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Sample records for kinetics long-time annealing

  1. Tritium release from neutron irradiated beryllium: Kinetics, long-time annealing and effect or crack formation

    SciTech Connect

    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.

  2. Radiation damage annealing kinetics

    NASA Technical Reports Server (NTRS)

    Dresselhaus, M. S.

    1971-01-01

    Various spectral response studies are reported that assess lithium doping effects on the recovery process of electron damaged silicon solar cells. Measurements of both the minority carrier lifetimes and the energy level spectrum of the defects are used to predict lifetime damage constants and carrier removal rates relevant to the operation of the solar lithium-doped cell and its annealing kinetics.

  3. Algorithmic developments of the kinetic activation-relaxation technique: Accessing long-time kinetics of larger and more complex systems

    NASA Astrophysics Data System (ADS)

    Trochet, Mickaël; Sauvé-Lacoursière, Alecsandre; Mousseau, Normand

    2017-10-01

    In spite of the considerable computer speed increase of the last decades, long-time atomic simulations remain a challenge and most molecular dynamical simulations are limited to 1 μ s at the very best in condensed matter and materials science. There is a need, therefore, for accelerated methods that can bridge the gap between the full dynamical description of molecular dynamics and experimentally relevant time scales. This is the goal of the kinetic Activation-Relaxation Technique (k-ART), an off-lattice kinetic Monte-Carlo method with on-the-fly catalog building capabilities based on the topological tool NAUTY and the open-ended search method Activation-Relaxation Technique (ART nouveau) that has been applied with success to the study of long-time kinetics of complex materials, including grain boundaries, alloys, and amorphous materials. We present a number of recent algorithmic additions, including the use of local force calculation, two-level parallelization, improved topological description, and biased sampling and show how they perform on two applications linked to defect diffusion and relaxation after ion bombardement in Si.

  4. X-ray and cathodoluminescence study on the effect of intentional long time annealing of the InGaN/GaN multiple quantum wells grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Jeong, T. S.; Kim, J. H.; Han, M. S.; Lim, K. Y.; Youn, C. J.

    2005-07-01

    GaN-based InGaN/GaN multiple quantum wells (MQWs) structure having a high-quality epilayer and coherent periodicity was grown by metalorganic chemical vapor deposition. After thermal annealing of InGaN/GaN MQWs, the increase in temperature and annealing time caused the intermixing between the barrier and the wells, which in turn caused a decrease in periodicity on the high-resolution X-ray diffraction patterns. Thereby, we confirmed that the structural performance of InGaN MQWs is successively degrading with increasing thermal annealing temperature. Especially, InGaN MQWs of the sample annealed at 950 °C were profoundly damaged. The cathodoluminescence (CL) measurement indicated that MQWs emission intensity decreases with increasing thermal annealing temperature. Thus, the integrated CL intensity ratio of InGaN MQWs to GaN dramatically decreased while thermal annealing temperatures increased. This result caused the intermixing in MQWs to deteriorate the active layer performance. Furthermore, the peak position of MQWs showed a tendency of the red shift after high thermal annealing. It is suggested that the annealing-induced red shift in MQWs is attributed to the reduction of the inhomogeneity of the In content in the MQWs leading to the reduction of the quantized energies. Consequently, it indicates that the high temperature and the long-time thermal annealing would be inevitably followed by the structural destruction of InGaN MQWs.

  5. OBJECT KINETIC MONTE CARLO SIMULATIONS OF CASCADE ANNEALING IN TUNGSTEN

    SciTech Connect

    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.

  6. Annealing kinetics of latent particle tracks in Durango apatite

    SciTech Connect

    Afra, B.; Rodriguez, M. D.; Giulian, R.; Kluth, P.; Lang, M.; Zhang, J.; Ewing, R. C.; Kirby, N.; Trautmann, C.; Toulemonde, M.

    2011-02-01

    Using synchrotron small-angle x-ray scattering we determine the ''latent'' track morphology and the track annealing kinetics in the Durango apatite. The latter, measured during ex situ and in situ annealing experiments, suggests structural relaxation followed by recrystallization of the damaged material. The resolution of fractions of a nanometer with which the track radii are determined, as well as the nondestructive, artefact-free measurement methodology shown here, provides an effective means for in-depth studies of ion-track formation in natural minerals under a wide variety of geological conditions.

  7. 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.

  8. Kinetic regime of hydrodynamic fluctuations and long time tails for a Bjorken expansion

    NASA Astrophysics Data System (ADS)

    Akamatsu, Yukinao; Mazeliauskas, Aleksas; Teaney, Derek

    2017-01-01

    We develop a set of kinetic equations for hydrodynamic fluctuations which are equivalent to nonlinear hydrodynamics with noise. The hydrokinetic equations can be coupled to existing second-order hydrodynamic codes to incorporate the physics of these fluctuations. We first show that the kinetic response precisely reproduces the renormalization of the shear viscosity and the fractional power (∝ω3 /2) which characterizes equilibrium correlators of energy and momentum for a static fluid. Then we use the hydrokinetic equations to analyze thermal fluctuations for a Bjorken expansion, evaluating the contribution of thermal noise from the earliest moments and at late times. In the Bjorken case, the solution to the kinetic equations determines the coefficient of the first fractional power of the gradient expansion (∝1 /(τT ) 3 /2) for the expanding system. Numerically, we find that the contribution to the longitudinal pressure from hydrodynamic fluctuations is larger than second-order hydrodynamics for typical medium parameters used to simulate heavy ion collisions.

  9. Activated desorption at heterogeneous interfaces and long-time kinetics of hydrocarbon recovery from nanoporous media

    PubMed Central

    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

  10. Activated desorption at heterogeneous interfaces and long-time kinetics of hydrocarbon recovery from nanoporous media.

    PubMed

    Lee, Thomas; Bocquet, Lydéric; Coasne, Benoit

    2016-06-21

    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.

  11. Activated desorption at heterogeneous interfaces and long-time kinetics of hydrocarbon recovery from nanoporous media

    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.

  12. Long-time atomistic evolution of grain boundary in nickel using the kinetic activation-relaxation technique

    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

  13. Front propagation versus bulk relaxation in the annealing dynamics of a kinetically constrained model of ultrastable glasses

    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.

  14. Subcontinuum mass transport of hydrocarbons in nanoporous media and long-time kinetics of recovery from unconventional reservoirs

    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.

  15. A derivation and scalable implementation of the synchronous parallel kinetic Monte Carlo method for simulating long-time dynamics

    NASA Astrophysics Data System (ADS)

    Byun, Hye Suk; El-Naggar, Mohamed Y.; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2017-10-01

    Kinetic Monte Carlo (KMC) simulations are used to study long-time dynamics of a wide variety of systems. Unfortunately, the conventional KMC algorithm is not scalable to larger systems, since its time scale is inversely proportional to the simulated system size. A promising approach to resolving this issue is the synchronous parallel KMC (SPKMC) algorithm, which makes the time scale size-independent. This paper introduces a formal derivation of the SPKMC algorithm based on local transition-state and time-dependent Hartree approximations, as well as its scalable parallel implementation based on a dual linked-list cell method. The resulting algorithm has achieved a weak-scaling parallel efficiency of 0.935 on 1024 Intel Xeon processors for simulating biological electron transfer dynamics in a 4.2 billion-heme system, as well as decent strong-scaling parallel efficiency. The parallel code has been used to simulate a lattice of cytochrome complexes on a bacterial-membrane nanowire, and it is broadly applicable to other problems such as computational synthesis of new materials.

  16. Efficient kinetic Monte Carlo simulation of annealing in semiconductor materials

    NASA Astrophysics Data System (ADS)

    Hargrove, Paul Hamilton

    As the semiconductor manufacturing industry advances, the length scales of devices are shrinking rapidly, in accordance with the predictions of Moore's Law. As the device dimensions shrink the importance of predictive process modeling to the development of the production process is growing. Of particular importance are predictive models which can be applied to process conditions not easily accessible via experiment. Therefore the importance of models based on physical understanding are gaining importance versus models based on empirical fits alone. One promising research area in physical-based models is kinetic Monte Carlo (kMC) modeling of atomistic processes. This thesis explores kMC modeling of annealing and diffusion processes. After providing the necessary background to understand and motivate the research, a detailed review of simulation using this class of models is presented which exposes the motivation for using these models and establishes the state of the field. The author provides a user's manual for ANISRA ( ANnealIng Simulation libRAry), a computer code for on-lattice kMC simulations. This library is intended as a reusable tool for the development of simulation codes for atomistic models covering a wide variety of problems. Thus care has been taken to separate the core functionality of a simulation from the specification of the model. This thesis also compares the performance of data structures for the kMC simulation problem and recommends some novel approaches. These recommendations are applicable to a wider class of model than is ANISRA, and thus of potential interest even to researchers who implement their own simulators. Three example simulations are built from ANISRA and are presented to show the applicability of this class of model to problems of interest in semiconductor process modeling. The differences between the models simulated display the versatility of the code library. The small amount of code written to construct and modify these

  17. Remarkable changes in interface O vacancy and metal-oxide bonds in amorphous indium-gallium-zinc-oxide thin-film transistors by long time annealing at 250 °C

    SciTech Connect

    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.

  18. Effect of ramp rate and annealing temperature on boron transient diffusion in implanted silicon: kinetic Monte Carlo simulations

    SciTech Connect

    Caturla, M. J.; Diaz de la Rubia, T.; Foad, M.

    1998-06-17

    We present results of recent kinetic Monte Carlo simulations of the effect of annealing time and ramp rate on boron transient enhanced diffusion (BTED) in low energy ion implanted silicon. The simulations use a database of defect and dopant energetics derived from first principle calculations. We discuss the complete atomistic details of defect and dopant clustering during the anneals, and the dependence of boron TED on ramp rate. The simulations provide a complete time history of the evolution of the active boron fraction during the anneal for a wide variety of conditions. We also studied the lateral spreading of the boron during the annealing for two different conditions, furnace anneal and ramp anneal.

  19. 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

  20. Annealing kinetics of boron-containing centers in electron-irradiated silicon

    SciTech Connect

    Feklisova, O. V. Yarykin, N. A.; Weber, J.

    2013-02-15

    The annealing kinetics of B{sub i}O{sub i} pairs created by fast-electron irradiation in Si wafers is studied. The wafers are grown by the Czochralski method and doped with boron to different levels. It is found that, at a particular temperature, the annealing rate steadily increases with increasing boron concentration. The results are described with a simple model that takes into consideration the interaction of interstitial boron atoms with oxygen atoms and substitutional boron atoms. In the context of the model, the temperature dependence of the dissociation rate of the B{sub i}O{sub i} complex is calculated.

  1. Application of an independent parallel reactions model on the annealing kinetics of BEPO irradiated graphite

    NASA Astrophysics Data System (ADS)

    Lasithiotakis, Michael; Marsden, Barry J.; James Marrow, T.

    2012-08-01

    Stored energy release rates have been determined for neutron irradiated graphite samples machined from an early air-cooled nuclear reactor (British Experimental Pile Zero or BEPO). The rate of release of stored energy was measured for both isothermal and linear rise heating rate differential scanning calorimetry experiments. The rate of release data were analysed using a thermal kinetics, independent parallel reactions model. The effect of annealing on the graphite crystalline structure was evaluated by investigating changes to X-ray diffraction spectra. A correlation between the calculated crystallite size and stored energy release is presented. A method for calculating the kinetic parameters for the annealing reaction is proposed and tested against the data. The method shows excellent consistency for both the isothermal and linear heating rate experiments (with less than 3% standard deviation).

  2. Kinetic Monte Carlo Annealing Simulation of Cascade Damage in a-Fe

    SciTech Connect

    Suzudo, Tomoaki; Golubov, Stanislav I; Stoller, Roger E; Yamaguchi, Masatake; Tsuru, Tomohito; Kaburaki, Hideo

    2011-01-01

    Molecular dynamics is a useful tool for simulating cascade damage in metals and alloys, but the time scale accessible to molecular dynamics is only about 10-10s. Kinetic Monte Carlo can be used to simulate annealing of cascade damage to permit analysis of the longer time evolution of cascade damage. We conducted a series of such annealing simulations in -Fe. The number of surviving displacements before annealing is ~0.3 of the Norgett-Robinson-Torrens (NRT) value in the case of primary knock-on atoms with energy more than ~10 keV, and it decreased by ~30% during the annealing at 300 K because of recombination of vacancies and self-interstitial atoms. The recombination ratio increased as the annealing temperature increased. These results can be meaningfully applied in models such as mean field reaction rate theory used to simulate long-term radiation damage accumulation. We also demonstrated that 1D motion of small SIA clusters can substantially influence the long-term accumulation of cascade damage.

  3. Modeling and Measuring 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.

    2016-12-01

    Understanding helium diffusion kinetics in apatite is critical for the accurate interpretation of (U-Th)/He thermochronometric data. This problem is complicated by the observation that helium diffusivity is not a simple function of temperature, but may evolve as a function of damage to the apatite crystal lattice resulting from alpha recoil. This `radiation damage' increases as a function of the amount of radiometric parent products, or effective uranium concentration, and time, but decreases due to thermal annealing of damage, necessitating a detailed understanding of radiation damage production and annealing in cases of burial heating over geologic timescales. Published observations [1,2] suggest that annealing rates of damage caused by alpha recoil and fission tracks in apatite differ. Existing models, however, assume the diffusion kinetics resulting from the two sources of damage are identical [3], demonstrating the need for further investigation of these damage sources. We present modeling and experimental work designed to interrogate the effects of radiation damage and its annealing on helium diffusion kinetics in apatite. Using previously published results [4] that investigated the effects of annealing temperature and duration on measured helium diffusivity, we fit a set of functions that are then integrated into a numerical model that tracks the evolution of radiation damage and apparent (U-Th)/He age. We compare the results of this model calibration to existing models [3]. In addition, we present data from two suites of diffusion experiments. The first suite, intended to test the published methodology and results, uses Durango apatite, while the second uses Sierran (CA) granite as a first test to determine if apatite of varying chemistry and age responds differently to the thermal annealing of radiation damage. Ultimately, the updated model and experimental results will benefit the interpretation of the effects of radiation damage accumulation and

  4. Kinetic Monte Carlo simulations of boron activation in implanted Si under laser thermal annealing

    NASA Astrophysics Data System (ADS)

    Fisicaro, Giuseppe; Pelaz, Lourdes; Aboy, Maria; Lopez, Pedro; Italia, Markus; Huet, Karim; Cristiano, Filadelfo; Essa, Zahi; Yang, Qui; Bedel-Pereira, Elena; Quillec, Maurice; La Magna, Antonino

    2014-02-01

    We investigate the correlation between dopant activation and damage evolution in boron-implanted silicon under excimer laser irradiation. The dopant activation efficiency in the solid phase was measured under a wide range of irradiation conditions and simulated using coupled phase-field and kinetic Monte Carlo models. With the inclusion of dopant atoms, the presented code extends the capabilities of a previous version, allowing its definitive validation by means of detailed comparisons with experimental data. The stochastic method predicts the post-implant kinetics of the defect-dopant system in the far-from-equilibrium conditions caused by laser irradiation. The simulations explain the dopant activation dynamics and demonstrate that the competitive dopant-defect kinetics during the first laser annealing treatment dominates the activation phenomenon, stabilizing the system against additional laser irradiation steps.

  5. Kinetic investigation of sulfidizing annealing of scorodite in processing of refractory oxidized gold-containing ores

    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.

  6. Displacement cascades and defect annealing in tungsten, Part II: Object kinetic Monte Carlo Simulation of Tungsten Cascade Aging

    SciTech Connect

    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.

  7. Kinetics modeling of precipitation with characteristic shape during post-implantation annealing

    SciTech Connect

    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.

  8. Kinetic Ising models with various single-spin-flip dynamics on quenched and annealed random regular graphs

    NASA Astrophysics Data System (ADS)

    Jedrzejewski, Arkadiusz; Chmiel, Anna; Sznajd-Weron, Katarzyna

    2017-07-01

    We investigate a kinetic Ising model with several single-spin-flip dynamics (including Metropolis and heat bath) on quenched and annealed random regular graphs. As expected, on the quenched structures all proposed algorithms reproduce the same results since the conditions for the detailed balance and the Boltzmann distribution in an equilibrium are satisfied. However, on the annealed graphs the situation is far less clear—the network annealing disturbs the equilibrium moving the system away from it. Consequently, distinct dynamics lead to different steady states. We show that some algorithms are more resistant to the annealed disorder, which causes only small quantitative changes in the model behavior. On the other hand, there are dynamics for which the influence of annealing on the system is significant, and qualitative changes arise like switching the type of phase transition from a continuous to a discontinuous one. We try to identify features of the proposed dynamics which are responsible for the above phenomenon.

  9. Growth kinetics of Al–Fe intermetallic compounds during annealing treatment of friction stir lap welds

    SciTech Connect

    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.

  10. Displacement cascades and defect annealing in tungsten, Part III: The sensitivity of cascade annealing in tungsten to the values of kinetic parameters

    SciTech Connect

    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.

  11. Role of filament annealing in the kinetics and thermodynamics of nucleated polymerization

    NASA Astrophysics Data System (ADS)

    Michaels, Thomas C. T.; Knowles, Tuomas P. J.

    2014-06-01

    The formation of nanoscale protein filaments from soluble precursor molecules through nucleated polymerization is a common form of supra-molecular assembly phenomenon. This process underlies the generation of a range of both functional and pathological structures in nature. Filament breakage has emerged as a key process controlling the kinetics of the growth reaction since it increases the number of filament ends in the system that can act as growth sites. In order to ensure microscopic reversibility, however, the inverse process of fragmentation, end-to-end annealing of filaments, is a necessary component of a consistent description of such systems. Here, we combine Smoluchowski kinetics with nucleated polymerization models to generate a master equation description of protein fibrillization, where filamentous structures can undergo end-to-end association, in addition to elongation, fragmentation, and nucleation processes. We obtain self-consistent closed-form expressions for the growth kinetics and discuss the key physics that emerges from considering filament fusion relative to current fragmentation only models. Furthermore, we study the key time scales that describe relaxation to equilibrium.

  12. How Surface Heterogeneity Affects Protein Adsorption: Annealing of OTS Patterns and Albumin Adsorption Kinetics*

    PubMed Central

    Hodgkinson, Gerald N.; Hlady, Vladimir

    2009-01-01

    Fluorescence microscopy and intensity histogram analysis techniques were used to monitor spatially-resolved albumin adsorption kinetics to model heterogeneous surfaces on sub-μm scales. Several distinct protein subpopulations were resolved, each represented by a normal distribution of adsorption densities on the adsorbent surface. Histogram analyses provided dynamic information of mean adsorption density, spread in adsorption density, and surface area coverage for each distinct protein subpopulation. A simple adsorption model is proposed in which individual protein binding events are predicted by the summation of multiple protein's surface sub-site interactions with different binding energy sub-sites on adsorbent surfaces. This model is predictive of the albumin adsorption on the patterns produced by one step μ-contact printing (μCP) of octadecyltrichlorosilane (OTS) on glass but fails to describe adsorption once the same patterns are altered by a thermal annealing step. PMID:19746205

  13. Kinetics of Ferrite Recrystallization and Austenite Formation During Intercritical Annealing of the Cold-Rolled Ferrite/Martensite Duplex Structures

    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.

  14. The influence of artificial radiation damage and thermal annealing on helium diffusion kinetics in apatite

    NASA Astrophysics Data System (ADS)

    Shuster, David L.; Farley, Kenneth A.

    2009-01-01

    Recent work [Shuster D. L., Flowers R. M. and Farley K. A. (2006) The influence of natural radiation damage on helium diffusion kinetics in apatite. Earth Planet. Sci. Lett.249(3-4), 148-161] revealing a correlation between radiogenic 4He concentration and He diffusivity in natural apatites suggests that helium migration is retarded by radiation-induced damage to the crystal structure. If so, the He diffusion kinetics of an apatite is an evolving function of time and the effective uranium concentration in a cooling sample, a fact which must be considered when interpreting apatite (U-Th)/He ages. Here we report the results of experiments designed to investigate and quantify this phenomenon by determining He diffusivities in apatites after systematically adding or removing radiation damage. Radiation damage was added to a suite of synthetic and natural apatites by exposure to between 1 and 100 h of neutron irradiation in a nuclear reactor. The samples were then irradiated with a 220 MeV proton beam and the resulting spallogenic 3He used as a diffusant in step-heating diffusion experiments. In every sample, irradiation increased the activation energy ( E a) and the frequency factor ( D o/ a2) of diffusion and yielded a higher He closure temperature ( T c) than the starting material. For example, 100 h in the reactor caused the He closure temperature to increase by as much as 36 °C. For a given neutron fluence the magnitude of increase in closure temperature scales negatively with the initial closure temperature. This is consistent with a logarithmic response in which the neutron damage is additive to the initial damage present. In detail, the irradiations introduce correlated increases in E a and ln( D o/a 2) that lie on the same array as found in natural apatites. This strongly suggests that neutron-induced damage mimics the damage produced by U and Th decay in natural apatites. To investigate the potential consequences of annealing of radiation damage, samples of

  15. Modulation of drug release kinetics of shellac-based matrix tablets by in-situ polymerization through annealing process.

    PubMed

    Limmatvapirat, Sontaya; Limmatvapirat, Chutima; Puttipipatkhachorn, Satit; Nunthanid, Jurairat; Luangtana-anan, Manee; Sriamornsak, Pornsak

    2008-08-01

    A new oral-controlled release matrix tablet based on shellac polymer was designed and developed, using metronidazole (MZ) as a model drug. The shellac-based matrix tablets were prepared by wet granulation using different amounts of shellac and lactose. The effect of annealing temperature and pH of medium on drug release from matrix tablets was investigated. The increased amount of shellac and increased annealing temperature significantly affected the physical properties (i.e., tablet hardness and tablet disintegration) and MZ release from the matrix tablets. The in-situ polymerization played a major role on the changes in shellac properties during annealing process. Though the shellac did not dissolve in acid medium, the MZ release in 0.1N HCl was faster than in pH 7.3 buffer, resulting from a higher solubility of MZ in acid medium. The modulation of MZ release kinetics from shellac-based matrix tablets could be accomplished by varying the amount of shellac or annealing temperature. The release kinetics was shifted from relaxation-controlled release to diffusion-controlled release when the amount of shellac or the annealing temperature was increased.

  16. Kinetics of Light-induced Metastable Defect Creation and Annealing in a-Si:H

    NASA Astrophysics Data System (ADS)

    Kodolbaþ, Alp Osman; Eray, Aynur; Öktü, Özcan

    2002-01-01

    Constant Photocurrent Method (CPM) and steady state photoconductivity measurements are used to investigate the creation of light-induced metastable defects in a-Si:H at room temperature and their annealing. Light-induced metastable defect concentration Nd varies with exposure time teas ter with r=0.34 ± 0.02, as expected from the recombination induced weak bond breaking model [1]. The validity of a stretched exponential model is also studied [2]. From the annealing experiments, the distribution of thermal annealing activation energies is calculated following the method proposed by Hata and Wagner [3]. Defects created at room temperature show a narrow distribution of annealing activation energies peaking at 0.97eV. The relation between photoconductivity and Nd is strongly nonlinear. Defects created at earlier times of illumination degrade photoconductivity more strongly, and these defects anneal out more easily than those created at later times of illumination.

  17. Influence of film structure on the dewetting kinetics of thin polymer films in the solvent annealing process.

    PubMed

    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.

  18. Modified growth kinetics of ion induced yttrium--silicide layers during subsequent thermal annealing

    SciTech Connect

    Alford, T.L.; Mayer, J.W. )

    1991-12-02

    Yttrium and amorphous silicon bilayers were irradiated with 600-keV inert ions between {minus}190 and 265 {degree}C. Ion-induced YSi{sub 1.7} layers occurred in those samples irradiated above {ge} (R18)205 {degree}C. These ion-mixed samples were thermally annealed at temperatures between 325 and 380 {degree}C. The diffusion-limited growth was observed only in those samples which had an ion-induced YSi{sub 1.7} layer present prior to thermal annealing. This type of growth is distinctly different from the interface limited, nonuniform, and irreproducible growth seen during typical thermal annealing of yttrium and silicon bilayers. This type of growth still occurred in those samples annealed after ion irradiations at {le}190 {degree}C.

  19. Kinetics of hardness evolution during annealing of gamma-irradiated polycarbonate

    SciTech Connect

    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.

  20. Recovery during annealing in a cold rolled low carbon steel. Part I: Kinetics and microstructural characterization

    SciTech Connect

    Martinez-de-Guerenu, A.; Arizti, F.; Diaz-Fuentes, M.; Gutierrez, I

    2004-07-12

    A cold rolled low carbon steel has been annealed at low temperatures (300-500 deg. C) in order to promote recovery without interaction with recrystallization. It has been shown that the recovery process can be monitored by means of non-destructive magnetic techniques using coercive field (H{sub c}) measurements. Transmission electron microscopy and electron backscattering diffraction (EBSD) observations were carried out in order to investigate the microstructural changes associated with the measured decrease in H{sub c} produced by the recovery. The EBSD image quality maps show that on a microstructural scale, the cold work stored energy is distributed heterogeneously among different texture components, in agreement with previous studies. Recovery mainly affects the {l_brace}1 1 1{r_brace} {gamma}-fibre orientations, leading to the formation of well defined subgrains.

  1. Decarburization and grain growth kinetics during the annealing of electrical steels

    SciTech Connect

    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.

  2. Understanding the phase formation kinetics of nano-crystalline kesterite deposited on mesoscopic scaffolds via in situ multi-wavelength Raman-monitored annealing.

    PubMed

    Wang, Zhuoran; Elouatik, Samir; Demopoulos, George P

    2016-10-26

    Kesterite, a highly promising photo-absorbing crystalline form of Cu2ZnSnS4 (CZTS), has been prepared via various routes. However, the lack of in-depth understanding of the dynamic phase formation process of kesterite leads to difficulties in optimizing its annealing conditions, hence its light harvesting performance. In this paper, in situ Raman monitored-annealing is applied to study the phase formation kinetics of nano-crystalline kesterite from a precursor deposited on a TiO2 mesoscopic scaffold. By performing in situ Raman annealing under different experimental conditions and wavelengths, several facts have been discovered: kesterite crystallization starts at as low as 170 °C, but after short time annealing at 300 °C followed by cooling, the initially formed kesterite is found to decompose. Annealing at 400 °C or higher is proven to be sufficient for stabilizing the kesterite phase. Annealing at the higher temperature of 500 °C is necessary though to promote a complete reaction and thus eliminate the parasitic copper tin sulfide (CTS) impurity intermediates identified at lower annealing temperatures. More importantly, the real-time temperature dependence of Raman peak intensity enhancement, shift and broadening for CZTS is established experimentally at 500 °C for 1 h, providing a valuable reference in future CZTS research. This work demonstrates the significance of using in situ Raman spectroscopy in elucidating the kesterite phase formation kinetics, a critical step towards full crystal phase control - a prerequisite for developing fully functional CZTS-based optoelectronic devices.

  3. Coarse-grained molecular dynamics modeling of the kinetics of lamellar block copolymer defect annealing

    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.

  4. Annealing simulation of cascade damage in -Fe- Damage energy and temperature dependence analyses

    SciTech Connect

    Suzudo, Tomoaki; Golubov, Stanislav I; Stoller, Roger E; Yamaguchi, Masatake; Tsuru, Tomohito; Kaburaki, Hideo

    2012-01-01

    In this paper, kinetic Monte Carlo method was applied to investigate the long time evolution of cascade damage prepared by molecular dynamics simulations in -Fe up to recoil energy of more than 200 keV. We conducted thorough investigation on how the surviving defects vary with cascade damage energy and annealing temperature. The results can be used for input parameters of rate equations to simulate microstructural evolution under irradiation. The study also suggested that neighboring sub-cascades evolves almost independently during annealing, and that the temperature dependence of the annealing results can be explained by the temperature dependence of vacancy-migration and vacancy-dissociation probabilities.

  5. 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.

  6. The kinetics of swelling in block copolymer thin films during ``solvo-microwave'' and solvo-thermal annealing: The effect of vapour pressure

    NASA Astrophysics Data System (ADS)

    Mokarian-Tabari, Parvanrh; Collins, Timothy; Cummins, Cian; Delgado Simão, Claudia; Sotomayor, Clivia; Morris, Michael A.

    2015-03-01

    Long annealing time associated with high chi block copolymers is a major disadvantage for their integration in industrial applications. Microwave-assisted microphase separation appears to offer considerable benefits in reducing annealing times for BCPs. However, despite the promise of this technique, little is known about the mechanism of how microwave irradiation might sponsor the molecular motion that accompanies microphase separation. In our earlier work we carried out an in situ temperature measurement during ``solvo-microwave'' annealing of poly(styrene-b-lactic acid) (PS- b-PLA) in presence of THF and also in the conventional oven. Comparing the results indicated that vapour pressure of THF might have a major role to achieve fast self- assembly (60 seconds) in PS- b-PLA film. Here, we study the kinetics of swelling by monitoring the pressure through in situ pressure experiments during ``solvo-microwave'' and solvo-thermal annealing. The preliminary data suggest that the rate at which the THF pressure increases is the key factor. This suggests that kinetics, i.e., the rate of film swelling and diffusion, affects the order and the coherence length of the pattern. We estimated the defect density in the patterns by our recently developed defect analysis software.

  7. Effects of Annealing, Thermomigration, and Electromigration on the Intermetallic Compounds Growth Kinetics of Cu/Sn-2.5Ag Microbump.

    PubMed

    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.

  8. Simulated annealing reveals the kinetic activity of SGLT1, a member of the LeuT structural family

    PubMed Central

    Longpré, Jean-Philippe; Sasseville, Louis J.

    2012-01-01

    The Na+/glucose cotransporter (SGLT1) is the archetype of membrane proteins that use the electrochemical Na+ gradient to drive uphill transport of a substrate. The crystal structure recently obtained for vSGLT strongly suggests that SGLT1 adopts the inverted repeat fold of the LeuT structural family for which several crystal structures are now available. What is largely missing is an accurate view of the rates at which SGLT1 transits between its different conformational states. In the present study, we used simulated annealing to analyze a large set of steady-state and pre–steady-state currents measured for human SGLT1 at different membrane potentials, and in the presence of different Na+ and α-methyl-d-glucose (αMG) concentrations. The simplest kinetic model that could accurately reproduce the time course of the measured currents (down to the 2 ms time range) is a seven-state model (C1 to C7) where the binding of the two Na+ ions (C4→C5) is highly cooperative. In the forward direction (Na+/glucose influx), the model is characterized by two slow, electroneutral conformational changes (59 and 100 s−1) which represent reorientation of the free and of the fully loaded carrier between inside-facing and outside-facing conformations. From the inward-facing (C1) to the outward-facing Na-bound configuration (C5), 1.3 negative elementary charges are moved outward. Although extracellular glucose binding (C5→C6) is electroneutral, the next step (C6→C7) carries 0.7 positive charges inside the cell. Alignment of the seven-state model with a generalized model suggested by the structural data of the LeuT fold family suggests that electrogenic steps are associated with the movement of the so-called thin gates on each side of the substrate binding site. To our knowledge, this is the first model that can quantitatively describe the behavior of SGLT1 down to the 2 ms time domain. The model is highly symmetrical and in good agreement with the structural information

  9. Simulated annealing reveals the kinetic activity of SGLT1, a member of the LeuT structural family.

    PubMed

    Longpré, Jean-Philippe; Sasseville, Louis J; Lapointe, Jean-Yves

    2012-10-01

    The Na(+)/glucose cotransporter (SGLT1) is the archetype of membrane proteins that use the electrochemical Na(+) gradient to drive uphill transport of a substrate. The crystal structure recently obtained for vSGLT strongly suggests that SGLT1 adopts the inverted repeat fold of the LeuT structural family for which several crystal structures are now available. What is largely missing is an accurate view of the rates at which SGLT1 transits between its different conformational states. In the present study, we used simulated annealing to analyze a large set of steady-state and pre-steady-state currents measured for human SGLT1 at different membrane potentials, and in the presence of different Na(+) and α-methyl-d-glucose (αMG) concentrations. The simplest kinetic model that could accurately reproduce the time course of the measured currents (down to the 2 ms time range) is a seven-state model (C(1) to C(7)) where the binding of the two Na(+) ions (C(4)→C(5)) is highly cooperative. In the forward direction (Na(+)/glucose influx), the model is characterized by two slow, electroneutral conformational changes (59 and 100 s(-1)) which represent reorientation of the free and of the fully loaded carrier between inside-facing and outside-facing conformations. From the inward-facing (C(1)) to the outward-facing Na-bound configuration (C(5)), 1.3 negative elementary charges are moved outward. Although extracellular glucose binding (C(5)→C(6)) is electroneutral, the next step (C(6)→C(7)) carries 0.7 positive charges inside the cell. Alignment of the seven-state model with a generalized model suggested by the structural data of the LeuT fold family suggests that electrogenic steps are associated with the movement of the so-called thin gates on each side of the substrate binding site. To our knowledge, this is the first model that can quantitatively describe the behavior of SGLT1 down to the 2 ms time domain. The model is highly symmetrical and in good agreement with the

  10. Microstructural Evolution and Recrystallization Kinetics of a Cold-Rolled, Ferrite-Martensite Structure During Intercritical Annealing

    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.

  11. Characterization of the kinetics of RNA annealing and strand displacement activities of the E. coli DEAD-box helicase CsdA.

    PubMed

    Stampfl, Sabine; Doetsch, Martina; Beich-Frandsen, Mads; Schroeder, Renée

    2013-01-01

    CsdA is one of five E. coli DEAD-box helicases and as a cold-shock protein assists RNA structural remodeling at low temperatures. The helicase has been shown to catalyze duplex unwinding in an ATP-dependent way and accelerate annealing of complementary RNAs, but detailed kinetic analyses are missing. Therefore, we performed kinetic measurements using a coupled annealing and strand displacement assay with high temporal resolution to analyze how CsdA balances the two converse activities. We furthermore tested the hypothesis that the unwinding activity of DEAD-box helicases is largely determined by the substrate's thermodynamic stability using full-length CsdA and a set of RNAs with constant length, but increasing GC content. The rate constants for strand displacement did indeed decrease with increasing duplex stability, with a calculated free energy between -31.3 and -40 kcal/mol being the limit for helix unwinding. Thus, our data generally support the above hypothesis, showing that for CsdA substrate thermal stability is an important rate limiting factor.

  12. Kinetic effects and mechanisms limiting substitutional solubility in the formation of supersaturated alloys by pulsed laser annealing

    SciTech Connect

    White, C.W.; Appleton, B.R.; Stritzker, B.; Zehner, D.M.; Wilson, S.R.

    1980-11-01

    Pulsed laser annealing of silicon implanted by Group (III,V) dopants leads to the formation of supersaturated alloys by nonequilibrium processes occurring in the interfacial region during liquid phase epitaxial regrowth. The distribution coefficient from the melt (k') and the maximum dopant substitutional solubility (C/sub s//sup max/) are far greater than equilibrium values and both are functions of growth velocity. Substitutional solubility is limited by lattice strain and by constitutional supercooling at the interface during regrowth. Values for C/sub s//sup max/ obtained at different velocities are compared with predictions of thermodynamic limits for solute trapping.

  13. Annealing studies of boron implanted emitters for n-silicon solar cells

    NASA Astrophysics Data System (ADS)

    Liang, Peng; Han, Peide; Yujie, Fan; Xing, Yupeng

    2014-03-01

    Effects of annealing on the properties of B-implanted Si for n-type solar cells were investigated by comparing rapid thermal annealing (RTA) and furnace annealing (FA) conditions. Profiles of boron and residual damage were theoretically simulated by technology computer aided design based on boron diffusion kinetics mechanism of transient enhanced diffusion. Compared with the rapid thermally annealed samples, the furnace annealed one showed the lowest remnant damage spectra obtained by channeling Rutherford backscattering spectrometry. Furthermore, the electrical properties of boron implanted samples were characterized by Hall and QSSPC technique, revealing a trend that increasing annealing thermal budget would result in higher active carrier density and lower emitter saturation current density. Finally, passivated emitter solar cells were fabricated to verify the influence of annealing conditions on the performances at device level. The champion cell with efficiency of 18.85% received FA for 20 min, whereas those with lower thermal budgets exhibited significantly lower performance. From diode parameters obtained by fitting dark I-V curves and short wavelength responses of internal quantum efficiency spectrum, it was found that B-implanted samples required an annealing temperature of at least 1000 °C together with a sufficiently long time. Rather low thermal budget such as RTA for dozens of seconds was far enough to realize full activation of boron and removal of implantation damage.

  14. Effect of thermal annealing on the kinetics of rehydroxylation of Eu3+:La2O3 nanocrystals.

    PubMed

    Méndez, Maria; Cesteros, Yolanda; Marsal, Lluís Francesc; Giguère, Alexandre; Drouin, Dominique; Salagre, Pilar; Formentín, Pilar; Pallarès, Josep; Aguiló, Magdalena; Díaz, Francesc; Carvajal, Joan Josep

    2012-06-04

    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.

  15. Dissolution kinetics of small amounts of oxygen in tantalum alloy T-111 and internal oxide displacement reactions during annealing

    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.

  16. Conversations with Long-Time Adult Educators.

    ERIC Educational Resources Information Center

    Maher, Patricia A.; Passmore, Denise

    A study conducted life history interviews with long-time adult educators regarding their career paths and choices, philosophical perspectives, influences in professional careers, changes witnessed in the field, and predictions about future trends in adult education. A literature review focused on the history of adult education in the United States…

  17. 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

  18. 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).

  19. Effect of the sample annealing temperature and sample crystallographic orientation on the charge kinetics of MgO single crystals subjected to keV electron irradiation.

    PubMed

    Boughariou, A; Damamme, G; Kallel, A

    2015-04-01

    This paper focuses on the effect of sample annealing temperature and crystallographic orientation on the secondary electron yield of MgO during charging by a defocused electron beam irradiation. The experimental results show that there are two regimes during the charging process that are better identified by plotting the logarithm of the secondary electron emission yield, lnσ, as function of the total trapped charge in the material QT. The impact of the annealing temperature and crystallographic orientation on the evolution of lnσ is presented here. The slope of the asymptotic regime of the curve lnσ as function of QT, expressed in cm(2) per trapped charge, is probably linked to the elementary cross section of electron-hole recombination, σhole, which controls the trapping evolution in the reach of the stationary flow regime.

  20. Comparison of crystallization kinetics in a-Si/Cu and a-Si/Al bilayer recording films under thermal annealing and pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Her, Yung-Chiun; Chen, Chih-Wei; Wu, Chun-Lin

    2006-06-01

    Under thermal annealing, the crystallization temperatures of a-Si in a-Si/Cu and a-Si/Al bilayer recording films were significantly reduced to around 485 and 357 °C, respectively, and the activation energies for crystallization were reduced to about 3.3 eV. The formation of Cu3Si phase prior to crystallization of a-Si was found to occur at around 175 °C in a-Si/Cu, while no Al silicide was observed in a-Si/Al before crystallization of a-Si. The reaction exponents for a-Si/Cu and a-Si/Al were determined to be around 1.8 and 1.6, respectively, corresponding to a crystallization process in which grain growth occurs with nucleation, and the nucleation rate decreases with the progress of grain growth. Under pulsed laser irradiation, the precipitation of Cu3Si phases and crystallization of a-Si were observed in a-Si/Cu, while the crystallization and reamorphization of a-Si took place sequentially in a-Si/Al. The reaction exponents for a-Si/Cu and a-Si/Al, determined to be about 2.0 and 2.2, respectively, are slightly higher than those under thermal annealing, indicating that the crystallization processes of a-Si/Cu and a-Si/Al under pulsed laser irradiation are similar to those under thermal annealing. However, the decrease of nucleation rate with the progress of grain growth is slower. At the same time, the activation energies for crystallization of a-Si/Cu and a-Si/Al, estimated to be about 0.18 and 0.22 eV, respectively, are nearly an order of magnitude lower than those under thermal annealing. This may be explained by the explosive crystallization of a-Si by mechanical impact, with a high power pulsed laser.

  1. Understanding memory effects in Li-ion batteries: evidence of a kinetic origin in TiO2 upon hydrogen annealing.

    PubMed

    Ventosa, E; Löffler, T; La Mantia, F; Schuhmann, W

    2016-09-20

    Memory effects in Li-ion battery materials have been explained on the basis of the thermodynamics of many-particles body, however the role of the (de-)intercalation kinetics is not yet clear. We demonstrate that kinetic aspects, specifically Li-ion mobility, are determining the magnitude of the memory effect in TiO2 by studying samples with different levels of oxygen vacancies.

  2. Short-time scale behavior modeling within long-time scale fuel cycle evaluations

    SciTech Connect

    Johnson, M.; Tsvetkov, P.; Lucas, S.

    2012-07-01

    Typically, short-time and long-time scales in nuclear energy system behavior are accounted for with entirely separate models. However, long-term changes in system characteristics do affect short-term transients through material variations. This paper presents an approach to consistently account for short-time scales within a nuclear system lifespan. The reported findings and developments are of significant importance for small modular reactors and other nuclear energy systems operating in autonomous modes. It is necessary to simulate the short time-scale kinetic behavior of the reactor as well as the long time-scale dynamics that occur with fuel burnup. The former is modeled using the point kinetics equations, while the latter is modeled by the Bateman equations. (authors)

  3. 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.

  4. Evidence for Kinetic Limitations as a Controlling Factor of Ge Pyramid Formation: a Study of Structural Features of Ge/Si(001) Wetting Layer Formed by Ge Deposition at Room Temperature Followed by Annealing at 600 °C

    NASA Astrophysics Data System (ADS)

    Storozhevykh, Mikhail S.; Arapkina, Larisa V.; Yuryev, Vladimir A.

    2015-07-01

    The article presents an experimental study of an issue of whether the formation of arrays of Ge quantum dots on the Si(001) surface is an equilibrium process or it is kinetically controlled. We deposited Ge on Si(001) at the room temperature and explored crystallization of the disordered Ge film as a result of annealing at 600 °C. The experiment has demonstrated that the Ge/Si(001) film formed in the conditions of an isolated system consists of the standard patched wetting layer and large droplike clusters of Ge rather than of huts or domes which appear when a film is grown in a flux of Ge atoms arriving on its surface. We conclude that the growth of the pyramids appearing at temperatures greater than 600 °C is controlled by kinetics rather than thermodynamic equilibrium whereas the wetting layer is an equilibrium structure. PACS: Primary 68.37.Ef; 68.55.Ac; 68.65.Hb; 81.07.Ta; 81.16.Dn

  5. [Long time regulation of arterial blood pressure: facts and hypothesis].

    PubMed

    Tsyrlin, V A

    2013-01-01

    The date about long time increase of blood pressure in conditions of excessive salt intake, constriction of renal artery in animals with initial low baroreceptor reflex is presented. Arterial hypertension in this case is accompanied by increase activity of sympathetic nervous system. The supposition that arterial baroreceptor reflex place a role in long time regulation of arterial blood pressure is expressed.

  6. Reduced annealing temperatures in silicon solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.

    1981-01-01

    Cells irradiated to a fluence of 5x10,000,000,000,000/square cm showed short circuit current on annealing at 200 C, with complete annealing occurring at 275 C. Cells irradiated to 100,000,000,000,000/square cm showed a reduction in annealing temperature from the usual 500 to 300 C. Annealing kinetic studies yield an activation energy of (1.5 + or - 2) eV for the low fluence, low temperature anneal. Comparison with activation energies previously obtained indicate that the presently obtained activation energy is consistent with the presence of either the divacancy or the carbon interstitial carbon substitutional pair, a result which agrees with the conclusion based on defect behavior in boron-doped silicon.

  7. Phase transformation and crystallization kinetics of a-Ge/Cu bilayer for blue-ray recording under thermal annealing and pulsed laser irradiation

    SciTech Connect

    Her, Yung-Chiun; Tu, Wei-Ting; Tsai, Ming-Hsin

    2012-02-15

    Similar phase formation and crystallization behaviors have been observed in the a-Ge/Cu bilayer under thermal annealing and pulsed laser irradiation. The Cu{sub 3}Ge phase would form prior to the crystallization of a-Ge. The crystallization temperature and activation energy for crystallization of a-Ge were reduced to 310 deg. C and 2.75 eV, respectively, due to the fast Ge diffusion in the already formed germanide phases. The reaction exponent m of {approx}2.0 for the a-Ge/Cu bilayer corresponds to a crystallization process in which grain growth occurs with nucleation, and the nucleation rate decreases with the progress of the grain growth process. Under pulsed laser irradiation, the maximum data-transfer-rates of 44, 56, 74, and 112 Mbit/s can be achieved in the write-once blue-ray disk at the recording powers of 3, 4, 5, and 6 mW, respectively. The a-Ge/Cu bilayer also demonstrated sufficient optical contrast and adequate absorptance for low power and high speed write-once blue-ray recording.

  8. The effect of vacuum annealing on corrosion resistance of titanium

    SciTech Connect

    Chikanov, V.N.; Peshkov, V.V.; Kireev, L.S.

    1994-09-01

    The effect of annealing on the corrosion resistance of OT4-1 sheet titanium in 25% HCl under various air pressures and self-evacuating conditions has been investigated. From the kinetic corrosion curves it follows that the least corrosion resistance of titanium is observed after vacuum annealing. Even low residual air pressure in a chamber improves corrosion resistance. The corrosion resistance of titanium decreases with vacuum-annealing time.

  9. Space Charge Models for Particle Tracking on Long Time Scales

    SciTech Connect

    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.

  10. 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.

  11. 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.

  12. Long time scaling behaviour for diffusion with resetting and memory

    NASA Astrophysics Data System (ADS)

    Boyer, Denis; Evans, Martin R.; Majumdar, Satya N.

    2017-02-01

    We consider a continuous-space and continuous-time diffusion process under resetting with memory. A particle resets to a position chosen from its trajectory in the past according to a memory kernel. Depending on the form of the memory kernel, we show analytically how different asymptotic behaviours of the variance of the particle position emerge at long times. These range from standard diffusive ({σ2}∼ t ) all the way to anomalous ultraslow growth {σ2}∼ \\ln \\ln t .

  13. Quantum simulated annealing

    NASA Astrophysics Data System (ADS)

    Boixo, Sergio; Somma, Rolando; Barnum, Howard

    2008-03-01

    We develop a quantum algorithm to solve combinatorial optimization problems through quantum simulation of a classical annealing process. Our algorithm combines techniques from quantum walks and quantum phase estimation, and can be viewed as the quantum analogue of the discrete-time Markov Chain Monte Carlo implementation of classical simulated annealing.

  14. Improved zircon fission-track annealing model based on reevaluation of annealing data

    SciTech Connect

    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.

  15. Improved zircon fission-track annealing model based on reevaluation of annealing data

    SciTech Connect

    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.

  16. 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.

  17. Storage life of parachutes -- long time material degradation

    SciTech Connect

    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.

  18. Long-time temperature drift in a commercial SQUID magnetometer

    NASA Astrophysics Data System (ADS)

    Kopelevich, Y.; Moehlecke, S.

    1995-02-01

    Temperature-calibration measurements using a Pt thermometer placed into a commercial SQUID magnetometer (Quantum Design) instead of the sample have shown a long-time (⩾ 8 h) temperature drift occurring in a SQUID body. It is found, that the amplitude of this drift depends on the measuring set temperature. We present also results of the mixed-state magnetic-moment measurements as a function of time and field performed on Bi 2Sr 2Ca 2Cu 3O 10 high- Tc superconductor, which illustrate that the magnetometer temperature drift essentially modifies the true magnetization behavior.

  19. How can the D-Wave machine exhibit long-time quantum behaviour

    NASA Astrophysics Data System (ADS)

    Drakova, D.; Doyen, G.

    2015-07-01

    Extensive experiments have demonstrated quantum behaviour in the long-time operation of the D-Wave quantum computer. The decoherence time of a single flux qubit is reported to be on the order of nanoseconds [1], which is much shorter than the time required to carry out a computation on the timescale of seconds [2, 3]. Previous judgements of whether the D-Wave device should be thought of as a quantum computer have been based on correlations of the input-output behaviour of the D-Wave machine with a quantum model, called simulated quantum annealing, or classical models, called simulated annealing and classical spin dynamics [4]. Explanations for a factor of 108 discrepancy between the single flux qubit decoherence time and the long-time coherent quantum behaviour of many integrated flux qubits of the D-Wave device have not been offered so far. In our contribution we investigate a model of four qubits with one qubit coupled to a phonon and (optionally) to environmental particles of high density of states, called gravonons. The calculations indicate that when no gravonons are present, the current in the qubit is flipped at some time and adiabatic evolution is discontinued. The time dependent wave functional becomes a non-correctable superposition of many excited states. The results demonstrate the possibility of effectively suppressing the current flip and allowing for continued adiabatic evolution when the entanglement to gravonons is included. This adiabatic evolution is, however, a coherent evolution in high dimensional spacetime and cannot be understood as a solution of Schrödinger's time dependent equation in 4 dimensional spacetime. Compared to Schrödinger's time development in 4D, the evolution is considerably slowed down, though still adiabatic. The properties of our model reflect correctly the experimentally found behaviour of the D-Wave machine and explain the factor of 108 discrepancy between decoherence time and quantum computation time. The observation

  20. Long-time dynamics through parallel trajectory splicing

    SciTech Connect

    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 Ag42Cu13 core–shell nanoparticles.

