Javier Ortensi; Abderrafi M Ougouag
2009-07-01
The Doppler feedback mechanism is a major contributor to the passive safety of gas-cooled, graphite-moderated high temperature reactors that use fuel based on Tristructural-Isotropic coated particles. It follows that the correct prediction of the magnitude and time-dependence of this feedback effect is essential to the conduct of safety analyses for these reactors. We present a fuel conduction model for obtaining better estimates of the temperature feedback during moderate and fast transients. The fuel model has been incorporated in the CYNOD-THERMIX-KONVEK suite of coupled codes as a single TRISO particle within each calculation cell. The heat generation rate is scaled down from the neutronic solution and a Dirichlet boundary condition is imposed as the bulk graphite temperature from the thermal-hydraulic solution. This simplified approach yields similar results to those obtained with more complex methods, requiring multi-TRISO calculations within one control volume, but with much less computational effort. We provide an analysis of the hypothetical total control ejection event in the PBMR-400 design that clearly depicts the improvement in the predictions of the fuel temperature.
Distributed energy storage: Time-dependent tree flow design
NASA Astrophysics Data System (ADS)
Bejan, A.; Ziaei, S.; Lorente, S.
2016-05-01
This article proposes "distributed energy storage" as a basic design problem of distributing energy storage material on an area. The energy flows by fluid flow from a concentrated source to points (users) distributed equidistantly on the area. The flow is time-dependent. Several scenarios are analyzed: sensible-heat storage, latent-heat storage, exergy storage vs energy storage, and the distribution of a finite supply of heat transfer surface between the source fluid and the distributed storage material. The chief conclusion is that the finite amount of storage material should be distributed proportionally with the distribution of the flow rate of heating agent arriving on the area. The total time needed by the source stream to "invade" the area is cumulative (the sum of the storage times required at each storage site) and depends on the energy distribution paths and the sequence in which the users are served by the source stream. Directions for future designs of distributed storage and retrieval are outlined in the concluding section.
Time dependence of energy storage across multiple ecosystems
NASA Astrophysics Data System (ADS)
Reed, D. E.; Frank, J. M.; Ewers, B. E.; Desai, A. R.
2015-12-01
Energy flow through ecosystems plays a critical role in processes at multiple spatial and temporal scales, from monthly growing season length of landscapes to sub-diurnal responses of soil respiration to temperature, photosynthesis and water inputs. The interaction of solar radiation and ecosystems is complex with terrestrial canopies and aquatic structure both connecting above- and below-ground processes via energy fluxes. Previous work by Leuning et al has shown that at 30-minute timescales, only 8% of eddy covariance sites in the La Thuile dataset observe energy closure and when averaged to 24-hour timescales, this goes up to 45%. This work examines the effect of temporal lags in energy storage in both terrestrial (shrub and forest) and aquatic (lake) ecosystems. Analyses show energy storage terms have unique temporal lags that vary between ecosystem and time of year, from having zero lag to several hour timescales within terrestrial ecosystems, depending primarily on water content. Large differences between ecosystem types are also highlighted as aquatic ecosystems have lags that range between daily and monthly timescales. Furthermore, ecosystem disturbance can alter time lags as well and results from a native bark beetle disturbance show vegetation lag decreasing while soil lag increasing following changes in water content. Energy storage lags can improve site energy closure by several percent, and these results will lead to a better understanding of surface energy budget closure, an as-of-yet unresolved issue in the flux community, as well as highlighting the importance of time-dependency of ecosystem energy fluxes as a unique method to examine ecosystem processes.
Time-dependent annealing and deposition on substrates with repulsive interactions
NASA Astrophysics Data System (ADS)
Venables, J. A.; Degraffenreid, J.; Kay, D.; Yang, P.
2006-08-01
In models of nucleation and growth of crystals on surfaces, it is often assumed that the energy surface of the substrate is flat, that diffusion is isotropic, and that capture numbers can be calculated in the diffusion-controlled limit. We lift these restrictions and formulate the general time-dependent problem in a two-dimensional (2D) potential field. We utilize the master equation discretization (MED) method to solve the 2D time-dependent diffusion field of adparticles on general nonuniform (rectangular grid) substrates, and compare it against competing algorithms, including the fast Fourier transform (FFT) and hybrid-FFT methods previously introduced, for periodic boundary conditions. The physical context is set by the importance of repulsive interactions in the nucleation and growth of many nanostructures, e.g., metal nanoclusters, hut clusters, and nanowires. The programs, realized in MATLAB®6.5 , are used to obtain quantitative capture numbers, aspect and direct impingement ratios, and other island growth quantities in the presence of potential fields, when particular surface processes are included. The case of no corner rounding is studied in detail. Strongly anisotropic potentials favor wire growth, which can be considerably influenced by alternate deposition and annealing, and the location of neighboring islands. Physical examples are given based on Ge/Si(001) material parameters. Essentially similar programs, differing only in outputs, are used to visualize the diffusion field and to produce realistic movies of crystal growth. Examples given here are linear deterministic calculations, but the framework allows for inclusion of nonlinear and statistical effects for particular applications.
Low-energy fusion dynamics of weakly bound nuclei: A time dependent perspective
NASA Astrophysics Data System (ADS)
Diaz-Torres, A.; Boselli, M.
2016-05-01
Recent dynamical fusion models for weakly bound nuclei at low incident energies, based on a time-dependent perspective, are briefly presented. The main features of both the PLATYPUS model and a new quantum approach are highlighted. In contrast to existing timedependent quantum models, the present quantum approach separates the complete and incomplete fusion from the total fusion. Calculations performed within a toy model for 6Li + 209Bi at near-barrier energies show that converged excitation functions for total, complete and incomplete fusion can be determined with the time-dependent wavepacket dynamics.
Simulating Time-Dependent Energy Transfer Between Crossed Laser Beams in an Expanding Plasma
Hittinger, J F; Dorr, M R; Berger, R L; Williams, E A
2004-10-11
A coupled mode system is derived to investigate a three-wave parametric instability leading to energy transfer between co-propagating laser beams crossing in a plasma flow. The model includes beams of finite width refracting in a prescribed transverse plasma flow with spatial and temporal gradients in velocity and density. The resulting paraxial light equations are discretized spatially with a Crank-Nicholson-type scheme, and these algebraic constraints are nonlinearly coupled with ordinary differential equations in time that describe the ion acoustic response. The entire nonlinear differential-algebraic system is solved using an adaptive, backward-differencing method coupled with Newton's method. A numerical study is conducted in two dimensions that compares the intensity gain of the fully time-dependent coupled mode system with the gain computed under the further assumption of a strongly-damped ion acoustic response. The results demonstrate a time-dependent gain suppression when the beam diameter is commensurate with the velocity gradient scale length. The gain suppression is shown to depend on time-dependent beam refraction and is interpreted as a time-dependent frequency shift.
Transient energy excitation in shortcuts to adiabaticity for the time-dependent harmonic oscillator
Chen Xi; Muga, J. G.
2010-11-15
We study for the time-dependent harmonic oscillator the transient energy excitation in speed-up processes ('shortcuts to adiabaticity') designed to reproduce the initial populations at some predetermined final frequency and time. We provide lower bounds and examples. Implications for the limits imposed to the process times and for the principle of unattainability of the absolute zero, in a single expansion or in quantum refrigerator cycles, are drawn.
Kovaleva, Agnessa; Manevitch, Leonid I; Kosevich, Yuriy A
2011-02-01
We demonstrate that in significant limiting cases the problem of irreversible energy transfer in an oscillatory system with time-dependent parameters can be efficiently solved in terms of the Fresnel integrals. For definiteness, we consider a system of two weakly coupled linear oscillators in which the first oscillator with constant parameters is excited by an initial impulse, whereas the coupled oscillator with a slowly varying frequency is initially at rest but then acts as an energy trap. We show that the evolution equations of the slow passage through resonance are identical to the equations of the Landau-Zener tunneling problem, and therefore, the suggested asymptotic solution of the classical problem provides a simple analytic description of the quantum Landau-Zener tunneling with arbitrary initial conditions over a finite time interval. A correctness of approximations is confirmed by numerical simulations. PMID:21405919
Fowlkes, Jason Davidson; Rack, Philip D
2010-01-01
Unknown parameters critical to understanding the electron-precursor substrate interactions during electron beam induced deposition (EBID) have long limited our ability to fully control this nanoscale, directed assembly method. We report here values for the fundamental interaction parameters of D, the precursor surface diffusion coefficient, delta, the sticking probability and tau, the mean surface residence time which are critical parameters for understanding the assembly of EBID deposits. Values of D=6.4um2s-1, delta=0.0250 and tau=3.2ms were determined for a commonly used precursor molecule tungsten hexacarbonyl W(CO)6. Space and time predictions of the adsorbed precursor coverage C(r,t) were solved by an explicit finite differencing numerical scheme. Evolving nanopillar surface morphology was derived from solutions of C(r,t) considering electron induced dissociation as the critical depletion term. This made it possible to infer the space and time dependent precursor coverage both on, and around nanopillar structures to better understand local precursor dynamics during mass transport limited (MTL) and reaction rate limited (RRL) EBID.
Time-dependent energy transfer rates in a conjugated polymer guest-host system
NASA Astrophysics Data System (ADS)
Herz, L. M.; Silva, C.; Grimsdale, A. C.; Müllen, K.; Phillips, R. T.
2004-10-01
We have investigated the energy transfer dynamics in films of a conjugated polyindenofluorene host doped with covalently attached perylene guests. By performing time-resolved measurements of the host luminescence decay under site-selective excitation conditions, we have examined the influence of exciton migration within the host on the temporal evolution of the host-guest energy transfer. We find that highly mobile excitons created at the peak of the host’s inhomogeneous density of states transfer to guests considerably faster than more localized excitons created in the low-energy tail, indicating a strong contribution of exciton migration to the overall energy transfer. These effects are significantly more pronounced at low temperature (7K) than at ambient temperature, suggesting that for the latter, up-hill migration of excitons in the host and a broadening of their homogeneous linewidth may prevent truly site-selective excitation of localized excitons. In the asymptotic long-time limit, the observed dynamics are compatible with long-range single-step Förster energy transfer. However, at early times (≲10ps) after excitation, the behavior notably deviates from this description, suggesting that diffusion-assisted energy transfer is more important in this regime. The measured changes in excitation transfer rates with temperature and excitation energy correlate well with those observed for the dynamic energy shifts of the vibronic emission peaks from the undoped polymer. Our results therefore indicate that energy-transfer rates in polymeric guest-host systems are strongly time-dependent, owing to a contribution both from exciton relaxation through incoherent hopping within the host’s density of states and direct Förster energy transfer.
Linking Neuromodulated Spike-Timing Dependent Plasticity with the Free-Energy Principle.
Isomura, Takuya; Sakai, Koji; Kotani, Kiyoshi; Jimbo, Yasuhiko
2016-09-01
The free-energy principle is a candidate unified theory for learning and memory in the brain that predicts that neurons, synapses, and neuromodulators work in a manner that minimizes free energy. However, electrophysiological data elucidating the neural and synaptic bases for this theory are lacking. Here, we propose a novel theory bridging the information-theoretical principle with the biological phenomenon of spike-timing dependent plasticity (STDP) regulated by neuromodulators, which we term mSTDP. We propose that by integrating an mSTDP equation, we can obtain a form of Friston's free energy (an information-theoretical function). Then we analytically and numerically show that dopamine (DA) and noradrenaline (NA) influence the accuracy of a principal component analysis (PCA) performed using the mSTDP algorithm. From the perspective of free-energy minimization, these neuromodulatory changes alter the relative weighting or precision of accuracy and prior terms, which induces a switch from pattern completion to separation. These results are consistent with electrophysiological findings and validate the free-energy principle and mSTDP. Moreover, our scheme can potentially be applied in computational psychiatry to build models of the faulty neural networks that underlie the positive symptoms of schizophrenia, which involve abnormal DA levels, as well as models of the NA contribution to memory triage and posttraumatic stress disorder. PMID:27391680
Space-time dependence between energy sources and climate related energy production
NASA Astrophysics Data System (ADS)
Engeland, Kolbjorn; Borga, Marco; Creutin, Jean-Dominique; Ramos, Maria-Helena; Tøfte, Lena; Warland, Geir
2014-05-01
The European Renewable Energy Directive adopted in 2009 focuses on achieving a 20% share of renewable energy in the EU overall energy mix by 2020. A major part of renewable energy production is related to climate, called "climate related energy" (CRE) production. CRE production systems (wind, solar, and hydropower) are characterized by a large degree of intermittency and variability on both short and long time scales due to the natural variability of climate variables. The main strategies to handle the variability of CRE production include energy-storage, -transport, -diversity and -information (smart grids). The three first strategies aim to smooth out the intermittency and variability of CRE production in time and space whereas the last strategy aims to provide a more optimal interaction between energy production and demand, i.e. to smooth out the residual load (the difference between demand and production). In order to increase the CRE share in the electricity system, it is essential to understand the space-time co-variability between the weather variables and CRE production under both current and future climates. This study presents a review of the literature that searches to tackle these problems. It reveals that the majority of studies deals with either a single CRE source or with the combination of two CREs, mostly wind and solar. This may be due to the fact that the most advanced countries in terms of wind equipment have also very little hydropower potential (Denmark, Ireland or UK, for instance). Hydropower is characterized by both a large storage capacity and flexibility in electricity production, and has therefore a large potential for both balancing and storing energy from wind- and solar-power. Several studies look at how to better connect regions with large share of hydropower (e.g., Scandinavia and the Alps) to regions with high shares of wind- and solar-power (e.g., green battery North-Sea net). Considering time scales, various studies consider wind
NASA Astrophysics Data System (ADS)
Samarin, Viacheslav
2014-03-01
Time-dependent Schrödinger equation is numerically solved by difference method for external neutrons of nuclei 6He, 18O, 48Са, 238U at their grazing collisions with energies in the vicinity of a Coulomb barrier. The spin-orbital interaction and Pauli's exclusion principle were taken into consideration during the solution.
Low Energy Excitations of a Bose-Einstein Condensate: A Time-Dependent Variational Analysis
Perez-Garcia, V.M.; Michinel, H.; Cirac, J.; Lewenstein, M.; Zoller, P.
1996-12-01
We solve the time-dependent Gross-Pitaevskii equation by a variational ansatz to calculate the excitation spectrum of a Bose-Einstein condensate in a trap. The trial wave function is a Gaussian which allows an essentially analytical treatment of the problem. Our results reproduce numerical calculations over the whole range from small to large particle numbers, and agree exactly with the Stringari results in the strong interaction limit. Excellent agreement is obtained with the recent JILA experiment and predictions for the negative scattering length case are also made. {copyright} {ital 1996 The American Physical Society.}
NASA Astrophysics Data System (ADS)
Mariotti, G.; Valentine, K.; Fagherazzi, S.
2015-02-01
This study aims to explore the behavior of a cohesive sediment bed that undergoes cycles of erosion and deposition under diluted conditions. A bed of bentonite (montmorillonite) sediment was placed in two annular flumes and subjected to daily erosion tests for a period of 80 days, mimicking intermittent moderate-energy disturbances like tidal currents and wind waves. After each erosion test, the suspended sediment was allowed to settle back in the flumes. The amount of suspended sediment measured at the top of the water column at the end of each erosion test decreased in the first 5 days, concurrently with an increase in the bulk-settling velocity near the bed. This pattern is explained by turbulence-induced flocculation of clay particles and consequent formation of a surface floc layer. After about 20 days, the amount of suspended sediment measured at the top of the water column at the end of each erosion test increased and the settling velocity decreased, whereas the suspended sediment concentration measured near the bed remained nearly constant. We explain such trend by the cumulative release of slow-settling particles from the bed. This experiment suggests that the superficial layer of a placed bed that is periodically eroded and redeposited experiences competing processes: the sediment that is resuspended at every cycle becomes less erodible, but prolonged exposure to shear stress increases the pool of eroded sediment over time. The total amount of resuspended sediment seems to become constant after several tens of cycle, suggesting that the release of particles from the bed by cumulative erosion is balanced by the binding of such particles to the bed.
Time dependence of carbon film deposition on SnO{sub 2}/Si using DC unbalanced magnetron sputtering
Alfiadi, H. Aji, A. S. Darma, Y.
2014-02-24
Carbon deposition on SnO{sub 2} layer has been demonstrated at low temperature using DC unbalanced magnetron-sputtering technique for various time depositions. Before carbon sputtering process, SnO{sub 2} thin layer is grown on silicon substrate by thermal evaporation method using high purity Sn wire and then fully oxidizes by dry O{sub 2} at 225°C. Carbon sputtering process was carried out at pressure of 4.6×10{sup −2} Torr by keeping the substrate temperature of 300 °C for sputtering deposition time of 1 to 4 hours. The properties of SnO{sub 2}/Si structure and carbon thin film on SnO{sub 2} is characterized using SEM, EDAX, XRD, FTIR, and Raman Spectra. SEM images and XRD spectra show that SnO2 thin film has uniformly growth on Si substrate and affected by annealing temperature. Raman and FTIR results confirm the formation of carbon-rich thin film on SnO{sub 2}. In addition, XRD spectra indicate that some structural change occur by increasing sputtering deposition time. Furthermore, the change of atomic structure due to the thermal annealing is analized by XRD spectra and Raman spectroscopy.
NASA Astrophysics Data System (ADS)
Aghamohammadi, A.; Saaidi, K.; Setare, M. R.
2011-04-01
We study the holographic dark energy on the subject of Hořava-Lifshitz gravity with a time dependent gravitational constant G( t), in the non-flat space-time. We obtain the differential equation that specify the evolution of the dark energy density parameter based on varying gravitational constant. We find out a relation for the state parameter of the dark energy equation of state to low red-shifts which containing varying G corrections in the non-flat space-time.
Latitude and local time dependence of precipitated low energy electrons at high latitudes
NASA Technical Reports Server (NTRS)
Gustafsson, G.
1972-01-01
Data from particle detectors on board the satellite OGO-4 were used to study the precipitation of electrons in the energy range 0.7 to 24 keV. The latitude dependence of these particles in the local time region from midnight to dawn was investigated in detail. The analysis shows that the precipitation of particles of energies 2.3 to 24 keV is centered at an invariant latitude of about 68 deg at midnight with a clear shift in latitude with increasing local time and this shift is more pronounced for lower energies. The highest fluxes of particles in this energy interval are measured at midnight and they decrease rapidly with local time. The data in the energy range 2.3 to 24 keV support a theory where particles are injected in the midnight region from the tail gaining energy due to a betatron process and then drift eastwards in a combined electric and magnetic field. The main part of the electrons at 0.7 keV show a different behavior. They seem to undergo an acceleration process which is rather local, sometimes giving field aligned fluxes which may be super-imposed on the background precipitation.
Quadrature algorithms to the luminosity distance with a time-dependent dark energy model
Yue, Nan-Nan; Liu, De-Zi; Pei, Xiao-Xing; Zhang, Tong-Jie; Yang, Zhi-Liang; Zhu, Fang-Fang E-mail: bingzi@mail.bnu.edu.cn E-mail: fiona-90@live.cn E-mail: zlyang@bnu.edu.cn
2011-11-01
In our previous work [1], we have proposed two methods for computing the luminosity distance d{sub L}{sup Λ} in ΛCDM model. In this paper, two effective quadrature algorithms, known as Romberg Integration and composite Gaussian Quadrature, are presented to calculate the luminosity distance d{sub L}{sup CPL} in the Chevallier-Polarski-Linder parametrization(CPL) model. By comparing both the efficiency and accuracy of the two algorithms, we find that the second is more promising. Moreover, we develop another strategy adapted for approximating d{sub L}{sup Λ} in flat ΛCDM universe. To some extent, our methods can make contributions to the recent numerical stimulation for the investigation of dark energy cosmology.
NASA Astrophysics Data System (ADS)
Haruyama, Jun; Suzuki, Takahiro; Hu, Chunping; Watanabe, Kazuyuki
2012-01-01
We present a simple and computationally efficient method to calculate excited-state nuclear forces on adiabatic potential-energy surfaces (APES) from linear-response time-dependent density-functional theory within a real-space framework. The Casida ansatz, which has been validated for computing first-order nonadiabatic couplings in previous studies, was applied to the calculation of the excited-state forces. Our method is validated by the consistency of results in the lower excited states, which reproduce well those obtained by the numerical derivative of each APES. We emphasize the usefulness of this technique by demonstrating the excited-state molecular-dynamics simulation.
NASA Technical Reports Server (NTRS)
Potgieter, M. S.; Le Roux, J. A.
1992-01-01
The time-dependent cosmic-ray transport equation is solved numerically in an axially symmetric heliosphere. Gradient and curvature drifts are incorporated, together with an emulated wavy neutral sheet. This model is used to simulate heliospheric cosmic-ray modulation for the period 1985-1989 during which drifts are considered to be important. The general energy dependence of the modulation of Galactic protons is studied as predicted by the model for the energy range 1 MeV to 10 GeV. The corresponding instantaneous radial and latitudinal gradients are calculated, and it is found that, whereas the latitudinal gradients follow the trends in the waviness of the neutral sheet to a large extent for all energies, the radial gradients below about 200 MeV deviate from this general pattern. In particular, these gradients increase when the waviness decreases for the simulated period 1985-1987.3, after which they again follow the neutral sheet by increasing rapidly.
NASA Astrophysics Data System (ADS)
Hung, L.; Guedj, C.; Bernier, N.; Blaise, P.; Olevano, V.; Sottile, F.
2016-04-01
We present the valence electron energy-loss spectrum and the dielectric function of monoclinic hafnia (m -HfO2) obtained from time-dependent density-functional theory (TDDFT) predictions and compared to energy-filtered spectroscopic imaging measurements in a high-resolution transmission-electron microscope. Fermi's golden rule density-functional theory (DFT) calculations can capture the qualitative features of the energy-loss spectrum, but we find that TDDFT, which accounts for local-field effects, provides nearly quantitative agreement with experiment. Using the DFT density of states and TDDFT dielectric functions, we characterize the excitations that result in the m -HfO2 energy-loss spectrum. The sole plasmon occurs between 13 and 16 eV, although the peaks ˜28 and above 40 eV are also due to collective excitations. We furthermore elaborate on the first-principles techniques used, their accuracy, and remaining discrepancies among spectra. More specifically, we assess the influence of Hf semicore electrons (5 p and 4 f ) on the energy-loss spectrum, and find that the inclusion of transitions from the 4 f band damps the energy-loss intensity in the region above 13 eV. We study the impact of many-body effects in a DFT framework using the adiabatic local-density approximation (ALDA) exchange-correlation kernel, as well as from a many-body perspective using "scissors operators" matched to an ab initio G W calculation to account for self-energy corrections. These results demonstrate some cancellation of errors between self-energy and excitonic effects, even for excitations from the Hf 4 f shell. We also simulate the dispersion with increasing momentum transfer for plasmon and collective excitation peaks.
Heßelmann, Andreas
2015-04-14
Molecular excitation energies have been calculated with time-dependent density-functional theory (TDDFT) using random-phase approximation Hessians augmented with exact exchange contributions in various orders. It has been observed that this approach yields fairly accurate local valence excitations if combined with accurate asymptotically corrected exchange-correlation potentials used in the ground-state Kohn-Sham calculations. The inclusion of long-range particle-particle with hole-hole interactions in the kernel leads to errors of 0.14 eV only for the lowest excitations of a selection of three alkene, three carbonyl, and five azabenzene molecules, thus surpassing the accuracy of a number of common TDDFT and even some wave function correlation methods. In the case of long-range charge-transfer excitations, the method typically underestimates accurate reference excitation energies by 8% on average, which is better than with standard hybrid-GGA functionals but worse compared to range-separated functional approximations. PMID:26574370
O'Brien, Sean T; Bohm, Eric R; Petrak, Martin J; Wyss, Urs P; Brandt, Jan-M
2014-03-21
The cost and time efficiency of computational polyethylene wear simulations may enable the optimization of total knee replacements for the reduction of polyethylene wear. The present study proposes an energy dissipation wear model for polyethylene which considers the time dependent molecular behavior of polyethylene, aspects of tractive rolling and contact pressure. This time dependent - energy dissipation wear model was evaluated, along with several other wear models, by comparison to pin-on-disk results, knee simulator wear test results under various kinematic conditions and knee simulator wear test results that were performed following the ISO 14243-3 standard. The proposed time dependent - energy dissipation wear model resulted in improved accuracy for the prediction of pin-on-disk and knee simulator wear test results compared with several previously published wear models. PMID:24480701
Energy deposition and dynamic response of materials
NASA Astrophysics Data System (ADS)
Perry, Frank C.
1993-07-01
We are exploring new applications of the technology of energy deposition and dynamic response. Early studies involved analytical solutions of the coupled thermal and elastic response of materials to pulsed energy deposition. Experiments designed to test the theory led to determinations of thermal pressure coefficients for a variety of materials and an understanding of the effects of the time dependence of the energy source on dynamic response. Subsequent experiments at higher deposited energies required analysis by an energy deposition-wave propagation code to explain the observed elastic-plastic behavior. Instrumentation included laser interferometry and holographic interferometry for multi- dimensional response. A possible application of this technology to Biomedical Science is a technique to measure ion transport in biological material. It requires a combination of holographic interferometry and spectroscopy, namely, Resonant Holographic Interferometry Spectroscopy (RHIS). The technique involves the absorption and refraction of light near absorption lines. Stress waves arising from the absorbed light can be assessed with the energy deposition-wave propagation code. Such calculations will require the inclusion of appropriate biomaterial properties.
ERIC Educational Resources Information Center
Collyer, A. A.
1974-01-01
Discusses the flow characteristics of thixotropic and negative thixotropic fluids; various theories underlying the thixotropic behavior; and thixotropic phenomena exhibited in drilling muds, commercial paints, pastes, and greases. Inconsistencies in the terminology used to label time dependent effects are revealed. (CC)
NASA Astrophysics Data System (ADS)
de Jong, Saskia; van Vliet, Ton; de Jongh, Harmen H. J.
2015-11-01
The recoverable energy (RE), defined as the ratio of the work exerted on a test specimen during compression and recovered upon subsequent decompression, has been shown to correlate to sensory profiling of protein-based food products. Understanding the mechanism determining the time-dependency of RE is primordial. This work aims to identify the protein-specific impact on the recoverable energy by stress dissipation via relaxation of (micro)structural rearrangements within protein gels. To this end, caseinate and gelatin gels are studied for their response to time-dependent mechanical deformation as they are known to develop structurally distinct network morphologies. This work shows that in gelatin gels no significant stress relaxation occurs on the seconds timescale, and consequently no time-dependency of the amount of energy stored in this material is observed. In caseinate gels, however, the energy dissipation via relaxation processes does contribute significantly to the time-dependency of reversible stored energy in the network. This can explain the obtained RE as a function of applied deformation at slow deformation rates. At faster deformation, an additional contribution to the dissipated energy is apparent, that increases with the deformation rate, which might point to the role of energy dissipation related to friction of the serum entrapped by the protein-network. This work shows that engineering strategies focused on controlling viscous flow in protein gels could be more effective to dictate the ability to elastically store energy in protein gels than routes that direct protein-specific aggregation and/or network-assembly.
NASA Astrophysics Data System (ADS)
Das, Diptarka
One of the most important results emerging from string theory is the gauge gravity duality (AdS/CFT correspondence) which tells us that certain problems in particular gravitational backgrounds can be exactly mapped to a particular dual gauge theory a quantum theory very similar to the one explaining the interactions between fundamental subatomic particles. The chief merit of the duality is that a difficult problem in one theory can be mapped to a simpler and solvable problem in the other theory. The duality can be used both ways. Most of the current theoretical framework is suited to study equilibrium systems, or systems where time dependence is at most adiabatic. However in the real world, systems are almost always out of equilibrium. Generically these scenarios are described by quenches, where a parameter of the theory is made time dependent. In this dissertation I describe some of the work done in the context of studying quantum quench using the AdS/CFT correspondence. We recover certain universal scaling type of behavior as the quenching is done through a quantum critical point. Another question that has been explored in the dissertation is time dependence of the gravity theory. Present cosmological observations indicate that our universe is accelerating and is described by a spacetime called de-Sitter(dS). In 2011 there had been a speculation over a possible duality between de-Sitter gravity and a particular field theory (Euclidean SP(N) CFT). However a concrete realization of this proposition was still lacking. Here we explicitly derive the dS/CFT duality using well known methods in field theory. We discovered that the time dimension emerges naturally in the derivation. We also describe further applications and extensions of dS/CFT. KEYWORDS: Holography, AdS/CFT correspondence, Quantum Quench, dS/CFT correspondence, Chaos.
NASA Astrophysics Data System (ADS)
Polidoro, B.; Iervolino, I.; Chioccarelli, E.; Giorgio, M.
2012-04-01
Probabilistic seismic hazard is usually computed trough a homogeneous Poisson process that even though it is a time-independent process it is widely used for its very convenient properties. However, when a single fault is of concern and/or the time scale is different from that of the long term, time-dependent processes are required. In this paper, different time-dependent models are reviewed with working examples. In fact, the Paganica fault (in central Italy) has been considered to compute both the probability of occurrence of at least one event in the lifespan of the structure, as well as the seismic hazard expressed in terms of probability of exceedance of an intensity value in a given time frame causing the collapse of the structure. Several models, well known or novel application to engineering hazard have been considered, limitation and issues in their applications are also discussed. The Brownian Passage Time (BPT) model is based on a stochastic modification of the deterministic stick-slip oscillator model for characteristic earthquakes; i.e., based on the addition of random perturbations (a Gaussian white noise) to the deterministic load path predicted by elastic rebound theory. This model assumes that the load state is at some ground level immediately after an event, increases steadly over time, reaches a failure threshold and relaxes instantaneously back to the ground level. For this model also a variable threshold has been considered to take into account the uncertainty of the threshold value. For the slip-predictable model it is assumed that the stress accumulates at a constant rate starting from some initial stress level. Stress is assumed to accumulate for a random period of time until an earthquake occurs. The size of the earthquake is governed by the stress release and it is a function of the elapsed time since the last event. In the time-predictable model stress buildup occurs at a constant rate until the accumulated stress reaches a threshold
Time-dependent absorption of very high-energy gamma-rays from the Galactic center by pair-production
Abramowski, Attila; Horns, Dieter; Ripken, Joachim; Gillessen, Stefan; Eldik, Christopher van
2008-12-24
Very high energy (VHE) gamma-rays have been detected from the direction of the Galactic center. The H.E.S.S. Cherenkov telescopes have located this {gamma}-ray source with a preliminary position uncertainty of 8.5'' per axis (6'' statistic+6'' sytematic per axis). Within the uncertainty region several possible counterpart candidates exist: the Super Massive Black Hole Sgr A*, the Pulsar Wind Nebula candidate G359.95-0.04, the Low Mass X-Ray Binary-system J174540.0-290031, the stellar cluster IRS 13, as well as self-annihilating dark matter. It is experimentally very challenging to further improve the positional accuracy in this energy range and therefore, it may not be possible to clearly associate one of the counterpart candidates with the VHE-source. Here, we present a new method to investigate a possible link of the VHE-source with the near environment of Sgr A*(within approximately 1000 Schwarzschild radii). This method uses the time- and energy-dependent effect of absorption of VHE {gamma}-rays by pair-production (in the following named pair-eclipse) with low-energy photons of stars closely orbiting the SMBH Sgr A*.
Spectral methods for time dependent problems
NASA Technical Reports Server (NTRS)
Tadmor, Eitan
1990-01-01
Spectral approximations are reviewed for time dependent problems. Some basic ingredients from the spectral Fourier and Chebyshev approximations theory are discussed. A brief survey was made of hyperbolic and parabolic time dependent problems which are dealt with by both the energy method and the related Fourier analysis. The ideas presented above are combined in the study of accuracy stability and convergence of the spectral Fourier approximation to time dependent problems.
Han, Lu; Liang, WanZhen; Zhao, Yi; Zhong, Xinxin
2014-06-07
The time-dependent wavepacket diffusive method [X. Zhong and Y. Zhao, J. Chem. Phys. 138, 014111 (2013)] is extended to investigate the energy relaxation and separation of a hot electron-hole pair in organic aggregates with incorporation of Coulomb interaction and electron-phonon coupling. The pair initial condition generated by laser pulse is represented by a Gaussian wavepacket with a central momentum. The results reveal that the hot electron energy relaxation is very well described by two rate processes with the fast rate much larger than the slow one, consistent with experimental observations, and an efficient electron-hole separation is accomplished accompanying the fast energy relaxation. Furthermore, although the extra energy indeed helps the separation by overcoming the Coulomb interaction, the width of initial wavepacket is much sensitive to the separation efficiency and the narrower wavepacket generates the more separated charges. This behavior may be useful to understand the experimental controversy of the hot carrier effect on charge separation.
Selfsimilar time dependent shock structures
NASA Technical Reports Server (NTRS)
Beck, R.; Drury, L. O.
1985-01-01
Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.
Selfsimilar time dependent shock structures
NASA Astrophysics Data System (ADS)
Beck, R.; Drury, L. O.
1985-08-01
Diffusive shock acceleration as an astrophysical mechanism for accelerating charged particles has the advantage of being highly efficient. This means however that the theory is of necessity nonlinear; the reaction of the accelerated particles on the shock structure and the acceleration process must be self-consistently included in any attempt to develop a complete theory of diffusive shock acceleration. Considerable effort has been invested in attempting, at least partially, to do this and it has become clear that in general either the maximum particle energy must be restricted by introducing additional loss processes into the problem or the acceleration must be treated as a time dependent problem (Drury, 1984). It is concluded that stationary modified shock structures can only exist for strong shocks if additional loss processes limit the maximum energy a particle can attain. This is certainly possible and if it occurs the energy loss from the shock will lead to much greater shock compressions. It is however equally possible that no such processes exist and we must then ask what sort of nonstationary shock structure develops. The ame argument which excludes stationary structures also rules out periodic solutions and indeed any solution where the width of the shock remains bounded. It follows that the width of the shock must increase secularly with time and it is natural to examine the possibility of selfsimilar time dependent solutions.
West, Niclas A; Winner, Joshua D; Bowersox, Rodney D W; North, Simon W
2016-07-01
The relaxation of highly vibrationally excited benzene, generated by 193 nm laser excitation, was studied using the transient rotational-translational temperature rise of the N2 bath, which was measured by proxy using two-line laser induced fluorescence of seeded NO. The resulting experimentally measured time-dependent N2 temperature rises were modeled with MultiWell based simulations of Collisional Energy Transfer (CET) from benzene vibration to N2 rotation-translation. We find that the average energy transferred in benzene deactivating collisions depends linearly on the internal energy of the excited benzene molecules and depends approximately linearly on the N2 bath temperature between 300 K and 600 K. The results are consistent with experimental studies and classical trajectory calculations of CET in similar systems. PMID:27394109
NASA Astrophysics Data System (ADS)
West, Niclas A.; Winner, Joshua D.; Bowersox, Rodney D. W.; North, Simon W.
2016-07-01
The relaxation of highly vibrationally excited benzene, generated by 193 nm laser excitation, was studied using the transient rotational-translational temperature rise of the N2 bath, which was measured by proxy using two-line laser induced fluorescence of seeded NO. The resulting experimentally measured time-dependent N2 temperature rises were modeled with MultiWell based simulations of Collisional Energy Transfer (CET) from benzene vibration to N2 rotation-translation. We find that the average energy transferred in benzene deactivating collisions depends linearly on the internal energy of the excited benzene molecules and depends approximately linearly on the N2 bath temperature between 300 K and 600 K. The results are consistent with experimental studies and classical trajectory calculations of CET in similar systems.
Time-Dependent Photodissociation Regions
NASA Technical Reports Server (NTRS)
Hollenbach, David; Natta, Antonella
1995-01-01
We present theoretical models of the time-dependent thermal and chemical structure of molecular gas suddenly exposed to far-ultraviolet (FUV) (6 eV less than hv less than 13.6 eV) radiation fields and the consequent time- dependent infrared emission of the gas. We focus on the response of molecular hydrogen for cloud densities ranging from n = 10(exp 3) to 10(exp 6)/cu cm and FUV fluxes G(sub 0) = 10(exp 3)-10(exp 6) times the local FUV interstellar flux. For G(sub 0)/n greater than 10(exp -2) cu cm, the emergent H(sub 2) vibrational line intensities are initially larger than the final equilibrium values. The H(sub 2) lines are excited by FUV fluorescence and by collisional excitation in warm gas. Most of the H(sub 2) intensity is generated at a characteristic hydrogen column density of N approximately 10(exp 21)/sq cm, which corresponds to an FUV optical depth of unity caused by dust opacity. The time dependence of the H(sub 2) intensities arises because the initial abundances of H(sub 2) at these depths is much higher than the equilibrium values, so that H(sub 2) initially competes more effectively with dust in absorbing FUV photons. Considerable column densities of warm (T approximately 1000) K H(sub 2) gas can be produced by the FUV pumping of H(sub 2) vibrational levels followed by collisional de-excitation, which transfers the energy to heat. In dense (n greater than or approximately 10(exp 5)/cu cm) gas exposed to high (G(sub 0) greater than or approximately 10(exp 4)) fluxes, this warm gas produces a 2-1 S(1)/1-0 S(l) H(sub 2) line ratio of approximately 0.1, which mimics the ratio found in shocked gas. In lower density regions, the FUV pumping produces a pure-fluorescent ratio of approximately 0.5. We also present calculations of the time dependence of the atomic hydrogen column densities and of the intensities of 0 I 6300 A, S II 6730 A, Fe II 1.64 microns, and rotational OH and H20 emission. Potential applications include star-forming regions, clouds
NASA Astrophysics Data System (ADS)
Colaïtis, A.; Hüller, S.; Pesme, D.; Duchateau, G.; Tikhonchuk, V. T.
2016-03-01
The Crossed Beam Energy Transfer (CBET) of two large laser beams is modeled using two approaches: (i) the time-independent Paraxial Complex Geometrical Optics (PCGO) for stochastically distributed Gaussian-shaped beamlets and (ii) the time-dependent conventional paraxial propagation of smoothed laser beams. Each description of the laser propagation is coupled to a hydrodynamics code. Both approaches are compared in a well-defined plasma configuration with density- and velocity- profiles corresponding to an inhomogeneous plasma, including a resonance zone in which the matching conditions for a resonant coupling between the two laser beams are fulfilled. The comparison is made for laser beams smoothed by random phase plates and for "regular beams" without speckles. The role of the laser speckles is also investigated for each approach. In general, a good agreement is found between the PCGO simulations and the fully time-dependent paraxial-type simulations, carried out with the code Harmony, past a transient period on the picosecond time scale. The PCGO-based CBET model is applied to the hydrodynamics simulations of a CBET experiment, the results of which reproduce essential features of the experimental data. Based on these comparisons, performed for interaction parameters up to 2 × 10 14 W cm - 2 μ m 2 , the PCGO approach proves to be a reliable method to be implemented in the hydrodynamics codes to describe the CBET in mm-scale plasmas.
Bhaskaran, Renjith; Sarma, Manabendra
2014-09-14
Low energy electron (LEE) induced cytosine base release in a selected pyrimidine nucleotide, viz., 2′-deoxycytidine-3′-monophosphate is investigated using ab initio electronic structure methods and time dependent quantum mechanical calculations. It has been noted that the cytosine base scission is comparatively difficult process than the 3′ C–O bond cleavage from the lowest π{sup *} shape resonance in energy region <1 eV. This is mainly due to the high activation energy barrier associated with the electron transfer from the π{sup *} orbital of the base to the σ{sup *} orbital of the glycosidic N–C bond. In addition, the metastable state formed after impinging LEE (0–1 eV) has very short lifetime (10 fs) which may decay in either of the two competing auto-detachment or dissociation process simultaneously. On the other hand, the selected N–C mode may cleave to form the cytosine base anion at higher energy regions (>2 eV) via tunneling of the glycosidic bond. Resonance states generated within this energy regime will exist for a duration of ∼35–55 fs. Comparison of salient features of the two dissociation events, i.e., 3′ C–O single strand break and glycosidic N–C bond cleavage in 3′-dCMPH molecule are also provided.
NASA Astrophysics Data System (ADS)
Bhaskaran, Renjith; Sarma, Manabendra
2014-09-01
Low energy electron (LEE) induced cytosine base release in a selected pyrimidine nucleotide, viz., 2'-deoxycytidine-3'-monophosphate is investigated using ab initio electronic structure methods and time dependent quantum mechanical calculations. It has been noted that the cytosine base scission is comparatively difficult process than the 3' C-O bond cleavage from the lowest π* shape resonance in energy region <1 eV. This is mainly due to the high activation energy barrier associated with the electron transfer from the π* orbital of the base to the σ* orbital of the glycosidic N-C bond. In addition, the metastable state formed after impinging LEE (0-1 eV) has very short lifetime (10 fs) which may decay in either of the two competing auto-detachment or dissociation process simultaneously. On the other hand, the selected N-C mode may cleave to form the cytosine base anion at higher energy regions (>2 eV) via tunneling of the glycosidic bond. Resonance states generated within this energy regime will exist for a duration of ˜35-55 fs. Comparison of salient features of the two dissociation events, i.e., 3' C-O single strand break and glycosidic N-C bond cleavage in 3'-dCMPH molecule are also provided.
Ghosh, Sandip; Sahoo, Tapas; Adhikari, Satrajit; Sharma, Rahul; Varandas, António J C
2015-12-17
We implement a coupled three-dimensional (3D) time-dependent wave packet formalism for the 4D reactive scattering problem in hyperspherical coordinates on the accurate double many body expansion (DMBE) potential energy surface (PES) for the ground and first two singlet states (1(1)A', 2(1)A', and 3(1)A') to account for nonadiabatic processes in the D(+) + H2 reaction for both zero and nonzero values of the total angular momentum (J). As the long-range interactions in D(+) + H2 contribute significantly due to nonadiabatic effects, the convergence profiles of reaction probabilities for the reactive noncharge transfer (RNCT), nonreactive charge transfer (NRCT), and reactive charge transfer (RCT) processes are shown for different collisional energies with respect to the helicity (K) and total angular momentum (J) quantum numbers. The total and state-to-state cross sections are presented as a function of the collision energy for the initial rovibrational state v = 0, j = 0 of the diatom, and the calculated cross sections compared with other theoretical and experimental results. PMID:26436891
NASA Astrophysics Data System (ADS)
Reiche, S.; Schlarb, H.
2000-05-01
For shorter bunches and narrower undulator gaps the interaction between the electrons in the bunch and the wake fields becomes so large that the FEL amplification is affected. For a typical vacuum chamber of an X-ray or VUV Free Electron Laser three major sources of wake fields exist: a resistance of the beam pipe, a change in the geometric aperture and the surface roughness of the beam pipe. The generated wake fields, which move along with the electrons, change the electron energy and momentum, depending on the electron longitudinal and transverse position. In particular, the accumulated energy modulation shifts the electrons away from the resonance condition. Based on an analytic model the energy loss by the wake fields has been incorporated into the time-dependent FEL simulation code GENESIS 1.3. For the parameters of the TESLA Test Facility the influence of the bunch length, beam pipe diameter and surface roughness has been studied. The results are presented in this paper.
Ziegler, Tom; Seth, Michael; Krykunov, Mykhaylo; Autschbach, Jochen; Wang, Fan
2009-04-21
It is shown that it is possible to derive the basic eigenvalue equation of adiabatic time-dependent density functional theory within the Tamm-Dancoff approximation (TD-DFT/TD) from a variational principle. The variational principle is applied to the regular Kohn-Sham formulation of DFT energy expression for a single Slater determinant and leads to the same energy spectrum as TD-DFT/TD. It is further shown that this variational approach affords the same electric and magnetic transition moments as TD-DFT/TD. The variational scheme can also be applied without the Tamm-Dancoff approximation. Practical implementations of TD-DFT are limited to second order response theory which introduces errors in transition energies for charge transfer and Rydberg excitations. It is indicated that higher order terms can be incorporated into the variational approach. It is also discussed how the current variational method is related to traditional DFT schemes based on variational principles such as DeltaSCF-DFT, and how they can be combined. PMID:19388731
Cao, Yixiang; Hughes, Thomas; Giesen, Dave; Halls, Mathew D; Goldberg, Alexander; Vadicherla, Tati Reddy; Sastry, Madhavi; Patel, Bhargav; Sherman, Woody; Weisman, Andrew L; Friesner, Richard A
2016-06-15
We have developed and implemented pseudospectral time-dependent density-functional theory (TDDFT) in the quantum mechanics package Jaguar to calculate restricted singlet and restricted triplet, as well as unrestricted excitation energies with either full linear response (FLR) or the Tamm-Dancoff approximation (TDA) with the pseudospectral length scales, pseudospectral atomic corrections, and pseudospectral multigrid strategy included in the implementations to improve the chemical accuracy and to speed the pseudospectral calculations. The calculations based on pseudospectral time-dependent density-functional theory with full linear response (PS-FLR-TDDFT) and within the Tamm-Dancoff approximation (PS-TDA-TDDFT) for G2 set molecules using B3LYP/6-31G*(*) show mean and maximum absolute deviations of 0.0015 eV and 0.0081 eV, 0.0007 eV and 0.0064 eV, 0.0004 eV and 0.0022 eV for restricted singlet excitation energies, restricted triplet excitation energies, and unrestricted excitation energies, respectively; compared with the results calculated from the conventional spectral method. The application of PS-FLR-TDDFT to OLED molecules and organic dyes, as well as the comparisons for results calculated from PS-FLR-TDDFT and best estimations demonstrate that the accuracy of both PS-FLR-TDDFT and PS-TDA-TDDFT. Calculations for a set of medium-sized molecules, including Cn fullerenes and nanotubes, using the B3LYP functional and 6-31G(**) basis set show PS-TDA-TDDFT provides 19- to 34-fold speedups for Cn fullerenes with 450-1470 basis functions, 11- to 32-fold speedups for nanotubes with 660-3180 basis functions, and 9- to 16-fold speedups for organic molecules with 540-1340 basis functions compared to fully analytic calculations without sacrificing chemical accuracy. The calculations on a set of larger molecules, including the antibiotic drug Ramoplanin, the 46-residue crambin protein, fullerenes up to C540 and nanotubes up to 14×(6,6), using the B3LYP functional and 6-31G
Time-dependent photoelectron angular distributions
NASA Astrophysics Data System (ADS)
Wang, Xiangyang
1999-09-01
I show that the angular distribution of electrons photoionized from gas phase targets by short light pulses is time-dependent, when the orbital momentum composition of the photocurrent changes with excitation energy so evolves with the time of detection. A theory of time- dependent photoionization is outlined and general formulas of time-dependent photoelectron flux and angular distribution are given. Two general propagator methods suitable to describe the time-dependent photoionization and scattering processes are developed. The photoionization process is viewed as a local excitation followed by a half scattering. The local excitation process is solved theoretically in a small region around the target core. This approach has been generalized to describe the evolution of a wavepacket in an unbound system. An asymptotic propagator theorem is discovered and used to derive analytic expressions for asymptotic propagators. The origin of the time dependence is explored by parameterizing the time delay and orbital momentum coupling in a two channel model. K-shell photoionization of N2 and CO are calculated with this time- dependent photoionization theory, implemented using a multiple scattering model. Numerical results demonstrate that the time dependence of photoelectron angular distributions is a realistic effect.
NASA Astrophysics Data System (ADS)
Liu, Jie; Liang, WanZhen
2013-01-01
This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011), 10.1063/1.3605504; J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)], 10.1063/1.3659312 on analytical excited-state Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with a conductor-like polarizable continuum model (CPCM). The formalism, implementation, and application of analytical first and second energy derivatives of TDDFT/CPCM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of excitation energies, excited-state geometries, and harmonic vibrational frequencies for a number of benchmark systems. The calculated results are in good agreement with the corresponding experimental data or other theoretical calculations, indicating the reliability of the current computer implementation of the developed algorithms. Then we made some preliminary applications to calculate the resonant Raman spectrum of 4-hydroxybenzylidene-2,3-dimethyl-imidazolinone in ethanol solution and the infrared spectra of ground and excited states of 9-fluorenone in methanol solution.
Wang, Dunyou; Huo, Winifred M.
2007-10-21
An eight dimensional time-dependent quantum dynamics wavepacket approach is performed for the study of the H₂+C₂H ! H + C₂H₂ reaction system on a new modified potential energy surface (PES) [Chem. Phys. Lett. 409, 249 (2005)]. This new potential energy surface is obtained by modifying Wang and Bowman's old PES [ J. Chem. Phys. 101, 8646 (1994)] based on the new ab initio calculation. This new modified PES has a much lower transition state barrier height at 2.29 kcal/mol than Wang and Bowman's old PES at 4.3 kcal/mol. This study shows the reactivity for this diatom-triatom reaction system is enchanced by vibrational excitations of H₂; whereas, the vibrational excitations of C₂H only have a small effect on the reactivity. Furthermore, the bending excitations of C₂H, comparing to the ground state reaction probability, hinder the reactivity. The comparison of the rate constant between this calculation and experimental results agree with each other very well. This comparison indicates that the new modified PES corrects the large barrier height problem in Wang and Bowman's old PES.
Dixon, David A; Gole, James L
2005-08-11
Time-dependent density functional theory calculations with a proper treatment of the asymptotic form of the exchange-correlation potential have been performed on R(R')Si=O to predict vertical excitation energies. The species R(R')Si=O is used as a model for the binding of the -(R)Si=O chromophore to a porous silicon surface. The calculated vertical excitation energies are substantially lower than those determined previously and show that vertical excitation of the lone chromophore is possible for all types of substituents including electronegative ones with KrF laser excitation in contrast to other predictions. If the substituents are electropositive, the chromophore can also be excited by a nitrogen laser. These results, in concert with the effect of the porous silicon surface on the R(R')Si=O excited states, confirm our previous explanation of the photoluminescence of porous silicon as being due to the presence of Si=O chromophores and provide new insights into the photoexcitation process. The results show that the differences in the vertical and adiabatic excitation energies are strongly dependent on whether the substituents are electronegative or electropositive with the former leading to larger differences and the latter leading to smaller differences. The results for the energy differences are explained in terms of the changes in the Si=O bond length on vertical excitation and on the changes in bond angles, which are related to the ability of the Si center in the excited state to undergo an inversion process. PMID:16852877
Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus J. J.; Jensen, Lasse
2013-12-10
A parallel implementation of analytical time-dependent density functional theory gradients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids, and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G, and a molecular host–guest complex (TTFcCBPQT^{4+}). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host–guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experimental data for most exchange-correlation functionals. Finally, however, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.
Time-dependent drift Hamiltonian
Boozer, A.H.
1983-03-01
The lowest-order drift equations are given in a canonical magnetic coordinate form for time-dependent magnetic and electric fields. The advantages of the canonical Hamiltonian form are also discussed.
Endo, A; Henshaw, J; Mignanelli, M A
1998-04-01
Time-dependent chemical compositions for 13N and 15O induced in the air atmosphere of a high energy electron accelerator room have been studied using a computer simulation method. A radiation chemistry model was developed to describe the chemical reactions of 13N and 15O species with the air molecules and their radiolytic products. By assuming several chemical forms of 13N and 15O generated by the (gamma, n) reaction, the variations of the concentrations of 13N and 15O species were simulated under a radiation field. From the comparison between the simulations and experiment in a 100 MeV electron linear accelerator (linac) facility, the following conclusions were obtained: (1) Just after the (gamma, n) reaction, 25-50% of 13N and 15O are present as atoms (13N, 15O) and/or their ions (13N+, 15O+) and the remainder as nitrogen and oxygen molecules (13NN, 15OO) and/or their ions (13NN+, 15OO+); (2) Neutralization of 13N+ and 15O+ ions into 13N and 15O atoms occurs instantaneously and the same is the case with the neutralization of 13NN+ and 15OO+ ions to 13NN and 15OO molecules; (3) The neutralized 13N and 15O atoms react with the air molecules and the radiolytic products to form nitrogen oxide compounds and ozone, while 13NN and 15OO remain as these molecules. Factors that control the chemical reactions of 13N and 15O are discussed. PMID:9525420
Time dependent view factor methods
Kirkpatrick, R.C.
1998-03-01
View factors have been used for treating radiation transport between opaque surfaces bounding a transparent medium for several decades. However, in recent years they have been applied to problems involving intense bursts of radiation in enclosed volumes such as in the laser fusion hohlraums. In these problems, several aspects require treatment of time dependence.
Analytic Time Depending Galaxy Models
NASA Astrophysics Data System (ADS)
Sala, F.
1990-11-01
RESUMEN. Considerando las hip6tesis de Chandrasekhar para el estudjo de la GalActicaq se han desarrollado varios modelos analiticos integrables con simetria axial y dependientes del . . By considering Chandrasekhar hypotheses +or the study o+ Galactic Dynamics, several integrable analytic axisymmetric time-depending galactic models have been developed. Ke ords; GALAXY-DYNAMICS - GALAXY-STRUCTURE
Time-dependent interstellar chemistry
NASA Technical Reports Server (NTRS)
Glassgold, A. E.
1985-01-01
Some current problems in interstellar chemistry are considered in the context of time-dependent calculations. The limitations of steady-state models of interstellar gas-phase chemistry are discussed, and attempts to chemically date interstellar clouds are reviewed. The importance of studying the physical and chemical properties of interstellar dust is emphasized. Finally, the results of a series of studies of collapsing clouds are described.
Time-Dependent Reliability Analysis
1999-10-27
FRANTIC-3 was developed to evaluate system unreliability using time-dependent techniques. The code provides two major options: to evaluate standby system unavailability or, in addition to the unavailability to calculate the total system failure probability by including both the unavailability of the system on demand as well as the probability that it will operate for an arbitrary time period following the demand. The FRANTIC-3 time dependent reliability models provide a large selection of repair and testingmore » policies applicable to standby or continously operating systems consisting of periodically tested, monitored, and non-repairable (non-testable) components. Time-dependent and test frequency dependent failures, as well as demand stress related failure, test-caused degradation and wear-out, test associated human errors, test deficiencies, test override, unscheduled and scheduled maintenance, component renewal and replacement policies, and test strategies can be prescribed. The conditional system unavailabilities associated with the downtimes of the user specified failed component are also evaluated. Optionally, the code can perform a sensitivity study for system unavailability or total failure probability to the failure characteristics of the standby components.« less
Yan, Pengxiu; Wang, Yuping; Li, Yida; Wang, Dunyou
2015-04-28
A time-dependent, quantum reaction dynamics calculation with seven degrees of freedom was carried out to study the energy efficiency in surmounting the approximate center energy barrier of OH + CH{sub 3}. The calculation shows the OH vibration excitations greatly enhance the reactivity, whereas the vibrational excitations of CH{sub 3} and the rotational excitations hinder the reactivity. On the basis of equal amount of total energy, although this reaction has a slight early barrier, it is the OH vibrational energy that is the dominate force in promoting the reactivity, not the translational energy. The studies on both the forward O + CH{sub 4} and reverse OH + CH{sub 3} reactions demonstrate, for these central barrier reactions, a small change of the barrier location can significantly change the energy efficacy roles on the reactivity. The calculated rate constants agree with the experimental data.
NASA Technical Reports Server (NTRS)
Hoffman, David K.; Sharafeddin, Omar; Judson, Richard S.; Kouri, Donald J.
1990-01-01
The time-dependent form of the Lippmann-Schwinger integral equation is used as the basis of several new wave packet propagation schemes. These can be formulated in terms of either the time-dependent wave function or a time-dependent amplitude density. The latter is nonzero only in the region of configuratiaon space for which the potential is nonzero, thereby in principle obviating the necessity of large grids or the use of complex absorbing potentials when resonances cause long collision times (leading, consequently, to long propagation times). Transition amplitudes are obtained in terms of Fourier transforms of the amplitude density from the time to the energy domain. The approach is illustrated by an application to a standard potential scattering model problem where, as in previous studies, the action of the kinetic energy operator is evaluated by fast Fourier transform (FFT) techniques.
Network-timing-dependent plasticity.
Delattre, Vincent; Keller, Daniel; Perich, Matthew; Markram, Henry; Muller, Eilif B
2015-01-01
Bursts of activity in networks of neurons are thought to convey salient information and drive synaptic plasticity. Here we report that network bursts also exert a profound effect on Spike-Timing-Dependent Plasticity (STDP). In acute slices of juvenile rat somatosensory cortex we paired a network burst, which alone induced long-term depression (LTD), with STDP-induced long-term potentiation (LTP) and LTD. We observed that STDP-induced LTP was either unaffected, blocked or flipped into LTD by the network burst, and that STDP-induced LTD was either saturated or flipped into LTP, depending on the relative timing of the network burst with respect to spike coincidences of the STDP event. We hypothesized that network bursts flip STDP-induced LTP to LTD by depleting resources needed for LTP and therefore developed a resource-dependent STDP learning rule. In a model neural network under the influence of the proposed resource-dependent STDP rule, we found that excitatory synaptic coupling was homeostatically regulated to produce power law distributed burst amplitudes reflecting self-organized criticality, a state that ensures optimal information coding. PMID:26106298
Network-timing-dependent plasticity
Delattre, Vincent; Keller, Daniel; Perich, Matthew; Markram, Henry; Muller, Eilif B.
2015-01-01
Bursts of activity in networks of neurons are thought to convey salient information and drive synaptic plasticity. Here we report that network bursts also exert a profound effect on Spike-Timing-Dependent Plasticity (STDP). In acute slices of juvenile rat somatosensory cortex we paired a network burst, which alone induced long-term depression (LTD), with STDP-induced long-term potentiation (LTP) and LTD. We observed that STDP-induced LTP was either unaffected, blocked or flipped into LTD by the network burst, and that STDP-induced LTD was either saturated or flipped into LTP, depending on the relative timing of the network burst with respect to spike coincidences of the STDP event. We hypothesized that network bursts flip STDP-induced LTP to LTD by depleting resources needed for LTP and therefore developed a resource-dependent STDP learning rule. In a model neural network under the influence of the proposed resource-dependent STDP rule, we found that excitatory synaptic coupling was homeostatically regulated to produce power law distributed burst amplitudes reflecting self-organized criticality, a state that ensures optimal information coding. PMID:26106298
NASA Technical Reports Server (NTRS)
Le Roux, J. A.; Potgieter, M. S.
1992-01-01
Time-dependent heliospheric cosmic-ray modulation for the period 1985-1989 is simulated by means of a time-dependent axially symmetric drift model with an emulated wavy heliospheric neutral sheet (HNS). The model is used to extend previous calculations to other energies in order to study a possible energy-dependence of the onset of new modulation at various radial distances in 1987. The model, with the outward propagating changes of the HNS as the only time-dependent parameters, is found to predict essentially no energy-dependence in the time when new modulation started in the simulated 1987. When a more practical approach in defining 'constant' modulation in 1987 is followed, the present calculations can be interpreted to indicate that the end of the recovery period in 1987 happened progressively earlier and the onset of new modulation progressively later the higher the rigidity of the cosmic rays. This period of relatively unchanged modulation is predicted to last longer with increasing radial distance.
Pulsar Electrodynamics: a Time-dependent View
Spitkovsky, Anatoly; /KIPAC, Menlo Park
2006-04-10
Pulsar spindown forms a reliable yet enigmatic prototype for the energy loss processes in many astrophysical objects including accretion disks and back holes. In this paper we review the physics of pulsar magnetospheres, concentrating on recent developments in force-free modeling of the magnetospheric structure. In particular, we discuss a new method for solving the equations of time-dependent force-free relativistic MHD in application to pulsars. This method allows to dynamically study the formation of the magnetosphere and its response to perturbations, opening a qualitatively new window on pulsar phenomena. Applications of the method to other magnetized rotators, such as magnetars and accretion disks, are also discussed.
Localized flow control with energy deposition
NASA Astrophysics Data System (ADS)
Adelgren, Russell Gene
A series of experiments with energy deposition via laser-induced optical breakdown of air, i.e., a laser spark, have been performed. These experiments have demonstrated the possibility of using a laser spark for supersonic flow control. In the first of these experiments, Rayleigh scattering flow visualization was taken for energy deposition into quiescent air. A time sequence of images showed the post breakdown fluid motion created by the laser spark for different laser energy levels. Blast wave radius and wave speed measurements were made and correlated to five different laser energy deposition levels. Laser energy was deposited upstream of a sphere in Mach 3.45 flow. The energy was deposited one sphere diameter and 0.6 diameters upstream of the front of the sphere. The frontal surface pressure on the sphere was recorded as the laser spark perturbed region interacted with the flow about the sphere. Tests for three different energy levels and two different incident laser beam diameters were completed. It has been demonstrated that the peak surface pressure associated with the Edney IV interaction can be momentarily reduced by 30% by the interaction with the thermal spot created by the laser spark. The effects of laser energy deposition on another shock interaction phenomena were studied. Laser energy deposition was used to modify the shock structure formed by symmetric wedges at Mach 3.45 within the dual solution domain. It was demonstrated experimentally that the Mach reflection could be reduced by 80% momentarily. The numerical simulations show a transition from the stable Mach reflection to a stable regular reflection. Two energy deposition methods (electric arcing and laser energy deposition) were used to force and control compressible mixing layers of axisymmetric jets. The energy deposition forcing methods have been experimentally investigated with the schlieren technique, particle image velocimetry, Mie scattering, and static pressure probe diagnostic
NASA Astrophysics Data System (ADS)
Casida, Mark E.; Gutierrez, Fabien; Guan, Jingang; Gadea, Florent-Xavier; Salahub, Dennis; Daudey, Jean-Pierre
2000-11-01
Time-dependent density-functional theory (TDDFT) is an increasingly popular approach for calculating molecular excitation energies. However, the TDDFT lowest triplet excitation energy, ωT, of a closed-shell molecule often falls rapidly to zero and then becomes imaginary at large internuclear distances. We show that this unphysical behavior occurs because ωT2 must become negative wherever symmetry breaking lowers the energy of the ground state solution below that of the symmetry unbroken solution. We use the fact that the ΔSCF method gives a qualitatively correct first triplet excited state to derive a "charge-transfer correction" (CTC) for the time-dependent local density approximation (TDLDA) within the two-level model and the Tamm-Dancoff approximation (TDA). Although this correction would not be needed for the exact exchange-correlation functional, it is evidently important for a correct description of molecular excited state potential energy surfaces in the TDLDA. As a byproduct of our analysis, we show why TDLDA and LDA ΔSCF excitation energies are often very similar near the equilibrium geometries. The reasoning given here is fairly general and it is expected that similar corrections will be needed in the case of generalized gradient approximations and hybrid functionals.
NASA Astrophysics Data System (ADS)
Salah, Wa'el; Coacolo, J.-L.; Hallak, A. B.; Al-Obaid, M.
2006-08-01
The energy loss by an accelerated electron bunch of a conical shape propagating in the laser-driven RF-photoinjector is expressed in terms of an expansion of the vector and scalar potentials into a series of eigenfunctions of the empty unit "pill-box" cavity. A versatile and simple analytical formula which can be easily applied to a bunch of any shape is obtained.
Pseudospectral time-dependent density functional theory
NASA Astrophysics Data System (ADS)
Ko, Chaehyuk; Malick, David K.; Braden, Dale A.; Friesner, Richard A.; Martínez, Todd J.
