annealing of photoinduced color centers
NASA Astrophysics Data System (ADS)
Glazkova, N. I.; Mikhaylov, R. V.; Kuznetsov, V. N.
2015-04-01
The kinetics of photoinduced formation and thermoprogrammed annealing of color centers in photochromic rutile ceramics has been studied in situ with the aid of a specially designed attachment for a spectrofluorimeter. Using a regime of constant heating rate, the spectra of color center annealing have been measured and the energy depths of hole traps responsible for the annealing of these centers have been determined.
Sands, D.; Howari, H.
2005-10-15
Double quantum wells of CdTe in CdMnTe were implanted with argon ions to create vacancies and interstitials. This destroyed the photoluminescence (PL) emission from the top well and reduced the intensity from the bottom well. Pulsed radiation from an excimer laser emitting at 308 nm, with a full width at half maximum pulse lengths of 26 ns, was used to anneal the implantation damage and restore the luminescence. An optimum fluence close to 50 mJ cm{sup -2} exists for laser annealing, with the best results being obtained if single pulses are employed. Prior irradiation at lower fluences prevents full recovery of the luminescence when the higher fluence pulse is applied, and irradiation at lower fluences on unimplanted material causes a reduction in the luminescence from the top well. These results are interpreted in terms of vacancy creation and annihilation during the laser pulse. Calculations of the total number of vacancies created suggest that annihilation of the Te vacancies is the limiting step in the recovery of the PL in implanted material. It is proposed that loss of material from the surface, amounting to less than a monolayer, leads to the effective diffusion of vacancies into the solid.
Space Charge Models for Particle Tracking on Long Time Scales
Holmes, Jeffrey A; Cousineau, Sarah M; Shishlo, Andrei P; Potts III, Robert E
2013-01-01
In order to efficiently track charged particles over long times, most tracking codes use either analytic charge distributions or particle-in-cell (PIC) methods based on fast Fourier transforms (FFTs). While useful for theoretical studies, analytic distribution models do not allow accurate simulation of real machines. PIC calculations can utilize realistic space charge distributions, but these methods suffer from the presence of discretization errors. We examine the situation for particle tracking with space charge over long times, and consider possible ideas to improve the accuracy of such calculations.
Long-time tails of correlation and memory functions
NASA Astrophysics Data System (ADS)
Sawada, Isao
2002-11-01
We review the generalized Langevin equation, which is a transformation and reformulation of equation of motion, from the two viewpoints: the projection operator method developed by Mori and the recurrence relations method developed by Lee. The fluctuating forces acting on the Bloch electrons’ current are clarified the strongly colored quantum fluctuations with the spontaneous interband transitions leading to a long-time tail of 1/ t for the envelope of the memory function. The velocity autocorrelation functions in the coupled harmonic oscillator on the Bethe lattice have a long-time tail of 1/t t. The oscillation and the form of decay found in correlation functions affect transport coefficients given by the integrated intensity up to infinity. We also study the force-force correlation functions often used as an approximation to the memory function.
Finite difference schemes for long-time integration
NASA Technical Reports Server (NTRS)
Haras, Zigo; Taasan, Shlomo
1993-01-01
Finite difference schemes for the evaluation of first and second derivatives are presented. These second order compact schemes were designed for long-time integration of evolution equations by solving a quadratic constrained minimization problem. The quadratic cost function measures the global truncation error while taking into account the initial data. The resulting schemes are applicable for integration times fourfold, or more, longer than similar previously studied schemes. A similar approach was used to obtain improved integration schemes.
Long-time behavior of many-particle quantum decay
Campo, A. del
2011-07-15
While exponential decay is ubiquitous in nature, deviations at both short and long times are dictated by quantum mechanics. Nonexponential decay is known to arise due to the possibility of reconstructing the initial state from the decaying products. We discuss the quantum decay dynamics by tunneling of a many-particle system, characterizing the long-time nonexponential behavior of the nonescape and survival probabilities. The effects of contact interactions and quantum statistics are described. It is found that, whereas for noninteracting bosons the long-time decay follows a power law with an exponent linear in the number of particles N, the exponent becomes quadratic in N in the fermionic case. The same results apply to strongly interacting many-body systems related by the generalized Bose-Fermi duality. The faster fermionic decay can be traced back to the effective hard-core interactions between particles, which are as well the decaying products, and exhibit spatial antibunching which hinders the reconstruction of the initial unstable state. The results are illustrated with a paradigmatic model of quantum decay from a trap allowing leaks by tunneling, whose dynamics is described exactly by means of an expansion in resonant states.
Fast computation of recurrences in long time series
NASA Astrophysics Data System (ADS)
Rawald, Tobias; Sips, Mike; Marwan, Norbert; Dransch, Doris
2014-05-01
The quadratic time complexity of calculating basic RQA measures, doubling the size of the input time series leads to a quadrupling in operations, impairs the fast computation of RQA in many application scenarios. As an example, we analyze the Potsdamer Reihe, an ongoing non-interrupted hourly temperature profile since 1893, consisting of 1,043,112 data points. Using an optimized single-threaded CPU implementation this analysis requires about six hours. Our approach conducts RQA for the Potsdamer Reihe in five minutes. We automatically split a long time series into smaller chunks (Divide) and distribute the computation of RQA measures across multiple GPU devices. To guarantee valid RQA results, we employ carryover buffers that allow sharing information between pairs of chunks (Recombine). We demonstrate the capabilities of our Divide and Recombine approach to process long time series by comparing the runtime of our implementation to existing RQA tools. We support a variety of platforms by employing the computing framework OpenCL. Our current implementation supports the computation of standard RQA measures (recurrence rate, determinism, laminarity, ratio, average diagonal line length, trapping time, longest diagonal line, longest vertical line, divergence, entropy, trend) and also calculates recurrence times. To utilize the potential of our approach for a number of applications, we plan to release our implementation under an Open Source software license. It will be available at http://www.gfz-potsdam.de/fast-rqa/. Since our approach allows to compute RQA measures for a long time series fast, we plan to extend our implementation to support multi-scale RQA.
Storage life of parachutes -- long time material degradation
Ericksen, R.H.; Whinery, L.D.
1995-04-01
This study considers the long-time storage of single-use nylon and Kevlar{reg_sign} parachutes. The authors present data from a 29-year-old nylon parachute, and nylon and Kevlar{reg_sign} test samples stored 14 years under ambient conditions in the absence of sunlight. They compare the results with existing predictions of parachute material degradation and other aging data. X-ray photoelectron spectroscopy analyses were preformed on Nylon and Kevlar{reg_sign} fabrics that were degraded by elevated temperature aging. The results suggest that this technique should be further examined as a {open_quotes}non-destructive{close_quotes} method of detecting degradation.
Long-time dynamics through parallel trajectory splicing
Perez, Danny; Cubuk, Ekin D.; Waterland, Amos; Kaxiras, Efthimios; Voter, Arthur F.
2015-11-24
Simulating the atomistic evolution of materials over long time scales is a longstanding challenge, especially for complex systems where the distribution of barrier heights is very heterogeneous. Such systems are difficult to investigate using conventional long-time scale techniques, and the fact that they tend to remain trapped in small regions of configuration space for extended periods of time strongly limits the physical insights gained from short simulations. We introduce a novel simulation technique, Parallel Trajectory Splicing (ParSplice), that aims at addressing this problem through the timewise parallelization of long trajectories. The computational efficiency of ParSplice stems from a speculation strategymore » whereby predictions of the future evolution of the system are leveraged to increase the amount of work that can be concurrently performed at any one time, hence improving the scalability of the method. ParSplice is also able to accurately account for, and potentially reuse, a substantial fraction of the computational work invested in the simulation. We validate the method on a simple Ag surface system and demonstrate substantial increases in efficiency compared to previous methods. As a result, we then demonstrate the power of ParSplice through the study of topology changes in Ag42Cu13 core–shell nanoparticles.« less
Long-time dynamics through parallel trajectory splicing
Perez, Danny; Cubuk, Ekin D.; Waterland, Amos; Kaxiras, Efthimios; Voter, Arthur F.
2015-11-24
Simulating the atomistic evolution of materials over long time scales is a longstanding challenge, especially for complex systems where the distribution of barrier heights is very heterogeneous. Such systems are difficult to investigate using conventional long-time scale techniques, and the fact that they tend to remain trapped in small regions of configuration space for extended periods of time strongly limits the physical insights gained from short simulations. We introduce a novel simulation technique, Parallel Trajectory Splicing (ParSplice), that aims at addressing this problem through the timewise parallelization of long trajectories. The computational efficiency of ParSplice stems from a speculation strategy whereby predictions of the future evolution of the system are leveraged to increase the amount of work that can be concurrently performed at any one time, hence improving the scalability of the method. ParSplice is also able to accurately account for, and potentially reuse, a substantial fraction of the computational work invested in the simulation. We validate the method on a simple Ag surface system and demonstrate substantial increases in efficiency compared to previous methods. As a result, we then demonstrate the power of ParSplice through the study of topology changes in Ag_{42}Cu_{13} core–shell nanoparticles.
Differential force microscope for long time-scale biophysical measurements
Choy, Jason L.; Parekh, Sapun H.; Chaudhuri, Ovijit; Liu, Allen P.; Bustamante, Carlos; Footer, Matthew J.; Theriot, Julie A.; Fletcher, Daniel A.
2011-01-01
Force microscopy techniques including optical trapping, magnetic tweezers, and atomic force microscopy (AFM) have facilitated quantification of forces and distances on the molecular scale. However, sensitivity and stability limitations have prevented the application of these techniques to biophysical systems that generate large forces over long times, such as actin filament networks. Growth of actin networks drives cellular shape change and generates nano-Newtons of force over time scales of minutes to hours, and consequently network growth properties have been difficult to study. Here, we present an AFM-based differential force microscope with integrated epifluorescence imaging in which two adjacent cantilevers on the same rigid support are used to provide increased measurement stability. We demonstrate 14 nm displacement control over measurement times of 3 hours and apply the instrument to quantify actin network growth in vitro under controlled loads. By measuring both network length and total network fluorescence simultaneously, we show that the average cross-sectional density of the growing network remains constant under static loads. The differential force microscope presented here provides a sensitive method for quantifying force and displacement with long time-scale stability that is useful for measurements of slow biophysical processes in whole cells or in reconstituted molecular systems in vitro. PMID:17477674
A method for detecting changes in long time series
Downing, D.J.; Lawkins, W.F.; Morris, M.D.; Ostrouchov, G.
1995-09-01
Modern scientific activities, both physical and computational, can result in time series of many thousands or even millions of data values. Here the authors describe a statistically motivated algorithm for quick screening of very long time series data for the presence of potentially interesting but arbitrary changes. The basic data model is a stationary Gaussian stochastic process, and the approach to detecting a change is the comparison of two predictions of the series at a time point or contiguous collection of time points. One prediction is a ``forecast``, i.e. based on data from earlier times, while the other a ``backcast``, i.e. based on data from later times. The statistic is the absolute value of the log-likelihood ratio for these two predictions, evaluated at the observed data. A conservative procedure is suggested for specifying critical values for the statistic under the null hypothesis of ``no change``.
Long Time Convergence of the Bose-Einstein Condensation
NASA Astrophysics Data System (ADS)
Lu, Xuguang
2016-02-01
We study long time behavior of the Bose-Einstein condensation of measure-valued solutions F_t of the space homogeneous and velocity isotropic Boltzmann equation for Bose-Einstein particles at low temperature. We prove that if F_0≥ 0 is a non-singular Borel measure on R_{≥ 0} satisfying a very low temperature condition and that the ratio F_0([0,\\varepsilon ])/\\varepsilon ^{α } is sufficiently large for all \\varepsilon in (0, R] for some constants 0<α <1, R>0, then there exists a solution F_t of the equation on [0,+∞) with the initial datum F_0 such that F_t({0}) converges to the expected Bose-Einstein condensation as t→ +∞. We also show that such initial data F_0 exist extensively.
Valproic Acid Induced Hyperammonemia in a Long Time Treated Patient
Seide, Margaret; Stern, Robert G.
2016-01-01
We report a case of a patient who had been on long time valproic acid for treatment of bipolar affective disorder. While being an inpatient, serology ammonia level testing revealed a very high ammonia level despite being asymptomatic. Dual therapy of carnitine and lactulose was provided to the patient for treatment of the hyperammonemia. It should also be noted that, during this treatment, valproic acid was not stopped. Consequently, this case illustrates that patients can present asymptomatically despite very high ammonia levels and hyperammonemia can occur in chronic valproic acid despite not increasing the dose of the medication and psychiatrists do not need to discontinue valproic acid in the presence of elevated levels of ammonia if the patient shows no signs of encephalopathy or delirium. PMID:27516916
Long time dynamical evolution of highly elliptical satellites orbits
NASA Astrophysics Data System (ADS)
Kuznetsov, E.; Zakharova, P.
2015-08-01
Dynamical evolution of objects near Molniya-type orbits is considered. Initial conditions correspond to highly elliptical satellite orbits with eccentricities 0.65 and a critical inclination 63.4°. Semi-major axis is varied near resonant value 26560 km in an interval 500 km. Variations were analyzed for positional orbital elements, an ascending node longitude and an argument of pericenter. Initial conditions determined when orbital elements variations are minimal. These regions can be used as orbits for safe stationing satellites which finish work on Molniya-type orbits. The study of dynamical evolution on long time intervals was performed on the basis of the results of numerical simulation. The model of disturbing forces taken into account the main perturbing factors. Time interval was up to 24 yr. Area-to-mass ratio varied from small values corresponding to satellites to big ones corresponding to space debris.
Relaxation Characteristics of 828 DGEBA Epoxy Over Long Time Periods
NASA Astrophysics Data System (ADS)
Hoo, Jasmine; Reprogle, Riley C.; Wisler, Brian; Arechederra, Gabriel K.; McCoy, John D.; Kropka, Jamie M.; Long, Kevin N.
The mechanical relaxation response in uniaxial compression of a diglycidyl ether of bisphenol-A epoxy was studied over long time periods. The epoxy, 828DEA, was Epon 828 cured with diethanolamine (DEA). A sample was compressed at constant strain rate and held at various strain levels for days to allow the sample to relax. The sample was then compressed further and held once more. The relaxation curves were fit with a stretched exponential function. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.
Valproic Acid Induced Hyperammonemia in a Long Time Treated Patient.
Aiyer, Rohit; Seide, Margaret; Stern, Robert G
2016-01-01
We report a case of a patient who had been on long time valproic acid for treatment of bipolar affective disorder. While being an inpatient, serology ammonia level testing revealed a very high ammonia level despite being asymptomatic. Dual therapy of carnitine and lactulose was provided to the patient for treatment of the hyperammonemia. It should also be noted that, during this treatment, valproic acid was not stopped. Consequently, this case illustrates that patients can present asymptomatically despite very high ammonia levels and hyperammonemia can occur in chronic valproic acid despite not increasing the dose of the medication and psychiatrists do not need to discontinue valproic acid in the presence of elevated levels of ammonia if the patient shows no signs of encephalopathy or delirium. PMID:27516916
Locally activated Monte Carlo method for long-time-scale simulations
NASA Astrophysics Data System (ADS)
Kaukonen, M.; Peräjoki, J.; Nieminen, R. M.; Jungnickel, G.; Frauenheim, Th.
2000-01-01
We present a technique for the structural optimization of atom models to study long time relaxation processes involving different time scales. The method takes advantage of the benefits of both the kinetic Monte Carlo (KMC) and the molecular dynamics simulation techniques. In contrast to ordinary KMC, our method allows for an estimation of a true lower limit for the time scale of a relaxation process. The scheme is fairly general in that neither the typical pathways nor the typical metastable states need to be known prior to the simulation. It is independent of the lattice type and the potential which describes the atomic interactions. It is adopted to study systems with structural and/or chemical inhomogeneity which makes it particularly useful for studying growth and diffusion processes in a variety of physical systems, including crystalline bulk, amorphous systems, surfaces with adsorbates, fluids, and interfaces. As a simple illustration we apply the locally activated Monte Carlo to study hydrogen diffusion in diamond.
Thermal annealing of GaAs concentrator solar cells
NASA Technical Reports Server (NTRS)
Curtis, H. B.; Brinker, David J.
1991-01-01
Isochronal and isothermal annealing tests were performed on GaAs concentrator cells which were irradiated with electrons of various energies to fluences up to 1 x 10(exp 16) e/sq cm. The results include: (1) For cells irradiated with electrons from 0.7 to 2.3 MeV, recovery decreases with increasing electron energy. (2) As determined by the un-annealed fractions, isothermal and isochronal annealing produce the same recovery. Also, cells irradiated to 3 x 10(exp 15) or 1 x 10(exp 16) e/sq cm recover to similar un-annealed fractions. (3) Some significant annealing is being seen at 150 C although very long times are required.
Attractors and Long Time Behavior of von Karman Thermoelastic Plates
Chueshov, Igor Lasiecka, Irena
2008-10-15
This paper undertakes a study of asymptotic behavior of solutions corresponding to von Karman thermoelastic plates. A distinct feature of the work is that the model considered has no added dissipation-particularly mechanical dissipation typically added to plate equation when long time-behavior is considered. Thus, the model consists of undamped oscillatory plate equation strongly coupled with heat equation. Nevertheless we are able to show that the ultimate (asymptotic) behavior of the von Karman evolution is described by finite dimensional global attractor. In addition, the obtained estimate for the dimension and the size of the attractor are independent of the rotational inertia parameter {gamma} and heat/thermal capacity {kappa}, where the former is known to change the character of dynamics from hyperbolic ({gamma}>0) to parabolic like ({gamma}=0). Other properties of attractors such as additional smoothness and upper-semicontinuity with respect to parameters {gamma} and {kappa} are also established. The main ingredients of the proofs are (i) sharp regularity of Airy's stress function, and (ii) newly developed (Chueshov and Lasiecka in Memoirs of AMS, in press) 'compensated' compactness methods applicable to non-compact dynamics.
Long-time observation of meteor induced layers with ionosonde
NASA Astrophysics Data System (ADS)
Yusupov, Kamil; Akchurin, Adel
2016-07-01
It is considered that the main theory explaining appearance of sporadic E is the theory of wind shear, which means (includes) the presence and movement of nodes converging tidal wind through the height region of the most frequent occurrence Es (120-140km) [Mathew et. all, 1998]. However, the appearance of intense layers, following its name, are sporadic, and such variability cannot to explain by the influence of tidal waves only. Another indication inconsistency theory of wind shear is the appearance of so-called transient Es layers [Maruiama, 2003]. The distinctive feature of this trace is the high critical frequency (> 5 MHz), a constant height, weak amplitude, all trace semitransparent and short lifetime [Maruiama et. all, 2003 and 2008 and references there]. Because of duration, such layer is opposite to the traditional persistent Es layer, which we do not consider in this paper. Various researchers have used different terms for such spontaneous Es, it is meteor echo, meteor induced Es, spontaneously formed sporadic Es patches resulting of the Fresnel scattering from a region of enhanced plasma density along the meteor trail, transitory Es and transient Es. Since the term transient Es is unstable, to avoid confusion, we will stick to this term. Since meteor echo is not fully satisfy this term by some parameter, we will describe the properties of transient Es based on the ionogram properties and not from physics of its origin. We used data from our ionosonde with one-minute ionogram repetition rate for 2010-2014 years. For processing performed a method are using to select beatings and the ionosphere reflectivity of the layers by means A-, H-and AΣ-map [Akchurin, 2011; Yusupov, 2014]. This maps allow to collect transient Es appearance over a long-time. Such statistics comparison with meteor showers activity showed good agreement. It shows the presence of the transient Es formation mechanism, which coupling with meteors.
Optimizing the search for transiting planets in long time series
NASA Astrophysics Data System (ADS)
Ofir, Aviv
2014-01-01
Context. Transit surveys, both ground- and space-based, have already accumulated a large number of light curves that span several years. Aims: The search for transiting planets in these long time series is computationally intensive. We wish to optimize the search for both detection and computational efficiencies. Methods: We assume that the searched systems can be described well by Keplerian orbits. We then propagate the effects of different system parameters to the detection parameters. Results: We show that the frequency information content of the light curve is primarily determined by the duty cycle of the transit signal, and thus the optimal frequency sampling is found to be cubic and not linear. Further optimization is achieved by considering duty-cycle dependent binning of the phased light curve. By using the (standard) BLS, one is either fairly insensitive to long-period planets or less sensitive to short-period planets and computationally slower by a significant factor of ~330 (for a 3 yr long dataset). We also show how the physical system parameters, such as the host star's size and mass, directly affect transit detection. This understanding can then be used to optimize the search for every star individually. Conclusions: By considering Keplerian dynamics explicitly rather than implicitly one can optimally search the BLS parameter space. The presented Optimal BLS enhances the detectability of both very short and very long period planets, while allowing such searches to be done with much reduced resources and time. The Matlab/Octave source code for Optimal BLS is made available. The MATLAB code is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A138
Long time black hole evaporation with bounded Hawking flux
NASA Astrophysics Data System (ADS)
Grumiller, D.
2004-05-01
The long time behaviour of an evaporating black hole presents a challenge to theoretical physics and touches relevant conceptual issues of quantum gravity, such as the information paradox. There are basically two strategies: top-down, i.e., constructing first a full quantum theory of gravity and discussing black hole evaporation as a particular application thereof, and bottom-up, i.e., sidestepping the difficulties inherent to the former approach by invoking `reasonable' ad hoc assumptions. Exploiting the fact that the Schwarzschild black hole can be described by means of an effective theory in 2D, a particular dilaton gravity model, the latter route is pursued. A crucial technical ingredient is Izawa's result on consistent deformations of 2D BF theory, while the most relevant physical assumption is boundedness of the asymptotic matter flux during the whole evaporation process. Together with making technical assumptions which can be relaxed, the dynamics of the evaporating black hole is described by means of consistent deformations of the underlying gauge symmetries with only one important deformation parameter. An attractor solution, the end-point of the evaporation process, is found. Its metric is flat. However, the behaviour of the dilaton field (which corresponds to the surface area) is non-trivial: it is argued that during the final flicker a first-order phase transition occurs from a linear to a constant dilaton vacuum. Consequently, a shock wave is emitted as a final `thunderbolt' with a total energy of a fraction of the Planck mass. Relations to ultrarelativistic boosts are pointed out. Another fraction of the Planck mass may reside in a cold remnant. The physical discussion addresses the lifetime, the specific heat, the Carter Penrose diagram, the information paradox and cosmological implications. The phenomenon of `dilaton evaporation' to a constant dilaton vacuum might be of relevance also for higher dimensional scalar tensor theories. Based on an
Improved zircon fission-track annealing model based on reevaluation of annealing data
Guedes, S.; Moreira, Pedro; Devanathan, Ramaswami; Weber, William J.; Hadler, J. C.
2012-11-10
The thermal recovery (annealing) of mineral structure modified by the passage of fission fragments has long been studied by the etching technique. In minerals like apatite and zircon, the annealing kinetics are fairly well constrained from the hour to the million-year timescale and have been described by empirical and semi-empirical equations. On the other hand, laboratory experiments, in which ion beams interact with minerals and synthetic ceramics, have shown that there is a threshold temperature beyond which thermal recovery impedes ion-induced amorphization. In this work, it is assumed that this behavior can be extended to the annealing of fission tracks in minerals. It is proposed that there is a threshold temperature, T 0, beyond which fission tracks are erased within a time t 0, which is independent of the current state of lattice deformation. This implies that iso-annealing curves should converge to a fanning point in the Arrhenius pseudo-space (ln t vs. 1/T). Based on the proposed hypothesis, and laboratory and geological data, annealing equations are reevaluated. The geological timescale estimations of a model arising from this study are discussed through the calculation of partial annealing zone and closure temperature, and comparison with geological sample constraints found in literature. It is shown that the predictions given by this model are closer to field data on closure temperature and partial annealing zone than predictions given by previous models.
Improved zircon fission-track annealing model based on reevaluation of annealing data
Guedes, Sandro; Moreira, Pedro A.F.P.; Devanathan, Ram; Weber, William J; Hadler, Julio C
2013-01-01
The thermal recovery (annealing) of mineral structure modified by the passage of fission fragments has long been studied by the etching technique. In minerals like apatite and zircon, the annealing kinetics are fairly well constrained from the hour to the million-year timescale and have been described by empirical and semi-empirical equations. On the other hand, laboratory experiments, in which ion beams interact with minerals and synthetic ceramics, have shown that there is a threshold temperature beyond which thermal recovery impedes ion-induced amorphization. In this work, it is assumed that this behavior can be extended to the annealing of fission tracks in minerals. It is proposed that there is a threshold temperature, T0, beyond which fission tracks are erased within a time t0, which is independent of the current state of lattice deformation. This implies that iso-annealing curves should converge to a fanning point in the Arrhenius pseudo-space (ln t vs. 1/T). Based on the proposed hypothesis, and laboratory and geological data, annealing equations are reevaluated. The geological timescale estimations of a model arising from this study are discussed through the calculation of partial annealing zone and closure temperature, and comparison with geological sample constraints found in literature. It is shown that the predictions given by this model are closer to field data on closure temperature and partial annealing zone than predictions given by previous models.