  1. Long-time dynamics through parallel trajectory splicing

    DOE PAGES

    Perez, Danny; Cubuk, Ekin D.; Waterland, Amos; ...

    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

  2. Collective variables for the study of long-time kinetics from molecular trajectories: theory and methods.

    PubMed

    Noé, Frank; Clementi, Cecilia

    2017-04-01

    Collective variables are an important concept to study high-dimensional dynamical systems, such as molecular dynamics of macromolecules, liquids, or polymers, in particular to define relevant metastable states and state-transition or phase-transition. Over the past decade, a rigorous mathematical theory has been formulated to define optimal collective variables to characterize slow dynamical processes. Here we review recent developments, including a variational principle to find optimal approximations to slow collective variables from simulation data, and algorithms such as the time-lagged independent component analysis. Using these concepts, a distance metric can be defined that quantifies how slowly molecular conformations interconvert. Extensions and open questions are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Influence of the prefactor to defect motion in α-Iron during long time scale simulations.

    PubMed

    Lazauskas, T; Kenny, S D; Smith, R

    2014-10-01

    We present a study of the influence of the prefactor in the Arrhenius equation for the long time scale motion of defects in α-Fe. It is shown that calculated prefactors vary widely between different defect types and it is thus important to determine these accurately when implementing on-the-fly kinetic Monte Carlo (otf-KMC) simulations. The results were verified by reproducing many events using Molecular Dynamics (MD) and Temperature-Accelerated Dynamics (TAD). The calculated prefactor was shown to increase the relative interstitial-vacancy diffusion rates by an order of magnitude compared to the assumption of a constant prefactor value and the ordering of the rate table for the interstitial defect migration mechanisms was also changed. In addition, low prefactor values were observed for the 4 interstitial dumbbells configuration with low barrier transitions.

  4. 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.

  5. A method for detecting changes in long time series

    SciTech Connect

    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``.

  6. 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.

  7. Toward Long-Time Simulation of Ballistic Gel Penetration

    NASA Astrophysics Data System (ADS)

    Lew, Adrian

    2011-06-01

    Ballistic gelatin is used as a surrogate for tissue to study the performance of armor and ammunition. Numerical simulations of impact and penetration of ammunition into ballistic gelatin have the potential to complement experimental work. Ballistic gelatin is a nearly incompressible material with viscoelastic features, which can recover from very large strains. As a result, a bullet penetrating the gel forms a large temporary cavity behind it, which at long times collapses to a very small one. This is a marked difference with the behavior of a fluid under similar circumstances. This poses strenuous challenges to current numerical tools, since an imperfect ``memory'' of the material elasticity leads to abnormally large remaining cavities. Reaching these later times in a simulation (~10 ms) is challenging to do in a reasonable time frame of a few hours. In this presentation I will first showcase the phenomena we are trying to capture through experiments in Permagel. Among others, these show the bullet rebounding after fully stopping, the importance of the gases inside the created cavity in its long-term dynamics, and the apparent appearance of mild plastic deformations and local melting in the gel. I will then discuss about the numerical tools we are creating to simulate it. I will show a suite of variational time-integration strategies able to reach long-time simulations with reasonable accuracy. Then, I will comment on novel automatic remeshing strategies we are creating, needed to simulate the large shear deformations in the gel while retaining accurate elastic recoveries. I will illustrate these ideas with simulations in highly parallel computing environments, and discuss the challenges we face to qualitatively recover a number of the experimental observations. Department of the Army Research Grant; contract/grant number: W911NF-07-2-0027.

  8. Infrared thermal annealing device

    NASA Astrophysics Data System (ADS)

    Gladys, M. J.; Clarke, I.; O'Connor, D. J.

    2003-07-01

    A device for annealing samples within an ultrahigh vacuum (UHV) scanning tunneling microscopy system was designed, constructed, and tested. The device is based on illuminating the sample with infrared radiation from outside the UHV chamber with a tungsten projector bulb. The apparatus uses an elliptical mirror to focus the beam through a sapphire viewport for low absorption. Experiments were conducted on clean Pd(100) and annealing temperatures in excess of 1000 K were easily reached.

  9. Recent progress of quantum annealing

    SciTech Connect

    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.

  10. Theoretical simulations of I-center annealing in KCl crystals

    NASA Astrophysics Data System (ADS)

    Popov, A. I.; Kotomin, E. A.; Eglitis, R. I.

    1995-12-01

    This paper focus on theory of diffusion-controlled annealing of the most mobile radiation-induced defects?I centers?in KCl crystals. The kinetics of annealing of pairs of close oppositely charged defects?α-I centers (arising as a result of the tunnelling recombination of primary Frenkel defects?F and H centers) and F-I centers (when H center trap electrons) is calculated taking into account defect diffusion and Coulomb/elastic interaction. Special attention is paid to the conditions under which multi-stage annealing arises; theoretical results are compared with the relevant experimental data.

  11. 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.

  12. Thermoluminescence properties of annealed natural quartz after beta irradiation.

    PubMed

    Yüksel, Mehmet; Dogan, Tamer; Unsal, Emre; Portakal, Z Gizem; Akca, Sibel; Yegingil, Zehra; Topaksu, Mustafa

    2016-12-01

    Here we investigated the effects of annealing, heating rate and fading (after annealing at 800 °C) on the thermoluminescence (TL) glow curves of natural quartz (NQ). All of the samples were annealed at different temperatures between 100 °C and 800 °C and then irradiated with a beta dose of about 34 Gray (Gy), in order to determine the effects of annealing treatments on TL peaks of natural quartz. TL glow curves of the samples were recorded. It was observed that the intensities of TL peaks were strongly sensitive to annealing temperatures at 800 °C. The heating rate and fading effect of TL peaks of natural quartz were examined for the annealed samples at 800 °C for 30 min. It was observed that the intensities of the TL peaks were differently affected from heating rate and fading. Additionally, TL kinetic parameters (activation energy, frequency factor and order of kinetics) of all peaks were determined for annealed samples using a computerized glow curve deconvolution (CGCD) method and Mathematica software. Copyright © 2016 John Wiley & Sons, Ltd.

  13. Long-time mean-square displacements in proteins.

    PubMed

    Vural, Derya; Hong, Liang; Smith, Jeremy C; Glyde, Henry R

    2013-11-01

    We propose a method for obtaining the intrinsic, long-time mean square displacement (MSD) of atoms and molecules in proteins from finite-time molecular dynamics (MD) simulations. Typical data from simulations are limited to times of 1 to 10 ns, and over this time period the calculated MSD continues to increase without a clear limiting value. The proposed method consists of fitting a model to MD simulation-derived values of the incoherent intermediate neutron scattering function, I(inc)(Q,t), for finite times. The infinite-time MSD, , appears as a parameter in the model and is determined by fits of the model to the finite-time I(inc)(Q,t). Specifically, the is defined in the usual way in terms of the Debye-Waller factor as I(Q,t=∞)=exp(-Q(2)/3). The method is illustrated by obtaining the intrinsic MSD of hydrated lysozyme powder (h=0.4 g water/g protein) over a wide temperature range. The intrinsic obtained from data out to 1 and to 10 ns is found to be the same. The intrinsic is approximately twice the value of the MSD that is reached in simulations after times of 1 ns which correspond to those observed using neutron instruments that have an energy resolution width of 1 μeV.

  14. Long-time mean-square displacements in proteins

    NASA Astrophysics Data System (ADS)

    Vural, Derya; Hong, Liang; Smith, Jeremy C.; Glyde, Henry R.

    2013-11-01

    We propose a method for obtaining the intrinsic, long-time mean square displacement (MSD) of atoms and molecules in proteins from finite-time molecular dynamics (MD) simulations. Typical data from simulations are limited to times of 1 to 10 ns, and over this time period the calculated MSD continues to increase without a clear limiting value. The proposed method consists of fitting a model to MD simulation-derived values of the incoherent intermediate neutron scattering function, Iinc(Q,t), for finite times. The infinite-time MSD, , appears as a parameter in the model and is determined by fits of the model to the finite-time Iinc(Q,t). Specifically, the is defined in the usual way in terms of the Debye-Waller factor as I(Q,t=∞)=exp(-Q2/3). The method is illustrated by obtaining the intrinsic MSD of hydrated lysozyme powder (h=0.4 g water/g protein) over a wide temperature range. The intrinsic obtained from data out to 1 and to 10 ns is found to be the same. The intrinsic is approximately twice the value of the MSD that is reached in simulations after times of 1 ns which correspond to those observed using neutron instruments that have an energy resolution width of 1 μeV.

  15. Annealing macromolecular crystals.

    PubMed

    Hanson, B Leif; Bunick, Gerard J

    2007-01-01

    The process of crystal annealing has been used to improve the quality of diffraction from crystals that would otherwise be discarded for displaying unsatisfactory diffraction after flash cooling. Although techniques and protocols vary, macromolecular crystals are annealed by warming the flash-cooled crystal, then flash cooling it again. To apply macromolecular crystal annealing, a flash-cooled crystal displaying unacceptably high mosaicity or diffraction from ice is removed from the goniometer and immediately placed in cryoprotectant buffer. The crystal is incubated in the buffer at either room temperature or the temperature at which the crystal was grown. After about 3 min, the crystal is remounted in the loop and flash cooled. In situ annealing techniques, where the cold stream is diverted and the crystal allowed to warm on the loop prior to flash cooling, are variations of annealing that appears to work best when large solvent channels are not present in the crystal lattice or the solvent content of the crystal is relatively low.

  16. Single-molecule binding experiments on long time scales.

    PubMed

    Elenko, Mark P; Szostak, Jack W; van Oijen, Antoine M

    2010-08-01

    We describe an approach for performing single-molecule binding experiments on time scales from hours to days, allowing for the observation of slower kinetics than have been previously investigated by single-molecule techniques. Total internal reflection fluorescence microscopy is used to image the binding of labeled ligand to molecules specifically coupled to the surface of an optically transparent flow cell. Long-duration experiments are enabled by ensuring sufficient positional, chemical, thermal, and image stability. Principal components of this experimental stability include illumination timing, solution replacement, and chemical treatment of solution to reduce photodamage and photobleaching; and autofocusing to correct for spatial drift.

  17. Long-time mean-square displacements in proteins

    SciTech Connect

    Vural, Derya; Hong, Liang; Smith, Jeremy C.; Glyde, Henry R.

    2013-11-08

    We propose a method for obtaining the intrinsic, long-time mean square displacement (MSD) of atoms and molecules in proteins from finite-time molecular dynamics (MD) simulations. Typical data from simulations are limited to times of 1 to 10 ns, and over this time period the calculated MSD continues to increase without a clear limiting value. The proposed method consists of fitting a model to MD simulation-derived values of the incoherent intermediate neutron scattering function, Iinc(Q,t), for finite times. The infinite-time MSD, r2 , appears as a parameter in the model and is determined by fits of the model to the finite-time Iinc(Q,t). Specifically, the r2 is defined in the usual way in terms of the Debye-Waller factor as I(Q,t = ∞) = exp( –Q2 r2 /3). The method is illustrated by obtaining the intrinsic MSD r2 of hydrated lysozyme powder (h = 0.4 g water/g protein) over a wide temperature range. The intrinsic r2 obtained from data out to 1 and to 10 ns is found to be the same. In conclusion, the intrinsic r2 is approximately twice the value of the MSD that is reached in simulations after times of 1 ns which correspond to those observed using neutron instruments that have an energy resolution width of 1 μeV.

  18. 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.

  19. 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

  20. Microstructural evolution during thermal annealing of ice-Ih

    NASA Astrophysics Data System (ADS)

    Hidas, Károly; Tommasi, Andréa; Mainprice, David; Chauve, Thomas; Barou, Fabrice; Montagnat, Maurine

    2017-06-01

    We studied the evolution of the microstructure of ice-Ih during static recrystallization by stepwise annealing experiments. We alternated thermal annealing and electron backscatter diffraction (EBSD) analyses on polycrystalline columnar ice pre-deformed in uniaxial compression at temperature of -7 °C to macroscopic strains of 3.0-5.2. Annealing experiments were carried out at -5 °C and -2 °C up to a maximum of 3.25 days, typically in 5-6 steps. EBSD crystal orientation maps obtained after each annealing step permit the description of microstructural changes. Decrease in average intragranular misorientation at the sample scale and modification of the misorientation across subgrain boundaries provide evidence for recovery from the earliest stages of annealing. This initial evolution is similar for all studied samples irrespective of their initial strain or annealing temperature. After an incubation period ≥1.5 h, recovery is accompanied by recrystallization (nucleation and grain boundary migration). Grain growth proceeds at the expense of domains with high intragranular misorientations, consuming first the most misorientated parts of primary grains. Grain growth kinetics fits the parabolic growth law with grain growth exponents in the range of 2.4-4.0. Deformation-induced tilt boundaries and kink bands may slow down grain boundary migration. They are stable features during early stages of static recrystallization, only erased by normal growth, which starts after >24 h of annealing.

  1. Gate Annealing of Cycling Endurance and Interface States for Highly Reliable Flash Memory

    NASA Astrophysics Data System (ADS)

    Kim, Nam-Kyeong; Hong, Se-Hee; Shim, Sa-Yong; Park, Min-Hee; Hwang, Kyung-Pil; Lee, Min-Kyu; Lee, Ju-Yeab; Woo, Won-Sic; Noh, Keum-Hwan; Lee, Hee-Kee; Om, Jae-Chul; Lee, Seok-Kiu; Bae, Gi-Hyun

    2008-01-01

    We report on superior cycling endurance due to a low interface trap density, which accounts for the high gate annealing temperature in flash memory. The interface trap density was characterized using a charge pumping method (CPM). The cycling VTH shift in an erase state value of 1.35 V at 850 °C temperature of an annealing, as measured on a 90-nm-technology 1-Mbit cell array, selected randomly from 1 Gbit cells, drops to less than 0.9 V after annealing at 950 °C. These superior electrical properties resulted from a complete relaxation of silicon interface trap charges due to a plasma-induced attack during gate annealing at temperatures over 950 °C for a long time. Therefore, the key factor for highly reliable endurance with cycling is believed to be the interface trap control of the thermal annealing carried out after gate etching.

  2. Effect of Annealing on the Thermoluminescence Properties of ZnO Nanophosphor

    NASA Astrophysics Data System (ADS)

    Kalita, J. M.; Wary, G.

    2017-02-01

    We report the effect of annealing on the thermoluminescence (TL) properties of zinc oxide (ZnO) nanophosphor. The sample was synthesised by a wet chemical process. The characterisation report shows that the size of the grains is within 123.0 nm-160.5 nm. TL measured at 2 K/s from a fresh un-annealed sample irradiated to 60 mGy shows a composite glow curve containing three peaks at 353.2 K, 429.1 K, and 455.3 K. On the other hand, samples annealed at 473 K and 573 K followed by irradiation to 60 mGy do not give TL. However, annealing at 673 K and 773 K followed by irradiation to the same dose produces a glow curve comprising two overlapping peaks at 352.3 K and 370.6 K. In the TL emission spectrum of un-annealed sample, two emission peaks were found in green ( 523 nm) and orange ( 620 nm) regions whereas in annealed samples, only a peak was found in the orange region ( 618 nm). Kinetic analysis shows that the activation energy corresponding to TL peaks at 353.2 K, 429.1 K, and 455.3 K of the un-annealed sample are 0.64 eV, 0.80 eV, and 1.20 eV whereas that of the peaks at 352.3 K and 370.6 K of 673 K and 773 K annealed samples are 0.64 eV and 0.70 eV, respectively. All peaks of un-annealed and annealed samples, except the one at 429.1 K of the un-annealed sample, follow first-order kinetics whereas the peak at 429.1 K follows second-order kinetics. Considering the kinetic and spectral features, an energy band model for ZnO nanophosphor has been proposed.

  3. Effect of Annealing on the Thermoluminescence Properties of ZnO Nanophosphor

    NASA Astrophysics Data System (ADS)

    Kalita, J. M.; Wary, G.

    2017-07-01

    We report the effect of annealing on the thermoluminescence (TL) properties of zinc oxide (ZnO) nanophosphor. The sample was synthesised by a wet chemical process. The characterisation report shows that the size of the grains is within 123.0 nm-160.5 nm. TL measured at 2 K/s from a fresh un-annealed sample irradiated to 60 mGy shows a composite glow curve containing three peaks at 353.2 K, 429.1 K, and 455.3 K. On the other hand, samples annealed at 473 K and 573 K followed by irradiation to 60 mGy do not give TL. However, annealing at 673 K and 773 K followed by irradiation to the same dose produces a glow curve comprising two overlapping peaks at 352.3 K and 370.6 K. In the TL emission spectrum of un-annealed sample, two emission peaks were found in green ( 523 nm) and orange ( 620 nm) regions whereas in annealed samples, only a peak was found in the orange region ( 618 nm). Kinetic analysis shows that the activation energy corresponding to TL peaks at 353.2 K, 429.1 K, and 455.3 K of the un-annealed sample are 0.64 eV, 0.80 eV, and 1.20 eV whereas that of the peaks at 352.3 K and 370.6 K of 673 K and 773 K annealed samples are 0.64 eV and 0.70 eV, respectively. All peaks of un-annealed and annealed samples, except the one at 429.1 K of the un-annealed sample, follow first-order kinetics whereas the peak at 429.1 K follows second-order kinetics. Considering the kinetic and spectral features, an energy band model for ZnO nanophosphor has been proposed.

  4. Velocity autocorrelation function in supercooled liquids: Long-time tails and anomalous shear-wave propagation

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Schober, H. R.; Voigtmann, Th.

    2016-12-01

    Molecular dynamic simulations are performed to reveal the long-time behavior of the velocity autocorrelation function (VAF) by utilizing the finite-size effect in a Lennard-Jones binary mixture. Whereas in normal liquids the classical positive t-3 /2 long-time tail is observed, we find in supercooled liquids a negative tail. It is strongly influenced by the transfer of the transverse current wave across the period boundary. The t-5 /2 decay of the negative long-time tail is confirmed in the spectrum of VAF. Modeling the long-time transverse current within a generalized Maxwell model, we reproduce the negative long-time tail of the VAF, but with a slower algebraic t-2 decay.

  5. 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.

  6. Molecular dynamics-based approaches for enhanced sampling of long-time, large-scale conformational changes in biomolecules

    PubMed Central

    2009-01-01

    The rugged energy landscape of biomolecules together with shortcomings of traditional molecular dynamics (MD) simulations require specialized methods for capturing large-scale, long-time configurational changes along with chemical dynamics behavior. In this report, MD-based methods for biomolecules are surveyed, involving modification of the potential, simulation protocol, or algorithm as well as global reformulations. While many of these methods are successful at probing the thermally accessible configuration space at the expense of altered kinetics, more sophisticated approaches like transition path sampling or Markov chain models are required to obtain mechanistic information, reaction pathways, and/or reaction rates. Divide-and-conquer methods for sampling and for piecing together reaction rate information are especially suitable for readily available computer cluster networks. Successful applications to biomolecules remain a challenge. PMID:20948633

  7. 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.

  8. Reactor vessel annealing system

    DOEpatents

    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).

  9. Fullerene formation and annealing

    SciTech Connect

    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.

  10. Long-Time Performance of a Stainless Steel Crossflow Filter with Simulated Hanford Tank Waste

    SciTech Connect

    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.

  11. Long time existence results for bore-type initial data for BBM-Boussinesq systems

    NASA Astrophysics Data System (ADS)

    Burtea, Cosmin

    2016-11-01

    In this paper we deal with the long time existence for the Cauchy problem associated to BBM-type Boussinesq systems of equations which are asymptotic models for long wave, small amplitude gravity surface water waves. As opposed to previous papers devoted to the long time existence issue, we consider initial data with nontrivial behavior at infinity which may be used to model bore propagation.

  12. Temperature effects on failure and annealing behavior in dynamic random access memories

    SciTech Connect

    Wilkin, N.O.; Self, C.T.

    1982-12-01

    Total dose failure levels and long time anneal characteristics of dynamic random access memories are measured while the devices are exercised under actual use conditions. These measurements were performed over the temperature range of -60 C to +70 C. The total dose failure levels are shown to decrease with increasing temperature. The anneal characteristics are shown to result in both an increase and decrease in the measured number of errors as a function of time. Finally a description of the test instrumentation and irradiation procedures are given.

  13. Temperature effects on failure and annealing behavior in dynamic random access memories

    NASA Astrophysics Data System (ADS)

    Wilkin, N. D.; Self, C. T.

    1982-12-01

    Total dose failure levels and long time anneal characteristics of dynamic random access memories are measured while the devices are exercised under actual use conditions. These measurements were performed over the temperature range of -60 C to +70 C. The total dose failure levels are shown to decrease with increasing temperature. The anneal characteristics are shown to result in both an increase and decrease in the measured number of errors as a function of time. Finally a description of the test instrumentation and irradiation procedures are given.

  14. Long Time, Large Scale Limit of the Wigner Transform for a System of Linear Oscillators in One Dimension

    NASA Astrophysics Data System (ADS)

    Komorowski, Tomasz; Stȩpień, Łukasz

    2012-07-01

    We consider the long time, large scale behavior of the Wigner transform W ɛ ( t, x, k) of the wave function corresponding to a discrete wave equation on a 1-d integer lattice, with a weak multiplicative noise. This model has been introduced in Basile et al. in Phys. Rev. Lett. 96 (2006) to describe a system of interacting linear oscillators with a weak noise that conserves locally the kinetic energy and the momentum. The kinetic limit for the Wigner transform has been shown in Basile et al. in Arch. Rat. Mech. 195(1):171-203 (2009). In the present paper we prove that in the unpinned case there exists γ 0>0 such that for any γ∈(0, γ 0] the weak limit of W ɛ ( t/ ɛ 3/2 γ , x/ ɛ γ , k), as ɛ≪1, satisfies a one dimensional fractional heat equation partialt W(t,x)=-hat{c}(-partialx2)^{3/4}W(t,x) with hat{c}>0. In the pinned case an analogous result can be claimed for W ɛ ( t/ ɛ 2 γ , x/ ɛ γ , k) but the limit satisfies then the usual heat equation.

  15. Resonant-state expansions and the long-time behavior of quantum decay

    SciTech Connect

    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.

  16. Universal long-time behavior of nuclear spin decays in a solid.

    PubMed

    Morgan, S W; Fine, B V; Saam, B

    2008-08-08

    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.

  17. Annealed Feynman-Kac Models

    NASA Astrophysics Data System (ADS)

    Moral, P. Del; Miclo, L.

    We analyze the concentration properties of an annealed Feynman-Kac model in distribution space. We characterize the concentration regions in terms of a variational problem involving a competition between the potential function and the mutation kernel. When the temperature parameter is evanescent with time and under appropriate hypotheses, the probability mass tends to concentrate on regions with minimal potential values. We give a precise description of these areas using non-linear semi-group contractions and large deviation techniques. We illustrate this annealed model with two physical interpretations related respectively to Markov motions in absorbing media and interacting measure valued processes.

  18. An Overview on Short and Long Time Relaxations in Glass-forming Supercooled Liquids

    NASA Astrophysics Data System (ADS)

    Karmakar, Smarajit

    2016-10-01

    Density fluctuations in supercooled liquids near the glass transition relax in multiple steps. The short time relaxation is known as β-relaxation and the final long time relaxation is called α-relaxation. It is believed that the long time α-relaxation is a cooperative phenomena associated with a growing length scales, whereas the short-time β-relaxation is often attributed to spatially local processes involving the rattling motion of a particle in the transient cage formed by its neighbors. Using molecular dynamics simulations of few model glass-forming liquids, we show that the β-relaxation is also cooperative in nature and the length scale extracted from the detailed finite-size scaling analysis of β-relaxation is found to be the same as that of the length scale that describes the spatial heterogeneity of local dynamics in the long-time α-relaxation regime. These results provide a clear connection between short-time dynamics and long-time structural relaxation in glass-forming liquids.

  19. 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…

  20. Annealing properties of rice starch.

    USDA-ARS?s Scientific Manuscript database

    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...

  1. Crystal microstructure of annealed nanocrystalline Chromium studied by synchrotron radiation diffraction

    NASA Astrophysics Data System (ADS)

    Wardecki, D.; Przeniosło, R.; Fitch, A. N.; Bukowski, M.; Hempelmann, R.

    2011-03-01

    The microstructure of electrodeposited nanocrystalline chromium (n-Cr) was studied by using synchrotron radiation (SR) diffraction, SEM, TEM, and EDX techniques. The as-prepared n-Cr samples show the standard bcc crystal structure of Cr with volume-averaged column lengths varying from 25 to 30 nm. The grain growth kinetics and the oxidation kinetics were studied by time resolved SR diffraction measurements with n-Cr samples annealed at 400, 600, and 800 °C. The grain growth process is relatively fast and it occurs within the first 10 min of annealing. The final crystallite size depends only on the annealing temperature and not on the initial grain size or on the oxygen content. The final volume-averaged column lengths observed after 50 min annealing are 40(4), 80(1), and 120(2) nm for temperatures 400, 600, and 800 °C, respectively. It is shown that annealing ex situ of n-Cr at 800 °C both under vacuum and in air gives a grain growth process with the same final crystallite sizes. The formation of the Cr2O3 and CrH phases is observed during annealing.

  2. 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.

  3. Long-time asymptotics of the Navier-Stokes and vorticity equations on R(3).

    PubMed

    Gallay, Thierry; Wayne, C Eugene

    2002-10-15

    We use the vorticity formulation to study the long-time behaviour of solutions to the Navier-Stokes equation on R(3). We assume that the initial vorticity is small and decays algebraically at infinity. After introducing self-similar variables, we compute the long-time asymptotics of the rescaled vorticity equation up to second order. Each term in the asymptotics is a self-similar divergence-free vector field with Gaussian decay at infinity, and the coefficients in the expansion can be determined by solving a finite system of ordinary differential equations. As a consequence of our results, we are able to characterize the set of solutions for which the velocity field satisfies ||u(.,t)||(L(2)) = o(t(-5/4)) as t-->+ infinity. In particular, we show that these solutions lie on a smooth invariant submanifold of codimension 11 in our function space.

  4. Long-time asymptotic behavior of the solutions of the Korteweg-De Vries equations

    SciTech Connect

    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.

  5. Efficient and accurate surface hopping for long time nonadiabatic quantum dynamics

    SciTech Connect

    Kelly, Aaron; Markland, Thomas E.

    2013-07-07

    The quantum-classical Liouville equation offers a rigorous approach to nonadiabatic quantum dynamics based on surface hopping type trajectories. However, in practice the applicability of this approach has been limited to short times owing to unfavorable numerical scaling. In this paper we show that this problem can be alleviated by combining it with a formally exact generalized quantum master equation treatment. This allows dramatic improvements in the efficiency of the approach in nonadiabatic regimes, making it computationally tractable to treat the quantum dynamics of complex systems for long times. We demonstrate our approach by applying it to a model of condensed phase charge transfer where our method is shown to be numerically exact in regimes where fewest-switches surface hopping and mean field approaches fail to obtain either the correct rates or long-time populations.

  6. Nonlinear Localized Dissipative Structures for Long-Time Solution of Wave Equation

    DTIC Science & Technology

    2009-07-01

    Fatemi, E., Engquist, B., and Osher, S., " Numerical Solution of the High Frequency Asymptotic Expansion for the Scalar Wave Equation ", Journal of...FINAL REPORT Grant Title: Nonlinear Localized Dissipative Structures for Long-Time Solution of Wave Equation By Dr. John Steinhoff Grant number... numerical method, "Wave Confinement" (WC), is developed to efficiently solve the linear wave equation . This is similar to the originally developed

  7. Date canning: a new approach for the long time preservation of date.

    PubMed

    Homayouni, Aziz; Azizi, Aslan; Keshtiban, Ata Khodavirdivand; Amini, Amir; Eslami, Ahad

    2015-04-01

    Dramatic growth in date (Phoenix dactylifera L.) production, makes it clear to apply proper methods to preserve this nutritious fruit for a long time. Numerous methods have been used to gain this goal in recent years that can be classified into non-thermal (fumigation, ozonation, irradiation, and packaging) and thermal (heat treatment, cold storage, dehydration, jam etc.) processing methods. In this paper these methods were reviewed and novel methods for date preservation were presented.

  8. Long-time states of inverse cascades in the presence of a maximum length scale

    NASA Technical Reports Server (NTRS)

    Hossain, M.; Matthaeus, W. H.; Montgomery, D.

    1983-01-01

    It is shown numerically, both for the two-dimensional Navier-Stokes (guiding-center plasma) equations and for two-dimensional magnetohydrodynamics, that the long-time asymptotic state in a forced inverse-cascade situation is one in which the spectrum is completely dominated by its own fundamental. The growth continues until the fundamental is dissipatively limited by its own dissipation rate.

  9. Strainrange partitioning life predictions of the long time Metal Properties Council creep-fatigue tests

    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.

  10. Accurate Long-Time Mixed Quantum-Classical Liouville Dynamics via the Transfer Tensor Method.

    PubMed

    Kananenka, Alexei A; Hsieh, Chang-Yu; Cao, Jianshu; Geva, Eitan

    2016-12-01

    In this Letter, we combine the recently introduced transfer tensor method with the mixed quantum-classical Liouville method. The resulting protocol provides an accurate, general, flexible and robust new route for simulating the reduced dynamics of the quantum subsystem for arbitrarily long times, starting with computationally feasible short-time mixed quantum-classical Liouville dynamical maps. The accuracy and feasibility of the methodology are demonstrated on a spin-boson benchmark model.

  11. Strainrange partitioning life predictions of the long time metal properties council creep-fatigue tests

    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.

  12. Long time behaviour of the nested ring diagrams in a quantum Lorentz gas

    NASA Astrophysics Data System (ADS)

    Hoogeveen, W.; Tjon, J. A.

    1983-05-01

    The contribution of the class of nested ring diagrams to the velocity autocorrelation function of a quantum Lorentz gas is considered. It is argued that this class gives rise to a t-( d/2+1) long time nail. This indicates that the t-( d/2) tail found recently by resummation of the leading order parts of these diagrams is removed by classes of less divergent contributions.

  13. Long-time coherence in fourth-order spin correlation functions

    NASA Astrophysics Data System (ADS)

    Fröhling, Nina; Anders, Frithjof B.

    2017-07-01

    We study the long-time decay of fourth-order electron spin correlation functions for an isolated singly charged semiconductor quantum dot. The electron spin dynamics is governed by the applied external magnetic field as well as the hyperfine interaction. While the long-time coherent oscillations in the correlation functions can be understood within a semiclassical approach treating the Overhauser field as frozen, the field dependent decay of its amplitude reported in different experiments cannot be explained by the central-spin model indicating the insufficiency of such a description. By incorporating the nuclear Zeeman splitting and the strain induced nuclear-electric quadrupolar interaction, we find the correct crossover from a fast decay in small magnetic fields to a slow exponential asymptotic in large magnetic fields. It originates from a competition between the quadrupolar interaction inducing an enhanced spin decay and the nuclear Zeeman term that suppressed the spin-flip processes. We are able to explain the magnetic field dependency of the characteristic long-time decay time T2 depending on the experimental setups. The calculated asymptotic values of T2=3 -4 μ s agree qualitatively well with the experimental data.

  14. Long-time tails in two-dimensional fluids by molecular dynamics

    NASA Astrophysics Data System (ADS)

    Ferrario, Mauro; Fionino, Antonino; Ciccotti, Giovanni

    1997-02-01

    We report on molecular dynamics simulation of long-time tails in the velocity and stress autocorrelation functions of a dense two-dimensional fluid. Large systems of the order of hundred thousand particles have been investigated, performing canonical averages over an ensemble of trajectories generated on a parallel computer. We find the well-known t-1 decay for the velocity autocorrelation function at two different densities of the fluid, together with a faster than linear time dependence for the mean-square displacement at long times. Although there are indications of an asymptotically faster decay, the data are not precise enough to discriminate whether the decay is in agreement with the (t lnt ) -1 prediction of consistent mode-coupling theory or it is due to finite size effects. No evidence, within the statistical errors, is found for a long-time tail in the stress autocorrelation function. This finding is in agreement with recent NEMD results [Hoover et al., Phys. Rev. E 51 (1995) 273; Gravina et al., Phys. Rev. E 52 (1995) 6123], who find an analytical dependence of the shear viscosity upon the shear rate with no evidence for divergence in the Green-Kubo value.

  15. 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.

  16. Enhanced reduction of silicon oxide thin films on silicon under electron beam annealing

    NASA Astrophysics Data System (ADS)

    Kennedy, J.; Leveneur, J.; Fang, F.; Markwitz, A.

    2014-08-01

    Electron beam annealing is an interesting alternative to other annealing methods as it can provide high temperature, rapid heating and cooling and low level of impurity as it operates under high vacuum environment. Furthermore swamping the materials with electrons can lead to dramatic changes in the component valence states with the mechanism involving oxido-reduction reactions. This is illustrated in the present case with the enhancement of the reduction of SiO2. Commercial thermally grown 100 and 400 nm SiO2 films on Si were annealed under three different environments: furnace annealing in open atmosphere with O2 flow, high vacuum furnace annealing and electron beam annealing. The reduction and oxidation of SiO2 films on Si are investigated using ion beam analysis. The validity of the measurement method was confirmed by measuring the oxidation rate through successive Rutherford backscattering spectrometry (RBS) measurements. The oxidation kinetics were observed to be in excellent agreement with literature values. At 1000 °C reduction of the SiO2 film is observed only with electron beam annealing. A model is proposed to explain the effect of the electron beam.

  17. Investigation of solvent annealing time dependence on morphology formation in polystyrene-block-polylactide thin films

    NASA Astrophysics Data System (ADS)

    Gnabasik, Ryan; Nelson, Gunnar; Baruth, Andrew

    2015-03-01

    Solvent vapor annealing exposes a block polymer film to the vapors of one or more solvents, swelling the film. This process increases polymer mobility and can direct a self-assembly process by tuning the surface energy. Despite its efficacy to produce well-ordered, periodic nanostructures, no standardized production scheme exists. This is primarily due to a lack of understanding the intricate role multiple, incommensurate parameters play. By analogy to thermal annealing of elemental solids, the time a thin film spends in an equilibrium solvent concentration is one factor that will dictate the degree of ordering. To elucidate, optimized annealing conditions for perpendicular cylinder forming polystyrene-block-polylactide exist at solvent concentrations just below the order-disorder transition, where the kinetic and thermal processes required for recrystallization and crystal growth are optimally fast (similar to thermal annealing). By use of a purpose-built, climate-controlled solvent annealing chamber, we map out the annealing time dependence for non-optimized solvent concentrations. Namely, at lower solvent concentrations, where mobility is limited, longer times are required for large lateral correlation lengths. In situ spectral reflectance monitors solvent concentration, regulated viaa mass-flow controlled solvent inlet, offering precision control over annealing. Atomic force microscopy, in conjunction with O2 plasma etching, provides 3-dimensional imaging of the nanoscale morphology. This work was funded by NASA Nebraska Space Grant.

  18. Quantum Speedup by Quantum Annealing

    NASA Astrophysics Data System (ADS)

    Somma, Rolando D.; Nagaj, Daniel; Kieferová, Mária

    2012-08-01

    We study the glued-trees problem from A. M. Childs, R. Cleve, E. Deotto, E. Farhi, S. Gutmann, and D. Spielman, in Proceedings of the 35th Annual ACM Symposium on Theory of Computing (ACM, San Diego, CA, 2003), p. 59. in the adiabatic model of quantum computing and provide an annealing schedule to solve an oracular problem exponentially faster than classically possible. The Hamiltonians involved in the quantum annealing do not suffer from the so-called sign problem. Unlike the typical scenario, our schedule is efficient even though the minimum energy gap of the Hamiltonians is exponentially small in the problem size. We discuss generalizations based on initial-state randomization to avoid some slowdowns in adiabatic quantum computing due to small gaps.

  19. 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.

  20. 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.

  1. Quantum annealing with antiferromagnetic fluctuations.

    PubMed

    Seki, Yuya; Nishimori, Hidetoshi

    2012-05-01

    We introduce antiferromagnetic quantum fluctuations into quantum annealing in addition to the conventional transverse-field term. We apply this method to the infinite-range ferromagnetic p-spin model, for which the conventional quantum annealing has been shown to have difficulties in finding the ground state efficiently due to a first-order transition. We study the phase diagram of this system both analytically and numerically. Using the static approximation, we find that there exists a quantum path to reach the final ground state from the trivial initial state that avoids first-order transitions for intermediate values of p. We also study numerically the energy gap between the ground state and the first excited state and find evidence for intermediate values of p for which the time complexity scales polynomially with the system size at a second-order transition point along the quantum path that avoids first-order transitions. These results suggest that quantum annealing would be able to solve this problem with intermediate values of p efficiently, in contrast to the case with only simple transverse-field fluctuations.

  2. Graphene Oxide Annealing Procedures for Graphene-Based Supercapacitors

    DTIC Science & Technology

    2015-09-01

    These procedures is referred to as dry/ wet anneal, wet anneal, and solvent-assisted wetting . 3 2.3 Dry/ Wet Anneal A dry/ wet anneal is ......GO, and again after the thermal reduction. The rGO mass in the cell (for dry anneal and dry/ wet anneal only) is calculated by subtracting the current

  3. 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.

  4. 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

  5. Conversion of basal plane dislocations to threading edge dislocations in 4H-SiC epilayers by high temperature annealing

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; Tsuchida, Hidekazu

    2012-06-01

    Conversion of basal plane dislocations (BPDs) to threading edge dislocations (TEDs) is found in 4H-SiC epilayers after being annealed simply at high temperatures. Grazing incidence reflection synchrotron x-ray topography for the dislocations in the epilayers before and after annealing confirmed that some of the BPDs in the epilayers had converted to TEDs from the epilayer surface by the annealing. Observations on the dislocation behavior during annealing are explained in detail, and the mechanism of BPD conversion is discussed. It is argued that the conversion proceeds through the cross slip of constricted BPD segments towards the surface on the prismatic plane driven by the image force as well as TED glide driven by the line tension. Certain kinetic processes during annealing may facilitate the formation of constriction.

  6. 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.

  7. 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.

  8. Precision blood-leak detector with high long-time stability

    NASA Astrophysics Data System (ADS)

    Georgiadis, Christos; Kleuver, Wolfram

    1999-11-01

    With this publication a precision blood-leak-detector is presented. The blood-leak-detector is used for recognition of fractures in the dialyzer of a kidney-machine. It has to detect safely a blood flow of ml/min to exclude any risk for the patient. A lot of systems exist for blood-leak-detection. All of them use the same principle. They detect the light absorption in the dialyze fluid. The actual used detectors are inferior to the new developed sensor in resolution and long-time stability. Regular test of the existing systems and high failure rates are responsible for the high maintenance.

  9. On the Long Time Simulation of Reaction-Diffusion Equations with Delay

    PubMed Central

    Zhang, Chengjian

    2014-01-01

    For a consistent numerical method to be practically useful, it is widely accepted that it must preserve the asymptotic stability of the original continuous problem. However, in this study, we show that it may lead to unreliable numerical solutions in long time simulation even if a classical numerical method gives a larger stability region than that of the original continuous problem. Some numerical experiments on the reaction-diffusion equations with delay are presented to confirm our findings. Finally, some open problems on the subject are proposed. PMID:24672296

  10. Single-Facility Scheduling over Long Time Horizons by Logic-Based Benders Decomposition

    NASA Astrophysics Data System (ADS)

    Coban, Elvin; Hooker, John N.

    Logic-based Benders decomposition can combine mixed integer programming and constraint programming to solve planning and scheduling problems much faster than either method alone. We find that a similar technique can be beneficial for solving pure scheduling problems as the problem size scales up. We solve single-facility non-preemptive scheduling problems with time windows and long time horizons that are divided into segments separated by shutdown times (such as weekends). The objective is to find feasible solutions, minimize makespan, or minimize total tardiness.

  11. Self-organized criticality, long-time correlations, and the standard transport paradigm

    SciTech Connect

    Krommes, J.A.

    2000-02-11

    Some aspects of low-frequency, long-wavelength fluctuations are considered. A stochastic model is used to show that power-law time correlations need not arise from self-organized criticality. A formula for the frequency spectrum of uncorrelated, overlapping avalanches is shown to be a special case of the spectral balance equation of renormalized statistical turbulence theory. It is argued that there need be no contradiction between the presence of long-time correlations and the existence of local transport coefficients.

  12. On long-time algebraic and exponential instabilities found in linear dispersive flows

    NASA Astrophysics Data System (ADS)

    Barlow, Nathaniel; King, Kristina; Zaretzky, Paula; Cromer, Michael; Weinstein, Steven

    2016-11-01

    A physically-motivated class of partial differential equations that describes the response of a system to disturbances is examined. Morphological differences are identified between system responses that exhibit algebraic growth and the more typical case of exponential growth. Specifically, the propagation characteristics of the response are examined in the context of spatio-temporal hydrodynamic stability theory. One key attribute of predicted algebraically growing solutions is the prevalence of transient growth in almost all of the response, with the long-time growth occurring asymptotically at precisely one wave speed.

  13. Time-dependent pseudo Jahn-Teller effect: Phonon-mediated long-time nonadiabatic relaxation

    SciTech Connect

    Vaikjärv, Taavi Hizhnyakov, Vladimir

    2014-02-14

    Our system under theoretical consideration is an impurity center in a solid. We are considering the time evolution of the center in a quasi-degenerate electronic state. Strict quantum mechanical treatment of non-adiabadicity of the state is used. The phonon continuum is taken into account in addition to the vibration responsible for the main vibronic interaction. To describe the dynamics of the excited state a master equation has been used. The theoretical considerations are illustrated by the calculations of the long-time evolution of vibrations of the center, influenced by the emission of phonons to the bulk.

  14. Morphology control in mesoporous carbon films using solvent vapor annealing.

    PubMed

    Qiang, Zhe; Xue, Jiachen; Cavicchi, Kevin A; Vogt, Bryan D

    2013-03-12

    Ordered mesoporous (2-50 nm) carbon films were fabricated using cooperative self-assembly of a phenolic resin oligomer with a novel block copolymer template (poly(styrene-block-N,N-dimethyl-n-octadecylamine p-styrenesulfonate), (PS-b-PSS-DMODA)) synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Due to the high Tg of the PS segment and the strong interactions between the phenolic resin and the PSS-DMODA, the segmental rearrangement is kinetically hindered relative to the cross-linking rate of the phenolic resin, which inhibits long-range ordering and yields a poorly ordered mesoporous carbon with a broad pore size distribution. However, relatively short exposure (2 h) to controlled vapor pressures of methyl ethyl ketone (MEK) yields significant improvements in the long-range ordering and narrows the pore size distribution. The average pore size increases as the solvent vapor pressure during annealing increases, but an upper limit of p/p0 = 0.85 exists above which the films dewet rapidly during solvent vapor annealing. This approach can be extended using mesityl oxide, which has similar solvent qualities to MEK, but is not easily removed by ambient air drying after solvent annealing. This residual solvent can impact the morphology that develops during cross-linking of the films. These results illustrate the ability to fine-tune the mesostructure of ordered mesoporous carbon films through simple changes in the processing without any compositional changes in the initial cast film.

  15. Thermal stability of dopants in laser annealed silicon

    NASA Astrophysics Data System (ADS)

    Takamura, Y.; Jain, S. H.; Griffin, P. B.; Plummer, J. D.

    2002-07-01

    As semiconductor device dimensions continue to decrease, the main challenge in the area of junction formation involves decreasing the junction depth while simultaneously decreasing the sheet resistance. Laser annealing is being investigated as an alternative to rapid thermal annealing to repair the damage from ion implantation and to activate the dopants. With this technique, uniform, box-shaped profiles are obtained, with dopant concentrations that can exceed equilibrium solubility limits at normal processing temperatures. Unfortunately, these super-saturated dopant concentrations exist in a metastable state and deactivate upon further thermal processing. In this article, we describe a comprehensive study of the deactivation kinetics of common dopants (P, B, and Sb) across a range of concentrations and annealing conditions. For comparison, As deactivation data from the literature is also presented. P and As deactivate substantially at temperatures as low as 500 degC, while Sb at moderate concentrations and B remain fully active until 700 to 800 degC. It is proposed that As and P deactivate through the formation of small dopant-defect clusters while B deactivates through precipitation. The proximity to the surface is shown to be a second-order effect.

  16. Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

    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.

  17. 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.

  18. Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

    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.

  19. Effects of Hydrogen Annealing, Sulfur Segregation and Diffusion on the Cyclic Oxidation Resistance of Superalloys: a Review

    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.

  20. Short- and Long- Time Transport Structures in a Three Dimensional Time Dependent Flow

    NASA Astrophysics Data System (ADS)

    Chabreyrie, Rodolphe; Llewellyn Smith, Stefan

    2012-11-01

    Lagrangian transport structures for three-dimensional and time-dependent fluid flows are of great interest in numerous applications, particularly for geophysical or oceanic flows. In such flows, chaotic transport and mixing can play important environmental and ecological roles, for examples in pollution spills or plankton migration. In such flows, where simulations or observations are typically available only over a short time, understanding the difference between short-time and long-time transport structures is critical. In this talk, we use a set of classical (i.e. Poincaré section, Lyapunov exponent) and alternative (i.e. finite time Lyapunov exponent, Lagrangian coherent structures) tools from dynamical systems theory that analyze chaotic transport both qualitatively and quantitatively. With this set of tools we are able to reveal, identify and highlight differences between short- and long-time transport structures inside a flow composed of a primary horizontal contra-rotating vortex chain, small lateral oscillations and a weak Ekman pumping. The difference is mainly the existence of regular or extremely slowly developing chaotic regions that are only present at short time. This research was funded by the ONR MURI Dynamical Systems Theory and Lagrangian Data Assimilation in 3D+1 Geophysical Fluid Dynamics.

  1. [Improving data warehouse environments for efficient analysis of long time-series data].

    PubMed

    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.

  2. Long-time visual functional results of cataract surgery on low vision patients

    PubMed Central

    Mönestam, Eva I; Lundqvist, Britta M; Jonsson, Åsa C

    2008-01-01

    Background/aims To assess longitudinal 5-year results of cataract surgery on low vision patients. Methods In this prospective, long-time, observational case-series, we report the outcome regarding the subjective visual function (n = 35) assessed by a visual function questionnaire (VF-14) and the visual acuity (n = 30) of surviving low vision patients 5 years after surgery. We compare with data recorded on the same patients before surgery and 4 months postoperatively. Results Five years after surgery, 57% had unchanged or better VF-14 score compared with preoperatively, and 37% compared with postoperatively. Maculopathy patients had a significantly larger deterioration 5 years after surgery compared with postoperatively (40.2 versus 51.7, p = 0.004), but for the glaucoma patients there was no significant change (52.6 versus 53.1). There were no significant associations between age of the patient and change in VF-14 score or change in visual acuity 5 years after surgery, neither compared with before surgery nor postoperatively. Conclusion Results suggest a favorable functional outcome 5 years after cataract surgery on most low-vision patients. Glaucoma patients have a more stable outcome than patients with macular degeneration. The severity of the disease-process for each individual patient might be the most important factor affecting the long-time results. PMID:19668403

  3. Methods for serial analysis of long time series in the study of biological rhythms

    PubMed Central

    2013-01-01

    When one is faced with the analysis of long time series, one often finds that the characteristics of circadian rhythms vary with time throughout the series. To cope with this situation, the whole series can be fragmented into successive sections which are analyzed one after the other, which constitutes a serial analysis. This article discusses serial analysis techniques, beginning with the characteristics that the sections must have and how they can affect the results. After consideration of the effects of some simple filters, different types of serial analysis are discussed systematically according to the variable analyzed or the estimated parameters: scalar magnitudes, angular magnitudes (time or phase), magnitudes related to frequencies (or periods), periodograms, and derived and / or special magnitudes and variables. The use of wavelet analysis and convolutions in long time series is also discussed. In all cases the fundamentals of each method are exposed, jointly with practical considerations and graphic examples. The final section provides information about software available to perform this type of analysis. PMID:23867052

  4. Universal Long-Time Behavior of Nuclear Spin Decays in Solid Hyperpolarized Xenon

    NASA Astrophysics Data System (ADS)

    Saam, Brian; Morgan, Steven W.; Fine, Boris V.