2008-03-01
Time-dependent density functional theory (TDDFT) is implemented within the Tamm-Dancoff approximation (TDA) using a pseudospectral approach to evaluate two-electron repulsion integrals. The pseudospectral approximation uses a split representation with both spectral basis functions and a physical space grid to achieve a reduction in the scaling behavior of electronic structure methods. We demonstrate here that exceptionally sparse grids may be used in the excitation energy calculation, following earlier work employing the pseudospectral approximation for determining correlation energies in wavefunction-based methods with similar conclusions. The pseudospectral TDA-TDDFT method is shown to be up to ten times faster than a conventional algorithm for hybrid functionals without sacrificing chemical accuracy.
Sadri, Keyvan Meyer, Hans-Dieter; Lauvergnat, David; Gatti, Fabien
2014-09-21
For computational rovibrational spectroscopy the choice of the frame is critical for an approximate separation of overall rotation from internal motions. To minimize the coupling between internal coordinates and rotation, Eckart proposed a condition [“Some studies concerning rotating axes and polyatomic molecules,” Phys. Rev. 47, 552–558 (1935)] and a frame that fulfills this condition is hence called an Eckart frame. A method is developed to introduce in a systematic way the Eckart frame for the expression of the kinetic energy operator (KEO) in the polyspherical approach. The computed energy levels of a water molecule are compared with those obtained using a KEO in the standard definition of the Body-fixed frame of the polyspherical approach. The KEO in the Eckart frame leads to a faster convergence especially for large J states and vibrationally excited states. To provide an example with more degrees of freedom, rotational states of the vibrational ground state of the trans nitrous acid (HONO) are also investigated.
Energy deposition in STARFIRE reactor components
Gohar, Y.; Brooks, J.N.
1985-04-01
The energy deposition in the STARFIRE commercial tokamak reactor was calculated based on detailed models for the different reactor components. The heat deposition and the 14 MeV neutron flux poloidal distributions in the first wall were obtained. The poloidal surface heat load distribution in the first wall was calculated from the plasma radiation. The Monte Carlo method was used for the calculation to allow an accurate modeling for the reactor geometry.
Energy deposition of corpuscular radiation in the middle atmosphere
NASA Technical Reports Server (NTRS)
Kudela, K.
1989-01-01
Main components of corpuscular radiation contributing to energy deposition (ED in eV/cu cm/s) in the atmosphere (10 to 100 km) are cosmic ray nuclei (CR - galactic and solar) and high energy electrons (HEE), mainly of magnetospheric origin. Galactic CR depending on solar cycle phase and latitude are dominant source of ED by corpuscular radiation below 50 to 60 km. Below 20 km secondaries must be assumed. More accurate treatment need assuming of individual HE solar flare particles, cut off rigidities in geomagnetic field and their changes during magnetospheric disturbances. Electrons E sub e greater than 30 keV of magnetospheric origin penetrating to atmosphere contribute to production rate below 100 km especially on night side. High temporal variability, local time dependence and complicated energy spectra lead to complicated structure of electron ED rate. Electrons of MeV energy found at geostationary orbit, pronouncing relation to solar and geomagnetic activity, cause maximum ED at 40 to 60 km. Monitoring the global distribution of ED by corpuscular radiation in middle atmosphere need continuing low altitude satellite measurements of both HEE and x ray BS from atmosphere as well as measurements of energy spectra and charge composition of HE solar flare particles.
Time-dependent behavior of positrons in noble gases
Wadehra, J.M. . Dept. of Physics and Astronomy); Drallos, P.J. )
1990-01-01
Both equilibrium and nonequilibrium behaviors of positrons in several noble gases are reviewed. Our novel procedure for obtaining the time-dependent behavior of various swarm parameters -- such as the positron drift velocity, average positron energy, positron annihilation rate (or equivalently Z{sub eff}) etc. -- for positrons in pure ambient gases subjected to external electrostatic fields is described. Summaries of time-dependent as well as electric field-dependent results for positron swarms in various noble gases are presented. New time-dependent results for positron swarms in neon are also described in detail. 36 refs., 4 figs., 3 tabs.
Time-dependent manipulation of ultracold ion bunches
NASA Astrophysics Data System (ADS)
Reijnders, M. P.; Debernardi, N.; van der Geer, S. B.; Mutsaers, P. H. A.; Vredenbregt, E. J. D.; Luiten, O. J.
2011-02-01
The combination of an ultracold ion source based on photoionization of a laser-cooled gas and time-dependent acceleration fields enables precise manipulation of ion beams. We demonstrate reduction in the longitudinal energy spread and transverse (de)focusing of the beam by applying time-dependent acceleration voltages. In addition, we show how time-dependent acceleration fields can be used to control both the sign and strength of the spherical aberrations. The experimental results are in close agreement with detailed charged particle tracking simulations and can be explained in terms of a simple analytical model.
NASA Astrophysics Data System (ADS)
Guedj, C.; Hung, L.; Zobelli, A.; Blaise, P.; Sottile, F.; Olevano, V.
2014-12-01
The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO2) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO2, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO2 may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.
Guedj, C.; Hung, L.; Sottile, F.; Zobelli, A.; Blaise, P.; Olevano, V.
2014-12-01
The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO{sub 2}) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO{sub 2}, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO{sub 2} may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.
Time-dependent nanomechanics of cartilage.
Han, Lin; Frank, Eliot H; Greene, Jacqueline J; Lee, Hsu-Yi; Hung, Han-Hwa K; Grodzinsky, Alan J; Ortiz, Christine
2011-04-01
In this study, atomic force microscopy-based dynamic oscillatory and force-relaxation indentation was employed to quantify the time-dependent nanomechanics of native (untreated) and proteoglycan (PG)-depleted cartilage disks, including indentation modulus E(ind), force-relaxation time constant τ, magnitude of dynamic complex modulus |E(∗)|, phase angle δ between force and indentation depth, storage modulus E', and loss modulus E″. At ∼2 nm dynamic deformation amplitude, |E(∗)| increased significantly with frequency from 0.22 ± 0.02 MPa (1 Hz) to 0.77 ± 0.10 MPa (316 Hz), accompanied by an increase in δ (energy dissipation). At this length scale, the energy dissipation mechanisms were deconvoluted: the dynamic frequency dependence was primarily governed by the fluid-flow-induced poroelasticity, whereas the long-time force relaxation reflected flow-independent viscoelasticity. After PG depletion, the change in the frequency response of |E(∗)| and δ was consistent with an increase in cartilage local hydraulic permeability. Although untreated disks showed only slight dynamic amplitude-dependent behavior, PG-depleted disks showed great amplitude-enhanced energy dissipation, possibly due to additional viscoelastic mechanisms. Hence, in addition to functioning as a primary determinant of cartilage compressive stiffness and hydraulic permeability, the presence of aggrecan minimized the amplitude dependence of |E(∗)| at nanometer-scale deformation. PMID:21463599
Time-Dependent Nanomechanics of Cartilage
Han, Lin; Frank, Eliot H.; Greene, Jacqueline J.; Lee, Hsu-Yi; Hung, Han-Hwa K.; Grodzinsky, Alan J.; Ortiz, Christine
2011-01-01
In this study, atomic force microscopy-based dynamic oscillatory and force-relaxation indentation was employed to quantify the time-dependent nanomechanics of native (untreated) and proteoglycan (PG)-depleted cartilage disks, including indentation modulus Eind, force-relaxation time constant τ, magnitude of dynamic complex modulus |E∗|, phase angle δ between force and indentation depth, storage modulus E′, and loss modulus E″. At ∼2 nm dynamic deformation amplitude, |E∗| increased significantly with frequency from 0.22 ± 0.02 MPa (1 Hz) to 0.77 ± 0.10 MPa (316 Hz), accompanied by an increase in δ (energy dissipation). At this length scale, the energy dissipation mechanisms were deconvoluted: the dynamic frequency dependence was primarily governed by the fluid-flow-induced poroelasticity, whereas the long-time force relaxation reflected flow-independent viscoelasticity. After PG depletion, the change in the frequency response of |E∗| and δ was consistent with an increase in cartilage local hydraulic permeability. Although untreated disks showed only slight dynamic amplitude-dependent behavior, PG-depleted disks showed great amplitude-enhanced energy dissipation, possibly due to additional viscoelastic mechanisms. Hence, in addition to functioning as a primary determinant of cartilage compressive stiffness and hydraulic permeability, the presence of aggrecan minimized the amplitude dependence of |E∗| at nanometer-scale deformation. PMID:21463599
Cosmological evolution of cosmic strings with time-dependent tension
Yamaguchi, Masahide
2005-08-15
We discuss the cosmological evolution of cosmic strings with time-dependent tension. We show that, in the case that the tension changes as a power of time, the cosmic string network obeys the scaling solution: the characteristic scale of the string network grows with the time. But due to the time dependence of the tension, the ratio of the energy density of infinite strings to that of the background universe is not necessarily constant.
Heating liquid dielectrics by time dependent fields
NASA Astrophysics Data System (ADS)
Khalife, A.; Pathak, U.; Richert, R.
2011-10-01
Steady state and time-resolved dielectric relaxation experiments are performed at high fields on viscous glycerol and the effects of energy absorption from the electric field are studied. Time resolution is obtained by a sinusoidal field whose amplitude is switched from a low to a high level and by recording voltage and current traces with an oscilloscope during this transition. Based on their distinct time and frequency dependences, three sources of modifying the dynamics and dielectric loss via an increase in the effective temperature can be distinguished: electrode temperature, real sample temperature, and configurational temperatures of the modes that absorbed the energy. Isothermal conditions that are desired for focusing on the configurational temperature changes (as in dielectric hole burning and related techniques) are maintained only for very thin samples and for moderate power levels. For high frequencies, say ν > 1 MHz, changes of the real temperature will exceed the effects of configurational temperatures in the case of macroscopic samples. Regarding microwave chemistry, heating via cell phone use, and related situations in which materials are subject to fields involving frequencies beyond the MHz regime, we conclude that changes in the configurational (or fictive) temperatures remain negligible compared with the increase of the real temperature. This simplifies the assessment of how time dependent electric fields modify the properties of materials.
Laser energy deposition and its dynamic uniformity for direct-drive capsules
Xu, Yan; Wu, SiZhong; Zheng, WuDi
2015-04-15
The total laser energy deposition of multi-laser-beam irradiation is not only associated with the dynamic behavior of capsule but also the time-dependent angular distribution of the energy deposition of each beam around its axis. The dynamic behavior of laser energy deposition does not linearly respond to the dynamic behavior of laser irradiation. The laser energy deposition uniformity determines the symmetry of implosion. The dynamic behavior of laser energy deposition non-uniformity in OMEGA for laser with square beam shape intensity profile is investigated. In the case of smaller laser spot, the initial non-uniformity caused by laser beam overlap is very high. The shell asymmetry caused by the high initial laser irradiation non-uniformity is estimated by the extent of distortion of shock front which is not as severe as expected before the shock driven by main pulse arrives. This suggests that the large initial non-uniformity due to smaller laser spot is one of the elements that seed disturbance before the main pulse. The rms of laser energy deposition during the main pulse remains above 2%. Since the intensity of main driving pulse usually is several times higher than that of picket pulses, the non-uniformity in main pulse period may jeopardize the symmetrical implosion. When dynamic behavior of capsule is considered, the influence of beam pointing error, the target positioning error, and beam-to-beam power unbalance is quite different for the case of static capsule.
Birefringence in time-dependent moving media
NASA Astrophysics Data System (ADS)
Lin, Shirong; Zhang, Ruoyang; Zhai, Yanwang; Wei, Jianye; Zhao, Qing
2016-08-01
Electromagnetic wave propagation in one- and two-dimensional time-dependent moving media is investigated in this paper. We identify another origin of linear birefringence caused by the component of the flow perpendicular to the wave vector. Previously, birefringence is induced by applying external electric and magnetic fields to non-crystalline material. Here it is shown that the time-varying velocity field also contributes to such a phenomenon. Our results indicate that the parallel component, time-dependent or not, will not yield birefringence. Furthermore, the time-dependent flow also results in a frequency shift. One-dimensional simulation is conducted to demonstrate these effects.
Tunable Time-Dependent Colloidal Interactions
NASA Astrophysics Data System (ADS)
Bergman, Andrew M.; Rogers, W. Benjamin; Manoharan, Vinothan N.
Self-assembly of colloidal particles can be driven by changes in temperature, density, or the concentration of solutes, and it is even possible to program the thermal response and equilibrium phase transitions of such systems. It is still difficult, however, to tune how the self-assembly process varies in time. We demonstrate control over the time-dependence of colloidal interactions, using DNA-functionalized colloidal particles with binding energies that are set by the concentration of a free linker strand in solution. We control the rate at which this free strand is consumed using a catalytic DNA reaction, whose rate is governed by the concentration of a catalyst strand. Varying the concentration of the linker, its competitor, and the catalyst at a fixed temperature, we can tune the rate and degree of the formation of colloidal aggregates and their following disassembly. Close to the colloidal melting point, the timescales of these out-of-equilibrium assembly and disassembly processes are determined by the rate of the catalytic reaction. Far below the colloidal melting point, however, the effects from varying our linker and competitor concentrations dominate.
Topic 5: Time-Dependent Behavior
Pfeiffer, P.A.; Tanabe, Tada-aki
1991-12-31
This chapter is a report of the material presented at the International Workshop on Finite Element Analysis of Reinforced Concrete, Session 4 -- Time Dependent Behavior, held at Columbia University, New York on June 3--6, 1991. Dr. P.A. Pfeiffer presented recent developments in time-dependent behavior of concrete and Professor T. Tanabe presented a review of research in Japan on time-dependent behavior of concrete. The chapter discusses the recent research of time-dependent behavior of concrete in the past few years in both the USA-European and Japanese communities. The author appreciates the valuable information provided by Zdenek P. Bazant in preparing the USA-European Research section.
Time dependent breakdown in silicon dioxide films
NASA Technical Reports Server (NTRS)
Svensson, C.; Shumka, A.
1975-01-01
An investigation was conducted regarding the possible existence of a time-dependent breakdown mechanism in thermal oxides of the type used as gate oxide in MOS circuits. Questions of device fabrication are discussed along with details concerning breakdown measurements and the determination of C-V characteristics. A relatively large prebreakdown current observed in one of the cases is related to the time-dependent breakdown.
NASA Astrophysics Data System (ADS)
Zeng, Qiao; Liu, Jie; Liang, WanZhen
2014-05-01
This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011); J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)] on analytical excited-state energy Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with molecular mechanics (MM). The formalism, implementation, and applications of analytical first and second energy derivatives of TDDFT/MM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of adiabatic excitation energies, and excited-state geometries, harmonic vibrational frequencies, and infrared intensities for a number of benchmark systems. The consistent results with the full quantum mechanical method and other hybrid theoretical methods indicate the reliability of the current numerical implementation of developed algorithms. The computational accuracy and efficiency of the current analytical approach are also checked and the computational efficient strategies are suggested to speed up the calculations of complex systems with many MM degrees of freedom. Finally, we apply the current analytical approach in TDDFT/MM to a realistic system, a red fluorescent protein chromophore together with part of its nearby protein matrix. The calculated results indicate that the rearrangement of the hydrogen bond interactions between the chromophore and the protein matrix is responsible for the large Stokes shift.
Zeng, Qiao; Liang, WanZhen; Liu, Jie
2014-05-14
This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011); J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)] on analytical excited-state energy Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with molecular mechanics (MM). The formalism, implementation, and applications of analytical first and second energy derivatives of TDDFT/MM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of adiabatic excitation energies, and excited-state geometries, harmonic vibrational frequencies, and infrared intensities for a number of benchmark systems. The consistent results with the full quantum mechanical method and other hybrid theoretical methods indicate the reliability of the current numerical implementation of developed algorithms. The computational accuracy and efficiency of the current analytical approach are also checked and the computational efficient strategies are suggested to speed up the calculations of complex systems with many MM degrees of freedom. Finally, we apply the current analytical approach in TDDFT/MM to a realistic system, a red fluorescent protein chromophore together with part of its nearby protein matrix. The calculated results indicate that the rearrangement of the hydrogen bond interactions between the chromophore and the protein matrix is responsible for the large Stokes shift.
Zeng, Qiao; Liu, Jie; Liang, WanZhen
2014-05-14
This work extends our previous works [J. Liu and W. Z. Liang, J. Chem. Phys. 135, 014113 (2011); J. Liu and W. Z. Liang, J. Chem. Phys. 135, 184111 (2011)] on analytical excited-state energy Hessian within the framework of time-dependent density functional theory (TDDFT) to couple with molecular mechanics (MM). The formalism, implementation, and applications of analytical first and second energy derivatives of TDDFT/MM excited state with respect to the nuclear and electric perturbations are presented. Their performances are demonstrated by the calculations of adiabatic excitation energies, and excited-state geometries, harmonic vibrational frequencies, and infrared intensities for a number of benchmark systems. The consistent results with the full quantum mechanical method and other hybrid theoretical methods indicate the reliability of the current numerical implementation of developed algorithms. The computational accuracy and efficiency of the current analytical approach are also checked and the computational efficient strategies are suggested to speed up the calculations of complex systems with many MM degrees of freedom. Finally, we apply the current analytical approach in TDDFT/MM to a realistic system, a red fluorescent protein chromophore together with part of its nearby protein matrix. The calculated results indicate that the rearrangement of the hydrogen bond interactions between the chromophore and the protein matrix is responsible for the large Stokes shift. PMID:24832314
Niobium Thin Film Properties Affected by Deposition Energy during Vacuum Deposition
Genfa Wu; H. Phillips; Ronald Sundelin; Anne-Marie Valente
2003-05-01
In order to understand and improve the super-conducting performance of niobium thin films at cryogenic temperatures, an energetic vacuum deposition system has been developed to study deposition energy effects on the properties of niobium thin films on various substrates. Ultra high vacuum avoids the gaseous inclusions in thin films commonly seen in sputtering deposition. A retarding field energy analyzer is used to measure the kinetic energy of niobium ions at the substrate location. A biased substrate holder controls the deposition energy. Transition temperature and residual resistivity ratio (RRR) of the niobium thin films at several deposition energies are obtained together with crystal orientation measurements and atomic force microscope (AFM) inspection, and the results show that there exists a preferred deposition energy around 115eV (the average deposition energy 64 eV plus the 51 V bias voltage).
Energy deposition via magnetoplasmadynamic acceleration: II. modeling and performance predictions
NASA Astrophysics Data System (ADS)
Mikellides, P. G.; England, B.; Gilland, J. H.
2009-02-01
A time-dependent, two-dimensional, axisymmetric magnetohydrodynamics code is employed to model, validate and extend the experimentally-limited performance characteristics of a gigawatt-level plasma source that utilized magnetoplasmadynamic (MPD) acceleration for gas energy deposition. Accurate modeling required an upgrade of the code's circuit routines to properly capture the pulse-forming-network current waveform which also serves as the primary variable for validation. Comparisons with experimentally deduced current waveforms were in good agreement for all power levels. The simulations also produced values for the plasma voltage which were compared with the measured voltage across the electrodes. The trend agreement was encouraging while the magnitude of the discrepancy is approximately constant and interpreted as a representation of the electrode fall voltage. Force computations captured the expected electromagnetic acceleration trends and serve as further verification. They also allow examination of the device as a very high power MPD thruster operating at power levels in excess of 180 MW. The computations offer insights into the plasma's characteristics at different power levels through two-dimensional distributions of pertinent parameters and identify design guidelines for effective stagnation temperature values as a function of the mass-flow rate.
Investigations of Low Temperature Time Dependent Cracking
Van der Sluys, W A; Robitz, E S; Young, B A; Bloom, J
2002-09-30
The objective of this project was to investigate metallurgical and mechanical phenomena associated with time dependent cracking of cold bent carbon steel piping at temperatures between 327 C and 360 C. Boiler piping failures have demonstrated that understanding the fundamental metallurgical and mechanical parameters controlling these failures is insufficient to eliminate it from the field. The results of the project consisted of the development of a testing methodology to reproduce low temperature time dependent cracking in laboratory specimens. This methodology was used to evaluate the cracking resistance of candidate heats in order to identify the factors that enhance cracking sensitivity. The resultant data was integrated into current available life prediction tools.
Time-Dependent Molecular Reaction Dynamics
Oehrn, Yngve
2007-11-29
This paper is a brief review of a time-dependent, direct, nonadiabatic theory of molecular processes called Electron Nuclear Dynamics (END). This approach to the study of molecular reaction dynamics is a hierarchical theory that can be applied at various levels of approximation. The simplest level of END uses classical nuclei and represents all electrons by a single, complex, determinantal wave function. The wave function parameters such as average nuclear positions and momenta, and molecular orbital coefcients carry the time dependence and serve as dynamical variables. Examples of application are given of the simplest level of END to ion-atom and ion-molecule reactions.
Time-dependent corona models - Scaling laws
NASA Technical Reports Server (NTRS)
Korevaar, P.; Martens, P. C. H.
1989-01-01
Scaling laws are derived for the one-dimensional time-dependent Euler equations that describe the evolution of a spherically symmetric stellar atmosphere. With these scaling laws the results of the time-dependent calculations by Korevaar (1989) obtained for one star are applicable over the whole Hertzsprung-Russell diagram and even to elliptic galaxies. The scaling is exact for stars with the same M/R-ratio and a good approximation for stars with a different M/R-ratio. The global relaxation oscillation found by Korevaar (1989) is scaled to main sequence stars, a solar coronal hole, cool giants and elliptic galaxies.
Energetic particle energy deposition in Titan's upper atmosphere
NASA Astrophysics Data System (ADS)
Westlake, J. H.; Smith, H. T.; Mitchell, D. G.; Paranicas, C. P.; Rymer, A. M.; Bell, J. M.; Waite, J. H., Jr.; Mandt, K. E.
2012-04-01
Titan’s upper atmosphere has been observed to be variable on a pass-by-pass basis. During the nominal mission where the Cassini Ion and Neutral Mass Spectrometer (INMS) only sampled the northern hemisphere this variability was initially believed to be tied to solar drivers manifest in latitudinal variations in the thermal structure of the upper atmosphere. However, when Cassini delved into the southern hemisphere the latitudinal dependence was not present in the data. Recently, Westlake et al. (2011) showed that the pass-by-pass variability is correlated with the deviations in the plasma environment as identified by Rymer et al. (2009) and Simon et al. (2010). Furthermore, the studies of Westlake et al. (2011) and Bell et al. (2011) showed that Titan’s upper atmosphere responds to changes in the ambient magnetospheric plasma on timescales of roughly one Titan day (16 Earth days). We report on recent studies of energy deposition in Titan’s upper atmosphere. Previous studies by Smith et al. (2009), Cravens et al. (2008), Tseng et al. (2008), and Shah et al. (2009) reported on energetic proton and oxygen ion precipitation. Back of the envelope calculations by Sittler et al. (2009) showed that magnetospheric energy inputs are expected to be of the order of or greater than the solar processes. We report on further analysis of the plasma environment around Titan during the flybys that the INMS has good data. We utilize data from the Magnetospheric Imaging Instrument to determine how the magnetospheric particle population varies from pass to pass and how this influences the net magnetospheric energy input prior to the flyby. We also report on enhanced energetic neutral atom emissions during select highly energetic passes. References: Bell, J., et al.: “Simulating the time-dependent response of Titan's upper atmosphere to periods of magnetospheric forcing”. Geophys. Res. Lett., Vol. 38, L06202, 2011. Rymer, A. M., et al.: “Discrete classification and electron
Wave function for time-dependent harmonically confined electrons in a time-dependent electric field.
Li, Yu-Qi; Pan, Xiao-Yin; Sahni, Viraht
2013-09-21
The many-body wave function of a system of interacting particles confined by a time-dependent harmonic potential and perturbed by a time-dependent spatially homogeneous electric field is derived via the Feynman path-integral method. The wave function is comprised of a phase factor times the solution to the unperturbed time-dependent Schrödinger equation with the latter being translated by a time-dependent value that satisfies the classical driven equation of motion. The wave function reduces to that of the Harmonic Potential Theorem wave function for the case of the time-independent harmonic confining potential. PMID:24070284
Exact solution of a quantum forced time-dependent harmonic oscillator
NASA Technical Reports Server (NTRS)
Yeon, Kyu Hwang; George, Thomas F.; Um, Chung IN
1992-01-01
The Schrodinger equation is used to exactly evaluate the propagator, wave function, energy expectation values, uncertainty values, and coherent state for a harmonic oscillator with a time dependent frequency and an external driving time dependent force. These quantities represent the solution of the classical equation of motion for the time dependent harmonic oscillator.
Acceleration in a nonplanar time-dependent billiard.
Raeisi, Sedighe; Eslami, Parvin
2016-08-01
We study the dynamical properties of a particle in a nonplanar square billiard. The plane of the billiard has a sinusoidal shape. We consider both the static and time-dependent plane. We study the affect of different parameters that control the geometry of the billiard in this model. We consider variations of different parameters of the model and describe how the particle trajectory is affected by these parameters. We also investigate the dynamical behavior of the system in the static condition using its reduced phase plot and show that the dynamics of the particle inside the billiard may be regular, mixed, or chaotic. Finally, the problem of the particle energy growth is studied in the billiard with the time-dependent plane. We show that when in the static case, the billiard is chaotic, then the particle energy in the time-dependent billiard grows for a small number of collisions, and then it starts to saturate. But when the dynamics of the static case is regular, then the particle average energy in the time-dependent situation stays constant. PMID:27627308
Modeling Atmospheric Energy Deposition (by energetic ions)
NASA Astrophysics Data System (ADS)
Parkinson, C. D.; Brain, D. A.; Lillis, R. J.; Liemohn, M. W.; Bougher, S. W.
2011-12-01
deposition is conducted including a comparison of the influence relative to other energy sources (namely EUV photons) and previous efforts using the guiding center approximation.
Time-Dependent Erosion of Ion Optics
NASA Technical Reports Server (NTRS)
Wirz, Richard E.; Anderson, John R.; Katz, Ira; Goebel, Dan M.
2008-01-01
The accurate prediction of thruster life requires time-dependent erosion estimates for the ion optics assembly. Such information is critical to end-of-life mechanisms such as electron backstreaming. CEX2D was recently modified to handle time-dependent erosion, double ions, and multiple throttle conditions in a single run. The modified code is called "CEX2D-t". Comparisons of CEX2D-t results with LDT and ELT post-tests results show good agreement for both screen and accel grid erosion including important erosion features such as chamfering of the downstream end of the accel grid and reduced rate of accel grid aperture enlargement with time.
Time-dependent oral absorption models
NASA Technical Reports Server (NTRS)
Higaki, K.; Yamashita, S.; Amidon, G. L.
2001-01-01
The plasma concentration-time profiles following oral administration of drugs are often irregular and cannot be interpreted easily with conventional models based on first- or zero-order absorption kinetics and lag time. Six new models were developed using a time-dependent absorption rate coefficient, ka(t), wherein the time dependency was varied to account for the dynamic processes such as changes in fluid absorption or secretion, in absorption surface area, and in motility with time, in the gastrointestinal tract. In the present study, the plasma concentration profiles of propranolol obtained in human subjects following oral dosing were analyzed using the newly derived models based on mass balance and compared with the conventional models. Nonlinear regression analysis indicated that the conventional compartment model including lag time (CLAG model) could not predict the rapid initial increase in plasma concentration after dosing and the predicted Cmax values were much lower than that observed. On the other hand, all models with the time-dependent absorption rate coefficient, ka(t), were superior to the CLAG model in predicting plasma concentration profiles. Based on Akaike's Information Criterion (AIC), the fluid absorption model without lag time (FA model) exhibited the best overall fit to the data. The two-phase model including lag time, TPLAG model was also found to be a good model judging from the values of sum of squares. This model also described the irregular profiles of plasma concentration with time and frequently predicted Cmax values satisfactorily. A comparison of the absorption rate profiles also suggested that the TPLAG model is better at prediction of irregular absorption kinetics than the FA model. In conclusion, the incorporation of a time-dependent absorption rate coefficient ka(t) allows the prediction of nonlinear absorption characteristics in a more reliable manner.
Time-dependent projected Hartree-Fock
Tsuchimochi, Takashi; Van Voorhis, Troy
2015-03-28
Projected Hartree-Fock (PHF) has recently emerged as an alternative approach to describing degenerate systems where static correlation is abundant, when the spin-symmetry is projected. Here, we derive a set of linearized time-dependent equations for PHF in order to be able to access excited states. The close connection of such linear-response time-dependent PHF (TDPHF) to the stability condition of a PHF wave function is discussed. Expanding this analysis also makes it possible to give analytical expressions for the projected coupling terms of Hamiltonian and overlaps between excited Slater determinants. TDPHF with spin-projection (TDSUHF) and its Tamm-Dancoff approximation are benchmarked for several electronically degenerate molecules including the dissociating H{sub 2}, F{sub 2} and O{sub 3} at equilibrium, and the distorted ethylene. It is shown that they give consistently better descriptions of excited states than does time-dependent HF (TDHF). Furthermore, we demonstrate that they offer not only singly but also doubly excited states, which naturally arise upon spin-projection. We also address the thermodynamic limit of TDSUHF, using non-interacting He gas. While TDPHF singly excited states tend to converge to those of HF with the size of the system due to the lack of size-extensivity of PHF, doubly excited states remain reasonable even at the thermodynamic limit. We find that the overall performance of our method is systematically better than the regular TDHF in many cases at the same computational scaling.
Time Dependent Behavior in the Weissenberg Effect
NASA Astrophysics Data System (ADS)
Degen, Michael M.; Andereck, C. David
1997-03-01
The Weissenberg effect is the climb of a non-Newtonian fluid up a rotating rod. We have found novel transitional effects in the behavior of a particular climbing fluid, STP(STP Oil Treatment distributed by First Brands Corporation.). The first state is a time-independent axisymmetric concave climb. As the rotation rate of the rod is increased, the first transition is to an axisymmetric climb with an ``onion dome'' shape. At higher rotation rates, the flow undergoes a symmetry breaking bifurcation to a time-dependent state. This time-dependent state exhibits an oscillation with a single frequency. Upon further increase of the rod rotation rate, the oscillation becomes modulated by a second frequency. The nature of each transition will be characterized, including the measurement of oscillation amplitudes and the frequency (or frequencies) of the time dependent states. These results will be compared with previous work.(G.S. Beavers, D.D. Joseph, J. Fluid Mech. 69), 475 (1975).(D.D. Joseph, R.L. Fosdick, Arch. Rational Mech. 49), 321 (1973).
Time-dependent projected Hartree-Fock
NASA Astrophysics Data System (ADS)
Tsuchimochi, Takashi; Van Voorhis, Troy
2015-03-01
Projected Hartree-Fock (PHF) has recently emerged as an alternative approach to describing degenerate systems where static correlation is abundant, when the spin-symmetry is projected. Here, we derive a set of linearized time-dependent equations for PHF in order to be able to access excited states. The close connection of such linear-response time-dependent PHF (TDPHF) to the stability condition of a PHF wave function is discussed. Expanding this analysis also makes it possible to give analytical expressions for the projected coupling terms of Hamiltonian and overlaps between excited Slater determinants. TDPHF with spin-projection (TDSUHF) and its Tamm-Dancoff approximation are benchmarked for several electronically degenerate molecules including the dissociating H2, F2 and O3 at equilibrium, and the distorted ethylene. It is shown that they give consistently better descriptions of excited states than does time-dependent HF (TDHF). Furthermore, we demonstrate that they offer not only singly but also doubly excited states, which naturally arise upon spin-projection. We also address the thermodynamic limit of TDSUHF, using non-interacting He gas. While TDPHF singly excited states tend to converge to those of HF with the size of the system due to the lack of size-extensivity of PHF, doubly excited states remain reasonable even at the thermodynamic limit. We find that the overall performance of our method is systematically better than the regular TDHF in many cases at the same computational scaling.
NASA Astrophysics Data System (ADS)
Isegawa, Miho; Truhlar, Donald G.
2013-04-01
Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel
Energy Deposition Processes in Titan's Upper Atmosphere
NASA Technical Reports Server (NTRS)
Sittler, Edward C., Jr.; Bertucci, Cesar; Coates, Andrew; Cravens, Tom; Dandouras, Iannis; Shemansky, Don
2008-01-01
Most of Titan's atmospheric organic and nitrogen chemistry, aerosol formation, and atmospheric loss are driven from external energy sources such as Solar UV, Saturn's magnetosphere, solar wind and galactic cosmic rays. The Solar UV tends to dominate the energy input at lower altitudes of approximately 1100 km but which can extend down to approximately 400 km, while the plasma interaction from Saturn's magnetosphere, Saturn's magnetosheath or solar wind are more important at higher altitudes of approximately 1400 km, but the heavy ion plasma [O(+)] of approximately 2 keV and energetic ions [H(+)] of approximately 30 keV or higher from Saturn's magnetosphere can penetrate below 950km. Cosmic rays with energies of greater than 1 GeV can penetrate much deeper into Titan's atmosphere with most of its energy deposited at approximately 100 km altitude. The haze layer tends to dominate between 100 km and 300 km. The induced magnetic field from Titan's interaction with the external plasma can be very complex and will tend to channel the flow of energy into Titan's upper atmosphere. Cassini observations combined with advanced hybrid simulations of the plasma interaction with Titan's upper atmosphere show significant changes in the character of the interaction with Saturn local time at Titan's orbit where the magnetosphere displays large and systematic changes with local time. The external solar wind can also drive sub-storms within the magnetosphere which can then modify the magnetospheric interaction with Titan. Another important parameter is solar zenith angle (SZA) with respect to the co-rotation direction of the magnetospheric flow. Titan's interaction can contribute to atmospheric loss via pickup ion loss, scavenging of Titan's ionospheric plasma, loss of ionospheric plasma down its induced magnetotail via an ionospheric wind, and non-thermal loss of the atmosphere via heating and sputtering induced by the bombardment of magnetospheric keV ions and electrons. This
Time-dependent Dyson orbital theory.
Gritsenko, O V; Baerends, E J
2016-08-21
Although time-dependent density functional theory (TDDFT) has become the tool of choice for real-time propagation of the electron density ρ(N)(t) of N-electron systems, it also encounters problems in this application. The first problem is the neglect of memory effects stemming from the, in TDDFT virtually unavoidable, adiabatic approximation, the second problem is the reliable evaluation of the probabilities P(n)(t) of multiple photoinduced ionization, while the third problem (which TDDFT shares with other approaches) is the reliable description of continuum states of the electrons ejected in the process of ionization. In this paper time-dependent Dyson orbital theory (TDDOT) is proposed. Exact TDDOT equations of motion (EOMs) for time-dependent Dyson orbitals are derived, which are linear differential equations with just static, feasible potentials of the electron-electron interaction. No adiabatic approximation is used, which formally resolves the first TDDFT problem. TDDOT offers formally exact expressions for the complete evolution in time of the wavefunction of the outgoing electron. This leads to the correlated probability of single ionization P(1)(t) as well as the probabilities of no ionization (P(0)(t)) and multiple ionization of n electrons, P(n)(t), which formally solves the second problem of TDDFT. For two-electron systems a proper description of the required continuum states appears to be rather straightforward, and both P(1)(t) and P(2)(t) can be calculated. Because of the exact formulation, TDDOT is expected to reproduce a notorious memory effect, the "knee structure" of the non-sequential double ionization of the He atom. PMID:26987972
Topologically nontrivial time-dependent chiral condensates
Suzuki, M.
1996-11-01
Topologically nontrivial time-dependent solutions of the classical nonlinear {sigma} model are studied as candidates of the disoriented chiral condensate (DCC) in 3+1 dimensions. Unlike the analytic solutions so far discussed, these solutions cannot be transformed into isospin-uniform ones by chiral rotations. If they are produced as DCC{close_quote}s, they can be detected by a distinct pattern in the angle-rapidity distribution of the neutral-to-charged pion ratio. {copyright} {ital 1996 The American Physical Society.}
Sublinear scaling for time-dependent stochastic density functional theory
Gao, Yi; Neuhauser, Daniel; Baer, Roi; Rabani, Eran
2015-01-21
A stochastic approach to time-dependent density functional theory is developed for computing the absorption cross section and the random phase approximation (RPA) correlation energy. The core idea of the approach involves time-propagation of a small set of stochastic orbitals which are first projected on the occupied space and then propagated in time according to the time-dependent Kohn-Sham equations. The evolving electron density is exactly represented when the number of random orbitals is infinite, but even a small number (≈16) of such orbitals is enough to obtain meaningful results for absorption spectrum and the RPA correlation energy per electron. We implement the approach for silicon nanocrystals using real-space grids and find that the overall scaling of the algorithm is sublinear with computational time and memory.
Boosting thermoelectric efficiency using time-dependent control
Zhou, Hangbo; Thingna, Juzar; Hänggi, Peter; Wang, Jian-Sheng; Li, Baowen
2015-01-01
Thermoelectric efficiency is defined as the ratio of power delivered to the load of a device to the rate of heat flow from the source. Till date, it has been studied in presence of thermodynamic constraints set by the Onsager reciprocal relation and the second law of thermodynamics that severely bottleneck the thermoelectric efficiency. In this study, we propose a pathway to bypass these constraints using a time-dependent control and present a theoretical framework to study dynamic thermoelectric transport in the far from equilibrium regime. The presence of a control yields the sought after substantial efficiency enhancement and importantly a significant amount of power supplied by the control is utilised to convert the wasted-heat energy into useful-electric energy. Our findings are robust against nonlinear interactions and suggest that external time-dependent forcing, which can be incorporated with existing devices, provides a beneficial scheme to boost thermoelectric efficiency. PMID:26464021
Time-Dependent Delayed Signatures from Energetic Photon Interrogations
Daren R. Norman; James L. Jones; Brandon W. Blackburn; Kevin J. Haskell; James T. Johnson; Scott M. Watson; Alan W. Hunt; Randy Spaulding; Frank Harmon
2007-08-01
Pulsed photonuclear interrogation environments generated by 8–24 MeV electron linac are rich with time-dependent, material-specific, radiation signatures. Nitrogen-based explosives and nuclear materials can be detected by exploiting these signatures in different delayed-time regions. Numerical and experimental results presented in this paper show the unique time and energy dependence of these signatures. It is shown that appropriate delayed-time windows are essential to acquire material-specific signatures in pulsed photonuclear assessment environments. These developments demonstrate that pulsed, high-energy, photon-inspection environments can be exploited for time-dependent, material-specific signatures through the proper operation of specialized detectors and detection methods.
Time-Dependent Delayed Signatures from Energetic Photon Interrogations
Daren R. Norman; James L. Jones; Brandon W. Blackburn; Kevin J. Haskell; James T. Johnson; Scott M. Watson; Alan W. Hunt; Randy Spaulding; Frank Harmon
2007-08-01
Pulsed photonuclear interrogation environments generated by 8–24 MeV electron linac are rich with time-dependent, material-specific, radiation signatures. Nitrogen-based explosives and nuclear materials can be detected by exploiting these signatures in different delayed-time regions. Numerical and experimental results presented in this paper show the unique time and energy dependence of these signatures. It is shown that appropriate delayed-time windows are essential to acquire material-specific signatures in the pulsed photonuclear assessment (PPA) environments. These developments demonstrate that pulsed, high-energy, photon- inspection environments can be exploited for time-dependent, material-specific signatures through the proper operation of specialized detectors and detection methods.
Boosting thermoelectric efficiency using time-dependent control.
Zhou, Hangbo; Thingna, Juzar; Hänggi, Peter; Wang, Jian-Sheng; Li, Baowen
2015-01-01
Thermoelectric efficiency is defined as the ratio of power delivered to the load of a device to the rate of heat flow from the source. Till date, it has been studied in presence of thermodynamic constraints set by the Onsager reciprocal relation and the second law of thermodynamics that severely bottleneck the thermoelectric efficiency. In this study, we propose a pathway to bypass these constraints using a time-dependent control and present a theoretical framework to study dynamic thermoelectric transport in the far from equilibrium regime. The presence of a control yields the sought after substantial efficiency enhancement and importantly a significant amount of power supplied by the control is utilised to convert the wasted-heat energy into useful-electric energy. Our findings are robust against nonlinear interactions and suggest that external time-dependent forcing, which can be incorporated with existing devices, provides a beneficial scheme to boost thermoelectric efficiency. PMID:26464021
Time-dependent diffusion in stellar atmospheres
NASA Astrophysics Data System (ADS)
Alecian, G.; Stift, M. J.; Dorfi, E. A.
2011-12-01
The chemical peculiarities of Ap stars are due to abundance stratifications produced by atomic diffusion in their outer layers. Theoretical models can predict such stratifications, but so far only provide equilibrium solutions which correspond to the maximum depth-dependent abundances for each element that can be supported by the radiation field. However, these stratifications are actually built up through a non-linear, time-dependent process which has never been modelled for realistic stellar atmospheres. Here, we present the first numerical simulations of time-dependent diffusion. We solve the continuity equation after having computed, as accurately as possible, atomic diffusion velocities (with and without a magnetic field) for a simplified fictitious - but still realistic - chemical element: cloudium. The direct comparison with existing observations is not the immediate aim of this work but rather a general understanding of how the stratification build-up proceeds in time and space. Our results raise serious questions as to the relevance of equilibrium solutions and reinforce the suspicion that certain accumulations of chemical elements might prove unstable.
The time-dependent Gutzwiller approximation
NASA Astrophysics Data System (ADS)
Fabrizio, Michele
2015-03-01
The time-dependent Gutzwiller Approximation (t-GA) is shown to be capable of tracking the off-equilibrium evolution both of coherent quasiparticles and of incoherent Hubbard bands. The method is used to demonstrate that the sharp dynamical crossover observed by time-dependent DMFT in the quench-dynamics of a half-filled Hubbard model can be identified within the t-GA as a genuine dynamical transition separating two distinct physical phases. This result, strictly variational for lattices of infinite coordination number, is intriguing as it actually questions the occurrence of thermalization. Next, we shall present how t-GA works in a multi-band model for V2O3 that displays a first-order Mott transition. We shall show that a physically accessible excitation pathway is able to collapse the Mott gap down and drive off-equilibrium the insulator into a metastable metal phase. Work supported by the European Union, Seventh Framework Programme, under the project GO FAST, Grant Agreement No. 280555.
Time-Dependent Delayed Signatures From Energetic Photon Interrogations
D. R. Norman; J. L. Jones; B. W. Blackburn; S. M. Watson; K. J. Haskell
2006-08-01
A pulsed photonuclear interrogation environment is rich with time-dependent, material specific, radiation signatures. Exploitation of these signatures in the delayed time regime (>1us after the photon flash) has been explored through various detection schemes to identify both shielded nuclear material and nitrogen-based explosives. Prompt emission may also be invaluable for these detection methods. Numerical and experimental results, which utilize specially modified neutron and HpGe detectors, are presented which illustrate the efficacy of utilizing these time-dependent signatures. Optimal selection of the appropriate delayed time window is essential to these pulsed inspection systems. For explosive (ANFO surrogate) detection, both numerical models and experimental results illustrate that nearly all 14N(n,y) reactions have occurred within l00 us after the flash. In contrast, however, gamma-ray and neutron signals for nuclear material detection require a delay of several milliseconds after the photon pulse. In this case, any data collected too close to the photon flash results in a spectrum dominated by high energy signals which make it difficult to discern signatures from nuclear material. Specifically, two short-lived, high-energy fission fragments (97Ag(T1/2=5.1 s) and 94Sr(T1/2=75.2 s)) were measured and identified as indicators of the presence of fissionable material. These developments demonstrate that a photon inspection environment can be exploited for time-dependent, material specific signatures through the proper operation of specially modified detectors.
Tokamak power reactor ignition and time dependent fractional power operation
Vold, E.L.; Mau, T.K.; Conn, R.W.
1986-06-01
A flexible time-dependent and zero-dimensional plasma burn code with radial profiles was developed and employed to study the fractional power operation and the thermal burn control options for an INTOR-sized tokamak reactor. The code includes alpha thermalization and a time-dependent transport loss which can be represented by any one of several currently popular scaling laws for energy confinement time. Ignition parameters were found to vary widely in density-temperature (n-T) space for the range of scaling laws examined. Critical ignition issues were found to include the extent of confinement time degradation by alpha heating, the ratio of ion to electron transport power loss, and effect of auxiliary heating on confinement. Feedback control of the auxiliary power and ion fuel sources are shown to provide thermal stability near the ignition curve.
Time-dependent nonlinear cosmic ray shocks confirming abstract
NASA Technical Reports Server (NTRS)
Dorfi, E. A.
1985-01-01
Numerical studies of time dependent cosmic ray shock structures in planar geometry are interesting because analytical time-independent solutions are available which include the non-linear reactions on the plasma flow. A feature of these time asymptotic solutions is that for higher Mach numbers (M approximately 5) and for a low cosmic ray upstream pressure the solution is not uniquely determined by the usual conservation laws of mass, momentum and energy. These numerical solutions clearly indicate that much work needs to be done before we understand shock acceleration as a time dependent process. The slowness of the process is possibly due to the fact that there is a diffusive flux into the downstream region in addition to the usual advective losses. Analytic investigations of thie phenomenon are required.
Student understanding of time dependence in quantum mechanics
NASA Astrophysics Data System (ADS)
Emigh, Paul J.; Passante, Gina; Shaffer, Peter S.
2015-12-01
[This paper is part of the Focused Collection on Upper Division Physics Courses.] The time evolution of quantum states is arguably one of the more difficult ideas in quantum mechanics. In this article, we report on results from an investigation of student understanding of this topic after lecture instruction. We demonstrate specific problems that students have in applying time dependence to quantum systems and in recognizing the key role of the energy eigenbasis in determining the time dependence of wave functions. Through analysis of student responses to a set of four interrelated tasks, we categorize some of the difficulties that underlie common errors. The conceptual and reasoning difficulties that have been identified are illustrated through student responses to four sets of questions administered at different points in a junior-level course on quantum mechanics. Evidence is also given that the problems persist throughout undergraduate instruction and into the graduate level.
Time-dependent thermoelectric transport for nanoscale thermal machines
NASA Astrophysics Data System (ADS)
Daré, A.-M.; Lombardo, P.
2016-01-01
We analyze an electronic nanoscale thermal machine driven by time-dependent environment: besides bias and gate voltage variations, we consider also the less prevailing time modulation of the couplings between leads and dot. We provide energy and heat current expressions in such situations, as well as expressions for the power exchanged between the dot+leads system and its outside. Calculations are made in the Keldysh nonequilibrium Green's function framework. We apply these results to design a cyclic refrigerator, circumventing the ambiguity of defining energy flows between subsystems in the case of strong coupling. For fast lead-dot coupling modulation, we observe transient currents which cannot be ascribed to charge tunneling.
Dosing time-dependent actions of psychostimulants.
Manev, H; Uz, T
2009-01-01
The concept of the dosing time-dependent (DTD) actions of drugs has been used to describe the effects of diurnal rhythms on pharmacological responsiveness. Notwithstanding the importance of diurnal variability in drug pharmacokinetics and bioavailability, it appears that in the central nervous system (CNS), the DTD actions of psychotropic drugs involve diurnal changes in the CNS-specific expression of genes encoding for psychotropic drug targets and transcription factors known as clock genes. In this review, we focused our discussion on the DTD effects of the psychostimulants cocaine and amphetamines. Both cocaine and amphetamines produce differential lasting behavioral alterations, that is, locomotor sensitization, depending on the time of the day they are administered. This exemplifies a DTD action of these drugs. The DTD effects of these psychostimulants correlate with diurnal changes in the system of transcription factors termed clock genes, for example, Period 1, and with changes in the availability of certain subtypes of dopamine receptors, for example, D2 and D3. Diurnal synthesis and release of the pineal hormone melatonin influence the DTD behavioral actions of cocaine and amphetamines. The molecular mechanism of melatonin's effects on the responsiveness of CNS to psychostimulants appears to involve melatonin receptors and clock genes. It is proposed that the DTD characteristics of psychostimulant action and the contributions of the melatonergic system may have clinical implications that include treatments for the attention deficit hyperactivity disorder and possibly neurotoxicity/neuroprotection. PMID:19897073
Infrared Blobs : Time-dependent Flags
NASA Astrophysics Data System (ADS)
McCullough, P. R.; Mack, J.; Dulude, M.; Hilbert, B.
2014-10-01
We describe the creation of time-dependent flags for pixels associated with "blobs" on the WFC3 IR detector. We detect the blobs on flat fields obtained by repeated observations of the night side of the Earth. We provide the most complete census of IR blobs' positions, radii, and times of first appearance. In aggregate, a set of 46 blobs, 27 "strong" and 19 "medium" in their effective scattering cross section, affect slightly less than 1% of the pixels of the detector. A second set of 81 "weak" (and typically smaller) blobs affect another 1% of the pixels. In the past, the "blob" flag, bit 9 (i.e. value = 512) in the data quality (DQ) array described in Table 2.5 of the WFC3 Data Handbook (Rajan et al. 2010) has been a static 2-D array; henceforth a set of such arrays, each associated with a "use after" date corresponding to the appearance of one or more new blobs, can be used. We prepared such DQ arrays using the 46 "strong" and "medium" blobs and discuss why we did not include the fainter blobs therein. As an added data product, we create and test a blob flat field that corrects the effects of blobs on extended emission; however, it should not be applied if stellar photometry is the goal.
Time dependent friction in a free gas
NASA Astrophysics Data System (ADS)
Fanelli, Cristiano; Sisti, Francesco; Stagno, Gabriele V.
2016-03-01
We consider a body moving in a perfect gas, described by the mean-field approximation and interacting elastically with the body, we study the friction exerted by the gas on the body fixed at constant velocities. The time evolution of the body in this setting was studied in Caprino et al. [Math. Phys. 264, 167-189 (2006)], Caprino et al. [Math. Models Methods Appl. Sci. 17, 1369-1403 (2007)], and Cavallaro [Rend. Mat. Appl. 27, 123-145 (2007)] for object with simple shape; the first study where a simple kind of concavity was considered was in Sisti and Ricciuti [SIAM J. Math. Anal. 46, 3759-3611 (2014)], showing new features in the dynamic but not in the friction term. The case of more general shape of the body was left out for further difficulties, and we believe indeed that there are actually non-trivial issues to be faced for these more general cases. To show this and in the spirit of getting a more realistic perspective in the study of friction problems, in this paper, we focused our attention on the friction term itself, studying its behavior on a body with a more general kind of concavity and fixed at constant velocities. We derive the expression of the friction term for constant velocities, we show how it is time dependent, and we give its exact estimate in time. Finally, we use this result to show the absence of a constant velocity in the actual dynamic of such a body.
Alternative time-dependent optimized effective potential
NASA Astrophysics Data System (ADS)
Nazarov, Vladimir
2013-03-01
The OEP is known as a single-particle potential minimizing the expectation value of a many-body Hamiltonian on the set of eigen-functions of a single-particle Hamiltonian. The time-dependent (TD) OEP can be constructed with the TD quantum stationary-action principle. Very useful conceptually in DFT and TDDFT, both OEPs are not practicable due to the complexity of their implementations. Here we report a TDOEP by minimizing the difference of LHS and RHS of the TD Schrödinger equation. If the orbitals are varied, then the TD Hartree-Fock equations are reproduced. Similarly, we now find the OEP. New OMP does not involve the inversion of the density-response function χs, which greatly facilitates implementations. Accordingly, the exchange-correlation kernel fxc involves of χs- 1 only, not its quadratic counterpart. To show the power of this method, we work out the fxch (q , ω) of the homogeneous electron gas to be used with the nearly-free electrons theory, where fxch is the main input. Partial support from National Science Council, Taiwan, Grant No. 100-2112-M-001-025-MY3 is acknowledged.
Time dependence of Hawking radiation entropy
Page, Don N.
2013-09-01
If a black hole starts in a pure quantum state and evaporates completely by a unitary process, the von Neumann entropy of the Hawking radiation initially increases and then decreases back to zero when the black hole has disappeared. Here numerical results are given for an approximation to the time dependence of the radiation entropy under an assumption of fast scrambling, for large nonrotating black holes that emit essentially only photons and gravitons. The maximum of the von Neumann entropy then occurs after about 53.81% of the evaporation time, when the black hole has lost about 40.25% of its original Bekenstein-Hawking (BH) entropy (an upper bound for its von Neumann entropy) and then has a BH entropy that equals the entropy in the radiation, which is about 59.75% of the original BH entropy 4πM{sub 0}{sup 2}, or about 7.509M{sub 0}{sup 2} ≈ 6.268 × 10{sup 76}(M{sub 0}/M{sub s}un){sup 2}, using my 1976 calculations that the photon and graviton emission process into empty space gives about 1.4847 times the BH entropy loss of the black hole. Results are also given for black holes in initially impure states. If the black hole starts in a maximally mixed state, the von Neumann entropy of the Hawking radiation increases from zero up to a maximum of about 119.51% of the original BH entropy, or about 15.018M{sub 0}{sup 2} ≈ 1.254 × 10{sup 77}(M{sub 0}/M{sub s}un){sup 2}, and then decreases back down to 4πM{sub 0}{sup 2} = 1.049 × 10{sup 77}(M{sub 0}/M{sub s}un){sup 2}.
Time dependence of Hawking radiation entropy
NASA Astrophysics Data System (ADS)
Page, Don N.
2013-09-01
If a black hole starts in a pure quantum state and evaporates completely by a unitary process, the von Neumann entropy of the Hawking radiation initially increases and then decreases back to zero when the black hole has disappeared. Here numerical results are given for an approximation to the time dependence of the radiation entropy under an assumption of fast scrambling, for large nonrotating black holes that emit essentially only photons and gravitons. The maximum of the von Neumann entropy then occurs after about 53.81% of the evaporation time, when the black hole has lost about 40.25% of its original Bekenstein-Hawking (BH) entropy (an upper bound for its von Neumann entropy) and then has a BH entropy that equals the entropy in the radiation, which is about 59.75% of the original BH entropy 4πM02, or about 7.509M02 ≈ 6.268 × 1076(M0/Msolar)2, using my 1976 calculations that the photon and graviton emission process into empty space gives about 1.4847 times the BH entropy loss of the black hole. Results are also given for black holes in initially impure states. If the black hole starts in a maximally mixed state, the von Neumann entropy of the Hawking radiation increases from zero up to a maximum of about 119.51% of the original BH entropy, or about 15.018M02 ≈ 1.254 × 1077(M0/Msolar)2, and then decreases back down to 4πM02 = 1.049 × 1077(M0/Msolar)2.
Time-dependence in mixture toxicity prediction
Dawson, Douglas A.; Allen, Erin M.G.; Allen, Joshua L.; Baumann, Hannah J.; Bensinger, Heather M.; Genco, Nicole; Guinn, Daphne; Hull, Michael W.; Il'Giovine, Zachary J.; Kaminski, Chelsea M.; Peyton, Jennifer R.; Schultz, T. Wayne; Pöch, Gerald
2014-01-01
The value of time-dependent toxicity (TDT) data in predicting mixture toxicity was examined. Single chemical (A and B) and mixture (A + B) toxicity tests using Microtox® were conducted with inhibition of bioluminescence (Vibrio fischeri) being quantified after 15, 30 and 45-min of exposure. Single chemical and mixture tests for 25 sham (A1:A2) and 125 true (A:B) combinations had a minimum of seven duplicated concentrations with a duplicated control treatment for each test. Concentration/response (x/y) data were fitted to sigmoid curves using the five-parameter logistic minus one parameter (5PL-1P) function, from which slope, EC25, EC50, EC75, asymmetry, maximum effect, and r2 values were obtained for each chemical and mixture at each exposure duration. Toxicity data were used to calculate percentage-based TDT values for each individual chemical and mixture of each combination. Predicted TDT values for each mixture were calculated by averaging the TDT values of the individual components and regressed against the observed TDT values obtained in testing, resulting in strong correlations for both sham (r2 = 0.989, n = 25) and true mixtures (r2 = 0.944, n = 125). Additionally, regression analyses confirmed that observed mixture TDT values calculated for the 50% effect level were somewhat better correlated with predicted mixture TDT values than at the 25 and 75% effect levels. Single chemical and mixture TDT values were classified into five levels in order to discern trends. The results suggested that the ability to predict mixture TDT by averaging the TDT of the single agents was modestly reduced when one agent of the combination had a positive TDT value and the other had a minimal or negative TDT value. PMID:25446331
Fission dynamics within time-dependent Hartree-Fock. II. Boost-induced fission
NASA Astrophysics Data System (ADS)
Goddard, Philip; Stevenson, Paul; Rios, Arnau
2016-01-01
Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus and the daughter products. Purpose: We explore the ability of dynamic mean-field methods to describe induced fission processes, using quadrupole boosts in the nuclide 240Pu as an example. Methods: Following upon the work presented in Goddard et al. [Phys. Rev. C 92, 054610 (2015)], 10.1103/PhysRevC.92.054610, quadrupole-constrained Hartree-Fock calculations are used to create a potential energy surface. An isomeric state and a state beyond the second barrier peak are excited by means of instantaneous as well as temporally extended gauge boosts with quadrupole shapes. The subsequent deexcitation is studied in a time-dependent Hartree-Fock simulation, with emphasis on fissioned final states. The corresponding fission fragment mass numbers are studied. Results: In general, the energy deposited by the quadrupole boost is quickly absorbed by the nucleus. In instantaneous boosts, this leads to fast shape rearrangements and violent dynamics that can ultimately lead to fission. This is a qualitatively different process than the deformation-induced fission. Boosts induced within a finite time window excite the system in a relatively gentler way and do induce fission but with a smaller energy deposition. Conclusions: The fission products obtained using boost-induced fission in time-dependent Hartree-Fock are more asymmetric than the fragments obtained in deformation-induced fission or the corresponding adiabatic approaches.
MCNPX benchmark of in-beam proton energy deposition
Corzine, K.; Ferguson, P.; Morgan, G.; Quintana, D.; Waters, L.; Cooper, R.; Liljestrand, R.; Whiteson, A.
2000-07-01
The MCNPX code is being used to calculate energy deposition in the accelerator production of tritium (APT) target/blanket system components. To ensure that these components are properly designed, the code must be validated. An energy deposition experiment was designed to aid in the code validation using thermocouple sensors in-beam and thermistor-type sensors in decoupler- and blanketlike regions. This paper focuses on the in-beam thermocouple sensors.
Time-dependent coupled-cluster method for atomic nuclei
Pigg, David A; Hagen, Gaute; Nam, Hai Ah; Papenbrock, Thomas F
2012-01-01
We study time-dependent coupled-cluster theory in the framework of nuclear physics. Based on Kvaal's bi-variational formulation of this method [S. Kvaal, arXiv:1201.5548], we explicitly demonstrate that observables that commute with the Hamiltonian are conserved under time evolution. We explore the role of the energy and of the similarity-transformed Hamiltonian under real and imaginary time evolution and relate the latter to similarity renormalization group transformations. Proof-of-principle computations of He-4 and O-16 in small model spaces, and computations of the Lipkin model illustrate the capabilities of the method
Time-Dependent Rate Phenomenon in Viruses
Aiewsakun, Pakorn
2016-01-01
ABSTRACT Among the most fundamental questions in viral evolutionary biology are how fast viruses evolve and how evolutionary rates differ among viruses and fluctuate through time. Traditionally, viruses are loosely classed into two groups: slow-evolving DNA viruses and fast-evolving RNA viruses. As viral evolutionary rate estimates become more available, it appears that the rates are negatively correlated with the measurement timescales and that the boundary between the rates of DNA and RNA viruses might not be as clear as previously thought. In this study, we collected 396 viral evolutionary rate estimates across almost all viral genome types and replication strategies, and we examined their rate dynamics. We showed that the time-dependent rate phenomenon exists across multiple levels of viral taxonomy, from the Baltimore classification viral groups to genera. We also showed that, by taking the rate decay dynamics into account, a clear division between the rates of DNA and RNA viruses as well as reverse-transcribing viruses could be recovered. Surprisingly, despite large differences in their biology, our analyses suggested that the rate decay speed is independent of viral types and thus might be useful for better estimation of the evolutionary time scale of any virus. To illustrate this, we used our model to reestimate the evolutionary timescales of extant lentiviruses, which were previously suggested to be very young by standard phylogenetic analyses. Our analyses suggested that these viruses are millions of years old, in agreement with paleovirological evidence, and therefore, for the first time, reconciled molecular analyses of ancient and extant viruses. IMPORTANCE This work provides direct evidence that viral evolutionary rate estimates decay with their measurement timescales and that the rate decay speeds do not differ significantly among viruses despite the vast differences in their molecular features. After adjustment for the rate decay dynamics, the
Time-Dependent Electronic Populations in Fragment-Based Time-Dependent Density Functional Theory.
Mosquera, Martín A; Wasserman, Adam
2015-08-11
Conceiving a molecule as being composed of smaller molecular fragments, or subunits, is one of the pillars of the chemical and physical sciences and leads to productive methods in quantum chemistry. Using a fragmentation scheme, efficient algorithms can be proposed to address problems in the description of chemical bond formation and breaking. We present a formally exact time-dependent density functional theory for the electronic dynamics of molecular fragments with a variable number of electrons. This new formalism is an extension of previous work [Phys. Rev. Lett. 111, 023001 (2013)]. We also introduce a stable density-inversion method that is applicable to time-dependent and ground-state density functional theories and their extensions, including those discussed in this work. PMID:26574438
Progress Report on Alloy 617 Time Dependent Allowables
Wright, Julie Knibloe
2015-06-01
Time dependent allowable stresses are required in the ASME Boiler and Pressure Vessel Code for design of components in the temperature range where time dependent deformation (i.e., creep) is expected to become significant. There are time dependent allowable stresses in Section IID of the Code for use in the non-nuclear construction codes, however, there are additional criteria that must be considered in developing time dependent allowables for nuclear components. These criteria are specified in Section III NH. St is defined as the lesser of three quantities: 100% of the average stress required to obtain a total (elastic, plastic, primary and secondary creep) strain of 1%; 67% of the minimum stress to cause rupture; and 80% of the minimum stress to cause the initiation of tertiary creep. The values are reported for a range of temperatures and for time increments up to 100,000 hours. These values are determined from uniaxial creep tests, which involve the elevated temperature application of a constant load which is relatively small, resulting in deformation over a long time period prior to rupture. The stress which is the minimum resulting from these criteria is the time dependent allowable stress St. In this report data from a large number of creep and creep-rupture tests on Alloy 617 are analyzed using the ASME Section III NH criteria. Data which are used in the analysis are from the ongoing DOE sponsored high temperature materials program, form Korea Atomic Energy Institute through the Generation IV VHTR Materials Program and historical data from previous HTR research and vendor data generated in developing the alloy. It is found that the tertiary creep criterion determines St at highest temperatures, while the stress to cause 1% total strain controls at low temperatures. The ASME Section III Working Group on Allowable Stress Criteria has recommended that the uncertainties associated with determining the onset of tertiary creep and the lack of significant
Relativistic Coulomb excitation within the time dependent superfluid local density approximation
Stetcu, I.; Bertulani, C. A.; Bulgac, A.; Magierski, P.; Roche, K. J.
2015-01-06
Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus ^{238}U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, the dipole pygmy resonance, and giant quadrupole modes are excited during the process. As a result, the one-body dissipation of collective dipole modes is shown to lead a damping width Γ↓≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.
Global Auroral Energy Deposition Derived from Polar UVI Images
NASA Technical Reports Server (NTRS)
Fillingim, M. O.; Brittnacher, M. J.; Elsen, R.; Parks, G. K.; Spann, J. F., Jr.; Germany, G. A.