Composition dependent thermal annealing behaviour of ion tracks in apatite
NASA Astrophysics Data System (ADS)
Nadzri, A.; Schauries, D.; Mota-Santiago, P.; Muradoglu, S.; Trautmann, C.; Gleadow, A. J. W.; Hawley, A.; Kluth, P.
2016-07-01
Natural apatite samples with different F/Cl content from a variety of geological locations (Durango, Mexico; Mud Tank, Australia; and Snarum, Norway) were irradiated with swift heavy ions to simulate fission tracks. The annealing kinetics of the resulting ion tracks was investigated using synchrotron-based small-angle X-ray scattering (SAXS) combined with ex situ annealing. The activation energies for track recrystallization were extracted and consistent with previous studies using track-etching, tracks in the chlorine-rich Snarum apatite are more resistant to annealing than in the other compositions.
Recent progress of quantum annealing
Suzuki, Sei
2015-03-10
We review the recent progress of quantum annealing. Quantum annealing was proposed as a method to solve generic optimization problems. Recently a Canadian company has drawn a great deal of attention, as it has commercialized a quantum computer based on quantum annealing. Although the performance of quantum annealing is not sufficiently understood, it is likely that quantum annealing will be a practical method both on a conventional computer and on a quantum computer.
GenAnneal: Genetically modified Simulated Annealing
NASA Astrophysics Data System (ADS)
Tsoulos, Ioannis G.; Lagaris, Isaac E.
2006-05-01
A modification of the standard Simulated Annealing (SA) algorithm is presented for finding the global minimum of a continuous multidimensional, multimodal function. We report results of computational experiments with a set of test functions and we compare to methods of similar structure. The accompanying software accepts objective functions coded both in Fortran 77 and C++. Program summaryTitle of program:GenAnneal Catalogue identifier:ADXI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXI_v1_0 Program available from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested: The tool is designed to be portable in all systems running the GNU C++ compiler Installation: University of Ioannina, Greece on Linux based machines Programming language used:GNU-C++, GNU-C, GNU Fortran 77 Memory required to execute with typical data: 200 KB No. of bits in a word: 32 No. of processors used: 1 Has the code been vectorized or parallelized?: No No. of bytes in distributed program, including test data, etc.:84 885 No. of lines in distributed program, including test data, etc.:14 896 Distribution format: tar.gz Nature of physical problem: A multitude of problems in science and engineering are often reduced to minimizing a function of many variables. There are instances that a local optimum does not correspond to the desired physical solution and hence the search for a better solution is required. Local optimization techniques are frequently trapped in local minima. Global optimization is hence the appropriate tool. For example, solving a non-linear system of equations via optimization, employing a "least squares" type of objective, one may encounter many local minima that do not correspond to solutions (i.e. they are far from zero). Typical running time: Depending on the objective function. Method of solution: We modified the process of step selection that the traditional Simulated
Klinger, G; Kunstmann, F W; Stelzner, A
1981-01-01
The total level of N-acetylneuraminic acid in serum was found to be affected by long-time application of hormonal contraceptives. That effect appeared to depend on oestrogen. The problem of reversibility is discussed. PMID:7053175
Long-Time Performance of a Stainless Steel Crossflow Filter with Simulated Hanford Tank Waste
Schonewill, Philip P.; Daniel, Richard C.; Shimskey, Rick W.; Burns, Carolyn A.; Billing, Justin M.; Peterson, Reid A.
2015-10-01
The long-time (>100 hours of operation) flux was measured for a set of tests where slurry waste simulant was separated and continuously recycled in a stainless steel crossflow filter. The tests were conducted at various constant axial velocities and transmembrane pressures. In all five tests, the flux continued to decay at long times and did not reach a steady-state. The long-time slope of the decay was unaffected by the axial velocity, and larger transmembrane pressure resulted in a larger slope. The experimental results are compared to theoretical predictions of the time to initiate cake formation and the time to reach steady-state, both of which do not imply long-time phenomena would be expected. A more reasonable match between theory and experiment was achieved using a model based on the principles of dead-end filtration.
NASA Astrophysics Data System (ADS)
Behrman, Elizabeth; Steck, James
We propose and develop a new quantum algorithm, whereby a quantum system can learn to anneal to a desired ground state. We demonstrate successful learning of entanglement for a two-qubit system, then bootstrap to larger systems. We also show that the method is robust to noise and decoherence.
NASA Astrophysics Data System (ADS)
Das, Arnab; Suzuki, Sei
2015-02-01
In this article we sketch a broad outline of quantum annealing as a framework for realizing analog quantum computation. We provide a short review of the basic ideas and discuss some issues relevant to the current scenario of condensed matter physics and quantum computation.
Resonant-state expansions and the long-time behavior of quantum decay
Garcia-Calderon, Gaston; Maldonado, Irene; Villavicencio, Jorge
2007-07-15
It is shown that a representation of the decaying wave function as a resonant sum plus a nonexponential integral term may be written as a purely discrete resonant sum by evaluating at long times the integral term by the steepest descents method, and then expanding the resulting expression in terms of resonant states. This leads to a representation that is valid along the exponential and the inverse power in time regimes. A model calculation using the {delta} potential allows us to make a comparison of the expansion with numerical integrations in terms of continuum wave functions and, in the long time regime, with an exact analytic expression of the integral term obtained using the steepest descents method. The results demonstrate that resonant states give a correct description of the long-time behavior of decay.
Universal Long-Time Behavior of Nuclear Spin Decays in a Solid
NASA Astrophysics Data System (ADS)
Morgan, S. W.; Fine, B. V.; Saam, B.
2008-08-01
Magnetic resonance studies of nuclear spins in solids are exceptionally well suited to probe the limits of statistical physics. We report experimental results indicating that isolated macroscopic systems of interacting nuclear spins possess the following fundamental property: spin decays that start from different initial configurations quickly evolve towards the same long-time behavior. This long-time behavior is characterized by the shortest ballistic microscopic time scale of the system and therefore falls outside of the validity range for conventional approximations of statistical physics. We find that the nuclear free-induction decay and different solid echoes in hyperpolarized solid xenon all exhibit sinusoidally modulated exponential long-time behavior characterized by identical time constants. This universality was previously predicted on the basis of analogy with resonances in classical chaotic systems.
Sibata, M N; Tedesco, A C; Marchetti, J M
2004-10-01
Long time circulation systems, such as polymeric micelles, represent a growing area in biomedical research. These microparticles can be used in many biological systems to provide appropriate drug levels with a specific biodistribution. Long time circulation micelles (LTCM) were routinely prepared using PEG-5000-DSPE (polyethyleneglycol-5000-distearoil-phosphatidyl-ethanolamine) and zinc(II) phthalocyanine (ZnPc) as a photosensitizer and fluorescent probe. This compound belongs to a second generation of photoactive agents, mainly used in photodynamic therapy (PDT) of neoplasic tissues. Their high selectivity for tumoral target tissues as well as high phototoxicity based on singlet oxygen generation renders the utilization of these compounds feasible as an alternative therapy for cancer treatment. LTCM were characterized by classical spectroscopic techniques. Absorbance measurements indicated that the drug was s completely loaded into LTCM (epsilon = 2.41 x 10(5) cm(-1)). This was also verified by steady state and time-resolved fluorescence measurements. The lifetime profiles of ZnPc decay curves were fitted according to biexponential function (tau1 = 3.9 ns and tau2 = 15.5 ns) indicating different locations for ZnPc into LTCM. The time-resolved spectroscopy measurements for ZnPc triplet excited state lifetimes (tauT) were calculated from the kinetic analysis of transient decays at the absorption maximum (480 nm), by using laser flash photolysis technique. All the spectroscopy measurements performed allowed us to conclude that, ZnPc in LTCM is a promising drug delivery system (DDS) for PDT. PMID:15451001
Bridging Home: Building Relationships between Immigrant and Long-Time Resident Youth
ERIC Educational Resources Information Center
Dryden-Peterson, Sarah
2010-01-01
Background: There is rising evidence that relationships that bridge between immigrants and long-time residents are critical to immigrant integration and to the overall heath of communities. The processes by which this bridging social capital is built are not well understood. Schools in new immigrant destinations, as spaces in which diverse youth…
Using time filtering to control the long-time instability in seismic wave simulation
NASA Astrophysics Data System (ADS)
Gao, L.; Brossier, R.; Virieux, J.
2016-03-01
Long-time instabilities have been observed in various scenarios of numerical simulation for seismic wave propagation. They appear as slowly magnifying spurious oscillations in the seismograms at the late stage of the simulation. Their magnifying speed is typically much slower than the magnifying speed observed when the Courant-Friedrichs-Lewy condition is violated. The simulations can therefore continue to proceed for a relatively long period without floating-point overflow. The impact of the long-time instabilities on the simulation accuracy at the early stage can be negligible in some cases. In existing literatures, spatial-filtering techniques that, in principle, average the solution within certain spatial range at the same time level are typically utilized to control the long-time instability. In this paper, we present an alternative time-filtering approach that, in principle, averages the solution at different time levels of the same spatial location to control the long-time instability. Comparing with the spatial filtering, the advantages of this time-filtering approach lie in its flexibility, particularly when boundaries or interfaces are involved, its simplicity and low additional arithmetic operations, at the expense of extra memory cost. When application of the time filtering is localized to regions where long-time instabilities are emitted from, for example, a boundary or an interface layer, the additional cost is negligible when compared with the cost of wave simulation. For linear wave equations, this time-filtering approach can be understood as the introduction of artificial diffusion. Its application has impact on the accuracy of the solution and the restriction of the time step size. We present an indicator-based approach to adjust the filtering parameters both spatially and temporally, in order to provide the best trade-off between accuracy and stability. The indicator is calculated heuristically by monitoring the spurious oscillation as the
A Study of the Batch Annealing of Cold-Rolled HSLA Steels Containing Niobium or Titanium
NASA Astrophysics Data System (ADS)
Fang, Chao; Garcia, C. Isaac; Choi, Shi-Hoon; DeArdo, Anthony J.
2015-08-01
The batch annealing behavior of two cold-rolled, microalloyed HSLA steels has been studied in this program. One steel was microalloyed with niobium while the other with titanium. A successfully batch annealed steel will exhibit minimum variation in properties along the length of the coil, even though the inner and outer wraps experience faster heating and cooling rates and lower soaking temperatures, i.e., the so-called "cold spot" areas, than the mid-length portion of the coil, i.e., the so-called "hot spot" areas. The variation in strength and ductility is caused by differences in the extent of annealing in the different areas. It has been known for 30 years that titanium-bearing HSLA steels show more variability after batch annealing than do the niobium-bearing steels. One of the goals of this study was to try to explain this observation. In this study, the annealing kinetics of the surface and center layers of the cold-rolled sheet were compared. The surface and center layers of the niobium steel and the surface layer of the titanium steel all showed similar annealing kinetics, while the center layer of the titanium steel exhibited much slower kinetics. Metallographic results indicate that the stored energy of the cold-rolled condition, as revealed by grain center sub-grain boundary density, appeared to strongly influence the annealing kinetics. The kinetics were followed by the Kernel Average Misorientation reconstruction of the microstructure at different stages on annealing. Possible pinning effects caused by microalloy precipitates were also considered. Methods of improving uniformity and increasing kinetics, involving optimizing both hot-rolled and cold-rolled microstructure, are suggested.
High-speed and long-time FBG interrogation system using wavelength swept laser
NASA Astrophysics Data System (ADS)
Yamaguchi, Tatsuya; Shinoda, Yukitaka
2015-05-01
The purpose of this research is the development of a system for fabricating high-speed and long-time measurements of wide-band vibration using fiber Bragg gratings (FBGs) to determine the health of structures. We developed a real-time FBG interrogation system using wavelength swept laser. This system can perform real-time measurement of reflected wavelength from a multiple FBG at a temporal resolution of 0.1 ms. The authors also constructed a database system for managing the data obtained from high-speed and long-time measurement. This database system manages data using a relational database and transfers information on FBG reflected wavelengths obtained from this measurement system via the local network. We have demonstrated that this system is able to measure reflected wavelengths from a multipoint FBG at a temporal resolution of 0.1 ms over 24 hours, it was shown that this system could also monitor instantaneously applied high-speed vibrations.
Long-time dynamic compatibility of two ethylene propylene elastomers with hydrazine
NASA Technical Reports Server (NTRS)
Coulbert, C. D.; Cuddihy, E. F.; Fedors, R. F.
1984-01-01
A test method is described for predicting the long-time survivability of elastomers in hydrazine under dynamic stressing conditions. The method selected is based upon the existence and approximate invariance of a 'physical property surface' relating the mechanical response of the elastomer in terms of stress, strain, time, and temperature. The property surface was generated for two selected elastomers (EPT-10 and AF-E-332). A novel carousel testing tank was designed to allow sequential testing of eight tensile specimens immersed in liquid hydrazine within a constant-temperature water bath. The test procedure and data reduction methods used to generate the property surface are described. The utility and validity of these results applied to fatigue and flexure loading to these elastomeric materials over long-time periods are discussed.
Long-time asymptotic behavior of the solutions of the Korteweg-De Vries equations
Buslaev, V.S.; Sukhanov, V.V.
1987-05-20
The complete asymptotic expansion of the dispersion tail in the long-time limit is described for the KdV equation and generalized wave operators are introduced. The long-time asymptotic behavior of the Schroedinger spectral equation is studied assuming a potential of the type of the KdV solution. It is shown that the KdV equation is specifically related with the asymptotic structure of the solutions of the spectral equation. As a corollary, they derive the well-known explicit formulas for the leading asymptotic terms of the KdV solutions in terms of the spectral values corresponding to the initial conditions. A sketch of a proof for the various results is suggested.
Exploring long-time response to radiation damage in MgO
NASA Astrophysics Data System (ADS)
Uberuaga, B. P.; Smith, R.; Cleave, A. R.; Henkelman, G.; Grimes, R. W.; Voter, A. F.; Sickafus, K. E.
2005-01-01
Using a variety of computational modeling and simulation methods, we examine the production and long-time evolution of damage created in irradiated MgO. We find that the damage produced in low energy (order 1 keV) collision cascades typically consists of point defects and small defect clusters. Over long times, interstitials annihilate with vacancies and aggregate with other interstitials, forming larger clusters that exhibit surprising behavior. For example, a six-atom interstitial cluster is found to have extremely high mobility. The implications of highly-mobile large clusters are explored via a rate theory model and comparison to other materials. We conclude that successful modeling of radiation damage evolution in MgO requires explicit treatment of large interstitial clusters.
NASA Technical Reports Server (NTRS)
Saltsman, J. F.; Halford, G. R.
1979-01-01
The method of strainrange partitioning is used to predict the cyclic lives of the Metal Properties Council's long time creep-fatigue interspersion tests of several steel alloys. Comparisons are made with predictions based upon the time- and cycle-fraction approach. The method of strainrange partitioning is shown to give consistently more accurate predictions of cyclic life than is given by the time- and cycle-fraction approach.
Long-time diffusivity of DNA chains in nanochannels: A Brownian dynamics study
NASA Astrophysics Data System (ADS)
Jain, Aashish; Dorfman, Kevin
2015-03-01
The simplest approach to calculate the diffusivity of any polymer chain is to use the double sum Kirkwood formula, which is based on preaveraging approximation of diffusion tensor. The error due to the preaveraging approximation has been reported by a number of researchers in the context of free solution by computing both Kirkwood diffusivity D (K) (also known as short-time diffusivity) and long-time diffusivity DL. In nanochannels, the main approach to compute the diffusivity is the Kirkwood formula. However, the error due to the preaveraging approximation is not known in a confined system. We use Brownian dynamics simulation algorithm with excluded volume and hydrodynamic interactions to calculate both short-time and long-time diffusivities of DNA chains in nanochannels, and compare them for a range of channel sizes and DNA chain sizes. Our results indicate that the long-time diffusivity is always smaller than the short-time diffusivity, which is consistent with the result obtained in free solution using linear response theory DL
Long-time behavior of material-surface curvature in isotropic turbulence
NASA Technical Reports Server (NTRS)
Girimaji, S. S.
1992-01-01
The behavior at large times of the curvature of material elements in turbulence is investigated using Lagrangian velocity-gradient time series obtained from direct numerical simulations of isotropic turbulence. The main objectives are: to study the asymptotic behavior of the pdf curvature as a function of initial curvature and shape; and to establish whether the curvature of an initially plane material element goes to a stationary probability distribution. The evidence available in the literature about the asymptotic curvature-pdf of initially flat surfaces is ambiguous, and the conjecture is that it is quasi-stationary. In this work several material-element ensembles of different initial curvatures and shapes are studied. It is found that, at long times the moments of the logarithm of curvature are independent of the initial pdf of curvature. This, it is argued, supports the view that the curvature attains a stationary distribution at long times. It is also shown that, irrespective of initial shape or curvature, the shape of any material element at long times is cylindrical with a high probability.
Direct Immersion Annealing of Block Copolymer Thin Films
NASA Astrophysics Data System (ADS)
Karim, Alamgir
We demonstrate ordering of thin block copolymer (BCP) films via direct immersion annealing (DIA) at enhanced rate leading to stable morphologies. The BCP films are immersed in carefully selected mixtures of good and marginal solvents that can impart enhanced polymer mobility, while inhibiting film dissolution. DIA is compatible with roll-to-roll assembly manufacturing and has distinct advantages over conventional thermal annealing and batch processing solvent-vapor annealing methods. We identify three solvent composition-dependent BCP film ordering regimes in DIA for the weakly interacting polystyrene -poly(methyl methacrylate) (PS -PMMA) system: rapid short range order, optimal long-range order, and a film instability regime. Kinetic studies in the ``optimal long-range order'' processing regime as a function of temperature indicate a significant reduction of activation energy for BCP grain growth compared to oven annealing at conventional temperatures. An attractive feature of DIA is its robustness to ordering other BCP (e.g. PS-P2VP) and PS-PMMA systems exhibiting spherical, lamellar and cylindrical ordering. Inclusion of nanoparticles in these films at high concentrations and fast ordering kinetics study with neutron reflectivity and SANS will be discussed. This is (late) Contributed Talk Abstract for Dillon Medal Symposium at DPOLY - discussed with DPOLY Chair Dvora Perahia.
Reactor vessel annealing system
Miller, Phillip E.; Katz, Leonoard R.; Nath, Raymond J.; Blaushild, Ronald M.; Tatch, Michael D.; Kordalski, Frank J.; Wykstra, Donald T.; Kavalkovich, William M.
1991-01-01
A system for annealing a vessel (14) in situ by heating the vessel (14) to a defined temperature, composed of: an electrically operated heater assembly (10) insertable into the vessel (14) for heating the vessel (14) to the defined temperature; temperature monitoring components positioned relative to the heater assembly (10) for monitoring the temperature of the vessel (14); a controllable electric power supply unit (32-60) for supplying electric power required by the heater assembly (10); a control unit (80-86) for controlling the power supplied by the power supply unit (32-60); a first vehicle (2) containing the power supply unit (32-60); a second vehicle (4) containing the control unit (80-86); power conductors (18,22) connectable between the power supply unit (32-60) and the heater unit (10) for delivering the power supplied by the power supply unit (32-60) to the heater assembly (10); signal conductors (20,24) connectable between the temperature monitoring components and the control unit (80-86) for delivering temperature indicating signals from the temperature monitoring components to the control unit (80-86); and control conductors (8) connectable between the control unit (80-86) and the power supply unit (32-60) for delivering to the power supply unit (32-60) control signals for controlling the level of power supplied by the power supply unit (32-60) to the heater assembly (10).
Fullerene formation and annealing
Mintmire, J.W.
1996-04-05
Why does the highly symmetric carbon cluster C{sub 60} form in such profusion under the right conditions? This question was first asked in 1985, when Kroto suggested that the predominance of the C{sub 60} carbon clusters observed in the molecular beam experiments could be explained by the truncated icosahedral (or soccer ball) form. The name given to this cluster, buckminsterfullerene, led to the use of the term fullerenes for the family of hollow-cage carbon clusters made up of even numbers of triply coordinated carbons arranged with 12 pentagonal rings and an almost arbitrary number of hexagonal rings. More than a decade later, we still lack a completely satisfying understanding of the fundamental chemistry that takes place during fullerene formation. Most current models for fullerene formation require a facile mechanism for ring rearrangement in the fullerene structure, but the simplest proposed mechanisms are believed to have unrealistically high activation barriers. In recent research calculations have suggested that atomic carbon in the reaction mixture could act as a catalyst and allow substantially lower activation barriers for fullerene annealing. This article discusses the background for this research and other adjunct research. 14 refs.
Long-Time Stability of Ni-Ti-Shape Memory Alloys for Automotive Safety Systems
NASA Astrophysics Data System (ADS)
Strittmatter, Joachim; Gümpel, Paul
2011-07-01
In automotive a lot of electromagnetically, pyrotechnically or mechanically driven actuators are integrated to run comfort systems and to control safety systems in modern passenger cars. Using shape memory alloys (SMA) the existing systems could be simplified, performing the same function through new mechanisms with reduced size, weight, and costs. A drawback for the use of SMA in safety systems is the lack of materials knowledge concerning the durability of the switching function (long-time stability of the shape memory effect). Pedestrian safety systems play a significant role to reduce injuries and fatal casualties caused by accidents. One automotive safety system for pedestrian protection is the bonnet lifting system. Based on such an application, this article gives an introduction to existing bonnet lifting systems for pedestrian protection, describes the use of quick changing shape memory actuators and the results of the study concerning the long-time stability of the tested NiTi-wires. These wires were trained, exposed up to 4 years at elevated temperatures (up to 140 °C) and tested regarding their phase change temperatures, times, and strokes. For example, it was found that A P-temperature is shifted toward higher temperatures with longer exposing periods and higher temperatures. However, in the functional testing plant a delay in the switching time could not be detected. This article gives some answers concerning the long-time stability of NiTi-wires that were missing till now. With this knowledge, the number of future automotive applications using SMA can be increased. It can be concluded, that the use of quick changing shape memory actuators in safety systems could simplify the mechanism, reduce maintenance and manufacturing costs and should be insertable also for other automotive applications.
Long-time Stability in Systems of Conservation Laws, Using Relative Entropy/Energy
NASA Astrophysics Data System (ADS)
Serre, Denis
2016-02-01
We study the long-time stability of shock-free solutions of hyperbolic systems of conservation laws, under an arbitrarily large initial disturbance in L 2∩ L ∞. We use the relative entropy method, a robust tool which allows us to consider rough and large disturbances. We display practical examples in several space dimensions, for scalar equations as well as isentropic gas dynamics. For full gas dynamics, we use a trick from C hen [1], in which the estimate is made in terms of the relative mechanical energy instead of the relative mathematical entropy.
On some long time dynamical features of the Trojan asteroids of Jupiter
NASA Astrophysics Data System (ADS)
Érdi, Bálint; Forgács-Dajka, Emese; Süli, Áron
2013-09-01
The equation of motion of long periodic libration around the Lagrangian point in the restricted three-body problem is investigated. The range of validity of an approximate analytical solution in the tadpole region is determined by numerical integration. The predictions of the model of libration are tested on the Trojan asteroids of Jupiter. The long time evolution of the orbital eccentricity and the longitude of the perihelion of the Trojan asteroids, under the effect of the four giant planets, is also investigated and a slight dynamical asymmetry is shown between the two groups of Trojans at and.
Hess, Siegfried; Kröger, Martin; Evans, Denis
2003-04-01
An effective viscosity coefficient is introduced based on definite time averages of equilibrium stress fluctuations rather than stress correlations. Analysis of this quantity via molecular dynamics of a simple model liquid reveals a crossover between the expected short-time elastic and the long-time viscous behavior with increasing averaging time. The procedure allows us to extract the zero-rate shear viscosity when the averaging time becomes one order of magnitude larger than the relevant relaxation time. A relationship between this effective viscosity and the dynamic viscosities is established. PMID:12786406
Long-time uncertainty propagation using generalized polynomial chaos and flow map composition
Luchtenburg, Dirk M.; Brunton, Steven L.; Rowley, Clarence W.