    2009-05-01

    We have observed a universal long-time behavior of ^129Xe FIDs and solid echoes in polycrystalline hyperpolarized xenon at 77 K. In all cases, a decay of the form F(t) = Ae^-γt(φt + φ) sets in after just a few times T2; the behavior is universal in the sense that the decay constant γ and the beat frequency φ, which together characterize the long-time decay are the same for the FID and for solid echoes having different interpulse delay times τ. These findings reveal a fundamental property of nuclear spin dynamics and are thus relevant to theoretical efforts that have been ongoing for decades to understand NMR lineshapes in solids. Moreover, the functional form and universality of this behavior were previously predicted on the basis of analogy with resonances in classical chaotic systems [2]. While we expect this behavior to be characteristic of nuclear-spin solids in general, ^129Xe is an ideal system to examine it with high precision because of the relatively long T2 1 ms and because spin-exchange optical pumping can be used to achieve greatly enhanced magnetization, allowing precise examination of the decay over 3-4 orders of magnitude. [1] S.W. Morgan, et al., PRL 101, 067601 (2008). [2] B.V. Fine, PRL 94, 247601 (2005).

  5. Long-time uncertainty propagation using generalized polynomial chaos and flow map composition

    SciTech Connect

    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.

  6. A dynamical polynomial chaos approach for long-time evolution of SPDEs

    NASA Astrophysics Data System (ADS)

    Ozen, H. Cagan; Bal, Guillaume

    2017-08-01

    We propose a Dynamical generalized Polynomial Chaos (DgPC) method to solve time-dependent stochastic partial differential equations (SPDEs) with white noise forcing. The long-time simulation of SPDE solutions by Polynomial Chaos (PC) methods is notoriously difficult as the dimension of the stochastic variables increases linearly with time. Exploiting the Markovian property of white noise, DgPC [1] implements a restart procedure that allows us to expand solutions at future times in terms of orthogonal polynomials of the measure describing the solution at a given time and the future white noise. The dimension of the representation is kept minimal by application of a Karhunen-Loeve (KL) expansion. Using frequent restarts and low degree polynomials on sparse multi-index sets, the method allows us to perform long time simulations, including the calculation of invariant measures for systems which possess one. We apply the method to the numerical simulation of stochastic Burgers and Navier-Stokes equations with white noise forcing. Our method also allows us to incorporate time-independent random coefficients such as a random viscosity. We propose several numerical simulations and show that the algorithm compares favorably with standard Monte Carlo methods.

  7. Experimental signature of programmable quantum annealing.

    PubMed

    Boixo, Sergio; Albash, Tameem; Spedalieri, Federico M; Chancellor, Nicholas; Lidar, Daniel A

    2013-01-01

    Quantum annealing is a general strategy for solving difficult optimization problems with the aid of quantum adiabatic evolution. Both analytical and numerical evidence suggests that under idealized, closed system conditions, quantum annealing can outperform classical thermalization-based algorithms such as simulated annealing. Current engineered quantum annealing devices have a decoherence timescale which is orders of magnitude shorter than the adiabatic evolution time. Do they effectively perform classical thermalization when coupled to a decohering thermal environment? Here we present an experimental signature which is consistent with quantum annealing, and at the same time inconsistent with classical thermalization. Our experiment uses groups of eight superconducting flux qubits with programmable spin-spin couplings, embedded on a commercially available chip with >100 functional qubits. This suggests that programmable quantum devices, scalable with current superconducting technology, implement quantum annealing with a surprising robustness against noise and imperfections.

  8. Semantic search via concept annealing

    NASA Astrophysics Data System (ADS)

    Dunkelberger, Kirk A.

    2007-04-01

    Annealing, in metallurgy and materials science, is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. We define concept annealing as a lexical, syntactic, and semantic expansion capability (the removal of defects and the internal stresses that cause term- and phrase-based search failure) coupled with a directed contraction capability (semantically-related terms, queries, and concepts nucleate and grow to replace those originally deformed by internal stresses). These two capabilities are tied together in a control loop mediated by the information retrieval precision and recall metrics coupled with intuition provided by the operator. The specific representations developed have been targeted at facilitating highly efficient and effective semantic indexing and searching. This new generation of Find capability enables additional processing (i.e. all-source tracking, relationship extraction, and total system resource management) at rates, precisions, and accuracies previously considered infeasible. In a recent experiment, an order magnitude reduction in time to actionable intelligence and nearly three orderss magnitude reduction in false alarm rate was achieved.

  9. 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.

  10. 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.

  11. Photoluminescence of annealed biomimetic apatites.

    PubMed

    Zollfrank, Cordt; Müller, Lenka; Greil, Peter; Müller, Frank A

    2005-11-01

    Biomimetic apatite coatings are widely used in orthopaedic applications to provide bioinert material surfaces with bioactive behaviour by means of initiating bone growth at the implant surface. In this study we manufactured biomimetic calcium phosphate coatings consisting of a calcium deficient carbonated apatite by immersing activated titanium platelets into simulated body fluid. The development of the crystal phases was monitored by X-ray diffractometry in addition to Fourier-transform infrared spectroscopy. The microstructure of the biomimetic apatites and phase composition was analysed using scanning and transmission electron microscopy as well as attached energy dispersive X-ray spectrometry. The samples were annealed in air yielding in an inherent luminescence of the biomimetic apatite up to temperatures of 600 degrees C. The photo-induced emission spectra were recorded in the range from 400 to 750 nm at excitation wavelengths ranging 310-450 nm. A blue (437 nm) and a green (561 nm) emission were found between 200 and 600 degrees C visually appearing white. Photoluminescence of annealed biomimetic apatites might be of interest for histological probing and monitoring of bone re-modelling. The results are discussed in terms of chemical and crystallographic changes in the calcium phosphate layer during heat treatment.

  12. Temperature Scaling Law for Quantum Annealing Optimizers

    NASA Astrophysics Data System (ADS)

    Albash, Tameem; Martin-Mayor, Victor; Hen, Itay

    2017-09-01

    Physical implementations of quantum annealing unavoidably operate at finite temperatures. We point to a fundamental limitation of fixed finite temperature quantum annealers that prevents them from functioning as competitive scalable optimizers and show that to serve as optimizers annealer temperatures must be appropriately scaled down with problem size. We derive a temperature scaling law dictating that temperature must drop at the very least in a logarithmic manner but also possibly as a power law with problem size. We corroborate our results by experiment and simulations and discuss the implications of these to practical annealers.

  13. 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.

  14. Combustion-Assisted Photonic Annealing of Printable Graphene Inks via Exothermic Binders.

    PubMed

    Secor, Ethan B; Gao, Theodore Z; Dos Santos, Manuel H; Wallace, Shay G; Putz, Karl W; Hersam, Mark C

    2017-09-06

    High-throughput and low-temperature processing of high-performance nanomaterial inks is an important technical challenge for large-area, flexible printed electronics. In this report, we demonstrate nitrocellulose as an exothermic binder for photonic annealing of conductive graphene inks, leveraging the rapid decomposition kinetics and built-in energy of nitrocellulose to enable versatile process integration. This strategy results in superlative electrical properties that are comparable to extended thermal annealing at 350 °C, using a pulsed light process that is compatible with thermally sensitive substrates. The resulting porous microstructure and broad liquid-phase patterning compatibility are exploited for printed graphene microsupercapacitors on paper-based substrates.

  15. Communication: Influence of external static and alternating electric fields on water from long-time non-equilibrium ab initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Futera, Zdenek; English, Niall J.

    2017-07-01

    The response of water to externally applied electric fields is of central relevance in the modern world, where many extraneous electric fields are ubiquitous. Historically, the application of external fields in non-equilibrium molecular dynamics has been restricted, by and large, to relatively inexpensive, more or less sophisticated, empirical models. Here, we report long-time non-equilibrium ab initio molecular dynamics in both static and oscillating (time-dependent) external electric fields, therefore opening up a new vista in rigorous studies of electric-field effects on dynamical systems with the full arsenal of electronic-structure methods. In so doing, we apply this to liquid water with state-of-the-art non-local treatment of dispersion, and we compute a range of field effects on structural and dynamical properties, such as diffusivities and hydrogen-bond kinetics.

  16. Kinetic Atom.

    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)

  17. Kinetic Atom.

    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)

  18. Long time stability of small-amplitude Breathers in a mixed FPU-KG model

    NASA Astrophysics Data System (ADS)

    Paleari, Simone; Penati, Tiziano

    2016-12-01

    In the limit of small couplings in the nearest neighbor interaction, and small total energy, we apply the resonant normal form result of a previous paper of ours to a finite but arbitrarily large mixed Fermi-Pasta-Ulam Klein-Gordon chain, i.e., with both linear and nonlinear terms in both the on-site and interaction potential, with periodic boundary conditions. An existence and orbital stability result for Breathers of such a normal form, which turns out to be a generalized discrete nonlinear Schrödinger model with exponentially decaying all neighbor interactions, is first proved. Exploiting such a result as an intermediate step, a long time stability theorem for the true Breathers of the KG and FPU-KG models, in the anti-continuous limit, is proven.

  19. 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.

  20. 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.

  1. Long-time stability of breathers in Hamiltonian { P }{ T }-symmetric lattices

    NASA Astrophysics Data System (ADS)

    Chernyavsky, Alexander; Pelinovsky, Dmitry E.

    2016-11-01

    We consider the Hamiltonian version of a { P }{ T }-symmetric lattice that describes dynamics of coupled pendula under a resonant periodic force. Using the asymptotic limit of a weak coupling between the pendula, we prove the nonlinear long-time stability of breathers (time-periodic solutions localized in the lattice) by using the Lyapunov method. Breathers are saddle points of the extended energy function, which are located between the continuous bands of positive and negative energy. Despite not rendering the energy minima, the breathers are shown to admit an approximate Lyapunov function which helps us to estimate evolution of perturbations on a long but finite time interval. The nonlinear stability analysis becomes possible for the { P }{ T }-symmetric lattice only because of the existence of a Hamiltonian structure.

  2. The Clodia database: a long time series of fishery data from the Adriatic Sea.

    PubMed

    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.

  3. Long-time average spectrograms of dysphonic voices before and after therapy.

    PubMed

    Kitzing, P; Akerlund, L

    1993-01-01

    Tape recordings before and after successful voice therapy from 174 subjects with non-organic voice disorders (functional dysphonia) were analysed by long-time averaged voice spectrograms (LTAS). In female as well as in male voices there was a statistically significant increase in level in the first formant region of the spectra. In the female voices there was also an increase in level in the region of the fundamental. The LTAS were compared to the results of a perceptual evaluation of the voice qualities by a small group of expert listeners. There was no significant change of the LTAS in voices with negligible amelioration after therapy. In the voices, where the change after therapy was perceptually rated to be considerable, the LTAS showed only an increase in intensity, but the general configuration of the spectral envelope remained unchanged. There was only a weakly positive correlation between the quality ratings and parameters of the spectra.

  4. Zinc oxide nanorod field effect transistor for long-time cellular force measurement

    PubMed Central

    Zong, Xianli; Zhu, Rong

    2017-01-01

    Mechanical forces generated by cells are known to influence a vast range of cellular functions ranging from receptor signaling and transcription to differentiation and proliferation. We report a novel measurement approach using zinc oxide nanorods as a peeping transducer to monitor dynamic mechanical behavior of cellular traction on surrounding substrate. We develop a ZnO nanorod field effect transistor (FET) as an ultrasensitive force sensor to realize long-time, unstained, and in-situ detection of cell cycle phases, including attachment, spread, and mitosis. Excellent biocompatibility and ultra-sensitivity of the biomechanical measurement is ensured by coating a parylene film on the FET sensor as a concealment, which provides complete electronic isolation between the sensor and cell. With unique features of ultra-sensitivity, label-free, easy handling, and good biocompatibility, the force sensor allows feasible for tracking cellular dynamics in physiological contexts and understanding their contribution to biological processes. PMID:28272551

  5. Lysozyme adsorption on polyethylene surfaces: why are long time simulations needed?

    PubMed Central

    Wei, Tao; Carignano, Marcelo A.; Szleifer, Igal

    2011-01-01

    The adsorption of lysozyme onto a polyethylene (PE) surface in an aqueous environment was investigated with molecular dynamics (MD) simulation. The adsorption can be divided into three processes: diffusion to the surface, dehydration induced by hydrophobic surface-protein interactions followed by denaturation. The dehydration process is very long and takes around 70ns. Structural deformations start soon after the protein reaches the surface and continue during the whole trajectory. The hydrophobic residues are slowly driven toward the surface, inducing changes in the protein’s secondary structure. The protein secondary structural components near the surface are more disturbed than those farther away from the surface. The lysozyme is adsorbed with its long axis parallel to the surface and displays an anisotropic mobility on the surface probably due to the intrinsic structure of the PE surface. Our study demonstrates the need of long-time atomistic simulation in order to gain a complete understanding of the adsorption process. PMID:21846132

  6. 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.

  7. Transient aggregation and long-time diffusion of bacterial suspensions in time periodic flows

    NASA Astrophysics Data System (ADS)

    Qin, Boyang; Winter, Rebecca; Gurjar, Madhura; Gagnon, David; Patteson, Alison; Arratia, Paulo

    2016-11-01

    In this talk, the transport dynamics of swimming bacteria in time-periodic flows is investigated in experiments and simulations. Experiments are performed by introducing swimming bacteria (Vibrio cholerae) in a low Reynolds number, two-dimensional flow driven electromagnetically. We observe two distinct transport regimes: (i) entrapment of bacteria inside vortex and near elliptic points and (ii) aggregation and subsequent transport along the flow manifolds. These time-dependent behaviors are set by the interaction between swimmer kinematics (e.g. speed, tumbling frequency, etc) and flow properties. Numerical simulation using a stochastic Langevin model are able to capture the main experimental results including the entrapment of bacteria near elliptic points and the rapid spreading along manifolds. Results show a significant reduction in long-time effective diffusion of the swimmer as vortex strength is increased. The conditions for bacterial entrapment in vortex flows are discussed.

  8. Long-time behavior of spreading solutions of Schrödinger and diffusion equations.

    PubMed

    Anteneodo, C; Dias, J C; Mendes, R S

    2006-05-01

    We investigate the asymptotic time behavior of the solutions of a large class of linear differential equations that generalize the free-particle Schrödinger and diffusion equations, containing the standard ones as particular cases. We find general scalings that depend only on characteristic features of both the arbitrary initial condition and the Green function associated with the evolution equation. Basically, the amplitude of a long-time solution can be expressed in terms of low order moments of the initial condition (if finite) and low order spatial derivatives of the Green function. These derivatives can also be of the fractional type, which naturally arise when moments are divergent. We apply our results to a large class of differential equations that includes the fractional Schrödinger and Lévy diffusion equations. In particular, we show that, except for threshold cases, the amplitude of a packet may follow the asymptotic law t-alpha, with arbitrary positive alpha.

  9. Interim analysis of long time creep behavior of columbium C-103 alloy

    NASA Technical Reports Server (NTRS)

    Klopp, W. D.; Titran, R. H.

    1976-01-01

    Analysis of 16 long time creep tests on columbium C-103 alloy (Cb-10Hf-1Ti-0.7Zr) indicates that the calculated stresses to give 1 percent creep strain in 100,000 hours at 1,255 K (1800 F) are 7.93 and 8.96 MPa (1,150 and 1,300 psi) for fine grained and course grained materials, respectively. The apparent activation energy and stress dependence for creep of this alloy are approximately 315 KJ/gmol (75,300 cal/gmol) and 2.51, respectively, based on Dorn-Sherby types of relations. However, the 90 percent confidence limits on these values are wide because of the limited data currently available.

  10. Long-time simulations of the Kelvin-Helmholtz instability using an adaptive vortex method.

    PubMed

    Sohn, Sung-Ik; Yoon, Daeki; Hwang, Woonjae

    2010-10-01

    The nonlinear evolution of an interface subject to a parallel shear flow is studied by the vortex sheet model. We perform long-time computations for the vortex sheet in density-stratified fluids by using the point vortex method and investigate late-time dynamics of the Kelvin-Helmholtz instability. We apply an adaptive point insertion procedure and a high-order shock-capturing scheme to the vortex method to handle the nonuniform distribution of point vortices and enhance the resolution. Our adaptive vortex method successfully simulates chaotically distorted interfaces of the Kelvin-Helmholtz instability with fine resolutions. The numerical results show that the Kelvin-Helmholtz instability evolves a secondary instability at a late time, distorting the internal rollup, and eventually develops to a disordered structure.

  11. Population dynamics under selection and mutation: Long-time behavior for differential equations in measure spaces

    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.

  12. A unified model of hysteresis and long-time relaxation in heterogeneous materials

    NASA Astrophysics Data System (ADS)

    Lebedev, A. V.; Ostrovsky, L. A.

    2014-09-01

    A physical model of stress-strain dynamics and long-time relaxation (slow time) in structured media is proposed. The model is based on the analysis of inter-grain contacts and the resulting surface force potential with a barrier. The result is a unified description of the classical acoustic nonlinearity, stress-strain hysteresis, and logarithmic relaxation law for sound velocity (and, hence, for the frequency of nonlinear resonance in samples of structured materials). Estimates of a characteristic volume of interacting contacts give close values for the variety of consolidated materials. For weak (linear) testing waves, the logarithmic relaxation occurs if a classical quadratic nonlinearity is added to the stress-strain relation.

  13. Long-time Behavior of Isolated Periodically Driven Interacting Lattice Systems

    NASA Astrophysics Data System (ADS)

    D'Alessio, Luca; Rigol, Marcos

    2014-10-01

    We study the dynamics of isolated interacting spin chains that are periodically driven by sudden quenches. Using full exact diagonalization of finite chains, we show that these systems exhibit three distinct regimes. For short driving periods, the Floquet Hamiltonian is well approximated by the time-averaged Hamiltonian, while for long periods, the evolution operator exhibits properties of random matrices of a circular ensemble (CE). In between, there is a crossover regime. Based on a finite-size scaling analysis and analytic arguments, we argue that, for thermodynamically large systems and nonvanishing driving periods, the evolution operator always exhibits properties of the CE of random matrices. Consequently, the Floquet Hamiltonian is a nonlocal Hamiltonian with multispin interaction terms, and the driving leads to the equivalent of an infinite temperature state at long times. These results are connected to the breakdown of the Magnus expansion and are expected to hold beyond the specific lattice model considered.

  14. 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.

  15. 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.

  16. The rebound shock model for solar spicules - Dynamics at long times

    NASA Technical Reports Server (NTRS)

    Sterling, Alphonse C.; Hollweg, Joseph V.

    1988-01-01

    The spicule model due to Hollweg is extended and developed. The dynamics is emphasized here; radiative and ionization losses, heat conduction, and nonshock heat input, are not included. In the model, a series of rebound shocks results in chromospheric material with spicule-like properties below a raised transition region. The shocks result from a single quasi-impulsive source in the photosphere. It is found that at long times, the model approaches a new hydrostatic equilibrium with the transition region remaining raised, and with a region of shock-heated chromosphere below it. Attention is given to the variation of the properties of the model in response to different values for the magnitude and location of the source, and to different initial transition region heights. It is concluded that the model is capable of generating structures with properties consistent with observations of spicules (with the exception of temperature) when only the dynamics is considered.

  17. Effects of Long-Time Reading Experience on Reaction Time and the Recognition Potential

    PubMed Central

    Rudell, Alan P.; Hu, Bin

    2010-01-01

    The proposition that long-time experience in reading a language gradually builds up rapidly acting neural processes that facilitate the processing of words in that language and speed them into conscious awareness was examined. Behavioral reaction time (RT) and electrophysiological responsiveness to visually displayed words and non-language images were measured in persons who differed in how much experience they had in reading English. The electrophysiological response was the recognition potential (RP). Behavioral RT and the latency of the RP to English words were both expected to depend upon how much English reading experience a person had. The short latency of the RP was expected to free it from the influence of non-perceptual factors that affect RT, such as speed/accuracy tradeoff. This expectation yielded the prediction that the behavioral and electrophysiological results would differ in a specific way. Long-time readers of English were expected to show shorter RP latency to English words than less experienced (China-educated) readers of English but no RP latency difference for non-language images, with which neither group had greater experience. In contrast, due to speed accuracy tradeoff, the China-educated subjects were expected to show longer RT for both the words and the non-language images. The prediction was confirmed. The amount of language experience that a person had showed a stronger relationship to RP latency than it did to RT. This helped to validate the use of the RP as a tool for investigating perception and demonstrated definite advantages that it has for studying acquired perceptual processes in humans. PMID:20307598

  18. DOE`s annealing prototype demonstration projects

    SciTech Connect

    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.

  19. Enzyme Kinetics.

    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)

  20. Enzyme Kinetics.

    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)

  1. Modeling of Reactor Kinetics and Dynamics

    SciTech Connect

    Matthew Johnson; Scott Lucas; Pavel Tsvetkov

    2010-09-01

    In order to model a full fuel cycle in a nuclear reactor, it is necessary to simulate the short time-scale kinetic behavior of the reactor as well as the long time-scale dynamics that occur with fuel burnup. The former is modeled using the point kinetics equations, while the latter is modeled by coupling fuel burnup equations with the kinetics equations. When the equations are solved simultaneously with a nonlinear equation solver, the end result is a code with the unique capability of modeling transients at any time during a fuel cycle.

  2. Features of an annealing-induced thermoluminescence peak in α-Al2O3:C,Mg

    NASA Astrophysics Data System (ADS)

    Kalita, J. M.; Chithambo, M. L.

    2017-08-01

    We report the thermoluminescence glow curves of beta irradiated single crystal α-Al2O3:C,Mg after annealing at 700 and 900 °C. A glow curve measured at 1 °C/s from samples irradiated to 1 Gy following annealing at 700 and 900 °C shows a high intensity peak at 163 °C and seven secondary peaks of weaker intensity at 43, 73, 100, 195, 280, 329 and 370 °C. Comparing the position of the peaks in the annealed samples with those in an un-annealed one, it is observed that the peak at 100 °C appears only after annealing at and above 700 °C. Kinetic analysis of this annealing-induced peak was carried out using the initial rise, whole glow peak, peak shape, curve fitting and variable heating rate methods. The order of kinetics of the peak was determined as first order using various methods including the Tm-Tstop technique and the dependence of Tm on irradiation dose. The activation energy of the peak is about 1.01 eV and the frequency factor of the order of 1012 s-1. The peak was found to be affected by thermal quenching in analysis based on change of peak intensity with heating rate. The activation energy of thermal quenching was evaluated as 1.06 ± 0.08 eV. We speculate that the annealing-induced peak is due to formation of a new electron trap after destruction of the F22+(2 Mg) centre when the sample is annealed at 700 °C. The annealing-induced peak fades with storage between irradiation and measurement. It was also concluded that electrons from traps corresponding to secondary peaks get re-trapped at the main electron trap.

  3. Modernizing quantum annealing using local searches

    NASA Astrophysics Data System (ADS)

    Chancellor, Nicholas

    2017-02-01

    I describe how real quantum annealers may be used to perform local (in state space) searches around specified states, rather than the global searches traditionally implemented in the quantum annealing algorithm (QAA). Such protocols will have numerous advantages over simple quantum annealing. By using such searches the effect of problem mis-specification can be reduced, as only energy differences between the searched states will be relevant. The QAA is an analogue of simulated annealing, a classical numerical technique which has now been superseded. Hence, I explore two strategies to use an annealer in a way which takes advantage of modern classical optimization algorithms. Specifically, I show how sequential calls to quantum annealers can be used to construct analogues of population annealing and parallel tempering which use quantum searches as subroutines. The techniques given here can be applied not only to optimization, but also to sampling. I examine the feasibility of these protocols on real devices and note that implementing such protocols should require minimal if any change to the current design of the flux qubit-based annealers by D-Wave Systems Inc. I further provide proof-of-principle numerical experiments based on quantum Monte Carlo that demonstrate simple examples of the discussed techniques.

  4. Variation of the viscosity of molten potassium niobate with annealing time

    NASA Astrophysics Data System (ADS)

    Hong, Xinguo; Chen, Yufeng

    1996-07-01

    Using the double-wire torsion pendulum method, we have measured the viscosity of a potassium niobate molten system with excess K 2O from 50 to 56 mol% at temperatures up to 1190°C in air. Both the viscosity and its activation energy show strong time dependence. While the values for viscosity increase for melts with 50 and 51 mol% K 2O, which are annealed at 1150°C in air, the viscosity, however, of the melt with more than 2 mol% excess K 2O shows a completely different time dependence, i.e. drastic decrease with annealing time. A similar striking reversed variation of temperature-dependent viscosity with annealing time is observed when the K 2O content in the melt is up to 52 mol%. These anomalous variations in viscosity give clear evidence why the KNbO 3 single crystal should be grown from mother melts with excess K 2O above 51 mol%, and after being annealed for a long time. This result also confirms that the double-wire torsion pendulum method is a useful tool to study the time-dependent viscosity of melts at high temperature in air.

  5. Raman scattering and photoluminescence from Si nanoparticles in annealed SiOx thin films

    NASA Astrophysics Data System (ADS)

    Nesheva, D.; Raptis, C.; Perakis, A.; Bineva, I.; Aneva, Z.; Levi, Z.; Alexandrova, S.; Hofmeister, H.

    2002-10-01

    Silicon-rich silicon oxide thin films have been prepared by thermal evaporation of silicon monoxide in vacuum. The SiOx film composition (1.1⩽ x ⩽1.7) has been controlled by varying the deposition rate and residual pressure in the chamber. Long time stability of all films has been ensured by a postdeposition annealing at 523 K for 30 min in Ar atmosphere. Some films were further annealed at 973 K and some others at 1303 K. Raman scattering measurements have implied the formation of amorphous silicon nanoparticles in films annealed at 973 K and Si nanocrystals in films annealed at 1303 K. The latter conclusion is strongly supported by high resolution electron microscopy studies which show a high density of Si nanocrystals in these films. Photoluminescence has been observed from both amorphous and crystalline nanoparticles and interpreted in terms of band-to-band recombination in the nanoparticles having average size greater than 2.5 nm and carrier recombination through defect states in smaller nanoparticles.

  6. Understanding the microwave annealing of silicon

    NASA Astrophysics Data System (ADS)

    Fu, Chaochao; Wang, Yan; Xu, Peng; Yue, Lei; Sun, Feng; Zhang, David Wei; Zhang, Shi-Li; Luo, Jun; Zhao, Chao; Wu, Dongping

    2017-03-01

    Though microwave annealing appears to be very appealing due to its unique features, lacking an in-depth understanding and accurate model hinder its application in semiconductor processing. In this paper, the physics-based model and accurate calculation for the microwave annealing of silicon are presented. Both thermal effects, including ohmic conduction loss and dielectric polarization loss, and non-thermal effects are thoroughly analyzed. We designed unique experiments to verify the mechanism and extract relevant parameters. We also explicitly illustrate the dynamic interaction processes of the microwave annealing of silicon. This work provides an in-depth understanding that can expedite the application of microwave annealing in semiconductor processing and open the door to implementing microwave annealing for future research and applications.

  7. Crystal growth and annealing method and apparatus

    DOEpatents

    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.

  8. A Rauch-Tung-Striebel smoother for the interpretation of long time series of ocean observations

    NASA Astrophysics Data System (ADS)

    Marchal, O.

    2012-04-01

    The interpretation of long time series of data in the presence of a model is an important problem both in modern oceanography and in paleoceanography. The adjective "long" refers here to time series extending over a decade or more. In modern oceanography, the problem arises from the analysis of data from the longest instrumental records at coastal and open-ocean stations. In paleoceanography, it arises from the analysis of any sediment record, which may span several thousands of years and even more. The quantitative combination of long ocean records with a circulation model is highly desirable, as it would lead to an interpretation of the data that is consistent with the equations of motion. Methods commonly used to combine records of ocean data with an ocean circulation model are sequential methods and Lagrange multiplier methods. In both cases, the estimation of the uncertainty of the ocean state is an issue, in the former because it may overwhelm the computation and in the latter because it is not part of the solution. Sequential methods appear as particularly attractive for the interpretation of long ocean records given their relatively large uncertainties. Here we will present a preliminary effort to develop a sequential method (Rauch-Tung-Striebel or RTS smoother) for combining long time series of sea surface temperature (SST) with a model of the circulation in a subtropical gyre. In order to learn about the ultimate capability to develop and apply such a method, a simplified model based on the linearized equations of motion and on the hydrostatic approximation is used. The bottom of the gyre is also assumed to be flat. The advantages of these assumptions are multiple. For example, the motion can then decomposed into vertical modes, where each mode satisfies a set of shallow-water equations for its horizontal structure. This modal decomposition allows the possibility to retain only the leading modes and the effect of various dynamical mechanisms such as

  9. Thermal control unit for long-time survival of scientific instruments on lunar surface

    NASA Astrophysics Data System (ADS)

    Ogawa, Kazunori; Iijima, Yuichi; Tanaka, Satoshi

    A thermal control unit (lunar survival module) is being developed for scientific instruments placed on the lunar surface. This unit is designed to be used on the future Japanese lunar landing mission SELENE-2. The lunar surface is a severe environment for scientific instruments. The absence of convective cooling by an atmosphere makes the ground surface temperature variable in the wide range of -200 to 100 degC, an environment in which space electronics can hardly survive. The surface elements must have a thermal control structure to maintain the inner temperature within the operable ranges of the instruments for long-time measurements, such as 1 month or longer beyond the lunar nights. The objectives of this study are to develop a thermal control unit for the SELENE-2 mission. So far, we conducted the concept design of the lunar survival module, and estimated its potential by a thermal mathematical model on the assumption of using a lunar seismometer designed for SELENE-2. The basic structure of the thermal module is rather simple in that a heat insulating shell covers the scientific instruments. The concept is that the conical insulator retains heat in the regolith soil in the daylight, and it can keep the device warm in the night. Results of the model calculations indicated the high potential of long-time survival. A bread board model (BBM) was manufactured, and its thermal-vacuum tests were conducted in order to estimate the validity of some thermal parameters assumed in the computed thermal model. The thermal condition of the lunar surface was simulated by glass beads paved in a vacuum chamber, and a temperature-controlled container. Temperature variations of the BBM in thermal cycling tests were compared to a thermal mathematical model, and the thermal parameters were finally assessed. Feeding the test results back into the thermal model for the lunar surface, some thermal parameters were updated but there was no critical effect on the survivability. The

  10. 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

  11. Parallel Object Oriented MD Simulation Program for Long Time Simulations of Metallic Glasses and Undercooled Liquids

    NASA Astrophysics Data System (ADS)

    Böddeker, B.; Teichler, H.

    The MD simulation program TABB is motivated by the need of long time simulations for the investigation of slow processes near the glass transition of glass forming alloys. TABB is written in C++ with a high degree of flexibility: TABB allows the use of any short ranged pair potentials or EAM potentials, by generating and using a spline representation of all functions and their derivatives. TABB supports several numerical integration algorithms like the Runge-Kotta or the modified Gear-predictor-corrector algorithm of order five. The boundary conditions can be chosen to resemble the geometry of bulk materials or films. The simulation box length or the pressure can be fixed for each dimension separately. TABB may be used in isokinetic, isoenergeric or canonic (with random forces) mode. TABB contains a simple instruction interpreter to easily control the parameters and options during the simulation. The same source code can be compiled either for workstations or for parallel computers. The main optimization goal of TABB is to allow long time simulations of medium or small sized systems. To make this possible, much attention is spent on the optimized communication between the nodes. TABB uses a domain decomposition procedure. To use many nodes with a small system, the domain size has to be small compared to the range of particle interactions. In the limit of many nodes for only few atoms, the bottle neck of communication is the latency time. TABB minimizes the number of pairs of domains containing atoms that interact between these domains. This procedure minimizes the need of communication calls between pairs of nodes. TABB decides automatically, to how many, and to which directions the decomposition shall be applied. E.g., in the case of one dimensional domain decomposition, the simulation box is only split into "slabs" along a selected direction. The three dimensional domain decomposition is best with respect to the number of interacting domains only for simulations

  12. Heating rate effects during non-isothermal annealing of AIK steel

    NASA Astrophysics Data System (ADS)

    Sahay, Satyam S.; Joshi, Kishor B.

    2003-04-01

    The effects of heating rate on microstructural size and shape parameters during annealing of cold rolled aluminum killed steel strips have been examined under non-isothermal condition. It is shown that decrease in the heating rate results in accelerated grain growth behavior compared with the prediction by quasi-isothermal based kinetics. The {111} and {112} crystallographic orientations, which enhance the normal anisotropy and deep drawability of cold rolled annealed sheets, are found to exhibit a strong correlation with the grain shape anisotropy. This grain shape anisotropy itself is strongly dependent on heating rates. Lower heating rates result in higher aspect ratios and thus better drawability of the cold rolled sheets. A Hall-Petch type relationship is observed between grain size and hardness of the annealed samples.

  13. Influence of interface mobility on the evolution of Austenite-Martensite grain assemblies during annealing

    SciTech Connect

    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.

  14. The Clodia database: a long time series of fishery data from the Adriatic Sea

    PubMed Central

    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

  15. Assessment of water quality of Rawal Lake by long-time monitoring.

    PubMed

    Ghumman, Abdul Razzaq

    2011-09-01

    Water quality of rivers, natural lakes, and reservoirs in developing countries is being degraded because of the contaminated inflows. There is a serious need for appropriate water quality monitoring for future planning and management of clean water resources. Quality of water in Rawal Lake Pakistan has been investigated in this paper. Flows from the upstream of Rawal Lake and its surrounding villages are highly polluted. Lake water quality parameters like pH, turbidity, alkalinity, calcium, nitrite, sulfate, biological oxygen dissolved, dissolved oxygen, chloride, total dissolved solids (TDS), and coliforms were investigated. Samples of water from different locations of Korang River were collected and tested. Most of the data was collected by field sampling and field visits. However, long-term information was taken from different departments. Statistical parameters (standard deviation, maximum, minimum, mean, mode, kurtosis, skew, and Euclidean distance) of variables were determined. A distinct parameter based on the difference of the maximum value the variable and maximum allowable value of that variable defined by World Health Organization was used for analysis. Grouping and clustering of elements was made on the basis of this parameter. Trend of increasing or decreasing of values of variables over a long time was also taken into account for grouping the variables. It was concluded that the concentration of seven contaminants was higher as compared to the permissible limits under environmental standards. These variables need immediate attention. The environmentally bad conditions of Rawal Lake can only be rectified by appropriate lake environmental supervision, watershed management, and implementation of environmental legislation.

  16. Designing Adaptive Low-Dissipative High Order Schemes for Long-Time Integrations

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, B.

    2005-01-01

    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. (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 non-linear 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.

  17. Long-time self-diffusion of charged spherical colloidal particles in parallel planar layers.

    PubMed

    Contreras-Aburto, Claudio; Báez, César A; Méndez-Alcaraz, José M; Castañeda-Priego, Ramón

    2014-06-28

    The long-time self-diffusion coefficient, D(L), of charged spherical colloidal particles in parallel planar layers is studied by means of Brownian dynamics computer simulations and mode-coupling theory. All particles (regardless which layer they are located on) interact with each other via the screened Coulomb potential and there is no particle transfer between layers. As a result of the geometrical constraint on particle positions, the simulation results show that D(L) is strongly controlled by the separation between layers. On the basis of the so-called contraction of the description formalism [C. Contreras-Aburto, J. M. Méndez-Alcaraz, and R. Castañeda-Priego, J. Chem. Phys. 132, 174111 (2010)], the effective potential between particles in a layer (the so-called observed layer) is obtained from integrating out the degrees of freedom of particles in the remaining layers. We have shown in a previous work that the effective potential performs well in describing the static structure of the observed layer (loc. cit.). In this work, we find that the D(L) values determined from the simulations of the observed layer, where the particles interact via the effective potential, do not agree with the exact values of D(L). Our findings confirm that even when an effective potential can perform well in describing the static properties, there is no guarantee that it will correctly describe the dynamic properties of colloidal systems.

  18. Stability of orbits in nonlinear mechanics for finite but very long times

    SciTech Connect

    Warnock, R.L.; Ruth, R.D.

    1990-07-01

    In various applications of nonlinear mechanics, especially in accelerator design, it would be useful to set bounds on the motion for finite but very long times. Such bounds can be sought with the help of a canonical transformation to new action-angle variables (J, {Psi}), such that action J is nearly constant while the angle {Psi} advances almost linearly with the time. By examining the change in J during a time T{sub 0} from many initial conditions in the open domain {Omega} of phase space, one can estimate the change in J during a much larger time T, on any orbit starting in a smaller open domain {Omega}{sub 0} {contained in} {Omega}. A numerical realization of this idea is described. The canonical transformations, equivalent to close approximations to invariant tori, are constructed by an effective new method in which surfaces are fitted to orbit data. In a first application to a model sextupole lattice in a region of strong nonlinearity, we predict stability of betatron motion in two degrees of freedom for a time comparable to the storage time in a proton storage ring (10{sup 8} turns). 10 refs., 6 figs., 1 tab.

  19. Long-time self-diffusion of charged spherical colloidal particles in parallel planar layers

    NASA Astrophysics Data System (ADS)

    Contreras-Aburto, Claudio; Báez, César A.; Méndez-Alcaraz, José M.; Castañeda-Priego, Ramón

    2014-06-01

    The long-time self-diffusion coefficient, DL, of charged spherical colloidal particles in parallel planar layers is studied by means of Brownian dynamics computer simulations and mode-coupling theory. All particles (regardless which layer they are located on) interact with each other via the screened Coulomb potential and there is no particle transfer between layers. As a result of the geometrical constraint on particle positions, the simulation results show that DL is strongly controlled by the separation between layers. On the basis of the so-called contraction of the description formalism [C. Contreras-Aburto, J. M. Méndez-Alcaraz, and R. Castañeda-Priego, J. Chem. Phys. 132, 174111 (2010)], the effective potential between particles in a layer (the so-called observed layer) is obtained from integrating out the degrees of freedom of particles in the remaining layers. We have shown in a previous work that the effective potential performs well in describing the static structure of the observed layer (loc. cit.). In this work, we find that the DL values determined from the simulations of the observed layer, where the particles interact via the effective potential, do not agree with the exact values of DL. Our findings confirm that even when an effective potential can perform well in describing the static properties, there is no guarantee that it will correctly describe the dynamic properties of colloidal systems.

  20. Long time-series of turbid coastal water using AVHRR: An example from Florida Bay, USA

    USGS Publications Warehouse

    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.

  1. Improving long time behavior of Poisson bracket mapping equation: A non-Hamiltonian approach

    SciTech Connect

    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.

  2. PyRQA-Conducting recurrence quantification analysis on very long time series efficiently

    NASA Astrophysics Data System (ADS)

    Rawald, Tobias; Sips, Mike; Marwan, Norbert

    2017-07-01

    PyRQA is a software package that efficiently conducts recurrence quantification analysis (RQA) on time series consisting of more than one million data points. RQA is a method from non-linear time series analysis that quantifies the recurrent behaviour of systems. Existing implementations to RQA are not capable of analysing such very long time series at all or require large amounts of time to calculate the quantitative measures. PyRQA overcomes their limitations by conducting the RQA computations in a highly parallel manner. Building on the OpenCL framework, PyRQA leverages the computing capabilities of a variety of parallel hardware architectures, such as GPUs. The underlying computing approach partitions the RQA computations and enables to employ multiple compute devices at the same time. The goal of this publication is to demonstrate the features and the runtime efficiency of PyRQA. For this purpose we employ a real-world example, comparing the dynamics of two climatological time series, and a synthetic example, reducing the runtime regarding the analysis of a series consisting of over one million data points from almost eight hours using state-of-the-art RQA software to roughly 69 s using PyRQA.

  3. Long-time analytic approximation of large stochastic oscillators: Simulation, analysis and inference

    PubMed Central

    2017-01-01

    In order to analyse large complex stochastic dynamical models such as those studied in systems biology there is currently a great need for both analytical tools and also algorithms for accurate and fast simulation and estimation. We present a new stochastic approximation of biological oscillators that addresses these needs. Our method, called phase-corrected LNA (pcLNA) overcomes the main limitations of the standard Linear Noise Approximation (LNA) to remain uniformly accurate for long times, still maintaining the speed and analytically tractability of the LNA. As part of this, we develop analytical expressions for key probability distributions and associated quantities, such as the Fisher Information Matrix and Kullback-Leibler divergence and we introduce a new approach to system-global sensitivity analysis. We also present algorithms for statistical inference and for long-term simulation of oscillating systems that are shown to be as accurate but much faster than leaping algorithms and algorithms for integration of diffusion equations. Stochastic versions of published models of the circadian clock and NF-κB system are used to illustrate our results. PMID:28742083

  4. Thermalization and long-time behavior of nonequilibrium correlated quantum systems

    NASA Astrophysics Data System (ADS)

    Fotso, Herbert F.

    2015-03-01

    Nonequilibrium dynamical mean field theory and nonequilibrium self-consistent strong coupling expansion are used to study the relaxation of correlated quantum systems driven out of equilibrium by DC electric fields. Both the Falicov-Kimball and the Hubbard model are found to exhibit regimes of monotonic or oscillatory themalization as well as regimes where they evolve in a monotonic or oscillatory manner towards a non-thermal state. This suggests that driven quantum systems have a richer behavior than their quenched counterparts and that integrability does not play as critical a role. In the monotonic thermalization scenario, the system evolves through successive quasi-thermal states and it is possible to extrapolate its long time properties from its transient; bridging the gap between the transient and the steady state with very little computational cost. Furthermore, regardless of the relaxation scenario, it is interesting to ask how the particles are distributed as the system evolves in time. We will show that non-trivial parameter-dependent patterns are formed when the system is visualized in momentum space. These features should be observable in current cold atom experiments. This work was supported by the National Science Foundation under Grant No DMR-1006605 and by the Air Force Office of Scientific Research under the MURI program grant No. FA9559-09-1-0617.

  5. Long-time analytic approximation of large stochastic oscillators: Simulation, analysis and inference.

    PubMed

    Minas, Giorgos; Rand, David A

    2017-07-01

    In order to analyse large complex stochastic dynamical models such as those studied in systems biology there is currently a great need for both analytical tools and also algorithms for accurate and fast simulation and estimation. We present a new stochastic approximation of biological oscillators that addresses these needs. Our method, called phase-corrected LNA (pcLNA) overcomes the main limitations of the standard Linear Noise Approximation (LNA) to remain uniformly accurate for long times, still maintaining the speed and analytically tractability of the LNA. As part of this, we develop analytical expressions for key probability distributions and associated quantities, such as the Fisher Information Matrix and Kullback-Leibler divergence and we introduce a new approach to system-global sensitivity analysis. We also present algorithms for statistical inference and for long-term simulation of oscillating systems that are shown to be as accurate but much faster than leaping algorithms and algorithms for integration of diffusion equations. Stochastic versions of published models of the circadian clock and NF-κB system are used to illustrate our results.

  6. 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.

  7. Theory of quantum annealing of an Ising spin glass.

    PubMed

    Santoro, Giuseppe E; Martonák, Roman; Tosatti, Erio; Car, Roberto

    2002-03-29

    Probing the lowest energy configuration of a complex system by quantum annealing was recently found to be more effective than its classical, thermal counterpart. By comparing classical and quantum Monte Carlo annealing protocols on the two-dimensional random Ising model (a prototype spin glass), we confirm the superiority of quantum annealing relative to classical annealing. We also propose a theory of quantum annealing based on a cascade of Landau-Zener tunneling events. For both classical and quantum annealing, the residual energy after annealing is inversely proportional to a power of the logarithm of the annealing time, but the quantum case has a larger power that makes it faster.

  8. Precision Laser Annealing of Focal Plane Arrays

    SciTech Connect

    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.

  9. Annealing and structural properties of composite films

    NASA Astrophysics Data System (ADS)

    Kotov, L. N.; Ustyugov, V. A.; Vlasov, V. S.; Turkov, V. K.; Dianov, M. Yu; Antonets, I. V.; Kalinin, Yu E.; Sitnikov, A. V.; Golubev, E. A.

    2017-02-01

    The composite films were investigated by AFM methods before and after annealing. Topographic and phase-contrast AFM images of the composite films at different annealing temperature were obtained. The separate metal granules and larger-scale labyrinth-like formations were described. These formations appear by the process of the film growth, also by film annealing. Strong changes of the structural properties of the films are observed after the percolation transition. The significant changes of the structural properties are connected with nanostructural transformations in the metal granules topology and presence of metal crystal phase.

  10. Excimer laser annealing of silicon nanowires

    SciTech Connect

    Misra, Nipun; Xu Li; Pan Yaoling; Cheung, Nathan; Grigoropoulos, Costas P.

    2007-03-12

    Nanowires can potentially be used with low-cost flexible plastic substrates for applications such as large-area displays and sensor arrays. However, high temperature processing steps such as thermal annealing that are incompatible with plastic substrates are still a major hindrance. Laser annealing permits localized energy input without affecting the underlying substrate and can help overcome this problem. In this study, the excimer laser annealing of silicon nanowires is demonstrated to be an efficient means of activating implanted dopants. The optical absorption of the nanowires is discussed and the effect of parameters such as fluence and number of pulses is investigated.

  11. Asymptotic Potential for Simulated Annealing.

    NASA Astrophysics Data System (ADS)

    Jones, Philip Andrew

    1995-01-01

    Potential theory is an important area of mathematical physics which has been intensively studied in the areas of partial differential equations and probability. The purpose of this thesis is to develop a potential theory for the time-inhomogeneous Markov chains defined by simulated annealing. First the notion of global recurrence orders is extended to that of global recurrence functions. Then this idea is condensed to local attractors (cups), resulting in improved and sharper estimates for the exit probabilities. For each cup, the weighted activity of a point in the cup is considered, that is the value of sum_sp {n=m}{sigma}lambda_sp {n}{c}P(X_ n=x) for a suitable value of c. Here sigma is the exit time from the cup, representing our localized viewpoint. The convergence as m goes to infinity is considered, the result having many properties of classical potentials, and hence is called the asymptotic potential. A consequence is to simplify previous results and produce calculable constants for estimates. This is important for practical applications where such knowledge is often required and used.

  12. Boron activation and diffusion in silicon and strained silicon-on-insulator by rapid thermal and flash lamp annealings

    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.

  13. Irradiation and annealing behavior of 15Kh2MFA reactor pressure vessel steel

    SciTech Connect

    Popp, K.; Bergmann, U.; Bergner, F.; Hampe, E.; Leonhardt, W.D.; Schuetzler, H.; Viehrig, H.

    1993-12-01

    This work deals with the mechanical properties of reactor pressure vessel (RPV) steels used in the pressurized water reactors (PWR) of former Soviet type WWER-440. The materials under investigation were a forging (base metal 15Kh2MFA) and the corresponding weld. Charpy 5-notch specimens and tensile test specimens were irradiated in the PWR WWER-2 Rheinsberg at about 270 C up to the two neutron fluence levels of 4 {times} 10{sup 18} and 5 {times} 10{sup 19} n/cm{sup 2} (E > 1 MeV). Post irradiation annealing heat treatments were performed, among others a 475 C/152 h treatment of technical interest. A set of experimental data is given regarding the influence of sampling depth (through-thickness position within the forging), neutron irradiation, and annealing on the properties derived from instrumented Charpy impact testing, tensile and hardness tests. The ferrite content varies through the thickness of the forging. The variation of the mechanical properties can be explained qualitatively with the varying ferrite content. The surface layer of the forging is more sensitive to neutron irradiation than material from the 1/4-T position. To evaluate the effect of annealing heat treatment, the kinetics of the recovery process for the hardness has been investigated. The recovery coefficients for different mechanical properties and parameters have been compared. The annealing behavior is too complex to predict the effect of a large-scale annealing of an RPV on the basis of single hardness measurements.

  14. Rapid annealing of severely deformed low carbon steel in subcritical temperature range

    NASA Astrophysics Data System (ADS)

    Ghiabakloo, H.; Kazeminezhad, M.