1997-01-01
Quantitative measurement of the transfer of energy and momentum to the ionosphere from the solar wind is one of the main objectives of the ISTP program. Global measurement of auroral energy deposition derived from observations of the longer wavelength LBH band emissions made by the Ultraviolet Imager on the Polar spacecraft is one of the key elements in this satellite and ground-based instrument campaign. These "measurements" are inferred by combining information from consecutive images using different filters and have a time resolution on the average of three minutes and are made continuously over a 5 to 8 hour period during each 18 hour orbit of the Polar spacecraft. The energy deposition in the ionosphere from auroral electron precipitation augments are due to Joule heating associated with field aligned currents. Assuming conjugacy of energy deposition between the two hemispheres the total energy input to the ionosphere through electron precipitation can be determined at high time resolution. Previously, precipitating particle measurements along the tracks of low altitude satellites provided only local measurements and the global energy precipitation could be inferred through models but not directly measured. We use the UVI images for the entire month of January 1997 to estimate the global energy deposition at high time resolution. We also sort the energy deposition into sectors to find possible trends, for example, on the dayside and nightside, or the dawn and dusk sides.
Towards time-dependent current-density-functional theory in the non-linear regime
Escartín, J. M.; Vincendon, M.; Dinh, P. M.; Suraud, E.; Romaniello, P.; Reinhard, P.-G.
2015-02-28
Time-Dependent Density-Functional Theory (TDDFT) is a well-established theoretical approach to describe and understand irradiation processes in clusters and molecules. However, within the so-called adiabatic local density approximation (ALDA) to the exchange-correlation (xc) potential, TDDFT can show insufficiencies, particularly in violently dynamical processes. This is because within ALDA the xc potential is instantaneous and is a local functional of the density, which means that this approximation neglects memory effects and long-range effects. A way to go beyond ALDA is to use Time-Dependent Current-Density-Functional Theory (TDCDFT), in which the basic quantity is the current density rather than the density as in TDDFT. This has been shown to offer an adequate account of dissipation in the linear domain when the Vignale-Kohn (VK) functional is used. Here, we go beyond the linear regime and we explore this formulation in the time domain. In this case, the equations become very involved making the computation out of reach; we hence propose an approximation to the VK functional which allows us to calculate the dynamics in real time and at the same time to keep most of the physics described by the VK functional. We apply this formulation to the calculation of the time-dependent dipole moment of Ca, Mg and Na{sub 2}. Our results show trends similar to what was previously observed in model systems or within linear response. In the non-linear domain, our results show that relaxation times do not decrease with increasing deposited excitation energy, which sets some limitations to the practical use of TDCDFT in such a domain of excitations.
Towards time-dependent current-density-functional theory in the non-linear regime
NASA Astrophysics Data System (ADS)
Escartín, J. M.; Vincendon, M.; Romaniello, P.; Dinh, P. M.; Reinhard, P.-G.; Suraud, E.
2015-02-01
Time-Dependent Density-Functional Theory (TDDFT) is a well-established theoretical approach to describe and understand irradiation processes in clusters and molecules. However, within the so-called adiabatic local density approximation (ALDA) to the exchange-correlation (xc) potential, TDDFT can show insufficiencies, particularly in violently dynamical processes. This is because within ALDA the xc potential is instantaneous and is a local functional of the density, which means that this approximation neglects memory effects and long-range effects. A way to go beyond ALDA is to use Time-Dependent Current-Density-Functional Theory (TDCDFT), in which the basic quantity is the current density rather than the density as in TDDFT. This has been shown to offer an adequate account of dissipation in the linear domain when the Vignale-Kohn (VK) functional is used. Here, we go beyond the linear regime and we explore this formulation in the time domain. In this case, the equations become very involved making the computation out of reach; we hence propose an approximation to the VK functional which allows us to calculate the dynamics in real time and at the same time to keep most of the physics described by the VK functional. We apply this formulation to the calculation of the time-dependent dipole moment of Ca, Mg and Na2. Our results show trends similar to what was previously observed in model systems or within linear response. In the non-linear domain, our results show that relaxation times do not decrease with increasing deposited excitation energy, which sets some limitations to the practical use of TDCDFT in such a domain of excitations.
Towards time-dependent current-density-functional theory in the non-linear regime.
Escartín, J M; Vincendon, M; Romaniello, P; Dinh, P M; Reinhard, P-G; Suraud, E
2015-02-28
Time-Dependent Density-Functional Theory (TDDFT) is a well-established theoretical approach to describe and understand irradiation processes in clusters and molecules. However, within the so-called adiabatic local density approximation (ALDA) to the exchange-correlation (xc) potential, TDDFT can show insufficiencies, particularly in violently dynamical processes. This is because within ALDA the xc potential is instantaneous and is a local functional of the density, which means that this approximation neglects memory effects and long-range effects. A way to go beyond ALDA is to use Time-Dependent Current-Density-Functional Theory (TDCDFT), in which the basic quantity is the current density rather than the density as in TDDFT. This has been shown to offer an adequate account of dissipation in the linear domain when the Vignale-Kohn (VK) functional is used. Here, we go beyond the linear regime and we explore this formulation in the time domain. In this case, the equations become very involved making the computation out of reach; we hence propose an approximation to the VK functional which allows us to calculate the dynamics in real time and at the same time to keep most of the physics described by the VK functional. We apply this formulation to the calculation of the time-dependent dipole moment of Ca, Mg and Na2. Our results show trends similar to what was previously observed in model systems or within linear response. In the non-linear domain, our results show that relaxation times do not decrease with increasing deposited excitation energy, which sets some limitations to the practical use of TDCDFT in such a domain of excitations. PMID:25725723
Calculation of energy deposition distributions for simple geometries
NASA Technical Reports Server (NTRS)
Watts, J. W., Jr.
1973-01-01
When high-energy charged particles pass through a thin detector, the ionization energy loss in that detector is subject to fluctuations or straggling which must be considered in interpreting the data. Under many conditions, which depend upon the charge and energy of the incident particle and the detector geometry, the ionization energy lost by the particle is significantly different from the energy deposited in the detector. This problem divides naturally into a calculation of the energy loss that results in excitation and low-energy secondary electrons which do not travel far from their production points, and a calculation of energy loss that results in high-energy secondary electrons which can escape from the detector. The first calculation is performed using a modification of the Vavilov energy loss distribution. A cutoff energy is introduced above which all electrons are ignored and energy transferred to low energy particles is assumed to be equivalent to the energy deposited by them. For the second calculation, the trajectory of the primary particle is considered as a source of secondary high-energy electrons. The electrons from this source are transported using Monte Carlo techniques and multiple scattering theory, and the energy deposited by them in the detector is calculated. The results of the two calculations are then combined to predict the energy deposition distribution. The results of these calculations are used to predict the charge resolution of parallel-plate pulse ionization chambers that are being designed to measure the charge spectrum of heavy nuclei in the galactic cosmic-ray flux.
Time-dependent response of dissipative electron systems
Tremblay, Jean Christophe; Krause, Pascal; Klamroth, Tillmann; Saalfrank, Peter
2010-06-15
We present a systematic study of the influence of energy and phase relaxation on dynamic polarizability simulations in the linear response regime. The nonperturbative approach is based on explicit electron dynamics using short laser pulses of low intensities. To include environmental effects on the property calculation, we use the time-dependent configuration-interaction method in its reduced density matrix formulation. Both energy dissipation and nonlocal pure dephasing are included. The explicit treatment of time-resolved electron dynamics gives access to the phase shift between the electric field and the induced dipole moment, which can be used to define a useful uncertainty measure for the dynamic polarizability. The nonperturbative treatment is compared to perturbation theory expressions, as applied to a simple model system, the rigid H{sub 2} molecule. It is shown that both approaches are equivalent for low field intensities, but the time-dependent treatment provides complementary information on the phase of the induced dipole moment, which allows for the definition of an uncertainty associated with the computation of the dynamic polarizability in the linear response regime.
Granular matter and the time-dependent viscous eikonal equation
NASA Astrophysics Data System (ADS)
Hadeler, K. P.; Schieborn, Dirk
2012-03-01
Deposition of granular matter under gravity can be described by the well-known two-layer model for a standing and a rolling layer. Matter from sources enters the rolling layer which flows along the gradient of the standing layer and finally enters the standing layer via interaction of the two layers. From this system of two coupled hyperbolic partial differential equations a time-dependent viscous eikonal equation is derived as a limiting case for weak sources, a thin rolling layer and fast convection of the rolling layer. This equation, supplied with boundary conditions, describes the deposition of dry sand from evenly distributed sources onto a flat table with a vertical rim of variable height. The stationary problem can also be seen as an application of the method of vanishing viscosity to the eikonal equation. For certain types of interaction between the two layers the resulting eikonal equation can be transformed into a linear equation. This transformation yields additional insight into the problem.
Global Auroral Energy Deposition Compared with Magnetic Indices
NASA Technical Reports Server (NTRS)
Brittnacher, M. J.; Fillingim, M. O.; Elsen, R.; Parks, G. K.; Germany, G. A.; Spann, J. F., Jr.
1997-01-01
Measurement of the global rate of energy deposition in the ionosphere via auroral particle precipitation is one of the primary goals of the Polar UVI program and is an important component of the ISTP program. The instantaneous rate of energy deposition for the entire month of January 1997 has been calculated by applying models to the UVI images and is presented by Fillingim et al. in this session. Magnetic indices, such as Kp, AE, and Dst, which are sensitive to variations in magnetospheric current systems have been constructed from ground magnetometer measurements and employed as measures of activity. The systematic study of global energy deposition raises the possibility of constructing a global magnetospheric activity index explicitly based on particle precipitation to supplement magnetic indices derived from ground magnetometer measurements. The relationship between global magnetic activity as measured by these indices and the rate of total global energy loss due to precipitation is not known at present. We study the correlation of the traditional magnetic index of Kp for the month of January 1997 with the energy deposition derived from the UVI images. We address the question of whether the energy deposition through particle precipitation generally matches the Kp and AE indices, or the more exciting, but distinct, possibility that this particle-derived index may provide an somewhat independent measure of global magnetospheric activity that could supplement traditional magnetically-based activity indices.
Time-dependent onshore tsunami response
Apotsos, Alex; Gelfenbaum, Guy R.; Jaffe, Bruce E.
2012-01-01
While bulk measures of the onshore impact of a tsunami, including the maximum run-up elevation and inundation distance, are important for hazard planning, the temporal evolution of the onshore flow dynamics likely controls the extent of the onshore destruction and the erosion and deposition of sediment that occurs. However, the time-varying dynamics of actual tsunamis are even more difficult to measure in situ than the bulk parameters. Here, a numerical model based on the non-linear shallow water equations is used to examine the effects variations in the wave characteristics, bed slope, and bottom roughness have on the temporal evolution of the onshore flow. Model results indicate that the onshore flow dynamics vary significantly over the parameter space examined. For example, the flow dynamics over steep, smooth morphologies tend to be temporally symmetric, with similar magnitude velocities generated during the run-up and run-down phases of inundation. Conversely, on shallow, rough onshore topographies the flow dynamics tend to be temporally skewed toward the run-down phase of inundation, with the magnitude of the flow velocities during run-up and run-down being significantly different. Furthermore, for near-breaking tsunami waves inundating over steep topography, the flow velocity tends to accelerate almost instantaneously to a maximum and then decrease monotonically. Conversely, when very long waves inundate over shallow topography, the flow accelerates more slowly and can remain steady for a period of time before beginning to decelerate. These results indicate that a single set of assumptions concerning the onshore flow dynamics cannot be applied to all tsunamis, and site specific analyses may be required.
Time-dependent radiation dose estimations during interplanetary space flights
NASA Astrophysics Data System (ADS)
Dobynde, M. I.; Shprits, Y.; Drozdov, A.
2015-12-01
Time-dependent radiation dose estimations during interplanetary space flights 1,2Dobynde M.I., 2,3Drozdov A.Y., 2,4Shprits Y.Y.1Skolkovo institute of science and technology, Moscow, Russia 2University of California Los Angeles, Los Angeles, USA 3Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics, Moscow, Russia4Massachusetts Institute of Technology, Cambridge, USASpace radiation is the main restriction for long-term interplanetary space missions. It induces degradation of external components and propagates inside providing damage to internal environment. Space radiation particles and induced secondary particle showers can lead to variety of damage to astronauts in short- and long- term perspective. Contribution of two main sources of space radiation- Sun and out-of-heliosphere space varies in time in opposite phase due to the solar activity state. Currently the only habituated mission is the international interplanetary station that flights on the low Earth orbit. Besides station shell astronauts are protected with the Earth magnetosphere- a natural shield that prevents significant damage for all humanity. Current progress in space exploration tends to lead humanity out of magnetosphere bounds. With the current study we make estimations of spacecraft parameters and astronauts damage for long-term interplanetary flights. Applying time dependent model of GCR spectra and data on SEP spectra we show the time dependence of the radiation in a human phantom inside the shielding capsule. We pay attention to the shielding capsule design, looking for an optimal geometry parameters and materials. Different types of particles affect differently on the human providing more or less harm to the tissues. Incident particles provide a large amount of secondary particles while propagating through the shielding capsule. We make an attempt to find an optimal combination of shielding capsule parameters, namely material and thickness, that will effectively decrease
Simulation of proton-induced energy deposition in integrated circuits
NASA Technical Reports Server (NTRS)
Fernald, Kenneth W.; Kerns, Sherra E.
1988-01-01
A time-efficient simulation technique was developed for modeling the energy deposition by incident protons in modern integrated circuits. To avoid the excessive computer time required by many proton-effects simulators, a stochastic method was chosen to model the various physical effects responsible for energy deposition by incident protons. Using probability density functions to describe the nuclear reactions responsible for most proton-induced memory upsets, the simulator determines the probability of a proton hit depositing the energy necessary for circuit destabilization. This factor is combined with various circuit parameters to determine the expected error-rate in a given proton environment. An analysis of transient or dose-rate effects is also performed. A comparison to experimental energy-disposition data proves the simulator to be quite accurate for predicting the expected number of events in certain integrated circuits.
A nuclear fragmentation energy deposition model
NASA Technical Reports Server (NTRS)
Ngo, D. M.; Wilson, J. W.; Fogarty, T. N.; Buck, W. W.; Townsend, L. W. (Principal Investigator)
1991-01-01
A formalism for target fragment transport is presented with application to energy loss spectra in thin silicon devices. A nuclear data base is recommended that agrees well with the measurements of McNulty et al. using surface barrier detectors. High-energy events observed by McNulty et al., which are not predicted by intranuclear cascade models, are well represented by the present work.
Spin-orbit torque induced spike-timing dependent plasticity
NASA Astrophysics Data System (ADS)
Sengupta, Abhronil; Al Azim, Zubair; Fong, Xuanyao; Roy, Kaushik
2015-03-01
Nanoelectronic devices that mimic the functionality of synapses are a crucial requirement for performing cortical simulations of the brain. In this work, we propose a ferromagnet-heavy metal heterostructure that employs spin-orbit torque to implement spike-timing dependent plasticity. The proposed device offers the advantage of decoupled spike transmission and programming current paths, thereby leading to reliable operation during online learning. Possible arrangement of such devices in a crosspoint architecture can pave the way for ultra-dense neural networks. Simulation studies indicate that the device has the potential of achieving pico-Joule level energy consumption (maximum 2 pJ per synaptic event) which is comparable to the energy consumption for synaptic events in biological synapses.
External orthogonality in subsystem time-dependent density functional theory.
Chulhai, Dhabih V; Jensen, Lasse
2016-08-01
Subsystem density functional theory (subsystem DFT) is a DFT partitioning method that is exact in principle, but depends on approximations to the kinetic energy density functional (KEDF). One may avoid the use of approximate KEDFs by ensuring that the inter-subsystem molecular orbitals are orthogonal, termed external orthogonality (EO). We present a method that extends a subsystem DFT method, that includes EO, into the time-dependent DFT (TDDFT) regime. This method therefore removes the need for approximations to the kinetic energy potential and kernel, and we show that it can accurately reproduce the supermolecular TDDFT results for weakly and strongly coupled subsystems, and for systems with strongly overlapping densities (where KEDF approximations traditionally fail). PMID:26932176
Spin-orbit torque induced spike-timing dependent plasticity
Sengupta, Abhronil Al Azim, Zubair; Fong, Xuanyao; Roy, Kaushik
2015-03-02
Nanoelectronic devices that mimic the functionality of synapses are a crucial requirement for performing cortical simulations of the brain. In this work, we propose a ferromagnet-heavy metal heterostructure that employs spin-orbit torque to implement spike-timing dependent plasticity. The proposed device offers the advantage of decoupled spike transmission and programming current paths, thereby leading to reliable operation during online learning. Possible arrangement of such devices in a crosspoint architecture can pave the way for ultra-dense neural networks. Simulation studies indicate that the device has the potential of achieving pico-Joule level energy consumption (maximum 2 pJ per synaptic event) which is comparable to the energy consumption for synaptic events in biological synapses.
Time-dependent, optically thick accretion onto a black hole
NASA Technical Reports Server (NTRS)
Gilden, D. L.; Wheeler, J. C.
1980-01-01
A fully relativistic hydrodynamics code which incorporates diffusive radiation transport is used to study time-dependent, spherically symmetric, optically thick accretion onto a black hole. It is found that matter free-falls into the hole regardless of whether the diffusion time scale is longer or shorter than the dynamical time. Nonadiabatic heating due to magnetic field reconnection is included. The internal energy thus generated affects the flow in a purely relativistic way, again ensuring free-fall collapse of the inflowing matter. Any matter enveloping a black hole will thus be swallowed on a dynamical time scale with relatively small net release of energy. The inclusion of angular momentum will not necessarily affect this conclusion.
Time-dependent study of bit reset
NASA Astrophysics Data System (ADS)
Chiuchiú, D.
2015-02-01
In its most conservative formulation, the Landauer principle states that at least k_BT\\ln2 of heat must be produced to reset one bit. Theoretical derivations of this result for practical systems require complex mathematical tools; additionally, real experiments are sophisticated and sensitive. In the literature, it's then common practice to look for a global heat production of k_BT\\ln2 without further concern for heat exchanges at intermediate times. In this paper we want to recover such kind of description: we take a Brownian particle that moves in a bistable potential as bit. We then consider a reset protocol with a net heat production of k_BT\\ln{2} and study the time evolution of internal energy, work and heat. In particular, we show that these quantities are fully characterized by the changes that the protocol induces over the wells of the bistable potential.
Time-Dependent CP Asymmetries in b {yields} s Penguins
Miyake, H.
2006-07-11
We present measurements of time-dependent CP asymmetry parameters in B{sup 0} {yields} {phi}(1020)K{sup 0}, {eta}'K{sup 0}, K{sub S}{sup 0}K{sub S}{sup 0}K{sub S}{sup 0} K{sub S}{sup 0}, K{sub S}{sup 0}{pi}{sup 0}, f{sub 0}(980)K{sub S}{sup 0}, {omega}(782)K{sub S}{sup 0} and K{sup +}K{sup -}K{sub S}{sup 0} decays based on a sample of 386 x 106BB(bar sign) pairs collected at the {upsilon}(4S) resonance with the Belle detector at the KEKB energy asymmetric e+e- collider. These decays are dominated by the b {yields} s gluonic penguin transition and are sensitive to new CP-violating phases from physics beyond the standard model. One neutral meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying B meson is identified from its decay products. CP-violation parameters are obtained from the asymmetries in the distributions of the proper-time intervals between the two B decays. We also perform measurement of time-dependent CP asymmetry parameters in B{sup 0} {yields} K{sub S}{sup 0}{gamma} decay that is dominated by the b {yields} s radiative penguin.
Time-dependent behavior of passive skeletal muscle
NASA Astrophysics Data System (ADS)
Ahamed, T.; Rubin, M. B.; Trimmer, B. A.; Dorfmann, L.
2016-03-01
An isotropic three-dimensional nonlinear viscoelastic model is developed to simulate the time-dependent behavior of passive skeletal muscle. The development of the model is stimulated by experimental data that characterize the response during simple uniaxial stress cyclic loading and unloading. Of particular interest is the rate-dependent response, the recovery of muscle properties from the preconditioned to the unconditioned state and stress relaxation at constant stretch during loading and unloading. The model considers the material to be a composite of a nonlinear hyperelastic component in parallel with a nonlinear dissipative component. The strain energy and the corresponding stress measures are separated additively into hyperelastic and dissipative parts. In contrast to standard nonlinear inelastic models, here the dissipative component is modeled using an evolution equation that combines rate-independent and rate-dependent responses smoothly with no finite elastic range. Large deformation evolution equations for the distortional deformations in the elastic and in the dissipative component are presented. A robust, strongly objective numerical integration algorithm is used to model rate-dependent and rate-independent inelastic responses. The constitutive formulation is specialized to simulate the experimental data. The nonlinear viscoelastic model accurately represents the time-dependent passive response of skeletal muscle.
Electron energy deposition in carbon monoxide gas
NASA Technical Reports Server (NTRS)
Liu, Weihong; Victor, G. A.
1994-01-01
A comprehensive set of electron impact cross sections for carbon monoxide molecules is presented on the basis of the most recent experimental measurements and theoretical calculations. The processes by which energetic electrons lose energy in CO gas are analyzed with these input cross sections. The efficiencies are computed of vibrational and electronic excitation, dissociation, ionization, and heating for CO gas with fractional ionization ranging from 0% to 10%. The calculated mean energy per ion pair for neutral CO gas is 32.3 eV, which is in excellent agreement with the experimental value of 32.2 eV. It increases to 35.6 eV at a fractional ionization of 1%, typical of supernovae ejecta.
Transonic flow control by means of local energy deposition
NASA Astrophysics Data System (ADS)
Aul'Chenko, S. M.; Zamuraev, V. P.; Kalinina, A. P.
2011-11-01
Experimental data for the feasibility of transonic flow control by means of energy deposition are generalized. Energy supplied to the immediate vicinity of a body in stream before a compression shock is found to result in the nonlinear interaction of introduced disturbances with the shock and the surface in zones extended along the surface. A new, explosive gasdynamic mechanism behind the shift of the compression shock is discovered. It is shown that the nonlinear character of the interaction may considerably decrease the wave resistance of, e.g., transonic airfoils. It is found that energy supply from without stabilizes a transonic flow about an airfoil—the effect similar to the Khristianovich stabilization effect. The dependence of the energy deposition optimal frequency on the energy source parameters and Mach number of the incoming flow at which the resistance drops to the greatest extent is obtained. The influence of the real thermodynamic properties and viscosity of air is studied.
NASA Astrophysics Data System (ADS)
Bernasconi, Leonardo; Webster, Ross; Tomić, Stanko; Harrison, Nicholas M.
2012-05-01
We describe a unified formulation of time-dependent Hartree-Fock (TD-HF) and time-dependent density-functional theory (TD-DFT) for the accurate and efficient calculation of the optical response of infinite (periodic) systems. The method is formulated within the linear-response approximation, but it can easily be extended to include higher-order response contributions, and, in TD-DFT, it can treat with comparable computational efficiency purely local, semi-local or fully non-local approximations for the ground-state exchange-correlation (XC) functional and for the response TD-DFT XC kernel in the adiabatic approximation. At variance with existing methods for computing excitation energies based on the diagonalisation of suitable coupling matrices, or on the inversion of a dielectric matrix, our approach exploits an iterative procedure similar to a standard self-consistent field calculation. This results in a particularly efficient treatment of the coupling of excitations at different k points in the Brillouin zone. As a consequence, our method has the potential to describe completely from first principles the optically induced formation of bound particle-hole pairs in wide classes of materials. This point is illustrated by computing the optical gaps of a series of representative bulk semiconductors, (non-spin polarised) oxides and ionic insulators.
Subsystem real-time time dependent density functional theory
NASA Astrophysics Data System (ADS)
Krishtal, Alisa; Ceresoli, Davide; Pavanello, Michele
2015-04-01
We present the extension of Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) to real-time Time Dependent Density Functional Theory (rt-TDDFT). FDE is a DFT-in-DFT embedding method that allows to partition a larger Kohn-Sham system into a set of smaller, coupled Kohn-Sham systems. Additional to the computational advantage, FDE provides physical insight into the properties of embedded systems and the coupling interactions between them. The extension to rt-TDDFT is done straightforwardly by evolving the Kohn-Sham subsystems in time simultaneously, while updating the embedding potential between the systems at every time step. Two main applications are presented: the explicit excitation energy transfer in real time between subsystems is demonstrated for the case of the Na4 cluster and the effect of the embedding on optical spectra of coupled chromophores. In particular, the importance of including the full dynamic response in the embedding potential is demonstrated.
Fermion Mass Renormalization Using Time-dependent Relativistic Quantum Mechanics
NASA Astrophysics Data System (ADS)
Kutnink, Timothy; Santrach, Amelia; Hocket, Sarah; Barcus, Scott; Petridis, Athanasios
2015-10-01
The time-dependent electromagnetically self-coupled Dirac equation is solved numerically by means of the staggered-leap-frog algorithm with refcecting boundary conditions. The stability region of the method versus the interaction strength and the spatial-grid size over time-step ratio is established. The expectation values of several dynamic operators are then evaluated as functions of time. These include the fermion and electromagnetic energies and the fermion dynamic mass, as the self-interacting spinors are no longer mass-eigenfunctions. There is a characteristic, non-exponential, oscillatory dependence leading to asymptotic constants of these expectation values. In the case of the fermion mass this amounts to renormalization. The dependence of the expectation values on the spatial-grid size is evaluated in detail. Statistical regularization is proposed to remove the grid-size dependence.
Time-dependent corona models - A numerical method
NASA Astrophysics Data System (ADS)
Korevaar, P.; van Leer, B.
1988-07-01
A time-dependent numerical method for calculating gas flows is described. The method is implicit and especially suitable for finding stationary flow solutions. Although the method is general in its application to ideal compressible fluids, this paper applies it to a stellar atmosphere, heated to coronal temperatures by dissipation of mechanical energy. The integration scheme is based on conservative upwind spatial differencing. The upwind switching is provided by Van Leer's method of differentiable flux-splitting. It is shown that the code can handle large differences in density: up to 14 orders of magnitude. Special attention is paid to the boundary conditions, which are made completely transparent to disturbances. Besides some test-results, converged solutions for various values of the initial mechanical flux are presented which are in good agreement with previous time-independent calculations.
Cosmological consequences of a time-dependent Λ term
NASA Astrophysics Data System (ADS)
Carvalho, J. C.; Lima, J. A. S.; Waga, I.
1992-09-01
The phenomenological approach to investigate the decay of the effective cosmological constant, as recently proposed by Chen and Wu, is generalized to include a term proportional to H2 on the time dependence of Λ, where H is the Hubble parameter. This new term can modify some features of the standard Friedmann-Robertson-Walker model and its free parameter may be adjusted in accordance with nucleosynthesis constraints. The model also allows a deceleration parameter q0 assuming negative values so that the density parameter Ω0 is smaller than 2/3 and the age of the Universe is always bigger than H-10. In these cases, the usual matter creation rate appearing in models with a decaying vacuum energy is smaller than the one present in the steady-state model.
Hu Mei; Liu Xinguo; Tan Ruishan; Li Hongzheng; Xu Wenwu
2013-05-07
A new global potential energy surface for the ground electronic state (1{sup 2}A Prime ) of the Ar+H{sub 2}{sup +}{yields}ArH{sup +}+H reaction has been constructed by multi-reference configuration interaction method with Davidson correction and a basis set of aug-cc-pVQZ. Using 6080 ab initio single-point energies of all the regions for the dynamics, a many-body expansion function form has been used to fit these points. The quantum reactive scattering dynamics calculations taking into account the Coriolis coupling (CC) were carried out on the new potential energy surface over a range of collision energies (0.03-1.0 eV). The reaction probabilities and integral cross sections for the title reaction were calculated. The significance of including the CC quantum scattering calculation has been revealed by the comparison between the CC and the centrifugal sudden approximation calculation. The calculated cross section is in agreement with the experimental result at collision energy 1.0 eV.
Self-Consistent and Time-Dependent Solar Wind Models
NASA Technical Reports Server (NTRS)
Ong, K. K.; Musielak, Z. E.; Rosner, R.; Suess, S. T.; Sulkanen, M. E.
1997-01-01
We describe the first results from a self-consistent study of Alfven waves for the time-dependent, single-fluid magnetohydrodynamic (MHD) solar wind equations, using a modified version of the ZEUS MHD code. The wind models we examine are radially symmetrical and magnetized; the initial outflow is described by the standard Parker wind solution. Our study focuses on the effects of Alfven waves on the outflow and is based on solving the full set of the ideal nonlinear MHD equations. In contrast to previous studies, no assumptions regarding wave linearity, wave damping, and wave-flow interaction are made; thus, the models naturally account for the back-reaction of the wind on the waves, as well as for the nonlinear interaction between different types of MHD waves. Our results clearly demonstrate when momentum deposition by Alfven waves in the solar wind can be sufficient to explain the origin of fast streams in solar coronal holes; we discuss the range of wave amplitudes required to obtained such fast stream solutions.
Nuclear stopping and energy deposition into the central rapidity region
Zingman, J.A.
1987-08-03
Nuclear stopping and energy deposition into the central rapidity region of ultrarelativistic heavy-ion collisions are studied through the application of a model incorporating hydrodynamic baryon flow coupled to a self-consistent field calculated in the flux tube model. Ultrarelativistic heavy ion collisions are modeled in which the nuclei have passed through each other and as a result are charged and heated.
Gamma-ray transfer and energy deposition in supernovae
NASA Technical Reports Server (NTRS)
Swartz, Douglas A.; Sutherland, Peter G.; Harkness, Robert P.
1995-01-01
Solutions to the energy-independent (gray) radiative transfer equations are compared to results of Monte Carlo simulations of the Ni-56 and Co-56 decay gamma-ray energy deposition in supernovae. The comparison shows that an effective, purely absorptive, gray opacity, kappa(sub gamma) approximately (0. 06 +/- 0.01)Y(sub e) sq cm/g, where Y is the total number of electrons per baryon, accurately describes the interaction of gamma-rays with the cool supernova gas and the local gamma-ray energy deposition within the gas. The nature of the gamma-ray interaction process (dominated by Compton scattering in the relativistic regime) creates a weak dependence of kappa(sub gamma) on the optical thickness of the (spherically symmetric) supernova atmosphere: The maximum value of kappa(sub gamma) applies during optically thick conditions when individual gamma-rays undergo multiple scattering encounters and the lower bound is reached at the phase characterized by a total Thomson optical depth to the center of the atmosphere tau(sub e) approximately less than 1. Gamma-ray deposition for Type Ia supernova models to within 10% for the epoch from maximum light to t = 1200 days. Our results quantitatively confirm that the quick and efficient solution to the gray transfer problem provides an accurate representation of gamma-ray energy deposition for a broad range of supernova conditions.
Estimating regional auroral electron energy deposition using ground-based optical measurements
NASA Astrophysics Data System (ADS)
Hampton, D. L.; Conde, M.; Ahrns, M. J.; Bristow, W.; Lynch, K. A.; Zettergren, M. D.
2014-12-01
Two key parameters for understanding the coupling between the magnetosphere and the thermosphere/ionosphere in polar regions are the characteristic energy and the total energy flux of precipitating auroral electrons. Ionization due to precipitating electrons modifies the ionospheric electron density profile and thereby the height-dependent conductivity in a complex manner in both time and space. Global or regional thermospheric dynamics models typically rely on empirical models (Ovation) or low-resolution global EUV imagery (POLAR) for electron precipitation input which smear out the mesoscale detail of the location and timing of auroral arcs. We have developed a method for measuring the time-dependent auroral electron energy deposition over a several-hundred km range with 25 km resolution using a combination of two ground-based optical instruments - a scanning-doppler imager observing green-line temperatures and a filtered all-sky imager measuring the N2+ first negative emission at 427.8 nm. We will discuss the details of the method, and show several examples including those from the MICA sounding rocket experiment as well as several events from the AMISR PINOT campaign. We will also show comparisons with alternate optical and radar techniques, compare our estimated energy flux to those from Ovation, and discuss limitations and advantages of the technique when examining mesoscale dynamics in the auroral zone.
Time-dependent radiation hazard estimations during space flights
NASA Astrophysics Data System (ADS)
Dobynde, Mikhail; Shprits, Yuri; Drozdov, Alexander
Cosmic particle radiation is a limiting factor for the out of magnetosphere crewed flights. The cosmic radiation uncrewed flights inside heliosphere and crewed flights inside of magnetosphere tend to become a routine procedure, whereas there have been only few shot time flights out of it (Apollo missions 1969-1972) with maximum duration less than a month. Long term crewed missions set much higher requirements to the radiation shielding, primarily because of long exposition term. Inside the helosphere there are two main sources of cosmic radiation: galactic cosmic rays (GCR) and coronal mass ejections (CME). GCR come from the outside of heliosphere forming a background of overall radiation that affects the spacecraft. The intensity of GCR is varied according to solar activity, increasing with solar activity decrease and backward, with the modulation time (time between nearest maxima) of 11 yeas. CME are shot term events, comparing to GCR modulation time, but are much more energetic. The probability of CME increases with the increase of solar activity. Time dependences of the intensity of these two components encourage looking for a time window of flight, when intensity and affection of CME and GCR would be minimized. Applying time dependent models of GCR spectra [1] and estimations of CME we show the time dependence of the radiation dose in a realistic human phantom [2] inside the shielding capsule. We pay attention to the shielding capsule design, looking for an optimal geometry parameters and materials. Different types of particles affect differently on the human providing more or less harm to the tissues. Incident particles provide a large amount of secondary particles while propagating through the shielding capsule. We make an attempt to find an optimal combination of shielding capsule parameters, namely material and thickness, that will effectively decrease the incident particle energy, at the same time minimizing flow of secondary induced particles and
Cumulative beam breakup in linear accelerators with time-dependent parameters
Jean Delayen
2004-10-01
A formalism presented in a previous paper for the analysis of cumulative beam breakup (BBU) with arbitrary time dependence of the beam current and with misalignment of the cavities and focusing elements [J. R. Delayen, Phys. Rev. ST Accel. Beams 6, 084402 (2003)] is extended to include time dependence of the focusing and coupling between the beam and the dipole modes. Such time dependence, which could result from an energy chirp imposed on the beam or from rf focusing, is known to be effective in reducing BBU-induced instabilities and emittance growth. The analytical results are presented and applied to practical accelerator configurations and compared to numerical simulations.
Kull; Pfirsch
2000-05-01
The time-dependent Hartree-Fock equations are derived from a variational principle for the general N-body action of a Slater determinant of single-electron orbitals. The variational principle generalizes commonly used variational treatments based on reduced two-body actions. The self-consistent field equations are found to contain time-dependent corrections to the standard mean-field interactions. Their physical significance is discussed and a time-dependent phase shift to the Slater determinant is obtained that properly accounts for the total interaction energy in the mean-field approach. PMID:11031657
Solution of the time-dependent Schrödinger equation using time-dependent basis functions.
Varga, Kálmán
2012-01-01
The time-dependent Schrödinger equation is solved by using an explicitly time-dependent basis. This approach allows efficient reflection-free time propagation of the wave function. The applicability of the method is illustrated by solving various time-dependent problems including the calculation of the above threshold ionization of a model atom and the optical absorption spectrum of a sodium dimer. PMID:22400699
Dirac equation with some time-dependent electromagnetic terms
NASA Astrophysics Data System (ADS)
Saeedi, K.; Zarrinkamar, S.; Hassanabadi, H.
2016-07-01
We study the motion of relativistic fermions in a time-dependent electromagnetic field within the framework of Dirac equation. We consider the time-dependent scalar potential of the exponential form and the vector potential of linear form. We obtain the eigenfunctions and eigenvalues.
Time-dependent simulations of disk-embedded planetary atmospheres
NASA Astrophysics Data System (ADS)
Stökl, A.; Dorfi, E. A.
2014-03-01
At the early stages of evolution of planetary systems, young Earth-like planets still embedded in the protoplanetary disk accumulate disk gas gravitationally into planetary atmospheres. The established way to study such atmospheres are hydrostatic models, even though in many cases the assumption of stationarity is unlikely to be fulfilled. Furthermore, such models rely on the specification of a planetary luminosity, attributed to a continuous, highly uncertain accretion of planetesimals onto the surface of the solid core. We present for the first time time-dependent, dynamic simulations of the accretion of nebula gas into an atmosphere around a proto-planet and the evolution of such embedded atmospheres while integrating the thermal energy budget of the solid core. The spherical symmetric models computed with the TAPIR-Code (short for The adaptive, implicit RHD-Code) range from the surface of the rocky core up to the Hill radius where the surrounding protoplanetary disk provides the boundary conditions. The TAPIR-Code includes the hydrodynamics equations, gray radiative transport and convective energy transport. The results indicate that diskembedded planetary atmospheres evolve along comparatively simple outlines and in particular settle, dependent on the mass of the solid core, at characteristic surface temperatures and planetary luminosities, quite independent on numerical parameters and initial conditions. For sufficiently massive cores, this evolution ultimately also leads to runaway accretion and the formation of a gas planet.
Time-dependent density functional theory of extreme environments
NASA Astrophysics Data System (ADS)
Shulenburger, Luke; Desjarlais, Michael; Magyar, Rudolph
2013-04-01
We describe the challenges involved when using time-dependent density functional theory (TDDFT) to describe warm dense matter (WDM) within a plane-wave, real-time formulation. WDM occurs under conditions of temperature and pressure (over 1000 K and 1 Mbar) where plasma physics meets condensed matter physics. TDDFT is especially important in this regime as it can describe ions and electrons strongly out of equilibrium. Several theoretical challenges must be overcome including assignment of initial state orbitals, choice of time-propogation scheme, treatment of PAW potentials, and inclusion of non-adiabatic effects in the potential energy surfaces. The results of these simulations are critical in several applications. For example, we will explain how the TDDFT calculation can resolve modeling inconsistencies in X-ray Thompson cross-sections, thereby improving an important temperature diagnostic in experiments. 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.
BEAM INDUCED ENERGY DEPOSITION IN MUON STORAGE RINGS.
MOKHOV,N.V.; JOHNSTONE,C.J.; PARKER,B.L.
2001-06-18
Beam-induced radiation effects have been simulated for 20 and 50 GeV muon storage rings designed for a Neutrino Factory. It is shown that by appropriately shielding the superconducting magnets, quench stability, acceptable dynamic heat loads, and low residual dose rates can be achieved. Alternatively, if a specially-designed skew focusing magnet without superconducting coils on the magnet's mid-plane is used, then the energy is deposited preferentially in the warm iron yoke or outer cryostat layers and internal shielding may not be required. In addition to the component irradiation analysis, shielding studies have been performed. Calculations of the external radiation were done for both designs but the internal energy deposition calculations for the 20 GeV Study-2 lattice are still in progress.
Beam-induced energy deposition in muon storage rings
Nikolai V. Mokhov; Carol J. Johnstone; Brett Parker
2001-06-22
Beam-induced radiation effects have been simulated for 20 and 50 GeV muon storage rings designed for a Neutrino Factory. It is shown that by appropriately shielding the superconducting magnets, quench stability, acceptable dynamic heat loads, and low residual dose rates can be achieved. Alternatively, if a specially-designed skew focusing magnet without superconducting coils on the magnet's mid-plane is used, then the energy is deposited preferentially in the warm iron yoke or outer cryostat layers and internal shielding may not be required. In addition to the component irradiation analysis, shielding studies have been performed. Calculations of the external radiation were done for both designs but the internal energy deposition calculations for the 20 GeV Study-2 lattice are still in progress.
Time-dependent potential-functional embedding theory
Huang, Chen; Libisch, Florian; Carter, Emily A.
2014-03-28
We introduce a time-dependent potential-functional embedding theory (TD-PFET), in which atoms are grouped into subsystems. In TD-PFET, subsystems can be propagated by different suitable time-dependent quantum mechanical methods and their interactions can be treated in a seamless, first-principles manner. TD-PFET is formulated based on the time-dependent quantum mechanics variational principle. The action of the total quantum system is written as a functional of the time-dependent embedding potential, i.e., a potential-functional formulation. By exploiting the Runge-Gross theorem, we prove the uniqueness of the time-dependent embedding potential under the constraint that all subsystems share a common embedding potential. We derive the integral equation that such an embedding potential needs to satisfy. As proof-of-principle, we demonstrate TD-PFET for a Na{sub 4} cluster, in which each Na atom is treated as one subsystem and propagated by time-dependent Kohn-Sham density functional theory (TDDFT) using the adiabatic local density approximation (ALDA). Our results agree well with a direct TDDFT calculation on the whole Na{sub 4} cluster using ALDA. We envision that TD-PFET will ultimately be useful for studying ultrafast quantum dynamics in condensed matter, where key regions are solved by highly accurate time-dependent quantum mechanics methods, and unimportant regions are solved by faster, less accurate methods.
Critical energy deposit in heavy ion complete fusion
Fonte, R.; Insolia, A. Dipartimento di Fisica dell'Universita di Catania corso Italia, 57-95129 Catania, Italy)
1991-07-01
In the framework of an {ital l}-window model for complete fusion reactions within a sharp cutoff approximation, the problem of the maximum excitation energy which can be deposited in a compound nucleus is discussed. Predictions about the spin distribution of the compound nucleus are compared with the conclusions of a recent analysis of the {sup 28}Si+{sup 28}Si fusion reaction.
Monte Carlo simulation of energy deposition by low-energy electrons in molecular hydrogen
NASA Technical Reports Server (NTRS)
Heaps, M. G.; Furman, D. R.; Green, A. E. S.
1975-01-01
A set of detailed atomic cross sections has been used to obtain the spatial deposition of energy by 1-20-eV electrons in molecular hydrogen by a Monte Carlo simulation of the actual trajectories. The energy deposition curve (energy per distance traversed) is quite peaked in the forward direction about the entry point for electrons with energies above the threshold of the electronic states, but the peak decreases and broadens noticeably as the electron energy decreases below 10 eV (threshold for the lowest excitable electronic state of H2). The curve also assumes a very symmetrical shape for energies below 10 eV, indicating the increasing importance of elastic collisions in determining the shape of the curve, although not the mode of energy deposition.
Synchronization of rigid microrotors by time-dependent hydrodynamic interactions.
Theers, Mario; Winkler, Roland G
2013-08-01
We investigate the emergent dynamical behavior of hydrodynamically coupled microrotors. The two rotors are confined in a plane and move along circles driven by active forces. The three-dimensional fluid is described by the linearized, time-dependent Navier-Stokes equations instead of the usually adopted Stokes equations. We demonstrate that time-dependent hydrodynamic interactions lead to synchronization of the rotational motion. The time dependence of the phase difference between the rotors is determined and synchronization times are extracted for various external torques and rotor separations by solving the underlaying integrodifferential equations numerically. In addition, an analytical expression is provided for the synchronization time. PMID:24032929
Time-dependent-S-matrix Hartree-Fock theory of complex reactions
NASA Astrophysics Data System (ADS)
Griffin, James J.; Lichtner, Peter C.; Dworzecka, Maria
1980-04-01
Some limitations of the conventional time-dependent Hartree-Fock method for describing complex reactions are noted, and one particular ubiquitous defect is discussed in detail: the post-breakup spurious cross channel correlations which arise whenever several asymptotic reaction channels must be simultaneously described by a single determinant. A reformulated time-dependent-S-matrix Hartree-Fock theory is proposed, which obviates this difficulty. Axiomatic requirements minimal to assure that the time-dependent-S-matrix Hartree-Fock theory represents an unambiguous and physically interpretable asymptotic reaction theory are utilized to prescribe conditions upon the definition of acceptable asymptotic channels. That definition, in turn, defines the physical range of the time-dependent-S-matrix Hartree-Fock theory to encompass the collisions of mathematically well-defined "time-dependent Hartree-Fock droplets." The physical properties of these objects then circumscribe the content of the Hartree-Fock single determinantal description. If their periodic vibrations occur for continuous ranges of energy then the resulting "classical" time-dependent Hartree-Fock droplets are seen to be intrinsically dissipative, and the single determinantal description of their collisions reduces to a "trajectory" theory which can describe the masses and relative motions of the fragments but can provide no information about specific asymptotic excited states beyond their constants of motion, or the average properties of the limit, if it exists, of their equilibrization process. If, on the other hand, the periodic vibrations of the time-dependent Hartree-Fock droplets are discrete in energy, then the time-dependent-S-matrix Hartree-Fock theory can describe asymptotically the time-average properties of the whole spectrum of such periodic vibrations of these "quantized" time-dependent Hartree-Fock droplets which are asymptotically stationary on a time-averaged basis. Such quantized time-dependent
Time-dependent buoyant puff model for explosive sources
Kansa, E.J.
1997-10-01
This paper presents a new model for explosive puff rise histories that is derived from the strong conservative form of the partial differential equations of mass, momenta, and total energy that are integrated over space to yield a coupled system of time dependent nonlinear ordinary differential equations (ODEs). By allowing the dimensions of the puff to evolve laterally and horizontally, the initial rising spherical shaped puff evolves into a rising ellipsoidal shaped mushroom cloud. This model treats the turbulence that is generated by the puff itself and the ambient atmospheric turbulence as separate mechanisms in determining the puff history. The puff rise history was found to depend not only upon the mass and initial temperature of the explosion, but also upon the local stability conditions of the ambient atmosphere through which the puff rises. This model was calibrated by comparison with the Roller Coaster experiments, ranging from unstable to very stable atmospheric conditions; the agreement of the model history curves with these experimental curves was within 10%.
Subsystem real-time time dependent density functional theory.
Krishtal, Alisa; Ceresoli, Davide; Pavanello, Michele
2015-04-21
We present the extension of Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) to real-time Time Dependent Density Functional Theory (rt-TDDFT). FDE is a DFT-in-DFT embedding method that allows to partition a larger Kohn-Sham system into a set of smaller, coupled Kohn-Sham systems. Additional to the computational advantage, FDE provides physical insight into the properties of embedded systems and the coupling interactions between them. The extension to rt-TDDFT is done straightforwardly by evolving the Kohn-Sham subsystems in time simultaneously, while updating the embedding potential between the systems at every time step. Two main applications are presented: the explicit excitation energy transfer in real time between subsystems is demonstrated for the case of the Na4 cluster and the effect of the embedding on optical spectra of coupled chromophores. In particular, the importance of including the full dynamic response in the embedding potential is demonstrated. PMID:25903875
Time-Dependent, Parallel Neutral Particle Transport Code System.
2009-09-10
Version 00 PARTISN (PARallel, TIme-Dependent SN) is the evolutionary successor to CCC-547/DANTSYS. The PARTISN code package is a modular computer program package designed to solve the time-independent or dependent multigroup discrete ordinates form of the Boltzmann transport equation in several different geometries. The modular construction of the package separates the input processing, the transport equation solving, and the post processing (or edit) functions into distinct code modules: the Input Module, the Solver Module, and themore » Edit Module, respectively. PARTISN is the evolutionary successor to the DANTSYSTM code system package. The Input and Edit Modules in PARTISN are very similar to those in DANTSYS. However, unlike DANTSYS, the Solver Module in PARTISN contains one, two, and three-dimensional solvers in a single module. In addition to the diamond-differencing method, the Solver Module also has Adaptive Weighted Diamond-Differencing (AWDD), Linear Discontinuous (LD), and Exponential Discontinuous (ED) spatial differencing methods. The spatial mesh may consist of either a standard orthogonal mesh or a block adaptive orthogonal mesh. The Solver Module may be run in parallel for two and three dimensional problems. One can now run 1-D problems in parallel using Energy Domain Decomposition (triggered by Block 5 input keyword npeg>0). EDD can also be used in 2-D/3-D with or without our standard Spatial Domain Decomposition. Both the static (fixed source or eigenvalue) and time-dependent forms of the transport equation are solved in forward or adjoint mode. In addition, PARTISN now has a probabilistic mode for Probability of Initiation (static) and Probability of Survival (dynamic) calculations. Vacuum, reflective, periodic, white, or inhomogeneous boundary conditions are solved. General anisotropic scattering and inhomogeneous sources are permitted. PARTISN solves the transport equation on orthogonal (single level or block-structured AMR) grids in 1-D
Functional differentiability in time-dependent quantum mechanics
Penz, Markus Ruggenthaler, Michael
2015-03-28
In this work, we investigate the functional differentiability of the time-dependent many-body wave function and of derived quantities with respect to time-dependent potentials. For properly chosen Banach spaces of potentials and wave functions, Fréchet differentiability is proven. From this follows an estimate for the difference of two solutions to the time-dependent Schrödinger equation that evolve under the influence of different potentials. Such results can be applied directly to the one-particle density and to bounded operators, and present a rigorous formulation of non-equilibrium linear-response theory where the usual Lehmann representation of the linear-response kernel is not valid. Further, the Fréchet differentiability of the wave function provides a new route towards proving basic properties of time-dependent density-functional theory.
Time-dependent rheological behaviour of bacterial cellulose hydrogel.
Gao, Xing; Shi, Zhijun; Kuśmierczyk, Piotr; Liu, Changqing; Yang, Guang; Sevostianov, Igor; Silberschmidt, Vadim V
2016-01-01
This work focuses on time-dependent rheological behaviour of bacterial cellulose (BC) hydrogel. Due to its ideal biocompatibility, BC hydrogel could be employed in biomedical applications. Considering the complexity of loading conditions in human body environment, time-dependent behaviour under relevant conditions should be understood. BC specimens are produced by Gluconacetobacter xylinus ATCC 53582 at static-culture conditions. Time-dependent behaviour of specimens at several stress levels is experimentally determined by uniaxial tensile creep tests. We use fraction-exponential operators to model the rheological behaviour. Such a representation allows combination of good accuracy in analytical description of viscoelastic behaviour of real materials and simplicity in solving boundary value problems. The obtained material parameters allow us to identify time-dependent behaviour of BC hydrogel at high stress level with sufficient accuracy. PMID:26478298
Quantum Drude friction for time-dependent density functional theory
NASA Astrophysics Data System (ADS)
Neuhauser, Daniel; Lopata, Kenneth
2008-10-01
way to very simple finite grid description of scattering and multistage conductance using time-dependent density functional theory away from the linear regime, just as absorbing potentials and self-energies are useful for noninteracting systems and leads.
Time-dependent {P} {T}-symmetric quantum mechanics
NASA Astrophysics Data System (ADS)
Gong, Jiangbin; Wang, Qing-hai
2013-12-01
The parity-time-reversal ( {P} {T})-symmetric quantum mechanics (QM) (PTQM) has developed into a noteworthy area of research. However, to date, most known studies of PTQM focused on the spectral properties of non-Hermitian Hamiltonian operators. In this work, we propose an axiom in PTQM in order to study general time-dependent problems in PTQM, e.g., those with a time-dependent {P} {T}-symmetric Hamiltonian and with a time-dependent metric. We illuminate our proposal by examining a proper mapping from a time-dependent Schrödinger-like equation of motion for PTQM to the familiar time-dependent Schrödinger equation in conventional QM. The rich structure of the proper mapping hints that time-dependent PTQM can be a fruitful extension of conventional QM. Under our proposed framework, we further study in detail the Berry-phase generation in a class of {P} {T}-symmetric two-level systems. It is found that a closed path in the parameter space of PTQM is often associated with an open path in a properly mapped problem in conventional QM. In one interesting case, we further interpret the Berry phase as the flux of a continuously tunable fictitious magnetic monopole, thus highlighting the difference between PTQM and conventional QM despite the existence of a proper mapping between them.
Relativistic Coulomb excitation within the time dependent superfluid local density approximation
Stetcu, I.; Bertulani, C. A.; Bulgac, A.; Magierski, P.; Roche, K. J.
2015-01-06
Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus 238U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, themore » dipole pygmy resonance, and giant quadrupole modes are excited during the process. As a result, the one-body dissipation of collective dipole modes is shown to lead a damping width Γ↓≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.« less
Time-dependent crack growth behavior of alloy 617 and alloy 230 at elevated temperatures
NASA Astrophysics Data System (ADS)
Roy, Shawoon Kumar
2011-12-01
Two Ni-base solid-solution-strengthened superalloys: INCONEL 617 and HAYNES 230 were studied to check sustained loading crack growth (SLCG) behavior at elevated temperatures appropriate for Next Generation Nuclear Plant (NGNP) applictaions with constant stress intensity factor (Kmax= 27.75 MPa✓m) in air. The results indicate a time-dependent rate controlling process which can be characterized by a linear elastic fracture mechanics (LEFM) parameter -- stress intensity factor (K). At elevated temperatures, the crack growth mechanism was best described using a damage zone concept. Based on results and study, SAGBOE (stress accelerated grain boundary oxidation embrittlement) is considered the primary reason for time-dependent SLCG. A thermodynamic equation was considered to correlate all the SLCG results to determine the thermal activation energy in the process. A phenomenological model based on a time-dependent factor was developed considering the previous researcher's time-dependent fatigue crack propagation (FCP) results and current SLCG results to relate cycle-dependent and time-dependent FCP for both alloys. Further study includes hold time (3+300s) fatigue testing and no hold (1s) fatigue testing with various load ratios (R) at 700°C with a Kmax of 27.75 MPa✓m. Study results suggest an interesting point: crack growth behavior is significantly affected with the change in R value in cycle-dependent process whereas in time-dependent process, change in R does not have any significant effect. Fractography study showed intergranular cracking mode for all time-dependent processes and transgranular cracking mode for cycle-dependent processes. In Alloy 230, SEM images display intergranular cracking with carbide particles, dense oxides and dimple mixed secondary cracks for time-dependent 3+300s FCP and SLCG test. In all cases, Alloy 230 shows better crack growth resistance compared to Alloy 617.
Feinberg-Horodecki states of a time-dependent mass distribution harmonic oscillator
NASA Astrophysics Data System (ADS)
Eshghi, M.; Sever, R.; Ikhdair, S. M.
2016-07-01
The solution of the Feinberg-Horodecki (FH) equation for a time-dependent mass (TDM) harmonic oscillator quantum system is studied. A certain interaction is applied to a mass m(t) to provide a particular spectrum of stationary energies. The related spectrum of the harmonic oscillator potential V(t) acting on the TDM m(t) oscillators is found. We apply the time version of the asymptotic iteration method (AIM) to calculate analytical expressions of the TDM stationary state energies and their wave functions. It is shown that the obtained solutions reduce to those of simple harmonic oscillator as the time-dependent mass reduces to m0.
Information theories for time-dependent harmonic oscillator
Choi, Jeong Ryeol; Kim, Min-Soo; Kim, Daeyeoul; Maamache, Mustapha; Menouar, Salah; Nahm, In Hyun
2011-06-15
Highlights: > Information theories for the general time-dependent harmonic oscillator based on invariant operator method. > Time dependence of entropies and entropic uncertainty relation. > Characteristics of Shannon information and Fisher information. > Application of information theories to particular systems that have time-dependent behavior. - Abstract: Information theories for the general time-dependent harmonic oscillator are described on the basis of invariant operator method. We obtained entropic uncertainty relation of the system and discussed whether it is always larger than or equal to the physically allowed minimum value. Shannon information and Fisher information are derived by means of density operator that satisfies Liouville-von Neumann equation and their characteristics are investigated. Shannon information is independent of time, but Fisher information is explicitly dependent on time as the time functions of the Hamiltonian vary. We can regard that the Fisher information is a local measure since its time behavior is largely affected by local arrangements of the density, whilst the Shannon information plays the role of a global measure of the spreading of density. To promote the understanding, our theory is applied to special systems, the so-called quantum oscillator with time-dependent frequency and strongly pulsating mass system.
Energy Deposition and Radiological Studies for the LBNF Hadron Absorber
Rakhno, I. L.; Mokhov, N. V.; Tropin, I. S.; Eidelman, Y. I.
2015-06-25
Results of detailed Monte Carlo energy deposition and radiological studies performed for the LBNF hadron absorber with the MARS15 code are described. The model of the entire facility, that includes a pion-production target, focusing horns, target chase, decay channel, hadron absorber system – all with corresponding radiation shielding – was developed using the recently implemented ROOT-based geometry option in the MARS15 code. Both normal operation and accidental conditions were studied. Results of detailed thermal calculations with the ANSYS code helped to select the most viable design options.
Atomic Layer Deposition of Bismuth Vanadates for Solar Energy Materials.
Stefik, Morgan
2016-07-01
The fabrication of porous nanocomposites is key to the advancement of energy conversion and storage devices that interface with electrolytes. Bismuth vanadate, BiVO4 , is a promising oxide for solar water splitting where the controlled fabrication of BiVO4 layers within porous, conducting scaffolds has remained a challenge. Here, the atomic layer deposition of bismuth vanadates is reported from BiPh3 , vanadium(V) oxytriisopropoxide, and water. The resulting films have tunable stoichiometry and may be crystallized to form the photoactive scheelite structure of BiVO4 . A selective etching process was used with vanadium-rich depositions to enable the synthesis of phase-pure BiVO4 after spinodal decomposition. BiVO4 thin films were measured for photoelectrochemical performance under AM 1.5 illumination. The average photocurrents were 1.17 mA cm(-2) at 1.23 V versus the reversible hydrogen electrode using a hole-scavenging sulfite electrolyte. The capability to deposit conformal bismuth vanadates will enable a new generation of nanocomposite architectures for solar water splitting. PMID:27246652
Metting, N.F.; Braby, L.A.; Rossi, H.H.; Kliauga, P.J.; Howard, J.; Schimmerling, W.; Wong, M.; Rapkin, M.
1986-08-01
The microscopic spatial distribution of energy deposition in irradiated tissue plays a significant role in the final biological effect produced. Therefore, it is important to have accurate microdosimetric spectra of radiation fields used for radiobiology and radiotherapy. The experiments desribed here were designed to measure the distributions of energy deposition around high energy heavy ion tracks generated at Lawrence Berkeley Laboratory's Bevalac Biomedical Facility. A small proportional counter mounted in a large (0.6 by 2.5 m) vacuum chamber was used to measure energy deposition distributions as a function of the distance between detector and primary ion track. The microdosimetric distributions for a homogeneous radiation field were then calculated by integrating over radial distance. This thesis discusses the rationale of the experimental design and the analysis of measurements on 600 MeV/amu iron tracks. 53 refs., 19 figs.
The computational foundations of time dependent density functional theory
NASA Astrophysics Data System (ADS)
Whitfield, James
2014-03-01
The mathematical foundations of TDDFT are established through the formal existence of a fictitious non-interacting system (known as the Kohn-Sham system), which can reproduce the one-electron reduced probability density of the actual system. We build upon these works and show that on the interior of the domain of existence, the Kohn-Sham system can be efficiently obtained given the time-dependent density. Since a quantum computer can efficiently produce such time-dependent densities, we present a polynomial time quantum algorithm to generate the time-dependent Kohn-Sham potential with controllable error bounds. Further, we find that systems do not immediately become non-representable but rather become ill-representable as one approaches this boundary. A representability parameter is defined in our work which quantifies the distance to the boundary of representability and the computational difficulty of finding the Kohn-Sham system.
Computational complexity of time-dependent density functional theory
NASA Astrophysics Data System (ADS)
Whitfield, J. D.; Yung, M.-H.; Tempel, D. G.; Boixo, S.; Aspuru-Guzik, A.
2014-08-01
Time-dependent density functional theory (TDDFT) is rapidly emerging as a premier method for solving dynamical many-body problems in physics and chemistry. The mathematical foundations of TDDFT are established through the formal existence of a fictitious non-interacting system (known as the Kohn-Sham system), which can reproduce the one-electron reduced probability density of the actual system. We build upon these works and show that on the interior of the domain of existence, the Kohn-Sham system can be efficiently obtained given the time-dependent density. We introduce a V-representability parameter which diverges at the boundary of the existence domain and serves to quantify the numerical difficulty of constructing the Kohn-Sham potential. For bounded values of V-representability, we present a polynomial time quantum algorithm to generate the time-dependent Kohn-Sham potential with controllable error bounds.
Handling Time-dependent Variables: Antibiotics and Antibiotic Resistance.
Munoz-Price, L Silvia; Frencken, Jos F; Tarima, Sergey; Bonten, Marc
2016-06-15
Elucidating quantitative associations between antibiotic exposure and antibiotic resistance development is important. In the absence of randomized trials, observational studies are the next best alternative to derive such estimates. Yet, as antibiotics are prescribed for varying time periods, antibiotics constitute time-dependent exposures. Cox regression models are suited for determining such associations. After explaining the concepts of hazard, hazard ratio, and proportional hazards, the effects of treating antibiotic exposure as fixed or time-dependent variables are illustrated and discussed. Wider acceptance of these techniques will improve quantification of the effects of antibiotics on antibiotic resistance development and provide better evidence for guideline recommendations. PMID:27025824
Two-stream instability with time-dependent drift velocity
Qin, Hong; Davidson, Ronald C.
2014-06-15
The classical two-stream instability driven by a constant relative drift velocity between two plasma components is extended to the case with time-dependent drift velocity. A solution method is developed to rigorously define and calculate the instability growth rate for linear perturbations relative to the time-dependent unperturbed two-stream motions. Stability diagrams for the oscillating two-stream instability are presented over a large region of parameter space. It is shown that the growth rate for the classical two-stream instability can be significantly reduced by adding an oscillatory component to the relative drift velocity.
Two-stream instability with time-dependent drift velocity
Qin, Hong; Davidson, Ronald C.
2014-06-26
The classical two-stream instability driven by a constant relative drift velocity between two plasma components is extended to the case with time-dependent drift velocity. A solution method is developed to rigorously define and calculate the instability growth rate for linear perturbations relative to the time-dependent unperturbed two-stream motions. The stability diagrams for the oscillating two-stream instability are presented over a large region of parameter space. It is shown that the growth rate for the classical two-stream instability can be significantly reduced by adding an oscillatory component to the relative drift velocity.
Choice of Variables and Preconditioning for Time Dependent Problems
NASA Technical Reports Server (NTRS)
Turkel, Eli; Vatsa, Verr N.
2003-01-01
We consider the use of low speed preconditioning for time dependent problems. These are solved using a dual time step approach. We consider the effect of this dual time step on the parameter of the low speed preconditioning. In addition, we compare the use of two sets of variables, conservation and primitive variables, to solve the system. We show the effect of these choices on both the convergence to a steady state and the accuracy of the numerical solutions for low Mach number steady state and time dependent flows.
Time Dependence of Joint Entropy of Oscillating Quantum Systems
NASA Astrophysics Data System (ADS)
Özcan, Özgür; Aktürk, Ethem; Sever, Ramazan
2008-12-01
The time dependent entropy (or Leipnik’s entropy) of harmonic and damped harmonic oscillator systems is studied by using time dependent wave function obtained by the Feynman path integral method. The Leipnik entropy and its envelope change as a function of time, angular frequency and damping factor. Our results for simple harmonic oscillator are in agreement with the literature. However, the joint entropy of damped harmonic oscillator shows remarkable discontinuity with time for certain values of damping factor. The envelope of the joint entropy curve increases with time monotonically. These results show the general properties of the envelope of the joint entropy curve for quantum systems.