2014-10-01
We present an efficient and accurate method for long-time uncertainty propagation in dynamical systems. Uncertain initial conditions and parameters are both addressed. The method approximates the intermediate short-time flow maps by spectral polynomial bases, as in the generalized polynomial chaos (gPC) method, and uses flow map composition to construct the long-time flow map. In contrast to the gPC method, this approach has spectral error convergence for both short and long integration times. The short-time flow map is characterized by small stretching and folding of the associated trajectories and hence can be well represented by a relatively low-degree basis. The composition of these low-degree polynomial bases then accurately describes the uncertainty behavior for long integration times. The key to the method is that the degree of the resulting polynomial approximation increases exponentially in the number of time intervals, while the number of polynomial coefficients either remains constant (for an autonomous system) or increases linearly in the number of time intervals (for a non-autonomous system). The findings are illustrated on several numerical examples including a nonlinear ordinary differential equation (ODE) with an uncertain initial condition, a linear ODE with an uncertain model parameter, and a two-dimensional, non-autonomous double gyre flow.
Correlation analysis for long time series by robustly estimated autoregressive stochastic processes
NASA Astrophysics Data System (ADS)
Schuh, Wolf-Dieter; Brockmann, Jan-Martin; Kargoll, Boris
2015-04-01
Modern sensors and satellite missions deliver huge data sets and long time series of observations. These data sets have to be handled with care because of changing correlations, conspicuous data and possible outliers. Tailored concepts for data selection and robust techniques to estimate the correlation characteristics allow for a better/optimal exploitation of the information of these measurements. In this presentation we give an overview of standard techniques for estimating correlations occurring in long time series in the time domain as well as in the frequency domain. We discuss the pros and cons especially with the focus on the intensified occurrence of conspicuous data and outliers. We present a concept to classify the measurements and isolate conspicuous data. We propose to describe the varying correlation behavior of the measurement series by an autoregressive stochastic process and give some hints how to construct adaptive filters to decorrelate the measurement series and to handle the huge covariance matrices. As study object we use time series from gravity gradient data collected during the GOCE low orbit operation campaign (LOOC). Due to the low orbit these data from 13-Jun-2014 to 21-Oct-2014 have more or less the same potential to recover the Earth gravity field with the same accuracy than all the data from the rest of the entire mission. Therefore these data are extraordinarily valuable but hard to handle, because of conspicuous data due to maneuvers during the orbit lowering phases, overall increase in drag, saturation of ion thrusters and other (currently) unexplained effects.
[Improving data warehouse environments for efficient analysis of long time-series data].
Kataoka, Hiromi; Hatakeyama, Yutaka; Okuhara, Yoshiyasu; Sugiura, Tetsuro
2012-07-01
Medical records contain enormous amounts of data. It is important to extract useful evidence from such data and feedback to clinical medicine. Evidence-based medicine (EBM) was introduced in the 1990s and has been widely used for more than 20 years, however, hospital information system environments that take advantage of the ideas of EBM have not yet been established. Recently, the numbers of medical institutions with multilateral search systems for the medical records stored in data warehouses (DWHs) have been increasing, but these institutions' systems cannot deal fully with issues such as data reliability and high-dimensional, high-speed searches. DWHs can control long time-series data. Although, the measurement methods and analytical equipment used have been modified and improved with advances in testing techniques, this may have induced shifting and/or fragmentation of these types of data. Furthermore, database design has to be flexible to satisfy the various demands of information retrieval; systems must therefore have the structures to deal with such demands. We report here our new system infrastructure, which exchanges data in order to absorb the data shifting associated with changes in the testing methods. The system enables the preparation of DWH environments that can be used to seamlessly analyze long time-series data, record in knowledge databases the results of comprehensive analyses of institutions' characteristics of laboratory diagnoses, and use the data in education, research and clinical practice. PMID:22973733
Long-time dynamics of Met-enkephalin: comparison of theory with Brownian dynamics simulations.
Kostov, K S; Freed, K F
1999-01-01
A recent theory for the long time dynamics of flexible chain molecules is applied for the first time to a peptide of biological importance, the neurotransmitter met-enkephalin. The dynamics of met-enkephalin is considerably more complicated than that of the previously studied glycine oligomers; met-enkephalin contains the interesting motions of phenyl groups and of side chains relative to the backbone, motions that are present in general flexible peptides. The theory extends the generalized Rouse (GR) model used to study the dynamics of polymers by providing a systematic procedure for including the contributions from the memory function matrices neglected in the GR theory. The new method describes the dynamics by time correlation functions instead of individual trajectories. These correlation functions are analytically expressed in terms of a set of equilibrium averages and the eigenvalues and eigenfunctions of the diffusion operator. The predictions of the theory are compared with Brownian dynamics (BD) simulations, so that both theory and simulation use identical potential functions and solvent models. The theory thus contains no adjustable parameters. Inclusion of the memory function contributions profoundly affects the dynamics. The theory produces very good agreement with the BD simulations for the global motions of met-enkephalin. It also correctly predicts the long-time relaxation rate for local motions. PMID:9876130
Pravdová, E; Macho, L; Hlavácová, N; Ficková, M
2007-09-01
Elevated serum resistin is implicated in insulin resistance associated with obesity and type 2 diabetes mellitus. Alcohol consumption interferes with the nutritional status, metabolic and hormonal activity of the drinker. Impact of ethanol intake on resistin level and resistin metabolic effects is unknown. Effect of long-time (28 days) ad libitum moderate alcohol (6% ethanol solution) intake on serum resistin and resistin mRNA level in adipose tissue of rats (A) was compared to control (C) and pair-fed (PF) animals. PF rats were fed the same caloric amount as A rats on previous day. Alcohol consumption resulted in reduction of food and energy intake, decreased body mass gain, epididymal fat pads mass and smaller adipocytes (vs. C rats). Alcohol intake significantly increased serum resistin and glucose, insulinemia remained unchanged. Systemic insulin resistance was not proved by HOMA, QUICKI and McAuley indexes, but impaired insulin effect on glucose transport in isolated adipocytes was present. Elevated serum resistin was positively correlated with glycemia (r = 0.88, p < 0.01) and negatively with fat cell size (r = -0.73, p < 0.05). High resistin level as the consequence of long-time alcohol intake could contribute to smaller adipocytes, higher glycemia, attenuation of insulin-stimulated glucose transport in adipocytes. Diminished resistin gene expression in adipose tissue of A and PF rats was present. PMID:18063850
Mathematical foundation of quantum annealing
Morita, Satoshi; Nishimori, Hidetoshi
2008-12-15
Quantum annealing is a generic name of quantum algorithms that use quantum-mechanical fluctuations to search for the solution of an optimization problem. It shares the basic idea with quantum adiabatic evolution studied actively in quantum computation. The present paper reviews the mathematical and theoretical foundations of quantum annealing. In particular, theorems are presented for convergence conditions of quantum annealing to the target optimal state after an infinite-time evolution following the Schroedinger or stochastic (Monte Carlo) dynamics. It is proved that the same asymptotic behavior of the control parameter guarantees convergence for both the Schroedinger dynamics and the stochastic dynamics in spite of the essential difference of these two types of dynamics. Also described are the prescriptions to reduce errors in the final approximate solution obtained after a long but finite dynamical evolution of quantum annealing. It is shown there that we can reduce errors significantly by an ingenious choice of annealing schedule (time dependence of the control parameter) without compromising computational complexity qualitatively. A review is given on the derivation of the convergence condition for classical simulated annealing from the view point of quantum adiabaticity using a classical-quantum mapping.
Energy dependence of defects in a-Si:H solar cells during degradation and annealing processes
Caputo, D.; Lemmi, F.; Palma, F.
1997-07-01
In this work the authors report on the effect of current-induced degradation and annealing on p-i-n amorphous silicon solar cells. Current-voltage curves and capacitance measurements under forward bias have been used to monitor the current-induced changes as a function of time. They found that the recovery rate increases with the annealing current, while the stabilized value of efficiency decreases. Comparison of short circuit current and capacitance evolution suggests that defect kinetics in the electronic gap occurs in a different way during degradation and annealing. This behavior can be modeled assuming a faster annealing of defects closest to the extended band and a slower annealing of mid-gap defects.
Quantum annealing speedup over simulated annealing on random Ising chains
NASA Astrophysics Data System (ADS)
Zanca, Tommaso; Santoro, Giuseppe E.
2016-06-01
We show clear evidence of a quadratic speedup of a quantum annealing (QA) Schrödinger dynamics over a Glauber master equation simulated annealing (SA) for a random Ising model in one dimension, via an equal-footing exact deterministic dynamics of the Jordan-Wigner fermionized problems. This is remarkable, in view of the arguments of H. G. Katzgraber et al. [Phys. Rev. X 4, 021008 (2014), 10.1103/PhysRevX.4.021008], since SA does not encounter any phase transition, while QA does. We also find a second remarkable result: that a "quantum-inspired" imaginary-time Schrödinger QA provides a further exponential speedup, i.e., an asymptotic residual error decreasing as a power law τ-μ of the annealing time τ .
NASA Astrophysics Data System (ADS)
Poulain, C.; Mazellier, N.; Chevillard, L.; Gagne, Y.; Baudet, C.
2006-09-01
We present the results of an experimental study of the spatial Fourier modes of the vorticity in a turbulent jet flow. By means of an acoustic scattering setup we have recorded the evolution in time of Fourier modes of the vorticity field, characterized by well defined wavevectors k. By computing the auto-correlation of the amplitude of the Fourier modes we evidence that, whatever the length scale (or equivalently k), the dynamic evolution of the vorticity field involves two well separated time scales. We have also performed the simultaneous acquisitions of pairs of Fourier modes with two wavevectors k and k'. Whatever the spectral gap k- k', any pair of Fourier modes exhibits a significant cross-correlation over long time delays, indicating a strong statistical dependence between scales.
Hybrid resonance and long-time asymptotic of the solution to Maxwell's equations
NASA Astrophysics Data System (ADS)
Després, Bruno; Weder, Ricardo
2016-03-01
We study the long-time asymptotic of the solutions to Maxwell's equation in the case of an upper-hybrid resonance in the cold plasma model. We base our analysis in the transfer to the time domain of the recent results of B. Després, L.M. Imbert-Gérard and R. Weder (2014) [15], where the singular solutions to Maxwell's equations in the frequency domain were constructed by means of a limiting absorption principle and a formula for the heating of the plasma in the limit of vanishing collision frequency was obtained. Currently there is considerable interest in these problems, in particular, because upper-hybrid resonances are a possible scenario for the heating of plasmas, and since they can be a model for the diagnostics involving wave scattering in plasmas.
Long-Time Autocorrelation Function of ECG Signal for Healthy versus Diseased Human Heart
NASA Astrophysics Data System (ADS)
Kulessa, B.; Srokowski, T.; Drozdz, S.
2003-01-01
Long-time ECG time series for healthy subjects and diseased patients are analysed. In the first case, the power spectrum has the 1/f shape in a broad frequency range. However, its behaviour for very low and very high frequency is different and the entire spectrum is integrable. For patients with post-ictal heart rate oscillation in partial epilepsy the 1/f noise is not present. We determine the power spectrum by evaluating the Fourier transform of the signal in both cases and calculate the signal autocorrelation function. It falls with time faster for diseased patients then for healthy people. The presented method can serve as a diagnostic tool of some heart diseases.
Long-time behavior of solution for the compressible nematic liquid crystal flows in R3
NASA Astrophysics Data System (ADS)
Gao, Jincheng; Tao, Qiang; Yao, Zheng-an
2016-08-01
In this paper, we investigate the global existence and long-time behavior of classical solution for the compressible nematic liquid crystal flows in three-dimensional whole space. First of all, the global existence of classical solution is established under the condition that the initial data are close to the constant equilibrium state in HN (R3) (N ≥ 3)-framework. Then, one establishes algebraic time decay for the classical solution by weighted energy method. Finally, the algebraic decay rate of classical solution in Lp (R3)-norm with 2 ≤ p ≤ ∞ and optimal decay rate of their spatial derivative in L2 (R3)-norm are obtained if the initial perturbation belong to L1 (R3) additionally.
Long-time behavior of a finite volume discretization for a fourth order diffusion equation
NASA Astrophysics Data System (ADS)
Maas, Jan; Matthes, Daniel
2016-07-01
We consider a non-standard finite-volume discretization of a strongly non-linear fourth order diffusion equation on the d-dimensional cube, for arbitrary d≥slant 1 . The scheme preserves two important structural properties of the equation: the first is the interpretation as a gradient flow in a mass transportation metric, and the second is an intimate relation to a linear Fokker–Planck equation. Thanks to these structural properties, the scheme possesses two discrete Lyapunov functionals. These functionals approximate the entropy and the Fisher information, respectively, and their dissipation rates converge to the optimal ones in the discrete-to-continuous limit. Using the dissipation, we derive estimates on the long-time asymptotics of the discrete solutions. Finally, we present results from numerical experiments which indicate that our discretization is able to capture significant features of the complex original dynamics, even with a rather coarse spatial resolution.
Phase-field model of long-time glasslike relaxation in binary fluid mixtures.
Benzi, R; Sbragaglia, M; Bernaschi, M; Succi, S
2011-04-22
We present a new phase-field model for binary fluids, exhibiting typical signatures of soft-glassy behavior, such as long-time relaxation, aging, and long-term dynamical arrest. The present model allows the cost of building an interface to vanish locally within the interface, while preserving positivity of the overall surface tension. A crucial consequence of this property, which we prove analytically, is the emergence of free-energy minimizing density configurations, hereafter named "compactons," to denote their property of being localized to a finite-size region of space and strictly zero elsewhere (no tails). Thanks to compactness, any arbitrary superposition of compactons still is a free-energy minimizer, which provides a direct link between the complexity of the free-energy landscape and the morphological complexity of configurational space. PMID:21599369
NASA Astrophysics Data System (ADS)
Ackleh, Azmy S.; Cleveland, John; Thieme, Horst R.
2016-07-01
We study the long-time behavior of solutions to a measure-valued selection-mutation model that we formulated in [14]. We establish permanence results for the full model, and we study the limiting behavior even when there is more than one strategy of a given fitness; a case that arises in applications. We show that for the pure selection case the solution of the dynamical system converges to a Dirac measure centered at the fittest strategy class provided that the support of the initial measure contains a fittest strategy; thus we term this Dirac measure an Asymptotically Stable Strategy. We also show that when the strategy space is discrete, the selection-mutation model with small mutation has a locally asymptotically stable equilibrium that attracts all initial conditions that are positive at the fittest strategy.
Short- and long-time dynamics of isolated many-body quantum systems
NASA Astrophysics Data System (ADS)
Tavora, Marco; Torres-Herrera, Jonathan; Ferreira Dos Santos, Lea
We show our results for the relaxation process of isolated interacting quantum spin chains in the integrable and chaotic regimes. The dynamics of the survival probability (the probability for finding the system still in its initial state at later times) and of few-body observables are analyzed. Different time scales are considered. While the short-time evolution is determined by the shape of the weighted energy distribution of the initial state, the long-time behavior depends on the bounds of the spectrum. Both numerical and analytical results are presented as well as comparisons with existing rigorous mathematical derivations. We consider initial states that can be prepared in experiments with cold atoms in optical lattices. Nsf Grant No. DMR-1147430.
Long-Time Sustainability of Rossby Wave Instability in Protoplanetary Disks with Dead Zone
NASA Astrophysics Data System (ADS)
Li, S.; Li, H.
2015-10-01
We have run 2D simulations to investigate the generation and sustainability of Rossby wave instability (RWI) in proto-planetary disks with constant viscosity and for disks with low viscosity regions (dead zone). For the constant viscosity case, the development of RWI requires a low viscosity and life time of the RWI is short. We also find that the vortex, when it migrates, does so much faster than the disk's viscous drift rate. For disks with dead zone case, a much larger viscosity can be used and the RWI vortex can be sustained for a long time, even the life time of the disk, depending on the width and depth of the dead zone. For a narrow dead zone, the vortex depicts a periodic pattern with a period inversely proportional to the viscosity. If the dead-zone width exceeds some threshold, the periodicity of the RWI disappears.
Grain growth of gold nanowires through laser zone annealing and rapid thermal annealing
NASA Astrophysics Data System (ADS)
Kim, Jung Yun
The grain boundary density in metals plays an increasingly important role as structures are shrinking down to dimensions comparable to the electronic mean free path. Metal nanowires prepared through electron beam lithography, electrodeposition and many other methods are nanocrystalline with an average grain diameter in the range of 2--50 nm. For these nanocrystalline metal nanowires with a lateral dimensions larger than the mean grain diameter, the electrical resistance is dominated by electron scattering at the grain boundaries as opposed to the external surfaces and the background. The deleterious effect of grain boundaries on the electrical properties provides strong motivation to develop post-processing methods for increasing the mean grain diameter. Thermal annealing has typically been used to induce grain growth. However, for metal nanowires patterned on a planar surface, a classic Rayleigh instability is observed resulting in decomposition of the nanowire to a periodic series of nanoparticles. In principle, grain growth requires short range motion of atoms while shape change requires mass displacement across large distances. Laser zone annealing was used to test whether the latter could be suppressed by rapidly heating a highly localized section of the wire followed by rapidly cooling. A piezoelectric motor was used to translate the wire at nanoscale steps over a 532 nm confocal laser source at range of power levels (2.5--10 mW) and translation rates (7--128 nm/s). Annealing at a laser power of 10 mW resulted in grain growth of nearly 300% from 27 nm to 85 nm. A second approach to inhibit shape change while allowing for grain growth was to encapsulate the nanowire with an alumina layer to constrict large scale atomic diffusion during isothermal annealing. The alumina coating maintained the shape of the nanowire up to a temperature of ˜669 K and grain growth approaching the limiting size was observed. To study the grain growth kinetics, in situ electrical
Processing-Structure-Property Relationships in Laser-Annealed PbSe Nanocrystal Thin Films.
Treml, Benjamin E; Robbins, Andrew B; Whitham, Kevin; Smilgies, Detlef-M; Thompson, Michael O; Hanrath, Tobias
2015-01-01
As nanocrystal (NC) synthesis techniques and device architectures advance, it becomes increasingly apparent that new ways of connecting NCs with each other and their external environment are required to realize their considerable potential. Enhancing inter-NC coupling by thermal annealing has been a long-standing challenge. Conventional thermal annealing approaches are limited by the challenge of annealing the NC at sufficiently high temperatures to remove surface-bound ligands while at the same time limiting the thermal budget to prevent large-scale aggregation. Here we investigate nonequilibrium laser annealing of NC thin films that enables separation of the kinetic and thermodynamic aspects of nanocrystal fusion. We show that laser annealing of NC assemblies on nano- to microsecond time scales can transform initially isolated NCs in a thin film into an interconnected structure in which proximate dots "just touch". We investigate both pulsed laser annealing and laser spike annealing and show that both annealing methods can produce "confined-but-connected" nanocrystal films. We develop a thermal transport model to rationalize the differences in resulting film morphologies. Finally we show that the insights gained from study of nanocrystal mono- and bilayers can be extended to three-dimensional NC films. The basic processing-structure-property relationships established in this work provide guidance to future advances in creating functional thin films in which constituent NCs can purposefully interact. PMID:25787088
Direct Immersion Annealing of Thin Block Copolymer Films.
Modi, Arvind; Bhaway, Sarang M; Vogt, Bryan D; Douglas, Jack F; Al-Enizi, Abdullah; Elzatahry, Ahmed; Sharma, Ashutosh; Karim, Alamgir
2015-10-01
We demonstrate ordering of thin block copolymer (BCP) films via direct immersion annealing (DIA) at enhanced rate leading to stable morphologies. The BCP films are immersed in carefully selected mixtures of good and marginal solvents that can impart enhanced polymer mobility, while inhibiting film dissolution. DIA is compatible with roll-to-roll assembly manufacturing and has distinct advantages over conventional thermal annealing and batch processing solvent-vapor annealing methods. We identify three solvent composition-dependent BCP film ordering regimes in DIA for the weakly interacting polystyrene-poly(methyl methacrylate) (PS-PMMA) system: rapid short-range order, optimal long-range order, and a film instability regime. Kinetic studies in the "optimal long-range order" processing regime as a function of temperature indicate a significant reduction of activation energy for BCP grain growth compared to oven annealing at conventional temperatures. An attractive feature of DIA is its robustness to ordering other BCP (e.g. PS-P2VP) and PS-PMMA systems exhibiting spherical, lamellar and cylindrical ordering. PMID:26351823
LAI, FAPAR and FCOVER products derived from AVHRR long time series: principles and evaluation
NASA Astrophysics Data System (ADS)
Verger, A.; Baret, F.; Weiss, M.; Lacaze, R.; Makhmara, H.; Pacholczyk, P.; Smets, B.; Kandasamy, S.; Vermote, E.
2012-04-01
Continuous and long term global monitoring of the terrestrial biosphere has draught an intense interest in the recent years in the context of climate and global change. Developing methodologies for generating historical data records from data collected with different satellite sensors over the past three decades by taking benefits from the improvements identified in the processing of the new generation sensors is a new central issue in remote sensing community. In this context, the Bio-geophysical Parameters (BioPar) service within Geoland2 project (http://www.geoland2.eu) aims at developing pre-operational infrastructures for providing global land products both in near real time and off-line mode with long time series. In this contribution, we describe the principles of the GEOLAND algorithm for generating long term datasets of three key biophysical variables, leaf area index (LAI), Fraction of Absorbed Photosynthetic Active Radiation (FAPAR) and cover fraction (FCOVER), that play a key role in several processes, including photosynthesis, respiration and transpiration. LAI, FAPAR and FCOVER are produced globally from AVHRR Long Term Data Record (LTDR) for the 1981-2000 period at 0.05° spatial resolution and 10 days temporal sampling frequency. The proposed algorithm aims to ensure robustness of the derived long time series and consistency with the ones developed in the recent years, and particularly with GEOLAND products derived from VEGETATION sensor. The approach is based on the capacity of neural networks to learn a particular biophysical product (GEOLAND) from reflectances from another sensor (AVHRR normalized reflectances in the red and near infrared bands). Outliers due to possible cloud contamination or residual atmospheric correction are iteratively eliminated. Prior information based on the climatology is used to get more robust estimates. A specific gap filing and smoothing procedure was applied to generate continuous and smooth time series of decadal
Schaefer, O; Eaton, R D; Timmermans, F J; Hildes, J A
1980-01-01
Spirometry, roentgenography and electrocardiography were performed during community health surveys in 1976-78 in 176 Inuit and other long-time residents of the northeastern (Arctic Bay) and western (Inuvik) Canadian Arctic, and the results were related to age, ethnic origin, occupation and history of climatic exposure, smoking and hospitalization for tuberculosis. In Arctic Bay the young men showed excellent respiratory function, normal-sized pulmonary arteries and normal electrocardiograms, but abnormalities of all three types were increasingly frequent and severe after age 25. The forced mid-expiratory flow (FMF) fell to less than 50% of the norm by age 40, and dilatation of the pulmonary artery, hypertrophy of the right ventricle, right bundle branch block and a pseudoinfarction pattern on the ECG were frequently associated. In contrast, the men in Inuvik, an urbanized centre, maintained above normal respiratory function until age 40, and the FMF and pulmonary artery diameter remained normal in the older men except for Inuit and white trappers over 60 years old who had run fox trap lines along the Arctic coast in the 1920s and 30s. These data suggest that inhalation of extremely cold air at maximum ventilation may be a prime factor in the chronic obstructive lung disease of Inuit hunters, whereas smoking has only a minor role and hospitalization for tuberculosis appears to protect from rather than contribute to this disorder. PMID:7448675
Long time-series of turbid coastal water using AVHRR: An example from Florida Bay, USA
Stumpf, R.P.; Frayer, M.L.
1997-01-01
The AVHRR can provide information on the reflectance of turbid case II water, permitting examination of large estuaries and plumes from major rivers. The AVHRR has been onboard several NOAA satellites, with afternoon overpasses since 1981, offering a long time-series to examine changes in coastal water. We are using AVHRR data starting in December 1989, to examine water clarity in Florida Bay, which has undergone a decline since the late 1980's. The processing involves obtaining a nominal reflectance for red light with standard corrections including those for Rayleigh and aerosol path radiances. Established relationships between reflectance and the water properties being measured in the Bay provide estimates of diffuse attenuation and light limitation for phytoplankton and seagrass productivity studies. Processing also includes monthly averages of reflectance and attenuation. The AVHRR data set describes spatial and temporal patterns, including resuspension of bottom sediments in the winter, and changes in water clarity. The AVHRR also indicates that Florida Bay has much higher reflectivity relative to attenuation than other southeastern US estuaries. ??2005 Copyright SPIE - The International Society for Optical Engineering.