    2017-09-01

    A low-carbon steel sheet containing 0.05 C, 0.203 Mn, and 0.0229 Si (all in wt%) was rapidly annealed in a temperature range of 300 °C to 600 °C after severe plastic deformation by using constrained groove pressing (CGP) technique. Microstructure evolution was investigated by scanning electron and optical microscopes. Mechanical properties were evaluated by hardness measurements and shear punch test. The results showed a thermal stability up to 400 °C where recrystallization did not occur in the specimens even after 7200 s. This thermal stability is in agreement with previously reported results of conventional annealing of the same steel after CGP. However, annealing at 500 °C and 600 °C led to recrystallization which started after holding times of 600 s and 20 s, respectively. Longer holding times resulted to grain growth and deterioration of strength and hardness, but the final strength and hardness were still higher than those of conventionally annealed specimens. The reason has been attributed to no abnormal grain growth in the present study, in contrast to that occurs after conventional annealing of CGPed low carbon steel. The kinetics of recrystallization at 600 °C was studied using the celebrated Johnson-Mehl-Avrami-Kolmogorov (JMAK) model; the results showed a bi-linear JMAK plot indicating two different stages of recrystallization rate before and after 70% recrystallization.

  15. Morphology evolution and structural transformation of solution-processed methanofullerene thin film under thermal annealing.

    PubMed

    Zheng, Lidong; Liu, Jiangang; Ding, Yan; Han, Yanchun

    2011-06-30

    The film morphology and nanostructure of the soluble fullerene, [6,6]-phenyl-C(61) butyric acid methyl ester (PCBM), are crucial for its applications in organic thin film devices, such as organic solar cells and organic thin film transistors. In this work, the morphology, structural transformation, and crystallite orientation of PCBM film under thermal annealing as a function of annealing temperature, processing solvents, and solution concentrations are systematically investigated. Crystalline PCBM films with needle-like crystallites, axialitic aggregates, and faceted slices are formed in the annealing process. The axialites, made up of needle-like aggregates, are proposed to be partially developed spherulites frozen at the early growth stage formed through low-angle branching. The faceted slices are found to be PCBM single crystallites with hexagonal packing in the film plane. The film undergoes both amorphous-to-crystalline and crystalline-to-crystalline phase transformations as the annealing temperature is increased. The former transformation, corresponding to the self-organization of disordered PCBM molecules in the kinetically frozen films, occurs at a relative low temperature once the motion of these molecules is thermally activated, whereas the later one, corresponding to the transformation between two thermally stable crystalline phases, occurs when further increasing the annealing temperature. The PCBM crystallites composing these films are found to have an orientation preference normal to the film surface, which can be attributed to the confinement of film thickness for PCBM crystallite growth.

  16. A search for long-time-scale, low-frequency radio transients

    NASA Astrophysics Data System (ADS)

    Murphy, Tara; Kaplan, David L.; Croft, Steve; Lynch, Christene; Callingham, J. R.; Bannister, Keith; Bell, Martin E.; Hurley-Walker, Natasha; Hancock, Paul; Line, Jack; Rowlinson, Antonia; Lenc, Emil; Intema, H. T.; Jagannathan, P.; Ekers, Ronald D.; Tingay, Steven; Yuan, Fang; Wolf, Christian; Onken, Christopher A.; Dwarakanath, K. S.; For, B.-Q.; Gaensler, B. M.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; McKinley, B.; Morgan, J.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R.; Wu, C.; Zheng, Q.

    2017-04-01

    We present a search for transient and highly variable sources at low radio frequencies (150-200 MHz) that explores long time-scales of 1-3 yr. We conducted this search by comparing the TIFR GMRT Sky Survey Alternative Data Release 1 (TGSS ADR1) and the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey catalogues. To account for the different completeness thresholds in the individual surveys, we searched for compact GLEAM sources above a flux density limit of 100 mJy that were not present in the TGSS ADR1; and also for compact TGSS ADR1 sources above a flux density limit of 200 mJy that had no counterpart in GLEAM. From a total sample of 234 333 GLEAM sources and 275 612 TGSS ADR1 sources in the overlap region between the two surveys, there were 99 658 GLEAM sources and 38 978 TGSS ADR sources that passed our flux density cut-off and compactness criteria. Analysis of these sources resulted in three candidate transient sources. Further analysis ruled out two candidates as imaging artefacts. We analyse the third candidate and show it is likely to be real, with a flux density of 182 ± 26 mJy at 147.5 MHz. This gives a transient surface density of ρ = (6.2 ± 6) × 10-5 deg-2. We present initial follow-up observations and discuss possible causes for this candidate. The small number of spurious sources from this search demonstrates the high reliability of these two new low-frequency radio catalogues.

  17. Long-time predictability in disordered spin systems following a deep quench.

    PubMed

    Ye, J; Gheissari, R; Machta, J; Newman, C M; Stein, D L

    2017-04-01

    We study the problem of predictability, or "nature vs nurture," in several disordered Ising spin systems evolving at zero temperature from a random initial state: How much does the final state depend on the information contained in the initial state, and how much depends on the detailed history of the system? Our numerical studies of the "dynamical order parameter" in Edwards-Anderson Ising spin glasses and random ferromagnets indicate that the influence of the initial state decays as dimension increases. Similarly, this same order parameter for the Sherrington-Kirkpatrick infinite-range spin glass indicates that this information decays as the number of spins increases. Based on these results, we conjecture that the influence of the initial state on the final state decays to zero in finite-dimensional random-bond spin systems as dimension goes to infinity, regardless of the presence of frustration. We also study the rate at which spins "freeze out" to a final state as a function of dimensionality and number of spins; here the results indicate that the number of "active" spins at long times increases with dimension (for short-range systems) or number of spins (for infinite-range systems). We provide theoretical arguments to support these conjectures, and also study analytically several mean-field models: the random energy model, the uniform Curie-Weiss ferromagnet, and the disordered Curie-Weiss ferromagnet. We find that for these models, the information contained in the initial state does not decay in the thermodynamic limit-in fact, it fully determines the final state. Unlike in short-range models, the presence of frustration in mean-field models dramatically alters the dynamical behavior with respect to the issue of predictability.

  18. Long-time predictability in disordered spin systems following a deep quench

    NASA Astrophysics Data System (ADS)

    Ye, J.; Gheissari, R.; Machta, J.; Newman, C. M.; Stein, D. L.

    2017-04-01

    We study the problem of predictability, or "nature vs nurture," in several disordered Ising spin systems evolving at zero temperature from a random initial state: How much does the final state depend on the information contained in the initial state, and how much depends on the detailed history of the system? Our numerical studies of the "dynamical order parameter" in Edwards-Anderson Ising spin glasses and random ferromagnets indicate that the influence of the initial state decays as dimension increases. Similarly, this same order parameter for the Sherrington-Kirkpatrick infinite-range spin glass indicates that this information decays as the number of spins increases. Based on these results, we conjecture that the influence of the initial state on the final state decays to zero in finite-dimensional random-bond spin systems as dimension goes to infinity, regardless of the presence of frustration. We also study the rate at which spins "freeze out" to a final state as a function of dimensionality and number of spins; here the results indicate that the number of "active" spins at long times increases with dimension (for short-range systems) or number of spins (for infinite-range systems). We provide theoretical arguments to support these conjectures, and also study analytically several mean-field models: the random energy model, the uniform Curie-Weiss ferromagnet, and the disordered Curie-Weiss ferromagnet. We find that for these models, the information contained in the initial state does not decay in the thermodynamic limit—in fact, it fully determines the final state. Unlike in short-range models, the presence of frustration in mean-field models dramatically alters the dynamical behavior with respect to the issue of predictability.

  19. Post-traumatic stress, depression, and community integration a long time after whiplash injury

    PubMed Central

    Stålnacke, Britt-Marie

    2010-01-01

    Psychological factors such as post-traumatic stress and depression may play an important role in the recovery after whiplash injuries. Difficulties in psychosocial functioning with limitations in everyday life may dominate for some time after the injury. Our study therefore investigates the relationships between pain, post-traumatic stress, depression, and community integration. A set of questionnaires was answered by 191 persons (88 men, 103 women) five years after a whiplash injury to assess pain intensity (visual analogue scale, VAS), whiplash-related symptoms, post-traumatic stress (impact of event scale, IES), depression (Beck depression inventory, BDI-II), community integration (community integration questionnaire, CIQ), life satisfaction (LiSat-11). One or more depressive symptoms were reported by 74% of persons; 22% reported scores that were classified as mild to severe depression. The presence of at least one post-traumatic symptom was reported by 70% of persons, and 38% reported mild to severe stress. Total scores of community integration for women were statistically significantly higher than for men. The total VAS score was correlated positively to the IES (r=0.456, P<0.456), the BDI (r=0.646, P<0.001), and negatively to the CIQ (r=−0.300, P<0.001). These results highlight the view that a significant proportion of people experience both pain and psychological difficulties for a long time after a whiplash injury. These findings should be taken into consideration in the management of subjects with chronic whiplash symptoms and may support a multi-professional rehabilitation model that integrates physical, psychological, and psychosocial factors. PMID:25478087

  20. Long time-constant behavior of the oculomotor plant in barbiturate-anesthetized primate.

    PubMed

    Sklavos, S; Dimitrova, D M; Goldberg, S J; Porrill, J; Dean, P

    2006-02-01

    The mechanics of the extraocular muscles and orbital tissue ("oculomotor plant") can be approximated by a small number of viscoelastic (Voigt) elements in series. Recent analysis of the eye's return from displacement in lightly anesthetized rhesus monkeys has suggested a four-element plant model with time constants (TCs) of approximately 0.01, 0.1, 1, and 10 s. To demonstrate directly the presence of long (1,10 s) TC elements and to assess their contribution quantitatively, horizontal eye displacement was induced in Cynomolgus monkeys under deep barbiturate anesthesia that prevented interference from spontaneous eye movements. The displacement was maintained for either a prolonged (30 s) or brief (0.2 s) period before release. Return to resting position took 20-30 s after prolonged displacement but only 1-2 s after brief displacement, consistent with the presence of long TC elements that would only be substantially stretched in the former condition. Quantitative fitting of the release curves after prolonged displacement indicated that the two long TC elements contribute a substantial proportion (approximately 30%) of the total plant compliance. A model based on the estimated compliance values is shown to account quantitatively both for our release data and for Goldstein and Robinson's data on hysteresis of ocular motoneuron firing rates measured after centripetal saccades following prolonged eccentric fixation. Long time-constant elements in the plant thus make a substantial contribution to some types of eye movement, and their inclusion in plant models can help interpret the firing patterns of single units in the oculomotor system.

  1. Network-linked long-time recording high-speed video camera system

    NASA Astrophysics Data System (ADS)

    Kimura, Seiji; Tsuji, Masataka

    2001-04-01

    This paper describes a network-oriented, long-recording-time high-speed digital video camera system that utilizes an HDD (Hard Disk Drive) as a recording medium. Semiconductor memories (DRAM, etc.) are the most common image data recording media with existing high-speed digital video cameras. They are extensively used because of their advantage of high-speed writing and reading of picture data. The drawback is that their recording time is limited to only several seconds because the data amount is very large. A recording time of several seconds is sufficient for many applications. However, a much longer recording time is required in some applications where an exact prediction of trigger timing is hard to make. In the Late years, the recording density of the HDD has been dramatically improved, which has attracted more attention to its value as a long-recording-time medium. We conceived an idea that we would be able to build a compact system that makes possible a long time recording if the HDD can be used as a memory unit for high-speed digital image recording. However, the data rate of such a system, capable of recording 640 X 480 pixel resolution pictures at 500 frames per second (fps) with 8-bit grayscale is 153.6 Mbyte/sec., and is way beyond the writing speed of the commonly used HDD. So, we developed a dedicated image compression system and verified its capability to lower the data rate from the digital camera to match the HDD writing rate.

  2. Studying the Heliosphere with Long Time Series of Ulysses HISCALE Ion Composition Data

    NASA Astrophysics Data System (ADS)

    Thomson, D. J.; Maclennan, C. G.; Lanzerotti, L. J.

    2004-12-01

    Ulysses has now been in orbit for fourteen years, over two full orbits and a full solar cycle. We take this opportunity to investigate the properties of long time series of ion composition data that have been acquired by the HI-SCALE instrument. We use daily average H and He fluxes measured by the Wart Pulse Height Analysis (PHA) system of HI-SCALE in the energy ranges of 0.35 MeV/nuc to 1.0 MeV/nuc for He/H ratios, and 0.5 to 2.0 MeV/nuc for species in the Z > 2 composition range from Helium to Iron. Preliminary results show the expected dependence on solar cycle as well as on heliographic latitude of the spacecraft, and S/C distance from the Sun. We show the statistical relationship between He and H fluxes over this entire time interval (and sub time intervals), as well as between Z > 2 ions and He fluxes. In addition, spectral analyses of the ln(He/H) flux ratios exhibit large spectral peaks (above 99% confidence levels at numerous frequencies. All the frequencies reported in the analyses of Thomson et al. (Nature, 1995) in the 0 to 5.8 uHz range are matched within 10 nHz at significance levels above 90% confidence. We suggest that the spectral peaks in the ion fluxes are evidence for the global oscillation (`breathing') of the heliosphere, where the driving source for the breathing is the Sun, i.e., solar oscillations. A 24 nHz fine-splitting visible on many of the lines suggests that the 1.38-year oscillation of the tachocline (Howe et al, Science, 2000) modulates the modes.

  3. 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.

  4. Annealing behavior of high permeability amorphous alloys

    SciTech Connect

    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.

  5. Biofilaments as annealed semi-flexible copolymers

    NASA Astrophysics Data System (ADS)

    Fierling, Julien; Mohrbach, Hervé; Kulic, Igor; Lee, Nam-Kyung; Johner, Albert

    2014-06-01

    In many in vivo or in vitro situations, biofilaments manifest some annealed heterogeneity and should be considered as annealed random copolymers. The building blocks of the filaments differ from each other, for example, by the internal structure of the monomer, by the presence of some adsorbed species or by the curvature. Based on the copolymer concept, we embed the description of these systems in a common formalism. We demonstrate how the annealed heterogeneous nature of the filament is reflected by statistical correlations like the tangent-tangent correlation function or the cyclization probability. Our results show that annealed filaments adapt cooperatively to external constraints. This could contribute to explain anomalous elasticity manifested by biofilaments.

  6. Enthalpy relaxation and annealing effect in polystyrene.

    PubMed

    Sakatsuji, Waki; Konishi, Takashi; Miyamoto, Yoshihisa

    2013-07-01

    The effects of thermal history on the enthalpy relaxation in polystyrene are studied by differential scanning calorimetry. The temperature dependence of the specific heat in the liquid and the glassy states, that of relaxation time, and the exponent of the Kohlrausch-Williams-Watts function are determined by measurements of the thermal response against sinusoidal temperature variation. A phenomenological model equation previously proposed to interpret the memory effect in the frozen state is applied to the enthalpy relaxation and the evolution of entropy under a given thermal history is calculated. The annealing below the glass transition temperature produces two effects on enthalpy relaxation: the decay of excess entropy with annealing time in the early stage of annealing and the increase in relaxation time due to physical aging in the later stage. The crossover of these effects is reflected in the variation of temperature of the maximum specific heat observed in the heating process after annealing and cooling.

  7. Coherent Coupled Qubits for Quantum Annealing

    NASA Astrophysics Data System (ADS)

    Weber, Steven J.; Samach, Gabriel O.; Hover, David; Gustavsson, Simon; Kim, David K.; Melville, Alexander; Rosenberg, Danna; Sears, Adam P.; Yan, Fei; Yoder, Jonilyn L.; Oliver, William D.; Kerman, Andrew J.

    2017-07-01

    Quantum annealing is an optimization technique which potentially leverages quantum tunneling to enhance computational performance. Existing quantum annealers use superconducting flux qubits with short coherence times limited primarily by the use of large persistent currents Ip. Here, we examine an alternative approach using qubits with smaller Ip and longer coherence times. We demonstrate tunable coupling, a basic building block for quantum annealing, between two flux qubits with small (approximately 50-nA) persistent currents. Furthermore, we characterize qubit coherence as a function of coupler setting and investigate the effect of flux noise in the coupler loop on qubit coherence. Our results provide insight into the available design space for next-generation quantum annealers with improved coherence.

  8. Laser annealing of thin organic films

    NASA Astrophysics Data System (ADS)

    Agashkov, A. V.; Ivlev, G. D.; Filippov, V. V.; Kashko, I. A.; Shulitski, B. G.

    2010-09-01

    Microstructure of defects in organic solar cells containing PEDOT:PSS:Sorbitol layer has been studied and conditions for successful pulsed laser annealing of them have been determined. Investigation with oblique illumination showed that radial symmetry of fine structure is an intrinsic property of either separated discotic defects or block structure. Our study shows that pulsed laser annealing of organic thin films in inert atmosphere has promising future.

  9. Laser annealing of thin organic films

    NASA Astrophysics Data System (ADS)

    Agashkov, A. V.; Ivlev, G. D.; Filippov, V. V.; Kashko, I. A.; Shulitski, B. G.

    2011-02-01

    Microstructure of defects in organic solar cells containing PEDOT:PSS:Sorbitol layer has been studied and conditions for successful pulsed laser annealing of them have been determined. Investigation with oblique illumination showed that radial symmetry of fine structure is an intrinsic property of either separated discotic defects or block structure. Our study shows that pulsed laser annealing of organic thin films in inert atmosphere has promising future.

  10. Quantum Simulations of Classical Annealing Processes

    NASA Astrophysics Data System (ADS)

    Somma, R. D.; Boixo, S.; Barnum, H.; Knill, E.

    2008-09-01

    We describe a quantum algorithm that solves combinatorial optimization problems by quantum simulation of a classical simulated annealing process. Our algorithm exploits quantum walks and the quantum Zeno effect induced by evolution randomization. It requires order 1/δ steps to find an optimal solution with bounded error probability, where δ is the minimum spectral gap of the stochastic matrices used in the classical annealing process. This is a quadratic improvement over the order 1/δ steps required by the latter.

  11. Magnetic induced heating for ferritic metal annealing

    SciTech Connect

    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.

  12. Annealed CVD molybdenum thin film surface

    DOEpatents

    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.

  13. Superheating, melting, and annealing of copper surfaces

    SciTech Connect

    Hakkinen, H.; Landman, U. )

    1993-08-16

    Dynamics of superheating, melting, and annealing processes at Cu(111) and Cu(110) surfaces, induced by laser-pulse irradiation, are investigated using molecular dynamics simulations, incorporating energy transfer from the electronic to the ionic degrees of freedom. Superheating occurs at Cu(111) for conditions that lead to melting of the Cu(110) surface. Highly damaged Cu(111) surfaces structurally anneal under the influence of a superheating pulse.

  14. Positron study of annealing of gallium arsenide

    SciTech Connect

    Rice-Evans, P.C.; Smith, D.L.; Evans, H.E.; Gledhill, G.A. )

    1991-02-01

    A positron beam has been used to investigate the sub-surface changes in semi-insulating gallium arsenide which had been annealed to a range of temperatures. The variations of the Doppler S parameter as a function of positron implantation energy, when subjected to a diffusion analysis, indicate variations in positron trapping at different depths. The results indicate the changes in the type of point defect that accompany the annealing.

  15. Comparative study of the performance of quantum annealing and simulated annealing.

    PubMed

    Nishimori, Hidetoshi; Tsuda, Junichi; Knysh, Sergey

    2015-01-01

    Relations of simulated annealing and quantum annealing are studied by a mapping from the transition matrix of classical Markovian dynamics of the Ising model to a quantum Hamiltonian and vice versa. It is shown that these two operators, the transition matrix and the Hamiltonian, share the eigenvalue spectrum. Thus, if simulated annealing with slow temperature change does not encounter a difficulty caused by an exponentially long relaxation time at a first-order phase transition, the same is true for the corresponding process of quantum annealing in the adiabatic limit. One of the important differences between the classical-to-quantum mapping and the converse quantum-to-classical mapping is that the Markovian dynamics of a short-range Ising model is mapped to a short-range quantum system, but the converse mapping from a short-range quantum system to a classical one results in long-range interactions. This leads to a difference in efficiencies that simulated annealing can be efficiently simulated by quantum annealing but the converse is not necessarily true. We conclude that quantum annealing is easier to implement and is more flexible than simulated annealing. We also point out that the present mapping can be extended to accommodate explicit time dependence of temperature, which is used to justify the quantum-mechanical analysis of simulated annealing by Somma, Batista, and Ortiz. Additionally, an alternative method to solve the nonequilibrium dynamics of the one-dimensional Ising model is provided through the classical-to-quantum mapping.

  16. Boosting quantum annealer performance via sample persistence

    NASA Astrophysics Data System (ADS)

    Karimi, Hamed; Rosenberg, Gili

    2017-07-01

    We propose a novel method for reducing the number of variables in quadratic unconstrained binary optimization problems, using a quantum annealer (or any sampler) to fix the value of a large portion of the variables to values that have a high probability of being optimal. The resulting problems are usually much easier for the quantum annealer to solve, due to their being smaller and consisting of disconnected components. This approach significantly increases the success rate and number of observations of the best known energy value in samples obtained from the quantum annealer, when compared with calling the quantum annealer without using it, even when using fewer annealing cycles. Use of the method results in a considerable improvement in success metrics even for problems with high-precision couplers and biases, which are more challenging for the quantum annealer to solve. The results are further enhanced by applying the method iteratively and combining it with classical pre-processing. We present results for both Chimera graph-structured problems and embedded problems from a real-world application.

  17. 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

  18. Effect of Long-time Heating for Polyvinyl Chloride and Polypropylene Resin Pellet Certified Reference Materials for Heavy Metal Analysis.

    PubMed

    Ohata, Masaki

    2016-01-01

    The effect of long-time heating for both polyvinyl chloride (PVC) and polypropylene (PP) resin pellet certified reference materials (CRMs) for heavy metal analysis, which contained Cd, Cr, Hg and Pb, was examined in the present study. The temperature of the drying oven was 80°C, which was used for drying these CRMs before analysis, and the long-time heating was carried out for up to 480 h. As a result, a relative decrease in mass of ca. 0.3% was observed for both CRMs. Moreover, a decrease in concentration of ca. 10% was observed for Cr, even though the concentrations for other elements did not change during the long-time heating. Since the chemical form of Cr was an organometallic compound with lower melting point, it was considered that concentration decreased due to the heat.

  19. Long-time tail of the velocity autocorrelation function in a two-dimensional moderately dense hard-disk fluid.

    PubMed

    Isobe, Masaharu

    2008-02-01

    Alder and Wainwright discovered the slow power decay ~t(-d/2) (d is dimension) of the velocity autocorrelation function in moderately dense hard-sphere fluids using the event-driven molecular dynamics simulations. In the two-dimensional (2D) case, the diffusion coefficient derived using the time correlation expression in linear response theory shows logarithmic divergence, which is called the "2D long-time-tail problem." We reexamined this problem to perform a large-scale, long-time simulation with 1x10(6) hard disks using a modern efficient algorithm and found that the decay of the long tail in moderately dense fluids is slightly faster than the power decay (~1/t) . We also compared our numerical data with the prediction of the self-consistent mode-coupling theory in the long-time limit [~1/(t sqrt[ln t])] .

  20. Determining long time-scale hyporheic zone flow paths in Antarctic streams

    USGS Publications Warehouse

    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

  1. 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.

  2. Analysis of long time Standard Precipitation Index series to detect the drought frequency changes in Hungary

    NASA Astrophysics Data System (ADS)

    Lakatos, M.; Bihari, Z.; Szentimrey, T.

    2010-09-01

    The precipitation has large temporal and spatial variability in Hungary. Monthly precipitation sum could be zero in any month in a year and at any place of the country, but it can be near or even above 200 mm as well. The year-to-year variability of the annual precipitation amount is high, so it has large influence on the agriculture and economy. The long-term precipitation trend shows decreasing pattern from the beginning of the last century. Calculation of the several drought indices is a commonly used method to detect the severe drought events. Analysis of the SPI (Standard Precipitation Index) series is performed in this study. In climate studies the homogeneity of data series is of primary importance, since the SPI (Standard Precipitation Index) drought index calculation based on long time data series. That is homogenized daily and monthly precipitation amounts are used for SPI calculations in Hungary. Homogenization and complementing of precipitation data is performed by method the MASH (Multiple Analysis of Series for Homogenization; Szentimrey, 1999). Usually the station data series in Hungary are homogenized once in a year, at the beginning of each year after collecting the data also from all traditional precipitation stations. The SPI calculator which is offered on the project page of DMCSEE (Drought Management Centre for Southeastern Europe) is applied for SPI calculations in Hungary. In the drought mapping there are two ways: the first is when the SPI values are calculated in each grid point after gridding (by gridding part of MISH (Meteorological Interpolation based on Surface Homogenized Data Basis; Szentimrey, Bihari, 2007)) the station precipitation data, and then SPI values at all the grid point covering Hungary is visualized; the second one is when the station based SPI values are interpolated by method MISH (Meteorological Interpolation based on Surface Homogenized Data Basis; Szentimrey, Bihari, 2007) and then visualize them with a GIS mapping

  3. 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

  4. 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.

  5. The correct kinetic Bohm criterion

    NASA Astrophysics Data System (ADS)

    Czarnetzki, Uwe; Tsankov, Tsanko Vaskov

    2016-09-01

    Space charge sheaths are characteristic for bounded plasmas and are a key element in plasma-surface interactions. Hence, one of the most fundamental concepts in plasma physics - the Bohm criterion - is related to the definition of a sheath edge. However, its kinetic formulation is stirring controversies for a long time - from questioning its validity at high collisionality to claiming a divergence in its formulation. Here, based on a solution of the Boltzmann equation for ions with charge-exchange collisions and ionization both of these disputes are resolved: 1) The obtained form of the kinetic Bohm criterion removes the divergence in the ionic part. 2) It also introduces a new equally important term that describes collisional and geometric effects. This new term reestablishes the validity of the criterion at high collisionality. 3) It also restores agreement with the fluid counterpart of the criterion. The developed theory is supported by non-invasive spatially resolved measurements and a numerical model.

  6. Numerical study of long-time dynamics and ergodic-nonergodic transitions in dense simple fluids.

    PubMed

    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 derived from

  7. Origin of reverse annealing effect in hydrogen-implanted silicon

    SciTech Connect

    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.

  8. Kinetics of stress fibers

    NASA Astrophysics Data System (ADS)

    Stachowiak, Matthew R.; O'Shaughnessy, Ben

    2008-02-01

    Stress fibers are contractile cytoskeletal structures, tensile actomyosin bundles which allow sensing and production of force, provide cells with adjustable rigidity and participate in various processes such as wound healing. The stress fiber is possibly the best characterized and most accessible multiprotein cellular contractile machine. Here we develop a quantitative model of the structure and relaxation kinetics of stress fibers. The principal experimentally known features are incorporated. The fiber has a periodic sarcomeric structure similar to muscle fibers with myosin motor proteins exerting contractile force by pulling on actin filaments. In addition the fiber contains the giant spring-like protein titin. Actin is continuously renewed by exchange with the cytosol leading to a turnover time of several minutes. In order that steady state be possible, turnover must be regulated. Our model invokes simple turnover and regulation mechanisms: actin association and dissociation occur at filament ends, while actin filament overlap above a certain threshold in the myosin-containing regions augments depolymerization rates. We use the model to study stress fiber relaxation kinetics after stimulation, as observed in a recent experimental study where some fiber regions were contractile and others expansive. We find that two distinct episodes ensue after stimulation: the turnover-overlap system relaxes rapidly in seconds, followed by the slow relaxation of sarcomere lengths in minutes. For parameter values as they have been characterized experimentally, we find the long time relaxation of sarcomere length is set by the rate at which actin filaments can grow or shrink in response to the forces exerted by the elastic and contractile elements. Consequently, the stress fiber relaxation time scales inversely with both titin spring constant and the intrinsic actin turnover rate. The model's predicted sarcomere velocities and contraction-expansion kinetics are in good

  9. An Interview with Alan J. Hovestadt: AAMFT Past President and Long-Time Marriage and Family Counselor Educator

    ERIC Educational Resources Information Center

    Juhnke, Gerald A.; Sunich, Michael F.; Coll, Kenneth M.; Lebron-Striker, Maritza

    2009-01-01

    Alan J. Hovestadt, EdD, is the immediate past president of the 24,000 member American Association for Marriage and Family Therapy (AAMFT) and a long-time IAMFC member who served as an IAMFC founding board member when American Counseling Association (ACA) first granted International Association of Marriage and Family Counselors (IAMFC) divisional…

  10. An Interview with Alan J. Hovestadt: AAMFT Past President and Long-Time Marriage and Family Counselor Educator

    ERIC Educational Resources Information Center

    Juhnke, Gerald A.; Sunich, Michael F.; Coll, Kenneth M.; Lebron-Striker, Maritza

    2009-01-01

    Alan J. Hovestadt, EdD, is the immediate past president of the 24,000 member American Association for Marriage and Family Therapy (AAMFT) and a long-time IAMFC member who served as an IAMFC founding board member when American Counseling Association (ACA) first granted International Association of Marriage and Family Counselors (IAMFC) divisional…

  11. Diffusion influence on Michaelis-Menten kinetics

    NASA Astrophysics Data System (ADS)

    Kim, Hyojoon; Yang, Mino; Choi, Myung-Un; Shin, Kook Joe

    2001-07-01

    Influence of diffusion on the Michaelis-Menten kinetics is investigated with the renormalized kinetic theory recently proposed by Yang et al. [J. Chem. Phys. 108, 117; 108, 8557; 108, 9069 (1998)]. The nonlinearity predicted previously by Zhou [J. Phys. Chem. 101, 6642 (1997)] in the Lineweaver-Burk plot for the high concentration of substrate with his empirical expression and simulation is correctly obtained by the kinetic theory. We discuss possible errors in the estimation of reaction parameters caused by ignoring this nonlinearity in an experimental analysis (performed at even lower concentrations of the substrate). The time evolution of the production rate shows a peak before it reaches the steady-state value. The long time asymptotic relaxation of the deviation of the enzyme concentration from the steady-state value shows t-1/2 power-law behavior instead of the exponential decay predicted by the classical kinetics.

  12. Reactor pressure vessel annealing -- Effective mitigation method

    SciTech Connect

    Brumovsky, M.; Brynda, J.

    1996-09-01

    Reactor pressure vessels of old generation were mostly manufactured from materials with high content of impurities which results in high increase in irradiation embrittlement values. Standard mitigation methods for decrease this damage--application of low-leakage core or dummy elements insertion--are inefficient if applied during the reactor operation. Thermal annealing of reactor pressure vessels has been shown as a very effective method for restoration of initial material properties in a high extent. Even though annealing process is not fully understood from the microstructural changes point of view, results from the testing were so promising that many annealing of WWER RPVs were performed. Nevertheless, some problems still remains, connected mainly with monitoring of the extent of annealing restoration as well as with re-embrittlement rate after such a properties restoration. Experience with WWER-440 RPVs is discussed, mainly because of the austenitic cladding existence. Cladding does not allow to take templates from the inner RPV surface and it is damaged during operation, as well. At the same time, no monitoring of cladding behavior during operation was planned within surveillance programs. Problems connected with material behavior monitoring after annealing as well as during further operation (re-embrittlement rate) are discussed together with the assessment of inaccuracies and possible solutions.

  13. 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.

  14. 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.

  15. Quantum Annealing and Many-Body Localization

    NASA Astrophysics Data System (ADS)

    Bray-Ali, Noah

    The quantum phase transition separating the Ising spin glass from the quantum paramagnet phase in one-dimension is many-body localized. We study quantum annealing across this transition using the recently developed, dynamical strong-disorder renormalization group approach. The probability of successful adiabatic quantum computation of the spin glass ground-state obeys a universal scaling function of system size, anneal rate, and strength of disorder, which we obtain. Measurement of this universal scaling behavior in a quantum annealing device, for example, would be the first direct test of the activated dynamics of a many-body localized quantum phase transition. Support provided by National Research Council Post-Doctoral Research Associateship.

  16. Computational multiqubit tunnelling in programmable quantum annealers

    PubMed Central

    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

  17. THERMAL ANNEALING OF REACTOR PRESSURE VESSELS

    SciTech Connect

    Sokolov, Mikhail A; Server, W. L.; Nanstad, Randy K

    2015-01-01

    Some of the current fleet of nuclear power plants is poised to reach their end of life and will require an operating life time extension. Therefore, the main structural components, including the reactor pressure vessel (RPV), will be subject to higher neutron exposures than originally planned. These longer operating times raise serious concerns regarding our ability to manage the reliability of RPV steels at such high doses. Thermal annealing is the only option that can, to some degree, recover irradiated beltline region transition temperature shift and recover upper shelf energy properties lost during radiation exposure and extend RPV service life. This paper reviews the experience accumulated internationally with development and implementation of thermal annealing to RPV and potential perspectives for carrying out thermal annealing on US nuclear power plant RPVs.

  18. Stochastic annealing simulation of cascades in metals

    SciTech Connect

    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.

  19. High temperature annealing of fission tracks in fluorapatite, Santa Fe Springs oil field, Los Angeles Basin, California

    USGS Publications Warehouse

    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

  20. Formation of epitaxial metastable NiGe{sub 2} thin film on Ge(100) by pulsed excimer laser anneal

    SciTech Connect

    Lim, Phyllis S. Y.; Yeo, Yee-Chia; Chi, Dong Zhi; Lim, Poh Chong; Wang, Xin Cai; Chan, Taw Kuei; Osipowicz, Thomas

    2010-11-01

    Epitaxial nickel digermanide (NiGe{sub 2}), a metastable phase, was formed by laser annealing Ni on (100) germanium-on-silicon substrates. The NiGe{sub 2} formation was investigated using transmission electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, Rutherford backscattering spectroscopy, and first-principles calculations. The formation mechanism of NiGe{sub 2} is discussed and is attributed to both the reduced interfacial energy at the NiGe{sub 2}/Ge(100) interface and the kinetic aspects of the laser annealing reaction associated with phase transformation and film agglomeration.

  1. 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.

  2. Rock melting tool with annealer section

    DOEpatents

    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.

  3. 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.

  4. 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.

  5. Kinetic Measurements for Enzyme Immobilization.

    PubMed

    Cooney, Michael J

    2017-01-01

    Enzyme kinetics is the study of the chemical reactions that are catalyzed by enzymes, with a focus on their reaction rates. The study of an enzyme's kinetics considers the various stages of activity, reveals the catalytic mechanism of this enzyme, correlates its value to assay conditions, and describes how a drug or a poison might inhibit the enzyme. Victor Henri initially reported that enzyme reactions were initiated by a bond between the enzyme and the substrate. By 1910, Michaelis and Menten were advancing their work by studying the kinetics of an enzyme saccharase which catalyzes the hydrolysis of sucrose into glucose and fructose. They published their analysis and ever since the Michaelis-Menten equation has been used as the standard to describe the kinetics of many enzymes. Unfortunately, soluble enzymes must generally be immobilized to be reused for long times in industrial reactors. In addition, other critical enzyme properties have to be improved like stability, activity, inhibition by reaction products, and selectivity towards nonnatural substrates. Immobilization is by far the chosen process to achieve these goals.Although the Michaelis-Menten approach has been regularly adapted to the analysis of immobilized enzyme activity, its applicability to the immobilized state is limited by the barriers the immobilization matrix places upon the measurement of compounds that are used to model enzyme kinetics. That being said, the estimated value of the Michaelis-Menten coefficients (e.g., V max, K M) can be used to evaluate effects of immobilization on enzyme activity in the immobilized state when applied in a controlled manner. In this review enzyme activity and kinetics are discussed in the context of the immobilized state, and a few novel protocols are presented that address some of the unique constraints imposed by the immobilization barrier.

  6. Kinetic measurements for enzyme immobilization.

    PubMed

    Cooney, Michael J

    2011-01-01

    Enzyme kinetics is the study of the chemical reactions that are catalyzed by enzymes, with a focus on their reaction rates. The study of an enzyme's kinetics considers the various stages of activity, reveals the catalytic mechanism of the enzyme, correlates its value to assay conditions, and describes how a drug or a poison might inhibit the enzyme. Victor Henri initially reported that enzyme reactions were initiated by a bond between the enzyme and the substrate. By 1910, Michaelis and Menten had advanced this work by studying the kinetics of the enzyme saccharase, which catalyzes the hydrolysis of sucrose into glucose and fructose. They published their analysis, and ever since, the Michaelis-Menten equation has been used as the standard to describe the kinetics of many enzymes. Unfortunately, soluble enzymes must generally be immobilized to be reused for long times in industrial reactors. In addition, other critical enzyme properties have to be improved like stability, activity, inhibition by reaction products, selectivity toward nonnatural substrates. Immobilization is by far the chosen process to achieve these goals.Although the Michaelis-Menten approach has been regularly adopted for the analysis of immobilized enzyme activity, its applicability to the immobilized state is limited by the barriers the immobilization matrix places upon the measurement of compounds that are used to model enzyme kinetics. That being said, the estimated value of the Michaelis-Menten coefficients (e.g., V(max), K(M)) can be used to evaluate effects of immobilization on enzyme activity in the immobilized state when applied in a controlled manner. In this review, enzyme activity and kinetics are discussed in the context of the immobilized state, and a few novel protocols are presented that address some of the unique constraints imposed by the immobilization barrier.

  7. High-temperature annealing of proton irradiated beryllium – A dilatometry-based study

    DOE PAGES

    Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; ...

    2016-04-07

    S—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 tomore » 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. Here, 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.« less

  8. 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.

  9. GPU-Accelerated Population Annealing Algorithm: Frustrated Ising Antiferromagnet on the Stacked Triangular Lattice

    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.

  10. Application of annealed red mud to Mn(2+) ion adsorption from aqueous solution.

    PubMed

    Chen, Hongliang; Zheng, Juan; Zhang, Zhongqiong; Long, Qian; Zhang, Qiuyun

    2016-01-01

    Physicochemical characteristics and Mn(2+) adsorption of annealed red mud were investigated in this study. The annealing temperature (105-900 °C) changed the mineralogical components and the point of zero charge of red mud. By comparison, annealed red mud at 700 °C (ARM700) had a better adsorption effect than other annealed samples, associated with the activated components of available Fe2O3, Al2O3, SiO2 and Na5Al3(SiO4)3CO3 (natrodavyne). The removal efficiency of Mn(2+) by ARM700 was dependent on initial pH, contact time, and initial Mn(2+) concentration of aqueous solution and was ∼56.5% with initial Mn(2+) concentration 385 mg/L at initial pH > 5. The kinetics process was predicted better by the pseudo-second-order model. The Langmuir isotherm displayed a better fitting model than the Freundlich isotherm and the Mn(2+) maximum adsorption capacity of ARM700 was 88.3 mg/g. The competing effects of Cu(2+) and Zn(2+) on Mn(2+) removal were most obvious. There was efficient Mn(2+) removal at the application of ARM700 to the leachate of electrolytic manganese residue.

  11. High-temperature annealing of proton irradiated beryllium – A dilatometry-based study

    SciTech Connect

    Simos, Nikolaos; Elbakhshwan, Mohamed; Zhong, Zhong; Ghose, Sanjit; Savkliyildiz, Ilyas

    2016-04-07

    S—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. Here, 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.

  12. Towards ultra-fast solvent evaporation, the development of a computer controlled solvent vapor annealing chamber

    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.

  13. Improving the creep resistance and tensile property of UHMWPE sheet by radiation cross-linking and annealing

    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.

  14. On the long time behavior of the doubly infinite toda lattice under initial data decaying at infinity

    NASA Astrophysics Data System (ADS)

    Kamvissis, Spyridon

    1993-05-01

    We provide rigorous analysis of the long time behavior of the (doubly infinite) Toda lattice under initial data that decay at infinity, in the absence of solitions. We solve (approximately and for large times) the Riemann-Hilbert matrix factorization problem equivalent to the related inverse scattering problem with the help of the Beals-Coifman formula, by reducing it to a simpler one through a series of contour deformations in the spirit of the Deift-Zhou method.

  15. The distinctive feature of long time adiabatic modulation in the context of cnoidal wave and Akhmediev breaser interaction

    NASA Astrophysics Data System (ADS)

    Makarov, V. A.; Petnikova, V. M.

    2017-02-01

    For a nonintegrable system of two coupled nonlinear Schrödinger equations the adiabatic approximation is extended for long time interaction. The method enables analytical description of the modulation of a cnoidal wave by Akhmediev breather in an isotropic nonlinear gyrotropic medium with Kerr nonlinearity and second-order group-velocity dispersion. The conditions which must be fulfilled for stable propagation of the obtained solution with amplitude and frequency modulation are determined.

  16. Influence of deformation behavior, oxydation, and temperature on the long time cyclic stress behavior of high temperature steels

    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.

  17. Long-Time Plasma Membrane Imaging Based on a Two-Step Synergistic Cell Surface Modification Strategy.

    PubMed

    Jia, Hao-Ran; Wang, Hong-Yin; Yu, Zhi-Wu; Chen, Zhan; Wu, Fu-Gen

    2016-03-16

    Long-time stable plasma membrane imaging is difficult due to the fast cellular internalization of fluorescent dyes and the quick detachment of the dyes from the membrane. In this study, we developed a two-step synergistic cell surface modification and labeling strategy to realize long-time plasma membrane imaging. Initially, a multisite plasma membrane anchoring reagent, glycol chitosan-10% PEG2000 cholesterol-10% biotin (abbreviated as "GC-Chol-Biotin"), was incubated with cells to modify the plasma membranes with biotin groups with the assistance of the membrane anchoring ability of cholesterol moieties. Fluorescein isothiocyanate (FITC)-conjugated avidin was then introduced to achieve the fluorescence-labeled plasma membranes based on the supramolecular recognition between biotin and avidin. This strategy achieved stable plasma membrane imaging for up to 8 h without substantial internalization of the dyes, and avoided the quick fluorescence loss caused by the detachment of dyes from plasma membranes. We have also demonstrated that the imaging performance of our staining strategy far surpassed that of current commercial plasma membrane imaging reagents such as DiD and CellMask. Furthermore, the photodynamic damage of plasma membranes caused by a photosensitizer, Chlorin e6 (Ce6), was tracked in real time for 5 h during continuous laser irradiation. Plasma membrane behaviors including cell shrinkage, membrane blebbing, and plasma membrane vesiculation could be dynamically recorded. Therefore, the imaging strategy developed in this work may provide a novel platform to investigate plasma membrane behaviors over a relatively long time period.

  18. Unraveling Quantum Annealers using Classical Hardness

    NASA Astrophysics Data System (ADS)

    Martin-Mayor, Victor; Hen, Itay

    2015-10-01

    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.

  19. Deformation and annealing study of Nicraly

    NASA Technical Reports Server (NTRS)

    Trela, D. M.; Ebert, L. J.

    1975-01-01

    Extensive experiments were carried out on the ODS alloy Nicraly, (an alloy prepared by mechanical alloying and consolidating a powder blend consisting of 16% chromium, 4% aluminum, 2-3% yttria, balance nickel), in efforts to develop methods of controlling the grain size and grain shape of the material. The experiments fell into two general categories: variations in the annealing parameters using the as-extruded material as it was received, and various thermomechanical processing schedules (various combinations of cold work and annealing). Success was achieved in gaining grain size and grain shape control by annealing of the as-extruded material. By proper selection of annealing temperature and cooling rates, the grain size of the as-received material was increased almost two orders of magnitude (from an average grain dimension of 0.023 mm to 1.668 mm) while the aspect ratio was increased by some 50% (from 20:1 to 30:1). No success was achieved in gaining significant control of the grain size and shape of the material by thermo-mechanical processing.

  20. Optimal Groundwater Management: 1. Simulated Annealing

    NASA Astrophysics Data System (ADS)

    Dougherty, David E.; Marryott, Robert A.

    1991-10-01

    Simulated annealing is introduced and applied to the optimization of groundwater management problems cast in combinatorial form. This heuristic, probabilistic optimization method seeks minima in analogy with the annealing of solids and is effective on large-scale problems. No continuity requirements are imposed on objective (cost) functions. Constraints may be added to the cost function via penalties, imposed by designation of the solution domain, or imbedded in submodels (e.g., mass balance in aquifer flow simulators) used to evaluate costs. The location of global optima may be theoretically guaranteed, but computational limitations lead to searches for nearly optimal solutions in practice. Like other optimization methods, most of the computational effort is expended in flow and transport simulators. Practical algorithmic guidance that leads to enormous computational savings and sometimes makes simulated annealing competitive with gradient-type optimization methods is provided. The method is illustrated by example applications to idealized problems of groundwater flow and selection of remediation strategy, including optimization with multiple groundwater control technologies. They demonstrate the flexibility of the method and indicate its potential for solving groundwater management problems. The application of simulated annealing to water resources problems is new and its development is immature, so further performance improvements can be expected.

  1. Graphene annealing: how clean can it be?

    PubMed

    Lin, Yung-Chang; Lu, Chun-Chieh; Yeh, Chao-Huei; Jin, Chuanhong; Suenaga, Kazu; Chiu, Po-Wen

    2012-01-11

    Surface contamination by polymer residues has long been a critical problem in probing graphene's intrinsic properties and in using graphene for unique applications in surface chemistry, biotechnology, and ultrahigh speed electronics. Poly(methyl methacrylate) (PMMA) is a macromolecule commonly used for graphene transfer and device processing, leaving a thin layer of residue to be empirically cleaned by annealing. Here we report on a systematic study of PMMA decomposition on graphene and of its impact on graphene's intrinsic properties using transmission electron microscopy (TEM) in combination with Raman spectroscopy. TEM images revealed that the physisorbed PMMA proceeds in two steps of weight loss in annealing and cannot be removed entirely at a graphene susceptible temperature before breaking. Raman analysis shows a remarkable blue-shift of the 2D mode after annealing, implying an anneal-induced band structure modulation in graphene with defects. Calculations using density functional theory show that local rehybridization of carbons from sp(2) to sp(3) on graphene defects may occur in the random scission of polymer chains and account for the blue-shift of the Raman 2D mode.

  2. Unraveling Quantum Annealers using Classical Hardness.

    PubMed

    Martin-Mayor, Victor; Hen, Itay

    2015-10-20

    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.

  3. Annealing of gold nanostructures sputtered on polytetrafluoroethylene

    PubMed Central

    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

  4. Unraveling Quantum Annealers using Classical Hardness

    PubMed Central

    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

  5. High temperature annealing of ion irradiated tungsten

    DOE PAGES

    Ferroni, Francesco; Yi, Xiaoou; Arakawa, Kazuto; ...

    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

  6. High temperature annealing of ion irradiated tungsten

    SciTech Connect

    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+/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 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 Ea=1.34±0.2 eV for the 700–1100°C range.

  7. Consideration on Isochronal Anneal Technique: From Measurement to Physics

    SciTech Connect

    Flament, O.; Fleetwood, D.M.; Leray, J.L.; Paillet, P.

    1999-03-09

    The isochronal anneal technique used to predict isothermal anneal behavior of MOS devices is analyzed as a function of experimental parameters. The effects of detrapping of trapped holes and compensating electrons are discussed.

  8. Atomic-Scale Investigation of Latent Fission Tracks in Fluorapatite: Physical Characteristics and Annealing Behavior.

    NASA Astrophysics Data System (ADS)

    Paul, Tracy Anne

    1993-01-01

    A JEOL JEM-2000FX analytical transmission electron microscope, equipped with a cold stage and anticontamination device, has been used to study the physical characteristics and annealing behavior of artificially induced fission tracks in fluorapatite. Near the atomic level, unetched fission tracks are not continuous, but are comprised of segments of extended damage that are separated by gaps of undamaged microstructure. From dark-field transmission electron microscopy (TEM) images, it appears that the crystalline damage around tracks, although intensive, is not extensive. As such, the defect density may be represented by a Gaussian-type distribution function. The disordered nature of the track core and defect distribution geometry supports the Ion-Explosion Theory that has been proposed for track formation. TEM analysis reveals that track width is crystallographically controlled. Parallel to the c-axis, tracks display widths of 5 to 13 nm and hexagonal faceting on the (0001) plane. Tracks perpendicular to the c-axis display widths of 3 to 9 nm and prismatic faceting on the (1000) plane. The track cross-section facets mimic etch-pit morphologies and provide a relative measure of the crystal's surface free energy. A consequence of differential bond strengths and elastic properties in the fluorapatite structure, track-width anisotropy resolves etching- and annealing-rate anisotropy that has been reported for fission tracks in fluorapatite. TEM observation of the behavior of fission tracks in response to electron beam exposure (i.e., radiolytic annealing), and temperature increase (i.e., thermal annealing), yields a physical and a kinetic description of the annealing process. Annealing commences with bulging at the track's tapered ends, followed by detachment of a single sphere. This process is replicated until a critical track radius is encountered at which the track geometry approaches an ideal right cylinder. A sinusoidal boundary develops at the track

  9. Understanding of PS-b-PMMA phase segregation under laser-induced millisecond thermal annealing

    NASA Astrophysics Data System (ADS)

    Jacobs, Alan G.; Liedel, Clemens; Ober, Christopher K.; Thompson, Michael O.