Hot-Jupiter Inflation due to Deep Energy Deposition
NASA Astrophysics Data System (ADS)
Ginzburg, Sivan; Sari, Re'em
2015-04-01
Some extrasolar giant planets in close orbits—“hot Jupiters”—exhibit larger radii than that of a passively cooling planet. The extreme irradiation {{L}eq} these hot Jupiters receive from their close in stars creates a thick isothermal layer in their envelopes, which slows down their convective cooling, allowing them to retain their inflated size for longer. This is still insufficient to explain the observed sizes of the most inflated planets. Some models invoke an additional power source, deposited deep in the planet's envelope. Here, we present an analytical model for the cooling of such irradiated and internally heated gas giants. We show that a power source {{L}dep}, deposited at an optical depth {{τ }dep}, creates an exterior convective region, between optical depths {{L}eq}/{{L}dep} and {{τ }dep}, beyond which a thicker isothermal layer exists, which in extreme cases may extend to the center of the planet. This convective layer, which occurs only for {{L}dep}{{τ }dep}\\gt {{L}eq}, further delays the cooling of the planet. Such a planet is equivalent to a planet irradiated with {{L}eq}{{(1+{{L}dep}{{τ }dep}/{{L}eq})}β }, where β ≈ 0.35 is an effective power-law index describing the radiative energy density as a function of the optical depth for a convective planet U\\propto {{τ }β }. Our simple analytical model reproduces the main trends found in previous numerical works and provides an intuitive understanding. We derive scaling laws for the cooling rate of the planet, its central temperature, and radius. These scaling laws can be used to estimate the effects of tidal or Ohmic dissipation, wind shocks, or any other mechanism involving energy deposition on the sizes of hot Jupiters.
Fossil fuel energy resources of Ethiopia: Oil shale deposits
NASA Astrophysics Data System (ADS)
Wolela, Ahmed
2006-10-01
The energy crisis affects all countries in the world. Considering the price scenarios, many countries in Africa have begun to explore various energy resources. Ethiopia is one of the countries that depend upon imported petroleum products. To overcome this problem, geological studies suggest a significant occurrence of oil shale deposits in Ethiopia. The Inter-Trappean oil shale-bearing sediments are widely distributed on the South-Western Plateau of Ethiopia in the Delbi-Moye, Lalo-Sapo, Sola, Gojeb-Chida and Yayu Basins. The oil shale-bearing sediments were deposited in fluviatile and lacustrine environments. The oil shales contain mixtures of algal, herbaceous and higher plant taxa. They are dominated by algal-derived liptinite with minor amounts of vitrinite and inertinite. The algal remains belong to Botryococcus and Pediastrum. Laboratory results confirm that the Ethiopian oil shales are dominated by long-chain aliphatic hydrocarbons and have a low sulphur content. Type-II and Type-I kerogen dominated the studied oil shales. Type-II and Type-I are good source rocks for oil and gas generation. Hydrogen index versus Tmax value plots indicated that most of the oil shale samples fall within the immature-early mature stage for hydrocarbon generation, consistent with the Ro values that range from 0.3% to 0.64%. Pyrolysis data of the oil shales sensu stricto indicate excellent source rocks with up to 61.2% TOC values. Calorific value ranges from 400 to 6165 cal/g. Palynological studies confirmed that the oil shale-bearing sediments of Ethiopia range from Eocene to Miocene in age. A total of about 253,000,000 ton of oil shale is registered in the country. Oil shale deposits in Ethiopia can be used for production of oil and gas.
Hot-electron energy deposition around unsupported laser targets
Eidmann, K.; Maaswinkel, A.; Sigel, R.; Witkowski, S.; Amiranoff, F.; Fabbro, R.; Hares, J.D.; Kilkenny, J.D.
1983-09-01
Free-falling spheres, released by a simple mechanism, are used as laser targets. Hot-electron energy transport upon one-sided irradiation with 300-ps iodine laser pulses (6 x 10/sup 15/ W cm/sup -2/) is studied by various methods, including x-ray pinhole photography and time-resolved shadowgraphy. Spatial energy deposition is consistent with hot-electron spreading in the presence of self-generated magnetic fields, as suggested by recent experiments and simulations. The insensitivity of the results to the presence of a supporting stalk is attributed to inductive decoupling of the target. Free-falling targets open the possibility of highly symmetric implosion experiments.
Theoretical study of energy deposition in ionization chambers for tritium measurements
NASA Astrophysics Data System (ADS)
Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi
2013-10-01
Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.
Theoretical study of energy deposition in ionization chambers for tritium measurements
Chen, Zhilin; Peng, Shuming; Meng, Dan; He, Yuehong; Wang, Heyi
2013-10-15
Energy deposition in ionization chambers has been theoretically studied for tritium measurements in gaseous form. A one-dimension model is introduced to establish the quantitative relationship between energy deposition rate and many factors, including carrier gas, gas pressure, wall material, chamber size, and gas temperature. Energy deposition rate has been calculated at pressure varying from 5 kPa to 500 kPa based on some approximations. It is found that energy deposition rate varies greatly for different parameters, especially at low gas pressure. For the same chamber, energy deposition rate in argon is much higher than in deuterium, as much as 70.7% higher at 5 kPa. Gold plated chamber gives highest energy deposition rate in the calculations while aluminum chamber results in the lowest. As chamber size gets smaller, β ray emitted by tritium will deposit less energy in the sensitive region of the chamber. For chambers flowing through with the same gas, energy deposition rate in a 10 L chamber is 23.9% higher than in a 0.05 L chamber at 5 kPa. Gas temperature also places slight influence on energy deposition rate, and 373 K will lead to 6.7% lower deposition rate than 233 K at 5 kPa. In addition, experiments have been performed to obtain energy deposition rate in a gold plated chamber, which show good accordance with theoretical calculations.
A modular method to handle multiple time-dependent quantities in Monte Carlo simulations
NASA Astrophysics Data System (ADS)
Shin, J.; Perl, J.; Schümann, J.; Paganetti, H.; Faddegon, B. A.
2012-06-01
A general method for handling time-dependent quantities in Monte Carlo simulations was developed to make such simulations more accessible to the medical community for a wide range of applications in radiotherapy, including fluence and dose calculation. To describe time-dependent changes in the most general way, we developed a grammar of functions that we call ‘Time Features’. When a simulation quantity, such as the position of a geometrical object, an angle, a magnetic field, a current, etc, takes its value from a Time Feature, that quantity varies over time. The operation of time-dependent simulation was separated into distinct parts: the Sequence samples time values either sequentially at equal increments or randomly from a uniform distribution (allowing quantities to vary continuously in time), and then each time-dependent quantity is calculated according to its Time Feature. Due to this modular structure, time-dependent simulations, even in the presence of multiple time-dependent quantities, can be efficiently performed in a single simulation with any given time resolution. This approach has been implemented in TOPAS (TOol for PArticle Simulation), designed to make Monte Carlo simulations with Geant4 more accessible to both clinical and research physicists. To demonstrate the method, three clinical situations were simulated: a variable water column used to verify constancy of the Bragg peak of the Crocker Lab eye treatment facility of the University of California, the double-scattering treatment mode of the passive beam scattering system at Massachusetts General Hospital (MGH), where a spinning range modulator wheel accompanied by beam current modulation produces a spread-out Bragg peak, and the scanning mode at MGH, where time-dependent pulse shape, energy distribution and magnetic fields control Bragg peak positions. Results confirm the clinical applicability of the method.
A modular method to handle multiple time-dependent quantities in Monte Carlo simulations.
Shin, J; Perl, J; Schümann, J; Paganetti, H; Faddegon, B A
2012-06-01
A general method for handling time-dependent quantities in Monte Carlo simulations was developed to make such simulations more accessible to the medical community for a wide range of applications in radiotherapy, including fluence and dose calculation. To describe time-dependent changes in the most general way, we developed a grammar of functions that we call 'Time Features'. When a simulation quantity, such as the position of a geometrical object, an angle, a magnetic field, a current, etc, takes its value from a Time Feature, that quantity varies over time. The operation of time-dependent simulation was separated into distinct parts: the Sequence samples time values either sequentially at equal increments or randomly from a uniform distribution (allowing quantities to vary continuously in time), and then each time-dependent quantity is calculated according to its Time Feature. Due to this modular structure, time-dependent simulations, even in the presence of multiple time-dependent quantities, can be efficiently performed in a single simulation with any given time resolution. This approach has been implemented in TOPAS (TOol for PArticle Simulation), designed to make Monte Carlo simulations with Geant4 more accessible to both clinical and research physicists. To demonstrate the method, three clinical situations were simulated: a variable water column used to verify constancy of the Bragg peak of the Crocker Lab eye treatment facility of the University of California, the double-scattering treatment mode of the passive beam scattering system at Massachusetts General Hospital (MGH), where a spinning range modulator wheel accompanied by beam current modulation produces a spread-out Bragg peak, and the scanning mode at MGH, where time-dependent pulse shape, energy distribution and magnetic fields control Bragg peak positions. Results confirm the clinical applicability of the method. PMID:22572201
Harbola, Upendra; Mukamel, Shaul
2004-11-01
Electrostatic and dispersive interactions of polarizable molecules are expressed in terms of generalized (nonretarded) charge-density response functions of the isolated molecules, which in turn are expanded using the collective electronic oscillator (CEO) eigenmodes of linearized time-dependent density-functional theory. Closed expressions for the intermolecular energy are derived to sixth order in charge fluctuation amplitudes.
NASA Astrophysics Data System (ADS)
Park, Jun Seok; Park, Joo Hyun; Lee, Min-Gyu; Sung, Ji Hyun; Cha, Kyoung Je; Kim, Da Hye
2016-05-01
Among the many additive manufacturing technologies, the directed energy deposition (DED) process has attracted significant attention because of the application of metal products. Metal deposited by the DED process has different properties than wrought metal because of the rapid solidification rate, the high thermal gradient between the deposited metal and substrate, etc. Additionally, many operating parameters, such as laser power, beam diameter, traverse speed, and powder mass flow rate, must be considered since the characteristics of the deposited metal are affected by the operating parameters. In the present study, the effect of energy input on the characteristics of H13 and D2 steels deposited by a direct metal tooling process based on the DED process was investigated. In particular, we report that the hardness of the deposited H13 and D2 steels decreased with increasing energy input, which we discuss by considering microstructural observations and thermodynamics.
Time-Dependent Interfacial Properties and DNAPL Mobility
Tuck, D.M.
1999-03-10
Interfacial properties play a major role in governing where and how dense nonaqueous phase liquids (DNAPLs) move in the subsurface. Interfacial tension and contact angle measurements were obtained for a simple, single component DNAPL (tetrachloroethene, PCE), complex laboratory DNAPLs (PCE plus Sudan IV dye), and a field DNAPL from the Savannah River Site (SRS) M-Area DNAPL (PCE, trichloroethene [TCE], and maching oils). Interfacial properties for complex DNAPLs were time-dependent, a phenomenon not observed for PCE alone. Drainage capillary pressure-saturation curves are strongly influenced by interfacial properties. Therefore time-dependence will alter the nature of DNAPL migration and penetration. Results indicate that the time-dependence of PCE with relatively high Sudan IV dye concentrations is comparable to that of the field DNAPL. Previous DNAPL mobility experiments in which the DNAPL was dyed should be reviewed to determine whether time-dependent properties influenced the resutls. Dyes appear to make DNAPL more complex, and therefore a more realistic analog for field DNAPLs than single component DNAPLs.
Pedagogical Aspects of Time-Dependent Rotation Operators.
ERIC Educational Resources Information Center
Leubner, C.
1980-01-01
Describes the reformulation of a classical magnetic moment interacting with various magnetic field configurations in terms of coordinate-free, time-dependent rotation operators. This approach provides useful exercises for the manipulation of three-dimensional rotation operators and provides examples for a number of quantum-mechanics related…
Student Understanding of Time Dependence in Quantum Mechanics
ERIC Educational Resources Information Center
Emigh, Paul J.; Passante, Gina; Shaffer, Peter S.
2015-01-01
The time evolution of quantum states is arguably one of the more difficult ideas in quantum mechanics. In this article, we report on results from an investigation of student understanding of this topic after lecture instruction. We demonstrate specific problems that students have in applying time dependence to quantum systems and in recognizing…
Time dependent solution for acceleration of tau-leaping
Fu, Jin; Wu, Sheng; Petzold, Linda R.
2013-02-15
The tau-leaping method is often effective for speeding up discrete stochastic simulation of chemically reacting systems. However, when fast reactions are involved, the speed-up for this method can be quite limited. One way to address this is to apply a stochastic quasi-steady state assumption. However we must be careful when using this assumption. If the fast subsystem cannot reach a steady distribution fast enough, the quasi-steady-state assumption will propagate error into the simulation. To avoid these errors, we propose to use the time dependent solution rather than the quasi-steady-state. Generally speaking, the time dependent solution is not easy to derive for an arbitrary network. However, for some common motifs we do have time dependent solutions. We derive the time dependent solutions for these motifs, and then show how they can be used with tau-leaping to achieve substantial speed-ups, including for a realistic model of blood coagulation. Although the method is complicated, we have automated it.
Adjoint-Based Methodology for Time-Dependent Optimization
NASA Technical Reports Server (NTRS)
Yamaleev, N. K.; Diskin, B.; Nielsen, E. J.
2008-01-01
This paper presents a discrete adjoint method for a broad class of time-dependent optimization problems. The time-dependent adjoint equations are derived in terms of the discrete residual of an arbitrary finite volume scheme which approximates unsteady conservation law equations. Although only the 2-D unsteady Euler equations are considered in the present analysis, this time-dependent adjoint method is applicable to the 3-D unsteady Reynolds-averaged Navier-Stokes equations with minor modifications. The discrete adjoint operators involving the derivatives of the discrete residual and the cost functional with respect to the flow variables are computed using a complex-variable approach, which provides discrete consistency and drastically reduces the implementation and debugging cycle. The implementation of the time-dependent adjoint method is validated by comparing the sensitivity derivative with that obtained by forward mode differentiation. Our numerical results show that O(10) optimization iterations of the steepest descent method are needed to reduce the objective functional by 3-6 orders of magnitude for test problems considered.
Dynamic structure evolution of time-dependent network
NASA Astrophysics Data System (ADS)
Zhang, Beibei; Zhou, Yadong; Xu, Xiaoyan; Wang, Dai; Guan, Xiaohong
2016-08-01
In this paper, we research the long-voided problem of formulating the time-dependent network structure evolution scheme, it focus not only on finding new emerging vertices in evolving communities and new emerging communities over the specified time range but also formulating the complex network structure evolution schematic. Previous approaches basically applied to community detection on time static networks and thus failed to consider the potentially crucial and useful information latently embedded in the dynamic structure evolution process of time-dependent network. To address these problems and to tackle the network non-scalability dilemma, we propose the dynamic hierarchical method for detecting and revealing structure evolution schematic of the time-dependent network. In practice and specificity, we propose an explicit hierarchical network evolution uncovering algorithm framework originated from and widely expanded from time-dependent and dynamic spectral optimization theory. Our method yields preferable results compared with previous approaches on a vast variety of test network data, including both real on-line networks and computer generated complex networks.
Spike-timing-dependent BDNF secretion and synaptic plasticity.
Lu, Hui; Park, Hyungju; Poo, Mu-Ming
2014-01-01
In acute hippocampal slices, we found that the presence of extracellular brain-derived neurotrophic factor (BDNF) is essential for the induction of spike-timing-dependent long-term potentiation (tLTP). To determine whether BDNF could be secreted from postsynaptic dendrites in a spike-timing-dependent manner, we used a reduced system of dissociated hippocampal neurons in culture. Repetitive pairing of iontophoretically applied glutamate pulses at the dendrite with neuronal spikes could induce persistent alterations of glutamate-induced responses at the same dendritic site in a manner that mimics spike-timing-dependent plasticity (STDP)-the glutamate-induced responses were potentiated and depressed when the glutamate pulses were applied 20 ms before and after neuronal spiking, respectively. By monitoring changes in the green fluorescent protein (GFP) fluorescence at the dendrite of hippocampal neurons expressing GFP-tagged BDNF, we found that pairing of iontophoretic glutamate pulses with neuronal spiking resulted in BDNF secretion from the dendrite at the iontophoretic site only when the glutamate pulses were applied within a time window of approximately 40 ms prior to neuronal spiking, consistent with the timing requirement of synaptic potentiation via STDP. Thus, BDNF is required for tLTP and BDNF secretion could be triggered in a spike-timing-dependent manner from the postsynaptic dendrite. PMID:24298135
The Time-Dependent Chemistry of Cometary Debris in the Solar Corona
NASA Technical Reports Server (NTRS)
Pesnell, W. D.; Bryans, P.
2015-01-01
Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation.
The time-dependent chemistry of cometary debris in the solar corona
Pesnell, W. D.; Bryans, P.
2014-04-10
Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation.
The Time-dependent Chemistry of Cometary Debris in the Solar Corona
NASA Astrophysics Data System (ADS)
Pesnell, W. D.; Bryans, P.
2014-04-01
Recent improvements in solar observations have greatly progressed the study of sungrazing comets. They can now be imaged along the entirety of their perihelion passage through the solar atmosphere, revealing details of their composition and structure not measurable through previous observations in the less volatile region of the orbit further from the solar surface. Such comets are also unique probes of the solar atmosphere. The debris deposited by sungrazers is rapidly ionized and subsequently influenced by the ambient magnetic field. Measuring the spectral signature of the deposited material highlights the topology of the magnetic field and can reveal plasma parameters such as the electron temperature and density. Recovering these variables from the observable data requires a model of the interaction of the cometary species with the atmosphere through which they pass. The present paper offers such a model by considering the time-dependent chemistry of sublimated cometary species as they interact with the solar radiation field and coronal plasma. We expand on a previous simplified model by considering the fully time-dependent solutions of the emitting species' densities. To compare with observations, we consider a spherically symmetric expansion of the sublimated material into the corona and convert the time-dependent ion densities to radial profiles. Using emissivities from the CHIANTI database and plasma parameters derived from a magnetohydrodynamic simulation leads to a spatially dependent emission spectrum that can be directly compared with observations. We find our simulated spectra to be consistent with observation.
Linear-response dynamics from the time-dependent Gutzwiller approximation
NASA Astrophysics Data System (ADS)
Bünemann, J.; Capone, M.; Lorenzana, J.; Seibold, G.
2013-05-01
Within a Lagrangian formalism, we derive the time-dependent Gutzwiller approximation for general multi-band Hubbard models. Our approach explicitly incorporates the coupling between time-dependent variational parameters and a time-dependent density matrix from which we obtain dynamical correlation functions in the linear-response regime. Our results are illustrated for the one-band model where we show that the interacting system can be mapped to an effective problem of fermionic quasiparticles coupled to ‘doublon’ (double occupancy) bosonic fluctuations. The latter have an energy on the scale of the on-site Hubbard repulsion U in the dilute limit but become soft at the Brinkman-Rice transition, which is shown to be related to an emerging conservation law of doublon charge and the associated gauge invariance. Coupling with the boson mode produces a structure in the charge response and we find that a similar structure appears in dynamical mean-field theory.
Time-dependent modes associated with finite time instabilities in unstable fluid flows
NASA Astrophysics Data System (ADS)
Babaee, Hessam; Sapsis, Themistoklis
2015-11-01
We apply a recently developed variational formulation for the determination of a finite-dimensional, time-dependent, orthonormal basis that captures the directions associated with finite-time instabilities. We demonstrate the capability of the method for two problems: the Orr-Sommerfeld/Squire operator and the vertical jet in crossflow. In the first problem we demonstrate that the time-dependent subspace captures the strongly transient non-normal energy growth (in the short time regime), while for longer times the modes capture the expected asymptotic behavior of the dynamics. We also consider the vertical jet in crossflow at the jet Reynolds number of Rej = 900 . We demonstrate that the subspace instantaneously captures the most unstable directions of the time-dependent flow. We explore the connection between the shear flow, non-normal growth and persistent instabilities. Supported by ARO Award # 66710-EG-YIP.
Modeling Planetary Atmospheric Energy Deposition By Energetic Ions
NASA Astrophysics Data System (ADS)
Parkinson, Christopher; Bougher, Stephen; Gronoff, Guillaume; Barthelemy, Mathieu
2016-07-01
The structure, dynamics, chemistry, and evolution of planetary upper atmospheres are in large part determined by the available sources of energy. In addition to the solar EUV flux, the solar wind and solar energetic particle (SEP) events are also important sources. Both of these particle populations can significantly affect an atmosphere, causing atmospheric loss and driving chemical reactions. Attention has been paid to these sources from the standpoint of the radiation environment for humans and electronics, but little work has been done to evaluate their impact on planetary atmospheres. At unmagnetized planets or those with crustal field anomalies, in particular, the solar wind and SEPs of all energies have direct access to the atmosphere and so provide a more substantial energy source than at planets having protective global magnetic fields. Additionally, solar wind and energetic particle fluxes should be more significant for planets orbiting more active stars, such as is the case in the early history of the solar system for paleo-Venus and Mars. Therefore quantification of the atmospheric energy input from the solar wind and SEP events is an important component of our understanding of the processes that control their state and evolution. We have applied a full Lorentz motion particle transport model to study the effects of particle precipitation in the upper atmospheres of Mars and Venus. Such modeling has been previously done for Earth and Mars using a guiding center precipitation model. Currently, this code is only valid for particles with small gyroradii in strong uniform magnetic fields. There is a clear necessity for a Lorentz formulation, hence, a systematic study of the ionization, excitation, and energy deposition has been conducted, including a comparison of the influence relative to other energy sources (namely EUV photons). The result is a robust examination of the influence of energetic ion transport on the Venus and Mars upper atmosphere which
Modeling Atmospheric Energy Deposition (by energetic ions): New Results
NASA Astrophysics Data System (ADS)
Parkinson, C.; Brain, D. A.; Lillis, R. J.; Liemohn, M. W.; Bougher, S. W.
2012-12-01
deposition is conducted including a comparison of the influence relative to other energy sources (namely EUV photons) and previous efforts using the guiding center approximation.
Time-dependent magnetohydrodynamic simulations of the inner heliosphere
NASA Astrophysics Data System (ADS)
Merkin, V. G.; Lyon, J. G.; Lario, D.; Arge, C. N.; Henney, C. J.
2016-04-01
This paper presents results from a simulation study exploring heliospheric consequences of time-dependent changes at the Sun. We selected a 2 month period in the beginning of year 2008 that was characterized by very low solar activity. The heliosphere in the equatorial region was dominated by two coronal holes whose changing structure created temporal variations distorting the classical steady state picture of the heliosphere. We used the Air Force Data Assimilate Photospheric Flux Transport (ADAPT) model to obtain daily updated photospheric magnetograms and drive the Wang-Sheeley-Arge (WSA) model of the corona. This leads to a formulation of a time-dependent boundary condition for our three-dimensional (3-D) magnetohydrodynamic (MHD) model, LFM-helio, which is the heliospheric adaptation of the Lyon-Fedder-Mobarry MHD simulation code. The time-dependent coronal conditions were propagated throughout the inner heliosphere, and the simulation results were compared with the spacecraft located near 1 astronomical unit (AU) heliocentric distance: Advanced Composition Explorer (ACE), Solar Terrestrial Relations Observatory (STEREO-A and STEREO-B), and the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft that was in cruise phase measuring the heliospheric magnetic field between 0.35 and 0.6 AU. In addition, during the selected interval MESSENGER and ACE aligned radially allowing minimization of the effects of temporal variation at the Sun versus radial evolution of structures. Our simulations show that time-dependent simulationsreproduce the gross-scale structure of the heliosphere with higher fidelity, while on smaller spatial and faster time scales (e.g., 1 day) they provide important insights for interpretation of the data. The simulations suggest that moving boundaries of slow-fast wind transitions at 0.1 AU may result in the formation of inverted magnetic fields near pseudostreamers which is an intrinsically time-dependent process
Enhancement of fast electron energy deposition by external magnetic fields
NASA Astrophysics Data System (ADS)
Honrubia, J. J.; Murakami, M.; Mima, K.; Johzaki, T.; Sunahara, A.; Nagatomo, H.; Fujioka, S.; Shiraga, H.; Azechi, H.
2016-03-01
Recently, generation of external magnetic fields of a few kT has been reported [Fujioka et al. Scientific Reports 2013 3 1170]. These fields can be used in fast ignition to mitigate the large fast electron divergence. In this summary, two fast ignition applications are briefly outlined. The first one deals with electron guiding by external B-fields applied at the end of the shell implosion of a re-entrant cone target. Preliminary results show that the B-field strength at the time of peak ρR may be sufficiently high for fast electron guiding. The second application deals with guiding of fast electrons in magnetized wires surrounded by plasma. Results show a significant enhancement of electron energy deposition at the end of the wire, which is particularly important for low-Z wires.
Energy deposition studies for the LBNE beam absorber
Rakhno, Igor L.; Mokhov, Nikolai V.; Tropin, Igor S.
2015-01-29
Results of detailed Monte Carlo energy deposition studies performed for the LBNE absorber core and the surrounding shielding with the MARS15 code are described. The model of the entire facility, that includes a pion-production target, focusing horns, target chase, decay channel, hadron absorber system – all with corresponding radiation shielding – was developed using the recently implemented ROOT-based geometry option in the MARS15 code. This option provides substantial flexibility and automation when developing complex geometry models. Both normal operation and accidental conditions were studied. Various design options were considered, in particular the following: (i) filling the decay pipe with air or helium; (ii) the absorber mask material and shape; (iii) the beam spoiler material and size. Results of detailed thermal calculations with the ANSYS code helped to select the most viable absorber design options.
Hypersonic Flow Control Using Upstream Focused Energy Deposition
NASA Technical Reports Server (NTRS)
Riggins David W.; Nelson, H. F.
1999-01-01
A numerical study of centerline and off-centerline power deposition at a point upstream of a two-dimensional blunt body at Mach 6.5 at 30 km altitude are presented. The full Navier-Stokes equations are used. Wave drag, lift, and pitching moment are presented as a function of amount of power absorbed in the flow and absorption point location. It is shown that wave drag is considerably reduced. Modifications to the pressure distribution in the flow field due to the injected energy create lift and a pitching moment when the injection is off-centerline. This flow control concept may lead to effective ways to improve the performance and to stabilize and control hypersonic vehicles.
Linear-response calculation in the time-dependent density functional theory
Nakatsukasa, Takashi; Inakura, Tsunenori; Avogadro, Paolo; Ebata, Shuichiro; Sato, Koichi; Yabana, Kazuhiro
2012-11-12
Linear response calculations based on the time-dependent density-functional theory are presented. Especially, we report results of the finite amplitude method which we have recently proposed as an alternative and feasible approach to the (quasiparticle-)random-phase approximation. Calculated properties of the giant resonances and low-energy E1 modes are discussed. We found a universal linear correlation between the low-energy E1 strength and the neutron skin thickness.
Statistical time-dependent model for the interstellar gas
NASA Technical Reports Server (NTRS)
Gerola, H.; Kafatos, M.; Mccray, R.
1974-01-01
We present models for temperature and ionization structure of low, uniform-density (approximately 0.3 per cu cm) interstellar gas in a galactic disk which is exposed to soft X rays from supernova outbursts occurring randomly in space and time. The structure was calculated by computing the time record of temperature and ionization at a given point by Monte Carlo simulation. The calculation yields probability distribution functions for ionized fraction, temperature, and their various observable moments. These time-dependent models predict a bimodal temperature distribution of the gas that agrees with various observations. Cold regions in the low-density gas may have the appearance of clouds in 21-cm absorption. The time-dependent model, in contrast to the steady-state model, predicts large fluctuations in ionization rate and the existence of cold (approximately 30 K), ionized (ionized fraction equal to about 0.1) regions.
A time dependent theory of crazing behavior in polymers
NASA Technical Reports Server (NTRS)
Chern, S. S.; Hsiao, C. C.
1982-01-01
The development of crazing is not only a function of stress, but also a function of time. Under a simple state of tension, a craze opening displacement is closely associated with the viscoelastic behavior of the original bulk polymer medium in which individual crazes initiate and develop. Within each craze region, molecular orientation takes place when conditions permit, and a new phase of rearranged molecules governs its local behavior. Based upon a time-dependent viscoelastic two-dimensional model, using a computer program the craze opening displacement field has been calculated, time-dependent craze length was also computed by taking into consideration the molecular orientation mechanism and large deformations in the craze region. Examples are given for simple viscoelastic media with simplified stress distributions. It is interesting to find out that the occurrence of crazing may be interpreted in terms of the stability or instability of the constitutive behavior of the bulk polymer.
Time-dependent buoyant puff model for explosive sources
Kansa, E.J.
1997-01-01
Several models exist to predict the time dependent behavior of bouyant puffs that result from explosions. This paper presents a new model that is derived from the strong conservative form of the conservation partial differential equations that are integrated over space to yield a coupled system of time dependent nonlinear ordinary differential equations. This model permits the cloud to evolve from an intial spherical shape not an ellipsoidal shape. It ignores the Boussinesq approximation, and treats the turbulence that is generated by the puff itself and the ambient atmospheric tubulence as separate mechanisms in determining the puff history. The puff cloud rise history was found to depend no only on the mass and initial temperature of the explosion, but also upon the stability conditions of the ambient atmosphere. This model was calibrated by comparison with the Roller Coaster experiments.
The Time-Dependent Structure of the Electron Reconnection Layer
NASA Technical Reports Server (NTRS)
Hesse, Michael; Zenitani, Seiji; Kuznetsova, Masha; Klimas, Alex
2009-01-01
Collisionless magnetic reconnection is often associated with time-dependent behavior. Specifically, current layers in the diffusion region can become unstable to tearing-type instabilities on one hand, or to instabilities with current-aligned wave vectors on the other. In the former case, the growth of tearing instabilities typically leads to the production of magnetic islands, which potentially provide feedback on the reconnection process itself, as well as on the rate of reconnection. The second class of instabilities tend to modulate the current layer along the direction of the current flow, for instance generating kink-type perturbations, or smaller-scale turbulence with the potential to broaden the current layer. All of these processes contribute to rendering magnetic reconnection time-dependent. In this presentation, we will provide a summary of these effects, and a discussion of how much they contribute to the overall magnetic reconnection rate.
Chromospheric extents predicted by time-dependent acoustic wave models
Cuntz, M. Heidelberg Universitaet )
1990-01-01
Theoretical models for chromospheric structures of late-type giant stars are computed, including the time-dependent propagation of acoustic waves. Models with short-period monochromatic shock waves as well as a spectrum of acoustic waves are discussed, and the method is applied to the stars Arcturus, Aldebaran, and Betelgeuse. Chromospheric extent, defined as the monotonic decrease with height of the time-averaged electron densities, are found to be 1.12, 1.13, and 1.22 stellar radii for the three stars, respectively; this corresponds to a time-averaged electron density of 10 to the 7th/cu cm. Predictions of the extended chromospheric obtained using a simple scaling law agree well with those obtained by the time-dependent wave models; thus, the chromospheres of all stars for which the scaling law is valid consist of the same number of pressure scale heights. 74 refs.
Chromospheric extents predicted by time-dependent acoustic wave models
NASA Technical Reports Server (NTRS)
Cuntz, Manfred
1990-01-01
Theoretical models for chromospheric structures of late-type giant stars are computed, including the time-dependent propagation of acoustic waves. Models with short-period monochromatic shock waves as well as a spectrum of acoustic waves are discussed, and the method is applied to the stars Arcturus, Aldebaran, and Betelgeuse. Chromospheric extent, defined as the monotonic decrease with height of the time-averaged electron densities, are found to be 1.12, 1.13, and 1.22 stellar radii for the three stars, respectively; this corresponds to a time-averaged electron density of 10 to the 7th/cu cm. Predictions of the extended chromospheric obtained using a simple scaling law agree well with those obtained by the time-dependent wave models; thus, the chromospheres of all stars for which the scaling law is valid consist of the same number of pressure scale heights.
Polymer dynamics in time-dependent periodic potentials
NASA Astrophysics Data System (ADS)
Kauttonen, Janne; Merikoski, Juha; Pulkkinen, Otto
2008-06-01
The dynamics of a discrete polymer in time-dependent external potentials is studied with the master equation approach. We consider both stochastic and deterministic switching mechanisms for the potential states and give the essential equations for computing the stationary-state properties of molecules with internal structure in time-dependent periodic potentials on a lattice. As an example, we consider standard and modified Rubinstein-Duke polymers and calculate their mean drift and effective diffusion coefficient in the two-state nonsymmetric flashing potential and symmetric traveling potential. Rich nonlinear behavior of these observables is found. By varying the polymer length, we find current inversions caused by the rebound effect that is only present for molecules with internal structure. These results depend strongly on the polymer type. We also notice increased transport coherence for longer polymers.
Quick Time-dependent Ionization Calculations Depending on MHD Simulations
NASA Astrophysics Data System (ADS)
Shen, Chengcai; Raymond, John C.; Murphy, Nicholas Arnold
2014-06-01
Time-dependent ionization is important in astrophysical environments where the thermodynamic time scale is shorter than ionization time scale. In this work, we report a FORTRAN program that performs fast non-equilibrium ionization calculations based on parallel computing. Using MHD simulation results, we trace the movements of plasma in a Lagrangian framework, and obtain evolutionary history of temperature and electron density. Then the time-dependent ionization equations are solved using the eigenvalue method. For any complex temperature and density histories, we introduce a advanced time-step strategy to improve the computational efficiency. Our tests show that this program has advantages of high numerical stability and high accuracy. In addition, it is also easy to integrate this solver with the other MHD routines.
Time-Dependent Coupled Harmonic Oscillators: Classical and Quantum Solutions
NASA Astrophysics Data System (ADS)
Macedo, Diego Ximenes; Guedes, Ilde
2015-10-01
In this work we present the classical and quantum solutions for an arbitrary system of time-dependent coupled harmonic oscillators, where the masses (m), frequencies (ω) and coupling parameter (k) are functions of time. To obtain the classical solutions we use a coordinate and momentum transformations along with a canonical transformation to write the original Hamiltonian as the sum of two Hamiltonians of uncoupled harmonic oscillators with modified time-dependent frequencies and unitary masses. To obtain the exact quantum solutions we use a unitary transformation and the Lewis and Riesenfeld invariant method. The exact wave functions are obtained by solving the respective Milne-Pinney equation for each system. We obtain the solutions for the system with m1 = m2 = m0eγt, ω1 = ω01e-γt/2, ω2 = ω02e-γt/2 and k = k0.
Time-dependent coupled harmonic oscillators: Classical and quantum solutions
NASA Astrophysics Data System (ADS)
Macedo, D. X.; Guedes, I.
2014-08-01
In this work we present the classical and quantum solutions for an arbitrary system of time-dependent coupled harmonic oscillators, where the masses (m), frequencies (ω) and coupling parameter (k) are functions of time. To obtain the classical solutions, we use a coordinate and momentum transformations along with a canonical transformation to write the original Hamiltonian as the sum of two Hamiltonians of uncoupled harmonic oscillators with modified time-dependent frequencies and unitary masses. To obtain the exact quantum solutions we use a unitary transformation and the Lewis and Riesenfeld (LR) invariant method. The exact wave functions are obtained by solving the respective Milne-Pinney (MP) equation for each system. We obtain the solutions for the system with m1 = m2 = m0eγt, ω1 = ω01e-γt/2, ω2 = ω02e-γt/2 and k = k0.
Time-dependent response of filamentary composite spherical pressure vessels
NASA Technical Reports Server (NTRS)
Dozier, J. D.
1983-01-01
A filamentary composite spherical pressure vessel is modeled as a pseudoisotropic (or transversely isotropic) composite shell, with the effects of the liner and fill tubes omitted. Equations of elasticity, macromechanical and micromechanical formulations, and laminate properties are derived for the application of an internally pressured spherical composite vessel. Viscoelastic properties for the composite matrix are used to characterize time-dependent behavior. Using the maximum strain theory of failure, burst pressure and critical strain equations are formulated, solved in the Laplace domain with an associated elastic solution, and inverted back into the time domain using the method of collocation. Viscoelastic properties of HBFR-55 resin are experimentally determined and a Kevlar/HBFR-55 system is evaluated with a FORTRAN program. The computed reduction in burst pressure with respect to time indicates that the analysis employed may be used to predict the time-dependent response of a filamentary composite spherical pressure vessel.
A semianalytical satellite theory for weak time-dependent perturbations
NASA Technical Reports Server (NTRS)
Cefola, P.; Mcclain, W.; Early, L.; Green, A.
1980-01-01
The modifications of the semianalytical satellite theory required to include these 'weak' time dependent perturbations are described. The new formulation results in additional terms in the short periodic variations but does not change the averaged equations of motion. Thus the m monthly terms are still included in the averaged equations of motion. This contrasts with the usual approach for the strongly time dependent perturbations in which the m monthly (or m daily, if tesseral harmonics are being considered) terms would be eliminated from the averaged equations of motion and included in the short periodics computation. Numerical test results for the GPS case obtained with a numerical averaging implementation of the new theory demonstrate the accuracy improvement.
Autoionization in time-dependent density-functional theory
NASA Astrophysics Data System (ADS)
Kapoor, V.
2016-06-01
We compute the exact exchange-correlation potential of the time-dependent density-functional theory (TDDFT) for the correlated process of autoionization. The potential develops barriers which regulate the autoionization rate. TDDFT employing known and practicable exchange-correlation potentials does not capture any autoionization dynamics. Approximate exchange-correlation potentials capturing such dynamics would necessarily require memory effects and are unlikely to be developed, as will be illustrated.
Designing for time-dependent material response in spacecraft structures
NASA Technical Reports Server (NTRS)
Hyer, M. W.; Oleksuk, Lynda L. S.; Bowles, D. E.
1992-01-01
To study the influence on overall deformations of the time-dependent constitutive properties of fiber-reinforced polymeric matrix composite materials being considered for use in orbiting precision segmented reflectors, simple sandwich beam models are developed. The beam models include layers representing the face sheets, the core, and the adhesive bonding of the face sheets to the core. A three-layer model lumps the adhesive layers with the face sheets or core, while a five-layer model considers the adhesive layers explicitly. The deformation response of the three-layer and five-layer sandwich beam models to a midspan point load is studied. This elementary loading leads to a simple analysis, and it is easy to create this loading in the laboratory. Using the correspondence principle of viscoelasticity, the models representing the elastic behavior of the two beams are transformed into time-dependent models. Representative cases of time-dependent material behavior for the facesheet material, the core material, and the adhesive are used to evaluate the influence of these constituents being time-dependent on the deformations of the beam. As an example of the results presented, if it assumed that, as a worst case, the polymer-dominated shear properties of the core behave as a Maxwell fluid such that under constant shear stress the shear strain increases by a factor of 10 in 20 years, then it is shown that the beam deflection increases by a factor of 1.4 during that time. In addition to quantitative conclusions, several assumptions are discussed which simplify the analyses for use with more complicated material models. Finally, it is shown that the simpler three-layer model suffices in many situations.
Time-dependent Brittle Deformation in Darley Dale Sandstone
NASA Astrophysics Data System (ADS)
Baud, P.; Heap, M. J.; Meredith, P. G.; Bell, A. F.; Main, I. G.
2008-12-01
The characterization of time-dependent brittle rock deformation is fundamental to understanding the long- term evolution and dynamics of the Earth's upper crust. The chemical influence of water promotes time- dependent deformation through stress corrosion cracking that allows rocks to deform at stresses far below their short-term failure strength. Here we report results from a study of time-dependent brittle creep in water- saturated samples of Darley Dale sandstone (initial porosity of 13%). Conventional creep experiments (or 'static fatigue' tests) show that time to failure decreases dramatically with the imposed deviatoric stress. They also suggest the existence of a critical level of damage beyond which localized failure develops. Sample variability results however in significant scattering in the experimental data and numerous tests are needed to clearly define a relation between the strain rate and the applied stress. We show here that stress-stepping experiments provide a means to overcome this problem and that it is possible this way to obtain the strain rate dependence on applied stress with a single test. This allows to study in details the impact of various thermodynamical conditions on brittle creep. The influence of effective stress was investigated in stress-stepping experiments with effective confining pressures of 10, 30 and 50 MPa (whilst maintaining a constant pore fluid pressure of 20 MPa). In addition to the expected purely mechanical influence of an elevated effective stress our results also demonstrate that stress corrosion appears to be inhibited at higher effective stresses. The influence of doubling the pore fluid pressure however, whilst maintaining a constant effective stress, is shown to have no effect on the rate of stress corrosion. We then discuss the results in light of acoustic emission hypocentre location data and optical microscope analysis and use our experimental data to validate proposed macroscopic creep laws. Finally, using
Time Dependent Models of Grain Formation Around Carbon Stars
NASA Technical Reports Server (NTRS)
Egan, M. P.; Shipman, R. F.
1996-01-01
Carbon-rich Asymptotic Giant Branch stars are sites of dust formation and undergo mass loss at rates ranging from 10(exp -7) to 10(exp -4) solar mass/yr. The state-of-the-art in modeling these processes is time-dependent models which simultaneously solve the grain formation and gas dynamics problem. We present results from such a model, which also includes an exact solution of the radiative transfer within the system.
Time-dependent MOS breakdown. [of Na contaminated capacitors
NASA Technical Reports Server (NTRS)
Li, S. P.; Bates, E. T.; Maserjian, J.
1976-01-01
A general model for time-dependent breakdown in metal-oxide-silicon (MOS) structures is developed and related to experimental measurements on samples deliberately contaminated with Na. A statistical method is used for measuring the breakdown probability as a function of log time and applied field. It is shown that three time regions of breakdown can be explained respectively in terms of silicon surface defects, ion emission from the metal interface, and lateral ion diffusion at the silicon interface.
Quasinormal modes in a time-dependent black hole background
NASA Astrophysics Data System (ADS)
Shao, Cheng-Gang; Wang, Bin; Abdalla, Elcio; Su, Ru-Keng
2005-02-01
We have studied the evolution of the massless scalar field propagating in a time-dependent charged Vaidya black hole background. A generalized tortoise coordinate transformation was used to study the evolution of the massless scalar field. It is shown that, for the slowest damped quasinormal modes, the approximate formulas in the stationary Reissner-Nordström black hole turn out to be a reasonable prescription, showing that results from quasinormal mode analysis are rather robust.
Quasinormal modes in a time-dependent black hole background
Shao Chenggang; Wang Bin; Abdalla, Elcio; Su Rukeng
2005-02-15
We have studied the evolution of the massless scalar field propagating in a time-dependent charged Vaidya black hole background. A generalized tortoise coordinate transformation was used to study the evolution of the massless scalar field. It is shown that, for the slowest damped quasinormal modes, the approximate formulas in the stationary Reissner-Nordstroem black hole turn out to be a reasonable prescription, showing that results from quasinormal mode analysis are rather robust.
Time-dependent first-principles approaches to PV materials
Miyamoto, Yoshiyuki
2013-12-10
Computational scheme for designing photovoltaic (PV) materials is presented. First-principles electron dynamics of photo-excitation and subsequent electron-hole splitting is performed based on the time-dependent density functional theory. Photo-induced enhancement of dipole moment was observed in a polar crystal and a donor-acceptor molecular pair. These experiences will pave a way to design PV material from first-principles simulations.
Shoulder pain and time dependent structure in wheelchair propulsion variability.
Jayaraman, Chandrasekaran; Moon, Yaejin; Sosnoff, Jacob J
2016-07-01
Manual wheelchair propulsion places considerable repetitive mechanical strain on the upper limbs leading to shoulder injury and pain. While recent research indicates that the amount of variability in wheelchair propulsion and shoulder pain may be related. There has been minimal inquiry into the fluctuation over time (i.e. time-dependent structure) in wheelchair propulsion variability. Consequently the purpose of this investigation was to examine if the time-dependent structure in the wheelchair propulsion parameters are related to shoulder pain. 27 experienced wheelchair users manually propelled their own wheelchair fitted with a SMARTWheel on a roller at 1.1m/s for 3min. Time-dependent structure of cycle-to-cycle fluctuations in contact angle and inter push time interval was quantified using sample entropy (SampEn) and compared between the groups with/without shoulder pain using non-parametric statistics. Overall findings were, (1) variability observed in contact angle fluctuations during manual wheelchair propulsion is structured (Z=3.15;p<0.05), (2) individuals with shoulder pain exhibited higher SampEn magnitude for contact angle during wheelchair propulsion than those without pain (χ(2)(1)=6.12;p<0.05); and (3) SampEn of contact angle correlated significantly with self-reported shoulder pain (rs (WUSPI) =0.41;rs (VAS)=0.56;p<0.05). It was concluded that the time-dependent structure in wheelchair propulsion may provide novel information for tracking and monitoring shoulder pain. PMID:27134151
Time-dependent global modeling of the inner heliosphere
NASA Astrophysics Data System (ADS)
Merkin, V. G.; Lyon, J.; Arge, C. N.; Lario, D.; Linker, J.; Lionello, R.
2015-12-01
We present results of time-dependent modeling of the inner heliosphere using the Lyon-Fedder-Mobarry (LFM) magnetohydrodynamic (MHD). Two types of simulations are performed: one concentrates on the background solar wind specification, while the other deals with the propagation of coronal mass ejections (CMEs). For simulations of the first type we coupled the LFM-helio code with the ADAPT-driven WSA model. We present some details of the coupling machinery and then simulate selected periods characterized by very low solar activity with no significant energetic particle events or CMEs. The results of the model are compared with MESSENGER, ACE, STEREO A and B spacecraft to probe both radial and temporal evolution of solar wind structure. The results indicate, in particular, the importance of time-dependent modeling for more accurate prediction of high-speed streams and heliospheric current sheet structure when the spacecraft skim its surface. We will comment on the formation of magnetic field reversals in pseudostreamer regions, which is an intrinsically time-dependent phenomenon, and on the current sheet corrugation caused by solar wind momentum shears. For the second type of time-dependent inner heliosphere simulations we have coupled LFM-helio with the MAS MHD model of the corona. We first present results of idealized coupled MAS/LFM-helio simulations with symmetric solar wind background and no rotation intended to test the interface for seamless propagation of transients from the corona into the inner heliosphere domain. We then simulate an event with a CME propagating through a realistic heliosphere background including corotating interaction regions. We show details of propagation of flux-rope CMEs through the boundary between MAS and LFM-helio and compare the results between the two codes in the heliospheric domain. The results indicate that the coupling works well, although some differences in the solutions are observed probably due to differences in numerical
Gamma time-dependency in Blaxter's compartmental model.
NASA Technical Reports Server (NTRS)
Matis, J. H.
1972-01-01
A new two-compartment model for the passage of particles through the gastro-intestinal tract of ruminants is proposed. In this model, a gamma distribution of lifetimes is introduced in the first compartment; thereby, passage from that compartment becomes time-dependent. This modification is strongly suggested by the physical alteration which certain substances, e.g. hay particles, undergo in the digestive process. The proposed model is applied to experimental data.
Stochastic protein production and time-dependent current fluctuations
NASA Astrophysics Data System (ADS)
Gorissen, Mieke; Vanderzande, Carlo
2011-03-01
Translation is the cellular process in which ribosomes make proteins from information encoded on messenger RNA. We model this process using driven lattice gases and take into account the finite lifetime of mRNA. The stochastic properties of the translation process can then be determined from the time-dependent current fluctuations of the lattice gas model. We illustrate our ideas with a totally asymmetric exclusion process with extended objects.
Time-dependent induced potentials in convoy electron emission
NASA Astrophysics Data System (ADS)
Acuña, G. P.; Miraglia, J. E.
2006-11-01
We study the time-dependent induced potentials at the convoy electron position due to the self-interaction with a metal surface and to the shock wave created by the positive hole (vacancy) left. The time evolution of these potentials are calculated using the linear response theory. Results obtained are fitted with simple functions. We find that those two potentials nearly cancel each other in the first ten atomic units of time.
Relating Time-Dependent Acceleration and Height Using an Elevator
ERIC Educational Resources Information Center
Kinser, Jason M.
2015-01-01
A simple experiment in relating a time-dependent linear acceleration function to height is explored through the use of a smartphone and an elevator. Given acceleration as a function of time, a(t), the velocity function and position functions are determined through integration as in v(t)=? a(t) dt (1) and x(t)=? v(t) dt. Mobile devices such as…
On the solution of time-dependent problems
NASA Astrophysics Data System (ADS)
Abdou, M. A.
2005-10-01
The time-dependent radiative transfer problems involving non-equilibrium coupling to the material temperature to differential equation and ballistic-diffusive equation have been solved by means of two different techniques, namely, flux-limited approach and maximum entropy method. The behaviour of the radiative intensity is shown graphically. Knowing the radiative intensity allows us to calculate directly some physical parameters such as the reflection function and heat flux that are numerically computed.
Analytic controllability of time-dependent quantum control systems
NASA Astrophysics Data System (ADS)
Lan, Chunhua; Tarn, Tzyh-Jong; Chi, Quo-Shin; Clark, John W.
2005-05-01
The question of controllability is investigated for a quantum control system in which the Hamiltonian operator components carry explicit time dependence which is not under the control of an external agent. We consider the general situation in which the state moves in an infinite-dimensional Hilbert space, a drift term is present, and the operators driving the state evolution may be unbounded. However, considerations are restricted by the assumption that there exists an analytic domain, dense in the state space, on which solutions of the controlled Schrödinger equation may be expressed globally in exponential form. The issue of controllability then naturally focuses on the ability to steer the quantum state on a finite-dimensional submanifold of the unit sphere in Hilbert space—and thus on analytic controllability. A relatively straightforward strategy allows the extension of Lie-algebraic conditions for strong analytic controllability derived earlier for the simpler, time-independent system in which the drift Hamiltonian and the interaction Hamiltonian have no intrinsic time dependence. Enlarging the state space by one dimension corresponding to the time variable, we construct an augmented control system that can be treated as time independent. Methods developed by Kunita can then be implemented to establish controllability conditions for the one-dimension-reduced system defined by the original time-dependent Schrödinger control problem. The applicability of the resulting theorem is illustrated with selected examples.
Time-dependent dynamic behavior of light diffraction in ferrofluid
NASA Astrophysics Data System (ADS)
Chung, Min-Feng; Chou, S. E.; Fu, Chao-Ming
2012-04-01
The time-dependent dynamic behavior of diffraction patterns induced by external magnetic field in a suspension of nano-sized magnetic particles (Fe3O4) in a water-based magnetic fluid was investigated. It was observed that the diffraction pattern changed with time as the magnetic field was applied. In the absence of applied magnetic field, there was no diffraction pattern in the screen. When the magnetic field was applied, the transmitted light was perpendicular to the magnetic field, and the diffraction pattern was unstable. There were many small lines and points moving with time. After one minute, the diffraction pattern turned stable, and the small lines became longer. This time-dependent behavior helps us to understand the evolution of the forming chains of magnetic nanoparticles. Moreover, we have measured the other diffraction pattern, the transmitted light propagating parallel to the applied field. These time-dependent diffraction patterns give a new point to understand the dynamic three-dimensional structure of magnetic fluid under a dc magnetic field.
Time dependent turbulence modeling and analytical theories of turbulence
NASA Technical Reports Server (NTRS)
Rubinstein, R.
1993-01-01
By simplifying the direct interaction approximation (DIA) for turbulent shear flow, time dependent formulas are derived for the Reynolds stresses which can be included in two equation models. The Green's function is treated phenomenologically, however, following Smith and Yakhot, we insist on the short and long time limits required by DIA. For small strain rates, perturbative evaluation of the correlation function yields a time dependent theory which includes normal stress effects in simple shear flows. From this standpoint, the phenomenological Launder-Reece-Rodi model is obtained by replacing the Green's function by its long time limit. Eddy damping corrections to short time behavior initiate too quickly in this model; in contrast, the present theory exhibits strong suppression of eddy damping at short times. A time dependent theory for large strain rates is proposed in which large scales are governed by rapid distortion theory while small scales are governed by Kolmogorov inertial range dynamics. At short times and large strain rates, the theory closely matches rapid distortion theory, but at long times it relaxes to an eddy damping model.
The multi-configurational time-dependent Hartree approach revisited.
Manthe, Uwe
2015-06-28
The multi-configurational time-dependent Hartree (MCTDH) approach facilitates accurate high-dimensional quantum dynamics simulations. In the approach, the wavefunction is expanded in a direct product of self-adapting time-dependent single-particle functions (SPFs). The equations of motion for the expansion coefficients and the SPFs are obtained via the Dirac-Frenkel variational principle. While this derivation yields well-defined differential equations for the motion of occupied SPFs, singularities in the working equations resulting from unoccupied SPFs have to be removed by a regularization procedure. Here, an alternative derivation of the MCTDH equations of motion is presented. It employs an analysis of the time-dependence of the single-particle density matrices up to second order. While the analysis of the first order terms yields the known equations of motion for the occupied SPFs, the analysis of the second order terms provides new equations which allow one to identify optimal choices for the unoccupied SPFs. The effect of the optimal choice of the unoccupied SPFs on the structure of the MCTDH equations of motion and their regularization is discussed. Generalized equations applicable in the multi-layer MCTDH framework are presented. Finally, the effects resulting from the initial choice of the unoccupied SPFs are illustrated by a simple numerical example. PMID:26133412
Particle creation in a time-dependent electric field revisited
Mahajan, Gaurang
2009-02-15
We adopt the general formalism for analyzing evolution of gaussian states of quantized fields in time-dependent backgrounds in the Schrodinger picture (presented in detail in Mahajan and Padmanabhan [G. Mahajan, T. Padmanabhan, Gen. Rel. Grav. 40 (2008) 661]) to study the example of a spatially uniform electric field background (in a time-dependent gauge) which is kept turned on for a finite duration of time. In particular, we study the time-dependent particle content, defined in terms of the concept of instantaneous eigenstates, and describe how it captures the time evolution of the quantized field modes. The actual particle creation process occurs over a relatively short interval in time, and the particle content saturates rather quickly. We also compare the power spectrum of the field modes, computed in the asymptotic limit, with the corresponding situation in a cosmological de Sitter background. Particle creation under the influence of a spiked electric field localized in time, as a particular limiting case of the above general model, is also considered.
The multi-configurational time-dependent Hartree approach revisited
Manthe, Uwe
2015-06-28
The multi-configurational time-dependent Hartree (MCTDH) approach facilitates accurate high-dimensional quantum dynamics simulations. In the approach, the wavefunction is expanded in a direct product of self-adapting time-dependent single-particle functions (SPFs). The equations of motion for the expansion coefficients and the SPFs are obtained via the Dirac-Frenkel variational principle. While this derivation yields well-defined differential equations for the motion of occupied SPFs, singularities in the working equations resulting from unoccupied SPFs have to be removed by a regularization procedure. Here, an alternative derivation of the MCTDH equations of motion is presented. It employs an analysis of the time-dependence of the single-particle density matrices up to second order. While the analysis of the first order terms yields the known equations of motion for the occupied SPFs, the analysis of the second order terms provides new equations which allow one to identify optimal choices for the unoccupied SPFs. The effect of the optimal choice of the unoccupied SPFs on the structure of the MCTDH equations of motion and their regularization is discussed. Generalized equations applicable in the multi-layer MCTDH framework are presented. Finally, the effects resulting from the initial choice of the unoccupied SPFs are illustrated by a simple numerical example.
Particle creation in a time-dependent electric field revisited
NASA Astrophysics Data System (ADS)
Mahajan, Gaurang
2009-02-01
We adopt the general formalism for analyzing evolution of gaussian states of quantized fields in time-dependent backgrounds in the Schrodinger picture (presented in detail in Mahajan and Padmanabhan [G. Mahajan, T. Padmanabhan, Gen. Rel. Grav. 40 (2008) 661]) to study the example of a spatially uniform electric field background (in a time-dependent gauge) which is kept turned on for a finite duration of time. In particular, we study the time-dependent particle content, defined in terms of the concept of instantaneous eigenstates, and describe how it captures the time evolution of the quantized field modes. The actual particle creation process occurs over a relatively short interval in time, and the particle content saturates rather quickly. We also compare the power spectrum of the field modes, computed in the asymptotic limit, with the corresponding situation in a cosmological de Sitter background. Particle creation under the influence of a spiked electric field localized in time, as a particular limiting case of the above general model, is also considered.
Technology Transfer Automated Retrieval System (TEKTRAN)
A series of studies were conducted using dual energy X-ray absorptiometry (DXA) to measure energy and protein deposition in pigs. In an initial validation study DXA was compared directly with slaughter analysis as a method for measuring body composition and energy deposition in pigs. Mean values fo...
Don W. Miller; Andrew Kauffmann; Eric Kreidler; Dongxu Li; Hanying Liu; Daniel Mills; Thomas D. Radcliff; Joseph Talnagi
2001-12-31
A comprehensive description of the accomplishments of the DOE grant titled, ''Local Measurement of Fuel Energy Deposition and Heat Transfer Environment During Fuel Lifetime using Controlled Calorimetry''.
Vapor-deposited porous films for energy conversion
Jankowski, Alan F.; Hayes, Jeffrey P.; Morse, Jeffrey D.
2005-07-05
Metallic films are grown with a "spongelike" morphology in the as-deposited condition using planar magnetron sputtering. The morphology of the deposit is characterized by metallic continuity in three dimensions with continuous and open porosity on the submicron scale. The stabilization of the spongelike morphology is found over a limited range of the sputter deposition parameters, that is, of working gas pressure and substrate temperature. This spongelike morphology is an extension of the features as generally represented in the classic zone models of growth for physical vapor deposits. Nickel coatings were deposited with working gas pressures up 4 Pa and for substrate temperatures up to 1000 K. The morphology of the deposits is examined in plan and in cross section views with scanning electron microscopy (SEM). The parametric range of gas pressure and substrate temperature (relative to absolute melt point) under which the spongelike metal deposits are produced appear universal for other metals including gold, silver, and aluminum.
Characterizing time-dependent mechanics in metallic MEMS
NASA Astrophysics Data System (ADS)
Bergers, L. I. J. C.; Delhey, N. K. R.; Hoefnagels, J. P. M.; Geers, M. G. D.
2010-06-01
Experiments for characterization of time-dependent material properties in free-standing metallic microelectromechanical system (MEMS) pose challenges: e.g. fabrication and handling (sub)-μm sized specimens, control and measurement of sub-μN loads and sub-μm displacements over long periods and various temperatures [1]. A variety of experimental setups have been reported each having their pros and cons. One example is a micro-tensile tester with an ingenious electro-static specimen gripping system [2] aiding simple specimen design giving good results at μN and sub-μm levels, but without in-situ full-field observations. Other progressive examples assimilate the specimen, MEMS actuators and load cells on a single chip [3,4] yielding significant results at nN and nm levels with in-situ TEM/SEM observability, though not without complications: complex load actuator/sensor calibration per chip, measures to reduce fabrication failure and unfeasible cofabrication on wafers with commercial metallic MEMS. This work aims to overcome these drawbacks by developing experimental methods with high sensitivity, precision and in-situ full-field observation capabilities. Moreover, these should be applicable to simple free-standing metallic MEMS that can be co-fabricated with commercial devices. These methods will then serve in systematic studies into size-effects in time-dependent material properties. First a numeric-experimental method is developed. It characterizes bending deformation of onwafer μm-sized aluminum cantilevers. A specially designed micro-clamp is used to mechanically apply a constant precise deflection of the beam (zres <50 nm) for a prolonged period, see fig. 1. After this period, the deflection by the micro-clamp is removed. Full-field height maps with the ensuing deformation are measured over time with confocal optical profilometry (COP). This yields the tip deflection as function of time with ~3 nm precision, see fig.2. To extract material parameters
Advances in time-dependent current-density functional theory
NASA Astrophysics Data System (ADS)
Berger, Arjan
In this work we solve the problem of the gauge dependence of molecular magnetic properties (magnetizabilities, circular dichroism) using time-dependent current-density functional theory [1]. We also present a new functional that accurately describes the optical absorption spectra of insulators, semiconductors and metals [2] N. Raimbault, P.L. de Boeij, P. Romaniello, and J.A. Berger Phys. Rev. Lett. 114, 066404 (2015) J.A. Berger, Phys. Rev. Lett. 115, 137402 (2015) This study has been partially supported through the Grant NEXT No. ANR-10-LABX-0037 in the framework of the Programme des Investissements d'Avenir.
Time dependence of delayed neutron emission for fissionable isotope identification
Kinlaw, M.T.; Hunt, A.W.
2005-06-20
The time dependence of delayed neutron emission was examined as a method of fissionable isotope identification. A pulsed bremsstrahlung photon beam was used to induce photofission reactions in {sup 238}U, {sup 232}Th, and {sup 239}Pu targets. The resulting delayed neutron emission was recorded between irradiating pulses and is a well-known technique for fissionable material detection. Monitoring the decay of delayed neutron emission between irradiating pulses demonstrates the ability to not only detect the presence of fissionable materials, but also to identify which fissionable isotope is present.
Brownian motion of electrons in time-dependent magnetic fields.
NASA Technical Reports Server (NTRS)
Iverson, G. J.; Williams, R. M.
1973-01-01
The behavior of a weakly ionized plasma in slowly varying time-dependent magnetic fields is studied through an extension of Williamson's stochastic theory. In particular, attention is focused on the properties of electron diffusion in the plane perpendicular to the direction of the magnetic field, when the field strength is large. It is shown that, in the strong field limit, the classical 1/B-squared dependence of the perpendicular diffusion coefficient is obtained for two models in which the field B(t) is monotonic in t and for two models in which B(t) possesses at least one turning point.
Time-Dependent Approach to Two-Proton Radioactivity
NASA Astrophysics Data System (ADS)
Oishi, Tomohiro; Hagino, Kouichi; Sagawa, Hiroyuki
We apply a time-dependent quantum three-body model to the two-proton emission of 6Be nucleus in order to discuss the role of pairing correlation between the emitted two protons during the tunneling process. With this method, we calculate the time-evolution of the two protons, which provides an intuitive way to understand this phenomenon. The calculated decay width is in a good agreement with the experimental data. Furthermore, we also show that the pairing correlation significantly enhances the probabilities of the diproton-like cluster emission, reflecting the "diproton correlation" in proton-rich nuclei.
Deterministic methods for time-dependent stochastic neutron transport
Baker, Randal S
2009-01-01
A numerical method is presented for solving the time-dependent survival probability equation in general (lD/2D/3D) geometries using the multi group SNmethod. Although this equation was first formulated by Bell in the early 1960's, it has only been applied to stationary systems (for other than idealized point models) until recently, and detailed descriptions of numerical solution techniques are lacking in the literature. This paper presents such a description and applies it to a dynamic system representative of a figurative criticality accident scenario.
A variational formulation for time-dependent climate models
NASA Technical Reports Server (NTRS)
Smith, G. L.
1984-01-01
A variational principle for time dependent diffusion problems is presented and is demonstrated by applying it to simple seasonal climate models. Two cases are treated. The first, a North-Coakley-type model with constant properties, is used as a tutorial example for the application of the technique. For the second case, heat capacity and thermal conductivity are considered to be latitude dependent in order to treat the effects of land/ocean distribution on the seasonal temperature distribution over the earth. The variational equations are derived and approximate analytical solutions are developed which delineate the influences of the physical asymmetries of the hemispheres in producing an asymmetric annual cycle.
Quantum description of a time-dependent mesoscopic RLC circuit
NASA Astrophysics Data System (ADS)
Pedrosa, I. A.
2012-11-01
In this paper, we present a comprehensive quantum description of a mesoscopic RLC circuit with time-dependent resistance, inductance and capacitance. Based on the dynamical invariant method and using quadratic invariants, we derive exact nonstationary quantum states for this circuit and write them in terms of solutions of the Milne-Pinney equation. Afterwards, we use quadratic invariants to construct coherent states for this quantized system and employ them to investigate quantum properties of the RLC circuit. In particular, we show that the product of the quantum fluctuations of the charge and the magnetic flux does not satisfy the minimum uncertainty relation.
Perspective: Fundamental aspects of time-dependent density functional theory
NASA Astrophysics Data System (ADS)
Maitra, Neepa T.