Dynamical decoupling sequences for multi-qubit dephasing suppression and long-time quantum memory
NASA Astrophysics Data System (ADS)
Paz-Silva, Gerardo A.; Lee, Seung-Woo; Green, Todd J.; Viola, Lorenza
2016-07-01
We consider a class of multi-qubit dephasing models that combine classical noise sources and linear coupling to a bosonic environment, and are controlled by arbitrary sequences of dynamical decoupling pulses. Building on a general transfer filter-function framework for open-loop control, we provide an exact representation of the controlled dynamics for arbitrary stationary non-Gaussian classical and quantum noise statistics, with analytical expressions emerging when all dephasing sources are Gaussian. This exact characterization is used to establish two main results. First, we construct multi-qubit sequences that ensure maximum high-order error suppression in both the time and frequency domain and that can be exponentially more efficient than existing ones in terms of total pulse number. Next, we show how long-time multi-qubit storage may be achieved by meeting appropriate conditions for the emergence of a fidelity plateau under sequence repetition, thereby generalizing recent results for single-qubit memory under Gaussian dephasing. In both scenarios, the key step is to endow multi-qubit sequences with a suitable displacement anti-symmetry property, which is of independent interest for applications ranging from environment-assisted entanglement generation to multi-qubit noise spectroscopy protocols.
A method for automatic validation of long time series of data in urban hydrology.
Mourad, M; Bertrand-Krajewski, J L
2002-01-01
Modelling in urban hydrology is largely based on the analysis of long time series of data. The quality of the results strongly depends on the quality of the data used. Doubtful or wrong data must be detected and eventually substituted by reliable ones when it is feasible before any further exploitation. This paper deals with the development of an automatic pre-validation procedure that detects doubtful and not reliable data, in order to facilitate their interpretation. This procedure consists in applying a set of seven tests based on the following criteria: the functioning state of the sensor, the physical range of the quantity, the locally realistic range, the duration since the last maintenance of the sensor, the signal's gradient, material redundancy and analytical redundancy. The results of the tests are coded with the letter A for reliable values, B for doubtful values and C for wrong values. After this automatic prevalidation, the ultimate validation of values marked B and C is carried out manually by the operator, with the assistance of specifically developed visual and graphical tools. PMID:11936642
Building a minimum frustration framework for brain functions over long time scales.
Tozzi, Arturo; Flå, Tor; Peters, James F
2016-08-01
The minimum frustration principle (MFP) is a computational approach stating that, over the long time scales of evolution, proteins' free energy decreases more than expected by thermodynamical constraints as their amino acids assume conformations progressively closer to the lowest energetic state. This Review shows that this general principle, borrowed from protein folding dynamics, can also be fruitfully applied to nervous function. Highlighting the foremost role of energetic requirements, macromolecular dynamics, and above all intertwined time scales in brain activity, the MFP elucidates a wide range of mental processes from sensations to memory retrieval. Brain functions are compared with trajectories that, over long nervous time scales, are attracted toward the low-energy bottom of funnel-like structures characterized by both robustness and plasticity. We discuss how the principle, derived explicitly from evolution and selection of a funneling structure from microdynamics of contacts, is unlike other brain models equipped with energy landscapes, such as the Bayesian and free energy principles and the Hopfield networks. In summary, we make available a novel approach to brain function cast in a biologically informed fashion, with the potential to be operationalized and assessed empirically. © 2016 Wiley Periodicals, Inc. PMID:27114266
The Clodia database: a long time series of fishery data from the Adriatic Sea
Mazzoldi, Carlotta; Sambo, Andrea; Riginella, Emilio
2014-01-01
Long-term time series of species abundances can depict population declines and changes in communities in response to anthropogenic activities, climate changes, alterations of trophic relationships. Here we present a database of historical marine fishery landing data, covering a remarkably long time series (1945–2013) and referring to one of the most exploited areas of the Mediterranean Sea, the Adriatic Sea. The database includes two time series of landing data, 1945–2013 and 1997–2013, from the official statistics of the fish market of Chioggia, where the major fishing fleet of the area operates. Comparisons between the landing data of the database and landing data from other fisheries or data from scientific surveys support the reliability of the time series in depicting changes in species abundances. The database is expected to be used by fishery biologists and ecologists interested in depicting and understanding temporal variations in species abundances and community composition, in relation to environmental and anthropogenic factors. PMID:25977775
Compression stress relaxation apparatus for the long-time monitoring of the incremental modulus
NASA Astrophysics Data System (ADS)
Horst, Roland H.; Stephens, Thomas S.; Coons, James E.; Winter, H. Henning
2003-11-01
A compression apparatus for aging experiments on soft rubbers and foams is presented. The sample is compressed between two parallel surfaces and held there for long-time relaxation studies. The specific purpose of the test is twofold: possible exposure of the sample to aggressive environment under compression during aging and measurement of sample modulus without unloading, i.e., while leaving the sample under constant compression at all times. To determine the restoring force in the compressed sample, the compression strain is modulated with an incremental strain while measuring the force response. The total force gives the compression modulus, and the slope of the force-strain curve allows the determination of the incremental modulus. Stress relaxation data for silicon foam, Dow Corning S-5370 RTV, with 68% void fraction are shown. The modulus of the compressed sample decays over long experimental times of several days. The decay can be described by two relaxation modes, a short mode at 1500 s and a long mode at about 105 s. The incremental modulus changes sharply in the first 1000 s (first mode) and then levels off. The apparatus consists of two self-contained components, the removable sample holder (compression jig) and the stationary test station, which performs the modulation of the strain and all measurements (restoring force and incremental modulus). This allows separation of functions. The apparatus design specifically focused on the control of the incremental strain modulation.
Long-time scale nonlinear simulation of RSAE/TAE instabilities
NASA Astrophysics Data System (ADS)
Spong, Don
2013-10-01
Both frequency sweeping and constant frequency fast ion driven Alfvén instabilities are often observed to persist for a few times 100,000 Alven times. Simulations for these time intervals are challenging both due to computational issues (numerical stability, error accumulation) and physics considerations (source/sink balancing, avoiding bursting/decay, resolution of nonlinear energy cascades, etc.). The usually invoked quasilinear saturation mechanisms do not allow maintenance of such long-lived turbulence; some form of self-organization due to effects such as zonal flows/currents is necessary to nonlinearly sustain Alfvén instabilities over these time intervals. The global mode structures of RSAE and TAE instabilities naturally drive such effects through the Reynold's and Maxwell stress terms. The TAEFL gyrofluid model is a useful tool for exploring such effects since it has the computational stability/efficiency and nonlinear Reynold's/Maxwell stress effects to follow long-time scale nonlinear Alfvénic turbulence. Since the evolving nonlinear mode structure can be quite different from linear mode structure, such effects can be of importance in evaluating fast ion losses and wall heating caused by the nonlocal wave-induced fast ion transport. This research has been supported by the US DOE SciDAC GSEP Center and by the US Department of Energy under Contract DE AC05 00OR22725 with UT-Battelle, LLC.
Improving long time behavior of Poisson bracket mapping equation: A non-Hamiltonian approach
Kim, Hyun Woo; Rhee, Young Min
2014-05-14
Understanding nonadiabatic dynamics in complex systems is a challenging subject. A series of semiclassical approaches have been proposed to tackle the problem in various settings. The Poisson bracket mapping equation (PBME) utilizes a partial Wigner transform and a mapping representation for its formulation, and has been developed to describe nonadiabatic processes in an efficient manner. Operationally, it is expressed as a set of Hamilton's equations of motion, similar to more conventional classical molecular dynamics. However, this original Hamiltonian PBME sometimes suffers from a large deviation in accuracy especially in the long time limit. Here, we propose a non-Hamiltonian variant of PBME to improve its behavior especially in that limit. As a benchmark, we simulate spin-boson and photosynthetic model systems and find that it consistently outperforms the original PBME and its Ehrenfest style variant. We explain the source of this improvement by decomposing the components of the mapping Hamiltonian and by assessing the energy flow between the system and the bath. We discuss strengths and weaknesses of our scheme with a viewpoint of offering future prospects.
Annealing properties of rice starch.
Technology Transfer Automated Retrieval System (TEKTRAN)
Thermal properties of starch can be modified by annealing, i.e., a pre-treatment in excessive amounts of water at temperatures below the gelatinization temperatures. This treatment is known to improve the crystalline properties, and is a useful tool to gain a better control of the functional proper...
An Introduction to Simulated Annealing
ERIC Educational Resources Information Center
Albright, Brian
2007-01-01
An attempt to model the physical process of annealing lead to the development of a type of combinatorial optimization algorithm that takes on the problem of getting trapped in a local minimum. The author presents a Microsoft Excel spreadsheet that illustrates how this works.
ERIC Educational Resources Information Center
Burgardt, Erik D.; Ryan, Hank
1996-01-01
Presents a unit on chemical reaction kinetics that consists of a predemonstration activity, the demonstration, and a set of postdemonstration activities that help students transfer the concepts to actual chemical reactions. Simulates various aspects of chemical reaction kinetics. (JRH)
ERIC Educational Resources Information Center
Wilson, David B.
1981-01-01
Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)
HPGe detectors long time behaviour in high-resolution γ spectrometry
NASA Astrophysics Data System (ADS)
Sajo-Bohus, L.; Rosso, D.; Sajo Castelli, A. M.; Napoli, D. R.; Fioretto, E.; Menegazzo, R.; Barros, H.; Ur, C. A.; Palacios, D.; Liendo, J.
2011-08-01
A large set of data on long term performance of n-type HPGe detectors used in GASP, EUROBALL and CLARA γ spectrometers, as well as environmental measurements have been collected over two decades. In this paper a detailed statistical analysis of this data is given and detector long term behaviour is provided to the scientific community. We include failure, failure mode, repair frequency, repair outcome and its influence in the energy efficiency and energy resolution. A remarkable result is that the life span distribution is exponential. A detector's failure is a memory-less process, where a previous failure does not influence the upcoming one. Repaired spectrometers result in high reliability with deep implications in the management of large scale high-resolution gamma spectrometry related projects. Findings show that on average, detectors initial counting efficiency is slightly lower (∼2%) than that reported by the manufacturers and the repair process (including annealing) does not affect significantly the energy efficiency, even after a long period of use. Repaired detector energy resolution statistics show that the probability, that a repaired detector will be at least as good as it was originally, is more than 3/4.
Applying Tep Measurements to Assess the Response of Hastelloy to Long Time Aging
NASA Astrophysics Data System (ADS)
Ifergane, S.; Gelbstein, Y.; Dahan, I.; Pinkas, M.; Landau, A.
2009-03-01
Hastelloy C-276 service temperature is restricted due to precipitation of the intermetallic compound μ. Time-temperature curves indicate that the highest precipitation rate is obtained at about 870° C. Thermoelectric Power (TEP) measurements were applied to monitor the precipitation kinetics during aging at 870° C. The TEP was found to be well correlated with the amount of μ phase formed during aging and with the reduction in impact energy and ductility. It was demonstrated that TEP measurements could be used to monitor aging of Hastelloy C-276.
ERIC Educational Resources Information Center
Moe, Owen; Cornelius, Richard
1988-01-01
Conveys an appreciation of enzyme kinetic analysis by using a practical and intuitive approach. Discusses enzyme assays, kinetic models and rate laws, the kinetic constants (V, velocity, and Km, Michaels constant), evaluation of V and Km from experimental data, and enzyme inhibition. (CW)
Inertial stochastic dynamics. I. Long-time-step methods for Langevin dynamics
NASA Astrophysics Data System (ADS)
Beard, Daniel A.; Schlick, Tamar
2000-05-01
Two algorithms are presented for integrating the Langevin dynamics equation with long numerical time steps while treating the mass terms as finite. The development of these methods is motivated by the need for accurate methods for simulating slow processes in polymer systems such as two-site intermolecular distances in supercoiled DNA, which evolve over the time scale of milliseconds. Our new approaches refine the common Brownian dynamics (BD) scheme, which approximates the Langevin equation in the highly damped diffusive limit. Our LTID ("long-time-step inertial dynamics") method is based on an eigenmode decomposition of the friction tensor. The less costly integrator IBD ("inertial Brownian dynamics") modifies the usual BD algorithm by the addition of a mass-dependent correction term. To validate the methods, we evaluate the accuracy of LTID and IBD and compare their behavior to that of BD for the simple example of a harmonic oscillator. We find that the LTID method produces the expected correlation structure for Langevin dynamics regardless of the level of damping. In fact, LTID is the only consistent method among the three, with error vanishing as the time step approaches zero. In contrast, BD is accurate only for highly overdamped systems. For cases of moderate overdamping, and for the appropriate choice of time step, IBD is significantly more accurate than BD. IBD is also less computationally expensive than LTID (though both are the same order of complexity as BD), and thus can be applied to simulate systems of size and time scale ranges previously accessible to only the usual BD approach. Such simulations are discussed in our companion paper, for long DNA molecules modeled as wormlike chains.
Ecotonal Control on Vadose-Zone Fluxes in Arid Regions Over Very Long Time Scales
NASA Astrophysics Data System (ADS)
Phillips, F. M.; Walvoord, M. A.; Sandvig, R.
2003-12-01
Recent studies indicate that vegetation plays an important role in regulating recharge in semiarid and arid basins over very long time scales. Several lines of evidence from desert floor environments in the southwestern United States suggest that vegetation has established essentially permanent upward hydraulic gradients, effectively precluding diffuse recharge since the transition from woodland to xeric scrub in the early Holocene. However, less xeric vegetation (such as the pygmy piñon and juniper forest) may support significant diffuse recharge. We show comparative water potential and porewater chemistry profiles collected from various vegetation communities in the Chihuahuan Desert of west Texas. The modeled soil water (vapor and liquid) flux regimes illustrate a conversion from substantial downward fluxes under the mixed woodland to upward fluxes under grassland and xeric scrub. Model results also indicated a trend in increasing drying front propagation depth from the grassland to recently-encroached xeric scrub to well-established xeric scrub. Drying fronts are the result of upward soil water fluxes initiated up to 16 thousand years ago in the xeric scrub community. In contrast, the nearby woodland community supports active, and likely episodic, recharge on the order of 5 to 15 mm yr-1. The mechanism by which some vegetation takes up essentially all seasonally available moisture within the root zone, preventing downward soil water fluxes for periods of thousands of years, but adjacent vegetation communities regularly permit downward fluxes, remains to be determined. Nevertheless, these results suggest that understanding the relation between vegetation community and vadose-zone hydrological processes may be the most profitable avenue toward quantifying diffuse groundwater recharge. We hypothesize that vegetation type may be a reasonable proxy for estimating recharge in semiarid and arid basins. Ongoing research is intended to test the hypothesis of ecotonal
On the causes of major Baltic inflows —an analysis of long time series
NASA Astrophysics Data System (ADS)
Schinke, Holger; Matthäus, Wolfgang
1998-01-01
Conditions for life in the deep water of the Baltic Sea are strongly influenced by inflows of highly saline and oxygenated water from the North Sea. These events - termed major Baltic inflows (MBI) - have episodic character, and are the only mechanisms by which the central Baltic deep water is renewed. Although the cycle of water renewal is well documented, certain meteorological and oceanographic processes determining it are either not very well understood or even partly unknown. Based on the data set of major inflows during the present century, long time series of relevant variables from the Baltic Sea itself (salinity, sea level), its drainage area (river runoff, precipitation), the whole Baltic region (air temperature) and from the North Atlantic and Europe (sea level pressure) are analyzed using statistical methods. Characteristic variations in the relevant meteorological, hydrological and oceanographic variables before and during major events are calculated in order to identify conditions favouring or preventing such events. Major Baltic inflows are characterized by two phases: (1) high pressure over the Baltic region with easterly winds followed by (2) several weeks of strong zonal wind and pressure fields over the North Atlantic and Europe. Major events may occur when only one of these is well developed, the probability of strong events is high if both phases are well developed and closely spaced in time. Variations in river runoff to the Baltic obviously have a greater impact on the occurrence of major events then hitherto supposed. The decreasing frequency and intensity of major inflows since the mid-1970s and the complete absence of such events from February 1983 to the beginning of 1993 is explained by increased zonal circulation linked with intensified precipitation in the Baltic region and increased river runoff to the Baltic. Possible anthropogenic impacts on changes in occurrence of major inflows due to river runoff regulations are indicated. The
Designing Adaptive Low-Dissipative High Order Schemes for Long-Time Integrations. Chapter 1
NASA Technical Reports Server (NTRS)
Yee, Helen C.; Sjoegreen, B.; Mansour, Nagi N. (Technical Monitor)
2001-01-01
A general framework for the design of adaptive low-dissipative high order schemes is presented. It encompasses a rather complete treatment of the numerical approach based on four integrated design criteria: (1) For stability considerations, condition the governing equations before the application of the appropriate numerical scheme whenever it is possible; (2) For consistency, compatible schemes that possess stability properties, including physical and numerical boundary condition treatments, similar to those of the discrete analogue of the continuum are preferred; (3) For the minimization of numerical dissipation contamination, efficient and adaptive numerical dissipation control to further improve nonlinear stability and accuracy should be used; and (4) For practical considerations, the numerical approach should be efficient and applicable to general geometries, and an efficient and reliable dynamic grid adaptation should be used if necessary. These design criteria are, in general, very useful to a wide spectrum of flow simulations. However, the demand on the overall numerical approach for nonlinear stability and accuracy is much more stringent for long-time integration of complex multiscale viscous shock/shear/turbulence/acoustics interactions and numerical combustion. Robust classical numerical methods for less complex flow physics are not suitable or practical for such applications. The present approach is designed expressly to address such flow problems, especially unsteady flows. The minimization of employing very fine grids to overcome the production of spurious numerical solutions and/or instability due to under-resolved grids is also sought. The incremental studies to illustrate the performance of the approach are summarized. Extensive testing and full implementation of the approach is forthcoming. The results shown so far are very encouraging.
Platinum-assisted post deposition annealing of the n-Ge/Y2O3 interface
NASA Astrophysics Data System (ADS)
Zimmermann, C.; Bethge, O.; Lutzer, B.; Bertagnolli, E.
2016-07-01
The impact of annealing temperature and annealing duration on the interface properties of n-Ge/Y2O3/Pt MOS-capacitors is investigated employing an ultrathin catalytically acting Pt-layer. X-ray photoelectron spectroscopy analysis has been used to verify an enhanced growth of GeO2 and thermally stabilizing yttrium germanate at the n-Ge/Y2O3 interface induced by an oxygen post deposition annealing (PDA). Especially at 500 °C and 550 °C high quality Ge/Y2O3 interfaces have been achieved resulting in very low interface trap density of 7.41*1010 eV‑1 cm‑2. It is shown that either a short oxygen annealing at higher temperatures (550 °C) or a long time annealing at lower temperatures (450 °C) are appropriate to realize low interface trap density (D it). It turns out that a Pt-assisted PDA in combination with a final PMA are needed to reduce hysteresis width significantly and to bring flat band voltages toward ideal values.
Porous silicon strain during in situ ultrahigh vacuum thermal annealing
NASA Astrophysics Data System (ADS)
Buttard, D.; Dolino, G.; Faivre, C.; Halimaoui, A.; Comin, F.; Formoso, V.; Ortega, L.
1999-05-01
In situ synchrotron radiation measurements of porous silicon (PS) strain have been performed during ultrahigh vacuum (UHV) thermal annealing. For a p+ sample, the initial lattice expansion shifts toward a contraction above 270 °C in relation with hydrogen desorption. For a p- sample, the strain variation is similar to that of a p+ one, but with effects five times larger: after hydrogen desorption, the contraction strain is large (>1.5%) and inhomogeneous. In both cases, most of these strains are elastic as an HF etch re-establishes the initial expansion with a narrow diffraction peak. For p+ samples, the lattice constant exhibited a slow variation during subsequent exposure to air due to a slow oxidation of the annealed porous samples. The origin of these strain variations is discussed in relation with the presence of hydrogen or oxide coverage. The observation of similar variations in other PS properties is also discussed. Finally, the absence of a strain effect during the introduction of water vapor in UHV is discussed as possibly due to a contamination of the PS sample by residual water during the long time passed under UHV at high temperature.
Simulated annealing model of acupuncture
NASA Astrophysics Data System (ADS)
Shang, Charles; Szu, Harold
2015-05-01
The growth control singularity model suggests that acupuncture points (acupoints) originate from organizers in embryogenesis. Organizers are singular points in growth control. Acupuncture can cause perturbation of a system with effects similar to simulated annealing. In clinical trial, the goal of a treatment is to relieve certain disorder which corresponds to reaching certain local optimum in simulated annealing. The self-organizing effect of the system is limited and related to the person's general health and age. Perturbation at acupoints can lead a stronger local excitation (analogous to higher annealing temperature) compared to perturbation at non-singular points (placebo control points). Such difference diminishes as the number of perturbed points increases due to the wider distribution of the limited self-organizing activity. This model explains the following facts from systematic reviews of acupuncture trials: 1. Properly chosen single acupoint treatment for certain disorder can lead to highly repeatable efficacy above placebo 2. When multiple acupoints are used, the result can be highly repeatable if the patients are relatively healthy and young but are usually mixed if the patients are old, frail and have multiple disorders at the same time as the number of local optima or comorbidities increases. 3. As number of acupoints used increases, the efficacy difference between sham and real acupuncture often diminishes. It predicted that the efficacy of acupuncture is negatively correlated to the disease chronicity, severity and patient's age. This is the first biological - physical model of acupuncture which can predict and guide clinical acupuncture research.
Quantum Annealing for Constrained Optimization
NASA Astrophysics Data System (ADS)
Hen, Itay; Spedalieri, Federico M.
2016-03-01
Recent advances in quantum technology have led to the development and manufacturing of experimental programmable quantum annealers that promise to solve certain combinatorial optimization problems of practical relevance faster than their classical analogues. The applicability of such devices for many theoretical and real-world optimization problems, which are often constrained, is severely limited by the sparse, rigid layout of the devices' quantum bits. Traditionally, constraints are addressed by the addition of penalty terms to the Hamiltonian of the problem, which, in turn, requires prohibitively increasing physical resources while also restricting the dynamical range of the interactions. Here, we propose a method for encoding constrained optimization problems on quantum annealers that eliminates the need for penalty terms and thereby reduces the number of required couplers and removes the need for minor embedding, greatly reducing the number of required physical qubits. We argue the advantages of the proposed technique and illustrate its effectiveness. We conclude by discussing the experimental feasibility of the suggested method as well as its potential to appreciably reduce the resource requirements for implementing optimization problems on quantum annealers and its significance in the field of quantum computing.
Determining long time-scale hyporheic zone flow paths in Antarctic streams
Gooseff, M.N.; McKnight, Diane M.; Runkel, R.L.; Vaughn, B.H.
2003-01-01
In the McMurdo Dry Valleys of Antarctica, glaciers are the source of meltwater during the austral summer, and the streams and adjacent hyporheic zones constitute the entire physical watershed; there are no hillslope processes in these systems. Hyporheic zones can extend several metres from each side of the stream, and are up to 70 cm deep, corresponding to a lateral cross-section as large as 12 m2, and water resides in the subsurface year around. In this study, we differentiate between the near-stream hyporheic zone, which can be characterized with stream tracer experiments, and the extended hyporheic zone, which has a longer time-scale of exchange. We sampled stream water from Green Creek and from the adjacent saturated alluvium for stable isotopes of D and 18O to assess the significance and extent of stream-water exchange between the streams and extended hyporheic zones over long time-scales (days to weeks). Our results show that water residing in the extended hyporheic zone is much more isotopically enriched (up to 11??? D and 2.2??? 18O) than stream water. This result suggests a long residence time within the extended hyporheic zone, during which fractionation has occured owing to summer evaporation and winter sublimation of hyporheic water. We found less enriched water in the extended hyporheic zone later in the flow season, suggesting that stream water may be exchanged into and out of this zone, on the time-scale of weeks to months. The transient storage model OTIS was used to characterize the exchange of stream water with the extended hyporheic zone. Model results yield exchange rates (??) generally an order magnitude lower (10-5 s-1) than those determined using stream-tracer techniques on the same stream. In light of previous studies in these streams, these results suggest that the hyporheic zones in Antarctic streams have near-stream zones of rapid stream-water exchange, where 'fast' biogeochemical reactions may influence water chemistry, and extended
A webgis supported snow information system with long time satellite data for Turkey
NASA Astrophysics Data System (ADS)
Surer, S.; Bolat, K.; Akyurek, Z.
2012-04-01
products have been produced for around 12 years from 2000 to 2012 and it is being produced daily as the data is available. 72% overall accuracy was obtained from the validation analysis. Our website will be available to give service to our users to make analysis on snow extent with a long time series database for free. By the help of WEBGIS interface it is going to be possible to produce time series of snow cover areas, and produce graphs and summary statistics for a better management of information on snow cover in various fields from flood forecast integration, energy production planning of hydropower plants which are fed from snow melting, and producing input for climate models.