    2015-03-01

    Laser thermal annealing of PS-b-PMMA is shown to modify phase segregation within the milliseconds timeframe at temperatures from the glass transition to far above the order-disorder transition temperature. We report the kinetics of phase segregation of cylinder forming PS-b-PMMA (53.8 kg/mol, fPS = 0.7) as probed by micro-beam grazing incidence small angle X-ray scattering. Structure evolution was probed as a function of peak temperature, time at temperature, and quench rate, with phase segregation readily occurring on millisecond time scales and at peak quench rates up to 107 K/s. The final film morphology is dependent on both the anneal time and the quench rate to ambient. With heating to sufficiently high temperatures, the thermal history is erased yielding a final state is purely dependent on the quench rate.

  10. Atomic scale simulations of arsenic ion implantation and annealing in silicon

    SciTech Connect

    Caturla, M.J.; Diaz de la Rubia, T.; Jaraiz, M.

    1995-01-23

    We present results of multiple-time-scale simulations of 5, 10 and 15 keV low temperature ion implantation of arsenic on silicon (100), followed by high temperature anneals. The simulations start with a molecular dynamics (MD) calculation of the primary state of damage after 10ps. The results are then coupled to a kinetic Monte Carlo (MC) simulation of bulk defect diffusion and clustering. Dose accumulation is achieved considering that at low temperatures the damage produced in the lattice is stable. After the desired dose is accumulated, the system is annealed at 800{degrees}C for several seconds. The results provide information on the evolution for the damage microstructure over macroscopic length and time scales and affords direct comparison to experimental results. We discuss the database of inputs to the MC model and how it affects the diffusion process.

  11. Annealing of aluminum bicrystals with S orientations deformed by channel die compression

    SciTech Connect

    Blicharski, M.; Liu, J.; Hu, H.

    1995-08-01

    The microstructural and textural changes during recovery and recrystallization in two high-purity aluminum bicrystals with S orientations deformed by channel die compression have been studied in detail. The deformation part of the study was reported previously [Blicharski et al., Acta metall. mater. 41, 2007 (1993)]. In the present study, the annealing kinetics, the microtextural characteristics of nucleation, and the textures at partial and full recrystallization, were carefully examined. The results of the present study, together with those of earlier investigations [Bunge, Texture Analysis in Materials Science, Butterworth, London (1982); Hjelen et al., Acta metall. mater. 39, 1377 (1991)], indicate strongly that either the oriented nucleation mechanism or the oriented growth mechanism alone appears to be inadequate for explaining the recrystallization textures. The authors believe that both of these mechanisms are equally important for the formation of annealing textures.

  12. Behaviour of implanted arsenic during rapid thermal annealing of Ti on Si

    NASA Astrophysics Data System (ADS)

    Ponpon, J. P.; Saulnier, A.; Stuck, R.

    1987-11-01

    The reaction during rapid thermal annealing of the Ti-Si couple with arsenic implanted either into titanium or into silicon has been investigated from the point of view of suicide formation kinetics and impurity redistribution. In contrast with similar experiments on other refractory metals, tungsten for example, the reaction is not blocked by the presence of arsenic but a temperature and dose dependent impurity effect leading to a lowering of the growth rate of the disilicide phase is observed. This has been attributed to arsenic segregation in the grain boundaries of the growing suicide which reduces the transport of silicon via easy diffusion paths towards the unreacted metal or a metal rich suicide phase. Arsenic, when present in the metal, has been found to produce the same effects as oxygen at the early beginning of the annealing. However, after the reaction has started the respective behaviour and influence of arsenic and oxygen become completely different.

  13. An Effect of Annealing on Shielding Properties of Shungite

    NASA Astrophysics Data System (ADS)

    Belousova, E. S.; Mahmoud, M. Sh.; Lynkou, L. M.

    2013-05-01

    Annealing of shungite is studied in oxidizing conditions in a chamber with NH4Cl, and in vacuum at 900 °C for 2h. Frequency dependencies of transmission and reflection coefficients of annealed shungite are measured in the frequency range of 8-12 GHz. The minimum reflection at 8-10 GHz was shown for shungite annealed in the oxidizing atmosphere.

  14. AUTOMATED MALLEABLE ANNEALING OVENS SLOWLY HEAT AND COOL CASTINGS AS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    AUTOMATED MALLEABLE ANNEALING OVENS SLOWLY HEAT AND COOL CASTINGS AS THEY MOVE IN BINS ALONG TRACKS IN THE OVEN BOTTOM IN THE MALLEABLE ANNEALING BUILDING. THIS PROCESS TRANSFORMS BRITTLE WHITE IRON CASTINGS INTO SOFTER, STRONGER MALLEABLE IRON. - Stockham Pipe & Fittings Company, Malleable Annealing Building, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

  15. Nucleocapsid Protein Annealing of a Primer-Template Enhances (+)-Strand DNA Synthesis and Fidelity by HIV-1 Reverse Transcriptase†

    PubMed Central

    Kim, Jiae; Roberts, Anne; Yuan, Hua; Xiong, Yong; Anderson, Karen S.

    2012-01-01

    Human immunodeficiency virus type-1 (HIV-1) requires reverse transcriptase (RT) and HIV-1 nucleocapsid protein (NCp7) for proper viral replication. HIV-1 NCp7 has been shown to enhance various steps in reverse transcription including tRNA initiation and strand transfer which may be mediated through interactions with RT as well as RNA and DNA oligonucleotides. With the use of DNA oligonucleotides, we have examined the interaction of NCp7 with RT and the kinetics of reverse transcription during (+)-strand synthesis with an NCp7-facilitated annealed primer-template. Using a pre-steady state kinetics approach, the NCp7-annealed primer-template has a substantial increase (3-7 fold) in the rate of incorporation (kpol) by RT as compared to heat annealed primer-template with single nucleotide incorporation. There was also a 2-fold increase in the binding affinity constant (Kd) of the nucleotide. These differences in kpol and Kd were not through direct interactions between HIV-1 RT and NCp7. When examining extension by RT, the data suggests that the NCp7-annealed primer-template facilitates the formation of a longer product more quickly compared to the heat annealed primer-template. This enhancement in rate is mediated through interactions with NCp7’s zinc fingers and N-terminal domain and nucleic acids. The NCp7-annealed primer-template also enhances the fidelity of RT (3-fold) by slowing the rate of incorporation of an incorrect nucleotide. Taken together, this study elucidates a new role of NCp7 by facilitating DNA-directed DNA synthesis during reverse transcription by HIV-1 RT that may translate into enhanced viral fitness and offers an avenue to exploit for targeted therapeutic intervention against HIV. PMID:22210155

  16. HIV-1 Nucleocapsid Protein Switches the Pathway of TAR RNA/DNA Annealing from Loop-Loop “Kissing” to “Zipper”

    PubMed Central

    Vo, My-Nuong; Barany, George; Rouzina, Ioulia; Musier-Forsyth, Karin

    2009-01-01

    Summary The chaperone activity of human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein (NC) facilitates multiple nucleic acid rearrangements that are critical for reverse transcription of the single-stranded RNA genome into double-stranded DNA. Annealing of the trans-activation response element (TAR) RNA hairpin to a complementary TAR DNA hairpin is an essential step in the minus-strand transfer step of reverse transcription. Previously, we used truncated 27-nucleotide (nt) mini-TAR RNA and DNA constructs to investigate this annealing reaction pathway in the presence and absence of HIV-1 NC. In this work, full-length 59-nt TAR RNA and TAR DNA constructs were used to systematically study TAR hairpin annealing kinetics. In the absence of NC, full-length TAR hairpin annealing is ∼10-fold slower than mini-TAR annealing. Similar to mini-TAR annealing, the reaction pathway for TAR in the absence of NC involves the fast formation of an unstable “kissing” loop intermediate, followed by a slower conversion to an extended duplex. NC facilitates the annealing of TAR by ∼105-fold by stabilizing the bimolecular intermediate (∼104-fold) and promoting the subsequent exchange reaction (∼10-fold). In contrast to the mini-TAR annealing pathway, wherein NC-mediated annealing can initiate through both loop-loop kissing and a distinct “zipper” pathway involving nucleation at the 3′/5′ terminal ends, full-length TAR hairpin annealing switches predominantly to the zipper pathway in the presence of saturated NC. PMID:19154737

  17. Kinetic theory and long range correlations in moderately dense gases

    SciTech Connect

    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.

  18. Kinetic percolation

    NASA Astrophysics Data System (ADS)

    Heinson, W. R.; Chakrabarti, A.; Sorensen, C. M.

    2017-05-01

    We demonstrate that kinetic aggregation forms superaggregates that have structures identical to static percolation aggregates, and these superaggregates appear as a separate phase in the size distribution. Diffusion limited cluster-cluster aggregation (DLCA) simulations were performed to yield fractal aggregates with a fractal dimension of 1.8 and superaggregates with a fractal dimension of D = 2.5 composed of these DLCA supermonomers. When properly normalized to account for the DLCA fractal nature of their supermonomers, these superaggregates have the exact same monomer packing fraction, scaling law prefactor, and scaling law exponent (the fractal dimension) as percolation aggregates; these are necessary and sufficient conditions for same structure. The size distribution remains monomodal until these superaggregates form to alter the distribution. Thus the static percolation and the kinetic descriptions of gelation are now unified.

  19. Prevalence of non-food allergies among non-immigrants, long-time immigrants and recent immigrants in Canada.

    PubMed

    Yao, Jiayun; Sbihi, Hind

    2016-12-27

    The prevalence of allergic conditions has been increasing worldwide, with the highest rates seen in Western countries like Canada. The development of allergies is known to be related to both genetic and environmental factors, but the causal pathways remain unclear. Studies on immigrants provide a unique opportunity to disentangle these two factors and provide a better understanding of the disease aetiology. The aim of this study was to investigate the relationship between immigration status and prevalence of non-food allergies in a population-based study of Canadians. Data of 116,232 respondents from the Canadian Community Health Survey (Cycle 3.1, 2005) were used in a multivariable logistic regression to assess the association between immigration status (non-immigrant, long-time immigrant [>10 years] and recent immigrant [≤10 years]) and self-reported doctor-diagnosed non-food allergies, adjusting for potential confounders. The highest prevalence of non-food allergies was found among non-immigrants (29.6%), followed by long-time immigrants (23.9%) and then recent immigrants (14.3%). The odds of non-food allergies were reduced by 60% (OR = 0.40, 95% CI: 0.35, 0.45) among recent immigrants and 25% (OR = 0.75, 95% CI: 0.70, 0.80) among long-time immigrants, compared with non-immigrants, after adjusting for sex, age, socio-economic status and rurality. This study finds a distinctly lower prevalence of non-food allergies among immigrants compared with non-immigrants, with the difference diminishing with longer duration of residence in Canada. The findings highlight the potential of environmental determinants of allergy development that warrant further investigation, and demonstrate the need for multicultural strategies to manage the public health burden of allergic conditions.

  20. Renormalizing SMD: The Renormalization Approach and Its Use in Long Time Simulations and Accelerated PMF Calculations of Macromolecules

    PubMed Central

    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

  1. Shock, Post-Shock Annealing, and Post-Annealing Shock in Ureilites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    The thermal and shock histories of ureilites can be divided into four periods: 1) formation, 2) initial shock, 3) post-shock annealing, and 4) post-annealing shock. Period 1 occurred approx.4.55 Ga ago when ureilites formed by melting chondritic material. Impact events during period 2 caused silicate darkening, undulose to mosaic extinction in olivines, and the formation of diamond, lonsdaleite, and chaoite from indigenous carbonaceous material. Alkali-rich fine-grained silicates may have been introduced by impact injection into ureilites during this period. About 57% of the ureilites were unchanged after period 2. During period 3 events, impact-induced annealing caused previously mosaicized olivine grains to become aggregates of small unstrained crystals. Some ureilites experienced reduction as FeO at the edges of olivine grains reacted with C from the matrix. Annealing may also be responsible for coarsening of graphite in a few ureilites, forming euhedral-appearing, idioblastic crystals. Orthopyroxene in Meteorite Hills (MET) 78008 may have formed from pigeonite by annealing during this period. The Rb-Sr internal isochron age of approx.4.0 Ga for MET 78008 probably dates the annealing event. At this late date, impacts are the only viable heat source. About 36% of ureilites experienced period 3 events, but remained unchanged afterwards. During period 4, approx.7% of the ureilites were shocked again, as is evident in the polymict breccia, Elephant Moraine (EET) 83309. This rock contains annealed mosaicized olivine aggregates composed of small individual olivine crystals that exhibit undulose extinction. Ureilites may have formed by impact-melting chondritic material on a primitive body with heterogeneous O isotopes. Plagioclase was preferentially lost from the system due to its low impedance to shock compression. Brief melting and rapid burial minimized the escape of planetary-type noble gases from the ureilitic melts. Incomplete separation of metal from silicates

  2. Comparison of Olivine Grain Growth during Dynamic Recrystallization, Post-deformational Annealing, and Static Annealing

    NASA Astrophysics Data System (ADS)

    Speciale, P. A.; Behr, W. M.; Hirth, G.; Tokle, L.

    2016-12-01

    Strain localization is associated with dynamic recrystallization in shear zones. However, whether localization persists to form long-lived plate boundaries is debated because of the possible counteracting effects of grain growth. We deformed Balsam Gap dunite, a natural olivine aggregate, under axial compression to examine the relative contributions of strain energy and surface energy in facilitating grain boundary migration (GBM) and grain growth. Experiments were conducted at 1100-1200°C, 10-4-10-5 s-1, and 1300 MPa confining pressure. Samples that were allowed to recover after deformation show abundant evidence of surface energy-driven GBM, but average grain size does not increase significantly compared to that in samples quenched prior to annealing. In contrast, samples that continued to deform at a reduced strain rate (for the same time as the annealed samples) show both strain energy- and surface energy-driven GBM, and an increased grain size. These observations suggest that growth is enhanced by continued deformation at low stress. More sluggish grain growth in deformed samples that annealed under static conditions may result from continued recrystallization during stress relaxation, grain boundary pinning by accessory chromite, or melt along grain boundaries and at triple junctions. To facilitate comparison of our results to published grain growth laws for olivine, we also conducted a hydrostatic grain growth experiment on 10-20 μm powders of Balsam Gap dunite and San Carlos olivine separated by a Pt disc and annealed for 24 hours at 1100°C. A similar experiment was run at 1000°C for 10 minutes to constrain the initial grain size before annealing. Both powdered materials exhibit grain growth after 24 hours. However, although they had the same starting grain size, the annealed San Carlos olivine is slightly coarser than the annealed Balsam Gap dunite, which suggests that grain growth is inhibited in the dunite.

  3. Shock, Post-Shock Annealing, and Post-Annealing Shock in Ureilites

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    The thermal and shock histories of ureilites can be divided into four periods: 1) formation, 2) initial shock, 3) post-shock annealing, and 4) post-annealing shock. Period 1 occurred approx.4.55 Ga ago when ureilites formed by melting chondritic material. Impact events during period 2 caused silicate darkening, undulose to mosaic extinction in olivines, and the formation of diamond, lonsdaleite, and chaoite from indigenous carbonaceous material. Alkali-rich fine-grained silicates may have been introduced by impact injection into ureilites during this period. About 57% of the ureilites were unchanged after period 2. During period 3 events, impact-induced annealing caused previously mosaicized olivine grains to become aggregates of small unstrained crystals. Some ureilites experienced reduction as FeO at the edges of olivine grains reacted with C from the matrix. Annealing may also be responsible for coarsening of graphite in a few ureilites, forming euhedral-appearing, idioblastic crystals. Orthopyroxene in Meteorite Hills (MET) 78008 may have formed from pigeonite by annealing during this period. The Rb-Sr internal isochron age of approx.4.0 Ga for MET 78008 probably dates the annealing event. At this late date, impacts are the only viable heat source. About 36% of ureilites experienced period 3 events, but remained unchanged afterwards. During period 4, approx.7% of the ureilites were shocked again, as is evident in the polymict breccia, Elephant Moraine (EET) 83309. This rock contains annealed mosaicized olivine aggregates composed of small individual olivine crystals that exhibit undulose extinction. Ureilites may have formed by impact-melting chondritic material on a primitive body with heterogeneous O isotopes. Plagioclase was preferentially lost from the system due to its low impedance to shock compression. Brief melting and rapid burial minimized the escape of planetary-type noble gases from the ureilitic melts. Incomplete separation of metal from silicates

  4. Stable long-time semiclassical description of zero-point energy in high-dimensional molecular systems.

    PubMed

    Garashchuk, Sophya; Rassolov, Vitaly A

    2008-07-14

    Semiclassical implementation of the quantum trajectory formalism [J. Chem. Phys. 120, 1181 (2004)] is further developed to give a stable long-time description of zero-point energy in anharmonic systems of high dimensionality. The method is based on a numerically cheap linearized quantum force approach; stabilizing terms compensating for the linearization errors are added into the time-evolution equations for the classical and nonclassical components of the momentum operator. The wave function normalization and energy are rigorously conserved. Numerical tests are performed for model systems of up to 40 degrees of freedom.

  5. Simulated annealing in orbital flight planning

    NASA Technical Reports Server (NTRS)

    Soller, Jeffrey

    1990-01-01

    Simulated annealing is used to solve a minimum fuel trajectory problem in the space station environment. The environment is unique because the space station will define the first true multivehicle environment in space. The optimization yields surfaces which are potentially complex, with multiple local minima. Because of the likelihood of these local minima, descent techniques are unable to offer robust solutions. Other deterministic optimization techniques were explored without success. The simulated annealing optimization is capable of identifying a minimum-fuel, two-burn trajectory subject to four constraints. Furthermore, the computational efforts involved in the optimization are such that missions could be planned on board the space station. Potential applications could include the on-site planning of rendezvous with a target craft of the emergency rescue of an astronaut. Future research will include multiwaypoint maneuvers, using a knowledge base to guide the optimization.

  6. Nanowire transformation and annealing by Joule heating.

    PubMed

    Hummelgård, Magnus; Zhang, Renyun; Carlberg, Torbjörn; Vengust, Damjan; Dvorsek, Damjan; Mihailovic, Dragan; Olin, Håkan

    2010-04-23

    Joule heating of bundles of Mo(6)S(3)I(6) nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo(6)S(3)I(6) into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m( - 1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

  7. Annealing of Solar Cells and Other Thin Film Devices

    NASA Technical Reports Server (NTRS)

    Escobar, Hector; Kuhlman, Franz; Dils, D. W.; Lush, G. B.; Mackey, Willie R. (Technical Monitor)

    2001-01-01

    Annealing is a key step in most semiconductor fabrication processes, especially for thin films where annealing enhances performance by healing defects and increasing grain sizes. We have employed a new annealing oven for the annealing of CdTe-based solar cells and have been using this system in an attempt to grow US on top of CdTe by annealing in the presence of H2S gas. Preliminary results of this process on CdTe solar cells and other thin-film devices will be presented.

  8. Mechanistic studies of mini-TAR RNA/DNA annealing in the absence and presence of HIV-1 nucleocapsid protein.

    PubMed

    Vo, My-Nuong; Barany, George; Rouzina, Ioulia; Musier-Forsyth, Karin

    2006-10-13

    HIV-1 reverse transcription involves several nucleic acid rearrangements, which are catalyzed by the nucleocapsid protein (NC). Annealing of the trans-activation response element (TAR) DNA hairpin to a complementary TAR RNA hairpin, resulting in the formation of an extended 98-base-pair duplex, is an essential step in the minus-strand transfer step of reverse transcription. To elucidate the TAR RNA/DNA annealing reaction pathway, annealing kinetics were studied systematically by gel-shift assays performed in the presence or absence of HIV-1 NC. Truncated 27 nucleotide mini-TAR RNA and DNA constructs were used in this work. In the absence of NC, the annealing is slow, and involves the fast formation of an unstable extended "kissing" loop intermediate, followed by a slower strand exchange between the terminal stems. This annealing is very sensitive to loop-loop complementarity, as well as to nucleic acid concentration, ionic strength and temperature. NC stimulates the annealing approximately 5000-fold by stabilizing the bimolecular intermediate approximately 100 to 200-fold, and promoting the subsequent strand exchange reaction approximately 10 to 20-fold. NC concentration dependence studies suggest that there is a direct correlation between the amount of NC required to stabilize the intermediate and the amount needed to induce mini-TAR aggregation. Whereas saturating levels of NC are required to efficiently aggregate nucleic acids, sub-saturating NC is sufficient to significantly enhance duplex destabilization. Equilibrium levels of mini-TAR RNA/DNA annealing were also measured under a variety of conditions. Taken together, the results presented here provide a quantitative accounting of HIV-1 NC's aggregation and duplex destabilizing activity, and provide insights into the universal nucleic acid chaperone activity of this essential viral protein.

  9. Annealing of paramagnetic centres in electron- and ion-irradiated yttria-stabilized zirconia: effect of yttria content

    SciTech Connect

    Costantini, Jean-Marc; Beuneu, Francois; Weber, William J

    2014-01-01

    We have studied the effect of the yttria content on the recovery of paramagnetic centres in electron-irradiated yttria-stabilized zirconia (ZrO2: Y3+). Single crystals with 9.5 mol% or 18 mol% Y2O3 were irradiated with electrons of 1.0, 1.5, 2.0 and 2.5 MeV. Paramagnetic centre thermal annealing was studied by X-band EPR spectroscopy. Hole-centres are found to be annealed more quickly, or at a lower temperature, for 18 mol% than for 9.5 mol% Y2O3. At long annealing times, a non-zero asymptotic behaviour is observed in the isothermal annealing curves of hole-centres and F+-type centres between 300 and 500 K. The normalized asymptotic concentration of both defects has a maximum value of about 0.5 for annealing temperatures near 375 K, below the onset of the (isochronal) recovery stage, regardless of the yttria content. Such an uncommon behaviour is analyzed on the basis of either kinetic rate equations of charge transfer or equilibria between point defects with different charge states.

  10. Microstructural analysis of the thermal annealing of ice-Ih using EBSD

    NASA Astrophysics Data System (ADS)

    Hidas, Károly; Tommasi, Andréa; Mainprice, David; Chauve, Thomas; Barou, Fabrice; Montagnat, Maurine

    2017-04-01

    . Decrease in average intragranular misorientation at the sample scale and modification of the misorientation across subgrain boundaries provide evidence for recovery from the earliest stages of annealing. This evolution is similar for all studied samples irrespective of their initial strain or annealing temperature. After an incubation period up to 2 hours, recovery is accompanied by recrystallization (nucleation and grain boundary migration). Grain growth proceeds at the expense of domains with high intra-granular misorientations and its kinetics fits the parabolic growth law. Deformation-induced microstructures (tilt boundaries and kink bands) are stable features during early stages of static recrystallization and locally slow down grain boundary migration, pinning grain growth. REFERENCES 1. Duval, P., Ashby, M.F., Anderman, I., 1983. Rate-controlling processes in the creep of polycrystalline ice. Journal of Physical Chemistry 87, 4066-4074. 2. Grennerat, F., Montagnat, M., Castelnau, O., Vacher, P., Moulinec, H., Suquet, P., Duval, P., 2012. Experimental characterization of the intragranular strain field in columnar ice during transient creep. Acta Materialia 60, 3655-3666. 3. Chauve, T., Montagnat, M., Vacher, P., 2015. Strain field evolution during dynamic recrystallization nucleation: A case study on ice. Acta Materialia 101, 116-124. Funding: Research leading to these results was funded by the EU-FP7 Marie Curie postdoctoral grant PIEF-GA-2012-327226 to K.H.

  11. Laser Annealing of GaAs

    DTIC Science & Technology

    1978-12-01

    annealing implanted layers. Sheet resistance measurements made on the irradiated semi- insulating GaAs samples indicate no significant change in the... sheet resistance after laser irradiation (typical decrease in the sheet resistance after laser irradiation was found to be less than a factor of two...OF THE SHEET - RESISTANCE (P ) THE EFFECTIVE SHEET ELECTRON CONCENTRATION (N ), AND THE EFFECTIVE MOBILITY _u)FOR SEMIb- INSULATING GaAs IMPLANTED WITH

  12. Simulated annealing algorithm for optimal capital growth

    NASA Astrophysics Data System (ADS)

    Luo, Yong; Zhu, Bo; Tang, Yong

    2014-08-01

    We investigate the problem of dynamic optimal capital growth of a portfolio. A general framework that one strives to maximize the expected logarithm utility of long term growth rate was developed. Exact optimization algorithms run into difficulties in this framework and this motivates the investigation of applying simulated annealing optimized algorithm to optimize the capital growth of a given portfolio. Empirical results with real financial data indicate that the approach is inspiring for capital growth portfolio.

  13. Laser Annealing of Ion Implanted Silicon.

    DTIC Science & Technology

    1981-08-01

    Lett. 35, 608 (1979). 6. B. L. Crowder, R. S. Title, M. H. Brodsky, and G. D. Petit, Appl. Phys. Lett. 16, 205 (1970). - 7. J. A. Van Vechten, R. Tsu ...LASER ANNEALING OF ION IMPLANTEDSILICON(U) ILLINOIS 2/2 UNIV AT URBANA C ORDI ATED SCIENCE LAO A SHATTACHARYYAI A iR9i 964-MCS2 UNCLASSIFIED RG1R-1

  14. Laser annealing of ion implanted silicon

    SciTech Connect

    White, C.W.; Appleton, B.R.; Wilson, S.R.

    1980-01-01

    Pulsed laser annealing of ion implanted silicon leads to the formation of supersaturated alloys by nonequilibrium crystal growth processes at the interface occurring during liquid phase epitaxial regrowth. The interfacial distribution coefficients from the melt (k') and the maximum substitutional solubilities (C/sub s//sup max/) are far greater than equilibrium values. Both K' and C/sub s//sup max/ are functions of growth velocity. Mechanisms limiting substitutional solubilities are discussed. 5 figures, 2 tables.

  15. Seismic traveltime tomography: a simulated annealing approach

    NASA Astrophysics Data System (ADS)

    Wéber, Zoltán

    2000-04-01

    Seismic traveltime tomography involves finding a velocity model that minimizes the error energy between the measured and the theoretical traveltimes. When solving this nonlinear inverse problem, a local optimization technique can easily produce a solution for which the gradient of the error energy function vanishes, but the energy function itself does not take its global minimum. Other methods such as simulated annealing can be applied to such global optimization problems. The simulated annealing approach to seismic traveltime tomography described in this paper has been tested on synthetic as well as real seismic data. It is shown that unlike local methods, the convergence of the simulated annealing algorithm is independent of the initial model: even in cases of virtually no prior information, it is capable of producing reliable results. The method can provide a number of acceptable solutions. When prior information is sparse, the solution of the global optimization can be used as an input to a local optimization procedure, such as, e.g., simultaneous iterative reconstruction technique (SIRT), producing an even more accurate result.

  16. Annealing studies of highly doped boron superlattices

    SciTech Connect

    Jackman, T. E.; Houghton, D. C.; Jackman, J. A.; Denhoff, M. W.; Kechang, S.; McCaffrey, J.; Rockett, A.

    1989-09-01

    Coevaporation of B/sub 2/ O/sub 3/ during silicon molecular-beam epitaxy at growth temperatures (/ital T//sub /ital G// ) varying from 540 to 800 /degree/C has been used to prepare superlattice structures (/ital pipi/'s) of varying boron concentration (3/times/10/sup 18/ --3/times/10/sup 20/ B cm/sup /minus/3/). The superlattices were subsequently subjected to various annealing procedures and the layers were examined by secondary ion mass spectrometry, electrochemical profiling, and cross-sectional transmission electron microscopy. A significant redistribution of boron was observed even before annealing for /ital T//sub /ital G// /gt/700 /degree/C and high boron concentrations. In addition, significant oxygen was incorporated for /ital T//sub /ital G// /le/700 /degree/C, with a growth rate of 0.5 nm s/sup /minus/1/ and a B/sub 2/ O/sub 3/ flux of 2/times/10/sup 13/ cm/sup /minus/2/ s/sup /minus/1/. After annealing, the boron diffusion coefficients were determined for the layers and found to vary significantly with /ital T//sub /ital G//.

  17. Annealing free magnetic tunnel junction sensors

    NASA Astrophysics Data System (ADS)

    Knudde, S.; Leitao, D. C.; Cardoso, S.; Freitas, P. P.

    2017-04-01

    Annealing is a major step in the fabrication of magnetic tunnel junctions (MTJs). It sets the exchange bias between the pinned and antiferromagnetic layers, and helps to increase the tunnel magnetoresistance (TMR) in both amorphous and crystalline junctions. Recent research on MTJs has focused on MgO-based structures due to their high TMR. However, the strict process control and mandatory annealing step can limit the scope of the application of these structures as sensors. In this paper, we present AlOx-based MTJs that are produced by ion beam sputtering and remote plasma oxidation and show optimum transport properties with no annealing. The microfabricated devices show TMR values of up to 35% and using NiFe/CoFeB free layers provides tunable linear ranges, leading to coercivity-free linear responses with sensitivities of up to 5.5%/mT. The top-pinned synthetic antiferromagnetic reference shows a stability of about 30 mT in the microfabricated devices. Sensors with linear ranges of up to 60 mT are demonstrated. This paves the way for the integration of MTJ sensors in heat-sensitive applications such as flexible substrates, or for the design of low-footprint on-chip multiaxial sensing devices.

  18. Effects of annealing temperature on shape transformation and optical properties of germanium quantum dots

    NASA Astrophysics Data System (ADS)

    Alireza, Samavati; Othaman, Z.; K. Ghoshal, S.; K. Mustafa, M.

    2015-02-01

    The influences of thermal annealing on the structural and optical features of radio frequency (rf) magnetron sputtered self-assembled Ge quantum dots (QDs) on Si (100) are investigated. Preferentially oriented structures of Ge along the (220) and (111) directions together with peak shift and reduced strain (4.9% to 2.7%) due to post-annealing at 650 °C are discerned from x-ray differaction (XRD) measurement. Atomic force microscopy (AFM) images for both pre-annealed and post-annealed (650 °C) samples reveal pyramidal-shaped QDs (density ˜ 0.26× 1011 cm-2) and dome-shape morphologies with relatively high density ˜ 0.92 × 1011 cm-2, respectively. This shape transformation is attributed to the mechanism of inter-diffusion of Si in Ge interfacial intermixing and strain non-uniformity. The annealing temperature assisted QDs structural evolution is explained using the theory of nucleation and growth kinetics where free energy minimization plays a pivotal role. The observed red-shift ˜ 0.05 eV in addition to the narrowing of the photoluminescence peaks results from thermal annealing, and is related to the effect of quantum confinement. Furthermore, the appearance of a blue-violet emission peak is ascribed to the recombination of the localized electrons in the Ge-QDs/SiO2 or GeOx and holes in the ground state of Ge dots. Raman spectra of both samples exhibit an intense Ge-Ge optical phonon mode which shifts towards higher frequency compared with those of the bulk counterpart. An experimental Raman profile is fitted to the models of phonon confinement and size distribution combined with phonon confinement to estimate the mean dot sizes. A correlation between thermal annealing and modifications of the structural and optical behavior of Ge QDs is established. Tunable growth of Ge QDs with superior properties suitable for optoelectronic applications is demonstrated. Project supported by Ibnu Sina Institute for Fundamental Science Study, Universiti Teknologi Malaysia

  19. Study of millisecond laser annealing on ion implanted soi and application to scaled finfet technology

    NASA Astrophysics Data System (ADS)

    Michalak, Tyler J.

    The fabrication of metal-oxide-semiconductor field effect transistors (MOSFET) requires the engineering of low resistance, low leakage, and extremely precise p-n junctions. The introduction of finFET technology has introduced new challenges for traditional ion implantation and annealing techniques in junction design as the fin widths continue to decrease for improved short channel control. This work investigates the use of millisecond scanning laser annealing in the formation of n-type source/drain junctions in next generation MOSFET. We present a model to approximate the true thermal profile for a commercial laser annealing process which allows us to represent more precisely specific thermal steps using Technology Computer Aided Design (TCAD). Sheet resistance and Hall Effect measurements for blanket films are used to correlate dopant activation and mobility with the regrowth process during laser anneal. We show the onset of high conductivity associated with completion of solid phase epitaxial regrowth (SPER) in the films. The Lattice Kinetic Monte Carlo (LKMC) model shows excellent agreement with cross section transmission electron microscopy (TEM), correlating the increase of conductivity with completion of crystal regrowth, increased activation, and crystal quality at various temperatures. As scaled devices move into the non-planar geometries and possibly adopt silicon-on-insulator (SOI) substrates, the crystal regrowth and dopant activation of amorphizing implants becomes more complicated and doping methods must adapt accordingly. Following the concept of the more recently proposed hot ion implantation and the benefits of laser anneal, we investigate a possible process flow for a 10/14 nm node SOI finFET by utilizing process and device TCAD. Device simulation parameters for the 10/14 nm node device are taken from a calibrated model based on fabricated non-planar 40 nm gate length device finFET. The implications on device performance are considered for the

  20. Ion-implanted laser annealed silicon solar cells

    NASA Technical Reports Server (NTRS)

    Katzeff, J. S.

    1980-01-01

    Development of low cost solar cells fabrication technology is being sponsored by NASA JPL as part of the Low Cost Solar Array Project (LSA). In conformance to Project requirements ion implantation and laser annealing were evaluated as junction formation techniques offering low cost-high throughput potential. Properties of cells fabricated utilizing this technology were analyzed by electrical, transmission electron microscopy, Rutherford backscattering and secondary ion mass spectrometry techniques. Tests indicated the laser annealed substrates to be damage free and electrically active. Similar analysis of ion implanted furnace annealed substrates revealed the presence of residual defects in the form of dislocation lines and loops with substantial impurity redistribution evident for some anneal temperature/time regimes. Fabricated laser annealed cells exhibited improved spectral response and conversion efficiency in comparison to furnace annealed cells. An economic projection for LSA indicates a potential for considerable savings from laser annealing technology.

  1. Application of laser annealing to solar cell junction formation

    NASA Technical Reports Server (NTRS)

    Katzeff, J. S.; Lopez, M.; Josephs, R. H.

    1981-01-01

    The possibility of using high-energy Q-switched Nd:glass lasers to form pn junctions in solar cells by annealing ion-implanted substrates is investigated. The properties of laser annealed cells are analyzed by electrical, transmission electron microscopy, Rutherford backscattering and secondary ion mass spectrometry techniques. Tests indicate the laser annealed substrates to be damage-free and electrically active. Similar reference analysis of ion-implanted furnace-annealed substrates reveals the presence of residual defects in the form of dislocation lines and loops with substantial impurity redistribution evident for some anneal temperature/time regimes. Fabricated laser annealed cells exhibit excellent conversion efficiency. It is noted that additional improvements are anticipated once the anneal parameters for a back surface field are optimized.

  2. The long time tail of molecular velocity correlation in a confined fluid: observation by modulated gradient spin-echo NMR

    NASA Astrophysics Data System (ADS)

    Stepišnik, Janez; Callaghan, Paul T.

    2000-11-01

    In addition to the fast correlation for local stochastic motion the molecular velocity correlation function in a fluid enclosed within the pore boundaries features a slow long time tail decay [1,2]. This article presents a study by the NMR modulated gradient spin-echo method (MGSE) [3] on a system of water trapped in the space between the closely packed polystyrene beads. The results prove that the obtained dependence of spin-echo attenuation on time, gradient strength and modulation frequency nicely corresponds to the recently developed NMR approach, which is able to describe the effects of arbitrarily shaped gradient pulse sequence on the spin-echo attenuation [4,5]. With an MGSE pulse sequence, a repetitive train of RF pulses with interspersed gradient pulses periodically modulates the spin-phase, giving the spin-echo attenuation proportional to a value of the velocity correlation spectrum at the modulation frequency. It enables to extract the low-frequency correlation spectrum of confined water molecules. The function exhibits a negative long time tail characteristic (a low-frequency decay of the spectrum), that can be well fitted with the spectrum calculated from the solution of the Langevin equation for restricted diffusion (which exhibits an exponential decay) as well as with the spectrum obtained when simulating the hydrodynamics of molecular motion constrained by capillary walls (which gives an algebraic decay).

  3. Enhanced constitutive invasion activity in human nontumorigenic keratinocytes exposed to a low level of barium for a long time.

    PubMed

    Thang, Nguyen D; Yajima, Ichiro; Ohnuma, Shoko; Ohgami, Nobutaka; Kumasaka, Mayuko Y; Ichihara, Gaku; Kato, Masashi

    2015-02-01

    We have recently demonstrated that exposure to barium for a short time (≤4 days) and at a low level (5 µM = 687 µg/L) promotes invasion of human nontumorigenic HaCaT cells, which have characteristics similar to those of normal keratinocytes, suggesting that exposure to barium for a short time enhances malignant characteristics. Here we examined the effect of exposure to low level of barium for a long time, a condition mimicking the exposure to barium through well water, on malignant characteristics of HaCaT keratinocytes. Constitutive invasion activity, focal adhesion kinase (FAK) protein expression and activity, and matrix metalloproteinase 14 (MMP14) protein expression in primary cultured normal human epidermal keratinocytes, HaCaT keratinocytes, and HSC5 and A431 human squamous cell carcinoma cells were augmented following an increase in malignancy grade of the cells. Constitutive invasion activity, FAK phosphorylation, and MMP14 expression levels of HaCaT keratinocytes after treatment with 5 µM barium for 4 months were significantly higher than those of control untreated HaCaT keratinocytes. Taken together, our results suggest that exposure to a low level of barium for a long time enhances constitutive malignant characteristics of HaCaT keratinocytes via regulatory molecules (FAK and MMP14) for invasion.

  4. Repetitive RNA unwinding by RNA helicase A facilitates RNA annealing.

    PubMed

    Koh, Hye Ran; Xing, Li; Kleiman, Lawrence; Myong, Sua

    2014-07-01

    Helicases contribute to diverse biological processes including replication, transcription and translation. Recent reports suggest that unwinding of some helicases display repetitive activity, yet the functional role of the repetitiveness requires further investigation. Using single-molecule fluorescence assays, we elucidated a unique unwinding mechanism of RNA helicase A (RHA) that entails discrete substeps consisting of binding, activation, unwinding, stalling and reactivation stages. This multi-step process is repeated many times by a single RHA molecule without dissociation, resulting in repetitive unwinding/rewinding cycles. Our kinetic and mutational analysis indicates that the two double stand RNA binding domains at the N-terminus of RHA are responsible for such repetitive unwinding behavior in addition to providing an increased binding affinity to RNA. Further, the repetitive unwinding induces an efficient annealing of a complementary RNA by making the unwound strand more accessible. The complex and unusual mechanism displayed by RHA may help in explaining how the repetitive unwinding of helicases contributes to their biological functions.

  5. Dewetting of Epitaxial Silver Film on Silicon by Thermal Annealing

    NASA Astrophysics Data System (ADS)

    Sanders, Charlotte E.; Kellogg, Gary L.; Shih, C.-K.

    2013-03-01

    It has been shown that noble metals can grow epitaxially on semiconducting and insulating substrates, despite being a non-wetting system: low temperature deposition followed by room temperature annealing leads to atomically flat film morphology. However, the resulting metastable films are vulnerable to dewetting, which has limited their utility for applications under ambient conditions. The physics of this dewetting is of great interest but little explored. We report on an investigation of the dewetting of epitaxial Ag(111) films on Si(111) and (100). Low energy electron microscopy (LEEM) shows intriguing evolution in film morphology and crystallinity, even at temperatures below 100oC. On the basis of these findings, we can begin to draw compelling inferences about film-substrate interaction and the kinetics of dewetting. Financial support is from NSF, DGE-0549417 and DMR-0906025. This work was performed, in part, at the Center for Integrated Nanotechnologies, User Facility operated for the U.S. DOE Office of Science. Sandia National Lab is managed and operated by Sandia Corp., a subsidiary of Lockheed Martin Corp., for the U.S. DOE's National Nuclear Security Administration under DE-AC04-94AL85000.

  6. Raman and XPS analyses of pristine and annealed N-doped double-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Sauer, Markus; Domanov, Oleg; Rohringer, Philip; Ayala, Paola; Pichler, Thomas

    2015-11-01

    N-doped single/multi-walled carbon nanotubes (CNTs) were studied for long time from synthesis to properties. However, the stability of N in the CNT lattice still needs further developments. In this work, to obtain more stable N-doped CNTs, concentric double-walled (DW) CNTs with more N were synthesized using benzylamine as C and N source. In order to test the stability of N-doped DWCNTs, high-temperature annealing in vacuum was performed. By XPS and Raman spectroscopic measurements, we found that the N-doped DWCNTs are still stable under 1500 $\\,^{\\circ}\\mathrm{C}$: the graphitic N does not change at all, the molecular N is partly removed, and the pyridinic N ratio greatly increases by more than two times. The reason could be that the N atoms from the surrounded N-contained materials combine into the CNT lattice during the annealing. Compared with the undoped DWCNTs, no Raman frequency shift was observed for the RBM, the G-band, and the G'-band of the N-doped DWCNTs.

  7. Comparing Monte Carlo methods for finding ground states of Ising spin glasses: Population annealing, simulated annealing, and parallel tempering.

    PubMed

    Wang, Wenlong; Machta, Jonathan; Katzgraber, Helmut G

    2015-07-01

    Population annealing is a Monte Carlo algorithm that marries features from simulated-annealing and parallel-tempering Monte Carlo. As such, it is ideal to overcome large energy barriers in the free-energy landscape while minimizing a Hamiltonian. Thus, population-annealing Monte Carlo can be used as a heuristic to solve combinatorial optimization problems. We illustrate the capabilities of population-annealing Monte Carlo by computing ground states of the three-dimensional Ising spin glass with Gaussian disorder, while comparing to simulated-annealing and parallel-tempering Monte Carlo. Our results suggest that population annealing Monte Carlo is significantly more efficient than simulated annealing but comparable to parallel-tempering Monte Carlo for finding spin-glass ground states.

  8. Comparing Monte Carlo methods for finding ground states of Ising spin glasses: Population annealing, simulated annealing, and parallel tempering

    NASA Astrophysics Data System (ADS)

    Wang, Wenlong; Machta, Jonathan; Katzgraber, Helmut G.

    2015-07-01

    Population annealing is a Monte Carlo algorithm that marries features from simulated-annealing and parallel-tempering Monte Carlo. As such, it is ideal to overcome large energy barriers in the free-energy landscape while minimizing a Hamiltonian. Thus, population-annealing Monte Carlo can be used as a heuristic to solve combinatorial optimization problems. We illustrate the capabilities of population-annealing Monte Carlo by computing ground states of the three-dimensional Ising spin glass with Gaussian disorder, while comparing to simulated-annealing and parallel-tempering Monte Carlo. Our results suggest that population annealing Monte Carlo is significantly more efficient than simulated annealing but comparable to parallel-tempering Monte Carlo for finding spin-glass ground states.

  9. Tolrestat kinetics

    SciTech Connect

    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.

  10. Radiation damage annealing mechanisms and possible low temperature annealing in silicon solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.

    1980-01-01

    Deep level transient spectroscopy and the Shockley-Read-Hall recombination theory are used to identify the defect responsible for reverse annealing in 2 ohm-cm n+/p silicon solar cells. This defect, with energy level at Ev + 0.30 eV, has been tentatively identified as a boron-oxygen-vacancy complex. It has been also determined by calculation that the removal of this defect could result in significant annealing at temperatures as low as 200 C for 2 ohm-cm and lower resistivity cells.

  11. Use of a simulated annealing algorithm to fit compartmental models with an application to fractal pharmacokinetics.

    PubMed

    Marsh, Rebeccah E; Riauka, Terence A; McQuarrie, Steve A

    2007-01-01

    Increasingly, fractals are being incorporated into pharmacokinetic models to describe transport and chemical kinetic processes occurring in confined and heterogeneous spaces. However, fractal compartmental models lead to differential equations with power-law time-dependent kinetic rate coefficients that currently are not accommodated by common commercial software programs. This paper describes a parameter optimization method for fitting individual pharmacokinetic curves based on a simulated annealing (SA) algorithm, which always converged towards the global minimum and was independent of the initial parameter values and parameter bounds. In a comparison using a classical compartmental model, similar fits by the Gauss-Newton and Nelder-Mead simplex algorithms required stringent initial estimates and ranges for the model parameters. The SA algorithm is ideal for fitting a wide variety of pharmacokinetic models to clinical data, especially those for which there is weak prior knowledge of the parameter values, such as the fractal models.

  12. Nucleation of fractal nanocrystallites upon annealing of Fe-based metallic glass

    DOE PAGES

    Diao, Jiecheng; Chen, Bo; Luo, Qiang; ...

    2017-03-13

    Bragg Coherent X-ray Diffraction Imaging has been used to determine the structure of the initial clusters of α-Fe nano crystals which form upon annealing of an Iron-based amorphous alloy or metallic glass. The method is able to identify the shapes and strain of these crystallites without any need for cutting the sample, so can visualize them in three dimensions in their intact state. In this way, the delicate dendritic structures on the exterior of the crystallites can be seen and its density vs radius relationship identifies a fractal dimension of the porous region that is consistent with diffusion-limited aggregation models.more » The crystal sizes were found to be around 60nm after annealing at 700°C growing to about 330nm after annealing at 750°C. This article introduces the BCDI method and describes its application to characterize previously recrystallized samples of Iron-based amorphous alloys. It paves the way for a possible future in situ nucleation/growth investigation of the relationship between kinetics and nanostructure of metallic glass.« less

  13. Annealing helicase HARP closes RPA-stabilized DNA bubbles non-processively.

    PubMed

    Burnham, Daniel R; Nijholt, Bas; De Vlaminck, Iwijn; Quan, Jinhua; Yusufzai, Timur; Dekker, Cees

    2017-05-05

    We investigate the mechanistic nature of the Snf2 family protein HARP, mutations of which are responsible for Schimke immuno-osseous dysplasia. Using a single-molecule magnetic tweezers assay, we construct RPA-stabilized DNA bubbles within torsionally constrained DNA to investigate the annealing action of HARP on a physiologically relevant substrate. We find that HARP closes RPA-stabilized bubbles in a slow reaction, taking on the order of tens of minutes for ∼600 bp of DNA to be re-annealed. The data indicate that DNA re-anneals through the removal of RPA, which is observed as clear steps in the bubble-closing traces. The dependence of the closing rate on both ionic strength and HARP concentration indicates that removal of RPA occurs via an association-dissociation mechanism where HARP does not remain associated with the DNA. The enzyme exhibits classical Michaelis-Menten kinetics and acts cooperatively with a Hill coefficient of 3 ± 1. Our work also allows the determination of some important features of RPA-bubble structures at low supercoiling, including the existence of multiple bubbles and that RPA molecules are mis-registered on the two strands. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  14. Skewness, long-time memory, and non-stationarity: Application to leverage effect in financial time series

    NASA Astrophysics Data System (ADS)

    Roman, H. E.; Porto, M.; Dose, C.

    2008-10-01

    We analyze daily log-returns data for a set of 1200 stocks, taken from US stock markets, over a period of 2481 trading days (January 1996-November 2005). We estimate the degree of non-stationarity in daily market volatility employing a polynomial fit, used as a detrending function. We find that the autocorrelation function of absolute detrended log-returns departs strongly from the corresponding original data autocorrelation function, while the observed leverage effect depends only weakly on trends. Such effect is shown to occur when both skewness and long-time memory are simultaneously present. A fractional derivative random walk model is discussed yielding a quantitative agreement with the empirical results.

  15. An implicit difference scheme for the long-time evolution of localized solutions of a generalized Boussinesq system

    SciTech Connect

    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.

  16. Annealing texture of nanostructured IF steel

    SciTech Connect

    Jamaati, Roohollah

    2015-08-15

    In the present work, the evolution of annealing texture in nanostructured interstitial free steel fabricated via accumulative roll bonding (ARB) process was investigated. Textural evolution after post-annealing of ARB-processed samples was evaluated using X-ray diffraction. There were several texture transitions in the γ-fiber and ζ-fiber during ARB and post-annealing treatment. It was found that with increasing the number of ARB cycles, the volume fraction of the low angle grain boundary decreased and the high angle grain boundary fraction increased. Also, the shear texture was dominant after the first cycle, while for other samples, the rolling texture was dominant. The one-cycle sample clearly indicated a weak α-fiber and γ-fiber and a relatively strong ζ-fiber. In addition, during the recrystallization and before the grain growth, the intensity of α-fiber and γ-fiber decreased, the intensity of ζ-fiber increased, and the intensity of (011)〈100〉 orientation in the ε-fiber and η-fiber increased. Moreover, it was concluded that the transition from the rolling texture to the shear one was a sign of occurrence of the recrystallization (before the grain growth). Finally, with increasing the number of ARB cycles, the intensity of rolling and shear textures saturated and a stable texture formed. - Highlights: • There were texture transitions in the γ-fiber and ζ-fiber. • When the number of cycles increased, the low angle grain boundaries decreased. • The shear texture was dominant after the first cycle. • Transition from rolling texture to shear one was a sign of recrystallization. • With increasing the number of ARB cycles, a stable texture formed.