2016-06-01
In the thirty-two years since the birth of the foundational theorems, time-dependent density functional theory has had a tremendous impact on calculations of electronic spectra and dynamics in chemistry, biology, solid-state physics, and materials science. Alongside the wide-ranging applications, there has been much progress in understanding fundamental aspects of the functionals and the theory itself. This Perspective looks back to some of these developments, reports on some recent progress and current challenges for functionals, and speculates on future directions to improve the accuracy of approximations used in this relatively young theory.
Rare B decays and time dependent mixing at CDF
Ragan, K.J.; CDF Collaboration
1995-06-01
We report recent results on rare B decays searches -- specifically, the decay modes B{sup 0} {yields} {mu}{sup +}{mu}{sup {minus}}, B{sup 0} {yields} {mu}{sup +}{mu}{sup {minus}}K{sup 0*}, and B{sup {plus_minus}} {yields} {mu}{sup +}{mu}{sup {minus}}K{sup {plus_minus}} -- from the CDF collaboration using data from the 1992--1993 run of the Tevatron collider. In addition, we present the first CDF measurement of time dependent B{sup 0} {minus} {bar B}{sup 0} mixing.
Optimal moving grids for time-dependent partial differential equations
NASA Technical Reports Server (NTRS)
Wathen, A. J.
1989-01-01
Various adaptive moving grid techniques for the numerical solution of time-dependent partial differential equations were proposed. The precise criterion for grid motion varies, but most techniques will attempt to give grids on which the solution of the partial differential equation can be well represented. Moving grids are investigated on which the solutions of the linear heat conduction and viscous Burgers' equation in one space dimension are optimally approximated. Precisely, the results of numerical calculations of optimal moving grids for piecewise linear finite element approximation of partial differential equation solutions in the least squares norm.
Optimal moving grids for time-dependent partial differential equations
NASA Technical Reports Server (NTRS)
Wathen, A. J.
1992-01-01
Various adaptive moving grid techniques for the numerical solution of time-dependent partial differential equations were proposed. The precise criterion for grid motion varies, but most techniques will attempt to give grids on which the solution of the partial differential equation can be well represented. Moving grids are investigated on which the solutions of the linear heat conduction and viscous Burgers' equation in one space dimension are optimally approximated. Precisely, the results of numerical calculations of optimal moving grids for piecewise linear finite element approximation of PDE solutions in the least-squares norm are reported.
Time Dependent Hartree Fock Equation: Gateway to Nonequilibrium Plasmas
James W. Dufty
2007-04-28
This is the Final Technical Report for DE-FG02-2ER54677 award “Time Dependent Hartree Fock Equation - Gateway to Nonequilibrium Plasmas”. Research has focused on the nonequilibrium dynamics of electrons in the presence of ions, both via basic quantum theory and via semi-classical molecular dynamics (MD) simulation. In addition, fundamental notions of dissipative dynamics have been explored for models of grains and dust, and for scalar fields (temperature) in turbulent edge plasmas. The specific topics addressed were Quantum Kinetic Theory for Metallic Clusters, Semi-classical MD Simulation of Plasmas , and Effects of Dissipative Dynamics.
Boundary Sensitivities for Diffusion Processes in Time Dependent Domains
Costantini, C. Gobet, E. Karoui, N. El
2006-09-15
We study the sensitivity, with respect to a time dependent domain D{sub s}, of expectations of functionals of a diffusion process stopped at the exit from D{sub s} or normally reflected at the boundary of D{sub s}. We establish a differentiability result and give an explicit expression for the gradient that allows the gradient to be computed by Monte Carlo methods. Applications to optimal stopping problems and pricing of American options, to singular stochastic control and others are discussed.
Time-dependent Kohn-Sham approach to quantum electrodynamics
Ruggenthaler, M.; Mackenroth, F.; Bauer, D.
2011-10-15
We prove a generalization of the van Leeuwen theorem toward quantum electrodynamics, providing the formal foundations of a time-dependent Kohn-Sham construction for coupled quantized matter and electromagnetic fields. We circumvent the symmetry-causality problems associated with the action-functional approach to Kohn-Sham systems. We show that the effective external four-potential and four-current of the Kohn-Sham system are uniquely defined and that the effective four-current takes a very simple form. Further we rederive the Runge-Gross theorem for quantum electrodynamics.
Time-dependent resonant scattering: an analytical approach.
Lecomte, J M; Kirrander, Adam; Jungen, Ch
2013-10-28
A time-dependent description is given of a scattering process involving a single resonance embedded in a set of flat continua. An analytical approach is presented which starts from an incident free particle wave packet and yields the Breit-Wigner cross-section formula at infinite times. We show that at intermediate times the so-called Wigner-Weisskopf approximation is equivalent to a scattering process involving a contact potential. Applications in cold-atom scattering and resonance enhanced desorption of molecules are discussed. PMID:24182008
Time-dependent resonant scattering: An analytical approach
NASA Astrophysics Data System (ADS)
Lecomte, J. M.; Kirrander, Adam; Jungen, Ch.
2013-10-01
A time-dependent description is given of a scattering process involving a single resonance embedded in a set of flat continua. An analytical approach is presented which starts from an incident free particle wave packet and yields the Breit-Wigner cross-section formula at infinite times. We show that at intermediate times the so-called Wigner-Weisskopf approximation is equivalent to a scattering process involving a contact potential. Applications in cold-atom scattering and resonance enhanced desorption of molecules are discussed.
SYNCHROTRON LIGHTCURVES OF BLAZARS IN A TIME-DEPENDENT SYNCHROTRON-SELF COMPTON COOLING SCENARIO
Zacharias, Michael; Schlickeiser, Reinhard E-mail: rsch@tp4.rub.de
2013-11-10
Blazars emit non-thermal radiation in all frequency bands from radio to γ-rays. Additionally, they often exhibit rapid flaring events at all frequencies with doubling timescale of the TeV and X-ray flux on the order of minutes, and such rapid flaring events are difficult to explain theoretically. We explore the effect of the synchrotron-self Compton cooling, which is inherently time-dependent, leading to a rapid cooling of the electrons. Having intensively discussed the resulting effects of this cooling scenario on the spectral energy distribution of blazars in previous papers, the effects of the time-dependent approach on the synchrotron lightcurve are investigated here. Taking into account the retardation due to the finite size of the source and the source geometry, we show that the time-dependent synchrotron-self Compton (SSC) cooling still has profound effects on the lightcurve compared to the usual linear (synchrotron and external Compton) cooling terms. This is most obvious if the SSC cooling takes longer than the light crossing timescale. Then, in most frequency bands, the variability timescale is up to an order of magnitude shorter than under linear cooling conditions. This is yet another strong indication that the time-dependent approach should be taken into account for modeling blazar flares from compact emission regions.
QUIPS: Time-dependent properties of quasi-invariant self-gravitating polytropes
Munier, A.; Feix, M.R.
1983-04-01
Quasi-invariance, a method based on group tranformations, is used to obtain time-dependent solutions for the expansion and/or contraction of a self-gravitating sphere of perfect gas with polytopic index n. Quasi-invariance transforms the equations of hydrodynamics into ''dual equations'' exhibiting extra terms such as a friction, a mass source or sink term, and a centripetal/centrifugal force. The search for stationary solutions in this ''dual space'' leads to a new class of time-dependent solutions, the QUIP (for Quasi-invariant polytrope), which generalizes Emden's static model and introduces a characteristic frequency a related to Jean's frequency. The second order differential equation describing the solution is integrated numerically. A critical point is seen always to exist for nnot =3. Solutions corresponding in the ''dual space'' to a time-dependent generalization of Eddington's standard model (n = 3) are discussed. These solutions conserve both the total mass and the energy. A transition between closed and open structures is seen to take place at a particular frequency a/sub c/. For n = 3, no critical point arises in the ''dual space'' due to the self-similar motion of the fluid. A new time-dependent mass-radius relation and a generalized Betti-Ritter relation are obtained. Conclusions about the existence of a minimum Q-factor are presented.
Handford, C.R. )
1990-08-01
Subaqueous deposits of aragonite, gypsum, and halite are accumulating in shallow solar salt ponds constructed in the Pekelmeer, a sea-level salina on Bonaire, Netherlands Antilles. Several halite facies are deposited in the crystallizer ponds in response to difference in water depth and wave energy. Cumulate halite, which originates as floating rafts, is present only along the protected, upwind margins of ponds where low-energy conditions foster their formation and preservation. Cornet crystals with peculiar mushroom- and mortarboard-shaped caps precipitate in centimetre-deep brine sheets within a couple of metres of the upwind or low-energy margins. Downwind from these margins, cornet and chevron halite precipitate on the pond floors in water depths ranging from a few centimetres to {approximately} 60 cm. Halite pisoids with radial-concentric structure are precipitated in the swash zone along downwind high-energy shorelines where they form pebbly beaches. This study suggests that primary halite facies are energy and/or depth dependent and that some primary features, if preserved in ancient halite deposits, can be used to infer physical energy conditions, subenvironments such as low- to high-energy shorelines, and extremely shallow water depths in ancient evaporite basins.
Deposition of dopant impurities and pulsed energy drive-in
Wickboldt, Paul; Carey, Paul G.; Smith, Patrick M.; Ellingboe, Albert R.
1999-01-01
A semiconductor doping process which enhances the dopant incorporation achievable using the Gas Immersion Laser Doping (GILD) technique. The enhanced doping is achieved by first depositing a thin layer of dopant atoms on a semiconductor surface followed by exposure to one or more pulses from either a laser or an ion-beam which melt a portion of the semiconductor to a desired depth, thus causing the dopant atoms to be incorporated into the molten region. After the molten region recrystallizes the dopant atoms are electrically active. The dopant atoms are deposited by plasma enhanced chemical vapor deposition (PECVD) or other known deposition techniques.
Deposition of dopant impurities and pulsed energy drive-in
Wickboldt, Paul; Carey, Paul G.; Smith, Patrick M.; Ellingboe, Albert R.
2008-01-01
A semiconductor doping process which enhances the dopant incorporation achievable using the Gas Immersion Laser Doping (GILD) technique. The enhanced doping is achieved by first depositing a thin layer of dopant atoms on a semiconductor surface followed by exposure to one or more pulses from either a laser or an ion-beam which melt a portion of the semiconductor to a desired depth, thus causing the dopant atoms to be incorporated into the molten region. After the molten region recrystallizes the dopant atoms are electrically active. The dopant atoms are deposited by plasma enhanced chemical vapor deposition (PECVD) or other known deposition techniques.
Deposition of dopant impurities and pulsed energy drive-in
Wickboldt, P.; Carey, P.G.; Smith, P.M.; Ellingboe, A.R.
1999-06-29
A semiconductor doping process which enhances the dopant incorporation achievable using the Gas Immersion Laser Doping (GILD) technique is disclosed. The enhanced doping is achieved by first depositing a thin layer of dopant atoms on a semiconductor surface followed by exposure to one or more pulses from either a laser or an ion-beam which melt a portion of the semiconductor to a desired depth, thus causing the dopant atoms to be incorporated into the molten region. After the molten region recrystallizes the dopant atoms are electrically active. The dopant atoms are deposited by plasma enhanced chemical vapor deposition (PECVD) or other known deposition techniques. 2 figs.
Extended gyrokinetic field theory for time-dependent magnetic confinement fields
Sugama, H.; Watanabe, T.-H.; Nunami, M.
2014-01-15
A gyrokinetic system of equations for turbulent toroidal plasmas in time-dependent axisymmetric background magnetic fields is derived from the variational principle. Besides governing equations for gyrocenter distribution functions and turbulent electromagnetic fields, the conditions which self-consistently determine the background magnetic fields varying on a transport time scale are obtained by using the Lagrangian, which includes the constraint on the background fields. Conservation laws for energy and toroidal angular momentum of the whole system in the time-dependent background magnetic fields are naturally derived by applying Noether's theorem. It is shown that the ensemble-averaged transport equations of particles, energy, and toroidal momentum given in the present work agree with the results from the conventional recursive formulation with the WKB representation except that collisional effects are disregarded here.
Resonance in the nonadiabatic quantum pumping of the time-dependent Josephson junction
NASA Astrophysics Data System (ADS)
Zhu, Rui; Liu, Mi
2016-01-01
In this work, we investigated the nonadiabatic transport properties of the one-dimensional time-dependent superconductor-normal metal-superconductor (SNS) Josephson junction biased by a current source and driven by a high-frequency-ac-gate-potential applied to the normal-metal layer. BCS superconductors are considered and treated with the time-dependent Bogoliubov-de Gennes equation. Using Floquet theory, we compute the transmission coefficients and the Wigner-Smith delay times as a function of the incident energy and find that they display resonances when one of the electron or hole Floquet wavevectors coincides with the bound quasiparticle state within the superconducting energy gap. The resonance varies with the phase difference between the two superconductors as a result of the bound quasiparticle level displacement. The supercurrent flowing through the SNS junction is dramatically enhanced by the resonances.
Time-dependent Jahn-Teller problem: Phonon-induced relaxation through conical intersection
Pae, Kaja Hizhnyakov, Vladimir
2014-12-21
A theoretical study of time-dependent dynamical Jahn-Teller effect in an impurity center in a solid is presented. We are considering the relaxation of excited states in the E⊗e-problem through the conical intersection of the potential energy. A strict quantum-mechanical treatment of vibronic interactions with both the main Jahn-Teller active vibration and the nontotally symmetric phonons causing the energy loss is given. The applied method enables us to calculate the time-dependence of the distribution function of the basic configurational coordinate. We have performed a series of numerical calculations allowing us, among other relaxation features, to visualise the details of the relaxation through the conical intersection. In particular, we elucidate how the Slonczewski quantization of the states in the conical intersection affects the relaxation.
Time-dependent strains and stresses in a pumpkin balloon
NASA Astrophysics Data System (ADS)
Gerngross, T.; Xu, Y.; Pellegrino, S.
This paper presents a study of pumpkin-shaped superpressure balloons consisting of gores made from a thin polymeric film attached to high stiffness meridional tendons This type of design is being used for the NASA ULDB balloons The gore film shows considerable time-dependent stress relaxation whereas the behaviour of the tendons is essentially time-independent Upon inflation and pressurization the instantaneous i e linear-elastic strain and stress distributions in the film show significantly higher values in the meridional direction However over time and due to the biaxial visco-elastic stress relaxation of the the gore material the em hoop strains increase and the em meridional stresses decrease whereas the em remaining strain and stress components remain substantially unchanged These results are important for a correct assessment of the structural integrity of a pumpkin balloon in a long-duration mission both in terms of the material performance and the overall stability of the shape of the balloon An experimental investigation of the time dependence of the biaxial strain distribution in the film of a 4 m diameter 48 gore pumpkin balloon is presented The inflated shape of selected gores has been measured using photogrammetry and the time variation in strain components at some particular points of these gores has been measured under constant pressure and temperature The results show good correlation with a numerical study using the ABAQUS finite-element package that includes a widely used model of
Time-dependent strains and stresses in a pumpkin balloon
NASA Technical Reports Server (NTRS)
Gerngross, T.; Xu, Y.; Pellegrino, S.
2006-01-01
This paper presents a study of pumpkin-shaped superpressure balloons, consisting of gores made from a thin polymeric film attached to high stiffness, meridional tendons. This type of design is being used for the NASA ULDB balloons. The gore film shows considerable time-dependent stress relaxation, whereas the behaviour of the tendons is essentially time-independent. Upon inflation and pressurization, the "instantaneous", i.e. linear-elastic strain and stress distribution in the film show significantly higher values in the meridional direction. However, over time, and due to the biaxial visco-elastic stress relaxation of the the material, the hoop strains increase and the meridional stresses decrease, whereas the remaining strain and stress components remain substantially unchanged. These results are important for a correct assessment of the structural integrity of a pumpkin balloon in a long-duration mission, both in terms of the material performance and the overall stability of the shape of the balloon. An experimental investigation of the time dependence of the biaxial strain distribution in the film of a 4 m diameter, 48 gore pumpkin balloon is presented. The inflated shape of selected gores has been measured using photogrammetry and the time variation in strain components at some particular points of these gores has been measured under constant pressure and temperature. The results show good correlation with a numerical study, using the ABAQUS finite-element package, that includes a widely used model of the visco-elastic response of the gore material:
Time Circular Birefringence in Time-Dependent Magnetoelectric Media
Zhang, Ruo-Yang; Zhai, Yan-Wang; Lin, Shi-Rong; Zhao, Qing; Wen, Weijia; Ge, Mo-Lin
2015-01-01
Light traveling in time-dependent media has many extraordinary properties which can be utilized to convert frequency, achieve temporal cloaking, and simulate cosmological phenomena. In this paper, we focus on time-dependent axion-type magnetoelectric (ME) media, and prove that light in these media always has two degenerate modes with opposite circular polarizations corresponding to one wave vector , and name this effect “time circular birefringence” (TCB). By interchanging the status of space and time, the pair of TCB modes can appear simultaneously via “time refraction” and “time reflection” of a linear polarized incident wave at a time interface of ME media. The superposition of the two TCB modes causes the “time Faraday effect”, namely the globally unified polarization axes rotate with time. A circularly polarized Gaussian pulse traversing a time interface is also studied. If the wave-vector spectrum of a pulse mainly concentrates in the non-traveling-wave band, the pulse will be trapped with nearly fixed center while its intensity will grow rapidly. In addition, we propose an experimental scheme of using molecular fluid with external time-varying electric and magnetic fields both parallel to the direction of light to realize these phenomena in practice. PMID:26329928
Rayleigh-Taylor mixing with time-dependent acceleration
NASA Astrophysics Data System (ADS)
Abarzhi, Snezhana
2015-11-01
We extend the momentum model to describe Rayleigh-Taylor (RT) mixing driven by a time-dependent acceleration. The acceleration is a power-law function of time, similarly to astrophysical and plasma fusion applications. In RT flow the dynamics of a fluid parcel is driven by a balance per unit mass of the rates of momentum gain and loss. We find analytical solutions in the cases of balanced and imbalanced gains and losses, and identify their dependence on the acceleration exponent. The existence is shown of two typical regimes of self-similar RT mixing -acceleration-driven Rayleigh-Taylor-type and dissipation-driven Richtymer-Meshkov-type with the latter being in general non-universal. Possible scenarios are proposed for transitions from the balanced dynamics to the imbalanced self-similar dynamics. Scaling and correlations properties of RT mixing are studied on the basis of dimensional analysis. Departures are outlined of RT dynamics with time-dependent acceleration from canonical cases of homogeneous turbulence as well as blast waves with first and second kind self-similarity. Support of National Science Foundation is warmy appreciated.
Time dependence in B → V ℓℓ decays
NASA Astrophysics Data System (ADS)
Descotes-Genon, Sébastien; Virto, Javier
2015-04-01
We discuss the theory and phenomenology of B d,s → V (→ M 1 M 2)ℓℓ decays in the presence of neutral-meson mixing. We derive expressions for the time-dependent angular distributions for decays into CP eigenstates, and identify the relevant observables that can be extracted from time-integrated and time-dependent analyses with or without tagging, with a focus on the difference between measurements at B-factories and hadronic machines. We construct two observables of interest, which we call Q {8/-} and Q 9, and which are theoretically clean at large recoil. We compute these two observables in the Standard Model, and show that they have good potential for New Physics searches by considering their sensitivity to benchmark New Physics scenarios consistent with current b → sℓℓ data. These results apply to decays such as B d → K ∗(→ K S π0)ℓℓ, B s → ϕ(→ K S K L )ℓℓ and B s → ϕ(→ K + K -)ℓℓ.
Efficient photoheating algorithms in time-dependent photoionization simulations
NASA Astrophysics Data System (ADS)
Lee, Kai-Yan; Mellema, Garrelt; Lundqvist, Peter
2016-02-01
We present an extension to the time-dependent photoionization code C2-RAY to calculate photoheating in an efficient and accurate way. In C2-RAY, the thermal calculation demands relatively small time-steps for accurate results. We describe two novel methods to reduce the computational cost associated with small time-steps, namely, an adaptive time-step algorithm and an asynchronous evolution approach. The adaptive time-step algorithm determines an optimal time-step for the next computational step. It uses a fast ray-tracing scheme to quickly locate the relevant cells for this determination and only use these cells for the calculation of the time-step. Asynchronous evolution allows different cells to evolve with different time-steps. The asynchronized clocks of the cells are synchronized at the times where outputs are produced. By only evolving cells which may require short time-steps with these short time-steps instead of imposing them to the whole grid, the computational cost of the calculation can be substantially reduced. We show that our methods work well for several cosmologically relevant test problems and validate our results by comparing to the results of another time-dependent photoionization code.
Inverse problem of quadratic time-dependent Hamiltonians
NASA Astrophysics Data System (ADS)
Guo, Guang-Jie; Meng, Yan; Chang, Hong; Duan, Hui-Zeng; Di, Bing
2015-08-01
Using an algebraic approach, it is possible to obtain the temporal evolution wave function for a Gaussian wave-packet obeying the quadratic time-dependent Hamiltonian (QTDH). However, in general, most of the practical cases are not exactly solvable, for we need general solutions of the Riccatti equations which are not generally known. We therefore bypass directly solving for the temporal evolution wave function, and study its inverse problem. We start with a particular evolution of the wave-packet, and get the required Hamiltonian by using the inverse method. The inverse approach opens up a new way to find new exact solutions to the QTDH. Some typical examples are studied in detail. For a specific time-dependent periodic harmonic oscillator, the Berry phase is obtained exactly. Project supported by the National Natural Science Foundation of China (Grant No. 11347171), the Natural Science Foundation of Hebei Province of China (Grant No. A2012108003), and the Key Project of Educational Commission of Hebei Province of China (Grant No. ZD2014052).
Time Circular Birefringence in Time-Dependent Magnetoelectric Media.
Zhang, Ruo-Yang; Zhai, Yan-Wang; Lin, Shi-Rong; Zhao, Qing; Wen, Weijia; Ge, Mo-Lin
2015-01-01
Light traveling in time-dependent media has many extraordinary properties which can be utilized to convert frequency, achieve temporal cloaking, and simulate cosmological phenomena. In this paper, we focus on time-dependent axion-type magnetoelectric (ME) media, and prove that light in these media always has two degenerate modes with opposite circular polarizations corresponding to one wave vector , and name this effect "time circular birefringence" (TCB). By interchanging the status of space and time, the pair of TCB modes can appear simultaneously via "time refraction" and "time reflection" of a linear polarized incident wave at a time interface of ME media. The superposition of the two TCB modes causes the "time Faraday effect", namely the globally unified polarization axes rotate with time. A circularly polarized Gaussian pulse traversing a time interface is also studied. If the wave-vector spectrum of a pulse mainly concentrates in the non-traveling-wave band, the pulse will be trapped with nearly fixed center while its intensity will grow rapidly. In addition, we propose an experimental scheme of using molecular fluid with external time-varying electric and magnetic fields both parallel to the direction of light to realize these phenomena in practice. PMID:26329928
Mesoscopic structure of neuronal tracts from time-dependent diffusion
Burcaw, Lauren M.; Fieremans, Els; Novikov, Dmitry S.
2015-01-01
Interpreting brain diffusion MRI measurements in terms of neuronal structure at a micrometer level is an exciting unresolved problem. Here we consider diffusion transverse to a bundle of fibers, and show theoretically, as well as using Monte Carlo simulations and measurements in a phantom made of parallel fibers mimicking axons, that the time dependent diffusion coefficient approaches its macroscopic limit slowly, in a (lnt)/t fashion. The logarithmic singularity arises due to short range disorder in the fiber packing. We identify short range disorder in axonal fibers based on histological data from the splenium, and argue that the time dependent contribution to the overall diffusion coefficient from the extra-axonal water dominates that of the intra-axonal water. This dominance may explain the bias in measuring axon diameters in clinical settings. The short range disorder is also reflected in the linear frequency dependence of the diffusion coefficient measured with oscillating gradients, in agreement with recent experiments. Our results relate the measured diffusion to the mesoscopic structure of neuronal tissue, uncovering the sensitivity of diffusion metrics to axonal arrangement within a fiber tract, and providing an alternative interpretation of axonal diameter mapping techniques. PMID:25837598
Endocannabinoids mediate bidirectional striatal spike-timing-dependent plasticity
Cui, Yihui; Paillé, Vincent; Xu, Hao; Genet, Stéphane; Delord, Bruno; Fino, Elodie; Berry, Hugues; Venance, Laurent
2015-01-01
Key points Although learning can arise from few or even a single trial, synaptic plasticity is commonly assessed under prolonged activation. Here, we explored the existence of rapid responsiveness of synaptic plasticity at corticostriatal synapses in a major synaptic learning rule, spike-timing-dependent plasticity (STDP). We found that spike-timing-dependent depression (tLTD) progressively disappears when the number of paired stimulations (below 50 pairings) is decreased whereas spike-timing-dependent potentiation (tLTP) displays a biphasic profile: tLTP is observed for 75–100 pairings, is absent for 25–50 pairings and re-emerges for 5–10 pairings. This tLTP induced by low numbers of pairings (5–10) depends on activation of the endocannabinoid system, type-1 cannabinoid receptor and the transient receptor potential vanilloid type-1. Endocannabinoid-tLTP may represent a physiological mechanism operating during the rapid learning of new associative memories and behavioural rules characterizing the flexible behaviour of mammals or during the initial stages of habit learning. Abstract Synaptic plasticity, a main substrate for learning and memory, is commonly assessed with prolonged stimulations. Since learning can arise from few or even a single trial, synaptic strength is expected to adapt rapidly. However, whether synaptic plasticity occurs in response to limited event occurrences remains elusive. To answer this question, we investigated whether a low number of paired stimulations can induce plasticity in a major synaptic learning rule, spike-timing-dependent plasticity (STDP). It is known that 100 pairings induce bidirectional STDP, i.e. spike-timing-dependent potentiation (tLTP) and depression (tLTD) at most central synapses. In rodent striatum, we found that tLTD progressively disappears when the number of paired stimulations is decreased (below 50 pairings) whereas tLTP displays a biphasic profile: tLTP is observed for 75–100 pairings, absent for 25
Time Dependent Relative Risks in Life Insurance Medical Underwriting.
Kneepkens, Robert F
2015-01-01
Introduction .- Life insurance medicine focuses on mortality hazards in specified periods. People are free to insure their lives for shorter or longer terms. Because the chosen terms range from 1 year to a life time, life insurers have to take into account the fact that the predictive value of risk indicators can and will change over time. The time a risk indicator keeps its predictive value, will be dependent on its biological effects, volatility, and treatability. For a given applicant this implies that the relative hazard (RH) calculated for his/her medical condition should be dependent on the term of the insurance. The main objective of this study is to determine if some commonly used risk indicators - previously used to study age dependency of relative risks - have a predictive value that increases with the observation period. (1) Methods .- This population-based cohort study uses NHANES-data files from the Third National Health and Nutrition Examination Survey (NHANES III) and the NHANES Linked Mortality Files 2010. Only participants aged 20 to 69 that were examined in mobile examination centers, without a history of some prevalent high risk diseases were included. The observed mortality was compared to the expected mortality in a Generalized Linear Model (GLM) with Poisson error structure with two reference populations, which both can serve as preferred reference for life insurers: The United States Life Tables 2008 (USLT) and the 2008 Valuation Basic Tables (VBT) based on the insured population of 35 US Life insurers. The time dependency of the RHs of the systolic blood pressure (SBP), aspartate aminotransferase (ASAT), lactate dehydrogenase (LDH), serum albumin and albuminuria, was assessed, with correction for ethnicity, household income, history of diabetes mellitus, BMI and serum cholesterol. To be able to compare the results with the results of the Age Dependency Study (ADS), the same data, risk indicators, statistical analysis method, and the
SYMTRAN - A Time-dependent Symmetric Tandem Mirror Transport Code
Hua, D; Fowler, T
2004-06-15
A time-dependent version of the steady-state radial transport model in symmetric tandem mirrors in Ref. [1] has been coded up and first tests performed. Our code, named SYMTRAN, is an adaptation of the earlier SPHERE code for spheromaks, now modified for tandem mirror physics. Motivated by Post's new concept of kinetic stabilization of symmetric mirrors, it is an extension of the earlier TAMRAC rate-equation code omitting radial transport [2], which successfully accounted for experimental results in TMX. The SYMTRAN code differs from the earlier tandem mirror radial transport code TMT in that our code is focused on axisymmetric tandem mirrors and classical diffusion, whereas TMT emphasized non-ambipolar transport in TMX and MFTF-B due to yin-yang plugs and non-symmetric transitions between the plugs and axisymmetric center cell. Both codes exhibit interesting but different non-linear behavior.
String pair production in a time-dependent gravitational field
Tolley, Andrew J.; Wesley, Daniel H.
2005-12-15
We study the pair creation of point particles and strings in a time-dependent, weak gravitational field. We find that, for massive string states, there are surprising and significant differences between the string and point-particle results. Central to our approach is the fact that a weakly curved spacetime can be represented by a coherent state of gravitons, and therefore we employ standard techniques in string perturbation theory. String and point-particle pairs are created through tree-level interactions between the background gravitons. In particular, we focus on the production of excited string states and perform explicit calculations of the production of a set of string states of arbitrary excitation level. The differences between the string and point-particle results may contain important lessons for the pair production of strings in the strong gravitational fields of interest in cosmology and black hole physics.
Time-dependent reliability analysis of ceramic engine components
NASA Technical Reports Server (NTRS)
Nemeth, Noel N.
1993-01-01
The computer program CARES/LIFE calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/or proof test loading. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program. CARES/LIFE accounts for the phenomenon of subcritical crack growth (SCG) by utilizing either the power or Paris law relations. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The effects of multiaxial stresses are modeled using either the principle of independent action (PIA), the Weibull normal stress averaging method (NSA), or the Batdorf theory. Inert strength and fatigue parameters are estimated from rupture strength data of naturally flawed specimens loaded in static, dynamic, or cyclic fatigue. Two example problems demonstrating proof testing and fatigue parameter estimation are given.
Equation-free analysis of spike-timing-dependent plasticity.
Laing, Carlo R; Kevrekidis, Ioannis G
2015-12-01
Spike-timing-dependent plasticity is the process by which the strengths of connections between neurons are modified as a result of the precise timing of the action potentials fired by the neurons. We consider a model consisting of one integrate-and-fire neuron receiving excitatory inputs from a large number-here, 1000-of Poisson neurons whose synapses are plastic. When correlations are introduced between the firing times of these input neurons, the distribution of synaptic strengths shows interesting, and apparently low-dimensional, dynamical behaviour. This behaviour is analysed in two different parameter regimes using equation-free techniques, which bypass the explicit derivation of the relevant low-dimensional dynamical system. We demonstrate both coarse projective integration (which speeds up the time integration of a dynamical system) and the use of recently developed data mining techniques to identify the appropriate low-dimensional description of the complex dynamical systems in our model. PMID:26577337
Optimal resolution of a time-dependent aberrationless magnetic lens.
Calvo, M
2004-05-01
We analyse the optimal conditions for operation of a time-dependent magnetic field lens recently proposed. The lens consists of an axially symmetric ellipsoidal coil producing a spatially homogeneous but time-pulsating magnetic field. This system is capable of focusing a beam of charged particles drifting parallel to the coil axis as well as forming images of an object emitting electrons. This lens has no spherical aberration and, consequently, opens the possibility of surpassing the resolving power of conventional round static field lenses. The cardinal elements of this lens are functions of time and thereby the image position, its magnification factor and orientation change in time. We show how by a suitable choice of the magnetic field pulse parameters and the introduction of screens with circular apertures, it is possible to render all the image characteristics stationary. The effect of diffraction is also discussed in the context of transfer function theory. PMID:15093944
Doppler tracking in time-dependent cosmological spacetimes
NASA Astrophysics Data System (ADS)
Giulini, Domenico; Carrera, Matteo
I will discuss the theoretical problems associated with Doppler tracking in time dependent background geometries, where ordinary Newtonian kinematics fails. A derivation of an exact general-relativistic formula for the two-way Doppler tracking of a spacecraft in homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetimes is presented, as well as a controlled approximation in McVittie spacetimes representing an FLRW background with a single spherically-symmetric inhomogeneity (e.g. a single star or black hole). The leading-order corrections of the acceleration as compared to the Newtonian expression are calculated, which are due to retardation and cosmological expansion and which in the Solar System turn out to be significantly below the scale (nanometer per square-second) set by the Pioneer Anomaly. Last, but not least, I discuss kinematical ambiguities connected with notions of "simultaneity" and "spatial distance", which, in principle, also lead to tracking corrections.
Time-dependent local density measurements in unsteady flows
NASA Technical Reports Server (NTRS)
Mckenzie, R. L.; Monson, D. J.; Exberger, R. J.
1979-01-01
A laser-induced fluorescence technique for measuring the relative time-dependent density fluctuations in unsteady or turbulent flows is demonstrated. Using a 1.5-W continuous-wave Kr(+) laser, measurements have been obtained in 0.1-mm diameter by 1-mm-long sampling volumes in a Mach 3 flow of N2 seeded with biacetyl vapor. A signal amplitude resolution of 2% was achieved for a detection frequency bandwidth of 10 kHz. The measurement uncertainty was found to be dominated by noise behaving as photon statistical noise. The practical limits of signal-to-noise ratios have been characterized for a wide range of detection frequency bandwidths that encompasses those of interest in supersonic turbulence measurements.
A time dependent anatomically detailed model of cardiac conduction
NASA Technical Reports Server (NTRS)
Saxberg, B. E.; Grumbach, M. P.; Cohen, R. J.
1985-01-01
In order to understand the determinants of transitions in cardiac electrical activity from normal patterns to dysrhythmias such as ventricular fibrillation, we are constructing an anatomically and physiologically detailed finite element simulation of myocardial electrical propagation. A healthy human heart embedded in paraffin was sectioned to provide a detailed anatomical substrate for model calculations. The simulation of propagation includes anisotropy in conduction velocity due to fiber orientation as well as gradients in conduction velocities, absolute and relative refractory periods, action potential duration and electrotonic influence of nearest neighbors. The model also includes changes in the behaviour of myocardial tissue as a function of the past local activity. With this model, we can examine the significance of fiber orientation and time dependence of local propagation parameters on dysrhythmogenesis.
XDAMP. Experimental Time-Dependent Data Analysis, Manipulation, Visualization GUI
Ballard, W.P.
1995-04-01
XDAMP is a graphical user interface (GUI) designed to allow the user to manipulate two-dimensional waveforms (data vs. time) that typically are generated during transient response experiments. A typical single data set from these facilities may generate more than 100 time-dependent waveforms. XDAMP can manipulate waveforms both in time and in amplitude. Typical operations are: time shifting, truncating before or after a specific time, adding, multiplying, integrating, and averaging. The software automatically maintains an audit trail for operations performed on each waveform. Annotation can be added to the overall file so that the data set contains full documentation. PostScript printing graphics and annotation is supported. Data are saved using the Hierarchical Data Format (HDF) from the National Center for Supercomputing Applications.
Time dependent electronic transport in chiral edge channels
NASA Astrophysics Data System (ADS)
Fève, G.; Berroir, J.-M.; Plaçais, B.
2016-02-01
We study time dependent electronic transport along the chiral edge channels of the quantum Hall regime, focusing on the role of Coulomb interaction. In the low frequency regime, the a.c. conductance can be derived from a lumped element description of the circuit. At higher frequencies, the propagation equations of the Coulomb coupled edge channels need to be solved. As a consequence of the interchannel coupling, a charge pulse emitted in a given channel fractionalized in several pulses. In particular, Coulomb interaction between channels leads to the fractionalization of a charge pulse emitted in a given channel in several pulses. We finally study how the Coulomb interaction, and in particular the fractionalization process, affects the propagation of a single electron in the circuit. All the above-mentioned topics are illustrated by experimental realizations.
Time-dependent reliability analysis and condition assessment of structures
Ellingwood, B.R.
1997-01-01
Structures generally play a passive role in assurance of safety in nuclear plant operation, but are important if the plant is to withstand the effect of extreme environmental or abnormal events. Relative to mechanical and electrical components, structural systems and components would be difficult and costly to replace. While the performance of steel or reinforced concrete structures in service generally has been very good, their strengths may deteriorate during an extended service life as a result of changes brought on by an aggressive environment, excessive loading, or accidental loading. Quantitative tools for condition assessment of aging structures can be developed using time-dependent structural reliability analysis methods. Such methods provide a framework for addressing the uncertainties attendant to aging in the decision process.
Memory Retention and Spike-Timing-Dependent Plasticity
Billings, Guy; van Rossum, Mark C. W.
2009-01-01
Memory systems should be plastic to allow for learning; however, they should also retain earlier memories. Here we explore how synaptic weights and memories are retained in models of single neurons and networks equipped with spike-timing-dependent plasticity. We show that for single neuron models, the precise learning rule has a strong effect on the memory retention time. In particular, a soft-bound, weight-dependent learning rule has a very short retention time as compared with a learning rule that is independent of the synaptic weights. Next, we explore how the retention time is reflected in receptive field stability in networks. As in the single neuron case, the weight-dependent learning rule yields less stable receptive fields than a weight-independent rule. However, receptive fields stabilize in the presence of sufficient lateral inhibition, demonstrating that plasticity in networks can be regulated by inhibition and suggesting a novel role for inhibition in neural circuits. PMID:19297513
Measuring time-dependent diffusion in polymer matrix composites
NASA Astrophysics Data System (ADS)
Pilli, Siva P.; Smith, Lloyd V.; Vaithiyalingam, Shutthanandan
2014-11-01
Moisture plays a significant role in influencing the mechanical behavior and long-term durability of polymer matrix composites (PMCs). The common methods used to determine the moisture diffusion coefficients of PMCs are based on the solution of Fickian diffusion in the one-dimensional domain. Fick's Law assumes that equilibrium between the material surface and the external vapor is established instantaneously. A time-dependent boundary condition has been shown to improve correlation with some bulk diffusion measurements, but has not been validated experimentally. The surface moisture content in a Toray 800S/3900-2B toughened quasi-isotropic laminate system, [0/±60] s , was analyzed experimentally using Nuclear Reaction Analysis (NRA). It was found that the surface moisture content showed a rapid increase to an intermediate concentration C 0, followed by a slow linear increase to the saturation level.
Retroactive modulation of spike timing-dependent plasticity by dopamine
Brzosko, Zuzanna; Schultz, Wolfram; Paulsen, Ole
2015-01-01
Most reinforcement learning models assume that the reward signal arrives after the activity that led to the reward, placing constraints on the possible underlying cellular mechanisms. Here we show that dopamine, a positive reinforcement signal, can retroactively convert hippocampal timing-dependent synaptic depression into potentiation. This effect requires functional NMDA receptors and is mediated in part through the activation of the cAMP/PKA cascade. Collectively, our results support the idea that reward-related signaling can act on a pre-established synaptic eligibility trace, thereby associating specific experiences with behaviorally distant, rewarding outcomes. This finding identifies a biologically plausible mechanism for solving the ‘distal reward problem’. DOI: http://dx.doi.org/10.7554/eLife.09685.001 PMID:26516682
Time-dependent diffusive acceleration of test particles at shocks
NASA Astrophysics Data System (ADS)
Drury, L. O'C.
1991-07-01
A theoretical description is developed for the acceleration of test particles at a steady plane nonrelativistic shock. The mean and the variance of the acceleration-time distribution are expressed analytically for the condition under which the diffusion coefficient is arbitrarily dependent on position and momentum. The formula for an acceleration rate with arbitrary spatial variation in the diffusion coefficient developed by Drury (1987) is supplemented by a general theory of time dependence. An approximation scheme is developed by means of the analysis which permits the description of the spectral cutoff resulting from the finite shock age. The formulas developed in the analysis are also of interest for analyzing the observations of heliospheric shocks made from spacecraft.
Measuring time-dependent diffusion in polymer matrix composites
Pilli, Siva Prasad; Smith, Lloyd V.; Shutthanandan, V.
2014-11-01
Moisture plays a significant role in influencing the mechanical behavior and long-term durability of polymer matrix composites (PMC’s). The common methods used to determine the moisture diffusion coefficients of PMCs are based on the solution of Fickian diffusion in the one-dimensional domain. Fick’s Law assumes that equilibrium between the material surface and the external vapor is established instantaneously. A time dependent boundary condition has been shown to improve correlation with some bulk diffusion measurements, but has not been validated experimentally. The surface moisture content in a Toray 800S/3900-2B toughened quasi-isotropic laminate system, [0/±60]s, was analyzed experimentally using Nuclear Reaction Analysis (NRA). It was found that the surface moisture content showed a rapid increase to an intermediate concentration C0, followed by a slow linear increase to the saturation level.
Optimization of Time-Dependent Particle Tracing Using Tetrahedral Decomposition
NASA Technical Reports Server (NTRS)
Kenwright, David; Lane, David
1995-01-01
An efficient algorithm is presented for computing particle paths, streak lines and time lines in time-dependent flows with moving curvilinear grids. The integration, velocity interpolation and step-size control are all performed in physical space which avoids the need to transform the velocity field into computational space. This leads to higher accuracy because there are no Jacobian matrix approximations or expensive matrix inversions. Integration accuracy is maintained using an adaptive step-size control scheme which is regulated by the path line curvature. The problem of cell-searching, point location and interpolation in physical space is simplified by decomposing hexahedral cells into tetrahedral cells. This enables the point location to be done analytically and substantially faster than with a Newton-Raphson iterative method. Results presented show this algorithm is up to six times faster than particle tracers which operate on hexahedral cells yet produces almost identical particle trajectories.
Shortcuts to adiabaticity in a time-dependent box
Campo, A. del; Boshier, M. G.
2012-01-01
A method is proposed to drive an ultrafast non-adiabatic dynamics of an ultracold gas trapped in a time-dependent box potential. The resulting state is free from spurious excitations associated with the breakdown of adiabaticity, and preserves the quantum correlations of the initial state up to a scaling factor. The process relies on the existence of an adiabatic invariant and the inversion of the dynamical self-similar scaling law dictated by it. Its physical implementation generally requires the use of an auxiliary expulsive potential. The method is extended to a broad family of interacting many-body systems. As illustrative examples we consider the ultrafast expansion of a Tonks-Girardeau gas and of Bose-Einstein condensates in different dimensions, where the method exhibits an excellent robustness against different regimes of interactions and the features of an experimentally realizable box potential. PMID:22970340
Time-dependent response of hydrogels under constrained swelling
NASA Astrophysics Data System (ADS)
Drozdov, A. D.; Sommer-Larsen, P.; Christiansen, J. deClaville; Sanporean, C.-G.
2014-06-01
Constitutive equations are developed for the viscoplastic behavior of covalently cross-linked hydrogels subjected to swelling. The ability of the model to describe the time-dependent response is confirmed by comparison of results of simulation with observations on partially swollen poly(2-hydroxyethyl methacrylate) gel specimens in uniaxial tensile tests with a constant strain rate and tensile relaxation tests. The stress-strain relations are applied to study the kinetics of unconstrained and constrained swelling. The following conclusions are drawn from numerical analysis: (i) maximum water uptake under constrained swelling a viscoplastic hydrogel is lower than that for unconstrained swelling of its elastic counterpart and exceeds maximum water uptake under constrained swelling of the elastic gel, (ii) when the rate of water diffusion exceeds the rate of plastic flow in a polymer network, swelling curves (mass uptake versus time) for viscoplastic gels under constraints demonstrate characteristic features of non-Fickian diffusion.
Time-dependent behavior of flax/starch composites
NASA Astrophysics Data System (ADS)
Varna, J.; Spārniņš, E.; Joffe, R.; Nättinen, K.; Lampinen, J.
2012-02-01
The time-dependent mechanical response of flax fiber-reinforced thermoplastic starch matrix composite and neat starch is analyzed. It is demonstrated that the response is highly sensitive to the relative humidity (with specific saturation moisture content in the composite) and special effort has to be made to keep it constant. It was found that the accumulation of micro-damage and the resulting reduction of the elastic modulus in this type of composite is limited. The highly nonlinear behavior of composites is related to the nonlinear viscoelasticity and viscoplasticity. These phenomena are accounted for by simple material models, as suggested in this study. The stress-dependent nonlinearity descriptors in these models are determined in creep and strain recovery tests at low as well as by high stresses.
Translation invariant time-dependent solutions to massive gravity
Mourad, J.; Steer, D.A. E-mail: steer@apc.univ-paris7.fr
2013-12-01
Homogeneous time-dependent solutions of massive gravity generalise the plane wave solutions of the linearised Fierz-Pauli equations for a massive spin-two particle, as well as the Kasner solutions of General Relativity. We show that they also allow a clear counting of the degrees of freedom and represent a simplified framework to work out the constraints, the equations of motion and the initial value formulation. We work in the vielbein formulation of massive gravity, find the phase space resulting from the constraints and show that several disconnected sectors of solutions exist some of which are unstable. The initial values determine the sector to which a solution belongs. Classically, the theory is not pathological but quantum mechanically the theory may suffer from instabilities. The latter are not due to an extra ghost-like degree of freedom.
Time-dependent local density measurements in unsteady flows
NASA Technical Reports Server (NTRS)
Mckenzie, R. L.; Monson, D. J.; Exberger, R. J.
1979-01-01
A laser-induced fluorescence technique for measuring the relative time-dependent density fluctuations in unsteady or turbulent flows is demonstrated. Using a 1.5-W continuous-wave Kr(+) laser, measurements have been obtained in 0.1-mm-diameter by 1-mm-long sampling volumes in a Mach 3 flow of N2 seeded with biacetyl vapor. A signal amplitude resolution of 2% was achieved for a detection frequency bandwidth of 10 kHz. The measurement uncertainty was found to be dominated by noise behaving as photon statistical noise. The practical limits of signal-to-noise ratios have been characterized for a wide range of detection frequency bandwidths that encompasses those of interest in supersonic turbulence measurements.
Relating Time-Dependent Acceleration and Height Using an Elevator
NASA Astrophysics Data System (ADS)
Kinser, Jason M.
2015-04-01
A simple experiment in relating a time-dependent linear acceleration function to height is explored through the use of a smartphone and an elevator. Given acceleration as a function of time1, a(t), the velocity function and position functions are determined through integration as in v (t ) =∫ a (t ) d t (1) and x (t ) =∫ v (t ) dt. Mobile devices such as smartphones or tablets have accelerometers that capture slowly evolving acceleration with respect to time and can deliver those measurements as a CSV file. A recent example measured the oscillations of the elevator as it starts its motion.2 In the application presented here the mobile device is used to estimate the height of the elevator ride. By estimating the functional form of the acceleration of an elevator ride, it is possible to estimate the height of the ride through Eqs. (1) and (2).
Reprint of : Time dependent electronic transport in chiral edge channels
NASA Astrophysics Data System (ADS)
Fève, G.; Berroir, J.-M.; Plaçais, B.
2016-08-01
We study time dependent electronic transport along the chiral edge channels of the quantum Hall regime, focusing on the role of Coulomb interaction. In the low frequency regime, the a.c. conductance can be derived from a lumped element description of the circuit. At higher frequencies, the propagation equations of the Coulomb coupled edge channels need to be solved. As a consequence of the interchannel coupling, a charge pulse emitted in a given channel fractionalized in several pulses. In particular, Coulomb interaction between channels leads to the fractionalization of a charge pulse emitted in a given channel in several pulses. We finally study how the Coulomb interaction, and in particular the fractionalization process, affects the propagation of a single electron in the circuit. All the above-mentioned topics are illustrated by experimental realizations.
Nonlinear fracture mechanics. Volume 1. Time-dependent fracture
Saxena, A.; Landes, J.D.; Bassani, J.L.
1989-01-01
Various papers on time-dependent fracture in nonlinear fracture mechanics are presented. Individual subjects considered include: numerical study of non-steady-state creep at stationary crack tips, crack growth in small-scale creep, growth of macroscopic cracks by void coalescence under extensive creeping conditions, creep embrittlement susceptibility and creep crack growth behavior in low-alloy steels, and experimental determination of the high-temperature crack growth behavior of Incoloy 800H. Also discussed are: three-dimensional transient analysis of a dynamically loaded three-point-bend ductile fracture specimen, experimental study of the validity of a Delta J criterion for fatigue crack growth, combined-mode low-cycle fatigue crack growth under torsional loading, fatigue crack-tip mechanics in 7075-T6 aluminum alloy from high-sensitivity displacement field measurements, and nonlinear fracture of concrete and ceramics.
Light pressure of time-dependent fields in plasmas
Zeidler, A.; Schnabl, H.; Mulser, P.
1985-01-01
An expression of the light pressure Pi is derived for the case of a nearly monochromatic electromagnetic wave with arbitrarily time-dependent amplitude. Thereby Pi is defined as the time-averaged force density exerted on a plasma by the wave. The resulting equations are valid for both transverse and longitudinal waves. The light pressure turns out to consist of two components: the well-known gradient-type term and a new nonstationary solenoidal term. This is true for warm as well as cold plasmas. The importance of the new term for the generation of static magnetic fields is shown, and a model in which shear forces may result is given. Formulas for the nonstationary light pressure developed previously are discussed.
Single trapped ion as a time-dependent harmonic oscillator
Menicucci, Nicolas C.; Milburn, G. J.
2007-11-15
We show how a single trapped ion may be used to test a variety of important physical models realized as time-dependent harmonic oscillators. The ion itself functions as its own motional detector through laser-induced electronic transitions. Alsing et al., [Phys. Rev. Lett. 94, 220401 (2005)] proposed that an exponentially decaying trap frequency could be used to simulate (thermal) Gibbons-Hawking radiation in an expanding universe, but the Hamiltonian used was incorrect. We apply our general solution to this experimental proposal, correcting the result for a single ion and showing that while the actual spectrum is different from the Gibbons-Hawking case, it nevertheless shares an important experimental signature with this result.
Spike-timing dependent plasticity in the striatum.
Fino, Elodie; Venance, Laurent
2010-01-01
The striatum is the major input nucleus of basal ganglia, an ensemble of interconnected sub-cortical nuclei associated with fundamental processes of action-selection and procedural learning and memory. The striatum receives afferents from the cerebral cortex and the thalamus. In turn, it relays the integrated information towards the basal ganglia output nuclei through which it operates a selected activation of behavioral effectors. The striatal output neurons, the GABAergic medium-sized spiny neurons (MSNs), are in charge of the detection and integration of behaviorally relevant information. This property confers to the striatum the ability to extract relevant information from the background noise and select cognitive-motor sequences adapted to environmental stimuli. As long-term synaptic efficacy changes are believed to underlie learning and memory, the corticostriatal long-term plasticity provides a fundamental mechanism for the function of the basal ganglia in procedural learning. Here, we reviewed the different forms of spike-timing dependent plasticity (STDP) occurring at corticostriatal synapses. Most of the studies have focused on MSNs and their ability to develop long-term plasticity. Nevertheless, the striatal interneurons (the fast-spiking GABAergic, NO-synthase and cholinergic interneurons) also receive monosynaptic afferents from the cortex and tightly regulated corticostriatal information processing. Therefore, it is important to take into account the variety of striatal neurons to fully understand the ability of striatum to develop long-term plasticity. Corticostriatal STDP with various spike-timing dependence have been observed depending on the neuronal sub-populations and experimental conditions. This complexity highlights the extraordinary potentiality in term of plasticity of the corticostriatal pathway. PMID:21423492
Time-Dependent Model of the Global Electric Circuit
NASA Astrophysics Data System (ADS)
Mallios, S. A.; Pasko, V. P.
2013-12-01
The Global Electric Circuit (GEC) is a circuit that is formed between the Earth's surface, which is a good conductor of electricity, and the ionosphere, a weekly-ionized plasma at around 80 km altitude [e.g., Rycroft et al., Space Sci. Rev., 137(1-4), pp. 83-105, 2008]. In the absence of any source, the GEC behaves as a leaky spherical capacitor, with the ground being the negative charged plate and the ionosphere the positive one, which discharges through the weakly conducting atmosphere creating fair-weather current, which is about 1 kA integrated over the entire Earth surface [e.g., Bering et al., Physics Today, Oct., 24-30, 1998]. It is accepted that thunderstorms are the main generators in the GEC [e.g., Williams, Atmospheric Research, 91, 140, 2009; Mareev, Physics Uspekhi, 53, 504, 2010]. In this current work, we developed a two-dimensional cylindrical time-dependent model, which calculates the quasi-electrostatic fields created by the slow accumulation of the charge in the cloud, by taking into account the Maxwellian relaxation of the charges in the conducting atmosphere. The model is capable of simulating the whole volume of the GEC and thus it has the same electrical properties as the three-dimensional spherical system. Two different kinds of boundary conditions (Dirichlet and homogeneous Neumann boundary conditions) were used in order to describe the global circulation of the current, and it has been found that both of them give the same results regarding the general contribution of a storm to the GEC. We present results regarding the response of the fair weather region to lightning transients that occur in the thunderstorm, and in the steady state limit the results of the time-dependent model are compared to static GEC solutions similar to those reported previously by Tzur and Roble [JGR, 90, 5989, 1985].
Time dependent patient no-show predictive modelling development.
Huang, Yu-Li; Hanauer, David A
2016-05-01
Purpose - The purpose of this paper is to develop evident-based predictive no-show models considering patients' each past appointment status, a time-dependent component, as an independent predictor to improve predictability. Design/methodology/approach - A ten-year retrospective data set was extracted from a pediatric clinic. It consisted of 7,291 distinct patients who had at least two visits along with their appointment characteristics, patient demographics, and insurance information. Logistic regression was adopted to develop no-show models using two-thirds of the data for training and the remaining data for validation. The no-show threshold was then determined based on minimizing the misclassification of show/no-show assignments. There were a total of 26 predictive model developed based on the number of available past appointments. Simulation was employed to test the effective of each model on costs of patient wait time, physician idle time, and overtime. Findings - The results demonstrated the misclassification rate and the area under the curve of the receiver operating characteristic gradually improved as more appointment history was included until around the 20th predictive model. The overbooking method with no-show predictive models suggested incorporating up to the 16th model and outperformed other overbooking methods by as much as 9.4 per cent in the cost per patient while allowing two additional patients in a clinic day. Research limitations/implications - The challenge now is to actually implement the no-show predictive model systematically to further demonstrate its robustness and simplicity in various scheduling systems. Originality/value - This paper provides examples of how to build the no-show predictive models with time-dependent components to improve the overbooking policy. Accurately identifying scheduled patients' show/no-show status allows clinics to proactively schedule patients to reduce the negative impact of patient no-shows. PMID:27142954
Time-Dependence and Pattern Formation in Flowing Granular Media.
NASA Astrophysics Data System (ADS)
Baxter, George William, III
1990-01-01
We study the time dependence and pattern formation of gravity driven flows of granular media in three experiments. In three dimensional flows of sand, the normal stress on the wall of a conical hopper is measured. There is no evidence of characteristic time scales predicted by a linear stability analysis of a current continuum theory of granular media. Instead, the signal is characterized by a power law power spectrum, and the time variation of the normal stress obeys a scaling law consistent with fractional Brownian motion with H ~ 0.2. As one of the best examples to date of fractional Brownian motion in a physical experiment, this provides a unique opportunity for a study of the theory's application. In digital subtraction radiography studies of sand flow through a thin (nearly two dimensional) wedge, density waves are found. The formation and motion of these depends on the geometry of the wedge and the roughness of the sand grains. The waves form in rough sand but not in smooth sand of the same approximate size, demonstrating that grain structure has a dramatic effect on the flow. Also, the position of stagnant regions along the sides of the wedge is found to scale as a power law of the wedge angle. Neither the density waves nor the position of the stagnant regions are predicted by current theories. Finally, a cellular automata model is proposed to model the two dimensional flow of ellipsoidal grains (such as grass seed) through a wedge. By including particle shape and orientation as degrees of freedom, this model is able to capture many features of real physical flows. In sum, these experiments demonstrate that flows of even simple materials like sand or grass seed contain time dependent patterns that are not predicted by current theoretical models. This demonstrates the need to include particle structure and orientation. Finally, the cellular automata model shows that even relatively simple models which include these added degrees of freedom can reproduce the
Understanding and Predicting Time-Dependent Dune Erosion
NASA Astrophysics Data System (ADS)
Long, J.; Stockdon, H. F.; Smith, J. R.
2014-12-01
The vulnerability of coastal ecosystems, habitats, and infrastructure is largely dictated by how protective sand dunes respond to extreme waves and water levels during storms. Predicting the type of dune response (e.g., scarping, overwashing, breaching) is often done with conditional storm-impact scale models (e.g. Sallenger 2000) however, these models do not describe the magnitude of expected changes or account for the continuum of dune responses throughout the duration of a storm event. Alternatively, process-based dune erosion models like XBeach explicitly compute interactions between waves, water levels, and sediment transport but are limited in regional applications due to computational requirements and inadequate knowledge of required boundary conditions. Using historical observations of storm-induced coastal change, we are developing and testing a variety of new static, probabilistic, and time-dependent models for dune erosion. Model development is informed by the observed dune response from four events that impacted geomorphically diverse regions along the U.S. Atlantic and Gulf of Mexico coastlines. Results from the static models indicate that alongshore differences in the magnitude of dune elevation change can be related to the depth of water over of the dune crest (e.g. freeboard) but that increasing freeboard does not always correspond to an increased lowering of the dune crest. Applying the concept of dune freeboard in a time-dependent approach that incorporates rising water levels that cause a dune to sequentially experience collision, overwash and then inundation shows that reasonable estimates of dune erosion are obtained. The accuracy of each of the models is now being evaluated along the large and diverse regions of coast that were impacted by Hurricane Sandy in 2012 where dune response was highly variable.
Time-Dependent DIII-D Heat Transport Simulations Using Neural-Network Models
NASA Astrophysics Data System (ADS)
Penna, J. M.; Smith, S. P.; Meneghini, O.; Luna, C. J.
2014-10-01
The neural network transport model BRAINFUSE has been developed to produce transport fluxes based on local parameters. The BRAIN-FUSE model has been integrated into the transport modeling framework ONETWO in order to develop time dependent solutions and has been validated by artificially varying the input neutral beam power and comparing the output to DIII-D scans. These efforts have led to the development of a time-dependent workflow within the OMFIT integrated modeling framework. The new work flow can evolve the electron and ion temperatures as a function of time dependent sources and equilibria. The effects of different engineering parameters can be explored and optimized in support of DIII-D operations. The efficiency of this workflow enables planning plasma operations of next-day experiments, as will be required for ITER. Work supported in part by the National Undergraduate Fellowship Program in Plasma Physics and Fusion Energy Sciences and the US Department of Energy under DE-FG02-94ER54235 & DE-FC02-04ER54698.
Monte Carlo calculation of energy deposition in ionization chambers for tritium measurements
NASA Astrophysics Data System (ADS)
Zhilin, Chen; Shuming, Peng; Dan, Meng; Yuehong, He; Heyi, Wang
2014-10-01
Energy deposition in ionization chambers for tritium measurements has been theoretically studied using Monte Carlo code MCNP 5. The influence of many factors, including carrier gas, chamber size, wall materials and gas pressure, has been evaluated in the simulations. It is found that β rays emitted by tritium deposit much more energy into chambers flowing through with argon than with deuterium in them, as much as 2.7 times higher at pressure 100 Pa. As chamber size gets smaller, energy deposition decreases sharply. For an ionization chamber of 1 mL, β rays deposit less than 1% of their energy at pressure 100 Pa and only 84% even if gas pressure is as high as 100 kPa. It also indicates that gold plated ionization chamber results in the highest deposition ratio while aluminum one leads to the lowest. In addition, simulations were validated by comparison with experimental data. Results show that simulations agree well with experimental data.