Determining long time-scale hyporheic zone flow paths in Antarctic streams
NASA Astrophysics Data System (ADS)
Gooseff, Michael N.; McKnight, Diane M.; Runkel, Robert L.; Vaughn, Bruce H.
2003-06-01
In the McMurdo Dry Valleys of Antarctica, glaciers are the source of meltwater during the austral summer, and the streams and adjacent hyporheic zones constitute the entire physical watershed; there are no hillslope processes in these systems. Hyporheic zones can extend several metres from each side of the stream, and are up to 70 cm deep, corresponding to a lateral cross-section as large as 12 m2, and water resides in the subsurface year around. In this study, we differentiate between the near-stream hyporheic zone, which can be characterized with stream tracer experiments, and the extended hyporheic zone, which has a longer time-scale of exchange. We sampled stream water from Green Creek and from the adjacent saturated alluvium for stable isotopes of D and 18O to assess the significance and extent of stream-water exchange between the streams and extended hyporheic zones over long time-scales (days to weeks). Our results show that water residing in the extended hyporheic zone is much more isotopically enriched (up to 11 D and 2·2 18O) than stream water. This result suggests a long residence time within the extended hyporheic zone, during which fractionation has occurred owing to summer evaporation and winter sublimation of hyporheic water. We found less enriched water in the extended hyporheic zone later in the flow season, suggesting that stream water may be exchanged into and out of this zone, on the time-scale of weeks to months. The transient storage model OTIS was used to characterize the exchange of stream water with the extended hyporheic zone. Model results yield exchange rates () generally an order magnitude lower (10-5 s-1) than those determined using stream-tracer techniques on the same stream. In light of previous studies in these streams, these results suggest that the hyporheic zones in Antarctic streams have near-stream zones of rapid stream-water exchange, where fast biogeochemical reactions may influence water chemistry, and extended hyporheic
Numerical study of long-time dynamics and ergodic-nonergodic transitions in dense simple fluids
NASA Astrophysics Data System (ADS)
McCowan, David D.
2015-08-01
Since the mid-1980s, mode-coupling theory (MCT) has been the de facto theoretic description of dense fluids and the transition from the fluid state to the glassy state. MCT, however, is limited by the approximations used in its construction and lacks an unambiguous mechanism to institute corrections. We use recent results from a new theoretical framework—developed from first principles via a self-consistent perturbation expansion in terms of an effective two-body potential—to numerically explore the kinetics of systems of classical particles, specifically hard spheres governed by Smoluchowski dynamics. We present here a full solution for such a system to the kinetic equation governing the density-density time correlation function and show that the function exhibits the characteristic two-step decay of supercooled fluids and an ergodic-nonergodic transition to a dynamically arrested state. Unlike many previous numerical studies—and in stark contrast to experiment—we have access to the full time and wave-number range of the correlation function with great precision and are able to track the solution unprecedentedly close to the transition, covering nearly 15 decades in scaled time. Using asymptotic approximation techniques analogous to those developed for MCT, we fit the solution to predicted forms and extract critical parameters. We find complete qualitative agreement with known glassy behavior (e.g. power-law divergence of the α -relaxation time scale in the ergodic phase and square-root growth of the glass form factors in the nonergodic phase), as well as some limited quantitative agreement [e.g. the transition at packing fraction η*=0.60149761 (10 ) ] , consistent with previous static solutions under this theory and with comparable colloidal suspension experiments. However, most importantly, we establish that this new theory is able to reproduce the salient features seen in other theories, experiments, and simulations but has the advantages of being
Assessment of phase-field-crystal concepts using long-time molecular dynamics
NASA Astrophysics Data System (ADS)
Baker, K. L.; Curtin, W. A.
2015-01-01
The ability of the phase-field-crystal (PFC) model to quantitatively predict atomistic defect structures in crystalline solids is addressed. First, general aspects of the PFC model are discussed within the context of obtaining quantitative results in solid materials. Then a specific example is used to illustrate major points. Specifically, accelerated molecular dynamics is used to compute the one-particle probability density ρ(1 )(r ) in a complex atomistic defect consisting of a Lomer dislocation with an equilibrium distribution of vacancies in the core, and the results are considered within the general framework of the PFC model. As expected, ρ(1 )(r ) shows numerous spatially localized peaks with integrated densities smaller than unity, as would arise in a PFC computation. However, the ρ(1 )(r ) actually corresponds to a time-averaged superposition of a few well-defined atomic configurations each having a well-defined energy. The deconvolution of ρ(1 )(r ) to obtain the actual distinct atomic configurations is not feasible. Using a potential energy functional that accurately computes the energies of distinct configurations, the potential energy computed using ρ(1 )(r ) differs from the actual average atomistic energy by ˜50 eV divided among approximately 46 atoms in the core of the defect. Attempts to rectify this deviation by introducing correlations cannot significantly reduce this error. The simulations show energy barriers between distinct configurations varying by up to 0.5 eV, indicating that the simple kinetic evolution law used in PFC cannot accurately capture the true time evolution in this problem. Overall, these results demonstrate, in one nontrivial case, that the PFC model is probably unable to predict atomistic defect structures, energies, or kinetic barriers at the quantitative levels needed for application to problems in materials science.
Study on the vegetation dynamic change using long time series of remote sensing data
NASA Astrophysics Data System (ADS)
Fan, Jinlong; Zhang, Xiaoyu
2010-10-01
The vegetation covering land surface is main component of biosphere which is one of five significant spheres on the earth. The vegetation plays a very important role on the natural environment conservation and improvement to keep human being's living environment evergreen while the vegetation supplies many natural resources to human living and development continuously. Under the background of global warming, vegetation is changing as climate changes. It is not doubt that human activities have great effects on the vegetation dynamic. In general, there are two aspects of the interaction between vegetation and climate, the climatic adaptation of vegetation and the vegetation feedback on climate. On the base of the research on the long term vegetation growth dynamics, it can be found out the vegetation adaptation to climate change. The dynamic change of vegetation is the direct indicator of the ecological environment changes. Therefore, study on the dynamic change of vegetation will be very interest and useful. In this paper, the vegetation change in special region of China will be described in detail. In addition to the methods of the long term in-situ observation of vegetation, remote sensing technologies can also be used to study the long time series vegetation dynamic. The widely used NDVI was often employed to monitor the status of vegetation growth. Actually, NDVI can indicate the vigor and the fractional cover of vegetation effectively. So the long time series of NDVI datasets are a very valuable data source supporting the study on the long term vegetation dynamics. Since 1980, a series of NOAA satellites have been launched successfully, which have already supplied more than 20 years NOAA/AVHRR satellites data. In this paper, we selected Ningxia Hui autonomic region of China as the case study area and used 20 years pathfinder AVHRR NDVI data to carry out the case study on the vegetation dynamics in order to further understand the phenomena of 20 years vegetation
Recursive Branching Simulated Annealing Algorithm
NASA Technical Reports Server (NTRS)
Bolcar, Matthew; Smith, J. Scott; Aronstein, David
2012-01-01
This innovation is a variation of a simulated-annealing optimization algorithm that uses a recursive-branching structure to parallelize the search of a parameter space for the globally optimal solution to an objective. The algorithm has been demonstrated to be more effective at searching a parameter space than traditional simulated-annealing methods for a particular problem of interest, and it can readily be applied to a wide variety of optimization problems, including those with a parameter space having both discrete-value parameters (combinatorial) and continuous-variable parameters. It can take the place of a conventional simulated- annealing, Monte-Carlo, or random- walk algorithm. In a conventional simulated-annealing (SA) algorithm, a starting configuration is randomly selected within the parameter space. The algorithm randomly selects another configuration from the parameter space and evaluates the objective function for that configuration. If the objective function value is better than the previous value, the new configuration is adopted as the new point of interest in the parameter space. If the objective function value is worse than the previous value, the new configuration may be adopted, with a probability determined by a temperature parameter, used in analogy to annealing in metals. As the optimization continues, the region of the parameter space from which new configurations can be selected shrinks, and in conjunction with lowering the annealing temperature (and thus lowering the probability for adopting configurations in parameter space with worse objective functions), the algorithm can converge on the globally optimal configuration. The Recursive Branching Simulated Annealing (RBSA) algorithm shares some features with the SA algorithm, notably including the basic principles that a starting configuration is randomly selected from within the parameter space, the algorithm tests other configurations with the goal of finding the globally optimal
Modeling of sediment flux at short, middle and long time scale in alpine torrents
NASA Astrophysics Data System (ADS)
Mazotti, Benoît.; Jaboyedoff, Michel; Loye, Alexandre; Bardou, Eric
2010-05-01
Sediments management has become an important issue in the alpine regions since all deposits of material must be removed from sediment traps to keep their efficiency. However, this is not sustainable to evacuate those deposits over long distances. The goals of this work is to quantify the sediment supply of alpine torrents and active gullies in order to make suatinable management over the long term. From a case study situated in the region of Zinal, Valais, Switzerland, we will try to give general recommendation. Several approaches are tested to create a model able to estimate the sediment budget at short, middle and long time scale. After a general analysis of the catchment rendering a geomorphological map (process and location), a quantitative assessment of sediment production is performed. Besides, a qualitative representation of sediment transport processes is created that enable the modelling of sediment cascade. Several new methods are tested combining field work and remote sensing data (DEM, Lidar acquisition and aerial photos). The torrent activity (maximum erosion volume) is estimated with the Slope Local Base Level (SLBL) constrained with field observations (e.g. presence of outcrop). Downstream and cross-sectional topographic profiles along the streams enable to determine their overall dynamics. The model is then composed of homogeneous sections of the torrent. Erosion rates are defined according to the activity observed on time series of aerial photos, historical data, etc. The climate forcing is also considered for assessing torrential dynamics in the prospective sediment balances. The preliminary conclusion is that 6 sets of information implemented in the model enable estimating the quantity of sediments transport by the torrents ((1) the geomorphologic map, (2) the division of the torrent in homogeneous sections, (3) the longitudinal profile of the torrent, (4) the calculation of the maximum volume mobilized by the torrent (with the SLBL), (5) the
Correlation of annealing with chemical stability in lyophilized pharmaceutical glasses.
Luthra, Suman A; Hodge, Ian M; Utz, Marcel; Pikal, Michael J
2008-12-01
This research constitutes a thorough study of the relationship between the chemical stability, aging state and global molecular motion on the one hand, and microscopic local mobility in multi-component systems on the other hand. The objective of the present work was to determine whether annealing a glass below T(g) affects its chemical stability and determine if the rate of chemical degradation couples with global relaxation times determined using calorimetery, and/or with T(1) and T(1rho) relaxation times measured using ssNMR. Model compounds chosen for this research were lyophilized aspartame/sucrose and aspartame/trehalose (1:10 w/w) formulations. The chemical degradation was assessed at various temperatures using high-performance liquid chromatography (HPLC) to determine the impact of annealing on chemical stability. The rate constant for chemical degradation was estimated using stretched time kinetics. The results support the hypothesis that thermal history affects the molecular mobility required for structural relaxation and such effect is critical for chemical stability, that is, a stabilization effect upon annealing is observed. PMID:18481306
NASA Technical Reports Server (NTRS)
Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.
1994-01-01
This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content, and is related to the classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is described by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.
Defect behavior, carrier removal and predicted in-space injection annealing of InP solar cells
NASA Technical Reports Server (NTRS)
Weinberg, I.; Swartz, C. K.; Drevinsky, P. J.
1992-01-01
Defect behavior, observed by deep level transient spectroscopy (DLTS), is used to predict carrier removal and the effects of simultaneous electron irradiation and injection annealing of the performance of InP solar cells. For carrier removal, the number of holes trapped per defect is obtained from measurements of both carrier concentrations and defect concentrations during an isochronal anneal. In addition, from kinetic considerations, the behavior of the dominant defect during injection annealing is used to estimate the degradation expected from exposure to the ambient electron environment in geostationary orbit.
NASA Technical Reports Server (NTRS)
Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.
1994-01-01
This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content and related to classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is governed by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.
Long-time atomistic simulations with the Parallel Replica Dynamics method
NASA Astrophysics Data System (ADS)
Perez, Danny
Molecular Dynamics (MD) -- the numerical integration of atomistic equations of motion -- is a workhorse of computational materials science. Indeed, MD can in principle be used to obtain any thermodynamic or kinetic quantity, without introducing any approximation or assumptions beyond the adequacy of the interaction potential. It is therefore an extremely powerful and flexible tool to study materials with atomistic spatio-temporal resolution. These enviable qualities however come at a steep computational price, hence limiting the system sizes and simulation times that can be achieved in practice. While the size limitation can be efficiently addressed with massively parallel implementations of MD based on spatial decomposition strategies, allowing for the simulation of trillions of atoms, the same approach usually cannot extend the timescales much beyond microseconds. In this article, we discuss an alternative parallel-in-time approach, the Parallel Replica Dynamics (ParRep) method, that aims at addressing the timescale limitation of MD for systems that evolve through rare state-to-state transitions. We review the formal underpinnings of the method and demonstrate that it can provide arbitrarily accurate results for any definition of the states. When an adequate definition of the states is available, ParRep can simulate trajectories with a parallel speedup approaching the number of replicas used. We demonstrate the usefulness of ParRep by presenting different examples of materials simulations where access to long timescales was essential to access the physical regime of interest and discuss practical considerations that must be addressed to carry out these simulations. Work supported by the United States Department of Energy (U.S. DOE), Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division.
Burton, Matthew G; Huang, Qi M; Hossain, Mohammed A; Wade, John D; Clayton, Andrew H A; Gee, Michelle L
2013-11-26
The interaction dynamics between a lytic peptide and a biomembrane was studied using time-lapse fluorescence lifetime imaging microscopy. The model membrane was 1,2-dipalmitoyl-sn-glycero-3-phosphochloine giant unilamellar vesicles (GUVs), and the peptide was the K14 derivative of melittin, to which the polarity-sensitive fluorescent probe AlexaFluor 430 was grafted. The interaction of the peptide with the GUVs resulted in a progressive quenching of the fluorescence lifetime over a period of minutes. From previous photophysics characterization of the peptide, we were able to deconvolve the contribution of three distinct peptide states to the lifetime trajectory and use this data to develop a kinetics model for the interaction process. It was found that the peptide-membrane interaction was well described by a two-step mechanism: peptide monomer adsorption followed by membrane surface migration, assembly, and insertion to form membrane pores. There was an equilibrium exchange between pore and surface monomers at all lipid/peptide (L/P) concentration ratios, suggesting that the fully inserted phase was reached, even at low peptide concentrations. In contrast to previous studies, there was no evidence of critical behavior; irrespective of L/P ratio, lytic pores were the dominant peptide state at equilibrium and were formed even at very low peptide concentrations. We suggest that this behavior is seen in GUVs because their low curvature means low Laplace pressure. Membrane elasticity is therefore relatively ineffective at damping the thermal fluctuations of lipid molecules that lead to random molecular-level lipid protrusions and membrane undulations. The transient local membrane deformations that result from these thermal fluctuations create the conditions necessary for facile peptide insertion. PMID:24168523
Effects of annealing and additions on dynamic mechanical properties of SnSb quenched alloy
NASA Astrophysics Data System (ADS)
El-Bediwi, A. B.
2004-08-01
The elastic modulus, internal friction and stiffness values of quenched SnSb bearing alloy have been evaluated using the dynamic resonance technique. Annealing for 2 and 4 h at 120, 140 and 160degreesC caused variations in the elastic modulus. internal friction and stiffness values. This is due to structural changes in the SnSb matrix during isothermal annealing such as coarsening in the phases (Sn, Sb or intermetallic compounds), recrystallization and stress relief. In addition, adding a small amount (1 wt.%) of Cu or Ag improved the bearing mechanical properties of the SnSb bearing alloy. The SnSbCu1 alloy has the best bearing mechanical properties with thermo-mechanical stability for long time at high temperature.
Comparing codes for error corrected quantum annealing
NASA Astrophysics Data System (ADS)
Mishra, Anurag; Albash, Tameem; Paz, Gerardo; Lidar, Daniel
2015-03-01
Previous work on the D-Wave Two (DW2) device has demonstrated the effectiveness of using error correction and suppression for quantum annealers. As the size of a quantum annealer increases, error correction becomes crucial for improved performance. We introduce a new type of code for error correction tailored to the hardware graph of the DW2, discuss the result of benchmarking this code on qubit chains, discuss various new decoding methods, and compare the performance to previous quantum annealing correction schemes.
Annealing of aromatic polyimide precursors
NASA Technical Reports Server (NTRS)
Wakelyn, N. T.
1975-01-01
A study has been made of the thermal behavior of polyimide precursors: an isomeric pair of crystals of the complex formed by p-phenylenediamine with the separated isomers of the di-isopropyl ester of pyromellitic acid. Specimens of this material were isothermally annealed in the temperature range 120 C to 170 C for periods of time up to 1 week. Although this temperature range is well below that customarily used for imidizations, the working hypothesis was that it would be more likely that a polymer embodying at least part of the precursor structure could be formed if the molecular motion was minimized to that actually required for the formation of the imide linkage. The progress of the annealing was followed by: infrared spectroscopy, differential thermal analysis, powder X-ray diffraction, and thermal gravimetric analysis. Single crystal X-ray analysis of the meta monomer yields a structure of chains of alternating acid and base and suggests that this monomer is amenable to polymerization with a minimum of geometrical disruption.
Quantum Annealing for Constrained Optimization
NASA Astrophysics Data System (ADS)
Hen, Itay; Spedalieri, Federico
Recent advances in quantum technology have led to the development and manufacturing of experimental programmable quantum annealers that could potentially solve certain quadratic unconstrained binary optimization problems faster than their classical analogues. The applicability of such devices for many theoretical and practical optimization problems, which are often constrained, is severely limited by the sparse, rigid layout of the devices' quantum bits. Traditionally, constraints are addressed by the addition of penalty terms to the Hamiltonian of the problem, which in turn requires prohibitively increasing physical resources while also restricting the dynamical range of the interactions. Here we propose a method for encoding constrained optimization problems on quantum annealers that eliminates the need for penalty terms and thereby removes many of the obstacles associated with the implementation of these. We argue the advantages of the proposed technique and illustrate its effectiveness. We then conclude by discussing the experimental feasibility of the suggested method as well as its potential to boost the encodability of other optimization problems.
NASA Astrophysics Data System (ADS)
Chen, Zhi-Tao; Xu, Ke; Guo, Li-Ping; Yang, Zhi-Jian; Pan, Yao-Bo; Su, Yue-Yong; Zhang, Han; Shen, Bo; Zhang, Guo-Yi
2006-05-01
We investigate mosaic structure evolution of GaN films annealed for a long time at 800°C grown on sapphire substrates by metalorganic chemical vapour deposition by high-resolution x-ray diffraction. The result show that residual stress in GaN films is relaxed by generating edge-type threading dislocations (TDs) instead of screw-type TDs. Compared to as-grown GaN films, the annealed ones have larger mean twist angles corresponding to higher density of edge-type TDs but smaller mean tilt angles corresponding to lower density of screw-type TDs films. Due to the increased edge-type TD density, the lateral coherence lengths of the annealed GaN films also decrease. The results obtained from chemical etching experiment and grazing-incidence x-ray diffraction (GIXRD) also support the proposed structure evolution.
Thermally activated switching at long time scales in exchange-coupled magnetic grains
NASA Astrophysics Data System (ADS)
Almudallal, Ahmad M.; Mercer, J. I.; Whitehead, J. P.; Plumer, M. L.; van Ek, J.; Fal, T. J.
2015-10-01
Rate coefficients of the Arrhenius-Néel form are calculated for thermally activated magnetic moment reversal for dual layer exchange-coupled composite (ECC) media based on the Langer formalism and are applied to study the sweep rate dependence of M H hysteresis loops as a function of the exchange coupling I between the layers. The individual grains are modeled as two exchange-coupled Stoner-Wohlfarth particles from which the minimum energy paths connecting the minimum energy states are calculated using a variant of the string method and the energy barriers and attempt frequencies calculated as a function of the applied field. The resultant rate equations describing the evolution of an ensemble of noninteracting ECC grains are then integrated numerically in an applied field with constant sweep rate R =-d H /d t and the magnetization calculated as a function of the applied field H . M H hysteresis loops are presented for a range of values I for sweep rates 105Oe /s ≤R ≤1010Oe /s and a figure of merit that quantifies the advantages of ECC media is proposed. M H hysteresis loops are also calculated based on the stochastic Landau-Lifshitz-Gilbert equations for 108Oe /s ≤R ≤1010Oe /s and are shown to be in good agreement with those obtained from the direct integration of rate equations. The results are also used to examine the accuracy of certain approximate models that reduce the complexity associated with the Langer-based formalism and which provide some useful insight into the reversal process and its dependence on the coupling strength and sweep rate. Of particular interest is the clustering of minimum energy states that are separated by relatively low-energy barriers into "metastates." It is shown that while approximating the reversal process in terms of "metastates" results in little loss of accuracy, it can reduce the run time of a kinetic Monte Carlo (KMC) simulation of the magnetic decay of an ensemble of dual layer ECC media by 2 -3 orders of magnitude
Rapid Annealing Of Amorphous Hydrogenated Carbon
NASA Technical Reports Server (NTRS)
Alterovitz, Samuel A.; Pouch, John J.; Warner, Joseph D.
1989-01-01
Report describes experiments to determine effects of rapid annealing on films of amorphous hydrogenated carbon. Study represents first efforts to provide information for applications of a-C:H films where rapid thermal processing required. Major finding, annealing causes abrupt increase in absorption and concomitant decrease in optical band gap. Most of change occurs during first 20 s, continues during longer annealing times. Extend of change increases with annealing temperature. Researchers hypothesize abrupt initial change caused by loss of hydrogen, while gradual subsequent change due to polymerization of remaining carbon into crystallites or sheets of graphite. Optical band gaps of unannealed specimens on silicon substrates lower than those of specimens on quartz substrates.
Classical Simulated Annealing Using Quantum Analogues
NASA Astrophysics Data System (ADS)
La Cour, Brian R.; Troupe, James E.; Mark, Hans M.
2016-08-01
In this paper we consider the use of certain classical analogues to quantum tunneling behavior to improve the performance of simulated annealing on a discrete spin system of the general Ising form. Specifically, we consider the use of multiple simultaneous spin flips at each annealing step as an analogue to quantum spin coherence as well as modifications of the Boltzmann acceptance probability to mimic quantum tunneling. We find that the use of multiple spin flips can indeed be advantageous under certain annealing schedules, but only for long anneal times.
Classical Simulated Annealing Using Quantum Analogues
NASA Astrophysics Data System (ADS)
La Cour, Brian R.; Troupe, James E.; Mark, Hans M.
2016-06-01
In this paper we consider the use of certain classical analogues to quantum tunneling behavior to improve the performance of simulated annealing on a discrete spin system of the general Ising form. Specifically, we consider the use of multiple simultaneous spin flips at each annealing step as an analogue to quantum spin coherence as well as modifications of the Boltzmann acceptance probability to mimic quantum tunneling. We find that the use of multiple spin flips can indeed be advantageous under certain annealing schedules, but only for long anneal times.
Rapid microwave annealing for perpendicular oriented cylinders in PS- b-PMMA thin films
NASA Astrophysics Data System (ADS)
Qiang, Zhe; Cavicchi, Kevin; Vogt, Bryan; University of Akron Team
Self-assembly of block copolymer (BCP) has been extensively studied for decades due to their wide range of potential applications such as lithography. Direct microwave annealing provides rapid ordering kinetics. However, the knowledge regarding the structural and orientation evolution of morphology during microwave annealing without solvents remains sparse. Herein, we report on how microwave-annealing conditions impact the morphology developed in cylinder forming PS-b-PMMA films on unmodified silicon wafers. The fraction of perpendicular cylinders developed during microwave annealing is primarily determined by temperature ramp from microwave heating itself. The heating of the substrate during microwave annealing is varied from 0.5 °C/s to 2.8 °C/s by two factors: (1) the microwave output energy and (2) the local heating position of BCP film in the microwave reaction vessel. A maximum in the fraction of perpendicular cylinders (97 %) occurs at 1.83 °C/s and appears independent of the microwave power used. This work demonstrates the importance of controlling conditions of microwave annealing in the morphology developed.
Evolution of subsurface nanocavities in copper under argon bombardment and annealing
NASA Astrophysics Data System (ADS)
Kulikov, D. V.; Kurnosikov, O.; Kharlamov, V. S.; Trushin, Yu. V.