  17. Optimised simulated annealing for Ising spin glasses

    NASA Astrophysics Data System (ADS)

    Isakov, S. V.; Zintchenko, I. N.; Rønnow, T. F.; Troyer, M.

    2015-07-01

    We present several efficient implementations of the simulated annealing algorithm for Ising spin glasses on sparse graphs. In particular, we provide a generic code for any choice of couplings, an optimised code for bipartite graphs, and highly optimised implementations using multi-spin coding for graphs with small maximum degree and discrete couplings with a finite range. The latter codes achieve up to 50 spin flips per nanosecond on modern Intel CPUs. We also compare the performance of the codes to that of the special purpose D-Wave devices built for solving such Ising spin glass problems.

  18. Shortcuts to adiabaticity for quantum annealing

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazutaka

    2017-01-01

    We study the Ising Hamiltonian with a transverse field term to simulate the quantum annealing. Using shortcuts to adiabaticity, we design the time dependence of the Hamiltonian. The dynamical invariant is obtained by the mean-field ansatz, and the Hamiltonian is designed by the inverse engineering. We show that the time dependence of physical quantities such as the magnetization is independent of the speed of the Hamiltonian variation in the infinite-range model. We also show that rotating transverse magnetic fields are useful to achieve the ideal time evolution.

  19. Thermal Annealing in Calorimetery for Super Bigbite

    NASA Astrophysics Data System (ADS)

    Riordan, Seamus; Wojtsekhowski, Bogdan; Jones, Mark; Shahinyan, Albert

    2015-10-01

    Radiation damage to lead glass in the form of optical darkening presents a serious challenge to electromagnetic calorimetry for modern high-luminosity experiments in an open environment. In particular, the Super Bigbite GEp measurement to Q2 = 12GeV2 using ep scattering at Jefferson Lab relies heavily on calorimetry in such an environment for elastic electron event triggering and event reconstruction. The novel technique of thermal annealing to maintain continuous optical transparency of the lead glass calorimeter blocks has been chosen to remedy this effect. An overview of the technical design considerations for such a calorimeter and results regarding the construction of smaller-scale prototypes will be presented.

  20. Kinetic buffers.

    PubMed

    Alibrandi, Giuseppe; Fabbrizzi, Luigi; Licchelli, Maurizio; Puglisi, Antonio

    2015-01-12

    This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH-sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH-t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di-copper(II) bistren complex in a single run, in a completely automatic experiment. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Following atomistic kinetics on experimental timescales with the kinetic Activation–Relaxation Technique

    SciTech Connect

    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.

  2. Annealing of gold nanostructures sputtered on glass substrate

    NASA Astrophysics Data System (ADS)

    Švorčík, V.; Siegel, J.; Šutta, P.; Mistrík, J.; Janíček, P.; Worsch, P.; Kolská, Z.

    2011-03-01

    The effects of annealing at 300 °C on gold nanostructures sputtered onto glass substrate were studied using XRD, SAXSees, the Van der Pauw method and ellipsometry. As-sputtered and annealed samples exhibit a different dependence of the gold lattice parameter on the sputtering time. With increasing sputtering time the average thickness of the layer and the size of gold crystallites increased. Another rapid enlargement of the crystallites is observed after annealing. The volume resistivity decreases rapidly with the increasing sputtering time for both, as-deposited and annealed structures. With increasing sputtering time initially discontinuous gold coverage changes gradually in a continuous one. Electrically continuous gold coverage on the as-sputtered and annealed samples exhibits the same concentration of free charge carriers and Hall mobility. Optical constants of as-deposited and annealed gold films determined by ellipsometry support resistivity measurements and clearly manifest the presence of plasmons in discontinuous films.

  3. Annealing ambient controlled deep defect formation in InP

    NASA Astrophysics Data System (ADS)

    Zhao, Y. W.; Dong, Z. Y.; Duan, M. L.; Sun, W. R.; Zeng, Y. P.; Sun, N. F.; Sun, T. N.

    2004-07-01

    Deep defects in annealed InP have been investigated by deep level transient capacitance spectroscopy (DLTS), photo induced current transient spectroscopy (PICTS) and thermally stimulated current spectroscopy (TSC). Both DLTS results of annealed semiconducting InP and PICTS and TSC results of annealed semi-insulating InP indicate that InP annealed in phosphorus ambient has five defects, while InP annealed in iron phosphide ambient has two defects. Such a defect formation phenomenon is explained in terms of defect suppression by the iron atom diffusion process. The correlation of the defects and the nature of the defects in annealed InP are discussed based on the results.

  4. Effect of annealing history on free volume in thermoplastics

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; St.clair, T. L.

    1986-01-01

    Two different types of thermoplastic glassy polymers have been investigated for the effects of thermal annealing on their free volumes. It has been observed that free volumes in glassy polymers decrease asymptotically to a steady level after about four thermal anneals lasting for 24 hours at a temperature about 50 C below their glass transition temperatures. These results indicate that composites incorporating properly annealed thermoplastic matrices may not experience any additional internal stresses due to subsequent thermal excursions experienced while in service.

  5. A coherent quantum annealer with Rydberg atoms.

    PubMed

    Glaetzle, A W; van Bijnen, R M W; Zoller, P; Lechner, W

    2017-06-22

    There is a significant ongoing effort in realizing quantum annealing with different physical platforms. The challenge is to achieve a fully programmable quantum device featuring coherent adiabatic quantum dynamics. Here we show that combining the well-developed quantum simulation toolbox for Rydberg atoms with the recently proposed Lechner-Hauke-Zoller (LHZ) architecture allows one to build a prototype for a coherent adiabatic quantum computer with all-to-all Ising interactions and, therefore, a platform for quantum annealing. In LHZ an infinite-range spin-glass is mapped onto the low energy subspace of a spin-1/2 lattice gauge model with quasi-local four-body parity constraints. This spin model can be emulated in a natural way with Rubidium and Caesium atoms in a bipartite optical lattice involving laser-dressed Rydberg-Rydberg interactions, which are several orders of magnitude larger than the relevant decoherence rates. This makes the exploration of coherent quantum enhanced optimization protocols accessible with state-of-the-art atomic physics experiments.

  6. Magnetic field annealing for improved creep resistance

    SciTech Connect

    Brady, Michael P.; Ludtka, Gail M.; Ludtka, Gerard M.; Muralidharan, Govindarajan; Nicholson, Don M.; Rios, Orlando; Yamamoto, Yukinori

    2015-12-22

    The method provides heat-resistant chromia- or alumina-forming Fe-, Fe(Ni), Ni(Fe), or Ni-based alloys having improved creep resistance. A precursor is provided containing preselected constituents of a chromia- or alumina-forming Fe-, Fe(Ni), Ni(Fe), or Ni-based alloy, at least one of the constituents for forming a nanoscale precipitate MaXb where M is Cr, Nb, Ti, V, Zr, or Hf, individually and in combination, and X is C, N, O, B, individually and in combination, a=1 to 23 and b=1 to 6. The precursor is annealed at a temperature of 1000-1500.degree. C. for 1-48 h in the presence of a magnetic field of at least 5 Tesla to enhance supersaturation of the M.sub.aX.sub.b constituents in the annealed precursor. This forms nanoscale M.sub.aX.sub.b precipitates for improved creep resistance when the alloy is used at service temperatures of 500-1000.degree. C. Alloys having improved creep resistance are also disclosed.

  7. Superplasticity of Annealed H13 Steel

    PubMed Central

    Duan, Zhenxin; Pei, Wen; Gong, Xuebo; Chen, Hua

    2017-01-01

    H13 steel is a widely used hot work die material. A new type of hot working method is imperative to develop complex and precise dies. In this paper, the heat treatment of H13 steel (AISI) was carried out by annealing, the final structure is a point or spherical pearlite, and the grain size is about 30–40 μm. The tensile properties of the annealed microstructure were investigated at 650, 750, and 850 °C with the strain rates of 1 × 10−3 s−1, 5 × 10−4 s−1, and 1 × 10−4 s−1. The tensile fracture and microstructure were analyzed by SEM and HREM. The results show that the tensile samples reach superplasticity at the strain rate of 1 × 10−4 s−1 in the temperature range of 750–850 °C. When the temperature is 850 °C, the maximum elongation rate reaches 112.5%. This demonstrates the possibility of making superplastic forming molds. During the tensile process, the refined M23C6 and other high hardness carbides which are dispersed uniformly in the matrix, effectively inhibits grain growth and hinders dislocation movement, leading to the improvement of plasticity. PMID:28773231

  8. A coherent quantum annealer with Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Glaetzle, A. W.; van Bijnen, R. M. W.; Zoller, P.; Lechner, W.

    2017-06-01

    There is a significant ongoing effort in realizing quantum annealing with different physical platforms. The challenge is to achieve a fully programmable quantum device featuring coherent adiabatic quantum dynamics. Here we show that combining the well-developed quantum simulation toolbox for Rydberg atoms with the recently proposed Lechner-Hauke-Zoller (LHZ) architecture allows one to build a prototype for a coherent adiabatic quantum computer with all-to-all Ising interactions and, therefore, a platform for quantum annealing. In LHZ an infinite-range spin-glass is mapped onto the low energy subspace of a spin-1/2 lattice gauge model with quasi-local four-body parity constraints. This spin model can be emulated in a natural way with Rubidium and Caesium atoms in a bipartite optical lattice involving laser-dressed Rydberg-Rydberg interactions, which are several orders of magnitude larger than the relevant decoherence rates. This makes the exploration of coherent quantum enhanced optimization protocols accessible with state-of-the-art atomic physics experiments.

  9. Annealing Would Improve beta" - Alumina Solid Electrolyte

    NASA Technical Reports Server (NTRS)

    Williams, Roger; Homer, Margie; Ryan, Margaret; Cortez, Roger; Shields, Virgil; Kisor, Adam

    2003-01-01

    A pre-operational annealing process is under investigation as a potential means of preventing a sudden reduction of ionic conductivity in a Beta"-alumina solid electrolyte (BASE) during use. On the basis of tests, the sudden reduction of ionic conductivity, followed by a slow recovery, has been found to occur during testing of the solid electrolyte and electrode components of an alkali metal thermal-to-electric converter (AMTEC) cell. At this time, high-temperature tests of limited duration have indicated the superiority of the treated BASE, but reproducible tests over thousands of hours are necessary to confirm that microcracking has been eliminated. The ionic conductivity of the treated BASE is also measured to be higher than untreated BASE at 1,073 K in low-pressure sodium vapor. Microcracking resulting in loss of conductivity was not observed with treated BASE in one high-temperature experiment, but this result must be duplicated over very long testing times to be sure of the effect. Shorter annealing times (10 to 20 hours) were found to result in significantly less loss of mass; it may be necessary for the packed powder mixture to evolve some Na2O before the Na2O can leave the ceramic.

  10. Coping with noise in programmable quantum annealers

    NASA Astrophysics Data System (ADS)

    Perdomo-Ortiz, Alejandro

    Solving real-world applications with quantum annealing algorithms requires overcoming several challenges, ranging from translating the computational problem at hand to the quantum-machine language, to tuning several other parameters of the quantum algorithm that have a significant impact on performance of the device. In this talk, we discuss these challenges, strategies developed to enhance performance, and also a more efficient implementation of several applications. For example, in http://arxiv.org/abs/1503.05679 we proposed an method to measure residual systematic biases in the programmable parameters of large-scale quantum annealers. Although the method described there works from a practical point of view, a few questions were left unanswered. One of these puzzles was the observation of a broad distribution in the estimated effective qubit temperatures throughout the device . In this talk, we will present our progress in understanding these puzzles and how these new insights allow for a more effective bias correction protocol. We will present the impact of these new parameter setting and bias correction protocols in the performance of hard discrete optimization problems and in the successful implementation of quantum-assisted machine-learning algorithms.

  11. Dielectric Signatures of Annealing in Glacier Ice

    NASA Astrophysics Data System (ADS)

    Grimm, R. E.; Stillman, D. E.; MacGregor, J. A.

    2015-12-01

    We analyzed the dielectric spectra of 49 firn and ice samples from ice sheets and glaciers to better understand how differing ice formation and evolution affect electrical properties. The dielectric relaxation of ice is well known and its characteristic frequency increases with the concentration of soluble impurities in the ice lattice. We found that meteoric ice and firn generally possess two such relaxations, indicating distinct crystal populations or zonation. Typically, one population is consistent with that of relatively pure ice, and the other is significantly more impure. However, high temperatures (e.g., temperate ice), long residence times (e.g., ancient ice from Mullins Glacier, Antarctica), or anomalously high impurity concentrations favor the development of a single relaxation. These relationships suggest that annealing causes two dielectrically distinct populations to merge into one population. The dielectric response of temperate ice samples indicates increasing purity with increasing depth, suggesting final rejection of impurities from the lattice. Separately, subglacially frozen samples from the Vostok 5G ice core possess a single relaxation whose variable characteristic frequency likely reflects the composition of the source water. Multi-frequency electrical measurements on cores and in the field can track annealing of glacier ice.

  12. Mean Field Analysis of Quantum Annealing Correction.

    PubMed

    Matsuura, Shunji; Nishimori, Hidetoshi; Albash, Tameem; Lidar, Daniel A

    2016-06-03

    Quantum annealing correction (QAC) is a method that combines encoding with energy penalties and decoding to suppress and correct errors that degrade the performance of quantum annealers in solving optimization problems. While QAC has been experimentally demonstrated to successfully error correct a range of optimization problems, a clear understanding of its operating mechanism has been lacking. Here we bridge this gap using tools from quantum statistical mechanics. We study analytically tractable models using a mean-field analysis, specifically the p-body ferromagnetic infinite-range transverse-field Ising model as well as the quantum Hopfield model. We demonstrate that for p=2, where the phase transition is of second order, QAC pushes the transition to increasingly larger transverse field strengths. For p≥3, where the phase transition is of first order, QAC softens the closing of the gap for small energy penalty values and prevents its closure for sufficiently large energy penalty values. Thus QAC provides protection from excitations that occur near the quantum critical point. We find similar results for the Hopfield model, thus demonstrating that our conclusions hold in the presence of disorder.

  13. Σ3 CSL boundary distributions in an austenitic stainless steel subjected to multidirectional forging followed by annealing

    NASA Astrophysics Data System (ADS)

    Tikhonova, Marina; Kuzminova, Yuliya; Fang, Xiaoying; Wang, Weiguo; Kaibyshev, Rustam; Belyakov, Andrey

    2014-12-01

    The effect of processing and annealing temperatures on the grain boundary characters in the ultrafine-grained structure of a 304-type austenitic stainless steel was studied. An S304H steel was subjected to multidirectional forging (MDF) at 500-800°C to total strains of ~4, followed by annealing at 800-1,000°C for 30 min. The MDF resulted in the formation of ultrafine-grained microstructures with mean grain sizes of 0.28-0.85 μm depending on the processing temperature. The annealing behaviour of the ultrafine-grained steel was characterized by the development of continuous post-dynamic recrystallization including a rapid recovery followed by a gradual grain growth. The post-dynamically recrystallized grain size depended on both the deformation temperature and the annealing temperature. The recrystallization kinetics was reduced with an increase in the temperature of the preceding deformation. The grain growth during post-dynamic recrystallization was accompanied by an increase in the fraction of Σ3n CSL boundaries, which was defined by a relative change in the grain size, i.e. a ratio of the annealed grain size to that evolved by preceding warm working (D/D0). The fraction of Σ3n CSL boundaries sharply rose to approximately 0.5 in the range of D/D0 from 1 to 5, which can be considered as early stage of continuous post-dynamic recrystallization. Then, the rate of increase in the fraction of Σ3n CSL boundaries slowed down significantly in the range of D/D0 > 5. A fivefold increase in the grain size by annealing is a necessary condition to obtain approximately 50% Σ3n CSL boundaries in the recrystallized microstructure.

  14. Burst annealing of high temperature GaAs solar cells

    NASA Technical Reports Server (NTRS)

    Brothers, P. R.; Horne, W. E.

    1991-01-01

    One of the major limitations of solar cells in space power systems is their vulnerability to radiation damage. One solution to this problem is to periodically heat the cells to anneal the radiation damage. Annealing was demonstrated with silicon cells. The obstacle to annealing of GaAs cells was their susceptibility to thermal damage at the temperatures required to completely anneal the radiation damage. GaAs cells with high temperature contacts and encapsulation were developed. The cells tested are designed for concentrator use at 30 suns AMO. The circular active area is 2.5 mm in diameter for an area of 0.05 sq cm. Typical one sun AMO efficiency of these cells is over 18 percent. The cells were demonstrated to be resistant to damage after thermal excursions in excess of 600 C. This high temperature tolerance should allow these cells to survive the annealing of radiation damage. A limited set of experiments were devised to investigate the feasibility of annealing these high temperature cells. The effect of repeated cycles of electron and proton irradiation was tested. The damage mechanisms were analyzed. Limitations in annealing recovery suggested improvements in cell design for more complete recovery. These preliminary experiments also indicate the need for further study to isolate damage mechanisms. The primary objective of the experiments was to demonstrate and quantify the annealing behavior of high temperature GaAs cells. Secondary objectives were to measure the radiation degradation and to determine the effect of repeated irradiation and anneal cycles.

  15. Isothermal annealing of a 620 nm optical absorption band in Brazilian topaz crystals

    NASA Astrophysics Data System (ADS)

    Isotani, Sadao; Matsuoka, Masao; Albuquerque, Antonio Roberto Pereira Leite

    2013-04-01

    Isothermal decay behaviors, observed at 515, 523, 562, and 693 K, for an optical absorption band at 620 nm in gamma-irradiated Brazilian blue topaz were analyzed using a kinetic model consisting of O- bound small polarons adjacent to recombination centers (electron traps). The kinetic equations obtained on the basis of this model were solved using the method of Runge-Kutta and the fit parameters describing these defects were determined with a grid optimization method. Two activation energies of 0.52±0.08 and 0.88±0.13 eV, corresponding to two different structural configurations of the O- polarons, explained well the isothermal decay curves using first-order kinetics expected from the kinetic model. On the other hand, thermoluminescence (TL) emission spectra measured at various temperatures showed a single band at 400 nm in the temperature range of 373-553 K in which the 620 nm optical absorption band decreased in intensity. Monochromatic TL glow curve data at 400 nm extracted from the TL emission spectra observed were found to be explained reasonably by using the knowledge obtained from the isothermal decay analysis. This suggests that two different structural configurations of O- polarons are responsible for the 620 nm optical absorption band and that the thermal annealing of the polarons causes the 400 nm TL emission band.

  16. Spectrophotometric analysis of tomato plants produced from seeds exposed under space flight conditions for a long time

    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

  17. Application of Simulated Annealing and Related Algorithms to TWTA Design

    NASA Technical Reports Server (NTRS)

    Radke, Eric M.

    2004-01-01

    decremented and the process repeats. Eventually (and hopefully), a near-globally optimal solution is attained as T approaches zero. Several exciting variants of SA have recently emerged, including Discrete-State Simulated Annealing (DSSA) and Simulated Tempering (ST). The DSSA algorithm takes the thermodynamic analogy one step further by categorizing objective function evaluations into discrete states. In doing so, many of the case-specific problems associated with fine-tuning the SA algorithm can be avoided; for example, theoretical approximations for the initial and final temperature can be derived independently of the case. In this manner, DSSA provides a scheme that is more robust with respect to widely differing design surfaces. ST differs from SA in that the temperature T becomes an additional random variable in the optimization. The system is also kept in equilibrium as the temperature changes, as opposed to the system being driven out of equilibrium as temperature changes in SA. ST is designed to overcome obstacles in design surfaces where numerous local minima are separated by high barriers. These algorithms are incorporated into the optimal design of the traveling-wave tube amplifier (TWTA). The area under scrutiny is the collector, in which it would be ideal to use negative potential to decelerate the spent electron beam to zero kinetic energy just as it reaches the collector surface. In reality this is not plausible due to a number of physical limitations, including repulsion and differing levels of kinetic energy among individual electrons. Instead, the collector is designed with multiple stages depressed below ground potential. The design of this multiple-stage collector is the optimization problem of interest. One remaining problem in SA and DSSA is the difficulty in determining when equilibrium has been reached so that the current Markov chain can be terminated. It has been suggested in recent literature that simulating the thermodynamic properties opecific

  18. Application of Simulated Annealing and Related Algorithms to TWTA Design

    NASA Technical Reports Server (NTRS)

    Radke, Eric M.

    2004-01-01

    decremented and the process repeats. Eventually (and hopefully), a near-globally optimal solution is attained as T approaches zero. Several exciting variants of SA have recently emerged, including Discrete-State Simulated Annealing (DSSA) and Simulated Tempering (ST). The DSSA algorithm takes the thermodynamic analogy one step further by categorizing objective function evaluations into discrete states. In doing so, many of the case-specific problems associated with fine-tuning the SA algorithm can be avoided; for example, theoretical approximations for the initial and final temperature can be derived independently of the case. In this manner, DSSA provides a scheme that is more robust with respect to widely differing design surfaces. ST differs from SA in that the temperature T becomes an additional random variable in the optimization. The system is also kept in equilibrium as the temperature changes, as opposed to the system being driven out of equilibrium as temperature changes in SA. ST is designed to overcome obstacles in design surfaces where numerous local minima are separated by high barriers. These algorithms are incorporated into the optimal design of the traveling-wave tube amplifier (TWTA). The area under scrutiny is the collector, in which it would be ideal to use negative potential to decelerate the spent electron beam to zero kinetic energy just as it reaches the collector surface. In reality this is not plausible due to a number of physical limitations, including repulsion and differing levels of kinetic energy among individual electrons. Instead, the collector is designed with multiple stages depressed below ground potential. The design of this multiple-stage collector is the optimization problem of interest. One remaining problem in SA and DSSA is the difficulty in determining when equilibrium has been reached so that the current Markov chain can be terminated. It has been suggested in recent literature that simulating the thermodynamic properties opecific

  19. The lateral In2O3 nanowires and pyramid networks manipulation by controlled substrate surface energy in annealing evolution

    NASA Astrophysics Data System (ADS)

    Shariati, Mohsen; Darjani, Mojtaba

    2016-02-01

    The continuous laterally aligned growth of In2O3 nanocrystal networks extended with nanowire and pyramid connections under annealing influence has been reported. These nanostructures have been grown on Si substrate by using oxygen-assisted annealing process through PVD growth technique. The formation of In2O3 nanocrystals has been achieved by the successive growth of critical self-nucleated condensation in three orientations. The preferred direction was the route between two pyramids especially in the smallest surface energy. The effects of substrate temperature in annealing process on the morphological properties of the as-grown nanostructures were investigated. The annealing technique showed that by controlling the surface energy, the morphology of structures was changed from unregulated array to defined nanostructures; especially nanowires 50 nm in width. The obtained nanostructures also were investigated by the (transmission electron microscopy) TEM, Raman spectrum and the (X-ray diffraction) XRD patterns. They indicated that the self-assembled In2O3 nanocrystal networks have been fabricated by the vapor-solid (VS) growth mechanism. The growth mechanism process was prompted to attribute the relationship among the kinetics parameters, surface diffusion and morphology of nanostructures.

  20. Self-organized morphological evolution and dewetting in solvent vapor annealing of spin coated polymer blend nanostructures.

    PubMed

    Roy, Sudeshna; Sharma, Ashutosh

    2015-07-01

    Dewetting pathways, kinetics and morphologies of thin films of phase separating polymer blends are governed by the relative mobilities of the two components. We characterize the morphological transformations of the nanostructures of a PS/PMMA blend by annealing in toluene and chloroform vapors. Toluene leads to faster reorganization of PS, whereas chloroform engenders the opposite effect. Spin coating produces a very rough PMMA rich layer that completely wets the substrate and forms a plethora of slender columns protruding through the continuous PS rich layer on top. The nanostructures were stable under long thermal annealing but in the vapor annealing, phase separation and dewetting occurred readily to form the equilibrium structures of dewetted droplets of PS on top of PMMA which also climbed around the PS droplets to form rims. Toluene and chloroform annealing required around 50 h and 1 h respectively to attain the equilibrium. Substantial differences are observed in the intermediate morphologies (heights of nanostructures, roughness and size). PMMA columns remained embedded in the dewetted PS droplets, whereas a high mobility of PMMA in chloroform allowed its rapid evacuation during dewetting to produce an intermediate swiss-cheese like morphology of PS domains. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Long-time averaged dynamics of a Bose-Einstein condensate in a bichromatic optical lattice with external harmonic confinement

    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.

  2. Protein denaturation and water-protein interactions as affected by low temperature long time treatment of porcine longissimus dorsi.

    PubMed

    Christensen, Line; Bertram, Hanne C; Aaslyng, Margit D; Christensen, Mette

    2011-08-01

    The relationship between water-protein interactions and heat-induced protein denaturation in low temperature long time (LTLT) treated pork Longissimus dorsi was investigated by combining low-field NMR T₂ relaxometry with DSC measurements and measures of shrinkage of porcine Longissimus dorsi heated to 53 °C, 55 °C, 57 °C and 59 °C for either 3 or 20 h. Water within the myofibrils, measured by NMR T₂₁ relaxation times, was affected by both temperature and holding time during LTLT treatment between 53 °C and 59 °C. The changes in NMR T₂₁ relaxation times were associated with decreased fiber diameter and increased cooking loss, revealing a relationship between transverse shrinkage, water-protein interactions and cooking loss. DSC measurements revealed a concomitant decrease in ΔH(68 °C), which suggests impact of collagen denaturation on the retention of water within the meat during LTLT treatment. Furthermore, a decrease in ΔH(75 °C) suggested that prolonged cooking (20 h) resulted in actin denaturation leading to decreased T₂₁ relaxation times and higher cooking loss. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Long-Time Numerical Integration of the Three-Dimensional Wave Equation in the Vicinity of a Moving Source

    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.

  4. Correlation-steered scanning for scanning probe microscopes to overcome thermal drift for ultra-long time scanning.

    PubMed

    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.

  5. Biological effects and biochemical studies of tomato plants grown from seeds exposed for a long time at the MIR station

    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

  6. Use of healthcare a long time after severe burn injury; relation to perceived health and personality characteristics.

    PubMed

    Wikehult, B; Willebrand, M; Kildal, M; Lannerstam, K; Fugl-Meyer, A R; Ekselius, L; Gerdin, B

    2005-08-05

    The aim of the study was to evaluate which factors are associated with the use of healthcare a long time after severe burn injury. After a review process based on clinical reasoning, 69 former burn patients out of a consecutive group treated at the Uppsala Burn Unit from 1980--1995 were visited in their homes and their use of care and support was assessed in a semi-structured interview. Post-burn health was assessed with the Burn-Specific Health Scale-Brief (BSHS-B) and personality was assessed with the Swedish universities Scales of Personality (SSP). The participants were injured on average eight years previously. Thirty-four had current contact with healthcare due to their burn injury and had significantly lower scores on three BSHS-B-domains: Simple Abilities, Work and Hand function, and significantly higher scores for the SSP-domain Neuroticism and the SSP-scales Stress Susceptibility, Lack of Assertiveness, and lower scores for Social Desirability. There was no relation to age, gender, time since injury, length of stay, or to the surface area burned. A routine screening of personality traits as a supplement to long-term follow-ups may help in identifying the patient's need for care.

  7. Drinking desalinated seawater for a long time induces anomalies in the development of new-born albino rats.

    PubMed

    Allam, Ahmed A

    2017-09-01

    The present study aimed to elucidate the abnormalities in the development of rat brains, livers, kidney and behaviours after drinking desalinated seawater prenatally. Three types of drinking water were employed as an experimental probe (bottled water, filtered desalinated seawater and tap desalinated seawater) to investigate neurobehavioral and morphological changes in the development of pup rats. Female rats from each group were administered water from their birth until gestation and lactation. The 1st and 2nd generation pups were divided into three groups: Group C, mothers and pups administered with bottled drinking water (the control group); Group F, mothers and pups administered with filtered drinking water; Group T, mothers and pups administered with unfiltered desalinated seawater (tap water). Morphological changes (CNS aberration) and neurobehavioral changes were studied. The aberrations recorded in the tissues (brain, liver, kidney and spinal cord) of rats from groups T and F may be due to oxidative stress in these tissues such as reduced glutathione, lipid peroxidation, peroxidase and super oxide dismutase. In conclusion, drinking desalinated seawater for a long time may cause teratogenic effects in the development of New-born rats.

  8. A Study on the Kinetics of a Disorder-to-Order Transition Induced by Alkyne/Azide Click Reaction

    SciTech Connect

    X Wei; L Li; J Kalish; W Chen; T Russell

    2011-12-31

    The kinetics of binary blends of poly(ethylene oxide)-block-poly(n-butyl methacrylate-random-propargyl methacrylate) (PEO-b-P(nBMA-r-PgMA)) diblock copolymer and Rhodamine B azide was investigated during a disorder-to-order transition induced by alkyne/azide click reaction. The change in the domain spacing and conversion of reactants as a function of annealing time were investigated by in situ small-angle X-ray scattering (SAXS) and infrared spectroscopy (IR), suggesting several kinetic processes with different time scales during thermal annealing. While a higher conversion can be realized by extending the annealing time, the microphase-separated morphology is independent of the annealing conditions, as long as both the reagents and final products have enough mobility.

  9. Kinetic Monte Carlo method applied to nucleic acid hairpin folding.

    PubMed

    Sauerwine, Ben; Widom, Michael

    2011-12-01

    Kinetic Monte Carlo on coarse-grained systems, such as nucleic acid secondary structure, is advantageous for being able to access behavior at long time scales, even minutes or hours. Transition rates between coarse-grained states depend upon intermediate barriers, which are not directly simulated. We propose an Arrhenius rate model and an intermediate energy model that incorporates the effects of the barrier between simulated states without enlarging the state space itself. Applying our Arrhenius rate model to DNA hairpin folding, we demonstrate improved agreement with experiment compared to the usual kinetic Monte Carlo model. Further improvement results from including rigidity of single-stranded stacking.

  10. Abbreviated annealing of high-speed steel

    SciTech Connect

    Zablotskii, V.K.; Bartel, G.P.

    1987-07-01

    The authors investigate the structural and phase transformations during the heating, holding, and cooling of high-speed steels of two basic groups: tungsten (R18, R12, R12F3, and R12F4K5) and tungsten-molybdenum (R6M5, 10R6M5, R6M5K5, R8M3, 10R8M3, and R8M3K6S) steels in the forged state. They propose a cooling regime with complete alpha-gamma recrystallization whose implementation at a Soviet steel plant has made it possible to reduce the duration of heat treatment and increase productivity by 20% in cutting the annealed high-speed steels.

  11. An answer checking method for quantum annealers

    NASA Astrophysics Data System (ADS)

    Perera, Dilina; Novotny, M. A.

    2016-09-01

    We present a generic approach for checking the validity of the solutions returned by quantum annealing devices to aid in the analysis of whether the solution is the true ground state of the desired problem. The underlying principle is to embed a mirrored graph G' of the original graph G, and connect the two graphs via strong ferromagnetic/antiferromagnetic couplings that span across the mirror plane. This allows one to dismiss solutions that do not agree with the underlying mirror symmetry inherent to the true ground state of the composite graph. Using a 1000 qubit D-Wave 2X device, we demonstrate this method by applying it to spin glass problems defined on the device's native Chimera architecture.

  12. Coupled Quantum Fluctuations and Quantum Annealing

    NASA Astrophysics Data System (ADS)

    Hormozi, Layla; Kerman, Jamie

    We study the relative effectiveness of coupled quantum fluctuations, compared to single spin fluctuations, in the performance of quantum annealing. We focus on problem Hamiltonians resembling the the Sherrington-Kirkpatrick model of Ising spin glass and compare the effectiveness of different types of fluctuations by numerically calculating the relative success probabilities and residual energies in fully-connected spin systems. We find that for a small class of instances coupled fluctuations can provide improvement over single spin fluctuations and analyze the properties of the corresponding class. Disclaimer: This research was funded by ODNI, IARPA via MIT Lincoln Laboratory under Air Force Contract No. FA8721-05-C-0002. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of ODNI, IARPA, or the US Government.

  13. Annealing a magnetic cactus into phyllotaxis.

    PubMed

    Nisoli, Cristiano; Gabor, Nathaniel M; Lammert, Paul E; Maynard, J D; Crespi, Vincent H

    2010-04-01

    The appearance of mathematical regularities in the disposition of leaves on a stem, scales on a pine-cone, and spines on a cactus has puzzled scholars for millennia; similar so-called phyllotactic patterns are seen in self-organized growth, polypeptides, convection, magnetic flux lattices and ion beams. Levitov showed that a cylindrical lattice of repulsive particles can reproduce phyllotaxis under the (unproved) assumption that minimum of energy would be achieved by two-dimensional Bravais lattices. Here we provide experimental and numerical evidence that the Phyllotactic lattice is actually a ground state. When mechanically annealed, our experimental "magnetic cactus" precisely reproduces botanical phyllotaxis, along with domain boundaries (called transitions in Botany) between different phyllotactic patterns. We employ a structural genetic algorithm to explore the more general axially unconstrained case, which reveals multijugate (multiple spirals) as well as monojugate (single-spiral) phyllotaxis.

  14. Remediation tradeoffs addressed with simulated annealing optimization

    SciTech Connect

    Rogers, L. L., LLNL

    1998-02-01

    Escalation of groundwater remediation costs has encouraged both advances in optimization techniques to balance remediation objectives and economics and development of innovative technologies to expedite source region clean-ups. We present an optimization application building on a pump-and-treat model, yet assuming a prior removal of different portions of the source area to address the evolving management issue of more aggressive source remediation. Separate economic estimates of in-situ thermal remediation are combined with the economic estimates of the subsequent optimal pump-and-treat remediation to observe tradeoff relationships of cost vs. highest remaining contamination levels (hot spot). The simulated annealing algorithm calls the flow and transport model to evaluate the success of a proposed remediation scenario at a U.S.A. Superfund site contaminated with volatile organic compounds (VOCs).

  15. Annealed Importance Sampling for Neural Mass Models

    PubMed Central

    Penny, Will; Sengupta, Biswa

    2016-01-01

    Neural Mass Models provide a compact description of the dynamical activity of cell populations in neocortical regions. Moreover, models of regional activity can be connected together into networks, and inferences made about the strength of connections, using M/EEG data and Bayesian inference. To date, however, Bayesian methods have been largely restricted to the Variational Laplace (VL) algorithm which assumes that the posterior distribution is Gaussian and finds model parameters that are only locally optimal. This paper explores the use of Annealed Importance Sampling (AIS) to address these restrictions. We implement AIS using proposals derived from Langevin Monte Carlo (LMC) which uses local gradient and curvature information for efficient exploration of parameter space. In terms of the estimation of Bayes factors, VL and AIS agree about which model is best but report different degrees of belief. Additionally, AIS finds better model parameters and we find evidence of non-Gaussianity in their posterior distribution. PMID:26942606

  16. The Annealing Process in Solid 4He

    NASA Astrophysics Data System (ADS)

    Rittner, Ann Sophie C.; Reppy, John D.

    2007-09-01

    We have used a torsional oscillator with square cross section and a resonance frequency of 185 Hz to confirm the nonclassical rotational inertia (NCRI) discovered by Kim and Chan (Nature 427:225, 2004; Science 305:1941, 2004). We have also found a strong correlation between the NCRI signal and a high dissipation Q -1 of 4×10-6 of the oscillation above the transition temperature. Here, we present preliminary results of the annealing process in 4He at a pressure of 26 bar. When holding the temperature constant above 1 K we have observed a immediate rise in the period and a slow decay of the dissipation. The equilibrium value of Q -1 decreases with increasing temperature.

  17. Thermoelectric properties by high temperature annealing

    NASA Technical Reports Server (NTRS)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Kumar, Shankar (Inventor); Lee, Hohyun (Inventor)

    2009-01-01

    The present invention generally provides methods of improving thermoelectric properties of alloys by subjecting them to one or more high temperature annealing steps, performed at temperatures at which the alloys exhibit a mixed solid/liquid phase, followed by cooling steps. For example, in one aspect, such a method of the invention can include subjecting an alloy sample to a temperature that is sufficiently elevated to cause partial melting of at least some of the grains. The sample can then be cooled so as to solidify the melted grain portions such that each solidified grain portion exhibits an average chemical composition, characterized by a relative concentration of elements forming the alloy, that is different than that of the remainder of the grain.

  18. Block Copolymer Nanocomposites in Electric Fields: Kinetics of Alignment

    SciTech Connect

    Liedel, Clemens; Pester, Christian; Ruppel, Markus A; Lewin, Christian; Pavan, Mariela J.; Urban, Volker S; Shenhar, Roy; Bosecke, Peter; Boker, Alexander

    2013-01-01

    We investigate the kinetics of block copolymer/nanoparticle composite alignment in an electric field using in situ transmission small-angle X-ray scattering. As a model system, we employ a lamellae forming polystyrene-block-poly(2-vinyl pyridine) block copolymer with different contents of gold nanoparticles in thick films under solvent vapor annealing. While the alignment improves with increasing nanoparticle fraction, the kinetics slows down. This is explained by changes in the degree of phase separation and viscosity. Our findings provide extended insights into the basics of nanocomposite alignment.

  19. Deformation and annealing response of TD-nickel chromium sheet

    NASA Technical Reports Server (NTRS)

    Kane, R. D.; Ebert, L. J.

    1973-01-01

    The deformation and annealing response of TD-nickel chromium (TD-NiCr) 0.1 inch thick sheet was examined using various cold-rolling and annealing treatments. Upon annealing (above 816 C (1500 F), the as-received material was converted from an initially ultra-fine grain size (average grain dimension 0.51 micron) to a large grain structure. Increases in grain size by a factor of 100 to 200 were observed for this transformation. However, in those material states where the large grain transformation was absent, a fine grain recrystallized structure formed upon annealing (above 732 C (1350 F)). The deformation and annealing response of TD-NiCr sheet was evaluated with respect to the processing related variables as mode and severity of deformation and annealing temperature. Results indicate that the large grain transformation, classical primary recrystallization occurs. Using selected materials produced during the deformation and annealing study, the elevated temperature tensile properties of TD-NiCr sheet were examined in the temperature range 593 C (1100 F) to 1093 C (2000 F). It was observed that the elevated temperature tensile properties of TD-NiCr sheet could be optimized by the stabilization of a large grain size in this material using the cold working and/or annealing treatments developed during the present investigation.

  20. Remote sensing of atmospheric duct parameters using simulated annealing

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-Feng; Huang, Si-Xun; Xiang, Jie; Shi, Wei-Lai

    2011-09-01

    Simulated annealing is one of the robust optimization schemes. Simulated annealing mimics the annealing process of the slow cooling of a heated metal to reach a stable minimum energy state. In this paper, we adopt simulated annealing to study the problem of the remote sensing of atmospheric duct parameters for two different geometries of propagation measurement. One is from a single emitter to an array of radio receivers (vertical measurements), and the other is from the radar clutter returns (horizontal measurements). Basic principles of simulated annealing and its applications to refractivity estimation are introduced. The performance of this method is validated using numerical experiments and field measurements collected at the East China Sea. The retrieved results demonstrate the feasibility of simulated annealing for near real-time atmospheric refractivity estimation. For comparison, the retrievals of the genetic algorithm are also presented. The comparisons indicate that the convergence speed of simulated annealing is faster than that of the genetic algorithm, while the anti-noise ability of the genetic algorithm is better than that of simulated annealing.

  1. BELL ANNEALING FURNACES, SHOWING EMPLOYEEDESIGN CENTER POST WITH THREE RADIAL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BELL ANNEALING FURNACES, SHOWING EMPLOYEE-DESIGN CENTER POST WITH THREE RADIAL ARMS FOR HANGING COILS. ANNEALING SOFTENS BATCHES OF COILS WHICH HAVE BEEN HARDENED BY ROLLING SO THAT THEY WILL BE SUITABLE FOR FURTHER PROCESSING. - American Brass Foundry, 70 Sayre Street, Buffalo, Erie County, NY

  2. Response of neutron-irradiated RPV steels to thermal annealing

    SciTech Connect

    Iskander, S.K.; Sokolov, M.A.; Nanstad, R.K.

    1997-03-01

    One of the options to mitigate the effects of irradiation on reactor pressure vessels (RPVs) is to thermally anneal them to restore the fracture toughness properties that have been degraded by neutron irradiation. This paper summarizes experimental results of work performed at the Oak Ridge National Laboratory (ORNL) to study the annealing response of several irradiated RPV steels.

  3. Annealed Importance Sampling Reversible Jump MCMC algorithms

    SciTech Connect

    Karagiannis, Georgios; Andrieu, Christophe

    2013-03-20

    It will soon be 20 years since reversible jump Markov chain Monte Carlo (RJ-MCMC) algorithms have been proposed. They have significantly extended the scope of Markov chain Monte Carlo simulation methods, offering the promise to be able to routinely tackle transdimensional sampling problems, as encountered in Bayesian model selection problems for example, in a principled and flexible fashion. Their practical efficient implementation, however, still remains a challenge. A particular difficulty encountered in practice is in the choice of the dimension matching variables (both their nature and their distribution) and the reversible transformations which allow one to define the one-to-one mappings underpinning the design of these algorithms. Indeed, even seemingly sensible choices can lead to algorithms with very poor performance. The focus of this paper is the development and performance evaluation of a method, annealed importance sampling RJ-MCMC (aisRJ), which addresses this problem by mitigating the sensitivity of RJ-MCMC algorithms to the aforementioned poor design. As we shall see the algorithm can be understood as being an “exact approximation” of an idealized MCMC algorithm that would sample from the model probabilities directly in a model selection set-up. Such an idealized algorithm may have good theoretical convergence properties, but typically cannot be implemented, and our algorithms can approximate the performance of such idealized algorithms to an arbitrary degree while not introducing any bias for any degree of approximation. Our approach combines the dimension matching ideas of RJ-MCMC with annealed importance sampling and its Markov chain Monte Carlo implementation. We illustrate the performance of the algorithm with numerical simulations which indicate that, although the approach may at first appear computationally involved, it is in fact competitive.

  4. Donor-deactivating defects above the equilibrium doping limit in GaAs:Te,Ge and GaAs:Te studied by annealing and Hall effect under pressure

    NASA Astrophysics Data System (ADS)

    Slupinski, T.; Wasik, D.; Przybytek, J.

    2017-06-01

    High temperature annealing experiments of n-type double-doped (co-doped) GaAs:Te,Ge single crystal samples close to or above the equilibrium doping limit are presented and compared to annealing results of very highly doped GaAs:Te known for a long time, but still not clarified satisfactorily. An addition of Ge impurity to GaAs:Te shifted the equilibrium doping limit to a lower free electron concentration - a result which is difficult to describe within models of doping limit assuming an electrical compensation mainly by native acceptors. Hall effect under hydrostatic pressure up to 1.5 GPa allowed to directly measure the change of concentration of GeGa donors caused by annealing, in addition to free electron concentration changes in GaAs:Te,Ge. GeGa donors were detected by the capture of free electrons by Ge DX states at high pressure, following the method described by Baj et al. [Phys. Rev. Lett.71, 3529 (1993)]. In highly doped GaAs:Te,Ge, the measured ratio of changes of free electrons and GeGa donors concentrations caused by high temperature annealing at 1100 °C, Δn / Δ [ GeGa ] =4.2+/- 0.6, supports the model of chemically bonded impurity-impurity molecules, probably of type Ge-Tem (where m =3÷4 atoms), which may be consistent with recently proposed models of paired impurities: DDX or double-DX centers.

  5. Kinetic parameters of lithium and aluminium doped quartz from thermoluminescence glow curves.

    PubMed

    Gómez-Ros, J M; Correcher, V; García-Guinea, J; Delgado, A

    2002-01-01

    The thermoluminescence (TL) glow curves of irradiated annealed and non-annealed synthetic beta-quartz (Li0.73Al0.73Si1.27O4) synthesised using the ceramic method have been studied. Annealed samples (1200 degrees C for 12 h) exhibit some changes of shape and intensity in the TL glow curves when compared to non-annealed samples in the range of 0.1-5 Gy. These changes can be attributed mainly to thermal alkali self-diffusion through the lattice interfaces involving modifications in the components of the luminescent traps. In non-annealed samples six groups of components at about 100 degrees C, 130 degrees C, 160 degrees C, 210 degrees C, 330 degrees C and 450 degrees C can be found, whereas annealed samples only display one very intense peak at a lower temperature (deconvoluted into three peaks at 90 degrees C, 105 degrees C and 130 degrees C) and a lower intensity second wide broad emission at approximately 240 degrees C. In this paper, a computerised curve-fitting based on general order kinetics has been used to characterise the glow curve structure resolving trapping parameters for each glow peak: trap depth (E), frequency factor (s) and the order of the kinetics (b). The dose dependence of the individual components of the glow curve has been also studied. These data allow us to select the most stable component for use in dosimetric purposes.

  6. Radiation damage annealing mechanisms and possible low temperature annealing in silicon solar cells

    NASA Technical Reports Server (NTRS)

    Weinberg, I.; Swartz, C. K.

    1980-01-01

    The defect responsible for reverse annealing in 2 ohm/cm n(+)/p silicon solar cells was identified. This defect, with energy level at e sub v + 0.30 eV was tentatively identified as a boron oxygen-vacancy complex. Results indicate that its removal could result in significant annealing for 2 ohm/cm and lower resistivity cells at temperatures as low as 200 C. These results were obtained by use of an expression derived from the Shockley-Read-Hall recombination theory which relates measured diffusion length ratios to relative defect concentrations and electron capture cross sections. The relative defect concentrations and one of the required capture cross sections are obtained from Deep Level Transient Spectroscopy. Four additional capture cross sections are obtained using diffusion length data and data from temperature dependent lifetime studied. These calculated results are in reasonable agreement with experimental data.

  7. Infrared studies of the evolution of the CiOi(SiI) defect in irradiated Si upon isothermal anneals

    NASA Astrophysics Data System (ADS)

    Angeletos, T.; Chroneos, A.; Londos, C. A.

    2016-03-01

    Carbon-oxygen-self-interstitial complexes were investigated in silicon by means of Fourier transform infrared spectroscopy. Upon irradiation, the CiOi defect (C3) forms which for high doses attract self-interstitials (SiIs) leading to the formation of the CiOi(SiI) defect (C4) with two well-known related bands at 939.6 and 1024 cm-1. The bands are detectable in the spectra both in room temperature (RT) and liquid helium (LH) temperature. Upon annealing at 150 °C, these bands were transformed to three bands at 725, 952, and 973 cm-1, detectable only at LH temperatures. Upon annealing at 220 °C, these bands were transformed to three bands at 951, 969.5, and 977 cm-1, detectable both at RT and LH temperatures. Annealing at 280 °C resulted in the transformation of these bands to two new bands at 973 and 1024 cm-1. The latter bands disappear from the spectra upon annealing at 315 °C without the emergence of other bands in the spectra. Considering reaction kinetics and defect metastability, we developed a model to describe the experimental results. Annealing at 150 °C triggers the capturing of SiIs by the C4 defect leading to the formation of the CiOi(SiI)2 complex. The latter structure appears to be bistable: measuring at LH, the defect is in configuration CiOi(SiI)2 giving rise to the bands at 725, 952, and 973 cm-1, whereas on measurements at RT, the defect converts to another configuration CiOi(SiI)2* without detectable bands in the spectra. Possible structures of the two CiOi(SiI)2 configurations are considered and discussed. Upon annealing at 220 °C, additional SiIs are captured by the CiOi(SiI)2 defect leading to the formation of the CiOi(SiI)3 complex, which in turn on annealing at 280 °C converts to the CiOi(SiI)4 complex. The latter defect anneals out at 315 °C, without being accompanied in the spectra by the growth of new bands.