Observation of the time dependence of B0d-B0d mixing
NASA Astrophysics Data System (ADS)
Buskulic, D.; de Bonis, I.; Decamp, D.; Ghez, P.; Goy, C.; Lees, J.-P.; Minard, M.-N.; Pietrzyk, B.; Ariztizabal, F.; Comas, P.; Crespo, J. M.; Delfino, M.; Efthymiopoulos, I.; Fernandez, E.; Fernandez-Bosman, M.; Gaitan, V.; Garrido, Ll.; Mattison, T.; Pacheco, A.; Padilla, C.; Pascual, A.; Creanza, D.; de Palma, M.; Farilla, A.; Iaselli, G.; Maggi, G.; Natali, S.; Nuzzo, S.; Quattromini, M.; Ranieri, A.; Raso, G.; Romano, F.; Ruggieri, F.; Selvaggi, G.; Silvestris, L.; Tempesta, P.; Zito, G.; Chai, Y.; Hu, H.; Huang, D.; Huang, X.; Lin, J.; Wang, T.; Xie, Y.; Xu, D.; Xu, R.; Zhang, J.; Zhang, L.; Zhao, W.; Blucher, E.; Bonvicini, G.; Boudreau, J.; Casper, D.; Drevermann, H.; Forty, R. W.; Ganis, G.; Gay, C.; Hagelberg, R.; Harvey, J.; Hilgart, J.; Jacobsen, R.; Jost, B.; Knobloch, J.; Lehraus, I.; Lohse, T.; Maggi, M.; Markou, C.; Martinez, M.; Mato, P.; Meinhard, H.; Minten, A.; Miotto, A.; Miquel, R.; Moser, H.-G.; Palazzi, P.; Pater, J. R.; Perlas, J. A.; Pusztaszeri, J.-F.; Ranjard, F.; Redlinger, G.; Rolandi, L.; Rothberg, J.; Ruan, T.; Saich, M.; Schlatter, D.; Schmelling, M.; Sefkow, F.; Tejessy, W.; Tomalin, I. R.; Veenhof, R.; Wachsmuth, H.; Wasserbaech, S.; Wiedenmann, W.; Wildish, T.; Witzeling, W.; Wotschack, J.; Ajaltouni, Z.; Badaud, F.; Bardadin-Otwinowska, M.; El Fellous, R.; Falvard, A.; Gay, P.; Guicheney, C.; Henrard, P.; Jousset, J.; Michel, B.; Montret, J.-C.; Pallin, D.; Perret, P.; Podlyski, F.; Proriol, J.; Prulhière, F.; Saadi, F.; Fearnley, T.; Hansen, J. B.; Hansen, J. D.; Hansen, J. R.; Hansen, P. H.; Møllerud, R.; Nilsson, B. S.; Kyriakis, A.; Simopoulou, E.; Siotis, I.; Vayaki, A.; Zachariadou, K.; Badier, J.; Blondel, A.; Bonneaud, G.; Brient, J. C.; Fouque, G.; Orteu, S.; Rougé, A.; Rumpf, M.; Tanaka, R.; Verderi, M.; Videau, H.; Candlin, D. J.; Parsons, M. I.; Veitch, E.; Focardi, E.; Moneta, L.; Parrini, G.; Corden, M.; Georgiopoulos, C.; Ikeda, M.; Levinthal, D.; Antonelli, A.; Baldini, R.; Bencivenni, G.; Bologna, G.; Bossi, F.; Campana, P.; Capon, G.; Cerutti, F.; Chiarella, V.; D'Ettorre-Piazzoli, B.; Felici, G.; Laurelli, P.; Mannocchi, G.; Murtas, F.; Murtas, G. P.; Passalacqua, L.; Pepe-Altarelli, M.; Picchi, P.; Colrain, P.; Ten Have, I.; Lynch, J. G.; Maitland, W.; Morton, W. T.; Raine, C.; Reeves, P.; Scarr, J. M.; Smith, K.; Smith, M. G.; Thompson, A. S.; Turnbull, R. M.; Brandl, B.; Braun, O.; Geweniger, C.; Hanke, P.; Hepp, V.; Kluge, E. E.; Maumary, Y.; Putzer, A.; Rensch, B.; Stahl, A.; Tittel, K.; Wunsch, M.; Beuselinck, R.; Binnie, D. M.; Cameron, W.; Cattaneo, M.; Colling, D. J.; Dornan, P. J.; Greene, A. M.; Hassard, J. F.; Lieske, N. M.; Moutoussi, A.; Nash, J.; Patton, S.; Payne, D. G.; Phillips, M. J.; San Martin, G.; Sedgbeer, J. K.; Wright, A. G.; Girtler, P.; Kuhn, D.; Rudolph, G.; Vogl, R.; Bowdery, C. K.; Brodbeck, T. J.; Finch, A. J.; Foster, F.; Hughes, G.; Jackson, D.; Keemer, N. R.; Nuttall, M.; Patel, A.; Sloan, T.; Snow, S. W.; Whelan, E. P.; Kleinknecht, K.; Raab, J.; Renk, B.; Sander, H.-G.; Schmidt, H.; Steeg, F.; Walther, S. M.; Wanke, R.; Wolf, B.; Bencheikh, A. M.; Benchouk, C.; Bonissent, A.; Carr, J.; Coyle, P.; Drinkard, J.; Etienne, F.; Nicod, D.; Papalexiou, S.; Payre, P.; Roos, L.; Rousseau, D.; Schwemling, P.; Talby, M.; Adlung, S.; Assmann, R.; Bauer, C.; Blum, W.; Brown, D.; Cattaneo, P.; Dehning, B.; Dietl, H.; Dydak, F.; Frank, M.; Halley, A. W.; Jakobs, K.; Lauber, J.; Lütjens, G.; Lutz, G.; Männer, W.; Richter, R.; Schröder, J.; Schwarz, A. S.; Settles, R.; Seywerd, H.; Stierlin, U.; Stiegler, U.; Denis, R. St.; Wolf, G.; Alemany, R.; Boucrot, J.; Callot, O.; Cordier, A.; Davier, M.; Duflot, L.; Grivaz, J.-F.; Heusse, Ph.; Jaffe, D. E.; Janot, P.; Kim, D. W.; Le Diberder, F.; Lefrançois, J.; Lutz, A.-M.; Schune, M.-H.; Veillet, J.-J.; Videau, I.; Zhang, Z.; Abbaneo, D.; Bagliesi, G.; Batignani, G.; Bottigli, U.; Bozzi, C.; Calderini, G.; Carpinelli, M.; Ciocci, M. A.; Ciulli, V.; dell'Orso, R.; Ferrante, I.; Fidecaro, F.; Foà, L.; Forti, F.; Giassi, A.; Giorgi, M. A.; Gregorio, A.; Ligabue, F.; Lusiani, A.; Mannelli, E. B.; Marrocchesi, P. S.; Messineo, A.; Palla, F.; Rizzo, G.; Sanguinetti, G.; Spagnolo, P.; Steinberger, J.; Tenchini, R.; Tonelli, G.; Triggiani, G.; Valassi, A.; Vannini, C.; Venturi, A.; Verdini, P. G.; Walsh, J.; Betteridge, A. P.; Gao, Y.; Green, M. G.; March, P. V.; Mir, Ll. M.; Medcalf, T.; Quazi, I. S.; Strong, J. A.; West, L. R.; Botterill, D. R.; Clifft, R. W.; Edgecock, T. R.; Haywood, S.; Norton, P. R.; Thompson, J. C.; Bloch-Devaux, B.; Colas, P.; Duarte, H.; Emery, S.; Kozanecki, W.; Lançon, E.; Lemaire, M. C.; Locci, E.; Marx, B.; Perez, P.; Rander, J.; Renardy, J.-F.; Rosowsky, A.; Roussarie, A.; Schuller, J.-P.; Schwindling, J.; Si Mohand, D.; Vallage, B.; Johnson, R. P.; Litke, A. M.; Taylor, G.; Wear, J.; Ashman, J. G.; Babbage, W.; Booth, C. N.; Buttar, C.; Cartwright, S.; Combley, F.; Dawson, I.; Thompson, L. F.; Barberio, E.; Böhrer, A.; Brandt, S.; Cowan, G.; Grupen, C.; Lutters, G.; Rivera, F.; Schäfer, U.; Smolik, L.; Bosisio, L.; della Marina, R.; Giannini, G.; Gobbo, B.; Ragusa, F.; Bellantoni, L.; Chen, W.; Conway, J. S.; Feng, Z.; Ferguson, D. P. S.; Gao, Y. S.; Grahl, J.; Harton, J. L.; Hayes, O. J.; Nachtman, J. M.; Pan, Y. B.; Saadi, Y.; Schmitt, M.; Scott, I.; Sharma, V.; Shi, Z. H.; Turk, J. D.; Walsh, A. M.; Weber, F. V.; Sau, Lan, Wu; Zheng, M.; Zobernig, G.
1993-09-01
The time dependence of B0d-B0d oscillations has been observed using events with a d*, decaying into a D0π+, and a lepton in opposite hemispheres. The time dependence of the oscillations is derived from the displacement of the D0 vertex and the D*-lepton charge correlation. From a fit for the oscillation frequency the mass difference of the B0d states is measured: Δm = [3.44+0.65-0.70(stat.)+0.26-0.20(syst.)] × 10-4 eV/c2. Supported by the US Department of Energy, contract DE-AC02-76ER00881.
Analytically solvable driven time-dependent two-level quantum systems
NASA Astrophysics Data System (ADS)
Barnes, Edwin; Das Sarma, Sankar
2013-03-01
Analytical solutions to the time-dependent Schrodinger equation describing a driven two-level system are invaluable to many areas of physics, but they are also extremely rare. Here, we present a simple algorithm based on a type of partial reverse-engineering that generates an unlimited number of exact analytical solutions for a general time-dependent Hamiltonian. We demonstrate this method by presenting several new exact solutions that are particularly relevant to qubit control in quantum computing applications. We further show that our formalism easily generates analytical control protocols for performing sweeps across energy level anti-crossings that execute perfect Landau-Zener interferometry and rapid adiabatic passage near the quantum speed limit. Work supported by LPS-CMTC, CNAM and IARPA
Hermann, M.R.; Fleck J.A. Jr.
1988-12-15
A spectral method previously developed for solving the time-dependent Schroedinger equation in Cartesian coordinates is generalized to spherical polar coordinates. The solution is implemented by repeated application of a unitary evolution operator in symmetrically split form. The wave function is expanded as a Fourier series in the radial coordinate and in terms of Legendre functions in the polar angle. The use of appropriate quadrature sets makes the expansion exact for band-limited functions. The method is appropriate for solving explicitly time-dependent problems, or for determining stationary states by a spectral method. The accuracy of the method is established by computing the Stark shift and lifetime of the 1s state in hydrogen, the low-lying energy levels for hydrogen in a uniform magnetic field, and the 2p-nd dipole transition spectrum for hydrogen.
Time-dependent calculations of double photoionization of the aligned H2 molecule
NASA Astrophysics Data System (ADS)
Ivanov, I. A.; Kheifets, A. S.
2012-01-01
We perform time-dependent calculations of single-photon two-electron ionization of the aligned H2 molecule by an xuv pulse. Solution of the time-dependent Schrödinger equation is sought in spherical coordinates on a radial grid by time propagation using the Arnoldi-Lanczos method. From these calculations, we derive the total integrated as well as fully differential ionization cross sections for equal energy sharing and various orientations of the internuclear axis relative to the polarization vector of light. Satisfactory agreement with available literature data validates the present theoretical model. We supplement our numerical computations with an amplitude analysis of differential cross sections using the atomiclike formalism of Feagin [J. Phys. BJPAPEH0953-407510.1088/0953-4075/31/18/004 31, L729 (1998)]. This analysis provides some additional insight into mechanisms of double photoionization of the aligned H2 molecule.
NASA Astrophysics Data System (ADS)
Sapsis, Themistoklis; Babaee, Hessam
2015-11-01
We introduce a variational formulation for the determination of a finite-dimensional, time-dependent, orthonormal basis that captures directions of phase space associated with finite-time instabilities. While these instabilities have finite lifetime they can play a crucial role either by altering the system dynamics through the activation of other instabilities, or by creating sudden nonlinear energy transfers that lead extreme responses. However, their essentially transient character makes their description a particularly challenging task. Here we develop a variational framework that focus on the optimal approximation of the system dynamics over finite-time intervals under the orthonormal basis constraint. This variational formulation results in differential equations that evolve a time-dependent basis so that it optimally approximates the most unstable directions over finite times. Supported by ARO Award # 66710-EG-YIP.
NASA Astrophysics Data System (ADS)
Rodriguez, R.; Espinosa, G.; Gil, J. M.; Rubiano, J. G.; Mendoza, M. A.; Martel, P.; Minguez, E.; Symes, D. R.; Hohenberger, M.; Smith, R. A.
2015-12-01
Radiative shock waves are ubiquitous throughout the universe and play a crucial role in the transport of energy into the interstellar medium. This fact has led to many efforts to scale the astrophysical phenomena to accessible conditions. In some laboratory experiments radiative blast waves are launched in clusters of gases by means of the direct deposition of the laser energy. In this work, by using a collisional-radiative model, we perform an analysis of the plasma level populations and radiative properties of a blast wave launched in a xenon cluster. In particular, for both the shocked and unshocked material, we study the influence of different effects such as LTE, steady-state or time-dependent NLTE simulations, plasma self-absorption or external radiation field in the determination of those properties and also in the diagnosis of the electron temperature of the blast wave.
Resonant formation of few-cycle pulses by hydrogen-like atoms with time-dependent resonance
NASA Astrophysics Data System (ADS)
Radeonychev, Y. V.; Antonov, V. A.; Kocharovskaya, O. A.
2013-08-01
We show the possibility of producing a short bunch of nearly bandwidth-limited few-cycle attosecond pulses based on time-dependent resonant interaction of an incident radiation pulse with the bound states of hydrogen-like atoms. Time-dependence of an atomic resonance is provided by a laser pulse far from resonance with an intensity well below the atomic ionization threshold via time-dependent tunnel ionization from the excited states and time-dependent adiabatic Stark splitting of the excited energy levels. Without external matching of the spectral components it is possible to produce pulses with durations up to 80 as at the carrier wavelength of 13.5 nm in Li2+-plasma, as well as pulses with durations up to 600 as at the carrier wavelength of 122 nm in atomic hydrogen.
On the time-dependent extra spatial dimensions in six dimensional space-time
NASA Astrophysics Data System (ADS)
Lien, Phan Hong; Hai, Do Thi Hong
2016-06-01
In this paper, we analyze the time-dependent extra spatial dimensions in six dimensional (6D) space-time. The 4-brane is assumed to be a de Sitter space. Based on the form of the brane-world energy-momentum tensor proposed by Shiromizu et al. and the five dimensions by Peter K. F. Kuhfittic, we extended the theory to the 2-codimension embedded in higher dimensions. The inflation scenario in 6D is investigated in two cases of cosmological constant: Ʌ > 0 and Ʌ < 0. The energy of two extra dimensions is calculated too.
NASA Technical Reports Server (NTRS)
Sharafeddin, Omar A.; Judson, Richard S.; Kouri, Donald J.; Hoffman, David K.
1990-01-01
The novel wave-packet propagation scheme presented is based on the time-dependent form of the Lippman-Schwinger integral equation and does not require extensive matrix inversions, thereby facilitating application to systems in which some degrees of freedom express the potential in a basis expansion. The matrix to be inverted is a function of the kinetic energy operator, and is accordingly diagonal in a Bessel function basis set. Transition amplitudes for various orbital angular momentum quantum numbers are obtainable via either Fourier transform of the amplitude density from the time to the energy domain, or the direct analysis of the scattered wave packet.
Nuclear data processing for energy release and deposition calculations in the MC21 Monte Carlo code
Trumbull, T. H.
2013-07-01
With the recent emphasis in performing multiphysics calculations using Monte Carlo transport codes such as MC21, the need for accurate estimates of the energy deposition-and the subsequent heating - has increased. However, the availability and quality of data necessary to enable accurate neutron and photon energy deposition calculations can be an issue. A comprehensive method for handling the nuclear data required for energy deposition calculations in MC21 has been developed using the NDEX nuclear data processing system and leveraging the capabilities of NJOY. The method provides a collection of data to the MC21 Monte Carlo code supporting the computation of a wide variety of energy release and deposition tallies while also allowing calculations with different levels of fidelity to be performed. Detailed discussions on the usage of the various components of the energy release data are provided to demonstrate novel methods in borrowing photon production data, correcting for negative energy release quantities, and adjusting Q values when necessary to preserve energy balance. Since energy deposition within a reactor is a result of both neutron and photon interactions with materials, a discussion on the photon energy deposition data processing is also provided. (authors)
Monte Carlo approach to the spatial deposition of energy by electrons in molecular hydrogen
NASA Technical Reports Server (NTRS)
Heaps, M. G.; Green, A. E. S.
1974-01-01
The Monte Carlo (MC) and continuous slowdown approximation (CSDA) approaches to the spatial deposition of energy by electrons are compared using the same detailed atomic cross section (DACS). It is found that the CSDA method overestimates the amount of energy that is deposited near the end of the path for electrons above a few hundred electron volts. The MC results are in approximate agreement with experimental data in such a way as to be relatively independent of the actual gas used. Our MC results are extended to obtain the three-dimensional deposition of energy by sub-keV electrons in molecular hydrogen.
Estimating the energy deposition based on anisotropic fluxes measured by POES MEPED
NASA Astrophysics Data System (ADS)
Sandanger, Marit Irene; Stadsnes, Johan; Nesse Tyssøy, Hilde; Glesnes Ødegaard, Linn-Kristine; Åsnes, Arne
2015-04-01
The Medium Energy Proton and Electron Detector (MEPED) onboard the Polar Orbiting Operational Environmental Satellites (POES) consists of two electron telescopes, one viewing nearly radially outward from Earth (the 0o detector) and the other viewing antiparallel to the satellite's velocity (the 90o detector). Energetic particle measurements from POES are often used to estimate the energy deposition in the mesosphere. The electron fluxes usually show strong pitch angle anisotropy. Until now, it has been customary to derive a lower estimate of the energy deposition in the mesosphere from the 0o detector, while an upper estimate is derived from the 90odetector. We have developed a method using measurements from both the 0o and 90o telescopes in a combination with theoretically determined pitch angle distributions, in order to give a more precise estimate of the energy deposition in the upper atmosphere. The derived anisotropic flux distributions are used to calculate the energy deposition during Relativistic Electron Precipitation (REP) events.
Immersion Freezing of Clay Minerals and its Time Dependence
NASA Astrophysics Data System (ADS)
Hiranuma, N.; Moehler, O.; Bundke, U.; Cziczo, D. J.; Danielczok, A.; Ebert, M.; Garimella, S.; Hoffmann, N.; Kanji, Z. A.; Kiselev, A. A.; Raddatz, M.; Stetzer, O.
2012-12-01
Immersion ice nucleation efficiency of clay minerals has been investigated using the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) cloud chamber. Various clay dust samples, including two illite as well as three kaolinite standards, have been examined in the temperature range between 238 K and 255 K. We observed two trends in immersion ice nucleation properties as cloud expansion conditions in the AIDA are varied. First, as previously described in the literature, the supersaturation required for the immersion freezing of clay minerals decreased with decreasing temperature and increasing inferred ice-active surface site densities. Second, the ice nucleation activity of clay minerals strongly depended on the solo-parameter, which is the rate change in temperature (i.e., dNice/dT = ∂Nice/∂t ÷ ∂T/∂t). Further time dependence of ice formation is investigated and discussed as a function of cooling rates, ice nuclei (IN), and aerosol concentrations. Ice residuals collected through a pumped counterflow virtual impactor are examined by electron microprobe analyses to seek the true chemical and physical identity of IN in clay minerals. Brief comparisons of AIDA measurement to the measurements with other ice nucleation chambers (e.g., ETH-PINC, FINCH, and commercially available DMT-SPIN) are also presented.
Some Consequences of a Time Dependent Speed of Light
NASA Astrophysics Data System (ADS)
Smith, Felix T.
2007-06-01
For reasons connected with both cosmology (the flatness and horizon problems) and atomic physics (n-body Dirac equation, etc.), various proposals have been made to modify general or special relativity(SR) to accommodate a cosmologically decreasing light speed [J. Magueijo, Rep. Prog. Phys. 66, 2025 (2003)]. Two such theories, projective SR [S.N. Manida, gr-qc/9905046; S. S. Stepanov, physics/9909009 and Phys. Rev. D, 62, 023507 (2000)] and symmetric SR [F.T. Smith, Ann. Fond. L. de Broglie, 30, 179 (2005)] adapt special relativity to in different ways to an expanding, hyperbolically curved position space and predict time-dependences of c within reach of measurement but differing by a factor of two. Both theories bring in a new constant λ-1=σ=c^2H0-1. As Magueijo points, out the role of c in physics and cosmology is so profound that many deep changes must follow if is not absolutely invariant in space and time. In particular, symmetric SR brings a new light to the Dirac large-number relationship between the constants of gravitation and atomic physics.
A time-dependent model for improved biogalvanic tissue characterisation.
Chandler, J H; Culmer, P R; Jayne, D G; Neville, A
2015-10-01
Measurement of the passive electrical resistance of biological tissues through biogalvanic characterisation has been proposed as a simple means of distinguishing healthy from diseased tissue. This method has the potential to provide valuable real-time information when integrated into surgical tools. Characterised tissue resistance values have been shown to be particularly sensitive to external load switching direction and rate, bringing into question the stability and efficacy of the technique. These errors are due to transient variations observed in measurement data that are not accounted for in current electrical models. The presented research proposes the addition of a time-dependent element to the characterisation model to account for losses associated with this transient behaviour. Influence of switching rate has been examined, with the inclusion of transient elements improving the repeatability of the characterised tissue resistance. Application of this model to repeat biogalvanic measurements on a single ex vivo human colon tissue sample with healthy and cancerous (adenocarcinoma) regions showed a statistically significant difference (p < 0.05) between tissue types. In contrast, an insignificant difference (p > 0.05) between tissue types was found when measurements were subjected to the current model, suggesting that the proposed model may allow for improved biogalvanic tissue characterisation. PMID:26298197
The Out-of-Equilibrium Time-Dependent Gutzwiller Approximation
NASA Astrophysics Data System (ADS)
Fabrizio, Michele
We review the recently proposed extension of the Gutzwiller approximation (Schirò and Fabrizio, Phys Rev Lett 105:076401, 2010), designed to describe the out-of-equilibrium time-evolution of a Gutzwiller-type variational wave function for correlated electrons. The method, which is strictly variational in the limit of infinite lattice-coordination, is quite general and flexible, and it is applicable to generic non-equilibrium conditions, even far beyond the linear response regime. As an application, we discuss the quench dynamics of a single-band Hubbard model at half-filling, where the method predicts a dynamical phase transition above a critical quench that resembles the sharp crossover observed by time-dependent dynamical mean field theory. We next show that one can actually define in some cases a multi-configurational wave function combination of a whole set of mutually orthogonal Gutzwiller wave functions. The Hamiltonian projected in that subspace can be exactly evaluated and is equivalent to a model of auxiliary spins coupled to non-interacting electrons, closely related to the slave-spin theories for correlated electron models. The Gutzwiller approximation turns out to be nothing but the mean-field approximation applied to that spin-fermion model, which displays, for any number of bands and integer fillings, a spontaneous Z 2 symmetry breaking that can be identified as the Mott insulator-to-metal transition.
Local time dependences of oxygen ENA periodicities at Saturn
NASA Astrophysics Data System (ADS)
Carbary, J. F.; Mitchell, D. G.; Brandt, P. C.
2014-08-01
The periodicities of energetic neutral atoms (90-170 keV oxygens) at Saturn are determined by applying Lomb-Scargle periodogram analyses to energetic neutral atom (ENA) fluxes observed in eight local time sectors of the equatorial plane between 5 and 15 RS (1 RS = 60,268 km). The analyses come from four long intervals (>180 days each) of high-latitude viewing from 2007 to 2013 and represent an essentially global view of Saturn's periodicities. The periodograms display rich and complex structures in local time. Sectors near midnight generally exhibit the strongest periodicities (in terms of highest signal-to-noise ratios) and often show the dual or single periods of the Saturn kilometric radiation (SKR). Sectors near noon display single or multiple periodicities or none. Furthermore, dayside periods may be much shorter (~10.3 h) than SKR periods. Sectors near dawn or dusk display periodicities intermediate between midnight and noon or may show no periodicities whatsoever. These patterns of local time dependence do not remain constant from interval to interval.
Time-dependent motor properties of multipedal molecular spiders
NASA Astrophysics Data System (ADS)
Samii, Laleh; Blab, Gerhard A.; Bromley, Elizabeth H. C.; Linke, Heiner; Curmi, Paul M. G.; Zuckermann, Martin J.; Forde, Nancy R.
2011-09-01
Molecular spiders are synthetic biomolecular walkers that use the asymmetry resulting from cleavage of their tracks to bias the direction of their stepping motion. Using Monte Carlo simulations that implement the Gillespie algorithm, we investigate the dependence of the biased motion of molecular spiders, along with binding time and processivity, on tunable experimental parameters, such as number of legs, span between the legs, and unbinding rate of a leg from a substrate site. We find that an increase in the number of legs increases the spiders’ processivity and binding time but not their mean velocity. However, we can increase the mean velocity of spiders with simultaneous tuning of the span and the unbinding rate of a spider leg from a substrate site. To study the efficiency of molecular spiders, we introduce a time-dependent expression for the thermodynamic efficiency of a molecular motor, allowing us to account for the behavior of spider populations as a function of time. Based on this definition, we find that spiders exhibit transient motor function over time scales of many hours and have a maximum efficiency on the order of 1%, weak compared to other types of molecular motors.
Time-dependent numerical simulation of vertical cavity lasers
Thode, L.E.; Csanak, G.; So, L.L.; Kwan, T.J.T.; Campbell, M.
1994-12-31
To simulate vertical cavity surface emitting lasers (VCSELs), the authors are developing a three-dimensional, time-dependent field-gain model with absorption in bulk dielectric regions and gain in quantum well regions. Since the laser linewidth is narrow, the bulk absorption coefficient is assumed to be independent of frequency with a value determined by the material and the lattice temperature. In contrast, the frequency-dependent gain regions must be solved consistently in the time domain. Treatment of frequency-dependent media in a finite-difference time-domain code is computationally intensive. However, because the volume of the quantum well regions is small relative to the volume of the multilayer dielectric (MLD) mirror regions, the computational overhead is reasonable. A key issue is the calculation of the fields in the MLD mirror regions. Although computationally intensive, good agreement has been obtained between simulation results and matrix equation solutions for the reflection coefficient, transmission coefficient, and bandwidth of MLD mirrors. The authors discuss the development and testing of the two-dimensional field-gain model. This field-gain model will be integrated with a carrier transport model to form the self-consistent laser code, VCSEL.
Time dependent ventilation flows driven by opposing wind and buoyancy
NASA Astrophysics Data System (ADS)
Coomaraswamy, Imran; Caulfield, Colm
2008-11-01
We consider flow in an enclosure containing an isolated heat source, ventilated by a windward high level opening and a leeward low level opening, so that prevailing wind acts to oppose buoyancy driven flow. Following the ``emptying filling box'' approach of Linden et al., Hunt & Linden demonstrate that multiple steady states can exist above a critical wind strength. We develop time dependent models for this system and apply them to an initial value problem - box filling with constant opposing wind. We identify the final state attained for any given heat load, wind strength and vent size. We note that the interface between the upper region of hot plume fluid and the lower region of cool ambient air can dramatically overshoot its final level before relaxing to equilibrium; in some cases, a fully mixed transient can occur before the stratified steady state is reached. Analogue laboratory experiments confirm the existence of these transient phenomena and elucidate the range of validity of our predictions. Linden, Lane-Serff & Smeed, J. Fluid Mech. 212, 309 (1990)., Hunt & Linden, J. Fluid Mech. 527, 27 (2005).
Time-dependent perturbation and the Born-Oppenheimer approximation
NASA Astrophysics Data System (ADS)
Jilcott, Steven Wayne, Jr.
2000-12-01
We discuss the physical problem of a molecule interacting with an electromagnetic field pulse and model the problem using a time-dependent perturbation of the Born- Oppenheimer approximation to the Schrödinger equation. Using previous results that develop asymptotic series solutions in the Born-Oppenheimer parameter ɛ, we derive a formal Dyson series expansion in the perturbation parameter μ, which is proportional to the electromagnetic field strength. We then prove that this series is asymptotically accurate in both parameters, provided that the Hamiltonian for the electrons has purely discrete spectrum. Under more general hypotheses, we show that the series is accurate to first order in μ, and that it is accurate to one higher order if we place conditions on the abruptness of the EM pulse. We also show how this series development provides a justification for the Franck-Condon factors in the case of a diatomic molecule.* *This work was supported by the Cunningham Research Fellowship provided by Virginia Tech.
Translation invariant time-dependent solutions to massive gravity II
Mourad, J.; Steer, D.A. E-mail: steer@apc.univ-paris7.fr
2014-06-01
This paper is a sequel to JCAP 12 (2013) 004 and is also devoted to translation-invariant solutions of ghost-free massive gravity in its moving frame formulation. Here we consider a mass term which is linear in the vielbein (corresponding to a β{sub 3} term in the 4D metric formulation) in addition to the cosmological constant. We determine explicitly the constraints, and from the initial value formulation show that the time-dependent solutions can have singularities at a finite time. Although the constraints give, as in the β{sub 1} case, the correct number of degrees of freedom for a massive spin two field, we show that the lapse function can change sign at a finite time causing a singular time evolution. This is very different to the β{sub 1} case where time evolution is always well defined. We conclude that the β{sub 3} mass term can be pathological and should be treated with care.
Hot Jupiter breezes: time-dependent outflows from extrasolar planets
NASA Astrophysics Data System (ADS)
Owen, James E.; Adams, Fred C.
2016-03-01
We explore the dynamics of magnetically controlled outflows from hot Jupiters, where these flows are driven by UV heating from the central star. In these systems, some of the open field lines do not allow the flow to pass smoothly through the sonic point, so that steady-state solutions do not exist in general. This paper focuses on this type of magnetic field configuration, where the resulting flow becomes manifestly time-dependent. We consider the case of both steady heating and time-variable heating, and find the time-scales for the corresponding time variations of the outflow. Because the flow cannot pass through the sonic transition, it remains subsonic and leads to so-called breeze solutions. One manifestation of the time variability is that the flow samples a collection of different breeze solutions over time, and the mass outflow rate varies in quasi-periodic fashion. Because the flow is subsonic, information can propagate inwards from the outer boundary, which determines, in part, the time-scale of the flow variability. This work finds the relationship between the outer boundary scale and the time-scale of flow variations. In practice, the location of the outer boundary is set by the extent of the sphere of influence of the planet. The measured time variability can be used, in principle, to constrain the parameters of the system (e.g. the strengths of the surface magnetic fields).
Learning Probabilistic Inference through Spike-Timing-Dependent Plasticity123
Pecevski, Dejan
2016-01-01
Abstract Numerous experimental data show that the brain is able to extract information from complex, uncertain, and often ambiguous experiences. Furthermore, it can use such learnt information for decision making through probabilistic inference. Several models have been proposed that aim at explaining how probabilistic inference could be performed by networks of neurons in the brain. We propose here a model that can also explain how such neural network could acquire the necessary information for that from examples. We show that spike-timing-dependent plasticity in combination with intrinsic plasticity generates in ensembles of pyramidal cells with lateral inhibition a fundamental building block for that: probabilistic associations between neurons that represent through their firing current values of random variables. Furthermore, by combining such adaptive network motifs in a recursive manner the resulting network is enabled to extract statistical information from complex input streams, and to build an internal model for the distribution p* that generates the examples it receives. This holds even if p* contains higher-order moments. The analysis of this learning process is supported by a rigorous theoretical foundation. Furthermore, we show that the network can use the learnt internal model immediately for prediction, decision making, and other types of probabilistic inference. PMID:27419214
Endocannabinoid dynamics gate spike-timing dependent depression and potentiation
Cui, Yihui; Prokin, Ilya; Xu, Hao; Delord, Bruno; Genet, Stephane; Venance, Laurent; Berry, Hugues
2016-01-01
Synaptic plasticity is a cardinal cellular mechanism for learning and memory. The endocannabinoid (eCB) system has emerged as a pivotal pathway for synaptic plasticity because of its widely characterized ability to depress synaptic transmission on short- and long-term scales. Recent reports indicate that eCBs also mediate potentiation of the synapse. However, it is not known how eCB signaling may support bidirectionality. Here, we combined electrophysiology experiments with mathematical modeling to question the mechanisms of eCB bidirectionality in spike-timing dependent plasticity (STDP) at corticostriatal synapses. We demonstrate that STDP outcome is controlled by eCB levels and dynamics: prolonged and moderate levels of eCB lead to eCB-mediated long-term depression (eCB-tLTD) while short and large eCB transients produce eCB-mediated long-term potentiation (eCB-tLTP). Moreover, we show that eCB-tLTD requires active calcineurin whereas eCB-tLTP necessitates the activity of presynaptic PKA. Therefore, just like glutamate or GABA, eCB form a bidirectional system to encode learning and memory. DOI: http://dx.doi.org/10.7554/eLife.13185.001 PMID:26920222
Mixed-mode, time-dependent rubber/metal debonding
NASA Astrophysics Data System (ADS)
Liechti, Kenneth M.; Wu, Jeng-Dah
2001-05-01
This paper examines the need to incorporate a rate-dependent traction-separation law in order to model quasi-static debonding between rubber and metal. A pseudo-stress model was used to account for the nonlinear, multi-axial and time-dependent nature of the filled rubber that was used in the experiments. The parameters for the traction-separation law were extracted on the basis of measurements of load, crack length and crack opening displacements in an opening mode experiment at one applied displacement rate. The form of the traction-separation law was consistent with observations of ligament content on the metal fracture surface. Additional experiments were then conducted in opening mode at different rates and in mixed mode with positive and negative shear so that comparisons with predictions from the calibrated cohesive zone model could be made. The crack length history proved to be the most discriminating measure of the validity of the model, which was most effective at higher loading rates.
Time-dependent radiation dose simulations during interplanetary space flights
NASA Astrophysics Data System (ADS)
Dobynde, Mikhail; Shprits, Yuri; Drozdov, Alexander; Hoffman, Jeffrey; Li, Ju
2016-07-01
Space radiation is one of the main concerns in planning long-term interplanetary human space missions. There are two main types of hazardous radiation - Solar Energetic Particles (SEP) and Galactic Cosmic Rays (GCR). Their intensities and evolution depend on the solar activity. GCR activity is most enhanced during solar minimum, while the most intense SEPs usually occur during the solar maximum. SEPs are better shielded with thick shields, while GCR dose is less behind think shields. Time and thickness dependences of the intensity of these two components encourage looking for a time window of flight, when radiation intensity and dose of SEP and GCR would be minimized. In this study we combine state-of-the-art space environment models with GEANT4 simulations to determine the optimal shielding, geometry of the spacecraft, and launch time with respect to the phase of the solar cycle. The radiation environment was described by the time-dependent GCR model, and the SEP spectra that were measured during the period from 1990 to 2010. We included gamma rays, electrons, neutrons and 27 fully ionized elements from hydrogen to nickel. We calculated the astronaut's radiation doses during interplanetary flights using the Monte-Carlo code that accounts for the primary and the secondary radiation. We also performed sensitivity simulations for the assumed spacecraft size and thickness to find an optimal shielding. In conclusion, we present the dependences of the radiation dose as a function of launch date from 1990 to 2010, for flight durations of up to 3 years.
Simple preconditioning for time-dependent density functional perturbation theory.
Lehtovaara, Lauri; Marques, Miguel A L
2011-07-01
By far, the most common use of time-dependent density functional theory is in the linear-reponse regime, where it provides information about electronic excitations. Ideally, the linear-response equations should be solved by a method that avoids the use of the unoccupied Kohn-Sham states--such as the Sternheimer method--as this reduces the complexity and increases the precision of the calculation. However, the Sternheimer equation becomes ill-conditioned near and indefinite above the first resonant frequency, seriously hindering the use of efficient iterative solution methods. To overcome this serious limitation, and to improve the general convergence properties of the iterative techniques, we propose a simple preconditioning strategy. In our method, the Sternheimer equation is solved directly as a linear equation using an iterative Krylov subspace method, i.e., no self-consistent cycle is required. Furthermore, the preconditioner uses the information of just a few unoccupied states and requires simple and minimal modifications to existing implementations. In this way, convergence can be reached faster and in a considerably wider frequency range than the traditional approach. PMID:21744884
Time-dependent corticosteroid modulation of prefrontal working memory processing
Henckens, Marloes J. A. G.; van Wingen, Guido A.; Joëls, Marian; Fernández, Guillén
2011-01-01
Corticosteroids are potent modulators of human higher cognitive function. They are released in response to stress, and are thought to be involved in the modulation of cognitive function by inducing distinct rapid nongenomic, and slow genomic changes, affecting neural plasticity throughout the brain. However, their exact effects on the neural correlates of higher-order cognitive function as performed by the prefrontal cortex at the human brain system level remain to be elucidated. Here, we targeted these time-dependent effects of corticosteroids on prefrontal cortex processing in humans using a working memory (WM) paradigm during functional MRI scanning. Implementing a randomized, double-blind, placebo-controlled design, 72 young, healthy men received 10 mg hydrocortisone either 30 min (rapid corticosteroid effects) or 240 min (slow corticosteroid effects), or placebo before a numerical n-back task with differential load (0- to 3-back). Corticosteroids’ slow effects appeared to improve working memory performance and increased neuronal activity during WM performance in the dorsolateral prefrontal cortex depending on WM load, whereas no effects of corticosteroids’ rapid actions were observed. Thereby, the slow actions of corticosteroids seem to facilitate adequate higher-order cognitive functioning, which may support recovery in the aftermath of stress exposure. PMID:21436038
Correlated electron dynamics with time-dependent quantum Monte Carlo: three-dimensional helium.
Christov, Ivan P
2011-07-28
Here the recently proposed time-dependent quantum Monte Carlo method is applied to three dimensional para- and ortho-helium atoms subjected to an external electromagnetic field with amplitude sufficient to cause significant ionization. By solving concurrently sets of up to 20,000 coupled 3D time-dependent Schrödinger equations for the guide waves and corresponding sets of first order equations of motion for the Monte Carlo walkers we obtain ground state energies in close agreement with the exact values. The combined use of spherical coordinates and B-splines along the radial coordinate proves to be especially accurate and efficient for such calculations. Our results for the dipole response and the ionization of an atom with un-correlated electrons are in good agreement with the predictions of the conventional time-dependent Hartree-Fock method while the calculations with correlated electrons show enhanced ionization that is due to the electron-electron repulsion. PMID:21806103
2009-01-01
The electronic structure and size-scaling of optoelectronic properties in cycloparaphenylene carbon nanorings are investigated using time-dependent density functional theory (TDDFT). The TDDFT calculations on these molecular nanostructures indicate that the lowest excitation energy surprisingly becomes larger as the carbon nanoring size is increased, in contradiction with typical quantum confinement effects. In order to understand their unusual electronic properties, I performed an extensive investigation of excitonic effects by analyzing electron-hole transition density matrices and exciton binding energies as a function of size in these nanoring systems. The transition density matrices allow a global view of electronic coherence during an electronic excitation, and the exciton binding energies give a quantitative measure of electron-hole interaction energies in the nanorings. Based on overall trends in exciton binding energies and their spatial delocalization, I find that excitonic effects play a vital role in understanding the unique photoinduced dynamics in these carbon nanoring systems. PMID:22481999
Charge balance and ionospheric potential dynamics in time dependent global electric circuit model
NASA Astrophysics Data System (ADS)
Jansky, J.; Pasko, V. P.
2014-12-01
We have developed a time-dependent model of global electric circuit (GEC)in spherical coordinates. The model solves time-dependent charge continuity equation coupledwith Poisson's equation. An implicit time stepping is used to avoid strict dielectricrelaxation time step condition, and boundary conditions for Poisson's equationare implemented to allow accurate description of time evolution of the ionospheric potential.The concept of impulse response of GEC is introduced that allows effective representationof complex time dynamics of various physical quantities in the circuit usingmodel results obtained for instantaneous deposition of a point charge.The more complex problems, like continuous charging of thunderstorms and different typesof lightning dischargesare then reconstructed using convolution and linearity principles.It is shown that for a thundercloud charging phase, typicallyrepresented by a current dipole, the ionospheric potential can be determined from the differenceof time integrals of two ionospheric potential impulse responsescorresponding to charge locations at the opposite ends of the current dipole.During a cloud to ground lightning discharge,the ionospheric potential changes instantaneously by a value proportionalto the charge moment change produced by lightning and then relaxes to zero.We will also discuss processes involving transient conductivity perturbations in GEC associated withextraterrestrial gamma ray bursts and sprites.
Reconsolidation of Motor Memories Is a Time-Dependent Process
de Beukelaar, Toon T.; Woolley, Daniel G.; Alaerts, Kaat; Swinnen, Stephan P.; Wenderoth, Nicole
2016-01-01
Reconsolidation is observed when a consolidated stable memory is recalled, which renders it transiently labile and requires re-stabilization. Motor memory reconsolidation has previously been demonstrated using a three-day design: on day 1 the memory is encoded, on day 2 it is reactivated and experimentally manipulated, and on day 3 memory strength is tested. The aim of the current study is to determine specific boundary conditions in order to consistently degrade motor memory through reconsolidation paradigms. We investigated a sequence tapping task (n = 48) with the typical three-day design and confirmed that reactivating the motor sequence briefly (10 times tapping the learned motor sequence) destabilizes the memory trace and makes it susceptible to behavioral interference. By systematically varying the time delay between memory reactivation and interference while keeping all other aspect constant we found that a short delay (i.e., 20 s) significantly decreased performance on day 3, whereas performance was maintained or small (but not significant) improvements were observed for longer delays (i.e., 60 s). We also tested a statistical model that assumed a linear effect of the different time delays (0 s, 20 s, 40 s, 60 s) on the performance changes from day 2 to day 3. This linear model revealed a significant effect consistent with the interpretation that increasing time delays caused a gradual change from performance degradation to performance conservation across groups. These findings indicate that re-stabilizing motor sequence memories during reconsolidation does not solely rely on additional motor practice but occurs with the passage of time. This study provides further support for the hypothesis that reconsolidation is a time-dependent process with a transition phase from destabilization to re-stabilization. PMID:27582698
Mean Velocity of Local Populations: Axiality, Age and Time Dependence
NASA Astrophysics Data System (ADS)
Cubarsi, Rafael; Alcobé, Santiago
2007-05-01
The mean velocity of local stellar populations is analyzed by building a set of hierarchically selected samples from Hipparcos catalog, with the full space motions. The technique for scanning populations, MEMPHIS (Maximum Entropy of the Mixture Probability from HIerarchical Segregation), is a combination of two separate procedures: A sample selecting filter (Alcobé & Cubarsi 2005, A&A 442, 292) and a segregation method (Cubarsi & Alcobé 2004, A&A 427, 131). By continuously increasing the sampling parameter, in our case the absolute value of the stellar velocity, we build a set of nested subsamples containing an increasing number of populations. A bimodal pattern is then applied in order to identify differentiated kinematic populations. The resulting populations can be identified as early-type stars, young disk stars, old disk stars, and thick disk stars. Discontinuities of the velocity dispersion are found for early-type and thick disk stars, while young and old disk stars show a continuous trend that is asymptotically represented by the thin disk galactic component. Similarly, the mean velocity of early-type stars shows a particular behavior, while the remaining populations share a similar average motion. The later populations are studied on the basis of a time-dependent and non-axial Chandrasekhar model, allowing to estimate the degree of deviation from axial symmetry and steady-state hypotheses, as well as the average age of each population. According to this model, the no net radial movement point can be evaluated, having heliocentric velocities U=-18 ± 1 km/s in the radial direction, which is very close to the radial mean velocity of early-type stars, and V=-76 ± 2 km/s in rotation. The remaining populations share a common differential galactic movement, suggesting a common dynamical origin for the rupture of the axial symmetry.
Pharmacokinetics: time-dependent changes--autoinduction of carbamazepine epoxidation
Bertilsson, L.; Tomson, T.; Tybring, G.
1986-07-01
Drugs labeled with stable isotopes have been useful to study time-dependent changes in kinetics. Early studies suggested that carbamazepine (CBZ) may induce its own metabolism, but this could not be proved until tetradeuterium-labeled CBZ (CBZ-D4) was synthesized and then given to patients. CBZ-D4 was administered to three children during long-term treatment of epilepsy with CBZ. After 17 to 32 days of treatment, the plasma clearance of CBZ-D4 was doubled, but during the next four months, there was no further increase, indicating that autoinduction was complete within one month. Two patients with chronic alcoholism were treated with CBZ for five days. Half of the first dose of 600 mg was comprised of CBZ-D4. The half-life of this CBZ-D4 dose in the two patients (20 and 26 hr, respectively) was similar to the post-steady-state half-life of CBZ (23 hr in both patients) measured later. A single dose of CBZ given one week after the last maintenance dose had a longer half-life (46 and 45 hr, respectively), which probably is close to the disposition of the drug before starting the treatment with CBZ. This shows that autoinduction of CBZ metabolism was completed during the very first doses of CBZ. Autoinduction also disappeared rapidly after stopping the treatment. We have shown that it is mainly the epoxide-diol pathway that is induced, both during autoinduction and after induction with other antiepileptic agents.
Solving the time dependent vehicle routing problem by metaheuristic algorithms
NASA Astrophysics Data System (ADS)
Johar, Farhana; Potts, Chris; Bennell, Julia
2015-02-01
The problem we consider in this study is Time Dependent Vehicle Routing Problem (TDVRP) which has been categorized as non-classical VRP. It is motivated by the fact that multinational companies are currently not only manufacturing the demanded products but also distributing them to the customer location. This implies an efficient synchronization of production and distribution activities. Hence, this study will look into the routing of vehicles which departs from the depot at varies time due to the variation in manufacturing process. We consider a single production line where demanded products are being process one at a time once orders have been received from the customers. It is assumed that order released from the production line will be loaded into scheduled vehicle which ready to be delivered. However, the delivery could only be done once all orders scheduled in the vehicle have been released from the production line. Therefore, there could be lateness on the delivery process from awaiting all customers' order of the route to be released. Our objective is to determine a schedule for vehicle routing that minimizes the solution cost including the travelling and tardiness cost. A mathematical formulation is developed to represent the problem and will be solved by two metaheuristics; Variable Neighborhood Search (VNS) and Tabu Search (TS). These algorithms will be coded in C ++ programming and run using 56's Solomon instances with some modification. The outcome of this experiment can be interpreted as the quality criteria of the different approximation methods. The comparison done shown that VNS gave the better results while consuming reasonable computational efforts.
From Induced Seismicity to Direct Time-Dependent Seismic Hazard
NASA Astrophysics Data System (ADS)
Convertito, V.; Maercklin, N.; Sharma, N.; Zollo, A.
2012-12-01
The growing installation of industrial facilities for subsurface exploration worldwide requires continuous refinements in understanding both the mechanisms by which seismicity is induced by field operations and the related seismic hazard. Particularly in proximity of densely populated areas, induced low-to-moderate magnitude seismicity characterized by high-frequency content can be clearly felt by the surrounding inhabitants and, in some cases, may produce damage. In this respect we propose a technique for time-dependent probabilistic seismic hazard analysis to be used in geothermal fields as a monitoring tool for the effects of on-going field operations. The technique integrates the observed features of the seismicity induced by fluid injection and extraction with a local ground-motion prediction equation. The result of the analysis is the time-evolving probability of exceedance of peak ground acceleration (PGA), which can be compared with selected critical values to manage field operations. To evaluate the reliability of the proposed technique, we applied it to data collected in The Geysers geothermal field in northern California between 1 September 2007 and 15 November 2010. We show that the period considered the seismic hazard at The Geysers was variable in time and space, which is a consequence of the field operations and the variation of both seismicity rate and b-value. We conclude that, for the exposure period taken into account (i.e., two months), as a conservative limit, PGA values corresponding to the lowest probability of exceedance (e.g., 30%) must not be exceeded to ensure safe field operations. We suggest testing the proposed technique at other geothermal areas or in regions where seismicity is induced, for example, by hydrocarbon exploitation or carbon dioxide storage.
Time-dependent computational studies of flames in microgravity
NASA Technical Reports Server (NTRS)
Oran, Elaine S.; Kailasanath, K.
1989-01-01
The research performed at the Center for Reactive Flow and Dynamical Systems in the Laboratory for Computational Physics and Fluid Dynamics, at the Naval Research Laboratory, in support of the NASA Microgravity Science and Applications Program is described. The primary focus was on investigating fundamental questions concerning the propagation and extinction of premixed flames in Earth gravity and in microgravity environments. The approach was to use detailed time-dependent, multispecies, numerical models as tools to simulate flames in different gravity environments. The models include a detailed chemical kinetics mechanism consisting of elementary reactions among the eight reactive species involved in hydrogen combustion, coupled to algorithms for convection, thermal conduction, viscosity, molecular and thermal diffusion, and external forces. The external force, gravity, can be put in any direction relative to flame propagation and can have a range of values. A combination of one-dimensional and two-dimensional simulations was used to investigate the effects of curvature and dilution on ignition and propagation of flames, to help resolve fundamental questions on the existence of flammability limits when there are no external losses or buoyancy forces in the system, to understand the mechanism leading to cellular instability, and to study the effects of gravity on the transition to cellular structure. A flame in a microgravity environment can be extinguished without external losses, and the mechanism leading to cellular structure is not preferential diffusion but a thermo-diffusive instability. The simulations have also lead to a better understanding of the interactions between buoyancy forces and the processes leading to thermo-diffusive instability.
A History of Spike-Timing-Dependent Plasticity
Markram, Henry; Gerstner, Wulfram; Sjöström, Per Jesper
2011-01-01
How learning and memory is achieved in the brain is a central question in neuroscience. Key to today’s research into information storage in the brain is the concept of synaptic plasticity, a notion that has been heavily influenced by Hebb's (1949) postulate. Hebb conjectured that repeatedly and persistently co-active cells should increase connective strength among populations of interconnected neurons as a means of storing a memory trace, also known as an engram. Hebb certainly was not the first to make such a conjecture, as we show in this history. Nevertheless, literally thousands of studies into the classical frequency-dependent paradigm of cellular learning rules were directly inspired by the Hebbian postulate. But in more recent years, a novel concept in cellular learning has emerged, where temporal order instead of frequency is emphasized. This new learning paradigm – known as spike-timing-dependent plasticity (STDP) – has rapidly gained tremendous interest, perhaps because of its combination of elegant simplicity, biological plausibility, and computational power. But what are the roots of today’s STDP concept? Here, we discuss several centuries of diverse thinking, beginning with philosophers such as Aristotle, Locke, and Ribot, traversing, e.g., Lugaro’s plasticità and Rosenblatt’s perceptron, and culminating with the discovery of STDP. We highlight interactions between theoretical and experimental fields, showing how discoveries sometimes occurred in parallel, seemingly without much knowledge of the other field, and sometimes via concrete back-and-forth communication. We point out where the future directions may lie, which includes interneuron STDP, the functional impact of STDP, its mechanisms and its neuromodulatory regulation, and the linking of STDP to the developmental formation and continuous plasticity of neuronal networks. PMID:22007168
Reconsolidation of Motor Memories Is a Time-Dependent Process.
de Beukelaar, Toon T; Woolley, Daniel G; Alaerts, Kaat; Swinnen, Stephan P; Wenderoth, Nicole
2016-01-01
Reconsolidation is observed when a consolidated stable memory is recalled, which renders it transiently labile and requires re-stabilization. Motor memory reconsolidation has previously been demonstrated using a three-day design: on day 1 the memory is encoded, on day 2 it is reactivated and experimentally manipulated, and on day 3 memory strength is tested. The aim of the current study is to determine specific boundary conditions in order to consistently degrade motor memory through reconsolidation paradigms. We investigated a sequence tapping task (n = 48) with the typical three-day design and confirmed that reactivating the motor sequence briefly (10 times tapping the learned motor sequence) destabilizes the memory trace and makes it susceptible to behavioral interference. By systematically varying the time delay between memory reactivation and interference while keeping all other aspect constant we found that a short delay (i.e., 20 s) significantly decreased performance on day 3, whereas performance was maintained or small (but not significant) improvements were observed for longer delays (i.e., 60 s). We also tested a statistical model that assumed a linear effect of the different time delays (0 s, 20 s, 40 s, 60 s) on the performance changes from day 2 to day 3. This linear model revealed a significant effect consistent with the interpretation that increasing time delays caused a gradual change from performance degradation to performance conservation across groups. These findings indicate that re-stabilizing motor sequence memories during reconsolidation does not solely rely on additional motor practice but occurs with the passage of time. This study provides further support for the hypothesis that reconsolidation is a time-dependent process with a transition phase from destabilization to re-stabilization. PMID:27582698
Structural instabilities involving time dependent materials : theory and experiment
NASA Astrophysics Data System (ADS)
Minahen, Timothy M.
The creep buckling of viscoelastic structures is studied analytically and experimentally to investigate structural stability in the presence of time dependent materials. The theory of linear viscoelasticity is used to model polymeric column specimens subjected to constant compressive end loads. A strength of materials approach (Euler-Bernoulli beam theory) is employed to model the moment-curvature relation for the column. The growth of initial imperfections is calculated using the hereditary integral formulation. Solution techniques are developed for small displacements and then generalized to include the effects of large displacements and rotations. A failure criterion based on maximum deformation allows the column life to be estimated directly from the material relaxation modulus. A discussion generalizing the results to include plates and shells is presented.Rectangular cross-section polymethylmethacrylate (PMMA) specimens with hinged boundary conditions are used to study viscoelastic buckling experimentally. Constant compressive end loads are applied using a servo-controlled load frame while the specimens are kept in a temperature cabinet at elevated temperatures (accelerating the creep behavior). Specimen shortening and out-of-plane deflections are monitored during the tests. The relaxation modulus of PMMA is approximated by a Prony-Dirichlet series and the model is used to simulate the laboratory experiments. Model and experimental results show good agreement during the "glassy" and slow growth phases of the column response. As the growth rate increases some deviations between theory and experiment are seen. It is shown that the deviations are not a result of geometric nonlinearities, but may, in part, be explained by material nonlinearities not accounted for in the model.
Time-dependent charge distributions in polymer films under electron beam irradiation
Yasuda, Masaaki; Kainuma, Yasuaki; Kawata, Hiroaki; Hirai, Yoshihiko; Tanaka, Yasuhiro; Watanabe, Rikio; Kotera, Masatoshi
2008-12-15
The time-dependent charge distribution in polymer film under electron beam irradiation is studied by both experiment and numerical simulation. In the experiment, the distribution is measured with the piezoinduced pressure wave propagation method. In the simulation, the initial charge distribution is obtained by the Monte Carlo method of electron scattering, and the charge drift in the specimen is simulated by taking into account the Poisson equation, the charge continuity equation, Ohm's law, and the radiation-induced conductivity. The results obtained show that the negative charge deposited in the polymer film, whose top and bottom surfaces are grounded, drifts toward both grounded electrodes and that twin peaks appear in the charge distribution. The radiation-induced conductivity plays an important role in determining the charge distribution in the polymer films under electron beam irradiation.
NASA Astrophysics Data System (ADS)
Raine, M.; Gaillardin, M.; Paillet, P.; Duhamel, O.; Martinez, M.; Bernard, H.
2015-12-01
The dispersion of heavy ion deposited energy is explored in nanometric electronic devices. Experimental data are reported, in a large thin SOI diode and in a SOI FinFET device, showing larger distributions of collected charge in the nanometric volume device. Geant4 simulations are then presented, using two different modeling approaches. Both of them seem suitable to evaluate the dispersion of deposited energy induced by heavy ion beams in advanced electronic devices with nanometric dimensions.
MCNPX benchmark of out-of-beam energy deposition in LiAl
Corzine, K.; Ferguson, P.; Morgan, G.; Quintana, D.; Waters, L.; Cooper, R.; Liljestrand, R.; Whiteson, A.
2000-07-01
The MCNPX code is currently being used to calculate energy deposition in the accelerator production of tritium (APT) target/blanket system components. To ensure that these components are properly designed, the code must be validated. An energy deposition experiment was designed to aid in the code validation using thermocouple sensors in-beam and thermistor-type sensors in decoupler- and blanketlike regions. This paper focuses on the out-of-beam thermistor sensors constructed of LiAl.
NASA Technical Reports Server (NTRS)
Rees, M. H.; Lummerzheim, D.; Roble, R. G.; Winningham, J. D.; Craven, J. D.
1988-01-01
Auroral images obtained by the Spin Scan Auroral Imager (SAI) aboard the DE-1 satellite were used to derive auroral energy deposition rate, characteristic electron energy, and ionospheric parameters. The principles involved in the imaging technique and the physical mechanisms that underlie the relationship between the spectral images and the geophysical parameters are discussed together with the methodology for implementing such analyses. It is shown that images obtained with the SAI provide global parameters at 12-min temporal resolution; the spatial resolution is limited by the field of view of a pixel. The analysis of the 12-min images presented yielded a representation of ionospheric parameters that was better than can be obtained using empirical models based on local measurements averaged over long periods of time.
Study of the energy deposit of muon bundles in the NEVOD detector
NASA Astrophysics Data System (ADS)
Bogdanov, A. G.; Dushkin, L. I.; Khokhlov, S. S.; Khomyakov, V. A.; Kindin, V. V.; Kokoulin, R. P.; Kovylyaeva, E. A.; Mannocchi, G.; Petrukhin, A. A.; Saavedra, O.; Shutenko, V. V.; Trinchero, G.; Yashin, I. I.
2015-08-01
In several cosmic ray experiments, an excess of multi-muon events in comparison with calculations performed in frame of the widely used hadron interaction models was found. In order to solve this puzzle, investigations of muon energy characteristics in EAS are required. An experiment on the measurement of the energy deposit of muon bundles in water has been started with the NEVOD-DECOR experimental complex. The results of the analysis of the first experimental data are discussed. It has been found that the average specific energy deposit in the Cherenkov calorimeter appreciably increases with zenith angle, thus reflecting the increase of the mean muon energy in the bundles. A possible evidence for an increase of the energy deposit at primary energies above 1017 eV is observed.
Engineering properties of superhard films with ion energy and post-deposition processing
Monteiro, Othon R.; Delplancke-Ogletree, Mari-Paule
2002-10-14
Recent developments in plasma synthesis of hard materials using energetic ions are described. Metal Plasma Immersion Ion Implantation and Deposition (MePIIID) has been used to prepare several hard films: from diamondlike carbon (DLC) to carbides, from nitrides to oxides. The energy of the depositing species is controlled to maximize adhesion as well as to change the physical and chemical properties of the films. Adhesion is promoted by the creation of a graded interface between the film and the substrate. The energy of the depositing ions is also used to modify and control the intrinsic stresses and the microstructure of the films. The deposition is carried out at room temperature, which is important for temperature sensitive substrates. A correlation between intrinsic stresses and the energetics of the deposition is presented for the case of DLC films, and means to reduce stress levels are discussed.
NASA Astrophysics Data System (ADS)
Correale, G.; Winkel, R.; Kotsonis, M.
2015-08-01
An experimental study aimed at the characterization of energy deposition of nanosecond Dielectric Barrier Discharge (ns-DBD) plasma actuators was carried out. Special attention was given on the effect of the thickness and material used for dielectric barrier. The selected materials for this study were polyimide film (Kapton), polyamide based nylon (PA2200), and silicone rubber. Schlieren measurements were carried out in quiescent air conditions in order to observe density gradients induced by energy deposited. Size of heated area was used to qualify the energy deposition coupled with electrical power measurements performed using the back-current shunt technique. Additionally, light intensity measurements showed a different nature of discharge based upon the material used for barrier, for a fixed thickness and frequency of discharge. Finally, a characterisation study was performed for the three tested materials. Dielectric constant, volume resistivity, and thermal conductivity were measured. Strong trends between the control parameters and the energy deposited into the fluid during the discharge were observed. Results indicate that efficiency of energy deposition mechanism relative to the thickness of the barrier strongly depends upon the material used for the dielectric barrier itself. In general, a high dielectric strength and a low volumetric resistivity are preferred for a barrier, together with a high heat capacitance and a low thermal conductivity coefficient in order to maximize the efficiency of the thermal energy deposition induced by an ns-DBD plasma actuator.
Unitarity Bounds and RG Flows in Time Dependent Quantum Field Theory
Dong, Xi; Horn, Bart; Silverstein, Eva; Torroba, Gonzalo; /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC
2012-04-05
We generalize unitarity bounds on operator dimensions in conformal field theory to field theories with spacetime dependent couplings. Below the energy scale of spacetime variation of the couplings, their evolution can strongly affect the physics, effectively shifting the infrared operator scaling and unitarity bounds determined from correlation functions in the theory. We analyze this explicitly for large-N double-trace flows, and connect these to UV complete field theories. One motivating class of examples comes from our previous work on FRW holography, where this effect explains the range of flavors allowed in the dual, time dependent, field theory.
Analytic solutions of the time-dependent quasilinear diffusion equation with source and loss terms
Hassan, M.H.A. ); Hamza, E.A. )
1993-08-01
A simplified one-dimensional quasilinear diffusion equation describing the time evolution of collisionless ions in the presence of ion-cyclotron-resonance heating, sources, and losses is solved analytically for all harmonics of the ion cyclotron frequency. Simple time-dependent distribution functions which are initially Maxwellian and vanish at high energies are obtained and calculated numerically for the first four harmonics of resonance heating. It is found that the strongest ion tail of the resulting anisotropic distribution function is driven by heating at the second harmonic followed by heating at the fundamental frequency.
Solvent effects in time-dependent self-consistent field methods. I. Optical response calculations.
Bjorgaard, J A; Kuzmenko, V; Velizhanin, K A; Tretiak, S
2015-01-28
We implement and examine three excited state solvent models in time-dependent self-consistent field methods using a consistent formalism which unambiguously shows their relationship. These are the linear response, state specific, and vertical excitation solvent models. Their effects on energies calculated with the equivalent of COSMO/CIS/AM1 are given for a set of test molecules with varying excited state charge transfer character. The resulting solvent effects are explained qualitatively using a dipole approximation. It is shown that the fundamental differences between these solvent models are reflected by the character of the calculated excitations. PMID:25637965
Solvent effects in time-dependent self-consistent field methods. I. Optical response calculations
Bjorgaard, J. A.; Kuzmenko, V.; Velizhanin, K. A.; Tretiak, S.
2015-01-22
In this study, we implement and examine three excited state solvent models in time-dependent self-consistent field methods using a consistent formalism which unambiguously shows their relationship. These are the linear response, state specific, and vertical excitation solvent models. Their effects on energies calculated with the equivalent of COSMO/CIS/AM1 are given for a set of test molecules with varying excited state charge transfer character. The resulting solvent effects are explained qualitatively using a dipole approximation. It is shown that the fundamental differences between these solvent models are reflected by the character of the calculated excitations.
Stabilizing laser energy density on a target during pulsed laser deposition of thin films
Dowden, Paul C.; Jia, Quanxi
2016-05-31
A process for stabilizing laser energy density on a target surface during pulsed laser deposition of thin films controls the focused laser spot on the target. The process involves imaging an image-aperture positioned in the beamline. This eliminates changes in the beam dimensions of the laser. A continuously variable attenuator located in between the output of the laser and the imaged image-aperture adjusts the energy to a desired level by running the laser in a "constant voltage" mode. The process provides reproducibility and controllability for deposition of electronic thin films by pulsed laser deposition.
Time-dependent Computational Studies of Premixed Flames in Microgravity
NASA Technical Reports Server (NTRS)
Kailasanath, K.; Patnaik, Gopal; Oran, Elaine S.
1993-01-01
This report describes the research performed at the Center for Reactive Flow and Dynamical Systems in the Laboratory for Computational Physics and Fluid Dynamics, at the Naval Research Laboratory, in support of NASA Microgravity Science and Applications Program. The primary focus of this research is on investigating fundamental questions concerning the propagation and extinction of premixed flames in earth gravity and in microgravity environments. Our approach is to use detailed time-dependent, multispecies, numerical models as tools to simulate flames in different gravity environments. The models include a detailed chemical kinetics mechanism consisting of elementary reactions among the eight reactive species involved in hydrogen combustion, coupled to algorithms for convection, thermal conduction, viscosity, molecular and thermal diffusion, and external forces. The external force, gravity, can be put in any direction relative to flame propagation and can have a range of values. Recently more advanced wall boundary conditions such as isothermal and no-slip have been added to the model. This enables the simulation of flames propagating in more practical systems than before. We have used the numerical simulations to investigate the effects of heat losses and buoyancy forces on the structure and stability of flames, to help resolve fundamental questions on the existence of flammability limits when there are no external losses or buoyancy forces in the system, to understand the interaction between the various processes leading to flame instabilities and extinguishment, and to study the dynamics of cell formation and splitting. Our studies have been able to bring out the differences between upward- and downward-propagating flames and predict the zero-gravity behavior of these flames. The simulations have also highlighted the dominant role of wall heat losses in the case of downward-propagating flames. The simulations have been able to qualitatively predict the
Time-dependent fiber bundles with local load sharing.
Newman, W I; Phoenix, S L
2001-02-01
Fiber bundle models, where fibers have random lifetimes depending on their load histories, are useful tools in explaining time-dependent failure in heterogeneous materials. Such models shed light on diverse phenomena such as fatigue in structural materials and earthquakes in geophysical settings. Various asymptotic and approximate theories have been developed for bundles with various geometries and fiber load-sharing mechanisms, but numerical verification has been hampered by severe computational demands in larger bundles. To gain insight at large size scales, interest has returned to idealized fiber bundle models in 1D. Such simplified models typically assume either equal load sharing (ELS) among survivors, or local load sharing (LLS) where a failed fiber redistributes its load onto its two nearest flanking survivors. Such models can often be solved exactly or asymptotically in increasing bundle size, N, yet still capture the essence of failure in real materials. The present work focuses on 1D bundles under LLS. As in previous works, a fiber has failure rate following a power law in its load level with breakdown exponent rho. Surviving fibers under fixed loads have remaining lifetimes that are independent and exponentially distributed. We develop both new asymptotic theories and new computational algorithms that greatly increase the bundle sizes that can be treated in large replications (e.g., one million fibers in thousands of realizations). In particular we develop an algorithm that adapts several concepts and methods that are well-known among computer scientists, but relatively unknown among physicists, to dramatically increase the computational speed with no attendant loss of accuracy. We consider various regimes of rho that yield drastically different behavior as N increases. For 1/2< or =rho< or =1, ELS and LLS have remarkably similar behavior (they have identical lifetime distributions at rho=1) with approximate Gaussian bundle lifetime statistics and a
Detailed modeling of microwave energy deposition in EBT devices
Batchelor, D.B.; Rasmussen, D.A.; Goldfinger, R.C.