2013-02-01
The experimental and theoretical studies of evolution of nanocavities in argon-irradiated copper under annealing are presented. The subsurface argon-filled nanocavities are formed during a short annealing at a temperature around 1000 K by migration and interaction of complexes of the simplest defects created by argon irradiation at room temperature. A long-time annealing at a temperature above 1075 K leads to decomposition of nanocavities and desorption of argon from the sample. Using the X-ray photoelectron spectroscopy and scanning tunneling microscopy and spectroscopy, valuable data sets including the density of nanocavities and their size and depth distribution are obtained. A theoretical model describing the nucleation and evolution of nanocavities is developed. Computer simulations based on this model show that the nanocavities grow at elevated temperatures by absorption of argon-vacancy complexes formed during the ion irradiation. By comparison the calculations with experimental results, the migration energy of these complexes is estimated to be around 2.5-2.75 eV. Also, the value of dissociation energy of a complex, consisting of two vacancies and two argon atoms, is found to be equal to approximately 1.10-1.18 eV. The calculation of concentration of nanocavities at different annealing conditions reveals a satisfactory agreement with the experimental observations.
DOE`s annealing prototype demonstration projects
Warren, J.; Nakos, J.; Rochau, G.
1997-02-01
One of the challenges U.S. utilities face in addressing technical issues associated with the aging of nuclear power plants is the long-term effect of plant operation on reactor pressure vessels (RPVs). As a nuclear plant operates, its RPV is exposed to neutrons. For certain plants, this neutron exposure can cause embrittlement of some of the RPV welds which can shorten the useful life of the RPV. This RPV embrittlement issue has the potential to affect the continued operation of a number of operating U.S. pressurized water reactor (PWR) plants. However, RPV material properties affected by long-term irradiation are recoverable through a thermal annealing treatment of the RPV. Although a dozen Russian-designed RPVs and several U.S. military vessels have been successfully annealed, U.S. utilities have stated that a successful annealing demonstration of a U.S. RPV is a prerequisite for annealing a licensed U.S. nuclear power plant. In May 1995, the Department of Energy`s Sandia National Laboratories awarded two cost-shared contracts to evaluate the feasibility of annealing U.S. licensed plants by conducting an anneal of an installed RPV using two different heating technologies. The contracts were awarded to the American Society of Mechanical Engineers (ASME) Center for Research and Technology Development (CRTD) and MPR Associates (MPR). The ASME team completed its annealing prototype demonstration in July 1996, using an indirect gas furnace at the uncompleted Public Service of Indiana`s Marble Hill nuclear power plant. The MPR team`s annealing prototype demonstration was scheduled to be completed in early 1997, using a direct heat electrical furnace at the uncompleted Consumers Power Company`s nuclear power plant at Midland, Michigan. This paper describes the Department`s annealing prototype demonstration goals and objectives; the tasks, deliverables, and results to date for each annealing prototype demonstration; and the remaining annealing technology challenges.
Ion implantation and laser annealing
NASA Astrophysics Data System (ADS)
Three ion implantation and laser annealing projects have been performed by ORNL through the DOE sponsored Seed Money Program. The research has contributed toward improving the characteristics of wear, hardness, and corrosion resistance of some metals and ceramics, as well as the electrical properties of semiconductors. The work has helped to spawn related research, at ORNL and elsewhere, concerning the relationships between microstructure and materials properties. ORNL research has resulted in major advances in extended life and non-corrosive artificial joints (hip and knee), high performance semiconductors, failure resistant ceramics (with potential energy applications), and solar cells. The success of the seed money projects was instrumental in the formation of ORNL's Surface Modification and Characterization Facility (SMAC). More than 60 universities and companies have participated in SMAC programs.
Energy Science and Technology Software Center (ESTSC)
2000-03-20
Given the space-independent, one energy group reactor kinetics equations and the initial conditions, this prgram determines the time variation of reactivity required to produce the given input of flux-time data.
Crystal growth and annealing method and apparatus
Gianoulakis, Steven E.; Sparrow, Robert
2001-01-01
A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing. An embodiment of the present invention comprises a secondary heater incorporated into a conventional crystal growth and annealing apparatus. The secondary heater supplies heat to minimize the temperature gradients in the crystal during the annealing process. The secondary heater can mount near the bottom of the crucible to effectively maintain appropriate temperature gradients.
Clarke, Amy J; Santofimia, Maria J; Speer, John G; Zhao, L; Sietsma, Jilt
2009-01-01
The quenching and partitioning (Q&P) process is a new heat treatment for the creation of advanced high-strength steels. This treatment consists of an initial partial or full austenitization, followed by a quench to form a controlled amount of martensite and an annealing step to partition carbon atoms from the martensite to the austenite. In this work, the microstructural evolution during annealing of martensite-austenite grain assemblies has been analyzed by means of a modeling approach that considers the influence of martensite-austenite interface migration on the kinetics of carbon partitioning. Carbide precipitation is precluded in the model, and three different assumptions about interface mobility are considered, ranging from a completely immobile interface to the relatively high mobility of an incoherent ferrite-austenite interface. Simulations indicate that different interface mobilities lead to profound differences in the evolution of microstructure that is predicted during annealing.
NASA Astrophysics Data System (ADS)
Fierro, Annalisa; de Candia, Antonio; Coniglio, Antonio
2002-02-01
The frustrated lattice gas model is studied in the quenched version where the interactions are quenched random variables, and in the annealed version where the interactions are allowed to evolve in time with a suitable kinetic constraint. The dynamical nonlinear susceptibility, recently introduced by Donati et al, is evaluated. In the annealed version we observe a behaviour very similar to the results for the p-spin models in mean field, and those for a Lennard-Jones mixture as found by Donati et al. In the quenched version we observe a substantially different behaviour of the dynamical susceptibility. The results suggest that the behaviour of the dynamical susceptibility in the annealed model can be interpreted as the imprint of the thermodynamic transition present in the quenched model and signalled by the divergence of the static nonlinear susceptibility. A similar mechanism might also be present in glassy systems.
NASA Technical Reports Server (NTRS)
Maile, K.
1982-01-01
The influence of different parameters on the creep-fatigue behavior of several steel alloys was investigated. The higher the temperature the lower the crack initiation value. Pauses during the cycle reduce the damage. Oxidation reduces and protective gas increases the lifetime. Prior loading and prior deformation reduce the lifetime. Short annealing slightly affects the cycle stress behavior. The test results do not satisfactorily agree with methods of extrapolation and damage accumulation.
Dryga, Anatoly; Warshel, Arieh
2010-01-01
Simulations of long time process in condensed phases in general and in biomolecules in particular, presents a major challenge that cannot be overcome at present by brute force molecular dynamics (MD) approaches. This work takes the renormalization method, intruded by us sometime ago, and establishes its reliability and potential in extending the time scale of molecular simulations. The validation involves a truncated gramicidin system in the gas phase that is small enough to allow very long explicit simulation and sufficiently complex to present the physics of realistic ion channels. The renormalization approach is found to be reliable and arguably presents the first approach that allows one to exploit the otherwise problematic steered molecular dynamics (SMD) treatments in quantitative and meaningful studies. It is established that we can reproduce the long time behavior of large systems by using Langevin dynamics (LD) simulations of a renormalized implicit model. This is done without spending the enormous time needed to obtain such trajectories in the explicit system. The present study also provides a promising advance in accelerated evaluation of free energy barriers. This is done by adjusting the effective potential in the implicit model to reproduce the same passage time as that obtained in the explicit model, under the influence of an external force. Here having a reasonable effective friction provides a way to extract the potential of mean force (PMF) without investing the time needed for regular PMF calculations. The renormalization approach, which is illustrated here in realistic calculations, is expected to provide a major help in studies of complex landscapes and in exploring long time dynamics of biomolecules. PMID:20836533
Precision Laser Annealing of Focal Plane Arrays
Bender, Daniel A.; DeRose, Christopher; Starbuck, Andrew Lea; Verley, Jason C.; Jenkins, Mark W.
2015-09-01
We present results from laser annealing experiments in Si using a passively Q-switched Nd:YAG microlaser. Exposure with laser at fluence values above the damage threshold of commercially available photodiodes results in electrical damage (as measured by an increase in photodiode dark current). We show that increasing the laser fluence to values in excess of the damage threshold can result in annealing of a damage site and a reduction in detector dark current by as much as 100x in some cases. A still further increase in fluence results in irreparable damage. Thus we demonstrate the presence of a laser annealing window over which performance of damaged detectors can be at least partially reconstituted. Moreover dark current reduction is observed over the entire operating range of the diode indicating that device performance has been improved for all values of reverse bias voltage. Additionally, we will present results of laser annealing in Si waveguides. By exposing a small (<10 um) length of a Si waveguide to an annealing laser pulse, the longitudinal phase of light acquired in propagating through the waveguide can be modified with high precision, <15 milliradian per laser pulse. Phase tuning by 180 degrees is exhibited with multiple exposures to one arm of a Mach-Zehnder interferometer at fluence values below the morphological damage threshold of an etched Si waveguide. No reduction in optical transmission at 1550 nm was found after 220 annealing laser shots. Modeling results for laser annealing in Si are also presented.
Klinger, G; Bonow, A; Hempel, E
1981-01-01
The behaviour of butanol-extractable iodine in serum was tested, during and on completion of administration of Non-Ovlon, Ovosiston, Gravistat, and Deposiston, the latter being a longacting contraceptive. Action of synthetic sexual steroids led to an increase in butanol-extractable iodine. However, this change proved to be easily reversible, soon after the end of medication, even after long-time application. Yet, complete normalisation should not be expected to occur before the second cycle without contraceptives, which applies, in particular, to women who had been on long-acting contraceptives. PMID:7223166
Embedding parameters for Quantum Annealing
NASA Astrophysics Data System (ADS)
Venturelli, Davide
Many optimization problems are defined on highly connected graphs and many interesting physical spin-glass systems are featuring long-range interactions. One method to solve for the optimum/ground state is quantum annealing (QA). Most architectures for QA devices, manufactured or proposed, are based on optimizing Hamiltonians having spins connected in a non-complete graph, with nodes with a small maximum degree, compared to the requirements. To overcome this limitation 'embedding' is employed: the native graph is 'tiled' with ferromagnetic chains of spins that now are meant to represent the logical binary variables. While it is known how the strength of the ferromagnetic bonds can ensure that the classical Ising ground state of the embedded system can be univocally mapped to the ground state of the original system, there is very little study on the impact of these parameters on QA. Programmers have taken conservative choices for the parameters and the common practices can be improved. Starting from the physics of connected ferromagnetic Ising chains, we will review several parameter choices and discuss previous and new results obtained on the D-Wave 2X machine, on carefully designed problems that allow to isolate and evaluate the role of connectivity in embedded systems.
Reduction of Cu2O Islands Grown on a Cu(100) Surface through Vacuum Annealing
NASA Astrophysics Data System (ADS)
Zhou, Guangwen; Yang, Judith C.
2004-11-01
The reduction of Cu2O islands grown on Cu(100) surfaces through vacuum annealing was visualized by an in situ ultrahigh vacuum transmission electron microscope. The shrinkage of the island followed a linear decay behavior. The complete reduction of the oxide islands leads to the formation of nanoindentations on the Cu surfaces. A simple phenomenological kinetic model based on the dissociation along the island perimeter suitably describes the reduction behavior of the surface oxide islands.
NASA Astrophysics Data System (ADS)
Lanzerath, F.; Buca, D.; Trinkaus, H.; Goryll, M.; Mantl, S.; Knoch, J.; Breuer, U.; Skorupa, W.; Ghyselen, B.
2008-08-01
We present experimental results on the activation and diffusion behaviors of boron in silicon-on-insulator and strained silicon-on-insulator using standard rapid thermal processing treatments as well as flash lamp annealing. After boron implantation at different doses and at a low energy of 1 keV, samples were annealed to activate the dopants, and secondary ion mass spectrometry and Hall measurements were carried out to determine boron diffusion and the amount of activated dopants, respectively. In contrast to rapid thermal annealing, flash lamp annealing enables the activation without significant diffusion of dopants. In addition, we investigated the effect of coating the samples with antireflection layers to increase the absorbed energy during flash annealing. As a result, the activation was increased significantly to values comparable with the activation obtained with standard annealing. Furthermore, the relation between the observed boron diffusion and activation as a function of the implantation and annealing parameters is discussed in terms of the kinetics of the defects involved in these processes.
Experimental evidence regarding the pressure dependence of fission track annealing in apatite
NASA Astrophysics Data System (ADS)
Schmidt, J. S.; Lelarge, M. L. M. V.; Conceicao, R. V.; Balzaretti, N. M.
2014-03-01
The main purposes of fission track thermochronology are unravelling the thermal histories of sedimentary basins, determining uplift and denudation rates, identifying the structural evolution of orogenic belts, determining sedimentary provenance, and dating volcanic rocks. The effect of temperature on fission tracks is well known and is used to determine the thermal history; however, the effect of pressure on the stability of tracks is still under debate. The present work aims to understand the role of pressure on the annealing kinetics of apatite fission tracks. The samples of Durango apatite used in our experiments were chosen for their international recognition as a calibration standard for geological dating. Neutron irradiation of the samples, after total annealing of their spontaneous tracks, produced induced tracks with homogeneous densities and lengths. The effect of pressure associated with temperature on fission track annealing was verified by experimental procedures using a hydraulic press of 1000 t with a toroidal chamber profile. The experiments consisted of a combination of applying 2 and 4 GPa with 20,150,190,235, and 290 °C for 1 and 10 h. The annealing rate was analysed by measuring the lengths of the fission tracks after each experiment using optical microscopy. The results demonstrate that the annealing of apatite fission tracks has a pressure dependence for samples subjected to 2 and 4 GPa. However, when extrapolated to pressures of ⩽150 MPa, compatible with the normal geological context in which apatite fission track methodology is broadly used, this dependence becomes insignificant compared to the temperature effect.
Zhang, W.; Konstantinidis, N.; Dobrovitski, V.; Harmon, B.; Santos, L.; Viola, L.
2008-03-27
The coherence time of an electron spin decohered by the nuclear spin environment in a quantum dot can be substantially increased by subjecting the electron to suitable dynamical decoupling sequences. We analyze the performance of high-level decoupling protocols by using a combination of analytical and exact numerical methods, and by paying special attention to the regimes of large interpulse delays and long-time dynamics, which are outside the reach of standard average Hamiltonian theory descriptions. We demonstrate that dynamical decoupling can remain efficient far beyond its formal domain of applicability, and find that a protocol exploiting concatenated design provides best performance for this system in the relevant parameter range. In situations where the initial electron state is known, protocols able to completely freeze decoherence at long times are constructed and characterized. The impact of system and control nonidealities is also assessed, including the effect of intrabath dipolar interaction, magnetic field bias and bath polarization, as well as systematic pulse imperfections. While small bias field and small bath polarization degrade the decoupling fidelity, enhanced performance and temporal modulation result from strong applied fields and high polarizations. Overall, we find that if the relative errors of the control pulse flip angles do not exceed 3%, decoupling protocols can still prolong the coherence time by up to 2 orders of magnitude.
Dopant activation in ion implanted silicon by microwave annealing
Alford, T. L.; Thompson, D. C.; Mayer, J. W.; Theodore, N. David
2009-12-01
Microwaves are used as a processing alternative for the electrical activation of ion implanted dopants and the repair of ion implant damage within silicon. Rutherford backscattering spectra demonstrate that microwave heating reduces the damage resulting from ion implantation of boron or arsenic into silicon. Cross-section transmission electron microscopy and selective area electron diffraction patterns demonstrate that the silicon lattice regains nearly all of its crystallinity after microwave processing of arsenic implanted silicon. Sheet resistance readings indicate the time required for boron or arsenic electrical activation within implanted silicon. Hall measurements demonstrate the extent of dopant activation after microwave heating of implanted silicon. Physical and electrical characterization determined that the mechanism of recrystallization in arsenic implanted silicon is solid phase epitaxial regrowth. The boron implanted silicon samples did not result in enough lattice damage to amorphize the silicon lattice and resulted in low boron activation during microwave annealing even though recrystallization of the Si lattice damage did take place. Despite low boron activation levels, the level of boron activation in this work was higher than that expected from traditional annealing techniques. The kinetics of microwave heating and its effects on implanted Si are also discussed.
Annealing behavior of high permeability amorphous alloys
Rabenberg, L.
1980-06-01
Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.
Kinetic theory and long range correlations in moderately dense gases
Petrosky, T.; Prigogine, I.
1997-01-01
The complex spectral representation of the Liouville operator is applied to moderately dense gases interacting through hard-core potentials in arbitrary d-dimensional spaces. It is shown that Markovian kinetic equations exist for all d. This provides an answer to the long standing question do kinetic equations exist in two dimensional systems. The non-Markovian effects, such as the long-time tails for arbitrary n-mode coupling, are estimated by superposition of the Markovian evolutions in each subspace as introduced in our spectral decomposition. The long-time tail effects invalidate the traditional kinetic theory based on a truncation of BBGKY hierarchy for d < 4, as well as the Green-Kubo formalism, as there appear contributions of order t{sup -1}, t{sup -{1/2}},... coming from multiple mode-mode couplings even for d = 3.
Magnetic induced heating for ferritic metal annealing
De Witt, G.L.; Huber, D.J.
1987-03-24
A method is described for annealing the wall of a nuclear reactor vessel, including, positioning an electromagnet within a vertically positioned nuclear reactor vessel by lowering the electromagnet into the vessel, supplying power to the electromagnet to generate substantially uniform heat in the vessel wall, maintaining the power to the electromagnet for a predetermined length of time which will anneal the vessel wall, and removing the electromagnet.
Annealed CVD molybdenum thin film surface
Carver, Gary E.; Seraphin, Bernhard O.
1984-01-01
Molybdenum thin films deposited by pyrolytic decomposition of Mo(CO).sub.6 attain, after anneal in a reducing atmosphere at temperatures greater than 700.degree. C., infrared reflectance values greater than reflectance of supersmooth bulk molybdenum. Black molybdenum films deposited under oxidizing conditions and annealed, when covered with an anti-reflecting coating, approach the ideal solar collector characteristic of visible light absorber and infrared energy reflector.
Error suppression and correction for quantum annealing
NASA Astrophysics Data System (ADS)
Lidar, Daniel
While adiabatic quantum computing and quantum annealing enjoy a certain degree of inherent robustness against excitations and control errors, there is no escaping the need for error correction or suppression. In this talk I will give an overview of our work on the development of such error correction and suppression methods. We have experimentally tested one such method combining encoding, energy penalties and decoding, on a D-Wave Two processor, with encouraging results. Mean field theory shows that this can be explained in terms of a softening of the closing of the gap due to the energy penalty, resulting in protection against excitations that occur near the quantum critical point. Decoding recovers population from excited states and enhances the success probability of quantum annealing. Moreover, we have demonstrated that using repetition codes with increasing code distance can lower the effective temperature of the annealer. References: K.L. Pudenz, T. Albash, D.A. Lidar, ``Error corrected quantum annealing with hundreds of qubits'', Nature Commun. 5, 3243 (2014). K.L. Pudenz, T. Albash, D.A. Lidar, ``Quantum annealing correction for random Ising problems'', Phys. Rev. A. 91, 042302 (2015). S. Matsuura, H. Nishimori, T. Albash, D.A. Lidar, ``Mean Field Analysis of Quantum Annealing Correction''. arXiv:1510.07709. W. Vinci et al., in preparation.
NASA Astrophysics Data System (ADS)
Elmer, Sidney P.; Pande, Vijay S.
2005-03-01
Using simulation to study the folding kinetics of 20-mer poly-phenylacetylene (pPA) oligomers, we find a long time scale trapped kinetic phase in the cumulative folding time distribution. This is demonstrated using molecular dynamics to simulate an ensemble of over 100 folding trajectories. The simulation data are fit to a four-state kinetic model which includes the typical folded and unfolded states, along with an intermediate state, and most surprisingly, a kinetically trapped state. Topologically diverse conformations reminiscent of α helices, β turns, and sheets in proteins are observed, along with unique structures in the form of knots. The nonhelical conformations are implicated, on the basis of structural correlations to kinetic parameters, to contribute to the trapped kinetic behavior. The strong solvophobic forces which mediate the folding process and produce a stable helical folded state also serve to overstabilize the nonhelical conformations, ultimately trapping them. From our simulations, the folding time is predicted to be on the order of 2.5-12.5 μs in the presence of the trapped kinetic phase. The folding mechanism for these 20-mer chains is compared with the previously reported folding mechanism for the pPA 12-mer chains. A linear scaling relationship between the chain length and the mean first passage time is predicted in the absence of the trapped kinetic phase. We discuss the major implications of this discovery in the design of self-assembling nanostructures.
NASA Astrophysics Data System (ADS)
Huang, Yu-Kun; Chen, Pochung; Kao, Ying-Jer; Xiang, Tao
2014-05-01
By using a different quantum-to-classical mapping from the Trotter-Suzuki decomposition, we identify the entanglement structure of the maximal eigenvectors for the associated quantum transfer matrix. This observation provides a deeper insight into the problem of linear growth of the entanglement entropy in time evolution using conventional methods. Based on this observation, we propose a general method for arbitrary temperatures using the biorthonormal transfer-matrix renormalization group. Our method exhibits a competitive accuracy with a much cheaper computational cost in comparison with two recently proposed methods for long-time dynamics based on a folding algorithm [Phys. Rev. Lett. 102, 240603 (2009), 10.1103/PhysRevLett.102.240603] and a modified time-dependent density-matrix renormalization group [Phys. Rev. Lett. 108, 227206 (2012), 10.1103/PhysRevLett.108.227206].
Christov, C.I.; Maugin, G.A.
1995-01-01
We consider the nonlinear system of equations built up from a generalized Boussinesq equation coupled with a wave equation which is a model for the one-dimensional dynamics of phases in martensitic alloys. The strongly implicit scheme employing Newton`s quasilinearisation allows us to track the long time evolution of the localized solutions of the system. Two distinct classes of solutions are encountered for the pure Boussinesq equation. The first class consists of oscillatory pulses whose envelopes are localized waves. The second class consists of smoother solutions whose shapes are either heteroclinic (kinks) or homoclinic (bumps). The homoclinics decrease in amplitude with time while their support increases. An appropriate self-similar scaling is found analytically and confirmed by the direct numerical simulations to high accuracy. The rich phenomenology resulting from the coupling with the wave equation is also investigated. 11 refs., 12 figs., 2 tabs.
NASA Astrophysics Data System (ADS)
Lubov, M. N.; Kulikov, D. V.; Trushin, Yu. V.; Kurnosikov, O.
2013-03-01
The kinetics of the formation of impurity clusters in subsurface nanopores in crystals is studied theoretically. A physical model of precipitation of the impurity phase in nanopores in a sample with sinks of various types is developed. This model forms the basis for the calculation of the annealing kinetics of copper containing subsurface pores and cobalt impurity atoms. The optimal annealing conditions are determined in which cobalt atoms diffuse predominantly into pores and form impurity clusters in them.
Enhanced annealing of GaAs solar cell radiation damage
NASA Technical Reports Server (NTRS)
Loo, R.; Knechtli, R. C.; Kamath, G. S.
1981-01-01
Solar cells are degraded by radiation damage in space. Investigations have been conducted concerning possibilities for annealing this radiation damage in GaAs solar cells, taking into account the conditions favoring such annealing. It has been found that continuous annealing as well as the combination of injection annealing with thermal annealing can lead to recovery from radiation damage under particularly favorable conditions in GaAs solar cells. The damage caused by both electrons and protons in GaAs solar cells can be substantially reduced by annealing at temperatures as low as 150 C, under appropriate conditions. This possibility makes the GaAs solar cells especially attractive for long space missions, or for missions in severe radiation environments. Attention is given to results concerning periodic thermal annealing, continuous annealing, and injection annealing combined with thermal annealing.
NASA Astrophysics Data System (ADS)
Zhang, Lin; Mashkov, V. A.; Leisure, R. G.
1995-02-01
Multiple interconversions of E' centers and peroxy radicals have been observed for the first time by means of anneal-interrupted x-irradiation experiments. It is shown that each of these defects can serve as the precursor of the other; under thermal anneal an E' center can convert to a peroxy radical due to the capture of an oxygen molecule, and under irradiation the peroxy radical can covert to an E' center due to irradiation-induced release of oxygen. The results for the defect production and anneal behavior are well described in terms of simple stretched-exponential defect-reaction kinetics.
Origin of reverse annealing effect in hydrogen-implanted silicon
Di, Zengfeng; Nastasi, Michael A; Wang, Yongqiang
2009-01-01
In contradiction to conventional damage annealing, thermally annealed H-implanted Si exhibits an increase in damage or reverse annealing behavior, whose mechanism has remained elusive. On the basis of quantitative high resolution transmission electron microscopy combined with channeling Rutherford backscattering analysis, we conclusively elucidate that the reverse annealing effect is due to the nucleation and growth of hydrogen-induce platelets. Platelets are responsible for an increase in the height and width the channeling damage peak following increased isochronal anneals.