  8. Yeast Pif1 Accelerates Annealing of Complementary DNA Strands

    PubMed Central

    2015-01-01

    Pif1 is a helicase involved in the maintenance of nuclear and mitochondrial genomes in eukaryotes. Here we report a new activity of Saccharomyces cerevisiae Pif1, annealing of complementary DNA strands. We identified preferred substrates for annealing as those that generate a duplex product with a single-stranded overhang relative to a blunt end duplex. Importantly, we show that Pif1 can anneal DNA in the presence of ATP and Mg2+. Pif1-mediated annealing also occurs in the presence of single-stranded DNA binding proteins. Additionally, we show that partial duplex substrates with 3′-single-stranded overhangs such as those generated during double-strand break repair can be annealed by Pif1. PMID:25393406

  9. Evolution of perpendicular magnetized tunnel junctions upon annealing

    NASA Astrophysics Data System (ADS)

    Devolder, Thibaut; Couet, S.; Swerts, J.; Furnemont, A.

    2016-04-01

    We study the evolution of perpendicularly magnetized tunnel junctions under 300 to 400 °C annealing. The hysteresis loops do not evolve much during annealing and they are not informative of the underlying structural evolutions. These evolutions are better revealed by the frequencies of the ferromagnetic resonance eigenmodes of the tunnel junction. Their modeling provides the exchange couplings and the layers' anisotropies within the stack which can serve as a diagnosis of the tunnel junction state after each annealing step. The anisotropies of the two CoFeB-based parts and the two Co/Pt-based parts of the tunnel junction decay at different rates during annealing. The ferromagnet exchange coupling through the texture-breaking Ta layer fails above 375 °C. The Ru spacer meant to promote a synthetic antiferromagnet behavior is also insufficiently robust to annealing. Based on these evolutions we propose optimization routes for the next generation tunnel junctions.

  10. Quantum annealing with all-to-all connected nonlinear oscillators

    NASA Astrophysics Data System (ADS)

    Puri, Shruti; Andersen, Christian Kraglund; Grimsmo, Arne L.; Blais, Alexandre

    2017-06-01

    Quantum annealing aims at solving combinatorial optimization problems mapped to Ising interactions between quantum spins. Here, with the objective of developing a noise-resilient annealer, we propose a paradigm for quantum annealing with a scalable network of two-photon-driven Kerr-nonlinear resonators. Each resonator encodes an Ising spin in a robust degenerate subspace formed by two coherent states of opposite phases. A fully connected optimization problem is mapped to local fields driving the resonators, which are connected with only local four-body interactions. We describe an adiabatic annealing protocol in this system and analyse its performance in the presence of photon loss. Numerical simulations indicate substantial resilience to this noise channel, leading to a high success probability for quantum annealing. Finally, we propose a realistic circuit QED implementation of this promising platform for implementing a large-scale quantum Ising machine.

  11. Yeast Pif1 accelerates annealing of complementary DNA strands.

    PubMed

    Ramanagoudr-Bhojappa, Ramanagouda; Byrd, Alicia K; Dahl, Christopher; Raney, Kevin D

    2014-12-09

    Pif1 is a helicase involved in the maintenance of nuclear and mitochondrial genomes in eukaryotes. Here we report a new activity of Saccharomyces cerevisiae Pif1, annealing of complementary DNA strands. We identified preferred substrates for annealing as those that generate a duplex product with a single-stranded overhang relative to a blunt end duplex. Importantly, we show that Pif1 can anneal DNA in the presence of ATP and Mg(2+). Pif1-mediated annealing also occurs in the presence of single-stranded DNA binding proteins. Additionally, we show that partial duplex substrates with 3'-single-stranded overhangs such as those generated during double-strand break repair can be annealed by Pif1.

  12. Simple and fast annealing synthesis of titanium dioxide nanostructures and morphology transformation during annealing processes.

    PubMed

    Park, Jongbok; Ryu, Yeontack; Kim, Hansoo; Yu, Choongho

    2009-03-11

    Wire- and belt-like single-crystalline titanium dioxide nanostructures were synthesized by using a simple thermal annealing method, which has often been avoided for the synthesis of metal oxide nanostructures from high melting point metals such as Ti. The synthesis method requires neither high reaction temperature nor complicated reaction processes, and can be used for producing dense nanomaterials with relatively short reaction time at temperatures much lower than the melting point of titanium and titanium dioxide. Key synthesis factors including the choice of eutectic catalyst, growth temperature, and annealing time were systematically investigated. The synthesis reaction was promoted by a copper eutectic catalyst, producing long nanostructures with short reaction times. For example, it was observed that only 30 min of annealing time at 850 degrees C was enough to produce densely grown approximately 10 microm long nanowires with diameters of approximately 100 nm, and longer reaction time brought about morphology changes from wires to belts as well as producing longer nanostructures up to approximately 30 microm. The nanostructures have the crystalline rutile structure along the [Formula: see text] growth direction. Finally, our simple and effective method for the synthesis of TiO2 nanostructures could be utilized for growing other metal oxide nanowires from high melting temperature metals.

  13. Anomalous Behavior Observed upon Annealing and Photodetachment of Anionic Copper Carbonyl Clusters in Argon Matrices

    NASA Astrophysics Data System (ADS)

    Ludwig, Ryan M.; Moore, David T.

    2014-06-01

    Using matrix isolation FTIR, we have observed the formation of anionic copper carbonyl complexes [Cu(CO)n]- (n=1-3) following co-deposition of Cu- and counter-cations (Ar+ or Kr+) into argon matrices doped with CO. When the deposition is carried out at 20 K, weak bands corresponding to the neutral copper carbonyl complexes Cu(CO)n (n=1-3) are also observed, and these grow in steadily as the matrix is annealed up to 30 K. This is in contrast to what is observed at 10 K (c.f. ISMS 2014 abstract #P631), where no appreciable neutral bands are observed, and indicates that some neutralization occurs during the formation of the complexes in the 20 K matrix. In addition, sharp peaks not previously observed grow in around the anionic bands upon annealing to 30 K; this is somewhat odd, since annealing typically simplifies the spectra of matrix samples as kinetically trapped metastable species relax to more stable forms. In this case, higher-resolution (0.125 wn) spectra reveal considerable new fine structure, with 5 and 20 peaks appearing in the regions of the mono- and tricarbonyl anions, respectively, each of which nominally has but a single IR-active CO-stretching mode. These new features are tentatively assigned (at least in part) to electric-field-induced splitting arising from long-range interactions with cationic species in the matrix. A second anomalous feature of these spectra is that, upon photodetachment, several new bands are observed in the region of the neutral copper carbonyl species. Upon annealing these bands then disappear, with concomitant growth of the expected neutral bands. This behavior raises the exciting possibility that these transient bands represent metastable "vertical detachment products", where the neutral species has been kinetically trapped by the matrix in the geometry of the anion. Evidence supporting this interpretation will be presented. Funding support from NSF CAREER Award CHE-0955637 is gratefully acknowledged Ryan M. Ludwig and David

  14. Self-consistent long-time simulation of chirping and beating energetic particle modes in JT-60U plasmas

    NASA Astrophysics Data System (ADS)

    Bierwage, A.; Shinohara, K.; Todo, Y.; Aiba, N.; Ishikawa, M.; Matsunaga, G.; Takechi, M.; Yagi, M.

    2017-01-01

    Recurring bursts of chirping Alfvén modes that were observed in JT-60U tokamak plasmas driven by negative-ion-based neutral beams (N-NB) are reproduced in first-principle simulations performed with an extended version of the hybrid code MEGA. This code simulates the interactions between gyrokinetic fast ions and magnetohydrodynamic (MHD) modes in the presence of a realistic fast ion source and collisions, so that it self-consistently captures dynamics across a wide range of time scales (0.01-100 ms). The simulation confirms that the experimentally observed phenomena known as ‘fast frequency sweeping (fast FS) modes’ are caused by bursts of energetic particle modes (EPM) with dominant toroidal mode number n  =  1. On the long time scale (1-10 ms), the simulation reproduces the chirping range (40-60 kHz), the burst duration (few ms) and intervals (5-10 ms). On the short time scale (0.01-0.1 ms), it reproduces pulsations and phase jumps, which we interpret as the result of beating between multiple resonant wave packets. Having reproduced at multiple levels of detail the dynamics of low-amplitude long-wavelength Alfvén modes driven by N-NB ions, the next goal is to reproduce and explain abrupt large-amplitude events (ALE) that were seen in the same experiments at longer time intervals (10-100 ms).

  15. Architecture for space habitats. Role of architectural design in planning artificial environment for long time manned space missions

    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

  16. Growing Lots of Food Very Fast Can Hurt our Water for a Long Time, Longer Than You Might Think

    NASA Astrophysics Data System (ADS)

    Van Meter, K. J.; Basu, N. B.

    2016-12-01

    More people arrive here every day, and we keep trying to grow enough food for them to eat. We try to grow more and more by adding things that can hurt our water and our air. We try to keep track of these things that we add, but we don't understand where it all goes. We don't understand how much is in the ground. We don't understand how much is in the water under the ground. We don't understand how long the water will be bad, even after we stop adding things to help grow more food. Many people have tried to stop adding these things, or to stop these things from getting to the water, and they get sad when they have worked hard to do better but the water stays bad. In our work, we try to help people understand how to make the water better, even when they have to grow a lot of food. We have looked at the ground all around where people grow a lot of food, and have found that some of the bad things stay behind in the ground. This means that even when we work hard to make our water good, the things left in the ground might make our water stay bad for a long time. We tried to find out how long it would take to make our water good if we are working our hardest to be better. It will take longer than you might think, maybe three times as many years as you have fingers.

  17. Changes in Lipid Oxidation and Fatty Acids in Altay Sheep Fat during a Long Time of Low Temperature Storage.

    PubMed

    Li, Yu; Li, Ying Biao; Liu, Cheng Jiang

    2017-04-03

    Previously, we have shown that the fatty acid composition of Altay sheep tail fat is of reasonable value and is suitable for further development of possible commercial products. Changes in lipids of Altay sheep tail fat during 50 days of 4°C refrigerated storage were investigated. Lipid oxidation and lipolysis occurred during the storage. The pH showed a continually decreased from first day to the end of the storage (p < 0.05). The lipid oxidation was determined by peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS). The increase PV was observed in Altay sheep fat up to 24 days of storage and decreased from then to the day 30 (p < 0.05). The increase in TBARS was significantly throughout the refrigerated storage (p < 0.05). The changes of the fatty acids identified by GS-MS demonstrated that saturated fatty acids increased from 43.6% to 56.3% and that polyunsaturated fatty acids and monounsaturated fatty acids decreased form 51.2% to 43.7% and from 2.4% to 2.1%, respectively. The content of the functional fatty acids except (C18:2 n-9), started to decrease after 20 days of storage. Those changes indicated that lipid oxidation occurred in Altay sheep tail fat during a long time of low temperature storage. In addition, the good correlation between PV/TBARS values and changes of individual fatty acids could be used as an indicator to monitor the changes of the unsaturated fatty acid during the development process of Altay sheep tail fat-related commercial products.

  18. Modeling of long-term defect evolution in heavy-ion irradiated 3C-SiC: Mechanism for thermal annealing and influences of spatial correlation

    SciTech Connect

    Guo, Daxi; He, Chaohui E-mail: hechaohui@mail.xjtu.edu.cn; Zang, Hang; Zhang, Peng; Martin-Bragado, Ignacio E-mail: hechaohui@mail.xjtu.edu.cn

    2014-11-28

    Based on the parameters from published ab-initio theoretical and experimental studies, and combining molecular dynamics and kinetic Monte Carlo simulations, a framework of multi-scale modeling is developed to investigate the long-term evolution of displacement damage induced by heavy-ion irradiation in cubic silicon carbide. The isochronal annealing after heavy ion irradiation is simulated, and the annealing behaviors of total interstitials are found consistent with previous experiments. Two annealing stages below 600 K and one stage above 900 K are identified. The mechanisms for those recovery stages are interpreted by the evolution of defects. The influence of the spatial correlation in primary damage on defect recovery has been studied and found insignificant when the damage dose is high enough, which sheds light on the applicability of approaches with mean-field approximation to the long-term evolution of damage by heavy ions in SiC.

  19. Recrystallization kinetics of an austenitic high-manganese steel subjected to severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Yanushkevich, Zh. Ch.; Molodov, D. A.; Belyakov, A. N.; Kaibyshev, R. O.

    2016-09-01

    The evolution of the microstructure and the properties of an austenitic high-manganese steel subjected to severe deformation by cold rolling and subsequent recrystallization annealing is investigated. Cold rolling is accompanied by mechanical structural twinning and shear banding. The microhardness and microstructural analysis of annealed samples are used to study the recrystallization kinetics of the high-manganese steel. It is shown that large plastic deformation and subsequent annealing result in rapid development of recrystallization processes and the formation of an ultrafine-grained structure. A completely recrystallized structure with an average grain size of 0.64 μm forms after 30-min annealing at a temperature of 550°C. No significant structural changes are observed when the annealing time increases to 18 h, which indicates stability of the recrystallized microstructure. The steel cold rolled to 90% and annealed at 550°C for 30 min demonstrates very high strength properties: the yield strength and the tensile strength achieve 650 and 850MPa, respectively. The dependence of the strength properties of the steel on the grain size formed after rolling and recrystallization annealing is described by the Hall-Petch relation.

  20. Annealed Scaling for a Charged Polymer

    NASA Astrophysics Data System (ADS)

    Caravenna, F.; den Hollander, F.; Pétrélis, N.; Poisat, J.

    2016-03-01

    This paper studies an undirected polymer chain living on the one-dimensional integer lattice and carrying i.i.d. random charges. Each self-intersection of the polymer chain contributes to the interaction Hamiltonian an energy that is equal to the product of the charges of the two monomers that meet. The joint probability distribution for the polymer chain and the charges is given by the Gibbs distribution associated with the interaction Hamiltonian. The focus is on the annealed free energy per monomer in the limit as the length of the polymer chain tends to infinity. We derive a spectral representation for the free energy and use this to prove that there is a critical curve in the parameter plane of charge bias versus inverse temperature separating a ballistic phase from a subballistic phase. We show that the phase transition is first order. We prove large deviation principles for the laws of the empirical speed and the empirical charge, and derive a spectral representation for the associated rate functions. Interestingly, in both phases both rate functions exhibit flat pieces, which correspond to an inhomogeneous strategy for the polymer to realise a large deviation. The large deviation principles in turn lead to laws of large numbers and central limit theorems. We identify the scaling behaviour of the critical curve for small and for large charge bias. In addition, we identify the scaling behaviour of the free energy for small charge bias and small inverse temperature. Both are linked to an associated Sturm-Liouville eigenvalue problem. A key tool in our analysis is the Ray-Knight formula for the local times of the one-dimensional simple random walk. This formula is exploited to derive a closed form expression for the generating function of the annealed partition function, and for several related quantities. This expression in turn serves as the starting point for the derivation of the spectral representation for the free energy, and for the scaling theorems

  1. Hybrid annealing: Coupling a quantum simulator to a classical computer

    NASA Astrophysics Data System (ADS)

    Graß, Tobias; Lewenstein, Maciej

    2017-05-01

    Finding the global minimum in a rugged potential landscape is a computationally hard task, often equivalent to relevant optimization problems. Annealing strategies, either classical or quantum, explore the configuration space by evolving the system under the influence of thermal or quantum fluctuations. The thermal annealing dynamics can rapidly freeze the system into a low-energy configuration, and it can be simulated well on a classical computer, but it easily gets stuck in local minima. Quantum annealing, on the other hand, can be guaranteed to find the true ground state and can be implemented in modern quantum simulators; however, quantum adiabatic schemes become prohibitively slow in the presence of quasidegeneracies. Here, we propose a strategy which combines ideas from simulated annealing and quantum annealing. In such a hybrid algorithm, the outcome of a quantum simulator is processed on a classical device. While the quantum simulator explores the configuration space by repeatedly applying quantum fluctuations and performing projective measurements, the classical computer evaluates each configuration and enforces a lowering of the energy. We have simulated this algorithm for small instances of the random energy model, showing that it potentially outperforms both simulated thermal annealing and adiabatic quantum annealing. It becomes most efficient for problems involving many quasidegenerate ground states.

  2. Sequential annealing gradient Gamma-Knife radiosurgery optimization

    NASA Astrophysics Data System (ADS)

    Ove, Roger; Popple, Richard

    2003-07-01

    Simulated annealing and gradient methods are commonly employed for inverse planning of radiotherapy delivery schemes. Annealing is effective in finding an approximation of the global solution, suffering from slow late convergence and in some cases poor dose homogeneity. Gradient methods converge well but not necessarily to the global minimum. We explored simulated annealing followed by gradient optimization to improve on either method alone, using radiosurgery as the model system. Simulated annealing and gradient inverse planning programs using the same objective function were adapted for radiosurgical optimization. The objective function chosen is a least-squares dose-matching function, with differential weighting of tissues. A simple test target allowing local minima in the objective function was evaluated. Two hundred trials using the gradient method were done. The gradient method approximated the global solution only 12% of the time, commonly finding a local minimum. The annealing-gradient technique converged to the global minimum in 78 out of 80 trials, more efficiently than annealing alone. Dose homogeneity was improved. In conclusion, sequential annealing-gradient optimization can improve on either method alone. The technique may be extensible to radiotherapy inverse planning in general, with benefit expected for problems characterized by slow gradient method convergence and local minima.

  3. Stepwise kinetic equilibrium models of quantitative polymerase chain reaction

    PubMed Central

    2012-01-01

    Background Numerous models for use in interpreting quantitative PCR (qPCR) data are present in recent literature. The most commonly used models assume the amplification in qPCR is exponential and fit an exponential model with a constant rate of increase to a select part of the curve. Kinetic theory may be used to model the annealing phase and does not assume constant efficiency of amplification. Mechanistic models describing the annealing phase with kinetic theory offer the most potential for accurate interpretation of qPCR data. Even so, they have not been thoroughly investigated and are rarely used for interpretation of qPCR data. New results for kinetic modeling of qPCR are presented. Results Two models are presented in which the efficiency of amplification is based on equilibrium solutions for the annealing phase of the qPCR process. Model 1 assumes annealing of complementary targets strands and annealing of target and primers are both reversible reactions and reach a dynamic equilibrium. Model 2 assumes all annealing reactions are nonreversible and equilibrium is static. Both models include the effect of primer concentration during the annealing phase. Analytic formulae are given for the equilibrium values of all single and double stranded molecules at the end of the annealing step. The equilibrium values are then used in a stepwise method to describe the whole qPCR process. Rate constants of kinetic models are the same for solutions that are identical except for possibly having different initial target concentrations. Analysis of qPCR curves from such solutions are thus analyzed by simultaneous non-linear curve fitting with the same rate constant values applying to all curves and each curve having a unique value for initial target concentration. The models were fit to two data sets for which the true initial target concentrations are known. Both models give better fit to observed qPCR data than other kinetic models present in the literature. They also give

  4. Evolution of weld metals nanostructure and properties under irradiation and recovery annealing of VVER-type reactors

    NASA Astrophysics Data System (ADS)

    Gurovich, B.; Kuleshova, E.; Shtrombakh, Ya.; Fedotova, S.; Zabusov, O.; Prikhodko, K.; Zhurko, D.

    2013-03-01

    The results of VVER-440 steel Sv-10KhMFT and VVER-1000 steel SV-10KhGNMAA investigations by transmission electron microscopy, scanning electron microscopy, Auger-electron spectroscopy and mechanical tests are presented in this paper. The both types of weld metals with different content of impurities and alloying elements were studied after irradiations to fast neutron (E > 0.5 MeV) fluences in the wide range below and beyond the design values, after recovery annealing procedures and after re-irradiation following the annealing. The distinctive features of embrittlement kinetics of VVER-440 and VVER-1000 RPV weld metals conditioned by their chemical composition differences were investigated. It is shown that the main contribution into radiation strengthening within the design fluence can be attributed to radiation-induced precipitates, on reaching the design or beyond design values of fast neutron fluencies the main contribution into VVER-440 welds strengthening is made by radiation-induced dislocation loops, and in case of VVER-1000 welds - radiation-induced precipitates and grain-boundary phosphorous segregations. Recovery annealing of VVER-440 welds at 475 °C during 100 h causes irradiation-induced defects disappearance, transformation of copper enriched precipitates into bigger copper-rich precipitates with lower number density and leads to almost full recovery of mechanical properties followed by comparatively slow re-embrittlement rate. The recovery annealing temperature of VVER-1000 welds was higher - 565 °C during 100 h - to avoid temper brittleness. The annealing of VVER-1000 welds leads to almost full recovery of mechanical properties due to irradiation-induced defects disappearance and decrease in precipitates number density and grain-boundary segregation of phosphorus. The re-embrittlement rate of VVER-1000 weld during subsequent re-irradiation is at least not higher than the initial rate.

  5. Using multi-layered roll bonding and reaction annealing to process gamma-titanium aluminide sheet material

    NASA Astrophysics Data System (ADS)

    Chaudhari, Gajanan Prabhakar

    The process of roll bonding and reaction annealing was used to process gamma-titanium aluminide sheets with a nearly fully lamellar microstructure. Cold roll bonding was employed to bond elemental Al and Ti foils. The bonded sheets were annealed at 600 °C to convert all of the Al into TiAl3. The effect of rolling strain on the reaction kinetics was studied. Accumulative roll bonding was also employed to study the effect of increased rolling strain on the microstructures resulting after annealing. After the first annealing stage, a cold rolling step resulted in a denser microstructure. A second annealing treatment at 1300 °C for 6 h resulted in a microstructure consisting of two phases, gamma and alpha2, along with Kirkendall porosity. Further densification of the sheets was carried out using hot rolling. A final heat treatment at 1400 °C for 0.3 h resulted in nearly fully lamellar microstructure. The porosity evolution was evaluated at different stages of processing. The mechanical properties of the processed sheet were determined and compared with the data available in the literature. The process of bi-metal multi-layer roll bonding was modeled using the equilibrium force balance method (slab method). The effect of anisotropy and strain hardening was included in the model. The effect of different variables such as total reduction, coefficient of friction, roll radius and initial foil thickness ratio, on the thickness fraction of metals in the bonded composite was investigated. The model enables the estimation of the final composition of the roll bonded composite. The results of the model were compared with the experimental results, and good agreement was observed.

  6. Embrittlement recovery due to annealing of reactor pressure vessel steels

    SciTech Connect

    Eason, E.D.; Wright, J.E.; Nelson, E.E.; Odette, G.R.; Mader, E.V.

    1996-03-01

    Embrittlement of reactor pressure vessels (RPVs) can be reduced by thermal annealing at temperatures higher than the normal operating conditions. Although such an annealing process has not been applied to any commercial plants in the United States, one US Army reactor, the BR3 plant in Belgium, and several plants in eastern Europe have been successfully annealed. All available Charpy annealing data were collected and analyzed in this project to develop quantitative models for estimating the recovery in 30 ft-lb (41 J) Charpy transition temperature and Charpy upper shelf energy over a range of potential annealing conditions. Pattern recognition, transformation analysis, residual studies, and the current understanding of the mechanisms involved in the annealing process were used to guide the selection of the most sensitive variables and correlating parameters and to determine the optimal functional forms for fitting the data. The resulting models were fitted by nonlinear least squares. The use of advanced tools, the larger data base now available, and insight from surrogate hardness data produced improved models for quantitative evaluation of the effects of annealing. The quality of models fitted in this project was evaluated by considering both the Charpy annealing data used for fitting and the surrogate hardness data base. The standard errors of the resulting recovery models relative to calibration data are comparable to the uncertainty in unirradiated Charpy data. This work also demonstrates that microhardness recovery is a good surrogate for transition temperature shift recovery and that there is a high level of consistency between the observed annealing trends and fundamental models of embrittlement and recovery processes.

  7. Long-wave theory of bounded two-layer films with a free liquid-liquid interface: Short- and long-time evolution

    NASA Astrophysics Data System (ADS)

    Merkt, D.; Pototsky, A.; Bestehorn, M.; Thiele, U.

    2005-06-01

    We consider two layers of immiscible liquids confined between an upper and a lower rigid plate. The dynamics of the free liquid-liquid interface is described for arbitrary amplitudes by an evolution equation derived from the basic hydrodynamic equations using long-wave approximation. After giving the evolution equation in a general way, we focus on interface instabilities driven by gravity, thermocapillary and electrostatic fields. First, we study the linear stability discussing especially the conditions for destabilizing the system by heating from above or below. Second, we use a variational formulation of the evolution equation based on an energy functional to predict metastable states and the long-time pattern morphology (holes, drops or maze structures). Finally, fully nonlinear three-dimensional numerical integrations are performed to study the short- and long-time evolution of the evolving patterns. Different coarsening modes are discussed and long-time scaling exponents are extracted.

  8. Multi-decadal ingredients of the secular variation of the geomagnetic field. Insights from long time series of observatory data

    NASA Astrophysics Data System (ADS)

    Demetrescu, Crisan; Dobrica, Venera

    2014-06-01

    The temporal evolution of the geomagnetic field is shown, on data from 24 observatories with 100-150 years long time series of annual means, to be composed of several ingredients, which we call the steady, the ∼80-year, the 22-year, and the 11-year variations. The latter is the result of incomplete averaging out in the annual mean of external effects and shows a characteristic 11-year solar-cycle-related evolution with an amplitude of 10-40 nT in H and Z and within ±0.05° in D. The other three characterize the main field. While the steady variation carries the largest part of the main field and is smoothly increasing or decreasing in time, the ∼80-year variation shows changes with amplitudes amounting to several hundred nT in the intensity components H and Z, and of 0.2-0.7° in declination; the 22-year variation changes with much smaller amplitudes, of 20-60 nT in H and somewhat larger in Z (20-100 nT), and of about 0.05-0.15° in D. The analysis of the first time derivative of declination for the 24 study observatories showed that the ∼80-year variation dominated the secular variation in the last 100 years and that the 22-year variation has gotten its importance in defining the time evolution of the first time derivative of declination, jerks included, since 1960. The external contribution is decisive though in establishing the very short time scale characterizing jerks and, to some extent, also the amplitude and timing of the jerk. The analysis of 400 years-long declination time-series from three European locations (London, Munich, Rome) resulted in tracing back of the ∼80-year variation to the 15th century and showed that what we called 'steady variation', based on 150 years of observatory data, proves to be only a part of a larger timescale variation, when 400 years of data are available. According to our results, the term 'jerk' loses its presently accepted meaning of sudden change in the temporal evolution of secular variation. A more complex

  9. Kriging-approximation simulated annealing algorithm for groundwater modeling

    NASA Astrophysics Data System (ADS)

    Shen, C. H.

    2015-12-01

    Optimization algorithms are often applied to search best parameters for complex groundwater models. Running the complex groundwater models to evaluate objective function might be time-consuming. This research proposes a Kriging-approximation simulated annealing algorithm. Kriging is a spatial statistics method used to interpolate unknown variables based on surrounding given data. In the algorithm, Kriging method is used to estimate complicate objective function and is incorporated with simulated annealing. The contribution of the Kriging-approximation simulated annealing algorithm is to reduce calculation time and increase efficiency.

  10. Annealing effects on the optical properties of semiconducting boron carbide

    SciTech Connect

    Billa, R. B.; Robertson, B. W.; Hofmann, T.; Schubert, M.

    2009-08-01

    Infrared vibrations of as-deposited and annealed semiconducting boron carbide thin films were investigated by midinfrared spectroscopic ellipsometry. The strong boron-hydrogen resonance at approx2560 cm{sup -1} in as-deposited films reveals considerable hydrogen incorporation during plasma-enhanced chemical vapor deposition. Extended annealing at 600 deg. C caused significant reduction in film thickness, substantial reduction of boron-hydrogen bond resonance absorption, and development of distinct blue-shifted boron-carbon and icosahedral vibration mode resonances. Our findings suggest that annealing results in substantial loss of hydrogen and in development of icosahedral structure, accompanied by strain relaxation and densification.

  11. Quantum Annealing via Environment-Mediated Quantum Diffusion.

    PubMed

    Smelyanskiy, Vadim N; Venturelli, Davide; Perdomo-Ortiz, Alejandro; Knysh, Sergey; Dykman, Mark I

    2017-02-10

    We show that quantum diffusion near a quantum critical point can provide an efficient mechanism of quantum annealing. It is based on the diffusion-mediated recombination of excitations in open systems far from thermal equilibrium. We find that, for an Ising spin chain coupled to a bosonic bath and driven by a monotonically decreasing transverse field, excitation diffusion sharply slows down below the quantum critical region. This leads to spatial correlations and effective freezing of the excitation density. Still, obtaining an approximate solution of an optimization problem via the diffusion-mediated quantum annealing can be faster than via closed-system quantum annealing or Glauber dynamics.

  12. Resolution of annealing experiments for the study of nonequilibrium states

    NASA Technical Reports Server (NTRS)

    Schwed, Philip

    1951-01-01

    The two techniques for conducting annealing experiments for the purpose of determining the distribution of atoms of a solid among non equilibrium states are considered. Related definitions for resolving power for annealing with steadily rising temperature and for annealing at a series of fixed temperatures are given. The necessary separation of activation energies for the resolution of two different non equilibrium states is found to be greater in the case of a steadily rising temperature, but of the order of 10 percent of the activation energy for both techniques. The resolving power in the case of a steadily rising temperature is independent of the rate of temperature rise.

  13. Excimer laser annealing for low-voltage power MOSFET

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Okada, Tatsuya; Noguchi, Takashi; Mazzamuto, Fulvio; Huet, Karim

    2016-08-01

    Excimer laser annealing of lumped beam was performed to form the P-base junction for high-performance low-voltage-power MOSFET. An equivalent shallow-junction structure for the P-base junction with a uniform impurity distribution is realized by adopting excimer laser annealing (ELA). The impurity distribution in the P-base junction can be controlled precisely by the irradiated pulse energy density and the number of shots of excimer laser. High impurity activation for the shallow junction has been confirmed in the melted phase. The application of the laser annealing technology in the fabrication process of a practical low-voltage trench gate MOSFET was also examined.

  14. Laser annealing of implanted silicon carbide and Raman characterization

    NASA Astrophysics Data System (ADS)

    Zergioti, I.; Kontos, A. G.; Zekentes, K.; Boutopoulos, C.; Terzis, P.; Raptis, Y. S.

    2006-05-01

    Pulsed-laser-based methods have been applied for post-implant annealing of p-type Al doped 4H-SiC wafers in order to restore the crystal structure and to electrically activate the doping species. The annealing was performed with the second (532nm) and third (355nm) harmonic of a Nd:YAG laser at 4ns pulse duration. The epilayers were characterized by micro-Raman spectroscopy under surface and cross sectional backscattering. Changes in the phonon mode-intensity were related to the laser annealing induced recrystallization of the implanted material. The results were compared with changes in the infrared reflectivity across the Restsrahlen band.

  15. Quantum Annealing via Environment-Mediated Quantum Diffusion

    NASA Astrophysics Data System (ADS)

    Smelyanskiy, Vadim N.; Venturelli, Davide; Perdomo-Ortiz, Alejandro; Knysh, Sergey; Dykman, Mark I.

    2017-02-01

    We show that quantum diffusion near a quantum critical point can provide an efficient mechanism of quantum annealing. It is based on the diffusion-mediated recombination of excitations in open systems far from thermal equilibrium. We find that, for an Ising spin chain coupled to a bosonic bath and driven by a monotonically decreasing transverse field, excitation diffusion sharply slows down below the quantum critical region. This leads to spatial correlations and effective freezing of the excitation density. Still, obtaining an approximate solution of an optimization problem via the diffusion-mediated quantum annealing can be faster than via closed-system quantum annealing or Glauber dynamics.

  16. Crystal growth and annealing for minimized residual stress

    DOEpatents

    Gianoulakis, Steven E.

    2002-01-01

    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.

  17. Global Diffusion Tractography by Simulated Annealing.

    PubMed

    Robini, Marc C; Ozon, Matthew; Frindel, Carole; Yang, Feng; Zhu, Yuemin

    2017-03-01

    Our goal is to develop a robust global tractography method for cardiac diffusion imaging. A graph is stretched over the whole myocardium to represent the fiber structure, and the solutions are minima of a graph energy measuring the fidelity to the data along with the fiber density and curvature. The optimization is performed by a variant of simulated annealing that offers increased design freedom without sacrificing theoretical convergence guarantees. Numerical experiments on synthetic and real data demonstrate the capability of our tractography algorithm to deal with low angular resolution, highly noisy data. In particular, our algorithm outperforms the Bayesian model-based algorithm of Reisert et al. (NeuroImage, vol. 54, no. 2, 2011) and the graph-based algorithm of Frindel et al. (Magn. Reson. Med., vol. 64, no. 4, 2010) at the noise levels typical of in vivo imaging. The proposed algorithm avoids the drawbacks of local techniques and is very robust to noise, which makes it a promising tool for in vivo diffusion imaging of moving organs. Our approach is global in terms of both the fiber structure representation and the minimization problem. It also allows us to adjust the trajectory density by simply changing the vertex-lattice spacing in the graph model, a desirable feature for multiresolution tractography analysis.

  18. Nonequilibrium self-organization of colloidal particles on substrates: adsorption, relaxation, and annealing.

    PubMed

    Araújo, Nuno A M; Dias, Cristóvão S; Telo da Gama, Margarida M

    2017-01-11

    Colloidal particles are considered ideal building blocks to produce materials with enhanced physical properties. The state-of-the-art techniques for synthesizing these particles provide control over shape, size, and directionality of the interactions. In spite of these advances, there is still a huge gap between the synthesis of individual components and the management of their spontaneous organization towards the desired structures. The main challenge is the control over the dynamics of self-organization. In their kinetic route towards thermodynamically stable structures, colloidal particles self-organize into intermediate (mesoscopic) structures that are much larger than the individual particles and become the relevant units for the dynamics. To follow the dynamics and identify kinetically trapped structures, one needs to develop new theoretical and numerical tools. Here we discuss the self-organization of functionalized colloids (also known as patchy colloids) on attractive substrates. We review our recent results on the adsorption and relaxation and explore the use of annealing cycles to overcome kinetic barriers and drive the relaxation towards the targeted structures.

  19. Nonequilibrium self-organization of colloidal particles on substrates: adsorption, relaxation, and annealing

    NASA Astrophysics Data System (ADS)

    Araújo, Nuno A. M.; Dias, Cristóvão S.; Telo da Gama, Margarida M.

    2017-01-01

    Colloidal particles are considered ideal building blocks to produce materials with enhanced physical properties. The state-of-the-art techniques for synthesizing these particles provide control over shape, size, and directionality of the interactions. In spite of these advances, there is still a huge gap between the synthesis of individual components and the management of their spontaneous organization towards the desired structures. The main challenge is the control over the dynamics of self-organization. In their kinetic route towards thermodynamically stable structures, colloidal particles self-organize into intermediate (mesoscopic) structures that are much larger than the individual particles and become the relevant units for the dynamics. To follow the dynamics and identify kinetically trapped structures, one needs to develop new theoretical and numerical tools. Here we discuss the self-organization of functionalized colloids (also known as patchy colloids) on attractive substrates. We review our recent results on the adsorption and relaxation and explore the use of annealing cycles to overcome kinetic barriers and drive the relaxation towards the targeted structures.

  20. The Effect of Long-Time Austenization on the Wear Resistance and Thermal Fatigue Properties of a High-Speed Steel Roll

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaodan; Liu, Wei; Godfrey, Andrew; Liu, Qing

    2009-09-01

    The effects of a long-time austenization treatment on a high-speed steel (HSS) roll have been investigated. Several interesting phenomena were observed, including the decomposition of the primary bulky M3C carbides on grain boundaries and the precipitation of a large number of MC carbides of size comparable to the primary MC carbides in the grains. As a consequence of these changes, the overall carbide size decreased and the homogeneity of the carbide distribution increased. The wear resistance and thermal fatigue properties of the HSS roll were also investigated, and it was found that the long-time austenization treatment resulted in improvements to both properties.

  1. Following atomistic kinetics on experimental timescales with the kinetic Activation–Relaxation Technique

    DOE PAGES

    Mousseau, Normand; Béland, Laurent Karim; Brommer, Peter; ...

    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 kineticmore » Monte Carlo methods, with on-the-fly cataloging, that have been proposed in the last few years.« less

  2. Chemical and Biological Kinetics

    NASA Astrophysics Data System (ADS)

    Emanuel', N. M.

    1981-10-01

    Examples of the application of the methods and ideas of chemical kinetics in various branches of chemistry and biology are considered and the results of studies on the kinetics and mechanisms of autoxidation and inhibited and catalysed oxidation of organic substances in the liquid phase are surveyed. Problems of the kinetics of the ageing of polymers and the principles of their stabilisation are discussed and certain trends in biological kinetics (kinetics of tumour growth, kinetic criteria of the effectiveness of chemotherapy, problems of gerontology, etc.) are considered. The bibliography includes 281 references.

  3. Mechanism of morphology transformation during annealing of nanostructured gold films on glass.

    PubMed

    Karakouz, Tanya; Tesler, Alexander B; Sannomiya, Takumi; Feldman, Yishay; Vaskevich, Alexander; Rubinstein, Israel

    2013-04-07

    Nanostructured, just-percolated gold films were prepared by evaporation on bare glass. Annealing of the films at temperatures close to or higher than the softening temperature of the glass substrate induces morphological transformation to discrete Au islands and gradual embedding of the formed islands in the glass. The mechanism and kinetics of these processes are studied here using a combination of in situ high-temperature optical spectroscopy; ex situ characterization of the island shape by high-resolution scanning electron microscopy (HRSEM), atomic force microcopy (AFM) and cross-sectional transmission electron microscopy (TEM); and numerical simulations of transmission spectra using the Multiple Multipole Program (MMP) approach. It is shown that the morphological transformation of just-percolated, 10 nm (nominal thickness) Au films evaporated on glass and annealed at 600 °C, i.e., in the vicinity of the substrate glass transition temperature (Tg = 557 °C), proceeds via three processes exhibiting different time scales: (i) fast recrystallization and dewetting, leading to formation of single-crystalline islands (minutes); the initial spectrum characteristic of a continuous Au film is transformed to that of an island film, displaying a surface plasmon (SP) absorption band. (ii) Reshaping and faceting of the single-crystalline islands accompanied by formation of circumferential glass rims around them (first few hours); the overall optical response shows a blue shift of the SP band. (iii) Gradual island embedding in the glass substrate (tens of hours), seen as a characteristic red shift of the SP band. The influence of the annealing atmosphere (air, vacuum) on the embedding process is found to be minor. Numerical modeling of the extinction cross-section corresponding to the morphological transformations during island recrystallization and embedding is in qualitative agreement with the experimental data.

  4. Microstructural evolution of nanocrystalline Fe–Zr alloys upon annealing treatment

    SciTech Connect

    Shi, X.H.; Chen, Y.Z.; Ma, X.Y.; Wang, H.T.; Liu, F.

    2015-05-15

    Nanocrystalline Fe–Zr alloys exhibit an extraordinary thermal stability at elevated temperatures, which enables their potential applications in various fields. However, there remain concerns regarding the controlling stabilization mechanisms responsible for their thermal stability. In this work, two nanocrystalline Fe–Zr alloys containing 1 at.% Zr and 5 at.% Zr were annealed at various temperatures (T{sub ann}) up to 900 °C. Microstructural evolution of the alloys upon annealing was investigated by means of an X-ray diffractometer equipped with a 2-dimensional detector and transmission electron microscopy. Below 600 °C, microstructures of the two alloys consist of single nanocrystalline ferrite whose grain size is rather stable upon annealing treatments. Above 600 °C, accompanying the precipitation of Fe{sub 3}Zr phase, an apparent grain coarsening of ferrite is observed, whereas the thermal stability of the alloys is still considerably higher than that of nanocrystalline pure Fe. Based on the experimental results, it was claimed that stabilization of the nanocrystalline Fe–Zr alloys should not be totally ascribed to the thermodynamic stabilization mechanism due to the reduction in grain boundary energy as suggested in earlier investigations [K.A. Darling et al., Scr. Mater. 59 (2008) 530 and K.A. Darling et al., Mater. Sci. Eng. A527 (2010) 3572]; when T{sub ann} is higher than 600 °C, along with the precipitation of Fe{sub 3}Zr, the effect of thermodynamic stabilization is weakened, the kinetic effect arising from Zener pinning of Fe{sub 3}Zr precipitates turns to be an important mechanism contributing to the stabilization of the nanoscale grain size. - Highlights: • We show clear evidence of precipitation of Fe{sub 3}Zr phase above 600 °C. • Stabilization of nanostructure is not solely controlled by thermodynamic mechanism. • Above 600 °C, Zener pinning plays an important role in stabilizing nanostructure.

  5. Cesium removal and kinetics equilibrium: Precipitation kinetics

    SciTech Connect

    Barnes, M.J.

    1999-12-17

    This task consisted of both non-radioactive and radioactive (tracer) tests examining the influence of potentially significant variables on cesium tetraphenylborate precipitation kinetics. The work investigated the time required to reach cesium decontamination and the conditions that affect the cesium precipitation kinetics.

  6. Pre-Oxidation Anneal Kinetics: Interface Degradation of Thin SIO2 Films on Silicon

    DTIC Science & Technology

    1992-07-13

    set describing the dependance of Io on the PreOxA time is shown in Fig. 3. From the fit of the data (solid line), and considering scatter in the data...300 360 420 480 540600 0 6 12 13 24 30 36 42 48 54 60 tA (8C) HzO conc. (ppmV) Figure 3. Typical dependance of I0 on PreOxA Figure 4. Dependance of

  7. Synthesis of boron nitride nanotubes by boron ink annealing

    NASA Astrophysics Data System (ADS)

    Li, Lu Hua; Chen, Ying; Glushenkov, Alexey M.

    2010-03-01

    Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. These improvements are caused by the addition of metal nitrate and ethanol, both of which can strongly boost the nitriding reaction, as revealed by thermogravimetric analysis. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs.

  8. Synthesis of boron nitride nanotubes by boron ink annealing.

    PubMed

    Li, Lu Hua; Chen, Ying; Glushenkov, Alexey M

    2010-03-12

    Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. These improvements are caused by the addition of metal nitrate and ethanol, both of which can strongly boost the nitriding reaction, as revealed by thermogravimetric analysis. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs.

  9. Simulated quantum annealing of double-well and multiwell potentials.

    PubMed

    Inack, E M; Pilati, S

    2015-11-01

    We analyze the performance of quantum annealing as a heuristic optimization method to find the absolute minimum of various continuous models, including landscapes with only two wells and also models with many competing minima and with disorder. The simulations performed using a projective quantum Monte Carlo (QMC) algorithm are compared with those based on the finite-temperature path-integral QMC technique and with classical annealing. We show that the projective QMC algorithm is more efficient than the finite-temperature QMC technique, and that both are inferior to classical annealing if this is performed with appropriate long-range moves. However, as the difficulty of the optimization problem increases, classical annealing loses efficiency, while the projective QMC algorithm keeps stable performance and is finally the most effective optimization tool. We discuss the implications of our results for the outstanding problem of testing the efficiency of adiabatic quantum computers using stochastic simulations performed on classical computers.

  10. Ultraclean suspended monolayer graphene achieved by in situ current annealing

    NASA Astrophysics Data System (ADS)

    Wang, Haidong; Zhang, Xing; Takamatsu, Hiroshi

    2017-01-01

    Ultraclean graphene is essential for studying its intrinsic transport properties or fabricating high-performance electronic devices. Unfortunately, the contamination on graphene is unavoidable after microelectromechanical system processing. Here, we report an in situ current-annealing method for achieving ultraclean suspended monolayer graphene. The charge mobility of cleaned graphene reached a surprising 3.8 × 105 cm2 V-1 s-1, one of the highest values ever reported. For the first time, the process of current annealing was recorded under a high-resolution electron scanning microscope. It was demonstrated that temperature was the only dominant factor of the current-annealing process. Meanwhile, the mobility of suspended graphene was found to be highly sensitive to structural defects. The mobility decreased by a factor of over 100 after ion irradiation on graphene. The results revealed the underlying mechanism of current annealing on graphene and provided an effective means of preparing ultraclean graphene membranes.

  11. Effect of Annealing on Elastic Moduli of a FSMA

    NASA Astrophysics Data System (ADS)

    Hossain, Md Sarowar; Rajini Kanth, B.; Mukhopadhyay, P. K.

    2017-07-01

    Ferromagnetic shape memory alloys (FSMA) are both ferromagnetic as well as have structural transformations from austenite to martensite and back. These structural transformations are generally studied through resistivity, magnetisation, etc. It is also known that annealing improves the physical properties of the FSMA systems. In this paper, we studied the effect of annealing on a typical CoNiAl FSMA system. However, in addition to the conventional methods, we also measured the elastic properties across the transition temperatures, and showed how the effect of annealing affects its elastic modulus. The measurements were done using a vibrating reed technique on thin samples that were annealed at two different temperatures. We also compared their properties in this paper.

  12. Evidence for quantum annealing with more than one hundred qubits

    NASA Astrophysics Data System (ADS)

    Boixo, Sergio; Rønnow, Troels F.; Isakov, Sergei V.; Wang, Zhihui; Wecker, David; Lidar, Daniel A.; Martinis, John M.; Troyer, Matthias

    2014-03-01

    Quantum technology is maturing to the point where quantum devices, such as quantum communication systems, quantum random number generators and quantum simulators may be built with capabilities exceeding classical computers. A quantum annealer, in particular, solves optimization problems by evolving a known initial configuration at non-zero temperature towards the ground state of a Hamiltonian encoding a given problem. Here, we present results from tests on a 108 qubit D-Wave One device based on superconducting flux qubits. By studying correlations we find that the device performance is inconsistent with classical annealing or that it is governed by classical spin dynamics. In contrast, we find that the device correlates well with simulated quantum annealing. We find further evidence for quantum annealing in the form of small-gap avoided level crossings characterizing the hard problems. To assess the computational power of the device we compare it against optimized classical algorithms.

  13. Regulation of multispanning membrane protein topology via post-translational annealing

    PubMed Central

    Van Lehn, Reid C; Zhang, Bin; Miller, Thomas F

    2015-01-01

    The canonical mechanism for multispanning membrane protein topogenesis suggests that protein topology is established during cotranslational membrane integration. However, this mechanism is inconsistent with the behavior of EmrE, a dual-topology protein for which the mutation of positively charged loop residues, even close to the C-terminus, leads to dramatic shifts in its topology. We use coarse-grained simulations to investigate the Sec-facilitated membrane integration of EmrE and its mutants on realistic biological timescales. This work reveals a mechanism for regulating membrane-protein topogenesis, in which initially misintegrated configurations of the proteins undergo post-translational annealing to reach fully integrated multispanning topologies. The energetic barriers associated with this post-translational annealing process enforce kinetic pathways that dictate the topology of the fully integrated proteins. The proposed mechanism agrees well with the experimentally observed features of EmrE topogenesis and provides a range of experimentally testable predictions regarding the effect of translocon mutations on membrane protein topogenesis. DOI: http://dx.doi.org/10.7554/eLife.08697.001 PMID:26408961

  14. A track process for solvent annealing of high-χ BCPs

    NASA Astrophysics Data System (ADS)

    Guerrero, Douglas J.; Sakavuyi, Kaumba; Xu, Kui; Gharbi, Ahmed; Tiron, Raluca; Servin, Isabelle; Pain, Laurent; Claveau, Guillaume; Stokes, Harold; Harumoto, Masahiko; Nicolet, Célia; Chevalier, Xavier

    2017-03-01

    High chi organic lamellar-forming block copolymers were prepared with 18 nm intrinsic period Lo value. The BCPs were coated on a neutral layer on silicon substrates and were either thermally annealed or exposed to solvent vapors both in a 300mm track. The effect of lowering the glass transition temperature (Tg) on the high chi BCP was investigated. Process temperatures and times were varied. It was found that the BCP having lower Tg exhibits faster kinetics and is able to reach alignment in a shorter time than a similar BCP having higher Tg. Fingerprint defect analysis also shows that the BCP with lower Tg has lower defects. The results show that fingerprint formation can be achieved with either ether or ester type solvents depending on the BCP used. The results show that a track process for solvent annealing of high-χ BCPs is feasible and could provide the path forward for incorporation of BCP in future nodes. Finally, directed self-assembly was demonstrated by implemented high chi polymers on a graphoepitaxy test vehicles. CD and line width roughness was evaluated on patterns with a multiplication factor up to 7.

  15. High-level incorporation of antimony in germanium by laser annealing

    NASA Astrophysics Data System (ADS)

    Bruno, E.; Scapellato, G. G.; Bisognin, G.; Carria, E.; Romano, L.; Carnera, A.; Priolo, F.