1983-08-01
Ray-tracing studies have been combined with a simple wave power balance model to provide a complete, albeit approximate, description of microwave power deposition in the ELMO Bumpy Torus (EBT-I), EBT-Scale (EBT-S), and EBT Proof-of-Principle (EBT-P) devices. Electron cyclotron absorption of ordinary and extraordinary waves by the combined core plasma and relativistic annuli is calculated using a fully relativistic damping package developed for the RAYS geometrical optics code. The rays are traced in finite-beta bumpy cylinder plasma equilibria that are obtained from the Oak Ridge National Laboratory (ORNL) two-dimensional (2-D) equilibrium code. These results for direct, single-pass absorption are combined with results from a statistical model for the deposition of multiply reflected and mode-converted waves to obtain estimates of the power deposited in the core, surface, and annulus plasma components. Wave absorption by the annuli and by the core components at the fundamental and second harmonic resonances, reflection and Budden tunneling of the extraordinary mode at the right-hand cutoff, and conversion between ordinary and extraordinary modes upon wall reflection are the processes included in the power balance model. Experimental measurements of wave power flux on the cavity wall in EBT-S made with a simple microwave calorimeter are in good agreement with predictions of the model for a variety of operating configurations.
Time-dependent large aspect-ratio thermal convection in the earth's mantle
NASA Astrophysics Data System (ADS)
Weinstein, Stuart A.; Olson, Peter L.; Yuen, David A.
Numerical simulations of two-dimensional time-dependent thermal convection in a Boussinesq, isoviscous, infinite Prandtl number fluid with isothermal, stress-free boundaries have been performed in large aspect-ratio configurations, in which the fluid is heated from below as well as internally. The value of the basal heated Rayleigh number ranged from 16000 to 800 000 and the Rayleigh number based on internal heat generation was varied from zero to 4 500 000. Large aspect-ratio cells are found to exist, however, they are time-dependent even at small values of the Rayleigh number. In the absence of internal heating, the onset of time-dependence occurs as a regular oscillation in the flow characteristics (Nusselt number, kinetic energy), and is accompanied by the presence of boundary layer instabilities (BLI) which exist within a large aspect-ratio circulation. At high values of the Rayleigh number the BLI are powerful features which leave the confines of the boundary layer and strongly perturb the large aspect-ratio circulation giving the flow a multi-scale character. Convective mixing of these powerful BLI results in heterogeneity in the cell interior which plays a role in the excitation of new BLI and establishes a negative temperature gradient in the cell interior. We have developed a fluid loop model which gives a qualitative explanation for the variation of the onset of time-dependence with aspect-ratio. The addition of internal heating tends to destabilize the large aspect-ratio cell configuration. Multi-cellular states last longer and occur more frequently with increasing amounts of internal heating. These calculations shed new light on a variety of time-dependent phenomena in geodynamics such as subduction, back-arc spreading, intraplate deformation, and the average geotherm. Recently, Jeanloz and Morris proposed that the seismic inhomogeneity parameter () can be used to measure the importance of internal heating in mantle convection. However, our
a Quantitative Study of Pattern Evolution and Time Dependence in Rayleigh Benard Convection
NASA Astrophysics Data System (ADS)
Heutmaker, Michael Steven
In a thin fluid layer, Rayleigh-Benard convection patterns typi- cally adapt to the geometry of the sidewalls through the formation of bent rolls and defects. Instead of a single wavenumber q, the two-dimensional wavevector field (')q((')r) must be used in order to quantitatively specify the structure of these textured patterns. Changes in the Rayleigh number R influence the form and stability of the flow. Quantitative measurements of the flow structure are needed to characterize stable and time-dependent regimes of pattern evolu- tion. In this investigation, digital image analysis was utilized to measure the wavevector field (')q((')r) from shadowgraph images. The local magnitude and direction of (')q were found from the spacing and orientation of roll boundaries. We found three regimes of pattern evolution. The stability of patterns in these regimes can be roughly predicted from a com- parison between the distribution of wavenumbers P(q) within the patterns and the band of stable wavenumbers predicted by non- linear stability theory. (1) Surprisingly, for R sufficiently close to the onset of convection (in the approximate range (epsilon) < 0.2, where (epsilon) = (R-R(,c))/R(,c)), flows are persistently and non-periodically time-dependent. (2) In an intermediate range 0.2 < (epsilon) < 3.5, textured patterns are stable. (3) Sufficiently far from onset, for (epsilon) > 3.5, patterns are non-periodically time-dependent. In the time-dependent regimes (1) and (3), P(q) exceeds the threshold of secondary instabilities that limit the stable wavenumber band. The presence of unstable wavenumbers provides a possible explanation for persistent time dependence close to onset, but stability theory alone cannot explain the variations of P(q) with (epsilon). We also compare transient evolution (regime (2) above) to the predictions of the Swift-Hohenberg model. In this model, pattern evolution minimizes a Lyapunov functional F, analogous to the mini- mization of the free energy
Quantum Mechanical Change Control and Time-Dependent Tunneling Phenomena in Heterostructures.
NASA Astrophysics Data System (ADS)
Saadat, Irfan Abdulqayyum
1990-01-01
Charge transfer and tunneling of electrons through heterostructures has been investigated using a self-consistent solution of Schrodinger and Poisson equations. The generalized solver developed can determine the charge distribution and the energy band edge for any number-of-heterojunctions and material compositions. The solver takes into consideration the position dependent effective mass and dielectric constant. The limitations and computational aspects of the solver are discussed. The solver is used to examine charge control in multi-channel modulation doped field effect transistors (MODFET's). Characteristics of fabricated multi-channel MODFET's have been analyzed. The deviation of the total sheet charge density in multi-channel MODFET's from the single-channel superposition value is explained. The influence of the gate potential to modulate the channel charge is examined. The role of the channel potential in creating parallel conduction is explored via a pseudo two-dimensional approach. Present methods for time dependent tunneling analysis are critically examined. A time dependent approach to solve the time-dependent Schrodinger equation is presented. It also examines the tunneling transient response. The formation of the initial wavefunction (superposition state) and the sensitivity of the time dependent solution to initial conditions has been explored. Two structures are proposed and analyzed based on the understanding acquired. The first one is a double quantum well tunneling resonator. The oscillation modes, tuning the frequency of oscillations, and potential applications have been analyzed in details. The conversion of this oscillator into a three terminal device and the effect of the third terminal are also examined using the time-dependent solver. The second device structure is a memory cell, where the charge is stored behind a tunnel barrier in the storage well. The device consists of two quantum wells separated by thin potential barrier. The upper well
Time Dependence of the freezing temperature for thin film spin glasses
NASA Astrophysics Data System (ADS)
Orbach, Raymond
There have been many measurements of the dependence of the ``freezing temperature'', Tf, on the thickness o of thin film spin glasses. Tf decreases with decreasing o, but never vanishes. This contribution suggests that the dependence of Tf on o is a time dependent relationship. Because the lower critical dimension of a spin glass, dl ~ 2 . 5 , when the spin glass correlation length ξ (t , T) grows to o, the spin glass dimensionality crosses over from d = 3 to d = 2 . What remains are spin glass correlations for length scales <= o . The time dependence of the magnetization dynamics are then activated, with activation energy equal to a largest barrier Δmax (o) , and an associated activation time τ. For measurements at time scales such that ξ (t , T) < o , the effective dimension d = 3 , and the characteristic cusp and knee of a spin glass is observed. For experimental time scales greater than τ, with ξ (t , T) ~ o , the zero-field cooled magnetization has grown to the field-cooled value of the magnetization, leading to the identification of Tf. Quantitative agreement with experiment is exhibited. Supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Science and Engineering under Award DE-SC0013599.
Biological characterization of low-energy ions with high-energy deposition on human cells.
Saha, Janapriya; Wilson, Paul; Thieberger, Peter; Lowenstein, Derek; Wang, Minli; Cucinotta, Francis A
2014-09-01
During space travel, astronauts are exposed to cosmic radiation that is comprised of high-energy nuclear particles. Cancer patients are also exposed to high-energy nuclear particles when treated with proton and carbon beams. Nuclear interactions from high-energy particles traversing shielding materials and tissue produce low-energy (<10 MeV/n) secondary particles of high-LET that contribute significantly to overall radiation exposures. Track structure theories suggest that high charge and energy (HZE) particles and low-energy secondary ions of similar LET will have distinct biological effects for cellular and tissue damage endpoints. We investigated the biological effects of low-energy ions of high LET utilizing the Tandem Van de Graaff accelerator at the Brookhaven National Laboratory (BNL), and compared these to experiments with HZE particles, that mimic the space environment produced at NASA Space Radiation Laboratory (NSRL) at BNL. Immunostaining for DNA damage response proteins was carried out after irradiation with 5.6 MeV/n boron (LET 205 keV/μm), 5.3 MeV/n silicon (LET 1241 keV/μm), 600 MeV/n Fe (LET 180 keV/μm) and 77 MeV/n oxygen (LET 58 keV/μm) particles. Low-energy ions caused more persistent DNA damage response (DDR) protein foci in irradiated human fibroblasts and esophageal epithelial cells compared to HZE particles. More detailed studies comparing boron ions to Fe particles, showed that boron-ion radiation resulted in a stronger G2 delay compared to Fe-particle exposure, and boron ions also showed an early recruitment of Rad51 at double-strand break (DSB) sites, which suggests a preference of homologous recombination for DSB repair in low-energy albeit high-LET particles. Our experiments suggest that the very high-energy radiation deposition by low-energy ions, representative of galactic cosmic radiation and solar particle event secondary radiation, generates massive but localized DNA damage leading to delayed DSB repair, and distinct cellular
String cosmology with a time-dependent antisymmetric tensor potential
Copeland, E.J.; Lahiri, A.; Wands, D. )
1995-02-15
We present a class of exact solutions for homogeneous, anisotropic cosmologies in four dimensions derived from the low-energy string effective action including a homogeneous dilaton [phi] and antisymmetric tensor potential [ital B][sub [mu][nu
Network Structures Arising from Spike-Timing Dependent Plasticity
NASA Astrophysics Data System (ADS)
Babadi, Baktash
Spike-timing dependent plasticity (STDP), a widespread synaptic modification mechanism, is sensitive to correlations between presynaptic spike trains, and organizes neural circuits in functionally useful ways. In this dissertation, I study the structures arising from STDP in a population of synapses with an emphasis on the interplay between synaptic stability and Hebbian competition, explained in Chapter 1. Starting from the simplest description of STDP which relates synaptic modification to the intervals between pairs of pre- and postsynaptic spikes, I show in Chapter 2 that stability and Hebbian competition are incompatible in this class of "pair-based" STDP models, either when hard bounds or soft bounds are imposed to the synapses. In chapter 3, I propose an alternative biophysically inspired method for imposing bounds to synapses, i.e. introducing a small temporal shift in the STDP window. Shifted STDP overcomes the incompatibility of synaptic stability and competition and can implement both Hebbian and anti-Hebbian forms of competitive plasticity. In light of experiments the explored a variety of spike patterns, STDP models have been augmented to account for interactions between multiple pre- and postsynaptic action potentials. In chapter 4, I study the stability/competition interplay in three different proposed multi-spike models of STDP. I show that the "triplet model" leads to a partially steady-state distribution of synaptic weights and induces Hebbian competition. The "suppression model" develops a stable distribution of weights when the average weight is high and shows predominantly anti-Hebbian competition. The "NMDAR-based" model can lead to either stable or partially stable synaptic weight distribution and exhibits both Hebbian and anti-Hebbian competition, depending on the parameters. I conclude that multi-spike STDP models can produce radically different effects at the population level depending on how they implement multi-spike interactions
Quantitation of absorbed or deposited materials on a substrate that measures energy deposition
Grant, Patrick G.; Bakajin, Olgica; Vogel, John S.; Bench, Graham
2005-01-18
This invention provides a system and method for measuring an energy differential that correlates to quantitative measurement of an amount mass of an applied localized material. Such a system and method remains compatible with other methods of analysis, such as, for example, quantitating the elemental or isotopic content, identifying the material, or using the material in biochemical analysis.
Evolution of Wilson loop in time-dependent N =4 super Yang-Mills plasma
NASA Astrophysics Data System (ADS)
Ali-Akbari, M.; Charmchi, F.; Davody, A.; Ebrahim, H.; Shahkarami, L.
2016-04-01
Using holography we study the evolution of the Wilson loop of a quark-antiquark pair in a dynamical strongly coupled plasma. The time-dependent plasma, whose dynamics is originated from the energy injection, is dual to the anti-de Sitter-Vaidya background. The quark-antiquark pair is represented by the endpoints of a string stretched from the boundary to the bulk. The evolution of the system is studied by evaluating the expectation value of the Wilson loop, throughout the process. Our results show that the evolution of the Wilson loop depends on the speed of the energy injection as well as the final temperature of the plasma. For high enough temperatures and rapid energy injection, it starts oscillating around its equilibrium value, immediately after the injection.
Optimized Effective Potential for Quantum Electrodynamical Time-Dependent Density Functional Theory.
Pellegrini, Camilla; Flick, Johannes; Tokatly, Ilya V; Appel, Heiko; Rubio, Angel
2015-08-28
We propose an orbital exchange-correlation functional for applying time-dependent density functional theory to many-electron systems coupled to cavity photons. The time nonlocal equation for the electron-photon optimized effective potential (OEP) is derived. In the static limit our OEP energy functional reduces to the Lamb shift of the ground state energy. We test the new approximation in the Rabi model. It is shown that the OEP (i) reproduces quantitatively the exact ground-state energy from the weak to the deep strong coupling regime and (ii) accurately captures the dynamics entering the ultrastrong coupling regime. The present formalism opens the path to a first-principles description of correlated electron-photon systems, bridging the gap between electronic structure methods and quantum optics for real material applications. PMID:26371646
Multi-configuration time-dependent density-functional theory based on range separation.
Fromager, Emmanuel; Knecht, Stefan; Jensen, Hans Jørgen Aa
2013-02-28
Multi-configuration range-separated density-functional theory is extended to the time-dependent regime. An exact variational formulation is derived. The approximation, which consists in combining a long-range Multi-Configuration-Self-Consistent Field (MCSCF) treatment with an adiabatic short-range density-functional (DFT) description, is then considered. The resulting time-dependent multi-configuration short-range DFT (TD-MC-srDFT) model is applied to the calculation of singlet excitation energies in H2, Be, and ferrocene, considering both short-range local density (srLDA) and generalized gradient (srGGA) approximations. As expected, when modeling long-range interactions with the MCSCF model instead of the adiabatic Buijse-Baerends density-matrix functional as recently proposed by Pernal [J. Chem. Phys. 136, 184105 (2012)], the description of both the 1(1)D doubly-excited state in Be and the 1(1)Σu(+) state in the stretched H2 molecule are improved, although the latter is still significantly underestimated. Exploratory TD-MC-srDFT/GGA calculations for ferrocene yield in general excitation energies at least as good as TD-DFT using the Coulomb attenuated method based on the three-parameter Becke-Lee-Yang-Parr functional (TD-DFT/CAM-B3LYP), and superior to wave-function (TD-MCSCF, symmetry adapted cluster-configuration interaction) and TD-DFT results based on LDA, GGA, and hybrid functionals. PMID:23464134
On the time-dependent resonant width for Landau damping: theory and PIC simulation
NASA Astrophysics Data System (ADS)
Grismayer, T.; Fahlen, J. E.; Decyk, V. K.; Mori, W. B.
2011-07-01
We use electrostatic partice-in-cell (PIC) simulations and theory to study the damping of 1D plasma waves. We consider the linear regime where the asymptotic damping rate is much bigger than the bounce frequency. In this regime the waves are typically very small and often below the thermal noise in simulations and experiments. These waves can be studied using a subtraction technique in which two simulations with identical random number generation seeds are carried out. In the first, a small amplitude wave is excited. In the second simulation no wave is excited. The results from each simulation are subtracted providing a clean linear wave that can be studied. Since the Landau derivation does not provide a description of damping in terms of individual particle trajectories, we analyze Landau damping using a Lagrangian approach based on energy conservation and the linearized particle trajectories. This method provides a time-dependent resonance curve and the energy transfer of the particles in the damping process. The time-dependent resonant width measured in the simulations is compared with the theoretical prediction. Simulations in which particles within the resonance width are removed are also presented.
Time-dependent density functional theory with twist-averaged boundary conditions
NASA Astrophysics Data System (ADS)
Schuetrumpf, B.; Nazarewicz, W.; Reinhard, P.-G.
2016-05-01
Background: Time-dependent density functional theory is widely used to describe excitations of many-fermion systems. In its many applications, three-dimensional (3D) coordinate-space representation is used, and infinite-domain calculations are limited to a finite volume represented by a spatial box. For finite quantum systems (atoms, molecules, nuclei, hadrons), the commonly used periodic or reflecting boundary conditions introduce spurious quantization of the continuum states and artificial reflections from boundary; hence, an incorrect treatment of evaporated particles. Purpose: The finite-volume artifacts for finite systems can be practically cured by invoking an absorbing potential in a certain boundary region sufficiently far from the described system. However, such absorption cannot be applied in the calculations of infinite matter (crystal electrons, quantum fluids, neutron star crust), which suffer from unphysical effects stemming from a finite computational box used. Here, twist-averaged boundary conditions (TABC) have been used successfully to diminish the finite-volume effects. In this work, we extend TABC to time-dependent modes. Method: We use the 3D time-dependent density functional framework with the Skyrme energy density functional. The practical calculations are carried out for small- and large-amplitude electric dipole and quadrupole oscillations of 16O. We apply and compare three kinds of boundary conditions: periodic, absorbing, and twist-averaged. Results: Calculations employing absorbing boundary conditions (ABC) and TABC are superior to those based on periodic boundary conditions. For low-energy excitations, TABC and ABC variants yield very similar results. With only four twist phases per spatial direction in TABC, one obtains an excellent reduction of spurious fluctuations. In the nonlinear regime, one has to deal with evaporated particles. In TABC, the floating nucleon gas remains in the box; the amount of nucleons in the gas is found to be
a Time-Dependent Many-Electron Approach to Atomic and Molecular Interactions
NASA Astrophysics Data System (ADS)
Runge, Keith
A new methodology is developed for the description of electronic rearrangement in atomic and molecular collisions. Using the eikonal representation of the total wavefunction, time -dependent equations are derived for the electronic densities within the time-dependent Hartree-Fock approximation. An averaged effective potential which ensures time reversal invariance is used to describe the effect of the fast electronic transitions on the slower nuclear motions. Electron translation factors (ETF) are introduced to eliminate spurious asymptotic couplings, and a local ETF is incorporated into a basis of traveling atomic orbitals. A reference density is used to describe local electronic relaxation and to account for the time propagation of fast and slow motions, and is shown to lead to an efficient integration scheme. Expressions for time-dependent electronic populations and polarization parameters are given. Electronic integrals over Gaussians including ETFs are derived to extend electronic state calculations to dynamical phenomena. Results of the method are in good agreement with experimental data for charge transfer integral cross sections over a projectile energy range of three orders of magnitude in the proton-Hydrogen atom system. The more demanding calculations of integral alignment, state-to-state integral cross sections, and differential cross sections are found to agree well with experimental data provided care is taken to include ETFs in the calculation of electronic integrals and to choose the appropriate effective potential. The method is found to be in good agreement with experimental data for the calculation of charge transfer integral cross sections and state-to-state integral cross sections in the one-electron heteronuclear Helium(2+)-Hydrogen atom system and in the two-electron system, Hydrogen atom-Hydrogen atom. Time-dependent electronic populations are seen to oscillate rapidly in the midst of collision event. In particular, multiple exchanges of the
NASA Astrophysics Data System (ADS)
Colgan, J.; Pindzola, M. S.; Robicheaux, F.
2002-07-01
A formulation of the time-dependent close-coupling theory is described which allows efficient calculation of the total ionization cross section for many electron energies. The Fourier transform method is applied to the electron-impact ionization of Li2+ and excellent agreement is found with experiment and a distorted-wave method.
On the Total Energy Deposition Between Periodically Occurring Activations of the Aurora
NASA Technical Reports Server (NTRS)
Spann, James F., Jr.; Germany, G. A.; Parks, G. K.; Brittnacher, M. J.; Winglee, R. W.
1998-01-01
Total energy deposition in the northern latitudes is used in models to determine the state of the magnetosphere. It is known that on occasion, a series of intensifications of the aurora occur that are regularly spaced. The energy profile of the total energy deposited reflects this occurance. What can be said of the state of the magnetosphere based on these profiles. We present the result of a study which looks at several of these periods when a series of intensifications occur. Conclusions as to what the magnetosphere may be doing are presented.
Aradag, Selin
2013-01-01
In this study, the impact of laser energy deposition on pressure oscillations and relative sound pressure levels (SPL) in an open supersonic cavity flow is investigated. Laser energy with a magnitude of 100 mJ is deposited on the flow just above the cavity leading edge and up to 7 dB of reduction is obtained in the SPL values along the cavity back wall. Additionally, proper orthogonal decomposition (POD) method is applied to the x-velocity data obtained as a result of computational fluid dynamics simulations of the flow with laser energy deposition. Laser is numerically modeled using a spherically symmetric temperature distribution. By using the POD results, the effects of laser energy on the flow mechanism are presented. A one-dimensional POD methodology is applied to the surface pressure data to obtain critical locations for the placement of sensors for real time flow control applications. PMID:24363612
NASA Technical Reports Server (NTRS)
Spann, J. F.; Brittnacher, M.; Fillingim, M. O.; Germany, G. A.; Parks, G. K.
1998-01-01
The global images made by the Ultraviolet Imager (UVI) aboard the IASTP/Polar Satellite are used to derive the global auroral energy deposited in the ionosphere resulting from electron precipitation. During a substorm onset, the energy deposited and its location in local time are compared to the solar wind IMF conditions. Previously, insitu measurements of low orbiting satellites have made precipitating particle measurements along the spacecraft track and global images of the auroral zone, without the ability to quantify energy parameters, have been available. However, usage of the high temporal, spatial, and spectral resolution of consecutive UVI images enables quantitative measurement of the energy deposited in the ionosphere not previously available on a global scale. Data over an extended period beginning in January 1997 will be presented.
Yilmaz, Ibrahim; Aradag, Selin
2013-01-01
In this study, the impact of laser energy deposition on pressure oscillations and relative sound pressure levels (SPL) in an open supersonic cavity flow is investigated. Laser energy with a magnitude of 100 mJ is deposited on the flow just above the cavity leading edge and up to 7 dB of reduction is obtained in the SPL values along the cavity back wall. Additionally, proper orthogonal decomposition (POD) method is applied to the x-velocity data obtained as a result of computational fluid dynamics simulations of the flow with laser energy deposition. Laser is numerically modeled using a spherically symmetric temperature distribution. By using the POD results, the effects of laser energy on the flow mechanism are presented. A one-dimensional POD methodology is applied to the surface pressure data to obtain critical locations for the placement of sensors for real time flow control applications. PMID:24363612
Hochstuhl, David; Bonitz, Michael
2011-02-28
The multiconfigurational time-dependent Hartree-Fock method (MCTDHF) is applied for simulations of the two-photon ionization of helium. We present results for the single and double ionizations from the ground state for photon energies in the nonsequential regime and compare them to direct solutions of the Schroedinger equation using the time-dependent (full) configuration interaction (TDCI) method. We find that the single ionization is accurately reproduced by MCTDHF, whereas the double ionization results correctly capture the main trends of TDCI.
Experiment of Flow Control Using Laser Energy Deposition Around High Speed Propulsion System
NASA Astrophysics Data System (ADS)
Lee, HyoungJin; Jeung, InSeuck; Lee, SangHun; Kim, Seihwan
2011-11-01
An experimental investigation was conducted to examine the effect of a pulsed Nd:YAG laser energy deposition on the shock structures in supersonic/hypersonic flow and quiescent air. The effect of the laser energy and pressure in the blast wave generation were also investigated. As a result, the strength of plasma and blast wave becomes stronger as pressure or laser energy increase. And the breakdown threshold of air by laser energy deposition is 0.015 bar at 508 mJ laser energy, the blast wave threshold generation in air by laser energy deposition is 0.100 bar at same laser energy. As qualitative analysis, schlieren images are also obtained. After the series of experiments, the effect of laser energy deposition (LED) on high speed flow around the shock—shock interaction created by a wedge and blunt body. By LED, the structure of shock—shock interaction was collapsed momentary and the pressure of the stagnation point was fluctuated while interference of wave.
Time-dependent hydrophilicity of nickel nanorod arrays
NASA Astrophysics Data System (ADS)
Albarakati, Nahla; Ye, Dexian
2014-03-01
Wetting properties of metals are fundamentally important in applications such as catalysis, solar energy conversion, and fuel cells. Complete wetting of transition metal surfaces by water is ascertained due to their high surface energy. On flat metal surfaces, zero contact angles (CAs) can only be observed on ultra-clean metal surfaces, while finite CAs are measured as soon as the surface is contaminated. However, it is not clear whether or not the hydrophilicity of a nanostructured metal surface can be maintained. Here, we design a series of experiments to test the hydrophilicity of nickel nanorods with heights ranging from 50 to 600 nm. We observe that all of our samples are initially superhydrophilic, but reduce their hydrophilicity over a time period of three months. Airborne hydrocarbon is believed to be the reason for the reducing hydrophilicity. A theory based on the Cassie-Baxter model is constructed to explain our observations in experiment.
Validating a time-dependent turbulence-driven model of the solar wind
Lionello, Roberto; Downs, Cooper; Linker, Jon A.; Mikić, Zoran; Velli, Marco; Verdini, Andrea E-mail: cdowns@predsci.com E-mail: mikic@predsci.com E-mail: verdini@oma.be
2014-04-01
Although the mechanisms responsible for heating the Sun's corona and accelerating the solar wind are still being actively investigated, it is largely accepted that photospheric motions provide the energy source and that the magnetic field must play a key role in the process. Verdini et al. presented a model for heating and accelerating the solar wind based on the turbulent dissipation of Alfvén waves. We first use a time-dependent model of the solar wind to reproduce one of Verdini et al.'s solutions; then, we extend its application to the case where the energy equation includes thermal conduction and radiation losses, and the upper chromosphere is part of the computational domain. Using this model, we explore the parameter space and describe the characteristics of a fast solar wind solution. We discuss how this formulation may be applied to a three-dimensional MHD model of the corona and solar wind.
Real-Time Time-Dependent DFT Study of Electronic Stopping in Semiconductors under Proton Irradiation
NASA Astrophysics Data System (ADS)
Yost, Dillon C.; Reeves, Kyle G.; Kanai, Yosuke
Understanding the detailed mechanisms of how highly energetic charged particles transfer their kinetic energy to electronic excitations in materials has become an important topic in various technologies ranging from nuclear energy applications to integrated circuits for space missions. In this work, we use our new large-scale real-time time-dependent density functional theory simulation to investigate details of the ion-velocity-dependent dynamics of electronic excitations in the electronic stopping process. In particular, we will discuss how point defects in semiconductor materials influence the electronic stopping process under proton irradiation, using silicon carbide (3C-SiC) as a representative material due to its great technological importance. Additionally, we will provide atomistic insights into existing analytical models that are based on the plane-wave Born approximation by examining velocity-dependence of the projectile charge from first-principles simulations.
NASA Astrophysics Data System (ADS)
Silaeva, Elena P.; Uchida, Kazuki; Suzuki, Yasumitsu; Watanabe, Kazuyuki
2015-10-01
High positive electrostatic (dc) field can break the bonds in molecules and strip away atoms from the solid surfaces. The dynamics of this field evaporation under laser pulse is studied for a H2 molecule and a Si4 cluster using time-dependent density functional theory combined with molecular dynamics. This allows us to monitor the position and charge state of the evaporated atom in real time. Our simulations demonstrate that the critical dc field for the evaporation is lower if the molecule/cluster is illuminated by a laser pulse. The behavior of the evaporation threshold as a function of laser intensity and dc field is in qualitative agreement with experiments and provides important insights into the mechanisms of laser-assisted field evaporation. Additionally, the laser-assisted field evaporation is found to be sensitive to the laser energy according to the photoabsorption spectra that demonstrate a pronounced redshift in the lower energy region at higher dc field values.
Initial Time Dependence of Abundances in Solar Energetic Particle Events
NASA Technical Reports Server (NTRS)
Reames, Donald V.; Ny, C. K.; Tylka, A. J.
1999-01-01
We compare the initial behavior of Fe/O and He/H abundance ratios and their relationship to the evolution of the proton energy spectra in "small" and "large" gradual solar energetic particle (SEP) events. The results are qualitatively consistent with the behavior predicted by the theory of Ng et al. (1999a, b). He/H ratios that initially rise with time are a signature of scattering by non-Kolmogorov Alfven wave spectra generated by intense beams of shock-accelerated protons streaming outward in large gradual SEP events.
Time-dependent closure relations for relativistic collisionless fluid equations.
Bendib-Kalache, K; Bendib, A; El Hadj, K Mohammed
2010-11-01
Linear fluid equations for relativistic and collisionless plasmas are derived. Closure relations for the fluid equations are analytically computed from the relativistic Vlasov equation in the Fourier space (ω,k), where ω and k are the conjugate variables of time t and space x variables, respectively. The mathematical method used is based on the projection operator techniques and the continued fraction mathematical tools. The generalized heat flux and stress tensor are calculated for arbitrary parameter ω/kc where c is the speed of light, and for arbitrary relativistic parameter z=mc²/T , where m is the particle rest mass and T, the plasma temperature in energy units. PMID:21230596
Time-dependent closure relations for relativistic collisionless fluid equations
Bendib-Kalache, K.; Bendib, A.; El Hadj, K. Mohammed
2010-11-15
Linear fluid equations for relativistic and collisionless plasmas are derived. Closure relations for the fluid equations are analytically computed from the relativistic Vlasov equation in the Fourier space ({omega},k), where {omega} and k are the conjugate variables of time t and space x variables, respectively. The mathematical method used is based on the projection operator techniques and the continued fraction mathematical tools. The generalized heat flux and stress tensor are calculated for arbitrary parameter {omega}/kc where c is the speed of light, and for arbitrary relativistic parameter z=mc{sup 2}/T, where m is the particle rest mass and T, the plasma temperature in energy units.
Effect of Low-Energy Ions on Plasma-Enhanced Deposition of Cubic Boron Nitride
NASA Astrophysics Data System (ADS)
Torigoe, M.; Fukui, S.; Teii, K.; Matsumoto, S.
2015-09-01
The effect of low-energy ions on deposition of cubic boron nitride (cBN) films in an inductively coupled plasma with the chemistry of fluorine is studied in terms of ion energy, ion flux, and ion to boron flux ratio onto the substrate. The ion energy and the ion to boron flux ratio are determined from the sheath potential and the ratio of incident ion flux to net deposited boron flux, respectively. For negative substrate biases where sp2-bonded BN phase only or no deposit is formed, both the ion energy and the ion to boron flux ratio are high. For positive substrate biases where cBN phase is formed, the ion energy and the ion to boron flux ratio are estimated in the range of a few eV to 35 eV and 100 to 130, respectively. The impact of negative ions is presumed to be negligible due to their low kinetic energy relative to the sheath potential over the substrate surface. The impact of positive ions with high ion to boron flux ratios is primarily responsible for reduction of the ion energy for cBN film deposition. Work supported in part by a Grant-in-Aid for Scientific Research (B), a Funding Program for Next Generation World-Leading Researchers, and an Industrial Technology Research Grant Program 2008.
Energy deposition dynamics of femtosecond pulses in water
Minardi, Stefano Pertsch, Thomas; Milián, Carles; Couairon, Arnaud; Majus, Donatas; Tamošauskas, Gintaras; Dubietis, Audrius; Gopal, Amrutha
2014-12-01
We exploit inverse Raman scattering and solvated electron absorption to perform a quantitative characterization of the energy loss and ionization dynamics in water with tightly focused near-infrared femtosecond pulses. A comparison between experimental data and numerical simulations suggests that the ionization energy of water is 8 eV, rather than the commonly used value of 6.5 eV. We also introduce an equation for the Raman gain valid for ultra-short pulses that validates our experimental procedure.
Stochastic spatial energy deposition profiles for MeV protons and keV electrons
NASA Astrophysics Data System (ADS)
Udalagama, C.; Bettiol, A. A.; Watt, F.
2009-12-01
With the rapid advances being made in novel high-energy ion-beam techniques such as proton beam writing, single-ion-event effects, ion-beam-radiation therapy, ion-induced fluorescence imaging, proton/ion microscopy, and ion-induced electron imaging, it is becoming increasingly important to understand the spatial energy-deposition profiles of energetic ions as they penetrate matter. In this work we present the results of comprehensive yet straightforward event-by-event Monte Carlo calculations that simulate ion/electron propagation and secondary electron ( δ ray) generation to yield spatial energy-deposition data. These calculations combine SRIM/TRIM features, EEDL97 data and volume-plasmon-localization models with a modified version of one of the newer δ ray generation models, namely, the Hansen-Kocbach-Stolterfoht. The development of the computer code DEEP (deposition of energy due to electrons and protons) offers a unique means of studying the energy-deposition/redistribution problem while still retaining the important stochastic nature inherent in these processes which cannot be achieved with analytical modeling. As an example of an application of DEEP we present results that compare the energy-deposition profiles of primary MeV protons and primary keV electrons in polymethymethacrylate. Such data are important when comparing proximity effects in the direct write lithography processes of proton-beam writing and electron-beam writing. Our calculations demonstrate that protons are able to maintain highly compact spatial energy-deposition profiles compared with electrons.
Coupling of MASH-MORSE Adjoint Leakages with Space- and Time-Dependent Plume Radiation Sources
Slater, C.O.
2001-04-20
In the past, forward-adjoint coupling procedures in air-over-ground geometry have typically involved forward fluences arising from a point source a great distance from a target or vehicle system. Various processing codes were used to create localized forward fluence files that could be used to couple with the MASH-MORSE adjoint leakages. In recent years, radiation plumes that result from reactor accidents or similar incidents have been modeled by others, and the source space and energy distributions as a function of time have been calculated. Additionally, with the point kernel method, they were able to calculate in relatively quick fashion free-field radiation doses for targets moving within the fluence field or for stationary targets within the field, the time dependence for the latter case coming from the changes in position, shape, source strength, and spectra of the plume with time. The work described herein applies the plume source to the MASH-MORSE coupling procedure. The plume source replaces the point source for generating the forward fluences that are folded with MASH-MORSE adjoint leakages. Two types of source calculations are described. The first is a ''rigorous'' calculation using the TORT code and a spatially large air-over-ground geometry. For each time step desired, directional fluences are calculated and are saved over a predetermined region that encompasses a structure within which it is desired to calculate dose rates. Processing codes then create the surface fluences (which may include contributions from radiation sources that deposit on the roof or plateout) that will be coupled with the MASH-MORSE adjoint leakages. Unlike the point kernel calculations of the free-field dose rates, the TORT calculations in practice include the effects of ground scatter on dose rates and directional fluences, although the effects may be underestimated or overestimated because of the use of necessarily coarse mesh and quadrature in order to reduce computational
Time-dependent simulations of a Compact Ignition Tokamak
Stotler, D.P.; Bateman, G.
1988-05-01
Detailed simulations of the Compact Ignition Tokamak are carried out using a 1-1/2-D transport code. The calculations include time-varying densities, fields, and plasma shape. It is shown that ignition can be achieved in this device if somewhat better than L-mode energy confinement time scaling is possible. We also conclude that the performance of such a compact, short-pulse device can depend greatly on how the plasma is evolved to its flat-top parameters. Furthermore, in cases such as the ones discussed here, where there is not a great deal of ignition margin and the electron density is held constant, ignition ends if the helium ash is not removed. In general, control of the deuterium--tritium density is equivalent to burn control. 48 refs., 15 figs.
TIME-DEPENDENT MODELING OF PULSAR WIND NEBULAE
Vorster, M. J.; Ferreira, S. E. S.; Tibolla, O.; Kaufmann, S. E-mail: omar.tibolla@gmail.com
2013-08-20
A spatially independent model that calculates the time evolution of the electron spectrum in a spherically expanding pulsar wind nebula (PWN) is presented, allowing one to make broadband predictions for the PWN's non-thermal radiation. The source spectrum of electrons injected at the termination shock of the PWN is chosen to be a broken power law. In contrast to previous PWN models of a similar nature, the source spectrum has a discontinuity in intensity at the transition between the low- and high-energy components. To test the model, it is applied to the young PWN G21.5-0.9, where it is found that a discontinuous source spectrum can model the emission at all wavelengths better than a continuous one. The model is also applied to the unidentified sources HESS J1427-608 and HESS J1507-622. Parameters are derived for these two candidate nebulae that are consistent with the values predicted for other PWNe. For HESS J1427-608, a present day magnetic field of B{sub age} = 0.4 {mu}G is derived. As a result of the small present day magnetic field, this source has a low synchrotron luminosity, while remaining bright at GeV/TeV energies. It is therefore possible to interpret HESS J1427-608 within the ancient PWN scenario. For the second candidate PWN HESS J1507-622, a present day magnetic field of B{sub age} = 1.7 {mu}G is derived. Furthermore, for this candidate PWN a scenario is favored in the present paper in which HESS J1507-622 has been compressed by the reverse shock of the supernova remnant.
Time-dependent Modeling of Pulsar Wind Nebulae
NASA Astrophysics Data System (ADS)
Vorster, M. J.; Tibolla, O.; Ferreira, S. E. S.; Kaufmann, S.
2013-08-01
A spatially independent model that calculates the time evolution of the electron spectrum in a spherically expanding pulsar wind nebula (PWN) is presented, allowing one to make broadband predictions for the PWN's non-thermal radiation. The source spectrum of electrons injected at the termination shock of the PWN is chosen to be a broken power law. In contrast to previous PWN models of a similar nature, the source spectrum has a discontinuity in intensity at the transition between the low- and high-energy components. To test the model, it is applied to the young PWN G21.5-0.9, where it is found that a discontinuous source spectrum can model the emission at all wavelengths better than a continuous one. The model is also applied to the unidentified sources HESS J1427-608 and HESS J1507-622. Parameters are derived for these two candidate nebulae that are consistent with the values predicted for other PWNe. For HESS J1427-608, a present day magnetic field of B age = 0.4 μG is derived. As a result of the small present day magnetic field, this source has a low synchrotron luminosity, while remaining bright at GeV/TeV energies. It is therefore possible to interpret HESS J1427-608 within the ancient PWN scenario. For the second candidate PWN HESS J1507-622, a present day magnetic field of B age = 1.7 μG is derived. Furthermore, for this candidate PWN a scenario is favored in the present paper in which HESS J1507-622 has been compressed by the reverse shock of the supernova remnant.
Exact-exchange time-dependent density-functional theory for static and dynamic polarizabilities
Hirata, So; Ivanov, Stanislav; Bartlett, Rodney J.; Grabowski, Ireneusz
2005-03-01
Time-dependent density-functional theory (TDDFT) employing the exact-exchange functional has been formulated on the basis of the optimized-effective-potential (OEP) method of Talman and Shadwick for second-order molecular properties and implemented into a Gaussian-basis-set, trial-vector algorithm. The only approximation involved, apart from the lack of correlation effects and the use of Gaussian-type basis functions, was the consistent use of the adiabatic approximation in the exchange kernel and in the linear response function. The static and dynamic polarizabilities and their anisotropy predicted by the TDDFT with exact exchange (TDOEP) agree accurately with the corresponding values from time-dependent Hartree-Fock theory, the exact-exchange counterpart in the wave function theory. The TDOEP is free from the nonphysical asymptotic decay of the exchange potential of most conventional density functionals or from any other manifestations of the incomplete cancellation of the self-interaction energy. The systematic overestimation of the absolute values and dispersion of polarizabilities that plagues most conventional TDDFT cannot be seen in the TDOEP.
Weckmann, K; Labermaier, C; Asara, J M; Müller, M B; Turck, C W
2014-01-01
Ketamine, an N-methyl-D-aspartate receptor (NMDAR) antagonist, has fast-acting antidepressant activities and is used for major depressive disorder (MDD) patients who show treatment resistance towards drugs of the selective serotonin reuptake inhibitor (SSRI) type. In order to better understand Ketamine's mode of action, a prerequisite for improved drug development efforts, a detailed understanding of the molecular events elicited by the drug is mandatory. In the present study we have carried out a time-dependent hippocampal metabolite profiling analysis of mice treated with Ketamine. After a single injection of Ketamine, our metabolomics data indicate time-dependent metabolite level alterations starting already after 2 h reflecting the fast antidepressant effect of the drug. In silico pathway analyses revealed that several hippocampal pathways including glycolysis/gluconeogenesis, pentose phosphate pathway and citrate cycle are affected, apparent by changes not only in metabolite levels but also connected metabolite level ratios. The results show that a single injection of Ketamine has an impact on the major energy metabolism pathways. Furthermore, seven of the identified metabolites qualify as biomarkers for the Ketamine drug response. PMID:25386958
NASA Astrophysics Data System (ADS)
Ido, Kota; Ohgoe, Takahiro; Imada, Masatoshi
2015-12-01
We develop a time-dependent variational Monte Carlo (t-VMC) method for quantum dynamics of strongly correlated electrons. The t-VMC method has been recently applied to bosonic systems and quantum spin systems. Here we propose a time-dependent trial wave function with many variational parameters, which is suitable for nonequilibrium strongly correlated electron systems. As the trial state, we adopt the generalized pair-product wave function with correlation factors and quantum-number projections. This trial wave function has been proven to accurately describe ground states of strongly correlated electron systems. To show the accuracy and efficiency of our trial wave function in nonequilibrium states as well, we present our benchmark results for relaxation dynamics during and after interaction quench protocols of fermionic Hubbard models. We find that our trial wave function well reproduces the exact results for the time evolution of physical quantities such as energy, momentum distribution, spin structure factor, and superconducting correlations. These results show that the t-VMC with our trial wave function offers an efficient and accurate way to study challenging problems of nonequilibrium dynamics in strongly correlated electron systems.
2007 Time_Dependent Density-Functional Therory (July 15-20, 2007 Colby College, Maine)
Ullrich Carsten Nancy Ryan Gray
2008-09-19
Time-dependent density-functional theory (TDDFT) provides an efficient, elegant, and formally exact way of describing the dynamics of interacting many-body quantum systems, circumventing the need for solving the full time-dependent Schroedinger equation. In the 20 years since it was first rigorously established in 1984, the field of TDDFT has made rapid and significant advances both formally as well as in terms of successful applications in chemistry, physics and materials science. Today, TDDFT has become the method of choice for calculating excitation energies of complex molecules, and is becoming increasingly popular for describing optical and spectroscopic properties of a variety of materials such as bulk solids, clusters and nanostructures. Other growing areas of applications of TDDFT are nonlinear dynamics of strongly excited electronic systems and molecular electronics. The purpose and scope of this Gordon Research Conference is to provide a platform for discussing the current state of the art of the rapidly progressing, highly interdisciplinary field of TDDFT, to identify and debate open questions, and to point out new promising research directions. The conference will bring together experts with a diverse background in chemistry, physics, and materials science.
The tunneling solutions of the time-dependent Schroedinger equation for a square-potential barrier
Elci, A.; Hjalmarson, H. P.
2009-10-15
The exact tunneling solutions of the time-dependent Schroedinger equation with a square-potential barrier are derived using the continuous symmetry group G{sub S} for the partial differential equation. The infinitesimal generators and the elements for G{sub S} are represented and derived in the jet space. There exist six classes of wave functions. The representative (canonical) wave functions for the classes are labeled by the eigenvalue sets, whose elements arise partially from the reducibility of a Lie subgroup G{sub LS} of G{sub S} and partially from the separation of variables. Each eigenvalue set provides two or more time scales for the wave function. The ratio of two time scales can act as the duration of an intrinsic clock for the particle motion. The exact solutions of the time-dependent Schroedinger equation presented here can produce tunneling currents that are orders of magnitude larger than those produced by the energy eigenfunctions. The exact solutions show that tunneling current can be quantized under appropriate boundary conditions and tunneling probability can be affected by a transverse acceleration.
Time-dependent Mott transition in the periodic Anderson model with nonlocal hybridization
NASA Astrophysics Data System (ADS)
Hofmann, Felix; Potthoff, Michael
2016-08-01
The time-dependent Mott transition in a periodic Anderson model with off-site, nearest-neighbor hybridization is studied within the framework of nonequilibrium self-energy functional theory. Using the two-site dynamical-impurity approximation, we compute the real-time dynamics of the optimal variational parameter and of different observables initiated by sudden quenches of the Hubbard-U and identify the critical interaction. The time-dependent transition is orbital selective, i.e., in the final state, reached in the long-time limit after the quench to the critical interaction, the Mott gap opens in the spectral function of the localized orbitals only. We discuss the dependence of the critical interaction and of the final-state effective temperature on the hybridization strength and point out the various similarities between the nonequilibrium and the equilibrium Mott transition. It is shown that these can also be smoothly connected to each other by increasing the duration of a U-ramp from a sudden quench to a quasi-static process. The physics found for the model with off-site hybridization is compared with the dynamical Mott transition in the single-orbital Hubbard model and with the dynamical crossover found for the real-time dynamics of the conventional Anderson lattice with on-site hybridization.
Measurement of Time-Dependent CP Asymmetry in B0->ccbar K(*)0 Decays
Aubert, : B.
2009-02-12
The authors present updated measurements of time-dependent Cp asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465 {+-} 5) x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric energy e{sup +}e{sup -} storage rings operating at the SLAC National Accelerator Laboratory. The time-dependent CP asymmetry parameters measured from J/{psi} K{sub S}{sup 0}, J/{psi}K{sub L}{sup 0}, {psi}(2S)K{sub S}{sup 0}, {eta}{sub c}K{sub S}{sup 0}, {chi}{sub c1}K{sub S}{sup 0} and J/{psi} K*(892){sup 0} decays are: C{sub f} = 0.024 {+-} 0.020(stat) {+-} 0.016(syst) and -{eta}{sub f}S{sub f} = 0.687 {+-} 0.028(stat) {+-} 0.012(syst).
NASA Astrophysics Data System (ADS)
Eliëns, I. S.; Ramos, F. B.; Xavier, J. C.; Pereira, R. G.
2016-05-01
We study the influence of reflective boundaries on time-dependent responses of one-dimensional quantum fluids at zero temperature beyond the low-energy approximation. Our analysis is based on an extension of effective mobile impurity models for nonlinear Luttinger liquids to the case of open boundary conditions. For integrable models, we show that boundary autocorrelations oscillate as a function of time with the same frequency as the corresponding bulk autocorrelations. This frequency can be identified as the band edge of elementary excitations. The amplitude of the oscillations decays as a power law with distinct exponents at the boundary and in the bulk, but boundary and bulk exponents are determined by the same coupling constant in the mobile impurity model. For nonintegrable models, we argue that the power-law decay of the oscillations is generic for autocorrelations in the bulk, but turns into an exponential decay at the boundary. Moreover, there is in general a nonuniversal shift of the boundary frequency in comparison with the band edge of bulk excitations. The predictions of our effective field theory are compared with numerical results obtained by time-dependent density matrix renormalization group (tDMRG) for both integrable and nonintegrable critical spin-S chains with S =1 /2 , 1, and 3 /2 .
NASA Astrophysics Data System (ADS)
Park, Youngyong; Do, Younghae; Altmeyer, Sebastian; Lai, Ying-Cheng; Lee, GyuWon
2015-02-01
We investigate high-dimensional nonlinear dynamical systems exhibiting multiple resonances under adiabatic parameter variations. Our motivations come from experimental considerations where time-dependent sweeping of parameters is a practical approach to probing and characterizing the bifurcations of the system. The question is whether bifurcations so detected are faithful representations of the bifurcations intrinsic to the original stationary system. Utilizing a harmonically forced, closed fluid flow system that possesses multiple resonances and solving the Navier-Stokes equation under proper boundary conditions, we uncover the phenomenon of the early effect. Specifically, as a control parameter, e.g., the driving frequency, is adiabatically increased from an initial value, resonances emerge at frequency values that are lower than those in the corresponding stationary system. The phenomenon is established by numerical characterization of physical quantities through the resonances, which include the kinetic energy and the vorticity field, and a heuristic analysis based on the concept of instantaneous frequency. A simple formula is obtained which relates the resonance points in the time-dependent and time-independent systems. Our findings suggest that, in general, any true bifurcation of a nonlinear dynamical system can be unequivocally uncovered through adiabatic parameter sweeping, in spite of a shift in the bifurcation point, which is of value to experimental studies of nonlinear dynamical systems.
System to quantify gamma-ray radial energy deposition in semiconductor detectors
Kammeraad, Judith E.; Blair, Jerome J.
2001-01-01
A system for measuring gamma-ray radial energy deposition is provided for use in conjunction with a semiconductor detector. The detector comprises two electrodes and a detector material, and defines a plurality of zones within the detecting material in parallel with the two electrodes. The detector produces a charge signal E(t) when a gamma-ray interacts with the detector. Digitizing means are provided for converting the charge signal E(t) into a digitized signal. A computational means receives the digitized signal and calculates in which of the plurality of zones the gamma-ray deposited energy when interacting with the detector. The computational means produces an output indicating the amount of energy deposited by the gamma-ray in each of the plurality of zones.
Biological consequences of nanoscale energy deposition near irradiated heavy atom nanoparticles
NASA Astrophysics Data System (ADS)
McMahon, Stephen J.; Hyland, Wendy B.; Muir, Mark F.; Coulter, Jonathan A.; Jain, Suneil; Butterworth, Karl T.; Schettino, Giuseppe; Dickson, Glenn R.; Hounsell, Alan R.; O'Sullivan, Joe M.; Prise, Kevin M.; Hirst, David G.; Currell, Fred J.
2011-06-01
Gold nanoparticles (GNPs) are being proposed as contrast agents to enhance X-ray imaging and radiotherapy, seeking to take advantage of the increased X-ray absorption of gold compared to soft tissue. However, there is a great discrepancy between physically predicted increases in X-ray energy deposition and experimentally observed increases in cell killing. In this work, we present the first calculations which take into account the structure of energy deposition in the nanoscale vicinity of GNPs and relate this to biological outcomes, and show for the first time good agreement with experimentally observed cell killing by the combination of X-rays and GNPs. These results are not only relevant to radiotherapy, but also have implications for applications of heavy atom nanoparticles in biological settings or where human exposure is possible because the localised energy deposition high-lighted by these results may cause complex DNA damage, leading to mutation and carcinogenesis.
Particle production and energy deposition studies for the neutrino factory target station
NASA Astrophysics Data System (ADS)
Back, John J.; Densham, Chris; Edgecock, Rob; Prior, Gersende
2013-02-01
We present FLUKA and MARS simulation studies of the pion production and energy deposition in the Neutrino Factory baseline target station, which consists of a 4 MW proton beam interacting with a liquid mercury jet target within a 20 T solenoidal magnetic field. We show that a substantial increase in the shielding is needed to protect the superconducting coils from too much energy deposition. Investigations reveal that it is possible to reduce the magnetic field in the solenoid capture system without adversely affecting the pion production efficiency. We show estimates of the amount of concrete shielding that will be required to protect the environment from the high radiation doses generated by the target station facility. We also present yield and energy deposition results for alternative targets: gallium liquid jet, tungsten powder jet, and solid tungsten bars.
Biological consequences of nanoscale energy deposition near irradiated heavy atom nanoparticles
McMahon, Stephen J.; Hyland, Wendy B.; Muir, Mark F.; Coulter, Jonathan A.; Jain, Suneil; Butterworth, Karl T.; Schettino, Giuseppe; Dickson, Glenn R.; Hounsell, Alan R.; O'Sullivan, Joe M.; Prise, Kevin M.; Hirst, David G.; Currell, Fred J.
2011-01-01
Gold nanoparticles (GNPs) are being proposed as contrast agents to enhance X-ray imaging and radiotherapy, seeking to take advantage of the increased X-ray absorption of gold compared to soft tissue. However, there is a great discrepancy between physically predicted increases in X-ray energy deposition and experimentally observed increases in cell killing. In this work, we present the first calculations which take into account the structure of energy deposition in the nanoscale vicinity of GNPs and relate this to biological outcomes, and show for the first time good agreement with experimentally observed cell killing by the combination of X-rays and GNPs. These results are not only relevant to radiotherapy, but also have implications for applications of heavy atom nanoparticles in biological settings or where human exposure is possible because the localised energy deposition high-lighted by these results may cause complex DNA damage, leading to mutation and carcinogenesis. PMID:22355537
Study on deposition rate and laser energy efficiency of Laser-Induction Hybrid Cladding
NASA Astrophysics Data System (ADS)
Wang, DengZhi; Hu, QianWu; Zheng, YinLan; Xie, Yong; Zeng, XiaoYan
2016-03-01
Laser-Induction Hybrid Cladding (LIHC) was introduced to prepare metal silicide based composite coatings, and influence of different factors such as laser type, laser power, laser scan speed and induction preheating temperature on the coating deposition rate and laser energy efficiency was studied systematically. Compared with conventional CO2 laser cladding, fiber laser-induction hybrid cladding improves the coating deposition rate and laser energy efficiency by 3.7 times. When a fiber laser with laser power of 4 kW was combined with an induction preheating temperature of 850 °C, the maximum coating deposition rate and maximum laser energy efficiency reaches 71 g/min and 64% respectively.
NASA Technical Reports Server (NTRS)
Cucinotta, Francis A.; Hajnal, Ferenc; Wilson, John W.
1990-01-01
The transport of nuclear fragmentation recoils produced by high-energy nucleons in the region of the bone-tissue interface is considered. Results for the different flux and absorbed dose for recoils produced by 1 GeV protons are presented in a bidirectional transport model. The energy deposition in marrow cavities is seen to be enhanced by recoils produced in bone. Approximate analytic formulae for absorbed dose near the interface region are also presented for a simplified range-energy model.
Harris, C.K.; Wiberg, P.L.
2001-01-01
A two-dimensional, time-dependent solution to the transport equation is formulated to account for advection and diffusion of sediment suspended in the bottom boundary layer of continental shelves. This model utilizes a semi-implicit, upwind-differencing scheme to solve the advection-diffusion equation across a two-dimensional transect that is configured so that one dimension is the vertical, and the other is a horizontal dimension usually aligned perpendicular to shelf bathymetry. The model calculates suspended sediment concentration and flux; and requires as input wave properties, current velocities, sediment size distributions, and hydrodynamic sediment properties. From the calculated two-dimensional suspended sediment fluxes, we quantify the redistribution of shelf sediment, bed erosion, and deposition for several sediment sizes during resuspension events. The two-dimensional, time-dependent approach directly accounts for cross-shelf gradients in bed shear stress and sediment properties, as well as transport that occurs before steady-state suspended sediment concentrations have been attained. By including the vertical dimension in the calculations, we avoid depth-averaging suspended sediment concentrations and fluxes, and directly account for differences in transport rates and directions for fine and coarse sediment in the bottom boundary layer. A flux condition is used as the bottom boundary condition for the transport equation in order to capture time-dependence of the suspended sediment field. Model calculations demonstrate the significance of both time-dependent and spatial terms on transport and depositional patterns on continental shelves. ?? 2001 Elsevier Science Ltd. All rights reserved.
Implosion Robustness, Time-Dependent Flux Asymmetries and Big Data
NASA Astrophysics Data System (ADS)
Peterson, J. L.; Field, J. E.; Spears, B. K.; Brandon, S. T.; Gaffney, J. A.; Hammer, J.; Kritcher, A.; Nora, R. C.; Springer, P. T.
2015-11-01
Both direct and indirect drive inertial confinement fusion rely on the formation of spherical implosions, which can be a challenge under temporal and spatial drive variations (either from discrete laser beams, a complex hohlraum radiation environment, or both). To that end, we examine the use of large simulation databases of 2D capsule implosions to determine the sensitivity of indirectly driven NIF designs to time-varying low-mode radiation drive asymmetries at varying convergence ratios. In particular, we define and calculate a large number of extensive quantities for the simulations within the database and compare with the equivalent quantities extracted from fully 3D simulations and those used in 1D hydrodynamic models. Additionally, we discuss some of the practical challenges of searching for physical insight in multi-petabyte datasets. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344, Lawrence Livermore National Security, LLC. LLNL-ABS-674884.
NASA Astrophysics Data System (ADS)
Coriani, Sonia; Pawłowski, Filip; Olsen, Jeppe; Jørgensen, Poul
2016-01-01
Molecular response properties for ground and excited states and for transitions between these states are defined by solving the time-dependent Schrödinger equation for a molecular system in a field of a time-periodic perturbation. In equation of motion coupled cluster (EOM-CC) theory, molecular response properties are commonly obtained by replacing, in configuration interaction (CI) molecular response property expressions, the energies and eigenstates of the CI eigenvalue equation with the energies and eigenstates of the EOM-CC eigenvalue equation. We show here that EOM-CC molecular response properties are identical to the molecular response properties that are obtained in the coupled cluster-configuration interaction (CC-CI) model, where the time-dependent Schrödinger equation is solved using an exponential (coupled cluster) parametrization to describe the unperturbed system and a linear (configuration interaction) parametrization to describe the time evolution of the unperturbed system. The equivalence between EOM-CC and CC-CI molecular response properties only holds when the CI molecular response property expressions—from which the EOM-CC expressions are derived—are determined using projection and not using the variational principle. In a previous article [F. Pawłowski, J. Olsen, and P. Jørgensen, J. Chem. Phys. 142, 114109 (2015)], it was stated that the equivalence between EOM-CC and CC-CI molecular response properties only held for a linear response function, whereas quadratic and higher order response functions were mistakenly said to differ in the two approaches. Proving the general equivalence between EOM-CC and CC-CI molecular response properties is a challenging task, that is undertaken in this article. Proving this equivalence not only corrects the previous incorrect statement but also first and foremost leads to a new, time-dependent, perspective for understanding the basic assumptions on which the EOM-CC molecular response property expressions
Coriani, Sonia; Pawłowski, Filip; Olsen, Jeppe; Jørgensen, Poul
2016-01-14
Molecular response properties for ground and excited states and for transitions between these states are defined by solving the time-dependent Schrödinger equation for a molecular system in a field of a time-periodic perturbation. In equation of motion coupled cluster (EOM-CC) theory, molecular response properties are commonly obtained by replacing, in configuration interaction (CI) molecular response property expressions, the energies and eigenstates of the CI eigenvalue equation with the energies and eigenstates of the EOM-CC eigenvalue equation. We show here that EOM-CC molecular response properties are identical to the molecular response properties that are obtained in the coupled cluster-configuration interaction (CC-CI) model, where the time-dependent Schrödinger equation is solved using an exponential (coupled cluster) parametrization to describe the unperturbed system and a linear (configuration interaction) parametrization to describe the time evolution of the unperturbed system. The equivalence between EOM-CC and CC-CI molecular response properties only holds when the CI molecular response property expressions-from which the EOM-CC expressions are derived-are determined using projection and not using the variational principle. In a previous article [F. Pawłowski, J. Olsen, and P. Jørgensen, J. Chem. Phys. 142, 114109 (2015)], it was stated that the equivalence between EOM-CC and CC-CI molecular response properties only held for a linear response function, whereas quadratic and higher order response functions were mistakenly said to differ in the two approaches. Proving the general equivalence between EOM-CC and CC-CI molecular response properties is a challenging task, that is undertaken in this article. Proving this equivalence not only corrects the previous incorrect statement but also first and foremost leads to a new, time-dependent, perspective for understanding the basic assumptions on which the EOM-CC molecular response property expressions are
Charge balance and ionospheric potential dynamics in time-dependent global electric circuit model
NASA Astrophysics Data System (ADS)
Jánský, Jaroslav; Pasko, Victor P.
2014-12-01
We have developed a time-dependent model of global electric circuit (GEC) in spherical coordinates. The model solves time-dependent charge continuity equation coupled with Poisson's equation. An implicit time stepping is used to avoid a strict dielectric relaxation time step condition, and boundary conditions for Poisson's equation are implemented to allow accurate description of time evolution of the ionospheric potential. The concept of impulse response of GEC is introduced that allows effective representation of complex time dynamics of various physical quantities in the circuit using model results obtained for instantaneous deposition of a point charge. The more complex problems are then reconstructed using convolution and linearity principles. For a point charge instantaneously deposited at a typical thundercloud altitude the impulse response of the charge density shows induction of the same value and polarity charge at the ionospheric boundary, while charge of the same value but opposite sign is moving down logarithmically with time and neutralizes the source point charge on time scale corresponding to the dielectric relaxation time at altitude of the source point charge. The ionospheric potential is modified immediately with input of the source point charge based on free space solution of Poisson's equation. Then the ionospheric potential relaxes. It is shown that during formation of two main charge centers of the thundercloud, typically represented by a current dipole, the ionospheric potential can be determined from the difference of time integrals of two ionospheric potential impulse responses corresponding to charge locations at the opposite ends of the current dipole. For latitude- and longitude-independent conductivity model, the total charge on the Earth is exactly zero at all times. During cloud-to-ground lightning discharge, the ionospheric potential changes instantaneously by a value proportional to the charge moment change produced by lightning
NASA Astrophysics Data System (ADS)
Martín, Jonatan; Torres, Diego F.; Rea, Nanda
2012-11-01
In this work, we present a leptonic, time-dependent model of pulsar wind nebulae (PWNe). The model seeks a solution for the lepton distribution function considering the full time-energy-dependent diffusion-loss equation. The time-dependent lepton population is balanced by injection, energy losses and escape. We include synchrotron, inverse-Compton (IC; with the cosmic-microwave background as well as with IR/optical photon fields), self-synchrotron Compton, and bremsstrahlung processes, all devoid of any radiative approximations. With this model in place we focus on the Crab nebula as an example and present its time-dependent evolution. Afterwards, we analyse the impact of different approximations made at the level of the diffusion-loss equation, as can be found in the literature. Whereas previous models ignored the escape term, e.g. with the diffusion-loss equation becoming advective, others approximated the losses as catastrophic, so that the equation has only time derivatives. Additional approximations are also described and computed. We study what the impact of these approaches is on the determination of the PWN evolution. In particular, we find the time-dependent deviation of the multi-wavelength spectrum and the best-fitting parameters obtained with the complete and the approximate models.
Energy deposition and thermal effects of runaway electrons in ITER-FEAT plasma facing components
NASA Astrophysics Data System (ADS)
Maddaluno, G.; Maruccia, G.; Merola, M.; Rollet, S.
2003-03-01
The profile of energy deposited by runaway electrons (RAEs) of 10 or 50 MeV in International Thermonuclear Experimental Reactor-Fusion Energy Advanced Tokamak (ITER-FEAT) plasma facing components (PFCs) and the subsequent temperature pattern have been calculated by using the Monte Carlo code FLUKA and the finite element heat conduction code ANSYS. The RAE energy deposition density was assumed to be 50 MJ/m 2 and both 10 and 100 ms deposition times were considered. Five different configurations of PFCs were investigated: primary first wall armoured with Be, with and without protecting CFC poloidal limiters, both port limiter first wall options (Be flat tile and CFC monoblock), divertor baffle first wall, armoured with W. The analysis has outlined that for all the configurations but one (port limiter with Be flat tile) the heat sink and the cooling tube beneath the armour are well protected for both RAE energies and for both energy deposition times. On the other hand large melting (W, Be) or sublimation (C) of the surface layer occurs, eventually affecting the PFCs lifetime.
Shi, Zongqian; Wang, Kun; Shi, Yuanjie; Wu, Jian; Han, Ruoyu
2015-12-28
Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ∼2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ∼18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.
NASA Astrophysics Data System (ADS)
Shi, Zongqian; Wang, Kun; Shi, Yuanjie; Wu, Jian; Han, Ruoyu
2015-12-01
Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ˜2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ˜18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.
Strong shock generation by fast electron energy deposition
Fox, T. E.; Pasley, J.; Robinson, A. P. L.