Origin of reverse annealing effect in hydrogen-implanted silicon
Di, Z. F.; Wang, Y. Q.; Nastasi, M.; Theodore, N. David
2010-04-12
In contradiction to conventional damage annealing, thermally annealed H-implanted Si exhibits an increase in damage or reverse annealing behavior, whose mechanism has remained elusive. In this work, we conclusively elucidate that the reverse annealing effect is due to the nucleation and growth of hydrogen-induced platelets. Platelets are responsible for an increase in the height and width of the channeling damage peak following increased isochronal anneals.
Annealing of ion implanted gallium nitride
Tan, H.H.; Williams, J.S.; Zou, J.; Cockayne, D.J.; Pearton, S.J.; Zolper, J.C.; Stall, R.A.
1998-03-01
In this paper, we examine Si and Te ion implant damage removal in GaN as a function of implantation dose, and implantation and annealing temperature. Transmission electron microscopy shows that amorphous layers, which can result from high-dose implantation, recrystallize between 800 and 1100{degree}C to very defective polycrystalline material. Lower-dose implants (down to 5{times}10{sup 13}cm{sup {minus}2}), which are not amorphous but defective after implantation, also anneal poorly up to 1100{degree}C, leaving a coarse network of extended defects. Despite such disorder, a high fraction of Te is found to be substitutional in GaN both following implantation and after annealing. Furthermore, although elevated-temperature implants result in less disorder after implantation, this damage is also impossible to anneal out completely by 1100{degree}C. The implications of this study are that considerably higher annealing temperatures will be needed to remove damage for optimum electrical properties. {copyright} {ital 1998 American Institute of Physics.}
The annealing robust backpropagation (ARBP) learning algorithm.
Chuang, C C; Su, S F; Hsiao, C C
2000-01-01
Multilayer feedforward neural networks are often referred to as universal approximators. Nevertheless, if the used training data are corrupted by large noise, such as outliers, traditional backpropagation learning schemes may not always come up with acceptable performance. Even though various robust learning algorithms have been proposed in the literature, those approaches still suffer from the initialization problem. In those robust learning algorithms, the so-called M-estimator is employed. For the M-estimation type of learning algorithms, the loss function is used to play the role in discriminating against outliers from the majority by degrading the effects of those outliers in learning. However, the loss function used in those algorithms may not correctly discriminate against those outliers. In this paper, the annealing robust backpropagation learning algorithm (ARBP) that adopts the annealing concept into the robust learning algorithms is proposed to deal with the problem of modeling under the existence of outliers. The proposed algorithm has been employed in various examples. Those results all demonstrated the superiority over other robust learning algorithms independent of outliers. In the paper, not only is the annealing concept adopted into the robust learning algorithms but also the annealing schedule k/t was found experimentally to achieve the best performance among other annealing schedules, where k is a constant and is the epoch number. PMID:18249835
NASA Astrophysics Data System (ADS)
Deshpande, A. R.; Wiezorek, J. M. K.
2004-03-01
The interplay between the ordering reaction with recovery and recrystallization of the as-deformed state leads to combined reactions (CRs) during annealing of cold-deformed disordered Fe-Pd intermetallics at temperatures below the critical ordering temperature. CRs can be exploited to control the scale and morphology of the Fe-Pd alloy microstructures in order to optimize alloy properties. Here, the magnetic age hardening behavior and microstructural evolution of cold-deformed (cold rolled to 97% reduction in thickness) binary equiatomic Fe-Pd has been studied for isothermal annealing at temperatures of 400°C, 500°C, and 600°C. The evolution of the microstructure during the annealing treatments has been characterized by a combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The magnetic age hardening behavior, the evolution of the coercivity as a function of annealing time, has been determined using a vibrating sample magnetometer (VSM). The microstructures of the transforming material have been characterized quantitatively using computer assisted image analysis methods. The CR transformed microstructures are morphologically equiaxed with average grain sizes in the sub-micron range and show coercivity up to five-fold larger than for conventionally processed equiatomic bulk Fe-Pd. During annealing the coercivity increases up to a maximum peak value and has been correlated with the increasing fraction of ordered material. The maximum coercivity obtains, as the ordering phase transformation is complete. With respect to conventionally processed material the ordering transformation in the cold-deformed material exhibits accelerated kinetics and is facilitated by a CR, which involves heterogeneous nucleation and growth processes akin to a 'massive ordering' reaction. Further annealing leads to decreasing coercivity, which has been attributed to the onset of grain growth in the population of CR-transformed grains. The characteristic magnetic
Ehrsson, H; Hassan, M; Ehrnebo, M; Beran, M
1983-07-01
Busulfan kinetics were studied in patients with chronic myelocytic leukemia after oral doses of 2, 4, and 6 mg. The plasma concentration-time data could be fitted to a zero-order absorption one-compartment open model. The elimination rate constant averaged 0.27 +/- 0.05 hr-1 (SD). The plasma AUC was linearly related to the dose. The lag time for the start of absorption, the time absorption ends, and the absorption rate constant showed some interindividual variations. About 1% of busulfan is excreted unchanged in urine over 24 hr. PMID:6574831
Naeser, Nancy D.; Crowley, Kevin D.; McCulloh, Thane H.; Reaves, Chris M.
1990-01-01
Annealing of fission tracks is a kinetic process dependent primarily on temperature and to a laser extent on time. Several kinetic models of apatite annealing have been proposed. The predictive capabilities of these models for long-term geologic annealing have been limited to qualitative or semiquantitative at best, because of uncertainties associated with (1) the extrapolation of laboratory observations to geologic conditions, (2) the thermal histories of field samples, and (3) to some extent, the effect of apatite composition on reported annealing temperatures. Thermal history in the Santa Fe Springs oil field, Los Angeles Basin, California, is constrained by an exceptionally well known burial history and present-day temperature gradient. Sediment burial histories are continuous and tightly constrained from about 9 Ma to present, with an important tie at 3.4 Ma. No surface erosion and virtually no uplift were recorded during or since deposition of these sediments, so the burial history is simple and uniquely defined. Temperature gradient (???40??C km-1) is well established from oil-field operations. Fission-track data from the Santa Fe Springs area should thus provide one critical field test of kinetic annealing models for apatite. Fission-track analysis has been performed on apatites from sandstones of Pliocene to Miocene age from a deep drill hole at Santa Fe Springs. Apatite composition, determined by electron microprobe, is fluorapatite [average composition (F1.78Cl0.01OH0.21)] with very low chlorine content [less than Durango apatite; sample means range from 0.0 to 0.04 Cl atoms, calculated on the basis of 26(O, F, Cl, OH)], suggesting that the apatite is not unusually resistant to annealing. Fission tracks are preserved in these apatites at exceptionally high present-day temperatures. Track loss is not complete until temperatures reach the extreme of 167-178??C (at 3795-4090 m depth). The temperature-time annealing relationships indicated by the new data
McCall, S; Fluss, M; Chung, B; Haire, R
2008-05-02
Results of radiation damage in Pu and Pu{sub 1-x}Am{sub x} alloys studied with magnetic susceptibility, {chi}(T), and resistivity are presented. Damage accumulated at low temperatures increases {chi}(T) for all measured alloys, with the trend generally enhanced as the lattice expands. There is a trend towards saturation observable in the damage induced magnetic susceptibility data, that is not evident in similar damage induced resistivity data taken on the same specimen. A comparison of isochronal annealing curves measured by both resistivity and magnetic susceptibility on a 4.3at% Ga stabilized {delta}-Pu specimen show that Stage I annealing, where interstitials begin to move, is largely transparent to the magnetic measurement. This indicates that interstitials have little impact on the damage induced increase in the magnetic susceptibility. The isochronal annealing curves of the Pu{sub 1-x}Am{sub x} alloys do not show distinct annealing stages as expected for alloys. However, samples near 20% Am concentration show an unexpected increase in magnetization beginning when specimens are annealed to 35K. This behavior is also reflected in a time dependent increase in the magnetic susceptibility of damaged specimens indicative of first order kinetics. These results suggest there may be a metastable phase induced by radiation damage and annealing in Pu{sub 1-x}Am{sub x} alloys.
Quantum annealing correction for random Ising problems
NASA Astrophysics Data System (ADS)
Pudenz, Kristen L.; Albash, Tameem; Lidar, Daniel A.
2015-04-01
We demonstrate that the performance of a quantum annealer on hard random Ising optimization problems can be substantially improved using quantum annealing correction (QAC). Our error correction strategy is tailored to the D-Wave Two device. We find that QAC provides a statistically significant enhancement in the performance of the device over a classical repetition code, improving as a function of problem size as well as hardness. Moreover, QAC provides a mechanism for overcoming the precision limit of the device, in addition to correcting calibration errors. Performance is robust even to missing qubits. We present evidence for a constructive role played by quantum effects in our experiments by contrasting the experimental results with the predictions of a classical model of the device. Our work demonstrates the importance of error correction in appropriately determining the performance of quantum annealers.
Black anneal marking with pulsed fiber lasers
NASA Astrophysics Data System (ADS)
Murphy, T.; Harrison, P.; Norman, S.
2015-07-01
High contrast marking of metals is used in a wide range of industries. Fiber laser marking of these metals provides non-contact marking with no consumables, offering many advantages over traditional methods of metal marking. The laser creates a permanent mark on the material surface combining heat and oxygen with no noticeable ablation. The focussed beam of the fiber laser in combination with precision control of the heat input is able to treat small areas of the material surface evenly and consistently, which is critical for producing black anneal marks. The marks are highly legible which is ideal for marking serial numbers or small data matrices where traceability is required. This paper reports the experimental study for producing black anneal marks on various grades of stainless steel using fiber lasers. The influence of metal surface finish, beam quality, spot size diameter and pulse duration are investigated for producing both smooth and decorative anneal marks.
Hydrogen Annealing Of Single-Crystal Superalloys
NASA Technical Reports Server (NTRS)
Smialek, James L.; Schaeffer, John C.; Murphy, Wendy
1995-01-01
Annealing at temperature equal to or greater than 2,200 degrees F in atmosphere of hydrogen found to increase ability of single-crystal superalloys to resist oxidation when subsequently exposed to oxidizing atmospheres at temperatures almost as high. Supperalloys in question are principal constituents of hot-stage airfoils (blades) in aircraft and ground-based turbine engines; also used in other high-temperature applications like chemical-processing plants, coal-gasification plants, petrochemical refineries, and boilers. Hydrogen anneal provides resistance to oxidation without decreasing fatigue strength and without need for coating or reactive sulfur-gettering constituents. In comparison with coating, hydrogen annealing costs less. Benefits extend to stainless steels, nickel/chromium, and nickel-base alloys, subject to same scale-adhesion and oxidation-resistance considerations, except that scale is chromia instead of alumina.
Computational multiqubit tunnelling in programmable quantum annealers.
Boixo, Sergio; Smelyanskiy, Vadim N; Shabani, Alireza; Isakov, Sergei V; Dykman, Mark; Denchev, Vasil S; Amin, Mohammad H; Smirnov, Anatoly Yu; Mohseni, Masoud; Neven, Hartmut
2016-01-01
Quantum tunnelling is a phenomenon in which a quantum state traverses energy barriers higher than the energy of the state itself. Quantum tunnelling has been hypothesized as an advantageous physical resource for optimization in quantum annealing. However, computational multiqubit tunnelling has not yet been observed, and a theory of co-tunnelling under high- and low-frequency noises is lacking. Here we show that 8-qubit tunnelling plays a computational role in a currently available programmable quantum annealer. We devise a probe for tunnelling, a computational primitive where classical paths are trapped in a false minimum. In support of the design of quantum annealers we develop a nonperturbative theory of open quantum dynamics under realistic noise characteristics. This theory accurately predicts the rate of many-body dissipative quantum tunnelling subject to the polaron effect. Furthermore, we experimentally demonstrate that quantum tunnelling outperforms thermal hopping along classical paths for problems with up to 200 qubits containing the computational primitive. PMID:26739797
Stochastic annealing simulation of cascades in metals
Heinisch, H.L.
1996-04-01
The stochastic annealing simulation code ALSOME is used to investigate quantitatively the differential production of mobile vacancy and SIA defects as a function of temperature for isolated 25 KeV cascades in copper generated by MD simulations. The ALSOME code and cascade annealing simulations are described. The annealing simulations indicate that the above Stage V, where the cascade vacancy clusters are unstable,m nearly 80% of the post-quench vacancies escape the cascade volume, while about half of the post-quench SIAs remain in clusters. The results are sensitive to the relative fractions of SIAs that occur in small, highly mobile clusters and large stable clusters, respectively, which may be dependent on the cascade energy.
Computational multiqubit tunnelling in programmable quantum annealers
Boixo, Sergio; Smelyanskiy, Vadim N.; Shabani, Alireza; Isakov, Sergei V.; Dykman, Mark; Denchev, Vasil S.; Amin, Mohammad H.; Smirnov, Anatoly Yu; Mohseni, Masoud; Neven, Hartmut
2016-01-01
Quantum tunnelling is a phenomenon in which a quantum state traverses energy barriers higher than the energy of the state itself. Quantum tunnelling has been hypothesized as an advantageous physical resource for optimization in quantum annealing. However, computational multiqubit tunnelling has not yet been observed, and a theory of co-tunnelling under high- and low-frequency noises is lacking. Here we show that 8-qubit tunnelling plays a computational role in a currently available programmable quantum annealer. We devise a probe for tunnelling, a computational primitive where classical paths are trapped in a false minimum. In support of the design of quantum annealers we develop a nonperturbative theory of open quantum dynamics under realistic noise characteristics. This theory accurately predicts the rate of many-body dissipative quantum tunnelling subject to the polaron effect. Furthermore, we experimentally demonstrate that quantum tunnelling outperforms thermal hopping along classical paths for problems with up to 200 qubits containing the computational primitive. PMID:26739797
Simulation of Storm Occurrences Using Simulated Annealing.
NASA Astrophysics Data System (ADS)
Lokupitiya, Ravindra S.; Borgman, Leon E.; Anderson-Sprecher, Richard
2005-11-01
Modeling storm occurrences has become a vital part of hurricane prediction. In this paper, a method for simulating event occurrences using a simulated annealing algorithm is described. The method is illustrated using annual counts of hurricanes and of tropical storms in the Atlantic Ocean and Gulf of Mexico. Simulations closely match distributional properties, including possible correlations, in the historical data. For hurricanes, traditionally used Poisson and negative binomial processes also predict univariate properties well, but for tropical storms parametric methods are less successful. The authors determined that simulated annealing replicates properties of both series. Simulated annealing can be designed so that simulations mimic historical distributional properties to whatever degree is desired, including occurrence of extreme events and temporal patterning.
NASA Astrophysics Data System (ADS)
Nechitailo, Galina S.; Yurov, S.; Cojocaru, A.; Revin, A.
The analysis of the lycopene and other carotenoids in tomatoes produced from seeds exposed under space flight conditions at the orbital station MIR for six years is presented in this work. Our previous experiments with tomato plants showed the germination of seeds to be 32%Genetic investigations revealed 18%in the experiment and 8%experiments were conducted to study the capacity of various stimulating factors to increase germination of seeds exposed for a long time to the action of space flight factors. An increase of 20%achieved but at the same time mutants having no analogues in the control variants were detected. For the present investigations of the third generation of plants produced from seeds stored for a long time under space flight conditions 80 tomatoes from forty plants were selected. The concentration of lycopene in the experimental specimens was 2.5-3 times higher than in the control variants. The spectrophotometric analysis of ripe tomatoes revealed typical three-peaked carotenoid spectra with a high maximum of lycopene (a medium maximum at 474 nm), a moderate maximum of its predecessor, phytoin, (a medium maximum at 267 nm) and a low maximum of carotenes. In green tomatoes, on the contrary, a high maximum of phytoin, a moderate maximum of lycopene and a low maximum of carotenes were observed. The results of the spectral analysis point to the retardation of biosynthesis of carotenes while the production of lycopene is increased and to the synthesis of lycopene from phytoin. Electric conduction of tomato juice in the experimental samples is increased thus suggesting higher amounts of carotenoids, including lycopene and electrolytes. The higher is the value of electric conduction of a specimen, the higher are the spectral maxima of lycopene. The hydrogen ion exponent of the juice of ripe tomatoes increases due to which the efficiency of ATP biosynthesis in cell mitochondria is likely to increase, too. The results demonstrating an increase in the content
NASA Astrophysics Data System (ADS)
Wang, Honglong; Xu, Lu; Li, Rong; Hu, Jiangtao; Wang, Mouhua; Wu, Guozhong
2016-08-01
Ultra-high molecular weight polyethylene (UHMWPE) sheet was cross-linked by γ irradiation in air with a dose of up to 300 kGy at a dose rate of 5 kGy/h and further treated by post-annealing at 120 °C for 4 h in vacuum. Variations in chemical structure, thermostability, crystallinity, creep resistance, and tensile properties were investigated and compared mainly by gel content, TGA, DSC, and creep and tensile measurements. Gel content measurements indicated that cross-linking was predominant over chain scission during irradiation and post-annealing. Radiation cross-linking resulted in an obvious improvement in the creep resistance and tensile properties of UHMWPE. Through cross-linking, the operational temperature and yield strength of the irradiated and subsequently annealed UHMWPE sheet were improved by more than 100 °C and 14%, respectively, at a dose of 300 kGy. Simultaneously, Young's modulus was increased to 1413 MPa, compared with 398 MPa of pristine UHMWPE. Annealing after irradiation further improved the creep resistance and Young's modulus. Highly cross-linked UHMWPE can even be maintained at 250 °C for a long time without any obvious deformation.
Quantum annealing correction with minor embedding
NASA Astrophysics Data System (ADS)
Vinci, Walter; Albash, Tameem; Paz-Silva, Gerardo; Hen, Itay; Lidar, Daniel A.
2015-10-01
Quantum annealing provides a promising route for the development of quantum optimization devices, but the usefulness of such devices will be limited in part by the range of implementable problems as dictated by hardware constraints. To overcome constraints imposed by restricted connectivity between qubits, a larger set of interactions can be approximated using minor embedding techniques whereby several physical qubits are used to represent a single logical qubit. However, minor embedding introduces new types of errors due to its approximate nature. We introduce and study quantum annealing correction schemes designed to improve the performance of quantum annealers in conjunction with minor embedding, thus leading to a hybrid scheme defined over an encoded graph. We argue that this scheme can be efficiently decoded using an energy minimization technique provided the density of errors does not exceed the per-site percolation threshold of the encoded graph. We test the hybrid scheme using a D-Wave Two processor on problems for which the encoded graph is a two-level grid and the Ising model is known to be NP-hard. The problems we consider are frustrated Ising model problem instances with "planted" (a priori known) solutions. Applied in conjunction with optimized energy penalties and decoding techniques, we find that this approach enables the quantum annealer to solve minor embedded instances with significantly higher success probability than it would without error correction. Our work demonstrates that quantum annealing correction can and should be used to improve the robustness of quantum annealing not only for natively embeddable problems but also when minor embedding is used to extend the connectivity of physical devices.
Hicks, D.R.; Kraml, M.; Cayen, M.N.; Dubuc, J.; Ryder, S.; Dvornik, D.
1984-10-01
The kinetics of tolrestat, a potent inhibitor of aldose reductase, were examined. Serum concentrations of tolrestat and of total /sup 14/C were measured after dosing normal subjects and subjects with diabetes with /sup 14/C-labeled tolrestat. In normal subjects, tolrestat was rapidly absorbed and disappearance from serum was biphasic. Distribution and elimination t 1/2s were approximately 2 and 10 to 12 hr, respectively, after single and multiple doses. Unchanged tolrestat accounted for the major portion of /sup 14/C in serum. Radioactivity was rapidly and completely excreted in urine and feces in an approximate ratio of 2:1. Findings were much the same in subjects with diabetes. In normal subjects, the kinetics of oral tolrestat were independent of dose in the 10 to 800 mg range. Repetitive dosing did not result in unexpected cumulation. Tolrestat was more than 99% bound to serum protein; it did not compete with warfarin for binding sites but was displaced to some extent by high concentrations of tolbutamide or salicylate.
Performance of quantum annealing in solving optimization problems: A review
NASA Astrophysics Data System (ADS)
Suzuki, S.
2015-02-01
Quantum annealing is one of the optimization method for generic optimization problems. It uses quantum mechanics and is implemented by a quantum computer ideally. At the earlier stage, several numerical experiments using conventional computers have provided results showing that quantum annealing produces an answer faster than simulated annealing, a classical counterpart of quantum annealing. Later, theoretical and numerical studies have shown that there are drawbacks in quantum annealing. The power of quantum annealing is still an open problem. What makes quantum annealing a hot topic now is that a quantum computer based on quantum annealing is manufactured and commercialized by a Canadian company named D-Wave Systems. In the present article, we review the study of quantum annealing, focusing mainly on its power.
Annealing Increases Stability Of Iridium Thermocouples
NASA Technical Reports Server (NTRS)
Germain, Edward F.; Daryabeigi, Kamran; Alderfer, David W.; Wright, Robert E.; Ahmed, Shaffiq
1989-01-01
Metallurgical studies carried out on samples of iridium versus iridium/40-percent rhodium thermocouples in condition received from manufacturer. Metallurgical studies included x-ray, macroscopic, resistance, and metallographic studies. Revealed large amount of internal stress caused by cold-working during manufacturing, and large number of segregations and inhomogeneities. Samples annealed in furnace at temperatures from 1,000 to 2,000 degree C for intervals up to 1 h to study effects of heat treatment. Wire annealed by this procedure found to be ductile.
The importance of annealing 316 LVM stents.
Meyer-Kobbe, C; Hinrichs, B H
2003-01-01
The annealing process is an important key step in the manufacture of high quality and reliable 316 LVM stents. [figure: see text] The methods commonly applied for verifying the outcome of the annealing process such as microhardness testing are inappropriate and should not be used. The tension testing of tubes, processed together with stents, provides reliable results of the final material properties of stents. During the course of the investigation the grain size was reduced significantly and the break elongation improved. The surface of the strain-tested material shows substantial improvements. All results are particularly important for thin-wall stents with filigree struts. PMID:12974121
Rock melting tool with annealer section
Bussod, Gilles Y.; Dick, Aaron J.; Cort, George E.
1998-01-01
A rock melting penetrator is provided with an afterbody that rapidly cools a molten geological structure formed around the melting tip of the penetrator to the glass transition temperature for the surrounding molten glass-like material. An annealing afterbody then cools the glass slowly from the glass transition temperature through the annealing temperature range to form a solid self-supporting glass casing. This allows thermally induced strains to relax by viscous deformations as the molten glass cools and prevents fracturing of the resulting glass liner. The quality of the glass lining is improved, along with its ability to provide a rigid impermeable casing in unstable rock formations.
Thermal annealing of tilted fiber Bragg gratings
NASA Astrophysics Data System (ADS)
González-Vila, Á.; Rodríguez-Cobo, L.; Mégret, P.; Caucheteur, C.; López-Higuera, J. M.
2016-05-01
We report a practical study of the thermal decay of cladding mode resonances in tilted fiber Bragg gratings, establishing an analogy with the "power law" evolution previously observed on uniform gratings. We examine how this process contributes to a great thermal stability, even improving it by means of a second cycle slightly increasing the annealing temperature. In addition, we show an improvement of the grating spectrum after annealing, with respect to the one just after inscription, which suggests the application of this method to be employed to improve saturation issues during the photo-inscription process.
Optimization of a Stochastically Simulated Gene Network Model via Simulated Annealing
Tomshine, Jonathan; Kaznessis, Yiannis N.
2006-01-01
By rearranging naturally occurring genetic components, gene networks can be created that display novel functions. When designing these networks, the kinetic parameters describing DNA/protein binding are of great importance, as these parameters strongly influence the behavior of the resulting gene network. This article presents an optimization method based on simulated annealing to locate combinations of kinetic parameters that produce a desired behavior in a genetic network. Since gene expression is an inherently stochastic process, the simulation component of simulated annealing optimization is conducted using an accurate multiscale simulation algorithm to calculate an ensemble of network trajectories at each iteration of the simulated annealing algorithm. Using the three-gene repressilator of Elowitz and Leibler as an example, we show that gene network optimizations can be conducted using a mechanistically realistic model integrated stochastically. The repressilator is optimized to give oscillations of an arbitrary specified period. These optimized designs may then provide a starting-point for the selection of genetic components needed to realize an in vivo system. PMID:16920827
NASA Astrophysics Data System (ADS)
Nelson, Gunnar; Wong, J.; Drapes, C.; Grant, M.; Baruth, A.