    2010-12-01

    In this work we investigate pulse laser annealing as an alternative approach to reach high-level incorporation of Sb in substitutional location in crystalline germanium. Laser irradiation is demonstrated to recover also those structural defects, like honeycomb structures, that form during high-fluence heavy-ion implantations in Ge and that cannot be eliminated by conventional thermal treatments. Indeed, concentrations of substitutional Sb higher than 1×1021 at./cm3 have been obtained, well above the solid solubility of Sb in Ge. The strain induced on the Ge host lattice is also investigated, evidencing that the obtained Sb doped Ge layer is pseudomorphic to the Ge substrate while positively strained by the substitutional Sb atoms present within the Ge matrix. The kinetics of this Sb-rich Ge alloy phase is finally investigated, showing that most of Sb goes out of lattice with increasing the annealing temperature up to 488 °C, leading to a decrease in the related lattice deformation. These results are very relevant for the future high-mobility channel technology.

  16. Regulation of multispanning membrane protein topology via post-translational annealing.

    PubMed

    Van Lehn, Reid C; Zhang, Bin; Miller, Thomas F

    2015-09-26

    The canonical mechanism for multispanning membrane protein topogenesis suggests that protein topology is established during cotranslational membrane integration. However, this mechanism is inconsistent with the behavior of EmrE, a dual-topology protein for which the mutation of positively charged loop residues, even close to the C-terminus, leads to dramatic shifts in its topology. We use coarse-grained simulations to investigate the Sec-facilitated membrane integration of EmrE and its mutants on realistic biological timescales. This work reveals a mechanism for regulating membrane-protein topogenesis, in which initially misintegrated configurations of the proteins undergo post-translational annealing to reach fully integrated multispanning topologies. The energetic barriers associated with this post-translational annealing process enforce kinetic pathways that dictate the topology of the fully integrated proteins. The proposed mechanism agrees well with the experimentally observed features of EmrE topogenesis and provides a range of experimentally testable predictions regarding the effect of translocon mutations on membrane protein topogenesis.

  17. Microstructural evolution at the initial stages of annealing in a Bi-2223 multifilament tape

    NASA Astrophysics Data System (ADS)

    Liu, Y. L.; Grivel, J.-C.; Wang, W. G.; Poulsen, H. F.

    2001-11-01

    The microstructural evolution at the initial stage of annealing in a multifilament Bi-2223 (2223) tape is studied in quenched samples using XRD, SEM and EDS. The annealing was carried out at 830 °C under reduced oxygen partial pressure. Samples were quenched in air upon reaching 830 °C, as well as after 1, 2, 5, 10, 30 and 52 h at 830 °C. It was found that the initial liquid formation was associated with alkaline-earth cuprate (AEC) particles such as (Ca,Sr)14Cu24Oz and (Ca,Sr)2CuO3. The liquid is rich of Pb and the AEC particles dissolve and supply Cu and Ca into the liquid through direct contact. The 2223 kinetics are well correlated with the structural parameters of liquid and AEC particles. During the first hour the liquid activity is confined to the neighbourhood of AEC particles and the rate of 2223 formation is very low. Between 2 and 10 h the liquid amount increases and the size (measured in tape plane) is comparable with the particle spacing indicating a liquid activity on an overall scale and sufficient feeding of Cu and Ca. Consequently, the 2223 develops at a fast rate. After 10 h the liquid amount is decreased, the particle spacing is far larger than the liquid size and the rate of 2223 formation slows down. The early 2223 forms as precipitates in the structure. The possible formation mechanisms are discussed.

  18. Crystallization Kinetics in Fluorochloroziroconate Glass-Ceramics

    NASA Astrophysics Data System (ADS)

    Alvarez, Carlos J.

    Annealing fluorochlorozirconate (FCZ) glasses nucleates BaCl2 nanocrystals in the glass matrix, resulting in a nanocomposite glass-ceramic that has optical properties suitable for use as a medical X-ray imaging plate. Understanding the way in which the BaCl¬2 nanocrystal nucleation, growth and phase transformation processes proceed is critical to controlling the optical behavior. However, there is a very limited amount of information about the formation, morphology, and distribution of the nanocrystalline particles in FCZ glass-ceramics. In this thesis, the correlation between the microstructure and the crystallization kinetics of FCZ glass-ceramics, are studied in detail. In situ X-ray diffraction and transmission electron microscopy annealing experiments are used to analyze the crystal structure, size and distribution of BaCl 2 nanocrystals in FCZ glass-ceramics as a function of annealing rate and temperature. Microstructural analysis of the early stages on nucleation identified the formation of both BaCl2 and BaF2 nanocrystals. Annealing FCZ glass-ceramics above 280°C can cause the formation of additional glass matrix phase crystals, their microstructure and the annealing parameters required for their growth are identified. As the crystalline phases grow directly from the glass, small variations in processing of the glass can have a profound influence on the crystallization process. The information obtained from these experiments improves the understanding of the nucleation, growth and phase transformation process of the BaCl¬2 nanocrystals and additional crystalline phases that form in FCZ glass-ceramics, and may help expedite the implementation of FCZ glass-ceramics as next-generation X-ray detectors. Lastly, as these glass-ceramics may one day be commercialized, an investigation into their degradation in different environmental conditions was also performed. The effects of direct contact with water or prolonged exposure to humid environments on the

  19. Kinetic Proofreading of Cytoskeletal Structures

    NASA Astrophysics Data System (ADS)

    Swanson, Douglas; Wingreen, Ned

    2010-03-01

    Cytoskeletal polymer dynamics play a role in cellular processes as varied as reproduction, locomotion, and intracellular transport. Microtubules are cytoskeletal biopolymers that grow by accumulating tubulin subunits bound to guanosine triphosphate (GTP). The subunits hydrolyze GTP to guanosine diphosphate (GDP), causing a conformational change in the protein that destabilizes the microtubule. GDP-bound subunits tend to depolymerize, leading to stochastic microtubule disassembly in a process known as dynamic instability. Over time polymerization and depolymerization come to steady state, leading to a local steady-state concentration of tubulin subunits. This may be viewed as a kind of ``kinetic proofreading,'' in which the system consumes energy actively to ``proofread'' the steady-state subunit concentration. We suggest that the same mechanism could also ``proofread'' between different cytoskeletal structures. For example, we show that a small free-energy difference between two polymer orientations, combined with dynamic instability, can strongly drive the system towards the lower free-energy state. This might help to explain the long-time stability of many cytoskeletal structures despite the short-time rapid turnover of the individual subunits.

  20. Long time series of soil moisture obtained using neural networks: application to AMSR-E and SMOS

    NASA Astrophysics Data System (ADS)

    Rodriguez-Fernandez, Nemesio J.; Kerr, Yann H.; de Jeu, Rcihard A. M.; van der Schalie, Robin; Wigneron, Jean Pierre; Ayaari, Amen al; Dolman, Han; Drusch, Matthias; Mecklenburg, Sussane

    2015-04-01

    The Soil Moisture and Ocean Salinity (SMOS) satellite is the first mission specifically designed to measure soil moisture (hereafter SM) from space. The instrument on-board SMOS is a L-band aperture synthesis radiometer, with full-polarization and multi-angular capabilities (Mecklenburg et al. 2012). The operational SM retrieval algorithm is based on a physical model (Kerr et al. 2012). In addition, Rodriguez-Fernandez et al. (2014) have recently implemented an inverse model based in neural networks using the approach of Aires & Prigent (2006), which consists in training the neural networks with numerical weather prediction models (ECMWF, Balsamo et al. 2009). In the context of an ESA funded project (de Jeu et al, this conference, session CL 5.7), we have studied this neural network approach to create a consistent soil moisture dataset from 2003 to 2014 using NASA/JAXA Advanced Scanning Microwave Radiometer (AMSR-E) and ESA SMOS radiometers as input data. Two neural networks algorithms have been defined and optimized using AMSR-E or SMOS as input data in the periods 2003-Oct 2011 and 2010-2014, respectively. The two missions overlapping period has been used to demonstrate the consistency of the SM dataset produced with both algorithms by comparing monthly averages of SM and by comparing with time series of in situ measurements at selected locations and other SM products such as the SMOS operational SM, ECMWF model SM, and AMSR-E LPRM SM (Owe et al. 2008). Finally, the long time series of SM obtained with neural networks will be compared to in-situ measurements and ECMWF ERA-Interim SM at selected locations. This long-term soil moisture dataset can be used for hydrological and climate applications and it is the first step towards a longer dataset which will include additional sensors. References Aires, F. & Prigent, C. Toward a new generation of satellite surface products? Journal of Geophysical Research: Atmospheres (1984--2012), Wiley Online Library, 2006, 11

  1. Predicting outgrowth and inactivation of Clostridium perfringens in meat products during low temperature long time heat treatment.

    PubMed

    Duan, Zhi; Hansen, Terese Holst; Hansen, Tina Beck; Dalgaard, Paw; Knøchel, Susanne

    2016-08-02

    With low temperature long time (LTLT) cooking it can take hours for meat to reach a final core temperature above 53°C and germination followed by growth of Clostridium perfringens is a concern. Available and new growth data in meats including 154 lag times (tlag), 224 maximum specific growth rates (μmax) and 25 maximum population densities (Nmax) were used to developed a model to predict growth of C. perfringens during the coming-up time of LTLT cooking. New data were generate in 26 challenge tests with chicken (pH6.8) and pork (pH5.6) at two different slowly increasing temperature (SIT) profiles (10°C to 53°C) followed by 53°C in up to 30h in total. Three inoculum types were studied including vegetative cells, non-heated spores and heat activated (75°C, 20min) spores of C. perfringens strain 790-94. Concentrations of vegetative cells in chicken increased 2 to 3logCFU/g during the SIT profiles. Similar results were found for non-heated and heated spores in chicken, whereas in pork C. perfringens 790-94 increased less than 1logCFU/g. At 53°C C. perfringens 790-94 was log-linearly inactivated. Observed and predicted concentrations of C. perfringens, at the time when 53°C (log(N53)) was reached, were used to evaluate the new growth model and three available predictive models previously published for C. perfringens growth during cooling rather than during SIT profiles. Model performance was evaluated by using mean deviation (MD), mean absolute deviation (MAD) and the acceptable simulation zone (ASZ) approach with a zone of ±0.5logCFU/g. The new model showed best performance with MD=0.27logCFU/g, MAD=0.66logCFU/g and ASZ=67%. The two growth models that performed best, were used together with a log-linear inactivation model and D53-values from the present study to simulate the behaviour of C. perfringens under the fast and slow SIT profiles investigated in the present study. Observed and predicted concentrations were compared using a new fail-safe acceptable

  2. Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

    NASA Technical Reports Server (NTRS)

    Rai, Amarendra K.; Schmitt, Michael P.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

    2014-01-01

    Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating.

  3. One-dimensional gratings evolving through high-temperature annealing: sine-generated solutions.

    PubMed

    Madrid, Marcos A; Salvarezza, Roberto C; Castez, Marcos F

    2012-01-11

    Sine-generated curves (i.e. curves in which the curvature is a sine function of the arc-length parameter) have been used in the past to describe river meanders. Here we show how these curves spontaneously appear during the decay of high-aspect-ratio surfaces mediated by surface diffusion. We obtained analytical results for the kinetic evolution of such processes relevant to a wide class of initial geometries. Our theoretical results were satisfactorily compared with numerical simulations and with results from previous approaches to the same problem, and they can be useful for interpreting and designing experiments related to the technologically important process of high-temperature annealing on nano/micro-structured samples.

  4. The fraction of substitutional boron in silicon during ion implantation and thermal annealing

    SciTech Connect

    Caturla, M.J.; Johnson, M.D.; Diaz de la Rubia, T.

    1998-05-01

    We present results from a kinetic Monte Carlo simulation of boron transient enhanced diffusion (TED) in silicon. Our approach avoids the use of phenomenological fits to experimental data by using a complete and self-consistent set of values for defect and dopant energetics derived mostly from {ital ab initio} calculations. The results predict that, during annealing of 40 keV B-implanted Si at 800{degree}C, there exists a time window during which all the implanted boron atoms are substitutional. At earlier or later times, the interactions between free silicon self-interstitials and boron atoms drive the growth of boron clusters and result in an inactive boron fraction. The results show that the majority of boron TED takes place during the growth period of interstitial clusters and not during their dissolution. {copyright} {ital 1998 American Institute of Physics.}

  5. Method and apparatus for selectively annealing heterostructures using microwave

    NASA Technical Reports Server (NTRS)

    Atwater, Harry A. (Inventor); Brain, Ruth A. (Inventor); Barmatz, Martin B. (Inventor)

    1998-01-01

    The present invention discloses a process for selectively annealing heterostructures using microwaves. A heterostructure, comprised of a material having higher microwave absorption and a material having lower microwave absorption, is exposed to microwaves in the cavity. The higher microwave absorbing material absorbs the microwaves and selectively heats while the lower microwave absorbing material absorbs small amounts of microwaves and minimally heats. The higher microwave absorbing material is thereby annealed onto the less absorbing material which is thermally isolated.

  6. Method and apparatus for selectively annealing heterostructures using microwaves

    NASA Technical Reports Server (NTRS)

    Atwater, Harry A. (Inventor); Brain, Ruth A. (Inventor); Barmatz, Martin B. (Inventor)

    1998-01-01

    The present invention discloses a process for selectively annealing heterostructures using microwaves. A heterostructure, comprised of a material having higher microwave absorption and a material having lower microwave absorption, is exposed to microwaves in the cavity. The higher microwave absorbing material absorbs the microwaves and selectively heats while the lower microwave absorbing material absorbs small amounts of microwaves and minimally heats. The higher microwave absorbing material is thereby annealed onto the less absorbing material which is thermally isolated.

  7. Annealing effects on microstrain of cobalt oxide nanoparticles

    SciTech Connect

    Deotale, Anjali Jain Nandedkar, R. V.; Sinha, A. K.; Singh, M. N.; Upadhyay, Anuj

    2014-04-24

    Cobalt oxide nanoparticles in different phases have been synthesized using ash supported method. The effect of isochronal annealing on micro-strain of cobalt oxide nanoparticles has been studied. The lattice strain contribution to the x-ray diffraction line broadening in the nanoparticles was analyzed using Williamson Hall (W-H) plot. It is observed that micro-strain was released at higher annealing temperature.

  8. Performance enhancement of hybrid solar cells through chemical vapor annealing.

    PubMed

    Wu, Yue; Zhang, Genqiang

    2010-05-12

    Improvement in power conversion efficiency has been observed in cadmium selenide nanorods/poly(3-hexylthiophene) hybrid solar cells through benzene-1,3-dithiol chemical vapor annealing. Phosphor NMR studies of the nanorods and TEM/AFM characterizations of the morphology of the blended film showed that the ligand exchange reaction and related phase separation happening during the chemical vapor annealing are responsible for the performance enhancement.

  9. An improved simulated annealing algorithm for standard cell placement

    NASA Technical Reports Server (NTRS)

    Jones, Mark; Banerjee, Prithviraj

    1988-01-01

    Simulated annealing is a general purpose Monte Carlo optimization technique that was applied to the problem of placing standard logic cells in a VLSI ship so that the total interconnection wire length is minimized. An improved standard cell placement algorithm that takes advantage of the performance enhancements that appear to come from parallelizing the uniprocessor simulated annealing algorithm is presented. An outline of this algorithm is given.

  10. Crowded surfaces change annealing dynamics of actin filaments.

    PubMed

    Popp, David; Yamamoto, Akihiro; Maéda, Yuichiro

    2007-04-27

    Changes in cell shape that occur in many cellular processes are thought to arise from polymerization of actin filaments near the cell membrane. End-to-end annealing of actin filaments is believed to play only a minor role in this process, as annealing in solution was shown to be a slow process, which is not typical for a bimolecular reaction, its rate constant decreasing over time, being inversely proportional to the filament length. Furthermore, in vitro studies on f-actin solutions were found to display an exponential steady-state length distribution. In the cell, many physiologically important parameters, such as mechanical strength or viscoelastic response are a direct function of the physical properties of the underlying actin cytoskeleton, such as actin filament length distribution and dynamics. How the underlying physical parameters of the actin cytoskeleton may be influenced by the cell surface or molecular crowding remains poorly understood. Using total internal reflection fluorescence (TIRF) microscopy we reinvestigated actin end-to-end annealing in vitro in a more realistic environment. We studied the process near a hydrophilic surface together with crowding agents, in order to mimic the physiological media near the cell membrane, which has substantial amounts of macromolecules present. We find that actin end-to-end annealing changes in three ways near a crowded hydrophilic surface as compared to solution. First the annealing rate becomes a factor of 20 faster than in solution. Second the rate of annealing becomes typical of a bimolecular reaction, shows no length dependence and is basically just a function of the square of the concentration of ends. Lastly the length distribution is Gaussian throughout the entire annealing process. This implicates that dynamic rearrangement of actin filaments by annealing near the leading edge of the cell, could change physical parameters like the mechanical response and contribute significantly to cell motility.

  11. Improved mapping of the travelling salesman problem for quantum annealing

    NASA Astrophysics Data System (ADS)

    Troyer, Matthias; Heim, Bettina; Brown, Ethan; Wecker, David

    2015-03-01

    We consider the quantum adiabatic algorithm as applied to the travelling salesman problem (TSP). We introduce a novel mapping of TSP to an Ising spin glass Hamiltonian and compare it to previous known mappings. Through direct perturbative analysis, unitary evolution, and simulated quantum annealing, we show this new mapping to be significantly superior. We discuss how this advantage can translate to actual physical implementations of TSP on quantum annealers.

  12. Significant improvement in the thermal annealing process of optical resonators

    NASA Astrophysics Data System (ADS)

    Salzenstein, Patrice; Zarubin, Mikhail

    2017-05-01

    Thermal annealing performed during process improves the quality of the roughness of optical resonators reducing stresses at the periphery of their surface thus allowing higher Q-factors. After a preliminary realization, the design of the oven and the electronic method were significantly improved thanks to nichrome resistant alloy wires and chopped basalt fibers for thermal isolation during the annealing process. Q-factors can then be improved.

  13. Precise annealing of focal plane arrays for optical detection

    DOEpatents

    Bender, Daniel A.

    2015-09-22

    Precise annealing of identified defective regions of a Focal Plane Array ("FPA") (e.g., exclusive of non-defective regions of the FPA) facilitates removal of defects from an FPA that has been hybridized and/or packaged with readout electronics. Radiation is optionally applied under operating conditions, such as under cryogenic temperatures, such that performance of an FPA can be evaluated before, during, and after annealing without requiring thermal cycling.

  14. Ultra High Temperature Rapid Thermal Annealing of GaN

    SciTech Connect

    Cao, X.A.; Fu, M.; Han, J.; Pearton, S.J.; Rieger, D.J.; Sekhar, J.A.; Shul, R.J.; Singh, R.K.; Wilson, R.G.; Zolper, J.C.

    1998-11-20

    All of the major acceptor (Mg, C, Be) and donor (Si, S, Se and Te) dopants have been implanted into GaN films grown on A1203 substrates. Annealing was performed at 1100- 1500 C, using AIN encapsulation. Activation percentages of >90Y0 were obtained for Si+ implantation annealed at 1400 C, while higher temperatures led to a decrease in both carrier concentration and electron mobility. No measurable redistribution of any of the implanted dopants was observed at 1450 C.

  15. Investigation of Silicon Surface Passivation by Microwave Annealing Using Multiple-Wavelength Light-Induced Carrier Lifetime Measurement

    NASA Astrophysics Data System (ADS)

    Sameshima, Toshiyuki; Ebina, Ryoko; Betsuin, Koichi; Takiguchi, Yuta; Hasumi, Masahiko

    2013-01-01

    A simple annealing method using a commercial 2.45 GHz microwave oven is reported to increase the minority carrier lifetime τeff for 4-in.-size 500-µm-thick 20 Ω cm n-type silicon substrates coated with 100-nm-thermally grown SiO2 layers. The microwave annealing was conducted with 2-mm-thick glass substrates, which sandwiched a silicon sample to maintain the thermal energy in silicon and realize gradual cooling. A 9.35 GHz microwave transmittance measurement system was used to measure τeff in the cases of continuous-wave 635 and 980 nm laser diode (LD) light illuminations. Radio-frequency Ar plasma irradiation at 50 W for 60 s to the top surface of a silicon sample markedly decreased τeff in the range from 6.0×10-6 to 2.4×10-5 s and from 4.2×10-5 to 6.4×10-5 s in the cases of 635 and 980 nm light illuminations, respectively, while τeff had the same distribution from 1.6×10-3 to 3.1×10-3 s for the initial samples. The finite element numerical analysis revealed that Ar plasma irradiation caused high densities of recombination defect states at the silicon top surface in the range from 1.3×1013 to 5.0×1013 cm-2. Microwave annealing at 700 W for 120 s markedly increased τeff in the range from 8.0×10-4 to 2.5×10-3 s, which were close to those of the initial samples. The density of recombination defect states was well decreased by microwave annealing to low values in the range from 7.0×1010 to 3.4×1011 cm-2. The high τeff achieved by microwave annealing was maintained for a long time above 5000 h.

  16. Explicit Runge-Kutta integrator with Hamiltonian correction for long-time simulations of guiding-center orbit in tokamak configurations

    SciTech Connect

    Xiao Xiaotao; Wang Shaojie

    2008-12-15

    Hamiltonian correction method is proposed to improve the variable time-step fourth-order Runge-Kutta methods in computing guiding-center orbits in a tokamak. It is found that the new method can significantly improve the computation efficiency of the conventional Runge-Kutta method in simulation of the long-time behavior of the guiding-center orbits.

  17. Degeneracy, degree, and heavy tails in quantum annealing

    NASA Astrophysics Data System (ADS)

    King, Andrew D.; Hoskinson, Emile; Lanting, Trevor; Andriyash, Evgeny; Amin, Mohammad H.

    2016-05-01

    Both simulated quantum annealing and physical quantum annealing have shown the emergence of "heavy tails" in their performance as optimizers: The total time needed to solve a set of random input instances is dominated by a small number of very hard instances. Classical simulated annealing, in contrast, does not show such heavy tails. Here we explore the origin of these heavy tails, which appear for inputs with high local degeneracy—large isoenergetic clusters of states in Hamming space. This category includes the low-precision Chimera-structured problems studied in recent benchmarking work comparing the D-Wave Two quantum annealing processor with simulated annealing. On similar inputs designed to suppress local degeneracy, performance of a quantum annealing processor on hard instances improves by orders of magnitude at the 512-qubit scale, while classical performance remains relatively unchanged. Simulations indicate that perturbative crossings are the primary factor contributing to these heavy tails, while sensitivity to Hamiltonian misspecification error plays a less significant role in this particular setting.

  18. Annealing characteristics of irradiated hydrogenated amorphous silicon solar cells

    NASA Technical Reports Server (NTRS)

    Payson, J. S.; Abdulaziz, S.; Li, Y.; Woodyard, J. R.

    1991-01-01

    It was shown that 1 MeV proton irradiation with fluences of 1.25E14 and 1.25E15/sq cm reduces the normalized I(sub SC) of a-Si:H solar cell. Solar cells recently fabricated showed superior radiation tolerance compared with cells fabricated four years ago; the improvement is probably due to the fact that the new cells are thinner and fabricated from improved materials. Room temperature annealing was observed for the first time in both new and old cells. New cells anneal at a faster rate than old cells for the same fluence. From the annealing work it is apparent that there are at least two types of defects and/or annealing mechanisms. One cell had improved I-V characteristics following irradiation as compared to the virgin cell. The work shows that the photothermal deflection spectroscopy (PDS) and annealing measurements may be used to predict the qualitative behavior of a-Si:H solar cells. It was anticipated that the modeling work will quantitatively link thin film measurements with solar cell properties. Quantitative predictions of the operation of a-Si:H solar cells in a space environment will require a knowledge of the defect creation mechanisms, defect structures, role of defects on degradation, and defect passivation and annealing mechanisms. The engineering data and knowledge base for justifying space flight testing of a-Si:H alloy based solar cells is being developed.

  19. Quantum versus simulated annealing in wireless interference network optimization

    NASA Astrophysics Data System (ADS)

    Wang, Chi; Chen, Huo; Jonckheere, Edmond

    2016-05-01

    Quantum annealing (QA) serves as a specialized optimizer that is able to solve many NP-hard problems and that is believed to have a theoretical advantage over simulated annealing (SA) via quantum tunneling. With the introduction of the D-Wave programmable quantum annealer, a considerable amount of effort has been devoted to detect and quantify quantum speedup. While the debate over speedup remains inconclusive as of now, instead of attempting to show general quantum advantage, here, we focus on a novel real-world application of D-Wave in wireless networking—more specifically, the scheduling of the activation of the air-links for maximum throughput subject to interference avoidance near network nodes. In addition, D-Wave implementation is made error insensitive by a novel Hamiltonian extra penalty weight adjustment that enlarges the gap and substantially reduces the occurrence of interference violations resulting from inevitable spin bias and coupling errors. The major result of this paper is that quantum annealing benefits more than simulated annealing from this gap expansion process, both in terms of ST99 speedup and network queue occupancy. It is the hope that this could become a real-word application niche where potential benefits of quantum annealing could be objectively assessed.

  20. Quantum versus simulated annealing in wireless interference network optimization.

    PubMed

    Wang, Chi; Chen, Huo; Jonckheere, Edmond

    2016-05-16

    Quantum annealing (QA) serves as a specialized optimizer that is able to solve many NP-hard problems and that is believed to have a theoretical advantage over simulated annealing (SA) via quantum tunneling. With the introduction of the D-Wave programmable quantum annealer, a considerable amount of effort has been devoted to detect and quantify quantum speedup. While the debate over speedup remains inconclusive as of now, instead of attempting to show general quantum advantage, here, we focus on a novel real-world application of D-Wave in wireless networking-more specifically, the scheduling of the activation of the air-links for maximum throughput subject to interference avoidance near network nodes. In addition, D-Wave implementation is made error insensitive by a novel Hamiltonian extra penalty weight adjustment that enlarges the gap and substantially reduces the occurrence of interference violations resulting from inevitable spin bias and coupling errors. The major result of this paper is that quantum annealing benefits more than simulated annealing from this gap expansion process, both in terms of ST99 speedup and network queue occupancy. It is the hope that this could become a real-word application niche where potential benefits of quantum annealing could be objectively assessed.

  1. Synthesis and characterization of Ar-annealed zinc oxide nanostructures

    NASA Astrophysics Data System (ADS)

    Kuthirummal, Narayanan; Smith, Gregory M.; Lopez, Leisha; Podila, Ramakrishna; Howell, Jason; Dun, Chaochao; Rao, Apparao M.

    2016-09-01

    Nanostructured zinc oxide samples were synthesized through CVD and annealed in argon. The samples were investigated using SEM, TEM, XRD, and UV/VIS/FTIR photoacoustic spectroscopy. The SEM/TEM images show relatively spherical particles that form elongated, connected domains post-anneal. XRD measurements indicate a typical wurtzite structure and reveal an increase in average grain size from 16.3 nm to 21.2 nm in Ar-annealed samples over pristine samples. Visible photoacoustic spectra reveal the contribution of defect levels on the absorption edge of the fundamental gap of zinc oxide. The steepness parameter of the absorption edge, which is inversely proportional to the width of the absorption edge, decreased from 0.1582 (pristine) to 0.1539 (annealed for 90 minutes) revealing increased density of defect states upon annealing. The FTIR photoacoustic spectra show an intense peak at 412 cm-1 and a shoulder at 504 cm-1 corresponding to the two transverse optical stretching modes of ZnO. These results may indicate a self-assembly mechanism upon anneal under Ar atmosphere leading to early-stage nanorod growth.

  2. Thermal Conductivity Changes in Titanium-Graphene Composite upon Annealing

    NASA Astrophysics Data System (ADS)

    Jagannadham, Kasichainula

    2016-02-01

    Ti-graphene composite films were prepared on polished Ti substrates by deposition of graphene platelets from suspension followed by deposition of Ti by magnetron sputtering. The films were annealed at different temperatures up to 1073 K (800 °C) and different time periods in argon atmosphere. The annealed films were characterized by X-ray diffraction for phase identification, scanning electron microscopy for microstructure, energy-dispersive spectrometry for chemical analysis, atomic force microscopy for surface roughness, and transient thermoreflectance for thermal conductivity and interface thermal conductance. The results showed that the interface between the composite film and Ti substrate remained continuous with the absence of voids. Oxygen concentration in the composite films has increased for higher temperature and time of annealing. TiO2 and TiC phases are formed only in the film annealed at 1073 K (800 °C). The thermal conductivity of the composite film decreased with increasing oxygen concentration. The effective thermal conductance of the film annealed at 1073 K (800 °C) was significantly lower. The interface thermal conductance between the composite film and the Ti substrate is also reduced for higher oxygen concentration. Formation of microscopic TiO2 phase bound by interface boundaries and oxygen incorporation is considered responsible for the lower thermal conductance of the Ti-graphene composite annealed at 1073 K (800 °C).

  3. Annealing effects in low upper-shelf welds (series 9)

    SciTech Connect

    Iskander, S.K.; Nanstad, R.K.

    1995-10-01

    The purpose of the Ninth Irradiation Series is to evaluate the correlation between fracture toughness and CVN impact energy during irradiation, annealing, and reirradiation (IAR). Results of annealing CVN specimens from the low-USE welds from the Midland beltline and nozzle course welds, as well as HSST plate 02 and HSSI weld 73W are given. Also presented is the effect of annealing on the initiation fracture toughness of annealed material from Midland beltline weld and HSST plate 02. The results from capsule 10-5 specimens of weld 73W confirm those previously obtained on the so-called undersize specimens that were irradiated in the Fifth Irradiation Series, namely that the recovery due to annealing at 343{degrees}C (650{degrees}F) for 1 week is insignificant. The fabrication of major components for the IAR facility for two positions on the east side of the FNR at the University of Michigan has begun. Fabrication of two reusable capsules (one for temperature verification and the other for dosimetry verification), as well as two capsules for IAR, studies is also under way. The design of a reusable capsule capable of reirradiating previously irradiated and annealed CVN and 1T C(T) specimens is also progressing. The data acquisition and control (DAC) instrumentation for the first two IAR facilities is essentially complete and awaiting completion of the IAR facilities and temperature test capsule for checkout and control algorithm development.

  4. Population annealing simulations of a binary hard-sphere mixture

    NASA Astrophysics Data System (ADS)

    Callaham, Jared; Machta, Jonathan

    2017-06-01

    Population annealing is a sequential Monte Carlo scheme well suited to simulating equilibrium states of systems with rough free energy landscapes. Here we use population annealing to study a binary mixture of hard spheres. Population annealing is a parallel version of simulated annealing with an extra resampling step that ensures that a population of replicas of the system represents the equilibrium ensemble at every packing fraction in an annealing schedule. The algorithm and its equilibration properties are described, and results are presented for a glass-forming fluid composed of a 50/50 mixture of hard spheres with diameter ratio of 1.4:1. For this system, we obtain precise results for the equation of state in the glassy regime up to packing fractions φ ≈0.60 and study deviations from the Boublik-Mansoori-Carnahan-Starling-Leland equation of state. For higher packing fractions, the algorithm falls out of equilibrium and a free volume fit predicts jamming at packing fraction φ ≈0.667 . We conclude that population annealing is an effective tool for studying equilibrium glassy fluids and the jamming transition.

  5. Quantum versus simulated annealing in wireless interference network optimization

    PubMed Central

    Wang, Chi; Chen, Huo; Jonckheere, Edmond

    2016-01-01

    Quantum annealing (QA) serves as a specialized optimizer that is able to solve many NP-hard problems and that is believed to have a theoretical advantage over simulated annealing (SA) via quantum tunneling. With the introduction of the D-Wave programmable quantum annealer, a considerable amount of effort has been devoted to detect and quantify quantum speedup. While the debate over speedup remains inconclusive as of now, instead of attempting to show general quantum advantage, here, we focus on a novel real-world application of D-Wave in wireless networking—more specifically, the scheduling of the activation of the air-links for maximum throughput subject to interference avoidance near network nodes. In addition, D-Wave implementation is made error insensitive by a novel Hamiltonian extra penalty weight adjustment that enlarges the gap and substantially reduces the occurrence of interference violations resulting from inevitable spin bias and coupling errors. The major result of this paper is that quantum annealing benefits more than simulated annealing from this gap expansion process, both in terms of ST99 speedup and network queue occupancy. It is the hope that this could become a real-word application niche where potential benefits of quantum annealing could be objectively assessed. PMID:27181056

  6. Phase separation in SiGe nanocrystals embedded in SiO{sub 2} matrix during high temperature annealing

    SciTech Connect

    Mogaddam, N. A. P.; Turan, R.; Alagoz, A. S.; Yerci, S.; Foss, S.; Finstad, T. G.

    2008-12-15

    SiGe nanocrystals have been formed in SiO{sub 2} matrix by cosputtering Si, Ge, and SiO{sub 2} independently on Si substrate. Effects of the annealing time and temperature on structural and compositional properties are studied by transmission electron microscopy, x-ray diffraction (XRD), and Raman spectroscopy measurements. It is observed that Ge-rich Si{sub (1-x)}Ge{sub x} nanocrystals do not hold their compositional uniformity when annealed at high temperatures for enough long time. A segregation process leading to separation of Ge and Si atoms from each other takes place. This process has been evidenced by a double peak formation in the XRD and Raman spectra. We attributed this phase separation to the differences in atomic size, surface energy, and surface diffusion disparity between Si and Ge atoms leading to the formation of nonhomogenous structure consist of a Si-rich SiGe core covered by a Ge-rich SiGe shell. This experimental observation is consistent with the result of reported theoretical and simulation methods.

  7. Fast wettability transition from hydrophilic to superhydrophobic laser-textured stainless steel surfaces under low-temperature annealing

    NASA Astrophysics Data System (ADS)

    Ngo, Chi-Vinh; Chun, Doo-Man

    2017-07-01

    Recently, the fabrication of superhydrophobic metallic surfaces by means of pulsed laser texturing has been developed. After laser texturing, samples are typically chemically coated or aged in ambient air for a relatively long time of several weeks to achieve superhydrophobicity. To accelerate the wettability transition from hydrophilicity to superhydrophobicity without the use of additional chemical treatment, a simple annealing post process has been developed. In the present work, grid patterns were first fabricated on stainless steel by a nanosecond pulsed laser, then an additional low-temperature annealing post process at 100 °C was applied. The effect of 100-500 μm step size of the textured grid upon the wettability transition time was also investigated. The proposed post process reduced the transition time from a couple of months to within several hours. All samples showed superhydrophobicity with contact angles greater than 160° and sliding angles smaller than 10° except samples with 500 μm step size, and could be applied in several potential applications such as self-cleaning and control of water adhesion.

  8. Distributional behavior of diffusion coefficients obtained by single trajectories in annealed transit time model

    NASA Astrophysics Data System (ADS)

    Akimoto, Takuma; Yamamoto, Eiji

    2016-12-01

    Local diffusion coefficients in disordered systems such as spin glass systems and living cells are highly heterogeneous and may change over time. Such a time-dependent and spatially heterogeneous environment results in irreproducibility of single-particle-tracking measurements. Irreproducibility of time-averaged observables has been theoretically studied in the context of weak ergodicity breaking in stochastic processes. Here, we provide rigorous descriptions of equilibrium and non-equilibrium diffusion processes for the annealed transit time model, which is a heterogeneous diffusion model in living cells. We give analytical solutions for the mean square displacement (MSD) and the relative standard deviation of the time-averaged MSD for equilibrium and non-equilibrium situations. We find that the time-averaged MSD grows linearly with time and that the time-averaged diffusion coefficients are intrinsically random (irreproducible) even in the long-time measurements in non-equilibrium situations. Furthermore, the distribution of the time-averaged diffusion coefficients converges to a universal distribution in the sense that it does not depend on initial conditions. Our findings pave the way for a theoretical understanding of distributional behavior of the time-averaged diffusion coefficients in disordered systems.

  9. The Kinetics of Formation and Decomposition of Austenite in Relation to Carbide Morphology

    NASA Astrophysics Data System (ADS)

    Alvarenga, Henrique Duarte; Van Steenberge, Nele; Sietsma, Jilt; Terryn, Herman

    2017-02-01

    The effect of the carbide morphology on the kinetics of austenite formation and its decomposition was investigated by a combination of measurements of austenite fraction by dilatometry and metallography. These measurements show that coarse carbide morphology is generated by fast cooling through the early stages of eutectoid transformation, enabling fast precipitation of pro-eutectoid ferrite, followed by slow cooling during the final stages of transformation, during the precipitation of carbides. Additionally, a strong influence of the morphology of carbides on the kinetics of austenite formation is observed. The presence of coarse carbides can determine the rate of austenite formation during intercritical annealing as a result of its slow dissolution kinetics.

  10. Gamma-irradiated dry fruits. An example of a wide variety of long-time dependent EPR spectra

    NASA Astrophysics Data System (ADS)

    Yordanov, Nicola D.; Pachova, Zdravka

    2006-03-01

    EPR spectra of dry, sugar containing fruits—raisins, sultanas, figs, dates, peaches, blue plums and chokeberry recorded before and after irradiation with gamma-rays, are reported. It is shown that weak singlet EPR line with 2.0031 ± 0.0005 can be recorded before irradiation of seeds, stones or skin of chokeberry, figs and raisins as well as flesh of blue plum, raisins and peaches. EPR signals of various shape are distinguished after irradiation in different parts of the fruits, as well as in randomly cut pieces of them: Seeds of raisins, chokeberry and figs give a singlet line. Stones from blue plums and peaches exhibit typical "cellulose-like" EPR signal consisting of an intense singlet line with g = 2.0033 ± 0.0005 and 2 week satellite lines situated ca. 30 G left and right to it. Stones of dates are the only sample in which "sugar-like" spectrum is recorded. Skin of raisins and figs exhibits "sugar-like" EPR spectrum whereas that of dates and chokeberry—a singlet line. Under the same experimental conditions skin of sultanas, peaches and blue plums are EPR silent. Flesh of raisins, sultanas, figs, dates and peaches exhibits "sugar-like" EPR spectrum, flesh of blue plums gives a singlet EPR line and that of chokeberry is EPR silent. As a result, randomly cut pieces of dry fruits suitable for EPR studies, containing various constituents, exhibit different in shape and intensity EPR spectra. Kinetic studies followed for 1 year on the time stability of all reported EPR signals indicate that intensity ratio between the simultaneously appearing EPR signals in particular fruit varies from 1:20 immediately after irradiation to 1:0.5 at the end of the period. These observations open a new possibility for identification of irradiated fruits - using the magnitude of the intensity ratio to find the approximate date of radiation processing in the first ca. 30-100 days.

  11. Local Resistance Profiling of Ultra Shallow Junction Annealed with Combination of Spike Lamp and Laser Annealing Processes using Scanning Spreading Resistance Microscope

    SciTech Connect

    Abo, Satoshi; Nishikawa, Kazuhisa; Ushigome, Naoya; Wakaya, Fujio; Takai, Mikio; Iwamatsu, Toshiaki; Oda, Hidekazu

    2011-01-07

    Local resistance profiles of ultra shallow boron and arsenic implanted into silicon with energies of 2.0 and 4.0 keV and doses of 2.0x10{sup 15} and 1.0x10{sup 15} ions/cm{sup 2} activated by a combination of conventional spike lamp and laser annealing processes were measured by scanning spreading resistance microscope (SSRM) with a depth resolution of less than 10 nm. The lowest local resistance at the low resistance region in 2.0 keV boron implanted silicon with 1050 deg. C spike lamp annealing followed by 0.35 kW/mm{sup 2} laser annealing was half of that without laser annealing. The lowest local resistance at the low resistance region in the arsenic implanted silicon activated by 1050 deg. C spike lamp annealing followed by 0.39 kW/mm{sup 2} laser annealing was 74% lower than that followed by 0.36 kW/mm{sup 2} laser annealing. The lowest local resistances at the low resistance regions in the arsenic implanted silicon with 0.36 and 0.39 kW/mm{sup 2} laser annealing followed by 1050 deg. C spike lamp annealing were 41 and 33% lower than those with spike lamp annealing followed by laser annealing. Laser annealing followed by spike lamp annealing could suppress the diffusion of the impurities and was suitable for making the ultra shallow and low resistance regions.

  12. Annealing effects on strain and stress sensitivity of polymer optical fibre based sensors

    NASA Astrophysics Data System (ADS)

    Pospori, A.; Marques, C. A. F.; Zubel, M. G.; Sáez-Rodríguez, D.; Nielsen, K.; Bang, O.; Webb, D. J.

    2016-04-01

    The annealing effects on strain and stress sensitivity of polymer optical fibre Bragg grating sensors after their photoinscription are investigated. PMMA optical fibre based Bragg grating sensors are first photo-inscribed and then they were placed into hot water for annealing. Strain, stress and force sensitivity measurements are taken before and after annealing. Parameters such as annealing time and annealing temperature are investigated. The change of the fibre diameter due to water absorption and the annealing process is also considered. The results show that annealing the polymer optical fibre tends to increase the strain, stress and force sensitivity of the photo-inscribed sensor.

  13. The RNA annealing mechanism of the HIV-1 Tat peptide: conversion of the RNA into an annealing-competent conformation

    PubMed Central

    Doetsch, Martina; Fürtig, Boris; Gstrein, Thomas; Stampfl, Sabine; Schroeder, Renée

    2011-01-01

    The annealing of nucleic acids to (partly) complementary RNA or DNA strands is involved in important cellular processes. A variety of proteins have been shown to accelerate RNA/RNA annealing but their mode of action is still mainly uncertain. In order to study the mechanism of protein-facilitated acceleration of annealing we selected a short peptide, HIV-1 Tat(44–61), which accelerates the reaction efficiently. The activity of the peptide is strongly regulated by mono- and divalent cations which hints at the importance of electrostatic interactions between RNA and peptide. Mutagenesis of the peptide illustrated the dominant role of positively charged amino acids in RNA annealing—both the overall charge of the molecule and a precise distribution of basic amino acids within the peptide are important. Additionally, we found that Tat(44–61) drives the RNA annealing reaction via entropic rather than enthalpic terms. One-dimensional-NMR data suggest that the peptide changes the population distribution of possible RNA structures to favor an annealing-prone RNA conformation, thereby increasing the fraction of colliding RNA molecules that successfully anneal. PMID:21297117

  14. Phase-field simulations of intragranular fission gas bubble evolution in UO2 under post-irradiation thermal annealing

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin

    2013-05-15

    Fission gas bubble is one of evolving microstructures, which affect thermal mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking, in operating nuclear fuels. Therefore, fundamental understanding of gas bubble evolution kinetics is essential to predict the thermodynamic property and performance changes of fuels. In this work, a generic phasefield model was developed to describe the evolution kinetics of intra-granular fission gas bubbles in UO2 fuels under post-irradiation thermal annealing conditions. Free energy functional and model parameters are evaluated from atomistic simulations and experiments. Critical nuclei size of the gas bubble and gas bubble evolution were simulated. A linear relationship between logarithmic bubble number density and logarithmic mean bubble diameter is predicted which is in a good agreement with experimental data.

  15. Influence of low-energy plasma annealing on structural and optical properties of silver nanoclusters grown by magnetron sputtering deposition

    NASA Astrophysics Data System (ADS)

    Antad, V.; Simonot, L.; Babonneau, D.

    2014-03-01

    Structural and optical modifications induced by low-energy (≤80 eV) bias-plasma annealing of silver nanoclusters (2-25 nm) grown by magnetron sputtering deposition are reported. By combining postmortem structural characterizations and real-time optical measurements, we show that etching effects associated with enhanced Ag mobility result in progressive and irreversible changes of both the morphology and organization of the nanoclusters (i.e., decrease of the cluster size and intercluster distance as well as increase of their out-of-plane aspect ratio). Surface plasmon resonance bands of the nanoclusters are also modified by plasma treatment, which causes a blue-shift together with an amplitude decrease and a narrowing of the band. In addition, the kinetics of plasma-induced modifications can be easily controlled by varying the applied bias voltage. Therefore, plasma annealing could emerge as an efficient alternative to more traditional thermal annealing treatments for tuning the plasmonic properties of noble metal nanoclusters with great flexibility.

  16. Low-temperature photoluminescence characterization of defects formation in hydrogen and helium implanted silicon at post-implantation annealing

    NASA Astrophysics Data System (ADS)

    Mudryi, A. V.; Korshunov, F. P.; Patuk, A. I.; Shakin, I. A.; Larionova, T. P.; Ulyashin, A. G.; Job, R.; Fahrner, W. R.; Emtsev, V. V.; Davydov, V. Yu.; Oganesyan, G.

    2001-12-01

    The systematical low-temperature (4.2 K) photoluminescence (PL) study of the formation kinetics of optically active centers in H and He implanted CZ Si, annealed in the temperature range of 200-1000°C is presented. The samples were implanted with H (energy E=80 keV, dose D=10 15/10 16 cm -2) and He ( E=150 keV, D=5×10 14 cm -2) ions. It was found that the annealing of H or He implanted samples leads to the appearance and evolution of a number of zero-phonon lines as well as of broad bands. The origin of the observed lines and bands is discussed. It is assumed that the strong stresses around hydrogen-related structural defects (voids, bubbles) during the annealing at 500-700°C of H implanted Si lead to the formation of a specific optical center M‧ (∼1.012 eV PL line).

  17. Apatite (U-Th)/He thermochronometry using a radiation damage accumulation and annealing model

    NASA Astrophysics Data System (ADS)

    Flowers, Rebecca M.; Ketcham, Richard A.; Shuster, David L.; Farley, Kenneth A.

    2009-04-01

    Helium diffusion from apatite is a sensitive function of the volume fraction of radiation damage to the crystal, a quantity that varies over the lifetime of the apatite. Using recently published laboratory data we develop and investigate a new kinetic model, the radiation damage accumulation and annealing model (RDAAM), that adopts the effective fission-track density as a proxy for accumulated radiation damage. This proxy incorporates creation of crystal damage proportional to α-production from U and Th decay, and the elimination of that damage governed by the kinetics of fission-track annealing. The RDAAM is a version of the helium trapping model (HeTM; Shuster D. L., Flowers R. M. and Farley K. A. (2006) The influence of natural radiation damage on helium diffusion kinetics in apatite. Earth Planet. Sci. Lett.249, 148-161), calibrated by helium diffusion data in natural and partially annealed apatites. The chief limitation of the HeTM, now addressed by RDAAM, is its use of He concentration as the radiation damage proxy for circumstances in which radiation damage and He are not accumulated and lost proportionately from the crystal. By incorporating the RDAAM into the HeFTy computer program, we explore its implications for apatite (U-Th)/He thermochronometry. We show how (U-Th)/He dates predicted from the model are sensitive to both effective U concentration (eU) and details of the temperature history. The RDAAM predicts an effective He closure temperature of 62 °C for a 28 ppm eU apatite of 60 μm radius that experienced a 10 °C/Ma monotonic cooling rate; this is 8 °C lower than the 70 °C effective closure temperature predicted using commonly assumed Durango diffusion kinetics. Use of the RDAAM is most important for accurate interpretation of (U-Th)/He data for apatite suites that experienced moderate to slow monotonic cooling (1-0.1 °C/Ma), prolonged residence in the helium partial retention zone, or a duration at temperatures appropriate for radiation

  18. Note: Improving long-term stability of hot-wire anemometer sensors by means of annealing.

    PubMed

    Lundström, H

    2015-08-01

    Annealing procedures for hot-wire sensors of platinum and platinum-plated tungsten have been investigated experimentally. It was discovered that the two investigated sensor metals behave quite differently during the annealing process, but for both types annealing may improve long-term stability considerably. Measured drift of sensors both without and with prior annealing is presented. Suggestions for suitable annealing temperatures and times are given.

  19. Note: Improving long-term stability of hot-wire anemometer sensors by means of annealing

    NASA Astrophysics Data System (ADS)

    Lundström, H.

    2015-08-01

    Annealing procedures for hot-wire sensors of platinum and platinum-plated tungsten have been investigated experimentally. It was discovered that the two investigated sensor metals behave quite differently during the annealing process, but for both types annealing may improve long-term stability considerably. Measured drift of sensors both without and with prior annealing is presented. Suggestions for suitable annealing temperatures and times are given.

  20. Note: Improving long-term stability of hot-wire anemometer sensors by means of annealing

    SciTech Connect

    Lundström, H.

    2015-08-15

    Annealing procedures for hot-wire sensors of platinum and platinum-plated tungsten have been investigated experimentally. It was discovered that the two investigated sensor metals behave quite differently during the annealing process, but for both types annealing may improve long-term stability considerably. Measured drift of sensors both without and with prior annealing is presented. Suggestions for suitable annealing temperatures and times are given.