2013-12-15
It has been suggested that fast electrons may play a beneficial role in the formation of the ignitor shock in shock ignition owing to the high areal density of the fuel at the time of the ignitor pulse. In this paper, we extend previous studies which have focused on monoenergetic electron sources to populations with extended energy distributions. In good agreement with analytic scalings, we show that strong shocks can be produced with peak pressures of a few hundred Mbar to over 1 Gbar using fast electron intensities of 1–10 PW/cm{sup 2} in a uniform deuterium-tritium plasma at 10 g/cm{sup 3}. However, the length required for shock formation increases with fast electron temperature. As this shock formation distance becomes comparable to the target size, the shock is not able to fully develop, and this implies a limit on the ability of fast electrons to aid shock formation.
Modelling heavy-ion energy deposition in extended media
NASA Astrophysics Data System (ADS)
Mishustin, I.; Pshenichnov, I.; Greiner, W.
2010-10-01
We present recent developments of the Monte Carlo model for heavy-ion therapy (MCHIT), which is currently based on the Geant4 toolkit of version 9.2. The major advancement of the model concerns the modelling of violent fragmentation reactions by means of the Fermi break-up model, which is used to simulate decays of hot fragments created after the first stage of nucleus-nucleus collisions. By means of MCHIT we study the dose distributions from therapeutic beams of carbon nuclei in tissue-like materials, like water and PMMA. The contributions to the total dose from primary beam nuclei and from charged secondary fragments produced in nuclear fragmentation reactions are calculated. The build-up of secondary fragments along the beam axis is calculated and compared with available experimental data. Finally, we demonstrate the impact of violent multifragment decays on energy distributions of secondary neutrons produced by carbon nuclei in water.
Nighttime auroral energy deposition in the middle atmosphere
NASA Technical Reports Server (NTRS)
Goldberg, R. A.; Jackman, C. H.; Barcus, J. R.; Soraas, F.
1984-01-01
Ionospheric rocket sounding data for eight nighttime auroral events are used to characterize relativistic electron showers and their effects on atmospheric ozone. The rockets were launched from the Poker Flat Research Range in Alaska and from Andoya, Norway over the period 1976-82. Energetic fluxes were always detected but were of insufficient magnitude to produce significant changes in stratospheric ozone. However, middle atmospheric energy sources were found to be dominated by relativistic electrons and X-ray bremmstrahlung, the latter from 40-55 km and the former from 55-60 km altitudes. The ionizing radiation is concluded to be a significant factor in mesospheric ion conductivity, mobility, electric field structure and analytical models for the ion-neutral chemistry.
One-dimensional time-dependent debris bed model. [PWR; BWR
Gorham-Bergeron, E.
1982-01-01
The dryout process is described for a particle bed using a time-dependent one-dimensional porous bed model. The model is based on momentum, energy and mass conservation equations for separated flow. The model is applicable to the case in which capillary forces can be neglected. For the case in which only laminar flow is considered exact algebraic solutions to the equations can be obtained. These are presented. Distinct regimes for the parameterized solutions can be identified and associated with moving fronts in the bed. Extension to the full turbulent and laminar equations is made with the aid of insights gained from solution of the laminar case. Comparison with recent experimental results and theoretical predictions is made. The model is seen to encompass and extend the theoretical models. It suggests additional experiments.
Time-dependent simulation of prebunched one and two-beam free electron laser
Mirian, N. S.; Maraghechi, B.
2014-04-15
A numerical simulation in one-dimension is conducted to study the slippage effects on prebunched free electron laser. A technique for the simulation of time dependent free electron lasers (FEL) to model the slippage effects is introduced, and the slowly varying envelope approximation in both z and t is used to illustrate the temporal behaviour in the prebunched FEL. Slippage effect on prebunched two-beam FEL is compared with the one-beam modeling. The evaluation of the radiation pulse energy, thermal and phase distribution, and radiation pulse shape in one-beam and two-beam modeling is studied. It was shown that the performance is considerably undermined when the slippage time is comparable to the pulse duration. However, prebunching reduces the slippage. Prebunching also leads to the radiation pulse with a single smooth spike.
Response-coefficient method for heat-conduction transients with time-dependent inputs
NASA Technical Reports Server (NTRS)
Ceylan, Tamer
1993-01-01
A theoretical overview of the response coefficient method for heat conduction transients with time-dependent input forcing functions is presented with a number of illustrative applications. The method may be the most convenient and economical if the same problem is to be solved many times with different input-time histories or if the solution time is relatively long. The method is applicable to a wide variety of problems, including irregular geometries, position-dependent boundary conditions, position-dependent physical properties, and nonperiodic irregular input histories. Nonuniform internal energy generation rates within the structure can also be handled by the method. The area of interest is long-time solutions, in which initial condition is unimportant, and not the early transient period. The method can be applied to one dimensional problems in cartesian, cylindrical, and spherical coordinates as well as to two dimensional problems in cartesian and cylindrical coordinates.
Hild, Markus; Schmitt, Felix; Tuerschmann, Ilona; Roth, Robert
2007-11-15
The response of ultracold atomic Bose gases in time-dependent optical lattices is discussed based on direct simulations of the time-evolution of the many-body state in the framework of the Bose-Hubbard model. We focus on small-amplitude modulations of the lattice potential as implemented in several recent experiments and study different observables in the region of the first resonance in the Mott-insulator phase. In addition to the energy transfer we investigate the quasimomentum structure of the system which is accessible via the matter-wave interference pattern after a prompt release. We identify characteristic correlations between the excitation frequency and the quasimomentum distribution and study their structure in the presence of a superlattice potential.
Time-dependent Dalitz Plot Analysis of B0 to D-K0Pi+ Decays
Polci, F
2008-01-08
We present for the first time a measurement of the weak phase 2{beta} + {gamma} obtained from a time-dependent Dalitz plot analysis of B{sup 0} {yields} D{sup {-+}}K{sup 0}{pi}{sup {+-}} decays. Using a sample of approximately 347 x 10{sup 6} B{bar B} pairs collected by the BABAR detector at the PEP-II asymmetric-energy storage rings, we obtain 2{beta} + {gamma} = (83 {+-} 53 {+-} 20){sup 0} and (263 {+-} 53 {+-} 20){sup o} assuming the ratio r of the b {yields} u and b {yields} c decay amplitudes to be 0.3. The magnitudes and phases for the resonances associated with the b {yields} c transitions are also extracted from the fit.
Chemical dynamics in the gas phase: Time-dependent quantum mechanics of chemical reactions
Gray, S.K.
1993-12-01
A major goal of this research is to obtain an understanding of the molecular reaction dynamics of three and four atom chemical reactions using numerically accurate quantum dynamics. This work involves: (i) the development and/or improvement of accurate quantum mechanical methods for the calculation and analysis of the properties of chemical reactions (e.g., rate constants and product distributions), and (ii) the determination of accurate dynamical results for selected chemical systems, which allow one to compare directly with experiment, determine the reliability of the underlying potential energy surfaces, and test the validity of approximate theories. This research emphasizes the use of recently developed time-dependent quantum mechanical methods, i.e. wave packet methods.
Spallative nucleosynthesis in supernova remnants. II. Time-dependent numerical results
NASA Astrophysics Data System (ADS)
Parizot, Etienne; Drury, Luke
1999-06-01
We calculate the spallative production of light elements associated with the explosion of an isolated supernova in the interstellar medium, using a time-dependent model taking into account the dilution of the ejected enriched material and the adiabatic energy losses. We first derive the injection function of energetic particles (EPs) accelerated at both the forward and the reverse shock, as a function of time. Then we calculate the Be yields obtained in both cases and compare them to the value implied by the observational data for metal-poor stars in the halo of our Galaxy, using both O and Fe data. We find that none of the processes investigated here can account for the amount of Be found in these stars, which confirms the analytical results of Parizot & Drury (1999). We finally analyze the consequences of these results for Galactic chemical evolution, and suggest that a model involving superbubbles might alleviate the energetics problem in a quite natural way.
Two-component hybrid time-dependent density functional theory within the Tamm-Dancoff approximation.
Kühn, Michael; Weigend, Florian
2015-01-21
We report the implementation of a two-component variant of time-dependent density functional theory (TDDFT) for hybrid functionals that accounts for spin-orbit effects within the Tamm-Dancoff approximation (TDA) for closed-shell systems. The influence of the admixture of Hartree-Fock exchange on excitation energies is investigated for several atoms and diatomic molecules by comparison to numbers for pure density functionals obtained previously [M. Kühn and F. Weigend, J. Chem. Theory Comput. 9, 5341 (2013)]. It is further related to changes upon switching to the local density approximation or using the full TDDFT formalism instead of TDA. Efficiency is demonstrated for a comparably large system, Ir(ppy)3 (61 atoms, 1501 basis functions, lowest 10 excited states), which is a prototype molecule for organic light-emitting diodes, due to its "spin-forbidden" triplet-singlet transition. PMID:25612698
Agnihotri, Neha; Steer, Ronald P
2016-06-01
Computational modeling of selected artificial special pairs has been carried out. The structures chosen are bio-inspired molecular models of the light harvesting system II that have been previously investigated experimentally. Time-dependent density functional theory calculations have been employed to characterize the inter-macrocycle interactions resulting from two zinc porphyrins that are covalently linked with rigid linkers that vary the inter-porphyrin distance and the inter-planar angle in a C2v framework. The effects of varying the linker structure have been explored for electronic states with energies up to and including the Soret-correlated states in the dimer. An expansion of the Gouterman four orbital model for the monomers to an eight orbital model in the dimers provides a reasonable explanation of the inter-macrocycle interactions and provides insight into their experimental properties. PMID:27212274
Measurement of time-dependent CP violation in B 0 → η'K 0 decays
Šantelj, L.; Yusa, Y.; Abdesselam, A.; Adachi, I.; Aihara, H.; Al Said, S.; Asner, D. M.; Aulchenko, V.; Aushev, T.; Ayad, R.; et al
2014-10-29
We present a measurement of the time-dependent CP violation parameters in B0 → η'K0 decays. The measurement is based on the full data sample containing 772×106 BB-bar pairs collected at the Υ(4S) resonance using the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured values of the mixing-induced and direct CP violation parameters are: sin 2φ1eff = +0.68 ± 0.07 ± 0.03, Aη'K0 = +0.03 ± 0.05 ± 0.04, where the first uncertainty is statistical and the second is systematic. The values obtained are the most accurate to date. Furthermore, these results are consistent with our previous measurements andmore » with the world-average value of sin 2φ1 measured in B0 → J/ψK0 decays.« less
Quantum work statistics of charged Dirac particles in time-dependent fields
NASA Astrophysics Data System (ADS)
Deffner, Sebastian; Saxena, Avadh
The quantum Jarzynski equality is an important theorem of modern quantum thermodynamics. We show that the Jarzynski equality readily generalizes to relativistic quantum mechanics described by the Dirac equation. After establishing the conceptual framework we solve a pedagogical, yet experimentally relevant, system analytically. As a main result we obtain the exact quantum work distributions for charged particles traveling through a time-dependent vector potential evolving under Schrödinger as well as under Dirac dynamics, and for which the Jarzynski equality is verified. Special emphasis is put on the conceptual and technical subtleties arising from relativistic quantum mechanics. SD acknowledges financial support by the U.S. Department of Energy through a LANL Director's Funded Fellowship.
Geometrical effects and signal delay in time-dependent transport at the nanoscale
NASA Astrophysics Data System (ADS)
Moldoveanu, Valeriu; Manolescu, Andrei; Gudmundsson, Vidar
2009-07-01
Nonstationary and steady-state transport through a mesoscopic sample connected to particle reservoirs via time-dependent barriers is investigated by the reduced density operator method. The generalized master equation is solved via the Crank-Nicolson algorithm by taking into account the memory kernel which embodies the non-Markovian effects that are commonly disregarded. The lead-sample coupling takes into account the match between the energy of the incident electrons and the levels of the isolated sample, as well as their overlap at the contacts. Using a tight-binding description of the system, we investigate the effects induced in the transient current by the spectral structure of the sample and by the localization properties of its eigenfunctions. In strong magnetic fields, the transient currents propagate along edge states. The behavior of populations and coherences is discussed, as well as their connection to the tunneling processes that are relevant for transport.
An implicit fast Fourier transform method for integration of the time dependent Schrodinger equation
Riley, M.E.; Ritchie, A.B.
1997-12-31
One finds that the conventional exponentiated split operator procedure is subject to difficulties when solving the time-dependent Schrodinger equation for Coulombic systems. By rearranging the kinetic and potential energy terms in the temporal propagator of the finite difference equations, one can find a propagation algorithm for three dimensions that looks much like the Crank-Nicholson and alternating direction implicit methods for one- and two-space-dimensional partial differential equations. The authors report investigations of this novel implicit split operator procedure. The results look promising for a purely numerical approach to certain electron quantum mechanical problems. A charge exchange calculation is presented as an example of the power of the method.
Measurement of time-dependent CP asymmetries in B0-->D(*)+/-D+/- decays.
Aubert, B; Barate, R; Boutigny, D; Couderc, F; Karyotakis, Y; Lees, J P; Poireau, V; Tisserand, V; Zghiche, A; Grauges, E; Palano, A; Pappagallo, M; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Battaglia, M; Borgland, A W; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kukartsev, G; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Ronan, M T; Wenzel, W A; Barrett, M; Ford, K E; Harrison, T J; Hart, A J; Hawkes, C M; Morgan, S E; Watson, A T; Fritsch, M; Goetzen, K; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schroeder, T; Steinke, M; Boyd, J T; Burke, J P; Chevalier, N; Cottingham, W N; Kelly, M P; Cuhadar-Donszelmann, T; Hearty, C; Knecht, N S; Mattison, T S; McKenna, J A; Khan, A; Kyberd, P; Teodorescu, L; Blinov, A E; Blinov, V E; Bukin, A D; Druzhinin, V P; Golubev, V B; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Bondioli, M; Bruinsma, M; Chao, M; Eschrich, I; Kirkby, D; Lankford, A J; Mandelkern, M; Mommsen, R K; Roethel, W; Stoker, D P; Buchanan, C; Hartfiel, B L; Weinstein, A J R; Foulkes, S D; Gary, J W; Long, O; Shen, B C; Wang, K; Zhang, L; Del Re, D; Hadavand, H K; Hill, E J; Macfarlane, D B; Paar, H P; Rahatlou, S; Sharma, V; Berryhill, J W; Campagnari, C; Cunha, A; Dahmes, B; Hong, T M; Lu, A; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Eisner, A M; Flacco, C J; Heusch, C A; Kroseberg, J; Lockman, W S; Nesom, G; Schalk, T; Schumm, B A; Seiden, A; Spradlin, P; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Piatenko, T; Porter, F C; Ryd, A; Samuel, A; Andreassen, R; Jayatilleke, S; Mancinelli, G; Meadows, B T; Sokoloff, M D; Blanc, F; Bloom, P; Chen, S; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Ruddick, W O; Smith, J G; Ulmer, K A; Wagner, S R; Zhang, J; Chen, A; Eckhart, E A; Soffer, A; Toki, W H; Wilson, R J; Zeng, Q; Feltresi, E; Hauke, A; Spaan, B; Altenburg, D; Brandt, T; Brose, J; Dickopp, M; Klose, V; Lacker, H M; Nogowski, R; Otto, S; Petzold, A; Schott, G; Schubert, J; Schubert, K R; Schwierz, R; Sundermann, J E; Bernard, D; Bonneaud, G R; Grenier, P; Schrenk, S; Thiebaux, Ch; Vasileiadis, G; Verderi, M; Bard, D J; Clark, P J; Gradl, W; Muheim, F; Playfer, S; Xie, Y; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Anulli, F; Baldini-Ferroli, R; Calcaterra, A; de Sangro, R; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Brandenburg, G; Chaisanguanthum, K S; Morii, M; Won, E; Dubitzky, R S; Langenegger, U; Marks, J; Schenk, S; Uwer, U; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Flack, R L; Gaillard, J R; Morton, G W; Nash, J A; Nikolich, M B; Taylor, G P; Charles, M J; Mader, W F; Mallik, U; Mohapatra, A K; Cochran, J; Crawley, H B; Eyges, V; Meyer, W T; Prell, S; Rosenberg, E I; Rubin, A E; Yi, J; Arnaud, N; Davier, M; Giroux, X; Grosdidier, G; Höcker, A; Le Diberder, F; Lepeltier, V; Lutz, A M; Oyanguren, A; Petersen, T C; Pierini, M; Plaszczynski, S; Rodier, S; Roudeau, P; Schune, M H; Stocchi, A; Wormser, G; Cheng, C H; Lange, D J; Simani, M C; Wright, D M; Bevan, A J; Chavez, C A; Coleman, J P; Forster, I J; Fry, J R; Gabathuler, E; Gamet, R; George, K A; Hutchcroft, D E; Parry, R J; Payne, D J; Schofield, K C; Touramanis, C; Cormack, C M; Di Lodovico, F; Sacco, R; Brown, C L; Cowan, G; Flaecher, H U; Green, M G; Hopkins, D A; Jackson, P S; McMahon, T R; Ricciardi, S; Salvatore, F; Brown, D; Davis, C L; Allison, J; Barlow, N R; Barlow, R J; Hodgkinson, M C; Lafferty, G D; Naisbit, M T; Williams, J C; Chen, C; Farbin, A; Hulsbergen, W D; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Simi, G; Blaylock, G; Dallapiccola, C; Hertzbach, S S; Kofler, R; Koptchev, V B; Li, X; Moore, T B; Saremi, S; Staengle, H; Willocq, S; Cowan, R; Koeneke, K; Sciolla, G; Sekula, S J; Taylor, F; Yamamoto, R K; Kim, H; Patel, P M; Robertson, S H; Lazzaro, A; Lombardo, V; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Côté, D; Taras, P; Viaud, B; Nicholson, H; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Monorchio, D; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M; Bulten, H; Raven, G; Snoek, H L; Wilden, L; Jessop, C P; Losecco, J M; Allmendinger, T; Benelli, G; Gan, K K; Honscheid, K; Hufnagel, D; Jackson, P D; Kagan, H; Kass, R; Pulliam, T; Rahimi, A M; Ter-Antonyan, R; Wong, Q K; Brau, J; Frey, R; Igonkina, O; Lu, M; Potter, C T; Sinev, N B; Strom, D; Torrence, E; Colecchia, F; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; Buono, L Del; de la Vaissière, Ch; Hamon, O; John, M J J; Leruste, Ph; Malclès, J; Ocariz, J; Roos, L; Therin, G; Behera, P K; Gladney, L; Guo, Q H; Panetta, J; Biasini, M; Covarelli, R; Pacetti, S; Pioppi, M; Angelini, C; Batignani, G; Bettarini, S; Bucci, F; Calderini, G; Carpinelli, M; Cenci, R; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Walsh, J; Haire, M; Judd, D; Paick, K; Wagoner, D E; Biesiada, J; Danielson, N; Elmer, P; Lau, Y P; Lu, C; Olsen, J; Smith, A J S; Telnov, A V; Bellini, F; Cavoto, G; D'Orazio, A; Marco, E Di; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Gioi, L Li; Mazzoni, M A; Morganti, S; Piredda, G; Polci, F; Tehrani, F Safai; Voena, C; Schröder, H; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B; Gopal, G P; Olaiya, E O; Wilson, F F; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P-F; Graziani, G; Hamel de Monchenault, G; Kozanecki, W; Legendre, M; London, G W; Mayer, B; Vasseur, G; Yèche, Ch; Zito, M; Purohit, M V; Weidemann, A W; Wilson, J R; Yumiceva, F X; Abe, T; Allen, M T; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmueller, O L; Claus, R; Convery, M R; Cristinziani, M; Dingfelder, J C; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W; Fan, S; Field, R C; Glanzman, T; Gowdy, S J; Hadig, T; Halyo, V; Hast, C; Hryn'ova, T; Innes, W R; Kelsey, M H; Kim, P; Kocian, M L; Leith, D W G S; Libby, J; Luitz, S; Luth, V; Lynch, H L; Marsiske, H; Messner, R; Muller, D R; O'grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Snyder, A; Stelzer, J; Strube, J; Su, D; Sullivan, M K; Suzuki, K; Swain, S; Thompson, J M; Va'vra, J; Weaver, M; Wisniewski, W J; Wittgen, M; Wright, D H; Yarritu, A K; Yi, K; Young, C C; Burchat, P R; Edwards, A J; Majewski, S A; Petersen, B A; Roat, C; Ahmed, M; Ahmed, S; Alam, M S; Ernst, J A; Saeed, M A; Saleem, M; Wappler, F R; Zain, S B; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Ritchie, J L; Satpathy, A; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bona, M; Gallo, F; Gamba, D; Bomben, M; Bosisio, L; Cartaro, C; Cossutti, F; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Poropat, P; Vitale, L; Martinez-Vidal, F; Panvini, R S; Banerjee, Sw; Bhuyan, B; Brown, C M; Fortin, D; Hamano, K; Kowalewski, R; Roney, J M; Sobie, R J; Back, J J; Harrison, P F; Latham, T E; Mohanty, G B; Band, H R; Chen, X; Cheng, B; Dasu, S; Datta, M; Eichenbaum, A M; Flood, K T; Graham, M; Hollar, J J; Johnson, J R; Kutter, P E; Li, H; Liu, R; Mellado, B; Mihalyi, A; Pan, Y; Prepost, R; Tan, P; von Wimmersperg-Toeller, J H; Wu, J; Wu, S L; Yu, Z; Greene, M G; Neal, H
2005-09-23
We present a first measurement of CP asymmetries in neutral B decays to D+D-, and updated CP asymmetry measurements in decays to D(*+)D- and D(*-)D+. We use fully reconstructed decays collected in a data sample of (232+/-3) x 10(6) gamma(4S)-->BB events in the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We determine the time-dependent asymmetry parameters to be SD(*+)(D-)=-0.54+/-0.35+/-0.07, CD(*+)(D-)=0.09+/-0.25+/-0.06, SD(*-)(D+)=-0.29+/-0.33+/-0.07, CD(*-)(D+)=0.17+/-0.24+/-0.04, SD+(D-)=-0.29+/-0.63+/-0.06, and CD+(D-)=0.11+/-0.35+/-0.06, where in each case the first error is statistical and the second error is systematic. PMID:16197131
Talamo, Alberto
2013-05-01
This study presents three numerical algorithms to solve the time dependent neutron transport equation by the method of the characteristics. The algorithms have been developed taking into account delayed neutrons and they have been implemented into the novel MCART code, which solves the neutron transport equation for two-dimensional geometry and an arbitrary number of energy groups. The MCART code uses regular mesh for the representation of the spatial domain, it models up-scattering, and takes advantage of OPENMP and OPENGL algorithms for parallel computing and plotting, respectively. The code has been benchmarked with the multiplication factor results of a Boiling Water Reactor, with the analytical results for a prompt jump transient in an infinite medium, and with PARTISN and TDTORT results for cross section and source transients. The numerical simulations have shown that only two numerical algorithms are stable for small time steps.
Large Eddy Simulation of an URBAN 2000 Experiment with Various Time-Dependent Forcing
Chan, S T; Leach, M J
2004-06-15
Under the sponsorship of the U.S. DOE and DHS, we have developed a Computational Fluid Dynamics (CFD) model for simulating airflow and dispersion of chemical/biological agents released in the urban environment. Our model, FEM3MP, is based on solving the three-dimensional, time-dependent, incompressible Navier-Stokes equations on massively parallel computer platforms. The numerical algorithm uses the finite element method for accurate representation of complex building shapes and variable terrain, together with a semi-implicit projection method and modern iterative solvers for efficient time integration (Gresho and Chan, 1998). Physical processes treated in our code include turbulence modeling via the RANS (Reynolds Averaged Navier-Stokes) and LES (Large Eddy Simulation) approaches, atmospheric stability, aerosols, UV radiation decay, surface energy budget, and vegetative canopies, etc.
NASA Astrophysics Data System (ADS)
Magrakvelidze, Maia; Madjet, Mohamed; Chakraborty, Himadri
2016-05-01
We investigate Wigner-Smith (WS) time delays of the photoionization from various subshells of xenon using the time-dependent local density approximation (TDLDA) with the Leeuwen and Baerends exchange-correlation functional. At the 4d giant dipole resonance region as well as near all the Cooper minimum anti-resonances in 5p, 5s and 4d photoemissions, effects of electron correlations uniquely determine the shapes of the emission quantum phase. The Wigner-Smith time delay derived from this phase indicates significant variations as a function of energy. The results qualitatively support our TDLDA predictions at the fullerene plasmon region and at 3p Cooper minimum in argon, and should encourage attosecond measurements of Xe photoemission via two-photon interferometric techniques, such as RABITT. The work is supported by the NSF, USA.
Two-component hybrid time-dependent density functional theory within the Tamm-Dancoff approximation
Kühn, Michael; Weigend, Florian
2015-01-21
We report the implementation of a two-component variant of time-dependent density functional theory (TDDFT) for hybrid functionals that accounts for spin-orbit effects within the Tamm-Dancoff approximation (TDA) for closed-shell systems. The influence of the admixture of Hartree-Fock exchange on excitation energies is investigated for several atoms and diatomic molecules by comparison to numbers for pure density functionals obtained previously [M. Kühn and F. Weigend, J. Chem. Theory Comput. 9, 5341 (2013)]. It is further related to changes upon switching to the local density approximation or using the full TDDFT formalism instead of TDA. Efficiency is demonstrated for a comparably large system, Ir(ppy){sub 3} (61 atoms, 1501 basis functions, lowest 10 excited states), which is a prototype molecule for organic light-emitting diodes, due to its “spin-forbidden” triplet-singlet transition.
Two-component hybrid time-dependent density functional theory within the Tamm-Dancoff approximation
NASA Astrophysics Data System (ADS)
Kühn, Michael; Weigend, Florian
2015-01-01
We report the implementation of a two-component variant of time-dependent density functional theory (TDDFT) for hybrid functionals that accounts for spin-orbit effects within the Tamm-Dancoff approximation (TDA) for closed-shell systems. The influence of the admixture of Hartree-Fock exchange on excitation energies is investigated for several atoms and diatomic molecules by comparison to numbers for pure density functionals obtained previously [M. Kühn and F. Weigend, J. Chem. Theory Comput. 9, 5341 (2013)]. It is further related to changes upon switching to the local density approximation or using the full TDDFT formalism instead of TDA. Efficiency is demonstrated for a comparably large system, Ir(ppy)3 (61 atoms, 1501 basis functions, lowest 10 excited states), which is a prototype molecule for organic light-emitting diodes, due to its "spin-forbidden" triplet-singlet transition.
NASA Astrophysics Data System (ADS)
Liang, Wenkel
This dissertation consists of two general parts: (I) developments of optimization algorithms (both nuclear and electronic degrees of freedom) for time-independent molecules and (II) novel methods, first-principle theories and applications in time dependent molecular structure modeling. In the first part, we discuss in specific two new algorithms for static geometry optimization, the eigenspace update (ESU) method in nonredundant internal coordinate that exhibits an enhanced performace with up to a factor of 3 savings in computational cost for large-sized molecular systems; the Car-Parrinello density matrix search (CP-DMS) method that enables direct minimization of the SCF energy as an effective alternative to conventional diagonalization approach. For the second part, we consider the time dependence and first presents two nonadiabatic dynamic studies that model laser controlled molecular photo-dissociation for qualitative understandings of intense laser-molecule interaction, using ab initio direct Ehrenfest dynamics scheme implemented with real-time time-dependent density functional theory (RT-TDDFT) approach developed in our group. Furthermore, we place our special interest on the nonadiabatic electronic dynamics in the ultrafast time scale, and presents (1) a novel technique that can not only obtain energies but also the electron densities of doubly excited states within a single determinant framework, by combining methods of CP-DMS with RT-TDDFT; (2) a solvated first-principles electronic dynamics method by incorporating the polarizable continuum solvation model (PCM) to RT-TDDFT, which is found to be very effective in describing the dynamical solvation effect in the charge transfer process and yields a consistent absorption spectrum in comparison to the conventional linear response results in solution. (3) applications of the PCM-RT-TDDFT method to study the intramolecular charge-transfer (CT) dynamics in a C60 derivative. Such work provides insights into the
NASA Astrophysics Data System (ADS)
Dagan, Shai; Hua, Yimin; Boday, Dylan J.; Somogyi, Arpad; Wysocki, Ronald J.; Wysocki, Vicki H.
2009-06-01
The use of silicon nanoparticles for laser desorption/ionization (LDI) is a new appealing matrix-less approach for the selective and sensitive mass spectrometry of small molecules in MALDI instruments. Chemically modified silicon nanoparticles (30 nm) were previously found to require very low laser fluence in order to induce efficient LDI, which raised the question of internal energy deposition processes in that system. Here we report a comparative study of internal energy deposition from silicon nanoparticles to previously explored benzylpyridinium (BP) model compounds during LDI experiments. The internal energy deposition in silicon nanoparticle-assisted laser desorption/ionization (SPALDI) with different fluorinated linear chain modifiers (decyl, hexyl and propyl) was compared to LDI from untreated silicon nanoparticles and from the organic matrix, [alpha]-cyano-4-hydroxycinnamic acid (CHCA). The energy deposition to internal vibrational modes was evaluated by molecular ion survival curves and indicated that the ions produced by SPALDI have an internal energy threshold of 2.8-3.7 eV. This is slightly lower than the internal energy induced using the organic CHCA matrix, with similar molecular survival curves as previously reported for LDI off silicon nanowires. However, the internal energy associated with desorption/ionization from the silicon nanoparticles is significantly lower than that reported for desorption/ionization on silicon (DIOS). The measured survival yields in SPALDI gradually decrease with increasing laser fluence, contrary to reported results for silicon nanowires. The effect of modification of the silicon particle surface with semifluorinated linear chain silanes, including fluorinated decyl (C10), fluorinated hexyl (C6) and fluorinated propyl (C3) was explored too. The internal energy deposited increased with a decrease in the length of the modifier alkyl chain. Unmodified silicon particles exhibited the highest analyte internal energy
Mihaila, B.; Cuculeanu, V.
1994-08-01
On the basis of the radioactivity levels in aerosol and atmospheric deposition samples due to the Chernobyl accident, the resuspension factor of {sup 137}Cs as a four-parameter function has been inferred. The standard procedure to derive the dependence of resuspension on time assumes that the initial deposit is instantaneous. A simple method assuming a constant deposition rate over a fixed period has been proposed. Also, based on existing experimental data, an attempt was made to consider a realistic time dependence of the deposition rate to cope with the particular case of the Chernobyl accident. The differences between the two models are outlined. The Chernobyl direct deposit has been assumed to be the deposit measured between 30 April and 30 June 1986. The calculated values of the resuspension factor are consistent with the IAEA`s recommended model and depend on the rainfall that occurred in June 1986 and the site-specific disturbance conditions during the first 100 d following 1 July 1986 and only on artificial disturbance by humans and vehicles after that. 16 refs., 5 figs., 3 tabs.
Chemical vapour deposition of thermochromic vanadium dioxide thin films for energy efficient glazing
Warwick, Michael E.A.; Binions, Russell
2014-06-01
Vanadium dioxide is a thermochromic material that undergoes a semiconductor to metal transitions at a critical temperature of 68 °C. This phase change from a low temperature monoclinic structure to a higher temperature rutile structure is accompanied by a marked change in infrared reflectivity and change in resistivity. This ability to have a temperature-modulated film that can limit solar heat gain makes vanadium dioxide an ideal candidate for thermochromic energy efficient glazing. In this review we detail the current challenges to such glazing becoming a commercial reality and describe the key chemical vapour deposition technologies being employed in the latest research. - Graphical abstract: Schematic demonstration of the effect of thermochromic glazing on solar radiation (red arrow represents IR radiation, black arrow represents all other solar radiation). - Highlights: • Vanadium dioxide thin films for energy efficient glazing. • Reviews chemical vapour deposition techniques. • Latest results for thin film deposition for vanadium dioxide.
Heterogeneous Shock Energy Deposition in Shock Wave Consolidation of Metal Powders.
NASA Astrophysics Data System (ADS)
Mutz, Andrew Howard
Shock wave consolidation of powder is a high deformation rate process in which a shock wave generated by an explosive or a colliding projectile rapidly densifies and bonds together the powder particles into a solid compact. The deposition of the shock energy during this process is highly inhomogeneous on the powder particle scale. Evidence of the extent and pattern of the energy deposition was provided by recovery experiments performed using a crystalline metallic glass forming alloy, and analyzed using a heat flow model. The energy deposited during the shock wave passage was best modeled as deposited partly into the particle bulk and partly onto particle surfaces. To investigate this inhomogeneity, and the powder parameters which influence it, a propellant driven gas gun was designed, built and utilized. The planarity of the shock waves produced using the targets designed for the gun was established. Powder - powder thermocouples were impacted with powders of varying sizes to establish the effect of particle size on energy deposition. Small particles in contact with large ones were inferred to absorb the greater fraction of shock energy. Hardened and unhardened steel powder was shocked to investigate the effect of particle hardness on energy distribution. The recovered compacts were not measurably affected by the initial hardness. Compaction experiments were performed on a Ni based super-alloy and on a SiC reinforced Ti matrix composite to test some of the practical applications of the process and the target designs developed. Superior tensile properties were observed in the shock consolidated and heat treated Ni based 718 alloy. The SiC reinforced composite was recovered in the intended net shape with no macro-cracks in the compact body, but with fractured SiC particles.
Wang, Y Y; Grygiel, C; Dufour, C; Sun, J R; Wang, Z G; Zhao, Y T; Xiao, G Q; Cheng, R; Zhou, X M; Ren, J R; Liu, S D; Lei, Y; Sun, Y B; Ritter, R; Gruber, E; Cassimi, A; Monnet, I; Bouffard, S; Aumayr, F; Toulemonde, M
2014-01-01
Modification of surface and bulk properties of solids by irradiation with ion beams is a widely used technique with many applications in material science. In this study, we show that nano-hillocks on CaF2 crystal surfaces can be formed by individual impact of medium energy (3 and 5 MeV) highly charged ions (Xe(22+) to Xe(30+)) as well as swift (kinetic energies between 12 and 58 MeV) heavy xenon ions. For very slow highly charged ions the appearance of hillocks is known to be linked to a threshold in potential energy (Ep) while for swift heavy ions a minimum electronic energy loss per unit length (Se) is necessary. With our results we bridge the gap between these two extreme cases and demonstrate, that with increasing energy deposition via Se the Ep-threshold for hillock production can be lowered substantially. Surprisingly, both mechanisms of energy deposition in the target surface seem to contribute in an additive way, which can be visualized in a phase diagram. We show that the inelastic thermal spike model, originally developed to describe such material modifications for swift heavy ions, can be extended to the case where both kinetic and potential energies are deposited into the surface. PMID:25034006
NASA Astrophysics Data System (ADS)
Paredes Marino, Joali; Morgavi, Daniele; Di Vito, Mauro; de Vita, Sandro; Sansivero, Fabio; Perugini, Diego
2016-04-01
Fractal fragmentation theory has been applied to characterize the particle size distribution of pyroclastic deposits generated by volcanic explosions. Recent works have demonstrated that fractal dimension on grain size distributions can be used as a proxy for estimating the energy associated with volcanic eruptions. In this work we seek to establish a preliminary analytical protocol that can be applied to better characterize volcanic fall deposits and derive the potential energy for fragmentation that was stored in the magma prior/during an explosive eruption. The methodology is based on two different techniques for determining the grain-size distribution of the pyroclastic samples: 1) dry manual sieving (particles larger than 297μm), and 2) automatic grain size analysis via a CamSizer-P4®device, the latter measure the distribution of projected area, obtaining a cumulative distribution based on volume fraction for particles up to 30mm. Size distribution data have been analyzed by applying the fractal fragmentation theory estimating the value of Df, i.e. the fractal dimension of fragmentation. In order to test our protocol we studied the Cretaio eruption, Ischia island, Italy. Results indicate that size distributions of pyroclastic fall deposits follow a fractal law, indicating that the fragmentation process of these deposits reflects a scale-invariant fragmentation mechanism. Matching the results from manual and automated techniques allows us to obtain a value of the "fragmentation energy" from the explosive eruptive events that generate the Cretaio deposits. We highlight the importance of these results, based on fractal statistics, as an additional volcanological tool for addressing volcanic risk based on the analyses of grain size distributions of natural pyroclastic deposits. Keywords: eruptive energy, fractal dimension of fragmentation, pyroclastic fallout.
Griesheimer, D. P.; Stedry, M. H.
2013-07-01
A rigorous treatment of energy deposition in a Monte Carlo transport calculation, including coupled transport of all secondary and tertiary radiations, increases the computational cost of a simulation dramatically, making fully-coupled heating impractical for many large calculations, such as 3-D analysis of nuclear reactor cores. However, in some cases, the added benefit from a full-fidelity energy-deposition treatment is negligible, especially considering the increased simulation run time. In this paper we present a generalized framework for the in-line calculation of energy deposition during steady-state Monte Carlo transport simulations. This framework gives users the ability to select among several energy-deposition approximations with varying levels of fidelity. The paper describes the computational framework, along with derivations of four energy-deposition treatments. Each treatment uses a unique set of self-consistent approximations, which ensure that energy balance is preserved over the entire problem. By providing several energy-deposition treatments, each with different approximations for neglecting the energy transport of certain secondary radiations, the proposed framework provides users the flexibility to choose between accuracy and computational efficiency. Numerical results are presented, comparing heating results among the four energy-deposition treatments for a simple reactor/compound shielding problem. The results illustrate the limitations and computational expense of each of the four energy-deposition treatments. (authors)
Measurements of the energy deposit of inclined muon bundles in the CWD NEVOD
NASA Astrophysics Data System (ADS)
Kokoulin, R. P.; Bogdanov, A. G.; Dushkin, L. I.; Khokhlov, S. S.; Khomyakov, V. A.; Kindin, V. V.; Kovylyaeva, E. A.; Mannocchi, G.; Petrukhin, A. A.; Saavedra, O.; Shutenko, V. V.; Trinchero, G.; Yashin, I. I.
2015-08-01
First results of investigations of the energy deposits of inclined muon bundles in the ground-based Cherenkov water detector NEVOD are presented. As a measure of the muon bundle energy deposit, the total number of photoelectrons detected by PMTs of the Cherenkov calorimeter is used. For each event, the local muon density at the observation point and the muon bundle arrival direction are estimated from the data of the coordinate-tracking detector DECOR. Registration of the bundles in a wide range of zenith angles allows to explore the interval of primary particle energies from ∼ 1016 to ∼ 1018 eV. Measurement results are compared with CORSIKA based simulations of EAS muon component. It is found that the mean energy of muons detected in the bundles rapidly increases with the zenith angle and reaches about 500 GeV near the horizon.
Analysis of CRRES PHA Data for Low-Energy-Deposition Events
NASA Technical Reports Server (NTRS)
McNulty, P. J.; Hardage, Donna
2004-01-01
This effort analyzed the low-energy deposition Pulse Height Analyzer (PHA) data from the Combined Release and Radiation Effects Satellite (CRRES). The high-energy deposition data had been previously analyzed and shown to be in agreement with spallation reactions predicted by the Clemson University Proton Interactions in Devices (CUPID) simulation model and existing environmental and orbit positioning models (AP-8 with USAF B-L coordinates). The scope of this project was to develop and improve the CUPID model by increasing its range to lower incident particle energies, and to expand the modeling to include contributions from elastic interactions. Before making changes, it was necessary to identify experimental data suitable for benchmarking the codes; then, the models to the CRRES PHA data could be applied. It was also planned to test the model against available low-energy proton or neutron SEU data obtained with mono-energetic beams.
NASA Astrophysics Data System (ADS)
Kanjilal, A.; Catalfano, M.; Harilal, S. S.; Hassanein, A.; Rice, B.
2012-03-01
Time dependent changes in 13.5 nm extreme ultraviolet (EUV) reflectivity of Ru mirrors due to variations in surface composition were investigated. The surface properties of Ru films were analyzed in situ by means of X-ray photoelectron spectroscopy (XPS), and further verified by Auger electron spectroscopy (AES). Moreover, the impact on EUV reflectivity (EUVR) with time was examined in situ via continuous and/or discrete EUV exposures. The rapid decrease in EUVR was observed in the presence of photoelectrons (PEs) from Ru mirror of the EUV setup, whereas no significant variation was recorded by screening out additional PEs. Detailed XPS and AES analyses suggest that carbon deposition via dissociation of residual hydrocarbons plays a dominant role in the presence of additional PEs, and thus reduces the reflectivity rapidly. Using EUV photoelectron spectroscopy, systematic reduction of the secondary electron yield from the Ru mirror surface was observed in consecutive scans, and therefore supports the formation of carbonaceous Ru surface in the presence of additional PEs.
NASA Astrophysics Data System (ADS)
Lambiase, Joseph J.; Suraya Tulot
2013-12-01
The depositional environments of the wave-dominant successions in the middle to late Miocene Belait and Sandakan Formations in northwestern and northern Borneo, respectively, were determined based on grain size distributions, sedimentary structures and facies successions, as well as trace and microfossil assemblages. Generally, progradational shoreface successions in the Belait Formation were deposited in very low wave energy environments where longshore currents were too weak to generate trough cross-bedding. Shoreface sands are laterally continuous for several km and follow the basin contours, suggesting attached beaches similar to the modern Brunei coastline. In contrast, trough cross-bedding is common in the coarser Sandakan Formation and back-barrier mangrove swamp deposits cap the progradational succession as on the modern northern Dent Peninsula coastline, indicating barrier development and higher wave energy conditions than in the Belait Formation. The Borneo examples indicate that barrier systems that include significant tidal facies form under higher wave energy conditions than attached beaches with virtually no tidal facies. Also, Borneo's low latitude climate promotes back-barrier mangrove which reduces tidal exchange and reduces tidal influence relative to comparable temperate climate systems. The results of the study indicate that depositional systems on low energy, wave-dominated coasts are highly variable, as are the sand bodies and facies associations they generate.
Effect of forage energy intake and supplementation on marbling deposition in growing beef cattle.
Technology Transfer Automated Retrieval System (TEKTRAN)
Glucose is the primary carbon source for fatty acid synthesis in intramuscular fat, whereas, acetate is primarily utilized by subcutaneous fat. Our objective was to examine the effect of forage energy intake and type of fermentation on marbling deposition by stocker cattle grazing dormant native ra...
Interferometric technique for determining the energy deposition in gas-flow nuclear-pumped lasers
Pikulev, A A
2001-06-30
An interference technique is developed for determining the energy deposition in gas-flow lasers pumped by uranium fission fragments. It is shown that four types of interference patterns may be formed. Algorithms are presented for determining the type of interference and for enumerating the maxima in interference pattern. (lasers, active media)
NASA Astrophysics Data System (ADS)
Agostini, Federica; Abedi, Ali; Suzuki, Yasumitsu; Min, Seung Kyu; Maitra, Neepa T.; Gross, E. K. U.
2015-03-01
The Born-Oppenheimer (BO) approximation allows to visualize the coupled electron-nuclear dynamics in molecular systems as a set of nuclei moving on a single potential energy surface representing the effect of the electrons in a given eigenstate. Many interesting phenomena, however, such as vision or charge separation in organic photovoltaic materials, take place in conditions beyond its range of validity. Nevertheless, the basic construct of the adiabatic treatment, the BO potential energy surfaces, is employed to describe non-adiabatic processes and the full problem is represented in terms of adiabatic states and transitions among them in regions of strong non-adiabatic coupling. But the concept of single potential energy is lost. The alternative point of view arising in the framework of the exact factorization of the electron-nuclear wave function will be presented. A single, time-dependent, potential energy provides the force driving the nuclear motion and is adopted as starting point for the development of quantum-classical approximations to the full quantum mechanical problem.
A fast real time time-dependent density functional theory simulation method
NASA Astrophysics Data System (ADS)
Wang, Lin-Wang; Wang, Zhi; Li, Shu-Sheng
2015-03-01
We have developed an efficient real-time time-dependent density functional theory (TDDFT) method that can increase the effective time step from <1 attosecond in traditional methods to 0.1 0.5 femtosecond. Our algorithm, which carries out the non-adiabatic molecular dynamics TDDFT simulations, can have comparable speed to the Born-Oppenheimer (BO) ab initio molecular dynamics (MD). As an application, we simulated the process of an energetic Cl particle colliding onto a monolayer of MoSe2. Our simulations show a significant energy transfer from the kinetic energy of the Cl particle to the electronic energy of MoSe2, and the result of TDDFT is very different from that of BO MD simulations. This new algorithm will enable the use of real-time TD-DFT for many new simulations involving carrier dynamics and electron-phonon couplings. This work is supported by the Director, Office of Science, BES/MSED, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, through the Material Theory program in LBNL. Zhi Wang is supported by the China Scholarship Council.
NASA Astrophysics Data System (ADS)
Kaur, Rajwant; Dhilip Kumar, T. J.
2015-11-01
Experiments have reported the high stability of HCS+ ion and inhibit to decompose over the range of collision energies. In this study, the various energy transfer channels of atomic H collision with CS+ molecular ion has been performed by ab initio computations at the multireference configuration interaction/aug-cc-pVQZ level of theory. The ground and several low-lying excited electronic state potential energy surfaces in three different molecular orientations, namely, two collinear configurations with, (1) H approaching the S atom (γ = 0°), (2) H approaching the C atom (γ = 180°) and one perpendicular configuration, (3) H approaching the centre of mass of CS (γ = 90°) with the diatom fixed at the equilibrium bond length, have been obtained. Nonadiabatic effects with Landau-Zener coupling leading to avoided crossings are observed between the ground- and the first-excited states in γ = 90° orientation, and also between the first- and second-excited states in γ = 180° orientation. Quantum dynamics have been performed to study the charge transfer using time-dependent wave packet method on the diabatic potential energy surfaces. The probability of charge transfer is found to be highest with 42% in γ = 180°. The high charge transfer probability result in the formation of H+ + CS channel which ascertains the high stability of HCS+ ion.
A new time dependent density functional algorithm for large systems and plasmons in metal clusters
Baseggio, Oscar; Fronzoni, Giovanna; Stener, Mauro
2015-07-14
A new algorithm to solve the Time Dependent Density Functional Theory (TDDFT) equations in the space of the density fitting auxiliary basis set has been developed and implemented. The method extracts the spectrum from the imaginary part of the polarizability at any given photon energy, avoiding the bottleneck of Davidson diagonalization. The original idea which made the present scheme very efficient consists in the simplification of the double sum over occupied-virtual pairs in the definition of the dielectric susceptibility, allowing an easy calculation of such matrix as a linear combination of constant matrices with photon energy dependent coefficients. The method has been applied to very different systems in nature and size (from H{sub 2} to [Au{sub 147}]{sup −}). In all cases, the maximum deviations found for the excitation energies with respect to the Amsterdam density functional code are below 0.2 eV. The new algorithm has the merit not only to calculate the spectrum at whichever photon energy but also to allow a deep analysis of the results, in terms of transition contribution maps, Jacob plasmon scaling factor, and induced density analysis, which have been all implemented.
Photon and neutrino spectra of time-dependent photospheric models of gamma-ray bursts
Asano, K.; Mészáros, P. E-mail: nnp@astro.psu.edu
2013-09-01
Thermal photons from the photosphere may be the primary source of the observed prompt emission of gamma-ray bursts (GRBs). In order to produce the observed non-thermal spectra, some kind of dissipation mechanism near the photosphere is required. In this paper we numerically simulate the evolution of the photon spectrum in a relativistically expanding shell with a time-dependent numerical code. We consider two basic models. One is a leptonic model, where a dissipation mechanism heats the thermal electrons maintaining their high temperature. The other model involves a cascade process induced by pp(pn)-collisions which produce high-energy electrons, modify the thermal spectrum, and emit neutrinos. The qualitative properties of the photon spectra are mainly determined by the optical depth at which the dissipation mechanism sets in. Too large optical depths lead to a broad and curved spectrum contradicting the observations, while for optical depths smaller than unity the spectral hardness becomes softer than observed. A significant shift of the spectral peak energy to higher energies due to a large energy injection can lead to an overly broad spectral shape. We show ideal parameter ranges for which these models are able to reproduce the observed spectra. For the pn-collision model, the neutrino fluence in the 10–100 GeV range is well above the atmospheric neutrino fluence, but its detection is challenging for presently available detectors.
Technology Transfer Automated Retrieval System (TEKTRAN)
A study was conducted to examine the effects of controlled intake, dietary protein (CP) level, and ractopamine supplementation on growth, body composition, and the efficiency of energy and protein deposition in pigs during uninterrupted or compensatory growth from 60 to 100 kg. Seven groups of pigs ...
Field quantization and squeezed states generation in resonators with time-dependent parameters
NASA Technical Reports Server (NTRS)
Dodonov, V. V.; Klimov, A. B.; Nikonov, D. E.
1992-01-01
The problem of electromagnetic field quantization is usually considered in textbooks under the assumption that the field occupies some empty box. The case when a nonuniform time-dependent dielectric medium is confined in some space region with time-dependent boundaries is studied. The basis of the subsequent consideration is the system of Maxwell's equations in linear passive time-dependent dielectric and magnetic medium without sources.
Time-dependent bridging and life prediction of SiC/SiC in a hypothetical fusion environment
Henager, C.H. Jr.; Lewinsohn, C.A.; Windisch, C.F. Jr.; Jones, R.H.
1996-10-01
Growth of subcritical cracks in SiC/SiC composites of CG-Nicalon fibers with a {approximately}1 {mu}m C-interphase has been measured on a related Basic Energy Sciences program using environments of purified argon and mixtures of argon and oxygen at 1073K to 1373K. Companion thermo-gravimetric (TGA) testing measured mass loss in identical environments. The TGA mass loss was from C-interphase oxidation to CO and CO{sub 2}, which was undetectable in argon and linear with oxygen concentration in argon-oxygen mixtures, and was converted into an interphase linear recession rate. Crack growth in pure argon indicated that fiber creep was causing time-dependent crack bridging to occur, while crack growth in argon-oxygen mixtures indicated that time-dependent C-interphase recession was also causing time-dependent bridging with different kinetics. A model of time-dependent bridging was used to compute crack growth rates in argon and in argon-oxygen mixtures and gave an estimate of useable life of about 230 days at 1073K in a He + 1.01 Pa O{sub 2} (10 ppm) environment.
PREFACE: The 395th Wilhelm and Else Heraeus Seminar: `Time-dependent phenomena in Quantum Mechanics'
NASA Astrophysics Data System (ADS)
Kleber, Manfred; Kramer, Tobias
2008-03-01
The 395th Wilhelm and Else Heraeus Seminar: `Time-dependent phenomena in Quantum Mechanics' took place at the Heinrich Fabri Institute in Blaubeuren, Germany, 12-16 September 2007. The conference covered a wide range of topics connected with time-dependent phenomena in quantum mechanical systems. The 20 invited talks and 15 short talks with posters at the workshop covered the historical debate between Schrödinger, Dirac and Pauli about the role of time in Quantum Mechanics (the debate was carried out sometimes in footnotes) up to the almost direct observation of electron dynamics on the attosecond time-scale. Semiclassical methods, time-delay, monodromy, variational principles and quasi-resonances are just some of the themes which are discussed in more detail in the papers. Time-dependent methods also shed new light on energy-dependent systems, where the detour of studying the time-evolution of a quantum states allows one to solve previously intractable problems. Additional information is available at the conference webpage http://www.quantumdynamics.de The organizer would like to thank all speakers, contributors, session chairs and referees for their efforts in making the conference a success. We also gratefully acknowledge the generous financial support from the Wilhelm and Else Heraeus Foundation for the conference and the production of this special volume of Journal of Physics: Conference Series. Manfred Kleber Physik Department T30, Technische Universität München, 85747 Garching, Germany mkleber@ph.tum.de Tobias Kramer Institut I: Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany tobias.kramer@physik.uni-regensburg.de Guest Editors Front row (from left): W Schleich, E J Heller, J B Delos, H Friedrich, K Richter, M Kleber, P Kramer, M Man'ko, A del Campo, V Man'ko, M Efremov, A Ruiz, M O Scully Middle row: A Zamora, R Aganoglu, T Kramer, J
Time-dependent 2.2-MeV and 0.5-MeV lines from solar flares
NASA Technical Reports Server (NTRS)
Wang, H. T.; Ramaty, R.
1975-01-01
The time dependences of the 2.2- and 0.51-MeV gamma-ray lines from solar flares are calculated, and the results are compared with observations of the 1972 August 4 and 7 flares. The time lag between the nuclear reactions and the formation of these two lines is caused by capture of the neutrons and subsequent deceleration of the positrons and decay of the radioactive nuclei. Our main results are that the calculation is consistent with the observed rise of the 2.2-MeV line on August 4, and it does not require different time dependences for the accelerated protons and high-energy electrons in the flare region. The above lags can explain the delayed gamma-ray emission observed on August 7. Positrons of energies greater than about 10 MeV could be detected in interplanetary space following large solar flares.
NASA Astrophysics Data System (ADS)
Tamba, T.; Pham, H. S.; Shoda, T.; Iwakawa, A.; Sasoh, A.
2015-09-01
Modulation of shock foot oscillation due to energy deposition by repetitive laser pulses in shock wave-boundary layer interaction over an axisymmetric nose-cylinder-flare model in Mach 1.92 flow was experimentally studied. From a series of 256 schlieren images, density oscillation spectra at each pixel were obtained. When laser pulses of approximately 7 mJ were deposited with a repetition frequency, fe, of 30 kHz or lower, the flare shock oscillation had a peak spectrum equivalent to the value of fe. However, with fe of 40 kHz-60 kHz, it experienced frequency modulation down to lower than 20 kHz.
The time-dependence of compaction localization in a porous sandstone
NASA Astrophysics Data System (ADS)
Heap, M. J.; Brantut, N.; Baud, P.; Meredith, P. G.
2015-12-01
Compaction bands in sandstone are laterally-extensive planar deformation features that are characterized by lower porosity and permeability than the surrounding host rock. As a result, this form of localization has important implications for both strain partitioning and fluid flow in the Earth's upper crust. To better understand the time-dependency of compaction band growth, we performed triaxial deformation experiments on water-saturated Bleurswiller sandstone (initial porosity = 0.24) under constant stress (creep) conditions in the compactant regime. Our experiments show that inelastic strain accumulates at a constant stress in the compactant regime, manifest as compaction bands. While creep in the dilatant regime is characterized by an increase in porosity and, ultimately, an acceleration in axial strain rate to shear failure, compaction creep is characterized by a reduction in porosity and a gradual deceleration in axial strain rate. The global decrease in the rates of axial strain, acoustic emission energy, and porosity change during creep compaction is punctuated at intervals by higher rate excursions, interpreted as the formation of compaction bands. The growth rate of compaction bands formed during creep is lower as the applied differential stress, and hence background creep strain rate, is decreased. However, the inelastic strain associated with the growth of a compaction band remains constant over strain rates spanning several orders of magnitude (from 10-8 to 10-5 s-1). We find that, despite the large differences in strain rate and growth rate (from both creep and constant strain rate experiments), the characteristics (geometry, thickness) of the compaction bands remain essentially the same. Several lines of evidence, notably the similarity between the differential stress dependence of creep strain rate in the dilatant and compactant regimes, suggest that, as for dilatant creep, subcritical stress corrosion cracking is the mechanism responsible for
TIME-DEPENDENT PHOTOIONIZATION OF GASEOUS NEBULAE: THE PURE HYDROGEN CASE
Garcia, J.; Elhoussieny, E. E.; Bautista, M. A.; Kallman, T. R. E-mail: manuel.bautista@wmich.edu E-mail: timothy.r.kallman@nasa.gov
2013-09-20
We study the problem of time-dependent photoionization of low density gaseous nebulae subjected to sudden changes in the intensity of ionizing radiation. To this end, we write a computer code that solves the full time-dependent energy balance, ionization balance, and radiation transfer equations in a self-consistent fashion for a simplified pure hydrogen case. It is shown that changes in the ionizing radiation yield ionization/thermal fronts that propagate through the cloud, but the propagation times and response times to such fronts vary widely and nonlinearly from the illuminated face of the cloud to the ionization front (IF). IF/thermal fronts are often supersonic, and in slabs initially in pressure equilibrium such fronts yield large pressure imbalances that are likely to produce important dynamical effects in the cloud. Further, we studied the case of periodic variations in the ionizing flux. It is found that the physical conditions of the plasma have complex behaviors that differ from any steady-state solution. Moreover, even the time average of ionization and temperature is different from any steady-state case. This time average is characterized by overionization and a broader IF with respect to the steady-state solution for a mean value of the radiation flux. Around the time average of physical conditions there is a large dispersion in instantaneous conditions, particularly across the IF, which increases with the period of radiation flux variations. Moreover, the variations in physical conditions are asynchronous along the slab due to the combination of nonlinear propagation times for thermal fronts/IFs and equilibration times.
Time-dependent evolution of cosmic-ray-modified shock structure: Transition to steady state
NASA Technical Reports Server (NTRS)
Donohue, D. J.; Zank, G. P.; Webb, G. M.
1994-01-01
Steady state solutions to the two-fluid equations of cosmic-ray-modified shock structure were investigated first by Drury and Volk (1981). Their analysis revealed, among other properties, that there exist regions of upstream parameter space where the equations possess three different downstream solutions for a given upstream state. In this paper we investigate whether or not all these solutions can occur as time-asymptotic states in a physically realistic evolution. To do this, we investigate the time-dependent evolution of the two-fluid cosmic-ray equations in going from a specified initial condition to a steady state. Our results indicate that the time-asymptotic solution is strictly single-valued, and it undergoes a transition from weakly to strongly cosmic-ray-modified at a critical value of the upstream cosmic ray energy density. The expansion of supernova remnant shocks is considered as an example, and it is shown that the strong to weak transition is in fact more likely. The third intermediate solution is shown to influence the time-dependent evolution of the shock, but it is not found to be a stable time-asymptotic state. Timescales for convergence to these states and their implications for the efficiency of shock acceleration are considered. We also investigate the effects of a recently introduced model for the injection of seed particles into the shock accelerated cosmic-ray population. The injection is found to result in a more strongly cosmic-ray-dominated shock, which supports our conclusion that for most classes of intermediate and strong cosmic-ray-modified shocks, the downstream cosmic-ray pressure component is at least as large as the thermal gas pressure, independent of the upstream state. As a result, cosmic rays almost always play a significant role in determining the shock structure and dissipation and they cannot be regarded as test particles.
Time-dependent evolution of cosmic-ray-modified shock structure: Transition to steady state
NASA Astrophysics Data System (ADS)
Donohue, D. J.; Zank, G. P.; Webb, G. M.
1994-03-01
Steady state solutions to the two-fluid equations of cosmic-ray-modified shock structure were investigated first by Drury and Volk (1981). Their analysis revealed, among other properties, that there exist regions of upstream parameter space where the equations possess three different downstream solutions for a given upstream state. In this paper we investigate whether or not all these solutions can occur as time-asymptotic states in a physically realistic evolution. To do this, we investigate the time-dependent evolution of the two-fluid cosmic-ray equations in going from a specified initial condition to a steady state. Our results indicate that the time-asymptotic solution is strictly single-valued, and it undergoes a transition from weakly to strongly cosmic-ray-modified at a critical value of the upstream cosmic ray energy density. The expansion of supernova remnant shocks is considered as an example, and it is shown that the strong to weak transition is in fact more likely. The third intermediate solution is shown to influence the time-dependent evolution of the shock, but it is not found to be a stable time-asymptotic state. Timescales for convergence to these states and their implications for the efficiency of shock acceleration are considered. We also investigate the effects of a recently introduced model for the injection of seed particles into the shock accelerated cosmic-ray population. The injection is found to result in a more strongly cosmic-ray-dominated shock, which supports our conclusion that for most classes of intermediate and strong cosmic-ray-modified shocks, the downstream cosmic-ray pressure component is at least as large as the thermal gas pressure, independent of the upstream state. As a result, cosmic rays almost always play a significant role in determining the shock structure and dissipation and they cannot be regarded as test particles.
NASA Astrophysics Data System (ADS)
Clay, M. P.; Yeung, P. K.; Warhaft, Z.
2015-11-01
Turbulence subjected to axisymmetric strain is a fundamental problem which is common in engineering equipment with variable cross-section, but is not yet fully understood. We have performed direct numerical simulations on a deforming domain with grids up to 10243 and a time-dependent strain history designed to mimic spatial gradients in wind-tunnel experiments. Isotropic turbulence with a specified energy spectrum is allowed to decay and then passed through a numerical conduit of 4:1 contraction ratio. The Reynolds stress tensor, velocity gradient variances, and longitudinal and transverse one-dimensional (1D) spectra are studied during both the contraction and subsequent relaxation. Contraction leads to amplification of energy in the compressed directions and departures from local isotropy. When the strain is removed local isotropy returns quickly while the energy decays with a power law exponent smaller than for decaying isotropic turbulence. The evolution of 1D spectra including changes in shape is consistent with experiments, but a large solution domain is important. Supported by NSF Grant CBET-1510749 (Fluid Dynamics Program).
Problem-free time-dependent variational principle for open quantum systems
NASA Astrophysics Data System (ADS)
Joubert-Doriol, Loïc; Izmaylov, Artur F.
2015-04-01
Methods of quantum nuclear wave-function dynamics have become very efficient in simulating large isolated systems using the time-dependent variational principle (TDVP). However, a straightforward extension of the TDVP to the density matrix framework gives rise to methods that do not conserve the energy in the isolated system limit and the total system population for open systems where only energy exchange with environment is allowed. These problems arise when the system density is in a mixed state and is simulated using an incomplete basis. Thus, the basis set incompleteness, which is inevitable in practical calculations, creates artificial channels for energy and population dissipation. To overcome this unphysical behavior, we have introduced a constrained Lagrangian formulation of TDVP applied to a non-stochastic open system Schrödinger equation [L. Joubert-Doriol, I. G. Ryabinkin, and A. F. Izmaylov, J. Chem. Phys. 141, 234112 (2014)]. While our formulation can be applied to any variational ansatz for the system density matrix, derivation of working equations and numerical assessment is done within the variational multiconfiguration Gaussian approach for a two-dimensional linear vibronic coupling model system interacting with a harmonic bath.
Shape evolution and collective dynamics of quasifission in the time-dependent Hartree-Fock approach
NASA Astrophysics Data System (ADS)
Umar, A. S.; Oberacker, V. E.; Simenel, C.
2015-08-01
Background: At energies near the Coulomb barrier, capture reactions in heavy-ion collisions result either in fusion or in quasifission. The former produces a compound nucleus in statistical equilibrium, while the second leads to a reseparation of the fragments after partial mass equilibration without formation of a compound nucleus. Extracting the compound nucleus formation probability is crucial to predict superheavy-element formation cross sections. It requires a good knowledge of the fragment angular distribution which itself depends on quantities such as moments of inertia and excitation energies which have so far been somewhat arbitrary for the quasifission contribution. Purpose: Our main goal is to utilize the time-dependent Hartee-Fock (TDHF) approach to extract ingredients of the formula used in the analysis of experimental angular distributions. These include the moment-of-inertia and temperature. Methods: We investigate the evolution of the nuclear density in TDHF calculations leading to quasifission. We study the dependence of the relevant quantities on various initial conditions of the reaction process. Results: The evolution of the moment of inertia is clearly nontrivial and depends strongly on the characteristics of the collision. The temperature rises quickly when the kinetic energy is transformed into internal excitation. Then, it rises slowly during mass transfer. Conclusions: Fully microscopic theories are useful to predict the complex evolution of quantities required in macroscopic models of quasifission.