Despite the promise of cheap and fast nanoscale ordering of block polymer thin films via solvent vapor annealing, a standardized, scalable production scheme remains elusive. Solvent vapor annealing exposes a nano-thin film to the vapors of one or more solvents with the goal of forming a swollen and mobile state to direct the self-assembly process by tuning surface energies and mediating unfavorable chain interactions. We have shown that optimized annealing conditions, where kinetic and thermal properties for crystal growth are extremely fast (<1s), exist at solvent concentrations just below the order-disorder transition of the film. However, when investigating the propagation of a given morphology into the bulk of a film during drying, the role of solvent evaporation comes under great scrutiny. During this process, the film undergoes a competition between two fronts; phase separation and kinetic trapping. Recent results in both theory and experiment point toward this critical element in controlling the resultant morphologies; however, no current method includes a controllable solvent evaporation rate at ultra-fast time scales. We report on a computer-controlled, pneumatically actuated chamber that provides control over solvent evaporation down to 15 ms. Furthermore, in situ spectral reflectance monitors solvent concentration with 10 ms temporal resolution and reveals several possible evaporation trajectories, ranging from linear to exponential to logarithmic. Funded by Dr. Randolph Ferlic Summer Research Scholarship and NASA Nebraska Space Grant.
NASA Astrophysics Data System (ADS)
Nechitailo, G.; Yurov, S.; Kuznetsov, A.; Kapitanov, A.
Experiments at orbital space stations were carried out with seeds of various plants -- welsh onion arabidopsis wheat pea maize barley tomato etc The results of these experiments showed some discrepancy concerning germinating capacity presence of chromosome aberrations and other parameters After short-term space flights most of plants did not exhibit any irreversible changes But prolongation of space flights to over one year leads to practically complete loss of the germinating capacity in for example Arabidopsis thaliana and Crepis capillaries The level of recessive mutations increased more than 3-fold as compared to the control variants after exposure of seeds during 840 days The objects studied in the experiments described here are tomato plants obtained from seeds carried for 6 years at the station MIR According to the results of the experiments the germinating capacity of the seeds was 32 versus 60 in the control The germination of the seeds began only on the 14-15 th days in the control -- on the 5 th day In the process of ontogenesis the level of mutations revealed in the experimental variants made up to 18 as compared to the 8 in the control After 6 years of exposure under space flight conditions practically all seeds lost their germinating capacity Most viable were seeds of wheat and tomato Biochemical analysis of tomato plants of the second generation produced from seeds exposed for a long time under space flight conditions was carried out The results of the analysis demonstrated an increased
NASA Astrophysics Data System (ADS)
Sakhel, Asaad R.
2016-07-01
The dynamics of a Bose-Einstein condensate are examined numerically in the presence of a one-dimensional bichromatic optical lattice (BCOL) with external harmonic confinement in the strongly interacting regime. The condensate is excited by a focusing stirring red laser. Two realizations of the BCOL are considered, one with a rational and the other with an irrational ratio of the two constituting wave lengths. The system is simulated by the time-dependent Gross Pitaevskii equation that is solved using the Crank Nicolson method in real time. It is found that for a weak BCOL, the long-time averaged physical observables of the condensate respond only very weakly (or not at all) to changes in the secondary OL depth V1 showing that under these conditions the harmonic trap plays a dominant role in governing the dynamics. However, for a much larger strength of the BCOL, the response is stronger as it begins to compete with the external harmonic trap, such that the frequency of Bloch oscillations of the bosons rises with V1 yielding higher time-averages. Qualitatively there is no difference between the dynamics of the condensate resulting from the use of a rational or irrational ratio of the wavelengths since the external harmonic trap washes it out. It is further found that in the presence of an external harmonic trap, the BCOL acts in favor of superflow.
Zhang, Liansheng; Long, Qian; Liu, Yongbin; Zhang, Jie; Feng, Zhihua
2016-07-01
The thermal effect is one of the most important factors that influence the accuracy of nanoscale measurement and the surface topography of samples in scanning probe microscopes (SPMs). We propose a method called correlation-steered scanning, which is capable of overcoming three-dimensional thermal drifts in real time for ultra-long time scanned images. The image is scanned band by band with overlapping parts between adjacent bands. The vertical drift can be considered as linear and can thus be eliminated together with the tilt of the sample by applying the flattening method. Each band is artificially divided into several blocks for conveniently calculating lateral drifts on the basis of the overlapping area of adjacent bands through digital image correlation. The calculated lateral drifts are compensated to steer the scanning of the subsequent blocks, thus ensuring that all bands are parallel to one another. Experimental results proved that images scanned by the proposed method exhibited less distortions than those obtained from the traditional raster scanning method. The nanoscale measurement results based on the image obtained by the proposed method also showed high accuracy, with an error of less than 1.5%. By scanning as many bands as needed, the correlation-steered scanning method can obtain a highly precise SPM image of an ultra-large area. PMID:27107628
NASA Astrophysics Data System (ADS)
Song, P. Y.; Ye, Z. H.; Huang, A. B.; Chen, H. L.; Hu, X. N.; Ding, R. J.; He, L.
2016-05-01
The dark currents of two short wave (SW) HgCdTe infrared focal plane arrays (IRFPA) detectors hybridized with direct injection (DI) readout and capacitance transimpedance amplifier (CTIA) with long time integration were investigated. The cutoff wavelength of the two SW IRFPAs is about 2.6 μm at 84 K. The dark current densities of DI and CTIA samples are approximately 8.0 × 10-12 A/cm2 and 7.2 × 10-10 A/cm2 at 110 K, respectively. The large divergence of the dark current density might arise from the injection efficiency difference of the two readouts. The low injection efficiency of the DI readout, compared with the high injection efficiency of the CTIA readout at low temperature, makes the dark current density of the DI sample much lower than that of the CTIA sample. The experimental value of injection efficiency of the DI sample was evaluated as 1.1% which is consistent with its theoretical value.
NASA Technical Reports Server (NTRS)
Ryabenkii, V. S.; Turchaninov, V. I.; Tsynkov, S. V.
1999-01-01
We propose a family of algorithms for solving numerically a Cauchy problem for the three-dimensional wave equation. The sources that drive the equation (i.e., the right-hand side) are compactly supported in space for any given time; they, however, may actually move in space with a subsonic speed. The solution is calculated inside a finite domain (e.g., sphere) that also moves with a subsonic speed and always contains the support of the right-hand side. The algorithms employ a standard consistent and stable explicit finite-difference scheme for the wave equation. They allow one to calculate tile solution for arbitrarily long time intervals without error accumulation and with the fixed non-growing amount of tile CPU time and memory required for advancing one time step. The algorithms are inherently three-dimensional; they rely on the presence of lacunae in the solutions of the wave equation in oddly dimensional spaces. The methodology presented in the paper is, in fact, a building block for constructing the nonlocal highly accurate unsteady artificial boundary conditions to be used for the numerical simulation of waves propagating with finite speed over unbounded domains.
NASA Astrophysics Data System (ADS)
Song, P. Y.; Ye, Z. H.; Huang, A. B.; Chen, H. L.; Hu, X. N.; Ding, R. J.; He, L.
2016-09-01
The dark currents of two short wave (SW) HgCdTe infrared focal plane arrays (IRFPA) detectors hybridized with direct injection (DI) readout and capacitance transimpedance amplifier (CTIA) with long time integration were investigated. The cutoff wavelength of the two SW IRFPAs is about 2.6 μm at 84 K. The dark current densities of DI and CTIA samples are approximately 8.0 × 10-12 A/cm2 and 7.2 × 10-10 A/cm2 at 110 K, respectively. The large divergence of the dark current density might arise from the injection efficiency difference of the two readouts. The low injection efficiency of the DI readout, compared with the high injection efficiency of the CTIA readout at low temperature, makes the dark current density of the DI sample much lower than that of the CTIA sample. The experimental value of injection efficiency of the DI sample was evaluated as 1.1% which is consistent with its theoretical value.
NASA Astrophysics Data System (ADS)
Borovský, Michal; Weigel, Martin; Barash, Lev Yu.; Žukovič, Milan
2016-02-01
The population annealing algorithm is a novel approach to study systems with rough free-energy landscapes, such as spin glasses. It combines the power of simulated annealing, Boltzmann weighted differential reproduction and sequential Monte Carlo process to bring the population of replicas to the equilibrium even in the low-temperature region. Moreover, it provides a very good estimate of the free energy. The fact that population annealing algorithm is performed over a large number of replicas with many spin updates, makes it a good candidate for massive parallelism. We chose the GPU programming using a CUDA implementation to create a highly optimized simulation. It has been previously shown for the frustrated Ising antiferromagnet on the stacked triangular lattice with a ferromagnetic interlayer coupling, that standard Markov Chain Monte Carlo simulations fail to equilibrate at low temperatures due to the effect of kinetic freezing of the ferromagnetically ordered chains. We applied the population annealing to study the case with the isotropic intra- and interlayer antiferromagnetic coupling (J2/|J1| = -1). The reached ground states correspond to non-magnetic degenerate states, where chains are antiferromagnetically ordered, but there is no long-range ordering between them, which is analogical with Wannier phase of the 2D triangular Ising antiferromagnet.
High-temperature annealing of proton irradiated beryllium - A dilatometry-based study
NASA Astrophysics Data System (ADS)
Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; Ghose, Sanjit; Savkliyildiz, Ilyas
2016-08-01
Ssbnd 200 F grade beryllium has been irradiated with 160 MeV protons up to 1.2 1020 cm-2 peak fluence and irradiation temperatures in the range of 100-200 °C. To address the effect of proton irradiation on dimensional stability, an important parameter in its consideration in fusion reactor applications, and to simulate high temperature irradiation conditions, multi-stage annealing using high precision dilatometry to temperatures up to 740 °C were conducted in air. X-ray diffraction studies were also performed to compliment the macroscopic thermal study and offer a microscopic view of the irradiation effects on the crystal lattice. The primary objective was to qualify the competing dimensional change processes occurring at elevated temperatures namely manufacturing defect annealing, lattice parameter recovery, transmutation 4He and 3H diffusion and swelling and oxidation kinetics. Further, quantification of the effect of irradiation dose and annealing temperature and duration on dimensional changes is sought. The study revealed the presence of manufacturing porosity in the beryllium grade, the oxidation acceleration effect of irradiation including the discontinuous character of oxidation advancement, the effect of annealing duration on the recovery of lattice parameters recovery and the triggering temperature for transmutation gas diffusion leading to swelling.
Mousseau, Normand; Beland, Laurent K; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-Francois; N'Tsouaglo, Gawonou Kokou; Restrepo, Oscar; Trochet, Mickael
2015-01-01
The properties of materials, even at the atomic level, evolve on macroscopic time scales. Following this evolution through simulation has been a challenge for many years. For lattice-based activated diffusion, kinetic Monte Carlo has turned out to be an almost perfect solution. Various accelerated molecular dynamical schemes, for their part, have allowed the study on long time scale of relatively simple systems. There is still a need, however, for methods able to handle complex materials such as alloys and disordered systems. Here, we review the kinetic Activation Relaxation Technique (k-ART), one of a handful of off-lattice kinetic Monte Carlo methods,more » with on-the-fly cataloging, that have been proposed in the last few years.« less
Mousseau, Normand; Béland, Laurent Karim; Brommer, Peter; El-Mellouhi, Fedwa; Joly, Jean-François; N’Tsouaglo, Gawonou Kokou; Restrepo, Oscar; Trochet, Mickaël
2014-12-24
The properties of materials, even at the atomic level, evolve on macroscopic time scales. Following this evolution through simulation has been a challenge for many years. For lattice-based activated diffusion, kinetic Monte Carlo has turned out to be an almost perfect solution. Various accelerated molecular dynamical schemes, for their part, have allowed the study on long time scale of relatively simple systems. There is still a desire and need, however, for methods able to handle complex materials such as alloys and disordered systems. In this paper, we review the kinetic Activation–Relaxation Technique (k-ART), one of a handful of off-lattice kinetic Monte Carlo methods, with on-the-fly cataloging, that have been proposed in the last few years.
High temperature annealing of ion irradiated tungsten
Ferroni, Francesco; Yi, Xiaoou; Arakawa, Kazuto; Fitzgerald, Steven P.; Edmondson, Philip D.; Roberts, Steve G.
2015-03-21
In this study, transmission electron microscopy of high temperature annealing of pure tungsten irradiated by self-ions was conducted to elucidate microstructural and defect evolution in temperature ranges relevant to fusion reactor applications (500–1200°C). Bulk isochronal and isothermal annealing of ion irradiated pure tungsten (2 MeV W+ ions, 500°C, 1014 W+/cm2) with temperatures of 800, 950, 1100 and 1400°C, from 0.5 to 8 h, was followed by ex situ characterization of defect size, number density, Burgers vector and nature. Loops with diameters larger than 2–3 nm were considered for detailed analysis, among which all loops had View the MathML source andmore » were predominantly of interstitial nature. In situ annealing experiments from 300 up to 1200°C were also carried out, including dynamic temperature ramp-ups. These confirmed an acceleration of loop loss above 900°C. At different temperatures within this range, dislocations exhibited behaviour such as initial isolated loop hopping followed by large-scale rearrangements into loop chains, coalescence and finally line–loop interactions and widespread absorption by free-surfaces at increasing temperatures. An activation energy for the annealing of dislocation length was obtained, finding Ea=1.34±0.2 eV for the 700–1100°C range.« less
High temperature annealing of ion irradiated tungsten
Ferroni, Francesco; Yi, Xiaoou; Fitzgerald, Steven P.; Edmondson, Philip D.; Roberts, Steve G.
2015-03-21
In this study, transmission electron microscopy of high temperature annealing of pure tungsten irradiated by self-ions was conducted to elucidate microstructural and defect evolution in temperature ranges relevant to fusion reactor applications (500–1200°C). Bulk isochronal and isothermal annealing of ion irradiated pure tungsten (2 MeV W^{+} ions, 500°C, 1014 W^{+}/cm^{2}) with temperatures of 800, 950, 1100 and 1400°C, from 0.5 to 8 h, was followed by ex situ characterization of defect size, number density, Burgers vector and nature. Loops with diameters larger than 2–3 nm were considered for detailed analysis, among which all loops had View the MathML source and were predominantly of interstitial nature. In situ annealing experiments from 300 up to 1200°C were also carried out, including dynamic temperature ramp-ups. These confirmed an acceleration of loop loss above 900°C. At different temperatures within this range, dislocations exhibited behaviour such as initial isolated loop hopping followed by large-scale rearrangements into loop chains, coalescence and finally line–loop interactions and widespread absorption by free-surfaces at increasing temperatures. An activation energy for the annealing of dislocation length was obtained, finding E_{a}=1.34±0.2 eV for the 700–1100°C range.
Thin-film designs by simulated annealing
NASA Astrophysics Data System (ADS)
Boudet, T.; Chaton, P.; Herault, L.; Gonon, G.; Jouanet, L.; Keller, P.
1996-11-01
With the increasing power of computers, new methods in synthesis of optical multilayer systems have appeared. Among these, the simulated-annealing algorithm has proved its efficiency in several fields of physics. We propose to show its performances in the field of optical multilayer systems through different filter designs.
Unraveling Quantum Annealers using Classical Hardness
Martin-Mayor, Victor; Hen, Itay
2015-01-01
Recent advances in quantum technology have led to the development and manufacturing of experimental programmable quantum annealing optimizers that contain hundreds of quantum bits. These optimizers, commonly referred to as ‘D-Wave’ chips, promise to solve practical optimization problems potentially faster than conventional ‘classical’ computers. Attempts to quantify the quantum nature of these chips have been met with both excitement and skepticism but have also brought up numerous fundamental questions pertaining to the distinguishability of experimental quantum annealers from their classical thermal counterparts. Inspired by recent results in spin-glass theory that recognize ‘temperature chaos’ as the underlying mechanism responsible for the computational intractability of hard optimization problems, we devise a general method to quantify the performance of quantum annealers on optimization problems suffering from varying degrees of temperature chaos: A superior performance of quantum annealers over classical algorithms on these may allude to the role that quantum effects play in providing speedup. We utilize our method to experimentally study the D-Wave Two chip on different temperature-chaotic problems and find, surprisingly, that its performance scales unfavorably as compared to several analogous classical algorithms. We detect, quantify and discuss several purely classical effects that possibly mask the quantum behavior of the chip. PMID:26483257
Annealing of gold nanostructures sputtered on polytetrafluoroethylene
NASA Astrophysics Data System (ADS)
Siegel, Jakub; Krajcar, Robert; Kolská, Zdeňka; Hnatowicz, Vladimír; Švorčík, Václav
2011-11-01
Gold nanolayers sputtered on polytetrafluoroethylene (PTFE) surface and their changes induced by post-deposition annealing at 100°C to 300°C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy, electrical sheet resistance by two point technique, zeta potential by electrokinetic analysis and chemical composition by X-ray photoelectron spectroscopy (XPS) in dependence on the gold layer thickness. Transition from discontinuous to continuous gold coverage takes place at the layer thicknesses 10 to 15 nm and this threshold remains practically unchanged after the annealing at the temperatures below 200°C. The annealing at 300°C, however, leads to significant rearrangement of the gold layer and the transition threshold increases to 70 nm. Significant carbon contamination and the presence of oxidized structures on gold-coated samples are observed in XPS spectra. Gold coating leads to a decrease in the sample surface roughness. Annealing at 300°C of pristine PTFE and gold-coated PTFE results in significant increase of the sample surface roughness.
Annealing of gold nanostructures sputtered on polytetrafluoroethylene
2011-01-01
Gold nanolayers sputtered on polytetrafluoroethylene (PTFE) surface and their changes induced by post-deposition annealing at 100°C to 300°C are studied. Changes in surface morphology and roughness are examined by atomic force microscopy, electrical sheet resistance by two point technique, zeta potential by electrokinetic analysis and chemical composition by X-ray photoelectron spectroscopy (XPS) in dependence on the gold layer thickness. Transition from discontinuous to continuous gold coverage takes place at the layer thicknesses 10 to 15 nm and this threshold remains practically unchanged after the annealing at the temperatures below 200°C. The annealing at 300°C, however, leads to significant rearrangement of the gold layer and the transition threshold increases to 70 nm. Significant carbon contamination and the presence of oxidized structures on gold-coated samples are observed in XPS spectra. Gold coating leads to a decrease in the sample surface roughness. Annealing at 300°C of pristine PTFE and gold-coated PTFE results in significant increase of the sample surface roughness. PMID:22078024
Unraveling Quantum Annealers using Classical Hardness.
Martin-Mayor, Victor; Hen, Itay
2015-01-01
Recent advances in quantum technology have led to the development and manufacturing of experimental programmable quantum annealing optimizers that contain hundreds of quantum bits. These optimizers, commonly referred to as 'D-Wave' chips, promise to solve practical optimization problems potentially faster than conventional 'classical' computers. Attempts to quantify the quantum nature of these chips have been met with both excitement and skepticism but have also brought up numerous fundamental questions pertaining to the distinguishability of experimental quantum annealers from their classical thermal counterparts. Inspired by recent results in spin-glass theory that recognize 'temperature chaos' as the underlying mechanism responsible for the computational intractability of hard optimization problems, we devise a general method to quantify the performance of quantum annealers on optimization problems suffering from varying degrees of temperature chaos: A superior performance of quantum annealers over classical algorithms on these may allude to the role that quantum effects play in providing speedup. We utilize our method to experimentally study the D-Wave Two chip on different temperature-chaotic problems and find, surprisingly, that its performance scales unfavorably as compared to several analogous classical algorithms. We detect, quantify and discuss several purely classical effects that possibly mask the quantum behavior of the chip. PMID:26483257
High mobility annealing of Transparent Conductive Oxides
NASA Astrophysics Data System (ADS)
Warzecha, M.; Owen, J. I.; Wimmer, M.; Ruske, F.; Hotovy, J.; Hüpkes, J.
2012-04-01
To improve electrical properties a high temperature annealing treatment was applied to several transparent conductive oxides (TCO), namely tin doped indium oxide (ITO), Ga- or Al- doped ZnO (ZnO:Al/Ga), ion beam assisted deposited (IBAD) ZnO:Ga and Ga doped zinc magnesium oxide (ZnMgO:Ga). All these films were grown by magnetron sputtering. During the annealing process all TCO films were capped with 50 nm of amorphous silicon in order to protect the films from environmental impact. Increase in mobility up to 72 cm2/Vs and low resistivity of 1.6 × 10-4 Ωcm was achieved for ZnO:Al after annealing at 650°C for 24 h. Independent of the deposition conditions and doping or alloying material almost all ZnO based films show a consistent improvement in mobility. Also for ITO films a decrease in resistivity with partially improved mobility was found after annealing. However, not all ITO films show consistent improvement, but carrier density above 1021 cm-3 while ZnO films show no clear trend for carrier density but a remarkable increase in mobility. Thus we propose the healing of defects and the activation of donors to be most significant effects for ZnO and ITO films, respectively.
In Situ Observation of High Temperature Creep Behavior During Annealing of Steel
NASA Astrophysics Data System (ADS)
Zhang, X. F.; Terasaki, H.; Komizo, Y.; Murakami, Y.; Yasuda, K.
2012-12-01
Previous studies on creep suggested a close relationship between polycrystal grain size, substructure, and creep rate. At present, however, our understanding of the influence of polycrystal grain size, substructure, and thermal stress on creep deformation behavior seems rather insufficient, especially as there is a general lack of in situ data on structural changes during creep. In this study, the effects of thermal stress, austenite grain size, and cooling rate on slip deformations in C-Mn-Al steel during annealing were investigated systematically on the basis of in situ observations using high temperature laser scanning confocal microscopy. Finally, a kinetics model based on thermal expansion anisotropy and temperature difference was developed to explain these interesting experimental results. The in situ investigation of slip deformation during annealing greatly contributes to the understanding of high temperature creep behavior.
NASA Astrophysics Data System (ADS)
Martinez, Vera
2007-02-01
The paper discusses concepts about the role of architecture in the design of space habitats and the development of a general evaluation criteria of architectural design contribution. Besides the existing feasibility studies, the general requisites, the development studies, and the critical design review which are mainly based on the experience of human space missions and the standards of the NASA-STD-3000 manual and which analyze and evaluate the relation between man and environment and between man and machine mainly in its functionality, there is very few material about design of comfort and wellbeing of man in space habitat. Architecture for space habitat means the design of an artificial environment with much comfort in an "atmosphere" of wellbeing. These are mainly psychological effects of human factors which are very important in the case of a long time space mission. How can the degree of comfort and "wellbeing atmosphere" in an artificial environment be measured? How can the quality of the architectural contribution in space design be quantified? Definition of a criteria catalogue to reach a larger objectivity in architectural design evaluation. Definition of constant parameters as a result of project necessities to quantify the quality of the design. Architectural design analysis due the application and verification within the parameters and consequently overlapping and evaluating results. Interdisciplinary work between architects, astronautics, engineers, psychologists, etc. All the disciplines needed for planning a high quality habitat for humans in space. Analysis of the principles of well designed artificial environment. Good quality design for space architecture is the result of the interaction and interrelation between many different project necessities (technological, environmental, human factors, transportation, costs, etc.). Each of this necessities is interrelated in the design project and cannot be evaluated on its own. Therefore, the design
NASA Astrophysics Data System (ADS)
Inguaggiato, Salvatore; Vita, Fabio; Calderone, Lorenzo; Sollami, Aldo
2015-04-01
Vulcano Island, located in the Aeolian Archipelago, is an active volcano that has been in state of solphataric activity, since the last eruption (1888-1890). At present, the main exhalative activity is in the northern part of the island, it is revealed by a wide fumaroles field, on the active edifice of "La Fossa" crater, (100°C <450°C). As part of the volcanic monitoring programs, the extensive parameters have a determining role in the evaluation of the mass-output involved. For this reason, in the last years the Vulcano continuous monitoring network was implemented with equipments to measure the fluxes of SO2 "plume" and CO2 soil emitted from the summit crater. In particular, in the 2007 a station to measure the soil CO2 degassing (VCS) was installed in the summit area outside of the fumarolic field. Moreover, inside of the NOVAC project program, an UV-scanning DOAS was installed in the Palizzi area to measure the total SO2 flux emitted from the entire degassing crater area. Here we present the long time variations recorded in the 2007-2014 period. The CO2 soil degassing showed an average flux of 1600 ± 250 g m-2 d-1 representing the background value during "normal" solphataric activity at the permanent station. In the investigated period anomalous values up to 16,000 g m-2 d-1 was recorded in the last months of 2009. The SO2 "plume" degassing showed an average flux of 12 t d-1 with an anomalous degassing process also recorded at the end of 2009 with values up to 100 t d-1. Moreover, a slight increasing trend of SO2 fluxes was recorded in the last years. In the monitoring of active volcanoes, the recorded contemporaneous variations of independent geochemical parameters highlights the importance of the extensive parameters, able to provide information about deeper changes driving the solphataric activity.